Background
Wayne Pfaff invented a computer chip socket and received a purchase order from Texas Instruments for the sockets in April 1981 — more than one year before he filed his patent application in April 1982. The critical date was April 1981 (one year before filing). During the on-sale period, Pfaff had accepted the Texas Instruments order and had detailed engineering drawings but had not yet built or tested a working prototype of the socket. The question was whether the invention was “on sale” under § 102(b) even though it had not been physically reduced to practice before the critical date.
The Federal Circuit applied its “totality of the circumstances” test and found the invention was on sale. The Supreme Court granted certiorari to address the standard for the on-sale bar.
The Court’s Holding
The Supreme Court unanimously established a two-part test for the on-sale bar: an invention is on sale when (1) the product is the subject of a commercial offer for sale, and (2) the invention is ready for patenting. The “ready for patenting” prong is satisfied if the invention is reduced to practice before the critical date OR if the inventor has prepared drawings or descriptions of the invention sufficiently specific to enable a person skilled in the art to practice the invention. Physical reduction to practice (actually building the invention) is not required.
Applying this test, Pfaff’s invention was on sale: Texas Instruments’ purchase order was a commercial offer for sale, and the detailed engineering drawings were sufficient to establish readiness for patenting even without a physical prototype. The patent was therefore invalid under the on-sale bar.
Key Takeaways
- The on-sale bar is triggered when (1) there is a commercial offer for sale of the claimed invention and (2) the invention is ready for patenting — either by actual reduction to practice or by drawings/descriptions enabling a skilled artisan to practice the invention.
- Physical reduction to practice (building a working prototype) is not required to trigger the on-sale bar — detailed engineering drawings enabling someone skilled in the art to make the invention establish readiness for patenting.
- Inventors and companies that accept commercial orders for a product before filing a patent application face on-sale bar invalidity risk, even if the product has not yet been manufactured — the commercial offer and readiness for patenting, not the physical product, control.
- The Pfaff test continues under the post-AIA § 102 framework: the AIA eliminated the one-year grace period for third-party sales but retained a grace period for inventor’s own disclosures — making pre-filing commercial activity analysis critical for patent validity.
Why It Matters
Pfaff v. Wells Electronics provided clarity on one of the most important and commercially consequential aspects of patent law: when does pre-filing commercial activity bar patent protection? The two-part test — commercial offer + ready for patenting — replaced the Federal Circuit’s subjective “totality of circumstances” approach with a more determinate standard that has governed on-sale bar analysis since 1998.
The practical implications are significant for product development and commercialization: companies that seek sales orders, license agreements, or distribution deals for products before a patent is filed must understand that these activities can trigger the on-sale bar, potentially invalidating any patent later filed more than one year after the first commercial offer. Patent counsel routinely advise clients to file before commercial activities begin or to ensure the one-year grace period has not elapsed — advice grounded directly in the Pfaff framework. The decision remains one of the most practically important patent law cases for startups, product companies, and manufacturers navigating the timing of patent filings and commercial activities.