Improved Valve Gear for Steam and other Fluid Pressure Motors.
Year: 1895

page_text: Date of Application, 2nd May, 1895
Complete Specification Left, 31st Dec., 1895-Accepted, 8th Feb.,
1896
PROVISIONAL SPECIFICATION.
Improved Valve Gear for Steam and other Fluid Pressure Motors.
We, FREDERICK CLENCH, and THOMAS SCOTT KING, both of Lincoln Works,
Chesterfield, County of Derby, Mechanical Engineers, do hereby declare the
nature of this invention to be as follows :-
--
The object of this invention is the improvement and simplification of valve gears
of steam and other fluid pressure motors, and more particularly to that type of
valve gear having two slide valves, i.e. one main slide valve and one expansion
slide valve. The main slide valve has a fixed travel and angular advance in
relation to the crank, the expansion slide valve being controlled automatically by
some mechanical combination such as a governor, or by hand.
According to our invention, the valve gear consists essentially of an ordinary
main slide valve of box section having the usual steam ports and exhaust cavity
working on the ports of the cylinder.
In the back of main slide valve, inclined ports are cut giving communication to
that end of cylinder to which their position corresponds.
The expansion slide valve has inclined openings similar to those in back of main
valve and is guided by a cross bar which moves it at right angles to the direction of
the main slide valve travel.
The cross bar is connected by a rod to suitable intermediate mechanism to the
regulator (governor) which may be automatic or hand adjustment.
The main and expansion slide valves have each a separate and definite motion
derived from independent eccentrics keyed on the crank shaft.
The initial steam opening or "lead" and the exhaust opening and closing are
unvarying in period and position in relation to the crank movement.
The distance of the edges of the ports of expansion slide valve from the outer
edges of the inclined ports in the back of main slide valve is variable according to
the position of the cross bar. It becomes negative for very early cut off and
positive for late cut off of steam to cylinder.
The invention therefore briefly consists of valve gears for steam and other fluid
pressure motors comprising a cross bar connected to a regulating device and
controlling the position of an expansion slide valve in a direction at right angles
to the movement of the main slide valve and in a plane parallel to it.
Dated this 2nd day of May love.
H. GARDNER,
Patent Agent, 166 Fleet Street, London,
Agent for the said Frederick Clench and Thomas Scott King.
We, FREDERICK CLENCH, and THOMAS SCOTT KING, both of Lincoln Works,
Chesterfield, County of Derby, Mechanical Engineers, 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:-
The object of this invention is the improvement and simplification of valve gears

page_text: of steam and other fluid pressure motors and more particularly of that type of valve
gear having two slide valves i.e. one main slide valve, and one expansion slide valve.
The main slide valve has a fixed travel and angular advance in relation to the
crank, the expansion slide valve being controlled by hand or automatically by some
mechanical combination, such as a governor.
According to our invention the valve gear consists essentially of an ordinary main
slide valve of box section having the usual steam ports and exhaust cavity working
on the ports of the cylinder.
In the back of main slide valve, inclined ports are cut giving communication to
that end of cylinder to which their position corresponds.
The expansion slide valve has inclined openings similar to those iu back of main
valve, and is guided by a cross bar which moves it at right angles to the direction
of the main slide valve travel.
The cross bar is connected by a rod to suitable intermediate mechanism to the
regulator (governor) which may be automatic or hand adjustment.
The main and expansion slide valves have each a separate and definite motion
derived from independent eccentrics keyed on the crank shaft.
The initial steam opening or "lead" and the exhaust opening and closing are
unvarying in period and position in relation to the crank movement.
The distance of the edges of the ports of expansion slide valve from the outer
edges of the inclined ports in the back of main slide valve is variable according to
the position of the cross bar.
The distance between the edges becomes negative for very early cut off and
positive for late cut off of steam to cylinder.
The annexed drawings illustrate our said invention.
Figure 1 section through part of cylinder showing end elevation of valves.
Figure 2 arrangement of governor and valves when the engine is at rest.
Figure 3 the valves and governor in position for early cut-off.
A ordinary main slide valve of box section. B valve chest. C expansion slide
valve operable at right angles to the main valve A by the governor, or by hand.
D cross bar by which expansion slide valve is suspended. E rod of cross bar
leading to governor mechanism if such be provided. F, F, inclined ports in
expansion slide corresponding with inclined ports in main slide valve A.
The lines G, G, in Figure 2 indicate the full distance the edges af the expansion
slide valve ports are from the outer edges of those of the main slide valve ports, the
lines H, H, in Figure 3 indicating the distances while the engine is running without
any load. The distances being variable according to the position of the expansion
slide by the use of inclined slots in the main and auxiliary slides it follows that
according to the vertical position the expansion slide occupies under the action of
the governor or by hand so the main slide will travel a greater or less distance
before cutting off steam thereby using steam proportional to the load put upon the
engine.
Having now particularly described and ascertained the nature of this inveu-
tion and in what manner the same is to be performed we declare that what we
claim is :-
The improved valve gear for steam and other fluid pressure motors comprising a
cross bar connected to a regulating device and controlling the position of an
expansion slide valve having inclined ports in a direction at right angles to the
movement of the main slide valve and in a plane parallel to it, the parts being
arranged for operation in the manner substantially as described.
The 31st day of December 1895.
H. GARDNER,
Patent Agent, 166 Fleet Street, London,
Agent for the said Frederick Clench and Thomas Scott King.