Patent claims and patent coverage

How much of a change avoids infringement?

The coverage of a patent is defined by its ‘claims’. Myths such as ‘a 10% change avoids patent infringement‘ are not helpful.

The wording of the claims is critical. Each claim is a single sentence that can be thought of as a list of features. Generally speaking, to infringe a patent claim, each and every feature of the claim must be taken.

Example patent claim

A plumbing fitting including:

  • an inlet conduit;
  • a first outlet conduit;
  • a second outlet conduit;
  • a valve for closing the first outlet conduit; and
  • a solenoid valve for closing the second outlet conduit.

Plumbing fittings which do not include a solenoid valve for closing the second conduit are not covered by this claim. Infringement could be avoided by substituting another type of valve for the solenoid valve.

On the other hand:

  • the claim simply specifies ‘a valve for closing the first outlet conduit’ – a plumbing fitting including any type of valve for closing the first outlet conduit is covered; and
  • the claim is silent on the inlet conduit having a valve, so the claim covers plumbing fittings with or without a valve on the inlet conduit.

A patent will typically include multiple claims of differing scope. To successfully enforce a patent, only one claim need be valid and infringed.

The approach to claim interpretation varies from country to country. In Australia, claim wording must be interpreted from the point of view of an individual familiar with the field of technology and given its plain and ordinary meaning in the context of the patent specification read as whole. Some countries, most notably the US, have rules which vary the scope of coverage relative to the plain meaning of the claim wording.

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