All About Engines
Forfatter: Edward Cressy
År: 1918
Forlag: Cassell and Company, LTD
Sted: London, New York, Toronto and Melbourne
Sider: 352
UDK: 621 1
With a coloured Frontispiece, and 182 halftone Illustrations and Diagrams.
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128 All About Engines
Fig. 79.—Mechanism of drop valve
to larger scale
tions on the cylinder as the Corliss valves, but they
open and close by being lifted from or allowed to
fall upon their seats, upon which they are pressed by
a spiral spring.
Fig. 78 is a diagrammatic section through the
cylinder of a drop-valve engine made by Marshall,
Sons, and Co., of
Gainsborough.
Each valve is fixed
to a long spindle,
the other end of
which ends in a
small piston fitting
in a small cylinder.
The spring keeps
the valve on its
seating, and the
piston prevents its
fall, after being
raised and released,
from being too
rapid. It is, in
fact, “ cushioned ”
by the enclosed
air. An arrange-
ment of this sort
is called a " dash-pot.” It prevents the valve knock-
ing itself to pieces.
In order to explain how these valves are worked
we shall require another diagram. In Fig. 79 there is
a lever, A, which works on a pin fixed to a bracket on