Abstract: A furnace assembly for automatically transporting circuit board of varying sizes through a firing chamber and for maintaining heat within the firing chamber and preventing ambient air from entering into the firing chamber by having an adjustable twin-track rail assembly for housing and positioning conveyor belts which secure the circuit boards and by having baffle gate chambers in which a series of baffle gates maintain a constant atmosphere at the open ends of the firing chamber.

Abstract: An electric immersion heater comprises a plurality of U-shaped heater sheaths having the terminal leads of the coils in the legs thereof extending up into a junction box from which the sheaths depend. The immersion heater is provided with a centrally disposed metal tube having the top thereof extending into the junction box and the bottom thereof contacting a metal support plate used to hold the legs of the U-shaped heater sheaths in spaced relation. The support plate is located at the level of the upper ends of the coils in the sheaths. A replaceable cylindrical cartridge is provided which encapsulates a one-shot thermal cutoff. The portion of the end lead terminals of the thermal cutoff extending above the upper end of the cartridge are twisted together and sufficiently stiff and long enough to enable the cartridge to be inserted into the tube so as to be seated therein.

Abstract: A hazard prevention control circuit is provided for an electric heater having heating coils enclosed in a quartz tube immersed in a tank of solution. A circuit breaker is connected in series with a contactor coil controlling a set of contacts connecting the main lines of a power supply to the heating coils of the heater. Upon sensing a hazard condition, the control circuit causes excess current to flow through the circuit breaker to open the circuit and deenergize the contactor coil so as to open the contacts connecting the power to the heating coils. Transformers are provided for coupling power supplied by the main lines to the control circuit and the contactor coil and for coupling the pulse output of the control circuit to trigger a triac which conducts the excess current through the circuit breaker.

Abstract: A pyrex tank for heating corrosive solutions is formed with a main body portion having an open top and with a small annular cavity portion depending from the bottom of the main body portion. A heater unit comprising a heating element enclosed in a quartz tube is securely mounted in an upright position on a support. The tank is positioned on the support with the central opening of its annular cavity receiving the quartz tube of the heating element. The solution in the main body portion of the tank is heated in the annular cavity portion thereof by convection. A thermocouple supported in an upright position on the support is inserted through the open lower end of an upright tube fixed to the bottom wall of the tank and extending upwardly into the interior thereof.