## Facts

- Vehicular Technologies Corp. (PowerTrax) owned U.S. Patent No. 5,413,015 covering an automatic locking differential for vehicles.
- The patented differential used a pin assembly with two concentric coil springs; the specification emphasized that the inner spring served as a backup if the outer spring failed.
- PowerTrax marketed its product incorporating the design, and competitors (collectively, Tractech) sold an accused differential called the E‑Z Locker.
- The E‑Z Locker used a single spring and a plug rather than two concentric springs and therefore lacked any backup-spring function.
- PowerTrax sued for infringement and sought preliminary injunctive relief based on the doctrine of equivalents, asserting the single-spring-plus-plug assembly was equivalent to the claimed double-spring assembly.
- The district court granted a preliminary injunction barring Tractech from making, using, or selling the accused differentials and ordered recall of products held by distributors.
- Tractech appealed the preliminary injunction to the Federal Circuit.

## Issues

1. Whether PowerTrax showed a reasonable likelihood of success on the merits under the doctrine of equivalents for purposes of a preliminary injunction.
2. Whether a single-spring-and-plug assembly that omits the claimed backup-spring function can be treated as equivalent to a claimed double-spring assembly.
3. Whether the evidentiary showing of equivalence at the preliminary-injunction stage was sufficiently particularized and linked to the claim limitations.

## Decision

- The Federal Circuit vacated the preliminary injunction and remanded.
- The court held the district court erred in finding PowerTrax likely to succeed on its doctrine-of-equivalents infringement theory.
- The record did not support treating the accused single-spring-and-plug structure as an equivalent to the claimed concentric double-spring structure, given the omission of the backup function highlighted in the patent.
- Judge Newman dissented, concluding the differences were insubstantial and the preliminary-injunction record supported the district court.

## Legal Principles

- A preliminary injunction in a patent case requires, among other factors, a showing of likelihood of success on the merits; when infringement is premised on the doctrine of equivalents, that showing must be strong.
- Doctrine-of-equivalents proof requires particularized evidence and a linking argument showing insubstantial differences (or satisfaction of the function-way-result test) for each asserted equivalent feature relative to the claimed limitation.
- When the patent’s disclosure identifies a structural feature and its specific functional advantage as a central benefit, an accused device that omits that function presents a substantial obstacle to equivalence.
- Courts may vacate broad preliminary relief, including recall obligations, when the predicate showing of likely infringement is inadequate.

## Conclusion

The Federal Circuit vacated preliminary injunctive relief because the patentee’s doctrine-of-equivalents showing did not establish likely infringement where the accused product replaced a claimed double-spring, backup-capable assembly with a single spring and plug lacking the disclosed backup function.


Vehicular Tech. Corp. v. Titan Wheel Int'l, Inc., 141 F.3d 1084 (Fed. Cir. 1998)