What are patent claims?

The claims of a patent define what a patent does and does not cover. The owner of the patent has the right to exclude others from making, using or selling, only those things which are described by the claims. Reading and understanding the claims of a patent is the key to determining if the patent is being infringed by a product or process. Even if a product seems very similar to the invention described in a patent, if the product does not infringe on the claims of the patent than the patent owner cannot claim infringement.

The claims section of the patent is separate and distinct from the other sections of the patent. It is possible for a carelessly drafted patent application to disclose parts of the invention in the specification section, but to omit claims to all the parts of the invention. In that case, the inventor could be granted a patent which would have holes that infringing products could slip through.

Reviewing the claims of a patent to determine what protection it grants:

claims are written in a very legalistic and stilted way;
the patent specification and drawings define the scope of words used in the claims, the words used in the claims don’t necessarily have the exact dictionary definition, they the must be properly interpreted and explained based on the specification and drawings;
the prosecution history, things that the patent owner said to the United States Patent and Trademark Office while the patent application was being reviewed, might mean some words used in the claims are more limited than they appear;
the “Doctrine of Equivalents” makes some words in the claims might mean more than they appear.

A claim is a sentence. A claim starts with a capital letter and ends with a period. In many cases, claims are typographically broken out in outline form, to make reading the claim easier – but it is not uncommon to find a claim which is presented as a half a page long run on sentence. Claims are numbered sequentially, with claim 1 being the broadest claim in the patent (but not always), and the sub-parts of a claim are often identified by an outline letter or number.

Claims are of two basic types: Independent and Dependent. Independent claims stand on their own. Dependent claims build off of the claims that came before it. Each dependent claim is more narrow than the claim on which it depends. Even though a dependent claims has coverage more narrow than the claim upon which the second claim depends, there are many advantages to using dependent claims.

An example of an independent claim is:

A transportation device for moving people and objects, having a frame, the device comprising:
1. a plurality of wheels coupled to the frame;
2. a steering handle coupled to the frame and to at least one of the plurality of wheels;
3. a plurality of platforms attached to the frame; and
4. means for supplying force to at least one of the plurality of wheels.

This claim has a preamble (“A transportation device…”), the connecting word (or “transitional phrase”) “comprising”, and a list of four elements – wheels, handle, platforms and means for supplying force. The use of the phrase “means for” is an example of words that have special meaning in patent law. When the phrase “means for” is used that triggers a reading of the patent specification to resolve what the claim covers. It is a complex analysis worthy of a blog post dedicated to the topic.

An example of some dependent claims are:

2. The transportation device of claim 1, in which the number of wheels is two.

3. The transportation device of claim 2, further comprising an sound device attached to the steering handle.

4. The transportation device of claim 3, in which the sound device is a bell.

In each of the dependent claims, the preceding broader claim is narrowed to further define the invention. But the dependent claims do not limit the claims that come before them an invention that does not infringe on claim 4 may still infringe on the earlier claims. The independent and dependent claims work together to reserve the broadest patent rights the United States Patent and Trademark Office will allow.