Many businessmen and engineers evaluate patents for one reason or another. Usually, the process boils down to an interpretation of patent claims. As defined in other posts on this site, patent claims are the governmental monopoly granted to an inventor in exchange for the inventor’s disclosure of technology.
Unfortunately, claims are usually stated in a technical and arcane language. Furthermore, U.S. courts have held that claims do not always mean what they say. In other words, to interpret the scope of the claims, one must often rely on more than just the “plain meaning” of the claim language.
To further complicate matters, Federal case law has also established legal doctrines which have both expanded claim breadth and have decreased claim breadth. So, to interpret the proper claim scope for any given claim, several sources are usually analyzed and several legal doctrines are usually applied.
To determine the meaning of a claim, the plain wording and terms of the claim are obviously consulted first. The wording and terms are then compared to the usage of the claim terms and wording as used in the patent specification. Often, the terms will be defined in the specification or used in ways which will limit the scope or meaning of the terms.
Next, the patent prosecution history will be consulted. The patent prosecution history is the back and forth negotiation with the USPTO to arrive at the allowable claims. In many situations during prosecution, the patentee will make statements or arguments which can be used later to define or limit the scope of the claims.
Other related patents or patent applications owned by the patentee may also be consulted to see if the patentee defined similar terms in these applications.
Patents are presumed to be valid. So, if a claim element can be interpreted in two different ways and one of those ways will invalidate the claim due to prior art, the claim element will be interpreted in such a manner as to uphold the validity of the patent.
Outside sources or extrinsic evidence such as industry dictionaries or reference materials (published around the time of the patent filing) may also be consulted in certain situations.
Finally, certain judicial doctrines are applied to the claim scope. For instance, under the doctrine of equivalents, certain patent claim terms may be broadened to include their “equivalents.” As an example, if the claim uses a nail, it is possible than a product that uses a screw might also infringe on the claim if the screw performs the same function as the nail, in the same way to achieve the same result.
The above process is only one suggested way of determining claim scope. When in doubt, talk to a patent lawyer.