Improvements in Steam Engines.
Year: 1893

page_text: Date of Application, 3rd Aug., 1893
Complete Specification Left, 3rd May, 1894-Accepted, 28th July, 1894
PROVISIONAL SPECIFICATION.
Improvements in Steam Engines.
I WILLIAM HENRY NORTHCOTT of Hatcham Ironworks Pomeroy Street
London S.E. Engineer-do hereby declare the nature of this invention to be as
follows:-
My improvements relate to engines in which the connecting rods are kept in
constant thrust by a constant steam pressure in one direction superior to the varying
pressure in the other direction.
From
In a steam cylinder constantly open to the boiler pressure at one end, and to the
exhaust pressure at the other end (and which other end is generally of larger
diameter) I place a wall or diaphragm forming an internal cylinder cover.
both sides of this diaphragm I project a tube forming a central valve chest. Two
annular pistons connected by two piston rods play in this cylinder the piston rods
going through stuffing boxes in the diaphragm and one of the outer covers of the
cylinder. The outside of one piston is always pressed upon by the full pressure
steam and the outside of the other is always pressed upon by the exhaust
pressure.
A central valve admits steam between the high pressure piston and the diaphragm,
and releases it to between the diaphragm, & the low pressed piston.
The same
valve alone or aided by a narrow port uncovered by the low pressed piston releases
the steam to exhaust. When the final pressure due to expansion is much above
the back pressure I sometimes release the steam by the narrow port uncovered
by the piston only.
The two pistons as above form a compound engine but by dispensing with the
lower piston a single engine is formed, whilst by employing more than two pistons
the steam may be expanded by more than two stages.
A triple engine may also be made in the same way as the compound above
described by putting the lower face of the large piston in communication alternately
with the steam from the second expansion space and the condenser or atmosphere.
In this case I prefer to employ an external slidevalve. For packing the piston
rods of these and other engines I use metallic washers alternately one fitting the
stuffing box and loose on the rod, another loose in the box but fitting the rod and
each pair having a flexible washer or ring between them. In the engine having
a central valve may sometimes give the valve casing itself an endway motion.
Dated this 11th day of July 1893.
WILLIAM HENRY NORTHCOTT.
COMPLETE SPECIFICATION.
Improvements in Steam Engines.
I WILLIAM HENRY NORTHCOTT Hatcham Ironworks, Pomeroy Street
London S.E. Engineer do hereby declare the nature of this invention and in.what
manner the same is to be performed, to be particularly described and ascertained
in and by the following statement :-
My improvements relate to engines in which the connecting rods are kept in

page_text: constant thrust by a constant steam-pressure in one direction superior to the varying
pressure in the other direction.
In a steam cylinder constantly open to the boiler pressure at one end, and to the
exhaust pressure at the other end (which other end is generally of larger
diameter) I place a wall or diaphragın forming an internal cylinder cover.
From both sides of this diaphragm I project a tube forming a central valve chest.
Two annular pistons connected by two piston rods play in this cylinder, the piston
rods going through stuffing boxes in the diaphragm and one of the outer covers
of the cylinder. The outside of one piston is always pressed upon by the full
pressure steam and the outside of the other is always pressed upon by the exhaust
pressure.
.
A central valve admits steam between the high pressure piston and the diaphragm,
and releases it to between the diaphragm and the low pressed piston. The same
valve alone or aided by a narrow port uncovered by the low pressed piston
releases the steam to exhaust. When the final pressure due to expansion much
above the back pressure, I sometimes release the steam by the narrow port
uncovered by the piston only.
The two pistons as above form a compound engine but by dispensing with. the,
lower piston a single engine is formed, whilst by employing more than two pistons
the steam may be expanded by more than two stages.
For packing the piston rods of these and other engines I use metallio washers
alternately one fitting the stuffing box and loose on the rod, another loose in the
box but fitting the rod and each pair having a flexible washer or ring between,
them. In the engine having a central valve I may sometimes give the valve casing.
itself an endway motion.
A Fig. 1 is a steam cylinder constantly open to the boiler pressure at the end
near the steam pipe B and to the exhaust pressure at the end near the exhaust
outlet C. The lower part of the cylinder is of larger diameter than the upper
part and the two parts are separated by a partition D. From both sides of this
partition projects a tube E serving as a valve chest. This tube is best in the
middle of the cylinder as shown but it may be excentric to the cylinder if preferred.
Two annular pistons F and G play in the cylinder A, and these pistons are
connected by two piston rods H and I passing through stuffing boxes as shown.
The upper side of the piston F is always. pressed upon by full pressure steam, and
the lower side of the piston G is always pressed upon by the exhaust pressure. A
central valve J admits steam between the piston F and the partition D then
releases it to between D and G and afterwards releases it to the condenser or
atmosphere. K L and M are steam ports cut in the central valve chest and N is
a supplementary port for releasing the steam to the condenser.
At Fig. 2 I show a modified form of this engine in which the two pistons are
coupled by a trunk and at Fig. 31 show a simple engine of the same type. The
central valve chest instead of projecting from D as shown in Fig. 1
from either or both covers.
may project
Also instead of the valve chest being stationary as
shown it may be made to reciprocate whilst the valve is stationary, or both the
valve chest and valve may be made to move.
At Fig. 4 I show a form of packing for the glands of these and other engines
made as described.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is
1. The combination of two annular pistons one always carrying the full pressure
and the other the exhaust pressure with the central valve and valve chest, the whole
forming a compound engine substantially as described.
2. The combination of one annular piston arranged to have the boiler pressure
I

page_text: always on one side of it, with a central valve and valve chest substantially as
described.
3. The combination of parts forming a stuffing box packing substantially as
decombed
W. H. NORTHCOTT.