Full opinion text
CALEB M. WRIGHT, Senior District Judge. Plaintiff, Johnson & Johnson (“J & J”) has brought an action against W. L. Gore & Associates, Inc. (“Gore”), charging infringement of U.S. Patent No. 3,002,770 covering a “Threaded Joint with Lubricating and Sealing Ribbon Interposed Between the Threads”. In its answer, defendant denies infringement, and asserts three grounds of invalidity with respect to the patent in suit: lack of inventorship under § 102(f), obviousness under § 103, and anticipation under § 102. In addition, defendant urges that the failure of plaintiff to reveal certain prior art to the Patent Office during prosecution of the patent application constitutes fraud which renders the patent unenforceable. Finally, defendant argues that plaintiff is barred from bringing the present suit on the grounds of laches and estoppel. Trial was had on the patent issues from January 27 to February 3, 1977. The following constitutes this Court’s findings of facts and conclusions of law as provided by Rule 52, Fed.R.Civ.P. 1. THE PATENT IN SUIT The patent in suit claims a threaded pipe joint sealed by a tape of unsintered polytetrafluoroethylene (“UPTFE” or “unsintered PTFE”) tape. It was issued to J & J as assignee of the named inventors, James A. Chesnut and Joseph D. Singalewitch, on October 3, 1961, pursuant to an application serial number 767,116, filed October 14, 1958, and a continuation-in-part application, serial number 849,536, filed October 29, 1959 while application number 767,116 was pending. All three claims of the patent are at issue here. Claim 1, which discloses most of the essential elements of the invention, recites: “1. A threaded joint comprising a male fitting having continuous male threads, a female fitting having continuous female threads adapted to mate with the threads on the male fitting, and a preformed transversely stretchable and compressible lubricating and sealing ribbon having a relatively low coefficient of friction and a high degree of lubricity wrapped circumferentially around the threads of the male fitting for at least one turn there around with the ends of the ribbon overlapped one upon the other by an appreciable amount, said overlapping end portions of the ribbon adhering to one another when pressed into contact by hand, said ribbon prior to turning the male and female fittings together being in the form of a flat coherent unsintered polytetrafluoroethylene film having a specific gravity in the range of about 1.2-1.8 and being about 1 to 20 mils in thickness, the male and female fittings being turned together with the ribbon compressed and conforming substantially with the shape of the space between the male and female threads and defined by said threads when the threads are turned together with the ribbon between them, the ribbon remaining in substantially continuous film form on the faces of the threads between the tips of said threads and providing the anti-binding and sealing barrier between the threads and a lubricated surface for turning the fittings with respect to one another at any time during the life of the joint, whereby there is provided a joint possessing the following properties: (a) leakproof tightness at low torque, (b) retention of leakproof tightness for the life of the joint, and (c) ease of opening the joint during its life. Claims 2 and 3 relate to the reusability feature of the completed joint. As is described by the specification, UPTFE tape is made by extruding and then calendaring a mixture of very fine, approximately spherical particles of UPTFE and a lubricant such as mineral spirits. After extrusion, the lubricant is evaporated, leaving a smooth, white porous tape which is inert to most chemicals. The tape is relatively flimsy, and can be torn easily by hand, yet can be stretched latitudinally as much as 100% without tearing. Tr. 17, 22. Due to the evaporation of the lubricant, the tape has a number of air voids or pores distributed throughout. Consequently, the tape has a specific gravity somewhat less than that of solid UPTFE, which is approximately 2.2. Since prior to the alleged invention of the patent in suit, UPTFE tape manufactured according to this process has been sold for use in wrapping wire to form an insulating coating. After the wire is wrapped with the tape, it is heated to a' temperature above the melting point of the UPTFE, thus sintering the UPTFE and creating a solid, nonporous insulating cover of sintered PTFE. Tr. 18. The process of making the joint is deceptively simple. The UPTFE tape is wrapped around the threads of the male member of the joint prior to assembly. The female member is then threaded onto the male member and tightened in the usual manner. When the female pipe joint member is turned onto the male member, it compacts the UPTFE material into the threads of the joint, compressing the material by squeezing out the air left in the tape. The tape is compressed to a density approximately that of solid PTFE. Tr. 24r-26. The formation of a reliably sealed pipe joint using the UPTFE tape is the result of the presence of tightly packed UPTFE completely surrounding at least one circumference of the threads. Pre-Trial Order, Admitted Facts, ¶ 11; Tr. 35. The claimed invention is a significant improvement over sealed threaded joints in the prior art. The tape is clean and easy to apply by hand, even at low temperatures, with virtually no waste. The joint may be sealed effectively at lower torques than are required using alternative methods. The tape itself is inert to most substances. The protective film formed by the tape resists corrosion and galling often experienced in galvanized iron threaded joints, and does not contaminate material carried through the pipe. The tape does not deteriorate due to age, cold or heat up to its sintering temperature of 320“ C. Because of the low coefficient of friction of the PTFE and the compressibility of the tape, the joint may be easily opened and can be resealed by applying slightly more torque than was required for the initial seal. Tr. 39-41. II. INVENTORSHIP Defendant’s first defense is that of derivation: that the named inventors, Chesnut and Singalewitch, derived the idea for the invention from a third party. According to defendant, Orrin G. Youngquist, an employee of E. I. du Pont de Nemours, first conceived the idea of using unsintered PTFE in tape form to seal threaded joints during the course of a meeting between sales representatives of du Pont and representatives of the Minnesota Mining and Manufacturing Co. (“3M”), in St. Paul, Minnesota in January, 1957. Youngquist allegedly subsequently disclosed the idea to Charles Carr, also of du Pont, in the spring of 1957. Carr in turn is alleged to have disclosed the idea to various employees of J & J, including James Chesnut, prior to March 19,1958, which has been admitted to be the date of alleged conception of Chesnut and Singalewitch. Pre-Trial Order, Admitted Facts ¶ 43; Tr. 247, 249-253, 303, 444. 35 U.S.C. § 102(f) provides that: “A person shall be entitled to a patent unless— . (f) he did not himself invent the subject matter sought to be patented To establish the defense of derivation under § 102(f), the defendant must prove both that the invention was previously conceived by another person, and that the complete conception was communicated to the party charged with derivation. Agawam Co. v. Jordan, 7 Wall. 583, 74 U.S. 583, 19 L.Ed. 177 (1868); Amax Fly Ash Corp. v. U. S., 514 F.2d 1041 (Ct.Cl.1975); Hedgewick v. Akers, 497 F.2d 905 (Cust. & Pat.App.1974); Erie Technological Products v. Die Craft Products, 318 F.Supp. 933 (N.D.Ill.1970), mod., 461 F.2d 5 (7th Cir. 1972). The presumption of validity set forth in 35 U.S.C. § 282 extends to the presumption that the inventors named in the patent are the true inventors. Acme Highway Products Corp. v. D. S. Brown Co., 431 F.2d 1074 (6th Cir. 1970), cert. denied, 401 U.S. 956, 91 S.Ct. 977, 28 L.Ed.2d 239 (1971). One who seeks to show that a patent is invalid under 35 U.S.C. § 102(f) must establish each element of the defense by clear and convincing proof, especially when much of the evidence is oral testimony unsupported by contemporaneous documentary evidence. Campbell v. Spectrum Automation Co., 513 F.2d 932 (6th Cir. 1975); Amax Fly Ash Corp. v. U. S., supra; Heyman Manufacturing Co. v. Hap Corp., 131 U.S.P.Q. 165 (D.R.I.1961). All the circumstances in the record must be considered in evaluating the sufficiency of the defendant’s proof. Hedgewick v. Akers, supra. A. Youngquist’s Conception On or about January 25, 1957, Orrin Youngquist, William Franta, and Charles H. Concklin, du Pont employees involved in selling Teflon resins in the Midwest, met with representatives of 3M at the 3M ch. fices in St. Paul, Minnesota. Tr. 216, 217 (Franta); 277-279 (Concklin); 435-436 (Youngquist). The independent testimony of Youngquist, Franta and Concklin is that during the course of the meeting, Youngquist suggested to the 3M personnel that the UPTFE tape then being manufactured as electric wire insulation might be useful in sealing threaded joints. Tr. 434 (Youngquist); 217-218 (Franta); 276-279 (Concklin). Following the meeting in St. Paul, the “Youngquist idea” was not disseminated generally to other customers. Tr. 243, 453. Youngquist did disclose the idea to Charles Carr, a du Pont salesman for Teflon products responsible for the Detroit region, on or about June 1957. Tr. 447, 471-472. Plaintiff introduced no direct contradictory testimony in rebuttal to defendant’s case. Plaintiff now urges the Court to discredit the testimony of defendant’s witnesses on the basis of circumstantial evidence with respect to the subsequent behavior of the individuals involved, especially the failure of du Pont or 3M to implement the “Youngquist idea”, and the failure of Youngquist to inform plaintiff’s personnel of his prior conception. Plaintiff urges the Court to infer from that behavior that the subject discussed at the 3M meeting was not the use of the UPTFE tape, but the use of UPTFE dispersions for sealing threaded joints. In view of all the circumstances presented in the record of this case, the Court cannot infer that the testimony of Youngquist, Franta and Concklin was unfounded or mistaken. Although the oral testimony of Youngquist, Franta and Concklin is uncorroborated by contemporaneous documentary evidence, it is sufficient to satisfy defendant’s burden of proof with respect to conception by Youngquist of the idea of using UPTFE tape as a pipe thread sealant. The testimony of all three men was credible. They were disinterested witnesses; each recalled the circumstances of the meeting independently. The minor discrepancies between their testimony do not detract from their credibility since those discrepancies do not go to the material elements of their testimony. When the alleged disclosure of the idea is put into context, plaintiff’s rebuttal arguments do not impeach the defense testimony. Youngquist, Franta and Concklin were all sales personnel with du Pont, concerned primarily with generating ideas for the use of Teflon in order to increase sales of Teflon resins, not with developing patentable inventions. As a general matter of corporate policy, du Pont had little interest in obtaining patents itself on end uses of Teflon, preferring to patent only the basic raw materials. Tr. 221, 479. In most cases, rather than experimenting with new ideas themselves, du Pont personnel would find an interested customer who was willing to develop the idea, and then would follow the customer’s progress. Tr. 248, 285,479. The Court, therefore, cannot infer from du Pont’s failure to implement Youngquist’s suggestion that no such suggestion was made, especially considering the volume of suggestions generated by the salesmen in various contacts with customers for Teflon resins. Similarly, no such inference can be drawn from 3M’s failure to experiment with the use of the tape as a pipe thread sealant. There could be numerous alternative reasons, such as reluctance to expand in a new market or failure to appreciate the commercial possibilities of the idea, which explain 3M’s apparent lack of interest. The fact that Youngquist did not mention his prior conception to plaintiff’s personnel when he was on notice of the plan to market the tape and Chesnut’s and Singalewitch’s claims of inventorship is not probative on the question of whether he in fact conceived the idea. Although the failure of an alleged inventor to make a claim of inventorship when other parties are being publicized as the true inventors is evidence which may permit the inference that the alleged inventor’s assertions are not sustainable, Honeywell, Inc. v. Sperry Rand Corp., 54 F.R.D. 593 (D.Minn.1973), the evidence as to Youngquist’s behavior does not support such an inference. It is consistent with his testimony that he did not inform anyone at Permacel that he had suggested the idea previous to Chesnut’s conception, especially when it is considered that soon after the patent was issued, Youngquist did relate the entire story to Ryan, who could most logically be expected to act upon that information if needed. See n. 15, supra. Having found that Youngquist did suggest the idea of using UPTFE tape to seal threaded joints during the 3M meeting in 1957, the Court must determine further whether that bare suggestion was a sufficient enabling disclosure to support the conception necessary for a defense of derivation. To establish derivation from a third party, that third party need not have reduced the invention to practice, but must have a clearly defined idea of the invention in all its essential attributes that is capable of being reduced to practice by the inventor or one skilled in the art. Amax Fly Ash Corp. v. U. S., supra. See also, Hedgewick v. Akers, supra; Erie Technological Products v. Die Craft Products, supra. Youngquist testified that he, “asked or stated that I thought a good application for unsintered tape might be to wrap joints of pipes”. Tr. 443-444. As was noted under similar facts in Erie Technological Products v. Die Craft Products, supra, the claimed apparatus is “simplicity itself in its breadth”. It does not take extraordinary skill or ingenuity to determine that by “wrapping joints of pipes”, Youngquist meant that the tape would be applied circumferentially around the male member, and the joint completed in the usual fashion. At the time, Franta understood Youngquist’s idea to involve wrapping the unsintered tape around the male threads, tearing it off, and then completing the joint. Tr. 218-219. The record amply supports the conclusion that any person with experience in sealing threaded joints with devices or materials of the prior art, would be able to implement the claimed invention on the basis of such a suggestion. See, e. g., Tr. 199-201. On the basis of the above, the Court finds that defendant has met its burden of proof with respect to the first prong of its defense, the prior conception of the idea. B. Communication to Chesnut and Singalewitch The evidence with respect to the communication of the Youngquist idea to Chesnut or Singalewiteh is far more equivocal than that advanced in support of the original conception by Youngquist, and falls well short of clear and convincing. Defendant relies on the oral testimony of Charles Carr, a du Pont salesman, and on DX-3, a memorandum sent by Carr to Youngquist in November, 1961, over four years after the events in question, which sets forth his version of the disclosure to Chesnut. Carr’s oral testimony in that regard is uncorroborated by any contemporaneous documentation. Youngquist and Carr both testified that Youngquist disclosed the idea of using UPTFE tape as a thread sealant to Carr, then a salesman of Teflon products assigned to the Detroit area, while Carr was in Detroit. Tr. 349-350, 380 (Carr); Tr. 447, 471-472 (Youngquist). In January, 1958, Carr was reassigned to the New Jersey area, which encompassed Permacel’s pilot plant in Milltown, and the Sales Division of Permacel in New Brunswick. Tr. 345. Carr visited the pilot plant installation and the main offices on a frequent, but not programmed basis. Tr. 357-358, 697-698, 703. Carr testified that he disclosed the Youngquist idea to personnel at Permacel, including James Chesnut, during the course of those visits sometime prior to March 19, 1958. Tr. 357-360. Carr’s testimony is contradictory and vague as to exactly when and whom at Permacel he first informed of the idea. More critically, Carr cannot specifically pinpoint the time of his alleged disclosure of the idea to Chesnut. His “best estimate” was February, 1958, but he admitted that it could just as well have been sometime in March. Tr. 394. Plaintiff’s version of Chesnut’s and Singalewitch’s alleged conception of the use of XJPTFE tape as a pipe thread sealant differs significantly from that offered by Carr. According to Singalewitch, the idea of using the tape as a sealant for threaded pipe joints came to him and Chesnut on the afternoon of March 19,1958 when a maintenance man reported having had trouble stopping a leak in the threaded joint of one of the plant’s steam lines. Tr. 697-698, 719, 742. Chesnut and Singalewitch suggested that he use some of the UPTFE tape available in the plant to seal the joint in an effort to stop the leak. Tr. 697. The same day, Chesnut and Singalewitch had lunched with Carr at a restaurant outside of the pilot plant. Tr. 700, 704-705. Singalewitch recalled that, during that lunch, Carr mentioned the use of Teflon “T-30” dispersions for sealing threaded joints. Tr. 719-720, 723, 735, 738. The date of the alleged conception was established by reference to Singalewitch’s notebook entry of March 19, 1958, which refers to the lunch with Chesnut and Carr: “. . .—Had lunch with JAC & Charles Carr; DuPont representative. Carr discussed application of ‘filled’ teflon tapes for mechanical application and use of new DuPont primer for forming cementable fused Teflon.—” DX-45. Carr’s dispersion suggestion was not mentioned in the notebook entry because Singalewitch did not think it was a viable product for Permacel. Tr. 720. On June 24, 1958, Chesnut made the following entry in his notebook with respect to the conception of the idea: “Discussed with Dr. Les Weidner the possibility of securing a patent on the use of Teflon film as a sealant and a lubricant in the connections of threaded pipe. This idea previously evolved during a conversation between Don Singalewitch, Charles Carr, DuPont Salesman, and the writer sometime in the spring, probably April of 1958. [March 19, 1958 according to Don Singalewitch’s notes]. It is not remembered who actually suggested the Teflon film be tried for this application. It is remembered that Charlie Carr initiated the subject by referring to the use for ‘Teflon’ 30 dispersion. After the conversation the writer evaluated some joints the threads having been wrapped withunsintered Teflon. The material is excellent for the use—conforming, reducing friction, being solid so all is used, easy to apply, insoluble, not messy, uniform, time saving, reusable. The writer then shortly (a matter of less than one week) contacted Mr. Farrell and Mr. Anderson concerning the marketing of unsintered Teflon as a pipe thread sealant and lubricant. Other materials were also tested for this use such as Skived Teflon and polyethylene. Altho these materials could be used, they did not display all the advantages of nonsintered Teflon. Primarily, they were difficult to seal before threading the pipe. Saran would not display this disadvantage & might be o. k.” DX-46. It is Singalewitch’s testimony that he understood the reference in the Chesnut entry to the effect that “it is not remembered who actually suggested that Teflon film be tried” to mean that Chesnut couldn’t remember whether he or Singalewitch made the initial suggestion. Tr. 722. While the patent application covering the use of UPTFE tape as a thread sealant was being drafted by Charles Harris, a Permacel attorney, Chesnut and Singalewitch had several discussions regarding the question of inventorship. Singalewitch recalls that although they felt that Carr’s dispersion suggestion may have started their thinking of PTFE generally, they concluded that they were the sole joint inventors of the patent joint. Tr. 735-738, 762, 797, 824-825. Singalewitch executed the application oath to that effect, in the belief that it was true. He testified that he would not have done so if he had thought Carr had suggested the idea, and that he was positive Carr had not done so. Tr. 750, 797. In light of all the evidence, the Court finds that defendant has failed to show, by clear and convincing evidence, that the idea of using UPTFE tape as a pipe thread sealant was communicated to either James Chesnut or Joseph Singalewitch prior to March 19, 1958. Singalewitch’s testimony was entirely credible. While the notebook entries are ambiguous, they are not inconsistent with Singalewitch’s story. The Chesnut entry, DX-46, corroborates Singalewitch’s testimony in its most important feature—that Carr had discussed the use of Teflon dispersions as pipe sealants during the lunch. The Court has no reason to doubt that Chesnut and Singalewitch felt, at the time they signed their oath of inventorship, that they had conceived the idea independently. Carr’s testimony, on the other hand, is uncorroborated. No contemporary documentary evidence was produced in support of his story, although Carr followed the company practice of filing call reports on the substance of meetings with customers. Tr. 295-297, 348-349. The testimony of Bullock and Farrell contradicted that of Carr as to whether he informed anyone at Permacel of the idea. Even if it is assumed that Carr suggested the use of UPTFE tape to Permacel personnel, Carr’s testimony as to the time he made those suggestions is vague and far from clear and convincing evidence that the alleged disclosure was made prior to March 19, 1958. Since Carr made frequent trips to the Permacel installations throughout the spring and summer of 1958, and was deeply involved in the sales program for the tape, it is possible that he has confused discussions with Chesnut, Farrell and Fitzgerald about the tape which took place sometime after March 19th with his alleged recollection of an earlier meeting. Further, Carr’s subsequent behavior casts considerable doubt on the credibility of his testimony. Carr was intimately involved with the development and marketing of the tape sealant by Permacel, Tr. 357-359, 364-366, 398-399, and supposedly knew that he had given Chesnut the idea. Nevertheless, he never mentioned that disclosure to anyone at Permacel, despite ample opportunity to do so. be Derivation from a third party cannot established unless communication to the named inventors is proved. Defendant has not carried its burden of proof with respect to that communication, and consequently the defense of derivation is without merit. III. OBVIOUSNESS As a second ground of invalidity and unenforceability, defendant argues that the invention claimed would be obvious over prior art to a person ordinarily skilled in the art. Under 35 U.S.C. § 103, an invention is not patentable, “if the differences between the subject matter sought to be patented and the prior art are such that the subject matter as a whole would have been obvious at the time the invention was made to a person having ordinary skill in the art to which said subject matter pertains. . . ” While the ultimate test of patent validity is one of law, Great A & P Tea Co. v. Supermarket Corp., 340 U.S..147, 71 S.Ct. 127, 95 L.Ed. 162 (1950), resolution of the obviousness issue entails several basic factual inquiries, as outlined in the landmark case of Graham v. John Deere Co., 383 U.S. 1, 17-18, 86 S.Ct. 684, 694, 15 L.Ed.2d 545 (1966): “. . Under § 103, the scope and content of the prior art are to be determined; differences between the prior art and the claims at issue are to be ascertained; and the level of ordinary skill in the pertinent art resolved. Against this background, the obviousness or non-obviousness of the subject matter is determined. Such secondary considerations as commercial success, long felt but unsolved needs, failure of others, etc., might be utilized to give light to the circumstances surrounding the origin of the subject matter sought to be patented. As indicia of obviousness or nonobviousness, these inquiries may have relevancy. The Court is mindful of the admonition that “. . . the simplicity of an invention is not a necessary bar to a patent”. Eagle Iron Works v. McLanahan Corp., 429 F.2d 1375, 1382 (3rd Cir. 1970). See also, Clopay Corp. v. Blessings Corp., 422 F.Supp. 1312 (D.Del.1976). After careful consideration of the factual inquiries mandated by Graham v. John Deere, supra, however, the Court concludes that the subject matter patented would have been obvious to one skilled in the art. A. Scope and Content of Prior Art In analyzing the obviousness question, the Court starts with the presumption that the patent is valid. The burden of demonstrating invalidity by clear and convincing proof rests on the party asserting it. 35 U.S.C. § 282; Aluminum Co. of America v. Amerola Products Corp., 194 U.S.P.Q. 1 (3rd Cir. 1977); Tokyo Shibaura Electric Co. Ltd. v. Zenith Radio Corp., 404 F.Supp. 547 (D.Del.1975), aff’d., 548 F.2d 88 (3rd Cir. 1977). When relevant prior art has not been considered by the Patent Office, however, the presumption of validity is weakened or overcome. Aluminum Co. of America v. Amerola Products Corp., supra; Philips Electronic & Pharmaceutical Industries Corp. v. Thermal & Electronics Industries, Inc., 450 F.2d 1164, 1176 (3rd Cir. 1971). The determination of the degree by which the presumption is weakened rests on a balancing of the pertinence of the newly cited art against the pertinence of the art actually considered by the Patent Office. Aluminum Co. of America v. Amerola Products Corp., supra. Tee-Pak, Inc. v. St. Regis Paper Co., 491 F.2d 1193, 1196 (6th Cir. 1974). The Patent Examiner cited eight U.S. and two foreign patents during examination of the application that matured into the ’770 patent. Of these, the Court finds the two Llewellyn patents Nos. 2,578,523 (DX-33), and 2,586,357 (DX-34), and the Couhig patent No. 1,875,708 (DX-29) to be pertinent. Defendant introduced several references not before the Patent Office, including two counterpart foreign patents corresponding to the same invention, seven publications and one physical exhibit. Of these, those which refer to the properties of PTFE used in various sealing applications are as relevant to the validity of the ’770 patent as were the three patents listed above which were considered by the Patent Examiner. As that art was not submitted to the Patent Examiner, the presumption of validity is substantially vitiated. Allegheny Drop Forge Co. v. Portee, Inc., 541 F.2d 383 (3rd Cir. 1976). The relevant prior art is that which one skilled in the art would reasonably be expected to' look to in order to solve a problem in the art. Tokyo Shibaura, supra; In re Grout, 377 F.2d 1019 (Cust. & Pat.App.1957). The problem to be solved in the instant case is leaking threaded pipe joints. The crux of the problem is to find a way to seal the joint effectively. In attempting to resolve that problem, one skilled in the art would reasonably be expected to look first to devices, compositions and materials being used in sealing threaded joints, and second to devices, compositions and materials used in analogous sealing applications. 1. Prior art sealants used with threaded joints. U.S. Patent No. 1,875,708 to Couhig, which was revealed to the Patent Office, teaches making a threaded joint with a sealing substance in the form of a thin strip, sheet or ribbon of woven fabric which is impregnated with a composition of asphaltum, graphite, soap and a lubricating oil. DX-29, p. 2, col. 1. The strip of material is wrapped circumferentially around the threads of the male member: In using the preferred embodiment of my invention, I take a strip of impregnated fabric, cut it to a suitable length, and wind it snugly over the male threads, See Figure 1, and into the valleys thereof and then assemble the joints in the ordinary way. DX-29, p. 2, col. 1; Tr. 602. In making up the joint, the cloth tape disintegrates under the destruction shearing forces produced by the tightening of the threads, leaving a residue of liquid and fibrous material within the joint. Tr. 1052-1054. Some of that material may leak out into the joint and contaminate the substances carried in the pipe. Tr. 1054. Couhig teaches that one object of his invention is to provide a method and means for sealing threaded pipe joints without causing the joint to stick together, as where paste compositions are employed, enabling the joints to be unscrewed for repair or replacement with facility. DX-29, p. 1, col. II; Tr. 600-601. The concept of winding a string-like material around the male threads before completing the joint is also taught by the use of candlewicking, a soft cotton string used by plumbers prior to 1958 primarily for sealing problem joints. Tr. 197-198, 201-202, 208; DX-78. As was demonstrated at trial, the candlewicking is wrapped snugly around the threads of the male member, so that the material fits into the valleys of the threads. As the candlewicking is soft and weak, it tends to disintegrate within the threads after the female member is tightened onto the male threads. Prior to the invention of the patent in suit, a commonly used method of sealing threaded joints was the application of certain pipe dopes or gunks, paste-like compositions which were applied to the male threads with a stick or brush before screwing the pipe members together. Those dopes or gunks which were commercially available, primarily white lead and red lead dopes, used a viscous liquid with some lubricating properties which contained finely divided solid materials such as graphite. Tr. 39-40, 89, 189-190, 459-460. The principal function of these gunks or dopes is to lubricate the threads to facilitate the high torques necessary to create a virtual metal to metal seal. The dopes are generally messy and unsatisfactory to use. As the joint is tightened, much of the dope is pushed out of the joint at both ends, resulting in waste and contamination of the pipe. Another type of thread sealant pipe dope available in the prior art contained fine particles of unsintered PTFE in a thickened dispersion form. To make the dope, a commercially available UPTFE dispersion of UPTFE particles and water is thickened by dissolving a substance such as polyvinyl alcohol in the dispersion. In the process, some of the dispersion is mixed in a Waring Blender to fibrillate some of the fine particles in the dispersion. Tr. 569, 1075-1077. The dope is applied to the joint in the same manner as other liquid dopes. Defendant’s expert, Dr. Wilbert Gore, testified that the UPTFE dope functions differently from the conventional prior art dopes. Whereas the conventional dopes act primarily as a lubricant, much of the paste being squeezed out of the joint, Gore testified that the UPTFE dope forms a substantially continuous film around the threads during assembly of the joint by virtue of the shearing forces generated by the turning, closely fitting members. According to Dr. Gore, the shearing forces fibrillate some of the UPTFE particles, forming a sort of matrix which retains the unfibrillated particles, but which lets the liquid dispersing medium escape from the joint. A sufficient amount of UPTFE material is retained within the joint to form a sealing film. Tr. 569-570, 574, 613-614, 650-659, 664, 669-670. Dr. Gore’s testimony was largely theoretical speculation based on his extensive knowledge of PTFE technology. He had not run tests or made up any joints using UPTFE dispersions to verify his hypothesis. Plaintiff’s expert, Dr. Cyrus Bemmels, testified that the UPTFE dispersion functions in the same manner as the conventional dopes, as a lubricating medium. He disputed Dr. Gore’s theory that it is largely water and liquid dispersing medium that is expelled from the joint during assembly, not the UPTFE particles themselves. According to Dr. Bemmels, both liquid and particles are squeezed out of the ends of the joint as the joint is completed. Tr. 1019-1020. He testified, based on personal observation of joints he had made using the dispersion, that the material which oozes out of the ends of the joint is identical in appearance to the starting medium. Tr. 1022. Plaintiff introduced into evidence two of the joints which had been prepared by Dr. Bemmels. The threads of the pipes contained a few film-like patches, but no continuous film could be observed around the threads. Tr. 1048-1052, 1096. Dr. Bemmels did not test those joints to see if an effective seal was obtained. In other tests, using the UPTFE dispersion, made to measure the torque necessary to seal dispersion joints, he was able to obtain a successful seal in four out of ten joints. Tr. 1033; PX-57. Plaintiff contends that the UPTFE dispersions are, in fact, inferior to conventional pipe dopes in performance and results. Since the UPTFE dispersion is in a liquid form, it possesses the same disadvantages as the conventional dopes, such as messiness, difficulty of application, and waste. There is no evidence in the record, however, that the UPTFE dispersions are inferior to other dopes. Plaintiff has offered no evidence comparing the performance of the UPTFE dopes with that of conventional dopes. All of the tests performed by Dr. Bemmels using the UPTFE dispersion were directed towards comparing the performance of the UPTFE dispersion with that of the UPTFE tape. The only evidence in the record with respect to a comparison of the UPTFE dopes with conventional dopes are several publication references cited by defendant, all of which teach that UPTFE dopes have distinct advantages over conventional pipe dopes, including corrosion resistance, prevention of galling, ease of assembly and disassembly (including partial takedown and retightening), lubricity and inertness. Two of the cited references teach that the UPTFE dispersion forms a film between the threads of the male and female members. 2. Prior art sealants used in applications not involving threaded joints. Other than the Teflon dispersions, solid UPTFE was known to have utility in certain sealing applications not involving threaded joints. U.S. Patent No. 2,578,523 to Llewellyn is directed to the manufacture of gaskets and shaft seals or packings made from UPTFE in the form of hard, tough, dense sheets. Although not heated above its sintering point, the material is rolled and pressed until it exhibits many of the properties of sintered PTFE, such as extreme toughness and densification. The patent teaches the advantages of a tight seal, resistance to corrosion and high temperatures, and lubricity. DX-33, p. 1, col. 1; p. 3, col. 5. An article in Plastics, January, 1958, entitled “Calendered PTFE Tape”, teaches that the unsintered PTPE tape may be effective in certain sealing applications: PTPE is, of course, now an established basic material in the manufacture of seals and gaskets and this also refers to engineering packings. For particular applications seals of spirally wound construction using unsintered tape to seal in a core are proving attractive. In the case of the braided type of packing, veneered tape alone or over asbestos holds the field at present but the unsintered type now appears to have advantages. DX-22, p. 32, col. 3; Tr. 591-592. 3. Prior art relating to unsintered PTFE tape. Defendant has also cited references which deal specifically with the properties of the calendared UPTPE tape, outside of the context of sealing applications. U.S. Patent No. 2,586,357 to Llewellyn, which was cited to the Patent Office, discloses a method of manufacturing an unsintered PTPE tape. The method disclosed is essentially the same as that described in the ’770 patent specifications. There is no disclosure of the use of the tape in its unsintered form other than as an intermediary product. The examples contemplate that the tape will be sintered in its final form. DX-34. There is no specific disclosure of the use of the tape, in any form, in a sealing application. The advantages of the use of the tape in its unsintered form are taught by the January, 1958, Plastics articles, DX-22, supra: An advantage of calendered tape over veneered tape or cast film is that it comes from the calendaring process in the unsintered condition and although it may be passed immediately through a sintering bath it is generally preferable to postpone this step until the tape has been applied to its final purpose. The particular merits of tape in this condition are that it is soft and pliable, lending itself to wrapping or shaping over irregular articles. DX-22, p. 32, col. 1; Tr. 590-591. The article cites the following “outstanding combinations” of PTPE properties: (a) unaffected by all known solvents and is completely inert to almost all acids, alkalies and other chemicals, (p. 32, col. i); (b) extremely low coefficient of friction. (p. 31, col. 1); (c) low transverse tensile strength and high transverse elongation, (p. 32, col. 1); and (d) could be fabricated in unsintered tape from in thicknesses of from 3 to 10 mils. (p. 32, col. 3). The same article teaches the usefulness of the unsintered tape in certain gasketing, packing and sealing applications. See, supra, at B. Differences Between Prior Art and Claims at Issue The prior art disclosed both the concept of sealing a threaded joint by wrapping the male threads with a ribbon or string before completion of the joint (Couhig patent, candlewicking), and the advantageous use of unsintered PTFE, in dispersion form, as a material for sealing threaded joints. Among the advantages cited in the prior art for the use of UPTFE dispersions are the following: (a) provides ease of assembly and dis-assembly due to the high lubricity (low coefficient of friction) of the UPTFE material. (b) eliminates mechanical galling and galvanic corrosion between male and female members of dissimilar materials. (e) provides biological inertness of the Teflon sealing material. (d) promotes integrity of the seal, even when joints are tightened or frequently disassembled. The prior art also disclosed that the use of UPTFE in other sealing applications had certain advantages over the use of alternative materials, including inertness, heat stability, and lubricity. Prior to the date of the invention in question, the art with respect to the properties of UPTFE tape recognized the conformability of the tape to wrapping or shaping over irregular articles. What the prior art did not disclose was the use of a coherent, compressible ribbon of unsintered UPTFE for sealing threaded pipe joints, which sealing material remained substantially intact and coherent within the joint after the joint was completed, and permitted the joint to be completely opened and resealed without addition of more sealing material. C. Level of Skill The pertinent art in the instant case comprises devices, compositions and materials used to seal threaded joints. In a field that diffuse, it is difficult to pinpoint a “substantial body of people who devote regular and substantial effort” to solving the type of problem solved by the alleged invention. Erie Technological Products v. Die Craft Products, supra. Almost anyone who has done ordinary home plumbing has faced the problem of fixing a leaking pipe joint. In determining the appropriate level of skill in the pertinent art, however, the Court must focus on the problem solver and not on the user of the solution. Systematic Tool & Machine Co. v. Walter Kidde and Co., Inc., 555 F.2d 342 (3rd Cir., 1977) (mechanically skilled individual familiar with the design of food slicing devices); Universal Athletic Sales Co. v. American Gym Rec. & Ath. Equipment Corp., Inc., 546 F,2d 530 (3rd Cir. 1976) (designer of body-training devices). In other words, one skilled in the art is a person who would reasonably be expected to come up with a solution to a given problem in the art. The appropriate level of skill in the instant case is greater than that of a plumber, who has familiarity only with the method of application and use of various materials used to seal threaded joints. One skilled in the art would also have familiarity with the nature and method of manufacture of the various devices, compositions and materials used to seal thread joints. For example, employees in the production and research departments of companies which manufacture the various' sealing devices, who are responsible for development and manufacture of the devices, would be considered skilled in the art. No extraordinary technical training or expertise is required, but the appropriate level of skill demands a familiarity with how the devices work, not just with their method of use. D. Analysis The invention claimed by the ’770 patent is a combination of elements which were old and well known prior to the date of filing of the application. If the combination produces an unexpected result different from the prior art, the invention may be patentable. U.S. v. Adams, 383 U.S. 39, 86 S.Ct. 708,15 L.Ed.2d 572 (1966); Eagle Iron Works v. McLanahan Corp., supra. The validity of the patent must be scrutinized, however, “with a care proportioned to the difficulty and improbability of finding invention in an assembly of old elements. . ” Great A & P Tea Co. v. Supermarket Corp., 340 U.S. 147, 152, 71 S.Ct. 127, 130, 95 L.Ed. 162 (1950); Sakraida v. Ag Pro., Inc., 425 U.S. 273, 281, 96 S.Ct. 1532, 1537, 47 L.Ed.2d 784 (1976). Although the threaded members of the joint function no differently than those of prior art, the UPTFE tape performs an entirely different function than prior art UPTFE tape. The only commercially known use of extruded UPTFE tape prior to the claimed invention was as an intermediary product used to insulate wire. In its final form, after being wrapped around the wire and heated, the tape formed a coherent, sintered mass, with properties qualitatively different from those of the original tape. In its unsintered form, the tape had no commercial application. Consequently, the claimed invention is distinguishable from those found obvious in Sakraida v. Ag Pro., supra, and Anderson’s-Black Rock v. Pavement Co., 396 U.S. 57, 90 S.Ct. 305, 24 L.Ed.2d 258 (1969), where the inventions merely combined old elements, each of which performed the same function it had in the prior art. That does not dispose of the obviousness problem. Although the inventors utilized a component which had previously been used only in another field, the Court must determine whether it would have been obvious to one skilled in the art to employ that component to solve the problem it solves in the alleged invention. Continental Can Co., Inc. v. Old Dominion Box Co., Inc., 393 F.2d 321 (2d Cir. 1968). At some point, the bringing together of knowledge held in widely diverse fields itself becomes invention. Ling-Temco-Vought, Inc. v. Kollsman Instrument Corp., 372 F.2d 263, 268, n. 1 (2d Cir. 1967). The mere fact, however, that the invention combines references from diverse fields does not necessarily render the invention nonobvious. If the fields utilize such similar principles of design or function that an inventor would reasonably be expected to look to that field for a solution of the problem which the patent device attempted to solve, the invention may be obvious. See, Tokyo Shibaura Electric Co., Ltd. v. Zenith Radio Corp., supra; Mott Corp. v. Sunflower Industries, Inc., 314 F.2d 872 (10th Cir. 1963); Novelart Manufacturing Co. v. Carlin Container Corp., 363 F.Supp. 58 (D.N.J.1973); In re Grout, supra. The essence of the claimed inventive contribution of Chesnut and Singalewitch lies in their joint recognition of the usefulness of UPTFE tape, which had previously been used only for a different purpose in an unrelated application, as a pipe sealant for threaded joints. The prior use of the tape as wire insulation bears very little relationship to its use as a threaded pipe joint sealant. Some of the properties which make the tape well suited for sealing threaded joints, such as compressibility, lubricity and self-adhesion, have little utility in insulating electrical wire, but are rather inherent qualities of the tape attributable to the use of UPTFE as the primary material and to the method of manufacture. The question to be determined is whether solving the problem of leaking joints by drawing on knowledge of a material used only in an unrelated application constitutes invention under § 103, or is rather the result of the natural development of the art which would be obvious to one skilled in the art. See, Amax Fly Ash Corp. v. U.S., supra. The Court finds that the teachings of the prior art would reasonably lead one skilled in the art to investigate different forms of UPTFE then available, including the UPTFE tape, for effectiveness in sealing threaded joints. The fact that the tape was currently being sold only for a non-analogous use is not persuasive on the issue of obviousness. The crucial link between the prior art and the claimed invention is the use of UPTFE as the sealing material. No teaching of the prior art indicated that UPTFE in tape form would not have utility as a threaded pipe joint sealant. The teachings rather would reasonably lead one skilled in the art towards the use of such tape. The prior art teaches that UPTFE has certain inherent qualities which make it a superior material in sealing applications. In particular, the UPTFE pipe dopes demonstrate the effectiveness of an unsintered PTFE in the precise sealing application here. Other forms of UPTFE were shown to be effective in a range of analogous sealing applications. Although there is no evidence in the record that the tape was widely used for any purpose other than wire insulation prior to 1958, the Plastics reference (DX-22) teaches that it was known to have utility in sealing and packing operations, largely because of its flexibility and conformability. The demonstrated utility of UPTFE in sealing applications would have made it obvious to anyone skilled in the art to look to the field of UPTFE technology, and the multitude of applications and uses which had been devised for UPTFE, for a solution to the problem of leaking pipe joints. In view of the teachings in the Couhig patent and the experience of persons skilled in the art with devices such as candlewicking, one of the most likely candidates available as a solution to that particular problem would be the UPTFE in a tape form. A second inquiry remains. If one skilled in the art had looked to other UPTFE applications, including UPTFE tape, would it have been obvious that the tape would effectively seal a threaded joint? The Court finds that it would have been obvious to one skilled in the art. The inherent properties of UPTFE, such as lubricity and inertness, and its effectiveness in sealing and prevention of mechanical galling were known in the art. Plaintiff’s expert, Dr. Bemmels, testified that the physical properties of the tape, such as its apparent flimsiness and weakness, would appear to be disadvantages to one skilled in the art, as one would expect that the tape would disintegrate under the destructive pressures created by the tightening of the joint. Tr. 32-33. The prior art teaches, however, that the tape has a high transverse elongation when stretched. This is confirmed by a physical examination of the tape. Tr. 17, 22. One skilled in the art would perceive that this elongation feature would enable the tape to fit over the crests and into the valleys of the threads without substantial tearing. Even if one skilled in the art would have expected some disintegration of the tape within the joint, he would not expect that the disintegration would impair the effectiveness of the tape as a sealant. Couhig clearly teaches that the tape disintegrates within the joint, but that an effective seal may nevertheless be obtained. The UPTFE dopes likewise are affected by the stresses with the joint, which force much of the material out of the joint, yet leave enough within the joint to seal effectively. Plaintiff contends that the tape sealed joint would not be obvious as it coacts in a completely different fashion than the UPTFE dopes, by compressing the tape within the threads to completely pack one circumference of the pipe. While the intentional use of UPTFE in a compressible form as a pipe thread sealant was not taught by the prior art, the Court still finds that the utility of the UPTFE tape as a threaded pipe sealant would have been obvious. Compressibility is an inherent feature of the tape. Even assuming that Chesnut and Singalewitch were the first to recognize the compressibility of the tape, recognition of the inherent properties of a material does not constitute invention. Armour Pharmaceutical Co. v. Richardson Merrell, Inc., 264 F.Supp. 1013 (D.Del.1967). As was found in Gould National Batteries, Inc. v. Guiton Industries, Inc., 361 F.2d 912, 914 (3rd Cir. 1966), where the allegedly novel feature of the invention is a structural element substantially similar to one old in the art, the claim to patentability may not rest on the discovery of a new use to which such an element was readily accommodable by reason of its intrinsic properties. The advantageous use of the compressibility feature by Chesnut and Singalewitch in making a sealed joint could not be said to be surprising. It would have been obvious to anyone skilled in the art that a tape which could be tightly compressed into the threads of the joint would be efficacious in effecting a tight seal, since it would form a protective barrier within the threads to halt leakage of any substance from within the pipe. Finally, plaintiff cites a number of secondary considerations outlined in Graham v. John Deere Co., supra, such as commercial success, long-felt need and failure of others to come up with the same solution despite availability of all of the necessary materials. The problem of leaking threaded joints is a universal one, which has plagued industries and homes alike. Chesnut and Singalewitch were the first to test the utility of the UPTFE tape as a pipe thread sealant. It is virtually undisputed that the tape has enjoyed substantial commercial success as a pipe thread sealant. Tr. 990-992; PX-54, 55. Those considerations, however, are entitled to “only measured weight” in determining obviousness, and cannot by themselves support a finding of non-obviousness if it is otherwise established that a patent’s disclosures are obvious in light of the prior art. Aluminum Co. of America v. Amerola Products Corp., supra ; Continental Can Co. v. Crown Cork & Seal Co., 415 F.2d 601, 602 (3rd Cir. 1969), cert. denied, 397 U.S. 914, 90 S.Ct. 916, 25 L.Ed.2d 94 (1970). Even if the primary considerations relating to the prior art were more equivocal, the Court does not find the evidence in the record with respect to the secondary considerations persuasive. Those considerations are most persuasive in cases such as Clopay Corp. v. Blessings Corp., supra, where a particular problem threatens to halt production entirely. In the instant case, leaking pipe joints were a widespread problem of long-standing, but there is no evidence of any ongoing effort to solve the particular problem solved by the claimed invention. No one group of people in any industry was focusing on developing a solution to the problem of leaking threaded joints. That the tape had never been used as a pipe threaded sealant prior to 1958, therefore is of little weight in determining obviousness. See, Aluminum Co. of America v. Amerola Products Corp., supra. Other methods of sealing pipe, while inferior to the tape, were available and used extensively prior to development of the tape as a sealant by Permaeel. The commercial success reflects the superiority of the tape over alternative methods, but is not evidence of its non-obviousness.. On the basis of the above, the Court finds the following: (1) It would have been obvious to one skilled in the art of sealing threaded pipe joints, as of 1958, to investigate other forms of UPTFE then being used in other applications, for possible utility as a pipe thread sealant. (2) It then would have been obvious to one skilled in the art that the UPTFE tape then being used for wire insulation would have utility as a pipe thread sealant. IV. ANTICIPATION Third, defendant argues that the product claimed by the ’770 patent lacks novelty under § 102, as it was substantially anticipated by the use of the UPTFE dispersions. To establish anticipation under § 102, defendant must show that a single prior art reference disclosed all the elements of the claimed invention, or their equivalents, functioning in essentially the same way: “Unless all of the same elements are found in exactly the same situation and united in the same way to perform the identical function” in a single prior art reference, “there is no anticipation.” Walker v. General Motors Corporation, 362 F.2d 56, 58 (9th Cir. 1966). See, also, Shanklin v. Springfield Photo Count Co., 521 F.2d 609 (1st Cir. 1975); Schroeder v. Owens-Coming Fiberglas Corp., 514 F.2d 901 (9th Cir. 1975); Universal Athletic Sales Co. v. American Gym, Recreational and Athletic Equipment Co., Inc., supra. Defendant argues that the completed joint claimed by the ’770 patent is substantially similar to the prior art joints made with UPTFE dispersion, and that therefore the patent in suit should be held invalid under § 102. The claims of the ’770 patent are product-by-process claims. The claims recite the method of forming the joint by wrapping a UPTFE ribbon circumferentially around the threads of the male fitting with the ends of the ribbon overlapped. The product claimed is the assembled pipe joint. For purposes of determining anticipation under § 102, only the structure of the claimed product, and not the process by which it was formed, may be considered. In re Freeman, 489 F.2d 742 (Cust. & Pat. App.1974); In re Brown, 459 F.2d 531, 59 CCPA 1036 (1972); General Electric Co. v. Jewel Incandescent Lamp Co., 146 F.2d 414 (3rd Cir. 1944), aff’d, 326 U.S. 242, 66 S.Ct. 81, 90 L.Ed. 43 (1945). If a product-by-process claim describes a product that is the same as a prior art product, the claim is unpatentable even though the prior art product may have been made by a process different from that recited in the claims. There are several significant differences between the product recited in the claims of the ’770 patent claimed here and the joint made with a UPTFE dispersion. The dispersion is not a preformed, transversely stretchable, coherent, compressible ribbon which completely separates the surfaces of the pipe threads after the joint is assembled. Although Dr. Gore testified that the dispersion forms a continuous film within the joint, that conclusion is supported only by unverified publication references, not by any empirical evidence. As was pointed out with respect to obviousness, the evidence does not establish that the UPTFE dispersion functions in the same way within the threaded joint as does the coherent tape. See, n. 33, infra. In addition, claims 2 and 3 of the patent in suit teach reusability of the joint after complete dissassembly without addition of more material—an element not taught by the prior art UPTFE dispersions. Accordingly, the Court finds that the product of the ’770 patent was not anticipated by the UPTFE dispersions used to seal threaded joints. V. INFRINGEMENT Assuming arguendo that the ’770 patent were valid and enforceable, the Court finds that defendant is infringing the claims of the patent. The defendant does not make, use or sell the patented joints, and therefore is not a direct infringer. Defendant can not dispute, however, that if there is direct infringement by purchasers of the tape, defendant would be guilty of actively inducing infringement under § 271(b) and contributory infringement under § 271(c). The issue, then, is whether the tape manufactured and sold by defendant falls within the scope of the patent claims. The tape manufactured by defendant differs from the tape described in the specifications of the ’770 patent primarily in the additional step of stretching the UPTFE material at an elevated temperature in the range of 300 °C, following extrusion and calendaring. Tr. 537. This additional process reduces the specific gravity of the tape from approximately 1.45 to, typically, .9. Under extreme magnification, the resulting expanded tape exhibits substantially more fibrillation than does the extruded, higher density tape. Tr. 542-546; DX-12, 13. The expanded tape also demonstrates a higher coefficient of friction, more self-adhesion, and greater conformability to the threads of the joint. A. Literal Infringement Defendant contends that the expanded tape, with a specific gravity of .9, falls outside the density range specified in the claims of the ’770 patent, and therefore does not literally infringe the patent. To determine whether the expanded tape falls within the literal meaning of the patent claims, the Court must juxtapose the claims of the patent and the accused product within the overall context of the claims and specifications, to determine whether there is exact identity of all material elements. Kreis A. G. v. American Hospital Supply Corp., 187 U.S.P.Q. 669 (W.D.Ill.1975); Clopay Corp. v. Blessings Corp., supra; Johnson & Johnson v. W. L. Gore & Associates, Inc., 377 F.Supp. 1353 (D.Del.1974); Kolene Corp. v. Motor City Metal Treating, Inc., 307 F.Supp. 1251 (E.D.Mich.1969), aff’d, 440 F.2d 77 (6th Cir. 1971), cert. denied, 404 U.S. 886, 92 S.Ct. 203, 30 L.Ed.2d 169 (1971).' The answer depends on whether a person skilled in the art would read the claim of the patent to contemplate a range which includes the accused product. Johnson & Johnson v. W. L. Gore & Associates, Inc., supra. The language of Claim 1 provides that the ribbon be “in the form of a flat coherent unsintered polytetrafluoroethylene film having a specific gravity in the range of about 1.2-1.8 and being about 1 to 20 mils in thickness”, (emphasis added). The numerical limitation on the specific gravity of the UPTFE tape is not absolute. In order to give the phrase “in the range of about 1.2-1.8” any meaning, the claims must be interpreted to read on some material with a specific gravity below 1.2. See, Johnson & Johnson v. W. L. Gore & Associates, Inc., supra. While the claim should not be unduly restricted by a narrow reading of the modifying language, however, the imprecision of the phrase does not render the limitation specified by a numerical range superfluous. See, Arvin Industries, Inc. v. Berns Air King Corp., 525 F.2d 182 (7th Cir. 1975). The language of the court in Borg-Warner Corp. v. Paragon Gear Works, Inc., 355 F.2d 400, 403-404 (1st Cir. 1965) in an analogous situation is particularly cogent: It is true that different words and symbols are able to connote different degrees of generality. Here plaintiff has employed perhaps the most specific symbol, a number, and then broadened its meaning by the modifier “substantial.” This is, of course, a useful and often necessary conjunction of words, but the modifier cannot be taken to negative entirely the specificity of the numeral it modifies. Rather, the phrase as a whole must be given a reasonable meaning. Plaintiff is correct that “substantially” and “approximately” cannot be read out o