| 摘要 |
<p>764,426. Automatic temperature control systems. GENERAL MOTORS CORPORATION. Jan. 19, 1955 [Feb. 2, 1954], No. 1628/55. Class 38 (4). [Also in Group XXXVII] In a system for automatically controlling an electric heater element, the heater element is either disconnected or has one or other of two voltages applied to it according to the temperature of a vessel on the heater element. In Fig. 2, the temperature of a cooking vessel 48 on a two-resistance electric heater element 46 is detected by a liquid-filled bulb 44 spring urged into contact with the bottom of the vessel. An expansible metal bellows 36 coupled by a capillary tube 42 to bulb 44 opens contacts 30, 62 to de-energize a relay 68 at a temperature determined by the setting of a cam 34 by a knob 131. This changes the connection of the two heater resistances from a source Ll L<SP>2</SP> to a source L<SP>2</SP>N of half the voltage. The desired temperature is thus maintained by alternate energization at the two voltages. If for any reason the temperature of the vessel rises a predetermined amount above the desired value, bellows 36 operate sufficiently to open contacts 32, 58 and de-energize the heater resistances. Over the lower portion of the. temperature range which includes " slow boiling," a cam 125, also operated by knob 131, opens contacts 86, 98 so that only one heater resistance is energized when contacts 30, 62 are open.</p> |
