PROVEMENTS 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 6th May 1878.
"IM-
WILLIAM TIMBRELL CLARK, of 4, Queen Street Place, London, Engineer.
PROVEMENTS 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 mid-
way from the ends, and that through one of the ends of the cylinder, for conveni-
ence 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 stricking
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 also
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
the piston proper, the enlarged head of the rod fitting into or against the piston air-
TD 0.77

page_text: 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
being the aperture by which the air passes to the cylinder for the next stroke of
the comprossing 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
Jarger than the piston rod, and it is secured to the piston. The difference in tho
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.