Design and Utility Patent Distinctions

What is the difference between design and utility patents? A design patent protects the appearance of an article to be manufactured. It does not protect the functional or structural features of the article. If the functional or structural features are to be protected, then a utility patent should be sought. Another difference is the duration of the patent -- 14 years from date of issuance for a design patent and generally 20 years from the earliest filing date of the utility patent application. The tests for infringement also are different. For a design patent, the test is the whether an ordinary observer (familiar with the art) believes the accused design is the same as the patented design and for a utility patent, the test requires construing the asserted claims and then determining whether the accused product or method is covered either literally or equivalently by the asserted claims.

In the automotive field, patents have been granted for tread patterns. For example, Goodyear has received design and utility patents regarding tread patterns. U.S. Patent No. 5,603,785 is a utility patent entitled "Tire Including Two Aquachannels on One Side." See this. U.S. Patent No. D534,859 is a design patent (available here) for tire tread. It appears that this patent covers Goodyear's Fortera TripleTred tire, as demonstrated below by an image of the tire (available here) and a figure from the patent:


Goodyear promotes the Fortera TripleTred tire as having "Three Innovative Tread Zones For Superb Traction In Any Weather - Rain, Ice Or Dry" and shows three images of the tread pattern with highlighting to demonstrate each zone -- water zone, ice zone, and dry zone. See this. Below are the three images from Goodyear's website (from left to right: water zone, ice zone, dry zone) above a figure from U.S. Patent No. D534,859:



According to Goodyear, the "Water Zone helps evacuate water off of the tread and away from the tire;" the "Ice Zone helps provide enhanced gripping power on icy or snowy roads;" and the "Dry Zone offers confident maneuvering around curves on dry pavement." Id.

Assuming that the patent does cover the Fortera TripleTred tire and given the manner in which Goodyear shows and describes the zones on its website, is the tread pattern depicted in the patent ornamental?