IMPROVEMENTS IN OR APPLICABLE TO STEAM PUMPS
Year: 1883

page_text: PROVISIONAL SPECIFICATION left by Frank Pearn, Sinclair Pearn, and
Thomas Addyman at the Office of the Commissioners of Patents on the
5th May 1883.
FRANK PEARN, SINCLAIR PEARN, and THOMAS ADDYMAN, of West Gorton,
Manchester, in the County of Lancaster, Engineers, " IMPROVEMENTS IN OR
APPLICABLE TO STEAM PUMPS,"
Our invention is applicable to direct acting steam pumps for pumping water, air,
or other fluids, and relates to means for actuating the slide valve of the main
steam cylinder which regulates the admission and exhaustion of the steain to and
from the main steam cylinder, and our invention consists in giving the main
steam valve a positive and uniform length of stroke partly from a piston working
in a separate small steam cylinder and partly from the movements of the piston
rod of the main steam cylinder, the movements from these two sources being
combined to act together and assist each other. According to our present
experience we prefer to carry out our invention by arranging the small steam
cylinder so that its piston rod will form part of or be connected directly with the
spindle of the valve of the main steam cylinder, but we form a cross slot in the
part connecting the rod and spindle for a sliding bearing which fits a small crank
on a small crank shaft in suitable bearings on the framing, so that the reciprocating
movement of the piston rod gives rotary movement to the crank, and the crank
thus determines and regulates the movements of the main steam slide valve.
Instead of the cross slot a connecting rod may be employed between the piston red
of the small steam cylinder and the crank.
The slide valve for admitting and exhausting steam to and from the small steam
cylinder is worked from an excentric on the small crank shaft.
On the small crank shaft there is another small crank with which one end of a
connecting rod is jointed the other end of which is also jointed to one end of a
lever on any suitable fulcrum, the other end of which lever is connected by a rod
with the main steam piston and pump rod, the leverage being proportioned so
that the full stroke of the main piston rod will be equal to the throw of the crank
upon the small crank shaft with which it is connected.
The two small cranks are so arranged in relation to cach other that they will
alternately assist each other over the "dead centres," and there is or may be

page_text: "play" in the movement of the levers actuated from the main piston rod to permit.
if desired, of variations to some extent in the stroke of the main steain piston and
pumps.
Instead of two small cranks, one only need be used if desired, the same crank
being acted upon by the cross slot as herein before described and a cross slot in
another rod or part placed at a right angle to the first named, the second cross
slotted rod or part being actuated by a bell crank lever or otherwise from the main
piston rod.
Or in place of the second cross slotted rod a bell crank lever may be used having
a connecting rod jointed to it attached to the same crank.
According to a modification of our invention we arrange the lever or levers or
fulcrum of the lever through which motion is transmitted from the main steam
piston so that the leverage can be varied according to the stroke of the main piston
rod, so that whatever be the stroke of the latter the same length of movement
will be transmitted to the small crank, and we make this change or variation
in the leverage by connecting the lever or its fulcrum with the piston rod of a
small cylinder, the piston of which is moved to and fro by liquid pumped by a
small pump actuated from the piston rod of the main pump.
If the pump increases in speed more water is pumped by the small pump than
can flow out in a given time through an adjustable cock or orifice, and this "acts
upon the piston to move it one way and thus the fulcrum or lever and vice versa
when the speed of the pump decreases.