How does the written description requirement relate to means-plus-function claim limitations?
Means-plus-function claim limitations have a special relationship with the written description requirement. According to MPEP 2163.03:
“A claim limitation expressed in means- (or step-) plus-function language ‘shall be construed to cover the corresponding structure, material, or acts described in the specification and equivalents thereof.’ 35 U.S.C. 112(f) or pre-AIA 35 U.S.C. 112, sixth paragraph.”
However, if the specification doesn’t provide sufficient corresponding structure, materials, or acts that perform the entire claimed function, two issues arise:
- The claim becomes indefinite under 35 U.S.C. 112(b) because the applicant hasn’t particularly pointed out and distinctly claimed the invention.
- The claim lacks adequate written description under 35 U.S.C. 112(a).
The MPEP explains:
“Such a limitation also lacks an adequate written description as required by 35 U.S.C. 112(a) or pre-AIA 35 U.S.C. 112, first paragraph, because an indefinite, unbounded functional limitation would cover all ways of performing a function and indicate that the inventor has not provided sufficient disclosure to show possession of the invention.”
Therefore, when using means-plus-function limitations, it’s crucial to provide clear and sufficient description of the corresponding structure in the specification to satisfy both the definiteness and written description requirements.
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