A theorethical patent situation:

Claims include: 1. A machine comprising device type A and device type B arranged to achieve X. 2. A machine according to claim 1 in which device type A is an M. 3. A machine according to claim 1 in which device type A is an N.

The device types A and B are known, the combination is not. Implementations of A as M, N and O are alredy known. In the patent description we describe embodiments of A as M, N and O. O is not included in the claims. O is feasible, but probably not a good idea.

My question is whether I understand the implications correctly:

1) Clearly there is not, independently, protection for implementing A as O. 2) An implementation of a machine to achieve X using O and B would be an infringement of claim 1, because O is a device type A. 3) Someone else cannot patent the implementation with O; it is now known. (In the unlikely event the inventor wants to use it.)

4) What is the advantage of the dependent claims of A as an M or N?

  • Unless the combination of A and B doing X does it unexpectedly (or at least unexpectedly well), you might not be able to get a patent because of obviousness. Just because something hasn't been done before doesn't make it automatically patentable.
    – Eric S
    Dec 6, 2019 at 18:05
  • I was aware of that but thank you for pointing it out. The real case is a little more complex, and not obvious.
    – Anders
    Dec 6, 2019 at 20:27

1 Answer 1


Dependent claims serve a few purposes. One is as a fallback in case the broader independent claim is rejected during prosecution or more importantly during enforcement. Another is a concern that the broader claim might be hard to grasp but the dependent claim hits you over the head in a case that is likely to occur. There is also something called claim differentiation. It holds that since dependent claims necessarily narrow the claim they depend upon some meaning broader than what is spelled out in the dependent is implied. In your example we know that A doesn’t need to be an M or else the dependent claim would be superfluous.

A, as any type of A (O for example) is protected by the independent claim. And your inclusion of A as O in the description means no one should be able to patent the special case of A as an O.

Not part of your question but “to achieve X” might not fly as is. Claims to devices typically define the structure of the device, not what the structure achieves. A subtly different “the coupling such that the action X occurs when A is turned” or something that makes it clear that the “archiving X” is part of a structural definition. “so configured such that X is achieved” also is a functional way to define a structure.

  • Thanks a lot. That clarifies it. I thought what you said about "to achieve X" just after i submitted the question. The case here is somewhat simplified, but you answered what I what i was looking for. Thank you.
    – Anders
    Dec 6, 2019 at 20:25
  • I, modestly, do not need the reputation points. But the way all stack exchange sites operate is by answers getting accepted by the questioner.
    – George White
    Dec 6, 2019 at 21:18

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