Webster’s Patent Model of a Hot-Air Furnace - ca 1866

This model was filed with the application to the U.S. Patent Office for Patent Number 55,564 issued to Edward W. Webster of Hartford, Connecticut on June 12, 1866. Webster’s patent was for improvements in efficiency and the ability to provide adjustable amounts of heated air to various apartments of a building. The furnace was cylindrical in shape and consisted of an inner cylinder which was surrounded by a slightly larger cylinder. The outer cylinder was intended to reduce radiation of heat inside the furnace room. Cold air entered into a compartment which was the diameter of the outer cylinder and located at the base of the furnace. A damper was provided to allow mixing of outside air and return air from the rooms being heated. This cold air was allowed to pass upward through the space between the cylinders as well as through a series of air-tubes around the circumference of the inner cylinder. These ran between the top of the cold air compartment up and through a plate near the top of the furnace (just below where the furnace tapers to a smaller volume as shown in the image of the model). The fire-pot, grate, and ash pit were located just above the cold air compartment. The combustion chamber was closed at the top by the plate through which passed the air-tubes. Thus, the air-tubes were surrounded by the hot combustion gases. The entire inner cylinder was also exposed to the combustion gas. Outside and return air was thus heated and rose upwards into the conical shaped plenum at the top of the furnace and then to the heated rooms via the ductwork. Webster claimed as new or improved in his patent a means for adding humidity to the heated air via an “evaporating dish” filled with water and located at the top of the plenum. He also claimed as new or improved a means of providing for the exhaust of the combustion chamber to be downwards via a funnel in the bottom of the furnace and then to the flue. He claimed this provided for more complete and even heating of the air-tubes and inner cylinder. A review of available advertisements and trade literature of the period did not provide any information on the commercial development of Webster’s patent. However, he was active in additional patents until at least the 1880s.