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
• • 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
• • 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
• • 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
• • 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
• • 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
• • 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"
• • 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
• • 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
• • 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
  • F15B2211/31—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
• • 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
• • 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
• • 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
• • 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
  • F15B2211/405—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
• • 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
• • 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
• • 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
  • F15B2211/50—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
• • 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 hydrau- lie 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 inde- pendently 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 de- pendence 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.
• 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.
• 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. 5 an associated working diagram
• 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 lower- ing 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 Be 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
• 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 addi- tional 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 pres- sure to PO. This pressure is required to overcome the preload of the load retaining valve 14.
• From X0 to XI 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 XI is the real control area when lowering the load.
• a pressure higher than P st0 p may be required.
• the slide of the control valve must move beyond XI. This gives a higher motor inflow pressure P A , while the move- ment speed of the motor is still limited by the opening of the load retaining valve 14 in the position Z ax 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 direc- tion 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 ap- pears 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.
• 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.

Applications Claiming Priority (3)

Publications (2)

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• 1998
  • 1998-01-12 DE DE19800721A patent/DE19800721A1/de not_active Withdrawn
• 1999
  • 1999-01-08 DE DE69922158T patent/DE69922158T2/de not_active Expired - Lifetime
  • 1999-01-08 WO PCT/DK1999/000009 patent/WO1999035407A1/en active IP Right Grant
  • 1999-01-08 AT AT99900439T patent/ATE283428T1/de not_active IP Right Cessation
  • 1999-01-08 AU AU19602/99A patent/AU1960299A/en not_active Abandoned
  • 1999-01-08 EP EP99900439A patent/EP1045992B1/de not_active Expired - Lifetime

Non-Patent Citations (1)

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