Improved Prismatic Piston Valve, being Improvements in Slide Valves and their Connections for Steam and other Engines.
Year: 1896

page_text: Date of Application, 26th May, 1896
Complete Specification Left, 19th Feb., 1897-Accepted, 17th Apr., 1897
Improved Prismatic Piston Valve, being Improvements in Slide
Valves and their Connections for Steam and other Engines.
1 JAMES JENNINGS CAMPBELL of 67 Warwick Road, Earl's Court London
Engineer do hereby declare the nature of this invention to be as follows:-
For distributing the working fluid in stearn and other engines
:-
I combine slide valves of special forms, designed to give the largest possible port
openings for their size, with specially formed adjustable "port pieces" (or hollow
castings containing admission and exhaust passages) connecting them with the
cylinder to be supplied, and allowing them to be maintained in equilibrium as
regards the pressure of the working fluid; and with suitable means for adjusting
the said "port-pieces" to take up any wear that may occur, without opening the
valve chest or stopping the engines.
For this purpose I construct valves which are practically piston valves but of
prismatic instead of cylindrical form; that is to say, having a cross section which
instead of being a circle is a polygon with any suitable number of sides, four or six
being generally preferred.
The ends or pistons of these valves are connected by a central tube for the
passage of the slide rod and by longitudinal bars at the angles of the polygons.
These valves may be made to open single or double ports at each end, and each face
of the valve has the necessary bars and ports for the distribution of the steam or
other fluid employed.
The valves work against the specially formed "port pieces" above mentioned;
or partly against such "port-pieces" and partly against suitable faces cast or bolted
on the cylinder to which the working fluid is to be supplied.
Each of these "port-pieces" (except in certain cases of three-sided valves) has
a V shaped face engaging two adjacent faces of the valve; and a flat face fitting,
& capable of sliding, steam-tight against a suitable face on the cylinder. They are
also pressed in two directions by springs or screws; viz. against the face on the
cylinder to make a steam tight joint & to keep them in position; and against the
valve to take up wear. When in work, the "port-pieces," having been set just to
touch the valve, will be prevented from pressing further against or moving back
from the valve, either by set screws jamming them against the cylinder, when springs
are used for taking up wear; or, when screws are used to make up wear by so
constructing & arranging them that the "port-pieces" can only be moved so far as
desired & no further.
When any wear may be expected to have taken place the jamming screws are
slightly eased allowing the springs, when so fitted, to set the "port-pieces" forward
against the valve; and immediately jammed down again. Or, when screws are used
to set the "port pieces" forward, & springs to keep them up to the cylinder, they
are simply screwed forward to touch the valve and the screws secured from turning
by a lock nut. The screws in all cases passing to the outside of the valve chest &
being fitted with means of working them there, & locking them when required.
Dated this 26th day of May 1896.

page_text: Improved Prismatic Piston Valve, being Improvements in Slide
Valves and their Connections for Steam and other Engines.
I, JAMES JENNINGS CAMPBELL of 67 Warwick Road, Earl's Court, London,
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 :-
The object of these improvements is to provide a valve which has a large port
area for its size, which works in equilibrium as regards the pressure of the steam or
other working fluid, and which can be maintained fluid tight by taking up the wear
without necessarily opening the valve chest or stopping the engine.
For this purpose I combine a slide valve of special form with specially formed
adjustable "port pieces" or hollow castings containing admission and exhaust
passages and connected with the cylinder; and I provide suitable means for
adjusting the "port pieces" to take up the wear.
The valve is practically a piston valve but of prismatic, (instead of the usual
cylindrical), form; that is to say, having a. cross section which is a polygon with
any suitable number of sides, but by preference four or six. The ends or pistons of
the valve are connected by a central tube for passing the slide rod through it, and
these ends also have longitudinal connecting bars at the angles of the polygon.
The valve may be made to open single or double ports at each end of cylinder.
The valve works against the aforesaid "port pieces" or partly against them and
partly against suitable faces cast or bolted on the cylinder. Each port piece (except
in certain cases of three sided. valves) has an angle shaped face engaging two
adjacent faces of the valve, and a flat face fitting steamtight against a face on the
cylinder. The port pieces are also by suitable spring or screw devices pressed fluid
tight against the cylinder face, and against the valve, and so that the wear may be
taken up as required. In some cases one of the port pieces may be cast on the
cylinder.
Fig. 1 of the accompanying drawings is a cross section through a cylinder with a
valve of square section and its port: pieces. Fig. 2 is a longitudinal section,
and Fig. 3 a longitudinal section at right angles to the last through one port piece
with the other removed to show the cylinder face and ports. The valve consists of
two piston ends A four corner bars A' and cross bars with intermediate ports on
the sides.
It is formed with a tube right through for the valve rod C. The port pieces B
form as it were a chamber wherein the valve works; they fit steam tight on the
cylinder face and are set up against it and against the valve either as shewn to the
left by means of screws D and springs at E, or as shewn to the right by springs at D'
and screws at E.
Fig. 4 is a cross section through a cylinder with hexagonal valve. In this case
if the port pieces B are adjusted by screws D on each side or by springs each side,
the pressure against the faces on the cylinder is effected by a wedge piece F which
is pressed down between the two port pieces B by means of a spring G as shewn in
full lines or a screw H as shewn by dotted lines.
Fig. 5 is a section of part of a double ported valve of square section, showing the
passages K from the ends of the valve to supply steam to the inner ports.
Fig. 6 shews a section through a b and a section through c d Fig. 5. A similar
arrangement may be adopted for the hexagon form of valve. The alternate
bars A', A', may be omitted both in the valve and in the port pieces B provided
that the valve be well fitted into the angular faces. This would increase the port

page_text: area for a given size of valve and allow the whole arrangement to be reduced in
size. Stops I are fitted at both ends of the port pieces B, as shown in Fig. 1.
When any wear on the working faces may be expected to have taken place the
jamming screws are slightly eased, allowing the springs when fitted to set the port
pieces forward against the valve, and immediately jammed down again. Or when
screws are used to set the port pieces forward, and springs to keep them up to the
cylinder face, they are simply screwed forward to touch the valve and the screws
are then secured from turning back by means of a lock nut. The screws in all
cases by preference pass to the outside so that they can be worked and secured from
without.
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. A prismatic or polygonal hollow piston valve formed with ports in combination
with a chamber comprising removable "port pieces" in which the valve is adapted
to work, and with screws or other suitable means for adjusting the port pieces by
preference from without and for taking up the wear substantially as set forth.
2. The constructions of valve and port pieces described with reference to the
drawings.
Dated this Nineteenth day of February 1897.
JENSEN & SON,
77 Chancery Lane, London, W.C., Patent Agents.