| 摘要 |
506,196. Temperature variable resistors. GENERAL MOTORS CORPORATION. Jan. 19, 1938, No. 1782. Convention date, Jan. 27, 1937. [Class 37] An electrical unit for detecting temperature variations in an engine water-cooling system, or on an aeroplane wing, or in steam boilers comprises a hollow plug in which is located a copper-copper oxide device 50, 52 insulated from the plug body by members 66, 68, the terminal bolt 62 having a head 58 and being also insulated at 70, 72 and 74 from the plug. The terminal head 58 engages with a layer 56 of graphite on the oxide film 52, and a copper block 48 is pressed into engagement with the member 50 by a plug 44. In order to age the oxide film so that its resistance variation is uniform over a given temperature range, the blank is heated at 950-960‹ C. for ten minutes in an atmosphere of nitrogen containing about 2 per cent oxygen; followed by five minutes exposure to air in the furnace. The oxide unit is then slowly cooled in air and again heated to a temperature higher than that under working conditions of the unit, and at the same time a current is passed through it from the oxide face. One such process includes heating to 280-300‹ F. and passing a current of 350 milliamperes. Barium may be alloyed with the copper in small amounts, for example 0À05 per cent, such an alloy producing a low resistance unit that can be employed for lowtemperature variations.
|
