EP0036761A2 - Circuit hydraulique avec clapet anti-retour - Google Patents

Circuit hydraulique avec clapet anti-retour Download PDF

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Publication number
EP0036761A2
EP0036761A2 EP81301185A EP81301185A EP0036761A2 EP 0036761 A2 EP0036761 A2 EP 0036761A2 EP 81301185 A EP81301185 A EP 81301185A EP 81301185 A EP81301185 A EP 81301185A EP 0036761 A2 EP0036761 A2 EP 0036761A2
Authority
EP
European Patent Office
Prior art keywords
fluid
cylinders
check valve
fluid pressure
valve means
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.)
Withdrawn
Application number
EP81301185A
Other languages
German (de)
English (en)
Other versions
EP0036761A3 (fr
Inventor
Donald L. Bianchetta
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.)
Caterpillar Inc
Original Assignee
Caterpillar Tractor Co
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 Caterpillar Tractor Co filed Critical Caterpillar Tractor Co
Publication of EP0036761A2 publication Critical patent/EP0036761A2/fr
Publication of EP0036761A3 publication Critical patent/EP0036761A3/fr
Withdrawn legal-status Critical Current

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Classifications

    • 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
    • F15B13/00—Details of servomotor systems ; Valves for servomotor systems
    • F15B13/01—Locking-valves or other detent i.e. load-holding devices

Definitions

  • This invention relates generally to fluid circuits, and more particularly to a fluid circuit having a load check and by-pass valve having zero leakage when associated with a fluid cylinder.
  • Construction vehicles such as hydraulic excavators, often employ work tools which are actuated by double-acting hydraulic cylinders.
  • the cylinders may be employed to actuate the boom, stick and bucket of the excavator selectively.
  • the hydraulic circuit employed to actuate the cylinders selectively generally includes a load check valve to ensure that the load carried by a cylinder upon its extension and isoloation, for example, will not decend abruptly upon loss of hydraulic fluid pressure in the circuit.
  • the load check valve takes the form of a standard poppet valve to block the escape of fluid from the cylinder when it is maintained in an actuated condition of operation.
  • poppet valves are difficult to control in respect to close modulation of fluid flow in the circuit.
  • the load check valve may include a reciprocal spool, and it is well known that spools of this type do notensure leakage control at an acceptable rate during normal operation.
  • a load check valve of this type is disclosed in U.S. A 4,102,250.
  • a fluid circuit comprises a fluid source, a fluid actuator, control means for selectively communicating pressurized fluid to the actuator from the source, and check valve means for isolating fluid pressure in the actuator in response to selective actuation of the control means, the check valve means including a load check valve having a reciprocal spool, and including means for communicating equalized fluid pressures to opposite ends of the spool from the actuator.
  • a fluid circuit has a pair of extensible and retractable fluid cylinders, load check valve means for communicating fluid pressure to each of the cylinders to extend or retract the same, and control means for interconnecting the load check valve means to permit gradual retraction of the cylinders upon loss of fluid pressure between the load check valve means, the control means including resolver valve means for movement between a first position to equalize the fluid pressures in the cylinders upon retraction of the cylinders and when the level of fluid pressure in one of the cylinders exceeds the level of fluid pressure in the other one of the cylinders, and a second position for gradually reducing the level of fluid pressure in the cylinders upon loss of fluid pressure between the load check valve means.
  • the check valve means of this invention will prevent an abrupt dropping of a load supported by the actuator and the load check valve thereof will function to control leakage therethrough to an acceptably low rate during normal operation.
  • the actuator constitutes a double-acting-hydraulic cylinder employed on a construction vehicle or the like and when the cylinder is extended and under load
  • the check valve means will function continuously to maintain the cylinder in its extended condition of operation without causing any appreciable decay in the pressurized fluid utilized and thus to maintain the cylinder in such extended condition.
  • the load check valve is adapted for attachment to the housing of the cylinder proper, thus avoiding the need for flexible lines interconnecting the same.
  • Figure 1 illustrates a fluid (hydraulic) circuit 10 adapted to selectively extend or retract a pair of fluid actuators 11 and 12, shown in the form of double-acting hydraulic cylinders.
  • a load is schematically shown, attached to the rod ends of the cylinders and may comprise a boom or bucket of an hydraulic excavator, for example.
  • fluid circuit 10 is adapted for the control of other types of actuators employed on construction vehicles or the like which are operated by pressurized fluid.
  • Fluid circuit 10 further includes a pressurized main fluid source 13 having an engine-driven pump 14 and a reservoir or tank 15.
  • a control means 16 including a manual pilot valve 17 connected to a low pressure or pilot pump 18 and a main control valve 19, are adapted to selectively communicate pressurized fluid from source 13 and pump 14 to cylinders 11 and 12.
  • shifting of three-position, four-way control valve 17 either rightwardly or leftwardly from its illustrated neutral position will function to communicate a pilot signal to valve 19 to shift the latter valve to communicate pump 14 with cylinders 11 and 12 for extension or retraction thereof.
  • the non-pressurized ends of the cylinders will, of course, be connected with tank 15 when exhausting them of fluid pressure.
  • a pair of load check valves 20 and 20' will become operative to control fluid flow upon pressurization and exhaustion of the head ends of the cylinders. Since check valves 20 and 20' are substantially identical in construction and arrangement, only check valve 20 will be described in detail with reference to Figure 2.
  • check valves of the spool type are widely utilized to isolate fluid pressure in the head end of cylinders of this type when the cylinders are extended to raise the load, for example.
  • check valves of the poppet type are used which are highly efficient for preventing leakage therethrough in the head ends of cylinders to prevent falling of the load.
  • poppet valves have not been widely accepted since they do not provide close control over modulation of fluid flow. Therefore, spool-type valves, such as that shown in above-referenced U.S'. Patent No.
  • 4,102,205 are normally employed as load check valves in this type of application, but they have the disadvantage of being unable to maintain leakage, therethrough at an acceptably low rate, particularly when the spools thereof have relatively large diameters. Also, it has proven difficult to mount these type of standard check valves directly on the housing of the associated hydraulic cylinder to avoid the need for flexible conduits interconnecting the valves and cylinders.
  • load check valve 20 comprises a housing 21 which may be secured directly to the casing of cylinder 11 to thus avoid the need for an interconnecting flexible conduit, such as schematically shown at 22 in Figure 1.
  • Extension of cylinder 11 to raise the load is effected by pressurized fluid communicated from pump 14, in the general manner described above, to a conduit 23 connected to an inlet 24 of valve 20.
  • the pressurized fluid is then communicated to an outlet passage 25, connected to conduit or passage 22 via a plurality of radial ports 26 defined in a reciprocal spool 27, a poppet valve 28 which is opened by the fluid pressure, and radial ports 29, also defined in spool 27.
  • Spool 27 is slidably mounted in an elongate bore 30, defined in housing 21, and has a plurality of additional ports 31 defined therein communicating with ports 26 for purposes hereinafter explained.
  • Poppet valve 28 is standard and comprises a valve member 32 reciprocally mounted in a bore 33, defined in spool 27, and a compression coil spring 34 for biasing the valve member towards a closed position on a seat 35, defined on the spoolo
  • check valve 20 A unique feature of check valve 20 is the provision of means 36 for communicating equalized fluid pressure from cylinder 11 to either end of spool 27 when control means 16 is not actuated, isolating fluid pressure in the head end of cylinder 11. This functions to reduce leakage around the spool and, in conjunction with hereinafter described check valves 60 and 61, to minimize any leakage from the circuit.
  • the check valves 20, 60, and 61 may be considered to comprise the "check valve means" for isolating fluid pressure in cylinder 11 upon selective-actuation of control means 16.
  • Means 36 includes an orifice 37 which communicates passage 25 with an elongate passage 38 to, in turn, communicate equalized fluid pressure from the head end of cylinder 11 to chambers 39 and 40, defined at opposite ends of spool 27. Passage 38 communicates with chamber 39 through a passage 41, whereas passage 38 communicates with chamber 40 through a resolver valve 42.
  • Means 36 may be considered to further include a pair of branch passages 43 and 44 which are interconnected between outlet passage 25 and chambers 45 and 46, respectively. Pressurized fluid is communicated to chamber 45 from passage 25 via a ball resolver 47' of a control or resolving means 47. As described more fully hereinafter, resolving means 47 further includes a passage 48 interconnecting passages 43 and 43' and having a restricted orifice 49 therein for intercommunicating check valves 20 and 20' via a balance line 50.
  • Pressurized fluid in chambers 45 and 46 will act respectively on the ends of pistons 51 and 52 which have the same cross-sectional area, with a compression coil spring 53 also acting on the left end of spool 27 in Figure 2 to supplement the force of piston 51.
  • Excessive pressures in passage 25 will be relieved by a standard relief valve 54, via a connecting passage 55 and a drain line 56.
  • a pilot line 57 will communicate a pressurized pilot signal to chamber 40 past resolver valve 42, to move spool 27 leftwardly against the opposed biasing force of spring 53.
  • metering holes 31 will intercommi- cate passages 25 and 24 to modulate venting of pressurized fluid in the head end of cylinder 11 to tank 15.
  • Figure 1 illustrates control circuit 10 in a neutral condition of operation whereby pilot control valve 17 and main control valve 19 are maintained in their intermediate positions, isolating pump 14 from cylinders 11 and 12. Raising of the load is effected by shifting pilot control valve 17 rightwardly in Figure 1 to communicate pilot fluid pressure from pump 18 to main control valve 19, via a line 58.
  • main control valve 19 will be shifted rightwardly to communicate fluid pressure from pump 14 to a line 79 which will open check valve 60 to, in turn, communicate such fluid pressure past a vented make-up or check valve 61 and to line 23.
  • a return line 62 which is common to the rod ends of cylinders 11 and 12 will communicate with tank 15 via a line 63.
  • a branch line 64 ( Figure 1) is interconnected between line 23 and load check valve 20' to pressurize the head end of cylinder 12 in a like manner, via a line 65.
  • pilot control valve 17 back to its intermediate or neutral position illustrated in Figure 1 to isolate the head ends of the cylinders. Since the same pressure is communicated to either end of valve spool 27 from the cylinder 11 via passage 25, orifice 37, and passage 38 which communicates with chambers 39 and 40, check valve 20 will be maintained in a "low leak" condition of operation. In particular, once the fluid pressure in passage 25 and in chambers 39 and 40 is equalized, no differential pressure will occur therebetween whereby the fluid will remain substantially static. It should be further noted that a pilot-operated vent valve 66 and valves 60 and 61 remain closed to prevent any fluid leakage out of lines 23 and 71.
  • pilot control valve 17 leftwardly in Figure 1 to connect pilot pressure from pump 18 to main control valve 19 via a line 67.
  • Main control valve 19 will be shifted leftwardly to communicate working pressure from pump 14 to line 62, and to connect drain line 63 with valve 60.
  • Pilot line 67 connects with a branch pilot line 68 which, in turn, communicates pilot pressure to line 59 and to a line 69 connected to vent valve 66, having a vent line 70.
  • Pilot pressure in line 69 will shift vent valve 66 leftwardly in Figure 1 to vent line 71, connected to passage 38 ( Figure 2) by a branch line 72.
  • a working chamber 73 of check valve 61 will be exhausted of fluid pressure with a poppet 74 of the check valve being solely held against a seat 75 by a relatively light spring 76.
  • line 72 will vent chamber 39, via passages 41 and 38, whereas resolver valve 42 will be shifted leftwardly in Figure 2 to close passage 38 thereat due to pilot pressure communicated thereto via pilot line 59 and passage 57.
  • Pilot pressure is thus communicated to chamber 40 to shift spool 27 leftwardly against the opposed modulating biasing force of spring 53 to place line 22 in communication with line 23 to gradually vent the head end of cylinder 11.
  • metering ports 31 will gradually communicate with passage 25 whereby pressurized fluid from the head end of cylinder 11 is permitted to communicate with passage 24 and, thus, line 23 via ports 26.
  • the various passages and ports just described may be suitably calibrated and arranged to provide the desired fluid flow patterns whereby a load may be permitted to descent at a predetermined rate.
  • check valve 61 can further function as a make-up valve if the pressure in line 23 drops below that in the tank, to add fluid to the cylinder to prevent cavitation in the cylinder, for example if the load tends to extend the cylinder itself.
  • a suitable step is also formed on check valve 60 to permit this valve to open also to connect line 23 with another drain line 79 during retraction of cylinder 11.
  • check valve 20' will function simultaneously with valve 20 and in a like manner, due to the common connections illustrated in Figure 1.
  • fluid circuit 10 Another feature of fluid circuit 10 is the interaction between check valves 20 and 20' by the resolver means 47 employed therein.
  • balance line 50 Upon extension of cylinders 11 and 12, balance line 50 will ensure that the fluid pressure in the head ends of the cylinders is equalized.
  • line 50 will communicate with the head end of cylinder 11, for example, via orifice 49; passages 48, 43, and 25; and line 22.
  • the ball of resolver valve 47' will have moved leftwardly to block passage 43 thereat, but to permit communication of the latter passage with chamber 45.
  • resolver valve 47' Upon retraction of cylinders 11 and 12, should the fluid pressure in the head end of cylinder 12 exceed the fluid pressure in the head end of cylinder 11, resolver valve 47' will shift rightwardly in Figure 2 to feed a pressure signal to chamber 45 via line 50. Fluid pressure in chamber 45 will move piston 51 and spool 27 rightwardly to at least partially close off metering holes 31 until the fluid pressure in the head ends of the cylinders is equalized. Also, some fluid pressure will be communicated to the head end of cylinder 11 via orifice 49 and passages 48 and 43.
  • check valves 60 and 61 an alternative embodiment of check valves 60 and 61 is shown.
  • conduit 23 communicates with valve 19 through check valve 60.
  • Flow from line 79 is in communication with tank 15 through check valve 61.
  • Check valves 60 and 61 open to communicate fluid flow between lines 23 and 79, 78 and 79 in response to vent 71 being vented too tank 15 through vent valve 66.

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Fluid-Pressure Circuits (AREA)
EP81301185A 1980-03-24 1981-03-19 Circuit hydraulique avec clapet anti-retour Withdrawn EP0036761A3 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
PCT/US1980/000321 WO1981002768A1 (fr) 1980-03-24 1980-03-24 Circuit de fluide avec soupape by-pass et de retenue de charge de fuite zero
WOPCT/US80/00321 1980-03-24

Publications (2)

Publication Number Publication Date
EP0036761A2 true EP0036761A2 (fr) 1981-09-30
EP0036761A3 EP0036761A3 (fr) 1982-04-07

Family

ID=22154257

Family Applications (1)

Application Number Title Priority Date Filing Date
EP81301185A Withdrawn EP0036761A3 (fr) 1980-03-24 1981-03-19 Circuit hydraulique avec clapet anti-retour

Country Status (3)

Country Link
EP (1) EP0036761A3 (fr)
JP (1) JPS57500347A (fr)
WO (1) WO1981002768A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20220220945A1 (en) * 2017-10-13 2022-07-14 Enerpac Tool Group Corp. Remote conduit de-coupling device

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1196927B (de) * 1962-05-18 1965-07-15 Beteiligungs & Patentverw Gmbh Einrichtung zur uebereinstimmenden Lauf-begrenzung der bewegten Teile von hydrostatischen Antrieben
US3500721A (en) * 1968-07-23 1970-03-17 Eaton Yale & Towne Hydraulic control for two hydraulic motors
DE2036547A1 (de) * 1970-07-23 1972-01-27 Krupp Gmbh Brems- und Sperr-Einrichtung für ein hydrostatisches Triebwerk
US3943825A (en) * 1972-04-17 1976-03-16 Caterpillar Tractor Co. Hydraulic control system for load supporting hydraulic motors
DE2554579A1 (de) * 1975-12-04 1977-06-08 Kodak Ag Lichtschutzvorrichtung fuer eine sofortbildkamera
US4102250A (en) * 1976-08-16 1978-07-25 Caterpillar Tractor Co. Load check and bypass valve

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3800670A (en) * 1969-10-21 1974-04-02 Caterpillar Tractor Co High pressure implement hydraulic circuit
JPS5226311B2 (fr) * 1973-08-24 1977-07-13
US4187877A (en) * 1975-01-13 1980-02-12 Commercial Shearing Inc. Compensated work port fluid valves
US4204459A (en) * 1978-04-19 1980-05-27 Caterpillar Tractor Co. Combination check and flow control valve for hydraulic systems

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1196927B (de) * 1962-05-18 1965-07-15 Beteiligungs & Patentverw Gmbh Einrichtung zur uebereinstimmenden Lauf-begrenzung der bewegten Teile von hydrostatischen Antrieben
US3500721A (en) * 1968-07-23 1970-03-17 Eaton Yale & Towne Hydraulic control for two hydraulic motors
DE2036547A1 (de) * 1970-07-23 1972-01-27 Krupp Gmbh Brems- und Sperr-Einrichtung für ein hydrostatisches Triebwerk
US3943825A (en) * 1972-04-17 1976-03-16 Caterpillar Tractor Co. Hydraulic control system for load supporting hydraulic motors
DE2554579A1 (de) * 1975-12-04 1977-06-08 Kodak Ag Lichtschutzvorrichtung fuer eine sofortbildkamera
US4102250A (en) * 1976-08-16 1978-07-25 Caterpillar Tractor Co. Load check and bypass valve

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20220220945A1 (en) * 2017-10-13 2022-07-14 Enerpac Tool Group Corp. Remote conduit de-coupling device
US11781529B2 (en) 2017-10-13 2023-10-10 Enerpac Tool Group Corp. Remote conduit de-coupling device

Also Published As

Publication number Publication date
EP0036761A3 (fr) 1982-04-07
JPS57500347A (fr) 1982-02-25
WO1981002768A1 (fr) 1981-10-01

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

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Effective date: 19810327

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Inventor name: BIANCHETTA, DONALD L.