On The Functional Limit In Patent Claim

There are a growing number of patent applications in electronic andmechanical field, and more and more foreign patents in China. And a lot ofpatent claims are described in the functional limit expression. The functionallimit has advantages in some situation. So many countries have makeprovision for it.On the issue of determining the scope of protection in China, because itis not a same standard explaining in patent application and infringementjudgment, a number of issues happened. In the stage of patent application，according to the ‘examination guideline’，the patent claims with functionallimit expression，should be explained as all means which can make thefunction works; In the stage of infringement judgment, according to the‘The supreme people’s court on the trial of infringing the patent dispute cases application of law in the explanation of some issues’,for the patentclaims with functional limit expression, the court should determining thescope of protection with patent specification and illustrations. However, thereare big differences and make the public bewilderedThis paper discussed the definition of functional limit, and explained thevalue and status of it. Then expound how to write a patent claim withfunctional limit. For its problem, with a case and the experience of US，givesome suggestion for China.