Unfortunately "obvious" in patent law tends to mean there is published work suggesting putting stuff together in that way. If nobody has discussed the problem (e.g., you were the first to work on it), it somehow doesn't matter that anyone competent would have promptly settled on the same solution you did, and we aren't getting anything of value in return for your generation-long monopoly on it.

http://en.wikipedia.org/wiki/Inventive_step_and_non-obviousn...