US3065736A - Pneumatic actuator - Google Patents

Description

Nov. 27, 1962 P. P. DEMAY 3,065,736

PNEUMATIC ACTUATOR Filed Dec. 8, 1960 INVENTOR.

PETER P. DEMAY 47' OR/VEY and provide a sealed chamber for the actuator.

United States Patent Minneapolis- Minneapolis, Minn,

My invention relates to fluid actuators and more particularly to an improved pneumatic actuator.

Fluid actuators and particularly pneumatic actuators are normally designed for bi-directional positioning and generally utilize the working medium for movement in one direction of work with a return spring for controlling the second direction of movement. This type of device has the disadvantage of imposing the additional load of the spring in adition to the work upon the actuator in oneworking direction limiting the output of the same. Where bi-directional actuators utilize fluid medium for controlling work movement in both directions, complex valving and porting is required such that a composite or self-contained device is not feasible. This type of apparatus requires auxiliary equipment to increase the cost and add to the complexity of the same. The present invention is directed to a complete self-contained actuator utilizing reversing valving and eliminating the need for a return spring to provide a small compact device which is capable of greater working force and ease in control. It further provides an apparatus which may be readily positioned by a control unit or relay or pilot positioner to accurately position the output movement of the main actuator minimizing reversal lags and improving the overall operation of the apparatus. Therefore it is an object of this invention to provide an improved positive positioning pneumatic actuator of the springless type. Another object of this invention is to provide in a device of this type an arrangement of parts including valving on a moveable element for the actuator to direct fluid medium to the respective working chambers of the actuator. It is a still further object of this invention to provide in an improved pneumatic actuator of this type an arrangement in which the working medium may be directed to the moveable element of the actuator and the valving for the same through moveable piping. These and other objects of this invention will become apparent from reading of the attached decription together with the drawings wherein:

The improved pneumatic actuator is shown in section to disclose the arrangement of parts.

As will be seen in the drawing, the improved pneumatic actuator includes a casing indicated generally at formed of a plurality of parts including a center section 11 which is cylindrical in form and having a threaded lower inner periphery to receive an end wall sealing section 12 which is threaded thereto and sealed therein through suitable sealing means such as indicated at 13. The opposite extremity of the cylindrical section 11 includes a second end wall portion 14 fitted into a shoulder portion 15 in cylindrical section 11 and held in position by a locking ring 16 which is fitted into a recess 17 in the casing section 11. The end wall portion 14 includes a sealing member 20 fitted in a grooved recess 21 in the wall portion to seal it to the cylinder Positioned within the casing section 11 is a piston member indicated generally at 25, which is formed by a pair of parts 26, 27 with a sealing means 29 therebetween, the parts being held in assembled relation through suitable means not shown. The piston is designed to be reciprocated within the cylindrical casing and divides 3,555,735 Patented Nov. 27, 1962 the casing into two working pressure chambers indicated at 28 and 30 such that a working medium or fluid medium, such as air, may be transmitted to one or the other of the Working chambers to move the piston within the casing in a conventional manner.

Attached to the lower section of the piston 25 is a flange member 40 designed to mount an output shaft or output means 41, shaft 41 extends through the end wall section 12 and a sealing means 42 therein, to transmit the output movement from the piston of the actuator. Also positioned within the piston 25 is a pair of conduit means 44, 45 which are independent of one another and each terminating in a pair of ports 48, 49, 50, 51 communicating with the opposite surfaces of the piston or the pressure chambers 28, 30. Thus it will be seen that the port 48 connects the conduit 4-4 to chamber 28 while the port 49 communicates with chamber 3t). Similarly the port 50 communicates with chamber 28 while the port 51 communicates with chamber 30. Positioned at the surface of these ports are valve seat members 52, 53, 54, 55 respectively which seat members have cooperating therewith valve closure members in the form of pivoted levers 56-59. Each of which are respectively pivoted on a raised hub mounted on the surface of the piston 25 such as is indicated at 60. The extremities at the levers 56-59 include valve closure members 61-64 respectively which cooperate with the seats 52-55 to control flow from the common conduits 44, 45 to one or the other sides of the pistons or the respective working chambers 28, 30. Thus there are two pairs of valves provided, each pair of which has a common conduit in the piston and each of the valves in the pair communicate respectively with opposite sides of the piston or opposite working chambers 28, 30. These valve closure members or the pivoted levers 56-59 are operated by an actuating shaft indi cated at 70 which extends through the reduced section 72 of the piston providing clearance for the pivotal movement of the levers. The shaft 70 is adapted to be positioned relative to the piston in a sliding movement, which as Will be later noted, causes selective operation of the respective valves formed by the closure members 61-6-4 and the valve seats 52-55. An 0 ring seal 75 is positioned in the reduced section 72 around the shaft 70 and seals the respective working chambers of the piston.

A pair of nuts or thrust members 78, are mounted on the actuating shaft 70 and engage the respective levers 56-59 to cause pivotal movement of the same thereby moving the respective closure members mounted thereon with respect to the valve seats. It will be seen in the drawing that the levers extend such that the nuts 78-, 80 are positioned between the extremities of the levers on each side of the piston and that these levers are held in position against the nut by means of springs 82, 83 which cause the levers to be held against the nuts 78, 80 to impart the control movement therefrom to the respective levers. Shaft 7t) normally has a neutral position in which all of the valves formed by the valve closure members 51-64 and the valve seats 52-55 are closed and movement to either side of this neutral position or sliding of the shaft 70 within the piston 25 will selectively cause one of the valves of each pair on opposite sides of the piston to open while the opposite valves of each pair will remain closed. This will connect the conduits 44-, 45 respectively to one or the other of the working chambers 28, 30. Thus with opening of the valve formed by the closure member 61 and valve seat 52, upon downward movement of the shaft and pivoting of the lever 56 the conduit 4-4 will be connected to chamber 28 while similar pivotal movement applied to the lever 59 will cause opening of the valve formed by the valve seat 55 and closure member 64. The opposite valves will remain closed since their respective levers while attempting to follow the movement of the actuating shaft will merely have their respective closure members urged against their respective valve seats through the force applied thereto by the springs 82, 83 to insure positive close off. Movement of the actuating shaft 70 in the opposite direction will open the opposite valves or those previously closed and close the Valves previously opened to interchange the connection of the conduits 44, 45 with the chambers 28, 30.

Piston 25 moves within the cylinder under the influence of a operating fluid medium, such as air, which is introduced into the actuator through a port in the casing indicated at 85. Also included in the casing is a vent port 86. The inlet and vent ports 85, 86 are connected to the conduits 44, 45 in the piston 25 by means of flexible connections or tubing indicated at 88, 89 respectively. It will be seen that these flexible conduits 88, 89 include a spring 90 positioned within the conduits and the conduits are sealed at the end wall section 12 or the inlet and exhaust ports 85, 86 by suitable sealing means such as rings 95. As the piston 25 moves within the casing, these inlet and exhaust lines will flex or bend accommodating full movement of the piston within the range of movement defined by the end wall sections 12 and 14 as controlled by movement of the actuating shaft 70 on the valves in the piston 25. Thus for downward movement in the actuating shaft, the working medium from the port 85 will be connected to the conduit 88 to the conduit 44 and through the valve defined by closure member 61 and seat 52 or port 48 to the working chamber 28 while the working chamber 30 will be exhausted through the valve defined by closure member 64 to valve seat 55 and port 51 through the conduit 45 and piping or conduit 89 to the exhaust port 86. The opposite direction of movement of the actuating shaft will reverse the introduction of the working fluid medium to the chamber 30 while venting the chamber 28 to the vent port 86 causing an opposite direction of movement of the piston 25 within the casing 10. Thus it will be seen that the working medium, such as air, may be directed to one or the other side of the piston or to the working chambers 28, 30 to cause directional control of the actuator and reversible movement of the output shaft 41 through control of the integral valving positioned in and on the piston 25 within the actuator. The output shaft 41 may be attached to any desired apparatus whose movement it is to effect, such as a valve, and the flange section 100 attached to the casing permits the mounting of such a device to be operated. It will be noted that there is no spring within the actuator and thus the force provided by the pressure of the Working medium on the piston area may be fully utilized in the output of the actuator.

The control of the actuating shaft 711 is shown herein as affected by a small pilot actuator 110 or positioner attached to or mounted on the casing 10. Pilot actuator 110 is similar to the pneumatic actuator design shown in my Patent 2,939,486 entitled Pneumatic Actuator and dated June 7, 1960. It includes a base or support member 112 which is fitted on to the end wall section 14 of casing 10 which support section or base has a branch inlet port 114 therein and a vent 116. The base includes extending flange port-ions 117 upon which is mounted a first cup shaped member 120 having a plurality of flanges 121 which extend down and fit on the flanges 117 of the support to secure the cup shaped member 120 thereto through suitable means such as screws 124. Nested or positioned within the cup shaped member 120 is a second cup shaped member 130 having a peripheral lip portion 131 which is positioned adjacent a flange portion 132 in the cup shaped member 120 for the purpose of clamping a beaded lip 135 of a diaphragm 136 which is nested in the cup shaped member 130. The lip of the diaphragm is held in position by means of a force applied between the cup shaped members 130, 120 through a nut-bolt connection provided by a threaded hub 140 on member 130 which extends through an aperture in the first cup shaped member and mounts a nut 141 on the other side of the same. Nested within the diaphragm and cup shaped member is a cup shaped thrust member 145 which fits the diaphragm against the cup shaped member 130 and moves with the diaphragm, as will be later seen, to impart the thrust to the actuating mechanism 70.

The pilot actuator has its motive pressure chamber defined by the area between the diaphragm 136 and the cup shaped member 131) and the skirt portion of the first cup shaped member 120 provides a surface for the rolling motion of the diaphragm as the pressure chamber of the actuator expands and the diaphragm is moved down or away from the cup shaped member 130. P0- sitioned under the.thrust plate 145 is a latch key and spring retainer member which is more fully explained in connection with my prior patent referred to above. This latch key, indicated at 146, is adapted to attach a thrust pin of the pilot actuator 110 to the actuating shaft 70. The latch key also serves as a spring retainer for a spring 152 and is shaped to receive a headed portion 155 of the thrust pin 150 so that this pin 50 may be se cured to the same. The latch key or plate 146 may, if desired, latch directly to the pin 150 through a key hole, (not shown), the narrow sides of which slip in a groove (not shown) at the end of the thrust pin 150 to eliminate the need for the headed portion 155 on pin 150. The opposite extremity of the pin 150 is threaded, as at 160, to fit into a connecting nut 161 which also mounts the threaded extremity 162 of the actuating shaft 70. A seal plug 165 is positioned in a threaded portion in the end wall 14 and surrounds the thrust pin 150 to seal leakage at this point. The pilot actuator 110 includes a pneumatic connection or piping extending from the branch line port 114 to a hub portion or inlet 172 in the cup shaped member 130 communicating with the pressure chamber for the pilot actuator. The connection may be of the flexible tubing type and is sealed in the hub portion and at the inlet port through suitable sealing means such as 0 rings, indicated at 175. Enclosing the actuator is a cover which mounts on the base portion 112 and encloses the cup shaped members 120, 130 being secured in position by a screw means 181 fitting into a tapped aperture in the upstanding flange 140 of cup shaped member 130. In addition a skirt 185 is attached to the support member 112 and fits down over the easing 11 to complete the cover design.

In operation, the improved actuator of the present invention will be positioned in accordance with movement of the actuating rod controlling the valves in the piston of the actuator. As disclosed herein this actuating rod is positioned by the small pilot actuator 110 in accordance with branch line pressure or control pressure applied to the motive chamber of this actuator. Thus as control pressure is applied to the working chamber of the pilot actuator 110 or against the diaphragm 136, the force against the diaphragm acts against the bias of the spring 152 and positions the shaft 150 and hence the actuating shaft 70 to selectively operate one or the other of the pair of control valves for the main actuator. Expansion of the working chamber of the pilot actuator 110 will move the actuating shaft 70 in a direction to open the valves formed by closure member 61, seat 52, closure member 64 and seat 55. This will introduce main or supply air or working medium from the conduit of port 85 to the working chamber 28 of the main actuator and at the same time will open the vent from chamber 30 to cause the piston 25 to move downward in the casing. The position assumed by the piston will be controlled by the position of the actuating shaft 70 and hence the position of the pilot actuator. Thus positional control is accomplished by the actual positioning of the actuating shaft 71) which is moved by the pilot actuator 110 in accordance with the control pressure applied thereto. The piston will move until such time as the actuating shaft stops with a balance of forces from the pilot pressure and spring rate for the pilot actuator. The valves in the piston of the main actuator will reach a closed position as the main actuator piston follows the movement of the operating shaft attached to and controlled by the pilot actuator and the remaining valves in the piston will remain closed. This will cause an equalization of pressure in the chambers of the main actuator and the output shaft 41 of the actuator will cease movement and remain fixed. A reversal in direction of operation of the pilot actuator will reverse the valves in the pairs of control valves to selectively open the chamber 28 to the vent and chamber 30 to the main line pressure or fluid working medium to position the piston in the opposite direction in a conventional manner.

It should be noted that operation or positioning of my improved actuator is independent of the load on the out put shaft 41 of the actuator. Any change of load will produce a temporary displacement of the shaft 41 and hence the piston 25 which will cause the valves therein to readjust the pressure in the chambers on each side of the piston 25 and return the output shaft to its original position. Further it Will be noted as the piston 25 moves the piping connections 88, 89 to the inlet port and vent will be flexed with the movement of the piston or will move therewith to provide a continuous connection between these points to the valving in the piston.

In considering this invention it should be remembered that the present disclosure is intended to be illustrative only and the scope of the invention is to be determined by the appended claims.

I claim as my invention:

1. A pneumatic actuator comprising, a cylindrical casing, a piston positioned within said casing, output means for said actuator connected to said piston and extending from said casing, wall means sealing the extremities of said casing to provide a pair of pressure chambers on opposite sides of said piston, two pair of valve seats positioned on the surfaces of said piston with valve seats of each pair being positioned on opposite surfaces of said piston, two pair of valve closure members pivotally mounted on opposite surfaces of said piston and cooperating with the valve seats to form two pairs of valves integral with said piston, a pair of conduit means each being connected in common with one of said pair of said valve seats positioned on opposite surfaces of said piston, connection means connecting each of said conduit means between said casing and said piston means and adapted to transmit an operating fluid medium to and from said chambers on the opposite sides of said piston as controlled by said valves, and actuating means extending through said sealing wall means of said casing and through said piston and adapted to engage said pivotally mounted valve closure members to selectively operate one of the valves of each pair to introduce said fluid medium to one of said chambers while fluid medium is being evacuated from the other of said chambers in said casing.

2. A pneumatic actuator comprising, a cylindrical casing, a piston positioned within said casing, output means for said actuator connected to said piston and extending from said casing, Wall means sealing the extremities of said casing to provide a pair of pressure chambers on opposite sides of said piston, two pair of valve seats positioned on the surfaces of said piston with valve seats of each pair being positioned on opposite surfaces of said piston, two pair of valve closure members pivotally mounted on opposite surfaces of said piston and cooperating with the valve seats to form a two pairs of valves integral with said piston means, a pair of conduit means each being connected in common with one of said pair of said valve seats positioned on opposite surfaces of said piston, flexible conduit means connecting each of said conduit means between said casing and said piston means and adapted to transmit operating fluid medium between said chambers on the opposite sides of said piston and said casing as controlled by said valves, and actuating means extending through said sealing wall means of said casing and through said piston and adapted to engage said pivotally mounted valve closure members to selectively operate one of the valves of each pair to introduce said fluid medium to one of said chambers while fluid medium is being evacuated from the other of said chambers in said casing.

3. A pneumatic actuator comprising, a cylindrical casing, a piston positioned within said casing, output means for said actuator connected to said piston means and extending from said casing, wall means sealing the extremities of said casing to provide a pair of pressure chambers on opposite sides of said piston means, two pair of valve seats positioned on the surfaces of said piston means with valve seats of each pair being positioned on opposite surfaces of said piston means, two pair of valve closure members pivotally mounted on opposite surfaces of said piston and cooperating with the valve seats to form two pairs of valves integral with said piston means, a pair of conduit means each connected in common with one of pair of said valve seats positioned on opposite surfaces of said piston means, a pair of continuously connected connection means extending between ports in said casing and said pair of conduit means in said piston means to transmit an operating fluid medium to and from said chambers on opposite sides of said piston means as controlled by said valves and movable with said piston means, and actuating means extending through one of said sealing wall means of said casing and through said piston and adapted to engage said pivotally mounted valve closure members to selectively operate one of the valves of each pair in said piston means.

*4. A pneumatic actuator comprising, a cylindrical casing, a piston positioned Within said casing, output means for said actuator connected to said piston and extending fro-m said casing, wall means sealing the extremities of said casing to provide a pair of pressure chambers on opposite sides of said piston, two pair of valve seats positioned on the surfaces of said piston with valve seats of each pair being positioned on opposite surfaces of said piston, two pair of valve closure members pivotally mounted on opposite surfaces of said piston and cooperating with the valve seats to form two pairs of valves integral with said piston, a pair of conduit means each connected in common with one of said pair of said valve seats positioned on opposite surfaces of said piston, a pair of continuously connected connection means extending between ports in said casing and said pair of conduit means in said piston to transmit an operating fluid medium to and from said chambers on opposite sides of said piston as controlled 'by aid valves and moveable with said piston, actuating means extending through one of said sealing wall means of said casing and through said piston and adapted to engage said pivotally mounted valve closure members to selectively operate one of the valves of each pair in said piston, and control means mounted on said casing and connected to said actuating means to position the same such that piston movement corresponds to movement of said control means.

5. A pneumatic actuator comprising, a cylindrical casing, a piston positioned within said casing, output means for said actuator connected to said piston and extending from said casing, wall means sealing the extremities of said casing to provide a pair of pressure chambers on opposite sides of said piston, two pair of valve seats positioned on the surfaces of said piston with valve seats of each pair being positioned on opposite surfaces of said piston, two pair of valve closures members pivotally mounted on opposite surfaces of said piston and cooperating with the valve seats to form two pairs of valves integral with said piston, a pair of conduit means each being connected in common with one of said pair of said valve seats positioned on opposite surfaces of said piston, connection means connecting each of said conduit means beaoamae tween said casing and said piston and adapted to transmit an operating fluid medium to and from said chambers on the opposite sides of said piston as controlled by said valves, and actuating means extending through said sealing wall means said casing and through said piston and adapted to engage said pivotally mounted valve closure members to selectively operate one of the valves in each pair to introduce said fluid medium to one of said chambers while fluid medium is being evacuated from the other of said chambers in said casing, and control means mounted on said casing and connected to said actuating means to position the same such that piston movement corresponds to movement of said control means.

6. A springless pneumatic actuator comprising, a sealed casing, a piston positioned in said casing and movable therein dividing said casing into a pair of motive pressure chambers, a plurality of pairs of valve means, each valve means including a pair of relatively movable parts one part of which is integral with said piston and the other part of which is mounted on a surface of said piston, a pair of conduits in said piston, the said one part of said valve means of each pair being connected in common to one of the conduits in said piston, said valve means of each pair being adapted to selectively connect said motive 9 0 pressure chamber on either side of said piston to their respective common conduit, output shaft means connected to said piston and transmitting movement of said piston through said sealed casing, actuating means extending through said casing and said piston and adapted to engage the movable parts of each of said valve means on the surface of said piston to selectively actuate the valves of each pair of said valve means, inlet and exhaust ports included in said casing, connection means connecting said inlet and exhaust respectively to said common conduits in said piston and being movable therewith, and pneumatic pilot means mounted on said casing and connected to said actuating means for said valve means to selectively operate said valve means, said pilot means being adapted to receive a control air pressure and control movement of said actuator.

References Cited in the file of this patent UNITED STATES PATENTS 1,385,858 Blasiar July 26, 1921 2,376,804 Orshansky May 22, 1945 2,520,374 Rockwell Aug. 29, 1950 2,532,462 Rockwell Dec. 5, 1950

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