US2942624A - Pressure responsive actuator - Google Patents

Description

June 28, 1960 A. GOOD PRESSURE RESPONSIVE ACTUATOR Filed Nov. 14, 1956 INVENTOR. flRT/fl/R L 60 United States Patent PRESSURE RESPONSIVE ACTUATOR Arthur L. Good, Elkhart, Ind., assignor-to Penn Controls,

Inc., Goshen, Ind.', a corporation of Indiana.

Filed Nov. 14, 1956, Ser. No. 622,060

3-Claims. (Cl. 137-793) This invention relates generally to pressure responsive actuator elements and particularly .to assemblies ofjthis type, having a relatively linear correlation of pressure, or loading, andv deflection.

As is well known, actuator elements of the type herein disclosed are used extensively for actuation of switches or other control apparatus which have application in the regulation of pressure and temperature in the refrigeration and allied fields. One problem existing in this and similar applications is that in the upper portion of the deflection range of the actuator element, the deflection of the flexible member for a given incremental change in internal pressure tends to decrease due to the inherent stiffness of the material from which the flexible member is formed and because of the inherent spring rate of the lever system or switch assembly which the actuator element must operate.

The present invention solves this difficulty by forming a corrugation in the flexible member which is so shaped, in profile, that increasing pressure within the actuator element, tending to spread apart the side walls of the corrugation, increases incrementally the force transmitted to theactuator thrust pin for the upper portion of the elements deflection range.

An object of the present invention is to provide an actuator element having a relatively uniform deflection rate over a wide range of loading.

A further object is to provide an actuator element of relatively small size which is reinforced so as to be safely operable under relatively large loading.

A further object is to provide a flexible element or diaphragm for a pressure responsive actuator which is formed so as to provide, when assembled into an actuator, a relatively linear pressure-temperature deflection characteristic.

These and other objects will become apparent as the description proceeds with reference to the accompanying drawings in which:

Figure 1 represents a cross-sectional view of an actuator assembly embodying the present invention.

Figure 2 is a schematic view illustrating, in exaggerated form, the locus of certain points on the diaphragm corrugation.

Figure 3 is a top view of the actuator housing with the other parts of the assembly removed.

Referring initially to Figure 1, there is shown generally at a cup-shaped housing having a bottom wall 11 and a cylindrical threaded side wall 12. A capillary tube 13 is soldered or otherwise rigidly secured within a central passage 14 in the wall 11. Overlying wall 11 is a flexible element or diaphragm 16 having a corrugation 17 adjacent its outer margin, the corrugation having an outer wall 17a spaced radially outward from its inner Wall 1711. The point of maximum curvature of the outer wall or the corrugation 17 is indicated at 18. The point of maximum curvature of the inner Wall of the corrugation is indicated at 19. Serving to clamp and seal the marginal edge of the diaphragm 16. against the wall 11 2,942,624 Patented June; 28, 1960-- isan annular ring 21 having groovesat 22 in its lowerface to provide for cold flowing of the material fromwhich the diaphragm 16 is formed as the ring 21 pressesher or screw 23 which is adapted to be tightened against ring 21' to thereby provide the force required to seal the diaphragm 16 against the wall 11.

A thrust pin 24 extends freely through an opening ;in the clamping member 23 and has a disc-shaped portion 26 which overlies the area of the diaphragm 16 within the corrugation 17. It will be understood that thrust pin 24 is adapted-to actuate, through an appropriate lever assembly (not shown), a switch or other control means; As may best be seen in Figure 3 the upper face ofthe lower wall 11 has radial grooves 27 therein which extend within the area of bottom wall 11 which underlies the corrugation 17. Presence of grooves 27 insure that the fluid fill has entry into the chamber formed by diaphragm 16 and wall 11 even though the central portion of the diaphragm 16 should be in near contact with the wall 11.

It will be understood that the pressure chamber formed. by the wall 11 and the diaphragm 16 is adapted to be filled by a pressure transmitting fluid through the cap-- illary tube 13. The remote end of the tube 13 (not. shown) may be joined to a temperature sensing bulb, the capillary and pressure chamber serving to extend. the diaphragm outwardly in a manner well known in the art. It will be further understood that the pressure chamber may respond to remote pressure changes, rather than temperature changes at the bulb, such pressure changes being transmitted to the chamber by means of a pressure transmitting fluid in the capillary, as, well known in the art. As shown in Figure 1, the diaphragm 17 is in a partially extended position indicating that the pressure within the chamber formed by the diaphragm 15 and the wall 11 is at an intermediate value. As the pressure within the chamber increases further to cause the pin 24 to move outwardly, the outer side wall of the diaphragm corrugation 17 will tend to bulge outwardly slightly. The force (the direction of which is shown at 28 in Figure 3) producing this slight distortion will correspondingly tend to move point 18 downwardly and, because of the resulting flattening of the top of the corrugation, will move point 19 upwardly. The force produced by this tendency to move point 19 upwardly is additive to the force of the fluid pressure exerted on the underside of the central portion of the diaphragm 16 which drives the pin 24 in an upward direction. The added incremental upward force provided by the action of the corrugation 17 tends to compensate for the added force required to overcome the increasing spring rate of the mechanism actuated by the pin 24 and tends to compensate for the spring rate, or increasing stiffness, of the diaphragm material as the actuator approaches, its fully extended position. Because of the reinforcement against bursting failure provided by the portion 26 of pin 24 overlying the marginal portion of the area of the diaphragm, the actuator assembly may be made relatively small and yet safely operate within a relatively high pressure range.

It will be understood that the invention herein described may be modified over that disclosed; the invention is to be limited only as defined in the following claims:

1. A disc-shaped diaphragm adapted to be sealed across the open end of a cup-shaped housing to form a pressure chamber and adapted to flex outwardly from an unextended position in response to an increase in the pressure within the pressure chamber, 831d diaphragm having an annular corrugation formed therein, said corrugation;1having an; outer wall generally normal to the plane of1the diaphragm; said corrugation having a cross sectional configurationisuch that a transverse line joining the. point of maximum curvature of therouter margin of said corrugation and the pointrof maximum curvature of the inner margin thereof forms an acute angle with theplane of said diaphragm when said diaphragm is in said unextended position, sideward flexure of said outer corrugation wall under increased pressure within saidv chamber thereby generating a force which tends to compensa'tje for the increased force-deflection ratio of, said diaphragm at the upper limit of its deflection range.

-2. A diaphragm was claimed in claim 1 which is formed it. y um-c pp '3. A disc-shaped diaphragm adapted to be supported atits circumference and to flex in one direction in response to an increase in pressure on one of its faces,

said diaphragm having an annular 'corrugation'formed therein with said one diaphragm face defining the con- 2,942,624 M g 7 I "cave portion of said corrugation, the outer walls of said ward flexure of said outer corrugation wall under increased pressure on said one face of said diaphragm thereby generating a force which tends to compensate for the increased force-deflection ratio of said-diaphragm i at the upper limit of its deflection range. t

References Cited inthe file of this patent UNITED STATES PATENTS 1,162,825 Turner Dec. 7, 1915 r 2,651,328 7 Gamble V r Sept. 8, 1953 72,697,352- Umph'reyr Dec. 21; 1954 2,724,4l0 Vorech Nov. 22, 1955 2,730,131 Asp et a1. Jan. 10, 1956 2,775,983 7 Johnson et al. Jan. 1, 1 957

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