| 摘要 |
450,710. Electromagnetic and thermal switches. GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, London.-(Patent Treuhand-Ges. fur Elektrische Gl³hlampen; 11, Ehrenbergstrasse, Berlin) March 25, 1935, Nos. 9230 and 9565. [Class 38 (v)] [See also Group XI] An arrangement for controlling electric currents comprising a switch in parallel with a resistor having a large negative temperaturecoefficient is controlled by current through the resistor so that the switch closes when the current reaches a predetermined value or when a predetermined amount of heat has been generated by it in the resistor, the switch and resistor being contained in a common closed envelope preferably evacuated or filled with neutral gas. As shown in Fig. 1 (9565/35), the high negative temperature-coefficient resistance 1 is normally in series with the operating coil 2 of an electromagnetic switch, both switch and resistor being mounted within the glass bulb 3 with screw cap 4. As the resistance 1 is heated by the current flowing through it and the coil 2, its resistance falls rapidly, the current correspondingly increasing until the armature is attracted and closes contacts short-circuiting the resistance. The armature is then maintained in its closed position. In a similar arrangement shown in Fig. 2 (9565/35), the resistance 1 is in series with a heating coil 51 surrounding a bimetallic strip which controls contacts 5 for short-circuiting the resistance. This action takes place when the current in the heating resistance rises to a sufficiently high value as the result of a corresponding decrease in the value of the resistance 1 so causing bending of the strip. The connections in this construction pass through a valve base 6. In a variant of this arrangement the resistance of high negative temperature-coefficient may act also as a heater, as shown in Fig. 1 (9230/35). In this case, the arrangement acts as a continuously-operating thermal interrupter for an incandescent lamp 3. The resistance 4 is of such a value that normally tho filament does not glow appreciably, but when the strip 5 is bont sufficiently by the heat transmitted to it by the rod 4 of uranium dioxide the contacts short-circuit the resistance and the lamp glows brightly. On cooling down, however, the strip opens the contacts, after which the cycle of operations is repeated. The switch and resistance may be mounted in the same onclosure as the lamp filament from which it is protected by a mica shield 9, Fig. 2 (9230/35). The switch in all of the constructions, togethor with the high negative temperature-coefficient resistance with which it is associated, is mounted within a sealed envelope 3 or 6, which may be evacuated or filled with a neutral gas. Other types of thermal switches than the bimetallic may be employed in conjunction with resistances of high negative temperature-coefficient, as for example the contact gas thermometer type 7 shown in Fig. 2 (9230/35), surrounded by resistor 8. A further similar type is employed in Fig. 3 (9565/35) (not shown). |
