Improvements in and connected with Balanced Slide Valves.
Year: 1891

page_text: COMPLETE SPECIFICATION.
[Communicated from abroad by JOHN MCDONALD, of The Railways, Shinbasi,
Tokio, in the Empire of Japan, Engineer.]
Improvements in and connected with Balanced Slide Valves.
1, WILLIAM EDWIN HEYS of 70 Market Street Manchester in the County of
Lancaster, Patent Agent, do hereby declare the nature of this invention, and in
what manner the same is to be performed, to be particularly described and ascer-
tained in and by the following statement :-
This invention relates to balanced slide valves and more particularly to the slide
valves of locomotive steam engines and other similarly constructed engines.
In a slide valve constructed according to these improvements the exhaust
chamber is made as large as practicable, and open upon the top or side further
from the ports. A cover is fitted within the exhaust chamber in such a manner
that it can slide perpendicularly to the face of the valve, and is provided with
packing strips or rings so as to make a tight joint between the live steam space and
the exhaust chamber. Above or beyond the sliding cover there is fixed a faced
plate in a plane parallel with the valve seating, and the sliding cover, in its highest
position, works against this faced plate, live steam being thereby excluded from the
back of the cover and consequently from so much of the slide valve as is occupied
by the cover. Atmospheric pressure may be admitted to the back of the cover
through an opening in the faced plate controlled by a suitable valve.
In an engine having a valve or valves constructed according to these improve-
ments, immediately upon shutting off the steam, air is admitted to the valve chest,
and any vacuum in the cylinder is destroyed and the engine can consequently run
more freely after the steam shut off than is the case with existing slide valves.
The arrangement is perfectly automatic, that is to say, when the steam is turned
on the sliding cover is lifted and the valve is working under atmospheric pressure
only upon the cover, and when steam is shut off the sliding cover falls away from
the faced plate, but if from any reason the balancing action should not come into
play, the driver will be notified of the fact by the escape of steam from the air
inlet through the faced plate. It will be seen also, that the improved valve may
be adapted to existing engines without material alteration, that since the action
does not depend upon springs, it is not liable to disarrangement from their failure,
and that the rectangular form which I prefer to employ, gives the largest available
balanced area.
I will more particularly describe the said invention with reference to the
accompanying drawings, in each of the figures of which similar parts or details are
denoted by similar letters of reference.
Figure is a transverse section, and Figure 2 is a section and plan of the
improved slide valve. Figure 3 is a longitudinal section of the valve and its
arrangement and Figure 4 is a plan of the air inlet valve.
A is the slide valve which is preferably rectangular and is constructed with an
open top so that the crown or cover B may be fitted therein in such a manner as to
be capable of a sliding movement perpendicularly to the face of the valve. The
joint between A and B is rendered steam tight by means of any suitable packing,
but it is preferred to employ the strips C and D in each of the contiguous vertical
faces of the cover and of the exhaust chamber of the valve respectively. The
strips C may be pressed into contact with the walls of the exhaust chamber by
means of the springs E which may be secured to the inner face of the cover by
the screws F and have their opposite ends G G curved so as to abut upon
projection H formed upon the backs of the strips C and passing through the walls

page_text: of the cover B. The back pressure of the exhaust chamber will be added to
the pressure exerted by the springs E and tend to make the joints tighter.
The packing strips D in the walls of the exhaust chamber are pressed into
contact with the walls of the cover B by live steam admitted from the valve
chest through the channels J J which communicate with the backs of the
strips.
K is a faced plate fixed parallel with the valve seating. This plate is longer
than the travel of the cover B plus its length, and wider than the cover, so that
at no part of its stroke is the live steam in the steam chest capable of gaining
access to the back of the cover when it is in contact with the plate K. Through
the faced plate K there is formed an opening L communicating with the atmosphere
through a valve such as M which is preferred to be a hit and miss" disc valve as
represented in Figures 3 and 4.
In ordinary work this valve is open, but if it should be desirable or necessary to
work the valve as an ordinary slide valve, it is closed. It may be fixed as indicated,
close to the valve chest, or it may be placed at the extremity of a pipe communi-
cating with Land carried through the smoke box.
Assuming the engine to be at rest, and the cover B to be in its lowest position
within the exhaust chamber of the slide valve and consequently out of contact with
the faced plate, upon opening the regulator or steam admission valve steam will
escape during the first few revolutions through L. The driver then momentarily
closes the admission of steam by shutting the regulator or otherwise, whereupon
the back-pressure of the exhaust in the exhaust chamber of the slide valve forces
up the cover B into contact with the faced plate K and the slide valve works nearly
balanced. It will be evident that when the valve is working as a balanced slide
valve, no steam escapes from the opening L, but if steam should escape therefrom,
it is an intimation to the driver that the slide valve is working as an ordinary valve,
and if upon momentarily closing the steam admission, steam continues to escape,
he may close the valve M, but this is an event which is very unlikely to occur.
The slide valve may be connected with the rod by means of the strap or
buckle N and the handle O of the valve M may be operated from the foot plate
or elsewhere by means of suitable connecting rods.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what I
claim is,
1. A balanced slide valve constructed and operating substantially as hereinbefore
described and as illustrated by the accompanying drawings.
2. In a balanced slide valve, the construction and arrangement of the sliding
cover B substantially as hereinbefore described and as illustrated by the accom-
panying drawings.
3. A slide valve constructed to work as an ordinary or as a balanced slide and
consisting essentially of a valve face an exhaust chamber and a sliding cover, in
combination with a faced plate having an opening therethrough communicating
with the atmosphere and controlled by a valve, constructed arranged and operating
substantially as hereinbefore described with reference to the accompanying
drawings.
Dated this 11th day of May A.D. 1891.
WILLIAM E. HEYS.