GB2212220A - Hydraulic control block - Google Patents

Hydraulic control block Download PDF

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Publication number
GB2212220A
GB2212220A GB8826322A GB8826322A GB2212220A GB 2212220 A GB2212220 A GB 2212220A GB 8826322 A GB8826322 A GB 8826322A GB 8826322 A GB8826322 A GB 8826322A GB 2212220 A GB2212220 A GB 2212220A
Authority
GB
United Kingdom
Prior art keywords
valves
control block
pressure
hydraulic
working
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.)
Granted
Application number
GB8826322A
Other versions
GB8826322D0 (en
GB2212220B (en
Inventor
Hans Schwelm
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.)
Hydrolux SARL
Original Assignee
Hydrolux SARL
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 Hydrolux SARL filed Critical Hydrolux SARL
Publication of GB8826322D0 publication Critical patent/GB8826322D0/en
Publication of GB2212220A publication Critical patent/GB2212220A/en
Application granted granted Critical
Publication of GB2212220B publication Critical patent/GB2212220B/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

Links

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
    • F15B13/01—Locking-valves or other detent i.e. load-holding devices
    • F15B13/015—Locking-valves or other detent i.e. load-holding devices using an enclosed pilot flow valve
    • 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
    • F15B11/00—Servomotor systems without provision for follow-up action; Circuits therefor
    • F15B11/16—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors
    • F15B11/161—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors with sensing of servomotor demand or load
    • F15B11/163—Servomotor systems without provision for follow-up action; Circuits therefor with two or more servomotors with sensing of servomotor demand or load for sharing the pump output equally amongst users or groups of users, e.g. using anti-saturation, pressure compensation
    • 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
    • F15B13/0405—Valve members; Fluid interconnections therefor for seat valves, i.e. poppet 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
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/30525—Directional control valves, e.g. 4/3-directional control valve
    • F15B2211/3053—In combination with a pressure compensating valve
    • F15B2211/30535—In combination with a pressure compensating valve the pressure compensating valve is arranged between pressure source and directional control valve
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/305—Directional control characterised by the type of valves
    • F15B2211/3056—Assemblies of multiple valves
    • F15B2211/30565—Assemblies of multiple valves having multiple valves for a single output member, e.g. for creating higher valve function by use of multiple valves like two 2/2-valves replacing a 5/3-valve
    • F15B2211/3057—Assemblies of multiple valves having multiple valves for a single output member, e.g. for creating higher valve function by use of multiple valves like two 2/2-valves replacing a 5/3-valve having two valves, one for each port of a double-acting output member
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/30—Directional control
    • F15B2211/32—Directional control characterised by the type of actuation
    • F15B2211/329—Directional control characterised by the type of actuation actuated by fluid pressure
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/40—Flow control
    • F15B2211/405—Flow control characterised by the type of flow control means or valve
    • F15B2211/40515—Flow control characterised by the type of flow control means or valve with variable throttles or orifices
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/40—Flow control
    • F15B2211/415—Flow control characterised by the connections of the flow control means in the circuit
    • F15B2211/41581—Flow control characterised by the connections of the flow control means in the circuit being connected to an output member and a return line
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/40—Flow control
    • F15B2211/42—Flow control characterised by the type of actuation
    • F15B2211/428—Flow control characterised by the type of actuation actuated by fluid pressure
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/40—Flow control
    • F15B2211/46—Control of flow in the return line, i.e. meter-out control
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/50—Pressure control
    • F15B2211/505—Pressure control characterised by the type of pressure control means
    • F15B2211/50509—Pressure control characterised by the type of pressure control means the pressure control means controlling a pressure upstream of the pressure control means
    • F15B2211/50536—Pressure control characterised by the type of pressure control means the pressure control means controlling a pressure upstream of the pressure control means using unloading valves controlling the supply pressure by diverting fluid to the return line
    • 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/605—Load sensing circuits
    • F15B2211/6051—Load sensing circuits having valve means between output member and the load sensing circuit
    • F15B2211/6054—Load sensing circuits having valve means between output member and the load sensing circuit using shuttle 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
    • F15B2211/00—Circuits for servomotor systems
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/635—Circuits providing pilot pressure to pilot pressure-controlled fluid circuit elements
    • F15B2211/6355—Circuits providing pilot pressure to pilot pressure-controlled fluid circuit elements having valve means

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Fluid-Pressure Circuits (AREA)
  • Percussive Tools And Related Accessories (AREA)
  • Forklifts And Lifting Vehicles (AREA)
  • Valve Device For Special Equipments (AREA)

Abstract

A hydraulic control block for a double-acting hydraulic cylinder 12 has four proportioning throttle seat-valves C1, C2, C3 and C4 integrated within the block which has a standardised connection pattern for hydraulic lines. The hydraulic pressure supplied to the working valves C1 and C3 is maintained constant by a load-pressure dependent presssure controller 14. The valves are servo-assisted proportional throttle seat valves with integrated low pressure feed back. Such valves are described in US patent specification 4,662,600. An electronically controlled pilot valve 10 control the operation of the valves C1, C2, C3, C4. <IMAGE>

Description

Hydraulic control block The present invention relates to a hydraulic control block for hydraulic units, in particular for controlling double-acting hydraulic cylinders having four integrated individual valves, lying in pairs one above the other and mutually opposite, arranged in two planes parallel to a surface area of the control block with standardized connection pattern, which valves can be triggered in pairs via a pilot valve.
Such a control block is known from DE-A136044210. In order that the control block can be used universally, the operating sequence of the doubleacting hydraulic cylinder is to take place at a constant speed. This is only possible if the throughflow of the hydraulic fluid on the consumer side is constant and corresponds to a value which can be set by a proportional controller. The through-flow through the 2-way fitted valves provided in the known control block is, however, dependent on the opening crosssection of the valves and on the pressure difference P between the pressure in the pumping line and the pressure in the consumer line. Since, however, in the case of the known control block, the pumping pressure is kept constant by a pressure-relief valve, the load pressure-dependent variations of P are compensated by corresponding adaptations of the opening cross-section of the valves.For this purpose, each valve is provided with a displacement transducer and the opening position of the valve pistons is constantly adjusted automatically until the measured maximum value of the through-flow of the hydraulic fluid corresponds to the desired value set. However, this electronic compensation of the position of the valve pistons requires considerable electronic complexity.
The known control block is admittedly free from leakage oil in the event of a power failure, since the oil pressure on the pumping side keeps all valves closed. However, in the event of a pressure failure on the pumping side, the known control block can no longer be described as free from leakage oil.
The two tank valves in the known control block are simple open/closed valves. Under normal working conditions, this is adequate. If, however, the load becomes negative, the control block goes into uncontrolled free running.
The object on which the present invention is based is to create a novel control block which is to avoid the above disadvantages while retaining the compact design and the standardized connection pattern.
This object is achieved according to the invention by a control block which has the features given in the main Claim. Further developments are in the sub Claims.
The invention is described in more detail below by means of an exemplary embodiment, with reference to the enclosed drawing.
This drawing schematically represents the circuit diagram of a control block, th arrangement of which corresponds to that of the control block known from DE-A1-3604410.
The control block consists primarily of the four valves denoted by C1 C2, C3 and C4 C1 and C3 being the working valves and C2 and C4 being the tank valves. The four valves are controlled as in the known control block via an electronically controlled pilot valve 10.
The double-acting hydraulic cylinder to be controlled is denoted by 12. During a first working cycle, the hydraulic oil flows out of a pumping line P through the valve C1 and the working line A into the piston space of the cylinder 12, so that the latter is moved to the right in the Figure. The oil from the piston rod space flows through the working line B and the opened valve C4 into the tank line T.
On changing-over oy the pilot valve 10, the valves C1 and C4 are closed and the valves C2 and C3 are opened. The hydraulic oil then flows out of the pumping line P through the valve C3 and the working line B into the piston rod space, so that the cylinder 12 is moved in the opposite direction. This time, the piston space is connected via the valve C2 to the tank line T.
In the case of the known control block, the 4 valves C1, C2, C3 and C4 consist of simple 2-way fitted valves. In the case of the control block according to the present invention the four valves C1, C2 C3 and C4 consist of servo-assisted proportional throttle seat valves with integrated load pressure check-back signal. Such a valve is described in US Patent Specification 4,662,660.
As already mentioned at the beginning, in the case of the known control block, the pumping pressure is kept constant and the through-flow through the working valves C1 and C3 is kept constant by the opening position of the valves being continually adapted to the load-pressure variations.
In the case of the control block according to the present invention as well, the through-flow is to remain constant, to be precise at a value which can be set by the pilot valve designed as proportional controller. In the case of the new control block, however, the opening cross-section of the valves is kept constant and the control takes place via a pressure controller 14 in the pumping line, which controller controls the pressure in the pumping line according to the load-pressure variations, to be precise such that the pressure difference P between pumping pressure and load pressure remains permanently constant. The size of this pressure difference P is predetermined by an adjustable spring 15.
The advantage of the control according to the invention is that the electronic complexity is simplified considerably in comparison with the known control.
The load-pressure measurement takes place in the way described in US Patent Specification 4,662,600 and the check-back signal goes via the lines 16 and 18, which are connected via a line 20 to the pressure controller.
In the load-pressure check-back signal line 20 there is in 22 an overriding pressure protection element, which represents a protection against abnormal excess pressure in the working line. If the load pressure exceeds a predetermined maximum value, the through-flow is closed by keeping the valve which is in operation, C1 or C3, closed until the load pressure has again dropped to below this maximum value, or in practice until the source of the fault has been eliminated.
The control block according to the invention is equipped with an automatic lowering brake function.
For this purpose, the two tank valves C2 and C4 are triggered via the lines 16 and 18 by the load pressure of the working valves C1 and C3. Under normal working conditions, that is to say with positive load, the tank vaLves C2 and C4 are completely open. If the load is negative, the through-flow opening of the tank valves C2 and C4 is automatically reduced, in order that the through-flow set via the pilot valve is preserved and these valves work as lowering-brake valves.
The control block according to the invention is absolutely free from leakage oil both in the event of a power failure and in the event of a pressure failure.
The non-return valves R1 and R2 fitted in the working lines prevent a return of the hydraulic fluid, so that the working cylinder 12 can be kept in neutral positions free from leakage oil.

Claims (5)

  1. Claims
    Hydraulic control block for hydraulic units, in nartacut3r for controlling double-acting hydraulic cylinders (12) having four integrated individual valves (;1 C2, C3 C4) lying in pairs one above the other and mutually opposite, arranged in two planes parallel to 3 surface area of the control block with standard connection pattern, which valves can be triggered in pairs via a pilot valve (10), characterized in that the individual valves (C1, C2, C3 and C4) consist of proportional throttle seat valves with integrated load-pressure checkback signal, and in that the through-flow through the working valves (C1 C3) is kept constant by a load pressure dependent pressure controller (14).
  2. 2. Control block according to Claim 1, character sized in that the pressure controller (14) is coupled to an overriding pressure protection (22). 914
  3. 3. Control block according to Claim 1, characterized in that the tank valves CC2, C4) are controlled by the load pressure of the working valves (C1, C3).
  4. 4. Control block according to Claim 1, characterized by non-return valves fitted in the working lines.
  5. 5. A hydraulic control block for hydraulic units such as double-acting hydraulic cylinders and substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.
GB8826322A 1987-11-12 1988-11-10 Hydraulic control block Expired - Fee Related GB2212220B (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
LU87045A LU87045A1 (en) 1987-11-12 1987-11-12 HYDRAULIC CONTROL BLOCK

Publications (3)

Publication Number Publication Date
GB8826322D0 GB8826322D0 (en) 1988-12-14
GB2212220A true GB2212220A (en) 1989-07-19
GB2212220B GB2212220B (en) 1992-01-08

Family

ID=19730988

Family Applications (1)

Application Number Title Priority Date Filing Date
GB8826322A Expired - Fee Related GB2212220B (en) 1987-11-12 1988-11-10 Hydraulic control block

Country Status (3)

Country Link
GB (1) GB2212220B (en)
LU (1) LU87045A1 (en)
NO (1) NO171425C (en)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0473030A1 (en) * 1990-08-31 1992-03-04 Hydrolux S.A.R.L. Proportional 4-way seat valve
WO1996021807A1 (en) * 1995-01-12 1996-07-18 Danfoss A/S Three-way or multi-way valve
WO1996021808A1 (en) * 1995-01-12 1996-07-18 Danfoss A/S Three-way or multi-way valve
WO1997013980A2 (en) * 1995-10-09 1997-04-17 Hans Schwelm Valve system
WO2001059305A1 (en) * 2000-02-11 2001-08-16 Zf Lenksysteme Gmbh Control device for a hydraulic control motor
CN104832485A (en) * 2015-05-19 2015-08-12 江苏柳工机械有限公司 Hydraulic control system for backhoe loader

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111089088B (en) * 2019-12-27 2022-03-29 中国航空工业集团公司沈阳飞机设计研究所 Multi-mechanism series connection motion coordination control loop

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1045764A (en) * 1963-05-16 1966-10-19 Hydraulic Unit Specialities Co Valve means for controlling operation of a fluid motor
GB1182641A (en) * 1966-07-06 1970-02-25 Koehring Co Pilot Operated Control Valve Mechanism

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1045764A (en) * 1963-05-16 1966-10-19 Hydraulic Unit Specialities Co Valve means for controlling operation of a fluid motor
GB1182641A (en) * 1966-07-06 1970-02-25 Koehring Co Pilot Operated Control Valve Mechanism

Cited By (15)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0473030A1 (en) * 1990-08-31 1992-03-04 Hydrolux S.A.R.L. Proportional 4-way seat valve
US5211196A (en) * 1990-08-31 1993-05-18 Hydrolux S.A.R.L. Proportional seat-type 4-way valve
GB2312252A (en) * 1995-01-12 1997-10-22 Danfoss As Three-way or multi-way valve
WO1996021808A1 (en) * 1995-01-12 1996-07-18 Danfoss A/S Three-way or multi-way valve
WO1996021807A1 (en) * 1995-01-12 1996-07-18 Danfoss A/S Three-way or multi-way valve
GB2312477A (en) * 1995-01-12 1997-10-29 Danfoss As Three-way or multi-way valve
GB2312477B (en) * 1995-01-12 1998-07-29 Danfoss As Three-way or multi-way valve
GB2312252B (en) * 1995-01-12 1998-07-29 Danfoss As Three-way or multi-way valve
WO1997013980A2 (en) * 1995-10-09 1997-04-17 Hans Schwelm Valve system
WO1997013980A3 (en) * 1995-10-09 1997-07-03 Hans Schwelm Valve system
US5975134A (en) * 1995-10-09 1999-11-02 Schwelm; Hans Valve system
CZ297720B6 (en) * 1995-10-09 2007-03-14 Class Industrietechnik Gmbh Valve system central block and valve block of two- or three-way valve and use thereof
WO2001059305A1 (en) * 2000-02-11 2001-08-16 Zf Lenksysteme Gmbh Control device for a hydraulic control motor
US6712091B2 (en) 2000-02-11 2004-03-30 Zf Lenksysteme Gmbh Control device for a hydraulic control motor
CN104832485A (en) * 2015-05-19 2015-08-12 江苏柳工机械有限公司 Hydraulic control system for backhoe loader

Also Published As

Publication number Publication date
GB8826322D0 (en) 1988-12-14
NO171425B (en) 1992-11-30
NO885035L (en) 1989-05-16
NO885035D0 (en) 1988-11-11
NO171425C (en) 1993-03-10
GB2212220B (en) 1992-01-08
LU87045A1 (en) 1988-05-03

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Legal Events

Date Code Title Description
PCNP Patent ceased through non-payment of renewal fee

Effective date: 19941110