Improvements in Piston Valves for Motive Power Engines.
Year: 1896

page_text: PROVISIONAL SPECIFICATION.
Improvements in Piston Valves for Motive Power Engines.
I, WALTER PAYTON of 138 Sheen Road Richmond in the County of Surrey
Engineer, do hereby declare the nature of this invention to be as follows:-
This invention relates to improvements in piston valves for motive power engines,
whereby such valves are enabled to move over ports or passages more efficiently,
and with less leakage of steam or other motive fluid, than is the case with piston
valves as ordinarily constructed.
In carrying out the said invention the piston is not made to act as one continuous
valve, but is formed of a number of separate segmental valves, grouped in the same
plane, around a central body and connected to it in such a way as will enable the
valves to be reciprocated by it, and at the same time allow of their moving in a
radial direction. The cylinder in which the piston moves is provided with a similar
number of ports having dividing bars between them, and such ports are alternately
opened, and closed, by the valves independantly of each other, when the piston is
reciprocated.
The valves may be constructed in any approved manner, but they may be con-
veniently made by providing them with lugs whereby they may be temporarily
bolted together so as to form a complete ring, in which state they may be turned
to fit the cylinder and the body of the piston. The valves and their corresponding
ports may be of any approved number, and their width on their faces is equal to
the width of their ports with the desired amount of lap added thereto.
The circumferntial faces of the valves are accurately fitted to the cylinder within
which they are to reciprocate, and each valve is provided at one of its ends with
a flange at a right angle to its face. The body of the piston is accurately fitted to
the cylinder and when in position it acts as a movable partition separating the
motive fluid on one side of the piston from the exhaust fluid on its other side.
The valves are located on the pressure side of the piston with their faces in contact
with the cylinder, and their flanged ends resting against the body of the piston. In
this position the valves are pressed by the motive fluid against the cylinder, and
also against the body of the piston, but to ensure that they shall be pressed in the
latter direction with sufficient force, portions of the circumferences of the pistons
are removed in order that a part of the flanged ends of the valves may be exposed
to the reduced pressure exerted by the exhausting fluid. The area of flange so
exposed should be sufficient to enable the excess of pressure on the pressure side
of the flanges to overcome the friction of the faces of the valves when moving in
the cylinder and when such is the case the valves will at all times be kept by the
motive fluid in close contact with the body of the piston and will continuously
reciprocate with it. The piston is provided with a junk ring to secure the valves in
place when no motive fluid is acting upon them. The parts of the body of the
piston not removed for the above purpose are formed as short arins, similar in width
to the bars which separate the ports in the cylinder and the radial lines of the
segmental valves meet in the centre of such arms in such a way that the valves
overlap their several ports and when reciprocated each valve opens and closes its
corresponding port separately and independantly. The pressure of the motive fluid
seeps the valves in close contact with the cylinder and the body of the piston and

page_text: thereby prevents the motive fluid passing as waste from the pressure side of the
piston to its exhaust side between the faces and flanges of the valves and the
cylinder and piston.
There will however be a small escape of motive fluid at the points where the radial
lines of the valves meet, but as such lines are always nearly covered by the arms of
the body of the piston such escape will be very small and may be either disregarded,
or be prevented by sliding plates covering the junctions of the valves and pressed
against the cylinder by springs. Means are provided for securing the valves
within the piston and preventing them revolving upon it, and suitable springs are
used for pressing the valves against the cylinder when no motive fluid is acting
upon them.
For use in motive power engines two such pistons and valves are coupled together
by a rod or otherwise and the motive fluid may be exhausted between them or
outside of them as desired. Suitable means are provided for keeping the arms of
the body of the piston coincident with the bars between the ports of the cylinder
when the piston is reciprocating.
When the cylinders in which the pistons move are formed as liners it is preferred
to make such finers with shoulders and secure them in place by means of suitable
packing and glands as by so doing the liners will be less subject to distortions
caused by unequal pressures and temperatures.
.Dated this 24th day of June 1896.
COMPLETE SPECIFICATION.
Improvements in Piston Valves for Motive Power Engines.
1, WALTER PAYTON of 138 Sheen Road Richmond in the County of Surrey.
Engineer do hereby declare the nature of this invention and in what manuer the
same is to be performed, to be particularly described and ascertained in and by
the following statement, reference being had to the accompanying sheet of
drawings on which :-
Fig. 1 is a longitudinal section,
Fig. 2 a section on line A Fig. 1,
Fig. 3 a section on line B Fig. 2,
Fig. 4 shows in plan the exhaust side of one of the pistons,
Fig. 5 is an elevation of one of the pistons and
Fig. 6 a section of one of the liners in which the pistons work.
The said drawings illustrate the improvements as arranged for use in a steam
engine cylinder but only that part of the cylinder that contains them is shown the
remaining part being immaterial.
In this arrangement the two pistons a, a¹ shown in Fig. 1 are used, one of which
is a section on line G Fig. 2, and the other an elevation and such pistons are
coupled together by the valve rod b and secured upon it by the nuts, b².
The pistons are fitted so as to reciprocate freely within the two cylindrical
liuers c, c and the motive steam is contained within the space between the two
pistons and exhausts outside of them. As the two pistons and their liners are
alike in all their parts, it is only necessary to describe the piston a,and liner c
shown in section by Figs. 1, 2, 3, by a plan in Fig. 4 and by an elevation in Fig. 5.
The cylindrical liner c is constructed as shown in Figs. 1, 2, 6 and has formed in it
four rectangular ports all in one plane and of equal dimensions and the ports are
seperated from each other by rectangular bars also of equal dimensions.
The liner is fitted and secured in the valve chest as shown in Figs. 1, 2 and

page_text: when in position its four ports are in direct communication with the steam passage
leading to the engine cylinder.
The liner may however be constructed and secured in the valve chest in any
other approved manner, so long as the ports and bars are formed as described, or
it may be dispensed with and the ports and bars be formed as part of the valve
chest.
The piston a is constructed as a disc.. It is fitted to the liner c so as to move
freely within it, and its centre is bored out to fit the valve rod b. The concentric
rectangular groove a is turned in its circumference and within the groove are
fitted the four similar segmental valves marked d.
Each of the valves has one of its edges flanged as shown in Fig. 3. and
about its centre it is provided with a lug which serves to hold it within the
groove a and is made hollow so that it may contain a helical spring capable
of pressing the valve a short distance out of the groove.
The valves are prevented turning within the piston or projecting too far out
of it by screws carried by the piston and engaging in slots cut in the lugs in
the way illustrated by d Figs. 1. 2, the latter of which shows one of the
segmental valves in plan. The width of the valves is that of the ports over
which they work plus the lap required to be given to them and when in position
in the piston they lie as shown in Figs. 1. 3. but to ensure that there shall be no
leakage of steam from the inside of the piston to its outer or exhaust side the
piston is cut away so as to provide cavities through which a portion of the
flanged edges of the valves may be exposed to the reduced pressure of
the steam on the exhaust side of the piston and thereby enable the greater
pressure of the steam on the opposite side of the flanges to continually press the
valves against the piston and in steam-tight contact with it.
The parts of the piston so cut away are alike and equal and are so shaped as to
leave short and equal arms between them corresponding to the four equal bars
between the ports of the liner c and the segmental valves when in position in the
piston meet at about the centre of the arms and more than cover the cavities over
which they lie.
This will be clearly understood by referring to Fig. 4 which shows the exhaust
side of the piston a in plan and in which c³, are the bars of the liner ca³ the corre-
sponding arms of the piston a, and a the cavaties behind which the valves are
shown by dotted lines.
The ratio of the area of the cavaties to that of the ports in the liner c must be
sufficient to ensure that the valves shall be constantly pressed by the steam against
the piston with a force sufficient to overcome the friction of the valves when moving
over the ports, and for this purpose the area of the cavaties should be about one
half that of the ports.
The valve rod is prevented turning upon its axis by any usual or suitable guide,
and the pistons when fixed upon the valve rod have their arms a coinciding with
the bars of the liner c as shown in Fig. 4. When the pistons are in position in
their liners the steam between them will press the valves upon their faces and in
close contact with the pistons, and when reciprocated there will be no escape of
steam from one side of the pistons to their other side except at the minuite points
where the outer ends of the valves meet under the arms a³ The amount of such
escape would however be very small and in large valves may be disregarded but
if found desirable it may be entirely obviated by inserting in the arms the sliding
pieces pressed outwards by helical springs shown at a Figs. 3. 4. 5.
To facilitate their construction the valves may be first formed and fitted as a
continuous ring and be then divided by sawing or otherwise into the number of
segments required, and such segments with their corresponding ports, arms, and
bars may be of any number from three upwards.
As the area of the faces of the valves is no more than is absolutely necessary
for properly opening, and closing the ports, the pressure upon them is only that
required to keep the valves in steam-tight contact with the liners, they will there-

page_text: ¡fore move with a minimum of friction and any distortion of the liners caused by
pressure or unequal temperatures will not materially affect them as each valve is
at liberty to adjust itself to its particular port without interference from any other
-valve.
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-
1st. The construction and arrangement of piston valves for motive power
engines, containing segmental valves moving over separate ports, and held in close
contact with the piston by the difference between the pressure of the motive fluid,
and that of the exhaust fluid, in the manner described herein, and illustrated by
the drawings hereunto annexed.
2nd. The construction and arrangement of piston valves and their liners, for
motive power engines, in the manner and for the purposes herein described and
illustrated by the drawings hereunto annexed, or any mere modification of the
same.
Dated thin 17th day of March 1907
WALTER PAYTON.