Court Opinion

ID: 9488425
Source: CourtListenerOpinion
Date Created: 2023-08-05 12:44:51.538681+00
Date Added: 2024-06-11T17:52:53.055478
License: Public Domain

NIES, Circuit Judge,
dissenting, with whom ARCHER, Chief Judge, joins Part IV, Sections C2-4, D, and E.
I dissent. I concur in Judge Plager’s dissent on the issue of infringement to the extent of his eloquent statement of the problem. However, I conclude that the determination of infringement under the “Doctrine of Equivalents,” as articulated in Graver Tank & Mfg. Co. v. Linde Air Products Co., 339 U.S. 605, 70 S.Ct. 854, 94 L.Ed. 1097, 85 USPQ 328 (1950) (Graver II), and prior Supreme Court precedent presents a series of questions of law, fact, and mixed law and fact. The meaning of the words in the claim must be defined by the court, a question of law. Also, the scope of protection which may be given the claim beyond its words is a question of law. In addition, the accused product or process must meet the limitations of the claim as defined by the court either literally or by equivalent means or steps, questions of fact.
Even though the ultimate finding of infringement is one of fact, once the words of the claim are interpreted and the elements of the accused product or process have been determined, “the correct application of the rule of equivalency” resolves itself into a question of law, whether trial is to the bench, Sanitary Refrigerator Co. v. Winters, 280 U.S. 30, 36, 50 S.Ct. 9, 10-11, 74 L.Ed. 147 (1929), or to the jury, Singer Co. v. Cramer, 192 U.S. 265, 275, 24 S.Ct. 291, 295, 48 L.Ed. 437 (1904). In this jury trial, the district court erred in denying the defendant’s motion to direct a verdict in its favor. No infringement can be found as a matter of law upon a correct application of the doctrine of equivalents.
*1551No matter what theory one espouses for the application of the doctrine of equivalents, fact, equity, law, or a combination thereof, infringement cannot be found in this ease. To hold that the process of Warner-Jenkin-son infringes violates the basic tenet that “courts have no right to enlarge a patent beyond the scope of its claim as allowed by the Patent Office.” Minerals Separation v. Butte & Superior Mining Co., 250 U.S. 336, 347, 39 S.Ct. 496, 499, 63 L.Ed. 1019 (1919). The doctrine of equivalents, as applied to a claim to a method embodying a series of steps, at most allows substitution of an equivalent step, within the boundaries of the invention as marked out by the claim. Here, there is no substitution of steps which are mere equivalent variants of those required. Hilton Davis must push out the metes and bounds of the area it claimed as its property to ensnare Warner-Jenkinson. A red house has not been painted blue. Rather, the front and back lot lines marked by the word fence of the claim have been moved to take in the adjoining property. Absent this enlargement, Warner-Jenkinson cannot be found an infringer. This expansive view is a misuse of the doctrine of equivalents. Further, prosecution history estoppel applies to specifically restrict one element of the claim in issue.
This appeal raises the basic question of a right to a jury trial on the issue of patent validity, which cries out for resolution. But, assuming that the jury has the role of resolving underlying factual issues, the district court’s instructions to the jury were defective. The district court invited guidance from this court on how to use a jury in a patent case. We have not accepted the plea. The entire case, not merely the issue of infringement, was taken in banc.1 I dissent from the order of the in banc court assigning the validity issue to the original panel.
I.
BACKGROUND
Both Warner-Jenkinson and Hilton Davis manufacture dyes known as FD & C Red # 40 and FD & C Yellow # 6 which are used as colorants principally in foods, drugs, and cosmetics. The ’746 patent claims a process for preparing dyes by subjecting their aqueous reaction mixtures to ultrafiltration under conditions that cause impurities to separate from the reaction mixture, yielding a high purity dye product.
Claim 1 is in Jepson format.2 Diazotization reactions to make the subject dyes have *1552been used for many years. The mixtures resulting from diazotization and coupling reactions contain impurities which must be removed to meet FDA specifications. For many years, both Warner-Jenkinson and Hilton Davis purified the dye solutions by a process known as “salting out.” This process produced what is called a press cake. Besides being labor intensive, this process had the disadvantages of the expense of the salt, disposal of the brine, and dye loss.
A third party, Osmonics, Inc., was known to specialize in the development of membranes and equipment for'fluid purification by ultrafiltration. On July 9, 1982, Dr. Sol-ter, then manager of research and development for the defendant, Warner-Jenkinson, instructed his engineering manager to contact Osmonics and have Osmonics process two of their dye preparations, including FD & C Red # 40. Osmonics performed the tests on August 17,18, and 19,1982, using its standard ultrafiltration process with various standard Osmonics membranes it selected as appropriate for the size of the molecules to be filtered. Osmonics’ standard membranes had a pore size range of 4 Angstroms to 20 Angstroms, a pH range of from 2 to 8)6 or 9, and a pressure range of 100 p.s.i.g. to 800 p.s.i.g. Despite successful indications, Warner-Jenkinson did not immediately continue with the project for FD & C Red # 40, but worked on other dyes not covered by the claims. Some years later after work on improvement of the Red # 40 dye chemistry for filtration purposes, after investigating various vendors of ultrafiltration equipment, Warner-Jenkinson went forward with commercial use of the process, utilizing Osmonics equipment. Such equipment was installed in February 1986 and Warner-Jenkinson was in commercial production, prior to being charged with infringement.
In 1982, Hilton Davis, like Warner-Jenkin-son, also decided to investigate a substitute for the salting out process and hired Dr. Wayne Cook to head the project. Neither Dr. Cook, nor anyone else on the Hilton Davis project, was knowledgeable in filtration techniques. Dr. Rebhahn suggested dialysis techniques be used and disclosed the location of an old unused Osmonics device which Hilton Davis had on hand. Dr. Cook then called Osmonics to see if Osmonics could solve his problem. Upon receiving a favorable reply, and just after Warner-Jen-kinson contacted Osmonics, Dr. Cook hired Osmonics to test Hilton Davis’ Red # 40 dye solutions. Osmonics did not use dialysis,3 but used the ultrafiltration process it had used for Warner-Jenkinson, except Osmonics hydrolyzed the membrane to a greater extent to achieve Hilton Davis’s economic goals by achieving faster results. The tests took place on August 24-26, 1982, one week after the tests for Warner-Jenkinson, and further tests were conducted on October 27-29,1982. A third test was run later on Hilton Davis’ Yellow # 6 dye.
On the basis of the test results, Hilton Davis filed a patent application in the names of Drs. Cook and Rebhahn on March 28, 1983, covering the ultrafiltration process for certain dyes. In response to rejections, in November 1984, a second (CIP) application was filed, changing various process parameters. After further amendments to overcome *1553cited prior art, the ’746 patent issued on December 24, 1985.
In mid-October 1986, Warner-Jenkinson learned of the ’746 patent through a reference to it in technical literature. It was unaware before then that Hilton Davis had developed a process similar to the one Warner-Jenkinson was using. On October 12, 1987, Warner-Jenkinson obtained an opinion of patent counsel: (1) that the patent was invalid for obviousness in view of a prior publication of ultrafiltration processes by Os-monics; and (2) that Warner-Jenkinson’s process, which was conducted under process limitations outside the ranges set forth in the ’746 claims, did not infringe literally or under the doctrine of equivalents.
Sometime later Hilton Davis tested a sample of Warner-Jenkinson’s dye and, upon analysis, concluded that it appeared to be prepared by ultrafiltration. It is not possible to tell from the dye what process was used. Representatives of Hilton Davis and Warner-Jenkinson happened to meet in December of 1989, at which time Hilton Davis indicated that it might bring suit against Warner-Jenkinson on the ’746 patent. Warner-Jenkinson denied infringement. Without further communication, Hilton Davis brought the instant suit a year later on April 1, 1991.
Tidal was to a jury. Warner-Jenkinson defended on the ground of noninfringement and various grounds of invalidity. Throughout the trial, by summary judgment and JMOL motions and by objection to the court’s instructions, Warner-Jenkinson urged that the issue of infringement under the doctrine of equivalents should not be submitted to the jury but on the record had to be decided by the court in its favor as a matter of law and/or equity. Respecting validity, Warner-Jenkinson also objected to giving the jury special verdicts requiring answers to ultimate legal issues. It lodged formal objections against the court’s instructions which required the jury to decide, for example, obviousness. The court overruled Warner-Jenkinson’s various objections to its proposed instructions and sent the case to the jury for answers to nine special verdicts covering the issues of obviousness, inventor-ship, best mode, willfulness, damages and infringement under the doctrine of equivalents. The jury returned verdicts in favor of Hilton Davis on Warner-Jenkinson’s defenses. The jury further found the infringement was not willful and awarded $3,546,705 on Hilton Davis’s claim. The district court entered judgment in accordance with the verdicts, denying Warner-Jenkinson’s renewed motion for judgment as a matter of law (JMOL). A final judgment awarding damages and a permanent injunction were entered. Warner-Jenkinson appeals both validity and infringement issues. Hilton Davis did not appeal.
II.
STANDARD OF REVIEW
To overturn a jury verdict on an ultimate issue of fact, the party against whom the verdict was rendered must satisfy either prong of the following test:
(1) that the jury’s findings of disputed material factual issues, implied or express, are not supported by substantial evidence or,
(2) that the findings do not support the verdict under the applicable legal standard.
Markman v. Westview Instruments, Inc., 52 F.3d 967, 975-76, 34 USPQ2d 1321, 1326 (Fed.Cir.1995) (in banc); Read Corp. v. Portec, Inc., 970 F.2d 816, 821, 23 USPQ2d 1426, 1431 (Fed.Cir.1992); Shatterproof Glass Corp. v. Libbey-Owens Ford Co., 758 F.2d 613, 618-619, 225 USPQ 634, 636 (Fed.Cir.), cert. dismissed, 474 U.S. 976, 106 S.Ct. 340, 88 L.Ed.2d 326 (1985); Railroad Dynamics, Inc. v. A. Stucki Co., 727 F.2d 1506, 1513, 220 USPQ 929, 936 (Fed.Cir.), cert. denied, 469 U.S. 871, 105 S.Ct. 220, 83 L.Ed.2d 150 (1984).
The “substantial evidence” standard of the first prong raises the question whether the jury’s resolution of a factual dispute was reasonable. See Dana Corp. v. IPC Ltd. Partnership, 860 F.2d 415, 417, 8 USPQ2d 1692, 1694 (Fed.Cir.1988), cert. denied, 490 U.S. 1067, 109 S.Ct. 2068, 104 L.Ed.2d 633 (1989). In determining reasonableness, the trial court cannot assess the weight of conflicting evidence, pass on the credibility of *1554the witnesses, or substitute its judgment for that of the jury. See Perkin-Elmer Corp. v. Computervision Corp., 732 F.2d 888, 893, 221 USPQ 669, 673 (Fed.Cir.), cert. denied, 469 U.S. 857, 105 S.Ct. 187, 83 L.Ed.2d 120 (1984); Railroad Dynamics Inc., 727 F.2d at 1512-13, 220 USPQ at 936. A finding of fact must stand unless the court concludes that on the entirety of the evidence of record, viewed in the light most favorable to the nonmovant and taking into account the required quantum of proof, no reasonable juror could have made the finding. Read Corp., 970 F.2d at 821, 23 USPQ2d at 1431.
The second prong of the JMOL standard requires the court to apply the correct legal standard for liability to the established and undisputed facts. The movant must convince the court that the proper legal standard, as applied to that set of facts, does not support the verdict as a matter of law. Boyle v. United Technologies Corp., 487 U.S. 500, 513-14, 108 S.Ct. 2510, 2519, 101 L.Ed.2d 442 (1988) (citing St. Louis v. Praprotnik, 485 U.S. 112, 118-120, 108 S.Ct. 915, 921-22, 99 L.Ed.2d 107 (1988) (plurality opinion)); Ebker v. Tan Jay Int’l Ltd., 739 F.2d 812, 825-26 n. 17 (2d Cir.1984) (Friendly, J.); and 9 C. Wright & A. Miller, Federal Practice and Procedure § 2537, pp. 599-600 (1971); Structural Rubber Prod. v. Park Rubber Co., 749 F.2d 707, 717, 223 USPQ 1264, 1271-72 (Fed.Cir.1984); Dana Corp. 860 F.2d at 417-18, 8 USPQ2d at 1694-95. On appeal, to determine the correctness of the district court's ruling on JMOL, the appellate court applies the JMOL standard anew to the issues presented by the appeal. Read Corp., 970 F.2d at 821, 23 USPQ2d at 1431. See also, Newell Cos. v. Kenney Mfg. Co., 864 F.2d 757, 762, 9 USPQ2d 1417, 1421 (Fed.Cir.1988), cert. denied, 493 U.S. 814, 110 S.Ct. 62, 107 L.Ed.2d 30 (1989).
Where an ultimate issue of law based on underlying disputed facts, e.g. obviousness of a patent, is submitted to a jury, our precedent holds that the same standard applies. Jurgens v. McKasy, 927 F.2d 1552, 1557, 18 USPQ2d 1031, 1035 (Fed.Cir.1991).
III.
VALIDITY
I dissent from the assignment of the issue of validity to a panel for decision. The Supreme Court has clearly stated that between infringement and validity, “validity has the greater public importance.” Cardinal Chemical Co. v. Morton Int’l, Inc., — U.S. -, -, 113 S.Ct. 1967, 1977, 124 L.Ed.2d 1, 26 USPQ2d, 1721, 1729 (1993); Sinclair & Carroll Co. v. Interchemical Corp., 325 U.S. 327, 330, 65 S.Ct. 1143, 1145, 89 L.Ed. 1644 (1945). In my view, the in banc court should resolve the important issues raised herein respecting the trial of validity issues before a jury. Our precedent is unclear, if not conflicting.4
A. Right to a Jury Tnal
The defendant Warner-Jenkinson raised the defense of invalidity of the '746 patent on various statutory grounds. Over the objection of Warner-Jenkinson, these issues were submitted by “special verdicts” to the jury with general instructions on the law applicable to the legal questions. The jury returned with verdicts inter alia that claims 1, 2, 3,13, and 14 were not proved invalid on any of the asserted grounds, namely (1) that the claimed invention would not have been obvious within the meaning of § 103; (2) that employees of Osmonics, rather than the named inventors, Drs. Cook and Rebhahn, invented all or a portion of the claimed invention (see § 102); and (3) that the inventors did not violate § 112 by failing to disclose a better mode of carrying out the invention than that set forth in the specification of the patent. Each of these issues is one of law, not fact, although based, of course, on underlying facts. The trial court denied Warner-Jenkinson’s renewed motion for JMOL on these issues.
*1555On appeal, Warner-Jenkinson argues that the validity of a patent is an issue of law, and that a new trial is required because the jury resolved the questions of obviousness, best mode, and inventorship, all of which are questions of law to be decided by the judge. I agree that Hilton Davis had no constitutional right to a jury trial on these issues for the reasons set out in my opinion in a case on which the Supreme Court has granted certiorari. In re Lockwood, 50 F.3d 966, 30 USPQ2d 1292 (Fed.Cir.1994), vacated, reh’g granted, and reh’g in banc denied, 50 F.3d 966, 33 USPQ2d 1406 (1995), 50 F.3d 966, 33 USPQ2d 1907 (Fed.Cir.1995) (Nies, J., dissenting from, denial of rehearing in banc), cert. granted sub nom. American Airlines, Inc. v. Lockwood, — U.S. -, 115 S.Ct. 2274, 132 L.Ed.2d 279 (1995). Essentially, validity is an issue of law because patent rights are public rights, not private rights, and historically cancellation of a patent for invalidity was an equitable remedy. It is also my understanding that the denomination of an issue as one of law means that the judge resolves any factual issues, not the jury. St. Louis v. Praprotnik, 485 U.S. 112, 124-126, 108 S.Ct. 915, 925-26, 99 L.Ed.2d 107 (1988) (plurality). I will limit my analysis to the obviousness issue.
The right to a jury trial on validity is critical to determining trial procedures and the standard for appellate review. Prior to the creation of this court, the other circuits were in conflict on the issue of how to treat the ultimate question of obviousness. Some circuits considered obviousness a question of law for the court. Julie Research Lab., Inc. v. Guildline Instruments, Inc., 501 F.2d 1131, 1135-36, 183 USPQ 1, 4-5 (2nd Cir.1974) (“The ultimate decision of invalidity/validity for obviousness/nonobviousness is one law.”); Blohm & Voss AG v. Prudential-Grace Lines, Inc., 489 F.2d 231, 245, 180 USPQ 165, 176 (4th Cir.1973) (“Thus, we come to the ultimate legal question of validity, and it is clear that it is, in the final analysis, a question of law.”), cert. denied, 419 U.S. 840, 95 S.Ct. 70, 42 L.Ed.2d 67 (1974); Dual Mfg. & Eng’g v. Burris Indus., Inc., 619 F.2d 660, 662-663, 205 USPQ 1157, 1160-1161 (7th Cir.) (in banc) (obviousness is a question of law), cert. denied, 449 U.S. 870, 101 S.Ct. 208, 66 L.Ed.2d 90 (1980). At least one circuit disagreed, concluding that obviousness presented a question of fact. Plastic Container Corp. v. Continental Plastics of Oklahoma, 708 F.2d 1554, 1558, 219 USPQ 26, 29 (10th Cir.1983) (“The Tenth Circuit treats the ultimate issue of obviousness as a question of fact subject to the ‘clearly erroneous’ standard of review.”).
In the Ninth Circuit, a slightly different practice evolved. There, district courts were permitted to give the issue of obviousness (a question of law) to the jury, but only for an advisory verdict. Garter-Bare Co. v. Munsingwear Inc., 723 F.2d 707, 710-711, 221 USPQ 751, 753 (9th Cir.) (court, in accepting jury verdict as advisory only, acted within its right in exercising duty to determine obviousness as a matter of law), cert. denied, 469 U.S. 980, 105 S.Ct. 381, 83 L.Ed.2d 316 (1984); Automation Electronics Corp. v. Sanders Instruments, Inc., 704 F.2d 1133, 1134, 218 USPQ 200, 201 (9th Cir.1983) (“Although the issue [of obviousness] may be submitted to the jury for a non-binding advisory opinion, it is the trial court’s responsibility to make the final determination independent of the jury’s recommendation.”).
This court recently held in Lockwood, supra, that the issue of validity of a patent must be given to the jury as a matter of constitutional right.5 A jury may be asked only the ultimate question of obviousness and, on JMOL, the judge must presume that the jury resolved all factual disputes in favor of the verdict winner. Warner-Jenkinson objects to that procedure. I would at least hold this appeal pending the decision of the Supreme Court in the Lockwood case.6
*1556B. Jury Instructions
Even following the Lockwood precedent that a jury decides the facts underlying questions of validity, I would hold that the instructions on validity in this case are fatally defective to achieve that purpose.
As an initial matter, the first step in determining validity or infringement is to interpret the claims in issue. Lemelson v. General Mills, Inc., 968 F.2d 1202, 1206, 23 USPQ2d 1284, 1287 (Fed.Cir.1992), cert. denied, - U.S. -, 113 S.Ct. 976, 122 L.Ed.2d 131 (1993). Furthermore, claims must have the same meaning and scope for both purposes. Intervet America, Inc. v. Kee-Vet Lab. Inc., 887 F.2d 1050, 1053, 12 USPQ2d 1474, 1476 (1989); SmithKline Diagnostics, Inc. v. Helena Lab. Corp., 859 F.2d 878, 882, 8 USPQ2d 1468, 1471 (Fed.Cir.1988); W.L. Gore & Associates, Inc. v. Garlock, Inc., 842 F.2d 1275, 1279, 6 USPQ2d 1277, 1280 (Fed.Cir.1988). We have recently held as an in banc court that the district court must interpret the claims in its instructions to the jury. Markman v. Westview, 52 F.3d 967, 981-982, 34 USPQ2d 1321, 1331 (Fed.Cir.1995) (“the trial court ... should have instructed the jury as to the meaning of the claims”). The district court did not do so here. Under Markman, the error of a trial judge in failing to so instruct the jury was rendered harmless by that court’s ruling on JMOL. Id. The same is not true here. Further, the district court ruled that an opinion of an “expert” on the meaning of the claim is fact evidence to be “weighed” by the jury in making their interpretation. Under Markman, such treatment of opinion testimony is improper by judge or jury. Id. at 983, 34 USPQ2d at 1332-33. The district court gave the following instruction to the jury:
The language of the Hilton Davis patent claims must be construed as it would be by those of ordinary skill in the art. In understanding the meaning of words used in the claims, you may consider the patent specification, the prosecution history of the patent, other claims of the patent, testimony of expert witnesses, the circumstances surrounding the inception of the patent application and the meaning of words as contained in technical literature which are part of the legal evidence and the state of the prior art.
This is an abdication of the court’s responsibility. Without knowing the meaning given to the claim language by the jury, the correctness of a validity or infringement verdict cannot be meaningfully reviewed. The jury may simply have misconstrued the claim, for example, determining where pressure must be measured.
The special verdicts requested from the jury were not fact verdicts under Rule 49(a) of the Federal Rules of Civil Procedure.7 As noted in Roberts v. Sears, Roebuck & Co., 723 F.2d 1324, 1340, 221 USPQ 504, 519 (7th Cir.1983) (in banc):
In this case the directions of Dual were not followed. The verdict form utilized was “special” only in the sense that the legal issue of patent validity was broken down into the components of obviousness and anticipation. Proper special verdicts, however, are to be addressed only to the subsidiary questions of fact that compose the Graham tripartite inquiry upon which the legal determination of validity must rest, not to the obviousness and anticipation components of patent validity themselves.
The district court here gave instructions which treated the validity issues as ultimate facts. For example, the court instructed:
The defendant has the burden of establishing the invalidity of the patent by clear and convincing proof.
I would hold that instruction to be plain error. The issue of obviousness is a conclusion drawn after facts are established. Resolution of the facts merely brings one to the legal question, not its answer, which is a judgment call. Newell Co. v. Kenney Mfg. Co., 864 F.2d 757, 762, 9 USPQ2d 1417, 1421 (Fed.Cir.1988) (“[Wjhere the only issue is, as *1557here, the application of the statutory standard of obviousness (35 U.S.C. § 103) to an established set of facts, there is only a question of law to be resolved by the judge.”), cert. denied, 493 U.S. 814, 110 S.Ct. 62, 107 L.Ed.2d 30 (1989). Accord Panduit Corp. v. Dennison Mfg. Co., 810 F.2d 1561, 1566-67, 1 USPQ2d 1593, 1596-97 (Fed.Cir.), cert. denied, 481 U.S. 1052, 107 S.Ct. 2187, 95 L.Ed.2d 843 (1987). A correct instruction would be that disputed facts underlying the legal conclusion of invalidity must be established by clear and convincing evidence.
The entirety of the instruction on obviousness appears as an Appendix to this section. The instructions refer to a number of difficult concepts without tying them to any factual dispute or evidence in this case. The jury was literally put to sea without navigational aid. It was repeatedly told it was the judge of the obviousness of the invention. As an example, I quote one paragraph, which in the context of the entirety of the instructions carries the same or greater force:
To reach a proper conclusion, you must step backward in time and into the shoes worn by that hypothetical person when the invention was unknown and just before it was made. You must then determine, in light of all the legal evidence, whether the patent challenger has convincingly established that the claimed invention as a whole would have been obvious at the time to that hypothetical person.
The instructions on obviousness could only have been gibberish to a lay jury. The instructions did not tell the jury what fact issues, if any, were in dispute which the jury must decide. An appellate court cannot provide proper appellate review on the basis of such general instructions. See Roberts, 723 F.2d at 1341, 221 USPQ at 519 (requiring instructions setting forth mandatory alternative verdicts).
These examples are sufficient to show that the instructions and special verdicts on validity issues in this case are fatally flawed. The ultimate decision on the validity of a patent should not be thrown into the black box of a jury to be reviewed under the substantial evidence standard. Structural Rubber, 749 F.2d at 718, 223 USPQ at 1272.8 If the judge decides that resolution of a particular fact issue settles the validity question, the judge needs to direct the jury to decide that fact issue in a special verdict or must give mandatory alternative verdict instructions. As the Roberts court stated:
[A] compulsory instruction must be given when a general verdict is utilized: “[I]t is the court’s duty to instruct the jury that it should return one verdict if the facts are found one way and a different verdict if the facts are found otherwise.” [Panther Pumps & Equipment Co. v. Hydrocraft, Inc., 468 F.2d 225, 175 USPQ 577 (7th Cir.1972), cert. denied, 411 U.S. 965, 93 S.Ct. 2143, 36 L.Ed.2d 685 (1973).] In other words, the jury must be instructed that if it finds facts A, B, C, and D, it must render a certain verdict. Anything less than strict adherence to this procedure by a trial court constitutes an abdication of its active duty to retain ultimate control over the issue of obviousness.
Roberts, 723 F.2d at 1341, 221 USPQ at 519. Here, there were no such instructions given. Meaningful review where there are material issues of fact is impossible. Structural Rubber, 749 F.2d at 723, 223 USPQ at 1276. Such error can be corrected only by a new trial. From the instructions in this case, it cannot be determined whether the jury decided against the defendant on the factual issues or the legal issues.
The trial court’s ruling on the JMOL motion compounds the problem by its legally erroneous interpretation of the claim. The judge repeatedly stated that the inventors conceived a special process which skipped the salting out process and produced FDA certified quality dye, and determined obviousness on that basis. The claims do not require skipping the salting out step or producing FDA certifiable dye. Thus, the court’s basis for distinguishing over the prior art is legally erroneous. Further, the court itself considered as evidence and relied on the legal *1558opinion of a proffered expert witness [Dr. Kinman] that the invention was not obvious over prior art. This was error. Mendenhall v. Cedarapids, Inc., 5 F.3d 1557, 1574, 28 USPQ2d 1081, 1096 (Fed.Cir.1993), cert. denied, - U.S. -, 114 S.Ct. 1540, 128 L.Ed.2d 192 (1994). The error in giving the issues of validity to the jury were not rendered harmless by the court’s ruling on JMOL. Because of erroneous instructions, a new trial is required.
C. Conclusion
The judgment that the ’746 patent was not invalid cannot stand. Regardless of what conclusion one might reach on the merits of the hotly contested issue of validity, particularly obviousness in view of Osmonics’ work and publications before testing for either party, the more important question is: Was this issue properly tried? I dissent to the denial of in banc to resolve the jury trial issues raised by this appeal.
APPENDIX TO VALIDITY

Jury Instructions On Obviousness in this Case

A patent granted by the Patent and Trademark Office is invalid if the claimed subject matter as a whole would have been obvious to a person of ordinary skill in the pertinent art at the time the patented invention was made. Patentability shall not be negatived by the manner in which the invention was made.
In determining obviousness of the claimed subject matter of each of the claims of the patent in suit, the following steps should be taken by you: One, you should determine the scope and content of the prior art relied upon against the patent in suit. Two, you should then identify the difference, if any, between each claim of the patent in suit and the prior art. And three, you should determine the level of ordinary skill in the pertinent art at the time the invention of the patent in suit was made.
You must make each of the determinations as to [sic] of the time the Hilton Davis invention was made.
You should consider such secondary considerations as commercial success, long-felt but unresolved need, failure of others to solve the problem and acquiescence in the patent by others.
The defendant Warner-Jenkinson must prove invalidity because of obviousness by clear and convincing legal evidence.
During the course of this trial you have heard the term “prior art” used frequently. One of Warner-Jenkinson’s assertions in this case is that there were certain prior public disclosures which constitute prior art within the meaning of the law. The term “prior art” includes that which was: One, known or used by others in this country before the date of invention by inventor; or
Two, patented or described in a printed publication in this or a foreign country before the date of invention; or
Three, patented or described in a printed publication in this or a foreign country for more than one year prior to the date of the application herein; or
Four, publicly used or on sale in this country more than one year prior to the date of the application therefor; or
Five, made or built by another person before the date of the invention where the thing made or built was not abandoned, suppressed or concealed.
The scope of the prior art is defined as that reasonably pertinent to the particular problem with which the inventor was involved.
I previously instructed you that when the United States Patent Office grants a patent it is presumed that the patent examiner is correct. If a patent challenger contends that a patent is invalid but relies only upon the same prior art that the examiner considered in granting the patent, he asserts that the examiner was wrong, and the presumption requires that he prove this by clear and convincing legal evidence.
If the patent challenger relies only on pri- or art, which is not more pertinent or relevant than the art considered by the examiner, then such challenger must also prove *1559invalidity by clear and convincing legal evidence.
If the patent challenger relies upon prior art which was not considered by the examiner, and which is more pertinent than that which was considered, then invalidity must still be proved by clear and convincing legal evidence, however, the patent challenger may have an easier time doing so.
In determining whether or not the claims of the patent in suit would have been obvious at the time, it is not necessary that there be absolute predictability of the result. It is only required that there be a reasonable probability the beneficial result will be achieved to show obviousness.
In reaching your determination on the issue of obviousness, you should consider whether the subject matter of the invention was also developed independently by other persons either before the alleged inventors of the patent in suit or about the same time.
It is fundamental in patent law that one who applies a known process to a known chemical does not thereby invent an unobvious patentable process unless it produces a different or an unexpected result over the prior art. If you find that defendant Warner-Jenkinson has proved by clear and convincing legal evidence that the process contained in the patent was an existing process, that plaintiff simply applied it to an existing chemical for ultrafiltration, and that the process failed to produce a different or unexpected result over the prior art, then you must find that the patented process is obvious and that the plaintiffs patent claims are invalid.
There have been frequent references to a person having ordinary skill in the art. Such a person is only hypothetical. It is that person who is presumed to be aware of all the pertinent prior art. The actual inventor’s skill is irrelevant to the inquiry. A person of ordinary skill in the art is also presumed to be one who thinks along the line of conventional wisdom in the art.
To reach a proper conclusion, you must step backward in time and into the shoes worn by that hypothetical person when the invention was unknown and just before it was made. You must then determine, in light of all the legal evidence, whether the patent challenger has convincingly established that the claimed invention as a whole would have been obvious at the time to that hypothetical person.
You are also to determine the level of ordinary skill in the art to which the claimed invention pertains at the time the claimed invention was made. Factors to be considered in determining the level of ordinary skill in the pertinent art are: The educational level and years of experience of the person or persons who you find to have developed the processes that are the subject of this case and of others working in the pertinent art, the types of problems encountered in the art, the teachings of the prior art, patents, and publications of other persons or companies, and the sophistication of the technology.
One of the considerations of obviousness is the difference between the pertinent prior art and the claims of the Hilton Davis patent. You must consider the claimed invention as a whole.
The differences may seem slight, but it may also have been the key to success and advancement in the art resulting from the invention.

Author’s Note

Instructions in early jury trials were directed to the particular case, not to legal abstractions. See, e.g., Coupe v. Royer, 155 U.S. 565, 570-573, 15 S.Ct. 199, 201-03, 39 L.Ed. 263 (1895); Johnson v. Root, 13 Fed.Cas. 823 (Cir.Ct.D.Mass.1858); Serrell v. Collins, 21 Fed.Cas. 1085 (Cir.Ct.S.D.N.Y.1857); Page v. Ferry, 18 Fed.Cas. 979 (Cir.Ct.E.D.Mich.1857).
IV.
INFRINGEMENT
A. Equivalents Under the Patent Act of 1952
“When all else fails, read the statute.” One cannot improve on this advice from a law school professor, now long deceased. The only reference to equivalents in the Patent *1560Act of 1952, the current statute, appears in 35 U.S.C. § 112. As will become evident, this part of the statute reflects one facet of the judicially created doctrine of equivalents and it was the only part enacted into law by Congress.9 Section 112 reads in pertinent part (hereinafter § 112, ¶ 6):
An element in a claim for a combination may be expressed as a means or step for performing a specified function without the recital of structure, material, or acts in support thereof, and such claim shall be construed to cover the corresponding structure, material, or acts described in the specification and equivalents thereof. [Emphasis added.]
If a patentee chooses to draft a claim in other form, it is reasonable to conclude Congress intended that the patentee should be bound by the literal language of the claim. In view of the liberality in current claiming practice, the need for the doctrine of equivalents because of difficulties in drafting claims to cover an invention in all possible forms is a rare case. If the invention can be claimed under § 112, ¶ 6, it should be so claimed so as to give notice that the inventor claims equivalents.10
In addition, the application of the doctrine of equivalents to a specific claim is suspect because of the statutory requirements enacted in 1952 for obtaining a broadened reissuance of a patent, which were much stricter than under prior statutes. Section 251 provides that a patentee seeking to broaden the claims of its patent must file for reissue within two years of the patent’s issuance. Moreover, under § 252, the period of protection is prospective only for the balance of the original term, not retroactive to the date of issuance of the patent, with respect to activities which do not infringe a claim in the original patent. Competitors are, thus, protected from liability for damages for infringement of claims broadened on reissue by provisions recognizing their “intervening rights.” P.J. Federico, Intervening Rights in Patent Reissues, 30 Geo.Wash.L.Rev. 603-637 (1961-62) (discussing intervening rights generally). This rational balanced system provided by Congress is undermined by the judicially created doctrine of equivalents. To draw a parallel to reissue, the asserted claims of the ’746 patent must be broadened to capture the accused process here; these claims are broadened more than two years after issuance of that patent; and no intervening rights are provided for the innocent user of the broadened claims.
The patentee is much better off evading the reissue procedure which Congress has provided, and resorting to its counterpart, the doctrine of equivalents, created out of the judiciary’s sense of “fairness.” If we are to persist in an extra-statutory remedy, it should be as fair to both sides as that provided in the statute.
Prior to the current statute, the judiciary created broadened reissues of a patent extra-statutorily as a matter of fairness to paten-tees, Miller v. Brass Co., 104 U.S. 350, 354, 26 L.Ed. 783 (1881), and later had to create the doctrine of intervening rights in fairness to infringers who had no notice in the time period between issuance and reissuance that their conduct would be held infringing. Sontag Chain Stores Co. v. Nat’l Nut Co., 310 U.S. 281, 293-294, 60 S.Ct. 961, 967, 84 L.Ed. 1204 (1940). Congress then amended the statute in 1952 to incorporate both “fairness” parts for broadened reissues.
Today, the doctrine of equivalents is as unfair as broadened reissues of a patent without intervening rights. Having created an extension of protection of a claim by the doctrine of equivalents, the judiciary should take it upon itself to establish intervening rights similar’ to those for claims changed on reissue. The absence of intervening rights has not been frozen statutorily. The doctrine is not in the current statute at all *1561except in § 112 ¶ 6. At a minimum, damages should be limited.
B. Infringement By Equivalents Under Graver II
Inasmuch as I stand alone in advocating a straightforward interpretation of the current statute, I must accept, as I have in the past, that the doctrine of equivalents as enunciated in Graver II, continues to be viable. However, the Graver II doctrine was, in any event, misapplied in this case.
The jury was instructed:
Hilton Davis asserts that the Warner-Jenkinson process for making food dyes infringes the Hilton Davis patent under the doctrine of equivalents. The doctrine of equivalents exists to prevent a fraud on the patent.
The concept of the doctrine of equivalents is designed to protect the patent holder from an unscrupulous infringer who appropriates the invention but avoids the literal language of the claims. In this regard, consideration must be given for the purpose for which a step is used in the claims of the patent and in defendant’s processes and the functions which they perform.
You may find infringement under the doctrine of equivalents when the accused process and the claimed invention perform substantially the same function in substantially the same way to yield substantially the same result even though the processes differ in name, form or shape.
Hilton Davis must prove infringement under the doctrine of equivalents by a preponderance of the legal evidence.
Though application of the doctrine of equivalents extends the protection of the patent beyond the literal words contained in the claims, it is not proper to erase the meaningful limitations of the claims on which the public is entitled to rely in avoiding infringement, and you must look to the claims section of the patent to determine the coverage and limitations of the patent.
The doctrine of prosecution history es-toppel precludes a patent owner from obtaining a claim construction through the application of the doctrine of equivalents that would resurrect subject matter surrendered during prosecution of a patent application. That is not to say, however, that whenever a limiting amendment or argument is made during prosecution, the patent owner loses all coverage between what the claims literally cover and what they would have covered prior to the amendment or argument. A close examination must be made as to, not only what was surrendered, but also the reason for such a surrender. The fact that claims were narrowed does not always mean that a patent owner is completely prohibited from recapturing some what was originally claimed. Depending on the nature and purpose of an amendment, it may have a limiting effect within a spectrum ranging from great to small to zero. Determination of the effect on the doctrine of equivalents from actions taken before the PTO requires consideration of the nature of such actions, the reasons therefore, the prior art distinguished, and the examiner’s objection thereby overcome.
A patent owner cannot obtain, under the doctrine of equivalents, coverage which could not have been obtained from the PTO by literal claims. In making this determination, you should consider whether the Hilton Davis patent claims as a whole, when interpreted to cover the Warner-Jenkinson’s processes, “read on” the prior art.
The district court entered judgment on the jury’s verdict of infringement and denied a JMOL motion. The majority approves the instructions as the sum and substance of the doctrine of equivalents, relying on closing argument of counsel to flesh them out to include the test it adopts of limiting infringement to “insubstantial” changes, a test not in the instructions. Nothing can save these instructions, least of all attorney argument. If nothing else, the district court told the jury that it must apply the law as stated in the court’s instructions.
The doctrine of equivalents is a much more complex concept than that set out in the jury instructions or in the majority opinion. The doctrine is comparable to the concept of de*1562termining fair use of a copyrighted work. The majority opinion recognizes some of the complexity but approves utter simplicity. The majority speaks of various factors that are important in finding infringement by equivalency, but none of the restraints it suggests made it into the jury instructions. Warner-Jenkinson’s wholly independent development of its process, for example, appears nowhere. Nor does the majority take them into account in affirming the judgment in this case.
The majority’s analysis of infringement under the doctrine of equivalent does not “restate” the Supreme Court standard. The majority in banc has “revised” the doctrine to eliminate the legal safeguards that Supreme Court precedent had built into the doctrine’s application to protect the public from unknowable infringement as here. Securing rewards to patentees may not override due process. Yet, the public’s right to reasonable notice of prohibited conduct surfaces nowhere in the majority opinion. Contrary to the majority, the Supreme Court placed clear limitations on the legal scope of protection of a claim under the doctrine. As now defined by this court, a doctrine which rests on fairness has been made wholly arbitrary. The majority holds, first, that a patent inherently covers equivalents of the product or process regardless of how the invention is described in the specification or claim and, second, that infringement depends on finding as a fact that the changes in the accused product or process are “insubstantial.”
From a review of Supreme Court precedent covering the doctrine under the predecessor statute, the determination of the scope of protection involves a judgment call by the district court that the words of the claim should or should not be controlling. The scope of a claim may be broader or narrower or the same as the words of a claim. But the scope can never be broader than the invention. That decision is, as Judges Plager and Lourie state, based in part on the equities but, in the past, the conclusion was not only made by the judge in equity but also at law. But whether made at law or in equity, the ultimate conclusion that the doctrine applies to a set of established facts has been subject to plenary review on appeal, as in Graver II.
Applying these principles to the present case, the district court erred in not determining the meaning and scope of the claim in suit. The question of scope is whether one of skill in the art would understand that a specific element of the claim is not the only means that may be used in the claimed invention. The answer depends on the nature of the invention, the claim language, the description of the invention in the specification, other claims in the patent, the arguments and amendments made during prosecution, the obviousness of the change, the prior art, the alleged infringer’s own conduct, and any other circumstances from which notice that the literal words of the claim are not meant to control might be inferred. In addition to the court’s determination of the range of equivalent components, the fact question of equivalency carries restrictions: (1) the doctrine of equivalents may not be used to enlarge a claim; infringement requires that every limitation of a claim must be met by at least an equivalent substituent in the accused product or process; (2) legal equivalency of a substituent is established by the knowledge in the art at the time the patent is issued; and (3) the substituent must perform essentially the same function as the element which it replaces so that ovex’all the accused product or process and the claimed invention can be said to operate by substantially the same means to achieve the same or substantially the same result. These restrictions must be part of the jury instructions.11
The majority entirely omits the step of determining whether, as a matter of law, an element of the claim extends to equivalents, a requirement of the Supreme Court after 1870. It contorts the doctrine to overall equivalency to the claimed invention and further states that equivalency is found as of the time of the infringement. “Known” equiva*1563lency of a substituent at the time of the patent’s issuance is no longer a requirement. Further, the finding of infringement is entirely a question of fact. With these departures from Supreme Court precedent, the doctrine has lost its moorings. I disagree with the majority’s analysis. In particular, I conclude that infringement under the doctrine of equivalents under Graver II, like the doctrine of fair use of copyrighted works,12 involves mixed questions of law and fact.
Prior Federal Circuit precedent has taken a generous view of the doctrine, making infringement by equivalents the automatic second step when literal infringement is not proved, as the majority reaffirms today.13 In addition, old and newly developed equivalents of an invention are covered by a claim even for an invention which was not a pioneer. Hughes Aircraft v. United States, 717 F.2d 1351, 219 USPQ 473 (Fed.Cir.1983). Further, in Hughes, we engrafted the doctrine upon claims drafted in accordance with § 112, ¶ 6 leading to a bizarre interpretation of the statute. We now have literal equivalents and nonliteral equivalents of claim elements. See, e.g., Johnston v. IVAC Corp., 885 F.2d 1574, 1577, 1580-81, 12 USPQ2d 1382, 1386-1387 (Fed.Cir.1989). We have made the infringement analysis so convoluted it is impossible for most district court judges untrained in “paténtese” to follow, much less jurors. At least today’s decision makes it simple — give the entire question of infringement under the doctrine to the jury under instructions which place the vaguest restraints on infringement by equivalency. I agree that a change should be made but not in that direction.
C. Historical Perspective What is the “Doctrine of Equivalents”? What makes the doctrine so contentious? Simply stated, despite the statutory provisions that define infringement as the unauthorized making, using, or selling of a patented invention (35 U.S.C. § 271), and that require the inventor to “particularly point[ ] out and distinctly claim[] the subject matter which the applicant regards as his invention” (§ 112, ¶ 2), infringement may or may not be restricted under our jurisprudence to what the inventor sets out in the claims which define his invention. But with the extension of the legal protection for a patented invention beyond the literal words of the claims, the public’s right to notice of what conduct is forbidden by a patent is compromised. How to balance these conflicting interests under the current statute and Patent Office procedures is a question the Supreme Court has not addressed.
1. Origin of the Doctrine
A review of the origins of the doctrine of equivalents is not merely interesting “filler” in this opinion. A prior decision respecting the doctrine of equivalents cannot be properly understood if the decision is divorced from the statutory and judicially imposed requirements for claim specificity, from examination procedures in the Patent Office applicable at the time to the patent in issue, and from the legal terminology of the period.
No mention of “claims” appears in the Act of 1790 or Act of Feb. 21, 1793, Ch. 11, 1 Stat. 318, and there was no procedure for administrative examination to determine pat-entability of an invention. Under these statutes, the invention merely had to be described so as to “distinguish [it from] other things before known” and “in the case of a machine [to explain] the principle by which it may be distinguished from other inventions.” See Karl B. Lutz, Evolution of the Claims of U.S. Patents, 20 J.Pat.Off.Soc’y 134 (Feb. 1938), 20 J.Pat.Off.Soc’y 377 (Apr.1938), 20 J.Pat.Off.Soc’y 457 (May 1938). One who used the “essence” of the invention was an infringer. See Odiorne v. Winkley, (No. 10,432) 18 F.Cas. 581 (C.C.Mass., 1814).
Recognizing that the public should be informed by the patent document itself as to *1564what was prohibited to them, the Supreme Court expressed a need “to put the public in possession of what the party claims as his own invention so as ... to guard against prejudice or injury from the use of an invention which the party may otherwise innocently suppose not to be patented.” See Evans v. Eaton, 20 U.S. (7 Wheat.) 356, 434, 5 L.Ed. 472 (1822).
In response to such judicial direction, the requirement for a claim to an invention first appeared in the Act of 1836. However, as interpreted by the Supreme Court, a claim under the 1836 Act did not limit the scope of protection.14 Under this claiming system, and there was generally only one claim, infringement continued as before to cover variations of the described embodiments. In essence, one continued to infringe the general description of the invention in the specification, not the specifics of the claim. See Ronald D. Hantman, Doctrine of Equivalents, 70 J.Pat. & Trademark Off.Soc’y 511, 516-37 (1988). In O’Reilly v. Morse, 56 U.S. (15 How.) 62, 123, 14 L.Ed. 601 (1853), the Supreme Court explained:
It is a well settled principle of law, that the mere change in the form of the machinery (unless a particular form is specified as the means by which the effect described is produced) or an alteration in some of its unessential parís; or in the use of known equivalent powers, not varying essentially the machine, or its mode of operation or organization, will not make the new machine a new invention. It may be an improvement upon the former; but that will not justify its use without the consent of the first patentee. [Emphasis added.]
The “well settled” principle of law there stated was not only a test for determining whether an accused device was an infringement, but also a test for determining whether a patent was valid. Indeed, the doctrine of equivalents originated as a test for patenta-bility. If the patented invention substituted a known equivalent for an element in a known process or product, merely varied the shape of a known product, or made other immaterial variations, the alleged invention was held to lack “invention”, being “anticipated”.15 Concomitantly, one did not avoid infringement by a mere change in form, by the substitution of a knoim equivalent element in a patented combination, or by leaving out a “nonessential” part from a patented invention.16 Prouty v. Draper, Ruggles & Co., 41 U.S. (16 Pet.) 336, 10 L.Ed. 985 (1842) (infringement); Evans v. Eaton, 16 U.S. (3 Wheat.) 454, 4 L.Ed. 433 (1818) (validity).
The conflict over the legitimacy of the doctrine as a test for infringement first surfaced in Winans v. Denmead, 56 U.S. (15 How.) 330, 14 L.Ed. 717 (1853), a 5-4 decision of the Supreme Court. The split in Winans was prompted by the Justices’ differing interpretations of the statutory requirement that a claim to an invention be made in a patent. The claim of the Winans patent was directed to coal cars which were *1565shaped “in the form of a frustum of a cone substantially as herein described.” The party charged with infringement used an octagonal shape instead of a circle. The majority held:
It is generally true, when a patentee describes a machine, and then claims it as described, that he is understood to intend to claim, and does by law actually cover, not only the precise forms he has described, but all other forms ivhich embody his invention; it being a familial’ rule that, to copy the principle or mode of operation described, is an infringement, although such copy should be totally unlike the original in form or proportions.
Patentees sometimes add to their claims an express declaration to the effect that the claim extends to the thing patented, hoiv-ever its form or proportions may be varied. Bid this is unnecessary. The law so interprets the claim without the addition of these words. The exclusive right to the thing patented is not secured, if the public are at liberty to make substantial copies of it, varying its form or proportions. And, therefore, the patentee, having described his invention, and shown its principles, and claimed it in that form which most perfectly embodies it, is, in contemplation of law, deemed to claim every form in which his invention may be copied, unless he manifests an intention to disclaim some of those forms.
Id. at 342-43, 14 L.Ed. 717 (emphasis added).
Four Justices, in vigorous dissent, voiced a contrary view of the effect of the statutory claim requirement:
The patentee is obliged, by law, to describe his invention in such full, clear, and exact terms, that from the description the invention may be constructed and used. Its principle and modes of operation must be explained; and the invention [sic] shall particularly “specify and point” out what he claims as his invention. Fulness, clearness, exactness, preciseness, and particularity, in the description of the invention, its principle, and of the matter claimed to be invented, will alone fulfil the demands of Congress or the wants of the country. Nothing, in the administration of this law,, will be more mischievous, more productive of oppressive and costly litigation, of exorbitant and unjust pretensions and vexatious demands, more injurious to labor, than a relaxation of these wise and salutary requisitions of the act of Congress. In my judgment, the principles of legal interpretation, as well as the public interest, require, that this language of this statute shall have its full significance and import.
Id. at 347, 14 L.Ed. 717.
The divergent views of the Justices in Winans are reiterated in the majority and dissenting opinions in Graver II, almost a hundred years later. The century-old debate over the function of patent claims has become crystallized under the rubrics of “central” claiming and “peripheral” claiming. As explained in Ellis, supra note 14, at § 4:
There are two general methods of defining an invention — central definition and peripheral definition. Central definition involves the drafting of a narrow claim setting forth a typical embodiment coupled with broad interpretation by the courts to include all equivalent constructions. Peripheral definition involves marking out the periphery or boundary of the area covered by the claim and holding as infringements only such constructions as lie within that area.
The majority in Winans endorsed central claiming, subordinating the claim to the fuller description and the drawings of the invention contained in other parts of the patent. As under earlier statutes, one infringed the material parts of the invention “as described” in the specification. A claim was treated essentially as a preferred embodiment of the invention. It continued to be left to the courts to sift through the entirety of the patent description to determine what were the material elements embodying the “principle” or “essence” of the invention for both validity and infringement purposes.17 *1566Even under this system, the construction of the patent claim was a matter of law exclusively for the court. Bischoff v. Wethered, 76 U.S. (9 Wall.) 812, 816, 19 L.Ed. 829 (1870); Turrill v. Michigan Southern & N. Indiana Railroad Co., 68 U.S. 491, 509-511, 17 L.Ed. 668 (1863); Winans v. New York & Erie R.R. Co., 62 U.S. (21 How.) 88, 100, 16 L.Ed. 68 (1859); Silsby v. Foote, 55 U.S. (14 How.) 218, 225, 14 L.Ed. 391 (1852); Hogg v. Emerson, 47 U.S. (6 How.) 437, 484, 12 L.Ed. 505 (1848).
The amendment of the patent statute by the Act of 1870,18 while a small language change, was interpreted to effect a major change from central to peripheral claiming, or at least a modified form of peripheral claiming. Claim language counted but certain equivalents of specified components of the claim might be recognized in determining infringement. In Union Water-Meter Co. v. Desper, 101 U.S. 332, 337, 25 L.Ed. 1024 (1879), the Court explained:
Our law requires the patentee to specify particularly what he claims to be new, and if he claims a combination of certain elements or parts, we cannot declare that any one of these elements is immaterial. The patentee makes them all material by the restricted form of his claim. We can only decide whether any part omitted by an alleged infringer is supplied by some other device or instrumentality which is its equivalent.
This view represented a clear departure from earlier cáse law. The courts were relieved by the “distinct” claiming requirement of the 1870 Act from sorting out “material” elements of an invention. Henceforth, that was done by what the inventor specified in the claims. All elements of a claim are “essential” or “material.” This development coincided with the development of substantive examination of patent applications by a corps of technical examiners in the Patent Office. The claim language became the focus of examination. As held in Keystone Bridge Co. v. Phoenix Iron Co., 95 U.S. 274, 278-79, 24 L.Ed. 344 (1877):
If the patentees have not claimed the whole of their invention, and the omission has been the result of inadvertence, they should have sought to correct the error by a surrender of their patent and an application for a reissue. They cannot expect the courts to wade through the history of the art, and spell out what they might have claimed, but have not claimed.... This duty is now cast upon the Patent Office. There his claim is, or is supposed to be, examined, scrutinized, limited, and made to conform to what he is entitled to. If the office refuses to allow him all that he asks, he has an appeal. But the courts have no right to enlarge a patent beyond the scope of its claim as allowed by the Patent Office, or the appellate tribunal to which contested applications are referred. When the terms of a claim in a patent are clear and distinct (as they always should be), the patentee, in a suit brought upon the patent, is bound by it. Merrill v. Yeomans, 94 U.S. 568 [24 L.Ed. 235.] He can claim *1567nothing beyond it. But the defendant may at all times, under proper pleadings, resort to prior use and the general history of the art to assail the validity of a patent or to restrain its construction. The door is then opened to the plaintiff to resort to the same kind of evidence in rebuttal; but he can never go beyond his claim. As patents are procured ex parte, the public is not bound by them, but the patentees are. And the latter cannot show that their invention is broader than the terms of their claim; or, if broader, they must be held to have surrendered the surplus to the public.
See also White v. Dunbar, 119 U.S. 47, 50-52, 7 S.Ct. 72, 74-75, 30 L.Ed. 303 (1886) (claim may not be enlarged by the “objective of the invention”); James v. Campbell, 104 U.S. 356, 370, 26 L.Ed. 786 (1881).
In addition to the requirement of distinct claims, the Act of 1870 changed the way patent cases were thereafter tried. Jury trials virtually disappeared, not to be seen again in any numbers for over a century, indeed, until the creation of this court.19 Prior to the 1870 Act, a patentee had to sue in equity for an injunction where monetary relief was in the form of an accounting for an infringer’s profits. To obtain “damages” for the patentee’s own losses, the patentee also had to sue at law. The 1870 Act gave equity courts in patent infringement suits the special power to award common law damages. See Root v. Railway Co., 105 U.S. (15 Otto) 189, 205-207, 26 L.Ed. 975 (1881). Since most patentees wanted an injunction available only in equity, as well as the equity discovery procedure to aid in proof of infringement, the equity court became the forum of choice.
Another development which was to have a profound effect on patent jurisprudence was the creation of the Circuit Courts of Appeal in 1890. These courts became effectively the final arbiters in patent cases with the Supreme Court intervening generally only where the circuits were in conflict on the validity or infringement of a particular patent. See e.g., Sanitary Refrigerator, 280 U.S. at 36, 50 S.Ct. at 10-11. As is well known, conflict in patent law developed and persisted among the circuits.20
When these developments occurred at the end of the 19th century, distinct claiming was in its infancy and the concept was not clearly understood. Some courts embraced peripheral claiming in its most rigid literalism. Infringement was limited to the literal language of the claim so that, absent claim language which brought in equivalent components, no equivalency infringement was recognized. Typical are the statements in Fulton Co. v. Powers Regulator Co., 263 F. 578, 580-81 (2d Cir.1920) (citation omitted):
[A] patent (ie., a claim) can never be given a construction broader than its terms in order to cover something which might have been claimed but was not.
and in Goodrich v. Ford Motor Co., 97 F.2d 427, 430-31 (6th Cir.1938):
The District Court invoked a literal reading of appellants’ claims and held that there was no infringement. This was sound.
For a review of the few cases where infringement by equivalents was found, see Ellis, supra note 14 at §§ 49-61.
It is important to keep in mind that the claiming concept was being developed by equity judges. Equity courts had full power to interpret and construe documents or even reform them in the interests of “equity.” An equity judge with a bent for liberal protection for particular important inventions felt free to go behind the literal letter of the document to examine the overall equities be*1568tween the parties. Lutz, pp. 470-71. In any event, during this era, the inventor was well advised to claim in a manner that literally encompassed equivalent components (i.e. “a spring or equivalent”; but see n. 23 infra) because of the strict constructionist views of many judges, but he then ran the risk of “over-claiming” and loss of his patent. However, reissuance to claim more narrowly was always available.
The Supreme Court decisions after the 1870 Act continued to apply a doctrine of equivalents test for infringement but in a restrained form. The principle of Winans that a claim covered other forms of the invention as a matter of law whether or not the patentee added an express declaration to that effect was no longer followed. The Court required language in the claim or at least in the specification which indicated that the claim should be interpreted or construed to cover equivalents.
This restrictive view is articulated in McClain v. Ortmayer, 141 U.S. 419, 425, 12 S.Ct. 76, 78, 35 L.Ed. 800 (1891), where the Court states:
It is true that, in a case of doubt, where the claim is fairly susceptible of two constructions, that one will be adopted which will preserve to the patentee his actual invention; but if the language of the specification and claim shows clearly what he desired to secure as a monopoly, nothing can be held to be an infringement which does not fall within the terms the patentee has himself chosen to express his invention.
Applying these familiar principles to the case under consideration, we are forced to the conclusion that the curved hook of the defendant is not an infringement of the double spring described in the plaintiffs specification and claim [even though a] single spring or hook embracing the fore wale of a collar may be equally as efficacious.
The Court treated “pioneer” inventions more generously. A typical claim during the latter part of the 19th century literally incorporated the specification into the claim and a typical question was whether the scope of protection should be limited to the structure disclosed in the specification. In Sessions v. Romadka, 145 U.S. 29, 31, 12 S.Ct. 799, 799-800, 36 L.Ed. 609 (1892), the claim at issue read:
3. The spring catches, I, constructed and applied to the front of the body, as described, in combination with the tongues or hasps, J, on the top, when arranged to operate as set forth.
The letter references are to parts set out in the specification. In reversing on the issue of infringement, the Court stated:
In view of the fact that Taylor was a pioneer in the art of making a practical metallic trunk fastener, and invented a principle which has gone into almost universal use in this country, we think he is entitled to a liberal construction of his claim, and that the Romadka device, containing as it does all the elements of his combination, should be held an infringement, though there are superficial dissimilarities in their construction.
Id. at 45, 12 S.Ct. at 803. Because of the pioneer nature of the invention, the Court concluded that the claim should not be limited by the letter references back to the specification. But see Lehigh Valley R. Co. v. Kearney, 158 U.S. 461, 469, 15 S.Ct. 871, 874, 39 L.Ed. 1055 (1895) (contra where the invention was merely an improvement).
The above cases illustrate the critical point. The scope of protection, whether liberal or narrow, was treated as a separate question from the fact of equivalency. Under the Act of 1870, the Court continued to hold that the construction of a patent claim was an issue of law for the court alone, not the jury. Market St. Cable Ry. Co. v. Rowley, 155 U.S. 621, 625, 15 S.Ct. 224, 226, 39 L.Ed. 284 (1895). The Court instructed the jury on the scope of the invention. Coupe, 155 U.S. at 579-80, 15 S.Ct. at 205. See also Singer Co., 192 U.S. at 275, 24 S.Ct. at 292; Heald v. Rice, 104 U.S. 737, 749, 26 L.Ed. 910 (1882).
In holding that the doctrine was not restricted to pioneer inventions, the Court reiterated in Continental Paper Bag Co. v. Eastern Paper Bag Co., 210 U.S. 405, 414, 28 S.Ct. 748, 749, 52 L.Ed. 1122 (1908), that the *1569legal effect, i.e., “construction” was a matter which courts determined:
The right view is expressed in Miller v. Eagle Mfg. Co., 151 U.S. 186, 207, [14 S.Ct. 310, 318-19, 38 L.Ed. 121] as follows: “The range of equivalents depends upon the extent and nature of the invention. If the invention is broad and primary in its character, the range of equivalents will be correspondingly bz’oad, under the liberal construction which the courts give to such inventions. ”
See also Westinghouse v. Boyden Power Brake Co., 170 U.S. 537, 569, 18 S.Ct. 707, 723, 42 L.Ed. 1136 (1898) (Court analyzing effect of claim language referring back to specification); Sanitary Refrigerator, 280 U.S. at 36, 50 S.Ct. at 11 (“Both Circuit Courts of Appeal recognized that the [patent in suit] had some range of equivalents.”); Singer Co., 192 U.S. at 285, 24 S.Ct. at 299 (Court “determined proper construction” and denied “broadening of the scope of the invention” beyond express limitations).
Under the foregoing precedent, infringement depended not only on the interpretation of the words of the claims, but also upon the court’s determination that the literal words of the claim should or should not control. Thus, the court determined both the meaning and scope of the claim. My reading of the Supreme Court’s decisions of the era leads me to conclude that the Court generally used the word “interpret” when it was speaking of the meaning of the words and “construe” in connection with determining protection beyond the words, that is, the “scope” of protection for the claim, as in contract law. 3 A. Corbin, Contracts § 534 (1960); 4 S. Williston, Contracts § 602 (Jaeger ed. 1961); ALI, Restatement (Second), Contracts § 226, Comment c. (Tent. Draft No. 5. Mar. 31,1970). This distinction leads to understanding some of the niceties in the Court’s analyses. However, interpretation and construction are now used interchangeably, see Markman, 52 F.3d at 976 n. 6, 34 USPQ2d at 1326 n. 6, and, in any event, any difference in these words is irrelevant to the issue in this case. Both the “meaning and scope” of a patent claim were treated as issues of law for the court to decide.21
Because of the narrow view of many judges respecting the legal scope of protection and, thus, the need to cover variations expressly in the turn of the century era, the numbers of claims in patents proliferated to cover variations. The Patent Office sometimes fixed the number of claims arbitrarily. It also became the practice to use broad terms so as to claim as broadly as possible. The elements in the claim were frequently described as a nonspecific “means” for performing a function. Ellis, supra note 14 at § 16. Thus, by claiming in this or a similar manner, an accused infringer could be brought under the literal claim language.22
The application of the doctrine of equivalents then took a twist. Despite the literal claim language expressed as a “means,” (i.e., any means), infringement extended only to the structure or elements disclosed in the specification as embodiments of the invention and equivalents of such structure- — not to all equivalents. See, e.g., Continental Paper Bag, 210 U.S. at 412-13, 28 S.Ct. at 748-49.23 The doctrine of equivalents was then used to determine whether
the claim should be restricted on the ground that a claim can validly cover only what the inventor discloses and equivalents thereof. In other words, so far as the patentee is concerned, the doctrine of equivalents is used negatively. It is used to narrow his claims — not to expand them. *1570Ellis, supra note 14 at § 49. In current “paténtese,” this would be called the “reverse” doctrine of equivalents, use of the doctrine to restrict infringement even though covered by the literal language of a claim. Use of the doctrine to restrict broad claims became almost the exclusive use of the doctrine. Id.
A critical decision of the Supreme Court on claiming practice was handed down in Halliburton Oil Well Cementing Co. v. Walker, 329 U.S. 1, 67 S.Ct. 6, 91 L.Ed. 3 (1946). The Court declared an invention could not be claimed by a functional “means” expression at the “point of novelty.” Such language rendered the claim “indefinite” under Rev. Stat. 4888. (This ruling was overruled in the 1952 Act, now 35 U.S.C. § 112, ¶ 6 which allows any element of a claim to be expressed as a “means.”)
During the 1930’s and 1940’s, the Supreme Court spoke frequently about the criticality of claim language so as to provide the public with notice of protected rights and to encourage innovation by others. In holding claims invalid, the Court stated, for example, in Permutit Co. v. Graver Corp., 284 U.S. 52, 60, 52 S.Ct. 53, 55, 76 L.Ed. 163 (1931):
The statute requires the patentee ... to inform the public during the life of the patent of the limits of the monopoly asserted, so that it may be known which features may be safely used or manufactured without a license and which may not.
And in United Carbon Co. v. Binney & Smith Co., 317 U.S. 228, 236, 63 S.Ct. 165, 170, 87 L.Ed. 232 (1942), it stated:
A zone of uncertainty which enterprise and experimentation may enter only at the risk of infringement claims would discourage invention only a little less than unequivocal foreclosure of the field.
However, the Court did not take the opportunity when presented to do away with the doctrine of equivalents, a principal cause of such uncertainty. See Martin J. Adelman and Gary L. Francione, The Doctrine of Equivalents in Patent Law: Questions that Pennwalt Did Not Answer, 137 U.Pa.L.Rev. 673, 682-83 (1989). In Exhibit Supply Co. v. Ace Patents Corp., 315 U.S. 126, 62 S.Ct. 513, 86 L.Ed. 736 (1942), the Court merely equivocated on the doctrine’s continued viability. Concluding that, in any event, estoppel precluded a finding of infringement by equivalency, the Court stated:
Whatever may be the appropriate scope and application of the doctrine of equivalents, where a claim is allowed without a restrictive amendment, it has long been settled that recourse may not be had to that doctrine to recapture claims which the patentee has surrendered by amendment.
Id. at 136, 62 S.Ct. at 518.
2. Legal Limitations on Infringing Equivalents
Under each of the variants of the doctrine, the Supreme Court limited the range of permissible infringing equivalents by rules and tenets of construction which provided a measure of certainty against unknowing infringement by equivalency.
a. Known Equivalents
It logically follows from the original rationale of Winans that a patentee intends to claim equivalents that an inventor could not be deemed to claim what one of skill in the art did not know at the time the patent issued. Thus, the Court limited the range of infringing substitutions to those in which components were substituted which were known to be equivalents. Where the invention was an improvement on a known process or machine, the substitution had to be known in that art as an equivalent at the time the patent issued. Seymour v. Osborne, 78 U.S. (11 Wall.) 516, 556, 20 L.Ed. 33 (1870). In Gill v. Wells, 89 U.S. (22 Wall.) 1, 28-30, 22 L.Ed. 699 (1874), the Court used the phrase “legal equivalent within the meaning of the Patent law” to identify this restriction on infringing equivalents. Equivalency-in-fact was not enough. The Court explained:
Questions of the kind usually arise in comparing the machine of the defendant in a suit for infringement with that of the plaintiff, and the rule is that if the defendant omits entirely one of the ingredients of the plaintiffs combination, without substituting any other, he does not infringe, and if he substitutes another in the place of the one *1571omitted, which is new or which performs a substantially different function, or even if it is old but ivas not known at the date of the plaintiffs patent as a proper substitute for the omitted ingredient, he does not infringe.* By an equivalent in such a case it is meant that the ingredient substituted for the one withdrawn performs the same function as the other, and that it was ivell known at the date of the patent securing the invention as a proper substitute for the one omitted in the patented combination.†
[I]t is clear law that the substituted ingredient cannot be regarded as a legal equivalent, within the meaning of the Patent law, unless it performs substantially the same function as the ingredient withdrawn, and was well knoivn as such an ingredient at the date of the original patent and as a proper substitute for the ingredient which was included in the patented combination.
Gill, 89 U.S. at 28, 30, 22 L.Ed. 699 (emphasis added).
The case of Gould v. Rees, 82 U.S. (15 Wall.) 187, 21 L.Ed. 39 (1872), cited in Gill, is particularly instructive on the legal insufficiency of an equivalency-in-fact test to determine infringement. The Court held that the instructions to the jury were legally erroneous in failing to preclude certain equivalents from the ambit of infringement. Id. at 194-95, 21 L.Ed. 39. On a challenge to the instructions, the Court stated:
Unexplained, the theory assumed by the court warranted the jury in finding for the plaintiff, though the defendant in constructing his machine omitted one of the ingredients of the plaintiffs combination and substituted another in its place to perform the same function, whether the ingredient substituted for the one omitted ivas or was not newly discovered, or was or was not well known at the date of the plaintiff’s patent as a proper substitute for the one omitted from the combination constituting the plaintiffs invention.
Tested by these principles, as the instruction in question must be, it is plainly erroneous, as it warranted the jury in finding for the plaintiff, whether the ingredient substituted for the one omitted was new or old, or whether the one substituted was or was not well known at the date of the plaintiff’s patent as a proper substitute for the omitted ingredient.
Id. at 193-95, 21 L.Ed. 39 (emphasis added).
As indicated, the Court mandated a broader range of infringing equivalents for what it termed “primary” or “pioneer” inventions or for an invention having particular merit.24 Continental Paper Bag, 210 U.S. at 415, 28 S.Ct. at 749-50; Miller v. Eagle Mfg. Co., 151 U.S. 186, 207, 14 S.Ct. 310, 318-19, 38 L.Ed. 121 (1894); Morley Sewing Machine Co. v. Lancaster, 129 U.S. 263, 273, 9 S.Ct. 299, 302, 32 L.Ed. 715 (1889); McCormick v. Talcott, 61 U.S. (20 How.) 402, 405, 15 L.Ed. 930 (1857); Eibel Process Co. v. Minnesota & Ontario Paper Co., 261 U.S. 45, 63, 43 S.Ct. 322; 328, 67 L.Ed. 523 (1923). However, even in the context of a pioneer patent, the Court applied a “known equivalents” rule, albeit appropriately modified to eliminate the requirement of being known in that previously unknown art at the time the patent issued. As explained in Morley Sewing Machine:
It may be true that the defendant’s peculiar form of stitch was unknown before; and it may also be true that his arrangement for carrying the buttons with their eyes upward, and turning the eyes into a horizontal plane by the twisting of the *1572conveyer-way, was not before known. Of course, they were not before known in a machine for automatically sewing buttons to a fabric, because Morley’s machine was the first to do that. But still, the defendant employs for the above purposes known devices, which, in mechanics, were recognized as proper substitutes for the devices used by Morley to effect the same results.
In this sense, the mechanical devices used by the defendant are known substitutes or equivalents for those employed in the Morley machine to effect the same result; and this is the proper meaning of the term “known equivalent,” in reference to a pioneer machine such as that of Morley. Otherwise, a difference in the particular devices used to accomplish a particular result in such a machine would always enable a defendant to escape the charge of infringement, provided such devices were new with the defendant in such a machine, because, as no machine for accomplishing the result existed before that of the plaintiff, the particular device alleged to avoid infringement could not have existed or been known in such a machine prior to the plaintiffs invention.
129 U.S. at 289-90, 9 S.Ct. at 308.
The tenet that the substitution had to be a known equivalent at the issue date was consistently applied prior to Graver and was explicitly reiterated in 1946 by the Supreme Court in Halliburton Oil Well Cementing, 329 U.S. at 13, 67 S.Ct. at 12, shortly before Graver II, where the Court explained:
[T]he alleged infringer could have prevailed if the substituted device (1) performed a substantially different function; (2) was not known at the date of Walker’s patent as a proper substitute for the resonator; or (3) had been actually invented after the date of the patent. [Emphasis added.]
Thus, the law preceding Graver II was that equivalency had to be known at the date of the patent.25
b. Prosecution History Estoppel
A construction of the claim to cover equivalents is precluded to the extent of the actions taken and the statements made by the patentee to the Patent Office in securing the patent grant. A patentee is not entitled, after patent issuance, to have protection from a claim extend to devices or processes or elements therein which during prosecution the inventor treated as a different invention from the one for which the inventor sought and obtained protection. Even where the scope could extend to equivalents, infringement is barred by reason of the patentee’s manifest intent.
The precedent is voluminous in which the Court applied estoppel based on prosecution as a matter of law. See Sutter v. Robinson, 119 U.S. 530, 541, 7 S.Ct. 376, 381-82, 30 L.Ed. 492 (1886) (“[Patentee] is not at liberty now to insist upon a construction of his patent [ie., legal effect] which will include what he was expressly required to abandon and disavow as a condition of the grant.”); Keystone Driller Co. v. Northwest Eng’g Corp., 294 U.S. 42, 48, 55 S.Ct. 262, 265, 79 L.Ed. 747 (1935) (Principle applied “that where such broad claims are denied and a narrower substituted, the patentee is estopped to read the granted claim as the equivalent of those which were rejected.” (footnote omitted)); *1573Smith v. Magic City Kennel Club, 282 U.S. 784, 790, 51 S.Ct. 291, 294, 75 L.Ed. 707 (1931) (“[WJhere a patentee has narrowed his claim in order to escape rejection, he may not ‘by resort to the doctrine of equivalents, give to the claim the larger scope which it might have had without the amendments which amount to a disclaimer.’ ”) (citing Weber Electric Co. v. E.H. Freeman Electric Co., 256 U.S. 668, 677, 41 S.Ct. 600, 603, 65 L.Ed. 1162 (1921)); and I.T.S. Rubber Co. v. Essex Rubber Co., 272 U.S. 429, 444, 47 S.Ct. 136, 141, 71 L.Ed. 335 (1926) (same).
c. Prior Art Limitations
Somewhat related to the rationale of prosecution history estoppel, which applies to an element, is the tenet that a claim to a product or process cannot be construed so as to encompass the same or substantially the same overall product or process in the prior art. Keystone Driller, 294 U.S. at 46-47, 55 S.Ct. at 264 (“We hold, in view of the prior art and of the file wrapper, the petitioner is not entitled to a broad reading of the claim.”); Computing Scale Co. v. Automatic Scale Co., 204 U.S. 609, 617, 27 S.Ct. 307, 310-11, 51 L.Ed. 645 (1907) (“[I]t is well settled that the claim as allowed must be read and interpreted with reference to the rejected claim, and to the prior state of the art, and cannot be so construed as to cover either what was rejected by the Patent Office or disclosed by prior devices.” (quoting Hubbell v. United States, 179 U.S. 77, 80, 21 S.Ct. 24, 25, 45 L.Ed. 95 (1900))); Knapp v. Morss, 150 U.S. 221, 224-25, 14 S.Ct. 81, 82, 37 L.Ed. 1059 (1893) (same). Accord Wilson Sporting Goods Co. v. David Geoffrey & Assoc., 904 F.2d 677, 684, 14 USPQ2d 1942, 1948 (Fed.Cir.), cert. denied, 498 U.S. 992, 111 S.Ct. 537, 112 L.Ed.2d 547 (1990).
d. No Enlargement of the Claim
Because of the importance of claim limitations in modern patent practice, litigants frequently argue today that infringement by equivalents ipso facto “enlarges” the claim to cover unclaimed subject matter. In a sense, that is true. When infringement is found under the doctrine, the claim protects something not literally specified in the claim. But a distinction can be drawn that is not too esoteric between substitution of an equivalent for a component in an invention and enlarging the metes and bounds of the invention beyond what is claimed. And it is a distinction that the Supreme Court has consistently drawn. Enlargement of the metes and bounds of the claim requires reexamination by the office charged with that function, now the Patent and Trademark Office. In contrast, assuming the PTO had done its job, as we must, known equivalents of a claim element were considered in determining pat-entability of an issued claim.26
Hilton Davis argues that the Warner-Jen-kinson process is an “equivalent” of the claimed process. In rejecting the patentee’s similar assertion of overall equivalency as the test for infringement, the Supreme Court held in Burr v. Duryee, 68 U.S. (1 Wall.) 531, 573, 17 L.Ed. 650 (1863):
The argument used to show infringement assumes that every combination of devices in a machine which is used to produce the same effect, is necessarily an equivalent for any other combination used for the same purpose. This is a flagrant abuse of the term “equivalent.”
Where a claim to an invention is expressed as a combination of elements, as here, “equivalents” in the sobriquet “Doctrine of Equivalents” refers to the equivalency of an element or part of the invention with one that is substituted in the accused product or process. The theory of infringement under the doctrine is that substitution of an equivalent for a part of a claimed combination means that the accused process or product is substantially the same as the claimed invention. Graver II, 339 U.S. at 608, 70 S.Ct. at 856; Sanitary Refrigerator, 280 U.S. at 41-42, 50 S.Ct. at 13; Union Paper Bag Machine Co. v. Murphy, 97 U.S. 120, 125, 24 L.Ed. 935 (1877). An infringing product or process may also be referred to as an “equivalent” of the invention, but more than overall equiva*1574lency is required. While a ballpoint and fountain pen may be equivalent overall, they are not equivalent in the sense of the doctrine because their components are not equivalent. As further explained in Burr, 68 U.S. at 572, 17 L.Ed. 650:
Now, the machine of Boyden has not one of the peculiar devices, or combination of devices, of the Wells machine, nor any substantial identity with it, unless by substantial identity is meant every machine which produces the same effect. These abstract phrases, “substantial identity,” “equivalent,” “mode of operation,” & c., are often used in such a vague and equivocal manner, that they mystify and lead many to absurd conclusions, who will not distinguish between things that differ. That two machines produce the same effect, will not justify the assertion that they are substantially the same, or that the devices used by one are, therefore, mere equivalents for those of the other. [Emphasis added.]
This view that the accused device or process must be more than “equivalent” overall reconciles the Supreme Court’s position on infringement by equivalents with its concurrent statements that “the courts have no right to enlarge a patent beyond the scope of its claims as allowed by the Patent Office.” Minerals Separation, 250 U.S. at 347, 39 S.Ct. at 499 (quoting Keystone Bridge, 95 U.S. at 278, 24 L.Ed. 344). The “scope” is not enlarged if courts do not go beyond the substitution of equivalent elements.
In Minerals Separation, the claims in issue specified the use of “a fraction of one percent of oil” in a process to improve the concentration of ore. The Court rejected the argument that the claims were indefinite because a precise fraction was not specified. Id. at 338, 39 S.Ct. at 496. But, by the same token, the express limitation to less than one percent fixed the scope of protection. Thus, the defendant’s use of oil in excess of one percent did not constitute infringement. Id. at 354, 39 S.Ct. at 501-02.
The prohibition against enlargement of a claim had been explicated earlier in the cited case Keystone Bridge, 95 U.S. at 278-79, 24 L.Ed. 344, as follows:
When a claim is so explicit, the courts cannot alter or enlarge it. If the patentees have not claimed the whole of their invention, and the omission has been the result of inadvertence, they should have sought to correct the error by a surrender of their patent and an application for a reissue.... [T]he courts have no right to enlarge a patent beyond the scope of its claim as allowed by the Patent Office, or the appellate tribunal to which contested applications are referred. When the terms of a claim in a patent are clear and distinct (as they always should be), the patentee, in a suit brought upon a patent, is bound by it.... As patents are procured ex parte, the public is not bound by them, but the patentees are. And the latter cannot show that their invention is broader than the terms of their claims; or, if broader, they must be held to have surrendered the surplus to the public.
If the patentee is entitled to a patent for [a] product [or process] ... and has failed ... to obtain it, the law affords him a remedy, by a surrender and reissue. When this is done, the world will have fan-notice of what he claims, of what his patent covers, and must govern themselves accordingly. ... [N]othing can be more just and fair, both to the patentee and to the public, than that the former should understand, and correctly describe, just what he has invented, and for what he claims a patent.
Similarly, the Court has repeatedly held that the complete elimination of an element in a claimed combination creates a different invention. Vance v. Campbell, 66 U.S. (1 Black) 427, 429-30, 17 L.Ed. 168 (1861); Schumacher v. Cornell, 96 U.S. 549, 554, 24 L.Ed. 676 (1877); accord Pennwalt v. Durand-Wayland, Inc., 833 F.2d 931, 4 USPQ2d 1737 (Fed.Cir.1987) (in banc), cert. denied, 485 U.S. 1009, 108 S.Ct. 1474, 99 L.Ed.2d 703 (1988). Equivalency encompasses merely substitutions in the patented combination. As held by the Court in Union Water-Meter, 101 U.S. at 337, 25 L.Ed. 1024:
It may be observed, before concluding this opinion, that the courts of this country cannot always indulge the same latitude *1575which is exercised by English judges in determining what parts of a machine are or are not material. Our law requires the patentee to specify particularly what he claims to be new, and if he claims a combination of certain elements or parts, we cannot declare that any one of these elements is immaterial. The patentee makes them all material by the restricted form of his claim. We can only decide whether any part omitted by an alleged infringer is supplied by some other device or instrumentality which is its equivalent.
See also Yale Lock Mfg. Co. v. Sargent, 117 U.S. 373, 378, 6 S.Ct. 931, 934, 29 L.Ed. 950 (1886) (“The defendant does not use the same combination, and employs no device as an equivalent and substitute for the omitted element.”, citing Union Water-Meter and Gage v. Herring, 107 U.S. 640, 2 S.Ct. 819, 27 L.Ed. 601 (1883)). In the Court’s view, where an equivalent is substituted for an element, the combination may remain essentially the same invention, not one broader than that of the claim, ie., a species claim remains a species claim. Conversely, to enforce the claim against a combination lacking even one element or its equivalent would extend coverage to a different invention because the claim is thereby broadened. The accused infringement is, ipso facto, not substantially the same as the patented invention without at least an equivalent substituent for each element of a claim. Infringement requires, inter alia, that every limitation of a claim be satisfied exactly or by an equivalent. Pennwalt, 833 F.2d at 935, 4 USPQ2d at 1739-40; Read Corp., 970 F.2d at 822, 23 USPQ2d at 1431. See Cimiotti Unhairing Co. v. American Fur Refining Co., 198 U.S. 399, 410, 25 S.Ct. 697, 702, 49 L.Ed. 1100 (1905), and cases cited therein.
It would unnecessarily lengthen this already lengthy opinion to review all of the permutations of the doctrine as applied to inventions of various types and character preceding the Graver II decision.27 Suffice here as a general summary that a finding of infringement under the doctrine required the court to determine the meaning and scope of the claim, based on the inventor manifesting an intent to cover equivalents in the claims or specification; the components of the accused product or process had to be equivalent in fact and finally, as a matter of law, the claim could cover only such equivalent sub-stituents in the accused product or process that did not violate the foregoing tenets.
3. Graver II
The majority states that “the Supreme Court mapped the modern contour’s of the doctrine of equivalents in its landmark Graver Tank decision,” slip op. at 1517, and concludes that infringement may be found under that precedent. Clearly not. The majority has taken an errant detour off the map drawn in the Graver II decision.
The importance of Graver II lies in the Court’s affirmation that the doctrine “continues today ready and available for utilization when the proper circumstances for its application arise.” Graver II, 339 U.S. at 608, 70 S.Ct. at 856. In the Graver decisions, the Supreme Court reviewed a ease raising issues of the validity and infringement of a patent owned by Linde Air Products Company for an electric welding process and for fluxes to be used therewith. The district court had held certain flux claims and all process claims invalid. Those claims merely required silicates or metallic silicates as the principal constituent of the flux. While nine operative silicates (including manganese) were listed in the specification,28 the claims were so broad as to include inoperative embodiments and processes. Linde Air Prods. Co. v. Graver Tank & Mfg. Co., 86 F.Supp. *1576191, 198, 75 USPQ 231, 237-38 (N.D.Ind.1947). However, the district court upheld four narrower flux claims and found infringement by application of the doctrine of equivalents. Id. at 199, 75 USPQ at 238. These valid flux claims (claims 18, 20, 22, and 23) specified a combination of ingredients, a major constituent being an alkaline earth metal silicate, such as magnesium silicate. The infringer used a nonalkaline earth metal, namely manganese, in the flux in place of magnesium. The district court first found that the two compositions were identical in operation, in the kind of weld produced, and for all practical purposes manganese silicate could be substituted in the claimed composition. The court then stated:
Whether it actually infringes these claims depends upon what application is made of the doctrine of equivalents.
Id. at 199, 75 USPQ at 238. To answer that question, the court considered the entirety of the patent and its prosecution. Looking to the specification, the court concluded that manganese was taught as a substituent in the invention and noted that the inventors specifically stated that other suitable materials including manganese could form the main body of the flux. Thus, applying the doctrine, the court entered judgment of infringement.
The Court of Appeals affirmed validity and infringement of the narrow claims, 167 F.2d 531, 538-39, 77 USPQ 207, 213 (7th Cir.1948), cert. granted, 335 U.S. 810, 69 S.Ct. 50, 93 L.Ed. 366 (1948), but reversed the judgment of invalidity of the broad claims, holding that they were valid as to the nine listed operative embodiments. Id. at 538, 77 USPQ at 212. In the first Supreme Court decision, Graver Tank Mfg Co. v. Linde Air Prods. Co., 336 U.S. 271, 69 S.Ct. 535, 93 L.Ed. 672 (1949) (Graver I), the Court unanimously upheld the validity and infringement of the narrow claims, two justices separately concurring on the issues of validity.29 The Court principally focused on the validity of the broad flux claims and held that the Court of Appeals erred in upholding their validity by restricting them to the nine operative embodiments in the specification, instead of evaluating the invention as claimed. Graver I, 336 U.S. at 277, 69 S.Ct. at 538-39.
The second Graver decision, 339 U.S. 605, 70 S.Ct. 854, 94 L.Ed. 1097 (Graver II), followed the grant of a petition for rehearing (337 U.S. 910, 69 S.Ct. 1046, 93 L.Ed. 1722) limited to the question of infringement of the four valid flux claims under the doctrine. Specifically, the Court stated that on rehearing the issue was limited to “the applicability of the doctrine of equivalents to the findings of fact in this case.” Id. at 910-11, 69 S.Ct. at 1046. See also Graver II, 339 U.S. at 606, 70 S.Ct. at 855. The infringer urged that the doctrine conflicted with the statutory requirement for distinct claims and should be eliminated as a basis for infringement. See Arthur H. Swanson, A Discussion of the Application of the Doctrine of Equivalents in the Graver v. Linde Case, 33 J.Pat.Off. Soc’y 19, 32 (Jan. 1951).
The Graver II analysis of infringement began by restating the general purposes behind recognition of infringement by an imitation which does not copy every literal detail of a patented invention. To accept literalism would encourage the unscrupulous copyist. “[Ujnimportant and insubstantial changes and substitutions in the patent” should not escape the reach of the law. Graver II, 339 U.S. at 607, 70 S.Ct. at 855-56. The Court denounced minor variations made to “conceal and shelter the piracy,” and saw unfairness in placing an inventor “at the mercy of ver-balism.” Id. The Court explained that the essence of the doctrine of equivalents, which had been applied since Winans (56 U.S. (15 How.) 330, 14 L.Ed. 717) and ever since, is that one may not practice a “fraud on a patent.” Graver II, 339 U.S. at 608, 70 S.Ct. at 856.
On the issue raised by the petition, the Court was unpersuaded to write an obituary for the doctrine. The Court reaffirmed its *1577viability, stating that it continued “ready and available for utilization when the proper circumstances for its application arise.” Graver II, 339 U.S. at 608, 70 S.Ct. at 856. It stated that a patentee may invoke this doctrine against a producer of a device that performs substantially the same function in substantially the same way to obtain the same result as the patented invention, quoting the tripartite test of Sanitary Refrigerator, 280 U.S. 30, 50 S.Ct. 9. Graver II, 339 U.S. at 608, 70 S.Ct. at 856.
The Court reaffirmed its precedent that both pioneer and secondary inventions were entitled to protection under the doctrine, although the area of equivalence may vary under the circumstances. It discussed the “reverse” doctrine of equivalents, citing Westinghouse, 170 U.S. 537, 568, 18 S.Ct. 707, 722, 42 L.Ed. 1136, a case with claims drafted referring back to the specification.30 It approved the application of the doctrine to chemical compositions “where there was equivalence between chemical ingredients” Graver II, 339 U.S. at 609, 70 S.Ct. at 856. With respect to determining equivalency of ingredients, it stated (emphasis added):
What constitutes equivalency must be determined against the context of the patent, the prior art, and the particular circumstances of this ease. Equivalence, in the patent law, is not the prisoner of a formula.... Consideration must be given to the purpose for which an ingredient is used in a patent, the qualities it has when combined with the other ingredients, and the function which it is intended to perform. An important factor is whether persons reasonably skilled in the art would have known of the interchangeability of an ingredient not contained in the patent ivith one that ivas.
A finding of equivalence is a determination of fact.
Id. As will be explained, I have added the emphasis to show how I believe the passage should be read.
Turning to the facts in Graver, the Court noted that the accused and patented products were “alike” in all respects except for the substitution of manganese for magnesium and stated:
The question which thus emerges is whether the substitution of the manganese which is not an alkaline earth metal for the magnesium which is, under the circumstances of this case, and in view of the technology and the prior art, is a change of such substance as to make the doctrine of equivalents inapplicable; or conversely, whether under the circumstances the change was so insubstantial that the trial court’s invocation of the doctrine of equivalents was justified.
Id. at 610, 70 S.Ct. at 857.
The Court noted the evidence of record and the findings of the trial judge therefrom that the accused “Lincolnweld” flux and the patented composition were substantially identical, that they were equivalent for welding purposes, and that “for all practical purposes, manganese silicate can be efficiently and effectually substituted for calcium and magnesium silicates as the major constituent of the welding composition.” These findings were held not clearly erroneous. Id. at 611-12, 70 S.Ct. at 858.
With respect to whether invocation of the doctrine was justified under the circumstances, the Court stated:
It is difficult to conceive of a case more appropriate for application of the doctrine of equivalents. The disclosures of the pri- or art made clear that manganese silicate was a useful ingredient in welding compositions. Specialists familiar with the problems of welding compositions understood that manganese was equivalent to and could be substituted for magnesium in the composition of the patented flux and then-observations were confirmed by the literature of chemistry. Without some explanation or indication that Lincolnweld was developed by independent research, the trial court could properly infer that the accused flux is the result of imitation rather than experimentation or invention. *1578Though infringement was not literal, the changes which avoid literal infringement are colorable only. We conclude that the trial court’s judgment of infringement respecting the four flux claims was proper, and we adhere to our prior decision on this aspect of the case.
Id. at 612, 70 S.Ct. at 858.
Once the Court decided to reendorse the doctrine, the Graver facts presented a routine case for affirming infringement. The infringer made a substitution for one ingredient in an improved patented flux composition. There was no “enlargement.” The substituted ingredient was known by those skilled in the art to be equivalent to the ingredient of the claim, having been used in prior art fluxes. The scope of the claim could include equivalents because of the extension to equivalents in the description in the specification and the broad (invalid) claims of the patent. Under such circumstances, the substitution of manganese for magnesium was only a “colorable” change.
It must be noted that the Court did not speak in Graver II of the need for notice to the public by the claim. However, the facts of Graver were unique: the manganese flux was a protected embodiment of the invention when the infringer began its use. It was disclosed in the specification as an example of the broad claims of the patent, as issued, to a flux containing metallic silicates. Graver I, 336 U.S. at 276, 69 S.Ct. at 538-39. Only after Graver I were these claims finally invalidated. Id. at 276-79, 69 S.Ct. at 538-40. Thus, the maxim that disclosed but unclaimed subject matter is deemed to be dedicated to the public31 did not apply. While the inventor’s attempt to claim his invention broadly failed, it was clear from the patent itself that the inventor did not intend to dedicate the disclosed manganese embodiment of his invention to the public. Clearly, the normal tension between the doctrine and notice to the public of the scope of an invention did not exist. The Graver infringer was on notice from the patent itself that it was taking an embodiment of the invention. A narrower application of the doctrine is hardly conceivable.
The majority seizes on the sentence “A finding of equivalence is a determination of fact,” Graver II, 339 U.S. at 609, 70 S.Ct. at 856-57, as a declaration by the Graver II Court that the determination of infringement under the doctrine is entirely a fact question and, therefore, for the jury. This would be a remarkable change from what the law had been. I read the statement in context to say “What constitutes equivalency ... of an ingredient not contained in the patent with one that was ... is a determination of fact.” It would be helpful to the position I advocate if the Court had expressly declared that the meaning and scope of a claim remain questions of law for the court. However, applying the doctrine of equivalents to the Court’s language, I equate “the application of the doctrine of equivalents,” the words the Court used, with determining the proper scope of the claim.
The Graver Court overturned none of its precedent that the meaning and scope of a claim are issues of law. To the contrary, the Court relied on Winans, Sanitary Refrigerator, Union Paper Bag Machine Co., Gould, and Westinghouse, id. at 608-09, 70 S.Ct. at 856, all of which reflect that principle. The legal effect of a claim, i.e., its scope, is a matter for the court to decide as an issue of law, not fact.
4. The Patent Act of 1952
The major revision of the patent statute in 1952 says nothing about infringement based on equivalency overall or to elements of a claim except in section 112, ¶ 6. It was argued, after enactment of the 1952 Act, post-Graver II, that the judicial doctrine of “equivalents” conflicted with the 1952 Act and should be eliminated. See Noll v. O.M. Scott Co., 467 F.2d 295, 299 n. 2, 175 USPQ 392, 396 n. 2 (6th Cir.1972), cert. denied, 411 U.S. 965, 93 S.Ct. 2143, 36 L.Ed.2d 685 (1973); 1970 Am.Pat.L. Ass’n Bull. 27-29. However, the appellate courts continued to apply Graver Tank both affirmatively and negatively under varying formulations of the standard. See Mead Digital Sys., Inc. v. A.B. Dick Co., 723 F.2d 455, 221 USPQ 1035 *1579(6th Cir.1983); CMI Corp. v. Barber-Greene Co., 683 F.2d 1061, 217 USPQ 456 (7th Cir.1982) (issue taken from jury); Sarkisian v. Winn-Proof Corp., 686 F.2d 671, 213 USPQ 912 (9th Cir.1981), on reh’g, 688 F.2d 647 (9th Cir.1982) (in banc), on remand, 697 F.2d 1313, 217 USPQ 702, cert. denied sub nom. Carsonite Int’l Corp. v. Carson Mfg. Co., 460 U.S. 1052, 103 S.Ct. 1499, 75 L.Ed.2d 930 (1983); Sealed Air Corp. v. United States Int’l Trade Comm’n, 645 F.2d 976, 209 USPQ 469 (CCPA 1981); Weidman Metal Masters Co. v. Glass Master Corp., 623 F.2d 1024, 207 USPQ 101 (5th Cir.1980), cert. denied, 450 U.S. 982, 101 S.Ct. 1519, 67 L.Ed.2d 817 (1981); Ziegler v. Phillips Petroleum Co., 483 F.2d 858, 177 USPQ 481 (5th Cir.), cert. denied 414 U.S. 1079, 94 S.Ct. 597, 38 L.Ed.2d 485 (1973); Graphicana Corp. v. Baia Corp., 472 F.2d 1202, 176 USPQ 455 (6th Cir.1973); Nelson v. Batson, 322 F.2d 132, 138 USPQ 552 (9th Cir.1963); Entron, Inc. v. Jerrold Elecs. Corp., 295 F.2d 670, 131 USPQ 209 (4th Cir.1961);
The Supreme Court itself has not spoken on the doctrine after enactment of the current statute. It has, however, used similar language in construing claims for validity purposes by reference to the specification, prior art, and the prosecution history. Graham v. John Deere, 383 U.S. 1, 33-34, 86 S.Ct. 684, 702, 15 L.Ed.2d 545 (1966) (claims carefully drafted; not free to assert broader view of invention);32 United States v. Adams, 383 U.S. 39, 48-51, 86 S.Ct. 708, 712-14, 15 L.Ed.2d 572 (1966) (no equivalent of invention in prior art).
Our precedent has also drawn a fact/law distinction, albeit not clearly, between the tripartite test and at least some restrictions on the scope of infringing equivalents. As stated in Thomas & Betts Corp. v. Litton Sys. Inc., 720 F.2d 1572, 1579, 220 USPQ 1, 6 (Fed.Cir.1983), we held:
A finding of equivalency, namely, that a device performs substantially the same function in substantially the same way to obtain the same result, is a determination of fact.
Conversely, we have declared de novo review is required for the legal questions of: (1) the meaning of the claim (Markman, 52 F.3d at 970-71, 34 USPQ2d at 1322; Read Corp., 970 F.2d at 821, 23 USPQ2d at 1431); (2) whether an asserted range of equivalents would cover what is already in the public domain (Wilson Sporting Goods, 904 F.2d at 683, 14 USPQ2d at 1948); and (3) prosecution history estoppel (Texas Instruments, Inc. v. United States Int’l Trade Comm’n, 988 F.2d 1165, 1173, 26 USPQ2d 1018, 1024 (Fed.Cir.1993)). Properly understood, as previously explained, these questions are merely subparts under the larger question of the scope of protection to which the claim is entitled. Accord Ziegler, 483 F.2d at 867, 177 USPQ at 487. We have, however, never articulated that under the doctrine the scope of equivalents is a separate legal question.
In sum, I conclude that a finding of infringement under the doctrine is a mixed question of law and fact. In a jury case, proper instructions must identify factual issues and legal limitations on finding equivalency. On the other hand, the meaning and scope of a claim are issues of law for the trial judge to decide. In ruling on the issue, I would require the trial judge to explain the basis for its conclusion that a competitor would have notice that the claim covers equivalent elements of the claimed product or process.
As will become evident, the trial judge in this case sent the ease to the jury without any restrictions on what was a legal equivalent beyond the tripartite test and their “finding” of no estoppel (an issue of law). Further, the court legally erred in holding, post-verdict, that “the doctrine of equivalents applies” under the circumstances of this ease.
D. Merits
1. The Patent Claims in Suit are Wrongfully Enlarged to Find Infringement
As indicated, the claimed invention consists of a combination of steps in a process for ultrafiltration of certain dyes. Specifically, *1580claim 1 requires, inter alia, three steps which are at issue here:
1. Ultrafiltration through a membrane having a nominal pore diameter of 5-15 Angstroms;
2. under a hydrostatic pressure of approximately 200 to 400 p.s.i.g.;
3. at a pH from approximately 6.0 to 9.0.
The accused process of Warner-Jenkinson operates at a hydrostatic pressure of 500 p.s.i.g.33 and at a pH of 5.0. Hilton Davis concedes that Warner-Jenkinson’s process does not literally satisfy either of those claim elements (elements 2 and 3). Infringement is asserted solely under the doctrine of equivalents.34 The court entered judgment upon the jury returning its verdict of infringement and issued an injunction enjoining Warner-Jenkinson from manufacturing or selling FD & C Red # 40 and FD & C Yellow # 6 dyes made at a pH less than 9.01 and at pressures at the input to the first membrane of less than 500 psig. Thus, the following comparison is appropriate:
Claimed Process Warner-Jenkinson Process Injunction Against Use of
Approx. 200-400 500 psig 500 psig or less psig
pH from approx. pH 5.0 any pH under
6.0-9.0 9.01
The majority nowhere recognizes the Supreme Court’s binding precedent prohibiting enlargement of the scope of a claim, which is dispositive of this appeal without further analysis.35 The claims are clear and specific. Nothing in the specification indicates that the invention extends beyond the specific ranges. There is no dispute that the Warner-Jenkin-son process does not meet all limitations of the claims. Under such circumstances, where there are no material issues of fact,
the question of infringement resolves itself in each case into one of law, depending upon a comparison between the structure disclosed on the face of the patent and the [accused device], and the correct application thereto of the rule of equivalency. Compare Singer Company v. Cramer, 192 U.S. 265, 275, 24 S.Ct. 291, 295, 48 L.Ed. 437.
Sanitary Refrigerator, 280 U.S. at 36, 50 S.Ct. at 11. Further, the most recent decision of the Supreme Court on point, Singer Co., 192 U.S. 265, 24 S.Ct. 291, held that under such circumstances the trial court erred in not directing a verdict for the defendant on a proper application of the doctrine of equivalents. As stated therein with emphasis added:
[I]t is unnecessary to consider and decide any other assignment [of error] than that based upon the exception to the refusal of the court, at the close of all the evidence, to instruct a verdict for the defendant on the ground that “no infringement whatever had been shown.” As in each of the patents in question it is apparent from the face of the instrument that extrinsic evidence is not needed to explain terms of art therein, or to apply the descriptions to the subject matter, and as we are able from mere comparison to comprehend what are *1581the inventions described in each patent and from such comparison to determine whether or not the Diehl device is an infringement upon that of Cramer, the question of infringement or no infringement is one of law and susceptible of determination on this writ of error.
Id. at 275, 24 S.Ct. at 295.
The Supreme Court then itself considered the structure of the accused device and, contrary to the majority opinion today, treated the issue of the “substantiality” of the change from the patented invention as a question for the court, not the jury:
Having determined the proper construction of the claim of the Cramer patent, which is relied upon, it remains only to consider whether, as correctly construed, infringement resulted from the employment by the Singer Company of the device covered by the Diehl patent. We find no difficulty in reaching a conclusion on this branch of the case. The treadle supports devised by Diehl, though they serve the same purpose as the device described and shown in the Cramer patent, are substantially different in construction. Irrespective of the question whether the treadle in the Diehl device is hung in the vertical cross brace proper, or in an addition thereto properly to be regarded as the lower cross rod or cross tie of the machine, it is manifest that the bearing is essentially different in construction from that of Cramer, and is not adapted to receive an oscillating bar; while the treadle is not supplied with long projections fitted to oscillate in the vertical cross bar on bearings therein, but is constructed to turn on point center screws which fit tightly in circular openings in projections from the vertical cross bar. There is no substantial identity in the character of the tivo devices, unless, by substantial identity, is meant every combination which produces the same effect. The differences between the Diehl device and the Cramer construction are substantial and not merely colorable. The trial court should have granted the motion to direct a verdict for the defendant.
Id. at 285-86, 24 S.Ct. at 299 (emphasis added).
In the present case, and as held in Singer, because we know what the claim means and we know what process parameters Warner-Jenkinson uses, the issue of infringement under the doctrine, that is, the scope of the claim, resolves itself into one of law. Under a correct application of the doctrine of equivalents, the trial court erred in denying Warner-Jenkinson’s JMOL.36
Nothing in Graver II warrants the finding of infringement in this case. The accused process does not substitute equivalents for each claim element. Hilton Davis set the range of equivalent pH and pressure values by the claim language “approximately 6.0 to 9.0” and “approximately 200 to 400 p.s.i.g.” It was not proved that 5.0 is the equivalent to one of skill in the art of approximately 6.0 to 9.0 pH or 500 p.s.i.g. is similarly equivalent to approximately 200-400 p.s.i.g. Hilton Davis had no claiming difficulties as in Graver.37 There is no indication in the specification that the invention was broader than claimed. In any event, the patentee merely had to set wider ranges during prosecution (or within two years from issuance) if the claim language did not reflect his invention. The claim would then have been examined for patentability on that basis. Whether such a claim would have been allowed, we do not know and cannot speculate. Hilton Davis is bound by the ranges it specified.
2. Prosecution History Estoppel
Finally, with respect to the pH step, an additional restriction comes into play. The examiner required the specific pH range to be added to the claim to overcome prior art. The prosecution history contains the following Examiner’s Interview Summary:
The Examiner stated that if claim 1 were amended to contain the pH range of 6 to 9, *1582the rejection on prior art would be overcome.
Hilton Davis amended its claim accordingly. Furthermore, Hilton Davis’s selection of a lower limit of 6.0 was intentional. Dr. Cook, an inventor, testified that Hilton Davis’s process foamed undesirably if the pH dropped below 6.0. The specific amendment of the pH range by Hilton Davis in response to the Examiner’s rejection precludes capturing the different process step of a pH of 6.0 used by W arner-J enkinson.
Finding a process with a pH of 5.0 to be an infringement, assuming a pH of 5.0 and a pH of 6.0 were equivalents, would violate the principle of prosecution history estoppel. In I.T.S. Rubber, 272 U.S. at 444-45, 47 S.Ct. at 141, the Court stated:
Nor can [the accused products] be held to be infringements even if we assume that, as asserted, they function in the same manner as three-point-contact lifts, and would infringe, as was conceded in the District Court, if the claims were not restricted by the limiting clause and were entitled to a construction warranting a wide range of equivalents. By the limitation of the claims in the Patent Office proceeding to the three-point-contact lift the patentee made this precise form a material element, and having thus narrowed the claims, cannot, as was said in the Weber Electric Company case, now enlarge their scope by a resort to the doctrine of equivalents. This would render nugatory the specific limitation.
Accord Exhibit Supply, 315 U.S. at 136-37, 62 S.Ct. at 518-19; Lehigh Valley, 158 U.S. at 469, 15 S.Ct. at 874.
Having narrowed the claim’s range of pH to secure the Examiner’s withdrawal of his prior rejection, Hilton Davis may not now resort to the doctrine to cover equivalents thereof. This would render nugatory the specific limitation of the range of pH.
Hilton Davis’s concession that a pH of 5.0 is not “approximately 6.0 to 9.0” and that 500 psig is not “approximately 200 to 400 psig” should have ended this charge of infringement as a matter of law. There was no material fact issue on infringement to give to the jury. The only disputed fact issue here relates to the pore size of the membrane. However, that dispute becomes immaterial because the undisputed facts are controlling in any event. Anderson v. Liberty Lobby, Inc., 477 U.S. 242, 248, 106 S.Ct. 2505, 2510, 91 L.Ed.2d 202 (1986). As a matter of law, the pH and pressure values in Warner-Jen-kinson’s process are outside the legal scope of protection of the ’746 patent. It is sur-plusage to point out that Warner-Jenkinson was not a “copyist” but developed its own process independently, an important factor in Graver II.
E. Conclusion
Under controlling Supreme Court precedent, the standard for infringement under the doctrine includes the legal limitation that a claim may not be enlarged beyond what was allowed by the Patent Office. In addition, the prosecution history creates an es-toppel respecting the pH limitation. As in Sanitary Refrigerator, 280 U.S. 30, 50 S.Ct. 9, and Singer Co., 192 U.S. 265, 24 S.Ct. 291, the issue of infringement resolves to a question of law.38 Upon a correct application of the doctrine of equivalents to undisputed facts, the accused process does not infringe. Thus, the district court erred in not granting JMOL and entering judgment for Warner-Jenkinson.39
As Warner-Jenkinson argues, it has been held liable without any possibility of notice that its process fell within the claims of the ’746 patent. Claims must tell the public not only what it cannot do but also what it can do. Permutit Co., 284 U.S. at 60, 52 *1583S.Ct. at 55. Cf. A.B. Small Co. v. American Sugar Ref. Co., 267 U.S. 233, 239, 45 S.Ct. 295, 297, 69 L.Ed. 589 (1925) (due process contravened where no specific or definite act was forbidden and liability depended on acts being “unjust and unreasonable in the estimation of the court and the jury.”).
I would reverse the judgment of infringement.

. See Asherman v. Meachum, 957 F.2d 978, 983-85 (2nd Cir.1992), for conflicting views on the propriety of this procedure under 28 U.S.C. § 46 and Fed.R.Civ.P. 35(a).

. In a Jepson claim, the preamble before the words "wherein the improvement comprises" recites what is old in the art. The invention of the applicant follows those words. See 2 D. Chisum, Patents, § 8.06[1][c]; Ex parte Jepson, 1917 C.D. 62, 243 O.G. 525 (Ass't Comm’r Pat. 1917).
Claim 1, the only independent claim found to be infringed, reads:
1. In a process for the purification of a dye selected from the group consisting of the diso-dium salt of l-[ (6-methoxy-4-sulfo-3-methyl-phenyl)azo]-2-naphthol-6-sulfonic acid, the disodium salt of l-[ (4-sulfophenyI)azo]-2-na-phthol-6-sulfonic acid, the trisodium salt of 1- [ 1 -(4-sulfonaphthyl)azo]-2-naphthol-3,6 — disulfonic acid, the disodium salt of 2 — [l—(4— sulfonaphthyl)azo]-l-naphthol-4-suIfonic acid and the sodium salt of 2-(2-quinoyl)-l,3-in-danedione-sulfonic acid as the products resulting, respectively, from the diazotization of 5-methoxy-2-methylsulfanilic acid in water with sodium nitrite in the presence of hydrochloric acid followed by the coupling under alkaline conditions of the resulting 5-methoxy-4-sulfo-2-methylphenyldiazonium chloride with sodium 2-naphthol-6-sulfonate; the diazotization of sulfanilic acid in water with sodium nitrite in the presence of hydrochloric acid followed by the coupling under alkaline conditions of the resulting 4-sulfophenyldiazonium chloride with sodium 2-naphthol-6-sulfonate; the dia-zotization of 4-aminonaphthalene-l-sulfonic acid in water with sodium nitrite in the presence of hydrochloric acid followed by the coupling under alkaline conditions of the resulting l-sulfonaphthyl-4-diazonium chloride with disodium 2-naphthol-3,6-disulfonate; the diazo-tization of 4-aminonaphthalene-l-sulfonic acid in water with sodium nitrite in the presence of hydrochloric acid followed by the coupling under alkaline conditions of the resulting 1-suIfonaphthyl-4-diazonium chloride with sodium l-naphthol-4-sulfonate; and the condensation of 2-quinaldine with phthalic anhy-dride followed by sulfonation of the resulting 2-(2-quinolyl)-l,3-indanedione, said dye being present in the resulting reaction mixtures, along with impurities,
*1552the improvement which comprises:
[a] subjecting an aqueous solution of the reaction mixture resulting from said coupling or said sulfonation to ultrafiltration
[b] through a membrane having a nominal pore diameter of 5-15 Angstroms
[c] under a hydrostatic pressure of approximately 200 to 400 p.s.i.g.,
[d] at a pH from approximately 6.0 to 9.0, to thereby cause separation of said impurities from said dye, said impurities of a molecular size smaller than the nominal pore diameter passing into the permeate on the downstream side of said membrane and said dye remaining in the concentrate, and when substantially all said impurities have been removed from said concentrate, as evidenced by their essential absence in said permeate, recovering said dye, in approximately 90% purity from said concentrate by evaporation of said concentrate to dryness.
(Alphabetic designations, paragraphing and emphasis added.) The dependent claims need not be considered separately in this case.

. Dialysis is quite unlike ultrafiltration. Dialysis utilizes a membrane separating two solutions having different concentrations, and works on the principle of diffusion (i.e. no applied pressure). See Ulrich Baurmeister, Encyclopedia op Chemical Technology, Vol. 8 at 58-59 (Mary Howe-Grant ed., 4th ed. 1993).

. The trial court opined, "Certainly if the Federal Circuit desires, they can instruct the District Courts of the country how to try patent cases to a jury in this vehicle if they choose to do so." We have left it in a mess. I would require at least insti-uctions on what facts are in dispute, as was done historically. The instructions in early jury trials were fact specific. See Appendix to Validity-

. This moots the question whether 35 U.S.C. § 281, providing the remedy of a “civil action” for patent infringement, provides a statutory right to a jury trial on the issue of validity.

. If the Lockwood case is dismissed by the Supreme Court on Lockwood’s pending motion, this appeal presents another vehicle for determining jury trial rights on the issue of validity. This is one of the few cases where a party has lodged proper objections.

. Rule 49(a) of the Federal Rules of Civil Procedure recites in pertinent part:
(a) Special Verdicts. The court may require a jury to return only a special verdict in the form of a special written finding upon each issue of fact....

. In Structural Rubber, there was no objection, as here, to trial of validity by either party. I would follow Structural Rubber where trial is to a jury by right or by agreement. 749 F.2d at 722-724, 223 USPQ at 1275-1277.

. The Department of Justice objected stating: "The section further introduces into the statute for the first time the controversial doctrine of equivalents without defining its scope.” Patent Law Codification and Revision: Hearings on H.R. 3760 Before Subcommittee No. 3 of the Committee on the Judiciary, 82nd Congress, 1st Sess. p. 95, (1951) (statement of T. Hayward Brown, Chief, Patent Litigation Unit, Claims Divisions, Department of Justice).

. Section 112, ¶ 6 does not cover single element claims. Special consideration may attend infringement by equivalents in such cases.

. I leave open the question whether infringement can extend to a later developed substituent under § 112, ¶ 6. If so, there should be some restraint, such as, that one of skill in the art would find it obvious to make the change. This is not part of the Graver II test which limited legal equivalents to pre-issuance knowledge of equivalency.

. See Harper & Row Publishers, Inc. v. Nation Enters., 471 U.S. 539, 560, 105 S.Ct. 2218, 2230, 85 L.Ed.2d 588 (1985); Fisher v. Dees, 794 F.2d 432, 436, 230 USPQ 421, 424 (9th Cir.1986); Maxtone-Graham v. Burtchaell, 803 F.2d 1253, 1258-59, 231 USPQ 534, 538 (2nd Cir.1986).

. The attempts by some judges to restrain it (see, e.g., London v. Carson Pirie Scott & Co., 946 F.2d 1534, 20 USPQ2d 1456 (Fed.Cir.1991)) have now been rejected.

. Section 6 of the statute recited, in pertinent part, that the inventor "shall particularly specify and point out the part, improvement, or combination, which he claims as his own invention or discovery.” Patent Act of 1836, Ch. 357, 5 Stat. 117. A typical claim was a catalog of selected elements without explanation of how they interacted, merely followed by words such as "constructed and adapted to operate substantially as set forth.” Ridsdale Ellis, Patent Claims, § 6 (1949).

. Until 1952, the statutory test for patentability was "invention.” R.S. § 4886. The term “anticipation" carried a broad meaning until the Patent Act of 1952. 66 Stat. 792. See, e.g., Yale Lock Mfg. Co. v. Greenleaf, 117 U.S. 554, 559, 29 L.Ed. 952 (1886) (claim "anticipated” because change over prior art device "would occur to rudest and most unskilled mechanic”); Yale Lock Mfg. Co. v. Sargent, 117 U.S. 536, 545-547, 6 S.Ct. 934, 938-40, 29 L.Ed. 954 (1886); Hotchkiss v. Greenwood, 52 U.S. (11 How.) 248, 268-69, 13 L.Ed. 683 (1850); The Corn-Planter Patent, 90 U.S. (23 Wall.) 181, 220, 23 L.Ed. 161 (1874) (reviewed machines of different construction for anticipation).
As we have previously noted in Argus Chem. Corp. v. Fibre Glass-Evercoat Co., 759 F.2d 10, 14 n. 5, 225 USPQ 1100, 1102 n. 5 (Fed.Cir.), cert. denied, 474 U.S. 903, 106 S.Ct. 231, 88 L.Ed.2d 230 (1985), the current meaning of "anticipation” is different. "Anticipation” now carries a narrower meaning, namely, that the invention lacks novelty. Under the current statute, any differences from a prior art device would be analyzed for "obviousness.” 35 U.S.C. § 103. Graham v. John Deere, 383 U.S. 1, 86 S.Ct. 684, 15 L.Ed.2d 545 (1966).

.See Hantman, supra.

. Throughout this period, patentability was treated as a question of fact in equity and at law. See, e.g., Tucker v. Spalding, 80 U.S. (13 Wall.) 453, 455, 20 L.Ed. 515 (1871) (jury trial); Bischoff *1566v. Wethered, 76 U.S. (9 Wall.) 812, 814, 19 L.Ed. 829 (1869) (jury trial); Gill v. Wells 89 U.S. 1, 22 L.Ed. 699 (1874) (jury trial on validity of reissue); Battin v. Taggert, 58 U.S. (17 How.) 74, 85, 15 L.Ed. 37 (1854) (jury trial); Cochrane v. Deener, 94 U.S. 780, 783, 24 L.Ed. 139 (1876) (equity); Seymour v. Osborne, 78 U.S. (11 Wall.) 516, 539, 20 L.Ed. 33 (1870) (equity); 3 William C. Robinson, The Law of Patents, § 1075 (1890).
That is no longer true under the current statute. Under the Patent Act of 1952, the Supreme Court has definitively ruled that "validity of a patent is a question of law.” Graham v. John Deere Co., 383 U.S. 1, 17, 86 S.Ct. 684, 694, 15 L.Ed.2d 545 (1966) (specifically adopting the view of the concurring opinion in Great Atlantic & Pacific Tea Co. v. Supermarket Equip. Corp., 340 U.S. 147, 155, 71 S.Ct. 127, 131-32, 95 L.Ed. 162, 87 USPQ 303, 307 (1950)). See also Sakraida v. Ag Pro, Inc., 425 U.S. 273, 280, 96 S.Ct. 1532, 1536, 47 L.Ed.2d 784 (1976) ("The ultimate test of patent validity is one of law.”); Lear, Inc. v. Adkins, 395 U.S. 653, 676, 89 S.Ct. 1902, 1914, 23 L.Ed.2d 610 (1969) (remanding so that Lear can argue invalidity "to the California courts in the first instance.”); Panduit Corp. v. Dennison Mfg. Co., 810 F.2d 1561, 1566-67, 1 USPQ2d 1593, 1596 (Fed.Cir.), cert. denied, 481 U.S. 1052, 107 S.Ct. 2187, 95 L.Ed.2d 843 (1987) ("Like all legal conclusions, that under § 103 rests on a factual evidentiary foundation.”).

. Act of July 8, 1870, Ch. 230, 16 Stat. 198, provided that the inventor "shall particularly point out and distinctly claim the part, improvement, or combination which he claims as his invention or discovery" (emphasis added). This statute, with some amendments not pertinent here, remained in effect until 1952.

. In Blonder-Tongue Lab. v. Univ. of Illinois Found., 402 U.S. 313, 336 n. 30, 91 S.Ct. 1434, 1447 n. 30, 28 L.Ed.2d 788 (1971), the Supreme Court noted that in the three year period spanning 1968-1970, only 13 of 382 patent cases going to trial were jury trials. In contrast, fiscal years 1992-1994 saw 163 of 274 patent trials being tried to a jury. See Lockwood, 50 F.3d at 980, 33 USPQ2d at 1408.

. See Report on S. 475, 75th Cong., 3d Sess., S.R. No. 1967 (1938), proposing a "Circuit Court for Patents”:
Judgments of the various courts on these important issues, even in litigation involving the same patents, are in many instances divergent, contradictory, and irreconcilable, and cause confusion and conflict hurtful alike to owners and users of the inventions in controversy.

. Markman reaffirmed that the interpretation of the words of a claim is exclusively an issue of law. If Markman should be reviewed by the Supreme Court, this case presents the complementary question whether determination of the scope of the claim likewise is a question of law.

. At the time, there was no statutory provision comparable to what is now § 112, ¶ 6.

. Similarly, claims which set out specific components but modified by the language "substantially as set forth” were held "to import into the claim the particulars of the specification.” Westinghouse, 170 U.S. at 558, 18 S.Ct. at 717. Such claims are no longer sanctioned by the PTO except for designs. Similarly, expressing an element in the claim as a specific structure "or equivalent" {e.g., a gear or equivalent) is not allowed in current practice although such language is appropriate in the specification.

 Gould v. Rees, 15 Wallace, 187, 21 L.Ed. 39.

. The term "pioneer” was defined in Westinghouse, 170 U.S. at 561-62, 18 S.Ct. at 718:
This word, although used somewhat loosely, is commonly understood to denote a patent covering a function never before performed, a wholly novel device, or one of such novelty and importance as to mark a distinct step in the progress of the art, as distinguished from a mere improvement or perfection of what had gone before. Most conspicuous examples of such patents are the one to Howe of the sewing machine; to Morse of the electrical telegraph; and to Bell of the telephone.
See also MAC Corp. v. Williams Patent Crusher & Pulverizer Co., 767 F.2d 882, 884 n. 3, 226 USPQ 515, 517 n. 3 (Fed.Cir.1985).

. Nat’l Cash Reg. Co. v. Boston Cash Indicator and Rec. Co., 156 U.S. 502, 516-17, 15 S.Ct. 434, 440, 39 L.Ed. 511 (1895); Hoyt v. Horne, 145 U.S. 302, 309, 12 S.Ct. 922, 924-25, 36 L.Ed. 713 (1892); Morley Sewing Machine, 129 U.S. at 289-90, 9 S.Ct. at 308; Electric RR Signal Co. v. Hall Railway Signal Co., 114 U.S. 87, 96, 5 S.Ct. 1069, 1075, 29 L.Ed. 96 (1885); Rowell v. Lindsay, 113 U.S. 97, 102, 5 S.Ct. 507, 510, 28 L.Ed. 906 (1885); Clough v. Gilbert & Barker Mfg. Co., 106 U.S. 166, 178, 1 S.Ct. 188, 197-98, 27 L.Ed. 134 (1882); Wicke v. Ostrum, 103 U.S. 461, 469, 26 L.Ed. 409 (1880); Goodyear Dental Vulcanite v. Davis, 102 U.S. 222, 227, 26 L.Ed. 149 (1880); Imhaeuser v. Buerk, 101 U.S. 647, 656, 25 L.Ed. 945 (1879); Fuller v. Yentzer, 94 U.S. 288, 297, 24 L.Ed. 103 (1876); Fuller v. Yentzer; Same v. Goodrich, 94 U.S. 299, 300, 24 L.Ed. 107 (1876); Gill, 89 U.S. at 30, 22 L.Ed. 699; Mitchell v. Tilghman, 86 U.S. (19 Wall.) 287, 418, 22 L.Ed. 125 (1873); Gould, 82 U.S. at 194, 21 L.Ed. 39; Seymour v. Osbourne, 78 U.S. (11 Wall.) 488, 556 (1870); McCormick, 61 U.S. at 405, 15 L.Ed. 930; O’Reilly, 56 U.S. at 123, 14 L.Ed. 601; Carver v. Hyde, 41 U.S. (16 Pet.) 513, 519, 10 L.Ed. 1051 (1842); Prouty, 41 U.S. at 341, 10 L.Ed. 985.

. Consideration of equivalents to elements of a claim has been part of examination of applications for patentability over prior art under all statutes. This concept is now embodied in examination under section 103. 35 U.S.C. § 103.

. The doctrine also encompassed changes other than substitution of an equivalent for a claim element, such as rearranging steps of a method, combining two parts into one, separating one element into two, and changes in shape. Sanitary Refrigerator involved reciprocal changes "in form and position"; the position of a lug was changed which required shortening the arm of a latch. 280 U.S. at 42, 50 S.Ct. at 13.

. At the time of filing the Linde application, the Patent Office restricted an applicant to three species claim. See L. Chasan, Graver v. Linde — A Valid Patent, J.Pat.Off.Soc’y, Vol. XXXII, No. 4, p. 285, 295-96 (April 1950) (PTO limited species claims to three in one application whereas the inventor in Graver had disclosed nine in its specification).

. The concurring opinion disagreed with the majority’s standard of review of validity as a finding of fact. In their view, "whether the thing patented amounts to a patentable invention is a question of law to be decided by the courts as such.” Graver I, 336 U.S. at 280, 69 S.Ct. at 540. That view prevailed ultimately in Graham v. John Deere, 383 U.S. 1, 86 S.Ct. 684, 15 L.Ed.2d 545 (1966).

. Because of current claiming practice, the reverse doctrine is now rarely invoked and even more rarely applied except under § 112, ¶ 6.

. Sontag Chain Stores, 310 U.S. at 293, 60 S.Ct. at 967.

. See Roy H. Wepner, The Patent Invalidity/Infringement Parallel: Symmetry or Semantics?, 93 Dickinson L.Rev. 67 (1988).

. The majority states that the Warner-Jenkin-son process operates at a pressure of 200 to 500 p.s.i.g. However, at the correct measuring point, the upstream side of the membrane, the pressure was 500 p.s.i.g. That the pressure reduces thereafter is irrelevant.

. There was no evidence of the pore size of the membranes in the ultrafiltration equipment used by Warner-Jenkinson. Warner-Jenkinson does not know the pore size of the membrane in its equipment and neither does Hilton Davis. Hilton Davis did not call the membrane supplier as a witness. The evidence is simply testimony that Warner-Jenkinson's pore size must be equivalent because the accused process works. In Malta v. Schulmerich Carillons Inc., 952 F.2d 1320, 21 USPQ2d 1161 (Fed.Cir.1991), cert. denied, 504 U.S. 974, 112 S.Ct. 2942, 119 L.Ed.2d 566 (1992), this court concluded that "conclusoiy statements” are "not sufficiently particularized evidence” to prove infringement under the doctrine of equivalents. Such evidence is clearly nonprobative that Warner-Jenkinson uses a membrane having the required pore size. Concluding Warner-Jenkinson’s membrane had the claimed pore diameter is nothing short of mere speculation. See Morton Int'l, Inc. v. Cardinal Chemical Co., 959 F.2d 948, 22 USPQ2d 1231 (Fed.Cir.1992) (no infringement based on mere speculation as to the existence of a claimed compound).

.The scope of enlargement of the pH value is staggering inasmuch as a change of one numerical value represents a relative change in the acidity equal to a factor of 10. A change of two numerical values represents a relative change in the acidity equal to a factor of 100 (i.e. the pH scale is logarithmic).

. That Warner-Jenkinson also argued it was entitled to judgment as a matter of equity does not take away from its right to judgment as a matter of law.

. See note 28, supra.

. Graver II did not overturn the precedent of Sanitary Refrigerator. Indeed, the Court cited that case with approval in Graver II.

. The injunction enjoining pH values of 2.0-4.0, in any event, is too broad. A process with a pH of 2.0-4.0 was not found to be infringing. Only an infringing process may be enjoined. KSM Fastening Sys. v. H.A. Jones Co., 776 F.2d 1522, 1526, 227 USPQ 676, 679 (Fed.Cir.1985) (contempt for violating an injunction limited to devices found to infringe).