Stratified combustion furnace

A plural stage, log burning, down draft heating apparatus for heating and delivering clean air to enclosed areas of a building comprising, in combination,

• (a) a primary combustion chamber of generally uniform rectangular horizontal cross-section through which solid fuel, such as logs, and air may be supplied for the purpose of combustion, and having an outlet substantially narrowed in one horizontal dimension only for the products of combustion at its lower extremity,
• (b) a grate of much smaller width than the unreduced horizontal width of the primary combustion chamber, disposed across said outlet, through which grate embers of restricted size and most of the gaseous products of combustion are required to pass downward,
• (c) convergent means in said combustion chamber for funneling solid fuel onto the grate,
• (d) means located beneath the grate for intercepting embers that fall through the grate and detaining them until they have been burned down to much smaller dimensions than the maximum that can be passed by the grate, so that a secondary down draft combustion chamber is provided,
• (e) a bottom receptacle communicating with said secondary combustion chamber for the reception and accumulation of ashes and the transmission of the gaseous products of combustion, and
• (f) upwardly extending gas discharge means communicating with the bottom receptacle and extending above the down draft heating apparatus for inducing the gaseous products of combustion to flow downward through the primary and secondary combustion chambers into said bottom receptacle and for discharging them thence upward into the atmosphere.