Noise cancellation device for centrifugal blower
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United States of America Patent
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May 31, 1994
Issued Date -
N/A
app pub date -
Aug 24, 1993
filing date -
Jan 13, 1992
priority date (Note) -
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status (Latency Note)
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Abstract
A noise cancellation device for a centrifugal blower comprises, in a first embodiment, a rod mounted in the output of a blower and generally axially parallel to the impeller so that as the impeller rotates, the blades of the impeller sweep past the rod much as in the manner that the blades sweep past the cutoff section of the blower output. The rod is positioned a specified distance away from the cutoff such that it generates a tone which interferes with the pure tone otherwise generated by the impeller blades sweeping past the cutoff in an out of phase condition to thereby eliminate the pure tone or 'spike' normally experienced at a fundamental frequency and harmonics thereof. In a second embodiment, a nose-like projection extends inwardly from a sidewall of said blower housing and is positioned substantially in the same position as the rod of the first embodiment. The nose-like projection may be integrally formed as part of the blower housing.
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