Let's say PERSON A has a patent idea for a new type of golf club... and in their patent application, they say the reason for the invention is that golfers need a better tool to do x,y, and z to help their golf game. They are granted the patent.

But let's say it turns out that this new golf club actually makes a really good cooking utensil as well... and ends up up being used for that purpose more than for the "intended" purpose.

Then PERSON B sees this and comes along and applies for a "new" patent for the exact same basic object, but claims that it is expected to be used as a cooking utensil and therefore doesn't infringe on the prior patent by person A.

Let's say then for the sake of argument that person B is granted the patent also.

Then let's say PERSON C has a completely unrelated invention... but having learned from what happened with persons A and B... they decide not to claim any specific purpose for their invention.

I guess what I'm asking is... is it necessary to specify the expected domain of usage for an invention... or can one simply only say... "it is an object with certain properties and behaviors."

2 Answers 2


A patent must cover something that is "useful" and the patent must disclose how to make and use the invention, usefully. However, if the claims all define the structure of an apparatus, that apparatus is what is covered. Use it to stir soup or to hit a golf ball; only the inventor can authorize one to make, sell, offer for sale, import or use the apparatus, even if the body of the patent and the preamble of the claim shows a particular motivation or use.

But not all claims are to the structure of a physical item. Some claims are to a process or method. The method might be a way to hit a golf ball with a regular golf club or it might be a method to hit a golf club with a novel golf club. Separately, there may be a claim to the structure of that novel golf club. When writing a patent application it can be desirable to have both an apparatus claim and a method claim.

Person B can't patent the thing disclosed by person A (not because it is patented but because it has been disclosed). But person B can patent a method of using the thing disclosed/patented by person A. New uses of aspirin keep being found and patented. If person A does have a patent on the thing itself, person B can't make, offer for sale, sell, use, or import that thing without permission from person A.

To make and sell something, person C studies the claims of person A and person B and tries to cleverly work around the wording of those claims. To patent something, person C comes up with a novel, non-obvious way to do something useful.

  • "If person A does have a patent on the thing itself, person B can't make, offer for sale, sell, use, or import that thing without permission from person B" - it seems to contain a minor typos. It should be '.... permission from A'. Dec 30, 2018 at 12:37

Short version: yes.

Long version:

I think there is an important lesson here. When you file a patent for an apparatus, you put it "out there". So if you did not describe a particular use well enough to draft a method claim on it, a competitor may be able to do so. And even though you invented the original apparatus, you will still need to pay the competitor a license fee if you want to practice the new use. So be sure to anticipate, describe (and maybe later claim) all such uses.

There is another issue relating to examination. Let's say (in the story above), person B did not know of patent A, he can be surprised during examination with this prior art. However, as he did a good job describing the method of use, may be able to get a patent on a method of use. Further, as when you re-purpose a structure for a new use you often need to make some changes, the act of thinking through and describing the usage scenario may help ensure that the patent does describe these changes (which may make it patentable).

All in all, i do consider the answer to the title question to be yes. It is not required by law but is very important for various practical considerations.

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