View source for Case 20: Pfaff vs. Wells Electronics (1998)

Pfaff created a design for a microchip socket. He offered the design to Texas Instruments before building or testing a prototype, as was his normal practice, before April 8, 1981. He filled the order in July of 1981, indicating a reduction to practice at that time. He filed for a patent on April 19, 1982; thus, the critical date for on-sale bar considerations was April 19, 1981. Pfaff sued Wells for infringement: in a series of decisions, the District Court said the patent was infringed because the patent on sale from the date of reduction to practice, and the Appellate Court overturned by saying the one-year period starts from the initial sale offering.

The Supreme Court concurred with the Appellate Court. They ruled that "invention" in the Code undoubtedly means the inventor's mental conception and not the physical product. The phrase "reduction to practice" is a judicial rather than a legislative term, and the requirement does not appear in the Code. Pfaff clearly could have filed for a patent when he offered the design to Texas Instruments, since the drawings were clear and detailed enough for a professional to produce the product. In addition, proof of reduction to practice is not required for an invention to be regarded as an invention; thus, the one-year grace period starts from the sale offering, not the reduction to practice. Finally, there are two conditions for the on-sale bar to apply. First, the product must be offered for sale. Second, the invention must be complete enough to be eligible for a patent. This requirement may be completed by either evidence of reduction to practice before the critical date, or evidence of detailed drawings and conceptions which were sufficient for a person with ordinary skill in the art to realize the invention. It is clear that both are satisfied in this case.