WO1980001826A1 - A signal converting unit intended to be incorporated in a pneumatic control system - Google Patents

A signal converting unit intended to be incorporated in a pneumatic control system Download PDF

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Publication number
WO1980001826A1
WO1980001826A1 PCT/SE1980/000057 SE8000057W WO8001826A1 WO 1980001826 A1 WO1980001826 A1 WO 1980001826A1 SE 8000057 W SE8000057 W SE 8000057W WO 8001826 A1 WO8001826 A1 WO 8001826A1
Authority
WO
WIPO (PCT)
Prior art keywords
signal
pneumatic
unit
control signal
piezoelectric element
Prior art date
Application number
PCT/SE1980/000057
Other languages
French (fr)
Inventor
J Formanek
A Jacobsson
Original Assignee
Saab Scania Ab
J Formanek
A Jacobsson
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 Saab Scania Ab, J Formanek, A Jacobsson filed Critical Saab Scania Ab
Priority to DE3034326T priority Critical patent/DE3034326C2/en
Priority to AT0901680A priority patent/ATA901680A/en
Publication of WO1980001826A1 publication Critical patent/WO1980001826A1/en
Priority to DK462080AA priority patent/DK150278B/en

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F15—FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
    • F15B—SYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
    • F15B5/00—Transducers converting variations of physical quantities, e.g. expressed by variations in positions of members, into fluid-pressure variations or vice versa; Varying fluid pressure as a function of variations of a plurality of fluid pressures or variations of other quantities
    • F15B5/003—Transducers converting variations of physical quantities, e.g. expressed by variations in positions of members, into fluid-pressure variations or vice versa; Varying fluid pressure as a function of variations of a plurality of fluid pressures or variations of other quantities characterised by variation of the pressure in a nozzle or the like, e.g. nozzle-flapper system
    • G—PHYSICS
    • G05—CONTROLLING; REGULATING
    • G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
    • G05D16/00—Control of fluid pressure
    • G05D16/20—Control of fluid pressure characterised by the use of electric means
    • G05D16/2006—Control of fluid pressure characterised by the use of electric means with direct action of electric energy on controlling means
    • G05D16/2013—Control of fluid pressure characterised by the use of electric means with direct action of electric energy on controlling means using throttling means as controlling means

Definitions

  • the present invention relates to a signal converting unit intended to be incorporated in a pneumatic control system and used to convert an electrical control signal received at the input of the unit into a pneumatic signal which is emitted at the output of the unit and the value of which should be proportional to the value of the control signal, comprising a tongue-shaped piezoelectric element which is loaded with a voltage dependent on the control signal so that the element carries out a lateral bending movement which varies with the voltage, a pneumatic line with a chamber which is supplied with compressed air via a throttle and from which compressed air is conducted away through a nozzle located near to one side of the piezoelectric element so that the air pressure in the chamber is regulated by the piezoelectric element as a function of the said voltage, and an outlet line leading out of the chamber, for transmitting the regulated air pressure to the control system as the said pneumatic signal.
  • a signal converter of this kind comprising a chamber with an inlet aperture and an outlet aperture.
  • a source of fluid pressure by means of which a pressure is obtained in the chamber is connected to the inlet aperture.
  • an electrically-actuated piezoelectric tongue Near to one of said apertures there is an electrically-actuated piezoelectric tongue.
  • the tongue can be made to move towards or away from the aperture so that the pressure in the chamber is influenced thereby.
  • a fluid pressure value associated with the control signal is derived from this pressure. According to the said published specification, an external force on the tongue is achieved with a feed-back circuit.
  • the level of the force is associated with the level of the pressure in the chamber and is said to act in the opposite direction to the bending of the tongue occasioned by the control signal.
  • the aim in this case is to restrict the bending of the tongue so that the bending force produced by the control signal is balanced against the fluid pressure.
  • the arrangement therefore works according to the force-balancing principle, i.e. the fluid pressure is dependent on the piezoelectric bending force as a function of the electrical control signal. Accordingly, factors such as the temperature-dependence, non-linearity, and hysteresis of the piezoelectric tongue, as well as the long time instability of the bending forces as a function of the electric control signal, will affect the accuracy of the conversion from an electrical control signal into a fluid pressure value.
  • the aim of the present invention is to provide a signal converter of the kind described in the introduction, with which it is possible to convert an electrical control signal into a corresponding pneumatic pressure value with a high degree of accuracy, and which does not have the above-mentioned disadvantages, and this is achieved in that the signal converter has the characteristics which are given in the attached Patent Claim.
  • Figure 1 shows schematically and partially as a block diagram a signal converting unit according to the invention for converting an electrical control signal into a corresponding pneumatic pressure value, that is, a so-called I/P converter.
  • Figure 2 shows in block diagram form an alternative embodiment of a signal converter according to the invention.
  • 1 is a line connected to a pneumatic pressure source 2, which ppens out in a nozzle 3.
  • a pneumatic pressure source 2 which ppens out in a nozzle 3.
  • a throttle 4 and a pneumatic pressure outlet 5.
  • a pneumatic pressure is produced in a chamber 1a between the nozzle 3 and the throttle 4 in the line 1.
  • a piezoelectric element 6 is arranged; this is sensitive to the effect of electrical signals, and has its end furthest from the nozzle firmly clamped in.
  • the side of the element 6 which is nearest the nozzle 3 is formed in such a way that there is a gap between the element and the nozzle through which the air can flow out.
  • the element 6 can be made to move towards or away from the nozzle 3, depending on the strength and polarity of the signal, so that the gap betwe the element and the nozzle is thereby reduced or increased
  • the out-flow of air through the nozzle 3 can be influenced in this way, and with it the pneumatic pressure in the chamber la and at the pressure outlet 5 is also regulated.
  • This pressure which can be used as a control pressure for a pneumatic amplifier or a cylinder-piston assembly, has been indicated on the Drawing by P . If no other measures are taken, then, as explained in the introduction, the accuracy is affected negatively by a number of factors when controlling the pneumatic pressure in this way.
  • a pressure transducer 7 is connected to the pressure outlet 5 for monitoring the pneumatic pressure in the line.
  • the pressure transducer 7 is designed to produce an electrical signal T which corresponds to the said control pressure.
  • the signal T is supplied to one signal input 8 of a comparator 9, the other input 10 of which is supplied with the electrical control signal, called I in the following, which it is desired to convert to a pneumatic pressure value.
  • the comparator 9 is designed to compare the signals T and I and to produce a difference signal corresponding to the difference between the said signals. This is supplied to an integrator 11, the output signal of which is a voltage and acts on the piezoelectric element 6.
  • the integrator 11 is preferably an integrating amplifier and its output signal corresponds to the time integral of the difference signal supplied to the integrator. This means that even small difference signals of a certain dura- tion give rise to output signals from the integrator 11 of the same order of magnitude as larger, but shorter, difference signals.
  • FIG. 9 and the integrator 11 correspond in their function to a proportional integrating regulator, or so-called P/I regulator.
  • P/I regulator a proportional integrating regulator
  • 12 is such a P/I regulator.
  • the said Pigure shows an alternative embodimentof an I/P converter according to the invention, with a fluid amplifier 13 connected to the pressure outlet 5.
  • the amplifier 13 is supplied with pressure from the pressure source 2 via a line 14, and has the task of producing an amplified flow of air and/or an increased pressure value in the outlet line 5 for applications where the flow of air via the throttle 4 is not adequate.
  • the pressure transducer 7 is connected to the output 15 of the amplifier which also forms the output of the I/P converter, i.e. the pneumatic pressure corresponding to the signal I is taken as a working pressure at the output 15.
  • Tbe working pressure may be used, for instance, for controlling the state of a cylinder-piston assembly which is not shown on the Drawing.
  • the signal converter according to the invention may be modified in many ways within the scope of the invention.
  • the piezo electric element 6 may be arranged so that it moves in only one direction, i.e. either away from or towards the nozzle 3, under the effect of the control signal.

Landscapes

  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Automation & Control Theory (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Supply Devices, Intensifiers, Converters, And Telemotors (AREA)
  • Preliminary Treatment Of Fibers (AREA)
  • Hydraulic Clutches, Magnetic Clutches, Fluid Clutches, And Fluid Joints (AREA)
  • Paper (AREA)
  • Transmission And Conversion Of Sensor Element Output (AREA)

Abstract

The unit serves to convert an electrical control signal (I) received at the input of the unit into a pneumatic signal (P). This is emitted at the output of the unit and its value should be proportional to the value of the control signal (I). The unit comprises a tongue-shaped piezoelectric element (6) which is loaded with a voltage dependent on the control signal, so that the element (6) carries out a lateral bending movement which varies with the voltage. The unit also comprises a pneumatic line (1) with a chamber (1a) which is supplied with compressed air via a throttle (4) and from which the compressed air is conducted through a nozzle (3) located near to one side of the piezoelectric element (6) so that the air pressure in the chamber is regulated by the piezoelectric element (6) as a function of the said voltage; and an outlet line (5) leading from the chamber for transmitting the regulated air pressure to the control system as the said pneumatic signal (P). To make the pneumatic signal (P) to the control system accurately follow the electrical control signal (1), a pressure transducer (7) is connected to the outlet line (5), being designed to produce an electrical signal (T) which corresponds to the regulated air pressure, and which is fed back via a feed-back circuit to the input of the unit. Furthermore, the input has a circuit (9, 11) which receives both the electrical control signal (1) and the fed-back electrical signal (T). The circuit has a device (9) for forming a difference signal by comparing the two signals (I, T) and a device (11) for integrating the difference signal and thereafter producing from the integrated difference signal the voltage with which the piezoelectric element (6) is loaded.

Description

A Signal Converting Unit intended to be incorporated in a Pneumatic Control System
The present invention relates to a signal converting unit intended to be incorporated in a pneumatic control system and used to convert an electrical control signal received at the input of the unit into a pneumatic signal which is emitted at the output of the unit and the value of which should be proportional to the value of the control signal, comprising a tongue-shaped piezoelectric element which is loaded with a voltage dependent on the control signal so that the element carries out a lateral bending movement which varies with the voltage, a pneumatic line with a chamber which is supplied with compressed air via a throttle and from which compressed air is conducted away through a nozzle located near to one side of the piezoelectric element so that the air pressure in the chamber is regulated by the piezoelectric element as a function of the said voltage, and an outlet line leading out of the chamber, for transmitting the regulated air pressure to the control system as the said pneumatic signal. In Swedish published specification 322.989 (with priority from US 588 057) a signal converter of this kind is described in more detail, comprising a chamber with an inlet aperture and an outlet aperture. A source of fluid pressure by means of which a pressure is obtained in the chamber is connected to the inlet aperture. Near to one of said apertures there is an electrically-actuated piezoelectric tongue. Depending on the strength and the polarity of the control signal, the tongue can be made to move towards or away from the aperture so that the pressure in the chamber is influenced thereby. A fluid pressure value associated with the control signal is derived from this pressure. According to the said published specification, an external force on the tongue is achieved with a feed-back circuit. The level of the force is associated with the level of the pressure in the chamber and is said to act in the opposite direction to the bending of the tongue occasioned by the control signal. The aim in this case is to restrict the bending of the tongue so that the bending force produced by the control signal is balanced against the fluid pressure. The arrangement therefore works according to the force-balancing principle, i.e. the fluid pressure is dependent on the piezoelectric bending force as a function of the electrical control signal. Accordingly, factors such as the temperature-dependence, non-linearity, and hysteresis of the piezoelectric tongue, as well as the long time instability of the bending forces as a function of the electric control signal, will affect the accuracy of the conversion from an electrical control signal into a fluid pressure value. To the extent that variations occur in the supply pressure from the fluid pressure source, these are not fully compensated, but the compensation process is affected by the said factors. The temperature-dependence which arises from the piezo crystals of the tongue and difficulties in producing a good adhesion between them entails an error in the order of magnitude of 0.05 - 0.5% per ºC. Hysteresis, which means that, for one and the same control signal value, the tongue carri out dissimilar bending depending on whether the said value is arrived at by increasing or reducing the control signal value, can amount to around 20% and it may take up to 20 hours for the tongue to attain a uniform, stable bending position corresponding to a specific control signal value. Long time stability is also bound up with the mechanical composition of the tongue. Those errors which occur as a result of a lack of long time stability is hard to separate from those which are caused by hysteresis.
In the processing industry in particular there is a need for arrangements which make it possible to carry out conversion of the above-mentioned type with a high degree of accuracy, but with the arrangements known up to the present time it has been possible only to reduce the effect of the said factors and therefore an adequately high level of accuracy has not been achieved. The aim of the present invention is to provide a signal converter of the kind described in the introduction, with which it is possible to convert an electrical control signal into a corresponding pneumatic pressure value with a high degree of accuracy, and which does not have the above-mentioned disadvantages, and this is achieved in that the signal converter has the characteristics which are given in the attached Patent Claim.
The invention will be explained in more detail in the following with reference to the attached Drawing, on which Figure 1 shows schematically and partially as a block diagram a signal converting unit according to the invention for converting an electrical control signal into a corresponding pneumatic pressure value, that is, a so-called I/P converter. Figure 2 shows in block diagram form an alternative embodiment of a signal converter according to the invention.
On the Drawing, 1 is a line connected to a pneumatic pressure source 2, which ppens out in a nozzle 3. Between the pressure source 2 and the nozzle 3 in the said arrangement there is a throttle 4 and a pneumatic pressure outlet 5. By means of the pressure source, a pneumatic pressure is produced in a chamber 1a between the nozzle 3 and the throttle 4 in the line 1. Near to the nozzle 3 a piezoelectric element 6 is arranged; this is sensitive to the effect of electrical signals, and has its end furthest from the nozzle firmly clamped in. The side of the element 6 which is nearest the nozzle 3 is formed in such a way that there is a gap between the element and the nozzle through which the air can flow out. Under the effect of the electrical signals, the element 6 can be made to move towards or away from the nozzle 3, depending on the strength and polarity of the signal, so that the gap betwe the element and the nozzle is thereby reduced or increased The out-flow of air through the nozzle 3 can be influenced in this way, and with it the pneumatic pressure in the chamber la and at the pressure outlet 5 is also regulated. This pressure, which can be used as a control pressure for a pneumatic amplifier or a cylinder-piston assembly, has been indicated on the Drawing by P . If no other measures are taken, then, as explained in the introduction, the accuracy is affected negatively by a number of factors when controlling the pneumatic pressure in this way.
As can be seen in Figure 1, according to the invention, a pressure transducer 7 is connected to the pressure outlet 5 for monitoring the pneumatic pressure in the line. The pressure transducer 7 is designed to produce an electrical signal T which corresponds to the said control pressure. The signal T is supplied to one signal input 8 of a comparator 9, the other input 10 of which is supplied with the electrical control signal, called I in the following, which it is desired to convert to a pneumatic pressure value. The comparator 9 is designed to compare the signals T and I and to produce a difference signal corresponding to the difference between the said signals. This is supplied to an integrator 11, the output signal of which is a voltage and acts on the piezoelectric element 6. The integrator 11 is preferably an integrating amplifier and its output signal corresponds to the time integral of the difference signal supplied to the integrator. This means that even small difference signals of a certain dura- tion give rise to output signals from the integrator 11 of the same order of magnitude as larger, but shorter, difference signals.
The arrangement shown in Figure 1 . works as an I/P converter and operates in a closed control loop in the following way: Depending on the size and p-olarity of the difference signals, the element 6 moves as described above, either away from or towards the nozzle 3, whereby the gap between the element and the nozzle is increased or reduced so that the pneumatic pressure in the chamber 1a, and with it also both the pneumatic pressure value P and the signal T , is varied. Obviously, it is possible to endow the control circuit with characteristics such that the pneumatic pressure value P corresponds very accurately with the signal I . The characteristics of the piezoelectric element 6 or variations in the supply pressure from the pressure source 2 do not affect the accuracy of the converter, which is affected only by the accuracy of the pressure transducer 7. The comparator. 9 and the integrator 11 correspond in their function to a proportional integrating regulator, or so-called P/I regulator. In Figure 2, 12 is such a P/I regulator. The said Pigure shows an alternative embodimentof an I/P converter according to the invention, with a fluid amplifier 13 connected to the pressure outlet 5.
The amplifier 13 is supplied with pressure from the pressure source 2 via a line 14, and has the task of producing an amplified flow of air and/or an increased pressure value in the outlet line 5 for applications where the flow of air via the throttle 4 is not adequate. The pressure transducer 7 is connected to the output 15 of the amplifier which also forms the output of the I/P converter, i.e. the pneumatic pressure corresponding to the signal I is taken as a working pressure at the output 15. Tbe working pressure may be used, for instance, for controlling the state of a cylinder-piston assembly which is not shown on the Drawing.
Obviously, the signal converter according to the invention may be modified in many ways within the scope of the invention. Por example, the piezo electric element 6 may be arranged so that it moves in only one direction, i.e. either away from or towards the nozzle 3, under the effect of the control signal.

Claims

P a t e n t C l a i m
A signal converting unit intended to be incorporated in a pneumatic control system and used to convert an electrical control signal (I) received at the input of the unit into a pneumatic signal (P) which is emitted at the output of the unit and the value of which should be proportional to the value of the regulating signal, comprising a tongue-shaped piezoelectric element (6) which is loaded with a voltage which depends on the control signal (I) so that the element (6) carries out a lateral bending movement which varies with the voltage, a pneumatic line (1) with a chamber (1a) which is supplied with compressed air via a throttle (4) and from which the compressed air is conducted through a nozzle (3) located near to one side of the piezoelectric element (6), so that the air pressure in the chamber (1a) is regulated by the piezoelectric element (6) as a function of the said voltage, and an outlet line (5) leading from the chamber (1a) for transmitting to the control system the regulated air pressure as the said pneumatic signal (P), characterised in that a pressure transducer (7) designed to produce an electrical signal (T) corresponding to the regulated air pressure is connected to the outlet line (5)» and is connected back via a feed-back circuit to the input of the unit, and that the input has a circuit (9, 11; 12) which receives both the electrical control signal (I) and the fed-back electrical signal, and which has a device (9) for forming a difference signal by comparing the two signals, and a device (11) for integrating the difference signal and thereafter producing from the integrated difference signal the voltage with which the piezoelectric element (6) is loaded, the pneumatic signal (P) to the control system accurately following the electrical control signal (I).
PCT/SE1980/000057 1979-03-01 1980-02-29 A signal converting unit intended to be incorporated in a pneumatic control system WO1980001826A1 (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
DE3034326T DE3034326C2 (en) 1979-03-01 1980-02-29 Signal converter for a pneumatic control system
AT0901680A ATA901680A (en) 1979-03-01 1980-02-29 SIGNAL CONVERTER FOR A PNEUMATIC CONTROL SYSTEM
DK462080AA DK150278B (en) 1979-03-01 1980-10-31 SIGNIFICANT DEVICE INTENDED TO ENTER INTO A PNEUMATIC REGULATION SYSTEM

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE7901841A SE420639B (en) 1979-03-01 1979-03-01 SIGNAL CONVERTER UNIT FOR CONVERTING AN ELECTRICAL CONTROL SIGNAL TO A PNEUMATIC SIGNAL WITH A PIEZOELECTRIC ELEMENT
SE7901841 1979-03-01

Publications (1)

Publication Number Publication Date
WO1980001826A1 true WO1980001826A1 (en) 1980-09-04

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ID=20337424

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/SE1980/000057 WO1980001826A1 (en) 1979-03-01 1980-02-29 A signal converting unit intended to be incorporated in a pneumatic control system

Country Status (10)

Country Link
EP (1) EP0024409A1 (en)
AT (1) ATA901680A (en)
CH (1) CH646230A5 (en)
DE (1) DE3034326C2 (en)
DK (1) DK150278B (en)
GB (1) GB2065331A (en)
NL (1) NL8020072A (en)
NO (1) NO803279L (en)
SE (1) SE420639B (en)
WO (1) WO1980001826A1 (en)

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0102528A2 (en) * 1982-08-16 1984-03-14 The Perkin-Elmer Corporation Voltage to pressure transducer
FR2539483A1 (en) * 1983-01-13 1984-07-20 Enfo Grundlagen Forschungs Ag ELECTRO-PNEUMATIC TRANSDUCER
EP0117039A1 (en) * 1983-01-14 1984-08-29 Vfp Fluid Power Limited Relief valve assembly
EP0120593A2 (en) * 1983-02-22 1984-10-03 The Babcock & Wilcox Company Electro-pneumatic control systems
EP0120594A2 (en) * 1983-02-24 1984-10-03 The Babcock & Wilcox Company Electro-pneumatic transducer assemblies
FR2543706A1 (en) * 1983-03-28 1984-10-05 Edison Int Inc SOLID STATE CURRENT-PRESSURE AND DISPLACEMENT CURRENT TRANSDUCER
EP0216206A2 (en) * 1985-09-11 1987-04-01 Gulde-Regelarmaturen GmbH & Co. KG Pneumatic regulator
EP0413683A4 (en) * 1986-09-30 1990-03-21 Rosemount Inc Frequency feedback on a current loop of a current-to-pressure converter.
EP0398862A2 (en) * 1989-05-19 1990-11-22 Hoerbiger Ventilwerke Aktiengesellschaft Signal converter
EP0405854A2 (en) * 1989-06-26 1991-01-02 Seiko Instruments Inc. Ultrasonic motor
EP0503894A1 (en) * 1991-03-13 1992-09-16 Watson Smith Limited I/P converters
US6017016A (en) * 1996-05-29 2000-01-25 Flight Refueling Limited Flapper valve

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4527583A (en) * 1983-07-12 1985-07-09 Dresser Industries, Inc. Electropneumatic transducer system
USRE33028E (en) * 1983-07-12 1989-08-22 Dresser Industries, Inc. Electropneumatic transducer system
JPS61173319A (en) * 1985-01-26 1986-08-05 Shoketsu Kinzoku Kogyo Co Ltd Regulator for fluid
DE4240802C2 (en) * 1992-12-01 1997-07-17 Hartmann & Braun Ag Electropneumatic converter

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1183778A (en) * 1956-09-28 1959-07-13 Thomson Houston Comp Francaise Piezoelectric crystal transducer for controlling hydraulic valves
SE322989B (en) * 1966-10-20 1970-04-20 Fisher Governor Co
US4061155A (en) * 1975-05-28 1977-12-06 Robert Bosch G.M.B.H. Electrohydraulic control system

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DE1673475U (en) * 1953-10-22 1954-03-11 Julius Fingerhut FABRIC BUTTON.
DE1588245B1 (en) * 1967-07-07 1970-11-12 Gulde Regelarmaturen Kg Electropneumatic positioner
DE2013688C3 (en) * 1970-03-21 1974-03-14 Gulde-Regelarmaturen-Kg, 6700 Ludwigshafen Electropneumatic signal converter
US3882881A (en) * 1973-01-12 1975-05-13 American Chain & Cable Co Pneumatic transmitter of electrical phenomena
GB1551039A (en) * 1976-08-06 1979-08-22 Ici Ltd Conversion of electric to pneumatic signals
DD138089B1 (en) * 1978-07-28 1983-06-01 Peter Domnitz ARRANGEMENT FOR ELECTRICAL PNEUMATIC AND PNEUMATIC ELECTRICAL SIGNAL CONVERSION

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR1183778A (en) * 1956-09-28 1959-07-13 Thomson Houston Comp Francaise Piezoelectric crystal transducer for controlling hydraulic valves
SE322989B (en) * 1966-10-20 1970-04-20 Fisher Governor Co
US4061155A (en) * 1975-05-28 1977-12-06 Robert Bosch G.M.B.H. Electrohydraulic control system

Cited By (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0102528A2 (en) * 1982-08-16 1984-03-14 The Perkin-Elmer Corporation Voltage to pressure transducer
EP0102528A3 (en) * 1982-08-16 1984-05-09 The Perkin-Elmer Corporation Voltage to pressure transducer
FR2539483A1 (en) * 1983-01-13 1984-07-20 Enfo Grundlagen Forschungs Ag ELECTRO-PNEUMATIC TRANSDUCER
EP0117039A1 (en) * 1983-01-14 1984-08-29 Vfp Fluid Power Limited Relief valve assembly
EP0120593A2 (en) * 1983-02-22 1984-10-03 The Babcock & Wilcox Company Electro-pneumatic control systems
EP0120593A3 (en) * 1983-02-22 1985-07-10 The Babcock & Wilcox Company Electro-pneumatic control systems
EP0120594A2 (en) * 1983-02-24 1984-10-03 The Babcock & Wilcox Company Electro-pneumatic transducer assemblies
EP0120594A3 (en) * 1983-02-24 1985-07-10 The Babcock & Wilcox Company Pneumatic servo arrangements and assemblies for electro-pneumatic control systems
FR2543706A1 (en) * 1983-03-28 1984-10-05 Edison Int Inc SOLID STATE CURRENT-PRESSURE AND DISPLACEMENT CURRENT TRANSDUCER
EP0216206A3 (en) * 1985-09-11 1989-03-08 Gulde-Regelarmaturen Gmbh & Co. Kg Pneumatic regulator
EP0216206A2 (en) * 1985-09-11 1987-04-01 Gulde-Regelarmaturen GmbH & Co. KG Pneumatic regulator
EP0413683A4 (en) * 1986-09-30 1990-03-21 Rosemount Inc Frequency feedback on a current loop of a current-to-pressure converter.
EP0413683A1 (en) * 1986-09-30 1991-02-27 Rosemount Inc Frequency feedback on a current loop of a current-to-pressure converter.
EP0398862A2 (en) * 1989-05-19 1990-11-22 Hoerbiger Ventilwerke Aktiengesellschaft Signal converter
EP0398862A3 (en) * 1989-05-19 1991-03-13 Hoerbiger Ventilwerke Aktiengesellschaft Signal converter
EP0405854A2 (en) * 1989-06-26 1991-01-02 Seiko Instruments Inc. Ultrasonic motor
EP0405854A3 (en) * 1989-06-26 1991-02-27 Seiko Instruments Inc. Ultrasonic motor
EP0503894A1 (en) * 1991-03-13 1992-09-16 Watson Smith Limited I/P converters
US5370152A (en) * 1991-03-13 1994-12-06 Watson Smith Limited I/P converters
US6017016A (en) * 1996-05-29 2000-01-25 Flight Refueling Limited Flapper valve

Also Published As

Publication number Publication date
DK150278B (en) 1987-01-26
DE3034326C2 (en) 1983-11-17
EP0024409A1 (en) 1981-03-11
SE420639B (en) 1981-10-19
CH646230A5 (en) 1984-11-15
NO803279L (en) 1980-10-31
SE7901841L (en) 1980-09-02
GB2065331A (en) 1981-06-24
ATA901680A (en) 1986-05-15
NL8020072A (en) 1981-04-29
DE3034326T1 (en) 1981-04-09
DK462080A (en) 1980-10-31

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