Abstract: A working machine is provided, which includes a prime mover, a first traveling pump driven by power of the prime mover to supply operation fluid through a connector fluid tube, a traveling motor including first and second ports connected to the connector fluid tube, the traveling motor configured to be switched in a first speed and a second speed higher than the first speed, a first pressure detector to detect first traveling-pump pressure near the first port, a second pressure detector to detect second traveling-pump pressure near the second port, and a controller configured, with the traveling motor switched in the second speed, to automatically shift down the traveling motor from the second speed to the first speed, when a differential pressure between the first traveling-pump pressure and the second traveling-pump is equal to or more than a deceleration threshold.

Abstract: An excavator includes a traveling body, an upper turning body rotatably provided on the traveling body, an attachment which has a boom, an arm, and a bucket and is attached to the upper turning body, and a controller configured to perform a control of a cylinder of at least one shaft of the attachment so as to suppress a vibration of the traveling body or the upper turning body, which is caused by an aerial operation of the attachment.

Abstract: A shovel that corrects the movement of an attachment regardless of the operating state of the attachment by an operator is provided. The shovel includes a traveling body, a turning body turnably mounted on the traveling body, an attachment attached to the turning body, a hydraulic actuator configured to drive the attachment, and a controller. The controller is configured to control the hydraulic actuator to minimize a change in orientation of the traveling body or of the turning body, in response to a change in moment caused by an aerial movement of the attachment.

Abstract: A flow control manifold apparatus includes a housing defining a first flow path from a flow input port to flow output port and a second flow path from a return inlet port to a return outlet port. A first flow regulating valve is placed inline the first flow path and an excess flow path fluidly couples the first flow path to the second flow path. An excess pressure valve is placed inline the excess flow path and is in a closed orientation when the first flow regulating valve is open so that all of the fluid exits through the flow output port. The excess pressure valve is then in a partially open orientation when the first flow regulating valve is partially closed so that a first portion of the fluid exits through the flow output port and a second portion of the fluid exits through the return outlet port.

Abstract: A hydraulic drive device for an industrial vehicle includes a variable displacement pump, a displacement control valve, a power steering cylinder, a power steering valve, a loading cylinder, a loading valve, a hydraulic oil passage, and a pilot line. The displacement control valve controls the variable displacement pump to increase displacement of the variable displacement pump when differential pressure between discharge pressure of hydraulic oil discharged from the variable displacement pump and pilot pressure generated in the pilot line is smaller than a predetermined set pressure. A spool of the loading valve is provided with a groove portion that forms a communication passage that makes communication between the hydraulic oil passage and the pilot line at a neutral position of the loading valve when the power steering valve is located in a neutral position.

Abstract: A pipe facing machine (PFM) system includes a PFM and a hydraulic power source having a single hydraulic pump arranged to provide a hydraulic oil flow to the PFM via single hydraulic circuit. The PFM includes a body defining an axis and a cutting head arranged to rotate and translate relative to the axis. Drive systems are arranged to drive clamping of the PFM on a workpiece, rotation of the cutting head about the axis, and translation of the cutting head along the axis. A hydraulic controller includes a plurality of control elements and hydraulically connects the drive systems. The hydraulic controller is arranged to direct and regulate hydraulic oil flow between the drive systems and the hydraulic controller based on signals from the control elements and a computer control system.

Abstract: A vehicle including a control valve to lift and lower a boom. The vehicle further includes a control circuit to control a speed of the boom lowering via a pressure compensator that balances a first pressure signal downstream of a control valve during the boom lowering and a second pressure signal from a hydraulic user interface so that, upon increasing of the first pressure signal during the boom lowering, the control valve progressively closes.

Abstract: A vacuum pump for pumping a gas includes a pump housing which defines a pump cavity, a shiftable vane, a pump rotor body, a separate axial rotor retaining arrangement, and a radial friction bearing. The pump housing includes a closed housing wall. The pump rotor body includes a vane slit which supports the shiftable vane to define rotating pumping chambers, an axial low-pressure end which is axially supported by the closed housing wall so that a gas pressure inside the pumping chambers is present at the low-pressure end, and an axial high-pressure end. The pump housing is fluidically open at the axial high-pressure end so that atmospheric pressure is present. The axial rotor retaining arrangement includes a retaining sheet body arranged in a transversal plane which axially in part blocks the axial high-pressure end. The radial friction bearing is arranged axially between the vane slit and the axial high-pressure end.

Abstract: An electrical system includes a cycloidal electric machine having a stator and a balanced rotor. The rotor is eccentrically positioned radially within the stator, such that the rotor moves with two degrees of freedom (2DOF). The 2DOF motion includes rotating motion about the rotor axis and orbiting motion about the stator axis. A rotor constraint mechanism constrains the motion of the rotor, such that the rotor is able to generate torque on a coupled load. Part of the rotor constraint mechanism may be integrally formed with the rotor. A coupling mechanism may be coupled to the rotor and configured to translate the 2DOF into 1DOF, i.e., rotation without orbital motion. The rotor may include mutually-coupled rotors. At least one counterweight may be connected to the rotor, e.g., externally or within the airgap. Balancing of the balanced rotor may be optionally provided via the multiple rotors and/or the counterweight(s).

Abstract: A hydraulic system of a work machine includes a first hydraulic device to operate in a first operation mode while pressure of hydraulic oil supplied from a hydraulic pump via a first oil passage is equal to or higher than a first pressure threshold. The hydraulic oil in the first oil passage is to be discharged via a second oil passage. A pilot check valve is provided in the second oil passage and has a pilot port to receive a pilot pressure of the hydraulic oil. The pilot check valve is closed to stop discharging the hydraulic oil in the first oil passage through the second oil passage while the pilot pressure is lower than the fourth pressure threshold. The pilot check valve is opened while the pilot pressure is higher than or equal to the second pressure threshold. The first hydraulic device is an operation control valve.

Abstract: The machine comprises distribution ducts connected to respective ones of first, second, and third enclosures (40, 42, 44), and a cylinder-capacity selector (21) suitable for being caused to take up a large cylinder capacity configuration in which the second enclosure (42) is connected to one of the main ducts (2), while the first and third enclosures (40, 44) are connected to the other main duct (1), and a small cylinder capacity configuration in which the second and third enclosures (42, 44) are connected to said one of the main ducts (2), while the first enclosure is connected to the other main duct (1). The machine further comprises a safety valve (150) having at least a first port (56) connected to said one of the main ducts (2), and a second port (58) connected to the third enclosure (44).

Abstract: A double-rod ram (1), preferably for an extruder, comprising an outer cylinder (10), an inner cylinder (20) installed therein and arranged concentrically therewith, a double-acting work piston (41) provided in the inner cylinder to be displaceable and a bypass device (50) with at least one bypass valve (52), wherein the work piston (41) divides the inner cylinder (20) into two compartments (42) and can be loaded with a hydraulic fluid from both compartments (42), wherein the bypass device (50) is so arranged that in a bypass position of the bypass valve (52) a fluid connection between the two compartments (42) is formed by a direct connection, preferably at least one bypass line, and in a work position of the bypass valve (52) no such fluid connection is present.

Abstract: A work machine includes a closed circuit system in which there is provided a flushing valve.

Abstract: An example valve assembly includes a meter-in valve configured to be fluidly coupled to a first source of pressurized fluid and control fluid flow from the first source of pressurized fluid into a first chamber of an actuator; a counterbalance valve including configured to open and control fluid flow from a second chamber of the actuator to a tank in response to a pilot pressure fluid signal received at a pilot port of the counterbalance valve; and a pressure reducing valve configured to be fluidly coupled to a second source of pressurized fluid and to be fluidly coupled to the pilot port of the counterbalance valve, where the pressure reducing valve is configured to receive pressurized fluid from the second source of pressurized fluid and, when actuated, provide the pilot pressure fluid signal to the pilot port of the counterbalance valve.

Abstract: A shovel is disclosed, which includes a lower traveling body; an upper rotating body mounted on the lower traveling body; an engine mounted on the upper rotating body; a hydraulic pump of a variable volume type; a hydraulic actuator to which pressurized oil is supplied from the hydraulic pump; a flow rate control valve configured to control, based on operation amount of an operation member, a flow rate of the oil to the hydraulic actuator from the hydraulic pump; and a controller configured to control the hydraulic pump. The controller calculates a virtual bleed flow rate from a bleed opening area of the flow rate control valve, determines a pump demand flow rate based on the calculated virtual bleed flow rate, and performs a virtual bleed-off control such that a discharge flow rate of the hydraulic pump becomes the determined pump demand flow rate.

Abstract: A hydraulic system is disclosed. The hydraulic system may include a fluid source and an actuator having a first passage and a second passage. The hydraulic system may further include a pump having a first port connected to the first passage, a second port connected to the second passage, and a third port connected to the fluid source. The first and second passages may be connected to each other via the first and second ports, and the first passage and the low-pressure fluid source may be connected to each other via the first and third ports. They hydraulic system may further include a charge circuit fluidly connected to the first and second passages, and at least one damping control valve configured to selectively allow fluid from the pump to pass into the charge circuit to dampen pressure oscillations between the actuator and the pump.

Abstract: Systems and methods according to one or more embodiments are provided for rate and position control modes used in the operations of a telescoping refueling boom system. In one example, a system includes a telescoping tube and an actuator coupled to the telescoping tube and configured to extend and/or retract the telescoping tube. A processor is coupled to the actuator and configured to select a telescoping tube rate control mode and/or a telescoping tube position control mode based on a telescoping tube current position error, a telescoping tube current rate of movement, and a value of a telescoping tube rate command.

Abstract: A hydraulic drive system of a construction machine includes: a control valve configured such that an opening area of a center bypass passage gradually decreases in accordance with increase in an operation signal; an operation device that outputs the operation signal; a bleed-off line; and a bleed-off valve that includes a pilot port to which a secondary pressure from a solenoid proportional valve is led, the bleed-off valve being configured such that: a bypass passage is open until the operation signal exceeds a first setting value, and the bypass passage is closed when the operation signal exceeds the first setting value; and an unloading passage is opened when the operation signal exceeds a second setting value, and an opening area of the unloading passage gradually decreases until the operation signal that has exceeded the second setting value reaches a third setting value.

Abstract: When an engine stall is likely to occur, the pressure of the back pressure chamber of a relief pressure valve is released to adjust the relief pressure of the relief pressure valve. This actuates a pressure compensating circuit to release the pressure in a control circuit to an oil tank. Thus, a rapid increase of the pressure due to a cargo handling operation is restricted, and an engine stall due to insufficient torque of the engine is avoided.

Abstract: A series hydraulic hybrid system for a vehicle is described. The hydraulic hybrid system has a hydraulic circuit and a high pressure accumulator. The hydraulic circuit has a first hydraulic displacement unit in fluid communication with a second hydraulic displacement unit. The high pressure hydraulic accumulator is in fluid communication with the hydraulic circuit and a low pressure hydraulic accumulator in fluid communication with the hydraulic circuit. The high pressure hydraulic accumulator is in fluid communication with the hydraulic circuit through a proportional flow control valve. The proportional flow control valve is adapted to continuously vary a flow of hydraulic fluid between the high pressure hydraulic accumulator and the hydraulic circuit.

Abstract: An electro-hydraulic actuation system includes a regeneration valve in fluid communication with a first fluid chamber and a second fluid chamber of a hydraulic actuator, and a dump valve is in fluid communication with the second fluid chamber and a fluid reservoir. A pump provides a flow of fluid to the first and second fluid chambers, a displacement of the pump controlling a velocity of the actuator during motion in the retraction and extension directions. An electric motor drives the pump, and a controller controls a state of the regeneration valve and the dump valve. At least one feedback device senses a system condition and provides a respective feedback signal indicative of the sensed system condition to the controller, the controller responsive to the feedback signal to determine an occurrence of an over-center load condition and control a state of the regeneration valve and the dump valve in response to the occurrence to maintain the velocity of the actuator.

Abstract: A vehicle powertrain hydraulic system (10) includes a clutch (12), a piston (62) disposed in a cylinder (60) to drive a shift selector (14), a pump (82) in fluid communication with a fluid supply (86) to pressurize fluid, and first and second fluid pressure lines (91, 92) from the pump to first and second sides of the piston. A third fluid pressure line (93) may extend to the clutch from the cylinder in a location between the first and second sides of the piston, such that the piston also may be a valve to control fluid flow to the clutch. The pump may be reversible and coupled to an electric motor (80), and a centrifugal regulator (84) may be coupled to the motor and in fluid communication with the first and second pump pressure lines to regulate fluid pressure therein. A related operational method is also disclosed.

Abstract: A hydraulic control apparatus is disclosed that controls a hydraulic pump in a construction machine in which a hydraulic actuator is connected to the hydraulic pump via a directional control valve of a closed center type, and in which a position of the directional control valve is changed according to an operation amount of an operation member. The hydraulic control apparatus includes a virtual negative control pressure calculating part configured to calculate, based on the operation amount of the operation member and a discharge pressure of the hydraulic pump, a virtual negative control pressure when a negative control system is assumed; and a part configured to calculate a control command value for the hydraulic pump based on the virtual negative control pressure.

Abstract: A cushioned swing circuit provides the reduction of oscillation common in the operation of heavy equipment such as with boom members. The circuit utilizes a transfer of high pressure fluid flow (caused by the inertial of the swing during rapid deceleration) from one leg of the circuit to the other leg of the circuit or to the sump which serves as decompression for the oil that would ordinarily be trapped in the leg. These phenomena create the swing cushioning effect.

Abstract: A hydraulic circuit of a construction machine including center bypass passages, into which a pressurized oil from hydraulic pumps is supplied, includes a directional control valve group in tandem with the center bypass passages; a bleed-off valve on a downstream side of each center bypass passage; and a merging circuit that merges the pressurized oil supplied into one center bypass passage and that in another center bypass passage, wherein each directional control valve includes a first internal passage that flows the pressurized oil into the center bypass passages, and a second internal passage that supplies the pressurized oil to a hydraulic actuator, wherein the center bypass passages and the first internal passage form a parallel passage, wherein an opening area of the bleed-off valve is changed, wherein the merging circuit includes a merging directional control valve that controls an inflow direction of the pressurized oil to be merged.

Abstract: A hydraulic control apparatus is disclosed which includes an unloading valve controlling part; an command value calculating part configured to calculate, based on an operation amount of an operation member for changing a position of the directional control valve and a discharge pressure of the hydraulic pump, a virtual negative control pressure, and calculates a control command value for the hydraulic pump based on the virtual negative control pressure; and a correcting part configured to operate under the situation where the directional control valve is in such a state that the fluid path to the hydraulic actuator is closed, wherein the correcting part corrects the control command value or a parameter, which is used in calculating the control command value, such that a discharge flow rate of the hydraulic pump is a predetermined flow rate.

Abstract: Lubricating oil system for a combustion engine, in particular for industrial or commercial vehicles, the system comprising a bypass connection suitable to bypass an oil pump associated to an engine oil circuit, a controllable valve suitable to adjust an amount of oil to be bypassed through the bypass connection, control means controlling the controllable valve, programmed to control said controllable valve as a function of the combustion engine speed.

Abstract: A hydraulic excavator is provided with an arm cylinder, an arm switching valve, a sixth pilot pressure control valve, a sixth electromagnetic proportional valve, a sixth upstream pilot flow path, a sixth hydraulic pressure sensor, and a control section. The control section selects at least one item of current value information from a plurality of items of current value information on the basis of a hydraulic pressure that is detected by the sixth hydraulic pressure sensor. The control section is configured to set a current value of a current that is output to the sixth electromagnetic proportional valve on the basis of the current value information that is selected.

Abstract: Apparatuses and systems that use a variable displacement motor-pump (VDMP) to control the position of a hose of an aerial refueling system are disclosed. At VDMP displacements greater than required to hold a position of the hose, the VDMP operates in a motor mode to retract the hose. For lesser VDMP displacements, the VDMP operates in a pump mode to control extension of the hose. In accordance with some embodiments, a dual orifice conveys hydraulic fluid at varying rates depending upon the VDMP operational mode.

Abstract: A work vehicle has a pump group with two fixed-displacement pumps, an electro-hydraulic diverter openable to divert flow from one of the pumps to a fluid reservoir, and a controller configured to command the diverter to open.

Abstract: A hydraulic drive system for driving a load includes a drive shaft; first and second hydraulic pumps driven by the drive shaft, and a control system that operates the hydraulic drive system in a plurality of modes including: a) a first mode where the second hydraulic pump pumps hydraulic fluid from a supply line to an accumulator; b) a second mode where the second hydraulic pump pumps hydraulic fluid from the accumulator to the supply line; c) a third mode where the second hydraulic pump pumps hydraulic fluid from the supply line to a reservoir; and d) a fourth mode where the second hydraulic pump pumps hydraulic fluid from the reservoir to the supply line. At least the second hydraulic pump is a variable displacement bidirectional pump.

Abstract: A hydraulic circuit for a construction machine including a direction control valve group including direction control valves provided in tandem to a center bypass passage, and a bleed-off valve provided to the center bypass passage downstream of the direction control valve group.

Abstract: A fluid delivery system includes a first hydraulic circuit, and a second hydraulic circuit. The first hydraulic circuit includes a first hydraulic pump, and a first hydraulic motor. The first hydraulic motor is fluidly connected to the first hydraulic pump and is configured to be driven by the first hydraulic pump. The second hydraulic circuit includes a second hydraulic pump, and a second hydraulic motor. The second hydraulic pump is mechanically coupled to the first hydraulic motor and configured to be driven by the first hydraulic motor. The second hydraulic motor is disposed in loop with the second hydraulic pump and configured to be driven by the second hydraulic pump. The fluid delivery system further includes a delivery pump mechanically coupled to the second hydraulic motor and fluidly connected to a fluid source. The delivery pump is configured to deliver a pressurized fluid.

Abstract: A hydraulic system is disclosed. The hydraulic system may have an over-center, variable-displacement pump, an actuator, and first and second passages that create a closed-loop circuit. The hydraulic system may also have first and second check valves disposed in the first and second passages, respectively, to allow flow only from the pump to the actuator. The hydraulic system may further have a first bypass line connecting the first passage at a location between the actuator and the first check valve to the first passage at a location between the first check valve and the pump, and a second bypass line connecting the second passage at a location between the actuator and the second check valve to the second passage at a location between the second check valve and the pump. The hydraulic system may additionally have a valve configured to control flow through the first and second bypass lines.

Abstract: A method and a device for controlling a load sensing hydraulic system, having a bypass valve (F), which is controlled by a pump pressure (P) and which when the hydraulic system is in operation diverts a pump flow of hydraulic fluid to a tank (E). The bypass valve (F) is pre-stressed towards a closed position and is put on load by the pump pressure (P) towards an open position against the action of the pre-stress. When the hydraulic system operates in a idling operation a first pre-stress element (I) limits the pre-stress to a first pressure and upon activation of the hydraulic system, a pressure regulator (10) increases the pre-stress to a second, substantially higher pressure by applying a hydraulic, constant second pre-stress force, that is added to the first pre-stress force and is substantially greater than this.

Abstract: A rotational system is provided for controlling rotation of one or more solar collectors to track the movement of the sun, to automatically keep the collectors locked in stow position during high wind conditions, and advantageously also to prevent damage to the rotational system due to high pressures caused by high temperature conditions. The system utilizes a bi-directional hydraulic rotational actuator hydraulically connected to a control system. The actuator advantageously includes a system of helical gears and a piston, and the control system includes hydraulic lines equipped with check valves that prevent circulation of hydraulic fluid through the hydraulic lines and the actuator when backpressure is exerted in one of the hydraulic lines as a result of high wind force on the collectors. In addition, the control system advantageously comprises a pressure-relief system to prevent damage to the actuator during high temperature conditions.

Abstract: Parasitic hydraulic loading on an engine is significantly reduced during cold starts by using an unloader valve to divert the flow of hydraulic fluid from a hydraulic pump to a hydraulic actuator, i.e., load source, recirculating the hydraulic fluid between the hydraulic pump and the unloader valve.

Abstract: A slewing-type working machine capable of reducing back pressure generated during slewing. The slewing-type working machine includes: a base carrier; an upper slewing body; a hydraulic motor including first and second ports and slewing the upper slewing body; a hydraulic pump, a slewing operation device including an operating member; a control valve controlling the hydraulic motor based on the operation signal of the slewing operation device; first and second pipe-lines connecting the first and second ports of the hydraulic motor to the control valve; a communication switching device capable of switching communication and cutting of between both pipe-lines and the tank; and a switching command section operating the communication switching devices, when the upper slewing body is slewed, to bring only a pipe-line, which corresponds to a discharge-side pipe-line of the hydraulic motor, of the pipe-lines into communication with the tank, while bypassing the control valve.

Abstract: A work vehicle includes a fluid circuit to operate at least one implement for performing work, the fluid circuit having at least a first operating mode and a second operating mode. The first operating mode is configured to operate within a first predetermined flow rate range within a first predetermined fluid pressure level range. The second operating mode is configured to operate within a second predetermined flow rate range and within a second predetermined fluid pressure level range. In response to the fluid circuit operating within the second operating mode, a maximum pressure value of the second predetermined fluid pressure level range is greater than a maximum pressure value of the first predetermined fluid pressure level range, and a maximum value of the second predetermined flow level range is less than a maximum value of the first predetermined flow level range.

Abstract: An apparatus includes a first plurality of cylinders, each coupled to a shared first port by a separate first valve and to a shared second port by a separate second valve. Each first and second valve has a chamber to which pressure from either the associated cylinder or the respective port is dynamically applied to select different operating modes. Each one of a second plurality of cylinders is coupled to the first port by a separate third valve and to a shared third port by a separate fourth valve. Each third and fourth valve has a chamber to which pressure from either the associated cylinder or the respective port is dynamically applied to select different operating modes. Selecting an operating mode enables the apparatus to act as a bidirectional pump or a hydraulic motor. Selectively controller the valves can deactivate an individual cylinder, while other cylinders remain active.

Abstract: An accessory flow recovery system includes an inlet that receives a first fluid flow, and a pump with a pump inlet and outlet. The pump inlet receives the first fluid flow from the inlet and discharges a second fluid flow from the outlet. The accessory flow recovery system has an actuation unit for supplying a third fluid flow to accessory components, a metering system to regulate the flow rate of the second fluid flow based on a flow demand, and an inlet pressurizing valve coupled between the outlet and the metering system. The inlet pressurizing valve regulates the second fluid flow between the pump and the metering unit. The accessory flow recovery system further includes a return switch valve to direct the third fluid flow to the metering system when the recovery system is operating in one mode, and to the inlet when the system is operating in another mode.

Abstract: A hydraulic transmission system for a vehicle is provided. The system includes a main pump serving to feed with fluid at least one hydraulic motor for driving a vehicle mover member; an auxiliary pump, the main pump and the auxiliary pump being suitable for being actuated jointly; and a “bypass” connection between a delivery orifice of the auxiliary pump and an unpressurized reservoir. In addition, a first constriction is arranged on the bypass connection, and configured to maintain a pump protection pressure in a pump protection portion of the bypass connection. This pressure is applied to the main orifices of the main pump when said pump is actuated but is not delivering, thereby ensuring that the pump is protected.

Abstract: A hydraulic fan circuit includes a primary pump, a motor fluidly connected to the primary pump, and a fan operably connected to and driven by the motor. The circuit also includes a supply passage extending from the primary pump to the motor, a return passage extending from the motor to the primary pump, and a pressure limiting valve configured to selectively reduce pressure of a flow of pilot fluid directed to the primary pump. The circuit further includes an override valve configured to selectively connect the supply passage to the pressure limiting valve.

Abstract: A slewing-type working machine includes: a hydraulic motor for slewing an upper slewing body; a hydraulic pump; a slewing operation device including an operation member; a control valve controlling the hydraulic motor based on an operation signal of the slewing operation device; first and second pipe-lines connecting first and second ports of the hydraulic motor to the control valve; communication switching devices switching communication and cutoff between both pipe-lines and a tank; an electric motor; an electric storage device; and a controller, which communicates an outlet-side pipe-line to the tank during slewing, makes a brake based on a regenerative action by the electric motor and the electric storage device and causes the electric storage device to store regenerative power, upon deceleration operation. Upon failure occurrence, the controller brings the communication switching devices to a communication-cutoff state and stops the regenerative action to secure slewing.

Abstract: A slewing-type working machine includes: a hydraulic motor having first and second ports and driving an upper slewing body to slew it; a hydraulic pump; a slewing operating device including an operating member; a control valve controlling the hydraulic motor based on an operation signal of the slewing operating device; first and second pipe-lines connecting the first and second ports of the hydraulic motor to the control valve; communication switching devices switchable between communication and cutoff between both pipe-lines and a tank; a slewing electric motor; an electric storage device; and a controller. During a slewing operation, the controller brings the communication switching devices into a communicated state and performs regenerative control by issuing a command on a regeneration amount corresponding to a reduction in back pressure by the communication switching devices in the communicated state to the slewing electric motor.

Abstract: A hydraulic transmission unit comprises at least one pressure regulation valve (1) and a pilot control valve (2) which is connected to the pressure regulation valve (1) by a pilot control line (35). A pre-filling valve (3, 303) sets a pre-filling pressure (p—3) to avoid draining of a clutch (20) and the lines (231, 331) connected to the clutch (20) in an operating condition in which the clutch (20) is not actuated. To avoid draining when the clutch when in the operating condition, the pilot control line (35) is also connected to at least one line (236, 238, 336, 338) which is pressurized with a second pre-filling pressure (p—3).

Abstract: A swing energy recovery system for a machine is disclosed. The swing energy recovery system may have a pump configured to pressurize fluid, a motor driven by a flow of pressurized fluid from the pump, and an energy recovery arrangement configured to receive pressurized fluid discharged from the motor and selectively supply pressurized fluid to the motor. The swing energy recovery system may also have a pressure relief valve associated with the motor, and a controller in communication with the energy recovery arrangement and the pressure relief valve. The controller may be configured to selectively adjust a setting of the pressure relief valve based on an operating condition of the energy recovery arrangement.

Abstract: A slewing-type working machine, including a base, an upper slewing body, a hydraulic motor slewing the upper slewing body, a hydraulic pump, a slewing operation device, a control valve controlling the hydraulic motor, pipe-lines connecting the hydraulic motor to the control valve, a hydraulic pressure source, communication valves switching communication and cutoff between the pipe-lines and a tank by pilot pressure, an electric motor, an electric storage device, communication selector valves on inlet sides of the communication valves, a switching control valve on an inlet side of the communication selector valves, and a controller. During slewing deceleration, the controller signals to switch the switching control valve to a connecting position and switch the communication selector valves to a pilot pressure supply position. In a slewing stopped state, the controller signals to switch the communication selector valves to a cutoff position and switch the communication valves to a communication cutoff position.

Abstract: A fluid-dynamic circuit includes a source of a pressurized fluid; a distributor valve for distributing the pressurized fluid to transport lines; a feeding line for feeding the pressurized fluid, which is interposed between the source and the valve; a main user apparatus, which is reciprocatingly operated by an actuator that includes a slider sealably fitted in a sliding seat of a containing element divided thereby into a first chamber and a second chamber in opposite positions and having variable volumes; and second and third transport lines for the pressurized fluid, which are interposed between the distributor valve and the first and second chamber respectively, a first derived transport line being interposed between the valve and at least one of the second and third transport lines, and having a normally closed quick discharge device mounted thereto, whose opening is designed to be controlled by the actuator.

Abstract: A hydraulic system for an operator controlled machine, the system including at least one actuator for moving a machine component, a source of pressurized fluid for delivering pressurized fluid at a system pressure to a control valve which is operable under operator control, to control the flow of fluid from the source to the actuator at a load pressure, along a load pressure path, a flow control apparatus for controlling the flow of fluid from the source to the control valve, the flow control apparatus including an actuating part which is biased by a resilient device to a condition in which the flow control apparatus provides for a maximum flow of fluid to the control valve, actuating part movement by the resilient device being resisted by system pressure fluid and being supported by fluid at a control pressure, the control pressure being derived from the load pressure, and wherein the system includes a pressure control device to which the load pressure is communicated, the pressure control device being opera