Thе Defendant-Appellant, Interface Architectural Resources, Inc. (“Interface”), seeks review of a final judgment by the United States District Court for the District of Maryland granting a motion by the Plaintiff-Appellees, Tate Access Floors, Inc. and Tate Access Floors Leasing, Inc. (together “Tate”) to preliminarily enjoin Interface from infringing claims 1-4 and 8-10 of United States Patent No. 4,625,491 (the “'491 patent”). Interface contends that the district court erred by granting the preliminary injunction because Tate failed to make the requisite showing of a reasonable likelihood of success on the merits of its infringement claim. Because the district court did not abuse its discretion in granting the preliminary injunction, we affirm.
I. BACKGROUND
A. The '191 Patent
Tate owns the '491 patent, which pertains to raised access flooring panels. '491 patent, col. 1,11. 6-9. Raised access flooring panels provide an elevated floor under which materials such as cables and pipes can be run. Id. at col. 1, 11. 15-19. The panels rest on pedestals. They are placed side-by-side to form an elevated floor. By lifting and removing certain panels, one can access the materials underneath the floor. Id. at col. 1,11. 30-32.
The panels addressed in the '491 patent have a laminated top surface. Id. at col. 1, 11. 57-63. The transparent laminate protects and covers a decorative top surface. Id. These decorative panels are formed by heat bonding a decorative top layer onto a number of layers оf underlying kraft paper using resin. Id. The resulting edges of the laminated panels are brittle; without protection they chip, crack, and appear aesthetically unpleasing.
Prior to the claimed invention, the industry employed an add-on trim strip to protect the edges of the panels and to make them look better. Id. at col. 1, 11. 33-36. Such trim was problematic because it increased the cost of panels, and tended to crack and become loose, and to collect dirt and moisture. Id. at col. 1, 11. 42-46. The '491 patent addresses the problems associated with the edges of the panels without employing an add-on trim strip.
Instead of adding trim, the '491 patent solves the problem of brittle edges by removing the top decorаtive layer from the periphery of the panels to form an integral trim edge. Id. at col. 1,1. 67 to col. 2,1. 4. The two independent claims at issue, claims 1 and 8, read as follows:
1. A floor panel for elevated floors comprising a rectangular base structure adapted to be supported at its corners and providing a load surface operable to support loads thereon, a floor covering mounted on said load surface providing a decorative exposed surface layer on the side thereof opposite said load surface, said floor covering providing an inner body portion having an appearance contrasting with the appearance of said decorative surface layer, said floor covering providing a border along the edges of said panels *1361 along which said decorative surface layer is removed to expose said inner body portion and thereby provide an integral contrasting border around said decorative surface layer.
8. A floor panel comprising a rectangular support structure providing a load surface operable to support loads thereon, a layered laminated floor covering mounted on said load surface providing a single visible decorative layer along the side of said floor covering also providing an inner layer contrasting with said decorative layer having a thickness substantially greater than the thickness of the decorative layer adjacent to said decorative layer along the side thereof facing said load surface, said floor сovering providing a border extending along the edges of said panel along which the decorative layer is removed to expose said inner layer.
Id. at col. 4,1. 67 to col. 5,1.11 and col. 5,1. 37 to col. 6,1.11 (emphasis added).
The specification includes figures depicting an embodiment of the claimed floor panels. The periphery of the panels has a sloping, or beveled portion, as well as a flat, horizontal portion. For example, Figure 4 of the '491 patent depicts a panel with edges that appear as follows:
[[Image here]]
B. The Accused Product
Interface’s accused floor panels have a decorative top layer with a beveled edge, but no horizontal, single-layered portion. An example of the accused panels follows,
*1362 [[Image here]]
Interface contends that its panels fall outside the scope of the asserted claims of the '491 patent, as properly construed, by virtue of their simple beveled edges. It argues that the “border” limitations of claims 1 and 8 encompass only the horizontal portion depicted in Figure 4 of the '491 patent. Because Interface’s panels lack a horizontal portion formed of a single layer of material, and contain only a beveled edge, Interface maintains that its panels do not infringe. Tate contends that panels with beveled edges meet the “border” limitations notwithstanding the absence of a horizontal portion formed of a single layer of material.
C. The District Court’s Grant of Preliminary Injunction
The district court prоperly noted that pursuant to this court’s precedent interpreting 35 U.S.C. § 283, Tate’s entitlement to a preliminary injunction hinged on proof regarding four factors: (1) likely success on the merits, including proof of infringement and lack of a substantial question regarding Interface’s invalidity defense; (2) irreparable harm absent an injunction; (3) that the balance of hardships favors granting the injunction; and (4) that public policy favors granting the injunction.
Tate Access Floors, Inc. v. Interface Architectural Res., Inc.,
On the first factor, likely success on the merits, the district court found that Tate established likely success on both validity and infringement.
Tate,
The remaining evidence of obviousness, under factors 1 and 3, involves the prior art in floor panels. Whether Interface is practicing the prior art constitutes an affirmative defense to infringement. Fiskars, Inc. v. Hunt Mfg. Co.,221 F.3d 1318 , 1323 (Fed.Cir.2000). I address this issue in discussing infringement.
Id.
The district court next determined that Tate had proved likely success on its infringement claim. Id. at 372-75. It noted, properly, that infringement analysis proceeds in two steps: 1) claim construction, which begins with an assessment of the intrinsic evidence and considers extrinsic evidence only if the intrinsic evidence is unclear, and then 2) comparison of the accused device to the construеd claims. Id. at 372.
Interface asserted that the term “border” in independent claims 1 and 8 must be construed to mean a “recessed horizontal border formed of a single layer.” Id. Under this construction, Interface’s panels would not infringe; their edges lack a horizontal layer, and are formed only of a multi-layered bevel. Interface also argued that the '491 patent could not be reasonably construed to cover its accused device. Id.
The district court rejected Interface’s claim construction. It noted that it was bound to presume the claim terms “mean what they say,” to accord them their ordinary and accustomed meaning, and to turn to extrinsic evidence only if the intrinsic evidence is unclear.
Id.
(quoting
Johnson Worldwide Assocs. v. Zebco Corp.,
The district court also rejected. Interface’s “practicing the prior art” defense, which it treated as a defense to infringement. Interface argued that if the '491 patent covers all beveled edges, it would impermissibly cover prior art panels with vertical edges and that Westinghouse had sold floor panels with edges beveled as in the accused device prior to Tate’s invention. Id. The court rejected this argument because it found that a vertically edged panel would lack the claimed integral contrasting border and decorative trim. Id. at 375. Second, the court noted that there was some testimony that Westinghouse sold “untrimmed laminate panels beveled in the way that the accused panels are beveled,” but found the conflicting testimony regarding Westinghouse’s prior art insufficient to defeat Tate’s likely success on the merits. Id. at 374-75. The district court concluded: “[although the issue is a somewhat close one, I find a likelihood of success for Tate.” Id. at 375.
*1364 After concluding that Tate had established the requisite likelihood of success on both infringement and validity, the district court analyzed the remaining three preliminary injunction factors. It found that Tate had established these factors as well. Tate established with objective evidence that it would suffer irreparable harm absent a preliminary injunction despite also being entitled to a presumption of irreparable harm due to its “strong showing of validity,” and “quite ‘clear’ ” showing on infringement. Id. at 375-78. Interface failed to rebut this presumption. Id. at 378. The district court next concluded that the balance of harms between Tate and Interface weighed slightly in Tate’s favor. Id. at 378-79. Finally, because it found no public health issue at stake and because of the strong public interest in protecting patent rights, the district court found that the final factor-public interest-also failed to preclude an injunction. Id. at 379. Accordingly, the district court preliminarily enjoined Interface from infringing claims 1-4 and 8-10 of the '491 patent. Tate Access Floors, Inc. v. Interface Architectural Res., Inc., No. 00 CV 2543 (D.Md. Mar. 9, 2001) (preliminary injunction order).
Interface appeals. We have jurisdiction pursuant to 28 U.S.C. § 1295(a)(1).
On appeal, Interface challenges only the district court’s determination regarding likely success on the merits of Tate’s infringement claim. Intеrface does not challenge the validity of the '491 patent, nor does it contend that the district court erred in its analysis of the remaining preliminary injunction factors. Accordingly, the crucial question is whether the district court properly construed the “border” limitations in independent claims 1 and 8 to include beveled edges without a single, horizontal layer such as those contained in Interface’s accused panels.
Interface argues that the district court erred in determining that Tate had demonstrated the likely success of its infringement argument for two reasons. Interface’s first and primary argument is that regardless of the claim construction, its accused products cannot literally infringe the asserted claims of the '491 patent beсause Interface merely practices the prior art. In addition, Interface argues that, as properly construed, the “border” limitations exclude simple beveled edges such as those found in its accused floor panels.
II. STANDARD OF REVIEW
The decision to grant a preliminary injunction under 35 U.S.C. § 283 rests within the district court’s sound discretion.
Amazon.com, Inc. v. Barnesandnoble.com, Inc.,
III. DISCUSSION
The moving party, here Tate, is entitled to a preliminary injunction if it shows the following four factors:
*1365 (1) a reasonable likelihood of success on the merits;
(2) irreparable harm absent an injunction;
(3) that the balance of hardships tips in its favor; and
(4) that the public interest favors an injunction.
Amazon.com,
In order to demonstrate likely success on the merits, Tate must show that, in light of the presumptions and burdens applicable at trial, it will likely prove that Interface infringes the asserted claims of the '491 patent and that the patent will likely withstand Interface’s challenges to its validity.
See id.
(citing
Genentech, Inc. v. Novo Nordisk, A/S,
Although the district court found that Tate had established likely success on the merits regarding both infringement and validity, only infringement is at issue in this appeal. As Interface confirmed at oral argument, Interface did not appeal and does not challenge the district court’s determination that Tate would likely prevail on the issue of validity. We will therefore affirm the district court’s order preliminarily enjoining Interface from infringing the asserted claims of the '491 patent unless the district court determined, improperly, that Tate would likely prevail on its contention that Interface’s panels infringe the asserted claims of the '491 patent.
Infringement analysis involves two steps: the court first construes the scope of the asserted clаims and then compares the accused device to the properly construed claims to determine whether each and every limitation of a claim is present, either literally or equivalently, in the accused device.
Amazon.com,
A. Practicing the Prior Art
Interface first argues that regardless of the proper claim construction, its panels cannot literally infringe because they merely practice the prior art, or that which would have been obvious in light of the prior art. This contention lacks merit.
See Baxter Healthcare Corp. v. Spectramed, Inc.,
This court made unequivocally clear in
Baxter
that there is no “practicing the prior art” defense to litеral infringement.
See
Implicit in Spectramed’s argument is that Baxter, in order to establish literal infringement, must рrove by a preponderance of the evidence that Spec-tramed’s accused devices embody all the limitations in the asserted claims, and in addition, Spectramed’s accused devices must not be an adoption of the combined teachings of the prior art. This is not a correct statement of the law governing patent infringement. There is no requirement that the accused device be nonobvious in light of the prior art, or otherwise be itself patentable. Literal infringement exists if each of the limitations of the asserted claim(s) read on, that is, are found in, the accused device, Questions of obviousness in light of the prior art go to validity of the claims, not to whether an accused device infringes.
Id.
at 1583,
Thus, our decision in
Baxter
direсtly forecloses Interface’s “practicing the prior art” argument. Interface attempts to distinguish
Baxter
on the grounds that it “merely addresses the parties’ respective burdens of proof when the prior art defense is raised.” It also seeks to glean authority for the putative “practicing prior art” defense to literal infringement from the doctrine of equivalents, the reverse doctrine of equivalents, and an extension of a Supreme Court case predating the 1952 Patent Act. We address these arguments below. Even if they had merit— which they do not — this panel would not be free to overrule
Baxter. See Vas-Cath Inc. v. Mahurkar,
Although the differing burdens of proof for infringement and validity are indeed important,
Baxter
in no way “merely addresses the parties’ respective burdens of proof when the prior art defense [to literal infringement] is raised.” The discussion in
Baxter
cited above makes clear that literal infringement is determined by construing the claims and comparing them to the accused device, not by comparing the accused device to the prior art.
Baxter,
Interface cites several doctrine of equivalents cases in an attempt to bolster its “practicing the prior art” defense to literal infringement. They hold that the scope of equivalents may not extend so far as to
*1367
ensnare prior art.
See Fiskars, Inc. v. Hunt Mfg. Co.,
With respect to literal infringement, these cases are inapposite. The doctrine of equivalents expands the reach of claims beyond their literal language. That this expansion is guided and constrained by the prior art is no surprise, for the doctrine of equivalents is an equitable doctrine and it would not be equitable to allow a patentee to claim a scope of equivalents encоmpassing material that had been previously disclosed by someone else, or that would have been obvious in light of others’ earlier disclosures. But this limit on the equitable extension of literal language provides no warrant for constricting literal language when it is clearly claimed.
Moreover, just as the doctrine of equivalents cannot extend so broadly as to ensnare prior art, claim language should generally be construed to preserve validity,
if possible. See, e.g., Whittaker Corp. v. UNR Indus., Inc.,
Our law requires patent challengers to prove invalidity by clear and convincing evidence. Where an accused infringer is clearly practicing only that which was in the prior art, and nothing more, and the patentee’s proffered constructiоn reads on the accused device, meeting this burden of proof should not prove difficult. Nevertheless, accused infringers are not free to flout the requirement of proving invalidity by clear and convincing evidence by asserting a “practicing prior art” defense to literal infringement under the less stringent preponderance of the evidence standard. Moreover, as in the doctrine of equivalents-ensnarement cases, and in the “construction to preserve validity” cases, the fact that the patentee happens to be practicing the pri- or art is irrelevant; it is the presence of the prior art and its relationship to the claim language that matters for invalidity. 1
*1368 Neither the reverse doctrine of еquivalents nor the remaining precedent Interface cites alters this result. Interface argues that the existence of the reverse doctrine of equivalents proves that the literal infringement inquiry cannot end upon a finding that a claim, as properly construed, reads on the accused device. The reverse doctrine of equivalents, Interface contends, may result in a finding of nonin-fringement even when the accused device possesses each and every limitation of an asserted claim. Interface therefore urges this court to adopt its “practicing the pri- or art” defense as a rebuttal similar to its conception of the reverse doctrine of equivalents.
We reject this argument. The Supremе Court referred to the reverse doctrine of equivalents in
Graver Tank & Manufacturing Co. v. Linde Air Products Co.,
Not once has this court affirmed a decision finding noninfringement based on the reverse doctrine of equivalents. And with good reason: when Congress enacted 35 U.S.C. § 112, after the decision in
Graver Tank,
it imposed requirements for the written description, enablement, definiteness, and means-plus-function claims that are co-extensive with the broadest possible reach of the reverse doctrine of equivalents.
See In re Donaldson Co.,
Even were this court likely ever to affirm a defense to literal infringement based on the reverse doctrine of equivalents, the presence of one anachronistic exception, long mentioned but rarely applied, is hardly reason to create another. We therefore decline the invitation to adopt Interface’s “practicing the prior art” defense on these grounds.
We also will not do so on the basis of Interface’s argument that the Supreme Court sanctioned the “practicing prior art” defense in
Scott Paper Co. v. Marcalus Mfg. Co.,
In
Scott Paper,
the Supreme Court carved out an exception to the doctrine of assignor estoppеl.
Id.
at 257,
The Supreme Court affirmed. It explained:
The judgment is affirmed for the reason that we find that the application of the doctrine of estoppel so as to foreclose the assignor of a patent from asserting the right to make use of the prior art invention of an expired patent, which anticipates that of the assigned patent, is inconsistent with the patent laws which dedicate to public use the invention of an еxpired patent. The assignor has a complete defense to an action for infringement where the alleged infringing device is that of an expired patent.
Id.
at 257-58,
As the above paragraph indicates, the Scott Paper rationale was based on the premise that the assigned patent would be invalid due to anticipation were it coextensive with the expired prior art patent. Id. The statement that, in such circumstances, the assignor has a “complete defense to an action for infringement ” must be understood in context. Id. (emphasis added). Of course, under the present scheme, invalidity is a defense to an action for patent infringement. This general statement provides no license for asserting that a particular defense, if successful, results in nonin-fringement as opposed to invalidity.
Moreover, the court of appeals decision that the Supreme Court affirmed in
Scott Paper
was premised on claim construction to preserve validity, not on noninfringement.
Id.
at 251,
*1370 B. Claim Construction
Interface’s second argument is that the district court erred in construing the “border” limitations in independent claims 1 and 8 to еncompass the simple beveled edges in its accused floor panels. This argument also fails.
Claim interpretation begins, as always, with the language of the claims.
Johnson Worldwide Assocs., Inc. v. Zebco Corp.,
One ordinarily skilled in the art of raised access floor panels would understand the term “border” to refer to the area or zone forming an edge or trim framing the decorative surface of the panel. Independent claim 1 recites “a border along the edges of said panels along which said decorative surface layer is removed to expose said inner body portion.” '491 patent, col. 4, 1. 67 to col. 5, 1. 11. Independent claim 8 recites “a border extending along the edges of said panel along which the decorative layer is removed to expose said inner layer.” Id. at col. 5,1. 37 to cоl. 6,1. 11. Nothing in the language of these claims requires the “border” to be horizontal or formed of a single layer.
The “border” in claim 1 is formed by exposing an “inner body portion.” A portion may certainly consist of one or more layers.
The “border” in claim 8 is formed by exposing “said inner layer.” That language refers to the phrase “an inner layer,” which first appears earlier in claim 8. '491 patent, col. 6, 1. 5. It is well settled that the term “a” or “an” ordinarily means “one or more.”
Tate Access Floors, Inc. v. Maxcess Techs., Inc.,
a single visible decorative layer along the side of said floor covering also providing an inner layer contrasting with said decorative layer having a thickness substantially greater than the thickness of the decorative layer adjacent to said decorative layer along the side thereof facing said load surface....
’491 patent, col. 6,11. 2-9 (emphasis added). The language “an inner layer” must be read in the context of the language claiming “a single visible decorative layer;” where the patentee meant to constrict the claim to one and only one particular layer, he said so clearly. Moreover, the reference to substantially greater thickness also suggests that the claimed inner layer may consist of one or more layers, because *1371 increasing the layers would increase the thickness. 3
Like the claim language, the remainder of the specification supports construing the term “border” to include multiple layers framing the decorative paper. Of course, limitations from elsewhere in the sрecification will not be read in where, as here, the claim terms are clear.
See, e.g., Toro Co. v. White Consol. Indus., Inc.,
Nevertheless we note that this is not a case in which the patentee acted as his own lexicographer, and that the written description supports our construction. In pertinent part, it reads:
Rearwardly of the decorative paper, the floor covering material is provided with layers of material having a contrasting color with respect to the decorative paper.
In accordance with the present invention, the surfaсe layer of protective material and the layer of decorative paper are cut away along the edge of the floor covering to expose the inner layers and provide a contrasting color integral border within the floor covering material itself.
’491 patent col. 1, 1. 65 to col. 2, 1. 4 (emphasis added). This language contradicts Interface’s position that the description requires construing the claimed “border” as a single, horizontal layer. Interface emphasizes the statement that “a uniform exposure of the layers of black paper is obtained.” '491 patent, col. 3, 11. 53-54. This language, however, merely underscores that the border is formed by uniformly exposing multiple layers, not by exposing a single layer. Thus, the written description plainly contemplates that the claimed contrasting color border can be formed of multiple layers of material.
Interface argues that notwithstanding this language, Figures 3 and 4 of the '491 patent compel its construction of the “border” limitations. This is allegedly so because the arrow corresponding to the “integral border or edge trim 14,” '491 patent, col. 2, 1. 54, aims at a horizontal, single layer of exposed trim. This argument fails. Even were we to accept the proposition that the arrow in Figures 3 and 4 points only to the horizontal, single-layered portion of the border rather than to the beveled portion (which is also clearly exposed, and which is formed of multiple layers of material) additional limitations from these figures сannot be imported into the unambiguous claim language.
Contrary to Interface’s next contention, nothing in the prosecution history, or elsewhere in the prior art of record, 4 renders proper a construction that *1372 limits the claimed “border” to a single, horizontal layer. Interface would have us adopt its narrow construction in order to preserve the validity of the '491 patent. It contends that the prior art would render the asserted claims obvious if they cover floor panels with simple beveled edges such as its accused products.
Even if this were so, where claim language is clear we must accord it full breadth even if the result is a claim that is clearly invalid.
Apple Computer, Inc. v. Articulate Sys., Inc.,
IV. CONCLUSION
The district court committed no abuse of discretion in determining that Tate demonstrated its entitlement to a preliminary injunction, including a reasonable likelihood of success on the merits of its infringement claim. The grant of preliminary injunction barring Interface from infringing claims 1-4 and 8-10 of the '491 patent is therefore affirmed.
AFFIRMED.
No costs.
Notes
. These ensnarement cases test the relationship between the prior art and the scope of the pertinent claims by asking whether a hypothetical claim thаt reads on the accused *1368 device would be unpatentable because it would be anticipated or obvious in light of the prior art. The accused device is surely a reference point for construing such a hypothetical claim. The crucial question, however, is whether the claims, if so construed, would be unpatentable.
. Interface also cites several cases from the Seventh Circuit in support of its practicing the prior art defense.
See Rex Chainbelt, Inc. v. Gen. Kinematics Corp.,
. Because we conclude independently that the "border” limitations in claims 1 and 8 both properly encompass one or more layers, we need not address the issuе of whether Interface is bound by this court’s prior determination in
Tate v. Maxcess,
. In construing claims, we look first to the intrinsic evidence of record — the patent, including the claims, remainder of the specification, and, if it is in evidence, the prosecution history.
Vitronics Corp. v. Conceptronic,
*1372
Inc.,