Determining if your invention is patentable
The US patent system will issue patents for an invention that is a process, a machine, a manufacture or a composition of matter so long as the invention is new, useful and non-obvious. Also, while abstract ideas cannot be patented, a particular application of an abstract idea is patent eligible.
The test for whether your invention is new and non-obvious involves comparing it to all of the knowledge that was available before you filed your application (called “prior art”). The core question for what is new is relatively simple—is your invention different from what has come before? In other words, if the combination of elements in your claim does not appear as a combination in the prior art, your invention is new. Meanwhile, the core question for what is non-obvious is this: if your invention is different from what came before, is it different enough? In order to be non-obvious, a person having ordinary skill in the field of your invention must look at your invention as a whole, including all of the differences, and conclude that he or she would not have come up with your invention based on the prior art available. For example, a trivial combination of items found in the prior art is not patentable.
You can come a long way in answering whether your invention is new and “different enough” by looking at prior art via searching the USPTO patents and publications database (http://patft.uspto.gov) and via Internet search engines. You may indeed find parts of your invention in the prior art, but looking through the eyes of the other authors and inventors may help you arrive at convincing reasons for why a person of ordinary skill would not have brought all of the parts together.