III. HIGH-PRESSURE COMPRESSORS.
A. Low-duty Apparatus.-
1. Piston Compressors acting directly on the air to be compressed . - Under this heading may be classed the compressors used for supplying air as motive-power for rock-drills, where but small volume is required.
The general construction of the Burleigh compressor is shown in
Fig. 145. There are two vertical inverted air-cylinders, the
pistons of which are moved by cranks, on a shaft which carries
at one extremity the fly-wheel, and at the other the crank which
is connected with a direct-acting inverted engine mounted on the
same support. The delivery-valves are placed in a chamber which
connects the upper parts of the two cylinders. They are cooled
by a stream of water, regulated to quantity by a suitable valve.
The machine may be said to furnish 85.3 cubic feet of air, at
4 atmospheres and at 90 revolutions per minute. This is one of
the most successful compressors for supplying power to drills
yet constructed.