US3575212A - Leakage control for closed center valves - Google Patents

Leakage control for closed center valves Download PDF

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Publication number
US3575212A
US3575212A US3575212DA US3575212A US 3575212 A US3575212 A US 3575212A US 3575212D A US3575212D A US 3575212DA US 3575212 A US3575212 A US 3575212A
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Prior art keywords
passage
service
bore
inlet
valve
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English (en)
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Raud A Wilke
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Husco International Inc
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Koehring Co
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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.
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Assigned to NORWEST BANK MINNESOTA, NATIONAL ASSOCIATION reassignment NORWEST BANK MINNESOTA, NATIONAL ASSOCIATION SECURITY INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: HUSCO INTERNATIONAL, INC.
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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
    • F15B13/02—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors
    • F15B13/04—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor
    • 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
    • F16K27/00—Construction of housing; Use of materials therefor
    • F16K27/04—Construction of housing; Use of materials therefor of sliding valves
    • F16K27/041—Construction of housing; Use of materials therefor of sliding valves cylindrical slide valves
    • F16K27/042—Hydraulic fluid leak traps
    • 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
    • Y10T137/86493—Multi-way valve unit
    • Y10T137/86574—Supply and exhaust
    • Y10T137/8667—Reciprocating valve
    • Y10T137/86694—Piston valve
    • Y10T137/8671—With annular passage [e.g., spool]

Definitions

  • VALVES ABSTRACT A hydraulic control valve wherein pressure fluid which leaks along the exterior of the movable valve element 137/625.69 from a high pressure inlet zone is intercepted before it reaches Fl6lk 11/07 any service passage of the valve and conducted along a path externally of the valve element to a low pressure return passage in the valve body.
  • This invention relates to hydraulic control and has more particular reference to control valves of the closed center, hold-in-neutral type.
  • valve element of a hold-in-neutral control valve prevents operation of a fluid motor governed thereby in the neutral position of the valve element in its chamber, at which it blocks flow of pressure fluid to and from the motor. Because there is no provision for pump output fluid entering the inlet chamber of a closed center control valve such as herein concerned to be returned to a reservoir through an open center passage in the valve body, fluid in the inlet chamber of the valve remains at high pressure all during the time the pump is in operation and the valve element is in neutral. Thus pressure ,fluid at high pressure is immediately available for operation of the motor upon shifting of the valve element to one of its operating positions.
  • H6. 1 is a sectional view of a closed center control valve embodying this invention.
  • FIG. 2 is a sectional view of a closed center control valve similar to that seen in H6. 1, but illustrating a modified embodiment of the invention.
  • FIG. 1 illustrates a closed center hydraulic control valve having a body 5 with a bore 6 therein defining a valve chamber.
  • An elongated valve element or spool 7 is closely fitted in the bore for lengthwise sliding movement therein between a neutral or hold position shown, and a pair of operating positions at opposite sides of its neutral position.
  • control valve chosen for illustration is intended to govern the operation of a double acting cylinder or other reversible fluid motor (not seen), although it will be appreciated that this invention is equally as well applicable to control valves for single acting service.
  • the body of the valve is provided with a pair of upwardly opening service passages 8 and 9 which are connectable with the opposite ends of the cylinder, and which communicate with the valve chamber or bore 6 at zones that are spaced apart a substantial distance along its axis.
  • These passages are selectively communicable with a pressure fluid source, such as a pump 10, by means of the valve spool 7, in one or the other of its operating positions.
  • the output of the pump is fed into an inlet chamber in the body of the valve, here shown by way of example as comprised of twin branches 11 and 12 which open to the bore 6 at locations spaced apart axially thereof from one another and intermediate the zones at which the service passages communicate with the bore.
  • the valve spool 7 is adapted to communicate the service passage 8 with the right-hand inlet branch 12 when the valve spool is shifted to its operating position to the right of neutral, and to communicate service passage 9 with the left-hand inlet branch 11 when the spool is shifted to its operating position to the left of neutral. In each of these operating positions, the spool is adapted to communicate the service passage not connected with the inlet chamber with an exhaust or return passage 13.
  • the valve spool 7 has five circumferential grooves therein, at axially spaced apart locations, and which, reading from left to right, are numbered l4, 15, 16, 17 and 18. In the neutral position of the spool shown, its groove 14 is in register with the junction between the bore and service passage 8, while its groove 17 is in register with the junction between the bore and service passage 9. The grooves 14 and 17 provide for communicating the service passages 8 and 9 with either the inlet chamber or the return passage 13, depending upon the direction the valve spool is shifted out of its neutral position.
  • the valve body is provided with a number of other passages through portions of which pressure fluid can flow to and from the service passages in the different operating positions of the valve spool.
  • these include the exhaust passage 13 mentioned previously, which can be considered as a low pressure bridge of U-shaped configuration, having a bight portion 20 that extends lengthwise of the bore 6 a distance therebelow, and substantially parallel opposite legs which define exhaust branches 21 and 22 that extend upwardly from the opposite ends of the bight portion and intersect the bore 6 at zones spaced outwardly along the bore from its zones of communication with the service passages 8 and 9, respectively, so as to receive return fluid from said service passages through the grooves 14 and 17 in the spool.
  • a bridge passage 24 to supply high pressure fluid to the service passages is also formed in the body.
  • the high pressure supply bridge is of inverted U-shaped providing a bight portion 25 which extends lengthwise of the bore 6, a distance thereabove, and opposite legs 26 and 27 which extend downwardly from the ends of the bight portion to the bore 6 at locations intermediate the service passages 8 and 9.
  • the leg 26 is adjacent to passage 6 and provides for supplying pressure fluid thereto through spool groove 14; while the leg 27 is adjacent to passage 9 to provide for supply of pressure fluid thereto through spool groove 17.
  • the two branches 11 and 12 of the inlet chamber open to the bore 6 at zones between those at which the high pressure bridge legs 26 and 27 communicate with the bore.
  • a short feeder passage 30 extends upwardly from the bore toward the bight portion 25 of the high pressure bridge 24.
  • This feeder passage is communicated with the high pressure bridge through a check valve 31 in a passageway 32 that joins the feeder passage 30 with the left-hand leg 26 of the bridge.
  • the check valve 31 is a so-called load holding check valve which is arranged to open only at times when pressure of fluid in feeder passage 30 exceeds the pressure of fluid in the high pressure bridge 24.
  • the feeder passage 30 opens to the bore 6 at a zone which is in register with the groove 16 in the valve spool when the spool is in its neutral position.
  • Feeder passage 1%) is communicated with the inlet branch 12 when the valve spool is shifted to its operating position to the right of neutral so that pump fluid can then flow to service passage 8 via the left-hand leg of the bridge 24.
  • passage 30 cooperates with bridge 24 to supply service passage 9 from inlet branch 11 when the valve spool is shifted to its operating position to the left of neutral.
  • outlet passage 35 in the neutral position of the valve spool.
  • the outlet passage 35 is here shown as located substantially centrally of the valve body, between the bore 6 and the bight position 20 of the low pressure bridge 13, and it is at all times communicated with the latter through a short connecting passageway 35'.
  • any high pressure fluid that leaks along the wall of the bore 6 from the inlet branch 11 in a direction toward the service passage 8 in the neutral position of the valve spool will be intercepted at the junction between the bore and the inner end of a venting passage 40 which has its outer end in communication with the outlet passage 35.
  • the inner end of the passage 40 opens to the bore 6 at a location between itsjunctions with the inlet branch 11 and the left-hand leg 26 of the high pressure bridge passage 24, and so as to be in register with the groove 15 in the valve spool in the neutral position of the latter.
  • the high pressure bridge is employed to conduct to the venting passage 40 any fluid that leaks out of the inlet branches 11 and/or 12 into the feeder passage 30.
  • High pressure leakage fluid in feeder passage 30 will be able to flow through passageway 32 and check valve 31 therein to the left-hand leg 26 of the high-pressure bridge, and from there across the spool groove 15 to the outlet passage 35 via passage 40.
  • the high-pressure bridge through which pressure fluid must flow to reach the service passages in the working positions of the valve spool, is vented in the neutral position of the spool. It thus constitutes a low pressure bridge in the neutral position of the valve spool, and it only becomes a high pressure bridge when the valve spool is moved to one or the other of its operating positions. At those times the bridge 24 is cut off from the venting passage 40 either by the spool land 36 or by the land 42 thereon defined by spool grooves 14 and 15.
  • valve spool 7 An important feature of this invention resides in the fact that the groove 18 in the valve spool 7 enables the spool to be placed in a float position when it is shifted to the left far enough to communicate the service passages 8 and 9 with one another through the low pressure bridge branches 21 and 22.
  • the closed center control valve illustrated in FIG. 2 has several features in common with that described above.
  • lt has a bore 6 with a valve spool 70 therein, but the spool has five annular grooves which, reading from left to right, are numbered 45, 46, 47, 48 and 49. These grooves define lands 50 and 51 at opposite sides of groove 45; lands 52 and 53 at opposite sides of groove 47; and lands 54 and 55 at opposite sides of groove 49.
  • the valve has an inlet chamber with but a single feeder branch 56 that opens to the bore 6 in register with the spool groove 47 in the neutral position of the spool shown, midway between the legs 26 and 27 of the high pressure bridge 24.
  • the spool lands 52 and 53 block flow of fluid into the bore 6 from the legs 26 and 27 of the high pressure bridge; while the lands 51 and 54 extend across the junctions of the service passages 8 and 9 with the bore to prevent flow of fluid therethrough to and from the service passages.
  • its body is provided with a pair of small U-shaped cores, 76 and 77, associated with the service passages 8 and 9, respectively.
  • the bight portion of the core 76 extends lengthwise of the bore 6, beneath the zone at which the service passage 8 joins with the bore but above the bight portion of the return passage 13.
  • the opposite legs 78 and 79 of core 76 extend upwardly from its bight to intersect the bore 6 at opposite sides of the service passage 8.
  • the left-hand leg is positioned to be intennediate the service passage 8 and the adjacent exhaust branch 21, in register with spool groove 45', while the right-hand leg 79 is positioned to be intermediate the service passage 8 and the adjacent leg 26 of the high-pressure bridge 24, in register with spool groove 46.
  • the U-shaped core 77 has opposite legs 80 and 81 which intersect bore 6 and lie at opposite sides of service passage 9, with the leg 80 intermediate said service passage and the adjacent leg 27 of the high pressure bridge, in register with spool groove 80; while the leg 81 is intermediate service passage 9 and the adjacent leg 22 of the low pressure bridge, in register with spool groove 49.
  • the bight of the core 77 joins the lower ends its legs 80 and 81, below the bore 6 but above the bight of the low-pressure bridge 13.
  • the inlet branch 56 is communicated through a passageway 82 and a load holding check valve 83 with the bight of the high-pressure bridge 24.
  • valve spool 70 is shiftable out of its neutral position shown at each of a pair of operating positions at opposite sides of neutral, to effect communication of either service passage 8 or 9 with the inlet branch 56 via the high pressure bridge, and to effect communication of the other service passage with the outlet passage 35 via the low-pressure bridge 13.
  • valve spool 70 must be shifted to its operating position to the right of its neutral position.
  • high-pressure fluid in the inlet or feeder 56 can flow past the check valve 83 into the high-pressure bridge 24, through its leg 26 and spool groove as into the leg 79 of cored passage 76, and through the leg 7% thereof and spool groove 45 to service passage 8.
  • Pressure fluid returning to service passage 9 from the controlled motor flows through spool groove 48 into leg 80 of core 77, and through leg M and spool groove 49 to branch 22 of the low pressure bridge 13.
  • Fluid flow to and from the service passages is reversed when the valve spool is shifted to its operating position to the left of neutral.
  • the same small U-shaped cores 76 and 77 which provide important segments of the paths along which pressure fluid flows both to and from the service passages 8 and 9 in the operating positions of the valve spool, also comprise the means for conducting to the return passage 13 high-pressure fluid that leaks axially outwardly along the wall of the bore 6 from the inlet branch as in the neutral position of the valve spool.
  • All such leakage fluid flowing along the wall of the bore to one or the other, or both, of the small U-shaped cores 76-77 enters their legs 79 or 8th closest to the high pressure bridge legs 26-27, and flows to the upright branches 21-22 of the low-pressure bridge 13 through the remote legs 78 and 81 of said cores.
  • the cores 76 and 77 conduct the leakage fluid to the low-pressure bridge 113, in bypass relation to the spool lands 5i and 54 that close off the service passages h and 9 from the bore.
  • this invention provides a closed center valve in which lwkage fluid from the inlet chamber of the valve is led to a return or outlet passage through duct means no part of which is comprised of drilled passages in the valve spool, and which duct means can comprise parts of the paths along which pressure fluid flows to and from the service passages of the valve.
  • a closed center hydraulic control valve having a body with a service passage that is selectively communicable with either an inlet or an outlet passage in one or the other of a pair of operating positions of a valve element in a chamber in which the valve element operates, and wherein said service passage is closed off from both the inlet and the outlet passage by the valve element in a neutral position thereof, characterized by:
  • IB. supply passage means having a portion communicating with said chamber at a location intermediate said zones, and through which pressure fluid from the inlet passage must flow to reach the service passage in one of said operating positions of the valve element;
  • C. means defining a vent passage in the valve body, which opens to said chamber and which is cooperable with the valve element in the neutral position thereof to conduct to the outlet passage pressure fluid that leaks along the wall of said chamber from the inlet passage toward the zone at which the service passage opens thereto.
  • a closed center control valve characterized by:
  • valve element in said chamber adapted to close off the inlet passage from the outlet passage in a neutral position of the valve element at which it is adapted to also close off the service passage from both the inlet and outlet passages, said valve element being adapted to effect communication of the service passage selectively with either the inlet or the outlet passage in different operating positions of the valve element;
  • vent passage means which extends through a portion of the body from the outlet passage toward the valve chamber and intersects the latter at a location between its junction with the service and inlet passages, said vent' passage being cooperable with the valve element in the neutral position thereof to conduct to the outlet passage pressure fluid from the inlet passage that leaks along the wall of the valve chamber toward its junction with the service passage.
  • a closed center control valve of the type having a body with a valve element which is operable to effect communication, through a chamber in which the valve element operates, of a service passage with either a pressure fluid supply passage or with an outlet passage in one or the other of a pair of operating positions to which the valve element is movable, characterized by:-
  • A. means on the valve element operable in a hold position thereof to close off the service passage from both the supply and the outlet passages, and to also close off the supply passage from the outlet passage;
  • vent passage means in the body comprising a branch of the outlet passage wholly externally of the valve element, said vent passage means intersecting the valve chamber at a location ahead of its junction with the service passage, with respect to the direction that fluid from the inlet passage tends to leak toward the service passage along the exterior of the valve element, so as to intercept such leakage fluid and prevent it from reaching the service passage.
  • a closed center hydraulic control valve of the type having a body with a service passage that is selectively communicable with either an inlet passage or with an outlet passage in one or the other of a pair of operating positions of a valve element in a chamber in which the valve element operates, and wherein said service passage is closed off from both the inlet and the outlet passage by the valve element in a neutral position thereof, characterized by:
  • C. means in the valve body defining a vent passage opening to said chamber and registering with said groove in the neutral position of the valve element, to communicate said supply passage means with the outlet passage along a path wholly externally of the valve element.
  • a control valve of the type having a body with an inlet, an outlet, supply passage means, a movable valve element, and a service passage which is selectively communicable with either the inlet or the outlet by the valve element, characterized by:
  • the supply passage means comprising a supply branch through which the inlet is communicated with the service passage by the valve element in one working position thereof, said supply branch being closed off from the inlet and from the service passage in a hold position of the valve element at which. it closes off the service passage from the outlet;
  • a closed center control valve of the type having a body with inlet and outlet passages, a service passage, a valve chamber with which said passages communicate at zones spaced from one another, and a movable valve element in said chamber to control communication of the service passage with the inlet and outlet passages, characterized by:
  • valve element being adapted in a hold position thereof to close off communication of the service passage with both the inlet and the outlet passages, and being adapted to communicate the service passage with either the inlet or the outlet passage in one or the other of a pair of operating positions to which the valve element is movable;
  • duct means rendered operative by the valve element in said hold position thereof for conducting to the outlet passage, in bypass relation to the service passage, pressure fluid from the inlet passage which leaks along the exterior of the valve element toward the service passage, said duct means being located entirely externally of the valve element and leading from a zone of said chamber between the zones at which said inlet and service passages communicate with said chamber.
  • a closed center valve having a body with a bore and an elongated valve spool in the bore movable from a hold position to a pair of operating positions to selectively communicate either of a pair of service passages with inlet means and the other service passage with return means, characterized by:
  • said outlet means comprising a return passage having a pair of branches, one for each service passage, said branches intersecting the bore at third zones each of which is adjacent to one of said first zones but at the side thereof remote from the adjacent second zone, and an outlet passage which is communicated with both of said return branches;
  • venting passage opens to the bore at a location between the inlet means and one of said second zones and is communicated with said one branch of the supply passage through a groove in the valve spool and the bore in which the spool operates.
  • valve spool to nonnally communicate the highpressure supply passage with the return means, said venting passage opening to the bore at a location intermediate said second zones but adjacent to one of them, and being cooperable with the valve spool in the neutral position thereof to communicate one branch of and an elongated valve spool slidable axially therein from a closed center neutral position to each of a pair of operating positions to communicate either of a pair of service passages with centrally disposed inlet means and the other service passage with outlet means through grooves in the valve spool and portions of the bore, characterized by:
  • said inlet means comprising a pair of inlet branches which open to the bore at axially spaced locations intennediate said second zones;
  • the outlet means being centrally located in the body, at
  • a U-shaped return passage in the body having opposite branches, one for eachof said bridge passages, said return passage branches intersecting the bore at zones axially outwardly of the bridge passages and having a bight joining its branches and extending substantially lengthwise of the bore at the same side thereof as the outlet means but spaced farther from the bore than the outlet means and the bights of the bridge passages;
  • valve spool in its neutral position, the valve spool having 1. lands that close off communication of the service passages and the supply passage branches with the bore,
  • a hydraulic control valve having a' body with a bore, and an elongated valve element shiftable in said bore to diflerent positions to selectively communicate fluid flow passages in the body with one another, wherein said fluid flow passages provide:
  • v A a pair of service passages that open from one side of the bore at first zones spaced apart lengthwise of the bore;
  • B a supply passage having a pair of branches, one for each service passage, and which branches open to the bore at second zones located axially inwardly of said first zones;
  • a return passage having a pair of branches, one for each service passage, and which return branches open to the bore at third zones located axially outwardly of said first zones;
  • inlet passage means providing for flow of supply fluid to the service passages via said supply passage under the control of the valve element, said inlet passage means intersecting the bore between the supply passage lL branches;
  • vent means intersecting the bore at zones axially inwardly of said first zones and cooperable with the valve element in the neutral position thereof to conduct leakage fluid from the inlet passage means to the return passage along a path wholly externally of the valve element.
  • valve element is operable to effect communication of the service passages with one another through the return passage.
  • a closed center control valve of the type having a body with a valve element which is operable to effect communication, through a chamber in which the valve B. vent passa e' means in the body l. coopera le with the valve element in the neutral position thereof to intercept pressurized supply fluid that leaks along the wall of the chamber before such leakage fluid reaches the junction between the chamber and the service passage, for conducting such.
  • vent passage being cooperable with the valve element to conduct pressurized supply fluid to the service passage in one of said operating positions of the valve element.

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Multiple-Way Valves (AREA)
  • Fluid-Pressure Circuits (AREA)
US3575212D 1969-11-03 1969-11-03 Leakage control for closed center valves Expired - Lifetime US3575212A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US87352169A 1969-11-03 1969-11-03

Publications (1)

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US3575212A true US3575212A (en) 1971-04-20

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ID=25361803

Family Applications (1)

Application Number Title Priority Date Filing Date
US3575212D Expired - Lifetime US3575212A (en) 1969-11-03 1969-11-03 Leakage control for closed center valves

Country Status (7)

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US (1) US3575212A (fr)
BE (1) BE753810A (fr)
DE (1) DE2049876C3 (fr)
FR (1) FR2071625A5 (fr)
GB (1) GB1303328A (fr)
NL (1) NL7015680A (fr)
SE (1) SE361919B (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4388949A (en) * 1980-12-11 1983-06-21 Bonney Roland W Multiple four-way control valve
US20070028973A1 (en) * 2003-08-04 2007-02-08 Hitachi Construction Machinery Co., Ltd. Directional control valve block

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2896662A (en) * 1956-09-07 1959-07-28 John V Thomas Multiple distribution valve
US3073340A (en) * 1959-12-10 1963-01-15 Electro Hydraulics Ltd Hydraulic systems
US3263570A (en) * 1965-03-29 1966-08-02 Robert E Heffron Hole milling attachment for machine tools
US3322150A (en) * 1964-12-10 1967-05-30 Gresen Mfg Company Valve

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2896662A (en) * 1956-09-07 1959-07-28 John V Thomas Multiple distribution valve
US3073340A (en) * 1959-12-10 1963-01-15 Electro Hydraulics Ltd Hydraulic systems
US3322150A (en) * 1964-12-10 1967-05-30 Gresen Mfg Company Valve
US3263570A (en) * 1965-03-29 1966-08-02 Robert E Heffron Hole milling attachment for machine tools

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4388949A (en) * 1980-12-11 1983-06-21 Bonney Roland W Multiple four-way control valve
US20070028973A1 (en) * 2003-08-04 2007-02-08 Hitachi Construction Machinery Co., Ltd. Directional control valve block

Also Published As

Publication number Publication date
DE2049876A1 (de) 1971-05-13
SE361919B (fr) 1973-11-19
BE753810A (fr) 1970-12-31
FR2071625A5 (fr) 1971-09-17
DE2049876C3 (de) 1978-09-28
NL7015680A (fr) 1971-05-05
DE2049876B2 (de) 1978-01-19
GB1303328A (fr) 1973-01-17

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