What is unity? How to judge whether a patent application is single?

How to judge whether a patent application is single? An application for a patent for design shall be limited to the use of one design for one product. This is also the principle of "one invention, one creation, one application". According to this principle, two or more inventions cannot be filed in one patent application, but should be filed separately. How to judge whether an application for a patent has more than two inventions or utility models that are singular but belong to the general inventive concept can be filed as one application. Whether two or more inventions or utility models belong to a general inventive concept should be judged by whether they are technically related to each other and whether they contain one or more identical or corresponding specific technical features, in which specific technical features refer to the technical features that each invention or utility model contributes to the existing technology as a whole. Claims of two or more invention applications belonging to a general inventive concept may be one of the following: (1) independent claims of two or more similar products or methods that cannot be included in one claim; (2) the independent claim of the product and the method for manufacturing the product; (3) the independent claim of the product and the use of the product; (4) the product, the method specially used for manufacturing the product and the independent claims for realizing the method and the use of the product; (5) the independent claim of the product, the method specially used for manufacturing the product, and the equipment specially designed for implementing the method; (6) the independent claims of the method and the equipment specially designed for implementing the method. Claims of two or more utility model patent applications belonging to a general inventive concept may be independent claims of two or more products that cannot be included in one claim. Designs of two or more products belonging to the same category and sold or used in sets may be filed as one application. To judge whether more than two designs can be filed as one application, we should look at whether the products used in the designs belong to the same subcategory in the product classification table stipulated in China's patent law, whether the design ideas of the products are the same, and whether they are sold and used at the same time in the customs. For example, the design of the China Zodiac with the same design concept as that used on the key ring can be applied as a patent for design.