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
Sealed the 28th January 1873, and dated the 30th July 1872.
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
Cumberland, Engineer, do hereby declare the nature of the said Inven-
tion for "IMPROVEMENTS IN SLIDE VALVES FOR STEAM ENGINES," to be as
follows:-
I place within the valve chest a balancing plate which is stationary,
and which relieves the slide valve itself of any undue pressure. This
balancing plate may or may not have attached to it a piston, and there
may be used in those cases where a piston is adopted one or more levers
connecting the piston with the balancing' plate.

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 Whinlatter, near Keswick, 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 FOR STEAM ENGINES," 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 In-
vention, 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 improvements consist in making slide valves for steam engines so
that they shall be in a state of equilibrium. At present the amount of
pressure which there is on the face of the valve forms of itself in most
cases and especially in the valves used in high-pressure engines a
considerable portion of the load of the engine and, as a consequence, the
effective working power of the engine is diminished. By my arrange-

page_text: ment however this useless and dead load on the engine is removed, and
its effective horse power is proportionately increased, for I cause the
valve to be equally balanced on all sides and only allowing sufficient
pressure to keep the valve in its proper position. For this purpose I
place within the valve chest a balancing plate which relieves the valve
of any pressure, and this balancing of this plate is effected by attaching
thereto a piston working air-tight by means of suitable metalic packing
or by attaching to it a wedge of a suitable shape, as hereafter
described.
The piston is attached to the balancing plate by means of levers, and
by adjusting the area of the piston and the position of the fulcrums of
the levers to the area of the valve face and pressure of steam this plate
is made to balance, and thus the pressure of steam is removed from the
slide valve which is made to move in contact with this plate. As a
modification of this I make the piston in the form of a wedge 3. This
wedge may or may not have levers attached to it, but in either case it
supports the balancing plate and relieves the valve of any unnecessary
pressure; moreover, the wedge and the cavity in which it is placed arc
so fashioned as will be seen on reference to the Drawing, Fig. 3, that in
case the valve face becomes worn, and the valve consequently becomes
thinner, the balancing plate will follow and will still remain in contact
with the valve, because the wedge will move upwards into the cavity,
thus permitting the balancing plate to descend. The wedge may be
supported by brackets or projections from the ends of the steam chest.
Steam has free access to the space above the balancing plate. In all the
above cases the balancing plate is stationary.
In Figures 1 and 2 steam is not permitted to enter the cavity above
the face of the piston, and in order the more particularly to describe my
improvements I have appended Drawing of the same.
In Fig. 10 shews cylinder face and ports, while V shews the slide
valve, Z the exhaust, and F the steam chest, the balancing plate being
indicated by P C; the piston is shewn at P O; and G shews a small
pipe, one end of which comes into space C while the other end enters
the exhaust and carries thereto any waste water for steam that may
escape from space F. The two levers which connect the piston with the
balancing plate as shewn at L. These are fastened to the centre of the
piston with a pin N which is also attached to the plate P, C. The

page_text: weight on this plate can be adjusted by making the piston larger or smaller
or by altering the positions of the fulcrums. Z shows a stud or screw
which is screwed to touch lever L to prevent the balance plate being
lifted from face of the valve in case of the steam being suddenly
reversed.
Figure 2 shews a different arrangement of the piston and of the lever,
the letters marking the same parts as in Figure 1, no further description
is needed.
Another modification of this is possible and may be necessary
in cases where the valve space is very limited, and that modification
consists in placing the piston at the end or the side of the valve chest
instead of at the top.
As a further modification of the same arrangement, and one which
requires no levers, the following arrangement is adopted :-The slide
valve is made hollow, and inside it is placed a hollow disc into which
steam is admitted, but the following description of Figure 3 will best
explain it :-V is slide valve; I mean O to be a hollow disc fixed on
disc O keeping both tight together; R is a pipe with a cock on, so as
the pressure on slide valve, and can be regulated by increasing or
diminishing the quantity of steam admitted into the disc O. The pipe
that is fastened to tube in disc should come from the boiler so that there
will be a greater pressure of steam in the disc than in the steam chest S.
The pressure in S is not the same as in boiler when the engine is running
or going.
Figure 4 shows modification of valve explained in Figure 3, and the
main difference between them consists in another mode of fastening
plate O; P is a slide valve made hollow; a hollow plate O is put inside a
chest. When the valve is down on the cylinder face the hollow plate O
is lifted up so as to touch plate Co that is made fast with the slide
valve; C slides with slide valve, in fact it is made fast at P, P. The
plate O is screwed fast to steam chest with bolts or screws, so that when
the valve slides C° rubs upon O. D is a pipe with a cock on it so as to
allow steam from boiler to go in behind hollow plate O and Co. S is
steam chest; X is the exhaust; this valve is similar to the last except
that the plate O is fixed in a different manner.
I have now particularly described the nature of my Invention and the
mode of carrying it into effect, and claim as my Invention, the

page_text: construction, use, and application or equilibrium slide valves, formed
substantially as herein-before described and illustrated by Figs. 1, 2, 3,
and 4 of the Drawings.
In witness. whereof, I, the said Francis Jackson, have hereunto set
my hand and seal, this Thirtieth day of January, in the year of
our Lord One thousand eight hundred and seventy-three.
"
FRANCIS JACKSON. (L.s.)