Changes and Extension to an existing Patent

Infringement is basically a simple proposition - to infringe a patent, your product or system or method must include each and every feature that is in any one of the claims of the patented product, system, or method. So let's take a very simplistic example. Let's assume that you are the first one to ever invent a chair, so the main claim of your patent, the broadest claim, recites a seat, at least one leg, because the chair can comprise a pedestal (one leg) type chair, and a back connected to the seat. If you produce a product which has a seat, at least one leg, and a back, you infringe that patent because your product has every feature that is claimed in the claim of the patent. So let's say you decide to make an ottoman - an ottoman does not have a back, so you will not infringe the patent. So, as I said, if your product, system, or method has every feature claimed within at least one claim of the patented system, product, or method, you infringe - if your product, system, or method does not have every feature, or an obvious/similar component, you do not infringe.

Here's a further scenario - let's say you come up with an improved chair - let's say you decide to affix a cushion to the seat - that makes the chair more comfortable. So you obtain a patent claiming a seat, at least one leg, a back attached to the seat, and a cushion attached to the seat. You still cannot manufacture your own patented chair because your patented chair, while containing the cushion, also contains a seat, at least one leg, and a back - hence, you infringe the first patent. But the owner of the first patent, we'll call him Mr. A, becomes aware of your chair and appreciates the improvement and the fact that people will probably want your chair as opposed to his chair because your chair is more comfortable, but he cannot manufacture your chair because he will then infringe your patent. What to do? You both cross-license each other agreeing that you both can manufacture your chair without each one of you infringing the other patent. So, it's not necessarily that your intended product is for a different purpose or use, infringement depends upon the claimed structural features.