IMPROVEMENTS IN VALVES FOR STEAM ENGINES
Year: 1878

page_text: 3
LETTERS PATENT to Alexander Melville Clark, of 53, Chancery Lane, in the
County of Middlesex, Patent Agent, for the Invention of "IMPROVEMENTS
IN VALVES FOR STEAM ENGINES." A communication from abroad by Gustave-
Arnoux. of Marseilles. France.
Sealed the 5th November 1878, and dated the 14th May 1878.
السلام بنات
PROVISIONAL SPECIFICATION left by the said Alexander Melville Clark at
the Office of the Commissioners of Patents on the 14th May 1878.
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of Middlesex,
Patent Agont. “IMPROVEMENTS IN VALVES FOR STEAM ENGINES." [A communi-
cation from abroad by Gustave Arnoux, of Marseilles, France.]
This Invention relates to improvements in rotary slide valves for steam engines
described in the Specification of Letters Patent granted to me bearing date No-
vember 15th, 1875, No. 3972. These valves are of circular form, have a continuous
circular motion, and movable seats, which the inventor terms distributors, but they
are open to the same objection as a common reciprocating slide valve, viz., that the
unbalanced pressure on the back of the valve, which is in proportion to the size of.
the valve, causes great wear of the valve and seat. This defect it is important to
avoid, especially in large engines where the slide valves are of considerable size, as it
involves considerable waste of power in overcoming the friction, and great labour
in reversing the valves.
The object of the present improvements is to obviate these disadvantages, and
render the working of the valves easy and sinooth, and the Invention consists, first,
in the combination with rotary slide valves of this description of a compensator
attached to and revolving with the valve and in contact with a seat on the valve
chest 'cover. The pressure of the steam on the inner surface of this compensator
may thus be made to balance that on the back of the valve to any extent required,
as by making the internal area of the compensator greater than that of the valve
the pressure on the latter becomes reduced proportionately to their difference in
13

page_text: area, and the valve may thus be made an equilibrium valve. A spring bears upon
a movable cover of the valve chest, the stress of the spring being capable of regu-
lation in order to obtain any desired pressure of the valve on its seat.
The Invention thus consists broadly in balancing rotary valves of this description
to any extent required by causing the pressure of the steam to act on two opposite
surfaces, the pressure being proportional to the areas of the said surfaces..
A simple and effectual means is also employed for obtaining a supplementary
distribution with variable expansion, so as to reduce the amount of steam consumed
uselessly, as herein-after detailed.
The reversing is effected either by means of a hand lever or toothed gear, according
to the arrangement or size of the engine.
In the Drawings accompanying this description the compensator is shown as cast
in one piece with the valve, but it may be made separate therefrom if desired.
The Drawings show the improvements applied to a compound engine of 500 horse
power.
Figure 1 is a vertical section of the engine on line M, N, Figure 2, which is a
horizontal section on line O, P, Figure 1.
Figure 3 is an elevation of the engine.
Figure 4 is a section on line Q, R, S, T, U, Figures 1 and 2; and Figure 5, a
The slide valve, as shown at A, is composed of the circular valve proper and of a
disc cast in one with it of such a diameter relatively to the valve that the respective
areas of the valve and disc will be such as to cause the pressure upon the back of
the valve to be balanced more or less, or altogether, as required, according to the
dimensions of the valve and power of the engine.
The construction of this apparatus, which is very simple, will be readily under-
stood. It forms a circular chamber, to which the steam is admitted through a
circular grating at the height of the steam pipe (B, Figure 2). The steam being pre-
vented from communicating along the external surfaces which slide in the packings
enters the compensator chamber, as indicated by the arrow f, which becomes a
variable expansion slide valve, the steam being distributed at will by means of a
pinion p, Figure 1, gearing with a segmental rack cast on or attached to the interior
of the circumference of the rear portion of the compensator chamber, whereby a
circular motion is imparted to the latter, which distributes and isolates the steam
in order to vary the expansion as desired, and whereby the highest possible grades
of expansion may be employed. By means of the pinion p, which is operated by
a hand wheel V, the position of the compensator chamber may be shifted for
reversing.
In the position of the valves shown in the Drawings the pistons are supposed to
be receiving steam at the commencement of the up stroke.
Suppose for a moment it is desired to work without expansion, the steam is cut
off from the compensator chamber and passed directly to the slide valve by raising
the valve off its seat s, thus working at the full boiler pressure without expansion,
The slide valve has a back of conical form, so as to afford greater resistance to
the steam pressure, and it is further strengthened by pillars varying in number,
according to the size of the valve. The distributors D, D¹, of the slide valves of
the two cylinders are each operated by an endless screw N, N',, to which motion

page_text: is transmitted in any suitable manner from hand wheel V, by means of which the
engine is started and the valves reversed.
As the distributors are no longer operated through the axes of the slide valves,
they may either be fast or loose upon their axes, which are also the axes of their
respective slide valves.
When a lever is used for reversing, as before mentioned, the axes should be fixed;
but when worm gear is used they need not necessarily be fixed, as the distributors
are thereby securely held in position, and are adjustable without risk of being
shifted or carried round with the valve.
Each part of the slide valve and distributor is lubricated by separate branch pipes
from the lubricator, which enables an escape of steam at any part to be readily
detected, owing to the communication thus established between the lubricator and
the part where the leakage occurs.
Figures 9, 10, 11, 12, 13, and 14 represent a modified arrangement, in which the
steam is excluded from the gearing. For this purpose the valve is connected to
the compensator by a shell or casing case, or otherwise connected steam-tight there-
with. The valve has also a loose outer ring forming part of its face, which revolves
with the valve, but is kept up to the seat on the cylinder by springs, so that
however much this ring may wear the steam will be prevented from escaping
between it and the seating, and so coming in contact with the gearing. This
arrangement is very advantageous, as it enables access to bo. had to the gearing
while working through a suitable opening in the valve chest, and the teeth of the
wheels being thus protected need not be made of any special material.
Figures 9 and 10 show longitudinal sections of this arrangement taken at right
angles to cach other.
Figure 11 shews an end view, and Figure 12 a section on line A, B, C, D, E, F,
G, H, I, J, Figure 9.
Figure 13 shows a section on line M, N, Figure 10; and Figure 14, a section on
line X, Y, Figure 9.
The slide valve A is connected to the compensator B by a casing C, by which the
steam is thus confined, and made to pass directly to the cylinder without coming in
contact with the gearing. D is the outer ring of the valve, made separate there-
from, and pressed up to its seat on the cylinder by springs E attached to the slide
valve by screws F. The ring D is caused to partake in the rotary motion of
the valve by studs G, Figures 10 and 12, but is freo to move slightly away from the
valve A as it is pressed up against its seat by the springs, so as to compensate for
wear. The valve A and ring Ď have each a circular groove opposite to and core-
sponding with one another to receive an india-rubber packing ring H, which is
pressed by a metallic ring I against the sides of the groove in A. and D, so as to
prevent any escape of steam between the two.
-
The distributor J of the expansion valve is also formed of a shell or casing having
openings K in its circumference, by which the steam is admitted. This chamber J
is pressed up by a spring L against the main valve, which in turn is pressed up
against its distributor.
The Drawing represents the cylinder of a small vertical engine of 12 horse power.
As the engine is not of great power, the springs E which press the ring D against
the seat are shown as fixed, but in the case of a powerful engine the springs
should be moveable, and their pressure be regulated by means of screws or other
wise.
In engines in which the slide valve is provided with means for excluding the
steam from the gearing, the admission and expansion slide valves are both regulated
with a single steam inlet by bringing the levers M, N, of the distributors of said
valves in a line with each other and locking them together by the pin O, so that
when the distributing valve is reversed the expansion valve is reversed also.
The engine having been started, if it is desired to work expansively the locking
pin O is withdrawn, in order to release the lever of the expansion valve, which is
then rotated to an extent corresponding with the degree of expansion desired, and

page_text: locked in this new position by the saine pin O fitting in one of a series of holes P,
see Figure 11. As the steam is excluded from the gearing, advantage is taken of
this to immerse thein in a bath of soap water, which lubricates them better than a
grease cup.
+
Openings Q, Figure 13, are provided in the valve chest, closed by screw plugs,
through which the gearing inay be inspected without the necessity of dismounting
the valve cliest. R, channels through which the lubricant is conveyed to the
frictional surfaces of the 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
12th November 1878: .
ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the County of Middlesex,
Patent-Agent:
IMPROVEMENTS IN VALVES FOR STEAM ENGINES." A communi-
cation from abroad by Gustave Arnoux, of Marseilles; France:
This, Invention relates to improvements in rotary slide valves for steam engines
of the kind described in the Specification of Letters Patent granted to me bearing
date November 15th, 1875, No. 3972. These valves are circular in form, have a
continuous circular motion, and are furnished with movable seats which the inventor
terms "distributors," but they are open to the same objection as a common recipro-
cating slide valve, viz., that the unbalanced pressure on the back of the valve causes
great wear both of the valve and seat. It is important to avoid this defect,
especially in powerful engines, as the slide valves, being of large size much power
is consumed in overcoming the friction, and great labor is required to reverse the
valves.
The present improvements are designed to obviate these disadvantages, and to
render the working of the valves smooth and easy; and the Invention consists,
first, in the combination with a rotary slide valve of the kind above referred to of
what the inventor terms a "compensator" attached to the valve and revolving
therewith against a seat on the valve chest cover. The pressure of the steam on
the inner surface of this compensator may be made to balance that on the back of
the valve to any 'extent required, and the valve may thus be made an equilibrium
valve. The valve chest cover is fitted in a stuffing box, and is pressed inwards by a
spring which is capable of regulation in order to obtain any desired pressure of the
valve on its seat.
The Invention thus consists broadly in balancing rotary valves of this description
to any extent required by causing the pressure of the steam to act on two opposite
surfaces, the pressures on the said surfaces being proportional to their areas.
A simple and effectual means is also employed for obtaining a supplementary
'distribution with variable expansion, so as to reduce the amount of steam consumed
uselessly as herein-after detailed.

page_text: -with the valve, but is kept up to the seat on the cylinder by springs, so that
however much this ring may wear the steam will be prevented from escaping
between it and the seating, and so coming in contact with the gearing. This
arrangement is very advantageous as it enables access to be had to the gearing while
the engine is working through a suitable opening in the valve chest, and the teeth
of the wheels being thus protected need not be made of any special material.
Figures 9 and 10 show longitudinal sections of this arrangement taken at right
angles to each other.
""
Figure 11 shows an end view, and Figure 12 a section on line A, B, C, D, E, F, G,
H, I, J, Figure 9.
Figure 13 shows a section on line M, N, Figure 10; and Figure 14, a section on
line X, Y, Figure 9.
"
The slide valve A is connected to the compensator B by a casing C, by which the
steam is thus confined and made to pass directly to the cylinder without coming in
contact with the gearing. D is the outer ring of the valve made separate there-
from, and pressed up to its seat on the cylinder by springs E attached to the valve
by screws F. The ring D is caused to partake in the rotary motion of the valve by
studs G, Figures 10 and 12, but it is free to move slightly away from the valve A
as it is pressed up against its seat by the springs so as to compensate for wear. The
valve A and ring D have each a circular groove opposite to and corresponding with
one another to receive an india-rubber packing ring H, which is pressed by a
metallic ring I against the sides of the groove in A and D, so as to prevent any
escape of steam between the two.
The distributor" J of the expansion valve is also formed of a shell or casing
having openings K in its circumference, by which the steam is admitted.
This
chamber J is pressed up by a spring L against the main valve, which in turn is
pressed up against its "distributor."
.
The Drawing represents the cylinder of a small vertical engine of 12 horse power.
As the engine is not of great power the springs E, which press the ring D against
its seat are shown as fixed, but in the case of a powerful engine the springs should
bo moveable, and their pressure be regulated by means of screws, wedges, or other-
wise.
In engines in which the steam is excluded from the gearing of the valve, the
admission and expansion valves are both regulated with a single steam inlet by
bringing the levers M, N, of the "distributors" of the said valves in a line with
each other, and locking them together by the pin O, so that when the distributing
valve is reversed the expansion valve is reversed also.
The engine having been started if it desired to work expansively the locking pin
O is withdrawn in order to release the lever of the expansion valve, which is then
rotated to an extent corresponding with the degree of expansion desired, and locked
in this new position by the same pin O fitting in one of a series of holes P, see
Figure 11. As the steam is excluded from the gearing advantage is taken of this
to immerse it in a bath of soapy water, which lubricates it better than a
grease cup:
Openings Q, Figure 13, are provided in the valve chest, closed by screw plugs
through which the gearing may be inspected without the necessity of dismounting
'the valve chest. Rare the channels through which the lubricant is conveyed to the
frictional surfaces of the valves.
"
. . 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 heroin-
before-in part recited-Letters Patent is,―
1st. The employment, in combination with the rotary slide valves aforesaid of
"compensators," so applied that the steam pressure on the back of the valves is
balanced more or less by the opposing pressure on the "compensators," substan-
tially as herein shown and described, whereby the valves of large engines are pre-
vented from pressing unduly against their seats.
•

page_text: 2nd. The arrangement of rotary valve and compensator, connected by a casing,
substantially as herein shown and described, by which the steam is excluded from
the gearing, so that the latter is not liable to become heated, and may be readily
inspected when necessary.
In witness whereof, I, the said Alexander Melville Clark, have hereunto set my
hand and seal, this Twelfth day of November, in the year of our Lord
One thousand eight hundred and seventy-eight.