Abstract: An electric fluid heater of the type in which the fluid is heated by passing electricity through it includes an electronic temperature control system responsive to a temperature sensor in the fluid for controlling the flow of electric current to the heating electrodes. The electronic controller includes means to limit the maximum current passed by the heating electrodes. Heat generated is controlled to demand by varying the duty cycle of back-to-back SCR's in series with one of the electrodes.

Abstract: An electric fluid heater includes a metallic container defining a heating chamber provided with a pair electrodes for passing electric current through the fluid for heating the fluid. The container has a fluid input port, a fluid output port and a safety port all communicating with the heating chamber. The ports have a reduced aperture portion of a substantial length to increase the resistance of the current leakage path from the electrodes to external ground connections. All surfaces of the metallic container including the fluid contacting surfaces of the heating chamber and ports are covered by an electrically insulative coating. An external pressure relief valve is connected to the safety port.

Abstract: An improved printer embodiment that includes a print head having thin "foil" electrodes and associated spacers fashioned to maintain very precisely controlled dimensions and positioning according to specific, improved fabrication techniques providing an exactly oriented row of spaced, aligned electrodes. Each electrode includes an integral "print-finger" adapted to resiliently skid over the passing print-substrate and, preferably, also including a companion contact adapted to engage an associated conductor terminal.