On summary judgment, the United States District Court for the District of Kansas ruled that Kinetic Concepts, Inc. and KCI Therapeutic Services, Inc. (collectively, Kinetic) did not infringe KCJ Corporation’s (KCJ’s) U.S. Patent No. 4,631,767 (’767 patent).
See KCJ Corp. v. Kinetic Concepts, Inc.,
I.
KCJ is the assignee of thе ’767 patent entitled “Air Flotation Mattress.” The patent claims therapeutic mattresses for preventing bedsores. These mattresses, according to the patent, “evenly distrib-utee ] the weight of the body without the necessity of internal spines or other patient-contacting solid supports ... [and] permit airflow to all areas of the skin to absorb moisture and prevent heat accumulation.” ’767 patent, col. 2,11. 31-35. Claim 1, the only indepеndent claim, recites (with bracketed notations added for ease of reference):
1. An air flotation, ventilated mattress apparatus comprising:
[ (a) ] means defining a lower, continuous, inflatable chamfer having an air-permeable, flexible upper wall portion,
[ (b) ] said upper wall portion being constructed for substantially uniform airflow therethrough over substantially the entire plan surface area of said upper wall portion;
[ (c) ] air-permeable secondary wall means above said chamber upper wall portion and operably coupled with said chamber-defining means,
[ (d) ] said secondary wall means being constructed for substantially uniform passage of air therethrough over substantially the entire plan surface area of said secondary wall means,
[ (e) ] said secondary wall means and upper wall cooperatively defining there-between an inflatable compartment above said chamber; and
[ (f) ] means for continuously introducing positive pressure air into said chamber in order to continuously maintain positive air pressure сonditions throughout the entirety of said chamber during the entirety of operation of said mattress apparatus and to inflate both' said chamber and compartment by passage of said air into said chamber and thence through said upper wall portion and thereby maintain positive air pressure conditions in said compartment, and to cause said continuous passage of air through said secondary wall means,
[(g)] said mattress apparatus being-free of solid internal support structure for supporting a patient,
[ (h) ] said air introduction means, upper wall portion and secondary wall means being cooperatively configured and arranged for continuous passage of sufficient positive pressure airflow through the chamber, upper wall portion, compartment, and secondary wall means for even, substantially uniform floiu of air from said mattress apparаtus so that a person lying atop the secondary wall means is supported by said pressurized air without the presence of weight-supporting structure within said mattress apparatus.
Id. at col. 6,11. 8-49 (emphasis added). As shown below, Figures 2 and 3 illustrate an embodiment of the invention: ■
*1354 [[Image here]]
[[Image here]]
Figure 2 is a perspective view of the mattress with a portion of the upper secondary wall folded back to reveal the upper wall. Figure 3 is a side sectiоnal view of the mattress 16 with a top wall 26. The bottom, side, and top walls 22, 24, and 26 define a lower inflatable chamber 34. See id. at col. 4,11. 20-22. Bottom wall 22 and side walls 24 are substantially impervious to airflow while the top wall 26 is pervious. See id. at col. 4, 11. 25-29. “[M]attress 16 is devoid of any internal solid patient supports which could present areas of pressure contact to a patient lying on the mattress.” Id. at col. 4,11. 47-50.
During prosecution of the ’767 patent application in the U.S. Patent and Trademark Office (PTO), the examiner rejected the claims under 35 U.S.C. § 103 (1994) as .obvious over Schild et ai.,,U.S. Patent No. 4,391,009, in view of Gammons et al., U.S. Patent No. 4,347,633. In response, the patentee amended claim 1 to add, inter alia, the “continuous” limitation in clause (a) and limitations that issued as clauses (b) and (d). The examiner then allowed the claims of the ’767 patent.
Kinetic makes and sells low-air-loss mattresses. Kinetic’s mattresses prevent skin breakdown by reducing the interface pressure between the skin of a bedridden patient and the support device. These accused devices include an inflatable mattress, an air supply unit, and a removable cover sheet. Each inflatable mattress is a one-piece unit consisting of three separately inflatable sections for the head, body, and legs of the patient.
*1355
In 1997, KCJ sued Kinetic, alleging infringement of the ’767 patent. On December 17, 1998, the district court held a hearing to сonstrue claim 1 of the ’767 patent.
See KCJ Corp. v. Kinetic Concepts, Inc.,
As to clauses (b) and (d), the district court determined:
“A person of ordinary skill in the art of air bed engineering would read ‘substantially uniform airflow’ to mean airflow that does not substantially fluctuate over time. When added to the words ‘over substantially the entire plan surface,’ the claim requires [an] air flow at substantially the same rate at substantially all locations on the surface.”
Id. at 1326.
After construing the claim, the district court granted Kinetic’s motion for summary judgment of noninfringement. See KCJ II. Adopting the claim construction of KCJ I, the district court determined that thе accused devices do not literally infringe claim 1 because “[KCJ] concedes that the limitations of Clause (a) and Clause (b) are not met by any of the accused devices.” Id. at 1289 n. 2. The district court further held as a matter of law that prosecution history estoppel barred a finding of infringement under the doctrine of equivalents. KCJ appeals.
II.
This court reviews without deference a district court’s grant of summary judgment.
See Cortland Line Co. v. Orvis Co.,
A patent infringement analysis involves two steps: claim construction and application of the properly construed claim to the accused product.
See Markman v. Westview Instruments, Inc.,
A.
The disputed claim construction on appeal involves limitations of clauses (a), (b), and (d). Clause (a) requires “a ... continuous ... chamber.” At the heart of the dispute over this limitation is the meaning of the article “a.” Specifically, does the article limit the number of chambers to only one or does it cover one or more chambers?
The district court limited clause (a) to only one non-interrupted inflatable chamber. The district court stated that “the concept of multiple chambers is at fundamental odds with the concept of continuity,
*1356
and discrete multiple chambers cannot be read into the patent without sacrificing the сoncept of continuity.”
KCJ I,
As noted before, the claim language itself governs claim scope.
See Vitronics,
This court has encountered “a” or “an” in patent claims on several occasions. This court has uniformly applied the general rule for indefinite articles. For instance, in
Abtox,
this court applied the rule and amplified: “The written description supplies additional context for understanding whether the claim language limits the patent scope to a single unitary [element] or extends to encompass a device with multiple [elements].”
Id.
at 1024,
Prosecution history also may assist claim interpretation. Indeed, prosecution history “limits the interpretation of claims so as to exclude any interpretatiоn that may have been disclaimed or disavowed during prosecution in order to obtain claim allowance.”
Standard Oil Co. v. American Cyanamid Co.,
Accordingly, when claim language or context suggests an ambiguity in application of the general meaning of an article, this court undertakes an examination of the written description and the prosecution history to ascertain whether to limit the meaning of “a” or “an.” For example, in
Insituform Technologies, Inc. v. Cat Contracting, Inc.,
In the present casе, neither the claim nor its context suggests an exceptional meaning for the article. The intrinsic evidence simply provides no support for departing from the general rule. At the outset, the claim language of clause (a), “a ... continuous ... chamber,” does not specify the number of elements. Thus, under the general rules of claim construction, this court presumes the customary meaning of “a” — one or more. Furthermore, the writtеn description does not trump that construction. Referring to Figure 3, the written description of the ’767 patent discloses that “the bottom, side and top walls 22, 24, and 26 cooperatively define a lower inflatable chamber broadly referred to by the numeral 34.” ’767 patent, col. 4,11. 20-22. Chamber 34 is operatively coupled to a secondary uppermost wall 36, which provides even airflow. See id. at col. 4, 11. 32-45. The written description at no point restricts the invention to only one chamber.
Similarly, the prosecution history of the ’767 patent does not disclaim multiple chambers. Neither the amendment itself nor the accompanying remarks limits “a ... continuous ... chamber” to only a single chamber. Rather, the remarks focus on the details of the airflow, which passes through the entirety of the chamber during all operations of the mattress. Accordingly, in view of the use of an indefinite articlе “a” in the claim language without numerical qualifiers and the absence of disclaimers in the written description and the prosecution history, this court holds that “a ... continuous ... chamber” covers one or more continuous chambers.
Thus, under the proper claim construction, an accused device having one or more continuous chambers would fall within the scope of clause (a). In the present case, undisputed evidence shows that Kinetic’s accused devices have three chambers. Accordingly, this court concludes that clause (a) reads on Kinetic’s accused devices. The district court’s misreading of the article in this claim, however, is harmless error in light of the meaning of the other clauses.
B.
The district court construed clause (b) — an “upper wall portion being constructed for substantially uniform airflow therethrough over substantially the entire plan surface area of said upper wall portion” — and clause (d) — “secondary wall means being constructed for substantially uniform passage of air therethrough over substantially the entire plan surface area of said secondary wall means” - to require “air flow at substantially the same rate at substantially all locations on the surface.”
KCJ I,
This court thus еxamines whether clauses (b) and (d) require an airflow uniform both in time and space. During the trial court’s proceedings, “[t]he parties agree[d] that when the claim language refers to ‘substantially uniform passage of air,’ it means airflow which is substantially steady, constant or continuous, as opposed to fluctuating intermittent or alternating over time.... [However,] [t]hey disagree[d] about ivhere the patent claims the substantially steady air flow will occur.” Id. at 1325-26. On appeal, KCJ maintains that the “continuous passage of air” requires uniform airflow only in a temporal sense. Specifically, KCJ asserts: “As used in clauses (b) and (d) of [c]laim 1 of the ’767 patent, ‘substantially uniform airflow over substantially the entire plan surface area’ means that wherever air comes through anywhere over the surface area, it *1358 will flow at a substantially uniform or constant rate over time.” This court, however, agreеs with the district court that claim 1 requires uniformity in space as well as time.
First, the claim language itself requires spatial uniformity. Clause (b) requires “uniform airflow therethrough over
substantially the entire plan surface area.”
’767 patent, col. 6, 11. 12-13 (emphasis added). Similarly, clause (d) requires “uniform passage of air therethrough over
substantially the entire plan surface area.” Id.
at col. 6, 11. 19-20 (emphasis added). As the district court aptly noted, “[t]he claim demands that air flow through all locations on the surfaces.”
KCJ I,
The written description of the ’767 patent reinforces the essential nature of spatial uniformity. The present invention is an “air floatation mattress ... supporting] a recumbent patient entirely by means of a throttled flow of pressurized air which also ventilates and cools all adjacent areas of the patient’s skin.” ’767 patent, col. 2, 11. 41-45. To enable the mattress to “continuously ventilat[e] аll areas of the skin adjacent the mattress,” there must be airflow over the entire plan surface area as the claim recites. Id. at col. 3, 11. 4-5. In fact, the written description explains:
[P]ressurized air passes evenly through virtually the entire plan surface area of the top wall 26. As a consequence, such air also serves to inflate the upper compartment 40 between top wall 26 and secondary wall 36. Such pressurized air then flows evenly through the suede or leather secondary wall 36; here again, this airflow is substantially even over substantially the entire plan surface area of the wall 36.
Id. at col. 5, 11. 18-25 (emphasis added). Unless the air mattress has uniform airflow over substantially the entire plan surface area, a patient lying on the secondary wall would not be “supported entirely by the inflatable compartment and chamber without the necessity of spines or other internal, non-inflatable solid support struсture within or forming a part of the mattress apparatus.” Id. at col. 2, 11. 63-66 (emphasis added).
The record of the administrative proceedings before the PTO supports this interpretation of claim 1. In seeking allowance of the pending claims, the patentee added clauses (b) and (d) to claim 1 and remarked:
In no way does the alternating pad of the Schild et al. reference supply positive pressure air throughout the entirety of the chamber during all operations of the mattress. ... Moreover, Gammons et al. does not provide means for continuously maintaining positive air pressurе conditions throughout the entirety of the lower chamber during the entirety of the operation of the mattress apparatus.
J.A. at 138-39 (emphasis added). The express statements of the patentee clarify that the airflow limitations require both a temporal and spatial uniformity. In sum, the prosecution history also supports the district court’s interpretation of clauses (b) and (d). To read the claim otherwise would ignore express language of the claim requiring airflоw “over substantially the entire plan surface area.” ’767 patent, col. 6,11.14-15.
The district court determined that clauses (b) and (d), when properly construed, do not read on Kinetic’s accused mattresses. Literal infringement of a claim occurs when every limitation recited in the claim appears in the accused device, i.e., when “the properly construed claim reads on the accused device exactly.”
Amhil Enters., Ltd. v. Wawa, Inc.,
III.
The district court also properly held on summary judgment that Kinetic’s devices do not infringe under the doctrine of equivalents. Infringement under the doctrine of equivalents requires that the accused product contain each limitation of the claim or its equivalent.
See Warner-Jenkinson Co. v. Hilton Davis Chem. Co.,
This court concludes that the prosecution history of the ’767 patent supports the district court’s refusal to apply the doctrine of еquivalents. The prosecution history reveals that KCJ, in an attempt to obtain allowance of the pending claims over the cited prior art Schild et al. • and Gammons et al., added clauses (b) and (d) in their entirety. Additionally, KCJ supplemented the claim amendment with the following remark:
[C]laim 1 as now amended specifically and unambiguously recites means for introduction of positive pressure air into the chamber in order to “continuously maintain positive air pressure conditions throughout the entirety of said chamber during the entirety of operation of said mattress apparatus.... ” In no way does the alternating pad of the Schild et al. reference supply positive pressure air throughout the entirety of the chamber during all operations of the mattress.
The Gammons et al. reference ... is likewise very different from the structure as claimed in the present claims.... [GJammons et al. does not employ a chamber having an upper wall which is constructed for substantially uniform air flow through substantially the entire plan surface of the upper wall. Moreover, Gammons et al. does not provide means for continuously maintaining positive air pressure conditions throughout the entirety of the loiuer chamber during the entirety of the operation of the mattress apparatus.
J.A. at 138-39 (emphasis added). Following the claim amendment and the accompanying remarks, the examiner allowed the pending claims.
On appeal, KCJ argues that the amendment and the rеmarks should impose only a temporal uniformity because spatial uniformity would not distinguish the pending claims over the prior art. However, this court concludes that KCJ’s statements reflect a clear and unmistakable surrender of mattresses without airflow “throughout the entirety of the lower chamber.” Id. The added claim language as well as the accompanying remarks show that KCJ narrowed the claims to require spatial and temporаl uniformity to obtain allowance of the pending claims. In fact, KCJ admits in its appeal brief that “KCJ added specific language, including the clauses at issue, for the express purpose of distinguishing the ’767 patent from the cited prior art.”
Accordingly, this court holds that the prosecution history precludes KCJ from recapturing subject matter surrendered during prosecution through the doctrine of equivalents. As mentioned above, KCJ concedеd that Kinetic’s devices do not satisfy the spatial uniformity limitation. KCJ *1360 may not now employ the doctrine of equivalents to extend clauses (b) and (d) to encompass Kinetic’s devices, which are not within the legal boundaries of claim 1. This court therefore affirms the district court’s grant of summary judgment of nonin-fringement under the doctrine of equivalents.
CONCLUSION
Because Kinetic’s accused mattresses do not infringe claim 1 of the ’767 patent, either literally or equivalently, this court affirms the district court’s grant of summary judgment of noninfringement.
COSTS
Each party shall bear its own costs.
AFFIRMED.