Patent ID: 8303264

Claim:
Device for adjusting the flow rate of a mobile oil-injected screw-type compressor driven by a thermal motor, the compressor having a gas inlet, a gas outlet and a pressure vessel connected to the outlet, the pressure vessel having an outlet pipe arranged to supply compressed gas, said device comprising: a control valve having a control valve inlet connected to the pressure vessel via a pressure pipe and which is arranged to supply a control pressure at an outlet thereof at a certain preset value of the pressure in the pressure pipe, which control pressure is in proportion to said pressure in the pressure pipe; an electronic speed controller arranged to adjust the rotational speed of the motor and which is connected to the control pressure of the control valve via a pressure sensor and a first control line, said speed controller arranged such that, as the control pressure rises, the motor is set at a lower rotational speed; a pneumatically controlled gas inlet valve at the gas inlet of the compressor, said gas inlet valve comprising a housing in which a valve element is mounted for axial reciprocal motion between an open and a closed position, and which is sealed on one side of the valve element so as to form a pressure chamber which is connected via a second control line to the control pressure of the control valve, said valve element being freely moveable in the housing, and a non-return valve biased towards a closed position by a spring and disposed in the line which connects the pressure chamber of the gas inlet valve to the control pressure of the control valve, said valve being movable towards an open position by the control pressure.