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November 14, 1986

THYSSEN-BORNEMISZA INC., a corporation formerly known as INDIAN HEAD, INC., Defendant

The opinion of the court was delivered by: HAIGHT


HAIGHT, District Judge:

 Plaintiff Slater Electric Inc. began in 1973 to manufacture and sell a molded plastic electrical outlet box incorporating a useful labor-saving innovation. An outlet box is the rectangular, open-faced box in which an electrical wall outlet unit is mounted. To secure the outlet in a wall, the outlet is ordinarily screwed into the box, and the box is nailed to a wall stud. Plaintiff's particular innovation was to develop a way to speed the process of screwing the outlet unit into the box. By means of small metal clips placed in identical, carefully designed holes at the top and bottom of the plastic box, plaintiff made it possible for the screws securing the outlet in the box to be pushed, rather than screwed, into place. Apparently this innovation satisfied a need in the construction industry, for the new box proved popular, and plaintiff's competitors allegedly scrambled to copy it. One of those scrambling competitors was defendant Thyssen-Bournemiza ("T-B"), which began in 1981 to manufacture an outlet box with a similar clip-and-hole device which accomplished the same labor-saving end.

 Plaintiff, which in the meantime had secured three patents on various aspects of its outlet box, promptly brought this suit for patent infringement. T-B has answered that its box does not infringe the patents on the Slater device, but that even if it does the patents are invalid. Presently before the Court are cross-motions for summary judgment addressed solely to the issue of infringement. Slater claims that the facts indisputably demonstrate infringement; T-B claims the exact opposite.

 I. The Invention and the Accused Device

 As noted above, the invention is an electrical outlet box into which screws securing the outlet may be pushed rather than screwed. The box has only two components, a molded plastic box and small metal clips inserted at each end of the box. Unthreaded holes are molded into bosses at each end of the box; the holes receive, but do not secure, the screws. The small clips, punched from sheet metal and inserted in slots next to the holes, secure the screws by means of a prong which projects from the clip into the hole and engages the threads of the screw. The prong is bent in the direction of inward movement of the screw. Because the prong is flexible, the threads of the screw slide over it, ratchet-like, as the screw is pushed in, but it catches the threads and resists if an attempt is made to pull the screw out, against the direction of the bend. This permits the screw to be tightened against the prong.

 The three drawings below, taken from one of plaintiff's patents, illustrate one, although not the only, physical embodiment of this invention. Figure 1 shows an exploded view of the outlet box and outlet. The boreholes which receive the screws are located in bosses formed at the top and bottom of the box; the clips, numbered 8, are inserted in the bosses near the holes. [See Figure 1 in original].

 Figure 2 is a sample clip. The prong which engages the screw threads is numbered 23. [See Figure 2 in original].

 Figure 3 is a cross-sectional view of the hole and clip with a screw inserted. [See Figure 3 in original].

 The invention is a rather simple one. It contains one additional feature which requires some discussion in order to clarify the terms of this dispute. A major design problem for this type of device is devising a means for securing the clip in the slot next to the hole. Some such means is necessary, for pushing the screw in tends to push the clip inward out of the slot, while tightening the screw against the prong tends to pull the clip out of the slot in the other direction. In the example shown in Figures 1-3, this problem is solved by way of the two additional prongs punched from the clip, numbered 21 and 22 in Figure 2. As can be seen from Figure 3, these two prongs grip either side of a ridge, numbered 10, molded into the box inside the clip-holding slot. By abutting the ridge, prong 21 resists the outward pull caused by tightening the screw while prong 22 resists the inward push produced when the screw is inserted.

 Because it works in a similar manner, the accused device is best described in relation to the sample invention shown above. The accused device is also a molded plastic outlet box with metal clips designed to permit screws to be pushed into them. The device uses an outlet box like that seen in Figure 1, with bosses for receiving the screws molded into either end of the box. The clip is inserted into a slot adjoining the screwhole, but the hole and clip are shaped differently from those of plaintiff's sample invention. Figures 4 and 5 are two views of defendant's clip, an L-shaped affair with several tabs. [See Figure 4 and Figure 5 in original]. Figure 6, analogous to Figure 3 above, is a cross-sectional view of the assembled clip and hole. [See Figure 6 in original].

 Although the clip and hole of the accused device are shaped differently from those of the sample invention, they have similar functional features. Two prongs, numbered 1 in Figures 4 and 5, engage the threads of the screw. Like prong 23 in the patented device, they are bent in the direction of inward movement of the screw; they give if the screw threads are pushed over them but catch the threads and resist if outward force is applied to the screw. A second set of prongs, numbered 2, engages a pair of ridges, numbered 3 in Figure 6, which are molded onto either side of the hole and prevents outward movement of the clip. The prongs and ridges are situated so that a screw slides between them when inserted. By preventing outward movement of the clip, these prongs perform the function of prong 21 of the patented device. In contrast to plaintiff's clip, defendant's is not wholly internal. The short leg of the "L" remains outside the hole. The screw is inserted through the a square in this leg. Flaps on either side of the short leg of the "L," numbered 5 in Figures 4 and 5, prevent inward movement of the clip by resting in grooves cut in the top of the boss on either side of the hole. These perform the function of prong 22 of the patented device.

 Plaintiff is suing for infringement of two patents. United States Patent No. 8,105,862 ("the '862 patent") covers an "outlet box having screw mounting means," i.e., the outlet box described generally above. United States Patent No. 4,188,854 ("the '854 patent") covers "screw mounting means," i.e., the clip and hole device described above which is used to secure the outlet in the box. Thus the '862 patent includes the device described in the '854 patent. In its cross-motion for summary judgment, plaintiff contends that defendant's outlet box and the means defendant's box uses to secure the outlet in the box fall within the description of the invention embodied in certain of the claims of the '862 and '854 patents. If the accused device falls clearly within the bounds of these claims a case of literal infringement is made out. Graver Tank & Manufacturing Co. v. Linde Air Products Co., 339 U.S. 605, 607, 94 L. Ed. 1097, 70 S. Ct. 854 (1950); Envirotech Corp. v. Al George, Inc., 730 F.2d 753, 759 (Fed.Cir. 1984). Defendant contends essentially the opposite: that when the claims in the patents are properly construed--that is, construed in light of the prosecution history and specifications of the patents--the accused device plainly falls outside of them. In addition, defendant claims that in various statements plaintiff made to the patent examiners during prosecution of these patents it effectively disclaimed coverage of a device like defendant's. As a result, it is argued, plaintiff is estopped from claiming infringement now.


 The Prosecution History of Plaintiff's Patents

 Central to defendant's motion is the prosecution history of the patents. Both arise from a 1971 application for a patent on a "screw mounting means." In that application, the drawings reproduced as Figures 1-3 were used to illustrate the "preferred embodiment" of the invention sought to be patented. *fn1" With a few exceptions, claim one of the 1971 application, the broadest claim, is identical to claim one of the '854 patent here at issue. *fn2" The examiner in the Patent Office rejected the 1971 application as both anticipated by the prior art and as an obvious modification of prior art structures. Claim one of the 1971 application was amended slightly *fn3" in an effort to persuade the examiner of its distinction from the cited prior art, but the effort was futile. The examiner again rejected the claims as anticipated, and plaintiff abandoned its application.

 In 1973 plaintiff tried again. A new application for a patent on a "screw mounting means" was submitted which carried over much of the material in the 1971 application but added an alternative preferred embodiment of the invention. The new embodiment involved use of a differently shaped clip, seen in Figure 9, infra. Claim one of the new application, designed to accommodate both embodiments, is identical to claim one of the '854 patent. *fn4" This application was considered by the same examiner who rejected the 1971 application and, perhaps not surprisingly, was rejected for similar reasons. In submitting an amended 1973 application, plaintiff amended claim one in an apparent attempt to define more precisely the role of the prong which engages the screw. This fared no better. The examiner once again rejected the broad claims. However, he did suggest a narrower combination of claims which he would accept. Plaintiff capitulated, and the 1973 application resulted in issuance of United States Patent No. 3,955,463. Plaintiff has not alleged that this patent is infringed.

 During plaintiff's prosecution of the 1973 application, the examiner brought to plaintiff's attention a new patent for a plastic electrical outlet box with a metal retaining clip granted to an inventor named Pringle. Pringle's patented device used a structure similar to plaintiff's preferred embodiment for its screw mounting means. Having filed its 1971 application prior to Pringle's filing of his application, plaintiff decided that it should have been recognized as the first inventor of this device. It sought to have itself declared the proper owner of the Pringle patent by provoking an interference. In order to do so, it filed a new application in 1975. The new application was similar to the 1971 application, but it included as one of its claims an electrical outlet box using the 1971 application's screw mounting means. After reviewing the 1975 application, an examiner who had not previously evaluated plaintiff's invention declared plaintiff the first inventor of the invention disclosed in the Pringle patent. Plaintiff was awarded priority. This award resulted in the '862 patent. Claim one of the Pringle patent became claim one of the '862 patent. Claim two of the '862 patent covers an electrical outlet box incorporating a screw mounting means which is described in language essentially identical to that used in claim one of the amended 1971 application.

 In 1977, prior to the grant of the '864 patent, plaintiff submitted a third application for a screw mounting means patent. Claim one of the application was identical to claim one of the '854 patent--in other words, identical to the language which had twice before, in the amended 1971 and initial 1973 applications, been rejected as anticipated by or obvious from prior art. The 1977 application was assigned to a different examiner than the first two applications. The new examiner apparently did not share the scruples of the initial examiner, for he eventually granted a patent, the '854 patent, on the claims included in the 1977 application.

 III. Prosecution History Estoppel

 In its moving brief, defendant describes this prosecution history in much greater detail, discussing at length the many arguments which Slater made to the various patent examiners in an effort to persuade them that its invention was patentable. Defendant asserts that during the course of these arguments Slater disclaimed coverage by its patent of a product embodying the features of defendant's accused device. By way of "prosecution history estoppel," defendant seeks to preclude plaintiff from now reclaiming this allegedly abandoned territory.

 "Prosecution history estoppel," frequently referred to in the past as "file wrapper estoppel," is invoked in relation to, and as a counter to, the doctrine of equivalents. Indeed, estoppel is "irrelevant" unless an equivalent is claimed. Fromson v. Advance Offset Plate, Inc., 720 F.2d 1565, 1571 (Fed. Cir. 1983). The doctrine of equivalents permits a patentee to claim broader scope for his or her patent than the literal language of the claims would otherwise allow. Pursuant to the doctrine, a patent is taken to cover not only embodiments within the literal language of the claims but devices which "perform[] substantially the same function in substantially the same way to obtain the same result." Graver Tank, supra, 339 U.S. at 608; Kinzenbaw v. Deere & Co., 741 F.2d 383, 389 (Fed.Cir. 1984), cert. denied, 470 U.S. 1004, 84 L. Ed. 2d 379, 105 S. Ct. 1357 (1985). Thus the patentee is protected from clever copyists who duplicate the essence of the invention while skirting the language of its patent's claims. Hughes Aircraft Co. v. United States, 717 F.2d 1351, 1361 (Fed.Cir. 1983).

 However, patent law also recognizes that a patentee cannot be permitted to use the doctrine of equivalents to expand the scope of the patent's claims to cover structures which could not have been patented. If a patent applicant submits a broad claim which he is forced by the Patent Office to narrow in order to avoid anticipation or interference from another patent, the patentee is not permitted to use the doctrine of equivalents to recapture the ground abandoned in narrowing the claim. It is here that the doctrine of prosecution history estoppel comes into play. In its purest form, the doctrine estops a patentee from reclaiming, through the doctrine of equivalents, coverage of devices which the patentee has expressly amended his claims to avoid. Prodyne Enterprises, Inc. v. Julie Pomerantz, Inc., 743 F.2d 1581, 1583 (Fed.Cir. 1984). Stated more generally, the doctrine "precludes a patent owner from obtaining a claim construction that would resurrect subject matter surrendered during the prosecution of his patent application." Hughes Aircraft Co. v. United States, supra, 717 F.2d at 1362. See also Brenner v. United States, 773 F.2d 306, 307 (Fed.Cir. 1985). Thus the doctrine may be invoked if the applicant has disavowed subject matter coverage by arguing a narrow claim construction to the Patent Office as well as when he or she has disavowed subject matter through amendment. Perkin-Elmer Corp. v. Computervision Corp., 732 F.2d 888, 900 (Fed.Cir.), cert. denied, 469 U.S. 857, 83 L. Ed. 2d 120, 105 S. Ct. 187 (1984); Thomas & Betts Corp. v. Litton Systems, Inc., 720 F.2d 1572, 1579-80 (Fed.Cir. 1983); Hughes Aircraft Co. v. United States, supra, 717 F.2d at 1362; Caterpillar Tractor Co. v. Berco, S.P.A., 714 F.2d 1110, 1117 (Fed.Cir. 1983) (Davis, J., dissenting in part); Coleco Industries, Inc. v. ITC, 65 C.C.P.A. 105, 573 F.2d 1247, 1257 (C.C.P.A. 1978).

 Estoppel by argument rests on the same theoretical footing as the more classic estoppel by amendment. Ordinarily estoppel by argument arises when an applicant has convinced an initially skeptical patent examiner that the literal language of a claim does not encompass forbidden prior art. In such situations, estoppel by amendment cannot arise, for the applicant has convinced the examiner that amendment to avoid the prior art is unnecessary. Nevertheless, the applicant has disclaimed the prior art as effectively as if he or she had actually amended the patent's claims. Therefore, it is reasoned, the applicant should not be permitted to recapture that which has been abandoned.

 Because the "argument" which forms the basis for estoppel by argument is ordinarily a statement that the literal reach of an applicant's claims does not cover a particular subject matter, it might seem that a finding that a particular accused device cannot be claimed as an equivalent because of estoppel by argument would a fortiori mean that the device did not literally infringe the patent's claims. However, it has been held that subject matter which a patentee is estopped from claiming as an equivalent may nevertheless fall within the literal reach of the patent's claims. Seattle Box Co. v. Industrial Crating & Packing, Inc., 731 F.2d 818, 829 (Fed.Cir. 1984). Defendant's request for summary judgment based on prosecution history estoppel is therefore a rather ambitious one. Even if plaintiff is estopped from claiming defendant's device as an equivalent, plaintiff would appear to be permitted under Seattle Box to prove literal infringement. See also Fromson v. Advance Offset Plate, Inc., supra, at 1571 ("If there be literal infringement, direct and contributory (as there may be here under a proper construction of the claims), the doctrine [of prosecution history] is irrelevant."). Indeed, in its cross motion plaintiff makes just that claim of literal infringement. Nonetheless, in order that all aspects of the case be dealt with, I shall first consider defendant's motion.

 IV. Defendant's Motion

 Defendant's presentation of its estoppel motion is at best scattershot. It has made no attempt to organize a series of discrete, well reasoned arguments centered around specific events in the prosecution history. Instead, defendant has chosen simply to recite a detailed history of the prosecution and highlight occasions on which plaintiff made statements which tend to distinguish the Slater invention from the accused device. I have sorted through what appear to be defendant's arguments, and I present a discussion of what I consider to be the most significant ones below.

 A. Estoppel by Amendment

 Defendant has little to argue in connection with estoppel by amendment. As noted above, claim one of the '854 patent, the only independent claim *fn5" amended in response to an examiner's objections, appears only slightly amended from its initial configuration in the 1971 application. When the 1971 application was initially submitted, the examiner rejected it as anticipated by prior art. One of the prior art patents cited, to Bengtson, U.S. Patent No. 2,940,782, was a means for fastening knobs--for example, radio or television dials--to their shafts. Bengtson's fastener is a flat metal spring clip designed to hold a knob in place on a D-shaped shaft by pressing between the flat side of the D and the inside surface of the mounting hole in the knob. The knob thus held can be readily pulled off, since only the friction between the spring clip and the flat side of the shaft holds it in place. In addition, the clip is not firmly fixed in the knob, for it is essentially wedged between the shaft and the inside of the knob. Bengtson's knob and two views of his clip are illustrated in Figure 7, which reproduces drawings taken from the patent. [See Figure 7 in original].

 Such an arrangement may be distinguished from the clip in plaintiff's invention in two ways: 1) once installed, plaintiff's clip is held firmly in place, and 2) the screw, equivalent to the Bengtson shaft, is also held firmly in place. As described above, once plaintiff's clip is installed, one of its prongs abuts against a fixture (a ridge in the illustration) in the outlet box, preventing its removal, and the screw may not be removed except by turning. Plaintiff argued this distinction to the claims examiner, and it amended its claim to reflect these distinctions. *fn6" Plaintiff's comments to the examiner reflect this logic. (1971 application, at 31-32). *fn7" Because defendant's device shares with plaintiff's the features which plaintiff sought through these amendments to distinguish from the prior art, the amendments could be of no help to defendant. Because they are the only significant amendments, *fn8" defendant cannot argue estoppel by amendment.

 B. Estoppel by Argument

 In seeking to invoke estoppel by argument, defendant cites a number of characterizations which plaintiff made of its invention in the course of responding to the examiners' many objections to its claims. Each of these characterizations is said to distinguish plaintiff's invention not only from the prior art but from defendant's device as well. It is these characterizations which defendant claims as a basis for estoppel. Before discussing this contention, I will review the various remarks in context.

 The prior art patent which was most forcefully cited against the 1971 application was Bengtson. As noted above, plaintiff distinguished Bengtson by noting that the clip there disclosed was not locked in place inside the knob, whereas its clip was firmly fixed in the outlet box, and gripped the shaft only by friction, whereas plaintiff's clip prevented the screw from being removed by solely a pulling (non-twisting) force. Plaintiff amended its claims to distinguish Bengtson in this manner. At the same time, plaintiff noted that Bengtson did not provide for the specific means for locking the clip in place which Plaintiff selected, that is, a narrow ridge gripped on both sides by the clip. This feature, while not specifically disclosed in claim one of the 1971 application, was disclosed in dependent claims three and five of the application. Defendant argues that this statement should limit plaintiff's invention to use of such a ridge, which it argues its device does not contain.

 In addition, in the later 1973 application, plaintiff also distinguished the complexity of manufacture of its clip from that of Bengtson's clip, which contains a number of bends. Referring to formation of Bengtson's clip as involving "complicated twisting and bending," plaintiff noted that its

 clip is "based on a mechanically simple design which does not require complicated bends for fabrication." (1973 application, at 47). Defendant is apparently of the opinion that ...

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