Let's look at a simplified example.

Patent Claim #1:
"A system for 'some function X' comprising:

a sending device...

a receiving device...

If a new product provides the function of the sending device but not the receiving device (or vice versa), does the new product infringe on the patented product? Moreover, if the new product only works with the patented receiving device being built and sold by the patent holder, does the new product infringe on the patented product? Lastly, if the new product which can provide the function of the sending device, does so as a free value-added feature and is not the main function of the new product, does the new product infringe on the patented product? Or does that even matter?

Would this new product be covered under the "exhaustion doctrine" or "first-sale doctrine" since it requires the purchase of the patented product to complete the "sending & receiving system"?

If the new product only contributes the functionality of one element of the claim and the patented product the other element of the claim, does the claim still "read on" the new product? Or does the "doctrine of equivalents" apply here?

Related Questions:
When does a patent prohibit the use of a patented product in another product?
Claim with three elements - are products infringing if they contain ANY of the elements or do they need to contain ALL of the elements in the claim?

3 Answers 3


This does not have to do with the exhaustion doctrine (it allows reselling) or the equivalents doctrine (if A is equivalent to B and A is patented, basically B gets protected too).

So the question as I get it is, do I infringe a patent if I sell a product directed at infringing patents?

The answer is, yes, if that's it's only use.

See for example here: https://www.law360.com/articles/429584/divided-infringement-of-system-claims-after-centillion

(Centillion Data Systems LLC v. Qwest Communications International Inc., 631 F.3d 1279 (Fed. Cir. 2010))

The Court also found that "[s]upplying the software for the customer to use is not the same as using the system."[6]

The Federal Circuit also noted that the only way the service provider could have been found to have "used" the system claims was if it was vicariously liable for the actions of its customers. The court explained, however, because it was entirely the decision of the customer to install and operate the software, the service provider could not be found vicariously liable for its customers’ actions.[7]

The second part states that if you can be found vicariously liable for your customers infringements -> if you sell something knowing it can only/will be used to infringe a patent, you are infringing.

If however the possibility of infringement is only a side effect (for example you sell glasses, somebody uses the lenses in an infringing microscope), you are not held responsible, but your customer is.


I referenced the article only to cite the part I did as the court stated there that supplying something that can be used to infringe a patent is no infringment. (I didn't register there and could read the article, but its not working anymore, don't know what happened there).

So yes, qwest products were found not to be infringing because of that, but the court says (and that is concludent with what I remembered when reading your question), that IF somebody directs a prdocut only or primarily at infringing or should know that it will be used for infringement, they may be held responsible too.

I'll have another try at exactly understanding what you are asking and elaborating further in that direction:

If a company A sells a product, let's say a sensor. And company B patented a system using sensors connected over special cables made out of handwavium and a unit registering all data.

Customer C buys the system with some sensors and the unit from B and adds a Sensor from A. Then C can be found to infringe B's patent by using a non licensed sensor and therefore a not completly licensed system. In reality B might be selling the system to be used with other sensors, basically giving away a license to use their base stations in arbitrary systems, but they don't have to.

A however is only liable if for examplethey sell a sensor that can be accessed only this way, accessed only, so they knew that C would have to infringe B's patent in order to use A's sensor.

  • The article you reference requires registering on the host site. Can you please post a publicly available version? Also, I fail to see how the court case you reference supports your claim. As far as I can tell, even after appeal, Qwest's product was found not to infringe. "So the question as I get it is, do I infringe a patent if I sell a product directed at infringing patents?" This is clearly not my question. Your statement precludes the possibility that infringement may not be occurring in the first place. Jan 17, 2017 at 4:51
  • In addition, in my example one of the parts of the multi-part claim is the actual patented device. Hence the reason I mentioned the "exhaustion doctrine". Correct me if I'm wrong, but in the case you reference, all parts were developed by Qwest. Jan 17, 2017 at 4:53
  • I edited the answer, was this what you were asking about? I don't know why I had access to that article and have it no more, but I had cited the interesting part already anyways.
    – user18033
    Jan 17, 2017 at 7:06

Generally, a product needs to do perform and every step or element recited in the claim to be infringing. In the cases you mentioned (doing either the job of the sending or receiving device, but not the other), you would not be considered to be infringing because you are not performing each and every step included within the claim.

As for the exhaustion doctrine, you would have to have an attorney look at the specifics of the product to be sure. Because you are (in that case) performing each and every step as recited in the claim, you could be considered to be infringing, but exhaustion could be a viable argument depending on the specifics of the product.


The answer depends strongly on the claim construction for your design. If your claim construction, directly or indirectly, recites or executes all the steps in the existing patented product, then your design is probably unpatentable. A lawyer is almost certainly in order here, as you would have to write your new patent carefully to design around the existing patent.

  • My question does not pertain to patentability of prior art. It is only meant to pertain to patent infringement. Sep 21, 2015 at 15:39

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