US3881775A

US3881775A - Mining method and apparatus therefor

Info

Publication number: US3881775A
Application number: US458467A
Authority: US
Inventors: Frank Alfred Mcpherson; Homer Charles Reed
Original assignee: Kerr-Mcgee Coal Corp
Current assignee: Kerr-Mcgee Coal Corp
Priority date: 1973-09-24
Filing date: 1974-04-08
Publication date: 1975-05-06
Anticipated expiration: 1992-05-06

Abstract

A method and apparatus for remote mining of a subterranean body of ore, through a bore hole, from a surface station. The apparatus includes an elongated rotatable member, an elongated powered cutting member pivotally attached near one end of said rotatable member and an actuator associated with the rotatable member and the cutting member adapted to move the cutting member between a position substantially perpendicular to the rotatable member and a stored position substantially parallel to the rotatable member. The apparatus further includes a surface station, connected to the other end of the rotatable member comprising means to rotate the rotatable member, means to insert and remove the rotatable member through a bore hole, means to control the cutting member and means to control the actuator. In a preferred method of operation the cutting member initially is positioned substantially parallel to the rotatable member and lowered into a bore hole extending into the body of ore to be mined. When the rotatable member and cutting member are in a desired position, the rotatable member is rotated, the cutting member is driven and extended from its initial position until it contacts the ore and begins to cut the ore into small pieces for recovery. The extension of the cutting member continues until it reaches a final outward position, generally about perpendicular to the rotatable member. Thus, the ore is mined from a large area by the elongated cutting member through a relatively small diameter access hole. The small pieces of ore are readily removable by conventional means such as, for example, a screw conveyor, vacuuming and the like. In accordance with a preferred method, the area being mined is flooded with a fluid having a specific gravity of from about 1.1 to about 2.5 whereby the small pieces of ore float in the fluid and are transportable by circulation of the fluid from the surface to the mined area and back to the surface.

Description

United States Patent [191 McPherson et al.

[ May6,1975

[ MINING METHOD AND APPARATUS THEREFOR [73] Assignee: Kerr-McGee Coal Corporation,

Oklahoma City, Okla.

[22] Filed: Apr. 8, 1974 [21] Appl. No.: 458,467

Related US. Application Data [63] Continuation-impart of Ser. No. 400,378, Sept. 24,

1973, abandoned.

Primary Examiner-Ernest R. Purser Attorney, Agent, or Firm-William G. Addison [57] ABSTRACT A method and apparatus for remote mining of a subterranean body of ore, through a bore hole, from a surface station. The apparatus includes an elongated rotatable member, an elongated powered cutting member pivotally attached near one end of said rotatable member and an actuator associated with the rotatable member and the cutting member adapted to move the cutting member between a position substantially perpendicular to the rotatable member and a stored position substantially parallel to the rotatable member. The apparatus further includes a surface station, connected to the other end of the rotatable member comprising means to rotate the rotatable member, means to insert and remove the rotatable member through a bore hole, means to control the cutting member and means to control the actuator.

[11 a preferred method of operation the cutting member initially is positioned substantially parallel to the rotatable member and lowered into a bore hole extending into the body of.ore to be mined. When the rotatable member and cutting member are in a desired position, the rotatable member is rotated, the cutting member is driven and extended from its initial position until it contacts the ore and begins to cut the ore into small pieces for recovery. The extension of the cutting member continues until it reaches a final outward position, generally about perpendicular to the rotatable member. Thus, the ore is mined from a large area by the elongated cutting member through a relatively small diameter access hole.

The small pieces of ore are readily removable by conventional means such as, for example, a screw conveyor, vacuuming and the like. In accordance with a preferred method, the area being mined is flooded with a fluid having a specific gravity of from about 1.1 to about 2.5 whereby the small pieces of ore float in the fluid and are transportable by circulation of the fluid from the surface to the mined area and back to the surface.

16 Claims, 5 Drawing Figures 'J-EENIELM 65375 3.881.775

sum 2 BF 4 K7 FIGURE 2 //////lY///////Il l-l/l/l/l/IYl f7///X\/ VV V v v 7 v v I v I l l/ V I b V DIRECTION OF ROTATION FIGURE 3 MENTEEW sears 3.881.775

SHEET 3 OF 4 FIGURE 4 OVERBURDEN MINING METHOD AND APPARATUS THEREFOR This application is a Continuation-In-Part of application Ser. No. 400,378, filed Sept. 24, 1973 now abandoned.

BACKGROUND OF THE INVENTION Coal is, of course, a valuable source of energy and is found in many areas throughout the United States. Coal generally is found in large deposits below the surface of the earth. In Wyoming, for example, the Wyodak coal seam ranges from 20 to 100 feet thick and the Bureau of Mines estimates the deposit to contain about 20 billion tons of coal. These deposits are as deep as 1,500 feet below the earths surface.

l-leretofore, the conventional methods of recovering coal have been by mining through a shaft and by strip mining.

When coal is mined through a shaft it necessarily follows that workers are required below the earths surface to operate the machines that remove the coal from the deposit or seam and transport it to the surface. in such mines there is the ever present danger of a cave-in or explosion from seeping gas or coal dust. To reduce the risk of a cave-in when mining thick seams of coal it is customary to leave pillars of coal to support the overhead. Generally, only about 50 to 80 percent of the coal is recoverable by such a method. Further, it is not possible to mine coal by such a method when the thickness of the coal seam is in excess of about 25 feet. Moreover, mining through a shaft requires the use of complex machinery to cut the coal loose from the seam, transport it to the surface and simultaneously provide the fresh air flow and minimum dust level required for the health and safety of the operators; see, for example, US. Pat. Nos. 3,642,325; 3,620,573 and 2,308,517.

In US. Pat. No. 2,937,049 there is proposed an apparatus for transporting coal from an underground shaft using the buoyancy of a heavy fluid media. The coal is crushed to an appropriate size such as to cause no damage to the valves of the apparatus through which the coal is transported.

in US. Pat. No. 1,406,349 there is disclosed a deepwell enlarging and cistern making machine. The machine primarily consists of earth cutting chain saws operated by a power means enclosed in a casing. The patent discloses lowering such a machine into a pilot hole to a desired depth at which the cutting chain is extended to cut a verticle kerf in the ore body. Thereafter, a different machine is lowered with a horizontal cutting chain saw to cut horizontal kerfs in the ore.

The patent does not disclose any means for cooling the cutter chain or bringing the cut ore to the surface. Moreover, the machine disclosed utilizes numerous gears and mechanical linkages which would be subject to failure as well as being jammed by the loose particles of ore. Obviously, such a machine would not be suitable from a commercial mining application. A somewhat similar device is disclosed in US. Pat. No. 2,890,858 which relates to a deep well chain saw. Patentee discloses using a water turbine to power the chain saw to cut vertical slots in a well. Patentees apparatus also is complex and provides no method for recovering ore from a subterranean body of the same.

More recently in US. Pat. No. 3,443,648 there is disclosed a device for enlarging bore holes wherein the enlargement of the bore hole is accomplished by hydraulically driven cutters. In the apparatus disclosed therein extensible cutting arms are arranged to extend angularly outward from a drill pipe. The drill pipe section upon which the cutting arms are mounted is held in position by stabilizers above and below the cutters. The cuttings from the earth formation fall into a crusher positioned below the cutter and are circulated up through the drill pipe by fluid being pumped into the bore hole.

In US. Pat. No. 3,472,553 there is disclosed a method and apparatus for extracting bitumen, in situ, from subterranean tar sands, shales and similar form ations. In accordance with the method disclosed therein a hole is drilled in the top of the formation and lined with casing. A sump is drilled in a formation below the casing. A solvent for bitumen is introduced into the sump and an expandable rotary agitating tool is inserted through the casing into the sump in the formation. Rotation of the tool breaks up the formation and hurls the solvent against the sump walls to aid in dislodging bitumen-bearing particles and to dissolve the bitumen therefrom. Such apparatus and method is not satisfactory for the recovery of an ore such as, for example, coal.

German Pat. No. 1,212,923 relates to a method and device for extracting and conveying minerals. A small diameter hole is run down through the overburden into a deposit of minerals, such as, for example, coal. Extendable cutting arms are rotated from the surface by a shaft to ream out the deposit and allow the freed mineral to be flushed to the surface.

None of the foregoing suggested methods or apparatus are entirely satisfactory for the commercial recovery of an ore such as coal from a subterranean deposit. The apparatus suggested heretofore is either complex such that it requires excessively high rotational forces at the surface or provides no satisfactory method of recovering the ore. Obviously, therefore, there still is need for an improved method and apparatus for mining subterranean ores from the surface.

SUMMARY OF THE INVENTION The present invention provides an improved method and apparatus for mining a subterranean body of ore such as, for example, coal. With the present method and apparatus it now is possible to mine a body of ore located as much as 200 feet or more below the surface of the earth without need of personnel working below the earths surface. In accordance with the present invention a subterranean body of ore is mined through a small bore hole from a surface station. The apparatus permits mining a large area of an ore body through a relatively small diameter bore hole, thus, disturbing substantially little of the earths surface and overburden.

Broadly, the apparatus comprises an elongated powered cutting member, a surface station and a rotatable member interconnecting the elongated cutting member and the surface station. The elongated cutting member is pivotally attached near one end of the rotatable member and has associated therewith an actuator to move the cutting member between a position substantially parallel to the rotatable member and a position angular (generally perpendicular) to the rotatable member. The surface station, connected to the other end of the rotatable member, includes means to insert and remove the rotatable member through a bore hole, means to control the cutting member, means to control the actuator and means to rotate the rotatable member.

In operation, a bore hole is cut through the overburden into the body of ore to be mined. The cutting member is positioned substantially parallel to the rotatable member and inserted into the bore hole, to a position within the body of ore, by the surface station. The rotatable member is rotated, the cutting member is driven and extended from its initial position until it contacts the ore and begins to cut the ore into small pieces for recovery.

The extension of the cutting member continues until it reaches a final outward position, generally about perpendicular to the shaft. The elongated cutting member generally has a length in excess of six times the diameter of the bore hole, thus the ore is mined from a large area by the elongated cutting member through a relatively small diameter access hole. Indeed, in accordance with the present invention it is possible to recover ore from an area in excess of 50 feet in diameter through, for example, a 36 inch diameter access hole.

When the ore body is coal, such as, for example, the Wyodak coal deposit which has an average thickness of about 70 feet, it is possible to recover in excess of 60 tons per hour of coal from a single 36 inch diameter bore hole. Further, such recovery is accomplished with a crew which may be as few in number as two men op erating from the relative safety of the earths surface.

The coal cut from the deposit may be brought to the surface by any number of means known to those versed in the art, such as, for example, a screw conveyer, vacuuming and the like.

In accordance with a preferred embodiment, the area being mined is flooded with a liquid and the mined ore is brought to the surface as a slurry. In accordance with one embodiment the liquid utilized has a specific density approximately equal to or greater than that of the ore to facilitate suspension of the ore in the liquid whereby the ore is floatable to the surface.

In another embodiment, the liquid is pumped under pressure through a passageway provided in the rotatable member, into the area being mined where it forms a slurry of ore, and then the liquid-coal slurry flows up the bore hole around the rotatable member for recovery on the surface. In accordance with yet another embodiment, a gas such as, for example, air, nitrogen and the like is injected under pressure into the liquid-coal slurry to further facilitate its passage to the surface.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation, in cross-section, of the apparatus of the invention shown in operation in an ore y;

FIG. 2 is a side elevation, partly in cross-section, of one embodiment of the cutter assembly of the apparatus with the elongated cutting member extended;

FIG. 3 is an end view of the elongated cutting member taken at a right angle to FIG. 2;

FIG. 4 is a side elevation, partly in cross-section, of the cutter assembly of the apparatus shown in operation in an ore body; and

FIG. 5 is a side elevation partly in cross-section of another embodiment of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS The present invention provides a novel method and apparatus for recovering subterranean ores from the earth's surface. The present invention is applicable to coal, potash, phosphate, uranium and the like. The invention is particularly applicable to the Wyodak coal deposits found in Northeastern Wyoming. Similar thick deposits also are found in Colorado, Utah, New Mexico and Montana.

Referring now to FIG. 1, there is depicted an embodiment of the apparatus of the present invention in operation. The apparatus includes a surface unit 1 which is provided with a derrick 2. Preferably the surface unit is mobile since the mining operations generally will be completed in from 1 to 3 days. In accordance with a particularly preferred embodiment the unit is selfpropelled and provided with tracks 3, wheels or the like.

The surface drilling unit 1 is positioned over a bore hole 18 which has already been drilled to the prescribed depth by independent conventional drilling means or alternatively it may be drilled by the surface unit. Cutter assembly 20 is suspended in the bore hole by a section of drill pipe 6 to which additional sections of drill pipe may be added. The drill pipe is held in position by power head 4 which is capable of applying a rotational force to the drill pipe. Power head 4 is in turn suspended from derrick 2 by known means such as, for example, cables 8 adapted to raise and lower the head 4. Alternatively, the power head 4 may be suspended from hydraulic cylinders (not shown). Bore hole 18 preferably is provided with a casing 30 which extends at least partially into the overburden and which is provided with a packing 32 to sealing engage drill pipe 6. Casing 30 also is provided with an outlet 34 which is in communication with conduit 36 to permit a flow of circulating fluid and ore to pass to collection tank 38. Pump 10 provides a flow of circulating fluid from reservoir 12 via

conduit

14 and 16 through drill pipe 6 and out through cutter assembly 20.

Cutter assembly 20 includes a housing 22 and an elongated cutting member 24 which preferably is a cut ting chain of the type used to cut kerfs in coal. The cutting chain is powered by a down hole hydraulic motor 28. Preferably the hydraulic motor is so selected as to provide a linear cutting chain speed of from about 300 to 1,200 feet per minute and to permit a direct connection of the output shaft of the motor to a drive sprocket on the chain saw. The cutter assembly also includes a hydraulic actuator 26. Hydraulic actuator 26 which may be, for example, a hydraulic piston, moves the elongated cutting member 24 from a stored position substantially parallel to housing 22 and drill pipe 6 to an extended position substantially perpendicular to housing 22 and drill pipe 6.

Surface station I also includes a source of hydraulic power 37 for the actuator and hydraulic motor. The source of hydraulic power may include, for example, a hydraulic pump, a hydraulic reservoir for the hydraulic fluid (preferably oil) circulating through the system and valves for control of the hydraulic flow. Such components are of conventional design and are not shown.

Referring now to FIG. 2, a cross section of the cutter assembly, it is seen that drill pipe 6 is provided with a passageway 40 for passage of a circulating fluid (to be described more fully later). Drill pipe 6 is connected to cutter housing 22 by a coupling 42 to provide communication between passageway 40 and passageway 44 in housing 22. Cutting chain assembly 24 is provided with a passageway 51 which is in communication with passageway 44 via movable conduit 46 which may be a flexible tube, a swivel joint and the like. Passageway 51 is provided with a plurality of openings 50 along the length of cutting chain assembly 24. Passageway 44 also extends through the length of housing 22 to provide a path for a flow of circulating fluid through opening 48 located in the lower portion of housing 22. Housing 22 also is provided with a recess 23 adapted to receive cutting chain assembly 24 in its stored position. It also is contemplated that housing 22 may be ballasted by means of an enlarged portion 25 or by suspending weights (not shown) from the housing. Alternatively, housing 22 may be provided with a cavity which can be ballasted by the inclusion therein of a heavy material such as, for example, lead. Hydraulic power to motor 28 and actuator 26 is provided via

conduits

54 and 52 respectively which may be, for example, hoses, tubing or the like.

FIG. 3 is an end view of the chain cutter assembly 24 of FIG. 2. As shown in FIG. 3 the leading edge of the chain cutter assembly is tilted with respect to a horizontal plane at an angle referenced generally by the numeral 49. It is an important feature of the present invention that the edge of the chain cutter assembly be adapted to have a tilt of at least 1 with respect to its axis. In operation the tilt is in the direction of rotation toward the face of the ore body being cut. It is the tilt that overcomes one of the problems of the prior art chain saw apparatus. More particularly, the prior art apparatus would make only vertical or horizontal cuts. With the present apparatus cutting is accomplished simultaneously in both a horizontal and vertical direction. The angle of tilt must be at least 1 and generally will be from at least about l to less than about 85. A preferred angle of tilt is from about l.5 to about 40.

It will be appreciated that the angle of tilt need not be uniform throughout the length of the chain cutter assembly. More particularly, in some instances it may be desirable to provide a greater angle of tilt at the end of the chain cutter assembly adjacent the housing than is provided at the other end. A varying angle of tilt such as just described is readily accomplished, for example, by putting a twist in the elongated chain guide member. Advantageously, the chain cutter assembly also is mounted in such a manner that it may be tilted after it is lowered into the hole and at least partially extended.

FIG. 4 shows an enlarged view of another embodiment of the cutter assembly of the present invention in an ore body shown in cross section. In this embodiment the chain cutter assembly is pivotally attached to the lower end of housing 22A. The flow of circulating fluid is depicted generally by arrows 56. The flow of fluid is shown coming down through housing 22A out into bore hole 18 where it picks up particles of the cut ore to form a fluid suspension which flows upward through bore hole 18 to the surface for recovery. Obviously, of course, the direction of flow of the circulating fluid could be reversed, if desired.

In FIG. 5 another embodiment of the invention is shown. Utilizing known directional drilling technique, a bore hole 18 is provided within a body of ore extending in a direction substantially parallel to the seam of the body of ore. In this embodiment chain cutter assembly 208 includes a housing 228 having a lower portion 102 which is pivotable about pivot point 100. Cutter assembly B is attached to an elongated rotatable member 104 which is provided with two

internal fluid passageways

106 and 40. The two fluid passageways are in communication via openings 108 which are located near cutter assembly 20B. Elongated rotatable member 104 may comprise, for example, two concentric drill pipes, one located within the other. Openings 108 may be a series of holes in the wall of the inner pipe, slots or the like.

The present invention also provides a novel method for recovery of ore from a subterranean body of the same. Broadly, the method comprises drilling a bore hole into the body of ore to be mined such as, for example, coal. A rotatable drill shaft having an elongated cutting member powered by a down hole hydraulic motoris lowered into the bore hole and thecutting member positioned in the body of ore. The elongated cutting member is extended from an initial position substantially parallel to the rotatable shaft until the body of ore is contacted. Power then is applied to the cutting member by the down hole motor and the shaft is rotated from the surface. A circulating fluid is introduced into the area being mined. The ore cut from the body is picked up by the fluid and carried back to the surface.

In the embodiment depicted in FIG. 5, after elongated cutting member 24 has been extended approximately from its initial position substantially parallel to housing 228, lower portion 102 then is pivoted from its initial position (indicated by the dotted lines) about pivot point by actuator 10] until it is substantially parallel with the elongated cutting member. The shaft continues to rotate while power is applied to the elongated cutting member to cut ore loose from the main body.

The circulating fluid passes down through the bore hole 18 in the area being mined where it picks up cut particles of ore and returns through openings 50 in the elongated cutting member and openings 46 in lower portion 102. The circulating fluid, along with the particles of ore, then passes through passageway 44 to internal passageway 40 in the elongated rotatable member. Obviously, of course, passageway 44 includes a movable connection 108 adjacent pivot point 100 to provide communication between passageway 44 in lower portion 102 and passageway 44 in housing 22B.

Air under pressure passes through passageway 106, through openings 108 and into passageway 44 where it assists in lifting the particles of ore to the surface. The air is introduced at a pressure of from 25 to psi, greater than that of the pressure of the circulating fluid at the point of air injection and preferably at a pressure of from 50 to 75 psi greater than that of the circulating fluid.

This particular embodiment provides two distinct advantages, namely, (1) it permits mining a greater volume of ore through a single access hole, and (2) it is not essential in this embodiment that a cave-in be prevented. More particularly, as the ore is recovered from an area a cave-in of the overburden actually is beneficial for it forces the circulating fluid back to the surface, thus, facilitating recovery of the circulating fluid.

The selection of the circulating fluid is an important feature of the present invention when the ore is coal and it is desired to recover the coal without introducing a gas under pressure to assist in lilting the ore particles to the surface. More particularly, the fluid should be a dense liquid, viz., a specific gravity of from about 1.1 to about 2.5. The preferred fluids are aqueous suspension of finely ground pyrite cinder, coal, hematite, magnetite, ferrosilicon, galena, limonite, barite, calcium chloride or mixtures thereof. The selected material preferably is ground to a particle size of from about 20 to 150 microns. A particularly preferred size is from 50 to 100 microns.

Three particularly preferred materials are ground hematite, magnetite and ground coal. Obviously, of course, when mining a body of coal, large amounts of inexpensive coal are available for grinding to form the desired suspension. Magnetite and hematite while more costly, are readily removable from an aqueous suspension of the same and coal by magnetic separation. Since magnetite and hematite are relatively expensive, when they are used, economics dictate that they be recovered for reuse.

Separation of the mined ore from the heavy liquid is readily accomplished by numerous known means such as, for example, filtration, centrifugal separators, magnetic separation for certain materials, settling tanks and the like.

The circulating fluid also should include a gelling agent for viscosity control. Suitable gelling agents include bentonite, carbomethyl cellulose and the like.

The gelling agent generally is added in an amount sufficient to provide an A.P.I. funnel viscosity of from about 35 to 80 seconds per quart, and preferably from about 40 to 60 seconds per quart. It has been found that at lower viscosities the circulating fluid will not effectively carry the coal particles without the use of a pressurized gas as hereinbefore described.

As shown in FIG. I a bore hole is provided through the earth's surface into a body of ore. Generally the bore hole will be from about 24 to 48 inches in diameter. A length of casing having a diameter of about 4 to 6 inches less than that of the bore hole is positioned in the bore hole and cemented in position to seal the casing to the bore hole.

The use of and the length of the casing will, of course, depend upon the nature of the formation. If the overburden covering the ore is, for example, a loose sand, it may be necessary to extend the casing down to the ore body or even extend it slightly into the ore body. When the overburden is a more stable formation, then the casing may not be required or only extend partially into the overburden for a depth of from about to 50 feet. The minimum depth to which the casing must extend varies from one type of earth formation to another. Such depth is readily determinable by experimentation.

After the casing is cemented in position, a section of drill shaft, having pivotally mounted near its lower end an elongated powered cutting member, is lowered into the casing. The elongated cutting member is positioned in the body of ore and pivoted outwardly to contact the ore. Power is applied to the elongated cutting member and the rotatable shaft and elongated cutting member are lowered and rotated whereby coal is cut from the body of ore. A dense fluid is circulated through the bore hole into the area being mined to form an aqueous suspension of coal which is recovered at the surface station.

It is a feature of this invention that the initial cutting of the ore body may be accomplished in such a manner as to reduce the tendency of cave-ins. More particularly, in FIG. 4 wherein the elongated cutting member is pivotally attached to the lower end of the cutting assembly the initial cut forms a dome having a stable hemispherical shape. Alternatively, when the elongated cutting member is pivotally attached near the upper end of the cutter assembly (FIGS. 1 and 2), the initial cut should be made in such a manner as to provide a roof having an angle of from about 30 to 60 with respect to the horizontal as indicated by reference number 5 in FIG. 1. It is preferred that the angle be within the range of from about 40 to 50.

The elongated cutting member is extended until it contacts the face of the ore body. Power is applied to the cutting member and the rotatable shaft simultaneously is rotated until the elongated cutting member has been extended to the desired angle. Thereafter, the shaft and cutting member are lowered as cutting and rotation continues until the elongated cutting member reaches a position substantially perpendicular to the shaft. After the elongated cutting member has reached its full extended position rotation and lowering continues until the desired amount of ore has been recovered.

It is a further feature of the present invention that the risk of a cave-in of the area being mined be substantially reduced by the use of the dense fluid described herein before. Further, it is contemplated that the circulating fluid be maintained under pressure to provide additional support for the overburden in those circumstances where such additional support is required.

What is claimed is:

l. Apparatus for mining ore comprising:

a. a rotatable shaft having a fluid passageway therethrough b. a cutter assembly including i. an elongated housing attached to one end of the rotatable shaft, the axes of the housing and shaft being substantially coincident, said housing having a fluid passageway providing communication between the passageway in the shaft at one end and an opening located near the other end of the housing;

ii. an elongated cutting chain assembly pivotally attached near one end of the housing, said assembly including a cutting chain in cooperative engagement with a drive sprocket and an elongated chain guide member, said cutting chain assembly being adapted to have a tilt of at least 1 and less than about with respect to its axis;

iii. chain cutter drive means to rotate said drive sprocket;

iv. an actuator attached to said housing and cutting chain assembly adapted to move said cutting chain assembly through any position between a stored position substantially parallel to said housing and an extended position substantially perpendicular to said housing and c. a surface station attached to the other end of the rotatable shaft and including means for rotating said shaft, means for raising and lowering said shaft, means for controlling said actuator and means for controlling said chain cutter drive means.

2. The apparatus of claim 1 wherein said chain cutter drive means is a hydraulic motor connected to said drive sprocket.

3. The apparatus of claim 2 wherein said actuator is a hydraulic piston.

4. The apparatus of claim 3 wherein said housing is provided with a recess adapted to receive said elongated cutting chain assembly in the stored position.

5. The apparatus of claim 4 wherein the lower end of said housing is ballasted.

6. The apparatus of claim 4 wherein said hydraulic motor drives said cutting chain at a linear velocity of from about 300 to 1,200 feet per minute.

7. The apparatus of claim 1 wherein said elongated cutting chain guide member is provided with a fluid passage therethrough to provide communication between this passageway in the housing and a plurality of openings in said guide member.

8. The apparatus of claim 1 wherein said housing is provided with a recess adapted to receive said elongated cutting chain assembly in the stored position.

9. The apparatus of claim 1 wherein the lower end of said housing is ballasted.

10. A method of mining a subterranean body of coal from a surface station comprising the steps of:

1. providing a bore hole extending from the surface into the body of coal;

2. introducing a rotatable member, having a fluid passageway therethrough and an elongated powered cutting member near its lower end, into the bore hole until the elongated cutting member is in the body of coal;

3. pivoting the elongated cutting member outwardly to contact the coal, applying power to the elongated cutting member and rotating the rotatable member and elongated cutting member whereby 10 coal is cut from the body;

4. circulating a fluid having a specific gravity of from about 1.1 to about 2.5 and an API funnel viscosity of from about 35 to seconds per quart into the area being mined and forming an aqueous suspension of the cut coal; and

5. recovering the aqueous suspension of coal at the surface station.

11. The method of claim 10 wherein the circulating fluid is pumped down through the passageway in the rotatable member and the aqueous suspension of coal is recovered from the surface end of the bore hole.

12. The method of claim 10 wherein the circulating fluid comprises an aqueous dispersion of hematite and has a specific gravity of about 1.5.

13. The method of claim 10 wherein the circulating fluid is pumped through the bore hole into the area being mined and the aqueous suspension of coal flows out of the area being mined through the passageway in the rotatable member.

14. The method of claim 13 wherein a gas is introduced into the aqueous suspension of coal in the fluid passageway of the rotatable member.

15. The method of claim 10 wherein the elongated cutting member is a cutting chain.

16. The method of claim 15 wherein the cutting chain is powered by a down hole hydraulic motor.

4 i l i

Claims

1. Apparatus for mining ore comprising: a. a rotatable shaft having a fluid passageway therethrough b. a cutter assembly including i. an elongated housing attached to one end of the rotatable shaft, the axes of the housing and shaft being substantially coincident, said housing having a fluid passageway providing communication between the passageway in the shaft at one end and an opening located near the other end of the housing; ii. an elongated cutting chain assembly pivotally attached near one end of the housing, said assembly including a cutting chain in cooperative engagement with a drive sprocket and an elongated chain guide member, said cutting chain assembly being adapted to have a tilt of at least 1* and less than about 85* with respect to its axis; iii. chain cutter drive means to rotate said drive sprocket; iv. an actuator attached to said housing and cutting chain assembly adapted to move said cutting chain assembly through any position between a stored position substantially parallel to said housing and an extended position substantially perpendicular to said housing and c. a surface station attached to the other end of the rotatable shaft and including means for rotating said shaft, means for raising and lowering said shaft, means for controlling said actuator and means for controlling said chain cutter drive means.

1. providing a bore hole extending from the surface into the body of coal;

3. pivoting the elongated cutting member outwardly to contact the coal, applying power to the elongated cutting member and rotating the rotatable member and elongated cutting member whereby coal is cut from the body;

3. The apparatus of claim 2 wherein said actuator is a hydraulic piston.

4. circulating a fluid having a specific gravity of from about 1.1 to about 2.5 and an API funnel viscosity of from about 35 to 80 seconds per quart into the area being mined and forming an aqueous suspension of the cut coal; and

5. recovering the aqueous suspension of coal at the Surface station.

5. The apparatus of claim 4 wherein the lower end of said housing is ballasted.

6. The apparatus of claim 4 wherein said hydraulic motor drives said cutting chain at a linear velocity of from about 300 to 1, 200 feet per minute.

9. The apparatus of claim 1 wherein the lower end of said housing is ballasted.

10. A method of mining a subterranean body of coal from a surface station comprising the steps of: 1. providing a bore hole extending from the surface into the body of coal; 2. introducing a rotatable member, having a fluid passageway therethrough and an elongated powered cutting member near its lower end, into the bore hole until the elongated cutting member is in the body of coal; 3. pivoting the elongated cutting member outwardly to contact the coal, applying power to the elongated cutting member and rotating the rotatable member and elongated cutting member whereby coal is cut from the body; 4. circulating a fluid having a specific gravity of from about 1.1 to about 2.5 and an API funnel viscosity of from about 35 to 80 seconds per quart into the area being mined and forming an aqueous suspension of the cut coal; and 5. recovering the aqueous suspension of coal at the Surface station.