General Clutch Corporation v Sbriggs Pty Ltd [1997] FCA 499

CATCHWORDS PATENTS - Infringement - construction of claim - "A spring clutch comprising" - whether "comprising" means "including" or "made up only of" - purposive construction - device needing integers in addition to those claimed in order that device can operate as a spring clutch. WORDS AND PHRASES - "comprising" in expression "a spring clutch comprising" in a claim in a patent. Decor Corporation Pty Ltd v Dart Industries Inc (1988) 13 IPR 385 Radiation Ltd v Galliers & Klaerr Pty Ltd (1938) 60 CLR 36 Winner v Morey Haigh & Associates (A'asia) Pty Ltd (1996) 33 IPR 215 GENERAL CLUTCH CORPORATION v SBRIGGS PTY LIMITED No NG 921 of 1995 Lindgren J Sydney 6 June 1997

IN THE FEDERAL COURT OF AUSTRALIA) NEW SOUTH WALES DISTRICT REGISTRY) No NG 921 of 1995 GENERAL DIVISION ) BETWEEN: GENERAL CLUTCH CORPORATION Applicant AND: SBRIGGS PTY LIMITED (ACN 007 415 518) Respondent CORAM: Lindgren J PLACE: Sydney DATE: 6 June 1997 MINUTE OF ORDERS THE COURT ORDERS THAT: 1. The application be, and the same is hereby, dismissed. 2. The applicant pay the respondent's costs. NOTE: Settlement and entry of orders is dealt with in Order 36 of the Federal Court Rules.

IN THE FEDERAL COURT OF AUSTRALIA) NEW SOUTH WALES DISTRICT REGISTRY) No NG 921 of 1995 GENERAL DIVISION ) BETWEEN: GENERAL CLUTCH CORPORATION Applicant AND: SBRIGGS PTY LIMITED (ACN 007 415 518) Respondent CORAM: Lindgren J PLACE: Sydney DATE: 6 June 1997 REASONS FOR JUDGMENT INTRODUCTION The applicant ("GC"), a corporation incorporated in the United States of America, is, and was at all material times, the registered proprietor of Australian Letters Patent No 557825 ("the Patent") for "improvements in spring clutches". GC alleges that the respondent ("Sbriggs"), which is incorporated in Australia, has infringed the Patent. It seeks declaratory and injunctive relief as well as damages and an inquiry as to damages, or, at GC's option, an account of profits. On 2 May 1996 I ordered that the claim for monetary relief be heard separately from the other claims. These Reasons for Judgment relate only to the issue of infringement and the claims for declaratory and injunctive relief. Sbriggs sells and distributes clutches. Without pre-empting any issue which I have to decide, I can say that the clutches are suitable for use in connection with the winding up and down, and holding in position, of window blinds: when the clutch is not engaged, the blind may be wound up and down; when it is engaged, the blind is held in position and cannot fall. Carmelo Joseph Licciardi Di Stefano, a director of Sbriggs, gave evidence that from about June 1994, to about May 1995, Sbriggs sold multiple spring clutches manufactured for it. Two clutches in evidence, the "KJW Clutch" and the "Valectro Clutch", are examples of the spring clutches sold by Sbriggs in that period. It is not suggested that the Valectro Clutch differs materially from the KJW Clutch. In early 1995, Sbriggs set about redesigning clutches of the Valectro Clutch and KJW Clutch kind. The result was what has been termed in the evidence "the Third Clutch" (I need not explain why it has been referred to in this way), an example of which is also in evidence. Although Mr Di Stefano does not say so in terms, his evidence seems to suggest that from about May 1995, the Third Clutch replaced the KJW Clutch and the Valectro Clutch as the form of the relevant spring clutch sold by Sbriggs. However, there is uncontradicted evidence that Sbriggs sold the Valectro Clutch as late as May 1996. Sbriggs threatens, unless restrained, to continue to sell the Third Clutch. In my opinion, for the purpose of the questions which arise in this case, there is no material difference between the three Clutches (see later). The substantial issue posed for decision is whether the KJW, Valectro and Third Clutches, infringe Claim 1 of the Patent. This is the only Claim on which GC relies. As one aspect of its defence, Sbriggs submits that the Patent is invalid. Sbriggs does not, however, cross claim for revocation. THE PATENT Description of invention, prior art, objects The title of the invention is "IMPROVEMENTS IN SPRING CLUTCHES". The Patent's "Abstract" of it is annexed to these Reasons for Judgment (see Appendix A). The Specification describes the "field" of the invention as follows: "This invention relates to spring clutches and more particularly to spring clutches with multiple springs which operate at different times." The Specification's account of the prior art commences as follows: "Many variations of spring clutches have been developed and are familiar to those skilled in the art. A typical spring clutch has (1) an input element to which an external source of motive force is connected, (2) an output element from which, when the clutch is engaged, torque can be transmitted to the connected load, (3) a spring which is used to effect the connection between the input and the output elements, and (4) a control element by means of which the clutch is engaged or disengaged. Such a clutch is commonly called a wrap spring clutch because a spring is controllably wrapped either around or within either the input or the output element. When the spring is caused to grip that element, the clutch can transmit torque and is said to be engaged. Conversely, when the spring is caused to be released from that element, the clutch will not transmit more than a small, residual amount of torque and is said to be disengaged. The control element is used to control the action of the spring, causing it to form the mechanical connection between the driving and the driven elements when the clutch is to be engaged, and causing that connection to be substantially interrupted when the clutch is to be disengaged. The output element can be a core, hub, or cylindrical member, about which the spring is disposed so as to be able to grip it, or it can be a cylindrical sleeve within which the spring is disposed so as to be able to grip the sleeve. In either case, if the clutch is to deliver the torque that is expected of it, the spring must, in its relaxed condition, have a particular dimensional relationship to the core or sleeve with which it co-operates. It is often desired to produce clutches of this type inexpensively and in large quantities by high volume production methods. However, the sizes of the spring and of the input and output elements must be closely controlled if the clutch is to have consistent and predictable operating characteristics. The maintainance [sic - maintenance] of these close dimensional tolerances becomes a significant factor in the cost of such clutches." The Specification goes on to describe six objects of the invention, one of which is: " ... to provide a spring clutch in which torque can be transmitted to the load in graduated steps to allow for a slower acceleration of the load than is the case when the maximum rated torque is applied suddenly to the load." There is set out a formula by which that torque which will cause a wrap spring clutch to "slip" can be ascertained. The formula itself does not matter for present purposes. The explanation which introduces it is as follows: "The capability of a spring clutch to transmit torque depends upon a number of factors. Among these are the size and stiffness of the spring wire; the diameter of the hub, the element to which the spring makes a frictional connection when the clutch is engaged; the coefficient of friction between the spring material and the material of the hub; the size of the spring when it is in its relaxed condition; and the number of coils of the spring. The diametral difference between the hub and the spring in its relaxed condition is called the interference." It is explained that: "Conventional spring clutches normally employ only a small amount of interference and a large number of turns" but that: " ... the interference must be made extremely small if the clutch is to retain a useful torque rating and yet slip to protect itself against an overload. The present invention uses two or more springs instead of the usual single spring. By using fewer turns in each of the springs, and more interference than in conventional designs, a clutch can be built which will have a large torque rating while retaining the ability to slip to protect itself against an overload. The wear on both the springs and the surface which the springs grip is increased due to the greater interference, but suitable choices of materials for the component parts can usually reduce the wear to an acceptable level." There follows an important passage (lines 21-27 on p 6 of the Specification): "There are two physical features which distinguish the subject clutch from those of the prior art. First, the clutch uses more than one spring to effect the connection between the input and output elements. Second, the positioning of the control surfaces within the clutch are such that the several springs can be made to operate at different times." Three embodiments The Specification refers to three embodiments of the invention. The first is illustrated in figures 1, 2, 3 and 4; the second in figures 5, 6 and 7; and the third in figures 8, 9, 10 and 11. Copies of all eleven figures are annexed to these Reasons for Judgment (see Appendix B). I do not find it necessary to set out the Specification's description of each of the three embodiments. I will, however, set out the first and refer to certain features of the second and third (of course, the descriptions of the embodiments can be understood only by reference to the figures annexed in Appendix B to these Reasons for Judgment). First embodiment "In the simple, overrunning, slip clutch of FIGS. 1-4, hub 24, about whose exterior surface springs 28 and 30 are disposed, is held within housing 22 by screw 36 and washer 38. Coaxial alignment of housing 22 and hub 24 are maintained on one end of the clutch by ring 26 which acts as a bearing between the housing and the hub, and on the other end by reduced hub diameter 40 and necked down housing diameter 42. Shafts or other connecting means such as pulleys or sprockets (not shown) can be attached to housing 22 and hub 24. Opening 44 in housing 22, as seen in FIG. 2, comprises two adjoining rectangular portions of differing arcuate lengths. As illustrated, the two portions of the opening are aligned on one end producing a single surface 46 at that end, while at the other ends surfaces 48 and 50 lie at different angular positions about the center of housing 22. The openings are oriented in this fashion as a matter of convenience, but any other angular positioning would work as well provided that the angles subtended by the openings are not equal. If another angular positioning of the openings were used, then surface 46 would be divided into two surfaces, one for each rectangular portion of the opening. Springs 28 and 30 each have a tab, 32 and 34 respectively, welded or otherwise firmly attached to one end or formed from the spring wire itself. The springs are disposed about hub 24 in like relative orientation, as shown in FIG. 2, tabs 32 and 34 protruding through opening 44 as shown in both FIGS. 3 and 4. If housing 22 is rotated in the counterclockwise direction as shown by arrow 53 in FIG. 3, surface 46 of opening 44 contacts both tab 32 of spring 28 and tab 34 of spring 30, causing both springs to release their grip on hub 24. Therefore, hub 24 can be easily restrained from rotating along with housing 22. If housing 22 is rotated in the clockwise direction as shown by arrow 52 in FIG. 4, however, then surface 48 of opening 44 will contact tab 32 of spring 28. If the restraint on hub 24 is sufficient to cause spring 28 to slip on hub 24, then, after some slippage has occurred, surface 50 of opening 44 will contact tab 34 of spring 30. After surface 50 has contacted tab 34, spring 30 will also begin to impart torque to hub 24. Additional rotation can cause continued slippage only if the slip torque of springs 28 and 30 combined is less than the torque required to maintain a constant angular relationship between housing 22 and hub 24. The forces exerted on the tabs by the surfaces of the opening will cause each of the springs to tighten about hub 24 so that each of the springs will impart a torque to hub 24 of a magnitude not greater than the torque required to cause that spring to slip on the hub. The use of multiple springs (only two are shown in FIGS. 1-4) with small numbers of coils increases the probability of obtaining the desired slip torque from each of the springs; it also provides an averaging effect. If housing 22 is again rotated in the direction of arrow 53 through a displacement sufficient to cause surface 46 to again contact both tab 32 and tab 34, then the tabs will be realigned, and another reversal to the direction of arrow 52 will cause the torque to be applied to hub 24 in increments as before. The operation of this embodiment of the clutch can be reversed by assembling the clutch with the spring reversed. That is, so that the springs would still appear as in FIG. 2 except that the tabs would be on the other ends of the springs." Second embodiment In the case of the second embodiment, shown in figures 5-7, housing 54 is the output element and hub 56 is the input element. In this case, each spring has two tabs, one being firmly attached near each end of the spring. Opening 76 in housing 54 is rectangular, having axially oriented and parallel load surfaces 70 and 72. According to the Specification: "Each of these two load surfaces should be thought of as two separate surfaces, one for each spring tab, which can, but need not, be in alignment so as to form a single surface." The Specification continues: "A control element, in the form of control cylinder 78, is positioned about housing 54 so as to be able to rotate somewhat about the housing and contact tabs 62, 64, 66, and 68 as required in operation." Importantly, the differential times of contact with the respective tabs is achieved, in the case of the second embodiment, by the presence of a "step" in key 82. Accordingly, the final paragraph in the description of the second embodiment is as follows: "In this embodiment the offset position of the two springs is achieved by a step in key 82. (Mulitple [sic - Multiple] steps should be used if there are three or more springs.) In the first embodiment the offset is built into the shape of opening 44 in housing 22. In the embodiment of FIGS. 8-11, the offset is a result of slight differences in the positioning of the tabs on the springs. Any of these methods, as well as others, may be used to achieve the desired result. Although in these examples only two springs have been used, it is clearly possible to use three or more to achieve an even more gradual acceleration of the load." Third embodiment In the third embodiment, depicted in figures 8-11, the clutch is used to support a load which always tends to move the output element in one direction. In this embodiment, the "step" in the key has been eliminated and the differential times of contact with the tabs is achieved by differences (as between the respective springs) of the locations of the tabs. General After describing the three embodiments, the Specification continues: "The present invention can be used in many types of spring clutches other than those shown herein. The illustrated embodiments allow the concepts to be easily understood. In these embodiments, the hub (the element with whose surface the springs make frictional contact) is the central piece in the clutch with the springs disposed about it. The outer element (the element which makes contact with the tabs of the springs) is concentrically mounted outside of the springs." Claim 1 There are eight Claims but, as noted earlier, GC relies only Claim 1, which is as follows: lines 8 "1. A spring clutch comprising a first shaft, a coax- 9 ially mounted second shaft, and at least first and second 10 springs, helically wound and coaxially disposed between said 11 first and second shafts, for making frictional contact with 12 said first shaft, 13 said at least first and second springs each having a 14 tab near at least one end, said tabs being radially directed 15 toward said second shaft, 16 said second shaft having at least first and second load 17 surfaces for engaging respective ones of said tabs, 18 rotation of one of said shafts in at least one direc- 19 tion causing said at least first and second springs to 20 rotate therewith and to apply a torque in the same direction 21 to the other of said shafts, 22 said tab near said one end of said first spring making 23 contact with said first load surface of said second shaft 24 before said tab near said one end of said second spring 25 makes contact with said second load surface of said second 26 shaft, said first spring slipping on said first shaft prior 27 to said tab near said one end of said second spring making 28 contact with said second load surface of said second shaft 29 if the torque applied to said first shaft exceeds a predeter- 30 mined value." Although Claims 4 and 6 are not relied on by GC, the opening paragraphs of them have been referred to in submissions: "4. A spring clutch comprising a first element, a second element, at least first and second clutch springs, a control element, .......... 6. A bi-directional spring clutch comprising an input element, a cylindrical output element, at least first and second clutch springs, and a fixed hub, .................................." There is an important difference between Claim 1 on the one hand and Claims 4 and 6 on the other. Claim 1 refers to two coaxially mounted shafts or elements, whereas Claims 4 and 6 refer to three. Sbriggs submits that the language of Claim 1 leaves no scope for the presence of the third shaft or element, in Claim 4 called "a control element" and in Claim 6 called "a cylindrical output element", but that just such an element is integral to the spring clutches which are the Valectro Clutch, the KJW Clutch and the Third Clutch. SBRIGGS' DEFENCE Sbriggs' defence consists substantially of non-admissions and denials. In para 6 of its defence, however, Sbriggs denies an allegation in para 6 of the statement of claim that the Patent is and was at all material times valid and subsisting. By its amended particulars of grounds of invalidity relating to Claim 1, Sbriggs says that the Patent is, and was at all material times, invalid and liable to be revoked, by reason of the fact that the Claim does not comply with sub-s 40 (2) and (3) of the Patents Act 1990 ("the Act"). Those sub-sections and sub-s 40 (4) are, relevantly, as follows: "(2)A complete specification must: (a)................................................... (b) where [the invention] relates to an application for a standard patent - end with a claim or claims defining the invention; and (c) ................................................. (3) The claim or claims must be clear and succinct and fairly based on the matter described in the specification. (4) The claim or claims must relate to one invention only." (underlining supplied) Sbriggs gives the following particulars of the non-compliance with sub-ss 40 (2) and (3) relevant to Claim 1: "(a)In claim ... 1, ... reference is made to 'first and second load surfaces'. These words are unclear as they do not specify whether the first and second load surfaces are two separate offset surfaces or a single surface. (b)In claim ... 1, ... reference is made to 'first and second load surfaces'. These words are not fairly based on the matter described in the specification as they do not clearly claim two separate offset surfaces. (c)Claim ... 1, ... [is] not fairly based on the matter described in the specification as [it does] not specify that the springs tighten about one of the shafts upon rotation of the other shaft." (underlining supplied) EVIDENCE GC's evidence in chief of infringement Associate Professor Richard Butler Frost, Head of the Design Department in the School of Mechanical and Manufacturing Engineering at the University of New South Wales, gave evidence on behalf of GC. He has qualifications and experience in mechanical and industrial engineering, and, in particular, in the area of design. He dismantled, inspected and photographed the Valectro Clutch and KJW Clutch and their component parts. As well, he dismantled and inspected the Third Clutch. Annexed to his affidavit are photographs which he took. Of particular importance is figure 2 annexed to his affidavit which is a photograph of the Valectro Clutch in a partially dismantled state. A copy of that photograph is annexed to these Reasons for Judgment (see Appendix C). It includes the numerals which were written on the copy annexed to Professor Frost's affidavit. I have included, as well, a "legend" indicating the part of the assemblage to which each numeral refers. Helpfully, Sbriggs' witnesses adopted Professor Frost's numeric system of identifying the parts of the Valectro Clutch and I shall do so too. The KJW Clutch and the Third Clutch contain the same components and the numerals therefore refer to the same parts of those Clutches too. In order to avoid confusion of this "figure 2" with "FIGURE 2" annexed to the Specification, I will refer to the former as "the photograph". It is convenient to mention here another useful form of reference which the parties used and which I will adopt. They referred to the first shaft (1) as "the first shaft", the "coaxially mounted second shaft" (2) as "the second shaft", and the "output shaft" (7) as "the third shaft". According to Professor Frost's affidavit, his examination of the component parts of the Valectro Clutch and the KJW Clutch showed that the corresponding components and the assemblies of the two Clutches were "substantially identical, topologically at least." He also said that their operation was identical in nature. Professor Frost expressed the opinion that the two Clutches contained each and every one of the features referred to in Claim 1 of the Patent. He identified those features by the numerals in brackets in the bold text below, and made the comments in respect of them which appear in ordinary typeface below: "'A spring clutch comprising a first shaft (1), a coaxially mounted second shaft (2), and at least first and second springs (3), helically wound and coaxially disposed between said first and second shafts, for making frictional contact with said first shaft, said at least first and second springs each having a tab (4) near at least one end, said tabs being radially directed toward said second shaft,' I observed every element of this feature in each of the Valectro clutch and the KJW clutch. In each of the said clutches there was in fact four such springs. 'said second shaft having at least first and second load surfaces (5) for engaging respective ones of said tabs,' In relation to this feature, the single surface labelled '5' in Figure 2 [the photograph] hereto may be regarded as several co-planar contiguous surfaces, each of which is associated with one of the four spring tabs labelled '4' in Figure 2 [the photograph]. I observed this feature. 'rotation of one of said shafts in at least one direction causing said at least first and second springs to rotate therewith and to apply a torque in the same direction to the other of said shafts,' I observed this feature. Torque is a motive agency tending to cause rotation. It is the rotational analogue of a linear force. In the instant case, the application of a force to a spring tab by a load surface causes the spring to slip around the 'said first shaft' and thereby to apply a torque to that shaft via the agency of friction. 'said tab near said one end of said first spring making contact with said first load surface of said second shaft before said tab near said one end of said second spring makes contact with said second load surface of said second shaft, said first spring slipping on said first shaft prior to said tab near said one end of said second spring making contact with said second load surface of said second shaft if the torque applied to said first shaft exceeds a predetermined value.' I observed this feature." Figures 3 and 4 annexed to Professor Frost's affidavit showed, for the KJW Clutch and the Valectro Clutch respectively, the different circumferential distance between the two tabs at the ends of each of the four springs. Professor Frost said that when one of the two sets of four corresponding tabs are simultaneously in contact with one load surface of the coaxially mounted second shaft, the other four tabs are not in a straight line as between themselves and are at different distances, as between themselves, from the other load surface of the coaxially mounted second shaft. Figures 5 and 6 annexed to Professor Frost's affidavit show an end view of what is seen in figures 3 and 4, with the coaxially mounted second shaft removed. Accordingly, figures 5 and 6 show one corresponding set of spring tabs substantially in alignment and the other corresponding set of spring tabs substantially out of alignment. Figures 7 and 8 annexed to Professor Frost's affidavit are end-on photographs of the four springs of the KJW Clutch and the Valectro Clutch respectively, demonstrating the extent to which there is a difference between the circumferential distance between the two tabs on the ends of the respective springs. Professor Frost deduced from a comparison of the four springs from the KJW Clutch, which, he had been told, was acquired in 1994, and the four springs from the Valectro Clutch, which, he had been told, was acquired in 1996, that it was not apparent that any re-engineering had occurred since acquisition. He expressed the following conclusion: "The effect of the different values of the circumferential distance between the tabs on each of the various springs will be to cause sequential rather than simultaneous contact between the spring tabs and the load surfaces on the 'said second shaft'."(Professor Frost's affidavit sworn 30.7.1996, para 18) Professor Frost's affidavit also referred to the question whether there was a load surface for each tab or whether there were only two load surfaces in all, one for the corresponding tabs on one end of the springs, and the other for the corresponding tabs on the other end of the springs. After referring to certain passages in the Specification, he expressed the following conclusion: "In my opinion, these passages in the specification recognise that a load surface or a spring contact surface which contacts more than one of a set of corresponding contact elements, eg more than one of a set of corresponding spring tabs, includes the two possibilities that the said surface either may be a single planar surface which could be regarded as a plurality of separate surfaces which happen to be coplanar, or may be a plurality of separate non-coplanar surfaces, subtending finite angles at the central axis of the clutch assembly, wherein one contact occurs on each such surface." (Professor Frost's affidavit sworn 30.7.1996, para 19) The differences suggested by Sbriggs between the KJW Clutch and the Valectro Clutch on the one hand, and the Third Clutch on the other Mr Di Stefano, a director of Sbriggs, gave affidavit evidence of shortcomings which Sbriggs had noted in the KJW Clutch and the Valectro Clutch, of a process of redesigning which Sbriggs had embarked upon from early 1995, and of the emergence, as a result, of the Third Clutch, designed by Sbriggs. He said of the KJW Clutch and the Valectro Clutch, that the tabs on the springs "were formed and cut manually which resulted in the shape and orientation of the tabs (4) not being always strictly uniform" (Mr Di Stefano's affidavit sworn 5 September 1996, para 11). However, he said that the variation in the alignment of the tabs in the Valectro Clutch and the KJW Clutch in evidence were not typical of the variations which he had observed in those clutches which Sbriggs had sold. He said that they were, in fact, "the most extreme examples" he had seen of such variations. To my mind, however, nothing turns on this evidence. Mr Di Stefano said that Sbriggs had found that the clutches which it distributed initially were too easily disengaged, because: "the opening in the shaft (2) of the springs (3) was too narrow and when coupled with variations in tab (4) orientation, would not reliably permit the key (9) to tighten the springs (3) to engage the shaft (1)." Moreover, according to Mr Di Stefano, "[t]he springs (3) were originally zinc coated which caused uneven frictional contact and contributed to the unreliable nature of the first clutches." Mr Di Stefano gave the following account of the redesigning by Sbriggs: "From early 1995, my company set about redesigning the first clutches [the first form of clutch sold by Sbriggs of which the KJW Clutch and the Valectro Clutch are examples]. In doing this my company aimed to make the manufacture of the spring (3) and tab (4) as uniform as possible to improve the reliability of the first clutch. In the redesigned clutch (...), the springs (3) and tabs (4) are manufactured by machine to a tolerance of 1 mm. Other significant modifications to the first clutches included (i) dispensing with zinc coating to improve the evenness of the friction between the fist [sic - first] shaft (1) and the springs (3), (ii) increasing the width of the opening in the shaft (2), and thickening the width of the plastic mounting to improve its strength." (Mr Di Stefano's affidavit sworn 5.9.1996, para 13) In his affidavit sworn 30 July 1996, Professor Frost had said that his opinion expressed in relation to KJW Clutch and the Valectro Clutch applied equally to the Third Clutch, and that he was therefore of the opinion that the Third Clutch also contained all the features referred to in Claim 1 of the Patent. General evidentiary issues between Professor Frost and Mr Delatycki on infringement Sbriggs led evidence from Oscar Delatycki, a retired university lecturer and an Academic Associate at the University of Melbourne. Mr Delatycki has worked in that University since 1963. He has qualifications and experience in the field of materials engineering and science. Like Professor Frost, Mr Delatycki disassembled, inspected, and reassembled the KJW Clutch, the Valectro Clutch, and the Third Clutch. Professor Frost swore an affidavit on 20 September 1996 partly in reply to Mr Delatycki's affidavit. It is convenient to address at the same time the issues between the two experts as they emerge from those affidavits. Professor Frost's affidavit also responded to the distinction attempted to be made in Mr Di Stefano's affidavit between the KJW Clutch and the Valectro Clutch on the one hand, and the Third Clutch on the other, but I will give an account of that response later. The cross-examination of Mr Delatycki included the following: "May we take it you would not regard your field of expertise as the area of spring clutches?---That's correct. And you would not regard yourself as a person who could give any definitive or authoritative opinion on spring clutches generally?---Outside of what I've studied in here that's correct, yes. When you say studied in here, you mean studied in the patent?---Studied in conjunction with the patent and whatever contact I had with spring clutches in the past. Do you say you had a lot of contact with spring clutches in the past?---No. The sort of contact that any engineer building equipment etcetera, as I did, a lot at the university would have. In your time you have come across a wide variety of spring clutches may we take it?---I have come across a narrow variety of small clutches, mainly clutches in laboratory equipment of special type." (T 121) I think that of the two experts, Professor Frost has the greater expertise relevant to spring clutches, although, in the event, I have not found this view to be decisive of any issue before me. Mr Delatycki observes that Professor Frost has drawn his conclusions from a visual inspection of the three Clutches in their assembled form and disassembled form without other testing, and expresses the view that unaided visual inspection of a disassembled clutch is not conclusive of the exact manner of operation of the clutch. He says that it is impossible to see the direct interaction between the key (9) of the output shaft (7) on the tabs (4) of the springs (3) in an assembled clutch. He says that, similarly, in order to understand the operation of the springs (3), a matter critical in Claim 1, it is necessary to test the Clutches in a properly equipped workshop. In reply, Professor Frost says that he inspected each Clutch visually, disassembled and reassembled it, and manipulated it manually in the course of his examination, and disagreed that these procedures were inadequate for the purpose of his arriving at the conclusions and opinions which he expressed. He says: "While it is not possible to examine the operation of the springs in the clutches directly when the clutch is assembled, any inferences that I drew in this regard were necessary inferences dictated by the structure and interplay of the component parts. The general nature of the operation of the springs in the clutches is easily discernible by a competent person by examination of the operation of the clutch with the output shaft (7) removed. I refer particularly to my opinion concerning the sequential engagement of the springs. It is not necessary to have direct visual access to the inside of the assembled clutch to arrive at the conclusion that, if the spring tab ends are different distances apart, they cannot engage simultaneously." (Professor Frost's affidavit sworn 20.9.1996, para 3 (13)) I accept the thrust of Professor Frost's response. While "a properly equipped workshop" may make it possible to identify and measure more precisely the operation of the key (9) of the output shaft (7) on the tabs (4) of the springs (3), and the operation of those springs in an assembled clutch, the essential nature of their operation is discernible once the output shaft (7) has been removed, by visual inspection coupled with manipulation. Mr Delatycki disagrees with Professor Frost's evidence that the corresponding component parts from the KJW Clutch and the Valectro Clutch are substantially identical, even "topologically at least." He says that there is a highly subjective element involved and that he is uncertain of Professor Frost's meaning. In particular, he says that he observed that a number of the tabs (4) of the springs (3) of the KJW Clutch and the Valectro Clutch were bent to varying degrees. Professor Frost does not accept Mr Delatycki's comments. He says, in particular, that the variations in the springs and spring tabs appear to be variations resulting from imperfections that can typically be attributed to the manufacturing process, and are not significant to the design of the Clutches or their operation. Again, I accept Professor Frost's response. The "bends" in the tabs (4) are not significant for any issue which I have to decide. Mr Delatycki says that even on a visual inspection, there are significant differences between the KJW Clutch and the Third Clutch. For example, he says that there are differences between the sets of tabs (4) of the springs (3), a difference between the arcuate distance of the opening in the coaxially mounted second shaft of the KJW Clutch as compared to that of the Third Clutch, and a difference between the surfaces of the springs themselves as between those two Clutches. Professor Frost replies to the effect that, inter alia, such variations as exist appear to have resulted from imperfections attributable to the manufacturing process, and are not significant to the design or operation of the Clutches. I accept Professor Frost's evidence in this respect. Mr Delatycki says, by reference to lines 21-27 on page 6 of the Specification (set out earlier in these Reasons), that the alleged two distinguishing features of the invention are said to be: . the use of multiple springs; and . stepping of the control surfaces to stage in time the operation of the springs. Professor Frost disagrees that the passage referred to requires the "stepping of the control surfaces to stage in time the operation of the springs", and says that it would not be regarded by an expert in the field as requiring this. Rather, Professor Frost says that the passage requires that "the positioning of the control surfaces within the clutch are such that the several springs can be made to operate at different times." According to Professor Frost, this is a different requirement, and insists only that the angular spacings of the control surfaces be different from those of the spring tabs. He says, "[i]f the spring tabs themselves are spaced at unequal intervals, the control surfaces need not be positioned at different angular positions within the clutch; they could, in fact, be co-planar." The issue between Professor Frost and Mr Delatycki in this respect concerns the meaning of the plural form "surfaces" which I address later. REASONING ON INFRINGEMENT Mr Delatycki challenges Professor Frost's dissection of Claim 1 and his conclusion that the KJW Clutch, the Valectro Clutch and the Third Clutch infringe that Claim. I will first address issues of general importance and then turn to the various specific issues relating to infringement. Outline of parties' submissions on the "spring clutch comprising" issue Sbriggs submits that Claim 1 claims a "first shaft", a "coaxially mounted second shaft", "at least first and second springs", and "further features in respect to the two shafts and the springs", and that what is not claimed by Claim 1, and therefore is disclaimed, is "an apparatus which has as one of the integers essential to it[s] being a spring clutch an integer not claimed in claim 1 (whether or not it otherwise exhibits each of the integers of claim 1)." In summary, Sbriggs submits that Claim 1 does not include any reference to a third shaft, yet a third shaft is essential to the spring clutches that are the Valectro Clutch, the KJW Clutch and the Third Clutch. Developing this submission, Sbriggs points out that Claim 1 refers three times to "at least first and second springs" (underlining supplied) and once to "at least first and second load surfaces" (underlining supplied), yet does not use such language as "at least" in relation to the first and second shafts. Again, Sbriggs refers to Claims 4 and 6, the opening words of which were quoted earlier. In those opening words there is, in each case, as noted earlier, a reference to a third shaft additional to the two mentioned in Claim 1. Sbriggs submits: "14................................................... The Respondent's product operates as a spring clutch only because of the inclusion therein of 3 cylinders or part cylinders. 15 [Cylinder] 3 is essential as the input element of the spring clutch, and the output of the generic clutch. [Cylinder] 2 is essential as the control of the spring clutch and the input of the generic clutch." Sbriggs submits that Claim 1 cannot be used to found a claim of infringement by its product which is a three part device, one of the three shafts being the control element, and refers to Winner v Morey Haigh & Associates (A'asia) Pty Ltd (1996) 33 IPR 215. In that case a steering wheel anti-theft locking device was held not to infringe. Although the device limited or prevented the rotation of the steering wheel, it did so by elements which cooperated by a different mechanical operation from that of the claimed invention. O'Loughlin J held that infringement required that each of the essential elements of the combination the subject of the Patent be taken, and considered that the device challenged lacked two of the integers found in the relevant claim in the case before him. Sbriggs submits that the only way to escape the same conclusion in the present case is to construe Claim 1 as claiming any spring clutch made from a combination of integers which includes, but is not necessarily limited to, the integers in Claim 1. Sbriggs submits that this construction should not be adopted because it involves a misconstruction of the word "comprising"; and because it is improbable since it would render the claim invalid under s 40 of the Act for failure to define the invention (sub-s 40 (2) (b)), to be clear and succinct (sub-s 40 (3)), and to be fairly based on the matter described in the Specification (sub-s 40 (3)). GC's submission in reply takes as its starting point the fact that subject to "two very narrow grounds", Sbriggs concedes that Claim 1 is valid, whatever it may mean. It points out that the grounds of invalidity relied on by Sbriggs are limited to two: (i) that the reference to "first and second load surfaces" in Claim 1 is ambiguous because it does not specify whether those surfaces are separate offset surfaces or a single surface, and, if they include a "single surface", Claim 1 is not fairly based; and (ii)the failure to specify that the springs tighten about one shaft on rotation of the other renders Claim 1 not fairly based. Subject to those two matters, GC submits that Sbriggs concedes that whatever meaning is properly to be ascribed to "spring clutch" and "comprising" in Claim 1, what is claimed is: (a) inventive; (b) novel; (c) useful, in the sense that it works and further fulfils the promises in the Specification; and (d) sufficiently described in the Specification. GC's submission continues as follows: "4 There are three elements in claim 1. 'Spring clutch', 'comprising', and the integers which are identified after the word 'comprising'. 5 If it be accepted that the 'integers' component of claim 1 includes the two shaft part of the Respondent's product, that 'device' is either a 'spring clutch' or it is not. 6 If, as the Respondent alleges, it is not a spring clutch and 'comprising' means 'consisting only of', claim 1 should be invalid because the product claimed is not a spring clutch. 7 We know that claim 1 is valid. It follows that there are two possibilities. Either 'the device' referred to in paragraph 5 is a 'spring clutch' or 'comprising' means 'includes'. 8 The Respondent says, in effect, that a skilled person looking at the 'device' would know that such a 'device' was not a 'spring clutch'. If that is so, such a person would understand that if that 'device' was within the 'integers' component of claim 1, that the patentee could not be saying that such a 'device' was a spring clutch. Such a person must also conclude that 'comprising' means 'including'. 9 If that is the correct construction, the Respondent necessarily concedes that the claim is valid. 10 There is nothing untoward or impermissible in the patentee claiming any spring clutch which includes certain features which are acknowledged to be inventive. In other words, the world is free to make any spring clutch it likes with whatever features it likes provided the inventive integers/features are not used. 11 There is no dispute that the Respondent manufactures a spring clutch. The Applicants contend that it includes the integers conceded to be inventive. 12 The Applicant does not allege that only a part of the Respondent's product infringes. It alleges that the whole product infringes because either: (a) the whole product is a spring clutch which includes the features identified in claim 1; or (b) the whole product includes a spring clutch with the features identified in claim 1 to which additional features have been added." The "spring clutch comprising" issue and the expressions "spring clutch" and "comprising" I find it convenient to address the construction of Claim 1 by taking, in turn, the expressions used in it. "A spring clutch" The following dictionary definitions of "clutch" may be noted. The Macquarie Dictionary (2nd Revised Edition): "8. a device for gripping something. 9. a coupling or appliance by which working parts of machinery (as a pulley and a shaft) may be made to engage or disengage at will;" (underlining supplied) The New Shorter Oxford English Dictionary: "II clutch only. 4 Mech. An arrangement for connecting or disconnecting working parts." (underlining supplied) The word "spring" is defined as follows in the same dictionaries. The Macquarie Dictionary (2nd Revised Edition): "44. an elastic contrivance or body, as a strip or wire of steel coiled spirally, which recovers its shape after being compressed, bent, etc." The New Shorter Oxford English Dictionary: "V17 A device, usu. of bent or coiled metal, having the ability to return to its normal shape on the removal of force or pressure and used esp. to drive clockwork or for cushioning in furniture or vehicles." (underlining supplied) Apparently, then, a "spring clutch" is a device, coupling or appliance involving the use of a spring, by which working parts of machinery may be made to engage or disengage at will. It seems to me, therefore, that as a concept, a spring clutch has four functional elements: (1) an input (or driving) element to which an external source of motive force is applied or connected; (2) an output (or driven) element from which, when the clutch is engaged, torque can be transmitted to a connected "load"; (3) a spring or springs used to effect the connection between the input and the output elements by gripping the output element and transmitting torque when engaged, and conversely releasing the output element and transmitting only a residual torque when disengaged; and (4) a control element which causes the spring to grip and thereby engage, or to release and thereby disengage. That a typical spring clutch has these four elements is recognised on page 1 of the Specification in the present case. "Comprising" Both parties' submissions addressed at some length the meaning of the word "comprising" in the expression "[a] spring clutch comprising ..." and otherwise in the context of Claim 1. The word can signify "consisting of", "constituted by", "made up of" or "composed of". But it can also signify "encompassing", "containing", or "including". The following dictionary definitions may be noted. The Macquarie Dictionary (2nd Revised Edition): "1. to comprehend; include; contain. 2. to consist of; be composed of." The New Shorter Oxford English Dictionary: "2 Include, contain; extend to, encompass; consist of, be made up of. ..................................................... 4 Make up, constitute, compose; in pass., be composed of, consist of." The New Lexicon Webster's Dictionary Of The English Language: "v.t. to be made up of, consist of, the course comprises 10 lessons to include, contain, this month's figures are comprised in the total". Books on English usage suggest that while the transitive verb "comprise" was, in earlier times, thought to signify merely "include", it is now commonly used to signify the intransitive form "be composed of" or "be constituted by": cf Pam Peters (ed), The Cambridge Australian English Style Guide (Cambridge University Press, 1995) at 155; Bryan A Garner, A Dictionary of Modern Legal Usage (Oxford University Press, 2nd Edition, 1995) at 187, subnom "compose; comprise"; Fowler's Modern English Usage (Oxford University Press, 2nd Edition, 1965) at 275-276, sub nom "include, comprise"; The Penguin Working Words: An Australian Guide to Modern English Usage (Viking, 1993) at 126-127 sub nom "compose/comprise/constitute". The effect of the opinions expressed in these works is that in a construction of the kind with which we are concerned in which the subject of the verb is the noun indicating the whole as distinct from the parts, prima facie the meaning is "consists of", "is made up of", "is composed of" or "is constituted by" (but that it is a misuse of "comprise" to use it in such a sense when the parts are the subject of the verb, as in the statement "[t]wenty six letters comprise the alphabet"). Fowler, supra, refers to the distinction between "include" and "comprise" as follows: "When two words have roughly the same meaning, examination will generally reveal a distinction; and the distinction in meaning between the present two seems to be that comprise is appropriate when what is in question is the content of the whole, and include when it is the admission or presence of an item. With include, there is no presumption (though it is often the fact) that all or even most of the components are mentioned; with comprise, the whole of them are understood to be in the list. The Guards, for instance, include the Coldstreams and the Life Guards, but comprise the Household Cavalry and the Brigade of Guards. Comprise is in fact, or would be if this partly recognized distinction were developed and maintained, equivalent to be composed of, whereas include is not." (at 275) Garner, supra, offers the following opinion in relation to the words "compose; comprise"; "Correct use of these words is simple, but increasingly rare. The parts compose the whole; the whole comprises the parts; the whole is composed of the parts; the parts are comprised in the whole. Comprise, the more troublesome word in this pair, means 'to contain; to consist of.' E.g., 'The evidence clearly showed that the committee comprised members from inside as well as outside the Bank.'/ 'Every act causing an obstruction to another in the exercise of the right comprised within this description would, if damage should be caused thereby to the party obstructed, be a violation of this prohibition.'" In the absence of context and authority, I would have approached the construction of the opening expression "[a] spring clutch comprising" in Claim 1 as meaning "a spring clutch [the 'whole'] consisting of, made up of, composed of, or constituted by, the following [parts] as its essential elements as a spring clutch". I would have done so on the basis of general linguistic usage. An exercise of construction of the present kind is not usually determined by authority, but authority can bear upon it. I will refer to the authorities in chronological order. In Chain Bar Mill v Wild (1939) 56 RPC 446, Sir John Bennett, the Vice Chancellor in the Chancery of the County Palatine of Lancaster, Manchester District, said: "One would, I think, most naturally expect the word 'comprising' to be followed by several items making up the whole." and "I do not think it is a good word to express the meaning intended in the Plaintiffs' Specification and it has given rise to suggestions by no means without force that it should be construed to mean 'including among other things'." (both at 453) The Vice Chancellor concluded that the word meant "consisting of". But in the case before him, there was only one substance mentioned, of which the oven cloth in question was "comprised", namely a length of fabric. In Dreyfus' Application (1945) 62 RPC 125, claim 1 of the patent was as follows: "Process for the production of artificial filaments, fibres, threads, yarns, films, foils, and like shaped articles which comprises shaping a solution of a synthetic fibre - or film-forming polyamide and setting it in a neutral or acid liquid medium comprising aliphatic alcohol or acid, said medium being a non-solvent for the polymer." (at 131) In relation to the use of the word "comprises" in claim 1 in that case, the Patents Appeal Tribunal said that it was"doubtful whether the word signified 'consisting exclusively of'" and that "[i]t may well be that such a meaning [was] negatived by the other parts of the Specification including, for example, claim 2; ..." (at 134). In Welch Perrin & Co Pty Ltd v Worrel (1961) 106 CLR 588 there were twenty-three claims. Numbers 1 to 10 commenced "[i]n a side delivery hay rake ..." followed by words descriptive of various mechanical integers. Claims 11 to 23, on the other hand, commenced "[a] side delivery rake comprising ...". The High Court held that the difference in language had the result that in the first group of claims, the invention claimed was a component of a hay rake, but in the second group it was a rake "made up of" components described. In Minnesota Mining and Manufacturing Company v Beiersdorf (Australia) Limited (1980) 144 CLR 253, the High Court was concerned with an action for infringement of letters patent for a "breathable" adhesive surgical tape. Claim 7 commenced as follows: "7. A breathable translucent pressure-sensitive adhesive tape adapted for use as surgical tape, and comprising a translucent nonwoven inextensible porous backing ..." (underlining supplied) Implicit in Aickin J's judgment, with which the other members of the Court concurred, is a treatment of the word "comprising" as meaning "made up of". Thus, his Honour said: "The various elements which combine to make up such a surgical tape may perhaps be analysed in more than one way but the most convenient classification is to take the features which comprise such tape in three groups." (at 266 - underlining supplied) In Asahi Kasei Kogyo Kabushiki Kaisha v W R Grace & Co (1991) 22 IPR 491, Heerey J had to consider a claim defining an invention, the opening words of which were: "1. A thermoplastic multi-layer packaging film having superior heat shrink and cold seal properties comprising at least an outer polymer layer, an inner heat sealing layer and optionally an oxygen barrier layer between said inner and said outer layer, characterised in that the heat sealing layer comprises a copolymer of ethylene and x to y % by weight, ..." (at 513 - underlining supplied) His Honour noted a submission that the words "comprising" and "comprised" "were used in an inclusive sense, that is to say they did not mean 'made up of', but rather 'include'". He noted that, according to this submission, the film the subject of the claim might contain "all sorts of things not mentioned such as an oxygen barrier layer or an adhesive layer" (at 514). His Honour accepted a submission that the word "comprises" in Claim 1 meant "consists of". His Honour added, "[t]hat seems to me to be the primary natural meaning of the word 'comprise' and in this context it gives a sensible and workable meaning." (at 515 - his Honour's decision was not disturbed on appeal: (1993) 25 IPR 481 at 500-501). In N V Philips Gloeilampenfabrieken v Mirabella International Pty Ltd (1993) AIPC [91-025] (an appeal to the High Court on an issue not presently relevant was dismissed: (1995) 183 CLR 655) Lockhart J (with whom Northrop J agreed), in obiter dicta, treated the word "comprise" as synonymous with "consists of", and as distinct from "has within it" (at 39,597, column 2). In Sumitomo Electric Industries Ltd v Pacific Dunlop Ltd (1995) 33 IPR 322 the invention concerned underwater cables incorporating a "plurality of optical fibres". The claims used the word "comprising". The Delegate of the Commissioner of Patents said: "... I agree that the wording of the specification leaves something to be desired. However, I also agree that the document is readily understandable and that the claims are clear. I find that the specification satisfies the requirements of s 40 of the Patents Act." (at 333) In Dearborn Chemical Co Ltd v Rohm and Haas Co (1995) 31 IPR 121, in refusing to allow amendments to the complete specification of an opposed application, the Delegate of the Commissioner of Patents said: "The word 'comprise' was considered in Asahi Kasei Kogyo Kabushiki Kaisa v WR Grace & Co (1991) 22 IPR 491 at 514, and the subsequent decision on appeal. In that case it was decided that 'comprise' meant 'consists of' and would not cover claims in respect of an infinite number of substances which might be added. I believe a similar construction of the word is appropriate in the present situation." (at 125) These observations were made in relation to a claim that "the biocide protector 'comprises' a zinc salt and the organic biocide 'comprises' an isothiazolone" (at 124). In Hope v Heggies Bulkhaul Ltd (1996) 34 IPR 584 (patent opposition proceedings) the opponent submitted that in claim 1: "the meaning or meanings of the term 'comprising' in the expression 'comprising a mixture comprising' is or are not clear, particularly in view of the use of the term "constitute" in claim 2: see the decision in Asahi Kasei Kogyo Kabushiki Kaisha v WR Grace & Co (1991) 22 IPR 491." (at 587) The applicant submitted that: "[i]t is clear that the term 'comprising' in claim 1 should be given an exclusive interpretation: see the judgment of Heerey J in Asahi v Grace, supra, at 515 where he said that 'the word simply meant 'consists of' and would not cover claims in respect of an infinite number of substances which might be added...'" (at 590) The Delegate of the Commissioner of Patents held that: "The double use of the term 'comprising' in claim 1 is potentially unclear. From p 2 lines 2 to 6 of the specification I note '...additional ingredients can be incorporated in the mixture. These additional ingredients can be selected from any one or more of the different types of fertiliser, manure, compost, sawdust, finely divided wood chips, peatmoss, and other such substances that promote or allow plant growth, or provide a matrix for growth.' Having regard also to examples 3 and 4, I interpret the 'comprisings' of claim 1 to mean that the optional ingredients specified in claim 1, and similar such ingredients, are present only in relatively minor amounts in relation to the combined amount of coal fines and sand, but that mixture may then itself be mixed with anything from a small to a substantial amount of an ordinary soil to form the so-called 'soil substitute' of the invention. Thus, however clumsy one might consider the expression 'comprising a mixture comprising', I believe the issue is determinable and that claim 1 does not thereby lack clarity." (at 592) The above survey shows that the preponderance of authority is consistent with the construction which I outlined earlier. Conclusion on the "spring clutch comprising" issue In my opinion, the words "spring clutch comprising" signify that what is claimed is a device which possesses the four functional elements to which I referred earlier, and which consists of, is made up of, is composed of, or is constituted by, the integers described in Claim 1, and no more. The descriptions of the integers should be construed, if the construction is reasonably open, to support a finding in them of the four functional elements. Such a construction of those integers is open, and refers to a two shaft device in which the control element is built into the second shaft, as in the case of the first embodiment. Claim 1 is not, however, infringed by a spring clutch which has the four functional elements only by reason of the inclusion of a third shaft to provide the control element, as in the case of the KJW Clutch, the Valectro Clutch and the Third Clutch. It is possible to test the matter by considering the KJW, Valectro and Third Clutches, first in the absence of the third shaft, and, in the alternative, in the absence of the second shaft. In either case one would have a two shaft device. But a device of the former kind would not be a clutch because it would not be possible, by means of it, to cause "gripping", "engagement" or "connection": it would be possible only to cause "release", "disengagement" or "disconnection" (see the dictionary definitions of "clutch" given earlier). On the other hand, a device of the latter kind would not be a clutch either, because it would not facilitate "release", "disengagement" or "disconnection": it would facilitate only "gripping", "engagement" or "connection". I am conscious of the fact that Professor Frost, in answer to a question in cross examination, said that Sbriggs' device with the "cover" (the third shaft) removed was a "spring clutch" (T 89). However, he continued by acknowledging, as is, with respect, obvious, that when the device is in that state, rotation of the second shaft in either direction can cause only release of the springs; that the springs do not apply a torque other than a small residual torque; that "[t]hey do not apply a gripping torque in the sense that that is referred to in the body of the patent" (T 89); that the device cannot cause the springs to tighten; that the device can operate only in what is called, in the body of the Patent, a "disengaged state"; and that the device has no control element enabling engagement or disengagement. Professor Frost's evidence must be understood as a whole. In the light of the meaning of a "spring clutch" to which I earlier referred, I am not persuaded by the particular answer that he gave, to accept that Sbriggs' device with the "cover" removed is a spring clutch within the meaning of the Specification. It would be possible to escape the conclusion to which I have referred by construing Claim 1 as claiming any spring clutch made from a combination of integers which included, but was not necessarily limited to, the integers identified in Claim 1. However, such a construction should not be adopted for the following reasons: (a) it gives the word "comprising" the significance of "including, but not limited to", and this is a construction which is out of harmony with the usage and the authorities to which I have referred; and (b) such a construction would encompass devices that are spring clutches made up of the integers in Claim 1 together with other unidentified integers, and would therefore render Claim 1 void under s 40 for failure to define the invention (sub-s 40 (2) (b)), and failure to be clear, succinct and fairly based on the matter described in the Specification (sub-s 40 (3)), and should therefore be avoided if possible. It is important to appreciate that what I have said above suffices to resolve the issue of infringement in favour of Sbriggs. But I will proceed to consider the respective expressions used in Claim 1. The question of the correct approach to the construction of claims in patents has often been discussed. It was the subject of comment recently by a Full Court of this Court in E Street Enterprises Inc v CPS Housewares Pty Ltd (1996) 36 IPR 431. I find it sufficient for present purposes, however, to set out the ten "rules of construction" distilled by Sheppard J in Decor Corporation Pty Ltd v Dart Industries Inc (1988) 13 IPR 385 (FCA/FC) (at 400): "(1) The claims define the invention which is the subject of the patent. These must be construed according to their terms upon ordinary principles. Any purely verbal or grammatical question that can be answered according to ordinary rules for the construction of written documents is to be resolved accordingly. (2) It is not legitimate to confine the scope of the claims by reference to limitations which may be found in the body of the specification but are not expressly or by proper inference reproduced in the claims themselves. To put it another way, it is not legitimate to narrow or expand the boundaries of monopoly as fixed by the words of a claim by adding to those words glosses drawn from other parts of the specification. (3) Nevertheless, in approaching the task of construction, one must read the specification as a whole. (4) In some cases the meaning of the words used in the claims may be qualified or defined by what is said in the body of the specification. (5) If a claim be clear, it is not to be made obscure because obscurities can be found in particular sentences in other parts of the document. But if an expression is not clear or is ambiguous, it is permissible to resort to the body of the specification to define or clarify the meaning of words used in the claim. (6) A patent specification should be given a purposive construction rather than a purely literal one. (7) In construing the specification, the court is not construing a written instrument operating inter partes, but a public instrument which must define a monopoly in such a way that it is not reasonably capable of being misunderstood. (8) The body, apart from the preamble, is there to instruct those skilled in the art concerned in the carrying out of the invention; provided it is comprehensible to, and does not mislead, a skilled reader, the language used is seldom of importance. (9) Nevertheless, the claims, since they define the monopoly, will be scrutinised with as much care as is used in construing other documents defining a legal right. (10)If it is impossible to ascertain what the invention is from a fair reading of the specification as a whole, it will be invalid. But the specification must be construed in the light of the common knowledge in the art before the priority date." There is a danger in considering the respective integers of a claim individually and in isolation as Professor Frost has done. One can easily give a literal construction as I think, with respect, he did, rather than a purposive one - perhaps an instance of "failing to see the wood for the trees". The point was made by Dixon J in Radiation Ltd v Galliers & Klaerr Pty Ltd (1938) 60 CLR 36 (at 51): "But, on a question of infringement, the issue is not whether the words of the claim can be applied with verbal accuracy or felicity to the article or device alleged to infringe. It is whether the substantial idea disclosed by the specification and made the subject of a definite claim has been taken and embodied in the infringing thing." Heeding the warnings and exhortations referred to above, I proceed to consider the terms in which Claim 1 is expressed. (i) "a first shaft". Professor Frost identified this as the central shaft of the KJW, Valectro and Third Clutches. Claim 1 does not expressly require that the central shaft be fixed. Sbriggs submits that the three Clutches said to infringe operate as spring clutches "because the central shaft is adapted to operate as a fixed hub". Unless shaft 1 is fixed, it will rotate with either the second shaft or the third shaft upon the second shaft's or third shaft's coming into contact with the tabs on the springs which grip the first shaft. Sbriggs submits that the "fixedness" of the first shaft in the KJW, Valectro and Third Clutches is an essential integer of them but is not claimed in Claim 1, and therefore, there is no infringement. Sbriggs draws attention to Claim 6, in which the first shaft is described as "a fixed hub" and suggests that this illustrates the propriety of referring to the fixed nature of the first shaft if it is an essential integer of the invention. I think that a fair and purposive reading of Claim 1 requires it to be supposed that the first shaft is a fixed hub. It is nonsensical to conceive of the device described in Claim 1 operating as a clutch unless the central shaft is fixed. The reference in the final paragraph of the Claim to the slipping of the first spring on the first shaft once the torque applied to it exceeds a predetermined value supports this construction. There is no slipping up to that point and only "slipping" (rather than rotation of the first shaft) after that point, because the first shaft is fixed. The numerous references in the body of the Specification to the first shaft as a "hub", a reference to it at page 7 of the Specification as being "held within housing 22 by screw 36 and washer 38", together with figure 1 (in appendix B to these Reasons for Judgment), also support the construction which I have suggested. (ii) "a coaxially mounted second shaft (2)". "Coaxially mounted" means "having the same or common axis of rotation". Mr Delatycki expresses doubt that, on the basis of visual inspection, the second shaft (2) can be said to be coaxially mounted with the first shaft (1). According to Mr Delatycki's affidavit, the mounting of the second shaft (2) has a "significant transverse movement" with the result that when the clutch is operating and a rotational force is applied to the second shaft (2), that shaft (2) and its axis are displaced in relation to the stationary first shaft (1) and its axis. Sbriggs submits that what brings about coaxial alignment is the mounting of the third shaft (7) on the first shaft (1) at one end and on the second shaft (2) at the other end. Sbriggs refers to the body of the Specification which, in the description of the first embodiment, refers to the maintenance of coaxial alignment by means of a ring or bearing at one end and a reduced hub diameter and "necked down housing" at the other end. Professor Frost's response is that "[a]ny minor deviation from perfect coaxial positioning during operation is ... trivial and non-essential" and that "[t]he deviation is, in any event, about the common axis of rotation, and of insignificant practical dimensions." I see no reason to disagree with this view. Visual inspection supports it. While the presence of the third shaft in the KJW, Valectro and Third Clutches does prevent some lateral movement of the second shaft which would otherwise be liable to occur, that lateral movement is, it seems to me, "trivial and non-essential" as Professor Frost says. (iii) "at least first and second springs, helically wound and coaxially disposed between said first and second shafts, for making frictional contact with said first shaft". Mr Delatycki observes that the second shaft has a large opening which extends transversely across approximately one third of its circumference and longitudinally along at least the entire distance of the springs. Sbriggs submits that the size of the gap in the second shaft signifies that the springs cannot be said to be coaxially disposed "between" the first and second shafts. I disagree. It is true that about a third of the wall of the cylinder which is the second shaft is missing, but two thirds is present and I think that the springs can be said to be coaxially disposed "between" the two shafts. (iv) "said at least first and second springs each having a tab near at least one end, said tabs being radially directed toward said second shaft". Mr Delatycki expresses the opinion that some tabs (4) of the springs (3) of the KJW Clutch and the Valectro Clutch inspected by him were not "radially directed" for at least one reason, namely, that many of them were bent and appeared to have been formed manually. Mr Delatycki asserts that: "To be radially directed, the tabs (4) must extend along a radius of the first shaft (1)." Professor Frost replies that," ... any minor deviation from the perfect extension of tabs along a radius does not defeat the correspondence between the spring clutches and the specification" and that"a reader of the Patent would correlate the tabs on the spring clutches in question with the text of the Patent specification, without any difficulty." I accept Professor Frost's evidence. "Perfect extension of tabs along a radius" is not of the essence of Claim 1. The tabs on the ends of the springs of the KJW Clutch, the Valectro Clutch and the Third Clutch are, in substance, "radially directed". (v) "said second shaft having at least first and second loadsurfaces for engaging respective ones of said tabs". Mr Delatycki gave affidavit evidence that the Valectro Clutch and the KJW Clutch have "a continuous linear surface as the load-bearing surfaces (5)." In his affidavit, Professor Frost said that the single surface labelled "5" in the photograph (see Appendix C to these Reasons for Judgment) "may be regarded as several co-planar contiguous surfaces, each of which is associated with one of the four spring tabs labelled '4' in Figure 2". Professor Frost's oral evidence included the following: "MR BANNON: Professor, you were asked some questions about the expression load surfaces?---Yes. Or questions which included those two words. What can you tell us is your understanding of the concept of a load and a load surface?---A load is either a force or a torque and a load surface is a surface which transmits either a force or helps to transmit a torque. How does that understanding fit in dealing with the item before you with the lid off, the cover off?---Well, there are surfaces in what we have been calling the second shaft which press against the spring tabs and those are the two surfaces on the second shaft which press against the spring tabs, they could be regarded as load surfaces in that they provide a point of contact between the second shaft and the spring tab and a load is transferred from the tab to that surface or vice versa and that force, acting on the spring tab, because it acts at a finite radius out from the centre of the device thereby forms a torque and the same can be said in relation to the side faces of the key which is in the outer element." (T 105) GC refers to the following parts of a letter dated 16 October 1995 from Sbriggs' solicitors to GC's patent attorneys, in which the former had no difficulty in referring to load surfaces of the clutch supplied to them by their client: "Coaxially disposed about the springs is a second shaft which includes load surfaces for engaging tangs which are located on the ends of the springs." " ..., the contact between the springs and the load surfaces is all linear and simultaneous which is a significant distinction between your client's patent and our client's product." (underlining supplied) GC also refers to a passage in that part of the Specification which describes the second embodiment (illustrated in figures 5 to 7, annexed to these Reasons for Judgment in Appendix B), and recognises that a single planar surface can be regarded as a plurality of load surfaces: "Opening 76 in housing 54 is rectangular, having axially oriented and parallel load surfaces 70 and 72. Each of these two load surfaces should be thought of as two separate surfaces, one for each spring tab, which can, but need not, be in alignment so as to form a single surface." (lines 28-32 on p 9 of the Specification) (underlining supplied) Sbriggs makes the following submission: "In construing 'second shaft having first and second load surfaces' it is relevant that this is the only integer in the claimed combination that can provide: (a) the control element, which must be present for it to be a spring clutch; (b) the sequential contact between tabs and load surfaces required by lines 22-26. Because they are load surfaces within shaft 2, of necessity shaft 2 must have 2 other surfaces so there is a gap in it. The 'load' surfaces in shaft 2 when they contact the tabs cause the spring clutch to engage. The other surfaces cause it to disengage. They are releasing or non-load surfaces. The two load surfaces expressly referred to, and the two releasing surfaces implied thereby, together form the control. A load surface is so used in the body of the specification. The load surfaces must be 'first' and 'second' in that they are so constructed, relative to the respective releasing surfaces that they will contact the tabs sequentially. The simplest way this can be done is by offset load surfaces and coplanar releasing surfaces ... . The claim is wide enough to include a reverse situation - coplanar load surfaces and offset releasing surfaces. But coplanar load surfaces and coplanar releasing surfaces would not achieve sequential contact. Reference to the body of the specification ... shows that the angles subtended by the load bearing surfaces must not be equal. If that was achieved by a coplanar contiguous surface at the load end, there would then need to be an offset at the other end to ensure the tabs when loosened move into a misaligned state for next contact with the load end. Therefore the claim can include a coplanar continuous load surface but only if the relative surface of shaft 2 is offset. Claim one does not include 2 coplanar load surfaces in shaft 2 plus an offset key in shaft 3 - it does not claim shaft 3 at all. Nor does claim 1 include coplanar load surfaces in shaft 2 plus a key in shaft 3 plus differing circumferential distances between the tabs on each end of each spring. (The latter is not claimed because it is made optional to have tabs on each end: line 14 and because it is not mentioned in the claim). Reference to the body of the specification shows three offset mechanisms have been devised: ... The offset devices of embodiments 2 and 3 are not claimed in claim 1. In the Respondent's product, the common surface of shaft 2 is not a 'load' surface: understood in the context of a spring clutch, a load surface is one through which a load can be transmitted through the gripping of springs. No such gripping occurs via shaft 2. Any sequential contact in the Respondent's product is the result not of the 'load' surface per se but (so Frost claims: ...) is the result of the differing circumferential distances between the tabs on each end of the springs. Thus the option of tabs at both ends (claim 1 line 14) becomes an essential element of the Respondent's product. Therefore no infringement. Also, on this analysis the common contacting surface of 2 is not constructed within shaft 2 so as to ensure that one tab is contacted first and its spring grips before the second tab is contacted and its spring grips. Therefore, they do not function as a first and second load surface." I accept the thrust of this submission. As ever, it is necessary to conceive of Sbriggs' three Clutches without the third shaft. In my opinion, when Claim 1 refers to "at least first and second load surfaces", it does not refer to the "only releasing" surfaces (5) of the resultant devices. Even if each of the two linear surfaces is regarded as comprising multiple co-planar surfaces, none of the latter are "load" surfaces within the meaning of Claim 1. It is, however, possible to have multiple co-planar "load" surfaces in a two shaft clutch satisfying the description in Claim 1, for example, the first embodiment with a reversal of the opening in the second shaft (in figure 2 of the Specification) so as to have offset releasing surfaces rather than offset load surfaces. However, it is necessary then to introduce additional essential integers, for example, one tab per spring and offset releasing surfaces. (vi) "rotation of one of said shafts in at least one direction causing said at least first and second springs to rotate therewith and to apply a torque in the same direction to the other of said shafts" Professor Frost says that the application of force to the spring tabs by the load surface causes the springs to "slip" around the first shaft and so to apply torque to it via friction. Mr Delatycki says that in the KJW Clutch and the Valectro Clutch, only the second shaft (2) is rotated, while the first shaft (1) remains fixed. He says that in his opinion the springs (3) are wound and the tabs (4) are formed, so that the action of the second shaft on the tabs causes the springs (3) to release from the first shaft. Professor Frost agrees, but says that Mr Delatycki's comment is consistent with the meaning of the quoted passage from Claim 1. Sbriggs submits that the releasing of the springs from the first shaft is not an application of a torque by those springs to that shaft, other than, at most, a small residual torque. Sbriggs further submits that the release of the springs is not "slippage". In my opinion, the "small residual torque" which rotation of the releasing springs applies to the first shaft does not satisfy this integer. Rather, in my view, in the context of Claim 1 this integer is referring to a tightening rotation. This construction is made clear, by the reference, in the integer next to be noted, to the exceeding of a predetermined value of torque. (vii) "said tab near said one end of said first spring making contact with said first load surface of said second shaft before said tab near said one end of said second spring makes contact with said second load surface of said second shaft, said first spring slipping on said first shaft prior to said tab near said one end of said second spring making contact with said second load surface of said second shaft if the torque applied to said first shaft exceeds a predetermined value". Mr Delatycki says that he was unable from his visual inspection of the KJW Clutch and the Valectro Clutch, to confirm whether any of the springs slipped when the clutch was in operation. Professor Frost says that the slipping can be observed by simply rotating the second shaft (2) with the fingers of one hand while holding the body of the clutch assembly in the other hand, with the output shaft (7) removed. He says that, alternatively, mere inspection of each of these Clutches with the output shaft (7) removed and the application of "a little logic" would lead a competent person to conclude, reliably and confidently, that the outcome described occurs when the output shaft is in position and the Clutch is operating in the normal manner in service. Professor Frost also replies to Mr Di Stefano's evidence that the Third Clutch differs significantly from the KJW Clutch and the Valectro Clutch. In short, Professor Frost says that the variations between the Third Clutch on the one hand and the KJW Clutch and the Valectro Clutch on the other hand, are not relevantly material. He says that all three Clutches have precisely the same essential features and the same method of operation, and that the different dimensions in certain of the components do not change the essential features of the three Clutches or their mode of operation. I accept Professor Frost's evidence in reply to Mr Di Stefano. Sbriggs points out that even if there is a difference in the tab alignment of the three Clutches, observable by the naked eye, a difference in timing of contact between the load surfaces and tabs as between the springs may occur only if the rotation of the second shaft commences when the tabs are out of alignment. One episode of rotation brings tabs into alignment. When the next episode of rotation in the same direction begins, the tabs are in alignment so that the present integer is not satisfied. Accordingly, Sbriggs submits: "Infringement is not satisfied where there is no proof that a particular integer will necessarily be present in operation, or if it is an accidental, occasional or undesired consequence." Sbriggs goes on to make the following submission: "(iii) most importantly, Frost does not adequately address the final four lines of the claim. Those lines require a certain event to occur (namely the first spring slipping on the first shaft prior to the tab on the second spring contacting the second load surface) in a particular circumstance (namely the torque applied to the first shaft exceeding a predetermined value). What is meant here is that the first spring tightens on the first shaft and thereby applies torque to it. When the torque exceeds a predetermined value, the first spring slips on the first shaft. Slippage here refers to a tightened spring moving around the first shaft as it is unable to tighten any further in response to the load applied to it. It is only after that occurs that the tab on the second spring contacts the second load surface of the first shaft. This is confirmed by the specification at pages 8-9 and throughout. It is this to which the formula applies. Unless it is so read, claim 1 has not claimed a spring clutch. It has only claimed a non-engaged device. By contrast, in the Respondent's product when shaft 2 turns: - the first spring releases on the first shaft - the first spring does not apply torque other than a residual torque to the first shaft - the first spring never slips on the first shaft - there is no predetermined value (the only given formula being inapplicable)". In my opinion, it should be accepted that the last four lines of Claim 1 refer to a tightening of the first spring on the first shaft, and to a "slipping" which will occur if the torque applied to the first shaft in tightening mode exceeds a certain predetermined value. It is true that even in the case of the three Clutches with which we are concerned, there will be, upon rotation of the second shaft, no "yielding" of the first spring, and therefore no engagement of the tab on the second spring, unless the torque applied to the first shaft by the first engaging surface of the second shaft through the first spring literally "exceeds" a certain "nominal threshold" value. But I do not think that this is what the last four lines of Claim 1 are referring to. I accept Sbriggs' submission (iii) quoted above. I accept Professor Frost's evidence that the modifications effected by Sbriggs are irrelevant for the purposes of any issue that I have to decide. In this respect, I refer to the one millimetre tolerance, the abandonment of the zinc coating on the springs, the greater width of the opening in the second shaft, and the increased thickness of the plastic mounting. Result on infringement Sbriggs' device, correctly regarded for the purpose of Claim 1 of the Patent as consisting only of two shafts and the springs, does not infringe that Claim. GC fares no better according to whether the two shafts are regarded as the first and second or the first and third shafts. In either case, what one has is not a spring clutch, and needs the third shaft to become one. Integers (v), (vi) and (vii) noted above, construed purposively in the way I have indicated, are not present in that device. INVALIDITY In the light of my conclusions on infringement above, I do not find it necessary to deal with the defence of invalidity. CONCLUSION For the foregoing reasons, the KJW Clutch, the Valectro Clutch and the Third Clutch do not infringe Claim 1 of the Patent and the application should be dismissed with costs. I certify that this and the preceding 59 pages are a true copy of the Reasons for Judgment of the Honourable Justice Lindgren. Associate: Dated: 6 June 1997 Heard: 8, 9, 10 October 1996 Last written submission received: 11 October 1996 Place: Sydney Decision: 6 June 1997 Appearances: Mr A J Bannon of counsel instructed by Clayton Utz, solicitors, appeared for the applicant. Mr J T Gleeson of counsel instructed by Moores, solicitors, appeared for the respondent.