BACKGROUND OF THE INVENTION
Hydraulic cutterhead dredges customarily are mounted on barges floating on water surfaces. The suction pipe and cutterhead are mounted on a girder called a ladder that swings downward to the water bottom from a pivotal mounting on the barge. The depth of excavation is limited by two factors. The lack of mechanical advantage of the cutterhead as it gets much deeper than 45 feet, and by cavitation at the pump caused by the vacuum to lift water and dredged materials, being below the vapor pressure of water at the surface.
SUMMARY OF THE INVENTION
By placing dredge pump at the bottom of the water body, the vacuum to lift water and dredged material to the pump is minimized. In addition, the mechanical advantage of the cutterhead can be greatly enhanced by mounting it directly to a submerged dredging chassis close to the pump. The present invention comprises, in addition to accessory apparatus specialized for submerged remote control, two related apparatuses:
Embodiment 1
An elegant chassis with a means to traverse the cutterhead and pump with, for instance, a rack and pinion, jack screw, or endless cableway in a path on a track along the chassis of the dredge. This embodiment also provides a hydraulic means to move the dredge position in any direction on the bottom to further the excavation. The dredge is held stationary, by utilizing multiple spuds just as utilized commonly on floating excavators. The chassis in this embodiment also provides hydraulic rams to crowd the track with traversing cutterhead and suction apart from the chassis and toward the workface.
Embodiment 2
The cutterhead and pump are swung in a curved path along the workface by attaching one end of a long beam or spar to the cutterhead and pump and attaching a large pointed plow to the other end. The spar pivoting on the buried plow at one end determines an arc that establishes the curvature radius of the path of the cutter and pump at the other end. Embodiment 2 carries the cutter end of the radius spar with large (optionally driven) wheels rolling in a curved path on the bottom of the excavation to facilitate swinging the cutter in an arc determined by the spar on its pivot. Cables anchored right and left and spooled on winches at the cutter end of the spar help swing the spar end right and left. A slight variation places the wheels supporting the spar on a curved metal track on the bottom of the excavation and allows for the use of a rack and pinion or endless cableway on the curved track to traverse the cutter and spar. The configuration of the cutter and pump is detailed in the descriptions of the embodiments with reference to the drawings.
Both embodiments rely on an ROV, its umbilical attached to the dredge umbilical to supply power, electronic control data, and compressed air to provide lightening buoyancy to reposition anchors and to perform other tasks on the bottom. Both embodiments should be about equally productive.
OBJECTS AND ADVANTAGES OF THE INVENTION
Objects and advantages of the invention are:
A closely coupled cutterhead pump assembly is at a great advantage dredging hard or rocky material. A remotely operated submerged dredge apparatus, can work far below the surface, hundreds, even thousands of feet. Other excavation methods, like open pit mining or hard rock underground mining, have a much larger footprint on a vulnerable environment and are far more expensive. An application for such a dredge in an environmentally sensitive region is diamond mining in Northern Canada. A kimberlite pipe containing diamonds is typically a narrow carrot shaped volcanic intrusion. If possible, the present invention would excavate only that narrow carrot shape eliminating the need to dewater, remove, stockpile, and eventually replace vast quantities of earth to access the carrot. At conclusion of operations, tailings would refill that smaller excavation.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a close up of the pump and cutterhead assembly.
FIG. 2 is a representation of the dredge at the workface making a new cut.
FIG. 3 is a representation of the pump, cutter and traveler track, showing three hydraulic cylinders deployed from the dredge chassis (not shown) to crowd the pump, cutter, and traveler track into the work face.
FIG. 4 is a representation of a single large air supply linked to individually valved buoyancy tanks on dredge and each section of dredge pipe to adjust individual buoyancies.
FIG. 5 is a representation of an embodiment that excavates in a curved path with pump, cutter and nearby structure supported by large driven wheels riding on the excavation bottom.
FIG. 6 is a representation of an embodiment that excavates in a curved path with a curved track supporting wheels.
FIG. 7 is a representation of the curved track with rack and pinion to traverse the cutter and pump.
FIG. 8 is a representation of the curved track with endless cableway to traverse the cutter and pump.
FIG. 9 is three views representing a specialized pump that integrates the closely coupled impeller and cutterhead.
REFERENCED DRAWING NUMBERS
1. A submersible dredge pump
2. A submersible motor
3. A cutterhead motor
4. A motor driven cutterhead
5. Two parallel trackways for traveler cars
6. and 6a traveler cars
7. A connecting beam
8. A spud, 8a four additional spuds,
9. A rack and pinion
10. A skid structures
11. Three hydraulic cylinders
12. An umbilical cable
13. An electric branch line
14. A second motor
15. A large hydraulic pump
16. Air control valve
17. Attitude control tanks
18. A dredge discharge pipe section
19. A buoyant submerged dredge discharge
20. A fixed discharge pipe
21. Flexible ball joints
22. Workface
23. A long spar
24. A large pointed plow
25. Large wheels
26. Drive motors
27. Cables anchored right and left
28. Winches
29. Curved metal track
30. Endless cableway
31. A rack
32. A pinion
33. Traveler car
34. Idlers
35. Motor driven capstan
36. Pump volute
37. Pump discharge
38. Integrated impeller and suction tube
39. Cutterhead on suction tube
40. Impeller vanes
41. Impeller bearing
42. Cutter bearing
43. Planet gear
44. Ring gear
45. Drive motor
46. ROV and its umbilical
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
The configuration of the assembly of dredge pump, (1) detailed in FIG. 1 driven for instance, by a direct coupled submersible electric motor, (2) and cutterhead (4) driven for instance, by a hydraulic motor (3). Cutterhead and pump are closely coupled to increase cutting power and pumping efficiency. A more remotely mounted pump has friction losses and a closely driven cutter has a greater mechanical advantage.
FIG. 2. A submerged hydraulic dredge comprising one track or two horizontal parallel tracks (5) each carrying a traveler car. (6 and 6a) One car mounts a submersible dredge pump, and dredge cutterhead driven, for instance by a hydraulic motor. (3 of FIG. 1) The movement of the traveler cars is coordinated by a connecting beam. (7) The other car (6a) mounts a skid spud (8) that, with all other spuds withdrawn, can be deployed into the bottom and traversed with the support of a traversing bottomed cutter to skid the chassis sideways. The traveler cars are traversed synchronously by rack and pinion (9) incorporated in each traveler track or by, for instance, jackscrews or endless cableways incorporated in each traveler track. Four additional spuds (8a) are attached, one onto either end of each track. Skid structures (10) are built into either end of the chassis. Two additional spuds (8b) are mounted in the skid structures to support corners of the remaining chassis. Not only can the dredge, skid itself right and left, it can also move fore and aft by articulating the spuds and movable traveler beam apart and together.
FIG. 3. The pump, cutter and traveler track standing apart from the dredge chassis, showing three hydraulic cylinders (11) deployed from the dredge chassis (not shown) to crowd the pump, cutter, and traveler track into the work face. Spuds on either end of the main traveler track stabilize it after it is crowded forward so the cutter can energetically engage the workface. Electric power, control data and high pressure air is supplied from surface facilities by umbilical cable (12) attached to the dredge convenient to the powered dredge pump. An electric branch line (13) leads to a second electric motor (14) powering a large hydraulic pump (15) mounted on the dredge. The hydraulic pump supplies hydraulic power to all spuds, various hydraulic cylinders and hydraulic motors identified elsewhere.
FIG. 4. The air supply is distributed by a control valve (16) to supply at least two variable buoyancy attitude control tanks (17) on the dredge two on each dredge discharge pipe section (18) and one tank on each anchor (27 of FIG. 5). A free swimming ROV, its umbilical attached to the dredge umbilical to supply power for motive thrusters, electronic control data, and compressed air to provide lightening buoyancy and to reposition anchors and to perform other tasks on the bottom. Each such component must, on occasion, float to the surface for maintenance. Buoyancy tanks on the dredge can lighten the dredge to facilitate moving it about the bottom. Buoyant submerged dredge discharge pipes (19) transport, a slurry of water and excavated material from the dredge to a fixed submerged discharge pipe (20) leading ashore. Buoyant pipe sections analogous to float pipe on a surface dredge float a few feet above the bottom of the excavation. As the percentage of solids in the dredge pipe increases, buoyancy must increase to keep pipes level and off the bottom. The pipes are interconnected by flexible ball joints (21) that allow dredge and float pipe to articulate independently of the fixed discharge pipe going ashore. Control from the surface by means of the umbilical cable to the dredge relies primarily upon control data from real time under water imaging, for instance by side scan sonar, for dredge control about the bottom of the excavation.
DESCRIPTION OF OTHER EMBODIMENTS
The dredge of embodiment 1, but alternative to a chassis supported on spuds as in FIG. 2, and skidding the chassis with traversing mechanisms and by alternately withdrawing or extending spuds and spreading them with hydraulic cylinders; the following variation is used:
FIG. 5. The cutterhead and pump are traversed in a curved path along the workface (22) by attaching one end of a long spar (23) to the cutterhead and pump and attaching a large pointed plow (24) to the other end. Both embodiments use the same submersible pump (1) and cutterhead (2), labeled in FIG. 1. The spar pivoting on the buried plow at one end determines an arc that establishes the curvature radius of the path of the cutter and pump at the other end. This embodiment carries the cutter end of the radius spar with large driven wheels (25), rolling in a curved path, on the bottom of the excavation driven by motors (26) to facilitate swinging the cutter in an arc determined by the spar on its pivot. Cables anchored right and left (27) and spooled on winches (28) at the cutter end of the spar assist to swing the spar end right and left.
FIG. 6. A slight variation of this embodiment places the wheels supporting the spar on a curved metal track (29) resting on the bottom of the excavation and allows for the use of a rack and pinion or endless cableway (30) on the curved track to traverse the cutter and spar.
FIG. 7 and FIG. 8. Shown are two representations of the curved metal track, FIG. 7 with a rack (31) and pinion (32) to traverse the car attached to the cutter and spar, FIG. 8 represents an endless cableway (30) running from traveler car (33) across idlers (34) around hydraulic motor driven capstan (35) back across idlers to the cable car.
FIG. 9. A modification is made to a conventional dredge pump. A cutterhead is closely coupled with the pump as in other embodiments herein and integrated with the pump impeller and rotates at pump speed as follows:
The pump volute (36) is made a relatively large diameter, leading to a single pump discharge (37). The throat of the impeller is projected into a suction tube integrating impeller and suction tube (38) incorporating a cutterhead (39) at its end. The impeller is of a large diameter and because of impeller diameter; the impeller vane (40) tips turn at a velocity producing a pressure typical of all dredge pumps. At the impeller mouth, close to the center of impeller rotation, the suction tube and cutter turn at a much slower peripheral velocity typical of dredge cutterheads. The rear impeller bearing (41) is confined within the volute and works with the cutter bearing (42) to keep the impeller and suction tube, turning true. The cutter bearing is supported (support structure not shown) for example, by structure leading from the pump volute or leading from the dredge chassis.
The impeller is driven by one or more planet friction wheels or gears (43) turning a ring or ring gear (44) attached to the face of the impeller. The planet gears are driven by one or more electric or hydraulic drive motors (45).
Patent Application
20100083542
