IMPROVEMENTS IN BALANCED SLIDE VALVES FOR COMPOUND AND SIMPLE ENGINES."
Year: 1878

page_text: PROVISIONAL SPECIFICATION left by Joseph Harrison Adams at the Office
of the Commissioners of Patents on the 4th December 1878.
"
JOSEPH HARRISON ADAMS, of Cornwall Street, Fulham, London, in the County
of Middlesex. IMPROVEMENTS IN BALANCED SLIDE VALVES FOR COMPOUND AND
SIMPLE ENGINES."
The valves on this principle are made in two pieces, and are adapted to both
compound and simple engines. One part of the valve bears against the high
pressure cylinder, the other part against the low pressure cylinder or against a
plane surface parallel to the cylinder face, as the case may be, whether it is a com-
pound or simple engine, the two surfaces being placed opposite and parallel to each
other. As stated above the valve is made in two parts, and the back of each
part is cylindrical.
The method of connecting each part together so that their junction may be
rendered steam tight is as follows:-One part is bored out; the other is turned so
as to fit it accurately. A piece of suitable packing is then placed round it at their
junction. The turned cylindrical part of one being placed for a short distance in
the bored out cylindrical part of the other, back to back, a certain amount of play
is thus allowed between the two surfaces. The steam is thus, by this arrangement,
free to press each part upon the opposite surface.
In a compound engine, each face of the valve is square or rectangular.
The steam enters the high pressure cylinder from the steam chest and exhausts
from the said cylinder to the inside of the valve; from thence it enters (by a
suitable arrangement of ports in the piece working on the opposite face) the larger
cylinder; from thence it exhausts in the usual manner.
In the case of single cylinder or simple engines that part of the piece working
against the surface parallel to the cylinder face, I do not make square or rectangular,
but the whole of that piece is cylindrical. As the steam exhausts from the cylinder
it passes through the valve and through an opening in the surface placed placed
parallel to the cylinder face, to the air or condenser, as the case may be.
When it is required to use an expansion valve in addition to this, the valve face is
lengthened (in the direction of the length of the cylinder). The face of the valve
n "

page_text: thus becomes rectangular. The steam ports are cast on this extended surface, and
the expansion valve works on it. The ends of the pieces forming the expansion
valve I connect together, thus enclosing the cylindrical part of the main valve.
It may sometimes be desirable to obtain this surface for the expansion valve
to work upon without so much increasing the length of the main valve. This may
be done by flattening opposite parts of the piece working against the high pressure
cylinder, and making it cylindrical again before its junction with the part working
on the low pressure cylinder face, or against other parallel surface, as the case may
be, whether the engine is compound or simple.
In the above I assume that the usual straight ports are used on the cylinder face
or faces. If there are circular ports the valve will be made circular at both its faces.
In the case of single cylinder engines the part working against the surface parallel
to the cylinder face is always made cylindrical throughout.
It will be seen from the above that by the means described I obtain a balanced
slide valve in which the steam pressure is used to keep both surfaces steam-tight,
so that in this valve the advantage is obtained of being able to dispense with
springs, &c., for the purpose of obtaining a steam tight working surface.
The essential feature of my Invention is that the valve is made in two parts and
connected together in the manner described.
By using a valve on this principle I obtain a simple means of regulating the
flow of steam to both cylinders, and as the passage of the steam from smaller
cylinder to larger is direct, the usual loss of pressure between the two is avoided. .