| 摘要 |
It has been discovered that by eliminating the cutoff in a centrifugal blower the tone or whistle-like noise usually produced by such blower may be eliminated without unreasonably affecting the performance of the centrifugal blower and in many instances without having any significant effect on such performance. Briefly, the invention is directed to a centrifugal blower and to a particular type of blower housing therefor, in which there is no such cutoff or like impediment to provide the allegedly required transition in the involute wall portion of the blower relatively proximate the blower outlet. Rather, in the present invention an extension wall portion extends from the end of the involute wall portion in a direction toward the blower outlet, preferably terminating at the latter so as to eliminate the conventional blower throat which leads to the blower outlet, with such extension wall portion, or at least a major part thereof, traveling therealong in a direction toward such blower outlet having an increasing radial spacing from the spiral center of the spiral shape housing and/or the radial center of the fan wheel.
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