Abstract: A hydraulically actuated vacuum street sweeper (2) of the motorized vehicular type includes a vacuum system (12) with a vacuum blower (14) for suctioning debris, and a cooling system (50) utilizing otherwise wasted exhaust air from the blower for cooling hydraulic oil. Hydraulic conduit (52) is in the exhaust path of the vacuum blower and cooled by exhaust air from the latter.

Abstract: A material spreader for spreading a topping material over a wet concrete surface utilizes a pair of hoppers which are driven back and forth on a bridge support spanning the surface. A gasoline engine mounts above the hoppers and furnishes power for a reversibly controllable hydraulic hopper drive motor. The motor is part of a hydraulic system in which the hydraulic fluid is cooled by using both a hopper wall as well as the flowing material being spread as heat sinks.

Abstract: In a hydraulic system for a combine harvester, each of three subsystems is supplied with fluid through its own individual reservoir outlet. The total return flows from the three subsystems is distributed between two inlet ports of the reservoir. A pair of wire mesh delivery tubes is connected between the respective return inlet ports and two of the outlet ports. The hydraulic circuitry is arranged so that the return flow at each inlet port exceeds the supply flow demanded at the corresponding outlet port so that, while some of the return fluid is directly recirculated through the delivery tube to that outlet, there is a net flow outwards through the wire mesh of the tubes to mix with the fluid supply held in the reservoir.

Abstract: A flushing valve system suitable for use in a closed circuit hydrostatic transmission including a variable displacement hydraulic pump, a hydraulic actuator and two main lines. The flushing valve system includes poppet valves mounted in passages for respectively communicating the main lines with a fluid tank, passages mounting throttles for causing the pressure in the main lines to act on pressure chambers to keep poppets of the poppet valves from moving to an open position, and a change-over valve responsive to the pressure differential between the main lines to communicate the pressure chamber of the poppet valve connected to the main line on the lower pressure side with the fluid tank. The poppet valve connected to the main line on the lower pressure side opens when a predetermined pressure level is exceeded by the pressure in the main line, to thereby allow working fluid in the main line to be drained to the fluid tank.

Abstract: A closed loop hydrostatic transmission is disclosed which includes an improved hydraulic fluid bleed arrangement. The fluid bleed arrangement includes a variable flow bleed valve hydraulically joined with each of the closed loops of the hydrostatic transmission. Each variable bleed valve is operatively associated with the control mechanism which selectively controls the reversible flow fluid pump of the closed loop for direction of fluid under pressure in forward and reverse directions in the loop. The variable action of each bleed valve permits a relatively greater amount of hydraulic fluid to be bled from the closed loop during periods of operation when the flow of hydraulic fluid otherwise lost from the closed loops is insufficient to permit adequate replenishment of fluid in the loops with cooler charging fluid.

Abstract: An improved apparatus, for cooling hydraulic fluid in a small horsepower internal combustion gasoline engine powered hydraulic drive system, mounts the blower and oil pump concentric of and so that they are driven by the engine drive shaft and includes a finned tube heat exchanger mounted between the blower and oil pump through which hot hydraulic fluid passes and is aided in cooling by air forced over the fins by the blower. An operator controlled relief valve is incorporated into the system.

Abstract: The dredge is of the type having a bucket wheel, driven by a hydraulic motor through a gearbox, on the front of a bucket wheel carrier hinged at its rear to the dredge hull, and lowered to or raised from working depth by a cable engaged with a lifting sheave block near the front of the carrier, the dredge being slewed by cables from anchors to both sides of the dredge and engaged with slewing sheave blocks near the front of the bucket wheel carrier. Hydraulic fluid is bled from the motor to the gearbox, and then by a bleed line connected to the bearings of the sheaves of the lifting sheave block and the slewing sheave blocks. A check valve maintains a predetermined pressure in the bleed line to apply internal pressure to the seals of the gearbox, the lifting sheave block and the slewing sheave blocks.

Abstract: A liquid reservoir has a rectangular shell in which crossed first and second partitions form first, second, third and fourth rectangular liquid chambers. The partitions are impervious between the first and fourth chambers and apertured between the first and second, second and third, and third and fourth chambers. Liquid flows serially through the first, second, third and fourth chambers via the apertured partitions and such flowing liquid is subjected to a heat exchange in the first, second, third and fourth chambers.

Abstract: The drive for rotating the drum of a vehicular cement mixer includes a mechanical power train mounted in a first chamber of a drive housing and a hydrostatic motor disposed in a second housing chamber substantially surrounded by yet another chamber defined in part by an outer wall of diecast aluminum formed on an outside surface with a plurality of outwardly extending fins and on an inside surface with a plurality of support plates connected to an inner housing well defining the inner chamber. The outer chamber communicates with the inner chamber by means of an overflow outlet at the top of the inner housing wall, oil escaping from the inner chamber via the outlet flowing down the support members to the inner surface of the outer housing wall.

Abstract: Fluid in the relatively long lines (22, 24) between a control valve (16) and a fluid actuator (14) can become overly viscous in cold weather. Herein, fluid is circulated through such lines (22, 24), at least during cold weather, even when the fluid actuator (14) is not being used. This flowing is discontinued in response to shifting of the control valve (16) to a position where it motivates the actuator (14) and in response to pressure in the circulating path (20) exceeding a selected level.

Abstract: In a crank press having a pedestal and a rotatable crank shaft journaled thereon and connected to a reciprocal top platen guidably mounted on the pedestal to form work pieces, the improvement which comprises a hydraulic motor mounted on the pedestal having a reversible drive shaft connected to the crank shaft, and a hydraulic transmission connected to the hydraulic motor. The transmission includes a pump assembly connected to a reservoir for delivering the pressure fluid selectively under the control of a servo directional valve in a closed hydraulic loop to the hydraulic motor for selective forward and reverse drive together with a safety control to automatically neutralize the pump assembly and control automatic braking of the hydraulic motor drive shaft.

Abstract: The invention relates to hydraulic steering apparatus of the type having valve gear for selectively directing pressurized fluid to and from opposite sides of a servomotor connected to vehicle wheels to be steered. This type of steering apparatus only requires pressurized fluid when actuated and may provide an auxiliary circuit with pressured fluid at times when it is not being actuated. Priority valves give priority to the steering apparatus. During extended intervals when pressured fluid is supplied to an auxiliary circuit, parts of the steering apparatus are subjected to substantial cooling. Then when the priority valve diverts hot pressurized fluid from the auxiliary circuit to the cooled steering apparatus the temperature differential causes an adverse effect on the steering apparatus by creating a tendency for binding of parts due to the unequal expansion of valve sleeves.

Abstract: A hydraulic cylinder arrangement of the type wherein the opposite ends of a cylinder are connected selectively to either a pump or sump by a control valve. Each end of the cylinder is provided with a pair of oppositely acting, uni-directional check valves, each connected to a port on the control valve by an individual conduit. The four check valves are so arranged that all the fluid discharged from either end of the cylinder in response to the reciprocation of the piston therein is constrained to flow to sump before it is pressurized and returned to the cylinder.

Abstract: A hydraulic circuit for a hydraulically driven vehicle comprising a pair of variable displacement pumps each driven by a common engine, a pair of variable displacement motors each connected with the respective variable displacement pumps in a closed loop circuit and driven thereby, a fixed displacement charge pump driven by the engine, and a pair of shuttle valves each connected in parallel with the respective closed loop circuits and has formed therein a neutral position and two offset positions wherein in the neutral positions of the shuttle valves both the closed loop circuits are connected with each other through the shuttle valves.

Abstract: A pair of pumps deliver pressurized fluid to a steering control valve assembly controlling the operation of a steering cylinder. The steering control valve assembly diverts any excess of the incoming pressurized fluid to a hoist control valve assembly controlling the operation of a pair of implement hoist cylinders. The hoist control valve assembly also diverts any excess of the incoming fluid away from the hoist cylinder pair, this time to a retarder or brake system for cooling same. The retarder receives additional cooling fluid from a hydraulic torque converter, to which the fluid has been forced from another pump. On leaving the retarder the pressurized fluid is cooled and then delivered to a transmission lubricating circuit.

Abstract: Hydraulic fluid actuated pistons are operatively connected to shaping molds used to shape glass sheets by moving the molds between a glass-engaging position and a retracted position. The piston is movably mounted within a piston cylinder to form two chambers. Hydraulic fluid is applied under pressure alternately to one or the other chamber to actuate movement of the piston and the glass sheet shaping mold connected to the piston. When hydraulic fluid is applied under pressure, it tends to become heated to a temperature at which the hydraulic fluid carbonizes and/or foams. Either of these occurrences reduces the efficiency of the hydraulic fluid to actuate uniform piston motion.

Abstract: A hydrostatic transmission, especially for a steer drive of a propulsion and steer drive transmission, having a variable displacement pump, a fixed displacement motor, and a pump displacement control, and including a low pressure fluid source supplying the charging and lubrication systems of the hydrostatic transmission and a high pressure source. The high pressure source, in a normal range of low hydrostatic power pressure values, provides control pressure regulated in proportion to high hydrostatic power pressure to meet the pressure requirements of the pump displacement control which increase with high hydrostatic power pressure. In an abnormal and lower range of low hydrostatic pressure values, the control pressure is regulated to decrease to zero as the low hydrostatic power pressure decreases to a minimum operating pressure value.

Abstract: A pump jack for pumping oil and like wells having a polish rod extending vertically out of a well casing is provided including a frame adapted to fit over said well, a hydraulic cylinder depending from said frame generally coaxially of said polish rod, a piston movable in said cylinder and having an end engaging said polish rod, a source of high pressure fluid connected to said cylinder for raising said piston in the cylinder, dump means on said frame simultaneously discharging the raising fluid from said cylinder and by-passing fluid from said source of high pressure fluid to said source of fluid, means on said piston selectively actuating said dump valve from a first position where all fluid from the source of high pressure fluid is delivered to one side of the cylinder for raising the piston to a second position where all fluid from the source and from said one side of the piston is simultaneously returned to the source and to the other side of the cylinder whereby the piston and polish rod are successivel

Abstract: A hydrostatic transmission having a pump and a motor of the radial piston type with each cylinder slipper bearing rotatably supported by a hybrid or combination hydrostatic and hydrodynamic bearing on an internal bearing. The hydrostatic bearing component has a restricted port connecting hydrostatic pressure fluid from the cylinder to supply a distribution recess in the slipper bearing surface for hydrostatic pressure feed of the fluid film providing hydrostatic balancing pressure gradient between the slipper and internal bearing to balance a high percentage of the hydrostatic pressure load and to meet flow requirements for low speed operation.

Abstract: A hydraulically operated vibration exciter for a vibrating compactor of the kind comprising a piston in a cylinder, the piston and cylinder being arranged to move to and fro relative to each other, a source of liquid under pressure, a pressure line connecting the source to the cylinder and means for causing the liquid to move to and fro between the source and the cylinder to bring about the relative movement between the piston and cylinder is cooled by a method in which, during the relative movement, a quantity of the liquid is withdrawn from the cylinder and this quantity is not returned to the cylinder in the subsequent stroke, but is replaced by a fresh quantity of liquid at a lower temperature.

Abstract: The present invention relates to an arrangement to cool oil used in a hydraulic control system of an automatic transmission for an industrial vehicle. The hydraulic control system includes an operating pressure feed line, a pressure regulator valve to regulate the magnitude of pressure in the operating pressure feed line, feed passage means for feeding oil under pressure from the operating pressure feed line to a hydrokinetic torque converter, exhaust passage means for exhausting the oil from the torque converter, a pressure maintaining valve disposed in the exhaust passage means to maintain the magnitude of pressure within the torque converter to a predetermined level, and a lubricating oil feed line communicating with the exhaust passage means via the pressure maintaining valve and also with a lubricating oil port of the pressure regulator valve via a flow restrictor. The lubricating oil feed lines have two portions which may be subjected to cooling.

Abstract: A hydraulic motor drives the cooling fan of an internal combustion engine. Fluid flow from a fixed displacement pump is directed through a pilot-operated pressure-compensated control valve to the hydraulic motor. The valve has a continuous bias to a fan-on position for directing fluid to the fan motor. Flow to the fan motor is diverted by the valve as a function of the pressure of the fluid in the system. In addition, flow to the fan motor is diverted as a function of a pilot pressure signal which is controlled by the temperature of the engine coolant fluid. The valve failsafes to a condition directing maximum flow to the fan motor in the event of loss of pilot fluid pressure.

Abstract: A hydraulic power pack having a framework, a prime mover driving a hydraulic pump, a hydraulic circuit including a reservoir and flow and return connectors. The power pack also includes an oil cooling system comprising a thermostatically operated valve and an oil cooler in the hydraulic circuit. The valve diverts flow of fluid to the oil cooler when the temperature of the fluid rises above a predetermined limit, before returning the fluid to the reservoir. The oil cooler has a pair of heat exchangers mounted at the respective outlets of a double acting centrifugal fan directly coupled to and driven by the prime mover.

Abstract: A hydrostatic transmission control system including a variable displacement pump driving a constant displacement motor arranged in a hydraulic circuit having a controlled by-pass valve interconnected for positioning the pump swash plate in two established positions corresponding respectively to a stand still position or a full speed position of the motor. A thermosensitive element is coupled to the valve control spool for bypassing the flow of the pump in the event of motor jamming.

Abstract: An apparatus is provided which is adapted to deliver or absorb variable amounts of torque or to deliver variable quantities of an incompressible fluid at a predetermined pressure. The device comprises a positive displacement pump capable of pumping a compressible fluid, an incompressible fluid or a mixture of a compressible fluid and an incompressible fluid together with appropriate pressure control and flow control mechanisms, check valve mechanisms and interconnecting duct means.

Abstract: A transmission control system (10) for a transmission including a torque converter (66) has fluid inlet and fluid outlet passages (64,80) connected to the torque converter (66), a pressure regulating valve (20) for relieving fluid from a pressure source (12,16) to the inlet passage (64) of the torque converter (66), and a flow limiting passage (96) directly connecting the inlet and outlet passages (64,80) for continually bypassing fluid past the torque converter (66) and controlling the pressure drop thereacross.

Abstract: An oil well pump jack with dual hydraulically operated piston and cylinder assemblies for pivoting the walking beam of the pump jack and including a unique control arrangement for controlling operation of the piston and cylinder assemblies. The pump jack includes a unique base or skid and an adjustable knee brace assembly to facilitate positioning of the pump jack in properly supported relation to the oil well at the oil well site. The control arrangement for the piston and cylinder assemblies includes a reversing valve, a linkage mechanism for operating the reversing valve to cause controlled oscillation of the walking beam and a cushioning device for controlling acceleration and deceleration of the oscillating walking beam to reduce abrupt tension forces exerted on the polish rod and sucker rods and impact forces imparted to the pump jack during oscillation of the walking beam.

Abstract: A power transmission including a motor, a "fixed-fill" fluid coupling and a gear box, at least the "fixed-fill" fluid coupling of which is liquid cooled.

Abstract: A hydraulic circuit for steering and front brake system of a vehicle wherein discharged hydraulic fluid from steering cylinders is utilized for cooling front disc brakes. The circuit comprises a conventional steering circuit including a pair of steering cylinders and a steering valve having a drain circuit connected therewith, the pair of steering cylinders being operatively connected with the steering valve, and a pair of disc brakes for front wheels wherein the disc brakes are connected with the drain circuit of the steering valve.

Abstract: The engine comprises a base having a spool fastened thereon, the spool including a hub symmetrical about a first axis and having a pair of side plates normal to and having inside faces spaced apart along the first axis. There are plate ports in the inside faces. A cylinder rotor includes a second hub rotatable on the first hub about the first axis and includes a pair of side discs normal to the first axis and having outside faces spaced apart axially between said side plates to establish first and second axial clearances between the side plates and the adjacent side discs. There are cylinders mounted radially on the cylinder rotor with ducts extending from the cylinders to the disc ports in the outside faces radially opposite the plate ports. A driven shaft symmetrical about a second axis is eccentrically journalled in and extends through the hub. A rotor is fast on the driven shaft and carries pivot pins.

Abstract: A machine, such as a self-propelled mobile crane, having an operator's cab and an engine for driving hydraulic pumps to supply fluid to hydraulic motors which drive crane components, is provided with a heating system for the operator's cab.

Abstract: A vehicle engine accessory drive system is disclosed including a hydraulic fan motor (41) and a power steering gear mechanism SG in series flow relationship. The vehicle power steering pump P is the sole source of fluid for the system and has its flow control setting at a flow rate X, which is substantially greater than the flow rate Z required by the power steering gear SG. The motor-valve apparatus includes a valve portion (43), including a bypass valve portion (43), including a bypass valve piston (113) connected in parallel across the fan motor (41), and operable to permit fluid flow from the inlet passage (83) to the outlet passage (91) at a flow rate which is at least a portion of X. The bypass valve piston (113) is biased toward the bypass position by the fluid pressure in the inlet passage (83), and is biased toward the closed position by fluid pressure in a signal chamber (115).

Abstract: Disclosed is a fluid coupling which includes: a housing being used as a rotary driving member; a rotor rotatably mounted in the housing and being used as a driven member, a fluid pump having a pump chamber defined between the housing and the rotor; a fluid inlet port and a fluid outlet port; and a fluid circulation passage between the chamber and the housing, such that fluid in the pump circulates from the fluid circulation passage into the pump chamber through the inlet port and from the pump chamber through the outlet port into the fluid passage.

Abstract: A control circuit (10) for the variable displacement pump (18) of a hydrostatic transmission (16) or the like comprises an underspeed actuator (31) connected to the servo system (19) of the pump (18), a venturi (15) interconnected between a source of pressurized working fluid (11) and the pump (18) and a pressure regulating valve (36) interconnected between a downstream side of the venturi (15) and the pump (18). A throat (29) and upstream side of the venturi (15) are connected to the underspeed actuator (31) for communicating a differential fluid pressure signal thereto to automatically control the displacement of the pump (18) under certain operating conditions of an engine of a vehicle.

Abstract: A vehicle engine accessory drive system is disclosed including a hydraulic fan motor and a power steering gear mechanism in series flow relationship. The vehicle power steering pump is the sole source of fluid for the system and has its flow control setting at a flow rate X, which is substantially greater than the flow rate Z required by the power steering gear. A temperature responsive bypass valve is connected in parallel across the fan motor and the bypass flow and motor outlet f1ow recombine, then flow to a steering gear flow control which communicates a flow rate Z to the steering gear mechanism and all fluid in excess of Z bypasses the steering gear, recombining with the output flow from the steering gear and returning to the pump inlet. This system provides a flow to the fan motor resulting in a fan speed-versus-engine speed similar to a "viscous curve".

Abstract: A transmission having hydraulic components including a hydrostatic unit with a variable displacement component having a hydraulic displacement control with a lubrication circuit for the components and a charge circuit for supplying fluid under pressure. First and second pumps are connected in series, with the first pump having a larger volume than the second pump to provide fluid to the second pump and to a lubricating circuit. A fluid line connects between the charge circuit and the lubrication circuit and has a lubrication priority valve therein which operates to provide fluid flow from the charge circuit to the lubrication circuit when required to maintain pressure in the lubrication circuit. Additionally, the charge circuit has a pair of branch lines, with one branch line having a charge priority valve therein which functions to control the flow through the one branch line leading to the hydraulic displacement control for the hydrostatic unit and to thus provide pressure control in the other branch line.

Abstract: A device using oil for heating the operator's cab of a machine driven by an air-cooled internal combustion engine, especially the operator's cab of a vehicle. The lubricating oil of the internal combustion engine is recooled in an oil cooler and is entirely or partially branched off from the oil cooler and is fed through valves, regulating and control devices to a heat exchanger in the operator's cab. The device includes a manually adjustable rotary valve for opening and closing the heating system together with two oil pressure dependent bypass valves in the heating circuit and with a bypass valve for a lubricating oil filter from a compact valve block. The valve block together with a support for the lubricating oil filter is designed as a one-piece housing and is flanged to the machine housing. Connecting bores for the supply and return conduits to the heating system in the operator's cab are arranged in the one-piece housing.

Abstract: Disclosed is a method of preventing thermal shock to a hydraulic motor in an open-loop hydraulic system. The method comprises the step of circulating warm oil through the motor when it is not in use. Preferably the method includes the further step of returning the warm oil to the tank after it has passed through the motor, and where appropriate it may also include the preliminary step of lowering the pressure of the warm oil before it is passed through the motor.The method is disclosed as applied to a vane motor, and means for carrying it out in that context are also disclosed.

Abstract: A hydraulic system which is monitored to control the application of fluid power in response to the temperature of the hydraulic fluid and a temperature responsive valve for use in the hydraulic fluid circuit to monitor the temperature of the fluid to control the application of fluid power to components of the system.

Abstract: A vehicle having an operators enclosure and an hydraulic circuit is provided with a heat exchanger to warm the enclosure. The heat exchanger is supplied with fluid from the return side of the hydraulic circuit thus eliminating the conventional engine coolant pipes.

Abstract: A cooling chamber and a heating chamber are employed to obtain a temperature differential for forcing a working gas through a fluid driven work producing device and which then is applied back to the cooling and heating chambers whereby the cycle is repeated. The cooling chamber is cooled with a gas under pressure while the heating chamber is heated with a liquid under pressure.

Abstract: A hydraulic motor maintains its speed substantially constant in spite of changes of hydraulic fluid pressure and flow. The motor comprises a rotor to which hydraulic fluid is delivered through a nozzle arrangement from an inlet port and exhausted from the rotor to an exit port. A by-pass duct interconnects the passageway for the incoming fluid with the passageway for the outgoing fluid, to by-pass the rotor. A spring-loaded piston is situated in relation to the entrance to the by-pass duct so that when the incoming fluid pressure is relatively high the piston is retracted to expose the by-pass duct to permit some of the hydraulic fluid to by-pass the rotor, and when the fluid pressure and flow rate decrease, the spring moves the piston to close up the entrance to the by-pass duct to reduce or even stop the flow through the by-pass. A manual diverter valve is situated to divert incoming fluid away from the rotor so that all the fluid is diverted directly out of the motor housing.

Abstract: A mixed loop hydrostatic transmission circuit for use principally with orbit, gear, vane and other non-piston type motors, which generate contaminants making them less suitable for applications using conventional closed loop hydrostatic transmission circuits. The mixed loop hydrostatic transmission drive retains the precise load control and high efficiency of a closed loop system, while introducing the benefits of contamination control of open loop hydrostatic transmission circuits. While maintaining the speed of the motor proportional to the output flow of the pump, both in positive and regenerative modes of operation, the flow of fluid is diverted from the motor to an injector type inlet booster connected to the reservoir, which supplies the full flow of fluid, required by the pump.

Abstract: A hydraulic arrangement for turning the rotor shaft of an axial flow elastic fluid turbine rotor. The arrangement includes a variable speed hydraulic motor, the torque produced thereby being dependent upon the pressure of motive fluid supplied therethrough. The motor is connected through suitable coupling or clutch to the shaft. A plurality of sources of motive fluid each at a predetermined pressure range are connected to the motor. A flow control arrangement for selectively introducing motive fluid from each of the plurality of sources to the hydraulic motor to provide the desired torque output from the motor is provided.

Abstract: A fan drive system comprises a constant pressure ring main circuit from a motor driven pump to, for example, three variable capacity motors driving three fans. The motors are connected in parallel with each other and in series circuit with the pump and each has a piston and cylinder device supplied with pressure from the ring main. A variable restrictor controlled by a temperature probe sets the pressure acting on each piston and cylinder device so that each fan is speed controlled in accordance with temperature.

Abstract: A hydraulic fluid supply system includes a single motor driven pump which supplies a dual pressure level output for providing both a high pressure oil output and a low pressure oil output. In combination with a turbomachine, the dual pressure level output of the oil pump obviates the requirement of pressure reducing valves in the low pressure supply lines and losses associated therewith. Moreover, since only a portion of the entire oil requirement is raised to the higher pressure level, the pump motor horsepower requirements are reduced to save energy and thereby improve overall system efficiency. A further improvement is a system of pressure differential valves whereby under certain conditions, high pressure oil flow is conserved even though the low pressure oil flow momentarily drops below a preset value.

Abstract: A system for providing auxiliary power comprises a primary circuit including a primary pump, an output line for providing primary power, and a return line. An auxiliary circuit includes an auxiliary pump, an output line for providing the auxiliary power and a return line. The auxiliary circuit also includes a valve for controlling fluid flow in the output and return line of the auxiliary circuit. A reservoir is connected to the primary return line and to the auxiliary return line. A controlled leakage apparatus for cooling the auxiliary pump is connected to the auxiliary circuit, the reservoir and the primary circuit, and in response to a predetermined output in the primary circuit directs a portion of auxiliary output fluid to the reservoir. Approximately all of the auxiliary output fluid is directed to the auxiliary output line when the primary circuit provides less than the predetermined output.

Abstract: A tank for oil or other hydraulic fluid is improved both for cooling the fluid during normal operation and for heating it up preliminarily at start-up time by an internal curtain spaced a narrow distance from the side walls and providing a cooling channel through which, during operation, the oil may be passed in immediate contact with the outer side walls of the tank to be cooled before flowing into the main storage chamber, a flap valve being turned at start-up time to a position to direct returning oil directly into the main storage chamber where it is relatively insulated from the outer side walls by the stagnant oil in the cooling channel, so that the heat developed by power-circulation of the oil is conserved and in cold weather the oil is more quickly brought up to satisfactory operating temperature. The peripheral cooling channel normally used also settles foreign particles from the hydraulic fluid, and dissipates any entrained air at its surface.

Abstract: An improved automatically shiftable direction control valve for a tractor hydraulic system wherein there is provided a charging pump, low pressure priority functions such as cooling and lubrication connected to the charging pump, a main pump, a continuously acting reversible function, a single-acting function, and a double-acting function all connected to the output of the main pump, and a manually operable direction control valve for each of the functions. The improved automatically shiftable direction control valve has a restricted passage causing a pressure drop which shifts the valve so as to direct the exhaust of the continuously-acting and double-acting functions to the charging circuit and to direct the exhaust of the single-acting function to the fluid reservoir.

Abstract: A hydraulic system having a plurality of hydraulic motors operated by fluid from a common reservoir includes means for circulating a flow of fluid from the reservoir through the housing of the motors to thereby maintain a substantially equal temperature between the motors and the fluid.