IMPROVEMENTS IN SLIDE VALVES FOR STEAM ENGINES
Year: 1872

page_text: LETTERS PATENT to Francis Jackson, of Whinlatter, near Keswick,
in the County of Cumberland, Engineer, for the Invention of
"IMPROVEMENTS IN SLIDE VALVES FOR STEAM ENGINES.”
PROVISIONAL SPECIFICATION left by the said Francis Jackson at the
Office of the Commissioners of Patents, with his Petition, on the
30th July 1872.
I; FRANCIS JACKSON, of Whinlatter, near Keswick, in the County of
5 Cumberland, Engineer, do hereby declare the nature of the said In-
vention for "IMPROVEMENTS IN SLIDE VALVES FOR STEAM ENGINES," to be as
follows:-
I place within the valve chest a balancing plate which relieves the
slide valve of any unnecessary pressure; this balancing plate is stationary
O and supported or relieved by means of circular or rectangular wedges or
springs.
The slide valve itself may be of that shape which is now commonly
used in steam engines.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Francis Jackson in the Great Seal Patent Office
on the 30th January 1873.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, FRANCIS
JACKSON, of Whineatter, in the County of Cumberland, Engineer, send
greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Thirtieth day of July, in the year of
our Lord One thousand eight hundred and seventy-two, in the thirty-
sixth year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said Francis Jackson, Her special licence that I,
the said Francis Jackson, my executors, administrators, and assigns, or
such others as I, the said Francis Jackson, my executors, administrators,
and assigns, should at any time agree with, and no others, from time to
time and at all times thereafter during the term therein expressed,
should and lawfully might make, use, exercise, and vend, within the
United Kingdom of Great Britain and Ireland, the Channel Islands,
and Isle of Man, an Invention for "IMPROVEMENTS IN SLIDE VALVES,"
upon the condition (amongst others) that I, the said Francis Jackson,
my executors or administrators, by an instrument in writing under my,
or their, or one of their hands and seals, should particularly describe
and ascertain the nature of the said Invention, and in what manner the
same was to be performed, and cause the same to be filed in the Great
Seal Patent Office within six calendar months next and immediately after
the date of the said Letters Patent.
NOW KNOW YE, that I, the said Francis Jackson, do hereby declare
the nature of my said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the
following statement :—
My improvement consists in arranging the slide valves for steam
engines, that they may be in a state of equilibrium. At present the
pressure which is exerted on the face of the valve forms of itself
a not inconsiderable portion of the load of the engine. This is especially
so in the case of high-pressure engines where the pressure of the steam
may be as much as 120 lbs. to the square inch, for it is manifest that
if the valve face be only 20 square inches, the dead load on the engine

page_text: arising from the slide valve alone must be 2400 lbs.
Besides this load
to be overcome the enormous pressure on the slide valve works very
detrimentally on the engine generally, inasmuch as it causes a very
large amount of unnecessary wear and tear of the working parts, such
as the cottreels, pins, and of the valve itself.
By my improvements I relieve the valve from all pressure, except
just sufficient to keep it down to the cylinder face, as has been proved
in numbers of cases where the valve has been in work for upwards of a
year, and in some of these cases although the engine made as many
as 240 strokes per minute, the valves have worked so satisfactorily that
there has been no need to examine it, or to repair any of the said pins,
cottreels, or other working gear belonging to it, and the saving in time
and material thus effected is considerable.
I will now describe the improvements and modification in my equi-
librium slide valves. I place within the valve. chest a balancing plate
to which is attached, as herein-after described, a piston which works
air-tight; both the piston and the balancing plate may be made in one
piece, this balancing plate is stationary and lies on the valve facc.
The valve in most cases need not be replaced in effecting alterations
from the old to the new principle, the only alteration required being
a new valve lid, and the insertion of the balancing plate, and other minor
defects.
And in order the more fully and plainly to set forth the nature of
this my said Invention, I have appended hereto a number of Drawings
which I shall now proceed to explain in detail.
Figure 1 shews a short cylinder face and its ports, while V shows a
slide valve of the usual shape; F is the steam chest in which valve V
works; Z is the exhaust, and P shows balancing plate, the steam chest
lid is marked C, in this there are recesses "E cast and turned; in these
there is supposed to be no steam space, E, E, in centre has no steam in
it, so also at E at each end. The full pressure of steam however acts
underneath plate P, and this plate P' being pressed from beneath relieves
B from all pressure, the spaces E are kept tight by means of ring X.
S is a spring through which a stud Y or screw comes, which also
passes through cover C. This stud pressing against the spring and
plate P at the same time, prevents valve V from lifting off the cylinder

page_text: face in case of a sudden reversion of steam. T is a recess in plate P,
and serves to keep the pressure equal when the valve and its ports are
open. R is a stud placed in the back of valve V, to this stud the valve
spindle W is connected to move valve V in space the central space E, E.
W shews valve spindle, and X, in these cases, shews the rings to keep
steam from passing into recesses. In all these cases there is a tube or
hole bored from centre recess to carry away into the exhaust any little
steam which may escape.
In Figure 2, as in Figure 1, O shows cylinder face and its ports, V
the slide valve, Z the exhaust, F the steam chest, and P the balancing
plate upon the valve B, as before; space E¹ is supposed to have no
steam in it; but in this case there is a partition plate U dividing space
E¹ and E² from each other; F2, the spaces between E¹ and E³ are
so arranged that the steam can be turned by a cock or tap G into F
to cause an upward pressure from the valve V; the ring X prevents the
steam from passing from one recess to another, and on plate P, C, there
is placed a bush where valve spindle W comes through, and is coupled
at the end next to valve by a little crank or lever, M being the slot in
valve B for lever in end to fit in, so that when valve spindle .W revolves
by means of excentric from engine shaft valve, and will move backwards
and forwards as in the ordinary way, this valve spindle can be worked
by either wheel or excentric.
Figure. 3 indicates an adaption of my equilibrium valve for use in a
locomotive, and shews how the valves would be placed between the
locomotive cylinders, O shewing cylinder face and ports, V the valves, Z
the exhaust, F the steam space, and P the balancing plate. The space
E in the centre of the plates is supposed to have no steam on either
side. E at each end is recessed, turned, and bored out, as in Figure 1,
and has no steam in the recesses for the steam, acts on both sides of this
in F, and presses them both together, thus taking the pressure off
valves V.
Figure 4 shews another method of placing my equilibrium slide
valves between locomotive cylinders'; O, shews cylinder face and ports;
V, the valves; Z, the exhaust, and F the steam space, as in the other
Figures; but by this plan there is only one recess in the centre. And
according as the space P, O, is made larger or smaller in diameter so
will the pressure be removed or laid on the valves. In this case there

page_text: is supposed to be in space E no steam, but exhaust pressure only. S
shows a spring in space E. merely to keep plates P against valves B
when there is no steam on. These plates can be arranged so that the
ordinary common valves can be balanced.
Figure 5 shows a very useful form of the valve for stationary engines.
Here, as in other Figures, O shows cylinder face ports; V, the
valve; Z, the exhaust, and F, the steam chest hire; P shows the
balancing plate which has a neck in its centre, while the end forms a
piston C. Here the steam chest cover is recessed for receiving the
piston P, and the upward pressure on piston P, O, counteracts the
pressure on plate P, C, and puts it in equilibrium. X is a ring to
keep steam from passing into recess Ę in the steam chest cover. There
are supports at G near the end of plate P, C, to prevent plate C
from working endways. Y, shews studs screwed through cover C, O,
against the piston to keep valve against face in case of a sudden
reversion of steam. A small hole is bored through the centre of neck
of P,O, to take away waste steam into exhaust from recess E. In this,
as in the other cases, the balancing plate is stationary, and the common
slide valve may be used with it, the only change necessary being a new
valve cover and a balancing plate.
Figure 6 shows a modification of the balancing plate, described under
Figure 5. The letters refer to the same parts as the other Figures.
Here the upper end of balancing plate, as in the last Figure, forms a
piston; but in this case the space E, Z, has no steam in it but exhaust
pressure. This is effected by means of ring X, which prevents any
steam passing from space F into E, Z. The projections at G, and the
set screws Y, serve the same purposes here as in the form described
under Figure 5.
Figure 7 illustrates another modification of the same valve. Here
the letters indicate the same parts as before. P, C, shews balancing
plate which has a neck or stud P passing through a hole or slot in
steam chest cover C; at the other end of the stud is an additional
plate P, O, with a ring X fit inside and bearing upon the cover C.
The pressure of the steam acting under the plate P, O, counteracts the
pressure on P, C, and thus causes valve V to be in equilibrio. The slot
in the steam chest cover O can be left long enough to allow plate P, C,
and P, O, to travel with valve V as far as may be thought necessary,

page_text: while the hole can be made small enough to resist it from moving
at all. On this said plate P, O, there may be an extra lid or cover C, O,
screwed down on steam chest cover C. There is a hole through centre
of neck P to take escaped' steam out space E into the exhaust. In
this, as in other cases, the ordinary common slide valves can be used.
Fig. 8 is a further modification of the above. I employ a balancing
plate B but without any springs attached to it; in lieu thereof I employ
a wedge W to support the balancing; and the wedge, with the end of
the balancing plate which touches it, are so placed that the plate is
supported in its proper position. If considered necessary small levers
may be used to support this wedge in position, the principle of action
of the balancing plate is the same in this as in the other cases above
described.
I have now particularly described the nature of my Invention, and
the mode of carrying into effect, and claim as my Invention the use,
application, and construction of slide valve for steam engines, formed
substantially as heretofore described and illustrated.
In witness whereof, I, the said Francis Jackson; have hereunto set
my hand and seal, this Twenty-ninth day of January, in the year
of our Lord One thousand eight hundred and seventy-three.
FRANCIS JACKSON. (L.S.)