Abstract: The invention discloses a power unit (1) which comprises: an accumulator battery (2); an electric converter (3) supplied by said accumulator battery (2); an electric motor (30) supplied by said converter (3); a hydraulic pump (4) mechanically connected to said electric motor (30), suited to put under pressure a liquid (50) which supplies one or more actuators (9) in order to lift a load (11) connected to them. Said pump (4) is of the reversible type and operates as a hydraulic motor suited to drive into rotation said electric motor (30) which operates as a generator supplying said battery (2) by means of said converter (3) whenever the descent by gravity of the load (11) supported by said one or more actuators (9) puts under pressure the oil held therein which passes through said pump (4) entering from the delivery opening (42) and coming out of the inlet opening (41).

Abstract: Hydraulic operating device, in particular for the operation of a selector fork of a gearbox, and gearbox provided with such an operating device. The device comprises a double-acting cylinder, which is coupled to the selector fork, and a reversible pump. The pump is connected to the working chambers of the cylinder by supply lines. A valve is mounted in each of the supply lines which is operated by fluid flow. This valve comprises a body, a bore formed in the body, a piston, which divides the bore into two chambers, a through-channel, formed in the piston and designed as a flow orifice, connecting the two chambers.

Abstract: A hydraulic device provided with a plurality of hydraulic actuators directly connected to a hydraulic pump for control. A hydraulic pump is operable in both rotational directions when the electric motor is rotated forwards and in reverse. Ports of each hydraulic actuator are connected via a connecting line in parallel with ports of the hydraulic pump. A plurality of electromagnetic valves are provided in the connecting lines to the hydraulic actuators. By opening or closing each electromagnetic valve, the operation of the associated hydraulic actuator is controlled. The operation direction of each hydraulic actuator is controlled by rotating the electric motor clockwise or counterclockwise. Further, a position sensor is provided for detecting displacement of the specified hydraulic actuator and the electric motor is controlled based on a signal transmitted from the position sensor.

Abstract: The hydraulic control system disclosed herein employs a pair of combination poppet/spool valves to control the operation of a hydraulic cylinder driven from a bidirectional pump. Flow introduced through the source port of one valve lifts the poppet of the other valve on its way to one side of the cylinder which in turn opens a throttling port to modulate return flow from the other side of the cylinder.

Abstract: An electrohydraulic control system that includes a bidirectional electric motor responsive to application of electrical power for rotation in either of two directions, and a hydraulic pump coupled to the motor and having ports for supplying hydraulic fluid in either of two flow directions as a function of direction of rotation of the electric motor. A hydraulic actuator is coupled to the pump for receiving fluid in either of two flow directions and performing work as a function thereof. An electronic controller applies electrical power to the electric motor so as to obtain a desired level of work at the actuator. The electronic controller includes one or more sensors operatively coupled to the actuator for applying electrical power to the motor as a function of motion at the actuator.

Abstract: A hydraulic circuit for supplying a plurality of series-operated consumers of a hydraulically controlled installation, in particular of an injection molding machine, having a pump with feed-flow pressure control, is described. To be able to slow down greater moving masses with very little expenditure in regard to circuitry and devices, only a portion of the consumers, such as the extruder, the injection unit and possibly the ejector are operated in open circulation, while at least one selected further consumer, such as the clamping unit of the injection molding machine, where a greater mass must be moved in alternating directions, is moved in semi-closed or closed circulation.

Abstract: Disclosed is a stiffness enhanced electrohydrostatic actuator for aircraft flight controls which eliminates the requirement for a central hydraulic system. The actuator replicates the blocked port condition of the central hydraulic system to provide static and dynamic stiffness by the use of valves having a first sleeve and spool and a second sleeve and spool disposed on either side of a valve seat with the first spool biased towards the valve seat.

Abstract: This pumping unit stroke reversal invention can be employed in various embodiments, and uses one or more resilient hydraulic-pneumatic accumulators which slow and stop each stoke, storing the kinetic energy, and returning this energy to begin and accelerate the next succeeding stroke. This storing and re-application of energy greatly increases the efficiency of any pumping unit which incorporates the stroke reversal system of this invention. Counterbalance force is mechanical, hydraulic-pneumatic, or a combination of the two, and is applied in linear or rotary fashion. Drive power is applied during the larger central portion of each stroke, either mechanically or hydraulicly, and in either linear or rotary fashion, and the drive mechanism is then passive during the remaining, reversal portions of the stroke cycle.

Abstract: An electrohydraulic device for generating a force acting on a movable piston rod including a cylinder, a piston disposed in the cylinder forming a first cylinder portion and a second cylinder portion, a first pump disposed adjacent to the cylinder and in communication with the second cylinder portion, a second pump disposed adjacent to the first pump and in communication with the first pump and with the first cylinder portion, a housing defining a reservoir for operating fluid of the electrohydraulic device, the second pump being in communication with the reservoir, and an electric motor coupled to the first and second pumps by a shaft such that when the electric motor rotates in a first direction, the shaft drives the first pump while the second pump is idle and when the electric motor rotates in a second direction, the shaft drives the second pump while the first pump is idle.

Abstract: A tilt cylinder for tilting an outboard engine has first and second cylinder chambers. A pair of on/off valves is movably disposed in respective fluid passages connected to a hydraulic pump and the first and second cylinder chambers, respectively. The on/off valves are operatively combined with respective shuttle valves which have respective oil passages in facing relationship to the on/off valves, respectively, and respective ball valve bodies for selectively opening the oil passage into communication with each other. When the hydraulic pump is actuated to develop a working oil pressure buildup, one of the on/off valves is opened by the working oil pressure buildup to establish an oil supply passage from the hydraulic pump to one of the first and second chambers, and the other of the on/off valves is opened by the coacting shuttle valve which is moved by the working oil pressure buildup to establish an oil return passage from the other of the first and second chambers to the hydraulic pump.

Abstract: A vehicle convertible top has hydraulic cylinders for moving the top between extreme raised and lowered positions. The cylinders each have a pair of fluid translating ports each connected to ports in an elongated housing. A reversible hydraulic pump is in one end of the housing, while a reservoir is in the other end, separated by a pump cap. The pump cap houses two fluid circuits each connected to a housing port and each including an end of cycle hydraulic locking device which comprises a normally-closed valve and a valve actuator in each circuit. In one direction of pump operation, one of the valves is opened by pressure fluid in the one circuit to enable the outflow of the pressure fluid to the cylinders. The other valve is forced open by its actuator, in response to pressure in the one circuit, to enable the return flow of fluid to the pump through the other circuit. The one valve closes when the pump ceases operation, preventing fluid backflow through the one circuit to the pump.

Abstract: The position of a controlled system is regulated with a hydraulic actuator, which is directly linked to a hydraulic pump. The pump is driven in either direction by an electric motor, which is controlled by the output of rotatory direction and driving power generated from a controller based on a desired position and the feedback input of the actual position of the controlled system and the rotatory speed of the electric motor. The controller further includes a gain-variable amplifier for amplifying a deviation of the controlled value from a desired value with a gain characteristic curve of a shape appropriate to the controlled system, attaining a stable and well follow-up control of position.

Abstract: A coaxial hydraulic actuator system utilizes a vane pump close coupled to a vane actuator. The vane pump includes a rotatable housing which is perpendicularly movable by a control piston to direct fluid flow through first and second fluid conduits in a pintle port transfer shaft. The transfer shaft conduits are in communication with first and second variable volume compartments in the vane actuator. Thus, controlled movement of the vane pump housing results in corresponding resulting angular movement between the actuator vane and the actuator housing. This relative angular positioning can be used to control the relative positioning between first and second loads, such as the rotors of a dual permanent magnet generator.

Abstract: A hydraulic lifting arrangement for a lift assembly on a materials-handling vehicle includes a working piston-cylinder device (17) for raising and lowering the lift assembly, a reversible pump assembly (40) for operating the piston-cylinder device, and an electric motor for driving the pump assembly. The piston-cylinder device (17) is a double-acting device and has two working chambers (28,29), which are connected to the pump assembly by connecting pipes (46,47). The pump assembly comprises a first and a second hydraulic pump (41,42) having fixed displacements. The pumps are so arranged in the system that together they supply hydraulic medium to and receive hydraulic medium from solely the first chamber (28) whereas only the pump motor (41) supplies and receives hydraulic medium to and from the second chamber (29).

Abstract: A closed loop hydraulic system for use in a rotary drilling apparatus includes an extendible-retractable feed cylinder and a valve for biasing the feed cylinder. A variable, reversible displacement pump is provided for pumping fluid from either of the first and second pump ports, including pumping fluid to the feed cylinder. A reservoir retains a supply of fluid for the system. A check valve is provided for supplying additional fluid to the pump in response to the feed cylinder being extended. An overcenter valve is connected to each of the first and second ports for controlling flow from the system in response to pressures received from the first and second ports when the feed cylinder is extended and retracted.

Abstract: A hydraulic door opening or closing device comprises a hydraulic fluid pump motor having two ports connected to each end of integral dual manifold and operating cylinder apparatus by way of two branch fluid lines. One branch line is fluidly connected to a particular end of the operating cylinder by way of a directional flow valve. The other branch line to the same end of the cylinder is fluidly connected to the cylinder by way of an associated manifold. Fluid communication with the cylinder through the manifold is accomplished by providing a plurality of valved openings linearly disposed along the end of the cylinder between the manifold and the cylinder. As a piston of the operating cylinder passes these openings, a door coupled to the piston is automatically slowed as fluid on the drive side of the piston is returned through the openings to the hydraulic fluid pump.

Abstract: A compact electric adjusting drive for locking systems, fan flaps or the like in motor vehicles includes a fluidic force transmission system between the electric motor and the adjusting element movable to and fro between two end positions.

Abstract: A pulse-actuated hydraulic pump includes a hydraulic chamber with a bellows having a volume increased or decreased by the selective application a force in an axial direction thereof by a piezoelectric actuator. Control means control electrically-driven valves to selective discharge fluid from the bellows in precisely controllable volumes through a first pumping port or a second pumping port.

Abstract: The flow matching valve disclosed herein incorporates a fill port in addition to the source, load and respective drain ports employed in previous load matching valves. The inclusion of the fill port allows reconfiguration of hydraulic systems to reduce leakage and improve reliability and to eliminate auxiliary check valves in certain configurations.

Abstract: Conventional piston-cylinder hydraulic actuators require external pressure sources. The hydraulic actuator disclosed utilizes the centrifugal head developed in its chambers. The piston (36) is attached to shaft extension (24) which is splined to the actuator cylinder (20). The cylinder (20) rotates with the shaft (16) to develop a centrifugal fluid head which is selectively directed from the outlet port (40a, 40b) of a contracting chamber through a servo valve (46) to the return passageway (46b, 46a) of an expanding chamber to axially displace piston (36) and shaft (16). An accumulator in the fluid circuit retains fluid displaced from the cylinder (20).

Abstract: A hydraulically operated elevator door mechanism includes a motor-driven shaft connected to rotate gears within a fluid reservoir. Fluid is "pumped" as the gears rotate, to one side of a piston, propelling the piston. The piston is connected to two pulleys over which a cable length is attached to the elevator door. Piston movement causes the pulleys to effectively shorten the length of cable between the pulley and door, which in turn, causes the door to slide.

Abstract: A device in machines (1) which are driven by means of a hydraulic cylinder, such as hydraulic presses and the like, and which has at least one pump (5) for the hydraulic fluid which pump is driven by a driving machine (6) through an energy accumulator, for example a flywheel (7). The object of the invention is to provide a considerable energy saving and recovery of energy. This has been achieved by at least one driving unit (5) connectable to the hydraulic system in the machine, said driving unit being arranged to bring back the elastically stored energy in the machine to the energy accumulator (7) during the decompression phase of the machine.

Abstract: A pumping unit particularly for pumping oil from an oil bore has an inner stationary cylinder unit and an outer cylinder unit reciprocatable relative to the inner unit by hydraulic fluid; the units are enclosed in a casing and the outer unit functions as a piston in the casing; as the outer unit moves downwardly in the down-stroke, under the action of gravity and hydraulic fluid, air in the casing beneath it is displaced into a reservoir to form a supply of pressurized air; in the upstroke the supply of pressurized air is exploited to drive the outer cylinder upwardly, aided by the hydraulic fluid.

Abstract: The valve disclosed herein functions as a flow matching device. By employing such a valve, hydraulic systems may be implemented in which filling and emptying of a variable volume load, such as a hydraulic piston, may be accomplished through simple check valve structures at controlled flow rates.

Abstract: A closed hydraulic system (10) of the type for steering a boat including a hydraulic cylinder (18) having port and starboard sides (20, 22) and a piston (24) within the cylinder (18) moveable therebetween. A steering pump (12) has first and second fluid outlets (14, 16). Port and starboard hydraulic lines (26, 28) interconnect the port and starboard sides (20, 22) to the first and second outlets (14, 16) respectively, for fluid communication therebetween. A closed separator tank (30) separates air from hydraulic fluid. The tank (30) includes port and starboard tank line (32, 34) in fluid communication with the port and starboard hydraulic lines (26, 28) respectively. The tank (30) includes a bleeder valve mechanism for selectively allowing fluid flow in one direction from the port tank line (32) into the separator tank (30) and out the starboard tank line (34) and alternatively in the opposite direction.

Abstract: A fluid system has a variable displacement pump connected in a closed-loop circuit to a fluid cylinder having a piston and one connecting rod extending from the piston through an opposite side wall such that the effective pressure responsive areas on the opposite sides of the piston are unequal. The fluid system includes a circuit which permits an unequal displacement cylinder to be connected in a closed-loop circuit to a fluid pump.

Abstract: This invention relates to integrated electro-hydraulic actuators for use aboard aircraft or elsewhere. A balanced, double-acting hydraulic ram or motor (12) is connected between a support (16) and a member to be moved relative to the support. The ram includes first and second changeable volume hydraulic chambers (30, 32). A reversible hydraulic pump (38) is connected by a pair of conduits (44, 46) to the ram chambers (30, 32). The pump (38) displaces hydraulic fluid from one chamber to another for the purpose of causing a pressure differential between them. A hydraulic accumulator (60) provides leakage makeup fluid to the actuator, and further provides a quiescent pressure to the actuator when it is in a substantially nonoperative condition. A conduit (62) may connect the accumulator (60) to the ram (12). A laminar leakage flow path within the actuator permits hydraulic connection of the accumulator (60) to the ram (12) without use of valves.

Abstract: A remote valve positioning apparatus is provided in which a valve spool is resiliently loaded at each end to a normal position, hydraulic fluid is delivered selectively to one end or the other of the valve spool at a fixed flow and the valve is positioned by pressure drop caused by the fixed flow over an orifice proportional to the stroke of the valve spool.

Abstract: A jacking mechanism for jacking a well casing or other well pipe vertically, and including a hydraulic control system in which a reversible variable displacement pump acts in one condition to deliver pressure fluid in parallel with another pump to the lower end of a jacking cylinder to actuate the piston thereof upwardly, with fluid discharging from the upper end of the cylinder to the variable displacement pump and being metered therethrough to regulate the rate of upward movement of the piston. In a second condition of the apparatus, flow through the variable displacement pump is reversed to lower the piston, and a variable restriction valve regulates discharge of fluid from the lower end of the cylinder to act with the variable displacement pump in regulating downward movement of the piston and supported pipe.

Abstract: A pump jack drive apparatus includes a pair of hydraulic cylinders connected to a walking beam of the pump jack for reciprocating the horsehead, and a pair of microswitches or proximity switches which are closed by the walking beam at the limits of the stroke thereof for controlling such stroke. The cylinders are driven and controlled by a pump and control unit which includes a valve for feeding hydraulic fluid to one or the other of the hydraulic cylinders, a control cylinder for controlling the valve, and two solenoid operated control valves for controlling movement of the control cylinder in response to closing of the switches by the walking beam.

Abstract: A power steering system, particularly advantageous for use on electric powered vehicles, in which the hydraulic pump operates only when steering commands are given. Torque applied to the steering shaft by rotation of the steering wheel is translated to axial stress on a thin walled tube, the direction and intensity of which depend on the direction and amount of steer angle change commanded. The axial stresses are detected by strain gages, and the motor which powers the hydraulic pump is activated only when stress is detected. Manual steering inputs enter the pump on one side, and the powered servo motor inputs enter on the opposite side, thus permitting the vehicle to be steered by manual input alone if the powered input fails. The components of the system are arranged in coaxial alignment, providing a compact system with improved heat dissipation qualities.

Abstract: The preferred embodiment is directed to an oil well pumping apparatus incorporating a walking beam having a horsehead at one end which connects to the sucker rods in the oil well. The opposite end of the walking beam is supported on a fixed pivot. A hydraulic and pneumatic combination unit connects from a supporting platform to a central point on the beam to raise and lower the beam. The improved apparatus utilizes air pressure to balance the static load on the apparatus and dynamically strokes the sucker rod string by imparting a reciprocating motion through hydraulic power applied at a specified rate to raise and lower the walking beam. A pump and motor system for a closed hydraulic loop is included. Alternate preferred embodiments are disclosed. In one form, a lubricating system is incorporated. First and second alternate forms of pickoff apparatus which powers the pneumatically balanced pumping apparatus is also included.

Abstract: The disclosure relates to improvements in a hydraulically-actuated control device used in an operation unit of treatment chair and the like in an interlocking relation with reciprocating movement of a hydraulic piston. The device is of the construction in which two control valves slow in closing and opening operation are disposed in the oil supply and discharge passages leading to a hydraulic cylinder having a hydraulic piston therein so as to prevent shock in starting and stopping of the operation unit by controlling opening and closing of the two control valves and operation of the hydraulic pump disposed in the oil supply passage.

Abstract: An electric stepping motor, operated by command signals from a computer or a microprocessor, rotates a rotary control member of a distributor valve, for sequencing hydraulic pressure and hence flow to the cylinders of an axial piston hydraulic machine. A group of the cylinders are subjected to pressure and flow and the remaining cylinders are vented to a return line. Rotation of the rotary control valve member sequences pressurization by progressively adding a cylinder to the forward edge to the pressurized group and removing a cylinder from the trailing edge of the pressurized group. The double ended pistons of each new pressurized group function to drive a wobble plate into a new position of equilibrium and then hold it in such position until another change in the makeup of the pressurized group. These pistons also displace hydraulic fluid from the opposite cylinder head which serves as the output of a pumping element.

Abstract: Means are disclosed for dissipating supercharge pressure in a hydraulic system including a reversible pump (18) directly connected to a hydraulic cylinder (22). Supercharge pressure results from unequal areas on either side of a piston (24) of a single-ended hydraulic cylinder (22). When the piston moves towards the blind end of the cylinder (22), more fluid is displaced from the cylinder than is admitted to the cylinder on the opposite side of the piston. Means responsive to a pressure at a first port (82) of the pump (18) opens a passage between the second port (76) of the pump (18) and a fluid reservoir (16), allowing fluid in excess of the pump's intake requirements to pass to the reservoir (16). In a first embodiment of the invention, a rocker mechanism (60) is actuated by a piston (66) responsive to pressure at the first port (82) pressing against a first end (20) of the rocker mechanism (60), the second end (74) of the rocker mechanism (60) displacing a check ball (38) of a keep-full valve.

Abstract: A counterbalancing hydraulic system for exerting a torque on a member such as a spud pile by means of at least two substantially identical hydraulic cylinders, piston rods of which engage the pile at a distance from one another, the pistons being subjected to pressure in opposite senses, while the portion of each cylinder remote from the piston rod communicates through a main displacer pump motor each with the portion of the other cylinder located on the side of the piston rod and the portion of each cylinder remote from the piston rod communicates through an auxiliary displacer pump motor with a medium reservoir.

Abstract: An automatic door operator for opening and closing a door such as a cold storage door which is mounted in a frame for sliding movement in a vertical plane has a hydraulic control system which includes an electric motor for rotating a reversible hydraulic pump, an electric control circuit which activates the electric motor to rotate the pump in the appropriate direction, and a reversible rotary hydraulic motor driven by the pump to rotate a chain drive which draws the door to its open and closed positions. The hydraulic control system also includes a means for cushioning the rapid start and stop of the door to provide smooth operation which includes a pair of check valves disposed in the control system such that one check valve is on either side of the hydraulic pump, and a first set of pressure relief valves disposed in the control system on either side of the pump between the pump and the check valves, and a second set of pressure relief valves between the check valves and the hydraulic motor.

Abstract: Disclosed are methods and apparatus for controlling the flow of hydraulic fluid to and from a work cylinder. The disclosed system includes a reversible variable displacement pump interconnected between a work cylinder and a selector valve which may connect the pump with any of a plurality of fluid reservoirs. The fluid reservoirs contain hydraulic fluid at variable pressures so that the pressure at the work cylinder may be raised to pressures well above the pressure differential capacity of the pump at maximum flow rate by selectively increasing the pressure on the reservoir side of the pump. The system includes means for controlling the pressure at each port of the pump so that the pressue on the output port is always greater than the pressure on the input port regardless of the direction of flow through the pump and regardless of pressures at other points in the system.

Abstract: A combination shuttle and high pressure relief valve is provided within a hydrostatic drive or transmission system. The valve is constructed with a spool member in two sections. The sections include hooks that interact with one another to lock the spool sections together in one mode of operation, yet permitting the spool sections to act independently in another mode of operation. Complete fluid charging of the fluid system is ensured by dual flow circuitry between the system pump and motor, while a restrictor valve means is connected to the shuttle and pressure relief valve to provide continuous flow of fluid through a system filter.

Abstract: A jack pump, such as the type capable of use in pumping crude oil from an oil well, the jack pump including a double acting piston and cylinder motor with the piston rod of the motor being adapted to be connected to the polished rod projecting upwardly from a well head. A variable displacement hydraulic pump, which is driven by a motor or engine, is included in a closed hydraulic loop wherein conduits are connected to a pair of output ports of the pump. A pump control means controls the direction and volume of flow in the loop so as to establish a total velocity profile during the complete pumping cycle and to determine the length and position of the stroke of the piston rod.

Abstract: A stop mechanism for a bending press, plate shear or the like machine, provided with a work-table and with a work-piece stop which is horizontally adjustable along the work table thereby defining the position of the work-piece relative to the machinery, the work-piece stop being coupled with a position control-unit which is provided with an indicator of the momentary position of the work-piece stop and can be programmed with the desired position, the stop being displaceable by means of a hydraulic piston-cylinder unit and a pump drive means controlled by the position control-unit.

Abstract: A rotary shredder for waste materials has a pair of counterrotating cutting shafts, each of which mounts a series of spaced-apart disc-type cutters. The cutters on one shaft extend into the spaces between cutters on the other shaft so that the cutters on the two shafts coact to shred material fed therebetween. The two shafts are driven by a reversible radial piston hydraulic motor through a gear train arranged to rotate one cutter shaft at twice the speed of the other. The hydraulic motor is driven by an electric motor-driven fixed or variable displacement pump. A flow-reversing valve in the hydraulic motor control circuit controls the direction of fluid flow through the hydraulic motor. The reversing valve is electrically actuated automatically by a fluid pressure-operated switch to reverse flow and the direction of rotation of the cutters to prevent jamming whenever fluid pressure in the motor circuit rises to an abnormally high level.

Abstract: A closed circuit hydraulic control system for an hydraulic motor including a cylinder, a piston movable in such a cylinder, and a rod connected to one side of the piston, such cylinder having a blind end and a rod end through which the rod extends. A reversible circulating pump having two ports is provided for supplying fluid under pressure to the blind end and to the rod end respectively of the cylinder. A first tubing interconnects the blind end of the cylinder to one port of the reversible pump, whereas a second tubing interconnects the rod end of the cylinder to the other port of the reversible circulating pump. Means are provided to accommodate the volume of fluid displaced by the rod as the piston is moved toward the blind end of the cylinder.

Abstract: A device for controlling the quantity of hydraulic fluid returned to a pump from a double-acting lifting cylinder for lifting and lowering a load which moves through a dead point includes a housing, a control piston slidable within the housing and defining two spaces within the housing, each of the spaces being adapted to be connected to a pump. Two further spaces are provided within the housing and adapted to be connected, one to each side of the double-acting lifting cylinder. Each further space is connected with one of the spaces by way of a valve, and each of the valves is operable by means of the control piston. During use, the quantity of hydraulic fluid allowed to return from the lifting cylinder, through one of the further spaces and its associated valve and space, and returned to the pump, is proportional to the displacement of the control piston which depends on the pressure exerted by the pump.

Abstract: A closed hydraulic system (10) of the type for steering a boat including a hydraulic cylinder (18) having port and starboard sides (20, 22) and a piston (24) within the cylinder (18) moveable therebetween. A steering pump (12) has first and second fluid outlets (14, 16). Port and starboard hydraulic lines (26, 28) interconnect the port and starboard sides (20, 22) to the first and second outlets (14, 16) respectively, for fluid communication therebetween. A closed separator tank (30) separates air from hydraulic fluid. The tank (30) includes port and starboard tank .[.line.]. .Iadd.lines .Iaddend.(32, 34) in fluid communication with the port and starboard hydraualic lines (26, 28) respectively. The tank (30) includes a bleeder valve mechanism for selectively allowing fluid flow in one direction from the port tank line (32) into the separator tank (30) and out the starboard tank line (34) and alternatively in the opposite direction.