Abstract: An axial flow fan impeller having a number of blades, which are rotatably journalled in a wheel rim (3), each with its blade root (4) which is connected with an adjusting device (10) for the blades. The wheel rim comprises as a supporting member for the blades an annular body of revolution (6) with bores (5) for the blade shafts and a cut-out for taking up a thrust bearing (7). The body of revolution is connected with the body plate (18) and the front plate (21) of the impeller through tubular connecting pieces (19, 20), which are symmetrical relative to the body of revolution and are elastically deformable by loading forces acting in the radial plane of the wheel, but have a relatively great rigidity against forces acting in the axial direction. The impeller may thus be fabricated by welding, without the occurrence of dynamic loads exceeding the allowable values for the welding joints (25, 26).

Abstract: Axial flow fan blade roots (1) are rotatably journalled to blade shafts (4) by bayonet plug and socket couplings. The socket recesses (30, 31) provide an axial play for the plug cam portions (28, 29). Screws (34, 35) extending through the blade root (1) have shoulders (43) abutting spring members arranged between the root and the shaft to thus bias the blade outwardly and establish frictional engagement between the bayonet coupling cam portions and recesses.

Abstract: A thrust being assembly in which two coupled coaxial thrust bearings are restricted by means of a blocking device to be allowed to turn in one direction of revolution only, so that rolling elements of each bearing in response to oscillating movement of the bearing assembly will be displaced to a new point of contact with the associated bearing race. The blocking device may comprise two oppositely oriented coaxial helical springs frictionally engaging an intermediate race ring of the bearing assembly.

Abstract: A considerable increase of the life time of metallic members, particularly the blades of fans or turbines, which are exposed to air-borne abrasive particles is obtained by providing such members with a wear-resisting attachment comprising at least two wear-resisting layers consisting of materials having complementary relationships of the erosion caused by said abrasive particles to the impact angle of the particles, said attachment being applied to surface portions of the members to be protected.

Abstract: The stall condition occurring in the unstable working range of an axial flow fan or compressor arranged in an air duct is detected by measuring the pressure difference between the total air pressure acting in a direction opposite to the direction of revolution of the fan wheel and a reference pressure corresponding substantially to the static pressure at the wall of the air duct in the same radial measuring plane. The detector device comprises first and second pressure measuring probes of an open tubular configuration for measuring said total pressure and reference pressure, respectively, and means for detecting the difference between the pressure values measured thereby, said probes being designed and arranged in the air duct so that the flow conditions around them are equal in the stable working range of the fan or compressor.