IMPROVEMENTS IN STEAM ENGINES FOR OBTAINING AN EFFICIENT STEAM DISTRIBUTION THEREIN
Year: 1871

page_text: LETTERS PATENT to Alexander Melville Clark, of 53, Chancery Lane,
in the County of Middlesex, Patent Agent, for the Invention of
"IMPROVEMENTS IN STEAM ENGINES FOR OBTAINING AN EFFICIENT STEAM
DISTRIBUTION THEREIN." -A communication from abroad by Paul
Henri Leblond and Albert Mulot, both of 13, Boulevart St. Martin,
Paris.
Sealed the 24th May 1872, and dated the 5th December 1871.
PROVISIONAL SPECIFICATION left by the said Alexander Melville
Clark at the Office of the Commissioners of Patents, with his
Petition, on the 5th December 1871.
I, ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the
County of Middlesex, Patent Agent, do hereby declare the nature of
the said Invention for "IMPROVEMENTS IN STEAM ENGINES FOR OBTAINING
AN EFFICIENT STEAM DISTRIBUTION THEREIN," to be as follows:-
To obtain an efficient steam distribution in steam engines it is neces-
sary, 1st, to reduce dead spaces to a minimum; 2nd, to open and close

page_text: the steam and eduction ports as quick as possible; 3rdly, to vary the
cut off by means of the governor. The old system of slide valve
operated by the eccentric does not generally realize the above conditions,
or at best but imperfectly.
Numerous arrangements of valves have been more recently devised
to meet these requirements, but the result is generally attained only at
a sacrifice of a good working arrangement; in fact such systems are
based on the employment of means for releasing at the proper moment
the parts connected with the steam distribution, which being operated
by a spring or other power suddenly close the ports until the parts are
again put in gear, when the ports are immediately uncovered. It will
be found on examining these several systems that they are composed of
a great number of parts of delicate construction, some of which are
liable to rapid wear.
The improved system of steam distribution of this Invention is pro-
posed as embodying the three fundamental conditions above stated freed
from the disadvantages referred to.
In the present arrangement the valve employed to regulate the passage
of the live and exhaust steam, instead of being connected to and
operated by the driving shaft through a combination of mechanism, is
provided with a piston and operated directly by the steam itself.
Having explained the principle of the Invention, I will now describe
The valve employed
the means by which it is carried into effect.
consists of a slide with a number of thoroughfares therein, being what
is termed a gridiron valve, which has this advantage, that an opening
of considerable area is obtained with a small extent of motion, while
it is not liable to the shocks which are the cause of the rapid wear of
some valves now in use. Four distinct valves are employed (two for
the live and two for the exhaust steam) as in other systems devised for
effecting the instantaneous cpening and closing of the ports.
slide valve is connected to two small single-acting pistons, whose com-
bined action produce the same result as one of double action. Steam
is admitted on the side of these pistons which is farthest from the valve
box by a pipe of small diameter which communicates alternately with
the boiler and with the condenser. The dimensions of these pistons is
so calculated that the pressure of the steam on one of the two will
always be sufficient to overcome the friction of the slide valve.
Each

page_text: When the communications with the steam space and the condenser
are reversed, a movement takes place which is continued until one of
the pistons reaches the bottom of its cylinder. This position may cor-
respond to the opening of the ports, while a movement in the reverse
direction closes the ports. These two small pistons may be rendered
steam-tight, either by means of the ordinary piston packing, or by
means of a valve suitably disposed without the use of packing, which
method I will describe more in detail as applied to one of the steam
inlet valves for example. Suppose the rear face of each of the small
pistons to be made of conical or valvular form and received in a seat in
the bottom of the cylinder, and suppose one of the pistons (the upper
one for instance) to have reached the end of its course, the valve on this
side will be closed, and there will consequently be no communication
on this side between the valve box which is filled with steam and the
condenser. The lower piston in this position receives an equal pressure
of steam on both sides, and there can consequently be no escape. By
inverting the two pistons the same action takes place in the reverse
direction. In this manner there can be no possible escape, except
during the motion of the slide, which occupies but a fraction of time.
The play between the piston and cylinder should be very slight if the
boring is properly done, while there is an absence of wear in consequence
of the pistons being mounted vertically.
For the eduction valves the principle is the same, but the piston valves
should be placed on the inside in the slide valve casing.
This improved arrangement, which is based on the employment of
valves attached to pistons, avoids the friction of packings, and has the
merit of being exceedingly simple. The wear of the valves and their
seats may be obviated in the manner shown in the accompanying
Drawings, in which it will be seen that valves of large diameter fixed
to the pistons are replaced by valves of small dimensions independent of
said pistons kept closed by weak spiral springs, and operated so as to
open and close in the same manner as above described for the attached
valves. Their action will be readily understood by the aid of the
Drawings. In this arrangement the shocks to the valves are less violent,
and their wear is consequently less, while they may be readily fitted at
but little cost.
The supply of steam to the slide valve pistons is regulated by the
following means:-Each of the cylinders in which these pistons work

page_text: communicates by means of a pipe of small diameter alternately with the
steam space in the boiler and with the condenser, which is effected by
connecting the two pipes of each valve box with a small D valve, whose
rod is kept up by a spiral spring against a cam, which performs the
same number of revolutions as the engine. This valve will be herein-
after referred to as the "distributor" valve, in order to avoid confusion
with the steam inlet and eduction slide valves. The cam above
mentioned is provided with two surfaces arranged to abut against the
end of the distributor valve rod and move it to its two extreme positions,
one of which covers and the other uncovers the ports of the corre-
sponding gridiron slide valve. Each of the steam and eduction valves
being operated by a distributor, which is in turn actuated by a cor-
responding cam, it is only necessary to arrange the several cams to open
and close the corresponding gridiron valve at the proper moment.
In order to vary the cut off by means of the governor when employing
this system of steam distribution, the two cams which govern the steam
inlet valves are made of same length and in the form of a helix or
spiral. The cams are mounted on the axis of the governor, and con-
nected so as to be operated by the vertical movement of the balls. It
should be mentioned that as there is no objection to opening the eduction
port at one end simultaneously with the closing of that at the other, the
two eduction valves may, under these circumstances, be governed by a
single distributor. It has been shewn that at each movement of one
of the distributors the corresponding slide valve will move in one or
other direction, and one of the valve pistons will abut against the bottom
of its cylinder with a force proportionate to the pressure of steam in
excess, and to the speed it has acquired, which however will never be
great owing to the short extent of its course, and the parts in contact
being the valve piston and the bottom of its cylinder there will be but
little wear.
The violence and noise of the shocks may be reduced if desired by
simply introducing a cock on each of the pipes conveying the steam to
the distributors, by means of which the supply of steam and rate of
motion of the valve pistons may be regulated by the driver, who is
enabled to judge by ear whether the engine is working in proper order
or not.

page_text: to serve for the lubrication of all the parts including the valve pistons,
slide valves, and also the cylinder.
The Drawings show the improvements as applied to a horizontal
engine of 100 horses' power; diameter of piston, 32 inches; stroke of
piston, 55 inches.
Sheet 1 shows details of of one of the steam valves, Figure 1 (one) being
a longitudinal section, and Figure 2 a transverse section of same. The
gridiron valve L is connected by 2 nuts and lock nuts to a screwed
stem T, to which are attached the two pistons A, A¹; C, C¹, parts fixed
to the pistons, and serving to open the valves B, B¹, by means of
studs D, D', fixed on the backs thereof; U, spring acting on a collar V
for the purpose of keeping the valve B in its seat; H, H, ends of valve
cylinder; E', F¹, pipes leading from the distributors; R, cover of the
valve box; S, pipe conveying steam to the engine cylinder.
Figures 3 and 4, Sheet 2, show a longitudinal and transverse section
of one of the eduction valves. L, gridiron valve connected to rod T
by the stem P. A, A', pistons attached one at either end of rod T;
B, B', valves held in their seats by springs E. These valves are opened
by the impact of the rear faces of the pistons. V, V, cylinder heads;
S, Figure 4, exhaust steam pipe leading to the condenser; G³, H', pipes
communicating with the distributors.
Figures 5 and 6, Sheet 3, show a vertical and horizontal section of one
of the distributors governing the steam inlet valves and the cam for
operating the same. F, valve face on which works the slide valve E;
R, cock for regulating the admission of steam to the distributor and the
movements of the valve pistons; A', pipe leading from the distributor
to the upper cylinder of the steam inlet slide valve; B¹, similar pipe
leading to the lower cylinder of said valve; I, eduction pipe leading to
the condenser; G, valve rod terminating in a head O in contact with the
operating cam P; H, collar or stop for limiting the motion of the valve
in one direction; K, spiral spring, one end of which bears on the
disc M and the other on the cross bar L, and serving to keep the head O
up to the cam P; U, rods by which the distributor is fixed to the
supports of the governor; Z, lubricator mounted on the distributor;
P, cam or wyper fixed to the sleeve S by a set screw V, said sleeve
being connected by a central rod to the vertically moving part of the
governor. The cams P govern the distributors of the inlet slide valves.

page_text: Steam may be admitted when the valve piston is at 0·010 from the end
of its course, and the cut off varies from ¼ to ½ of the stroke of the
piston. The incline 1 on the cam serves to open the steam port, and
incline 2 for shutting off or expansion; 3 shows the maximum and 4 the
minimum degree of expansion. Figures 7 and 8 show an elevation and
plan of the cam for governing the eduction slide. The eduction port
may be opened and closed at 0.10 from the end of the stroke of the
piston.
Figures 9, 10, and 11, Sheet 4, show a side view, end view, and plan
of the whole apparatus of this Invention for effecting the distribution of
steam. a¹, a³, steam slide valve cases; 61, 62, eduction slide valve cases;
c, branch steam pipes connected at d to the steam pipe; f, branch pipes
connected at g to exhaust pipe leading to condenser; r, governor;
h, distributor valve governing the front steam slide valve; k, cam by
which it is operated; i, distributor valve governing the rear steam slide
valve; L, its cam; j, distributor governing the two eduction slide valves;
m, its cam; n, horizontal shaft transmitting motion to the governor
spindle from an inclined shaft p driven from the main shaft. The red
lines in Figure 10 show the communication between the steam pipe and
the distributors, and the blue lines the communication between the
distributors and the exhaust.

page_text: inasmuch as the slide valves are not connected by mechanism with any
of the working parts, the distributors may be placed at any part of the
engine and connected by pipes with the slide valves.
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 4th June 1872.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ALEXANDER
MELVILLE CLARK, of 53, Chancery Lane, in the County of Middlesex,
Patent Agent, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Fifth day of December, in the
year of our Lord One thousand eight hundred and seventy-one, in the
thirty-fifth year of Her reign, did, for Herself, Her heirs and suc-
cessors, 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, exercise, and vend, within the United
Kingdom of Great Britain and Ireland, the Channel Islands, and Isle
of Man, an Invention for "IMPROVEMENTS IN STEAM ENGINES FOR OBTAINING
AN EFFICIENT STEAM DISTRIBUTION THEREIN," a communication to me from
abroad by Paul Henri Leblond and Albert Mulot, both of 13, Boulevart
St. Martin, Paris, upon the condition (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 scals, should particularly describe and ascertain the nature
of the said Invention, and in what manner the same was to be per-
formed, and cause the same to be filed in the Great Scal Patent Office
within six calendar months next and immediately after the date of the
said Letters Patent.

page_text: the same is to be performed, to be particularly described and ascertained
in and by the following statement, reference being had to the accom-
panying Sheet of Drawings and to the letters and figures marked
thereon (that is to say) :-
To obtain an efficient steam distribution in steam engines it is
necessary, 1st, to reduce dead spaces to a minimum; 2ndly, to open
and close the steam and eduction ports as quickly as possible; 3rdly, to
vary the cut off by means of the governor. The old system of slide valve
operated by an eccentric does not generally realize the above conditions,
or at best but imperfectly.
Numerous arrangements of valves have been more recently devised to
meet these requirements, but the result is generally attained only at the
sacrifice of a good working arrangement. In fact such systems are based
on the employment of devices for releasing at the proper moment the
parts governing the steam distribution, which being operated by a spring
or other power suddenly close the ports until the parts are again put in
gear, when the ports are immediately uncovered. It will be found on
examining these several systems that they are composed of a great
number of parts of delicate construction, some of which are liable to
rapid wear.
The improved system of steam distribution of this Invention is pro-
posed as embodying the three fundamental conditions above stated freed
from the disadvantages referred to.
In the present arrangement the valve employed to regulate the
passage of the live and exhaust steam, instead of being connected to
and operated by the driving shaft through a combination of mechanism,
is provided with a piston, and operated directly by the steam itself.
Having explained the principle of the Invention, I will now describe
the means by which it is carried into effect. The valve employed
consists of a slide with a number of thoroughfares therein, being what is
termed a gridiron valve, which has this advantage, that an opening of
considerable area is obtained with a small extent of motion, while it is
not liable to the shocks which are the cause of the rapid wear of some
valves now in use. Four distinct valves are employed (two for the live
and two for the exhaust steam), as in other systems devised for effecting
the instantaneous opening and closing of the ports. Each slide valve is
connected to two small single-acting pistons, whose combined action

page_text: produce the same result as one of double action. Steam is admitted
on the sides of these pistons which are farthest from the valvo by a
pipe of small diameter, which communicates alternately with the boiler
and with the condenser. The dimension of these pistons is so calculated
that the pressure of the steam on one of the two will always be sufficient
to overcome the friction of the slide valve.
When the communications with the steam space and the condenser
are reversed a movement takes place which is continued until one of the
pistons reaches the bottom of its cylinder. This position may correspond
to the opening of the ports, while a movement in the reverse direction
closes the ports. These two small pistons may be rendered steam-tight
either by means of the ordinary piston packing or by means of a valve
suitably disposed without the use of packing, which method I will
describe more in detail as applied to one of the steam inlet valves
for example. Suppose the rear face of each of the small pistons to be
made of conical or valvular form and received in a seat in the bottom of
the cylinder, and suppose one of the pistons (the upper one for instance)
to have reached the end of its course, the valve on this side will be
closed, and there will consequently be no communication on this sido
between the valve box, which is filled with steam, and the condenser.
The lower piston in this position receives an equal pressure of steam on
both sides, and there can consequently be no escape. By inverting the
two pistons the same action takes place in the reverse direction. In this
manner there can be no possible escape except during the motion of the
slide, which occupies but a fraction of time. The play between the
piston and cylinder should be very slight if the boring is properly donc,
while there is an absence of wear in consequence of the pistons being
mounted vertically.
For the eduction valves the principle is the same, but the piston valves
should be placed on the inside within the slide valve casing.
This improved arrangement, which is based on the employment of
valves attached to pistons, avoids the friction of packings, and has
the merit of being exceedingly simple. The rapid wear of the valves
and their seats may be obviated in the manner shown in the accom-
panying Drawings, in which it will be seen that valves of large diameter
fixed to the pistons are replaced by valves of small dimensions independent
of said pistons, closed by weak spiral springs, and operated so as to open
and close in the same manner as above described for the attached valves.

page_text: Their action will be readily understood by the aid of the Drawings. In
this modified arrangement the shocks to the valves are less violent, and
their wear is consequently less, while they may be readily fitted at but
little cost.
The supply of steam to the slide valve pistons is regulated by the
following means:-Each of the cylinders in which these pistons work
communicates by means of a pipe of small diameter alternately with the
steam space in the boiler and with the condenser, which is effected by
connecting the two pipes of each valve box with a small D valve, whoso
rod is kept up by a spiral spring against a cam, which performs the same
number of revolutions as the engine. This valve will be herein-after
referred to as the "distributor" valve in order to avoid confusion with
the steam inlet and eduction slide valves. The cam above mentioned is
provided with two surfaces, arranged to abut against the end of the
distributor valve rod and move it to its two extreme positions, one of
which covers and the other uncovers the ports of the corresponding grid-
iron slide valve. Each of the steam and eduction valves being operated
by a distributor, which is in turn actuated by a corresponding cam,
it
is only necessary to arrange the several cams to open and close the
corresponding gridiron valve at the proper moment.
In order to vary the cut off by means of the governor when employing
this system of steam distribution, the two cams which govern the steam
inlet valves are made of some length, and in the form of a helix or
spiral. The cams are mounted on the axis of the governor, and con-
nected so as to be operated by the vertical movement of the balls. It
should be mentioned that as there is no objection to opening the
cduction port at one end simultaneously with the closing of that of
the other, the two eduction valves may under these circumstances be
governed by a single distributor. It has been shown that at each
movement of one of the distributors the corresponding slide valve will
move in one or other direction, and one of the valve pistons will abut
against the bottom of its cylinder with a force proportionate to the
excess pressure of steam and to the speed it has acquired, which however
will never be great owing to the short extent of its course, and the parts
in contact being the valve piston and the bottom of its cylinder, there
will be but little wear.
:0 Jan 11-

page_text: the distributors, by means of which the supply of steam and rate of
motion of the valve pistons may be regulated by the driver, who is
enabled to judge by car whether the engine is working in proper order
or not.
A lubricator is placed on each distributor, that is to say three in all,
to serve for the lubrication of all the parts, including the valve pistons,
slide valves, and also the cylinder.
Figures 1 and 2 show details of one of the steam valves, Figure 1
being a longitudinal section and Figure 2 a transverse section of same.
The gridiron valve L is connected by two nuts and lock nuts to a
screwed stem T, to which are attached the two pistons A, A'; C, C¹,
parts fixed to the pistons and serving to open the valves B, B', by means
of studs D, D', fixed on the backs thereof; U, spring acting on a collar
V for the purpose of keeping the valve B in its seat; H, H', ends of
valve cylinder; E, F, pipes leading from the distributors; R, cover of
the valve box; S, pipe conveying steam to the engine cylinder.
Figures 3 and 4 show a longitudinal and transverse section of one of
the eduction valves. L, gridiron valve connected to rod T by the
stem P; A, A¹, pistons attached one at either end of rod T; B, B¹,
valves held in their seats by springs E. These valves are opened by
the impact of the rear faces of the pistons. V, V, cylinder heads; S,
Figure 4, exhaust steam pipe leading to the condenser; G', H', pipes
communicating with the distributors.
Figures 5 and 6 show a vertical and horizontal section of one of the
distributors governing the steam inlet valves, and the cam for operating
the same. F, valve face, on which works the slide valve E; R, cock
for regulating the admission of steam to the distributor and the move-
ment of the valve pistons; A', pipe leading from the distributor to the
upper cylinder of the steam inlet slide valve; B', similar pipe leading to

page_text: the lower cylinder of said valve; I, eduction pipe leading to the con-
denser; G, valve rod terminating in a head O in contact with the
operating cam P; H, collar or stop for limiting the motion of the valve
in one direction; K, spiral spring, one end of which bears on the disc M
and the other on the cross bar L, and serving to keep the head O up to
the cam P; U, rods by which the distributor is fixed to the supports of
the governor; Z, lubricator mounted on the distributor; P, cam or
wyper fixed to the sleeve S by a set screw V, said sleeve being connected
by a central rod to the vertically moving part of the governor. The
cams P govern the distributors of the inlet slide valves. Steam may be
admitted when the valve piston is at 0.010 from the end of its course,
and the cut off varies from 1 to ½ of the stroke of the piston. The
incline 1 on the cam serves to open the steam port, and incline 2 for
shutting off or expansion. 3 shows the maximum and 4 the minimum
'
the lower cylinder of said valve; I, eduction pipe leading to the con-
denser; G, valve rod terminating in a head O in contact with the
operating cam P; H, collar or stop for limiting the motion of the valve
in one direction; K, spiral spring, one end of which bears on the disc M
and the other on the cross bar L, and serving to keep the head O up to
the cam P; U, rods by which the distributor is fixed to the supports of
the governor; Z, lubricator mounted on the distributor; P, cam or
wyper fixed to the sleeve S by a set screw V, said sleeve being connected
by a central rod to the vertically moving part of the governor. The
cams P govern the distributors of the inlet slide valves. Steam may be
admitted when the valve piston is at 0.010 from the end of its course,
and the cut off varies from ¼ to ½ of the stroke of the piston. The
incline 1 on the cam serves to open the steam port, and incline 2 for
shutting off or expansion. 3 shows the maximum and 4 the minimum
degree of expansion.
Figures 7 and 8 show an elevation and plan of the cam for governing
the eduction slide. The eduction port may be opened and closed at
0.10 from the end of the stroke of the piston.
Figures 9, 10, and 11 show a side view, end view, and plan of the
whole apparatus of this Invention for effecting the distribution of steam.
a', a, steam slide valve cases; b', 6', eduction slide valve cases; c,
branch steam pipes connected at d to the steam pipe; f, branch pipes
connected at g to exhaust pipe leading to condenser; ", governor;
h, distributor valve governing the front steam slide valve; K, cam by
which it is operated; i, distributor valve governing the rear steam slide
valve; L, its cam; j, distributor governing the two eduction slide
valves; m, its cam; n, horizontal shaft transmitting motion to the
governor spindle from an inclined shaft p driven from the main shaft.
The red lines in Figure 10 show the communication between the steam
pipe and the distributors, and the blue lines the communication between
the distributors and the exhaust.

page_text: 9
instantaneously effected, while a variable expansion is obtained under
the control of the governor.
To show how the dead spaces are reduced, it may be stated that in an
engine of 100 horses' power such as that berein-before referred to, such
useless spaces would amount to about 1037 cubic inches. Thus if the
capacity of the cylinder be 42903 inches, the dead spaces would be less
than th of the cylinder instead of averaging oth or roth as in
ordinary engines. Besides this the three conditions before referred to
are obtained without sacrificing efficiency or causing undue wear of
the parts of the mechanism.
This improved system of steam distribution may be very advan-
tageously applied to marine engines. In such engines, which are
generally of large dimensions, the Stephenson expansion gear is usually
employed. The expansion is thus effected under unfavorable conditions,
the steam being wiredrawn to a considerable extent. A proper degree
of expansion is very important when very high pressure is employed,
and a considerable economy may be effected by the use of this improved
system of steam distribution. In ordinary engines the reversing gear is
sometimes of heavy and complicated construction, and a small auxiliary
steam engine is often required for the purpose of starting the engines,
while by the improved system of this Invention the engine is reversed
simply by a half revolution of the distributor cams.
Another important advantage of this system of steam distribution is
the facility with which it may be applied to existing engines, forasmuch
as the slide valves are not connected by mechanism with any of the
working parts, the distributors may be placed at any part of the engine
and communicate by pipes with the slide valves.
By the adoption of these improvements considerable economy in fuel
may also be obtained in existing engines.
Having described the nature of the Invention and the manner of
performing the same, I declare that what I claim as the Invention to be
protected by the hercin-before in part recited Letters Patent is, governing
the steam distribution in steam engines by the direct action of the steam
itself on the steam distributing valves, substantially as herein-before set
forth

page_text: I also claim the combination and arrangement of parts for effecting
this object, substantially as berein-before described and shown in the
Drawings annexed.
In witness whereof, I, the said Alexander. Melville Clark, have
hereunto set my hand and seal, this Fourth day of June, 5
in the year of our Lord One thousand eight hundred and
seventy-two.