Vas-Cath Inc. v. Mahurkar
935 F.2d 1555 (Fed. Cir. 1991)
Mahurkar invented a new type
of catheter. He received a design patent on it and it became very
popular. He then filed a utility patent in Canada with the same drawings
but a more thorough textual description.
Design patents generally
just consist of a picture of the invention, and are mostly used for
things that are just aesthetic improvements to industrial items.
It was probably a mistake
for him to file a design patent.
More than a year later,
Mahurkar went back and filed two utility patent applications that added a
few claims to the original design patent.
Mahurkar called them continuations of the original patent, and claimed the filing
date of the original patent.
Vas-Cath made a similar
catheter and sued for a declaratory judgment saying that its catheters
didn't infringe on Mahurkar's new patents.
Vas-Cath argued that
Mahurkar's new patents were invalid because they were anticipated by the Canadian patent.
See 35 U.S.C. §102(b), which says that if there is prior art
published more than a year before your patent application is filed, it
That's true even though
Mahurkar wrote the Canadian patent!
Vas-Cath also argued that
Mahurkar's new patents couldn't be continuations of the original patent because the original
patent didn't describe the invention in a way that disclosed the new
Under 35 U.S.C. §112, you can't make any claims for things that
are not fully described in the written description of the patent.
Basically, if the new
patents were described in the original patent, then they could use the
original patent's date (because they would be a continuation), and thus predate the Canadian patent. If
not, then the Canadian patent would predate the new patents, and so the
new patents would be invalid because they'd been anticipated by the Canadian patent.
The Trial Court found for
Vas-Cath. Mahurkar appealed.
The Trial Court found that
the text of the original patent didn't explain the catheter in enough
detail to support the claims in the new patents. Therefore they couldn't
be a continuation.
The Appellate Court reversed
The Appellate Court found
that the pictures in the design patent were probably good enough to
support the claims in the utility patent, but the case was remanded to
the Trial Court to decide.
The Court found that the written
description is different from the enablement, and the difference is important in two
When claims are not
presented in the original application but are presented in an amended
When an amended application
seeks to use the original patent filing date to avoid problems with prior
art (like in this case).