US3613711A - Fluid motor control mechanism - Google Patents

Fluid motor control mechanism Download PDF

Info

Publication number
US3613711A
US3613711A US3613711DA US3613711A US 3613711 A US3613711 A US 3613711A US 3613711D A US3613711D A US 3613711DA US 3613711 A US3613711 A US 3613711A
Authority
US
United States
Prior art keywords
fluid
passage
exhaust
pressure
pilot
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 US3613711A publication Critical patent/US3613711A/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.
Anticipated expiration legal-status Critical
Assigned to NORWEST BANK MINNESOTA, NATIONAL ASSOCIATION reassignment NORWEST BANK MINNESOTA, NATIONAL ASSOCIATION SECURITY INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: HUSCO INTERNATIONAL, INC.
Expired - Lifetime legal-status Critical Current

Links

Images

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
    • F15B13/02—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors
    • 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
    • Y10T137/2496—Self-proportioning or correlating systems
    • Y10T137/2559—Self-controlled branched flow systems
    • Y10T137/2574—Bypass or relief controlled by main line fluid condition
    • Y10T137/2605—Pressure responsive
    • Y10T137/2612—Common sensor for both bypass or relief valve and other branch valve
    • 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
    • Y10T137/7722—Line condition change responsive valves
    • Y10T137/7758—Pilot or servo controlled
    • Y10T137/7762—Fluid pressure type
    • Y10T137/7764—Choked or throttled pressure type
    • Y10T137/7766—Choked passage through main valve head
    • 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
    • Y10T137/87233—Biased exhaust valve
    • Y10T137/87241—Biased closed

Definitions

  • a normally closed pilot controllable exhaust valve mechanism governs the discharge of return fluid from the exhaust passage of a fluid motor control mechanism.
  • a first pilot instrumentality effects opening of the exhaust valve mechanism in consequence of rise in pressure of fluid in the exhaust passage to a predetermined value.
  • a second pilot instrumentality effects opening of the exhaust valve mechanism at times when the pressure of fluid in a source connected supply fluid passage rises to a predetermined value exceeding the first, to assure that there will be substantially no obstruction to discharge of exhaust fluid from the exhaust passage at times when a hydraulic motor governed by the control mechanism is under heavy load.
  • the main purpose of the invention resides in the provision of a fluid motor control mechanism having high-pressure fluid supply and low-pressure fluid return passages, and which features means for effecting elevation to and maintenance of the pressure of motor exhaust fluid in the low-pressure fluid return passage at a predetermined positive value as long as the pressure of fluid in the fluid supply passage is below a predetermined value.
  • Still another object of the invention resides in the provision of a fluid motor control device such as described above, which is exceptionally well suited for the prevention of voids in a hydraulic cylinder governed by said device.
  • control valve mechanism comprises two sections of a sectional valve mechanism, namely, a motor control section 5, and an outlet section 6 to which the control section is secured with pressure fluid supply and return passages 7 and 8, respectively in each section in register with one another and providing supply and return headers 7 and 8' respectively.
  • the control section contains an elongated valve spool 10 which is axially slidable in a bore 11 in the body of the control section between a neutral position (shown) and a pair of operating positions at opposite sides of neutral.
  • the spool is operable to communicate either of a pair of service ports 12 and 13 with the fluid supply passage 7 while at the same time communicating the other service port with the return passage 8 via an exhaust passage 14 in the body of the control section.
  • the control section is adapted to govern the operation of a reversible fluid motor, such as a double-acting cylinder 15, in that it enables pressure fluid from a pump P to be directed into either end of the cylinder while at the same time providing for exhaust of fluid from the other end of the cylinder to a reservoir via the exhaust passage 14 and return header 8'.
  • a reversible fluid motor such as a double-acting cylinder 15
  • the open center passage can be of the type illustrated by way of example as comprising a pair of upstream branches l6 spaced from but flanking a single downstream branch 17.
  • the downstream branch can be communicated substantially directly with the reservoir in any adjacent upstream branch 16 of the open center passage.
  • the supply passage 7 is communicated with the high-pressure bridge passage 18 through the customary check valve 217
  • the exhaust passage 14 can be considered as a low-pressure bridge passage having a pair of branches 22 and 23, one for each service passage l2'-l3. These branches open to the bore 11 at zones axially outwardly of their respective service passages.
  • valve spool 10 moves to its operating position to the right of neutral closes off the open center passage and diverts pressure fluid to supply passage 7 and to the service port 12 via the left-hand branch 19 of the high-pressure bridge 18, and a groove in the adjacent portion of the valve spool, and the service passage 12'.
  • the service port 13 is communicated with the return passage 8 via service passage 13, a groove in the adjacent portion of the valve spool, and the right-hand branch 23 of the low-pressure bridge passage 14.
  • the exhaust valve mechanism governs such discharge flow of exhaust fluid from the exhaust chamber 25.
  • the exhaust valve mechanism comprises a fluid-pressure responsive plunger 28 which is urged by a spring 29 axially toward engagement with an annular seat 30, through which seat the exhaust chamber 25 is communicated with the outlet passage 26.
  • the plunger 28 is hollow, and it has a small hole 32 in its seat engaging end to allow exhaust fluid in the chamber 25 to flow into the hollow interior of the plunger to a pressure chamber 33 behind it. Consequently, the spring 29 as well as pressure fluid in the pressure chamber 33 exerts closing force on the plunger 28 of the exhaust valve mechanism to hold it closed.
  • the plunger 28 of course, is adapted to be opened under force exerted on its seat engaging end by the pressure of return fluid in the exhaust chamber 25. It will not respond to such spending force, however, until the pressure chamber 33 behind it is vented to allow fluid therein to flow through an outlet 34 to the outlet passage 26.
  • the outlet 34 of pressure chamber 33 is communicable with the outlet passage 26 through either of a pair of venting passages governed by fluidpressure-responsive pilot valve mechanisms 35 and 36, which are respectively responsive to the pressure of fluid in the exhaust chamber 25 and in the supply passage 7 and its header 7
  • One of these venting passages 37 has an annular valve seat 38 formed therein, and the other venting passage 39 similarly has an annular valve seat 40 formed in it.
  • a pilot poppet 41 is urged by a spring 42 into engagement with the seat 38, and another pilot poppet 43 is urged by a spring 44 into engagement with its seat 40.
  • the spring forces with which the pilot poppets 41 and 42 are held on their seats can be varied by means of adjusting screws 45 and 46 respectively.
  • the pressure of return fluid in the chamber 33 for the exhaust valve plunger 28 at all times exerts opening force upon the pilot poppet 41.
  • the pressure of supply fluid in passage 7 and its header 7' is utilized to exert opening force on the pilot poppet 43.
  • the pilot poppet 43 is provided with a plunger or stem 48 which extends into a passage 49 that can be communicated with the supply passage portion 7 in the outlet section, or in any suitable way with the supply header 7'.
  • the stem 48 not only serves to guide the seating and unseating motions of the pilot poppet 43, but it also carries a seal 50 to prevent leakage of supply fluid from the header 7' into an annular chamber 51 surrounding the stem and located downstream from the poppet seat 40, between the latter and the seal 50.
  • the downstream branch of the venting passage 39 governed by the pilot poppet 43 communicates the chamber 51 with the outlet passage 26.
  • the pilot poppet 41 is adapted to be opened when the pressure of exhaust fluid in communicated chambers 25 and 33 reaches a predetermined value; while the pilot poppet 43 is adapted to be opened when the pressure of fluid in the supply header 7' reaches a higher predetermined value.
  • the spring 42 for the pilot poppet 41 can be set to allow the latter to open whenever the pressure of fluid in the exhaust chamber 25 rises to a value of 300 p.s.i.; and the spring 44 for pilot poppet 43 can be set to allow the same to open when pressure of fluid in the supply header 7' reaches a value of 1,000 p.s.i.
  • the exhaust valve mechanism constitutes an obstruction to and precludes free discharge of fluid from the exhaust chamber 25 except at such times as the pressure of exhaust fluid in said chamber exceeds 300 p.s.i., or when the pressure of supply fluid in header 7 exceeds 1,000 p.s.i.
  • the pressure of fluid in the supply header is determined by the load on the cylinder governed by the control valve mechanism 5.
  • each exhaust passage branch 22-23 extends alongside its associated service passage l2'13 and is communicated therewith through a cylinder port relief valve 53 and also through a check valve 54.
  • the relief valve 53 associated with either service port will open when the pressure of exhaust fluid in said port achieves a predetermined relief value, to allow such fluid to flow around the low-pressure bridge passage 14 and to pass through the check valve 54 associated with the other service passage, for recirculation to the expanding end of thecylinder and the relief of a void therein.
  • the exhaust valve mechanism 27 is a valuable adjunct to the above-described void control scheme. In effect, it closes off the low-pressure bridge passage 14 from the reservoir until a predetermined pressure obtains in the exhaust chamber 25, thus assuring that load-pressurized fluid from the contracting end of the cylinder will be available for recirculation back to the expanding end of the cylinder at pressure values that can exceed the 300 p.s.i. mentioned hereinbefore, depending upon the adjustment of the screw 45 bearing upon the spring 42 of the pilot poppet 41.
  • exhaust fluid from the chamber 25 can flow through the check valve controlled passageway 56 and the supply header 7 to the supply passage 7 in the control section 5 whenever the pressure of supply fluid in the header 7 drops to a value below the pressure of fluid in the exhaust chamber 25.
  • the exhaust fluid thus flowing to the supply passage 7 in the control section 5 can then flow past the check valve 21 to the supply bridge 18 and to whichever cylinder port is in communication therewith.
  • exhaust fluid recirculated back to the supply passage 7 in the control section 5 will augment the flow of pump output fluid to the expanding end of the cylinder to prevent formation of a void therein.
  • the exhaust fluid thus led back to the control section 5 will be load-pressurized fluid maintained under substantial pressure, because of the obstruction which the exhaust valve mechanism 27 presents to free flow of ex haust fluid to the reservoir.
  • the last-described antivoid means can be used with the highpressure relief and check valve combinations described earlier, which function for void relief at times when the valve spool is returned to its neutral position also.
  • the exhaust valve mechanism 27 is either fully open, or fully closed. When it is closed, the force of its spring 29 is augmented by the closing force which exhaust fluid in the chamber 33 exerts upon the rear of the plunger 28. It opens whenever its chamber 33 is vented through either of the pilot valve mechanisms 35 or 36, in response to the force which exhaust fluid in the chamber 25 exerts upon the seat-engaging end of plunger 28.
  • the plunger 28 is never partly open during operation of the cylinder 15 under the control of the valve spool 10. It can only be fully open or fully closed, depending upon the conditions of the two pilot poppets that govern it.
  • pilot control means for said exhaust valve mechanism comprising 1. a first pilot instrumentality which is operable to effect opening of the exhaust valve mechanism whenever the pressure of exhaust fluid in said second passage rises to a first predetermined value,
  • pilot control means comprising first and second vent passageways leading from said chamber
  • said pilot instrumentalities comprising a pair of pilot valves, one for each vent passageway.
  • pilot means normally closing said first passageway and movable to open position in consequence of increase in pressure of fluid in the low-pressure passage to a first predetermined value
  • pilot means normally closing said second passageway and movable to open position in consequence of increase in pressure of fluid in the high-pressure passage to a predetermined value in excess of said first predetermined value.
  • a fluid motor control instrumentality having an outlet passage and a pressure fluid supply passage from which the ports of a reversible hydraulic motor can receive working fluid, characterized by:
  • a pilot controllable valve member normally blocking exhaust fluid flow to the outlet passage but movable to open position under force exerted thereon by pressure of fluid in the exhaust passage provided pressure fluid can escape from a chamber in which a portion of the valve member operates;
  • first and second pilot mechanisms each operable to effect venting of said chamber so that the valve member can open in consequence of force exerted thereon by pressure fluid in the exhaust passage
  • said first pilot mechanism being operable in response to rise in pressure in the exhaust passage to a predetermined value
  • said second pilot mechanism being operable in response to rise in pressure in the supply passage to a predetermined value in excess of said first designated pressure value
  • a fluid motor control mechanism of the type having a movable valve element for selectively directing pressure fluid from a supply passage to either of a pair of service passages while concurrently directing to an exhaust passage pressure fluid returning to the nonselected service passage, characterized by:
  • a first pilot instrumentality for the exhaust valve mechanism operable to effect opening thereof in consequence of pressure of fluid in the exhaust passage only after said exhaust fluid pressure has increased to a predetermined value, whereby pressurized exhaust fluid will be available for flow along a first path leading through the exhaust passage and said antivoid passage to said one service passage at times when the pressure of supply fluid being directed thereto by the valve element drops to a value below that of fluid in the exhaust passage at said increased pressure;
  • a check-valve-controlled bypass communicating the exhaust passage with the supply passage to provide for flow of pressurized exhaust fluid to said one service passage, at said aforementioned times, along a second path which leads through the supply passage;

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Fluid-Pressure Circuits (AREA)
  • Safety Valves (AREA)
US3613711D 1969-12-23 1969-12-23 Fluid motor control mechanism Expired - Lifetime US3613711A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US88748069A 1969-12-23 1969-12-23

Publications (1)

Publication Number Publication Date
US3613711A true US3613711A (en) 1971-10-19

Family

ID=25391234

Family Applications (1)

Application Number Title Priority Date Filing Date
US3613711D Expired - Lifetime US3613711A (en) 1969-12-23 1969-12-23 Fluid motor control mechanism

Country Status (7)

Country Link
US (1) US3613711A (zh)
JP (1) JPS508144B1 (zh)
BE (1) BE753996A (zh)
DE (1) DE2056165C3 (zh)
FR (1) FR2071628A5 (zh)
GB (1) GB1288129A (zh)
SE (1) SE357036B (zh)

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3771558A (en) * 1972-07-20 1973-11-13 Cross Manuf Inc Combined open-center pressure control and regeneration valve
US3800670A (en) * 1969-10-21 1974-04-02 Caterpillar Tractor Co High pressure implement hydraulic circuit
US3951162A (en) * 1971-11-03 1976-04-20 Koehring Company Control valve with flow control means
USRE29292E (en) * 1971-05-20 1977-07-05 Sundstrand Corporation Control valve means for fluid motors
US4040438A (en) * 1974-04-18 1977-08-09 Koehring Control valve with flow control means
US4139021A (en) * 1972-07-19 1979-02-13 Cross Manufacturing, Inc. Hydraulic control instrumentality
US4178962A (en) * 1972-10-30 1979-12-18 Tomco, Inc. Control valve with flow control means
US5988028A (en) * 1993-02-02 1999-11-23 Putzmeister Aktiengesellschaft Process for conveying thick matter containing preshredded scrap metal or similar solids
US6116143A (en) * 1996-07-05 2000-09-12 Parker Hannifin Gmbh Controller for a fluid cylinder
US6231321B1 (en) * 1998-07-31 2001-05-15 Tokico Ltd. Air compressor
US20160377098A1 (en) * 2014-04-11 2016-12-29 Kyb Corporation Valve structure

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2890683A (en) * 1952-02-06 1959-06-16 John S Pilch Fluid actuated control valve means for fluid motors
US3151455A (en) * 1963-05-16 1964-10-06 Hydraulic Unit Specialities Co Pilot operated control valve mechanism
US3216446A (en) * 1963-02-05 1965-11-09 Parker Hannifin Corp Spool valve assembly with dual check valve assembly
US3228306A (en) * 1964-02-10 1966-01-11 Case Co J I Control valve
US3273467A (en) * 1965-01-26 1966-09-20 Fawick Corp Hydraulic system
US3299903A (en) * 1964-03-26 1967-01-24 Parker Hannifin Corp Fluid system and valve assembly therefor
US3416561A (en) * 1966-12-21 1968-12-17 Caterpillar Tractor Co Dual pressure relief valve with shock damping
US3472261A (en) * 1966-01-05 1969-10-14 Racine Hydraulics Inc Directional control valve

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2890683A (en) * 1952-02-06 1959-06-16 John S Pilch Fluid actuated control valve means for fluid motors
US3216446A (en) * 1963-02-05 1965-11-09 Parker Hannifin Corp Spool valve assembly with dual check valve assembly
US3151455A (en) * 1963-05-16 1964-10-06 Hydraulic Unit Specialities Co Pilot operated control valve mechanism
US3228306A (en) * 1964-02-10 1966-01-11 Case Co J I Control valve
US3299903A (en) * 1964-03-26 1967-01-24 Parker Hannifin Corp Fluid system and valve assembly therefor
US3273467A (en) * 1965-01-26 1966-09-20 Fawick Corp Hydraulic system
US3472261A (en) * 1966-01-05 1969-10-14 Racine Hydraulics Inc Directional control valve
US3416561A (en) * 1966-12-21 1968-12-17 Caterpillar Tractor Co Dual pressure relief valve with shock damping

Cited By (12)

* 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
USRE29292E (en) * 1971-05-20 1977-07-05 Sundstrand Corporation Control valve means for fluid motors
US3951162A (en) * 1971-11-03 1976-04-20 Koehring Company Control valve with flow control means
US4139021A (en) * 1972-07-19 1979-02-13 Cross Manufacturing, Inc. Hydraulic control instrumentality
US3771558A (en) * 1972-07-20 1973-11-13 Cross Manuf Inc Combined open-center pressure control and regeneration valve
US4178962A (en) * 1972-10-30 1979-12-18 Tomco, Inc. Control valve with flow control means
US4040438A (en) * 1974-04-18 1977-08-09 Koehring Control valve with flow control means
US5988028A (en) * 1993-02-02 1999-11-23 Putzmeister Aktiengesellschaft Process for conveying thick matter containing preshredded scrap metal or similar solids
US6158313A (en) * 1993-02-02 2000-12-12 Putzmeister Aktiengesellschaft Process for conveying thick matter containing preshredded scrap metal or similar solids
US6116143A (en) * 1996-07-05 2000-09-12 Parker Hannifin Gmbh Controller for a fluid cylinder
US6231321B1 (en) * 1998-07-31 2001-05-15 Tokico Ltd. Air compressor
US20160377098A1 (en) * 2014-04-11 2016-12-29 Kyb Corporation Valve structure

Also Published As

Publication number Publication date
GB1288129A (zh) 1972-09-06
DE2056165A1 (de) 1971-07-01
JPS508144B1 (zh) 1975-04-02
BE753996A (fr) 1970-12-31
SE357036B (zh) 1973-06-12
FR2071628A5 (zh) 1971-09-17
DE2056165B2 (de) 1979-07-26
DE2056165C3 (de) 1980-03-20

Similar Documents

Publication Publication Date Title
USRE26523E (en) Pilot operated control valve mechanism
US4418612A (en) Power transmission
US3878864A (en) Bypass valve
US3613711A (en) Fluid motor control mechanism
US3874269A (en) Hydraulic actuator controls
US3951162A (en) Control valve with flow control means
US3592216A (en) Flow control valve
US3595264A (en) Load control and holding valve
GB1182641A (en) Pilot Operated Control Valve Mechanism
US3974742A (en) Lock valve assembly
US3593741A (en) Compound relief valve
US3926210A (en) Valve combination for hydraulic systems
US2786452A (en) Fluid actuated cylinder having fluid cushion means
US4461314A (en) Electrohydraulic valve
GB1599196A (en) Control apparatus for an hydraulic working implement
US4040438A (en) Control valve with flow control means
US3608859A (en) Controllable check valve
US3893471A (en) Pressure compensating fluid control valve
US3134402A (en) Hydraulic control valve having void control means
US3989062A (en) Source fluid supply and pressure control system for hydraulic motors
US3349671A (en) Holding valve with thermal relief
US3464444A (en) Pilot controllable valve mechanism
US3543647A (en) Control valve means for a two-way hydraulic cylinder
US3207178A (en) Combination motor control valve and exhaust flow control
US3730219A (en) Control valve means for fluid motors

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