In re Patent Infringement: Doctrine of Equivalants

Doctrine of Equivalants
= it is a legal rule in most of the world's patent systems that allows a court to hold a party liable for patent infringement even though the infringing device or process does not fall within the literal scope of a patent claim, but nevertheless is equivalent to the claimed invention. U.S. judge Learned Hand has described its purpose as “being or temper unsparing logic and prevent an infringer from stealing the benefit of the invention.” A classical case in United State is, Graver Tank & Manufacturing Co. v. Linde Air Products Co., (1950)

There are two limitations suppress Doctrine of Equivalents: 1) all element test; and 2) prosecution history estoppel.

All element test is is a legal test used in US patent law to determine whether a given reference anticipates a patent claim. The rule is also applicable to an obviousness analysis. Under the rule, a single reference (for anticipation) or the combination of references relied upon (for obviousness) - plus the ordinary knowledge of persons skilled in the art-must explicitly or implicitly provide each and every claimed element.

Prosecution history estoppel is a term used in United States patent law to indicate that a person who has filed a patent application, and then makes amendments to the application to accommodate the patent law, has no cause of action for infringement to the pre-amendment patent claims that were amended.