Abstract: In an impeller for use in an axial flow fan and having blades (5) which are adjustable during operation of the fan, each blade (5) is, through a blade shaft (7) connected to a hub (1) designed as a compact unit.The blade shaft (7) and an axial thrust bearing device (9) on which the blade (5) is journalled in such a manner that it can, through a control mechanism, be pivoted about its axis for controlling the blade angle, are retained axially in a bearing housing (8) screwed into a threaded bore (18) in the periphery of the hub (1).For adjusting the radial distance between the periphery of the hub (1) and the blade tip the thrust bearing device (9) is held against a closed end of the bearing housing (8) by a spring (43) and a nut (14) screwed onto a threaded portion (15) of the blade shaft (7) and lockable in an arbitrary position by a lock screw (16).

Abstract: 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.