In the United States a design patent can be granted for a "new, original,
and ornamental design for an article of manufacture". It may only have
a single claim. A design patent lasts for 14 years from the date granted.
Design patents MUST be for the design and not the function
or utility of an invention.
Where a design contains both functional and non-functional elements,
the scope of the claim will be construed in order to identify the non-functional
aspects of the design as shown in the patent.
Furthermore, the scope is limited to the "overall ornamental visual impression".
Designs that are hidden in their end use, or are necessary for the proper
functioning of the device are not ornamental and therefore not patentable
as a design patent.
Below are a few examples, as well as an index of the 33 design classes.
The column labeled "popularity" shows the relative number of
patents in each class with an orange graph: