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The case involved two competing manufacturers of equipment used in procedures such as angioplasty for automatically injecting contrast media into a patient from a plastic syringe. Because the syringe can be subject to pressures of 1,000 lbf/in2 or more, the conventional approach had been to house the syringe in a pressure jacket and to load the syringe into the jacket from the back. Liebel-Flarsheim (LF) developed an improved injection system that still used a pressure jacket but allowed the syringe to be loaded from the front, which technicians found more convenient. LF applied for a patent on its improved system. In its claims, it specified that the syringe was loaded into a front opening of a pressure jacket.