Mannesmann Demag Corporation (Man-nesmann) appeals the final judgment of the United States District Court for the Dis *1281 trict of Delaware holding that claims 1, 2, 5-12, 14, 15, 18, and 19 of U.S. Patent No. 4,207,060 (the ’060 patent), invented by Ludger Zangs and assigned to Mannes-mann, were not infringed by Engineered Metal Products Co., Inc. (EMPCO). EMP-CO cross-appeals from the district court’s holding that the ’060 patent is not invalid in terms of 35 U.S.C. § 103. We affirm the district court’s judgment in both respects.
Background
The background of this litigation and the issues at trial are well set out by the district court.
Mannesmann Demag Corp. v. Engineered Metal Products Co.,
1. A vessel for a metal smelting furnace having a smelting zone including a heat-resistant interior wall, and cooling means for protecting the interior of said vessel, characterized by
(a) at least a portion of the interior wall of said vessel above the smelting zone consisting of at least one cooling pipe coil;
(b) said coil including fluid passage-forming sections;
(c) said cooling pipe coil being exposed to the center of the vessel, and
(d) neighboring sections of said coil being arranged in a contacting relation.
The cooling pipe coil structure is illustrated in Figure 1 of Zangs '060 patent, which shows the pipe coil sections in a contacting relation:
[[Image here]]
EMPCO manufactures and sells cooling pipe coils for use in electric arc furnaces. As found by the district court, the accused coils comprise a рlurality of pipe sections, separated from neighboring pipe sections by a bar of about % inch diameter called a “slag-stopping bar”, which is welded to one side of a pipe section and separated from the neighboring section by a tolerance of Vm to Vs2 inch. The EMPCO pipe coils, described as having pipe sections about 2V2 inches in diameter, also have backbone bars welded to alternate pipe sections on the exterior side as a means of support. An EMPCO pipe coil was pictured in cross-section as follows, in exhibit PX-33:
*1282 [[Image here]]
EMPCO asserts that the spacing due to the bar between its pipes has the additional function of anchoring a protective layer of solidified slag, that the separation by Vie to Via inch of the slag-stopping bar from the neighboring pipe section must be strictly construed in view of the prosecution history of the Zangs patent, and thus that the patent claims are not infringed by the EMPCO structure.
Mannesmann charged EMPCO with direct infringement, inducing infringement, and contributory infringement of the ’060 patent, all either literally or by application of the doctrine of equivalents.
Literal Infringement
Literal infringement requires that the accused device embody every element of the patent claim.
Stewart-Warner Corp. v. City of Pontiac,
Analysis of patent infringement involves two inquiries: determination of the scope of the claims, if there is a dispute as to claim interpretation or construction; followed by determination of whether properly interpreted claims encompass the accused structure. The threshold question of claim interpretation is, on appeal, reviewed for legal correctness. The application of the claim to the accused structure is a matter of fact, reviewed for clear error.
See Loctite Corp. v. Ultraseal Ltd.,
At the trial EMPCO denied literal infringement on two grounds. First, EMP-CO argued that the phrase “consisting of” in clause (a) of claim 1 is an exclusionary term thаt prevents infringement by EMP-CO’s coils because they contain additional structures not set forth in claim 1, namely the slag-stopping and backbone bars. The district court correctly observed that the phrase “consisting of” appears in clause (a), not the preamble of the claim, and thus limits only the element set fоrth in clause (a). The court correctly declined to read this usage of “consisting of" as excluding all other elements from the claim as a whole.
Referring to the patent’s prosecution history, the district court observed that “consisting of” was added to clause (a) by Mannesmann during prosecution in order to distinguish thе claims from cited references disclosing composite wall structures partly containing cooling pipes, and that the phrase was limiting only to the extent that it required “at least one cooling pipe coil” forming a wall structure. Accordingly the court correctly rejected EMP-CO’s argument that literal infringement was avoided merely by the addition of the slag-stopping and backbone bars to the cooling pipe coil. The court held that these bars did not detract from the coil’s structural integrity as a wall.
Mannesmann,
Turning to clause (d)' of claim 1, Mаnnesmann contends that the court clearly erred in holding that the clause “neighboring sections of said coil being arranged in a contacting relation” requires that the sections actually touch. Mannesmann argues that EMPCO’s neighboring coil sections are in substantial if not actual contact, because they are sufficiently close to prevent the flow of slag through the coil to the exterior wall. Mannesmann also argues that EMPCO’s interposition of the % inch slag-stopping bar between the pipes is no more than a reshaping of the pipe sections, and can not avoid the plain reading and intent of the claims. Mannesmann asserts that the Vis to Vso inch gap places the sections “in a contacting relation” as stated in clause (d), and that this gap is within manufacturing tolerances. EMPCO argues that Zangs gave up the opportunity so to interpret the claims when he changed “closely adjacent” to “in a contacting relation”.
The district court reviewed the prosecution history, and determined that Zangs had originally employed the term “closely adjacent” to describe the spacing between pipe sections. Upon the examiner’s objection to “closely adjacent” on the two-fold ground of indefiniteness аnd not distinguishing from certain cited references, Zangs substituted the words “in a contacting relation”. The district court also observed that the dictionary defines “contacting” as meaning physical touching.
The district court also declined to construe the phrase “sections of said coil” in clause (d) literally to include the combination of a slag-stopping bar welded to a pipe, the court stating that its construction of the term “sections of said coil” to mean only pipes was the more reasonable, in light of the specification.
The district court also observed that even the combination of the pipе and slag-stopping bar in the EMPCO system, did not touch the neighboring pipe but was separated by a Vie to Via inch gap. Mannes-mann disputes both the existence and the significance of this gap. The district court referred favorably to the testimony of Mr. Wunsche, the President of EMPCO, to the effect that EMPCO “intentionally welded the [slаg-stopping] bar to only one adjacent pipe to ensure flexibility and thereby avoid cracking of the panel structure”.
Mannes-mann,
The district court concluded that the words in clause (d), “in a contacting relation”, require strict construction in view of the prosecution history and the prior art, and thus that the claims are not literally infringed by EMPCO’s coils or vessels containing EMPCO’s coils.
Mannesmann,
Estoppel
Mannesmann argues that even if literal infringement does not lie, the district court clearly erred in finding no infringement by equivalents. Mannesmann argues that the EMPCO structure “performs substantially
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the same function in substantially the same way to obtain the same result”, the standard for equivalency discussed in
Graver Tank & Mfg. Co. v. Linde Air Products Co.,
The district court held that Mannesmann is estopped to assert infringement by equivalents, as applied to the Zang claims and the EMPCO structure, because of Zang’s amendments and arguments during prosecution of the patent application. Specifically, the district court held that the insertion into clause (d) of the limitation that neighboring sections of cooling pipe coil be arranged “in a contacting relation”, rather than “closely adjacent” as originally phrased, bars recourse to the doctrine of equivalents to cover the EMPCO coils.
Mannesmann cites
Deere & Co. v. International Harvester Co.,
The doctrine of prosecution history estoppel is “an equitаble tool for determining the permissible scope of patent claims” as against a specific structure accused of infringement.
Builders Concrete,
Amendment of claims during patent prosecution does not necessarily bar all benefit of the doctrine of equivalents. In
Hughes Aircraft, 717
F.2d at 1363,
Depending on the nature and purpose of an amendment, it may have a limiting effect within a spectrum ranging from great to small to zero. The effect mаy or may not be fatal to application of a range of equivalents broad enough to encompass a particular accused product. It is not fatal to application of the doctrine itself.
See also Loctite Corp.,
Mannesmann thus argues that it is entitled to some range of equivalents, while accepting that it is not entitled to the original scope of its unamended claims. Man-nesmann argues that in amending its claims to meet the examiner’s rejections under 35 U.S.C. §§ 103 and 112, it relinquished no more than was necessary to distinguish the references. Mannesmann argues that it is entitled to the benefit of its inventive concept, plainly distinguished from the prior art, and that the claims retain a scope of equivalency that is more than sufficient to encompass the EMPCO structure.
Determination of the scope of an estoppel deriving from actions taken before the Patent and Trademark Office requires review of not only the nature of
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such actions, but the reasons therefor: the prior art thereby distinguished, and the examiner’s objections thereby overcome. The reasons for amendment of claims during patent prosecution necessarily depend on the facts and circumstances of the particular case.
Loctite Corp.,
The Zangs application was rejected under 35 U.S.C. § 103 based on a patent to Hennenberger et al. (U.S. Patent No. 3,034,776, issued May 15, 1962) in view of certain patents to Moore and Wamser. These references were discussed in detail by the district court, princiрally in connection with validity, but are plainly pertinent to the court’s interpretation-of the claims.
See Mannesmann,
On the basis of this amendment the district court held that estoppel lies, even if the EMPCO structure were equivalent to that of the claims. The distriсt court found that Mannesmann was attempting “to reclaim the very thing it surrendered by way of amendment”, and that Mannesmann was estopped to recover the “closely adjacent” scope it had relinquished.
Id.
at 1380,
Thе district court did not hold that Man-nesmann is deprived of all equivalents to the invention as claimed in the ’060 patent, and precedent does not so require. However, the enlarged claim interpretation that Mannesmann seeks to apply to the EMPCO structure falls squarely within the claim scope that Mannesmann relinquished to overcome the cited references. There is little distance between “closely adjacent” and “in a contacting relation”, and on these facts we discern no error in the district court’s application of prosecution history estoppel to hold that Zangs’ claims are not infringеd.
Validity
We have thoroughly reviewed the district court’s holding that the Zangs patent is not invalid under 35 U.S.C. § 103. We have considered all of the cited references, and all the issues presented on appeal. We discern no error in the court’s factual findings or legal conclusions, and affirm the court’s holding that the ‘060 patent is not invalid, for the reasons stated in its opinion.
See Mannesmann,
AFFIRMED.