Abstract: A hydraulic control system has a pilot pressure supply circuit that applies a pressure differential dependent on engine speed to opposite sides of an anti-stall valve to turn off the pilot flow when the pressure differential falls below a certain value, resulting in holding the positions of the hydraulic devices being controlled until engine speed recovers.

Abstract: Construction machinery which is capable of improving fuel efficiency of the engine and also capable of effectively utilizing surplus energy in a light-load mode. The construction machinery includes an engine, a hydraulic pump driven by the engine, and actuators driven by oil pressure supplied from the hydraulic pump. In the light-load mode where the engine torque at the intersection point of an iso-horsepower curve of the necessary horsepower and a governor characteristic curve of the engine is smaller than that of a rated output point of the engine, the number of revolutions of the engine is reduced while the engine torque is increased with respect to the intersection point, and the horsepower is made to exceed the iso-horsepower curve. With surplus torque generated therefrom, a power generator is operated so as to generate electric power, which is stored in a power accumulation apparatus.

Abstract: A hydrostatic continuously variable transmission includes a hydraulic pump and a hydraulic motor, supported by a common support shaft, and hydraulically connectable to each other through a hydraulic circuit including an inside passage and an outside passage. A clutch device includes a valve spool, which is slidably disposed in a hollow internal bore formed in the transmission support shaft. The valve spool is operable to make or interrupt fluid communication between the inside passage and the outside passage, according to the movement thereof. A governor mechanism is mounted to a pump casing of the hydraulic pump, and the governor mechanism generates a governor force corresponding to the rotating speed of a clutch cap, by use of centrifugal force generated by the rotation thereof. The valve spool is effectively moved in the hollow internal bore, using the governor force generated from the governor mechanism, to engage or disengage the clutch.

Abstract: A method and apparatus are provided for controlling the operation of a pump, such as a centrifugal pump, featuring steps of either adjusting the operation of the pump, or issues a warning to a user of the pump of an undesirable operating condition, or both, based on a comparison of an actual torque value and a corrected torque value either alone or in combination with a further step of compensating the corrected torque value based on a mechanical power offset correction. The corrected torque value may include a Best Efficiency Point (BEP) torque value and may also be compensated for based on at least the current operating speed of the pump. The pump has a controller for performing the steps of the method. The controller can compensate the corrected torque value based on the square of the speed change of the pump. The comparison may include a ratio of the actual torque value to the corrected torque value.

Abstract: There is provided an oil supply unit for a running power transmission of a vehicle. The oil supply unit includes a housing, a hydraulic pump of a variable displacement type, a detecting mechanism and a control mechanism. The detecting mechanism is constructed to monitor a driven state of an engine. The control mechanism is constructed to operate an output adjusting member of the hydraulic pump to thereby regulate the discharge quantity against the suction quantity of the hydraulic pump based on the driven state of the engine.

Abstract: A machine body controller 70A includes a modification control unit 70Ab for computing a torque modification value based on detected signals from environment sensors 75 to 83, and modifies a maximum absorption torque of a hydraulic pump controlled by a basic control unit 70Aa. An engine controller 70B includes a modification control unit 70Bb for computing an injection modification value based on detected the signals from the environment sensors 75 to 83, and modifies a fuel injection state of a fuel injection device 14 controlled by a basic control unit 70Ba. The controllers 70A, 70B further include computation element altering units 171, 181. A communication controller 70C downloads alteration data obtained from an external terminal 150 to the computation element altering units 171, 181, whereby corresponding computation elements contained in the modification control units 70Ab, 70Bb are altered.

Abstract: A method is provided for controlling hydraulic flow to a hydraulic actuator in fluid communication with a pump. The method includes generating a signal representative of a speed of the pump and selecting a relationship from a plurality of relationships between valve commands and an operator input. The selection is based upon the speed signal. A valve is modulated to control the hydraulic flow to the hydraulic actuator based on the selected relationship and the operator input.

Abstract: A hydraulic circuit for a tree-cutting machine having a feed mechanism powered by hydraulic fluid at the output of a hydraulic motor. The hydraulic motor may comprise a variable-displacement motor. The hydraulic circuit may comprise elements which provide an anti-stall mode, wherein the feed mechanism is operated to withdraw the cutting element upon pressure at an input port of the hydraulic motor exceeding a threshold.

Abstract: A hydraulic actuating device for a convertible top assembly of a motor vehicle. The actuating device comprises a hydraulic pump with an associated electric pump motor and one or more hydraulic actuators, each for driving an associated movable part of the convertible top assembly. The actuating device also comprises a control circuit for effecting a defined sequence of movements of the one or more actuators and feedback means, which are connected to the control unit, for feeding information relating to the sequence of movements of an actuator back to the control unit. The feedback means comprise means for measuring the electric power consumed by the pump motor, which means transmit a feedback signal to the control unit.

Abstract: If an instruction to move a ram (5U) is issued, a ram instructed speed is instructed to be suppressed to a certain warming-up speed not higher than a target speed until a release speed determination section (75) determines that a moving speed of the ram (5U) calculated by a ram moving speed calculation section (51) reaches a predetermined warming-up release speed; if the release speed determination section determines that the moving speed of the ram (5U) reaches the predetermined warming-up release speed, the warming-up speed is released to accelerate the ram (5U) to the target speed.

Abstract: Control valves are respectively provided in a pair of variable displacement hydraulic pumps. If an ultra low speed travel signal is issued in response to an ultra-low-speed switch turned on, one of the control valves is fixed to a neutral position by a solenoid valve. And a displacement amount of a travel motor is fixed at a maximum displacement by another solenoid valve. In this way, an upper limit for motor rotation speed is significantly reduced. As a result, it is possible to realize the ultra low speed travel with maximum operation of an accelerator pedal, without the need for subtle operation of the accelerator pedal.

Abstract: First and second hydraulic pumps each adapted to operate plural actuators are activated by separate electric motors respectively. In accordance with signals provided from a controller on the basis of operations of levers, the number of revolutions of the electric motor and that of the electric motor are controlled each independently and simultaneously to control the discharge rates of both hydraulic pumps.

Abstract: Hybrid powered construction equipment is capable of making effective use of the output energy of an engine; increasing operating speed while keeping noise level low, and assuring operation power more than the performance of the engine. To this end, the hybrid powered construction equipment has a hydraulic pump powered by the engine; hydraulic actuators activated by discharge oil from the hydraulic pump; a motor-generator working in conjunction with the engine; and a battery for storing electric power generated by the electric motor-generator, the construction equipment further comprising a power-up switch disposed in an operating lever or operation panel and a controller which inputs a signal released from the power-up switch, wherein the controller constantly controls the revolution speed of the engine in response to a signal from the power-up switch and controls the output torque of the electric motor-generator such that torque for assisting powering of the hydraulic pump is output.

Abstract: A hydraulic actuating device for a closure assembly, for example of a vehicle, which closure assembly comprises a closure element which can be moved between a closed position, in which the closure element closes off an opening, and an opened position. The hydraulic actuating device comprises a hydraulic actuator for moving the closure element, which actuator has a housing having a closing chamber and an opening chamber. Further provided are a hydraulic pump having an associated electric pump motor and a reservoir for hydraulic fluid. The hydraulic actuating device further comprises a first pressure-limit valve, which is connected to the opening chamber, and a second pressure-limit valve, which is connected to the closing chamber. Control means are further provided for controlling the supply of hydraulic fluid under pressure to the opening chamber or to the closing chamber of the actuator.

Abstract: A hydraulic power system includes a reversible pump, a variable-speed servomotor for driving the pump, a pressure sensor for detecting load pressure, a detector for detecting the motor speed, signal command units for generating preprogrammed pressure and flow rate commands, a rotational speed controller and a signal processor. The signal processor preferentially outputs a speed command corresponding to the flow rate command by a limiter operation when the difference signal between the pressure command and the pressure detection signal is higher than a predetermined level, whereas it preferentially outputs a speed command corresponding to the difference signal when the difference signal is equal to or lower than said level. The rotational speed controller controls the magnitude of a driving current supplied to the servomotor by a closed loop on the basis of the speed command and the detected signal so that the speed of the servomotor corresponds to the speed command.

Abstract: A combination of an electronically controlled vehicle and a hydraulic system and method of operating same for monitoring and controlling the flow of hydraulic fluid in a hydraulic system having at least one hydraulic actuator is provided. An electronic control system (ECS) processes system parameters and information and allocates engine power and controls pump output while maintaining optimum engine performance. The combination of an electronically controlled vehicle and a hydraulic system prevents hydraulic overloads, avoids increased engine RPM, and reduces unnecessary wear and tear on system components while significantly reducing fuel consumption and the emissions of pollutants and noise during operation.

Abstract: A forward/backward switching control apparatus for a hydraulic drive vehicle, comprising: a variable displacement type hydraulic pump driven by an engine for discharging pressure oil in both directions; an electromagnetic pump inclination angle control mechanism for making the discharge displacement of the variable displacement type hydraulic pump variable and for causing the same to discharge in both directions; electric control means for outputting signals to run the hydraulic drive vehicle forward, backward and forward/backward; and control means for outputting, when the electric control means is switched forward/backward to output the forward/backward signal and when the time for switching the forward/backward signal is not longer than a preset time, a first modulate signal for delaying the return times from the forward position to the neutral position and from the backward position to the neutral position, to the electromagnetic pump inclination angle control mechanism.

Abstract: A method for controlling a fluid system is provided. The system may include a hydraulic circuit having a pump driven by an engine, wherein the pump delivers fluid to an actuator through a valve assembly. The method may include receiving an operator input and determining a condition of the hydraulic circuit. The condition of the hydraulic circuit may include at least one of a flow rate of fluid to the actuator, an engine speed, and a pump displacement. The method may include determining a valve transform function as a function of a position of a linkage associated with the actuator and the condition of the hydraulic circuit. The method may further include determining a valve command in response to the valve transform function and the operator input, wherein the valve command results in a consistent deadband. The valve command is delivered to the valve assembly.

Abstract: A method is provided for controlling hydraulic flow to a hydraulic actuator in fluid communication with a pump. The method includes generating a signal representative of a speed of the pump and selecting a relationship from a plurality of relationships between valve commands and an operator input. The selection is based upon the speed signal. A valve is modulated to control the hydraulic flow to the hydraulic actuator based on the selected relationship and the operator input.

Abstract: A speed control apparatus and method of a working vehicle which can reduce a working speed and a traveling speed of the vehicle to a desired speed range in correspondence to a change of working conditions at a time of a vehicle crane operation. A controller sets an optional hydraulic pump absorbing curve when an operator selects the crane operation mode. When the speed is adjusted by the operator, a pump tilt and rotation angle is automatically controlled to a pump absorbing torque in correspondence to the crane working speed along the optional pump absorbing torque curve.

Abstract: Various work machines in which safety of operation and operation efficiency can be enhanced in accordance with variation in the kind of operation and operation condition when operation is carried out based on a previously set operation mode of an operation machine, and operation speed of the operation machine or running speed of the work machine can finely be adjusted is provided. The work machine comprises mode switching means having a mode switching switch and the like of operation modes of one or more operation machines. A speed finely-adjusting switch is disposed for finely adjusting an operation speed and/or a running speed to values out of range set in each mode by manual operation. An engine, a pump, a flow rate adjusting valve disposed in a driving circuit of one or more operation machine and running motor and the like are operated by a signal output by operating the speed finely-adjusting switch, and the engine revolution number and the pump discharge amount are adjusted.

Abstract: A multilevel speed regulation method for a jack and a multilevel speed regulation jack use a hydraulic speed regulation line which includes at least two parallel hydraulic sub-lines extending between the input and output cylinders and the pressure applied by the output cylinder against the load is taken as the control signal to control the opening and closure of the hydraulic sub-lines or their combination at different speed levels. Application of the method in this invention provides the jack with the capability to automatically transfer between different speed levels in the case of different loads, and thus the lifting efficiency is improved. Additionally, this invention also provides a multilevel speed regulation jack, in which a hydraulic speed regulation line of at least three speed levels is connected in series between the input and output cylinders. This hydraulic speed regulation line consists of at least two parallel hydraulic sub-lines.

Abstract: A control system for a utility vehicle, particularly a compact utility tractor, that is speed-controlled by a hydrostatic transmission, prevents engine stalling by automatically reducing the stroke of a pump of the hydrostatic transmission, and thus reducing the vehicle speed, when the unloaded engine speed drops below a predetermined threshold. The apparatus includes a servo controlled hydrostatic transmission, an engine speed sensor, a throttle position sensor and a controller. The unloaded engine speed is determined by either an engine throttle lever position or by an engine speed capture algorithm that continuously monitors engine speed and records engine speed occurring when the transmission control pedals are positioned in neutral.

Abstract: The stump grinder has a rotating cutting wheel that is mounted onto an arm for raising and lowering movement and is driven by a hydraulic motor. The arm is capable of being moved about a generally upright axis to control the rate of laterally feed of the cutting wheel. The actuator movement is controlled as a function of the pressure to the hydraulic motor driving the cutting wheel so that as the pressure increases, the rate of feeding movement laterally of the cutting wheel is reduced. The rate of movement is controlled in both directions of swinging of the post about an upright axis, by utilizing variable opening or proportional flow pilot operated valves on the lines to the actuator for controlling the swing. As pressure to the motor increases the variable outlet or proportional pilot operated valve connected to the pressurized end of the swing actuator opens a greater amount diverts a portion of the hydraulic fluid flow to drain to slow movement of the swing actuator.

Abstract: The invention provides an improved fluid motor powered lift system having a valve arrangement for reducing or interrupting the fluid flow supplied to the motor when the pressure in the lift system exceeds a predetermined pressure. A valve arrangement is provided to shut-off or throttle back the fluid supplied to the fluid motor when the fluid pressure in the lift reaches a predetermined level. When the pressure in the lift system exceeds the predetermined level, pilot pressure is supplied to an automatic shut-off valve, and this in turn reduces fluid flow to fluid air motor thereby reducing or preventing pump pressure.

Abstract: The invention relates to an apparatus for manipulating in the height and in particular setting down of a load. The apparatus comprises a suspension on a lifting device, which suspension comprises a drive, with which drive the load can be manipulated in the height; a weighing device with which the weight of the load can be determined; a memory connected to the weighing device for storing an initial weight of the load; and comparing means for comparing an actual weight with the initial weight stored in the memory for the purpose of selective energizing of the drive in response to the comparison.

Abstract: A differential pedal interface system for controlling the forward and reverse speed, acceleration, deceleration, and jerk of a work machine including foot pedals coupled to each other for differential movement, displacement of one pedal controlling movement in the forward direction and displacement of the other pedal controlling movement in the reverse direction. The present system further includes at least one sensor coupled to one of the pedals for determining their displacement and rate of movement and an electronic controller coupled to the at least one sensor for receiving signals therefrom, the controller being operable to control the speed, acceleration, deceleration, and jerk of the work machine based upon the signal inputs.

Abstract: An electrohydraulic pressure supply unit involving the joint operation of two energy converters, which can be adjusted independent of each other, including an electric motor with speed control that drives a variable displacement pump with a variable displacement volume. The electric motor converts electrical output (loss-encumbered), into mechanical output, meaning into speed n and torque T. The pump then converts this mechanical output (also loss-encumbered) into hydraulic output. The hydraulic output is determined by the pressure difference &Dgr;p across the pump and the volume flow Q. The pressure difference &Dgr;p generally is impressed by the consumer or load on the system. The volume flow Q is the result of the displacement volume V and the motor speed n. The torque T, which must be generated by the motor, is derived from the displacement volume V and the pressure differential &Dgr;p.

Abstract: The present invention provides a method and apparatus for controlling a electro-hydraulic system of an earthmoving machine. The electro-hydraulic system may include a pump providing fluid to at least one fluid system. The electro-hydraulic system also includes an engine connected to the pump, and a controller for providing a commands to the engine. The method includes the steps of determining a desired characteristic of the fluid system, comparing the desired characteristic with a deliverable characteristic of the fluid system, and generating a power boost in response to the comparison; thereby controlling the electro-hydraulic system.

Abstract: The present invention provides a method and apparatus for controlling a fluid system. The fluid system includes a hydraulic circuit having a pump driven by an engine. The pump delivers fluid to an actuator through a valve assembly. The method includes the steps of receiving an operator input, determining a condition of the hydraulic circuit, determining a valve command in response to the circuit condition and the operator input, and delivering the valve command to the valve assembly.

Abstract: A hydraulically operated industrial machine has hydraulic work components such as a boom, bucket or the like, and also uses hydraulic motors for propelling the machine. The motors and cylinders are controlled by pilot pressure valves to provide pressure to pilot operated valves. A pressure reducing valve is utilized for providing hydraulic fluid at a pilot pressure to the pilot valves. The reducing valve regulates the pilot pressure as a function of one or more parameters indicating the consumption of hydraulic power in the system, such as drive engine speed, or other signals including oil temperature, throttle position, and, if desired, feedback signals from the system.

Abstract: An operating mechanism for a folding top (1) of a convertible has an electric motor (10) with a rotational speed that can be regulated for driving a hydraulic gear mechanism (11). A control unit (7) for actuating the electric motor (10) has a memory (18) for rotational speeds intended according to the positions of the folding top (1). As a result, the rotational speeds are stored as software that is easy to change.

Abstract: A power assisted steering system 12 has a control valve 28, a pump 22 coupled to the control valve 28, and a motor 20 coupled to the pump. A controller 18 is coupled to the motor. The controller generates a control signal having a voltage and a current. The controller 18 generates a desired motor current in response to a desired flow rate and valve angle of the control valve 28.

Abstract: The invention relates to a control device for hydraulic power cylinders, in particular power cylinders of a road truck tailgate, comprising a hydraulic pump (1) driven by a motor (M). Said pump can be connected to a supply of medium and, via pump branch pipes, to a chamber of the operating cylinder (14) by means of allocated control valves (12,13). An adjustable electrical pressure gauge and switch unit (15-18) is connected to the chamber or corresponding pump branch pipe of the power cylinder. Said unit is fitted with a computer (15) for entering maximum pressure limits and used to stop the pump motor drive (2, 19) and activate a signal transmitter (20) when a preset maximum pressure is exceeded. In addition, a safety valve (22) set at a cut-in pressure lower than the preset maximum pressure is connected to the chamber or corresponding branch pipe (8″,A,B) via an electromagnetic valve (23) which opens when the device is not operating.

Abstract: A hydraulic drive system is provided with a signal guide system for guiding a delivery pressure of a pump as a command pressure via a line and a port, another signal guide system for guiding a pilot pressure of a pilot pump as another command pressure via a line and a port, a tilting control unit for controlling the displacement of the pump by the command pressures guided to the ports, a controller having a command current-setting unit for setting a relationship between a target engine speed and a command current, a target engine speed-indicating unit for an engine, and a solenoid-operated proportional valve for allowing the pilot pressure of the line to pass as is while no drive signal is outputted from the controller but for being reduced in opening to change the pilot pressure to a smaller value when a drive signal is outputted from the controller.

Abstract: In an electrohydraulic clamping module for a clamping element of a tooling machine comprising a pressure regulating valve in a flow line towards said clamping element is provided for regulating the clamping pressure. A pressure surveying sensor is integrated into said pressure regulating valve surveying said clamping pressure. Said pressure regulating valve is a leakage-free seat valve having a closure member which can be moved in relation to a stationary valve seat and can be adjusted by means of a control piston which is displaceable by the regulated pressure downstream of said valve seat and in closing direction of said closure member counter to a regulating force. Said pressure surveying sensor can be actuated by said control piston.

Abstract: A torque control system for a hydraulic pump in a hydraulic construction machine wherein if an engine output lowers due to change of the environment, modification gain calculating portions 70m-70u and a torque modification value calculating portion 70v receive signals detected by sensors 75-82 and estimate a lowering of the engine output power as a torque modification value &Dgr;TFL. A speed sensing torque deviation modifying portion 70i subtracts the torque modification value &Dgr;TFL from a speed sensing torque deviation &Dgr;T1. A resulting torque modification &Dgr;TNL is added to a pump base torque TR0 to determine a suction torque TR1 (target maximum suction torque), and a resulting signal is output to a solenoid control valve 32. The solenoid control valve 32 controls respective servo valves 22 for total horsepower control, thereby controlling the maximum suction torque of the hydraulic pumps 1, 2.

Abstract: An engine speed control system for a construction machine is arranged in association with its hydraulic circuit, which has main pumps, a communication line through which input ports of travel-controlling directional control valves are connected with each other, and a travel-controlling communication valve arranged in the communication line.

Abstract: A vehicle that has a drive train with an internal combustion engine, a transmission, and a number of ground engaging wheels. An operator-adjustable throttle control is monitored to provide a position signal corresponding to position of the throttle control. A sensor provides an observed speed signal corresponding to speed of the vehicle and a controller responds to the position signal and the observed speed signal to generate a target speed signal and an error signal. The target speed signal corresponds to a desired speed of the vehicle and is generated from a predetermined relationship between vehicle speed and throttle control position in accordance with the position signal. The error signal corresponds to a difference between the target speed signal and observed speed signal. The engine responds to the error signal to provide the desired vehicle speed for all operating speeds of the vehicle including a stopped or idle condition.

Abstract: A hybrid electric hydraulic drive system, having a first cylinder (75) having a left chamber (32) and a right chamber (34) separated by a piston (22). A second cylinder (76) has a single or sole chamber (74) for receiving hydraulic fluid with the second cylinder enclosing a second piston (78). The second cylinder is substantially equal in length to the first cylinder and is rigidly attached to the first cylinder. A pump (14) is fluidly connected to the left chamber (32) by a first fluid passage (16) and is fluidly connected to the right chamber (34) by a second fluid passage (18). A third fluid passage (80) is directly connected to the right chamber (34) and to the sole fluid chamber (74) of the second cylinder (76). A first rod (30) is connected to the piston (22) and a second rod (84) is connected to the second piston (78). The first and second rods are connected by a connecting element so the rods move in unison.

Abstract: A regenerative power steering system 10 for a vehicle, alternatively operable in an unassisted, straight steering mode, a powered assist mode which provides a powered assist to entry of the vehicle into a turn and an energy regeneration mode which recovers energy while the vehicle exits a turn. The system comprises a motor pump 24 connected to a fluid delivery line 20 and a reservoir structure 76, in turn connected to a closed-center control valve assembly 38 for actuating a power cylinder 18 connected to the vehicle wheels. The pump 24 is connected to the delivery line 20 and the reservoir structure 76 by a four-way cross-over valve 30.

Abstract: A relief pressure controlling device comprises a driving side relief pressure controlling valve, a capacity detector which detects the capacity of a hydraulic pump, and an engine throttle opening detector. When the hydraulic pump and the hydraulic motor which are connected by a first oil passage and a second oil passage constituting a hydraulic closed circuit are driven by an engine, the relief pressure controlling valve controls the relief pressure of the oil passage on the driving side that is either the first oil passage or the second oil passage whose pressure becomes higher than the other, to a target relief pressure. The target relief pressure is determined in correspondence with the engine output and corrected on the basis of the pump efficiency which is predetermined in relation to the capacity of the hydraulic pump and to the throttle opening, and this corrected target relief pressure is set as a driving side target relief pressure.

Abstract: A hydrostatic drive system is provided for a vehicle, in particular an industrial truck, with a hydrostatic traction drive system (16), a hydraulic work system (13) and a hydraulic steering system (9). The invention provides a drive system that is compact and exhibits improved operating behavior during the change from traction operation to coasting operation.

Abstract: There are provided an electric motor driven by (electric) power from a battery; a hydraulic pump driven by the electric motor; a hydraulic motor driven by operating oil discharged from the hydraulic pump; an operating member for performing a predetermined operation by the drive of the hydraulic motor; and operating levers for operating the operating member by switching a flow and a shut-off of the operating oil discharged from the hydraulic pump. The operating levers are operatable between a neutral position at which the hydraulic motor stops operation and an operating position at which the hydraulic motor operates. An accel-trimmer is provided to adjust the supply amount of power from the battery to the electric motor in the state where the operating levers are operated to the operating position.

Abstract: A hydrostatic drive system is provided for a vehicle, in particular an industrial truck having a hydrostatic traction drive system (16), a hydraulic work system (20) and a hydraulic steering system (8). The drive system is compact and the energy utilization in the drive system is improved by providing a hydraulic pump (1) with an adjustable delivery volume working in an open circuit to supply the traction drive system (16), the hydraulic work system (20) and the steering system (8). In one configuration of the invention, there is at least one traction drive control valve (23) in the delivery line (5b) of the pump (1), whereby upstream of the traction drive control valve (23) in the delivery line (5b) of the pump (1) there is a priority valve (18) for the hydraulic work system (20), and upstream of the priority valve (18) of the hydraulic work system (20) there is a priority valve (6) for the steering system (8).

Abstract: An apparatus to maintain optimum engine speed and cutter wheel speed to maintain peak power output of the engine and peak flywheel effect of the stump cutter wheel and method for maintaining optimum engine speed. The stump cutter has a rotating cutting wheel powered by an engine, and the cutter is mounted to be moved laterally. The mounting includes a boom and at least a first hydraulic cylinder for urging the boom to move along the path of travel over the surface of a stump. The hydraulic cylinder is activated by a hydraulic circuit which includes a source of pressurized hydraulic fluid. A pressure hydraulic line connects the source of hydraulic fluid to a first port of the hydraulic cylinder and a return line is connected to a second port of the hydraulic cylinder. A valve diverts a portion of flow from the pressure line to the return line or to a sump. The valve is shiftable between at least a first and a second position.

Abstract: Hydraulic actuating drive for a clutch, including a control unit, a hydraulic pump which can be driven by a drive and which feeds a pressure accumulator, and an actuating cylinder which is connected via a control valve with the pressure accumulator. The drive of the hydraulic pump is provided with a sensor for detecting the power consumption by the drive, and signals are sent to the control unit so that the hydraulic pump is controllable depending on the power consumption of the drive.

Abstract: In the arm-crowding or track operation, a calculating portion (700d2 or 700d4) calculates a modification gain (KAC or KTR) depending on an operation pilot pressure and a calculating portion (700g) calculates a decrease modification (DND) based on the KAC or KTR, while a calculating portion (700m or 700p) calculates a modification gain (KACH or KTRH) depending on an operation pilot pressure and calculating portions (700q-700s) calculate an increase modification (DNH) based on the KACH or KTRH. A reference target engine revolution speed NR0 is modified using the DND and DNH. In other operations than the arm-crowding and track operations, NR0 is modified using only the decrease modification (DND) calculated from the modification gain just depending on the operation pilot pressure. In the operation where an engine revolution speed is desired to become higher as an actuator load increases, the engine revolution speed can be controlled in accordance with change of the actuator load as well.

Abstract: A device for matching the operation of a travelling unit in a construction vehicle is disclosed. The device reduces the required levering force of a travelling control pedal, easily controls the rotating force of an engine, and safely changes the engine output torque in accordance with both the levering stroke of the travelling control pedal and a travelling resistance. The device has a pressure reduction valve which is synchronized with a levering motion of a travelling control pedal in order to feed pilot fluid from a pilot pump to a direction select valve. A branch line is branched from a fluid line extending between the pressure reduction valve and the direction select valve. A hydraulic cylinder is connected to the branch line and selectively receives the pilot fluid through the branch line when the travelling control pedal is levered.

Abstract: In an electric lift truck, an asynchronous electric motor, a reversible sealed pump driven by the motor, communicating with the hydraulic actuators and also with a reservoir, a device which measures the angular position and the angular velocity of the motor, and a control and monitoring unit which causes the motor to be supplied according to the required speed of raising and lowering of the load support and on the basis of data supplied by the measuring device are used for raising and lowering the load support by means of one or more hydraulic actuators. There is a saving of energy in raising; there is also a recovery of energy in lowering, in which the motor acts as a generator to recharge the accumulator batteries of the lift truck.