position usually allows a flow rate of from 10 to 20 by volume of the air flowing from the blower means 50 to flow through nevertheless the control means 78 90 are held such that when one is open the other is closed and vice versa thus unequal opposed airflows occur in the passage 38 such currents are a main flow from the slots 76 or 74 associated with the semi chamber 56 which maintains the corresponding control means 62 or 60 substantially open and also the return flow control means 90 or 78 open and a secondary flow from the slots 74 or 76 associated with the semi chamber 56 which maintains the control means 60 62 only partially open and the air return flow control means 78 or 90 closed the main flow is dominant and transfers the fabric 4 to the corresponding chamber 2 or 20 nevertheless the secondary flow provides a slight braking force whereby the fabric 4 is compacted possibly forming wrinkles 5 which are not maintained in the fabric as stated above the control means 60 62 are preferably butterfly valves and are offset in 90 u00b0 it is contemplated that the common shaft 64 be provided with a radial lever arm 93 held in place by a clamp 97 and which may be moved between adjustable stops 94 95.