AN IMPROVED COMBINATION OF VALVES FOR MACHINES USED IN COMPRESSING AIR AND OTHER GASEOUS FLUIDS
Year: 1877

page_text: PROVISIONAL SPECIFICATION left by Joseph Christopher Leaver at the Office
of the Commissioners of Patents on the 19th June 1877.
JOSEPH CHRISTOPHER LEAVER, of Rostherne House, Castelnau, Barnes, in the
County of Surrey. "AN IMPROVED COMBINATION OF VALVES FOR MACHINES
USED IN COMPRESSING AIR AND OTHER GASEOUS FLUIDS."
My Invention consists in the application to compressors of air and other gaseous
fluids of a slide valve worked mechanically by a cam, eccentric, or any other suit-
able means, in combination with a free valve, that is to say, a valve not worked
mechanically, but free to move only when required.
The object in view in employing such combination is as follows:-The complete
shutting of the ports which establish the communication between the inside of the
compressor and the receiver for the compressed air or gas, and also with the atmos-
pheric air or gas holder from which the gas to be compressed is supplied, must take
place at the same point of stroke of the piston in the cylinder, and is effected by
the mechanical motion of the slide valve, the travel of which is always in the same
relative position with the piston.
The opening of the ports, on the contrary, must take place only when there is
equilibrium of pressure between the air or gas inside the cylinder and the receiver
when compression takes place, or between the compressed air or gas left in the
neutral spaces or clearance and the atmospheric air or the supplying gas holder
when suction takes place, and is obtained by using the free valve which works only
when required, preventing any early return of compressed air or gas inside the
cylinder, or any over compression beyond the required pressure.
The shutting of the ports depending only on the slide valve, the free valve
remains in a state of equilibrium and closes slowly and softly, avoiding any shock
or concussion of any kind, and therefore cannot be thrown out of working order.
The slide valve shutting the inlet ports at the required point of stroke of the
piston ensures the certainty of compressing into the receiver the full volume of air
or gas contained in the cylinder.
The opening of the inlet ports being affected only by the free valve, when the
pressure inside the cylinder has been reduced to the atmospheric pressure or to the
pressure in the supplying gas holder, prevents any loss of power by utilizing the
pressure of the air or gas left in the neutral or clearance spaces.

page_text: As the free valves, both for the inlet and outlet, are not used for the shutting of
the ports, they can be allowed to open to the full extent of their area without
running any risk of working them at an injurious speed, and avoid any wire draw-
ing of the air or gas..
The action of this combination of valves being entirely certain, the compressor
may be effectually run at any speed.
To effect these results I use any form of slide valve, such word being employed
in its most general sense, meaning conical or cylindrical cocks revolving on their
axes, or sliding parallel to them, and valves of any shape revolving on any axis or
sliding in any direction, such slide valves being worked by cams, excentrics, friction,
or any other suitable means, and any free valve, round, square, flaps, or any other
shape of valve, inetallic or otherwise, such free valves being fixed on the slide
valves or any other part of the machine, and such combination of valves being
placed on the cover or the sides of the cylinder, or any other convenient place.