FEDERAL COURT OF AUSTRALIA
Azuko Pty Ltd v Old Digger Pty Ltd [2001] FCA 1079
INTELLECTUAL PROPERTY – patents – alleged infringement – whether substance of invention taken – whether modification of patented invention had practical significance – consideration of essential and non-essential integers of the claims said to be infringed – whether or not an essential integer missing in the relevant patent claims – revocation – alleged anticipation – alleged prior “secret use” – whether invention “secretly used” – whether reasonable trial and experiment – whether use in the course of a confidential disclosure – whether confidential manufacture prior to application for patent amounted to “use” – consideration of historical basis for “secret use” ground of revocation – consideration of definitions of “use”, “secretly use”, “secretly used”, “not … used”, and “exploit” in current previous legislation – whether there had been a “de facto” extension of the patent term – consideration of the test of illegitimate extension of the patent term.
WORDS AND PHRASES – “use”, “used”, “secretly used”, “reasonable trial and experiment”.
Patents Act 1990 (Cth)
Patents Act 1903 (Cth)
Patents Act 1952 (Cth)
Patents and Designs Act 1932 (Imp)
Patents Act 1949 (Imp)Sale of Goods Act 1895 (SA)
Sargant Report 1931 (UK)
Statute of Monopolies 1623Birmingham Sound Reproducers Ltd v Collaro Limited [1956] RPC 232 referred to
Bramah v Hardcastle (1789) Holroyd 81 followed
Bristol-Myers Co v Beecham Group Ltd [1974] AC 646 applied
Betts v Menzies (1859) 120 ER 1181 followed
Catnic Components Limited v Hill & Smith Limited [1982] RPC 183 distinguished
Commonwealth Industrial Gases Limited v MWA Holdings Pty Ltd (1970) 180 CLR 160 applied
Fellows v Thomas William Lench (1917) 34 RPC cited
Fomento Industrial SA v Mentmore Manufacturing Co Limited [1956] RPC 87 not followed
Hudson Scott & Sons Ltd v Barringer Wallis & Manners Ltd (1906) 23 RPC 79 cited
Interlego A.G. v Toltoys Pty Ltd (1973) 130 CLR 461 cited
Merrell Dow Pharmaceuticals Inc v H V Norton & Co Ltd [1996] RPC 76 referred to
Minnesota Mining and Manufacturing Co v Beiersdorf (Australia) Ltd (1980) 144 CLR 253 referred to
Morgan v Seaward (1837) 2 M & W 544, 150 ER 874 followed
Nicaro Holdings Pty Ltd v Martin Engineering Co (1990) 91 ALR 513 referred to
Populin v HB Nominees (1982) 41 ALR 471 referred to
Radiation Limited v Galliers & Klaerr Proprietary Limited (1938) 60 CLR 36 referred to
Rodi and Wienenberger AG v Henry Showell Limited [1969] RPC 367 referred to
R v Patents Appeal Tribunal, Ex parte Beecham Group Ltd [1974] AC 646 referred to
Raleigh Cycle Coy Ltd v H Miller & Coy Ltd (1948) 65 RPC 141 referred to
Re Wheatley’s Application (1984) 2 IPR 450 distinguishedRehm Pty Ltd v Websters Security Systems (International) Pty Ltd (1988) 81 ALR 79 referred to
Robertson v Purdey (1907) 24 RPC 273 followed
State Rail Authority v Earthline Constructions (1999) 73 ALJR 306; (1999) 160 ALR 588 referred to
Welch Perrin Co…
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Details
- Case
- [2001] FCA 1079
- Decision Date
CaseChat Overview and Summary
Azuko Pty Ltd appealed against findings of the primary judge that Old Digger Pty Ltd's Premier tools infringed claims of Azuko's SDS patent and that the Giehl patent was valid. Azuko contended that the SDS patent was invalid because it lacked novelty and was obvious, having regard to the prior art base and prior information available in Australia before the relevant priority date. Azuko also argued that the Giehl patent was invalid because it had been anticipated by the Giehl patent, which had an earlier priority date. The Full Court of the Federal Court of Australia considered these issues and found in favour of Old Digger on the validity of the Giehl patent and the infringement of the SDS patent by the Premier tools.
The Court found that the Giehl patent was valid because it had not been anticipated by the earlier Giehl patent. The Court noted that the earlier Giehl patent described a compensating ring that was designed to provide an effective seal between the bore of the hole and the drill tube and to wear down at a similar rate as the drill bit. However, the earlier patent did not describe a sacrificial transmission sleeve that encircled a portion of the drill bit in such a manner as to form a continuous shroud around at least a part of the grooves so as to assist in the downward passage of the exhaust air to the face of the drill bit. The Court held that the invention claimed in the Giehl patent was not anticipated by the earlier Giehl patent.
The Court also found that the Premier tools infringed claims of the SDS patent. The Court held that the gauge sleeve on the Premier tools was a sacrificial transmission sleeve that encircled a portion of the drill bit in a manner to form a continuous shroud to assist in the downward passage of the exhaust air to the cutting face of the drill bit. The Court noted that the gauge sleeve worked in combination with the drive sub on the Premier tool to direct the flow of exhaust air, and to restrain it until released at the head of the drill bit proximate to the face of the bit. The Court held that the Premier tools were substantially as described in the body of the SDS patent and Figure 1 which accompanied the specification.
In conclusion, the Court found in favour of Old Digger on the validity of the Giehl patent and the infringement of the SDS patent by the Premier tools. The Court allowed the appeal in part, set aside the orders made at first instance that claims 2, 8, 13 and 14 of the SDS Patent were infringed and enjoined that infringement, and ordered that the appellants pay the respondent’s costs of the appeal.
The Court found that the Giehl patent was valid because it had not been anticipated by the earlier Giehl patent. The Court noted that the earlier Giehl patent described a compensating ring that was designed to provide an effective seal between the bore of the hole and the drill tube and to wear down at a similar rate as the drill bit. However, the earlier patent did not describe a sacrificial transmission sleeve that encircled a portion of the drill bit in such a manner as to form a continuous shroud around at least a part of the grooves so as to assist in the downward passage of the exhaust air to the face of the drill bit. The Court held that the invention claimed in the Giehl patent was not anticipated by the earlier Giehl patent.
The Court also found that the Premier tools infringed claims of the SDS patent. The Court held that the gauge sleeve on the Premier tools was a sacrificial transmission sleeve that encircled a portion of the drill bit in a manner to form a continuous shroud to assist in the downward passage of the exhaust air to the cutting face of the drill bit. The Court noted that the gauge sleeve worked in combination with the drive sub on the Premier tool to direct the flow of exhaust air, and to restrain it until released at the head of the drill bit proximate to the face of the bit. The Court held that the Premier tools were substantially as described in the body of the SDS patent and Figure 1 which accompanied the specification.
In conclusion, the Court found in favour of Old Digger on the validity of the Giehl patent and the infringement of the SDS patent by the Premier tools. The Court allowed the appeal in part, set aside the orders made at first instance that claims 2, 8, 13 and 14 of the SDS Patent were infringed and enjoined that infringement, and ordered that the appellants pay the respondent’s costs of the appeal.
Orders
Orders of the court
1. Appeal allowed in part.
2. Set aside that part of the orders made at first instance as declared that claims 2, 8, 13 and 14 of the SDS Patent were infringed and enjoined that infringement.
3. Appeal otherwise dismissed.
4. Order that the appellants pay the respondent’s costs of the appeal.
Background
Background to the litigation
Revocation of the patents was sought by claims of alleged invalidity that were largely common to both patents, although it was also claimed that the SDS patent was invalid because it had been anticipated by the Giehl patent, which had an earlier priority date. (The priority date of the Giehl patent was 19 April 1990. There was a dispute about the priority date of the claims in the SDS patent contained in the specification as sealed, but Digger alleged a priority date of 26 April 1990.) Azuko contended that the alleged inventions lacked novelty and were obvious, having regard to the prior art base and prior information available in Australia before the relevant priority dates. The prior art base alleged comprised the publication of a number of earlier patents, and the use of other drill assemblies said to incorporate transmission sleeves and shrouds which anticipated the inventions claimed in the patents in suit. A number of other publications in mining journals were also relied on. It was further contended that the alleged inventions had been secretly used in Australia by the inventor, Werner Giehl, before the respective priority dates of the patents, thus invalidating the patent. BACKGROUND FACTS FOUND BY THE PRIMARY JUDGE Von Doussa J made the following findings, which were not challenged on the appeal, with respect to the background facts:(a) Problems to which improvements in drilling techniques had been directedqThe subject inventions have application in exploratory drilling where cuttings from the drill hole are collected for analysis by geologists. The object is to recover the greatest possible percentage of cuttings from the drill face, free of contamination from material from elsewhere in the drill hole, and to accurately determine the depth from which a sample has been collected. Problems, to which improvements in drilling techniques have been directed, include the reduction of sample loss, and the prevention of contamination. qIn the early 1970’s, exploratory drilling was carried out by rotary drilling with tri-cone bits. Initially, cuttings from the bits were recovered by delivering high pressure air through a central duct in the drill string to the bottom of the drill hole, the cuttings being then entrained and carried to the surface by the air in the annular gap between the drill string and the wall of the hole. This mode of conveying cuttings to the surface is known as a conventional drilling system. As cuttings travel up the annular space, there is a significant risk of contamination by additional materials from elsewhere in the hole which can be collected on the way. During the 1970’s, coaxial (dual walled) drilling rods became available. With these rods, it was possible to deliver high pressure air to the bottom of the hole through one system of ducts, and to recover the cuttings combined with the air released at the bottom of the hole through another duct system, namely the central duct in the drill string. This mode of recovery of the cuttings reduced the risk of contamination from material higher in the hole collected as air returned to the surface (as with a conventional drilling system). However, contamination could still occur if material higher in the hole fell to the bottom, and intermixed with fresh cuttings as the drill string rotated.qRotary drilling with tri-cone bits was largely overtaken in the late 1970’s by the use of down hole percussion hammers, consisting of an air operated reciprocating piston which rapidly strikes the head of an anvil bit. At the same time, the drill string is rotated by mechanical force applied at the drilling rig on the ground surface, thereby rotating the bit. The components of a down hole percussive hammer include an outer sleeve or housing for the body of the hammer, an upper sub assembly which fastens the hammer to the drill string, and a lower sub assembly into which the drill bit fits and through which rotational force is applied. (The lower sub assembly is commonly referred to as the “drive sub”.) The face of the bit is armed with tungsten carbide buttons. The force of the hammer blows, transmitted to the rock at the face of the bit, breaks the rock into small fragments. qIn early models of down hole percussive hammers, air expelled after driving the hammer was exhausted through an opening at the centre of the bit face. This air flowed outwards across the face of the bit, carrying with it loose cuttings that were then carried to the surface in the exhaust air through the annular space between the drill string and the wall of the hole in the same way as the conventional drilling system used in rotary drilling. However, with the advent of coaxial drilling rods, “crossover subs” were introduced to enable the application of a reverse circulation system. The upper sub assembly incorporated external channels and a passageway leading from the annular space between the outer housing of the hammer body and the wall of the hole to the central duct in the drill string. By restricting air flow by sealing means between the upper sub assembly and the wall of the drill hole above the crossover passageways, the exhaust air and cuttings from the drill face were directed into the central duct in the drill string, and carried to the surface. qThis substantially reduced the risk of contamination from material higher in the hole, but did not reduce the risk of contamination from material in the wall of the hole from the face of the bit to the crossover sub, a distance of several feet. Over this distance, the cuttings continued to pass through the annular space between the outer sleeve of the hammer and the wall of the hole. The reverse circulation system, combined with a crossover sub, helped to reduce sample contamination, but introduced a new problem not present in conventional drilling: it was not possible to completely seal the annular space between the upper sub assembly of the hammer and the wall of the hole, as this would jam the hammer in the hole. Some gap was necessary, but through this gap, air and cuttings could escape, causing “blow back”. The greater the gap, the greater the escape of cuttings up the outside of the drill stem to the surface. Further, material from the wall of the hole could fall, and if the gap permitted, this material would drop below the sealing means, and contaminate cuttings entering the crossover sub.qThe next major improvement in reverse circulation drilling was the advent of face sampling down hole percussion hammers. The intended mode of collection of cuttings in these hammers involves the release of air at or below the drive sub, so that air travels down the outside of the drill head, then across the face of the bit carrying the cuttings to ducts in the face of the bit. These lead, in turn, to the passage in the centre of the drill string, then to the surface. The intent of this process is that cuttings are collected direct from the face of the drill bit, further reducing the risk of contamination. As with earlier forms of reverse circulation drilling, the efficiency of sample collection was influenced by the effectiveness of the sealing means employed to prevent air escaping through the annular space between the outer sleeve of the hammer and the wall of the hole. qEarly face sampling hammers included (in about 1976 or 1977) the Bakerdrill, (then some ten years later) the Bulroc, the Samplex, the Halco-Lister, the Mincon, the Klemm (Hydroc) and the Ingersol-Rand hammers, each of which Azuko pleaded as relevant prior art – either by the publication of patents of which the hammers were said to be the commercial embodiments, by their description in brochures and literature publicly available in Australia, or by their use in Australia. These hammers did not receive widespread acceptance in the mining industry in Australia. Indeed, apart from a version of the Bulroc hammer (which differed from the preferred embodiment described in the Bulroc patent) the hammers were hardly used, but remained with suppliers as display items. There was evidence that the Bulroc hammer was tested by a number of drilling companies, but it seems that its commercial use in Australia was limited. The industry perception was that the drilling capability of the hammer was slow, and, more important for present purposes, the sampling efficiency was inadequate. The hammer did not recover a sufficient proportion of the cuttings. qBefore the priority dates of the subject patents, it was common general knowledge in the drilling industry that the efficiency of sample recovery in face sampling reverse circulation drilling depended, in part, upon the effectiveness of the sealing means engaged to prevent blow-back of air. It was generally thought that if the annular space between the outer sleeve of the hammer and the hole could be sufficiently sealed, enough exhaust air from the hammer would flow into the ducts in the face of the drill bit to ensure that a sufficient sample was returned to the surface through the central passage inside the drill string. It was generally understood that the sealing means should be near the lower end of the down hole hammer, so as to minimise the risk of contamination, and of air dissipating into the surrounding strata. A complete seal was practically impossible, as this would cause the hammer to jam in the hole. Features of some of the prior art patents were directed to achieving sealing means between the hammer and the wall of the hole. It was also generally understood that sample recovery was assisted by directing airflow, which exhausted from the hammer through the drive sub, towards the head of the bit. qAnother drilling problem arose from inevitable wear to the tungsten carbide buttons on the drill bit. The diameter of the hole being drilled is determined by the outermost buttons forming the gauge row. As the gauge row buttons wear, the diameter of the hole diminishes, thus narrowing the annular gap between the outer housing of the hammer and the wall of the hole. Before the introduction of a compensating sleeve (fitted to the outer surface of the housing of the hammer) which wore down in sympathy with the wearing of the gauge row buttons, the reducing diameter of the hole led to a risk of the hammer jamming. Jamming, at the least, causes unproductive down time; and, at worst, may lead to the loss of expensive equipment down the hole, and the abandonment of the hole. Drillers were faced with a dilemma: if a drilling pass commenced with a drill bit that provided minimal clearance between the outer housing of the hammer and the wall of the hole, a good recovery was initially achieved, but the length of the pass possible before the risk of jamming occurred was diminished. Alternatively, if a gap was initially provided which allowed for wear of the bit as the hole deepened, the efficiency of the sample recovery was compromised.qOne of the patents pleaded by Azuko as an anticipation of the inventions claimed in the patents in suit was Australian Patent, application no. 43643/89, published on 26 April 1990 (the DTA compensating ring patent). The application was filed by Digger (then named Drilling Tools Australia Pty Ltd (“DTA”)), for a “Compensating Ring for a Down Hole Hammer”. The invention described in the application was “a sacrificial compensating ring … designed to provide an effective seal between the bore of the hole and the drill tube and to wear down at a similar rate as the drill bit to maintain such seal as the drill bit wears”. The specification stated that “[s]acrificial in the context of the present invention means that the compensating ring is intended to be consumed in drilling much the same as the drill bit is”. The compensating ring had been invented and developed by four of DTA’s personnel at that time – Brian Sanfead, John Elsby, John Urquhart Dewar and Andrew Greathead. Messrs Elsby, Greathead and Sanfead were also the inventors of the invention the subject of the SDS patent. DTA had started to develop a prototype reverse circulation hammer in late 1987. The potential for such hammers was seen as promising and a period of twelve months rigorous testing was undertaken by the company. This led to the development of the compensating ring.qThe incorporation of features reflecting the above-mentioned common knowledge into those face sampling reverse circulation hammers which preceded embodiments of the patents in suit did not satisfactorily overcome the problem of inefficient sample recovery. A continuing problem was described in the preamble in the body of the specification of the Giehl patent as follows:“Australian Patent Application No. 80143/87 … describes an arrangement characterised by a drill stem comprising coaxial air ducts. Compressed air flows down one of the ducts to a reciprocating valveless motor. The other air duct is connected to the collection ducts. The arrangement allows for collection of material chips from a known drill depth with minimal contamination of other materials from other depths and sources. Such an arrangement has proved to be of significant improvement compared to previous arrangements. But, there has been a problem of significant loss of chips recovered from the cutting head. Experimentation has shown that the air transports only about 70% of the chips [to] the surface.To discover the cause of loss of chips has required very extensive investigations, trials and discovery. The chips form a very important source of information regarding the cut material. This is particularly the case where substances drilled for are found only in small concentrations.Accordingly, the problem has been to provide an arrangement and method by which some greater efficiency of drilling and collection of chips can be achieved.”[Australian Patent Application No. 80143/87, upon grant became the 1987 Giehl patent (discussed later) which, Azuko contended, anticipated the Giehl patent in suit.]The consistory clause describes the invention in the subject Giehl patent as follows:“The invention may be said to reside in a drill bit assembly … the bit having a plurality of outermost channels extending in direction parallel to the axis of the bit down the outer side of the bit and having a collection duct or ducts passing through the bit with its collection opening or openings through the face of the bit and an outlet at the axially aligned opposite end of the bit, and an outermost cover acting as a shroud which is located to engage against and extend around the outer side of the drill bit and form with the channels conduits which are shaped and positioned so that air flow to clear the cuttings will be directed by reason of passage through … one or more of the conduits directly at the periphery of the cutting face of the bit for subsequent passage across the face of the bit to the collection opening or openings …” (emphasis added by his Honour).The specification goes on to explain:“What appears to happen with such an assembly is that the air is constrained within the conduit shape defined by the respective channel and the enclosing shroud and it is therefore caused to flow in strongly directed manner directly at the periphery of the cutting face of the bit and thereby over the periphery of the working face and thence across the face.”qThe continuing problem, which still existed in April 1990, is described in more detail in the preamble in the body of the specification of the SDS patent:“In general, in the art of reverse circulation drilling, a relatively small annular clearance, of typically 3mm, is provided between the drill tube and the bore of the hole being drilled. The clearance must be kept relatively small so that air preferentially travels around the drill bit and forces the rock cuttings from the bottom of the hole through a passageway in the drill itself and the drill string to the surface by the action of compressed air exhausted around the sides of the drill bit and at the face of the bit. To further minimise leakage of air and/or rock cuttings into the annular space, the exhaust ports at the sides of the drill bit, and the drive sub or chuck must be adapted so as to direct air to the face of the bit. A further requirement of reverse circulation drilling is [to] maximise the recovery of rock sample from the bottom of the hole. This aim is achieved in practice by having the maximum outside diameter of the drill bit as close as possible to the maximum outside diameter of the drill tube. However, as the cutting face of the drill bit bores out the hole, it wears down and becomes smaller in diameter. When the diameter of the drill bit approaches that of the drill tube, the drill bit would normally be replaced to prevent damage to the drill tube occurring through contact between the drill tube an[d] the wall of the hole.If a drill bit is used with a maximum outside diameter greater than that of the drill tube, the clearance between the drill tube and the bore of the hole is increased. This type of arrangement leads to longer bit life but increases the leakage of air into the annular clearance, reduces the rate of sample recovery and results in higher sample contamination.”q(As has been noted above) the combination of the integers comprising the invention described in the SDS patent is said to address these problems, since the transmission sleeve (a) is sacrificial in that it is intended to be consumed in drilling in much the same way as the drill bit; it is intended to wear preferentially avoiding the replacement of other more expensive components, and allows the use of larger drill bits for a given diameter drill tube than would otherwise be the case; (b) provides an improved and effective seal between the bore hole and the drill tube throughout the lifetime of the drill bit, because it seals the hole closer to the face of the bit, and the seal is maintained over a longer length; and (c) provides an improved rate of sample recovery, without undue sample contamination or undue air consumption, by releasing the exhaust air from the hammer closer to the face of the drill bit.(b) The SDS hammers
Evidence
Evidence Before The Court
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Decision
Reasons for decision
The invention the subject of the Giehl patent was made by Werner Giehl. Mr Giehl’s tertiary training and earlier professional experience was as a surgical and orthopaedic instrument maker; but, since 1968, he had also designed and manufactured items of drilling equipment. At the time that he applied for patent protection for his invention (the provisional specification was filed on 19 April 1990) he was not associated with Digger, which later acquired the invention from him. Digger was the owner of the patent at the time that Joseph Purcell worked for SDS; and he was aware of it when designing the Premier tools.THE PRIMARY JUDGE’S FINDINGS AND CONCLUSIONS ON THE SDS INFRINGEMENT CLAIM His Honour’s process of reasoning towards his findings and conclusions was as follows:·It is helpful to compare Fig. 1 from the SDS patent specification (relating to the preferred embodiment of the invention) with a comparable drawing of a Premier tool prepared by Joseph Purcell. The figure from the SDS patent is descriptive of the commercial embodiment of the invention in the SDS hammers, although it must be borne in mind that the relevant comparison that must be made in determining infringement is not between the features of the SDS hammers and Premier tools, but between the claims in the patents and the Premier tools. Figure 1 is as follows:Figure 1 is relevantly described in the SDS specification as follows:“Shown in figure 1 … is a down hole hammer 10 comprising a drill bit 12 having air passages 13, a cutting face 14 and a plurality of apertures 16 extending into a central aperture 18. The drill bit 12 is retained in a drill bit retaining means in the form of a drive sub 20 [or chuck] by slip split rings 22 and splines 23 which are dimensioned so as to allow for exhaust air passages 13 between the drill bit 12 and the drive sub 20 in known manner. The drive sub 20 is held in an outer sleeve 24 typically by way of a threaded portion 26 of the outer sleeve 24. The outer sleeve 24 surrounds porting means (not shown) of known type to enable a piston (not shown) to reciprocally strike the bit 12 in known manner. … Longitudinally intermediate of the outer sleeve 24 and the drive sub 20 is a sacrificial transmission sleeve 28 having a body 29 comprising a first inner surface 30 substantially conforming to the drive sub 20 and a second outer surface 32. … As may also be seen, the body 29 is partially proud of the outer sleeve 24.Preferably, the diameter of the transmission sleeve 28, as measured at the body 29 … is substantially the same as that of the drill bit 12.The transmission sleeve 28 further comprises an annular flange 38 extending from the body 29 of the transmission sleeve 28 towards the drill bit 12. The flange 38 is disposed with an interior surface 40 overlying the drive sub 20 extending beyond the drive sub 20 towards the drill bit 12.…The flange 38 is adapted to encircle a portion of the drill bit which defines longitudinal grooves forming the exhaust air passages 13 in the sides of the bit in such a manner as to form a continuous shroud around at least a part of the grooves so as to assist in the downward passage of the exhaust air to the face of the drill bit 12. …The transmission sleeve 28 of the present invention serves to provide a more effective seal with the hole 108 than the compensating ring of our earlier Australian Patent Application No. 43643/89, as it seals the hole 108 closer to the face 14 of the drill bit 12. Further, the flange 38 allows the seal to be maintained over a longer length. This reduces the chances of sample contamination and/or increased air consumption.·It was common ground that “transmission sleeve 28” is so described above because it transmits air in the manner described in the specification.·The Premier tools incorporate a gauge sleeve which in shape, dimensions and position is similar to the transmission sleeve in the SDS hammer. The Premier gauge sleeve has a body and an annular flange. The outer diameter of the body of the gauge sleeve is greater than the outer diameter of the outer sleeve (the hammer housing) and substantially the same diameter as the drill bit. The annular flange has a diameter which is substantially the same as the drill bit. Moreover, the Premier gauge sleeve extends from the body towards the drill bit. These are features of the sacrificial transmission sleeve claimed in claim 1 of the SDS patent. However, as can be seen from the above diagrams, the gauge sleeve in the Premier hammers does not extend in an axial direction downward from the drive sub. In the Premier hammers, the drive sub has been extended so that it terminates flush with the lower end of the gauge sleeve.·The Premier tools comprise a hammer of the type described, and claimed, in the SDS patent. The expression “drill bit retaining means” is not an engineering term; it carries its ordinary meaning. The SDS patent describes the drill bit retaining means as being in the form of a drive sub. The Premier tools plainly have a drill bit retaining means of the kind described in the SDS patent. Further, the Premier tools are used with a gauge sleeve that is “sacrificial” in nature. The gauge sleeve fitted to the Premier tools is consumed in much the same way as the drill bit; and it wears in preference to other components of the hammer assembly, and, in particular, the outer housing of the hammer and the drive sub. ·In their defence, Azuko contended that whilst the gauge sleeve of the Premier tool is sacrificial, it is not a “transmission” sleeve within the meaning of the SDS claims, as it does not transmit air; because it does not transmit air, the gauge sleeve simply fulfils the function of a compensating ring, like that described in the DTA compensating ring patent (above); in the Premier tools, the transmission of air is performed by the drive sub which ends flush with the gauge sleeve. Azuko further contended that the wear characteristics of the Premier gauge sleeve are not “similar to that of the drill bit”; and that the Premier gauge sleeve does not wear at a “similar rate” within the meaning of the final integer of claim 1 in the SDS patent.·On a literal construction of the claims, a gauge sleeve, to meet the description “transmission sleeve” will be a sleeve that transmits air. In the manner in which the Premier tools have been designed and manufactured, the gauge sleeve is not performing that function. But authorities (see below) teach that infringement is a question of fact, and infringement may occur where the respondent “takes the substance of the invention, yet stays outside the express words of the claim, unless the wording of the claim makes it clear that the relevant area has been deliberately left outside the claim”. ·The extension of the Premier drive sub is a minor variation, a “trifling variation of no mechanical significance”. The configuration of the extended portion of the drive sub in the Premier tools, which masks the inner surface of the gauge sleeve, serves merely to replace channels formed in the bit and enclosed by the inner surface of the transmission sleeve described in the SDS patent with mirror image channels formed in the drive sub, and enclosed by the surface of the drill bit. In normal operation, the variation does not result in the Premier tool losing any of the advantages of the invention claimed in the SDS patent. The Premier tool is “the functional equivalent” of the SDS invention. This is a plain case of Azuko taking “the substantial idea” disclosed in the specification of the SDS patent and “seeking to avoid the literal meaning of the claims by a contrived modification that has no practical significance in the normal operation of the drilling apparatus”.·By their terms, none of the claims indicates that a modification of the kind undertaken by Azuko has been deliberately left outside the scope of any of the claims. Rather, the body of the SDS patent specification concludes with the statement that:“Modifications and variations such as would be apparent to a skilled addressee are deemed within the scope of the present invention.” ·A modification of the kind made by Azuko would be apparent to a skilled addressee, particularly having regard to claim 5 and the accompanying figure representing that embodiment.·The gauge sleeve on the Premier tools acts to seal the annular space between the hammer assembly and the bore hole much closer to the face of the bit than was known before April 1990. The gauge sleeve works in combination with the drive sub on the Premier tool to direct the flow of exhaust air, and to restrain it until released at the head of the drill bit proximate to the face of the bit. The gauge sleeve is also a sacrificial component of the Premier tools.·In relation to claim 2 of the SDS patent, Azuko contended that even if the drive sub and gauge sleeve are treated as a combined item which constrains and directs exhaust air until released, the gauge sleeve and drive sub do not encircle a portion of the drill bit “in such manner as to form a continuous shroud to assist in the downward passage of the exhaust air to [the] cutting face of the drill bit”. But the Premier drive sub/gauge sleeve combination does encircle a portion of the length of the drill bit in a manner to form a continuous shroud to assist in the downward passage of exhaust air to the cutting face of the drill bit. This arrangement in the Premier tool shrouds the longitudinal grooves in the side of the drill bit head at their commencement in the shoulder of the bit; and it directs the passage of exhaust air into these grooves, and directly at the cutting face, particularly when the hammer is operating in the closed (i.e. normal operating) position. The Premier tools, like Digger’s hammers, are designed and intended for use in hard conditions. The expert evidence demonstrated that the operating gap between the weight bearing surface of the drive sub and the shoulder of the head of the bit would be very small, and not such that the combination of the gauge sleeve and a drive sub in Premier tools would not perform the function of directing exhaust air into the longitudinal grooves of the drill bit proximate to the cutting face.·It is not a requirement of either claim 1 or claim 2 of the SDS patent that the sacrificial transmission sleeve encircle and cover part of the head of the drill bit below the weight bearing shoulder. There is nothing in the claims in the SDS patent, or in the specification, to suggest such a requirement.·The gauge sleeve on the Premier tools is clamped to the hammer between the outer sleeve of the hammer and the drill bit retaining means, namely the drive sub, and that integer of claim 3 is present. ·In the result, the Premier tools infringe claims 1, 2, 3, 7, 8, and 9 of the SDS patent. The Premier tools also infringe the omnibus claims in claims 13 and 14, which incorporate the drawings into the claim. The Premier tools are substantially as described in the body of the SDS patent and Figure 1 which accompanies the specification.
Ratio Decidendi
Legal Principle Established
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