Hillson’s Patent Model of a Hot-Air Furnace - ca 1848

<< >>
This model was filed with the application to the U.S. Patent Office for Patent Number 5,459 issued to Robert Hillson of Albany, New York on February 29, 1848. Mr. Hillson’s patent was for an improved design for hot air furnaces. Claimed advantages included the ability to circulate hot air via horizontal pipes to rooms on the same floor as the furnace; an improved design for air tight seals for doors entering into the furnace; the use of double-walled hot air ductwork to avoid heat loss and reduce the threat of fire; a fire grate design that prevented the coal from becoming packed and clogged; and an improved mechanism for dumping the cinders from the fire grate. The overall design of the furnace was a rectangular brick box mounted on a thick brick foundation. The upper portion of the furnace had double brick walls with four inches of space between the inner and outer. This provided channels for cold air to enter the furnace and circulate from its top to bottom. The interior of the furnace was a complicated series of brickwork chambers, flues and channels that circulated the hot gases from the firepot so as to expose large areas of hot surface to heat the air. The cylindrical fire pot and hot air chamber were mounted on a brick floor above the cold air chamber at the bottom of the furnace. The fire grate design, which Hillson claimed as new, was for a circular metal grate that had a semi-hemispherical raised section in the middle and a flat grate for the remainder of the area. Hillson claimed that this shape avoided the packing and clogging of the coal. Above the hot air chamber were located two doughnut-shaped compartments through which the hot gases from the combustion chamber passed. Air to be heated was in contact with the exterior of these compartments, and Hillson claimed the design offered greater heat radiating surfaces and better heating efficiency. A key claim made by Hillson was the ability to heat rooms on the same floor as the furnace via horizontal pipes. His idea was to draw the combustion air for his furnace from the rooms being heated. This produced a pressure differential between the furnace and the rooms thereby drawing the heated air from the furnace into the rooms. A review of available advertisements and trade literature of the period did not provide any information on the commercial development of Hillson’s patent. However, Hillson remained active in heating design until shortly before his death in 1888.
The patent model is constructed of brass, lead, and painted wood. The model illustrates the various doors, air inlets, outlets, and flues as well as many of the interior details of the patent design including the grate, hot air chamber, air circular and smoke circular. The doors on the model have details of the tongue and groove seal that Hillson claimed added air-tightness to the furnace.
Currently not on view
date made
ca 1848
patent date
Hillson, Robert
place made
United States: New York, Albany
overall: 8 1/2 in x 7 1/4 in x 6 1/4 in; 21.59 cm x 18.415 cm x 15.875 cm
ID Number
accession number
catalog number
patent number
Credit Line
Transfer from Department of the Interior
Patent Models
See more items in
Work and Industry: Mechanical and Civil Engineering
Patent Models
Engineering, Building, and Architecture
Data Source
National Museum of American History


Add a comment about this object