Claim drafting is one of the most important skills that patent attorneys must master. I sort of have this love/hate relationship with claims.
I love claims because claims basically define the scope of patent protection, and for the most part, they're all you need to worry about during prosecution (as long as you have a solid spec and drawings).
But I hate claims because they can be very frustrating to write. For starters, some patent examiners can be very particular about word choices. Also, your entire claim can be rejected even though a prior art reference does not actually claim whatever you're claiming, so long as the prior art discloses whatever you're claiming.
Recently, I've been teaching someone how to write claims, so I thought I'd share some pointers I've used to teach.
I think of drafting claims as building the invention. If I have an apparatus, I usually pick out the biggest component and use it as a foundation to build upon it like I'm building a house. I'll stop adding elements to my foundation component when it is operable. Then I identify one element that distinguishes my invention from the prior art inventions. I add that one element to my foundation. This claim now becomes my independent claim. Additional elements are then introduced in my dependent claims.
I'll use a wheelchair as an example. Let's say that the wheelchair has a frame, a seat, a backrest, front wheels, rear wheels, handles, and a pair of footrests. What makes this invention special? The novel feature of this wheelchair is a front wheel lock.
1. A wheelchair, comprising:
a wheelchair frame connected to a seat and a backrest;
wherein said seat is substantially perpendicular to said backrest;
a front portion of said wheelchair frame having a pair of front wheels;
a front wheel lock connected to said pair of front wheels;
wherein said front wheel lock prevents said pair of front wheels from rotating in a locked position;
a rear portion of said wheelchair frame having a pair of rear wheels.
I stop here. Notice I did not add the handles and the footrests because you don't need handles and footrests to have a working wheelchair. So I introduce these elements in dependent claims.
2. The wheelchair of claim 1, further comprising handles attached to a top portion of said wheelchair frame.
3. The wheelchair of claim 1, further comprising a pair of footrests pivotally attached to a lower portion of said wheelchair frame.
The wheelchair frame structure probably needs to be better defined if these claims were to be used for a real patent application. But you get the idea.