The Patent Act of 1952 clarified and simplified existing U.S. patent law. It also effected substantive changes, including the codification of the requirement for non-obviousness^[1][2] and the judicial doctrine of contributory infringement.^[3] As amended, it is codified in Title 35 of the United States Code.

The Act originally divided the patent law into three parts:

Part I — Patent and Trademark Office

contains provisions governing that Office, its powers and duties, and related matters.

Part II — Patentability of Invention and Grant of Patents

sets out when and how patents may be obtained.

Part III — Patents and Protection of Patent Rights

relates to the patents themselves and the protection of rights under patents.

A later amendment added

Part IV — Patent Cooperation Treaty

Intended to simplify the filing of patent applications for an invention in different countries, the Patent Cooperation Treaty, signed by 35 countries by December 31, 1970, provides (inter alia) centralized filing procedures and a standardized application format. It helps expand established programs of American industry to file foreign patent applications, and encourages smaller businesses and individual investors to become more active in seeking patent protection abroad.

Other amendments to Title 35 concern the renaming from "Patent Office" to "Patent and Trademark Office"; revised fee schedules for application and issue of patents; and modifications in procedures related to the protection of patents.

§ 121 of the Patent Act of 1952 was the first time, when the US Congress addressed the problem of double patenting. Prior to 1952, even when a patent examiner required splitting a patent application into several divisionals, the resulting divisionals were used against each other in courts as grounds for double patenting invalidation. This was an unfair practice to patent owners, who were faced with a loss-loss situation. The Congress did away with the problem, adding § 121, which provides that, when an inventor files a divisional application in response to a restriction requirement, one restricted application “shall not be used as a reference” against the other.^[4]