Pumps

3877

ial vacuum beneath, which is immediately!
filled with water forced in through the snorer '
and bottom valve F, by the atmospheric pres-
sure acting on the surface of the water in the
bore-hole. When the bucket reaches the top
of its stroke its motion is reversed, and it

FIG.I.
"DOUBLE-ACTING BUCKET

AND PLUNGER PUMP „

(BUCKST OQIWO UP)

FIG. 2.

SINGLE-ACTING
BUCKET PUMP
(BUCKET GOING UPl

Pumps.

commences to descend. The water beneath it
attempts to get back into the bore-hole, but
is prevented from doing so by the bottom
valve F, which immediately closes. The water
is thus caught between the descending bucket
and the valve, p, and, as it is practically in-
compressible, it forces the valve in the bucket
G open. As the bucket descends, the water
passes through it to the upper side.

When the second double stroke commences
there is already three ft. of water above the
bucket, at the commencement of the thirc
stroke six ft,, of the fourth stroke nine ft.

and so on. until the rising main is full up to
the level of the outlet at or ubuve the sur-
face of the ground, and water commences to
be discharged—a volume of water equal to
the stroke of the pump limes the cmxc-sec-
tional area of the vrorkins: barrel beincr then
delivered at each double stroke.

As shown in Ficr. i, this pump is double-
acting—I.e. it delivers water on both the up
and the down stroke. This is effected by the
use of the plunger E, which is a closed cylinder
forming part of the pump rods. As the bucket
moves up three ft., the plunger does the
same, and half the water lifted by the bucket
goes into the space left by the retreating
Dlunger, and half goes up the rising main to
the discharge. As the bucket goes down, the
plunger follows, and, as the water beneath
cannot escape downward, forces its own bulk
of water up the rising main to the reservoir.
In this manner half the total quantity
pumped per double stroke is lifted on the up-
stroke, and half is forced on the downstroke.

The purap illustrated in Fig. 2 is of similar
description, but is single - acting. The dis-
charge is effected on the upstroke of the
bucket, so that the pump is intermittent in
its action.

Direct - Acting Steam Pumps.—A direct-
acting pump is one in which the motion of
the driving piston is transmitted direct to the
water piston or plunger by a rod or rods. In
its simplest form it consists of a steam end
containing a reciprocating piston connected
to one end of a piston rod, the other end be-
ing attached to the water plunger. Such a
pump, known as a single pump or a simplex
pump, is shown in section in Fig. 3. The
pump is driven by steam which is admitted
alternately on opposite sides of the piston by
a valve located above tbe steam cylinder.
When the piston nears the end of its stroke,
it comes in contact with the stem of a small
poppet valve in the head of the cylinder and
lifts the valve. The opening of this valve re-
leases the steam pressure on the end of the
slide valve, and the unbalanced condition thus
set up causes the slide valve to move, uncov-
ering the steam port and admitting steam be-
hind the piston. The piston is then driven to
the opposite end of the cylinder by the ac-
tion of the steam, until it strikes the poppet-
valve stem at that end, when the motion is
again reversed in the same way as before.
The piston rod at its left end is fastened to
the water plunger which is thus given a re-
ciprocating motion. The pump is double-ac-
ing. When the plunger moves to the right, it