IMPROVEMENTS IN STEAM ENGINES
Year: 1873

page_text: LETTERS PATENT to Michael Henry, of Fleet Chambers, 68, Fleet
Street, in the City of London, Patent Agent, for the Invention of
"IMPROVEMENTS IN STEAM ENGINES."-A communication from abroad
by Marcel Deprez, of 17, Boulevart Saint Martin, Paris, France.
PROVISIONAL SPECIFICATION left by the said Michael Henry at the
Office of the Commissioners of Patents, with his Petition, on the
1st September 1873.
I, MICHAEL HENRY, of Fleet Chambers, 68, Fleet Street, in the City
of London, Patent Agent, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN STEAM ENGINES," (communicated to me
from abroad by Marcel Deprez, of 17, Boulevart Saint Martin, Paris,
France,) to be as follows:-
This Invention relates to the portions of steam engines known as the
variable expansion gear, the reversing gear, and the valves and valve
gear, and it mainly consists in the construction and arrangement thereof
A

page_text: in such manner that the expansion of the steam may be varied,
and the direction of motion reversed by means of a single lever or
handle.
Various arrangements may be used for the purpose.
. In one arrangemont, according to the Invention, an excentric is keyed i
on an axis at the opposite end to the driving crank, its excentric radius
being equal to the sum of the outer lap of the valve and the linear lead
at the inlet. The excentric rod is of a length from five to ten times that
of the excentric radius. It is jointed to a head or slide block, which
works in a link, and to a rod connected with a jointed or bell-crank 1
lever, which the engineer works on a centre. The end of this lever is
in connection with a worm wheel, by turning which the inclination of
the jointed lever is adjusted, and hence the position of the excentric rod
to accommodate various degrees of expansion. The link is struck from
a radius equal to that of the excentric rod, and is formed in a ring in 1
which the driving shaft turns. This ring is keyed to the valve rod, and
it is guided by guides or by a parallel motion.
When the jointed lever is so inclined that the head of the excentric
rod is at its highest point in the link, the link and slide valve will so
work that the steam will be admitted into the cylinder during half the 3
stroke, and even more; and when the head of the excentric rod is at
the centre of the link the inlet of steam will be reduced to a very small
fraction of the stroke.
When the jointed lever is in such position that the block or head of
the excentric rod works in the lower part of the link the direction of a
motion will be reversed, and it will vary as before from 3 (10%) of the
stroke of the piston to a very small fraction. The various positions of
the rod in the link correspond with various degrees of expansion.
The apparatus is of simple construction. There are fewer joints than
in other variable expansion gear. The steam is supplied regularly on
both sides of the piston in both directions of motion. The lead of the
slide valve is uniform whichever the direction of motion, and whatever
the degree of expansion.
Another arrangement of the gear has for object an improved mode of
supplying the steam when circular excentrics are used.
The theory of the arrangement will be understood by reference to the
accompanying Diagram.

page_text: A, B, is the driving crank. The axis of the cylinder is in the
horizontal direction indicated by the line J, K; B, I, connecting rod
part only shewn; A, C, excentric radius of an auxiliary excentric
keyed on the driving shaft A at right angles to the crank A, B%;
C, D, excentric rod guided at D in the direction J, K; E, auxiliary rotary
shaft situated in the line J, K. On this shaft are keyed the two excen-
trics of an ordinary link motion, or the single excentric of the improved
link motion above described; E, F, crank driving the shaft E, and
receiving motion from a small connecting rod F, G, jointed to the
excentric rod C, D, at a point G on that rod. Now as the crank A
turns, the point G of the bar. C, D, works in a nearly elliptical path, that
is to say, the point describes a curve which is nearly an ellipsis, the
major axis L, M, of which is twice the length of the excentric radius A, C,
and its minor axis P, N, depends on the position of the point G on the
rod C, D, that is to say, the axis is shorter as the point G is nearer to
the point D. If the shaft E be in the centre of the ellipsis, and E, F,
F, G, be of suitable lengths the following ratio is obtained between the
angles a, a', described by the driving crank and by the crank E, F, and
computed in respect of each shaft from the respective position of such
crank when the piston is at the end of its stroke.
This equation or ratio shows that when the crank A, B, describes the
angles 0°, 90°, 180°, 270°, and 360°, the crank E, F, will describe exactly
the same angles; but, and this is the essential feature of this arrange-
ment, the crank E, F, turns between 0°. and 90° with greater velocity
than the crank A, B, whereas the converse is the case between 90° and
180°. The same peculiarity exists between 180° and 270° on the one
hand, and 270° and 360° on the other. Therefore if the driving shaft A
move with uniform velocity the shaft E, which works the valve gear,
will work with irregular velocities; and this non-uniformity of speed
considerably improves the working of the valve and distribution of the
steam when the valve gear is any ordinary excentric gear, the excentric
being mounted on the shaft E instead of on the driving shaft A.
One modification in which this plan is carried into effect is especially
adapted for locomotives; the purpose is to prevent the disturbance of the
valve gear from the vibrations of the springs. The excentric is keyed

page_text: on the driving shaft and works a piece shaped like an excentric and
having a belt and pulley, but only working in a right line, being guided
for that purpose in the direction of the slide valve by a block or stud
loose on the driving shaft and sliding in a rectangular frame opening or
guide way formed in the excentric shaped piece.
In another modification which is particularly adapted for mine engines,
the slide valve has a considerable lead but a very small lap, so that if it.
works alone it would only let in steam for about 99 per cent. of. the
stroke of the piston. A plate is superimposed on the slide valve and.
receives to-and-fro motion in proportion to that of the piston and in the
same direction as it. This motion is communicated to the plate by an
excentric keyed in the same direction as the driving crank, the excentric
rod being to the excentric radius in the same ratio as the driving con-
necting rod to the driving crank, or instead of such excentric the plate
may be driven by a lever or arm jointed to the piston rod. The full
travel of this plate and the width of its ports or orifices should be so
regulated that the corresponding steam ports or openings in the slide
valve shall never be entirely closed by the plate. There are also two
adjustable plates which are stationary while the engine is at work.
They are attached to small connecting rods jointed to the ends of equal
cranks mounted on the same axis, such axis being situated in the plane
of the joints which connect the connecting rods with these plates.
. When the small cranks are turned at any angle on the axis the
adjustable plates approach towards or recede from a vertical line passing
through the axis, which axis passes through the valve box. Now the
movement of the sliding plate with relation to the valve does not affect
the induction of steam because the holes in the valve are not closed by
this plate, but the plate having reciprocating motion the outer edges of
its steam orifices meet the corresponding outer edges of the adjustable
plates and consequently the steam is shut off and expansion com-
mences at a point as near to the starting of the piston stroke as the
two.plates are near to or rather distant from each other. The interval
between the plates is regulated by the position or inclination of the

page_text: piston and works in a cylinder filled with water, the two ends com-
municating by a pipe furnished with a stop cock. When this cock is
opened to a small extent and the plunger tends to move in one
direction, the water can only flow in the opposite direction at a speed
much greater than that of the plunger which thus has to undergo
resistance which increases with the square of its velocity, and thus the
accelerating action exerted on it by the steam engine piston will be
counterbalanced or neutralized.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Michael Henry in the Great Seal Patent Office on
the 27th February 1874.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, MICHAEL
HENRY, of Fleet Chambers, 68, Fleet Street, in the City of London,
Patent Agent, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria by Her Letters
Patent, bearing date the First day of September, in the year of our
Lord One thousand eight hundred and seventy-three, in the thirty-seventh
year of Her reign, did, for Herself, Her heirs and successors, give and
grant unto me, the said Michael Henry, Her special license that I,
the said Michael Henry, my executors, administrators, and assigns,
or such others as I, the said Michael Henry, my executors, admini-
strators, 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 STEAM ENGINES," communicated to me from abroad by Marcel Deprez,
of 17, Boulevard Saint Martin, Paris, France, upon the condition
(amongst others) that I, the said Michael Henry, my executors or admi-
nistrators, 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.

page_text: NOW KNOW YE, that I, the said Michael Henry, do hereby
declare the nature of the said Invention, and in what manner the
same is to be performed, to be particularly described and ascertained
in and by the following statement thereof, as communicated to me,
reference being had to the accompanying Drawings, and to the letters
and figures marked thereon, that is to say :—
This Invention relates to the portions of steam engines known as the
expansion gear, reversing gear, and valves and valve gear, and it mainly
consists in the construction and arrangement of such portions in such
manner that the expansion of the steam may be varied and the direction.
of motion may be reversed by means of a single (that is to say, by the
same) lever or handle.
Various arrangements may be used for the purposes of this Invention,..
and these I proceed to describe.
The arrangement shewn in Figure 1 may be used, according to which
the inlet and outlet of steam and the reversing of the motion is obtained
|with a continuous lead by means of a single slide valve actuated by a
single excentric, and without employing link motion.
If in the arrangement shewn in Figure 1 instead of using the valve
rod a, b, a rigid circumference or are is used, having in it a slot of the
same radius a, b, in which there moves a slide block or head of the slide
rod fixed to the point a, to which are jointed the excentric rod a, c, and
the suspension rod a, d. The arrangement thus obtained comes within
the general formulæ of construction above set forth. This arrangement
is shewn in Figure 2. According to this Invention, therefore, a grooved
or slotted piece or slide K, in which is the non-jointed stud or slide
block, or slide rod head n (that is to say, a single piece, as is shewn in
Figure 2) is used. Evidently therefore this piece may be cast, formed,
or cut readily in wrought steel or iron, and it carries a valve rod K, n.
The fixed point O is attached to the suspension rod by a lever O, D,
which is the raising or lifting lever.
The above described slide block is guided by the stuffing box of the
valve box, and by a rod with a guide eye, as shewn in Figure 2.
The excentric rod and the slide block or slide rod head are jointed by
a forked bar Figure 2, as also is the suspension rod, which may be forked
at both ends, but it is better to make it double so as to prevent it from
oscillating in a direction at right angles to the plane of the excentric.

page_text: In Figure 3 a guiding arrangement is shewn which may be employed
with advantage in substitution for the arrangement above described in
certain cases.
Two bars of equal size I and I' may be jointed at M and M', Figure 3,
and fixed at Tand T" in such manner that the Figure or form obtained
by joining M¹, T, and M, T', is a parallelogram, the centre of which is
precisely the centre of the figure of the grooved or slotted piece.
In the rectilineal movement of this piece, the rods I and I¹ oscillate
round the points T and T", and the circular piece carrying the valve rod
is therefore guided in a straight line. The object of this arrangement is 1
to reduce the influence of the obliquity of impulse or motion, and hence
to prevent any locking between the parts.
In order to calculate the factors or elements of the supply or passage
of steam, the following description is annexed. Figure 4 shews the
calculation of the respective dimensions of the parts of the said 1
appliances controlling the supply or passage of steam.
Those arrangements which will be herein-afler described only work
satisfactorily when cach of the parts has been calculated according to
the diagram about to be explained.
M'
First, must be taken into consideration the relation of the connecting
B
rod or crank rod with the crank in the engine to be constructed, say
this relation being equal, let us say for instance, to 5. Now the outer
lap (of the slide valve) is given in like manner to the slide valve, as
also its linear lead. These quantitics vary according to the description
and work of the engine.
"
When these three factors are obtained the diagram of the engine is
completed in the following manner :-Let a circle, Figure 4, be described
from the radius 0, D, equal to the sum of the lap and of the lead, then
the positions of the radius of excentricity corresponding with th of the
stroke of the piston is taken on this circle.
Now for this purpose
suppose the cylinder is placed at the right hand in the centre O of the
circle, the horizontal diameter of this circle, which coincides with the
axis of the cylinder, is prolonged to an extent, say D, B, equal to this
diameter niultiplied by the ratio of the length of the connecting rod or
crank rod with the length of the stroke of the piston. From B a line.

page_text: B, B', is struck equal in length to D, D', and this line is divided into ten
equal parts. Taking cach of these points of division as a centre with a
radius equal in length to B, D, an arc of a circle is described which cuts
the circumference or periphery D, D', at points placed symmetrically
with respect to the diameter D, O, D¹. These points 1, 2, 3 . . . . 7, 8, 9,
1, 2, 3 ... 81, 91, are precisely the positions of the centre of the
excentric wheel or piece which correspond respectively to each tenth
part of the piston stroke. When this has been done, then from two
points equi-distant from the centro O of the circle to the lap arcs are
described having for their respective radii the excentric rod.
•
In order to define the length of the excentric rod, it may be taken as
equal to seven times the sum of the lap and the lead, but then this must
be tried in order to see if symmetrical openings are obtained with it; if
not it must be tried again and again in order to obtain this result by
adjusting the length. This is explained herein-after in this Specification.
This may be found by a very simple emperical formula without such
adjustment. For this purpose the stroko of the slide valve corresponding
with the admission of 50 per cent. of steam is arrived at which may be
done by an engineer's diagram or by calculation, or by a dianenometer.
When this is done the amount is multiplied by the relation of the lengthi
of the connecting rod to the piston stroke and the product gives the length
of the excentric rod which ought to be adopted. In any case, when the
length of this excentric rod has been ascertained arcs C, C¹, are described
from the points A, A³, stated as above described. These arcs show the
geometrical position of the excentricity of the eccentric rod when the
piston is at one end of its stroke.
Now by way of illustration, suppose that the point 1 is taken as the
centre, with a radius equal in length to that of the eccentric; an arc is
described. This arc will cut the arc of the circle C¹, C', at a point a',
which will indicate the position which the end of the eccentric rod
should assume in order that the slide valve may intercept the intro-
duction of steam when the piston has travelled one-tenth of its stroke in
a right hand direction, because the eccentric is keyed at the end opposite
to that at which the crank is. The point 1 is determined in like
manner, and thus the position a at the end of the eccentric rod is
determined at the instant at which the slide valve intercepts the
admission of steam, the piston being then at the first tenth proportional
part of its stroke from right to left. Thus it is certain that the intro-

page_text: duction of steam will be stopped exactly at 4th of the stroke of the
piston on each side or face of such piston, provided that the end of the
eccentric rod be guided in any line (say, for instance, a curved line, such
as an arc of a circle) passing through the points a and a¹. Now in
order to guide the end of this rod in the direction of an arc of a circle it
is connected with a suspension rod of such length that the position
a, a¹, shall not deviate too much from a straight line. When the length
of this suspension rod is ascertained the position of its other end is
determined by describing from the points a and a³, as centres with the
length of this rod as radius arcs, which intersect each other at a point F
situated in a perpendicular line drawn at right angles to the straight
line a, a¹, through its centre. When this has been done as regards the
points 1 and 1¹, it is repeated for the points 2, 21, 3, 3¹, and so on in fine
for the successive inlet openings1, 101, 10, whereby the positions
F, G, H, I, K, of the end of the suspension rod corresponding with these
various degrees of inlet are obtained, supposing the revolution of the
engine to be in the direction indicated by the arrow.
Now in order to determine the positions of the end of the suspension
rod corresponding with the back or reverse motion the before described
process is repeated, except that the numerical order of the points
1, 1¹, 2, 2¹ . . . . 9, 9¹, &c., is reversed, that is to say, they are numbered
in a direction reverse to that of the arrow. Thus the positions E, D, C,
B, A, of the end of the suspension rod are determined in such manner that
the steam shall be shut off at 10, 10, , and, of the stroke of the
piston when the engine is reversed. Thus, if the end of the suspension
rod takes consecutively the positions A, B, C. . . . I, K, the steam will
C....
be introduced and supplied expansively under regulation and with
provisions for reversing the lead being continuous, and the inlet of
steam uniform on both sides of the piston. To carry this into effect a
simple line must be sought, say, for instance, an arc of a circle, which is
as closely as possible approximative to the geometrical position of the
points A, B, C... . I, K. To this definition a few experimental trials
enable the engineer to arrive. When this circle is determined, all that
has to be done in order to bring the end of the suspension rod in such
position as to describe the circle is to connect it with a lever or rod
working on the centre L of the circle and of a length equal to its
radius.
In order to Wove thin the following
lanationa
dal.

page_text: geometrical position of the points A, B . . . . I, K, not forming a circle,
it follows that in substituting for it the last-mentioned curve there is an
crror which should be recognized. For this purpose suppose that, for
example, it is desirable to verify the regularity of the distribution of
steam for inlet at half stroke. It is known that the inlet of steam is
exactly identical on both sides or faces of the piston. If the suspension
rod has its ends at K the intersecting point of the two arcs K, M, and
K, M', respectively described from the points g, g', as centres. If the
end of the suspension rod be placed on any point of the arc K, M, it is
evident that the steam will enter at or during one-half of the stroke of
the piston when it moves from left to right, hence if the inlet be on a
point of the arc K, M', it will take place at the half stroke from right to
left. Now it is evident that these two arcs K, M, and K, M³, will
intersect the arc of a circle described by the end of the lifting lever at
two points M, M³, very near each other. Then if the end of the lever
be placed at the centre of the interval or distance which separates them
the absolute equality of inlet on both faces or sides of the piston will
be reached approximatively. The same reasoning is applicable to all the
other points or stages. of inlet, and these modes of proving show that in
every instance the various stages of distributing the steam (inlet pres-
sure, maximum opening of the parts and anticipated inlet) are very
nearly approximatively to absolute uniformity on both sides of the piston
and in both directions of the engines' motion.
Figure 5 shows another arrangement or modification in which a circle
whose radius is equal to the eccentric rod in length is free to slide in
another circle, the moveable circle or ring a acting as a slide block in a
guide groove. The suspension rod is jointed at M, and it is worked by
hand or otherwise. In this arrangement the wear is distributed over
the whole surface of the circle or ring a, and thus is reduced to zero.
Figure 5* shows another arrangement or modification especially
applicable to locomotives when directly applied on the motive shaft or
working axle. Its object is to prevent or neutralize the influenco
exerted by the oscillations of the engine springs on the parts which
control or regulate the distribution or passage of the steam. In this
arrangement or modification a cam or excentric E is keyed on the
driving shaft, and works through its excentric rod M, a rod or bar F which
actuates an excentric provided with a collar C and pulley N, but only
working in a straight line, being guided for that purpose in the direction

page_text: of the slide valve by means of a slide head or block P freely mounted on
the driving shaft, which is capable of to-and-fro sliding motion in a
rectangular frame mounted on N. The slide valve rod is the rod A, the
lifting of H is effected by a screw K.
I now proceed to describe an arrangement in which the relation or
ratio of the rotary velocity of the cam with respect to that of the
driving shaft is variable.
The mode of distributing or supplying and discharging steam effected
by the apparatus above described may be improved for certain purposes
by giving to the excentric which actuates the link motion a rotary 1
motion, the velocity of which shall be in a ratio or proportion to that of
the driving shaft which shall undergo periodical variations during each
stroke of the piston.
There are a great number of laws of variation, yet one such law must
be determined upon which shall carry out the principle practically and 1
casily. Hence the Inventor has obtained the desired result by the
tangent a
following ratio,
=K, in which a denotes the angle described
tangent a
by the working shaft, and reckoned from one of the dead points of the
working crank; a₁ is the angle described by the eccentric which actuates
the link motion, and K is a constant quantity greater than unity.
2
Figure 6 represents an arrangement shewing pratically an approxi-
mative mode of carrying this ratio or proportion into effect. On tho
driving shaft is keyed an eccentric or cam C of any radius, but of as
long a radius as possible having an eccentric rod L which is guided in
the direction of a right line passing through the axis A. At any 2
point D of this rod a small connecting or crank rod D, E, is jointed, such
rod being connected with a small crank B, E, keyed on the shaft or
axis B on which the distributing eccentric is mounted. The remaining
parts of the arrangement are precisely similar to the arrangement repre-
sented in Figure 2.
The ratio of the lengths D, E, and E, B, must be determined; this is 3
effected by the construction shown in Figure 7. On any point A of the
rod or arm A, L, of the eccentric C describe an oval nearly of the shape
of an ellipse having its major axis D, D¹, equal to twice the radius of
excentricity, and the length of the minor axis A, A', depends on the
position of the point A on the excentric rod. Now taking D, D¹, 3

page_text: as. a diameter describe a circle thereon, such circle intersecting the
prolongation of the minor axis at the point E. Now from the centre e
of the line A, E, draw a perpendicular line e, B, of any desired length,
and join B, A, to B, O. These latter two straight lines will be precisely
the direction of the connecting rod or crank rod D, E, and the crank E, B,
represented in Figure 6. The elements of the excentric which turns on
the centre of the ellipse are also determined as shown in Figure 2.
It is evident that since the auxiliary excentric Figure 2 is keyed at
right angles on the driving crank and has any desirable length of radius,
but such radius being as long as possible, the machinery can be greatly
simplified in engines in which there are two cylinders whose pistons act
on cranks set at right angles as in locomotive and marine steam
engines, &c. In fact the crank and connecting or crank rod of each of the
engines may act with respect to the other crank just as the auxiliary
excentric, and the excentric rod act in the arrangement shewn in
Figure 2: This allows of the auxiliary excentrics being dispensed with,
and also of having ellipses of great dimensions.
The position of the centre of the ellipse described on the major axis
has an important influence on the regularity of the valvą arrangements
for the passage of steam, and in fact it corrects the error due to the
driving crank rod, such error not being infinite. Its position should
consequently vary with the ratio of the connecting rod or crank rod.
In other words if instead of causing the centre of rotation of the
crank O, B, to coincide with the centre of the larger arc of the ellipsis
it be placed on the minor axis, the supply or passage of steam into the
cylinder will be rendered more regular.
Another method of generating elliptical motion is as follows:-When
the two ends of a straight line A, B, Figure 8, of constant length move
over two other straight lines situated in the same plane any point. C of
the moveable straight line will describe an ellipse, the horizontal axis
of which is equal to A, C, and the vertical axis to B, C; the central
point O will describe a circle, the centre of which is at O, and the radius
is equal to O, O¹, and then this constant equation is obtained, A, O¹, =
O', B, = O, O'. If a line O¹, D, is drawn through the point O¹ parallel
to the stationary straight line O, X, the angle D, O', B, will be equal to
O', B, O, and hence to O³, O, B, because the triangle O¹, O, B, is
isosceles; the right line O¹, B, then turns around the point O', that
=

page_text: point being itself carried in the direction of rotation O, O', round the
point O, the right line O¹, B, turning round the said point O' with a
velocity of angular motion continuously equal, but with a sign (plus or
minus) contrary to that of the angular velocity wherewith the right line
O, O¹ moves round the point O. Now reciprocally give the right line
O', B, a determined angular velocity while its end O¹ is itself carried in
a rotary direction around a fixed point O with angular velocity equal
but in a contrary direction to that of the line O¹, B. Take on this right
line from the point O¹ equal lengths O¹, A, = 0³, B, = 0¹, 0, it will
follow from the foregoing explanation that the points A and B will
describe two rectangular straight lines passing through the point O, and
consequently each of the points of this right line will describe an ellipse,
the horizontal axis of which shall be equal to A, C, the vertical axis
being equal to B, C. Thus a new combination is obtained, which
enables one to give to the steam supply excentric a motion indicated by
tangent α,
the equation
=K, and which is more practical and com-
tangent a
pact in many instances than are the formula above described. Suppose
that O, X, is the extension of the axis of the cylinder, and that the
point O¹ is connected with the driving shaft O by means of a crank, and
that at this point O' is attached another small crank O¹, C¹, receiving by
an arrangement herein-after described an angular velocity equal to and
in a contrary direction to that of the crank O, C; suppose also that the
end O¹ of this crank slides in a rectilineal guide slot cut in a third crank
O, C¹, mounted so as to turn by friction on the driving shaft O of the
engine; ascertain the angle a, which shall form this third crank O, C¹,
with the axis O, X; then calling a the angle O¹, O, X, described by the
driving crank, we shall get,-

page_text: Figure 9 shows how to give the smaller crank O', C', an angular
velocity round the point O¹ equal but. contrary to that of O, O'. Let:
O, O₁, O¹, be a train of toothed gear wheels the centres of which form
the angles of a triangle of invariable form, and let this triangle turn
round the centre O of the first wheel which is kept stationary, then the
angular velocity of a right line connected with the wheel O¹ shall be
connected with the velocity of the line in which are the centres O, O', by
the ratio a¹= (1 – K) a. In this formula K designates the ratio of the
diameter of the wheel O to that of the wheel O¹, the diameter of the
intermediate wheel O₁ being of any length; call K = 2, then we get
a¹a, which in other words implies that the wheel O' turns with an
angular velocity equal to but contrary to that of the wheel O.
-
13
Now in order to construct and arrange the parts of the engine on this
principle, all that has to be done is to mount on a cylinder or bushi
concentric with the driving shaft O a stationary wheel, against which
rolls a planet wheel O, of any desired diameter, and caused to gear. with
a third wheel O', the diameter of which is half the length of the diameter
of the wheel O. This wheel O¹ is mounted on a crank O' keyed on the
driving axis. On this same crank O, O', is bolted a plumber block or
bearing P, O₁, which supports the wheel O₁, so that the three points O,
O₁, O¹, form the three angles of an invariable triangle. On the axis of
the wheel O' is keyed a small crank O¹, C³, on one end of which C¹ is a
stud which works in a rectilinear guide slot cut in a crank O, D, free on
the driving shaft O. This crank O, D, moves with it either the
3 excentric in the arrangement shewn in Figure 2, or the two excentrics
of a Stephenson link motion or other contrivance. The diagram of the
valve gear motion produced according to this plan is effected in the same
manner as that in the circular plan Figure 2.
The straight guide way in the crank C, D, may be dispensed with,
and the jointed arrangement O, A, B, shewn in Figure 7, may be used.
instead.
When the elliptical arrangement is applied to ordinary steam valve
gear, the inlet of steam may be varied much beyond the usual limits,
and without modifying the construction of the valve or slide itself, and
5 without increasing the stroke. Also by means of this arrangement the
onening of the ports is increased for cach degree of expansion, and to

page_text: link motion gear giving an inlet or induction of steam at from
this.
to ths. of the stroke of the piston would be rendered suitable for
producing inlet comprised between 8ths. and 12ths. of the stroke
without increasing the stroke of the slide valve when the elliptical
arrangement is adopted.
:

page_text: F, F, are plates, which are kept stationary while the engine is at
work. These plates are connected with two small arms or rods I, H, I, H²,
which are jointed to the ends I, I', of two small cranks I, G, I¹, G³, of
equal size, and placed opposite each other; they are both keyed on the
same axis G. This axis should be placed in the same plane as the two.
joints H, H³, which connect the small connecting arms or crank rods.
with the plates F, F¹. Hence when the little cranks are turned at any
angle on the axis G the plates F, F¹, recede from and advance to a
hypothetical vertical line passing through the point G, and to the same
extent. The axis G, where it passes through the valve box, traverses a
stuffing hav

page_text: Figure 13 shews the arrangement of the various parts which actuate
the slide valves shewn in Figure 10. In this Figure 13, O is the driving
shaft; O, D, driving crank; O, B, excentric for the forward travel;
O, A, excentric for reversing the engine; O, C, excentric keyed in the
same direction as the working crank, and actuating the plate E, E;
E, F, ordinary reversing gear link motion; E, K, suspension lever of
the link motion; K, L, M, lever working on the fixed point L, and
transmitting to the link motion the proper movement for reversing;
M, N, rod jointéd at M to the lever K, L, M, and jointed at N to the
reversing lever N, G₁, P, which works on the point G; I, H, and I, H',
two small connecting rods or crank rods jointed at I and I¹ to the
lever P, G, N, and at H, and H¹ to the expansion plates F, F¹,
Figure 10.
Figure 13 shews these mechanical arrangements in the position they
occupy during the reverse or backing motion, the steam entering the
cylinder during 99 hundredths of the stroke of the piston. The
lever P, G³, N, which works at the same time both the link motion and
the expansion plates makes an angle of 30° with the the vertical on the
left side. If the lever be moved 60°, so that it may stand at an angle
of 30° with the vertical on the right side the interval or distance between
the plates will be such that the steam will be shut off and the engine
will stop working. But while this angular motion of 60° is being
imparted to the lever P, G', N, the rod N, M, will also be shifted, and it
will move the link motion; and it would appear at first sight that the
motion of the slide valve D, D, itself would be considerably altered, but
on a little consideration it is found that the motion or change of position
of the slide valve is very little affected. In fact if the rod N, M, is of
sufficient length with respect to the crank G, N, the change of place of
the point N may be regarded as being perceptibly equal to the change
of position of the vertical projection of the point N (that is to say, a line
passing through the point N). Now let us indicate by the letter L the
length G³, N, & by the letter the length G¹, I=G³, I', and by the
letter a the angle made by the crank P, G', N, with a vertical line, and
let us call x and X the paths travelled by the points H and H' on the
one hand, and N on the other hand. These paths are reckoned from
the centre, round which the points oscillate in a symmetrical manner,
we then shall have―
x=1 sine a X=L cosine a. Now by way of example let us say that

page_text: 1=100 millimetres and L=200 millimetres, and let us suppose that a has
the following values:
-
-
This table shews that the angle a varying from 30° (position repre-
sented at Figure 11) to + 30° (position represented in Figure 12); the
space travelled by each of the plates F and F is from 50 - (50)
= 100 millimetres, when the point M descends from 200. 173 = 27
millimetres, when the angle a varies from -30° to 0° and rises again to
its previous position, when a increases from 0° to + 30°. The point M, and
consequently the link motion E, F, only undergoes an oscillation of 27
millimetres; while the plates F, F, pass from the position of the greatest
degree of induction to that in which there is no induction. Now the
length of the link motion being 400 millimetres this oscillation is abso-
lutely without any influence on the passage of steam effected by the
slide valve D, D.
Now starting from a = 30° to a = 90° the plates move each 50 milli-
metres, which would increase the distance or interval between the two
plates to 100 millimetres, but this is not important because from even
a = 30° the interval between them is sufficient to cut off the steam
completely. During this angular motion, on the contrary, the link
motion descends say 173 millimetres; then while the angle a is changing
from 90° to 150° the plates will come to the position in which the
interval between them will be that which they would have for a = 30º.
The steam being still completely shut off the link motion descends a

page_text: fresh interval of 173 millimetres, which brings the entire descent or
change of place to 378 millimetres, reckoning from its highest position.
Thereupon the excentric O, B, which actuates the slide valve D, D, and
the direction of motion are reversed; and if the angle a be increased
from 150° to 210° the distance between the plates will pass from the
value which corresponds with the non-admission of steam to that which
corresponds with the inlet or induction at 99% of the stroke, while the
link motion will only undergo a trifling oscillation of 27 millimetres.
Thus by means of a single lever (or handle) the expansion can be varied
and the direction of motion of the engine reversed at the same time, so
that this arrangement is especially applicable to mining engines. More-
over the ratio of the length of the eccentric rod O, C, to the radius of
this excentric being equal to the ratio of the working crank rod or
connecting rod to the working crank it follows that the openings of the
ports and the degrees. of expansion are invariably alike on, both sides of
the piston whichever be the direction of motion.

page_text: The arrangement shown in Figure 10 may be modified by dispensing
with the intermediate plates E, E, and by actuating the centre G on
which the plates F, F, are jointed by the excentric rod keyed in the
direction of the crank. Thus these plates will shift while the engine is
at work, and their interval of separation which will remain the same for
any given degree of expansion will depend on the manipulation of the
engineer or on an automatic or self-acting regulator, which will actuate

page_text: before described, having the method of action above set forth for the
purposes herein explained.
In witness whereof, I, the said Michael Henry, have hereunto set
my hand and seal, this Twenty-sixth day of February, One
thousand eight hundred and seventy-four.
Witness,
E. DE PASS,
'Patent Office,
68, Fleet Street,
London.
M. HENRY. (L.S.)