The purpose of a patent under U.S. Federal Law is to protect an inventor by preventing others from making, using or selling the patented invention in the United States or from importing the invention into the U.S.To be eligible for a patent, an invention must be, at a minimum, novel and non-obvious. Additionally, inventions also must be useful in order to be eligible for a utility patent.
The rules for eligibility of a patent depend on what type of patent an applicant applies for. U.S. laws provide for utility patents, design patents and plant patents, with utility patents being the most common, and plant patents being the least common. According to the U.S Patent and Trademark Office, a plant patent is granted for the invention or discovery and asexual reproduction of "a distinct and new variety of plant, other than a tuber propagated plant or a plant found in an uncultivated state." Utility patents apply to functional inventions of any type, while design patents apply to non-functional inventions of any type.
A basic requirement of all three types of patents is that the invention must be novel, meaning new and original. To determine whether an invention is novel, the inventor must conduct extensive searches of existing patents on file with the U.S. Patent and Trademark Office. If the invention already falls under an existing patent, the invention is not novel and therefore is not eligible for any type of patent.
All three patents also require the invention to be non-obvious. Describing what is obvious or non-obvious can be challenging, but in general, an invention is non-obvious if somebody experienced in the field would consider the invention as innovative or surprising.
An invention does not have to be useful to qualify for a plant patent or a design patent, but it does have to be useful to qualify for a utility patent. Useful is a very broad term, and it can apply to inventions that are only theoretical. Generally, an invention is useful if any person might consider it useful, even if other people would not consider the invention useful. Common examples of utility patents include new manufacturing technology, computers and cell phones, batteries and pharmaceutical drugs.