IMPROVEMENTS IN THE VALVES OF ENGINES OR PUMPS
Year: 1868

page_text: PROVISIONAL SPECIFICATION left by Walter William Tonkin at the
Office of the Commissioners of Patents, with his Petition, on the
23rd October 1868.
I, WALTER WILLIAM TONKIN, of 141, De Beauvoir Road, Kingsland,
in the County of Middlesex, Engineer, do hereby declare the nature of
the said Invention for "IMPROVEMENTS IN THE VALVES OF ENGINES OR PUMPS,"
to be as follows:-
My Invention relates more especially to such piston or slide valves of
steam or other motive-power engines or pumps as are actuated by the
direct pressure of the steam or other fluid employed to give motion to
the engine, or which, as in the case of the pump, is itself set in motion
thereby.
The improvements consist in certain methods of constructing piston
or slide valves actuated in the manner above described whereby the
necessity heretofore existing of maintaining a constant pressure always

page_text: acting in one direction upon a small arca, which is periodically over-
come by a pressure acting in an opposite direction upon a larger arca, is
obviated.
In one method of carrying my Invention into effect I employ a piston
or slide valve so constructed in relation to the ordinary steam and
exhaust ports and to the auxilliary steam ports supplying steam from
the cylinder for moving the valve, that the admission of steam from the
cylinder to the valve, and the emission thereof from it, shall be wholly
governed by the valve itself, the steam piston, and the auxilliary ports
in the cylinder without the intervention of secondary valves, tappets, or
other similar mechanical devices, and so arranged that when the valve
is at rest at either end of its stroke both ends of it are open to exhaust.
By one modification I am enabled to effect the entire movement of
the valve without employing the expansive action of the steam to
complete the movement commenced by the direct pressure of the steam
taken from the cylinder. I thus avoid any uncertainty in the movement
of the valve consequent upon the said expansive action. This I effect
by so adjusting the relative positions of the ports and working edges of
the valves, together with the relative surfaces of certain parts, that as
soon as or before the motion of the valve shall have cut off the com-
munication between itself and the steam side of the cylinder the pressure
of the steam from the boiler (or of fluid from other source) shall be
brought to bear upon another surface of the valve, and the pressure
thercon shall complete the movement and tend to retain the valve in its
proper position until nearly the completion of the stroke of the working
piston, when the movement of the valve is again commenced by steam
from the cylinder and completed by steam from the boiler as before.
The steam employed to produce the initial movement of the valve
may be exhausted if desired immediately after the boiler pressure begins
to act thereon.
By another modification I am enabled to apply my said improved
valves to pumps instead of the ordinary valves. For this purpose I
employ a piston or slide valve moved by the combined suction and
forcing action of the fluid passing through the pump.
I also adapt an arrangement of valve similar to that last referred to for
the distribution of steam or other fluid in an engine worked by fluid

page_text: pressure, but in this case I employ a tappet or other mechanical device
to effect the first portion of the travel of the valve, the remainder being
effected by the steam or other fluid direct from the boiler or other source
of pressure instead of from the cylinder as heretofore.