Abstract: The present invention relates to a hydraulic circuit for a boom cylinder combination having a float function which is capable of implementing a leveling work in such a manner that a leveling work is performed by lowering a boom based on its self-weight without using an operation oil discharged from a hydraulic pump using an excavator during a leveling work which includes a first inner path which is formed in one side of the boom cylinder combining spool and connects a hydraulic pump and a boom cylinder large chamber in a switching mode, a second inner path which is formed in the other side of the boom cylinder combining spool and connects an operation oil from the hydraulic pump to a hydraulic tank in a switching mode, and a third inner path which is formed in the other side of the boom cylinder combining spool and combines the operation oils from the small chamber and large chamber of the boom cylinder in a switching mode and connects the same to the hydraulic tank.

Abstract: The present invention provides a hydraulic circuit for a crane wherein a switching valve is provided between a plurality of motor circuits connected in series within the same actuator group, and at the time of simultaneous operation of the motor circuits, the switching valve is switched from a first position to a second position whereby the series connection between the motor circuits is cut off, and they are driven by each of separate hydraulic sources, thereby enabling prevention of pressure interference at the time of simultaneous operation of the motor circuits within the same actuator group without increasing hydraulic sources.

Abstract: Hydraulic oil supplied from pumps (12),(13) to an attachment actuator (60) is controlled by attachment control valves (27),(28). Hydraulic oil supplied from pumps (12),(13) to other actuators (52),(54),(56),(58) is controlled by other control valves (21) through (26). Control conditions for operating the attachment actuator (60) alone and control conditions for operating the attachment actuator (60) simultaneously with any of the other actuators (52),(54),(56),(58) are discriminated by the pilot pressure sensors (32),(34),(36),(38). Control characteristics of the attachment control valves (27),(28) are controlled by a controller (43) based on the discriminated control conditions.

Abstract: A hydraulic system includes at least two consumers, e.g., a closing unit and an injection unit of an injection molding machine. At least two displacement pumps are provided to produce a fluid flow under pressure to the consumers, whereby at least one control valve is provided for each of the consumers. At least one further valve is provided to control a fluid communication between the output sides of the displacement pumps, wherein at least one of the consumers is supplied with pressure from the outlet of the displacement pumps separately or together in groups.

Abstract: A hydraulic actuating device, for a vehicle cover and an associated lock for locking the cover in the closed position, has a cover actuator and a lock actuator which each are provided with a first and second connection, which are respectively in communication with an associated first and second opening adjoining the actuator space. The cover actuator is provided with a third opening, which is connected to the second connection of the lock actuator. The first connection of the cover actuator and the first connection of the lock actuator are connected to a common connecting line with a single actuable valve, which in a first position connects the delivery port of the pump to the connecting line. The second connection of the cover actuator is in communication with the delivery port of the pump.

Abstract: According to the invention, traveling bypass cut-off valves are disposed in center bypass passages respectively which are located between traveling direction control valves and working direction control valves disposed downstream of the valves, wherein, when at least a traveling motor and any of working actuators are operated simultaneously, the traveling bypass cut-off valves are switched from neutral position to another position. Thereby, when travel and work by working actuators are performed simultaneously, interference between pressure oil fed to traveling motors and pressure oil fed to the working actuators is to be prevented.

Abstract: The displacement of fluid translating devices are normally controlled by changing the angle of an eccentric or a cam plate to change the pumping stroke of the pistons within the device. In the subject arrangement, the displacement of the fluid translating device is controlled by controlling the flow being delivered into or away from each of the associated pressure chambers defined therein by the respective ones of a plurality of pistons. By not permitting the flow from every piston to be directed into useful work, the volume of fluid being directed into or away from the fluid translating device can be altered. Likewise, the direction of fluid flow within the fluid translating device can be selectively changed thus permitting the subject fluid translating device to be capable of pumping or motoring in both directions of flow relative to the first and second inlet/outlet ports thereof.

Abstract: The present invention relates to a hydraulic circuit for a boom cylinder combination having a float function which is capable of implementing a leveling work in such a manner that a leveling work is performed by lowering a boom based on its self-weight without using an operation oil discharged from a hydraulic pump using an excavator during a leveling work which includes a first inner path which is formed in one side of the boom cylinder combining spool and connects a hydraulic pump and a boom cylinder large chamber in a switching mode, a second inner path which is formed in the other side of the boom cylinder combining spool and connects an operation oil from the hydraulic pump to a hydraulic tank in a switching mode, and a third inner path which is formed in the other side of the boom cylinder combining spool and combines the operation oils from the small chamber and large chamber of the boom cylinder in a switching mode and connects the same to the hydraulic tank.

Abstract: A first given pressure is provided to a first side of an air pressure cylinder that in turn drives a cutting member under the influence of the first given pressure. A second given pressure is provided to a second side of the air pressure cylinder that is greater than the first given pressure during a non-cutting state of the air cylinder. The cutting member remains stationary as long as the second given pressure is greater than the first given pressure. To transition to a cutting state, the second given pressure is rapidly reduced to a value below the first given pressure value during a cutting state of the air pressure cylinder for moving the cutting member to cut a web.

Abstract: A backhoe hydraulic system includes a first source of hydraulic fluid, a tank or reservoir, a boom lift cylinder, and a directional control valve that controls fluid flow between the boom swing cylinder and the tank and reservoir. The system also includes a second source of hydraulic fluid (at a higher pressure than the first source) that is connected to one port of the boom lift cylinder via a separate boost valve.

Abstract: A hydraulic actuating unit for integration into a preassembled folding roof unit of a motor vehicle is adapted for mounting as a single unit in a motor vehicle with the hydraulic actuating unit integrated therein. The preassembled folding roof unit has a folding roof with a foldable cover and a framework for the cover. A main bow is pivoted by a hydraulic main bow actuator and a rear bow is pivoted by a hydraulic rear bow actuator, each actuator being of the double-acting type. The hydraulic actuating unit also has an actuable two-position control valve, which control valve has an outlet port, an inlet port and a reservoir port, the outlet port being connected to a working chamber of the main bow actuator and/or a working chamber of the rear bow actuator. The control valve, in a first position, connects the associated outlet port to the reservoir port and, in a second position, connects the associated outlet port to the inlet port of the control valve.

Abstract: An off road machine is provided with a hydraulic system for operating drive motors for propelling the machine, as well as operating actuators for machine functions. The hydraulic system utilizes three pumps, with the pumps connected to a single high pressure relief valve. Additionally, two of the pumps normally are used for driving traction motors for the machine, and when a valve is operated the third pump flow is provided to both of the drive motors for the vehicle to increase the speed of machine movement. Additionally, a dump valve is used for insuring that the flow from the pump will be diverted to tank unless an operator ready signal is present.

Abstract: A hydraulic drive system for a supersized hydraulic working machine such as a hydraulic excavator includes hydraulic pumps connected to main lines through a delivery line and a supply line. Branch portions from the main line include flow control valves for allowing a hydraulic fluid to flow from the hydraulic pumps toward hydraulic cylinders. A hydraulic reservoir is connected to the main lines through a reservoir line and a drain line. Other branch portions for the drain line include flow control valves for allowing a hydraulic fluid to flow from the hydraulic cylinders toward the hydraulic reservoir. A line branched for the delivery line includes a bypass valve for supplying the hydraulic fluid delivered from the hydraulic pumps to the supply line at a desired flow rate and returning the remaining hydraulic fluid to the hydraulic reservoir.

Abstract: A pressurized hydraulic fluid supply apparatus capable of merging or separating a plurality of hydraulic pump lines according to the driving states of a plurality of actuators. The pressurized hydraulic fluid supply apparatus has a merge/separation valve 40 that merges or separates the hydraulic fluids delivered under pressure by the first hydraulic pump 1 and the second hydraulic pump 11. The merge/separation valve 40 is set to a flow separation state upon driving of the second hydraulic actuator 16 and is preferentially shifted to a flow merging state when the third hydraulic actuator 21 is driven. Hence, even when a manually driven operation valve is used, the merge/separation valve 40 is automatically switched between the flow separation state and the flow merging state according to the operation of the operation valve. This apparatus prevents an unintended flow rate difference between the first and second actuators from being produced upon driving of the third actuator.

Abstract: Arranged on a side of a first pump are a flow control valve for controlling a first boom cylinder, a flow control valve for an arm, said flow control valve being connected in tandem with said flow control valve and being adapted to control an arm cylinder, and a flow control valve for a second boom, said flow control valve being connected to a downstream side of the flow control valve and being adapted to control a second boom cylinder.

Abstract: Hydraulic control unit, in particular for the folding roof of a vehicle, comprising a reservoir for hydraulic fluid, a pump for drawing hydraulic fluid out of the reservoir and provided with a delivery port for delivering compressed hydraulic fluid, and also at least one first hydraulic actuator of the double-acting type with a first and a second variable working chamber, which working chambers are separated by a piston and are provided with a first and a second connection respectively for supplying hydraulic fluid to said working chambers, further comprising a control valve assembly with a first exit port and a second exit port, which are connected respectively to the first and the second connection of the first actuator, for controlling the movements of the first actuator. The control valve assembly comprises one or more operable control valves and is designed for selectively connecting one of the two or both exit ports thereof to the delivery port of the pump or the reservoir.

Abstract: A construction machine comprising two hydraulic pumps; right and left traveling motors for causing the construction machine to travel; work machine actuators for actuating a work machine of the construction machine; a control valve which makes control so that a hydraulic oil discharged from the two hydraulic pumps is fed to at least either the right and left traveling motors or the work machine actuators and so that when both traveling operation and work machine operation are performed simultaneously, the hydraulic oil discharged from one of the two hydraulic pumps is fed to the traveling motors and the hydraulic oil from the other hydraulic pump is fed to the work machine actuators, the control valve providing communication between the two hydraulic pumps through a pump communication path; a drive signal detecting device which detects drive signals with respect to the two hydraulic pumps when the traveling operation and the work machine operation are performed simultaneously; and a controller which controls

Abstract: The multiple pump apparatus includes first and second variable displacement closed circuit pumps. The multiple pump apparatus pressurizes fluid to be subsequently supplied to drive load devices. The first and second pumps each have fluid communication lines connected to load devices through flow control valves. Each of the pumps has a swashplate for varying its displacement. The swashplates are of the over-center type, enabling each pump to supply pressurized fluid in either direction, thus providing both forward and reverse function to the load devices. The first pump has its fluid communicating lines connected to fluid communicating lines between first and second two-position four-way flow control valves. The opposite side of the first flow control valve has fluid communicating lines connected to a load device which drives a harvesting mechanism, in this case a rotor motor.

Abstract: A system for supplying an implement with hydraulic fluid includes a first hydraulic pump generating a first flow, a second hydraulic pump generating a second flow and a valve assembly adapted to be coupled to the implement and coupled to the first and second flows. The valve assembly couples the first flow to the implement. The valve assembly also selectively adds the second flow to the first flow to provide a low flow or a high flow. The valve assembly couples the first flow to the implement via a first coupling in response to a first signal and via a second coupling in response to a second signal. The system further includes a manually operable control coupled to the valve assembly and movable between the first position which the first signal is generated, a second position in which the second signal is generated and a third position in which a third signal is generated. The system also includes a foot pedal control coupled to the manually operable control and to the valve assembly.

Abstract: A power machine includes a pair of traction motors to provide for travel of the machine. The power machine also includes a boom, an arm and a tool (such as a bucket). The power machine includes a hydraulic power circuit which has a valve stack that enables the boom and at least one of the arm and tool to be operated simultaneously.

Abstract: A cut-off valve is mounted so that it can open and close an oil passage which leads a pressure oil discharged from a first pump into a hydraulic oil tank in a neutral state of a spool valve for boom. When an operating lever for boom and an operating lever for arm have simultaneously been operated to a boom raising side and an arm pulling side, respectively, the cut-off valve is closed in proportion to a boom raising or arm pulling pilot pressure. The cut-off valve is controlled using as a parameter a differential pressure between the arm pulling pilot pressure and the boom raising pilot pressure. By doing so, there is obtained a low gain operability in the crane work, while in the parallel pulling work there is obtained an operability of a relatively high gain which matches a quick motion of the arm.

Abstract: A rodless cylinder rope tensioning apparatus maintains tension in an endless rope system operable for threading a web in a paper-making apparatus and includes at least one rodless cylinder having at least one yoke sheave attached to the internal piston in the rodless cylinder. A rope is stretched around an entry guide roller and the yoke sheave and is stretched by operation of the rodless cylinder, which selectively causes the piston to relocate the yoke sheave along the length of the rodless cylinder and apply a selected degree of tension to the rope. In a preferred embodiment a pair of entry guide rollers is provided in a frame containing a pair of parallel rodless cylinders, each having a yoke sheave independently movable along the respective rodless cylinder by operation of the corresponding rodless cylinder piston, to effect tensioning of a pair of ropes in the paper-making apparatus.

Abstract: Pilot change-over valves for operating actuators are connected in a center bypassing form and a cut-off valve is disposed downstream of each such pilot change-over valves. Commands which are in a proportional relation to each other are outputted from a controller to a pilot port of the cut-off valve and a pilot port of a pilot change-over valve for boom. Both valves are closed synchronously. Operation commands for both valves can be altered with a volume control for setting operation characteristics. Hydraulic pump oils for arm are joined together by a confluent valve. Consequently, highly responsive operations can be attained in operating the attachment of a hydraulic excavator. This is effective in the ground hardening work with a bucket, the work for removing mud from the machine body and the work for scattering soil.

Abstract: Disclosed is an apparatus for increasing the operating capability of a construction machine during a fine operation mode and a method for the same. The apparatus being capable of preventing a merged hydraulic fluid from being supplied into a hydraulic actuator and increasing the pressure of the hydraulic fluid being supplied into the hydraulic actuator during the fine operation mode. The apparatus includes a detector that detects the RPM count of the engine of the construction machine and determines whether the engine is switched into the fine operation mode. A first anti-confluence valve and a second anti-confluence valve prevent a first hydraulic fluid supplied into the first actuator and a second hydraulic fluid supplied into the second actuator from merging while either the first actuator or the second actuator is operating. An anti-confluence relay turns the first anti-confluence valve and the second anti-confluence valve on/off.

Abstract: A hydraulic circuit enables a plurality of hydraulic actuators to be locked or unlocked at the same time no matter whether control valves controlling pressurized oil feed to the hydraulic actuators are pilot-controlled or not. To this end, the circuit is provided with oil lines leading from hydraulic pumps to an oil reservoir without passing through the control valves and with first and second selector valves 20 and 24 opening or closing the oil lines.

Abstract: The present invention relates to a hydraulic circuit for a hydraulically driven working vehicle which allows the vehicle to travel at an almost constant speed during high-speed traveling, provides a great digging force during working, does not need a charging pressure for preventing cavitation, loses a small amount of energy, and has a simple structure. To this end, the hydraulic circuit has a hydraulic travel pump (2) and a working machine hydraulic pump (4) which are driven by the power of an engine (1) for discharging pressurized oil to a HST travel circuit and a working machine-driving hydraulic circuit, respectively, wherein pressurized oil from the working machine hydraulic pump (4) joins pressurized oil from the hydraulic travel pump (2) to effect high-speed traveling, while pressurized oil from the hydraulic travel pump (2) joins pressurized oil in the working machine hydraulic pump (4) to generate a large digging force to effect digging.

Abstract: A pilot pressure sensor detects a pilot pressure from an arm operating unit and outputs a pilot pressure signal. A drive signal corresponding to the pilot pressure signal is then outputted from a controller to a solenoid-operated proportional valve. Through the solenoid-operated proportional valve, a pilot pressure is fed to an auxiliary selector valve so that an opening of said auxiliary selector valve becomes greater. Of pressure oil delivered from a first hydraulic pump, a flow rate of the pressure oil to be branched to a side of a by-pass circuit is hence increased. The pressure oil fed through the by-pass circuit passes through a merging directional control valve and is caused to merge with pressure oil fed from a second hydraulic pump. The thus-merged pressure oil is then fed to a hydraulic arm cylinder.

Abstract: Description of a system of a thermodynamic steam pump for water propulsion, its heating, disinfection and sterilization, or propulsion of other liquids, characterized by use of water steam pressure as the propelling media of a liquid mass directly, without intermediate equipment to convert the energy, which is composed of a pressure tank, an electric input valve, steam under pressure provided by an external source and means for introduction by gravity of the liquid mass to be impulsed, with electromechanical elements to control level and flow, including a heat exchanger where recycled steam is forced through a tube panel which over heats the liquid thus eliminating the existing microbes and bacteria or just taking advantage of said heat exchanger to pre-heat and fluidify heavy crude oils or other viscous liquids with no expense of additional energy. This same thermo-hydro-dynamic system installed in a surface vessel (ship) can act as propulsor of the same by the action and reaction principle. (Jet propulsion.

Abstract: A fluid joining device for construction vehicles is disclosed. The device has a bypass line control valve which is mounted to a second center bypass line of the second pump. The bypass line control valve normally opens the second center bypass line but selectively closes the second center bypass line in response to a pilot pressure. A second pilot line control valve is mounted to a second pilot line and controls the second pilot line in response to an outside signal. The second pilot line extends from the first pilot line control valve and selectively drives the first pilot line control valve. The device selectively performs the fluid joining function in accordance with operational conditions of the actuators, thus smoothly operating the actuators and improving operational effect of the construction vehicle.

Abstract: A fluid power control system for use in a mini-excavator, in which a first control section (S2) includes first and second control valves respectively connectable to first (2) and second (4) implement functions; and in tandem with one another. A first gear pump (P2) supplies the actuator connected principally to the first implement (2), and a second gear pump (P3) supplies working fluid to the interconnection between the first and second control valves. The advantage of this arrangement is that, as the first control valve switches from its neutral position to a position selecting its associated implement (2), progressively more of the fluid passing through the second control valve is supplied by the second pump (P3) until, when the implement (2) to which the first control valve is principally connected is fully selected, the two implements (2, 4) are supplied separately by the respective gear pumps (P2, P3).

Abstract: Pump ports 9p, 10p, 11p, 13p of boom, arm, bucket and first travel directional control valves 9-11, 13 are connected to first and second hydraulic pumps 1a, 1b through feeder lines 93a, 93b; 103a, 103b; 113a, 113b; 133a, 133b. Auxiliary valves 91a, 91b; 101a, 101b; 111a, 101b; 131a, 131b controlled respectively by proportional solenoid valves 31a, 31b; 32a, 32b; 33a, 33b; 34a, 34b are disposed in those feeder lines. The auxiliary valves each have a function as a reverse-flow preventing function and a variable resisting function including a flow cutoff function, whereby a joining circuit and a preference circuit can be realized in the closed center circuit with a simple structure and further, a preference degree and metering characteristics can be set independently of each other during the combined operation of plural actuators.

Abstract: An apparatus for controlling the lifting operation comprising an operation mode selection switch which is selectively set to an ordinary operation mode or to a lifting operation mode and a hydraulic circuit isolating means. The hydraulic circuit isolating means isolates the hydraulic circuit into a running drive hydraulic circuit which feeds the pressurized fluid of one of the variable-capacity hydraulic pumps to the actuators of the running apparatuses when the operation mode selection switch is set to the lifting operation mode and a hydraulic circuit for driving the apparatus on the side of the turning body, which feeds the pressurized fluid of the other variable-capacity hydraulic pump to the actuators other than those of the running apparatuses.

Abstract: In a hydraulic device at least one control valve with at least three control positions is connected with a variable capacity pump, whereby the controlling device of the variable capacity pump is connected with the supply line downstream the control valve via a feedback line with the purpose of adjusting the pump output so as to maintain a constant operational pressure gradient. The back flow pipe is conducted over the control valve, which is connected with the consumers by connecting valves associated to mentioned consumers, whereby a transducer is associated to the back flow pipe, which together with the transducer of the supply line constitutes a regulating variable for a control unit. This way a precise and energy saving regulation or control of the consumers in both flow directions by a control valve at a reasonable price is achieved.

Abstract: A hydraulic circuit for a working vehicle comprising a first pump, a second pump, a first actuator, a second actuator, and a selector valve having a plurality of control positions. The selector valve is switchable between a first position for connecting the first pump to the first actuator and the second pump to the second actuator, and a second position for connecting the first pump and the second pump to the second actuator. This circuit includes a first relief valve disposed between the selector valve and the first pump, and a second relief valve disposed between the selector valve and the second pump. The first relief valve is set to a higher relief pressure than the second relief valve.

Abstract: The invention relates to a valve system for supplying fluid from a pair of fluid pressure sources to a load. A feed valve is provided which feeds--when required--a partial flow of the second fluid pressure source into the feed line of the load which is connected to the first fluid pressure source through a directional control valve. The feed valve comprises a pressure-compensating valve to control the volume of the partial flow and a switching valve to automatically open the pressure-compensating valve when required.

Abstract: A service valve circuit of a hydraulic excavator connected beforehand for use in controlling a special attachment in addition to a prescribed actuator control valve. The service valve circuit comprises a confluence valve 17 for performing electromagnetic proportional flow rate control, disposed in a confluence circuit 16 in communication with the section between inflow circuits 3F and 3R of two variable pumps 2F and 2R, an electrical switch 21 for switching the confluence valve 17 on or off according to a required flow rate and a volume 22 for adjusting the quantity of flow after passing through a confluence valve 17 in a range of flow for a maximum of one to two pumps. Since the requirement of confluence with respect to a required quantity of flow for a special attachment e and the quantity of confluence are set in advance, there will be no excess or shortage of the quantity of confluence.

Abstract: An oil hydraulic circuit for a hydraulic shovel with which a composite operation can be performed readily and smoothly without special skill in operation of the hydraulic shovel. The oil hydraulic circuit comprises a first actuator which can operate with pressure oil from a predetermined one or both of a pair of hydraulic directional control valve sets, a second actuator which operates only with pressure oil from the other hydraulic directional control valve set, a proportional changing over device interposed intermediately in a pipe line communicating the other hydraulic directional control valve set with a first actuator for adjusting the maximum meter-in opening value to the first actuator in response to a magnitude of a signal received at a signal receiving portion of the proportional changing over device, and a controller for arbitrarily adjusting the signal to be supplied to the signal receiving portion of the proportional changing over device.

Abstract: A control system having a flow-dividing selector valve mechanism (52) for changing the channels for causing a pressure fluid to flow from two main pumps (40), (50) into two control valve groups (60), (70) therethrough, and confluent selector valve mechanisms (80), (90) for causing the pressure fluid flowing into each group to flow into a working device control valve of the other group. The confluent selector valve mechanism (80) of the group wherein the working device control valve (62) has a need to compensate for the flow of fluid thereinto cancels the confluence function. The system has a mechanism for restricting the stroke of the spool of a working device control valve (160) to be subjected to varying loads to cause the fluid discharged from the actuator connected thereto to flow into the actuator again when the load is small. A sequence valve (170) operates the spool stroke restricting mechanism (190) by a pilot primary pressure.

Abstract: A single rod three chamber fluid motor is driven in a forward stroke which includes a rapid initial advance followed by a relatively short and slow feed stroke under high pressure. The rapid advance is performed by a closed loop system in which a high displacement main pump, pumps fluid to act against a first equal area at the head side of the piston and receives fluid expelled from a second equal area at the rod side of the piston while an accumulator maintains the third chamber exposed to a third area of the head side of the piston filled with fluid. Upon shifting to the feed stroke, the main pump is disconnected and a feed pump applies pressure to both of the first and third areas at the head side of the piston and receives fluid expelled by the second equal area and from a charge pump. The access fluid added to the feed pump circuit by the charge pump is returned via the accumulator to the charge pump sump during the return stroke of the piston.

Abstract: Apparatus is provided for delivering a controllable, variable flow of pressurized fluid. Conduits define a circulating fluid flow system, the flow system passing through a transducer for transferring energy as a mechanical input or output to or from pressurized fluid circulating in the system. At least first and second volumetric pumps are connected to conduits of the flow system in parallel relation to each other and in flow communication with the transducer. An operating shaft, preferably a single shaft, engages the first and second pumps. Valves and piping are provided for selectively shunting and isolating the first and second pumps from the fluid flow system. Thus, energy applied to the fluid flow system through either the shaft or transducer may be applied to the other of the shaft or transducer with variable pressure and flow velocity in the flow system, depending on whether one or both of the pumps are in operating mode with the flow system.

Abstract: An excavator has a number of different hydraulically powered functions that are controlled by a closed center hydraulic system that features a pair of variable displacement, engine driving hydraulic pumps, the displacement of which is responsive to the demands of the system. The flow to the various hydraulic motors is controlled by pilot operated load sensing control valves that direct fluid pressure to a load sensing line when one of the hydraulic motors in the system is being operated. The load sensing line is connected to the control system of the pumps to place the pumps in stroke when a flow of pressurized fluid is required. The flow of the load sensing pressure to the controls for one of the pumps can be optionally disconnected to place said pump in a standby condition and thereby reduce the flow capacity of the hydraulic system at the option of the operator.

Abstract: A control system for the boom and bucket operation system on a front end loader that includes an unloader valve responsive to pilot valve pressure to bypass hydraulic fluid pumped by an auxiliary pump to the reservoir while maintaining the primary pump supply to a loader valve which supplies pressure to the boom and bucket cylinders in response to the operation of pilot valves. The unloader valve bypasses the auxiliary pump flow when the pressure is below a predetermined value and when the pressure is above a second higher predetermined value.

Abstract: The invention contemplates hydraulic-lift mechanism which employs a power integrator in the connection between a charged hydraulic accumulator and the actuator for a vertically positionable load; the power integrator, additionally, has a prime-mover connection, and the pressurized charge of the accumulator is advisedly set to fully accommodate a preselected level of average load upon the actuator. The hydraulic circuit importantly includes check valves, with a pilot-operated check valve interposed between the power integrator and the accumulator and another pilot-operated check valve interposed between the power integrator and the load actuator. The pilot-operated check valves cooperate with other check valves to assure automatic transfer of hydraulic fluid under pressure from the accumulator to the load actuator, and vice versa, as may be determined by selected control of or via the power integrator.

Abstract: A pressurized fluid feed system is provided intended to be temporarily connected to a fluid system formed of a pressurized fluid generator circuit and a fluid distributor circuit, this latter circuit including a tank and being intended to feed user devices an outlet of which is connected to an inlet of the tank, the temporary feed system being adapted to replace the fluid generating circuit.

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: Control arrangement for regulating the speed of movement of a hydrostatic energy consumer is provided in which the ratio between pressure supplied and power on the output side is constant, in particular, a piston capable of sliding in a cylinder connected to a pressure main line, characterized in that an initial hydrostatic displacement machine is connected between the pressure main line and the consumer and is coupled with a second hydrostatic displacement machine on the shaft side, the second hydrostatic displacement machine is adjustable with respect to its displacement volume per revolution and is connected on the one hand to the pressure main line and on the other hand to a chamber carrying a lower pressure, where the adjusting element of this second displacement machine is connected with an r.p.m.-regulating device.

Abstract: An electrohydraulic control system which includes first and second electrically controlled fully variable hydraulic pumps adapted to be driven by the vehicle engine. In the specific embodiment of the invention herein disclosed, the first pump is coupled to the steering and braking control valves, and the second pump is coupled to the bucket and hoist control valves. An electrically controlled poppet valve selectively interconnects the respective pump outputs. Operator-responsive controllers, namely a bucket/hoist joy-stick controller, a vehicle propulsion controller and a steering controller, provide associated electrical signals as respective functions of operator demand. Electrically operated valves control application of hydraulic fluid to the bucket and hoist drive mechanisms, and pressure and position sensors are connected to such valves and actuating mechanisms.

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 control arrangement is provided for controlling the operation of an hydraulic assist turbocharger of the type including an hydraulic turbine driven by an hydraulic fluid under pressure to supplementally drive a turbocharger during engine operating conditions when supplemental air flow is required. The control arrangement includes a dual function control valve responsive to engine speed and load to regulate the supply of hydraulic fluid to the hydraulic turbine in accordance with engine air flow requirements.

Abstract: A hydraulic drive system for civil engineering and construction machinery having at least one hydraulic pump driven by a prime mover, at least one hydraulic actuator connected to the hydraulic pump, and at least one hydraulic cylinder, the hydraulic actuator and hydraulic cylinder being adapted to operate movable members. The hydraulic drive system is provided with a hydraulic pump-motor coupled to the prime mover, a first conduit for connecting the hydraulic pump-motor to one side of the hydraulic cylinder which moves a movable member in a direction in which the potential energy thereof increases in magnitude upon feeding of liquid under pressure thereinto, a second conduit for connecting the other side of the hydraulic cylinder to a reservoir, and an arrangement for controlling the hydraulic pump-motor in such a manner that it functions as a motor when the operator operates the system to move the movable member in a direction in which the potential energy thereof is reduced in magnitude.