US2756037A - Mining machines having oppositely rotating boring heads - Google Patents

Description

July 24, 1956 M. B. KIRKPATRICK MINING MACHINES HAVING OPPOSITELY ROTATING BORING HEADS 5 Sheets-Sheet 1 Filed Dec. 21. 1953 Gm o R K a m 2 W l mfi mm 4., m O q. QM B m M. 1k. W5. (kl LM NW M M A 0\\1M./0 Z..\\\\mh Q \QLG. M Y I WA B O a Q \mC\/. o V H Q) A fi w x w w Q 5 o b w M L m \m MW. .M N l R w I. My

Jilly 24, 1956 M. B. KIRKPATRICK 2,756,037

MINING MACHINES HAVING OPPOSITELY ROTATING BORING HEADS Filed D80. 21. 1953 5 Sheets-Sheet 2 v INVENTOR. MAX 3 K/EKPA TE/CK g gm y 1955 M. B. KIRKPATRICK 2,756,037

MINING MACHINES HAVING OPPOSITELY ROTATING BORING HEADS Filed Dec. 21. 1953 5 Sheets-Sheet 3 Q I u* INVENTOR.

M u MAX 5. MEKPAfQ/C'K 7' Qb\ BY M gww b WW A rroe/ve v6 III July 24, 1956 M. B. KIRKPATRICK MINING MACHINES HAVING OPPOSITELY ROTATING BORING HEADS 5 Sheets-Sheet 4 Filed Dec. 21. 1953 W E mg 6 mm m K 60 7 B. 5 9 M M M Y B July 24, 1956 M. B. KIRKPATRICK MINING MACHINES HAVING OPPOSITELY ROTATING BORING HEADS 5 Sheets-Sheet 5 Filed Dec. 21. 1953 K 0 mm w V .Wm mm B m A K mm 5 \N M I v M Y w .v \h BM Kw .H. JQW w Q Tl L l u J Q United States Patent MINING MACHINES HAVING OPPOSITELY ROTATING BORING HEADS Max B. Kirkpatrick, Anchorage, Territory of Alaska Application December 21, 1953, Serial No. 399,255

17 Claims. (Cl. 262-7) In Alaska there are known and proven seams of coal of good grade, and of great thickness, regularity, and extent. Except for the coastal cities, of which none are large or populous, it is impractical to import oil as a fuel. For the remainder of the Territory, and even for the coastal cities, coal would be a near-ideal fuel, if it could be made available at a reasonable price from local mines.

The principal obstacle to doing so is the relatively large amount of labor required in mining the coal under the prevailing conditions, coupled with the high cost of labor in Alaska. As to the conditions, Alaska coal is largely found beneath heavy overburdens, and in formations tilted appreciably, say at 30. iv As a conservation measure it is required that mining operations commence at the lowest point in a seam or tract, and proceed thence uphill. This imposes a severe burden on any mining machine heretofore tried, slows down the operation, and requires additional labor. The extra labor adds to the cost of providing housing and maintaining the laborers.

As a result of such economic factors the mining of coal in Alaska has not been conducted on a large scale, notwithstanding the tremendous deposits. Such considerations have given rise to the present invention. With it, the mining under such conditions can be carried out with a very minimum of labor, the tilt of the coal beds is no deterrent, but is in fact converted into a favorable factor, there need be no timbering of mine shafts and tunnels, the percentage of recovery is as high or higher than in other known methods other than stripmining (which in Alaska is impractical because of the heavy overburden, and climatic considerations), and the operation can be effected the year round by a machine of comparatively small cost in relation to the value of the coal mined, of great ruggedness and simplicity, and which is capable of operating at high efficiency.

In general, the machine of the present invention includes an outer shell, which is nonrotative and which advances into a bore as the breaking away of the working face progresses, this breaking away of the working face being accomplished in general by the coaction of an outer collar journaled at the forward end (in the direction of advance) of the nonrotative shell, and an inner collar also at the forward end, journaled within and spaced from the outer collar, but rotative difierentially-usually and preferably in the opposite rotative sense'-together with means for conveying the broken-oflf coal to the rear of the machine where it can be conveyed or chuted to a collecting point or vehicle, and supplemented-wherever necessary by face cutters radially disposed between the two collars and rotating as they revolve with one or the other of such collars, to break away the face material intervening between the collars. Such a machine may be operated by an operator stationed within the annular space between the inner and outer shells, protected by the outer shell from falling debris, and shielded against dust by proper seals at the journal points, whereby a single operator may operateand con- 2,756,037 Patented July 24, 1956 trol the machine, or the operator may, in proper cases, be dispensed with and the machine may be controlled by a remotely-stationed operator. Since the bore is cylindrical, it forms its own roof and floor fillets, and requires no timbering.

By appropriate changes in size and arrangement, the principles of the machine may be adapted to the obtaining of core samples, and such a coring machine would, of course, be of relatively small size and remotely controlled.

Such a machine may be advanced by traction means which are carried by the shell and which engage the bore walls, so that the shell may be advanced positively and with great force, and will advance as readily uphill as on a level, or downhill. Moreover, it is adapted for transportation from one bore to a point of beginning of the next bore, by a transport shell, which in effect constitutes an extension of the bore which is about to be commenced.

The machine is so assembled that it can be disassembled with reasonable ease, even when at the end of a bore, should there be a need to do so.

It is believed that the objects of the invention and the principles which distinguish it may be readily ascertained from the above. More particularly, the invention comprises those features and those combinations of struc ture which are shown in the accompanying drawings in representative forms, and which will be more fully explained hereinafter and defined in the claims.

Figure l is an axial sectional view of the machine, shown within a bore and in process of removing material .from the working face; certain parts have been broken looking towards its forward end.

Figure 4 is a diagrammatic view, illustrating the manner in which a new bore is started in a typical tilted formation.

Figure 5 is an exploded isometric view of the machine, for comparison with Figure 3, showing how certain major subassemblies may be disassembled.

Figure 6 is a partial forward end view, and Figure 7 is a fragmentary axial section through the forward end, showing the addition of face cutters which may be used when required.

Figure 8 is a fragmentary axial sectional view through the machine along the line 8-8 of Figure 2, illustrating a torque-resisting keying means optionally usable.

Figure 9 is an axial sectional view of a core-sampling machine which employs the principles of this invention.

The outer shell 1 is generally cylindrical and can be formed of metal plates, reinforced at points of greatest stress. It is open at both ends. Such a shell is conveniently supported and advanced into a bore B of approximately the same size by means of traction devices, such as the crawler tracks 2, distributed angularly about the shell and each protruding through a longitudinally disposed slot therein. Each crawler track 2 is carried on a driven front roller 20 and a rear roller 21, and is supported as needed by intermediate rollers 22, the whole being mounted preferably upon the immediate frame 24. This frame 24 is supported by struts 27' from a generally U-shaped trough or frame, indicated at 23, which is itself fixed secured to the shell 1 by securing means 26. Preferably, the forward struts 27' intermediate the frame 24 and the fixed frame 23 are adjustable by means such as the screw devices indicated at 25, so that the crawler track, and particularly its driven front rollers 20, can be forced hard against the bore within which the shell 1 is entered. At the rear end spring means, indicated at 27, may be interposed between the struts 27' and fixed frame 23, for urging the crawler track 2 outwardly against the bore wall and for holding it in contact with the latter.

It is desired to emphasize that the traction means 2 are not steering means, but the direction in which the device is advanced can be altered gradually by means which will be described later.

At the forward end of the shell 1 is journaled an outer collar 3, which is of the same or slightly larger diameter than the shell 1. Thrust bearings are indicated at 31 and a retainer ring 39 within the forward end of the, outer shell 1 but fixed upon the collar 3, or a rearward extension thereof, retains the collar in place. A seal 32 is preferably provided to exclude coal particles and dust from the space within the outer shell 1. The forward edge of the rotative collar 3 is provided with cutting teeth 33 and 33' or with equivalent devices for cuttinginto the working face,

Coaxially disposed within and fixedly supported from the outer shell 1 is an inner shell or duct 4, spaced from the outer shellto provide a rather appreciable annular space between the two shells. This duct 4 is provided with what is in effect an integral forward extension 40, and upon this extension 40, or in effect upon the forward end of the duct 4, is journaled a rotative inner collar 5. This collar, like the outer collar 3, is provided at its forward edge with teeth 50 and 50', or other means to cut into the working face and to break it away. Preferably, the forward end of the inner collar 5 and of the duct 4, or its extension 40,,are all left open for entrance of material, but in addition the extension 40 inwardly, or to the rear of the inner collar 5,is apertured at 49, for entrance of material from the space between the inner and outer collars.

The outer collar 3 is provided with a rearwardly directed generally conical extension or terminus 34, the rear end of which closely embraces the rear portion of the duct extension 40,to the rear of the aperture 49, and is journaled thereon as indicated at 35 (Figure l), and here again a seal 36 serves to prevent or at least minimize entrance of coal particles or dust into the annular space between the shells 1 and 4. In addition, the conical terminus 34 is provided interiorly with lifting vanes 37 which, as the outer collar 3 rotates, will elevate material broken off and falling into the space between the collars, and will deposit that material through the aperture 49 into the interior of the duct 4, or its extension 40.

Interiorly of the inner duct 4 a screw conveyor 6, or the like, may be provided, carried upon a rotative shaft 60,

so pitched and directed as to convey material deposited withln the duct 4, or its extension 40, to the rear of the machine. The shaft 6, together with a forward extension 66, is journaled from the inner duct 4, as indicated at 61 and 62, and the shaft is driven by a sprocket gear 63, which is keyed to the shaft 69, or to a connecting section 64 thereof which joins the shaft 6t) and the forward extension 66 thereof. The sprocket gear 63 extends radially outwardly beyond the inner duct 4, between the latter and its forward extension 40, and these elements 4 and 40 are appropriately connected by bridging elements 43,.

which house in the sprocket gear 63.

A large bull gear 38 is carried upon the collar 3 or upon The two collars are driven from. a motor 9, which may,

be an electric or an air motor, and through gearing 90 to drive a sprocket chain 69, and so to drive the sprocket wheel 63 and the inner collar 5, and to drive a pinion 39 l in mesh with the bull gear 38, and so to drive the latter and the outer collar 3. With the arrangement described, the outer collar 3 will be rotated in a given rotativesense and the innercollar 5 will be rotated in the opposite rota-1 l 4 tive sense. With proper choice of the size of the gears employed, the peripheral speed of each collar or its cutting edge may be made identical with that of the other collar, or approximately so, and when this is done the two collars will advance into the working face of the coal seam at approximately the same speed of advance. It is the differential rotation of the collars that breaks up the coal between them, but the counterrotation of the collars, which is the preferred type of differential rotation, cqualizes the torque as between them, and relieves the traction means 2 of appreciable torque stresses.-

The coal seams in which this mining machine is designed to operate are quite generally uniform in thickness and in direction. However, for gradually changing the direction of advance, whenever that is necessary, there are provided direction-controlling elements such as the wheels 7, journaled in short levers 70, pivotally mounted at 71 at the rear end of the outer shell 1, and distributed angularly thereabout. Preferably, there are four such rollers 7, distributed at intervals, and each is secured by such means as the turnbuckle device 72 in a fixed position, but a position which is subject to change. lengthening the lower turnbuckle element 72 and shortening the upper one, the rear end of the shell 1 may be tilted upwardly and it will then advance in a generally, but only slightly, downward direction. By similarly relatively adjusting the two lateral rollers 7, the machine may be tilted to advance to one side or to the other from its general previous direction of advance.

In the large machine, which may be, for instance, eight feet in diameter, an operator may sit upon a seat S within the space between the inner shell 4 and the outer shell 1, in a position where he can control the motor 9 for rotating the two collars and where he can also control the motors 91, which drive the several traction devices 2. Thus located, the operator is thoroughly protected by the shell 1 against falling material, and even in r the event of a cave-in behind him he is reasonably well protected, and there are hoses leading, to him for supply of air and the like, and an electric line for delivery of power. It has been found that the bore, being cylindrical in Shape, requires no timbering, and that the mine roof can be wholly supported, during the entire time that coal is being mined, by the pillar walls intermediate adjoining bores. By successive bores, close together or interconnecting throughout the height of the seam, a very high percentage of the available coal can be removed.

the pillars and the rounding fillets at top and bottom of the bore roof and floor being the only coal not readily recoverable.

It is intended to operate by advancing a tunnel Tor shaft alongthe lower edge of the mine area, large enough to permit the turning of the machine transversely, even though this tunnel or shaft may have to be timbered. The machine is then transported into this tunnel T within a transport shell A, and at the spot chosen for the start of a new bore B or drift the machine, reacting fronrthe transport shell, is advanced against the working face-of coal, and'bores its way into the same, advancing along the same angle as the angle of slope of the seam, all as is illustrated in Figure 4. When it has advanced clear of the transport shell A, the latter may be removed. Thereafter, all coal which is delivered at the rear end of the machine by the feed screw 6 may be received upon a conveyor, or within a chute, according to the slope, and

so transported or chuted into the main tunnel, where it.

can be received in mine cars or upon a master conveyor C, and so conveyed out of the mine.

There may be times or locations where the material.

doesnot break otf readily intermediate the teeth33, 33',

and 50, 50, or if it does break off, breaks off in chunks' which-aretoo large to handle readily. To fit such a situation, face cutters, preferably in the form of radially disposed and generally slightly conical rollers 8 ands80, are provided. These are best arranged in pairs, angularly For instance, by

disposed about the forward end of the machine, and provided over their peripheral surfaces with cutters 81. The

roller 8 may be carried on a shaft 83 journaled at 82 in a ring 58 which is loose and interposed between the inner collar 5 and the extension 40, and the outer end of the shaft 83 is journaled at 84 at the inner side of the rotative outer collar 3. At the inner end of the shaft 83 is provided with a gear 85 which meshes with a gear 69 upon the shaft extension 66.

As the outer collar 3 revolves, it of necessity efiects' bodily revolution of the roller 8, and since the paired roller 80 is similarly journaled but is gear-connected at 86 to the shaft 83, the pairs of rollers 8 and 80 revolve with the outer collar 3, carrying with them the loose collar 58. At the same time, because of the intermeshing of the gears 85 and 69, the shaft 83 is rotated, and the rollers 8 and 80 through their interconnection at 86 are rotated in relatively opposite senses, preferably toward one another. ers 8 and 80 revolve bodily with the collar 3 and each individually rotates relatively to the paired roller while they revolve. Thus revolved and rotated they serve to break off the working face of the seam, and to break up any chunks until they are small enough to handle. The size of the chunks can, in a measure, be regulated by the spacing between the face cutter rollers 8 and 80.

As has been stated, the counterrotation of the inner and outer collars relative to one another serves to equalize the torque on the shell 1, but in order to insure against the shells rotation, and to relieve the crawler tracks 2 of torque-induced stresses in the highest possible degree, the keying means of Figure 8 may be employed. A key cutter 100 is carried by a shaft 101 which is generally radially disposed, but directed somewhat laterally and downwardly (see Figure 2) to cut into the fillet portion of the coal seam. The shaft 101 is journaled in the shell 1, and carries gear means, such as the pin gear 102 which meshes with the bull gear 38, whereby to rotate the cutter 100. An air jet 103, acting within the housing 104, or any equivalent means, serves to elevate the cut-away coal and to deliver it, through a duct 105, into the inner duct 4.

A key 106, adjustably mounted in a subframe 107 for radial projection or retraction relative to the shell 1, can follow in the keyway K which the cutter 100 cuts, and by its engagement therein serves to absorb most of the unbalanced torque stresses. It will be understood that the cutter 100 as well as the key 106 may be retractable, and so will not require power when conditions permit its non-use.

Alternatively, it may be desired to utilize the principles of the mining machine described above for core sampling. In such case, as shown in Figure 9, the outer shell and the inner shell are greatly reduced in size and are made more nearly of the same size. the axial shaft is made hollow to receive the core sample, and so is enlarged, say to three inches in diameter. The inner shell, while reduced in actual diameter, is still larger in relation to the greatly reduced outer shell (which may be some eight inches in diameter, for example). The small clearance between the inner and outer shells requires some revision of drive arrangements. It will suffice topoint out those features wherein the coring machine of Figure 9 differs from the larger size mining machine already described.

The outer shell 1 and the inner shell 4 are provided with their respective collars 3' and 5'. In order that these may rotate oppositely'a motor 9' drives the'inner shell 4' by a direct gear connection at 90', 63, and the gear 90' also drives a countershaft 93, which at 94 carries a pinion that meshes with the bull gear 38'. The bull gear in turn drives pinions 95, which through clutch means at 96 of a type which can yield upon encountering excessive resistance (as a hydraulic torque converter), drive the several traction means 2.

The final result is that the face cutter roll- 9 In addition,

The helical screw conveyor 6, as before, is fixed to the shaft 60, but the latter is now hollow and integral its entire length. At its forward edge are mounted cutting diamonds 69' or the like, for cutting a core which exits through the hollow shaft.

Such a core sampling machine operates by remote control, and the larger mining machine may be similarly operated and controlled.

The machine has been shown and described in certain specific forms, not for purposes of limitation to such specific forms, but by way of example. It will be understood that the machine and its several components may take other forms, and still come within the principles of this invention, as defined in the claims. Also, while its use in mining coal, and under the conditions prevailing in Alaska, has been stressed, obviously it can be used for the mining of any mineral deposits found in seams or thick beds, and anywhere in the world. The references to Alaska coal mining are not to be taken as limiting, but as indicative of a place and type of mining for which the machine is eminently suited, and in Which the problems involved gave rise to this invention.

I claim as my invention:

1. A mining machine comprising a generally cylindrical outer shell, traction means carried thereby and protruding therefrom for engagement with a bore wall to advance the shell axially into such bore, an inner duct axially disposed within and spaced from the outer shell, an outer collar journaled at the forward end of the outer shell and an inner collar journaled at the forward end of the inner duct, each collar at its forward edge being formed for cutting into the bores working face, means to rotate the collars in relatively opposite rotative senses to-detach material from the working face as the shell is advanced into the bore, and the inner duct being open at its forward end to receive material through the inner collar, and constituting a duct for conveyance thereof to the rear end of the machine.

2. A mining machine comprising a generally cylindrical shell, traction means carried thereby and protruding therefrom at angularly spaced locations for engagement with a bore wall to advance the shell axially into such bore, an inner duct axially disposed within and spaced from the outer shell, an outer collar journaled at the forward end of the outer shell, formed at its forward edge for cutting, and at its rear end formed conically toterminate at the inner duct, a bull gear carried externally of said conical terminus, but within the outer shell, a rotative shaft located and journaled within said inner duct, a

sprocket gear mounted upon said shaft and extending raby in a given rotative sense, said inner collar being formed.

at its forward edge for cutting, and drive means Within the space between the inner duct and the outer shell, to

the rear of the collars, and operatively connected to said bull gear and to said sprocket gear to rotate the same, in opposite rotative senses.

3. A mining machine as in claim 2, including a feed screw within said inner duct and its forward extension,

and connected for rotation with the shaft, to convey materials entering the duct to the rear.

4. A mining machine as in claim 2, including generally radially disposed vanes carried interiorly of the outer collars conical terminus, to lift broken-off material andto deposit the same, through the inner ducts aperture, within the inner duct for delivery at the rear of the machine.

5. A mining machine as in claim 2, including a plurality of angularly distributed pairs of generally radially disposed and generally conical face cutter rollers, a loose collar interposed between the inner collar and the inner duet; wherein said rolle'rsare journale'd, heating means for saidrollerscarried by and rotative-with the outer collar,-= antl me'ans operatively interen gaging the inner ends of saidrollers with the shaftto rotate the rollers as they're volve with the outer collars, said rollers being formed ontheirperipheralsurfaces for cutting.

65A mining machine comprising a generally cylindrical shell, an inner duct supported fromand' coaxially of said shell, an outer collar rotatively mounted upon and as a continuation of the shells forward end, and formed for cutting at its forward edge and outwardly thereof suf' ficientlyfoi' working clearance, material collecting and elevating means carried by and rotative with-said outer collar, at its-inner end, the inner duct having an aperture adjacent its fo'rward-endlocated to receive material detachedby the outer collar s cuttingedg'e and collected and elevated by said-collecting and elevating means, an inner collan also formed for cutting about its forward edge, and rotatively mounted upon-and as a continuation of the forward end of said inner duct, and openthrough for direct admission to the inner duct of material detached by and entering through said inner collar, to-join the material dii ected crawler tracks mounted within but protruding from the outer shell to engage the bore wall, and angularlyspaced about the axis of the outer shell to support the latter generally centralized within the clearance space, and means to drive said crawler tracks for advance of the shell.

8. Amining machine as in claim 6, including cutting means projecting radially of the outer shell to cut a key way into the bore wall as the shell advances, and a key separate from said cutting means, carried by the shell and projecting therefrom, andextending longitudinally in position to engage in said keyway and to resist torque forces tending to rotate the shell.

9.'A mining machine as in claim 8, including means operatively connected to each of the keyway cutter and the key, and operable to retract the same at will.

10. A mining machine as in claim 7, including means to force the crawler tracks outwardly from the shell into firtn 'engagement with the bore wall, regardless of variations in-the clearance.

11'. vA miningmachineas in claim 7, including positive- 1y -acting'means at the forward end of the crawler tracks to force the latter outwardly-from the hull by a distance approximating the clearance space, for engagement with the bore wall, and means resiliently urging outwardly the rearend of the crawler tracks, the drive for the crawler F traeksbeing operatively connected to the front end thereof.

12. A mining machine as in claim 6, including a rearwardly directed conical extension formed upon the outer collar, and joined thereto about acircle intermediate its forward cutting edge and its rear rotative mount upon the outeushell, andjournaled about the inner duct to the rear of the latters aperture, to seal off the material collecting 14.4: A miningmachine-as in claim 6, wherein the collarrotating means is organizedand arranged, in relation'to the"relativesizesof the/cutting edgesof the outer and inner collars,-to rotate each such collar and its cutting edgeatsubstantially the same lineal speed.

l5 A'mining machine comprising a generally cylindri-- cal shell capable of advance into a bore being cut, an inner'duct-supported from and coaxially-of said shell, and apertured to the rear of its forward end, an outer collar rotatively mounted upon and as a continuation of the shells forward end, and formed for cutting at its forward edge, material collecting and elevating means carried by and rotative with said outer collar, inwardly of its forward end, to deposit material within said inner duct,

' throughthe latters aperture, an inner collar journaled upon the forward end of said inner duct, ahead of its aperture, and open to the inner duct for passage of material, the forward edgeof said inner collar being also formed for cutting, a screw conveyor within the inner duct for moving materials rearwardly therein, formed with an axially directedshaft; and drive means for the outer collar with its material collecting and elevating means, for the inner collar, and for the screw conveyor, comprising ,a driven Wheel on the screw conveyor shaft, to the rear of the inner ducts aperture, the inner duct beingdivided for protrusion of said driven wheel, bridging elements joiningthe divided parts of the inner duct and substantially, housing said driven wheel, the screw conveyor shaft extending forwardly and directly connected to the.inner collar to drive the latter, a drive gear upon said .outer collar, to the rear ofthe material collecting and .elevating ,means, and means located intermediate the outer shelll and the inner duct, and 'operatively connected to,each.,of..said drive gear and said driven wheel to rotate themnand their respective collars, in opposite rotative senses.-

16.. Aminingmachine comprising a generally cylindrical shell, for, advance axially into a here being cut, an outericollervformed for cutting, at its forward edge and rotativelygmounted upon the forward end of .said shell, an inner collar also formed for cutting at its forward edge and rotatively supported from the shell within said outercollar, drive means operatively connected to said collars -to revolve the same coincidentally but differentially, radially disposed facecutters distributed about the annular;space;between the inner and outer collars and their cutting; edges,,,and mounted.in oneof the-collars toqrevolve:therewith,.each face cutter being formed as a body of revolution about its general radial axis and with cutting bits distributedlengthwise, and means to rotate each face .eutter about its aXis while it revolves bodily with its mounting ,collar.

17. A .mining;.machine as in claim 16, wherein .the face cutters are arranged in pairs, and their rotating means are arranged. tovrotateuthe cuttersof each pair in .rela' tively opposite rotative senses.

References, Cited in the fileof this patent UNITED STATES PATENTS 1,043,185 Wittich Nov. 5, 1912 1,326,480 Dana Dec. 30, 1919 1,511,957 Freda Oct. 14, 1924 1,639,215 De Grassi Aug. 16, 1927 1,645,007 Johansen Oct. 11, 1927 1,653,111 Lobbey Dec. 20, 1927 2,669,441 Castanoli Feb. 16, 1954

Claims (1)

1. A MINING MACHINE COMPRISING A GENERALLY CYLINDRICAL OUTER SHELL, TRACTION MEAND CARRIER THEREBY AND PROTRUDING THEREFROM FOR ENGAGEMENT WITH A BORE WALL TO ADVANCE THE SHELL AXIALLY INTO SUCH BORE, AN INNER DUCT EXIALLY DISPOSED WITHIN AND SPACED FROM THE OUTER SHELL, AN OUTER COLLAR JOURNALED AT THE FORWARD END OF THE OUTER SHELL AND AN INNER COLLAR AT ITS FORWARD EDGE BEING FORMED THE INNER DUCT, EACH COLLAR AT ITS FORWARD EDGE BEING FORMED FOR CUTTING INTO THE BORE''S WORKING FACE, MEANS TO ROTATE THE COLLARS IN RELATIVELY OPPOSITE ROTATIVE SENSE TO DETACH MATERIAL FROM THE WORKING FACE AS THE SHELL IS ADVANCED INTO THE BORE, AND THE INNER DUCT BEING OPEN AT ITS FORWARD END TO RECEIVE MATERIAL THROUGH THE INNER COLLAR, AND CONSTITUTING A DUCT FOR CONVEYANCE THEREOF TO THE REAR END OF THE MACHINE.

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