US1695103A - Thermoelectric switch - Google Patents

Description

Dec. 11, 1928. 1,695,103

A. U. HOOK THERMOELECTRIC SWITCH Filed May 16, 1927 /19 /za l 2 PE' 25 30 I FIE 7 vi# 4.0 30 @num/Lto@ 33? ARLEY u- HaaK aftozum Patented Dec. 1l, 1928.

vUNITED STATES ARLEY U. HOOK, OF NEW WASHINGTON, OHIO.

THEBMOELECTBIC SWITCH.

Application ,filed Hay 16,

This invention relates to improvements in thermo switches for electric current and moreV particularly to devices for cutting oil' an felectric current supply as soon as the desired 5,1 heat or objectionable heat is created.

An ob'ect of the invention is to form a simplifie device permitting adjustmentfor action at any desired degree of heat. An-

' other object of the inventlon is the construction of a simple device for making and breakin the circuit by a spring snap action. Other ojects of the invention will be more' readily understood from the following descri t1on and the annexed drawings referred to t erein inlwhichz- Fig. 1 shows the side view of the improved thermo-electric switch;

Fi 2, a lon itudinal section through they mid e of the evice;

Fig. 3, a top view of Fig. 2 showing the arrangement of the contact members and the shifting spring;

Fig. 4 is an end view of the device;

Fig. 5 is a section on line 5-5 of Fig. 3;

Fig. 6 is a plan view of the spring or shiftln member for the contact members; Fig, a side view of the spring shown in i 6.

shownz theswitch device comprises a hollow, boxlike frame member 2 open at the top and provided with upwardly extending end wal/ls 3 and 4. The bottom or middle portion 5 connecting the end walls 3 and 4 is `slotted at 6, and a composite metal thermal bar 7 of U-form, connected by screws 8 to the middle portion 5, extends through the slot to the inside of frame 2. The thermal bar is composed of two thin strips of different metals preferably cop er and zinc welded o together at both ends.k he free end 9 of the thermal bar is upewardly bent to contact with a spring mem r 10 of special shape which will later be particularly described. As specifically shown in Figls. 2 and 3, the spring member 10 is rigidly eld at 11 in an adjustable supporting member or plate 12 connected to end wall 4 of body 2 by va screw -14 slidably confined in a slot 15 of wall 4. The supporting member 12 may be vertically shifted to change the position of the end support of spring 10, and in order to facilitate such shifting thev top portion of plate 12 is bent to form an abutment for an adjustingscrew 16 screwed into the bottom 5 of body 2 so that slight loosening of screw saw cuts in the branches o 1927. Serial No. 191,854.

14 will ermit a very accurate shifting of plate 12 y screw 16.

The end wall 3 of body 2 is bent rectangularly to form an offset extension parallel to the bottom 5, and is divided into two partsy or prongs 18 and 19 by a slot 20 cut into this extension and extending into the end wall'3. Slot 20 permits the spring 10 to extend outside of the body 2 and said spring. 10 bears at its free end a contact plate 21 adapted to engage contact plates 22 arranged on the prongs 18 and 19.

Spring member 10 is alsosupported by a second supporting member 23 of yoke shape having grooves 24 for the edges of the sprin 10 engaged therein. These rooves are smal the member 23 and are engaged by extensions 25 on the spring 10 and provide a rigid fulcrum support permitting slight pivotal movement of member 10 at the supporting oints. Supporting member 23 is also adjustable horizontally or lengthwise of the spring by an adjusting screw 26 screwed into end wall 3 and cooperating with screw 21 to support the member 23 on wall 3. By adjustment of plate l2 and member 23 spring 10 may be put under preliminary or normal tension so that contact plate 21 is closed with contact plates 22', but under certain other circumstances a sudden shift of member 10 mayoccur, causing .the end of spring member 10 bearing contact plate 21 to travel sud- -denly a relatively large distance to break thecontact without great arcing, as mayy occur with direct current by a relatively'- slow break.

The sha e of the sprin 10 is such, and the place o contact of the t ermal bar therewith is so chosen, that it will automatically spring back to its set position when the pressure of the thermal bar .is released. To achieve this purpose spring 10 is sharply bent close to its rigid support 12 at one end as at 40, and the bearing end of the thermal bar on spring 10 is located quite close to said end of the spring. By this arrangement a relatively small movement of the end of thermo band will elect a quick shift of member 10 and snap action of the switch. 105 The free or extended end of the spring 10 has a rib 3() pressed therein which increases the stiffness or rigidity of the free end of the spring.

In operation, the pressure of the thermo un band under the inuence of excessive heat will bend the spring 10 until it passes center' and it will then snap the contacts open. Vhen the pressure is released the kink 40 in the spring will have the effect of restoring or snapping back the spring to original position thereby closing the contacts. If desired, the spring may be made without this kink, in which event the switch will remain open after actuation, if desired; but by pro- Vision of the kink in the spring it will restore the circuit as before stated.

The adjustment of the plate l2 is important, as it permits a setting for operation according to the desired temperature. That is, by adjusting the plate one way or another by means of the screw 1G the position of the spring l0 relative to the expansion member 9 may be varied so much the temperature at which the spring will act to open the circuit. This permits the device to be used under various conditions or with different appliances.

I claim:

1. A thermal switch having a spring fixed at one end and free at the other, the free end carrying a contact, and a support between the ends of the spring, the spring being bowed under tension between said support and the xed end, and a thermal element bearing against the bowed part of the spring, the fixed end of the spring being adjustable crosswise of the spring Vto vary the pressure of the spring against the thermal element.

2. A thermal switch as set forth in claim l, the free end of the spring having a longitudinal rib to increase its stiffness.

3. A thermal switch comprising a frame having its endwall slotted and rovided with two prongs extending outwar 1y from said wall7 a bowed spring in tension in the frame and projecting through the slot, and with its free end beside the prongs, contacts on the prongs and said end, and a. thermal element supported in the frame and bearing against the spring.

In testimony wlhereof, I do aix my signature.

ARLEY U. HOOK.

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