US3555967A - Closed loop servoactuator - Google Patents

Closed loop servoactuator Download PDF

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Publication number
US3555967A
US3555967A US793347*A US3555967DA US3555967A US 3555967 A US3555967 A US 3555967A US 3555967D A US3555967D A US 3555967DA US 3555967 A US3555967 A US 3555967A
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United States
Prior art keywords
cylinder
screwshaft
cylindrical member
translation
input shaft
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Expired - Lifetime
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US793347*A
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English (en)
Inventor
Howard M Geyer
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General Electric Co
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General Electric Co
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Publication date
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    • 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
    • F15B13/00—Details of servomotor systems ; Valves for servomotor systems
    • F15B13/16—Special measures for feedback, e.g. by a follow-up device
    • 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
    • F15B9/00—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member
    • F15B9/02—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member with servomotors of the reciprocatable or oscillatable type
    • F15B9/08—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member with servomotors of the reciprocatable or oscillatable type controlled by valves affecting the fluid feed or the fluid outlet of the servomotor
    • F15B9/12—Servomotors with follow-up action, e.g. obtained by feed-back control, i.e. in which the position of the actuated member conforms with that of the controlling member with servomotors of the reciprocatable or oscillatable type controlled by valves affecting the fluid feed or the fluid outlet of the servomotor in which both the controlling element and the servomotor control the same member influencing a fluid passage and are connected to that member by means of a differential gearing

Definitions

  • An actuator having an integral position servo is 5 3.1 U9 9 C s U n 5 disclosed in which the input and feedback means comprise a rotatable input shaft, a feedback shaft which rotates in response to axial translation of the actuator piston, and a rotatable and translatable cylindrical member having a groove 6 0 0 8 /6 6 7 o e 0 G mh. "c r "a e S LM d Ld 1mm.. .1] O 55 .III.
  • the cylindrical member being translatable in response to either of said input and said feedback shafts to operate the servovalve.
  • This invention relates to actuators, and more particularly to actuators having an integral closedloop position servo.
  • the actuator include an integral position servo so that the actuator extension'position will be proportional to-an input signal applied at the actuator.
  • An actuator with an integralposition servo provides several advantages. Among these are the capability of synchronizing the operation of several such OBJECTS OF THE INVENTION It is an object of this invention, therefore, to provide an actuator having a mechanically simplified integral position ser- DESCRIPTION OF THE DRAWINGS a While the specificationconcludes withclaims particularly pointing out and distinctly claiming the subject of this invention, the invention will be better understood by reference to the text below and the accompanying drawing in which:
  • FIG. 1 is a perspective sectional view of an actuator
  • FIG. 2 is a partially fragmented perspective sectional view of the input and feedback means included in the actuator of FlG.l;and 7
  • FIG. 3 is a perspective view of an alternate form of the invention.
  • FIG. 1 illustratesin section an actuator embodying the present invention.
  • Theactuator 20 comprises a body member 22 which includes a cylinder 24 havinga cylindrical bore 26 therein and an extended head end 28 forcontaining the servocomponents a piston 30 defining an extend chamber 32 and retract chamber 34 in the cylinder 24 and including a cylindrical rod 36 extending through one end of body member 22, a servovalve 38 mounted to the head'end 28 of the actuator 20, and means for providing input and feedback to servovalve 38.
  • Piston 30 includes a high lead threaded insert 40 which is rotationally secured thereto, and piston 30 itself is prevented from rotating relative to body member 22 by a combination of the attaching means 42 fastened to the outer end of piston rod 36 and the clevis member (not shown) to which piston rod 36 is attached for actuation thereof.
  • a high lead screw 44 is journaled in body member 22 by means of a bearing 46 supported therein adjacent the head end of cylindrical bore 26 and is engaged with threaded insert 40 in' such a manner that axial movement of piston 30 will cause lead screw 44 to rotate through an angle which is proportional to the said axial movement.
  • the lead screw 44 includes a second threaded portion 48 which extends beyond bearing 46in the direction of the servovalve 38 input-output means.
  • the servovalve 38 input-output means comprises an input shaft 50 which is rotationally supported in a bearing 52 in the with the second threaded portion 48 of screw shaft 44 an operating lever 58 which is engaged at its one end with groove 56 and is engaged at its other end with a piston 60 in servovalve 38, the operating lever 58 being pivotally connected at a point 62 intermediate its two ends tobody 22 of actuator 20.
  • input shaft 50 slidably extends into a hole 64 which is concentric with the outer surface of cylindrical member 54. Relative rotation between input shaft 50 and cylindrical member 54 is precluded by the combination of an axial slot 66 on theenlarged surface of input shaft 50 and a key means 68 which is secured to cylindrical member 54 and is slidable in slot 66.
  • mating splines or other means could be provided with the enlarged end of the input shaft and the cylindrical member to accomplish the same function.
  • cylindrical member 54 contains internal threads 70 which engage the threadedportion 48 of screw shaft 44.
  • cylindrical member 54 is caused to translate relative to screw shaft 44 and, assuming that piston is temporarily located in a given position, cylindrical member 54 also translates relative to body member 22 of actuator 20.
  • this translation combined with the threading action of spiral groove 56 on operating lever 50 causes operating lever 50 to pivot about point 62 and moves the servovalve piston 60 to direct pressurized hydraulic 'fluid to either extend chamber 32 or retract chamber 34, de-
  • the servovalve 38 comprises a body member 72 having a cylindrical bore 74 in which piston 60 is slidable.
  • Piston 60 includes lands 76, 78 at its ends which sealingly engage bore 74 to prevent leakage of hydraulic fluid therefrom and a pair of intermediate lands 80, 82 spaced from each other and from end lands 76, 78. That portion of piston 60 which connects the lands 76, 78, 80, 82 has a reduced cross section so as to prohydraulic source.
  • Two annuli 98, 100 are provided in body member 72 at locations which correspond to the positions of the two intermediate piston lands 80, 82 when piston 60 is in a null position.
  • annuli 98, 100 have a width which is only very slightly less than the axial length of lands 80, 82 and are connected by suitable conduits 102, 104 to extend chamber 32 and retract chamber 34 respectively.
  • the end of piston 60 containing first outer land 68 includes an extension 106 which is pivotally connected to operating lever 58 hereinbefore described.
  • actuator 20 Operation of actuator 20 is as follows. If the direction of input is as indicated by arrow 108, cylindrical member 54 will translate as shown by arrow 110 and simultaneously rotate spiral groove 56 to cause further translation of the lower end of operating lever 56, servovalve piston '60 will be directed in a direction away from the operating lever end of the servovalve 38, causing the first intermediate land 82 to uncover the first annulus 98 and expose it to fluid return which connects retract chamber 34 to return by conduit 104. At the same time the second intermediate land moves to expose the second annulus to hydraulic source port 96, there by providing fluid pressure to extend chamber 32 through conduit 102. An oppositely directed input would, of course, have a directly opposite affect.
  • piston 30 Upon the admission of pressurized fluid to extend chamber 26, piston 30 begins to move in the direction indicated by arrow 112. This axial translation of piston 30 causes a corresponding rotation of screw shaft 44 proportional to the pistons movement, which rotation correspondingly causes translation of cylindrical member 54 relative to screw shaft 44 by means of the threaded engagement of the threaded extension 48 of screw shaft 44 with the inner end of cylindrical member 54. Assuming that input shaft 50 is now in a steady rotational position, there will also be a translation of cylindrical member 54 relative to actuator body 22 in a direction opposite to that caused by input rotation of input shaft 50, which will cause operating lever 58 to pivot in a direction to shut off the supply of fluid to extend chamber 32.
  • the servovalve piston 60 will move to a position which allows pressurized fluid to enter retract chamber 34 and which drains extend chamber 32, and piston 30 will thus be directed back toward the position demanded by the angular position of input shaft 50. Depending upon the dynamic characteristics of the system, this cycling will repeat a few times until piston 30 is at or very near the demanded position.
  • FIG. 3 illustrates an alternate embodiment of the present invention. Only the input, feedback, and servovalve means are shown, the remainder of the actuator being constructed similarly to that shown in H6. 1.
  • the actuator includes a screw shaft 114, similar to the one shown in FIG. 1, which is similarly supported by the bearing mounted at the head end of the actuator bore.
  • the input feedback means comprises (1) a cylindrical member or shaft 116 rotationally and slidably supported by a suitable bearing (not shown) at the head end of the actuator, (2) a worm 118 concentric with the cylindrical member 116 and fixedly connected therewith, (3) a hollow cylindrical collar 120 concen tric with the screw shaft 114 and integrally connected therewith, (4) means 122 for slidably supporting and rotationally interlocking worm 118 with hollow cylindrical collar 120, an input shaft 124 journaled in the body of the actuator at right angles to the axis thereof, (6) a worm wheel 126 secured to said input shaft 124 and meshing with worm 118, and (7) an operating lever 128 which is pivotally connected at 130 to the actuator body member, has its other end engaged with a groove 132 in cylindrical member 116, and is pivotally connected intermediate its ends to a piston 134 in servovalve 136, which has a construction identical with that shown in FIG. 1.
  • hollow cylindrical collar 120 on the end of the screw shaft 114 is slidably engaged and rotationally interlocked with worm 118 can be seen by reference to the cutaway view of hollow collar 120.
  • Worm 118 contains on its inner end an enlarged cylindrical portion 138 and a key 140 extending from a portion of its cylindrical surface, and the hollow cylindrical collar 120 includes a corresponding slot 142 cut substantially along its length.
  • the dimensional relationships between the hollow cylindrical collar 120, the cylindrical portion 138 is freely slidable in hollow cylindrical collar 140.
  • mating splines or other suitable rotational locking means could be substituted for the structure shown.
  • an input rotation of input shaft 124 from an external source will cause rotation of worm wheel 126 and a corresponding translation of worm 118 and cylindrical member 116 due to the rack and pinion interaction between worm 118 and the worm wheel 126.
  • Translation of cylindrical member 116 and of groove 132 on the surface thereof will cause operating lever 128 to pivot about pin 130 and cause a corresponding movement of the servovalve piston 134, thereby directing high pressure fluid to either the extend or retract chamber of the actuator in a manner similar to that described in connection with FIG. 1.
  • a responsive movement of the actuator piston will ensue, which will cause a proportionate rotation of screw shaft 114 and, by virtue of the rotational interlocking of screw shaft 114 and worm 118, will cause worm 118 to be threaded axially on worm wheel 126 in a direction opposite the input translation.
  • This will cause the servovalve piston 134 through the linkage comprising operat ing lever 128, to seek a null position.
  • any overshoot ofthe piston beyond its demanded position will cause servovalve 136 to reverse flow of high pressure fluid between the extend and retract chambers, thereby causing the piston to return toward its demand position.
  • An actuator comprising:
  • valve actuating means supported by said cylinder, said actuating means comprising:
  • a translatably and rotatably supported cylindrical member including a groove on its surface
  • a worm coaxially connected to said cylindrical member and meshed with said worm wheel
  • feedback means for causing a reverse translation of said groove with respect to said cylinder, said feedback means being connected with said screwshaft and comprising, means for rotating said worm comprising a hollow cylindrical collar fastened to said screwshaft, a cylindrical portion included on said worm and slideably disposed in said hollow collar, and key means for preventing relative rotation between said collar and said cylindrical portion while permitting relative translation therebetween; and
  • valve means for selectively directing pressurized fluid into one of said extend and retract chambers and venting the other of said chambers.
  • An actuator comprising:
  • a piston positioned for reciprocation within said cylinder and defining an extend and retract chamber therein;
  • a screwshaft rotatably supported in said cylinder and operatively connected to said piston so as to rotate in response to translation thereof;
  • valve means for selectively directing pressurized fluid into one of said extend or retract chambers and for venting the other of said chambers;
  • valve actuating means supported by said cylinder, said actuating means comprising;
  • said cylindrical member including means for producing rotation thereof upon rotation of said input shaft and translation thereof upon rotation of said screwshaft;
  • said cylindrical member containing a groove spirally oriented on the outer surface thereof;
  • lever means connected on one end of said spiral groove and on an opposite end of said valve means
  • An actuator as recited in claim 2 further characterized in positioned between that portion of said screwshaft which that said translation producing means for said cylindrical is rotatably supported by said cylinder and the input shaft; member comprise;

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Transmission Devices (AREA)
  • Actuator (AREA)
US793347*A 1969-01-23 1969-01-23 Closed loop servoactuator Expired - Lifetime US3555967A (en)

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US79334769A 1969-01-23 1969-01-23

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US3555967A true US3555967A (en) 1971-01-19

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US793347*A Expired - Lifetime US3555967A (en) 1969-01-23 1969-01-23 Closed loop servoactuator

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US (1) US3555967A (enrdf_load_stackoverflow)
BE (1) BE744651A (enrdf_load_stackoverflow)
DE (1) DE2002718A1 (enrdf_load_stackoverflow)
FR (1) FR2029001A1 (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4235156A (en) * 1978-11-16 1980-11-25 Zenny Olsen Digital servovalve and method of operation

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1363880A (en) * 1970-12-17 1974-08-21 Hartmann Laemmle Ohg Fluid-pressure follow-up control apparatus
DE3342239A1 (de) * 1983-11-23 1985-05-30 Mannesmann Rexroth GmbH, 8770 Lohr Steuervorrichtung fuer einen hydraulisch beaufschlagten arbeitszylinder
DE3412352C1 (de) * 1984-04-03 1985-09-12 Mannesmann Rexroth GmbH, 8770 Lohr Steuervorrichtung für einen hydraulisch beaufschlagten Arbeitszylinder
EP0336887B1 (de) * 1988-04-08 1991-01-30 SIG Schweizerische Industrie-Gesellschaft Druckmittel-Servoverstärker

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2583407A (en) * 1945-12-12 1952-01-22 Lidgerwood Mfg Co Power steering mechanism
US2809532A (en) * 1953-12-01 1957-10-15 Deere Mfg Co Hydraulic steering mechanism
US2886008A (en) * 1953-08-03 1959-05-12 Gen Motors Corp Locking actuator and valve mechanism therefor
US3457836A (en) * 1967-05-29 1969-07-29 Superior Electric Co Digitally operated electrohydraulic power system

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2583407A (en) * 1945-12-12 1952-01-22 Lidgerwood Mfg Co Power steering mechanism
US2886008A (en) * 1953-08-03 1959-05-12 Gen Motors Corp Locking actuator and valve mechanism therefor
US2809532A (en) * 1953-12-01 1957-10-15 Deere Mfg Co Hydraulic steering mechanism
US3457836A (en) * 1967-05-29 1969-07-29 Superior Electric Co Digitally operated electrohydraulic power system

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4235156A (en) * 1978-11-16 1980-11-25 Zenny Olsen Digital servovalve and method of operation

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DE2002718A1 (de) 1970-07-30
BE744651A (fr) 1970-07-01
FR2029001A1 (enrdf_load_stackoverflow) 1970-10-16

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