Abstract: The present invention provides an addressable multi-channel peristaltic pump. According to the invention, this pump design allows for selection and operation of one or more pump heads on a drive shaft, while locking other non-selected pump heads in a stationary position. It is possible to operate the multi-channel pump using a limited number of motors, preferably two motors: a selector motor and a dispense motor. Thus, the pump provides for pumping or dispensing of one or more fluids without the need for multiple pumps. Likewise, compared with typical single motor multi-channel systems, where all pump heads on the drive shaft must rotate at the same time, the present invention provides for selective dispensing of one or more fluids. The pumps of the present invention are suitable for any multiple fluid transfer application, including in automated multi-channel reagent dispensing systems, such as nucleic acid purification systems.

Abstract: A method of servicing a wellbore, comprising establishing a pumping profile having a performance plan, operating a first pump according to a first pumping parameter value, and operating a second pump according to the second pumping parameter value, wherein the second pumping parameter value is selected relative to the first pumping parameter value to improve a conformance of a phase sensitive combined pump effect operational characteristic to the performance plan. A wellbore servicing system, comprising a pump group comprising a plurality of plungers wherein at least some of the plurality of plungers are substantially configured according to an equal phase angle distribution arrangement.

Abstract: A displacement control valve (32) is connected to a variable displacement compressor. An open passage (53) in which a refrigerant gas flows is formed within a rod (31) and a valve body (30) of the displacement control valve (32). Further, an inner circumferential surface of a valve chamber (36) is formed as a guide portion (40) for moving the valve body (30) along an axis (L1) of the valve chamber (36). A valve portion (30a) of the valve body (30) is formed in a circular arc cross sectional shape along a surface of a sphere (K) in which an intermediate point of a length of the guide portion (40) along the axis (L1) of the valve chamber (36) is set to a center (N) on the axis (L1), and a distance from the center (N) to a contact point between a valve seat (36a) and the valve portion (30a) is set to a radius (r).

Abstract: The dynamic fluid device has a first pumping arrangement and second pumping arrangement arranged in parallel with each other to pump a pressurized fluid to user devices; at least a distributor member interposed amongst the first pumping arrangement, second pumping arrangement and the user devices and connected to them with connection arrangements, the at least a distributor member being arranged to connect singly and/or jointly and/or according to predetermined sequences, the first pumping arrangement and/or the second pumping arrangement to the user devices.

Abstract: A hydraulic drive for an aircraft includes: a gear, a first hydraulic pump and a second hydraulic pump, wherein the gear is installed in a gear housing and wherein the first hydraulic pump and the second hydraulic pump in each case are installed in a pump housing that is affixed to the gear housing, or the two together are installed in a pump housing that is affixed to the gear housing; a hydraulic supply device including a first and a second hydraulic system for operating actuators of the aircraft; and a monitoring and drive device, with the hydraulic supply device including a first hydraulic drive for coupling the latter to a first engine, and a second hydraulic drive for coupling the latter to a second engine, wherein each hydraulic drive includes: a gear drive shaft for coupling the respective hydraulic drive to an engine output shaft of the respective associated engine; two hydraulic pumps that are coupled to a gear output shaft, in each case with a connection device for connecting the hydraulic pump to

Abstract: The present invention provides a fluid control system and associated methods. The fluid control system includes a source of a pressurized fluid and a first spool valve having at least two positions, wherein the first spool valve is connected in fluid communication with the source of the pressurized fluid. The fluid control system further includes a second spool valve having at least two positions, wherein the second spool valve is connected in fluid communication with the first spool valve and the source of the pressurized fluid. When the first spool valve is in a first position and the second spool valve is in a second position, a first portion of the pressurized fluid is directed from the source of the pressurized fluid to the second spool valve via the first spool valve.

Abstract: A rotary compressor having two different compression capacities is provided. The rotary compressor may include a driving shaft that is rotatable in both a clockwise and counterclockwise direction, and having an eccentric portion at an end thereof. The compressor may also include cylinder having a predetermined inner volume, and a roller rotatably installed on an outer circumferential portion of the eccentric portion so as to contact an inner circumference of the cylinder and form a fluid chamber therebetween. A vane is elastically installed in the cylinder and contacts the roller, and upper and lower bearings are respectively installed at upper and lower portions of the cylinder so as to rotatably support the driving shaft and hermetically seal the inner volume of the cylinder. Suction and discharge ports communicate with the fluid chamber based on a rotational direction of the driving shaft so as to provide a different compression capacity depending on the rotational direction of the driving shaft.

Abstract: A blending pump assembly for accurately maintaining the proper ratio of two fluid components. Flow of a first fluid is utilized to drive a fluid motor, which in turn drives a pumping mechanism to inject a proportional amount of a second fluid into the flow of the first fluid. The fluid motor and pump are sized so that a predetermined ratio between the two fluids is maintained regardless of changes in pressure and flow rate of such first fluid.

Abstract: A split-pressure, dual-pump system for supplying hydraulic fluid to a multi-speed transmission is provided. The system includes a low-pressure work circuit operatively connected to a fixed displacement pump, and a high-pressure work circuit operatively connected to a variable displacement pump. The system also includes a regulator valve fluidly coupled to the variable displacement pump via a decrease circuit and an overage circuit for regulating the flow of fluid to the high-pressure work circuit. The invention consists of separating the high-pressure needs of the system into a separate work circuit from the low-pressure needs of the system, and optimizing pump design separately for each work circuit to maximize transmission efficiency and reduce parasitic losses. A method of supplying hydraulic fluid to a multi-speed transmission at variable flow and pressure is also provided.

Abstract: In order to provide a compressed air manufacturing facility which can increase a stability of a supply pressure while obtaining an energy saving effect, in a compressed air manufacturing facility provided with a compressor compressing an air, an electric motor driving the compressor, and an inverter variably controlling a rotating speed of the electric motor, the compressed air manufacturing facility is provided with a pressure sensor detecting a discharge pressure of the compressor at an upstream side position of a discharge air system connected to a discharge side of the compressor, and a control apparatus computing a pressure loss of the discharge air system in correspondence to a rotating speed of the electric motor, and changing a control range of the discharge pressure of the compressor at the upstream side position of the discharge air system on the basis of the computation in such a manner that a terminal pressure at a downstream side position of the discharge air system comes to a predetermined range

Abstract: A control system for a work machine (101) including an electric machine (202), a hydraulic machine (204) and at least one hydraulic cylinder (108). The electric machine (202) is connected in a driving manner to the hydraulic machine (204). The hydraulic machine (204) is connected to a piston side (208) of the hydraulic cylinder (108) via a first line (210) and a piston-rod side (212) of the hydraulic cylinder (108) via a second line (214). The hydraulic machine (204) is adapted to be driven by the electric machine (202) and supply the hydraulic cylinder (108) with pressurized hydraulic fluid from a tank (216) in a first operating state and to be driven by a hydraulic fluid flow from the hydraulic cylinder (108) and drive the electric machine in a second operating state.

Abstract: The invention relates to a hydraulic system (1) comprising a main pump (12) and a precompression pump (5), whereby the outlet (8) of the precompression pump (5) is connected by a connecting line (9) to the inlet (11) of the main pump (12). The outlet (16) of the main pump (12) can be connected by a working line (17) to a consumer (A, B). The volume flow at the inlet (11) of the main pump (12) is changeable. The aim of the invention is to achieve greater efficiency. The precompression pump (5) comprises an adjusting device (6) for adjusting the flow rate.

Abstract: A metering pump includes an actuating mechanism, and a plurality of piston cylinders coupled to the actuating mechanism. A first of the cylinders has a working volume that differs from a second of the cylinders. The actuating member is centrally located and the cylinders are arranged radially about the actuating mechanism. The working volume of the cylinders can be varied by adjusting the spacing of the cylinders from the actuating mechanism, thus varying the stroke of pistons housed within the cylinders, and/or by providing the cylinders with different inner diameters. A method of metering fluids includes independently adjusting stroke of a plurality of pistons to adjust the volume of metered fluid, and selecting different cylinder diameters to adjust the volume of metered fluid.

Abstract: The invention relates to a hydrostatic machine (1) comprising at least one first hydrostatic unit (E1) and one second hydrostatic unit (E2), each hydrostatic unit (E1, E2) comprising respective pistons (14a, 14b) guided in respective cylinder drums (13a, 13b) and supported by respective swiveling bodies (17a, 17b) that can be adjusted by respective adjustment devices (6a, 6b), and further comprising respective control bodies (25a, 25b). A one-piece main housing body (2) radially surrounds the cylinder drums (13a, 13b), the control bodies (25a, 25b), and the adjustment devices (6a, 6b) of both hydrostatic units (E1, E2), and assigns pressure channels for supplying a pressure medium to and discharging it from the control bodies (25a, 25b) of both hydrostatic units (E1, E2). A first add-on housing body (3a) is disposed on a first side of the main housing body (2), and bears a swiveling body (17a) of the first hydrostatic unit (E1).

Abstract: A variable displacement vane-type fluid pump is provided which permits improved regulation of the pump discharge such that the pump can meet the various requirements of lubrication for internal combustion engines at all speeds with minimized use of power. Of course, the vane pump may also be utilized in a wide range of power transmission and other fluid distribution applications. The vane pump of the invention may also use both hydrostatic and mechanical actuators to control the position of its containment ring or eccentric ring and hence, regulate the output of the pump. According to yet another aspect of the present invention, to prevent inlet flow restriction or cavitation, a valve may be provided to permit some of the pump outlet or discharge flow to bleed into the pump inlet to provide needed velocity energy to the fluid flow into the pump inlet.

Abstract: A pump system for multi-phase fluids that includes a drive-shaft (11), mechanical differential units (12, 22, 23, 23′, D1 . . . Dn) and pumps (14, 14′, 25, 25′, 25″, 25′″, B1 . . . Bn) where the differential units allow for the changing of pump rotation speeds between pumps(14, 14′, 25, 25′, 25″, 25′″, B1 . . . Bn) so as to adjust the compressibility of fluids in order to reduce or eliminate circulatory flow. There is also a description of the method of operating the system according to the invention.

Abstract: A fuel injection pump includes a plurality of plungers and a cam shaft having a plurality of drive cams (31, 32) corresponding to the plungers. The cam shaft is rotated by a power from the outside so as to reciprocate the plurality of plungers by the corresponding drive cams, and fuel is pressurized and force-fed in the forward stroke of each plunger. All or a part of the drive cams (31, 32) are installed with the phase thereof shifted, and the cam lobes (31a, 32a) of the drive cams are formed asymmetrical so that the amount of displacement of the plungers relative to a unit cam rotating angle is reduced in the forward stroke more than in the backward stroke of the plunger. Thus, the pressure variation in a common rail is reduced, the pressure resistance of the entire system is lowered, and the drive torque is reduced so as to reduce the load and noise of a drive system.

Abstract: A pump assembly which comprises a vane pump and a second hydraulic pump driven together with this vane pump. The vane pump has a suction region in which first pressure spaces between the vanes and second, rear pressure spaces behind the vanes become larger and a pressure region in which the pressure spaces become smaller and in which the pressure spaces are fluidically connected to a pressure outlet. This vane pump is intended particularly for supplying operating cylinders of a hydromechanical transmission of a motor vehicle with pressure fluid under relatively high pressure. The second hydraulic pump has positively driven displacement elements and is intended for supplying a circuit having a relatively low system pressure, in particular a lubricating-oil circuit of the motor vehicle, with pressure fluid.

Abstract: A pump system is provided where low pressure (4) and high pressure (6) pumps are coaxially mounted to receive motive power from a shared drive (300). The drive shafts are arranged such that one extends within a void in the other and both have shear regions such that, in the event of torque overload, either shaft can shear so as to disconnect the drive to it's associated pump while the other pump and shaft can continue to work.

Abstract: In a work vehicle that has several hydraulic actuators a system and method for controlling and scaling flow between the actuators includes an electronic controller that is connected to several hand controls that provide a proportional signal indicating how far the operator has moved the hand controls. The controller reads the hand controls and proportionally scales the total available flow to make sure the operator does not demand too much fluid from the hydraulic pump.

Abstract: To permit forcedly stopping combining flows of pressure fluid from two hydraulic pumps when a load pressure on a combined-flow-driven actuator in which the flows of pressure fluid are combined together exceeds a predetermined pressure and hence to permit driving the combined-flow-driven actuator with the pressure fluid from only one of the hydraulic pumps, a hydraulic drive system is provided with a flow-combining valve 2 connected to a directional control valve 1 in a first group of directional control valves via a center bypass passage 3, a flow-combining circuit 5 communicating the flow-combining valve 2 and a supply port of a flow-combining directional control valve 4 with each other, and a combined-flow-driven actuator 20 controlled by the flow-combining directional control valve 4, and performs overall power control such that a total value of input torques to the two hydraulic pumps 15,18 does not exceed an output torque from an engine 30.

Abstract: A screw compressor system comprises a plurality of screw compressors the capacity of each of which is controlled by repeating load operation and no-load operation. Using a timer output corresponding to compressed gas consumption in a demander including gas consumption equipments, a parent controller determines the number of compressors to be operated among the plurality of compressors. Among the compressors determined to be operated, all compressors other than one are put in load operation. In accordance with a load factor of the excepted one screw compressor, the parent controller controls discharge pressure of each compressor. At this time, the control is made so that discharge pressure of the screw compressor system measured by a pressure gauge be lower than that upon the maximum gas consumption.

Abstract: A serial, dual piston high pressure fluid pumping system that overcomes the difficulties of gas in the fluid stream without the need for added mechanical valves or fluid paths. A bubble detection and recovery mechanism monitors compression and decompression volumes of the serially configured dual pump head pump, and the overall system delivery pressure. Bubble detection is effected by sensing a ratio of compression to decompression volume and determining if the ratio exceeds an empirical threshold that suggests the ratio of gas-to-liquid content of eluent or fluid in the system is beyond the pump's ability to accurately meter a solvent mixture. The magnitude of the ratio of compression to decompression volume indicates that either the intake stroke has a bubble or that the eluent has a higher-than-normal, gas content.

Abstract: Liquid filtering apparatus includes a plurality of reverse osmosis filters for receiving seriatim under pressure a mixture of feed liquid and recirculated concentrate. Feed liquid such as salt water is introduced into the inlet of each reverse osmosis filter to dilute the recirculated concentrate.

Abstract: A compressed air production facility includes at least one variable speed compressor and a plurality of constant speed compressor, which are connected in parallel with one another. The variable speed compressor and the plurality of constant speed compressors are capacitively controlled with the use of a pressure in an air reservoir into which discharge air from these compressor are led. Both upper limit pressure at which the variable speed compressor is turned into its load operation mode into its unload operation mode and a lower limit pressure at which the variable speed compressor is turned into its unload operation mode into its load operation mode are set between an upper limit change-over pressure at which all of the plurality of constant speed compressors are turned into their load operation into their unload operation and a lower limit change-over pressure at which all of the plurality of constant speed compressors are changed over from their unload operation into their load operation.

Abstract: A multi-pump controlling means and method controls and drives two or more reciprocating pumps creating proportioned flows of fluids. The multi-pump controlling means in use is situated between a driving means, such as a double acting ram, and the pumps. The multi-pump controlling means includes two or more cams that each interact with a cam follower attached to the pumps. The cams may be set or adjusted to different gradients, meaning the cam followers following those gradients when the multi-pump controlling means is reciprocated by the driving means, will have different path lengths. The path lengths of the cam followers control the stroke lengths of the respective pumps and thus the volume of fluid pumped by each of the respective pumps.

Abstract: A metering apparatus for delivery of a metered amount of fluid includes an axial piston pump and a rotary drive having an output, a coupling for connecting the rotary drive output to a piston of the axial piston pump wherein said piston is cardanically connected to said coupling.

Abstract: A serial, dual piston high pressure fluid pumping system that overcomes the difficulties of gas in the fluid stream without the need for added mechanical valves or fluid paths. A bubble detection and recovery mechanism monitors compression and decompression volumes of the serially configured dual pump head pump, and the overall system delivery pressure. Bubble detection is effected by sensing a ratio of compression to decompression volume and determining if the ratio exceeds an empirical threshold that suggests the ratio of gas-to-liquid content of eluent or fluid in the system is beyond the pump's ability to accurately meter a solvent mixture. The magnitude of the ratio of compression to decompression volume indicates that either the intake stroke has a bubble or that the eluent has a higher-than-normal gas content.

Abstract: The invention relates to a device for the output regulation of at least one variable displacement pump (1), delivering into a working line, driven by a motor, through adjustment of its displacement by means of a setting device (7) biased in the direction of maximum displacement and which can be acted upon with a setting pressure (20), having a regulation valve (18) associated with the setting device (7), which regulation valve can be acted upon by a counter-pressure corresponding to the working pressure in the working line, whereby the regulation valve (18) responds when the control pressure is greater than the counter-pressure, and so regulates the setting pressure action on the setting device (7) in the direction of a reduction of the displacement of the variable displacement pump (1) that the product of working pressure and output is constant.

Abstract: The present invention relates to a pump, more particularly a radial piston pump, including at least two pump pistons (10) with an associated working chamber (13) each, wherein the working chambers (13) are connected to suction lines (4) by way of suction valve devices (8) and to a joint pressure line (5) by way of pressure valve devices (9), wherein at least one of the suction valve devices (8) opens during the pressure stroke in dependence on the pressure in one of the associated lines (4, 5), and wherein at least one of the suction valve devices (8) opens during the pressure stroke in dependence on the pressure in the pressure line (5).

Abstract: A total power regulation device for a plurality of variable displacement pumps (1, 2), each having a regulation valve (18) which regulates its displacement volume, which is acted upon--against a counter-pressure--by a control pressure corresponding to the working pressure of the variable displacement pump. When the control pressure exceeds the counter-pressure, the regulation valve regulates the variable displacement pump along a characteristic line (KL) of constant torque. To adjust the desired values of the individual drive torques simply, and to prevent torques from exceeding a desired value, an electronic control unit (16)--connected to measuring detectors (25) for detecting the displacement volumes of the variable displacement pumps--stores the desired value totals of the counter-pressures and the torque characteristic lines (KL) of the variable displacement pumps, and has a desired value setting device (27) for dividing the desired value total.

Abstract: A serial, dual piston high pressure fluid pumping system that overcomes the difficulties of gas in the fluid stream without the need for added mechanical valves or fluid paths. A bubble detection and recovery mechanism monitors compression and decompression volumes of the serially configured dual pump head pump, and the overall system delivery pressure. Bubble detection is effected by sensing a ratio of compression to decompression volume and determining if the ratio exceeds an empirical threshold that suggests the ratio of gas-to-liquid content of eluent or fluid in the system is beyond the pump's ability to accurately meter a solvent mixture. The magnitude of the ratio of compression to decompression volume indicates that either the intake stroke has a bubble or that the eluent has a higher-than-normal gas content.

Abstract: An apparatus for and a method of controlling the engine and pumps of hydraulic construction equipment capable of achieving automation of the hydraulic construction equipment by controlling the oil quantity fed to solenoid controlled proportional valves such that it is proportional to the manipulation amount of a manipulation command unit through a computation performed by a controller on the basis of engine RPM data from an engine RPM detection unit and pump delivery pressure variation data from a pump delivery pressure detection units so that the suction horse power of each of the pumps corresponds to the maximum output horse power of the engine and by controlling the oil quantity fed to the hydraulic cylinders 105a and 105b by oil quantity control valves such that it corresponds to the manipulation amount and manipulation ratio from the manipulation command unit.

Abstract: Apparatus for controlling flow of a liquid includes a variable displacement liquid pump and a variable displacement liquid meter, the pump and meter being driven by the same drive motor. Containment structure defines a liquid flow path between the pump and meter for containing liquid received from the pump.

Abstract: The invention relates to a power control device for two variable displacement pumps, each with an adjusting device which can be acted upon by adjusting pressure, a power control valve associated therewith, which is acted upon by a first control pressure corresponding with the operating pressure of the variable displacement pump to be adjusted against a pressure difference in the direction of the control position, in which the adjusting pressure loading is controlled in the direction of reduced displacement of the variable displacement pumps along a hyperbolic control curve, whereby the pressure difference results from a spring-arrangement backpressure counteracting the first control pressure and a second control pressure corresponding with the operating pressure of the other variable displacement pump and with increase of the same drops from a maximum value to a minimum value.

Abstract: A two stage main pump has a first pump drivingly connected to a transmission input shaft, and a second pump is drivingly connected to the output member of a friction clutch that is spring applied and pressure released. The input member of the clutch is driven, through a pair of one-way clutches, by the transmission input shaft or the vehicle output, whichever is rotating more rapidly.

Abstract: An engine-driven pump supplies pressurized hydraulic fluid to vehicle brake and steering circuits. A ground driven variable displacement pump controlled by a control circuit is de-stroked when the engine-driven pump is operational. The variable displacement pump includes a movable piston which divides a bore into a pilot chamber and a pump chamber. An outlet line with a check valve communicates fluid one way from the pump chamber to the vehicle circuits. An inlet line with a check valve communicates fluid one way from a reservoir to the pump chamber. A ground-driven rotatable cam member reciprocates the piston. A spring urges the piston towards the cam member and towards a full stroke position. A pilot line which communicates fluid pressure from an outlet of the engine-driven pump to the pilot chamber. When the engine-driven pump is operational the pressure in the pilot line moves the piston away from the cam member, thus de-stroking the variable displacement pump.

Abstract: In the present fluid system, a variable pressure inlet system is provided and operational to control the operating pressure level of a charge pump in response to various operating parameters of the fluid system. The charge pump provides pressurized fluid to an inlet of a hydraulic pump to insure filling of the pumping chambers therein. By having the operating pressure level of a variable pressure relief valve that is connected to the charge pump controlled between a minimum pressure level and a maximum pressure level responsive to various operating perimeters of the system, the degree of horsepower needed to drive the charge pump is controlled.

Abstract: An apparatus for controlling hydraulic pumps for a construction machine wherein the construction machine includes first and second hydraulic pumps adapted to be driven by an engine and hydraulic actuators hydraulically connected to the first and second hydraulic pumps via first and second actuating valves is disclosed. A controlling section calculates extra horse powers .DELTA.HP.sub.1 and .DELTA.HP.sub.2 based on reference allowable absorptive horse powers set relative to the first and second hydraulic pumps and actual absorptive horse powers (HP.sub.01) and (HP.sub.02) derived from the first and second hydraulic pumps. In addition, the controlling section calculates allowable discharge capacities (V.sub.1P) and (V.sub.2P) based on the number (N) of revolutions of the engines, pressures (P.sub.1) and (P.sub.2) of hydraulic oils discharged from the first and second hydraulic pumps, the extra horse powers .DELTA.HP.sub.1 and .DELTA.HP.sub.2 and allowable discharge capacities (V.sub.1P) and (V.sub.2P).

Abstract: A loading machine equipped with a first and a second pump for supplying hydraulic oil to at least one hydraulic operated working component, such as a hydraulic piston-cylinder device or a hydraulic motor having a varying oil-pressure and flow requirement, wherein the pumps can be connected together for mutual coaction, when necessary. The second, larger pump is a fixed displacement pump. The first pump is provided with a pump regulator which is influenced by the load pressure prevailing in the hydraulic system and is intended to influence the first pump in a manner to maintain between the outlet of the pump and the load pressure on the pump regulator a pressure difference determined by the pump regulator, wherein the first pump is connected to the working component via a variable restriction. A control device is operative to connect the second and larger pump to the system solely when there is a need for a smooth increase in flow which cannot be achieved solely by the first pump.

Abstract: A control device for a variable displacement hydrostatic machine having a stroke-volume regulator which is responsive to an actuating pressure. The control device includes a booster pump. The delivery pressure of the machine is the actuating pressure unless the delivery pressure of the machine is insufficient in which case the actuating pressure is a feed pressure produced by the booster pump. The control device includes a plurality of delivery-pressure lines and a proportioning pressure regulator having an outlet pressure which is proportionally reduced relative to the intake pressure connected between each delivery-pressure line and the stroke-volume regulator.

Abstract: A method and apparatus for saving energy in a chilled water air conditioning system employing secondary pumping for supply chilled water and primary pumping for return chilled water wherein the primary pumping is eliminated comprising directing all of said supply chilled water to the secondary pumps and eliminating any flow of return chilled water through the secondary pumps.

Abstract: Reversible, variable displacement, hydraulic devices are useful in transmitting power from an engine to a driven device. The hydraulic components of such devices are generally quite bulky and difficulty to center to swash plate thereof. The subject device includes a pair of servo valves adjustably disposed within a case for individually controlling the flow of actuating fluid to and from a pair of hydraulic servo actuators. A servo feedback mechanism is provided to mechanically move a valve spool of one of the servo valves to a position for exhausting fluid from one of the servo actuators as the spool of the other servo valve is moved to a position for directing actuating fluid to the other of the servo actuators. The feedback mechanism also moves the spools substantially to their neutral position when a swash plate controlled by the servo actuators reaches a desired angular position after the other spool is first moved to the position for directing actuating fluid to the other servo actuator.

Abstract: Connected to a pressure conduit are a plurality of fixed displacement pumps and a variable displacement pump which are connectable and disconnectable in accordance with the amount of fluid withdrawn. The maximum delivery rate of the variable displacement is greater than the delivery rate of each fixed displacement pump. For the minimum and maximum delivery rate of the variable displacement pump two switching points are defined at each of which a fixed displacement pump is connected or disconnected. This gives a reliable fluid supply of the pressure conduit without any danger of erroneous switchings.

Abstract: In a summation power output regulating system for first and second hydrostatic machines (3, 4), having a common drive and comprising at least two hydrostatic transmissions (1, 2), each of the machines (3, 4) having a hydraulic control device (7, 8), wherein the second machine (4) is provided with a hydraulic power output regulator (24) which regulates the pressure acting on the control device (8) in dependence on the power output of the second machine at that time and a control pressure, dependant on the working pressure of the first machine, is transmitted by means of a hydraulic actuator to the power output regulator (24), substantially 100% utilization of the power available is attained with a simple construction and function by providing the first machine (3) with a power output measuring valve (34; 63, 64) which determines the power output at the time and regulates the control pressure (P.sub.3) in dependence on the power output of the first machine.

Abstract: A hydraulic drive circuit system is equipped with an accelerator pedal and an accelerator lever for respectively instructing target revolution numbers for an engine, a link plate for selecting greater one of the instruction values, and a linkage and a switch for controlling valves respectively so as to close the flow passage of a line interposed between a charge pump and a low pressure line irrespective of the instruction value of the accelerator pedal when the accelerator lever has not been controlled but for controlling the valves so as to restrict the flow passage of the line in accordance with the instruction value of the accelerator pedal when the accelerator lever has been controlled.

Abstract: A variable stroke positive displacement piston pump in which the effective eccentricity of the crankshaft controlling the stroke is adjustable by means of a worm/worm gear combination driving a hub to which eccentric rings are keyed.

Abstract: A control system for controlling input power to hydraulic pumps of a hydraulic system including a prime mover and a plurality of variable displacement hydraulic pumps driven by said prime mover. The control system comprises: a first computing unit for computing, for each of the hydraulic pumps, an input torque control value concerning a distribution of input torques of said hydraulic pumps from a representative pressure obtained on the basis of a discharge pressure of at least one other hydraulic pumps; a second computing unit for determining an input torque for each of the hydraulic pumps on the basis of a corresponding one of the input torque control values determined by the first computing unit; and a third computing unit for determining an object discharge rate of each of the hydraulic pumps from the input torque obtained by the second computing unit and an own discharge pressure of each of the hydraulic pumps.

Abstract: A method of controlling an output of an internal combustion engine having an electronic governor device and/or that of at least one variable displacement hydraulic pump driven by the engine in which, when the engine is operated in a range of high speed revolutions approximately equal to or exceeding the number of revolutions of the engine at a rated point on a governor control curve specific to the engine, the engine is operated by the action of the electonic governor device at a given point of a curve of equal horsepower of the engine where an engine output torque is higher than that in the high speed revolution range and where fuel consumption is lower than that in the range.

Abstract: A serial, dual piston high pressure fluid pumping system that overcomes the difficulties of gas in the fluid stream without the need for added mechanical valves or fluid paths. A bubble detection and recovery mechanism monitors compression and decompression volumes of the serially configured dual pump head pump, and the overall system delivery pressure. Bubble detection is effected by sensing a ratio of compression to decompression volume and determining if the ratio exceeds an empirical threshold that suggests the ratio of gas-to-liquid content of eluent or fluid in the system is beyond the pump's ability to accurately meter a solvent mixture. The magnitude of the ratio of compression to decompression volume indicates that either the intake stroke has a bubble or that the eluent has a higher-than-normal gas content.