Year: 1885

page_text: I FREDERICK ELIOT DUCKHAM of Millwall Docks in the County of Middlesex
Engineer do hereby declare the nature of this Invention to be as follows:-
My Invention relates to apparatus for dredging or removing and depositing mud
and other spoil raised from the bottom of Docks, Harbours and from other places
and is in part an improvement on the invention forming the subject of previous
Letters Patent dated December 18th 1875 N° 4400.
In the apparatus therein described the mud or spoil was received directly from
the dredging buckets in a tank or tanks whence it was expelled through outlet
pipes by means of compressed air admitted at the upper part of the tank, assisted
by compressed air and water injected at the bottom of the tank, to agitate the
mud and prevent thick deposit.
In that arrangement the outlet pipes descend externally from the bottom of the
tanks and curve upwards in the direction of the site of discharge.
My first improvement consists in arranging the outlet pipes within the tank and
making them adjustable therein. The said pipes ascend internally vertically or
nearly so the lower extremity or inlet being at a suitable distance above the bottom
of a shallow well in the tank and the upper portion passing through a stuffing box
in the top of the tank and fitted with screws or other means of adjustment, whereby
the spoil will have a straighter course of exit and the mouth of the pipe may
normally be kept low enough to empty the tank, but may be raised when
requisite to allow large lumps to pass which may occasionally block the narrow
passage.
When two tanks are used side by side the two outlet pipes may converge above
the tanks and be received in a breeches pipe provided with suitable stuffing boxes
and gear for adjusting the pipes telescopically therein, the breeches piece being
surmounted by an elbow pipe capable of being turned in any required direction.
In addition to the admission of water at the bottom of the tank, I inject water
at the top of the tank in the form of rain for the purpose of washing sandy or
other agglomerated deposit down to the outlet.
This water is preferably introduced by longitudinal perforated pipes extending
along the upper part of the tank.

page_text: Besides using the air pumps for expelling mud or spoil from the tanks, I propose
to employ the same or other pumps for filling the tanks with spoil. The said
pumps being for the time used as suction or vacuum pumps and applied to exhaust
the tank in which the mud or spoil is to be received.
The same pipe may be used both as the outlet and inlet by connecting it with
a flexible but non-collapsible pipe, which may be led to the bottom of the harbour
or dock or to any other place whence the spoil is to be removed or I may employ
separate inlet and outlet pipes fitted with such valves or shutters as may be
necessary.
The pumps for filling the tanks may either simply exhaust the air therefrom and
so draw the spoil in or may wholly or in part also remove any water which may.
enter the tank with the mud or spoil or the pumps may be hydraulic pumps only,
the tank or tanks which in that case would be kept full of water serving to
intercept and retain sand and other solid matter which may be deposited by
subsidence from the water on its way to the pump.
The inlet pipe from the bottom of the harbour or other source of spoil as
likewise the pipe to the pump would be connected with the upper part of the tank
or tanks which would be provided with telescopically adjustable outlet pipes and
with pipes for the injection of water and compressed air all as before described.

page_text: Depositing "Spoil."
I, FREDERIC ELIOT DUCKHAM of Millwall Docks in the County of Middlesex
Engineer, do hereby declare the nature of this invention and in what manner
the same is to be performed, to be particularly described, and ascertained in and
by the following statement :-
My Invention relates to apparatus for dredging or raising mud and other spoil
from the bottom of docks, harbours, and from other navigable places, and for
transporting and depositing the same where required; and it is in part an improve-
ment on the Invention forming the subject of previous Letters Patent dated
December 18th 1875 and numbered 4,400.
Reference is to be had to the accompanying drawings forming part of this
Specification wherein figure 1 is a cross-section of a dredger containing a pair of
tanks provided with improved outlets for the spoil, and with injection pipes for
spraying water upon the spoil to assist its ejection as hereafter described; and
figure 2 is a longitudinal section of a tank as arranged for intercepting mud or
spoil raised by hydraulic pumping. Figure 3 shews the air pumps provided with
means for enabling the pumps to be used both for filling and emptying the tanks.
In the apparatus described in my aforesaid patent the mud or spoil was received
directly from the dredging buckets in a tank or tanks whence it was expelled
through outlet pipes by means of compressed air admitted at the upper part of the
tank assisted by compressed air and water injected at the bottom of the tank for
the purpose of agitating the mud and preventing thick deposit. In that arrange-
ment the outlet pipes were connected to the bottom of the tanks and curved
upwards externally in the direction of the site of discharge.
According to my present Invention, I arrange the outlet pipe or pipes A to dip
down within the tank so that the spoil will have a straight course of exit. Each
outlet pipe preferably dips into a shallow well B formed at the bottom of the tank
into which the spoil gravitates, the dip pipe being made adjustable as to height, in
order that the mouth of the pipe may normally be kept low enough to empty the
tank but may be raised when requisite to allow large lumps to enter the pipe.
For this purpose the pipe passes through a stuffing box C at or near the top of.
the tank and is provided with means of raising and lowering it in the tank, the
pipe A passing through a second stuffing box C¹ on a fixed pipe E above, in which
the upper end of the pipe A is received telescopically. In the example shewn,
a pair of adjusting screws F are provided, one at each side of the pipe A, the
screws turning in bearings on the stuffing boxes and working through corre-
spondingly threaded holes in ears fixed on the pipe. The screws being prevented
by collars from having any longitudinal motion, the ears are caused to traverse
along them when they are turned by a key, whereby the pipe is adjusted as
required.
When two tanks, arranged side by side, as in figure i are employed, the two
outlet pipes A may converge and be received in a breeches pipe E common to both

page_text: and provided with stuffing boxes and gear for adjusting the pipes telescopically
therein as before described, the breeches piece being surmounted by an elbow pipe G
so jointed to the breeches piece as to be capable of being turned in any required
direction. To permit of this motion, the circular flanged lower end of the elbow
pipe is held in a seat formed in the flanged upper end of the breeches pipe by a
collar bolted to the flange of the breeches pipe, as shewn.
In addition to the admission of water at the bottom of the tank as described in
my aforesaid patent, I inject water at the top of the tank in the form of rain or
spray for the purpose of washing sandy or other agglomerated deposit down
towards the mouth of the outlet pipe. This water is preferably introduced by
longitudinal perforated pipes H extending along the upper part of the tank,
as shewn in figure 1, and connected with force pumps by which the water is
injected concurrently with the compressed air forced in by the air pumps.
Besides using the air pumps for expelling mud or spoil from the tanks, I propose
to employ the same pumps for filling the tanks with spoil the said pumps being for
the time used as suction or vacuum pumps and applied to exhaust the tank in
which the mud or spoil is to be received. To enable this to be done the arrange-
ment shown in figure 3 may be employed. In this arrangement, the pipe K
connecting the air pump with the tank communicates by branch pipes 8 d with
suction and delivery valves SD of the pump, and the branch pipes are furnished
with three-way cocks c c by means of which the suction valves are put into com-
munication with the tank and the delivery valves with the atmosphere for filling
the tank, and the suction valves are put into communication with the atmosphere
and the delivery valves with the tank for emptying the tank. The same dip-pipe
may be used both as the outlet and inlet for spoil by connecting it with a flexible
but non-collapsible pipe which may be led to the bottom of the harbour or dock,
or to any other place where the spoil is to be removed, or where it is to be dis-
charged, as the case may be. Or, I may employ separate inlet and outlet pipes
fitted with such valves or shutters as may be necessary.
The filling of the tanks with spoil may be effected by simply exhausting the air
therefrom, and so drawing the spoil into the tank, by atmospheric pressure, and
the pumps may also remove along with the air any water which may enter the
tank with the mud or spoil. Or, the pumps may be hydraulic pumps only, the
tank or tanks being in that case, kept full of water and serving to intercept
and retain sand and other solid matters which may be deposited from the water.
on its way to the pump. In this case the tank would be arranged as shewn in
.figure 2, that is to say, the inlet pipe I from the bottom of the harbour or other
source of spoil would be connected with the top of the tank at one end thereof,
the outlet pipe K. for water only and to which the pump is connected being
similarly connected with the top of the tank at the opposite end thereof, in order
to afford an opportunity for the subsidence, during the passage of the water
through the tank, of the heavy solid matters in suspension. The tank is provided
with a telescopically adjustable dip-pipe A and a well B as before, for the discharge
of the spoil which is effected at the required time by the injection of compressed
air as before described, assisted by water sprayed upon the spoil by perforated
pipes arranged within the upper part of the tank, as represented in figure 1. The
compressed air may be forced in by either of the pipes I or K, or by a separate
pipe, all outlets, except that through pipe A, being, of course, closed.
Having now particularly described and ascertained the nature of the said
Invention, and in what manner the same is to be performed I declare that
what I claim is;—
1. In a dredger tank whence the dredgings are to be expelled by air-pressure,
the use of an adjustable pendent outlet pipe for the dredgings arranged within the
tank, substantially as specified.
2. In a dredger tank whence the dredgings are to be expelled by air-pressure as
described, the use of a pendent outlet pipe made adjustably by sliding through the

page_text: upper part of the tank as described, in combination with a well in the bottom of
the tank into which said pipe dips, substantially as specified.
3. In a dredger tank, the use of an adjustable pendent telescopically sliding
outlet pipe in combination with a pair of adjusting screws arranged to operate the
movable pipe, substantially as shewn and described.
4. The combination with a pair of dredger tanks each provided with adjustable
pendent outlet pipes dipping therein, of a breeches pipe common to both outlet
pipes which slide telescopically therein through suitable stuffing boxes and are
operated by adjusting screws, and of a rotating elbow pipe, all substantially as
described and shewn in figure 1 of the drawings.
5. In a dredger tank whence the dredgings are expelled by air pressure acting
on the surface thereof as described, the injection at the upper part of the tank of
water in the form of rain or spray for the purpose of facilitating the gravitation of
the dredgings towards the outlet, as described.
6. The combination with the same dredger tank of means whereby the dredging
operation may be performed and the tank may be filled with spoil by the aid of a
vacuum, and the spoil may be discharged therefrom by a plenum by making the
same pumps available for the two operations substantially as specified.
7. The herein described system of dredging wherein the spoil and, water are
received in an intercepting tank provided with inlet and outlet pipes so arranged
that the tank will be kept always full of water, the solid matters will subside
and be retained in the tank, and the water alone will pass on to the pumps,
substantially as specified.