Patent drawing rules are a bit peculiar and limiting. This is especially true in view of modern computers which have revolutionized drawing technologies in nearly every field imaginable. Not patents. The patent rules leave us in the dark ages.
Patent drawings are not typically like engineering drawings. Engineering drawings are meant to provide a very high level of detail. Patent drawings are meant to provide a high level of breadth. These two conflicting objectives can prevent one from using engineering drawings in a patent application. For this reason, it is sometimes best to hire a patent draftsmen familiar with the rules and objectives of patent applications. You might find any one of the following useful in assisting you with your patent drawings.