EP0074266B1 - Hydraulic cylinder with position sensor - Google Patents

Hydraulic cylinder with position sensor Download PDF

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Publication number
EP0074266B1
EP0074266B1 EP82304667A EP82304667A EP0074266B1 EP 0074266 B1 EP0074266 B1 EP 0074266B1 EP 82304667 A EP82304667 A EP 82304667A EP 82304667 A EP82304667 A EP 82304667A EP 0074266 B1 EP0074266 B1 EP 0074266B1
Authority
EP
European Patent Office
Prior art keywords
bar
bore
wiper
hydraulic cylinder
cylinder 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
Application number
EP82304667A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0074266A1 (en
Inventor
Ronnie Franklin Burk
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.)
Deere and Co
Original Assignee
Deere and Co
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 Deere and Co filed Critical Deere and Co
Priority to AT82304667T priority Critical patent/ATE18286T1/de
Publication of EP0074266A1 publication Critical patent/EP0074266A1/en
Application granted granted Critical
Publication of EP0074266B1 publication Critical patent/EP0074266B1/en
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
    • F15B15/2815—Position sensing, i.e. means for continuous measurement of position, e.g. LVDT
    • F15B15/2853—Position sensing, i.e. means for continuous measurement of position, e.g. LVDT using potentiometers

Definitions

  • This invention relates to a hydraulic cylinder with a position sensor comprising a bar fixed to the closed end of the cylinder housing extending into and being slidably guided in a bore in the piston rod, a potentiometer element on a support surface of the bar, and a wiper carrier attached to the piston rod, with a wiper which moves along the potentiometer element as the piston rod moves in the housing.
  • US-A-3,726,191 discloses one solution to this problem.
  • a resistance and conductor element support bar are reciprocably received in a piston rod bore.
  • a conductive wiper assembly is carried for movement with the piston and rod.
  • the known transducer construction requires a relatively large transducer cross section which displaces a large volume of hydraulic fluid as the cylinder rod moves with respect to the transducer assembly.
  • the bore required in the cylinder rod to accommodate such a transducer of large cross section and to provide an escape path for displaced hydraulic fluid is so large as to prevent its use in many hydraulic cylinders where compact size is required.
  • the wiper contacts are suspended in the fluid escape path, allowing flow forces to vibrate or bend the contact leaf, resulting in operating noise or loss of signal.
  • the support bar is supported only at one end by a plastics sealing element which is subject to mechanical stress and failures.
  • FR-A-1 382 342 discloses an improvement in which the distal end of the bar is provided with a piston which slides inside the hollow piston rod whereby the bar is supported as a simple beam. It is not supported in the vicinity of the wiper and once again fluid flow past the wiper can introduce vibration and noise in the signal.
  • the object of this invention is to provide a hydraulic cylinder with a position sensor wherein the bar is always supported at the wiper and wherein adverse fluid flow effects are substantially precluded.
  • the invention is characterised in the manner set forth in claim 1 below.
  • An advantage of the present invention is that it provides a position-sensing cylinder with good immunity to electrical noise caused by hydraulic flow-induced vibration.
  • the potentiometer element support rod can combine good rigidity with low cross-sectional area, because it is mechanically supported along the length of its engagement with the cylinder rod bore.
  • a further advantage of the preferred construction is that it provides a position-sensing cylinder with an improved fluid pressure seal which is spaced apart from the support rod and thus, not subject to mechanical stress caused by the support of the support rod.
  • the support rod is a T-section support rod with one end welded or fixed to a hollow metallic sleeve which is press fitted into a fitting which is screwed into the closed end of the cylinder.
  • a ceramic plug seals the interior of the sleeve but provides no support for and is separate from the support rod.
  • Further support for the potentiometer support rod is provided by the sliding engagement between its edges and the wall of the rod bore within which the support rod reciprocates.
  • a wiper carrier co-operates with the bore wall and the potentiometer support to prevent fluid flow in the vicinity of the flexible wiper contacts.
  • a hydraulic cylinder 10 includes a housing 12 having a hollow cylindrical barrel portion 14 within which reciprocates a piston 16 connected to a rod 18.
  • a rod-receiving cap 20 is screwed into the rod end of the housing 12.
  • a blind stepped bore 22 extends into the piston 16 and the rod 18. As best seen in Fig. 2, the bore 22 has a large diameter portion 24 with a snap ring groove 26 therein and an annular ridge 28 at one end, a smaller diameter portion 30 and an annular shoulder 32 extending therebetween.
  • the housing 12 includes a threaded axial bore 34 at its closed end for receiving a steel outer transducer fitting 36.
  • the fitting 36 has an annular flange 38 for butting against a corresponding housing shoulder 40.
  • An O-ring 42 maintains a fluid-tight seal between the fitting 36 and the housing 12.
  • the fitting 36 also includes a stepped axial bore 44 extending therethrough.
  • a steel terminal sleeve 46 is press fitted into the fitting bore 44.
  • the sleeve 46 has an annular groove 48 which receives a back-up ring 50 and an O-ring 52 for maintaining a fluid seal between the fitting 36 and the terminal 46.
  • a plug of ceramic material 54 is formed in the hollow interior of the sleeve 46 to form a hermetic seal.
  • the sleeve 46 is formed as a separate piece for fitting 36 so that, when the ceramic material 54 is heated within the terminal 46, the fitting 36 is not degraded by the high temperatures to which it would otherwise be exposed if the fitting 36 and the terminal 46 were a single piece.
  • a steel support bar 60 extends into the bore 22 from an end 62 received by and welded to the sleeve 46.
  • the end 62 of the support 60 is rigidly supported with respect to the housing 12 by metallic pieces 36 and 46, whereas other position sensing cylinders, such as that described in US Patent No. 3,726,191, have supported the transducer support element by press fitting the support into a plastics insulating sleeve, which is, in turn, received by a metallic threaded fitting.
  • the transducer support is less rigidly supported at its supported end and the plastics insulating material is subject to stress failures, such as cracking, which then degrades its sealing properties.
  • the ceramic seal 54 is subject to very little mechanical stress caused by supporting the support 60. Instead, the ceramic seal 54 need only withstand the hydraulic pressures which it is designed to withstand, with the result that the embodiment of the invention has increased integrity with respect to fluid pressure sealing.
  • the support bar 60 has a substantially T-shaped cross-section (as best seen in Figs. 3 and 4) formed by a cross piece 64 and from which perpendicularly extends a stiffening web 66 perpendicular thereto.
  • the face of the cross piece 64 which is opposite the web 66 forms a planar support surface 68.
  • a circular edged notch 70 is formed in the end 62 of the support 60, as best seen in Figs. 2 and 4.
  • the cross piece 64 and the web 66 divide the bore 22 into three fluid chambers 65, 67 and 69, of which chambers 65 and 67 are visible in Fig. 2.
  • curved outer edges 59, 61 and 63 of the support 60 slidably engage the wall of the bore 22. This engagement adds rigidity to the support 60 and helps to prevent deformation of the support 60 and reduces vibration to which the support 60 would be subject if it were cantilevered, i.e., supported merely at one end.
  • a resistance or potentiometer assembly 72 is placed on the planar support surface 68 of the cross piece 64.
  • the assembly includes an electrically insulating base 74 fixed to the support surface 68 and which may be formed of material such as "Kapton" (a Trade Mark of DuPont).
  • the assembly 72 also includes a conductive plastics potentiometer element 76, of which the largest elongated central portion thereof is laid directly upon the insulating base 74.
  • the ends 78 and 80 of the potentiometer element 76 are overlaid on to portions of copper or metallic electrical conductive ground and power strips 82 and 84, respectively.
  • the potentiometer element 76 terminates at edges 79 and 81, respectively.
  • the Conductive ground strip 82 terminates at edge 83, under the end 78 of the potentiometer element 76, as shown in dashed line Fig. 5.
  • a conductor 86 is soldered to the other end of the ground strip 82.
  • the conductive power strip 84 terminates at an edge 85 under end 80 of the potentiometer element 76, as also shown in dashed line in Fig. 5.
  • the overlaps between the conductive strips 82, 84 and the potentiometer element ends 78, 80 need only be sufficient to provide good electrical continuity therebetween.
  • the other end of the power strip 84 is joined via a solder joint to a conductor 88.
  • a metallic or electrical conductive commutator strip 90 extends from an edge indicated by reference numeral 92 to an end 94 to which is soldered to a conductor 96.
  • An overlay strip 98 of conductive plastics material is positioned on top of the commutator strip 90 and extends from edge 99 to an edge also indicated by reference numeral 92.
  • the major portion of the power strip 84 is separated from the commutator strip 90 by the middle or potentiometer strip 76 to reduce the possibility of metallic particles forming undesirable short circuit connections between the power strip 84 and the commutator strip 90.
  • the transducer element 72 is not received in a recess or channel in the support 60, but rather is positioned on top of the planar support surface 68. The absence of a recess or channel reduces the likelihood of metallic particles forming undesirable short circuit connections between the support 60 and the outer edges of the power strip 84 and the commutator strip 90.
  • the thicknesses of the various strips in Figs. 6a-d are exaggerated.
  • the conductors 86, 88 and 96 extend from their solder joints, through the notch 70, the terminal cup 46 and the ceramic seal 54 to respective connector terminals 100, 102 and 104, two of which are visible in Fig. 2.
  • a conventional female plug-type connector may be coupled to the connector terminals 100, 102 and 104.
  • a wiper carrier 110 is received by bore portion 24 of the bore 22, as best seen in Fig. 2.
  • the wiper carrier 110 has a generally cylindrical body 112 of an insulating material such as glass-reinforced nylon with an annular rebate 114 in one end thereof.
  • the rebate 114 registers with the ridge 28 only when the carrier 110 is properly mounted in the bore portion 24, otherwise, the annular ridge 28 will prevent the carrier 110 from being inserted far enough into bore portion 24 to allow insertion of snap ring 126 into snap ring groove 26.
  • a wiper support web 116 extends inwardly from a portion of the body 112.
  • a two-pronged conductive wiper 118 is embedded in and supported by the web 116 so that prongs 120 and 122 resiliently and slidably engage the surfaces of the plastics conductive strip 98 above commutator strip 90 and the potentiometer element portion 76, respectively.
  • the wiper 118 is exposed to the fluid in the chamber 65.
  • the prongs 120 and 122 have multiple fingers.
  • a rectangular recess 124 is formed in the inner surface 125 of the carrier web 116 so that the inner surface 125 closely registers with the surface 68 of the support element 60 and with the transducer element 72.
  • the carrier 110 is coupled for movement with the rod 18 and piston 16 between the snap ring 126 and a resilient wave washer 128.
  • a voltage is applied across terminals 102 and 100 to apply a corresponding voltage across the resistance element 76.
  • the wiper 118 moves with the piston 16 and rod 18 and with respect to the support 60 and the transducer element 72.
  • the voltage which the wiper 118 taps off varies from ground potential to approximately the voltage at the power strip 84, depending upon the longitudinal position of the wiper 118 relative to the resistance element 76.
  • the voltage on the wiper 118 is communicated to the exterior of the cylinder housing 12 via the commutator strips 98 and 90, conductor 96 and connector terminal 104, from where it can be monitored to indicate the position of cylinder 10.

Landscapes

  • Engineering & Computer Science (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Actuator (AREA)
  • Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)
  • Vehicle Body Suspensions (AREA)
  • Characterised By The Charging Evacuation (AREA)
  • Looms (AREA)
  • Devices For Conveying Motion By Means Of Endless Flexible Members (AREA)
  • Fluid-Pressure Circuits (AREA)
  • Reciprocating Pumps (AREA)
  • Valve Device For Special Equipments (AREA)
  • Forklifts And Lifting Vehicles (AREA)
  • Body Structure For Vehicles (AREA)
EP82304667A 1981-09-08 1982-09-06 Hydraulic cylinder with position sensor Expired EP0074266B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT82304667T ATE18286T1 (de) 1981-09-08 1982-09-06 Hydraulikzylinder mit stellungsfuehler.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US30033181A 1981-09-08 1981-09-08
US300331 1981-09-08

Publications (2)

Publication Number Publication Date
EP0074266A1 EP0074266A1 (en) 1983-03-16
EP0074266B1 true EP0074266B1 (en) 1986-02-26

Family

ID=23158660

Family Applications (1)

Application Number Title Priority Date Filing Date
EP82304667A Expired EP0074266B1 (en) 1981-09-08 1982-09-06 Hydraulic cylinder with position sensor

Country Status (11)

Country Link
EP (1) EP0074266B1 (es)
JP (1) JPS5854208A (es)
AT (1) ATE18286T1 (es)
AU (1) AU549902B2 (es)
BR (1) BR8205185A (es)
CA (1) CA1180916A (es)
DE (2) DE74266T1 (es)
DK (1) DK400982A (es)
ES (1) ES515508A0 (es)
MX (1) MX154307A (es)
ZA (1) ZA826527B (es)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3744254A1 (de) * 1987-12-24 1989-07-13 Integral Hydraulik Co Unter oel betriebenes linearpotentiometer
US6725761B1 (en) 2002-09-30 2004-04-27 Prince Manufacturing Corporation Spooling device assembly for hydraulic cylinder and method of assembling same

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE436072B (sv) * 1983-03-22 1984-11-05 Hara Ab Potentiometeranordning for legesbestemning av hydraulkolvar och liknande
US8100045B2 (en) 2008-10-21 2012-01-24 Clark Equipment Company Hydraulic cylinder rod position sensor

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3175094A (en) * 1962-05-24 1965-03-23 Guerin Engineering Inc Electrohydraulic actuator
FR1382342A (fr) * 1963-11-09 1964-12-18 Mitchell Hydraulics Ltd Perfectionnements aux dispositifs de commande mécanique actionnés par un fluide sous pression
US3412391A (en) * 1964-10-31 1968-11-19 Gullick Ltd Pressure-fluid-operated devices and means for indicating the condition thereof
US3726191A (en) * 1971-02-08 1973-04-10 Bunker Ramo Electrically controlled hydraulic system and transducer therefor

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3744254A1 (de) * 1987-12-24 1989-07-13 Integral Hydraulik Co Unter oel betriebenes linearpotentiometer
US6725761B1 (en) 2002-09-30 2004-04-27 Prince Manufacturing Corporation Spooling device assembly for hydraulic cylinder and method of assembling same

Also Published As

Publication number Publication date
ZA826527B (en) 1984-04-25
ES8402054A1 (es) 1984-01-01
MX154307A (es) 1987-06-30
DE3269407D1 (en) 1986-04-03
DE74266T1 (de) 1983-08-04
BR8205185A (pt) 1983-08-16
DK400982A (da) 1983-03-09
ATE18286T1 (de) 1986-03-15
JPS5854208A (ja) 1983-03-31
AU8745882A (en) 1983-03-17
AU549902B2 (en) 1986-02-20
EP0074266A1 (en) 1983-03-16
ES515508A0 (es) 1984-01-01
CA1180916A (en) 1985-01-15
JPH0233883B2 (es) 1990-07-31

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