Wood burning furnace

DETAILED DESCRIPTION The features of the present invention solve many of the problems associated with the prior art furnaces, the result of which is to substantially increase the heating efficiency of wood or coal burning furnaces.
In one aspect, the furnace of the present invention includes a preheating chamber and duct system which are attached directly to the outer surface of the furnace housing.
Air is first drawn into this preheating system and preheated before it is admitted into an air circulation chamber.
This preheating of the air has been found to substantially increase the heating capacity of the system.
In another aspect, the furnace of the present invention includes a combustion chamber supported in a furnace housing with an ash pan assembly located under the combustion chamber.
A number of heat transfer tubes extend through the ash pan assembly, immediately below the combustion chamber.
The logs to be burned are placed on these tubes.
Set below the tubes is a grate for catching burning cinders that fall through the spaces between the tubes.
An air circulation chamber completely surrounds the combustion chamber for passing ambient air for heating.
The furnace further includes an air intake means for admitting air into the air circulation chamber.
Air, upon being admitted into the air circulation chamber, passes through the heat transfer tubes, where it is heated by the fire burning directly on the tubes' upper surface and by the burning cinders located below the lower surface of the tubes, and then around the remainder of the air circulation chamber, where it is heated by the surfaces of the combustion chamber.
The heated air is then exhausted out into the area to be heated through an air outlet opening.
The combination of circulating air through heat exchange tubes which are directly heated on both their upper and lower surfaces and of placing the fire grate below the combustion chamber so that the entire surface of that chamber is heated substantially increases the efficiency of heat exchange