US3678684A - Hydraulic systems - Google Patents

Hydraulic systems Download PDF

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Publication number
US3678684A
US3678684A US76760A US3678684DA US3678684A US 3678684 A US3678684 A US 3678684A US 76760 A US76760 A US 76760A US 3678684D A US3678684D A US 3678684DA US 3678684 A US3678684 A US 3678684A
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hydraulic
pump
voltage
control
servo
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Leif Erik Sorensen
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ANSTAILT fur ELEKTROHYDRAULISC
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ANSTAILT fur ELEKTROHYDRAULISC
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B9/00—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member
    • F15B9/02—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member with servomotors of the reciprocatable or oscillatable type
    • F15B9/04—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member with servomotors of the reciprocatable or oscillatable type controlled by varying the output of a pump with variable capacity
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/22—Hydraulic or pneumatic drives
    • E02F9/2221—Control of flow rate; Load sensing arrangements
    • E02F9/2239—Control of flow rate; Load sensing arrangements using two or more pumps with cross-assistance
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/22—Hydraulic or pneumatic drives
    • E02F9/2221—Control of flow rate; Load sensing arrangements
    • E02F9/2239—Control of flow rate; Load sensing arrangements using two or more pumps with cross-assistance
    • E02F9/2242—Control of flow rate; Load sensing arrangements using two or more pumps with cross-assistance including an electronic controller
    • E—FIXED CONSTRUCTIONS
    • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02F—DREDGING; SOIL-SHIFTING
    • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20—Drives; Control devices
    • E02F9/22—Hydraulic or pneumatic drives
    • E02F9/2278—Hydraulic circuits
    • E02F9/2292—Systems with two or more pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/16—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors
    • F15B11/17—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors using two or more pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B7/00—Systems in which the movement produced is definitely related to the output of a volumetric pump; Telemotors
    • F15B7/001—With multiple inputs, e.g. for dual control
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B7/00—Systems in which the movement produced is definitely related to the output of a volumetric pump; Telemotors
    • F15B7/003—Systems in which the movement produced is definitely related to the output of a volumetric pump; Telemotors with multiple outputs
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B7/00—Systems in which the movement produced is definitely related to the output of a volumetric pump; Telemotors
    • F15B7/005—With rotary or crank input
    • F15B7/006—Rotary pump input
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H43/00—Other fluid gearing, e.g. with oscillating input or output
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02B—INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B3/00—Engines characterised by air compression and subsequent fuel addition
    • F02B3/06—Engines characterised by air compression and subsequent fuel addition with compression ignition
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/205—Systems with pumps
    • F15B2211/2053—Type of pump
    • F15B2211/20561—Type of pump reversible
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/205—Systems with pumps
    • F15B2211/20576—Systems with pumps with multiple pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/27—Directional control by means of the pressure source
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/30505—Non-return valves, i.e. check valves
    • F15B2211/3051—Cross-check valves
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/40—Flow control
    • F15B2211/405—Flow control characterised by the type of flow control means or valve
    • F15B2211/40515—Flow control characterised by the type of flow control means or valve with variable throttles or orifices
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/40—Flow control
    • F15B2211/415—Flow control characterised by the connections of the flow control means in the circuit
    • F15B2211/41554—Flow control characterised by the connections of the flow control means in the circuit being connected to a return line and a directional control valve
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/40—Flow control
    • F15B2211/45—Control of bleed-off flow, e.g. control of bypass flow to the return line
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/63—Electronic controllers
    • F15B2211/6303—Electronic controllers using input signals
    • F15B2211/6336—Electronic controllers using input signals representing a state of the output member, e.g. position, speed or acceleration
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/705—Output members, e.g. hydraulic motors or cylinders or control therefor characterised by the type of output members or actuators
    • F15B2211/7058—Rotary output members
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/71—Multiple output members, e.g. multiple hydraulic motors or cylinders
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/78—Control of multiple output members
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S60/00—Power plants
    • Y10S60/911—Fluid motor system incorporating electrical system

Definitions

  • R I a pump unit powered by a prime mover, for example a diesel engine or an electric motor, for providing the required UNITED STATES PATENTS hydraulic R19,694 9/1935 Ernst ..60/52 HF ll Cllllm, 4 Drawing Figures 9 n1" i 51! I c 116 I20 5 (2 ll 39,; '6
  • INVEN TOR [a Emil 72 an,
  • HYDRAULIC SYSTEMS In such hitherto known hydraulic systems a pump-unit has been used, consisting of one or more adjustable pressure compensated pumps, each having its discharge port connected, ofien through a pressure accumulator, to the cylinder or cylinders of the hydraulic motor, whereas a valve device, usually a slide valve, is inserted in the connection, by means of which valve device the flow of hydraulic fluid to the cylinder or cylinders can be directed either to the one or to the other of the inlets thereof or can be fully cut oil, and the outlet of each cylinder of the hydraulic motor if through the valve device connected to a reservoir for hydraulic fluid, to which also the suction port or ports of the pump or pumps are connected.
  • a valve device usually a slide valve
  • the rate of movement of the piston of a hydraulic motor in addition to being dependent on the degree of opening of the valve device, depends essentially on the forces counteracting the movements of the piston and, in case more cylinders of the hydraulic motor are connected to the same pump and are operated simultaneously, on the number of cylinders simultaneously operated by pressurized fluid from the pump, as well as on the pressure in the cylinder of the most loaded hydraulic motor.
  • the main object of the present invention is to provide a hydraulic system of the type concerned, by means of which it is possible, in any case within the load limits of the prime mover and the maximum capacity of the hydraulic motor, to obtain any desired working speed of the hydraulic piston, from zero to maximum speed, simply by adjusting the control device to a definite position corresponding to the desired working speed.
  • the control device is adjusted by a servo-actuator, operated partly by an operating value-adjustment, adjustable for example by a handle, and by an actualvalue-adjustment actuated by the movement of the hydraulic, this may cause that the working speed will, under normal working conditions, be dependent only on the rate of movement of the operating handle of the operation-value-adjustment.
  • the pump unit comprises an adjustable hydraulic pump connected solely to the hydraulic motor and of the type having for each adjustment a constant voluminal yield, and being in a manner known per se, by means of the control device of the corresponding hydraulic motor preferably continuously but at least stepwise adjustable from delivery of maximum positive voluminal yield to one inlet of the hydraulic motor, through a neutral position to delivery of maximum negative yield to the other inlet of the hydraulic motor.
  • a hydraulic motor will usually consist of one single jack, or of a number of interconnected jacks, but is is that the hydraulic motor for a secondary working device of a mechanical unit can include two or more mutually independent jacks, to which the hydraulic fluid is distributed by means of valve devices with fixed or adjustable setting.
  • a hydraulic pump of the said type will by each setting of the control device, apart from neutral, always yield the same volume of hydraulic fluid irrespective of counterpressure, and therefore each setting of the control device will secure the same constant working speed of the piston or pistons of the corresponding hydraulic motor, in any case as long as the counterpressure is not high enough to cause an overloading of the prime mover and thereby a reduction of its normally constant number of revolutions.
  • the hydraulic system since the control of such a pump does not cause any loss through throttling, the hydraulic system will work with an essentially higher efficiency than it has been possible by the valve controlled hydraulic systems hitherto used.
  • a further essential advantage is that by a hydraulic system according to the present invention and comprising a number of hydraulic motors connected to a pump each, the hydraulic motors can be operated simultaneously and each with the working speed most convenient, without the operation of the individual hydraulic motor effecting the operation of the others, so that a mechanical unit provided with such a hydraulic system can be operated at an essentially higher speed than like mechanical units provided with conventional valve controlled hydraulic systems.
  • each hydraulic pump and the hydraulic motor connected thereto will usually operate so that the hydraulic fluid leaving the hydraulic motor will fully or partly return to the hydraulic pump. Therefore, in case the hydraulic piston is exposed to considerable forces, acting in the direction of the desired movement of the piston, the hydraulic pump will function as a generator supplying energy unloading the prime mover, but since the voluminal yield of fluid supplied to the suction side of the hydraulic cylinder is constant, depending on the setting of the hydraulic pump, a vacuum may develop in the suction side providing cavitation in the hydraulic fluid, also in the part thereof to be found in the hydraulic pump, and such cavitation will not only result in a considerable noise in the pump but also, in the long run, involve too early destruction thereof.
  • the hydraulic connection between at least one of the inlets of the hydraulic motor and the corresponding port of the hydraulic pump comprises a valve device adapted to throttle the flow of hydraulic fluid in direction away from the hydraulic motor, so that a counterpressure is developed on the pressure side of the hydraulic cylinder of such'a' magnitude that no cavitation producing vacuum develop on the suction side of the hydraulic cylinder.
  • Another advantage is that such a throttling valve device will fully or partly absorb and transform into heat the potential or kinetic energy of the piston rod of the hydraulic motor and the devices connected thereto, so that there is no need of otherwise frequently required brake devices, involving additional cost of the hydraulic systems and comprising devices prevent ing the prime mover from racing.
  • the hydraulic system may comprise means for measuring the load of the prime mover, means for measuring the total output of the hydraulic pumps, means for comparison of said load and the said output, and control-actuating devices adapted to actuate the control devices of the hydraulic pumps, whenever said total output exceeds the output corresponding to full load of the prime mover.
  • the prime motor of hydraulic systems consists often of an internal combustion engine equipped with a governor depending on the load and having a slidable or rotatable fuel control rod able to take up one position corresponding to idling without load; one position corresponding to full load at maximum number of revolutions; and one position corresponding to full load at minimum number of revolutions, that is maximum overload, and in such cases the control devices of each pump of the hydraulic system is connected to and adapted to be adjusted by a corresponding electrically controlled servoactuator.
  • control rod is adapted to operate, at least during its movements between the position corresponding to full load at maximum number of revolutions and its position corresponding to full load at minimum number of revolutions, to move the slidable tap of an adjustable electric resistance, for example a potentiometer, in such a manner that the voltage over an electric safety circuit, fed through the resistance and containing one or more actuating devices for actuation of a control device in the feed circuit of each individual servo-actuator, is changed so that the yield of the hydraulic pump corresponding to each servo-actuator is reduced during the said movement of the control rod.
  • an adjustable electric resistance for example a potentiometer
  • a govenor as the one referred to tends, where the engine is loaded up to nominal power, to maintain a constant number of revolutions and may be said to be a device, by means of which the effect produced by the engine, corresponding to the effect transmitted through the hydraulic pumps, is compared with the load of the prime mover, that is with the adjustment of the fuel supply system, while the control rod is at any time adjusted to the result of the said comparison.
  • a control device as described will not be actuated until incipient overloading develops, in which case, however, the yield of the hydraulic pumps immediately declines and the more the higher the incipient overloading is, whereby an overload involving stoppage of the prime mover is avoided.
  • FIG. 1 is a diagram of an embodiment of the hydraulic system adapted to actuate three hydraulic motors in the form of hydraulic jacks;
  • FIG. 2 is a diagram of another embodiment of the hydraulic system comprising, however, for the sake of clarity, only one single jack, the different pressure conditions in the pipes being indicated by the use of lines of different thickness for the pipes;
  • FIG. 3 is a schematical block diagram, illustrating the electric devices of the hydraulic system adapted to prevent over loading
  • FIG. 4 in a similar manner another embodiment of a system for preventing overloading.
  • the hydraulic system illustrated in FIG. 1 is provided with three hydraulic jacks, WA, 108 and C.
  • Each jack comprises a cylinder 11, a piston 12 reciprocably arranged therein, and a piston rod 13 connected to the piston 12.
  • Each cylinder 11 has two inlets, an inlet 14 opening into the part of the cylinder opposite to the free end of the piston 12, and an inlet 15 opening into the part of the cylinder, through which the piston rod 13 is passing.
  • the hydraulic systems for the three jacks comprises a common hydraulic fluid reservoir 16 communicating with a return pipe 17 provided with a non-return valve 18 and a filter 19, and with a suction pipe 20.
  • the two pipes 17 and 20 are interconnected through a non-return valve 21 preventing passage of fluid from the return pipe I! to the suction pipe 20.
  • the three hydraulic systems comprise, moreover, a common safety return pipe 22 which, through a relief valve 23, is connected to the return pipe 17.
  • the hydraulic system for each jack 10 includes a hydraulic pump 24 with two ports 25 and 26.
  • the three pumps 24A, 24B and 24C are driven by a common shaft 27 powered by a prime mover indicated by a circular arrow 28.
  • the shaft 27 and the prime mover 28 are shown in connection with each of the pumps 24, although they are used for all of the pumps jointly.
  • Each pump 24 is preferably a variable volume reversible swash plate type pump.
  • the adjustment of the angular position of the swash plate is affected by means of a servo-actuator 29, the action of which, in a manner known per se, depends partly on a manually operated operating-valueadjustment, and partly on an actual-value-adjustment depending on the position of the corresponding piston 12 in the cylinder 11.
  • the pump port 25 is by means of a connecting pipe 30 comprising a flexible hose and a pilot check valve 40 connected to the inlet 14 of the jack 10, whereas the pump port 26 through a connecting pipe 32 with a flexible hose 33 is connected through a pilot check valve 39 to the inlet 15 of the jack [0.
  • the two connecting pipes 30 and 32 are, through non-return valves, 34 and 35 respectively, connected to the safety return pipe 22, each of these non-return valves permitting only transfer of hydraulic fluid from the corresponding connecting pipe 30 or 32 to the safety return pipe, but only in case the pressure in the connecting pipe rises above permissible limits, the safety pressure being controlled by the relief valve 23.
  • the connecting pipe 32 is moreover connected to the suction pipe 20 through a non-return valve 36 permitting passage of fluid only from the suction pipe 20 to the connecting pipe 32.
  • the connecting pipe 30 is connected to the return pipe [7 though a pilot controlled check valve 37 normally preventing passage of fluid from the connecting pipe 30 to the return pipe 17 but controlled by the pressure in the connecting pipe 32, and so that it opens when the pressure in the pipe 32 exceeds a certain value.
  • the pump 24 may, if required, be provided with a relief valve, functioning as a safety valve, which through a pipe 38 is connected to the return pipe 17.
  • the pump 24A is a multicylinder piston pump, and assuming that the shaft 27 is rotated at a constant number of revolutions, it is easily seen that the rate at which the piston lZA moves upwards depends solely on the voluminal yield of the pump 24A, which, in turn, depends on the position to which the swash plate is adjusted.
  • pilot controlled check valve 39A is introduced into the connection between the cylinder-inlet 15A and the connecting pipe 32A so controlled by the pressure in the connecting pipe 30A that it does not open and permit outlet through the cylinder inlet 15A, until the pump has built up a certain pressure in the connecting pipe 30A, wherealter the degree of opening of the valve 39A depends on this pressure. This involves that the discharge from the cylinder 1 1A is throttled to such an extent that the movement of piston 12A is always controlled by the hydraulic fluid flowing to inlet MA from the pump 24A.
  • the swash plate of pump 24A is adjusted to neutral by means of the servoactuator 29A; when the pump 24A is in its neutral position, it acts as a closed valve for the hydraulic fluid within the cylinder so that the fluid on both sides of the piston 12A becomes enclosed in such a manner that the piston cannot move unintentionally.
  • a corresponding prevention of the piston 12A being driven from the mechanical component towards the inlet MA is attained by means of a pilot controlled check valve 40A inserted between the inlet 14A and the connection 30A and controlled by the pressure in the connecting pipe 32A.
  • this is assumed to be connected to a mechanical component that can exert a motive power on the piston 128 during its inward movement only, wherefore, in connection with the jack 103, only one check valve 403 corresponding to the check valve 40A is used, inserted between the cylinder inlet 14B and the connecting pipe 303.
  • the jack C is assumed to be connected to a mechanical component that can exert a force acting on piston 12C when the piston 12C is moving in the direction of the cylinder inlet ISC, wherefore, also in connection with this jack 10C only one check valve 39C corresponding to the pilot controlled check valve 39A is used, and this valve 39C is inserted between the cylinder inlet 15C and the connecting pipe 32C and controlled by the pressure in the connecting pipe 31C.
  • FIG. 2 shows schematically another embodiment of the present hydraulic system, but only one single jack with corresponding hydraulic system is shown, although a number of jacks may be included.
  • This hydraulic system includes, indicated by the supplementary letter D, elements corresponding to the elements 10 to 16, 24 to 26, 30 and 32 explained in connection with FIG. 1.
  • the hydraulic pump MD is also in this embodiment controlled through a servoactuator, which is not indicated.
  • a feeder pipe 50 in connected to the hydraulic fluid reservoir 16D.
  • discharge valves 51 and 52 respectively are inserted, opening when pressure is applied to the corresponding pump port.
  • the pipe part between the pump port 250 or 26D and the corresponding non-return valve 5] or 52 respectively are through suction valves 53 and 54 respectively connected to a pipe 55, which, in turn, through a pipe 56 is connected to the common pipe 50.
  • the two connecting pipes 30D and 320 are directly connected to the inlets 14D and 15D respectively of the jack 10D.
  • a pilot controlled throttle valve 58 is inserted, being opened by the pressure in the part of the connecting pipe 32 arranged between the pump port 260 and the non-return valve 52.
  • the throttle valve 58 can be said to be inserted in a shunt inserted between the inlet MD of the jack 10D and the suction valve 53.
  • a corresponding pilot controlled throttle valve 60 is inserted in a shunt 61 between the inlet 15D of the jack 10D and the suction valve 54 and controlled by the pressure in the connection between the pump port 25D and the discharge valve 51.
  • the pipe 56 may be doubled, if necessary, in such a manner that, in one of the pipes, a suction valve is inserted permitting flow of fluid only from the pipe 50 to the pipe 55, while, in the other pipe, a relief valve is inserted that secures a certain overpressure in the shunt pipe 59, which results in the pump 24D functioning as a motor, supplying energy to the prime mover.
  • a pilot controlled throttle valve is connected to each of the connecting pipes 30D and 32D. lf, however, the piston [2D and in turn the mechanical element connected thereto can only be moved by an external force in one direction, one of the two pilot controlled throttle valves may be left out. In this case also the corresponding discharge valve 51 or 52 can be left out.
  • each jack, or each group of interconnected jacks is operated by means of a pump having the sole purpose of operating the cylinder, or the group of cylinders, involves, in comparison with corresponding hydraulic systems in which all jacks are operated from one single pump, an essentially higher risk of overloading of the prime mover, partly in case several jacks are being operated simultaneously with a considerable load and a high operating speed, partly in case of a single jack suddenly encountering unexpected high resistance, such as may be the case, for example, where the shovel of a power shovel hits a stone or other object difficult to move.
  • overloading can, of course, be prevented by insertion of an overload protector in the connection between the prime mover and the shaft powering the pumps; this measure will, however, involve stoppage of the machinery in its entirety.
  • the invention includes an excess-load control that actuates all or in any case the more essential of the control devices of the pumps, by which a comparison is currently made between the load of the prime mover and the total effect produced by the hydraulic pumps, and so that, when the effect of the pumps exceeds the load, the control actuating devices are actuated to reduce the yield of the pumps.
  • FIG. 3 shows schematically the electronic control system for adjustment of for example, the hydraulic pumps 24A, 24B, and 24C serving to operate the jacks 10A, 10B, and 10Cv
  • the pumps as well as the jacks are indicated schematically only, and the hydraulic connections between the pumps and the jacks, shown in FIG. 1 or FIG. 2, are left out for the sake of clarity.
  • the direct control can be effected by means of an operating-value-adjustment 210, shown as a potentiometer, the tap 211 of which can be adjusted by a handle 212.
  • the operatingvalue-potentiometer cooperates with an actual-value-potem tiometer 213 having its tap 214 drive-connected to the piston rod 13A of the jack 10A, and so that it is moved proportionally to the movement of the piston rod.
  • the ends of the two potentiometers are interconnected by leads, 215 and 216 respectively, connected one each to the terminals of a voltage source 217, shown as an electric batter with connection to zero or to earth.
  • the voltage source 217 is common to the entire number ofjacks 10.
  • the two taps 211 and 214 are connected to one input terminal each of an operational amplifier A1, that is an electronic amplifier provided with two input terminals and one output terminal, affording a very strong amplification, and supplying a voltage that, in respect of both sign and magnitude, depends on the voltage difference between the two input terminals.
  • the output terminal of the operational amplifier is connected to earth through two resistors R1 and R2 constituting jointly a voltage divider.
  • a lead is branched out, which through a resistor R3 is connected to one of the input terminals of an operational amplifier A2, the other input terminal of which is connected to earth through a resistor R4.
  • the output terminal of the amplifier A2 is, through a lead 219 connected to the input terminal of a servo-actuator 220 having the output terminal connected to earth.
  • the servo-actuator 220 is shown schematically as a solenoid with an armature 221 that is resiliently urged towards a central position, and that is connected to the control device of the hydraulic pump 24A, indicated by an arrow 222.
  • the hydraulic pumps 24 are powered by a diesel engine provided with a governor of the type, often used at the present time, operating a control rod 225 which, at the nominal number of revolutions for regulating the fuel supply in dependence of the load, moves between positions which, in respect of the right end of the rod, on the drawing, are indicated by positions A and B, the position A corresponding to idling, and the position B to full load.
  • the diesel engine can be overloaded, however, which involves a reduced number of revolutions, and at maximum overloading the control rod 225 reaches the position corresponding to position C. In case of further increased overload the engine will usually stop. Beyond the position C the control rod 225 has another position D, corresponding to starting position.
  • a housing 226 is placed at the end of the control rod 225, through which housing a displaceable spindle 227 extends, which is provided with a head 228 at the end facing the control rod 225 and outside of the opposite end of the housing 226 with a set collar 229, whereas a compression spring 230, inserted between the head 228 and the housing 226, urges the head 228 as far as possible away from the housing 226.
  • a potentiometer 231 is arranged, the tap 232 of which is attached to the spindle 227 in such a manner that it is placed at the end of the potentiometer 231 nearest the control rod 225, when the head 228 takes up its extreme position away from the housing 226.
  • the said end of the potentiometer 231 is connected to a lead 233, and the opposite end to a lead 234, a voltage source 235, shown as a battery, being inserted between the said two leads.
  • the tap 232 of the potentiometer 231 is connected to a lead 236.
  • Each electronic control system shown comprises a photoelectric resistance 237 inserted between the lead 218 and earth, for example of the type having in the dark a resistance of about 10 ohm, which is reduced, however, through exposure to full light to 100 ohm.
  • Light is given to the photoelectric resistance 237 by an incandescent lamp 238, the filament of which is connected to the two said leads 233 and 236.
  • the control rod 225 will be moved between the positions B and C, whereby the tap 232 is moved correspondingly along the coil of the potentiometer 231, so that the voltage between the leads 233 and 236 will increase rapidly. Consequently, the light from the incandescent lamp 238 is intensified, and in turn the resistance of the photo-resistance 237 reduced, whereby the output voltage of the amplifier A2 is also reduced, and thus the servo-actuator 220 is brought to reduce the output of the pump 24A.
  • the arrangement may be a such that the control circuits for the jack cylinders providing lifting of the shovel are so adjusted that an overloading aflects the corresponding hydraulic pumps essentially more than the other hydraulic pumps. The same can be attained even when uniform control circuits are used by insertion of difierent filters between the incandescent lamps 238 and the photo-electric resistances 237.
  • potentiometer 231 has the part of its windings along which the tap 232 is moving when the control rod 225 is moved between the positions C and D, short-circuited, so that the incandescent lamp 237 will be lighting at full intensity also during the starting of the diesel engine.
  • control rod 225 is longitudinally displaceable. In just as many cases, however, the control rod is rotatable, in which cases it is most appropriate to connect it to an annular potentiometer, providing the same ef' feet as described above in connection with the use of a slide; potentiometer.
  • FIG. 4 An electronically functioning control system for the hydraulic pumps 24 provided with another overload-protector for the prime mover is shown in FIG. 4.
  • the resistor R5 inserted between the resistor R3 and the output terminal of the operational amplifier is a feedback resistor.
  • the shah 27 of the prime mover, or some other shaft of the engine is provided with a four-poled star wheel 240, opposite to which a magnetic pick-up 241 is stationarily arranged, emitting a pulse whenever the stray field of the magnet of the pick-up is changed through the effect of the poles of the star wheel 240, which is made of steel.
  • sawtooth-pulses are provided, triggering a monostable multivibrator 242 providing a square voltage of constant height and length. This square voltage is applied to a meanvaluemeter 243 producing a DC. voltage proportional to the mean value of the square voltage, with a suitable time-constant.
  • this voltage will be proportional to the number of revolutions of the engine, and within a wide field the effect produced by the engine will likewise be proportional to the number of revolutions.
  • a closer approximation of the voltage to the effect produced by the engine can be obtained, how ever, through insertion after the mean value meter 243 of a resistance-diode-matrix, whereby it is possible to make the mean value voltage follow a curve fairly close corresponding over a still wider field to the dependency of the engine effect on the number of revolutions.
  • the mean value voltage thus attained is through a resistor R6 applied to one of the input terminals of an operational amplifier A3, functioning as a differential amplifier, this input terminal being, moreover, connected to earth through a resistor R7.
  • each individual hydraulic pump or transmitted where it functions as a motor, is the product of the amount of fluid given ofi by the pump per unit of time and the pressure diflerence between suction and pressure side of the pump.
  • the voltage applied by the output terminal of the operational amplifier A2 to the coil of the servo-actuator 220 is proportional to the amount of fluid given off.
  • each pump 24 is connected to a pressuredif ference transducer, the ports 25 and 26 of the pump being connected to one end each of a pressure-difference indicator 244, which is connected to the adjustable tap 245 of a potentiometer 246, and in such a manner that zero pressure difference between the two ports 25 and 26 makes the tap 245 take up its central position on the potentiometer 246.
  • a differential amplifier 247 is used to attain multiplication of the voltage indicating the output of the hydraulic pump, and of the voltage indicating the pressure difference between the two ports of the pump.
  • This amplifier 247 is energized from a DC. source 248, the negative voltage thereof being ap' plied to a lead 249, and the positive voltage to a lead 250.
  • the difl'erential amplifier 247 is provided with two NPN transistors T1 and T2, the emitters thereof being, through equal resistors R8 and R9, connected to a lead 251, which through a resistor R10 is connected to the positive lead 250.
  • the collectors of the transistors are connected, through equal resistors RI! and R12, to the negative lead 249.
  • the resistance of the resistor R10 exceeds considerably the sum of the resistance of the resistors R8 and R1 or R9 and R12, ensuring that the current passing through the resistor R10 will be approximately constant.
  • the potentiometer of the transducer 244, 245, 246 is inserted between the collectors of the transistors T1 and T2. To the base of the transistor T1 is applied through a resistor R13 the voltage given ofl by the operational amplifier A2, whereas the base of the transistor T2 through a resistor R14 of the same resistance as the resistor R13 is connected to earth.
  • the current passing through the coil of the potentiometer 246, from the collector of the transistor T2 to the collector of the transistor T1, will be proportional to the voltage given ofl by the operational amplifier A2, the signs being taken into account.
  • the load on the hydraulic pump 24 is a such that the pump functions as a motor and supplies energy to the prime mover, the tap 245 will be moved to the opposite side of the middle-position and give off a voltage of opposite sign.
  • the voltage at the tap 245 is through a resistor R trans mitted to an interconnecting lead 252, whereby the taps 245 of all of the transducers of the hydraulic pumps 24 are interconnected in a corresponding manner.
  • the lead 252 is connected to one input terminal of an operational amplifier A4, the other input terminal of this amplifier being connected to a voltage divider consisting of two resistors R16 and R17, connected to the two leads 249 and 250.
  • aforesaid constant voltage is balanced. This involves that the the voltage given off from the output terminal of the operational amplifier A4 is proportional to the sum of the effects of the hydraulic pumps, with signs.
  • the outlet terminal of the amplifier A4 being through a feedback resistance R18 connected to the input terminal first mentioned, is, through a lead 253 connected to earth through a resistor R19 as well as to the other input terminal of the operational amplifier A3 through a resistor R20.
  • This operational amplifier undertakes a comparison of the effect produced by the prime mover, that is the load of the prime mover, and the total aggregate effect produced by the hydraulic pumps 24, and the amplifier A3 will emit a voltage proportional to the difference of the two effects, with signs, in such a manner that it is positive, when the effect produced by the hydraulic pumps is higher than corresponding to the load of the prime mover.
  • the output terminal of the operational amplifier A3 is through a rectifier 254, for example a diode, connected to one, 233, of the two leads connected to the incandescent lamps, whereas the other, 236, of these leads is connected to earth.
  • the rectifier 254 ensures that no current will pass to the lead 233 unless the pumpeffect exceeds the load of the prime mover, but in such case the lamps 238 will be lighting and affect the photo-electric resistances, the result being that the effect of the hydraulic pumps 24 is reduced.
  • the operational amplifier A3 must be adapted to produce full voltage at a slight difference between the input voltages, that is it must be over-excited for a voltage of a few per cent of the maximum input voltage.
  • an incandescent lamp 238 is placed opposite each photo-electric resistance 23'], but nothing prevents, of course, that all, or a number of the photoelectric resistances 237 being so placed that exposure can be efiected by means of one single incandescent lamp 238.
  • a voltage proportional to the effect produced by the hydraulic pumps 24 can be obtained in other way than by use of pressure transducers 244, 245, 246, as aforementioned.
  • a simple pressure transducer may be connected to each pump port, for example so that each of the potentiometer coils of the two sets of transducers is inserted between a branch-out from the output terminal of the corresponding operational amplifier A2 and earth, and the two branch-outs are connected to one input terminal each of an operational amplifier, which may be a joint device for the circuits belonging to the individual hydraulic pumps, and which may have its output terminal connected to a differential amplifier corresponding to the amplifier A3 in FIG. 4.
  • a hYdraulic system comprising in combination a plurality of mutually independent double acting hydraulic motors
  • each said hydraulic motor being provided with an inlet for each direction of movement
  • a main control device adapted to control and reverse said hydraulic motor independently of the remaining hydraulic motors
  • a hydraulic system as defined in claim 1, at least one said hydraulic connection comprising a main pipe interconnecting said inlet and said port, said main pipe comprising a discharge valve preventing flow of liquid from said hydraulic motor to said pump, a shunt pipe bridging said discharge valve, a pilot controlled throttle valve inserted in said shunt and controlled by the pressure in the other one of said two hydraulic connections, and so that it is maintained closed at a pressure below a certain minimum value in said second one of said two hydraulic connections, whereas its flow area increases with increasing pressure in the last said hydraulic connection.
  • a hydraulic system as defined in claim 1, comprising first means for measuring the load of said prime mover, second means for measuring the total output of said hydraulic pumps, third means for comparison of the said load and the said output, and control-actuating devices adapted to provide actua tion of the said pump control devices For said hydraulic pumps, whenever said total output exceeds the output corresponding to full load of said prime mover.
  • control actuating devices comprise a unit adapted to emit a warning signal.
  • control actuating devices being adapted to actuate said pump control devices to control the effect produced by individual ones of said hydraulic pumps.
  • said prime mover being an internal combustion engine, said engine being equipped with a governor responsive to the load on said engine and comprising a moveable fuel control rod able to take up a first position corresponding to idling without load, a second position corresponding to full load at maximum number of revolutions, and a third position corresponding to full load at minimum number of revolutions, that is maximum overload;
  • said pump control device of each said hydraulic pumps being connected to and adapted to be adjusted by a corresponding electrically controlled servo-actuator, an electric safety circuit; coupling means coupling said servo-actuators to said safety circuit;
  • said safety circuit being fed through an adjustable electric resistance, for example a potentiometer, provided with a slidable tap; said control rod being adapted during its movement between its said second position and its said third position to operate said slidable tap thereby changing the voltage over said safety circuit for through said coupling means amending the adjustment of said servo-actuators, so that the yield of the said hydraulic pumps controlled through said serv
  • said safety circuit including at least one electric incandescent lamp, preferably one for each said servo-actuator; each said servoactuator having a control circuit; said control circuit includinG as said coupling means a light-sensitive electric resistance exposed to the light from said incandescent lamp, or one of said lamps; said light-sensitive electric resistance being arranged in said control circuit, preferably between a connection thereof, affecting the feed current of said servo-actuator, and zero, in such a manner that increase of the light intensity involves such an adjustment of the said servo-actuator that a reduction of the yield of the corresponding one of the said hydraulic pumps results.
  • each said pump control device being connected to and controlled by a corresponding electric servo-actuator; an electronic measuring device connected to said prime mover and adapted to emit a pilot voltage substantially proportional to the load on said prime mover; a voltage difference indicator, for example an operation amplifier, said pilot voltage being applied to the one input of said first voltage difi'erence indicator; each said servoactuator having a control circuit, means for tapping from said control circuit a second voltage proportional to the feed current of said servo-actuator; a difl'erential amplifier; said second voltage being applied to the one input terminal of said difl'erential amplifier, the second input terminal of said differential amplifier being applied with a constant voltage, preferably zero voltage; a pressure-difierence transducer inserted between said two ports of each said hydraulic pump, said pressure-difference transducer comprising a control potentiometer having a slidable tap, the position of which depends on the pressure-difference between said two ports;
  • control actuating means being one or more incandescent lamps; said actuator control device being a light-sensitive electric resistance exposed to the light from said incandescent lamp, or
  • one of said lamps and arranged in said control circuit in such a manner, preferably between a connection thereof, affecting the feed current of said servo-actuator, and zero, that increase of the light intensity involves such an adjustment of said servoactuator that a reduction of the yield of the corresponding one of said hydraulic pumps results.

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  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • Mining & Mineral Resources (AREA)
  • Civil Engineering (AREA)
  • Structural Engineering (AREA)
  • Fluid-Pressure Circuits (AREA)
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Cited By (9)

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Publication number Priority date Publication date Assignee Title
US3841795A (en) * 1972-07-17 1974-10-15 Caterpillar Tractor Co Combined engine speed and pressure responsive control for variable displacement pumps
US4047578A (en) * 1974-03-27 1977-09-13 The Richmond Manufacturing Company Portable earth boring machine
US5599073A (en) * 1993-12-30 1997-02-04 Samsung Heavy Industry Co., Ltd. Hydraulic system for controlling a brake system and a suspension system of a wheel-type excavator
US20060026955A1 (en) * 2004-06-18 2006-02-09 Rolf Bogelein Pressure-medium-actuated actuation device, in particular for a vehicle steering apparatus
US20060168955A1 (en) * 2005-02-03 2006-08-03 Schlumberger Technology Corporation Apparatus for hydraulically energizing down hole mechanical systems
WO2007006260A1 (de) * 2005-07-08 2007-01-18 Wilhelm Karmann Gmbh Hydraulische betätigungsanordnüng
US20070295416A1 (en) * 2006-05-18 2007-12-27 Gerhard Huber Hydraulic circuit for actuation of a hydraulic working cylinder
US20130098014A1 (en) * 2011-10-21 2013-04-25 Jeffrey L. Kuehn Closed-loop hydraulic system having force modulation
US12085099B1 (en) * 2020-06-18 2024-09-10 Vacuworx Global, LLC Flow control block for use with a vacuum material handler

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT401675B (de) * 1989-03-30 1996-11-25 Weber Gisela Steuereinrichtung für hydraulische arbeitszylinder
DE19716081C1 (de) * 1997-04-17 1998-08-13 Hydac Technology Gmbh Antrieb für einen hydraulischen Differentialzylinder

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US19694A (en) * 1858-03-23 Xwater-tight w washstaetd
US2312213A (en) * 1941-06-18 1943-02-23 Oilgear Co Hydraulic press
US2328980A (en) * 1942-05-16 1943-09-07 Vickers Inc Power transmission
US2400685A (en) * 1941-12-18 1946-05-21 Baldwin Locomotive Works Equalizing system
US2640323A (en) * 1950-12-15 1953-06-02 Detroit Harvester Co Power unit of the fluid pressure type
US2984985A (en) * 1959-02-16 1961-05-23 Macmillin Hydraulic Engineerin Hydraulic operating and control system
US3018902A (en) * 1955-12-06 1962-01-30 Manning Maxwell & Moore Inc Hydraulic crane
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US19694A (en) * 1858-03-23 Xwater-tight w washstaetd
US2312213A (en) * 1941-06-18 1943-02-23 Oilgear Co Hydraulic press
US2400685A (en) * 1941-12-18 1946-05-21 Baldwin Locomotive Works Equalizing system
US2328980A (en) * 1942-05-16 1943-09-07 Vickers Inc Power transmission
US2640323A (en) * 1950-12-15 1953-06-02 Detroit Harvester Co Power unit of the fluid pressure type
US3018902A (en) * 1955-12-06 1962-01-30 Manning Maxwell & Moore Inc Hydraulic crane
US2984985A (en) * 1959-02-16 1961-05-23 Macmillin Hydraulic Engineerin Hydraulic operating and control system
US3161245A (en) * 1961-06-19 1964-12-15 Vehicle propulsion

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3841795A (en) * 1972-07-17 1974-10-15 Caterpillar Tractor Co Combined engine speed and pressure responsive control for variable displacement pumps
US4047578A (en) * 1974-03-27 1977-09-13 The Richmond Manufacturing Company Portable earth boring machine
US5599073A (en) * 1993-12-30 1997-02-04 Samsung Heavy Industry Co., Ltd. Hydraulic system for controlling a brake system and a suspension system of a wheel-type excavator
US20060026955A1 (en) * 2004-06-18 2006-02-09 Rolf Bogelein Pressure-medium-actuated actuation device, in particular for a vehicle steering apparatus
US20060168955A1 (en) * 2005-02-03 2006-08-03 Schlumberger Technology Corporation Apparatus for hydraulically energizing down hole mechanical systems
WO2007006260A1 (de) * 2005-07-08 2007-01-18 Wilhelm Karmann Gmbh Hydraulische betätigungsanordnüng
US20070295416A1 (en) * 2006-05-18 2007-12-27 Gerhard Huber Hydraulic circuit for actuation of a hydraulic working cylinder
US7788918B2 (en) 2006-05-18 2010-09-07 Hoerbiger Automatisierungstechnik Holding Gmbh Hydraulic circuit for actuation of a hydraulic working cylinder
US20130098014A1 (en) * 2011-10-21 2013-04-25 Jeffrey L. Kuehn Closed-loop hydraulic system having force modulation
US8973358B2 (en) * 2011-10-21 2015-03-10 Caterpillar Inc. Closed-loop hydraulic system having force modulation
US12085099B1 (en) * 2020-06-18 2024-09-10 Vacuworx Global, LLC Flow control block for use with a vacuum material handler

Also Published As

Publication number Publication date
BE757019A (fr) 1971-03-16
NL7014491A (xx) 1971-04-08
DE2048782A1 (de) 1971-04-22
ES384578A1 (es) 1973-09-01
CH524772A (de) 1972-06-30
ZA704229B (en) 1971-03-31
FR2065002A5 (xx) 1971-07-23

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