IMPROVEMENTS IN STEAM ENGINES
Year: 1874

page_text: PROVISIONAL SPECIFICATION left by Samuel Graham Browne at the
Office of the Commissioners of Patents, with his Petition, on the
3rd October 1874.
I, SAMUEL GRAHAM BROWNE, of Cavendish Road, Kilburn, in the
County of Middlesex, Engineer, do hereby declare the nature of the
said Invention for "IMPROVEMENTS IN STEAM ENGINES," to be as follows:-
The object of my Invention is to simplify the distribution of steam,
more particularly in direct action engines.
My improvements consist in a special arrangement of steam passages,
and in a cut off of novel construction.
I propose to use a cylinder having the ordinary main steam ports and
exhaust preferably entering the cylinder at some distance from each
end, and also two small ports leading directly to each end of the
cylinder.
The main ports may have the lead of the small or cushioning ports, so
that the opposite main exhaust may be opened, or partially opened,

page_text: before the steam can enter the small ports to cushion the main
piston.
The main and small ports may, if desirable, be actuated by the same
valve separated by suitable diaphragms.
I propose to provide the cylinder with a valve chamber or supplemental
cylinder, preferably of a cylindrical form, with corresponding valve, but I
may adopt an ordinary flat valve let into the actuating piston of the
supplemental cylinder, which piston will be of two different diameters on
each side of the said valve, the diameters of the steam-tight casing or
supplemental cylinder following those of the supplemental piston, which
is cast hollow with the ends closed, but receiving steam by a suitably
placed duct. I thus form distinct cylinders, subject to such alternate
action of steam or exhaust on the different diameters of the supplemental
piston (carrying the main valve) as may be required.
Between the valve chamber and near each end of the cylinder I
propose having a passage, each passage being in such a position that
when uncovered by the main piston on the latter nearing the end of its
stroke, the steam shall be admitted into the larger diameter of the sup-
plemental cylinder, and behind the greatest diameter of the supplemental
piston, although the passage will terminate in the smallest diameter of
supplemental cylinder, a conduit leading from thence to the largest
diameter; the result being that when the supplemental piston is forced
towards the opposite end the smaller diameter will in its traverse cover and
close the aforesaid passage, this cut off being so arranged as to make the
action reciprocal, whether working with steam expansively or otherwise.
Thus, the supplemental piston being at one end of its stroke, one passage
is open to steam and the other closed, although the main cylinder is filled
with steam.
I further propose to have two other passages, onc connecting with
each smallest diameter of supplemental cylinder, and either the small or
cushioning ports, the before mentioned steam passages, or directly with
the main cylinder, thus each being actuated by steam or exhaust, as the
case may be. I propose that these passages should enter the smallest
cylinders at a short distance from their external ends, so as to be covered
by the supplemental piston at the end of its traverse. But they may be a
placed in any position so as to preserve the equilibrium when steam is at
both ends of the smallest supplemental piston.

page_text: To preserve the equilibrium between the two chambers of smallest
diameter, I may find it desirable to have a passage in the solid of the
supplemental piston of smallest diameter, running to its end, so
placed that the piston traversing over the corresponding passage from
the main cylinder cuts off the steam, a similar arrangement being placed
at each end.
To cushion the supplemental piston, if desirable, I make a small port
near each end of the smallest diameter of supplemental piston communi-
cating with the steam therein; which ports will alternately in the come
and go of the piston come momentarily over corresponding ports in the
smallest diameter of the cylinder, leading steam directly to the extreme
end of the cylinder for the cushioning of the said piston.
Further, these ports may assist in preserving the equilibrium between
the two cylinders of smallest diameter when one of the passages
working the smallest diameter of supplemental piston is covered.
I also propose having two exhaust ports, one at each end of the traverse
of the largest diameters of supplemental piston, opening alternately to
exhaust when the piston has completed its stroke in one or other direction,
but I may find it desirable to use other means of relieving the chambers
from steam pressure for making a return stroke.
I will now briefly describe the action:-For example, the engine
having made one stroke, been cushioned, the main valve open to steam
and exhaust, and the supplemental piston held in equilibrium, the piston
traverses till it covers the main exhaust port and opens the passage
connecting with the large diameter of supplemental piston and changes
the action in it from exhaust to pressure (the opposite passage being shut
in the traverse of the supplemental piston, but steam being admitted
behind the smallest diameter of piston through the passage at the
opposite end of the cylinder connected with the smallest diameter);
steam rushing through this passage and acting on the large diameter,
and the corresponding large diameter being open to exhaust (the smaller
being on steam balance), forces the supplemental piston towards the
opposite end, the smaller diameter closing this passage at the desired
point; as soon as the valve has traversed far enough to open the exhaust
with the opposite end of the main cylinder, a passage or passages on that
side will be connected with the exhaust till the smaller piston passes
over and closes the passage connecting with smallest diameter of
.

page_text: supplemental cylinder confining any surplus exhaust steam. The small
piston port passing its corresponding passage allows steam to rush behind
the end of this piston, and being compressed cushions it. When the largest
diameter has reached the end of its traverse the exhaust is opened, and
the supplemental piston and valve is ready for the return stroke, it.
being in balance. In the meantime the main piston has been cushioned,
as when the supplemental valve is opening the exhaust it has admitted
steam to the cushioning ports, which steam is compressed and reacts till
the main port is opened. When the piston completes its traverse a similar
action takes place in the opposite direction.
I may modify the above plan and carry the main ports directly to the
ends of the main cylinder, dispense with the cushioning ports, or even
with the use of steam in the smaller supplemental cylinders, and I
propose to use any means which I may find most convenient to secure
the equilibrium of pressure between the cylinders of the smallest
diameter, while using the exposed area of the larger diameter as the
actuating force for moving the main valve, or actuate the small diameters
from the live steam contained in the hollow supplemental piston by
suitable ports and exhaust. To this, or any steam engine, I propose to
apply a cut off worked directly by steam. The cut off may be a throttle
or any desirable valve actuated by two cylinders connected by one piston,
in direct connection with the cylinder of an engine so arranged that the
main piston of the engine will uncover a port connected with one cylinder
whilst the other connection with the other cylinder is in the exhaust,
and thus force the piston rod towards the other cylinder. This rod is
connected by any desirable appliance to the cut off valve, which shuts off,
or partially shuts off, the steam, as desired, till the piston passes the port
connected with the other cylinder and establishes an equilibrium. A
spring, or any other rapid means, may be used for opening the cut off
valve so as to have the steam in readiness for the return stroke of the
main engine. The cylinders are open on one end, unless a special
exhaust to each is desirable. Moveable bosses may be placed upon the
piston rod to regulate the cut off, and I purpose adopting any suitable
means of preserving the equilibrium between both cylinders when
requisite.