US2949132A - Pressure responsive power element - Google Patents

Description

Aug. 16, 1960 G. ASAKAWA ETAL PRESSURE RESPONSIVE POWER ELEMENT Filed June 2, 1955 m m #0 w 3 MM V E SE INMW [m 4 Gr 41% H; M T R 65 M G3 5 v B United States Patent George Asakawa and Sergius Vernet, Yellow Springs,

Ohio, assignors to Antioch College, Yellow Springs, Ohio, an Ohio corporation Filed June 2, 1955, Ser. No. 512,707

2 Claims. (Cl. 137-789) This invention relates to a pressure responsive power element.

Power elements of the type with which we are concerned generally comprise a vessel in which is contained or into which is introduced the pressure-producing medium. This pressure-producing medium may be a material responsive on temperature increase to expand and exert a pressure, as for example, material 16 disclosed in United States Patent No. 2,534,497, issued on December 19, 1950, to John C. Albright. The pressure-producing medium may also be a material introduced into the vessel under pressure, as in the Fig. 3 arrangement of the above-identified Albright patent.

The pressures produced by the pressure-producing medium are transmitted through a diaphragm to a body or plug of pressure-transmitting material positioned within a cover-like housing overlying the diaphragm. A

piston is slidably positioned in the cover-like housing and is spring urged into the housing interior in opposition to the action of the pressure-producing medium. Pressure decrease in the pressure-producing medium allows the spring to move the piston into the housing, and 1 pressure increase in said medium moves said piston out of the housing.

It is desirable that the piston move immediately in response to pressure change within the pressure-producing medium. It is accordingly necessary that the pressure-transmitting plug be of an incompressible pliable material and be so housed in the power element as to at all times occupy the full space between the piston and diaphragm, thereby precluding any lost motion between the pressure-producing medium and piston.

It is also desirable that after successive pressure change cycles the piston return to its same position in the housing. It is accordingly necessary that no flow of material take place into or out of the power element interior, as such flow of material would vary the returned position of the piston.

It is further desirable that each successive pressure change cycle be accompanied by the same total piston travel. It is accordingly necessary that none of the pressure-producing medium escape from within the power element, as such escape would reduce the total piston travel.

It is further desirable that the power element retain the above discussed characteristics over a relatively large number of pressure change cycles. It is accordingly necessary that the diaphragm be relatively free from ruptureproducing forces during flexure (as on pressure change of the pressure-producing medium). Such rupture-producing forces occur when the diaphragm is caused to stretch. It is accordingly desirable to avoid stretching the diaphragm.

One object of the present invention is to provide a power element comprising a pressure-producing medium and piston, wherein the piston moves immediately in response to pressure change within the pressure-producing medium.

Another object is to provide a power element wherein no material is allowed to flow into or out of the power element interior.

Another object is to provide a pressure responsive power element comprising a piston, wherein the piston returns to its same position after successive pressure change cycles.

Another object is to provide a power element comprising a pressure-producing medium and diaphragm, wherein none of the pressure-producing medium is allowed to escape from within the power element.

Another object is to provide a power element comprising a pressure-producing medium and piston, wherein successive pressure change cycles are accompanied by the same piston travels.

Another object is to provide a power element which will retain a useful operative life over a large number of pressure change cycles.

Another object is to provide a power element including a flexible diaphragm, wherein the diaphragm is relatively free from rupture-producing forces during flexure.

Another object is to provide a diaphragm which flexes without stretching.

Other objects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein likereference characters designate corresponding parts in the several views.

In the drawings:

Fig. 1 is an elevational view of one embodiment of the invention,

Fig. 2 is a sectional view taken on line 22 in Fig. l, and

Fig. 3 is an elevational view of a pressure-transmitting plug employed in the Fig. 2 embodiment.

Before explaining the present invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings,

since the invention is capable of other embodiments and of being practiced or carried out iri various ways. Also, it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

The power element is generally designated by reference numeral 1 and includes a cylindrical cup or vessel 2. A pressure-producing medium '3 is contained in or introduced into cup 2.

The power element may be employed as a thermostat or as a pressurestat. When the power element is employed as a thermostat medium 3 is contained in cup 2 and includes a thermally expansible material, as for example the material disclosed in United States Patent No. 2,259,846. When the power element is employed as a pressurestat cup 2 is provided with a conduit 4 and medium 3 is a material introduced into cup 2 under pressure through conduit 4.

Cup 2 is provided at its mouth with a flange 5, and sealingly seated on this flange is a concavo-convex diaphragm 6 of flexible material, preferably vulcanized rubger. The central portion 7 of diaphragm 6 is thickene A cover-like housing 15 overlies diaphragm 6 and is provided 'with a sleeve-like extension 8. An opening 9 18 provided in extension 8 and a piston 11 is slidably positioned in this opening. Against an inner surface of extension 8 there is positioned an anti-extrusion washer 12, and in an elongated bore 17 formed in extension 8 there is positioned a plug-like body of pressure-transmitting material 13. Washer 12 wipingly engages the wall of piston 11 and prevents any of material 13 from being carried out with the piston, although material 13 is preferably of a non-sticking character so as to aid in preventing carry out of material. Material 13 is preferably the same, solid, cohesive, non-sticking, reshapeable material as that disclosed in United States-patent application, Serial No. 498,655,-now Patent 2,906,123, filed on April 1, 1955. As disclosed therein the material comprises discrete solid resinous particles (as for ex ample polytetrafluoroethylene) dispersed in and coated by a flowable binder (as for example polyhutene). The flowable binder separates the resinous particles so as to prevent them from sintering together into a rigid mass. Material 13 thus has the advantage of easy reshapa bility for eflicient pressure transmission, as well as non-fluidity for minimum leakage. Prior to its insertion into the interior of extension 8 material 13 takes the cylindrical shape shown in Fig. 3. A spring (not shown) urges piston 11 into the interior of the power element and forces material 13 to conform to the wall surfaces of extension 8, piston 11 and diaphragm 6.

In the case where material 3 includes a thermally expansible material, assembly of the power element is effected by first positioning a body or pellet of medium 3 in cup 2. The pellet is formed with a depression 14- and diaphragm 6 is seated on flange 5 so as to have its convex surface conform to the contour of depression 14. Washer 12 and plug 13 are positioned within housing 15, and a ring 16 is employed to clampingly retain housing 15 and cup 2 in their Fig. 2 positions. Piston 11 is inserted into housing 15 and releasably urged therein by the aforementioned spring. Spring-urging of piston 11 into housing 15 causes material 13 to exert a pressure against diaphragm 6 so as ot compress portion 7 against the surface of depression 14.

Operation of the power element is such that on pressure increase of material 3 diaphragm 6 is flexed upwardly, and 'material 13 is caused to squeeze or push piston 11 outwardly against the action of its spring. Pressure decrease of material 3 allows the spring to move piston 11 downwardly to its Fig. 2 position.

Pressure change of material 3 is accompanied by flexing of diaphragm 6 but without any stretching thereof. As a result the life of the diaphragm and power element are increased.

During both pressure increase and pressure decrease of material 3 pliable material 13 easily and immediately conforms to the changing positions of piston 11 and diaphragm 6. As a result no void spaces are formed within the power element interior such as might allow for entrance of matter from the surrounding atmosphere.

Consequently there is no lost motion of the piston, and piston travels are uniform over successive pressure change cycles.

Having thus described our invention, we claim:

1. A power element comprising a cup; pressureproducing material within said cup; a concavo-convex diaphragm having its peripheral edge seated on the rim of thecup and having its central portion depending into the cup interior; an annular housing having an annular face clampingly seated on the diaphragm periphery and having an elongated tubular extension projecting axially away from the cup; an annular wall projecting radially inward from theterminal end of the extension to define an opening substantially smaller than the internal diameter of said extension; a piston closely fitting the opening and slidably extending therethrough to a point adjacent the diaphragm; a body of solid pliable, pressuretransmitting material surrounding the piston in the space between the diaphragm and wall opening; said pressuretrans-mitting material comprising discrete solid resinous particles dispersed in and coated by a flowable binder so as to permit the material to easily reshape itself in accordance with pressure changes without tendency to return to its original shape; whereby, on development of increased pressures within the cup the diaphragm is caused to flex in the direction of the housing so as to force the easily reshapable pressure-transmitting material to squeeze against the piston and drive it through the opening; the easily reshapable character of the pressure-transmitting material allowing it to efficiently transmit the pressures, and the solid character of the pressuretransmitting material preventing it from easily leaking through the wall opening; the annular portion of the pressure-transmitting material within the tubular extension being packed therein to act as a piston guide as well as a seal preventing the entrance of ambient media.

2. The combination of claim 1 wherein the pressuretransmitting material has a volume substantially equal to the internal volume of the tubular extension, thereby permitting said pressure-transmitting material to be initially formed as a cylindrical block and inserted into the annular housing prior to assembly with the piston.

References Cited in the tile of this patent UNITED STATES PATENTS 2,208,149 Vernet July 16, 1940 2,400,091 Alfthan May 14, 1946 2,534,497 Albright Dec. 19, 1950

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