A patent has a preamble in its specification. The preamble is an introductory phrase to introduce the subject matter of the claims, defines a work concept or states of purpose or use of the invention. The preamble does not define the scope of invention rather it is an introduction to body of that claim which serves the function.
The preambles can be of any length; however, shorter preambles are mostly preferred. The preamble is similar to the preambles of the claims, but can vary as needed. In one example, a preamble such as, i) ‘an apparatus comprising’ can be considered overly broad or ii) composition of matter that describe a new material.
Typically, claims of patent specification contain three major components which are i) a preamble, ii) a transition term and iii) a body. The preamble should not embrace unnecessary limitations; if a constraint is needed for the claim, it should be included in the body of the claim, using ‘whereby’ or wherein clause. Further, it is important that the preamble should match the invention described in the patent specification. If the specification describes ‘a chain’, then the claim should not specify ‘a bracelet’; similarly, if the invention can be used in headphone or watch, the claim should not specify just ‘headphone’ or ‘watch’.
A good strategy for drafting a preamble is to include preamble terms that make the claim scope seems rational, however it can be drafted that these limitations may not construe to narrow the claim.