53 (4) (2001), p. 48.
JOM is a publication of The Minerals, Metals & Materials Society
It is generally understood that opinions of legal specialists are required
to obtain a reliable interpretation of the scope of a patent claim. Frequently,
others engage in claim reading to get an initial impression regarding what a
A patent application must contain a sufficiently detailed, written description of the invention to enable one skilled in the particular art to which it relates to practice the invention without having to engage in undue experimentation. The claims, which are the numbered paragraphs that appear at the end of the patent, define the scope of the exclusionary property rights, giving the patent owner the right to keep others from making, offering for sale, selling, using, and importing the patented invention. It is, therefore, critical to be able to determine with a reasonable degree of certainty which practices are embraced by the claims and which are not.
In an article published in the November 1995 issue of JOM, guidance was provided regarding general aspects of reading a patent claim. This article is directed toward a statutory provision that permits an element in a claim, or a combination, to be expressed as “a means or step for” performing a particular function. (For simplicity of discussion herein, the expression “means for” will be used as embracing both the “means for” use in connection with the structures of products and apparatus, as well as compositions of matter, and also embracing the corresponding expression “step for,” which would be the more commonly used term in method type claims.) The claim is not required to recite the structure, material, or acts in support of the functional recital. The statute requires that the expression be interpreted to cover items disclosed in the specification which will perform the recited function and “equivalents thereof.” In the past, this last recital created a divergence of interpretation between the U.S. Patent and Trademark Office and the courts.
A number of years ago, the Patent and Trademark Office, when looking at patentability of an invention, felt that the means plus function recital in a claim, or step plus function recital in a claim, embraced what was expressly disclosed in the patent application and any item that would perform the same function. The courts, in looking at issued patents, took a more restricted view and limited the scope of such a recital to what was expressly disclosed in the patent and equivalents thereof.
For example, suppose that a patent application claimed a particular assembly and stated that component A was secured to component B by mechanical fasteners, with screws and nails both being expressly disclosed. Suppose also that the claim recited “means for securing component A to component B.” If the Patent and Trademark Office examiner found identical or similar components secured to each other by an adhesive, rather than screws or nails, the examiner might well take the position that the use of adhesive was embraced within the claim and known in the prior art and, therefore, the claim was not patentable. By contrast, the courts might have looked at the same situation and concluded that, in the context of infringement or validity of a patent claim, the adhesive was not an “equivalent” of the mechanical fasteners and therefore, was not embraced by the claim. In the past, therefore, the Patent and Trademark Office and the courts did not agree on this issue.
Current practice is uniform. The Patent and Trademark Office employs the standard that a claim covers what it disclosed in the application and what amounts to reasonable equivalents thereof. This is the view the courts had taken previously and continue to use.
The result is that the interpretation of a “means for” recital in a claim may result in a narrower construction than would have been the case with the prior Patent and Trademark Office approach. This has caused more patent practitioners to draft claims with recitals of elements or steps in terms that do not use the “means for” expression either in lieu of or in addition to such “means for” expression.
Additional considerations may complicate the interpretation of a claim. For example, it is clear that within certain parameters one is entitled to have claims that are broader than the actual disclosure. If, for example, one were to invent an upholstered chair having four legs, a seat, a backrest, and a pair of armrests, unless prohibited by other considerations, one might have a patent claim that said, “A chair comprising a seat, a plurality of depending legs and a backrest.” This hypothetical claim, which contains no “means for” recital, would certainly cover a number of chairs that were not expressly disclosed in the application. For example, the claim does not require that the chair be upholstered, does not require that there be armrests, and does not require that it have four legs. The concept of law illustrated by this example, as well as the foregoing discussion of “means for” recitals, are examples of how patent claims are not necessarily limited to what is expressly disclosed in the specification.
The “doctrine of equivalents” also provides property rights broader than what is expressly recited in the claim. This judicially created doctrine, in effect, states that even though something is not expressly disclosed in a patent application and also does not literally satisfy every recital of a claim, as a matter of equity, one may be held to be an infringer if an element or elements not found in the alleged infringing structure or practice has an equivalent. This standard of equivalents is different from the “means for” standard in that it requires that, for each claim element not found in the article, there is, on an element by element basis, a substitute for a recited element which accomplishes substantially the same function in substantially the same way to achieve substantially the same result. Considering this principle in the context of the previously discussed example of the disclosures of securing component A to component B by mechanical fasteners, such as nails or screws, under the doctrine of equivalents, one might conclude that an adhesive would be an equivalent which results in the claim covering the structure.
It is important to bear in mind that a too literal, expansive interpretation of a “means for” recital in a claim can lead to an overly broad, erroneous conclusion as to what is covered by a particular claim. The underlying principle involves a balancing of interests between the patentee, who has created or acquired the patent rights, with the legitimate right of the public to engage in practices that are beyond the scope of the patent claims.
The analysis requires an understanding of what elements or steps in the specification are actually disclosed and, in addition, what would be the equivalent thereof. The ultimate decision, when the issue goes beyond casual interest to being a matter of legal significance, should be left to a specialist in intellectual property law.
Arnold B. Silverman is chair of the Intellectual Property Department and a member of Eckert Seamans Cherin & Mellott, LLC in Pittsburgh, Pennsylvania.
For more information, contact A.B. Silverman at Eckert Seamans
Cherin & Mellott LLC, 600 Grant Street, 44th Floor, Pittsburgh, Pennsylvania
15219; (412) 566-2077; fax (412) 566-6099; e-mail email@example.com.
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