IMPROVEMENTS IN COMPOUND STEAM ENGINES
Year: 1877

page_text: PROVISIONAL SPECIFICATION left by William Clark at the Office of the
Commissioners of Patents on the 27th August 1877. A communication from
abroad by Gideon Blackburn Massey, of the City, County, and State of New
York, United States of America.
WILLIAM CLARK, of 53, Chancery Lane, in the County of Middlesex, Patent
Agent. "IMPROVEMENTS IN COMPOUND STEAM ENGINES." [A communication from
abroad by Gideon Blackburn Massey, of the City, County, and State of New York,
United States of America.]
The object of this Invention is to construct an engine in which the steam may
exhaust from the high-pressure cylinder into the low-pressure cylinder at the most
advantageous point in the stroke. This I accomplish in some cases by employing
two pistons in the smaller or high-pressure cylinder, which serve the double purpose
of a piston and exhaust valve. In other cases I employ a single piston in the high-
pressure cylinder, and exhaust through a port formed in the centre of the cylinder
into the low-pressure cylinder. In still other cases I accomplish the same result by
employing the ordinary slide valve.
In one simple form of engine the high-pressure cylinder is longer than would be
commonly employed for an engine of the same stroke. At each end of the cylinder
there are supply ports, through which steam is admitted by the usual oscillating
valves.
The low-pressure cylinder is joined to the high-pressure cylinder, and communi-
cation between the two cylinders is effected through ports located at the ends of the
larger or low-pressure cylinder, and entering the smaller or high-pressure cylinder at
about one-third the length of the cylinder from its ends. The low-pressure cylinder
contains a single piston, which is connected with a crank on the main shaft by
means of an ordinary piston rod and connecting rod. The high-pressure cylinder
contains two pistons attached to a single piston rod, and separated by a distance
equal to that which separates the ports communicating between the two cylinders.
The piston rod is connected with a second crank on the main shaft by a connecting
rod, the crank being set at right angles to the one first mentioned.

page_text: When steam is admitted to the high-pressure cylinder it drives the piston forward
until it passes one of the two ports communicating with the low-pressure cylinder,
when the port being open the steam passes from the high-pressure cylinder to the
larger or low-pressure cylinder at the beginning of the stroke of the piston in the
latter cylinder. At the same instant steam escapes from the opposite end of the low-
pressure cylinder through the other of the two ports into the space in the high-
pressure cylinder between the pistons, and thence through the exhaust opening to
the condenser, or to the open air.
It will be seen that the length of the passage between the two cylinders is
small, and that in consequence there is little or no waste of steam. It will also be
observed that as the cranks are set at right angles to each other there can be no dead
points to overcome...
When the engine is made reversible, the wall between the cylinders is sufficiently
thick to contain two crossed passages which connect the ports, and are controlled
by two four-way valves by means of which steam may be conveyed from one of the
ports of the high-pressure cylinder to the diagonally opposite end of the low-pressure
cylinder. The valves are connected with the reversing mechanism of the engine,
so that when the engine is reversed they are turned to effect the result already
indicated.
In compounding a locomotive engine on this improved plan the high-pressure
cylinder containing a single piston is connected in the usual way by means of a
piston rod and connecting rod with the crank pin on one of the driving wheels of
the locomotive. The low-pressure cylinder is placed on the opposite side of the
boiler, and is provided with ports and steam passages, and a valve for controlling
the entrance of the steam with a valve chest, which chest receives steam from a
central port formed in the high-pressure cylinder. In this case the piston of the
latter cylinder acts as a valve as in the former arrangement.
Instead of employing a central port, the cylinder may have ports and steam
passages of the usual description, and a plane slide valve, may be worked by an
eccentric so as to permit steam to escape at the proper instant from the high-pressure
cylinder to the low-pressure cylinder.
In adapting the improvements to beam engines, the high-pressure cylinder is.
provided with two pistons, which are connected with the beam by means of the
piston rod and link. This cylinder is provided with supply valves of the ordinary
kind, and the exhaust ports which are arranged in relation to the piston, similar to
those of the first-described arrangement, are placed upon opposite sides of the
cylinder, and communicate with low-pressure cylinders which are secured to opposite
sides of the cylinder. Each low-pressure cylinder contains a piston attached to a
common rod, and placed apart a distance equal to the sum of external diameter
of the high-pressure cylinder, the stroke of the engine, and the clearance of the
pistons:
The pistons are directly connected by a connecting rod with the same crank on
the main shaft with which the beam is connected. It will thus be seen that the
line force exerted by one of the cylinders is at right angles to that of the other
cylinder, so that there are no dead points to overcome.