Liquid contact relay incorporating gas-containing finely reticular solid

Abstract

It has been discovered that electrically conducting, vitreous pyrolytic carbon in broken-bubble, foam-type, reticulated structures can be used as an extremely fast and efficient electrically operated motor to actuate mechanical devices, such as mercury liquid contact relays, by electrothermally-produced gas expansion. The gas pressure change is produced evenly and almost instantaneously throughout the volume of the reticular motor to move mercury contacts, to open or close a liquid contact relay, thus avoiding the expensive electromagnetic coils now used as relay motors. By passing an electrical current through conducting reticulated material formed from pyrolytic carbon, metals, conductive ceramics or plastics, the microscopic network of interconnecting filaments is heated, thus heating and expanding the fluid (air, hydrogen, helium, argon, etc.) contained in the reticular motor. The time required to operate the device depends on the thermal gradient and the square of the average thermal diffusion distance between the gas and the nearest heating filament. Since the diffusion distance is very small, the device is very fast and efficient. For fast repetative motor operation, a reticulated material of high thermal conductivity such as silver, silicon nitride, or boron nitride, is sealed to the inside walls of the motor. The reticular electrothermal motor is useful for operating mechanical devices including both miniature logic relays and large industrial relays. The high power requirement of the latter may be supplied by using change of state expansion of volatilizable liquids such as are used as refrigerants or as propellants in aerosol spray containers.