Crocker’s Patent Model of a Hot-Air Furnace - 1874

This model was filed with the application to the U.S. Patent Office for Patent Number 163,050 issued to William O. Crocker on May 11, 1875. Crocker’s patent was for improvements in a hot-air furnace. The coal-fired furnace design provided an inner combustion chamber which was surrounded by an intermediate metal jacket. Cold air entered at the bottom of the furnace and was communicated via a set of holes in the base into the annular space between the combustion chamber and the intermediate jacket where it was heated. The diameter of the intermediate jacket increased from the base to top of the furnace. This allowed the heated air to expand efficiently into the air chamber at the top of the furnace where it was then conveyed via ducts to the building. The intermediate jacket was surrounded by an outer casing, the purpose of which was to increase efficiency by reducing radiation of heat from the hot intermediate jacket. Another design feature which claimed to increase efficiency was provision for both direct and indirect draft for the combustion chamber. The fire-pot had vertical partitions that extended from the top of the chamber three quarters of the way to the bottom. Two flues were provided, one near the top of the combustion chamber and one just above the fire-pot. The upper flue could be closed off so that the products of combustion would have to travel up into the combustion chamber and then back down behind the partitions through the fire-pot and back up its front to the lower flue exit. The object was to more evenly distribute the heated gases over the entire surface of the combustion chamber. A review of available advertisements and trade literature of the period did not provide any information on any commercial development of Crocker’s patent.
The patent model is constructed of tin sheet. It illustrates the key design features of the patent: the outer casing, combustion chamber, and the intermediate jacket around the combustion chamber. The perforated openings at the base of the furnace which provide air circulation around the combustion chamber and intermediate jacket are clearly represented. The direct and indirect flues are also shown.
Currently not on view
Object Name
patent model, furnace, hot-air
date made
patent date
Crocker, William O.
overall - from catalog card: 8 1/2 in; 21.59 cm
overall: 8 7/8 in x 6 5/8 in x 6 1/8 in; 22.5425 cm x 16.8275 cm x 15.5575 cm
associated place
United States: Massachusetts, Turners Falls
ID Number
catalog number
accession number
patent number
Engineering, Building, and Architecture
Patent Models
See more items in
Work and Industry: Mechanical and Civil Engineering
Patent Models
Data Source
National Museum of American History, Kenneth E. Behring Center
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