Your mom was right––sometimes saying bad things (in this case about the prior art) can get you in trouble. Many patent specifications highlight the advantages of the claimed products or methods by pointing out shortcomings of the prior art and describing how the described invention addresses the problems. While such an approach can be effective, the strategy can have unintended consequences, particularly when a broad claim construction is needed. The Federal Circuit decision in Bamberg v Dalvey highlights this issue.

This dispute arises from an interference proceeding in which Bamberg copied claims from four patents issued to Dalvey. The claims at issue disclose a method for the transfer of printed images onto dark colored textiles by ironing over a transfer paper that contains:

  1. a removable substrate coated with silicon,
  2. a hot-melt adhesive,
  3. a white layer and
  4. an ink-receptive layer.

When heat is applied to the transfer paper, the hot-melt adhesive melts causing the white layer and the ink-receptive layer to adhere to the fabric while at the same time providing an image that is visible against the dark fabric.

Dalvey challenged the interference claims under 35 USC 112, alleging that Bamberg’s claims were invalid for lack of written description. Dalvey argued that Bamberg’s specification only disclosed a white layer that melts above 220°C, while the claims cover a white layer that melts over a wide range of temperatures.

The claims in an interference are reviewed in light of the specification from which the claims are copied. As a result, the patent specification of Bamberg was required to provide adequate written description for the claims when the claim terms were construed according to the Dalvey specification.

The Board found that Dalvey disclosed a “generic” white layer that did not have limitations regarding the melting temperature of the white layer (the specification, in fact, included embodiments of the white layer that melted over a wide range of temperatures). Therefore, the Bamberg specification was required to support a generic description of the white layer.  However, the Bamberg specification described the white layer as comprising elastic plastics filled with white pigment, each of which melted only at temperatures over 220°C. The specification pointed out that this arrangement was advantageous in providing a strong adhesive layer and a clearer image on the textile. Of note, the original claims in Bamberg’s PCT application contained a limitation that the white layer did not melt below 220°C.

The Board concluded the Bamberg specification failed to provide adequate written description for a generic white layer as described in Dalvey.

On appeal, Bamberg argued that the Board impermissibly imported limitations from the specification into the claims. The Federal Circuit rejected this argument and upheld the Board’s finding. The court cited Tronzo v Biomet, Inc. as instructive. In Tronzo, the patent applicant described a specific conically shaped cup as a hip implant while at the same time criticizing other shapes as inferior by detailing the advantages of the conically shaped cup. As a result, the Tronzo court held that the patent specification described only conically shaped cups and nothing broader. The court applied the same analogy here, reasoning that since the Bamberg specification “specifically distinguished” the use of white layers that melt below 220°C as having undesirable properties, the Bamberg specification could not provide adequate written description support for a white layer that melted below 220°C.

[W]e find that Bamberg does not possess a white layer that melts below 220°C because it specifically distinguished white layers that melt below 220°C as producing an “undesired” result.

Bamberg further argued that it did not distinguish the prior art as inferior, but stated that a melting white layer was undesirable. The panel viewed this argument as a “distinction without a difference” stating that “We are not persuaded by the assertion that one skilled in the art would understand that an inventor possesses something that it deems undesirable, but not something that it deems inferior.”

While this case is presented in the context of an interference, it serves as a reminder about how to properly describe the benefits of an invention in the patent specification. Would Bamberg have been better served by simply describing the composition of the white layer broadly and providing a specific embodiment for a white layer that did not melt below about 220°C? Was the criticism of the prior art required to be in the specification or could it have been provided in the form of an inventor declaration at a later date if needed? Patent drafters should  use caution when including statements criticizing the prior art in the patent specification and realize such statements can result in a narrower interpretation of the claims.