IMPROVEMENTS IN PUMPS "
Year: 1880

page_text: LETTERS PATENT to Robert Graham Abercrombie, of Alloa, in the County
of Clackmannan, North Britain, for an Invention of "IMPROVEMENTS IN
PUMPS "
PROVISIONAL SPECIFICATION left by the said Robert Graham Abercrombie
at the Office of the Commissioners of Patents on the 17th December 1880.
ROBERT GRAHAM ABERCROMBIE, of Alloa, in the County of Clackmannan,
North Britain. "IMPROVEMENTS IN PUMPS."
This Invention, which has for its object improvements in plunger pumps, is
applicable to all such pumps wherein a pressure regulator is required, and it
is especially adapted to pumps used in pumping disintegrated clay or other
potters' material admixed with water (technically called "slip") into potters' filter
presses.
Hitherto with pumps employed for this purpose the pump works easily until the
filter bags of the press are nearly full. After that the pump at each stroke forces
more "slip" than the press can accommodate the surplus running back into a tank
through an ordinary safety valve.
The pump is thus made to perform an amount of useless work, and in lifting the
safety valve at every stroke throws a sudden pressure on the press and bags, and
the
pump valves are in full operation all the while.
To obviate these defects the plunger of the pump is, under this Invention, made
in two parts, namely, an inner part and an outer annular part, wherein the inner
part is kept tight by a cup leather at the foot. Both parts are generally, by
preference, of equal area, although in some sizes of pumps it may be found desirable
to employ other proportional areas. Between the bearing surfaces of the two parts
india-rubber or equivalent springs are inserted, and the inner part is loaded with a
number of cast iron weights, sufficient to exert the maximum pressure required per
square inch, any less pressure being obtained by removing a proportional number
of weights. The plunger receives reciprocating motion from links attached to its
outer part, so that as long as the pressure in the press does not exceed the pressure
per square inch exerted by the weights on the inner part the two parts of the
plunger work together as one plunger. When however the pressure does exceed
the limit mentioned the inner plunger will rise as the outer one descends, and vice
versa, the valves of the pump remaining at rest, and a constant pressure being so
kept on the filter, a saving of wear and tear, both as regards the filter bags and
pump valves, is effected.
In conjunction with the arrangement a quick return motion similar to that used
in a slotting machine is employed, so that when the outer plunger lifts it shall be
at the slow part of its stroke.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Robert Graham Abercrombie in the Great Seal Patent Office on the
16th June 1881.
ROBERT GRAHAM ABERCROMBIE, of Alloa, in the County of Clackmannan,
North Britain. "IMPROVEMENTS IN PUMPS."
My said Invention, which has for its object improvements in plunger pumps, is
applicable to all such pumps wherein a pressure regulator is required, and is
especially adapted to pumps used in pumping disintegrated clay or other
potter' material admixed with water, and technically called "slip" into potters'
filter presses.
In the pumps hitherto employed for this purpose the apparatus works easily
until the filter bags of the press are nearly full, but after that the pump at each
stroke forces more "slip" than the press can accommodate, and the surplus runs
into a tank through an ordinary safety valve.
The pump is thus made to perform an amount of useless work, and in lifting the
safety valve at every stroke it throws a sudden pressure on the press and filter bags,
the pump valves being in full operation all the while.
To obviate these defects is the object of the present Invention.
And in order that the system, mode, or manner in or under which my said
Invention is or may be used or carried out in practice may be properly understood
I have hereunto appended an explanatory Sheet of Drawings, on which Figure 1 is
a front elevation, and Figure 2 a transverse section of the improved pump.
As shown more particularly by Figure 2 the plunger of the pump is made in
two parts, namely, an inner part or plunger a and an outer annular part or
plunger b, wherein the inner plunger a is kept tight by a cup leather c attached
to its foot. Both plungers are generally, and by preference, of equal area, although
in some sizes of pumps it may be found desirable to employ other proportional
areas, and on the upper end of the inner plunger a collar disc or platform d is
secured. Between the bearing surfaces of the collar platform or disc and the upper
end of the outer plunger b a steel or other metal spiral or equivalent spring is
inserted, as seen at e, Figure 2, and the inner plunger is loaded with cast iron
weights f, placed on the collar disc or platform d'in numbers sufficient to exert the
maximum pressure per square inch, any less pressure being obtained by removing
a proportional number of weights.
The plungers receive vertically reciprocating motion from links g, actuated by
eccentrics h, secured on a shaft k, which is carried in bearings at the upper part
of the framing 7 of the pump and rotated by the spur wheel and pinion m, m³, a
belt pulley or drum being secured on the axis of the pinion, as shown. The
links g are attached to a cross head n formed on or secured to the outer plunger b,
and the ends of which slide in vertical guides o secured to the side frames.
By this arrangement so long as the pressure in the press does not exceed the
pressure per square inch exerted by the weights ƒ on the inner plunger a, both
plungers a and b work together or in unison as one plunger. When however the
pressure does exceed the limit mentioned the inner plunger a will rise as the outer
one descends, and vice versa, the valves p of the pump remaining at rest, and a
constant pressure being so kept on the filter, a saving of wear and tear, both as
regards the filter bags and the pump, is attained, whilst at the same time it is found
that a saving of time in filling the said bags is also effected.
Figure 3 shows a modification of the arrangement by which a like effect is
produced, and wherein the plungers a, b, instead of being situated one at the
interior of the other, as hereinbefore described, occupy different positions on the

page_text: valve chamber T. The plunger b is connected direct to the eccentric h and is
reciprocated by it, whilst the plunger a is merely weighted so as to give the pressure
required. Both plungers are situated between the inlet and outlet valves of the
press, so that the pressure in the chamber must become less than that due to
the weighted plunger a before the reciprocating plunger 6 can draw more liquor
or "slip" through the inlet valve.
In conjunction with both arrangements of the plunger b a quick return motion,
similar to that used in a slotting machine, may be employed, so that when the
plunger lifts it shall be at the slow part of its stroke.
Having now described and particularly ascertained the nature of my said
Invention, and the system, mode, or manner in or under which the same is or may
be used or carried out in practice, I would observe in conclusion that what I
consider to be novel and original, and therefore claim as the Invention secured to
me by the herein before in part recited Letters Patent is,―
First. In a plunger pump the combination in one plunger of an inner weighted
plunger a and an outer annular plunger b, substantially as and for the purposes
herein before described with reference to Figures 1 and 2 of the appended
Drawings.
Second. In a plunger pump the combination of a weighted plunger a with a
reciprocating plunger b, both being situated between the inlet and outlet valves,
substantially as and for the purposes hereinbefore described with reference to
Figure 3 of the Drawings annexed.
In witness whereof, I, the said Robert Graham Abercrombie, have hereunto
set my hand and seal, this Fifteenth day of June, in the year of our Lord
One thousand eight hundred and eighty one.
Witness,
GEO. M. CRUIKSHANK,
Patent Agent,
Glasgow.
ROBERT GRAHAM ABERCROMBIE. (L.S.)