Year: 1886

page_text: I EDWIN POWLEY ALEXANDER of 36 Southampton Buildings in the County of
Middlesex Fellow of the Institute of Patent Agents do hereby declare the nature of
this invention (communicated to me from abroad by Charles Schmid of Chicago,
County of Cook State of Illinois United States of America) and in what manner
the same is to be performed to be particularly described and ascertained in and
by the following statement :-
The present Invention has relation to the improvement of that class of Blide
valve mechanism wherein means are employed to lessen the back pressure or
resistance in the cylinder upon the exhaust side of the piston, and in particular
does it relate to the improvement of that form of slide valve mechanism wherein
the main slide valve is provided with escape ports and with a supplemental valve
for opening and closing said ports in such manner that there will be a free exhaust
from the main cylinder during the time that the steam therein is acting both
directly and expansively. In valves of this construction it has been heretofore
proposed to control the movements of the supplemental valve by auxiliary pistons
operated by steam and enclosed within the body of the main slide valve.
In the improved form of slide valve mechanism hereinafter described I employ a
main slide valve having escape ports therein through which steam may escape from.
the exhaust side of the cylinder and a supplemental valve, but instead of operating
this supplemental valve by means of steam actuated pistons I provide the supple-
mental valve with mechanism adapted to co-operate with some relatively fixed
part of the engine structure (preferably the steam chest) in such manner that as
the slide valve moves back and forth the supplemental valve will be positively
shifted to open and close the escape ports therein at the proper times.
invention consists in the novel features of construction hereinafter described and
illustrated in the accompanying drawing, and particularly defined in the claims at
the end of this specification.
This
Fig. 1 is a view in longitudinal transverse section through the steam-chest, the
slide valve and the main cylinder. Figure 2 is a view in side elevation the cover
of the steam chest and of the main slide valve being removed. Figure 3 is a view

page_text: 1
similar to fig. 2 with the slide valve in different position. Fig. 4 is a view in
central vertical section through the steam chest and the slide-valve. Fig. 5 is a
detail view of the slide valve with its cover and the supplemental valve removed
therefrom. Fig. 6 is a view in vertical section on line of fig. 5. Fig. 7 is a
view in longitudinal section on line y-y of fig. 5. Fig. 8 is a view in side
elevation of the main slide valve from the rear side. Fig. 9 is an enlarged detail
view in longitudinal section of the main slide valve.
A is the main cylinder of the engine provided with the usual steam ways a
and a¹ and exhaust port a³, B denotes the steam chest within which upon its
appropriate seat is placed the main slide valve which is operated by the valve rod C
in the usual manner. The body of the main slide valve is preferably cast in such
manner as to form the outer walls or sides D in single piece with the port
plate D' and the central plate D' these plates being connected together at the
corners and by the central web d and the webs d. Between the sides of the
central plate D² and, the walls D of the valve are formed the long escape ports d'
and d³ which communicate with the spaces d' beneath the central plate D.; in the
port plate D' are formed the escape ports d³ and do which communicate with
the chamber that is formed by the walls D of the main valve and the cover D* that
is suitably bolted thereto. At the ends of the central plate and port plate and
between the webs d'and the walls D of the valve are formed the transverse escape
ports d' which are in constant communication with the exhaust port a² of the main
cylinder and the exhaust cavity d³ of the slide valve. Within the central web d
is formed a seat adapted to receive one end E of the arbor E³ of the supplemental
valve E¹ this arbor being preferably cast in one piece with such valve and the
upper face of the port plate D¹ will be suitably ground to form a seat whereon
the valve may turn. Within a recess formed in the port plate D¹ fits the edge of
the guard ring F, the flange f of which overlaps the flanged portion e of the
supplemental valve E¹ and serves to hold this valve in position upon its seat. The
guard ring F is connected to the port plate by means of suitable bolts G entering
threaded seats in the plate these bolts being provided preferably upon their outer
ends with sets nuts ġ which enable the ring to be drawn more or less tightly
against the flange of the supplemental valve to secure an accurate working of the
parts and compensate for wear. Within the supplemental valve E¹ are formed the
radial apertures e' and e³ corresponding in shape and location with the ports d³
and d in the port plate D¹ although it will be understood that the size arrange-
ment and number of such apertures may be varied as desired. From the outer
face of the supplemental valve El extends the arbor E that passes through the
cover D' of the slide valve and is provided with the annular shoulder e between
which and the inner face of the cover D is fitted the washer h¹, and on the
arbor E and bearing against the supplemental valve E¹ is placed the washer h.
Encircling the arbor between the washers h and h¹ is the coiled spring E the ends
of which are fixed in the washer so that the spring bears constantly upon the
supplemental valve and the inner face of the cover D'. I have found in practice
that if the supplemental valve be drawn firmly to its seat by the guard ring F
when the parts are cold the unequal expansion of the parts is apt to cause the
supplemental valve to bind upon its seat when the parts become heated in the
working of the engine, my purpose therefore in providing the coiled spring H is to
hold the supplemental valve at all times snugly against the seat. Within the
opening formed in the coyer D₁ of the main valve is fitted the threaded steel
journal ring i upon which the arbor E' will bear and upon the reduced outer end
of this arbor is keyed the crank arm K which serves to determine the movement
of the supplemental valve as the main valve is reciprocated. At the outer end of
this crank arm is pivotally connected one end of the rod L the opposite end of this
rod being held upon the journal pin M of the bracket plate N that is bolted as
shewn at n to the end of the steam chest. A steel sleeve m is preferably fitted
upon the journal pin M to avoid wear and it will be understood that like provision
for a similar purpose may be made where desired,

page_text: From the foregoing construction the operation of my improved mechanism will
be seen to be as follows: Assuming the parts to be in the relative positions shewn
in fig. 1 of the drawings at this instant live steam is being admitted from the steam
chest B through the steam way a into the main cylinder. behind the piston and' is
being exhausted through the steam way a¹ and through the exhaust cavity d³ and
the exhaust port a' in the usual manner of ordinary slide valve mechanism and as
well also through the escape port d³ and space. d' and the ports d' of the port plate,
the ports of the supplemental valve, the chamber D³ of the main valve the
end ports d' and the exhaust port a² of the main cylinder. The exhaust thus
continues until the main slide valve has completed its movement and has been so
reversed as to cut off the steam and cause it to work expansively. When the steam
has thus been cut off by closing the steam way a¹ the direct communication is also
broken between the steam way a¹ and the exhaust cavity d but there is a free
outlet for the exhaust steam through the long ports the ports des chamber D³
end ports d' and main exhaust port so that as the steam is acting expansively. to.
move the piston the exhaust steam can escape freely from the main cylinder by
reason of this coincidence of the apertures d³ of the supplemental valve with the
ports de of the main valve. As the main slide valve continues to move backward
after having cut off the steam the rod L and crank K by reason of their connection
with the arbor of the supplemental valve cause this valve to partially rotate until
the apertures e of the supplemental valve no longer coincide with the ports dº of the
main valve and these ports are closed. The complete closing of the ports de by
the partial rotation of the supplemental valve occurs when the main valve is about
mid-stroke and just before the main piston has completed its stroke my purpose in
cutting off the escape steam at this point being to retain sufficient steam upon the
exhaust side of the piston to afford a proper cushion for the piston. As the main
slide valve now continues to move backward from its mid stroke position the rod L
and the crank K cause the further rotation of the supplemental valve until the
apertures e of this valve are brought coincident with the ports d³ of the main valve
this coincidence occurring by the time the main slide valve has moved backward
far enough to permit live steam to enter from the steam chest through the steam
way a behind the main piston. As the live steam is admitted through the steam
way a¹ the exhaust steam will escape through the steam way a directly into the
exhaust cavity ds and main exhaust port a³ and indirectly through the long escape
port of the main valve, the ports do and apertures e¹ of the supplemental valve the
chamber D³ the end ports d' and the main exhaust port a³ of the cylinder. This
direct and indirect escape of the exhaust steam thus continues until the main valve
is reversed and the live steam cut off from the port a² after which the entire escape
of exhaust steam occurs through the long escape ports d and d³ of the main valve
the ports d³ the apertures e¹ of the supplemental valve the chamber D³ the ports d'
and the main exhaust ports a². It will be observed that as long as live steam is
passing through the steam way a the ports d³ of the main valve are closed by the
supplemental valve and these ports remain so closed whilst the steam thus admitted
is acting expansively and until the main piston has about completed its stroke.
So also when live steam is being admitted through the steam way a¹ the ports dⓇ
of the main valve are closed by the supplemental valve and remain closed while
the steam on their end of the cylinder is acting expansively and until about the
completion of the return. stroke of the piston-It will thus be seen that the ports d³
and d of the main slide valve are alternately opened and closed by the supple-
mental valve so that there can be no escape of live steam through the ports d³
whilst the exhaust steam is passing through the ports do and vice versa.
It will be observed that the ports do and do of the main slide valve and the
apertures e¹ and e' of the supplemental valve are so arranged with respect to each
other that in the moving of the main slide valve the complete coincidence of the
ports d' with the apertures et occurs, while the complete closing of the ports d
by the supplemental valve will be effected and vice versa, this operation being
preferably accomplished by forming the upper port d³ and the upper port de of the

page_text: main valve at a greater distance from the horizontal bisecting line than the lower
port d and the lower port do, the apertures of the supplemental valve being
reversely arranged with respect to such ports.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what
I claim is :-
1. In slide valve mechanism the combination with the main chambered slide
valve having escape ports therein of a supplemental valve for said ports having
apertures therein adapted to be brought coincident with the ports of the main slide
valve and suitable mechanism for controlling the movement of said supplemental
¸valve substantially as described.
2. In slide valve mechanism the combination with the main slide valve having
escape ports therein of a supplemental disc valve for said ports and suitable
.mechanism for controlling the movement of said supplemental valve substantially
as described.
3. In slide valve mechanism the combination with the main slide valve having
escape ports therein of a supplemental rotating valve within said main valve an
arbor leading from said supplemental valve, a crank connected to said arbor and a
rod connecting said crank to the steam chest substantially as described.
4. In slide valve mechanism the combination with the main slide valve having
escape ports therein of a supplemental rotating or disc valve a guard ring for said
valve, and a suitable arbor and controlling mechanism for said valve substantially
as described.
5. In slide valve mechanism the combination with the main slide valve having
escape ports therein of a supplemental rotating or disc valve for said ports having
its arbor formed integral therewith and suitable mechanism for turning said arbor
substantially as described.
6. In slide valve mechanism the combination with the main chambered slide
valve having suitable escape ports therein of a supplemental disc valve located
within said main slide valve and adapted to control the escape ports thereof, the
escape ports of said main valve and the apertures of said disc valve-being. relatively
arranged substantially as described.
7. In slide valve mechanism the combination with the main slide valve having
suitable escape ports therein of a supplemental rotating or disc valve journalled
within said main valve and a coiled spring on the arbor of said supplemental valve
for pressing it against its seat substantially as described.
8. In slide valve mechanism the combination with the chambered slide valve
having the cover D', the central portion D' and port plate D¹ and having the
ports d², d³, d³, do, spaces d' and end ports d' the supplemental valve E¹ having
apertures e¹ and e³ therein, the arbor E³ the crank K and rod L substantially as
described.