IMPROVEMENTS IN EXPANSION SLIDE VALVE GEAR FOR STEAM AND OTHER MOTIVE POWER ENGINES
Year: 1869

page_text: LETTERS PATENT to William Walker, of Newton Heath, near Man-
chester, in the County of Lancaster, Mechanical Draughtsman, for
the Invention of "IMPROVEMENTS IN EXPANSION SLIDE VALVE GEAR
FOR STEAM AND OTHER MOTIVE POWER ENGINES."
Sealed the 7th September 1869, and dated the 9th March 1869.
PROVISIONAL SPECIFICATION left by the said William Walker at the
Office of the Commissioners of Patents, with his Petition, on the
9th March 1869.
I, WILLIAM WALKER, of Newton Heath, near Manchester, in the
County of Lancaster, Mechanical Draughtsman, do hereby declare the
nature of the said Invention for "IMPROVEMENTS IN EXPANSION SLIDE VALVE
GEAR FOR STEAM AND OTHER MOTIVE POWER ENGINES," to be as follows:-
These improvements relate to that class of slide valve in which a cut-
off plate slides in frictional contact with the back of the slide valve,
having openings formed through such cut-off plate corresponding with
similar openings formed through the back of such slide valve, and

page_text: consist in the method of actuating the cut-off plates of such slide valves
so as to use the steam expansively, by means of a novel adaptation to the
purpose of the well known archimedean screw, which is mounted in a
suitable bracket or pedestal, and has a square formed upon its extremity
to prevent it turning in its bearing in the bracket or pedestal, and is
jointed to the governor at the other extremity, so as to move in the
direction of its length by the action of the governor, but not to turn upon
its axis, thereby removing all strain from and not interfering with the
correct action of the governor. A nut is threaded or screws upon such
archimedean screw having arms or wings branching from it, which
come in contact with and actuate the cut off plate as hercin-after de-
scribed. When such cut-off plate is actuated on the outside of the
steam chest, a spindle is joined to it working either in a parallel line
with or at right angles to the slide valve spindle. The spindle of the
cut-off plate passes through a stuffing box in the steam chest and is
connected on the outside to a rectangular frame which embraces the
arms or wings of the nut herein-before mentioned, and has a spring
connected to cross trees at either end, sufficiently strong to stop the
progress of the cut-off plate at different parts of its traverse for the
width of its port, and after that time the slide valve comes in contact
with the ends of the cut-off plate and overcomes the elasticity of the
springs, which latter also serve to render the action of the valve gear
noiseless.
The main feature of this Invention is that it allows of a larger
number of ports through the cut-off plate and slide valve than has
hitherto been practicable, and its peculiarity is that it reverses its ports
and then proceeds with the slide valve so as to give the full pressure
of the steam in the cylinder up to almost half the stroke of the piston.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said William Walker in the Great Seal Patent Office 30
on the 9th September 1869.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, WILLIAM
WALKER, of Newton Heath, near Manchester, in the County of
Lancaster, Mechanical Draughtsman, send greeting.

page_text: WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Ninth day of March, in the year
of our Lord One thousand eight hundred and sixty-nine, in the
thirty-first year of Her reign, did, for Herself, Her heirs and suc-
cessors, give and grant unto me, the said William Walker, Her special
licence that I, the said William Walker, ny executors, administrators,
and assigns, or such others as I, the said William Walker, 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
EXPANSION SLIDE VALVE GEAR FOR STEAM AND OTHER MOTIVE POWER ENGINES,"
upon the condition (amongst others) that I, the said William Walker,
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 William Walker, 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 :-
These improvements relate to that class of slide valve in which a cut-
off plate slides in frictional contact with the back of the slide valve,
having openings formed through such cut-off plate corresponding with
similar openings formed through the back of such slide valve, and
consist in the method of actuating the cut-off plates of such slide
valves so as to use the steam expansively, by means of a novel adaptation
to the purpose of the well known archimedcan screw, which is mounted
in a suitable bracket or pedestal, and has a square formed upon its
extremity to prevent it turning in its bearing in the bracket or pedestal,
and is jointed to the governor at the other extremity, so as to move in
the direction of its length by the action of the governor but not to turn
upon its axis, thereby removing all strain from and not interfering with
the correct action of the governor. A uut is threaded or screws upon such

page_text: archimedean screw having arms or wings branching from it, which come
in contact with and actuate the cut-off plate as herein-after described.
When such cut-off plate is actuated on the outside of the steam chest,
a spindle is joined to it, working either in a parallel line with or at
right angles to the slide valve spindle. The spindle of the cut-off plate
passes through a stuffing box in the steam chest, and is connected on
the outside to a rectangular frame, which embraces the arms or wings
of the nut herein-before mentioned, and has a spring connected to cross
trees at either end, sufficiently strong to stop the progress of the cut-
off plate at different parts of its traverse for the width of its ports, and
after that time the slide valve comes in contact with the ends of the cut-
off plate, and overcomes the elasticity of the springs, which latter also
serve to render the action of the valve gear noiseless.
The main feature of this Invention is that it allows of a larger number
of ports through the cut-off plate and slide valve than has hitherto
been practicable, and its peculiarity is that it reverses its ports and then
proceeds with the slide valve, so as to give the full pressure of the
steam in the cylinder up to almost half the stroke of the piston.
In order that this my said Invention may be the more readily seen
and understood I have hereunto annexed two Sheets of Drawings, drawn
to a scale of about half size and illustrating two modifications of my
improvements.
On Sheet 1, Fig. 1 is a sectional plan of part of a cylinder of a steam
engine, having one modification of my improvements applied thereto,
shewing a section through the centre of the slide valve chest, slide
valve, and cut-off plate; Fig. 2 is a side view (partly in section) of
Fig. 1; and Fig. 3 is an end view of the bracket which supports the
wing nut and archimedean screw herein-after described.
On Sheet 2, Fig. 4 is an exterior view of a valve box or chest of a
steam engine cylinder, shewing another modification of my improve-
ments; Fig. 5 is an end sectional view, and Fig. 6 a side sectional
view of Fig. 4; Fig. 7 represents (about full size) the projections on the
back of the cut-off plate, used in Figs. 4, 5, and 6, shewing also the
wing for actuating the cut-off plate as herein-after described. Similar
letters are used to denote similar parts in all the views.
In Figs. 1, 2, and 3 A represents that part of a steam engine cylinder
which contains the ordinary steam passages B, and the exhaust port C;

page_text: D is the slide valve connected to the excentric in. the usual manner,
by means of the valve spindle E passing through the stuffing box F.
Through the back of the slide valve D a number of narrow openings G
are formed; H is a cut-off plate working in frictional contact with the
back of the slide valve D, and having corresponding openings I formed
in it to those in the slide valve, but so disposed over its surface that only
half the number of the ports G in the slide valve shall be uncovered
at one time as illustrated. This cut-off plate H at each end of its stroke
comes in contact with the projections J, J, on the back of the slide
valve, and thus from the moment of its coming in contact with such
projections the cut-off plate is compelled to travel along with the slide
valve. To the back of the cut-off plate is affixed the actuating rod K,
which passes through the stuffing box L to the outside of the steam
chest, where it is connected to one end of a rectangular frame M, the
other end of which is in the form of a guide rod supported and guided
in the fixing N. Within the rectangular frame M are mounted the
cross trees O, the spindles of which are in contact with spiral steel
springs, (or which springs may be formed of india-rubber and metallic
washers placed alternately, the same as ordinarily used for railway buffers,)
situated in the cells or cavities O¹ formed for their reception in either
end of the rectangular frame M; P is a bracket or pedestal affixed to
any convenient part of the framework of the engine, in which is
mounted the archimedean screw Q, which has a square R on its lower
extremity working in a corresponding hole formed in the lower part of
the bracket P, and is connected at its upper extremity to the lifting
rod S, which is worked up and down by being connected to the ordinary
governor. It will thus be noticed that this archimedean screw can be
raised or lowered in the direction of its length by the action of the
governor, but is prevented turning upon its axis by the square R upon
its lower extremity. Upon the archimedean screw Q is mounted a
winged nut T, which is arranged to work within the rectangular
frame M so as to come in contact with the cross trees O as herein-after

page_text: stroke of the piston. The cut-off plate H travels along with the slide
valve D until one of the cross trees O comes in contact with one of
the wings of the nut T, when the cut-off plate is thereby held stationary
whilst the slide valve travels beneath it, thus reversing its ports G and
proceeding onwards until one of the projections J, J, on the slide valve
comes in contact with the cut-off plate when such cut-off plate is again
carried along with the slide valve to the end of its stroke, the spiral or
other spring in the cell or cavity O', which is being impinged against
meanwhile yielding by compression to allow the cut-off plate to do so,
and the square R on the archimedean screw Q receiving all the strain that
may be incurred through such reversal of the cut-off plate without
allowing it to interfere in the least degree with the correct action of the
governor.
It will be noticed as a peculiarity of this Invention that it allows a
larger number of ports through the cut-off plate and back of the slide
valve than has hitherto been practicable, which feature, together with
the peculiar reversing action of the cut-off plate and subsequent travelling
on with the slide valve, allows the full boiler pressure of the steam to
be exerted in the cylinder up to within a fraction of half its stroke.
The foregoing modification is worked on the outside of the steam chest,
but it is practicable to have a wing to actuate the cut-off plate situated
inside the valve chest, which is described in the following modification
of my improvements.
In Figs. 4, 5, 6, and 7, a is the slide valve having openings 6 formed
through its back, and fitted with a cut-off plate e provided with cor-
responding openings to those marked on the slide valve; this cut off
plate has projections d, d, on its exterior, the faces of which projections
are covered with a series of steel plates which act as a cushion and thus
render the action of the cut-off plate noiseless. The motion of the cut-
off plate c is controlled by the action of the governor which is connected
by means of the connecting rod e to the archimedean screw f, which
latter is mounted in the fixing g and prevented turning upon its axis
by the collar h passing through it, and working up and down in a slot
provided for it in the fixing g. This archimedean screw is formed by
preference of spiral grooves i cut into it, and its upper extremity passes
through the boss of the bevil wheel j working in a suitable bearing on
the pillar fixed upon the valve chest lid. This bevil wheel has

page_text: threads formed in its boss to work in the spiral grooves in the archi-
medean screw, so that as the archimedean screw is lifted up and down
by the action of the governor such bevil wheel is caused to revolve,
and, by being geared into the bevil wheel 1, to turn the spindle m at the
same time. The spindle m passes through the stuffing box n, and inside
the valve chest has a wing o affixed upon its extremity to control the
travel of the cut-off plate, and thereby enable the steam to be used
expansively. In this modification when the engine is at work the slide
valve a carries the cut-off plate c along with it until the steel plates upon
the projections d, d, come in contact with the wing o (see Fig. 7,) when
the cut-off plate remains stationary and the slide valve travels beneath
it, so cutting off the steam. The point of stroke at which the cut off
takes place is regulated by the governor simply raising or lowering the
archimedcan screw fin the direction of its length, and imparting motion
to the spindle m through the bevil wheels j and 1, and thereby arranging
the angle at which the wing o shall come in contact with the pro-
jections d, d, on the cut-off plate, all strain being taken off the archi-
medean screw f by the cotter h, which cotter at the same time prevents
the action of the governor being interfered with.
It will be readily apparent that there are many ways of applying the
action of the archimedean screw and winged nut to working the cut-
off plate of expansion slide valve gear, amongst which may be mentioned
that of allowing the archimedean screw to turn upon its axis and causing
the nut to move to and fro upon it, but as these are simply modifications
of the same principle I have only considered it necessary to specify two
modifications illustrating the application of my improvements to both
the outside and inside of a steam chest.
Having now particularly described and ascertained the nature of this
my said Invention, together with the best methods with which I am
acquainted for carrying the same into practical effect, I wish it to be
understood that I do not confine myself to the precise details, relative
proportions, or dimensions of the various parts illustrated on the accom-
panying Drawings, as the same may be considerably varied without
departing from the Invention, but what I claim is,-
1st. The use and application of an archimedean screw and wings for
actuating the cut-off plate of expansion slide valve gear, substantially as
and for the purpose described.

page_text: 2nd. The arrangements and combinations of mechanism for working the
cut-off plates of expansion slide valve gear as illustrated in the accom-
panying Drawings and herein-before described.
In witness whereof, I, the said William Walker, have hereunto
set my hand and seal, this Eighth day of September, in the year
of our Lord One thousand eight hundred and sixty-nine.
Witness,
JOHN G. WILSON,
Patent Agent,.
. 1, Market Place,
Manchester.
WILLIAM (L.S.) WALKER.