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Publication numberUS3456371 A
Publication typeGrant
Publication dateJul 22, 1969
Filing dateMay 6, 1965
Priority dateMay 6, 1965
Also published asDE1634854A1, DE1634854B2
Publication numberUS 3456371 A, US 3456371A, US-A-3456371, US3456371 A, US3456371A
InventorsJohn R Graham, Algernon A Mabson
Original AssigneeKennecott Copper Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Process and apparatus for mining deposits on the sea floor
US 3456371 A
Abstract  available in
Images(6)
Previous page
Next page
Claims  available in
Description  (OCR text may contain errors)

July 22, 1969 j GRAHAM ET AL 3,456,371

PROCESS AND APPARATUS FOR MINING DEPOSITS ON THE SEA FLOOR Filed May 6, 1965 6 SheetsSheet 1 F/G./. F/G.8.

5 MOVEMENT OI SHIP DIRECTION OF UREDGING July 22, 1969 J. R. GRAHAM ET AL 3,456,371

PROCESS AND APPARATUS FOR MINING DEPOSITS ON THE SEA FLOOR Filed May 6, 1965 6 Sheets-5heet 2 July 22, 1969 J, GRAHAM ET AL 3,456,371

PROCESS AND APPARATUS FOR MINING DEPOSITS ON THE SEA FLOOR- Filed May 6, 1965 6 Sheets-Sheet S July 22, 1969 GRAHAM ET AL 3,456,371

PROCESS AND APPARATUS FOR MINING DEPOSITS ON THE SEA FLOOR Filed May 6, 1965 6 Sheets-Sheet 4 F/G.5. F/GZ July 22, 1969 J. R. GRAHAM ET AL 3,456,371

PROCESS AND APPARATUS FOR MINING DEPOSITS UN Till-i SEA FLOOR Filed May 6, 1965 6 Sheets-Sheet b FIG.

2" WIRE PIPE LlNE case PENDENT s'rRucwxE PIPE A \l I \IG l July 22, 1969 G M ET AL 3,456,371

PROCESS AND APPARATUS FOR MINING DEPOSITS ON THE SEA FLOOR Filed May 6, 1965 6 Sheets-Sheet 6 .rzmozmu m2: UNIS of uni maowxn don xufim United States Patent M 3,456,371 PROCESS AND APPARATUS FOR MINING DEPOSITS ON THE SEA FLOOR John R. Graham, Newport Beach, and Algernon A. Mabson, Long Beach, Calif, assignors to Kennecott Copper Corporation Filed May 6, 1965, Ser. No. 453,734 Int. Cl. E02f 1/00, 3/ 88, 3/90 U.S. Cl. 37195 11 Claims ABSTRACT OF THE DISCLOSURE Deposits of manganese nodules and other minerals are found on the sea floor at depths of a thousand feet and greater. These nodules lie exposed on the sea floor, either directly on the surface of the sea floor or buried. For example, the presence of such nodules has been photographed on the floor of the North American Basin, off the coast of Florida.

These nodules contain manganese and iron in substantial quantity, and in addition, valuable amounts of copper, cobalt, nickel, and other metals. The nodules vary in size and shape. They tend to be spherical, and their largest dimension may be up to about eight inches or larger. The economic recovery of these nodules poses several challenging problems.

One object of the present invention is to provide a new and practical process for mining deposits on the sea floor. A related object of the invention is to provide practical equipment for practicing this process.

A more specific object of the invention is to provide practical processes and devices for the economic recovery of manganese nodules from sea floor deposits.

Another object of the invention is to provide new and practical techniques for transporting liquid-solid mixtures upwardly from the sea floor, through relatively long lengths of dredge pipe.

A further object of the invention is to provide new and practical techniques for mining valuable deposits that are distributed on the surface of the sea floor and that are embedded in the first few inches or feet of the sea floor.

Still another object of the invention is to provide efficient, effective techniques and equipment for recovering manganese nodules from the sea floor, at costs that can be economically competitive considering the value of the recoverable minerals that are available in the nodules.

Other objects of the invention will be apparent hereinafter from the specification and from the recital of the appended claims.

In the drawings:

FIGURE 1 is a fanciful, fragmentary view showing a surface vessel underway on the surface of the sea, a gathering vehicle for movement on the sea floor, and an articulated dredge pipe interconnecting the surface vessel and the gathering vehicle, all in accordance with one preferred embodiment of the present invention;

FIGURE 2 is a fragmentary side elevation on an enlarged scale, of the gathering vehicle on the sea floor,

3,456,371 Patented July 22, 1969 with the direction of movement of the vehicle being indicated by an arrow;

FIGURE 3 is atop plan view thereof;

FIGURE 4 is a fragmentary section taken on the line 44 of FIGURE 3, looking in the direction of the arrows;

FIGURE 5 is a fragmentary side elevation, partly broken away, of a section of the dredge pipe and an adjacent and connected section of a compressed air pipe, that communicates with a jacket about the dredge pipe for injecting air under pressure into the dredge pipe;

FIGURE 6 is a sction taken on the line 66 of FIG- URE 5, looking in the direction of the arrows;

FIGURE 7 is a fragmentary part elevation, part section, of the receiving tank into which the dredge pipe discharges when an air lift is employed to transport the mined nodules mixed with sea water through the dredge FIGURE 8 is a fragmentary part side elevation, part vertical section, on an enlarged scale, of different kinds of joints that are employed between adjacent sections of the dredge pipe;

FIGURE 9 is a side elevation of a pump, and of a cage in which it is mounted, for producing a hydraulic lift to transport mined material upwardly through the dredge pipe, with the direction of flow indicated by arrows;

FIGURE 10 is a fragmentary side elevation of a surface vessel for supporting the dredge pipe and temporarily storing the mined nodules, and

FIGURE 11 is a fanciful elevation showing the gathering vehicle in a series of different positions through which it would be moved when hoisted from the sea floor up into the surface vessel, or vice versa.

Referring now in detail to the drawings by numerals of reference, the numeral 14 denotes generally a gathering vehicle or tractor that is designed for movement over the floor of the sea. A surface vessel 15 is shown under way on the surface of the sea, in proximity to the position of the tractor. A dredge pipe 16 is suspended from the vessel 15, and is buoyed up by multiple buoyancy tanks 18 that are secured to the dredge pipe at intervals below the surface of the sea. The lower end of the dredge pipe forms, under its own weight, a shape that is referred to herein as a catenary 19, although it is recognized that drag and other forces also act on this pipe, so that it is technically not a true catenary. Several of the sections of the pipe are interconnected with each other, in this catenary portion, by flexible ball joints 20. A sturdy line 21 is anchored at its lower end to the tractor 14, and is connected at its upper end to a buoy 22 that is shown floating in close proximity to the surface vessel 15.

THE TRACTOR The tractor 14 is designed and equipped to be remotely controlled from the surface vessel 15. Its function is to move over the sea floor, following a pattern of back and forth movement, and to skim nodules from the sea floor. Essentially, the tractor performs a strip mining operation.

Referring now particularly to FIGURES 2, 3 and 4, the tractor 14 is formed with a rugged metal frame that is, however, formed of a light metal such as, for example, aluminum, to keep the over-all weight low, so that the bearing pressure on the surface of the sea floor will be less than one pound per square inch. The frame includes a front cross tube 24, a rear cross tube 25, and a center bracing structure that is generally indicated by the numeral 26 (FIGURE 4), all three of which interconnect the two side beams 28. A pair of drive sprockets 29 are mounted at the opposite ends of the front cross tube 24.

Each of these drive sprockets 29 is connected through its own respective shafting 30 and gear train 31 to its own individual electric drive motor 32. Each of these drive motors is individually mounted and rigidly secured on its own platform 34, that is supported on cross braces 35 that extend between the front cross tube 24 and the side beams 28, and between the side beams 28 and the center bracing structure 26, respectively. Each motor is independent of the other so that the tracks 38 need not be operating at simultaneously equal speeds or in the same direction.

A plurality of tires 36 are mounted along each side of the gathering vehicle, and each tire is separately and individually suspended from one of the side beams 28. A pair of crawler tracks 38 is mounted, one at each side of the tractor, about the drive sprockets 29 and the tires 36. The tires 36 are preferably hollow and filled with liquid, to avoid collapse at operating depths.

A heavy bumper 39 is secured to the front cross tube 24, and is proportioned to extend across the entire width of the front end of the tractor. The bumper 39 projects in advance of the tractor and protects the crawler tracks as well as the tractor body.

A pair of masts 40 are secured to the center brace 26, at opposite sides of the tractor respectively. A cross beam 41 is secured between the upper ends of the masts 40, so that the masts 40 and cross beam 41 together form a structure that is generally in the shape of an inverted U. An eye plate 42 is secured centrally on the cross beam 41, to face the front of the vehicle, for a purpose to be described presently. A similar eye plate 44 is secured to the upper surface of the cross beam 41, projecting upwardly, to provide anchorage for the pendent line 21. The apex of an A-shaped truss 45 is rigidly secured to the rear face of the cross beam 41 at its apex, and each of its legs is rigidly secured to opposite sides respectively of the rear cross tube 25.

Individually mounted heavy spring rake tines 46 are supported by a cross beam 47. The lower, free ends of the rake tines are disposed to project a short distance below the lower surfaces of the crawler tracks 38. This ar- .rangement permits the tines to rake the surface of the sea floor and to deflect by swinging toward the rear and upwardly, upon encountering some unusually large or immovable obstruction.

A pair of scraper blades 49, 50, are each respectively secured to the center brace 26 of the vehicle frame for pivotal movement about vertical axes by pins 51, 52, respectively. These pins interconnect the frame and the outboard ends of a pair of frontally-disposed web portions 54, 55, that are integral with the scraper blades, respectively. These web portions 54, 55 are in turn pivotally secured by pins 53, 57, respectively, to the pistons of spring plungers 56, 58, repectively, that spring-press the scraper baldes to the diagonal position shown best in FIG- URE 3, in which the two scraper blades converge together toward the rear or trailing end of the tractor.

Several desirable accessory items for the tractor are not illustrated, in order to simplify the drawings. For example, the tractor should be protected from damage by sonic or supersonic scanning of its immediate path, and for this purpose, a forward searching sonar unit may be mounted on the tractor. It is also desirable to provide closed system television, with floodlights trained to illuminate the path. The provision of an inclinometer on the tractor, and of a pan and tilt device on the TV camera to permit inclinometer readings, also is desirable. To operate underwater television successfully at depths greater than about 6,000 feet, it may be desirable to install amplifiers in the cable. Water-tight connectors are used for this purpose.

Each of the crawlers of the tractor preferably is independently driven by its individual motor, as shown in the drawing. By way of example, for a tractor weighing about 20,000 pounds, and carrying none of the Weight of the dredge pipe, each crawler can be powered by a 75 H.P. submersible, two speed, reversible electric motor with a built-in gear reduction.

There motors may be supplied with three-phase AC. power at 4,000 volts, depending on depth. Suitable controls on the surface vessel are provided to start, stop and reverse the motors, and also to change speeds as may be necessary. The tractor may be turned by slowing one of the crawler units, or by going forward on one crawler unit and to the rear on the other. The same electric power cable may provide power for a pump for jetting on the sea floor, in the path of the tractor.

THE DREDGE PIPE As is best shown in FIGURE 10, the surface vessel 15 is formed with an open center well 61. A pneumatic or hydraulic shock absorber or shock plunger 62 is mounted within this well, and the upper end of the dredge pipe is secured to the shock plunger.

The dredge pipe is formed from sections that are preferably about eighty feet long, and that are interconnected in the following manner. Over the main portion of the length of the dredge pipe, each of the pipe sections 64 (FIGURE 8) is formed with a flange fitting 65 at each of its ends. The flange fittings of adjacent pipe sections are held together with clamp fittings 66, in watertight fashion.

In those portions of the pipe where flexibility is required, such as, for example, in the catenary portion 19 at the lower end of the pipe, ball joints are employed between adjacent pipe sections where required. One form of ball joint, that may be employed, consists of a female fitting 68 that is welded or otherwise secured to one end of a pipe section. The confronting end of the adjacent pipe section is provided with a mating male fitting 69, that can be received in substantially watertight engagement within the female fitting. A clamping collar 70 is secured to the end of the female fitting 68 by a plurality of pivoted bolts 71 that are secured in angularly spaced relation about the female fitting. The collar 70 is proportioned to restrain the two fittings 68, 69 against relative axial movement, While permitting relative rotary movement, in a manner well known in the art.

Preferably, the individual sections of the dredge pipe are selected for optimum strength and weight characteristics. For example, the lower sections of the dredge pipe, that are secured to the gathering vehicle, may be made of welded aluminum. The wall thicknesses of the pipe sections may be progressively increased, from the sea floor upward, as needed, to provide adequate strength for supporting the lower pipe sections, and the upper sections of the dredge pipe may be formed from high tensile welded steel, rather than from aluminum.

For long strings of dredge pipe, buoyancy tanks 18 or other buoyant items or materials are secured to the dredge line, below the surface, to provide support for a substantial part of the weight of the dredge pipe.

At its lower end, the last section 72 of the dredge pipe is operatively connected to the tractor in the following manner. An eye plate 74 (FIGURE 2) is secured to the end of the pipe section 72 that is remote from the tractor, and a line 75 interconnects the eye plate 74 with a ring 76 that is secured in the pendent line 21. A collar '78 is mounted intermediate the ends of the pipe section 72. This collar is formed with a pair of eyes, and one line 79 interconnects the collar 78 with the frontfacing eye plate 42 on the cross beam 41 of the tractor, and a second line 80 interconnects the collar with an eye bolt that is secured to the front cross tube 24.

The pipe section 72 is connected through an L fitting 84 with a flexible ball joint 85, that permits limited move ment of the dredge pipe relative to the tractor. The ball joint 85 is mounted on an L 86 (FIGURE 4) that is secured to the center brace 26 of the tractor by a cradle of supporting webs 88. The L 86 in turn is connected through a flexible ball joint 89 with a short stub pipe 90 on which the collector head 91 is mounted.

The collector head 91 is formed with a lower face 92 that confronts the sea floor during normal mining operations. This lower face 92 is formed with a large, generally rectangular opening, across which a heavy screen or grille 94 is mounted, to prevent the entrance of undesirably large articles into the dredge pipe.

A pair of lugs 95 are secured to the opposite respective sides of the collector head, adjacent its upper end. A pair of arms 96 are rigidly secured to these lugs, and project toward the rear of the tractor. These arms 96 are formed, at their respective free ends, with massive, slotted guide members 98. The rear frame tube of the tractor is slidably received within the slots of these guide members. A pair of stop rings 97 are secured on the tube 25, on the outboard sides of the guide members 98 respectively, to limit movement of the guide members lengthwise of the tube.

The two guide members 98 are rigidly interconnected together by a transverse heel member 99, that is disposed beneath the frame tube 25. The heel member 99 is formed with a rounded lower face, to ride on the sea floor, and with an upwardly curved central lip portion 100.

During movement of the tractor, the lower face of the heel 99 rides over the sea floor, but when an irregularity is encountered, the heel 99 and the guides 98 rise up or drop down, and as they do so, they cause the arms 96 to move correspondingly, carrying the collector head 91 up or down with them.

In strings of dredge pipe over 9,000 feet long, at least two buoyancy tanks are ordinarily used, each having a positive buoyancy of at least about 100,000 lbs. These tanks are provided with an initial internal air pressure of about 1,000 p.s.i., before being submerged, attached to sections of the dredge pipe.

If desired, a plurality of buoyancy tanks can be employed of smaller buoyancy capacity than mentioned above. The use of a plurality of such tanks produces a more uniform distribution of stress along the length of the dredge pipe and makes possible the use of less heavy and therefore less strong dredge pipe sections and joints.

To provide for the catenary at the lower end of the dredge pipe, and to provide flexibility and limited mobility for mining operations at a depth of about 6,000 feet, about 7,000 feet of pipe should be used; and for operations at about 12,000 feet, about 13,500 feet of pipe should be used. For deeper operations, appropriate additional increments of pipe should be provided.

THE AIR LIFT To transport mined material from the surface of the sea floor up through the dredge pipe, it is preferred to employ an air lift. This transporting technique utilizes an injection of compressed air into the dredge pipe, at some distance below the sea surface and at some distance above the sea floor, to form within the dredge pipe first a two phase mixture of air and sea water, and then, as operations begin, a three phase mixture of air, sea water, and dredged solid material. These mixtures are lighter than the sea water surrounding the dredge pipe, and the pressure of the surrounding sea water forces the mixture up through the dredge pipe.

Referring now particularly to FIGURES 5 and 6, to provide for the air lift, a section 102 of relatively small diameter pipe is secured by straps 104 to each section of dredge pipe, above the air injection site, to carry compressed air to the injection site. A quick-disconnect fitting 101 is secured to each end of each air pipe section. The quick-disconnect fittings 101, at the end of each air section, are connected to the confronting fittings of adjacent air pipe sections through short, flexible interconnecting flexible nipples 105.

At the air injection site, a special dredge pipe section 106 is provided with an external jacket 108, intermediate its ends. The wall of the dredge pipe section 106, that is enclosed within the jacket 108, is formed with a plurality of perforations 109, to admit air from the jacket into the dredge pipe. A pair of curved pipes 110 interconnect and provide communication between the lower end of the air pipe 102 and the interior of the jacket 108.

For efficient operation of the air lift, the dredge pipe is mounted to discharge into a chamber at superatmospheric pressure. This chamber is provided in a tank 111 (FIGURE 7) that is mounted on a movable base 112. A connecting pipe 114 is mounted to provide communication between the upper end of the dredge pipe, that is suspended from the shock plunger 62, and the tank 111. A curved baifie 115 is mounted within the tank chamber, over the discharge opening of the connecting pipe 114, to deflect the stream that is injected into the tank chamber, and to preserve the tank against wear.

A rotary valve 116, at the bottom of the tank, permits continuous discharge of nodules from the tank, during operations. A riser 118 is connected to the tank chamber at its lower end, and is open to the atmosphere at its upper end. At different elevations, sliding gates or valves (not shown) are connected to the pipe, to permit sea Water to run out of the pipe into one or more of several troughs 117, that are secured to the pipe 118 in positions, respectively, to receive the runoff water. This arrangement facilities control over the head that is maintained within the tank 111.

The tank 111 is maintained at superatmospheric pressure to avoid the pinch effect that would otherwise occur during air lift operations. The pinch effect can be explained in the following manner. A bubble of air that is rising, under generally isothermal conditions, through several hundred feet of water to the surface, will expand to many times its original volume. For example, if the bubble rises 3400 feet, it will expand to approximately 100 times its original volume. Moreover, 50 percent of the total expansion will take place in the final 34 feet of the ascent, where the static head or back pressure is lowest. Such a tremendous expansion, in the final section of the dredge pipe, could tend to generate unfavorable conditions.

THE SURFACE VESSEL The surface vessel 15 is provided with a derrick 119 that is mounted over the vessels center well 61, to facilitate handling the dredge pipe sections when raising and lowering, or simply changing the length of, the dredge pipe. A crane 120 is mounted adjacent the derrick, for hoisting the pipe sections, and transporting them to and from the storage racks 121, or from supply vessels. An A-frame and boom 122 are mounted at the front of the ship, for handling the pendent line 21, when necessary. The pressurized discharge tank 111 is mounted adjacent the derrick 119 and the center well 61, to facilitate connecting the dredge pipe for discharge.

The surface vessel is preferably equipped for dynamic positioning, that makes it possible for the surface vessel to maintain a substantially fixed position on the surface of the sea, for indefinite periods of time, or to move in a predetermined path, as necessary.

HYDRO-LIFT Instead of using an air lift for transporting material up the dredge pipe, other transport systems can be em ployed. A preferred alternative makes use of at least one rotary pump, located in the dredge pipe, for developing enough lifting action to transport mined material effectively.

One form of pump, that may be employed in connection with such an alternative embodiment of the invention, is illustrated in FIGURE 9. The pump 125 is a centrifugal type rock pump having a non-clogging impeller, and is mounted in a particular section 126 of the dredge pipe 16. The pump is provided with a pair of discharge pipes 128, that are parallel for a short distance, to provide the inner part of a cage structure about the enclosed submersible electric motor 129 that drives the pump. These discharge pipes are connected together above the motor, to communicate with a single section of the dredge pipe. Preferably, an outer cage structure 130 is provided, through which there is no flow, and whose purpose is to provide the supporting structure for the motor and pump, and also to maintain the tensile strength of the dredge pipe.

More than one pump may be used, as necessary, depending upon the depth of the Water at which mining is 10 taking place. If more than one pump is used, the pumps are mounted and operated in series, The pumps function to generate sufficient Water pressure and velocity so that the nodules, and other solids, are entrained and are transported by the sea water upwardly through the dredge OPERATION Operation of this equipment will now be described, utilizing air-lifting techniques for causing transport of the mined material.

The surface vessel preferably is equipped with auxiliary equipment and supplies, to permit operations at a substantial distance from land bases, without the need of direct or continuous land-based support other than for transportation of mined materials, food and supplies, and emergency assistance.

When an area of the sea floor, that is to be mined, has been established, a series of at least four taut line buoys is set to a known and recorded pattern. Each of these buoys is equipped with a sonar transponder, battery powered, with a signaling life of several months. These initial buoys form the master buoys for the area to be mined, and subsequent mapping and setting of auxiliary marker buoys, of which there will normally be very many, are related to the original master buoys. The sonar transponders are serviced and repowered, at regular intervals as needed, by divers.

After an explored area has been staked out, the surface vessel 15 is moved into operating position. The gathering vehicle or tractor 14 is carried by the surface A vessel, either on deck, in the center well 61, or suspended directly beneath the center well, when operations are pending.

To begin operations, the tractor 14 is slowly lowered, by adding on the appropriate dredge pipe sections to lengthen the dredge pipe sufficiently to lower the tractor to the sea floor. The pendent wire line 21 is held out from the bow of the ship on the boom 122 as the tractor is lowered, and this automatically forms the desired catenary 19 at the lower end of the dredge pipe, as the tractor is lowered to the sea floor.

When the final section of dredge pipe has been connected to the shock plunger 62, the entire weight of the dredge pipe is transferred to a spider (not shown) that is mounted at the level of the main deck of the surface vessel. After the dredge pipe has been secured to the spider," the receiving tank 111 is placed in position and secured in place for operations.

The swing joint 85, through which the dredge pipe is connected with the tractor, permits the tractor to move in wide sweeps transversely of the direction of travel of the surface vessel. This decreases the required speed of the surface vessel, and results in smaller drag forces on the dredge pipe.

The movement of the tractor on the surface of the sea floor is remotely controlled from the surface vessel, in order to cause the tractor to move in a predetermined pattern of movement, or as indicated by the topography of the sea floor, to skim the surface of the sea floor in the areas traversed. Before the tractor is started on its sweeps over the sea floor, the air lift is placed in operation, to start a current of sea water up through the dredge pipe.

As the tractor moves over the sea floor, the sea floor is raked to loosen up the material forming the sea floor, and to free up the manganese nodules. The scraper blades 49 and 50 plow all of the nodules, and other solid material, into a bed in the path of the collector head. This bed is immediately traversed by the collector head 91. As the collector head passes through the bed of nodules and other material from the sea floor, the current of sea water passing into the collector head sweeps the bed up, through the screen in the lower face 92 of the collector head, andthence through the stub pipe and the successive fittings into the dredge pipe.

For efi'icient mining operations, the area to be mined should be relatively flat. When the nodule concentration, of nodules lying on the surface and within the first six inches of depth of the surface of the sea floor, is about four pounds per square foot of sea floor surface or greater, strip mining in accordance with the procedure herein described ordinarily is eifective and efficient. The tractor can be driven at a speed of about one or two feet per second, and the rate of recovery of nodules may be on the order of to 200 pounds per second, depending upon the size of the collector head.

For mining manganese nodules at two typical operational depths, the following conditions are recommended for producing satisfactory results:

TABLE 1 [Values are approximate] Water depth, it.

I.D. of dredge pipe, inches 15. 0 l5. 0 Fluid velocity of two phase flow (nodules, other solids, and sea water), in the bottom portion of dredge pipe, fiL/see 17. 1 17. 1 Maximum elocity of nodules in two phase flo ftJsec 14. 4 14. 4 Minimum velocity of nodules in two phase flow,

ft./sec 7.7 7.7 Average probable velocity of nodules in three phase flow (solids including nodules, sea water, and air),

ft./sec 73 73 Distance of air injection below surface of water,

It 1, 375 2, Percent of water depth to point of air injection 23 18 Injection air pressure to start system (gauge), lbs./

Volume of air-quantity, c.r.m 10, 600 16, 000 Compressor horsepower to maintain system 1, 800 3, 400 Compressor horsepower total on dredge 4, 000 8, 000 Total flow (slurry), lbs. min 87, 300 87, 300 Total flow (nodules), lbs/min 9, 000 9, 000

As indicated in the foregoing table, in order to start the initial upward flow of sea water through the dredge pipe, it is necessary to use air that is in excess of the static head of the water at the injection point, so as to start a pumping effect from the injected air. However, after the water is in motion, the pressure of the air can be lowered considerably to a maintenance level that is still sufficient to keep the fluid in motion. At the collector head, the inward rush of sea water sweeps the nodules and other loose material, that have been formed into a bed by the scraper blades, into the collector head and up the dredge pipe.

At the upper end of the dredge pipe, the material discharges into the chamber of the tank 111. This chamber is maintained at a superatmospheric pressure, such as, for example, about 22 p.s.i.g. or higher. The solids portion of the three phase mixture, that is discharged into the tank 111, settles rapidly. The solids are transferred through the rotary valve 116 from the bottom of the tank into a material handling system, such as, for example, a transfer conveyor, that will transfer the solid materials into appropriate hoppers. The sea water is allowed to run off and return directly to the sea.

The figures for nodule recovery are based upon nodules having a largest dimension of about 8", about 0.6 sphericity, specific gravity 2.1, and density of about 131 lbs/cu. ft.

For operating at a 6,000 foot depth, the air injection site preferably is located about 1,375 feet below the surface of the sea, and at the operating injection pressure of 9 355 p.s.i.a., the daily air rate is about 15.4 std. MCF. Preferably, the compressors withdraw air from the tank 111 into which the dredge pipe discharges. This air is then compressed and returned to the dredge pipe at the injection site.

As a design precaution, it is preferred that the compressed air system by flexible, with multiple compressor units, with at least 100 percent of standby capacity, and reserve high pressure air tanks, all capable of delivering compressed air in a wide range of pressure.

For mining in water depths of up to about 12,000 feet, an exemplary dredge pipe string would be constituted as follows, from the sea floor up:

To minimize the power required for operations, it is preferred that the air injection site be located at a depth of at least 1,000 feet blow the surface of the sea.

When hydraulic lifting is employed rather than air lifting, centrifugal pumps replace the air injection system, and the dredge pipe discharges directly into the atmosphere instead of into a pressurized discharge chamber. For mining operations down to about 6,000 feet of water, it is preferred to employ two pumps of 1500 HP. each, operating in series, located about 600 feet below the surface of the sea. These pumps should be constant speed, A.C. powered pumps, with adequate motors to meet maximum emergency power fluctuations. For mining operations at depths on the order of 12,000 feet, it is preferred to employ four pumps, operating in series and located about 1,000 feet below the surface of the sea.

OTHER FACTORS In the event of damage to the dredge pipe or tractor, or after exhaustion of a particular mining area, the dredge pipe and tractor can be hauled aboard the surface vessel, as indicated schematically in FIGURE 11. In the event that a storm requires that the surface vessel abandon a particular area quickly, the dredge pipe can be disconnected from the surface vessel, but left connected to the buoy 22 through the pendent line 21, and the dredge pipe can simply be laid on the sea floor, for retrieval after the storm.

Preferably, a sonar transponder or repeating target is mounted adjacent preselected joints, at intervals along the length of the dredge pipe, and, as well, on the gathering vehicle. These units will respond to the ultrasonic sound of a sonar transmitter on the surface vessel, and their transmitted energy will in turn be received on the ship. By a suitable display of these signals in both plan and elevation, the configuration of the pipe line, and the location of the gathering vehicle relative to the surface vessel, are ascertained.

All of the electric power supply that is required to drive the bottom vehicle and control it, for the underwater television equipment and flood lights, and for the instruments, preferably is supplied in one composite cable. This power supply cable is attached to each section of the dredge pipe by means of a suitable quick-connecting clamp. For convenience, cable reels are mounted on the deck of the surface vessel, for stowing and reeling out of the cable. The cable preferably is prepared in lengths of approximately 6,000 feet, with watertight connectors at the joints. Amplifiers for the underwater television are inserted in these joints, as needed.

The composite cable is made up of individual wires as needed for power, lights, electronics and controls, all suitably assembled in one unit and then covered with a moisture-impermeable insulation, protected by double armor, reverse lay wrapping. The end of the cable is let out of the center axle of the cable reel, and is terminated in suitable connectors that are connected up for operation after the vehicle is in operative position on the sea floor.

While the invention has been disclosed herein by reference to the details of preferred embodiments thereof, it is to be understood that such disclosure is intended in an illustrative, rather than in a limiting sense, and it is contemplated that various modifications in the construction and arrangement of the various parts of the equipment described herein will readily occur to those skilled in this art, all within the spirit of the invention.

What is claimed is:

1. A device for skimming and collecting deposits from the sea floor, comprising:

tractor means for movement over the sea floor, including drive means disposed at opposite sides of said tractor for supporting and driving said tractor on the sea floor;

a dredge pipe for transporting collected deposits;

a collector head that is mounted on said tractor intermediate said drive means and remote from the leading end and rearward of said leading end of the tractor and said collector head having openings on a face thereof opening toward the leading end of said tractor and disposed to receive deposits from the sea floor;

means interconnecting and providing communication between said collector head and said dredge pipe, and

a pair of scraper blades that are mounted intermediate said drive means, for movement upon movement of said tractor, and that are disposed for skimming the sea floor and that converge together toward said collector head, to direct skimmed deposits toward the collector head, but terminating forwardly of said collector head to provide an outlet for said deposits, said collector head inlet openings being disposed opposite said scraper blade outlet.

2. A device in accordance with claim 1 wherein said interconnecting means is formed to permit horizontal and vertical movement of said dredge pipe relative to said tractor.

3. A device in accordance with claim 1, wherein said collector head is formed with a free, trailing end that is disposed for sliding movement over obstructions on the sea floor, and is also formed with a collecting opening in advance of its free end in the direction of movement of the tractor, said collecting opening being disposed to confront the skimmed deposits and wherein said collector head is mounted on said tractor for pivotal movement about a generally horizontal axis thereon.

4. Means for mining deposits from the sea floor, comprising, in combination:

a surface vessel;

tractor means for movement over the sea floor, including drive means disposed at opposite sides of said tractor for supporting and driving said tractor on the sea floor;

a dredge pipe for transporting collected deposits;

a collector head that is mounted on said tractor intermediate said drive means and remote from the leading end and rearward of said leading end of the tractor and said collector head having openings on a face thereof opening toward the leading end of said tractor and disposed to receive deposits from the sea floor;

means interconnecting and providing communication between said collector head and said dredge pipe, and

a pair of scraper blades that are mounted intermediate said drive means, for movement upon movement of said tractor, and that are disposed for skimming the sea floor and that converge together toward said collector head, to direct skimmed deposits toward the collector head, but terminating forwardly of said collector head to provide an outlet for said deposits, said collector head inlet openings being disposed opposite said Scrapper blade outlet; and means communicating with said dredge pipe intermediate said vehicle and said vessel, for effecting transport of said gathered deposits through said pipe.

5. .Mining means in accordance with claim 4 wherein the collector head gathers a mixture of said deposits and a volume of sea water to serve as a carrier medium for transporting the deposits and wherein a force generating means is used for generating within said dredge pipe, at a location intermediate its ends, a sufiicient lifting force to cause a continuous flow of said mixture of sea water and deposits upwardly through said pipe.

6. Mining means in accordance with claim 5 wherein said force generating means comprises means for injecting compressed air into the mixture of sea water and deposits.

7. Mining means in accordance with claim 5 wherein said dredge pipe is suspended at its upper end from said vessel and wherein said pipe is articulated for flexibility.

8. Mining means in accordance with claim 5, including buoyancy means secured to said dredge pipe intermediate its ends, to support a substantial portion of the pipe weight below said buoyancy means, and to relieve said means interconnecting said collector head and said dredge pipe of substantially all stress attributable to the weight of the dredge pipe thereabove.

9. Means for mining deposits for the sea floor, comprising, in combination:

a surface vessel;

a self-propelled gathering vehicle for movement over the sea floor;

collector means mounted on said vehicle, for gathering therein a mixture of said deposits from the sea floor and a volume of sea Water to serve as a carrier medium for transporting the deposits;

an articulated dredge pipe that communicates with said collector means, for delivering said mixture from said vehicle to said vessel;

air compressor means mounted on said vessel;

auxiliary pipe means secured to said dredge pipe at least along an upper portion of the length of the dredge pipe, and communicating with said dredge pipe at least at one location intermediate said vehicle and said vessel, to provide communication between said compressor and said dredge pipe, for injecting compressed air into said dredge pipe to effect transport of said mixture of sea water and deposits upwardly through said dredge pipe;

a tank mounted on said vessel;

means for maintaining said tank under superatmospheric pressure;

said dredge pipe being disposed to discharge into said tank under the ambient pressure of the tank; and means permitting the discharge of the sea water and of the gathered deposits from the tank into the atmosphere, while permitting the maintenance of superatmospheric pressure in the tank.

10. Means for mining nodular deposits from the sea floor, comprising, in combination:

a surface vessel;

a self-propelled gathering vehicle comprising tractor means for movement over the sea floor, under remote control from the surface vessel;

an articulated sectional dredge pipe for delivering gathered deposits from said tractor to said vessel, said dredge pipe being supported at its upper end from said vessel, and said dredge pipe being disposed in the form of a catenary adjacent its lower end, and with a plurality of ball joints intermediate dredge pipe sections respectively along the length of the catenary;

means supporting at least a substantial part of the 12' weight of the underlying portion of the dredge pipe at at least one location beneath the surface vessel and intermediate the ends of the dredge pipe;

a collector head that is mounted on said tractor and that is disposed for gathering therein a mixture of said deposits and a volume of sea water to serve as a carrier medium for transporting the deposits, said collector head being mounted on said tractor for pivotal movement about a generally horizontal axis thereon, with a free end thereof formed and disposed for sliding movement over obstructions on the sea floor, and wherein said collector head is formed with a collecting opening ahead of its free end in the direction of movement of the tractor, said collecting opening being disposed to confront the gathered deposits;

means mounted for movement upon movement of said tractor, and disposed to gather deposits and direct them toward said collector head;

means interconnecting and providing communication between said collector head and the lower end of said dredge pipe, said interconnecting means being formed to permit horizontal and vertical movement of said dredge pipe relative to said tractor and said,

collector head; and

means for generating within said pipe, at a location intermediate said tractor and said vessel, a sufiicient lifting force to cause a continuous flow of said mixture of sea water and of said gathered deposits through said dredge pipe up to said vessel.

11. A process for mining deposits on the sea floor,

comprising:

skimming the sea floor;

mixing the skimmed material with a suflicient volume of sea water to serve as a carrier;

delivering the mixture to a dredge pipe;

injecting compressed air into the dredge pipe at least at one location intermediate the ends of the dredge pipe and at a substantial distance below the surface of the sea, to create a pressure differential in the dredge pipe to cause an upward flow of the mixture therethrough; and

discharging the dredge pipe into a chamber under superatmospheric pressure to collect the skimmed material.

References Cited UNITED STATES PATENTS 1,997,149 4/1935 Lake.

216,686 6/1879 Lewis 37-59 523,838 7/1894 Hussey 37-59 692,815 2/1902 Bates 37-63 1,415,113 5/1922 Phillips 37-61 XR 1,556,128 10/1925 Roos 3'7-195 XR 2,826,836 3/1958 Hofiman 37-58 3,226,854 1/1966 Mero 37-58 3,286,286 11/1966 Nelson 37-72 XR FOREIGN PATENTS 939,644 10/1963 Great Britain.

8/ 1964 Canada. 9/1951 France.

OTHER REFERENCES Engineering Aspects of Mineral Recovery From the Ocean Floor by George S. Lockwood. Mining Engineering, August 1964, pp. 45-49. (Referred to as the Lockwood article.)

ANTONIO F. GUIDA, Primary Examiner A. E. KOPECKI, Assistant Examiner U.S. Cl. X.R. 172-777

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Classifications
U.S. Classification37/195, 37/335, 37/314, 285/261, 37/321
International ClassificationE21C50/00, E02F3/88
Cooperative ClassificationE02F3/8858, E21C50/00
European ClassificationE21C50/00, E02F3/88F