It was found that the method developed by "A" (newer designers) versus "B" (the original designers and holders of a patent) was more complex. I think it falls into the improvement patents category, in the same application domain and with the same scope and goals. Nothing is new here.

But "A" has a bit more complex of using the procedure B, which is entirely patented by "B". Using, it means "black box", nothing is changed, the idea is the same. But the method created by "A" also has procedure A which is not included in the patent held by "B". So it is like "A" is using the patented procedure B in certain cases and, depending on the inputs into the system, switches to the procedure A.

I understand that USPTO might reject the approval of patent from "A" based on not too much novelty compared to "B" and being for more than 2 years away from approval of "B".

But, is this also a situation in which "A" is actually infringing the patent "B"? And this would require a licensing of "B"?

  • I think the person who gave a -1 vote abused his/her right in doing so. Especially when it could be called an unjust and unfriendly exercise. This question has all the rights to be here. You that gave the negative vote, check the FAQs saying questions could be asked on the patent law system. If, however, your negative vote was on Mr Silverman's opinion, that is your right too, but put it in words in a comment section. Feb 2, 2013 at 20:36
  • I have not voted on the question or the answer. The question could be improved by telling us what patents are being discussed. If the question is intended to be more general, about the system rather that a particular pair of patents, then the question might be formed in a more pointed way so it could be directly answered.
    – George White
    Feb 2, 2013 at 20:58
  • Thanks for feedback. I obviously cannot give details on the new "improvement patent" as it was not disclosed yet. It is under preparation by the "A" inventors and this issue of potential infringement came during prior art search. But I did not asked this forum for a specific response, not being able to disclose the "A" content, yet. It was more general question. Feb 3, 2013 at 12:04
  • I think that the 3 and 4 leg chair example is a good aproximation of the problem. With 4 legs, you get more stability to side movements but does not fundamentally changes the idea of the 3 leg chair. So using a 4 leg chair patent in a real product is infringing the 3 leg chair patent, if everyone agrees with Mr. Silverman. Feb 3, 2013 at 12:12
  • There are multiple ways to claim a three legged chair: [ a) a chair comprising three legs . . . b) a chair whose support from the floor consists of three legs . . . c) a chair requiring no more than three legs to achieve effective stability . . .] In the case of a) a four legged chair could infringe because "comprising" is open ended. In the case of b) a four legged chair could not infringe because "consists of" is closed. In the case of c) adding a functionally unneeded 4th leg to a three legged chair would not get one out of infringement. This can be a deep and subtle field.
    – George White
    Feb 3, 2013 at 20:00

3 Answers 3


The Silverman article is correct, though as George White says, it depends on exactly what is claimed.

Infringement and patentability - specifically novelty - can involve some similar questions. Sometimes it's said 'what infringes if done after, anticipates if done before'. Confused? I'm not surprised, it's a specific and subtle point.

So while you need to consider the big picture - what you can do, and what you can stop others doing - infringement and patentability are different questions and I would always recommend you consider them separately, it's too easy to get confused otherwise, even for people who do patent work day to day.

So for infringement, does A read onto any of B's claims? That's it. There's a whole process to this of course, you will have to construe what B's claim means, apply the doctrine of equivalents, keep in mind contributory/indirect infringement and so on.

For obviousness - the part of patentability that causes most grief - the test is simply, would the difference between A and B (and the other prior art) be obvious to one with ordinary skill?

For an 'improvement' patent, this might mean that working invention B needs A's permission. But A couldn't use B's invention either. In a Venn diagram, A would be the yolk in B's egg. A third party wanting to use B's invention would need permission from both A and B.

If A's got a really good improvement, B might want to use it too, so you might be able to negotiate a cross licence. In some countries, sometimes A can even force B to issue a licence.

  • I really appreciate your help, PNH. It is very enlightening. Feb 4, 2013 at 21:41

I found this information searching the Internet. It belongs to Mr. Arnold B. Silverman, a partner in the law firm Eckert Seamans Cherin & Mellott. He wrote an article in http://www.tms.org/pubs/journals/JOM/matters/matters-9501.html from which I quote:

Another issue of importance is whether someone obtaining an improvement patent can practice the improvement without infringing the basic patent.

There is a common misconception that obtaining a patent gives the right to practice the patented invention. A patent grants the patent owner a negative right (i.e., the right to prevent others from making, using, or selling the patented invention); it does not give the patentee the right to practice the invention. In many instances, a patented improvement cannot be made, used, or sold without infringing the basic patent.

A simplistic example: a basic patent is obtained for a chair having three legs. Another may decide that a chair would be more stable if it had four legs and obtains a patent for a chair with four legs. The improvement patent would give the owner the right to keep others from making, using, or selling chairs having four legs. As the original patent claimed a chair with three legs, making, using, or selling the four-legged version would infringe the basic patent. The presence of an additional leg permits the inventor of the improvement to obtain a patent, but does not avoid infringement of the basic patent for a chair with three legs.

Please feel free to add responses to this topic, personal experience or disagreements included. Thank you.


I think the short answer would be that you are right in your statements and question (i.e. the answer is yes).

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