IMPROVEMENTS IN PISTONS AND VALVES FOR STEAM ENGINES, AND IN THE PISTONS AND PISTON RODS FOR AIR COMPRESSORS, SUCH IMPROVEMENTS BEING ALSO APPLICABLE FOR OTHER PURPOSES
Year: 1878

page_text: PROVISIONAL SPECIFICATION left by William Timbrell Clark at the Office
of the Commissioners of Patents on the 25th October 1878.
WILLIAM TIMBRELL CLARK, of Crick, Nr. Rugby, Northamptonshire, Engineer.
"IMPROVEMENTS IN PISTONS AND VALVES FOR STEAM ENGINES, AND IN THE PISTONS
AND PISTON RODS FOR AIR COMPRESSORS, SUCH IMPROVEMENTS BEING ALSO
APPLICABLE FOR OTHER PURPOSES."
This Invention of improvements in pistons and valves for steam engines consists
in combining the piston and valves in a steam engine on the principle of which the
following arrangement is an illustration.
Taking an ordinary cylinder of an engine, and supposing the piston to be
midway from the ends, and that through one of the ends of the cylinder, for con-
venience called the forward end, the piston rod projects to join the connecting rod
in connection with the fly wheel shaft, the steam or compressed air from the boiler
or reservoir is utilised as follows:-
In the interior of the piston two hollow chambers are provided; to each chamber
is solidly fitted a hollow tube which passes through glands or stuffing boxes in the
back end cover of the cylinder; the one pipe is the exhaust and is free to the
atmosphere, the other is surrounded by a steam-tight pipe in connection with
the boiler or reservoir.
Also in connection with the chambers are fitted two tubes sliding through the
chamber and through apertures in the piston, so that each end may project beyond
the piston as required either to the forward or backward end of the cylinder; these
tubes are the valves or steam and exhaust ports, and their respective chambers may
be termed the steam and exhaust chambers; the tubes are moved into their
respective positions by striking against the cylinder ends, and are so arranged that
the openings and the diaphragms in the tubes at each completion of the stroke of
the piston shall alternately give steam to one side of the piston, and give free
escape to the steam on the other side of the piston.
The improvements in the pistons and piston rods for air compressors relates to
an arrangement of the piston and valve in combination, the valve being formed
by an enlargement of the end of the piston rod working in loose connection with

page_text: the piston proper; the enlarged head of the rod fitting into or against the piston
air-tight when acting to compress the air in the cylinder and forcing it out, but on
the return stroke receding for a short distance without the piston, the space thus
formed between the aperture by which the air passes to the cylinder for the
next stroke of the compressing piston. One way of making the connection is as
follows The head of the piston rod being turned to a parallel section of a cone,
the piston is turned out to correspond, the head of the piston rod sinking rather
below the surface of the piston, a ring near the size of the piston is now placed
over the head, its annular space being larger than the piston rod, and it is secured
to the piston; the difference in the depth of the piston rod. head and the piston-
is, the amount of play an eighth of an inch less or more as required, and this
space forms the airway. In some cases portions of the ring or the piston rod head
_may_be_bevelled-away-to-increase-the-airway-especially-as-will-be-afterwards
mentioned, when such a piston and piston rod is applied to pumps.
The piston
may be applied singly or in pairs in the same cylinder, or one of these pistons and
an ordinary piston may be applied, or two of these improved pistons in one
cylinder connected to one rod, one end of which is attached to the connecting
rod of the fly wheel shaft, and the other made hollow forms the air inlet; by this
arrangement each backward and forward stroke compresses the air, and the piston
is double-acting.