Dredging apparatus

A floating dredge and hydraulic dredging apparatus for mining underwater mineral bearing deposits is disclosed. The dredge includes an overburden excavator and an ore excavator mounted to a pontoon for removing overburden and ore material, respectively. Processors on the pontoon receive material from the excavators. Dredging control components coordinate the operation of the ore and overburden excavators to efficiently remove and mine the desired material.

TECHNICAL FIELD 
This invention relates generally to dredging, and more particularly to 
hydraulic dredges and the mining of alluvial deposits. 
BACKGROUND OF THE INVENTION 
A common method of mining alluvial deposits, such as those in and around 
river beds, is to utilize a floating dredge or pontoon having an 
excavating device positioned at one end thereof. The excavating device 
removes material from the bed of the river or other body of water in which 
it is working, and delivers the material to the pontoon. There it is 
processed to separate the desired minerals or other pay material from 
waste material. The waste material is then transported off the pontoon, 
normally to reclaim the area which has just been dredged. 
This method of mining alluvial deposits has been in use for well over one 
hundred years, as evidenced by U.S. Pat. No. 285,565 to Brotherhood. The 
Brotherhood patent discloses a floating pontoon having an endless bucket 
line conveyor for excavating material from underwater and directing it to 
the pontoon. An endless bucket line is very often used in mining of this 
type since the dredging is continuous and a high capacity of material is 
capable of being removed. 
Other apparatus and methods of dredging ore utilize a hydraulic suction 
device or a bucket line type conveyor in combination with a hydraulic 
suction device. U.S. Pat. No. 1,148,816 to Alleman illustrates the use of 
a suction device for underwater dredging. The Alleman patent also shows 
the use of an agitating belt to loosen the dredged material so that it can 
be received into the suction pipe. 
U.S. Pat. No. 748.804 to Smith et al. illustrates the use of a bucket line 
conveyor and hydraulic suction device in combination. The suction device 
transports fine material, while the bucket line excavates and transports 
larger material. The in-feed ends of both dredging systems are adjacent to 
one another. Both are carried by the same support frame and move in unison 
with respect to the supporting pontoon. 
Some alluvial type deposits have as much as 90 to 100 feet of material 
above bedrock. Very often, particularly in the case of gold or other heavy 
metals, most all of the desired minerals are found in the lower 20% or so 
of the material overlying the bedrock. Accordingly, in a deposit with one 
hundred feet of total material overlying bedrock, most all of the gold 
bearing material would be in the lower twenty feet. This leaves a total of 
eighty feet of overburden material overlying what is commonly referred to 
as the "pay zone" containing the gold. To get to that pay material, the 
overburden must first be removed. Accordingly, there is approximately four 
times the volume of waste overburden material which needs to be removed 
with respect to the volume of pay material. 
Prior art dredging devices, such as those just described, can be used to 
excavate this large volume of material. However, where the proportion of 
overburden material to that of the pay material is great, a large amount 
of waste material is processed by the dredge before ever reaching the pay 
material. That is, all material is treated identically to extract the 
desired minerals from the waste material. This means that in the example 
discussed above, for every cubic yard of pay material processed there are 
four cubic yards of overburden material also processed. Because of this, a 
large percentage of the material processing time is wasted in merely 
cycling overburden material through the processors so that it can be 
eventually removed from the barge. 
It should thus be readily apparent that such prior art devices and methods 
of dredging are extremely inefficient in excavating deposits having a 
large amount of overburden material in proportion to underlying pay 
material. Accordingly, a need remains for improved methods and apparatus 
which are capable of mining such deposits in an efficient manner.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The following disclosure of the invention is submitted in compliance with 
the constitutional purpose of the Patent Laws "to promote the progress of 
science and useful arts" (Article 1, Section 8). 
The apparatus of the instant invention is designed to efficiently and 
economically excavate a large amount of overburden material simultaneously 
while excavating smaller volumes of underlying pay material containing 
desired minerals. The excavation of the overburden and pay materials is 
carried on in a separate yet coordinated manner. The invention also 
comprises an improved hydraulic dredging apparatus. 
A dredging apparatus for excavating overburden and ore material is 
indicated generally with reference numeral 10. Dredge 10 includes a 
floating pontoon section 12 which supports various dredging equipment. A 
building-like enclosure 14 atop pontoon 12 protects the various equipment 
from the weather. 
A first excavating means 16, alternately termed overburden excavator 16, is 
mounted to and extends from the forward or bow end of pontoon 12 for 
excavating and transporting overburden material thereto. A second 
excavating means 18, alternately termed ore excavator 18, extends from 
pontoon 12 for excavating and transporting underlying ore material to 
pontoon 12 simultaneously while the overburden material is being excavated 
by first excavating means 18. The first and second excavating means extend 
from pontoon 12 in the same generally vertical plane. Second excavating 
means 18 is positioned rearwardly of first excavating means 16 such that 
the first excavating means excavates longitudinally ahead of the second 
excavating means. Both first and second excavating means are each mounted 
to pontoon 12 for pivotal movement about respective transverse horizontal 
axes 17, 19, respectively. 
The outermost end portion of first excavating means 16 is connected by a 
cable assembly 30 to an overhead crane support 32 extending from the bow 
end of pontoon 12. Cables 30 can be effectively extended or shortened by 
conventional winches to pivot first excavating means 16 about its 
transverse pivot axis 17. This raises or lowers the outermost end of first 
excavating means 16 relative to the water level and face of overburden 
material being excavated. Such pivotal movement also selectively moves the 
outward end of the first excavating means longitudinally in an arcuate 
manner relative to pontoon 12. A conventional water cannon 31 is also 
mounted to crane support 32 for removing material on the portion of the 
face of material extending above the water line. 
A series of cables 34 also extends downwardly from the rear portion of 
crane assembly 32 for connecting adjacent the outer end of second 
excavating means 18. The effective length of cables 34 can also be 
shortened or lengthened using conventional winches for moving the outer 
end of second excavating means 18 relative to the face of pay material 
being excavated. 
Processing means 20, well known in the art, are provided on pontoon 12 for 
receiving material from second excavating means 18 for separation into 
retained pay material and waste material. Processing means 20 is 
preferably in the form of pairs of conventional trommels and jigs used to 
separate the desired minerals from waste material in the dredged ore. The 
pay material is generally retained on the pontoon for subsequent removal 
while the waste material from the dredged ore is discharged outwardly from 
the pontoon. 
First excavating means 16 has a hydraulic conveyor system 22 which 
transports the excavated overburden material to the rear of the pontoon 
and discharges it into a dewatering trommel 23. The oversize and waste 
material passing through trommel 23 is discharged onto a belt conveyor 25. 
The water and undersize material passing from trommel 23 can be discharged 
overboard, or more preferably the undersize material separated by a hopper 
27 positioned beneath trommel 23. The undersize material is then 
transported from hopper 27 to the feed section of processing means 20 to 
collect any values that might be present in the overburden material. 
Belt conveyor 25 extends rearwardly of pontoon 12 and is supported by a 
swingable discharge conveyor support arm 24. Discharge support arm 24 also 
receives a discharge pipe or hydraulic conveyor 86 extending from a 
selected topsoiling fines waste portion of processing means 20. Support 
arm 24 is mounted for pivotal movement about both horizontal and vertical 
axes and is supported by a controllable cable and winch assembly 26. 
Side-to-side swinging movement is imparted by a conventional winch 
structure 90. With such a construction, discharge material can be 
conveniently spread rearwardly of pontoon 12 at any desired elevation. 
The first and second excavating means can take a variety of forms. First 
excavating means 16 is preferably constructed to function as a hydraulic 
dredging apparatus removing material cut from a face by suction. Second 
excavating means 18 is preferably in the form of a conventional endless 
bucket line conveyor. The first excavating means preferably has a higher 
dredging capacity or rate than the second excavating means for moving the 
greater volume of overburden material. 
Referring to FIGS. 4-8, a first excavating means 18 in accordance with the 
invention includes an "A" shaped support arm structure 36 connected at its 
base to the bow end of pontoon 12. The tip or outermost end of A-shaped 
support structure 36 carries a cutting head assembly 38. Cutting head 
assembly 38 is comprised of two rotary cutting wheels 40, 42 transversely 
spaced from one another a predetermined distance along a transverse 
cutting axis 44. Cutting wheels 40, 42 each comprise a plurality of 
projecting teeth 46 preferably spaced from one another by a predetermined 
angular spacing. Teeth 46 of each wheel are configured or oriented for 
cutting primarily axially or transversely outward in opposing first and 
second directions generally along transverse cutting axis 44 when cutting 
wheels 40, 42 are caused to rotate in a clockwise direction as viewed in 
FIGS. 4, 7 and 8. Accordingly, each cutting wheel is adapted for cutting 
primarily in its one generally outward transverse direction relative to 
the length of pontoon 12 as wheels 40, 42 are caused to rotate and cutting 
head assembly 38 to be moved transversely relative to pontoon 12. 
The predetermined angular spacing between teeth 46 is designed such that 
material removed from the face of a predetermined size is able to pass 
between adjacent teeth and into the space between the wheels. Alternate 
and more complex teeth geometries could also of course be employed which 
enable removed material to pass to the space between the wheels. A 
preferred example would be to mount teeth to project in a circumferential 
manner along rapidly projecting vanes. The vanes would be angled to direct 
removed material inwardly to the space between the wheels as the wheels 
rotate and cut material from the face. 
Wheels 40, 42 are rotatably driven by a drive motor 50 which is mounted 
within a watertight vault 74 rearwardly adjacent the cutting wheels. 
Wheels 40. 42 and their associated cutting teeth 46 function as a rotary 
ripping means for removing material from a face of material upon their 
rotation by drive motor 50. 
First excavating means 16 further includes suction means 48 positioned in 
the space between cutting wheels 40, 42 for hydraulically transporting 
removed material away therefrom. A pump drive motor 54 is mounted within 
another watertight vault 76 rearward of vault 74 for rotatably driving 
pump 52. An input suction pipe 55 extends outwardly from pump to a 
position between cutting wheels 40, 42 and below cutting axis 44. The 
outermost end of input suction pipe 55 includes an extendable end section 
in the form of an arcuately movable telescoping pipe section 56. Pipe 
section 56 includes a radially projecting pivot arm 60 which extends to a 
pivot pin 62 for supporting pipe section 56 for pivotal movement about a 
transverse pivot axis. Telescoping section 56 is selectively movable into 
and out of the end of pipe 55 by means of a piston/cylinder assembly 58 
connected between support arm 36 and pivot arm 60. In this manner, the 
outermost end of suction means 48 is extendible generally in the direction 
of the face of material to function as an adjustment means. The adjustment 
means is utilized to maintain the suction force in close proximity to the 
face of material as cutting head assembly 38 is moved elevationally 
relative thereto, as will be more fully described below. 
A sizing grill or grate 64 is positioned between cutting wheels 40, 42 
elevationally above cutting axis 44. Grate 64 has a generally arcuate 
outer shape conforming to the arcuate outer shape of cutting wheels 40, 
42. A shroud 66 is positioned above the rearwardmost end of grate 64 and 
extends rearwardly to vault 74 in which cutting wheel drive motor 50 is 
retained. Grate 64 functions to down-size overburden material removed from 
the face of material by cutting wheels 40, 42 as it is drawn toward 
suction pipe 55 by suction action. 
Referring again to FIG. 1, a headline system is employed for anchoring 
pontoon 12. The system consists of a headline 68 extending from the upper 
fore end of the dredge, along crane assembly 32, to an anchoring device 69 
which is located in front of the dredge on shore. Anchor 69 to which 
headline 68 is secured serves as the pivot point about which the pontoon 
is pivoted from side to side in an arcuate path when dredging. A pair of 
swing lines 70 is secured to the bow end of pontoon 12 and secured to 
additional anchoring devices (not shown) located on shore. These shore 
anchors are generally in the form of winches or motorized vehicles for 
pulling on one of swing lines 70 to cause the pontoon to be arcuately 
moved about the pivot point. The rear portion of pontoon 12 is anchored by 
a pair of lines 72 extending therefrom to additional anchors 73 located on 
shore for keeping headline 68 taut. 
Both first and second excavating means 16, 18 are independently operable of 
each other. Dredging control means are provided for coordinating their 
operation to efficiently remove both overburden and ore material during 
their simultaneous operation. A block diagram of microprocessor controlled 
dredging control means is illustrated in FIG. 9. The dredging control 
means includes a microprocessor 78 which receives information and controls 
both the hydraulic and mechanical operational aspects of the dredge. The 
microprocessor operates to coordinate the various dredging components so 
that the alluvial deposits are most efficiently dredged. Most preferably, 
the deposits being dredged have been surveyed and sampled prior to 
beginning the dredging operation. Information obtained from the survey and 
sampling are input into memory components 77 accessible by the 
microprocessor for proper mining of the overburden and ore material by the 
respective overburden and ore excavators in the most efficient manner. 
A typical method of excavating overburden material and ore material using a 
pontoon mounted floating dredge such as the one just described follows. To 
begin operation, pontoon 12 is first positioned so that both the 
overburden and ore excavators 16, 18 can reach the face material to be 
excavated. Next, overburden excavator 16 is lowered until it is in 
position to excavate overburden material 82 adjacent the water line (FIG. 
2). Drive motor 50 is then engaged to start cutter wheels 40, 42 rotating 
clockwise. Additionally, suction pump 52 is engaged by pump motor 54 to 
begin the suction action. With cutter wheels 40, 42 rotating and suction 
pump 52 operating pontoon 12 is caused o pivot about headline anchor 69 by 
pulling on one of swing lines 70 to pull the pontoon in one arcuate 
direction. The one of cutting wheels 40 or 42 in the pulling direction 
engages the face of the overburden material and rips material therefrom as 
it rotates. The other of cutting wheels 40 or 42 provides minimal cutting 
action against the face when moving in the transverse direction towards 
the other wheel. A portion of the removed material is forced upwardly by 
the clockwise rotation of the cutting wheel and drawn through grates 64 by 
suction action towards the outer end of suction pipe section 56. 
Additional removed material travels between the teeth of the cutting wheel 
from the leading direction of the cut toward the suction pipe section 56. 
In this manner, the rotating cutting wheels also function as a rotary 
grizzly means for downsizing removed material as it is fed to the suction 
means. In other words, material larger than the spacing between adjacent 
teeth on the leading cutting wheel is worked by the wheel until its size 
is reduced to the point where it is able to pass between adjacent cutter 
teeth 46. 
Upon reaching the end of the cutting stroke in one direction, 
microprocessor 78 acts to lower support 36 to position cutting head 38 
downwardly on the face of overburden material 82. The barge is then pulled 
in the other direction making the cutting wheel which was trailing now the 
leading cutter. This operation is continued until such time as overburden 
excavator 18 has reached the upper portion of "pay" material 80. 
The preferred operational arrangement with respect to the suction means is 
to keep the end of suction pipe 56 as close as practical to the face of 
material adjacent here the cutting teeth are working. FIGS. 7 and 8 
illustrate that telescoping section 56 of suction pipe 55 is progressively 
extended outwardly towards the mined face of overburden material 82 as 
cutting head 38 is moved downwardly. FIG. 7 illustrates that when the 
support arm of the cutting wheel is configured to be near horizontal or 
near the water line, the telescoping section 56 is retracted as the 
cutting teeth work against the face adjacent the entrance to the suction 
pipe. As support arm 36 is moved downwardly, telescoping section 56 is 
extended to effectively place the outermost extent of suction pipe 55 near 
that portion of the cutting teeth which are acting on the face, as shown 
in FIG. 8. 
Overburden excavator 16 is operated until a cut profile such as shown in 
FIG. 2 is attained. Namely, the overburden material is excavated to 
provide a longitudinal spacing between the face of overburden material 82 
and the face of pay material 80. At this point, the bucket line excavator 
18 is lowered to a position at the top of the face of the pay material 80. 
Overburden excavator 16 is positioned adjacent the water line. With both 
in position, pontoon 12 is swung to one side. As it swings, ore excavator 
18 removes a layer of pay zone material which is conveyed to processing 
means 20 on pontoon 12. The desired ore material is there separated and 
retained on the pontoon. Waste material from the processing means is 
either dropped directly overboard or selected top soiling material is 
directed to the shore through pipe 86 supported by conveyor support 24. At 
the same time, overburden excavator 16 removes a layer of overburden 
material. The excavated overburden material is discharged into trommel 23, 
with the oversize and waste material dumping onto belt conveyor 25 and 
deposited externally onto the spoil pile. The undersize material is 
collected by hopper 27 and pumped up and added to the processing means 20 
system of recovery. When dredge 10 reaches its limit of travel in one 
direction, both the ore excavator and overburden excavator would be 
rotated downwardly a suitable amount so as to begin excavating a new layer 
of ore and overburden material respectively. This procedure is repeated 
until the ore excavator has excavated all of the "pay" material down to 
bedrock layer 84. 
The dredging control means coordinates the dredging rates and positioning 
of the dredges to effectively remove the ore and overburden material. As 
should be readily apparent, the overburden excavator has a greater 
capacity of removing overburden material in the preferred embodiment. 
Referring to FIGS. 10 and 11, an alternate dredging head assembly is 
indicated generally by reference numeral 138. Dredging head 138 includes 
an alternate adjustment means for maintaining the suction means in close 
proximity to the face of the material as the cutting head is moved 
elevationally relative thereto. The cutting wheels of cutting head 138 
have been removed for clarity. The outside diameter of such cutting wheels 
however is indicated by line 140. 
As in the previous design, a support arm 136 supports various components at 
the end of cutting head assembly 138. A movable end section 149 is 
provided in the end of the suction means to accommodate desired 
positioning of the suction means relative to the face of material being 
mined. The outermost end of end section 149 tapers inwardly to form an 
elongated suction mouth 150. A pair of plate like pivot arms 142, 144 are 
pivotally mounted at the outer end of support arm 136 and operably connect 
support arm 136 to movable end section 149. The elongated width of suction 
mouth 150 extends substantially the entire distance between pivot arms 
142, 144 and correspondingly the cutting wheels. 
Pivot arms 142, 144 are positioned immediately inward and adjacent of the 
cutting wheels (not shown), and are pivotal between extreme positions "A" 
and "B" about a pivot axis 145 on support arm 136. A piston/cylinder 
assembly 146 is supported atop support arm 136 above pivot axis 145. 
Assembly 146 engages an interconnection bar (not shown) extending between 
arms 142, 144 for simultaneously pivoting arms 142, 144 about axis 145. 
Pivot arms 142, 144 pivotally suspend extendible end section 149 
therebetween for movement relative to the face of material being mined. In 
the depicted embodiment, this is accomplished by a circular 
cross-sectioned support bar 152 which is anchored to and extends between 
arms 142, 144. An elongated, square cross-sectioned receiver tube 154 is 
formed from metal strips atop end section 149 adjacent suction mouth 150. 
Formed tube 154 slidably receives support bar 152 therethrough in such a 
manner that the movable end section 149 and support bar 152 are pivotal 
relative to one another. End section 149 could also of course be pivotally 
suspended in other manners between plates 142, 144, such as by a support 
bar engaging beneath the end section. Alternately, end section 149 could 
be pivotally suspended from its sides relative to each of pivot arms 142, 
144. 
FIG. 10 illustrates the extent of pivotal movement of pivot arms 142, 144 
and correspondingly the typical extreme positions between which suction 
mouth 150 is movable to assist in maintaining the suction mouth in close 
proximity to the face of material being worked. The "A" position would be 
employed for operational configurations of the hydraulic dredge such as, 
for example, shown in FIG. 8. The "B" position would be used where the 
dredge is configured as, for example, shown in FIG. 7. 
To accommodate longitudinal movement of end section 149 relative to support 
arm 136 and correspondingly the face of material being mined, end section 
149 is preferably telescopically connected to a fixed suction tube (not 
shown) near the end of support arm 136. Alternately, a flexible and 
expandable tube could interconnect the fixed suction tube with movable end 
section 149, such as for example shown in U.S. Pat. Nos. 4,242,814 and 
4,302,893. any possible connections would exist as will be appreciated by 
the artisan. 
FIGS. 12-14 illustrate another dredging head 238. The 238 head is similar 
to the 138 head such that only the differences will be highlighted. In 
this embodiment, the end section 249 tapers inwardly to a narrower width 
suction mouth 250. The suction mouth width is approximately half the 
predetermined distance between pivot arms 142, 144. Because of this 
narrower width a greater amount of suction force is exerted at mouth 
opening 250 than at mouth opening 150 of head 138. Suction mouth 250 is 
movable transversely to any position between pivot arms 142, 144 and 
correspondingly the rotary cutting wheels. 
A piston and cylinder assembly 256 extends between pivot arms 142, 144 
rearwardly adjacent support bar 152 and engages support tube 154 mounted 
atop the end section 249. A piston 257 of assembly 256 is supported by a 
rod 259 extending therethrough and between pivot arms 142, 144. A cylinder 
261 surrounds piston 257 and is in fluid sealing engagement relative to 
rod 259. The length of cylinder 261 is approximately equal to the width of 
mouth 250. Cylinder 261 is secured relative to end section tube 154 by a 
pair of support arms 263, 265. 
By selectively charging cylinder 261 with fluid either to the left or right 
of piston 257, the suction mouth 250 can selectively be driven in the left 
or right direction, respectively. Accordingly, assembly 256 functions as a 
positioning means for selectively moving suction mouth 250 transversely 
between the rotary cutting wheel to selectively orient the mouth adjacent 
to one of the wheels. Alternate positioning means could of course be 
employed as will be appreciated by the artisan. 
Operation of such a dredging head could proceed as follows. FIG. 14 
illustrates the desired orientation of suction mouth 250 when the 
hydraulic dredging head is being swung to the right as viewed from FIG. 
14. Suction mouth 250 is positioned by piston/cylinder assembly 256 to the 
right. This concentrates a greater amount of suction force immediately 
adjacent the working wheel than in the previously described embodiments. 
When the swinging stroke to the right is completed, mouth 250 would be 
swung to the opposite (left) side between the wheels and the dredging head 
swung to the left. 
The width of mouth 250 could of course be some other width than 
approximately one-half the distance between plates 142, 144 and 
correspondingly the cutting wheels. The mouth width should preferably be 
some significant amount less than that of the FIGS. 10 and 11 embodiment 
to enable a concentration of suction force in the direction of cutting 
head movement. 
FIGS. 15-17 illustrate yet another alternate construction dredging head 338 
for concentrating suction force in the direction of dredging head 
movement. Head 338 is similar to head 238 such that only the differences 
are described. The movable end section 349 is constructed to form two 
generally opposed suction mouths 350 and 351. Both suction mouths 350, 351 
are elongated, being wider than they are high. Each face in opposite 
transverse directions. The overall width of the outer end of movable end 
section 349 is again less than the overall spacing between pivot arms 142, 
144. A combination piton/cylinder assembly 256 is again provided between 
pivot arms 142, 144 to accommodate side to side transverse movement of end 
section 349 between the cutting wheels. 
The operational configuration of end section 349 between the cutting wheels 
is, however, exactly opposite to that employed in the FIGS. 12-14 
embodiment. For example, referring to FIG. 17, when the dredge head is 
being swung to the right, movable end section 349 is positioned to the 
left. This effectively closes off the left suction mouth 351 which bears 
against pivot arm 142. This enables all of the suction force to be drawn 
through suction mouth 350 which is facing in the direction of dredging 
head movement. 
The overall width of the outer end of end section 349 is preferably 
constructed to be greater than one-half of the distance between arms 142, 
144. This places the particular working suction mouth in reasonably close 
proximity to the working cutting wheel. The diameter however is not so 
great as to permit the particular arm 142 or 144 which is positioned in 
front of the working suction mouth to have a significant adverse effect on 
the suction which is generated. 
In compliance with the statute, the invention has been described in 
language more or less specific as to structural features. It is to be 
understood, however, that the invention is not limited to the specific 
features shown, since the means and construction herein disclosed comprise 
a preferred form of putting the invention into effect. The invention is, 
therefore, claimed in any of its forms or modifications within the proper 
scope of the appended claims, appropriately interpreted in accordance with 
the doctrine of equivalents.