Improvements in Compound Engines.
Year: 1885

page_text: COMPLETE SPECIFICATION.
Improvements in Compound Engines.
I, SAMUEL BUTLER, of N° 127, Bute Road, Cardiff, in the County of Glamorgan,
Engineer, do hereby declare the nature of my invention for IMPROVEMENTS IN
COMPOUND ENGINES and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement :-.
This invention has for its object to effect certain improvements in the mode by
which the compounding of Engines is accomplished and refers more especially to
that class of Engine known as single acting, that is to say Engines having a valve
arrangement which admits steam to one side of the piston only.
By my invention I connect the pistons of two single acting engines with
cylinders of different sizes by a piston rod, the smaller piston actuated by high
pressure stean, and the larger piston actuated by low pressure steam.
This arrangement of pistons is accompanied by a valve which admits steam to
the underside of the high pressure piston, and exhausts it direct to the top side of
the low pressure piston.
It will thus be seen that as one piston has an upward thrust and the other a
downward thrust, there being an alternate action of the steam first on one piston
and then on the other, a double acting compound Engine is constituted.
If it be necessary to work this description of Engine as single acting, that is to
say if a downward thrust be required on both pistons instead of an upward on one
and a downward on the other, all that is necessary is to keep live steain continually
on the top of the high pressure piston.
I now refer to the drawings-Figure I is a sectional elevation of my Engine.
A is a high pressure piston, B a low pressure piston connected to each other by a
piston rod C.
This piston rod C passes through metallic packing, formed by blocks overlapping
each other and kept up tight against the rod by springs as represented in Figure V.
Again referring to Figure I. D is a slide valve working in connection with three
ports, E being the port for the admission of high pressure steam to piston A.
F the port for the admission of the exhaust from the high pressure cylinder to the

page_text: low pressure, and being the port for the
cylinder.
mmar exnausU LIUDI
At the top of the high pressure cylinder is a port H communicating with the
box which encloses the working parts, which box also receives the exhaust on its
way to the atmosphere or condenser.
Figures II and III show respectively end and sectional views of the Engine with
reversing gear for the valve.
The action of the steam or motive fluid in the Engine is as follows:
When the crank is on its bottom centre, and the piston just about to rise, the
valve is descending and beginning to open the port E for the admission of steam
to the under side of the high pressure piston A. At the same time the valve is
also opening the port F of the low pressure cylinder into communication with
the exhaust port G.
Steam thus forces the high pressure piston upwards, and so by its connection to
the low pressure piston, and connecting rod, draws the crank up to its top centre,
by which time the valve has closed the ports E and G.
As the crank turns over its top centre the valve which is rising, opens communi-
cation between the ports E and F, thus allowing steam to flow from the high
pressure cylinder into low pressure cylinder, where acting upon the low pressure
piston, it forces it, and with it the crank, to its bottom centre.
During the revolution of the Engine the upper end of the high pressure cylinder
being in communication with the exhaust through the port H, there is no pressure
exerted in going one way or the other upon the top side of the high pressure
piston.
A piston valve may also be used for this engine equally as well as a slide valve.
Figure IV shews a sectional elevation of my improved engine, in which the upper
end of the high pressure cylinder, instead of being in communication with the
exhaust is constantly open to the full steam pressure through the port I, while
the valve D regulates the admission of steam and exhaust to both cylinders as
before.
In this way the combined engine becomes single acting, the high pressure steam
acting upon the top of high pressure piston on the downward stroke, at the same
time that the exhaust from its under side acts upon the low pressure piston, while
upon the upward stroke high pressure steam is admitted to the under side of the
high pressure piston, and the low pressure steam is exhausted from the low pressure
cylinder.
.
I prefer to use this kind of engine for high speeds singly upon one crank, or in
two or more sets arranged side by side, and acting upon separate cranks, so as to
perfectly balance all the working parts and working pressures, and so that all wear
is automatically taken up by the constant pressure on the bigh pressure piston,
thus preventing any knocking such as takes place in double acting engines.
I also prefer to use a piston valve for this kind of Engine as shown, in order to
relieve the eccentric from work; and when necessary, I make the upper part of
the valve, of rather larger diameter than the lower, so that the pressure of steam
on the difference in area, keeps the valve and gear acting downwards on the
eccentric, thus taking up all slack and "knocking."
Communication is made between the upper and lower sides of the valve in order
that the steam may act both above and below it.
Having now particularly described and ascertained the nature of my said
Invention, and in what manner the same is to be performed, I declare that what
I claim is
1. The combination of parts in an Engine, as herein described, having two
pistons of unequal dimensions attached to a single piston-rod, the smaller of
which pistons is driven by high pressure steam, and the larger by low pressure

page_text: steam exhausted from the high pressure cylinder; and having a single slide or
piston valve, so constructed as to govern the supply of steam and the exhaust of
both cylinders alternately.
2. The combination of two single acting engines with pistons of different sizes,
upon which the pressure acts in opposite directions, connected so as to form a
double-acting compound Engine, substantially as herein described.
3. The method of applying blocks of metallic packing to a piston-rod, so as to
over-lap, and of holding the same tight by external pressure afforded by springs as
herein set forth.