Although the answer should be a resounding "no," the answer is actually "yes."
Why? The U.S. Supreme Court, in Warner-Jenkinson v. Hilton Davis Chemical Co., 520 U.S. 28, 37 ruled: "The proper time for evaluating equivalency--and thus knowledge of interchangeability between elements--is the time of infringement, not at the time the patent was issued" (emphasis added).
This ruling undermines the public policy behind patent claims -- that claims are supposed to provide to the public clear notice of what the inventor has claimed. Suppose that an inventor has claimed an electronic device, and one of the elements specifically called for in each of the independent claims is a "vacuum tube" (and suppose this was before transistors were invented).
Several years later, the transistor is invented and recognized as being a better substitute for a vacuum tube, because a vacuum tube has high power consumption, lower efficiency, and requires a heater to generate waste heat. A competitor gets the idea that he can improve on the design of the original patented electronic device by using a transistor instead of a vacuum tube.
Will that change be considered infringement? It might be under the Supreme Court's standard, because equivalency is measured at the time of infringement. The power for the competitor (and the public at large) to rely on the language of the claims has been completely taken from them by the courts. Now it is up to the judge to determine whether he considered the changed element an "insubstantial variation" of the element that had been replaced. The U.S. Supreme Cour therefore took us from a bright line rule serving its notice function ("is this element a vacuum tube, or isn't it?) to a much more subjective, nebulous test (Was the transistor an "insubstantial variation" of a vacuum tube at the time of infringement?) and for no real added public policy benefit.
Why? The U.S. Supreme Court, in Warner-Jenkinson v. Hilton Davis Chemical Co., 520 U.S. 28, 37 ruled: "The proper time for evaluating equivalency--and thus knowledge of interchangeability between elements--is the time of infringement, not at the time the patent was issued" (emphasis added).
This ruling undermines the public policy behind patent claims -- that claims are supposed to provide to the public clear notice of what the inventor has claimed. Suppose that an inventor has claimed an electronic device, and one of the elements specifically called for in each of the independent claims is a "vacuum tube" (and suppose this was before transistors were invented).
Several years later, the transistor is invented and recognized as being a better substitute for a vacuum tube, because a vacuum tube has high power consumption, lower efficiency, and requires a heater to generate waste heat. A competitor gets the idea that he can improve on the design of the original patented electronic device by using a transistor instead of a vacuum tube.
Will that change be considered infringement? It might be under the Supreme Court's standard, because equivalency is measured at the time of infringement. The power for the competitor (and the public at large) to rely on the language of the claims has been completely taken from them by the courts. Now it is up to the judge to determine whether he considered the changed element an "insubstantial variation" of the element that had been replaced. The U.S. Supreme Cour therefore took us from a bright line rule serving its notice function ("is this element a vacuum tube, or isn't it?) to a much more subjective, nebulous test (Was the transistor an "insubstantial variation" of a vacuum tube at the time of infringement?) and for no real added public policy benefit.
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