Copyright © Françoise Herrmann
Just to clarify the differences between design and utility patents, beyond statutory form since design patents only have one claim and an optional description or specification, here is an explanation of the conceptual differences per US Code Title 35, Sections 101 and 171, as stated in a USPTO brochure intended for applicants.
In general terms, a “utility patent” protects the way an article is used and works (35 U.S.C. 101), while a "design patent" protects the way an article looks (35 U.S.C. 171). Both design and utility patents may be obtained on an article if invention resides both in its utility and ornamental appearance. While utility and design patents afford legally separate protection, the utility and ornamentality of an article are not easily separable. Articles of manufacture may possess both functional and ornamental characteristics. (USPTO, p. 2)
It follows then that a single artefact can be patented both for its utility or function and its visual or ornamental properties, depending on whether these separate aspects of invention fulfill all the conditions of patentability. This is the case, for example, with the Frank O. Gehry wood lattice furniture where the visual or ornamental appeal of the furniture is patented as design patents, and the manufacturing process of the interlocking wood lattice is patented in utility patents.
Specifically, the Gehry wood lattice furniture is patented in design patents such as: USD344191 titled Dining chair, USD334098 titled Chair or USD341263 titled Club chair, and the wood lattice manufacturing process of this furniture is also patented in two utility patents, US5284380 and US5154486, both titled Furniture comprising laminated slats and methods of manufacturing such furniture
Included below is the abstract for the utility patent US5154486 titled Furniture comprising laminated slats and methods of manufacturing such furniture, and a patent figure with corresponding image of the marketed product -- just to anchor the beautiful basket weaving of this line of furniture into something you can see!
Furniture comprises a strong, aesthetically appealing, woven lattice of interlocking slats. The slats are made of wood laminate having indentations allowing fitting of the slats across one another so as to form the lattice. Advantageously, the furniture may be manufactured of a single type of material, that of the bent wood laminate slats. No other supporting structural material is needed to make the furniture simultaneously possess the advantages of being sturdy, aesthetically appealing, economical to manufacture, and light in structure and appearance. The methods of manufacturing such furniture has also been included. [US5154486]
USPTO: Guide to filing a design patent application