GB2078951A - Detecting position of axially movable member - Google Patents

Detecting position of axially movable member Download PDF

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Publication number
GB2078951A
GB2078951A GB8120837A GB8120837A GB2078951A GB 2078951 A GB2078951 A GB 2078951A GB 8120837 A GB8120837 A GB 8120837A GB 8120837 A GB8120837 A GB 8120837A GB 2078951 A GB2078951 A GB 2078951A
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GB
United Kingdom
Prior art keywords
light
movable member
axially movable
instrument
positions
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.)
Withdrawn
Application number
GB8120837A
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.)
BP PLC
Original Assignee
BP PLC
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 BP PLC filed Critical BP PLC
Priority to GB8120837A priority Critical patent/GB2078951A/en
Publication of GB2078951A publication Critical patent/GB2078951A/en
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01D—MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE; ARRANGEMENTS FOR MEASURING TWO OR MORE VARIABLES NOT COVERED IN A SINGLE OTHER SUBCLASS; TARIFF METERING APPARATUS; MEASURING OR TESTING NOT OTHERWISE PROVIDED FOR
    • G01D5/00—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable
    • G01D5/26—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light
    • G01D5/32—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light
    • G01D5/34—Mechanical means for transferring the output of a sensing member; Means for converting the output of a sensing member to another variable where the form or nature of the sensing member does not constrain the means for converting; Transducers not specially adapted for a specific variable characterised by optical transfer means, i.e. using infrared, visible, or ultraviolet light with attenuation or whole or partial obturation of beams of light the beams of light being detected by photocells

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Length Measuring Devices By Optical Means (AREA)
  • Indication Of The Valve Opening Or Closing Status (AREA)

Abstract

One or more positions of an axially movable member is (are) determined by a light source and detector disposed so that in the desired positions of the member the light path between source and detector is completed. As described, a valve actuating shaft 14 has a position detector (2) which comprises a light source contacting light fibre 4, a light detector contacting light fibre 24 and reflecting prisms (12) and (16) located in the shaft. Only in two positions if the shaft (14) is the light path completed by one of the prisms (12) or (16) which are located to correspond fully open or fully closed positions of the valve. <IMAGE>

Description

SPECIFICATION Apparatus for indicating the position of a movable member The invention relates to an instrument for detecting the position of a movable member such as a valve.
An instrument for detecting the position of a liquid surface has been previously used in petrol tankers and involves detecting reflected light. The instrument comprises an internally reflecting prism, a light source connected by fibre optics to the prism and a light detector also connected by fibre optics to the prism. When the level of petrol rises to reach the prism the internal reflection ceases, the light path is broken and light is no longer received by the detector.
In oilfield operations it is frequently important to be able to determine whether a valve is in the fully open or fully shut position, particularly valves employed in subsea oil production facilities. Such valves are actuated by a shaft which moves along its axis to open and close the valve.
It is an object of the present invention to provide an instrument capable of performing this function.
According to the present invention an instrument in combination with an axially movable member for detecting the position of said axially movable member, comprises a light source and light detector disposed with respect to the movable member so that the light path between the source and detector is completed in at least one, but not in other, positions of the axially movable member.
A light reflector can be provided and is movable with the axially movable member, the light reflector completing the light path between the source and reflector in said at least one, but not in other, positions of the axially movable member.
A plurality of light reflectors can be provided located at spaced apart positions along the movable member so that the light path is completed in a plurality of positions of the axially movable member.
The reflectors can be disposed so that the light path is completed at the limits of travel of the axially movable member.
The means for transmitting the light from source to reflector and from reflector to receiver can be a bundle of fibre optics. Each bundle can be shaped to provide the required tolerance or position of the movable member.
The light source can conveniently be a light emitting diode and the receiver can conveniently be a photodiode which may include an electronic amplifier. The output from the photodiode can be converted into a frequency suitable for transmission through an inductive coupler or into a DC level representing the open or closed state.
According to another aspect of the present invention, a method of determining the position of a movable member comprises employing a reflector carried by the movable member to complete the light path between a light source and a light reflector.
The invention is illustrated by reference to the accompanying drawings in which: Figure 1 is a vertical section showing the instrument installed in a position to indicate one of the limits of travel of a valve actuating shaft.
Figure 2 is an enlarged view of the path of the light.
The instrument indicated generally by numeral 2 comprises two bundles of glass fibre optics 4 and 24.
At the upper end of bundle 4 is a light source in the form of a light emitting diode (LED) 6 and at the upper end of bundle 24 is a receiver in the form of a photodiode 8, there being a light shield 10 located therebetween. Located below the lower end of the bundles 4 and 24 is a right anlge prism 12 conveniently made of plastic disposed so that light from the LED is internally reflected and transmitted through the bundle 4 to the photodiode 8. The gap between the lower end of bundle 4 and the face of the prism 12 is not more than 0.020 inches and will normally be in the range 0.012 to 0.020 inches. The prism 12 is mounted in a valve actuating shaft 14 and a similar prism 16 is also mounted in the shaft 14 at a position corresponding to the limit of travel of the shaft 14.
Only in two positions of the shaft 14, i.e. the fully open or fully closed position, will the prisms 12 and 16 complete the light transmission path.
Discrimination between the two limits of travel can be made by incorporating a second light receiving system (not shown) by which the outputs can be combined to produce a different frequency. Alternatively, discrimination between the two positions can be obtained by differences of voltage polarity applied to the voltage controlled oscillator (not shown) to give the different frequencies.
The instrument has been installed by forming an aperture 5 in the valve body 3 and a gap 9 in the valve shaft housing 11.
The potted electronics assembly 13 is inserted in the aperture 5 and held by a plate 15 secured by bolts 17.
1. An instrument in combination with an axially movable member for detecting the position of said axially movable member, said instrument comprising a light source and light detector disposed with respect to the movable member so that the light path between source and detector is completed in at least one, but not in other, positions of the axially movable member.
2. An instrument as claimed in claim 1 wherein a light reflector is provided and is movable with the axially movable member, the light reflector completing the light path between the source and reflector in said at least one, but not in other, positions of the axially movable member.
3. An instrument as claimed in claim 2 wherein a plurality of light reflectors are provided located at spaced apart positions along the movable member so that the light path is completed in a plurality of positions of the axially movable member.
4. An instrument as claimed in claim 3 wherein the reflectors are disposed so that the light path is completed at the limits of travel of the axially
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Apparatus for indicating the position of a movable member The invention relates to an instrument for detecting the position of a movable member such as a valve. An instrument for detecting the position of a liquid surface has been previously used in petrol tankers and involves detecting reflected light. The instrument comprises an internally reflecting prism, a light source connected by fibre optics to the prism and a light detector also connected by fibre optics to the prism. When the level of petrol rises to reach the prism the internal reflection ceases, the light path is broken and light is no longer received by the detector. In oilfield operations it is frequently important to be able to determine whether a valve is in the fully open or fully shut position, particularly valves employed in subsea oil production facilities. Such valves are actuated by a shaft which moves along its axis to open and close the valve. It is an object of the present invention to provide an instrument capable of performing this function. According to the present invention an instrument in combination with an axially movable member for detecting the position of said axially movable member, comprises a light source and light detector disposed with respect to the movable member so that the light path between the source and detector is completed in at least one, but not in other, positions of the axially movable member. A light reflector can be provided and is movable with the axially movable member, the light reflector completing the light path between the source and reflector in said at least one, but not in other, positions of the axially movable member. A plurality of light reflectors can be provided located at spaced apart positions along the movable member so that the light path is completed in a plurality of positions of the axially movable member. The reflectors can be disposed so that the light path is completed at the limits of travel of the axially movable member. The means for transmitting the light from source to reflector and from reflector to receiver can be a bundle of fibre optics. Each bundle can be shaped to provide the required tolerance or position of the movable member. The light source can conveniently be a light emitting diode and the receiver can conveniently be a photodiode which may include an electronic amplifier. The output from the photodiode can be converted into a frequency suitable for transmission through an inductive coupler or into a DC level representing the open or closed state. According to another aspect of the present invention, a method of determining the position of a movable member comprises employing a reflector carried by the movable member to complete the light path between a light source and a light reflector. The invention is illustrated by reference to the accompanying drawings in which: Figure 1 is a vertical section showing the instrument installed in a position to indicate one of the limits of travel of a valve actuating shaft. Figure 2 is an enlarged view of the path of the light. The instrument indicated generally by numeral 2 comprises two bundles of glass fibre optics 4 and 24. At the upper end of bundle 4 is a light source in the form of a light emitting diode (LED) 6 and at the upper end of bundle 24 is a receiver in the form of a photodiode 8, there being a light shield 10 located therebetween. Located below the lower end of the bundles 4 and 24 is a right anlge prism 12 conveniently made of plastic disposed so that light from the LED is internally reflected and transmitted through the bundle 4 to the photodiode 8. The gap between the lower end of bundle 4 and the face of the prism 12 is not more than 0.020 inches and will normally be in the range 0.012 to 0.020 inches. The prism 12 is mounted in a valve actuating shaft 14 and a similar prism 16 is also mounted in the shaft 14 at a position corresponding to the limit of travel of the shaft 14. Only in two positions of the shaft 14, i.e. the fully open or fully closed position, will the prisms 12 and 16 complete the light transmission path. Discrimination between the two limits of travel can be made by incorporating a second light receiving system (not shown) by which the outputs can be combined to produce a different frequency. Alternatively, discrimination between the two positions can be obtained by differences of voltage polarity applied to the voltage controlled oscillator (not shown) to give the different frequencies. The instrument has been installed by forming an aperture 5 in the valve body 3 and a gap 9 in the valve shaft housing 11. The potted electronics assembly 13 is inserted in the aperture 5 and held by a plate 15 secured by bolts 17. CLAIMS
1. An instrument in combination with an axially movable member for detecting the position of said axially movable member, said instrument comprising a light source and light detector disposed with respect to the movable member so that the light path between source and detector is completed in at least one, but not in other, positions of the axially movable member.
2. An instrument as claimed in claim 1 wherein a light reflector is provided and is movable with the axially movable member, the light reflector completing the light path between the source and reflector in said at least one, but not in other, positions of the axially movable member.
3. An instrument as claimed in claim 2 wherein a plurality of light reflectors are provided located at spaced apart positions along the movable member so that the light path is completed in a plurality of positions of the axially movable member.
4. An instrument as claimed in claim 3 wherein the reflectors are disposed so that the light path is completed at the limits of travel of the axially movable member.
5. An instrument as claimed in any one of claims 1 to 4 wherein the light detector is a photodiode and includes an electronic amplifier.
6. A method of detecting the position of an axially movable member which method comprises employing a light source and detector disposed with respect to the movable member so that the light path between the source and detector is completed in at least one but not in other positions of the axially movable member.
7. An instrument in combination with an axially movable member substantially as hereinbefore de scribed with reference to Figures 1 and 2.
GB8120837A 1980-07-05 1981-07-06 Detecting position of axially movable member Withdrawn GB2078951A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB8120837A GB2078951A (en) 1980-07-05 1981-07-06 Detecting position of axially movable member

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8022124 1980-07-05
GB8120837A GB2078951A (en) 1980-07-05 1981-07-06 Detecting position of axially movable member

Publications (1)

Publication Number Publication Date
GB2078951A true GB2078951A (en) 1982-01-13

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Family Applications (1)

Application Number Title Priority Date Filing Date
GB8120837A Withdrawn GB2078951A (en) 1980-07-05 1981-07-06 Detecting position of axially movable member

Country Status (1)

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GB (1) GB2078951A (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2159942A (en) * 1984-06-09 1985-12-11 Michael Roderick Oliver Fluid valve position sensor
GB2238611A (en) * 1989-11-22 1991-06-05 Univ Bristol Apparatus for checking the positioning accuracy of a mobile component
EP0844425A1 (en) * 1996-11-19 1998-05-27 ISI Norgren, Inc. Valve spool position detector apparatus
EP1069319A3 (en) * 1999-07-13 2002-05-08 Smc Corporation Pilot operated directional control valve having position detecting function

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2159942A (en) * 1984-06-09 1985-12-11 Michael Roderick Oliver Fluid valve position sensor
GB2238611A (en) * 1989-11-22 1991-06-05 Univ Bristol Apparatus for checking the positioning accuracy of a mobile component
GB2238611B (en) * 1989-11-22 1993-10-06 Univ Bristol Position checking
EP0844425A1 (en) * 1996-11-19 1998-05-27 ISI Norgren, Inc. Valve spool position detector apparatus
US5826616A (en) * 1996-11-19 1998-10-27 Isi Norgren, Inc. Valve spool position detector apparatus
EP1069319A3 (en) * 1999-07-13 2002-05-08 Smc Corporation Pilot operated directional control valve having position detecting function

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WAP Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1)