View source for HW2: Bread Machine

Patent 4538509 - Automatic Bread Baking Machine - cites patents 4202258 (Cooking apparatus) and 4294166	(Apparatus for mixing and baking of bread).

Patent 4202258 outlines a device with two chambers for kneading and baking bread.  Patent 4294166 also outlines a bread baking machine which can knead and heat-rise bread dough before cooking it.  The biggest difference between these two patents and Patent 4538509 is the integration of a cold water tank and other mechanisms to allow for raw ingredients to be added and mixed at a pre-programmed time.

Based on the 1850 ruling of Hotchkiss v. Greenwood, this patent would probably have been ruled invalid, because similar self-contained kneading and baking mechanisms had already been patented, and chilled water tanks most certainly had been previously used publicly. The case of the breadmaker is different from the doorknob case because it does not revolve simply around the substitution of a material into a previously widely used application.  Using the same ideas, however, this case would suggest that the nature of these previous patents would preclude the eligibility of the 'Automatic Bread Baking Machine' due to previous use and the obviousness of the invention.  Justice Woodbury's dissenting opinion suggests that new combinations can create value and should therefore be allowed to obtain patents, and using these ideals this patent would have remained valid.

Based on the 1950 ruling of A. & P. Tea Co. v. Supermarket Corp., Patent 4538509 would have been ineligible for patent simply because it is a combination of known things.  The supermarket counter is a more extreme case of combining well-known items and mechanisms. Nevertheless, the bread maker is simply a combination of well known tools.