AN IMPROVED APPARATUS OR MACHINERY FOR REGULATING THE ADMISSION OF STEAM TO THE CYLINDERS OF STEAM ENGINES
Year: 1850

page_text: TO ALL TO WHOM THESE PRESENTS SHALL COME, I, CHARLES
ATHERTON, of Devonport, Engineer, Member of the Institution of Civil
Engineers of London, send greeting.
WHEREAS Her present most Excellent Majesty Queen Victoria, by Her
Royal Letters Patent under the Great Seal of Great Britain, bearing date at
Westminster, the Seventh day of February, in the thirteenth year of Her reign,
did, for Herself, Her heirs and successors, give and grant unto me, the said
Charles Atherton, Her especial license, full power, sole privilege and authority,
that I, the said Charles Atherton, my exors, admors, and assigns, and such
other as I, the said Charles Atherton, my exors, adññiors, or assigns, should at
any time agree with, and no others, from time to time during the term of years
therein mentioned, should and lawfully might make, use, exercise, and vend,
within England, Wales, and the Town of Berwick-upon-Tweed, my Invention
of "AN IMPROVED APPARATUS OR MACHINERY FOR REGULATING THE ADMISSION OF
STEAM TO THE CYLINDERS OF STEAM ENGINES;" in which said Letters Patent is
contained a proviso, obliging me, the said Charles Atherton, by an instrument
in writing under my hand and seal, particularly to describe and ascertain the
nature of my said Invention, and in what manner the same is to be performed,
and cause the same to be enrolled in Her Majesty's High Court of Chancery
within six calendar months next and immediately after the date of the said in
part recited Letters Patent, as in and by the same, reference being thereunto
had, will more fully and at large appear.

page_text: NOW KNOW YE, that in compliance with the said proviso, 1, the said
Charles Atherton, do hereby declare that the nature of my said Invention, and
the manner in which the same is to be performed, are particularly described
and ascertained in and by the following description thereof, reference being
had to the Drawings hereunto annexed, and to the letters and figures marked
thereon, that is to say:-
of
My said Invention consists, in the first place, in the peculiar mode of con-
structing an eccentric wheel or crank motion, to be applied for the purpose
driving the expansion slide of a steam engine, the said eccentric wheel or
crank motion, as the case may be, (the one being a mere modification of the
other to suit the circumstances of its application,) being so constructed as to
admit of its extent of throw being varied, and at the same time its position on
the crank shaft of the engine (or detached shaft, if so fitted) so altered and
adjusted at discretion; and whilst the engine is either still or in motion, as to
operate on the expansion slide in such manner that the admission of steam
may cease at any point of the engine's stroke exceeding a certain fixed
minimum portion of the stroke, during which portion the steam will have
admission through the expansion slide.
My said Invention consists, secondly, in constructing the expansion slide
with a series of cylindrical rings or pipes connected together and formed in
one piece of suitable material or casting, or composed of several pieces and so
put together and connected as to form a cylindrical surface, with one, two, or
more annular apertures, through which the steam may pass or be obstructed
from passing, according as the position of the apertures through the slide box
may be opposite to the corresponding apertures through the expansion slide, or
be covered by the face or solid part of the slide.
The object of thus giving the expansion slide a cylindrical shape, and con-
structing it with one, two, or more annular apertures, is, that the moving of it
may not be affected by the pressure of the steam so much as is the case with
flat slides, and also to lessen the necessary travel of the expansion slide, and
reduce the necessary dimensions of the box or casing which contains it, as
compared with the travel of the slide and the size of slide box which would
be required for a flat-faced single aperture slide with an equal area of
steam way.
The improved apparatus or machinery above referred to constitute an
improved construction of expansion apparatus, based on the same principle of
operation as the expansion gear or apparatus referred to in a Patent which
was granted to me for Scotland, for an improvement or improvements upon

page_text: the steam engine, bearing date the Fourteenth day of November, One thousand
eight hundred and thirty-four.
I will now illustrate the working operation, and describe the construction of
my improved eccentric wheel or crank motion, which constitutes the first part
of my Invention. :
Figure 1 represents a direct-action steam engine, in which M represents a
common steam slide; N, the piston; N, n, the centre line of the piston rod;
n, A, the centre line of the connecting rod; A being the centre of the crank
pin; C, the centre or axis of rotation of the crank shaft; A, B, D, the circle
described by the centre of the crank pin; F, F, the flat faces of an expansion
slide, arranged for being driven by an eccentric wheel attached to the crank
shaft, as originally invented by me, and illustrated by the Drawings of my said
former Patent, dated Fourteenth November, One thousand eight hundred and
thirty-four; E, an aperture through the expansion slide, or between the plates
F, F; which aperture we will suppose to be, as usual, a rectangular oblong
figure, of which E represents the distance between the plates F, F. F¹, F,
represent the face on which the expansion slide works; E¹, an aperture
through the slide case, of corresponding dimensions with the aperture E, and
through which the steam must pass to get access to the steam slide M. The
apertures E and E¹ are not necessarily of corresponding dimensions, but for
facility of description we assume them to be so.
Now, supposing the piston to be at N, the extremity of its stroke, or in any
other position at which it is intended that the steam shall be just about to be
admitted, the expansion slide must then be in such position that the apertures
E and E shall be on the verge of each other, as shewn on Figure 1; if, now,
the piston be put in motion, causing the crank to move in the direction shewn
by the arrow >, and the expansion slide F, F, be driven by an eccentric,
the aperture E will be made to commence its motion across the aperture E',
and steam will be admitted to the steam slide M; but when either of the
plates F, F, are opposite the aperture E³, the steam passage will be closed, and
the steam will be obstructed or cut off. The expansion slide starting from the
position shewn in the Drawing must travel over a space equal to the sum of
the width of the two apertures, that is, 2 E, (E and E' being equal,) before
the aperture E will have got completely across the aperture E', during which
time steam will be admitted to the slide; and if the motion or travel of the
expansion slide be continued, then the aperture E' will be covered by one or
other of the plates F, F, and consequently the steam will be cut off.
The working of an expansion slide by the action of an eccentric wheel is not
new; it was one of the subjects of my said Scotch Patent, in the year One

page_text: thousand eight hundred and thirty-four; but my "improved apparatus or
machinery" provides now for varying at pleasure the eccentricity or throw of
the eccentric, and at the same time for altering the position of its centre with
reference to the position of the crank, in such manner that it shall communicate
to the expansion slide the required motion, whereby the steam may get admis-
sion at the proper period, and be cut off at any portion of the engine's stroke
exceeding a certain fixed minimum portion of the stroke.
On Figure 1 the point C represents the axis of rotation of the crank shaft,
on which shaft the eccentric wheel is supposed to be placed. Let h, h, g, and
h, i, represent the apparatus by which the eccentric rod is connected with the
spindle or rod of the expansion slide; let this apparatus h, h, g, and h, i, bo
suitably adjusted, and in its proper position with reference to the indicated
position of the expansion slide and other parts of the engine; the levers h, g,
and h, i, being of equal length, whereby the travel of the expansion slide F, E, F,
will be equal to the throw of the eccentric wheel, which drives it from the
point g; draw g, C, and project the line to X, and from the point C on this line
g, X, take C, a, and C, 6, each equal to half the sum of the apertures E and E',
which apertures being here supposed equal to each other, we shall have C, a,
and C, b, each equal to the aperture E. Now, through the points a, C, and b,
respectively, draw the lines a,a, a', y, C, y', and 2, 6, 21, each of them perpendicular
to the plane which passes through g, X, and the axis of rotation of the crank
shaft C: the lines a, a, x¹, and z, b, z', will then be perpendicular to g, X, and
parallel to each other, and at a distance apart equal to twice the aperture of
the steam passage E. If now an eccentric wheel (or crank motion, as the case
may be,) be fitted upon the crank shaft, so that the centre of the eccentric
wheel may be at some point p on the line a, a, and the wheel be connected
with the slide F, E, F, by means of the eccentric rod p, g, and at the same
time the piston and other parts of the engine be in the position at which it is
intended that steam be admitted (as shewn by Figure 1), and the engine be
now put in forward motion, causing the crank to move in the direction shewn
by the arrow >, the centre of the eccentric wheel (p) will describe a circle
of which the radius will be C, p: let this circle cut the lines 2, 2, and x, x², at
the points s, s', p', p; it is apparent that as the centre of the eccentric wheel
is passing between the lines x, x¹, and z, z', the aperture E will be passing
over the aperture E', and the steam will be admitted to the steam slide M; but
when the centre of the eccentric wheel is describing the portions of its circular
course not embraced between the lines a, a, a¹, and z, b, z', the aperture E' will
be covered by one or other of the plates F, F, and the steam will be cut off
It is also evident that the portion of the stroke during which the steam will be

page_text: admitted will be that portion which the piston describes whilst the centre of
the eccentric wheel moves from p to s, describing the arc p, C, s, and that the
portion of the stroke during which the steam will be cut off will be that portion
which the piston describes whilst the centre of the eccentric wheel moves from
s to s¹, describing the arc s, C, s¹; and again, for the return stroke the steam
will be admitted whilst the centre of the eccentric wheel moves from s¹ to p¹,
describing the arc s¹, C, p', and cut off whilst it moves from p¹ to p, describing
the arc p¹, C, p.
If it be required that the steam be admitted during the whole stroke of the
engine, the position of the centre of the eccentric wheel must be such that it
may not travel beyond the limits of the lines x, a, a, and 2, b, 2¹, that is, the
centre of the eccentric wheel may coincide with the point a; but if it be required
that the steam be cut off in order that the engine may act by the expansive
force of the steam, then the greater the radius C, p, shall be made in proportion
to the line C, a, the more will the ares s, C, s¹, and p¹, C, p, exceed the arcs
p, C, s, and s¹, C, p¹, and consequently the greater will be the portion of the
stroke from which the steam will be cut off, as compared with the portion to
which the steam will be admitted.
In order now to determine the exact position which the centre of the eccen-
tric must be made to assume on the line a, x, so that the steam may be admitted
only during a given portion of the stroke, say, whilst the piston moves from
N to N¹, let n, A, and n¹, A¹, be the positions of the connecting rod, corre-
sponding respectively with the positions of the piston denoted by N and N¹:
A, C, A', will then be the angle of revolution described by the crank and crank
shaft, whilst the piston moves from N to N¹ simultaneously with the motion of
the crank through the arc A, C, A', and the centre of the eccentric will neces-
sarily describe an equal are of revolution. The object, therefore, now is to find
the position of the point p, the centre of the eccentric wheel on the line α, x, such
that the angle p, C, s, shall be equal to the angle A, C, A', which is obviously
done by drawing the line C, r, in such direction that the angle y, C, r, may
be equal to half the angle A, C, A. The point p, at which the line C, r, cuts
the line a, a, will be the position required, for the lines a, x, and b, z, being
parallel to and equally distant from C, y, a circle drawn with the radius C, p,
will cut the line b,, at such point (8) that the angle y, C, s, will equal the angle
y, C, p, and therefore the whole angle p, C, s, will equal the angle A, C, A¹;
consequently, whilst the piston moves from N to N', the centre p of the
eccentric wheel will move through p, s, causing the aperture E to pass over
the aperture E', whereby steam will be admitted to the steam slide M. The
forward action of the engine in the direction shewn by the arrow > has

page_text: thus been illustrated, and in cases of engines being reversed it is not usual to
work expansively, but in such cases the expansion apparatus is thrown out of
operation, and made to assumo such position that the steam aperture is con-
tinuously open, which is proposed to be done as usual with the expansion
apparatus herein referred to. But I now proceed to show what properties will
be required in order that the construction of expansion apparatus now being
described may admit of the reverse motion of the engine being worked
expansively.
If the crank C, A, instead of moving continuously in the direction shown by the
arrow >, be required to move in the opposite direction, whereby the
direction of the motion of the eccentric wheel (if fixed on the crank shaft as usual)
would also be reversed, then the position of the centre of the eccentric wheel
would require to be shifted on the line x, x', from the point (p) to the point p¹,
the distance a, p', being equal to the distance a, p, but on the other side of the
line C, g. And if the expansion gear were originally set so as to take on the
steam at the turn of the stroke, denoted by the point A, nothing more would
be required to be done; but if it were originally set to take on the steam before
the piston arrived at the end of its stroke, say, when the crank pin was at the
point Q, then take the distance A, Q, equal to the distance A,Q: Q' will be
the point at which the steam will require to be admitted when the motion of
the engine is reversed. In this case, in addition to the process of shifting the
centre of the eccentric wheel from p to p¹, the eccentric would require to be so
connected with the shaft as to be loose, excepting when driven by a stop, which
should not impel the eccentric until the crank after being reversed shall have
arrived at the point Q'; such stops being usually applied to the eccentric wheel
which drives the steam slide, their application need not be further described.
It therefore appears that if an eccentric wheel or crank motion for driving
the expansion slide be so constructed that the centre of the eccentric wheel (or
the centre of the crank pin, as the case may be,) is capable of being moved
along the line a, a, a, so as to be adjusted to any required point on that line,
the position of the line a, a, a, being determined, as before described, by the
distance C, a, being made equal to half the sum of the apertures E and E¹, (or
some measure thereof, either greater or less, as may be determined by the pro-
portion in which, through the agency of the levers h, g, and h, i, or other
mechanical arrangement, the total throw of the eccentric wheel or crank motion
may be greater or less than the required total travel of the expansion slide,)
such an eccentric wheel or crank, as the case may be, will have the property
embraced by the present Patent.
Eccentric wheels and crank motions, having the property above described,

page_text: may be practically constructed in a great variety of ways, and I proceed to
shew the following methods.
Figure 2 represents an eccentric wheel K, K, K; connected with a crank
shaft, of which the axis of rotation is C. Let x, a, a, be the line determined, as
before described with reference to Figure 1, along which it is required that the
centre of the eccentric wheel be made to move; on the line a, a, a, take a, p,
and a, p', as the extreme distance over which the centre of the eccentric is
required to travel; from the point (a) as a centre, draw the skeleton eccentric
wheel K, K, K, embracing the.shaft, and having its own central part L, L, L,L,
void and clear of the shaft to such extent as to admit the centre of the eccen-
tric wheel being moved to any point. on the line p, a, p', and in order thus to
shift the eccentric wheel, let it be provided. with a screw 0, 0, which we will
call the leading screw, which leading screw is fixed at each end to the skeleton
eccentric wheel K, K, but passes.freely through. the shaft, the. hole through
the shaft being cylindrical to fit the screw, and being in such position that the
centre line or axis of the screw O shall be parallel to the line p, a, p¹, and the
leading screw O being furnished with two nuts R, R, one on each side of
the shaft and properly seated: it is apparent that the screw O may be operated
upon by means of the nuts R, R, so that the centre of the eccentric wheel may
be made to traverse the line a, p, or a,p', and the eccentric wheel may be
screwed tight or fixed upon the shaft whenever its centre may have arrived at
the required point on the line p, a, p¹; but by this arrangement, as shewn by
Figure 2, the motion of the engine must be stopped whenever it may be
required to alter the adjustment of the eccentric wheel. If the shaft be square,
and the crank so placed that the opposite sides of the shaft may be parallel
to p, a,p,,the sides of the void space L, L, L, L, may also be made parallel;
and be seated so as to slide. upon the shaft.
Figure 3 shows an arrangement which may be preferred as obviating the
piercing of the shaft, which was necessary by the arrangement on Figure 2.
The skeleton eccentric wheel K, K, K, Figure 8, is supplied with two leading
screws 0, 0, which are fixed to the rim of the eccentric wheel in such position
that they are parallel to each other, and also parallel to the line p, a, p', and at
such distance apart that they pass one on each side of the shaft through rings
or car pieces P, P, which project direct from the shaft, and to which ear pieces.
the eccentric wheel may be fixed by means of the nuts R, R, so that the centre
of the eccentric wheel may be fixed at any required point on the line p, a, p';:
the piercing of the shaft is thus obviated: and, further, if the pieces P, P,
instead of proceeding direct from the shaft, be made to project from a ring or
saddle piece M, M, concentric with the shaft and running loose thereon, with

page_text: provision by means of a clutch for being retained in any position on the shaft,
or for being thrown out of gear, by this arrangement the motion of the
eccentric wheel may cease and admit of the adjustment being altered without
stopping the engine, provided it be thrown out of gear when the apertures
(E and E, Figure 1,) are opposite each other, or other arrangements be made
to produce that effect.
Figure 4, and its section Figure 5, shew an arrangement for altering the
adjustment of the eccentric wheel without stopping the action of the engines or
of the expansion slide. In this case the leading screw O is fixed at each end to
the rim of the eccentric wheel, and passes through the shaft, as in Figure 2,
but in such position that the axis or centre line of the screw O is not only
parallel to p, a, p', but also passes through the axis C of the shaft, and a nut
(R), of which the circumference forms a bevelled pinion wheel, is attached to
the shaft like a swivel, and on being turned round operates upon the screw O,
as is done by the nut R, in Figure 2.
Now, in order to turn the nut or pinion wheel R without stopping the engine,
there is placed on each side of the eccentric wheel a bevelled wheel Q and Q,
concentric with the axis of the shaft and running loose thereon, but in gear
with the pinion R: if now, when the engine is in motion, one of the wheels, say
Q, be arrested by hand, or otherwise prevented from going round with the shaft,
it will evidently cause the pinion R to turn round, and the wheels Q and Q¹,
being at opposite extremities of the diameter of the pinion R, it follows, that if
one of the wheels Q be arrested, the motion of R will be in one direction, but
if the other Q' be arrested, the motion of R will be in the other direction; con-
sequently, the screw O can be operated upon so that the centre of the eccentric
wheel can be made to move in either direction along the line p, a, p'; and if
neither of the wheels Q or Q¹³ be arrested, the pinion R will not be made to
revolve round the axis of the screw O, and the adjustment of the eccentric will
remain unaltered.
In Figures 6,7,8,9, which represent different views of another form of eccentric
apparatus, the leading screw O does not pass through the shaft, as in Figure 4,
but two leading screws 0, 0, are made to pass one at each side of the shaft,
analagous to Figure 3, and each of these screws is fitted with a nut (R), the
circumference of which is fashioned to form an endless screw wheel or rack
work, which is operated upon and turned round by the tangent screws S, S.
and the nuts R, R, being confined between the snugs or cars P, P, which
project (see Figure 6) from the shaft or from the ring or saddle M, which is
fitted to the shaft, as before described in Figure 3, the snugs P, P, being so
situated on the shaft that the centre line or axis of the leading screws 0, 0,

page_text: shall be parallel to the line p, a, p'; it follows, then, that the leading screws
0, 0, will be so fitted that the centre of the eccentric wheel may be made to
move in either direction on the line p, a, p', according to the direction in
which the tangent screws S, S, are turned.
Now, in order that the tangent screws S, S, may be turned in either
direction, let each end of the spindle of each tangent screw be fitted with a
pinion wheel V and V', and let one side of the eccentric wheel be fitted with
a spur wheel Q, as shewn in Figure 7, running loose upon the saddle M,
concentric with C, and in gear with the pinion V, and let the other side of the
eccentric, as shewn by Figure 8, be fitted with a spur wheel Q', running loose
on the saddle, but communicating with the pinion V₁ by means of the inter-
mediate wheel V2, with which Q and V₁ are always in gear, all which parts
are also shewn by the section Figure 9; by which arrangement the tangent
screws S, S, will be turned in either direction at pleasure, according as the
wheels Q on the one side or Con the other may be arrested; or Q, V, and Q', V',
instead of being toothed wheels, may be grooved pullies, connected by bands
so arranged as to produce the same result; and for the purpose of arresting
the wheels or pullies Q and Q1, stop handles Z, Z, as in Figure 5, may be
attached to Q and Q¹; or stop levers Z, Z, as in Figure 9, may be provided
and fitted to obstruct the motion of Q or Q', which stop levers may if required
be so constructed as to be connected with the engine governor in such manner
that the self-acting operation of the governor upon the expansive gear may
regulate the speed of the engine.
Figures 10 and 11 shew an arrangement which may be adopted when the
eccentric wheel K, K, is fitted to a shaft detached from the crank shaft of
the engine, but driven by wheels or a pitched chain or other suitable apparatus
at the required speed. In this case the eccentric wheel K, K, is formed with
a void space L, L., L, L, as in Figure 2, and fitted upon the shaft so that the
leading screw O shall be parallel to p, a, p', and pass through the head piece
P, P, formed on the shaft, and be operated upon by a nut R, formed as in
Figure 6, with a screw wheel or rack round its circumference, this nut R
being turned round by means of the tangent screw S, the axis of which
coincides with the axis of rotation C, C, of the shaft. By this arrangement it is
apparent that the tangent screw S may be turned in either direction by means
of a winch handle Z or other apparatus attached to its spindle, and that if the
engine be in motion the nut R will be turned in one direction by the handle Z
being turned round faster than the shaft revolves, or the nut R will be turned
in the other direction by the handle Z being held still whilst the engine is in
motion, or turned in the opposite direction to that in which the shaft revolves;

page_text: consequently the centre of the eccentric wheel will be made to move in either
direction as required in the line p, a, p¹.
Figures 12, 13, 14, shew different sectional views of a crank motion fitted
upon a detached shaft, so that the centre of the crank pin may be made to
move as required on the line p, a, p¹. In this case the crank pin is attached
to or forms part of the frame K, K, K, which is made to slide in the slot or
vacant space L, L, which is formed in the double arm of the crank, so that
the frame K, K, K, may move in either direction parallel to the line p, a, p³,
and for a space equal to a, p, or a, p¹. In this case the leading screw O is
fixed at each end to the frame K, K, and is operated upon by the nut R,
formed as in Figure 10, which nut R is turned in either direction by the
tangent screw S, of which the axis is coincident with the axis of rotation
(C, C,) of the shaft, and operated upon by means of the winch handle Z,
whereby, as before described with reference to Figure 10, the centre of the
crank pin may be made to travel in either direction on the line p, a, p', according
to the motion which may be given to Z, with reference to the rotatory. motion
of the shaft.
Figures 15 and 16 shew a construction of eccentric wheel adapted for the
forward motion only, it being intended in this caso when the engine is reversed,
that the expansion slide be thrown out of gear and made to assume the position
which gives an open port.
.In Figures 15 and 16, L, L, L, L, is the open space of the skeleton eccentric
wheel. The leading screw O is fixed to the rim of the eccentric wheel K, K, K,
and does not pierce the shaft. M, M, M, M, is a block or saddle piece, upon
which the eccentric wheel is made to slide in the required direction (a, p),
the block M being fitted upon the shaft, and either fixed thereto in the
required position with reference to the lines 9, C, X, herein-before described,
or else running loose, and thrown in and out of connection with the shaft
by means of a clutch suitably constructed for driving it in proper position.
When in gear, the nut R, which works upon the screw O, is inserted in
the block M, and runs loose therein like a swivel, and is furnished with
arms which project beyond the block M on both sides, forming a ratchet
wheel, whereby the nut R can be turned by hand when the eccentric wheel
is out of gear; or the nut R may be operated upon whilst the eccentric
wheel is in motion by means of a moveable tooth or finger piece Z, being
fitted on each side of the eccentric wheel in such manner that with each
revolution of the eccentric wheel one of the arms of the ratchet wheel may
strike against the finger piece on one side or the other of the eccentric wheel,
whereby the nut R. may. be turned in either direction as may be required,

page_text: thereby operating upon the leading screw O, and causing the centre of the
eccentric wheel to move as required on the line (a, p), the finger pieces Z, Z,
being made to assume a position free of the ratchet wheel when the adjust-
ment of the eccentric wheel is duly effected. Or the nut R, instead of being
fitted with a ratchet wheel, may be fitted with a screw wheel, and be operated
upon by means of a tangent screw, as in Figure 6, the axle or spindle of the
tangent screw being furnished with a ratchet wheel on one or both sides of the
eccentric wheel, and operated upon by a finger piece, so as to be turned in
either direction, whereby the centre of the eccentric wheel may be adjusted as
required on the line (a, p). Further, as in practice it may not be necessary
that the steam have access through the expansion slide to the steam slide whilst
the steam slide is itself cutting off the steam from getting access to the piston,
purpose in some cases to limit the construction and use of my eccentric wheel
to that portion of the engine's stroke which cannot be advantageously worked
expansively by the steam slide, by which option! limitation in the application
of my expansion apparatus its necessary size may be considerably reduced.
I
I now proceed to describe the second part of my Invention, viz., the con-
struction of the expansion slide.
In Figures 17, 18, and 19, which shew different sections of the same appa-
ratus, A, A, A, A, represents the expansion slide box or casing, which is
supposed to be attached to the casing of the steam slide of the engine;
B, B, B, B, is the moveable slide, consisting of a series of cylindrical rings
or pipes F, F, F, F, connected together so as to have a cylindrical surface;
E, E, E, are a series of annular apertures, formed in the cylindrical pipe, or
5 left between the cylindrical rings F, F, F, F, all these apertures (E, E,)
having the same extent of opening, and so distributed that the consecutive
parts F, F, F, F, into which the cylinder is divided, may all be of equal dimen-
sions. The steam slide thus formed may contain any required number of
annular apertures E, the aggregate of which must give the amount of steam
way that may be required. The illustrations given by the sections, Figures
17 and 18, shew three such apertures through the slide. C, C, is the rod or
spindle, to which the expansion slide is connected, and by which the motion
of the eccentric or other driving gear may be communicated to the slide. The
slide casing A, A, A, A, forms a belted pipe, which is bored so that the turned
5 cylindrical surface of the expansion slide may fit therein, and through the
belted part of which annular apertures E¹, E¹, E', are likewise formed of such
dimensions and distance apart as to correspond with the apertures E, E, E, in
the expanson slide F¹, F', representing the faces between the apertures E¹, E'.
G is the steam pipe, whereby the steam has constant and free access to the

page_text: interior of the expansion slide; and it is apparent that if the apertures E be
opposite to the apertures E¹, the steam will pass and get access to the steam
slide; but if the faces E of the expansion slide be opposite the apertures E¹,
then the faces F¹ will also cover the apertures E, and the steam will not pass,
but be what is termed cut off.
In constructing this expansion slide with a view to its being worked by the
eccentric wheel or crank motion hercin-before described, and produce the effect
of cutting off the steam at any required period of the stroke for which the
said eccentric may have been adapted, it is requisite that the length of the
respective faces F, F, or spaces between the apertures E, be not less than
the radius of the largest circle which the centre of the eccentric wheel or centre
of the crank pin of the crank motion can be made to describe.
The operation of the slide will be the same, whether it be fitted to the steam
slide casing, as shewn in Figure 17, with the steam passing in the direction
shewn by the arrows, or whether it be otherwise fitted, so that the
steam may pass in the contrary direction; also, the steam may be made to
enter the slide casing A, A, A, A, both above and below the slide B, B, B, B,
whereby it will have access to the apertures E, E, E, more freely than if it
enter at one end only, as shewn by the Drawings 17 and 18. It is also evident
that the plan of successive apertures may be applied to a flat-faced slide,
provided that the slide faces or spaces between the successive apertures and
beyond the extreme apertures be proportioned as above described, videlicet,
the measure of the slide faces respectively in the direction of their travel to
be not less than the radius of the largest circle which the eccentric or crank
motion which drives it may be capable of describing.
Having now described my Invention, and the manner of carrying the same
into effect, I wish it to be understood that I do not claim the application or
use of an eccentric wheel or crank motion for driving the expansion steam
slide, but I do claim the construction, application, and use of eccentric wheels
or crank motions so constructed that the centre of the eccentric wheel or the
centre line of the crank pin, as the case may be, shall be made moveable by a
continuous sliding motion in either direction at pleasure over a definite line or
space, such line of motion not radiating directly towards or from the axis of
rotation of the shaft to which the said eccentric wheel or crank motion may
be attached, but be made to move in a direction passing the said axis at a
given distance therefrom; and I claim this construction and use of eccentric
wheels or crank motions, whether the same be effected principally by the agency
of regulating or leading screws, as above shewn and described, or by any other
combination of mechanical arrangements.

page_text: Also, I do not claim the constructing of expansion slides with a continuous
cylindrical surface or circular form, as adopted in any of the various forms of
double-beat valve heretofore in use, or as heretofore applied to the steam slides
of engines; nor do I claim the gridiron valve, as usually constructed and used,
and by the operation of which the port or aperture for the passage of steam
is open during the period that the slide itself is making its turn of stroke or
changing the direction of its motion; but I do claim the construction of
cylindrical slides such that consecutive cylindrical surfaces are respectively
divided from each other by an annular aperture of given width, the width of
the faces or distance between the said apertures being dependent on the said
given width of aperture jointly with the extreme degree in which the engine
may be required to act expansively, and the arrangements or construction
being such as to admit that the steam apertures shall be opened and closed,
not during the turn of stroke or reciprocating motion of the slide, but by the
respective apertures of the slide passing directly and completely across the
corresponding apertures of the box or casing, and the slide being made to
perform its reciprocating movement or change of direction of its motion, not
during the admission of steam, but during the period when the steam is cut
off; and I claim the above-described construction of the eccentric wheel or
crank motion and expansion valve, whether they be used together or used
separately.
In witness whereof, I, the said Charles Atherton, have hereunto set my
hand and seal, this Third day of August. in the year of our Lord One