AN IMPROVED DISTRIBUTION AND EXPANSION VALVE
Year: 1879

page_text: LETTERS PATENT to Alexander Melville Clark, of 53, Chancery Lane, in the
County of Middlesex, Patent Agent, for the Invention of "AN IMPROVED
DISTRIBUTION AND EXPANSION VALVE." A communication from abroad by
the Firm of Escher Wyss and Company, of Paris, France.
Sealed the 28th October 1879, and dated the 10th May 1879.
PROVISIONAL SPECIFICATION left by the said Alexander Melville Clark at
the Office of the Commissioners of Patents on the 10th May 1879.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of Middlesex,
Patent Agent. "AN IMPROVED DISTRIBUTION AND EXPANSION VALVE." [A com-
munication from abroad by the Firm of Escher Wyss and Company, of Paris,
France.]
This Invention relates to a distribution and automatic expansion valve for steam
and other engines. I will describe one arrangement which may be adapted to
existing engines, but which is capable, with but slight modifications, of being
applied in other cases.
The Invention is illustrated in the accompanying Drawings, in which Figure 1
represents a transverse section of the apparatus; Figure 2, a half plan half hori-
zontal section; and Figure 3, a diagram of the working faces of the valve. m is a
valve box attached by flange E to the valve chest of a steam engine, and by
flange A to the steam pipe, either from the boiler or the steam jacket of the
cylinder.
It contains a double seated conical valve F and a fixed sleeve D for the cock C;
n, cover of valve box; and H is a small hand wheel upon a screw cap H' screwing
onto a neck on the cover n to enable H, H', to be raised or lowered. The double
seated conical expansion valve F is attached to a stem 9 guided at the upper end in
the cover n, the valve fitting at the underside on a short guiding stem K fixed in
the valve box m, and having a thoroughfare t through its centre to allow the steam
in the lower part of the valve casing to act upon the entire under surface of the
valve; ', spiral spring pressing the valve down upon its seats. Thus by unscrewing

page_text: and raising H, H¹, steam being admitted at A, the valve will be raised by the
steam pressure and steam will pass through chamber E to the cylinder, as well as
through the passages b, b, b', and holes a, a, in the valve to the upper side of the
valve, which will fall onto its seat when the weight of the valve plus the pressure
of the spring and of the steam upon its upper side overcome the pressure of the
steam upon its under side. The following proportions between the faces of the
valve exposed to the pressure of the steam are observed, viz. :-
=
==
f being the total upper face, f¹ the central face, and fo the annular lower face.
The sleeve D is fixed by a set screw p, and the cock C, which is fitted to partially
rotate therein, is closed at each extreme position. A slotted lever X is fixed to the
end of the plug of cock C and connected with parts receiving to and fro motion by
the rise and fall of a governor, whereby the cock is turned in one direction or the
other, so as to vary or entirely cut off the communication between passages b, b,
and . Thus when the governor is in its highest position cock C will be closed
and passages b, 61, interrupted, the valve will remain on its seats, and all communi-
cation between spaces B and E above and below the valve will be cut off. In the
lowest position of the governor the passage b will be quite open, as shown in the
Drawing. When the engine is not working the valve F is screwed down upon its
seats by the hand wheel H pressing on the end of its stem q, the passage b remaining
open.
In order to start the engine the wheel H is unscrewed or raised, whereupon the
steam in A will lift the valve F and pass into E, and thence to the valve chest of
the engine. It passes at same time through the holes a, a, passages b, b, and b³, to
the upper side of the valve. These several passages being of but small area, as
compared with that of the steam pipe, the steam will not pass suddenly but
gradually to the top side of the valve, and will only acquire the same pressure as
that on the underside after a certain lapse of time. The valve F when raised
presents equal surfaces to the steam pressure on both sides (neglecting the slight
difference caused by the area of the valve stem), and the pressure being thus equal
on both sides the valve will close down upon its seat by its own gravity and the
pressure of the spiral spring. The valve in effect closes when the pressure of the
steam passing through a, b, b, b', to its upper side added to the weight of the valve
and the pressure of the spring exceeds the steam pressure acting against its under
face plus the resistance due to friction. Immediately on the closing of the valve
expansion commences in the cylinder, the steam contained in space B above the
valve being also expanded. On starting the engine, the hand wheel H being in its
highest position, the lever X will be in its lowest position, the passage b' in cock C
will be quite open, and at the end of the period of expansion the pressure will be
almost the same in B as behind the piston immediately at the dead point or at the
moment the piston changes its direction. When however the engine is working
under normal conditions and the governor is in its medium position the passage bl
is partially closed. Thus during the period of expansion, that is to say, while the
valve is closed, less steam will pass from space B into the cylinder than when
passage b' is more open, and there is thus at the dead point a greater pressure than
before above the valve, and consequently the increased pressure due to the passage
of the steam through a, b, b, b', to the upper side of the valve during the admission
will close the valve more suddenly, the equilibrium between the two pressures
being established in a shorter space of time. The greater the increase of speed in
the engine the more will the passage b¹ be contracted and the less will the pressure
in space B tend to become reduced, the result being that the pressure necessary for
the closure of the valve is more quickly established and the admission of stean to
the cylinder correspondingly diminished. On the other hand, when the engine
slackens its speed in consequence of an increase in the work to be done the
passage b¹ will open wider, valve F will remain for a longer time open, and the
engine will receive more steam.

page_text: It should be observed that the size and number of the holes a, as well as the
diameter of passages b, b, must be so regulated that the excess pressure operating
in space B to close the valve shall take effect exactly at the moment when the
period of admission corresponding to the power to be developed by the engine
should cease. It will be evident that this improved steam distributing apparatus
may be applied with suitable modifications to all kinds of steam engines as well as
to hydraulic motors, and also for the distribution of fluids generally.
In locomotives, marine, mining, and other engines provided with reversing gear
the cock C would be rotated by means of a hand lever, thus affording a ready
means of so regulating the degree of expansion as to ensure the proper working of
the engine.

page_text: 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
8th November 1879.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of Middlesex,
Patent Agent.
"AN IMPROVED DISTRIBUTION AND EXPANSION VALVE." A com-
munication from abroad by the Firm of Escher Wyss and Company, of Paris,
France.
This Invention relates to an improved distribution and automatic expansion valve
for steam and other engines. The arrangement herein described may be adapted
to existing engines and with little modification to new engines.
The Invention is illustrated in the accompanying Drawings, in which Figure 1
represents a transverse section of the valve; Figure 2, a half plan half horizontal
section; and Figure 3, a diagram of the upper and lower faces of the valve.
The valve box m is attached by a flange on E to the valve chest of the steam
engine, and by a flange on A to the steam pipe coming either from the boiler
or the steam jacket of the cylinder. The valve box, which is closed by a
cover n, contains the valve F and a fixed sleeve D for the cock C; H is a
small hand wheel upon a screw cap H₁ screwing onto a neck on the cover n to
enable H, H', to be raised or lowered. The expansion valve F is a double seated
conical valve, and is attached to a stem 7 guided at the upper end in the cover n,
the valve fitting at the underside on a short guiding stem K fixed in the valve
box m and having a thoroughfare t through its centre to allow the steam in the
lower part of the valve casing to act upon the entire under surface of the valve; "
is a spiral spring pressing the valve down upon its seats; a, a, are small holes
through the valve, and b, b, are passages in the valve box connecting the spaces
above and below the valve with the thoroughfare b¹ of cock C. By unscrewing
and raising H, H', steam being admitted at A, the valve will be raised by the steam
pressure, and steam will pass through chamber E to the cylinder, and also through
the passages b, b, b', and holes a, a, to the upper side of the valve, which will fall
outo its seat when the steam pressure on its underside is overcome by that on its
upper side plus the weight of the valve and the pressure of the spring. The
following proportions between the faces of the valve exposed to the pressure of the
steam are observed, viz. :-f: f¹ : ƒ² = 1 : / : 1/3, f being the total upper face, f¹
the central face, and f2 the annular lower face, these different parts being repre-
sented in Figure 3 by the different styles of cross hatching corresponding to the
examples annexed thereto. The sleeve D is fixed by a set screw p, and the cock C,
which is fitted to partially rotate therein, is closed at each extreme position. A
slotted lever X is fixed to the end of the plug of cock C and connected with parts
operated by the rise and fall of a governor, whereby the cock is turned in one
direction or the other, so as to vary or entirely cut off the communication between
passages b, b, and b'. Thus when the governor is in its highest position cock C
will be closed and passages b, b', interrupted, the valve will remain on its seats, and
all communication between spaces B and E above and below the valve will be cut
off. In the lowest position of the governor the passage b' will be quite open, as
shown in the Drawing. When the engine is not working the valve F is screwed
down upon its seats by the hand wheel H pressing on the end of its stem q, the
passage b' remaining open.
In order to start the engine the wheel H is raised, whereupon the steam in A
will lift the valve F and pass into E, and thence to the valve chest of the engine.
It passes at same time through the holes a, a, passages, b, b, and b'; to the upper
side of the valve. These several passages being of but small area as compared
with that of the the steam pipe the steam will not pass suddenly but gradually to the
top side of the valve, and will only acquire a pressure equal to that at the underside
after a certain lapse of time. The valve F when raised presents equal surfaces to

page_text: the steam pressure on both sides (neglecting the slight difference caused by the area
of the valve stem), and the pressure being thus equal on both sides the valve
will close down upon its seat by its own gravity and the pressure of the spiral
spring. The valve in effect closes when the pressure of the steam passing through
a, b, b, b, to its upper side added to the weight of the valve and the pressure of
the spring exceeds the steam pressure acting against its under face plus the
resistance due to friction. Immediately on the closing of the valve expansion
commences in the cylinder, the steam contained in space B above the valve being
also expanded. On starting the engine, the hand wheel Ef being in its highest
position, the lever X will be in its lowest position and the passage b' in cock C will
be quite open, and as the piston approaches the end of its stroke the pressure will
be almost the same in B as in the cylinder. When however the engine is working
under normal conditions and the governor is in its medium position the passage b
is partially closed, so that less steam will pass from space B into the cylinder after
the cut off valve F is closed, and the pressure above the valve, when the piston
arrives at the end of its stroke, will be greater than before; consequently at the
next stroke less steam will be required to pass through a, b, b, b₁, to the upper side
of the valve in order to balance the pressure beneath the valve. The latter pressure
will therefore be more quickly overcome and the valve will be closed earlier. The
greater the increase of speed in the engine the more will the passage b¹ be contracted
and the less will the pressure in space B become. reduced, so that the pressure
necessary to close valve F will be more quickly attained and the cut off will be
earlier. When however the engine slackens speed in consequence of an increase in
the work to be done the passage b₁ will be opened wider, valve F will remain for a
longer time open, and steam will be cut off later.
It should be observed that the size and number of the holes a, as well as the
diameter of passages b, b, must be so regulated that the excess pressure in space B
shall close the cut off valve F exactly at the proper moment, according to the power
required.
It will be evident that this valve may be applied with suitable modifications to
all kinds of steam engines as well as to hydraulic motors, and also for the distri-
bution of fluids generally. In locomotives, marine, mining, and other engines
provided with reversing gear the cock C would be rotated by means of a hand
lever, thus affording a ready means of so regulating the grade of expansion as to
ensure the proper working of the engine.
Having described the nature of the said Invention, and the manner of performing
the same, I declare that what I claim as the Invention to be protected by the
herein before in part recited Letters Patent is,-
.
1st. The valve opened and closed automatically by the pressure of the steam
acting upon both sides, substantially as herein described and illustrated by way of
example in the accompanying Drawing.
2nd. The application of the herein described apparatus for the direct distribution
of steam or other fluid in steam and other engines (subject to such modifications as
may, be necessary in practice), substantially as shown and described.
In witness whereof, I, the said Alexander Melville Clark, have hereunto set
my hand and scal, this Seventh day of November, in the year of our Lord
One thousand eight hundred and seventy nine.