CATALOG OP THE MECHANICAL COLLECTIONS I43 



JOHNSTON AIR COMPRESSOR, 1879 



U.S.N.M. no. 308706 ; original patent model ; transferred from the United States 

 Patent Office; not illustrated. 



This model was submitted with the application for the patent 

 issued to William Johnston, of Washington, D. C, November 4, 

 1879, no. 221318. 



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 under side of the 

 shaft and extends downward to the cylinder casing. 



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 approxi- 

 mately 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 es- 

 capes 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. 



INTERNAL-COMBUSTION ENGINES 



Early history. — Strictly speaking the history of the internal com- 

 bustion engine begins in the thirteenth century with the first use of 

 the cannon. However, the first explosive engine capable of produc- 

 ing work was that designed by the Abbe Hautefeuille, the son of 

 an Orleans (France) baker. In 1678 he suggested a motor to raise 

 water by burning pow'der in a vessel communicating with a reservoir 

 of water. As the gases of combustion cooled a partial vacuum was 

 formed in the vessel and atmospheric pressure raised the water from 

 the reservoir. In 1682 he described a machine in which water was 

 raised by the direct expansive action of the gases of combustion. 

 Christian Huygens in 1680 was the first to employ a cylinder and 

 piston in an explosive engine, and Denys Papin in 1690 made an 

 improvement in the valves of the Huygens engine. Huygens died 

 in 1695, and Papin turned his attention to steam, and for a hundred 

 years no new explosive engine was produced. In 1791 John Barber 

 of England made an engine in which wood, coal, or petroleum gas 

 was mixed with air and pumped into a vessel termed the "exploder'', 



