Rotary Actuator

1. Field of the Invention

This invention relates generally to rotary actuator devices for converting reciprocable motion to rotary motion.

2. Description of the Prior Art

Rotary actuators are commonly provided for converting linear movement to rotary movement, and are commonly used for opening and closing butterfly valves used in chemical processes and in water treatment facilities. Such rotary actuators have commonly employed a rack and pinion assembly for converting linear to rotary movement, the rack being actuated by a solenoid or a fluid power cylinder. Solenoid operated rotary actuators require appreciable current, sometimes over sustained periods of time, while fluid power cylinder operated rotary actuators involve the usual seal problems and close tolerances in machining the cylinder. It is therefore desirable to provide a fluid power operated type of rotary actuator employing a bellows for providing the operating force rather than the usual cylinder and piston.

A rotary actuator including a bellows having an inlet for admitting fluid under pressure thereto thereby to cause expansion thereof from collapsed to expanded positions. Means are provided for mounting the bellows for expansion and contraction along a first axis, and resilient means are provided for resisting expansion of the bellows and for returning the same to its collapsed position upon release of the fluid pressure. Cooperating rack and pinion elements are provided and means are provided for mounting the rack element for linear movement along the first axis. Means are provided for mounting the pinion element for rotary movement on a second axis normal to the first axis, and means are provided for operatively connecting the rack element to the bellows so that the pinion element is rotated in opposite directions in response to expansion and contraction of the bellows. The pinion element has two angularly spaced abutments thereon and stop members are provided respectively engaging the abutments in first and second rotational positions of the pinion element thereby limiting its rotational movement.

It is accordingly an object of the invention to provide an improved fluid powered rotary actuator.

Another object of the invention is to provide an improved rotary actuator for converting linear to rotary movement incorporating a bellows as the force-exerting element.

The above-mentioned and other features and objects of this invention and the manner of attaining them will become more apparent and the invention itself will be best understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings.

FIG. 1 is a side cross-sectional view showing the improved rotary actuator of the invention; and

FIG. 2 is a cross-sectional view taken along the line 2--2 of FIG. 1.

Referring now to the drawing, the improved rotary actuator of the invention, generally indicated at 10, comprises first and second end plate members 12, 14 connected by four guide rod assemblies 16. Each of the guide rod assemblies 16 comprises a tubular member 18 having opposite ends 20, 22. End 20 of tubular member 18 is received in opening 26 in end plate member 12. Cap 28 is secured by welding to end 20 of tubular member 18. End 22 of tubular member 18 is seated in recess 34 in bushing 36 which is seated in opening 38 in end plate member 14. Threaded member 40 is seated in end 22 of tubular member 18 and secured thereto, as by welding. Threaded fastener 42 engages threaded member 40 and has head 44 engaging bushing 36.

Bellows unit 46 formed of suitable resilient material, such as rubber, is disposed within guide rod members 16 and has one side 48 secured to end plate member 12, as by threaded fasteners 50. Pneumatic line 52 extends through opening 54 in end plate member 12 and communicates with the interior of bellows 46. Valve 56 in pneumatic line 52 selectively admits air under pressure to the interior of bellows 46 thereby to cause the same to expand from its collapsed position, as shown in solid lines in FIG. 1 to an expanded position, as shown in dashed lines at 58. Valve 56 has exhaust port 60 for exhausting air from the interior of bellows 46 upon collapse thereof, as will hereinafter be described.

Guide plate member 62 is movable mounted on guide rod members 16 by bearing members 64. Bellows 46 has its other side 66 connected to guide plate member 62, as by threaded fasteners 68.

Rack member 74 is provided mounted for linear reciprocable movement in bearing member 76. Bearing member 76 is supported between plate members 78, 80 mounted on plate member 82 secured to end plate member 14, as by threaded fasteners 84. Bearing member 76 extends through openings 86, 88 in end plate 14 and mounting plate 82. Inner end 90 of rack 74 extends inwardly from end plate member 14, as shown.

Rack 74 cooperatively meshes with segmented pinion 92 corresponding in shape to the sector of a circle having sides 94, 96 defining arcuate toothed segment 98 therebetween. Pinion 92 is mounted on shaft 100 rotatably supported by bearings 102 respectively mounted in plate member 78, 80. Stop screws 104, 106 are threaded in openings in bottom plate 108 and are held in the desired positions by stop nuts 110. Stop screws 104, 106, respectively engage sides 94, 96 of pinion 92 thereby selectively to limit the rotational extremities of its rotation movement.

Spring seat member 112 is secured to guide plate member 62, as by threaded fasteners (not shown). Ball joint 114 has stud portion 116 threaded in opening 118 of spring seat member 112 and is secured thereto by lock nut 120. Ball joint 122 is similarly secured to end 90 of rack 74. Link 124 connects ball joints 114, 122.

Spring seat member 126 is secured to end plate member 14, as by threaded fasteners (not shown). Coil compression spring 128 extends between end plate member 14 and guide plate member 62 surrounding ball joint 114, link 124, ball joint 122 and end 90 of rack 74 and having its opposite ends respectively seated on spring seat members 112, 126. Housing 130 extends between end plate members 12, 14 and encloses guide rod members 16, bellows 46 and spring 128. Breather plug 132 in end plate member 14 permits entry and exhaust of air from cavity 134 defined by housing 130 as bellows 46 expands and contracts.

It will now be seen that admission of air or other fluid under pressure to the interior of bellows 46 by valve 56 will result in expansion of bellows 46 toward its expanded position, thus imparting linear movement to rack 74 on its axis 136 through guide plate 62 moving on guide rod members 16 and link 124, spring 126 resisting movement of bellows 46 toward its expanded position. Linear movement of rack 74 on its axis 136 in the direction shown by arrow 136 will result in rotation of pinion 92 in the direction shown by arrow 138. Pinion shaft 100 may be provided with square ends 140 adapted to be connected to the device to be actuated, such as a butterfly valve. Upon actuation of valve 56 to terminate application of air under pressure to the interior of bellows 46, spring 128 expands thereby returning bellows 46 to its collapsed position, in turn moving rack 74 in the direction opposite that shown by arrow 136 and rotating pinion 92 and pinion shaft 100 in the direction opposite that shown by arrow 138. It will further be seen that the limits of the angular rotation of pinion 92 and pinion shaft 100 are established by adjustment of screws 104, 106.

Screws 42 are preferably sufficiently long so that the pressure exerted by spring 128 is fully relieved before screws 42 become disengaged with threaded members 40. In a physical embodiment of the improved rotary actuator 10 shown in the drawing in which the diameter of housing 30 was approximately 181/2 inches and the overall length of housing 130 approximately 201/2 inches, expansion of bellows 46 from its collapsed position toward its fully expanded position by approximately four inches provided 90.degree. rotation of pinion 92 on pinion shaft 100. In that physical embodiment, an "Airstroke" No. 21 actuator manufactured by Firestone Rubber Company was employed for bellows 46.

While there have been described above the principles of this invention in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of the invention.