IMPROVEMENTS IN OR APPLICABLE TO STEAM PUMPS
Year: 1881

page_text: LETTERS PATENT to Frank Pearn, Sinclair Pearn, and Thomas Addyman, of
West Gorton, Manchester, in the County of Lancaster, Engineers, for an
PROVISIONAL SPECIFICATION left by the said Frank Pearn, Sinclair Pearn,
and Thomas Addyman at the Office of the Commissioners of Patents on the
13th May 1881.
"
FRANK PEARN, SINCLAIR PEARN, and THOMAS ADDYMAN, of West Gorton,
Manchester, in the County of Lancaster, Engineers. IMPROVEMENTS IN OR
APPLICABLE TO STEAM PUMPS."
Firstly. Our Invention relates to direct acting steam pumps where the valves of
the main steam cylinder or cylinders are worked by a double acting piston in a
small steam cylinder, the object of our Invention being an improved arrangement
for "cushioning" the movements of the small piston and its connected parts, and
our Invention consists in so forming, combining, and arranging the cylinder, piston,
valve, and ports, that the same small piston will not only work the valve or valves
for the main steam cylinder but "cushion" the movements.
The cylinder, piston, and slide valve used are ordinary parts, but the cylinder is
made with two ports for each end, one for steam to enter, the other for it to pass
out or exhaust; the slide valve is made with extended lap at each end, so that in
its central position all the ports will be covered. When the small slide valve is
moved one way to admit steam at one end of the cylinder, the exhaust port at
that end and the inlet port at the other end of the cylinder are covered, but the
other exhaust port is uncovered. By the time the small piston has moved until
the valve or valves of the main steam cylinder or cylinders has partly opened, the
small piston will have covered the exhaust port left open, and the steam or mixed
steam and air left at that end of the cylinder thus acts as a "cushion," as there is
no escape for it except by its pressure lifting the slide valve from its facing. The
action is the same for the reverse movement.
If desired there is or may be a small lifting valve at each end of the small
cylinder to allow steam when sufficiently compressed to escape from the cylinder
into the steam chest or into the exhaust cavity.

page_text: Secondly. Our Invention refers to means for governing the speed of the engine
by regulating the throttle valve supplying steam to the main cylinder or cylinders
of direct acting steam pumps where the valve or valves of the main piston or
pistons are moved by a small steam piston and cylinder, and consists in combining
with the throttle valve a ram or piston and spring or weight, the spring or weight
opening the throttle valve, and the pressure of water pumped by a small pump
attached to the engine acting upon the ram or piston by increase of pressure as the
speed increases to close the throttle valve, this arrangement being similar to
those described under the second head of the Specification of Letters Patent granted
to us, and numbered 3942, and dated the 29th day of September 1880, for
governing the position of a ram or piston carrying or in connection with a
T lever for working the slide valve of the small cylinder, the piston of which
works the valve or valves of the main cylinder or cylinders, and this part of
our Invention also consists in combining our present improvements with the
improvements described in our aforesaid Specification.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filel
by the said Frank Pearn, Sinclair Pearn, and Thomas Addyman in the
Great Seal Patent Office on the 10th November 1881.
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 relates to direct acting steam pumps where the valves of the
main steam cylinder or cylinders are worked by a double acting piston in a small
steam cylinder, the object of our Invention being an improved arrangement for
'cushioning" the movements of the small piston and its connected parts, and our
Invention consists in so forming, combining, and arranging the cylinder, piston,
valve, and ports, that the same small piston will not only work the valve or valves
for the main steam cylinder but "cushion" the movements.
The cylinder, piston, and slide valve used are ordinary parts, but the cylinder is
made with two ports for each end, one for steam to enter, the other for it to pass
out or exhaust; the slide valve is made with extended lap at each end, so that
when in its central position all the ports will be covered.
When the small slide valve is moved one way to admit steam at one end of the
cylinder, the exhaust port at that end and the inlet port at the other end of the
cylinder are covered, but the other exhaust port is uncovered. By the time the small
piston has moved until the valve or valves of the main steam cylinder or cylinders
has partly opened the small piston will have covered the exhaust port left open,
and the steam or mixed steam and air left and thus enclosed at that end of the
cylinder acts as a "cushion," as there is no escape for it except by its pressure
lifting the slide.valve from its facing against the pressure of the steam on the back
of the valve which does not occur in ordinary working.
The action is the same for the reverse movement of the valve.
Fig. 1 is a side elevation, and Fig. 2 is a plan view, each Figure partly in section
illustrating a direct acting steam pump with our improvements applied.
Fig. 3 is a section on an enlarged scale, and detached, of the small cylinder,
ports, and valve, showing the piston and parts of the valve rods according to our
Invention.
a is the base plate or any suitable bed; b, the double acting pump of ordinary
construction; c, the pump and steam piston rod; d, the main steam cylinder;
e, the main slide valve worked by a spindle e¹ passing through a stuffing box, and
then through another stuffing box in the small steam cylinder f where it is
connected with a piston f¹.
This cylinder is formed with two ports, one f* for steam, the other f³ for exhaust
at each end of the cylinder f, and has an exhaust cavity f*.
The small slide valve ƒ³ covers all the ports fs and f³ when in mid-position, as
shown in Fig. 3.
f is the spindle for actuating the small slide valve (f³) and passes through a
stuffing box, and is connected by a slot with one arm of a T lever f', having its
fulcrum f carried on a bar or beam f' extending and secured to the side of the
glands of the pump and main steam cylinder.
This beam (f) also carries the small cylinder f and a bracket fx that acts as a
guide through which the small valve spindle ƒ slides.
The horizontal arms of the T lever f' are curved, and are acted upon by a
projection c¹ carried on the main piston and pump rod c near each end of the
stroke so as to oscillate the T lever f', and thus move the small slide valve ƒ³ at
each end of the stroke of the main steam piston.

page_text: When the main steam piston d' moves to the end of its stroke in the direction
of the pump, the small slide valve f³ will have been moved in the direction of the
main steam cylinder (d), and this movement will uncover the steam port f' at that
end of the small cylinder (f) furthest from the main cylinder (d), and will also uncover
by the same movement the exhaust port fƒ³ at the opposite end of the small
cylinder (f), and steam will thus be admitted to and excluded from the small
cylinder while the small piston fl moves towards the large steam cylinder c; but
after the small piston arrives in the position, shown in Fig. 3, it covers and closes
the exhaust f at that end towards which it is moving, and thus the fluid retained
in that end of the small cylinder then acts as a " cushion to arrest the sudden
movement imparted to the small piston 'f' and connected parts at each change of
position.
"
When the main piston (d¹) has moved to the other end of its stroke, the move-
ments above described of the small valve f³ and piston f1 are reversed, and so on
for each stroke, the fluid retained at the ends of the small cylinder by the closing
of the ports f by the small piston acting to cushion the movements.
Our Invention is applicable when the main slide valve is connected with and
actuated by two small pistons, one at each side, each piston in a separate small
cylinder open to the main valve chest at one end and attached to or forming part
of it, these cylinders having each two ports and passages communicating with the
corresponding ports covered by the small slide valve when in mid-position.
Fig. 4 illustrates by an elevation in section the modification last referred to;
d, main steam cylinder; c, piston rod; e, main slide valve connected by rods e¹ to
the two piston f¹ in cylinders f
fs, small slide valve; f6, its rod; and f³, f³, valve passages and ports;
f, exhaust cavity.
The exhaust port f* communicates with the exhaust cavity of the main slide
valve, and steam is or may be taken from the main valve chest to the small valve
chest by a pipe or passage, or direct from the steam pipe supplying the main
steam valve.
We have now particularly described the nature of our said Invention and the
mode of carrying the same into effect, and claim as our Invention,―
Firstly. The combination of a small steam cylinder or of two cylinders with
ports, slide valve and piston, or pistons arranged to actuate the main steam slide
valve of direct acting steam pumps, and to "cushion" the movements of the valve
and its connected parts, substantially as hereinbefore described and illustrated by
the Drawings.
Secondly. The combinations and arrangements of the valve mechanism of direct
acting steam pumps, substantially as hereinbefore described and illustrated by the
Drawings.
In witness whereof, I, the said Frank Pearn, on my own behalf and on
behalf of the said Sinclair Pearn and Thomas Addyman, have hereunto
set my hand and seal, this Ninth day of November, in the year of our
Lord One thousand eight hundred and eighty one.
FRANK PEARN. (L.S.)