Abstract: The present disclosure relates to a hydraulic control circuit for crane slewing gear having directional valves arranged in work lines and controllable separately for the inflow and outflow to the hydraulic motor for the carrying out of a rotational movement of the slewing gear, wherein an inflow valve serves the control of the oil inflow from a hydraulic pump via the work line to the hydraulic motor and an outflow valve is provided via which the hydraulic motor can be relieved to the tank, wherein the work lines are each connected via at least one check valve to a common inlet of the outflow valve to relieve the hydraulic motor independently of the direction of rotation of the slewing gear via an outflow valve into the tank.

Abstract: A fluid-powered high-speed spindle (100) having a longitudinal axis (A) defining an upper end defined by a shank and a lower end accepting a tool. The spindle includes a body (120), a rotatable shaft (530) supported by at least one bearing (508) within the body (120), a seal housing (150) connected to the body (120) at the lower end thereof, a cover (180) connected to the seal housing (150) at the lower end thereof, a fluid channel system for directing fluid from an entry port (102) to a nozzle (576) for turning a turbine (570) attached to the shaft (530); and a flinger (660) attached to the shaft (530) and positioned above the turbine (570). The flinger (660) and the seal housing (150) combine to form a non-contact seal (900) configured to impede the flow of fluid toward the at least one bearing (508).

Abstract: A hydraulic drive system designed so that while maintaining intact a structure of a relief valve having a shockless function, the drive unit hydraulic drive system facilitates changing a driving pressure or braking pressure of a hydraulic swing motor and hence, changing a maximum driving torque or braking torque of the hydraulic swing motor. Inside a swing motor unit is arranged a first swinging relief valve provided with a shockless function to limit a driving pressure or braking pressure of the hydraulic swing motor in order to prevent the pressure from exceeding a first setting pressure. Also, a second swinging relief valve is provided for limiting the driving pressure or braking pressure of the hydraulic swing motor in order to prevent the pressure from exceeding a second setting pressure that is lower than the first setting pressure.

Abstract: This invention consists of the addition of a novel clutch arrangement which facilitates speed changing gears on both the output and input of the transmission and provides for a compact packaging configuration for a plurality of hydraulic pump/motors. The use of a small accumulator without a valve and a related reservoir absorbs the pressure shocks from rapidly opening and closing the valves that that select or de-select the pump/motors. It is also disclosed that two adjacent pump/motors on the same shaft can be constructed such that they share an input or output port thereby reducing the size of the combination. The transmission can perform the retarder function by placing a flow retarding valve in the re-circulating path in one or more of the pump/motors.

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 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: This invention consists of two or more fixed displacement hydraulic pump/motors mounted on a common input shaft hydraulically connected to two or more fixed hydraulic pump/motors mounted on a common output shaft. The relative displacements of the pump/motors are chosen such that by selectively activating the individual pump/motors, the transmission ratio can be changed in the case when the input devices and acting as pumps driving the output devices as motors (conversely when driving the vehicle in reverse). Further, a hydraulic accumulator and reservoir are attached in a manner that allows the pressurized fluid to augment the flow produce by the input pumps in order to increase the transmission ratio. Similarly, the transmission ratio can also be reduced by causing the input pumps to pump fluid into the accumulator at the same time they are pumping fluid through the output motors.

Abstract: A motor control device for construction machinery includes a hydraulic pump; a hydraulic motor driven by pressure oil from the hydraulic pump; a control valve that controls a flow of the pressure oil from the hydraulic pump to the hydraulic motor; a pair of main conduit lines that connect the hydraulic motor and the control valve on a delivery side and a return side thereof; an operation member that operates a spool of the control valve to either a neutral position that does not allow the pressure oil for driving from the hydraulic pump to pass through control valve to the hydraulic motor or a non-neutral position that allows the pressure oil for driving to pass through the control valve to the hydraulic motor; a braking pressure generating device that generates braking pressure in the main conduit lines on the return side in a state where the spool of the control valve is positioned in the neutral position as a result of being operated by the operation member, the braking pressure opposing rotation of the hy

Abstract: A reverse torque drive system for a wellhead has a hydraulic pump having an inlet and an outlet, and a hydraulic motor having a first port and a second port. There is a valve body having a first position that connects the outlet of the hydraulic motor to the first port and the second port to the inlet, and a second position that connects the outlet to the second port and the first port to the inlet. One or more sensors are connected to measure a condition, and a controller moves the valve body from the first position to the second position upon the sensor sensing a predetermined condition.

Abstract: A machine includes a hydraulic fan system for circulating cooling air through an engine compartment. Periodically, the fan rotation direction is briefly reversed in order to dislodge any material debris that may have accumulated at the inlet to the engine compartment. When a fan reversal event is initiated, the fan motor will continue to rotate due to angular momentum even after the pump output flow has been switched from a first motor port to a second motor port. During this continued rotation as the fan decelerates to zero speed, vacuum pressure levels can arise at the first motor port, and a pressure spike can develop at the second motor port. In order to alleviate these conditions, a pressure transfer valve briefly opens to facilitate fluid flow directly from the second motor port to the first motor port as the fan motor decelerates towards zero speed before reversing direction, simultaneously alleviating vacuum and pressure spike conditions.

Abstract: An invention relating to a control apparatus and a control method for a hydraulically driven cooling fan for reducing the peak pressure produced upon reversing the switch position of a switching valve, without stopping an engine, and without greatly modifying existing hydraulic circuitry or increasing the apparatus cost. In the invention, in the case that a reversing switch has been operated so as to output a reversal processing commencement instruction signal, control is carried out such that, under the condition that the rotational speed of the engine has decreased to not more than a stipulated rotational speed, capacity adjusting means is controlled, so as to reduce the capacity of a hydraulic pump, and thus reduce the fan rotational speed, and then the switch position of the switching valve is reversed.

Abstract: A hydraulic motor is driven by a fixed displacement, three stage gear-type pump. The three equal displacement sections provide 3 equally-stepped flows so that the hydraulic motor can have three speeds. Valving and controls are provided for remote on-the-fly shifting of the speeds, automatic pump unloading in neutral, and adjustable maximum pressure. A closed loop system permits use of a relatively small reservoir. The contamination tolerance of the system is greater than that of variable displacement piston-type pumps typically used. Direct recirculation of hydraulic fluid is provided for unused speeds to permit hydraulic fluid to recirculate in the pump without doing work. A unique control circuit is provided to control the first speed valve in conjunction with a logic cartridge which controls hydraulic motor direction to permit fluid flow to the hydraulic motor to be stopped when coming to neutral without slamming the hydraulic motor and rotating drill pipe to a stop.

Abstract: A transmission for a vehicle includes a fixed displacement pump operable to produce a high pressure flow and a fixed displacement motor. A fluid flow path is disposed between the pump and the motor. The fluid flow path is integrated into a housing containing at least one of the pump and the motor. A single control valve controls the direction and the speed of the motor.

Abstract: The present invention includes: a hydraulic pump 10 that is driven by a driving motor; a travel motion motor 12 that is driven with pressure oil supplied from the hydraulic pump 10; a travel motion control valve 11 that controls a flow rate of the pressure oil supplied from the hydraulic pump 10 to the travel motion motor 12; a means for operation 22a with which the travel motion control valve 11 is operated; a means for rotation rate detection 95 that detects a rotation rate N of the travel motion motor 12; and a means for motor over rotation prevention 14, 17, 32 that reduces the rotation rate of the travel motion motor 12 if the means for rotation rate detection 95 detects a rotation rate equal to or higher than a predetermined rotation rate upper limit Nmax.

Abstract: An open hydraulic circuit comprising a main pump (P), a hydraulic motor (M), two main ducts (10, 12) constituting a feed main duct and a discharge main duct and connected to the pump or to a reservoir (R) via a feed selector (14). The circuit further comprises a multifunction valve device comprising a multifunction selector (20) for connecting the main duct that is at the higher pressure to a pressure limiter (24) and for connecting the main duct that is at the lower pressure to booster means (16), and for interconnecting the main ducts by connecting them to the pressure limiter when the pressures in the main ducts are substantially mutually equal.

Abstract: A rotary control valve for a vehicle hydrostatic transmission includes a hydraulic pump and a hydraulic motor. The valve is configured to control both a direction and a speed of the hydrostatic transmission. The rotary control valve includes a rotary valve plate configured to oscillate through a range of less than 180 degrees independently of the pump and the motor.

Abstract: A motor arrangement for a pneumatic tool includes a motor cylinder defining a motor chamber, an inlet passage adapted to receive a flow of motive fluid, forward and reverse passages communicating with the motor chamber, a throttle port, and at least one exhaust port. A motor rotor rotates in a forward direction in response to motive fluid flowing into the motor chamber from the forward passage and in a reverse direction in response to motive fluid flowing into the motor chamber from the reverse passage. A valve actuates to selectively place one of the forward and reverse passages in communication with the inlet passage for the provision of motive fluid from the inlet passage to the selected one of the forward and reverse passages. A throttle mechanism including a throttle actuator extends through the throttle port and is actuable to control the flow of motive fluid through the inlet passage.

Abstract: A machine includes a hydraulic fan system for circulating cooling air through an engine compartment. Periodically, the fan rotation direction is briefly reversed in order to dislodge any material debris that may have accumulated at the inlet to the engine compartment. When a fan reversal event is initiated, the fan motor will continue to rotate due to angular momentum even after the pump output flow has been switched from a first motor port to a second motor port. During this continued rotation as the fan decelerates to zero speed, vacuum pressure levels can arise at the first motor port, and a pressure spike can develop at the second motor port. In order to alleviate these conditions, a pressure transfer valve briefly opens to facilitate fluid flow directly from the second motor port to the first motor port as the fan motor decelerates towards zero speed before reversing direction, simultaneously alleviating vacuum and pressure spike conditions.

Abstract: A hydraulic motor is driven by a fixed displacement, three stage gear-type pump. The three equal displacement sections provide 3 equally-stepped flows so that the hydraulic motor can have three speeds. Valving and controls are provided for remote on-the-fly shifting of the speeds, automatic pump unloading in neutral, and adjustable maximum pressure. A closed loop system permits use of a relatively small reservoir. The contamination tolerance of the system is greater than that of variable displacement piston-type pumps typically used. Direct recirculation of hydraulic fluid is provided for unused speeds to permit hydraulic fluid to recirculate in the pump without doing work. A unique control circuit is provided to control the first speed valve in conjunction with a logic cartridge which controls hydraulic motor direction to permit fluid flow to the hydraulic motor to be stopped when coming to neutral without slamming the hydraulic motor and rotating drill pipe to a stop.

Abstract: A hydraulic control apparatus for marine reversing gear assembly for watercraft includes a pressure reducing valve 22 for adjusting the pressure of a working oil supplied from a working oil supply pump 1, and supplying the working oil to forward and reverse clutches 2a, 2f; a proportional electromagnetic valve 21 for controlling the supply of the working oil to a pilot chamber of the pressure reducing valve 22; and a spring-type switching valve 23 for switching to a circuit for supplying the working oil to a control piston chamber for controlling a set spring force of the pressure reducing valve 22 or to a circuit for draining the working oil from the control piston chamber; wherein a pressure output from the proportional electromagnetic valve 21 acts upon the switching valve 23 as a pilot pressure; and wherein, when the pilot pressure falls below a predetermined value, the switching valve switches to the circuit for supplying the working oil to the control piston chamber via the spring of the switching valve

Abstract: Apparatuses for converting pressure differences of gaseous or liquid media into rotary motion are provided. In some embodiments, apparatuses for utilizing the pressure differences of gaseous, vaporous or liquid media by pressure expansion of the media are provided, the apparatuses comprising: a housing having an inner wall with a length; a plurality of hose pieces positioned in the housing on the inner wall with a length corresponding at least to the length of housing wall; inlet valves and outlet valves coupled to the hose pieces that substantially synchronously regulate a sequence of filling and emptying of the hose pieces by the media; a roller that is positioned between the hose pieces, that rotates on an eccentric, and that rotates in connection with the tilling and emptying of the hose pieces; and a shaft coupled to the roller at the eccentric that rotates as the roller rotates.

Abstract: A hydraulic hybrid powertrain system includes a power plant generating a high pressure fluid at an output, at least one drive motor responsive to the high pressure fluid for generating rotary motion at an output, and a mode selection device connected to the power plant output and the drive motor for selecting a mode of operation from a plurality of drive motor modes of operation including at least two of a drive mode, a neutral mode, a reverse mode and a park mode. The system includes a control device connected to the power plant and the drive motor for controlling operation of the drive motor in the plurality of modes of operation, a selectively actuated brake device for interrupting high pressure fluid flow to the drive motor, and a check valve bridge circuit for connecting the drive motor to a low pressure fluid source when the brake device is actuated.

Abstract: The circuit includes a main pump, a hydraulic motor, two main ducts, a selector for connecting the main ducts to the main pump or to a reservoir or for isolating them therefrom, a boost duct, and two pressure limiters disposed between the main ducts. A relief valve device that can take up a retention position and a relief position in which it connects one main duct (14, 16) to a relief enclosure can take up its relief position when, with the selector isolating the main ducts from the main pump and from the reservoir, the difference between the pressure in the main duct to which the control duct is connected and a relief pressure higher than the boost pressure changes sign.

Abstract: An apparatus comprises a valve body having a cylindrical bore centered on an axis. A cylindrical core extends axially within the bore and is fixed relative to the valve body. A sleeve within the bore extends circumferentially about the core and is rotatable about the axis relative to the core. A passage extends radially through the sleeve and provides a radial flow path from the core through the passage to the valve body. Alignment of the passage is circumferentially selectable by rotation of the passage with the sleeve about the axis.

Abstract: An apparatus controls fluid flow to an actuator. A feedback mechanism responds to a pressure differential that occurs across the actuator by altering the fluid flow. That pressure differential indicates acceleration of the actuator that can occur when the load acting thereon varies. Thus as the actuator accelerates, the apparatus reduces the flow of fluid which counteracts the acceleration and maintains the actuator speed relatively constant. A unique directional control valve incorporates the feedback mechanism that functions regardless of the direction in which the actuator moves.

Abstract: An oil-hydraulic vehicle comprising (i) at least one oil-hydraulic pump 10 driven by an engine E, an input shaft of said oil-hydraulic pump being directly coupled with a crankshaft C of the engine, (ii) at least one oil-hydraulic motor 30 to drive at least one wheel 31 in both forward and backward directions, (iii) an oil-hydraulic circuit 50 to connect said oil-hydraulic pump 10 and said oil-hydraulic motor 30, and (iv) at least one flow control valve 60 provided between said at least one oil-hydraulic pump 10 and said at least one oil-hydraulic motor 30.

Abstract: A spool valve includes a first valve port coupled to a fluid source at a first pressure range, a second valve port coupled to a fluid source at a second, lower, pressure range, and first and second output ports coupled to a hydraulic device. The valve includes a valve spool configured to selectively channel fluid from the first and second valve ports to the first and second output ports, respectively, while in a first position, from the second valve port to both the output ports while in a second position, and from the second and first valve ports to the first and second output ports respectively, while in a third position, and a check valve to permit one-way fluid passage from the second output port to the first valve port. The valve may include an anti-reverse check valve configured to prevent fluid from flowing into the valve via the first output port.

Abstract: A cooling system for use in a work machine is provided, in which an increase in the load imposed on a fan driving circuit and occurrence of abnormal noise can be prevented without fail by means of an inexpensive arrangement at the time of switching the rotating direction of a cooling fan. To this end, the cooling system comprises: (1) a variable displacement hydraulic pump driven by the engine; (2) a forwardly and reversely rotatable hydraulic motor operated by hydraulic oil supplied from the hydraulic pump; (3) a cooling fan driven by the hydraulic motor; (4) an electromagnetic selector valve for switching the rotating direction of the hydraulic motor between a forward direction and a reverse direction; (5) controlling means for controlling switching of the electromagnetic selector valve and controlling the hydraulic pump so as to minimize the discharge oil rate of the hydraulic pump during switching of the electromagnetic selector valve.

Abstract: A hydraulic drive system has a variable displacement hydraulic pump; a prime mover driving the hydraulic pump; a variable displacement hydraulic motor fed hydraulic fluid by the hydraulic pump, the hydraulic motor having internal torque control and speed modulation via the variable displacement; and a shaft driven by the hydraulic motor. The prime mover is either an electric motor or an internal combustion engine, advantageously a diesel engine. The system is either an open loop hydraulic system or a closed loop hydraulic system. With the system, relatively low output prime movers are used without reduction in the systems maximum torque output.

Abstract: A loop flushing circuit for a hydrostatic transmission module includes a three position, three port pilot pressure operated loop flushing valve having a first inlet port fluidly connected to the first system pressure line, a second inlet port fluidly connected to the second system pressure line and an outlet port fluidly connecting the loop flushing valve to the case drain through a drain line having a drain orifice therein. A loop flushing and lubrication line fluidly connected to the drain line upstream of the drain orifice extends within the casing and has an open end directed toward the rotating elements of one of the pump and motor. The three position valve has an intermediate position operatively located between the opposite end positions. System pressure from at least one of the first and second system pressure lines is always routed to the loop flushing and lubrication line through the valve regardless of which of the three positions the valve is in.

Abstract: If a first control valve 71 is arranged so as to change between a flow position A and a throttling position C by a fluid for switching purpose guided through a pilot channel 77, the flow area of a first intermediate channel can be changed in two steps. As a result, the injection-valve opening pressure and time of a first relief valve 48 change between two types of values, whereby the physical shock occurring when a crawler vehicle stops can be switched between two types of shock.

Abstract: A hydraulic motor driving apparatus includes a directional control valve for supplying discharge pressure fluid from a hydraulic pump into a first or second port of a hydraulic motor and returning the hydraulic fluid from the second or first port into a tank, and a pilot pressure applying valve for controlling the directional control valve. The directional control valve is urged to its neutral position by springs, to its first position by hydraulic pressure against its first pressure receiving portion and to its second position by hydraulic pressure against its second pressure receiving portion. Discharge pressure fluid from the hydraulic pump is supplied via a check valve into the first and second ports of the hydraulic motor when the directional control valve is at the neutral position. The discharge pressure fluid is supplied into the first port of the hydraulic motor and a hydraulic pressure fluid of the second port flows into the tank, when the directional control valve is at the first position.

Abstract: A reverse rotation preventing apparatus for a hydraulic actuator includes a hydraulic actuator for driving an inertia member, a main valve which is switched to a driving position in which a pressure oil is supplied to one of first and second ports of the hydraulic actuator and another one thereof is communicated with a tank and to a neutral position in which the first and second ports are shut off, a relief valve adapted to flow out a pressure oil in the first or second port to the tank at a time when a pressure on the side of the first or second port is higher than a set high pressure, a suction valve adapted to suck the pressure oil to the first or second port at a time when the pressure on the side of the first or second port is negative, and a reverse rotation preventing valve adapted to communicate the first and second port sides with the tanks respectively at a time when the pressure on the sides of the first and second ports is higher than a set pressure which is a pressure lower than the set high pres

Abstract: A hydraulic system for driving an axial piston type hydraulic motor wherein a swash plate can tilt at a right angle relative to a shaft.

Abstract: An automatic hydrostatic transmission in which two vane pumps have their pumping chambers coupled together in a closed circuit with a constant volume of hydraulic fluid, the volume of each pump being changed by the axial displacement of a moving side of the chamber and the respective rotor toward and away from a diaphragm through which the vanes can extend so that either pump can act as the displacement inducer or as the driven member. One of the rotors has a nut provided on a large-pitch screw for automatic adjustment of the pump chamber volume in accordance with load conditions while the other moving side assembly has a key and keyway connection to its shaft.

Abstract: A hydrostatic transmission is disclosed comprising a radial ball pump (11) and a radial ball motor (13) wherein the normal journal member (33) may be replaced by an alternative or modified journal member (33'), such that even with a reverse direction of actuation of the displacement control (49), the HST still operates in the forward direction, with no other changes required. The present invention also includes a simplified dump valve member (107) comprising a single, unitary member which may be merely inserted to its assembled position in which a pair of retention portions (123, 135) retain the dump valve, and permit it to pivot about the retention portions from an unactuated position to an actuated position.

Abstract: Roughness or jerkiness in a hydraulic swing circuit in an implement having a plurality of control circuits each having a work performing device (28), (30), (32) including a swing circuit having a hydraulic motor (32), which when under an aiding load may function as a pump, is avoided in a construction that includes a source (10) of hydraulic fluid under pressure and a plurality of control valves (22), (24), (26) for the circuits which are interconnected between the source (10) and the associated work performing device (28), (30), (32). The system includes a pair of hydraulic conduits (34), (36) extending from the control valve (26) for the swing circuit to the hydraulic motor (32). A pair of pilot operated, dual level pressure relief valves (56), (58) are connected oppositely across the conduits (34), (36) at a location between the control valve (26) for the swing circuit and the hydraulic motor (32).

Abstract: A hydraulic system comprises a mechanical brake assembly having a brake piston engageable with an output rotation shaft of a hydraulic motor, a cylindrical casing having the brake piston slidably received therein and a brake spring resiliently urging the brake piston to engage with the output rotation shaft of the hydraulic motor. The brake piston and the cylindrical casing collectively define a main hydraulic chamber held in fluid communication with a release fluid passageway which is communicable with a hydraulic pump and a reservoir tank through a shuttle valve and a directional control valve. The brake piston and the cylindrical casing further collectively define a secondary hydraulic chamber held in fluid communication with the release fluid passageway through a fluid feed/return passageway on which a brake resistance restrictor provided for restricting flow of the working fluid in the fluid feed/return passageway.

Abstract: Roughness or jerkiness in a hydraulic swing circuit in an implement having a plurality of control circuits each having a work performing device (28), (30), (32) including a swing circuit having a hydraulic motor (32), which when under an aiding load may function as a pump, is avoided in a construction that includes a source (10) of hydraulic fluid under pressure and a plurality of control valves (22), (24), (26) for the circuits which are interconnected between the source (10) and the associated work performing device (28), (30), (32). The system includes a pair of hydraulic conduits (34), (36) extending from the control valve (26) for the swing circuit to the hydraulic motor (32). A pair of pilot operated, dual level pressure relief valves (56), (58) are connected oppositely across the conduits (34), (36) at a location between the control valve (26) for the swing circuit and the hydraulic motor (32).

Abstract: A hydraulic drive system for actuating a reciprocating member such as a polished rod in a pump jack device, and for acting as a counterbalance and/or for energy conservation. The system has two hydraulic circuits and a prime mover. A first circuit includes a cylinder for driving an output member which may be connected to the polished rod, a first pump of the variable displacement, reversible flow type, together with a pair of fluid lines forming with the cylinder a closed-loop circuit. A controller is programmed to control the setting of the first pump so as to establish the velocity profile of the output member. A second hydraulic circuit is also in the form of a closed-loop containing first and second pumps, at least one of which is of the variable displacement type and is also controlled by the controller.

Abstract: A hydraulic drive system has a consumer of hydraulic power connected to a pressure medium source, e.g., a hydraulic motor 1. The consumer can be actuated by a control valve 4 throttling in intermediate positions; its width of opening is determined by a pressure difference formed at the control valve 4. The pressure difference is derived from a control pressure to be prescribed and the load pressure of the consumer. The consumer can thus be driven with a definite power or a definite torque. To limit the movement speed of the consumer, it is proposed to reduce the control pressure as a function of the speed of movement. The control pressure is present in a control pressure line 7 or 8, which empty at a charging space of the control valve 4, active in the opening direction. A drain line 16 branches from the control pressure line 7 or 8, in which a multiway valve spring-loaded in the closing direction and throttling in intermediate positions is located.

Abstract: An inertial body drive mechanism which is arranged to prevent a reversing motion of a hydraulic motor 1 after an inertial rotation and which is capable of stopping the hydraulic motor 1 quickly together with an inertial body. An oil chamber 26 of a reversing motion preventive valve 21 and an oil reservoir chamber 34 of an oil suction feeder 32 are communicated with each other through a tank conduit 27 with a throttle 38. Operating oil is supplied into and out of the oil chamber 26 by way of the oil reservoir chamber 34 of the oil suction feeder 32 in relation with displacement of a piston operating in response to oil pressure acting in a pilot chamber 33. When inertial rotation of the hydraulic motor 1 is once stopped, operating oil is supplied from the oil reservoir chamber 34 to the oil chamber 26 thereby sliding the reversing motion preventive valve 21 from a closed position (a) to an open position (b) to prevent reversing motions of the hydraulic motor 1.This application is a designated filing under 35 U.

Abstract: A hydrostatic drive system including a pump and a hydraulic motor in an open circuit which includes a feed line and a control valve in the feed line on the inflow side of the hydraulic motor to control the quantity of hydraulic pressure medium supplied to the hydraulic motor. A brake valve is located in the open circuit on the outflow side of the hydraulic motor to receive hydraulic pressure medium flowing out of the hydraulic motor. The control valve and the brake valve are constructed for independent actuation so that the functions of the control valve and the brake valve can be reversed when the direction of rotation of the hydraulic motor is reversed and the actuating pressure on the brake valve in the braking phase depends on the inflow pressure to the hydraulic motor independently of the actuating pressure on the control valve.

Abstract: A method and device for regulation of the output power of a fluid power motor involving the bypass of a selected portion of the supplied pressure fluid to the motor exhaust as a means of effectively reducing the available pressure drop across the motor and thereby its power output.

Abstract: The assembly of a fluid motor with two cubic capacities and of a brake which is coupled thereto, is disclosed. According to the invention, the large cubic capacity of the motor can be selected only when the brake is in its brake-release configuration. One application of the invention is the production of a "braked" motor provided with a relatively small, but operationally reliable brake.

Abstract: The invention refers to a hydraulic circuit for limiting the torque of a hydrostatic hydraulic motor connected in closed circuit to a hydraulic pump, which in braking mode operates as a hydraulic pump, in which pressure control valves are connected before and after the hydraulic motor. For the solution of this problem to develop such a hydraulic circuit which limits the maximum torque at the shaft of the hydraulic motor to approximately identical values independent of the fact whether the hydraulic motor is operated in the motor mode or in the pump mode, the pressure control valves consist of pilot-operated pressure control valves (6,7; 8,9). There is provided at least one on-off valve (5) which, when the hydraulic motor (2) is in the motor mode, switches the pilot-operated pressure control valve of the pressure side to a higher maximum pressure, and in pump mode it switches the pilot-operated pressure control valve of the other pressure side to a lower maximum pressure.

Abstract: A hydraulic-motor drive circuit system includes an auxiliary hydraulic source connected to one end of an auxiliary line, a low-pressure selector connected to the other end of the auxiliary line and a pair of main lines for causing the other end of the auxiliary line to communicate with one of the main lines on the low pressure side during rotation of a hydraulic motor for driving an inertia load, and a switching control arranged in the auxiliary line for supplying the hydraulic fluid from the auxiliary hydraulic source to the other end of the auxiliary line when the directional control valve is in a neutral position, cutting off the hydraulic fluid from the auxiliary hydraulic source to the other end of the auxiliary line when the directional control valve is in an operative position.

Abstract: A hydraulic drive traveling system has a pressure compensated low control valve connected between a hydraulic pump and a variable displacement type hydraulic motor for controlling a flow rate of the hydraulic fluid supplied to the motor. The flow rate is controlled in accordance with the delivery pressure of the pump and demanded traveling speed of the motor. When the delivery pressure of the pump is at a high level, the motor is shifted to a first capacity. When the delivery pressure of the pump is low, the motor is shifted to either the second capacity or the first capacity depending upon the demanded traveling speed.

Abstract: A slewing control device for a hydraulic slewing crane adapted to supply a discharge oil from a hydraulic pump through a slewing control valve to a slewing motor and control a rotational direction and a rotational speed of the slewing motor. The slewing control device includes a brake pressure control valve for variably controlling a discharge pressure of the slewing motor, an acceleration pressure control valve for variably controlling a suction pressure of the slewing motor, and a controller for outputting to both pressure control valves a pressure control signal to be determined according to an operational condition of the crane upon braking of a slewing body and controlling both the discharge pressure and the suction pressure of the slewing motor to control a pressure differential therebetween. Accordingly, even when a braking torque is small, the slewing body can be smoothly braked to be stopped at a target position accurately with no oscillation of a suspended load remaining.