GB682649A - Electrical time delay control device - Google Patents

Abstract

682,649. Temperature-variable resistances. BENDIX AVIATION CORPORATION. Dec. 28, 1950 [Jan. 28, 1950], No. 31513/50. Class 37. In a thermal time delay device the cooling rate of a temperature-variable resistor is varied independently of the heating rate by means of a heat retaining body in heat exchange relation thereto. A sealed envelope 1, Fig. 1, has a series of pins 3, 5, 7, 9, 11, 13, 15 sealed into its base 2 and adapted to fit into an associated socket. A pair of parallel mica discs 17, 19 are mounted on and spaced apart by the pins 3, 7, 9, 11, 15. A temperature-variable resistor 21, which may be of the thermistor type, and a ceramic body 23 extend through apertures in the discs 17, 19 and are supported by the discs. The body 23 has a different heat capacity than the resistor 21 so that it cools more slowly. An insulating sleeve 29 surrounds the resistor 21 and heating coils 25, 27 are wound on the resistor 21 and ceramic body 23. As shown in Fig. 4, the heating coils 25, 27 are connected in series by strips 31 connected to the pin 9, the lower ends of the coils being connected to pins 15, 7 by strips 33, 35. The resistor 21 is connected to pins 3, 11. The heated body 23 radiates heat to the resistor 21 when the heater windings 25, 27 are de-energized, and delays the cooling of the resistor 21. The envelope 1 may be filled with one or more gases, such as hydrogen or helium, at about one-half atmosphere to provide for heat exchange between the body 23 and the thermistor 21 by conduction as well as by radiation. Specification 603,610 is referred to.