IMPROVEMENTS IN OR RELATING TO SLIDE-VALVES
Year: 1882

page_text: PROVISIONAL SPECIFICATION left by John William Joyce at the Office of
the Commissioners of Patents on the 24th May 1882.
JOHN WILLIAM JOYCE of Murton Colliery, in the County of Durham,
"IMPROVEMENTS IN OR RELATING TO SLIDE-VALVES
"
This invention relates to a special arrangement of valve and also of the cylinder
face as will presently appear.
The valve is like an ordinary slide valve but what is usually solid metal is left
hollow and long slots or openings in the side faces communicate with the hollow
interior of the valve The cylinder face is also hollow where this can conveniently
be arranged and suitable ports or openings are provided in the edges of the face
which correspond with those in the valve face. Ports or openings are also provided
at the ends of the cylinder face and so arranged as to come within the valve casing
when that is in place By this arrangement the steam or other fluid enters the
hollow under the face by the end ports or openings passes through the openings in
the edges of the face and the long slots in the edges of the valve face into the
hollow interior of the valve thereby counteracting the pressure upon the back of
the valve and very greatly reducing the friction during working. I prefer in all
cases to form the exhaust port of the same breadth as the steam ports as I find I
obtain more economical results in this way.
A modification of the above valve is made with a rather larger exhaust recess
and having a bridge across it tbus forming two ports which travel over those of the
cylinder face. These are so arranged that when the valve is at the centre of its
stroke, the exhaust port of the cylinder is covered by the bridge and both steam
ports are open to the recess in the valve, so that steam can pass from one end of
the cylinder to the other and act upon both sides of the piston at once and the
exhaust port is then, subsequently, opened and the other steam port closed leaving
a "cushion" shut in before the next stroke commences; by proper adjustment of the
valve the steam will act as a cushion before it exhausts instead of taking fresh
boiler steam in the usual manner and a considerable source of waste is thus avoided
-Communication can be stablished between the two ends of the cylinder at a
convenient part of the stroke, say for example at three quarter stroke.

page_text: This valve is specially designed for high pressures and the balancing device is also
employed with it. By the use of this valve the stroke may be reduced and.
therefore the size of the excentric and the strength of the excentric rod and valve
spindle and connections.
Another way of introducing the steam for balancing the valve, is to dispense
with the end balance ports within the steam chest and carry a port to the outside
of the casing so that a branch from the main, steam pipe can be attached to it. In
this arrangement it is sometimes necessary to alter the form of the casing and
allow the "balance" opening to come below the flange; but this of course depends
upon individual cases and will be arranged as required. A small drain cock for
running off condensed water may be inserted where required.
Where it is undesirable to ease the friction of the valve upon the Cylinder face
by the counter pressure of the steam or other fluid from within the casing, an
alternative arrangement may be adopted by simply compressing the air or other
suitable fluid in any convenient manner (as for instance by employing the end of
the valve spindle as a pump plunger) and admitting it to the balance opening as
already described. When the requisite pressure upon the valve face has been
attained a cock or valve may be closed and the supply stopped for a time.