Many inventions are not entirely new concepts, they are simply improvements over other inventions. So the question of how different is different enough often arises. This question has different answers depending upon whether the inquirer wants to avoid infringing an already issued patent or wants to obtain patent protection of his or her own.
In the case where a patent already exists and the inquirer simply wishes to avoid infringement, the question of “How different is different enough?” may be answered pretty straightforwardly. First, the patent must be reviewed to determine if it is still a valid, enforceable patent. Some things that may render a patent unenforceable are the non-payment of maintenance fees or an expired patent term. If the patent is invalid or unenforceable, the patent cannot be infringed. However, if the patent is valid and enforceable, the claims of the patent must be reviewed to make a determination of infringement. The claims are the numbered paragraphs at the end of an issued patent. Each claim generally comprises several elements. If any device contains each and every element of any single claim of a valid, enforceable patent the device infringes the patent. The expertise of a patent professional should be employed to determine the presence or absence of any element because each element of a patent often has a specific meaning which may be different than the common meaning of the terms used to describe the element.
In the case where a person wishes to obtain a patent on something similar to a device disclosed in an existing patent, the question of “How different is different enough?” is somewhat harder to answer. In order to obtain a patent on a device, the device must be both novel and non-obvious. This means that it cannot have already been invented and that it cannot be an obvious combination of previously invented components. Generally, there is not much difficulty in determining whether or not an invention is novel. It is novel if the exact same thing has not already been invented. The difficulty lies in determining whether the invention is obvious. This determination is somewhat subjective. Consultation with a patent attorney is recommended to discuss the possibility of a patent examiner deeming a particular invention obvious.