AN IMPROVEMENT IN THE MODE OF APPLYING STEAM OR OTHER FLUID PRESSURE ACTING ON A PISTON TO PRODUCE CIRCULAR MOTION
Year: 1864

page_text: PROVISIONAL SPECIFICATION left by Gerard Finch at the Office of
the Commissioners of Patents, with his Petition, on the 13th February
1864.
I, GERARD FINCH, of 28, Clarendon Gardens, Maida Hill, in the County
of Middlesex, do hereby declare the nature of the said Invention for "AN
IMPROVEMENT IN THE MODE OF APPLYING STEAM OR OTHER FLUID PRESSURE ACTING
ON A PISTON TO PRODUCE CIRCULAR MOTION," to be as follows:-
The steam or other fluid pressure here meant is that produced by steam or
compressed or heated air, gas, vapour, water, or any similar fluid, and it is
exerted on the piston in an annular cylinder. An idea of such a cylinder may
be formed by regarding it as a tube bent into the form of a circle, so that the
extreme sections meet and coincide. The tube may have any form of bore,
rectilinear or curvelinear. For simplicity of description the bore is here
supposed rectilinear, and the "annular cylinder" is such that its interior surface
would be that traced out by the revolution of a rectangle round an axis in its
own plane parallel to one of the sides of the rectangle and exterior to it. The
piston is of the exact dimensions and form of this rectangle, and moves round
the interior with its plane when produced, always coinciding with the axis of
the cylinder. Placed transversely across the interior of the annular cylinder
are one or more valves or doors, which divide the annular cylinder into com-
partments, and effectually shut off all communication between adjacent parts.
These "doors" are capable of sliding back into boxes fitted outside the
cylinder. For simplicity the "doors" are assumed to be two in number, and
separated from each other by half a circumference. On each side of the

page_text: "doors" there is an aperture in the cylinder regulated by a valve for the
admission or escape of the steam, which may be supposed to be the fluid used.
In order to produce motion steam is introduced into the cylinder between the
piston and the "door" next behind it, which is supposed to be closed. The
steam pushes the piston round towards the other "door," which on the
approach of the piston is made to slide back into the box to allow the piston
to pass, returning immediately afterwards to its former closed position.
Between this latter "door" and the moving piston new steam is introduced
through the adjacent aperture before mentioned, which pushes the piston on
in the same direction to the first "door," and there the same process is
repeated. When the steam has pushed the piston through half a circum-
ference up to or just beyond the next "door," it is allowed to escape by one
of the valves before mentioned, the work being taken up by a newly admitted
supply. In order to apply the motion of the piston to a machine a part of the
surface of the annular cylinder symmetrical with respect to the axis is made
detached from the rest, and capable of rotating round the axis, retaining, at
the same time accurate contact with the adjacent edges of the fixed part of
the cylinder. This detached portion is firmly fastened to the piston, and by
means of spokes to a shaft whose axis coincides with the axis of the cylinder.
In this way the piston and detached portion of surface and shaft rigidly con-
nected rotate together round a common axis by the pressure of the steam on
the piston, and circular motion is produced directly by the fluid pressure
instead of by the indirect means by which it is usually communicated, and
which so much diminishes the useful work resulting in the machine.
The foregoing description is given without prejudice to the Inventor's right
to use any arrangement or system of the valves or doors, which slide across
the annular cylinder, for the purpose of dividing it into compartments, or to
his right to use any arrangement or system of valves for the admission of fluid
into the cylinder and for its exhaustion or escape, and is without prejudice to
his right to use any description of annular cylinder, and any mode analogous
to those described or alluded to above of connecting the motion of the pistor
with the machine it is required to work.