Heat-insulated telemetry system for vacuum furnace

Abstract

A heat-insulating box houses a telemetry system of high accuracy for use within a high-temperature vacuum furnace. The container includes an inner box formed by a block of rigid heat-insulating material having a cavity which contains a telemetry system chassis and its components, including such items as batteries, transmitters, switches, thermocouple elements including transition tubes, isothermal double-layer terminal strips, and the like. A plurality of very fine thermocouple conductors of dissimilar metal extend from the thermocouple junction tips on work pieces outside of the box through the heat-insulating inner block to the thermocouple transition tubes, and then, by way of the isothermal double-layer terminal strip to the transmitters. An antenna lead is carried through the wall of the box to a transmitting antenna mounted on the front wall of the box. Pressure switches in the cavity within the box control the ON-OFF condition of the transmitters. These pressure switches are normally open and do not close until the pressure falls to a vacuum pressure corresponding to the pressure in the vacuum furnace, and the switches open when the pressure rises to a preselected value. Thus, the transmitters are ON for only a portion of a complete work cycle. Battery energy is conserved and battery life extended. Various features of the construction of the telemetry box and its contents contribute toward insulating the telemetry transmitters from the high heat of the furnace.