Improvements in Piston Valves.
Year: 1888

page_text: Date of Application, 6th Dec., 1888
Complete Specification Left, 23rd July, 1889-Accepted, 21st Sept., 1889
PROVISIONAL SPECIFICATION.
Improvements in Piston Valves.
I WALTER MACKERSIE SMITH of 10, Otterburn Terrace, Jesmond, Newcastle-on-
Tyne in the County of Northumberland, Engineer do hereby declare the nature of this
invention to be as follows:-
This invention has for object improvements in piston valves 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. To expand the rings steam is admitted
behind them so that it presses on their ulterior surface, forcing them outwards and
into close contact with the liner or cylinder. The part of the ring which is over the
port is exposed to the pressure in the cylinder, and this pressure is exercised in a con-
trary direction to the pressure behind the ring tending to make it contract. Likewise
if a part of the ring passes through and beyond the liner or cylinder it becomes
exposed to the steam pressure on its exterior surface. The exterior surface of the
rings exposed to the steam pressure is never so great as the interior surface, and con-
sequently the rings are always pressed outwards, and make a tight joint between the
steam and the exhaust passages.
•
A suitable construction for a piston valve according to this invention has two rings
each turned somewhat larger in diameter than the bore of the liner or cylinder.
These rings are cut or divided, preferably with an oblique cut and sprung into their
places. One ring is much wider than the other and is put next the steam chest, the
narrow ring being at the exhaust side. The cut in the broad ring allows the steam
to flow through into the space behind, while the cut in the narrow ring is fitted with
a tongue which prevents the steam passing through to the exhaust. The cuts in the
two rings are not opposite each other, and a pin fixed in the body of the valve taking
into holes in the rings prevents relative motion of the parts. This pin is so placed
that the cuts in the rings come over bars between the ports.
D
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أيم
1
1
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1000
W. LLOYD WISE,
Per F. J. Brougham,
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicant.
COMPLETE SPECIFICATION.
Improvements in Piston Valves.
I, WALTER MACKERSIE SMITH, of 10 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:―
This invention has for object improvements in piston valves 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. To expand the rings, steam is admitted
behind them so that it presses on their interior surface forcing them outwards and
into close contact with the liner or cylinder. The part of the ring which is over the
port is exposed to the pressure in the cylinder and this pressure is exercised in a con-
trary direction to the pressure behind the ring and tending to make it contract.
Likewise, if a part of the ring passes through and beyond the liner or cylinder,
it becomes exposed to-the steam pressure on its exterior surface. The exterior surface
077

page_text: of the rings exposed to the steam pressure is never so great as the interior surface
and consequently the rings are always pressed outwards, and make a tight joint
between the steam and the exhaust passages.
A suitable construction for a piston valve according to this invention has two rings
each turned somewhat larger in diameter than the bore of the liner or cylinder.
These rings are cut or divided, the cut as I prefer to make it being oblique and the
rings are sprung into their places. One ring is much wider than the other and is put
next the steam chest, the narrow ring being at the exhaust side. The cut in the broad
ring allows the steam to flow through into the space behind, while the cut in the
narrow ring is fitted with a tongue that prevents the steam passing through to the
exhaust. The cuts in the two rings are not opposite each other, and a pin fixed in
the body of the valve and taking into holes in the rings prevents relative motion of
the parts.
This pin is so placed that the cuts in the rings come opposite bars
between the ports.
Referring to the accompanying two sheets of drawings:
Fig. 1 is a longitudinal section through the steam chest of a steam engine
cylinder with piston valves according to this invention.
Fig. 2 is a transverse section on the line a-b of Fig. 1.
Fig. 3 is an end elevation on the line c-d of Fig. 1 of part of one of the valve
heads.
Fig. 4 is an end elevation of the packing rings and a screw to prevent them
rotating.
Fig. 5 is a plan thereof.
Fig. 4 shows a modification.
Fig 6 is a development of one of these sets of steam ports in the liners with which
the steam chest is fitted.
Fig. 7 is a developement in section on the line e-f Fig. 1 and g- Fig. 6 of a
rough casting of one of the liners; the part below the line?-k and which is at the
inner side of the liner, is removed by boring when finishing the liner for use.
Fig. 8 is a part section of a modified form of piston valve with liner and cylinder,
this section being through the line c¹ d' e¹ (Fig. 9).
Fig. 9 is a side elevation of part of the piston valve and ring shewn in Fig. 8.
Fig. 10 is a developed view shewing part of one set of steam ports.
Fig. 11 is a part transverse section taken through the line f¹-g¹ (Fig. 8).
Referring to Figs. 1 to 7 inclusive,
1 is part of the working cylinder of an engine; 2 the steam chest; and 3, 3 liners
fixed in the steam chest and in which the piston valves work. 4, 4 are live steam
spaces. 5 (Fig. 1) is an exhaust steam space. 6, 7 are steam ports in each liner.
8, 8 are cylinder ports.
I will now describe one of the piston valves. The body 9 of the piston valve has a
flange or junk ring 10 fitted to it. It has likewise two rings 11 and 12 which work
in the liner 3. It will be understood that the two valves connected as shown, con-
stitute a compound valve. Two sets of ports may be formed in the liner for each
valve, the steam ports 6 being shewn in Fig. 6 and the port 7, by which steam enters
from the boiler, in Fig. 2. In some cases the liners 3 may be dispensed with the
steam chest being then cast with equivalent parts in which the valves work. In such
cases steam ports corresponding to the ports 6 only would be required. The exhaust
steam passes into the exhaust space between the two ends of the compound piston
valve, and thence to an exhaust pipe. It will be seen that where the ring 11 is cut
so as to allow it to be sprung into the liner 3 an opening or space 13 (Figs. 4 & 5) is
formed through which the steam can pass into the chamber 14 behind the ring 11.
This steam would also escape through the opening 15 in the ring 12 but this opening
is closed by a tongue 16 (Fig. 4) which prevents the escape of steam from the steam
space 4 and chamber 14 to the exhaust chamber 5; or instead of using a tongue 16
the ring 12 may be cut zig-zag as shewn in Fig. 4*. When the valve travels so that
steam is admitted to the steam port 8, the steam presses on the outside circumference
of the ring 11 and partly counterbalances the pressure on its inner, side and thereby

page_text: reduces the friction between it and the liner. When steain is being admitted to the
steam port 8 the ring 12 will have travelled beyond the steam port openings 6 in the
liner and will only be exposed to the pressure of the steam on its inside circum-
ference, which steam will press the ring into close contact with the interior of the
liner thereby forming a steam tight joint.
The rings 11 & 12 are held in position by a stud 17 (Figs. 3 & 4) so that where
they are cut, they travel over a bridge 18 (Fig. 6) formed in the liner 3 and thereby
prevent the steam from passing into the cylinder by the steam port 8 through the
opening 13 in the ring 11. The ring 12 may also be made solid; in this case it
should be a working fit in the liner 3.
According to the modification shewn in Figs. 89, 10 & 11 one ring only is used;
in this case the piston valve is made a working fit into the liner 3, and is fitted with a
part ring 19 placed opposite to the joint in the ring 11 and pressed against the liner 3
by a spring 20. This part ring may be provided with a projection 19° arranged to
enter a recess in the ring 11 and prevent this ring turning so that its slotted part 13
will always travel over the bridge 18. If steam be admitted by the ends of the com-
pound or duplex piston valve, then each piston valve must fit the liner on the inside as
shewn in Fig. 8. If steam be admitted between the two piston valves forming the
compound piston valve, then each piston valve should fit the liner on the outside; or
the piston valve may fit the liner on both sides of the ring, in which case the joint 13
may be fitted with a closing piece so as to render it steam-tight, steam being
admitted to the chamber 14 by a hole or holes in communication with the steam
chest.
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. In a piston valve for distributing steam in a locomotive or other engine, the
combination of two packing rings arranged substantially as heroinabove described in
such a manner that the necessary fluid tight contact is effected between tho packing
rings and the surface of the liner or cylinder in which they work by the pressure of
the fluid acting behind the said rings and without the aid of springs or other similar
devices for forcing the said rings outward.
2. The improved distributing piston valve arranged substantially as hereinabove
described and as illustrated in Figs. 1 to 7 inclusive of the drawings annexed.
3. The modification described with reference to and illustrated in Figs. 8 to 11
inclusive of the drawings annexed.
1
CT 1080
W. LLOYD WISE,
46, Lincoln's Inn Fields, London, W.C., Agent for the Applicant.