EP0262098A1 - A flow recovery system for hydraulic circuits with pumps and pressure compensated distributor valves for working members of earth-moving machines - Google Patents

A flow recovery system for hydraulic circuits with pumps and pressure compensated distributor valves for working members of earth-moving machines Download PDF

Info

Publication number
EP0262098A1
EP0262098A1 EP87830015A EP87830015A EP0262098A1 EP 0262098 A1 EP0262098 A1 EP 0262098A1 EP 87830015 A EP87830015 A EP 87830015A EP 87830015 A EP87830015 A EP 87830015A EP 0262098 A1 EP0262098 A1 EP 0262098A1
Authority
EP
European Patent Office
Prior art keywords
pressure
valve
discharge
delivery
actuator
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP87830015A
Other languages
German (de)
French (fr)
Other versions
EP0262098B1 (en
Inventor
Piero Tha
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Trinova SpA
Original Assignee
Trinova SpA
CHS VICKERS SpA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Trinova SpA, CHS VICKERS SpA filed Critical Trinova SpA
Priority to AT87830015T priority Critical patent/ATE52560T1/en
Publication of EP0262098A1 publication Critical patent/EP0262098A1/en
Application granted granted Critical
Publication of EP0262098B1 publication Critical patent/EP0262098B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • EFIXED CONSTRUCTIONS
    • E02HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02FDREDGING; SOIL-SHIFTING
    • E02F9/00Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20Drives; Control devices
    • E02F9/22Hydraulic or pneumatic drives
    • E02F9/2278Hydraulic circuits
    • E02F9/2292Systems with two or more pumps
    • EFIXED CONSTRUCTIONS
    • E02HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02FDREDGING; SOIL-SHIFTING
    • E02F9/00Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20Drives; Control devices
    • E02F9/22Hydraulic or pneumatic drives
    • E02F9/2221Control of flow rate; Load sensing arrangements
    • E02F9/2225Control of flow rate; Load sensing arrangements using pressure-compensating valves
    • EFIXED CONSTRUCTIONS
    • E02HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02FDREDGING; SOIL-SHIFTING
    • E02F9/00Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20Drives; Control devices
    • E02F9/22Hydraulic or pneumatic drives
    • E02F9/2221Control of flow rate; Load sensing arrangements
    • E02F9/2232Control of flow rate; Load sensing arrangements using one or more variable displacement pumps
    • EFIXED CONSTRUCTIONS
    • E02HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
    • E02FDREDGING; SOIL-SHIFTING
    • E02F9/00Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
    • E02F9/20Drives; Control devices
    • E02F9/22Hydraulic or pneumatic drives
    • E02F9/2278Hydraulic circuits
    • E02F9/2296Systems with a variable displacement pump
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/02Systems essentially incorporating special features for controlling the speed or actuating force of an output member
    • F15B11/024Systems essentially incorporating special features for controlling the speed or actuating force of an output member by means of differential connection of the servomotor lines, e.g. regenerative circuits
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B11/00Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/02Systems essentially incorporating special features for controlling the speed or actuating force of an output member
    • F15B11/024Systems essentially incorporating special features for controlling the speed or actuating force of an output member by means of differential connection of the servomotor lines, e.g. regenerative circuits
    • F15B2011/0243Systems essentially incorporating special features for controlling the speed or actuating force of an output member by means of differential connection of the servomotor lines, e.g. regenerative circuits the regenerative circuit being activated or deactivated automatically
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/20Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/205Systems with pumps
    • F15B2211/2053Type of pump
    • F15B2211/20546Type of pump variable capacity
    • F15B2211/20553Type of pump variable capacity with pilot circuit, e.g. for controlling a swash plate
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/20Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/205Systems with pumps
    • F15B2211/20576Systems with pumps with multiple pumps
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/30Directional control
    • F15B2211/305Directional control characterised by the type of valves
    • F15B2211/30525Directional control valves, e.g. 4/3-directional control valve
    • F15B2211/3053In combination with a pressure compensating valve
    • F15B2211/30535In combination with a pressure compensating valve the pressure compensating valve is arranged between pressure source and directional control valve
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/30Directional control
    • F15B2211/305Directional control characterised by the type of valves
    • F15B2211/3056Assemblies of multiple valves
    • F15B2211/30565Assemblies of multiple valves having multiple valves for a single output member, e.g. for creating higher valve function by use of multiple valves like two 2/2-valves replacing a 5/3-valve
    • F15B2211/3058Assemblies of multiple valves having multiple valves for a single output member, e.g. for creating higher valve function by use of multiple valves like two 2/2-valves replacing a 5/3-valve having additional valves for interconnecting the fluid chambers of a double-acting actuator, e.g. for regeneration mode or for floating mode
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/30Directional control
    • F15B2211/315Directional control characterised by the connections of the valve or valves in the circuit
    • F15B2211/3157Directional control characterised by the connections of the valve or valves in the circuit being connected to a pressure source, an output member and a return line
    • F15B2211/31576Directional control characterised by the connections of the valve or valves in the circuit being connected to a pressure source, an output member and a return line having a single pressure source and a single output member
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/30Directional control
    • F15B2211/32Directional control characterised by the type of actuation
    • F15B2211/329Directional control characterised by the type of actuation actuated by fluid pressure
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/50Pressure control
    • F15B2211/505Pressure control characterised by the type of pressure control means
    • F15B2211/50509Pressure control characterised by the type of pressure control means the pressure control means controlling a pressure upstream of the pressure control means
    • F15B2211/50545Pressure control characterised by the type of pressure control means the pressure control means controlling a pressure upstream of the pressure control means using braking valves to maintain a back pressure
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/50Pressure control
    • F15B2211/505Pressure control characterised by the type of pressure control means
    • F15B2211/50563Pressure control characterised by the type of pressure control means the pressure control means controlling a differential pressure
    • F15B2211/50581Pressure control characterised by the type of pressure control means the pressure control means controlling a differential pressure using counterbalance valves
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/50Pressure control
    • F15B2211/515Pressure control characterised by the connections of the pressure control means in the circuit
    • F15B2211/5156Pressure control characterised by the connections of the pressure control means in the circuit being connected to a return line and a directional control valve
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/50Pressure control
    • F15B2211/55Pressure control for limiting a pressure up to a maximum pressure, e.g. by using a pressure relief valve
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/70Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/71Multiple output members, e.g. multiple hydraulic motors or cylinders
    • F15B2211/7135Combinations of output members of different types, e.g. single-acting cylinders with rotary motors
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/70Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/71Multiple output members, e.g. multiple hydraulic motors or cylinders
    • F15B2211/7142Multiple output members, e.g. multiple hydraulic motors or cylinders the output members being arranged in multiple groups
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/70Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/78Control of multiple output members
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B2211/00Circuits for servomotor systems
    • F15B2211/80Other types of control related to particular problems or conditions
    • F15B2211/88Control measures for saving energy

Definitions

  • the present invention relates in general to hydraulic control circuits for the working members of earth-moving machines.
  • the invention relates to a hydraulic control circuit of the type including a pump for supplying a hydraulic fluid under pressure and a plurality of reversible hydraulic actuators, in part linear and in part rotary, for the actuation of respective working members each of which has an associated hydraulic spool valve connected with the delivery and the discharge of the associated working member and positionable, with continuous adjustment, by means of associated control means, into three positions corresponding to displacement of the working member in a first direction, stopping thereof, and displacement in a second direction opposite the first, and pressure compensators of the "load-sensing" type interposed between the said source of supply and the said distributor valves for maintaining the difference between the pressure delivered by the said supply source and the pressure in the working members substantially constant, the said pressure compensators including normally open two-way spool valves each having an end subjected to an opening pressure coming from the associated working member downstream of the associated distributor valve as well as to the action of a biasing spring, and an opposite end subjected to a closure pressure coming from the input of the associated distributor valve
  • the end of the cylinder housing the linear actuator rod is connected during the movement to the "load-sensing" pump which therefore sends to this side a flow of fluid proportional to the product of the delivery flow cross-section ("meter-in") of the distributor valve and the square root of the "load-sensing" pressure difference, whilst from the end of the actuator cylinder there is discharged a flow rate proportional to the product of the discharge flow cross-section of the distributor valve and the square root of the load pressure.
  • the object of the present invention is that of obviating the above-mentioned disadvantage, avoiding unnecessary demands for fluid flow from the pump in the said conditions or in similar operating conditions.
  • the subject of the present invention is a hydraulic circuit of the type initially defined, characterised by the fact that at least one of the hydraulic actuators has associated therewith a fluid flow recovery device including at least one recovery line which interconnects the actuator discharge, upstream of the associated distributor valve with respect to the discharge flow, to the delivery of the actuator between the associated compensator and the associated distributor valve, the said fluid flow recovery line including a unidirectional valve operable to allow the passage of fluid only from the discharge towards the delivery of the actuator to obtain an additional closure pressure on the spool of the compensator.
  • the advantage is obtained that, in the case of lowering of a load, the output to the actuator rod end of the actuator cylinder is provided by the flow of fluid leaving the base end which is divided between the discharge cross-section and the delivery cross-section of the distributor. By suitably dimensioning these areas it is possible to avoid the need for an anti-cavitation valve on the rod end of the actuator cylinder.
  • the preceding considerations can be applied to the case in which the operating conditions of the linear actuator are reversed with respect to what has been described above with reference to the lowering of a negative load by the lifting arm of an excavator.
  • the invention permits the unnecessary requirements for output of the "load-sensing" pump towards the base end of the actuator cylinder. In this case,however,it is not in general possible to eliminate the need for an-anti-cavitation valve.
  • the invention can provide a double configuration , when necessary, by providing the fluid flow recovery device with two recovery lines in parallel for the purpose of obtaining the above-described effect in both directions of operation of the corresponding linear actuator.
  • the recovery device according to the invention is equally applicable, in a double configuration with two recovery lines, to one or more of the rotary hydraulic actuators.
  • Figure 1 the essential components of a hydraulic control circuit for the working members of an earth-moving machine are illustrated.
  • these working members comprise a series of linear hydraulic actuators 1, 2, 3, 4 serving for the actuation of the excavator arm (raising-penetration-positioning-crowding) and a series of rotary hydraulic motors 5, 6, 7 the first two of which are utilised for the translation manoeuvres of the excavator and the third for the rotation of the excavator arm.
  • the linear actuators 1-4 are gathered in a group, generally indicated 10, separate and distinct from the group, indicated 11, of rotary motors 5-7.
  • Supply and discharge of the actuators 1-4 and 5-7 is provided by respective distributor valves 8, 9 associated with the two groups 10,11 respectively.
  • Each distributor valve 8, 9 is positionable in three conditions, corresponding respectively to displacement in a first direction of the associated actuator 1-7, stopping thereof, and displacement in a second direction opposite the first.
  • the input-output connections between the distributors 8, 9 and the associated actuators 1-7 are indicated in the drawing with A 1 , B 1 together a 7 , B 7 .
  • the positioning of the spools of the distributors 8, 9 in the three possible positions is obtained thanks to hydraulic control effected from a servo controlled valve unit, not illustrated in the drawing, including a series of control levers and pedals, known per se, which can be manually positioned in different positions corresponding to the said conditions of the distributors 8, 9.
  • the input-output control connections between the servo controls and the distributors 8, 9 are indicated a l , b 1 Vietnamese 7 , b 7 .
  • the pump 12 is provided with a "load-sensing" control of type known per se, formed by means of a control circuit 14 by means of which the "load -sensing" pressure signals are derived by taking off signals 15 from the distributors 8 and signals 16 from the distributors 9.
  • compensators 17, 18 Associated with the distributor valves 8, 9 are respective compensators 17, 18 constituted by normally open two-way spool valves inserted in the delivery line 19 of the pump 12 between this latter and the associated distributor valves 8, 9.
  • the compensators 17, 18, which will be returned to below, have, in a manner known per se, the function of maintaining during operation the difference between the pressure delivered by the pump 12 and that in the working members 1-7 substantially constant for the purpose of ensuring the simultaneity of the various possible working movements of the machine independently of the controlled loads.
  • the hydraulic servo control devices are fed by the pump 13 under the control of a maximum pressure valve 20. Associated with this maximum pressure valve is a valve device, generally indicated 21, the function of which is that of preventing the hydraulic circuit from being able to find itself in saturation conditions.
  • the ways in which the depressurisation valve unit 21 can operate are described and illustrated in European Patent Application No. 85830286.2 by the same applicant.
  • the rotary hydraulic motors 5, 6 and 7 are associated with braking valve means controlled by the pressure in the delivery duct 19 and prearranged to vary the discharge resistance of the motors in dependence on the pressure existing in the supply duct.
  • These braking valve means are constituted, in a manner known per se from Italian Patent Application No. 67086-A/86 and from corresponding European Patent Application No. 868302 60.5,_ by a single counterbalanced controlled valve 22 inserted in a discharge duct 23 which is common to the three distributors 9 and subjected to the action of a control pressure coming from the pump 13 through a pressure limiting unit, generally indicated 24.
  • This control pressure signal which corresponds to the lowest supply pressure of the rotary actuators 5-7, could alternatively be derived from a selector valve logic system in a manner known from the above-mentioned Patent documents.
  • one or more of the actuators 1-7 can be associated with a fluid flow recovery device operatively cooperating with the corresponding compensators 17, 18 to avoid unnecessary demands for delivery from the pump 12 in certain operating conditions.
  • Figure 2 relates to the application of the fluid-flow recovery device, generally indicated 25, to the linear hydraulic actuator 1 provided for raising and lowering the excavator arm.
  • Figure 2 shows in simplified and diagrammatic form the delivery circuit from the pump 12 and discharge to a reservoir 26 of the linear actuator 1 in the position of the associated distributor valve 8 corresponding to lowering of a load.
  • the distributor valve 8 has been omitted for simplicity and its representation replaced by two schematic representations 8a, 8b of the associated delivery sections ("meter-in” area) and discharge sections ("meter-out” area) respectively through a delivery line 27 and a discharge line 28.
  • the liquid under pressure coming from the pump 12 is supplied to the cylinder la of the linear actuator 1 on the side of the rod lb, whilst the opposite end lc of the cylinder la is connected to the discharge.
  • the compensator 17, which is inserted in the duct 19 between the pump 12 and the distributor valve 8, is constituted by a normally open two-position and two-way spool valve 29 having a side 29a subjected to an opening pressure coming from the linear actuator 1 through a line 30 as well as to the action of a biasing spring 31, and an opposite side 29b subjected to a closure pressure coming from the input of the distributor valve 8 through a line 32.
  • a non-return valve 33 Between the compensator 17 and the distributor valve 8 there is disposed a non-return valve 33.
  • the fluid flow recovery device 25 includes, in the case of Figure 2, a recovery line 34 which interconnects the discharge 28 from the base end lc of the actuator 1, upstream of the discharge section 8b of the distributor valve 8 with respect to the discharge flow, and the delivery 27 to the rod end Ib of the actuator 1, upstream of the delivery section 8a of the distributor valve with respect to the delivery flow.
  • a unidirectional valve 35 operable to allow the passage of fluid only from the discharge 28 towards the delivery 27 of the actuator 1, and a calibrated throttle 36 for control of the fluid flow.
  • the line 32 is connected upstream of the unidirectional valve 33 with respect to the delivery flow.
  • this line 32 could alternatively be connected downstream of the valve 33, as is illustrated in the variant of Figure 3 in which the same reference numerals as in Figure 2 have been utilised.
  • FIG. 4 shows the application of the flow rate recovery device 25 according to the invention to the case in which the linear actuator 1 is in discharge through the discharge section 8b of the distributor valve 8 from the rod end 1b and in delivery from the base end lc through the delivery section 8a of the distributor valve 8.
  • the circuit configuration and the manner of operation are entirely identical to those previously described with reference to Figure 3.
  • the recovery device 25 can have a double configuration, as illusrtrated in Figure 1 with reference to the linear actuator 2, by utilising two recovery lines 34 in parallel, with respective non-return valves 34 and throttles 36 connected one to the line 27 and the other to the line 28 of the actuator.
  • Figure 5 in which the same reference numerals are used as in the preceding Figures (and in which 9a, 9b indicate respectively the delivery sections and discharge sections of the distributor valve 9), illustrate the application to a rotary motor 5 with a single recover line 34, whilst Figure 1 shows the application of the double configuration to the rotary motor 6 with two recovery lines 34 joined together in parallel.

Abstract

A hydraulic control circuit for the working members of earth-moving machines having linear and rotary reversible hydraulic actuators (1-7) each of which is associated with an associated hydraulic distributor valve (8, 9) and a pressure compensator (17, 18) of the "load-sensing" type. One or more of the actuators (1-7) is further associated with a flow recovery device (25) including at least one recovery line (34) between the discharge (28) and the delivery (27) of the actuator for obtaining an additional closure pressure on the spool (29) of the compensator (17,18) in such a way as to cancel out unnecessary demands on the fluid flow rate from the pump (12).

Description

  • The present invention relates in general to hydraulic control circuits for the working members of earth-moving machines.
  • More particularly, the invention relates to a hydraulic control circuit of the type including a pump for supplying a hydraulic fluid under pressure and a plurality of reversible hydraulic actuators, in part linear and in part rotary, for the actuation of respective working members each of which has an associated hydraulic spool valve connected with the delivery and the discharge of the associated working member and positionable, with continuous adjustment, by means of associated control means, into three positions corresponding to displacement of the working member in a first direction, stopping thereof, and displacement in a second direction opposite the first, and pressure compensators of the "load-sensing" type interposed between the said source of supply and the said distributor valves for maintaining the difference between the pressure delivered by the said supply source and the pressure in the working members substantially constant, the said pressure compensators including normally open two-way spool valves each having an end subjected to an opening pressure coming from the associated working member downstream of the associated distributor valve as well as to the action of a biasing spring, and an opposite end subjected to a closure pressure coming from the input of the associated distributor valve.
  • In some operating conditions of hydraulic circuits of the said type situations can arise in which the supply pump sends to one or more of the actuators a considerable output not required by the energy balance of the manoeuvre. This situation can occur, for example, in the case of a linear actuator which controls the raising and lowering of the arm of an excavator, during the movement of a negative load (lowering of the load). In fact, in this case the negative load acts on the end of the linear actuator cylinder and the movement is controlled by the discharge flow cross-section ("meter-out") of the associated distributor valve and the flow of fluid is normally all discharged. The end of the cylinder housing the linear actuator rod is connected during the movement to the "load-sensing" pump which therefore sends to this side a flow of fluid proportional to the product of the delivery flow cross-section ("meter-in") of the distributor valve and the square root of the "load-sensing" pressure difference, whilst from the end of the actuator cylinder there is discharged a flow rate proportional to the product of the discharge flow cross-section of the distributor valve and the square root of the load pressure.
  • Since the load on the end of the actuator generates a pressure (of the order of 250 bar) very much greater than that of the "load-sensing" (of the order of 20 bar) and taking account of the ratio (about 1:1.5) of the volumes of the rod end/base end of the actuator cylinder, the flow of fluid sent to the actuator rod end of the cylinder is insufficient and an anti-cavitation valve must be installed on this end of the cylinder.
  • Since such anti-cavitation valves draw in oil only by the discharge reservoir back pressure,their intervention is not sufficient to provide the required flow rate to the actuator rod end: the pump therefore sends to this end a considerable flow of fluid which is not required by the energy balance of the manoeuvre, with a consequent useless dissipation of power.
  • The object of the present invention is that of obviating the above-mentioned disadvantage, avoiding unnecessary demands for fluid flow from the pump in the said conditions or in similar operating conditions.
  • With a view to achieving this object, the subject of the present invention is a hydraulic circuit of the type initially defined, characterised by the fact that at least one of the hydraulic actuators has associated therewith a fluid flow recovery device including at least one recovery line which interconnects the actuator discharge, upstream of the associated distributor valve with respect to the discharge flow, to the delivery of the actuator between the associated compensator and the associated distributor valve, the said fluid flow recovery line including a unidirectional valve operable to allow the passage of fluid only from the discharge towards the delivery of the actuator to obtain an additional closure pressure on the spool of the compensator.
  • Thanks to this idea unnecessary demands on the pump capacity in the previously described conditions are cancelled out thanks to the closure of the compensator which isolates the pump from the distributor and the associated actuator.
  • Moreover, with the arrangements according to the invention the advantage is obtained that, in the case of lowering of a load, the output to the actuator rod end of the actuator cylinder is provided by the flow of fluid leaving the base end which is divided between the discharge cross-section and the delivery cross-section of the distributor. By suitably dimensioning these areas it is possible to avoid the need for an anti-cavitation valve on the rod end of the actuator cylinder.
  • Naturally, the preceding considerations can be applied to the case in which the operating conditions of the linear actuator are reversed with respect to what has been described above with reference to the lowering of a negative load by the lifting arm of an excavator. For example, in the case of the linear actuator for control of the penetration of the excavating tool of an excavator, the invention permits the unnecessary requirements for output of the "load-sensing" pump towards the base end of the actuator cylinder. In this case,however,it is not in general possible to eliminate the need for an-anti-cavitation valve.
  • Further, the invention can provide a double configuration , when necessary, by providing the fluid flow recovery device with two recovery lines in parallel for the purpose of obtaining the above-described effect in both directions of operation of the corresponding linear actuator.
  • Moreover, the recovery device according to the invention is equally applicable, in a double configuration with two recovery lines, to one or more of the rotary hydraulic actuators.
  • The invention will now be described in detail with reference to the attached drawings, provided purely by way of non-limitative example, in which:
    • Figure 1 is a hydraulic control circuit diagram according to the invention;
    • Figure 2 is a simplified diagrammatic view on an enlarged scale of a part of the circuit of Figure 1;
    • Figure 3 is a first variant of Figure 2;
    • Figure 4 is a second variant of Figure 2; and
    • Figure 5 is a simplified diagrammatic view on an enlarged scale of another part of the circuit of Figure 1.
  • In Figure 1 the essential components of a hydraulic control circuit for the working members of an earth-moving machine are illustrated.
  • In the illustrated example these working members comprise a series of linear hydraulic actuators 1, 2, 3, 4 serving for the actuation of the excavator arm (raising-penetration-positioning-crowding) and a series of rotary hydraulic motors 5, 6, 7 the first two of which are utilised for the translation manoeuvres of the excavator and the third for the rotation of the excavator arm.
  • The linear actuators 1-4 are gathered in a group, generally indicated 10, separate and distinct from the group, indicated 11, of rotary motors 5-7. Supply and discharge of the actuators 1-4 and 5-7 is provided by respective distributor valves 8, 9 associated with the two groups 10,11 respectively. Each distributor valve 8, 9 is positionable in three conditions, corresponding respectively to displacement in a first direction of the associated actuator 1-7, stopping thereof, and displacement in a second direction opposite the first. The input-output connections between the distributors 8, 9 and the associated actuators 1-7 are indicated in the drawing with A1, B1...... A7, B7.
  • The positioning of the spools of the distributors 8, 9 in the three possible positions is obtained thanks to hydraulic control effected from a servo controlled valve unit, not illustrated in the drawing, including a series of control levers and pedals, known per se, which can be manually positioned in different positions corresponding to the said conditions of the distributors 8, 9. The input-output control connections between the servo controls and the distributors 8, 9 are indicated al, b1 ..... a7, b7.
  • Supply to the distributors 8, 9 (and therefore to the working members 1-7) and to the servo controls, is obtained in the case of the illustrated example by means of two separate hydraulic pumps 12, 13.
  • The pump 12 is provided with a "load-sensing" control of type known per se, formed by means of a control circuit 14 by means of which the "load -sensing" pressure signals are derived by taking off signals 15 from the distributors 8 and signals 16 from the distributors 9.
  • Associated with the distributor valves 8, 9 are respective compensators 17, 18 constituted by normally open two-way spool valves inserted in the delivery line 19 of the pump 12 between this latter and the associated distributor valves 8, 9. The compensators 17, 18, which will be returned to below, have, in a manner known per se, the function of maintaining during operation the difference between the pressure delivered by the pump 12 and that in the working members 1-7 substantially constant for the purpose of ensuring the simultaneity of the various possible working movements of the machine independently of the controlled loads. The hydraulic servo control devices are fed by the pump 13 under the control of a maximum pressure valve 20. Associated with this maximum pressure valve is a valve device, generally indicated 21, the function of which is that of preventing the hydraulic circuit from being able to find itself in saturation conditions. The ways in which the depressurisation valve unit 21 can operate are described and illustrated in European Patent Application No. 85830286.2 by the same applicant.
  • The rotary hydraulic motors 5, 6 and 7 are associated with braking valve means controlled by the pressure in the delivery duct 19 and prearranged to vary the discharge resistance of the motors in dependence on the pressure existing in the supply duct. These braking valve means are constituted, in a manner known per se from Italian Patent Application No. 67086-A/86 and from corresponding European Patent Application No. 86830260.5,_ by a single counterbalanced controlled valve 22 inserted in a discharge duct 23 which is common to the three distributors 9 and subjected to the action of a control pressure coming from the pump 13 through a pressure limiting unit, generally indicated 24. This control pressure signal, which corresponds to the lowest supply pressure of the rotary actuators 5-7, could alternatively be derived from a selector valve logic system in a manner known from the above-mentioned Patent documents.
  • According to the invention, one or more of the actuators 1-7 can be associated with a fluid flow recovery device operatively cooperating with the corresponding compensators 17, 18 to avoid unnecessary demands for delivery from the pump 12 in certain operating conditions.
  • Embodiments of these fluid-flow recovery devices are illustrated in more detail in Figures 2-5.
  • Figure 2 relates to the application of the fluid-flow recovery device, generally indicated 25, to the linear hydraulic actuator 1 provided for raising and lowering the excavator arm. Figure 2 shows in simplified and diagrammatic form the delivery circuit from the pump 12 and discharge to a reservoir 26 of the linear actuator 1 in the position of the associated distributor valve 8 corresponding to lowering of a load. In this Figure the distributor valve 8 has been omitted for simplicity and its representation replaced by two schematic representations 8a, 8b of the associated delivery sections ("meter-in" area) and discharge sections ("meter-out" area) respectively through a delivery line 27 and a discharge line 28. As is seen, in the said operating conditions the liquid under pressure coming from the pump 12 is supplied to the cylinder la of the linear actuator 1 on the side of the rod lb, whilst the opposite end lc of the cylinder la is connected to the discharge.
  • The compensator 17, which is inserted in the duct 19 between the pump 12 and the distributor valve 8, is constituted by a normally open two-position and two-way spool valve 29 having a side 29a subjected to an opening pressure coming from the linear actuator 1 through a line 30 as well as to the action of a biasing spring 31, and an opposite side 29b subjected to a closure pressure coming from the input of the distributor valve 8 through a line 32. Between the compensator 17 and the distributor valve 8 there is disposed a non-return valve 33.
  • The fluid flow recovery device 25 includes, in the case of Figure 2, a recovery line 34 which interconnects the discharge 28 from the base end lc of the actuator 1, upstream of the discharge section 8b of the distributor valve 8 with respect to the discharge flow, and the delivery 27 to the rod end Ib of the actuator 1, upstream of the delivery section 8a of the distributor valve with respect to the delivery flow. In the recovery line 34 there are inserted a unidirectional valve 35 operable to allow the passage of fluid only from the discharge 28 towards the delivery 27 of the actuator 1, and a calibrated throttle 36 for control of the fluid flow. In the operating conditions described above with reference to Figure 2, during a lowering movement of a load, the load on the base end lc of the actuator 1 generates a pressure (of the order of 250 bar) very much greater than that sent to the rod end lb so that the pump must normally send to this side a considerable flow of fluid which is not required by the energy balance of the manoeuvre. The presence of the fluid flow recovery device 25 according to the invention in practice cancels out this requirement for fluid flow from the pump 12 in that the pressure acting on the base end Ic of the actuator 1 is transmitted through the recovery line 34 to a point upstream of the delivery section 8a of the distributor valve 8. This pressure then acts through the line 32 on the side 29b of the spool 29 of the compensator 17, with a value significantly greater than that acting on the side 29a and corresponding to the pressure on the rod end 1b of the actuator 1 and the load of the spring 31. Consequently the spool 29 of the compensator 17 is moved to the closure position blocking the requirement for fluid flow from the pump 12.
  • In the case of Figure 3 the line 32 is connected upstream of the unidirectional valve 33 with respect to the delivery flow. However, this line 32 could alternatively be connected downstream of the valve 33, as is illustrated in the variant of Figure 3 in which the same reference numerals as in Figure 2 have been utilised.
  • The variant of Figure 4 shows the application of the flow rate recovery device 25 according to the invention to the case in which the linear actuator 1 is in discharge through the discharge section 8b of the distributor valve 8 from the rod end 1b and in delivery from the base end lc through the delivery section 8a of the distributor valve 8. The circuit configuration and the manner of operation are entirely identical to those previously described with reference to Figure 3.
  • The recovery device 25 can have a double configuration, as illusrtrated in Figure 1 with reference to the linear actuator 2, by utilising two recovery lines 34 in parallel, with respective non-return valves 34 and throttles 36 connected one to the line 27 and the other to the line 28 of the actuator.
  • Figure 5, in which the same reference numerals are used as in the preceding Figures (and in which 9a, 9b indicate respectively the delivery sections and discharge sections of the distributor valve 9), illustrate the application to a rotary motor 5 with a single recover line 34, whilst Figure 1 shows the application of the double configuration to the rotary motor 6 with two recovery lines 34 joined together in parallel.
  • The modes of operation of the recovery device 25 applied to such hydraulic motors are entirely similar to those described previously with reference to linear actuators.

Claims (3)

1. A hydraulic control circuit for working members of earth-moving machines including a pump for supplying a hydraulic fluid under pressure and a plurality of reversible hydraulic actuators, in part linear and in part rotary, for the actuation of associated working members, each of which has associated therewith a respective hydraulic spool valve connected to the delivery and discharge of associated working members and positionable with continuous adjustment by associated control means into three positions corresponding to the displacement of the working member in a first direction, stopping thereof, and displacement in a second direction opposite to the first, and pressure compensators of the "load-sensing" type interposed between the said supply source and the said distributor valves for maintaining substantially constant the difference between the delivery pressure from the said supply source and the pressure of the working members, the said compensators including normally open two-way spool valves each having a side subjected to an opening pressure coming from the associated working member downstream of the associated distributor valve as well as the action of a biasing spring, and an opposite side subjected to a closure pressure coming from the inlet of the associated distributor valve, characterised in that at least one of the hydraulic actuators (1-7) has associated therewith a fluid-flow recovery device (25) including at least one recovery line (34) which interconnects the discharge (28) of the actuator (1-7) upstream of the associated distributor valve (8,9) with respect to the discharge flow, and the delivery (27) of the actuator (1-7) between the associated compensator (17,18) and the associated distributor valve (8,9), the said fluid-flow recovery line (34) including a unldirectional valve (35) operable to allow The passage of fluid only from the discharge (28) towards the delivery (27) of the actuator (1-7) to obtain an additional closure pressure on the spool (29) of the compensator (17, 18)
2. A circuit according to Claim 1, characterised in that the recovery line (34) further includes a calibrated throttle (36).
3. A circuit according to Claim 1 or Claim 2, characterised in that the or each fluid-flow recovery device includes two recovery lines (34) connected in parallel.
EP87830015A 1986-09-24 1987-01-19 A flow recovery system for hydraulic circuits with pumps and pressure compensated distributor valves for working members of earth-moving machines Expired - Lifetime EP0262098B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT87830015T ATE52560T1 (en) 1986-09-24 1987-01-19 FLOW RECOVERY SYSTEM FOR HYDRAULIC CIRCUITS WITH PUMPS AND PRESSURE-COMPENSATED DISTRIBUTION VALVES FOR WORKING LINKS OF EARTH-MOVING EQUIPMENT.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
IT67731/86A IT1195178B (en) 1986-09-24 1986-09-24 FLOW RATE RECOVERY SYSTEM FOR HYDRAULIC CIRCUITS WITH PUMPS AND PRESSURIZED PRESSURE INSTRUMENTS FOR WORKING PARTS OF EARTH-MOVING MACHINES
IT6773186 1986-09-24

Publications (2)

Publication Number Publication Date
EP0262098A1 true EP0262098A1 (en) 1988-03-30
EP0262098B1 EP0262098B1 (en) 1990-05-09

Family

ID=11304850

Family Applications (1)

Application Number Title Priority Date Filing Date
EP87830015A Expired - Lifetime EP0262098B1 (en) 1986-09-24 1987-01-19 A flow recovery system for hydraulic circuits with pumps and pressure compensated distributor valves for working members of earth-moving machines

Country Status (7)

Country Link
EP (1) EP0262098B1 (en)
JP (1) JP2564308B2 (en)
AT (1) ATE52560T1 (en)
DE (1) DE3762639D1 (en)
ES (1) ES2015967B3 (en)
GR (1) GR3000479T3 (en)
IT (1) IT1195178B (en)

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0287529A1 (en) * 1987-04-14 1988-10-19 TRINOVA S.p.A. Hydraulic circuit with a booster circuit for operating the working members of earth-moving machines
EP0297682A2 (en) * 1987-06-30 1989-01-04 Hitachi Construction Machinery Co., Ltd. Hydraulic drive system
EP0312130A1 (en) * 1987-10-05 1989-04-19 Hitachi Construction Machinery Co., Ltd. Hydraulic drive system
EP0445703A2 (en) * 1990-03-05 1991-09-11 Hitachi Construction Machinery Co., Ltd. Hydraulic drive system
BE1006417A3 (en) * 1992-05-15 1994-08-23 Caterpillar Inc Fluid system recovery.
EP0656481A1 (en) * 1993-12-02 1995-06-07 Hitachi Construction Machinery Co., Ltd. Hydraulic control system for construction machines
EP0704629A3 (en) * 1994-09-29 1997-12-17 Samsung Heavy Industries Co., Ltd Mono-block control valve with regeneration conduit
EP0831181A1 (en) * 1996-09-20 1998-03-25 Shin Caterpillar Mitsubishi Ltd. Hydraulic circuit
EP1016762A2 (en) * 1998-12-16 2000-07-05 J.C. Bamford Excavators Limited Earth moving machine
WO2001057405A1 (en) * 2000-02-04 2001-08-09 O & K Orenstein & Koppel Aktiengesellschaft Method and device for controlling a lift cylinder, especially of working machines
WO2004070211A1 (en) * 2003-01-14 2004-08-19 Hitachi Construction Machinery Co., Ltd. Hydraulic working machine
WO2004083646A1 (en) * 2003-03-17 2004-09-30 Hitachi Construction Machinery Co., Ltd. Oil pressure circuit for working machines
EP4063668A1 (en) * 2021-03-23 2022-09-28 CNH Industrial Belgium NV System to reduce line loss in pressure control hydraulic circuit

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3844401C2 (en) * 1988-12-30 1994-10-06 Rexroth Mannesmann Gmbh Control device for a variable displacement pump

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1401412A (en) * 1964-04-23 1965-06-04 Faucheux Ets Device for hydraulically correcting the movement of a mechanical component, for example a bucket, at the end of a lifting arm
US3467126A (en) * 1966-03-21 1969-09-16 Hydranamic Systems Corp Hydraulic load compensating directional control valve
US4216702A (en) * 1978-05-01 1980-08-12 Eaton Yale Ltd. Pressure sensing regenerative hydraulic system
US4364304A (en) * 1976-01-21 1982-12-21 Danfoss A/S Arrangement for influencing the operating quantity of a servomotor
US4383412A (en) * 1979-10-17 1983-05-17 Cross Manufacturing, Inc. Multiple pump load sensing system
FR2537184A1 (en) * 1982-12-03 1984-06-08 Orenstein & Koppel Ag HYDRAULIC PROCESS AND CIRCUIT FOR SAVING ENERGY WHEN OPERATING A MANEUVERING CYLINDER ON A HYDRAULIC EXCAVATOR

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
IT1234937B (en) * 1985-02-14 1992-06-02 Cinotto Hydraulic ANTI-SATURATION SYSTEM FOR HYDRAULIC CONTROL CIRCUITS WITH PUMPS AND PRESSURE-CONTROLLED DISTRIBUTORS FOR WORKING PARTS OF EARTH-MOVING MACHINES
IT1187892B (en) * 1986-02-04 1987-12-23 Chs Vickers Spa HYDRAULIC CONTROL CIRCUIT FOR WORKING BODIES OF EARTH-MOVING MACHINES WITH CENTRALIZED ACTUATOR BRAKING

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1401412A (en) * 1964-04-23 1965-06-04 Faucheux Ets Device for hydraulically correcting the movement of a mechanical component, for example a bucket, at the end of a lifting arm
US3467126A (en) * 1966-03-21 1969-09-16 Hydranamic Systems Corp Hydraulic load compensating directional control valve
US4364304A (en) * 1976-01-21 1982-12-21 Danfoss A/S Arrangement for influencing the operating quantity of a servomotor
US4216702A (en) * 1978-05-01 1980-08-12 Eaton Yale Ltd. Pressure sensing regenerative hydraulic system
US4383412A (en) * 1979-10-17 1983-05-17 Cross Manufacturing, Inc. Multiple pump load sensing system
FR2537184A1 (en) * 1982-12-03 1984-06-08 Orenstein & Koppel Ag HYDRAULIC PROCESS AND CIRCUIT FOR SAVING ENERGY WHEN OPERATING A MANEUVERING CYLINDER ON A HYDRAULIC EXCAVATOR

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN, vol. 7, no. 261 (M-257)[1406], 19th November 1983; & JP-A-58 142 003 (MITSUBISHI JUKOGYO K.K.) 23-08-1983 *

Cited By (27)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0287529A1 (en) * 1987-04-14 1988-10-19 TRINOVA S.p.A. Hydraulic circuit with a booster circuit for operating the working members of earth-moving machines
EP0297682A2 (en) * 1987-06-30 1989-01-04 Hitachi Construction Machinery Co., Ltd. Hydraulic drive system
EP0297682A3 (en) * 1987-06-30 1989-04-12 Hitachi Construction Machinery Co., Ltd. Hydraulic drive system
US4945723A (en) * 1987-06-30 1990-08-07 Hitachi Construction Machinery Co., Ltd. Flow control valves for hydraulic motor system
EP0312130A1 (en) * 1987-10-05 1989-04-19 Hitachi Construction Machinery Co., Ltd. Hydraulic drive system
US4938022A (en) * 1987-10-05 1990-07-03 Hitachi Construction Machinery Co., Ltd. Flow control system for hydraulic motors
EP0445703A2 (en) * 1990-03-05 1991-09-11 Hitachi Construction Machinery Co., Ltd. Hydraulic drive system
EP0445703A3 (en) * 1990-03-05 1992-04-08 Hitachi Construction Machinery Co., Ltd. Hydraulic drive system
US5168705A (en) * 1990-03-05 1992-12-08 Hitachi Construction Machinery Co., Ltd. Hydraulic drive system
BE1006417A3 (en) * 1992-05-15 1994-08-23 Caterpillar Inc Fluid system recovery.
EP0656481A1 (en) * 1993-12-02 1995-06-07 Hitachi Construction Machinery Co., Ltd. Hydraulic control system for construction machines
US5479778A (en) * 1993-12-02 1996-01-02 Hitachi Construction Machinery Co., Ltd. Hydraulic control system for construction machines
EP0704629A3 (en) * 1994-09-29 1997-12-17 Samsung Heavy Industries Co., Ltd Mono-block control valve with regeneration conduit
EP0831181A1 (en) * 1996-09-20 1998-03-25 Shin Caterpillar Mitsubishi Ltd. Hydraulic circuit
EP1016762A2 (en) * 1998-12-16 2000-07-05 J.C. Bamford Excavators Limited Earth moving machine
EP1016762A3 (en) * 1998-12-16 2000-10-25 J.C. Bamford Excavators Limited Earth moving machine
WO2001057405A1 (en) * 2000-02-04 2001-08-09 O & K Orenstein & Koppel Aktiengesellschaft Method and device for controlling a lift cylinder, especially of working machines
US6701823B2 (en) 2000-02-04 2004-03-09 O&K Orenstein & Koppel Aktiengesellschaft Method and device for controlling a lift cylinder, especially of working machines
US7562615B2 (en) 2003-01-14 2009-07-21 Hitachi Construction Machinery Co., Ltd. Hydraulic working machine
WO2004070211A1 (en) * 2003-01-14 2004-08-19 Hitachi Construction Machinery Co., Ltd. Hydraulic working machine
EP1591669A1 (en) * 2003-01-14 2005-11-02 Hitachi Construction Machinery Co., Ltd. Hydraulic working machine
US8336443B2 (en) 2003-01-14 2012-12-25 Hitachi Construction Machinery Co., Ltd. Hydraulic working machine
EP1591669A4 (en) * 2003-01-14 2010-12-08 Hitachi Construction Machinery Hydraulic working machine
WO2004083646A1 (en) * 2003-03-17 2004-09-30 Hitachi Construction Machinery Co., Ltd. Oil pressure circuit for working machines
CN100378343C (en) * 2003-03-17 2008-04-02 日立建机株式会社 Oil pressure circuit for working machines
US7127887B2 (en) 2003-03-17 2006-10-31 Hitachi Construction Machinery Co., Ltd. Oil pressure circuit for working machines
EP4063668A1 (en) * 2021-03-23 2022-09-28 CNH Industrial Belgium NV System to reduce line loss in pressure control hydraulic circuit

Also Published As

Publication number Publication date
ATE52560T1 (en) 1990-05-15
EP0262098B1 (en) 1990-05-09
ES2015967B3 (en) 1990-09-16
JP2564308B2 (en) 1996-12-18
GR3000479T3 (en) 1991-06-28
JPS6383808A (en) 1988-04-14
DE3762639D1 (en) 1990-06-13
IT8667731A0 (en) 1986-09-24
IT1195178B (en) 1988-10-12

Similar Documents

Publication Publication Date Title
EP0262098B1 (en) A flow recovery system for hydraulic circuits with pumps and pressure compensated distributor valves for working members of earth-moving machines
US4738103A (en) Hydraulic control circuit for working members of earth-moving machines with centralized braking of the actuators
US5490384A (en) Hydraulic flow priority system
DE112006000783T5 (en) Electro-hydraulic steering control system
US5447094A (en) Hydraulic system for bucket self-leveling during raising and lowering of boom
US4724673A (en) Power transmission
EP1588057A1 (en) Hydraulic system for linear drives controlled by a displacer element
CA2179818A1 (en) Hydraulic flow priority system
JP2618680B2 (en) Hydraulic circuit with booster circuit for actuating working members of earthmoving machines
US4610193A (en) Load control system
DE112014003379T5 (en) Hydraulic control circuit with regeneration valve
CZ63897A3 (en) Apparatus for recovery of energy
EP0041199A1 (en) Power transmission
US3878679A (en) Compensated multi-function hydraulic system
EP0191275B1 (en) Anti-saturation system for hydraulic control circuits for working members of earth-moving machines
EP3492661B1 (en) Excavator, and control valve for excavator
EP0111208A1 (en) Power transmission
EP2910796B9 (en) Assembly with a control valve device with a float position
DE3901207C2 (en) Valve arrangement for several hydraulic drives, in particular for the drives of a crane
WO2023104331A1 (en) Hydraulic control system in working machine
US20190234049A1 (en) Work machine having hydraulics for energy recovery
CN114207225B (en) Hydraulic control system
FI66466C (en) ANORDNING FOER ATT BEGRAENSA EN HYDRAULKOLVS HASTIGHET I AENDLAEGENA.
JPS61151333A (en) Hydraulic circuit device for construction machine
DE19957027B4 (en) Hydrostatic drive system

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AT BE CH DE ES FR GB GR IT LI LU NL SE

17P Request for examination filed

Effective date: 19880421

RAP1 Party data changed (applicant data changed or rights of an application transferred)

Owner name: TRINOVA S.P.A.

17Q First examination report despatched

Effective date: 19890706

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): AT BE CH DE ES FR GB GR IT LI LU NL SE

REF Corresponds to:

Ref document number: 52560

Country of ref document: AT

Date of ref document: 19900515

Kind code of ref document: T

ITF It: translation for a ep patent filed

Owner name: JACOBACCI & PERANI S.P.A.

REF Corresponds to:

Ref document number: 3762639

Country of ref document: DE

Date of ref document: 19900613

ET Fr: translation filed
REG Reference to a national code

Ref country code: GR

Ref legal event code: FG4A

Free format text: 3000479

PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed
ITTA It: last paid annual fee
PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: AT

Payment date: 19931213

Year of fee payment: 8

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: LU

Payment date: 19931216

Year of fee payment: 8

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: CH

Payment date: 19931217

Year of fee payment: 8

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GR

Payment date: 19931223

Year of fee payment: 8

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: BE

Payment date: 19931227

Year of fee payment: 8

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: ES

Payment date: 19940114

Year of fee payment: 8

EPTA Lu: last paid annual fee
PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: NL

Payment date: 19940131

Year of fee payment: 8

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: LU

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 19950119

Ref country code: AT

Effective date: 19950119

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: ES

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 19950120

EAL Se: european patent in force in sweden

Ref document number: 87830015.1

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: LI

Effective date: 19950131

Ref country code: CH

Effective date: 19950131

Ref country code: BE

Effective date: 19950131

BERE Be: lapsed

Owner name: TRINOVA S.P.A.

Effective date: 19950131

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GR

Free format text: THE PATENT HAS BEEN ANNULLED BY A DECISION OF A NATIONAL AUTHORITY

Effective date: 19950731

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: NL

Effective date: 19950801

REG Reference to a national code

Ref country code: CH

Ref legal event code: PL

REG Reference to a national code

Ref country code: GR

Ref legal event code: MM2A

Free format text: 3000479

NLV4 Nl: lapsed or anulled due to non-payment of the annual fee

Effective date: 19950801

REG Reference to a national code

Ref country code: ES

Ref legal event code: FD2A

Effective date: 19990301

REG Reference to a national code

Ref country code: GB

Ref legal event code: IF02

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 20030131

Year of fee payment: 17

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20040803

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 20041210

Year of fee payment: 19

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 20050105

Year of fee payment: 19

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: SE

Payment date: 20050107

Year of fee payment: 19

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: IT

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES;WARNING: LAPSES OF ITALIAN PATENTS WITH EFFECTIVE DATE BEFORE 2007 MAY HAVE OCCURRED AT ANY TIME BEFORE 2007. THE CORRECT EFFECTIVE DATE MAY BE DIFFERENT FROM THE ONE RECORDED.

Effective date: 20050119

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20060119

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: SE

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20060120

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: FR

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20060131

EUG Se: european patent has lapsed
GBPC Gb: european patent ceased through non-payment of renewal fee

Effective date: 20060119

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

Effective date: 20060929