Short Claims Are Usually Broader Than Long Claims

Many people think of patent claims the way they think of ordinary real estate property claims. They think that a long claim is like a bigger piece of property; it has as more "stuff" in it and is more valuable. But exactly the reverse is true. Every word in a patent claim is another limitation, and the longer the claim is the narrower it is. A shorter claim is almost always better than a longer one, and is more cost effective because it includes more subject matter. As a first example, consider the first person who invents a two-legged chair. Yes, a two-legged chair does exist.

Figure 39 — A Two-Legged Chair Does Exist

Lets assume that the inventor believes metal is the only material strong enough to support a two-legged chair, and he also thinks that metal chairs are only viable if they are covered with fabric. Thus, his broadest claim is "A two-legged chair made of metal and covered with fabric". That might seem like a nice, short, claim, but it is way too narrow as shown by the following series of diagrams. The set of all two-legged chairs is shown graphically below.

Figure 40 — The World Of Two-Legged Chairs

The set of two-legged chairs made of metal is smaller than that (a "proper subset"), and includes only the smaller circle in the diagram below.

Figure 41 — Two-Legged Chairs Made Of Metal

The set of two-legged chairs covered with fabric is also smaller than the set of all two-legged chairs, but in a different manner from two legged chairs made of metal.

Figure 42 — Two-Legged Chairs Covered With Fabric

Finally, the set of two-legged chairs made of metal and covered in fabric is smaller still, because it only includes the overlap of the two subsets. Thus, a claim to a "two-legged chair made of metal and covered with fabric" is too narrow because it contains unnecessary limitations. If the inventor was truly the first person to devise a two-legged chair, the better claim would be to simply state "A chair having two legs".

Figure 43 — Two-Legged Chairs Made Of Metal And Covered With Fabric

As an aside, there is no statute requiring that patent claims be written as a single sentence. That, however, is the tradition, and the USPTO enforces that tradition .