Blade angle control device for use in an axial flow fan the blades of which are adjustable during operation

摘要

A blade angle control device for an axial flow fan, the blades (7) of which are adjustable between two extreme positions during operation, comprises a control ring (9) coaxial with the hub (1) of the fan impeller and connected, through links (15), with control arms of each blade. In an initial position, where the blades are in one extreme position, the control ring (9) abuts on one face of the hub (1) which is located in a radial plane of the impeller. A pneumatically operated piston device (11, 12,14) connected to the control ring (9) and located radially within the ring may shift the ring axially from the initial position towards a position in which the blades are in their other extreme position. A plurality of precompressed springs are located in tubes (18) extending through bores in the hub radially outside the piston device. Each spring surrounds a pin (19) connected to the control ring and biases the ring towards its initial position. The mass of the impeller is concentrated on a short axial length so that the impeller can be secured directly to the shaft (2) of a drive motor. By varying the number springs and possibly their length and precompression the total spring force, preload and spring rate of the control device can be adapted to any need. "