The specification is an indispensable tool for claim interpretation. As stated in a prior post, "a patentee can be his own lexicographer." This means that the patentee can invent and define new terms within his specification, or even give existing terms different meanings than their ordinary definitions.
However, there is a Canon of Construction that prevents the specification from being used to add limitations to the claims. Frequently, the patentee will wish to incorporate such limitations to avoid the prior art, or an alleged infringer will wish to incorporate such limitations to avoid a finding of patent infringement. The practice of adding limitations from the specification into the claims is impermissible in either case.
The only exception to the rule that: "limitations found in the specification cannot be read into the claims" occurs in what are known as "means-plus-function" claims. This is a special format of claiming an invention reciting a "means for" accomplishing some function or series of functions, but with no actual structure recited in the claim. In "means-plus-function" claims, the structure in the specification is actually what is used to structurally limit the claims. The use of "means plus function" claiming is in precipitous decline, however, since such claims currently appear in less than 10% of all patent applications filed. Fifteen years ago, nearly one quarter of all patent applications included at least one means-plus-function claim.
For more information on means-plus-function claiming, please see the article at Patently-O:
http://patentlyo.com/patent/2013/01/means-plus-function-claiming.html
However, there is a Canon of Construction that prevents the specification from being used to add limitations to the claims. Frequently, the patentee will wish to incorporate such limitations to avoid the prior art, or an alleged infringer will wish to incorporate such limitations to avoid a finding of patent infringement. The practice of adding limitations from the specification into the claims is impermissible in either case.
The only exception to the rule that: "limitations found in the specification cannot be read into the claims" occurs in what are known as "means-plus-function" claims. This is a special format of claiming an invention reciting a "means for" accomplishing some function or series of functions, but with no actual structure recited in the claim. In "means-plus-function" claims, the structure in the specification is actually what is used to structurally limit the claims. The use of "means plus function" claiming is in precipitous decline, however, since such claims currently appear in less than 10% of all patent applications filed. Fifteen years ago, nearly one quarter of all patent applications included at least one means-plus-function claim.
For more information on means-plus-function claiming, please see the article at Patently-O:
http://patentlyo.com/patent/2013/01/means-plus-function-claiming.html
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