Can a patent drawing have numbers like 6A02, 6A04 etc?

Question

My patent specification has around 20 chapters and each chapter has multiple drawings.

My drawings are numbered like this. FIG. 1A, FIG. 1B, FIG. 2A etc. i.e. If Chapter 2 has only 2 drawings, then the drawings will have numbers like FIG. 2A and FIG. 2B.

And I have numbered each unique feature like 202, 204 etc. This kind of numbering works fine when you don't have more than 50 unique features.

My chapter 6 has around 20 drawings and more than 50 unique features. So I would like to name the feature numbers like 6A02, 6A04 etc.

Is this accepted or I have to follow some standard for diagram numbers?

Answer 1

The MPEP says reference characters are preferably numerical. Patent applications do not usually have "chapters" and there is no need to invent a convention like that. As mentioned, even numbers let you add a number later without worrying about re-numbering but renumbering would not be needed anyway. That is not true of drawings - they need to be in order. There is no requirement that says a reference 500 can't appear on a figure full of references in the 200's. If you have a "2nd embodiment" and want to have all of the reference designators remind the reader of that, feel free to start with 2000 rather than 200. MPEP on drawings

Answer 2

The more complicated we make to understand drawings then there are high chances that even the examiner will get confused and issue an office action on it. The basic necessity of patent application is it should enable a person skilled in the art to understand.

Using numbers than characters are preferable.