Improvements in Balanced Slide Valves.
Year: 1893

page_text: Date of Application, 13th Jan., 1893-Accepted, 18th Feb., 1893
COMPLETE SPECIFICATION.
Improvements in Balanced Slide Valves.
I EDWARD KENWORTHY DUTTON of the firm of E. K. Dutton & Co. of
No. 5 John Dalton Street, Manchester, in the County of Lancaster, Consulting
Engineer and Fellow of the Chartered Institute of Patent Agents, do hereby
declare the nature of this invention (communicated to me from abroad by John
P. Lightbody of San Francisco, California, United States of America, Engineer,)
and in what manner the same is to be performed to be particularly described
and ascertained in and by the following statement and accompanying drawings :-
My invention relates to that class of balanced slide valves in which an expansible
metallic ring is interposed between the top of the steam chest and a circular rib
on the top plate of the valve, so as to make a steam tight joint to exclude the steam
pressure from the top of the plate. My improvements consist first, in forming the
outer face of the rib, and the inner face of its surrounding ring on curved lines, so
that the rib and ring form a section of a ball joint. When constructed in this
manner a close fit and consequently a steam tight joint will always be preserved, no
matter how much the top plate of the valve may become tipped from wear or other-
wise, so that it is no longer parallel or in the exact plane of the cover of the
chest. My improvements further consist in a peculiar joint or clip for closing the
ring at the point where it is cut through to permit it to expand, and finally, in
certain improvements in the construction of the ring itself, all of which will be
more fully hereinafter explained in this Specification and are shown in the
accompanying drawings.
Fig. 1, represents a longitudinal section of the valve chamber, valve and steam
chest cover;
Fig. 2, is a plan view of the valve with the expansible ring in position ;.
Fig. 3, is a cross-section of the expansible ring;
Fig. 4, is a plan view of the ring and the clip for closing it;
Fig. 5, is a broken elevation of the meeting ends of the ring at the point where
the clip which closes it is inserted.
A is an ordinary slide valve, B the walls of the steam chest, and C the steam
chest cover.
D is a circular plate secured to the top of the valve in any suitable
way, for example as by bolts or screws or formed in one piece with the valve, if
preferred. The plate D is provided with an annular rib E, raised on its upper face,
and of such height as to leave a clear space between such rib and the steam chest
cover of from an eighth to a quarter of an inch, according to the size of the valve
and plate. The exterior face or periphery of the rib E is shaped in the form of a
segment of a sphere. G is an elastic or expansible ring cut through as shown at I.
and having its inner face made concave, to fit the exterior face of the rib E, and
thus form a spherical steam tight joint. The interior diameter of the ring G is
slightly less than the exterior diameter of the rib E, so that when in working
position, the upper face of the ring will press against the steam chest cover, while
the steam pressure against the outside surface of the ring forces the ring against
the spherical face of the rib, and thus both joints are held constantly tight.
At the point where the ring is cut through transversely as shown at I, its ends
are slotted horizontally, as shown at j. A curved strip k, made of the same
vertical thickness as the ring G is formed with a tongue m on its inner face
which fits the slotted ends of the ring. The strip is riveted to one end of
the ring as shown at n, in Fig. 5. The upper edge of the strip k pressing
against the steam chest cover forms a tight joint in the ring horizontally, while
the rib or tongue m extending through the side of the ring, presses against the
rib E, and thus forms a tight joint vertically.

page_text: I now describe certain special improvements in the construction of the expan-
sible ring itself, referring particularly to Figs. 3 and 4. In using these expansible
rings for making a steam tight joint in slide valves, it is evident that when a ring
expands the strain, instead of being diffused throughout the length of the ring is
mainly concentrated at a single point, which is the point opposite the slit or cut
which permits the ring to expand. Where the ring is of equal thickness through-
out its whole extent the effect of this strain or pressure is to weaken the metal
at the point thus exposed to it, causing the ring to lose, in time, a part of its
elasticity, and thus rendering it unfit for use. I have found that by increasing
the thickness of the ring at the point opposite the opening, and causing it to
taper in both directions to the opening, the strain or pressure is diffused throughout
the extent of the ring, so that no particular point is affected by it. This construc-
tion is shown in Figs. 3 and 4 where it will be seen that the ring G, is thickest at
a point opposite the opening and tapers in both directions, the result being that
the amount of metal in the ring is gradually increased towards the point where the
strain caused by expansion is most severe.
The increased thickness of the ring would naturally permit the steam to exert
a greater pressure on the side opposite the opening, such pressure gradually
diminishing as the ring tapers from that side. To compensate for this inequality
in pressure, I form in the upper face of the ring a tapering groove or recess o, so
proportioned as to be of sufficient capacity to admit enough steam to compensate
for the variation in the pressure below, just alluded to.
I have shown this groove as tapering, because the ring itself tapers and so the
capacity of the groove must be in proportion to the thickness of the ring; but it
is evident that when a ring of equal thickness throughout is used and the steam
pressure on the bottom of such ring is sufficient to cause too much friction with
the cover of the steam chest, such friction may be reduced by forming a groove
in the top of the ring of any size or shape to receive steam enough to produce a
pressure on top and compensate for the excess of friction. The ring shown in
Figs. 3 and 4 is, like that shown in Fig. 1 formed with a curved or spherical inner
face, and I prefer in most cases to use this ring instead of a ring of equal thick-
ness throughout. The cross section of the ring may however be changed to adapt
it to valve plates of substantially the same character but of different shape so
long as the differential thickness is maintained.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is:
1. In a balanced slide valve the combination with the steam chest and valve of
a top plate secured to the valve an annular rib on said plate the outer face of which
is shaped in the form of a segment of a sphere and an expansible ring enclosing
said rib and having a concave inner face substantially as set forth.
2. In a balanced slide valve a top plate secured to the valve and having an
annular rib, and an expansible ring enclosing said rib, said rib and ring forming a
section of a ball and socket joint, substantially as described.
3. In combination with the ring G, cut through transversely and having the
meeting ends slotted, the curved plate K, secured to one end of the ring and
having the tongue m, substantially as set forth.
4. An expansible ring for a slide valve cut through at a certain point and
increasing in thickness gradually in both directions from said point, and having
upon its upper surface a tapering groove or recess, substantially as set forth.
Dated this 12th day of January 1893.
EDWARD K. DUTTON,
5, John Dalton Street, Manchester, Agents.