Prior Art Used to Construe Claim

In Laryngeal Mask Co. Ltd v. Ambu A/S, 2010-1028 (Fed. Cir. September 21, 2010), the Federal Circuit dealt with some complicated claim construction issues.  One issue concerned the meaning of the word “backplate” used in a laryngeal mask patent.  The oral argument for this case was featured in an earlier post as the Oral Argument of the Month [Link]. 

What caught my eye in today’s opinion was the use of prior art patents as a guide to construe a claim term.  The court wrote:

Although there was no dictionary or treatise defini-tion introduced for backplate, there are two prior art patents also related to laryngeal mask devices which use the term. U.S. Patent No. 5,355,879 (’879 patent); U.S. Patent No. 5,305,743 (’743 patent). Both prior art patents list the same inventor as the patent at issue, Dr. Brain. Both of these patents disclose a backplate, but neither includes a tube joint. This prior art use of the term would further inform one of skill in the art as to the common meaning of the term backplate.

The term backplate has a somewhat self-descriptive nature. As the prior art patents indicate it is the plate on the back. In light of the claims, specification, prosecution history, and prior art patents, we conclude that one of skill in the art would understand the claimed backplate to be “the relatively rigid mask structure surrounded by the cuff.” We conclude that one of skill in the art would not conclude that the backplate must have a tube joint. We also conclude that the inventor did not act as his own lexicographer here and clearly require the backplate to have a tube joint. Because the district court’s judgment of noninfringement was based on an erroneous claim con-struction, we vacate that judgment and remand for fur-ther proceedings.


The court’s statement  “in view of the claims, specification, prosecution history, and prior art patents” is a little redundant because the prior art patents were cited during the prosecution history — therefore under Phillips v. AWH, 415 F.3d 1303 (Fed. Cir. 2005) those cited prior art patents actually form part of the prosecution history.  See Phillips at 1317 (“The prosecution history, which we have designated as part of the “intrinsic evidence,” consists of the complete record of the proceedings before the PTO and includes the prior art cited during the examination of the patent. Autogiro, 384 F.2d at 399.”).

This case is reminiscent of Arthur A. Collins, Inc. v. Northern Telecom Ltd., 216 F.3d 1042 (Fed. Cir. 2000), where the court said:

Even when prior art is not cited in the written description or the prosecution history, it may assist in ascertaining the meaning of a term to a person skilled in the art. See Vitronics Corp. v. Conceptronic, Inc., 90 F.3d 1576, 1584, 39 USPQ2d 1573, 1578 (Fed.Cir.1996). When prior art that sheds light on the meaning of a term is cited by the patentee, it can have particular value as a guide to the proper construction of the term, because it may indicate not only the meaning of the term to persons skilled in the art, but also that the patentee intended to adopt that meaning.

You can read the entire Laryngeal Mask opinion here: [Read].

Comments are closed.