I. - Low-Pressure Compressors.
A. Low-duty Apparatus.-This class includes hand and
forge bellows; also, forcing-pumps for supplying air to respiratory
apparatus used by firemen, etc. The Fayal pump, Fig. 131, consists
of a leather bellows, fixed between heads, in which are inlet
and delivery valves. In the centre of the bellows is a piston
of wood, connected by a split connecting-rod with the crank-shaft
and wheel. The air is driven into a sheet-iron reservoir in the
lower portion of the machine, which communicates with the delivery-valve,
and by a lateral tube with the air-conduit. This apparatus furnishes
air under pressure of from 11.7 to 15.6 inches of water, and this
excess of pressure of from .04 to .03 atmosphere is sufficient
to supply fresh air to five or six miners with their lamps at
a distance of some 300 feet from the compressor.