Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates generally to dredges and more
particularly to a diluvial dredging apparatus for removing
material from below the beds of rivers and other bodies of
water.
BACKGROUND OF TH~ INVENTION
Placer gravels containing precious metals such as gold
are found in both the alluvial gravels on the surface of
riverbeds and in the diluvial gravels beneath the beds of
rivers. In the past, there have been many different types of
dredging apparatus used for dredging placer gravels in order to
recover gold and other precious metals. These dredges have used
endless conveyors with buckets attached thereto and suction-type
apparatus for bringing the material to the surface for final
separation and further processing. These dredges can generally
remove the material on the surface of the riverbeds, the
alluvial gravels, but they cannot penetrate the actual riverbed
containing the more compacted and rocky diluvial gravel. This
is a problem now, as much o~ the alluvial sands have been
depleted oE precious material and there is a need to access new
metal and ore containing sites such as the diluvial gravels.
The present invention overcomes this problem by
providing a dredging apparatus capable of digging into the river
bed and penetrating and collecting the diluvial gravels
containing the precious metals.
SUMMARY OF INVENTION
Broadly, the present invention provides a recovery
unit for use in a dredging apparatus which comprises a lower
primary boom and an upper secondary boom. The primary boom has
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an endless conveyor with material digging and removal means
attached thereto. The secondary boom has material separating
means and means for removal of the separated material. The
recovery unit also includes means for longitudinally moving the
two booms relative to one another.
The present invention also provides a dredging
apparatus for the recovery of material from below the beds of
rivers and other bodies of water. This apparatus comprises the
above-described recovery unit which is movably supported on a
platform and includes means for raising and lowering the
recovery unit. Means are also provided for washing and
separating the material removed by the removal means of the
primary boom.
The present invention also provides for a method for
dredging material from below the beds of rivers and other bodies
of water utilizing a dredging apparatus having a primary and
secondary boom recovery unit. This method includes the steps of
washing and separating the material retrieved by the primary
boom on the dredging apparatus whereby the material fines are
collected, the washed material is discarded, and the wash water
is returned to the body of water with minimal silt disturbance.
The method further includes the steps of separating material ln
situ which caves in on the secondary boom and removing the fines
separated from the caved-in material to the surface for
collection on the dredging apparatus.
BRIEF D~;:SCRIPTION OF THE DRAWINGS
A specific embodiment of the invention is described in
further detail with reference to the drawings in which:
FIGURE 1 is a side view of an embodiment of the
invention in situ;
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FIGURE 2a is a cross-section of the recovery unit and
FIGURE 2b is an end-view of the unit;
FIGURE 3 is a perspective view of the lower end of the
recovery unit showing the primary boom in greater detail;
FIGURE 4 is a schematic drawing of the fines removal
system of the secondary boom;
FIGURE 5 is an end-on view of an embodiment of the
invention with the recovery unit in a horizontal position,
detailing the support structure for the recovery unit;
FIGURE 6 is a schematic drawing of the side view of
the recovery unit when in the horizontal position, detailing the
structure of its upper end; and
FIGURE 7 is a pictorial representa~ion of an
embodiment of the invention in operation.
DETAILED DESCRIPTION
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Referring to FIG. 1, the dredging apparatus of the
preferred embodiment is shown to basically comprise a floating
platform 1, such as two barges combined in a manner similar to a
catamaran (see FIG. 5), which supports a recovery unit 22 by
means of a mast 5. The platform 1 also supports a wash area 3
at the stern and a hoist 23 which is centrally located. A wash
water return hose G leads from wash area 3 to the recovery unit
22. Various storage areas and operation control stations are
also present on platform 1 but are not specifically shown in the
drawing; ~he platform has an anchor line 2 which is connected
to a winch (not shown) on the shore.
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Details of the recovery unit 22 are shown in FIGS. 2
to 4 and 6. The recovery unit 22 includes an upper boom 7 and a
lower boom 8. These booms are slidably movable with respect to
one another along their longitudinal axes by means of long
stroke hydraullc cylinders 4 (see FIGS. 1 and 6), attached at
the up~er end and on each side of the recovery unit 22. As
shown in FIG. 6, the hydraulic cylinders 4 are attached to the
upper and lower booms 7, 8 in an angled manner. Clips 9 are
located along the length of both sides of the recovery unit 22
and attach the lower corners of the upper boom 7 and the upper
corners of the lower boom 8 together in such a way that the
booms are movable with respect to each other along their
longitudinal axes only. The clips ~ prevent the booms rom
separating from one another and moving independently.
Referring now to FIGS. 2a, 2b and 3, the lower boom 8
includes a support structure for an endless conveyor made up of
two parallel loops of connected links 12 which are supported on
parallel pairs of transverse rollers 13 at the lower end and
parallel pairs of transverse rollers 35 at the upper end.
Although not specifically shown, transverse rollers ara also
located in a spaced manner along the length of the lower boom 8
in order to support the connected links 12 in an even manner.
Each pair of rollers rotates on a cylindrical roller shaft 10
which is connected to the support structure of the lower boom in
such a way that the shaft 10 can rotate on its longitudinal axis
while supporting the rollers and other components of the
conveyor. Buckets 11 are attached at each end thereo~ to the
loops of connected links 12. The buckets 12, therefore,
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maintain a constant distance between the loops of connected
links 12 and keep the links 12 on the rollers 13 and 35. Rakes
(not shown) may be interspersed between the buckets 11 and
attached to the loops of connected links 12 in a similar manner
as the buckets 11. Such rakes may aid in the filling of the
buckets or may help prevent the buckets 11 from catching on
boulders or bedrock during operation. The wash water re-turn
hose 6 channels water from the wash area 3 into the lower boom
8. The water then follows the downward path of the buckets to
the area being worked.
Details of the structure of the upper boom 7 will be
described with reference to FIGS. 2a, 2b and 4. As can be seen
in FIG 2a, upper boom 7 consists of a hollow ballast chamber 19
having a substantially rectangular cross-section upon which is
attached a sluice separator 18, each having distinct functions.
The sluice separator 18 extends from the lower end of the upper
boom 7 up to the point along the lower boom 8 which is at the
deck level of the floating platform 1. Both sluice separator 18
and ballast chamber 19 are covered by a rectangular shaped
solid end cap 17 (FIG. 2b). Means for filling and emptying
ballast chamber 19 are located on deck. These means are not
shown in the figures but can include pumps and hoses Gr other
similar standard equipment available to those skilled in the
art.
The sluice separator 18 includes a transversely and
longitudinally extending grating 14, a transversely and
longitudinally extending fine-mesh screen 15, a fines chamber 2
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and a pipe system 20, 21 including a venturi nozzle 16 [see FIG.
4]. The grating 14 includes transversely extending parallel
bars which prevent large pieces of material from damaging the
fine-mesh screen 15 which is located a short distance beneath
it. The mesh size of the fine-mesh screen 15 will depend on the
size of the particles that are to be collected. ~lternatively,
several different screens can be used in the sluice separator,
placed one above another and ranging from a coarse mesh on top
to a fine meshed screen on the bottom. In this manner, only the
very fine material will be in contact with the fine screen, thus
preventing damage to the screen by large objects that would
normally pass through the grating 14.
The fines chamber 24 has a rectangular cross section,
its upper surface being the fine-mesh screen 15. Within fines
chamber 24 is the pipe system 20, 21. A pipeline 20 o~ circular
cross section extends from deck level to the lower end of the
upper boom 7 along a bottom corner of the fines chamber 24. At
the lower end, pipeline 20 has a right angle bend to a short
section running parallel to the end cap 17 and ends with a
venturi nozzle 16. The venturi 16 has a frustoconical portion
ending with a cylindrical portion of lesser cross sectional area
than that of pipeline 20, thereby causing the velocity o~ the
fluid being transported through pipeline 20 to be increased when
exiting the nozzle.
Pipeline 21 is of similar configuration to that of
pipeline 20, however, it extends from deck level to the lower
end of the upper boom 7 along the opposite bottom corner of
fines chamber 24. The pipeline 21 does not have a venturi
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nozzle at its end. In order to create a negative pressure in
the fines chamber 24 so that the ~ines will be transported to
the deck through pipeline 21, the venturi 16 of pipeline 20 is
inserted into the opening of pipeline 21. The circumferential
gap ~see FIGS. 2a and 4] that occurs between the outer perimeter
of the venturi 16 and the inner perimeter o~ pipeline 21 aiiows
material to flow through it and into pipeline 21.
Means for pumping a 1uid through pipeline 20 are
located on the deck of the platform 1, but are not specifically
shown in the figures. Also on the deck but not shown are
collection means for the fines that are brought to the surface
through pipeline 21.
The recovery unit 22 is supported by a mast 5 which is
further supported by the support structure 29. The support
structure 29 and the means of attachment of the recovery unit 22
and mast 5 to it are presented in FIG. 5. FIG. 5 depicts the
support structure 29 as a framework located on and supported by
the floating platform 1. Cylindrical shafts 25 which are used
to pivot the recovery unit 22 during operation are rotatably
supported on either side of the recovery unit 22 by pillow
blocks 26 having bushings through which shafts 25 pass. In the
embodiment shown in FIG. 5, there are four pillow blocks 26
which are bolted to the support structure 29 supporting the
shafts 25 proximally and distally to recovery unit 22.
Attached to the proximal end of each shaft 25 is a
cylindrical roller 28. Each roller 28 rests between guides 27
defined by vertically spaced elongated sections of angle irons.
These guides 27 (see also FIG. 6) are attached to the lower
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boom 8 in such a way that the pivot point of the recovery unit
22 is slightly below the level of roller shafts 10 o~ the lower
boom 8.
The mast 5 (not shown in FIG. 5) is attached to
support structure 29 at pivot~ble attachment points 30. In this
embodiment of the invention, attachment points 30 are attached
to the support structure 29 at four points, two on either side
of recovery unit 22. The mast 5 moves with the recovery unit 22
at all times.
In FIG. 6, the upper end of the recovery unit 22 is
depicted at A and the part of the unit that is at and just below
deck level when the unit is submerged is depicted at B. The
side view o~ the recovery unit 22 shows in general, the upper
and lower booms 7, 8, connecting clips 9 and buckets 11. The
sluice separator 18 is shown at B to end at deck level. Guides
27 are attached to lower boom 8.
At A, buckets 11 empty their contents into hopper 31,
rotate over rollers 35 and are then trànsported within the lower
boom 8 to the lower end of the recovery unit 22. Rollers
35 at the upper end of lower boom 8 are the only pair of rollers
in the endless conveyor which have a drive mechanism connected
thereto (not shown). This mechanism rotates rollers 35 and
causes the endless conveyor to move. The hopper 31 has t~o side
panels located on either side of the recovery unit 22 which
attach to the mas~ 5 above the recovery unit 22 at pivot point
36~ The hopper 31 is pivotable so tha~ it can remain vertical
when the recovery unit and mast are at different angular
positions during operation. The hopper 31 is shaped like a
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large funnel. Its lower tube-like portion is directed into the
wash area 3 (see FIG. 1).
The hydraulic cylinders 4 are connected to a standard
hydraulic pump and control system ~not shown) which is located
on the deck of the floating platform 1.
The recovery unit 22 is connected to mast 5 by means
of a lug 34, cable 33 and pulley 32. The lug 34 is attached to
the upper end of the lower boom 8 and the pulley 32 is located
at the upper end of the mast. Cable 33 is connected at deck
level to hoist 23. A multiple pulley system could also be used
in order to reduce the amount of work required to move the
boom. Note that the recovery unit 22 is generally raised to
float on the water and lowered into the water by emptying or
filling the ballast chamber 19 of the upper boom 7 with water.
When the recovery unit 22 is to be raised from the floating
position to a horizontal position above the water level, hoist
23 and pulley 32 are utilized.
The operation of the dredging apparatus as it i5 used
when practicing the preferred method of the invention will now
be described.
The preferred embodiment of the invention provides a
dredging apparatus for use in rivers or other bodies of water
for material removal and separation of diluvial material taken
from below the riverbed. In particular, this apparatus is
designed for use in placer gold recovery operations.
Firstly, the floating platform 1 is moved to the
desired location in the river and is anchored to the shore by
means of the anchor line 2 (see FIGS. 1 and 7) which is attached
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on the shore to a winch. The recovery unit 22 is in an almost
horizontal position floating on the water, the ballast chamber
19 filled with air.
Once the platform 1 is positioned, dredging is
commenced. In order to lower the recovery unit into the water,
the ballast chamber 19 is flooded with water. The recovery unit
22 pivots about the rollers 28 between the guides 27. Depending
on the conditions of the material being dredged, weighted mud
may be used with water in the ballast chamber 19 to provide more
weight to the recovery unit.
When the end of the recovery unit 22 hits the
riverbed, the operation of the endless conveyor is begun. The
buckets 11 on the endless conveyor dig into the riverbed while
removing material to the surface. The filled buckets 11 empty
their contents into the hopper 31 tFIG. 6) and then travel over
rollers 35 and back through the inner portion of the lower boom
8.
As the buckets 11 dig a channel into the riverbed,
material on either side of the channel may cave in onto the
grating 14 of the upper boom 7 ~FIG. 2a]. The material which
passes through the grating 14 falls onto the fine-mesh screen 15
which separates the fines from the coarser material. The fines
which pass through ~he fine-mesh screen into the fines chamber
24 settle toward the lower end o~ the upper boom 7 due to
gravity and negative pressure. The negative pressure is caused
- by pressurized air flowing from pipeline 20 through the venturi
nozzle 16 at an increased velocity and into pipeline 21. The
negative pressure draws the water containing the fines through
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the circumferential gap bet~een the venturi 16 and opening of
pipeline 21 and into pipeline 21 through which it is transported
to the deck where it is collected. The collection means may
simply be storage tanks where the fines and water are kept until
they are removed to the shore for final settling and
separation. Alternatively, settling tanks or hydrocyclones may
be present on deck to effect final separation in situ.
As previously mentioned, the material recovered by the
buckets 11 of the lower boom is emptied into the hopper 31. The
hopper 31 feeds the material into the wash area 3 located on the
deck of the plat~orm 1 for washing and separation. The wash
area can comprise a sluice separator which separates the large
pieces of gravel or rock from the fines. The washed gravel and
rocks are disposed of overboard into an area that is not to be
dredged or has already been dredged. The fines are collected
for storage prior to final separation and processing on shore.
The cleaned wash water is returned through the hose 6 to the
river. In order to prevent a large amount of silt disturbance
from occurring, thç wash water is returned through the hose 6
into the lower boom 8 where it follows the downward path of the
buckets ll.
When the recovery unit has dug down to the desired
depth in the riverbed, the entire dredging apparatus is
gradually moved by means of the anchor-line 2 and winch towards
the shore as shown in FIG. 7. As can be seen in FIG. 7 r
dredging has just begun at position A and the recovery unit 22
has reached the desired depth in the riverbed. As the winch
pulls the apparatus toward the shore, the buckets ll of the
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endless conve~or dig into the riverbed and recover more
material. If the recovery unit 22 encounters a boulder which is
too large to be dug out (as seen between positions A and B), the
lower and upper booms, 8 and 7, are moved relative to one
another by means of the hydraulic cylinders 4 so that they
"walk" over the boulder. The buckets 11 of the endless conveyor
continue to remove material as the unit moves over the boulder
and back down to the desired depth. Between positions B and C,
the recovery unit 22 is shown to be removing material from just
above the bedrock. At position ~ the dredging apparatus has
almost reached the shore and dredging the channel is completed.
The recovery unit is then "walked" out of the channel that has
been dug. The water in the ballast chamber 19 is pumped out so
that the recovery unit 22 rises to float on the surface of the
river. The dredging apparatus can then be moved back to
position A to repeat the dredging method a short distance away
and parallel to the location previously dredged.
An important feature of the dredging apparatus of the
preferred embodiment is that the recovery unit 22 is pivotably
raised and lowered passively in the water by means of the
ballast chamber 19 being filled with air or water. The hoist 23
is only used when the recovery unit 22 is to be raised out of
the water into the horizontal position. This is done when
repairs and maintenance to the recovery unit 22 are being
performed, or when the dredging apparatus is to travel long
distances in the water.
The preferred embodiment has been described utilizing
a floating platform 1. Alternatively, the platform could be
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based on land, depending on the location to be dredged. The
land based platform could be mounted for example, on tracks,
wheels or a skid. The platform could still be moved by means of
a winch and anchor-line 2.
In the preferred embodiment end cap 17 completely
covers both the sluice separator 18 and ballast chamber 19.
Alternatively, the end cap 17 may completely cover the ballast
chamber 19 and fines chamber 24 while having a grating having
transversely extending parallel bars extending across the area
between grating 14 and fine-mesh screen 15. In this way,
material passing through gxating 14 but too large to pass
through the fine-mesh screen 15 will be able to pass through the
grating o end cap 17 thereby preventing the area between
grating 14 and fine-mesh screen 15 from getting clogged.
The preferred embodiment of the apparatus has been
described using specific components. It will be readily
apparent to those skilled in the art that many types of
standard, readily available components can be used to construct
the dredging apparatus. For example, the hydraulic cylinders ~
used to move the upper and lower booms, 7 and 8, relative to one
another can be replaced by a pulley or rack and pinion
arrangement. The buckets 11 can also be of various shapes
depending on the type and the conditions of the material that is
to be dredged. Different shaped buckets can be alternated on
the conveyor so that the material can be more efficientl~
loosened and remoYed. As previously mentioned, rakes can also
be interspersed with the buckets in order to loosen the
material. There are many ways in which the buckets and conveyor
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can be assembled in order that the material being dredged easily
falls into hopper 31. The material can fall into the hopp~r by
means of gravity, or high pressure water jets may be used to
empty out the buckets. Although not shown in the drawings, the
upper end o~ the endless conveyor may also be altered so that
the conveyor makes an angle downward over additional rollers 35
so that the openings o~ the buckets 11 are inverted downward and
the material held therein is emptied into the hopper 31.
Further alterations and variations to the apparatus
will be readily apparent to those skilled in the art, therefors
the scope of protection to the present invention is not intended
to be limited by the above described embodiments, but solely by
the claims attached hereto.
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