A. & P. Tea Co. v. Supermarket Corp. (1950)
The court disputed the validity of the claims on a grocery counter invention: "a cashier's counter equipped with a three-sided frame, or rack, with no top or bottom, which, when pushed or pulled, will move groceries deposited within it by a customer to the checking clerk and leave them there when it is pushed pack to repeat the operation. It is kept on the counter by guides."
The decision consisted in whether or not the combination of known items culminating in the counter constituted an invention, especially considering the only "invention" within the counter was its extension, which was not mentioned in the claims.
The patent was ruled invalid, as the mere extension of the counter (which is all that differentiated it from prior art) was not substantive enough to make the counter worthy of a patent.
In terms of non-obviousness, the court agrees that combinations of old things which together perform a new or different function previously not performed by them, does constitute an invention. In other words, the combination of old items is only patentable when the whole exceeds the collection of individual items.