Abstract: An apparatus for controllably moving an implement is provided. The implement is connected to a work machine and is movable between first and second implement positions in response to operation of a hydraulic actuator. The apparatus includes a joystick with first and second positions and a neutral position. The joystick is normally biased in a neutral position and is movable between the first and second positions. The apparatus senses the position of the joystick and responsively generates a joystick position signal. The joystick maintained at the first and second detent positions in response to manual movement of the joystick to the respective first and second detent positions. The joystick is released from the detent position in response to receiving a release detent signal. The apparatus senses the position of the work implement with respect to the work machine. The apparatus provides hydraulic fluid flow to the hydraulic actuator in response to a magnitude of an electrical valve signal.

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: Method and apparatus for reduction of fluid borne noise in a hydraulic system are disclosed. An improved isolating hose assembly comprising first, second and third volumetrically compliant members with first and second inductive flow members providing fluidic coupling therebetween is disclosed. The improved isolating hose assembly acts similarly to an electronic low pass filter network in deterring fluid borne noise from entering portions of the hydraulic system located therebeyond. A modified isolating hose assembly comprising a resistive member introduced within the second volumetrically compliant member in order to eliminate the possibility of a deleterious resonance in the assembly is disclosed. In addition, apparatus for additionally reducing structure borne noise in hydraulic systems comprising direct hydraulic coupling of the first volumetrically compliant member to internal output ports of the hydraulic system's pump is disclosed.

Abstract: A full hydraulic type steering control system is provided with a steering control valve for outputting a flow of a pressurized discharge fluid of a hydraulic pump in proportion to an amount of steering at a steering wheel, and a directional control valve for delivering the pressurized discharge fluid of the hydraulic pump into a steering control cylinder, with the output flow of pressurized fluid of the steering control valve being switched as a pilot fluid pressure. The directional control valve comprises a spool adapted to be slidably inserted in a spool bore of a valve body.

Abstract: A pneumatic tool includes a body having a pressure accumulation chamber formed therein for accumulating compressed air. A cap are mounted on the body and has a cap chamber formed therein for communication with the pressure accumulation chamber. The cap has a joint for connection with an air hose from a compressed air source. A gasket is interposed between the pressure accumulation chamber and the cap chamber from each other. The gasket itself forms a valve for preventing a counterflow of the air from the pressure accumulation chamber to the cap chamber, so that exhaust sounds of the air is prevented from being produced when the air hose is disconnected from the joint.

Abstract: Unbalanced oscillatory pressures, developed on the power piston of hydraulic servoactuator systems cause vibrations on actuator housing supports. An unbalanced oscillatory force results, when two sides of the power piston are subjected to two unequal oscillatory forces induced by a disturbance. The two important disturbances are: pump flow rate oscillations, caused by power source torque oscillations; and, load oscillations. The invention is a hydraulic actuator connected in parallel to the power piston and designed to cancel vibrations by eliminating the unbalanced oscillatory pressure on the power piston. This is accomplished by designing the piston frequency of the invention, defined as tuning frequency, to be equal to the unbalanced oscillatory pressure frequency.

Abstract: A hydraulically supported power steering system is disclosed for motor vehicles including a double-acting hydraulic displacement unit or piston/cylinder unit for generating an auxiliary hydraulic force. For this purpose, the displacement body working spaces or piston working spaces can be acted upon by controllable hydraulic pressure or relieved of hydraulic pressure by means of associated conduits controlled by a servo-valve. The displacement unit or piston/cylinder unit also undertakes the function of a steering damper by means of damper valves arranged on the conduit connections. The damper valves include a perforated disc type of support part which can be clamped in the manner of a spacer ring between a bearing surface of a connecting mouthpiece arranged on a housing of one of the servo-valve and the displacement unit and an opposite bearing surface of a connecting part of a conduit, said connecting part being detachably connected to the connecting mouthpiece.

Abstract: Method and apparatus for reduction of fluid borne noise in a hydraulic system are disclosed. The apparatus is an improved isolating hose assembly having first and second volumetrically compliant sections fluidly connected by an inductive flow member. Each of the first and second volumetrically compliant sections may, in addition, include a resistive flow element. The resistive flow elements are used to eliminate resonant conditions in the first and second volumetrically compliant sections at selected frequencies where capacitive behavior thereof would otherwise be compromised.

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: In many hydraulic systems, fluid borne noise is generated during operation due to the effects of the hydraulic pump. This fluid borne noise is many times transmitted to the hydraulic valves, hydraulic lines, and other structures that valves and lines are mounted on. The structure then emits vibrations that create the largest portion of the system air borne noise. In the subject invention, an apparatus is provided for the attenuation of fluid borne noise in a hydraulic system. The apparatus includes a fluid vessel having a volumetric space of a predetermined size located in the system generally adjacent a pump and a flow restrictor located in the system downstream of the fluid vessel. In the subject arrangement, the flow restrictor may be adjustable in response to various system parameters so that the fluid borne noise is effectively controlled over wide ranges of system pressures, pump drive speeds, and pump displacements.

Abstract: In many hydraulic systems, fluid borne noise is generated during operation due to the effects of the hydraulic piston pump. This fluid borne noise is transmitted to various structures of the hydraulic system which emit vibrations that create the largest portion of the system air borne noise. In the subject invention, an apparatus is provided for the attenuation of fluid borne noise. The apparatus includes a sensor arrangement operative to sense operating system parameters and deliver signals representative thereof to a microprocessor, a porting arrangement within the hydraulic piston pump that includes a secondary port, a fluid chamber, and first and second passageways interconnecting the secondary port, the fluid chamber, and a discharge passage. The microprocessor receives the signals from the sensor arrangement and directs electrical command signals to an electrically controlled valve mechanism disposed in the first and second passageways.

Abstract: A hydraulic system for machines provided with tools, particularly for wheel loaders, fork lifts or the like, including comprising at least one hydraulic accumulator, distributing valves, manometric switches and at least one nozzle for variably adapting the load pressure of the hydraulic accumulator to the load pressure of the lifting cylinder, wherein the load-damping system formed by the hydraulic accumulator is connected to the hydraulic lines responsible for lifting and lowering and extending between the hydraulic cylinder(s) and a control valve.

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 tuner hose assembly for a motor vehicle power steering system including a flexible hose, a first flexible tuner tube inside the flexible hose having an upstream end connected to a pump, and a second flexible tuner tube inside the flexible hose having a downstream end connected to a power steering gear. A downstream end of the first flexible tuner tube is longitudinally separated from an upstream end of the second flexible tuner tube by a wave interference gap which terminates where an inner wall of the flexible hose is clamped against the upstream end of the second flexible tuner tube. The length of the second flexible tuner tube is selected, i.e. "tuned", to attenuate higher order pump fluid-borne noise and simulates a rigid metal tube of a prior tuner hose assembly having greater overall length.

Abstract: Method and apparatus for reduction of fluid borne noise in a hydraulic system are disclosed. An improved isolating hose assembly comprising first and second volumetrically compliant members with an inductive flow member providing fluidic coupling therebetween is disclosed. The improved isolating hose assembly acts similarly to an electronic low pass filter network in deterring fluid borne noise from entering portions of the hydraulic system located therebeyond. In addition, a sound barrier comprising a heavy-walled boot surrounding the first volumetrically compliant member is disclosed. The heavy-walled boot surrounding the first volumetrically compliant member acts to prevent acoustic sound sourced at the wall surface thereof from entering the surrounding atmosphere.

Abstract: A method of controlling a cylinder apparatus includes the steps of supplying compressed air of a first high pressure to one chamber of a cylinder which is divided into two chambers by a piston, and exhausting air from the other chamber so as to move the piston from the start position at an end portion of one chamber toward an end position at an end portion of the other chamber along the extending direction of the cylinder, and detecting if the position has passed the position of a sensor. In addition, a moving speed of the piston is decreased by supplying air of a second high pressure lower than the first high pressure to the other chamber after an elapse of a predetermined wait time from when the piston has passed the position of the sensor, so that the piston reaches the end position in a shock-free state.

Abstract: The device embodying the invention uses a phase shifter controlled by a dual-effect hydraulic acting element comprising a phase shifting chamber connected to the distributor output via a circuit comprising a nonreturn valve and a hydraulic accumulator whose load pressure can be limited by means of a limiter and a rephasing chamber whose pressure is controlled by a pressure regulator so that a predetermined phase shift corresponds with each regulator control value. The invention applies notably to the driving into the ground of objects such as stakes or sheet piles.

Abstract: A power vacuum truck having a movable roof to accommodate expanding vacuum bags, and a method of raising the roof are disclosed. The power vacuum truck utilizes a hydraulic pump to drive a fan and compressor in order to eliminate mechanical linkages and the concomitant breakdown and maintenance associated therewith, and eliminates holes in the roof previously necessary to accommodate the expandable vacuum bags. An vehicle having an automatic transmission can be used.

Abstract: A lift truck having a hydraulic circuit with a muffler for reducing noise created by the hydraulic pump and motor assembly. The muffler includes a cylindrical body and first and second end caps which define an expansion volume which reduces the magnitude of pressure pulsations generated by the pump, thereby reducing noise. In one embodiment, the muffler includes mounting pads, located on the muffler body, for attaching the muffler to the truck frame, and a flexible hose interconnects the muffler and pump.

Abstract: Hydraulically-operated equipment such as travelling equipment or working equipment for use in construction machinery such as a power shovel, shoveldozer and bulldozer. The hydraulically-operated equipment comprises a hydraulic driving mechanism actuated by hydraulic pressure, a hydraulic pressure supplying device for supplying hydraulic pressure to a hydraulic pipeline system for the hydraulic driving mechanism and a controller for controlling the hydraulic pressure supplying device such that the supplying rate at which hydraulic pressure is supplied to the hydraulic pipeline system according to the supply of hydraulic pressure is decreased in a specified period after a dead zone period in which hydraulic pressure starts to rise. This arrangement prevents an operational lag in the hydraulic driving mechanism as well as a shock at the time of start-up and shut-down.

Abstract: Described herein is a brake valve which is arranged to prevent low pressure relief actions by relief valves (59A) and (59B) at the time of starting an actuator, for improving the response characteristics and the safety of operation. This brake valve has relief valves (59A) and (59B) and check valves (70A) and (70B) located in coaxial positions, the check valves (70A) and (70B) being arranged to seat on fore end portions of valve seat members (62A) and (62B) when opened, thereby to substantially block the communication of the valve seat members (62A) and (62B) with inlet link passages (56A) and (56B). Therefore, when the check valve (70A) or (70B) is opened at the time of starting the actuator, the valve seat member (62A) or (62B) is supplied with only a throttled flow of hydraulic pressure through the notched portions (73A) or (73B).

Abstract: An implement control system is provided for controllably raising and lowering an implement relative to a work vehicle. The implement is pivotally connected to the work vehicle and movable between maximum raised and lowered positions in response to the extension and retraction of a hydraulic cylinder. The implement control system is operative for controllably connecting the hydraulic cylinder to a hydraulic accumulator as the implement reaches its desired position, thereby slowing movement of the implement in a smooth manner.

Abstract: A damper for use in a hydraulic clutch actuator to attenuate vibrations transmitted from the crankshaft of the engine of the associated vehicle to the clutch pedal. The baffle includes an elongated cylindrical housing positioned in the conduit interconnecting the master and slave cylinders of the actuator coaxial with the axis of the conduit and including a spring biased piston mounted in the bore of the housing. The housing is open at its rear end and closed at its front end by an end wall defining an outlet port for the damper and the piston includes a central through passage defining the inlet port of the damper at the rear end of the through passage. A baffle is provided at the front end of the piston to provide a circuitous path between the central passage of the piston and the outlet port of the damper.

Abstract: A vibration and sound proofing system for a working vehicle such as a tractor or a lawn mower having a hydrostatic stepless transmission (HST) included in a propelling transmission system for transmitting engine output to wheels. The HST is mounted in a case secured to intermediate mounting plates attached to a gear transmission case through vibration and sound absorbers. Output shafts of the HST are connected to input shafts of a gear transmission through vibration absorbing shaft couplings.Each of the vibration absorbers includes a metallic outer tube, a metallic inner tube disposed concentrically with the outer tube, and a rubber element filled tight in an annular space defined between the outer and inner tubes.

Abstract: In a hydraulic drilling machine with a boom, arm and bucket as working parts, one or more of the working parts can be vibrated automatically to perform effective drilling with reduced resistance in various types of operations when the soil changes. Adequate vibration can be automatically generated by setting the working mode (Bo, A, Bu, Sk) and vibration mode (L, M, S) according to the soil or operation form beforehand and by setting the automatic vibration mode. Furthermore, since the control input of the working part lever can be added to the automatic vibration, simple and minute repeated operations, such as pressure-shifting, sifting or drilling conducted while the bucket is vibrated, can be performed readily and uniformly without exhausting the operator, and workability can thus be greatly improved.

Abstract: An hydraulic liquid system wherein a pump moves liquid from one location to another such as in supplying one or more loads in an underwater environment. The system includes two hydro-pneumatic chambers utilized such that one is filled by liquid from the pump while the other supplies the load, and as one hydro-pneumatic chamber empties, valves reconfigure the system such that the hydro-pneumatic chamber reverse roles. Each hydro-pneumatic chamber includes a liquid side and a gas side separated by a movable barrier with the gas sides of the hydro-pneumatic chambers being connected to one another thereby providing a large acoustic transmission drop across a liquid-gas boundary and subsequent gas-liquid boundary to interrupt the liquid noise path from the pump to the load.

Abstract: A hydraulic system for a wheel loader having an implement arranged for elevational and tilting movements relative to a frame of the loader. The hydraulic system includes selectively operable lifting and tilting circuitry for adjusting the position of the implement and a shock absorbing mechanism arranged in combination with the lift circuitry for allowing relative movement between the implement and the frame to provide a cushioning effect which reduces pitching of the loader. To inhibit inadvertent vertical displacement of the implement, the shock absorbing mechanism is responsive to an initial lifting action of the implement. In a preferred form of the invention, the shock absorbing mechanism is responsive to hydraulic conditions indicative of imminent tilting movement of the implement thereby eliminating inadvertent vertical displacement of the implement when the implement reaches a limit of its tilting travel.

Abstract: In the case of a hydraulic control device for an oscillating load moving system comprising a double-acting hydroconsumer (V), which is adapted to be selectively connected to a pressure source (P) or to a reservoir (T) via two separate main lines (9, 10) and a control valve (C), and further comprising a load supporting valve (H), which is arranged in at least one main line (10) between the control valve (C) and the hydroconsumer (V) and which is adapted to be opened from the other main line (9) via a pilot line (16), a damping device (X), which consists of a bypass line (23) and an interference throttle aperture (D2), is connected to the pilot line (16) of the load supporting valve (H). The pilot line (16) has provided therein a throttle aperture (D1) which is smaller than the interference throttle aperture (D2).

Abstract: A hydraulic drive system has a hydraulic pump (1), an actuator (2), a flow control valve (5) disposed between the hydraulic pump and the actuator, a pressure compensating valve (8; 8A; 8B) having a valve spool (23; 23A; 23B) that controls the differential pressure (Pz-PLS) across the flow control valve, and a pump delivery rate control device (9) for controlling a flow rate of the hydraulic fluid delivered from the hydraulic pump dependent on a differential pressure (Pd-PLS) between a pump pressure and a load pressure of the actuator.

Abstract: A damper for use with a hydraulic clutch actuator of the type including a master cylinder and a slave cylinder with a conduit interconnecting the outlet of the master cylinder and the inlet of the slave cylinder. The damper is positioned in the conduit between the master cylinder and slave cylinder and includes a diaphragm having a front face constituting a barrier wall of the hydraulic system so that the diaphragm can deflect in response to vibrations transmitted through the hydraulic fluid in the system to effect damping of the vibration and further includes a structure confronting but spaced from the rear face of the central region of the diaphragm which operates to limit the deflection of the central region of the diaphragm to a predetermined maximum magnitude to limit the stress at the center of the diaphragm to an acceptable level and thereby improve the fatigue life of the diaphragm.

Abstract: A working machine such as a hydraulic excavator is provided with a working apparatus including a boom pivotally mounted on the body of the working apparatus and a boom-cylinder hydraulic system for the working apparatus. The hydraulic system includes an actuator for moving the boom up and down and a directional selecting valve. The directional selecting valve is arranged to effect selective switching of the feed of a pressurized working fluid to and the discharge of the working fluid from with respect to the rod-side and the bottom-side hydraulic chamber. The hydraulic system further includes a device for relieving the pressure of the bottom-side hydraulic chamber of the actuator. This relieving device is connected to the bottom-side hydraulic chamber of the actuator via a hydraulic circuit. When the pressure in the bottom-side hydraulic chamber changes from rise to fall, the pressure is released to a low-pressure side of the hydraulic circuit, thereby suppressing oscillation of the boom.

Abstract: A float attachment for hydraulic systems, such as those used in controlling dozer blades, front end loaders, snow plow blades and the like where the blade, bucket or the like is controlled with a double acting cylinder. The float apparatus includes a float cylinder that is connected in parallel with the double acting cylinder. The float cylinder contains a free floating piston and may have, at the end connected to the lowering end of the hydraulic cylinder, a check valve preventing flow into the float cylinder and a pressure relief valve by-passing the check valve. The relief valve controls the pressure of the blade on the ground and allows the blade to float if that pressure is exceeded.

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: 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 running apparatus for an agricultural vehicle comprising an oil stepless change speed device, an oil circuit for an oil pump and an oil motor to actuate the oil stepless change speed device and an accumulator. The accumulator accumulates a surplus of an output pressure of the oil pump when the pressure is higher than a predetermined value and discharges the accumulated pressure when the output pressure of the oil pump is lower than the predetermined value.

Abstract: In a hydraulic transmission comprising: an input shaft connected to a flywheel of a crankshaft of an engine through a rotary container of a centrifugal oil filter; and an oil supply pump adapted to be driven by the input shaft, wherein the rotary container has its inside communicating at one side with a discharge port of the supply pump and at the other with a transmission oil circuit, a shock absorbing system characterized: in that a torque absorbing member is interposed between the rotary container connected to the input shaft and a thrust plate fitted rotatably on the outer circumference of the container, the torque absorbing member being adapted to be deformed in response to the relative rotations of the two; and in that the thrust plate is connected the flywheel.

Abstract: A control system for a hydraulic circuit including at least first and second variable displacement volume type hydraulic pumps, at least first and second hydraulic actuators driven by the pumps, and valves for controlling hydraulic connections between the pumps and the actuators. The control system includes a device for deciding the order of priority of hydraulic connections between the first actuator and the first and second hydraulic pumps and the order of priority of hydraulic connections between the second pump and the first and second actuators. A first sensor is provided for sensing maximization of the displacement volume of the first pump, sensing that the displacement volume of the second pump has become substantially zero. A device decides target displacement volumes of the first and second pumps based on information supplied at least by the priority order deciding device and first and second sensor.

Abstract: A control system for a hydraulic circuit having at least first and second hydraulic pumps of the variable displacement type, a first hydraulic actuator arranged for hydraulic connection with the first pump through first valve to be driven thereby, and a second hydraulic actuator arranged for selective hydraulic connection with said first and second pumps through second and third valve respectively to be driven thereby.

Abstract: A hydraulic supply system of a pulsatory press has two pumps (4 and 5) supplying through non-return valves (8 and 9) and through overflow valves (10 and 11), two slide dividers (17 and 19). The divider (17) in the position I directs oil to the working space V.sub.n under the servo-motor piston, whereas the divider (19) directs oil to the rotary divider (20) wherefrom a pulsating stream of oil gets into the working space under the part of the piston of a smaller diameter and into the run-off. The divider (17) in the position II directs oil to the space V.sub.p over the servo-motor piston at a simultaneous connection of the space V.sub.w via a slide valve (24) with the run-off, whereby the value of pressure in the space V.sub.p over the servo-motor piston is limited by means of an overflow valve (15).The conduit supplying oil from the divider (19) to a rotary divider (20) is connected via a cut-off valve (22) and a throttle valve (23) with a conduit supplying oil from the divider (17) to the space V.sub.

Abstract: A pneumatic power tool having a torque sensing control system is disclosed which is capable of consistently applying a precise torque to a fastener so that uniform tightening of any number of fasteners can be obtained. A torsional strain responsive transducer is mounted internally in the tool body and includes a strain gauge network mounted on a torsionally resilient portion of one of the gear cases of the drive train of the tool, the gear case being subject to a reaction component of the torque being transmitted through the drive train. The strain gauge network provides a control signal which effects energization of a solenoid-actuated air shut-off valve in the handle of the tool to automatically terminate the operation of the tool when a predetermined torque is obtained at the output spindle. The control system permits adjustment of the torque output of the tool and provides a visual readout of such output.

Abstract: A fixed displacement pump including a variable capacitance flow regulator for absorbing the excess fluid flow from the pump which is not required by a hydraulic system. The variable capacitance flow regulator, in a hydraulic embodiment, includes a pair of pistons slidably movable within a housing for independent movement relative to each other. The fluid pressure in the hydraulic system is communicated to a first of the pistons to bias it to various positions within the housing depending upon the pressure level in the hydraulic system. The second or varibale capacitance piston is acted upon by the fluid pressure in the pump discharge chamber, and when the pressure in the hydraulic system exceeds the spring pre-load against the first piston, the first piston will be displaced away from the second piston.

Abstract: A control system is disclosed for use with pressure-driven loads, such as reversible motors. The system allows the loads to be driven at varying speeds and also allows the loads to be reversed. However, the system is so designed that an operator cannot subject the loads to pressure shock caused by abrupt changes in pressure by adjusting the system too rapidly. The system disclosed is suitable for use with either hydraulic or pneumatic loads.

Abstract: In a cement-mixer truck having a mixing drum rotated via a step-up transmission by a hydrostatic motor in turn energized by a power pump driven by the vehicle engine, the motor is disposed in a chamber at least partially filled with coolant replenished by leakage from the power pump and the motor and by oil from a valve housing supplied via a pressure-regulating and a bleeding valve respectively tapping high-pressure and low-pressure pumping conduits of a hydraulic circuit. The motor coolant chamber is surrounded by an oil reservoir connected at an output via an internal filter and a second engine-driven pump to the hydraulic circuit for feeding oil thereto and at an input via a heat exchanger to the motor chamber for drawing hot fluid from the motor bath, the reservoir serving in part to reduce noise from the hydraulic motor. A ventilating fan at the heat exchanger and a water pump are driven directly by the same shaft that is connected to the step-up transmission.

Abstract: A fluid pump control for a tractor having a fluid pump controlled by an operator's handle connected to the pump by force-responsive members which do not transmit the pump vibration to the handle. The control is for a tractor transmission driven through a variable displacement pump which inherently develops vibrations. The handle is a pivotally mounted lever and the connections between the handle and the pump are four cables, and two intervening compression springs, all for transmitting the force on the lever to the pump while avoiding transmitting the pump vibrations back to the lever. The springs also are arranged with the cables to automatically return the pump to a neutral position when the operator releases hand force on the lever.

Abstract: A fluid flow control valve assembly provides metering of the hydraulic fluid from a cylinder port at a constant desired rate for lowering a load at a corresponding constant rate which has been raised by the cylinder. The valve assembly comprises a normally closed valve having an input orifice communicating with the cylinder port and an output orifice and is selectively actuable for permitting the flow of fluid from the cylinder. A normally closed pressure compensating valve has an input orifice communicating with the normally closed valve output orifice, an output orifice, and a control input adapted for direct communication with the cylinder port for continuously sensing the fluid pressure within the cylinder. The pressure compensating valve maintains a constant fluid flow pressure differential and a constant fluid flow rate from the cylinder.

Abstract: The air hammer is of the type employing a body having a first portion with a central bore and a piston reciprocable in the bore by pressurized air under control of an automatic valve. The body has a second or muffler portion which embraces the first portion and is operative to muffle the noise created by exhaust air from the bore. The muffler portion is provided with pressurized air passage means through which the pressurized air must pass for causing operation of the piston. The passage means are so arranged that removal of the muffler portion from the body disrupts the supply of pressurized air to the piston and thereby renders the hammer inoperative. Headers are provided on the ends of the body and are drawn tightly against the ends of the muffler portion by tie bolts which extend through through-passages, respectively, in the muffler portion.

Abstract: A power assembly for supplying power to a hydraulic piston and cylinder unit for raising and lowering an elevator car. The power assembly may comprise: a hydraulic fluid reservoir; a hydraulic pump assembly, the intake of which is connected to the reservoir and the outlet of which is connected to the piston and cylinder unit; and a control valve disposed above the hydraulic reservoir for controlling the flow of fluid to and from the piston and cylinder unit.

Abstract: A hydraulic transmission drive assembly having a pair of hydrostatic units mounted in a housing assembly for suspension from a primary housing and with the housing assembly supported on the primary housing by noise attenuation means including a pair of isolation mountings each of which are of a multi-layer construction with a plurality of plates for connection to either the primary housing or the housing assembly, with resilient material bonded therebetween and with mounting means extended through openings in said plates and surrounded by resilient material which is spaced from an opening in a center plate of the isolation mounting whereby axial loads result in compression of the resilient material and flexure of the plates and torsional and transverse loading results in shear of the resilient material under light loading and, under heavier loading, the resilient material surrounding the mounting means additionally acts in compression.

Abstract: A vibration reducing shoe for biasing a cam ring of a variable displacement ball pump into engagement with a surface of the pump housing. In a hydrostatic transmission having a variable displacement pump and a fixed displacement motor a pair of shoes are located within bores in the pintle. The shoes are slidably received in the bores and exert a force against the cam ring which is proportional to the pressure of the fluid used to rotate the motor. Since the pump is reversible, one shoe is in fluid communication with one of the passages directing fluid to the motor and the other shoe is in fluid communication with the other passage. Accordingly, the force exerted on the cam ring by the shoes increases and decreases with increases and decreases in the pressure of the fluid from the pump to the motor.