No matter what product has drawings, you can apply for a patent as long as you can explain the structural connection and working principle of the product according to the drawings.
There are too many specific contents of patent application. If you want to apply for it yourself, I suggest you have a look at the Patent Law, its implementing rules and the patent examination guide. Usually, after a month of hard study, you can go through the application procedures. However, if you want to write qualified patent documents (claims, specifications and drawings), you usually need to work as a patent agent for at least three to five years under the guidance of an agent with twenty or thirty years of patent litigation experience. Therefore, it is recommended to find a professional agency to represent your patent.
Note: Obtaining a patent certificate and obtaining real patent protection are two completely different concepts. You may get a patent certificate by studying the Patent Law, the Detailed Rules for the Implementation of the Patent Law and the Patent Examination Guide for about a month, but you can't accurately define the technical scope that needs to be protected (if the scope is large, others will be invalid; If the scope is small, it is easy for others to change the product out of your protection scope. So, in fact, getting a certificate can't protect it.