Abstract: A piston/cylinder unit having a selectively inhibited movement includes a cylinder filled with a hydraulic medium and a piston arranged on a piston rod and dividing the cylinder into working spaces. A flow connection system having a flow connection is arranged between the first and second working spaces. The flow connection system includes an on-off valve having a movable valve element which opens the flow connection as a function of a position of the movable valve element. The flow connection system further includes a load-dependent valve arranged in series with the on-off valve for inhibiting complete flow through the flow connection independently from the on-off valve when a load on the piston/cylinder unit is lower than an inhibiting load.

Abstract: To perform boom-down operation by operating a boom cylinder (6) by an external load (W) while simultaneously operating an arm cylinder (26) or a bucket cylinder (27) in the state the bucket is off the ground, a first boom directional control valve (2) and a regeneration boom valve (13) are controlled to the neutral position and the open position respectively so that the hydraulic oil is regenerated from a line (9) located at the oil-returning side of the boom cylinder (6) through the regeneration boom valve (13) to a line (5) located at the oil-feeding side. Therefore, the volume of the hydraulic oil that can be supplied from the pressurized oil source (4) to the arm cylinder (26) or the bucket cylinder (27) via the second arm directional control valve (24) or the bucket directional control valve (25) is increased by the amount equivalent to the amount of the oil that is not supplied from the pressurized oil source (4) to the boom cylinder (6).

Abstract: The invention relates to a device for adjusting the pressure in the chambers of a hydraulic jack comprising a hollow valve seat extending substantially longitudinally between two end sections, the body of the valve seat being connected to a source of pressurised fluid, each of the end sections of the valve seat being linked to a chamber of the hydraulic jack and adapted to receive a valve allowing to control the refilling with hydraulic fluid of said chamber of the jack, characterised in that a valve return spring is placed inside said valve seat and in that each of the ends of said valve return spring is attached to one of said valves.

Abstract: An electromotor M of a electrohydraulic motor pump aggregate G drives at least one pump stage P, P1, P3. An attached element C is inserted between at least one pressure side port of the pump stage, a return line 13, and at least one consumer port A, B, 5, 6. A multiways control valve 3 is installed between the consumer port and the pressure side port. A pressure limiting valve R1, R2 constructed as a seated valve is installed between the consumer port A, B, 5, 6 and the return line 13. The motor pump aggregate G has an automatic hydraulic pressure relieving device D for relieving the system pressure whenever the electromotor M is switched off.

Abstract: A piston/cylinder unit, in particular a gas spring, includes a valve device for the operational motion of a piston rod. The valve device is activatable by an activation device, the activation device being connected near an actuation device and being connected to a load contact device, which influences the function of the valve device. The load contact device connects the actuation device to the valve device for the purpose of changing the adjustability of the valve device when the gas spring is loaded.

Abstract: A fluid circuit is provided to independently control the flow of fluid into and out of each end of an actuator. This is accomplished by having two different independently controlled valves controlling the flow of fluid into and out of one end of the actuator and by having two other independently controlled valves controlling the flow of fluid into and out of the other end of the actuator. Regeneration of the fluid flow from one end of the actuator to the other end of the actuator is provided by blocking the exhaust flow of fluid to the reservoir by one of the independently controlled valves and redirecting the flow across the other of the independently controlled valves to join with the flow of the pump that is being directed to the other end of the actuator. This arrangement permits a portion or all of the fluid from one end of the actuator to be regenerated to the other end of the actuator.

Abstract: A hydraulic system includes an air sucking hydraulic circuit 8, an air sucking control valve 5, and a check valve 6 provided in or before and after the air sucking hydraulic circuit 8, hereby allowing a hydraulic fluid from the air sucking control valve 5 to flow to the hydraulic actuator 4 and preventing a flow of a hydraulic fluid from the hydraulic actuator 4 to the air sucking control valve 5.

Abstract: A hydraulic system for damping the motion of rotation of a swivel joint between two vehicle parts of an articulated vehicle, of an articulated bus for example, comprising a hydraulic damping device as well as an electrically triggerable proportional pressure control valve, whereas the proportional pressure control valve is arranged between the force side and the suction side of the damping device, a mechanical pressure control valve (103) being provided in addition to the proportional pressure control valve (104) in the conduit between the suction side and the force side of the damping device, and whereas a multiple-way valve is provided for the alternative drive of the pressure control valve (103) or of the proportional pressure control valve (104).

Abstract: The two working chambers (2, 2′, 3) of a working cylinder (1) of a hydraulic actuation arrangement may be directly connected with one another via a switchable dual-position valve (11), if necessary, whereby a resistance-free manual displacement of the components to be actuated is possible to a large extent—regardless of the working cylinder (1) that is driven by the hydraulic circuit (6) or also in case of a malfunctioning or a turned-off pressure medium source.

Abstract: A work machine is disclosed. The work machine includes a work implement and a fluid cylinder mechanically coupled to the work implement. The fluid cylinder is controlled by an apparatus that automatically places the fluid cylinder in a float mode of operation when a control valve fluidly coupled to the fluid cylinder is placed in a neutral position.

Abstract: An air pressure tube assembly for elevation-adjustable seat stand is constructed to include a barrel, an inner tube mounted inside the barrel, a top cap mounted in one end of the barrel, a first valve and a second valve connected in a line between the top cap and the inner tube inside the barrel, a bottom cap fastened to one end of the inner tube remote from the top cap, a pin adapted to close/open the first valve and the second valve, a bolt fastened to the top cap and extended out of the barrel, a piston assembly axially movably mounted in the inner tube, and small and big O-rings sealed between the parts of the air pressure tube assembly, the top cap, the first valve, the second valve, the inner tube and parts of the piston assembly being respectively injection-molded from plastics.

Abstract: An attachment connectable to a boom member of a machine for performing work functions generally consisting of a handle pivotally connectable to a boom member of the machine, a ground engageable arm member pivotally connected to the handle and an extendable strut assembly interconnecting the handle and arm member consisting of a hydraulic cylinder assembly having a cylinder member pivotally connected to the handle and a rod member pivotally connected to the arm member, and including means intercommunicating the base and rod ends of the cylinder member, at least one electrically operable valve disposed in the intercommunicating means and operatively connectable to control means disposed on the machine, selectively operable to open the valve and permit the free flow of fluid between the base and rod ends of the cylinder member, and correspondingly the angular displacement of the arm member relative to the handle upon maneuvering the arm member by an operator of the machine, and to close and preclude the free flo

Abstract: An improved method and apparatus utilizing regenerative hydraulic control principles are disclosed. A regenerative valve is operatively connected in a hydraulic control circuit with a primary hydraulic cylinder for controlling the speed at which the piston and attached rod of the hydraulic cylinder operatively move. The regenerative valve and control apparatus and method control speed of operation of the primary hydraulic cylinder when moving in both its power and its return strokes, to significantly reduce the cylinder's cycle time. A unique regenerative valve configuration enables significantly enhanced volumes of hydraulic fluid to be transferred during a regeneration cycle between the rod and blind sides of the hydraulic cylinder.

Abstract: The present invention is directed to a control circuit for automatically bringing a hydraulically operated work arm into a particular position without having to manually reverse the direction of the hydraulic operating system.

Abstract: A hydraulic system for a forklift includes a handle angle sensor for outputting a rotational angle signal indicative of a rotational angle of a handle, a wheel angle sensor for outputting a wheel angle signal indicative of a steering angle of wheels, and a controller. The controller calculates a rotation angular velocity of the handle based on the rotational angle signal from the handle angle sensor to discharge from the hydraulic pump the hydraulic fluid of a flow rate in conformity with this rotation angular velocity, and controls the flow rate of the hydraulic fluid supplied to the power steering cylinder based on the rotational angle signal from the handle angle sensor and the wheel angle signal from the wheel angle sensor to steer the wheels in conformity with the rotational angle of the handle.

Abstract: A fluid control system provides a float capability for a double-acting actuator. The system includes pilot operated check valves disposed between the double-acting actuator and first and second ports of a pilot operated directional control valve. The directional control valve and the check valves are cooperatively operable under first and second pilot signal conditions to extend and retract the double-acting actuator. The system includes a valve arrangement connected to the check valves and the directional control valve for producing the first and second pilot signal conditions thereon, including also directing the first pilot signal condition to the second pilot signal condition when the first pilot signal condition reaches a predetermined signal strength, to initiate a float capability.

Abstract: A fluid control circuit providing a float capability for a double-acting actuator having first and second actuating chambers is provided. The fluid circuit includes signal controlled load check valves disposed between the actuating chambers and a directional control valve. The directional control valve is movable from a centered, neutral position towards first and second operative positions and a float position. The directional control valve and the load check valves are cooperatively operable in one operable position to allow fluid flow from the first actuating chamber to the exhaust port, and fluid flow from the pump port to the second actuating chamber. In the float position of the directional control valve, both of the signal controlled load check valves are opened to allow open fluid flow between the first and second actuating chambers thus allowing the tool attached to the actuator to float.

Abstract: To provide a particularly simple and cost effective design of a power-assisted steering unit for motor vehicles for supplying a servo-cylinder (3) with a hydraulic fluid as a function of the travelling speed and the steering rate, comprising a steering valve (1) by means of which the left and right chambers (16, 17) of the servo-cylinder (3) can be pressurized with hydraulic fluid via a pump (2) when there is a steering movement, and a bypass valve (10) connected in parallel to the servo-cylinder (3), by means of which a portion of the hydraulic fluid for pressurizing the servo-cylinder (3) that is directed past the servo-cylinder (3) is controlled, a throttling unit (26) is connected in series with the bypass valve (10). The hydraulic fluid inflow or return flow of the servo-cylinder (3) flows through this throttling unit (26) depending on the steering direction.

Abstract: An attachment connectable to a boom member of a machine for performing work functions generally consisting of a handle pivotally connectable to a boom member of the machine, a ground engageable arm member pivotally connected to the handle and an extendable strut assembly interconnecting the handle and arm member consisting of a hydraulic cylinder assembly having a cylinder member pivotally connected to the handle and a rod member pivotally connected to the arm member, and including means intercommunicating the base and rod ends of the cylinder member, at least one electrically operable valve disposed in the intercommunicating means and operatively connectable to control means disposed on the machine, selectively operable to open the valve and permit the free flow of fluid between the base and rod ends of the cylinder member, and correspondingly the angular displacement of the arm member relative to the handle upon maneuvering the arm member by an operator of the machine, and to close and preclude the free flo

Abstract: The invention relates to a hydraulic unit for feeding an object at a desired feed speed a distance in a given feed direction during a working stroke and, in a return stroke, bringing the object back to the initial position at a considerably greater return speed, comprising a double-acting working cylinder (1) with a piston (16), the piston rod (17) of which is connected to the object which is to be moved, and a receiver cylinder (2) which is provided with a second piston (28) and designed to be filled with oil from the working cylinder during the return stroke, the first piston (16) and the second piston (28) being interconnected by a rigid connecting member (31) which forces the second piston to follow the movements of the first piston.

Abstract: A hydraulic actuator and a method for degassing hydraulic actuators having t least two chambers are disclosed. For actuating a hydraulic element, for example a piston in a piston-and-cylinder unit the hydraulic actuator may be supplied with pressurized hydraulic fluid from a hydraulic source via gate valves. The chambers may be interconnected via another gate valve such that when the other gate valve is open, a closed flushing circuit may be configured, starting from a hydraulic fluid container via a hydraulic pump, a first gate valve, a first chamber, the additional valve, a second chamber, a second gate valve and back to the hydraulic fluid container.

Abstract: For a hydraulic rack-and-pinion steering assembly for which a working piston is guided in a hydraulic cylinder which features an end limit stop by which, in an end position of the working piston, a path for the pressure agent supplied to the working piston by drill holes for the pressure agent is formed from the working space under pressure to a space of less pressure, in order to improve the hydraulic rack-and-pinion steering assembly such that it is simple to manufacture at limited cost, a rack-and-pinion steering assembly is improved by having, in the region of each pressure supply drill hole, at least one drill hole which can be executed and sealed from the housing exterior and which can be connected by means of a connecting line to the respective pressure supply.

Abstract: In order to improve speed controllability both in low and high speeds, thereby stabilizing the speed of a hydraulic cylinder, both the flow-in amount of hydraulic operating fluid flowing from a hydraulic source to the hydraulic cylinder having a run-around circuit and the flow-in amount of hydraulic operating fluid flowing from the run-around circuit to the hydraulic cylinder are controlled simultaneously by a control valve, so that the speed of the hydraulic cylinder is controlled.

Abstract: Cylinder drift resulting from internal leakage of a recycling circuit, which recycles oil returned from the arm cylinder of a hydraulic shovel to the hydraulic supplying end, is reduced by an hydraulic circuit which includes a recycle valve attached directly to a control valve. When working fluid is returned from a rod chamber of arm cylinder into the control valve, the recycle valve recycles a part of the working fluid through a recycle selector valve to the hydraulic supplying end. A pilot operated check valve is disposed in the oil channel that connects the rod chamber and recycle selector valve together. When extending arm cylinder of the hydraulic shovel, pilot pressure from control valve shifts a pilot selector valve in such a direction as to open pilot operated check valve. When control valve is at the neutral position, pilot selector valve is shifted back to the return position and closes pilot operated check valve so that return oil of arm cylinder is prevented from working on recycle selector valve.

Abstract: A novel adjustment assembly for use with a hydraulic control apparatus. The hydraulic control apparatus is attached to a hydraulically operated tool to provide a desired hydraulically powered function. The present invention allows the hydraulic control apparatus to be used with either a constant volume (open-center) hydraulic system or constant pressure (closed-center) hydraulic power system. The novel adjustment assembly of the present invention provides a structure which can be configured to force open shuttle spool valves in the control apparatus in a neutral condition for use with a constant volume power supply. The adjustment assembly can also be configured to be disengaged from the shuttle spool valves in a neutral condition for use with a constant pressure hydraulic power system. Operation of the adjustment assembly is made using standard tools and without disassembly of the control apparatus.

Abstract: A valve includes a distributor with four ports and two positions. In a first position, a first non-return valve allows only circulation of a fluid from the first port toward the third port, while the second port and the fourth port are directly in communication with one another. In a second position, the third port and the fourth port are directly in communication with one another, while a second non-return valve allows only circulation of fluid from the third port and the fourth port in communication toward the first port.

Abstract: This power steering cylinder assembly, may replace the cylinder assembly in some present power steering systems, or may be used in a new system. When the oil pressure drops or disappears, in some of the power steering systems in use today, manual steering must be used. The piston is then pushed back and forth in a fluid filled cylinder. The oil in the chamber in front of the piston, must then be pushed through a small opening back to reservoir, and the oil in the chamber in back of the piston must be drawn from the pump. This results in an additional resistance load on the piston. By using the new cylinder assembly when the pressure drops or disappears, the oil will readily circulate from the chamber in front of the piston to the chamber in back of the piston, thereby relieving much of the resistance of the piston as it is being pushed back and forth by manual steering.

Abstract: The use of an accumulator attached to a chamber of a cylinder allows for the reduction in pressure spikes in constant force hydraulic control systems. Constant force hydraulic control systems often use a differential pressure valve that may have a reaction time of up to one second. By using the accumulator, pressure spikes which might have occurred in the past can be smoothed out and reduced, thus preventing damage to a workpiece or agricultural product. Additionally, by using two cylinders of different sizes, in which one of the cylinders has a barrel end with the approximately the same area as the rod end of the larger cylinder, coordination of devices attached to the cylinders can be maintained without a mechanical link when the hydraulic control system is in a manual mode.

Abstract: The hydraulic circuit directional control valve 20 is provided in a line connected with a lower chamber 13 of the hydraulic cylinder 1 and the B-port of the servo valve 3. A check valve 22 permitting oil flowing into the P-port of the servo valve 3 from the lower chamber 13 is provided in the line in parallel with the hydraulic circuit directional control valve 20 and connected with the lower chamber 13 and the P-port of the servo valve 3. When making the ram 15 move downward with high speed, the hydraulic differential circuit is constituted by changing the hydraulic circuit directional control valve 20 such that the delivery oil exhausted from the lower chamber 13 returns to the P-port of the servo valve 3. The hydraulic oil supplied from the hydraulic pump 1 flows into the upper chamber 12 through the servo valve 3. The delivery oil exhausted from the lower chamber 13 returns to the suction side of the P-port of the servo valve 3 through the check valve 22, assisting the flow rate of the hydraulic pump 2.

Abstract: The present invention is directed to a vehicular power steering system having an "open-center" control valve that has substantially zero hydraulic flow gain at zero input deflection angle and yet has minimal control orifice area. An improved valving sub-assembly is used in the control valve with functions to rapidly restore hydraulic gain at relatively small input deflection angles. The improved valving arrangement includes small transverse leakage slots formed in a valve spool that are in fluid communication with either input or return flow distribution slots. The leakage slots are configured to form parasitic flow orifices which fluidically interconnect the output slots formed in the valve sleeve and which communicate with the fluid chambers formed on opposite sides of the piston in the power cylinder. Accordingly, a selectively variable leakage path is provided across the power cylinder.

Abstract: A hydraulic power drive unit (36) including a linear hydraulic piston cylinder unit (64) with a set of longitudinally spaced gear teeth (84) in the form of a rack. A pinion gear (86) is operatively engaged and driven by the rack (84). A differential which may include a carrier (102), planet gears (108, 110) and sun gears (120, 122) may be driven by the pinion gear (86) to selectively transfer drive power to two separate rotary drive outputs (38, 40). A switching valve (160) may be provided which is responsive to a reversal of hydraulic supply pressure. Operation of the switching valve (160) may be limited by mechanical interference between an inhibit dog (181) and a cam surface (196) on the carrier (102). The carrier (102) may also include a separate cam surface (140) positioned for actuation of separate electrical switches (146, 148) in order to monitor position of the drive outputs (38, 40).

Abstract: A hydraulic control apparatus for use with a hydraulically operated tool comprises a valve body operatively and having a valve bore defining an axis. The valve body also defines a pressure port and a return port for connecting the valve bore to a source of hydraulic fluid, and a cross port communicating between the valve bore and the hydraulic tool. A tubular conduit has one end in communication with the valve bore and an opposite end in communication with the hydraulic tool. A selector member is moveable between a first position for defining a passage communicating between the cross port and the opposite end of the tubular conduit to provide a return path for hydraulic fluid between the pressure port and the return port, and a second position for closing off this passage.

Abstract: The invention relates to a hydraulic motor having a motor body comprising a first and a second part (71, 72) which are joined to each other in a parting plane (74). A motor chamber (2) with driving cogwheels (10, 11) is formed by borings (84, 85), which extend from the parting plane into a certain depth in at least one of the first and second parts (71, 72). A by-pass conduit (15) is provided between the inlet and outlet hydraulic conduits of the motor chamber. In the by-pass conduit there is provided a main valve (20) for closing and opening the by-pass conduit for starting and for stopping the hydraulic motor, respectively. The by-pass conduit is formed by portions (16, 17) of a first (100) and a second (101) connection between the parting plane (74) and the inlet conduit (5), and between the parting plane (74) and the outlet conduit (7), respectively, and by a cross link (18) between the first and second connections (100, 101).

Abstract: A fluid actuator of the type for producing reciprocal movement is provided having a cylindrical housing adapted to be secured to a relatively stationary object. The cylindrical housing includes first and second end portions and respective first and second fluid ports positioned therein. A piston is disposed for relative movement within the cylindrical housing and defines first and second fluid chambers within the housing. The first fluid chamber is in communication with the first fluid port and the second fluid chamber is in communication with the second fluid port. A piston rod connects to the piston and extends outwardly from the first end portion of the housing. The piston rod is adapted to be connected to an object to be moved. A conduit communicates with the first fluid chamber through the first fluid port in the first end portion of the housing and extends longitudinally from the first fluid port alongside the housing to the second end portion of the housing.

Abstract: A double acting hydraulic cylinder is a die cushion for a press, with an upper and a lower chamber in communication with each other and with a differential pressure between the two chambers automatically controlled by a valve mechanism. With the differential pressure controlled according to one of several desired curves, the die cushion capability during press operation can be changed and adjusted to a valve suitable for the product to be processed and so a wide variety of products can be produced in high quality and high efficiency.

Abstract: The invention relates to an auxiliary power steering system, especially for motor vehicles having a double acting servocylinder with two working chambers and a servopiston. A hydraulic steering limitation device has a valve that coacts with the servopiston responsive to a predetermined extent of power stroke to open a flow path from the pressurized working chamber to the tank connected working chamber to promptly stop the power stroke leaving the servopiston in position for prompt reversal of steering direction under pressure power. A stationary flow channel member extends the substantial length of the servocylinder and passes through a bore in the servopiston with which it has a sliding relationship. At a predetermined end of a power stroke, bores and a passage in the channel member communicate with the working chambers of the servocylinder to equalize the pressure at tank pressure for stopping the power stroke.

Abstract: A power assisted vehicle steering system of the speed responsive kind has a ram 6 fluid flow to chambers 4 and 5 of which from a pump 9 is directed by an open center steering valve 1. Communication between the chambers 4 and 5 is permissible through a by-pass valve 13 adjustable by a solenoid 17 in response to vehicle speed to open such communication as speed increases (and thereby decrease power assistance) and vice versa. The valve 13 has a spool 22 which is spring loaded relative to a control spindle 18 of the solenoid. Adjustment of the spool 22 in response to speed variations opens or closes by-pass ports 14 and 15 to opposite ends of a restrictor 32 which provides such fluid flow communication.A spring loaded spool 41 in the valve 13 is responsive through chambers 39 and 40 to fluid pressure at opposite sides of the restrictor 32. When the fluid pressure differential across the restrictor 32 exceeds a predetermined differential, the spool 41 is displaced to direct fluid pressure to spool chamber 55.

Abstract: A hydraulic shock absorber controller for a wheel crane having a suspension provided with hydraulic shock absorbers. The hydraulic shock absorber controller connects a line connected to the active chambers of the hydraulic shock absorbers and a line connected to the inert chambers of the same before the wheel crane starts running to enable the working fluid to flow rapidly from the compressed chamber to the expanding chamber of each hydraulic shock absorber so that the hydraulic shock absorbers are able to function properly for shock absorbing operation while the wheel crane is running.

Abstract: Device and procedure for the supply, with recovery of the raising energy, of press actuators having a cylinder within which a piston delimits two chambers, namely an upper and a lower chamber, which are supplied with pneumatic power, the said device having a pneumatic control unit connected to the mains and including at least one supply line to the upper chamber of the actuator and one supply line to the lower chamber of the actuator, these lines having supply and discharge valves, in which device the supply lines to the chambers of the actuator pass through an economizer unit interposed between the control unit and the actuator and including a servocontrolled valve which intercepts the supply line to the upper chamber, a servocontrolled valve which intercepts the supply line to the lower chamber, and a connecting pipe between the supply line of the lower chamber and that of the upper chamber, downstream of the said intercepting valves, and provided with its own servocontrolled intercepting valve, while means

Abstract: In a hydraulic drive, in which a double-acting working cylinder (10) is connected to the hydraulic power source by very long working lines (20, 22), it is proposed to connect a bypass line (36) containing a normally closed bypass valve (38) to the ends of the working lines (20, 22) nearest the cylinder. The bypass valve (38) is periodically opened to allow the fluid contained in the working lines (20, 22) to be completely replaced.

Abstract: A power steering trim control system for use with steering mechanisms provided in automotive vehicles. The trim system includes a flow distribution valve (38) which selectively directs fluid pressure to segregated groups (34, 36) of valve lands (32) of a rotary valve (24) in proportion to the deflection of a torsion bar (22). The valve lands (32) are angularly off-set from those found in the prior art in order to produce a desired biasing, or torque compensation. The torque which is manually transmitted is progressively supplemented by fluid pressure delivered to the pressure movable part (14) of a steering linkage (16). The invention also includes a process control circuit (60) which is provided with a vehicle speed sensor (60) for generating an electrical signal representative of vehicle speed.

Abstract: An apparatus for suppressing vibratory or quaky movements in travel of mobile type cranes, which facilitates the operation of re-starting the vehicle after temporarily stopping the engine, for example, at a gas station for fuel replenishment as well as operations for switching the mode of operation between vehicle travel and working modes. The apparatus includes for this purpose a memory means for storing at least information as to the mode of operation under engine working conditions before an engine cut-off, and a controller adapted to reproduce automatically the mode of operation before the engine cut-off, by setting a mode selector means in a reproducing position upon re-starting the engine based on the information stored in the memory means.

Abstract: According to the displacement suppressing mechanism for a travelling crane of the present invention, when a mode selection switch selects an operation mode and a detected value by a boom position detecting means is smaller than a lower limit value of an appropriate travelling range, a change-over valve for replenishment capable of changing over the position of an auxiliary pressure oil source selectively to a communicating position for communication of the auxiliary pressure oil source with a first oil chamber of a boom raising and lowering hydraulic cylinder and a communication cutting-off position is shifted to the communicating position by a control means to supply a predetermined amount of pressure oil to the first oil chamber of the hydraulic cylinder.

Abstract: A mechanism for effectively suppressing vibrations in travel of mobile type crane includes; a boom lifting hydraulic cylinder connected between a vehicle body of the mobile crane and a boom; a main hydraulic pump; a direction control valve for supplying the discharge oil of the main hydraulic pump selectively to and from a first load-supporting oil chamber and an opposingly located second oil chamber of the boom lifting cylinder.

Abstract: An apparatus for supressing vibration and quaky movements of a pivotally mounted boom on a mobile crane. The boom is supported for pivotal movement by a hydraulic cylinder which is subjected to abrupt forces when the crane is in motion. A hydraulic circuit is constructed to prevent such forces from damaging the hydraulic cylinder and vehicle body of the crane. The circuit is selectively operative to place the hydraulic cylinder in either a working or travel made. The circuit includes an accumulator and three change-over valves to control the flow of fluid in the hydraulic cylinder during the work and travel modes of operation.

Abstract: An apparatus for damping quaky movements of a mobile type crane includes the prohibition of the formation of a closed damping circuit through the opposing oil chambers of a boom uplifting cylinder in working mode or a crane operation in travel mode of the crane, enhancing safety in crane operation while ensuring effective quake damping action in vehicle travel.

Abstract: A static hydraulic continuously variable transmission includes a cylinder block which is secured to an output shaft and comprises a pump cylinder of a hydraulic pump and a motor cylinder of a hydraulic motor, these cylinders being connected to each other, wherein, a number of pump cylinder bores and a number of motor cylinder bores are annularly arranged respectively in the pump cylinder and the motor cylinder and the transferring of a working oil between the group of the pump cylinder bores and the group of the motor cylinder bores is conducted through the medium of a pair of oil chambers which are concentrically provided around the output shaft communincation between these cylinder bores is controlled by a number of first and second dispensing valves extending between both the oil chambers and adapted to be reciprocally radially moved.

Abstract: Actuator control system includes two parallel connected orifices between a pair of fluid passages providing communication between an actuator and a flow control valve. Relief valves in series with the respective orifices block fluid flow through the orifices at low differential pressures between the fluid passages, thereby preserving the original high pressure gain of the control valve in a region about valve null. At higher differential pressures outside the valve null region, the relief valves open to permit restricted flow through the respective orifices to reduce the pressure gain of the control valve in a region outside the valve null region, which effectively reduces the stiffness of the control valve.

Abstract: An improved energy-conserving servoactuator has at least one valve operatively associated with a double-acting fluid-powered actuator. When a load is applied to the actuator, the pressure in one actuator chamber will be greater than in the other. If the load is "opposing" with respect to the desired direction of actuator movement, fluid is supplied to the higher pressure chamber and is permitted to flow from the lower pressure chamber. However, if the load is "aiding" with respect to the desired direction of actuator movement, fluid in the higher pressure chamber is permitted to flow into the lower pressure chamber without drawing fresh fluid from the source.

Abstract: A mechanism (47) is provided for converting rotational movement to substantially linear movement. The mechanism is adapted for incorporation into a vehicle (12) having front and rear wheel steering assemblies (14, 16) and a closed hydraulic system (22) for driving the mechanism in response to-and-fro steering movement of the front wheel steering assembly. The mechanism includes a support housing (98) rotated about an axis (93b) of a drive pinion (93) driven by the closed hydraulic system, a nut (100) threadably receiving a shaft (99) mounted for rotation by the support housing and having an axis (99c) normal to and intersecting an extension of the drive pinion axis (93b), a stepper motor for rotating the shaft to vary the position of the nut with respect to the drive pinion axis (93b), a logic (107) for energizing the motor and positioning the nut as a function of vehicle speed. In one embodiment the nut transmits substantially linear movement directly to the rear wheel steering assembly.