Let's take a look at the definition of utility model patents and invention patents (excerpted from the Patent Law of the People's Republic of China):
An invention is a new technical solution proposed for a product, method or improvement thereof.
Utility model refers to the shape, structure or combination of products proposed for practical new technical solutions.
From the above definition, it can be seen that utility model patents can only be used to protect a product, and the product should be manufactured by industrial methods, with a certain shape, structure and occupy a certain space of the entity.