Improvements in Dredging Apparatus.
Year: 1893

page_text: Date of Application, 1st Apr., 1893
Complete Specification Left, 1st Jan., 1894-Accepted, 31st Mar., 1894
PROVISIONAL SPECIFICATION.
Improvements in Dredging Apparatus.
I FREDERIC ELIOT DUCKHAM of Millwall Docks, London E. Engineer do
hereby declare the nature of this invention to be as follows:-
My invention relates to the dredging of sand, mud, and the like, by centrifugal
pumps or other means whereby the effect of suction may be caused to act on the
matter to be raised, and it has for its object to provide means whereby the proper
proportion of sand or other solid matter to the conveying current of water may
be maintained so that on the one hand choking of the apparatus by an excess
of solid matter and on the other hand waste of power by pumping water holding
less than its proper proportion of matter in suspension may be avoided.
The invention consists in providing the suction inlet nozzle which in the
operation of dredging becomes more or less buried in the sand or other matter to
be raised, with a tubular sleeve surrounding the nozzle at a distance and rising to
such a height that although its lower end may be buried in the sand or mud, its
upper end will rise above the same so as to provide between the sleeve and nozzle a
constantly open annular downcast passage way for water which by acting on the
sand or mud in which the inlet orifice of the nozzle is buried will disintegrate it
and by mingling with it in due proportion will efficiently act as a carrying current
and prevent the choking of the apparatus, the relative height of the lower end of
the sleeve and of the inlet orifice of the nozzle being such that a free passage for
water unmixed with solid matter cannot be afforded..
For this purpose the sleeve is made adjustable on the nozzle by means of screws
or otherwise so that the relative height of the two may be regulated to suit the
nature of the soil operated on and the other incidental circumstances of the case.
The proportional amount of water passing through the sleeve may moreover be
governed directly by regulating the area of the admission passage at the upper end
of the sleeve for instance by partly closing the upper end of the annular space and
by carrying a pipe up thence for any convenient distance so that a regulating cock
or valve therein may be manipulated from on board the dredger.
DAL 1 CA1 1000
F. E. DUCKHAM,
By A. M. & Wm. Clark,..
53, Chancery Lane, London, Chartered Patent Agents.
COMPLETE SPECIFICATION.
Improvements in Dredging Apparatus.
I, FREDERIC ELIOT DUCKHAM, of Millwall Docks, London, E., 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 dredging apparatus for the subaqueous excavation of
sand, mud, and the like, by suction, and the invention has for its object to provide
means whereby the proper proportion of water to act as the conveying current, to
the sand or other solid matter may be maintained, so that on the one hand choking
of the pipe by excess of solid matter and on the other hand waste of power by
A

page_text: pumping water holding less than its proper proportion of solid matter in suspension
may be avoided.
The invention consists in providing the downwardly-directed mouth of the
suction nozzle with a downcast water passage open at top to the water and
terminating at its lower end (which is in the form of a sleeve surrounding the mouth
of the nozzle) at such a height above the mouth of the nozzle that by the burying
of the latter in the sand or mud there will, under normal conditions of working, be
a certain quantity of solid matter constantly exposed to the scouring action of the
water current which by mingling in due proportion with the solid matter will act
efficiently as a carrying current and prevent choking of the conveying pipe.
Reference is to be had to the accompanying drawings, forming part of this
Specification, wherein Figures 1 and 2 are part longitudinal and cross-sections
illustrating the arrangement suited for sand pump dredgers in which the suction
nozzle is at a considerable and variable inclination, whilst Figure 3 is a longitudinal
section of the form of the nozzle suited for use in a more or less vertical position
as in clearing out foundation cylinders for instance.
b
A is the suction tube or nozzle connected at the upper end, by a joint about
which it can swing, to the inlet of a centrifugal or other form of sand pump on
board the dredging vessel. B is the downcast passage for water, having a sectional
area rather more than half that of the tube A, the lower part 6 being annular and
surrounding the mouth a of the nozzle, the mouth 6 terminating at such a height
above the level of the mouth a that the latter will constantly bury itself in the
sand or mud to the depth of about one sixth the diameter of the inner pipe, more
or less, so that there will be a certain and constantly renewed depth of solid matter
directly exposed to the scouring action of the stream of water passing from B
into A. The passage B, which may be wholly concentric with the nozzle A, as in
Figure 3, or be concentric therewith only at the lower end or mouth and extend
up alongside of the nozzle A, as in Figure 1, should rise to such a height that its
upper end will always be open to the water in which the apparatus is working.
In the straight form of nozzle shewn in Figure 3 the relative height of the
mouths a and may be varied in order to vary the relative proportions of water
and solid matter passing up through the nozzle A according to the nature of the
material excavated and other incidental circumstances by making B longitudinally
adjustable on A by means of screw-rods C and nuts c.
In Figure 1 in which the lower ends of A and B are bent so that their mouths
are downwardly directed whilst the pipes are inclined at a considerable angle, the
same end may be attained by controlling the admission of water to the upper end
of passage B by means of a slide D operated from on board the dredging vessel by
any suitable means, the upper end of the passage B being closed in the latter case
except through the aperture regulated by the slide.
Suitable tackle is provided for raising and lowering the nozzle from on board the
dredger as usual in such cases.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. In dredging apparatus for the subaqueous excavation of sand, mud, and the
like, by suction, the combination, with the downwardly-directed mouth of the inlet
suction nozzle, of a downcast water passage open at the upper end to the water
and terminating at the lower end at a level slightly above that of the suction inlet
so that by the burying of the latter in the sand or mud there will always be a
certain amount of solid matter directly exposed to the scouring action of the
current of water passing from said passage to the suction inlet, substantially as
specified.
2. The application to the subaqueous excavation of sand or mud and the like of
the suction inlet nozzle surrounded by an annular sleeve open at top to the water
and forming a downcast passage therefor, the sleeve terminating, slightly above

page_text: the suction inlet and being adjustable with regard thereto, substantially as
specified.
3. The application to the subaqueous excavation of sand, mud, and the like,
of a suction inlet nozzle whose mouth is downwardly-directed and is surrounded by
an annular water passage terminating slightly above said inlet, the passage being
continued upwards alongside the nozzle and provided with means of regulating the
admission of water to its upper end, substantially as specified.
1004
F. E. DUCKHAM,
By A. M. & Wm. Clark,
53, Chancery Lane, London, Chartered Patent Agents.