US3437012A - Valve system for hydraulic elevators - Google Patents

Valve system for hydraulic elevators Download PDF

Info

Publication number
US3437012A
US3437012A US3437012DA US3437012A US 3437012 A US3437012 A US 3437012A US 3437012D A US3437012D A US 3437012DA US 3437012 A US3437012 A US 3437012A
Authority
US
United States
Prior art keywords
valve
slide
elevator
control valve
lowering
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
Inventor
Ludvig Bjorklund
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.)
ABB Norden Holding AB
ABB Norden Holding AB
Original Assignee
ASEA AB
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
Priority to SE1681365A priority Critical patent/SE309834B/xx
Application filed by ASEA AB filed Critical ASEA AB
Application granted granted Critical
Publication of US3437012A publication Critical patent/US3437012A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • BPERFORMING OPERATIONS; TRANSPORTING
    • B66HOISTING; LIFTING; HAULING
    • B66BELEVATORS; ESCALATORS OR MOVING WALKWAYS
    • B66B1/00Control systems of elevators in general
    • B66B1/24Control systems with regulation, i.e. with retroactive action, for influencing travelling speed, acceleration, or deceleration
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B66HOISTING; LIFTING; HAULING
    • B66BELEVATORS; ESCALATORS OR MOVING WALKWAYS
    • B66B1/00Control systems of elevators in general
    • B66B1/34Details, e.g. call counting devices, data transmission from car to control system, devices giving information to the control system
    • B66B1/36Means for stopping the cars, cages, or skips at predetermined levels
    • B66B1/40Means for stopping the cars, cages, or skips at predetermined levels and for correct levelling at landings
    • B66B1/405Means for stopping the cars, cages, or skips at predetermined levels and for correct levelling at landings for hydraulically actuated elevators
    • YGENERAL 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
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00Fluid handling
    • Y10T137/8593Systems
    • Y10T137/87169Supply and exhaust
    • Y10T137/87193Pilot-actuated
    • Y10T137/87209Electric
    • YGENERAL 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
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00Fluid handling
    • Y10T137/8593Systems
    • Y10T137/87169Supply and exhaust
    • Y10T137/87217Motor
    • YGENERAL 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
    • Y10TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10TTECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T137/00Fluid handling
    • Y10T137/8593Systems
    • Y10T137/87169Supply and exhaust
    • Y10T137/87233Biased exhaust valve
    • Y10T137/87241Biased closed

Description

April 8, 1969 L. BJCiRKLUND 3,437,012

VALVE SYSTEM FOR HYDRAULIC ELEVATORS Filed Dec. 28, 1966 1N VENT OR. Z00 viqgj'ankwuv 6 Trot/vex;

April 969 1.. BJCiRKLUND 3,437,012

VALVE SYSTEM FOR HYDRAULIC ELEVATORS Filed Dec. 28. 1966 Sheet 2 or 2 lNvENmR. [.uovia Bran/w. 0ND

fiTTaRNEY:

United States Patent CH US. Cl. 91-446 7 Claims ABSTRACT OF THE DISCLOSURE A hydraulic elevator controlled system includes a circuit connecting pump to a hydraulic cylinder; included in this circuit are first a branch containing an overflow (bypass) valve; then a non-return (check) valve; then a branch containing a load controlled lowering valve and then a control valve operated by a control motor.

The present invention relates to a valve system for a hydraulic elevator inserted in a pressure conduit between a liquid pump and the lifting cylinder of the elevator.

When constructing valve systems for hydraulic elevators, the following conditions and aims must be borne in mind. Smooth starting and stopping is desirable both on the way up and down so that the system must comprise some sort of control valve. Further, there must be no undesired movement when the elevator is stationary and, especially, no undesired lowering, which means that the valves in the system must be absolutely tight. Further, for the upward movement the pump device of the elevator should be able to start independently of the control system itself and the valve system should therefore contain an overflow valve of some sort.

There is already a great number of known constructions which fulfill these requirements and desires but most of these known constructions contain either rather many or relatively complicated valve components, since attempts have been made to combine several functions in the various valves so that particularly the demand for tightness is diflicult to fulfill without complicating the valves. It is extremely diflicult to make a simple adjustable valve which also fulfills the demand for tightness.

A valve system according to the present invention is remarkable since the number of valves is small although each valve has only one function, thus making the construction of the various valves simple. A valve system according to the the invention is characterised in that it comprises an overflow valve in a branch of the presure conduit between the pump and the lift cylinder, a nonreturn orcheck valve, a lowering valve in another branim of the pressure conduit and a control valve controlled by an operating device which provides a certain desired opening and shutting time for said control valve. These valves are connected in the pressure conduit in the mentioned sequence. In this way a minimum number of valves is achieved, impart the same control valve is used for both the upward and the downward movement. Most important is, however, the fact that the sealing function rests only on the non-return valve and the lowering valve so that the tightness requirements of the control valve are moderate and this valve may therefore have a simple construction. Furthermore, the non-return valve and lowering valve as well as the control valve are always filled with oil under pressure so the risk of air bubbles in the hydraulic system is very small, which is a great advantage for the same operation of the elevator. The simple design 3,437,012 Patented Apr. 8, 1969 of the different valves also means that they can be built together in a common housing.

The invention will be further described with reference to the accompanying drawing where FIGURE 1 shows a diagram of a valve system according to the invention while FIGURES 2 and 3 show different views of an embodiment of a combined valve aggregate according to the invention.

FIGURE 1 shows a motor 1 which drives a pump 2 which pumps oil from a liquid container 3 into a pressure conduit 7. In a branch 13 of this pressure conduit is arranged an overflow valve 4 from which the oil can flow back to the liquid container when the pump starts. In the pressure conduit 7 a non-return valve 5 is arranged and after this a lowering valve 9 in a branch 14. After this branch comes a control valve 6 with an operating device 12 and from this control valve a pressure conduit 17 leads further to the lifting cylinder 8 of the elevator car The The lowering valve 9 is suitably controlled with the help of the pressure from the lifting cylinder 8 supplied to the lowering valve through a pilot valve 10. The system may also be provided with a manual drop valve 11.

For upwards movement the motor 1 is started and the pump 2 then pumps oil through the overflow valve 4 :which is a single spring-loaded over-pressure valve. When the operating device 12, which suitably consists of a motor 121 with mechanical gearing 122, opens the control valve 6 the oil will flow through the non-return valve 5 and as the control valve opens the oil flow will increase in the pressure conduit 17 to the lifting cylinder 8 and the elevator car 80 is accelerated to full speed. When the elevator approaches the desired stopping level, the operating device 12 receives an impulse and the control valve 6 slowly closes so that the elevator approaches the stopping level with gradually decreasing speed and stops at the desired position. Thereafter, the motor 1 and the pump 2 are stopped.

For downward movement the lowering valve 9 is first opened with the help of the pilot valve 10, after which the operating device 12 slowly opens the control valve 6 and the elevator starts slowly in downward direction. When the elevator approaches the desired stopping level the operating device 12 receives an impulse to close the control valve and the speed gradually decreases until the elevator stops at the desired level. Since both the non-return valve 5 and the lowering valve 9 are extremely simple valves with suflicient tightness, it is seen that the demand for tightness in the control valve 6 is rather small since a small leakage in the control valve does not influence the correct operation of the elevator.

A simple embodiment of the control valve 6 is shown in FIGURES 2 and 3 which also show how the valves 5, 6, 9 and 10 which are placed within the dotted line in FIGURE 1 may suitably be built together to a common aggregate. The reference numbers used in FIGURE 1 are also used in FIGURES 2 and 3.

FIGURES 2 and 3 show how the valve 6 is made as a slide valve comprising a slide 61 arranged in a cylinder 62 arranged perpendicular to the pressure conduit 17. The slide 61 consists of a cylindrical part 64 and a conical part 63. At the ends of the active part of the slide 61 sealing rings 6-5 are arranged to ensure that oil does not run out between the cylinder 62 and the ends of the slide. Further the cylindrical part 64 is made with such a diameter that it slides easily in the cylinder 62. Such a sliding fit is not sufficiently tight to prevent oil under pressure from the lifting cylinder 8 from leaking through the control valve, but this does not matter as a sealing is obtained by the non-return valve 5 and the drop valve 9. This is a great advantage when manufacturing the slide valve since the slide 61 and the cylinder 62 can then be manufactured with relatively large tolerance in relation to each other and a certain Wear on the slide valve may be permitted.

The operating device 12 for the slide valve consists of an electric motor 121 with gearing 122 and a disc 125 with a crank pin 123 and connecting rod 124 which at its lower end is attached to the slide 61. At its lower end the slide is provided with an extension 66 having a diameter less than that of the slide cylinder 64 and at the ends of the narrower part of this extension are conical surfaces 67 and 68. By means of these surfaces it is possible to control operating contacts 18 and 19 which have contact-fingers 181 and 191 resting on the surface of the projection 66.

When the elevator is to be started the motor 121 is started and the slide 61 is moved slowly downwards. The operating contacts 18, 19 are at first inoperative. When the slide 61 reaches its lowest position the coincal surface 67 will press on the contact finger 181 thus breaking the current to the motor 121 with the contact 18 and the slide stops. When the elevator approaches the desired stopping level, the motor 121 is started again and the slide is pulled upwards towards closing position. Before the slide reaches its upper position the surface 68 will press on the contact finger 191 and the contact 19 breaks the motor current. The slide valve 6 is thus not completely closed and the elevator continues with low speed until the correct position is reached, after which the valve 6 is completely closed. In this way the control valve 6 also acts as a precision adjustment valve without involving extra stages in construction.

The contacts 18 and 19 are adjustable on supporting arms 1'82 and 192 respectively so that the correct position of the contacts in relation to the movement of the slide can be obtained. Further operating contacts corresponding to 18 and 19 may be arranged, for example to control the lift during the precision adjustment interval. When the control valve closes as the elevator approaches the desired level, therefore, the contact 19 will first break the current to the operating motor 121. Just before the stopping position the operating motor is started again and when the control valve reaches closed position the operating motor is stopped by the surface 68 operating a contact, not shown, of the same type as contact 19. No extra precision adjustment valve is thus required according to the invention.

FIGURE 2 shows how the three valves 5, 6 and 9 are suitably built together in a common housing 15 provided with a T-bore 16. It is seen that the slide valve 6 is arranged in the middle of this T-bore and that such a positioning of this slide valve would be rather inconvenient from the manufacturing point of view if the demands for tightness in the slide valve were great. The pressure conduit 17 leading to the lifting cylinder 8 is connected to the right-hand branch of the T-bore.

In the lower branch of the T-bore the non-return valve is arranged at the junction of the pressure conduit 7 from the pump. The non-return valve may, for example, be a simple ball-valve with a ball which seals against a seat.

In the left-hand branch of the T-bore the drop valve 9 is arranged comprising the actual lowering valve consisting of a valve cone 91 resting against a seat 92. On the valve spindle for the lowering valve is arranged a piston 93 in a pressure cylinder 94. When the elevator is stationary or moving upwards this pressure cylinder is under pressure from the pressure conduit 17 through bores 20 and 21 in the housing 15. These bores open into a chamber 105 in a pilot valve comprising a valve cone 101 controlled by an electro-magnetie control device 102 and loaded by a spring 103. On the downwards movement the valve cone 101 is opened by the electro-magnetic operating device 102 against the pressure of the spring 103. The bore 20 is throttled somewhat by the valve cone 101 and the oil from the cylinder 94 escapes through the bore 21, holes 106, in the cone or piston 101 and return conduit 104 from the pilot valve. The spring 95 will then press the piston 93 downwards, thus opening the valve cone 91 of the lowering valve. When the operating device 12 afterwards opens the slide valve 6 the oil from the pressure conduit 17 will flow out through the lowering valve.

FIGURE 2 also shows how the lowering valve 9 may suitably comprise a constant-flow valve by making the valve spindle for the drop valve with varying thickness. For this purpose the valve spindle is provided with a coincal collar 96, the outer diameter of which exceeds the diameter of the valve seat 92. Depending on the load in the elevator the pressure from the pressure conduit 17 will influence the valve surface 96 with a pressure which, to a lesser or greater extent, counteracts the pressure from the spring 95. In this way the opening between the valve cone 91 and the valve seat 92 will be decreased with increased load in the elevator car, and the product of the oil pressure and opening area in the lowering valve will be kept more or less constant so that a more or less const-ant downward speed is obtained for the elevator regardless of the load in the elevator.

Furthermore, in FIGURE 2 has been indicated with dotted lines how the non-return valve 5 instead of being arranged in a lower branch of the T-bore, can be arranged at the left-hand end of a throughrunning bore in the valve housing 15. The valve ball and pressure conduit from the pump have been designated 5' and 7 respectively. In certain cases this may provide a simplified embodiment of the valve housing 15 which is an advantage from the manufacturing point of view. Which embodiment is to be preferred, however, depends mostly on the arrangement of the other components in the system.

I claim:

1. In a hydraulic elevator comprising a liquid pump and a hydraulic lift cylinder; a pressure conduit connecting said liquid pump to said lift cylinder; a liquid tank at the input side of said pump; a valve system for said hydraulic elevator in said pressure conduit; said valve system comprising nearest to said pump a first branch connected to said pressure conduit and leading to said liquid tank; an overflow valve in said first branch; a non-return valve in said pressure conduit after said first branch; a second branch connected to said pressure conduit after said non-return valve and leading to said liquid tank; a lowering valve in said second branch; a control valve in said pressure conduit after said second branch; operating means for said control valve; said operating means opening or closing said control valve with a certain, predetermined speed.

2. A valve system as claimed in claim 1; said control valve being formed like a slide valve comprising a cylinder arranged perpendicular to said pressure conduit and a slide arranged in said cylinder; said slide comprising a cylindrical part fitting into said cylinder and a conical part co-axial to said cylindrical part; said slide being movable in the longitudinal direction of said cylinder and connected to said operating means.

3. A valve system as claimed in claim 2; a common housing for said non-return valve, said control valve and said lowering valve; said housing provided with a T-bore; said control valve arranged in the middle of said T-bore; said non-return valve, said lowering valve and a connection from said control valve to said lift cylinder being arranged each at its own branch of said T-bore.

4. A valve system as claimed in claim 2; a common housing for said non-return valve, said control valve and said lowering valve; said housing provided with a T-bore; said non-return valve and said control valve arranged each at its own end of the straight part of said T-bore; said lowering valve arranged in a branch of said T-bore.

5. A valve system as claimed in claim 2; said slide provided with an extension outside said cylinder; control means for said operating device; said control means arranged in connection with said extension.

6. A valve system as claimed in claim 1; said lowering valve being a constant flow valve.

5 6 7. A valve system as claimed in claim 1; said operating 2,359,112 9/1944 Hymans. means being arranged for opening and closing operation 2 495 735 1 1950 Stephens 91 44 of said control valveg said closling operation being a dtwo 2 501 483 3/1950 Taylor stage operation; the rst of sai two stages correspon ing to a closing interval from a fully open control valve to a 5 3113432 12/1963 Watson 137 596'16 nearly closed control valve; the second of said two stages 3,216,444 11/1965 Hefner 91-443 corresponding to an interval from a nearly closed control 3,276,547 10/1966 Muller 91469 valve to a fully closed control valve.

CARROLL B. DORITY, JR., Primary Examiner. References Cited 10 UNITED STATES PATENTS l- -R- 2,272,684 2/1942 Vickers 91443 91-448, 454; 137596.2, 596.16, 596.17

US3437012D 1965-12-28 1966-12-28 Valve system for hydraulic elevators Expired - Lifetime US3437012A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
SE1681365A SE309834B (en) 1965-12-28 1965-12-28

Publications (1)

Publication Number Publication Date
US3437012A true US3437012A (en) 1969-04-08

Family

ID=20302807

Family Applications (1)

Application Number Title Priority Date Filing Date
US3437012D Expired - Lifetime US3437012A (en) 1965-12-28 1966-12-28 Valve system for hydraulic elevators

Country Status (4)

Country Link
US (1) US3437012A (en)
DE (1) DE1456340A1 (en)
DK (1) DK119529B (en)
SE (1) SE309834B (en)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0057355A2 (en) * 1981-02-04 1982-08-11 Vickers Systems GmbH Hydraulic lifting device
FR2507796A1 (en) * 1981-06-16 1982-12-17 Otis Elevator Co Apparatus for the electromechanical control of hydraulic lift and elevator control by such an apparatus
US4409887A (en) * 1978-06-13 1983-10-18 Tokyo Shibaura Denki Kabushiki Kaisha Hydraulic apparatus
US4612846A (en) * 1984-02-22 1986-09-23 Vickers Systems S.A. High pressure hydraulic distributor having a mechanically controlled discharge valve
US4676140A (en) * 1984-09-15 1987-06-30 Beringer-Hydraulik Gmbh Hydraulic control system
US4711155A (en) * 1985-10-10 1987-12-08 Heilmeier & Weinlein Fabrik Fur Oel-Hydraulic Gmbh & Co. Kg Hydraulic control device
US5125324A (en) * 1988-02-10 1992-06-30 Daia Industry Co. Ltd. Portable hydraulically operated device incorporating automatic drain valve
US5209153A (en) * 1990-02-28 1993-05-11 Daia Industry Co., Ltd. Portable hydraulically operated device incorporating automatic drain valve
US6446538B2 (en) * 2000-02-22 2002-09-10 Hoerbiger Hydraulik Gmbh Arrangement for hydraulic actuation of a movable component on vehicles
US20110108370A1 (en) * 2008-07-23 2011-05-12 Ronald Therriault Elevator alert

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4687078A (en) * 1986-06-23 1987-08-18 Wilson Chester K Hydraulic elevator system

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2272684A (en) * 1931-06-12 1942-02-10 Vickers Inc Hydraulically actuated member and speed control therefor
US2359112A (en) * 1943-08-14 1944-09-26 Otis Elevator Co Hydraulic elevator
US2495785A (en) * 1945-01-11 1950-01-31 Hydraulic Equipment Company Lowering valve
US2501483A (en) * 1948-04-03 1950-03-21 Warner Swasey Co Hydraulic power system
US3113432A (en) * 1960-04-14 1963-12-10 Applied Power Ind Inc Method and apparatus for controlling high pressure fluid by low pressure blocking
US3216444A (en) * 1964-09-02 1965-11-09 Herner Ray Howard Bi-directional variable flow rate control valve
US3276547A (en) * 1963-07-04 1966-10-04 Ver Flugtechnische Werke Stationary hydraulic lifting apparatus

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2272684A (en) * 1931-06-12 1942-02-10 Vickers Inc Hydraulically actuated member and speed control therefor
US2359112A (en) * 1943-08-14 1944-09-26 Otis Elevator Co Hydraulic elevator
US2495785A (en) * 1945-01-11 1950-01-31 Hydraulic Equipment Company Lowering valve
US2501483A (en) * 1948-04-03 1950-03-21 Warner Swasey Co Hydraulic power system
US3113432A (en) * 1960-04-14 1963-12-10 Applied Power Ind Inc Method and apparatus for controlling high pressure fluid by low pressure blocking
US3276547A (en) * 1963-07-04 1966-10-04 Ver Flugtechnische Werke Stationary hydraulic lifting apparatus
US3216444A (en) * 1964-09-02 1965-11-09 Herner Ray Howard Bi-directional variable flow rate control valve

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4409887A (en) * 1978-06-13 1983-10-18 Tokyo Shibaura Denki Kabushiki Kaisha Hydraulic apparatus
EP0057355A2 (en) * 1981-02-04 1982-08-11 Vickers Systems GmbH Hydraulic lifting device
EP0057355A3 (en) * 1981-02-04 1982-12-15 Sperry Vickers Zweigniederlassung Der Sperry Gmbh Hydraulic lifting device
FR2507796A1 (en) * 1981-06-16 1982-12-17 Otis Elevator Co Apparatus for the electromechanical control of hydraulic lift and elevator control by such an apparatus
US4418794A (en) * 1981-06-16 1983-12-06 Otis Elevator Company Electromechanical control for hydraulic elevators
US4612846A (en) * 1984-02-22 1986-09-23 Vickers Systems S.A. High pressure hydraulic distributor having a mechanically controlled discharge valve
US4676140A (en) * 1984-09-15 1987-06-30 Beringer-Hydraulik Gmbh Hydraulic control system
US4711155A (en) * 1985-10-10 1987-12-08 Heilmeier & Weinlein Fabrik Fur Oel-Hydraulic Gmbh & Co. Kg Hydraulic control device
US5125324A (en) * 1988-02-10 1992-06-30 Daia Industry Co. Ltd. Portable hydraulically operated device incorporating automatic drain valve
US5209153A (en) * 1990-02-28 1993-05-11 Daia Industry Co., Ltd. Portable hydraulically operated device incorporating automatic drain valve
US6446538B2 (en) * 2000-02-22 2002-09-10 Hoerbiger Hydraulik Gmbh Arrangement for hydraulic actuation of a movable component on vehicles
US20110108370A1 (en) * 2008-07-23 2011-05-12 Ronald Therriault Elevator alert
US8051955B2 (en) 2008-07-23 2011-11-08 Ronald Therriault Elevator alert for fluid overflow into elevator pit

Also Published As

Publication number Publication date
DK119529B (en) 1971-01-18
SE309834B (en) 1969-04-08
DE1456340A1 (en) 1968-12-05

Similar Documents

Publication Publication Date Title
KR100482901B1 (en) Fuel injection device for internal combustion engines
US2367682A (en) Landing gear by-pass valve
EP1654456B1 (en) Fuel injection device for an internal combustion engine
EP1701074B1 (en) Soft ventable relief valve
US2267284A (en) By-pass valve
US6439193B2 (en) Fuel injection valve for reciprocating internal combustion engine
EP0216439B1 (en) Non-flowing modulating pilot operated relief valve
US3763881A (en) Liquid level control devices
DE60214076T2 (en) Shock-free working cylinder
US2573563A (en) Flow control and pressure regulating device
US4463929A (en) Pressure responsive valve
US2477669A (en) Control valve for double-acting hydraulic systems
JP3617841B2 (en) Load holding brake valve
EP0976013B1 (en) Pressure regulating valve
JPH10141174A (en) Hydraulic actuation type fuel injector having pressure spike relief valve
EP0638746A1 (en) Pilot stage for a pressure control valve
US2467508A (en) Hydraulic system
US6119722A (en) Pilot operated pressure valve
US3730215A (en) Diaphragm controlled air relief valve
US4566492A (en) Fluid distributing device, more especially for remote control
US4274434A (en) Automatic low-friction check valve
US2947258A (en) Self-regulating reciprocating piston pumps, in particular for the injection of fuel into internal combustion engines
WO2005033566A1 (en) Feed pressure valve
JP6097402B2 (en) Valve device
US2805038A (en) Pressure actuated bye-pass valves