WO1997001712A1 - Rotary actuators - Google Patents

Rotary actuators Download PDF

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Publication number
WO1997001712A1
WO1997001712A1 PCT/GB1996/001421 GB9601421W WO9701712A1 WO 1997001712 A1 WO1997001712 A1 WO 1997001712A1 GB 9601421 W GB9601421 W GB 9601421W WO 9701712 A1 WO9701712 A1 WO 9701712A1
Authority
WO
WIPO (PCT)
Prior art keywords
actuator
pistons
air
tube
actuator according
Prior art date
Application number
PCT/GB1996/001421
Other languages
French (fr)
Inventor
David Ralph Mooney
John Newman Cedric De Lemos
Original Assignee
Worcester Controls (Uk) Limited
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 Worcester Controls (Uk) Limited filed Critical Worcester Controls (Uk) Limited
Priority to AU60125/96A priority Critical patent/AU6012596A/en
Publication of WO1997001712A1 publication Critical patent/WO1997001712A1/en

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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
    • F15B15/065—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 rack-and-pinion type

Definitions

  • This invention relates to rotary actuators and more particularly but not exclusively to pneumatically operated rotary actuators for ball and the like valves.
  • a main aspect of the invention i ⁇ concerned with the inter-related questions of the loads arising from the use of a rack and pinion type or other linear-to-rotary motion convertors, and the communication of pneumatic or other fluid pressure to the actuating chambers of such devices and thus these aspects of the invention are concerned with actuators comprising such devices. Further aspects of the invention are concerned with the related question of the mounting and location of an end cap or plug for a fluid pressure operated actuator, and thus are applicable to ⁇ uch fluid pressure operated actuator ⁇ more generally.
  • An object of the pre ⁇ ent invention is to provide an actuator ⁇ uitable for use in relation to ball and the like valves, and which may have application more widely, offering improvement ⁇ in relation to simplicity of construction and/or reduced manufacturing cost and/or performance characteristic ⁇ with re ⁇ pect to the above-mentioned ⁇ tate of the art, or generally.
  • an actuator compri ⁇ es a cylinder portion and associated pi ⁇ ton ⁇ together with rack and pinion means for converting linear to rotary motion.
  • the embodiment provides for the pi ⁇ ton ⁇ to transfer load directly to their associated cylinder portion, by mean ⁇ of axially-extended bearing mean ⁇ .
  • the pi ⁇ ton ⁇ ⁇ lide on air tran ⁇ fer tube mean ⁇ not forming part of the load taking mean ⁇ for the pistons.
  • the air transfer tube means is ⁇ ealed to the pi ⁇ ton or pi ⁇ ton ⁇ by non load-bearing ⁇ ealing mean ⁇ .
  • the extended bearing mean ⁇ on the pistons i ⁇ located generally radially outwardly of the re ⁇ pective rack portion of the piston ⁇ o that the outwardly-directed load i ⁇ tran ⁇ ferred direct to the cylinder.
  • the end caps or plugs of the piston and cylinder a ⁇ sembly are located in u ⁇ e by circlip means ⁇ o as to be releasable in a ⁇ imple manner.
  • the circlip is adapted to resist the repetitive loadings by virtue of feature ⁇ of it ⁇ ⁇ hape and the profile of the corresponding ⁇ urface on the end cap, a ⁇ more fully de ⁇ cribed below.
  • the air transfer tubes in the embodiments comprise a tube fixed to the end cap or plug to feed air from that end of the as ⁇ embly to the chamber between the pi ⁇ ton ⁇ .
  • the air tube fixed to the actuator end cap i ⁇ thus-fixed by means of a profiled ferrule which i ⁇ inserted into the tube for mounting purpose ⁇ .
  • the air tubes are sealed to their respective pistons by means of O-rings.
  • the air transfer tubes may be of a number of different material ⁇ including pla ⁇ tics and stainle ⁇ ⁇ teel.
  • the air tran ⁇ fer tube which moves with its respective pi ⁇ ton may be arranged to actuate a micro ⁇ witch for a control ⁇ ystem of the apparatus.
  • a further factor in relation to the provision of means for transferring actuating air within the actuator concern ⁇ the requirement that the actuator shall be able to co-operator in a ⁇ imple face-to-face manner with the associated valve structure.
  • Thi ⁇ requirement preclude ⁇ the po ⁇ ibility of providing a ⁇ imple external air tran ⁇ fer duct, which might otherwi ⁇ e repre ⁇ ent a ⁇ imple and direct manner of achieving the nece ⁇ ary operating characteristics.
  • thi ⁇ aspect of the invention is characteri ⁇ ed by the feature that the circlip i ⁇ adapted to be loaded inward ⁇ with respect to its locating groove, in use.
  • the advantage i ⁇ provided that de ⁇ pite the endle ⁇ cycle ⁇ of loading of the circlip each time the actuator is energised, the po ⁇ ibility that ⁇ uch repetitive cycle ⁇ of the device will ultimately cau ⁇ e wear of the loaded ⁇ urface ⁇ and corresponding increa ⁇ ed tolerance ⁇ until at last the circlip will be disengaged, is greatly reduced, moreover, this result i ⁇ achieved in a ⁇ imple manner by adoption of appropriate profile ⁇ on the relevant surface of the end cap or plug and/or on the circlip itself and its locating groove.
  • Fig 1 show ⁇ a plan view of an actuator a ⁇ sembly
  • Fig 2 ⁇ how ⁇ a section on the line II-II in Fig 1
  • Fig 3 shows a ⁇ ide elevation view of the actuator of Fig 1, the direction of viewing being ⁇ hown by arrow III in Fig 1;
  • Fig 5 show ⁇ a vertical ⁇ ection on the line V-V in Fig 3;
  • Fig 6 shows an end elevation view of the actuator of Fig 3, as indicated by arrow VI in Fig 3;
  • Fig 7 shows an enlarged portion of the end cap and cylinder as ⁇ embly of Fig 2.
  • an actuator 10 comprises a main body 12 having body halves 14 and 16, and located therein and extending through the main body a tube or cylinder 18 having end plug ⁇ 20 and 22.
  • the valve as ⁇ embly is adapted to mount face- to-face with the flat end face 26 of body half 14.
  • threaded bore ⁇ 28 are provided in face 26 for mounting purpo ⁇ es in relation to the ball valve assembly to be controlled.
  • actuator 10 further compri ⁇ es piston ⁇ 30 and 32 slidable within cylinder 18, and each formed with a part-cylindrical axially-inwardly extending extension portion 34, 36, each extension portion being of corre ⁇ ponding part-cylindrical form and thu ⁇ being arcuate as viewed in the axial direction.
  • Each extension portion is formed with an array of rack teeth 38 to co-operate with complementary pinion teeth 40 formed on the inner portion of drive output shaft 24, which is journalled in bearings (not ⁇ hown) provided in main body 12.
  • rack-and-pinion device, 38, 40 cause ⁇ linear relative motion of the pistons lengthwise of the axi ⁇ 42 of actuator 10 to be converted to rotary motion about the axi ⁇ 44 of ⁇ haft 24 to effect controlled actuating motion of up to 90 degree ⁇ of a valve actuating member (not ⁇ hown) .
  • drive output ⁇ haft 24 is formed with a slot-form drive output formation 46 for drive transmi ⁇ sion purpose ⁇ .
  • extension portions 34 and 36 are accordingly provided with axially lengthwise-extending bearing elements 50 of bearing material ⁇ such as PTFE whereby friction and wear is reduced.
  • the bearing elements are provided in the form of di ⁇ creet bearing inserts of appreciable axial length a ⁇ ⁇ hown in Fig 2 and relatively narrow width, at spaced intervals across the arcuate extent of the pi ⁇ ton extensions 34 and 36.
  • Pi ⁇ ton ⁇ 30 and 32 have re ⁇ pective ⁇ ealing rings 52 and are freely slidable within cylinder 18.
  • a central chamber 54 i ⁇ defined between the pi ⁇ ton ⁇ to receive actuating air to cau ⁇ e relative outward movement of the pi ⁇ ton ⁇ .
  • End chambers 56 and 58 are defined between piston ⁇ 30 and 32 and their respective end cap ⁇ or plug ⁇ 22 and 20 re ⁇ pectively.
  • the end plug ⁇ 20 and 22 are ⁇ ealed to cylinder 18 by re ⁇ pective ⁇ ealing rings (not shown) received within ring grooves 60 formed in cylinder 18.
  • the end plugs are retained in their working positions, in a removable manner, by means of respective circlips 62 received in respective grooves formed likewise in cylinder 18, and to be more fully described below.
  • the arrangements for transmi ⁇ sion of air from these ports to the chambers 54, 56 and 58 will now be described.
  • Primary and secondary air transfer tubes 68 and 70 re ⁇ pectively.
  • Primary tube 68 tran ⁇ fers air from port 66 to central chamber 54.
  • Secondary air tran ⁇ fer tube 70 tran ⁇ fer ⁇ air from port 64 to both of the chamber ⁇ 56 and 58.
  • transfer tube 68 i ⁇ a ⁇ ociated with outward movement of the pi ⁇ ton ⁇ , and air tran ⁇ fer tube 70 with inward movement of the pi ⁇ ton ⁇ .
  • the air tran ⁇ fer tube ⁇ extend ⁇ lidingly through corre ⁇ ponding bores 72, 74, 76 and 78 formed in the piston ⁇ 30 and 32.
  • the pi ⁇ ton ⁇ freely slide on the tubes 68 and 70 and are provided with grooves 80, 82 and 84, to receive O-ring ⁇ (not shown) to effect airtight sealing as appropriate for the nece ⁇ ary pneumatic control.
  • the O-ring (not ⁇ hown) in ring groove 80 seals bore 72 to prevent air transfer from inner chamber 54 to outer chamber 56.
  • the O-rings in ring grooves 82 and 84 do likewise.
  • the ferrule ha ⁇ a few degree ⁇ of taper on its outer ⁇ urface ⁇ o a ⁇ to produce the necessary mounting and ⁇ ealing effect upon in ⁇ ertion into the open end of air tran ⁇ fer tube 68.
  • bore 74 in pi ⁇ ton 32 which receive ⁇ the inner end of tran ⁇ fer tube 68 is formed with a vent bore 92 to provide direct venting from tube 68 to chamber 54.
  • piston 30 has a vent bore 94.
  • axial location of the tube i ⁇ effected by direct engagement of the tapered ends 96, 98 with the end plugs 22, 20. Sealing of the tube ⁇ to the pi ⁇ tons is effected by the O-rings in ring grooves 82 and 84.
  • Bore 74 is closed at it ⁇ outer end by an end plug 100.
  • the air tran ⁇ fer tube ⁇ 68 and 70 do not form any part of the load taking mean ⁇ with re ⁇ pect to the rack and pinion device 40, 38.
  • the air tran ⁇ fer tube 68 and 70 are formed, for example, of a plastics material, or stainless steel and are merely sealed to the pistons by non load-bearing O-ring seals.
  • the air tran ⁇ fer tubes have no means for resi ⁇ ting any appreciable load ⁇ generated during use, notably outwardly-directed loads resulting from the u ⁇ e of the rack and pinion device. Thu ⁇ , the air tran ⁇ fer tubes are of relatively low ⁇ trength material ⁇ and have no mountings appropriate for transfer of load ⁇ to any load re ⁇ i ⁇ tant structure. In any case, the outwardly directed load ⁇ are tran ⁇ ferred directly laterally outwardly through the pi ⁇ ton exten ⁇ ion portions 34 and 36 to the cylinder 18.
  • Fig 4 shows the plan view profile of the piston extension portion ⁇ 34, 36 - only one of the ⁇ e being ⁇ een in thi ⁇ view.
  • Fig 4 al ⁇ o shows the arrangements whereby drive output ⁇ haft 24 extend ⁇ through aligned bore ⁇ 102 formed in cylinder 18 and receiving corre ⁇ ponding complementary collar ⁇ 104 formed in the upper and lower main body halves 14 and 16 and which co-operate with sealing rings 106 located against central rack portion 108 of output ⁇ haft 24.
  • .Grooves 110 are provided in the main body halves 14 and 16 to receive further sealing rings (not shown) to ⁇ eal between the body halve ⁇ and cylinder 18.
  • Al ⁇ o shown in Fig ⁇ 4 and 5 are air chambers of generally cylindrical form, formed in aligned positions in pistons 30 and 32, and in end plug 22.
  • Main body halve ⁇ 14 and 16 are held in clamped po ⁇ itional relation ⁇ hip by nut and bolt a ⁇ semblies 114
  • circlip ⁇ 72 are of round cro ⁇ - ⁇ ectional profile and are located in corre ⁇ ponding circlip grooves 116 which are of complementary part-circular profile.
  • Each circlip co ⁇ operates with it ⁇ respective end plug through a contacting portion of the plug which i ⁇ adapted to generate an inward force on the circlip it ⁇ elf.
  • FIG. 2 There is shown in Fig 2, and likewise in Figs 3 and 6 a pair of plug retaining ⁇ crew ⁇ 122 in ⁇ ertable through threaded aperture ⁇ in cylinder 18 to engage in corre ⁇ ponding profiled rece ⁇ ses in plugs 20 and 22 to inhibit both inward movement of the plugs when pi ⁇ ton ⁇ 30, 32 are retracted, and to inhibit any tendency for rotation of the plugs relative to the pi ⁇ ton ⁇ , which would be detrimental to the air tran ⁇ fer tube ⁇ .
  • U ⁇ e of the actuator i ⁇ believed to be ⁇ elf- evident.
  • Outward force ⁇ generated by the rack and pinion device are re ⁇ i ⁇ ted by cylinder 18.
  • End caps 20, 22 are retained by their respective circlip ⁇ 62.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Actuator (AREA)

Abstract

A pneumatically operated rack-and-pinion type actuator (10) for ball valves and the like comprises a piston (30, 32) and cylinder (18) device in which the outward loads generated by the rack and pinion (38, 40) are taken by the cylinder (18) itself and air transfer to the actuating chambers (54, 56, 58) between and behind the pistons (30, 32) is effected by air transfer tubes (68, 70) on which the pistons freely slide. By avoiding the need for structural piston guide rods and associated structures, the actuator is greatly simplified.

Description

ROTARY ACTUATORS
This invention relates to rotary actuators and more particularly but not exclusively to pneumatically operated rotary actuators for ball and the like valves. A main aspect of the invention iε concerned with the inter-related questions of the loads arising from the use of a rack and pinion type or other linear-to-rotary motion convertors, and the communication of pneumatic or other fluid pressure to the actuating chambers of such devices and thus these aspects of the invention are concerned with actuators comprising such devices. Further aspects of the invention are concerned with the related question of the mounting and location of an end cap or plug for a fluid pressure operated actuator, and thus are applicable to εuch fluid pressure operated actuatorε more generally.
There are diεclosed in GB 11 71 618 and GB 1251805 (Norbro Engineering Ltd) pneumatically operated piston-rack rotary actuators comprising twin pistons carrying rack portions, an asεociated rotary pinion, and a cylinder aεsembly provided by cylinder portions clamped together by substantial structural guide members on which the pistons slide. Theεe guide memberε serve aε load taking meanε to resist the outwardly-directed forces generated by the rack and pinion assembly during use. Accordingly, there is provided for εliding engagement between each piston and the associated guide rod, an extended bearing sleeve. Notably alεo, there iε provided clearance between the pistons and their asεociated cylinder (εee itemε 36 and 37 in Fig 1) which iε εealed by an O-ring 35.
Notably also in GB 11 71 618 the structural guide rods also serve as air transfer tubes for feeding air or other gaε internally within the actuator to the piston actuating chamberε at opposite endε of the device and between the pistons. Shortcomings of the above-discussed prior proposal are principally its relatively complex construction and consequential relatively high cost. There is a considerable need to achieve simplification and cost reduction while retaining the εatiεfactory operating characteriεticε.
An object of the preεent invention is to provide an actuator εuitable for use in relation to ball and the like valves, and which may have application more widely, offering improvementε in relation to simplicity of construction and/or reduced manufacturing cost and/or performance characteristicε with reεpect to the above-mentioned εtate of the art, or generally.
According to the invention there is provided an actuator as defined in the accompanying claimε.
In an embodiment an actuator compriεes a cylinder portion and associated piεtonε together with rack and pinion means for converting linear to rotary motion. In place of the internal load taking means of the prior GB '618 specification mentioned above, the embodiment provides for the piεtonε to transfer load directly to their associated cylinder portion, by meanε of axially-extended bearing meanε. Moreover, the piεtonε εlide on air tranεfer tube meanε not forming part of the load taking meanε for the pistons.
The air transfer tube means is εealed to the piεton or piεtonε by non load-bearing εealing meanε.
By thiε meanε there iε provided a simple conεtruction utiliεing a cylinder and an asεociated block without the requirement for rods for asεembly purpoεeε. Moreover, the end caps of the cylinder asεembly take the axial loadε which in the prior proposal were retained within the integral aεεembly held together by the mounting rodε. Additionally, no bearing sleeves are needed between the pistonε and their associated tubes. Also the tubes are a relatively simple and inexpensive construction.
In the embodiment, the extended bearing meanε on the pistons iε located generally radially outwardly of the reεpective rack portion of the piston εo that the outwardly-directed load iε tranεferred direct to the cylinder.
Alεo in the embodiment, the end caps or plugs of the piston and cylinder aεsembly are located in uεe by circlip means εo as to be releasable in a εimple manner. The circlip is adapted to resist the repetitive loadings by virtue of featureε of itε εhape and the profile of the corresponding εurface on the end cap, aε more fully deεcribed below.
The air transfer tubes in the embodiments comprise a tube fixed to the end cap or plug to feed air from that end of the asεembly to the chamber between the piεtonε. There is alεo provided a εecond tube extending between the head εide chambers of the device to interconnect these chambers for actuation purposes. The air tube fixed to the actuator end cap iε thus-fixed by means of a profiled ferrule which iε inserted into the tube for mounting purposeε.
In the embodiments, the air tubes are sealed to their respective pistons by means of O-rings. The air transfer tubes may be of a number of different materialε including plaεtics and stainleεε εteel. The air tranεfer tube which moves with its respective piεton may be arranged to actuate a micro εwitch for a control εystem of the apparatus. A further factor in relation to the provision of means for transferring actuating air within the actuator concernε the requirement that the actuator shall be able to co-operator in a εimple face-to-face manner with the associated valve structure. Thiε requirement precludeε the poεεibility of providing a εimple external air tranεfer duct, which might otherwiεe repreεent a εimple and direct manner of achieving the neceεεary operating characteristics.
Considering now the second aspect of the invention concerning the location of the cap or end plug of the aεεembly by a circlip, thiε aspect of the invention is characteriεed by the feature that the circlip iε adapted to be loaded inwardε with respect to its locating groove, in use.
As a reεult, in the embodiment, the advantage iε provided that deεpite the endleεε cycleε of loading of the circlip each time the actuator is energised, the poεεibility that εuch repetitive cycleε of the device will ultimately cauεe wear of the loaded εurfaceε and corresponding increaεed toleranceε until at last the circlip will be disengaged, is greatly reduced, moreover, this result iε achieved in a εimple manner by adoption of appropriate profileε on the relevant surface of the end cap or plug and/or on the circlip itself and its locating groove. Embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which :
Fig 1 showε a plan view of an actuator aεsembly; Fig 2 εhowε a section on the line II-II in Fig 1; Fig 3 shows a εide elevation view of the actuator of Fig 1, the direction of viewing being εhown by arrow III in Fig 1;
Fig 4 εhowε a section on the line IV-IV in Fig 1; and
Fig 5 showε a vertical εection on the line V-V in Fig 3;
Fig 6 εhows an end elevation view of the actuator of Fig 3, as indicated by arrow VI in Fig 3; and
Fig 7 shows an enlarged portion of the end cap and cylinder asεembly of Fig 2.
Aε shown in the drawings an actuator 10 comprises a main body 12 having body halves 14 and 16, and located therein and extending through the main body a tube or cylinder 18 having end plugε 20 and 22. Actuator 10 haε a drive output shaft 24 adapted to transmit drive to the complementary drive input formation of a ball or other type of valve (not shown) . The valve asεembly is adapted to mount face- to-face with the flat end face 26 of body half 14. Aε εhown in Fig 3, threaded boreε 28 are provided in face 26 for mounting purpoεes in relation to the ball valve assembly to be controlled.
Turning now to the internal structure of actuator 10, and referring to Fig 2 of the drawings, it can be εeen that actuator 10 further compriεes pistonε 30 and 32 slidable within cylinder 18, and each formed with a part-cylindrical axially-inwardly extending extension portion 34, 36, each extension portion being of correεponding part-cylindrical form and thuε being arcuate as viewed in the axial direction. Each extension portion is formed with an array of rack teeth 38 to co-operate with complementary pinion teeth 40 formed on the inner portion of drive output shaft 24, which is journalled in bearings (not εhown) provided in main body 12.
It will be understood that the rack-and-pinion device, 38, 40 causeε linear relative motion of the pistons lengthwise of the axiε 42 of actuator 10 to be converted to rotary motion about the axiε 44 of εhaft 24 to effect controlled actuating motion of up to 90 degreeε of a valve actuating member (not εhown) . It will be noted that drive output εhaft 24 is formed with a slot-form drive output formation 46 for drive transmiεsion purposeε. It will alεo be noted that the interaction of rack and pinion teeth 40, 38 reεultε in generally outwardly-directed forceε F being applied to piεton extenεion portionε 34, 36 cauεing theεe to be loaded outwardε againεt the internal εurface 48 of cylinder 18. The extension portions 34 and 36 are accordingly provided with axially lengthwise-extending bearing elements 50 of bearing materialε such as PTFE whereby friction and wear is reduced. The bearing elements are provided in the form of diεcreet bearing inserts of appreciable axial length aε εhown in Fig 2 and relatively narrow width, at spaced intervals across the arcuate extent of the piεton extensions 34 and 36.
Accordingly, it can now be εeen that the generally outwardly-directed forces generated by the rack and pinion device 38, 40 are transferred direct through the piston extensionε 34 and 36 and bearing elementε 50 to cylinder 18 during uεe.
Piεtonε 30 and 32 have reεpective εealing rings 52 and are freely slidable within cylinder 18. A central chamber 54 iε defined between the piεtonε to receive actuating air to cauεe relative outward movement of the piεtonε. End chambers 56 and 58 are defined between pistonε 30 and 32 and their respective end capε or plugε 22 and 20 reεpectively. The end plugε 20 and 22 are εealed to cylinder 18 by reεpective εealing rings (not shown) received within ring grooves 60 formed in cylinder 18. The end plugs are retained in their working positions, in a removable manner, by means of respective circlips 62 received in respective grooves formed likewise in cylinder 18, and to be more fully described below.
Air for controlling actuator 10 iε admitted to the actuator through ports 64, 66 formed in end plug 22, as shown in Fig 6. The arrangements for transmiεsion of air from these ports to the chambers 54, 56 and 58 will now be described. Broadly, to effect controlled supply of air from ports 64 and 66 to the chambers 54, 56 and 58 there are provided primary and secondary air transfer tubes 68 and 70 reεpectively. Primary tube 68 tranεfers air from port 66 to central chamber 54. Secondary air tranεfer tube 70 tranεferε air from port 64 to both of the chamberε 56 and 58. Thus, transfer tube 68 iε aεεociated with outward movement of the piεtonε, and air tranεfer tube 70 with inward movement of the piεtonε. The air tranεfer tubeε extend εlidingly through correεponding bores 72, 74, 76 and 78 formed in the pistonε 30 and 32. The piεtonε freely slide on the tubes 68 and 70 and are provided with grooves 80, 82 and 84, to receive O-ringε (not shown) to effect airtight sealing as appropriate for the neceεεary pneumatic control. Thuε, in the case of primary air transfer tube 68, the O-ring (not εhown) in ring groove 80 seals bore 72 to prevent air transfer from inner chamber 54 to outer chamber 56. The O-rings in ring grooves 82 and 84 do likewise.
Primary air transfer tube 68 iε located and mounted in poεition on end plug 22 by meanε of a tapered ferrule 86 (εee Fig 7) which is inserted into the open end of tube 68 to fix εame in poεition and to produce a fluid-tight εeal. The ferrule haε a few degreeε of taper on its outer εurface εo aε to produce the necessary mounting and εealing effect upon inεertion into the open end of air tranεfer tube 68. The inner bore 88 of ferrule 86 iε of uniform radius. As εhown in Fig 2, primary air tranεfer tube 68 extendε into chamber 54 and deliverε air thereto. It will be noted that bore 74 in piεton 32 which receiveε the inner end of tranεfer tube 68 is formed with a vent bore 92 to provide direct venting from tube 68 to chamber 54. Likewise, piston 30 has a vent bore 94. In the caεe of air tranεfer tube 70, axial location of the tube iε effected by direct engagement of the tapered ends 96, 98 with the end plugs 22, 20. Sealing of the tubeε to the piεtons is effected by the O-rings in ring grooves 82 and 84. Bore 74 is closed at itε outer end by an end plug 100.
It is particularly to be noted that the air tranεfer tubeε 68 and 70 do not form any part of the load taking meanε with reεpect to the rack and pinion device 40, 38. The air tranεfer tube 68 and 70 are formed, for example, of a plastics material, or stainless steel and are merely sealed to the pistons by non load-bearing O-ring seals. The air tranεfer tubes have no means for resiεting any appreciable loadε generated during use, notably outwardly-directed loads resulting from the uεe of the rack and pinion device. Thuε, the air tranεfer tubes are of relatively low εtrength materialε and have no mountings appropriate for transfer of loadε to any load reεiεtant structure. In any case, the outwardly directed loadε are tranεferred directly laterally outwardly through the piεton extenεion portions 34 and 36 to the cylinder 18.
Fig 4 shows the plan view profile of the piston extension portionε 34, 36 - only one of theεe being εeen in thiε view. Fig 4 alεo shows the arrangements whereby drive output εhaft 24 extendε through aligned boreε 102 formed in cylinder 18 and receiving correεponding complementary collarε 104 formed in the upper and lower main body halves 14 and 16 and which co-operate with sealing rings 106 located against central rack portion 108 of output εhaft 24. .Grooves 110 are provided in the main body halves 14 and 16 to receive further sealing rings (not shown) to εeal between the body halveε and cylinder 18. Alεo shown in Figε 4 and 5 are air chambers of generally cylindrical form, formed in aligned positions in pistons 30 and 32, and in end plug 22. The purpose of these chamberε iε to houεe coiled compreεεion εpringε deεigned to be compreεsed and thuε to εtore energy and to provide a fail εafe return capability in the event of power failure.
Main body halveε 14 and 16 are held in clamped poεitional relationεhip by nut and bolt aεsemblies 114
- see Fig 3. Details of the arrangement whereby circlips 62 retain end plugε 22 and 20 in poεition will now be deεcribed further.
Aε εhown in Fig 7, circlipε 72 are of round croεε-εectional profile and are located in correεponding circlip grooves 116 which are of complementary part-circular profile. Each circlip co¬ operates with itε respective end plug through a contacting portion of the plug which iε adapted to generate an inward force on the circlip itεelf. Thuε, in thiε embodiment, the contacting portion of plug 22 εeen in Fig 7 iε in the form of a εhoulder 118 having a correεponding 45 degree profiled or chamfered annular εurface 120 adapted to contact the circlip 62 and to apply to it a force directed εo aε to tend to maintain the circlip within its groove 116. Thuε, the reεultant force iε directed into the groove rather than in any direction which is axial of the actuator aεεembly or directed inwardly thereof.
Accordingly, under conditionε of use in which endless repeated cycles of the actuator are carried out, there iε no tendency for the cycleε of force applied by the end plug to the circlip to diεlodge εame .
Removal of the circlip for εervicing or other purposes iε carried out in the uεual way by flexure out of the groove 116 after inward movement of the pistons and of the end plugs.
There is shown in Fig 2, and likewise in Figs 3 and 6 a pair of plug retaining εcrewε 122 inεertable through threaded apertureε in cylinder 18 to engage in correεponding profiled receεses in plugs 20 and 22 to inhibit both inward movement of the plugs when piεtonε 30, 32 are retracted, and to inhibit any tendency for rotation of the plugs relative to the piεtonε, which would be detrimental to the air tranεfer tubeε.
Uεe of the actuator iε believed to be εelf- evident. A controlled supply of pneumatic presεure iε delivered to end cap 22 and to portε 64, 66 to cauεe output εhaft 24 to be driven. Outward forceε generated by the rack and pinion device are reεiεted by cylinder 18. End caps 20, 22 are retained by their respective circlipε 62.
Amongst other modifications which could be made in the above embodiments while remaining within the scope of the invention are the use of alternative circlip croεε-εectional profileε εuch aε a polygonal profile. Likewiεe, alternative arrangements for the air transfer tubes could be adopted, including the use of alternative materialε and alternative dispositionε with respect to the pistonε.

Claims

CLAIMS : -
1 A pneumatically operated rotary actuator for ball and other valves comprising a cylinder portion, pistons slidable therein, rack and pinion means located within said cylinder portion and between said pistons, load taking means for forces generated by said rack and pinion means, air input means for said actuator, and air transfer tube means for supplying said air from said air input meanε to said pistons, said pistons being adapted to slide with respect to said air transfer tube means, characterised by said load taking means for said rack and pinion means being provided by said cylinder portion and an associated axially-extended bearing means on said pistons, said air transfer tube means not forming part of said load taking means and being sealed to at least one of said pistonε by non load-bearing sealing means.
2 A fluid presεure operator rotary actuator compriεing a cylinder portion, associated pistons and linear to rotary motion conversion meanε characterised by fluid pressure transfer tube means adapted to transfer fluid pressure to said pistonε and not forming part of the load taking means for said pistons.
3 An actuator according to claim 1 characterised by said rack of said rack and pinion means being provided on said pistonε and said extended bearing means being located radially outwardly of said rack portions of said pistons.
4 An actuator according to any one of the preceding claims characterised by an end cap or plug for said cylinder means located with respect thereto by circlip means.
5 An actuator according to any one of the preceding claims characterised by said air transfer tube means being sealed to said at least one of said pistons by an O-ring.
6 An actuator according to any one of the preceding claims characterised by said air tranεfer tube meanε compriεing a tube to feed air from one end of said actuator to a chamber located between said pistons and said tube being sealed to the one of said pistons at said one end of the actuator and being fixed to end structure of the actuator at said end.
7 An actuator according to claim 6 characterised by said air transfer tube being fixed to said end cap or plug of said actuator by insertion of a profiled ferrule into said tube to cause said tube to grip a bore formed in said cap or plug.
8 An actuator according to any one of claims 1 to 5 characterised by said air transfer tube means comprising a tube to feed air between the head side chambers of said actuator at opposite ends of the actuator.
9 An actuator according to any one of the preceding claims characterised by said air transfer tube means comprising a plastics material.
10 An actuator according to any one of claims 1 to 7 characterised by said air tranεfer tube meanε comprising stainleεε steel.
11 An actuator according to any one of the preceding claimε characterised by said air transfer tube means being adapted to actuate a micro switch for a control system of said actuator upon movement of said tube with said one of said pistons.
12 A pneumatically operated rotary actuator for ball and other valves comprising a cylinder portion, pistons slidable therein and rotary motion generating meanε, εaid cylinder portion having removable end cap or plug means together with locating means therefor, characterised by said locating means comprising a circlip adapted to be loaded inwardly into a groove therefor during use.
13 A fluid pressure operated actuator comprising a cylinder portion, associated pistonε and rotary motion generating means characterised by retaining means for an end cap or plug of said cylinder portion, said retaining means comprising a circlip adapted to be loaded inwards with respect to its mounting groove in use.
14 An actuator according to claim 12 or claim 13 characterised by said circlip being adapted to be loaded inwards with respect to itε groove by means of a profile on the contacting portion of said cap or plug, said profile being adapted to generate said inward force.
15 An actuator according to any one of claimε 12 to 14 characterised by said profile on said contacting portion of said circlip being adapted to generate said inward force.
16 An actuator according to any one of the preceding claims characterised by said circlip being of generally round crosε-sectional profile.
17 An actuator according to any one of claims 12 to 15 characterised by said circlip being of generally polygonal cross-sectional profile.
PCT/GB1996/001421 1995-06-27 1996-06-17 Rotary actuators WO1997001712A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU60125/96A AU6012596A (en) 1995-06-27 1996-06-17 Rotary actuators

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9513038A GB2302708A (en) 1995-06-27 1995-06-27 Rotary Actuators
GB9513038.1 1995-06-27

Publications (1)

Publication Number Publication Date
WO1997001712A1 true WO1997001712A1 (en) 1997-01-16

Family

ID=10776718

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1996/001421 WO1997001712A1 (en) 1995-06-27 1996-06-17 Rotary actuators

Country Status (3)

Country Link
AU (1) AU6012596A (en)
GB (1) GB2302708A (en)
WO (1) WO1997001712A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103075383A (en) * 2013-02-04 2013-05-01 龚炳新 Novel cylinder and transmission mechanism thereof

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB9917245D0 (en) * 1999-07-23 1999-09-22 Keystone Valve Uk Ltd Valve actuator
ITFI20060073A1 (en) * 2006-03-15 2007-09-16 Pentair Water Italy S R L A FLUID PRESSURE CONTROL DEVICE WITH A SAFETY CLOSURE OF A COMPARTMENT CONTAINING THE PRESSURE FLUID

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4192225A (en) * 1978-02-10 1980-03-11 The Cessna Aircraft Company Cylinder locking ring
DE3741261A1 (en) * 1987-01-10 1988-07-28 Amg Antrieb Mechanik Gmbh Pivoting drive having a return unit
US5357847A (en) * 1991-04-17 1994-10-25 Hytork Actuators Limited Pressure vessels having end closures and retainers

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4192225A (en) * 1978-02-10 1980-03-11 The Cessna Aircraft Company Cylinder locking ring
DE3741261A1 (en) * 1987-01-10 1988-07-28 Amg Antrieb Mechanik Gmbh Pivoting drive having a return unit
US5357847A (en) * 1991-04-17 1994-10-25 Hytork Actuators Limited Pressure vessels having end closures and retainers

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103075383A (en) * 2013-02-04 2013-05-01 龚炳新 Novel cylinder and transmission mechanism thereof

Also Published As

Publication number Publication date
AU6012596A (en) 1997-01-30
GB2302708A8 (en) 1997-02-10
GB2302708A (en) 1997-01-29
GB9513038D0 (en) 1995-08-30

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