Abstract: An electric heater for heating diesel fuel includes a housing having an inlet and an outlet. A flat disk-shaped PTC thermistor is centrally mounted in the housing and is arranged so that the inlet directs fuel against one side of the thermistor to divert the flow of fuel outwardly around the marginal edges of the thermistor. An electrical resistance heater unit surrounds the thermistor between the walls of the housing and the thermistor and is provided with spaces through which the outwardly diverted fuel passes. A divider wall in the housing spaced from the heater unit and thermistor directs the fuel passing through the heater unit across the opposite side of the thermistor to the housing outlet. The PTC thermistor and electric heater unit are connected electrically in series whereby the thermistor functions to control heating output of the fuel heater in accordance with ambient temperature conditions.

Abstract: A glow plug control circuit uses two normally closed thermally actuated switches in series with a power relay and a timer switch across the battery when the ignition switch is turned on; the power relay connects the glow plugs to the battery. At least one of the two switches cycles on and off to limit the temperature of the glow plugs. Another normally closed thermally operated switch has a heating element in series with the glow plugs for turning off a lamp after the glow plugs are energized for a predetermined time. If one or more of the glow plugs are open-circuited, the lamp is cycled on and off with the cycling on and off of current through the glow plugs by the power relay, to signal a fault condition.

Abstract: A diesel fuel filter in which wax crystals that tend to clog the filter at low ambient temperatures are directly heated to melt the crystals, allowing them to pass through the filter. A low energy heating element is positioned adjacent the filter element in the region where wax normally accumulates. The heater melts the wax without significantly raising the temperature of the fuel.

Abstract: A crash-sensing switch assembly for breaking an electrical circuit has a weight pivotally supported on a horizontal surface with the center of gravity above the surface. The weight is free to move away from the surface if the assembly is inverted. Movement of the weight away from the surface, either by tilting or falling, brings the weight into engagement with the trip lever of a latch, releasing a switch to break the circuit.

Abstract: The sensor includes a linearly movable mass including two sections and spring means urging one of the sections into operative engagement with means including an actuating element. The sensor also includes means releasably securing the two sections together and means releasing the securing means when the two sections have moved a predetermined distance against the urging of the spring. The two sections may be rollers of a rolamite unit. A flexible band extends around a portion of the two rollers. One example of a use for such a sensor is in an air bag safety restraint system.

Abstract: A sensor which utilizes the difference in thermal characteristic between two fluids to detect the presence of one fluid or the other. A continuously heated thermal expansion element activates a switch. When the element is brought in thermally conductive contact with a liquid, the heated element drops in temperature, shortening the length of the expansion element and activating the switch.

Abstract: A solenoid in which the coil is positioned inside a housing of magnetic material. The housing has a tubular projection forming a recess in the inside of the end wall along the axis of the coil, one end of the plunger projecting beyond the coil into the recess when the plunger is in the energized position. The portion of the plunger that extends into the recess is tapered to obtain a constant force-displacement characteristic for the full travel of the plunger.