EP0134744B1 - Proportionales Nachlaufsteuerschiebersystem - Google Patents

Proportionales Nachlaufsteuerschiebersystem Download PDF

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Publication number
EP0134744B1
EP0134744B1 EP84420120A EP84420120A EP0134744B1 EP 0134744 B1 EP0134744 B1 EP 0134744B1 EP 84420120 A EP84420120 A EP 84420120A EP 84420120 A EP84420120 A EP 84420120A EP 0134744 B1 EP0134744 B1 EP 0134744B1
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EP
European Patent Office
Prior art keywords
spool
main
chamber
driving
chambers
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
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EP84420120A
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English (en)
French (fr)
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EP0134744A2 (de
EP0134744A3 (en
Inventor
Kenneth W. Zeuner
Steven K. Zeuner
Thomas A. Zeuner
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Individual
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Individual
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Priority to AT84420120T priority Critical patent/ATE52575T1/de
Publication of EP0134744A2 publication Critical patent/EP0134744A2/de
Publication of EP0134744A3 publication Critical patent/EP0134744A3/en
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Publication of EP0134744B1 publication Critical patent/EP0134744B1/de
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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
    • F15B13/02—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
    • F15B13/0401—Valve members; Fluid interconnections therefor
    • F15B13/0402—Valve members; Fluid interconnections therefor for linearly sliding valves, e.g. spool valves
    • 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
    • F15B13/0416—Fluid distribution or supply devices characterised by their adaptation to the control of servomotors for use with a single servomotor with means or adapted for load sensing
    • F15B13/0417—Load sensing elements; Internal fluid connections therefor; Anti-saturation or pressure-compensation valves

Definitions

  • This invention relates generally to the field of servo follower proportional control spool valves.
  • Servo follower proportional control valves are well known in the art and are generally described in 1980-81 Fluid Power Handbook and Directory, page A-141 and in National Conference on Fluid Power, 1976 Electro-proportional Position Controls - An Analysis for Application on Various Hydraulic Control Functions by D. W. Swaim.
  • Prior proportional control valves have left much to be desired with respect to rapid response to input commands which may be rapidly changing.
  • rapid response was adversely affected by the use of dynamic seals.
  • the seals would enter the space between the bore and the active valve element and thus increase friction. In this way, such seals were known to cause breakaway and running friction between the valve element and bore, thereby decreasing the ability to rapidly respond as well as decreasing ion frequency tracking ability.
  • a proportional follower spool valve system which provides output fluid flow proportional to a positional control.
  • the system includes a housing having a main passage, a main spool slidable in the main passage and having an inner passage and a pilot spool which is slidable in the inner passage.
  • First fluid connections are controlled by the main spool and they are effective to control output fluid flow in accordance with the position of the main spool.
  • the pilot spool is movable from a null position with the main spool in either a first or second direction and in accordance with the positional control.
  • First and second driving chambers are formed by the main spool each having a driving area substantially less than the largest solid cross-sectional area of the main spool.
  • Second fluid connections are controlled by the pilot spool for admitting fluid under pressure (i) to the first chamber when the pilot spool moves in the first direction away from the first chamber and (ii) to the second chamber when the pilot spool moves in the second direction away from the second chamber.
  • the main spool is moved in the same direction as the pilot spool until a null position is reached.
  • the first and second driving chambers are separated from and fluidly isolated from the end chambers at both ends of the main spool.
  • Each of the first and second driving chambers has substantially less volume than an end chamber, which end chambers are maintained at substantially exhaust pressure.
  • each of the first and second driving chambers are disposed between a respective end chamber and a return pressure connection thereby to avoid dynamic seals on the main spool.
  • a servo follower proportional control spool valve 10 which comprises a housing 15 having a cylindrical bore 15a for slidably receiving a main spool 12.
  • the main spool has an open bore 12a for slidably receiving a pilot spool 11.
  • Valve 10 may be coupled to a pump 17 for pumping hydraulic fluid from a sump 16a through an inlet line 17a to an inlet passage 32 of valve 10.
  • a fluid operated actuator operated by valve 10 may be a piston 22a operating in a cylinder 22.
  • One end of cylinder 22 is connected through a line 24 to an outlet cylinder passage 27 of valve 10.
  • the opposite end of cylinder 22 is similarly connected through another line 25 to another outlet cylinder passage 29.
  • the load (not shown) may be coupled to the shaft of piston 22a in conventional manner.
  • Further valve 10 has a return passage 40 which is connected through a return line 18 back to sump 16a.
  • Main spool 10 has cylindrically lands 60, 61, 67 and 68 spaced axially with respect to longitudinal axis 16.
  • Chamfered main flow metering grooves or passages 64, 48a are formed on the left and right sides of land 60 and similar main flow metering grooves 48b, 65 are formed on the left and right sides of land 61.
  • Grooves 48a, b extend downwardly into spool 12 to define a cylindrical pressure groove or recess 43.
  • a transverse inlet metering orifice 42 extends between groove 43 and bore 12a in main spool 12.
  • a cylindrical tank groove or recess 70 is formed between main flow metering groove 64 and land 67 with a restricted orifice 70a formed between groove 70 and bore 12a.
  • a cylindrical tank groove 71 is formed on spool 12 between groove 65 and land 68 with a restricted orifice 71a defined between groove 71 and bore 12a.
  • Land 67 extends into a reduced diameter cylindrical section 72 which defines the left end of main spool 12 while land 68 extends into reduced diameter section 73 which defines the right end of spool 12.
  • Connecting passages 46, 47 are formed transverse of axis 16 and provide connecting passages between bore 12a and chambers formed by the outer surfaces of sections 46, 47 respectively.
  • Lands 60, 61, 67 and 68 on main spool 12 are slidably but sealingly received in cylindrical bore 15a.
  • This bore presents a cylindrical land surface 31 disposed between annular recess 30 leading to cylinder passage 27 and annular pressure recess 44 leading to pressure inlet passage 32.
  • cylindrical land surface 33 of bore 15a is disposed between annular recess 35 which leads to cylinder passage 29 and pressure recess or cavity 44.
  • recesses 43, 44 form an annular pressure chamber 45.
  • bore 15a presents cylindrical land surfaces 36 and 37.
  • Land 36 is disposed between recess 30 and an annular return recess 40a and land 37 is disposed between recess 35 and return recess 40b.
  • Return recesses 40a, b lead to return passage 40 and form annular return chambers with recesses 70, 71 respectively in the spool 12 neutral position.
  • bore 15a forms an elongated end recess 74 for receiving land 67 and a floating annular spacer 50 which abutts an end wall of end cap 78.
  • Spacer 50 has its inner cylindrically shaped bore surface 50d ground to receive the outer surface of section 72.
  • a slot is formed on the outer surface of spacer 50 to provide for an 0-ring 50a for sealing engagement between the spacer and recess 74. It is in this manner that spacer 50 is effective to "float" within recess 74.
  • annular slot 50b leading to return passage 19 is undercut at the left end of spacer 50 which slot is coupled by way of a passage 50c to end chamber 55 formed by the inner bore of spacer 55 and wall 78b.
  • end chamber 55 is referenced to tank.
  • Wall 78b is formed by a left end cap 78 which threadedly engages housing 15 to seal the bore 15a by way of an O-ring 78a.
  • a left end driving chamber 20 is formed by a right wall 20a of spacer 50, a left wall 20b of land 67 and the upper surface of section 72. The purpose and operation of driving chamber 20 will later be described in detail.
  • V-groove piston 14 defined by a pair of metering lands 14a, b where the V-groove 14c is formed between the lands.
  • V-groove 14c is in communication with metering orifice 42.
  • Metering lands 14a, b each form a sharp metering edge with a respective wall of orifice 42 and sealingly engage bore 12a so that there is no flow of fluid from orifice 42 into the left or right side of bore 12a.
  • Spool 11 also has two axially spaced cylindrical lands 11c, d formed at the left and right ends of the spool to sealingly engage the left and right ends of open bore 12a in all positions of spool 11.
  • Metering land 14a and land 11c are integrally interconnected by stem portion 11 a which defines an elongated longitudinally directed annulus forming a longitudinal passage which extends almost one-half of the length of spool 11.
  • stem portion 11b interconnects a metering land 14b and land 11d with an elongated longitudinal annulus forming a passage extending almost half the length of spool 11.
  • Passage 11 a leads through to passage 46 and to orifice 70a while passage 11 b leads through to orifice 71a and to passage 47.
  • the left end of spool 11 terminates in an end portion 11e which is adapted to engage a stop 78c of end cap 78.
  • a right end portion 11f of spool 11 is adapted to engage a stop 80c of right end cap 80.
  • an actuator 23 which is rigidly connected as shown through the center of left end portion 11e to the left section of spool 11. Actuator 23 extends through chamber 55 and through the axis of end stop 78 and in sealing relation thereto.
  • spools 11 and 12 are in their center position within bore 15a and the spools are in their null position with respect to each other.
  • main spool 12 is at a neutral position in bore 15a with land 60 sealingly engaging lands 36 and 31 and land 61 sealingly engaging lands 33 and 37. Accordingly, in this neutral position of main spool 12 in bore 15a there is no flow of fluid from the inlet passage 32 to either outlet passage 27 or 29.
  • metering land 14a disengages from the left wall of metering orifice 42 and fluid from inlet passage 32 flows through chamber 45, orifice 42 (flow 45a) and then through annular passage 11 a and passage 46 to chamber 20.
  • the pressure in this chamber 20 is effective between fixed wall 20a and moveable wall 20b to move wall 20b of main spool 12 to the right to the position shown in Fig. 3.
  • the opening between land 14a and the left wall of orifice 42 remains open, there is pressure applied to chamber 20 to move spool 12 to the right until that opening closes and spools 11, 12 are at null one with the other. In this position as shown in Fig.
  • spool 12 has moved out of the neutral or central position with respect to the lands in bore 15a. Specifically lands 61, 60 disengage from lands 33, 36 respectively. Therefore fluid from inlet passage 32 flows through chamber 45, metering groove 48b, groove 35 and then to cylinder line 25. In addition, return flow of fluid from cylinder line 24 flows through passage 27, recess 30, through metering groove 64 to return groove 40a and thence to tank.
  • valve 10 provides an output hydraulic flow proportional to actuator 25 movement or to an electrical signal where the electrical signal is effective to move actuator 25 in a manner later to be described.
  • valve 10 In the control position shown in Fig. 3 with spools 11, 12 at null, there is no flow of fluid between the spools and thus there is avoided loss of energy which in prior systems would result from a continuous flow of fluid between the spools.
  • pilot spool 11 Another example of the movement of pilot spool 11 is shown in Fig. 4, in which main spool 12 is in its position shown in Fig. 1 and the pilot spool is moved to the left from its position in Fig. 1.
  • an opening is formed between land 14b and the right wall of orifice 42.
  • fluid flow 45b may be traced from inlet passage 32, chamber 45, orifice 42, passage 11b, connecting passage 47 and thence to chamber 21.
  • pressure on wall 21 b is effective to move main spool 12 to the left until it reaches a null position with pilot spool 11 at its new control position.
  • land 60 disengages from land 31 and land 61 disengages from land 37.
  • valve 10 operates as a servo follower and proportional control valve.
  • each of end driving chambers 20 and 21 have a minimum fluid volume.
  • these chambers only require sufficient volume to provide the force required to move main spool 12 to overcome the flow effects on the main spool.
  • One of these flow effects is shown in Fig. 3 as the flow from inlet 32 through chamber 45 and metering groove 48b to recess 35 and outlet passage 29.
  • these flow effects comprise the Bernoulli effect as well as other effects of flow across main spool 12.
  • ring shaped chambers 20 and 21 are constructed having minimum volume by their provision, in one dimension, of having an outer diameter equal to bore 12a and an inner diameter equal to the outer diameters of recesses 72,73 respectively.
  • chambers 20, 21 are constructed of minimum volume by means of the sidewalls of floating spacers 50, 51 respectively and lands 67, 68 respectively. It is in this manner that chambers 20, 21 operate effectively and each have substantially less volume than that of the spool end chambers 55, 56 respectively.
  • the drive area of chamber 20 defined by wall 20b is substantially less than the transverse solid or metal cross sectional area of main spool 12 itself at its largest diameter. That largest cross sectional area may be that taken at land 67 perpendicular to axis 16.
  • section 72 The remaining cross sectional area defined by the end of section 72 is at return pressure in chamber 55.
  • wall 21 b is of substantially less area than the largest solid cross sectional area of spool 12.
  • the end of section 73 is at return pressure.
  • spacers 50, 51 provide the walls of one side of chambers 20, 21 respectively without imposing side loads on the system.
  • Spacers 50, 51 effectively float in main bore 15a and allow the ends of both spools 11, 12 in chambers 55, 56 to operate at tank or exhaust pressure. It is in this way that the ends of spools 11, 12 do not play any role in the movement.
  • driving chamber 20 is positioned adjacent the left end section of spool 12 between tank groove 40a and end chamber 55 also at tank or return pressure. In this manner, any minimal leakage from drive chamber 20 flows harmlessly to tank rather than flowing to and adversely affecting a control port such as port 30.
  • chamber 21 is between groove 40b and end chamber 56. Thus any leakage flows harmlessly to tank rather than adversely affecting control port 35. It is in this way that valve 10 does not require dynamic seals on spools 11 and 12. In this way, valve 10 rapidly follows rapidly changing step functions, for example, slow movements for accurate positioniong resolution.
  • annular passages 11a, 11b are sized to provide minimum volume passageways between orifice 42 and chambers 20, 21 thereby to minimize compressibility losses in the trapped volume.
  • valve 10 achieves high magnitude response to big step functions in the movement of pilot spool 11 and small magnitude response as the step function decreases.
  • bleed orifice 70a is provided in order to bleed off fluid from chamber 20. This chamber is being compressed as in Fig. 4 when main spool 12 moves to the left. Similarly, bleed orifice 71a a is provided to bleed off fluid from chamber 21 when this chamber is compressed by movement of spool 12 to the right as shown in Figs. 2 and 3.
  • the size of orifices 70a, 71 is a factor in determining the dynamics of the system of valve 10 since the compression of the respective chambers 20 and 21 is determined by the size of that orifice.
  • the flow from bleed orifices 70a, 71a through return recesses 40a, 40b may be returned to tank separately from return passages 19, 19a. Further, orifices 70a, 71a may be connected (not shown) through the center of spool 11 to respective end chambers 55, 56 which are in turn connected to tank.
  • pilot spool 11 is pressure balanced so that it may be moved by a very light force applied to actuator 23.
  • pressure balance it is meant that there is no spring biasing applied to pilot spool 11 and end chambers 55, 56 within which the pilot spool reciprocates and is balanced at tank or drain.
  • a light force to actuator 23 may be applied by a digital drive motor such as a bi-directional linear actuator Series 9200 made by Airpax, Cheshire, Connecticut 06410.
  • a linear actuator provides a half a thoustandths linear motion for each applied digital pulse. In this manner, for a digital input to the linear actuator, pilot spool 11 is accordingly moved and is accurately followed by main spool 12.
  • valve 10 provides accurate and repeatable flow from pressure input 32 to cylinder ports 27, 29.
  • actuator 23 may be moved manually or may be moved by a linear solenoid of the proportioonal or on/off type which is coupled to each end of spool 11.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Servomotors (AREA)
  • Multiple-Way Valves (AREA)
  • Magnetically Actuated Valves (AREA)
  • Fluid-Driven Valves (AREA)
  • Outside Dividers And Delivering Mechanisms For Harvesters (AREA)
  • Harvester Elements (AREA)
  • Fluid-Pressure Circuits (AREA)

Claims (6)

1. Proportionales Nachfolge-Steuerschieber-System zur Bereitstellung einer zu einer Positionssteuerung proportionalen Ausgangsströmung eines Fluids, mit einem Gehäuse (15), das einen Hauptdurchlaß (15a) hat; einem in dem Hauptdurchlaß (15a) verschieblichen Hauptschieber (12), der einen Innendurchlaß (12a) hat; erste Fluidanschlüsse (43, 30, 34), die durch den Hauptschieber (12) gesteuert sind, um die Ausgangsströmung des Fluids in Abhängigkeit von der Position des Hauptschiebers zu steuern; einem in dem Innendurchlaß (12a) verschieblichen Hilfsschieber (11); und Mitteln zum Bewegen des Hilfsschiebers (11) aus einer Nullposition bezüglich des Hauptschiebers (12) entweder in einer ersten oder in einer zweiten Richtung in Abhängigkeit von der Positionssteuerung; wobei der Hauptdurchlaß (15a) an den beiden Enden des Hauptschiebers (12) mit Endkammern (55, 56) versehen ist; durch den Hauptschieber (12) eine erste und eine zweite Antriebskammer (20, 21) ausgebildet ist, die jeweils eine Antriebsfläche wesentlich kleiner als die Querschnittsfläche des Hauptschiebers aufweisen; die erste und die zweite Antriebskammer (20, 21) jeweils an einem Abschnitt mit verringertem Durchmesser des Hauptschiebers (12) ausgebildet sind; und durch den Hilfsschieber (11) gesteuerte zweite Fluidanschlüsse (11a, 11b) Fluid unter Druck (i) in die erste Antriebskammer (20) einlassen, wenn sich der Hilfsschieber in der ersten Richtung weg von der ersten Antriebskammer bewegt, und (ii) in die zweite Antriebskammer (21), wenn sich der Hilfsschieber in der zweiten Richtung weg von der zweiten Antriebskammer bewegt, wodurch der Hauptschieber (12) bis zum Erreichen einer Nullposition in der gleichen Richtung wie der Hilfsschieber (11) bewegt wird, dadurch gekennzeichnet, daß die erste und die zweite Antriebskammer (20, 21) von den Endkammern (55, 56) getrennt und fluidmäßig isoliert sind; daß jede Antriebskammer ein wesentlich kleineres Volumen als eine Endkammer (50, 56) aufweist; und daß die Endkammern (50, 56) im wesentlichen auf dem Auslaßdruck gehalten sind.
2. Steuerschieber-System nach Anspruch 1, dadurch gekennzeichnet, daß die erste und die zweite Antriebskammer (20, 21) an dem Hauptschieber (12) neben seinen beiden Endbereichen ausgebildet sind.
3. Steuerschieber-System nach Anspruch 1, dadurch gekennzeichnet, daß die zweiten Fluidanschlüsse (11a, 11b) erste und zweite längliche Bereiche mit verringertem Durchmesser des Hilfsschiebers (11) einschließen, die mit der ersten und der zweiten Antriebskammer (20,21) fluidmäßig verbunden sind, sowie Meß- und Dosiermittel (42,14) für ein Einlassen des Fluids unter Druck (i) zu dem ersten Bereich (11a), wenn sich der Hilfsschieber in der ersten Richtung bewegt, und (ii) zu dem zweiten Bereich (11 b), wenn sich der Hilfsschieber in der zweiten Richtung bewegt.
4. Steuerschieber-System nach Anspruch 3, dadurch gekennzeichnet, daß die Meß- und Dosiermittel (14) eine mit zwei Steuerbünden (14a, 14b) versehene V-Nut (14c) einschließen.
5. Steuerschieber-System nach Anspruch 1, dadurch gekennzeichnet, daß dritte Fluidanschlüsse (70a, 71a) vorgesehen sind, um für die zweiten Fluidanschlüsse (11a, 11b) einen Rücklaufdruck bereit zu stellen, wobei die erste und die zweite Antriebskammer (20, 21) zwischen einer jeweils zugeordneten Endkammer (55, 56) und einem dritten Fluidanschluß ausgebildet sind und dadurch dynamische Dichtungen an dem Hauptschieber (12) vermieden werden.
6. Steuerschieber-System nach Anspruch 1, dadurch gekennzeichnet, daß in den beiden Endkammern (55, 56) erste und zweite schwimmende Abstandsstücke (50, 51) unbeweglich angeordnet sind, welche den verringerten Durchmesserbereich des Hauptschiebers (12) verschieblich aufnehmen und jeweils eine feste Wand der zugeordneten Antriebskammer (20, 21) bilden.
EP84420120A 1983-07-07 1984-07-06 Proportionales Nachlaufsteuerschiebersystem Expired - Lifetime EP0134744B1 (de)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT84420120T ATE52575T1 (de) 1983-07-07 1984-07-06 Proportionales nachlaufsteuerschiebersystem.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US51157683A 1983-07-07 1983-07-07
US511576 1995-08-04

Publications (3)

Publication Number Publication Date
EP0134744A2 EP0134744A2 (de) 1985-03-20
EP0134744A3 EP0134744A3 (en) 1988-03-16
EP0134744B1 true EP0134744B1 (de) 1990-05-09

Family

ID=24035495

Family Applications (2)

Application Number Title Priority Date Filing Date
EP84420120A Expired - Lifetime EP0134744B1 (de) 1983-07-07 1984-07-06 Proportionales Nachlaufsteuerschiebersystem
EP85420098A Withdrawn EP0202385A1 (de) 1983-07-07 1985-05-24 Ventilanordnung zur Regelung der Haspelgeschwindigkeit

Family Applications After (1)

Application Number Title Priority Date Filing Date
EP85420098A Withdrawn EP0202385A1 (de) 1983-07-07 1985-05-24 Ventilanordnung zur Regelung der Haspelgeschwindigkeit

Country Status (5)

Country Link
EP (2) EP0134744B1 (de)
JP (1) JPH0776561B2 (de)
AT (1) ATE52575T1 (de)
CA (1) CA1229022A (de)
DE (1) DE3482205D1 (de)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA1229022A (en) * 1983-07-07 1987-11-10 Kenneth W. Zeuner Proportional follower spool valve system
SE463324B (sv) * 1988-11-03 1990-11-05 Monsun Tison Ab Staelldon foer distansstyrning med moejlighet till direktstyrning av hydrauliska riktningsventiler
DK170122B1 (da) * 1993-06-04 1995-05-29 Man B & W Diesel Gmbh Stor totakts forbrændingsmotor
CN104074825B (zh) * 2014-07-17 2016-01-13 圣邦集团有限公司 双向选择型合流负载传感多路阀

Family Cites Families (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2462983A (en) * 1943-10-20 1949-03-01 Bendix Aviat Corp Fluid actuated valve
US2526709A (en) * 1945-11-29 1950-10-24 Sperry Corp Fluid operated motor valve
US2665704A (en) * 1948-03-26 1954-01-12 Borg Warner Constant speed flow control valve
US2555755A (en) * 1948-12-11 1951-06-05 Wyman Gordon Co High-pressure hydraulic valve with pilot valve
US2600348A (en) * 1949-12-30 1952-06-10 Gen Electric Two-stage hydraulic control valve
US3089517A (en) * 1958-07-17 1963-05-14 Walter D Ludwig Compound valve
US3060969A (en) * 1960-02-24 1962-10-30 Alkon Products Corp Hydraulic valve
US3152610A (en) * 1961-09-11 1964-10-13 New York Air Brake Co Hydraulic device
US3530895A (en) * 1968-02-09 1970-09-29 Palmer Supply Co Automatic fluid pressure switching valve
GB1231687A (de) * 1969-08-15 1971-05-12
US3749128A (en) * 1971-04-08 1973-07-31 Koehring Co High frequency response servo valve
JPS50111600U (de) * 1974-02-12 1975-09-11
JPS5820702U (ja) * 1981-07-31 1983-02-08 日立建機株式会社 スプ−ル操作弁
CA1229022A (en) * 1983-07-07 1987-11-10 Kenneth W. Zeuner Proportional follower spool valve system

Also Published As

Publication number Publication date
EP0134744A2 (de) 1985-03-20
DE3482205D1 (de) 1990-06-13
CA1229022A (en) 1987-11-10
JPS60121305A (ja) 1985-06-28
JPH0776561B2 (ja) 1995-08-16
EP0134744A3 (en) 1988-03-16
EP0202385A1 (de) 1986-11-26
ATE52575T1 (de) 1990-05-15

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