US3685540A - Fluid flow controlling device for reversible fluid motors - Google Patents

Fluid flow controlling device for reversible fluid motors Download PDF

Info

Publication number
US3685540A
US3685540A US3685540DA US3685540A US 3685540 A US3685540 A US 3685540A US 3685540D A US3685540D A US 3685540DA US 3685540 A US3685540 A US 3685540A
Authority
US
United States
Prior art keywords
fluid
service
valve element
valve
flow
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.)
Expired - Lifetime
Application number
Other languages
English (en)
Inventor
Raud A Wilke
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.)
Husco International Inc
Original Assignee
Koehring 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 Koehring Co filed Critical Koehring Co
Application granted granted Critical
Publication of US3685540A publication Critical patent/US3685540A/en
Assigned to KOEHRING COMPANY, A CORP. OF DE reassignment KOEHRING COMPANY, A CORP. OF DE ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: KOEHRING COMPANY A WI CORP.
Assigned to NORWEST BANK ST. PAUL, NATIONAL ASSOCIATION reassignment NORWEST BANK ST. PAUL, NATIONAL ASSOCIATION SECURITY INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: HUSCO INTERNATIONAL, INC. A CORP OF DE.
Assigned to HUSCO INTERNATIONAL, INC., W239 N218 PEWAUKEE ROAD, WAUKESHA, WISCONSIN, A CORP OF DELAWARE reassignment HUSCO INTERNATIONAL, INC., W239 N218 PEWAUKEE ROAD, WAUKESHA, WISCONSIN, A CORP OF DELAWARE ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: KOEHRING COMPANY, A CORP OF DE.
Assigned to NORTHWESTERN NATIONAL LIFE INSURANCE COMPANY, C/O WASHINGTON SQUARE FINANCIAL reassignment NORTHWESTERN NATIONAL LIFE INSURANCE COMPANY, C/O WASHINGTON SQUARE FINANCIAL MORTGAGE (SEE DOCUMENT FOR DETAILS). Assignors: HUSCO INTERNATIONAL, INC.
Assigned to NORWEST BANK MINNESOTA, NATIONAL ASSOCIATION reassignment NORWEST BANK MINNESOTA, NATIONAL ASSOCIATION SECURITY INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: HUSCO INTERNATIONAL, INC.
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • 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
    • F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
    • F16K11/00—Multiple-way valves, e.g. mixing valves; Pipe fittings incorporating such valves
    • F16K11/02—Multiple-way valves, e.g. mixing valves; Pipe fittings incorporating such valves with all movable sealing faces moving as one unit
    • F16K11/06—Multiple-way valves, e.g. mixing valves; Pipe fittings incorporating such valves with all movable sealing faces moving as one unit comprising only sliding valves, i.e. sliding closure elements
    • F16K11/065—Multiple-way valves, e.g. mixing valves; Pipe fittings incorporating such valves with all movable sealing faces moving as one unit comprising only sliding valves, i.e. sliding closure elements with linearly sliding closure members
    • F16K11/07—Multiple-way valves, e.g. mixing valves; Pipe fittings incorporating such valves with all movable sealing faces moving as one unit comprising only sliding valves, i.e. sliding closure elements with linearly sliding closure members with cylindrical slides
    • 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
    • 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
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00—Fluid handling
    • Y10T137/8593—Systems
    • Y10T137/87169—Supply and exhaust
    • Y10T137/87177—With bypass
    • Y10T137/87185—Controlled by supply or exhaust valve

Definitions

  • a fluid flow controlling device having independent service passages extending therethrough which provide portions of the service lines leading to a reversible fluid motor from the control valve governing the direction of motor operation.
  • a single fluid pressure actuatable valve element in the device functions as a counterbalance valve and acts to restrict return flow of motor exhaust fluid through either service'passage in consequence of decrease in the pressure of source fluid flowing through the other service passage to the motor.
  • .Check valves can be located in portions of the service passages so as to be bypassed by return flow of motor exhaust fluid.
  • FLUID FLOW CONTROLLING DEVICE FOR REVERSIBLE FLUID MOTORS BACKGROUND OF THE INVENTION This invention relates to flow control instrumentalities for use in fluid pressure operated systems incorporating a reversible fluid motor such as a double acting hydraulic cylinder; and it has more particular reference to improvements in flow correlating or counl shovels. All of these are characterized by a heavy boom structure that constitutes a load which is movable up and down about a horizontal axis. The boom of a power shovel, however, must also be movable from side to side about a vertical axis.
  • the boom is raised, for example, as a consequence of flow of pump fluid into one end of its lift cylinder, and it is lowered as a result of flow of pump fluid into the opposite end of said cylinder.
  • fluid expelled from the contracting end of the cylinder is returned to the reservoir of the system through the directional control valve.
  • the boom structure of earth handling apparatus such as mentioned above is easily started downwardly when pump fluid is directed into the load lowering" end of its lift cylinder, and its descent is accelerated by the force of gravity. As a result, the boom tends to fall at an uncontrolled rate and to thus effect expulsion of pressure fluid from the contracting end of its cylinder faster than the pump can supply fluid to its expanding end.
  • the boom swing cylinder of a power shovel which moves the boom about a vertical axis, also tends at times to be driven in one direction or the other by the load, especially when the shovel is in operation on an inclined surface.
  • the dipstick of a backhoe is an example of an overcenter load which is movable about a horizontal axis, and which can be hydraulically driven toward and beyond a vertically pendant position from either side of said pendant position. In that case also, both ends of the dipstick cylinder can have voids drawn therein, and the motion of the stick is difficult to control, especially if the bucket on its outer end is loaded.
  • This invention has as its purpose the provision of a flow coordinating or counterbalance valve mechanism for use with reversible fluid motors such as double acting hydraulic cylinders and their control valves, wherein the likelihood of malfunctioning is much less than in any such mechanism proposed heretofore.
  • Another object of the invention resides in the provision of a flow correlating valve mechanism embodying a single counterbalancing valve element and service passages so arranged as to enable load drop check valves to be incorporated therein without interfering with return flow of fluid through said passages.
  • FIG. 1 is a diagrammatic view illustrating a fluid pressure operated system including a double acting hydraulic cylinder, a control valve for governing the direction of motor operation, and a fluid flow controlling valve of this invention connected between the control valve and cylinder;
  • FIG. 2 is a longitudinal section through the flow controlling valve seen in FIG. 1, showing the same in a nonoperating or hold position;
  • FIG. 3 is a sectional view similar to FIG. 2 but showing the flow restricting action of the device
  • FIG. 4 is a diagrammatic view of a fluid pressure operated system like that seen in FIG. 1, but illustrating a modified form of flow controlling device;
  • FIGS. 5 and 6 are sectional views of the flow controlling device seen in FIG. 4, showing different operating positions thereof.
  • the numeral 5 designates a reversible fluid motor here shown as a double acting hydraulic cylinder.
  • the cylinder is shown in a vertical position merely by way of example, and it has a piston 6 fixed to r the inner end of a piston rod 7, that projects from the bottom of the cylinder'to be operatively connected withaload 8.
  • thJdirection in which the piston 6 is driven can be governed by a substantially conventional control or main valve 10.
  • the control valve which has been diagrammatically illustrated, is of the manually operated type having a valve spool movable from a neutral position shown to each of a pair of operating normally connects the exhaust port l6-aswell as the cylinderports of the control valve 10 with the reservoir 12', and a pair of service lines S1 and S2 connect the cylinder ports of the control valve with motor ports 17 and 18 in the top and bottom ends, respectively, of the cylinder 5. 5
  • the flow controlling or counterbalance valve 19 of this invention can be consideredas a throttling device that can meter the rate at which fluid is expelled from the cylinder 5 under the influence of the load thereon.
  • the counterbalance valve is connected in the'service lines 51-82 at a location between the cylinder 5 and the main valve 10. It comprises a body 20 having a bore 21 extending therethrough to receive an axially slidable fluid pressure actuatable spool type valve element 22.
  • the opposite end portions 23 and 24 of the spool are reduced in diameter and they project into the interiors of cup-like covers 25 which not only serve to close the opposite ends of the bore 21 but to also house the spool centering springs 26.
  • Thesprings encircle the opposite end portions 23 and 24 of the valve spool, and they bear against lands 27 and 28 thereon to normally hold the spool in the neutral position seen in FIG. 2.
  • a third branch 43 of the service passage provides a cylinder" port which is com municated with the motor port 17 of cylinder 5 by that section of the supply line S1 which extends downstream from the counterbalance valve.
  • This third branch of service passage 38 leads from the bore 21 at. a zone situated between the junctions of the bore and the first two branches 40-41 of the service passage, and it is communicable with the intermediate branch 41 through the bore 21 under the control of the counterbalance valve spool therein.
  • the inlet branch'44 is communicable with the intermediate branch 45 through a check valve 46; and the intermediate branch is also communicable with the outlet branch or second cylinder port -47 through the bore 21 under the control of the valve spool 22.
  • each of the hydraulic actuators comprises a piston provided by one end portion of the spool, and a pressure chamber or cylinder provided by the interior of the adjacent spring cover 25, in which the pistons operate.
  • Axial passages 52 in the end portions 23-24 of the valve spool open outwardly into the interiors of the cylinders of actuators 50 and 51 and communicate the latter with the inlet branches 40 and 44 of service passages 38 and 39, respectively, through radial holes 53 in the spool at each of its grooves 29 and 32.
  • the holes 53 and passages 52 in the end portions of the spool provide for pilot flow of pump fluid under pressure entering either service passage to the adjacent hydraulic actuator for actuation of the valve spool out of its neutral position to one or the other a pair of working positions at opposite sides of neutral.
  • the main control valve is actuated to communicate service passage 38 with the pump and to communicate service passage 39 with the reservoir, some of the pump fluid entering the inlet branch 40 of service passage 38 will flow to the actuator 50 and exert force on the lefthand end of the spool to shift it to the right of neutral, to its operating position seen in FIG. 3.
  • fluid displaced from the cylinder of, actuator 51 by the valve spool will be vented to the inlet branch 44 of service passage 39 through the axial passage 52 and hole 53 in the right-hand end portion of the spool.
  • main control valve 10 If the main control valve 10 is actuated to reverse the direction of flow to the work cylinder, pump fluid flows to inlet branch 44 of service passage 39, and a pilot flow of such pump fluid will enter the cylinder of actuator 51 to effect actuation of spool 22 to a working position to the left of neutral. Fluid then displaced from the cylinder of actuator 50 is returned to the reservoir via the inlet branch 40 of service passage 38 and the passages in the main control valve 10.
  • the main control valve 10 acts in the nature of a pilot valve for thehydraulic actuators 50 and 51 for the counterbalance valve spool 22, since it controls the supply of .pilot fluid to the cylinder of either actuator while simultaneously venting the cylinder of the other actuator.
  • control valve 10 Upon actuation of control valve 10 to start the load downwardly, pressure fluid flows through service line S1 to the inlet branch 40 of service passage 38 and to the interior of the cylinder for actuator 50 to effect movement of the valve spool to the right, to a working position such as seen in FIG. 3.
  • supply fluid entering the inlet branch 40 can unseat the check valve 42 and flow into the intermediate branch 41 of service passage 38. It can then flow to the cylinder port 43 through the bore 21 and groove in spool 22. Exhaust fluid from the cylinder 5 flows directly from cylinder port 47 to inlet branch 44 via the bore 21 and spool groove 31.
  • the land 33 will have moved toward a position restricting the flow of supply fluid to cylinder port 43 from the intermediate branch 41 of the service passage 38. This has the effect of raising the pressure in the inlet branch 40 of service passage 38, and in the left hand actuator 50 for the valve spool 22.
  • valve spool Return motion of the valve spool will cease, of course, when the fluid pressure force imposed upon the left hand end of the valve spool by actuator 50 balances the return force of the spring 26 acting on the right hand end of the spool.
  • the spool'22 can float back and forth in its right hand working position, in accordance with changes in pressure in the expanding end of the cylinder as detected in the left hand hydraulic actuator 50 for the valve spool, to meter the exhaust of fluid vfrom the cylinder 5 to whatever extent is necessary for controlled descent of the load and to minimize void formation in the upper end of the cylinder.
  • the counterbalance spool will be returned to neutral promptly in response to actuation of the main control spool to its neutral position. Assurance of such response of the counterbalance spoolis had by reason of the fact that with the main valve spool in neutral, the inlet branches 40 and 44 of the service passages in the counterbalance valve are vented to the reservoir. Otherwise, fluid might become trapped in the inlet branches 40, 44 of the service lines, in which event such trapped fluid could interfere with proper return of the counterbalance spool to its neutral or hold position.
  • the hydraulic motor 5 should comprise the swing cylinder of a backhoe, by which its boom is swung back and forth about a vertical axis, or even the crowd cylinder of the backhoe, it can at times be driven in either direction by the load operatively connected thereto.
  • the counterbalance valve of this invention
  • the throttling or counterbalance valve of this invention is flow responsive, since its valve spool will never close off flow from the motor as long as pump fluid is flowing to one or the other of its service passages.
  • FIG. 4 illustrates a simpler version 64 thereof which can be used to the same advantage when control over the exhaust flow of fluid from one endonly of the motor is needed, as when it merely drives its load up. and down.
  • a double acting lift cylinder 60 has been shown as such a motor; and its direction of operation is governed by a control valve 61 1 which difiers from the valve 10 hereinbefore described in that it has a hold-in-neutral spool and a conventional load drop check valve arrangement.
  • the counterbalance valve device 64 comprises .a
  • Plugs 68 and 69 close the opposite. ends of the bore, and the plug 68 provides a'stop which defines the left hand limit of motion of the spooL' i It is at all timesurged to that position under force im-;v
  • the service lines S1 and S2 in this case, alsolead to the cylinder 60 through service passages 71 and 72 in the body of the counterbalance valve 64.
  • 'lhese service lines can be said to comprise upstream branches 73 and 74', respectively, which extend between the control valve 61 and the counterbalance valve,- and downstream branches 75 and 76, respectively, which extend between the counterbalance valve and the work cylinder 60. 1
  • the inlet-branches 77 and 78 of service passages 71 and 72 respectively, open .to the bore 66 ataxially spaced zones located a short distanceinwardly of the plugs 68-69 and a greater distance from one another.
  • the outlet ports 79 and 80 of service passages 71 and 72 respectively, opento the bore at-locations between the zones at which the inlet ports join with the bore, and spaced from one another and from thosezones.
  • the left-hand end of the counterbalance spool 67 projects into a hydraulic actuator chamber 82 which is communicated with the inlet port 77 through a substantially small diameter passageway 83(Hence, whenever 7 pump outputv fluid is directed into the inlet branch 77 from the main valve 61, the pressure of such fluid will be manifested in the chamber 82, and hydraulic force will thus be imposed upon the left-hand end of the, counterbalance spool to move it to an operating posi-v tion.
  • the spool .67 has two circumferential grooves 84 and 85 therein, which grooves define axially spaced lands 86 and 87.
  • the groove 84 normally registers with the inlet branch 77 of service passage 71
  • the groove 85 normally registers with the outlet port 80 of service passage 72.
  • the land 86 normally blocks communication through the bore 66 betweenthe inlet branch 77 and outlet port 79 of service passage 71; while the land 87 similarly normally blocks communication through the bore between the inlet branch 78 and outlet port 80 of service passage 72.
  • a metering notch (or notches) 89 is formed in that face of the land 86 which is defined by the groove 84; and a similar notch (or notches) 90 is formed in that face of the land 87 which is defined by the groove 85 It will thus be apparent that when the main valve spool is shifted to the right of its position shown, it will closing the right hand end of the direct pump fluid to the inlet branch 77 of .service passage 71 of the counterbalance valve 64.
  • the counterbalance spool 67 will seek a stable metering position somewhere between its left hand'limit of motion and a full flow operating position, depending upon the pressure in the upper end of the work cylinder, and at which position the spring return force on the spool will be in balance with the hydraulic actuating force thereon.
  • the spool of course, will be returned to its normal position, at its left hand limit of motion, under the influence of the return spring 70 as soon as the spool of the main control valve is returned to neutral.
  • the flow of pressure fluid to and from the work cylinder 60 will bypass the counterbalance valve device 64 when the main valve spool is actuated to the left, to a load raising position.
  • branches 74 and 76 of supply line S2 are connected with one another by .a bypass duct 92 containing a check valve 93.
  • the check valve opens to allow pump fluid flowing through branch 74 to flow directly to branch 76 in bypass relation to the counterbalance valve 64.
  • the branches 73 and 75 of supply line S2 are connected by a bypass duct 94 containing a check valve 95.
  • Check valve 95 opens in the direction to allow return fluid from the upper end of the cylinder to flow to the supply line branch 73 in bypass relation to the counterbalance valve.
  • a control device for regulating flow of fluid in the service lines connecting the opposite sides of a reversible fluid motor with the control valve governing the direction of motor operation characterized by the following:
  • valve element in the bore movable between a working position providing for such flow through the service passages and a hold. position blocking said flow therethrough;
  • a hydraulic actuator activated by pressure of source fluidin said first service passage for shifting the valve element toward its said working position a distance determined by the pressure of said activating fluid, whereby decrease in the pressure of the latter causes return motion of the valve element under the force of said spring means;
  • control device of claim 1 further characterized by: l 1
  • said hydraulic actuator comprising a cylinder
  • control device of claim 3 further characterized by:
  • said first service passage comprising inlet and outlet branches communicating with the bore at axially spaced locations;
  • control valve of claim 1 further characterized A. said first service passage comprising communicating inlet and inten'nediate branches which open to the bore at axially spaced first and second zones, and an outlet branch which opens to the bore at a location between said zones;
  • control valve of claim 1 further characterized A. said first service passage comprising communicating inlet and intermediate branches which open to the bore at axially spaced first and second zones, and an outletbranch which opens to the bore at a location between said first and second zones;
  • valve element having means thereon to effect communication of said outlet branch with the inlet branch via the intermediate branch in said working position of the .valve element and to effect communication of said outlet branch with the inlet branch in bypass relation to the intermediate branch in another working position of the valve element.
  • control device of claim 1 further characterized by:
  • control device of claim 6 further characterized by:
  • each of said service passages comprising l. a passageway having a portion extending lon- 12 gitudinally along-the bore at one side thereof to have its ends communicate with the. bore at axially spaced first and second zones,
  • a control valve for governing operation of a reversible fluid motor characterized by the following:
  • a hydraulic actuator activated vby pressure of fluid from said source in.the upstream portion of said one service line for shifting the valve element out of its neutral position toward said operating position thereof a distance determined by the pressure of said activating fluid, whereby decrease in the pressure of the latter causes return motion of the valve element toward neutral under the force of i said spring means;
  • throttle means on the valve element operable upon such return motion thereof to increasingly restrict flow through said other service line.

Landscapes

  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Fluid-Pressure Circuits (AREA)
US3685540D 1971-01-18 1971-01-18 Fluid flow controlling device for reversible fluid motors Expired - Lifetime US3685540A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US10701971A 1971-01-18 1971-01-18

Publications (1)

Publication Number Publication Date
US3685540A true US3685540A (en) 1972-08-22

Family

ID=22314432

Family Applications (1)

Application Number Title Priority Date Filing Date
US3685540D Expired - Lifetime US3685540A (en) 1971-01-18 1971-01-18 Fluid flow controlling device for reversible fluid motors

Country Status (6)

Country Link
US (1) US3685540A (enExample)
JP (1) JPS5767103U (enExample)
AU (1) AU454352B2 (enExample)
DE (1) DE2200568A1 (enExample)
FR (1) FR2122408B1 (enExample)
GB (1) GB1366669A (enExample)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5579676A (en) * 1995-07-13 1996-12-03 Husco International, Inc. Hydraulic valve to maintain control in fluid-loss condition
US5664417A (en) * 1996-03-20 1997-09-09 Husco International, Inc. Control valve for prime mover speed control in hydraulic systems
US5791142A (en) * 1997-03-27 1998-08-11 Husco International, Inc. Hydraulic control valve system with split pressure compensator

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1452609A (en) * 1973-05-15 1976-10-13 Sperry Rand Ltd Hydraulic systems
US4353289A (en) * 1980-05-29 1982-10-12 Sperry Corporation Power transmission
DE3245288A1 (de) * 1982-12-03 1984-06-14 O & K Orenstein & Koppel Ag, 1000 Berlin Verfahren zur einsparung von energie beim stellen eines ausruestungszylinders an einem hydraulikbagger durch eine hydraulikschaltung
DE3443692A1 (de) * 1984-11-30 1986-06-12 Wessel-Hydraulik Günther Wessel, 2940 Wilhelmshaven In zwei richtungen wirkendes bremsventil mit einem ventilschieber
GB2216632B (en) * 1988-03-17 1992-09-30 Trans Nordic Hydraulics Limite Spool valves
DE102016007754A1 (de) 2016-06-24 2018-01-11 Hydac System Gmbh Ventilvorrichtung zum Beeinflussen eines Medienstromes
CN111520368B (zh) * 2020-04-21 2022-03-04 中联重科股份有限公司 负载敏感系统的流量分配控制方法

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3272085A (en) * 1963-11-19 1966-09-13 Parker Hannifin Corp Fluid system and valve assembly therefor
US3513877A (en) * 1968-03-27 1970-05-26 Koehring Co Control valve with counter-balancing and direction controlling valve element
US3568718A (en) * 1969-02-17 1971-03-09 Koehring Co Pilot operated control valve

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3272085A (en) * 1963-11-19 1966-09-13 Parker Hannifin Corp Fluid system and valve assembly therefor
US3513877A (en) * 1968-03-27 1970-05-26 Koehring Co Control valve with counter-balancing and direction controlling valve element
US3568718A (en) * 1969-02-17 1971-03-09 Koehring Co Pilot operated control valve

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5579676A (en) * 1995-07-13 1996-12-03 Husco International, Inc. Hydraulic valve to maintain control in fluid-loss condition
WO1997003293A1 (en) * 1995-07-13 1997-01-30 Husco International, Inc. Hydraulic valve to maintain control in fluid-loss condition
US5664417A (en) * 1996-03-20 1997-09-09 Husco International, Inc. Control valve for prime mover speed control in hydraulic systems
US5791142A (en) * 1997-03-27 1998-08-11 Husco International, Inc. Hydraulic control valve system with split pressure compensator

Also Published As

Publication number Publication date
JPS5767103U (enExample) 1982-04-22
GB1366669A (en) 1974-09-11
AU3798772A (en) 1973-07-19
DE2200568A1 (de) 1972-08-03
FR2122408A1 (enExample) 1972-09-01
FR2122408B1 (enExample) 1976-12-03
AU454352B2 (en) 1974-10-31

Similar Documents

Publication Publication Date Title
US4480527A (en) Power transmission
US4201052A (en) Power transmission
US3563137A (en) Hydraulic self-leveling control for boom and bucket
US3267961A (en) Valve
EP0066151B1 (en) Hydraulic control system comprising a pilot operated check valve
US2489435A (en) Power transmission
US3049101A (en) Hydraulic mechanism
US4153075A (en) Load responsive control valve
US3934742A (en) Valve mechanism for automatic control of a number of fluid motors
US2980136A (en) Hydraulic flow control system and valve with anti-cavitation feature
US3840049A (en) Compact fluid motor control system with float position
US3685540A (en) Fluid flow controlling device for reversible fluid motors
GB1404562A (en) Hydraulic systems
US3357451A (en) Speed and directional control valve for double-acting lift cylinder
US3033168A (en) Hydraulic mechanism
US3604313A (en) Hydraulic power circuit with rapid lowering provisions
US3216448A (en) Spool valve assembly
US4611528A (en) Power transmission
US3477347A (en) Hydraulic power circuit affording parallel regeneration paths
US2420052A (en) Control apparatus for hydraulic machines
US3213874A (en) Pressure responsive flow control valve for directional control valve
US3746040A (en) Directional control valve
US2954052A (en) Pressure fluid control system and valve
JPH07101042B2 (ja) 油圧制御装置
US2722102A (en) Hydraulic system and pressure relief valve therefor

Legal Events

Date Code Title Description
AS Assignment

Owner name: KOEHRING COMPANY 200 EXECUTIVE DRIVE, BROOFIELD, W

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:KOEHRING COMPANY A WI CORP.;REEL/FRAME:003995/0514

Effective date: 19810505

AS Assignment

Owner name: NORWEST BANK ST. PAUL, NATIONAL ASSOCIATION

Free format text: SECURITY INTEREST;ASSIGNOR:HUSCO INTERNATIONAL, INC. A CORP OF DE.;REEL/FRAME:004504/0783

Effective date: 19851206

AS Assignment

Owner name: HUSCO INTERNATIONAL, INC., W239 N218 PEWAUKEE ROAD

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:KOEHRING COMPANY, A CORP OF DE.;REEL/FRAME:004509/0989

Effective date: 19851206

Owner name: NORTHWESTERN NATIONAL LIFE INSURANCE COMPANY, C/O

Free format text: MORTGAGE;ASSIGNOR:HUSCO INTERNATIONAL, INC.;REEL/FRAME:004528/0361

Effective date: 19851205

AS Assignment

Owner name: NORWEST BANK MINNESOTA, NATIONAL ASSOCIATION

Free format text: SECURITY INTEREST;ASSIGNOR:HUSCO INTERNATIONAL, INC.;REEL/FRAME:005080/0850

Effective date: 19890301