IMPROVEMENTS IN AND RELATING TO VALVES AND VALVE CASINGS FOR MOTIVE-POWER CYLINDERS
Year: 1876

page_text: PROVISIONAL SPECIFICATION left by William Phillips Thompson at the
Office of the Commissioners of Patents on the 1st December 1876. A com-
munication from abroad by Edward Purvis, of New York, in the United
States.
WILLIAM PHILLIPS THOMPSON, of 6, Lord Street, Liverpool, in the County of
Lancaster, Consulting Engineer and Patent Agent. "IMPROVEMENTS IN AND
RELATING TO VALVES AND VALVE CASINGS FOR MOTIVE-POWER CYLINDERS." A
communication from abroad by Edward Purvis of New York, in the United
States.
This Invention consists in improvements on the communicator's prior Invention?
for which Letters Patent were grauted to Alfred Vincent Newton, bis agent, dated
18th April, No. 1620, 1876.
My improvements are as follows:-I do away with the passages through the
valve, which are found inconvenient in some respects, and substitute therefor
passages in the valve casing, or between the valve casing and valve, and embedded
in one or both of them.
As in the former Specification above referred to there are two larger areas in
opposition to each other and two smaller areas. The two larger areas are alternately
in communication with the steam induction and the interior of the cylinder, and
oach of the smaller areas with the cylinder port at the opposite end of the cylinder
to that on which it is situated. There are various modes of effecting these arrange-
anents, I instance the following:-
1st plan. The valve can have five steam-tight dividing flanges in its central
portion; the central division thus formed is continually open to the exhaust, the
outer two to steam. The outside flanges of these divisions, like the others, fill up
the entire cross sectional area of the valve chest; beyond them, at each end, is a
neck connecting the main valve with a smaller piston or head working steain-
tightly in the valve chest end; the area of this head is much less than the annular
area of flange adjoining the neck, the latter is the "large area," the foriner the small.
one; the passage from the cylinder is alternately blocked by the head and open into
the "larger area." As soon as the. head has entirely blocked the said passage a
steam passago is cleared by the flange, and admits steam from the steam space into
"
TD 037

page_text: the larger area." The smaller area is always in communication with the opposite
cylinder port. The mode of action is substantially the same as that described
in connection with the longitudinal valve chest of my previous Patent referred to.
"
2nd plan. The central portion of the valve has always free communication with
the steam; a chamber therein is also open to the exhaust. The "larger area may
be either terminal or annular, that is, either as described in 1st plan, or changing
places with the small area; in this latter case the terminal area is of course of
considerable size, or is conjoined to an annular area differing in diameter from the
"smaller area," also annular; the "larger area " is then alternately connected with
the steam space by incans of a passage through the valve or the casing and with the
interior of the cylinder by direct passages, as shown in former, beforo mentioned.
3rd plan. Two central chambers formed by the valve and the valve chest are
alternately open to the steam and exhaust, and 'always open to their respective
cylinder ports. At the dead centre both exhaust ports may be slightly uncovered,
and a considerable lap be put on the ring or piston operating on the steam chest.
These central chambers thus act as "smaller areas," being smaller than the terminal
ones, by the area of the shank of the valve uniting the flange regulating the steam
admission with the remaining part of the valve. The terininal or "larger areas
are connected alternately with the steam admission by passages in the casing and
with the interior of the cylinder by the direct passages. The principle of working
in all these valves is identical.
"