Abstract: In a working machine, a controller is configured or programmed to control actuation of a blocking switching valve and a solenoid valve, to cause the blocking switching valve to unblock a first pilot fluid passage to perform switching to a first operation pattern in which an operation device operates a first device via a first control valve and a first hydraulic actuator, and cause the blocking switching valve to block a second pilot fluid passage and control the solenoid valve based on pilot pressure detected by a pressure detector to perform switching to a second operation pattern in which the operation device operates a second device via a second control valve and a second hydraulic actuator.

Abstract: A construction machine with a hydraulic system has a hydraulic control, which comprises a joystick, a hydraulic pressure source, and two hydraulic drives. Main control valves are controlled by a joystick. The construction machine comprises multiple components, and a hydraulic drive is assigned for moving these components. The hydraulic control comprises an electrically-actuatable priority proportional valve in the hydraulic connection of a drive. The priority valve is electrically connected to the electronic control unit and generates additional hydraulic resistance. The hydraulic control comprises sensors, on the components, for detection of the positions thereof. The detected sensor values are transferred to the control unit. At least one trajectory is stored in the control unit. A control mode can be activated, in which each priority valve is controlled using the current sensor values upon actuation of the joystick so that the stored trajectory is run by control of the drives.

Abstract: A hydraulic control device for a hydraulic actuation machine including a main oil pump configured to supply oil to the hydraulic actuation machine, a sub oil pump configured to temporarily supply oil to the hydraulic actuation machine based on a drive request so as to compensate for an oil shortfall when supply of oil from the main oil pump to the hydraulic actuation machine is stopped or insufficient, and a drive unit configured to drive the sub oil pump, wherein when an elapsed time elapsed from a time point when the sub oil pump is driven reaches a predetermined time, the hydraulic control device generates an air discharge command for discharging air accumulated in the sub oil pump and outputs the air discharge command to the drive unit, and the drive unit drives the sub oil pump to discharge the air accumulated in the sub oil pump based on the output air discharge command.

Abstract: An electrohydraulic control device for an adjustable hydraulic pump system includes a valve device, an electronic control unit and a first fluid sensor. The valve device includes a pressure inlet, a tank outlet and a first electromagnetically actuated valve. An outlet pressure of the first adjustable hydraulic pump system is applied to the pressure inlet. The first fluid sensor detects an actual value of a fluid parameter of the first adjustable hydraulic pump system and transmits it to the electronic control unit. The electronic control unit includes computer-based modeling of the dynamics of the first adjustable hydraulic pump system, and actuates the first electromagnetically actuated valve based on the actual value of the fluid parameter and the computer-based modeling.

Abstract: A work machine that can keep the control accuracy of actuators irrespective of temperature variation of a hydraulic operating fluid that passes through flow rate controllers that control the flow rates of supply to the actuators is provided. For this purpose, the flow rate controllers each have a valve body that is disposed on a main hydraulic line connecting a delivery line of a hydraulic pump and the actuator and that moves according to an operation pressure from a solenoid proportional pressure reducing valve, a sampling hydraulic line that branches from the main hydraulic line, and a temperature sensor set on the sampling hydraulic line. The controller is configured to correct a command electrical signal to the solenoid proportional pressure reducing valve according to a signal from the temperature sensor.

Abstract: A housing of a multi-control valve includes an arm parallel passage, an arm crowding supply passage, an arm pushing supply passage, a boom parallel passage, a boom raising supply passage, and a boom lowering supply passage. The housing further includes: a slide hole; a head-side passage that is branched off from the boom raising supply passage and extends to the slide hole; a rod-side passage that is branched off from the boom lowering supply passage and extends to the slide hole; and a regeneration passage that extends from the slide hole to the arm parallel passage. The slide hole receives a boom sub spool therein. The boom sub spool is either a boom recycling spool or a boom regeneration spool.

Abstract: According to the present invention, a display system of a turning work vehicle is used for the turning work vehicle in which a work machine having a bucket 8 can be offset relative to a revolving superstructure in the horizontal direction. The display system includes: an arithmetic unit that calculates the position of the bucket on the basis of a detection result obtained by a position detecting device provided on the turning work vehicle, and calculates a necessary revolving amount of the revolving superstructure and a necessary offset amount of the work machine that are needed to align a side section of the bucket with a side edge of a predetermined excavation area; and a display device that displays the positional relationship between the bucket and the predetermined excavation area.

Abstract: A method for monitoring health of a hydraulic fluid subsystem is presented. The method includes determining a plurality of forces acting on an actuator of the hydraulic fluid subsystem, determining a plurality of parameters based on at least one of an actuator inlet flow rate, an actuator outlet flow rate, and the plurality of forces acting on the actuator, receiving a valve inlet pressure of at least one of oil and gas flowing through a pipe while entering a valve operationally coupled to the actuator and a valve outlet pressure of the at least one of the oil and the gas flowing through the pipe while flowing out of the valve, and monitoring the health of the hydraulic fluid subsystem based on at least one of the plurality of parameters, the valve inlet pressure, and the valve outlet pressure.

Abstract: Provided is a hydraulic machine including an actuator, a first pump and a second pump configured to supply pressurized fluid to the actuator, a driving motor configured to drive the first and second pumps, a first operator input device through which an operator's desire to operate the actuator is input, and a controller. The controller determines displacements of the first and second pumps corresponding to the operator's desire and a speed of rotation of the driving motor and controls the first pump, the second pump, and the driving motor to operate according to the displacements of the first and second pumps and the speed of rotation of the driving motor finally determined in the determination of the displacements of the first and second pumps.

Abstract: A power transfer unit includes a first hydraulic circuit, a second hydraulic circuit fluidly connected to the first hydraulic circuit, a pump and motor assembly fluidly connected between the first hydraulic circuit and the second hydraulic circuit, an isolation valve arranged along the first hydraulic circuit and fluidly connected to an inlet of the pump and motor assembly. The isolation valve is movable between a closed position and an open position to prevent and enable high-pressure fluid flow to the inlet, respectively. An unloader valve is arranged along the second hydraulic circuit and fluidly connected to an outlet of the pump and motor assembly, and an orifice is arranged along the second hydraulic circuit and fluidly connected to the unloader valve to reduce back pressure in the second hydraulic circuit.

Abstract: A hydraulic system for a working machine includes a hydraulic pump to output a hydraulic fluid, an operation device operable to supply a pilot fluid in accordance with an amount by which the operation device is operated, a hydraulic actuator to be operated by the hydraulic fluid, a pilot fluid passage connected to the operation device, a first control valve connected to the pilot fluid passage and to be operated by the pilot fluid to control a flow of the hydraulic fluid, a second control valve to be operated by the pilot fluid to control a flow of the hydraulic fluid, a proportional valve to change a pressure of the pilot fluid to operate the second control valve, a pressure detector provided in the pilot fluid passage to detect a pressure in the pilot fluid passage, and a controller to control the proportional valve based on the pressure.

Abstract: A movement processing unit is configured to generate operation signals of a work equipment and a swing body for moving a bucket to a loading point based on a start command of an automatic movement of the bucket. A stop processing unit is configured to brake a swing of the swing body based on a stop command of the automatic movement of the bucket, and is further configured to generate an operation signal for retreating the work equipment when a height of the bucket is lower than the loading point.

Abstract: A shovel includes a hydraulic actuator, an operating apparatus used to operate the hydraulic actuator, an obtaining device configured to obtain information concerning the vibration of the body of a shovel, and a hardware processor. The hardware processor is configured to perform such control as to reduce the responsiveness of the hydraulic actuator to the operation of the operating apparatus when the body of the shovel is vibrating or the vibration is likely to occur in the body of the shovel, based on the output of the obtaining device.

Abstract: A control system for controlling an implement that is movable between a work mode and a transport mode. The control system includes a source of hydraulic fluid, a first actuator and a second actuator. The first and second actuators are fluidly coupled to the source and disposed parallel to one another. A sensor detects movement of the first and second actuators between their retracted and fully extended positions, and a control valve is disposed in communication with the sensor and in fluid communication with the first and second actuators. As the implement moves to its transport mode, the sensor detects movement of the first and second actuators towards their fully extended positions. The control valve inhibits movement of the first and second actuators before either actuator reaches its fully extended position.

Abstract: When a machine-control ON/OFF switch is switched to the ON position, a controller outputs either a first control signal generated by an operation lever or a second control signal that operates a boom cylinder in accordance with a predetermined condition; when the ON/OFF switch is switched to the OFF position, the controller outputs the first control signal; when a control signal has been switched from one of the first control signal and the second control signal to the other control signal by the operation of the ON/OFF switch, the controller applies a rate limit to the control signal, and controls the boom cylinder on the basis of the control signal obtained after the limitation.

Abstract: A hydraulic valve control unit is for an open center hydraulic system including a pump, a shunt valve and one or more actuator valves coupled to the shunt valve. Each actuator valve controls a corresponding actuator's position. The hydraulic valve control unit has a processor and a memory, containing instructions executable by the processor, and is configured to obtain user input data indicative of a desired actuator's position, determining opening area values of the one or more actuator valves using a predetermined relation dependent on the user input data, determining an opening area value of the shunt valve using the predetermined relation dependent on the user input data, controlling the shunt valve based on the opening area value of the shunt valve, and controlling the one or more actuator valves based on the opening area values of the one or more actuator valves.

Abstract: Provided is a construction machine capable of driving each hydraulic actuator at a suitable speed while suppressing delivery flow rate of a hydraulic pump, both at a single operation time of driving each hydraulic actuator respectively singularly and at a combined operation time of simultaneously driving a plurality of hydraulic actuators.

Abstract: A system for controlling hydraulic fluid flow within a work vehicle includes a flow control valve fluidly coupled to a fluid supply conduit upstream of a hydraulic actuator such that the flow control valve is configured to control the flow rate of hydraulic fluid to the hydraulic actuator. Furthermore, the system includes a computing system configured to receive an input associated with a selected flow rate of the hydraulic fluid being supplied to the hydraulic actuator. Moreover, the computing system is configured to control an operation of the flow control valve such that flow control valve is at a maximum flow position at which an adjustable orifice defined by the valve has a maximum cross-sectional area. Additionally, the computing system is configured to control an operation of a pump such that the pump supplies the hydraulic fluid to the hydraulic actuator through the adjustable orifice at the selected flow rate.

Abstract: A slewing hydraulic work machine includes a slewing control device performing a slewing control in accordance with an applied slewing command operation, a boom control device performing a boom-raising control in accordance with an applied boom-raising command operation, a boom angle detector, and a capacity control section. The capacity control section calculates a command motor capacity based on a boom angle, generates a capacity command signal corresponding to the command motor capacity and inputs the signal to a slewing motor. During the performance of slewing and boom-raising operation, the capacity control section sets the command motor capacity to a value equal to or less than a base capacity when the boom angle is equal to or less than a slewing priority angle and sets the command motor capacity to a value greater than the base capacity when the boom angle is greater than the slewing priority angle.

Abstract: A shovel includes a lower traveling body, an upper turning body turnably mounted on the lower traveling body, a hydraulic pump mounted on the upper turning body, a hydraulic actuator configured to be driven with hydraulic oil discharged by the hydraulic pump, a bleed valve configured to control the flow rate of a portion of the hydraulic oil discharged by the hydraulic pump, the portion flowing to a hydraulic oil tank without going through the hydraulic actuator, and a control device configured to control the opening area of the bleed valve in accordance with the magnitude of pulsation in the pressure of hydraulic oil supplied from the hydraulic pump to the hydraulic actuator.

Abstract: A hydraulic system includes: an operation device that outputs an operation signal corresponding to an operating amount of an operating unit; a pump that supplies hydraulic oil to a hydraulic actuator via a control valve; a bleed valve that defines a bleed flow rate, at which the hydraulic oil is released to a tank; and a controller that controls the bleed valve, so an opening area of the valve decreases in accordance with increase in the operation signal. The controller: when a rapid acceleration operation is not performed on the device, changes the opening area of the valve between a maximum value and zero along a normal opening line; and when the rapid acceleration operation is performed, changes the opening area of the valve between the maximum value and minimum value greater than zero along a special opening line from when the operation is started until a predetermined time elapses.

Abstract: Methods of controlling an actuator during operation using a hydraulic circuit, and related apparatus, are described. The circuit has a first path section along which fluid is supplied to a first chamber of the actuator using a first valve and a second path section along which fluid is extracted from a second chamber of the actuator using a second valve. Pressure data associated with a pressure of the fluid supplied to the first side of the actuator are obtained, a pilot pressure pPilot is produced based on the data and the first and second valves are configured based on the pilot pressure pPilot.

Abstract: A balanced panel punch drive system. The system includes a main hydraulic drive including an outer casing forming an internal housing and a main piston slidably disposed within the internal housing. A main fluid chamber, a first output chamber and a second output chamber are formed within the internal housing. A pump is fluidly connected to the main fluid chamber by an input line. A first die hydraulic cylinder and a second die hydraulic cylinder each have an outer casing forming an internal housing and a die piston slidably disposed within the internal housing. An opening is formed through an end of the outer casing sized to receive a distal end of the die piston therethrough. A first output line fluidly connects the first output chamber to the first die hydraulic cylinder and a second output line fluidly connects the second output chamber to the second die hydraulic cylinder.

Abstract: A work machine has a controller which has an area limiting control section correcting the pilot pressures of pilot lines, a regeneration control section adjusting the flow rate of the hydraulic fluid caused to flow from a tank side line of an arm cylinder into a pump side line thereof between zero and a predetermined upper limit value, and a regeneration control switching section that issues an order to the regeneration control section to set the predetermined upper limit value to a first set value when the function of the area limiting control section is invalid and that issues an order to the regeneration control section to set the predetermined upper limit value to a second set value that is smaller than the first set value when the function of the area limiting control section is effective.

Abstract: A control system for construction machinery includes a main control valve installed in a hydraulic line between a hydraulic pump and actuators, and including a first group of electro proportional pressure reducing valves outputting a secondary pressure in proportion to an external pressure command signal to a first spool for controlling a first group of actuators of the actuators, and a second group of electro proportional pressure reducing valves outputting a secondary pressure in proportion to an external pressure command signal to a second spool for controlling a second group of actuators of the actuators, a first pressure sensor configured to detect the secondary pressure outputted from the first group of electro proportional pressure reducing valves and a second pressure sensor configured to detect the secondary pressure outputted from the second group of electro proportional pressure reducing valves, and a controller configured to output pressure command signals to the electro proportional pressure redu

Abstract: Apparatuses, systems and methods are provided for controlling one or more fluid actuated devices; e.g., actuators such as hydraulic cylinders. A method is provided, for example, involving actuation fluid, a first actuator and a second actuator. During this method, a quantity of the actuation fluid within the second actuator is pressurized using a quantity of the actuation fluid within the first actuator.

Abstract: A work machine pump control system includes: a pump horsepower control valve (22) which causes a first urging force determining a limited horsepower (F) of a hydraulic pump and a second urging force due to a delivery pressure of the hydraulic pump to act on a spool in opposition to each other and which controls the pump flow rate such that it does not exceed the limited horsepower (F); a target pump flow rate computation section (42) computing a target pump flow rate based on an operation pressure (px) and a load pressure (py); a target horsepower computation section (41) which computes a required horsepower (Freq) corresponding to an operation pressure (px) from a relationship related to the operation pressure (px) and which computes a target horsepower (Ftar) based on the required horsepower (Freq); and a pump horsepower control section (35) which controls the pump horsepower control valve (22) such that the target pump flow rate (Qtar) is delivered with the limited horsepower (F) determined by the pump hor

Abstract: A method for controlling a valve spool that includes providing a control valve having a first end and a second end with a spool disposed therebetween, a hydraulic component, a controller, a first control circuit and a second control circuit, selectively controlling the pressure in the first end and the second end with the controller, identifying an active state, with the controller, and applying an active pressure to both the first end and the second end with the corresponding first control circuit and second control circuit during the active state, and identifying a first command, with the controller, and providing a command pressure to the first end through the first control circuit and a release pressure to the second end through the second control circuit during the first command. Wherein, the spool is moved within the control valve and the hydraulic component is engaged during the first command.

Abstract: A work vehicle detects pressure of hydraulic oil supplied to an arm cylinder. The work vehicle determines operation details for an arm. The work vehicle includes a relief valve capable of setting a relief pressure of hydraulic oil in a hydraulic circuit at one of a first set pressure and a second set pressure that is greater than the first set pressure. The work vehicle sets the relief pressure of the relief valve at the first set pressure, on the conditions that the detected pressure is equal to or greater than a predetermined value, and that it is determined that the operation details indicate an excavation operation. The work vehicle sets the relief pressure of the relief valve at the second set pressure when the conditions are not satisfied.

Abstract: A straight traveling apparatus for a construction machine and a control method thereof are provided which can allow a curved travel when the working device is operated during the curved travel.

Abstract: In a hydraulic driving system for construction machines, when track motors 3f and 3g are operated and the delivery pressure of a main pump 2 increases to a second value PS2 of the set pressure of a main relief valve 14, the set pressure of a signal pressure relief valve 16 increases from a third value PA1 to a fourth value PA2, which is smaller than the second value PS2 of the set pressure of the main relief valve 14, the difference between the second value PS2 and the fourth value PA2 being smaller than the target LS differential pressure. With such a structure, even if one of actuators reaches the stroke end and the delivery pressure of the hydraulic pump rises to the set pressure of the main relief valve, the other actuators do not stop, and further when the main relief valve is configured to increase the set pressure during operation of a specific actuator, the load pressure of the specific actuator does not increase to the increased set pressure of the main relief valve.

Abstract: The hydraulic fluid energy recovery apparatus includes a fluid communication line for holding a bottom-side hydraulic fluid chamber and a rod-side hydraulic fluid chamber of a hydraulic cylinder in fluid communication with each other, a fluid communication valve connected to the fluid communication line for adjusting the pressure and/or flow rate of a hydraulic fluid passing through the fluid communication line in a manner that allows for adjustment of a degree of opening of the fluid communication valve, first pressure detecting means for detecting a signal indicative of pressure at the bottom-side hydraulic fluid chamber of the hydraulic cylinder, an amount-of-operation detecting means for detecting an amount of operation of the operating means, and a control device for capturing the signal of pressure at the bottom-side hydraulic fluid chamber of the hydraulic cylinder detected by the first pressure detecting means.

Abstract: A hydraulic apparatus based on a confluence control mode includes a load sensing unit provided with first and second reversing valves, and a throttle governing unit provided with a fourth reversing valve. A confluence valve and a one-way valve, which communicate with the load sensing unit and the throttle governing unit, are arranged on a parallel oil path arranged in parallel with the fourth reversing valve. The confluence valve includes a confluence channel that controls opening and closing of the parallel oil path to shunt fluid of the throttle governing unit to the load sensing unit. A first pilot pressure acting on the first reversing valve and a second pilot pressure acting on the second reversing valve act on the confluence valve independently or simultaneously to change a position of the confluence channel, thus implementing reversing of the confluence valve.

Abstract: Systems and methods for use with a variable pressure actuator control system for a gas turbine engine are provided. A variable pressure actuator control system for a gas turbine engine may comprise a controller, a pressure regulating electro-hydraulic servo valve assembly (P-EHSV), including a variable restriction flow path, in electronic communication with the controller, a position regulating electro-hydraulic servo valve assembly (X-EHSV), including a network of flow paths, in electronic communication with the controller, a bypass regulator (BPR) in fluid communication with at least one of a pump, the P-EHSV, or the X-EHSV, the BPR configured to be controlled by the P-EHSV via a bypass pressure to vary an available pressure, and an actuator comprising an actuator piston. The variable pressure actuator control system may minimize pressure when possible to increase mission capability for a gas turbine engine.

Abstract: A hydraulic control device that reduces the loss of the power of a pump in combined operation of boom lowering and arm pushing. A controller performs single control of increasing capacity of a first pump in accordance with increase in an operation amount of a boom operation member, in a single operation of the boom lowering. On the other hand, the controller restricts the capacity of the first pump compared to capacity in the single control, during a restriction control period when the combined operation of boom lowering and arm pushing is detected, and the operation amount of the boom operation member is a prescribed operation amount or more.

Abstract: An electrical pressure control load sense system having a pump connected inline to an operator control spool valve and a compensation circuit. The system also has a plurality of sensors, at least one pressure transducer, a micro-processor, a fixed orifice, a proportional pressure relief valve, and a swashplate angle sensor.

Abstract: A hydraulic circuit for a construction machine including a center bypass passage including a group of directional control valves arranged in tandem; and a bleed-off valve arranged in the center bypass passage on a downstream side of the group, wherein each directional control valve includes a first internal passage causing the pressurized oil supplied to the directional control valve to flow out to the center bypass passage and a second internal passage supplying the pressurized oil to a cylinder port, wherein a parallel passage is formed by the center bypass passage and the first internal passage by causing the pressurized oil discharged from the hydraulic pump to flow to the center bypass passage on the downstream of the directional control valve, wherein the second internal passage supplies the pressurized oil from the center bypass passage through an opening of a spool and/or the bypass passage to the cylinder port.

Abstract: A pressure control valve for a construction machine is disclosed, which prevents self-weight descent of a working device due to leakage of hydraulic fluid in a neutral position of the working device.

Abstract: The present disclosure relates to a hydraulic pressure control device for a swing motor for construction machinery, and more particularly, to a hydraulic pressure control device for a swing motor for construction machinery, which supplements working fluid in the swing motor when a turning operation of an upper body of construction machinery is performed and then stopped. The hydraulic pressure control device for the swing motor for construction machinery according to the present disclosure including the aforementioned configuration may rapidly secure the amount of makeup fluid required by the swing motor when the swing motor is stopped by directly receiving the working fluid discharged from the hydraulic pump P, thereby improving durability of equipment and preventing a cavitation phenomenon.

Abstract: A work machine includes a swing hydraulic motor and a swing electric motor for driving an upper swing structure. A capacitor supplies electricity to the swing electric motor and an operating device outputs through one operation, an operating signal for concurrently operating the swing hydraulic motor and the swing electric motor. A main controller switches between a hydraulic-alone drive mode and an electric-alone drive mode, the hydraulic-alone drive mode being a mode to drive only the swing hydraulic motor selected from the swing hydraulic motor and the swing electric motor when the operating device is operated, the electric-alone drive mode being a mode to drive only the swing electric motor selected from the swing hydraulic motor and the swing electric motor when the operating is operated. Therefore, the actuator that malfunctions can easily be specified among the plurality of mounted actuators.

Abstract: To provide a work machine that can suppress a steep fluctuation in engine power.

Abstract: The present invention controls a proportional control valve controlling the maximum flow of the flow pump to perform controlling the maximum flow of the hydraulic oil pump after checking whether the pump joint control is normal, receiving a flow value of the flow pump controlled by the proportional control valve, checking an error when the flow value received during a control of the maximum flow has an error, and assigning a weight value to the checked error to compensate for the flow value. Therefore, the present invention may decrease a number of an engine revolution speed and lower a driving fuel consumption and reduce a driving noise.

Abstract: The invention relates to a hydraulic apparatus comprising a hydraulic pump (30) which is connectable to a hydraulic fluid tank, an electric motor (2) as a drive means for the hydraulic pump (30), which electric motor comprises a motor shaft and a motor housing cover (4), and a control valve assembly (12) connected to the pump (30) to control at least one hydraulic consumer which is connectable to the pump (30) and is to be supplied by the pump (30) with hydraulic fluid from the hydraulic fluid tank, wherein the pump (30) is fixed on the motor housing cover (4) and the motor housing cover (4) comprises a holding adapter (10) on which the control valve assembly (12) is fixed.

Abstract: A hydraulic actuation system includes a differential unit having a hydraulically-actuated differential, a power steering unit, a hydraulic pump, a reservoir, a controller, an electronically-controlled flow control manifold, and a proportional pressure control solenoid valve. A flow control manifold may control fluid flow to the power steering unit and the differential. The manifold may include a manifold inlet connected to a pump; first manifold outlet connected to a differential; second manifold outlet connected to a reservoir; third manifold outlet connected to a power steering unit; two-way solenoid valve connected to a manifold inlet and controlled by a controller; flow control valve connected to a two-way solenoid valve and a first manifold outlet; and a pressure differential sensing valve connected to a two-way solenoid valve, the manifold inlet, and the third manifold outlet. A proportional pressure control solenoid valve may connect the first manifold outlet and the differential.

Abstract: Electronic control systems and related control methods for controlling electric drive motors for propelling a vehicle and electric auxiliary motors for performing work. The apparatus is shown in use with a vehicle that includes a mowing deck. Features of the control systems allow for safe and efficient use of the vehicle. These features include a power take-off timeout, automatic fail-safe brake (parking), and customized drive characteristics.

Abstract: A control system for hybrid construction machine includes an engine, a main pump to be driven by the engine, a rotary shaft linking an assist pump, a regenerative hydraulic motor and a motor generator, and a clutch for linking the engine and the rotary shaft.

Abstract: A hydraulic system for an access arrangement having a platform configured for movement between a deployed position and a stowed position, the hydraulic system including: at least one hydraulic power unit configured to urge hydraulic fluid through a hydraulic circuit; at least one hydraulic cylinder directly or indirectly connected to a portion of the platform and configured to urge the platform towards at least one of the stowed position and the deployed position, wherein the at least one hydraulic cylinder is in fluid communication with the hydraulic power unit; and a pressure regulating valve in a path between the at least one hydraulic power unit and the at least one hydraulic cylinder, wherein the pressure regulating valve is operable to prevent the at least one hydraulic cylinder from urging the platform to the stowed position if a load on the platform exceeds a specified threshold.

Abstract: In the working machine, first and second pilot flow paths are directly or indirectly connected to a tank flow path (52). A first restrictor is disposed between the first pilot flow path and the tank flow path. A second restrictor is disposed between the second pilot flow path and the tank flow path. An actuator control unit is configured to control an actuator based on a hydraulic pressure detected by a first hydraulic pressure detector unit and that detected by a second hydraulic pressure detector unit sensor.

Abstract: There is provided a driving device for a work machine, having a closed hydraulic circuit system for driving cylinders with hydraulic pumps, the driving device making the speed of operation substantially the same in both directions of piston rod extension and contraction.

Abstract: A hydraulic control system includes a first oil passage, a first oil pump, a second oil passage, a second oil pump and a check valve. The first oil pump is disposed in the first oil passage. The second oil passage bypasses the first oil pump, includes an intake oil passage and a discharge oil passage, the intake oil passage and the first oil passage are connected to each other at a connection point, and the discharge oil passage includes an air vent hole. The second oil pump is disposed in the second oil passage, configured to take in oil from the intake passage, and configured to discharge the oil into the discharge oil passage. The check valve is provided between the connection point and the air vent hole, configured to restrict flow of the oil from the air vent hole toward the connection point via the second oil pump.