Abstract: A hydraulic controlling device in which, when performing a combined operational process, a position of a straight travel valve is switched to a straight travel position to drive both a travel motor and a working actuator by separate pumps. In this case, to prevent a sudden reduction in travel speed resulting from a reduction in a flow amount at a travel side, pump lines of both pumps are connected to each other at an intermediate position by a connection path, so that a portion of oil at a working side is sent towards the travel side. With such a structure, when a rotational speed of an engine is less than a set rotational speed, an opening amount of the connection path is reduced through a straight travel proportional valve by a controller, thereby preventing pressure interference causing, for example, the working actuator to no longer move.

Abstract: A hydraulic circuit for heavy construction equipment to reduce a speed of a swing apparatus while a working apparatus such as a boom is concurrently operated has a work control valve which controls a working apparatus cylinder; a confluence valve which combines a hydraulic fluid of the second hydraulic pump with the work unit flow path based on a positions switch; a swing control valve which controls the hydraulic swing motor; and a disconnection valve which disconnects the hydraulic fluid supplied to at least one of the swing motors.

Abstract: The invention relates to a hydraulic control system for building machinery, particularly for controlling hydraulic consumers of an excavator. According to the invention, pump channels which ensure that the hydraulic consumers are supplied in parallel by means of a spool valve of the main control unit of the piece of building machinery are provided in addition to previously existing pump channels that ensure said hydraulic consumers are serially supplied with hydraulic fluid. The additional pump channels are arranged parallel to the previously existing ones.

Abstract: An arrangement for delivering hydraulic fluid to at least one hydraulic actuator of a work vehicle for moving a work implement and/or steering the vehicle includes at least two pumps which are adapted to be operatively driven by a power source and adapted to operatively drive said at least one hydraulic actuator via hydraulic fluid. A first pump is operated with a phase shift relative to a second pump.

Abstract: The invention relates to a hydraulic group comprising a reservoir (28) for oil, in which a multiple piston pump (60) is arranged. The individual pumps (61) are cyclically driven by an eccentric ring (29). In order to ensure a permanent immersion of the individual pumps in the reservoir (28), an auxiliary reservoir (47) providing oil for refilling the reservoir (28) is arranged above the reservoir. The auxiliary reservoir (47) is connected to an additional tank (45) by means of a connection line (48).

Abstract: A traveling device for crawler type heavy equipment is provided, which can improve the manipulability by preventing an abrupt decrease/increase of a traveling speed of the equipment when a combined operation, in which a left/right traveling device and a working device are simultaneously driven, is performed.

Abstract: A hydraulic circuit for construction equipment is disclosed, which can prevent an abrupt rotation of a swing device when a switching valve for the swing device is shifted in a state that switching valves for a traveling device and a working device have been shifted.

Abstract: A hydraulic circuit is provided, which can prevent the bucket from being separated from the bucket rest by preventing a change of stroke of a boom cylinder or an arm cylinder during long traveling of wheel type heavy equipment, and can secure safety since it is not required for an operator to adjust the position of a working device like boom and arm. The hydraulic circuit includes first and second hydraulic pumps, a boom cylinder, an arm cylinder, a boom confluence logic valve, a first port formed to connect with a large chamber of the boom cylinder in a housing in which a spool for the boom cylinder is shiftably installed, a second port formed to connect with a hydraulic tank in the housing, and a first orifice formed between the housing and a land part of the spool for the boom cylinder located between the first port and the second port.

Abstract: A machine having a hydraulic power management system. The machine includes an internal combustion engine driving first and second fixed displacement pumps to produce a combined flow of pressurized fluid. Main and auxiliary implements are operable in response to a flow of pressurized fluid, and a control valve selectively directs the combined flow to the main and auxiliary implements. A power management system is operable to stop the flow of pressurized fluid to the main implement from the second pump when the pressure of the combined flow exceeds a pressure indicative of the impending engine stall. A means for providing the combined flow to the auxiliary implement without regard to the pressure of the combined flow is also provided, and may take the form of a power management override or bypass mechanism.

Abstract: The hydraulic system for a work vehicle includes a main hydraulic pump, a main supply circuit through which pressurized oil from the main hydraulic pump flows, a sub hydraulic pump, and a sub supply circuit through which pressurized oil from the sub hydraulic pump flows. The main supply circuit supplies pressurized oil to a hydraulic travel motor that drives a travel device and a service actuator that is disposed in an attachment with which the work vehicle is detachably furnished. The sub supply circuit merges with the main supply circuit and supplies pressurized oil to the service actuator. The hydraulic system for a work vehicle further includes a flow amount adjustment valve that adjusts the flow amount of the pressurized oil from the sub supply circuit that merges with the main supply circuit.

Abstract: A hydraulic system that provides hydraulic fluid to a power steering system of a vehicle at a substantially constant flow rate and can also divert excess hydraulic fluid to the air cooling fan of an associated vehicle at low engine speeds is disclosed. The resulting hydraulic system increases fan speed and increases cooling at low engine speeds while also limiting the input horsepower to one or more driving pumps based at least in part on the outlet pressure of the hydraulic pump unit.

Abstract: A hydraulic control device of an excavator is provided for controlling combined operation of boom-raising and swing on a slope. A swing priority valve (20) is provided on a pressured fluid supply line (8) that connects a first hydraulic pump (1) to a boom high-speed control valve (7). If an excavator performs its tasks on a slope, the swing priority valve (20) is automatically shifted under a control of an electronic controller (28) into a throttling position to thereby restrict hydraulic flow through the boom high-speed control valve (7) so that an increased amount of hydraulic flow can be supplied to a swing motor (14), thus increasing a swing operating pressure more rapidly than a boom operating pressure and consequently facilitating combined operation of boom-raising and swing on a slope.

Abstract: To provide a hydraulic circuit with a compact and simple structure while securing the amount of a hydraulic oil necessary for right and left running motors so as to prevent the limitation of a running speed. A first system has a changing valve for a right side running motor and a changing valve for a first actuator, and a second system has a changing valve for a left side running motor and a changing valve for a second actuator. The changing valves for the right side and the left side running motors and the changing valves for the first and second actuators are tandem-connected, respectively.

Abstract: A straight traveling hydraulic circuit is disclosed, which, in the case of performing a combined operation in which working and traveling devices are simultaneously driven, can prevent a declination of equipment due to an overload of the working devices. The straight traveling hydraulic circuit includes first and second variable hydraulic pumps, a left traveling motor and a first working device connected to the first hydraulic pump, switching valves installed in a flow path of the first hydraulic pump, a right traveling motor and a second working device connected to the second hydraulic pump, switching valves installed in a flow path of the second hydraulic pump, a straight traveling valve installed in the flow path of the second hydraulic pump, and a control valve installed in a branch flow path branched from the flow path of the second hydraulic pump.

Abstract: A work vehicle includes a traveling vehicle, a backhoe having a base frame detachably connected to a rear portion of the traveling vehicle and an excavator detachably attached to a rear portion of the base frame. The base frame includes a pair of upper and lower base plates and a partitioning wall disposed at a fore-and-aft intermediate portion of the base plates for connecting the two base plates with each other and partitioning a space delimited between the plates relative to a fore and aft direction. A control box is mounted on the base frame. At least one swing cylinder is mounted to the base frame through the partitioning wall for pivoting the excavator. A control valve unit is attached to the partitioning wall downwardly of the control box for controlling a working fluid for driving the swing cylinder and the excavator. At least one swing hose is extended through the partitioning wall for hydraulically connecting the control valve unit to the swing cylinder.

Abstract: The present disclosure is directed to a hydraulic system. The system includes a first source of pressurized fluid and at least one fluid actuator. The system also includes a first valve disposed between the first source and the at least one fluid actuator being configured to selectively communicate pressurized fluid from the first source to a source of low pressure. The system further includes a controller configured to determine a first amount of displacement of the first valve, determine a second amount of displacement of the first valve, and modify the first amount of displacement as a function of the second amount of displacement when a first pressure is less than or equal to a pressure of pressurized fluid acting on the at least one fluid actuator.

Abstract: A hydraulic system including a first pump, a second pump, an auxiliary passage, and a supplemental apparatus. The first pump is in fluid communication with a first valve, and the second pump is in fluid communication with a second valve. The auxiliary passage is in fluid communication with the first valve and the second valve. The supplemental apparatus is in fluid communication, by way of a supplemental passage, with the second valve and the auxiliary passage.

Abstract: An apparatus for increasing an operation speed of a boom on excavators is disclosed, which enables an unskilled operator to conveniently manipulate a working device by decreasing a rotation speed and increasing a lifting speed relatively when the excavator performs combined operation of boom lift and swing drive to improve its working efficiency. The apparatus includes first and second hydraulic pumps, a first actuator, a pair of second actuators, first to third control valves, a block valve installed in a flow path between the selected second actuator and the second control valve, supplying the hydraulic fluid from a second hydraulic pump to the selected actuator only when the second actuators are driven to be switched according to a control signal of boom lift at combined operation in which the first and second actuators are simultaneously driven, to replenish the first actuator with the hydraulic fluid to be supplied to the second actuator.

Abstract: A hydraulic controlling device in which, when performing a combined operational process, a position of a straight travel valve is switched to a straight travel position to drive both a travel motor and a working actuator by separate pumps. In this case, to prevent a sudden reduction in travel speed resulting from a reduction in a flow amount at a travel side, pump lines of both pumps are connected to each other at an intermediate position by a connection path, so that a portion of oil at a working side is sent towards the travel side. With such a structure, when a rotational speed of an engine is less than a set rotational speed, an opening amount of the connection path is reduced through a straight travel proportional valve by a controller, thereby preventing pressure interference causing, for example, the working actuator to no longer move.

Abstract: A hydraulic control system for a hydraulic excavator of the present invention comprises a boom control valve in a first oil path for providing pressure oil from a first hydraulic pump with a boom cylinder according to operation of a boom operating means, an arm control valve in a second oil path for providing pressure oil from a second hydraulic pump with an arm cylinder according to operation of an arm operating means, a confluence switching valve having a confluence position for joining the paths and a confluence stop position for stopping the confluence, a flow control valve for returning pressure oil in the first oil path to a tank, and a control means for controlling the valves, so as to switch the confluence switching valve to the confluence position and close the flow control valve when the arm operating means is operated independently and so as to switch the confluence switching valve to the confluence stop position and open the flow control valve when both of the operating means are operated simultan

Abstract: An improvement to the Nelson Flywheel Power Plant comprising a piston (100 and 101) in each outer chamber (40 and 41) situated at the interface of the compressible fluid and incompressible fluid (120) and slidably adjoining the center shaft (14) and rotatable housing (10). A method of using the improvement comprising the steps of introducing a compressed fluid along a path (110) that acts on one of the pistons (100) to move the incompressible fluid along a path (120); then moving the spool (15) to permit return of the incompressible fluid; and then introducing a compressed fluid to act on the other piston (101) to return the incompressible fluid.

Abstract: A joining directional control valve 13 is disposed to supply, to an arm cylinder 4, not only a hydraulic fluid delivered from a first hydraulic pump 1, but also a hydraulic fluid delivered from a second hydraulic pump 2 when an arm directional control valve 14 is driven. Respective delivery pressures of the hydraulic pumps 1, 2 are detected by pressure sensors 101, 102, and the opening area of a recovery control valve 6 is controlled depending on a lower one of the detected pressures from the pressure sensors 101, 102 such that, even in the combined operation of the arm cylinder 4 and another actuator 3, 4, the hydraulic fluid can be recovered for return to the arm cylinder 4 when the load pressure of the arm cylinder 4 is low. Thus, by supplying the hydraulic fluids from the two hydraulic pumps to the particular actuator for which the hydraulic fluid is to be recovered, a recovery flow rate is ensured when the load of the particular actuator is low in the combined operation.

Abstract: A hydraulic system for a vehicle has a hydraulic, load carrying assembly which has a movable structural element and a hydraulic device for actuating the structural element. The hydraulic system has a primary circuit having a servo device, a stationary hydraulic pump, a directional valve, and the hydraulic device, which are arranged in order to operate the assembly. The hydraulic system has a supplementary circuit, being connected to the primary circuit and including a variable hydraulic pump which is arranged in order to supply an adjustable addition of hydraulic oil to the hydraulic device, and a proportional valve being arranged between the variable hydraulic pump and the hydraulic device in order to regulate the flow of hydraulic oil to the hydraulic device as a function of a received flow signal.

Abstract: A hydraulic control apparatus which is used in order to prevent the blade from falling over on the pitch back side during a dual tilting operation, and to operate the left and right tilting cylinders in a uniform manner even in case where there is a large difference in the load pressure between the left and right tilting cylinders. In cases where it is desired to perform a dual tilting operation, the operator moves the operating lever either leftward or rightward while pressing the dual tilting switch of the operating lever. As a result of the switch being pressed, an electrical control signal that places the flow-combining/flow-dividing switching valve or flow-combining/flow-dividing valve in the flow-dividing position is generated by the controller, and the electrical control signal is output to the flow-combining/flow-dividing switching valve so that the flow-combining/flow-dividing switching valve or flow-combining/flow-dividing valve is switched to the flow-dividing position.

Abstract: Hydraulic flow to tractor attachments such as a sweeper, snow thrower, breaker, auger or cold planer may be increased by diverting pressurized hydraulic fluid from the auxiliary pump. A diverter valve between the auxiliary pump and the auxiliary circuit of the loader hydraulic system may direct flow to either the backhoe hydraulic system, the rockshaft hydraulic system, or the auxiliary circuit of the loader hydraulic system. The additional flow from the auxiliary pump is provided at a mid-inlet position and is not available to the loader boom or bucket circuits, to preserve tractive horsepower needed during loader work.

Abstract: The present invention provides a hydraulic circuit for a crane wherein a switching valve is provided between a plurality of motor circuits connected in series within the same actuator group, and at the time of simultaneous operation of the motor circuits, the switching valve is switched from a first position to a second position whereby the series connection between the motor circuits is cut off, and they are driven by each of separate hydraulic sources, thereby enabling prevention of pressure interference at the time of simultaneous operation of the motor circuits within the same actuator group without increasing hydraulic sources.

Abstract: Hydraulic oil supplied from pumps (12),(13) to an attachment actuator (60) is controlled by attachment control valves (27),(28). Hydraulic oil supplied from pumps (12),(13) to other actuators (52),(54),(56),(58) is controlled by other control valves (21) through (26). Control conditions for operating the attachment actuator (60) alone and control conditions for operating the attachment actuator (60) simultaneously with any of the other actuators (52),(54),(56),(58) are discriminated by the pilot pressure sensors (32),(34),(36),(38). Control characteristics of the attachment control valves (27),(28) are controlled by a controller (43) based on the discriminated control conditions.

Abstract: A hydraulic system includes at least two consumers, e.g., a closing unit and an injection unit of an injection molding machine. At least two displacement pumps are provided to produce a fluid flow under pressure to the consumers, whereby at least one control valve is provided for each of the consumers. At least one further valve is provided to control a fluid communication between the output sides of the displacement pumps, wherein at least one of the consumers is supplied with pressure from the outlet of the displacement pumps separately or together in groups.

Abstract: A hydraulic valve is used to judiciously shunt oil from lowering ends of the hoist and stick cylinders that have been plumbed to achieve near horizontal movement. This allows the use of cylinders that have unequal rod/bore ratios or to compensate for certain transient effects that may require the exchange of oil to the reservoir. The action of the hydraulic valve acts without obtrusive operator intervention and is essentially automatic. This allows for greater flexibility in the design of the boom system, allows the boom system to perform various tasks, while not requiring obtrusive intervention from the operator.

Abstract: According to the invention, traveling bypass cut-off valves are disposed in center bypass passages respectively which are located between traveling direction control valves and working direction control valves disposed downstream of the valves, wherein, when at least a traveling motor and any of working actuators are operated simultaneously, the traveling bypass cut-off valves are switched from neutral position to another position. Thereby, when travel and work by working actuators are performed simultaneously, interference between pressure oil fed to traveling motors and pressure oil fed to the working actuators is to be prevented.

Abstract: The two boom members and hydraulic cylinders of a knuckle boom tree harvesting machine are so arranged and proportioned that with a single control movement during reaching and retracting actions the working tool head is made to travel in an approximately horizontal path. The cylinders and control valve are so connected that during horizontal reaching action load-supporting pressurized oil from a collapsing cylinder is not required to be dumped to the reservoir in the conventional heat generating manner, but is rather shunted directly to an extending cylinder where it continues to do useful load support work. Energy waste to hydraulic oil heat and fuel consumption is significantly reduced. Although these advances have been particularly developed for disc saw felling and stroke delimbing of trees they can also be applied to other knuckle boom applications where horizontal reaching is a major function.

Abstract: A hydraulic fluid diverting arrangement for a utility vehicle provides additional pressurized hydraulic fluid supply to an installed backhoe attachment by diverting hydraulic fluid from the unused rockshaft or three-point hitch of the utility vehicle. A solenoid operated valve manifold is switch actuated by contact from the backhoe during installation of the backhoe to the utility vehicle and diverts hydraulic fluid flow from rockshaft hydraulic cylinders to backhoe hydraulic cylinders. The system increases the available horsepower to the backhoe by using hydraulic fluid otherwise dedicated to the idle rockshaft.

Abstract: A hydraulic control arrangement which is provided for the demand-feed-regulated supply of pressure medium to preferably a plurality of hydraulic consumers by proportionally adjustable directional valves. There are hydraulic pumps by which pressure medium can be conveyed in a quantity corresponding to the demand into a common inflow line leading to the directional valves. A first demand-feed regulator is assigned to the first hydraulic pump and a second demand-feed regulator to the second hydraulic pump. The two demand-feed regulators are capable of being acted upon, with the effect of increasing the pressure medium quantity discharged into the inflow line by the corresponding hydraulic pump, by a spring and, on a first active surface, by the pressure in a load-signaling line and, with the effect of reducing the pressure medium quantity discharged into the inflow line by the corresponding hydraulic pump, on a second active surface, by a pump pressure.

Abstract: A hydraulically operated drive system for mini-loaders and like machines is disclosed. The system incorporates hydraulically operated wheels or sprocket/track arrangements as well as auxiliary functional mechanisms. Tandem hydraulic pumps are used, each one thereof being connected to a multiple spool series valve, providing two separated hydraulic circuits, each of which has a separate relief valve. Each multiple spool series valve controls a wheel motor and a loader/lift or like function. Each multiple spool series valve includes a single-acting spool connected to a common spool valve to provide auxiliary power control.

Abstract: Hydraulic oil supplied from pumps (12),(13) to an attachment actuator (60) is controlled by attachment control valves (27),(28). Hydraulic oil supplied from pumps (12),(13) to other actuators (52),(54),(56),(58) is controlled by other control valves (21) through (26). Control conditions for operating the attachment actuator (60) alone and control conditions for operating the attachment actuator (60) simultaneously with any of the other actuators (52),(54),(56),(58) are discriminated by the pilot pressure sensors (32),(34),(36),(38).

Abstract: Provided are hydraulic pumps 1,2, a control valve group 15a connected to the pump 1 and including a bypass on/off valve 7, a control valve group 15b connected to the pump 2 and including a reserve-actuator-controlling, directional control valve 11, a communication line 13 communicating a most upstream side of the control valve group 15a with a supply line 11a to the reserve-actuator-controlling, directional control valve 11, a merge control valve 14 for communicating or cutting off the communication line 13, an interlocked control means for changing over the merge control valve 14 to an open position and the bypass on/off valve 7 to a closed position in association with a change-over operation of the reserve-actuator-controlling, directional control valve 11, and a selective control valve 28 capable of taking one of a state, in which the operation to change over the merge control valve 14 by the interlocked control means is feasible, and another state in which the operation to change over the merge control va

Abstract: A hydraulically operated drive system for mini-loaders and like machines is disclosed. The system incorporates hydraulically operated wheels or sprocket/track arrangements as well as auxiliary functional mechanisms. Tandem hydraulic pumps are used, each one thereof being connected to a multiple spool series valve, providing two separated hydraulic circuits, each of which has a separate relief valve. Each multiple spool series valve controls a wheel motor and a loader/lift or like function. Each multiple spool series valve includes a single-acting spool connected to a common spool valve to provide auxiliary power control.

Abstract: A backhoe hydraulic system includes a first source of hydraulic fluid, a tank or reservoir, a boom lift cylinder, and a directional control valve that controls fluid flow between the boom swing cylinder and the tank and reservoir. The system also includes a second source of hydraulic fluid (at a higher pressure than the first source) that is connected to one port of the boom lift cylinder via a separate boost valve.

Abstract: A backhoe hydraulic system includes a first source of hydraulic fluid, a tank or reservoir, a boom lift cylinder, and a directional control valve that controls fluid flow between the boom swing cylinder and the tank and reservoir. The system also includes a second source of hydraulic fluid (at a higher pressure than the first source) that is connected to one port of the boom lift cylinder via a separate boost valve.

Abstract: The invention describes a control unit for at least two tools (2, 3) operated by a pressurized medium (6), in particular hydraulic oil (7), e.g. emergency cutters (4), emergency jacks (7), etc., a delivery circuit (10, 11) for the pressurized medium (6) being provided for each tool (2, 3) and at least one pressure generator (9). At least one control device (15) comprising a control valve (23, 24) is provided in each of the delivery circuits (10, 11) for the tools (2, 3) and the control valves (23, 24) are placed in a flow connection via at least one connecting passage (25) or a connecting line as required.

Abstract: A hydraulic circuit comprises a first and a second merging line capable of supplying pressure oil from a third pump for a third circuit to directional control valves in a first and a second circuit, respectively, and a merging valve for selectively communicating or cutting off the first and the second merging line with or from the third pump. The merging valve has a first shift position at which the third pump is connected to the second merging line, and a second shift position at which the third pump is connected to the first and the second merging line. The merging valve is shifted continuously between the shift positions. The hydraulic circuit can efficiently distribute pressure oil supplied from the third pump to the first and/or second circuit as well, and can prevent lowering of the operability of each of actuators connected to the first or second circuit.

Abstract: A hydraulic system includes at least two consumers, e.g., a closing unit and an injection unit of an injection molding machine. At least two displacement pumps are provided to produce a fluid flow under pressure to the consumers, whereby at least one control valve is provided for each of the consumers. At least one further valve is provided to control a fluid communication between the output sides of the displacement pumps, wherein at least one of the consumers is supplied with pressure from the outlet of the displacement pumps separately or together in groups.

Abstract: The two boom members and hydraulic cylinders of a knuckle boom tree harvesting machine are so arranged and proportioned that with a single control movement during reaching and retracting actions the working tool head is made to travel in an approximately horizontal path. The cylinders and control valve are so connected that during horizontal reaching action load-supporting pressurized oil from a collapsing cylinder is not required to be dumped to the reservoir in the conventional heat generating manner, but is rather shunted directly to an extending cylinder where it continues to do useful load support work. Energy waste to hydraulic oil heat and fuel consumption is significantly reduced. Although these advances have been particularly developed for disc saw felling and stroke delimbing of trees they can also be applied to other knuckle boom applications where horizontal reaching is a major function.

Abstract: When simultaneous operation of rotating and arm pulling is detected by a detector, a switching controller recognizes that both signals are output simultaneously, and switches a switching valve to a second position, so that oil flows discharged from a plurality of hydraulic pumps are united and supplied to a rotating motor and an arm cylinder. A meter-in flow controller restricts a quantity of oil supplied to the arm cylinder. Thereby, even where rotating and arm pulling are operated simultaneously, each of operations can be done quickly, and the delay of the rotating operation is overcome, to enable proper rotating and arm pulling operations.

Abstract: A hydraulic circuit includes first and second pumps, a first discharge passage receiving hydraulic fluid discharged from the first pump and communicating with a main gallery, a second discharge passage receiving hydraulic fluid discharged from the second pump and communicating with an actuator, a communication passage ensuring communication between the first and second discharge passages, and a relief valve arranged with the communication passage to be opened at a predetermined pressure for the second discharge passage.

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: An off road machine is provided with a hydraulic system for operating drive motors for propelling the machine, as well as operating actuators for machine functions. The hydraulic system utilizes three pumps, with the pumps connected to a single high pressure relief valve. Additionally, two of the pumps normally are used for driving traction motors for the machine, and when a valve is operated the third pump flow is provided to both of the drive motors for the vehicle to increase the speed of machine movement. Additionally, a dump valve is used for insuring that the flow from the pump will be diverted to tank unless an operator ready signal is present.

Abstract: The present invention provides a hydraulic circuit for a crane wherein a switching valve is provided between a plurality of motor circuits connected in series within the same actuator group, and at the time of simultaneous operation of the motor circuits, the switching valve is switched from a first position to a second position whereby the series connection between the motor circuits is cut off, and they are driven by each of separate hydraulic sources, thereby enabling prevention of pressure interference at the time of simultaneous operation of the motor circuits within the same actuator group without increasing hydraulic sources.

Abstract: A hydraulic control device for a working vehicle capable of enhancing excavating ability even when earth to be excavated is hard is provided.

Abstract: A hydraulic circuit which, when applied to a turning excavator having hydraulic actuators for the working arms and the turning excavator body supplied with pressure oil from three pumps, can increase the operation speed of the booms and arms without providing a separate hydraulic pump to improve the work efficiency. During the individual driving, the boom cylinder (CY1) is supplied with a pressure oil from the first and third pumps (P1, P3), the arm cylinder (CY2) from the second and third pumps (P2, P3), the bucket cylinder (CY3) from the first pump (P1), and the turning motor (M) from the third pump (P3). During the simultaneous driving of the boom and arm cylinders (CY1, CY2), the arm is supplied with an operation speed increasing pressure oil from the third pump (P3). When the boom cylinder (CY1) and the turning motor (M) are simultaneously operated, a part of the pressure oil to the turning motor (M) from the third pump (P3) is supplied to the boom cylinder (CY2).