US1812719A - Drilling mechanism - Google Patents

Description

June 30, 1931. R, E SCHRQDER 1,812,719

DRILLING MECHANI SM Filed Oct. 19, 1928 4 Sheets-Sheet 1 R. E. scHRoDl-:R

DRI LLING MECHANI SM Filed oct.

June 30, 1931.

19, 1928 4 Sheets-Sheet 2 `lune 3(1), 1931.

R. E. scHRoDER DRILLING MECHANISM 4 sheets-sheet 3 Filed Oct. 19, 1928 4, geen! 'Hi June 3o, 1931. R, E, SCHRODER 1,812,719

vDRILLING MECHANISM Filed Oct. 19, 1928 4 Sheets-Sheet 4 11| IIIIILI l (gmini "l,

Patented June 30, 1931 UNITED STATES PATENT OFFICE ROBERT E. SCHRODER, OF CHICAGO, ILLINOIS, ASSIGNOR TO GOODMAN )BILANULEAC'IUR IN'G- COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS DRILL'NG viszrnescelrvrslrr Application filed October 19, 1928. Serial No. 313,445.

My invention relates to a new and novel means for drilling holes of a large diameter in coal or other analogous substances and has for its principal object to provide a machine for making breakthroughs in mines having a new and improved drilling or cutting means with a cuttings expulsion means incorporated therewith. Other objects of my invention will appear from time to time in the following specification.

Heretofore breakthroughs have been driven by hand to permit ventilation of the working places in the mine. This is an expensive operation requiring a good deal of hand labor, and requiring the use of an undercutting mining machine t-o make the cutting operation, and furthermore cutting' away more coal than is required for adequate ventilation,

The device embodied in my invention will quickly and efficiently cut breakthroughs at a minimum cost and remove enough material to provide ample ventilation for the working face and provide an opening of large enough diameter to receive a man and to allow said man to escape through said breakthrough .in cas-es of necessity, as an explosion or cave in.

My invention may best be understood by reference to the accompanying drawings, wherein;

Figure 1 is a top plan view of the device embodied in my invention;

Figure 2 is a side elevation of the device shown in Figure 1 with parts broken away and in section to more clearly show the details of my invention;

Figure 3 is a fragmentary front end view of the device shown in Figure 1 with the drilling element in a different position than is shown in VFigure 1, with parts in section to more clearly show the details of. construction thereof; i

Figure is a fragmentary sectional view showinga means for raising and lowering the drillingmeans embodying my invention;

Figure 5 is an enlarged fragmentary sectional view showing the details of construction of the drilling vmechanism embodying my invention;

Figure 6 is a sectional view of the cuttings propelling mechanism taken on line 6 6 of Figure 5;

Figure 7 is a fragmentary enlarged end lView of the device shown in Figure 1 showing the details of the gearing mechanism for rotating 'and feeding the drilling mechanism;

Figure 8 is an enlarged fragmentary to view of the device shown in Figure 1 with parts shown in section to more clearly show the details of the gearing mechanism for rotating and feeding the drilling mechanism; Figure 9 is an enlarged fragmentary sectional view taken on line 9 9 of Figure 2;

Figure 10 is an enlarged fragmentary sectional view taken on line 10-10 of Figure 2;

Figure 11 is a fragmentary sectional View showing an extension to the drilling arm Figure 12 is an end elevation of the. drilling mechanism embodied in my invention driving a breakthrough in a mine wall;

Figure 13 is an end elevation of the drilling mechanism embodied in my invention driving a breakthrough in a mine wall with the extension shown in F igure 11 added thereto;

Figure 111 is an end elevation of the drilling mechanism embodied in my invention driving a breakthrough in a mine wall with the drilling mechanism further advanced in said mine wall `than is shown 1u Figures 12 and 13; and

Figure 15 is a sectional view taken on line 12-12 of Figure 5.

Like numerals refer to like parts throughout the various figures.

Referring now to the drawings, I have shown a drilling mechanism generally indicated at 1 supported on a portable power truck 2 which comprises a truck frame 3 supported on axles 4 and track wheels 5, 5. Suitable power means are provided en said truck to drive the drilling mechanism 'and to drive said truck from working place to working place which may be of any form. but which is herein indicated as an electric motor 6. Y

The drilling mechanismv 1 is supported and journaled on a supporting frame 7 freely mounted for either rotatable or vertical move ifi is moved about the cylinder 8 by hand and is vertically adjustable thereon by means of a manually operable self-locking screw mechanism. Said screw mechanism herein comprises a. shaft 10 threaded in the lower end of the supporting frame 7 having a head 11 at its lower end abutting the underside of a fiange 12 of a sleeve-13 mounted on the cylinder 8 beneath the supporting frame 7 Ior rotatable movement thereabout, and having a bevel pinion 15 feathered to its upper end driven by a bevel pinion 16 on a shaft 17 which may be driven by a hand crank (not shown) detachably connected with a squared end 19 of the shaft 17. A collar 1.4 is threaded to the lower portion of the sleeve 13 to prevent vertical movement thereof. It may thus be seen that rotation of the threaded shaft 10 causes vertical movement of the supporting frame 7 to adjust the drilling meehanisrr 1 for drilling at various heights in thc niine wall.

'lne drilling mechanism 1 comprises in general a drilling arm 2O carrying suitable drilling and cutting mechanism at its forward end which will hereinafter be more fully described. Said drilling arm is connected to a movable carriage 21 at its rearward end and is movable with said carriage. and is joui'- naled for translational and rotational movement in a portion of the supportingr frame 7 near its forward end. An auxiliary i'novable support 23 is detachably connectible with the forward portion of the drilling arm 2O to support said drilling arm as it is being fed into the material to be drilled. A plurality of rotatable cutting elements project outward from the drilling arm 2O and are inclined towards the rearward portion of said drilling arm so that the cutting elements adjacent the central portion of said drilling arm engage the material to be cut ahead of the cutters more distant from the center of said drilling arm. Said cutting elements are also rotatable about their axis of inclination at a speed, greater than they speed of rotation of the drilling arm 20. A pilot drill 26 is provided on the extreme forward portion of the drilling arm 2O and is rotated by means of a, shaft 27 journaled within said drilling arm at a. speed higher than the speed of rotation of the drilling arm and in a direction of rotation opposite to that of the drilling arm 20.

The carriage 21 is slidably mounted on supporting and guiding bars 28 and 29 interposed between a portion 30 and the portion 22 of the supporting frame 7, and drive shafts 31 and 32 journaled in the portions 30 and 22 of the supporting frame 7 so that movement of the carriage 21 will cause movement of the drilling arm 2O to provide a means for feeding said drilling arm into the material to be drilled. A threaded shaft 33 is threaded through a portion 34 of the car` riage 2l and is journaled in the portions 30 and 22 of the supportingr frame 7 so that rotation of said shaft in one direction or the other causes movement of the carriage 21 along the supporting and guiding bars 28 and 29. Said threaded shaft is 'driven from the motor 6 by a suitable train of reduction gears which will hereinafter more fully be described.

The drilling arm 20 is made up of a rearward section 40 and a forward section 4l. Said sections are detachably connectible with each other so that an intermediate section 42 having a means to clear the cuttings from the hole being drilled generally indicated at 43 thereon may be interposed between the sections 40 and 4l or so that an extension section 45 may be inserted in said drilling arm to increase the length of said arm when desired. The drilling arm 20 is rotated by a gear 46 keyed to a rearward portion 47 of the rearward section 40 of the drilling arm 20. The rearward portion 47 of the section 40 is journaled within the carriage 21 and drives the section 40 of the drilling arm 20 from the motor 6 in a clockwise direction with reference to the face of the coal through a suitable gear train which will hereinafter be described.

The drive shaft 27 is journaled within the section 40 of the drilling arm 20. A gear 49 is keyed to the rearward end of said shaft and is connected with the motor 6 through a suitable system of reduction gearing for driving said shaft in a counter clockwise direction or in a direction opposite to the direction of rotation of the drilling arm 2O while a squared socket 50 is provided on the forward end of said shaft. The squared socket 50 is adaptable to receive the squared end of a shaftto provide a means for driving the pilot drill 2G when the length of the drilling arm 2O is extended beyond the normal length. As herein shown the sijua red end of a shaft 53 journaled within the section 4l may be inserted in the socket 50 to drive the pilotdrill 2G or a shaft 54 journaled within the section 42 carrying the cuttings expulsion means 43 may be interposed het ween the shafts 27 and 53 to provide a means for expeiling the cuttings from the drill hole and driving the pilot drill 2G at the same time, or still further a shaft 57 journaled within the extension section 45 may be interposed between the shafts 27 and 54 or 27 and 53 so that the pilot drill 26 may be rotated at various lengths of the drilling arm 20. It may be understood with reference to the drawings .that the shafts 53, 54 and 577 have a squared end on one end and a squared socket on the opposite end so that one shaft may always drive the next adjacent shaft.

The pilot drill 26 may be of any Well known type, but is herein shown as a fish tail type drill detachably connected to the end of a shaft by means of a suitable nut and bolt as indicated at 61. The shaft 60 is journaled within an end iece 62 held on the end of the section 41 of) the drilling arm 20 by any suitable means such as nuts and boltsv (not herein shown). Said shaft has a groove 63 therein adaptable to receive the end of a set screw 64 to prevent longitudinal movement of said shaft in the end piece 62. A s uared end 65 is provided on the shaft 60 to n t in a squared socket on the forward end of the shaft 53 to provide a means for drivingsaid shaft from the shaft 53.

A bevel pinion 66 is provided on the shaft 53 which meshes with and drives a bevel pinion 67 keyed on a shaft 68 and journ'aled within a portion 69 of the section 41 of the drilling arm 20. The shaft 68 has a cutter holding member keyed thereon which is journaled on the portion 69 of the section 41 of the drilling arm 20. The cutter holding member 70 has a plurality of cutters 72, 72, thereon which may be detachably held thereto by any suitable means, said means being herein shown as nuts and bolts 73. The cut-- ters 72 extend the entire length of the cutter holding member 70 and have a plurality of V shaped teeth thereon. Said cutters are inclined towards the direction of rotation of the cutter holding element 70 and are so arranged' that the teeth of each respective cutter are in staggered relation with respect to each other to prevent gering of the material being cut.

It may now be seen that the drilling arm 2() is rotated at one speed in one direction by means of the gear 46 which in turnrotates the cutters 72 about a horizontal axis.v It may also be seen that said cutters are simultaneously rotated about the axis of the shafts G8 through the bevel pinions 66 and 67 and the shaftr53 at a higher speed than the speed of rotation of the drilling arm 2O and in a clockwise direction or in the same relative direction as the direction of rotation of the drilling arm 2() so that the cutters 72 will cut in to the material to be cu't and not roll along the face of said material as would result if said cutters were rotating in the opposite direction. and that the pilot drill 26` is also rotated by means of the gear 49 and shaft 27 at a higher speed than the speedof rotation of said drilling arm in an opposite dip Arection to the direction of rotation of said drilling arm. This provides a drilling apparatus having a pilot drill rotating at a relatively high speed and cutters inclined rearwardly from the pilot drill 26 and rotating about the axis of said pilot drill ata speed' slower than the speed of rotation of said pilot drill to allow for the difference in circumferential speed between the outermost teeth of the cutters 72, and the pilot 'said drive shaft.

drill 26 and also rotatin about their axis of inclinatlon so that eaci cutter may independently perform its cutting operation as i said cutters are rotated about allorizontalaxis by means of the drilling ar1n2() Vand propel the cuttings away from the next following cutter.

The cuttings expulsion means 43 on the section 42 of the'drilling arm 2,0 comprises a plurality of propellers 75 rotating with the drilling arm 2() and also rotating about an axis perpeinlicula'r to ,the axis of rotation 0f the drilling arm 20 to clear the drill hole from allcuttings expelled by the cutters 72, 72. One propeller 75 is mounted on one side of the section 42 oi the drilling arm 2O and to one side of the shaft 54 journaled in said section While another propeller75 is mounted on the opposite side of said section and on theopposite side of the shaft 54. The pros pellers 75 are keyed on the ends of shafts 76 journaledin the section 42 of the drilling arm 20. Worin gears 77 are keyed to each of said shafts and are housed within the section 42 of the drilling arm 2() and are rotated by a worm 78 keyed to the shaftl 54 (see Figures :i and t5) providing a. means forpropclling the. cuttings from the drill hole to prevent said cuttings from clogging the cutters 72 while said cutters are drilling said hole.

Referring now to the means for driving and feeding the drilling mechanism l, thc motor 6 is provided with a skew bevel pinion 80 which drives a skew bevel gear 81 rotatable on the support 9 fOr the cylinder 8. A. hub 82 is provided on the skew bevel gear SU and has a spur gear 83 integral therewith which drives a spur pinion 84 on a vertical.

shaft 'lhevertical shaft has a bevel pinion 8G feathered thereon so said bevel pinion may be driven by said sha ft at the various elevations of the drilling mechanism 1.

The bevel pinion 86 meshes with a bevel pinion 87 on one end of a horizontal shaft 88 to drive said shaft. lhe horizontal shaft 88 is journaled on the `supporting frame 7 and has a spur gear 89 keyed to its opposite end which drives a spur gear 90 keyed on the drive shaft 3l. The spur gear 90 drives a spur gear 91 on the drive shaft 32 and rotates A spur gear 92 is keyed on the drive shaft 32 and meshes with and drives aV spurgear 93 freely mounted on the threadyed shaft 33. Clutch jaws 94 are provided withdrawthe drilling VAarm 20vfrom the com# I i pleted drill'hole at a relatively high rate of speed. 'A spur pi-nion 97 is keyed on the out er end of the shaft 32 and meshes with and drives a spur gear 98 freely mounted on the threaded shaft 33. Friction clutch means generally indicated at 99 are herein provided f providing a means to move the carriage 21 forwardly on the supporting and guiding bars 28 and 29 to feed the drilling arm 20 into the material to be drilled. Said friction clutch means may be of any suitable type but is herein shown as a cone clutch of an ordinar construction having one face 100 integralwith the spur gear 98 and another face 101 engageable with the face 100 integral with the clutch member 96 so that the threaded shaft 33 may be driven by either the gear 93 or 97 through the same clutch operating means, and so that it is only possible to connect the gear 98 to the threaded shaft 33 when the gear 93 is disconnected from said shaft and vice-versa.

The clutch member 96 is operated by a hand wheel 102, through a suitable system of levers of the usual type.

The shaft 31 has a keyway 103 extending between the portions and 30 of the supporting frame 7. A spur pinion 104 is feathered on the shaft 31 and has a hub 105 thereon journaled within a portion of the movable carriage 2l. A collar 106 is provided on the opposite end of the hub 105 from the spur pinion 104 to abutthe portion of the movable carriage 21 so that the pinion 104 may be movable with the movable carriage 21. Said spur pinion meshes with and drives the gear 4G keyed to the rearward portion 47 of the rearward section 40 of the drilling arm 20 to drive said drilling arm. Similarly the shaft 32 has a. keyway 107 extending between the portions 22 and 30 of the supporting frame 7 and has a spur pinion 108 feathered thereon. The Spui' pinion 108 has a hub 109 thereon which is ournaled within a portion of the movable carriage 21 and has a collar 110 abutting said movable carriage so said spur pinion may move with the movable carriage 21. The pinion 108 meshes with and drives the spur gear 49 keyed to the drive shaft 27 to drive said drive shaft and the pilot drill 26 at a higher speed and in an opposite direction to the direction of rotation of the drilling arm 20.

The truck 2 may be driven b y any suitable means to move the drilling mechanism about the mine.

As herein shown said truck is driven by a bevel armature pinion 115 on the rearward end of the armature shaft 79 of the motor 6 which meshes with bevel gears 116 and 117 freely mounted on a transverse shaft 118. Friction clutch mea-ns 119 and 120 are provided to connect either of the beveled gears 116 or 117 with the shaft 118 so said shaft may be driven in opposite directions by either one of said bevel gears. Drive chains 121 are provided to operatively connect the sha-ft 118 with the track wheels 5, 5, to drive said track wheels and thus drive the truck 2 in either a forward or rearward direction.

The auxiliary movable support 23 com-l prises a journal box 123 having a removable cap piece 124 held thereto by means of cap screws or any other suitable holding means.

, The drilling arm 20 is adaptable to be journaled in said journalbox when said drilling arm is in a drilling position transverse of the truck frame 3 and has a collar 125 held thereon by means of set screws 126 so it may bear against the rearward end of the journal box 123 to move said journal box along with said drilling arm as said drilling arm is being fed into the material to be cut. The journal box 123 is supported on guide rails 127, 127, extending transversely of the truck frame 3 near the forward end thereof which are. slidable in guides 128 in the truck frame 3, by means of upright rods 129 fixed in the journal box 123 and held in aframe member 130 fixed to the guide rails 127. It may here be observed that when the drilling arm 20 is in a drilling position transversely of the truck frame 3 as indicated in dotted lines in Figure 1 that the journal box 123 may be fastened to said drilling arm ahead of the collar 125 and that when said journal box is fastened to said arm, a movable support is provided for said arm which supports said arin as it moves into the material to be eut and thus assures a steady support for said drilling arm when said arm is drilling at a substantial distance beyond the frame 3.

Figure 1 shows the drilling mechanism 1 extending longitudinally of the truck 2 in a travelling position. The truck 2 travels intoV the mine room on the mine rails. The truck is stopped where it is desired to drive a breakthrough and the drilling mechanism 1 is turned in the position shown in dotted lines in Figure 1. The auxiliary supporting frame 23 is then fixed to-said drilling arm and the drilling mechanism is fed tothe face of the coal by means of the threaded shaft 33 and movable carriage 21, the auxiliary supporting frame 23 moving therewith. The pilot drill 26 and cutters 72 are then fed into the coal face and the breakthrough is started as shown in Figure 12. In Figure 12 the mine track is at such a distance from the mine wall that the entire breakthrough cannot be drilled in one operation. When the Adrilling arm 20 reaches the end of its forf .ward travel the drilling mechanism is stopped and the auxiliary movable supporting frame 23 is disconnected from the drilling arm and the section 40 is disconnected from thesection 42. The section 40 is moved rearwardly truck by means of the carriageQl and threaded shaft 33, and .the extension section 45 is inserted between the sections 40 and 42 thereby lengthening the drilling arm 20 to enable said drilling arm to feed its cutting elements further into the coal as shown in YI" i'gure 12. The auxiliary support is attached to the extension 42 andthe cuttingof the breakthrough is continued as shown in Figure 14. InY cases ,where the mine rails are close to the face of the coal it is not necessary to use. the-extension section 42, said section only being used when the breakthrough is exceptionally deep or where the mine rails are a substantial distance from the face'of the coal.

From the description above it may be seen that I have provided a drilling mechanism mounted on a truck adaptable to drill holes of a large diameter such as breakthroughs in a coal mine., which is adjustable to drill ataI various heights with respect to the truck frame and has an extensible drilling arm adaptable to drill holes ol varying depths` and has a movable support to support said drilling arm adjacent the face ot the coal beyond the drilling truck. lt may also be seen that I have provided a cutting clement having a multiplicity of cutters thereon having a pilot drill of small diameter rotating lin one direction .and a plurality ot rotating cutters cuttinginto the coal and inclined rearwardly from said pilot drill and also rotating about the axis of said pilot drill in an opposite direction to the direction otrotation of said pilotdrill and at a slower speed than the speed of rotation oit said pilot drill to compensate for the difference in circumferential speed between the pilotdrill QG and the outermost extremities of the cutters '72 and that I have flirther provided a means ot' a new and improved design to clear the cuttings from nrveutting element.

IVhile I have shown one form of my invention in this specilieation it will be understood that this form may be varied without departing from the scope of my invention except as limited in the appended claims.

I claim as my invention:

1. In a drilling apparatus. a support. a rotatable drilling arm. a pilot drill `iournaled within said drilling arm, a plurality of cutters extending radially outwardly Jfrom said drilling arm. and a cuttings clearing device on said drilling arm comprising a plurality of propellers rotatable with said drillingr arm and rotatable on axes perpendicular to the axis of rotation of said drilling arm.

Q. In a drilling apparatus, a support, a motor, a horizontally extending rotatable drilling arm, a shaft journaled Within said drilling arm, a pilot drill operatively connectible with the forward end of said shaft, a plurality of cutters extending radially outward from said drilling arm, a cuttings clearing device on said drilling arm rearwardly of said cutters comprising a plurality of Propellers rotatable with said drilling arm, and on axes perpendicular to the axis of rotation of said drilling arm, and driving meansconnectible with said shaft for rotatlng said propellers.

8. In a drilling apparatus, a support, a motor, a rotatable drilling arm, a shaft j ournaled within said drilling arm and rotatable in a direction opposite to the direction of rotation of said drilling arm having a pilot drill connectible with lthe forward end thereof, a plurality of cutters extending radially outward from said drilling arm, a cut- .tings clearing device on said drilling arm rearwardly of said cuttersV comprising a plurality of propellers rotatable with said drilling arm and rotatable ou axes perpendicular to the axis of rotation of said drilling arm, and gear reduction means conncctible with said shaft for rotating each of said propellers about an axis perpendicular to the axis of rotation of said drillingarm.

l. In a drilling apparatus, a' support, a motor, a rotatable drilling arm, a shaft journaled within said drilling arm and rotatable in a direction opposite to the direction of rotation of said drilling arm, a pilot drill connectible with the forward end of said shaft. a. plurality of cutters journaled on radial extensions from said drilling arm,` a cuttings clearing device on said drilling arm rcarwardlyof said cutters comprising a plurality of propellers rotatable with said drilling arm and rotatable on axes perpendicular to the axis of rotation of said drilling arm, a bevel geared connect-ion on said shaft for rotating each of said cut-ters about its respective radial axis as said drilling arm is being rotated about a horizontal axis, and a worm on said shaft, connectible with a plurality of worm gears for rotating each of said propellers.

5. In a drilling appara-tus, a support, a

` motor, a drilling arm, a pilot drill journaled within said drilling arm, a. plurality of cutters extending radially from said drilling armV and inclined rearwardly with respect thereto and means conneetible with said inotor for simultaneously rotating said drilling arm in one direction, rotating said pilot drill in anV opposite direction and rotating each of said cutters about its respective radial axis as said cutters rotate about the axis of rotation of said drilling arm.

6. In a. drilling apparatus, a support, a motor, a drilling arm, a pilot drill journaled within said drillino'arm, a plurality of cutters extending ra ially from said drilling arm, means connectible with said motor for translat-ionally moving said drilling arm t0 feed said drilling arm into the material to be cut, and means connectible with said motor for simultaneously rotating said drilling arm in one direction, rotating said pilot drill in an opposite direction, and rotating each of said cutters about its respective radial axis as said cutters rotate about the axis of rotation of said drilling arm.

7. In a drilling apparatus, a. support, a motor, a drilling arm, a. pilot drill journaled Within said drilling arm, a plurality of cutters extendin radially from said drilling arm and inc ined rearwardly with respect thereto, means connectible With said motor for translationally moving said drilling arm to feed said drilling arm into the material to be cut, and means connectible `with said motor for simultaneously rotating said drilling arm in one direction, rotating said pilot drlll in an opposite direction, and rotating each of said cutters about its respective radial axis as said cutters rotate about the axis of rotation of said drilling arm.

8. In a drilling apparatus, a support, a motor, a drilling arm, a pilot drill journaled Within said drilling arm, a plurality of sup-,I ports projecting radially from said drilling' arm, cutters journaled on said supports, and means connectible With said motor for simultancously driving said pilot drill in one direfriou, said drilling arm in an opposite diufrtiou, and said cutters about their respective axis in the same relative direction of r0- tation as said drilling arm.

propeller driven by said means for driving said pilot drill about an axis disposed transversely of the axis of rotation of said pilot drill.

12. In a drilling apparatus, a support, a motor, drilling mechanism including a drillin arm and a pilot drill journaled Within sa1d drilling arm, means for driving said drilling arm from said motor, means for drivin said pilot drill from said motor, and a cuttings clearing device on said drilling arm and rotatable therewith and driven by said means for driving said pilot drill.

Signed at Chicago, in the county of Cook and State of Illinois, this 16th day of October, A. D. 1928.

ROBERT E. SCHRODER.

9. In a drilling apparatus, a support, a

motor, a rotatable drilling arm, a pilot drill j ournaled Within said drilling arm, a pluralit y oi' supports extending radially from said drilling arm and inclined rearwardly with respect thereto, a plurality of cutters journaled on said supports and projecting radially outward therefrom, means connectible with said motor for rotating said drilling arm in one direction, and means independent of said drilling arm connectible with said motor for rotating'tlie said cutters about said supports, as said supports and cutters are rotated by said drilling arm.

10. In a drilling apparatus, a support, a motor, a drilling arm, a pilot drill journaled within said drilling arm, a drive shaft connectible with said motor and parallel With said drilling arm, means driven from said shaft for rotating said drilling arm, means driven from said shaft for rotating said pilot drill in a direction opposite to the direction of rotation of said drilling arm, a plurality of supports extending radially from said drilling arm and inclined rearwardly with respect thereto, a plurality of cutters journaled on said supports and projecting radially therefrom, and means connectible with said drive shaft for rotating said cutters on said supports simultaneously with rotation of said drilling arm and pilot drill.

11. In a drilling apparatus, a support, a motor, drilling mechanism, including a pilot drill, means "for driving said pilot drill from said motor, and a cuttings clearing device rearwardly of said pilot drill comprising a

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