US1592111A - Automatic switch for electric heaters - Google Patents

Description

M. KLETTNER AUTOMATIC SWITCH FOR ELECTRIC HEATERS Filed NOV; 14, 1924 Inventor:

Patented July 13, 1926.

UNITED STATES MARTIN KLETTNER, OF DBESDEN-ALSTADT, GERMANY.

AUTOMATIC SWITCH FOR-ELECTRIC HEATERS.

Application filed. November 14, 1924, Serial No. 749,942, and in Germany August 23, 1924.

The object of the present invention is an automatic switch for electric heaters. The device is intended to be used in connection with electric heaters like fiatirons, pots, rarming plates, heating cushions, warming .abinets, electric stoves, etc., and purposes to stop automatically the electric current the moment the temperature of the heater exceeds a certain limit and to start the current again automatically as soon as the temperature falls below a certain level, which may be higher or lower, according to the purpose of the heater. The switch to which this invention refers can be employed for all sorts of heaters as the contact screws actuating the contact device are adjustable.

The use of the automatic switch effectively prevents any burning through of the heaters. Damages caused, for example, by electric flatirons, which are left standing for a certain time, cannot happen, if this switch is used. The heater is always connected to the line and is therefore always ready for use without consuming too much current, because, as already mentioned, the current is automatically cut off as soon as the temperature of the'heater exceeds a previously chosen and adjusted limit. For cooking vessels, warming'plates, and heating cushions the arrangement can be made ,so as to maintain even temperatures below 100 C. with very slight fluctuations.

One form of the invention is illustrated in the accompanying drawing, in which Figure 1 is a side view of the switch with par tially opened casing; and Fig. 2 a vertical section ab of Fig. 1.

To the plate 1, whichis made from insulating material like hard rubber, is attached a layer of asbestos 2. 3 and 3 are the terminals, which are firmly embedded in the plate 1. On top of plate 1 is arranged theasbestos layer 2, to both of which the casing 4,.which also consists of insulating material, has been secured by screws 5. The casing 4 has partly. been removed in Fig. 1 to permit a, look into the inside of the apparatus, while it has been completely omitted in Fig. 2.

To plate 1 and an asbestos layer 2 has been attached also a laterally U-shaped frame 6 by means of screws 7. In frame 6, by means of screws 8, a container 9 capable of cuit passes accommodating a liquid of high cubically expansive power has been arranged, and one wall 10 of this container has been executed as a membrane. 11 is, a contact screw with head 12. The contact screw 11 is guided with its thread in a guide member 13 secured to a spring 14, which is attached to a member 16 which in turn is ad justable by means of the screw 15. The spring 14'carries at its lower end the plate 17. To the member 16 is also attached a two-legged permanent magnet 18, through the legs of which the contact screw 11 passes freely. The magnet cooperates with the plate 17. On plate 17, by means of a holder 19, a button 20 has been arranged, which causes an electric connection between the container '9 and'terminal 3* by electrically connecting the two members 21 lying between them, one of which being secured to the terminal 3 and the other to the container '9. 22 is a set screw, which is insulated and guided in frame 6 by placing the insulating isc 23 between them. 24, 25, 26, 27, 28 and 29 are fastening screws for the reception of the wire connections. Screws 24 and 27 on one hand and screws 25 and 26 on the other are electrically connected by means of the metal pieces 30 and31. From screw 26 a connecting wire 32 leads to screw 26 and thus to terminal 3*. Another wire 32 leads from screw 29 to terminal 3, and finally a third wire leads from screw 27 to the set screw 22.

The method of operation is as follows: The device has the outer appearance of an ordinary two-pin wall plug and is attached to the heater in the ordinary manner by meansof the pins provided for the reception of the plug in each heaterf The current carriers areconnected to the screws 24 and 25, respectively. In this manner one clrdirectly from the screw 25 over screw 26 and the wire 32 to the terminal 3", while the other circuit passes from the screw 24 over screw 27, the set screw 22 and the button 20 tothe terminal 3*, provided the set screw has been adjusted so as to touch the button 20 withits front point. The heater gets warm in the usual and known manner, and a part of the heat passes over the terminals towards the container 9. The liquid kept within this container will now expand. If a certain maximum temperature has been reached, the membrane 10 is pressed outwardly far enough to cause the set screw 11 to be pressed to the right in the manner indicated in Fig. 1. In this way the spring, contrary to the action of the magnet 18, is torn away with its plate 17,

from the magnet with the result that the button 20 is placed in a-certain distance from the point of the set screw 22. This causes an interruption of current. If the heater cools off, the liquid in the container 9 will contract, the membrane returns to its original position, and the plate 17 of the spring 14 is pulled back into its original position through spring action. The button 20 returns to its place at the point of set screw 22, and the connection is reestablished. In this way a certain temperature ,can be constantly maintained.

The regulation of the temperature desired, which as already mentioned, depends on the nature and purpose of the heater,

takes place by means of the screw 11 of the button '12, which is thus placed in varying distance from the membrane, audit is therefore a greater or smaller expansion of the liquid required to cause an interruption of current.

I claim An electric switch for electric heaters com prising a U-shaped frame, in which aclosed hollow body containing an expansible liquid, a. two-legged permanent magnet, an ad ust- "able spring contact with a button connecting two heat conducting members are arranged, the said springcontact being influenced by the expansible liquid on one hand and by the permanent magnet on the other hand, while the said liquid and magnet counteract each other, the U-sha ed frame being fitted with screws into a p ug casing comprising a bottom-plate for the reception of the terminals, a covering insulating layer, connecting terminals for current supply, the transmission of expansible liquid taking place over the terminals, one connecting member, the button, theE1 other connecting member, and the hollow bo y. o

In testimony whereof I afiix my signature MARTIN KLETTN ER.

heat from the heater to the"

Images