Abstract: Mixing section for outdoor air and return air in an air-conditioning apparatus, the mixing section being positioned between a supply duct supplying outdoor air into a room and a return duct removing exhaust air from the room for mixing outdoor air and return air. The supply and return ducts comprise adjusting devices for adjusting the air flows. To control the air flows at different mixing ratios and to make the mixing more efficient, guides are provided after the adjusting devices of both the supply device and the return device in a mixing space so as to divide the air flows passing through the adjusting devices into a plurality of separate interlapping air jets crossing each other.

Abstract: Disclosed is a centrifugal-blower impeller made from a back plate and a front plate and blades attached between these plates. The back plate or the front plate of the impeller or both of them are prestressed in a direction opposite to the stresses produced by centrifugal force when the impeller rotates. According to a preferred embodiment of the impeller the back plate is prestressed by means of a stressing member having the shape of a truncated cone, which is supported by the inner end of the hub of the driving shaft of the blower. In addition a stressing flange is attached to said hub and is tightened to the back plate by means of bolts. The front plate may be prestressed by means of a stressing ring mounted on the suction ring of the front plate.

Abstract: Disclosed is an impeller in a centrifugal blower, especially a high-pressure blower, wherein the curved part of the front plate of the impeller is replaced by a conical supporting ring. The upper edge of the supporting ring is attached to the blades of the impeller and the lower edge to the cylindrical suction ring of the impeller. A guide ring made of thin plate is mounted inwards from the supporting ring.

Abstract: Disclosed is a centrifugal-blower impeller, which consists of a center part and radially outer part, which has a smaller thickness of material than the center part. The outer part consists of ring segments attached by welding to the periphery of the center part. The ring segments are first welded to the center part and thereafter radially to each other so that the ring segments are subject to tensile stress and the center part to compressive stress.