Improvements in Piston Valves.
Year: 1891

page_text: Date of Application, 20th Aug., 1891
Complete Specification Left, 13th Apr., 1892-Accepted, 14th May, 1892
PROVISIONAL SPECIFICATION.
Improvements in Piston Valves.
WALTER MACKERSIE SMITH of 16 Otterbury Terrace Jesmond Newcastle-on-
Tyne in the County of Northumberland Engineer do hereby declare the nature of
this invention to be as follows:-
In the Specification of a former application No. 17,833 dated 6th December
1888, there is described a form of piston valve and has reference to means. for
keeping the packing rings tight against the liner or cylinder in which the valve
works, and for balancing or counteracting the steam pressure which at certain
periods comes against the outside of the rings.
Now according to this invention, which is a modification of the invention described
in the said Specification, I make one or both of the rings in segments, and so
arranged that they are pressed outwards by a spring or springs, and are kept tight
against the liner, in which they work, by steam pressure, the rings and springs
being kept in the required position by suitable projections and recesses formed on
the various parts, the arrangement being such that should the pressure on the out-
side rings or part rings exceed that on the inside of the rings or part rings, the
rings, part rings, or one of them will be forced from the face on which they work
and the excessive pressure which may occasionally accumulate in the cylinders is
allowed to escape direct to the exhaust chamber or it may be returned to the steam
chest according as it is desired.
Dated this Nineteenth day of August 1891.
WALTER M. SMITH.
COMPLETE SPECIFICATION.
Improvements in Piston Valves.
I, WALTER MACKERSIE SMITH, of 16 Otterburn Terrace, Jesmond, Newcastle-
on-Tyne, in the County of Northumberland, Engineer, 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 :-
When piston valves are used as distributing valves in steam engines, and water,
due to priming or other cause accumulates in the engine cylinder in greater quantity
than is sufficient to fill the steam ports and the clearance between the one end of
the cylinder and the piston when the same is at the corresponding end of its stroke,
it sometimes happens that the cylinder, cylinder cover or some other part of the
engine is fractured. Now my invention has for object to remedy this disadvantage
and so prevent serious accident.
For this purpose I construct a piston valve with one or more packing rings, made,
or each made, in two or more circular parts or segments (hereinafter called
segments) that are or may be pressed outwards by a spring or springs, and are kept
tight against the liner in which they work by steam pressure, and with means for
preventing steam passing direct from the steam chest to the exhaust through the
openings between the said segments, the arrangement being such that should the
pressure of fluid on the outside of the packing ring or rings from any cause such as
mentioned, exceed the combined pressure of the steam and springs on the inner side
thereof, the segments of such ring or rings will be forced from the face on which
they work and will open a communication leading to the exhaust chamber or to
the steam chest as may be desired, and thereby relieve the excessive pressure by
allowing some of the said fluid to escape.

page_text: To the accompanying drawings,
Fig. 1 is a longitudinal section of a piston valve constructed according to this
invention arranged within a liner formed with steam ports.
Fig. 2 is a transverse section thereof on the line A B Fig. 1.
Fig. 3 is a transverse section through the steam ports of the liner, shewing
the piston valve in elevation, its end cap and one of the packing rings being
removed.
Fig. 4 is a part longitudinal section on the line C D Fig. 3; and
Fig.
is a side elevation, shewing the relative positions of the slits in the
packing rings.
Fig. 6 is a developed view of part of the liner shewing two of the steain ports
therein and the intermediate bridge over which the divided or slit portions of the
packing rings work.
Fig. 7 is a longitudinal section shewing a modification.
Fig. 8 is a part end elevation thereof shewing one of the small part rings and
spring hereinafter referred to, and also part of the liner which is shewn in section;
and
Fig. 9 is a plan of part of the body of the valve with segmental packing ring
and part ring.
The body of my improved piston valve may be made in one piece or in two pieces
as in the construction shewn in Figs. 1 to 6 inclusive which I will now proceed to
describe. 1, 1 are the two parts of the piston body provided with a packing ring
which according to this invention is made in two or more segments 2, there being
three segments in the example shewn. The segments 2 are formed at each side
with a flange 2 that enters recesses 3,3" in the two parts 1, 1" of the body of the valve
which is made hollow as shewn. When the valve is in use the segmental packing ring
is arranged to work inside a cylindrical liner or seat 4, the left hand side of the
valve being the steam side, and the right hand side of the valve being the exhaust
side. Each segment 2 is forced outward and into close contact with the liner 4 by
a spring 5 arranged in a recess 6 in the part 1 of the body of the valve and acting
against a projection 2 on the inside of the corresponding segment. Each segment
is also forced outward when the valve is in use, by the pressure against its inner
side of steam that passes from the steam chest through the hollow portion 1" of the
valve by the openings 7 and 8 in such hollow portion. The springs 5 are made of
sufficient strength to carry the segments and to prevent them clattering when the
engine is running without steam. In some cases the springs 5 may be dispensed
with as when the outer flanged portion of the part 1 of the valve body closes or
nearly so the spaces
between the segments.
10 is a second packing ring (hereinafter called for distinction the auxiliary
packing ring) carried by the valve body; it is split at one part only and formed with
projections 10 each arranged opposite the opening 9 between two adjacent segments 2
of the first packing ring so as to prevent the direct passage through such openings
of steam from the steam chest to the exhaust chamber. Each projection 10" of the
auxiliary packing ring 10 is arranged to travel over a bar 11 between two adjacent
steam parts 12 in the liner 4, the said ring being kept in the proper position by a
projection 13 that is carried by the part 1 of the valve body and enters a recess 14
in the auxiliary packing ring as shewn in Figs. 3 and 4. 15 is a tongue arranged
to close the opening 16 between the ends of the split auxiliary ring 10 and prevent
the passage of steam therethrough from the interior of the packing ring to the
exhaust. This opening 16° is arranged so as not to come opposite either of the
openings 9 between the segments. As will be seen the arrangement is such that
when the valve is in position to admit steam to the steam ports 12 in the liner 4
the pressure of steain on the inside of the segments 2 will be counterbalanced
by the pressure of steam on the outside thereof, and when the external pressure
on the segments due to the compression by the motor piston of priming water or 5
water of condensation becomes sufficiently greater than that of the steam on the
inside to overcome the action of the springs 5, the segments 2 will be forced

page_text: from the inner face of the liner on which they normally work, and permit the
water to pass through the partly annular spaces 10b between the projections 10*
on the auxiliary packing ring 10, and into the exhaust chamber at the right hand
side of the valve.
The segments 2 may conveniently be formed by casting a ring of metal with the
inwardly extending flanges 2" and projections 25 and machining the same to the
required diameter, and afterwards cutting it into the required number of parts or
segments, sufficient space being left between the adjacent segments to allow of
their being pressed radially inward either simultaneously or independently so as to
uncover the space or spaces 10" through which the priming water can freely
escape. To prevent the segments 2 leaving the valve body when the valve is.
removed from the liner 4, the flanges 2 of the segments 2 may be formed with
outwardly extending lips or projections 2", those on one side fitting into a circular
recess 1 in the outer end of the part 1 of the valve body, and those on the
other side fitting into a recess in the auxiliary ring 10 which is also formed with
an outwardly extending annular lip or projection 10° that fits into a circular
recess 1 formed in the part 1 of the body of the valve.
If the body of the valve 1 1" be formed in one piece, the segments 2 are formed
without projections 2 and the body of the valve without the circular recesses 1
and 1" the segments being kept from falling out by set screws.
In the modification shewn in Figs. 7, 8 and 9, the valve body and the segmental
packing ring are constructed like those shewn in Figs. 1 to 6 inclusive, but instead
of using an auxiliary split packing ring 10, part rings, or packing pieces 16 are.
used to prevent steam passing through the openings 9 between the segments 2.
These part rings or packing pieces (hereinafter called part rings) fit into pockets
or recesses 18 formed in the valve body, and are forced outward against the liner 4
in which they work by springs 17 and it may be also by the pressure of steam.
For each opening 9 between the segments 2 a bridge 11 is formed in the liner to
prevent the escape of steam from the inner side of the packing ring to the adjacent
steam port 12.
In some cases instead of using radially movable part rings 16 corresponding parts
may be cast in one with the part 1 of the body of the valve, in which case these
parts should be a working fit in the liner. 19 is the valve rod, and 20 a nut for
securing the parts of the valve body together.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is:
1. A piston valve constructed with a packing ring made in two or more movable
parts or segments each arranged to be pressed outward and adapted to be kept
tight by steam pressure against the liner or valve face in or against which it works
and with means such as described for preventing steam passing direct from the
steam chest to the exhaust through the openings between the parts or segments
of the packing ring, the arrangement being such that when the fluid pressure on
the outer side of the packing ring exceeds the pressure at the inner side thereof,
the movable parts or segments constituting the said packing ring will move inward
and open a relief passage to the steam chest or to the exhaust substantially as
hereinbefore described for the purpose set forth.
2. The construction of piston valves of the kind herein referred to with divided.
packing rings or segments and auxiliary packing rings formed in separate parts as
hereinabove described and represented respectively in Figs. 1 to 6 and in Figs. 7 to 9
of the drawings.
ed this 13th day of April 1632.
W. Lloyd Wise,
W. M. SMITH.
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicant.