IMPROVEMENTS IN SLIDE VALVES AND VALVE GEAR FOR STEAM ENGINES
Year: 1862

page_text: LETTERS PATENT to John Franklin Allen, of the City, County, and
State of New York, in the United States of America, Engineer, for the
Invention of "IMPROVEMENTS IN SLIDE VALVES AND VALVE GEAR FOR
STEAM ENGINES."
Sealed the 4th July 1862, and dated the 24th April 1862.
PROVISIONAL SPECIFICATION left by the said John Franklin Allen at the
Office of the Commissioners of Patents, with his Petition, on the 24th
April 1862.
I, JOHN FRANKLIN ALLEN, of the City, County, and State of New York,
in the United States of America, Engineer, do hereby declare the nature of
the said Invention for "IMPROVEMENTS IN SLIDE VALVES AND VALVE GEAR FOR
STEAM ENGINES," to be as follows, that is to say:-
The said Invention consists in the construction of a slide valve when
adopted only to perform a single office either of admitting or of releasing the
steam, in form similar to the usual cup valve, having a cavity in it, which is
open only on its face. The valve seat is elevated above the bottom of the
chest, and terminates at such distance from the port that when the front end
of the valve commences to uncover the said port the cavity in the valve will
commence to overhang the edge of the seat, whereby two communications
will be opened from the chest into the cylinder passage, and the steam can
enter past the front end of the valve, and also through its cavity.
To increase still farther the amount of opening two valves may be arranged
for each port or steam passage, whereby four communications are opened

page_text: simultaneously into each end of the said cylinder. When the valve performs
the double purpose of admitting and releasing the steam a duct or passage is
formed, which passes over or around the exhaust cup, and is independent of it.
The two ends of this duct open on the face of the valve at equal distances in
front of and behind the exhaust cup respectively. The position of the edges
or ends of the valve seats are made such relatively to the ports that when the
valve is moved forward so that its rear end uncovers the port, the front end
of the passage or duct will overhang the front edge of the seat about as far as
the end of the valve has opened the port, whereby steam can enter the rear
end of the cylinder both past the end of the valve, and also at the same time
through the passage or duct in the valve, and these two passages for the entry
of steam into the one end of the cylinder will be opened and closed nearly
simultaneously by the movements of the valve. By reason of the symetrical
form of the valve and seat steam will be admitted to the other end of the
cylinder, when the valve is moved back by entering the port both past the
front end of the valve, and also through the passage or duct by the rear end
of the said passage overhanging the rear edge of the seat.
The said Invention consists, secondly, in the employment of separate valves
for admitting and for releasing the steam in and out of the cylinder; the
valves for releasing the steam being located in cavities formed between the
steam chest and the cylinder, and in giving to the induction and eduction
valves movements wholly distinct from each other, so that each shall perform
their respective functions without in any manner affecting or being affected by
the movements of the other. By which arrangements any amount of cut-off
may be given to the steam valves, and at the same time the correct exhaust
action will, under all circumstances, be maintained.
The said Invention further consists in the arrangement of the valve gearing
in that class of steam engines in which the steam and exhaust ports are
opened and closed by separate valves in such a manner as to give to the steam
valves a slow motion after the ports have been covered, and at the same time
to give to them a motion while the ports are open more rapid than would be
imparted to them by the motion of the excentric direct, aud further, to effect
each of these results in combination in a much higher degree than has hitherto
been attained; and also to effect them in nearly the same degree, whatever
the throw of the excentric may be, and at whatever point in the stroke the
steam may be cut off. For this purpose an excentric rod is employed, which
at a short distance from the excentric is divided into two rods, which are
attached respectively to arms secured to separate rock shafts, by the vibration
of which said rock shafts motion is communicated through other arms and

page_text: rods to the valves for admitting the steam at the opposite ends of the cylinder
independent of one another. By the arrangement of the arms on the rock
shafts and their respective motions through any desired portions of the circle,
we obtain after the familiar principle of the toggle joint, a more slow or more
rapid motion than that of the excentric rod, which can be imparted to the
valve or valves, which are operated by one rock shaft without being in any
manner affected by the similar motion to be given to the valve or valves
which are operated by the other rock shaft. These entirely independent
movements of the different valves are derived from the revolution of a single
excentric. The movements of the exhaust valve or valves are derived from the
same single excentric, but are nevertheless wholly distinct from those of either
of the said induction or steam valves, and are obtained from the vibration of a
separate arm secured on one or on cach of the aforesaid rock shafts, which is
caused to vibrate through such an arc as to give the required movements.
The excentric is for this purpose secured to the crank shaft, so as to cut off.
the steam at the desired point of the stroke. To the excentric strap two
excentric rods are attached connected to separate arms respectively, which are
secured on independant rock shafts, one of which passes through the other, so
as to have a common centre. On the end of each rock shaft other cranks or
arms are fastened, communicating through suitable rods motion to the valves
on both ends of the cylinder independently of each other. The position of
these arms which work the valves are such that said arms operate the valves
for the purpose of apening or closing the ports while the same travel a part
of an arc, having relatively to the length of arc passed over a very large versed
sine, and act upon the valves after the ports have been closed while travelling
through that part of an are where the versed sine diminishes, while the distance
of the are travelled through by the arm increases, and consequently only very
little motion is derived in proportion to the amount of travel of the arm. This
accelerated motion to one or more valves while opening or closing the port on
one end of the cylinder, at the same time that the valves covering the port on
the other end of the cylinder receive a very slow motion while being both
driven from one and the same single excentric, we obtain from the arrange-
ment of the arms working independent of each other on the opposite sides of
the centre line which passes through the centre of motion of the rock shafts, and
through the centre of the slide valve rods. On either of the crank shafts an
arm or lever is attached, connected through a suitable rod with the exhaust.
valves. This arm is placed in such a position as to work said exhaust valves in '
the usual manner, but when said exhaust valves are separated then they must
be operated by separate arms placed on each of the rock shafts.

page_text: This Invention further consists in the combination of a vibrating lever or
"link," operated by a single excentric; when these are so arranged that the
horizontal and perpendicular throws of the excentric combined produce in
the aforesaid lever or link movements possessing the characteristics of the
movements of that part of the well-known Stephenson's link motion, which is
termed the "link." And, further, in the construction of said link in such a
manner that while the steam valves are moved by any part of said link, which
will cause them to effect the desired cut off, the exhaust valves shall always
receive motion from that part of the same link which is best suited to give
them correct action. For this purpose a curved lever or "link" is pivoted
centrally by a fulcrum pin to the end of a sustaining rod hinged to a fixed pin.
This lever or link is attached to or forms part of the strap of an excentric,
which is secured to the main shaft of the engine. The link is slotted or
mortized through nearly from end to end, in which said slot two sliding blocks
are held, which can pass each other. One of these blocks is connected
through a rod and suitable arms with the exhaust valves, and is fixed at a
point in the link, from which in connection with the said arms or other
gearing it will give to the said exhaust valves the correct motion. The other
block is connected to a rod, to which a short distance from the link another
rod is attached. These two rods are attached to separate arms secured to
separate and independant rock shafts, one passing through the other, so as to
have a common centre of motion. On the other ends of these rock shafts
other arms are attached communicating through suitable rods motion to the
steam valves on each end of the cylinder. The position of these arms (con-
nected with the steam valves) above and below the centre line running
through the centre of the rock shafts and the slide valve rods is similar, and
the manner of operating the valves is equal to the arrangement above
described, where said arms are worked by means of a single excentric. The
portion of the piston's stroke during which the steam valves will remain open,
will increase in proportion as the block which works said steam valves
occupies parts of the link more remote from the fulcrum pin. The block from
which the steam valves derive their movements being separated from and
working independent of the block from which the exhaust valves derive their
movements, any position of the block operating the steam valves, and con-
sequently the extent to which expansion may be advantageously carried, will
not interfere with the correct action of the exhaust valve or valves, as would
be the case if the motion of the steam and exhaust valves was taken from one
and the same block or point in the link.
In stationary steam engines the point or position of the block in the link

page_text: from which the steam valves receive their motion can be adjusted by the
action of a governor, by connecting the governor rod with said block, whereby
the different degrees of expansion according to the load on the engine will be
regulated.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said John Franklin Allen in the Great Seal Patent Office on tho
23rd October 1862.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JOHN
FRANKLIN ALLEN, of the City, County, and State of New York, in the United
States of America, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Twenty-fourth day of April, in the year of our Lord
One thousand eight hundred and sixty-two, in the twenty-fifth year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me, the
said John Franklin Allen, Her special license that I, the said John Franklin
Allen, my executors, administrators, and assigns, or such others as I, the said
John Franklin Allen, my executors, administrators, and assigns, should at any
time agree with, and no others, from time to time and at all times thereafter
during the term therein expressed, should and lawfully might make, use,
exercise, and vend, within the United Kingdom of Great Britain and Ireland,
the Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN
SLIDE VALVES AND VALVE GEAR FOR STEAM ENGINES" upon the condition (amongst
others) that I, the said John Franklin Allen, my executors or administrators, by
an instrument in writing under my or their hands and seals, should parti-
cularly 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 monthis next and immediately
after the date of the said Letters Patent.
NOW KNOW YE, that I, the said John Franklin Allen, do hereby declare
the nature of the said Invention, and in what manner the same is to be per-.
formed, to be particularly described and ascertained in and by the following.
statement thereof, that is to say :-
The object of this Invention is, first, to give to the steam a more free-
passage to and from the cylinder, and to effect' the opening and closing of the

page_text: ports with greater rapidity than has usually been done, so that, especially at
high velocities of the piston, the boiler pressure of the steam may be obtained
in the cylinder at the commencement of the stroke, and the highest pressure
reached may be maintained during the continuance of the stroke, and up to
the point of suppression, and that in non-condensing engines back pressure
above that of the atmosphere may be more completely avoided, while at the
same time a large reduction is made both in the size of the valves employed,
and in the motion given to them.
Secondly, to perform the two operations of suppressing the steam and of
releasing and compressing it, in such manner that neither shall at all interfere
with or modify the other.
Thirdly, to obtain a high degree of simplicity in the parts and movements
which are employed for effecting these results.
The nature of this Invention consists, first, in the employment of a valve
which, in that form of it which is adapted to perform only the single office of
admitting or of releasing the steam, has a cavity in the face, and in that form
which is adapted to perform the double office of admitting and releasing the
steam, has a passage over the cup, which valve, moving on a seat of cor-
responding form, uncovers at the same time two openings for the passage of
the steam into one port.
In steam engines it is desirable to uncover a large area of steam port or
passage by a slight movement of the valve, especially at that part of its move-
ment where it is commencing to uncover the port or passage, and also to
close the same as quickly as possible, whereby, in the case of admitting and
cutting off the steam, the wasteful effects of wire drawing are in a great
measure avoided, and in "exhausting" speedy release is attained.
In view of these considerations I construct the valve as shewn in Figure I.,
which represents the cross section of the steam chest, and of a valve adapted
only to perform a single office, either of admitting or releasing the steam. The-
valve (A) is in form similar to the usual cup valves, having a cavity (a) in it,
which is open only on its face. The valve seat (B) is elevated above the bottom
of the valve chest (C), and terminates at such distance from the passage (P), that
when the front end of the valve (A) commences to uncover the said passage the
cavity (a) in the valve will commenco to overhang the edge () of the seat,
whereby two communications will be opened from the chest into the cylinder 3
passage (P), and steam can enter past the end of the valve (A), and also through
its cavity (a), which cavity when the valve is wide open overbangs equally the
passage (P) and the edge (b) of the seat. The mouth of the passage (P) adjacent
to the valve seat is widened, so that when the valve (A) is wide open the

page_text: aggregate width of the two passages thus afforded shall equal the general
width of the passage (P). The seat (B) may be furnished with wings on the
sides for the support of the side edges of the valve.
From the foregoing description it is evident that the valve (A) opens or
closes double the area of steam port that it would do with the same movement
if it opened communication with the port only by its end uncovering the
same, or that it would do if, after the manner of many steam pumps, it
opened such communication only by the cavity (a) overhanging the edge of
the seat.
The application of this Invention as an eduction or "exhaust" valve will
be readily understood by imagining the passage (P) open to the atmosphere,
and the valve (A) as lying in a chamber open to one end of the cylinder.
Instead of elevating the valve seat above the surface of the chest bottom, as
above described, an excavation or depression of the surface adjacent to the
termination (6) of the seat sufficient to allow proper passage into the cavity of
the valve is an equivalent construction.
To increase still further the amount of opening, two valves may be arranged
for each port or steam passage, as represented in Figures IV. and VIII.,
which illustrate the application of two valves for admitting steam, constructed
as above described, to each end of the cylinder, and shewing the arrangement
of the ports whereby four communications are opened simultaneously into
each end of the said cylinder.
In these Figures (A', A", A, and A¹¹¹¹) represent the four valves (B¹, B",
B, and B) their respective seats terminating respectively at (6¹, bu, b,
and ); (a¹, a, a, and a;) are the cavities in the valves. Branch pas-
sages (p, ) lead from the valves (A¹, A",) into the main passage (P1), and
similar branch passages (p, p,) lead from the valves (A", A,) to the main
passage (P). The valves (A", and A",) are about to open, and a movement of
the same to the left from the indicated position will open four communi-
cations into the main port (P"), two past the right-hand ends of the valves (A'
and A), and two through their cavities (a¹¹¹ & a¹¹¹).
Figures II. and III. show cross sections of a valve and part of a cylinder
where the valve performs the double office of admitting and releasing the
steam. These Figures exhibit this form of the valve in two positions. In
Figure II. the valve is about (by a movement to the right) to open two.
passages into the port leading to the left-hand end of the cylinder,, and in
Figure III. is has already, by a movement to the left, opened wide two
passages into the port leading to the right-hand end of the cylinder. This
modification is designed as a substitute for the ordinary cup or D valve, and.

page_text: can be used only in the same situations in which that could be employed.
Its advantage and superiority consists in this, that a valve of a given size
opens by a given movement an area for the admission of steam twice as great
as it would do if in the ordinary form.
Figs. III., III., and III., show cross sections of a modification of the above
valve and part of a cylinder, where also the valve performs the double office
of admitting and releasing the steam. The valve in these Figures is con-
structed of two cups a and b, the cup b being placed inside the cup a, thereby
leaving a duct or passage between the two cups. The cup bis mounted on
the valve stem in such a manner as to be capable of remaining stationary
for a second after the outer cup a has started; in other words, the cup bis
capable of having a slight endway motion in and independent of the outer
cup a. These Figures III., III, and III. exhibit this form of valve in
three positions. In Fig. III. the valve is at the extreme left of its action,
and has opened two passages into the port F' leading to the right-hand end of
the cylinder, and in Fig. III. the valve has commenced a movement to the
right, thereby cutting off the steam from the port F¹, that is, the outer cup a,
baving moved forward a short distance without moving the inner cup b, has
cut off the induction steam at the two points c and d, at the same time the
inner cup not having moved will leave the port F at the other end of the
cylinder and also the middle or eduction port G fully open, so that the steam
will have free exit from the cylinder. The entire valve, that is, the two
cups a and b, will then continue their motion to the right until they arrive at
the position shewn at Fig. III., when it will have opened wide two passages
into the port F leading to the left-hand end of the cylinder. On the return
stroke a similar operation will take place, and steam will be cut off from the
port F, while the cup 6 will keep open the eduction port G and the port F.
for the escape of the steam from that end of the cylinder. In these Figures
E is the valve seat, and F and F¹ the two ports or passages leading therefrom
to the rear and front ends of the steam cylinder respectively; G is the exhaust
or eduction passage. The valve seat E is elevated above the bottom of the
chest, and terminates at c and d at equal distances from the ports F and F
respectively. The valve being constructed, as before mentioned, of two cups a
and b, a duct or passage is formed between them, and steam can therefore
pass over or around the exhaust cup f, and is independent of it. The two
and h of this duct open on the face of the valve at equal distances in
front and behind the exhaust cup f respectively. The distance between the
ends g and of the passage should be at least so great that the said passage
1
cannot at any time open communications between the ports F and F¹. The
ends

page_text: extreme length of the valve J must be such as to afford sufficient sliding
surface between its ends and the ends g and h of the passage 1 to pack steam-
tight when these parts are on the seat, but these surfaces must be less in width
than the ports F and F by the amount necessary for the said ports to be
opened for the entry of steam. The valve J receives motion in the usual
way by a rod k. The position of the edges c and d of the seat E are such
relatively to the ports F and F, that when the valve is moved forward so
that its rear end uncovers the port F, the front end h of the passage / will
overhang the front edge of the seat about as far as the end of the valve has
opened the port F (see Figure II.), whereby steam can enter the rear end of
the cylinder both past the end of the valve, and also at the same time through
the passage or duct in the valve, and these two passages for the entry of
steam into the one end of the cylinder will be opened and closed nearly
simultaneously by the movements of the valve. By reason of the symmetrical
form of the valve and seat, when the valve J is moved back steam will be
admitted to the front end of the cylinder (see Figure II.) by entering the
port F, both past the front end of the valve, and also through the passage
by the rear end of the said passage overhanging the rear edge c of the
seat.
The greatest value of this Invention is obtained in its application to engines
which are furnished with a "link" motion or other cut-off gear which gives
to the valve a movement comparatively slow at the points of cut-off, as the
increased area of port closed by a slight movement of the valve which is
obtained by this said Invention lessens the waste which the slow closing of the
port occasions by wire-drawing the steam.
This Invention consists, secondly, in the employment of separate valves for
admitting and for releasing the steam in and out of the cylinder, the valves
for releasing the steam being located in cavities formed between the steam
chest and the cylinder, and in giving to the "induction" and "eduction"
valves movements wholly distinct from each other, so that each shall perform
their respective functions without in any manner affecting or being affected
by the movements of the other. When slide valves, which perform the several
offices of admitting, cutting off, and releasing steam to and from the
cylinder are operated by a "link" motion, or a similar variable cut off gear,
and are so connected with the same as to cause the said valve to cut off the
supply of steam at any earlier period of the piston's stroke, than the points
which correspond nearly with the end of the piston's stroke, then the action
of the valve in exhausting is such that effects arise prejudicial to economy in

page_text: the use of steam, because excessive exhaust lead is produced at the acting
end of the cylinder, while at the opposite or non-acting end excessive
cushioning occurs.
For the purpose of obviating this difficulty one or more steam or "induction"
valves, and one or more exhaust or "eduction" valves are employed in this
Invention, the said steam valves being separated from the said exhaust valves
and receiving motions independent of those given to the latter, said "educ-
tion" valves being located in cavities formed between the steam chest, and
the cylinder as represented in Figures IV. and VIII. where A¹, A", and
A, A, are the steam valves working on surfaces made in the steam chest
D, as above described. H, H', are the exhaust valves moving in suitable
recesses P1, P, in the bottom of the steam chest, and sliding on the surfaces
E, E, on the cylinder C. On each end of the cylinder two openings, F¹, F",
and G, G", are made. The openings F, F", forming a passage between
the ends of the cylinder, and the passages or recesses P1, P", in the steam
chest, while the openings or ports G, G", communicate with the exhaust
opening G, leading to the condenser or atmosphere. The exhaust valves II,
H', are formed similar to the usual cup valves, and are connected to a valve
rod w, passing through the ports F¹, F", as well as through the exhaust
passage G, and receive through said rod a motion independent from the
motion given to the steam valves, by which arrangement any amount of cut off
may be given to the steam valves, and at the same time the correct exhaust
action will under all circumstances be maintained.
This Invention further consists in the arrangement of the valve gearing in
that class of steam engines in which the steam and exhaust ports are
opened and closed by separate valves, in such a manner as to give to the
steam valves a slow motion after the ports have been covered, and at the same
time to give to them a motion while the ports are open, more rapid than would
be imparted to them by the motion of the excentric direct, whereby also it
becomes practicable to employ much smaller valves, and further to effect
each of these results in combination in a much higher degree than has hitherto
been obtained, and also to effect them in nearly the same degree, whatever
the throw of the excentric may be, and at whatever point in the stroke the
steam may be cut off. For this purpose an excentric rod is employed, which at
a short distance from the excentric is divided into two rods, which are attached
respectively to arms' secured to separate rock shafts, by the vibration of which
said rock shafts motion is communicated through other arms and rods to the
valves for admitting the steam at the opposite ends of the cylinder independent

page_text: of one another. Two excentrics set in the same position on the shaft or
two separate straps on one excentric would be an equivalent construction for
the split excentric rod.
By the arrangement of the arms on the rock shafts, and their respective
motions through any desired portion of the circle I obtain after the familiar
principle of the "toggle joint" a more slow or more rapid motion than that
of the excentric rod, which can be imparted to the valve or valves without
being in any manner affected by the similar motion to be given to the valve or
valves, which are operated by the other rock shaft. These entirely independent
movements of the different valves are derived from the revolution of a single
excentric. The movements of the valve or valves for exhausting the steam
are derived from the same single excentric, but are nevertheless wholly distinct
from those of either of the said inductive valves. The movements of the said
eduction valves when derived from the revolution of an excentric are obtained
from the vibration of a separate arm secured on one or on each of the aforesaid
rock shafts, and caused to vibrate through such an are as to give the required,
movement to said valves..
Figure IV. represents parts of a steam engine, in which the aforesaid,
separate movements of the said induction and eduction valves are derived from a
single excentric, and where the steam is suppressed at a fixed point of the
stroke. Figure V. is a diagram explanatory of the movements of the vibrating
arms shown in Figure IV.
In the above mentioned Figures K represents the excentric secured to the,
crank shaft (L) so as to cut off the steam at the desired point of the stroke; (J).
is the excentric strap, to which two excentric rods (M and N) are attached,
connected to separate arms or levers R, S, respectively. These armis (R, S,);
are secured on independent rock shafts, one of which passes through the other,
so as to have a common centre.. On the end of the shaft, on which the arm,
(R) is fast, an arm (R¹) is attached communicating through the rod (M) motion
to the valves (A", A"",) at one end of the cylinder, and on the end of the shaft
on which the arm (S) is fast, an arm (S') is attached communicating through,
the rod (N¹) motion to the valves (A¹, A",) at the other end of the cylinder, the
positions of the arms (R and S) relatively to their corresponding arms (R¹ and
S¹) are such that said arms (R¹, S',) operate the respective valves for the
purpose of opening or closing the ports while the same travel a part of an
are, having relatively to the length of the are passed over a very large versed.
sine, and that said arins act upon the valves after the ports have been closed
while travelling through a part of the arc, where the versed sine diminishes
while the distance of the are travelled through by the arm increases, and

page_text: consequently only a very little, and a very slow motion is communicated in
proportion to the amount of travel of the arm or lever. This accelerated
motion to one or more valves, while opening or closing the port on one end
of the cylinder, at the same time the valves covering the port at the other
end of the cylinder receive a very slow motion, while being both driven from
one and the same single excentric. I obtain from the arrangement of the
arms (R, S',) working independent of each other on the opposite sides of the
centre line (X, X',) (see Figure V.)
In Figure IV. the piston is represented at its bottom stroke, and the valves
(Ani A) communicating with the passages (pp) leading to the bottom
of the piston just about to open. By reference to the Diagram, Figure V., it
will be perceived that the excentric stands at the point marked (1) on the shaft,
while the arm (R'), to which the valves (A", A,) are connected, stands at the
point of its circle marked (1), below the centre line (X, X',) which represents
the line passing through the centre of motion of the rock shaft, and through the
centre of the slide valve rods, and in which said position of the arm (R',) the
valves (A, A,) are just ready to open the ports (1, 1). When the
excentric moves to point (2) around the shaft, the arun R' travels to point (2)
on the circle, opening thereby the ports to their greatest extent in the short
travel through the arc of its circle from (1 to 2), and closes the same quite as
fast, while the excentric travels from (2 to 3) around the shaft, at which latter
position the arm (R) is moved back again to point (1) in the circle, and has
closed the ports again. During the time the eccentric completes the revolution
around the shaft from point (3) until it arrives again at point (1), the arm (R¹)
is made to move in its circle through the arc from (1 to 5) and back again to (1),
travelling through an arc near the centre line (X, X',) and even passing said
centre line a short distance, consequently communicating only very little, and
a very slow motion during all this time to the valves (A", A").
When the excentric has arrived at point (4) around the shaft, the piston bas.
travelled through the length of the cylinder, and has arrived at the top end of
the same, or nearly so. The excentric (K), which, as above described, has
operated through its rod (M) the arm (R) with which the arm (R) is connected;
so that the latter has moved the valves (A, A1.) over the ports (1, 2).
operates likewise through the rod (N); the arm (S), to which the armi (S) is
connected, and has moved when arrived at point (4) around the shaft, said arm s
(S') to the point (4) in its circle above the centre line (X, X',) in which position
the valves (A, A,) at the top end of the cylinder, are on the point of opening the
ports (p, p,) for the admission of the steam into the top end of the cylinder.
When the excentric arrives at point (5) on the shaft, the arm (S') has moved to
.

page_text: point (5) on its circle, and opens full the ports (p', p,) and when the excentric
arrives at point (6) on the shaft, the arm (S) is moved back again to point (4) on
its arc, and the valves (A', A",) have closed again the ports (p', p"). During the
time the excentric travels around the shaft from point (6), until it arrives again
at point (4), and which said excentric operates through its rod (M), the arms (R
and R'), and through the latter the valves (A", A") as above described, the
rod (N) of said excentric acts upon the arm (S), so as to cause the arm (S') to move
in the arc from (4 to 2), near the centre line (X, X,) and back again, keeping,
during that time, the valves (A', A",) over the ports (p, p",) and communicating
only very little and a very slow motion to the same. On cither of the rock
shafts an arm or lever (T) is attached, connecting through the rod (U), attached
to the valve rod (w), to which the exhaust valves (I, II',) are fastened. This
arm is placed in such a position as to work the exhaust valves in the usual
manner. The exhaust valves as represented in Figure IV., are both con-
nected by the one rod (w), in which case the same can be operated by one
arm or lever (1), placed on either of the rock shafts, but when said valves are
separated, then they must be operated by separate arms placed on each of the
rock shafts.
This Invention further consists in the combination of a vibrating lever or
"link" operated by a single excentric, when these are so arranged that the
horizontal and perpendicular throws of the excentric combined, produce in the
aforesaid lever or "link" movements possessing the characteristics of the
movements of that part of the well-known "Stephenson's link motion" which
is termed the link ;" and further, in the construction of said "link" in such
a manner that while the steam valves are moved by any part of said "link
which will cause them to effect the desired cut off, the exhaust valves shall
always receive motion from that part of the said link which is best suited to
give them correct action.
"
"
In steam engines where it is desirable to employ a variable cut off gear
which shall open and close the valves with positive movements, the well-known
Stepbenson's link motion" is generally used actuated by two excentrics.
The movements derived from this specific link motion and communicated to
the valve or valves, may be employed with my above described arrangements
of separate induction and education valves, and the object of this improvement
is to furnish a substitute for the above specific link motion, which will produce
in the valve or valves with which it is connected movements similar to those
derived from the said Stephenson's link motion, and which shall at the same
time possess greater simplicity and also certain facilities of application by
reason of its compactness.

page_text: Figure VI. represents the valve gearing of a steam engine in which the
separate movements of the induction and eduction valves are derived from a
"link" operated by the revolution of a single excentric, operating the induction
and eduction valves independently of each other, and capable of adjusting the
points of cut off of the steam valves as well as of reversing the motion of the
engine. Figure VII. is a diagram explanatory of the movements of the link
and of the vibrating arms shewn in Figure VI.
In the Figures above referred to, A is a curved rocking lever or "link,"
which is pivotted centrally by the fulcrum pin (a) to the upper end of a
sustaining rod (d), which is hinged at its lower end to a fixed pin (f). This lever
or "link" (A) is attached to or forms part of the strap of an excentric (K), which
excentric is secured to the main shaft (L) of the engine. The link (A) is slotted
or morticed through nearly from end to end. In this slot are held two sliding
blocks (m and n), which can pass each other (see Figure VI.) The block (m)
is connected through the rod (Q) with an arm (T) on a rock shaft (h), on which
another arm is attached, connected through the rod (U) with the exhaust valves.
This block (m) is fixed at a point in the link (A), from which in connection with
the arm or other gearing, it will give to the said exhaust valves the correct
motion. The block (22) is connected to a rod (M), to which, a short distance
from the link, the rod (N) is attached. These rods (M) and (N) are attached to
separate arms (R.) and (S), secured to separate and independent rock shafts, of
which one passes through the other, so as to have a common centre of motion
(x). On the end of the shaft to which the arm (R) is fastened, an arm (R') is
attached, communicating through the rod (M) motion to the steam valves on
one end of the cylinder, and on the end of the shaft to which the arm (S) is
fastened, an arın (S') is attached, communicating through the rod (N¹) motion to
the steam valves on the other end of the cylinder. The position of the arms
(R) and (S) working above and below the line (X, X',) running through the
centre of the rock shaft, and the slide valve rods is similar; and the manner of
working the valves equal to the arrangement above described and represented
in Figures IV. and V., where similar arms are worked by means of a single
excentric. The curvatures of the slots in the lever or link (A) in which the
blocks (m) and (n) are held and move, are circular. When the centres of the
excentric (K), the fulcrum pin (a), the shaft (L), and the centre from which the
curvature of the slots is described, lie in the same straight line, which will occur
twice in each revolution of the shaft, the lever or link (A) will be in such a
position that the blocks (m) and (1) may be moved from end to end in the slots
in said link without altering the position of either of the steam or of the exhaust
valves, but the position of the valves at one of these points will be advanced

page_text: from the position at the other by the amount of the excentric's throw. The
excentric (K) is so set relatively to the engine crank that these said points will
coincide or nearly coincide with the commencement of each stroke of the
piston, and the lap on the valves is made such that at one end of the said
points, the steam valve is about commencing to admit steam to the rear end
of the cylinder, while at the other it is about commencing to admit steam to
the front end of the cylinder. The portion of the piston's stroke during which
the steam valves will remain open, will increase in proportion as the block (n)
occupies parts of the link (A) more remote from the fulerum pin (a). The
movement of the valve derived from the lower half of the link (A) will cause
the engine to run in an opposite direction from those derived from its upper
half. The block () from which the steam valves derive their movements being
separated from and working independent from the block (m), from which the
exhaust valves derive their movements, any position of the said block (n), and
consequently the extent to which "expansion" may be advantageously carried,
will not interfere with the correct action of the exhaust valve, as would be the
case if the motion of the steam and exhaust valves was taken from one and
the same block or point in the lever or link (A).
Figuro VIII. represents a side elevation of a horizontal steam engine, with
the cylinder and steam chest in section, and in which are shown the several
features of my Invention, with the induction and eduction valves separated
and operated independently of each other from a "link" operated by a single
excentric, and adjusting the position of the block in the link from which the
steam valves receive their motion by the action of a governor. In this de-
scription of engine it is not desired to have the motion of the engine reversible,
in consequence of which the upper or lower half of the link (A) [as the case may
require] can be dispensed with, and the link be made only with a single slot;
in which the block (2) which operates the steam valves is moveable. The
exhaust valves derive their motion in that case from a pin (m) fixed in the solid
part of the link. The governor rod (W) is connected with the block (n),
whereby the different degrees of expansion according to the load on the engine
will be regulated.
Having now fully described and set forth my Invention, I hereby declare
that I claim as my Invention and desire to secure by Letters Patent,―
First, the mode of constructing the slide valve and seat as represented in
Figure 1. the several parts being so arranged relatively to each other that an
opening equal in breadth to twice the distance traversed in the same time by
the valve may be made into one end of the steam cylinder in the manner
described.

page_text: Secondly, I claim a cup slide valve having formed in it a passage which
is independent of the exhaust.cup, and which opens on the face of the valve
in front of and behind the said exhaust cup in combination with an elevated
seat or its equivalent, as shewn in Figures II. and III., in which it will be seen
that the said valve and seat are so arranged relatively to each other that at proper
times two passages are opened for the entry of steam into either end of the
cylinder. I also claim constructing the cup valve in such a manner that the
parts a and b, Figures III., III, and
III. may have a certain amount of
motion independent of each other as herein set forth.
Thirdly, I claim separating and arranging the valves in the manner set
forth. I claim particularly placing the valves for releasing the steam in
separate chambers between the induction valves and the cylinder.
Fourth, I claim the arrangement of a divided excentric rod with a single
excentric or other mechanical equivalent in combination with arins or levers
made to vibrate through any desired parts of a circle for giving substantially
in the manner set forth separate and independent movements to the valves for
admitting or for releasing the steam at the opposite ends of the cylinder in
the manner and for the purpose specified.
Fifth, I claim the combination of a single link motion or its equivalent
with one or more steam valves and one or more exhaust valves; the steam
valves have movements independent of and different from those of the exhaust
valves, and all the said valves receive their respective movements from the
said "link" in the manner herein-before set forth.
Sixth, I claim adapting the governor to the movable block of a "link,"
from which block the induction valves receive their motion for the purpose of
regulating the speed of the engine by varying the point of cut-off, substantially
as set forth and specified.
In witness whereof, I, the said John Franklin Allen, have hereunto
set my hand and seal, this Twenty-second day of October, in the year
of our Lord One thousand eight hundred and sixty-two.
JOHN FRANKLIN ALLEN. (L.S.)