Improvements in Balanced Slide Valves.
Year: 1895

page_text: PROVISIONAL SPECIFICATION.
Improvements in Balanced Slide Valves.
We, JOHN BROKENSHIRE FURNEAUX, of Victoria Works, Gateshead, in the
County of Durham, Engineer, and ALEXANDER HORNE, of Victoria Works
aforesaid, Engineer, do hereby declare the nature of this invention to be as
follows:-
This invention has reference to a construction of balanced slide valve wherein
the slide valve is provided with an extension that enters and forms a steam tight
joint with a cylinder or cap that is arranged to move with the valve but is carried
independently thereof and the interior of which is in connection with the exhaust
cavity of the valve, the arrangement being such that the pressure with which the
valve is forced against the cylinder valve face is proportional to the ratio of the
internal cross sectional area of the cylinder or cap subject to the pressure of exhaust
steam and the area of the valve face.
In one arrangement according to this invention the slide valve is an ordinary
D slide having a centre exhaust cavity and connected to a valve spindle by stirrups.
Above the valve is a plate between which and the top of the valve a thin metallic
diaphragm is secured by a screw stud. Surmounting the whole is a cylinder or cap
which extends down around the plate, and bears against the diaphragm. This
cylinder or cap is carried by parallel motion bars that allow it to be maintained
in a fixed position relatively to the valve while the latter is being reciprocated.
Extending through the back of the valve are passages connecting the exhaust
cavity of the valve with the interior of the cylinder or cap.
The action of the balancing arrangement is as follows:-The steam pressure
obtaining in the valve chest, acts on the entire area of the cylinder or cap exposed
to such pressure, but the effective area inside of the said cylinder or cap exposed
to the pressure of exhaust steam entering from the exhaust cavity of the valve is so
regulated in proportion to the valve area that there is just sufficient downward
tendency or pressure towards the valve face to keep the valve in position. The
pressure outside the cylinder or cap being greater than inside, the diaphragm is
pressed tightly against, or it may be secured to, the bottom face of the cylinder or
cap, thus preventing boiler steam entering the cylinder or cap from the steam
chest. The load on the said cylinder or cap due to boiler pressure less the exhaust
or back pressure, is sustained by the parallel motion, so that the total load on the
slide valve is reduced in proportion to the ratio of the internal cross sectional area
of the cylinder or cap to valve face area. The parallel motion may consist of
a lever connected by knife edge bearings to the top of the cylinder or cap and to
liuks that are similarly connected to fixed pins in the valve chest.
In a modified arrangement, the parallel motion is dispensed with and the
cylinder or cap supported, preferably through a number of antifriction balls or
rollers, by the valve face on which the slide valve works. The antifriction balls or
rollers, when used, may be mounted in a cage to prevent them from altering their
relative positions.

page_text: The plate and diaphragm used in the preceding arrangements, may be replaced
by a piston arranged to work steam tight in the aforesaid cylinder or cap.
Dated this 19th day of August 1895.
For the Anulinanda
W. LLOYD WISE,
6 Lincoln's Inn Fields, London, W.C., Chartered Patent Agent.
:
improvements in‹Balanced Slide, valves.
We, JOHN BROKENSHIRE FURNEAUX, of Victoria Works, Gateshead, in the
County of Durham, Engineer, and ALEXANDER HORNE, of Victoria Works,
aforesaid, Engineer, do hereby declare the nature of this invention and in what
manner the same is to be performed to be particularly described and ascertained in
and by the following statement :-
This invention has reference to a construction of balanced slide valve wherein
the slide valve is provided with an extension that enters and forms a steam tight
joint with a cylinder or cap that is arranged to move with the valve but is carried
independently thereof and the interior of which is in connection with the exhaust
cavity of the valve, the arrangement being such that the pressure with which the
valve is forced against the cylinder valve face is proportional to the ratio of the
internal cross sectional area of the cylinder or cap subject to the pressure of
exhaust steam and the area of the face of the valve.
Figs. 1, 2 and 3 of the accompanying drawings are respectively a longitudinal
vertical section, a cross section and a sectional plan showing one arrangement
of slide valve according to this invention in position for use within a valve chest.
In this arrangement the slide valve 1 is an ordinary D slide having a central
exhaust cavity 2 and connected to a valve spindle 3 by a ring or stirrup 4. Above
the valve is a plate 5 between which and the top of the valve a thin metallic
diaphragm 6 is secured by a screw stud 7. Surmounting the whole is a cylinder or
cap 8 which extends down around the plate 5 and bears against the diaphragın 6.
This cylinder or cap is carried by parallel motion bars that allow it to be
maintained in a fixed position relatively to the valve while the latter is being
reciprocated. In the example shown in the arrangement now being described, the
parallel motion comprises a pair of bent bars 9, 9 that are suspended at one end
from a bracket 10 by a link 11, are supported at the other end upon a bracket 12
by a link 13, and from the central portion of which the cylinder or cap 8 is
Buspended, the several parts being supported on knife-edge bearings 14, as shown,
to diminish friction. Extending through the back of the valve 1, the plate 5 and
the diaphragm 6 are passages 15 that connect the exhaust cavity 2 of the valve
with the interior of the cylinder or cap 8.
The action of the balancing arrangement is as follows:-
-The steam pressure
obtaining in the valve chest 16, acts on the entire area of the cylinder or cap 8
exposed to such pressure, but the effective area inside of the said cylinder or cap
exposed to the pressure of exhaust steam entering from the exhaust cavity 2 of the
valve I is so regulated in proportion to the area of the valve in plan that there is
just sufficient downward tendency or pressure towards the vaive face to keep the
valve in position. The pressure outside the cap being greater than inside, the
diaphragm 6 is pressed tightly against, or it may be secured to, the bottom face of
the cap, thus preventing boiler steam entering the cap from the steam chest and
also partly balancing the pressure on the said cap. The effective load on the
said cap due to the boiler pressure less the exhaust or back pressure, is sustained
by the parallel motion, so that the total load on the slide valve 1 is reduced in

page_text: proportion to the ratio of the internal cross sectional area of the cap to the area of
the face of the valve, that is to say to the area of the valve in plan.
In the modified arrangement shown in Figs. 4, 5, and 6 and in Figs. 7, 8 and 9
which are similar views to Figs. 1, 2 and 3 respectively, the parallel motion is
dispensed with and the cap 8, which is secured to the diaphragm 6 and to a tubular
distance piece or extension 8 by screws 8, is supported, preferably through
a number of antifriction balls 17 (Figs. 4, 5 and 6) or rollers 17* (Figs. 7, 8
and 9), by the valve face on which the slide valve 1 works. The antifriction balls
or rollers, when used, may be mounted in a cage or be otherwise connected together
to prevent them from altering their relative positions. In the example shown in
Figs. 4 5 and 6, the antifriction balls 17 are arranged at two opposite sides of the
valve, each set of balls being mounted in a case or frame 17°. In Fige. 7, 8
and 9 there are two antifriction rollers 17 arranged at two opposite sides of the
valve to work in channels 18, each pair of rollers being connected by a pair of
links 17°.
The plate 5 and diaphragm 6 used in the preceding arrangements, may be
replaced by a piston arranged to work steam tight in the aforesaid cylinder
or cap.
Figs. 10, 11 and 12 are similar views to Figs. 1, 2 and 3 respectively, illustrating an
arrangement of this kind wherein the upper part 1" of the valve 1 fits steam tight in
the cylinder or cap 8 which is suspended by a motion similar to that shown in
Figs. 1, 2 and 3 except that both of the brackets 10 and 12 and links 11 and 13
are arranged below the ends of the bars instead of one below and one above
whereby a vertical motion is given to the cylinder or cap 8, though the parallel
motion may be adopted if desired. The ring or stirrup 4 for operating the valve 1
in this case encircles the cylinder or cap 8.
Figs. 13, 14 and 15 show an arrangement in which the piston like extension 1*
of the valve 1 works steam tight in a cylinder 8 the load on which is taken
through antifriction balls 17 by the valve face on which the valve works.
Figs. 16, 17 and 18 show a similar arrangement to that shown in Figs. 13, 14
and 15 but in which anti-friction rollers 17" are substituted for anti-friction balls.
In each of the modified arrangements shown, it will be seen that the pressure
with which the valve is forced against its seat by the pressure of the steam in the
valve chest is proportional to the ratio of the internal cross sectional area of the
cylinder or cap 8 subjected to the pressure of exhaust steam and the area of the face
of the valve.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed we declare that what we
claim is :-
1. A balanced slide valve wherein the slide valve is provided with an extension
that enters and forms a steam tight joint with a cylinder or cap that is arranged to
move with the valve but is carried independently thereof and the interior of
which is in connection with the exhaust cavity of the valve, substantially as herein
described.
2. Our improved balanced slide valves constructed arranged and operating
substantially as hereinbefore described with reference respectively to and shown
in Figs. 1, 2 and 3; in Figs. 4, 5 and 6; in Figs. 7, 8, and 9; in Figs. 10, 11
and 12;
in Figs. 13, 14 and 15; and in Figs. 16, 17 and 18 of the drawings
annexed.
Dated this 90th dow of M 1906