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 is invalid. 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 claims. 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 and remanded. 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 situations: When claims are not presented in the original application but are presented in an amended application. When an amended application seeks to use the original patent filing date to avoid problems with prior art (like in this case).