The channel (39) on the delivery side of the blower (15) is fitted to the blower cover (20) or crankcase and is entered via a slot entry (28) whose fitted baffle (34) is used to guide the flow so as to close off the main air flow entry (28) to the rear of the baffle. The slot lies close to the blower wheel and within the wheel diameter and comes in bow shape, specifically the arc of a circle to extend over an angle of 30 deg. The slot is adjoined by a flat wide part of the channel (30). In the case of several entry slots arranged in parallel normal to the air flow, each slot has its own baffle sheet arranged along the leading edge of the slot to lie at 1.5 to 4mm away from the trailing edge. The extent of the sheet exceeds the width of the associated slot, the slots arranged between guiding gills. Gills or sheets are arranged at 15-20 deg. to the air flow and the channel (3) is made from flexible material.
