IMPROVE- MENTS IN STEAM ENGINES, AND IN PARTS CONNECTED THEREWITH
Year: 1868

page_text: LETTERS PATENT to Alexander Melvin Clark, of 53, Chancery
Melvin
Lane, in the County of Middlesex, for the Invention of "IMPROVE-
MENTS IN STEAM ENGINES, AND IN PARTS CONNECTED THEREWITH."—A
communication from abroad by Charles Julien Quétil, Civil
Engineer, of 29, Boulevart St. Martin, Paris.
Sealed the 7th July 1868, and dated the 31st January 1868.
PROVISIONAL SPECIFICATION left by the said Alexander Melville
Clark at the Office of the Commissioners of Patents, with his
Petition, on the 31st January 1868.
I, ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the
County of Middlesex, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN STEAM ENGINES, AND IN PARTS CONNECTED
THEREWITH," to be as follows:-
This Invention relates to improvements in steam engines, and also
to the arrangement and mode of operating the various parts constituting
it, including the pistons, steam distribution, improved cut-off, fixed
or variable, either by hand or by the aid of the governor, improved
metallic packings to be used in place of stuffing boxes, and an im-

page_text: One,
proved reversing motion operated by means of the eccentric.
two, three, four, or more cylinders may be used with this improved
engine.
The Drawings annexed are those of a steam engine of six horse-power.
The engine has two cylinders indicated by the numbers 1 and 2. Each of
these cylinders is provided with a steam chest indicated by corresponding
numbers 1, 2, and each cylinder is double-acting. The stroke is four
inches; the diameter of piston, four inches; the number of revolutions
per minute, 350; the average pressure in the cylinder, about 60 pounds
on the square inch.
Sheet 1 of the Drawings shows a plan of the engine. A is the steam
pipe through which the steam is supplied to the governor and to the
engine; E is the exhaust pipe. In this engine the exhaust takes
place between the two cylinders. The cranks are also placed at right
angles to avoid the dead points. The crank pins are fixed in cast-iron
parts x, x, and B, and work in brasses a, a¹, up and down inside
of the slide bars G, G¹, fixed to the rods T, T', by means of keys μ, μ¹.
The piston rods are screwed in the pistons, or may be fixed in any
other way. In the part B are fixed the ends of the two crank pins.
The parts X, X³, are fixed on the driving shaft, but B is not fixed
on the shaft and is merely suspended and held by the ends of the
two crank pins. The engine shown in the Drawings has a variable
cut-off operated by hand without stopping the engine, which may also
be rendered variable by the aid of the governor by a simple modification
herein-after described. The engine is also provided with a reversing
motion. When it is desired to have a variable cut-off operated by the
governor I prefer to place the governor between the two cylinders, and
when the cut-off is to be regulated by hand the governor may be
placed at any point of the steam pipe. When the engine is to work
at full pressure without any cut-off it is only necessary to have two
eccentrics B and B', and when the cut-off is to be used I add two
other eccentrics D and D'. The plan of the engine shows the backward
motion. The crank pin corresponding to cylinder 1 is in a horizontal
position, and the one corresponding to cylinder 2 is vertical and raised.
The steam is conveyed to the steam chests by means of pipes entering
at the side and centre.
Sheet 2 of the Drawings represents a side view of the engine. The
frame F is shown moved horizontally by the eccentric D; there is also

page_text: for the other cylinder Number 2 a frame F moved by an eccentric D
shown in Sheet 1. In Sheet 2 I have for simplification omitted the
parts x, x, and B. In this engine the exhaust takes place through
the pistons by channels communicating with the exhaust channel
placed in the middle and between the two cylinders. A. rod working two
valves traverses the whole length of the piston, this rod being carrie
at each end by guides a and a¹ in said piston. The details of
exhaust are shown in Sheets 13, 14, and 15. The piston is providea
with a packing composed of two metallic rings and ¹ at each
end, the joints being on opposite sides of the piston. When the
piston reaches one end of the cylinder the channels a and a in
piston correspond with the exhaust port of the cylinder, and when
piston is returning the steam which arrives at full pressure
the piston and end of the cylinder shuts one valve and opens th
so that while the piston is moving back the steam escapes
the seat of the open valve, and the channel 7 communicating with the
exhaust port of the cylinder I may dispense with channels a and a¹ in
the piston and fix on the outside of the piston valves o and o¹ small
rods or projections, which abut against the cover of the cylinder, so
as to shut one valve and open the other when the piston arrives at the
end of the cylinder.
Sheet 3 shows an end view of the engine. Some of the parts which
are sufficiently indicated on the other Sheet are omitted in this, so
as not to complicate the Drawing and facilitate the explanation of
the engine. In effecting the distribution of the steam I place the
slide valves as near as possible to the cylinders to economise room
and also to reduce the length of the channels. By placing the slide
valves in such position with regard to the axis of the cylinder and
exhausting through the piston I believe to have combined a steam
engine without any objectionable spaces. It is only the steam which
has been admitted in the cylinder to work the piston that passes out
or exhausts through the piston, while in other steam engines it is not
only that volume of steam which exhausts, but also a volume contained
in the channel through which the steam passes to the piston.
I will now give details of the steam distribution shown in Sheets 5
and 6.
Figure 1, Sheet 5, shows a horizontal section. thronal

page_text: through line A, B, Figure 2, Sheet 6, which shows a cross section
through the centre of cylinder and steam chest. If I use only one
double acting cylinder as in ordinary engines I use but one eccentric B
and two slide valves and t, which are in this case mounted on the
same rod extending the whole length of the steam chest. With these
o small slide valves and the one eccentric I am able to work the
tw
cut-on
lue without cutting off the steam, and in either direction with the
one eccentric, as will be hercin-after shown. If it is desired to have
a fixed cut-off I use a second eccentric D moving a frame F, and two
other small slide valves , &, carried on the same rod. If a variable
is required to be operated by hand I use two other small slide
.es fand f, actuated by a rad o turning in a nut fixed in the upper
t of guide Z fixed itself on the steam chest. This rod o is turned by
the aid of a hand wheel V, and as it moves up and down the two
In cases
valves and f¹ will approach or recede from each other.
where the cut-off is fixed the two parts fand f¹ are also fixed and may
be cast with the cylinder. The rod o operates the valves f,f, by means
of levers 7 and q', shown in Figure 2, Sheet 6. If a variable cut-off
is to be obtained by the aid of the governor I dispense with the wheel V
and attach or suspend the rod o to another part fixed on the top of a
governor like that of Pickering, and as shown at Figure 2, Sheet 16,
rising and falling with the rod of the governor. I also dispense with
the nut at the top of guide Z, and substitute a brass washer in which
the rod o will slide. In this manner the rod o will move like that of
the governor, and the valves f and f¹ will move with the balls of the
governor. When the balls open outward the rod o will fall and the
valves and f¹ will separate farther one from the other; and when
the balls fall inwards the rod o will rise and the valves fand f' will
approach each other. Figure 2, Sheet 16, shows on a scale of one inch
and a half to the foot the mode of attaching the rod o to the part
By
placed on the top of the governor, or it may be otherwise arranged.
following out the motion of the two valves and as shown in
Sheets 7, 8, 9, and 10 for each position of the crank and of the eccentric
the distribution of the steam will be readily understood.
Sheet 7 shows the respective positions of the piston, valves, cranks,
Sheet 8
and eccentrics of cylinder 1 during the backward motion.
shows the position of the same during the forward motion. Sheet 9 shows
the same for cylinder 2 during the backward motion. Sheet 10 shows
the same for cylinder 2 for the forward motion.

page_text: In the Drawings shown the engine is not intended to cut off at above
one-half of the stroke, and if it were intended to cut off above, for
example, at three-fourths of the stroke the valves and should be
made as wide as valves and t, and have the same alternating motion
without intermittence imparted by an eccentric placed close to
eccentric B and keyed at a right angle therewith, serving as a substitute
for eccentric D. The engine would then work at full pressure all the
time; the opening between the parts fand f' and the abutments in the
steam chest is twice as wide as the ports in cylinder, and by moving
parts and the cut-off may be obtained at any part of the stroke.
This improved engine may be readily constructed, and is provided with
a variable cut-off and reversing motion. Each slide valve t and should
be twice as wide as the steam port of cylinder, and in the engine shown
the steam ports are two inches long and half an inch wide, the valves t
and having a motion of one inch. The cut-off valves and have
only half an inch motion, their motion being intermittent and ot
continuous like that of valves & and t, that is to say, the valves & and, t
will move, for example, half an inch, and for another quarter revolution
will remain stationary, they will then move again half an inch back and
remain stationary during another quarter revolution. This motion is
insured by the form of the eccentric D, as will be readily understood,
and by means of this eccentric D I may, with the engine running at a
high speed, obtain a variable cut-off without any vibration or noise. The
steam continuously fills the whole of the steam chest, and the steam
ports are entirely closed when the slides f and f¹ come in contact with
the abutments 8 of the steam chest. When the cut-off is variable the
same rod cannot work the slides and on account of the position of
the parts and f¹, and motion is imparted to slide valve (by another
short rod communicating with the first by means of levers band d and
rod c, as shown in Sheet 2.
In Sheets 7, 8, 9, and 10, are shown the positions of the slides
corresponding to those of the eccentrics. Instead of exhausting
through the pistons I may exhaust through two ports, one at each
end of the cylinder, and one opposite the corresponding steam port
at cach end, the piston would then be made solid and without any
valves, rods, or channels. In this case I also dispense with the
exhaust port at mid length of the cylinder which is used when
exhausting through the piston, and open or close the exhaust ports
by two other small valves like those for the admission. The eccentric

page_text: has an opening or slot in the middle for reversing the motion by means
of which slot I can reverse the motion by moving the eccentric on
the shaft. At Sheet 7, position 2, the crank is shown in its lowest
position the corresponding position of the eccentric being also seen.
The motion is backward, that is to say, if I move the eccentric from
Right to left by any means so as to bring it to the position 4, Sheet S,
and keep the eccentric in that position while the crank is still down
the motion is instantly reversed. To render this clear it is only
necessary to examine the corresponding position of the valves in the
two positions of the eccentric. It will be scen that by this motion
of the eccentric the steam is immediately intercepted or prevented
from entering on the side of the piston where it had previously been
introduced and is on the contrary admitted instantly to the opposite
side of the piston which is necessary and sufficient for reversing the
motion.
I claim as part of the Invention this new mode of reversing the
motion in steam engines by means of the slot in the eccentric and
of the new mode of applying this peculiarity of the eccentric.
I will now describe how I change the position of the eccentric
while the engine is at work. This as seen in Sheet 11 is effected by
means of a lever turning on a fixed point or shaft V carried in bearings
S, Sheet 2. This lever is connected at its lower part to a ring C in
which turns the eccentric B touching only at one point as seen in
Figure 1, Sheet 18, and Figure 4, Sheet 20. By moving this ring
through the aid of lever L the eccentric B may be slid on the shaft
as seen in the other Figures of Sheets 18, 19, and 20. The motion
is communicated from the shaft to the eccentric by means of a clutch
m keyed on the shaft and having a circular tongue 10. shown in
Figure 4, Sheet 17, which tongue according to the position of the
eccentric enters corresponding mortises or cavities 11 and 12 in the
eccentric. Figures 1, 2, and 3, Sheet 17, shows the back view of the
eccentric in different positions on the shaft. In the position 1, Sheet 18,
the motion is backward and the tongue of the clutch or coupling m
is entered in the mortises or cavities 12 of eccentric B. Supposing now
that by means of a fork the motion is communicated to coupling m
causing it to slide on the shaft so that the tongue is withdrawn from
the eccentric, and that at same time through lever L the eccentric B
(which no longer turns with the shaft and is free thereof) be brought,

page_text: by the aid of ring C to the position 3, Sheet 19, the tongue 10 being
moved in the coupling by a spring, or the coupling fork will enter
the cavity 11 of the eccentric and the motion will be thus reversed.
As soon
as by a slight motion of lever L the eccentric B has
reached the position 2, Sheet 18, all the openings for the admission
of steam are shut, and if the lever L were left in the corresponding
position the engine would stop, thus it is necessary to bring the
lever to that position when it is desired to stop the engine. By con-
tinuing to move lever L in the same direction the steam will be
introduced on the opposite side to when in the position 1, and the
distribution of the steam will cause the engine to begin to turn in the
opposite direction, and when the eccentric has reached position 3,
Sheet 19, the tenon of coupling m will enter the mortise of eccentric B
and the engine will be ready to turn in the other direction.
In this motion in passing from position 3, Sheet 19, to position 4,
Sheet 20, the eccentric will bring the ring C and lover L to the
position 4. In this position, which is exactly the same for the lever
as position 1, Sheet 18, the eccentric turns in the ring C without any
resistance therefrom as it only touches it slightly while in motion.
Reciprocally one can pass from the forward motion to the backward
motion by uncoupling the part m, and bringing the lever L back to
the position 6, Sheet 20, and coupling anew the part m with the
eccentric. In this change of position of the lever there is another
stopping position 5, Sheet 19, differing from the stopping position 2,
Sheet 18, which I have before mentioned. This reversing motion
has this peculiarity that when the lever L is vertical the engine
can work either forward or backward according to the position
of the eccentric on the shaft, and pass from one motion to the other
by moving the lever one way or the other according to the position
of the eccentric. There are also two different positions of the lever at
which the engine can be stopped, one point on one side of the vertical,
and the other on the other side. In the positions 2, Shect 18, and 5,
Sheet 19, it will be readily seen that the tenon of coupling m cannot
enter the eccentric, and for the purpose of causing the tenon to enter
I employ a spring pressing it constantly against the eccentric. In
order to uncouple it is simply necessary to act on the spring, after
which the coupling m may be again connected with the eccentric by
means of the spring when the eccentric has arrived at the right
position. The engine may also be readily stopped as in the positions 2

page_text: and 5, the tenon of the coupling cannot enter the eccentric. In
order to utilize the two stopping positions of the lever it is necessary
when the motion of the slide valve is very limited, as in this example
of a 6 horse-power engine, to use two rings fixed in bearings S,
and mounted on the same centre of rotation as lever L. The two
stopping points are so near the vertical that the two slots in the rings
might form but one, with two rings each of them would have a slot
and the lever would have two tenons, one on one face and one on
the other. If it is only necessary to have one stopping point then one
ring with a slot and one tenon on lever L would be sufficient. When
the motion of the valve is considerable, or as in the case of locomotives,
there is room enough for several mortises or cavities in the eccentric
in which the tenon of the coupling m can enter, and by fixing the
eccentric in different positions in the shaft it will be possible, as is
the case with the Stephenson link, to vary the course of the slide valve.
I could consequently, using the ordinary mode of distribution of the
steam, vary by means of the improved arrangement of eccentric of this
Invention the motion of the slide valve and work a locomotive forward
and backward with only two of these improved eccentrics and without
a Stephenson link. There should be as before no mortise in the eccentric
at the middle point of the slot. I may also reverse the motion in a
different way by giving a different form to the ring and also to the
part of the eccentric in which the ring acts, as shown in Sheet 21,
and also by causing the eccentric to revolve on the shaft as long as
the shaft turns, by adopting the arrangement shown at Figure 1,
Sheet 21. The shaft is made larger at the point where the eccentric
is placed, and of the form shown at Figure 1, Sheet 21, with a flat
.surface above and below which will cause the eccentric to revolve and
will also guide it when moved on the shaft. In this arrangement the
cccentric will revolve when at the position corresponding to 2 and 5
before referred to as long as the shaft itself will revolve, but the valves
will not move either way and the ports of admission of the steam
will be all closed.
will be seen that the form
act in reversing the motion
On referring to Figure 3, Sheet 21, it
given to ring C is intended to cause it to
always on the same side of the eccentric. It will be understood that
when the eccentric is once at the mid-point without this peculiar form
of ring, and of the part of the eccentric on which the ring acts, the
eccentric would be free to take up a position either for forward or

page_text: backward motion if each side of the eccentric were acted on successively
by the same side of the ring.
Having explained the action with an engine having only one cylinder,
I will now proceed to describe the engine illustrated in the Drawings
which is a six horse-power engine with two double acting cylinders
placed side by side. In this engine there is a steam chest 2 for
cylinder 2 arranged exactly the same as steam chest 1, the only
difference consisting in the position of the valves of the one chest and
the other.
In Sheets 7, 8, 9, and 10 are shown the positions for the forward
and backward motion of the eccentrics and of the cranks driven by the
two pistons as well as the corresponding positions of the valves and
pistons. In this double cylinder engine there are two eccentrics B
and B and two rings C and C₁ for reversing the motion, the one C
moves from left to right by the aid of lever L operated by hand for
moving eccentric B horizontally, the other ring C₁ moves upwards,
moving eccentric B₁ vertically and reciprocally when ring C is moved
by lever L in the other direction, eccentric B will move from right to
This
left and the other ring C₁ will move eccentric B' downwards.
motion of the two rings and of the two eccentrics is produced by the
aid of levers and shafts L, H, I, N, J, U, shown in Sheets 11 and 16.
In Sheet 11 it will be seen that by moving forward lever L on the
fixed shaft U, the part H will also move forward carrying the lever I
from right to left, which lever I being fixed on shaft N by means of
a pin will cause this shaft to turn and also the lever J so as to raise
the ring O and eccentric B¹. Lever J has a circular opening to
allow of its moving up and down without interfering with shaft U,
said shaft U being carried on two bearings S and S¹ fixed at one side
on the steam chest, and on the other side on a cast-iron plate uniting
This shaft U does
the bearings P and P¹ at one end of the engine.
not turn it being fixed by means of pins to bearings S. The shaft N
is supported in bearings K and K' shown in Sheets 2 and 3 and fixed
on the flanges of cylinders 1 and 2, and the motion of the clutches m
and m is obtained by means of parts Y and Y₁ set in motion by disc R,
5 see Figures 1 and 5, Sheet 16. These parts Y and Y' are the forks
for imparting sliding motion to the clutches m and m². The disc R
turns on a pivot mounted on shaft U and is set in motion by lever I
operated by hand. When the disc R turns from left to right as shown

page_text: in Sheet 16, Figure 3, the clutches m and m¹ by the aid of forks Y
and Y¹ will connect with the eccentrics B and B', and when the disc R
is turned the contrary way, the clutches m and m' will be disengaged
therefrom. Shaft U may be provided with a spring, one end of which
is fixed on disc R and turns with it, said spring serving both for
coupling or uncoupling.
In Figure 3, Sheet 16, the spring is shown as applied for uncoupling,
the lever being held by a catch or pin on the part uniting P and P
before referred to, by releasing which lever the parts may be readily
uncoupled. In order to couple it is simply necessary to pull the
handle of lever with the right hand and act on lever L cither
with the left or both hands. As shown in Sheet 12 at Figures 8 and 9
the eccentrics B and B have each a convex part on which are fixed
the collars and flat cylindrical part on which the rings C and C' act.
Figure 1, Sheet 12 represents the eccentric B as seen from behind,
while Figure 2 shows the coupling fork and clutch.
Figure 7, Sheet 12, shows a front view of eccentric B with rectangular
cavities 15 in which enter the tenons 16 of eccentrics D shown in
Figures 3, 4, 5, 6, and S, Sheet 12. By means of these tenons when
the motion is reversed excentric D is caused to partake in the motion of
eccentric B, which forces it into its place. These tenons are in width
half the length of cavities 15, and they serve to communicate the motion
to eccentric D from eccentric B. When the motion is reversed, passing,
for example, from position 1 Sheet 18 to position 3 Sheet 19, the eccen-
tric D will not move before eccentric B has reached position 2, Slicet
18, and in passing from position 2 to position 3 the eccentric D is
forced into its place by eccentric B by the aid of tenons 16.
Figures 6 and 8, Sheet 12, represent eccentrics B and D coupled
together; beside eccentric B¹ there is also placed an eccentric D' for
working the cut-off valves of steam chest 2. When it is desired to
work without cutting off the steam the engine may be considerably
simplified and eccentrics D, D', dispensed with, as also the cut-off
valves and parts f and f'; and when it is desired in an engine
furnished with cut-off valves to work temporarily without cutting off
the steam it is only necessary by means of hand wheels V, V, to place
the parts ff, f, f, in such position that the opening of the
passage between these parts and the full part of the steam chest shall
be double the width of the admission opening of the cylinders. In this

page_text: manner the cut-off valves cannot close the opening through which the
steam passes to the second compartment of the steam chest. The ends
of rods a, a', work in brass guides o, o', fixed on the ends of the steam
chests.
There now only remains to describe the metallic packings to be used
in lieu of the ordinary stuffing boxes, and the improvements consist in
preventing the leakage of steam where rods have to work through the
ends of the steam chests and cylinders by the employment of metallic
rings similar to those placed round pistons, instead of using hemp or
packing as usual.
In the Drawings I have shown three kinds of metallic packing
rings in Sheets, 2, 4, and 5.
One form of packing ring is shown in Figures 1 and 2, Sheet 5, for
box 2, in which works the rod a; for this purpose I increase the
diameter of the rod at the desired point, and make a cavity thercat, in
which are placed two iron or steel rings. Each of these rings is made
open, the opening of the one being opposite the solid part of the
other.
The second arrangement of packing ring is shown in Figure 1,
Sheet 5; it consists of two metallic rings of which the exterior part
is made conical instead of cylindrical as before. In this case the
diameter of the rod is not increased, and the joint is made between the
outside of the rod and the inside of the rings. The cover of the box
is also made of conical form on the interior, and it will be seen that
by forcing the cover into the box by means of screws the rings will
be compressed and fit tightly on the rod so as to prevent all leakage of
steam.
The third arrangement of metallic packing boxes is shown in Sheet 1
and Figures 2 and 3, Sheet 4, for the piston rods T, T; these packing
boxes are composed of two open metallic rings placed one beside the
other; these rings are surrounded by four segments, each of which is
as wide as both rings together; the segments press on the rings by
means of four screws fitted in the metallic boxes, a cavity being provided
in the box for the segments. These metallic packing boxes are new,
simple, and will economise space and friction.
Finally, by these improvements I have endeavoured to combine an
engine requiring but little space, possessing simplicity, and having all

page_text: the improvements applied. By giving more length to the cylinders I
can cut off the steam to better advantage, and produce an engine which
will not occupy more room than those considered the most compact
and of the same power. By placing two other double-acting cylinders
in front of the two first, 1 and 2 already described, and uniting the
two piston rods of these additional cylinders to the same sliding parts G
and G' I obtain (supposing these two additional cylinders to be of the
some diameter and length as the first) a twelve horse-power engine, of
which the total length will be about three feet. These additional
cylinders I will term 3, 4, and their slide valves may be operated by
the same eccentrics B, B', D, D¹; for this purpose it is simply necessary
to attach the rods working the valves of steam chests 3 and 4 to each
of the eccentrics B, B', on the opposite side to the first. In this case
the frames F, F, will impart a direct motion to the cut off valves
of steam chests 3, 4, and will be sufficiently guided by the metallic
packing or stuffing boxes of said steam chests. In this case also the
guides fixed on the transverse part uniting the bearings P, P', as well
as said bearings themselves would be dispensed with, the bearings S, S¹,
being carried from one cylinder to the opposite one. The exhaust
for the four cylinders would be through the same chest to which the
exhaust pipe is fixed, and the reversing motion would be the same
as before without any variation.
When four cylinders are employed I may provide each with a double-
acting pump cylinder and work the four pumps by simply lengthening
the slides G, G', in a vertical direction, the pump rods being fixed
to said slides.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Alexander Melville Clark in the Great Seal Patent
Office on the 30th July 1868.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ALEXANDER 3
MELVILLE CLARK, of 53, Chancery Lane, in the County of Middlesex,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Thirty-first day of January, in the
year of our Lord One thousand eight hundred and sixty-eight, in the 3

page_text: thirty-first year of Her reign, did, for Herself, Her heirs and successors,
give and grant unto me, the said Alexander Melville Clark, Her
special licence that I, the said Alexander Melville Clark, my executors,
administrators, and assigns, or such others as I, the said Alexander
Melville Clark, 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, excrcise, 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, AND IN PARTS CONNECTED
THEREWITH," a communication to me from abroad by Charles Julien
Quétil, Engineer, of 29, Boulevart St. Martin, Paris, upon the con-
dition (amongst others) that I, the said Alexander Melville Clark, my
executors or administrators, by an instrument in writing under my,
or their, or one of their hands and seals, should particularly describo
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 Alexander Melville Clark, 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, reference being had to the
twelve Sheets of Drawings hereunto annexed, and to the letters and
figures marked thereon, that is to say :-
This Invention relates to improvements in steam engines, and also
to the arrangement and mode of operating the various parts constituting
the same, including the pistons, steam distribution, improved cut off,
fixed or variable, either by hand or by the aid of the governor, and
an improved reversing motion operated by means of the eccentric, all
of which improvements are applicable to steam engines generally.
One, two, three, four, or more double-acting cylinders may be used
with this improved engine. The Drawings annexed are those of a
steam engine of six horse-power of full dimensions, with the exception
of Sheet 5, where the Figures are shown half size. This engine has
two cylinders indicated by the numbers 1 and 2; each of those
cylinders is provided with a steam chest indicated by corresponding
numbers 1 and 2; each cylinder is double acting, the stroke is four

page_text: inches, the diameter of piston four inches, the number of revolutions
per minute 350, the average pressure of the cylinder about 60 pounds
on the square inch, equal to from five to five and a half atmospheres.
Sheet 1 of the Drawings shows a plan of the engine. A is the
pipe through which the steam is supplied to the governor and to
the engine; E is the exhaust pipe. In this engine the exhaust takes
place between the two cylinders, but it will be understood that the
arrangement of the steam and exhaust pipes may be varied as desired.
The piston rods T, T', pass through metallic packings, although I
may if desired use ordinary stuffing boxes. The cranks are keyed at
right angles to avoid the dead points, the cylinders being placed onc
beside the other. The crank pins are fixed in cast-iron discs X, X, and B,
and work in brasses a and 2¹, which move up and down inside the
slide bars G and G fixed to the rods T and T by means of keys
μ and μ¹. By removing these keys the pistons may be readily removed
at any time at the left of the plan for the purpose of examining
them. The piston rods are screwed in the pistons, which are of cast
metal, or may be fixed by means of keys or otherwise. In the disc ẞ
which occupies the centre of the engine are fixed the ends of the two
crank pins. The parts x, x', are fixed on the driving shaft. The
engine may work either expansively or not, in the latter case the cut-
off
I may be fixed or variable cither by hand or by the aid of the
governor.
The example shown in the Drawings has a variable cut-off by hand
without stopping the engine, which may also be rendered variable by
the aid of the governor by a simple modification herein-after described.
The engine is also provided with a reversing motion which is omitted
in Sheet 1, to prevent complication. When it is desired to have a
variable cut-off operated by the governor, I prefer to place the governor
between the two cylinders, and when the cut-off is to be regulated
by hand, the governor may be placed at any point of the steam pipe.
When the engine is to work at full pressure without any cut-off, it
is only necessary to have two eccentrics B and B', and when the cut-
off is to be used I add two other eccentrics or cams D and D'. The
plan of the engine shows the parts in position for the backward motion.
The crank pin corresponding to cylinder 1 is horizontal and the one
corresponding to cylinder 2 is vertical and raised. The steam is conveyed
to the steam chests by means of pipes entering at the side and centre.

page_text: Sheet 2 of the Drawings represents a side view of the engine. The
frame F is shown as moved horizontally by the expansion eccentric D.
There is also for the other cylinder No. 2 a frame F moved by an
eccentric D' shown in Sheet 1. In Sheet 2, I have for simplification
omitted the parts x, x, and B. In this engine the exhaust takes place
through the piston by channels communicating with the exhaust
channel placed at mid-length of the cylinder and on the side between
the two cylinders. A rod working two valves e, e, also traverses
the whole length of the piston, as shown in Sheet 7. The valve
is closed on that side of the piston on which the steam acts, and open
on the exhaust side. This rod is carried at each end in guides a and a¹
in said piston. The details of this exhaust are shown in Sheet 7.
The piston is cylindrical, and provided with a packing composed of
two metallic rings u and at each end, the joints being on opposite
sides of the piston. When the piston reaches one end of the cylinder
the channels a and a¹ in the piston correspond with the exhaust port
of the cylinder, and when the piston returns the steam continues to
escape through channel 7, which is throughout the whole course of
the piston in communication with the exhaust port of the cylinder.
Sheet 3 shows an end view of the engine; some of the parts which
are sufficiently indicated on the other sheets are omitted in this one,
so as not to complicate the Drawings, and to facilitate the explanation
of the engine. In effecting the distribution of the steam I place the
slide valve as near as possible to the cylinders to ecconomise room,
and also to reduce the length of the channels. By putting the slide
valves in such position with regard to the transverse axis of the cylinder
and exhausting through the piston, I believe to have combined a steam
engine without any objectionable spaces, as it is only the steam which
has been admitted in the cylinder to work the piston that passes out
or exhausts through the piston, while in other steam engines it is not
only this steam which exhausts, but also that contained in the channels
through which the steam passes to the piston.
I will now give details of the steam distribution shown on Sheets 4
and 5. If I use only one double-acting cylinder as in ordinary engines,
I use but one eccentric B, and two slide walves t and t, Sheet 4, which
are in this case mounted on the same rod a, extending the whole
length of the steam chest. With these two small slide valves and the
one eccentric I am able to work the engine without cutting off the

page_text: steam and in either direction, as will be herein-after shown. If it is
desired to have a fixed cut-off I use a second eccentric or cam D,
moving a frame F, Sheet 1, and two other small slide valves and t
carried on the same rod a¹. If a variable cut-off is required to be
operated by hand I use two other small slide valves f and f¹ actuated
by a rod o, turning in the upper part of the guide Z fixed to the steam
chest. This rod o is turned by the aid of a hand wheel V, and as
it moves up and down the two valves and f¹, will approach or recede
from each other by the aid of levers q, q'. If a variable cut-off is
to be obtained by the aid of the governor I dispense with the wheel V,
and instead of screwing rod o to the nut at the top of guide Z I
simply make it slide up and down in said support by the aid of the
governor itself; when the balls fall inwards the rod O will rise, and
when extended it will fall. For this purpose it is simply necessary
to fix a part on the top of the governor as indicated by Figure Z,
at Sheet 8. The mode of attaching the rod O to the part on the top
of the governor may be otherwise arranged. By following out the
motion of the two valves & and f, as shown in Sheet 5 for each position
of the eccentric the distribution of the steam will be readily understood.
This engine may be readily constructed and occupies but little space.
Each slide valve t and t should be twice as wide as the steam port of
cylinder, and in the engine shown the steam ports are two inches long
and half an inch wide, the valves and having a motion of one inch.
The cut-off valves and have only half an inch motion, which is
intermittent and not continuous like that of valves and f, that i
to say, the valves and will move for example for half an inch,
and will remain stationary during a quarter revolution of eccentric D,
which motion is ensured by the form of the said eccentric as will be
readily understood. The variable expansion valves .f, are provided
at the upper and lower parts with small pins or studs running in
grooves made in the steam chest for their reception, although as the
parts ff are already tightly fitted to the steam chest, the pins or
studs may be dispensed with. The steam continually fills the steam
chest between the valves f, f, and when said valves are separated
either by hand or by the aid of the governor, the balls of said governor
also expand, so that the steam may be introduced during a smaller
portion of the stroke of the piston. The steam admission ports may
also be entirely closed when the slides f. f', come in contact with the
abutments of the valve box. When the cut-off is variable the same

page_text: rod which when working at full pressure with a fixed cut-off passes
through the whole length of the steam chest, cannot work the slides t
and on account of the position of the parts f and f, and motion
is imparted to slide valves by another short rod communicating with
the first by means of levers band d, and rods c and e, as shown in
Sheet 2. The eccentric has an opening or slot in the middle for
reversing the motion, by means of which slot I can reverse the motion
by moving the eccentric on the shaft. In Sheet 5, position 2, the
crank is shown in its lowest position, the corresponding position of
the eccentric being also scen. The motion is backward, that is to say,
if I move the eccentric from right to left by any means, so as to
bring it to the position 4, and keep the eccentric in that position
while the crank is still down, the motion is instantly reversed.
render this clear it is only necessary to examine the corresponding
position of the valves in the two positions of the eccentric. It will
be seen that by this motion of the eccentric the steam is immediately
intercepted or prevented from entering on the side of the piston where
it had previously been introduced, and is on the contrary admitted
instantly to the opposite side of the piston, which is necessary and
sufficient for reversing the motion.
To
I will now describe how I change the position of the eccentric
while the eccentric is at work. This as seen in Figure, Sheet 6, is
effected by means of a lever L turning on a fixed point or shaft U
carried in bearings S, Sheet 2. This lever is connected at its lower
part to a ring C in which turns the eccentric B touching only at one
point as seen in Figures 1 and 4, Sheet 9. By moving this ring
through the aid of lever L, the eccentric B may be slid on the shaft as
seen in other Figures of this Sheet. The motion is communicated
from the shaft to the eccentric by means of a coupling piece m, Sheet 1
keyed on the shaft and having a circular tongue 10 shown in Sheet 9,
which tongue according to the position of the eccentric enters
corresponding mortises or cavities 11 and 12 in the eccentric. In the
position 1 of Sheet 9 the motion is backward and the tongue of the
coupling m is entered in the mortises or cavities 12 of eccentric B.
Supposing now by means of a fork the motion is communicated to
coupling m causing it to slide on the shaft so that the tongue is
withdrawn from the eccentric, and that at same time by means of
ever L, the eccentric B is moved forward by the aid of ring C to the
position 3, Sheet 9, the tongue 10 being moved with the coupling by a

page_text: spring or by the aid of the coupling fork, will enter the cavity 11 of
the eccentric and the motion will be then reversed. As soon as by a
slight motion of lever L, the eccentric B has reached the position 2
all the openings for the admission of steam are closed as shown in
Sheet 5, and if the lever L were left in the corresponding position the
_engine would stop, thus it is necessary to bring the lever to that
position when it is desired to stop the engine. By continuing to move
lever L in the same direction the steam will be introduced on the
opposite side to when in the position 1, and the engine will begin to
turn in the opposite direction, and when the eccentric has reached
position 3 the tongue of coupling m will enter the mortise 11 of
eccentric B and the engine will be ready to turn in the other direction.
Even supposing the speed of the engine to be too great, as in the case
fa locomotive, to reverse the motion instantly, two or three turns of
the shaft is sufficient to effect this object by shifting the position of
the eccentric as before mentioned. In this motion in passing from
position 3, Sheet 9, to position 4 the eccentric will bring the ring C
and lever L to the vertical position 4. In this position, which is exactly
the same for the lever as Josition 1, the eccentric turns in the ring C
without any resistance therefrom as it only touches it slightly while
in motion; reciprocally, one can pass from the forward motion to the
backward motion
tion by uncoupling the part m and bringing the lever L
back to the position 6 and coupling anew the part m with the cccentric.
In this bange of position of the lever there is another stopping
position 19 differing from the stopping position 2 which I have before
mentioned in which the eccentric remains as before, but the lever and
ring are changed in position. This reversing motion has the peculiarity
that when the lever L is vertical the engine can go either forward or
backward according to the position of the eccentric on the shaft. There
are also two different positions of the lever at which the engine can be
stopped, one point on one side of the vertical line and the other on the
other side according to whether it is desired to stop when moving
forward or backward. In the positions 2 and 5 it will be readily
seen that the tongue of coupling m cannot enter the eccentric,
and for the purpose of causing it to enter I employ a spring
pressing it constantly against the eccentric. In order to uncouple it
is simply necessary to act on the spring, after which the coupling m may
be again connected with the eccentric by means of the spring when
the eccentric will be moved in position on the shaft, the engine may

page_text: also be readily stopped as in the positions 2 and 5; the tongue of the
coupling cannot enter the eccentric. The lever may also be made to
work between two rings fixed on bearing S, each having a part
corresponding to the stopping positions, while the reversing lever
would be provided with two small tongues operated on by a spring
which are received in recesses at the desired time when it is desired to
stop the engine. In the six horse-power engine the motion of the
valve is so limited and the two stopping points are so near the vertical
that the two slots in the rings might form but onc, while in an
engine of greater power, such as a locomotive, one ring is sufficient
with two recesses. There may, however, be only one stopping point in
all cases with one ring and one recess. If it is only necessary to use
one stopping point then one ring with a slot and one tongue on lever L
would be sufficient. When the motion of the valve is considerable
as is the case of locomotives there is room enough for several mortises
or cavities in the eccentric in which the tongue of the coupling m
can enter, and by fixing the eccentric in different positions on the
shaft it will be possible (as is the case with the Stephenson link) to
vary the course of the slide valve, I could consequently, using the
ordinary mode of distribution of the steam, vary the motion of the slide
valve by means of the improved arrangement of eccentric of this
Invention.
Having explained the action with an engine having only one cylinder
I will now proceed to describe the engine illustrated in the Drawings,
which is a six horse-power engine with two double-acting cylinders
placed side by side. In this engine there is a steam chest 2 for
cylinder 2, arranged exactly the same as steam chest 1, the only
difference consisting in the relative position of the valves with that of
valves,,, . In Sheet 5 is shown the positions for the forward
and backward motion both of the eccentrics and cranks driven by the
two pistons, as well as the corresponding positions of the valves and
pistons. In this double cylinder engine there are two eccentrics B
and B', the two rings C and C₁ for reversing the motion, the one C
moved from left to right by the aid of lever L, operated by hand
horizontally, the other ring C' moves upwards bringing eccentric B to
vertical position and reciprocally, when ring C is moved by lever J.
in the other direction eccentric B will move from right to left, and
he other ring C" will move eccentric B downwards. This motion of
he two rings and of the two entries is proained by the aid of

page_text: reversing levers and shafts L, H, I, N, J, C, C', U, shown in Sheets 2,
3, 6, and 8. In Sheet 6 it will be seen that by moving forward
lever L mounted on the fixed shaft U the part I will also move
forward carrying the lever I from right to left, which lever I being
fixed on shaft N by means of a pin will cause the shaft to turn and
raise the lever J as well as the ring C¹ and eccentric B. Lever Jas
a circular opening to allow of its moving up and down without
interfering with shaft U, said shaft U being carried in two bearings S
and S', fixed at one side on the steam chests and on the other side
on a cast-iron plate uniting the bearings P and P. This shaft U
does not turn, it being fixed in position by means of pins passing through
bearings S. The shaft N is supported in bearings K and K', shown
in Sheet 3, and fixed on the flanges of cylinders 1 and 2, and the
motion of the clutches m and m' is obtained by means of parts Y, Y',
set in motion by disc R. These parts Y and Y are the forks for
imparting sliding motion to the clutches and m. The disc R turns
on a pivot formed on shaft U, and is set in motion by lever operated
by hand. When the disc R turns from left to right as shown in
Sheet 8, the clutches m and m¹ by the aid of the forks Y, Y will
connect with the eccentrics B and B', and when the disc R is turned
the contrary way the clutches m and will be disengaged therefrom.
Shaft U is provided with a spring, one end of which is fixed on disc R
and turns with it, said spring serving both for coupling or uncoupling.
In Sheet 6 the spring is shown as applied for uncoupling the lever 7,
being held by a catch or pin entering a recess made in a part bolted
to the plate uniting and before referred to, by releasing which
lever the parts may be readily uncoupled by the aid of the spring.
In order to couple it is simply necessary to pull the handle of
lever with the right hand and bear on lever 1 with the left. As
shown in Sheet 6, the eccentrics B and B' have each a convex part
o'n which are fixed their straps, and a flat cylindrical part on which
the rings C and C' act.
Figure 2, Sheet 6, represents the eccentric B as seen from behind,
while Figure 3 shows the coupling fork and clutch; Figure 4 shows a
front view of eccentric B with the rectangular cavities 15 in which
enters the tongue 16 of the expansion eccentric D shown in Figures 7,
8, and 9. By means of these Longites when the motion is reversed
eccentric D is caused to partake in the motion of eccentric B, which
forces it into its place. These tongues are equal in width to half of

page_text: ength of cavities 15, and they serve
motion to eccentric D from eccentric B.
to communicate rotary
When the motion is reversed,
passing for example from position 1, Sheet 9, to position 3, the
expansion eccentric D will not move before eccentric B has reached
position 2, and in passing from position 2 to position the D
is forced into its place by eccentric B by the aid of tongues 16.
Figures 5, 6, and 8 represent eccentrics B and D coupled together.
Besides eccentric B' there is also an expansion eccentric D' for working
the cut-off valves of cylinder 2. If it is desired to work without
cutting off the steam, the eccentric may be considerably simplified, the
cut-off valves, and parts and being dispensed with. When
it is desired, in an engine furnished with cut-off valves, to work
temporarily without cutting off the stean it is only necessary by
means of hand wheels V and V₁ to place the parts f, fr, ƒ³,
in such position that the opening between these parts and the full
part between the steam chest shall be double the width of the admission
opening through which the steam passes to the second compartment
of the steam chest. The ends of rods a and a work in brass guides o
and o fixed on the ends of the valve boxes.
By the aid of these improvements I combine an engine requiring
little space, possessing simplicity, and having all the improvements
applied. By giving more length to the cylinders I can cut off the
steam to better advantage and produce an engine which will not
require more room than those considered as the most compact and of
the same power.
By placing two other double-acting cylinders in
front of the two first, 1 and 2, already described, and uniting the rods
of these additional cylinders to the same sliding part G and G¹ I obtain
(supposing those two additional cylinders to be of the same diameter
and length as the first) a twelve horse-power engine of which the total
length will be about three feet. Calling these additional cylinders 3 and
4 their slide valves will be moved by the same eccentrics B, B', D,
1, for this purpose it is only necessary to attach the rods working
the valves of steam chests 3 and 4 to each of the eccentrics B and
B on the opposite side to the first. In this case the frames F and
will give a direct motion to the cut-off valves of steam chests 3
and, and will be sufficiently guided by the metallic packings or
stuffing boxes of those steam chesis the guides fixed in the transverse

page_text: part uniting the hearings P and P as also these bearings woult
dispensed with the bearings S and S' being carried from one cylinder
to the opposite one. The exhaust for the four cylinders would he
through the same box to which the exhaust pipe is fixed and the
re sing motion would be the same without any variation. When
employing four cylinders I may provide each with a double-acting
pump cylinder and work these pumps by simply lengthening slides G
and G in a vertical direction on which slides the pump rods would
be placed.
When exhausting through the piston I may if desired dispense
with channels a, a, Sheet 7, and place small projecting stems on the
outside of valves, which at the end of each stroke would abut
against the covers of the cylinders and close the valves. In cases
where it is desired to cut off at more than half the stroke (for ex-
ample at three-fourths), the eccentric D may be replaced by one keyed
at right angles to eccentric B for imparting the same motion to the
slide valves, P, as that of valves b, t. The valves &,, would
also have the same extent of motion as t, t. The openings between
the parts ff, and the fixed parts or abutments of the valve box
would be equal in width to the stroke of the valves when working
at full pressure, and the valves,, would also be as wide as
valves t, t¹. By varying the position of the parts f, f', so as to
have openings of less width the desired degree of expansion is ob-
tained. In the engine herein described of six horse-power the stroko
of the slide valve is one inch only. In a locomotive or marine engine
a longer stroke would permit of several mortises or cavities being
made in eccentric B to enable it to be stopped in different positions
on the shaft and of varying the stroke of the slide valve with regard
to that of the ordinary slide of locomotives. Thus I not only use
two eccentrics instead of four for reversing the motion but I am also
enabled to dispense with the Stephenson locomotive slide or link with-
out changing the actual mode of distributing the steam in locomotives.
I may also modify the mode of reversing the motion as follows:-
Immediately the tongue 11 of coupling m leaves eccentric B the latter
becomes loose on the shaft and consequently, ceases to turn therewith,
supposing this should result in sometimes preventing the eccentric
being presented to ring C in a suitable position to he moved hori-
zontally, I remedy this by causing the eccentric B to turn with the

page_text: shalt. For this purpose I slighly enlarge the shaft at the point wher
the eccentric is placed so as to obtain a flat surface above and below
as shown in Figure 1, Slicet 10, for guiding the eccentric in it
sliding motion, and at same time always acts for the purpose o
5 turning the eccentric.
Figure 2, Sheet 10, shows the form that may be given to the part of
the eccentric B on which the ring C acts, while Figure 3 in the same
sheet shows the improved form of said ring C. This form is necessary,
as the ring is always required to act on the same side of eccentric B
in order that the latter may change in position on the shaft and pass,
for example, from position 4, Sheet 9, to position ( in the same Sheet.
It will be scon that by this arrangement the parts not required to
touch in the change of position escape one from the other. In order
to obtain a more perfect guide for the eccentric and to prevent its
slipping further along the shaft than is desired I employ two rings
intersected in the manner shown at Figures 4, 5, 6, Sheet 10. Figure 4
shows the backward motion; Figure 5, the dead point; and Figure 6
the forward motion. For this purpose I cast two parts ", b, on the
eccentric; the round part of A is acted on by ring A, and the round
part by the ring B. E is the eccentric on which is fixed the strap C.
The two projecting parts a, b, are placed in different planes, and the
rings A, B, are rivetted at their point of intersection. The upper and
lower paris of the rings may be omitted and the mid parts united so
as to form a frame capable of hcing guided horizontally. I may also
dispense with the rings and use a coupling for guiding the eccentric,
which is placed in an oblique position, as shown in Figures 5, 7, and 10,
Sheet 11. An examination of Figure 5 will show that by sliding the
tongue T into the eccentric the latter may be moved from right to left,
the face i of tongue T acting on the eccentric, while by disconnecting
tongue T from the eccentric the face g of said tongue T will move the
cccentric from left to right. As the tongue always remains in the
mortise c of the eccentric, as seen in the other Figures of Sheet 11,
he latter is always kept in place thereby, and thus serves as a key
or fixing it to the shaft; it in fact forms a movable key enabling the
ccentric to move backwards and forwards in a direction at right angles
o the length of shaft R. The coupling M is
haft by means of keys f, g, on which it slides
he eccentric is held in place by means of two
further fixed on the
and turns therewith.
rings D, E, the latter
eing reduced at its upper part so as to fit under the projection a formed

page_text: on the eccentric, and at same time permit of mortise c having the
necessary length. Figures 1 and 2 represent the two eccentrics in
position for the forward motion, and Figures 3 and 4 for the backward
motion. Figure 11 shows the arrangement by means of which the
couplings are slid on the shaft for moving the eccentric. It will be
scon that by pulling rod X in one direction the couplings will be dis-
connected from the eccentrics, the reverse effect taking place on its being
pulled in the opposite direction. It will also be seen that the eccentric
is caused to turn with the shaft by means of a flat part formed
thereon in contact with the fat part of the slide. Figures 9 and 10
show a mode of applying the eccentric on the round part of a shaft
without reducing it at that point. In this case the ring D is provided
with a tongue 4, Figure 9, which is received in a mortise made in
the lower part of the eccentric, the length of which mortise is equal to
the width of the tongue plus the degree of eccentric motion required.
In this manner the eccentric will be caused to turn with the shaft by
means of tongues T, 4, the former of which also holds it in place. The
improvement consists in obtaining with this slide a constant backward
and forward movement. In Figure 2 the diameter U, Y, of the eccentric
is shown as inclined to an angle W, S, Y, corresponding to the forward
motion indicated by the line S, O', which shows the distance between
the centre of the shaft and the degree of horizontal motion of the
eccentric. The eccentric slide being in the vertical position shown in
Figure 2 it will be seen that by sliding the eccentric on the shaft the
centre o will he moved parallel to the centre S of the shaft, so that
point o will be always opposite point o', and that consequently the
distance S, O', or advance, will be always the same. In Figure 4 it
will be seen that the advance is exactly the same both for the forward
and backward motion. The levers J, J', serve to transfer the movement
of the eccentric bars to the arms K, K', operating the slide valve rods
in locomotives. In other engines the eccentric bars act directly on the
slide valves without the aid of intermediate levers. The forks for
moving the couplings are liable to great wear on the sides, and it is
preferable in lieu thereof to employ a bar I, Figure 10, which is suspended
from and operated by the levers, and bears with only slight friction on
the sides of the grooved coupling. The friction being thus equally
distributed over the ring it will wear less quickly than the forks. I may
also produce a variable cut-off by means of the governor by placing the
axis of wheel V, Figure 11, in communication with said governor.

page_text: The couplings M, M', are thus caused to partake in the motion of
the balls of the governor, the eccentrics being consequently acted on
so as to regulate the cut-off by varying the motion of the slide
valvc.
In Sheet 12 I have shown some modifications in the system of steam
distribution. In order to shorten the cylinders and pistons P, P¹,
instead of having the exhaust through the piston at a single orifice
placed at the centre of the cylinder I make the piston solid and
exhaust through two openings one at each end of the cylinder placed
between the two cylinders in a casing just opposite the admission
orifices. Four small slide valves a, b, c, d, are placed in this casing
serving for the exhaust of the two cylinders. Motion is communicated
directly from the eccentrics to the rods working the valves t, t, e, f,
which communicate motion to the rods of exhaust valves by means
of levers G, G¹, mounted on a projecting part of the cylinder covers.
The above orifices may further be made in each of the covers of the
cylinders and placed in communication with the exhaust pipes in
which are placed discs for opening and closing the exhaust at the
desired times set in motion by parts fixed on the piston rod.
There now only remains to describe the metallic packings to be
used in lieu of the ordinary stuffing boxes to prevent the leakage of
steam where rods have to work through the ends of the steam chests
or cylinders. These packings consist of metallic rings similar to those
placed round pistons which are used instead of hemp or packing for
the purpose as usual.
In the Drawings I have shown three kinds of metallic packing
rings in Sheet 4, one form of packing is shown in Sheet 4 in which
works the rod a, the diameter of the rod being increased at the
desired point and a cavity made thereat in which are placed two iron
or steel rings. Each of these rings is open and the opening of one
is opposite the solid part of the other.
The second arrangement of packing is also shown at g, g', Sheet 4.
It consists of two metallic rings of which the exterior part is made
conical instead of cylindrical as in the first instance. In this casc
the diameter of the rod is not increased and the joint is made
between the exterior part of the rod and the inside of the rings. The

page_text: cover of the box itself is made of conical form on the inside, and it
will be seen that by forcing the cover into the box by means of
screws the rings will be compressed and fit tightly on the rod so as
to prevent all leakage of steam.
The third arrangement of metallic packing is also shown in Sheet 4,
in which the piston rods T and T work. These packings are
composed of two metallic rings 1, 2, placed one beside the other;
these rings are surrounded by four segments, each of which is as
wide as both rings together; these segments press on the rings by
means of four screws fixed in the metallic boxes, a cavity being
left in the box for the segments; these metallic packing boxes will
economize space and friction.
Having described the nature of this Invention and the manner of
performing the same, I declare that what I claim as the Invention
to be protected by the hcrcin-before in part recited Letters Patent,
is,.
1st. The combination and arrangement of parts comprising the
improvements in steam engines described and illustrated in Sheet 1,
2, and 3 of the accompanying Drawings, the improvements being
applicable to all kinds of motive-power engines, whether stationary,
locomotive, marine, or other engines.
2ndly. I claim more particularly the arrangement of the eccentric,
whereby it may be made to perform the same functions and servo
the same purposes as the Stephenson or Polonceau slide, that is to
say, 1st, for reversing the motion; 2ndly, for varying the expansion
while working, either by hand or by the aid of the governor, or by
means of a ring or rings or inclined wedge, or in other suitable
manner, all as herein-before described.
3rdly. I claim the mode of distribution cither when working at
full pressure or with a fixed or variable cut-off regulated by hand;
or by the aid of the governor, as and for the purpose described and
as illustrated in Sheet 4 of the accompanying Drawings.
4thly. I claim exhausting through the piston, and at the middle
of the cylinder in the manner described and illustrated in Sheet 7
of the Drawings.

page_text: 5thly. I claim the mode of distributing and exhausting the steam
described and illustrated in Sheet 12 of the Drawings.
In witness whereof I, the said Alexander Melville Clark, have
hereunto set my hand and seal, this Thirtieth day of July, in
the year of our Lord One thousand eight hundred and sixty-
night
A. M. CLARK. (L.S.)