Abstract: In a compressor control system, surge upon a sharp demand for lower airflow is avoided by placing an offset value above the minimum airflow absolute limit. When reaching downward under inlet valve modulation such offset limit, the master-controller initiates bypass valve modulation and a subcontroller brings the inlet valve from the offset limit down to the absolute minimum airflow position. Provision is made against exceeding the offset limits during such excessive demand downward by imposing a limit to the inlet valve position command. Upon a return upward toward normal operation, provision is made against an intervening and sudden downward demand by imposing a limit to the inlet valve position command representing the minimum airflow operation.

Abstract: A variable-delivery vane-type rotary compressor includes passage means for defining a by-pass passage establishing communication between an aspirator chamber and a compression chamber, the by-pass passage having end openings exposed to the aspirator chamber and the compression chamber; and control means for mechanically controlling the amount of fluid by-passed from the compression chamber to the aspirator chamber through the passage means in accordance with pressure in the aspirator chamber and a discharge chamber.

Abstract: In a variable displacement vane-type rotary compressor, a rotational displacement of an adjust member relative to a front member fixedly closing a front end of a cam ring varies a compression starting point of a rotary vane in a working chamber formed in the cam ring. The front member is formed with an induction port and a bypass port, and the adjust member is formed with a bypass recess. The induction port and the bypass recess are in communication with each other in the working chamber irrespective of a position of the vane under all of the rotational displacement of the adjust plate to establish a communication between the induction port and the bypass port in the working chamber irrespective of the position of the vane when the bypass port overlaps with the bypass recess.

Abstract: A variable capacity vane compressor has a cylinder including a plurality of vanes slidably fitted in respective vane slits formed in a rotor thereof. Vane back pressure chambers are defined within the vane slits by respective ones of the vanes. A control element is rotatably arranged in the cylinder for varying the compression starting timing and hence the capacity of the compressor. Back pressure compensation holes are formed through the control element and communicating with a high pressure zone having high pressure of the compressor. The back pressure compensation holes are communicatable with each of the vane back pressure chambers for introducing the high pressure within the high pressure zone into the each vane back pressure chamber when the control element is in a first position wherein the compression starting timing is most retarded.

Abstract: In a variable-delivery vane-type rotary compressor, a rotational displacement of an adjust member relative to a front member fixedly closing a front end of a cam ring varies a compression starting point of a rotary vane in a working chamber formed in the cam ring. The rotational displacement of the adjust member is controlled by an adjust member actuating unit in response to a pilot pressure applied to the adjust member actuating unit from a pilot pressure applying unit. The pilot pressure applying unit includes a first passage communicating the adjust member actuating unit with a valve unit, a second passage communicating an induction chamber with the valve unit, and a third passage communicating a discharge chamber with the valve unit.

Abstract: A screw type vacuum pump has in a passage leading to its suction port a check valve which is adapted to open the valve securely by hydraulic pressure to open the gas flow passage without the hunting phenomenon. This permits the selection of a spring with a suitable spring constant for seating the valve body on the valve seat securely and promptly to prevent reverse gas flows.

Abstract: A variable capacity compressor includes a control element for determining timing of start of compression of a refrigerant gas. Control pressure which prevails in a high-pressure chamber acts on the control element. The high-pressure chamber communicates with a suction chamber via a communicating passage, across which is arranged a control valve device for opening and closing the communicating passage to change the control pressure within the high-pressure chamber. The control valve device comprises a valve body, a spring urging the valve body in a closing direction, and a bellows expansible and contractible in direct response to suction pressure within the suction chamber for urging the valve body in an opening direction against the force of the spring when it is expanded.

Abstract: A variable capacity compressor for use in a heat-exchange circuit. A pressure responsive valve is provided in a communication passageway extending between a low pressure chamber and a pressure controlled chamber. The pressure responsive valve is operative in response to pressure within the low pressure chamber for opening and closing the communication passageway to control pressure within the pressure controlled chamber, thereby varying the capacity of the compressor in such a manner as to reduce the capacity when the pressure within the low pressure chamber decreases to a level lower than a predetermined value. An electrically operated control device is operative in response to pressure or temperature of refrigerant gas in an evaporator of the heat-exchange circuit for maintaining the capacity large independently of operation of the pressure responsive valve, even if the pressure within the low pressure chamber decreases to a level lower than the predetermined value.

Abstract: A compressor unloader controller for placing a compressor in an unloaded condition when the compressor is being started. A compressor inlet valve, movable between a normally open and a closed position, admits fluid flow to the compressor when the valve is in the open position. A pressure reservoir contains pressure sufficient to bias the inlet valve into the closed position. A starter valve applies pressure from the pressure reservoir to the inlet valve only when the compressor is in a starting mode. The inlet valve may also be actuated, during normal compressor operation, by a pressure regulating device which is connected to a compressor outlet line.

Abstract: A rotary compressor of variable displacement type comprises a cylinder, a rotor accommodated in the cylinder in an eccentric relationship therewith, at least one vane incorporated in the rotor through an outer periphery of the latter and movable relative to the rotor reciprocatively in a longitudinal direction of the vane, and two side plates closing the cylinder at both axial ends of the latter. A suction port is formed in at least one of the side plates, while an opening portion is formed in a rear side portion of the vane as viewed in a direction of rotation of the rotor and being opened at a surface of the vane making sliding contact with the rotor. This opening portion is repeatedly communicated with and interrupted from a working space in the compressor according to the reciprocative movement of the vane relative to the rotor.

Abstract: A variable capacity vane compressor has an annular control element angularly displaceably received within an annular recess formed in one of side blocks defining a cylinder. The control element is angularly displaced in response to a difference in pressure between first and second pressure chambers formed in the one side block and communicating with a zone under lower pressure and a zone under higher pressure, respectively, and to the biasing force of a biasing member, thereby varying the opening angle of at least one second inlet port formed in the one side block and hence controlling the capacity of the compressor.

Abstract: A method of controlling the air output of a screw compressor, wherein the average air output of the compressor during operation is adapted to air consumption by throttling the flow of suction air or by connecting the compressor alternately to full air output capacity and idle operation capacity. In order to reduce the power consumption of the compressor, the air output is controlled first by throttling the flow of suction air and by simultaneously measuring underpressure in the suction conduit of the compressor. Thereafter the compressor is controlled so as to operate alternately at full air output capacity and idle operation capacity, and the pressure rise rate in the air-pressure network is measured when the compressor operates at full output capacity and the pressure fall rate is measured when the compressor operates at idle operation capacity.

Abstract: An improved valve assembly (100) is disclosed for use in a vacuum system (10). The valve assembly is provided with a valve (116) which is movable between a first position and a second position. In the first position, the vacuum reservoir (12) is isolated from the vacuum pump (14). In the second position, the valve permits air to flow from the vacuum reservoir to the vacuum pump only through metering ports (114). The valve assembly reduces the horse power requirement for initial start up of the vacuum system by restricting air flow from the vacuum reservoir to the vacuum pump. Also, an immediate vacuum is created in the valve assembly on start up to return oil from a separator (16) to the pump (14).

Abstract: A variable displacement vane compressor for an air conditioning system used in an automobile has a cylinder assembly having a bore which receives a rotor to form at least one crescent or compressing chamber between the rotor and the bore. The crescent chamber receives a refrigerant which is returned from the air conditioning system. The rotor has vanes which are extendably fitted therein so that the free end of the vanes are in contact with the circumferential inner surface of the bore during the rotation of the rotor, whereby when the vane passes through the crescent chamber, the refrigerant received therein can be compressed. The amount of the refrigerant introduced into the crescent chamber is adjustable in response to a change of a cooling load at the air conditioning system.

Abstract: A variable capacity compressor having a cylinder defining compression spaces therein. A control element is rotatable substantially in response to the difference between low pressure supplied from a suction chamber and control pressure created from high pressure supplied from a discharge pressure chamber for varying compression starting timing in the compression spaces and hence the capacity of the compressor. A capacity-reducing valve is operable in response to the control pressure for causing pressure within the least one of the compression spaces to leak into a low pressure side when the control element is in such an extreme position as to minimize the capacity of the compressor, to thereby further retard the compression starting timing and hence reduce the compressor capacity.

Abstract: In a compressor having a plurality of banks of cylinders, smaller steps of unloading are achieved by unloading a single cylinder in a bank. When only one cylinder is to be unloaded, gas bypass is used in order to maintain a closer balance of forces in the bank. When the entire bank is unloaded, it is preferably done via the suction cutoff method.

Abstract: A variable-displacement rotary compressor comprises a rotor with a vane and a side plate disposed to abut a side face of the rotor. The side plate has a suction port formed therein to open to both a working chamber abutment face thereof abutting to the rotor side face and a low pressure chamber, and the rotor has a suction path formed therein to open to the working chamber and to an abutment surface of the rotor. The suction path of the rotor communicates with the suction port of the side plate through rotation of the rotor so that a fluid is sucked from the low pressure chamber into the working chamber under suction stroke through the suction path and the suction port.

Abstract: A variable capacity compressor has first and second discharge pressure chambers provided, respectively, on opposite sides of a cylinder. A first communication passage communicates the first and second discharge pressure chambers with each other. A discharge port directly communicates with the first discharge pressure chamber. A capacity control device is operable in response to control pressure for controlling the capacity of the compressor and has a control pressure chamber in which the control pressure prevails. A second communication passage communicates the second discharge pressure chamber with the control pressure chamber. The second discharge pressure chamber is formed of an oil sump section communicating with the first discharge pressure chamber through the first communication passage, and a high pressure-introducing section supplied with compression medium delivered from the cylinder, wherein partition walls are provided which isolate the high pressure-introducing section from the oil sump section.

Abstract: A variable capacity compressor has a control element rotatably arranged within a cylinder, which has two pressure-receiving portions slidably received, respectively, in first and second pressure working chambers formed in the cylinder such that the first pressure working chamber is divided into a first lower-pressure chamber and a first higher-pressure chamber, and the second pressure working chamber into a second lower-pressure chamber and a second higher-pressure chamber. The first and second lower-pressure chambers are supplied with low pressure. A first passage extends between one of the first and second higher-pressure chambers and a compression space for supplying the former with discharge pressure from the latter. A second passage communicates between the first and second higher-pressure chambers. A control valve device is operable in response to suction pressure in the compressor for controlling pressure within the first and second higher-pressure chambers.

Abstract: An unloader device for controlling the output of a hydraulic pump, for example, in a constant pressure-type motor vehicle braking circuit. Delivery to hydraulic accumulators in the circuit is halted by a resilient seal defining an annulus forming part of the inlet fluid flow path to the pump and to which the pump delivery pressure is applied to expand the seal in the sense to close the annulus, by a valve operable when the delivery pressure reaches a predetermined value.

Abstract: Variable flow pump comprising at least a piston (1) associated with a chamber (2), said piston (1) cooperating with a surface (3) driven in a constant displacement reciprocating movement, characterized in that the piston (1) is free of any continuous mechanical connection with said surface (3); and wherein said chamber (2) is associated with a flow regulating system (9) placed upstream, and wherein it is equipped with a clack valve (7) on the feed and with a clack valve (8) on the delivery; said regulating system (9) being fed by a booster pump (10).

Abstract: A hydraulic system is provided including a hydraulic pump which is continuously coupled with the engine of a utility such as a dump truck utilized for snow-ice removal. When hydraulic implements employed on the truck are not actuated, the pump operates in a cavitation mode. During this cavitation mode of operation, there is no ingress of air through seals or the like to a venting of the gear pump chamber essentially to tank or atmosphere. A poppet valve is actuated in conjunction with periodic use of hydraulic elements on the truck to actuate the pump to an operational or pressurized mode. A key actuated calibrating system is employed to calibrate snow-ice removal components in a secure manner. Calibration is provided in conjunction with EEPROM memory.

Abstract: In a pressure control valve (28) of a variable capacity compressor, a pressure detecting part (48) which compares suction pressure of the compressor with atmospheric pressure, a valve (52) urged to close by a spring (53), a rod driven by the pressure detecting part and an electromagnetic coil (55) for attracting and opening the valve are provided, thereby to change capacity of the compressor continuously.

Abstract: An air conditioning system includes a refrigerating circuit, and a variable capacity compressor forming part of the refrigerating circuit and having a high pressure zone and a device for varying the delivery quantity thereof in response to pressure in the high pressure zone. A high pressure communication passage communicates the high pressure zone with the refrigerating circuit. A pressure control valve is associated with the high pressure zone and the high pressure communication passage, and is operable in response to the pressure in the high pressure zone to reduce the opening degree of the high pressure communication passage when the pressure in the high pressure zone is lower than a predetermined value.

Abstract: In a variable capacity compressor having a rotary type cylinder compartment (24a), plural return ports (33) formed in a volume-decrease-step space in the cylinder compartment (24a), an exit (34) formed in a volume-increase-step space in the cylinder compartment (24a), a C-shaped guide passage (35) for connecting the plural return ports (33) and the exit (34), an arc-shaped slider (36) provided slidably for gradually opening and closing the plural return ports (33), a spring (37) for pushing the arc-shaped slider (36), and a pressure control valve (42) for pushing the arc-shaped slider (36) in opposite direction to the pushing of the spring are provided; and thereby a wide variable capacity range is realized with compact size and high efficiency.

Abstract: An air conditioning system includes an evaporator and a variable capacity compressor. The compressor has a lower pressure zone including a suction chamber connected to the outlet of the evaporator, a higher pressure zone, a bellows displaceable in response to pressure representative of a thermal load on the system, a control valve device responsive to displacement of the bellows for bringing the higher pressure zone into and out of communication with the lower pressure zone to thereby control the difference between pressure from the higher pressure zone and pressure from the lower pressure zone, and a control element responsive to change in the difference between pressure from the higher pressure zone and pressure from the lower pressure zone for varying the delivery quantity of the compressor.

Abstract: A rotary compressor is comprised of a first housing having an intake chamber for receiving therein a fluid of variable pressure, and a second housing having an inner peripheral surface to define a working chamber and an inlet communicating between the working and intake chambers. A rotor is rotatably mounted in the working chamber and has a vane slidably supported in the rotor to maintain contact with the inner peripheral surface of the second housing during the rotation of the rotor to thereby compress the fluid flowing into the working chamber through the inlet. A rotary valve is rotatably disposed between the intake chamber and working chamber for regulating the flow rate of the fluid flowing through the inlet in response to angular displacement of the rotary valve. A piston is slidably disposed in a cylinder provided in the first housing.

Abstract: A gas compressor of the variable volume type having a rotary plate which is rotated to move recesses therein communicating with a compression chamber of a cylinder relative to communication ports formed in a front side block fixed to the one side of the cylinder so that the volume of the compression chamber may be made variable in accordance with the fast or slow running state of the gas compressor. The rotary plate is moved rotatably by means of a self-contained and self-actuated hydraulic cylinder which is driven by oil within the compressor in response to the intake pressure of the compressor's intake chamber.

Abstract: A variable capacity compressor including a pumping device, and a control element the position of which can be changed to determine the capacity of the pumping device. The compressor comprises: a detector for detecting change in the position of the control element in a continuous manner; and a capacity-indicating device for visually indicating an output value thereof in a manner continuously variable in response to a continuous change in output from the detector, whereby the output value visually indicated by the capacity-indicating device varies continuously with a continuous change in the capacity of the pumping device.

Abstract: A variable displacement compressor includes a lubrication oil supply passage defined in a side block for interconnecting a displacement adjustment mechanism disposed in the side block and a high pressure oil sump defined in the side block. With this lubrication oil supply passage, a sufficient lubrication of the displacement adjustment mechanism is achieved.

Abstract: A variable capacity vane compressor having compression spaces defined between a cylinder and a rotor at diametrically opposite locations. A control element rotatably arranged in the cylinder, which has two cut-out portions circumferentially extending at diametrically opposite locations through which inlet ports and respective corresponding compression spaces are communicatable with each other. The cut-out portions are disposed relative to the respective corresponding compression spaces such that compression commences in each of the compression spaces when a trailing vane passes a forward end edge of a corresponding cut-out portion with respect to the rotation of the rotor. The control element is rotatable between a partial capacity position and a full capacity position for varying the capacity of the compressor.

Abstract: A variable capacity vane compressor has an annular control element angluarly displaceably received within an annular recess formed in one of side blocks defining a cylinder. The control element is angularly displaced in response to a difference in pressure between first and second pressure chambers formed in the one side block and communicating with a zone under lower pressure and a zone under higher pressure, respectively, and to the biasing force of a biasing member, thereby varying the opening angle of at least one second inlet port formed in the one side block and hence controlling the capacity of the compressor.

Abstract: A variable capacity compressor for an air conditioning system. A passage extends between a suction chamber and a high-pressure chamber, in which is arranged a control valve device having a pressure-responsive portion displaceable in response to change in pressure within the passage. A capacity control device controls the delivery quantity of the compressor in response to opening and closing of the passage by the control valve device. The control valve device opens and closes the passage in response to change in pressure within the suction chamber representative of a thermal load on the air conditioning system to thereby cause the capacity control device to vary the delivery quantity of the compressor. An auxiliary low-pressure chamber is provided in the passage, within which the pressure-responsive portion is disposed. A restriction hole communicates the suction chamber with the auxiliary low-pressure chamber for introducing pressure within the suction chamber into the auxiliary low-pressure chamber.

Abstract: A variable capacity type compressor in which a control element is mounted in one of side blocks formed with inlet ports for rotation about its own axis in opposite circumferential directions between a first extreme position providing the maximum capacity of the compressor, and a second extreme position providing the minimum capacity of the compressor, to vary the compression starting timing. The control element has cut-out portions through which compression medium is drawn into compression spaces, of which one upstream end with respect to the direction of rotor rotation determines the compression starting timing in cooperation with vanes passing same. The cut-out portion is formed of first and second portions circumferentially arranged.

Abstract: A variable-delivery vane-type rotary compressor includes means for controlling discharge by-passed from an actuating chamber and an inhalator chamber by changing area of opening provided between a front plate and a cam ring. The means can control discharge by rotation of a disc having at least one by-pass opening. The disc can rotate in accordance with signals produced from at least one sensor.

Abstract: A hydraulic gear pump for the oil lubrication system of an automobile engine is disclosed, and wherein the meshing teeth of the gears define fluid cells which are expanded in the intake portion and receive the fluid from an inlet, and then compressed in the discharge portion to expel the fluid. The inlet to the pump includes at least two parallel fluid lines which are each connected to a tank. A pressure controlled valve is connected to one or both of the fluid lines, and during the normal operating range of output pressure, the valve is controlled by the pressure in the pump discharge chamber so as to decrease the flow through the lines from a maximum flow rate to a lower flow rate as the output pressure increases. In the event the engine and oil are cold, the output pressure will increase beyond the normal operating range, since the oil consumption is small.

Abstract: A vane compressor is provided with a control valve device having a deformable member disposed within a zone under low pressure for expansion and contraction in response to pressure therein. A pressure-responsive control device is associated with the control valve device for controlling the capacity of the compressor. The deformable member contracts and causes the control device to bring the compressor into full-capacity operation when the pressure within the zone under low pressure is higher than a predetermined value, whereas the deformable member expands and causes the control device to bring the compressor into partial-capacity operation when the pressure within the zone under low pressure is lower than the predetermined value. A device is provided which is operable in response to excessive expansion of the deformable member for causing the control device to bring the compressor into full-capacity operation.

Abstract: A variable displacement vane compressor for an air conditioning system used in an automobile has a cylinder assembly having a bore which receives a rotor to form at least one crescent or compressing chamber between the rotor and the bore. The crescent chamber receives a refrigerant which is returned from the air conditioning system. The rotor has vanes which are extendably fitted therein so that the free end of the vanes are in contact with the circumferential inner surface of the bore during the rotation of the rotor, whereby when the vane passes through the crescent chamber, the refrigerant received therein can be compressed. The amount of the refrigerant introduced into the crescent chamber is adjustable in response to a change of a cooling load at the air conditioning system.

Abstract: A variable displacement vane compressor for an air conditioning system having at least one crescent chamber (R1, R2) defined by vanes (8), a rotor (6), and a bore of a cylindrical body (3). The cooling capacity is adjusted by rotational displacement of an annular plate member (21) for controlling the amount of refrigerant introduced into the crescent chamber (R1, R2). The annular plate member (21) is rotated by a spool (25) driven by a dynamic pressure balance between a first compartment (S1) to which a refrigerant gas under a discharging pressure is introduced, and of a second compartment (S2) to which an oil under a discharging pressure is introduced. The spool (25) is connected to the annular plate member (21) through a pin (26) penetrating an arcuate slot 27 formed in a front end wall plate member (4).

Abstract: A lubrication circuit connected to rotary vacuum pumps is composed of a hydraulic circuit and of the relative pump unit for lubrication and for auxiliary controls, including isolation of the negative pressure space from the pump on the stopping of the latter, with the aid of a closure member (10), for the operation of which use is made of the pressure of the fluid present in the pump discharge space with the aid of a duct (33, 34) between said discharge space and a means (8, 9) operating the closure member (10), which duct is subdivided into two portions between which is disposed a control member (27, 31) the operation of which is dependent on the oil pressure produced by the pump unit and propagated, with complete absence of flow, through a duct (23) so as to reach a control member (27, 31) which supervises the operation of the closure member (10).

Abstract: A variable displacement vane compressor for an air conditioning system used in an automobile has a cylinder assembly having a bore in which a rotor (7) is received to form at least one crescent chamber (R1, R2) between the rotor (7) and the bore. The cooling capacity is adjusted in accordance with a cooling load of the air conditioning system by displacement of an annular plate member (21) for controlling the amount of refrigerant introduced into a crescent chamber (R1, R2). The annular plate member (7) is driven by a driving units (25, 25a, 26, 27, 28, S1, S2) in which a dynamic pressure balance between a first compartment (S1) to which a refrigerant gas under a discharging pressure is introduced, and of a second compartment (S2) to which an oil under a discharging pressure is introduced.

Abstract: A variable displacement vane compressor including a rotor rotatably supported between a pair of side plates secured to a cylinder, vanes movably supported in the rotor to define variable compression chambers in the cylinder, a reciprocally rotatable displacement control plate located between the rotor and one of the side plates for controlling the largest displacement of the compression chambers when closed, a spool chamber provided in one side plate and opposed to the displacement control plate, a spool which reciprocates in the spool chamber to define a first pressure chamber in which a refrigerant having a discharge pressure is introduced and a second pressure chamber in which an oil having the discharge pressure is introduced through a control valve unit in response to the suction pressure, the spool and the displacement control plate being interconnected by a connecting member and moving together, a seal ring between the displacement control plate and the one side plate, for isolating a high pressure are

Abstract: A variable-capacity gas compressor comprising a cylinder front and rear side blocks attached to both ends of the cylinder, a control plate formed with a recess or suction port which communicates with a communication port in the front side block and thereby forms a path for gas to flow into a cylinder chamber. The control plate is secured to the inner side of the front side block so that it may rotate within a given angular range. A driving means for driving the control plate and a control mechanism for controlling the driving means are provided so that the gas comnpressor is able to increase the cooling efficiency in the passenger compartment of an automobile in the beginning period of operation and to subsequently prevent any excessive cooling during continuous operation.

Abstract: An improved variable capacity vane compressor comprises at least one second inlet port formed in a rear side block of the cylinder and communicating a suction chamber with at least one of compression chambers on a suction stroke, defined within the cylinder, and an opening angle control device arranged in the rear side block for varying the opening angle of the at least one second inlet port. The opening control device has a pressure receiving portion defining a first pressure chamber supplied with a high pressure and a second pressure chamber supplied with a low pressure, both arranged in the rear side block, and being angularly displaceable in response to a difference between the high pressure and the low pressure for causing the opening angle control device to vary the opening angle of the at least one second inlet port.

Abstract: The invention has a control pressure extracting port in the delivery side of the low-pressure stage compressor to apply the control pressure to a piston device of the suction throttle valve, thereby making it possible to reliably cancel the starting unload operation and shift the operation mode to the full-load operation in a multi-stage compressor.

Abstract: A variable capacity vane compressor has a cylinder including a cam ring having an inner peripheral surface with an oblong cross section and within which a rotor is rotatably received, a plurality of vanes carried by the rotor, and a control plate disposed in the cylinder for rotation in opposite circumferential directions and having a peripheral edge formed with at least one cut-out portion. The control plate is disposed to rotate in response to a difference between pressure from a lower pressure zone and pressure from a higher pressure zone to cause a change in the circumferential position of the cut-out portion, thereby varying the compression commencing timing of the compressor and hence the capacity of same.

Abstract: In a variable capacity compressor having a capacity control mechanism so as to keep a suction pressure constant by detecting the suction pressure, plural return ports (18), a return passage (10) and an exit (19) are provided for bypassing refrigerant gas from a volume-decrease-step space in a cylinder compartment (5a) to a volume-increase-step space in that, and a guide passage (8) wherein a slider slides by a pressure of refrigerant gas is provided for controlling an amount of bypassing gas; and thereby it is possible to control capacity correctly and stably.

Abstract: A variable capacity vane compressor has a cylinder within which a pair of compression spaces are defined between the cylinder and a rotor rotatably received within the cylinder at diametrically opposite locations, and a control element disposed in the cylinder for rotation about its own axis in circumferentially opposite directions in response to a difference between pressure from a lower pressure zone and pressure from a higher pressure zone. The control element has its outer peripheral edge formed with a pair of cut-out portions at substantially diametrically opposite locations, which each have a leading end in the direction of rotation of the rotor. The rotation of the control element causes a change in the circumferential position of each cut-out portion to thereby vary the timing of commencement of compression in the corresponding compression space and hence vary the compressor capacity.

Abstract: A hydraulic gear pump is disclosed wherein the meshing teeth of the gears define fluid cells which are expanded in the intake portion and receive the fluid from an inlet, and then compressed in the discharge portion to expel the fluid. The contact ratio of the cooperating driving flanks of the meshing teeth is smaller than the contact ratio of the cooperating sealing flanks of the meshing teeth, which serves to minimize the power requirement of the pump. The inlet to the pump includes at least two parallel lines which are each connected to a tank, and the first line is provided with a fixed throttle and the second line is provided with a pressure control valve which is controlled by the pressure in the pump discharge line.

Abstract: A single-stage oilless screw compressor system includes a single-stage oilless screw compressor of the type which is capable of operation without requiring oil to be fed to a working chamber of the compressor and which has a pressure ratio (discharge pressure/suction pressure) of over 4, preferably in the range between 7 and 8. The system further includes a precooler located in a gas passage on the discharge side of the compressor, a check valve located on the outlet side of the precooler and a cooler located on the outlet side of the check valve, for supplying a clean gas having no oil incorporated therein which has a pressure of above 4 kgf/cm.sup.2.