Primary gas furnace control

Claim 1

In a primary control for gas furnaces, the combination including a low voltage circuit adapted to be connected to a source of low voltage AC current, said low voltage circuit including a thermostatic switch, an electrically operable pilot gas valve, an electrically operable main gas valve, pulse generating means, and first relay means controlling the energization of said main gas valve and said pulse generating means, a high voltage spark generating circuit including spaced electrodes disposed in the path of gas emanating from said pilot valve, means interfacing said low voltage circuit and said spark generating circuit and providing a substantially higher voltage in said spark generating circuit than in said low voltage circuit, and flame sensing means including a probe disposed in the path of gas emanating from said pilot gas valve and being subjected to the heat of the gas flame when gas ignition is obtained by said spark generating circuit whereby flame rectification is effected, said flame sensing means controlling said main gas valve and said pulse generating means through said first relay means, said means interfacing said low voltage circuit and said spark generating circuit including voltage doubler means and step up transformer, means.