IMPROVEMENTS IN COMPOUND STEAM ENGINES, AND IN COMPOUNDING HIGH PRESSURE OR OTHER ENGINES
Year: 1881

page_text: PROVISIONAL SPECIFICATION left by Edward Davies at the Office of the
Commissioners of Patents on the 24th March 1881.
EDWARD DAVIES, of Liverpool, in the County of Lancaster. "IMPROVEMENTS IN
COMPOUND STEAM ENGINES, AND IN COMPOUNDING HIGH PRESSURE OR OTHER
ENGINES."
My Invention relates,—
First. To compounding high pressure engines. To accomplish this I attach to
the rear end of a high pressure cylinder a larger cylinder or low pressure cylinder.
This cylinder has a steam chest and slide valve of corresponding travel to the one
on the high pressure cylinder, and may be driven from the same eccentric or from
another having the same throw. By this method I can alter either portable,
stationary, locomotive, or marine engines to the compound principle at a very
reasonable cost so that there shall be a saving in fuel, whilst in many cases the
alteration can be made without disturbing the high pressure cylinder.
Second. To accomplish the above, instead of the high pressure cylinder exhausting
the steam into the atmosphere, I convey the said steam into the steam chest of the
low pressure cylinder, thereby using the same steam over again or compounding.
.
Third. In constructing new compound engines, I prefer to attach or secure the
high and low pressure cylinders together with a metallic partition secured between
the two, so as to form an end for each of them, instead of the usual plan of having
two separate cylinders with a space between them and a gland in the end of each
for the piston rod to work through.
· Fourth. In some cases when necessary I shall make the high and low pressure
cylinders the same diameter the entire length. When this is done I put a tube or
internal trunk for half the length of the whole cylinder, so as to reduce the area
of that part of the cylinder for the high pressure steam. This trunk is cast on the
end of the high pressure part of the cylinder, so that when the end of the cylinder
is taken off the tube or trunk comes away with it. At a distance of half the
length of the cylinder inside I have a partition of iron, thus dividing the cylinder
into two lengths, being high and low pressure or compound. In carrying this out
I use for the high pressure end what may be called an annular piston, or two
pistons in one, but only taking up the space of one in thickness. There are two

page_text: lots of rings in this piston; the larger or outer rings press against the walls of the
cylinder, and the inner or smaller ones press against the tube or trunk with their
inner periphery. The same springs keep the two sets of rings up to their work so
as to be steam tight.
Fifth. When fitting up engines as above, I should have two piston rods to the
high pressure piston working through two glands in cover or end of cylinder
with a cross head attached to them. From said cross, head I shall connect the
cross head of low pressure piston by two rods running along the outsides of
cylinder, so that by this means the two pistons are connected and must travel
together, that is, the pistons in high and low pressure cylinders, the low pressure
piston working on to crank.
Sixth. I shall as a rule, when the high and low pressure cylinders are of different
diameters, have two piston rods to the low pressure piston. The said rods will
work through two glands at the end of the low pressure cylinder where it is
connected to the high pressure cylinder. The said two piston rods will run along
each side of the high pressure cylinder, and be connected with the cross head on the
high pressure piston rod, or by any other suitable means, so as to have the high
and low pressure pistons so connected that they will travel together.
Seventh. It will be seen from the foregoing description that all the heat possible
is retained in the cylinders, and that all cooling surfaces are as much as possible
done away with, thereby saving condensation and insuring economy in steam.
Eighth. In the case of large stationary or marine engines, I can attach a condenser
to the low pressure cylinder of any form suitable for the purpose for which it is
required.
Ninth. Another advantage of this improved method of compounding engines is
that a double compound engine or, say, two compound engines can be put to work
where at present only one is employed, as, for instance, on the boiler of a portable
engine, and also where there are two high pressure cylinders working on to two
cranks and in other places. As will be seen from the above, I can do with one crank
for one compound engine on this principle, thus doing away with a lot of expense
and a lot of friction as compared with the present system of working compound
engines.
Where two piston rods from an annular or larger cylinder pass along the sides
of the cylinder of smaller external diameter, I frequently carry up the stuffing
boxes on long sleeves or trunks from the annular or large piston to a level with
the stuffing box of the other cylinder to reduce the exposure, or otherwise cover in
or jacket as large a surface as possible of the two long piston rods. In other
respects too I do not propose to confine myself to the exact details shown, and in
rare instances I may couple both pistons to the same rod and place a stuffing box
or bearing in the dividing plate with oil hole passing through the metal plate to
the outside. This, however, except where room is scarce, is a bad plan, as the
central stuffing box is very difficult to get at to pack.