Free World Trust v. Électro Santé Inc., 2000 SCC 66, [2000] 2 SCR 1024

Free World Trust v. Électro Santé Inc., [2000] 2 S.C.R. 1024

Free World Trust         Appellant

v.

Électro Santé Inc., Paul Demers and Noël Desjardins                    Respondents

and

Promotion R.A.S. (1992) Inc. and Électronique SEM Inc.              Plaintiffs before

the Superior Court

and

Procter & Gamble Inc.                                                                      Intervener

Indexed as:  Free World Trust v. Électro Santé Inc.

Neutral citation:  2000 SCC 66.

File No.:  26406.

1999:  December 14; 2000:  December 15.

Present:  L’Heureux‑Dubé, Gonthier, McLachlin, Iacobucci, Major, Bastarache and Binnie JJ.

on appeal from the court of appeal for quebec

Patents – Infringement – Validity – Scope and ambit of patent owner’s monopoly – Anticipation by publication – Extent to which patent monopoly protects “substance” of invention – Whether claims patented sufficiently elastic to catch competitor’s machine.

The appellant is the owner of two patents of invention issued in 1981 and 1983 which relate to an apparatus that bombards different parts of the human body with low frequency electro-magnetic waves.  The system discovered by the appellant was for a new method of controlling the amplitude and frequency of the electro‑magnetic waves by “circuit means”.  The respondent company developed and marketed an apparatus which achieved similar therapeutic purposes, but employed somewhat different technology, using instead a “microcontroller”.  The appellant acknowledged the difference, but argued that the end result was the same and therefore its patent monopoly was infringed.  The trial judge ruled the patents anticipated and thus invalid.  The Court of Appeal reversed the finding of invalidity but found there was no infringement.

Held:  The appeal should be dismissed.

The interpretive task of the court in claims construction is to separate and distinguish the essential from the inessential and to give to the “field” of the monopoly framed by the essential elements of the claims the legal protection to which the holder of a valid patent is entitled.  The essential elements common to the claims of both patents in suit include a control to regulate the peak amplitude and frequency of electro‑magnetic waves by “circuit means”.  The claimed invention effected an ingenious combination rather than a mere aggregation of previously known components.  The invention was not anticipated by a prior publication that did not address the technical problems dealt with in these patents.

The more difficult issue is how best to resolve the tension between “literal infringement” and “substantive infringement”.  The Patent Act  seeks both fairness and predictability.  Its objective of promoting research and development would be undermined if competitors fear to tread in the vicinity of the patent because its scope lacks a reasonable measure of precision and certainty.  Predictability is achieved by tying the patentee to its claims and fairness is achieved by interpreting those claims in an informed and purposive way.

The greater the level of discretion left to courts to peer below the language of the claims in a search for the “spirit of the invention”, the less the claims can perform their public notice function, and the greater the resulting level of unwelcome uncertainty and unpredictability.  “Purposive construction” does away with a purely literal interpretation but disciplines the scope of the “substantive” claims construction in the interest of fairness to both the patentee and the public.  Some elements of a claimed invention are essential while others are non‑essential.  These are identified, on the basis of the common knowledge of the worker skilled in the art to which the patent relates as of the date the patent is published (under the current provisions of the Patent Act  the date of publication is the “laid open” date).  There is no infringement if an essential element is different or omitted in the allegedly infringing device, but there may still be infringement if non‑essential elements are substituted or omitted.  For an element to be considered non‑essential and thus substitutable, it must be shown either that on a purposive construction of the words of the claim it was clearly not intended to be essential, or that at the date of publication of the patent, the skilled addressee would have appreciated that a particular element could be substituted or omitted without affecting the working of the invention.

Based on the foregoing principles, the respondents' device does not infringe.  The ingenuity of these patents lay not in their identification of a desirable result but in teaching particular means to achieve it.  The claims cannot be stretched to allow the patentee to monopolize anything that achieves the desirable result.  The respondents' device differs both structurally and operationally from the device contemplated in the claims.  The use of a “microcontroller” substituted a totally different technology and was fatal to the appellant's allegation of infringement.

Cases Cited

Referred to: Clothworkers of Ipswich Case (1653), Godb. 252, 78 E.R. 147; Minerals Separation North American Corp. v. Noranda Mines, Ltd., [1947] Ex. C.R. 306; Consolboard Inc. v. MacMillan Bloedel (Sask.) Ltd., [1981] 1 S.C.R. 504; General Tire & Rubber Co. v. Firestone Tyre & Rubber Co., [1972] R.P.C. 457; Beloit Canada Ltd. v. Valmet OY (1986), 8 C.P.R. (3d) 289; The King v. Uhlemann Optical Co., [1952] 1 S.C.R. 143; Domtar Ltd. v. MacMillan Bloedel Packaging Ltd. (1977), 33 C.P.R. (2d) 182; Grip Printing and Publishing Co., of Toronto v. Butterfield (1885), 11 S.C.R. 291; Graver Tank & Mfg. Co. v. Linde Air Products Co., 339 U.S. 605 (1950); Electrolier Manufacturing Co. v. Dominion Manufacturers Ltd., [1934] S.C.R. 436; Smith Incubator Co. v. Seiling, [1936] S.C.R. 251; J. K. Smit & Sons, Inc. v. McClintock, [1940] S.C.R. 279; Gillette Safety Razor Co. of Canada v. Pal Blade Corp., [1933] S.C.R. 142; Warner-Jenkinson Co. v. Hilton Davis Chemical Co., 520 U.S. 17 (1997); Clark v. Adie (1873), L.R. 10 Ch. 667; Electric & Musical Industries Ld. v. Lissen Ld. (1939), 56 R.P.C. 23; Catnic Components Ltd. v. Hill & Smith Ltd., [1982] R.P.C. 183; Interpress Associates Ltd. v. Pacific Coilcoaters Ltd. (1994), 29 I.P.R. 635; Smale v. North Sails Ltd., [1991] 3 N.Z.L.R. 19; Populin v. H.B. Nominees Pty. Ltd. (1982), 59 F.L.R. 37; Rhone-Poulenc Agrochimie SA v. UIM Chemical Services Pty. Ltd. (1986), 68 A.L.R. 77; Multotec Manufacturing (Pty.) Ltd. v. Screenex Wire Weaving Manufacturers (Pty.) Ltd., 1983 (1) SA 709; Sappi Fine Papers (Pty.) Ltd. v. ICI Canada Inc. (Formerly CIL Inc.), 1992 (3) SA 306; Improver Corp. v. Raymond Industrial Ltd., [1991] F.S.R. 233; Eli Lilly & Co.v. O'Hara Manufacturing Ltd. (1989), 26 C.P.R. (3d) 1; R. v. Nova Scotia Pharmaceutical Society, [1992] 2 S.C.R. 606; R.C.A. Photophone, Ld. v. Gaumont-British Picture Corp. (1936), 53 R.P.C. 167; Western Electric Co. v. Baldwin International Radio of Canada, [1934] S.C.R. 570; Mobil Oil Corp. v. Hercules Canada Inc. (1995), 63 C.P.R. (3d) 473; Computalog Ltd. v. Comtech Logging Ltd. (1992), 44 C.P.R. (3d) 77; Feherguard Products Ltd. v. Rocky's of B.C. Leisure Ltd. (1995), 60 C.P.R. (3d) 512; Cutter (Canada) Ltd. v. Baxter Travenol Laboratories of Canada Ltd. (1983), 68 C.P.R. (2d) 179; Johnson Controls, Inc. v. Varta Batteries Ltd. (1984), 80 C.P.R. (2d) 1; Whirlpool Corp. v. Camco Inc., [2000] 2 S.C.R. 1067, 2000 SCC 67; Whirlpool Corp. v. Maytag Corp., [2000] 2 S.C.R. 1116, 2000 SCC 68; Improver Corp. v. Remington Consumer Products Ltd., [1990] F.S.R. 181; Biogen Inc. v. Medeva PLC, [1997] R.P.C. 1; Dyson Appliances Ltd. v. Hoover Ltd., [2000] E.W.J. No. 4994 (QL); AT & T Technologies, Inc. v. Mitel Corp. (1989), 26 C.P.R. (3d) 238; Lovell Manufacturing Co. v. Beatty Bros. Ltd. (1962), 23 Fox Pat. C. 112; P.L.G. Research Ltd. v. Jannock Steel Fabricating Co. (1991), 35 C.P.R. (3d) 346; Foseco Trading A.G. v. Canadian Ferro Hot Metal Specialties, Ltd. (1991), 36 C.P.R. (3d) 35;  Incandescent Gas Light Co. v. De Mare Incandescent Gas Light System, Ld. (1896), 13 R.P.C. 301.

Statutes and Regulations Cited

Convention on the Grant of European Patents (European Patent Convention), October 5, 1973.

Patent Act, R.S.C., 1985, c. P-4, ss. 10  [rep. & sub. c. 33 (3rd Supp.), s. 2 ; rep. & sub. 1993, c. 15, s. 28], 27(1), 28(2), 34, 44, 55(2) [rep. & sub. c. 33 (3rd Supp.), s. 21 ; rep. & sub. 1993, c. 15, s. 48].

Statute of Monopolies (1623).

Authors Cited

Annand, Ruth E.  “Infringement of Patents —  Is “Catnic” the Correct Approach for Determining the Scope of a Patent Monopoly Under the Patents Act 1977?” (1992), 21 Anglo-Am. L. Rev. 39.

Boudreau, Jean-Claude.  “AT&T Technologies: A Contribution to the Purposive Construction Approach for Patent Infringement Analysis in Canada” (1998-99), 15 C.I.P.R. 323.

Fox, Harold G.  The Canadian Law and Practice Relating to Letters Patent for Inventions, 4th ed.  Toronto: Carswell, 1969.

Goldsmith, Immanuel.  Patents of Invention.  Agincourt, Ont.: Carswell, 1981.

Hitchman, Carol V. E., and Donald H. MacOdrum.  “Don't Fence Me In:  Infringement in Substance in Patent Actions” (1990-91), 7 C.I.P.R. 167.

Sajewycz, Mark.  “Patent Claim Interpretation as It Should Be:  Promoting the Objects of the Patent Act ” (1996-97), 13 C.I.P.R. 173.

Scott, David W.  “The Record of Proceedings in the Patent Office in Canada & Foreign Countries as Evidence in Infringement & Validity Contests” (1985-86), 2 C.I.P.R. 160.

Solov'eva, G. R.  “Instrumentation and Applications of Low-Frequency Magnetotherapy” (1975), 8 Biomedical Engineering 166.

Sotiriadis, Bob H.  “Purposive Construction in Canadian Patent Infringement Cases Since O'Hara” (1996), 11 I.P.J. 111.

Takenaka, Toshiko.  “Doctrine of Equivalents after Hilton Davis:  A Comparative Law Analysis” (1996), 22 Rutgers Computer & Tech. L.J. 479.

Terrell on the Law of Patents, 15th ed.  By S. Thorley, R. Miller, G. Burkill and C. Birss.  London: Sweet & Maxwell, 2000.

Turner, Jonathan D. C.  “Purposive Construction:  Seven Reasons Why Catnic is Wrong” (1999), 21 E.I.P.R. 531.

APPEAL from a judgment of the Quebec Court of Appeal[1997] R.J.Q. 2907, 81 C.P.R. (3d) 456, [1997] Q.J. No. 3479 (QL), allowing in part the appellant’s appeal from a judgment of the Superior Court, holding that the appellant’s patents were invalid and that they had not been infringed by the respondents.  Appeal dismissed.

Louis Masson and Nathalie Vaillant, for the appellant.

No one appeared for the respondents.

Bruce W. Stratton and Dino P. Clarizio, for the intervener.

The judgment of the Court was delivered by

1                                   Binnie J. – The principal question that arises on this appeal is the extent to which a patent monopoly protects “the substance” or “the spirit” of an invention, as distinguished from what is literally described in the written claims, and whether on the facts of this case the claims patented by the appellant are sufficiently elastic to catch the electro-magnetotherapy machine of the respondent Électro Santé Inc.

2                                   More specifically, the appellant concedes that the respondents' machine, which is used in the treatment of such bodily ills as rheumatism and arthritis, is not precisely as described in the written claims of its patents.  It says, however, that the respondents have stolen the substance of its invention and claims an injunction plus compensatory and punitive damages.

3                                   The appeal thus raises important questions about the scope and ambit of a patent owner's monopoly.  Too much elasticity in the interpretation of the scope of the claims creates uncertainty and stifles competition.  Too little protection robs inventors of the benefit they were promised in exchange for making a full and complete disclosure of the fruits of their ingenuity.  The Quebec Court of Appeal held that the respondents' machines took neither the letter nor the substance of the appellant’s patents.  I think this conclusion was correct, although I get there by a somewhat different route.  The appeal must therefore be dismissed.

I.  Facts

4                                   The appellant, Free World Trust, is the owner of two patents of invention numbered 1,113,156 (the “'156 patent”) and 1,150,361 (the “'361 patent”) issued in 1981 and 1983 respectively.  The patents relate to an apparatus that bombards different parts of the human body with low frequency electro-magnetic waves.  Electro-magnetotherapy is not new, but the appellant persuaded the Commissioner of Patents that it had discovered a new method of controlling the amplitude and frequency of the electromagnetic waves by “circuit means” with desirable and beneficial effects.  The appellants put the invention described in these patents on the market in the form of an apparatus called Rhumart, which was a commercial success.  In 1991, the appellant sold 3,525 Rhumart systems for a total of $13,683,240.

5                                   On March 4, 1992, the respondent Paul Demers, one of the appellant’s sales representatives, quit his employ with the appellant and started the respondent company for the purpose of developing and marketing electro-magnetotherapy machines in competition with his former firm.  Within approximately six months of Demers' departure from the appellant company, the “new” product was on sale.  The respondent Noël Desjardins, formerly an independent distributor for the Rhumart system, joined Demers to provide distribution and marketing expertise.

6                                   The respondents' apparatus (which it called “Électro-Santé”) achieved similar therapeutic purposes, but employed somewhat different technology.  The present controversy revolves around these differences, and whether they are sufficiently substantial to put the respondents outside the appellant's monopoly.  Of particular importance is the fact that the appellant's patents teach the use of “control circuits” to regulate the magnetic field of waves or pulses whose frequency, orientation and amplitude are critical to therapy.  Its Rhumart apparatus employed such “control circuits”.  The respondents' Électro-Santé machines, on the other hand, used a “microcontroller” which, according to the appellant's own expert, is a [translation] “highly versatile element, similar to an IBM PC computer or the like”.  He acknowledged that this method of regulating the magnetic field is different from what is contemplated in the claims of the patent.  The appellant's position, however, is that the end result was the same and that its monopoly was thereby infringed.

II.  Judgments

1.  Trial Judgment (Quebec Superior Court -- Bergeron J.)

7                                   The trial judge ruled against the validity of the patents obtained by the appellant.  The Patent Act, R.S.C., 1985, c. P-4 , provides that a patent cannot be granted for an invention in a publication printed in Canada or in any other country more than two years prior to the patent application (ss. 27(1)  and 28(2) ).  In Bergeron J.'s view, the invention described in the patent claims was anticipated by a 1975 article authored by G. R. Solov'eva, entitled “Instrumentation and Applications of Low-Frequency Magnetotherapy”.  The Solov'eva article, he concluded, conveys all of the fundamental elements needed to produce the claimed invention, thereby rendering the patents anticipated and thus invalid:

[translation]  In my view, the Solov'eva article discloses all of the fundamental elements necessary to allow a person skilled in the art or science of the relevant field to make or construct the invention.  We find present in this article all the essential characteristics described in the patent claims.  This is a publication that describes the invention that is the subject of patents 1,113,156 and 1,150,316.

In light of this conclusion, Bergeron J. dismissed the action without expressing an opinion on the issue of patent infringement.  The allegation of unfair competition on the part of the respondents Demers and Desjardins was also rejected.

2.  Court of Appeal (Rousseau-Houle J.A. for the Court) (1997), 81 C.P.R. (3d) 456

8                                   Rousseau-Houle J.A. cited the provision of the Patent Act  which creates a presumption in favour of the validity of a patent.  The burden of proving the invalidity of the appellant's patents on a balance of probabilities rested on the respondents.  The respondents failed to discharge this onus.  The Solov'eva article did not contain all of the essential elements of the patent claims and a reading of it would not provide a person skilled in the art the information necessary to build, without risk of error, the patented device.  Rousseau-Houle J.A. also rejected the arguments of lack of ingenuity and inventiveness.  Accordingly, the trial finding of invalidity was reversed and patents '156 and '361 were declared valid.

9                                   On the issue of infringement, Rousseau-Houle J.A. considered the principles applicable to claims construction and noted that the appellant's case rested on an allegation of “substantive” infringement.  Rousseau-Houle J.A. identified certain differences and similarities between the Électro-Santé and Rhumart systems and concluded that there were sufficient differences to distinguish the Électro-Santé device and therefore rejected the allegation of infringement.  The appeal with respect to an injunction and damages was therefore dismissed.

10                               The respondents' trustee in bankruptcy elected not to participate in the appeal to this Court.  However, Procter & Gamble Inc. successfully applied to intervene in support of the correctness of the outcome arrived at by the Quebec Court of Appeal.

III.  Relevant Statutory Provisions

11                               As the patents in suit were issued prior to October 1, 1989, the provisions of the former Patent Act  apply.  The relevant sections of the Patent Act, R.S.C., 1985, c. P-4 , provide as follows:

Section 27(1).  [Application for Patents]

Subject to this section, any inventor or legal representative of an inventor of an invention that was

(a)  not known or used by any other person before he invented it,

(b)  not described in any patent or in any publication printed in Canada or in any other country more than two years before presentation of the petition hereunder mentioned, and

(c)  not in public use or sale in Canada for more than two years prior to his application in Canada,

may, on presentation to the Commissioner of a petition setting out the facts, in this Act termed the filing of the application, and on compliance with all other requirements of this Act, obtain a patent granting to him an exclusive property in the invention.

Section 28(2).  [Limitation of Two Years]

No patent shall be granted on an application for a patent for an invention that had been patented or described in a patent or publication printed in Canada or any other country more than two years before the date of the actual filing of the application in Canada, or had been in public use or on sale in Canada for more than two years prior to that filing.

Section 34.  [Specification]

(1)       An applicant shall in the specification of his invention

(a)  correctly and fully describe the invention and its operation or use as contemplated by the inventor;

(b)  set out clearly the various steps in a process, or the method of constructing, making, compounding or using a machine, manufacture or composition of matter, in such full, clear, concise and exact terms as to enable any person skilled in the art or science to which it appertains, or with which it is most closely connected, to make, construct, compound or use it;

(c)  in the case of a machine, explain the principle thereof and the best mode in which he has contemplated the application of that principle;

(d)  in the case of a process, explain the necessary sequence, if any, of the various steps, so as to distinguish the invention from other inventions; and

(e)  particularly indicate and distinctly claim the part, improvement or combination that he claims as his invention.

(2)  Claims to be stated distinctly–The specification referred to in subsection (1) shall end with a claim or claims stating distinctly and in explicit terms the things or combinations that the applicant regards as new and in which he claims an exclusive property or privilege.

Section 44.  [What Patent Shall Contain and Confer]

Every patent granted under this Act shall contain the title or name of the invention, with a reference to the specification, and shall, subject to the conditions prescribed in this Act, grant to the patentee and his legal representatives for the term therein mentioned, from the granting of the patent, the exclusive right, privilege and liberty of making, constructing, using and vending to others to be used the invention, subject to adjudication in respect thereof before any court of competent jurisdiction.

12                               The relevant amended provisions of the Patent Act, R.S.C., 1985, c. P-4 , as amended by S.C. 1993, c. 15, provide as follows:

Section 10 .  [Inspection by the Public]

(1)  Subject to subsections (2) to (6) and section 20, all patents, applications for patents and documents filed in connection with patents or applications for patents shall be open to public inspection at the Patent Office, under such conditions as may be prescribed.

(2)  Confidentiality period – Except with the approval of the applicant, an application for a patent, or a document filed in connection with the application, shall not be open to public inspection before a confidentiality period of eighteen months has expired.

(3)  Beginning of confidentiality period–The confidentiality period begins on the filing date of the application or, where a request for priority has been made in respect of the application, it begins on the earliest filing date of any previously regularly filed application on which the request is based.

Section 55.  [Liability for Patent Infringement]

(1)  A person who infringes a patent is liable to the patentee and to all persons claiming under the patentee for all damage sustained by the patentee or by any such person, after the grant of the patent, by reason of the infringement.

(2)  Liability damage before patent is granted–A person is liable to pay reasonable compensation to a patentee and to all persons claiming under the patentee for any damage sustained by the patentee or by any of those persons by reason of any act on the part of that person, after the application for the patent became open to public inspection under section 10  and before the grant of the patent, that would have constituted an infringement of the patent if the patent had been granted on the day the application became open to public inspection under that section.

IV.  Analysis

13                               Patent protection rests on the concept of a bargain between the inventor and the public.  In return for disclosure of the invention to the public, the inventor acquires for a limited time the exclusive right to exploit it.  It was ever thus.  Even before the Statute of Monopolies (1623), the Crown rewarded an inventor with a limited monopoly in exchange for public disclosure of “a new invention and a new trade within the kingdom ... or if a man hath made a new discovery of any thing”:  Clothworkers of Ipswich Case (1653), Godb. 252, 78 E.R. 147, at p. 148, where the court went on to say that the effect of an unjustified monopoly was “to take away free-trade, which is the birthright of every subject”.  The argument for the respondents is that the appellant has failed to live up to its side of the bargain in two ways.  In the first place, it did not make a new discovery of anything.  The appellant's patents teach nothing that was not well known beforehand.  Its patents are therefore invalid.  Secondly, even if the patents are valid, the appellant overreaches its bargain with the public by now asserting a monopoly over devices that are in no way disclosed, taught or claimed in its patents.  The appellant is trying to get something for nothing.  The appellant has given no consideration for the patent protection it now seeks.  That is the argument.

1.  The Claims in Suit

14                               Patent claims are frequently analogized to “fences” and “boundaries”, giving the “fields” of the monopoly a comfortable pretence of bright line demarcation.  Thus, in Minerals Separation North American Corp. v. Noranda Mines, Ltd., [1947] Ex. C.R. 306, Thorson P. put the matter as follows, at p. 352:

By his claims the inventor puts fences around the fields of his monopoly and warns the public against trespassing on his property.  His fences must be clearly placed in order to give the necessary warning and he must not fence in any property that is not his own.  The terms of a claim must be free from avoidable ambiguity or obscurity and must not be flexible; they must be clear and precise so that the public will be able to know not only where it must not trespass but also where it may safely go.

15                               In reality, the “fences” often consist of complex layers of definitions of different elements (or “components” or “features” or “integers”) of differing complexity, substitutability and ingenuity.  A matrix of descriptive words and phrases defines the monopoly, warns the public and ensnares the infringer.  In some instances, the precise elements of the “fence” may be crucial or “essential” to the working of the invention as claimed; in others the inventor may contemplate, and the reader skilled in the art appreciate, that variants could easily be used or substituted without making any material difference to the working of the invention.  The interpretative task of the court in claims construction is to separate the one from the other, to distinguish the essential from the inessential, and to give to the “field” framed by the former the legal protection to which the holder of a valid patent is entitled. 

16                               The issue in this case turns on the construction of claim 1 in each of the two patents (as the other claims incorporate and build on claim 1, they need not be considered at length).

(a)   The '156 Patent

17                               1.    An electro-magnetic low frequency therapeutic system comprising a magnetization coil, said magnetization coil being stationary during a magnetic field treatment, for creating a preselected therapeutic magnetic field in response to preselected coil energizing-current waveforms whereby said magnetic field has desired treatment characteristics, said magnetic field having an adjustable intensity set by adjustable control means, said control means also having:

(i)  circuit means for controlling the peak amplitude of the said magnetic field for achieving a specific modulation of said peak amplitude in a given time;

(ii)  means to select the orientation and/or direction of the therapeutic magnetic field with respect to a tissue to be treated;

(iii)  circuit means to select the frequency of interruption of the coil energizing-current to obtain a selected one of different therapeutic magnetic field time patterns;

(iv)  means to select a desired treatment time;  automatic demagnetizing means responsive to a preselected demagnetizing time and mode for attenuating said field in a desired manner to terminate a magnetic field treatment.

(b)  The '361 Patent

18                               Claim 1 of the '361 patent offers certain improvements to the '156 patent; the major innovations lie in a more detailed treatment of the control means.  Though it does not refer to a “stationary” coil, it requires “means to secure said coil in a predetermined fixed position” and repeats the requirement of a “control circuit means” to control amplitude and frequency.  The broad monopoly asserted in claim 1 reads:

1.    An electro-magnetic low-frequency therapeutic system comprising a magnetization coil for creating an electro-magnetic field, means to secure said coil in a predetermined fixed position, generator means for feeding said coil with predetermined treatment signals to obtain a desired magnetic field characteristic, control circuit means for selecting desired characteristics of said treatment signals, said control circuit means having (i) circuit control means for controlling the peak intensity of said desired magnetic field, (ii) frequency control means to select the frequency of said treatment signals to obtain a selected type of a plurality of treatment signals, (iii) adjustment means to preset the duration time of said treatment signals and said electro-magnetic field, said desired magnetic field characteristics being predetermined from a magnetic field pattern chart representative of the parameters of the field of said magnetization coil in the surrounding environment of said coil whereby to obtain a desired range of intensity of said field and a desired orientation thereof relative to a position of said coil.

19                               This appeal raises questions of both validity and infringement.  The task of claims construction is antecedent to both inquiries.

2.  Claims Construction

20                               Based on the expert evidence given at trial as to the meaning of the terms used, and the understanding that these terms would convey at the date of the patent to an ordinary worker skilled in the art of electro-magnetotherapy devices and possessing the common knowledge of people engaged in that field, it appears that while some of the elements of the '156 and '361 patents are essential if the devices are to work as contemplated and claimed by the inventor, others are non-essential.  The non-essential elements may be substituted or omitted without having a material effect on either the structure or the operation of the invention described in the claims.

(a)   The Essential Elements

21                               The essential elements common to the claims of both the '156 and '361 patents include at least the following:

1.  a control to regulate the peak amplitude and frequency of interruption of the current which “energizes” the coil;

2.  such control to be provided by “circuit means”.

22                               For purposes of this appeal, it is unnecessary to detail the other features of the invention.  The argument is that a device which does not include these essential elements is clearly “outside the fence” of the claimed monopoly.

(b)  The Non-essential Elements

23                               The '156 patent includes a number of additional claims dependent on claim 1.  Thus, for example, claims 4 and 5 claim a “repeatedly discharged capacitor” that fires an electric current through a damping resistor into a magnetization coil and can be wired to break the current up into pulses (“pulsatile” wave forms) to produce magnetic fields.  The appellant argues that any such apparatus would infringe its patent.  However, the evidence is that much of this equipment is commonly used in university science laboratories and in other settings involving the production of magnetic fields using electric currents through coiled wires.  They are included in the patent only because of their use in conjunction with “essential” elements of the invention described in claim 1.  In the case of some of these specific components, anyone skilled in the art reading the patent at the date of its publication would immediately have appreciated that there existed different commonly known substitutes or mechanical equivalents that would do the job just as well.  The claims of the '361 patent also contemplate a number of interchangeable components that do not constitute part of the essential invention.  Thus, claims 5, 14 and 20 of the '361 patent refer to the use of switches in conjunction with the device described in claim 1.  These components themselves were not patented on their own –  indeed, they could not be patented since they represent equipment commonly known and used by persons skilled in electrical engineering.  They came to be included in the claim as an element of an ingenious combination.  Substitution of one type of switch for another in this case would not strike at the essentials of the invention.

3.  Validity of the Patents in Issue

24                               The trial judge declared the patents to be invalid because he agreed with the respondents that the inventions described in the '156 and '361 patents were fully anticipated by the publication of the article in 1975 by Solov'eva.  The “invention” was thus considered to have been described “in a . . . publication printed in Canada or any other country more than two years” before the filing of the patent application and thus unpatentable by virtue of s. 28(2) of the Act.

25                               Anticipation by publication is a difficult defence to establish because courts recognize that it is all too easy after an invention has been disclosed to find its antecedents in bits and pieces of earlier learning.  It takes little ingenuity to assemble a dossier of prior art with the benefit of 20-20 hindsight.  In this case, the respondents contended that all of the essential elements of the appellant's alleged inventions were disclosed in a single publication, the Solov'eva article, which predated the patent application by almost 4 years.  If this is correct, the patent would be invalid.

26                               The Solov'eva article was drawn to the respondents' attention by the appellant who cited it  as prior art in the specification of the '361 patent itself.  The legal question is whether the Solov'eva article contains sufficient information to enable a person of ordinary skill and knowledge in the field to understand, without access to the two patents, “the nature of the invention and carry it into practical use without the aid of inventive genius but purely by mechanical skill” (H. G. Fox, The Canadian Law and Practice Relating to Letters Patent for Inventions (4th ed. 1969), at pp. 126-27).  In other words, was the information given by Solov'eva “for [the] purpose of practical utility, equal to that given in the patents in suit”?  (Consolboard Inc. v. MacMillan Bloedel (Sask.) Ltd., [1981] 1 S.C.R. 504, per Dickson J. at p. 534), or as was memorably put in General Tire & Rubber Co. v. Firestone Tyre & Rubber Co., [1972] R.P.C. 457 (Eng. C.A.), at p. 486:

A signpost, however clear, upon the road to the patentee's invention will not suffice.  The prior inventor must be clearly shown to have planted his flag at the precise destination before the patentee.

The test for anticipation is difficult to meet:

One must, in effect, be able to look at a prior, single publication and find in it all the information which, for practical purposes, is needed to produce the claimed invention without the exercise of any inventive skill.  The prior publication must contain so clear a direction that a skilled person reading and following it would in every case and without possibility of error be led to the claimed invention.

(Beloit Canada Ltd. v. Valmet OY (1986), 8 C.P.R. (3d) 289 (F.C.A.), per Hugessen J.A., at p. 297)

27                               It is clear, with respect, that the Solov'eva article does not address, let alone solve, the technical problems dealt with in the patents in suit.  It is nothing more than a four-page overview of the history of electro-magnetotherapy.  It describes some of the various systems available in 1975 in Europe and Japan.  The appellant, it must be appreciated, does not claim to have invented electro-magnetotherapy.  It obtained a patent for a particular means.  Although the various components were earlier known to persons skilled in the art, the inventor brought the elements together to achieve what the Commissioner of Patents considered a new, useful and ingenious result.  The claimed invention effected an ingenious combination rather than a mere aggregation of previously known components (The King v. Uhlemann Optical Co., [1952] 1 S.C.R. 143, per Rinfret C.J., at p. 150; Domtar Ltd. v. MacMillan Bloedel Packaging Ltd. (1977), 33 C.P.R. (2d) 182 (F.C.T.D.), at pp. 189-91).  The ingenious combination was neither taught nor anticipated in the Solov'eva publication.  None of the other arguments against validity are convincing.  The patentee lived up to its side of the bargain by disclosing an invention.  The patents are valid.

4.  Infringement Issues

28                               The appeal in this Court was essentially directed to the infringement issues.  It has been established, at least since Grip Printing and Publishing Co. of Toronto v. Butterfield (1885), 11 S.C.R. 291, that a patent owner has a remedy against an alleged infringer who does not take the letter of the invention but nevertheless appropriates its substance (or “pith and marrow”).  This extended protection of the patentee is recognized in Anglo-Canadian law, and also finds expression in modified form in the United States under the doctrine of equivalents, which is said to be available against the producer of a device that performs substantially the same function in substantially the same way to obtain substantially the same result:  Graver Tank & Mfg. Co. v. Linde Air Products Co., 339 U.S. 605 (1950), at p. 608.

29                               It is obviously an important public policy to control the scope of “substantive infringement”.  A purely literal application of the text of the claims would allow a person skilled in the art to make minor and inconsequential variations in the device and thereby to appropriate the substance of the invention with a copycat device while staying just outside the monopoly.  A broader interpretation, on the other hand, risks conferring on the patentee the benefit of inventions that he had not in fact made but which could be deemed with hindsight to be “equivalent” to what in fact was invented.  This would be unfair to the public and unfair to competitors.  It is important that the patent system be fair as well as predictable in its operation. 

30                               The argument for the respondents is that even if the patents are valid, the appellant is not sticking to the bargain it made.  It is pushing the envelope of the doctrine of “substantive infringement” beyond anything disclosed or claimed in its patent specifications.  The inventor brought together known components to achieve a useful and ingenious result, but now attacks the respondents' device which brings together different components to achieve a comparable result. 

31                               The appeal thus raises the fundamental issue of how best to resolve the tension between “literal infringement” and “substantive infringement” to achieve a fair and predictable result.  There has been considerable discussion of this issue in Canada and elsewhere, which I will discuss briefly in support of the following propositions:

(a)   The Patent Act  promotes adherence to the language of the claims.

(b)   Adherence to the language of the claims in turn promotes both fairness and predictability.

(c)   The claim language must, however, be read in an informed and purposive way.

(d)   The language of the claims thus construed defines the monopoly.  There is no recourse to such vague notions as the “spirit of the invention”  to expand it further.

(e)   The claims language will, on a purposive construction, show that some elements of the claimed invention are essential while others are non-essential.  The identification of elements as essential or non-essential is made:

(i) on the basis of the common knowledge of the worker skilled in the art to which the patent relates;

(ii) as of the date the patent is published;

(iii)       having regard to whether or not it was obvious to the skilled reader at the time the patent was published that a variant of a particular element would not make a difference to the way in which the invention works; or

(iv)       according to the intent of the inventor, expressed or inferred from the claims, that a particular element is essential irrespective of its practical effect;

(v)       without, however, resort to extrinsic evidence of the inventor's intention.

(f)    There is no infringement if an essential element is different or omitted.  There may still be infringement, however, if non-essential elements are substituted or omitted. 

32                               Based on the foregoing principles, I conclude that the appellant's arguments must be rejected.  As stated, the ingenuity of the patent lies not in the identification of a desirable result but in teaching one particular means to achieve it.  The claims cannot be stretched to allow the patentee to monopolize anything that achieves the desirable result.  It is not legitimate, for example, to obtain a patent for a particular method that grows hair on bald men and thereafter claim that anything that grows hair on bald men infringes.  I turn then to the first of the propositions listed above.

(a)  The Patent Act  Promotes Adherence to the Language of the Claims

33                               The Patent Act  requires the letters patent granting a patent monopoly to include a specification which sets out a correct and full “disclosure” of the invention, i.e., “correctly and fully describe[s] the invention and its operation or use as contemplated by the inventor” (s. 34(1) (a)).  The disclosure is followed by “a claim or claims stating distinctly and in explicit terms the things or combinations that the applicant regards as new and in which he claims an exclusive property or privilege” (s. 34(2) ).  It is the invention thus claimed to which the patentee receives the “exclusive right, privilege and liberty” of exploitation (s. 44 ).  These provisions, and similar provisions in other jurisdictions, have given rise to two schools of thought.  One school holds that the claim embodies a technical idea and claims construction ought to look to substance rather than form to protect the inventive idea underlying the claim language.  This is sometimes called the “central claim drafting principle” and is associated with the German and Japanese patent systems:  T. Takenaka, “Doctrine of Equivalents after Hilton Davis:  A Comparative Law Analysis” (1996), 22 Rutgers Computer & Tech. L. J. 479, at pp. 491, 502 and 519.  The other school of thought supporting what is sometimes called the “peripheral claiming principle” emphasizes the language of the claims as defining not the underlying technical idea but the legal boundary of the state-conferred monopoly.  Traditionally, for reasons of fairness and predictability, Canadian courts have preferred the latter approach.

34                               The “spirit of the invention” school in this country relies on Electrolier Manufacturing Co. v. Dominion Manufacturers Ltd., [1934] S.C.R. 436.  In that case, which involved a method to pivot handles for coffins, Rinfret J. spoke of “the spirit of the invention” but did so in a direct quote from the patent itself, at p. 443:

What the appellant did – and in that his infringement truly consists – was to take the idea which formed the real subject-matter of the invention.  It does not matter whether he also adopted the substitution of the two holes for the bar in the pivoting means.  The precise form of these means was immaterial.  In the language of the patent, they could be changed “without departing from the spirit of the invention”.  [Emphasis added.]

Rinfret J. went on at p. 444 to tie explicitly his finding of infringement to a “fair interpretation of the language of the specification”. 

35                               The debate between the advocates of the “central claiming principle” and advocates of the “peripheral claiming principle” can each find precedents to support them.  As long ago as Smith Incubator Co. v. Seiling, [1936] S.C.R. 251, at p. 259, counsel pointed out that there appeared to be these two mutually inconsistent lines of authority:

According to one of these it is proper to consider what is “the pith and substance” or the “spirit” of the invention and to give effect to the patent accordingly.  The other is to regard the claims as definitely determining the scope of the monopoly which the patent purports to grant and to give or refuse them effect according to the expressions they contain when these expressions are properly construed and their meaning determined.

To which Rinfret J., for the Court, responded at pp. 259-60:

In our view, the rule is that the claims must be regarded as definitely determining the scope of the monopoly, having regard to the due and proper construction of the expressions they contain.

36                               In J. K. Smit & Sons, Inc. v. McClintock, [1940] S.C.R. 279, Duff C.J., for the Court, reversed the Exchequer Court finding of infringement because he could not “find in these claims the description of a monopoly which clearly and plainly includes a prohibition” (p. 287) against the alleged infringement.  Gillette Safety Razor Co. of Canada v. Pal Blade Corp., [1933] S.C.R. 142, per Rinfret J. at p. 147, is to the same effect.

37                               With respect to the United States, I mentioned earlier the seminal Graver Tank case in 1950.  More recently, the United States Supreme Court revisited the doctrine of equivalents in Warner-Jenkinson Co. v. Hilton Davis Chemical Co., 520 U.S. 17 (1997), and concluded, per Thomas J., at pp. 28-29:

We do, however, share the concern of the dissenters below that the doctrine of equivalents, as it has come to be applied since Graver Tank, has taken on a life of its own, unbounded by the patent claims.  There can be no denying that the doctrine of equivalents, when applied broadly, conflicts with the definitional and public-notice functions of the statutory claiming requirement.

38                               The U.S. approach is to disaggregate the invention as described in the patent claims into its constituent parts, as we do, but instead of characterizing an element as essential or non-essential, they treat all elements as “material”, per Thomas J., at p. 29:

Each element contained in a patent claim is deemed material to defining the scope of the patented invention, and thus the doctrine of equivalents must be applied to individual elements of the claim, not to the invention as a whole.  It is important to ensure that the application of the doctrine, even as to an individual element, is not allowed such broad play as to effectively eliminate that element in its entirety.

Flexibility is thus achieved under the U.S. doctrine of equivalents by asking whether each of the component elements of the invention as claimed is present in the accused device either as literally described in the claim, or by its “equivalent”.  Knowledge of interchangeability is evaluated as at the date of infringement, not the date of the patent (ibid., at p. 37).  The U.S. approach thus uses the patent claims as a springboard to other considerations (including prosecution history estoppel) some of which are extrinsic to the claims themselves.

39                               The English courts have also engaged in a debate about the proper reach of a patent monopoly.  In Clark v. Adie (1873), L.R. 10 Ch. 667, at p. 675, James L.J. spoke of “an essence or substance of the invention underlying the mere accident of form; and that invention, like every other invention, may be pirated by a theft in a disguised or mutilated form”.  On the other hand, in Electric & Musical Industries Ld. v. Lissen Ld. (1939), 56 R.P.C. 23 (H.L.), Lord Russell stated at p. 39:

A patentee who describes an invention in the body of a specification obtains no monopoly unless it is claimed in the claims. . . . [T]here is no such thing as infringement of the equity of a patent. . . .

The primacy of the language of the claims was emphatically affirmed in the celebrated case of Catnic Components Ltd. v. Hill & Smith Ltd., [1982] R.P.C. 183 (H.L.).  The Catnic approach has been accepted in New Zealand:  Interpress Associates Ltd. v. Pacific Coilcoaters Ltd. (1994), 29 I.P.R. 635 (H.C.), and Smale v. North Sails Ltd., [1991] 3 N.Z.L.R. 19 (H.C.); and in Australia in Populin v. H.B. Nominees Pty. Ltd. (1982), 59 F.L.R. 37 (Fed. Ct. (Gen. Div.), at p. 43, and Rhone-Poulenc Agrochimie SA v. UIM Chemical Services Pty. Ltd. (1986), 68 A.L.R. 77 (Fed. Ct. (Gen. Div.)), at pp. 92-93; in South Africa in Multotec Manufacturing (Pty.) Ltd. v. Screenex Wire Weaving Manufacturers (Pty.) Ltd., 1983 (1) SA 709 (App. Div.), and Sappi Fine Papers (Pty.) Ltd. v. ICI Canada Inc. (Formerly CIL Inc.), 1992 (3) SA 306 (App. Div.); and in Hong Kong in Improver Corp. v. Raymond Industrial Ltd., [1991] F.S.R. 233 (C.A.).  The Catnic decision has its critics, of course, particularly among those who feel its subsequent application under the European Patent Convention denies the patentee the higher level of protection for patentees afforded in continental Europe.  For some critics, the claims should more properly be treated not as a “fence” but as a “guidepost”:  J. D. C. Turner, “Purposive Construction:  Seven Reasons Why Catnic is Wrong” (1999), 21 E.I.P.R. 531; M. Sajewycz, “Patent Claim Interpretation as It Should Be:  Promoting the Objects of the Patent Act ” (1996-97), 13 C.I.P.R. 173; R. E. Annand, “Infringement of Patents -- Is “Catnic” the Correct Approach for Determining the Scope of a Patent Monopoly Under the Patents Act 1977?” (1992), 21 Anglo-Am. L. Rev. 39.

40                               The judgment of Lord Diplock was considered and applied by our Federal Court of Appeal in Eli Lilly & Co. v. O'Hara Manufacturing Ltd. (1989), 26 C.P.R. (3d) 1, and its progeny.  The primacy of the claims language was already rooted deeply in our jurisprudence and should, I think, be affirmed again on this appeal.

(b)   Adherence to the Language of the Claims in Turn Promotes both Fairness and Predictability

41                               The scope of patent protection must not only be fair, it must be reasonably predictable.  A patent is, after all, a public instrument issued under statutory authority which may result in severe financial consequences for its infringement.  The scope of its prohibition should be made clear so that members of the public may know where they can go with impunity.  As was said in another public law connection by Gonthier J. in R. v. Nova Scotia Pharmaceutical Society, [1992] 2 S.C.R. 606, at p. 639, precision in public enactments is required to “sufficiently delineate an area of risk”. 

42                               The patent system is designed to advance research and development and to encourage broader economic activity.  Achievement of these objectives is undermined however if competitors fear to tread in the vicinity of the patent because its scope lacks a reasonable measure of precision and certainty.  A patent of uncertain scope becomes “a public nuisance” (R.C.A. Photophone, Ld. v. Gaumont-British Picture Corp. (1936), 53 R.P.C. 167 (Eng. C.A.), at p. 195).  Potential competitors are deterred from working in areas that are not in fact covered by the patent even though costly and protracted litigation (which in the case of patent disputes can be very costly and protracted indeed) might confirm that what the competitors propose to do is entirely lawful.  Potential investment is lost or otherwise directed.  Competition is “chilled”.  The patent owner is getting more of a monopoly than the public bargained for.  There is a high economic cost attached to uncertainty and it is the proper policy of patent law to keep it to a minimum. 

43                               The patent owner, competitors, potential infringers and the public generally are thus entitled to clear and definite rules as to the extent of the monopoly conferred.  This in turn requires that the subjective or discretionary element of claims interpretation (e.g., the elusive quest for “the spirit of the invention”) be kept to the minimum, consistent with giving “the inventor protection for that which he has actually in good faith invented” (Western Electric Co. v. Baldwin International Radio of Canada, [1934] S.C.R. 570, at p. 574).  Predictability is achieved by tying the patentee to its claims; fairness is achieved by interpreting those claims in an informed and purposive way.  

(c)   The Claims Must Be Construed in an Informed and Purposive Way

44                               The courts have traditionally protected a patentee from the effects of excessive literalism.  The patent is not addressed to an ordinary member of the public, but to a worker skilled in the art described by Dr. Fox as

a hypothetical person possessing the ordinary skill and knowledge of the particular art to which the invention relates, and a mind willing to understand a specification that is addressed to him.  This hypothetical person has sometimes been equated with the “reasonable man” used as a standard in negligence cases.  He is assumed to be a man who is going to try to achieve success and not one who is looking for difficulties or seeking failure.

(Fox, supra, at p. 184)

It is the “common knowledge” shared by competent “ordinary workers” that is brought to bear on the interpretation:  Fox, supra, at p. 204; Terrell on the Law of Patents (15th ed. 2000), at p. 125; I. Goldsmith, Patents of Invention (1981), at p. 116.  The present appeal does not raise great subtleties of interpretation.  The experts called by the parties here more or less agreed on the significance of what is stated in the claims.  The electro-magnetotherapy is to be controlled by “circuit means”.  The present appeal turns on the scope of the legal protection that arises out of that fact.

(d)   The Language of the Claims Thus Construed Defines the Monopoly.  There Is no Recourse to such Vague Notions as “Spirit of the Invention” to Expand it Further

45                               There appears to be a continuing controversy in some quarters as to whether there are two approaches to infringement (literal and substantive) or only one approach, namely infringement of the claims as written but “purposively” construed.

46                               In the two-step approach, the court construes the claims and determines whether the device accused of infringement has literally taken the invention.  If not, the court proceeds to the second step of asking itself whether “in substance” the invention was wrongfully appropriated.  On occasion, treatment of the second step in specific cases has attracted criticism as being subjective and unduly discretionary.  Once the inquiry is no longer anchored in the language of the claims, the court may be heading into unknown waters without a chart.  The one-step approach has to build flexibility and common sense into the initial claims construction because there is no second step.

47                               The “single cause of action” approach was advocated by Lord Diplock in Catnic, supra, at p. 242:

My Lords, in their closely reasoned written cases in this House and in the oral argument, both parties to this appeal have tended to treat “textual infringement” and infringement of the “pith and marrow” of an invention as if they were separate causes of action, the existence of the former to be determined as a matter of construction only and of the latter upon some broader principle of colourable evasion.  There is, in my view, no such dichotomy; there is but a single cause of action and to treat it otherwise, particularly in cases like that which is the subject of the instant appeal, is liable to lead to confusion.

48                               The Catnic approach was adopted in O'Hara, and has been carried forward by the Federal Court of Appeal in cases such as Mobil Oil Corp. v. Hercules Canada Inc. (1995), 63 C.P.R. (3d) 473, per Marceau J.A., at p. 489:

It is my opinion that one should not endeavour to create a distinction between a substantial and a literal infringement in a case such as this; one should construe the claims so as to determine what exactly lies within the scope of the inventor's rights.  Once this has been determined, then one can consider the defendant's product to decide if it falls within the scope of the claim.

However, other decisions of different panels of our Federal Court of Appeal have occasionally sought to breathe life into the earlier dichotomy:  see Computalog Ltd. v. Comtech Logging Ltd. (1992), 44 C.P.R. (3d) 77, at pp. 80-81, and Feherguard Products Ltd. v. Rocky's of B.C. Leisure Ltd. (1995), 60 C.P.R. (3d) 512.  B. H. Sotiriadis in “Purposive Construction in Canadian Patent Infringement Cases Since O'Hara” (1996), 11 I.P.J. 111, notes at p. 116:

In fact, notwithstanding O'Hara, the Court of Appeal [in Imperial Oil v. Lubrizol (1992), 45 C.P.R. (3d) 449] went so far as to state that the notion of the “pith and marrow” of an invention in patent cases was a principle that remains “alive and well and applicable in the case before the court.”

49                               Similarly, in C. V. E. Hitchman and D. H. MacOdrum, “Don't Fence Me In:  Infringement in Substance in Patent Actions” (1990-91), 7 C.I.P.R. 167, the authors, at p. 201, cite Cutter (Canada) Ltd. v. Baxter Travenol Laboratories of Canada Ltd. (1983), 68 C.P.R. (2d) 179 (F.C.A.), and Johnson Controls, Inc. v. Varta Batteries Ltd. (1984), 80 C.P.R. (2d) 1 (F.C.A.), as evidence of continuing post-Catnic adherence to the two-step approach and conclude, “[i]t is too early to say whether that Court following O'Hara will focus solely on the Catnic test”.

50                               I do not suggest that the two-stage approach necessarily ends at a different destination than the one-stage approach, or that the two-stage approach has resulted in abuse.  I think we should now recognize, however, that the greater the level of discretion left to courts to peer below the language of the claims in a search for “the spirit of the invention”, the less the claims can perform their public notice function, and the greater the resulting level of unwelcome uncertainty and unpredictability.  “Purposive construction” does away with the first step of purely literal interpretation but disciplines the scope of “substantive” claims construction in the interest of fairness to both the patentee and the public.  In my view its endorsement by the Federal Court of Appeal in O'Hara was correct.

(e)   The Claims Language Will, on a Purposive Construction, Show that Some Elements of the Claimed Invention Are Essential While Others Are Non-essential.  This Allocation Will Be Made in the Following Manner:

(i)    On the Basis of the Common Knowledge of the Worker Skilled in the Art to which the Patent Relates

51                               This point is addressed more particularly in Whirlpool Corp. v. Camco Inc., [2000] 2 S.C.R. 1067, 2000 SCC 67 and Whirlpool Corp. v. Maytag Corp., [2000] 2 S.C.R. 1116, 2000 SCC 68, released concurrently.  The involvement in claims construction of the skilled addressee holds out to the patentee the comfort that the claims will be read in light of the knowledge provided to the court by expert evidence on the technical meaning of the terms and concepts used in the claims.  The words chosen by the inventor will be read in the sense the inventor is presumed to have intended, and in a way that is sympathetic to accomplishment of the inventor's purpose expressed or implicit in the text of the claims.  However, if the inventor has misspoken or otherwise created an unnecessary or troublesome limitation in the claims, it is a self-inflicted wound.  The public is entitled to rely on the words used provided the words used are interpreted fairly and knowledgeably. 

(ii)   What Constitutes an “Essential” Element Is to Be Interpreted in Light of the Knowledge of the Art at the Date of the Publication of the Patent Specification

52                               The substitutability of non-essential elements derives from an informed interpretation of the language of the claims at the time they are revealed to the target audience of persons skilled in the relevant art.  Thus Dickson J., in Consolboard, supra, spoke at p. 523 of “what a competent workman reading the specification at its date would have understood it to have disclosed and claimed” (emphasis added).  See also Fox, supra, at p. 204.  The date of publication was identified by Lord Diplock in Catnic, supra, and picked up by Hoffmann J. (as he then was) in Improver Corp. v. Remington Consumer Products Ltd., [1990] F.S.R. 181 (Pat. Ct.), at p. 182:

Would this (i.e.: that the variant had no material effect) have been obvious at the date of publication of the patent to a reader skilled in the art?  If no, the variant is outside the claim.  [Emphasis added.]

53                               The date of publication continues to be the critical date in England:  Terrell, supra, at p. 106, although Lord Hoffmann (as he now is) has observed that “there is an important difference between the 1949 [Patent Act ] and the 1977 [Patent Act ]” which requires the date of application (or priority date) to become the critical date for certain purposes:  Biogen Inc. v. Medeva PLC, [1997] R.P.C. 1 (H.L.), at p. 54.  In that case the court was dealing with the sufficiency of disclosure, but some English judges have taken the cue to construe claims as of the date of application as well, e.g., Dyson Appliances Ltd. v. Hoover Ltd., [2000] E.W.J. No. 4994 (QL)(Pat. Ct.), at para. 48 (k).  In Canada, Reed J. advocated a similar position in AT & T Technologies, Inc. v. Mitel Corp. (1989), 26 C.P.R. (3d) 238 (F.C.T.D.), at p. 260, even in the absence of these statutory changes.  While there may be some advantages to the establishment of a single critical date for multiple purposes including obviousness, sufficiency and claims construction, my view is that Canadian law does not support the date of application as the critical date for claims construction.

54                               There remains, however, a choice between the date of issuance of the patent and the date of its publication because under the former Act the date of issue and the date of publication were the same.  Now, as a result of the obligations assumed by Canada under the 1970 Patent Cooperation Treaty implemented by s. 10 of the new Act (S.C. 1993, c. 15, s. 28), the patent specification is “laid open” 18 months after the effective date of the Canadian patent application.  In my view, the same logic that favoured the date of issuance/publication as the critical date for claims construction under the former Act, favours the choice of the “laid open” date under the new Act.  On that date, the invention is disclosed to the public, those interested have some ability to oppose the grant of the patent applied for, and the applicant for the patent is eventually allowed to claim reasonable compensation (s. 55(2)), provided the patent is ultimately granted, from and after the “laid open” date.  The public, the patentee, its competitors and potential infringers all have an interest and/or concern from that date forward.  The notional skilled addressee has a text available for interpretation.  In summary, public disclosure and the triggering of legal consequences on the “laid open” date, as well as the policy considerations that underpinned the earlier case law, favour that date over the other possibilities as the critical date for the purpose of claims construction.

(iii)  Regard Is to Be Had to Whether It Was Obvious at the Time the Patent Was Published that Substitution of a Different Variant Would Make a Difference to the Way in Which the Invention Works

55                               It would be unfair to allow a patent monopoly to be breached with impunity by a copycat device that simply switched bells and whistles, to escape the literal claims of the patent.  Thus the elements of the invention are identified as either essential elements (where substitution of another element or omission takes the device outside the monopoly), or non-essential elements (where substitution or omission is not necessarily fatal to an allegation of infringement).  For an element to be considered non-essential and thus substitutable, it must be shown either (i) that on a purposive construction of the words of the claim it was clearly not intended to be essential, or (ii)

that at the date of publication of the patent, the skilled addressees would have appreciated that a particular element could be substituted without affecting the working of the invention, i.e., had the skilled worker at that time been told of both the element specified in the claim and the variant and “asked whether the variant would obviously work in the same way”, the answer would be yes:  Improver Corp. v. Remington, supra, at p. 192.  In this context, I think “work in the same way” should be taken for our purposes as meaning that the variant (or component) would perform substantially the same function in substantially the same way to obtain substantially the same result.  In Improver Corp. v. Remington, Hoffmann J. attempted to reduce the essence of the Catnic analysis to a series of concise questions, at p. 182:

(i)  Does the variant have a material effect upon the way the invention works?  If yes, the variant is outside the claim.  If no: –

(ii)  Would this (i.e.: that the variant had no material effect) have been obvious at the date of publication of the patent to a reader skilled in the art?  If no, the variant is outside the claim.  If yes: –

(iii)  Would the reader skilled in the art nevertheless have understood from the language of the claim that the patentee intended that strict compliance with the primary meaning was an essential requirement of the invention?  If yes, the variant is outside the claim.

56                               The three questions are not exhaustive but they encapsulate the heart of Lord Diplock's analysis, and have been endorsed in subsequent English cases.

57                               In AT & T Technologies, supra, at p. 257, Reed J. derived a series of interpretive principles from Catnic, supra, O'Hara, supra, and other cases.  Her third principle is as follows:

(3) if a variant of an aspect of a claim has no material effect on the way the invention works there is a presumption that the patent is infringed and that the patentee intended that that variant falls within the scope of the claim. . . .  [Emphasis added.]

The desirability of such a presumption is supported by some commentators (see, e.g., J.-C. Boudreau, “AT&T Technologies:  A Contribution to the Purposive Construction Approach for Patent Infringement Analysis in Canada” (1998-99), 15 C.I.P.R. 323).  If this proposition is taken to mean that a presumption of non-essentiality will arise if it is established in light of the knowledge of substitutability existing at the date of the infringement (AT & T Technologies, supra, at p. 262) that a variant would have no material effect on the way the invention works then, with respect, I disagree with it.  The effect would be that the ambit of the monopoly would grow over the life of the patent as new substitutes are developed and absorbed into the common knowledge of the skilled worker.  The inventor cannot be thought to have the necessary “intent” in relation to after-created knowledge except in the irrelevant sense of intending to reap the benefit of the maximum coverage available.  In my view, Catnic, supra, and O'Hara, supra, were correct to put the onus on the patentee to establish known and obvious substitutability at the date of publication of the patent.  If the patentee fails to discharge that onus, the descriptive word or expression in the claim is to be considered essential unless the context of the claims language otherwise dictates.

(iv)  According to the Intent of the Inventor Expressed or Inferred from the Claims of the Patent

58                               The inventor is addressing others in the same line of work.  Words have layers of significance and secondary meanings.  A reference to “turf” means something different to racehorse owners than it does to warring business executives.  The word “bench” means a physical object to weightlifters but has numerous secondary meanings for members of the legal profession.  The courts recognize the pitfalls of language and will do what they can to give the inventor “protection for that which he has actually in good faith invented” (Western Electric, supra, at p. 574), but there are limits.

59                               In O’Hara, supra, the Federal Court of Appeal held that a patent for a pill coating machine that specified a flexible exhaust could not be interpreted to cover a machine that fulfilled the same function and contained all of the other essential elements but which utilized a fixed exhaust.  Pratte J.A., for the court, considered it important that the patentee had specified “exhaust inlet flexibly biased”, and must be taken to have attached significance to the words chosen (at p. 7):

. . . unless it be obvious that the inventor knew that a failure to comply with that requirement would have no material effect upon the way the invention worked. 

Pratte J.A. also stated:

A court must interpret the claims; it cannot redraft them.  When an inventor has clearly stated in the claims that he considered a requirement as essential to his invention, a court cannot decide otherwise for the sole reason that he was mistaken. 

To the same effect see J. K. Smit & Sons, supra, per Duff C.J., at p. 285.

60                               The facts of O'Hara have an echo in the facts of this case.  Claim 1 of the '156 patent stipulates the “said magnetization coil being stationary” during treatment.  Whether the magnetization coil is stationary may or may not affect the way the device works, but the inventor has explicitly so stipulated.

(v)   Based on the Patent Specification Itself Without Resort to Extrinsic Evidence

61                               In O'Hara, supra, Pratte J.A. commented at p. 7 that in claims interpretation the Court “is merely trying to find out what was the intention of the inventor”, and this comment has given rise to the contention that some forms of extrinsic evidence should be admissible in claims construction to establish the inventor's intention.

62                               The intervener, Procter & Gamble Inc. urges the Court to allow proof of the intent through evidence of representations to the Patent Office in the course of patent prosecution, i.e., the negotiations over the wording of the claims leading up to issuance of the patent.  In her reasons, Rousseau-Houle J.A. made limited reference to the prosecution history in the present case as follows (at pp. 461-62):

[translation]During his study of the patent applications, the Commissioner analyzed various systems described in American and German patents which also were developed to treat the human body through the creation of magnetic fields.  He examined the article by Solov'eva which the appellant quoted and specifically commented in patent application 361. . . .  He requested additional details with respect to certain of the claims described in the patents and ordered amendments to the descriptions of certain functions and the deletion of any reference to methods of treatment because methods are not patentable.  [Emphasis added.]

63                               In the United States, representations to the Patent Office were historically noted on the file cover or “wrapper”, and the doctrine is thus known in that country as “file wrapper estoppel” or “prosecution history estoppel”.  In its recent decision in Warner-Jenkinson Co., supra, the United States Supreme Court affirmed that a patent owner is precluded from claiming the benefit of the doctrine of equivalents to recapture ground conceded by limiting argument or amendment during negotiations with the Patent Office.  The availability of file wrapper estoppel was affirmed, but it was narrowed in the interest of placing “reasonable limits on the doctrine of equivalents”, per Thomas J., at p. 34.  While prosecution history estoppel is still tied to amendments made to avoid the prior art, or otherwise to address a specific concern – such as obviousness -- that arguably would have rendered the claimed subject matter unpatentable, the court placed the burden on the patentee to establish the reason for an amendment required during patent prosecution.  Where no innocent explanation is established, the court will now presume that the Patent Office had a substantial reason related to patentability for including the limiting element added by amendment.  In those circumstances, prosecution history estoppel bars the application of the doctrine of equivalents as to that element.

64                               The use of file wrapper estoppel in Canada was emphatically rejected by Thorson P. in Lovell Manufacturing Co. v. Beatty Bros. Ltd. (1962), 23 Fox Pat. C. 112 (Ex. Ct.), and our Federal Court has in general confirmed over the years the exclusion of file wrapper materials tendered for the purpose of construing the claims:  see, e.g., P.L.G. Research Ltd. v. Jannock Steel Fabricating Co. (1991), 35 C.P.R. (3d) 346 (F.C.T.D.), at p. 349.  No distinction is drawn in this regard between cases involving allegations of literal infringement and those involving substantive infringement.

65                               Counsel for Procter & Gamble Inc. argues that prosecutions history ought to be admissible in some circumstances in the interest of obtaining consistent claims interpretation here and in the United States, where many Canadian patents have their origin.  There is some nourishment for this proposition in commentary by other experienced practitioners (e.g., D. W. Scott, “The Record of Proceedings in the Patent Office in Canada & Foreign Countries as Evidence in Infringement & Validity Contests” (1985-86), 2 C.I.P.R. 160).  References to the intention of the inventor in Catnic, supra, and O'Hara, supra, are said to leave the door ajar to the possibility of reconsideration. 

66                               In my view, those references to the inventor's intention refer to an objective manifestation of that intent in the patent claims, as interpreted by the person skilled in the art, and do not contemplate extrinsic evidence such as statements or admissions made in the course of patent prosecution.  To allow such extrinsic evidence for the purpose of defining the monopoly would undermine the public notice function of the claims, and increase uncertainty as well as fuelling the already overheated engines of patent litigation.  The current emphasis on purposive construction, which keeps the focus on the language of the claims, seems also to be inconsistent with opening the pandora's box of file wrapper estoppel.  If significant representations are made to the Patent Office touching the scope of the claims, the Patent Office should insist where necessary on an amendment to the claims to reflect the representation.

67                               This is not to suggest that prosecution history can never be relevant for a purpose other than defining the scope of the grant of the monopoly:  Foseco Trading A.G. v. Canadian Ferro Hot Metal Specialties, Ltd. (1991), 36 C.P.R. (3d) 35 (F.C.T.D.), at p. 47.  That point does not arise in this case for decision and lies outside the scope of these reasons.

(f)    Based on the Foregoing Principles, the Respondents' Device Is Outside the Claimed Monopoly and the Appeal Must Be Dismissed

68                               While the foregoing principles will have to be adapted to the exigencies of different types of patents, it may be helpful to summarize how they apply in this case.

(1)   At the claims construction stage, the wording of the claims was analysed to isolate the descriptive words and phrases which identify the elements of the invention.  There is no need here to make heavy weather in the details.  The claims specify the presence of “circuit means” to control the electro-magnetotherapy.  There is nothing in the context of the claims to suggest that the inventor considered circuit means to be non-essential.  On the contrary, it is the core of the invention.  Equally, there was no evidence that at the date of publication of the patent the ordinary skilled worker would have appreciated that there were variants that could perform substantially the same function in substantially the same way to achieve substantially the same result as the circuit means specified in the patent.

(2)   Control of the magnetotherapy by circuit means was therefore an essential element of the invention.

(3)   At the infringement analysis stage, the accused Électro-Santé device is now to be examined and its constituent elements similarly identified.

(4)   If the accused device takes all of the essential elements of the invention, there is infringement.

69                               The appellant complains, with some justice in my view, that having stated its legal test of infringement, the Quebec Court of Appeal then erred in making a comparison between the device of the appellant and the device of the respondents, and coming to the conclusion (which the appellant did not dispute) that the devices were different.

70                               The appellant contends that the proper comparison is between the claims set out in its patents and the devices marketed by the respondents.  I agree, but I believe that on reading the reasons of the Quebec Court of Appeal in their entirety, the court did make the proper comparison, even though that court went on to make a superfluous comparison between the two devices themselves.

71                               The appellant points out that the Électro-Santé device features many of the characteristics described in claim 1 of the '156 patent.  It is an “electro-magnetic low frequency therapeutic system”.  The magnetic field intensity is adjustable by the user.  There are means for controlling the magnetic field's peak amplitude and frequency.  As Wills J. said in Incandescent Gas Light Co. v. De Mare Incandescent Gas Light System, Ld. (1896), 13 R.P.C. 301 (Q.B.D.), at p. 330:

It is seldom that the infringer does the thing, the whole thing, and nothing but the thing claimed in the Specification.

72                               The appellant however failed to establish that a skilled reader would have understood in 1981 and 1983, when these patents were published, that (i) the inventions as contemplated were intended to include departures (or variants) from the specified circuit technology, (ii) that it would have been obvious to such a skilled reader that substituting variants for the specified “circuit means” would perform substantially the same function in substantially the same way to produce substantially the same result, and (iii) that when the inventor specified “circuit means” he didn't really mean the description to be taken literally.  Had the appellant been able to establish these points, its patents would probably have been declared invalid for covetous claiming.

73                               The claims clearly require “circuit means”.  As mentioned, a skilled reader in 1981 or 1983 would associate that descriptive phrase with specific technology and consider the use of such technology essential to the claimed invention.  The fact that the Électro-Santé device uses a microcontroller to perform a similar or even the same function does not bring it within the claim.  It performs the function in a very different way.  Moreover, there is no reason to think the inventor didn't mean what he said, or considered the use of “circuit means” a non-essential element of the claims, or intended to claim more broadly than “circuit means” and thereby put at risk for “covetous claiming” the validity of the patents.  As the Court of Appeal observed, the means of control of amplitude and frequency is precisely the difference that validated the patents over the prior art embodied in such predecessor magnetotherapy machines as the Magnétopace, Myodynamic and Elec devices. 

74                               In sum, the respondents' device differs both structurally and operationally from the device contemplated in the claims.  Substitution of a microcontroller for the “circuit means” substitutes a totally different technology for the core of the '156 and '361 patents and of itself is clearly fatal to the appellant's allegation of infringement.

75                               The appellant having failed to establish that the respondents' Électro-Santé system included all of the essential elements of the monopoly set out in its patent claims, purposively construed, the action was rightly dismissed.

V.  Disposition

76                               The appeal is dismissed without costs.

Appeal dismissed.

Solicitors for the appellant:  Joli-Cœur, Lacasse, Lemieux, Simard, St-Pierre, Sillery, Québec.

Solicitors for the intervener:  Dimock Stratton Clarizio, Toronto.