Full opinion text
OPINION McKELVIE, District Judge. This is a patent case. Plaintiff KX Industries, L.P. is a limited partnership organized under the laws of Delaware with its principal place of business in Orange, Connecticut. Plaintiff Koslow Technologies Corporation is a Connecticut corporation with its principal place of business in Orange, Connecticut. Koslow Technologies is the owner of U.S.Patents Nos. 5,249,948 (“the ’948 patent”), 5,189,092 (“the ’092 patent”), 5, 147,722 (“the ’722 patent”) and 5,019,811 (“the ’311 patent”), all pertaining to extruded carbon blocks used in water filters. KX Industries is the exclusive licensee of the ’948, ’092, ’722, and ’311 patents. Defendant Culligan Water Technologies, Inc. is a Delaware corporation with its principal place of business in Northbrook, Illinois. Defendant Plymouth Products, Inc. is a Delaware corporation with its principal place of business in Sheboygan, Wisconsin. Plaintiffs filed a complaint on February 24, 1998, alleging defendants have willfully infringed and continue to willfully infringe the ’948 patent, that defendants have engaged in false advertising, and that defendants misappropriated KX Industries’ trade secrets. On May 12, 1998, plaintiffs filed an amended complaint alleging, in addition, defendants have willfully infringed and continue to willfully infringe the ’092, ’311, and ’722 patents. On May 19, 1998, defendants filed an answer denying plaintiffs’ claims and asserting counterclaims, including non-infringement and invalidity of the ’092, ’948,-’311, and ’722 patents. On October 28, 1998, defendants filed an amended answer asserting various defenses, including the affirmative defense of unenforceability of the ’948, ’311, and ’722 patents. On November 24, 1998, this court dismissed with prejudice claims including plaintiffs’ false advertising claim and defendants’ counterclaim and affirmative defense of unenforce-ability of the ’948 patent pursuant to the parties’ stipulation. On February 11, 1999, the court held a hearing in accordance with Markman v. Westview Instruments, Inc., 517 U.S. 370, 116 S.Ct. 1384, 134 L.Ed.2d 577 (1996) to construe disputed claims of the ’092, ’948,-’311, and ’722 patents. This is the court’s construction of those disputed claims. I. FACTUAL BACKGROUND The court draws the following facts from the parties’ evidentiary submissions, and the testimony and evidence presented during the claim construction hearing. A. The Parties Koslow Technologies is the owner of the ’092, ’948, ’311 and ’722 patents. KX Industries is the exclusive licensee of these patents. KX Industries develops, manufactures and sells carbon blocks used in residential and commercial water filters. The court shall refer to the two plaintiffs collectively as “KXI.” Dr. Evan E. Koslow is the inventor of the ’722, ’092, and ’311 patents, and the joint inventor of the ’948 patent. He is KX Industries’ founder and CEO, and Koslow Technologies’ founder and president. Culligan Water Technologies manufactures and sells water filtration systems and related products, including carbon block filters. Culligan makes some of its carbon block filters by an extrusion process using carbon and a binder. Since this action commenced, Culligan Water Technologies has been acquired by United States Filter Corporation. Plymouth has been a wholly-owned subsidiary of Culli-gan Water Technologies since August 1997. Plymouth manufactures and sells a variety of water filtration products, including the extruded carbon blocks which are the subject of the patent infringement claims. The court shall refer to the two defendants collectively as “Culligan.” B. The Technology Carbon block filters are solid filters that use carbon to remove particulate and chemical impurities and offensive odors from water. They are made of granular activated carbon and a plastic binder material that has a lower softening temperature than carbon. Carbon block can be made through extrusion or molding processes. In both processes, the carbon and binder are mixed together and then heated to a temperature above the softening or melting point of the binder, but below that of the carbon. As a result, the binder softens and surrounds the carbon particles, while still leaving voids and pores that expose carbon particles and allow water to pass through the block. Extrusion is the process of forcing a material through a die. A well-known example of an extruder is a pasta maker, in which dough is mixed and then forced down a tube until it passes through a die that shapes it into a form. Making extruded carbon block involves feeding a powdered mixture of granular activated carbon and a binder into an extruder, heating the mixture to a temperature above the softening temperature of the binder but below that of the carbon, pushing the mixture through a die which shapes the block, then applying pressure and cooling the block so it forms a solid material. C. The Patents 1. The ’811 Patent The ’311 patent is entitled “Process for the Production of Material Characterized by a Continuous Web Matrix or Force Point Bonding.” It discloses a method for forming a composite material from primary particles and binder particles which have a lower softening temperature than primary particles. The particles are mixed together to create a “substantially uniform mixture” and then are heated to a temperature above the softening point of the binder particles, but below that of the primary particles. The softened binder particles partially fill the spaces between the primary particles. The patent’s specification and claims disclose applying pressure and shear to the mixture to create bonds between the primary particles and the binder particles. The patent’s specification describes the resulting bonds as a “substantially continuous webbing structure” or as “forced point-bonds.” The patent’s specification and claims disclose “rapidly” cooling the mixture to stabilize the composite material. The resulting product is a porous solid in which the binder forms a structure supporting the primary particles. Claims 1 and 94 of the ’311 patent teach the process for forming the composite material. The claims disclose the application of pressure and shear “to convert at least a portion of the binder material particles into a substantially continuous webbing structure through the composite material.” “Continuous webbing matrix” is defined in the ’311 patent specification as “a thin, substantially continuous film or ‘web’.” U.S.Patent 5,019,311, col. 4, lines 42-45. The specification further describes the matrix as a “continuous phase” but with voids present, resulting in a permeable structure with a “large volume of pores filled with air or other atmospheric gas.” Id. at col. 5, lines 27-34. Claim 94 of the ’311. patent discloses the application of pressure and shear to “cause forced point-bonding of the particles of the primary material by the binder material.” “Forced point-bonds” are described in the ’311 patent’s specification as having “adhesive-like bonds between the particles caused by the melting of the binder resin and squeezing this material to a point insufficient to consolidate into a continuous web.” Id. at col. 15, lines 21-25. a. Prosecution History The predecessor application to the application which led to the ’311 patent is Application Serial No. 07/314,615. It is entitled “Process for the Production of Materials by In-Situ Fiberizing and Force Point Bonding and Materials Produced by the Process.” Koslow originally filed the predecessor application with the Patent and Trademark Office (“PTO”) on February 23, 1989. On November 20, 1989, the PTO issued an office action finding the invention in claims 1-86 and 166-182 (“group I claims”) distinct from the invention in claims 87-165 and 183-191 (“group II claims”). According to the PTO, the group I claims were “drawn to a method of forming a composite material by either force point bonding or in-situ fiberizing techniques,” and the group II claims were “drawn to a composite material[.]” The PTO restricted the applicant to one of the inventions, pursuant to 35 U.S.C. § 121. On December 19, 1989, Koslow elected to continue to prosecute the group I claims in this application. On December 22, 1989, Koslow filed the application which led to the ’311 patent, known as Application Serial No. 07/455,-997. This was filed as a continuation-in-part of the co-pending 07/314,651 application. The application is entitled “Process for the Production of Materials and Materials Produced by the Process.” On February 5, 1990, the PTO issued a notice of allowability, allowing claims 1-86 and 166-182 of the 07/314,651 application. On July 23, 1990, the applicant expressly abandoned the 07/314,651 application pursuant to 37 CFR 1.138, in favor of the application which led to the ’311 patent. On July 25, 1990, the PTO issued a notice of allowability, allowing claims 1-86, 166-182, 192-205, and 207 of the application. The ’311 patent issued on May 28, 1991 under the title “Process for the Production of Materials Characterized by a Continuous Web Matrix or Forced Point-Bonding.” Koslow assigned the ’311 patent to Koslow Technologies Corporation. b. Disputed Terms KXI claims Culligan has infringed claims 87 and 94 of the ’311 patent. Claim 87 is dependent upon claim 1 of the ’311 patent. These claims read as follows, with disputed terms and phrases in italics: 1. A method of forming a composite material which comprises: providing a quantity of first particles of a binder material, said first particles having diameters between about 0.1 and about 150 micrometers; providing a quantity of second particles of a primary material having a softening temperature substantially greater than the softening temperature of said binder material, said second particles having diameters between about 0.1 and about 3,000 micrometers; combining the first and second quantities of particles in a substantially uniform mixture wherein said binder material is present in an amount of at least about 3% by weight of the mixture; heating said substantially uniform mixture, in the absence of pressure or shear sufficient to convert the binder particles into a continuous phase through the composite material, to a temperature substantially above the softening temperature of said binder material but to a temperature less than the softening temperature of said primary material; thereafter applying pressure and shear to the heated mixture sufficient substantially immediately to convert at least a portion of the binder material particles into a substantially continuous webbing structure through the composite material; and substantially immediately after formation of said continuous binder structure, rapidly cooling said mixture to below the softening point of the binder material to retain said converted binder material in its continuous webbing structure condition to produce the composite material. 87. The method of claims 1, 3, 5, 7, 9, or 15 wherein the heat, pressure and shear are applied in an extrusion process. 94. A method of forming a composite material which comprises: providing a quantity of first particles of a binder material, said first particle having diameters between about 0.1 and about 150 micrometers; providing a quantity of second particles of a primary material having a softening temperature substantially greater than the softening temperature- of ■ said binder material, said second particles having diameters between about 0.1 and about 8,000 micrometers; combining the first and second quantities of particles in a substantially uniform mixture wherein said binder material is present in an amount of at least about 3% by weight of the mixture; heating said substantially uniform mixture, in the absence of pressure or shear sufficient to convert the binder particles, to a temperature substantially above the softening temperature of said binder material but to a temperature less than the softening temperature of said primary material; thereafter applying pressure and shear to the heated mixture sufficient to substantially immediately convert at least a portion of the binder material particles into a substantially continuous webbing structure or cause forced point-bonding of the particles of the primary material by the binder material; and substantially immediately after formation of said binder particles into a webbing structure or forced point-bonds, rapidly cooling said mixture to below the melting point of the binder material to retain said converted binder material in its continuous webbing structure or forced point-bonded condition to produce the composite material. 2. The ’722 Patent The ’722 patent is entitled “Process for the Production of Materials and Materials Produced by the Process.” The ’722 patent is directed to producing a composite porous article containing primary particles and binder particles which have a lower softening temperature than the primary particles. The patent discloses a composite article in which the primary particles form a matrix that is supported and held in place by the binder particles. The primary particle matrix is replete with pores and voids, which are partially filled by .the binder material. Claim 1 of the ’722 patent describes the binder particles as forming “a substantially continuous thermoplastic binder phase supporting and enmeshing” the primary particles. Claim 77 of the ’722 patent describes the binder as forming “forced point-bonds between the primary particles[.]” a. Prosecution History On January 25, 1990, Koslow filed the application which led to the ’722 patent, known as Application Serial No. 07/571,-075. Koslow filed it as a divisional application of the co-pending application which led to the ’311 patent. On May 3, 1991, the PTO issued an office action rejecting claims 87-165, 182-191, and 206 and canceling claims 1-86, 166-182, 192-205, and 207. The examiner characterized the invention as “the concept of a plurality of primary particles and a matrix binder, the particles having a higher softening temperature than the binder.” He rejected the pending claims as unpat-entable over the admitted prior art in view of the Stastny (U.S.Patent No. 2,865,800), Stayner (U.S.Patent No. 3,608,010), Shannon ’341 (U.S.Patent No. 3,325,341) and Oleott et al. (U.S.Patent No. 4,180,211) patents. On August 29, 1991, Koslow filed a response, arguing that the examiner had grossly over-simplified “the novel products produced by applicant’s process.” Koslow argued the application discloses other characteristics not disclosed in the cited prior art references which are “the result of following applicant’s process of applying a specified pressure to the heated mixture, followed by rapid cooling.” On January 10, 1992, the PTO issued a final rejection of all pending claims as 'unpatentable again over the admitted prior art in view of the Stastny, Stayner, Shannon ’341 and Olcott et al. patents. According to'the examiner, the instant claims call for the concept of a plurality of primary particles and a matrix binder, the particles having a higher softening temperature than the binder. This would, in any ease, be basically simple and obvious so as not to destroy the particles as particles. Apparently this concept is old in the admitted prior art.... On February 27, 1992, Koslow submitted an amendment and request for reconsideration. Koslow canceled claims 88 and 94, and amended claims 87 and 183. Claim 87 appears as the ’722 patent’s claim 1 and claim 183 appears as the ’722 patent’s claim 77. Koslow amended claim 87 as follows: A porous composite [composition of matter] article comprising: a plurality of primary particles having relatively high softening temperatures, said particles having a diameter between about 0.1 and about 3000 micrometers; and a matrix of from 3 to 30% by weight of a substantially continuous thermoplastic binder phase [material] supporting and enmeshing said primary articles, said continuous binder phase being formed from binder particles having a diameter of between about 0.1 to about 150 micrometers, said [a] binder particles [material] being substantially incapable of fibrillation under normal conditions into micro fibers of less than 10 micrometers diameter at room temperature and having a softening temperature substantially below the softening temperature of the primary particles, and where such primary particles are consolidated into a [high density and] uniform matrix with the' continuous binder material present as a dilute material within the pores between the primary particles, the remainder of the pore volume comprising a continuous [or discontinuous] volume of voids and said binder material being forced into macro-pores and exterior voids of individual primary particles having such macro-pores and exterior voids. Koslow amended claim 183 as follows: A porous composite article [composition of matter] comprising: a plurality of primary particles having relatively high softening temperatures, said particles having a diameter between 0.1 and 3000 micrometers; and a matrix of from 3 to 30% by weight of a thermoplastic binder material having a ■ softening temperature substantially below the softening temperature of the primary particles, said matrix being formed from binder particles having a diameter of from about 0.1 to about 150 micrometers; wherein the primary particles are consolidated into a [high density] uniform matrix with melted and resolidified binder matrix present as forced point-bonds between the primary particles, wherein binder material is forced into macro-pores and exterior voids of individual primary particles to form physical connections between particles having such macropores and exterior voids. In distinguishing the application from the prior art, Koslow argued his “invention employs a novel process ... to produce novel porous composite articles which are characterized by a three-phase structure, primary particles, binder and gas.... ” On March 23, 1992, the PTO issued a notice of allowability, allowing the ’722 patent application’s claims 87, 89-93, 95-164, 183-191, 206, and 208. The ’722 patent issued on September 15, 1992. Koslow assigned the patent to Koslow Technologies Corporation. b. Terms in Dispute KXI claims Culligan has infringed claims 33 and 81 of the ’722 patent. Claim 33 is dependent on claim 1, and claim 81 is dependent on claim 77. These claims read as follows, with disputed terms and phrases in italics. 1. A porous composite article comprising: a plurality of primary particles having relatively high softening temperatures, said particles having a diameter between about 0.1 and about 3000 micrometers; and a matrix from 8 to 80% by weight of a substantially continuous thermoplastic binder phase supporting and enmeshing said primary particles, said continuous binder phase being formed from binder particles having a diameter of between about 0.1 to about 150 micrometers, said binder particles being substantially incapable of fibrillation under normal conditions into micro fibers of less than 10 micrometers diameter at room temperature and having a softening temperature substantially below the softening temperature of the primary particles, and where such primary particles are consolidated into a uniform matrix with the continuous binder material present as a dilute material unthin the pores between the primary particles, the remainder of the pore volume comprising a continuous volume of voids and said binder material being forced into macropores and exterior voids of individual primary particles having such macropores and exterior voids. 33. The composition of claim 1 wherein the binder material forming the matrix is a crystalline thermoplastic polymer selected from the group consisting of polyolefins, po-lyvinyls, polyvinyl esters, polyvinyl ethers, polyvinyl sulfates, polyvinyl phosphates, polyvinyl amines, po-lyxidiazoles, polytriazols, polycar-bodiimides, ethylene-vinyl acetate copolymers, polysulfones, polycar-bonates, polyethers, polyarylene oxides, and polyesters. 77. A porous composite article comprising: a plurality of primary particles having relatively high softening temperatures, said particles having a diameter between 0.1 and 3000 micrometers; and a matrix of from 3 to 30% by weight of a thermoplastic binder material having a softening temperature substantially below the softening temperature of the primary particles, said matrix being formed from binder particles having a diameter of from about 0.1 to about 150 micrometers; wherein the primary particles are consolidated into a uniform matrix with melted and resolidified binder matrix present as forced point-bonds between the primary particles, wherein binder material is forced into macropores and exterior voids of individual primary particles to form physical connections between particles having such macro-pores and exterior voids. 81. The composition of claim 77 wherein the primary particles are granular or powdered carbon. 3. The ’092 Patent The ’092 patent is entitled “Method and Apparatus for the Continuous Extrusion of Solid Articles.” It discloses a method and apparatus for making composite solid articles from feed mixtures comprised of a “substantially uniform mixture” of primary particles and binder particles which have a softening temperature below that of the primary particles. The feed mixture is a solid material in powdered form. Claim 1 of the ’092 patent discloses an extruder apparatus capable of extruding solid composite materials. This extruder consists of an extruder barrel connected to an extrusion die. The feed mixture is fed into one end of the extruder barrel. The extruder barrel houses an extrusion screw. As it turns, the screw forces the mixture forward into the extrusion die. The material is heated in the extrusion die, and then pushed through the die and formed into a shape. Claim 1 teaches that back-pressure is applied to the material as the material is pushed out of the die, and that this back-pressure is from a source external to the die. The material is then cooled until it forms a solid. Claims 2-11 are dependent claims, offering modifications of the method described in claim 1. a. Prosecution History On April 8, 1991, Koslow filed the application which led to the ’092 patent, known as Application Serial No. 07/682,182. As originally filed, the application included the claims that would make up the ’948 patent as well as the claims of the ’092 patent. On August 23, 1991, the PTO issued an office action rejecting all of the application’s twenty-two claims as unpatentable over the prior art of the Breton et al. patent (U.S.Patent No. 4,194,090). The Breton et al. patent discloses a process and an article of manufacture composed of polytetrafluroethylene and another particulate material. The PTO also rejected claims 1-22 for double patenting, finding these claims disclose the same invention as the ’311 patent’s claims 1-118. On September 20, 1991, Koslow amended his application and requested reconsideration. Koslow argued there was no double-patenting with respect to claims 13-16, because these claims are directed to an extrusion apparatus, and the ’311 patent’s claims are method claims, directed to forming composite material. Also, Koslow argued there was no double-patenting with respect to claims 1-12 because these claims are directed to a method of extruding a solid composite material not disclosed by the ’311 patent. According to Koslow, the ’092 patent’s extrusion method claims teach “(1) extruding a substantially uniform mixture (of the binder particles and primary material particles) into a die of substantially uniform cross-section; and (2) applying sufficient back pressure, from without the die, to the heated mixture.” Koslow argued these process steps are different from the ’311 patent’s process steps for forming extruded composite material. Koslow distinguished the Breton et al. patent by arguing that it does not refer to articles made by extrusion. Moreover, Koslow argued, the Breton process involves “cold compression ... utilizing pressures of 50,000 to 200,000 psi or high-erf.]” He argued that the invention in the application does not use cold compression or pressures this high. On December 11, 1991, the PTO issued a final action, allowing claims 1-12, and rejecting claims 13-22. On February 25, 1992, Koslow requested reconsideration of claims 13-22. On June 11, 1992, the PTO issued an advisory office action, again rejecting claims 13-22. On May 26, 1992, Koslow filed a supplemental amendment, requesting the PTO cancel claims 13-22 without prejudice. Koslow also amended claim 1 by inserting in line 15 the term “from an extruder barrel” after the word “mixture” and inserting in line 10 the phrase “which cross-section is not substantially smaller than the cross-section of the inside diameter of the extruder barrel” after “cross-sectionf.]” The ’092 patent issued on February 23, 1993. Koslow assigned the patent to Koslow Technologies Corporation. b. Terms in Dispute KXI claims Culligan has infringed claims 2 and 3 of the ’092 patent. Both claims 2 and 3 are dependent on claim 1. These claims read as follows, with disputed terms and phrases in italics. 1.A method of extruding a solid composite material which comprises: providing a quantity of first particles of a binder material, said first particles having diameters between about 0.1 and about 250 micrometers; providing a quantity of second particles of a primary material having a softening temperature substantially greater than the softening temperature of said binder material, said second particles having diameters between about 0.1 and about 3,000 micrometers; combining the first and second quantities of particles in a substantially uniform mixture wherein said binder material is present in a amount of at least about 3% by weight of the mixture; extruding said substantially uniform mixture from an extruder barrel into a die of substantially uniform cross-section which cross-section is not substantially smaller than the cross-section of the inside diameter of the ex-truder barrel; heating said substantially uniform mixture unthin said die to a temperature substantially above the softening temperature of said binder material but to a temperature less than the softening temperature of said primary material; applying sufficient back pressure, from without said die, to the heated mixture within said die to convert said heater mixture into a substantially homogeneous composite material; rapidly cooling said composite material to below the softening point of the binder material to produce the composite material; and extruding said composite material from said die as an extruded solid composite material product. 2. The method of claim 1 wherein the back pressure is applied to the extruded solid composite material product. 3. The method of claim 1 wherein the back pressure applied to the heated mixture in the die cavity is a pressure of between about 5 and about 400 psi. 4.The ’9J/.8 Patent The ’948 patent is entitled “Apparatus for the Continuous Extrusion of Solid Articles.” It was originally filed as a eontinuation-in-part application of the ’092 patent, and has the same specification. The patent claims an apparatus for extruding a solid composite porous article from a solid, powdered feed mixture composed of a “substantially uniform mixture” of particulate primary material and particulate binder material. The ’948 patent discloses an extruder apparatus. The patent specification includes figures 1-4, which are diagrams of an example of an extruder. The same figures are included in the ’092 patent specification. Figures 1 and 3 from the ’948 patent are reproduced below. This example extruder depicted in figures 1 and 3 has a feed bin (10) which contains the food mixture. The example extruder has an extruder barrel (12) housing an extrusion screw (14), which is comprised of a solid core (16) surrounded by helical flights (18). The particulate material is fed from the feed bin (10) into the extruder barrel (12). It is then pushed through the barrel (12) by the extrusion screw (14) and into a die assembly (24) which contains a die (26). The diagram depicts heating elements (28) at the input end of the die. Claim 1 discloses “an elongated, smooth extrusion die” attached to the extruder barrel’s feed outlet. The die has an inlet end attached to the feed outlet, and an extrusion end. The die must have “a substantially uniform cross-section, which cross section is not substantially smaller than the cross-section of an inside diameter of the extruder barrel.” Claim 1 discloses the apparatus must have “means for forcibly injecting” the mixture into the inlet end of the die cavity, as well as means in the die “adjacent to the inlet end” for heating the mixture “to a temperature substantially above the softening temperature” of the binder material, but léss than the primary material’s softening temperature. Claim 1 discloses there must be means external to the die cavity for applying pressure to the heated mixture “within the die cavity during extrusion[,]” and means for “rapidly cooling” the “mixture within the die cavity” to below the binder material’s softening temperature. Claims 2-6 are dependent claims, disclosing modifications to the mechanism disclosed in claim 1. Claim 2 discloses using a back-pressure force as the means for applying pressure to the extruded material. a. Prosecution History On October 17, 1991, Koslow filed the application which led to the ’948 patent as a continuation-in-part application of the co-pending application which led to the ’092 patent. It was known as Application Serial No. 07/778,266. Claims 1-8 and 12-19 of the application were the same as claims 1-8 and 11-18, respectively, of the application which led to the ’092 patent. On April 28, 1992, the PTO issued an office action requiring Koslow to restrict the application to one of four inventions embodied in the claims: claims 1-13, drawn to a method; claims 14-17, drawn to an apparatus; claims 18-24, drawn to an article, or claims 25-31, drawn to a composition. On May 7, 1992, Koslow elected to prosecute apparatus claims 14-17. On July 6, 1992, the PTO issued an office action, rejecting claims 14-17 as un-patentable over the Leitl patent in view of the Zavasnik patent. The examiner described the Leitl patent’s invention as follows: Leitl discloses an extrusion apparatus comprising an extruder barrel (3) housing an extrusion screw (2), an extrusion die (41b) at the outlet end of the extrusion barrel and having a uniform cross section larger than that of the barrel, said screw forcibly injecting the material into the inlet end of the die cavity and means (43) external of the die cavity for applying a back pressuring force on the extruding material. The numbers in parentheses correspond to the reference numbers on the figures accompanying the patent. The PTO described the Zavasnik patent’s invention as follows: Zavasnik discloses an extrusion apparatus similar to that of Leitl, wherein the die is heated and cooled such that the extrudate is prevented from prematurely freezing in the die, but is allowed to solidify at the outlet end of the enlarging cross section die, said extrudate undergoing back pressurization by means of a movable resilient annular member (18). The examiner found that both the Leitl and the Zavasnik patents disclose extrud-ers with back-pressuring means external to the dies. The examiner found the ’948 patent application obvious in light of the prior art of the Leitl and Zavasnik patents. According to the examiner, it would have been obvious to one skilled in the art at the time of the invention to modify the extruder disclosed in the Leitl patent to include heating and cooling means within the die, as the ’948 patent’s inventors did, so that the extruder could be used with a wider range of materials. On October 2, 1992, Koslow amended his application and requested reconsideration. Koslow canceled claims 1-13 and amended claim 14 as follows: 14. Apparatus [for] capable of the continuous extrusion manufacture of a solid composite [material] article from a substantially uniform particulate mixture of a quantity of particles of a binder material and a quantity of particles of a primary material, said primary material having a substantially higher softening temperature than [the] a softening temperature of said binder material, which comprises: an extruder barrel housing an extrusion screw, said extruder barrel having a feed inlet and feed outlet; an extrusion die attached to the feed outlet of the extruder barrel, said die defining a cavity having an inlet end, an extrusion end, and a substantially uniform cross-section, which cross-section is not substantially smaller than the cross-section of an inside diameter of the extruder barrel; means for forcibly injecting said particulate mixture into the inlet end of said die cavity; means for heating said particulate mixture within said die cavity to a temperature substantially above the softening temperature of said binder material but less than the softening temperature of said primary material; means external of said die cavity for providing pressure of between about 5 to about 400 psi to said heated particulate mixture within the die cavity during extrusion of the particulate mixture [to a pressure between about 5 to about 400 psi]; and means for rapidly cooling said particulate mixture within the die cavity to below the softening [point] temperature of the binder material to form a monolithic solid composite material whereby said solid composite material is extruded from said die cavity as a solid composite article. Koslow also added new claims 32 and 33. Koslow argued that the prior art references cited by the examiner disclose ex-truders designed to extrude liquid or fluidized feed compositions. Koslow distinguished the application which led to the ’948 patent from the Leitl and Zavas-nik patents by arguing the application discloses an extruder designed to extrude solid particulate feed mixtures. According to Koslow, the extruder die disclosed by the Leitl patent is tapered, meaning “progressively reduced. in diameter” and as such, is “totally unsuitable and unable to extrude solid párticulate material into a solid composite article.” Koslow distinguished the Zavasnik patent based upon design differences. According to Koslow, the application which led to the ’948 patent discloses cooling the mixture of heated primary material and binder material mixture " in the extrusion die itself. Koslow argued “deformation, consolidation, and solidification of the particulate material” all occur in the die cavity. In contrast, Koslow argued, “the ex-truder disclosed in the Zavasnik patent includes a. thermal barrier between the cooling liquid and the extrusion die[,]” and, as a result, the extruded material is only cooled “after leaving the extrusion forming die.” . , Koslow also argued the extruder disclosed in the Zavasnik patent employs a different structure from the extruder described in the application which led to the ’948 patent. According to Koslow, the forming die taught in the Zavasnik patent “must be of increasing cross-sectional area” whereas the extrusion die disclosed in the application has a “substantially uniform cross-section.” On December 30,1992, the PTO issued a final rejection, rejecting claims 14-17, 32, and 33 as being unpatentable over the Leitl patent taken together with the Za-vasnik patent. The examiner found it would have been obvious to one skilled in the art at the time of the invention to modify the die of .the extruder disclosed in the Leitl patent to include both heating and cooling means within the die, thus allowing the extruder to be used with a wide range of materials. The examiner rejected Koslow’s contention that the Zavasnik patent does not disclose a die cavity in which the extrusion material is both heated and cooled. Referring to the extruder disclosed in the Za-vasnik patent, the examiner found “the extrusion die (26) is clearly heated at its inlet end by its close proximity to the heated extruder barrel (11), and secondly, the die is cooled at its extrusion end by cooling water within the passage (33).” The numbers in parentheses correspond to the reference numbers on the figures accompanying the patent. Figures 1 and 3 are reproduced below. On March 10, 1993, Koslow amended the ’948 patent application and requested reconsideration. Koslow amended claim 14 as follows: 14. Apparatus capable of the continuous extrusion manufacture of a solid composite porous article from a substantially uniform particulate mixture of a quantity of particles of a binder material and a quantity of particles of a primary material, said primary material having a substantially higher softening temperature than a softening temperature of said binder material, which comprises: an extruder barrel housing an extrusion screw, said extruder barrel having a feed inlet and feed outlet; an elongated, smooth extrusion die attached to the feed outlet of the ex-truder barrel, said die defining a cavity having an inlet end, an extrusion end, and a substantially uniform cross-section, which cross-section is not substantially smaller than the cross-section of an inside diameter of the extruder barrel; means for forcibly injecting said particulate mixture into the inlet end of said die cavity; means in said die adjacent to the inlet end thereof for heating said particulate mixture within said die cavity to a temperature substantially above the softening temperature of said binder material but less than the softening temperature of said primary material; means external of said die cavity for continuously providing controlled pressure of between about 5 to about 400 psi to said heated particulate mixture within the die cavity during extrusion of the particulate mixture; and means in said die adjacent to the extrusion end thereof for rapidly cooling said particulate mixture within the die cavity to below the softening temperature of the binder material to form a monolithic solid composite material whereby said [solid composite material] substantially uniform particulate mixture is deformed, consolidated into a desired form and solidified in the extrusion die and is extruded from said die cavity as a solid composite porous article. Koslow repeated his arguments that the Leitl and Zavasnik patents disclose extrud-ers for liquid or fluidized compositions which could not extrude solid particulate mixtures. With respect to the Leitl patent, Koslow argued that the tapered nozzle disclosed is incapable of “extruding (deforming and shaping)” a solid particulate mixture. Furthermore, Koslow argued, the Leitl patent discloses no means for heating or cooling the material in the extrusion die cavity. Koslow argued that the extruder disclosed in the Zavasnik patent has a structure different from the extruder disclosed in the application, and is not capable of extruding solid particulate feed mixtures. Koslow pointed out that the patent disclosed cooling the extruded material after it leaves the “extrusion forming die.” Kos-low argued that by contrast, in the present invention the extruded material is cooled in the extrusion die. Koslow pointed out that the extruder disclosed in the Zavasnik patent contains a thermal barrier between the “cooling liquid and the extrusion die,” and that therefore, solidification of the molten thermoplastic does not occur in the extrusion die. Koslow argued that, in contrast, the application discloses a method for consolidating and solidifying particulate material in the die cavity itself. Koslow pointed out that the Zavasnik patent discloses heating the particulate material in the “extruder barrel (11)” not in the “forming die (26)” and discloses “the extruder is distinct and apart from [the] forming die.” Koslow argued “[i]n contrast, the non-heated ex-truder barrel in the present invention is merely a means for conveying the particulate mixture into the extrusion die.” Koslow argued that the examiner’s finding that the extruder disclosed in the Za-vasnik patent has heating and cooling mechanisms in the same die is clearly erroneous. In support, Koslow argued there is< a “thermal barrier (25)” separating the “extrusion die (11)” from the “forming die (26),” and that there are not both heating and cooling means within the -cavity of either die. According to Koslow, “the mere fact that forming die (26) is in ‘close proximity to’ extrusion die (11), as contended by the PTO would not permit heating necessary to occur within the forming die. (26), particularly in view of the thermal barrier (25) between the two dies.” Koslow also pointed out design differences between the ’948 patent invention and the extruder disclosed in the Zavasnik patent. He argued that while the forming-die “(26)” disclosed by Zavasnik must be of “increasing cross-sectional area,” the extrusion die disclosed in the application has a “substantially uniform cross-section.” On March 11, 1998, the PTO allowed claims 14-17, 32 and 38, and renumbered them as claims 1-6, respectively. The PTO issued the acceptance contingent upon the cancellation of claims 18-31. The ’948 patent issued on October 5, 1993. Koslow assigned the patent to Koslow Technologies Corporation. b. Terms in Dispute KXI claims Culligan has infringed claim 2 of the ’948 patent. Claim 2 is dependent upon claim 1. These claims read as follows, with disputed terms and phrases in italics. 1. Apparatus capable of the continuous extrusion manufacture of a solid composite porous article from a substantially uniform particulate mixture of a quantity of particles of a binder material and a quantity of particles of a primary material, said primary material having a substantially higher softening temperature than a softening temperature of said binder material, which comprises: an extruder barrel housing an extrusion screw, said extruder barrel having a feed inlet and feed outlet; an elongated smooth extrusion die attached to the feed otitlet of the ex- truder barrel, said die defining a cavity having an inlet end, an extrusion end, and a substantially uniform cross-section, which cross-section is not substantially smaller than the cross-section of an inside diameter of the extruder barrel; means for forcibly injecting said particulate mixture into the inlet end of said die cavity; means in said die adjacent to the inlet end thereof for heating said particulate mixture within said die cavity to a temperature substantially above the softening temperature of said binder material but less than the softening temperature of said primary material; means external of said die cavity for continuously providing controlled pressure of between about 5 to about jOO psi to said heated particulate mixture within the die cavity during extrusion of the particulate mixture; and means in said die adjacent the extrusion end thereof for rapidly cooling said particulate mixture within the die cavity to below the softening temperature of the binder material to form a monolithic solid composite material whereby said substantially uniform particulate mixture is deformed, consolidated into a desired form and solidified in the extrusion die and is extruded from said die cavity as a solid composite porous article. 2. The apparatus of claim 1 wherein the means for pressurizing comprises means for applying a back-pressuring force to the extruding solid composite material. II. DISCUSSION A. What is the Legal Standard Under Which a Court Should Construe the Claims of a Patent? Claim construction is a matter for the court. Markman v. Westview Instruments, Inc., 52 F.3d 967, 979 (Fed.Cir.1995) (en banc), aff'd, 517 U.S. 370, 116 S.Ct. 1384, 134 L.Ed.2d 577 (1996). Claims are construed from the vantage point of a person of ordinary skill in the art at the time of the invention. Id. at 986. In construing a claim, a court looks first to the intrinsic evidence of record, namely, the language of the claim, the specification, and the prosecution history. Insituform Tech. Inc. v. Cat Contracting, Inc., 99 F.3d 1098, 1105 (Fed.Cir.1996), cert. denied, 520 U.S. 1198, 117 S.Ct. 1555, 137 L.Ed.2d 703 (1997). The claim language itself defines the scope of the claim, and “a construing court does not accord the specification, prosecution history, and other relevant evidence the same weight as the claims themselves, but consults these sources to give the necessary context to the claim language.” Eastman Kodak Co. v. Goodyear Tire & Rubber Co., 114 F.3d 1547, 1552 (Fed.Cir.1997). Although extrinsic evidence such as expert testimony may be considered if needed to assist the court in understanding the technology at issue or in determining the meaning or scope of technical terms in a claim, Hoechst Celanese Corp. v. BP Chems. Ltd., 78 F.3d 1575, 1579 (Fed.Cir.), cert. denied, 519 U.S. 911, 117 S.Ct. 275, 136 L.Ed.2d 198 (1996), reliance on any extrinsic evidence is improper where the public record, i.e., the claims, specification, and file history, unambiguously defines the scope of the claims. Vitronics Corp. v. Conceptronic, Inc., 90 F.3d 1576, 1583 (Fed.Cir.1996). While the Court of Appeals for the Federal Circuit has held that claims should be read in view of the specification, see, e.g., id. at 1582, the court has repeatedly cautioned against limiting the scope of a claim to the preferred embodiment or specific examples disclosed in the specification. See, e.g., Ekchian v. Home Depot, Inc., 104 F.3d 1299, 1303 (Fed.Cir.1997); see also Intervet America, Inc. v. Kee-Vet Laboratories, Inc., 887 F.2d 1050, 1053 (Fed.Cir.1989) (“[Limitations appearing in the specification will not be read into claims, and ... interpreting what is meant by a word in a claim ‘is not to be confused with adding an extraneous limitation appearing in the specification which is improper.’ ”) (citations omitted). There is presumed to be “a difference in meaning and scope when different words or phrases are used in separate claims.” United States v. Telectronics, Inc., 857 F.2d 778, 783 (Fed.Cir.1988), cert. denied, 490 U.S. 1046, 109 S.Ct. 1954, 104 L.Ed.2d 423 (1989). Under the doctrine of “claim differentiation,” a presumption exists against construing claims as so similar as to “make a claim superfluous.” Id. Federal patent law permits claims in a patent to be written in “means-plus-function” language. 35 U.S.C. § 112(6). The statute provides that “[a]n element in a claim for a combination may be expressed as a means or step for performing a specified function without the recital of structure, material, or acts in support thereof.” The statute also provides that if a claim is written in a means-plus-function language, the court shall construe the claim to “cover the corresponding structure, material, or acts described in the specification and equivalents thereof.” Id. That is, the court will treat the terms “means” as a “generic reference [to] the corresponding structure disclosed in the specification.” Chiuminatta Concrete Concepts, Inc. v. Cardinal Indus., Inc., 145 F.3d 1303, 1308 (Fed.Cir.1998). If an element contains the word “means,” the court will presume the inventor used the term “to invoke the statutory mandates for means-plus-function clauses.” Sage Products, Inc. v. Devon Indus., Inc., 126 F.3d 1420, 1426 (Fed.Cir.1997) (citations omitted). However, that presumption is not conclusive. See id. A claim that uses the word “means,” but does not specify a corresponding function, will not invoke section 112. See, e.g., York Products, Inc. v. Central Tractor Farm & Family Center, 99 F.3d 1568, 1574 (Fed.Cir.1996) (finding that the word “means” in a claim does not invoke section 112, paragraph 6, because the claim “does not link the term ‘means’ to a function,” but instead recites structure). B. Disputed Terms and Phrases in the ’092 and ’918 Patents 1. What is the Proper Construction of the Phrase “substantially uniform mixture” in the ’092 patent and “substantially uniform particulate mixture” in the ’918 patent? Claim 1 of the ’092 patent contains the phrase “particles in a substantially uniform mixture” to describe the feed mixture composed of primary particles and binder particles. Claim 1 of the ’948 patent contains the phrase “substantially uniform particulate mixture” to describe the feed mixture composed of primary particles and binder particles. KXI contends the words should be given their ordinary meaning, and that these phrases refer to a largely— but not necessarily wholly — even distribution of particles. KXI contends there are no other mixing requirements and no special methods of mixing required. The test for proper mixing, according to KXI, is stated in the ’092 patent’s specification at column 8, lines 7-14 and the ’948 patent’s specification at column 8, lines 13-19: An experienced operator can also readily notice a reduction in the flow characteristics of the powder mixture that indicates the formation of the desired bonds between particles. Samples smeared on a black surface show no residual binder aggregates which would be indicated by the presence of small white streaks. Culligan argues that the specifications of the ’092 and ’948 patents define the terms “substantially uniform mixture” and “substantially uniform particulate mixture” in a special way. According to Culligan, “substantially uniform” is a limitation requiring the formation of stable attachments between the primary particles and binder particles. Culligan argues that the claim requires vigorous mixing until stable “pre-bonds” or “microaggregates” are formed between the primary particles and binder particles throughout the mixture. Culli-gan points to provisions of the specifications reading: Correct methods of mixing produce a material composed of microaggregates of primary particles and binder particles .... Poorly mixed materials, or use of binder or primary particles lacking the ability to form stable “prebonds” results in mixtures where binder and primary particles separate, or where primary particles of widely varying density or morphology separate because stable aggregates have not been formed. It is these stable aggregates, formed during mixing that allow this process to bond particles that cannot normally be maintained in a stable mixture. It appears that, as a rule, the process is generally not workable with poorly mixed materials or with materials in which the binder particles have not become attached to the primary particles during the mixing step. Culligan argues that here the ’092 and ’948 patents’ specifications tell a person knowledgeable in the art that they must mix the primary and binder particles in a certain way to practice the invention; so as to create stable “prebonds” or “microaggre-gates.” The Federal Circuit has held that “[t]he specification acts as a dictionary when it expressly defines terms used in the claims or when it defines terms by implication.” Vitronics Corp. v. Conceptronic, Inc., 90 F.3d 1576, 1582 (Fed.Cir.1996). Culligan argues that the specifications of the ’948 and ’092 patents expressly defines the phrase “substantially uniform.” KXI argues in response that it is only appropriate to give a term a special meaning where “the special definition of the term is clearly stated in the patent specification or file history.” Id. at 1582. The court agrees with KXI that the patentee did not give special meaning to the phrase “substantially uniform mixture” or “substantially uniform particulate mixture” in the ’092 and ’948 patent’s specifications The court construes the words “substantially uniform particulate mixture” and “substantially uniform mixture” according to their ordinary meaning. Accordingly, the court construes the phrases “substantially uniform mixture” and “substantially uniform particulate mixture” as meaning a largely — but not wholly- — even distribution of particles. 2. What is the Proper Construction of the Terms “barrel” and “die” in the ’092 and ’9U8 Patents? Claim 1 of the ’092 patent and claim 1 of the ’948 patent contain the terms “extruder barrel” and “die.” KXI and Culligan dispute where the “extruder barrel” ends and the “die” begins. KXI contends in both patents the “extruder barrel” and “die” are co-joined tubes, the “extruder barrel” the part that houses the extrusion screw, and the “die” the part that does not house the extrusion screw. Essentially, KXI’s position is that the die begins where the helical flights of the extrusion screw end. Culligan contends in both patents the “die” is a distinct structure from the “barrel.” Culligan contends the “die” is the structure that imparts shape and form to the feed mixture, and the “barrel” is the structure that houses the feed screw. In support of its construction, KXI cites column 3, lines 2-5, 19-20, and 35-42 of the ’092 patent, and column 3, lines 8-11, 25-26, and 41-48 of the ’948 patent. Here, the specifications state: The feed bin 10 feeds into an extruder barrel 12 which contains a feed screw 14. The feed screw 14 comprises a solid core 16 surrounded by conventional helical flights 18 .... The output end of the extruder barrel 12 feeds the input end of a die assembly 24.... KXI argues this passage defines the term “extruder barrel” as the structure containing the feed screw. In support of its construction, KXI cites a 1996 letter written by Joseph Jochman, Esq. to Plymouth. Jochman was Plymouth’s outside patent counsel at the time. The letter concerned changes Plymouth contemplated making to its carbon block extruder. Plymouth had contemplated removing flights from the extrusion screw. Jochman stated “the removal of a few downstream flights from. the extruder screw would result in a de facto extension in the upstream direction of the die cavity. In other words, the flightless part of the extruder barrel in effect becomes part of the die.” KXI argues the Jochman letter is extrinsic evidence, and should be considered to show that Culligan, through its patent counsel, agrees with KXI’s interpretation of the terms “extruder barrel” and “die.” In support of its construction, Culligan cites figures 1 and 8 accompanying the ’948 and ’092 patents, reproduced supra. These figures depict the extruder, including the extruder barrel, referred to as “12,” and the die, referred to as “26.” Culligan argues that the figures depict the extruder barrel (12), and the die (26), as two separate tubular structures. Culligan argues the separate structures are distinguished by the beginning and end of their respective tubes, and not by the ends of the extrusion screw’s flights. Culligan argues the position of the “input end of the die” as depicted in the figures accompanying the ’948 and ’092 patents is downstream from the expansion flange (56) and well downstream from the points where the flights on the feed screw terminate in the barrel (12). Culligan argues KXI’s definitions- of the terms “extruder barrel” and “die” are inconsistent with the ’948 and ’092 patents’ specifications. According to Culligan, the patents describe the extruder barrel and die as two structures, and do not define either one by the extrusion screw. Culli-gan cites the ’092 patent at column 3, line 2-5 and the ’948 patent at column 3, lines 8-11, which state that the extruder barrel “contains a feed screw 14” and that the feed screw “comprises a solid core (16) surrounded by conventional helical flights 18.” Culligan cites the ’092 patent’s specification at column 3, lines 25-26 and the ’948 patent’s specification at column 3, lines 31-32, which state that “[t]he input end of the die 26 is provided with heating elements 28[.]” Culligan argues that KXI’s interpretation of the meaning of the terms “extruder barrel” and “die” is not supported by the prosecution history. During the prosecution of the ’948 patent, the application was rejected over the prior art Zavasnik ex-truder, which does not contain a feed screw. Culligan points out that both the patentee and the examiner described the Zavasnik extruder as having an “extruder barrel (11)” and an' “extruder die (26).” Culligan argues this description “directly undercuts plaintiffs’ current logic, which would define the entire Zavasnik extruder as a ‘die’ because no portion of the extruder tubes contains a screw.” KXI responded that Culligan’s argument is based on a mistake. The Zavasnik patent includes figures that depict the invention, reproduced supra. The different parts of the invention are numbered in the figures. According to KXI, during prosecution of the ’948 patent, the examiner called the -structure denoted as “11” the “barrel,” and the patentee called it the “die.” KXI argued that throughout the prosecution, the patentee’s position was that “11” represented the “die.” According to KXI, however, the patentee accidentally adopted- the examiner’s terminology and called “11” the “barrel” “once, maybe twice” during the prosecution. Culligan argues that KXI defines the terms at issue contrary to the common meaning of “die.” As support for its position, Culligan cites the McGraw Hill Dictionary of Scientific and Technical terms which defines “die” as “[a] tool or mold used to impart shapes to, or to form impressions on, materials such as metals and ceramics.” McGraw-Hill Dictionary of Scientific and Technical Terms (4th ed.1989). The court finds there is no reason to define the term “extruder barrel” by where the extruder screw ends. The court gives the ordinary meaning to the terms. Accordingly, the court will construe “ex-truder barrel” and “die” as separate structures, the “extruder barrel” being the structure that houses the feed screw, and the “die” being the structure that imparts shape and form to the extrudate. 3. What is the Proper Construction of the Phrase “substantially uniform cross-section” in the ’092 and ’918 Patents? Claim 1 of the ’092 patent and claim 1 of the ’948 patent contain the phrase “a die of substantially uniform cross-section.” KXI contends the term “substantially” means “at least a 10% change in size.” KXI contends that as applied to the claim, the phrase “substantially uniform cross-section” means “the die should not change in diameter by more than 10%.” Culligan contends the phrase “substantially uniform cross-section” in the ’092 and ’948 patents means the internal cross-section of the die must vary less than about 0.010 inch along the length of the die. The contested phrase reads: “a substantially uniform cross-section, which cross-section is not substantially smaller than the cross-section of an inside diameter of the extruder barrel[.]” KXI contends the word “substantially” in the phrase “substantially uniform cross-section” should be defined consistently with the term “substantially” in the phrase “not substantially smaller than the cross-section of an inside diameter of the extruder barrel[J” KXI contends the phrase “not substantially smaller” is defined in the ’092 and ’948 patents’ specifications. The relevant parts of the specifications read: [T]here are distinct limitations on the ability to compress the material into a die smaller than the extruder. However, it has been discovered that, if that is to be attempted ... the ratio of the cross-sectional area of the die mouth to the extruder output are should not be less than approximately 0.9. KXI interprets this to mean that the cross-section of the die can be 10% smaller than the size of the cross-section of the barrel. KXI contends the term “substantially” as used both in “substantially smaller” and “substantially uniform cross-section” means up to a 10% change in size. Accordingly, KXI argues “a substantially uniform cross-section” means the die’s diameter should not change by 10%. KXI cites a recent federal district court e