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EP0301845B1 - Abtastvorrichtung - Google Patents

Abtastvorrichtung Download PDF

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Publication number
EP0301845B1
EP0301845B1 EP19880306940 EP88306940A EP0301845B1 EP 0301845 B1 EP0301845 B1 EP 0301845B1 EP 19880306940 EP19880306940 EP 19880306940 EP 88306940 A EP88306940 A EP 88306940A EP 0301845 B1 EP0301845 B1 EP 0301845B1
Authority
EP
European Patent Office
Prior art keywords
piston
magnetic
cylinder
magnetic particles
proportion
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
Application number
EP19880306940
Other languages
English (en)
French (fr)
Other versions
EP0301845A1 (de
Inventor
Frank Allan Webb
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.)
Norgren Ltd
Original Assignee
Norgren Martonair Ltd
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 Norgren Martonair Ltd filed Critical Norgren Martonair Ltd
Publication of EP0301845A1 publication Critical patent/EP0301845A1/de
Application granted granted Critical
Publication of EP0301845B1 publication Critical patent/EP0301845B1/de
Expired legal-status Critical Current

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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
    • F15B15/00—Fluid-actuated devices for displacing a member from one position to another; Gearing associated therewith
    • F15B15/20—Other details, e.g. assembly with regulating devices
    • F15B15/28—Means for indicating the position, e.g. end of stroke
    • F15B15/2807—Position switches, i.e. means for sensing of discrete positions only, e.g. limit switches

Definitions

  • This invention relates to non-contact positional sensing systems and has particular reference to non-contact positional sensing systems for a piston movable longitudinally within a cylinder.
  • Non-contact positional sensing of pneumatic cylinder pistons is common practice. Normally, a permanent magnet is fitted to the piston and a reed switch or magnetically sensitive proximity sensors are attached to the cylinder barrel around its diameter.
  • the magnets which have been used heretofor have been of the ring type in various materials dependent upon the required field strength. Typical examples have been Samarium Cobalt, Ceramic Ferrite or a plastics material with a ferrite filler.
  • the magnetic ring may be located between split piston halves.
  • DE-A 3 424 461 A similar positional sensing system for a piston movable longitudinally within a cylinder is described in DE-A 3 424 461.
  • the purpose of the piston in the device of DE-A 3 424 461 is to concentrate the indicative force produced by an external coil, thereby providing positional information by way of feedback.
  • the specifc material disclosed in DE-A 3 424 461, namely Permalloy is of the type that is very effective in concentrating magnetic flex but that cannot be permanently magnetisesd to any appreciable extent.
  • a present non-contact positional sensing system for a piston movable longitudinally within a cylinder, in which the cylinder is formed of non-ferromagnetic material, there is a magnetically sensitive proximity sensor on the outside of the cylinder and the piston incorporates a permanent magnet, characterised in that the piston is formed substantially entirely from permanently magnetic material.
  • the piston may be moulded from magnetic material comprising magnetic particles in a non-magnetic matrix of plastics material.
  • the piston may be moulded by injection moulding.
  • the proportion of magnetic particles is preferably as high as practical and may be in the range 60-90%, preferably 70-90% and more preferably 80-90% by weight of the magnetic material.
  • the plastics material may be nylon and is preferably nylon 6/10.
  • the magnetic material may be a strontium ferrite filler. There may be present 88% by weight of strontium ferrite material.
  • the piston may be provided with non-magnetic seals which may be of conventional form.
  • the seals may be cup seals or '0' ring seals or disc seals.
  • a piston comprising a pair of moulded plastics halves 1, 2 which are conjoined together by an inner sleeve 3.
  • the two halves 1 and 2 trap between them a ring magnet 4.
  • the pair of seals 5, 6 seal the piston within a cylinder.
  • the cylinder and proximity sensors are well known and conventional and are not described herein.
  • the magnetic piston comprises an injection moulded body 7 formed of 6/10 nylon and 88% by weight of strontium ferrite.
  • the piston has a blind bore 8 permitting it to be attached to a piston rod, further piston or other piston follower.
  • Cup seals 9 and 10 seal the piston within the cylinder.
  • the piston may be a hollow piston as shown in Figure 3 in which the piston 11 is in the form of an injection moulded tubular member having cup seals 12 and 13.
  • the piston is formed almost entirely of magnetic material, significant savings in the length of the piston can be achieved by using a moulded form of magnetic material.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
  • Pistons, Piston Rings, And Cylinders (AREA)

Claims (8)

1. Berührungsloses Lagemeßsystem für einen Kolben, der innerhalb eines Zylinders in Längsrichtung beweglich ist, bei dem der Zylinder aus einem nicht ferromagnetischen Werkstoff gebildet ist, wobei sich außerhalb des Zylinders ein magnetisch empfindlicher Annäherungssensor befindet und der Kolben einen Permanentmagneten enthält, dadurch gekennzeichnet, daß der Kolben (11) im wesentlichen vollständig aus einem permanentmagnetischen Werkstoff gebildet ist,
2. System nach Anspruch 1, bei dem der Kolben (11) aus einem magnetischen Werkstoff geformt ist, der in einer nicht magnetischen Matrix aus Kunststoff magnetische Teilchen enthält.
3. System nach Anspruch 1, bei dem der Anteil der magnetischen Teilchen in dem Bereich von 60 bis 90 Masse% des magnetischen Werkstoffs liegt.
4. System nach Anspruch 3, bei dem der erwähnte Anteil in dem Bereich von 70 bis 90% liegt.
5. System nach Anspruch 3, bei dem der erwähnte Anteil in dem Bereich von 80 bis 90% liegt.
6. System nach einem der Ansprüche 2 bis 5, bei dem der Kunststoff Polyamid ist.
7. System nach einem der Ansprüche 2 bis 6, bei dem die magnetischen Teilchen aus Strontiumferrit bestehen.
8. System nach einem der Ansprüche 2 bis 6, bei dem die magnetischen Teilchen aus Samarium-Cobalt-Werkstoff oder aus keramischem Ferritwerkstoff bestehen.
EP19880306940 1987-07-31 1988-07-28 Abtastvorrichtung Expired EP0301845B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8718173 1987-07-31
GB878718173A GB8718173D0 (en) 1987-07-31 1987-07-31 Sensing system

Publications (2)

Publication Number Publication Date
EP0301845A1 EP0301845A1 (de) 1989-02-01
EP0301845B1 true EP0301845B1 (de) 1990-12-05

Family

ID=10621614

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19880306940 Expired EP0301845B1 (de) 1987-07-31 1988-07-28 Abtastvorrichtung

Country Status (3)

Country Link
EP (1) EP0301845B1 (de)
DE (1) DE3861224D1 (de)
GB (1) GB8718173D0 (de)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT404290B (de) * 1996-10-28 1998-10-27 Hygrama Ag Kolben für einen pneumatischen oder hydraulischen arbeitszylinder
DE102006006677A1 (de) * 2006-02-14 2007-08-23 Parker Hannifin Gmbh & Co. Kg Magnetkolben für Pneumatikzylinder
DE102006030999A1 (de) * 2006-07-05 2008-01-17 Zf Friedrichshafen Ag Einrichtung zur Sensierung der Position, Drehzahl und/oder des Drehwinkels eines Kolbens

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS6013405U (ja) * 1983-07-05 1985-01-29 株式会社　東京衡機製造所 アクチユエ−タ

Also Published As

Publication number Publication date
DE3861224D1 (de) 1991-01-17
EP0301845A1 (de) 1989-02-01
GB8718173D0 (en) 1987-09-09

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