Year: 1886

page_text: Date of Application, 7th July, 1886.
Complete Left, 7th Apr., 1887.
Complete Accepted, 10th May, 1887.
I, WILLIAM WESTWOOD, of 525 Manchester Road, Isle of Dogs, London, Engineer,
do hereby declare the nature of this invention to be as follows:-
This invention has reference to a kind of balanced slide valve in which in order to
counteract in part pressure at the back of the valve tending to press its face against
the face upon which it works the valve is formed or provided with a cylinder or
chamber fitted with a piston. One side of this piston is subject to the same pressure
per square inch as the portion of the back of the valve that surrounds it, that is to
say, the pressure that obtains for the time being in the valve chest. Within a cavity
at the opposite or face side of the valve are provided levers supported by anti-friction
wheels or rollers. These levers are connected to the piston in such a manner that the
pressure acting upon that side of the piston exposed to the fluid in the valve chest is
caused to communicate through the levers to the slide valve, pressure in an opposite
direction. The valve may be actuated in any convenient way.
Motion of the piston
in a rotary sense may be prevented by a feather or equivalent device. The cylinder
valve face may be provided with a bar or supporting surface extending across the
port or ports therein for the purpose of carrying the anti-friction wheels or rollers.
Dated this 7th day of July A D 1886

page_text: 1, WILLIAM WESTWOOD, of 525 Manchester Road, Isle of Dogs, London, 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 kind of balanced slide valve in which, in order to
counteract in part, pressure at the back of the valve tending to press its face against
the face upon which it works, the valve is formed or provided with a cylinder or
chamber fitted with a piston.
One side of this piston is subject to the same pressure per square inch as the
portion of the back of the valve that surrounds it, that is to say the pressure that
obtains for the time being in the valve chest.
Within a cavity at the opposite or face side of the valve are provided levers supported
by anti-friction wheels or rollers.
These levers are connected to the piston in such a manner that the pressure acting
upon that side of the piston exposed to the fluid in the valve chest is caused to
communicate through the levers to the slide valve pressure in an opposite direction.
The valve may be actuated in any convenient way. Motion of the pistion in a
rotary sense may be prevented by a feather or equivalent device. The cylinder valve
face may be provided with a bar or supporting surface extending across the port or
ports therein for the purpose of carrying the anti-friction wheels or rollers.
Referring to the accompanying two sheets of drawings.
Fig. 1 shews in vertical section a steam chest and adjacent part of a cylinder fitted
with a balanced slide valve according to this invention. Fig. 2 is a plan with the
steam chest cover and slide valve removed. Fig. 3 is an end view; Fig. 4 a plan or
top view; Fig. 5, a vertical section on the line A.B Fig. 4; and Fig. 6 an underside view
of the balanced slide valve alone. 1 is a slide valve having formed in it a cylinder or
chamber 2 fitted with a piston 3. The rod 4 of this piston passes through a hole at 5
in the valve and is connected to two pairs of lever 6,6 situated in the exhaust cavity 7 of
the valve. Each pair of levers is pivotted at 8 to an antifriction wheel or roller 9
which serves as its fulcrum one lever being arranged at each side of the wheel or
roller as shown in fig. 6. One end of each lever is, as already stated, jointed to the
lower end of the piston rod, while its other end takes against the under surface of
the valve as shown. 10 is a bar of plate let into the cylinder valve face so as to be
flush therewith; it is secured in place by screws 11, and serves as a path for the
antifriction wheels or rollers 9. 12 is a feather on the piston rod 4; and serves to
prevent rotary motion of the said rod and piston; and the consequent displacement of
the levers and anti-friction wheels or rollers.
The pressure of motive fluid acting on the upper side of the piston is communicated
through the piston rod 4 and levers 6 to the under side of the valve and thus counter-

page_text: balances the pressure of motive fluid on the remaining part of the back of the valve
to an extent that will depend upon the ratio of the area of such back portion of the
valve to that of the piston. The area of the piston should always be less than that of
the remaining part of the back of the valve in order that the valve may be always
kept to its seat.
In fig. 1, the balanced slide valve is shown in place on a cylinder valve face and
within a steam chest 13. 14 is the valve rod connected to the valve by means of a
nut 15 introduced sideways into a cavity 16 in the valve as indicated by arrows,
Fig. 6. A second cavity 16* is provided to allow of the valve being turned end for
end. The valve rod may however be connected to the valve in any other suitable
manner. Any steam leaking past the piston escapes into the exhaust port through a
fine hole made for the purpose.
Having now particularly described and ascertained the nature of this invention and
in what manner it is to be performed, I declare that what I claim in connection
with a slide valve is :-
1.) A piston subject to the pressure of the actuating fluid, and so arranged that the
pressure it experiences tends to raise the valve from the valve face substantially as
described.
2.) A piston moving with the valve and connected with levers provided with anti-
friction rollers the said levers being so disposed that they convert the pressure on the
back of the piston into a force tending to raise the valve substantially as described.
3.) The improved balanced slide valve constructed, arranged and operating
substantially as hereinbefore described with reference to and shown in the drawings
annexed.