Abstract: Disclosed are a hydraulic system, a control method and a working machine. The hydraulic system includes an oil tank, a working pump, a control cylinder controlling a displacement changing mechanism, a working oil line communicating with an output main path of the working pump, a load-sensing system including a load-sensing circuit outputting hydraulic pressure based on load, a load-sensing valve and a switching-control valve switchable between a first-valve-position and a second-valve-position. When differential pressure between the first and second control ports is greater than a first threshold, the output main path communicates with an input port of the control cylinder; when it is less than the first threshold, the input port communicates with an oil return port of the oil tank. Based on this, operators can switch the hydraulic system between the fixed-displacement mode and the fixed/variable-displacement mode, thereby achieving a better balance between energy conservation and performance.

Abstract: An example valve housing comprises: a longitudinal bore; a first and second workport passages intercepting the longitudinal bore and configured to be fluidly coupled to an actuator; a first and second return cavities intercepting the longitudinal bore; a first inlet port configured to be fluidly coupled to a first source of fluid; a second inlet port configured to be fluidly coupled to a second source of fluid; an outlet port fluidly coupled to the first and second return cavities and configured to be fluidly coupled to a reservoir; a first dual-wing passage fluidly coupled to the first inlet port; a second dual-wing passage fluidly coupled to the second inlet port; and a third dual-wing passage fluidly coupled to the second inlet port.

Abstract: A universal control scheme for mobile hydraulic equipment has switches to activate and/or control any number of different tools or accessories that may be used to configure the equipment. Additionally, a single controller command may be reassigned from one set to another set of hydraulic line pairs. Furthermore, at different times, two separate controller commands may be used to control the same hydraulic line pair. The control scheme also provides for consolidating hydraulic line pair functions to separate for dedicated use those line pairs associated with operating hydraulic cylinders to extend or retract a member and those line pairs used to provide hydraulic fluid for operating tools.

Abstract: Disclosed is a hydraulic pump for construction machinery for controlling to inhibit one-way driving when compound-operating two-way driving and work devices, such as a boom, to enhance operation efficiency.

Abstract: A hydraulic drive system is mounted on a hydraulic excavator, and is provided with a directional control valve 23 for a boom, a directional control valve 24 for an arm, a boom control device 25 for selectively controlling the directional control valve 23 for the boom, and an arm control device 26 for selectively controlling the directional control valve 24 for the arm. The directional control valves 23,24 control a boom cylinder 6 and an arm cylinder 7, respectively, which are driven by pressure oil delivered from a main hydraulic pump 21. The hydraulic drive system is provided with a communication control means for communicating a rod chamber 6b of the boom cylinder 6 and a bottom chamber 7a of the arm cylinder 7 with each other when a stroke of the arm control device 26 has become a predetermined amount S or greater.

Abstract: An implement attachment interface is described, that is used for the coupling of operating implements to a utility vehicle, and that contains six double-acting hydraulic cylinders, that are adjustable in length and which are arranged in the manner of a hexapod between the utility vehicle and a coupling frame. This contains two upper hydraulic cylinders that are arranged alongside each other and extend in a direction converging towards each other, two lower hydraulic cylinders arranged alongside each other and converging towards each other as well as two hydraulic cylinders at the sides. According to the invention means are provided that for a pendulous movement to the right the lower right hydraulic cylinder and the upper left hydraulic cylinder extend synchronously and the lower left hydraulic cylinder and the upper right hydraulic cylinder are retracted synchronously. For a pendulous movement to the left the hydraulic cylinders operate in the opposite direction.

Abstract: An optimal pump flow for both dual tilt operations and single tilt operations is obtained at low cost without increasing the complexity of the device constitution. Where there is a wish to implement a dual tilt operation, a switch is selectively operated and, in accordance with this selection result, the differential pressure set value decreases and a comparatively small flow is supplied from the hydraulic pump to the left and right tilt cylinders. Accordingly, the extension/retraction speed of the left and right tilt cylinders decreases. Where there is a wish to implement a single tilt operation, a switch is selectively operated and, in accordance with this selection result, the differential pressure set value increases and a comparatively large flow is supplied from the hydraulic pump to the left cylinder. Accordingly, the extension/retraction speed of the left tilt cylinder increases.

Abstract: A system for simultaneously operating first and second hydraulic cylinders has an inlet node for connection to a source of pressurized fluid and an outlet node for connection to a tank. A two-position, three-way primary control valve has a first port connected to the inlet node, a second port connected to the outlet node, and a common port. A first electrohydraulic proportional valve connects the common port to a first port of the first cylinder, and a second electrohydraulic proportional valve connects the common port to a first port of the second cylinder. A third electrohydraulic proportional valve connects the inlet node to a second port of the first cylinder and a second port of the second cylinder. Selectively operating the primary control valve and one of the third and fourth electrohydraulic proportional valves determines the direction in which the first and second cylinders move.

Abstract: A fluid control system is disclosed that includes a reservoir, a pump in fluid communication with the reservoir, a first double-acting actuator having a first head end chamber and a first rod end chamber, a second double-acting actuator having a second head end chamber and a second rod end chamber. The first and second double-acting actuators are selectively fluidly connected via a conduit. A first independent metering valve is configured to selectively provide fluid flow to the first and second double-acting actuators, and a second independent metering valve is configured to selectively provide fluid flow to the first and second double-acting actuators. The fluid control system also includes a proportional valve attached to the conduit between the first double-acting actuator and the second double-acting actuator. The proportional valve is capable of operating the fluid control system in either an independent function mode or a regenerative function mode.

Abstract: To provide a dual tilt control system for a work vehicle, the system being capable of using a switching valve adapted to low pressure and low flow rates and left and right tilt cylinders of the same diameter and yielding large force during pitch and dual tilt operations and requiring no piston valve. A left tilt cylinder driving hydraulic circuit and a right tilt cylinder driving hydraulic circuit for respectively supplying pressure oil from a hydraulic pump to the left and right cylinders are arranged in parallel and comprise a left tilt cylinder actuation switching valve and a right tilt cylinder actuation switching valve, respectively. In a pilot pressure signal circuit for controlling the tilt cylinder actuation switching valves, a pilot switching valve for switching a blade between the pitch operation, a single tilt operation and the dual tilt operation by means of the left and right cylinders is provided.

Abstract: A power machine has a base, an operator support portion, and a hydraulic slew motor coupled to move the operator support portion relative to the base. A boom, an arm, and a tool are all coupled to one another and to the operator support portion and are powered by hydraulic actuators. A slew valve is coupled to receive hydraulic fluid under pressure from a hydraulic power circuit and is also coupled to the slew motor to provide hydraulic fluid to the slew motor and receive hydraulic fluid from the slew motor. A first power actuator valve is coupled to receive hydraulic fluid from the slew valve and is coupled to provide hydraulic fluid to one of the hydraulic boom actuator, the hydraulic arm actuator and the tool actuator. The slew valve is coupled in series with the power actuator valve.

Abstract: An improved pressure-compensated hydraulic system for feeding hydraulic fluid to one or more hydraulic actuators. A remotely located, variable displacement pump provides an output pressure equal to input pressure plus a constant margin. A pressure compensation systems requires that a load-dependent pressure be provided to the pump input through a load sense circuit. A reciprocally spooled, multi-ported isolator transmits the load-dependent pressure to the pump input but prevents fluid in the load sense circuit from leaving the load sense circuit and flowing through a relatively long conduit leading to the remotely located pump. In a multi-valve array, at least one valve section has a backflow-preventing shuttle valve which prevents backflow through the pressure compensation system if a main relief valve is operative.

Abstract: A straight travelling apparatus for heavy construction equipment, equipped with a travel supplement circuit, including a variable orifice disposed in a fluid line connected to the supply-side of the control valve of a bucket and controlled to vary an opening degree thereof by a predetermined pilot signal that is applied to the variable orifice in response to an operation of at least one of right and left travel motors in order to keep the variable orifice at a relatively closed state while being released in response to the travel motors not operating in order to keep the variable orifice in a relatively opened state, thereby capable of supplementing a sufficient amount of fluid to a travelling system when the bucket is operated during, thereby preventing an abrupt reduction in travelling speed caused by operatings the straight travelling apparatus.

Abstract: A hydrostatic drive system including a pump (1) and consumers (6, 8) which can each be actuated by a directional control valve (5,7) is disclosed. Each directional control valve (5, 7) is assigned a pressure compensator (9, 10) which can be controlled by a signal difference formed from a load pressure signal and a delivered pressure signal. The load pressure signal is derived from the highest of the load pressures occurring downstream of the directional control valves (5, 7), and the delivered pressure signal is derived from the pressure upstream of the directional control valves (5, 7). To limit the driving force and driving moment of at least one of the consumers, the signal difference across the pressure compensator (9) of at least one consumer (6) can be influenced by a controllable pressure output signal of an infinitely variable pressure control valve in such a way as to adjustably limit through-flow across the pressure compensator.

Abstract: This invention aims at providing a hydraulic circuit apparatus for supplying pressurized fluid into cylinders for a work implement arranged such that during normal operation of the work implement the flow rate of fluid discharged by a pump is controlled such that the difference between the discharge pressure of the pump and the load pressure is always kept constant, whilst during inching operation of the work implement the flow rate of fluid discharged by the pump is reduced.

Abstract: In a controller (229) of a hydraulic control system for construction machines, a valve control signal calculating function (301) works such that when an operation pattern signal (A-I) for actuators (201, 202 . . . ) is outputted, it selects corresponding one of plural output patterns for an auxiliary valve control pressure stored, as a function of a differential pressure signal between a pump delivery pressure and a maximum load pressure, in relation to the operation pattern signals, followed by calculating an auxiliary valve control pressure (Pc) dependent upon the differential pressure signal based on the selected output pattern, and also selects corresponding one of plural sets of rates of change (K . . . , K . . . ) for the auxiliary valve control pressure stored in relation to the operation pattern signals, followed by combining the calculated auxiliary valve control amount with the selected set of speed changes to calculate each of valve control signals (S21-S26).

Abstract: When a hydraulic circuit for driving actuators of a construction machine or the like includes a single hydraulic pump and a plurality of direction changeover valves connected to the hydraulic pump for controlling the respective actuators, operation of one of the direction changeover valves may result in undesirable change in the output oil pressure of the other direction changeover valves. The inventive hydraulic circuit includes means for driving a regulator of the hydraulic pump in response to any oil puressure change at the inlets of the direction changeover valves corresponding to the output oil pressure change, thereby compensating for the pressure change.

Abstract: A hydraulic system including a pump having a discharge line and a number of hydraulic energy consumers connected to the pump discharge line. A controller for the load-independent distribution of a pressure medium from the pump to the consumers includes a multiway valve located in the discharge line between the pump and each consumer to actuate the consumers. A pressure compensator for determining the flow of pressure medium to each multiway valve is located in the discharge line upstream of each multiway valve. Each pressure compensator is actuated as a function of a first pressure difference resulting from the pressure upstream of a multiway valve and the pressure downstream of the multiway valve and of a second pressure difference resulting from the discharge pressure from the pump and the highest load pressure of the consumers. At least one pressure difference of at least one pressure compensator is adjustable.

Abstract: A hydraulic circuit arranged to prevent the load pressure in one of the hydraulic actuators at the time of starting from becoming abnormally high thereby preventing fluid under pressure from being relieved by the safety valve when a plurality of hydraulic actuators are operated at the same time, wherein the function of one of the pressure compensating valves is temporarily enhanced by introducing the load pressure in the hydraulic actuator so as to supply a large quantity of fluid under pressure to the hydraulic actuator connected to the pressure compensating valve so that the operating speed of the hydraulic actuator can be increased.

Abstract: A hydraulic drive system comprising a prime mover (21), a hydraulic pump (22) driven by the prime mover, a plurality of hydraulic actuators (23-28) driven by hydraulic fluid supplied from the hydraulic pump, a plurality of flow control valves (29-34) for controlling flow of the hydraulic fluid supplied to the actuators, and a plurality of pressure compensating valve (35-40) for controlling respective differential pressures across the respective flow control valves, in which each of the pressure compensating valves applies a control force (f-F.sub.c) in a valve opening direction for setting a target value of the differential pressure across the flow control valve. There are provided a first detector (60) for detecting the target rotational speed (N.sub.0) of the prime mover (21), and controllers (61, 62, 63) for controlling the control force on the basis of the target rotational speed detected by at least the first detector such that the control force (f-F.sub.

Abstract: A load-referenced, pressure reducing valve, and a system which incorporates one or more of such valves provide needed response to rapidly changing hydraulic system load demands which are experienced with automatic control systems. The valve provides rapid response for pressure regulation by providing the load pressure to one side of the valve so that immediate, load referenced valve adjustment occurs instantly upon change of load conditions at a system load, and pressure regulation begins immediately without need for fluid flow.

Abstract: A hydraulic driving apparatus has at least one hydraulic pump, a plurality of hydraulic actuators driven by hydraulic fluid discharged from the hydraulic pump, a tank to which return fluid from the plurality of hydraulic actuators is discharged, and a flow control valve associated with each of the plurality of hydraulic actuators. The flow control valve has a first main variable restrictor for controlling flow rate of the hydraulic fluid supplied from the hydraulic pump to the hydraulic actuator, and a second main variable restrictor for controlling flow rate of the return fluid discharged from the hydraulic actuator to the tank. A pump control operative in response to the difference between the discharge pressure of the hydraulic pump and the maximum load pressure of the hydraulic actuators normally controls the discharge rate of the hydraulic pump so that the pump discharge pressure is raised more than the maximum load pressure by a predetermined value.

Abstract: A hydraulic drive system for a crawler mounted vehicle has a hydraulic pump, a plurality of actuators including a pair of left and right travel motors and at least one other actuator that are driven by hydraulic fluid delivered from the hydraulic pump. The system further contains a plurality of flow control valves for controlling flows of the hydraulic fluid supplied to the respective actuators, and a plurality of distribution compensating valves for controlling differential pressures across the respective flow control valves, the plurality of distribution compensating valves each having drive parts to set a target value of the differential pressure across the associated flow control valve. The hydraulic drive system also has a speed selector for outputting a select signal to change operation speeds of the pair of travel motors, and a controller and a control pressure generator for controlling the drive parts of the distribution compensating valves associated with the pair of travel motors.

Abstract: A hydraulic system for a construction machine comprising plural hydraulic actuators (23-28) driven by fluid supplied from a pump (22), first and second flow control valves (29-34) for controlling flows of fluid supplied to the first and second actuators, and first and second distribution compensating valves (35-40) for controlling first differential pressure (.DELTA.P v1-.DELTA.P v6) produced between inlets and outlets of the first and second flow control valves. The first and second distribution compensating valves have respective drives (45-50, 35c-40c) for applying control forces (Fc1-Fc2) in accordance with the second differential pressure to the associated distribution compensating valves, to thereby set target values of the first differential pressures. The hydraulic system includes first means (59) for detecting the second differential pressure (.DELTA.

Abstract: A hydraulic circuit for controlling the deck swiveling speed of a working vehicle comprises a hydraulic actuator for driving the swivel deck, a flow control valve for controlling a rate of oil flow to the hydraulic actuator, and a direction control valve for switching an operating direction of the hydraulic actuator. The flow control and direction control valves are operatively connected to a swivel control lever. The greater amount of swivel control lever is operated toward a right or left swivel position, to the greater extent the flow control valve is shifted in a flow increasing direction. The direction control valve is operable to switch oil lines in response to an operation of the swivel control lever.

Abstract: A control valve is disclosed for use in controlling flow of hydraulic fluid from a hydraulic pump to a plurality of actuators. The control valve includes a valve housing within which are formed control bores, pressure-compensating bores, a feed passage communicating between the pressure-compensating bores, a selected-load pressure transmitting passage communicating between the pressure-compensating bores, a pair of return passages communicating between the control bores and a reservoir tank, control passages communicating respectively between each of the control bores and each of the pressure-compensating bores, and feeding and exhausting passages, as well as actuator ports, communicating between the control bores and the actuators. Control valve spools are slidably mounted, respectively, in the control bores, and pressure-compensating valves are slidably mounted, respectively, the pressure-compensating bores.

Abstract: An article handling apparatus is disclosed which comprises two independently controllable fluid actuated drives. The first fluid actuated drive comprises a cylinder and a differential piston which defines a large chamber and a smaller chamber. Also, a control system is provided which maintains a differential pressure between the large and small chambers in each of several operating positions. The second fluid actuated drive is mounted to the movable member of the first drive, and the second drive is controlled by fluid lines leading respectively to the large and small chambers of the first drive.

Abstract: A hydraulic drive system has first and second flow control valves. Each of the control valves has a main valve of the seat valve type with a valve body for controlling communication between an inlet port and an outlet port which are both connected to a main circuit. Each further have a variable restrictor capable of changing an opening degree thereof in response to displacements of the valve body, and a back pressure chamber communcating with the inlet port through the variable restrictor and producing a control pressure to urge the valve body in the valve-closing direction. A pilot valve is connected to a pilot circuit which is connected between the back pressure chamber and the outlet port of the main valve; and an auxiliary valve is connected to the pilot circuit for controlling a differential pressure between the inlet pressure and the outlet pressure of the pilot valve.

Abstract: In a hydraulic drive system, first and second flow control valves means comprise each: a main valve having a valve body for controlling communication between an inlet port and an outlet port both connected to a main circuit, a variable restrictor capable of changing an opening degree thereof in response to displacements of the valve body, and a back pressure chamber communicating with the outlet port through the variable restrictor and producing a control pressure to urge the valve body in the valve-opening direction; a pilot valve connected to a pilot circuit which is connected between the inlet port of and the back pressure chamber of the main valve; and an auxiliary valve connected to the pilot circuit for controlling a differential pressure between the inlet pressure and the outlet pressure of the pilot valve.

Abstract: A fluid pressure control system comprising a first selector valve for controlling the action of a first actuator, a second selector valve for controlling the action of a second actuator, a first flow control valve for controlling a fluid to be supplied to the first actuator, and a second flow control valve for controlling a fluid to be supplied to the second actuator. A pressure reducing valve is provided for reducing the pressure of the fluid supplied to the second actuator. The pressure on the outlet side of the pressure reducing valve is controlled by the proportional pressure relief valve which is controlled by an external pilot pressure. This system is applicable, for example, to a hydraulic excavator.

Abstract: A hydraulic circuit for a construction machine which operates an actuator for working machine simultaneously with an actuator for working element without degrading the operation of the actuator for working machine. The hydraulic circuit comprises a first hydraulic pump, a first directional control valve connected to the first hydraulic pump and controlling an operation of the working machine actuator, a third directional control valve controlling an operation of the working element actuator, a second directional control valve connected to a second hydraulic pump, a first pilot operating device for controlling an operation of the first directional control valve and a second pilot operating device for controlling an operation of the third directional control valve.

Abstract: A grader has a grader blade which can be pressed against the ground or lifted off it by means of piston-cylinder drives. To be able to vary the downard pressure of the grader blade in its float position, either the piston chamber or the piston ring chamber of each drive can be charged with a working fluid under pressure when the grader blade is in the float position, so that the corresponding drive exerts a force on the grader blade which increases or decreases the downward pressure of the grader blade on the ground. While still allowing the grader blue to follow the contour of the ground.

Abstract: A method of operating a boom which comprises an elongate member mounted on a base for pivotal movement about a first axis transverse to the axis of the elongate member, first fluid operated power means mounted between the base and the elongate member to control raising and lowering of the member about said first axis, an implement mounted at one end of the member for pivotal movement about a second axis transverse to the axis of the elongate member, second fluid operated power means comprising a double acting ram having a cylinder and plunger slidable therein, mounted between the implement and the member to control movement of the implement about the second axis, means to feed fluid under pressure to and from the first fluid operated power means along first feed lines via a first operating valve, means to feed fluid under pressure to and from the second fluid operated power means along second feed lines via a second operating valve, a displacement means comprising a further double acting fluid operated ram co

Abstract: A control block is made up of a plurality of directional valves which serve to actuate a plurality of hydraulic drives to which in some cases a different pressure is to be supplied. For this purpose two pressure-limiting valves adjustable to different pressures are provided, the valve adjustable to the lower pressure being connected to the last valve unit. This gives a simple construction and substantial freedom in the association of the drives.

Abstract: A pressure compensated hydraulic valve (2) is provided with a housing (4) having a reciprocal spool (6) for communicating hydraulic fluid to work ports (8,10). Pressure compensating means (58) is provided in the same housing with the valve and senses work port pressure by hydraulic fluid flow through the spool from the work port and creates a substantially fixed differential pressure across the spool by controlling the pressure after the flow has passed through the spool.

Abstract: A system for controlling the pressure of hydraulic operating fluid selectively supplied from a pressurized hydraulic fluid source into an actuator or actuators for speed-change clutch-brakes of a multi-stage power shift transmission through hydraulic fluid circuits by the interposition of predetermined directional control valves selected from a plurality of directional control valves connected with the actuators, respectively, has a hydraulic fluid pressure control valve assembly including a pressure modulating valve, a modulating relief valve, and a device for raising a preset relief pressure of the modulating relief valve. The preset relief pressure raising device comprises a balance piston-cylinder assembly actuated by a pressurized pilot fluid supplied from the pressurized hydraulic fluid source.

Abstract: A hydraulic control device is incorporated in a hydraulic control system for a mine roof support assembly. The hydraulic control system includes a plurality of hydraulic control valves which are controlled by the hydraulic control device. The hydraulic control device is constituted by a longitudinal slide valve having a slide member longitudinally reciprocable in a slide valve housing. A rotary drive is provided for moving the slide member within the slide valve housing. The slide member is provided with two axial bores each of which opens into a respective pair of axially-spaced radial bores which terminate at the peripheral surface of the slide member. A first radial bore of each axial bore opens into a respective annular groove formed in the slide valve housing. The second radial bore of each axial bore is connected to a respective group of control ports provided on the slide valve housing.

Abstract: A multiple consumer hydraulic device is provided having a pump and at least two consumers, where a multiway control valve throttling in the intermediate positions is located in front of each of these consumers and a hydraulically controlled additional valve is located in the line between the pump and this mulitway control valve and is acted upon in the closing direction by the pressure in front of this multiway control valve and is loaded in the opposite direction by the pressure of the assigned consumer in which case, in order to achieve a load-independent proportioning of the pump stream for both pumps with and pumps without load-sensing, the additional multiway valve is provided with two additional control pressure chambers, of which the one acting in the closing direction is acted upon by the pressure of the one of the consumers carrying the highest pressure, and the oppositely acting additional control pressure chamber is acted upon by the pressure in the delivery line of the pump.

Abstract: A pump 1 supplies hydraulic fluid from a reservoir 2 to hydraulically operated equipment 4 through a main flow line 3, the fluid being returned to the reservoir 2 through a return supply line 5. If the pump 1 should fail the equipment 4 may be supplied from an independent pump unit which can be connected to flow and return lines 6, 7. Because the pump 1 has failed it will be incapable of operating a dump valve 15 so the fluid will not be fed to the reservoir 2. Should there be a blockage in the equipment 4 pressure will build up in a relief valve 13 which will therefore open to allow the fluid to pass directly to the return line 5 (or 7). If the system is to be used as a source of pressurized hydraulic fluid for another unit then a change over valve 12 will be operated to de-couple the unit 4 and allow the fluid to pass to the other unit through the auxiliary supply lines 6, 7.

Abstract: A hydraulic drive system for civil engineering and construction machinery in which at least first and second hydraulic circuits having at least first and second hydraulic pumps, respectively, are provided for driving a plurality of actuators such as left and right travelling actuators, a boom actuator and an arm actuator. The first circuit includes a first travelling directional control valve for one of the left and right travelling actuators located downstream of a first boom directional control valve for the boom actuator and a first arm directional control valve for the arm actuator that the latter to receive a hydraulic fluid supply from the first pump by taking priority over the first travelling valve.

Abstract: A hydraulic circuitry for a backhoe in which a hydraulic motor for driving one of right and left crawlers and a hydraulic cylinder for vertically oscillating a working arm assembly are connected in parallel to each other to a first pump through a multiplex valve assembly having a first center bypass, and a hydraulic motor for driving the other crawler, a hydraulic motor for slewing a platform, a hydraulic cylinder for flexing and stretching the arm assembly, a cylinder for actuating a bucket and a cylinder for actuating a dozer are connected in parallel to one another to a second pump through a further multiplex valve assembly having a second center bypass. The invention provides a circuit to permit fluid pressure from the first pump to enter the circuit connected to the second pump to provide confluence therein, when the dozer actuating cylinder connected to the second pump, for example, is operated while the backhoe is running.

Abstract: Pipe thrust-jacking apparatus includes a pressure ring 5 which is advanceable by a plurality of hydraulic rams 3. The rams are controlled by hydraulic control means having a plurality of hydraulic control valves 19. Each control valve is associated with a respective hydraulic ram, and is connected to a first input line and to a second input line. Each of the first input lines is connected to a respective hydraulic fluid feed line 9, and each of the second input lines 17 is connected to a common hydraulic fluid supply line 11 and to an auxiliary pump P2. The common supply line is connected to all of the feed lines. Means 12,15 are provided for selectively connecting each of the hydraulic control valves to its first input line and/or its second input line.

Abstract: A hydraulic vehicular transmission has a plurality of drive speed establishing devices (e.g. clutches) to be actuated for selecting a drive speed, and a pair of similar drive direction establishing devices to be actuated for selecting a drive direction. The drive establishing devices are all actuated and deactuated hydraulically by respective solenoid operated control valves via respective pilot operated valves. Since the solenoid valves are susceptible to malfunctioning, as in the event of trouble in the associated electrical circuitry, emergency control valves are interposed respectively between the solenoid valves and the pilot operated valves. Each emergency control valve is to be hand operated in the event of the malfunctioning of the associated solenoid valve for actuating or deactuating the associated speed or direction establishing device via the associated pilot operated valve. Additional features are incorporated for the greater utility of the transmission control system.

Abstract: A hydraulic circuit system of a construction machine having first and second hydraulic circuit, and a bypass circuit for connecting the first and second circuits together. The first circuit includes a first hydraulic pump and a first valve group having a plurality of directional control valves for controlling a flow of hydraulic fluid from the first pump, and the second circuit includes a second hydraulic pump and a second valve group having a plurality of directional control valves for controlling a flow of hydraulic fluid from the second pump. A plurality of actuators are driven by the hydraulic fluid supplied from the first and second pumps through the valves. The bypass circuit includes a bypass line for connecting the first travel valve in series with the second travel valve in a position downstream thereof through the selecting valve.

Abstract: Container handlers comprise a plurality of double-acting hydraulic cylinders to effect the various side shift, twist lock, tilt, height adjustment, and spread modes of operation. Separate control valves and hoses, entrained over the mast assembly having the attachment thereon, are required to effect such functions selectively. This invention is directed to a programmed electro-hydraulic control circuit when reduces the required number of hoses to two and provides a non-complex system which can be operated expeditiously.

Abstract: A hydraulic valve is provided which can be modified to provide priority compensation, parallel pressure compensation, inlet check functions and a float function by changing a flow through inlet valve portion in the inlet chamber of the valve.

Abstract: A hydraulic valve is provided which can be modified to provide priority compensation, parallel pressure compensation, inlet check functions and a float function by changing a flow through inlet valve portion in the inlet chamber of the valve.

Abstract: A fluid power system for actuating three separately controllable double acting fluid motors each selectively providing a separate function in which the number of hydraulic lines to the motors is minimized. A first function valve supplies power to the first motor and a second function valve provides power to a selector valve which selectively connects the power to the second and third motors. The selector valve is pilot actuated from one of the lines to the first motor and a control valve supplies power to the one line for actuating the selector valve. The system is particularly useful for a lift truck for minimizing the number of hydraulic lines connected to the motors on the carriage of the truck.

Abstract: A device for reciprocating motion of a rotating drilling body of a drilling machine in the longitudinal direction of a hole drilled in rock or ground includes two cylinder-piston devices which via chains are connected to a carriage carrying the drilling body and which comprise parallel piston rods, the ends of which are supported by a frame on the machine, and cylinders movable along the piston rods and connected to each other and via the chains also to the carriage. To increase the feeding velocity of the carriage or to increase the force of the carriage one of the cylinders or both cylinders, respectively, are selectively fluid pressurized.

Abstract: A pressure control mechanism for the hydraulic control system of a log skidder. Hydraulic circuits for the boom and the grapple of a log skidder are interconnected to provide a pressure control mechanism for the grapple of the skidder. Provided in the interconnecting hydraulic lines for the grapple cylinder and the boom cylinder, between the rod end of the boom cylinder and the base end of the grapple cylinder, is a two-way valve and a check valve. This mechanism provides flow from the boom cylinder to the grapple cylinder. The weight of the load pressurizes the boom cylinder and this pressure is transferred to the grapple cylinder.