Abstract: A dual fuel system for use with internal combustion engines comprising (a) a manually actuated dual fuel valve, (b) a liquified gas to gaseous fuel converter combining a liquified fuel lock-off valve responsive to engine vacuum and a fuel metering valve responsive to a predetermined positive pressure modulated by engine vacuum, and (c) a positive pressure gaseous fuel and air mixer having a compact plunger structure in which the fuel valve is located within the air valve structure. In one embodiment, the mixer employs a relatively large piston which travels a relatively short distance to meter the flow of air between the lower surface of the piston and a coaxial annular surface. A second embodiment of the mixer utilizes a smaller diameter piston which travels a relatively longer distance, but which utilizes a relatively flat plunger to meter air flow. The fuel valve carried by the plunger structure may be of the needle valve or slotted tube type and may serve as a guide for the air valve structure.

Abstract: A dual fuel system for use with internal combustion engines comprising a manually actuated dual fluid valve which alternatively supplies gasoline to the engine's carburetor or engine intake manifold vacuum to a single-stage liquified gas to gaseous fuel converter having a liquified fuel inlet valve actuated in response to intake manifold vacuum by a diaphragm of substantially the same diameter as a second diaphragm which actuates a valve to a converter gaseous expansion chamber where desired gaseous pressure is maintained and is automatically reduced during cruise conditions by compression of a bellows which acts on the second diaphragm in response to reduced engine intake manifold pressure during such cruise conditions, and a pressurized gaseous fuel and air mixer having a plunger structure responsive to venturi vacuum which meters air flow and actuates a valve needle to meter fuel flow.