US3898399A - Apparatus for detecting the position of a piston rod - Google Patents

Apparatus for detecting the position of a piston rod Download PDF

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Publication number
US3898399A
US3898399A US499677A US49967774A US3898399A US 3898399 A US3898399 A US 3898399A US 499677 A US499677 A US 499677A US 49967774 A US49967774 A US 49967774A US 3898399 A US3898399 A US 3898399A
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United States
Prior art keywords
bar
piston rod
cylinder
dog
annular bearing
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
US499677A
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English (en)
Inventor
Koichi Yasui
Yuzo Nakahara
Kenji Yamano
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.)
Fuji Electric Co Ltd
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Fuji Electric Co 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 Fuji Electric Co Ltd filed Critical Fuji Electric Co Ltd
Application granted granted Critical
Publication of US3898399A publication Critical patent/US3898399A/en
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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
    • H01H19/00—Switches operated by an operating part which is rotatable about a longitudinal axis thereof and which is acted upon directly by a solid body external to the switch, e.g. by a hand
    • H01H19/02—Details
    • H01H19/10—Movable parts; Contacts mounted thereon
    • H01H19/14—Operating parts, e.g. turn knob
    • H01H19/18—Operating parts, e.g. turn knob adapted for actuation at a limit or other predetermined position in the path of a body, the relative movement of switch and body being primarily for a purpose other than the actuation of the switch, e.g. door switch, limit switch, floor-levelling switch of a lift
    • H01H19/186—Operating parts, e.g. turn knob adapted for actuation at a limit or other predetermined position in the path of a body, the relative movement of switch and body being primarily for a purpose other than the actuation of the switch, e.g. door switch, limit switch, floor-levelling switch of a lift with travelling nuts

Definitions

  • a limit switch dog bar is pivotably connected at one end by a ball joint to a piston rod externally of a cylinder which slidably carries the piston rod.
  • the cylinder having positioned thereon, at the end proximate to the ball joint connection, an annular bearing slidably receiving the switch dog bar with the bearing having a spherical surface between it and a fixed sleeve to allow slight inclination of the bar with respect to the axis of the piston rod.
  • Limit switches mounted to the cylinder adjacent the annular bearing lie in the path of movement of dogs fixed to the bar and movable therewith. The switches transmit signals representing the position of the piston rod correlated to positions of the dog operating the limit switches.
  • the present invention relates to, an'improvement in an apparatus for detecting the position of a piston rod which slidably moves within. a linear motor cylinder housing the same, and 'more particularly, to an improved arrangement for mounting a limit switch dog bar ,to that slidable piston rod. a
  • a piston rod or plunger extends externally of a linear motor cylinder and reciprocates axially within the' cylinder regardless of whether such linear motor is of the electrically driven type or of the fluid pressure actuated type.
  • a certain class of linear motors of the electrically driven type have been equipped with limit switches which limit switches are adapted to transmit signals related to the position of a movable element forming a part thereof.
  • this signal merely represents the fact that the piston has traveled excessively in one direction or the other to alert the operator to an accidental overload condition of the electrical linear motor, and therefore it is not intended for the usual control of linear motors or equivalent cylinder means.
  • linear motors of either the electrical or hydraulic, pneumatic type fall into two types.
  • a'timer is incorporated in such a way'that the timer is started concurrently with the commencement of movement of the linear motor, that is, operation of the cylinder means so that the position of the pistonrod may be represented by the elapsedtime period.
  • a predetermined time expires, an assumption is made that a predetermined position has been reached by the linear moving piston rod for effecting subsequent processes.
  • the linear motor cylinder means are provided with a limit switch dog which moves linearlybr axially,'supported by the cylinder itself or by a-ma'chine body'in which the cylinder is'incorporated and the limit switch dog is adapted to be moved synchronously with the piston rod or linearly moving element of the cylinder means.
  • This limit switch dog engages stationary limit switches which are positionedin the path of travel of the limit switch dog as the piston rod or its equivalent moves axially, whereby signals are transmitted from the switches to associated apparatus to inform that apparatus that the piston rod has reached or passed a predetermined position in its stroke.
  • the first type of measurement is-inconvenient in that there is no conviction that the predetermined position has actually been reached by the piston rod or that the piston rod has been stopped at an intermediate'position relative to its stroke. While the second typeof measurement is free of those problems, it is still unacceptable for the reason that the limit switches and 'the limit switch dog or dogs must be attached to the cylinder means only after the completion of the assembly of that hydraulic motor, electrical linear motor, or other device forming the cylinder means which makes the mass production of the cylinder SUMMARY OF THE INVENTION
  • the piston rod detection apparatus of the present invention acts as an improvement for linear motors, whether hydraulic or electric, wherein a longitudinally or axially movable piston rod extends outwardly of a cylinder and a limit switch dog is fixedly coupled to that piston rod and overlies the cylinder and is movable axi-.
  • the improvement resides in coupling the bar at one end only to the piston rod externally of the cylinder by means of a ball joint and providing an annular bearing which is fixed to the cylinder near that end which is proximate to the ball joint coupling with the switch dog bore being slidably received within the annular bearing and wherein the limit switch means are fixed to the casing in juxtaposition to that annular bearing.
  • the bearing has a spherical surface in contact with its support to allow a slight inclination of the bar and bearing with respect to the axis of the piston rod without materially,
  • FIG. 1 is a side elevational view of an electrical linear motor equipped with a conventional apparatus for detecting the longitudinal position of the linear motor piston rod.
  • FIG. 2 is a plan view of an electrical linear motor incorporating the improved means of the present invention for detecting the position of its piston rod.
  • FIG. 3 is a longitudinal view, partially in section, of the linear motor of FIG. 2.
  • FIG. 1 the prior art ar-J rangement is shown in conjunction with a linear motor which may comprise either an electric motor, or a fluid reciprocating motor, in either case a cylinder C which is fixed, has extending therefrom paired piston rods P which are extended from the cylinder C and retracted therein, that is, the rods P move to the right and left of the cylinder C causing plate Q and a rod-like dog bar B to slide axially of cylinder C, the dog bar being supported for parallel longitudinal movement by way of paired bearings R at respective ends of cylinder C.
  • the length I which is the length of the dog bar B is greater than at.
  • the dog bar B moves synchronously with the piston rod P, and it is required that the dog barB be maintained parallel to the axis of the piston rod in order to obtain a smooth sliding motion of the dog bar.
  • the manufacture and assembly of the cylinder and the associated piston rod detection apparatus must be achieved in a highly accurate manner which prevents the adaptation of mass production and necessarily leads to an increase in manufacturing cost for this type of prior art apparatus.
  • the detecting arrangement of the present invention is provided for a linear motor indicated generally at L which includes an elongated cylinder'lO, the linear motor L being of the electric type including an electric drive motor which operates to extend and retract paired piston rods 1 which are supported by way of bearings 20 at the right end of the linear motor, the rods being joined to each other at that end by a thrust coupling 3 which also permits the movable portion of the piston rod assembly to be joined to a load (not shown). It is necessary only to realize that the paired pistons 1 may extend and retract within the cylinder 10 of the linear motor, that is, the rod and the thrust coupling 3 move axially.
  • the extent of such movement and the position of the piston rod is measured or sensed by way of an improved mechanism which involves an annular bearing 2 positioned near the end of the cylinder 10 from which the piston rods I extend.
  • the bearing member 2 is positioned at the end of the cylinder 10 which is proximate to the coupling point between the limit switch dog bar and the thrust coupling 3.
  • the limit switch dog bar 5 constitutes a rod-like member having a diameter on the order of the opening within the annular bearing member 2 which receives the bar and the outer surface of the bearing 2 facing its support sleeve 18 is spherical, as is the sleeve 18, to permit a slight inclination of the bar 5 with respect to the longitudinal axis of the linear motor L.
  • Sleeve 18 is fixed to cylinder by screws 19.
  • the second element of the improvement resides in the employment of a ball joint 4 for coupling one end only of the limit switch dog bar 5 to the movable piston rods 1.
  • the female member 17 of the ball joint 4 is fixed to the end shaft 5 while the male member 16 received thereby projects vertically upward from the said thrust coupling 3 and terminates in a spherical'surface which is received within the spherical recess of element 17 extending coaxially from rod 5.
  • a pair of cylindrical dogs 6 and 7 are mounted on the bar 5, these dogs being slidable along the length of the bar but being fixedly located by means of set screws 1 1 carried by the dogs but permitting by rotation of the screws the fastening of the dogs 6 and 7 to the bar at desired axial positions on the bar to respective sides of the annular bearing member 2.
  • a pair of limit switches 8 and 9 are located in close proximity to the bearing member 2 fixed to cylinder 10, on respective sides thereof, the limit switches being provided with switch actuators as at 12 and 13 respectively which are positioned in the path of the moving dogs 6 and 7.
  • the 'cylindrical dogs 6 and 7 are provided with tapered end faces as at 14 which make contact with the actuators l2 and 13 during the reciprocation of the piston rods 11 to change the state of the switches and provide signals indicative, upon contact by the dogs 6 and 7 with the switch actuators l2 and 13, of predetermined positions of bar 5 and corresponding positions in terms of the piston rods 1.
  • the stroke of the piston rods 1 can be conveniently controlled by adjusting the position of dogs 6 and 7.
  • the spherical outer surface of the bearing member 2, in combination with-the ball joint 4, allows a slight inclination of bar 5 with respect to the axis of the piston rods so that the bar can move smoothly irrespective of such minor inclination.
  • the limit switches are positioned near the bearing means, that is, annular bearing 2, the position detection is effected without involving substantial error regardless of the inclination of the bar, the spherical contact surfaces of the annular bearing 2 facing rod 5 and the ball and joint connection at 4 between members 16 and 17 permitting such inclination freely.
  • apiston rod is extended axially from and retracted axially into one end of a linear motor cylinder
  • a limit switch dog bar is fixedly coupled to said piston rod, overlies the cylinder and moves axially with the piston rod
  • dog means are fixed to said bar for movement therewith
  • at least one limit switch is positioned adjacent the bar and in the path of movement of said dog means for contact actuation to indicate the position of said piston rod
  • said bar is fixedly coupled at one end only to said piston rod by a ball joint
  • an annular bearing concentrically receives said bar and is fixed to said cylinder at the end of said cylinder proximate to the ball joint coupling
  • said annular bearing includes means permitting a slight inclination of the bar with respect to the axis ofthe cylinder without impairing its movement longitudinally in synchronism with said piston rod.

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US499677A 1973-08-22 1974-08-22 Apparatus for detecting the position of a piston rod Expired - Lifetime US3898399A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP1973098504U JPS5335668Y2 (ja) 1973-08-22 1973-08-22

Publications (1)

Publication Number Publication Date
US3898399A true US3898399A (en) 1975-08-05

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Application Number Title Priority Date Filing Date
US499677A Expired - Lifetime US3898399A (en) 1973-08-22 1974-08-22 Apparatus for detecting the position of a piston rod

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US (1) US3898399A (ja)
JP (1) JPS5335668Y2 (ja)

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3987323A (en) * 1974-11-08 1976-10-19 Metallwerk Max Brose & Co. Electric motor with resiliently mounted rotor
US4137432A (en) * 1974-05-10 1979-01-30 Kamm Lawrence J Limit switch assembly for manufacturing machine
US4307799A (en) * 1979-12-05 1981-12-29 Andco Actuator Products, Inc. Linear actuator
US4352035A (en) * 1979-10-20 1982-09-28 Robert Bosch Gmbh Electric motor operated adjusting drive
US4500805A (en) * 1984-02-07 1985-02-19 Esco Design, Inc. Electromechanical linear actuator
US4759386A (en) * 1987-01-20 1988-07-26 Pennwalt Corporation Electromechanical linear actuator
EP1116687A1 (de) * 2000-01-12 2001-07-18 Mannesmann Rexroth Aktiengesellschaft Prospektzug
US20060021862A1 (en) * 2002-08-07 2006-02-02 Vae Gmbh End position detector for movable switch parts
US7262377B1 (en) * 2006-11-23 2007-08-28 Hiwin Mikrosystem Corp. Limit switch control device for an actuator
US20080178665A1 (en) * 2007-01-29 2008-07-31 Hispano Suiza Device for measuring the position of a piston in a cylinder
US20090045297A1 (en) * 2005-05-18 2009-02-19 Vae Eisenbahnsysteme Gmbh Device for checking the end positions of movable parts of a railway switch
US20110155864A1 (en) * 2008-09-11 2011-06-30 Vae Eisenbahnsysteme Gmbh Device for fixing a switch setting device on stock rails of a rail switch
US20180259045A1 (en) * 2014-12-25 2018-09-13 Hirata Corporation Screw feeding device and actuator using same

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1924777A (en) * 1932-05-19 1933-08-29 Allen M Flanders Limit switch

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1924777A (en) * 1932-05-19 1933-08-29 Allen M Flanders Limit switch

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4137432A (en) * 1974-05-10 1979-01-30 Kamm Lawrence J Limit switch assembly for manufacturing machine
US3987323A (en) * 1974-11-08 1976-10-19 Metallwerk Max Brose & Co. Electric motor with resiliently mounted rotor
US4352035A (en) * 1979-10-20 1982-09-28 Robert Bosch Gmbh Electric motor operated adjusting drive
US4307799A (en) * 1979-12-05 1981-12-29 Andco Actuator Products, Inc. Linear actuator
US4500805A (en) * 1984-02-07 1985-02-19 Esco Design, Inc. Electromechanical linear actuator
US4759386A (en) * 1987-01-20 1988-07-26 Pennwalt Corporation Electromechanical linear actuator
EP1116687A1 (de) * 2000-01-12 2001-07-18 Mannesmann Rexroth Aktiengesellschaft Prospektzug
US7135648B2 (en) * 2002-08-07 2006-11-14 Vae Eisenbahnsysteme Gmbh End position detector for movable switch parts
US20060021862A1 (en) * 2002-08-07 2006-02-02 Vae Gmbh End position detector for movable switch parts
US20090045297A1 (en) * 2005-05-18 2009-02-19 Vae Eisenbahnsysteme Gmbh Device for checking the end positions of movable parts of a railway switch
US7262377B1 (en) * 2006-11-23 2007-08-28 Hiwin Mikrosystem Corp. Limit switch control device for an actuator
US20080178665A1 (en) * 2007-01-29 2008-07-31 Hispano Suiza Device for measuring the position of a piston in a cylinder
US7587930B2 (en) * 2007-01-29 2009-09-15 Hispano Suiza Device for measuring the position of a piston in a cylinder
US20110155864A1 (en) * 2008-09-11 2011-06-30 Vae Eisenbahnsysteme Gmbh Device for fixing a switch setting device on stock rails of a rail switch
US20180259045A1 (en) * 2014-12-25 2018-09-13 Hirata Corporation Screw feeding device and actuator using same
US10436298B2 (en) * 2014-12-25 2019-10-08 Hirata Corporation Screw feeding device and actuator using same

Also Published As

Publication number Publication date
JPS5043194U (ja) 1975-05-01
JPS5335668Y2 (ja) 1978-08-31

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