Priority of Patents and Continuation-in-Part

A patent application is assigned a priority date for the art disclosed in the application. Any aspect of the patent application which was known to the public before the priority date cannot be claimed as an invention. From the priority date onwards the knowledge contained in a patent application must be considered as prior art and excludes others from any attempt to patent the same subject matter. In general the first filing of a patent application establishes the priority. Referring back to the initial priority date, further applications in other countries can be made within a period of usually 12 months. Applications first filed in the European Patent Office or in individual PCT member states can also be used to claim a priority date for a PCT application. 

Although the same basic rules on the priority apply to USA patent applications, two special provisions of the US patent laws should be mentioned which have some influence on the effective priority date of an invention. 

Until a US patent is issued, a Continuation-in-Part (CIP) may be filed by the applicant. The same or a similar invention is refiled with new information which may enable the inventor to change or extend the patent claims and to better define the subject matter and its use. If the CIP is based on the same invention and not on later art than the original application, the priority date of the first application may be maintained. To retain the priority is, in fact, the intention of most CIP applications. New patent claims which are based upon information added in the CIP ( new matter ) will get a separate, later priority. 

Similarly, in Australia, a provisional patent application can be lodged to establish priority the complete application must be filed within 12 months. 

A second exception in the USA which influences the effective priority date of an invention (but not the official priority of the patent ) is the so-called swearing-back according to the Code of Federal Regulations, Title 37 (37 CFR, 1.131). If there is an interference with other patents or patent applications, the US patent authority will ask the applicant of USA-derived inventions to provide detailed information on the actual time of conception of the invention, reduction to practice and on all further steps which finally led to the current application. Proof of those activities can be provided by laboratory notebooks and other relevant documents, e.g. those which prove the involvement of a patent attorney during the process of drafting and filing the application in question. This information will be considered in order to assess the effective time when the invention was made and when it was reduced to practice in order to fulfil the requirements for patentability. 

---