239 F.3d 1225 (Fed. Cir. 2001)
WENGER MANUFACTURING, INC., Plaintiff-Appellant,v.COATING MACHINERY SYSTEMS, INC. and vECTOR CORPORATION, Defendants-Appellees.
00-1121
United States Court of Appeals for the Federal Circuit
DECIDED: February 6, 2001Rehearing Denied: March 2, 2001.

Appealed from: United  States  District  Court  for  the Southern, of DesDistrict of Iowa
Judge Robert W. Pratt [Copyrighted Material Omitted][Copyrighted Material Omitted]
John M. Collins, Hovey, Williams, Timmons & Collins, of Kansas City, Missouri, argued for plaintiff-appellant. With him on the brief were Scott R. Brown and Jill D. Singer.
Kirk M. Hartung, Zarley, McKee, Thomte, Voorhees & Sease, PLC, of Des Moines, Iowa, argued for defendants-appellees. With him on the brief was Jeffery D. Harty.
Before NEWMAN, LOURIE, and GAJARSA, Circuit Judges.
LOURIE, Circuit Judge.


1
Wenger Manufacturing, Inc. appeals from the decision of the United States  District Court for the Southern District of Iowa granting the motion of  Coating Machinery Systems, Inc. and Vector Corporation (collectively "CMS")  for summary judgment of noninfringement of U.S. Patent 5,100,683, and  denying Wenger's cross-motion for partial summary judgment of infringement.  Wenger Mfg., Inc. v. Coating Mach. Sys., Inc., No. 4-98-CV-90083 (S.D. Iowa  Nov. 16, 1999) (final judgment) ("Wenger III"). Because the district court  erred in granting summary judgment that the accused CMS machines do not  infringe claims 1 and 2 of the '683 patent, and abused its discretion in  denying summary judgment of infringement, we reverse and remand.

BACKGROUND

2
Wenger is the assignee of the '683 patent, which relates to an apparatus  for coating and drying food products such as breakfast cereals and snack  foods with sugar, salt, or other flavored coatings. The food products  generally require drying prior to packaging and storage in order to prevent  spoilage. '683 patent, col. 1, ll. 18-24. In the prior art, flavored  coatings were typically applied to the food product in a separate machine  located downstream from the product dryer. Id. at col. 1, ll. 30-32.  Because it was applied in slurry form, the flavored coating added moisture  to the food product and adversely affected the product by sealing in the  added moisture after the surface of the coating dried. Id. at col. 1, ll.  39-43.


3
The '683 patent is directed to a method and apparatus for combined product  coating and drying. The claimed apparatus includes "a combined dryer and  spray unit which includes an axially rotatable reel provided with a  perforate sidewall." Id. at col. 1, ll. 61-63. Inside the reel, at least  one spray nozzle deposits the coating in slurry form onto the product. Id.  at col. 1, ll. 63-66. The reel is surrounded by a housing that "includes a  heat exchanger for heating the air and a circulating fan for forcing air  through the perforations in the sidewall of the reel." Id. at col. 2, ll.  8-11. As the product passes through the rotating reel, air is circulated  through the reel to dry the product. Id. at col. 1, l. 67 to col. 2, l. 1;  Id. at col. 2, ll. 42-43. As a result, the product is coated and dried in a  single operation and in an apparatus that occupies a minimum amount of  floor space. Id. at col. 1, ll. 58-60.


4
The '683 patent contains eight claims, the first two of which are at issue.  During prosecution, all of the original claims were rejected on various  grounds. Paper No. 2 at 4. Claim 14, which later became claim 1, was  initially rejected as anticipated by U.S. Patent 3,167,035 ("the Benson  patent"), but was allowed by the examiner after an amendment. Paper No. 6  at 1. As amended, independent claim 1 reads as follows: 1.   An  apparatus  for  coating and drying a fooder No. 6 product comprising:


5
a dryer housing;


6
an elongated reel presenting a longitudinal axis and having an inlet, an outlet, and a sidewall defining an interior and presenting a plurality of perforations, said side wall being located substantially within said housing whereby said perforations are surrounded by said housing;


7
means for introducing the product into the interior of said reel through said inlet;


8
means for rotating said reel within said housing;


9
means for selectively inclining said reel with said inlet elevated relative to said outlet;


10
air circulating means associated with said dryer housing for circulating air through said reel, the air circulating means including means for drawing air from the interior of the reel into said housing in order to provide positive air flow through the apparatus; and


11
means defining a plurality of separate product coating zones longitudinally spaced along said reel, each of said zones including at least one spray nozzle directed toward said sidewall for pressurized spraying of a coating on the food product during passage of said food product from said inlet to said outlet.


12
'683 patent, col. 7, l. 23 to col. 8, l. 2 (emphasis added). Claim 2, which  depends from claim 1, reads as follows:


13
2.   An apparatus for coating  and  drying  a food2, whichproduct  as  set  forth  in claim 1 including structure2, whichassociated with said housing  defining a plenum therein2, whichfor   receiving  said  air  passing   through   saidumi2, whichperforations from the interior of said reel.


14
Id. at col. 8, ll. 3-7. In addition, claim 3, which depends from claim 2,  reads as follows:


15
3.   An  apparatus  for  coating and drying a foodfrom claim 2,product as set forth in claim 2  including  means  fordfrom claim 2,exhausting a first portion of said air received in saidplenum  and  recirculating a second portion of said airaim 2,back into the interior of said reel.


16
Id. at col. 8, ll. 8-12 (emphasis added).


17
Figure 4 of the patent illustrates an embodiment of the claimed apparatus  as follows: [Tabular or Graphical Material Omitted]


18
As illustrated in Figure 4, the combined product coating and drying  apparatus 10 has a rotatable reel 14 that is enclosed within a housing 12.  Id. at col. 3, ll. 20-22. The housing 12 includes a spray unit 24 for  depositing coating material such as sugar or salt slurry onto the food  product as it passes through the reel 14. Id. at col. 4, ll. 33-35. The  spray unit 24 includes individual nozzles 108 that maintain proper and  equal pressure during spraying. Id. at col. 4, ll. 38-43. Above the housing  12, there is an air circulation unit 22 that "provides for the circulation  of drying air across the reel 14 and through the product passing  therethrough." Id. at col. 4, ll. 48-51. An exhaust flue 120 allows  "moisture-laden" air to be removed from the apparatus 10, and an exhaust  fan 122 ensures "positive airflow" through the apparatus 10. Id. at col. 4,  ll. 55-58. As a result, "the drying air is channeled through apparatus 10  along routes defined by the housing 12 and the reel 14." Id. at col. 4, ll.  59-60.


19
Wenger filed suit against CMS, alleging that several of CMS's coating and  drying machines literally infringed claims 1 and 2 of the '683 patent.  Wenger Mfg., Inc. v. Coating Mach. Sys., Inc., No. 4-98-CV-90083 (S.D. Iowa  Mar. 31, 1999) ("Wenger I"). CMS moved for summary judgment of  noninfringement, and Wenger cross-moved for partial summary judgment of  literal infringement. Id. at 1. The district court denied CMS's motion and  granted Wenger's corresponding cross-motion after: (1) construing "air  circulating means" as a means-plus-function limitation, requiring  "structural features that allow air to be recirculated through the  apparatus;" (2) concluding that the "means defining a plurality of separate  product coating zones" is not a means-plus-function limitation, and  includes "reels with alternating perforate and imperforate sections as well  as fully perforate reels;" and (3) concluding that the accused machines  literally met both of the disputed claim limitations. Id. at 7, 10-11, 15-  16.


20
CMS subsequently filed a motion for reconsideration, which the district  court granted after concluding that the accused device did not have the  same or equivalent structure as the claimed "air circulating means" because  it lacked the ability to recirculate air. Wenger Mfg., Inc. v. Coating  Mach. Sys., Inc., No. 4-98-CV-90083 (S.D. Iowa Sept. 30, 1999) ("Wenger  II"). As a result, the court amended its previous order and on  reconsideration, granted CMS's motion for summary judgment. Id. at 11.


21
Wenger appeals from the district court's entry of judgment of  noninfringement in favor of CMS. Wenger III at 1. We have jurisdiction  pursuant to 28 U.S.C. § 1295(a)(1) (1994).

DISCUSSION
A.   Principles of Law

22
Summary judgment is appropriate "if the pleadings, depositions, answers to  interrogatories, and admissions on file, together with the affidavits, if  any, show that there is no genuine issue as to any material fact and that  the moving party is entitled to a judgment as a matter of law." Fed. R.  Civ. P. 56(c). "The evidence of the nonmovant is to be believed, and all  justifiable inferences are to be drawn in his favor." Anderson v. Liberty  Lobby, Inc., 477 U.S. 242, 255 (1986). We review a district court's grant  of a motion for summary judgment de novo. Ethicon Endo-Surgery, Inc. v.  United States Surgical Corp., 149 F.3d 1309, 1315, 47 USPQ2d 1272, 1275  (Fed. Cir. 1998). "In reviewing a denial of a motion for summary judgment,  we give considerable deference to the trial court, and will not disturb the  trial court's denial of summary judgment unless we find that the court has  indeed abused its discretion." Elekta Instrument S.A. v. O.U.R. Scientific  Int'l, Inc., 214 F.3d 1302, 1306, 54 USPQ2d 1910, 1912 (Fed. Cir. 2000).


23
When both parties move for summary judgment, the court must evaluate each  motion on its own merits, resolving all reasonable inferences against the  party whose motion is under consideration. McKay v. United States, 199 F.3d  1376, 1380 (Fed. Cir. 1999). "If there are no material facts in dispute  precluding summary judgment, our task is to determine whether the judgment  granted is correct as a matter of law." Elekta, 214 F.3d at 1306, 54 USPQ2d  at 1912.


24
A determination of infringement requires a two-step analysis. Gentry  Gallery, Inc. v. Berkline Corp., 134 F.3d 1473, 1476, 45 USPQ2d 1498, 1500  (Fed. Cir. 1998). "First, the claim must be properly construed to determine  its scope and meaning. Second, the claim as properly construed must be  compared to the accused device or process." Id. (quoting Carroll Touch,  Inc. v. Electro Mech. Sys., Inc., 15 F.3d 1573, 1576, 27 USPQ2d 1836, 1839  (Fed. Cir. 1993)). "Literal infringement requires that every limitation of  the patent claim be found in the accused device." Gen. Mills, Inc. v. Hunt-  Wesson, Inc., 103 F.3d 978, 981, 41 USPQ2d 1440, 1445 (Fed. Cir. 1997).


25
Claim construction is an issue of law, Markman v. Westview Instruments,  Inc., 52 F.3d 967, 970-71, 34 USPQ2d 1321, 1322 (Fed. Cir. 1995) (en banc),  aff'd, 517 U.S. 370 (1996), that we review de novo. Cybor Corp. v. FAS  Techs., Inc., 138 F.3d 1448, 1456, 46 USPQ2d 1169, 1172 (Fed. Cir. 1998)  (en banc). "Whether certain claim language invokes 35 U.S.C. § 112, ¶ 6 is  an exercise of claim construction and is therefore a question of law,  reviewable de novo by this court." Personalized Media v. Int'l Trade  Comm'n, 161 F.3d 696, 702, 48 USPQ2d 1880, 1886 (Fed. Cir. 1998).  Determination of infringement, whether literal or under the doctrine of  equivalents, is a question of fact. Bai v. L & L Wings, Inc., 160 F.3d  1350, 1353, 48 USPQ2d 1674, 1676 (Fed. Cir. 1998).

B. Claim Construction

26
Wenger argues that the district court erred in interpreting the "air  circulation means" limitation as requiring structure capable of  recirculating air. Wenger contends that, as a means-plus-function  limitation, the term "air circulation means" is limited to structure for  performing the recited function of circulating air, not recirculating air.  Wenger emphasizes the fact that the function of recirculation is found in  dependent claim 3, which specifically includes the additional limitation of  "means for exhausting . . . and recirculating." Wenger argues that  recirculation is an additional feature of the preferred embodiment that  should not be imported into the disputed claim limitation. Wenger further  argues that, during prosecution, claim 1 was distinguished over the Benson  patent based on the claimed housing structure, not on the ability to  recirculate air.


27
CMS responds that the claimed "air circulation means" requires a structure  that recirculates air through the reel. CMS asserts that the ordinary  meaning of the term "circulate" includes or implies recirculation. CMS  further asserts that the doctrine of claim differentiation is not a rigid  rule, and that the "air circulation means" limitation in claim 1 must be  interpreted in accordance with § 112, ¶ 6, without regard to the other  claims, including dependent claim 3. CMS notes that the specification  explains that the housing allows "recirculating air" to enter the reel, and  that the air circulating unit creates a "positive air flow," which causes  air to flow in a "substantially closed circuit" through the housing. CMS  contends that Wenger used the terms "circulating" and "recirculating"  synonymously during prosecution, and distinguished the Benson patent based  on its inability to recirculate air, not on its lack of a housing. CMS also  contends that the district court erred in concluding that the claimed  "means defining a plurality of separate product coating zones" includes  fully perforate reels.


28
In interpreting claims, a court "should look first to the intrinsic  evidence of record, i.e., the patent itself, including the claims, the  specification and, if in evidence, the prosecution history." Vitronics  Corp. v. Conceptronic, Inc., 90 F.3d 1576, 1582, 39 USPQ2d 1573, 1577 (Fed.  Cir. 1996). Absent an express intent to impart a novel meaning, "terms in a  claim are to be given their ordinary and accustomed meaning." Renishaw PLC  v. Marposs Societa' Per Azioni, 158 F.3d 1243, 1249, 48 USPQ2d 1117, 1121  (Fed. Cir. 1998); Carroll Touch, 15 F.3d at 1577, 27 USPQ2d at 1840 ("[T]he  words of a claim are generally given their ordinary and accustomed meaning,  unless it appears from the specification or the file history that they were  used differently by the inventor.").

1) Air Circulating Means

29
As an initial matter, we agree with the parties that the "air circulation  means" limitation should be construed as a means-plus-function limitation  under § 112, ¶ 6. In determining whether a claim limitation is a means-  plus-function limitation, "the use of the word `means' creates a  presumption that § 112, ¶ 6 applies." Personalized Media, 161 F.3d at 703,  48 USPQ2d at 1886. However, a limitation that uses the word "means" but  does not recite a function that corresponds to the means does not invoke  § 112, ¶ 6. Rodime PLC v. Seagate Tech., Inc., 174 F.3d 1294, 1302, 50  USPQ2d 1429, 1434 (Fed. Cir. 1999). Likewise, even when a limitation does  recite a function, if it also recites sufficiently definite structure for  performing that function, then § 112, ¶ 6 does not apply. Id. In this case,  the "air circulation means" limitation uses the word "means" and therefore  is presumed to invoke § 112, ¶ 6. Moreover, the claim language recites the  corresponding function of "circulating air through said reel," without  reciting any structure for performing that function. Accordingly, the  district court correctly concluded that the "air circulation means" falls  under § 112, ¶ 6.


30
However, we agree with Wenger that the district court erred in interpreting  the "air circulation means" limitation as requiring structure capable of  recirculating air. In construing a means-plus-function limitation, a court  must identify both the claimed function and the corresponding structure in  the written description for performing that function. Micro Chem., Inc. v.  Great Plains Chem. Co., 194 F.3d 1250, 1258, 52 USPQ2d 1258, 1263 (Fed.  Cir. 1999). Under § 112, ¶ 6, a court may not import functional limitations  that are not recited in the claim, or structural limitations from the  written description that are unnecessary to perform the claimed function.  Id. In this case, the district court correctly identified "circulating air"  as the recited function. Wenger II at 4 ("The function recited in the claim  and clearly associated with the means language in the claim is the function  of circulating air through the apparatus, not the recirculation of air  through the apparatus."). However, the court then concluded that "[t]he  structure corresponding to the function of circulating air through the  apparatus requires the ability to recirculate air." Id. By doing so, the  court improperly restricted the "air circulation means" limitation to  structure that was disclosed in the preferred embodiment, but was not  necessary to perform the recited function of circulating air.


31
Given its ordinary meaning, the term "circulate" denotes that the "air  circulating means" is capable of moving air in a circuit through the reel  and dryer housing. See, e.g., Webster's New World Dictionary 254 (3d ed.  1988) (defining "circulate" as "to move in a circle, circuit, or course and  return to the same point"). However, the term "circulate" neither connotes  nor requires that the "air circulation means" have structure capable of  "recirculating," i.e., circulating the air again after it has circulated  once before. See id. at 1116 (defining the prefix "re-" as "again, anew,  over again" and listing "recirculate" as a word). For example, in common  parlance, it is customary to speak of "circulating" something once (e.g.,  an inter-office memorandum), without "recirculating" it a second time. We  therefore do not agree with CMS that the ordinary meaning of the term  "circulate" necessarily includes or implies recirculation.


32
Moreover, while claim 1 recites the function of "circulating" air through  the reel, dependent claim 3 expressly recites the additional limitation of  "means for exhausting a first portion of said air received in said plenum  and recirculating a second portion of said air back into the interior of  said reel." '683 patent, col. 8, ll. 9-12 (emphasis added). Under the  doctrine of claim differentiation, each claim in a patent is presumptively  different in scope. Comark Communications, Inc. v. Harris Corp., 156 F.3d  1182, 1187, 48 USPQ2d 1001, 1005 (Fed. Cir. 1998). However, claim  differentiation is not a "hard and fast rule of construction," and cannot  be relied upon to "broaden claims beyond their correct scope." Kraft Foods,  Inc. v. Int'l Trading Co., 203 F.3d 1362, 1368, 53 USPQ2d 1814, 1818 (Fed.  Cir. 2000) (citations and quotation marks omitted). Although the judicially  created doctrine of claim differentiation cannot override the statutory  requirements of § 112, ¶ 6, Laitram Corp. v. Rexnord, Inc., 939 F.2d 1533,  1538, 19 USPQ2d 1367, 1371 (Fed. Cir. 1991), it does not necessarily follow  that means-plus-function limitations must be interpreted without regard to  other claims. Claim differentiation, while often argued to be controlling  when it does not apply, is clearly applicable when there is a dispute over  whether a limitation found in a dependent claim should be read into an  independent claim, and that limitation is the only meaningful difference  between the two claims.


33
Citing Laitram, CMS argues that independent claim 1 must be interpreted in  accordance with § 112, ¶ 6, without regard to dependent claim 3. In  Laitram, the disputed claim limitation was a "means for joining" a  plurality of link ends for a conveyor belt. Id. at 1535 n.3, 19 USPQ2d at  1369 n.3. The corresponding structure in the specification consisted of  link elements and cross members. Id. at 1536, 19 USPQ2d at 1370. This court  rejected the argument that the "means for joining" limitation could not  include a cross member because that limitation was explicitly recited in a  dependent claim. We explained that "[a] means-plus-function limitation is  not made open-ended by the presence of another claim specifically claiming  the disclosed structure which underlies the means clause or an equivalent  of that structure." Id. at 1538, 19 USPQ2d at 1371. We then held that "one  cannot escape [the] mandate [of § 112, ¶ 6] by merely adding a claim or  claims specifically reciting structure or structures." Id. Thus, Laitram  held that the stringencies of a means-plus-function limitation are not to  be avoided by the mere addition of a dependent claim that recites the  corresponding structure disclosed in the specification. However, Laitram  does not stand for the broader proposition suggested by CMS, viz., that a  means-plus-function limitation must be interpreted without regard to other  claims.


34
We agree with Wenger that the examination of other claims in a patent may  provide guidance and context for interpreting a disputed means-plus-  function limitation, especially if they recite additional functions.  Because claim 3 recites a separate and distinct function (i.e.,  "recirculating"), one that is not recited in claim 1, the doctrine of claim  differentiation indicates that these claims are presumptively different in  scope. Comark, 156 F.3d at 1187, 48 USPQ2d at 1005. The dependency of claim  3 on claim 1 strengthens this presumption. Compare Dow Chem. Co. v. United  States, 226 F.3d 1334, 11341-42, 56 USPQ2d 1014, 1019-20 (Fed. Cir. 2000)  (applying the doctrine of claim differentiation and concluding that an  independent claim should be given broader scope than a dependent claim to  avoid rendering the dependent claim redundant), and Karlin Tech. Inc. v.  Surgical Dynamics, Inc., 177 F.3d 968, 971-72, 50 USPQ2d 1465, 1468 (Fed.  Cir. 1999) (explaining that the doctrine of claim differentiation "normally  means that limitations stated in dependent claims are not to be read into  the independent claim from which they depend"), with Kraft, 203 F.3d at  1368, 53 USPQ2d at 1818 (holding that the presumption arising from the  doctrine of claim differentiation was overcome in a case involving two  separate independent claims). Accordingly, the doctrine of claim  differentiation supports the conclusion that the "air circulation means"  limitation in claim 1 should be limited to structure for performing the  recited function of circulating air, and should not be interpreted as  requiring structure capable of performing the additional function of  recirculation, which is expressly recited in dependent claim 3 and not  found in claim 1.


35
Our conclusion is consistent with the specification, which discloses the  function of "circulating" in the context of drawing air through the reel in  order to dry the food product, and discloses "recirculation" as a separate  function involving the return of a portion of the drying air back into the  reel. In the summary of the invention, for example, the specification  states that "[t]he reel is rotatable and permits the circulation of drying  air therethrough." '683 patent, col. 1, ll. 56-58 (emphasis added). The  specification further states that "[t]he product is presented as a tumbling  bed which is agitated as it passes through the reel with drying air  circulated therearound." Id. at col. 1, l. 67 to col. 2, l. 1 (emphasis  added). In the next paragraph, however, the specification then explains that "[i]n preferred forms," the housing is configured "to draw additional  air through the openings at each end of the reel whereby both fresh and  recirculating air is introduced into the reel." Id. at col. 2, ll. 4, 11-14  (emphasis added). Later, in describing the preferred embodiment, the  specification states that the circulating component 22 and exhaust fan 122  create "positive air flow," which causes the air to flow "in a  substantially closed circuit through the housing." Id. at col. 5, ll. 30-  33. Thus, in the preferred embodiment, after the air is drawn from the  interior of the reel into the housing, it may either be exhausted from the  housing or returned back to the reel for recirculation. By disclosing  recirculation as an additional feature of the preferred embodiment, the  specification thus further supports the conclusion that the "air  circulation means" should not be limited to structure capable of performing  the unrecited function of recirculation.


36
CMS argues that the prosecution history supports the conclusion that the  "air circulation means" in claim 1 should be limited to structure capable  of recirculating air.1 We disagree. Original claim 14, which  later became claim 1, was initially rejected as anticipated by the Benson  patent. Paper No. 2 at 4. In response to the examiner's rejection, the  applicant amended the claim as follows, with additions indicated by  underlining:


37
14. (Amended) An apparatus for coating and drying a food product comprising:


38
. . . .


39
air circulating means associated with said dryer housing for circulating air through said reel, the air circulating means including means for drawing air from the interior of the reel into said housing in order to provide positive air flow through the apparatus;


40
Paper No. 5 at 2. The applicant also added the following new claim, which  later became dependent claim 3:


41
25.  An apparatus  for  coating  and drying a food whichproduct as set forth in claim 24 including  a means for whichexhausting a first portion of said air received in saidplenum and recirculating a second portion  of  said airwhichback into the interior of said reel.


42
Id. at 3 (emphasis added). In the "remarks" section, the applicant stated  that the claimed apparatus resulted in numerous advantages, including the  ability to "ensure that air is drawn into the housing from the interior of  the reel in order that the air drawn from the reel may be recirculated  through the reel or exhausted from the housing." Id. at 6 (emphasis added).


43
It is evident from the prosecution history that claim 14 was amended to  specify that the "air circulating means" draws air from the interior of the  reel into the housing. As emphasized by Wenger, the applicant did not add a  "recirculation" limitation to that claim. Instead, the applicant added a  new claim, claim 25, which expressly recited the function of recirculation.  In view of these amendments, the applicant's statement that the claimed  apparatus is capable of recirculating air through the reel or exhausting it  from the housing indicates that the function of recirculation is an  optional feature that is made possible by the housing, but is not required  by claim 14.


44
While CMS argues that Wenger distinguished the prior art based on its inability to recirculate air, we agree with Wenger that the Benson patent  was distinguished based on its lack of a housing.2 According to  the applicant, because the Benson patent disclosed a machine that was  "essentially open" and mostly "exposed to atmosphere," nothing in the  Benson patent taught or suggested the use of an elongated reel "located  substantially within a housing such that the perforations provided in the  side wall of the reel are surrounded by the housing." Id. at 7. The  applicant explained that:


45
[B]ecause air is drawn from the interior of the reel into the housing, there is less of a likelihood that warm, dust-laden air within the reel will be exhausted from the ends of the reel or will be released through the perforations provided in the sidewall of the reel to atmosphere without first being directed through a housing and any other suitable exhaust treating devices deemed to be appropriate.


46
Id. at 6. Moreover, the applicant expressly stated that "there is nothing  taught by the Benson patent which would have suggested a construction as  claimed, wherein it is possible to circulate air through the reel and draw  air from the interior of the reel into a housing surrounding the reel." Id.  Thus, according to the applicant, the Benson patent did not disclose the  claimed housing structure, which enabled the air to be circulated through  the reel and exhausted in an appropriate manner.

2)Product Coating Zones

47
We next turn to CMS's contention that the district court erred in  concluding that the claimed "means defining a plurality of separate product  coating zones" includes fully perforate reels. CMS raises this issue as  another ground for affirming the district court's judgment of  noninfringement. CMS argues that § 112, ¶ 6 applies to the "product coating  zones" limitation because there is no structure recited for performing the  claimed function of "defining." CMS also argues that the only embodiment  disclosed in the specification has a reel with alternating perforate and  imperforate sections, and that the claimed "product coating zones" are  limited to imperforate sections. Wenger responds that § 112, ¶ 6 does not  apply to the "product coating zones" limitation because there is no  function that corresponds to the word "means." Wenger alternatively argues  that there is sufficiently definite structure recited for performing the  function of "defining." Wenger also asserts that the specification  discloses fully perforate reels, and that the "product coating zones"  limitation should not be limited to the preferred embodiment.


48
We conclude that the district court did not err in construing the "product  coating zones" limitation. The court concluded that the "product coating  zones" limitation was not subject to § 112, ¶ 6 because there is no  function recited that corresponds to the word "means." The court further  concluded that, even if there was a corresponding function, the claim  recited sufficiently definite structure to fall outside of § 112, ¶ 6.  Wenger I at 8-9.

Claim 1 reads in relevant part as follows:

49
1.   An  apparatus  for  coating and drying a food ¶ 6.product comprising:


50
. . . .


51
means defining a plurality of separate product coating zones longitudinally spaced along said reel, each of said zones including at least one spray nozzle directed toward said sidewall for pressurized spraying of a coating on the food product during passage of said food product from said inlet to said outlet.


52
'683 patent, col. 7, ll. 24-25; col. 7, l. 45 to col. 8, l. 2 (emphasis  added). Because the "product coating zones" limitation uses the word  "means," there is a presumption that § 112, ¶ 6 applies. Personalized  Media, 161 F.3d at 703, 48 USPQ2d at 1886. However, it is unclear whether  there is any function recited that corresponds to the word "means." See  York Prods., Inc. v. Cent. Tractor Farm & Family, 99 F.3d 1568, 1574, 40  USPQ2d 1619, 1624 (Fed. Cir. 1996) ("Without an identified function, the  term `means' in this claim cannot invoke 35 U.S.C. § 112, ¶ 6.").


53
CMS asserts that the function of "defining" is the function that  corresponds to the word "means." Even assuming that is correct, we agree  with Wenger that § 112, ¶ 6 does not apply because the claim recites  sufficiently definite structure for performing the function of "defining."  See Rodime, 174 F.3d at 1302, 50 USPQ2d at 1434 ("[E]ven if the claim  element specifies a function, if it also recites sufficient structure or  material for performing that function, § 112, ¶ 6 does not apply."). The  claim specifically recites structure including spray nozzles that are  directed toward the sidewall of the reel, which "define" (i.e., establish  the boundaries of) the separate product coating zones that are  longitudinally spaced along the reel. We therefore conclude that the  district court did not err in concluding that the "product coating zones"  limitation was not subject to § 112, ¶ 6.


54
CMS further argues that, even if § 112, ¶ 6 does not apply, the claimed  "product coating zones" do not include fully perforated reels, and should  be limited to imperforate reel sections. According to CMS, the only  embodiment disclosed in the specification is a reel with imperforate  sections separated by perforate sections, with spray nozzles for coating  the food product located in each of the imperforate sections. Based on this  embodiment, CMS argues that the claimed "product coating zones" requires a  reel with "spaced apart" imperforate sections wherein product coating takes  place. We disagree. Although claims must be read in light of the  specification of which they are a part, it is improper to read limitations  from the written description into a claim. Tate Access Floors, Inc. v.  Maxcess Techs., Inc., 222 F.3d 958, 966, 55 USPQ2d 1513, 1518 (Fed. Cir.  2000). While claim 1 expressly recites that the reel has "a plurality of  perforations," it does not require that the reel have imperforate sections,  nor does it limit the claimed "product coating zones" to such reel  sections. See '683 patent, col. 7, l. 24 to col. 8, l. 2 (emphasis added).  Likewise, the specification states that the claimed apparatus includes "an  axially rotatable reel provided with a perforate sidewall"; it does not  state that the reel must have imperforate sections, or that the "product  coating zones" must be limited to such sections. Id. at col. 1, ll. 61-63  (emphasis added). Moreover, as the district court correctly noted, the  references in the specification to imperforate sections and spraying zones  that correspond to those sections are not limiting, as they merely describe  the preferred embodiment. See Tate Access, 222 F.3d at 966, 55 USPQ2d at  1518 ("[A]lthough the specification may well indicate that certain  embodiments are preferred, particular embodiments appearing in the  specification will not be read into the claims when the claim language is  broader than such embodiments."). We therefore agree with Wenger that the  district court did not err in concluding that the "product coating zones"  limitation may be satisfied by fully perforate reels as well as reels with  alternating perforate and imperforate sections.

C. Infringement

55
Wenger argues that the district court erred in granting CMS's motion for  summary judgment of noninfringement and abused its discretion in denying  Wenger's corresponding cross-motion for partial summary judgment of  infringement. Wenger contends that there is no genuine issue of material  fact that the accused machines perform the function of circulating air  using the same structural components disclosed in the '683 patent. Wenger  further contends that the district court correctly found that there is no  genuine issue of material fact that the accused machines literally meet all  of the other limitations of claims 1 and 2.


56
CMS responds that the district court did not err in granting its motion for  summary judgment of noninfringement because prosecution history estoppel  precludes a finding of infringement by a machine that does not recirculate  air, and it is undisputed that the accused machines do not recirculate air.  CMS also contends that the district court did not abuse its discretion in  denying Wenger's corresponding cross-motion because there is a genuine  issue of material fact as to whether the accused machines have alternating  perforate and imperforate sections.


57
Literal infringement of a means-plus-function claim requires that the  accused device have structure for performing the identical function recited  in the claim. Odetics, Inc. v. Storage Tech. Corp., 185 F.3d 1259, 1267, 51  USPQ2d 1225, 1229 (Fed. Cir. 1999). In addition, the structure in the  accused device must be either identical or equivalent to the corresponding  structure in the specification. Id.


58
In light of our construction of the disputed claim limitations, we conclude  that the district court erred in granting CMS's motion for summary judgment  of noninfringement based on its construction of the "air circulating means"  limitation and the undisputed fact that the accused machines do not  recirculate air. Properly construed, the "air circulating means" limitation  encompasses all structure in the specification corresponding to the  function of circulating air, and any equivalents thereof. See '683 patent,  col. 4, ll. 51-52 (disclosing an "air circulation unit" that includes an  electric motor for driving a fan impeller, and that may be selected from  "SQA plug fans manufactured by Chicago Airfoil"). CMS does not challenge  the district court's finding that: "[t]he CMS machines clearly circulate  air, i.e. perform the identical function as that identified in the `air  circulation means' clause." Wenger II at 6. Nor does CMS dispute that the  accused machines circulate air using the same structure disclosed in the  '683 patent. In fact, CMS explicitly agrees with Wenger's description of  the structure of the accused machines. See Appellee's Br. at 5 ("The  construction of the CMS machines as set forth in the Wenger principal brief  at pages 16-20 is substantially accurate."). CMS instead relies on the fact  that the accused machines do not have any structure that permits air to be  recirculated. However, having previously determined that the "air  circulating means" does not require structure capable of recirculating air,  we conclude that this claim limitation is satisfied by the accused machine.


59
CMS further argues that prosecution history estoppel precludes a finding of  infringement by a machine that does not recirculate air. We disagree. This  court has previously stated that the doctrine of prosecution history  estoppel is "irrelevant" to the determination of literal claim scope.  Biodex Corp. v. Loredan Biomedical, Inc., 946 F.2d 850, 862, 20 USPQ2d  1252, 1262 (Fed. Cir. 1991). In Biodex we recognized a "clear line of  distinction" between using prosecution history to construe disputed claim  language, and applying the doctrine of prosecution history estoppel to  prevent a patentee from obtaining under the doctrine of equivalents  coverage of subject matter that was relinquished during prosecution. Id.  However, we subsequently explained that:[J]ust as prosecution history estoppel may act to estop an equivalence argument under the doctrine of equivalents, positions taken before the PTO may bar an inconsistent position on claim construction under § 112, ¶ 6. Clear assertions made in support of patentability thus may affect the range of equivalents under § 112, ¶ 6.


60
Cybor, 138 F.3d at 1457, 46 USPQ2d at 1169 (citations omitted). We further  stated that "the relevant inquiry is whether a competitor would reasonably  believe that the applicant had surrendered the relevant subject matter."  Id.


61
We agree with Wenger that no reasonable competitor skilled in the art could  conclude that the applicant surrendered coverage of machines that do not  recirculate air. As we stated earlier, the applicant distinguished the  Benson patent based on its lack of a housing, not on its inability to  recirculate air. Moreover, while CMS argues that means-plus-function  limitations should not be construed to cover structure that is identical to  the structure of prior art that was explicitly distinguished during  prosecution, it is undisputed that the accused machines have a housing, and  thus do not have structure that is identical to the structure disclosed in  the Benson patent. Accordingly, Wenger is not barred from arguing that the  "air circulating means" limitation is met by machines that do not  recirculate air.


62
CMS additionally argues that there is a genuine issue of material fact as  to whether the accused machines have alternating perforate and imperforate  sections. However, as properly construed by the district court, the  "product coating zones" encompass "both a fully perforated reel and a reel  with alternating perforate and imperforate sections." Wenger I at 14.  Because the claimed "product coating zones" are not limited to alternating  perforate and imperforate reel sections and CMS does not dispute that its  machines have perforated reels, we conclude that the "product coating  zones" limitation was satisfied by the accused machines.

CONCLUSION

63
Because there is no genuine issue of material fact that the "air  circulating means" and "product coating zones" limitations are met by the  accused machine, and because CMS's machines satisfy every other limitation  in claims 1 and 2,3 we conclude that no reasonable jury could  find that claims 1 and 2 are not infringed. We therefore reverse the  judgment of noninfringement, order entry of judgment of infringement, and  remand for appropriate further proceedings.4


64
REVERSED and REMANDED.



Notes:


1
 In  support   of   its   prosecution  historyd arguments,  CMS  relies  heavily  on an unsigned draft amendment,historyd which  was  never entered into the file  wrapper.   The  districthistoryd court properly  refused to consider that draft amendment.  Wengertoryd I at 6 n.3; Manual  of  Patent  Examining Procedure §§ 714.19(E), 714.21  (7th  ed.  rev.  1 2000) (indicating  that  an  unsignedtct; 714.19(E), amendment  is ordinarily denied  entry  and  that  inadvertentlydct; 714.19(E), entered amendments have no legal effect).


2
 While  CMS argues that the housing alone does.19(E), not  distinguish claim 1 over the prior  art,  and  that  absentlne does.19(E), recirculation,  claim 1 would have been obvious in view of Frenchne does.19(E), patent 2,502,466, we decline to consider this reference as it was not in evidence before the district court, and is not part of the record on appeal.


3
 See  Wenger  I  at  15-16  (finding  that theaccused  machines literally met the other limitations of claims 16  (finding  that the and 2).


4
 In  light  of  our  decision,  we  considerinding  that the Wenger's pending motion to strike material not in the record from the appendix to be moot.


