US2837918A - Temperature sensing element - Google Patents

Description

June 10, 1958 A. L. GOOD 2,837,918

TEMPERATURE SENSING ELEMENT Filed March 9, 1956 'f FIG. I 23 INVENTOR.

ARTHUR l GOOD ATTORNEY United States Patent TEMPERATURE SENSING ELEMENT Arthur L. Good, Elkhart, Ind., assignor to Penn Controls Incorporated, Goshen, Ind, a corporation of Indiana Application March 9, 1956, Serial No. 570,4sa

1 Claim. c1. 73--368.4)

This invention relates generally to temperature sensing elements and particularly to a dual thermal sensing element capable of responding to a temperature change, the response being accommodated in independent energy transmission systems.

In the control of domestic hot water heating systems, for example, it is often required that the circulator operating control and the high temperature limit control each have a water temperature sensing bulb located in the Water circulating system at approximately the same spot. In the past dual temperature sensing bulbs have been accommodated in a single bulb sheath or well. If the bulbs and well are circular in cross-section, a form giving maximum rigidity and strength, then with the two cylindrical bulbs inserted side by side in the cylindrical well, a substantial volume of air space must exist between the inner surface of the well wall and the bulbs; the heat transfer from the well walls to the bulbs is, therefore, relatively slow. If the bulbs are shaped, other than circular in cross-section, so that all of the inner surface of the well wall is in contact with one or the other of the bulbs, thereby increasing the rapidity of heat transfer, then the departure from the circular cross-sectional shape must be .payed for by a loss in strength and rigidity of the bulbs.

A principal object of the present invention is to provide a dual bulb assembly in which the bulbs are formed of a cross-sectional shape giving maximum strength and yet having a relatively rapid heat transfer characteristic with respect to its enclosing sheath or well.

A further object is to provide a dual bulb assembly in which the bulbs are substantially concentric and coextensive, the inner bulb being supported at both of its ends.

A further object is to provide a dual bulb assembly wherein the bulb volumes can more readily be controlled, the assembly being so formed as to lend itself to mass production machines and techniques.

These and other objects will be made apparent by the detailed description hereafter set out and the drawing in which:

Figure 1 is a sectional view of the dual bulb assembly and its enclosing sheath or well.

Figure 2 is an end view of one of the elements shown in Figure 1.

Reference numeral refers to a panel member which may be secured by any suitable means to a control member or switch assembly (not shown). Member 10 carries rigidly mounted thereon, a bushing member 11. A sheath or well support element 12 is rigidly mounted on the member 11 by means of setscrew 13 and a cooperating groove in the member 11. A tubular well member 16 having an outer closed end is secured by any suitable means, such as solder to the outer end of the element 12. Element 12 is externally threaded and is thereby adapted to be inserted into a fluid container or conduit.

Slidably mounted within the well member 16 is an elongated tubular bulb member 17, having an outer closed end bottomed against the closed end of member 16. The inner open end of the bulb member 17 is closed by a flanged header member 18, which is sealed, by any suitable means, into the bulb member 17. An inner bulb member 19 is nested within the bulb member 1'7 and is supported at its closed end by contact with the end of member 17. The opposite end of member 19 extends through and is sealed to a central opening 21 in the header 18. A radially offset opening 22 provides a path for fluid communication between the space defined by the walls of bulb members 17 and 19 and a conventional capillary tube 20. The tube 20 provides a fluid transmission conduit to a power element 23, of a conventional type, which may be mounted with the control assembly (not shown). Similarly, a capillary type tube 24 independently connects the inner bulb member 19 to a power element 26 similar to the power element 23.

In operation, the well member 16 is-adapted to extend into a fluid the temperature of which is to be sensed. Heat from the fluid is conducted through member 16, through the walls of bulb member 17 to the thermally responsive fluid filling the space between bulbs 17 and 19. The matching circular cross-section configuration of well 16 and member 17 provide a maximum area of heat conducting contact. The thermally responsive fluid filling the space between the bulb members 17 and 19, consequently, reflects the temperature of the fluid surrounding the well member 16 with a relatively small time lag.

The thermally responsive fluid filling bulb 19 receives heat, in turn, by conduction through the liquid between bulbs 17 and 19 and through the walls of bulb l9. Depending on the relative size, in cross-section, of tubes 17 and 19 and therefore on the volume of fluid between members 17 and 19, the response of the fluid within bulb member 19 will be somewhat slower than the response of its companion system. The inner bulb member 19 may be formed of somewhat thinner less rigid stock than the outer bulb member 17 since it need Withstand only the pressure difference between the two independent thermally responsive systems,

From the foregoing it will be apparent that the present invention provides a dual bulb assembly which because of the tube and header construction lends itself to mass production. In addition, the relative volumes of bulb members 17 and 19 can readily be controlled. The construction wherein the outer bulb 17 is closely nested within well member 16 and bulb member 19 is supported at both its ends provide a rigid and strong assembly. Alterations may be made in the disclosure herein presented without departing from the scope of the invention which is to be limited only by the appended claim.

What is claimed is:

A dual thermal responsive bulb assembly adapted to independently accommodate the thermally sensitive fluid for a dual fluid pressure transmitting system comprising an elongated tubular outer bulb having one closed and one open end, an inner bulb generally concentric with said outer bulb and coextensive therewith, one end of said inner bulb being in supporting engagement with the closed end of said outer bulb, a header member closing the open end of said outer bulb and supporting the adjacent end of said inner bulb, means including openings in said header member providing independent fluid passages to both said outer and inner bulbs, and a well assembly adapted to support and sheath said bulb assembly.

References Cited in the file of this patent UNITED STATES PATENTS 2,135,078 Hubbard et al. Nov. 1, 1938 2 477,835 Smith Apr. 12, 1949 FOREIGN PATENTS 228,687 Switzerland Sept. 16, 1943

Images