“[E]ven if, as plaintiff argues, construing the patent to require the dough be heated to 400 degrees to 850 degrees Farenheit [sic] produces a nonsensical result, the court cannot rewrite the claims. Plaintiff’s patent could have easily been written to reflect the construction plaintiff attempts to give it today. It is the job of the patentee, and not the court, to write patents carefully and consistently.” – Colorado United States District Court
Patent claim drafting requires careful attention. The difference between the use of “to” and “at” in a claim directed to a method of producing dough, resulted in the difference between a worthless patent claim and a patent claim that might have had value. This is why going the DIY route with a non provisional utility patent application is very difficult.
Chef America Inc owned US Patent 4,761,290 directed to a process of producing a dough product with certain desirable attributes. Chef lost when it sued Lamb-Weston for infringement because the patent claim literally required the dough “to be heated to a temperature in the range of about 400° F to 850° F” in Chef America v. Lam-Weston, Inc., 358 F.3d 1371 (Fed. Cir. 2004). Heating the dough to that temperature would result in dough that was burned to a crisp, resembling a charcoal briquet. Instead, that patent owner really meant that the dough had to be heated at that temperature. In other words, the oven needed to be set at that temperature. But the internal temperature of the dough did not need to reach that temperature.
Chef American argued that one skilled in the art would recognize the claim meant “at” rather than “to” given the nonsensical result that the dough would be completely burnt if the dough was heated to about 400° F to 850° F. But the court refused to change the claim to avoid the burnt dough result. The district court said:
[E]ven if, as plaintiff argues, construing the patent to require the dough be heated to 400 degrees to 850 degrees Farenheit [sic] produces a nonsensical result, the court cannot rewrite the claims. Plaintiff’s patent could have easily been written to reflect the construction plaintiff attempts to give it today. It is the job of the patentee, and not the court, to write patents carefully and consistently
The Appellate court agreed saying that “courts may not redraft claims, whether to make them operable or to sustain their validity.” The court further stated “Even a nonsensical result does not require the court to redraft the claims of a patent.”
The court noted that references to temperatures in the description of the patent used “at” and “to” in different places. Therefore when the patent owner choose “to” for use in the claims, the court was constrained from finding it meant “at.”
The court concluded that the claim unambiguously requires that the dough be heated to a temperature in range of 400° F. to 850° F–in other words to be completely burnt to a crisp. As a result, Lamb-Weston did not infringe and Chef America’s patent claims at issue were essentially worthless.
Sometimes errors in a patent can be fixed. In this case the patent owner did not request an amendment to the claims. Rather the patent owner wanted the court to read the claim the way most people would have understood it. But the court would not do that. Patent drafting is not easy. And careful attention is required when drafting patent applications.