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Utility patents are granted for inventing or discovering a new machine, device, process, manufactured object, or composition of matter, such as a new chemical compound (or improving a current machine, device, process, manufactured object, or composition of matter). Utility patents are granted for a 20 year period. Utility patents are the most common type of patent and can include a wide range of things, such as velcro, computer hardware components or software, new medicines, and more, almost anything that can be manufactured by humans could be eligible for a utility patent.
USPTO Utility Patent Application Filing Guide
Example of a utility patent: Cargo carrier, Patent No. US 427948A
Design patents are granted for inventing a new, original, and ornamental design for a manufactured item. This could apply to the design of items including lamps, buildings, cell phone cases, and more. Design patents protect only the appearance of the item; they are only for designs that are ornamental, but not functional. Design patents are granted for a 14 year period.
Design Patent Application Guide
Example of a design patent: Solar panel arrangement, Patent No. US D600200 S1
Plant patents are granted for inventing or discovering any distinct, new variety of plant that can be asexually reproduced (plant patents apply only to plants that do not naturally reproduce through pollination). Plant patents are granted for a 20 year period.
USPTO information about plant patents
Example of a plant patent: Strawberry Plant Named 'DrisStrawThirty,' Patent No. US 20130276183 P1