JPS56146093A - Spiral fan - Google Patents

Abstract

PURPOSE: To prevent a temperature rise in the case when flow rate lowers or a fan is completely cut off by mounting outside-air introducing passages opened and closed by a valve body responding to the inner pressure of a casing, which builds in an impeller and has a suction port and a discharge port, near to the discharge port of the casing.

CONSTITUTION: A detecting means 15 for directly detecting the pressure of an internal passage of a fan is mounted into a cylindrical case 16 near to a discharge port 5, which reaches the highest temperature, of a casing 3, which builds in an impeller 14 and has a suction port 7 and the discharge port 5, and outside-air introducing passages (an opening and a communicating port) 19, 20 are installed which are opened and closed by a valve body 17 in the case 16 responding to the inner pressure of the casing 3. In this case, pressure can be detected extremely accurate because pressure in the fan is detected directly. According to such constitution, the valve body 17 is opened in response to the inner pressure of the casing 3 and cold is introduced from the outside-air introducing passages 19, 20 when flow rate lowers or the fan is completely cut off, thus preventing a temperature rise.

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