Be careful when using mathematical terms that have very broad even if precise definitions. While the applicant here clearly intended to convey only the basic idea that the shape of the intonation portions is not arced like the crest of a sine wave, they ended up reciting a mathematical relationship that on its face was much broader. The sad part is that there are several immediately apparent alternatives that would be just as broad as intended without being infinite, but this is a reminder of the value of a good patent attorney – one small oversight can bring down an entire patent. (As an aside, it is worth pointing out that the negative limitation inserted only to carve out the prior art was not objected to for lack of written description by the court, even though they noted that the term sinusoidal does not appear anywhere in the detailed description.)
Background / Facts: The patent here relates to guitar parts designed to optimize the intonation along each of the instrument’s strings. The nut and the bridge of a guitar each typically include slots or saddle positions for receiving each string, and those opposing saddle positions together define the effective length of each string. To allow for adjusting the effective length of each string individually, to keep each one in tune across all of the frets, claim 1 recites a “compensated” nut having a number of individual “intonation portions,” such as cut-outs, provided in the front side of the nut. During prosecution, all of the independent claims were amended to add negative limitations excluding configurations of the intonation portions that are “sinusoidal,” in response to repeated obviousness rejections over a reference showing a specific sinusoidal arrangement.
Issue(s): Whether the particularly chosen language specifying “that a line extending through the one or more fixed intonation portions does not form a sinusoidal arc” is indefinite.
Holding(s): Yes. “While the district court reasonably interpreted the term ‘sinusoidal’ according to its plain meaning as ‘a configuration that strictly conforms to the shape of a sine wave or arc,’ that construction does not resolve the fundamental problem facing anyone attempting to divine the very broad boundaries of claim 1: the intonation portions of any compensated nut represent only a handful of discrete points that cannot unambiguously define a single line extending therethrough.” The court harshly but correctly noted that for a discrete number of points, there are an infinite number of lines therethrough that can be made from a sine wave and an infinite number of lines that can be made from other functions. (See the figures provided by the court on p. 16 of the opinion – in essence, drawing a sine wave with a high frequency that passes through each point one at a time on each cycle.) Thus, for any configuration of intonation portions, it is impossible to determine whether a generic “line extending therethough” would or would not be sinusoidal.