THE COLLIERY GUARDIAN

AND journal of the coal AND !RON trades.

Vol. CV.

FRIDAY, APRIL 11, 1913.

No. 2728.

THE ROTOPLUNGE PUMP.

The merits and demerits relative to the properties of
the reciprocating pump with its positive’action to those
of the rotary-driven centrifugal type, and vice versa,
have always been the subject of much discussion by
engineers in general, and it is therefore thought that
the advent of a new pump, which appears to embody
the happy medium of the two former types, will be
found of interest. Such a pump was invented some
time ago by a Mr. Vincent, of Cardiff, and the pump
has now been placed on the market by the Rotoplunge
Company Limited, of Albert Chambers, High-street,
Cardiff.

By reference to the first two illustrations the con-
struction of the pump may be followed. These figures
show respectively the side and end cross-section of the
arrangement, by which it w’ill be seen that the outer
casing of the pump is so shaped that adjacent to the
inlet and outlet branches are two segmental ports of
large area arranged round the circumference of a
rotating drum. This drum is turned by means of the
pump shaft, to which it is solidly keyed. In its mass,
radially to the centre, holes are bored which form the
cylinders and accommodate the pistons as shown in fig. 1.
In the illustration one row of six pistons is shown, but,
where extremely large quantities of water have to be
dealt with, as in the case of marine and salvage pumps,
it is possible to place two rows of pistons side by side,
doubling the capacity of the pump with only a slight
increase in the weight and over-all size.

At each end of the pump casing on the inside surface
of the end covers are formed circular grooves or guides
which, however, are eccentric with the main axis of rota-
tion, the centre of the guide circle being virtually over
the centre of the shaft and removed from it a distance
of one-half of the depth of each cylinder in the drum.
Projections on the piston rods engage in these guides,
and as the drum rotates causes the pistons to slide along
the cylinders, each making a complete stroke and return
for each turn of the drum. Owing to the eccen-
tricity of the guide paths, each piston, as the cor-
responding cylinder reaches a point vertically over the
shaft, reaches the full extension of its outward stroke,
as shown in the first illustration. As the rotation con-
tinues (counter clock-wise in the drawing) the cylinder
passes the dividing segment and reaches the inlet port;
the piston then commences to move inwards, drawing
water into the cylinder. This continues as the cylinder
passes downward, the motion of the piston being
gentle at the start, being at maximum velocity when
the cylinder is horizontal, and diminishing to zero when
the cylinder is verically below the shaft. Hence all
shock on the water or irregular reaction on the pump is
avoided. As the cylinder reaches the bottom of the
casing, it passes behind the lower division segment, and,
full of water, with its piston at the inner extremity of
the stroke, passes forward to the discharge port of the
pump. Here the water is ejected from the cylinder by
the piston, at first gently, then with increasing velocity
till the cylinder is horizontal, and then with diminishing
velocity as the circle is completed, the water, therefore
being discharged without shock. This, in principle, is
the action of the pump, which is most simple in
construction.

The pump has a most economical fuel consumption.
A 9 in. diameter pump worked by a single cylinder
without flywheel), 8 in. diameter and 1ft. stroke, with
steam at 601b. pressure, and when running at 200
revolutions per minute, has been found to discharge
60,000 gallons, or about 270 tons per hour on an over-all
head of 40 ft. It can be regulated to suit any flow
required. The pump is said to work equally well at the
slowest revolutions possible as it does at full speed and
will not lose its water, which is a positive quantity at
each revolution. It never requires priming, and it is
very accessible, as the whole of the plungers can be with-
drawn and replaced in a very short time. The wear and
tear are obviously practically nil. It occupies very little

Fig i

Fig 2

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Fig. 3.



floor space; the floor space taken up by the above-
mentioned pump, including the engine, is 2 ft. 6 in. by
5 ft. 8 in., and is of comparatively small weight and is
easily handled.

The compact appearance of the pump will be readily
agreed by reference to the third illustration, which is
shown running at 200 revolutions per minute and is
discharging water at the rate of 60,000 gallons per hour
through a 9 in. discharge pipe and fitted with a suction
pipe of equal diameter.



The results of some very interesting tests have been
kindly furnished, but which we are unfortunately unable
to give for the benefit of our readers, for the want of
space. We may mention, however, that the tests were
carried out by Mr. J. G. Walliker at Cardiff on a pump
built by the well-known Bath firm of engineers, Messrs.
Stothert and Pitt Limited. The tests successfully
demonstrated the pump’s mechanical efficiency and its
power of producing a vacuum to within half an inch of
the barometer.