EP0034882A1 - Drehbetätigungsvorrichtung - Google Patents

Drehbetätigungsvorrichtung Download PDF

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Publication number
EP0034882A1
EP0034882A1 EP81300305A EP81300305A EP0034882A1 EP 0034882 A1 EP0034882 A1 EP 0034882A1 EP 81300305 A EP81300305 A EP 81300305A EP 81300305 A EP81300305 A EP 81300305A EP 0034882 A1 EP0034882 A1 EP 0034882A1
Authority
EP
European Patent Office
Prior art keywords
piston
piston assembly
housing
actuator according
spring
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Withdrawn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
EP81300305A
Other languages
English (en)
French (fr)
Inventor
Wallace Mccormack
David Bowditch
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.)
CAMTORC Ltd
Original Assignee
CAMTORC 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 CAMTORC Ltd filed Critical CAMTORC Ltd
Publication of EP0034882A1 publication Critical patent/EP0034882A1/de
Withdrawn legal-status Critical Current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
    • F15B15/02—Mechanical layout characterised by the means for converting the movement of the fluid-actuated element into movement of the finally-operated member
    • F15B15/06—Mechanical layout characterised by the means for converting the movement of the fluid-actuated element into movement of the finally-operated member for mechanically converting rectilinear movement into non- rectilinear movement
    • F15B15/066—Mechanical layout characterised by the means for converting the movement of the fluid-actuated element into movement of the finally-operated member for mechanically converting rectilinear movement into non- rectilinear movement the motor being of the scotch yoke type

Definitions

  • This invention relates to a pressure fluid-operated rotary actuator of the kind comprising a housing with a cylindrical bore, a piston assembly comprising a pair of spaced-apart pistons coupled together for simultaneous sliding movement within said cylindrical bore, a cam situated between the two pistons and secured to a shaft rotatable about an axis fixed relative to the housing and disposed substantially at right angles to the longitudinal axis of said cylindrical bore with the peripheral surface of the cam engaging the confronting surfaces of the two pistons of said piston assembly, spring means urging said piston assembly in a first direction towards a limit position within said cylindrical bore, and means for supplying pressurised fluid to a space in said cylindrical bore for moving said piston assembly away from said limit position in a second direction opposite to said first direction.
  • the shaft may operate various forms of rotary fluid-control valves or be used to control the opening and closing of doors or the setting of the air vanes in an air conditioning plant.
  • the rotation of the shaft may be employed to control the actuation of one or more electrical switches which in turn control some form of electrical apparatus.
  • the spring means of the actuator returns the piston assembly to said limit position when the supply of pressurised fluid to said space is cut off and the space is connected to exhaust, and acts as a fail-safe device in the event of failure of the supply of pressurised fluid to the actuator. Return of the piston assembly to said limit position may be assisted by supplying pressurised fluid to a second space in said cylindrical bore.
  • a disadvantage of rotary actuators of the kind referred to is that more and more energy is used in loading the spring means the farther the piston assembly moves away from said limit position in said second direction. Consequently, the torque available at the shaft of the actuator decreases the farther the piston assembly moves from said limit position in said second direction.
  • the present invention aims to provide a rotary actuator of the kind referred to in which the torque available from said shaft is more nearly constant throughout the movement of the piston assembly from said limit position in said second direction.
  • a rotary actuator of the kind referred to is characterised in that the force exerted by the spring means on the piston assembly as the latter moves from said limit position in said second direction is at least partly balanced by a third pressurised fluid-operated piston acting on the spring means.
  • Said third piston may be slidable in said cylindrical bore in which case a fluid-tight partition would be provided in the housing to divide the cylindrical bore into two coaxial compart ments in which the piston assembly and the third piston, respec tively, would be located, a rod slidable in a fluid-tight manne in said partition being interposed between said piston assembly and said third piston.
  • said third piston is slidable in a hollow cylindrical casing secured to-said housing.
  • said cylindrical casing should be mounted on one end of said housing, preferably with the longitudinal axes of the housing and casing in alignment with one another.
  • a common end closure may be provided for both the housing and said cylindrical casing, a rod slidable in a fluid-tight manner in said common end closure member being interposed between the piston assembly and said third piston.
  • the spring means of the actuator is preferably a helical spring and the movement of the piston assembly from said limit position in said second direction may place the spring under tension.
  • the spring is arranged so that movement of the piston assembly frem said limit position in said second direction places the spring under increasing compression.
  • the rotary actuator shown in Figures 1 to 3 comprises a housing 1 having a circular cylindrical bore 2 therein and end closure members 3 and 4. Slidable within the bore 2 is a piston assembly, generally designated by the numeral 5, which comprises two pistons 6, 7 held together in spaced-apart relationship by tubes 8 to which the pistons are secured by screws 9.
  • a shaft 10 is rotatably mounted in bearings 11 in the walls of the housing 1, the axis of the shaft being disposed between the pistons 6, 7 at right angles to the longitudinal axis of the bore 2.
  • a disc cam 12 is secured to the shaft 10 and has its peripheral surface bearing against discs 13 of low friction material, for example polytetrafluoroethylene, secured in the confronting surfaces of the pistons 6, 7.
  • the numeral 16 designates a hollow cylindrical casing which is secured between the closure member 4 and an end cap 17 by means of tie rods 18 and nuts 19, the longitudinal axis of the casing 16 being aligned with the longitudinal axis of the bore 2.
  • a piston 20 is slidable in the casing 16 and a helical spring 21 is housed in the casing l6 between the piston 20 and the end cap 17.
  • the end closure member 3 has a screw-threaded through-bore 24 for attachment of a conduit (not shown) by means of which compressed air can be supplied to, or exhausted from, the cylinder space 25 between the piston 6 and the end closure member 3.
  • the end closure member 4 has a first screw-threaded through-bore 26 for attachment of a conduit (not shown) by means of which compressed air can be supplied to, or exhausted from, the cylinder space 27 between the piston 7 and the end closure member 4.
  • the end closure member 4 has a second screw-threaded through-bore 28 for attachment of a conduit (not shown) by means of which compressed air can be supplied to, or exhausted from, the cylinder space 29 between the piston 20 and the end closure member 4.
  • the cylinder space 30 between the piston 20 and the end cap 17 is connected to atmosphere by a through-bore 31 in the end cap 17.
  • Figure 1 shows the actuator with the piston assembly 5 in the limit position into which it is urged by the spring 21. If compressed air is supplied to the cylinder space 25, with the cylinder space 27 connected to exhaust, the piston assembly 5 will be moved to the right (as viewed in Figure 1) to cause rotation of the cam 12 and its shaft 10 in a clockwise direction (as viewed in Figure 1).
  • the profile of the cam 12 is designed so that it always makes contact with the inwardly-facing surface of the piston 6 substantially at the centre of this surface. If the action of the spring 21 is ignored, this means that a substantially constant output torque would be delivered by the shaft 10 as the piston assembly 5 moves from left to right as viewed in Figure 1.
  • the casing 16 is formed integrally with, and a ⁇ an extension of, the housing 1, as indicated by the chain lines 16b in Figure 2.
  • the end closure member 4 may be formed as a partition wall in the combined casing and housing.
  • the spring 21 of the embodiment of Figures 1 to 3 is replaced by a tension spring 21a housed in a spring casing 16a mounted at the opposite end of the housing 1 compared with the casing 16 of Figures 1 to 3.
  • the housing 1, the piston assembly 5, the cam 12 and the shaft 10 are of the same construction as in the embodiment of Figures 1 to 3.
  • the end closure member 3 of the housing 1 serves as a common end closure member for the housing 1 and the casing 16a.
  • a piston 20a is slidable in the casing 16a, and this piston is connected to the piston 6 of the piston assembly 5 by a ⁇ rod 22a.
  • the rod 22a is slidable in a fluid-tight bearing 33 in the end closure member 3.
  • the tension spring 21a has one of its ends secured to the end cap 17 and its other end secured to the piston 20a.
  • the cylinder space 30 is open to atmosphere and a bore 34 communicating with the cylinder space 29 would be connected to a conduit (not shown) for supplying compressed air to, and withdrawing it from, the cylinder space 29.
  • a conduit not shown
  • movement of the piston assembly 5 away from the end closure member 3 results in tensioning of the spring 21a,'and tensioning of the spring is assisted by supplying compressed air via the bore 34 to the cylinder space 29.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Actuator (AREA)
EP81300305A 1980-01-24 1981-01-23 Drehbetätigungsvorrichtung Withdrawn EP0034882A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB8002371 1980-01-24
GB8002371 1980-01-24

Publications (1)

Publication Number Publication Date
EP0034882A1 true EP0034882A1 (de) 1981-09-02

Family

ID=10510857

Family Applications (1)

Application Number Title Priority Date Filing Date
EP81300305A Withdrawn EP0034882A1 (de) 1980-01-24 1981-01-23 Drehbetätigungsvorrichtung

Country Status (2)

Country Link
EP (1) EP0034882A1 (de)
AU (1) AU6658281A (de)

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2321059A1 (fr) * 1975-08-12 1977-03-11 Gachot Jean Actionneur pneumatique a pistons antagonistes

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2321059A1 (fr) * 1975-08-12 1977-03-11 Gachot Jean Actionneur pneumatique a pistons antagonistes

Also Published As

Publication number Publication date
AU6658281A (en) 1981-07-30

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Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Designated state(s): CH DE GB NL SE

17P Request for examination filed

Effective date: 19820225

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN

18D Application deemed to be withdrawn

Effective date: 19831122

RIN1 Information on inventor provided before grant (corrected)

Inventor name: BOWDITCH, DAVID

Inventor name: MCCORMACK, WALLACE