EP1045992B1 - Control arrangement for a hydraulic motor - Google Patents
Control arrangement for a hydraulic motor Download PDFInfo
- Publication number
- EP1045992B1 EP1045992B1 EP99900439A EP99900439A EP1045992B1 EP 1045992 B1 EP1045992 B1 EP 1045992B1 EP 99900439 A EP99900439 A EP 99900439A EP 99900439 A EP99900439 A EP 99900439A EP 1045992 B1 EP1045992 B1 EP 1045992B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- valve
- control
- pressure
- throttle
- inflow
- 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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Classifications
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- 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
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B66—HOISTING; LIFTING; HAULING
- B66C—CRANES; LOAD-ENGAGING ELEMENTS OR DEVICES FOR CRANES, CAPSTANS, WINCHES, OR TACKLES
- B66C13/00—Other constructional features or details
- B66C13/18—Control systems or devices
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B66—HOISTING; LIFTING; HAULING
- B66C—CRANES; LOAD-ENGAGING ELEMENTS OR DEVICES FOR CRANES, CAPSTANS, WINCHES, OR TACKLES
- B66C13/00—Other constructional features or details
- B66C13/18—Control systems or devices
- B66C13/20—Control systems or devices for non-electric drives
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B66—HOISTING; LIFTING; HAULING
- B66F—HOISTING, LIFTING, HAULING OR PUSHING, NOT OTHERWISE PROVIDED FOR, e.g. DEVICES WHICH APPLY A LIFTING OR PUSHING FORCE DIRECTLY TO THE SURFACE OF A LOAD
- B66F9/00—Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes
- B66F9/06—Devices for lifting or lowering bulky or heavy goods for loading or unloading purposes movable, with their loads, on wheels or the like, e.g. fork-lift trucks
- B66F9/075—Constructional features or details
- B66F9/20—Means for actuating or controlling masts, platforms, or forks
- B66F9/22—Hydraulic devices or systems
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02F—DREDGING; SOIL-SHIFTING
- E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
- E02F9/20—Drives; Control devices
- E02F9/22—Hydraulic or pneumatic drives
- E02F9/2203—Arrangements for controlling the attitude of actuators, e.g. speed, floating function
- E02F9/2207—Arrangements for controlling the attitude of actuators, e.g. speed, floating function for reducing or compensating oscillations
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- 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
- F15B11/003—Systems with load-holding valves
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- 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
- F15B11/02—Systems essentially incorporating special features for controlling the speed or actuating force of an output member
- F15B11/04—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed
- F15B11/042—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed by means in the feed line, i.e. "meter in"
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- 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
- F15B11/02—Systems essentially incorporating special features for controlling the speed or actuating force of an output member
- F15B11/04—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed
- F15B11/044—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed by means in the return line, i.e. "meter out"
- F15B11/0445—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the speed by means in the return line, i.e. "meter out" with counterbalance valves, e.g. to prevent overrunning or for braking
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- 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
- F15B2211/30505—Non-return valves, i.e. check valves
- F15B2211/30515—Load holding valves
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- 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
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- 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
- F15B2211/31—Directional control characterised by the positions of the valve element
- F15B2211/3144—Directional control characterised by the positions of the valve element the positions being continuously variable, e.g. as realised by proportional valves
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- 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
- F15B2211/315—Directional control characterised by the connections of the valve or valves in the circuit
- F15B2211/3157—Directional control characterised by the connections of the valve or valves in the circuit being connected to a pressure source, an output member and a return line
- F15B2211/31576—Directional control characterised by the connections of the valve or valves in the circuit being connected to a pressure source, an output member and a return line having a single pressure source and a single output member
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- 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
- F15B2211/321—Directional control characterised by the type of actuation mechanically
- F15B2211/324—Directional control characterised by the type of actuation mechanically manually, e.g. by using a lever or pedal
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- 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
- F15B2211/35—Directional control combined with flow control
- F15B2211/351—Flow control by regulating means in feed line, i.e. meter-in control
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- 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
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- 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
- F15B2211/40553—Flow control characterised by the type of flow control means or valve with pressure compensating valves
- F15B2211/40561—Flow control characterised by the type of flow control means or valve with pressure compensating valves the pressure compensating valve arranged upstream of the flow control means
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- 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
- F15B2211/41—Flow control characterised by the positions of the valve element
- F15B2211/413—Flow control characterised by the positions of the valve element the positions being continuously variable, e.g. as realised by proportional valves
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- 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
- F15B2211/41527—Flow control characterised by the connections of the flow control means in the circuit being connected to an output member and a directional control valve
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- 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
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- 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
- F15B2211/50545—Pressure control characterised by the type of pressure control means the pressure control means controlling a pressure upstream of the pressure control means using braking valves to maintain a back pressure
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- 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
- F15B2211/50563—Pressure control characterised by the type of pressure control means the pressure control means controlling a differential pressure
- F15B2211/50581—Pressure control characterised by the type of pressure control means the pressure control means controlling a differential pressure using counterbalance valves
Definitions
- the invention concerns a control arrangement for a hydraulic motor, which is, at least in one working direction, loadable by an external force, with a control valve having for this working direction an inflow control throttle in an inflow path extending between the pump connection and the inflow motor connection and a return control throttle in a return path extending between the return motor connection and the tank connection, with a load retaining valve having a load retaining throttle in the return path, and with a compensation valve maintaining a constant pressure drop at a throttle arranged in the return path.
- a control arrangement as mentioned in the introduction is known from DE 38 00 188 C2.
- a normal manually operated three-position valve constructed as a proportional valve serves as control valve.
- a switching valve In the inflow path a switching valve has a first throttle assuming such a position that the pressure drop at the throttle is constant.
- Fixedly connected with the first throttle is a second throttle arranged in the return path, the second throttle serving as load retaining valve and assuming a position determined by the first throttle.
- a compensation valve is connected in series with the load retaining valve in the return path, which compensation valve keeps the pressure drop at the load retaining valve constant. Due to the connection between the inflow-side first throttle and the return-side second throttle and the balancing system with suction pipe between the return path and the inflow path required for this reason it is difficult to obtain an accurate, load independent control, which is stable towards oscillations.
- auxiliary valve in series with a control valve on the inflow side of a hydraulic motor.
- this auxiliary valve is operated so that the pressure drop at the inflow control throttle is kept constant, a constant inflow quantity occurs independently of the load pressure.
- a pilot pipe is provided between inflow path and return path, which pilot pipe has a series connection of a fixed pilot throttle and a pilot throttle adjustable by means of the control valve, the auxiliary valve can be activated in dependence of the pressure drop at the fixed pilot throttle, which causes that a pressure which is substantially dependent on the position of the control valve prevails at the inflow motor connection, which pressure is independent of the load.
- the invention is based on the task of providing a control arrangement of the kind described in the introduction, which is to a large extent load independent and stable towards oscillations.
- control valve is part of a pressure control in which the motor inflow pressure is substantially determined by the position of the control valve, and that the load retaining valve opens in dependence of the difference between the motor inflow pressure and a reference pressure, which can be picked off between the load retaining valve and the return control throttle.
- This construction gives an inflow side pressure control and a return side flow control.
- the pressure control causes an internal pressure feedback, which is extremely stabilising and enables an approximately oscillation-free lowering.
- the load retaining valve ensures that a lowering is only possible when a positive motor inflow pressure is available, that is cavitation cannot occur, and together with the compensation valve the load retaining valve provides that during lowering the returning quantity is limited and cannot exceed a maximum quantity specified by the full opening of the control valve.
- This relation with the motor inflow pressure causes a load independent lowering.
- the return quantity may certainly have a different value than the inflow quantity, as is the case with a hydraulic cylinder with different piston areas.
- the pressure control has a pilot pipe extending between the inflow path and the return path, which pilot pipe comprises the series connection of a fixed pilot throttle and a pilot throttle adjustable by means of the control valve, as well as an auxiliary valve opening in dependence of the pressure drop at the fixed pilot throttle and arranged in series with the inflow control throttle.
- a pressure control of this kind has a very simple construction and can be accommodated in the housing of the control valve.
- the load retaining valve has a slide, which is loaded in one direction by the reference pressure and a spring and in the other direction by the motor inflow pressure. This gives a very simple construction of the load retaining valve.
- the slide is additionally loaded by the inlet pressure of the load retaining valve, the slide having a larger pressure surface for the motor inflow pressure and a smaller pressure surface for the inlet pressure.
- the load retaining valve can also work as pressure-relief valve. As the influence of the inlet pressure proportional to the pressure surface only amounts to a fraction of that of the motor inflow pressure, the load retaining valve does not open until the excess pressure has reached a value which is a multiple of the normal working pressure.
- the load retaining valve has a spring chamber, which can be pressure-relieved independently of the reference pressure.
- the intended effect particularly occurs when the compensation valve maintains a constant pressure drop at the load retaining valve.
- the compensation valve maintains a constant pressure drop at the return control throttle.
- the inflow side pressure control and the return side flow control occur in a particularly pronounced way at the control valve.
- the compensation valve is arranged in the return path. It may be arranged between the return motor connection and the load retaining valve, between the load retaining valve and the return control throttle or between the return control throttle and the tank connection.
- the compensation valve is arranged in a pilot pipe system and additionally influences the pilot pressure for an adjustable throttle. In this connection only a small compensation valve is required, which is interesting for weight and space reasons.
- a pilot pipe extending between the inflow motor connection and the tank connection comprises a series connection of a fixed throttle and the compensation valve and therebetween the branching to a pressure surface of the load retaining valve.
- Another, also preferred embodiment provides that the compensation valve bypasses the pilot throttle adjustable by means of the control valve.
- the overridden control of the auxiliary valve available in the inflow side by means of the compensation valve causes the auxiliary valve to maintain a constant pressure drop at the return control throttle.
- load retaining valve is constructed as a pressure relief valve and the return control throttle is open in the neutral position of the control valve. This gives an additional utilisation of the load retaining valve.
- the control arrangement in Fig. 1 operates a motor 1, here shown as a so-called piston-cylinder unit, which can be loaded in the lowering direction by an external force 2.
- the diagram only shows the details required of the lowering movement.
- a usual flow control can be used for the hoisting.
- a control valve 3 which is adjustable manually by a regulating arrangement 4 or via a remote control, has an inflow control throttle 5 in an inflow path 6 extending between a pump connection P and a motor connection A, and a return control throttle 7 in a return path 8 extending between a return motor connection Bc and a tank connection T.
- a pilot pipe 9 connects the inflow path 6 at the inlet of the inflow control throttle 5 with the return path 8 at the outlet of the return control throttle 7.
- a fixed pilot throttle 10 and a pilot throttle adjustable together with the inflow and return throttles 5 and 7 are arranged.
- the inflow control throttle 5 is connected in series with an auxiliary valve 12, which maintains a constant pressure drop at the fixed pilot throttle 10. This results in a pressure control according to which the motor inflow pressure P A has a value, which is mainly determined by the position of the control valve 3.
- a compensation valve 13 and a load retaining valve 14 are arranged in series.
- the load retaining valve 14 receives the motor inflow pressure P A via a pilot pipe 15 and a reference pressure P R via an additional pilot pipe 16, which reference pressure rules at the outlet B of the load retaining valve 14.
- the compensation valve 13 is controlled so that it maintains a constant pressure drop at the load retaining valve 14.
- the series connection of compensation valve 13 and load retaining valve 14 is bypassed by an antiparallel connection of a pressure relief valve 18 and a non-return valve 19 opening during the lifting movement.
- the motor inflow pressure P A is applied on the right half via the adjusting path X of the control valve, that is in particular the slide of a proportional valve.
- the control path Z of the load retaining valve 14 changes in dependence of the motor inflow pressure P A .
- the area from 0 to X0 corresponds to the dead band of a proportional valve.
- the pressure is built up from a standby pressure to PO. This pressure is required to overcome the preload of the load retaining valve 14.
- From X0 to X1 the motor inflow pressure changes from P0 to P stop , which is the pressure required to move the slide of the load retaining valve 14 towards the end stop.
- the area from X0 to X1 is the real control area when lowering the load.
- a pressure higher than P stop may be required.
- the slide of the control valve must move beyond X1. This gives a higher motor inflow pressure P A , while the movement speed of the motor is still limited by the opening of the load retaining valve 14 in the position Zmax and from the throttling through the compensation valve.
- the vertical line starting at S is idealised. It only appears when the control throttles of the control valve 3 work without losses, which is not possible in practice.
- the dash-and-dot line L shows that a certain pressure P A on the motor inflow connection A belongs to a certain position X of the slide of the control valve 3, and that with this motor inflow pressure a certain position Z of the load retaining valve is specified, which position Z in connection with the compensation valve 13 results in a predetermined return quantity.
- the slide of the load retaining valve 114 is loaded in the closing direction by the spring 17 and the reference pressure P R and in the opposite direction by the motor inflow pressure P A and, via an additional pilot pipe 20, by the inlet pressure P E of the load retaining valve 114.
- the motor inflow pressure P A is still prevailing, which appears from the fact that the pressure chamber connected with the pilot pipe 15 has a larger pressure surface 21 than the pressure surface 22 of the pressure chamber connected with the pilot pipe 20.
- the pressure surface exposed to the reference pressure through P R is preferably equal to the sum of the pressure surfaces 21 and 22.
- Fig. 4 differs from the one in Fig. 3 in that the compensation valve 13 is connected to the output side of the load retaining valve 114 in the return path 8, and that the compensation valve maintains a constant pressure drop at the return control throttle 7.
- the outlet pressure of the load retaining valve 114 is chosen as reference pressure P R .
- the function of the pressure relief valve 18 is incorporated in the load retaining valve 114, meaning that the spring 17 gets a corresponding preload and the pressure surface relation is chosen accordingly.
- the chamber for the spring 17 can be relieved separately from the chamber for the reference pressure P R , for example towards the atmosphere or the tank.
- the working diagram of Fig. 5 applies, which corresponds to the right half of the diagram of Fig. 2.
- the area from 0 to X0 forms the dead band of the control valve 3.
- the motor inflow pressure P A is built up from a small stand-by pressure to a pressure P0, which must be high enough to serve as pilot pressure, to open the load retaining valve without available force 2.
- the load retaining valve 114 has a pilot relation 4:1. As pressure relief valve it is set at 300 bar. Without the force 2 a load pressure of 20 bar is measured due to the own weight.
- the compensation valve 113 is made as a small pilot valve. It is arranged in a pilot pipe 115 in series with a fixed pilot throttle 23. The pick-off 24 arranged between them leads to the pressure chamber with the larger pressure surface 121 of the load retaining valve 114.
- the compensation valve 113 maintains a constant pressure drop at the return control throttle 7, as deviations are balanced by a superposed adjustment of the slide of the load retaining valve 114.
- the compensation valve 113 is again made as a pilot valve. It maintains a constant pressure drop at the return control throttle 7 in that the adjustable pilot throttle 11 is bypassed through a pilot branch 25 meaning that the inflow side auxiliary valve 12 is additionally acted upon.
- the compensation valve 113 can be arranged in the housing or in the slide of the control valve 3. Further, the advantage is obtained that only the required pressure is built up on the outlet side.
- the compensation valve can also be connected to the output side of the return control throttle.
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- Mechanical Engineering (AREA)
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- Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Structural Engineering (AREA)
- Transportation (AREA)
- Civil Engineering (AREA)
- Automation & Control Theory (AREA)
- Combustion & Propulsion (AREA)
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- Life Sciences & Earth Sciences (AREA)
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- Fluid-Pressure Circuits (AREA)
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Abstract
Description
- The invention concerns a control arrangement for a hydraulic motor, which is, at least in one working direction, loadable by an external force, with a control valve having for this working direction an inflow control throttle in an inflow path extending between the pump connection and the inflow motor connection and a return control throttle in a return path extending between the return motor connection and the tank connection, with a load retaining valve having a load retaining throttle in the return path, and with a compensation valve maintaining a constant pressure drop at a throttle arranged in the return path.
- When hoisting or lowering a load, for example in connection with crane booms, lifting platforms, fork lifts, excavators etc., it is important out of regard for the controllability that the movements are performed without oscillations. It is also desirable for the movements to be performed at a speed which is determined by the operator not by the load size. With hoisting movements there are normally no problems in meeting both wishes. With lowering movements, however, it is very difficult to meet these requirements.
- A control arrangement as mentioned in the introduction is known from DE 38 00 188 C2. A normal manually operated three-position valve constructed as a proportional valve serves as control valve. In the inflow path a switching valve has a first throttle assuming such a position that the pressure drop at the throttle is constant. Fixedly connected with the first throttle is a second throttle arranged in the return path, the second throttle serving as load retaining valve and assuming a position determined by the first throttle. A compensation valve is connected in series with the load retaining valve in the return path, which compensation valve keeps the pressure drop at the load retaining valve constant. Due to the connection between the inflow-side first throttle and the return-side second throttle and the balancing system with suction pipe between the return path and the inflow path required for this reason it is difficult to obtain an accurate, load independent control, which is stable towards oscillations.
- From DE 38 02 672 it is known to arrange an auxiliary valve in series with a control valve on the inflow side of a hydraulic motor. When this auxiliary valve is operated so that the pressure drop at the inflow control throttle is kept constant, a constant inflow quantity occurs independently of the load pressure. If, however, a pilot pipe is provided between inflow path and return path, which pilot pipe has a series connection of a fixed pilot throttle and a pilot throttle adjustable by means of the control valve, the auxiliary valve can be activated in dependence of the pressure drop at the fixed pilot throttle, which causes that a pressure which is substantially dependent on the position of the control valve prevails at the inflow motor connection, which pressure is independent of the load.
- The invention is based on the task of providing a control arrangement of the kind described in the introduction, which is to a large extent load independent and stable towards oscillations.
- According to the invention this task is solved in that the control valve is part of a pressure control in which the motor inflow pressure is substantially determined by the position of the control valve, and that the load retaining valve opens in dependence of the difference between the motor inflow pressure and a reference pressure, which can be picked off between the load retaining valve and the return control throttle.
- This construction gives an inflow side pressure control and a return side flow control. Seen from a purely control technical point of view the pressure control causes an internal pressure feedback, which is extremely stabilising and enables an approximately oscillation-free lowering. Due to its control, the load retaining valve ensures that a lowering is only possible when a positive motor inflow pressure is available, that is cavitation cannot occur, and together with the compensation valve the load retaining valve provides that during lowering the returning quantity is limited and cannot exceed a maximum quantity specified by the full opening of the control valve. This relation with the motor inflow pressure causes a load independent lowering. In this connection the return quantity may certainly have a different value than the inflow quantity, as is the case with a hydraulic cylinder with different piston areas.
- It is recommended that the pressure control has a pilot pipe extending between the inflow path and the return path, which pilot pipe comprises the series connection of a fixed pilot throttle and a pilot throttle adjustable by means of the control valve, as well as an auxiliary valve opening in dependence of the pressure drop at the fixed pilot throttle and arranged in series with the inflow control throttle. A pressure control of this kind has a very simple construction and can be accommodated in the housing of the control valve.
- Further, it is advantageous that the load retaining valve has a slide, which is loaded in one direction by the reference pressure and a spring and in the other direction by the motor inflow pressure. This gives a very simple construction of the load retaining valve.
- In this connection it is advantageous that the slide is additionally loaded by the inlet pressure of the load retaining valve, the slide having a larger pressure surface for the motor inflow pressure and a smaller pressure surface for the inlet pressure. Thus, the load retaining valve can also work as pressure-relief valve. As the influence of the inlet pressure proportional to the pressure surface only amounts to a fraction of that of the motor inflow pressure, the load retaining valve does not open until the excess pressure has reached a value which is a multiple of the normal working pressure.
- Further, it has turned out to be advantageous that the load retaining valve has a spring chamber, which can be pressure-relieved independently of the reference pressure.
- The intended effect particularly occurs when the compensation valve maintains a constant pressure drop at the load retaining valve. However, also the frequently preferred opportunity exists that the compensation valve maintains a constant pressure drop at the return control throttle. In this case the inflow side pressure control and the return side flow control occur in a particularly pronounced way at the control valve.
- Expediently, the compensation valve is arranged in the return path. It may be arranged between the return motor connection and the load retaining valve, between the load retaining valve and the return control throttle or between the return control throttle and the tank connection.
- Another preferred opportunity is that the compensation valve is arranged in a pilot pipe system and additionally influences the pilot pressure for an adjustable throttle. In this connection only a small compensation valve is required, which is interesting for weight and space reasons.
- In a preferred embodiment it is provided that a pilot pipe extending between the inflow motor connection and the tank connection comprises a series connection of a fixed throttle and the compensation valve and therebetween the branching to a pressure surface of the load retaining valve. The fact that the additional control with the compensator overrides the control of the load retaining valves causes that a constant pressure drop can be maintained at the return control throttle.
- Another, also preferred embodiment provides that the compensation valve bypasses the pilot throttle adjustable by means of the control valve. Thus, the overridden control of the auxiliary valve available in the inflow side by means of the compensation valve causes the auxiliary valve to maintain a constant pressure drop at the return control throttle.
- An additional advantage in these latter cases is obtained in that the compensation valve is built into the control valve, which is usually possible because of the small dimensions of the compensation valve.
- An additional advantageous embodiment involves that the load retaining valve is constructed as a pressure relief valve and the return control throttle is open in the neutral position of the control valve. This gives an additional utilisation of the load retaining valve.
- In the following the invention is described on the basis of preferred embodiments on the basis of the drawings, showing:
- Fig. 1
- the connection diagram of a control arrangement according to the invention
- Fig. 2
- an associated working diagram
- Fig. 3
- a second embodiment of a control arrangement according to the invention
- Fig. 4
- a third embodiment
- Fig. 5
- an associated working diagram
- Fig. 6
- a fourth embodiment
- Fig. 7
- a fifth embodiment
- The control arrangement in Fig. 1 operates a motor 1, here shown as a so-called piston-cylinder unit, which can be loaded in the lowering direction by an
external force 2. The diagram only shows the details required of the lowering movement. For the hoisting a usual flow control can be used. - A
control valve 3, which is adjustable manually by a regulating arrangement 4 or via a remote control, has aninflow control throttle 5 in aninflow path 6 extending between a pump connection P and a motor connection A, and a return control throttle 7 in areturn path 8 extending between a return motor connection Bc and a tank connection T. Apilot pipe 9 connects theinflow path 6 at the inlet of theinflow control throttle 5 with thereturn path 8 at the outlet of the return control throttle 7. In this pilot pipe 9 afixed pilot throttle 10 and a pilot throttle adjustable together with the inflow andreturn throttles 5 and 7 are arranged. Theinflow control throttle 5 is connected in series with anauxiliary valve 12, which maintains a constant pressure drop at thefixed pilot throttle 10. This results in a pressure control according to which the motor inflow pressure PA has a value, which is mainly determined by the position of thecontrol valve 3. - In the return path 8 a
compensation valve 13 and aload retaining valve 14 are arranged in series. Theload retaining valve 14 receives the motor inflow pressure PA via apilot pipe 15 and a reference pressure PR via anadditional pilot pipe 16, which reference pressure rules at the outlet B of theload retaining valve 14. Thus the load retaining valve adjusts under the influence of aspring 17 so, that it does not open until the pressure difference PA - PR has overcome the spring force. Thecompensation valve 13 is controlled so that it maintains a constant pressure drop at theload retaining valve 14. The series connection ofcompensation valve 13 and load retainingvalve 14 is bypassed by an antiparallel connection of a pressure relief valve 18 and anon-return valve 19 opening during the lifting movement. - In the working diagram of Fig. 2 the motor inflow pressure PA is applied on the right half via the adjusting path X of the control valve, that is in particular the slide of a proportional valve. In the left half it is shown how the control path Z of the
load retaining valve 14 changes in dependence of the motor inflow pressure PA. The area from 0 to X0 corresponds to the dead band of a proportional valve. Here the pressure is built up from a standby pressure to PO. This pressure is required to overcome the preload of theload retaining valve 14. From X0 to X1 the motor inflow pressure changes from P0 to Pstop, which is the pressure required to move the slide of theload retaining valve 14 towards the end stop. The area from X0 to X1 is the real control area when lowering the load. When the movable part of the motor meets a resistance, for example, is pressed into the earth or has to be packed up, a pressure higher than Pstop may be required. In such cases the slide of the control valve must move beyond X1. This gives a higher motor inflow pressure PA, while the movement speed of the motor is still limited by the opening of theload retaining valve 14 in the position Zmax and from the throttling through the compensation valve. - The vertical line starting at S is idealised. It only appears when the control throttles of the
control valve 3 work without losses, which is not possible in practice. The dash-and-dot line L shows that a certain pressure PA on the motor inflow connection A belongs to a certain position X of the slide of thecontrol valve 3, and that with this motor inflow pressure a certain position Z of the load retaining valve is specified, which position Z in connection with thecompensation valve 13 results in a predetermined return quantity. Thus, on the inlet side it is ensured that in the inflow path 6 a cavitation preventing pressure is maintained and that in thereturn path 8 the quantity drained off is limited. - In the embodiment according to Fig. 3 the slide of the
load retaining valve 114 is loaded in the closing direction by thespring 17 and the reference pressure PR and in the opposite direction by the motor inflow pressure PA and, via anadditional pilot pipe 20, by the inlet pressure PE of theload retaining valve 114. However, the motor inflow pressure PA is still prevailing, which appears from the fact that the pressure chamber connected with thepilot pipe 15 has a larger pressure surface 21 than thepressure surface 22 of the pressure chamber connected with thepilot pipe 20. The pressure surface exposed to the reference pressure through PR is preferably equal to the sum of the pressure surfaces 21 and 22. - The embodiment of Fig. 4 differs from the one in Fig. 3 in that the
compensation valve 13 is connected to the output side of theload retaining valve 114 in thereturn path 8, and that the compensation valve maintains a constant pressure drop at the return control throttle 7. Here again the outlet pressure of theload retaining valve 114 is chosen as reference pressure PR. Further, the function of the pressure relief valve 18 is incorporated in theload retaining valve 114, meaning that thespring 17 gets a corresponding preload and the pressure surface relation is chosen accordingly. The chamber for thespring 17 can be relieved separately from the chamber for the reference pressure PR, for example towards the atmosphere or the tank. - For the embodiment in Fig. 4 the working diagram of Fig. 5 applies, which corresponds to the right half of the diagram of Fig. 2. Here again the area from 0 to X0 forms the dead band of the
control valve 3. Here the motor inflow pressure PA is built up from a small stand-by pressure to a pressure P0, which must be high enough to serve as pilot pressure, to open the load retaining valve withoutavailable force 2. This is explained by the following example: Theload retaining valve 114 has a pilot relation 4:1. As pressure relief valve it is set at 300 bar. Without the force 2 a load pressure of 20 bar is measured due to the own weight. The required pilot pressure PPmax therefore is (300-20)/4 = 70 bar. As shown in Fig. 5, the start pressure P0 at the end of the dead band is slightly larger than this maximum pilot pressure. With aforce 2 the required pilot pressure gets lower. With maximum force, for example 240 bar, the pilot pressure Ppmin = 15 bar. - Thus, it is provided that on each operation the motor inflow pressure PA is so high that the
load retaining valve 114 is opened. When the pressure drop over the return control throttle 7 is then kept constant by thecompensation valve 13, for example at 10 bar, the quantity drained off is so limited that it can do no damage. - In the embodiment according to Fig. 6 the
compensation valve 113 is made as a small pilot valve. It is arranged in apilot pipe 115 in series with a fixed pilot throttle 23. The pick-off 24 arranged between them leads to the pressure chamber with thelarger pressure surface 121 of theload retaining valve 114. Thecompensation valve 113 maintains a constant pressure drop at the return control throttle 7, as deviations are balanced by a superposed adjustment of the slide of theload retaining valve 114. - In the embodiment according to Fig 7 the
compensation valve 113 is again made as a pilot valve. It maintains a constant pressure drop at the return control throttle 7 in that theadjustable pilot throttle 11 is bypassed through apilot branch 25 meaning that the inflow sideauxiliary valve 12 is additionally acted upon. Thecompensation valve 113 can be arranged in the housing or in the slide of thecontrol valve 3. Further, the advantage is obtained that only the required pressure is built up on the outlet side. - Deviations from the embodiments shown are possible within the scope of the appended claims. For example, the compensation valve can also be connected to the output side of the return control throttle.
Claims (15)
- Control arrangement for a hydraulic motor, which is, at least in one working direction, loadable by an external force, with a control valve having for this working direction an inflow control throttle in an inflow path extending between the pump connection and the inflow motor connection and a return control throttle in a return path extending between the return motor connection and the tank connection, with a load retaining valve having a load retaining throttle in the return path, and with a compensation valve maintaining a constant pressure drop at a throttle arranged in the return path, characterised in that the control valve (3) is part of a pressure control in which the motor inflow pressure (PA) is substantially determined by the position of the control valve (3), and that the load retaining valve (14; 114) opens in dependence of the difference between the motor inflow pressure (PA) and a reference pressure (PR), which rules between the load retaining valve (14) and the return control throttle (7).
- Control arrangement according to claim 1, characterised in that the pressure control has a pilot pipe (9) extending between the inflow path (6) and the return path (8), which pilot pipe (9) comprises the series connection of a fixed pilot throttle (10) and a pilot throttle (11) adjustable by means of the control valve (3), as well as an auxiliary valve (12) opening in dependence of the pressure drop at the fixed pilot throttle (10) and arranged in series with the inflow control throttle (5).
- Control arrangement according to claim 1 or 2, characterised in that the load retaining valve (14; 114) has a slide, which is loaded in one direction by the reference pressure (PR) and a spring (17) and in the other direction by the motor inflow pressure (PA).
- Control arrangement according to claim 3, characterised in that the slide is additionally loaded by the inlet pressure (PE) of the load retaining valve (114), the slide having a larger pressure surface (21) for the motor inflow pressure (PA) and a smaller pressure surface (22) for the inlet pressure (PE).
- Control arrangement according to one of the claims 1 to 4, characterised in that the load retaining valve (14; 114) has a spring chamber, which can be pressure-relieved independently of the reference pressure (PR).
- Control arrangement according to one of the claims 1 to 5, characterised in that the compensation valve (13) maintains a constant pressure drop at the load retaining valve (14; 114).
- Control arrangement according to one of the claims 1 to 5, characterised in that the compensation valve (13; 113) maintains a constant pressure drop at the return control throttle (7).
- Control arrangement according to one of the claims 1 to 7, characterised in that the compensation valve (13) is arranged in the return path (8).
- Control arrangement according to claim 8, characterised in that the compensation valve (13 is arranged between the return motor connection (BC) and the load retaining valve (14).
- Control arrangement according to claim 8, characterised in that the compensation valve (13) is arranged between the load retaining valve (114) and the return control throttle (7).
- Control arrangement according to one of the claims 1 to 7, characterised in that the compensation valve (113) is arranged in a pilot pipe system and additionally influences the pilot pressure for an adjustable throttle.
- Control arrangement according to claim 11, characterised in that a pilot pipe (115) extending between the inflow motor connection (A) and the tank connection (T) comprises a series connection of a fixed throttle (23) and the compensation valve (113) and therebetween the branching (24) to a pressure surface (121) of the load retaining valve (114).
- Control arrangement according to claims 2 and 11, characterised in that the compensation valve (113) bypasses the pilot throttle (11) adjustable by means of the control valve (3).
- Control arrangement according to claim 13, characterised in that the compensation valve (114) is built into the control valve (3).
- Control arrangement according to one of the claims 1 to 14, characterised in that the load retaining valve (114) is constructed as a pressure relief valve and the return control throttle (7) is open in the neutral position of the control valve (3).
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE19800721A DE19800721A1 (en) | 1998-01-12 | 1998-01-12 | Control device for a hydraulic motor |
DE19800721 | 1998-01-12 | ||
PCT/DK1999/000009 WO1999035407A1 (en) | 1998-01-12 | 1999-01-08 | Control arrangement for a hydraulic motor |
Publications (2)
Publication Number | Publication Date |
---|---|
EP1045992A1 EP1045992A1 (en) | 2000-10-25 |
EP1045992B1 true EP1045992B1 (en) | 2004-11-24 |
Family
ID=7854325
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP99900439A Expired - Lifetime EP1045992B1 (en) | 1998-01-12 | 1999-01-08 | Control arrangement for a hydraulic motor |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP1045992B1 (en) |
AT (1) | ATE283428T1 (en) |
AU (1) | AU1960299A (en) |
DE (2) | DE19800721A1 (en) |
WO (1) | WO1999035407A1 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7328646B2 (en) | 2004-05-19 | 2008-02-12 | Sauer-Danfoss Aps | Hydraulic valve arrangement |
US7353744B2 (en) | 2004-12-22 | 2008-04-08 | Sauer-Danfoss Aps | Hydraulic control |
Families Citing this family (13)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE10308484A1 (en) * | 2003-02-26 | 2004-09-09 | Bosch Rexroth Ag | Hydraulic control arrangement |
EP1626183B1 (en) * | 2004-08-10 | 2007-01-03 | Walvoil S.p.A. | Inlet section for load sensing directional control valves |
DE102004048642A1 (en) * | 2004-10-04 | 2006-04-06 | Bosch Rexroth Aktiengesellschaft | Hydraulic control arrangement |
US7302797B2 (en) * | 2005-05-31 | 2007-12-04 | Caterpillar Inc. | Hydraulic system having a post-pressure compensator |
DE102005043367B4 (en) * | 2005-09-12 | 2016-09-08 | Laeis Gmbh | Control device and control method for a piston-cylinder arrangement |
JP2007263142A (en) | 2006-03-27 | 2007-10-11 | Toyota Industries Corp | Hydraulic control device |
DE102007027567B4 (en) * | 2007-06-15 | 2018-03-01 | Robert Bosch Gmbh | Control arrangement with pipe rupture function |
DE202011107397U1 (en) | 2011-11-02 | 2011-11-23 | Palfinger Ag | Truck |
IT201700047745A1 (en) * | 2017-05-03 | 2018-11-03 | Cnh Ind Italia Spa | VEHICLE EQUIPPED WITH AN ARM INCLUDING A HYDRAULIC CONTROL CIRCUIT WITH A LOAD CONTROL VALVE |
CN108423550B (en) * | 2017-11-30 | 2019-10-15 | 中船华南船舶机械有限公司 | A kind of crane |
CN108423577B (en) * | 2017-11-30 | 2019-10-15 | 中船华南船舶机械有限公司 | A kind of crane autobalance and force balance system and method |
CN108423549B (en) * | 2017-11-30 | 2019-10-15 | 中船华南船舶机械有限公司 | A kind of crane hydraulic system and working method |
WO2019210341A1 (en) * | 2018-05-04 | 2019-11-07 | Palfinger Ag | Hydraulic system |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE3800188A1 (en) * | 1988-01-07 | 1989-07-20 | Danfoss As | HYDRAULIC SAFETY BRAKE VALVE ARRANGEMENT |
-
1998
- 1998-01-12 DE DE19800721A patent/DE19800721A1/en not_active Withdrawn
-
1999
- 1999-01-08 EP EP99900439A patent/EP1045992B1/en not_active Expired - Lifetime
- 1999-01-08 DE DE69922158T patent/DE69922158T2/en not_active Expired - Lifetime
- 1999-01-08 AU AU19602/99A patent/AU1960299A/en not_active Abandoned
- 1999-01-08 AT AT99900439T patent/ATE283428T1/en not_active IP Right Cessation
- 1999-01-08 WO PCT/DK1999/000009 patent/WO1999035407A1/en active IP Right Grant
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7328646B2 (en) | 2004-05-19 | 2008-02-12 | Sauer-Danfoss Aps | Hydraulic valve arrangement |
US7353744B2 (en) | 2004-12-22 | 2008-04-08 | Sauer-Danfoss Aps | Hydraulic control |
Also Published As
Publication number | Publication date |
---|---|
ATE283428T1 (en) | 2004-12-15 |
EP1045992A1 (en) | 2000-10-25 |
DE69922158D1 (en) | 2004-12-30 |
WO1999035407A1 (en) | 1999-07-15 |
DE19800721A1 (en) | 1999-07-15 |
AU1960299A (en) | 1999-07-26 |
DE69922158T2 (en) | 2005-11-24 |
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