Spindelfabrik Suessen-Schurr, Stahlecker & Grill GmbH v. Savio S.p.A. (778 F. Supp. 839, 1991)

United States District Court for the Western District of North Carolina 1991-09-06

Citations

Full opinion text

MEMORANDUM OF DECISION

ROBERT D. POTTER, District Judge.

FINDINGS OF FACT

1. This is a patent infringement action in which the Plaintiffs claim that the Defendants have infringed Claim 18 of U.S. Patent No. 4,059,946 [hereinafter the ’946 Patent]. Plaintiffs’ Exhibit [“PX”] 273.

2. Subject matter jurisdiction, in personam jurisdiction, and propriety of venue are all admitted. The Court has subject matter jurisdiction of this action under 28 U.S.C. § 1338(a).

3. Defendants have filed two counterclaims. The first is for a declaratory judgment that Claim 18 is not infringed, invalid, and unenforceable. The second is based on the antitrust laws. Discovery and trial as to the antitrust claim have been severed and stayed.

4. The issues of infringement, validity, and unenforceability of Claim 18 were tried before this Court at Charlotte, North Carolina without a jury on October 29, 30, and 31, and November 1, 2, 5, and 6, 1990. Post-Trial briefs have been filed and a final hearing was held May 31, 1991. Plaintiffs were represented by Bell, Seltzer, Park and Gibson, Attorneys at Law. Defendants were represented by Kennedy, Covington, Lobdell & Hickman of the North Carolina Bar, and Hedman, Gibson, Costigan & Hoare, P.C. of the New York Bar.

5. The damage issue has been deferred by stipulation of the parties, approved by this Court.

6. The ’946 Patent was issued on November 29, 1977 on application Serial No. 637,050 filed on December 2, 1975, and is part of the open-end rotor spin technology used in the textile industry.

7. The system is used for mending yarn breaks, a process commonly referred to as “piecing.”

8. The Plaintiffs have asserted that two different systems of the Defendants’ infringe Claim 18 of the ’946 Patent. The Defendant’s allegedly infringing systems will be referred to as the “old FRS system [hereinafter “OFRS”] and the “new FRS system” it also referred to as the “modified FRS” [hereinafter “NFRS”].

9. The individual Plaintiffs are two brothers, Hans Stahlecker and Fritz Stahlecker, citizens of Germany and joint owners of the Patent in suit.

10. The corporate Plaintiffs Spindelfabrik Suessen-Schurr, Stahlecker & Grill GmbH are hereinafter referred to as “Suessen.” The transcript will be referred to as “Tr.”

11. Suessen is a German corporation located in Suessen, Germany, and is the exclusive licensee of the Patent in suit. One of the principal products of Suessen is rotor spin boxes for open-end rotor spinning machines. [Tr. 25; 146-148].

12. Hans Stahlecker is the chief executive officer of Suessen. [Tr. 146].

13. Fritz Stahlecker is the chief executive officer of Wilhelm Stahlecker GmbH [WST] which is not a party to this litigation. WST conducts research, development, and engineering in the field of open-end spinning for Suessen under a contractual arrangement. [Tr. 23-24].

14. Fritz Stahlecker and Hans Stahlecker own the entire right and interest to the '946 Patent and in WST. [Tr. 146; 23; PX 274, Paper No. 8].

15. Suessen does not manufacture complete open-end rotor spinning machines, but manufactures components thereof. Sues-sen’s main business in the open-end rotor spinning field is the production and sale of vital components for open-end rotor spinning machines. One such component is the spinbox. [Tr. 146-147],

16. Defendant Savio S.p.A. [hereinafter “Savio”] is a corporation organized and existing under the laws of Italy, and has its principal place of business in Pordenone, Italy. [Tr. 686].

17. Defendant American Savio Corporation [hereinafter “American Savio”] is a corporation organized and existing under the laws of the State of North Carolina, and has its principal place of business in Charlotte, North Carolina [Docket Entry 54]. [Docket Entry will be referred to as “DE” hereinafter].

18. Savio is a manufacturer of textile machinery, including the accused systems of Defendants’ FRS machines. [Tr. 686]. American Savio is the exclusive distributor of Savio’s textile machines in the United States. [Tr. 793]. It is jointly owned by Savio and ENI, Savio’s Italian parent, and is in the business of selling, erecting, and servicing Savio’s machines in the United States.

19. Among these machines and in issue here are two versions of the Savio FRS automated open-end rotor spinning machine, which are manufactured by Savio in Italy, sold by Savio to American Savio, and exclusively distributed by American Savio in the United States. [Tavazani Conf. Tr. 3-4],

Open End Rotor Spinning

20. Referring to Fig. 1, infra p. 845, in open-end spinning, a continuous strand of untwisted loosely assembled fibers (called sliver) is drawn into the system by means of a feed roller which, in turn, feeds the sliver to a comber or opening roll. The comber roll has teeth on the outside and rotates at a high rate of speed, 5,000 to 8,000 r.p.m., separating individual fibers of the sliver and directing these fibers through a feed tube or fiber transfer tube into a cup-shaped rotor with an interior annular groove. This process occurs within 5 milliseconds. The rotor is usually confined in an underpressure (vacuum) chamber, and rotates at very high speeds feeding individual fibers combed from the sliver through the feed tube by action of the vacuum in the spinning chamber. The fibers fed to the interior of the rotor are directed by centrifugal force into the rotor groove where they form a ring of fibers. During spinning, twist is continuously inserted into this ring of fibers. These fibers are then pulled out of the rotor groove in the form of twisted yarn, while at the same time, the spinning chamber containing the ring of fibers is continuously replenished with new fibers from the feed tube. [Tr. 32-37; PX 500, pp. 8-9]. In another version, the separated fibers are drawn through the feed tube from a vacuum generated by perforated holes in the rotor or by an independent vacuum source. [Tr. 119-125; PX 327, 328],

21. In order to start this continuous spinning operation, a length of twisted yarn is inserted down into the yarn withdrawal tube and into contact with the fiber ring where it attaches itself to a point on the fiber ring and begins to insert twist into the fiber ring at that point. Upon attachment (piecing), the inserted twisted yarn end is then pulled out of the yarn withdrawal tube, bringing the newly formed twisted yarn with it, and spinning is restarted. This is called “start-spinning” and the area where the yarn end is joined with the fiber ring is known as the “piecing point” [PX 500, p. 9; Tr. 37; 576-77].

22. From the rotor grooves, the fibers are twisted and drawn out of the rotor through an extraction tube as yarn. This yarn is then transferred by rollers to the yarn package.

23. If there is a yarn break the spinning process is interrupted and the twisted yarn separates from the ring of fibers in the groove of the rotor. The sliver feed stops, but the comber roll continues to rotate. Depending on the length of time feeding is stopped, the lead end of the sliver may be damaged and the fibers broken or shortened by the action of the comber roll. The lead end of the sliver is called the fiber “beard” or “tuft.” [PX 500, p. 10; Tr. 559-61].

24. In commercial open-end spinning operations, when a yarn breaks, a detector generates a signal which causes the supply roller to be stopped. In this manner, no additional sections of fiber are fed to the comber roll; however, fibers are still being transported into the rotor because the remaining fiber beard continues being combed out. These fibers end up in the spinning rotor. Before a piecing operation is performed, the spinning rotor is stopped for a brief period of time. [Tr. 39-40]. The opening or comber roll continues to turn. [Tr. 41]. There is necessarily a lapse of time between the moment of break and the moment at which a patrolling operator or an automatic traveling piecer learns of the break and begins to restart spinning by piecing up. This lapse of time necessarily varies depending upon the whereabouts of the operator or automatic traveling piecer at the moment of the break, how long it takes to recognize the existence of the break, and other factors. Because of this time variable, when piecing is ultimately initiated, the nature (i.e., the amount of fibers remaining on the comber roll versus the amount of fibers which have already been combed out by the continuously operating comber roll after the sliver feed was stopped) of the constantly aging fiber beard is unknown. If fibers from this unknown fiber beard are then deposited in the rotor groove so as to be used in forming the ring of fibers necessary for piecing up, the piecing point itself will thus include an unknown quantity of fibers, and the resulting piecing points will vary in size from piecing to piecing depending upon how long the fiber beard happened to be when combed out. [PX 500, p. 10; Tr. 36, 46-47, 50; PX 273, Col. 2, L. 9-26].

25. Thus, commercial spinners needed a system for use on open-end spinning machines to eliminate an unknown, inconsistent quantity of fibers from the fiber beard being fed into the rotor where they formed the ring of fibers and are then incorporated into the piecing point. [Tr. 46-47]. An inconsistent quantity of fibers in the ring typically resulted in piecing points which were either too thin, and thus prone to break, requiring further piecing by the operator, or which were undesirably too thick. When such points were too thick, and where quality yarn was required, the package of spun yarn would typically be taken to another machine for rewinding to still another package, during which the thick spots would be identified, cut out, and replaced with a knot. Such knots, though smaller than piecing points, were themselves still considered to be defects, in that they were identifiable in fabrics made from the yarn. [Tr. 38-39].

Development of the Solution

26. In 1971, Suessen introduced to the trade its Fritz Stahlecker/WST developed open-end “Spintester” featuring the “Twin Disc” bearing invention. This development was a breakthrough in open-end spinning technology in that its use permitted a quantum jump in spinning rotor speeds of up to 100,000 r.p.m. or more. With the advent of this new bearing technology, the need for automation of the open-end piecing process became paramount, since manual piecing at such high speeds would be impossible. [Tr. 42-45].

27. Thus, work was begun as early as 1972 by Fritz Stahlecker and WST to automate the piecing process. In its conceptual form, the automation process, which WST dubbed “Spincat” and “CleanCat,” was to involve robots designed to be mounted on rails and travel the length of an open-end spinning machine, typically equipped with about 200 spinboxes. The Cleancat would be adapted to travel along and automatically clean the spinboxes, as required. The Spincat would be adapted to travel along and automatically piece up stopped spinning positions, as required. [Tr. 45-49; 61-63],

28. In the ensuing three-year period (1972-1975) work commenced at WST to begin designing and building a series of prototype robots directed to accomplishing these various automated functions. The earlier prototypes were directed to solving problems associated with the robotic Spin-cat tasks of stopping the winding package at the disabled spinning position; locating the yam end on the package and gaining control over it; preparing a proper length of the yarn end; positioning the yarn end at the opening of the yarn exit tube of the spinbox for reinsertion into the spinbox; feeding the correct length of yarn into the spinbox for piecing; restarting the sliver feed; withdrawing the yarn after piecing; restarting the package winding operation; and transferring the yarn back to the spinning machine for resumption of normal spinning. [Tr. 45-49].

29. The process of solving this multitude of problems resulted in a considerable number of inventions for Fritz Stahlecker and his team of engineers at WST. Concomitantly, they filed for and were issued a significant number of patents. Among these, for example, are U.S. Patent Nos. 3,962,855, 3,950,926, 3,942,311, and 3,924,-394 [PX 212; 211; 210; 208], which relate variously to locating the broken end on the package and preparing it for reintroduction into the rotor. These U.S. Patents are based on corresponding German applications filed in 1973. [Tr. 963-64, 967].

30. Another of the many patents which resulted from this work is U.S. Patent No. 3,987,610 [hereinafter the '610 Patent] [PX 155A], which likewise is based on a corresponding German patent filed in 1973. This German patent is also referred to and described in the specification of the ’946 Patent in suit. The invention protected by the ’610 Patent represents a prior attempt to solve the problem of inconsistent piecing points. However, it achieved only modest success. It is directed to the correlation of the runup of the sliver feed with the runup of the rotor speed. Such sliver feed runup can be accomplished according to a smooth controlled curve. [PX 155A, Fig. 1 of the ’610 Patent]. Alternatively, it can be accomplished by stepwise approximation wherein the sliver feed drive is alternately energized and deenergized in a so-called “stutter” manner. [PX 155A, Fig. 2 of the ’610 Patent], The sliver feed itself, however, does not start and stop, but only alternates periods of acceleration with periods of constant speed. [Tr. 71-72, 99-102].

Figs. 1 & 2 of the ’610 Patent:

31. Fritz Stahlecker recognized the problems in obtaining uniform piecing points, particularly with higher speed open-end rotor spinning machines, when Sues-sen’s “Twin Disc” development was unveiled. Having done so, Fritz Stahlecker came to the realization very early in the Spincat development project that in order to get consistency in piecing points from piecing to piecing at the same spinning position and, further, piecing point consistency from spinning position to spinning position, something would have to be done to address the problem of the unknown, aging fiber beard and its ubiquitous negative effect in obtaining piecing points of consistently uniform size. To this end he conceived that his automatic piecer would need the ability to gain control over the quantity of fibers in the fiber ring at the moment the piecing point is formed. He further conceived that this could be achieved in the piecing sequence by first forming a totally new fiber beard, while eliminating the old, unknown, aged fiber beard from the system, and thereafter in a controlled, known time period, start feeding fibers into the rotor to form a new, controlled fiber ring, and then introducing the yarn end into contact with that controlled fiber ring. By doing this, the fiber ring would now have the same quantity of fibers provided to it from the new, known fiber beard every time the piecing sequence was performed. [Tr. 54-61].

32. Having realized that uniformity of the fiber beard was obtainable with proper timing during the piecing sequence, it became apparent to Fritz Stahlecker and his WST co-inventors of the ’946 Patent, Bottcher and Schulz, that such a properly timed piecing sequence was readily achievable with an apparatus or automatic piecer which would (1) always perform the sequence in the same manner within a consistent, known time period, and (2) perform the necessary steps in the coordinated manner required by high spinning speeds. To this end, therefore, electromechanical controls consisting of a combination of electrical circuits and a set of cams for accomplishing these functions were designed in the latter half of 1974 and incorporated into still another Spincat prototype. [Tr. 54-61; DX 401 Day 2, pp. 49-51].

33. The Stahlecker, et al. concept of achieving uniform piecings thus merged with the concept of piecing automation. As a result, the WST research team developed the first technique for producing consistent piecing points of acceptable quality in open-end rotor spinning machines. This technique at the same time readily lent itself to automation even on high speed open-end rotor spinning machines. [Tr. 60-61].

The ’9&6 Patent-In-Suit

34. Plaintiffs’ U.S. Letters Patent No. 4,059,946 [’946], the Patent in suit, is entitled “Method and Apparatus for Start-Spinning a Thread on open-end Spinning Units.” [PX 273].

35. The ’946 Patent issued on November 29, 1977, on application Serial No. 637,-050 filed in the United States Patent and Trademark Office on December 2, 1975, in the name of Dieter Bottcher, Heinz Schulz and Plaintiff, Fritz Stahlecker, all citizens of Germany. [PX 273; Tr. 69].

36. On December 2, 1975, pursuant to 35 U.S.C. § 119, the applicants for the '946 Patent claimed in connection with their application the right of priority of West German Patent Application Serial No. 24 58 042, filed in West Germany on December 7, 1974, and simultaneously therewith, filed in the United States Patent and Trademark Office a certified copy of the original west German application, specification and drawings showing that the application was duly filed in the West German Patent Office on December 7, 1974. [PX 273; PX 274],

37. Pursuant to 35 U.S.C. § 119, the ’946 application is properly considered as having a U.S. filing date of December 7, 1974. [PX 500, p. 4].

38. The invention protected by the ’946 Patent has for its object the provision of a method and apparatus for providing precise control of the fiber feed during the restart of the spinning operation at an individual spinning position so that the quantity of fibers fed for forming the ring of fibers in the rotor groove to which the broken end is to be placed can be controlled to thereby obtain uniform, quality yarn piecing points — that is, piecing points which closely match the appearance and strength of the yarn itself, and which can be repeated from piecing point to piecing point on the same spinning unit and between different spinning units. [PX 273, Col. 1, L. 57-61]. To this end, according to the Patent, the invention is based upon the fact that the size of the piecing point can be precisely controlled only if it can be assured that the fiber beard offered to the opener roller at the beginning of the sliver feed for forming the fiber ring for piecing up is always identical. This assures that no uncontrolled or unknown quantity of fibers are allowed to find their way into the rotor groove and become a part of the fiber ring used to form the piecing point. [PX 273, Col. 2, L. 9-13]. Thus, according to the Patent, before beginning the sliver feed for forming the ring of fibers in the rotor for the actual piecing operation, a precisely controlled sliver prefeed is initiated in such a way as to eliminate from the system (e.g., as by suction) the combed out sliver beard consisting of an unknown quantity of fibers and replace it with a new fiber beard consisting of a known quantity of fibers. [Tr. 69-71; 208-210; PX 273, Col. 4, L. 18-25].

39. This precisely controlled sliver prefeed is shown in a graph drawn by Fritz Stahlecker during his testimony at trial, which is Plaintiffs’ Exhibit 326 and is reproduced here in reduced form.

The portion to the left of the vertical line GB shows the sliver being prefed so that the fibers of the unknown fiber tuft are combed and eliminated to waste via vacuum while being prevented from being captured in the rotor, and thus from becoming part of the fiber ring for piecing. [Tr. 57].

40. Once this elimination of the unknown fiber beard is completed, represented by line GB itself, any point along the portion to the right of the line GB then represents a known, uniform fiber tuft and can be utilized in forming the ring for piecing, so long as such point is selected consistently in a known fashion each time piecing occurs. It does not matter whether such point is on the flat portion of the curve, while the sliver feed is still running, or on the exponential decay portion of the curve, while the fiber beard is being combed out in a known way, or after the sliver is restarted, if indeed it is first stopped and then restarted. One point is as good as another. [Tr. 57-58].

41. The portion to the left of the point labeled “O FST” in Plaintiffs’ Exhibit 326 is the same as that shown on Figure 2 of the ’946 Patent to the left of the ordinate. The portion to the right of the point “0 FST” is essentially like that shown to the right of the ordinate in Figure 2, and has to do with the situation where it is desired to piece up when the rotor is at less than full operational speed, and the sliver feed run-up must be correlated with the rotor speed runup. [Tr. 58-59]. Figure 2 of the ’946 Patent, infra at 852.

42. As such, this portion to the right of the ordinate in Figure 2 of the ’946 Patent and to the right of the point “0 FST” in Plaintiffs’ Exhibit 326 represents the subject matter of Plaintiffs’ prior ’610 Patent. [PX 155A]. This subject matter may optionally be utilized in combination with the controlled prefeed of the ’946 Patent in suit, but does not have to be so utilized. [Tr. 71-72, 99-102],

43. The foregoing would be understood by any person of ordinary skill in the art studying Figure 2 of the ’946 in conjunction with the specification thereof, and such overall understanding is not negated or diminished by the fact that the preferred embodiment disclosed in the ’946 Patent happens to select a point on the exponentially decaying portion of the curve shown hereinabove as well as to the left of the ordinate in Figure 2 of the ’946 Patent. That is, such preferred embodiment actually acts to start, run and stop the sliver feed to renew and establish a fiber beard of known and controlled quantity, and thereafter restart that feed for piecing, all in controlled fashion. [Tr. 57-59].

44. The ’946 invention was unveiled to the public in October 1975 with the introduction by Suessen at the ITMA Exhibition in Milan, Italy, of its then latest prototype version of its “SpinCat” and “CleanCat” automated piecing and rotor cleaning devices, and was enthusiastically received and highly acclaimed. [Tr. 62-63; 158].

45. The big bone of contention in this whole matter is whether the Defendant's machine, the NFRS, infringes on Claim 18 of the Plaintiff’s ’946 Patent [PX 273] under the doctrine of equivalents. That claim reads as follows:

18. Apparatus according to claim 17.

(a) 17. Apparatus for thread piecing in an open-end spinning assembly comprising:

(b) opening means for opening sliver being supplied to a spinning rotor of said spinning assembly,

(c) feeding means for feeding sliver to said fiber opening means,

(d) piecing means including means for introducing a thread end back into said spinning rotor to be pieced together with a fiber ring formed in said spinning rotor,

(e) rotor control means for moving said spinning rotor from a stop condition toward an operating spinning speed to accommodate piecing by said piecing means,

(f) and fiber supply preparing means for (1) preparing said spinning assembly for a piecing operation prior to movement of said spinning rotor from its stopped position, said fiber supply preparing means including means for (2) starting and operating said feeding means for a period of time and then stopping said feeding means, said starting and stopping being accompanied by a continuously operating opening means, whereby (3) uniform (4) fiber tufts are arranged at said sliver feeding means to accommodate said piecing operating to be subsequently performed.

(g) further comprising

(5) means for supplying a vacuum to said spinning rotor to remove any fiber supplied during said preparation of said spinning assembly by said preparing means.

46. This claim is illustrated by Fig. 2 of the ’946 Patent on page 852, infra.

47. The Plaintiff’s patent is titled “Method and Apparatus for start-spinning a thread on open-end spinning units.”

48. The crucial paragraph to be construed is paragraph (f) of claim 17, which is incorporated into claim 18.

49. Paragraph (f) provides for a fiber supply preparing means in order to prepare the spinning assembly for a piecing operation prior to the movement of the spinning rotor from its stopped position.

50. Thus, the first limitation is the preparation of the spinning assembly prior to the movement of the spinning rotor from its stopped position. That is accomplished by the second limitation which is the starting and operating of the feeding means for a period of time, followed by stopping the feeding means, where the starting and stopping are accompanied by a continuously operating opening means (i.e., the comber roll continues to operate and comb out fibers from the end of the sliver which has been stopped for a known period of time), so that a uniform fiber tuft is arranged at said sliver feeding means to accommodate performing the piecing operation.

51. Claim 18 provides for supplying a vacuum to the spinning rotor to remove any fiber supplied during the preparation of the spinning assembly by said preparing means.

52. The ’946 Patent [PX 273] in Col. 1, L. 6-55 reviews different methods which have been used to try to accomplish start spinning points which are uniform in appearance and strength in repeat start spinning on the same spinning unit and between different spinning units, in the event of a thread break.

53. The ’946 Patent then continues in Col. 1, L. 57 through 62:

It is the object of the present invention to permit even more precise control of the sliver feed than previously, so that the quantity of the fibers fed during the start spinning operation can be matched to the start spinning speed even more precisely than had previously been the case.

54. The ’946 Patent continues in Col. 1, L. 63-68 and Col. 2, L. 1-31, as follows:

According to the present invention, this object is solved by a method for start-spinning a thread on open-end spinning units, in which an end of the thread is returned to a spinning rotor running in an under-pressure chamber, placed on a ring of fibers formed from individual fibers separated from a fed sliver and deposited in the spinning rotor, and then drawn off again, whereby in order to form a ring of fibers which is suitable for the start-spinning operation the feed of the sliver is switched on for a given period of time prior to the end of the thread being placed on the ring of fibers and the thread being drawn off again, the feed then being interrupted again and finally only switched on again for the actual start-spinning operation.

The present invention is based upon the realization that the sliver feed can only actually be precisely controlled if it can be assumed that the fiber tuft offered to the opener roller at the beginning of the sliver feed prior to the start-spinning operation is always the same. This was not always so in many cases. Tests have shown that the nature of the fiber tuft is greatly dependent upon the standstill period following which the sliver feed is started again. If a second start-spinning operation with controlled feed of the sliver is performed after a very brief standstill period, for example after an unsuccessful start-spinning attempt, the fiber tuft will be significantly thicker than would be the case after a long standstill period, after which the fiber tuft would have been heavily combed and become correspondingly thin. Consequently, in spite of precisely maintained uniform sliver-feed starting conditions, different quantities will be fed. According to the present invention, this possibility is eliminated in that prior to every start-spinning operation a precisely defined fiber tuft, which always recurs in the same shape, is produced by briefly switching on the sliver feed; the fiber tuft then permits precise control of the quantity of fibers fed.

55. Thus, the essence of the ’946 Patent is the formation of a uniform fiber tuft for each piecing operation; that is, control over the quantity of fibers in the ring of fibers in the spinning rotor at the time the piecing point is formed.

Under Claim 18 this is accomplished by ... including means for starting and operating said feeding means for a period of time and then stopping said feeding means, said starting and stopping being accompanied by a continuously operating opening means, whereby uniform fiber tufts are arranged at said sliver feeding means to accommodate said piecing operation to be subsequently performed ... further comprising means for supplying a vacuum to said spinning rotor to remove any fiber supplied during said preparation of said spinning assembly by said preparing means. [Claims 17 and 18 Col. 9, L. 61-68; Col. 10, L. 1-4],

In order to provide proper control of the quantity of fibers being fed, the present invention stipulates that before the actual start-spinning operation and the sliver feed occurring in the connection therewith, there is a sliver feed operation at time Tu which is then switched off again at time Tv, thereby providing a precisely defined standstill period for the sliver feed, causing the same remainder Qr to be provided in all cases, so that precise control of the start-spinning quantity Q’a is then achieved on the basis of this remainder Qr and start-spinning quantity Q’a is the same in all cases. In this connection, it is practical for the sliver-feed switch-on time, which increases in accordance with dash-dotted curve 5a, to be maintained for a certain period of time, during which operating feed Qb is provided with certainty, as the influence of a remainder could otherwise still be disturbingly noticed with this brief sliver feed, the so-called preliminary feed. Since the spinning rotor is braked or stopped during the preliminary sliver feed operation, the fibers supplied to it are sucked away by means of an underpressure line, thereby preventing them from being deposited in the spinning rotor. The ring of fibers on which the return end of the thread is placed is thus formed only by the fibers supplied in the controlled sliver feed operation. [Col. 4, L. 1-25] (emphasis added).

The OFRS

56. The Defendants’ version of how the OFRS worked is on Page 95 of their Post Trial Findings of Fact and Conclusions of Law as follows:

Savio developed an OES machine and identified the machine as the FRS. The Savio FRS machine included a number of spinning units serviced by a travelling carriage for piecing as well as other automatic functions. [Ferro Tr. 699-700]. The automatic piecing system of the travelling carriage for the FRS machine followed the steps utilized for piecing on the BD-200 machine; a preparatory cycle including sliver prefeeding, and a start-spinning cycle including piecing. [Ferro Tr. 699-700],

In the old FRS prefeed system, as in the BD-200 prefeed system, upon detecting a thread break, the feeding stops. When the piecing unit (or operation) arrives, the feeding means are started, operated and then stopped to perform a preliminary feed (prefeed), the spinning unit is opened, and the rotor is disconnected from its drive mechanism and stopped. After stopping, the rotor is cleaned. After the rotor is cleaned, the spinning unit is closed and the piecing operation starts. The time period between stopping the feed roller after the preliminary feed and starting the feed roller for piecing (i.e., for opening the spinning unit, cleaning the spinning unit, closing the spinning unit and starting the feed roller for piecing) varied from one yarn piecing to another. [DX 50(A); DX 51; Ferro Tr. 703-717] [Vaughn Tr. 595-97].

57. The Plaintiffs contend that: Paragraph (b) of Claim 18 reads onto the comber roll in PX 313, the OFRS (combing roll and opening roll in PX 313 are the same.) [Tr. 262].

58. Paragraph (c) of Claim 18 reads onto the feed roller at the bottom left corner of PX 313.

59. Paragraph (d) of Claim 18 reads onto the yarn reserve lever and grippers of the untwisting unit and the withdrawal tube of the rotor [Tr. 262-263].

Paragraph (e) of Claim 18, rotor control, reads onto the brake that stops the rotor, and the pivoting open of the spinbox cover which lifts the spindle of the rotor off its drivebelt and applies a brake to stop it. [Tr. 263-264], The stopping and starting of the rotor, spinbox door opening, rotor cleaning with vacuums, sliver prefeed, and piecing feed, yarn end introduction, and withdrawal of thread are all diagrammed on PX 306. [Tr. 264].

Referring to PX 306, Plaintiffs contend that as in ¶ (f), Claim 18 hereinbefore set out there is an opening means which is the comber roll on PX 313, the old or original and modified or NFRS. [Plaintiff’s PT Findings of Fact p. 36].

60. Paragraph (f) of the ’946 Patent, the fiber supply preparing means, is demonstrated on PX 306. That is, there is a prefeed of sliver, the rotor is then stopped by opening the spinbox door and is then cleaned by a vacuum. The rotor is started, there is a piecing feed of sliver, the yam is introduced to the ring of fibers, piecing occurs and the thread is withdrawn. Meantime, although the comber roll is disengaged, it continues to rotate by inertia until the rotor box is closed and the drive is reengaged. [Tr. 263-267].

61. At the end of the prefeed in the OFRS the unknown fiber tuft is eliminated and a new fiber tuft is formed and time controlled until used. [Tr. 320].

62. There is precise control between the end of the prefeed in the OFRS and the beginning of the piecing feed, or at least the capability of precise control. [Tr. 320].

63. The Defendants’ experts Vaughn and Ferro testified on direct examination that the restarting time of the sliver feed for piecing varied considerably, that the time period between the end of the sliver feed for the preliminary feed and the beginning of the sliver feed for piecing varied by about 2-3 seconds from piecing to piecing. [Tr. 589-592; 707-710],

64. Apparently this variation occurs because the rotor box is opened automatically by pneumatic systems and those systems are somewhat inconsistent in terms of the time they carry out that function [Tr. 591]. The Defendants contend that because of this and the result that there is not a uniform fiber tuft there is no infringement. [Tr. 590-593; 645-646; 707-709].

65. The Plaintiffs’ expert Bartlett testified that he caused a continuous time sequence to be placed on a videotape of the OFRS machine [PX 418] and found that the time between the end of prefeed to the beginning of piecing feed was an average of 16.75 seconds with a variance of only 0.2 seconds, and the average time from door opening to door closing was 8.35 seconds with a variation of .05 seconds. [Tr. 981-982],

66. Even more important however, as the Plaintiffs’ expert Bartlett testified, adjustments can be made to the OFRS machine on piecing so that uniform fiber tufts could be obtained. [Tr. 982-985].

67. On the OFRS adjustments could be made to make the piecing point thinner or thicker by adjusting the amount of fibers in the ring. [Tr. 763-764].

68. Thus, it appears to the Court that Claim 18 of the ’946 Patent reads literally and directly on the OFRS. That claim provides:

(a) a preparatory cycle including sliver prefeeding [Tr. 701-702];

(b) a combing or opening roller which functions to open sliver being supplied to the spinning rotor [PX 313; Tr. 261];

(c) a sliver feed roller to feed the sliver to the opener roll [PX 313];

(d) a means for introducing a thread end back into the spinning rotor to be pieced together with a fiber ring formed in the spinning rotor. [Tr. 262];

(e) means for moving the spinning rotor from a stopped to an operating spinning speed to accommodate piecing by said piecing means. [Tr. 264];

(f) a fiber supply preparing means for

(1) preparing said spinning assembly, for a piecing operation prior to movement of said spinning rotor from its stopped position for a piecing operation. [Tr. 263-264; PX 306].

(2) the fiber supply preparing means included means for starting and operating said feeding means for a period of time and then stopping said feeding means, said starting and stopping being accompanied by a continuously operating opening means. [Tr. 263-266; PX 306].

(3) The timewise coordinates of the functions of these elements arranges uniform tufts at the sliver feed roll to accommodate the piecing operation to be subsequently performed. [Tr. 266-268];

(g) a means for supplying a vacuum to said spinning rotor to remove any fiber supplied during said preparation of said spinning assembly by said preparing means. [Tr. 268-269; PX 306].

69. Mr. Ferro, Defendants’ expert witness testified on direct examination as follows:

Q. Turning your attention to the FRS machine, would you generally describe the piecing operation in the event of a yarn break?

A. Yes. The FRS machine was meant to be operating with the traveling carriage and when a spinning unit required the operation of the automation carriage, this unit would communicate to the carriage to stop. The carriage would stop and receive the information on the type of cycle required and consequently would do its operation.

For example, in case of a piecing cycle, the first operation carried out by the carriage was to activate the sliver feed for a period of time which was sufficient to eliminate the damaged fibers which were present on the end of the sliver. After this first phase, the feeding would be stopped and the carriage opened the spinning unit.

Once the spinning unit was completely opened, the rotor would disengage from its drive belt and it was braked. After that an automation arm would move inside the unit that was open at this time in order to clean the rotor.

After having cleaned the rotor, the arm would return to its position, the unit would be closed again. At the same time other automatic functions were looking for the yarn end on the package. At this point, the yarn end was prepared for the piecing, introduced in the discharge tube of the spinning unit. At this point, feeding will start again. The yarn would be released inside the rotor in order to come into contact with the fibers and it would be re-extracted by utilizing the pressure roller of the machine.

[Tr. 701-02].

The NFRS System

70. The NFRS fiber deflection system is also directed to a method and apparatus for effecting piecing of a broken thread end but by introducing a full flow, that is, 100% combed fibers into a rotor operating at full yarn-producing speed at the time of piecing. The NFRS operates in principle by deflecting the flow of fibers (which normally enter the spinning rotor during yarn spinning) away from the spinning rotor operating at yarn-producing speed, and only returning the flow of fibers to the spinning rotor after the piecing operation is started. The full flow of fibers is redirected to the spinning rotor in timed relation to the introduction of the thread end into the rotor for piecing. [Tr. 720-28; 735-40; 590-600; DX 52B, 52A-1-3, 53 and 57].

71. Dr. Vaughn illustrated his testimony with DX 33 {infra) wherein the upper line represents the rotor and the lower line the fiber feed. He testified that at the instant of breakage on the NFRS machine, the rotor continues to operate and the fiber feed is stopped by activation of the yam detector [Tr. 599-600]. The rotor is then stopped by the opening of the box. There is then a period in which both the rotor and the fiber feed are stopped. The rotor is started again and gets up to full operating speed. At that point, the fiber feed starts, deflecting away the fed fiber. The Plaintiffs contend this is a “pre-feed”. Upon the rotor reaching 100% of its operating rate, and at the time it is necessary for the fibers to be in the spinning chamber groove, the fibers are redirected to the spinning groove and piecing occurs.

72. Dr. Vaughn continued to describe the contrast in piecing with the ’946 Patent and DX 33. Dr. Vaughn indicated that when breakage occurs with the ’946 apparatus, the rotor is stopped and the fiber feed is stopped. Further, during the period the rotor is stopped, there is a fiber feed [See 5A on DX 33] and that feed is stopped and continues to be combed by the comber roll [See 5B on DX 33]. [See ’946 Patent; PX 273; Fig. 2]. The rotor is then started, the fiber feed is started again, and piecing occurs where the lines representing the rotor and the fiber-feed come together.

73. Mr. Ferro, Defendants’ expert, testified further that the NFRS combines an open-end rotor spinning machine which includes a number of spinning units (e.g. 216) with a traveling carriage which serves the spinning units. The traveling carriage for the machine includes the fiber deflection system known as “TOP PIECER” which repairs yarn breaks. [Tr. 726-28 and 747-48; DX 52A-1 to 3].

74. To aid understanding of what next occurs, two illustrations are provided below. [Based upon Figures A and B of DX 57]. Figure A shows the NFRS fiber deflection system in operation during the yarn break {i.e., the suction conduit of the “TOP PIECER” engages the spinning unit). Figure B shows the resumption of the normal yarn spinning process (i.e., the removal of the suction conduit of the “TOP PIECER” from the spinning unit).

75. As illustrated in Figure A, upon detection of a thread break by the break detection lever, the feed roller (5) stops. When the traveling carriage of the FRS machine arrives, the spinning unit (1) is opened, the rotor (9) is disconnected from its drive mechanism, and is stopped. After stopping, the rotor is cleaned. After the rotor (9) is cleaned, the spinning unit (1) is closed (which starts the rotor) and the piecing operation can commence. During this entire time the feed roller (5) remains at rest while the end of the sliver (3) is progressively depleted and damaged by the comber roll (2) which continues to rotate. [DX 51, 52B, 53; Tr. 724-28 and 738-40]. Once the rotor (9) is started for the piecing operation of the NFRS, it is not disconnected from its drive mechanism nor is it stopped or slowed in any way [DX 53; Tr. 724-28 and 738-40], As will be developed, the same is true for the feed roller (5). Once it is started, it is not stopped or slowed in any way. [DX 53].

76. After cleaning, the rotor (9) is started by closing the spinning unit (1) (cover of unit not shown). As the rotor (9) moves towards its full yarn production speed, the suction conduit (19) of the “TOP PIECER” moves from the traveling carriage (not shown) and engages the trash removal system (11, 17 and 18) of the unit (1). Next, a flap valve in the vacuum source of the “TOP PIECER” opens to create a suction flow through conduit for removal of damaged fibers from the spinning unit (1) (including from the comber roll 2 and the interspace 7) to remove the fibers damaged by the action of the continually rotating comber roll (2) upon the sliver (3) at the stopped feed roller (5). The feed roller (5) is then started, whereupon the sliver (3) is again fed into the unit (1). Once the feed roller (5) starts, it is not disconnected from its drive mechanism, nor stopped or slowed in any way. [Tr. 723; DX 53]. The comber roll (2) continues to comb the sliver into individual fibers and those fibers also are deflected away from the path (8) to the rotor and out of the spinning unit (1) “upstream” of the rotor (9), via the temporarily applied vacuum source (19). This vacuum conduit (19) is not part of the spinning unit (1) but rather of the “TOP PIECER” on the traveling carriage. The deflected fibers never reach the vicinity of the rotor (9). During this time, the rotor (9) is operating at full yarn-producing speed. [Tr. 723-25; DX 52B; DX 57, pp. 11-12],

77. When the feed roller has reached full operating speed and the full (100%) flow of fibers is being deflected away from the vicinity of the rotor (9), the vacuum via the suction conduit (19) is shut off by the flap valve and the full flow of fibers is directed towards the rotor (9). At the same time, the vacuum conduit (19) is withdrawn from engagement with the unit (1) (Figure B). The full flow of fibers operating at full feed roller speed now enters the rotor (9) which is operating at full yarn-producing speed. By entering the rotor (9), a fiber ring for piecing is formed and, when the broken thread end is returned to the rotor, it meets with the fiber ring, and piecing occurs. [Tr. 723-29; DX 52B; DX 53; DX 57, 11-12]. Thereafter the yam forming process resumes as shown in Figure B, p. 858.

78. The flap valve in the vacuum source serves to influence and shut off the vacuum and is activated in timed relation with the introduction of the thread end into the rotor. Specifically, the thread end to be pieced is held in a gripper above the thread withdrawal tube and when the thread is released this activates the flap valve. Thus, the thread end is drawn into the rotor, as is the full flow of fibers, by the underpressure created by the rotor. [Tr. 723-24; DX 53],

79. ■ After piecing, the yarn is withdrawn with the full flow of fibers being continuously fed into the rotor and onto the package as for “normal” yam production.

As to the Equivalence of the NFRS (The Accused Device) to the ’946 Suessen Machine

80. We start with the general proposition as stated in Graver Tank & Mfg. Co. v. Linde Co., 339 U.S. 605, 70 S.Ct. 854, 94 L.Ed. 1097 (1950) that a patentee may invoke the doctrine of equivalents to proceed against the producer of a device if it performs substantially the same function in substantially the same way to obtain the same result. The Graver court stated:

What constitutes equivalency must be determined against the context of the patent, the prior art, and the particular circumstances of the case. Equivalence, in the patent law, is not the prisoner of a formula and is not an absolute to be considered in a vacuum. It does not require complete identity for every purpose and in every respect. In determining equivalents, things equal to the same thing may not be equal to each other and, by the same token, things for most purposes different may sometimes be equivalents. Consideration must be given to the purpose for which an ingredient is used in a patent, the qualities it has when combined with the other ingredients, and the function which it is intended to perform. An important fact is whether persons reasonably skilled in the art would have known of the interchangeability of an ingredient not contained in the patent with one that was.

Graver, 339 U.S. at 609, 70 S.Ct. at 856.

81. The accused device and the ’946 machine are both methods and Apparatuses for start-spinning a thread on open-end spinning units, and both obtain the same result: piecing of broken thread. Thus, the only question before the Court is whether the way the accused device performs the work is the same as the way the ’946 Patent does it, or at least whether the way the NFRS does it is equivalent to the way the Suessen machine performs the work.

The NFRS machine works as follows: The NFRS performs an automated piecing procedure without incorporating a prefeed and does that in a task oriented sequence and prepares the spinning chamber or has the fibers prepared for the piecing operation by using a technique called “deflection.” At the instant of breakage of the thread in the new FRS machine, the rotor continues to operate, the fiber feed is stopped by activation of the yarn detector, and then the rotor is stopped by the opening of the box. There is a period when the rotor is stopped and the fiber feed is stopped. Then the rotor is started again. It gets up to full operating speed, and after that the fiber feed is started and deflected away. The rotor reaches 100 percent of its operating rate, and at the time that it is necessary for the fibers to be in the spinning chamber, in the spinning groove, the fibers are redirected to that spinning groove and the piecing event occurs. [Tr. 599-600; DX 33].

In contrast, in the ’946 Patent, there is a breakage, the rotor is operating, the fiber feed is stopped and the rotor is stopped, during the period that the rotor is stopped, and while the rotor is in its stopped position, there is a feeding of fiber, and that feed is carried out for a period of time and then that feed is stopped again, and then afterwards the rotor is started and the feed is started again and then piecing occurs at a point thereafter. Figure 2 of the '946 Patent illustrates this. Looking at Figure 2 supra, p. 852, the preliminary feed operation begins at time TU. The preliminary feed operation is briefly stopped at point TV. The fiber beard remains known, and an exactly determined amount of fiber can be fed into the rotor. The process of feeding fibers starts at Line QB in Figure 2. The yarn draw off starts at point TA. The dotted line is the good line. The dotted line takes into consideration the mass of the known fiber beard. The solid line below the dotted line is identical with the preceding Patent 610 [Tr. 71; Figure 2 Patent; DX 27A; PX 273]. See Fig. 2 supra p. 852.

82. Both the ’946 Patent and the NFRS have a method for cleaning the rotor while it is stopped. In the ’946 Patent Claim 18, paragraph (g) provides:

(g) further comprising

(5) means for supplying a vacuum to said spinning rotor to remove any fiber supplied during said preparation of said spinning assembly by said preparing means.

83. Plaintiffs’ witness Bartlett explained this vacuum when he said in essence that there is a part (8a) just below the rotor as shown in Figure 3 of the ’946 Patent reproduced infra. See Bartlett Tr. 226-27. The part (8a) is a vacuum part that connects to a source of underpressure or supply of vacuum and is in the rotor chamber (8) shown in Figure 3. Thus, the rotor is subjected to a vacuum. The primary function of that vacuum is to lift and convey the opened individual fibers from the opening roll up the fiber supply tube into the rotor. That is the primary function of the vacuum, and the vacuum must be there when the rotor is spinning or spinning would not occur. The vacuum has a secondary function also depicted in Figure 3. That is, when the rotor is stopped, as there is then no centrifugal force to hold the fiber in the rotor groove, the vacuum will suck out any fiber making its way into the rotor and take it away. This secondary function further comprises the means for supplying a vacuum to the spinning rotor to remove any fiber supply during the preparation of the spinning assembly by the preparing means. Bartlett further testified that the preparation of the spinning assembly consisted of the sliver prefeed followed by a specific time for forming a uniform tuft. The fiber from the prefeed comes into the rotor but is sucked out because the rotor is stationary. The secondary function of the vacuum sucks away this fiber, (i.e., the unknown quantity of fiber from the prefeed). In addition, any fiber that is combed over afterwards will be sucked away by this vacuum from the stationary rotor. It is this secondary function of the vacuum that Paragraph (g) of claim 18 reads onto. [Tr. 226-227].

84. In contrast to the above-described process, in the NFRS machine, when there is a thread break, a traveling unit arrives at the stopped spinning position. While the rotor continues operating at full operational speed, the cover of the spinbox is unlatched and opened. The rotor is then lifted off its drivebelt, a brake is applied to stop the rotor, and the rotor is then cleaned by a vacuum in the traveling unit. The cleaning head is then pulled away and the spinbox door closes. The rotor then starts and the auxiliary vacuum, or fiber suction vacuum, comes on while the rotor is accelerating to its operational speed. Then, before the auxiliary vacuum goes off, the sliver feed comes on, but because the auxiliary vacuum is operating, all fibers from the sliver feed are sucked out as waste through the vacuum snout [PX 314]. This diversion to waste continues until the fiber suction is switched off.

85. Bartlett prepared a chart [PX 308] reproduced infra to illustrate his testimony.

86. Looking at PX 308, Bartlett testified that the reason for the broken line on the sliver feed line, to the left of which is “prefeed,” is that although the sliver feed is on, none of the fibers can be captured in the rotor. As explained above, this is because the fiber suction vacuum has rendered the rotor inoperative for spinning fibers. That is, fibers fed in the first part of the sliver feed, as the rotor accelerates to operating speed, are just taken to waste by the fiber suction vacuum. Then the auxiliary vacuum is switched off and the fibers can continue around to be captured by the rotor. The rotor is then operating at full speed, so captured fibers fed by the sliver feed go to the rotor and form a piecing ring and are then continually forming the fiber ring for spinning. The yarn end is introduced at a very precisely controlled time, and in a matter of thousandths of a second, the yarn is withdrawn. As the starter is withdrawn, the yarn is the making of the piecing point and it continues as spinning continues. [Tr. 258-282; PX 306, 308, 313, 314].

CONCLUSIONS OF LAW

Under the doctrine of equivalents, infringement may be found (but not necessarily) if an accused device performs substantially the same overall function or work, in substantially the same way, to obtain substantially the same overall result as the claimed invention. Pennwalt Corp. v. Durand-Wayland, Inc., 833 F.2d 931 (Fed.Cir.1987) (citing Perkin-Elmer Corp. v. Computervision Corp., 732 F.2d 888, 901-02 (Fed.Cir.), cert. denied, 469 U.S. 857, 105 S.Ct. 187, 83 L.Ed.2d 120 (1984)); Graver Tank, 339 U.S. at 608, 70 S.Ct. at 856. That formulation, however, does not mean one can ignore claim limitations.

The Federal Circuit further held in Perkin-Elmer Corp. v. Westinghouse Elec. Corp., 822 F.2d 1528, 1532-33 (Fed.Cir. 1987):

In Hughes Aircraft Co. v. United States, 717 F.2d 1351, 1364, 219 U.S.P.Q. 473, 482 (Fed.Cir.1983), this court noted that it was legal error not to “apply the doctrine of equivalents to the claimed invention as a whole.” The statement dealt with an infringement inquiry implicating an entire claim, as distinguished from a section 112 ¶ 6 inquiry implicating only a “means plus function” limitation of a claim. That statement also was a recognition that, in applying the doctrine of equivalents, each limitation must be viewed in the context of the entire claim. The statement should not be interpreted as sanctioning the treatment of claim limitations as insignificant or immaterial in determining infringement. “It is ... well settled that each element of a claim is material and essential, and that in order for a court to find infringement, the plaintiff must show the presence of every element or its substantial equivalent in the accused device.” Lemelson v. United States, 752 F.2d 1538, 1551, 224 U.S.P.Q. 524, 533 (Fed.Cir.1985). To be a “substantial equivalent,” the element substituted in the accused device for the element set forth in the claim must not be such as would substantially change the way in which the function of the claimed invention is performed. (Footnotes omitted).

Thus, in the case before the Court, the Plaintiffs have the burden to prove that the accused device performed its work in substantially the same way as the apparatus in the ’946 Patent. To do so, the Plaintiffs must prove that all limitations of claim 18 are satisfied at least equivalently by the accused device. Becton Dickinson & Co. v. C.R. Bard, Inc., 922 F.2d 792, 798 (Fed.Cir.1990).

Further limitations to the doctrine of equivalents are set out in Loctite Corp. v. Ultraseal Ltd., 781 F.2d 861, 870 (Fed.Cir. 1985):

First, the doctrine will not extend to an infringing device within the public domain, i.e., found in the prior art at the time the patent issued; second, prosecution history estoppel will not allow the patentee to recapture through equivalence certain coverage given up during prosecution. See, e.g., Perkins-Elmer Corp. v. Computervision Corp., 732 F.2d 888, 900, 221 U.S.P.Q. 669, 678 (Fed. Cir.1984), cert. denied, 469 U.S. 857, 105 S.Ct 187, 83 L.Ed.2d 120 (1984).

In further. discussion of the prior art limitation to the doctrine of equivalents, the Federal Circuit in Wilson Sporting Goods v. David Geoffrey & Assoc., 904 F.2d 677, 684 (Fed.Cir.1990) suggested:

Whether prior art restricts the range of equivalents of what is literally claimed can be a difficult question to answer. To simplify analysis and bring the issue onto familiar turf, it may be helpful to conceptualize the limitation on the scope of equivalents by visualizing a hypothetical patent claim, sufficient in scope to literally cover the accused product. The pertinent question then becomes whether that hypothetical claim could have been allowed by the PTO [Patent and Trademark Office] over the prior art. If not, then it would be improper to permit the patentee to obtain that coverage in an infringement suit under the doctrine of equivalents. If the hypothetical claim could have been allowed, then prior art is not a bar to infringement under the doctrine of equivalents.

As to the second limitation, the doctrine of prosecution history estoppel, the Federal Circuit in Builders Concrete, Inc. v. Bremerton Concrete Products Co., 757 F.2d 255, 258-59 (1985) stated:

“Prosecution History (File Wrapper) Estoppel

This doctrine is an equitable tool for determining the permissible scope of patent claims. As we said in Caterpillar Tractor Co. v. Berco, S.p.A., 714 F.2d 1110, 1115, 219 U.S.P.Q. 185, 187 (Fed. Cir.1983), “[t]he interplay between the doctrines of equivalents and estoppel governs determination of infringement ... and is in turn governed by the prosecution history____” Material representations made to the PTO in response to references cited by the PTO, with the result that the scope of patent claims is changed in order to obtain the patent grant, are pertinent to the subsequent determination of the permissible scope of the patent claims (emphasis added). As this court said in Thomas & Betts Corp. v. Litton Systems, Inc., 720 F.2d 1572, 1579, 220 U.S.P.Q. 1, 6 (Fed.Cir.1983):

[P]rosecution history estoppel, which precludes a patentee from obtaining a claim construction that would resurrect subject matter surrendered during prosecution of his patent application ... limits a patentee’s reliance on the doctrine of equivalents ...

Thus, whenever the doctrine of prosecution history estoppel is invoked, a close examination must be made as to, not only what was surrendered, but also the reason for such a surrender. The fact that claims were narrowed does not always mean that the doctrine of prosecution history estoppel completely prohibits a patentee from recapturing some of what was originally claimed.

Bayer Aktiengesellschaft v. Duphar Intern. Research, 738 F.2d 1237, 1243 (Fed. Cir.1984).

As was stated by the court in ZMI Corp. v. Cardiac Resuscitator Corp., 844 F.2d 1576 at 1580 (Fed.Cir.1988):

Resort to extrinsic evidence such as the prosecution history, is necessary to interpret disputed claims. Moeller [v. Ionetics, Inc.], 794 F.2d [653] at 656, 229 U.S.P.Q. [992] at 994; SSIH Equipment S.A. v. USITC, 718 F.2d 365, 376, 218 U.S.P.Q. 678, 688 (Fed.Cir.1983) (the prosecution history is always relevant to proper claim interpretation). “[T]he prosecution history (or file wrapper) limits the interpretation of claims so as to exclude any interpretation that may have been disclaimed or disavowed during prosecution in order to obtain claim allowance.” Standard Oil Co. v. American Cyanamid Co., 774 F.2d 448, 452, 227 U.S.P.Q. 293, 296 (Fed.Cir.1985); see also McGill, Inc. [v. John Zink Co.], 736 F.2d [666] at 673 (Fed.Cir.1984).

As the court said in Prodyne Enterprises, Inc. v. Julie Pomerantz, Inc., 743 F.2d 1581, 1583 (Fed.Cir.1984):

While the doctrine of equivalents may sometimes be applied to amended claims,

The doctrine of prosecution history estoppel precludes a patent owner from obtaining a c