Self-cleaning single loop mist type lubrication system for screw

Abstract

Intermeshed helical screw rotors are mounted for rotation by anti-friction bearings surrounding integral shafts extending axially outward of the ends of the intermeshed screw rotors and within respective high pressure outlet and low pressure inlet bearing housings, sealed to the exterior. Oil from a separator/sump at or near compressor discharge pressure feeds via a closed passage to annular cavities surrounding the rotor shafts upstream of the outlet housing bearings. Oil seeps through very narrow annular gaps functioning as self-cleaning upstream capillaries to the outlet bearing cavities with the pressure reduction causing oil mist lubrication of the confined bearings within the outlet bearing housing. Further passages fluid connect the outlet bearing housing cavities to similar cavities within the inlet bearing housing where mist lubrication of the inlet bearings occurs. Further, oil passage means connect the inlet bearing housing cavities to an oil injection port via a downstream capillary with the oil injection port opening to the working chamber first closed thread. The upstream and downstream capillaries insure proper pressure reduction through the single loop lubrication system and the downstream capillary functions to maintain a pressure differential between the inlet bearing housing and the suction side of the intermeshed screws when the slide valve shifts to full unloaded position such that the oil injection port is open directly to the suction port of the compressor.