A utility patent is the most used and known type of patent. Utility patents cover structural and functional aspects of an invention. Design patents cover the aesthetic features, to cover the ornamental design of an object that has practical utility. Examples include a new shape of a perfume bottle, the shape and features of the tread of a shoe, the shape of a toy, and computer icons. Designs that are related to the function of the article, such as the shape of a gear, cannot be covered by a design patent. Articles that exist for purely aesthetic reasons, such as a work of art, also cannot be covered by a design patent. (The work would be covered by copyright instead.)
An invention may be entitled to both a utility patent and a design patent. The utility patent would protect the structure of the inventive article and the way it works, and the design patent would protect the way the article looks.
The requirements for both utility and design patents require the structure or design, respectively, to be novel and non-obvious. In design patents, the drawings constitute the claims of the design patent, and the drawings must clearly show the features sought to be protected. For utility patents, the claims are separately written and must be supported by the detailed description and the drawings. The drawings of the design patent will typically be more detailed than in a utility application as they will often show more views of the invention than the utility patent.
Design patents are generally easier and less costly to prepare than utility patents. The pendency (from filing to issuance) for design applications are considerably shorter than for utility patents. Utility patents require maintenance fees to be paid, while design patents do not. The term of a utility patent is 20 years from the date of filing, while the term of a design patent is 14 years from the date of issuance. Inventors should always consider whether their inventions are eligible for both design and utility patent protection.