Full opinion text
JULIUS J. HOFFMAN, District Judge. This is a patent infringement action originally brought as three separate actions which were consolidated for trial. Plaintiffs allege infringement of two patents, Nos. 2,395,449 and 2,919,807, granted respectively on February 26, 1946, and January 5, 1960, in the name of Southwick W. Briggs, one of the plaintiffs. Patent No. 2,395,449 expired on February 26, 1963; patent No. 2,919,807 is still in force. Plaintiffs specifically allege infringement of claims 9, 10,11, and 12 of patent No. 2,395,449 (hereinafter abbreviated to ’449) and claims 4, 6, 8, 9, 10 and 11 of patent No. 2,919,807 (hereinafter abbreviated to ’807). Both of these patents are directed to the oil filtration field, and specifically to filters using a pleated filter element. Defendants deny infringement of both patents and contend that both patents are invalid. Civil Action No. 62 C 1434, filed July 23, 1962, Civil Action No. 62 C 1436, filed July 23, 1962, and Civil Action No. 62 C 1921, filed October 15, 1962, were consolidated for trial on January 23, 1963, inasmuch as the same plaintiffs and the same patents are involved in the three actions, and the accused structures manufactured and/or sold by the various defendants for the purposes of this litigation are substantially identical. Plaintiff Southwick W. Briggs is a resident of Chevy Chase, Maryland, and is the named inventor in both patents in suit and is the owner of both patents. Plaintiff Stone Filter Company, Incorporated, is a corporation of Maryland, formed on March 31, 1959, and has a regular and established place of business in the Branchville section of College Park, Maryland. Stone is, and has been since its inception, engaged in the business of manufacturing and selling pleated paper lubricating oil filters for diesel locomotives under license from Briggs. Stone holds an exclusive license, subject to a nonexclusive license to a third party, under the ’449 patent; Stone is the exclusive licensee under the ’807 patent. Defendant M & J Diesel Locomotive Filter Corporation is an Illinois corporation organized in 1946 and has a regular and established place of business in Chicago, Illinois, within the Northern District of Illinois. The corporation is, and has been since its inception, engaged in the manufacture and sale of railroad equipment and supplies, including cotton waste lubricating oil filters for diesel locomotives. Since March, 1961, M & J has been engaged in the sale of pleated paper lubricating oil filters for diesel locomotives, the accused structures in this litigation. It does not itself manufacture the accused structures, but acquires them from defendant Allied Filter Engineering, Inc. Defendant Robert W. McNeily is a resident of Western Springs, Illinois, and is president of M & J as well as president of Allied Filter Engineering, Inc. Defendant Superior Diesel Filter Company is a partnership organized in 1953 and has a regular and established place of business and a manufacturing plant in Chicago, Illinois, within the Northern District of Illinois. At the time this action was brought, the partners in Superior were defendants Barbara A. Giacobbe (nee Bair), Clara A. Bair, Irwin R. Bair, and Dorothy Bair Nichols. The partnership is, and has been since its inception, engaged in the manufacture and sale of railroad equipment and supplies, including cotton waste type lubricating oil filters for diesel locomotives. Since March, 1961, it has been engaged in the sale of pleated paper lubricating oil filters for diesel locomotives — the accused structures in this litigation. Superior does not itself manufacture the accused structures but acquires them from defendant Allied. Defendant J. R. McGrath was formerly a partner in Superior. Defendant Stanley G. Bair was formerly a partner in Superior and founded Superior in 1953. The evidence shows that he has authority over personnel in Allied, Superior, and M & J. Defendant Allied Filter Engineering, Inc., is an Illinois corporation organized in August, 1960, and has a regular and established place of business in Chicago, Illinois and a manufacturing plant at Franklin Park, Illinois, within the Northern District of Illinois. The corporation is, and has been since its inception, engaged in the business of manufacturing and selling to defendants M & J and Superior pleated paper lubricating oil filters for diesel locomotives. M & J and Superior have common ownership and a common source of manufacture of the accused structures. M & J, Superior, and Allied are closely interrelated companies having common control at the top and share common office space. The court has jurisdiction of the parties and of the subject matter. PLAINTIFFS’ RIGHT TO SUE Defendants contend that neither Southwick W. Briggs nor Stone Filter Company has the right to sue for infringement of the ’807 patent. The parties agree that plaintiffs have the burden of establishing their right to bring this action. It is undisputed that Briggs is, and since the respective dates of issuance has been, owner of both the ’449 and the ’807 patents. By an agreement of January 4, 1957, Briggs granted to Stone Paper Tube Company an exclusive license under the ’449 patent, subject only to a nonexclusive license previously granted by Briggs to the Briggs Filtration Company. Briggs further granted to Stone, in this agreement, an exclusive license on all his inventions made within a period of ten years from the date of the agreement. Subsequently, Stone Paper Tube was merged with the parent corporation, Stone Straw Corporation of Washington, D. C. Stone Straw manufactured pleated paper filters under the license of January 4, 1957, until March 31, 1959, when Stone Filter Company, plaintiff, was formed as a subsidiary of Stone Straw to manufacture and sell pleated paper filters for diesel toeomotives under the January 4, 1957, agreement with Briggs. It is clear that if only the 1957 agreement is considered, the ’449 and ’807 patents fall within its terms and consequently both Briggs and Stone have the right to sue for their infringement. Defendants assert, however, that the ’807 patent falls within the terms of an earlier agreement, of August 3, 1956, between Briggs and the Briggs Filtration Company (hereinafter called BFC). Defendants contend that under this agreement BFC has the exclusive right to sue for infringement of the ’807 patent. Plaintiffs admit that if BFC has such right, then Stone could not receive any rights with respect to that patent under the 1957 contract, nor would Briggs have a right to sue for its infringement. Plaintiffs deny, however, that the 1956 agreement applies to ’807. Paragraph 8 of the 1956 contract provides, in pertinent part, as follows: “If, during the existence of this agreement, there is_ any infringement by others of any patent or patentable improvements herein licensed to Company, Company shall have the sole right, in case such patent or patentable improvement is licensed to it under paragraph 2 hereof, to institute or bring and to prosecute any suit or proceedings of any kind, either in the name of Company, in the name of Briggs, or in their joint names, for the purpose of enjoining such infringement and recovering damages.” (Emphasis added.) Paragraph 2 of this agreement provides in pertinent part, as follows: “Briggs hereby grants to Company an exclusive license to make, use and sell and sublieense others to make, use, and sell * * * products or devices embodying all inventions covered by a claim in Letters Patent numbers 2,746,608; 2,669,318; 2,468,862; 2,454,033; 2,420,414; 2,407,247; 2,390,494; 2,374,976; 2,249,681 and patent applications Serial No. 43,797; Serial No. 486,850, and any and all patents which may issue thereon, together with all patentable improvements or modifications thereon which may be acquired, owned or controlled by Briggs. The license hereby granted shall extend throughout the life for which Letters Patent for said inventions and improvements may have been or may be granted to Briggs and shall include all reissues, divisions, continuations, patentable improvements or modifications which cover directly or indirectly the subject matter hereof.” Defendants maintain that the ’807 patent, issued on January 5, 1960, is a “patentable improvement or modification” of certain of the patents listed in paragraph 2, particularly since the paragraph specifies “patentable improvements or modifications which cover directly or indirectly the subject matter hereof.” Since certain of the patents listed in paragraph 2 concern filters containing a pleated filter element, defendants argue, the ’807 patent, which likewise concerns a filter with a pleated filter element, is an improvement or modification thereon. Plaintiffs contend that the ’807 patent is not an improvement or modification of any patent listed in paragraph 2. I agree. When paragraph 2 is viewed in the context of the entire agreement, and when the nature of the patents listed in paragraph 2 is compared with the nature of ’449, '807, and other patents covered by the contract, the conclusion is compelled that '807 is not comprised within the improvements and modifications clauses of paragraph 2. These clauses, by their nature, must be strictly construed. Gas Tool Patents Corp. v. Mould, 133 F.2d 815 (7th Cir. 1943). A brief statement of the circumstances leading up to this contract is found therein. The contract recites that by a previous contract and two supplemental agreements, “said agreement as so supplemented being sometimes herein called ‘Agreement',” Briggs had granted to BFC exclusive license to all his inventions pertaining to the field of oil filtration. The contract further recites that disputes had arisen between the parties concerning royalties. By paragraph 18 of the contract, the “Agreement” previously in force is terminated and cancelled. In paragraph 1, the contract provides that “Company hereby releases Briggs from any obligations in Agreement to grant to Company any rights under any future inventions of Briggs pertaining to the field of oil filtration.” Having thus cancelled the effect of the earlier contracts, the contract then proceeds to specify in detail what particular licenses BFC it to possess. In paragraph 2, set forth above, Briggs grants to BFC exclusive license to certain specified patents and improvements and modifications thereon. In paragraph 3, Briggs grants to BFC nonexclusive license to certain specified patents and improvements and modifications thereon. Paragraphs 4 and 5 define the rights of the parties regarding other specified patents. Paragraph 6 provides that BFC releases its exclusive license on the '449 patent, and Briggs grants to BFC a nonexclusive royalty free license with respect to that patent. This paragraph contains nothing about improvements or modifications of the '449 patent. In these paragraphs, the contract clearly purports to delineate the respective rights of the parties concerning all of the patents and inventions of Briggs to which BFC has any right or claim. Paragraph 2 must be read in this context of the contract. Returning to the language of that paragraph, we must first inquire, is '807 an improvement or modification of any of the patents listed therein (or the patent applications listed therein, which subsequently issued as patents Nos. 2,768,754 and 2,850,169) ? The evidence establishes that only two of these patents, 2,468,862 and 2,420,414, relate to filters with radially pleated filter elements. The remaining patents use other types of filter elements or do not concern the type of filter material employed. Is '807, then, an improvement or modification of 2,468,862 or 2,420,414, within the meaning of those terms as used in the contract? Patent '862 concerns the construction details and disposition of certain portions of a pair of end plates of a filter, using a pleated element which is composed of a layer of ribbed cellulose wadding and a layer of filter paper. Patent '414 concerns the construction details and disposition of certain clamping members for detachably securing a radially pleated or folded filter element to a foraminous tubular core. Neither of these is a basic patent for a filter employing a radially pleated filter element with grooves running radially from the core. Rather, they concern particular features of a filter employing a radially pleated filter element, and their subject matter, dealing with such specific features, is different from the subject matter of '807, which concerns the bonding of a cover member to the outside edges of the radial pleats when the pleat walls are of unequal depth. As '862 and '414, then, are not basic patents, it is reasonable to conclude that the parties to the 1956 contract had in mind the particular functions of these patents, rather than the broad field of any kind of filter using a radially pleated filter element, when they spoke of improvements and modifications on these patents. Cf., Gas Tool Patents Corp. v. Mould, 133 F.2d 815 (7th Cir. 1943). Moreover, at least one of the mechanical elements of each claim of '862 and ’414 is absent from the ’807 structure. This fact, too, indicates that ’807 is not an improvement or modification of these earlier patents. Ibid. When the provisions of other paragraphs of the contract are considered, the indications become even stronger that the improvements and modifications provisions of paragraph 2 do not comprise the ’807 patent. Paragraph 6, dealing with ’449, grants no rights to BFC with-respect to improvements or modifications thereon. Paragraph 3, which grants to BFC a nonexclusive license, lists one patent covering a filter with a radially pleated filter element, which patent is just as closely related to ’807 as are ’862 and ’414. The paragraph 3 patent, 2,401,222, concerns a radially pleated filter element employing absorbent material in conjunction with filtering material. As is the case with the paragraph 2 patents, the ’807 structure does not employ all of the mechanical elements of any of the claims of the ’222 patent. Thus, it would be illogical to say that because two patents using a radially pleated filter element are found in paragraph 2, ’807 is an improvement or modification thereof because it, too, uses such an element. If this line of reasoning were followed, as plaintiffs have pointed out in their brief, ’807 would be an improvement or modification of patents in both paragraph 2 and paragraph 3, and BFC would have both an exclusive and a nonexclusive license to ’807. Defendants rely heavily upon certain testimony of plaintiffs’ expert witness elicited on cross-examination, as follows: “Q. Mr. Fishleigh, do you agree it would be possible to make the pleated filter paper of patent 2,468,862 utilizing the method of the ’807 patent ? “A. I think that might be possible”. The relevance of this testimony is not apparent. That it might be possible to make the pleated filter paper of ’862 utilizing the method of '807 (i. e., using a Chandler pleater) does not indicate that ’807 is an improvement or modification of ’862. Even if the testimony indicated that it would be possible to construct the filter described in ’862 using the bonding method of ’807 on the cover member, my conclusion would be the same. ’862 is not a basic patent as regards ’807, and ’807 does not concern or modify or improve upon the specific subj'eet matter of ’862 or employ all the elements of any claim thereof. The evidence discussed above establishes that BFC does not have an exclusive right to sue for infringement of ’807. It is worthy of mention that other circumstances, too, are consistent with and lend support to this conclusion. Specifically, neither BFC nor any successor thereto has ever claimed any rights regarding ’807. Moreover, the 1956 contract between Briggs and BFC marked a “parting of the ways” under an agreement which did not prevent Briggs from competing with BFC and did not oust him for any period of time from the oil filtration field. Briggs, as owner of patents ’449 and ’807, has the right to sue for infringement thereof. Stone, under its 1957 license agreement with Briggs, also has the right to sue for infringement of these patents. RELEVANT HISTORY OF PAPER FILTERS FOR DIESEL LOCOMOTIVE AND OF BRIGGS’ ACTIVITIES IN THE OIL FILTRATION FIELD Before the maj'or issues of validity and infringement are considered, it will be useful to set forth certain relevant history regarding oil filtration in diesel locomotives and Briggs’ background in this field. During the decade of the 1940’s, the steam locomotive was being replaced by the diesel locomotive in the United States. Evidence regarding the Seaboard Airline Railroad, for example, shows that by April, 1947, a portion of its fleet of locomotives had been converted to diesels, and that by 1954, the entire Seaboard fleet were diesels. The proper lubrication and oil filtration of a diesel locomotive comprises the single most important item of maintenance of such locomotives. Improper lubrication and oil filtration can result in engine parts failures, or complete engine failures, which can be very costly, and the nature of the oil and filters used affect the frequency of the need to change oil and filters. Briggs made a survey in 1957 in which he found that there were approximately 30,000 diesel locomotives in operation in the Uniffed States. Each diesel locomotive used an average of four or five filters ; consequently, if the filters could be used for a thirty day period, there was a market for approximately 125,000 diesel locomotive lubricating filters per month. In 1957, the filters used by the American railroads were almost exclusively cotton waste filters. At that time, M & J and Superior were major manufacturers of cotton waste filters. The cotton waste filter, a depth type filter, was unsatisfactory in diesel locomotives in several ways. First, filter changes were required about every fifteen days. Second, the cotton waste filter is not a full flow filter and cannot pass the full flow of oil even when new. Third, maximum engine wear occurs from abrasive particles in the oil stream ranging in size up to twenty microns. Small particles, below five microns, have much less tendency to produce wear than do larger particles. A Seaboard study showed that the cotton waste filters remove the smaller particles, but permit larger wear producing particles to pass into the engine, with the result that the bulk of the wear producing particles remain in the lubricating oil. Fourth, each time a cotton waste filter is removed from the diesel locomotive, it retains approximately two gallons of oil which is lost when the filter is discarded. On the Seaboard Airline Railroad eighty per cent of the total oil consumption on the railroad is make-up oil to replace that lost when the filters are changed and discarded. These shortcomings of the cotton waste filter led to attempts to develop a more satisfactory filter. The National Filter Corporation, with M. A. Simpson as its president and general manager, attempted from 1956 to 1960 to develop a pleated paper filter for diesel locomotives. When National went out of business in 1960, the National filter would have still required more money for development. Briggs Clarifier Company, prior to 1957, sold a paper disk pack refill to one or two railroads. Another company, Hi Ball, developed a filter using chopped paper, but tests made by Seaboard Airline Railroad showed it to be unsatisfactory. Prior to 1957, a company by the name of Winslow, located in Oakland, California, attempted to make a paper filter, but its filter could not be made small enough to satisfy the railroads. Also prior to 1957, a company by the name of Marrow, located outside of Baltimore, Maryland, attempted to market a filter made of blocks containing paper. But only a few such filters were sold, the railroads showing little interest in the filter. Briggs began working in the field of oil filtration, and specifically with oil filters, in 1928. His principal efforts since then have been directed to that same field. Briggs has been granted in excess of thirty patents in the field of oil filtration. In 1956 Briggs was interested in entering the field of pleated paper filters for diesel locomotives, and he convinced Mr. Platt, president of Stone Straw Corporation, that the Stone organization should go into this business. Briggs and Stone began a program to develop a satisfactory lubricating oil filter for diesel locomotives and to convince the railroads of its superiority over the cotton waste filter. Briggs had obtained the ’449 patent while he was with the Briggs Clarifier Company. After entering into the agreement of January 4, 1957, with the Stone organization, Briggs went to the Blandy Paper Company, acquired some filter paper, and then went to Ayer, Massachusetts, to the Chandler Company, to have the paper pleated on a Chandler pleater. Briggs took this paper back to Washington, D. C., and, in late February or early March, 1957, built experimental pleated paper filters for diesel locomotives. Briggs had known Mr. Vincent Long, director of research of the Blandy Paper Company, for more than twenty years. Mr. Long made a satisfactory paper for use in diesel locomotives under Briggs’ specifications and developed by Briggs. Prior to 1961, plaintiffs bought all of their corrugated paper for their filters from Blandy. Although corrugated filter paper had previously been on the market, no such paper suitable for use in diesels had been on the market. In 1960, Blandy was selling plaintiffs a corrugated paper having a 90 pound basis weight with a five-second A.C. flow rate. Plaintiffs are still using paper developed by plaintiffs and made by Blandy in 1957. In the spring of 1957, plaintiffs bought a Chandler pleater to pleat the paper for their filters. Chandler pleaters produce uneven pleats or pleats of unequal depth, and all the filters sold by Stone have used pleats with walls of unequal depth. Filters of diesel locomotives are of the order of thirty inches in length, and the paper filter element is soft and stretchable; consequently, the pleats will collapse under the pressure of oil unless the outsides of the pleats are securely held in position. A force of only four or five grams will cause such pleat collapse in plaintiffs’ filters. Briggs found that the usual methods of adhesively securing the outsides of the pleats to the cover would not work using the paper pleated on the Chandler pleater, because the shorter of the pleats did not touch the cover member. To overcome this problem, he devised a method of simultaneously shrinking and bonding the cover member about the pleats, thereby placing the pleat walls under stress and bowing the longer walls to achieve contact between the cover and the shorter walls. The ’807 patent was granted to Briggs covering the bonding of pleats having walls of unequal depth to the cover member and his method of achieving this result. The pleated paper filters which Briggs produced removed the abrasive particles successfully, but the first Stone filters did not produce visually clean oil because they did not remove some of the smaller particles, of one micron or less, and the railroads generally prefer visually clean oil, considering it indicative of proper oil filtration. After certain changes were made in the Stone filters to overcome this difficulty, Briggs supplied approximately one hundred of his filters for extensive road and bench tests by the Baltimore & Ohio Railroad, comparing them with the cotton waste filters. The road tests on the Baltimore & Ohio Railroad were made on regular passenger locomotives in scheduled operation. Each of these locomotives had two diesel engines. Cotton waste filters were used in in one engine, and Briggs’ filters in the other. These tests showed that the pleated paper filter removed the abrasive material from the lubricating oil a good deal better than the cotton waste filter. They also showed that the paper filter absorbed about one-half gallon of oil, while the cotton waste filter absorbed about two gallons of oil, which oil was lost when the filter was discarded. Similar tests on the Seaboard Airline Railroad, reported in March, 1961, produced almost identical results with those obtained by the Baltimore & Ohio. In 1957, Stone sold no filters at all. For the fiscal year 1958, 100 were sold, at a price of $352.80; for 1959, 16,000 were sold, at a price of $57,517; for 1960, 75,-000 were sold, at a price of $265,047; for 1961, 120,000 were sold, at a price of $443,000; for 1962, 225,000 were sold, at a price of $868,000; and for 1963, up to September 30, 280,000 were sold, at a price of slightly more than a million dollars. Plaintiffs were the first to build canless filters for diesel locomotives, and such filters, with metal and caps, were built and sold by plaintiffs at least by 1959. VALIDITY OF THE PATENTS Presumption of Validity The patent laws provide, in 35 U.S.C. 282, that “A patent shall be presumed valid. The burden of establishing invalidity of a patent shall rest on a party asserting it.” Defendants maintain that in the circumstances of this case, the statutory presumption is destroyed or at least greatly weakened as to both paterits in issue. The first question to be resolved regarding validity, then, is: to what extent, if any, does the statutory presumption of validity apply to patents ’449 and ’807? The Patent Defendants assert that Greene patent No. 1,639,133, which concerns a pleater paper filter, was not considered by the Examiner who issued the ’449 patent. Therefore, defendants contend, the statutory presumption is inapplicable because “Even one prior art reference, which has not been considered by the Patent Office, may overthrow the presumption of validity.” Dresser Industries, Inc. v. Smith-Blair, Inc., 322 F.2d 878, (9th Cir. 1963). It is well settled that where the Patent Office has not considered pertinent prior art, the statutory presumption of validity is seriously weakened or completely destroyed. See, e. g., Murray Co. of Texas, Inc. v. Continental Gin Co., 264 F.2d 65 (5th Cir. 1959); Cornell v. Adams Engineering Co., 258 F.2d 874 (5th Cir. 1958); Fritz W. Glitsch & Sons, Inc. v. Wyatt Metal & Boiler Works, 224 F.2d 331 (5th Cir. 1955). On the other hand, failure of the Patent Office to cite a patent does not necessarily rebut the presumption. “It has been held, and we think with logic, that it is as reasonable to conclude that a prior art patent not cited was considered and cast aside because not pertinent, as to conclude that it was inadvertently overlooked.” Artmoore Co. v. Dayless Mfg. Co., 208 F.2d 1, 4 (7th Cir. 1953). Examination of the cases cited above reveals that where a patent not cited by the Patent Office and not otherwise shown to have been considered thereby is highly pertinent, or the most pertinent, prior art, the statutory presumption is considered weakened or destroyed. Where the patent is not as relevant as the patents considered by the Patent Office, however, the statutory presumption is not affected. In Adams v. Columbus Mfg. Co., 180 F.Supp. 921, 930 (M.D.Ga.1960), the court stated: “Furthermore, references not of record in the patent office cannot weaken the statutory presumption if they do not involve some substantial element in the defense of anticipation which was not considered by the patent office. Otto v. Koppers Company, 4 Cir., 1957, 246 F.2d 789, 801.” Is the Greene patent, then, such pertinent prior art that failure of the Patent Office to cite it renders the presumption weak or non-existent? I find that it is not. Mr. Lauer, defendants’ expert witness, testified that the Greene patent “as set up” could not be used to filter lubricating oil in an internal combustion machine. The patent itself discloses that the filter involved is an air filter. Mr. Lauer noted that the Greene filter element was “screen cloth.” It is not paper, as defendants state in their brief, but as described in the patent, “wire screening” or “woven wire screen.” Moreover, it is not pleated, in the sense of the ’449 patent, where the edges of the pleats are alternately adjacent the inner core and the outer periphery of the filter, but rather it is corrugated or provided with “projections” and then is rolled into several layers, the corrugations or projections of the element serving to space apart the layers of material and to direct the flow of air through the layers in sequence. Mr. Lauer testified that the three best prior art references were Briggs patents Nos. 2,092,548 and 2,321,985 and Vokes British patent No. 401,287. All of these were cited as references by the Patent Office, and are far more pertinent than the Greene patent. The conclusion is compelled that failure of the Patent Office to cite the Greene patent has no effect upon the presumption that the ’449 patent is valid. The three most pertinent references, by Mr. Lauer’s own testimony, were considered by the Patent Office, which conducted a thorough examination of the patent application. Under these circumstances, the statutory presumption is strengthened, not weakened. See Anderson Co. v. Sears, Roebuck & Co., 265 F.2d 755, 761 (7th Cir. 1959); Lewyt Corp. v. Health-Mor, Inc., 181 F.2d 855, 857 (7th Cir. 1950). The ’807 Patent Defendants contend that Raymond W. Colton, the attorney who prosecuted the ’807 patent before the Patent Office, found, in his own prior art search, three patents concerning pleated paper filters which he did not include in the specifications of the ’807 patent. These are: Bell patent No. 2,642,187; Layte No. 2,663,660; and Parker No. 2,739,916. Defendants state further that although Mr. Colton included two patents, Hough No. 2,785,805 and Fricks et al. No. 2,749,265, in the specifications, he did not call to the Examiner’s attention the “pertinence” of these patents. Defendants note that the only reference cited by the Examiner is Fricke patent No. 2,748,948. Defendants rely upon Tipper Tie, Inc. v. Hercules Fasteners, Inc., 130 F.Supp. 3 (D.N.J.1955), affirmed, 232 F.2d 635 (3d Cir. 1956), as involving “less flagrant” circumstances than those here involved, and holding that the patent applicants’ neglect to call a certain patent to the attention of the Patent Office rendered the presumption of validity weak. The Tipper Tie case is readily distinguishable from the circumstances here presented. There, the applicants knew of the most significant reference, but called it to the attention of the Patent Office only after the patent had issued and only by an amendment adding a claim in which the name of the patentee but not the patent number of this reference was listed. In marked contrast, in the case at bar the evidence shows that Mr. Colton included in the patent specification the two patents which he regarded as the most pertinent prior art references. Defendants make the somewhat curious assertion that Mr. Colton did not call the attention of the Patent Office to the “pertinence” of the two references which he cited in the specification. Obviously he cited them because he regarded them as pertinent, and it would certainly be apparent to the Patent Office that he cited them for that reason. The Examiner himself did not cite these particular patents ; but under the circumstances, it is far more logical to assume that he did not cite them because he regarded them as less significant than the patent he cited, than to assume that he neglected to consider them. Mr. Colton’s failure to cite the Bell, Layte, and Parker patents, which he found but did not include in the specification, and the Examiner’s failure to cite these patents, does not affect the presumption of validity. Defendants assert that these patents “concern pleated paper filters and are therefore on their face, pertinent art.” Defendants, however, do not show, either by argument or by citation to any evidence of record, how these patents are pertinent. They are far less relevant than the patent cited by the Examiner and those included by Mr. Colton in the specification. The Bell, Layte, and Parker patents all relate to filters with pleated filter elements that are bonded or cemented to the end discs or end plates, rather than to the outer cover or wrapper, as is the case with ’807. Mr. Lauer did not testify with respect to the Parker and Layte patents, which were admitted into evidence for a limited purpose. But he did testify that the three most pertinent patents in defendants’ exhibit 2, which included the Bell patent, were Fricke 2,748,948; Fricke 2,749,265; and Foust 2,914,179, in that order. The three latter patents concern pleated filter elements with outside edges of the pleats secured to the cover wrapper or member. It seems obvious that Bell, Layte, and Parker are not so pertinent that failure of Mr. Colton to specify them and failure of the Examiner to cite them affects the presumption of validity. The most pertinent prior art was considered by the Patent Office, which thoroughly examined the application for this patent. “Obviousness” of the Inventions The ’hU9 Patent Having determined that the statutory presumption of validity attaches to the ’449 patent, we now turn to the question whether defendants have sustained their burden of establishing its invalidity. The presumption “can be overcome only by clear and convincing proof * * *, and reasonable doubts must be resolved in favor of validity.” Moon v. Cabot Shops, Inc., 270 F.2d 539, 541 (9th Cir. 1959). Defendants contend that the ’449 patent is invalid for “obviousness.” The patent statute provides as follows: “A patent may not be obtained though the invention is not identically disclosed or described as set forth in section 102 of this title, 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.” 35 U.S.C. § 103. Defendants assert that claims 9,10,11, and 12 of the ’449 patent are invalid because they “define nothing more than taking the prior art wadding filter material of Briggs '548 (No. 2,092,548) and folding it to make radial pleats as in Greene (1,639,133), Poelman et al. (2,-122,111) or Vokes (British patent 401,-287).” (Def. Br. 15.) “This,” defendants assert, “would have been obvious to a person having ordinary skill in the art.” It should first be noted that there is no testimony in the record, by defendants’ expert or otherwise, indicating that the ’449 structure would have been obvious to one with ordinary skill in the art. Several facts, established in the record, indicate to the contrary. It should also be noted that the only references which were noticed by defendants under 35 U.S.C. § 282 as prior art against the ’449 patent were the following: 1,639,133 Greene 2,092,548 Briggs 2,122,111 Poelman et al. 327,234 Vokes (British) 401,287 Vokes (British) These patents, I have ruled, are the only ones that defendants may rely upon to show the state of the prior art at the time of the application for Briggs ’449. The ’449 patent concerns a filter with a pleated filter element having ribs extending radially of the pleats to provide passage for the flow of oil. More specifically, claims 9, 10, 11, and 12 disclose a filter element in the form of a tubular body comprising a web of filter material folded to extend back and forth between the inner and outer peripheral surfaces of the tubular body, with the folds of the web at the inner surface of the tubular body being juxtaposed and in contact with each other. The web of filter material is variously described in these claims as ribbed cellulosie filter material with the ribs extending in a general radial direction with respect to the tubular body; or with well defined grooves formed in the web, which grooves extend lengthwise of the web or in a general radial direction with respect to the tubular body, to provide passages between the contacting surfaces and thereby permit the free flow of a fluid between such surfaces; or ribbed eellulosie wadding, the ribs extending lengthwise of the web and radially of the tubular body to form passages for a fluid between the inner contacting folds. Significant in these claims is that the inner edges of the pleats are juxtaposed and in contact with each other, and that to permit the flow of liquid between the contacting surfaces, grooves are provided in the filter material running radially of the tubular body. Because the inner pleats are juxtaposed, a large number of pleats can be achieved, and consequently a greater filtering surface than if the inner edges of the pleats had to be spaced apart. The grooves or ribs serve to allow fluid to flow, even though the inner surfaces of the pleats are in contact. The result of these factors is a workable oil filter. None of the prior patents cited by defendants incorporated juxtaposed inner surfaces of the pleats with grooves extending radially to permit the flow of fluid through the filter material. Filters with radial pleats are found in the prior art, as defendants assert. But defendants have not cited any prior art involving a pleated filter for fluid with either inner pleat edges juxtaposed or with grooves or corrugations running radially of the tubular body. Defendants, in their brief, point to Greene patent No. 1,639,133; Poelman et al. patent No. 2,122,111; and Vokes Br. 401,287 as showing that radially pleated filters are “old.” None employs l-adial grooves or ribs, as mentioned. With the possible exception of Poelman, which is not a fluid filter, none employs radial pleats in contact with each other at any point. The Greene patent is an air filter. While in a sense it employs “pleats,” they bear little resemblance in either appearance or function to those of ’449. (The Greene filter is described in more detail, supra, in the section of this memorandum concerning the presumption of validity of the ’449 patent.) Defendants’ expert conceded that it would be unsuitable for oil filtration. The Poelman et al. ’Ill patent concerns a gas mask. The drawings of this patent show radial pleats with the inner edges of the pleats in contact. But, again, defendants’ expert conceded that this filter would be unsuitable for oil filtration. The Vokes ’287 patent discloses a filter using a screen formed of felt or fabric stitched to a rather light wire gauze or lying between two layers of such gauze. The screen is bent into a pleated cylindrical or star shape. The patent fails to disclose filter material having ribs or grooves therein. Moreover, the patent does not disclose or claim pleats the inner edges of which are juxtaposed, and the drawing shows inner edges of the pleats spaced apart and not juxtaposed. Defendants’ expert conceded that the filter shown in this patent might not be suitable as an oil filter and that he would not make an oil filter that way. The Vokes ’234 patent (not discussed in defendants’ brief, though noticed under the statute to plaintiffs as a prior art reference) shows an oil filter with radial pleats, but there are no radial ribs or grooves. The patent contains no disclosure or claim regarding contact of the pleats at the inner edges, and the drawing shows pleats spaced apart at the inner edges. The only patent referred to as prior art by defendants which employs filter material with ribs or grooves is Briggs No. 2,092,548. In this patent, corrugated wadding is used as a filter material. Unlike ’449, however, the wadding is wound around the central core of the filter, to form a plurality of layers. The ribs extend lengthwise of the filter, rather than radially thereof. And the oil generally flows through the material and not lengthwise of the channels as in the ’449 structure. The grooves in ’548 are not provided for the purpose of channeling the flow of oil, but to prevent the wadding from softening when exposed to water by giving the wadding greater “body” or strength. (P. 1, col. 2 of the patent.) Moreover, the ’548 filter is a depth type filter with some surface filtering, whereas the ’449 filter is solely a surface type filter. I do not think that from the prior art relied upon by defendant, the ’449 structure would have been obvious to a person skilled in the filter art. Ribbed or corrugated filter material was not used in any of the references relied upon by defendants to permit the flow of oil between stretches of material lying in contact with each other. I find that the ’449 patent discloses something novel, i. e., a filter with pleats lying close together at the inner folds, with grooves achieved by using ribbed material in such a way that the high points of the ribs on one stretch meet the high points of the ribs on adjoining stretches, the grooves thus formed permitting the fluid to flow between the stretches rather than being stopped or slowed down by the filter material where the stretches are in contact. The result of this invention is an advance in the art, a significant improvement over prior mechanism. See Curtiss-Wright Corp. v. Link Aviation, Inc., 182 F.Supp. 106, 114 (N.D.N.Y.1959). As has already been stated, the cotton waste filter, used exclusively to filter the lubricating oil in diesel locomotives prior to 1957, was unsatisfactory in several ways, including the fact that it is not a full flow filter and cannot pass the full flow of oil even when new, and the fact that it retains a great deal of oil that is lost when the filter is discarded. A paper filter was thought to be possible which would overcome these and other difficulties. But to be efficient, the paper filter would have to have a considerable amount of filter surface. The ’449 structure provides this by using radial pleats lying in contact at the inner edges. But without the grooves or ribs of the ’449 patent, the evidence shows, such a radially pleated paper filter is not workable, because it allows less flow of oil through the filter. Defendants tried a radially pleated filter that did not have such grooves, and it proved unsatisfactory. Further indication that the ’449 patent claims represent a significant advance in the art is provided by defendants’ imitation thereof. Kurtz v. Belle Hat Lining Co., 280 F. 277, 281 (2d Cir. 1922). Until defendants began to employ radial pleats juxtaposed at the inner edges along with ribs or grooves running radially of the tubular body, they met with little success. The claims in issue of the ’449 patent have not been shown by the defendants to be invalid as “obvious” at the time of the invention. To the contrary, the evidence shows that the claims in issue of the ’449 patent represent invention. Double Patenting. Defendants contend that claims 9, 10, 11, and 12 of the ’449 patent are invalid for double patenting. They assert that the claims of ’449 show no invention beyond the claims of Briggs patent No. 2,321,985, the application for which was copending with that for ’449. The ’985 Briggs patent concerns a filter element of ribbed cellulose wadding, rolled to form multiple layers, with the resulting channels formed between the layers running lengthwise of the element. The fluid flows downward through the channels, and the solids in the fluid are separated out by being deposited upon fibers of the wadding. Copending applications of the same inventor are not prior art as to each other; but under the doctrine of double patenting, “the claim of the later patent [here ’449] must show an invention beyond the claim of the first.” Weather-head Co. v. Drillmaster Supply Co., 227 F.2d 98, 102 (7th Cir. 1955). In In re Copeman, 135 F.2d 349, 352, 30 C.C.P.A., Patents, 962 (1943), relied upon in the Weatherhead opinion, supra, the Court of Customs and Patents Appeals stated: “It is not a question here as to whether, standing alone, appellant’s process of coloring the rubber is inventive, but the important question is whether it is inventive over the claimed process of appellant’s reissue patent * * To the same effect, see Application of Bigelow, 194 F.2d 550, 552, 39 C.C.P.A., Patents, 835 (1952). In applying the test of invention in this context, it is instructive to bear in mind the purpose of the double patenting rule. In Weatherhead, the Court, after stating the previously quoted rule that the claims of the later patent must involve invention over the claims of the first patent, further stated as follows: “The test for double patenting adopted by the Court of Customs and Patent Appeals seems to us to be the correct one. The principal reason for prohibiting double patenting, is to prevent inventors from getting more than the seventeen year monopoly on one invention. An extension of monopoly is only justified by the presence of invention which grants the second application as much dignity as the first. In the instant case, for example, the appellants have absolutely nothing to gain by patent 217 except an extension of their monopoly by almost one year. No one could manufacture the device claimed in 217 without infringing 413. Application of Coleman, 38 C.C.P.A., Patents, 1156, 189 F.2d 976, 979. The later patent is not at all necessary to protect the packing ring described therein * * In Coleman, 189 F.2d at 979, 38 CCPA 1156, cited in the above quotation, the Court of Customs and Patents Appeals stated: “A further factor to be accorded probative value in the determination of distinctness is whether the claims of the patent may be practiced without infringing the subsequent application claim, if allowed, and whether the subsequent claim may be practiced without infringing the claims of the patent.” With these guides in mind, we must ask whether the claims of the ’449 patent show invention over the claims of ’985 and whether by the grant of the ’449 patent Briggs achieved, in effect, an extension of the monopoly obtained by the grant of the ’985 patent without showing any inventive advance thereover. I find that the claims in issue of the ’449 patent show invention over the claims of ’985. Defendants argue that the use of grooves formed by ribs in the filter material and used to channel the flow of fluid cannot be the “invention” of ’449, because it was the “invention” of ’985. But this argument isolates the only common features of the two patents. Defendants’ expert, Mr. Lauer, conceded that “the only similarity between the ’449 patent and the Briggs Patent No. 2,321,985 is that each of them employ in quite different ways filter material that is ribbed.” (Tr. 1449) He also admitted that none of the claims of the ’985 patent covers the ’449 structure and that none of the claims of ’449 covers the ’985 structure. These two filters operate in very different ways, aside from the obvious difference that one has a rolled filter material and the other a pleated one. In ’985, the flow of liquid is from the top downward; in ’449 it is from the outside inward. In '985, the liquid flows lengthwise through the channels, and does not pass through the paper; in ’449, the liquid flows both lengthwise through the channels and through the paper as well. I find that the ’449 patent involves invention over the ’985 patent claims. The ’449 patent does not involve an improper extension of the monopoly granted to Briggs by the ’985 patent. The claims of the ’985 patent can be practiced without infringing the ’449 claims, and the claims of the ’449 patent can be practiced without infringing the ’985 claims. It should be noted that the Patent Office was aware that the applications of ’985 and ’449 were eopending. We may assume that the Patent Office considered there was no double patenting when it issued the ’449 patent. The ’807 Patent Inasmuch as the statutory presumption of validity applies to the ’807 patent, the question presented is whether defendants have sustained their burden of establishing its invalidity “by clear and convincing proof * * * [with] reasonable doubts * * * resolved in favor of validity.” Moon v. Cabot Shops, Inc., 270 F.2d 539, 541 (9th Cir. 1959). The claims in question are claims 4, 6, 8, 9, 10, and 11 of the ’807 patent. They read as follows: “4. A filter comprising a permeable impregnated paper filter element having axial pleats with walls of unequal depths defining a plurality of inner and outer peaks, said outer peaks being spaced apart and lying substantially in a cylinder, a substantially uniformly permeable core disposed within said element for engagement with said inner peaks, an annular cover member permeable substantially throughout its length embracing said outer peaks throughout their length, and an adhesive bonding said cover member to outer peaks.” “6. A filter as set forth in claim 4 wherein said adhesive is thermosetting.” “8. A filter as set forth in claim 4 wherein said walls are under stress.” “9. A filter as set forth in claim 4 wherein said peaks engage said core and certain of said walls are bowed.” “10. A method of maintaining adjacent pleats of an annular filter element in spaced relationship comprising circumscribing said element with a cover member and simultaneously shrinking said cover member about and bonding it to peripheral protions of said pleats.” “11. A method as set forth in claim 10 wherein said shrinking and bonding are effected as a superatmospheric temperature.” This patent is not a basic patent with regard to the type of filter disclosed. That is, the patent itself acknowledges that the basic arrangement of an annular pleated filter element, circumscribed by a cover member and containing a core, with impregnated paper used as the filter element, is found in the prior art. The invention, if any, of this patent, concerns the securing of the outer peaks of the pleats to the cover member, by bonding, where the walls of the pleats are of unequal length, and the inner peaks of the pleats engage the inner core. The patent was intended to solve a particular problem encountered in a filter having the basic arrangement described. It was considered desirable to bond the outer edges of the pleats to the cover member in order to hold the pleats in spaced relationship and thereby to overcome the tendency of adjacent pleats to stick together as an effect of adherent cake formations and the resulting increase of differential pressures. But prior methods of bonding the outer pleat edges to the cover member would not work with filter material pleated on a commercial paper pleating machine, because such a machine produced pleats of unequal length. The aim of the patent, then, was to present a method whereby pleats of unequal length could be bonded to the cover member. The only patents or other publications which were noticed by defendants under 35 U.S.C. § 282 as prior art against the ’807 patent were the following: 2,122,111 Poelman et al. 2,642,187 Bell 2,683,536 Kasten 2,689,652 Gretzinger 2,749,265 Fricke et al. 2,914,179 Foust. In addition, defendants asserted use and sale of a filter by National Filter Corporation from 1956 to 1960. The patents listed above, I have ruled, are the only ones that defendants may rely upon to show the state of the prior art at the time of the application for Briggs ’807. Defendants make three principal contentions : (1) that prior patents disclosed filters with the basic arrangements described above and with the outer edges of the pleats bonded or otherwise secured to the cover member; (2) that prior patents disclosed filters with this basic arrangement and with bowed or stressed walls; and (3) that a prior patent disclosed (in the words of the defendants) “the method of maintaining adjacent pleats in spaced relationship by circumscribing a pleated filter element with a cover member or protector strip and shrinking or contracting the cover member about the peripheral portions of the pleats.” (Def. Br. 21-22) Claims 4, 6, 8, and 9 of ’807 would have been obvious to one with ordinary skill in the art, defendants assert, because of points (1) and (2) above. Claims 10 and 11, the method claims, would have been obvious, defendants assert, because of point (3) above. To appraise this argument, we must view in combination the several features of the prior art relied upon by defendants. Before this view can be taken, however, the several patents and their respective features must be reviewed singly. (1) Prior Art Patents Disclosing Bonding of the Outer Edges of the Pleats to the Cover Member Defendants correctly assert that both Fricke et al. patent No. 2,749,265 and Foust patent No. 2,914,179 show a permeable impregnated paper filter element having axial pleats with walls defining a plurality of inner and outer peaks, said outer peaks being spaced apart and lying in a cylinder, a substantially uniformly permeable core disposed within said element for engagement with said inner peaks, an annular cover member permeable substantially throughout its length embracing said outer peaks throughout their length, and an adhesive or cement bonding (in the case of Foust ’179, staples or an adhesive securing) said cover member to said outer peaks. Defendants also note that the filter produced by the National Filter Corporation under the Foust patent from 1956 to 1960 used an adhesive bonding the cover wrap to the outside edges of the pleats. Plaintiffs note that certain significant differences exist between the Fricke ’265 patent, the Foust patent, and the National filter, on the one hand, and the ’807 claims on the other hand. As to Fricke ’265, the claims thereof specifically define the pleats as being uniform; consequently, it is clear that this patent does not deal with the pleat collapse problem presented when the pleats are unequal. Moreover, the filter shown in Fricke ’265 is small and is intended for use in automobiles; consequently, the pleat collapse problem would not be as serious as it is with regard to a filter of the ’807 type. The patent does not teach that the pleats should be bowed or stressed in order to achieve the bonding necessary to solve the pleat collapse problem where pleats are not uniform; nor does it disclose the use of thermosetting adhesive to bond the outer cover to the outer peaks of the pleats. As to Foust ’179, the patent drawings show pleats of uniform depth. Nothing in the patent concerns pleats of unequal depth, or walls that are bowed or stressed. Thus, it does not deal with the pleat collapse problem where the pleats are not of uniform depth and it does not teach a solution to this problem. The only “collapse” problem discussed in ’179 is that which results when the pleats cave in toward the core or center tube. The patent teaches that “stiffening fingers” should be used to reinforce the pleats to prevent this “caving in” from occurring. The Foust patent does not teach the use of resin impregnated paper as the filter element, and it does not teach the use of a thermosetting adhesive to bond the cover to the pleats. As to the National filter, it was unsatisfactory in operation, and National went out of business in 1960, after efforts at improvement of substantially all of the filter components. The filter paper used in the National filter was very heavy with a basis weight of over 300 pounds, and for this reason a force in excess of three pounds (as compared with a few grams as to the Stone filter) is required to move adjacent pleats together when the pleats are not bonded to the cover member. The National lubricating oil filter was made in two sections, further reducing the likelihood of pleat collapse. The problem of pleat collapse is most acute when light, resin impregnated paper is used as the filter material; consequently, the pleat collapse problem in the National filter was not as acute as with the ’807 type filter, if it existed at all. The pleats on the National filter were made on a manually operated pleat-er and were uniform. The walls of the pleats were not bowed or stressed. The National filter thus did not encounter or teach a solution to the problem of pleat collapse when the pleats are not uniform. Somewhat similar to the Fricke ’265 and Foust ’179 patents, which defendants have compared with ’807 as involving securing the outer wrap to the outer edges of the pleats, is Fricke et al. patent No. 2,749,948. While not available to defendants as prior art on ’807, because not noticed under 35 U.S.C. § 282, we may take note that it was regarded by both plaintiffs’ and defendants’ experts as the best prior reference, and was cited as a reference by the Patent Office. In this patent, the outer edges of the pleats are bonded to the cover member. The outer cover member is not permeable 'substantially throughout its length; rather, the outer shell is impervious, but is somewhat shorter than the filter element in order to leave spaces at the top and bottom for the passage of fluid. The pleats of the filter element in Figure 2 of the patent appear to be of uniform length, and nothing in the patent indicates to the contrary. The patent does not recognize the problem of pleat collapse where the pleats are of unequal length, nor teach a solution to this problem. The walls of the pleats are not under stress and are not bowed to afford the necessary bonding to avoid pleat collapse. The patent does not teach the use of a thermosetting adhesive to bond the outer cover or shell to the peaks of the pleats, nor does it suggest the shrinking of the outer cover or the simultaneous shrinking of the cover and bonding thereof to the outer edges of the pleats, or the use of super-atmospheric temperature for the shrinking and bonding process. (2) Prior Art Patents Allegedly Disclosing Pleats With Bowed or Stressed Walls Defendants assert that Poelman et al. patent No. 2,122,111; Bell patent No. 2,642,187; and Gretzinger patent No. 2,689,652 disclose bowed and stressed pleat walls in pleated paper filters. Defendants also assert that the Bell patent shows the use of thermosetting adhesive in such a filter. Bell ’187 does not show bowed or stressed walls. Defendants point in their brief to Figure 2 of this patent. That figure shows curved outer peaks of the pleats, but the walls thereof are substantially straight. Nothing in the patent indicates that these walls are under stress. The outer peaks of the pleats are not bonded to the cover wrapper, but rather the zig-zag ends of the pleats are bonded to the end discs of the filter. A thermosetting adhesive is used to make this bond. Poelman, the gas mask patent which has been discussed previously in this memorandum, shows as an alternative construction for the radial pleats, in Figure 4, pleats that are all bent over in the same direction. In lines 67-71 of the patent, it is said, “In annular shaped filters, the faces of the plaits of the paper band can themselves be undulated or bent, all in the same direction, for instance as shown in Fig. 4.” The outer peaks are not bonded to the cover member; as in the Bell patent, the ends of the pleated element are cemented to the end disks. As has previously been noted, defendants’ expert conceded that this patent discloses an air filter which is unsuitable for use in oil filtration. The Gretzinger patent discloses pleats which are uniformly curved or involuted, all in the same direction. As in the Bell and Poelman patents, the ends of the pleated element are cemented to the end plates, and the outer peaks of the pleats are not bonded to the cover member. The Bell and Gretzinger patents, as conceded by defendants’ expert, are small filters not suitable for use in diesel locomotives. These, as well as the Poelman patent, do not indicate that the pleats are of unequal length, they do not concern the pleat collapse problem presented where pleat walls are of unequal length, and they suggest no solution to that problem. Def