How to write patent claims. How to draft claims for a patent application

Claims drafting is as much art as science. There is a body of law that has built up over the past 300 or so years in which patents have been granted in North America, which dictates to some degree how claims must be drafted. Within that framework, however, there are many interpretations of how best to encapsulate an invention in words, and the ultimate arbiter of any patent claim is the Court.

As an overview, a claim is made up of three parts: the preamble, the transitional phase and the body. In discussing claims construction, let's use an example, perhaps the original velocipede patented by Pierre Lallement:

The velocipede consists of a frame having a pivoting fork, two wheels, of which the front wheel pivots within the fork and has pedals, a seat and a handlebar also attached to the pivoting fork. So an example claim might read:

A two-wheeled velocipede for transportation (preamble), comprising (transition):
a frame for receiving a rear wheel, the frame having a seat mounted thereon;
a fork pivotally mounted within said frame, having a handlebar extending from its top, the fork for receiving a front wheel;
a rear wheel rotatably mounted within said frame;
a front wheel rotatably mounted within said fork, the front wheel having two pedals mounted opposite to one another
wherein the pedals are pushed to provide motive force to the front wheel, and the handlebars may be turned so that the front wheel pivots (body).

The preamble describes the invention using normal words (as velocipede was back in the day), and the transition set up the components. The word "comprising" means minimally including, so that more elements may be present than are listed here. If a list of components is exhaustive, in that any more components would prevent the invention from working, for example, As you can see, the bulk of the claim is the body which describes components, describes how they fit together, and then usually a "wherein" clause describes how the invention operates. In choosing the components to describe, what you are looking for is the minimal elements that are required to make the invention perform. Anything bonus or not strictly necessary should be left out

The entire claim language must correspond with the language used for the same components in the description. Also, elements must be introduced by an indefinite article ("a"), and thereafter referred to by a definite article ("the"). Punctuation is important - the claim is one big sentence separated by semicolons or commas; a period only appears at the end.