Google has launched a service that will allow users to search over seven million patents granted in the US.

Under the new patent search facility consumers will be able to view details of copyright granted by the US patent and trademark office to products such as contact lenses and the unicycle.

Software engineer Doug Banks said: "It's a natural extension of our mission to make this public domain government information more easily accessible using Google's search technology."

He added that the search engine company hoped to eventually extend the service to other patent providers.

Users will be able to view patents dating back to 1790 and can search by key words, inventors' names and filing dates.

The service uses the same technology as Google's online book search facility, which allows consumers to scroll through pages and zoom in on text and illustrations.

Earlier this month, the search engine company announced the closure of Answers - the service which let users ask researchers a question on any subject they wished.