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A large slide valve member concentrically mounts a small slide valve member or slide stop at one end thereof proximate to a helical screw rotary compressor discharge port with the small and large slide valve members movable as a unit for varying the built in volume ratio of the compressor. The small

A large slide valve member concentrically mounts a small slide valve member or slide stop at one end thereof proximate to a helical screw rotary compressor discharge port with the small and large slide valve members movable as a unit for varying the built in volume ratio of the compressor. The small slide valve member is shiftable independently of the large slide valve member to vary the capacity of the machine. A large diameter cylinder fixedly mounted to the end of the compressor casing remote from an outlet port slidably mounts interiorly a smaller diameter cylinder fixed to the large slide valve via a spindle. The small slide valve is fixed to one end of a piston rod which extends through a bore within the large slide valve member and the spindle and terminates internally of the small diameter sliding inner cylinder and has fixed thereto a piston. Hydraulic fluid supplied to one side of the piston and removed from the other side shifts the small slide valve independent of the position of the large slide valve member. A stepping motor fixed to the outer cylinder has an output shaft fixed to an elongated ball screw mounted for rotation with its axis parallel to the concentric inner and outer cylinders and a cylindrical ball nut concentrically positioned on the ball screw, is flange connected through a slot opening within the side of the fixed outer cylinder, to the outer periphery of the inner cylinder. Bearing balls positioned between opposing screw threads of the ball screw and the ball nut move through a circulating loop such that the inner cylinder and thus the slide stop and the large slide valve member is driven bidirectionally, incremented by the stepping motor.

대표청구항 ▼

In a positive displacement helical screw rotary compressor including a casing provided with a barrel portion defined by laterally intersecting bores with coplanar axes located between axially spaced end walls, and having helical screw rotors each having grooves and mounted for rotation within respec

In a positive displacement helical screw rotary compressor including a casing provided with a barrel portion defined by laterally intersecting bores with coplanar axes located between axially spaced end walls, and having helical screw rotors each having grooves and mounted for rotation within respective bores with the grooves of respective rotors intermeshed, an axially extending recess, open to an inlet port and provided within the barrel portion of the casing in open communication with said parallel bores, a slide valve mounted for axial movement in the recess, the slide valve having an inner face in sealing relationship with the rotor, said slide valve having a discharge face at one end thereof remote from the end wall provided with said inlet port containing a radial discharge port opening and having a rear face at its opposite end, and a slide stop mounted for axial movement in said recess with said slide stop having an inner face in sealing relationship with the rotor, a slide stop front face engageable with the slide valve rear face to form a composite axially movable assembly operative to close the axially extending recess to the inlet port, said slide valve and said slide stop being movable axially apart to provide an opening therebetween of variable size and axial position in communication with the inlet port through said recess, first actuating means for shifting said slide valve between axially extreme positions with said slide stop front face engaged with the slide valve rear face and with the compressor at full load condition, to a position where said slide valve rear face is at a maximum remote position from said slide stop front face in a direction towards a compressor outlet port and second actuating means for axially shifting said slide stop and said slide valve as a unit with said slide stop front face and said slide valve rear face in contact with each other between positions of minimum compressor volume ratio with the discharge face of the slide valve remote from the discharge port to a second position of maximum compressor volume ratio with the discharge face of the slide valve proximate to said outlet port, the improvement wherein; an outer cylinder is fixedly mounted to a compressor casing to the side proximate to said slide stop, coaxially with said slide stop and said slide valve, an inner cylinder is mounted concentrically within said outer cylinder for axial sliding movement therein, said slide stop is provided with an axial bore, said inner cylinder being closed at opposite ends by transverse end walls, a tubular slide stop spindle is fixedly coupled at one end to the inner cylinder end wall proximate to the slide stop and at an opposite end to the slide stop such that the slide stop is driven directly by said inner cylinder, an axial bore is provided within the end wall of said inner cylinder proximate to the slide stop and is n axial alignment with the bore through the slide stop, a slide valve piston rod projects through said aligned bores within said slide stop and said inner cylinder end wall, is fixedly coupled at one end to said slide valve and has an opposite end terminating internally within said inner cylinder, a slide valve unloader piston is fixedly mounted to said opposite end of said piston rod and is in sealed engagement with the inner surface of the inner cylinder to form sealed chambers to opposite sides of the slide valve unloader piston, means are provided for selectively supplying hydraulic fluid to one of said chambers and for removing hydraulic fluid from the other chamber to drive the slide valve unloader piston axially within said inner cylinder and to shift said slide valve between said extreme positions with said piston and inner cylinder defining said first actuating means, and low friction, mechanical direct drive means are fixedly mounted to the outer cylinder and engage said inner cylinder for axially shifting said inner cylinder relative to the outer cylinder and to thereby axially shift the slide stop and the slide valve as a unit to vary the volume ratio of the compressor.