Wang v. Viking Drill — Priority Gap Lets Inventor’s Own Publication Defeat Patent

Background

Hongjia Wang owned a patent covering a twist drill with cutting-blade groups arranged on a cone-shaped portion. Viking Drill & Tool challenged the patent in two inter partes review proceedings, and the Patent Trial and Appeal Board found every challenged claim unpatentable on multiple grounds.

The decisive dispute concerned priority. Wang’s patent claimed the benefit of an earlier application, but Viking argued that the earlier filing did not adequately describe cutting blades “formed spirally.” If the priority claim failed, Wang’s own earlier publication could be used as prior art against the later patent.

The Court’s Holding

The Federal Circuit affirmed. The parties had agreed that “formed spirally” required axial relief—cutting blades slanted rather than perpendicular to the drill’s rotational axis. Substantial evidence supported the Board’s finding that the earlier application did not expressly or inherently disclose that feature.

The court accepted the Board’s reading of language about “connecting lines of the flutes.” In context, those lines described the angular positions of flutes, not the slanted cutting blades Wang needed for written-description support. A skilled person’s general knowledge that axial relief was old and familiar could not supply a feature absent from the priority document itself.

Without adequate written-description support, the later patent could not claim the earlier filing date. Wang’s own publication therefore qualified as prior art and, combined with other references, rendered all challenged claims obvious. Because that ground resolved every claim, the court did not reach Viking’s other invalidity grounds.

Key Takeaways

• A priority application must clearly show every limitation of the later claim; ordinary technical knowledge cannot fill a disclosure gap.
• An inventor’s earlier publication can become invalidating prior art when a continuation-in-part lacks support for newly claimed subject matter.
• Arguments inconsistent with an agreed claim construction, or not preserved before the Board, may be forfeited on appeal.

Why It Matters

The decision illustrates a recurring risk in continuation-in-part practice. Adding a feature to later claims does not bring that feature within the earlier filing date unless the original application conveys possession of it with reasonable clarity. When that link breaks, a patent owner’s own publication may become the reference that defeats the claims.

Patent applicants should therefore audit priority support limitation by limitation, especially when later claims use geometric or functional language not plainly shown in the original text and drawings.