EP0884483B1 - Differential pressure switch - Google Patents

Differential pressure switch Download PDF

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Publication number
EP0884483B1
EP0884483B1 EP98107635A EP98107635A EP0884483B1 EP 0884483 B1 EP0884483 B1 EP 0884483B1 EP 98107635 A EP98107635 A EP 98107635A EP 98107635 A EP98107635 A EP 98107635A EP 0884483 B1 EP0884483 B1 EP 0884483B1
Authority
EP
European Patent Office
Prior art keywords
pressure
piston
differential
control valve
valve according
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP98107635A
Other languages
German (de)
French (fr)
Other versions
EP0884483A1 (en
Inventor
Martin Dipl. Ing. Heusser
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.)
Hawe Hydraulik GmbH and Co KG
Original Assignee
Hawe Hydraulik GmbH and Co KG
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 Hawe Hydraulik GmbH and Co KG filed Critical Hawe Hydraulik GmbH and Co KG
Publication of EP0884483A1 publication Critical patent/EP0884483A1/en
Application granted granted Critical
Publication of EP0884483B1 publication Critical patent/EP0884483B1/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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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
    • F15B11/028—Systems essentially incorporating special features for controlling the speed or actuating force of an output member for controlling the actuating force
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H35/00—Switches operated by change of a physical condition
    • H01H35/24—Switches operated by change of fluid pressure, by fluid pressure waves, or by change of fluid flow
    • H01H35/38—Switches operated by change of fluid pressure, by fluid pressure waves, or by change of fluid flow actuated by piston and cylinder
    • 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
    • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/205—Systems with pumps
    • F15B2211/2053—Type of pump
    • F15B2211/20538—Type of pump constant capacity
    • 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
    • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/205—Systems with pumps
    • F15B2211/20576—Systems with pumps with multiple pumps
    • F15B2211/20592—Combinations of pumps for supplying high and low 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
    • F15B2211/20—Fluid pressure source, e.g. accumulator or variable axial piston pump
    • F15B2211/21—Systems with pressure sources other than pumps, e.g. with a pyrotechnical charge
    • F15B2211/212—Systems with pressure sources other than pumps, e.g. with a pyrotechnical charge the pressure sources being accumulators
    • 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
    • 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
    • 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
    • F15B2211/31—Directional control characterised by the positions of the valve element
    • F15B2211/3105—Neutral or centre positions
    • F15B2211/3111—Neutral or centre positions the pump port being closed in the centre position, e.g. so-called closed centre
    • 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
    • F15B2211/327—Directional control characterised by the type of actuation electrically or electronically
    • 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
    • F15B2211/41—Flow control characterised by the positions of the valve element
    • F15B2211/411—Flow control characterised by the positions of the valve element the positions being discrete
    • 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
    • F15B2211/41509—Flow control characterised by the connections of the flow control means in the circuit being connected to a pressure source 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
    • F15B2211/426—Flow control characterised by the type of actuation electrically or electronically
    • 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
    • F15B2211/45—Control of bleed-off flow, e.g. control of bypass flow 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
    • F15B2211/50—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
    • F15B2211/50—Pressure control
    • F15B2211/505—Pressure control characterised by the type of pressure control means
    • F15B2211/50554—Pressure control characterised by the type of pressure control means the pressure control means controlling a pressure downstream of the pressure control means, e.g. pressure reducing 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
    • F15B2211/50—Pressure control
    • F15B2211/515—Pressure control characterised by the connections of the pressure control means in the circuit
    • F15B2211/5151—Pressure control characterised by the connections of the pressure control means in the circuit being connected to a pressure source 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
    • F15B2211/50—Pressure control
    • F15B2211/52—Pressure control characterised by the type of actuation
    • F15B2211/528—Pressure 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
    • F15B2211/55—Pressure control for limiting a pressure up to a maximum pressure, e.g. by using a pressure relief 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
    • F15B2211/60—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
    • 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
    • F15B2211/615—Filtering 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
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/625—Accumulators
    • 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
    • F15B2211/63—Electronic controllers
    • F15B2211/6303—Electronic controllers using input signals
    • F15B2211/6306—Electronic controllers using input signals representing a pressure
    • F15B2211/6309—Electronic controllers using input signals representing a pressure the pressure being a pressure source supply 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
    • F15B2211/60—Circuit components or control therefor
    • F15B2211/63—Electronic controllers
    • F15B2211/6303—Electronic controllers using input signals
    • F15B2211/6306—Electronic controllers using input signals representing a pressure
    • F15B2211/6313—Electronic controllers using input signals representing a pressure the pressure being a load 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
    • F15B2211/60—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
    • 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
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/705—Output members, e.g. hydraulic motors or cylinders or control therefor characterised by the type of output members or actuators
    • F15B2211/7051—Linear output members
    • F15B2211/7052—Single-acting output members
    • 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
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/705—Output members, e.g. hydraulic motors or cylinders or control therefor characterised by the type of output members or actuators
    • F15B2211/7051—Linear output members
    • F15B2211/7053—Double-acting output members
    • 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
    • F15B2211/70—Output members, e.g. hydraulic motors or cylinders or control therefor
    • F15B2211/76—Control of force or torque of the output member

Definitions

  • the invention relates to a differential pressure switching valve in the preamble of the claim 1 specified Art.
  • the differential pressure switching valve is used to one higher-level control unit to report if the by means of a proportional pilot valve set clamping pressure in the hydraulic motor of the clamping device Machine tool is reached or if a predetermined ratio between the pilot pressure and the clamping pressure is present. Only then will the control unit conduct another processing step.
  • the movement of the piston assembly will by an analog displacement sensor, a position switch or an electrical Switches scanned with contacts.
  • the structure of the differential pressure switching valve is complex and multi-part.
  • the pilot pressure must be significantly higher than the reference pressure (Clamping pressure) to the piston assembly against the force of one for the Basic position to be able to adjust necessary spring.
  • the high pilot pressure is inconvenient because of the proportional pilot valve and a flow control valve connected to it unavoidable leaks that are proportional to the pressure head occur Maintaining the pilot pressure makes it difficult or impossible, even if the proportional pilot valve is mechanically blocked when a fault occurs. The increased leakage at the high pilot pressure complicates proper Monitoring the clamping pressure. High standards apply to such clamping devices Safety requirements. For example, the clamping pressure in the event of a malfunction held and a correct message to the higher-level control unit are given.
  • a pressure-controlled electrical switching unit known from DE-A-38 19 459 actuates either one provided with two equally large contact surfaces, Pistons pressurized by both pressures against the force using an angle lever the bias spring the electrical switch, or a differential piston with different large contact surfaces the electrical switch via a control curve of the differential piston.
  • a pressure switch which acts on the switching pressure Includes spool, which is via a spring cup with molded plunger actuated the actuating element of the electrical switch.
  • the invention has for its object to provide a differential pressure switching valve that is structurally simple and reliably precise within a large pressure range responsive to the predetermined relationship between the pressures.
  • the switch point of the switch should be independent of the pressure value of the set one Clamping pressure over the entire work area as close as possible to the Clamping pressure.
  • the application area for the pilot pressure is a multiple of the application area for the actual clamping pressure representing the clamping device Reference pressure, can be used to precisely scan the relationship between use a very low pilot pressure, even one Needs to be a fraction of the reference pressure.
  • the to generate the in the jig provided the pilot pressure representing the target clamping pressure Components can be structurally simple due to the low pressure head. Especially the problem of leakages is advantageously eliminated since at the low one Pressure level of the pilot pressure no significant leakage on the pilot side more occurs or a structurally simple measure is sufficient to avoid leakage. This is expedient in a tensioning device in which the pilot pressure is used the clamping pressure is set and monitored and for safety reasons the parent Control unit must be reported whether the clamping pressure is reached, or Not.
  • This message is also used if there is a fault in the system during the Tension pressure must also be maintained and monitored to avoid damage to avoid for the clamping device or the workpiece. Because of the bias spring the switching points of the switch remain scarce over the entire working range under the clamping pressure, so that at low, but reached clamping pressure a Error message and if the clamping pressure is high and the clamping pressure is not reached, a Good reporting can be avoided. Because of the low pilot pressure, the differential pressure switching valve well suited for jigs that are always or only temporarily with very high system pressure, e.g. up to approx. 400 bar or more become. The differential pressure switching valve is structurally simple and due to only less Individual parts compact. The axially interlocking pistons enable an optimal short overall length. The stroke of the piston assembly can be chosen short what the use of a simple, short-stroke switch allows and no gear reduction between the piston assembly and the switch.
  • the ratio between the pressures to be compared sample without interference.
  • the smooth movement of the piston assembly by a Misalignment between pistons is not affected. Furthermore, the smaller; move the second piston loaded by the reference pressure without jamming force, although it mechanically attacks the larger first piston.
  • the biasing spring is directly between in a structurally simple manner the two pistons effective.
  • the bias of the bias spring for example by screwing the lens body or by inserting or removing it change washers as required.
  • the switch compared to that to which the pilot pressure can be applied Chamber sealed, due to the low pilot pressure a simple seal is sufficient here.
  • the switching point of the switch can be adjusted if necessary the switch housing or the switch can be precisely adjusted in the frame.
  • the switch is a small, inexpensive microswitch with a short stroke.
  • an electro-hydraulic clamping device S in Fig. 1 in particular for a Workpiece or tool of a machine tool, the movements of a Hydraulic motor W used for tensioning, and the clamping pressure and possibly monitoring a return pressure to a higher-level, not shown Control unit, e.g. a turning, drilling, milling machine or the like, operation steps display and report whether each operation step is correct or incorrect is executed.
  • the hydraulic motor W reported and whether the predetermined clamping pressure is reached or not, and regardless of the selected clamping pressure level.
  • Two pumps P1 and P2 are provided as pressure sources, which are driven by a motor M to be driven.
  • the pump P1 is for a higher flow rate and a high one System pressure, e.g. for accumulator operation by means of a pressure accumulator 1 ', and connected to a pump line 1 and a return line 2.
  • the pump P2 with a smaller delivery rate is connected to its own pressure line 3 and via one Pressure limiter 4 connected to the return line 2, the pressure limiter 4 the pressure in the further pressure line 3 to a low value, e.g. 25 Bar, limited.
  • Both pumps P1, P2 are constant feed pumps.
  • An essential part of the tensioning device S is a hydraulic control device H with an adjusting device E for the clamping pressure.
  • the setting device is a Proportional pilot valve V and a safety valve F arranged downstream of it, wherein the proportional pilot valve V to one of the further pressure line 3 branching control line 20 connected and with the safety valve is connected via parallel control lines 14, 15.
  • the control line 14 leads one from the proportional pilot valve V depending on the energization of a proportional solenoid P variable pilot pressure, while the control line 15 with an unlocking pressure for the safety valve F (in the embodiment shown a seat valve 7) which can be released hydraulically against a spring 8 can be acted upon.
  • the adjusting valve D is a pressure regulating in the embodiment shown Pressure reducing valve, which via a line 19 to the pump line 1 and a line 21 is connected to the return line 2, and of which one Supply line 17 to a directional control valve consisting of two seat valves J extends, the two seat valves (for example 3/2-way valves) with the Hydromotor W (e.g. a double-acting hydraulic cylinder) via consumer lines 5, 6 are connected.
  • Clamping pressure controlled by the setting valve D depending on the pilot pressure in the control line 12 in accordance with the energization of the proportional magnet P is set and held in its pressure value.
  • a differential pressure switching valve L provided with a switch G, structurally from Adjustment valve D is used separately between the control line 12 and a control line 22.
  • the control line 22 branches off from the consumer line 5 and has one reference pressure derived from the clamping pressure.
  • a throttle 42 can be arranged near the differential pressure switching valve L.
  • the differential pressure switching valve L by a bias spring 23 in the effective direction of the differential pressure.
  • the control valve D is controlled by a control pressure from the supply line 17 and a Control spring 11 acted upon.
  • the control spring 11 is actuated by an actuating piston 10 in a Chamber 9 so loaded that the effective spring force of the control spring 11 directly depends on the pilot pressure which acts in the chamber 9 via the control line 12. Will the pilot pressure by changing the energization of the proportional solenoid P raised, then the clamping pressure is raised accordingly, and vice versa.
  • the safety valve F by the spring 8 in the in Fig. 1st Shut-off position shown is adjusted before the pilot pressure in the control line 12 can fall off.
  • the adjusting valve D keeps the clamping pressure at the set one Height.
  • the differential pressure switching valve L with its switch G is also then still able to correctly report whether the clamping pressure is present or not.
  • the clamping pressure can be up to 400 bar or more, while the pilot pressure in the control line 12 is less than that set by the pressure limiter 4 Pressure in the further pump line 3. It can, for example: only between 3 and 20 Bar, i.e. only a fraction of the clamping pressure.
  • the hydraulic motor W like the directional control valve J designed as a seat valve leakproof. Leak tightness is also given with adjusting valve D, such as also in the differential pressure switching valve L and in the safety valve in the shut-off position F. This means that the clamping pressure or reference pressure in the Control line 22 as well as the pilot pressure in the control line 12 over considerable Time can be kept unchanged.
  • the directional control valve J could be a single one, e.g. 4/3-way control valve, expediently in seat valve design.
  • a single pump could also serve as a pressure source, whereby then appropriately an additional pressure reducing valve upstream of the proportional pilot valve V. is provided in the control line 20 to the input pressure of the proportional pilot valve V to the sufficient for the low pilot pressure To reduce the pressure height.
  • the control line 20 could be from the Branch off pump line 1 or pressure line 19.
  • the differential pressure switching valve L structurally combined with the switch G in FIG. 2 has in a housing 24 a housing bore 25 in which a first piston 26, expediently a pot piston, sealed with a large contact area A1 is movable.
  • the piston 26 carries a plunger 27, which is on an actuating element 28 of the switch G designed as a microswitch is aligned and penetrates a sealing body 29 containing a seal 30, which the Switch G facing the end of the housing bore 25 closes.
  • the first piston 26 dips from the surface facing away from the action surface A1 Side a coaxial second piston 31, which has a cylinder portion 32 with an acting surface A2 has, which is significantly smaller than the exposure area A1.
  • the ratio between the application areas A2 and A1 can be between 1: 5 and about 1:25, and is preferably about 1:15 to 1:20.
  • the second piston 31 preferably has an axial distance from the cylinder section 32 spherical driver head 33, which with a driver surface 34 in the first Piston 26 cooperates and one that transmits movement to the right in FIG. 2 Coupling forms.
  • the driver surface 24 is conical, on the one hand around the second piston 31 in addition to lead, on the other hand to any relative movements between the Allow pistons 26, 31.
  • a disk body 35 is positioned in the housing bore 25 and has a guide bore 36 for the cylinder section 32 of the second piston 31 contains.
  • the lead length the guide bore 36 is advantageously shorter than the diameter of the cylinder section 32.
  • the switch G is contained in a switch housing 43, which is in a frame 44 is fixed to the housing 24 and may be used to adjust the switching point of the actuating element 28 in the axial direction of the housing bore 25 can be adjusted.
  • the biasing spring 23 (see FIG. 1) has one end on the disc body 35 supported and is at its other end on a ring 45, the is intercepted on the driver head 33.
  • the switch G is with that, not shown higher-level control unit of the tensioning device is electrically connected.
  • the interior of the first piston 26 and the space between the housing 24 and the frame 44 are relieved of pressure to the return T.
  • the differential pressure switching valve L is in a switching position in which the clamping pressure is reported because the plunger 27 pressed the actuating element 28 Has.
  • the pilot pressure acts on the larger area A1 while the reference pressure acts on the smaller loading area A2, the Via the driver head 33, the first piston 26, for example until it comes into contact with Sealing body 29, adjusted.
  • the bias spring 23 acts in the same direction as that Reference pressure on the contact surface A2. Falls with unchanged Pilot pressure the reference pressure, then the first piston 26 in Fig. 2 to the left moves until the plunger 27 releases the actuator 28.
  • the switch G reports "Tension pressure not available".
  • the switching point of switch G must be independent of the pressure value of the clamping pressure are just below the clamping pressure. Were the bias spring 23 not would then exist for low clamping pressure below this low The corresponding switching point of the switch at high clamping pressure are too far below the high clamping pressure. The desk would respond too early at high clamping pressure and a faulty good signal submit.
  • the ratio between the application areas A2 and A1 adjusted so that the switch point of the switch at high clamping pressure would be optimally just below the high clamping pressure, then the corresponding would be Switching point at a low switching point above the low clamping pressure, so that no good signal would be generated at low clamping pressure.
  • the bias spring 23 causes an adjustment of the line of the switching points (the line of the switching pressures) to the Span pressure line over the entire work area so that the two lines in the are essentially parallel to each other and the switching points for all clamping pressures only are just below the respective clamping pressure.
  • the differential pressure switching valve D with its switch G is therefore able to operate over a very wide clamping pressure range generate correct and meaningful signals, i.e. The relation between the reference pressure and the low clamping pressure regardless of the height of the reference pressure or the pilot pressure.
  • differential pressure switching valve can be constructed differently with the same function.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Switches Operated By Changes In Physical Conditions (AREA)
  • Fluid-Driven Valves (AREA)
  • Fluid-Pressure Circuits (AREA)
  • Measuring Fluid Pressure (AREA)
  • Vehicle Body Suspensions (AREA)
  • Safety Valves (AREA)

Abstract

The valve (G) has an electric switch (G) for monitoring the clamp pressure, with a housing bore (25) receiving a piston device displaced axially relative to a switch operating element (28). The piston device has a pair of different size surfaces (A2,A1) acted on by a reference pressure representing the actual pressure and a pre-control pressure determining the required clamp pressure, respectively. The piston is also acted on by a spring (23) in the direction of the reference pressure.

Description

Die Erfindung betrifft ein Differenzdruck-Schaltventil der im Oberbegriff des Anspruchs 1 angegebenen Art.The invention relates to a differential pressure switching valve in the preamble of the claim 1 specified Art.

Gemäß DE-A-44 46 538 wird das Differenzdruck-Schaltventil verwendet, um einer übergeordneten Steuereinheit zu melden, wenn der mittels eines Proportional-Vorsteuerventils eingestellte Spanndruck im Hydromotor der Spannvorrichtung der Werkzeugmaschine erreicht ist bzw. wenn ein vorbestimmtes Verhältnis zwischen dem Vorsteuerdruck und dem Spanndruck vorliegt. Die Steuereinheit leitet erst dann einen weiteren Bearbeitungsschritt ein. Die Bewegung der Kolbenanordnung wird durch einen Analog-Wegaufnehmer, einen Stellungsschalter oder einen elektrischen Schalter mit Kontakten abgetastet. Der Aufbau des Differenzdruck-Schaltventils ist aufwendig und vielteilig. Der Vorsteuerdruck muß deutlich höher sein als der Referenzdruck (Spanndruck), um die Kolbenanordnung gegen die Kraft einer für die Grundstellung notwendigen Feder verstellen zu können. Der hohe Vorsteuerdruck ist ungünstig, da im Proportional-Vorsteuerventil und einem damit verbundenen Stromregelventil unvermeidbare, der Druckhöhe proportionale Leckagen auftreten, die das Aufrechthalten des Vorsteuerdrucks erschweren oder unmöglich machen, selbst wenn das Proportional-Vorsteuerventil bei Eintritt einer Störung mechanisch blockiert wird. Die bei dem hohen Vorsteuerdruck verstärkte Leckagen erschweren eine ordnungsgemäße Überwachung des Spanndrucks. Für solche Spannvorrichtungen gelten hohe Sicherheitsanforderungen. Beispielsweise müssen der Spanndruck bei einer Betriebsstörung gehalten und eine korrekte Meldung an die übergeordnete Steuereinheit gegeben werden.According to DE-A-44 46 538 the differential pressure switching valve is used to one higher-level control unit to report if the by means of a proportional pilot valve set clamping pressure in the hydraulic motor of the clamping device Machine tool is reached or if a predetermined ratio between the pilot pressure and the clamping pressure is present. Only then will the control unit conduct another processing step. The movement of the piston assembly will by an analog displacement sensor, a position switch or an electrical Switches scanned with contacts. The structure of the differential pressure switching valve is complex and multi-part. The pilot pressure must be significantly higher than the reference pressure (Clamping pressure) to the piston assembly against the force of one for the Basic position to be able to adjust necessary spring. The high pilot pressure is inconvenient because of the proportional pilot valve and a flow control valve connected to it unavoidable leaks that are proportional to the pressure head occur Maintaining the pilot pressure makes it difficult or impossible, even if the proportional pilot valve is mechanically blocked when a fault occurs. The increased leakage at the high pilot pressure complicates proper Monitoring the clamping pressure. High standards apply to such clamping devices Safety requirements. For example, the clamping pressure in the event of a malfunction held and a correct message to the higher-level control unit are given.

Bei einer aus DE-A-38 19 459 bekannten, druckgesteuerten elektrischen Schalteinheit betätigt entweder ein mit zwei gleich großen Beaufschlagungsflächen versehener, von beiden Drücken beaufschlagter Kolben über eine Winkelhebel gegen die Kraft der Vorspannfeder den elektrischen Schalter, oder ein Differentialkolben mit unterschiedlich großen Beaufschlagungsflächen den elektrischen Schalter über eine Steuerkurve des Differentialkolbens. In a pressure-controlled electrical switching unit known from DE-A-38 19 459 actuates either one provided with two equally large contact surfaces, Pistons pressurized by both pressures against the force using an angle lever the bias spring the electrical switch, or a differential piston with different large contact surfaces the electrical switch via a control curve of the differential piston.

Aus US-A-3 419 692 ist ein Druckschalter bekannt, der einen vom Schaltdruck beaufschlagten Schieberkolben enthält, der über einen Federtopf mit angeformtem Stößel das Betätigungselement des elektrischen Schalters betätigt.From US-A-3 419 692 a pressure switch is known which acts on the switching pressure Includes spool, which is via a spring cup with molded plunger actuated the actuating element of the electrical switch.

Weiterer Stand der Technik ist enthalten in DE-B-23 10 193 und DE-A-22 19 928.Further prior art is contained in DE-B-23 10 193 and DE-A-22 19 928.

Der Erfindung liegt die Aufgabe zugrunde, ein Differenzdruck-Schaltventil zu schaffen, das baulich einfach ist und zuverlässig innerhalb eines großen Druckbereiches präzise auf das vorbestimmte Verhältnis zwischen den Drücken anspricht. Insbesondere soll der Schaltpunkt des Schalters unabhängig vom Druckwert des jeweils eingestellten Spanndrucks über den gesamten Arbeitsbereich möglichst knapp unter dem Spanndruck liegen.The invention has for its object to provide a differential pressure switching valve that is structurally simple and reliably precise within a large pressure range responsive to the predetermined relationship between the pressures. In particular the switch point of the switch should be independent of the pressure value of the set one Clamping pressure over the entire work area as close as possible to the Clamping pressure.

Die gestellte Aufgabe wird mit den Merkmalen des Anspruchs 1 gelöst.The object is achieved with the features of claim 1.

Da die Beaufschlagungsfläche für den Vorsteuerdruck ein Vielfaches der Beaufschlagungsfläche für den in der Spannungsvorrichtung den Ist-Spanndruck repräsentierenden Referenzdruck ist, läßt sich zum präzisen Abtasten des Verhältnisses zwischen den Drücken ein sehr niedriger Vorsteuerdruck verwenden, der sogar nur ein Bruchteil des Referenzdrucks zu sein braucht. Die zum Erzeugen des in der Spannvorrichtung den Soll-Spanndruck repräsentierenden Vorsteuerdrucks vorgesehenen Komponenten können wegen der geringen Druckhöhe baulich einfach sein. Besonders vorteilhaft wird das Problem der Leckagen eliminiert, da bei dem niedrigen Druckniveau des Vorsteuerdrucks keine nennenswerte Leckage auf der Vorsteuerseite mehr auftritt bzw. baulich einfache Maßnahme ausreichen, Leckage zu vermeiden. Dies ist in einer Spannvorrichtung zweckmäßig, bei der mittels des Vorsteuerdrucks der Spanndruck eingestellt und überwacht und aus Sicherheitsgründen der übergeordneten Steuereinheit gemeldet werden muß, ob der Spanndruck erreicht ist, oder nicht. Diese Meldung wird auch bei einer Störung im System gebraucht, während der Spanndruck auch aufrechterhalten und überwacht werden muß, um einen Schaden für die Spannvorrichtung bzw. das Werkstück zu vermeiden. Wegen der Vorspannfeder bleiben die Schaltpunkte des Schalters über den gesamten Arbeitsbereich knapp unter dem Spanndruck, so daß bei niedrigem, jedoch erreichten Spanndruck eine Fehlermeldung und bei hohem Spanndruck und nicht erreichtem Spanndruck eine Gutmeldung vermieden werden. Wegen des niedrigen Vorsteuerdrucks ist das Differenzdruck-Schaltventil für Spannvorrichtungen gut geeignet, die stets oder nur vorübergehend mit sehr hohem Systemdruck, z.B. bis ca. 400 Bar oder mehr, betrieben werden. Das Differenzdruck-Schaltventil ist baulich einfach und aufgrund nur weniger Einzelteile kompakt. Die axial ineinandergreifenden Kolben ermöglichen eine optimal kurze Baulänge. Der Hubweg der Kolbenanordnung kann kurz gewählt werden, was die Verwendung eines einfachen, kurzhubigen Schalters erlaubt und keiner Bewegungsuntersetzung zwischen der Kolbenanordnung und dem Schalter bedarf.Since the application area for the pilot pressure is a multiple of the application area for the actual clamping pressure representing the clamping device Reference pressure, can be used to precisely scan the relationship between use a very low pilot pressure, even one Needs to be a fraction of the reference pressure. The to generate the in the jig provided the pilot pressure representing the target clamping pressure Components can be structurally simple due to the low pressure head. Especially the problem of leakages is advantageously eliminated since at the low one Pressure level of the pilot pressure no significant leakage on the pilot side more occurs or a structurally simple measure is sufficient to avoid leakage. This is expedient in a tensioning device in which the pilot pressure is used the clamping pressure is set and monitored and for safety reasons the parent Control unit must be reported whether the clamping pressure is reached, or Not. This message is also used if there is a fault in the system during the Tension pressure must also be maintained and monitored to avoid damage to avoid for the clamping device or the workpiece. Because of the bias spring the switching points of the switch remain scarce over the entire working range under the clamping pressure, so that at low, but reached clamping pressure a Error message and if the clamping pressure is high and the clamping pressure is not reached, a Good reporting can be avoided. Because of the low pilot pressure, the differential pressure switching valve well suited for jigs that are always or only temporarily with very high system pressure, e.g. up to approx. 400 bar or more become. The differential pressure switching valve is structurally simple and due to only less Individual parts compact. The axially interlocking pistons enable an optimal short overall length. The stroke of the piston assembly can be chosen short what the use of a simple, short-stroke switch allows and no gear reduction between the piston assembly and the switch.

Gemäß Anspruch 2 wird mit einem Topfkolben eine kompakte Baugröße ermöglicht.According to claim 2, a compact size is made possible with a pot piston.

Gemäß Anspruch 3 wird mit einem Verhältnis von beispielsweise 1:20 für einen Spanndruck von 400 Bar nur ein Vorsteuerdruck von 20 Bar eingesetzt, was die Druckregelung auf der Vorsteuerseite erheblich vereinfacht und die Ansprechgenauigkeit beeinflussende Leckageverluste vermeidet.According to claim 3 with a ratio of 1:20 for example Clamping pressure of 400 bar only a pilot pressure of 20 bar is used, which the Pressure control on the pilot side is considerably simplified and the response accuracy avoids influencing leakage losses.

Gemäß Anspruch 4 läßt sich das Verhältnis zwischen den zu vergleichenden Drücken ohne Störeinflüsse abtasten.According to claim 4, the ratio between the pressures to be compared sample without interference.

Gemäß Anspruch 5 werden Einflüsse von Fertigungstoleranzen auf die leichtgängige Bewegung der Kolbenanordnung vermieden. Diese Kopplung zwischen den Kolben toleriert auch geringfügige Fehlausrichtungen zwischen den Kolben.According to claim 5 influences of manufacturing tolerances on the smooth Avoid movement of the piston assembly. This coupling between the pistons also tolerates slight misalignment between pistons.

Gemäß Anspruch 6 ergibt sich eine baulich einfache und funktionssichere sowie leichtgängige Dichtführung für den vom Referenzdruck beaufschlagten Kolben.According to claim 6 results in a structurally simple and reliable as well smooth sealing guide for the piston loaded by the reference pressure.

Gemäß Anspruch 7 wird die leichtgängige Bewegung der Kolbenanordnung durch eine Fehlausrichtung zwischen den Kolben nicht beeinträchtigt. Ferner kann sich der kleinere; vom Referenzdruck beaufschlagte zweite Kolben klemmkraftfrei bewegen, obwohl er am größeren ersten Kolben mechanisch angreift. According to claim 7, the smooth movement of the piston assembly by a Misalignment between pistons is not affected. Furthermore, the smaller; move the second piston loaded by the reference pressure without jamming force, although it mechanically attacks the larger first piston.

Gemäß Anspruch 8 ergeben sich einfache Herstellung und Montage und trotz leichtgängiger Bewegung des kleineren Kolbens eine gute Dichtwirkung. Die Drosselöffnung erlaubt ein gedämpftes Ansprechen bei Druckschwankungen.According to claim 8 simple manufacture and assembly result and despite smooth operation Movement of the smaller piston has a good sealing effect. The throttle opening allows a damped response in the event of pressure fluctuations.

Gemäß Anspruch 9 ist die Vorspannfeder auf baulich einfache Weise direkt zwischen den beiden Kolben wirksam.According to claim 9, the biasing spring is directly between in a structurally simple manner the two pistons effective.

Gemäß Anspruch 10 läßt sich die Vorspannung der Vorspannfeder beispielsweise durch Verschrauben des Scheibenkörpers oder durch Einsetzen oder Herausnehmen von Unterlegteilen nach Wunsch verändern.According to claim 10, the bias of the bias spring, for example by screwing the lens body or by inserting or removing it change washers as required.

Gemäß Anspruch 11 wird der Schalter gegenüber der mit dem Vorsteuerdruck beaufschlagbaren Kammer abgedichtet, wobei aufgrund des niedrigen Vorsteuerdrucks eine hier einfache Dichtung ausreicht.According to claim 11, the switch compared to that to which the pilot pressure can be applied Chamber sealed, due to the low pilot pressure a simple seal is sufficient here.

Gemäß Anspruch 12 kann der Schaltpunkt des Schalters bei Bedarf durch Verstellen des Schaltergehäuses oder des Schalters in dem Rahmen präzise einjustiert werden.According to claim 12, the switching point of the switch can be adjusted if necessary the switch housing or the switch can be precisely adjusted in the frame.

Gemäß Anspruch 13 ist der Schalter ein kleinbauender, kostengünstiger Mikroschalter mit kurzem Hub.According to claim 13, the switch is a small, inexpensive microswitch with a short stroke.

Anhand der Zeichnung wird eine Ausführungsform des Erfindungsgegenstandes erläutert. Es zeigen:

Fig. 1
ein Blockschaltbild einer Spannvorrichtung mit wenigstens einem eine Bewegungsrichtung eines Hydromotors überwachenden Differenzdruck-Schaltventil, und
Fig. 2
einen Längsschnitt durch eine Ausführungsform des Differenzdruck-Schaltventils.
An embodiment of the subject matter of the invention is explained with the aid of the drawing. Show it:
Fig. 1
a block diagram of a tensioning device with at least one differential pressure switching valve monitoring a direction of movement of a hydraulic motor, and
Fig. 2
a longitudinal section through an embodiment of the differential pressure switching valve.

In einer elektrohydraulischen Spannvorrichtung S in Fig. 1, insbesondere für ein Werkstück oder Werkzeug einer Werkzeugmaschine, werden die Bewegungen eines zum Spannen verwendeten Hydromotors W gesteuert, und werden der Spanndruck und gegebenenfalls ein Rückholdruck überwacht, um einer übergeordneten, nicht gezeigten Steuereinheit, z.B. einer Dreh-, Bohr-, Fräs-Maschine oder dgl., Operationsschritte anzuzeigen und zu melden, ob jeder Operationsschritt korrekt oder fehlerhaft ausgeführt ist. Es wird eine ordnungsgemäße Beaufschlagung des Hydromotors W gemeldet und ob der vorbestimmte Spanndruck erreicht oder nicht erreicht ist, und zwar unabhängig von der gewählten Höhe des Spanndrucks.In an electro-hydraulic clamping device S in Fig. 1, in particular for a Workpiece or tool of a machine tool, the movements of a Hydraulic motor W used for tensioning, and the clamping pressure and possibly monitoring a return pressure to a higher-level, not shown Control unit, e.g. a turning, drilling, milling machine or the like, operation steps display and report whether each operation step is correct or incorrect is executed. The hydraulic motor W reported and whether the predetermined clamping pressure is reached or not, and regardless of the selected clamping pressure level.

Als Druckquelle sind zwei Pumpen P1 und P2 vorgesehen, die von einem Motor M getrieben werden. Die Pumpe P1 ist für eine größere Förderleistung und einen hohen Systemdruck ausgelegt, z.B. für Speicheriadebetrieb mittels eines Druckspeichers 1', und an eine Pumpenleitung 1 sowie eine Rücklaufleitung 2 angeschlossen. Die Pumpe P2 mit kleinerer Förderleistung ist an eine eigene Druckleitung 3 und über einen Druckbegrenzer 4 an die Rücklaufleitung 2 angeschlossen, wobei der Druckbegrenzer 4 den Druck in der weiteren Druckleitung 3 auf einen niedrigen Wert, z.B. 25 Bar, begrenzt. Beide Pumpen P1, P2 sind Konstantförderpumpen.Two pumps P1 and P2 are provided as pressure sources, which are driven by a motor M to be driven. The pump P1 is for a higher flow rate and a high one System pressure, e.g. for accumulator operation by means of a pressure accumulator 1 ', and connected to a pump line 1 and a return line 2. The pump P2 with a smaller delivery rate is connected to its own pressure line 3 and via one Pressure limiter 4 connected to the return line 2, the pressure limiter 4 the pressure in the further pressure line 3 to a low value, e.g. 25 Bar, limited. Both pumps P1, P2 are constant feed pumps.

Ein wesentlicher Teil der Spannvorrichtung S ist eine hydraulische Steuervorrichtung H mit einer Einstellvorrichtung E für den Spanndruck. In der Einstellvorrichtung ist ein Proportional-Vorsteuerventil V und diesem nachgeordnet ein Sicherheitsventil F angeordnet, wobei das Proportional-Vorsteuerventil V an eine von der weiteren Druckleitung 3 abzweigende Steuerleitung 20 angeschlossen und mit dem Sicherheitsventil über parallele Steuerleitungen 14, 15 verbunden ist. Die Steuerleitung 14 führt einen vom Proportional-Vorsteuerventil V in Abhängigkeit von der Bestromung eines Proportionalmagneten P variierbaren Vorsteuerdruck, während die Steuerleitung 15 mit einem Entsperrdruck für das Sicherheitsventil F (bei der gezeigten Ausführungsform ein hydraulisch gegen eine Feder 8 entsperrbares Sitzventil 7) beaufschlagbar ist. Mit dem Vorsteuerdruck in der Steuerleitung 14, die sich stromab des Sicherheitsventils F als Steuerleitung 12 fortsetzt, wird der mittels eines Einstellventils D regelbare Spanndruck eingestellt. Das Einstellventil D ist in der gezeigten Ausführungsform ein druckregelndes Druckminderventil, das über eine Leitung 19 an die Pumpenleitung 1 und eine Leitung 21 an die Rücklaufleitung 2 angeschlossen ist, und von dem sich eine Versorgungsleitung 17 zu einem aus zwei Sitzventilen bestehenden Wegesteuerventil J erstreckt, wobei die beiden Sitzventile (beispielsweise 3/2-Wegeventile) mit dem Hydromotor W (z.B. einen doppeltwirkenden Hydraulikzylinder) über Verbraucherleitungen 5, 6 verbunden sind. in der Verbraucherleitung 5 wird beispielsweise der Spanndruck eingesteuert, der vom Einstellventil D in Abhängigkeit vom Vorsteuerdruck in der Steuerleitung 12 nach Maßgabe der Bestromung des Proportionalmagneten P in seinem Druckwert eingestellt und gehalten wird. Zur Überwachung des Spanndrucks und zum Melden, ob der Spanndruck erreicht ist, oder nicht, ist ein Differenzdruck-Schaltventil L mit einem Schalter G vorgesehen, und zwar baulich vom Einstellventil D getrennt zwischen die Steuerleitung 12 und eine Steuerleitung 22 eingesetzt. Die Steuerleitung 22 zweigt von der Verbraucherleitung 5 ab und ist mit einem vom Spanndruck abgeleiteten Referenzdruck beaufschlagt. In der Steuerleitung 22 kann nahe dem Differenzdruck-Schaltventil L eine Drossel 42 angeordnet sein. Ferner wird das Differenzdruck-Schaltventil L durch eine Vorspannfeder 23 in Wirkrichtung des Differenzdrucks beaufschlagt.An essential part of the tensioning device S is a hydraulic control device H with an adjusting device E for the clamping pressure. In the setting device is a Proportional pilot valve V and a safety valve F arranged downstream of it, wherein the proportional pilot valve V to one of the further pressure line 3 branching control line 20 connected and with the safety valve is connected via parallel control lines 14, 15. The control line 14 leads one from the proportional pilot valve V depending on the energization of a proportional solenoid P variable pilot pressure, while the control line 15 with an unlocking pressure for the safety valve F (in the embodiment shown a seat valve 7) which can be released hydraulically against a spring 8 can be acted upon. With the pilot pressure in the control line 14, which is downstream of the safety valve F continues as the control line 12, the clamping pressure which can be regulated by means of a setting valve D is increased set. The adjusting valve D is a pressure regulating in the embodiment shown Pressure reducing valve, which via a line 19 to the pump line 1 and a line 21 is connected to the return line 2, and of which one Supply line 17 to a directional control valve consisting of two seat valves J extends, the two seat valves (for example 3/2-way valves) with the Hydromotor W (e.g. a double-acting hydraulic cylinder) via consumer lines 5, 6 are connected. in the consumer line 5, for example Clamping pressure controlled by the setting valve D depending on the pilot pressure in the control line 12 in accordance with the energization of the proportional magnet P is set and held in its pressure value. To monitor the Clamping pressure and for reporting whether the clamping pressure has been reached or not is a differential pressure switching valve L provided with a switch G, structurally from Adjustment valve D is used separately between the control line 12 and a control line 22. The control line 22 branches off from the consumer line 5 and has one reference pressure derived from the clamping pressure. In the control line 22, a throttle 42 can be arranged near the differential pressure switching valve L. Furthermore, the differential pressure switching valve L by a bias spring 23 in the effective direction of the differential pressure.

Das Einstellventil D wird durch einen Steuerdruck aus Versorgungsleitung 17 und eine Regelfeder 11 beaufschlagt. Die Regelfeder 11 wird durch einen Stellkolben 10 in einer Kammer 9 derart belastet, daß die wirksame Federkraft der Regelfeder 11 direkt vom Vorsteuerdruck abhängt, der über die Steuerleitung 12 in der Kammer 9 wirkt. Wird der Vorsteuerdruck durch Änderung der Bestromung des Proportionalmagneten P angehoben, dann wird auch der Spanndruck entsprechend angehoben, und umgekehrt.The control valve D is controlled by a control pressure from the supply line 17 and a Control spring 11 acted upon. The control spring 11 is actuated by an actuating piston 10 in a Chamber 9 so loaded that the effective spring force of the control spring 11 directly depends on the pilot pressure which acts in the chamber 9 via the control line 12. Will the pilot pressure by changing the energization of the proportional solenoid P raised, then the clamping pressure is raised accordingly, and vice versa.

Bei einer Funktionsstörung, z.B. einem Stromausfall, einem Kabelbruch, einem Leitungsbruch oder dgl., wird das Sicherheitsventil F durch die Feder 8 in die in Fig. 1 gezeigte Absperrstellung verstellt, ehe der Vorsteuerdruck in der Steuerleitung 12 abfallen kann. Dadurch hält das Einstellventil D, den Spanndruck auf der eingestellten Höhe. Ferner ist das Differenzdruck-Schaltventil L mit seinem Schalter G auch dann noch in der Lage, korrekt zu melden, ob der Spanndruck vorhanden ist, oder nicht. Der Spanndruck kann bis zu 400 Bar oder mehr betragen, während der Vorsteuerdruck in der Steuerleitung 12 geringer ist als der durch den Druckbegrenzer 4 eingestellte Druck in der weiteren Pumpenleitung 3. Er kann z.B.: nur zwischen 3 und 20 Bar betragen, d.h. nur einen Bruchteil des Spanndrucks. In the event of a malfunction, e.g. a power failure, a cable break, a line break or the like., The safety valve F by the spring 8 in the in Fig. 1st Shut-off position shown is adjusted before the pilot pressure in the control line 12 can fall off. As a result, the adjusting valve D keeps the clamping pressure at the set one Height. Furthermore, the differential pressure switching valve L with its switch G is also then still able to correctly report whether the clamping pressure is present or not. The clamping pressure can be up to 400 bar or more, while the pilot pressure in the control line 12 is less than that set by the pressure limiter 4 Pressure in the further pump line 3. It can, for example: only between 3 and 20 Bar, i.e. only a fraction of the clamping pressure.

Der Hydromotor W kann wie das als Sitzventil ausgebildete Wegesteuerventil J leckagedicht sein. Beim Einstellventil D ist Leckagedichtheit ebenfalls gegeben, wie auch im Differenzdruck-Schaltventil L und im in der Absperrstellung befindlichen Sicherheitsventil F. Dies bedeutet, daß der Spanndruck bzw. Referenzdruck in der Steuerleitung 22 wie auch der Vorsteuerdruck in der Steuerleitung 12 über beträchtliche Zeit unverändert gehalten werden.The hydraulic motor W, like the directional control valve J designed as a seat valve leakproof. Leak tightness is also given with adjusting valve D, such as also in the differential pressure switching valve L and in the safety valve in the shut-off position F. This means that the clamping pressure or reference pressure in the Control line 22 as well as the pilot pressure in the control line 12 over considerable Time can be kept unchanged.

Zum Detailaufbau des Proportional-Vorsteuerventils V und des Sicherheitsventils F wird auf DE-A-44 23 541 und DE-A-44 23 585 hingewiesen.For the detailed structure of the proportional pilot valve V and the safety valve F reference is made to DE-A-44 23 541 and DE-A-44 23 585.

Anstelle des als regelndes Druckminderventil ausgebildeten Einstellventils D könnte auch ein mittels der Regelfeder 11 und dem Stellkolben arbeitendes Druckbegrenzungsventil 10 vorgesehen sein. Das Wegesteuerventil J könnte ein einziges, z.B. 4/3-Wegesteuerventil sein, zweckmäßigerweise in Sitzventilbauweise. Anstelle der zwei Pumpen P1, P2 könnte auch eine einzige Pumpe als Druckquelle dienen, wobei dann zweckmäßigerweise vor dem Proportional-Vorsteuerventil V ein Zusatz-Druckminderventil in der Steuerleitung 20 vorgesehen ist, um den Eingangsdruck des Proportional-Vorsteuerventils V auf die für den niedrigen Vorsteuerdruck ausreichende Druckhöhe zu mindern. Bei nur einer Pumpe könnte die Steuerleitung 20 von der Pumpenleitung 1 oder der Druckleitung 19 abzweigen.Instead of the adjusting valve D designed as a regulating pressure reducing valve also a pressure relief valve working by means of the control spring 11 and the adjusting piston 10 may be provided. The directional control valve J could be a single one, e.g. 4/3-way control valve, expediently in seat valve design. Instead of two pumps P1, P2 a single pump could also serve as a pressure source, whereby then appropriately an additional pressure reducing valve upstream of the proportional pilot valve V. is provided in the control line 20 to the input pressure of the proportional pilot valve V to the sufficient for the low pilot pressure To reduce the pressure height. With only one pump, the control line 20 could be from the Branch off pump line 1 or pressure line 19.

Das in Fig. 2 mit dem Schalter G baulich vereinigte Differenzdruck-Schaltventil L weist in einem Gehäuse 24 eine Gehäusebohrung 25 auf, in der ein erster Kolben 26, zweckmäßigerweise ein Topfkolben, mit einer großen Beaufschlagungsfläche A1 abgedichtet verschieblich ist. Der Kolben 26 trägt einen Stößel 27, der auf ein Betätigungselement 28 des als Mikroschalter ausgebildeten Schalters G ausgerichtet ist und einen eine Dichtung 30 enthaltenden Dichtkörper 29 durchsetzt, der das dem Schalter G zugewandte Ende der Gehäusebohrung 25 verschließt.The differential pressure switching valve L structurally combined with the switch G in FIG. 2 has in a housing 24 a housing bore 25 in which a first piston 26, expediently a pot piston, sealed with a large contact area A1 is movable. The piston 26 carries a plunger 27, which is on an actuating element 28 of the switch G designed as a microswitch is aligned and penetrates a sealing body 29 containing a seal 30, which the Switch G facing the end of the housing bore 25 closes.

In den ersten Kolben 26 taucht von der der Beaufschlagungsfläche A1 abgewandten Seite ein koaxialer zweiter Kolben 31 ein, der einen Zylinderabschnitt 32 mit einer Beaufschlagungsfläche A2 aufweist, die erheblich kleiner ist als die Beaufschlagungsfläche A1. Das Verhältnis zwischen den Beaufschlagungsflächen A2 und A1 kann zwischen 1:5 und ca. 1:25 betragen, und liegt vorzugsweise bei etwa 1:15 bis 1:20.The first piston 26 dips from the surface facing away from the action surface A1 Side a coaxial second piston 31, which has a cylinder portion 32 with an acting surface A2 has, which is significantly smaller than the exposure area A1. The ratio between the application areas A2 and A1 can be between 1: 5 and about 1:25, and is preferably about 1:15 to 1:20.

Der zweite Kolben 31 weist in axialem Abstand vom Zylinderabschnitt 32 einen vorzugsweise balligen Mitnehmerkopf 33 auf, der mit einer Mitnehmerfläche 34 im ersten Kolben 26 zusammenarbeitet und eine in Fig. 2 nach rechts bewegungsübertragende Kupplung bildet. Die Mitnehmerfläche 24 ist kegelig, einerseits um den zweiten Kolben 31 zusätzlich zu führen, andererseits um etwaige Relativbewegungen zwischen den Kolben 26, 31 zu erlauben.The second piston 31 preferably has an axial distance from the cylinder section 32 spherical driver head 33, which with a driver surface 34 in the first Piston 26 cooperates and one that transmits movement to the right in FIG. 2 Coupling forms. The driver surface 24 is conical, on the one hand around the second piston 31 in addition to lead, on the other hand to any relative movements between the Allow pistons 26, 31.

In der Gehäusebohrung 25 ist ein Scheibenkörper 35 positioniert, der eine Führungsbohrung 36 für den Zylinderabschnitt 32 des zweiten Kolbens 31 enthält. Die Führungslänge der Führungsbohrung 36 ist zweckmäßigerweise kürzer als der Durchmesser des Zylinderabschnitts 32. Angrenzend an den Scheibenkörper 35 ist in der Gehäusebohrung 25 ein Abschlußteil 38 abgedichtet eingesetzt, der in einer Dichtung 39 eine Gleithülse 40 positioniert, in der der Zylinderabschnitt 32 ebenfalls verschiebbar ist, derart, daß die Beaufschlagungsfläche A2 des zweiten Kolbens 31 in einer Kammer 41 liegt, die über die Drossel 42 (s. Fig.1) an die Steuerleitung 22 für den Referenzdruck anschließbar ist.A disk body 35 is positioned in the housing bore 25 and has a guide bore 36 for the cylinder section 32 of the second piston 31 contains. The lead length the guide bore 36 is advantageously shorter than the diameter of the cylinder section 32. Adjacent to the disk body 35 is in the Housing bore 25 inserted a sealing part 38 sealed in a seal 39 positioned a sliding sleeve 40, in which the cylinder section 32 can also be moved is such that the pressure surface A2 of the second piston 31 in one Chamber 41 is located on the throttle 42 (see Fig.1) to the control line 22 for the Reference pressure can be connected.

Der Schalter G ist in einem Schaltergehäuse 43 enthalten, das in einem Rahmen 44 am Gehäuse 24 festgelegt ist und sich gegebenenfalls zur Einjustierung des Schaltpunktes des Betätigungsselementes 28 in Achsrichtung der Gehäusebohrung 25 verstellen läß. Die Vorspannfeder 23 (s. Fig. 1) ist mit ihrem einen Ende am Scheibenkörper 35 abgestützt und liegt mit ihrem anderen Ende an einem Ring 45 an, der am Mitnehmerkopf 33 abgefangen ist. Der Schalter G ist mit der nicht dargestellten übergeordneten Steuereinheit der Spannvorrichtung elektrisch verbunden. Der Innenraum des ersten Kolbens 26 und der Zwischenraum zwischen dem Gehäuse 24 und dem Rahmen 44 sind zum Rücklauf T druckentlastet.The switch G is contained in a switch housing 43, which is in a frame 44 is fixed to the housing 24 and may be used to adjust the switching point of the actuating element 28 in the axial direction of the housing bore 25 can be adjusted. The biasing spring 23 (see FIG. 1) has one end on the disc body 35 supported and is at its other end on a ring 45, the is intercepted on the driver head 33. The switch G is with that, not shown higher-level control unit of the tensioning device is electrically connected. The interior of the first piston 26 and the space between the housing 24 and the frame 44 are relieved of pressure to the return T.

In Fig. 2 befindet sich das Differenzdruck-Schaltventil L in einer Schaltstellung, in der der Spanndruck gemeldet wird, weil der Stößel 27 das Betätigungselement 28 gedrückt hat. Auf der größeren Beaufschlagungsfläche A1 wirkt der Vorsteuerdruck, während auf der kleineren Beaufschlagungsfläche A2 der Referenzdruck wirkt, der über den Mitnehmerkopf 33 den ersten Kolben 26, beispielsweise bis zur Anlage am Dichtkörper 29,verstellt. Die Vorspannfeder 23 wirkt in der gleichen Richtung wie der Referenzdruck auf der Beaufschlagungsfläche A2. Fällt bei unverändert gehaltenem Vorsteuerdruck der Referenzdruck, dann wird der erste Kolben 26 in Fig. 2 nach links bewegt, bis der Stößel 27 das Betätigungselement 28 freigibt. Der Schalter G meldet "Spanndruck nicht vorhanden". Steigt der Referenzdruck durch Einflußnahme des Einstellventils D wieder auf die vorbestimmte Höhe, dann wird über den zweiten Kolben 31 und die Vorspannfeder 23 der erste Kolben 26 wieder in die gezeigte Stellung verschoben. Der Schalter G meldet "Spanndruck erreicht". Wird, um den Spanndruck zu erhöhen, über den Proportionalmagneten P der Vorsteuerdruck erhöht, dann wird der erste Kolben 26 wieder nach links verschoben, bis der Schalter G meldet "Spanndruck nicht erreicht". Aufgrund des erhöhten Vorsteuerdrucks hebt das Einstellventil D den Druck in der Verbraucherleitung 5 entsprechend an, bis der Referenzdruck am zweiten Kolben 31 den ersten Kolben 26 wieder in die gezeigte Stellung verschiebt und der Schalter G meldet " Spanndruck erreicht".2, the differential pressure switching valve L is in a switching position in which the clamping pressure is reported because the plunger 27 pressed the actuating element 28 Has. The pilot pressure acts on the larger area A1 while the reference pressure acts on the smaller loading area A2, the Via the driver head 33, the first piston 26, for example until it comes into contact with Sealing body 29, adjusted. The bias spring 23 acts in the same direction as that Reference pressure on the contact surface A2. Falls with unchanged Pilot pressure the reference pressure, then the first piston 26 in Fig. 2 to the left moves until the plunger 27 releases the actuator 28. The switch G reports "Tension pressure not available". If the reference pressure increases due to the influence of the Adjustment valve D back to the predetermined level, then the second piston 31 and the bias spring 23 of the first piston 26 again in the position shown postponed. Switch G reports "clamping pressure reached". Will to the tension pressure increase, the pilot pressure is increased via the proportional magnet P, then the first piston 26 is shifted to the left again until the switch G reports "Tension pressure not reached". The control valve lifts due to the increased pilot pressure D the pressure in the consumer line 5 accordingly until the reference pressure on the second piston 31, the first piston 26 again in the position shown moves and the switch G reports "clamping pressure reached".

Der Schaltpunkt des Schalters G muß unabhängig vom Druckwert des Spanndrucks jeweils knapp unterhalb des Spanndrucks liegen. Wäre die Vorspannfeder 23 nicht vorhanden, dann würde bei für niedrigen Spanndruck unterhalb dieses niedrigen Spanndrucks liegendem Schaltpunkt der entsprechende Schaltpunkt des Schalters bei hohem Spanndruck zu weit unterhalb des hohen Spanndrucks liegen. Der Schalter würde bei hohem Spanndruck zu früh ansprechen und ein fehlerhaftes Gutsignal abgeben. Wäre das Verhältnis zwischen den Beaufschlagungsflächen A2 und A1 hingegen so abgestimmt, daß der Schaltpunkt des Schalters bei hohem Spanndruck optimal knapp unterhalb des hohen Spanndrucks läge, dann wäre der entsprechende Schaltpunkt bei niedrigem Schaltpunkt oberhalb des niedrigen Spanndrucks, so daß bei niedrigem Spanndruck kein Gutsignal erzeugt würde. Die Vorspannfeder 23 bewirkt ein Anpassen der Linie der Schaltpunkte (der Linie der Schaltdrücke) an die Spanndrucklinie über den gesamten Arbeitsbereich derart, daß die beiden Linien im wesentlichen zueinander parallel sind und die Schaltpunkte für alle Spanndrücke nur knapp unterhalb des jeweiligen Spanndrucks liegen. Das Differenzdruck-Schaltventil D mit seinem Schalter G ist deshalb in der Lage, über einen sehr breiten Spanndruck-Bereich korrekte und aussagefähige Signale zu erzeugen, d.h. das Verhältnis zwischen dem Referenzdruck und dem niedrigen Spanndruck unabhängig von der Höhe des Referenzdruck bzw. des Vorsteuerdrucks präzise abzutasten.The switching point of switch G must be independent of the pressure value of the clamping pressure are just below the clamping pressure. Were the bias spring 23 not would then exist for low clamping pressure below this low The corresponding switching point of the switch at high clamping pressure are too far below the high clamping pressure. The desk would respond too early at high clamping pressure and a faulty good signal submit. Would be the ratio between the application areas A2 and A1 however, adjusted so that the switch point of the switch at high clamping pressure would be optimally just below the high clamping pressure, then the corresponding would be Switching point at a low switching point above the low clamping pressure, so that no good signal would be generated at low clamping pressure. The bias spring 23 causes an adjustment of the line of the switching points (the line of the switching pressures) to the Span pressure line over the entire work area so that the two lines in the are essentially parallel to each other and the switching points for all clamping pressures only are just below the respective clamping pressure. The differential pressure switching valve D with its switch G is therefore able to operate over a very wide clamping pressure range generate correct and meaningful signals, i.e. The relation between the reference pressure and the low clamping pressure regardless of the height of the reference pressure or the pilot pressure.

Fig. 2 verdeutlicht eine ausgewählte Ausführungsform. Das Differenzdruck-Schaltventil kann mit gleicher Funktions konstruktiv anders ausgebildet sein.2 illustrates a selected embodiment. The differential pressure switching valve can be constructed differently with the same function.

Claims (13)

  1. Differential-pressure control valve (L) with an electrical switch (G), in particular for monitoring the clamping pressure in an electrohydraulic clamping device (S) of a machine tool, having a housing bore (25) in which a piston arrangement which is acted upon by a preloading spring (23) and has application areas (A2, A1) of different size is axially adjustable relative to an actuating element (28) of the switch (G), it being possible for a reference pressure to be applied to one application area (A2) in one adjusting direction and for a variable pilot-control pressure to be applied to another application area (A1) in the opposite adjusting direction of the piston arrangement, and the application area (A1) for the pilot-control pressure being a multiple of the application area (A2) for the reference pressure, and the piston arrangement being additionally acted upon by the preloading spring (23) in the application direction of the reference pressure, characterized in that the piston arrangement loaded by the preloading spring (23) parallel to the reference pressure has a first piston (26), forming the larger application area (A1) and having a plunger (27) directed from the larger application area (A1) towards the actuating element (28) of the switch (G), and a second piston (31) which forms the smaller application area (A2), is guided in a displaceable sealed-off manner and, from that side of the piston (26) which is remote from the larger application area (A1), plunges into the first piston and is directed towards a driving surface (34) of the first piston.
  2. Differential-pressure control valve according to Claim 1, characterized in that the first piston (26) is a skirt-type piston.
  3. Differential-pressure control valve according to Claim 1, characterized in that the ratio of the application areas (A2:A1) is between 1:5 and about 1:25, preferably around about 1:15 to 1:20.
  4. Differential-pressure control valve according to Claim 3, characterized in that a section of the housing bore (25) provided between the sealing guides, together with the outside and the interior space of the first piston (26), is pressure-relieved.
  5. Differential-pressure control valve according to Claim 1, characterized in that the second piston (31) has a crowned driving head (33), and in that the driving surface (34) preferably has a conical or frustoconical shape.
  6. Differential-pressure control valve according to Claim 1, characterized in that the second piston (31) has a cylindrical section (32) which passes in a slidable manner through a guide bore (36) fixed to the housing, the length of this guide bore (36) preferably being smaller than the diameter of the cylindrical section (32), and in that the cylindrical section (32) passes through a sliding sleeve (40) adjacent to the guide bore (36), this sliding sleeve (40) being positioned by elastic sealing means (39) on the outside.
  7. Differential-pressure control valve according to at least one of the preceding Claims 5 or 6, characterized in that the sealing guide of the second piston (31) and the driving head (33) are at a distance apart which is a multiple of the diameter of the cylindrical section (32).
  8. Differential-pressure control valve according to Claim 6, characterized in that a disc body (35) is positioned in the housing bore (25), this disc body (35) containing the guide bore (36) and having a bearing surface for the sealing means (39) and the sliding sleeve (40), and in that a closure part (38) is secured in the housing bore (25) on that side of the disc body (35) which faces away from the piston (26), and this closure part (38), with the sealing guide of the piston (31), defines a chamber (41) which can be connected to a feed for the reference pressure via a restrictor opening (42).
  9. Differential-pressure control valve according to Claim 8, characterized in that the disc body (38) has an abutment for the preloading spring (23), the other end of which is supported on the second piston (31), preferably on a ring (45) held loosely on the driving head (33).
  10. Differential-pressure control valve according to Claim 9, characterized in that the disc body (35) can be screwed in the housing bore (25) or can be located in different axial positions by means of removable shim parts.
  11. Differential-pressure control valve according to at least one of the preceding claims, characterized in that the other end of the housing bore (25) is closed by a sealing body (29) which has an elastic seal (30) for the plunger (27) and which, with the first piston (26), defines a chamber to which a pilot-control pressure can be applied.
  12. Differential-pressure control valve according to at least one of the preceding claims, characterized in that the switch (G) has a switch housing (43), which if need be is connected to the pressure relief of the housing bore (25) and is arranged in a vertically adjustable manner in a frame (44) fastened to the valve housing.
  13. Differential-pressure control valve according to one of the preceding claims, characterized in that the switch (G) is an electric microswitch.
EP98107635A 1997-06-10 1998-04-27 Differential pressure switch Expired - Lifetime EP0884483B1 (en)

Applications Claiming Priority (2)

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DE29710128U 1997-06-10
DE29710128U DE29710128U1 (en) 1997-06-10 1997-06-10 Differential pressure switching valve

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EP0884483A1 EP0884483A1 (en) 1998-12-16
EP0884483B1 true EP0884483B1 (en) 2003-08-13

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DE9310931U1 (en) 1993-07-21 1993-09-30 Heilmeier & Weinlein Fabrik für Oel-Hydraulik GmbH & Co KG, 81673 München Proportional pressure control valve in slide design
DE4446538A1 (en) 1994-12-24 1996-06-27 Bosch Gmbh Robert Hydraulic tensioning device e.g. for programmable machine tool

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10217583B2 (en) 2014-10-24 2019-02-26 Halliburton Energy Services, Inc. Pressure responsive switch for actuating a device

Also Published As

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EP0884483A1 (en) 1998-12-16
ATE247233T1 (en) 2003-08-15
DE59809258D1 (en) 2003-09-18
DE29710128U1 (en) 1997-08-14

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