Lubricating liquid fed from a reservoir to a compression mechanism is collected by a circumferential wall that surrounds the drive shaft of the compression mechanism and rotates synchronously with it immediately after liquid is discharged into the space inside the housing with or without compressed fluid. Liquid is then urged outward under centrifugal force from an outlet formed at a preset axial location of the circumferential wall. Exiting liquid is received by a fixed liquid return cover that surrounds the circumferential wall near its outlet and led back to the reservoir.