Johnston Air Compressor, Patent Model
date: label: date made
content: 1879
label: patent date
content: 1879-11-04
name: label: inventor
content: Johnston, William
notes: label: Description
content: This model was submitted to the U.S. Patent Office with the application for the patent issued to William Johnston, of Washington, DC, November 4, 1879, no. 221318.
label: Description
content: The compressor represented by the model is in effect a bellows. It is constructed as a cylindrical casing mounted upon a stationary horizontal shaft about which it oscillates. Two diaphragms extend in radial planes from the inside and top of the casing to a bearing on the upper side of the shaft. The space between these diaphragms is wedge-shaped. The two spaces thus formed are valve spaces, inlet and outlet, respectively. Flap valves are let into the diaphragm connecting the valve spaces with the lower part of the casing interior. A third diaphragm, called a lug, is fixed to the underside of the shaft and extends downward to the cylinder casing.
label: Description
content: In use the casing is filled with water to the level of the center of the shaft. When the case is rocked the water is held approximately stationary by the lug and the air between the surface of the water and the diaphragm on the down side is compressed while a partial vacuum is formed in the space between the surface of the water and the diaphragm on the up side. The compressed air escapes through the outlet valve and air is drawn into the up side through the inlet valve. As the casing is rocked back and forth it is in effect a double-acting bellows.
label: Description
content: Reference:
label: Description
content: This description comes from the 1939 Catalog of the Mechanical Collections of the Division of Engineering United States Museum Bulletin 173 by Frank A. Taylor.
label: Location
content: Currently not on view
place: label: place made
content: United States: District of Columbia, Washington
label: associated place
content: United States: District of Columbia, Washington
setName: label: See more items in
content: Work and Industry: Mechanical and Civil Engineering
label: See more items in
content: Bulletin 173
label: See more items in
content: Engineering, Building, and Architecture
label: See more items in
content: Work
label: See more items in
content: Industry & Manufacturing
publisher: label: Related Publication
content: Frank A. Taylor. Catalog of the Mechanical Collections of the Division of Engineering United States National Museum, Bulletin 173
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: MC.308706
label: catalog number
content: 308706
label: accession number
content: 89797
label: patent number
content: 221,318
objectType: label: Object Name
content: engine, steam, model
label: Object Name
content: patent model, compressor, air
label: Object Type
content: Patent Model
physicalDescription: label: Physical Description
content: wood (overall material)
label: Measurements
content: overall: 9 3/8 in x 10 1/8 in x 9 in; 23.8125 cm x 25.7175 cm x 22.86 cm