US3179911A - Heater assembly for thermoelectric devices - Google Patents

Description

April 20, 1965 D. J. SCHMITT HEATER ASSEMBLY FOR THERMO-ELECTRIC DEVICES Filed Jan. 17, 1962 INV EN TOR 00/1410 J. Jam/7r United States Patent 3,179,911 HEATER ASSEMBLY FOR THERMO- ELECTRIC DEVICES Donald J. Sehmitt, Mansfield, Ohio, assignor to Therm-=0 Disc, Incorporated, Mansfield, Ohio, a corporation of Did Filed Jan. 17, 1962, Ser. No. 166,836 3 Claims. (Cl. 338-301) This invention relates generally to a thermally operated control device, and more particularly to a heater for such device and the method of constructing the same.

In thermo-electric control devices, it has been customary heretofore to providea bi-metallic member or assembly upon which a suitable heating or resistance wire is wound or with which the Wire is otherwise associated. Such a bi-metallic assembly is disclosed in my co-pending application, Serial No. 846,725, filed October 15, 1959, now abandoned. In assembling heating wire about a suitable support which in some cases may consist of a ceramic, metal'or bi-metallic member or the like, as shown in said application, where it is desired to obtain uniform resistance capacity of a heating wire on the support, considerable trouble has been experienced in fixing the first turn of the wire so that it will not become displaced from a predetermined or desired position. For this purpose, a band has been provided. Also cement has been used, and in other cases it has been necessary to weld or braze the wire so as to locate the leading end of the wire per- 'manently with respect to the support. Another drawproduce the desired heating results.

The present invention is directed to a novel bimetallic assembly having a heating element associated therewith which avoids the various disadvantages heretofore noted with respect to the application of heating wire to supporting structures and which is particularly well suited for a valve structure as shown in my co-pending application.

It is among the objects of this invention to provide novel and improved heaters for thermo-electric devices wherein a uniform wattage eliect may be produced by such heaters from lengths of heating Wire which may have varying resistance values.

It is another object of the invention to provide a method of applying heating wire to a supporting structure Whereby a uniform heat output may be effected.

A still further object of the invention is to provide a heater assembly for thermo-electric controls which is characterized by simplicity and economy of construction reliability, efiiciency and uniformity of operation and ability to actuate the control within predetermined uniform limits.

These and other objects and advantageous features of j the invention, not at this time more particularly pointed out, will become apparent as the nature of the invention is better understood from the following detailed description, taken in conjunction with the accompanying drawing, wherein like reference characters denote corresponding parts, and wherein,

FIGURE 1 isa vertical sectional view taken through a gas valve embodying the improved heating element of the subject invention,

FIGURE 2 is a side elevational view taken through a gas valve embodying the improved heating element of the subject invention,

FIGURE 2 is a side elevational view partly in section of a heating element and bimetal assembly constructed in accordance with the present invention,

FIGURE 3 is a front detail view of the bimetal element shown in FIGURE 2,

FIGURE 4 is a sectional view taken on the line 4-4 of FIGURE 3,

FIGURE 5 is a perspective view illustrating the first step in winding the heating Wire upon the bimetal support,

FIGURE 6 is a perspective view illustrating the completion of the winding of the heating wire on the bimetal element, and

FIGURE 7 is a perspective view showing the completed heater element ready for assembly in the valve of FIGURE 1.

With reference to the accompanying drawing, there is illustrated a thcrmo-electrically operated valve for controlling the flow of gas to a gas burner made in accordance with the invention disclosed in my co-pending application, Serial No. 846,725, and including a body or housing generally indicated by the reference numeral Iii. This valve housing is suitably constructed from a piece of hexagonal stock, such as brass. The lower end of the valve housing is of reduced diameter and is externally threaded as at 11 to receive a coupling nut (not shown) for attachment to a gas outlet line. A gas outlet passage 12 is formed in the reduced end of the body of the valve.

At the juncture between the main portion of the valve housing 19 and its externally threaded reduced diameter lower end 11, there is formed a horizontally inwardly extending annular wall 13 upon which an annular valve seat 14 is positioned. The valve seat 14 embodies an annular ring 15 which is adapted to seat on the annular wall 13 and surrounds an opening serving as a passageway from the interior of the housing 10 to the outlet 12. Overlying member 15 is a ring shaped member 16, formed of a suitable rubber-like material having a depending annular wall portion 17 which provides a seat to be engaged by a ball type, or other suitable valve member 18. Above the annular wall 13 the body portion of the valve housing iii defines a cylindrical gas chamber 19. The upper end of the wall portion is threaded as at 20 to receive a threaded plug 21. The plug is formed with an axial passage 22 which communicates with the upper end of the gas chamber 19 for delivering gas into the chamber. The end of the plug 21 is externally threaded to receive a coupling nut (not shown) for connecting this end of the valve to a gas line leading from a suitable source of gas supply.

The spherical ball 18 constitutes the actuating valve member of the valve and has a diameter slightly larger than the opening through the portion 17 of the valve seat 14. Normally the ball 18 seats by gravity on the valve seat 14 to close the outlet passage 12 from the gas chamber 19.

In accordance with the present invention, there is provided a novel thermo-electrically operated assembly for controlling the position of the ball 13 with respect to the valve seat portion 17. Referring to FIGURE 2 of the drawings, this thermo-electrically operated assembly includes a first bi-metallic member generally indicated by the number 23 and includes a mounting segment 24 which is arranged to be secured to the inside Wall surface of the valve housing 10 by means of a rivet 25 adjacent to the upper end of the valve gas chamber 19. This bi-metallic member 23 also has a horizontal segment 26 which is joined integrally to the mounting end 2.4 and extends there- 3 p from inwardly toward the longitudinal center line of the gas chamber 19. At its inner end this inwardly extending segment 26 is bent at right angles to form an elongated segment27 which extends downwardly at a location approximately midway between the wall surface of the gas chamber and the center line of the chamber and is adapted to serve as a support for the heating wire 28.

In assembling the heating wire 23 on the elongated downwardly extending segment 27 of the bi-metallic member 23, a layer of insulating tape 29, preferably Fiberglas, is wound around the segment 27. As shown in FIG- URES and 6 the length of tape used is sufficient to provide an overlapping portion on the face of the segment 27. The leading end of the heating wire 28 is formed into a V shaped portion 30 as shown in FIGURE 5 with the free end 31 thereof leading to the terminal connection of the source of current and the other end 32 projecting parallel with the overlapped portion of the insulating tape Fiberglas and continuing thereabout for sevcral'convolutions, and then bent downwardly along the base of the member 23 and secured therebelow.

In the bi-metallic member 23, the arrangement of the metals which have different coefficients of expansion is such that when the elongated leg 27 thereof is heated, its

lower end moves laterally inward away from the inner 'wall surface of the housing toward the center line of the gas chamber 19. In the operation of the present valve, the heat which produces such movement of the bimetallic member is furnished by thewattage dissipated by the heating wire ZS'surrounding the same.

In accordance with the present invention, a second bimetallic member, designated generally by the reference character 34, is attached to the base of the movable lower end of the first bi-metallic member 23. As best shown in FIGURES 2 and 7, this second bi-metallic member is formed with a segment 35 at its upper end which is welded to the lower end of'the depending leg 27 of the first bimetallic member. The end of the heating wire 28 is secured between the abutting surfaces of the segments 35 and 27 of the respective members. The second bi-metallic member 34 at its lower end is formed with an inwardly protruding horizontal foot 37, which faces toward the ball 18 at a location well below the center of gravity of the ball.

The arrangement of the metals which make up the second bi-metallic member 34, which metals have different heat expansion characteristics, is such that when this bi metallic member is subjected .to heat its lower end tends to move counterclockwise, or outwardly away from the center line of the gas chamber 19. Thus, the second bimetallic member 34.has an opposite direction of movement from the first bi-metallic member 23 when subjected to-heat.

The heat transfer relationship between the heating wire 28 and the second bi-metallic member 34 is greatly reduced from the heat transfer relationship between the heating wire and the first bi-metallic member 23 on which it is supported. Accordingly, when the heating wire carries current it has an appreciable heating effect on the first bi-metallic member 23, but only a negligible effect on the second bi-metallic member 34.

The upper end 31 of the heating wire 28 (FIGURE 1) is secured to one end of a flat, flexible metal strip 36. The opposite end of this strip is secured to a rivet 38 which extends through the side wall of the valve housing 10, opposite the wall on which the bi-metallic member 23 is mounted. The outer end of this rivet is connected to a terminal 40, which may be connected to an external electric circuit in any suitable manner. An additional rivet 41 is provided for clamping the lower end of the terminal against the valve housing 10. A flat strip of suitable electrical insulating material 42 is engaged between the outside wall of the valve housing and the vertically extending leg 40a of the terminal. A smaller strip 43 of the same insulating material is engaged between the inner face of the wall of the valve housing and the mounted end of the strip 36. An O-ring 45 of suitable resilient insulation material extends around the shank of rivet 38 at the opening in the valve housing through which the rivet extends. When the rivetis drawn up tight this O-ring 45 is flattened between the insulation strips .42 and 43 to provide an effective gas type seal around the rivet 38 as well as to insulate the rivet 38 from the housing 10.

As previously noted, the resistance of the heating wire is not always uniform, but may vary from time to time in uniform lengths of wire of substantially thesame diameter, thus the amount of heat induced into the sup porting bimetal member from such wire will vary. 7 Such condition would cause non-uniformity in the operation of the thermo-electric device. It is important therefore to provide a method of assembling the heating wire on its bi-metallic supporting member to obtain a uniform amount of heat input, for only under such conditions will the bimetal assembly be effective to activate the thermoelectric device within a predetermined period of time following the initiation of the flow of current to the heating wire.

As will be apparent from the foregoing description there is provided a method of assembling heating wire upon a support which is effective to produce apredetermined or desired amount of heat. In assembling the length of wire on the support, the number of convolutions of the wire about the support is determined as well as the length of wire leading from the first convolution on the support to the terminal. The remaining portion of the wire which is required to produce'the desired amount of heat is incorporated in the V-shaped portion 30 disposed below the overlapped portion of the insulating tape. The V-shaped portion can be varied to compensate for different lengths of heating wire. By prior checkingthe different lengths of wire for their wattage characteristics, it is possible to provide means for developing a uniform heat application in the production of a quantity of the devices described, thus enabling a standardization of performance in any series of devices intended for identical.

scope of my invention as defined by the appended claims.

I claim: 1. In a thermo-electric control, a bi-metallic heater assembly therefore comprising a bi-metallic member, in-

sulating means surrounding said bi-metallic member and having an overlapping portion, a length of heating wire adapted to supply a predetermined amount of heat to the bimetallic memberhaving one end secured to the. terminal of a source of electric current and the other end attached to said bi-metallic member, a portion of said heating wire encircling the insulating means in a series of convolutions, a second portion of said wire intermediate the first convolution and the terminal, being diSPosed within the overlapped portion of said insulating means to provide means for readily adjusting the length of said heating wire and to provide a positive attachment to said bi-metallic member for the leading end of the first convolution of said heating wire. a

2. In a thermo-electric control, a bi-metallic heater assembly therefore comprising a bi-metallic member, insulating means surrounding said bi-metallic member and having an over lapping portion, a predetermined length of heating wire adapted to supply a uniform amount of heat to said bi-metallic member having one end secured to the terminal of a source of electric current. and theother end attached to said bi-metallic member, a first portion of said heating wire encircling the insulating means in a series sulating means to provide means for readily adjusting the length of said heating wire and to provide a positive attachment for the leading end of the first convolution.

3. In a thermo-electric control, a bi-metallic heater assembly therefore comprising a bi-metallic member, insulating means surrounding said bi-metallic member and having an overlapping portion, heating Wire adapted to supply heat to said bi-mctallic member having one end leading from the terminal of a source of electric current and the other end attached to said bi-metallic member, a portion of said heating wire encircling the insulating means in a series of convolutions, a second portion of said Wire intermediate the first convolution and the terminal being disposed within the overlapped portion of said insulating means to provide means for varying the length 15 d of Wire within the overlapped portion of the insulating means to effect a uniform heating of the bi-metallic member in a predetermined period of time.

References Cited by the Examiner UNITED STATES PATENTS 2,077,735 4/37 Beckler 251-11 X 2,731,230 1/56 Schell 251-11 2,743,574 5/56 McCorkle 60-23 10 3,073,938 1/63 Turner et al 200 122 X RICHARD M. WOOD, Primary Examiner. ISADOR WEIL, Examiner.

Claims (1)

1. IN A THEMO-ELECTRIC CONTROL, A BI-METALLIC HEATER ASSEMBLY THEREFORE COMPRISING A BI-METALLIC MEMBER, INSULATING MEANS SURROUNDING SAID BI-METALLIC MEMBER AND HAVING AN OVERLAPPING PORTION, A LENGTH OF HEATING WIRE ADAPTED TO SUPPLY A PREDETERMINED AMOUNT OF HEAT TO THE BI-METALLIC MEMBER HAVING ONE END SECURED TO THE TERMINAL OF A SOURCE OF ELECTRIC CURRENT AND THE OTHER END ATTACHED TO SAID BI-METALLIC MEMBER, A PORTION OF SAID HEATING WIRE ENCIRCLING THE INSULATING MEANS IN A SERIES OF

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