AN IMPROVEMENT IN THE SLIDE VALVES OP STEAM ENGINES
Year: 1858

page_text: LETTERS PATENT to Joseph Hall, Marble Mason, of Derby, in the County
of Derby, for the Invention of "AN IMPROVEMENT IN THE SLIDE VALVES
OP STEAM ENGINES."
Sealed the 7th December 1858, and dated the 12th June 1858.
PROVISIONAL SPECIFICATION left by the said Joseph Hall at the
Office of the Commissioners of Patents, with his Petition, on the
12th June 1858.
I, JOSEPH HALL, Marble Mason, of Derby, in the County of Derby, do
hereby declare the nature of the said Invention for "AN IMPROVEMENT IN THE
SLIDE VALVES OF STEAM ENGINES," to be as follows:-
This Invention consists of an alterative expansion valve, so constructed and
of
arranged as to afford facility of cutting off the steam at any required part
the stroke of the piston, and which being connected to the governor, so as to
vary with the alteration of speed of the engine, dispenses entirely with the
necessity for a throttle valve. The slide valve is of the ordinary construction,
with the addition of a steam port at each end, which ports are covered by
flap valves lying on the top and mounted one at each end of a lever, which
vibrates upon a central fulcrum attached to the back of the valve, and is kept
in position by means of a spring. These flap valves are each furnished with
a friction roller, which is acted on by a fixed cam placed at each end of the
throw of the slide valve. As the flap valves are raised, they are held by
retaining levers (acted upon by a spring) until the return of the slide valve
brings these levers alternately against one or other of two stop pieces attached

page_text: to slides. The valve lever is thus released, and the cam at the other end
brings the valve down & shuts off the steam. This can be done at any part
of the stroke, as the slides which carry the stops are moveable, & so con-
nected by a pinion & racks as to be capable of being moved nearer to or
further from each other. A lever attached to this pinion is connected to the
governor of the engine in such a way that as the speed of the engine varies
the stops are moved nearer to or further from each other, and thus the
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said Joseph Hall in the Great Seal Patent Office on the
11th December 1858.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOSEPH
HALL, Marble Mason, of Derby, in the County of Derby, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twelfth day of June, in the year of our Lord
One thousand eight hundred and fifty-eight, in the twenty-first year of
Her reign, did, for Herself, Her heirs and successors, give and grant unto
me, the said Joseph Hall, Her special licence that I, the said Joseph Hall,
my executors, administrators, and assigns, or such others as I, the said
Joseph Hall, 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 "AN IMPROVEMENT
IN THE SLIDE VALVES OF STEAM ENGINES," upon the condition (amongst others)
that I, the said Joseph Hall, my executors or administrators, by an instru-
ment 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 imme-
diately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Joseph Hall, do hereby declare the
nature of my said Invention, and in what manner the same is to be per-
formed, to be particularly described and ascertained in and by the following
statement in writing, and on reference to the accompanying Drawings, that
is to say:

page_text: My Invention consists of an alterative expansion valve, so constructed and
arranged as to afford facility for cutting off the steam at any required part of
the stroke of the piston, and which being connected to the governor so as to
vary with the alteration of speed of the engine dispenses entirely with the
necessity for a throttle valve. The slide valve is of the ordinary construction,
with the addition of a steam port at each end, which ports are covered by
flap valves lying on the top, and mounted on levers vibrating upon a central
fulcrum attached to the back of the valve. These flap valves are each fur-
nished with a pin or friction roller, which is acted on by a fixed cam placed
at each end of the throw of the slide valve. As the flap valves are raised by
the cams they are held by retaining levers (acted upon by a spring) until the
return of the slide valve brings these levers alternately against one or other
of two stop pins attached to slides. The. flap valves are thus alternately
raised and released, and falling by their own gravity shut off the steam.
can be done at any part of the piston's stroke, as the slides which carry the
stop pins are moveable, and so connected by a pinion and racks that as the
speed of the engine. varies the stop pins are moved nearer to or further
from each other, and thus the amount of steam allowed to enter the cylinder
is regulated. These slides move so easily that the governor acts upon them
instantly, and consequently regulates the speed of the engine very quickly
when the load is increased or decreased.
1
This
..In order more clearly to illustrate the construction and practical application
of my Invention, I have annexed hereunto, two Sheets of Drawings repre-
senting various views of the same, and have marked thereon Figures and
letters of reference corresponding with those in the following explanation
thereof.
t
On Sheet. 1 of the Drawings, Figure 1 represents a side elevation of my
improved alterative expansion, valve, the slides and stop pins being in such a
position as not to release the flap. valves until they have arrived at half the
stroke of the piston,.and consequently the steam is working expansively the
remaining, half; Figure 2 is a ground plan of the valve in the same position.
On Sheet 2, Figure 3 is, a longitudinal section of the valve, also in the
same position, and Figure 4 is a similar view of the saine when cutting off at
about quarter-stroke, and working the remaining portion expansively. A,,A,
is the cylinder facing; B, B, the valve box; C, C, the exhaust, and D, D*,
the steam passages leading to each end of the cylinder; E, is the slide valve,
the centre part of which is the same as usual, but it is furnished at each end
with an extra port F, F, which ports are closed as required by flap valves
G, G*. These valves are respectively mounted upon levers H, H, vibrating

page_text: upon a fulcrum at I, and are furnished at a, a, (see Figures 1 and 2,) with
small pins or friction rollers, acted upon alternately by the fixed cams K, K*,
one at each end of the stroke of the valve. L, L*, are retaining levers or
catches acted upon by the spring b, b, so as to hold each valve by means of
the projecting part Q, Q, when it is raised by the cams until forced to
release it by coming against one of the stop pins c, c, d, d. The stop pins
c, c, are fixed in the side of the steam box, and are at such a distance apart
as to cause the levers to release the flap valves the instant that the slide valve
has arrived at the end of its stroke: The stop pins d, d*, are fixed to slides
M, M, and are capable of being moved further from each other, so as to
release the valves sooner in order to work the steam expansively. These
slides are also furnished with two step pieces or ledges e, e, on to which the
flap valves 'fall when it is requisite to cut off beyond the half stroke of the
piston. These ledges e, e, are fixed one to the top and one to the bottom
slide, and slightly lower than the catch part of the levers L, L*. As
these levers are detached by coming against the pins, the flap valves fall on
to the ledges e, e, which keep them up until they reach the proper point for
cutting off as determined by the position of the slides.
soon as
It will be seen on referring to Figures 3 and 4, Sheet 2, that the slides
M, M, are provided at the back with racks f,f, and that a rack pinion g, g,
is in gear with both. It is advisable to have this toothed wheel as large as
possible, in order that a slight movement of the governor may move the slides
quickly. The axis of this pinion passes out of the valve chest through a
stuffing box h, h, (see Figure 2,) and on the end is keyed a crank or lever i, i,
to which a rod from the "governor" is connected. The consequence is, that
as the balls of the "governor" expand, the lever i, i, is raised, and by means
of the pinion and racks will move the slides M, M, into the position in which
they are shewn in Figure 4. The stop pins d, d*, being thus moved further
from each other, will cause the levers L, L*, to release their respective valves
before the slide valve has arrived at the end of its stroke, and thus to shut off
the steam and work expansively for the remaining part of the stroke. It will
be obvious that any increase or decrease of speed in the engine will cause the
'governor" to act upon the lever i, i, and consequently move the stop pins
d, d*, nearer to or further from each other, and thus cut off the steam later
or earlier, as required.
66
In Figure 4 the stop pin d is représented as just upon the point of causing
the lever L to release the flap valve G, and allow it to close and shut off th
steam whilst the steam passage D is only half uncovered.
off" is early, the steam will of course become attenuated in
When the ".
cut-
the cylinder and

page_text: under the flap valve, and consequently there would be a great pressure on the
pin and cam to lift the flap valve. To obviate this, I cut a groove m in the
face of the valve seat, opening from the steam box to the end ports of the
valve (see Sheet 2), so that the steam is admitted under the flap valve just
before the commencement of the lift; therefore there is nothing but the
weight of the valve on the pin and cam.
In order to prevent the noise which would be occasioned by the falling of
the flap valves on to the back of the slide valve, I propose to furnish the
latter with steam chambers or recesses k, k, the width of the valve, and to
attach a solid piece or piston 1, 1, of a corresponding size to the recess, to the
under side of the levers H, H, so that the flap valve would fall as it were on
a steam cushion, or the same end may be attained by having india-rubber or
other elastic cushions or buffers, or by other similar means.
The valve as here described is arranged for an horizontal cylinder feeding
from the centre, but it is of course equally applicable to vertical cylinders
feeding close to the top and bottom, it being only necessary to have a long
steam box and slide valve with two ports at each end, the levers and slides
being worked in a similar manner as heretofore described.
Having thus described the nature and object of my said Invention for an
"Improvement in the Slide Valves of Steam Engines," together with the
manner of carrying the same into practical effect, I would remark, in con-
clusion, that I claim as my Invention the general construction and arrange-
ment of the apparatus constituting an alterative expansion valve, as above
described, and shewn in the annexed Drawings, and more especially the
application of flap valves at the back of the slide valve to cut off the steam
suddenly, whereby the "wire-drawing" of the steam caused by closing the
ports gradually by slides, as heretofore, is avoided.
In witness whereof, I, the said Joseph Hall, have hereunto set my
hand and seal, this Seventh day of December, in the year of our
Lord One thousand eight hundred and fifty-eight.
Witness,
SAMUEL BARTON, Agent,
Derby.
JOSEPH HALL. (L.S.)