IMPROVEMENTS IN APPARATUS FOR WORKING PUNKAHS BY MEANS OF COMPRESSED AIR
Year: 1878

page_text: PROVISIONAL SPECIFICATION left by Richard Clere Parsons and Edward
Palliser at the Office of the Commissioners of Patents on the 14th March
1878.
RICHARD CLERE PARSONS, of No. 10, Connaught Place, in the County of Middle-
sex, and EDWARD PALLISER, of No. 5, Charleville Road, Kensington, also in the
County of Middlesex. "IMPROVEMENTS IN APPARATUS FOR WORKING PUNKAHS
BY MEANS OF COMPRESSED AIR."
In the Specification to Letters Patent granted to John Imray on the 20th March,
1874, No. 981, was described a method of working punkahs by means of com-
pressed air acting in a cylinder on a piston connected to the punkahs. This
Invention relates to improvements in apparatus for this purpose, the principal
object of these improvements being to obtain an automatic action of the slide
governing the cylinder ports for the admission and emission of the compressed air,
so that, although the pressure of the air may be considerably varied, the punkahs
shall continue to reciprocate with a greater or less stroke. For this purpose we
provide the air cylinder with ports governed by a slide of ordinary construction.
We connect this slide by a slotted rod to one arm of a three-armed tumbling lever,
to which arm is also linked a spring. The other, two arms of the tumbling lever
project into the path of the piston rod of the air cylinder, on which rod is fixed a
tappet. As the piston approaches the middle of its stroke in either direction the
tappet acts on the one or the other of the arms, and thereby causes the tumbling
lever to make a partial revolution on its fulcrum, straining the spring that is linked
to it. On the lever passing the middle point of its stroke the spring re-acting
would cause it rapidly to complete its stroke but for a retarding apparatus, which
we will now describe.
This apparatus consists of a cataract cylinder charged with oil or other suitable
liquid, and having a piston connected to the slide rod. The piston is made to fit
the middle part of the cylinder, but to work loosely on either side thereof.
As the cataract piston is passing the middle part of its stroke when the spring
begins to act so as to move the tumbling lever this movement is retarded by the
resistance of the liquid; but when the piston has passed the middle narrow part

page_text: of the cataract cylinder the liquid getting free passage from the one side to the
other of the piston ceases to retard it, and the spring thereupon causes the remaining
part of the stroke of the tumbling lever to be rapidly completed. The slide being
thus moved by the tumbling lever the compressed air which previously acted on
the one side of the piston is allowed to escape, and a fresh supply of compressed air
is admitted to act on the other side of the piston. If therefore the piston makes a
stroke sufficient only to move the tumbling lever a little beyond the middle of its
stroke, straining the spring, the recoil of the spring effects the rest of the stroke,
and so reverses the supply and discharge of air, causing the piston to make its
return stroke.
For the purpose of adjusting the time of the successive strokes a passage for
liquid is provided from the one end of the cataract cylinder to the other, the said
passage being fitted with a screw plug or cock, by which its area can be regulated
as desired, so as to give less or greater freedom of passage to the liquid, and so
more or less retard the movement of the slide.