How strict are patent claims?

Question

If there were a patent US1111111, which read:

US1111111: A "thing" for doing something.

The invention claimed is:

1. A "thing".
2. A "thing" of claim 1, which uses a "thing 2".

Say my invention was also a "thing" that instead uses a "thing 3", would my "thing" infringe on patent US1111111? I am still unsure as to how strict patent claims are.

Answer 1

I am still unsure as to how strict patent claims are.

If an accused product falls within the literal meaning of at least one of the patent's claims, then the patent is "literally" infringed.

There is also infringement under the doctrine of equivalents. A product that falls outside the literal meaning of the claims may still be considered infringing if it contains an "equivalent" for each claim limitation not literally present.

So the answer to your question is "yes", since at least one claim is infringed. It doesn't matter how many other claims you don't infringe.