Patent ID: 8491280
Filing Date: 2013-07-23
Classification: F04B,F04C

Abstract:
1. An oil-flooded screw compressor, comprising: a casing; a pair of rotors each having a screw-thread-shaped groove and being housed in the casing; an electric motor for rotationally driving the pair of rotors; a control device for controlling the electric motor; an oil feeding mechanism for feeding oil into working chambers formed by being enclosed by the casing and the pair of rotors in which teeth thereof are meshed to each other; and an oil separating mechanism for separating the oil from compressed gas discharged from the working chambers; wherein during the time interval in which the pair of rotors in normal operation is brought to a halt and then the electric motor is started up to bring the pair of rotors back into normal operation, the control device exercises control such that at least part of the oil fed into an internal space of the casing that houses the pair of rotors is discharged outside the internal space, and wherein upon receipt of a halt instruction, the control device stops the electric motor to bring the pair of rotors to a halt and exercises control so as to discharge, into the atmosphere, high-pressure compressed gas that remains inside a discharge pipe that communicates with a delivery port provided on the casing and for the working chambers to discharge the high-pressure compressed gas, and the control device then exercises control such that the pair of rotors rotate at a low speed for a fixed amount of time after the pressure near the delivery port decreases to the pressure near a suction port provided for the working chambers.