Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to a device :Eor collecting
solid bodies on an underwater bed, a primary application o~
the device being the collection of polymetallic nodules on
a sea floor.
In response to the economic attention focused on
the potential mineral resource o:Efered by nodule deposi~s,
many types of equipment have been developed for extrac~ing
nodules from sedimentary material on a sea floor which can
lie at a considerable depth below the surface of the sea~
Thus the different devices which are already
known travel along the bottom and are equipped with means
for collecting and storing nodules. Devices of this type
can either be operated from the surace by means of cables
which draw them along the sea bed or alternatively, ~hey
can be equipped with means which permit independent dis-
placement along said sea bed.
Some nodule-collecting devices which have their
own source of energy can also be designed not only to
collect nodules but also to raise them to the surface.
However, the devices of the above-mentioned type
which were designed prior to the present invention are
subject to a disadvantage in that they do not make it
possible to obtain a sufficiently high nodule-collection
yield in respect of a given swept surface æ ea of the sea
floor.
In factr tnese devices are so designed that the
efficiency of their collecting means decreases when their
specific weight in water increases, especially as a result
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of storage of the nodules.
A further drawback attached to collecting and
storing devices lies in the fact that they do not permit
of satisfactory separation of the nodules from the support-
ing sediment.
The precise aim of the present invention is to
provide a device which serves to collect solid bodies on
an underwater bed and makes it possible to overcome the
disadvantages mentioned above.
This device essentially comprises :
- at least one structure for collecting solid bodies, said
structure being intended to be applied against said
underwater bed,
- a structure for storing collected bodies, said structure
being intended to be applied against said bed,
- means for displacing structures along said bed, said
means being rigidly fixed to the storage structure,
- means for collecting solid bodies, said means being
rigidly fixed to the collecting structure or structures,
- means for providing a coupling between each collecting
structure aforesaid and the storage structure which
permit a relative movement of one structure with respect
to the other and make it possible to maintain said
collecting means in a predetermined position with respect
to said underwater bed at the time of collection of
bodies, said means for providing a coupling between a
collecting structure and the storage structure being such
as to comprise at least one link-arm connected to each
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structure in order to ensure at least three degxees o~
~reedom between said structures,
- means for transferring collected bodies into said storage
structure.
One of the chiPf advantages of the device as
defined in the foregoing lies in the fact that it serves
to maintain preferentiaL positioning of the collecting
means with respect to the sea floor at the time of
extraction of bodies such as nodules. In fact, the device
is so designed that its collecting means are advantageously
carried by a structure which has a substantially constant
specific weight at the time of extraction of nodules and
is capable of following the variations in profile of the
sea floor in a suitable manner. In more exact terms, the
collecting structure or structures are capable of following
variations in profile of the sea bed at least in pitc~ir.g
motion, rolling motion, ramming and lateral drift.
Moreover, said collecting structure is preferably
supported on the sea bed by means of a bearing surface
~aving two portions located respectively upstream and down-
stream of said collecting means according to the direction
of displacement of said structures, the front end of each
po~tion aforesaid being provided with a convex curvature
- with respect to said sea bed.
In accordance with an advantageous feature of the
invention, the means for collecting solid bodies com~rise a
plurality of extraction blades parallel to the direction
of displacement, said extraction blades being pivotally
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mounted on a shaft located at right ang-les to said blades,
means for positioning the extraction blades and defining
the work position of the extraction blades with respect to
said sea bed, at least one flexihle-blade wheel for
impelling the extracted bodies, said wheel being mounted
above said extraction blades on a shaft which is sub-
stantially parallel to the extraction-blade shaft and
means for driving said wheel in rotation.
The advantage of the distinctive feature thus
mentioned lies in the fact that maximum separation from the
sea-~ed material is achieved when collecting solid bodies
such as nodules.
In accordance with this distinctive feature, the
upstream and downstream portions of the bearing surface of
the collecting structure are so dimensioned that the
pivotal axis of the extraction blades remains in a sub-
stantially constant relative position with respect to the
sea bed irrespective of the variations in profile of the
bed and in the quantity of nodules which are present in the
transfer means.
Furthermore, the device in accordance with the
invention can advantageously be provided in addition with
means for measuring variations in slope of the sea bed
between two zones located respectivel~ upstream and down-
stream of the collecting means and means which are actuated
by said measuring means and serve to control the means ~or
positioning the extraction blades.
In accordance with another advantageous feature
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which is provided for ensuring operational safe~y, ~he
aforesaid means for positioning the extraction blades are
preferably capable of permitting withdrawal of the
extraction blades when a force e!xceeding a predekermined
threshold value is applied to the blade tips, then of
restoring said extraction blades to the work positions
thereof when said force is below said thrashold value.
Moreover, the blade-positioning means can advantageously
be associated with means for defining a limiting position
of blade withdrawal so that each extraction blade in this
position constitutes a bearing member which supports the
collecting structure on said sea bed.
It is thus possible to forestall any potential
dangeriof jamming and fracture of the extraction blades
on an obstacle and to assist the passage of the collecting
structure over this latter.
In accordance with yet another distinctive
feature of the invention, the means for transferring solid
bodies comprise a unit for discharging collected bodies
into said s~orage structure, said unit being pivotally
mounted on said collecting structure, at least one
conveyor for bringing the collected bodies into the dis-
charging unit and means for guiding and driving sald
conveyor.
In accordance with the in~ention, the flexible-
blade wheel and the conveyor can be driven either by mQ~ors
or from at least one unit which is rigidly fixed to said
collecting ~tructure in such a manner as to be applied
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against said sea bed and to be set in motion by reaction on
the bed at the time of propulsion of the structures.
In accordance with the invention, the means for
propelling said structures can be constituted by a cable
secured at each end respectively to the storage structure
and to a surface vehicle or by a cable or link-arm for
coupling the storage structure to the body of an underwater
vehicle. These propulsion means can also be constituted by
units for carrying the storage structure, said units being
capable of setting said structure in motion by reaction on
said sea bed.
Furthermore, the collecting structure of the
device in accordance with the invention can constitute the
dredge of the nodule-collecting vehicle as described in
Canadian patent application No. 295,125 filed on January
17th, 1978 in the name of the present Applicant.
Further distinctive features and advantages of
the present invention will become more readily apparent
from the following description of preferential embodiments
of the device in accordance with the invention for collect-
ing nodules on a sea floor.
This description will be given with reference to
the accompanying arawings, in which:
Figure 1 is a general view in perspective showing
a first embodiment of the device according to the invention
in which this latter is drawn and supplied with power by
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means of a cable ;
- Fig. 2 is a rear view of the device of Fig. 1,
this view being taken along the plane Pl of Fig. 1;
- Fig. 3 is a partial side view of the front end
of the device of Fig. 1 ;
- Fig. 4 is a front view of the device of Fig. 1,
- this view being taken along`the plane P2 of Fig. 1 ;
- Figs. 5a and ~ are views in elevation showing
the mode of operation of a device in accordance with the
invention ;
- Fig. 6 is a view in elevation showing a
second embodiment of the device in accordance with the
in~ention ;
- Figs. 7a and 7b show alternative forms of
construction of the collecting unit.
In Fig. 1, there is shown in perspective a first
embodiment o~ the ~evice in accordance with the invention
for collecting polymetallic nodules on a sea floor as it
travels along the sea-floor surface S.
The device in accordance wi-th the invention is
essentially constituted by ~wo distinct structures A and B
having the respective functions of collection of nodules
on the seà-floor surface S and of storage of these latter.
Assuming that the collecting structure A is travelling in
the direction of the arrow Fl said structure comprises
from the front end to the rear end a nodule-collecting unit
R and a unit T for transferring collected nodules into the
structure B.
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In accordance with the essential feature of the
invention, the collecting structure A is coupled to the
storage structure B in order that the collecting unit R
can be maintained in a predetermined position with respect
to the sea-floor surface S at the time of collection o~
nodules.
It is thus apparent from Figs. 1 and 2 that the
structures A and B are coupled together by means of link-
arms 2 and ~ each pivotally mounted by means of swivel-
bearing systems 2r and 4r on the one hand on each side of
the collecting unit R and on the other hand on the
- -structure B at the front end of this latter.
It can already be noted that the respective
bodies o the structures A and B are constituted by open
structures having a suitable specific weight in water.
Said structures are fabricated from liyhtweight materials
and equipped if necessary with means of a type known per se
for fixing their specific weights such as, or example, a
container or a composite material of known type.
It can be seen in Figs. 1 and 2 that the storage
structure B is essentially composed of a storage bin 6
fixed on two longitudinal members 8 and 9, the collecting
structure A being located between said members in front of
the storage bin 6. In the embodiment shown in Fig. 1, the
structures A and B are drawn along the sea-floor surface S
by means of a cable 7 which is secured to the structure B.
Said structures are supported on the sea floor S by bearing
surfaces lOa-, lO'a, lO'b and lO"b which are so designed
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that a convex area is always applied against the sea-
bottom terrain. Thus a reduction in supporting capacity
of the sea bed or an increase in pressure of the structure
B on said sea bed are compensated by an increase in the
bearing area.
As shown in Fig. 1, the collecting unit R of the
structure A comprises a pluxality of parallel extraction
blades 12 mounted at right angles on a pivotal shaft 14
associated with means MR for positioning the extraction
blades 12 with respect to the sea floor S and permitting
the withdrawal of said blades whenever these latter
encounter an obstacle. Said collecting unit also comprises
a blade-wheel 16 which is intended to provide mechanical
assistance for the collection of nodules. Said blade-wheel
is mounted above the extraction blades 12 on a shaft 15
which is substantially parallel to the shaft 14 and asso-
ciated with means (not shown in this figure~ for driving
the blade-wheeI in rotation. Said wheel is equipped with
flexible blades 17 which are capable of engaging the
nodules after these latter have been dislodged from the sea
bed S by the extraction blades 12 and of thrusting them
towards the transfer unit T. It should be noted that,
taking into account its curved shape, the structure lO'A
also constitutes the equivalent of a bumper or fender for
protecting the wheel 16 and its flexible blades 17 from
obstacles which may be encountered in the sea bed.
It will be noted that the two bearing surfaces
lO'a and lOa of the structure A are located respectively
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upstream and downstream of said collecting unit R in order
to prevent clogging or sticking of this latter in the
sediment at the time of a variation in profile of the sea
floor S. The dimensions of said bearing surfaces are such
that, at the time of variations in profile of the sea
floor S and in the quantity of nodules which are present
in the transfer unit T, the shaft 14 remains su~s~antially
in the same relative position with respect to the sea
floor S.
In Figs. 3 and 4 in which the components of the
device already shown in Figs. 1 and 2 are designated by
the same references and in which the surface lO'a has been
omitted for the sake of enhanced clarity, the aforesaid
means MR associated with the pivotal shaft 14 of the
extraction blades 12 are shown in greater detail.
Figs. 3 and 4 accordingly show that each end of
said shaft 14 is rigidly fixed to a grooved sector 2Q for
a cable 22 which is secured to the end of a spring 24
housed within a casing 25. Said spring works in tension
in order to bring said sector 20 into position against a
stop 26 which defines the working angle of the extraction
blades 12 with respect to the sea-floor surface S or so-
called work position in which said extraction blades 12
are buried in the sea bed S at a suitable angle and the
edges of which are located beneath the nodules W to be
extracted.
It should be noted that a suitable adjustmen-t of
the position of the shaft 14 with respect to the bearing
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surface lOa can be associated with the means M~.
Also worthy of mention is the fact that the
spring 24 is calibrated in such a manner as to ensure that
the extraction blades 12 are caused to retract to a limiting
position of withdrawal defined b~y the stop 28 in respect of
a predetermined value of resistance of the sea floor at the
tips of the blades 12. Said stop 28 is so designed that
the retracted extraction blades 12 form part of the
bearing surface of the structure A which is applied on the
sea floor S and prevent ~ailure of the blades when these
latter encounter a hard obstacle.
. Furthermore, the positioning of the stop 28 can
be adjusted by means of a feeler 11 as a function of
variations in profile of the sea bottom upstream of the
structure A, a feeler transducer 13 being intended to
actuate a unit 15 for controlling the positioning of the
: stop 28. It is noted that the feeler 11 could be replaced
by any detector which is responsive to the characteristics
of the sea floor upstream of the structure A.
Another point worthy of note is the fact that the
extraction blades 12 are mounted on the shaf~ 14 with a
reIative spacing which is slightly smaller than t~e size
of the polymetallic nodules N. Said extraction blades can
be of various shapes such as prismatic, conical or
pyramidal whilst the blade profile and material are such
as to ensure minimum resistance to penetration into the
sea bed S. It should be added that provision can be made
for injection of water at the blade tips in order to ensure
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necessary lubrication with respect to certain salts which
have a strongly adheren.t character.. ..
In Fig. 4, there is also shown diagrammatically
the method adopted for driving t:he blade-wheel 16.
Thus it can be seen in this figure that said
blade-wheel 16 is centered on a shaft 15 which is sub~.
stantially parallel to the sea-floor surface in the same
manner as the shaft 14 and constituted by a sleeve 30
which is rigidly fixed to the body of the collecting
structure A, said wheel 16 being driven in rotation by the
reduction-gear motor set 32 which is housed within the
interior of said sleeve 30. - - -
In the case in which the specific weight isadjusted by means of composite materials fixed on the
vertical flanks of the structure A, it is possible not to
place the reduction-gear motor sets within the sleeve 30
but to place these latter within the composite structure,
these means being employed.to drive the shaft 16.
It is apparent from Fi~s. 1 and 3 that the
transfer unit T is essentially made up of a belt conveyor
36 and a discharge chute 38 which is pivotally mounted on
the structure A. The belt conveyor is constituted by a set
of belts carried by guide rollers or idlers 40 and 42 and
by a driving roller 44. The rollers are posi~ioned în
such a m~nner as to ensure that the collected nodules can
be carried to a height and a distance from their point of
collection which are suficient to discharge them into the
storage bin 6. It is noted in Figs. 1 and 3 that the
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discharge chute 38 is pivotally mounted on the shaft of the
guide roller 40 of the belt conveyor 36 and applied
against the structure B within the storage bin 6. This
permits a variation in the angle o~ tilt of the discharge
chute 38 with respect to the structure A at the time of
penetration of the structure B into the sea bed S when the
storage bin 6 is being filled with nodules. The set of
belts 36 which forms the conveyor can be replaced by a
flight conveyor which is well known to anyone versed in
the art. It can be recalled briefly that a flight conveyor
of this type consists of two driving side chains mounted
on the driving rollers and of flights located at right
angles to the direction of motion of the conveyor, the ends
of the flights being attached to the chains. Said flights
are at right angles to bars which are rigidly fixed to the
structure. ~lthough this form of construction has not been
illustrated, the substitution of this type of conveyor for
the belt conveyor 36 shown in Figs. 1 and 3 will appear
evident to anyone versed in the art. Furthermore, an
arrangement of this type makes it possible to ensure a
certain calLbration o~ bodies to be collected prior to
transfer to the storage means.
It should be'mentioned that the conveyor belt 36 r
which has a smooth'carrying surface in this example of
construction, is so designed as to pass beneath the
bearing surface lOa in such a manner as to increase the
relative veIoc:ity of this latter with'respect to the sea
floor S and to entrain water with a view to reducing
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friction.
The principle of opera-tion of the de.~ice in
accordance wi~h the invention will be described herein-
after with reference to Figs. 3, 5a and 5b. Figs. Sa and
5b have the configuration of the device in accordance with
the invention respectively at the beginning and.during
extraction of nodules from the sea floor S.
At the time of extraction of nodules by displace-
ment of the structures A and B over the sea floor S, the
structure A which ensures collection of nodules is sub-
- jected only to a tractive force which is substantially
parallel to the floor by virtue of the fact that it is
coupled to the structure B by means of the link-arms 2 and
4 whilst the specific weigh~ of said collecting structure
is practically not subject to any variation.
Preferably, the specific weight of the structure
A is fixed at a value such that the pressure on the sea bed
at any point of its bearing surfaces lO'a and lOa is lower
than the maximum supporting capacity of the sea bed.
It is recalled that the collecting structure A
is in any case capable of following the variations in
profile of the sea floor S, not only in pitching motion
but also in rolling motion, ramming an~ lateral drif-t
within the limits set by the structure B.
Thus it is apparent from Figs. 5a and 5b that
the means MR (20, 22, 24, 25, 26) which are controlled by
the feeler 11 make it possible to obtain a given angle of
penetration of the extract~on blades 12 into the sea bed S
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during a collecting operation~ this being achieved
irrespective of the degree of penetration of the structure
B into said sea bed.
A satisfactory result is therefore achieved at
the time of displacement of the device along the sea-
floor surface S in that the nodules are lifted and
separated from the sediment by t,he extraction blades 12~
propelled towards the rear by the flexible blades 17 of the
blade wheel 16, then engaged by the belt conveyor 36 and
thus directed into the storage bin 6 of the structure B.
Moreover, it can.be -seen from Fig. 3 that, when
the extraction blades 12 enco,unter an element which is
either too heavy or too deeply embedded in the sea floor S,
said blades are in that case subjected to a torque which
causes them to withdraw to the stop 28 in opposition to the
resistance of the spring 24. After withdrawal, the
extraction blades 12 are thus supported and permit lifting
of thè structure'A as this latter passes over said
obstacle without any attendant danger of blade failure.
A further noteworthy advantage is that sticking
of the extraction blades 12 in the sediment at the time of
a variation in profile of the sea floor is prevented by
means of the feeler 11 and/or the bearing surface lO'a
upstream,of the blades. -~ -
In Fig.'6, there is ~hown a second embodiment of
the device according to the invention. This em~odiment
comprises a high-capacity storage structure B which is so
,designed as to carry out displacement of the device and
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upward transfer of collec-ted nodules to the surface, and
a plurality of collecting structures A. It will at once
be observed that each collecting structure A is designed
and coupled to the storage structure B in much the same
manner as the device shown diagrammatically in the
preceding figures and that the unit constituted by these
structures can be pivotally mounted on the storage
structure.
In accordance with one of the distinctive features
of the embodiment of the device shown in the figure now
under consideration, said storage structure B is equipped
with means both for supporting and propelling it along the
surface S of the sea floor.
Thus in Fig. 6, the references 50 designate units
which are rigidly fixed to a helical propulsion fin 52.
Said units are intended to support the structure B on the
sea floor S by means of their external walls and to effect
the propulsion of the structure B once they have been
driven in rotation.
In accordance with another distinctive feature
of this embodiment, the structure B is constituted by two
s_parable modules Bl and B2 which are shown separately in
Fig. 6, the upper module B2 being intended to permit upward
transfer of collected nodules to the surface of the sea.
To this end, said module B2 has its own source of
energy, a suitable ballast capacity at a set of propulsion
units for underwater operation of the module.
It will further be noted that the module B2 is
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provided with a storage bin 54 into which the nodules are
transferred. After being collected by each structure ~,
said nodules are first transferred, as explained earlier,
into a buffer sto~age space 6' provided at the front end of
the structure B.
In Fig. 6, the reference numeral 56 designates
screw conveyors which are intencled to transfer the nodules
in the upward direction from the buffer storage space 6'
into the storage bin 54.
There is also shown in dashed lines in Fig. 6 a
hood 57 of the structure B which serves to protect the
collecting structures A against external shocks,
especially when they are raised to the surface, and which
reduces hydrodynamic drag of the device as a whole.
In Figs. 7a and 7b, there are shown two forms
of construction of the mechanism employed for driving the
1exible-blade wheel 16 and the belt conveyor 36 in the
case of a device according to the invention which is drawn
by a cable 7 from the surface of the sea~ ~
- 20 In these alternative embodiments, driving of the
bIade-wheel 16 and of the belt conveyor 36 is performed by
means of elements which are set in motion by reaction on
the sea floor at the time of displacement of the structure A.
Thus in the alternative embodiment of Fig. 7a,
the collecting structure A comprises at least one endless
screw or auger 56 which engages in the sea bed S in such a
manner as to be driven in rotation at the time of displace-
ment of the structure. Thus the flexible-blade wheel 16
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and the belt conveyor 36 are driven in rotation from said
auger by means of the shaft 58, the motion converter 60,
the pulley 44' and the belts 62 and 64.
In the alternative embodiment of Fig. 7b, the
structure A comprises at least one blade-wheel 66 which
engages in the sea bed S and is intended to drive the
flexible-blade wheel 16 and conveyor belt 36 in rotation by
means of the belt 58', the pulley 44" and the belts 62' and
64'.
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