IMPROVEMENTS IN COMPOUND ENGINES
Year: 1881

page_text: LETTERS PATENT to Alexander Melville Clark, of 53, Chancery Lane, in the
County of Middlesex, Patent Agent, for an Invention of "IMPROVEMENTS
IN COMPOUND ENGINES." A communication from abroad by Gideon Blackburn
Massey, of the City, County, and State of New York, United States of
America
COMPLETE SPECIFICATION filed by the said Alexander Melville Clark at the
Office of the Commissioners of Patents on the 20th December 1881.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of
Middlesex, Patent Agent. "IMPROVEMENTS IN COMPOUND ENGINES." A com-
munication from abroad by Gideon Blackburn Massey, of the City, County, and
State of New York, United States of America.
These improvements relate to the class of engines in which low pressure cylinders
for using the exhaust steam are combined with the cylinders using steam under
high pressure.
The object of the Invention is to obviate the difficulty heretofore experienced
from back pressure and long openings or connecting pipes, which I accomplish by
direct and continuously open connections between the two cylinders and a com-
pound piston in the high pressure cylinders, by which the primary and secondary
exhausts are regulated, as hereinafter described and claimed.
In the accompanying Drawings forming part of this Specification Figure 1 is a
longitudinal section of the engine, Figure 2 is a longitudinal section of the high
pressure cylinder in a plane at right angles to Figure 1, and Figure 3 is a sectional
elevation showing the Invention as applied to a beam engine.
Similar letters of reference indicate corresponding parts in Figures 1 and 2.
A is the high pressure cylinder, B is the low pressure cylinder, shown as bolted
directly to a cored side extension a of the cylinder A, but the two cylinders may
be cast together and cored as shown. The cylinders communicate by ports b, b,
through the connection a at the ends of cylinder B, opening into cylinder A a
distance from its ends equal to about half the length of the stroke.

page_text: The ports are connected for reversing the engine, and in connection with
ports breversing valves c, c, are fitted for operation to open and close them simul-
taneously by a hand lever d. These valves may be dispensed with in a stationary
engine, or one designed to work in one direction only. At the ends of cylinder A
there are exhaust ports c, e, and steam ports e¹ communicating with the main
steam and exhaust openings f, f¹, and at the mid length of cylinder A is an
exhaust port g; h, h, h², h¹, are valves fitted in connection with ports c, and
operated by suitable connections from a rocking lever or link at i. The lever i
will be moved by eccentrics on the main shaft k. 1, 1, are pistons in cylinder A
connected by rod m; n is the slide of the piston rod connected by a rod o to one
crank of the shaft ; p is the piston of cylinder B; q is the piston rod from
slide q' that connects by rod to a second crank on shaft, the two cranks being
quartered. The space between the two pistons is slightly less than the length of
stroke, so that the middle or secondary exhaust port g is continuously between the
pistons, and at half stroke both primary exhaust ports bare covered, the piston p
of cylinder B being at the same moment at the end of its stroke. In the Drawing
the pistons are shown at half stroke moving downward. At this point steam is
cut off from the boiler.
l
The operation is as follows:-
Steam entering through the upper steam port e', piston is forced down at half
stroke, steam valve h' is closed, thereby cutting off steam from the boiler, and at
this point piston.-passing-port.b, the steam_exhausts_on_pistons p_of_cylinder B,
which is forced downward simultaneously with piston by the force of expanding
steam until piston reaches the end of its stroke, and piston q is at half stroke,
when piston commences its return stroke, while piston q continues downward.
As soon as piston returns above port b, steam from cylinder B exhausts through
ports band g to the open air or condenser. At the same instant upper exhaust
valve his opened, and the steam shut in the upper end of cylinder A is exhausted
through ports f, which communicates with exhaust port g. It will be seen that
piston returns through the first half of its return stroke against steam after
expansion almost to its maximum or condition of least pressure, so that this engine
is relieved of fully eighty per cent. of back pressure excrted in the ordinary
compound engine.
In case condensers are used a vacuum may be obtained through the last half of
the return stroke in cylinder A in addition to that through the entire stroke of
piston of cylinder B, which will more than overbalance the back pressure on
piston through the first half of its return stroke. It is to be observed that this
engine has no long openings to connect the high and low pressure cylinders or
receiver between the two, which reduces the pressure of the expanding steam
before it reaches the low pressure cylinder by increase of volume and by con-
densation, nor has it any working valves to the low pressure cylinder, the pistons
of the high pressure cylinder serving in place of valve to open and close the
ports.
In reversal the connected ports b allow exhaust to the same end of cylinder B
as before, thus maintaining the lead of a half stroke of the high pressure piston.
In the application of the compound cylinders to a beam engine, as shown in
Figure 3, the low pressure cylinder B is placed vertically, and its rod p connected
to the beam, while the high pressure cylinder A is horizontal, and the piston rod m
connects to a crank on the shaft. The cylinder A passes through cylinder B at
its midlength, the longitudinal axis being removed from the centre line to allow
passage of the piston rods, and in the sides of cylinder A are the ports 61, b¹, that
admit steam to cylinder B. In this case the low pressure cylinder being divided,
there are two pistons q, q, on the one rod, and working in the opposite ends of
the cylinders. In this form the cylinder B needs no heads in its outer ends for
its proper working, but I prefer to use heads, as shown, and connect the cylinder
ends by a pipe t that allows the enclosed air to pass back and forth as the pistons
reciprocate. The dotted ports are for reversal of the engine. For use as an air

page_text: pump or compressor the cylinder B may be fitted, as shown in Figure 3, with a
valve u in its lower end for inlet of air, and beneath the valve is a spring v for
counteracting the weight of the valve, so as to prevent the usual clatter occasioned
when the engine is slowed.
Having described the nature of the Invention, and the manner of performing
the same, I declare that what I claim as new and desire to secure by Letters
Patent is,
1st. In compound engines, the combination of two contiguous cylinders in direct
connection by ports at the end of the low pressure cylinder, the high pressure
cylinder having exhaust and steam ports at its ends, and an exhaust port at its
mid-length, there being two pistons on the rod of the high pressure cylinder, and
a piston and rod in the low pressure cylinder, substantially as shown and described
for operation as set forth.
2nd. In compound engines, the combination of cylinder A having ports 6, b, e, e',
and 9, and pistons 1, 1, and the cylinder B provided with piston p, substantially as
shown and described.
3rd. In compound engines, the pistons 1, 2, and rod m in combination with the
high pressure cylinder A, provided with end ports e, e¹, exhaust port g between
the pistons and intermediate ports b, b, opening to the second cylinder, all sub-
stantially as shown and described.
4th. In compound engines, the combination of the intersecting cylinders A, B,
communicating by ports b', pistons l, l, on rod m, pistons q, q, on rod p, and the
steam and exhaust ports e, e, g, of the high pressure cylinder, substantially as
shown in Figure 3.
5th. The combination with high pressure cylinder A of the low pressure
cylinder B connected directly therewith, the pistons q, q, rod p, and valve v,
substantially as shown and described.
6th. The combination and arrangement of the reversing valves c, c, in the ports
between the high and low pressure cylinders of a compound engine, substantially
as shown and described.
7th. In compound engines, the combination of two cylinders connected by open
ports, and a compound piston in the high pressure cylinder fitted to act as valves
for the low pressure cylinder, substantially as described.
8th. The combination of connected exhaust ports b and reversing valves c with
the cylinders A, B, substantially as shown, to allow reversal of the engine and
maintain the proper lead of the bigh pressure pistons.
In witness whereof, I, the said Alexander Melville Clark, have hereunto set
my hand and seal, this Twentieth day of December, in the year of our
Lord One thousand eight hundred and eighty one.
AT DU
A. M.
M. CLARK.
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