for Steam and other Motive Power Engines.
Year: 1887

page_text: Date of Application, 5th May, 1887.
Specification Accepted, 7th June, 1887.
for Steam and other Motive Power Engines.
We, DAVID ROBERTSON of 47 Langlands Road, Govan, in the Counties of Lanark
and Renfrew; North Britain, and JAMES ARCHIBALD MCKIE of Ernespie, Castle
Douglas in the Stewartry of Kirkcudbright, North Britain 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:
Our Invention which relates to improvements in and in connection with equilibrium
slide valves for steam and other engines consists in the construction of the slide valve
with its face and back of the same area and so arranged that its back which is also
formed with a flat face works against the flat face of an adjusting cover or plug plate
which fits steamtight in the steain chest. The said cover or plug plate is held in its
place within the steam chest and against the valves by spiral springs or the equivalent
thereof. The tension of these springs or their equivalent is so adjusted as to counteract
the pressure on the inner side of the plug plate and as the steam does not pass behind
the working faces of the valve, the valve is held in equilibrium and works with a
minimum of friction.
In order that our Invention may be properly understood and readily carried into
effect, we will now proceed to describe the drawings hereunto annexed.
Figure 1, of the accompanying drawings is a transverse section of an equilibrium
slide valve constructed and mounted in accordance with our said Improvements.
Figure 2, is a plan corresponding to Figure 1, and shewing certain parts
corresponding to Figure 3, which is an elevation, one half being a section of the said
valve with arrangements whereby it is adapted to a low pressure or condensing
engine.
The slide valve A, is constructed with its face a, and back a¹ of equal areas as shewn
in Figures 1 and 3, its back a¹, working against the flat face of the steam chest cover
or plug plate B. The said plug plate is fitted steam-tight within the steam chest C,
by the stuffing box b, and gland 6. The said plug plate is held elastically in its place
and against the valve A, by the spiral springs D. "The said springs are carried by the

page_text: bolts E, which are screwed through the bushes f, in the bridges F, the said bridges
being fixed to the steam chest C, at each side thereof, by the bolts f¹. The tension of
the springs is adjusted by the nuts e, upon the said screwed bolts E, the regulating
of the spring tension being such as will only resist the pressure upon the inner side of
the steam chest cover or plug plate B. As the steam cannot pass behind the working
faces of the valve A, the said valve is held in equilibrium and works with a minimum
of friction.
In the case of low pressure condensing engines the plug plate B, is connected by
means of bell-crank levers and links g, g', g, to the piston /, of a cylinder H, as shewn
more particularly in Figures 2 and 3. The said cylinder H, is in communication with
the condensor so that the vacuum therein may counteract the vacuum on the exhaust
of the slide valve A.
Having now particularly described and ascertained the nature of our said Invention
and in what manner the same is to be performed, we declare that what we claim is :-
1. In equilibrium slide valves for steam and other engines, the slide valve A, having
the upper and lower working surfaces of equal area, together with the adjustable plug
plate B, fitted with packing to render it steam tight and held in elastic tension against
one of the faces of the slide valve by means of adjustable springs or their equivalents
substantially as hereinbefore described and shewn on the accompanying drawings.
2. In equilibrium slide valves for low pressure condensing steam engines, the
connecting of the plug plate B, by means of bell crank levers or their equivalents, to
a piston contained in a cylinder open to the condenser substantially as hereinbefore
described and shewn on the accompanying drawings.
DL
L 1
M
1007
J. H. JOHNSON, DAY & JOHNSON,
115, St. Vincent Street, Glasgow,
Applicants' Agents.