Freedman manufactures seats used in public transportation vehicles. Its product line includes stowable seats, which are seats that have the ability to fold away in order to create more interior space in a vehicle. They are particularly useful for accommodating passengers with wheelchairs, but may be used whenever more interior space is needed.

In due course, both parties filed motions for summary judgment on the issue of infringement. Freedman also moved for summary judgment of validity of the ’389 patent... With respect to the issue of infringement, the court stated that there really was no dispute as to claim construction or the structure of the accused product.

American Seating argued that its support member and moveable end were not equivalent to the corresponding structure claimed by the ’389 patent... The district court disagreed.... The court therefore granted Freedman summary judgment of infringement by equivalence.

As to the issue of invalidity, American Seating opposed Freedman’s motion for summary judgment on the ground that, at a minimum, there were genuine issues of material fact as to whether the invention of the ’389 patent was obvious. Again, the district court disagreed.

The district court granted summary judgment in favor of Freedman both on the issue of infringement under the doctrine of equivalents and on American Seating’s counterclaim of invalidity by reason of obviousness.

In the main appeal, American Seating contends that the district court erred in granting summary judgment for Freedman on the issues of infringement, validity, and enforceability.

We review summary judgment decisions de novo, reapplying the standard used by the district court. Frank’s Casing Crew & Rental Tools, Inc. v. Weatherford Int’l, Inc., 389 F.3d 1370, 1376 (Fed. Cir. 2004); Ellison v. Robertson, 357 F.3d 1072, 1075 (9th Cir. 2004). Under that standard, summary judgment must be granted “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). In other words, summary judgment must be granted if no “reasonable jury could return a verdict for the nonmoving party.” Anderson v. Liberty Lobby, Inc., 477 U.S. 242, 248 (1986). In making this determination, “[t]he evidence of the non-movant is to be believed, and all justifiable inferences are to be drawn in [the non-movant’s] favor.” Id. at 255.

Patent infringement is a two step inquiry. First, the court must construe the asserted claim. RF Del., Inc. v. Pac. Keystone Techs., Inc., 326 F.3d 1255, 1266 (Fed. Cir. 2003). Second, the court must determine whether the accused product or process contains each limitation of the properly construed claims, either literally or by a substantial equivalent. Id. The first step is a question of law; the second step is a question of fact. Id.

Under the doctrine of equivalents, “a product or process that does not literally infringe upon the express terms of a patent claim may nonetheless be found to infringe if there is ‘equivalence’ between the elements of the accused product or process and the claimed elements of the patented invention.” Warner-Jenkinson Co. v. Hilton Davis Chem. Co., 520 U.S. 17, 21 (1997) (citing Graver Tank, 339 U.S. at 609). The doctrine evolved in recognition of the fact that

[t]he language in the patent claims may not capture every nuance of the invention or describe with complete precision the range of its novelty. If patents were always interpreted by their literal terms, their value would be greatly diminished. Unimportant and insubstantial substitutes for certain elements could defeat the patent, and its value to inventors could be destroyed by simple acts of copying.

Festo Corp. v. Shoketsu Kinzoku Kogyo Kabushiki Co., 535 U.S. 722, 731 (2002); Graver Tank, 339 U.S. at 605 (“[T]o permit imitation of a patented invention which does not copy every literal detail would be to convert the protection of the patent grant into a hollow and useless thing.”). At the same time, the doctrine of equivalents necessarily adds uncertainty to the scope of patent claims, and thereby detracts from the public-notice function of patent claims and risks deterring non-infringing and potentially innovative endeavors. See Festo, 535 U.S. at 727 (“If the range of equivalents is unclear, competitors may be unable to determine what is a permitted alternative to a patented invention and what is an infringing equivalent.”); Warner-Jenkinson, 520 U.S. at 29 (“There can be no denying that the doctrine of equivalents, when applied broadly, conflicts with the definitional and public-notice functions of the statutory claiming requirements.”). In recognition of this risk, and in an effort to strike the proper balance between protecting patentees while also providing sufficient notice to the public, various rules of law have emerged to constrain when and how the doctrine of equivalents is to be applied.

Infringement is determined by considering infringement limitation by limitation, whether literal or equivalent.

Equivalence cannot be applied if it would vitiate the meaning of the limitation. Vitiate seems vague to me; obviate might be better. The essence is that equivalence is inapplicable if the significance of a limitation is lost by broadening it to afford equivalence.

Of relevance to this case is the “all limitations” rule. The rule holds that an accused product or process is not infringing unless it contains each limitation of the claim, either literally or by an equivalent. See, e.g., Warner-Jenkinson, 520 U.S at 29; Kustom Signals, Inc. v. Applied Concepts, Inc., 264 F.3d 1326, 1333 (Fed. Cir. 2001). This principle has two primary implications for the doctrine of equivalents. First, the all limitations rule requires that equivalence be assessed on a limitation-by-limitation basis, as opposed to from the perspective of the invention as a whole. Warner-Jenkinson, 520 U.S. at 29 (“Each element contained in a patent claim is deemed material to defining the scope of the patented invention, and thus the doctrine of equivalents must be applied to individual elements of the claim, not to the invention as a whole.”); Pennwalt Corp. v. Durand-Wayland, Inc., 833 F.2d 931, 935 (Fed. Cir. 1987) (en banc). Second, an element of an accused product or process is not, as a matter of law, equivalent to a limitation of the claimed invention if such a finding would entirely vitiate the limitation. Warner-Jenkinson, 520 U.S. at 29 (“It is important to ensure that the application of the doctrine [of equivalents], even as to an individual element, is not allowed such broad play as to effectively eliminate that element in its entirety.”); Lockheed Martin Corp. v. Space Sys./Loral, Inc., 324 F.3d 1308, 1321 (Fed. Cir. 2003) (“[I]f a court determines that a finding of infringement under the doctrine of equivalents ‘would entirely vitiate a particular claim[ed] element,’ then the court should rule that there is no infringement under the doctrine of equivalents.” (citation omitted)); Bell Atl. Network Servs., Inc. v. Covad Communications Group, Inc., 262 F.3d 1258, 1279-80 (Fed. Cir. 2001) (same).

There is no set formula for determining whether a finding of equivalence would vitiate a claim limitation, and thereby violate the all limitations rule. Rather, courts must consider the totality of the circumstances of each case and determine whether the alleged equivalent can be fairly characterized as an insubstantial change from the claimed subject matter without rendering the pertinent limitation meaningless. See, e.g., Novartis Pharm. Corp. v. Abbott Labs., 375 F.3d 1328, 1338-39 (Fed. Cir. 2004) (“Permitting such an element in the accused product to come within the bounds of the claimed element would impermissibly extend the scope of the claim language beyond what the patentee actually claimed.”); Moore U.S.A., Inc. v. Standard Register Co., 229 F.3d 1091, 1106 (Fed. Cir. 2000) (“If our case law on the doctrine of equivalents makes anything clear, it is that all claim limitations are not entitled to an equal scope of equivalents.”); Ethicon Endo-Surgery, Inc. v. U.S. Surgical Corp., 149 F.3d 1309, 1317-21 (Fed. Cir. 1998) (indicating that assessing infringement under the doctrine of equivalents is dependent on the facts of each case); Sage Prods., Inc. v. Devon Indus., Inc., 126 F.3d 1420, 1425 (Fed. Cir. 1997) (“Because th[e] issued patent contains clear structural limitations, the public has a right to rely on those limits in conducting its business activities.”).

In the ruling, the CAFC used the example of Ethicon Endo-Surgery, Inc. v. U.S. Surgical Corp., where equivalence is defined as to degree of similarity.

In doing so, we explained that our finding did not vitiate any limitations of claim 24 because the noted difference “is a subtle difference in degree, not a clear, substantial difference or difference in kind, as was the case regarding claim 6.”.

Other examples provided in the ruling indicated a case-by-case approach required, depending upon factual details. But the gist seemed consistent that, if applying equivalence resulted in broadening the scope of the limitation so as to make the stated limitation insignificant, equivalence is inapplicable.

Perhaps one way to look at equivalence is to compare a limitation with its literal reading to its expanded reading under equivalence (expanded to where infringement would be found). If one could read the literal version and the expanded version as much the same, applying the doctrine of equivalence would be appropriate. But, if the two versions of a limitation's interpretation themselves read as being significantly different, in other words, the limitation itself is not equivalent if applying the doctrine of equivalence, then applying the doctrine of equivalence is inappropriate.

Freedman argues that the slider crank claimed in the ’389 patent and the fourth link mechanism used in the EZ Fold function in the same way to produce identical results...The problem, however, is that taken to its logical conclusion, Freedman’s argument would mean that any support member capable of allowing translational and rotational motion would be equivalent to a support member “slidably mounted to said seatbase,” which reads “slidably mounted” completely out of the claims. This is the precise type of overextension of the doctrine of equivalents that the claim vitiation doctrine is intended to prevent.

In sum, we hold that the district court’s finding of infringement entirely vitiated the “slidably mounted” limitation of the ’389 patent. We therefore reverse the court’s grant of summary judgment and remand with instructions to enter judgment of non-infringement in favor of American Seating.

Because we conclude that the judgment of infringement under the doctrine of equivalents has the effect of vitiating a limitation of the claims of the ’389 patent, we reverse the judgment and remand the case to the district court with instructions to enter judgment of non-infringement in favor of American Seating. Because we conclude that genuine issues of material fact remain as to obviousness, we also reverse the district court’s grant of summary judgment of validity and remand for further proceedings.