Abstract: The present invention generally relates to an air control module unit for a portable pneumatic tool, more particularly, to an air control module unit that actuates a valve stem inside an air inlet block of the air inlet module by a correspondent air bleed valve in the air actuation module. The air control module unit for a portable pneumatic tool comprising: an air inlet module, which has at least one valve stem inside an air inlet block, the air inlet block having plug screws on both ends towards the valve stem and one plug screw on the intersectional direction of the valve stem with at least one air inlet port opening for hooking up the compressed air; an air actuation module having a bleed valve inside the valve block; a plurality of flexible air hoses with a plurality of dimensions and being prepared for connecting the air inlet module and air actuation module; and a plurality of hose connectors and rubber seats with a plurality of types for connecting the air inlet module and the air operation module.

Abstract: A hydraulic circuit including a first throttle disposed upstream of pressure-reducing valves of a remote-control valve, which operates a control valve of hydraulic pilot type, so as to reduce primary pressures supplied from a pilot pump to the pressure-reducing valves. Bleed-off lines connect pilot lines to tanks. Second throttles are disposed on the bleed-off lines, respectively, so as to moderate rises in the pilot pressures supplied to pilot ports of the control valve. The hydraulic circuit prevents detrimental effects such as deterioration of operability while ensuring shock absorption during quick operation.

Abstract: Of a plurality of hydraulic signals output from an operating device, a hydraulic signal is input into a control valve serving as a hydraulic control device without conversion, and particular hydraulic signals are converted into electric signals corresponding to their hydraulic pressures by signal converting devices, such as pressure sensors, and are then input into a controller. The controller controls the drive of an electric actuator, such as a rotating electric motor, on the basis of the electric signals. Hydraulic fluid flow paths communicating to the pressure sensors are connected to each other via a throttle, and air in one of the hydraulic fluid flow paths is removed using the other hydraulic fluid flow path.

Abstract: A control unit for a work machine that allows automatically obtaining optimal operability even when the weight of a work arm in the work machine is changed. In a work machine where at least a part of a work arm to be operated by a fluid pressure actuator is provided so as to be replaceable, a control unit for a work machine includes: a pilot-operated control valve that controls the fluid pressure actuator; a proportional solenoid valve that pilot-controls the pilot-operated control valve by a pilot control pressure according to an electrical signal corresponding to a manual operation amount; a measuring means that measures a weight of at least the part of the work arm; and a controller that converts characteristics between the manual operation amount and the pilot control pressure of the proportional solenoid valve to characteristics according to the weight of the work arm measured by the measuring means.

Abstract: There is provided a hydraulic controller for a working machine in which a pilot hydraulic pressure source is connected in common to a plurality of pilot-operated hydraulic devices each having a pilot pressure input unit, and a common pilot pressure input switching valve is adapted to control the switching between a pilot pressure input from the pilot hydraulic pressure source to each pilot pressure input unit and a relief of the input. The switching control of a pilot pressure input by the pilot pressure input switching valve is performed based on the operating state of the working machine and pilot pressure input conditions of the respective pilot-operated hydraulic devices.

Abstract: The invention relates to a pilot valve (3) for a hydraulic motor which is used for lifting loads in a device. Said pilot valve (3) is designed as a directional control valve in which a control slide (20) is movably disposed in a longitudinal bore (22) of the valve body (21) so as to control the flow of hydraulic oil between two working connecting bores (A, B), a pump connecting bore (P), and a reservoir connecting bore (T). A check valve (32) which is biased with the aid of a bias spring (33) is disposed within the control slide (20). Said check valve (32) is connected to an auxiliary control groove (28) via a first transversal bore (29) while being connected to the B-reservoir groove (23) via a second transversal bore (31). The check valve (32) is to be opened from working connecting bore B while the auxiliary control groove (28) is arranged between the B control groove (24) and the B reservoir groove (23) and is delimited on both sides by means of sealing cylindrical areas (35, 36).

Abstract: A hydraulic circuit for a working machine includes hydraulic actuators which respectively drive a plurality of kinds of working devices and which are driven by a drive circuit having circuit states that correspond to the working devices, a directional control valve unit which, when one of the working devices is attached to the attachment, switches in response to a signal from a controller to select one of the circuit states, a detection sensor that detects the actual circuit state, and a display operated by the controller. The controller activates the display when the detected actual circuit state and the selected circuit state do not match.

Abstract: An asymmetric volume booster assembly includes an actuator movable in a first direction and a second direction, a first booster in fluid communication with the actuator, and a second booster in fluid communication with the actuator. The first booster includes a first supply passage and a first exhaust passage, wherein the first supply passage supplies fluid to the actuator and the first exhaust passage exhausts fluid from the actuator. The first exhaust passage is configured to produce a first fluid flow resistance. The second booster includes a second supply passage and a second exhaust passage, wherein the second supply passage supplies fluid to the actuator and the second exhaust passage exhausts fluid from the actuator. The second exhaust passage is configured to produce a second resistance to fluid flow. The first fluid flow resistance is greater than the second fluid flow resistance, such that the actuator moves substantially symmetrically in the first direction and the second direction.

Abstract: The valve arrangement for the activation of a structural element has three inlet switching valves through which a pressure-loaded medium can be conducted. These inlet switching valves are connected on their inflow side to a pressure supply by inflow lines and are arranged parallel to one another in flow terms. Moreover, the valve arrangement has a connection element, which is connected to outflow sides of all the inlet valves by pressure lines. A control line acted upon by the medium is connected to the pressure supply. The three switching-valve groups can be activated by the control line, and in each case two switching valves and in each case one inlet switching valve are assigned to each switching-valve group. A activation valve can be interposed in each case between a switching-valve group and the control line. Three outflow lines for the medium can be arranged between an outflow location for the medium and the connection element.

Abstract: A hydraulic control system for high flow applications in motor vehicles, in particular for active wheel suspensions and active steering arrangements, includes at least one passive high flow valve which is controlled hydraulically by at least one low flow valve.

Abstract: A hydraulic system comprises a plurality of primary hydraulic circuits and a secondary hydraulic circuit for satisfying flow continuity of the primary hydraulic circuits.

Abstract: A work machine includes an attachment movable by an actuator, an operational member for operating the attachment through the actuator; and a controller operable to output an operation signal for operating the actuator in response to an operation of the operational member. The controller allows setting of a change amount in the operation signal corresponding to an operational amount of the operational member, independently for each operational direction of the actuator.

Abstract: A fastener driving tool includes a frame defining therein an accumulator that accumulates compressed air, a cylinder, a piston movable between a top dead center and a bottom dead center, a main valve section having a main valve movable between a top dead center and a bottom dead center to alternately open and block fluid communication between a piston upper chamber and the accumulator, a trigger valve section having a plunger movable between a top dead center and a bottom dead center so as to alternately open and block fluid communication from the accumulator to a main valve chamber, and fluid communication from the main valve chamber to atmosphere, and a trigger adapted to press the plunger when operated by a user. The piston moves from the top dead center to the bottom dead center within 11.3 msec when the plunger is pressed.

Abstract: A fluid power system includes a hydraulic machine. A pilot-controlled supply valve controls high-pressure fluid to the machine. The valve is coupled between the hydraulic machine and a high-pressure fluid source, and includes a control port for an actuation signal. The supply valve allows passage of fluid from the machine to the fluid source, but blocks passage of fluid from the fluid source to the machine while closed, or permits passage of fluid from the fluid source to the machine while open. The supply valve biases toward closed or open according to an actuation signal at the control port. A pressurization valve is also coupled between the hydraulic machine and the high-pressure fluid source. The pressurization valve blocks passage of fluid from the fluid source to the machine while in a first position, and allows a restricted passage of fluid between its input and output ports while in a second position, to allow pressure to equalize on either side of the supply valve before the supply valve opens.

Abstract: A hydraulic system having at least one hydraulic valve for controlling a transmission, in particular a continuously variable transmission. The hydraulic valve is controlled by a pilot circuit including at least one control element having a variable flow resistance and one control element having a constant flow resistance. The control element having a variable flow resistance is connected upstream of the control element having a constant flow resistance.

Abstract: A control for a working apparatus having a boom arm. The apparatus includes a controller operable to receive signals from at least one pressure sensor. The at least one pressure sensor detects pressure of hydraulic fluid in at least one chamber of a control valve. The controller compares the signals from the at least one pressure sensor to parameters generated by testing the working apparatus. The controller predicts boom arm oscillations based on the comparison of the signals with the parameters, and generates a control signal in response to predicting the boom arm oscillations.

Abstract: A pneumatic valve includes a housing having an inlet port and a delivery port and an exhaust port. A valve element is movable in the housing to control air flow between the inlet port and the delivery port and the exhaust port. The valve includes a rolling element actuator for converting a rotary actuation force to linear movement of the valve element.

Abstract: The present invention provides a pressure control system having a control solenoid with plurality of coils disposed therein, and operable to provide a plurality of pressure gain characteristics to a torque-transmitting mechanism. By selectively energizing the individual coils or a combination thereof, multiple pressure gains may be achieved with a minimum of additional system hardware.

Abstract: The invention relates to hydraulic control in a hydraulic system for the operation of a machine tool such as a press for processing material of a certain type, especially for the operation of the scrap cutters. Said control allows for impact attenuation and combined rapid motion switching with load compensation and transfer of a hydraulic medium of a hydraulic cylinder for the movement of the other. According to the invention, said control comprises hydraulic media of a hydraulic cylinder for pre-control of a first main valve element (2.4.0), a second main valve element (2.7.0) and a third main valve element (3.7.0) which are functionally combined and a fourth valve (2.5).

Abstract: The invention relates to a reciprocating engine and a working fluid inlet system therefore. The engine includes at least one cylinder with a reciprocating piston therein and a variable volume expansion chamber capable of receiving a working fluid via an inlet valve. The inlet system includes a pilot valve having an open condition and a closed condition. In the open condition, the secondary fluid passes therethrough to act on the inlet valve. The system also includes an actuating means for controlling the condition of the pilot valve. The inlet valve is adapted to open in response to the action of the secondary fluid. The engine may also include exhaust means, possibly by porting in the piston and a cylinder wall. The working fluid may be used as the secondary fluid.

Abstract: A crowd control mechanism for a power shovel includes an extendible dipper handle having an extended position and a retracted position. A double acting hydraulic cylinder having a an extendible ram has one of the cylinder and the ram fixed to the dipper handle and the other of the cylinder and the ram is stationary relative to the dipper handle. At least one of the cylinder and the ram have at least one of a blind end port and a rod end port, and at least one of the cylinder and the ram have the other of the blind end port and the rod end port, wherein hydraulic fluid flowing into the cylinder through the blind end port urges the ram toward an extended position to extend the dipper handle, and hydraulic fluid flowing into the rod end port urges the ram toward a retracted position to retract the dipper handle. Hydraulic fluid flowing into and out of the cylinder is controlled by one or more pilot operated poppet valves.

Abstract: A pneumatically operated fastener driving tool capable of reducing a time period from operation timing of a trigger to downward movement of a driver blade for fastener driving, and reducing a time period from the release timing of the trigger to a timing at which respective components are returned to their initial positions for a subsequent nail driving. As components a main valve and a trigger valve is provided. The main valve is movable within a main valve chamber connected to a main valve control channel. The trigger valve selectively provides fluid communication between the accumulator and a main valve chamber through the main valve control channel and between the main valve chamber and the atmosphere through the main valve control channel. A ratio of cross-sectional area of the main valve control channel to an internal volume of the main valve chamber is defined to a specified ratio.

Abstract: The present invention is a transbrake system for a transmission of a drag race car, the transmission comprising: (a) a transmission housing having an exterior, typically of aluminum; (b) a transmission valve body contained in the transmission housing; the transmission housing having an aperture connecting the exterior of the transmission housing with the transmission valve body; (c) a pneumatic solenoid disposed outside the transmission housing and having an actuating piston extending through the aperture to the transmission valve body, so as to be moveable from a position braking the transmission to a position releasing the transmission; (d) a source of compressed air; (d) an electrical air control valve to control the supply of compressed air from the source of compressed air to the pneumatic solenoid; (e) a fluid conduit extending from the electrical air control valve to the pneumatic solenoid.

Abstract: A torque-transmitting mechanism control valve disposed between a hydrostatic source of pressure and a torque-transmitting mechanism is effective to direct fluid pressure to engage the torque-transmitting mechanism when a control pressure is present, effective to retain the valve closed when source pressure is present but control pressure is not, and to retain the valve closed when torque-transmitting apply pressure is present and source pressure is not and control pressure is not present.

Abstract: In series between pump and tank are two throttle devices, one of which includes a controllable throttle valve having a piston, of which one side supports a valve head, which forms the boundary of an annular gap between an inflow duct and an outflow duct. A hydraulic control path extends from the inflow duct through the throttle opening to the tank, running through a precontrol bore in the piston. To prevent an unwanted leakage fluid stream, one end of the precontrol bore at the annular gap in the region of the inflow duct is positioned so that it remains opened for a closed annular gap, and the other end of the precontrol bore on the other side of the piston is arranged where the piston, in response to the controllable throttle valve being completely opened, pushes against a stop face and, in so doing, automatically closes this other end.

Abstract: A hydraulic device includes a passage block with a first hole, an internal body received in the first hole connected to a hydraulic module and an actuator. The actuator has a cylindrical shell integrally connected at its one side to the passage block and projecting at its other side from the passage block. The passage block has a first and second passageway to communicate the hydraulic module with a groove means on the internal body, and a third passageway to communicate the groove means with a first chamber of the actuator. A connecting member connects the fluid distributor unit to the other side of the actuator to communicate the groove means with a second chamber of the actuator.

Abstract: The present invention relates to a control apparatus of a hydraulic valve for holding load in which a drain line of a holding valve adapted to preclude momentary drop of load in a hydraulic actuator is substituted with a path in the interior of a directional control valve, so that a pipe line of a drain side functioning as a hydraulic hose and exposed to the outside is not needed in the present invention. The control apparatus of a hydraulic valve for holding load comprises a drain line adapted to allow hydraulic fluid returned during a switching operation of the sub-spool to flow in a pilot line of the side of a drain corresponding to the opposite side of a pilot line adapted to pressurize the spool of the directional control valve.

Abstract: The present invention relates to a variable flow control apparatus for an actuator of a heavy construction equipment capable of implementing constant flow of hydraulic fluid from a hydraulic pump to an actuator even when a pilot pressure capable of driving a seat valve openably and closably installed in a discharge flow path of the hydraulic pump exceeds a certain pressure level.

Abstract: A pumping system. The pumping system has a cylinder pump, a first group of switching devices, and a second group of switching devices. The first group of switching devices enable the cylinder pump to pump the liquid by feeding the gas provided by the gas source into the cylinder pump through a first ventilator according to a first enabling signal, and the second group of switching devices enable the cylinder to output the liquid by feeding the gas provided by the gas source into the cylinder pump through a second ventilator according to a second enable signal.

Abstract: An oil hydraulic circuit having a pilot operated control valve, for performing control of pressure oil supply to a hydraulic actuator and a pilot valve gear for outputting a pilot pressure to the control valve, that improves operationality when a fine operation is performed. The pilot valve gear has a first pressure controller that outputs a pilot pressure corresponding to the degree of operation of an operating lever and a second pressure controller that reduces the pilot pressure outputted from the first pressure controller based on a signal from an operating speed changeover switch and outputs the reduced pilot pressure to the control valve.

Abstract: A seat valve body mounted in a hydraulic line between a pump line and feeder lines to control hydraulic fluid supplied to variable throttles and to auxiliarily control hydraulic fluid flowing in a load line comprises a first seat valve having a variable control throttle displaced by a difference between a load pressure of the load line and a discharge pressure of the hydraulic pump and varying an opening area from the pump line to the feeder lines based on a displacement amount thereof, a second seat valve having a pilot variable control throttle displacing with respect to the first seat valve, determining a displacement amount of the first seat valve, and varying an opening area based on a displacement amount thereof; and a pilot spool having a pilot variable throttle determining a displacement amount of the pilot variable control throttle of the second seat valve upon switching.

Abstract: A pilot operated valve has a main poppet that selectively controls bidirectional flow of fluid between two ports in response to pressure in a control chamber on one side of the main poppet. The main poppet has a pilot orifice that is opened and closed by a pilot poppet. A unique mechanism is provided to compensate for variation of a pressure differential on opposite sides of the pilot orifice. This mechanism has a pair of annular end members between which extends a spring formed by a plurality of helices. Multiple passages with check valves extend through the main poppet to communicate the greatest pressure among the two ports to the control chamber and the lowest pressure among the two ports to the side of the pilot orifice that is opposite the control chamber.

Abstract: A working cylinder (A) having at least one working chamber (6, 7) defined by the cylinder barrel (1), at least one of the end sections (2, 3) and a piston (4), at least one supply port (9a, 9b) and a exhaust port (12a, 12b) for the working medium. The exhaust port (12a, 12b) has a valve (13a, 13b) that may be regulated by the pressure of the working medium, which is applied at the supply port (9a, 9b) in order to obtain a smaller dimension of at least the valve and to better utilize the already existing space, specifically within the cylinder, and to better and more efficiently adjust the output capacity of the individual elements. A valve (V), particularly a switch valve (W) of a rocker valve design has therefore at least one inlet (16) and at least one outlet (17a, 17b) for the working medium, as wells as at least one control port (18).

Abstract: There is disclosed a stop block for controlling a hydraulic consumer in which a main piston having an advanced opening can be lifted off a valve seat in a return function by means of a push piston. A pressure chamber confined by the main piston on the one hand and by the control piston on the other hand is connected to a tank or low-pressure passage both in the return function and in the non-return function of the stop block so that the changeover from the return function to the non-return function and vice versa can be effected very quickly.

Abstract: An actuator assembly has a first and second pilot valve. Each valve has inlets in communication with a fluid supply source and outlets in communication with the control valve. An in-line actuator housing disposed between the fluid powered device and a low connector supports the pilot valves. An elongated sleeve being axially slidably mounted over the in-line housing covers the in-line housing. A radially extending actuating member is coupled to the elongated sleeve whereby movement of the sleeve in one direction operates the first pilot valve to provide a fluid pressure necessary to actuate a first portion of the control valve so that fluid pressure is introduced into the fluid-powered device on the front side of the piston, and movement of the sleeve in the opposite direction causes operation of the second pilot valve so that fluid pressure is introduced into the fluid powered device on the back side of the piston causing the fluid powered device to move in a direction opposite of the first direction.

Abstract: A seat valve body mounted in a hydraulic line between a pump line and feeder lines to control hydraulic fluid supplied to variable throttles and to auxiliarily control hydraulic fluid flowing in a load line comprises a first seat valve having a variable control throttle displaced by a difference between a load pressure of the load line and a discharge pressure of the hydraulic pump and varying an opening area from the pump line to the feeder lines based on a displacement amount thereof, a second seat valve having a pilot variable control throttle displacing with respect to the first seat valve, determining a displacement amount of the first seat valve, and varying an opening area based on a displacement amount thereof; and a pilot spool having a pilot variable throttle determining a displacement amount of the pilot variable control throttle of the second seat valve upon switching.

Abstract: In the construction machinery equipped with an engine, a hydraulic control unit and a machine controller, there is provided an antitheft device for the construction machinery, which can prevent the engine from starting and the hydraulic control unit from working with reliability no matter how the starter circuit of the engine is modified. The initial state of the machine controller is so set that the fuel injection by a fuel injection unit of the engine is halted and that the operations of control units in the hydraulic control unit are halted, and an antitheft control unit is provided to release the initial state of the machine controller upon receiving a release signal from the antitheft control unit.

Abstract: A dual counterbalance valve is added in the hydraulic lines between the steering unit and the steering cylinders on an implement to maintain pressure in the steering lines by metering hydraulic fluid to and from the cylinders under pressure so that the steered wheels stay in phase. Since the steering system is kept under constant pressure, the wheels can only be steered by the steering unit and not by tractive soil forces so toe in and toe out problems are eliminated without need for a mechanical tie rod connecting the steered wheels. The valve is added in-line to the system so that current machines can be easily retrofitted.

Abstract: The present invention is an actuator assembly for use with the fluid control valve having an inlet in communication with the fluid supply source and an outlet in communication with a fluid powered device. Additionally, the fluid control valve is in communication with at least one adjustable flow control port. The fluid powered device defines a chamber having a pressure driven piston disposed therein. The pressure driven piston has a front side and a back side that substantially divides the chamber of the fluid powered device into two main portions.

Abstract: In an oil hydraulic circuit comprising a pilot operated type control valve for performing control of pressure oil supply to a hydraulic actuator and a pilot valve gear for outputting a pilot pressure to this control valve, in order to improve operationality in a case where a fine operation is performed, the pilot valve gear (8) comprises a first pressure controller (9) for outputting a pilot pressure corresponding to the degree of operation with an operating lever (12) and a second pressure controller (10) for reducing the pilot pressure outputted from this first pressure control means based on a signal from an operating speed changeover switch 16 and outputting the reduced pilot pressure to the control valve 5.

Abstract: The present invention relates to an electro-pneumatic positioner for use with a pneumatically controlled two-chamber actuator comprising a first valve unit (10) comprising a first air supply valve (14) and a first air outlet valve (37) connected to a conduit (30, 38, 50), which in turn is connectable to a chamber of the actuator, a second valve unit (12) comprising a second air supply valve (14′) and a second air outlet valve (37′) connected to a conduit (30′, 38′, 50′), which in turn is connected to a second chamber of the actuator; a first control device (60, 74) acting on the first air supply valve, which first control device comprises a first control valve (60); a second control device (60′, 76) acting on the said second air supply valve, which second control device comprises a second control valve (60′).

Abstract: A crane having an upper works rotatably mounted on a lower works and a boom pivotally mounted on the upper works includes a hydraulic boom hoist cylinder and a hydraulic circuit for controlling the hydraulic boom hoist cylinder. The hydraulic cylinder is pivotally connected to a mast on the upper works and pendently connected to the boom. The boom hoist cylinder preferably comprises two double-acting hydraulic cylinders. The hydraulic circuit includes a closed loop pump and a hydraulic controller connecting the closed loop pump and the double-acting cylinders such that fluid from the pump can be directed either to extend or retract the cylinders, with the hydraulic fluid exiting the cylinders being directed to return to the pump.

Abstract: A system for remotely controlling an undersea device. The system employs a gas-pressurized liquid reservoir that can be recharged from at least one replaceable gas bottle. A pressure-regulating valve is employed to control the pressure of the liquid leaving the reservoir. A number of one-shot units, each in the form of a squib-actuated valve coupled with a piston accumulator, are employed to create a hydraulic pilot for a hydraulic direction control valve. The control valve functions to direct pressurized liquid from the reservoir to a hydraulic actuator or other type of hydraulic device.

Abstract: A pilot control system for maintaining a constant operating hydraulic fluid pressure in a hydraulic system throughout a range of hydraulic fluid flow and temperature conditions. The pilot control system has a pilot pump and a pilot relief valve in fluid communication with the pilot pump. A first pressure reducing valve is in fluid communication with the pilot pump and the pilot relief valve so as to reduce the pressure to components downstream of the pressure reducing valve.

Abstract: In a hose rupture control valve unit comprising a main valve constituted by a poppet valve member and a pilot valve constituted by a spool valve member, a hydraulic fluid can be supplied from a hose connection chamber to a cylinder connection chamber even in the condition of a pilot pressure acting upon the spool valve member, so that the smooth operation can be obtained without a delay in opening of the poppet valve member upon an abrupt reversed lever operation.

Abstract: A hydraulic control circuit for controlling the operation of an attachment or tool associated with a particular work machine wherein such circuit includes an actuator for controlling the operation of the attachment or tool, a control valve operable to control fluid flow to the actuator, a fluid path communicating the control valve with the actuator, and a pilot signal control device positioned in communication with both the control valve and a pilot pressure source and having a signal port in communication with the actuator for sensing the pressure associated therewith, the control device being responsive to the pressure associated with the actuator and being operable for sending a control signal to the control valve when a pressure condition in the actuator reaches a predetermined value, the control signal actuating the control valve so as to at least partially close such valve and maintain an operative pressure on the attachment actuator while, at the same time, decreasing the fluid flow through the control

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: A hydraulic system is provided with a pump supplying pressurized hydraulic fluid through a first supply line to a closed center control valve. From the control valve the fluid is directed through work lines to a hydraulic motor. Exhausted hydraulic fluid from the hydraulic motor is directed through the control valve to an exhaust line having a back pressure check valve set at a first pressure level. The hydraulic motor is provided with a pressure relief valve and an anti-cavitation valve that are mounted in parallel with one another. The anti-cavitation valve is hydraulically coupled to the exhaust line. To keep the exhaust line fully charged a second supply line extends between the first supply line and the exhaust line. The second supply line is provided with a pressure reducing valve that is set at a second pressure level. The second pressure level of the pressure reducing valve is less than the first pressure level of the back pressure check valve.

Abstract: A hydraulic oil flow controller for a construction machine comprises an operating valve 6 for supplying hydraulic oil discharged from hydraulic pimps 1 and 2 to an attachment, an attachment operating unit 11 for transmitting a pilot signal corresponding to the manipulated variable of the operating valve 6 and a solenoid control valve 12 for changing the flow characteristics of the pilot signal in accordance with a command from a controller 19. An increase and/or decrease signal is sent to the solenoid control valve 12 through the controller 19 from a monitor device 18 so that the flow of the hydraulic oil supplied to the actuator of the attachment is increased and/or decreased. Accordingly, a coefficient of fluctuation of the flow relative to a coefficient of fluctuation of the manipulated variable can be decreased in the work of the attachment of a hydraulic shovel and the operation efficiency upon operation of the attachment can be improved.

Abstract: The system controls the position of a pneumatically operated valve using an electrical control signal from a controller. A pilot circuit of the system has multiple piezo valves that are subject to electrical signals from the controller to provide pneumatic output signals to a volume booster circuit of the system. Relatively small volume pneumatic pilot signals from the piezo valves are used to determine the opened or closed state of higher volume valve assemblies of the booster circuit which connect or disconnect the actuator of the valve to be operated with a source of pressurized gas. Both the piezo valves and the booster valve assemblies are subjected to gas at the same operating pressure, but the surface area of pistons in the booster valve assemblies exposed to the piezo valves is substantially larger than the surface area of the pistons exposed to operating pressure such that the pneumatic signals shift the pistons even when pressure is the same on both sides thereof.