Ayer's Patent Model of a Refrigerator Car - 1876

Ayer's Patent Model of a Refrigerator Car - 1876

This model was filed with the application to the U.S. Patent Office for Patent Number 184,029 issued to John M. Ayer on November 7, 1876. Ayer’s invention was a design for a railroad refrigerator car that would have improved insulation properties while also being lighter than other cars of the time. The ultimate goal of the improved design was to allow longer shipments of perishable goods without the cost and delay of ice replenishment. Ayer claimed that these goals were achieved without sacrifice in the strength or durability of the car. The basic idea of the patent was to create a double-walled car in which the inner and outer walls of the car were separated by air chambers. The roof of the car also had an air chamber between it and the inner ceiling. The air chambers were interconnected and vented to the outside air so as to permit circulation. This reduced the heating of the insulating air by prolonged contact with the exterior walls and roof when exposed to direct sun. The outer wall and roof were constructed of wood. The inner walls and ceiling were made from a layer of pasteboard (or similar paper product) and a layer of rubber . Both of these materials provided additional insulation, and the inner walls and ceiling were intended to be nearly air tight. The patent provided for double entry doors, and these were constructed of an outer layer of wood with an inner layer of the same pasteboard and rubber. The doors had beveled edges with the inner surfaces being smaller than the outer. The inner rubber surfaces were shaped to form a seal when the doors were secured thus adding to the airtightness of the car. Cars of Ayer’s design were constructed and used on railroads and were documented as still being used in 1903.
The patent model is constructed of wood. There are two cut away sections, one on the side of the car and one on the roof. These show the essential elements of the patent - the air chambers and the inner wall and ceiling of the car. Double doors mounted in the side of the car are shown open to illustrate the seals and beveled edges.
Currently not on view
Object Name
refrigerator car, model
patent model, refrigerator car
date made
patent date
Ayer, John M.
place made
United States: Illinois, Chicago
associated place
United States: Illinois, Chicago
Physical Description
wood (overall material)
overall: 6 3/4 in x 14 5/8 in x 5 3/8 in; 17.145 cm x 37.1475 cm x 13.6525 cm
ID Number
accession number
catalog number
patent number
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
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