Patent ID: 7481634
Filing Date: 2009-01-27
Classification: F04C

Abstract:
1. Volumetric screw compressor, comprising: a casing in which it is possible to identify a suction chamber and a delivery chamber, between which a pair of screw rotors is included; a pan containing oil; an adjustment unit suited to adjust the delivery of said compressor, comprising: a slide valve externally cooperating with said rotors; a fluid-operated actuator constituted by a cylinder in which it is possible to identify an active chamber with a sliding piston connected to said slide valve through a rod; a plurality of flow paths made in said cylinder in correspondence with said active chamber; at least one oil delivery duct connected to said pan; a plurality of oil drain ducts connecting said flow paths of said active chamber to said suction chamber; on-off solenoid valves inserted in said drain ducts; at least one control unit for said on-off solenoid valves, wherein said adjustment unit also comprises a flow switching unit that connects said active chamber of said fluid-operated actuator with said pan and with said suction chamber and is constituted by a flow switch removably associated with a switching solenoid valve electrically connected to said control unit, said switching solenoid valve being suited to be associated, alternatively, with flow switches, with separate fluid ducts depending on the open or closed positions of said on-off solenoid valves and said switching solenoid valve and on the position of said slide valve with respect to said rotors, to obtain separate deliveries of compressed fluid.