Johnston v. IVAC Corp. (JWB)
Description: The inventor, Turner, invented a thermometer probe cover that stays on (this was owned by AMEC). It kept the cover on via a sharp metal hook to tear into the cover’s plastic. IVAC developed a thermometer that served a similar purpose of keeping the probe cover on, except that it did so with a ring on the probe (to hold the cover via friction). IVAC intentionally left the probe free of any sharp edge to ease the removal of the probe cover when needed. District Court of Southern California ruled in summary judgment that IVAC’s thermometer probe covers do not infringe AMEC’s. On appeal from AMEC, the Court of Appeals affirmed the judgment. A ring that does not tear the plastic cover is not equivalent to the hook that does.