A NEW AND IMPROVED BALANCED SLIDE VALVE
Year: 1865

page_text: PROVISIONAL SPECIFICATION left by William Edward Newton at the
Office of the Commissioners of l'atents, with his Petition, on the
22nd February 1865.-A communication from abroad by James Rankin,
of Detroit, in the State of Michigan, United States of America.
I, WILLIAM EDWARD NEWTON, of the Office for Patents, 66, Chancery
Lane, in the County of Middlesex, Civil Engineer, do hereby declare the
nature of the said Invention for "A NEW AND IMPROVED BALANCED SLIDE
VALVE," to be as follows:-
The object of this Invention is to balance the pressure of the steam on the
back of a slide valve in such a manner that the same will work equally as free
under a pressure of a hundred pounds or more to the square inch as it does in
the open atmosphere. This object is obtained by combining with the valve a
small cylinder in which works a piston, and through a series of intervening
levers, rockers, and links, the upward pressure of the steam on the piston is
made to counterbalance the downward pressure on the back of the valve, and
the valve is therefore perfectly balanced. The bottom of the valve chest forms
the seat for the slide valve, and a reciprocating motion is imparted to this
valve in the usual manner. From the back of the valve rise two lugs which
form the bearings for the fulcrum pins of the lever which is supported by the
pins at about the middle of its length. One end of the lever is provided with

page_text: a notch which rests upon the upper end of a rocker that is stepped in suitable
bearings on the bottom of the valve chest. The opposite end of the lever is
suspended from a link which is connected by a pivot with a lever, one end of
which rests upon a knife edge bearing which is rigidly connected to the side
of the valve chest, whereas its other loose end extends through a slot in the
piston rod.
This rod extends from a piston which is fitted into a cylinder
supported by the top of the steam chest, and open at its inner end. An
aperture in the top of the cylinder forms an escape for that portion of stean
which may pass the piston. If steam is admitted to the steam chest it forces
the piston up and the valve down, and the connection between the piston and
valve and the areas of the parts are so proportioned that the upward pressure
on the piston just balances the downward pressure on the valve. At the
same time the valve is allowed to move freely on its seat, the lever being
arranged to partake of the vibrating motion of the valve. The pressure which
holds the valve down on its seat can be easily regulated by changing the
position of the pin which connects the link with the lever. If this point is
moved closer to the knife edge bearing the power which tends to raise the
valve from its seat is increased, and consequently the power which holds the
valve down on its seat is diminished, and by removing the pin from the knife
edge bearing closer to the piston rod, the upward pressure is diminished, and
consequently the pressure which holds the valve down on its seat is increased.
By this means the slide valve can be adjusted so nicely that it will work
equally free under a high pressure as it does when the steam is shut off,
and that it is held down on its seat with just power enough to prevent
leakage.