Abstract: A variable capacity screw compressor comprises a suction port, at least two screw rotors and a discharge port being configured in relation to a selected rotational speed that operates at least one screw rotor at an optimum peripheral velocity that is independent of a peripheral velocity of the at least one screw rotor at a synchronous motor rotational speed for a rated screw compressor capacity. A motor is configured to drive the at least one screw rotor at a rotational speed at a full-load capacity that is substantially greater than the synchronous motor rotational speed at the rated screw compressor capacity. A variable speed drive receives a command signal from a controller and generates a control signal that drives the motor at the selected rotational speed. A method for sizing at least two variable capacity screw compressors and a refrigeration chiller incorporating a variable capacity screw compressor are separately presented.

Abstract: A refrigerant compressor assembly for a refrigeration circuit controls the temperature within a temperature controlled space. The refrigerant compressor assembly includes a first unloading valve, a first valve actuator, and a first valve control system that adjusts the first valve actuator via a pulse-width-modulated signal, a second unloading valve, a second valve actuator, and a second valve control system that adjusts the second valve actuator via a pulse-width-modulated signal. The refrigerant compressor assembly also includes a third unloading valve. The first valve actuator is coupled to the first and third unloading valves and controlled by the first valve control system. The unloading valves selectively allow or resist fluid flow from higher to lower pressure areas within the refrigerant compressor assembly.

Abstract: A single screw compressor is arranged to vent the flutes of its main rotor at all times, without having to provide a check valve in the discharge port of the main rotor casing. An additional outlet port in the casing vents gas from the discharge ends of the flutes into the body of a slide instead of to the discharge port. The vented gas is guided to an exit port of the slide, from where it can reach either the discharge port or the bypass port of the casing at all times during use of the compressor and under all loading conditions. The design of the slide further allows the use of an offset •? discharge port in the casing, in relation to the main rotor. This means that pressure acting through the discharge port in use of the compressor tends to press the slide against another structure than the main rotor, for instance a bearing housing, giving better support to the slide. The slide also provides an improved oil delivery arrangement.

Abstract: A compressor (20) has an unloading slide valve (100). The valve has a valve element (102) having a range between a first condition and a second condition, the second condition being unloaded relative to the first condition. A first surface (200) of the valve element (102) is in sliding engagement with a second surface (202) of the housing (22) during movement between the first and second conditions. The valve element is coupled to an actuating piston (124). The compressor includes a linear bearing (132) guiding a piston shaft (122).

Abstract: A compressor (20) has at least a first rotor (26; 28) at least partially within a bore (276; 278) of a housing. A slide valve element (102; 300) is positioned at least partially within a channel (200; 301) in the housing and has a first surface facing the first rotor. The slide valve element includes a body (268; 302) and a coating (270; 306) on the body. The coating forms the first surface.

Abstract: A compressor having a dual slide valve assembly is disclosed. The slide valve assembly includes: i) a volume slide valve mechanism that is slidably movable to control compressor volume ratio and power input to the compressor; and ii) a capacity and volume slide valve mechanism that is in operational association with the volume slide valve mechanism, and the capacity and volume slide valve mechanism is slidably movable to control compressor capacity and to control volume ratio and power input to the compressor. In at least some embodiments, the compressor is a rotary gas compressor for a compression (e.g., refrigeration) system. A method of increasing compressor efficiency using the dual slide valve assembly is also disclosed. Compressor volume load and/or volume ratio and/or compressor power input can be simultaneously controlled by both the volume slide mechanism and the capacity and volume slide mechanism. Advantageously, compressor efficiency is increased.

Abstract: A valve for varying volume ratio in a screw compressor to balance a compression pocket pressure and a discharge pressure in the screw compressor comprises a valve body and a reed valve. The valve body defines a duct and an auxiliary port. The duct includes an open end in communication with a discharge chamber of the compressor and thereby the discharge pressure. The auxiliary port extends from a rotor bore of the compressor to the duct and provides fluid communication therebetween for communicating the compression pocket pressure to the duct. The reed valve is disposed within the duct for regulating fluid flow between the compression pocket and the duct. The reed valve is operable via a pressure differential between the compression pocket pressure and the discharge pressure.

Abstract: A compressor (20) has an unloading slide valve (100). The valve has a valve element (102) having a range between a first condition and a second condition, the second condition being unloaded relative to the first condition. A piston (124) is in a cylinder (128) and mechanically coupled to the valve element. A control valve (40; 42) is coupled to a headspace (138) of the cylinder to selectively expose the headspace to a fluid source (144), pressure of fluid in the headspace producing a force on the piston and valve element in a direction from the second condition toward the first condition. The compressor includes means (190, 192; 210; 220) for relieving excess pressure in the headspace.

Abstract: The present invention relates to a screw compressor and a method for operating the compressor primarily for gaseous refrigerants, comprising a compressor housing (4) and a male (8) and a female (10) screw rotor arranged in screw rotor bores in the compressor housing (4), which male and female rotor are co-rotatingly drivable and interacting for compressing the refrigerant, which screw compressor comprises at least one slider (22) movable in relation to the male and the female rotor, where movement of the slider controls the internal volume ratio of the screw compressor, which slider is moveable in a slider housing (20) in a direction sideways to the plane formed by the rotational axes of the male and the female rotor, which slider, interacting with the male and the female rotor, comprises at least two surfaces (152, 154) cooperating with subsequent surfaces (156, 158) placed in conjunction with the slider housing for controlling the angular and linear placement of the slider in its forward position.

Abstract: A compressor apparatus (20) has a housing (22) having first (53) and second (58) ports along a flow path. One or more working elements (26; 28) cooperate with the housing (22) to define a compression path between suction (60) and discharge (62) locations along the flow path. An unloading valve (100) has a valve element (102) having a range between a first condition and a second condition, the second condition being unloaded relative to the first condition. Means (120, 160) bias the valve element toward a third condition intermediate the first and second conditions.

Abstract: A compressor includes a slide valve (24) having a passage that can be in fluid communication with a discharge plenum (22) and a suction plenum (20). The slide valve (24) position may be axially adjusted to control an amount of refrigerant that is compressed between a male rotor (14) and a female rotor (12) in the compressor based upon a system control scheme that determines capacity demand. The passage (28) is in fluid communication with the discharge plenum (22) and the suction plenum (20) when the slide valve is in a fully unloaded position or a partially unloaded position. A compressor housing blocks an opening to the passage when the slide valve (24) is in a fully loaded position. The location of the opening (36) in the slide valve determines what point in axial travel of the slide valve that fluid bypass begins.

Abstract: A system is provided for controlling the balance piston pressure in a screw compressor. The system can use the slide valve of the compressor as a valve to control the flow of fluid from a fluid source to the balance piston. When the slide valve prevents direct flow between the fluid source and the balance piston, an alternate path is used to provide fluid at a reduced pressure to the balance piston. The reduced pressure fluid is obtained by passing the fluid from the fluid source through an orifice to lower the fluid pressure.

Abstract: A compressor (20) has an unloading slide valve (100). The valve has a valve element (102) having a range between a first condition and a second condition, the second condition being unloaded relative to the first condition. A first surface (200) of the valve element (102) is in sliding engagement with a second surface (202) of the housing (22) during movement between the first and second conditions. The compressor includes means for lubricating the first (200) and second (202) surfaces.

Abstract: A screw compressor (10) comprises a housing (12, 14, 16), a slide valve assembly (23) and a pulsation damper. The housing (12, 14, 16) receives a supply of working matter from a pair of intermeshing screw rotors (18, 20), and comprises a slide recess (51), a pressure pocket (32), and a piston cylinder (54). The slide valve assembly (23) regulates the capacity of the screw compressor (10), and comprises a slide valve (36) axially movable within the slide recess (51) and the pressure pocket (32), a piston head (40) axially movable within the piston cylinder (54), and a piston shaft (38) connecting the slide valve (36) with the piston head (40). The pulsation damper comprises a flange (58) for separating the pressure pocket (32) from the piston cylinder (54), a bore (60) for receiving the piston rod (38), and a damping channel (46A) extending through the flange (58).

Abstract: A four stroke diesel engine combined with a supercharger is operable to supply varying amounts of air to the engine responsive to the load on the engine. The supercharger has a pair of rotors driven by the engine operable to move air to the engine. Gates associated with the rotors control the amount of air and pressure of the air moved by the rotors to the diesel engine.

Abstract: A method of supplying lubrication oil to a two-stage screw compressor is disclosed in which a low-pressure stage screw compressor and a high-pressure stage screw compressor are integrally constructed. A compression space is formed by a male rotor and a female rotor, and operation gas is fed for compression to the compression space. The method prevents degradation of volumetric efficiency caused by return of lubrication oil, coming from a bearing and a shaft sealing device, to the low-pressure stage screw compressor, and as a result, refrigeration capacity is improved and the amount of the lubrication oil is reduced.

Abstract: In a screw compressor, a pair of rotors are located in a housing to be rotatable around their rotary axes to form in the housing a compression chamber in which gas sucked from a suction port of the housing is compressed thereby discharging the compressed gas from a discharge port of the housing. The suction port is provided in the housing at a position radial outside of the rotors, and the housing is provided with a communication passage through which the suction port communicates with the compression chamber before being communicated with the suction port. Furthermore, the communication passage is provided such that the gas sucked from the suction port flows into the communication passage in a direction approximately parallel with an axial direction of the rotors.

Abstract: Various embodiments of the invention provide a screw compressor for compressing a refrigerant in a refrigeration system. The screw compressor includes a rotor case, which accommodates a primary helical rotor that is intermeshed with at least one secondary helical rotor, to compress the refrigerant in the rotor case. The rotor case also includes a slide valve supporting member that is fixed on an inner wall of the rotor case. Moreover, a slide valve, located in the rotor case, slides axially on the slide valve supporting member. The slide valve controls the volume of refrigerant during compression. The slide valve is fitted with at least one internal pressure relief valve, to relieve internal pressure in the screw compressor.

Abstract: An intended purpose of this invention is to realize a gear pump suitable for delivery of high-pressure and high-viscosity fluids by using helical gears 2 and 3 meshing with each other. For this purpose, the gear pump includes introduction paths 121 and 131 for introducing the fluid from a discharge side toward shaft end sides of gear shafts 21 and 31 to apply shaft ends of the gear shafts 21 and 31 with fluid pressures counterbalancing axial thrusts produced by the helical gears 2 and 3.

Abstract: A compressor (20) has an unloading slide valve (100). The valve has a valve element (102) having a range between a first condition and a second condition, the second condition being unloaded relative to the first condition. A piston (124) is in a cylinder (128) and mechanically coupled to the valve element. A control valve (40; 42) is coupled to a headspace (138) of the cylinder to selectively expose the headspace to a fluid source (144), pressure of fluid in the headspace producing a force on the piston and valve element in a direction from the second condition toward the first condition. The compressor includes means (190, 192; 210; 220) for relieving excess pressure in the headspace.

Abstract: A compressor (20) has an unloading slide valve (100). The valve has a valve element (102) having a range between a first condition and a second condition, the second condition being unloaded relative to the first condition. A piston (124) is in a cylinder (128) and mechanically coupled to the valve element. A control valve (140) is coupled to a headspace (138) of the cylinder to selectively expose the headspace to a flu source (144), pressure of fluid in the headspace producing a force on the piston and valve element in a direction from the second condition toward the first condition. The compressor includes a pressure relief valve coupling (180) in the headspace to suction conditions to unload the compressor responsive to an overpressure.

Abstract: A screw compressor according to the present invention includes a slide valve adapted to move forward and backward in parallel with the axis of a pair of screw rotors and also includes a plurality of hydraulic cylinders for moving the slide valve forward and backward, the plural hydraulic cylinders imparting, in synchronization with each other, a driving force to the slide valve in the same direction. With this configuration, it is possible to quicken an operation of the slide valve and improve the responsivity in volume control without increasing the diameters of pistons of the hydraulic cylinders for actuating the slide valve and without complicating equipment.

Abstract: A compressor apparatus has a housing (22) having first (53) and second (58) ports along a flowpath. One or more working elements (26, 28) cooperate with the housing to define a compression path between suction and discharge locations along the flowpath. A check valve (70) has a valve element having a first condition permitting downstream flow along the flowpath and a second condition blocking a reverse flow. Sound suppressing means (120, 220, 320) at least partially surround the flowpath upstream of the valve element (70).

Abstract: In order to improve a screw compressor for compressing refrigerant in a refrigerant circuit, comprising a compressor housing, in which a screw rotor receiving means and an inlet channel as well as an outlet channel for the refrigerant to be compressed are provided, at least one screw rotor arranged in the screw rotor receiving means, a drive for the at least one screw rotor and a lubricant supply which conveys lubricant from a lubricant reservoir acted upon by pressure via a line system at least to the at least one screw rotor during operation, in such a manner that the operation and the monitoring of the screw compressor are reliable it is suggested that a valve be provided in the line system of the lubricant supply, this valve being controllable by way of a difference in pressure between the pressure in the outlet channel and a reference pressure influenced by a pressure in the refrigerant circuit and opening when the screw rotor is compressing refrigerant as well as closing when the screw rotor is not comp

Abstract: A compressor apparatus (20) has a housing (22) having first (53) and second (58) ports along a flow path. One or more working elements (26; 28) cooperate with the housing (22) to define a compression path between suction (60) and discharge (62) locations along the flow path. An unloading valve (100) has a valve element (102) having a range between a first condition and a second condition, the second condition being unloaded relative to the first condition. Means (120, 160) bias the valve element toward a third condition intermediate the first and second conditions.

Abstract: A volumetric compressor comprising: a casing provided with a suction chamber and a delivery chamber, between which a pair of screw rotors is included; a pan containing oil, and a delivery adjustment unit equipped with a slide valve, cooperating with the rotors and with a fluid-operated actuator, in which it is possible to identify an active chamber with a sliding piston connected to the slide valve. The adjustment unit comprises a flow switching unit, that connects the active chamber of the actuator to the pan and to the suction chamber and comprises a static flow switch removably associated with a switching solenoid valve electrically connected to a control unit. The switching solenoid valve is suited to be associated, alternatively, with different static flow switches that make it possible to obtain deliveries of compressed fluid varying discretely or continuously, depending on the position of the slide valve with respect to the rotors.

Abstract: A compressor having a high pressure slide valve assembly is disclosed. The slide valve assembly includes: a volume slide valve mechanism, the mechanism slidably movable to control compressor volume ratio and power input to the compressor. The assembly also includes a capacity slide valve mechanism that is in operational association with the volume slide valve mechanism, the capacity slide valve mechanism slidably movable to control compressor capacity. At least one of the volume slide valve mechanism and the capacity slide valve mechanism includes at least one groove or channel, and the at least one groove or channel provides for lubrication to ensure relative movement between the slide mechanisms in a high pressure environment. A method of controlling compressor volume ratio, power input and capacity in a compressor operating in a high pressure environment is also disclosed.

Abstract: A compressor (20) has at least a first rotor (26; 28) at least partially within a bore (276; 278) of a housing. A slide valve element (102; 300) is positioned at least partially within a channel (200; 301) in the housing and has a first surface facing the first rotor. The slide valve element includes a body (268; 302) and a coating (270; 306) on the body. The coating forms the first surface.

Abstract: A screw compressor (20) has compressor lubrication network having a lubricant outlet port (242) along a low pressure cusp (244). An unloading slide valve element (102) may be along a high pressure cusp (105).

Abstract: A method and system is provided for reducing chatter in multi-capacity compressors having disengageable eccentric structures. The multi-capacity fluid compressor includes a compression chamber having a discharge end and an inner surface. The compressor also includes a compression member having a disengageable eccentric structure allowing the compressor to provide discrete compression capacities. A valve portion is disposed adjacent to the discharge end of the compression chamber and is arranged and disposed to discharge a compressed fluid when the compression member has completed. A discharge arrangement is arranged and disposed to discharge at least a portion of fluid remaining in the compression chamber at the completion of the compression cycle. The discharge of at least a portion of the fluid remaining in the compression chamber reduces or eliminates forces on the disengageable eccentric structure to limit rotational acceleration of the disengageable eccentric structure.

Abstract: In an arrangement on an oil-flooded screw compressor with two rotors, a male rotor having essentially convex lobe flanks and a female rotor having essentially concave flank portions, with the male rotor having a drive-shaft end and an oil-pressure loaded balancing piston supplied with oil via a pressure line, both rotors are enclosed in housing sections, with a regulating device arranged either on or in the compressor the inputs of which are at least connected to measuring means for the pressure on the suction side and measuring means for determination of the input power, wherein according to the invention means for changing the pressure in the pressure line to the balancing piston are arranged with said means having a control interconnection to the regulating device, with the latter having an algorithm between operating parameters representing input variables for the regulating device and the pressure in the pressure line to the balancing piston.

Abstract: Disclosed is a screw compactor comprising two screw rotors which are disposed in screw rotor bores inside a compressor housing and compress a coolant that enters at a coolant inlet and discharge said coolant at a coolant outlet, and a coolant inlet that is arranged within the compressor housing, said coolant being supplied by a coolant-injecting device via a conduit system in order to additionally cool the screw compressor. The inlet is disposed so as to extend into compression spaces that are enclosed by the screw rotors and the screw rotor bores. The aim of the invention is to create a screw compactor in which the compressive oscillations occurring at the inlet do not travel at all or only in an attenuated manner into the conduit system for the coolant-injecting device.

Abstract: A rotary screw vacuum pump system includes a vacuum bypass system, which communicates with a first closed cell formed by the rotor system. An air bypass valve within an air communication conduit is controlled by a solenoid valve that operates in response to a pressure switch. The pressure switch is in communication with a vacuum pump suction conduit that draws suction for a suction system attached thereto. The solenoid valve is activated by the pressure switch at a vacuum level slightly below the point at which the undesirable cavitation noise generated at terminal vacuum condition begins.

Abstract: An object of this invention is to prevent drop of life of a bearing by an axial force when using a pump as a compressor. In a vacuum pump 1 compressing and discharging gas in a direction of a rotor axis by rotation of screw rotors 3, 4 engaged together which are supported rotatably in a casing 2, balance pistons 13, 14 are disposed on shafts 6, 7 of said screw rotors at inlet side of said casing. The balance pistons separate a receiving section 17 at area of the screw rotor and a pressurizing section 16 at area of the balance piston, and a thrust force of the screw rotors at a pressurizing condition is canceled by acting the discharge pressure in the pressurizing section. The pump is used as a compressor when the discharge pressure is acted on the balance pistons 13, 14. When the pump is used as a vacuum pump, air at discharge side is sucked as cool air through a cooler toward a place near to the discharge side of the receiving section 17 at area of the screw rotor.

Abstract: A screw rotor device has a housing with an inlet port and an outlet port, a male rotor, and a female rotor. The male rotor has a pair of helical threads with a phase-offset aspect, and the female rotor has a corresponding pair of helical grooves. The female rotor counter-rotates with respect to the male rotor and each of the helical grooves respectively intermeshes in phase with each of the helical threads. The phase-offset aspect of the helical threads is formed by a pair of teeth bounding a toothless sector. The arc angle of the toothless sector is a least twice the arc angle that subtends either one of the teeth. The helical grooves have a radially narrowing axial width at the periphery of the female rotor. The male and female rotors may include a buttress thread profile and may be limited in length to a single pitch.

Abstract: A supercharger includes multiple back flow ports which are controlled by valves. The valves regulate the timing and area for back flow of pressurized outlet air into the rotor chambers. The back flow air tends to equalize air pressure in the chambers prior to their exhausting into the outlet and thereby reduces flow back noise. The multiple ports are opened selectively or sequentially to provide noise control with improved efficiency at varying speeds.

Abstract: A screw compressor is connected to a motor to be driven by the motor even during periods of low compressed air consumption. During such periods, the screw compressor is at least partially unloaded to make it easier and less costly to drive the compressor. The unloading is performed by removing air from the compressor. Preferably, that is done by communicating the air inlet of a small capacity vacuum device with the air outlet of the screw compressor. Suction from the vacuum device is transmitted to the air outlet of the screw compressor to suck air out of the screw compressor to reduce the engine horsepower needed to rotate the screw compressor. The vacuum device can also be used to boost the air volume and/or the air pressure. The system can be used in a drilling rig which drills holes in the ground. The screw compressor can be unloaded during start up of the motor by briefly driving the vacuum device by pressurized liquid from a pre-pressurized hydraulic accumulator.

Abstract: A pressure equalization method and system is provided for starting a compressor while maintaining the condenser at a high pressure and includes a valve and a bleed port. The compressor has a compressor inlet for receiving a fluid at a first pressure and a compressor outlet for discharging the fluid at a second pressure, and is operable to compress the fluid from the first pressure to the second pressure. The valve is proximate to and in fluid communication with the compressor outlet and is movable to an open position when the compressor is operating to permit the fluid at the second pressure to flow through the valve and is movable to a closed position when the compressor stops operating to prevent backflow of the fluid at the second pressure through the valve toward the compressor inlet. The bleed port is upstream of the valve and in fluid communication with the compressor inlet to equalize the pressure of the fluid contained in the compressor when the compressor stops operating.

Abstract: An automatic regulator of the air intake in a tank installed in a circuit for the production of compressed air wherein the regulator provides that the intake orifice (7) which aspires external air is operated in opening/closing by means of a disk shutter. The disk shutter is provided with a tang which idly slides on a central hub. The disk shutter is subjected to the biasing action of a spring which sits in the hub and to the balancing action of a flux of air removed from the separator tank.

Abstract: An axial slide valve is provided with an axially extending fluid chamber at each end with one chamber receiving a spring and being acted on by suction pressure and the other chamber coacting with a fixed piston and being acted upon by discharge pressure or the like whereby the slide valve is positioned so as to balance the spring and fluid pressures and thereby the compressor capacity.

Abstract: An axial slide valve is provided with an axially extending fluid chamber at each end with one chamber receiving a spring and being acted on by suction pressure and the other chamber coacting with a fixed piston and being acted upon by discharge pressure or the like whereby the slide valve is positioned so as to balance the spring and fluid pressures and thereby the compressor capacity.

Abstract: A package-type screw compressor includes a low-pressure stage state compressor and a high-pressure stage compressor. Motive power is transmitted from an electric motor to the two compressors via a speed increaser. The discharge gas, compressed and heated to a high temperature by the low-pressure stage compressor, is cooled by an intercooler. The discharge gas, compressed and heated to a high temperature by the high-pressure stage compressor, is cooled by an aftercooler. A casing of the intercooler and that of the aftercooler are formed integrally with a speed increaser casing, reducing the number of component parts. A cooler portion, formed by the intercooler and the aftercooler, is spaced from the speed increaser casing, thereby preventing heat, produced by the compressed air, from being transmitted to the speed increaser casing.

Abstract: A screw compressor 1 comprises a screw compressor body 2 having a pair of female and male screw rotors 21 meshed with each other encased in a rotor casing 22, and a motor casing 4 having a motor 3 for driving a male rotor 21b of the screw rotor 21 encased therein. The screw compressor body 2 and the motor casing 4 are connected integrally. The male rotor 21b and the motor 3 are connected by a common rotor shaft 23. In the common rotor shaft 23, the counter motor 3 side is supported by a rolling bearing and a projecting end of the motor 3 is supported by a rolling bearing 7 on the motor side, and a portion between the motor 3 and the screw rotor 21 is supported by an intermediate rolling bearing 6.

Abstract: A screw compressor includes a compressor housing defining parallel rotor housing sections, each rotor housing section containing a rotor, and adjacent rotors defining compressor pairs, the housing further including a suction port and a discharge port for each of the compressor pairs, and further including additional ports selected from first closed lobe ports, last closed lobe ports, and economizer ports, wherein at least one of the additional ports is communicated with a first pair of the at least two pairs, and another of the additional ports is communicated with a second pair of the at least two pairs whereby interaction between the additional ports is reduced. In accordance with a further aspect of the invention, configurations are provided so that the first discharge port has a lower volume index ratio (Vi) than the second discharge port.

Abstract: A screw rotor device has a housing with an inlet port and an outlet port, a male rotor, and a female rotor. The male rotor has a pair of helical threads with a phase-offset aspect, and the female rotor has a corresponding pair of helical grooves. The female rotor counter-rotates with respect to the male rotor and each of the helical grooves respectively intermeshes in phase with each of the helical threads. The phase-offset aspect of the helical threads is formed by a pair of teeth bounding a toothless sector. The arc angle of the toothless sector is a least twice the arc angle that subtends either one of the teeth. The helical grooves have a radially narrowing axial width at the periphery of the female rotor.

Abstract: A pressure equalization method and system is provided for starting a compressor while maintaining the compressor at a high pressure and comprises a valve and a bleed port. The compressor has a compressor inlet for receiving a fluid at a first pressure and a compressor outlet for discharging the fluid at a second pressure, and is operable to compress the fluid from the first pressure to the second pressure. The valve is proximate to and in fluid communication with the compressor outlet and is movable to an open position when the compressor is operating to allow the fluid at the second pressure to flow through the valve and is movable to a closed position when the compressor stops operating to prevent backflow of the fluid at the second pressure through the valve toward the compressor inlet. The bleed port is upstream of the valve and in fluid communication with the compressor inlet to equalize the pressure of the fluid contained in the compressor when the compressor stops operating.

Abstract: A package-type screw compressor includes a low-pressure stage state compressor and a high-pressure stage compressor. Motive power is transmitted from an electric motor to the two compressors via a speed increaser. The discharge gas, compressed and heated to a high temperature by the low-pressure stage compressor, is cooled by an intercooler. The discharge gas, compressed and heated to a high temperature by the high-pressure stage compressor, is cooled by an aftercooler. A casing of the intercooler and that of the aftercooler are formed integrally with a speed increaser casing, reducing the number of component parts. A cooler portion, formed by the intercooler and the aftercooler, is spaced from the speed increaser casing, thereby preventing heat, produced by the compressed air, from being transmitted to the speed increaser casing.

Abstract: An air compressor assembly of the rotary screw type. The air compressor assembly comprises a housing having an inlet end and a discharge end. An internal working chamber extends within the housing and terminates in a discharge end face at the discharge end of the housing. At least one rotor is mounted for rotation and axial movement within the working chamber. The rotor has a discharge end surface having a step defined thereon. A thrust piston extends from the rotor and is positioned within a thrust piston chamber. A pressure source is associated with the thrust piston chamber and is controllable between a high pressure condition and a reduced pressure condition to control the position of the rotor relative to the discharge end face. A method of mounting a rotor with a desired end clearance is also provided.

Abstract: A screw compressor having an unloader valve with a movable valve member, the unloader valve being capable of indicating when the valve member is installed incorrectly. The valve member is manufactured such that if it is installed incorrectly it provides a leakage path sufficiently large to be detected during full load testing of the compressor. When the screw compressor fails the load test, the compressor is partially disassembled, and the valve is reinstalled in the proper orientation and the compressor is re-tested. The valve member leakage path is provided while maintaining low costs for production and assembly of the compressor.

Abstract: The present invention relates to a variable capacity helical screw compressor for compressing a gaseous medium, usually air. The compressor includes at least one lift valve (1) which connects with a first compression chamber in the compressor.