US2105505A - Mining machine - Google Patents

Description

Jan. 1s, 193,8. E. RAMs/w 2,105,505

MINING MACHINE Filed May ll, 1936 '7 Sheets-Sheet l ATTORNEYS E. RAMSAY MINING MACHINE Jan. 18, 1938.

Filed May I1, 195e 'I sheets-sheet 2 INVENTOR ATTORNEY E. RAMSAY MINING MACHINE Jan. 18, 1938.

Filed May ll, 1936 7 sheetsfsheet 5 NVENTOR ATTORNEY Jan. 18, 1938.

E. RAMSAY 2,105,505

MINING MACHINE Filed May 11. 1956 Sheets-sheet 4 Jan. 18, 1938. E, RAMSAY 2,105,505

MINING MACHINE ATTORNEY Jan. 18, 1938.

Fi'led May 1l, 1936 '7 Sheets-Sheet 6 m. Y n K s M m `W QN Wm. m. I WPS IIE -ululnl No mv mh mmm; W \\\\|U mm mmm l .Umm Km. Q ,Il `S mm Mg af II mm f( 'Ill v2 uw. wm* Nw m um wm m. i XH E MY E. RAMSAY MINING MACHINE Jan. 18, 1938.

Filed May 11, l936 '7 Sheets-Sheet 7 INVENTOR Rs/fl N: RAMs/:Y

BY WV ATTORNEY! Cil Patented Jan. 18, 1938 UNITED ST 18 Claims.

My invention relates to a mechanism for carrying into effect a novel mining system, wherein the face of the mineral to be mined is removed by the requisite number of saws in relatively thin slices, the saws moving in a plane parallel with, and juxtaposed to, the face so that the mineral slab as it is sliced oi is weak enough to break away in iront of the advancing saw shafts and iall without being handled onto a conveyor by which it is loaded into mine cars.

More particularly, my invention discloses mechanism for carrying into eiect the mining method which formsthe subject matter of my pending application, Serial No. 39,707, leol the 19th day of September, 1935.

My present invention has in view the provision of a self Vpropelling slicing machine comprising the requisite number of saws according to the thickness of the seam being mined, which saws have a cutting capacity with relation to which the movement of the machine as a whole isrcoordinated so that it will feed itself along the face as fast as the saws will permit, the saws being so designed that they will break away by a wedging action the slab ofthe mineral as it is cut from the face, and being preferably stepped to produce an undercut face so that their kerfs will be left open below to permit the immediate discharge of dust as it is produced and to allow the'conveyor to work under the different levels so that the mineral as it is broken oi will fall freely and directly onto such conveyor.

My invention covers novel features in relation to the mounting and drive of the back cutting saws; of means for producing their relative adjustment; of means for connecting and disconnecting them with the power drive; and of means for reversing the movement of the slicing machine and controlling these several operations from a conveniently placed operators platform.

My invention further comprises a novel method for mounting and driving the bottom and top cutters which remove any mineral left on the floor or roof that would interfere with the advance of the mining machinery as its work progresses. 1

My invention further contemplates mounting the top and bottom cutter bearings in fixed relation with the adjacent back cutting saws and adapted to be jointly adjustable therewith, each cutter being driven from its respective saw shaft.

My invention further comprises the novel details of construction and arrangements of parts which, in their preferred embodiment only, are illustrated in the accompanying drawings hereinafter described and claimed, reference being had to the accompanying drawings, in which:-

Fig. 1 shows` a plan view of my mining method in use, the slicing machine being shown in plan (Cl. MS2- 9) view with part of the props broken away for clarity; the complete conveyor system being shown in plan and the mineral face being shown in cross section.

Fig. 2 is a diagrammatic view in elevation,

Fig. 6 is an end elevation of the mining may chine shown with the saws arranged for producing an undercut stepped face.

Fig. 7 is a horizontal cross sectional view taken on the line VTI- VII of Fig. 4.

Figs. 8 and 9 are detail cross sectional views taken respectively on the lines vnr- VIII of Fig.

4 and IX-IX of Fig. '7.

Fig. 10 is a sectional view taken in a vertical plane through a saw kerf and showing the manner in which the slab as it is sliced orf is broken away from the face by the saw.

Fig. 11 is a detail cross sectional view enlarged taken on the line Q-U of Fig. 6 with its shaft and its housing shown broken away between its front and rear frame bearings.

Fig. l2 is a view illustrating the wedging action of the saw teeth.

In Fig. l I show conventionally a coal mine in which It represents the face of the coal to be mined and II is a typical haulage way having a track I2 therein for mine cars I3 which are adapted to assume position under an elevating and loading conveyor I4 which is driven by a motor I5 and disposed to receive the coal continuously, as it is mined, from the conveyor i6 which runs parallel with the iacel IUl and is also driven draulic cylinders 20 having plungers 2I which carry roof engaging elongated caps 22 that overhang the mining machine and support the roof close to the face being mined. These cylinders 2t are supplied with hydraulic pressure by any` suitable means, such as a flexible hose, not shown, which connects to the nipples 23. A track may be formed for the mining machine by a. series oi conveyor pans 25.

These pans carry Z-bars 24 along their front? and rear edges which serve as guides for the slicing machinery which will be later described. The pans are supported above the mine iioor 215 by a series of shoes 2l' which are suitably connected to the main pan sections 25 and to the under pan 28 which house between them the return iiight of the endless conveyor i6. The ights of this conveyor travel along on a front extension apron 29 loosely connected to the forward edge of the under pans 28 and adapted to rest freely on the oor in position to support the working flight of the conveyor I8 close to the face. The flights of the conveyor are guided and held spaced by longitudinal guide elements generally indicated by the numeral 30. With this arrangement, only the working flight of the conveyor is exposed and its blades extend forwardly into juxtaposition to the face lil being mined.

The mechanism for slicing the face, representing the preferred embodiment' of my present invention, comprises a portable frame 3l, sho-wn in front elevation in Fig. 3, which comprises a top shield 32 which overhangs the frame at one end so as to protect a cable reel 33 journalled in the bearings 34 on the end w'all of the frame 3l and having coiled about it a conductor cable 35 which supplies the current through the leads 35 (Fig. 7) under control of a switch 31 to the motor drive for the machine.

The front face of the machine toward the wall being minedpis closed by a plate 38 having a housing 39 (Fig. 5) attached thereto and projecting forwardly of the machine to receive the sprockets 40 and 4l (Fig. 3) about which the chain 42 is passed, one end of the chain toward the haulage way being suitably anchored to the pan 25 and its other end being made fast as by means of the jack 43, shown more clearly in Fig. 2.

The housing 39 has openings at its ends for the chain 42 to approach and leave these sprockets 40, 4 I, the sprocket 49 being suitably journalled on a` stud bearing in the frame and operating as an idler, while the sprocket 4l is fast on a shaft journalled in the frame and driven through a suitable reversib-le clutch such as that shown in Figs. 5 and 7. The clutch, as illustrated, comprises the outer drum elements 44 and 45 with an interposed axially shiftable inner drum 46, there being sets of plates 4l interposed between the drum 45 on the one hand and each of the drums 44 and d5 on the other hand. These latter drums each carry a sprocket 48, which sprockets are reversely driven by chains 49 and 59, (Fig. 4) which respectively engage the sprockets 5l and 52. The sprocket 5l is fast on the low speed countershaft 53 which is driven by the gear 54 that meshes the pinion 55 (see Fig. 3) fast on a drive shaft 56 connected at its inner end to a shaft 517 (see Fig. 5) which turns in a bearing 53 mounted in an intermediate partition 59a in the frame.

The shaft 57 has free thereon a multiple VVsprocket 59 adapted to be driven` through a toothed clutch @il by means of a multiple sprocket 6l housed in a back housing extension on the casing 38 and having suitable bearings in the back wall 62 of the frame. This sprocket 5l is driven by suitable chains from the sprocket 53 on the drive'shaft of the motor 64, suitably mounted within the frame.

In Fig. 7 it will be seen that the sprocket 5S, free on the shaft 5l, carries integral therewith one of the elements of the clutch 6l] which is adapted to be moved into and out of engagement with the other clutch element, driven by the sprocket 6|, through the instrumentality of the yoke 65 controlled by arms fast on a vertical shaft 66 (see Fig. 5) which in turn is adapted to be rocked by a crank 6l controlled by an operating rod 68 (see Fig, 7). Ihe shaft 56 is journalled in the upper and lower bearings T suitably mounted within the frame and on its upper end it carries a second clutch yoke 1|, by means of which it is adapted to shift the multiple sprocket 'l2 on its shaft '13, causing a clutch element thereon to engage or disengage a complemental clutch element driven by a multiple sprocket 16, mounted in the rear housing extension above the sprocket 6i and driven by a sprocket 11 on the shaft of the motor 'IS (Fig. 4) which is mounted immediately above and in line with the motor 64 and which also receives its power direct from the cable 35 under control of the switch 3l. Both of these motors are turning in the same direction and at the same speed, and both multiple sprockets 6I and i6 are likewise driven at the same speed and in the same direction. The shaft 13 is journalled in bearings i4 and l5 in the frame.

The clutch drum elements 44 and 45 are con stantly driven in reverse directions through the drive mechanism described, and according to the position of the drum 46 they will either leave the tubular drive shaft 80 (Fig. 5) idle or they will give it a forward or reverse drive. The forward drive, transmitted through the drum 45, is a slow speed drive and its motion is imparted to the sprocket 4i which by engagement with the chain d2 .advances the machine parallel with the face i@ being mined. When the drum element 44 is interlocked with the drum 4S the drive to the sprocket fil'is reversed and is a high speed drive preferably about three times the forward drivingr speed. Thus the mining machine can be backed to starting position rapidly to save time.

'Ihe position of the movable drum 46 is controlled by the shaft 8l which telescopes in the tubular shaft 8f! and by means of the key 32 (see Fig. working through a longitudinal slot in the tubular shaft Sil, it engages the hub of drum 45, and acts to shift said drum either to neutral, or forward, or reverse driving positions as above described. The shaft 8l is controlled by a yoke 83 (Fig. 5) which swings on a rocker shaft 84 mounted on bearings 85 (Fig. 6) carried by the middle partition 59a. This shaft 84 extends forwardly through the machine, as seen more clearly in Fig. '7, and is controlled by a lever 8B conveniently accessible from the operators platform 8l'.

The lever is shown in neutral position in Fig. 7 and the dotted lines (Fig. 6) show its positions for the forward or reverse drive. The operator from the platform El can also reach the rod 68, which controls the clutch operating shaft 65 and serves to engage or disengage the machinery with the motors` 64 and '18. It will of course be understood that a single motor may be substituted for the two motors 54 and i8, but I prefer to use the two smaller motors as it gives me a more compact construction and simplifies the drive.

I have illustrated my invention in Fig. 3 as comprising three saws 9@ which work in vertical alignment in a common plane, whereas in Fig. 6 I show the same saws set back in stepped relation with the upper saw pitched upwardly to out its slice at an obtuse angle to the roof. The saws are shown in vertical alignment in both views, but they may be transversely stepped one ahead of the other, preferably with the lower saw ahead and the saws above it dropping back in order `from bottom to` top, and when I referto stepped I mean the term toincludethe stepped relation of the 4saws. in a plane 4normal to the face as well as in a plane parallel with the face, either or both.

The saws have tubular hubs 9| fast on the forward ends of their respective. drive shafts 92, which shafts turn in. tubular housings 93. The housingV 93 for the lower saw shaft, as seen` more clearly in Fig. 1l, has fast thereon at each end the collars. 94 and 94d.,v each having a flange that slides in its respective vertical ychannel 9,5, 95a as a guide and each 4flange has a pair of verti- 'cally elongated slots 96 which receive the cross pins 91 which permitvertical adjustment of the lower saw assembly. The housing for the middle saw shaft carries flanged. collars 94, 94a, which, however, are rigidly connected to the kchannels 95, 95a by bolts. and are therefore not adjustable. The upper saw housing is adjustably mounted in the channels 95, 95a like the lower saw housing.

For the lower and middle saw housing, I provide a yoke |00 integral withcollar 94a at one end and at the other end bored to receive its respective housing 93 and rigidly secured thereto. Within each yoke |001 mount a multiple sprocket |0| on its respective saw shaft 92. The lower sprocket |0| is driven by the chain |02 from the sprocket 59 (Fig. 4) on the shaft 51. I mount. a ball bearing |03 in each collar 94a and each bearing housingl and |31, (Fig. 6).

When the upper saw shaft housing is parallel with the lower saw shaft, it is mounted in the channels y9.5, 95a exactly. like the lower shaft housing above described. But when the housing for the upper saw 92 is inclined upwardly, as shown in Figs. 6 and 8, it is mounted in an elongated yoke |04, the outer leg of which is similar to that described for the other yokesandA is similarly adjustable in the rear channel 95a but the forward leg |05 of the yoke |04 extends entirely across the machine andis there attached directly to a plate. 94h (Fig. 8) `which has a vertical adjustment by the pins 9 1 and slots 90 in the forward channel 95.

For effecting vertical adjustment of the lower saw shaft I provide, as seenin Fig. 6, bell cranks |06 mounted'in bearings |01, |01a, bearing |01 being mounted on the front frame element 36 so as to overhang forwardly therefrom so that a bell crank |00 can be pivotally connected overhead to a bearing housing |08 fast on the lower shaft housing 93, while the rear bell crank |06 is mounted in its bearing .|.01a attached to the bottom of the frame with its rear end overhung to be engaged to the forward end of the yoke |00. These two bell cranks are connected by right and left hand threaded rods |09 (Fig. 6), which rods screw into the right and left hand threaded hub of a hand wheel H0.

By turning this hand wheel the bell cranks can be correspondinglyrocked .to raise or lower the lower shaft housing 9 3 Without disturbing its horizontal alignment. 'Ihis identical housing adjustment means may be applied to the upper shaft when it works horizontal, but in the case of the inclined upper shaft, as shown in Figs. 6 and 8, a hand wheel is provided, which turns a shaft. carrying a worm, not shown, which meshes the worm gear ||2 that turns in a housing ||3 and is fast upon a shaft ||4 turning in a housing ||5 connected at an intermediate point to housing |3 andat its ends to the front and rear walls of the machine. The rear end of the shaft |4 overhangs beyond therear wall of the machine and carries a pinion ||5 which meshes a rack ||1 fast on an extension of the rear arm of the yoke |04 which overlaps the rear side of the rear channel 95a. The shaft ||4 carries a forward pinion H8 which works opposite a slot in the housing I5 through which a rack |20, fast on the forward yoke arm |05, passes. By this arrangement, the turning of the hand wheel I i, will raise and lower the yoke |04 without changing the alignment of its upper saw shaft.

In the yoke |04 I mount a multiple sprocket |2 l, which turns loose on a stub shaft |22 and at its forward end the sprocket has formed thereon a bevelled gear |23.' Forward of the gear |23 the stub shaft carries an angled bearing |24 for the upper saw shaft 92. 'I'his upper saw shaft is fast to a bevelled gear |25 meshing the gear |23. The multiple sprocket |0| for the intermediate shaft and i 2| for the upper shaft are driven by means ofa common chain |25, (Fig. 4) which chain passes under an idler sprocket |21 and about the sprocket 12 driven by the motor 18.

By the mechanism described, the upper and lower saw shafts are capable of adjustment in parallelism, the slack in their driving chains being taken up by the idler sprockets |21 and |28.

The saw ange 90, which tapers from .the hub toward its marginal edge, is formed with radial bit sockets I 3|. These sockets open at their inner ends into a countersunk recess |32 in the face of the saw in the center of the flange, and radial saw teeth |33 are suitably anchored in the bit sockets |3|. The saws are set to cut only in one direction of rotation.

The bearing housing |08, fast on the forward end of the lower shaft housing 93, has a dependent arm which forms a vertical bearing for the drive shaft for the bottom cutting saw |34 (Fig.

6) fast on a shaft which carries at its upper end a bevelled gear |35 which meshes a bevelled gear |36 fast on the shaft 92. Thus, this lower shaft serves to drive the lower saw 90 and the bottom cutter |34. In like manner I mount fast on the housing 93 for the upper saw shaft a housing |31 (Fig. 6) similar to the housing |03 and carrying in its upper end the top cutting saw |38 having a drive shaft, turning in a bearing |39 formed as an extension of the housing |31 and driven by a bevelled gear |40 meshing a driving pinion I4! fast on the upper shaft 92. In this manner the upper saw and the top cutter have a common drive.

By reason of the manner of mounting the top and bottom cutters, they always work in fixed relation to the upper and lower saws and for this reason are mounted so as to be adjustable with said saws.

It is important to note the manner in which the advancing saws act to break off ahead of them the mineral which they slice off from the face l0. The teeth |33 are set at an angle to the plane of progress of the saw and each stands free beyond the saw anges. The kerf cut by the tip of the teeth is a relatively narrow kerf and as' each tooth advances the pitch of its outer face causes that face of the tooth to rake with an outward pressure against the outer face of the kerf cut by the tips of the teeth. As the pressure becomes greater there is a yielding of the min- F eral and also a giving of the toot-h which tends to produce a chatter or vibration of a tooth so that as the saw advances it will act most effectively to break off the mineral in pieces, such as |42 illustrated in Figs. 'l and 12. Moreover,

I to be cut.v

this outward pressure is exerted radially with respectl to the axis of the saw and as it breaks Vdown the mineral pieces M2, it will cause them to part with radial fractural lines as indicated typically in Fig. l0. it is preferable to obtain this wedging and breaking of the mineral by the `action of the teeth rather than the bevelled saw ange, as the latter will produce a constant frictional rdrag Without that vibration which the individual tooth will give and which facilitates the fracture. The taper of the saw flange, however, will engage any portions of the severed slice which contact it and will insure that the mineral slice is broken away in advance of the saw shaft.

In operation, assuming the saws arranged as disposed in Fig. 6 with the roof supports in place and raised by hydraulic pressure so as to support the roof above the machine and its track, the motor I5 is started up to put the conveyor into service and the operator, having thrown the lever 68 to engage the clutch elements 59 and t@ and having closed switch 3l' so as to pass current from conductor 35 to the motors 66 and lil, takes his position on the platform 3l and the machine is ready for operation, with the clutch element S still and the drums @lli and i5 reversely rotated by the motor Sli. The operator then grasps the handle 86 and throws the clutch element i6 so as to engage drum element Q5 and thereby to drive the shaft 8i). The drive of shaft Si) rotates the sprocket ti that is fast thereon and which,

beingvin mesh with the chain 2, will start the machine in forward motion along its track,

bringing its saws into engagement with the face The saws are being constantly driven by the motors it and till, motor i3 acting through chain |26 to drive the two upper saws, while motor 64 through chain m2 drives the lower saw. The saws having been correctly set with relation to the roof and floor so that the top and bottom cutters work as close as practicable toroof and floor respectively, the operation of slicing off the face of the seam of coal, or other mineral, thereupon proceeds. Each saw as it advances cuts a thin slice or surface section of the face and breaks the slice away ahead of its shaft as indicated in Fig. 7. The saws cut the face into inwardly overhung benches or steps, as seen in Fig. S, which being unsupported underneath will fall clear, as

/ the cutting and breaking away proceeds, so the saws will not bind. The sliced mineral, as it is broken away by the wedging action of the advancing saw teeth, drops onto the apronf and is carried forward by the exposed conveyor flights l5. The conveyor is in position to gather up the mineral as it is cut and deliver it without handling to the elevating conveyor l! which "deposits in a mine car i3.

When the machine reaches the end of its cutting travel, which normally will be at the inner end of the face it, the operator throws lever 86 to cause clutch element l5 to engage and be reversely driven by the drum element M which rotates at a higher speed than element d5, being driven directly from the motor counter-shaft 56 (Fig. 3) while element 5 is driven with a speed reduction from shaft 53. This runs the machine back at a rapid speed, to cut down idle time, into position with its saws standing clear of the face i8 in the haulage way ii. Thereupon, the conveyor supports andv the lmachine run-way is pushed forward by any suitable mechanism until it again assumes the proper spacing with relation to the new face i6. The hydraulic roof supports I9, 20, 2l, 22 are also'advanced from time saw cutting operation is again repeated and the face is sliced oif and conveyed away as fast as it falls. The mineral comes down in desirable sized lumps without any more dust than is produced by the relatively thin saws.

The saws will be designed and arranged according to the conditions to be dealt with in the face being worked, their number, size, the'pitch of their outer wedging farces, the spacing of the top and bottom cutters, and the adjustment of the saw shafts being all such as are best suited to the character of the mineral, the partings, if any, therein, the character of the mine roof and floor, and such other considerations as enter into the successful operation of this improved method of mining which, as such, forms the subject matter of my co-pending application, Serial No. 39,707.

It is important to note that the conveyor extends the full length of the face being worked and is interposed between the mining machine track and the face with its working flight traveling along the floor in position to engage the coal as it falls, due to the breaking away of the sliced face, without handling. The periodic advance of the mining machine track carries forward at the same time the hinged apron upon which the working flight of the conveyor travels. In the drawings we show a baiTle |56 in Fig. 6, which will tend to deflect the coal from the upper bench -so that it will fall directly onto the conveyor apron. By adapting the machinery to cut the slices thin enough so that as they are broken away in front of the saws, the machine will bring down the face, otherwise unbroken, throughout its full vertical extent as it progresses along the face and no horizontal intermediate cutting or other preparation of the face is required, it being noted that applicants cutters i311 and H38 work on the roof and the floor behind the face and do not out the face in front of the slicing saws. Thus these saws constitute the complete means for bringing down the face without requiring other treatment thereof.

While I have shown my invention in but two forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications, without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claim is:-

l. In a mining machine, a carriage movable back and forth along the face to be mined, a track for the carriage extending along and movable to follow the receding face being mined, a plurality of back-cutting saws mounted in said carriage to rotate at different levels in planes parallel with the face opposite them and close thereto to sever therefrom readily breakable slices, a drive means for said saws, and cutting teeth on the saws which present to the mineral slice cut free from the face an inclined edge disposed to exert a'wedging action in a direction to break off the sliced mineral as the saws advance along the face.

2. In a mining machine, a carriage movable back and forth along the face to be mined, a track for the carriage extending along and movable to follow the receding face being mined, a

saw mounted in said carriage to rotate in a plane parallel with and juxtaposed to the face, a drive means for said saw, and cutting teeth on said saw which present to the mineral slice cut free from the face an inclined edge disposed to exert a Wedging vibratory working force outwardly from the face in a direction to break off the sliced mineral as the saw advances along the face.

3. In a mining machine, a carriage movable along the face to be mined, a track for the carriage movable to follow the receding face being mined, a plurality of saws mounted in said carriage to rotate in planes parallel with the face opposite them and adapted to break away the sliced mineral ahead of them, a drive means for said saws, and -means to adjust the saws relatively to vary their respective cutting levels, the saws being juxtaposed to break away the entire face lying between the uppermost and lowermost saw kerf.

4. In a mining machine, a carriage movable along the face to be mined, a track for the carriage movable to follow the receding face being mined, a plurality of saws mounted in said carriage in stepped relation and disposed to rotate in planes parallel with the face opposite them, and a drive means for said saws.

5. In a mining machine, a carriage movable along the face to be mined, a track for the carriage movable to follow the receding face being mined, a plurality of saws mounted in said carriage to rotate in planes parallel with theface opposite them and set so that each progressively undercuts the mineral being sliced oif by the saw next above it, a drive means for said saws, andl means to break down the mineral slice cut by each saw.

6. In a mining machine, a carriage movable along the face to be mined, a track for the carriage movable to follow the receding face being mined, a plurality of saws mounted in said carriage to rotate in planes parallel with the face opposite them, and means to cause each saw to break down the mineral slice which it cuts.

7. In a mining machine, a carriage movable along the face to be mined, a track for the carriage movable to follow the receding face being mined, a plurality of saws mounted in said carriage to rotate in planes parallel with the face opposite them and staggered to produce an undercut stepped face, a drive means for said saws, and means to break down the mineral slice which each saw cuts.

8. In a mining machine, a carriage movable along the face to be mined, a track for the carriage movable to follow the receding face being mined, a plurality of saws mounted in said carriage to rotate in planes parallel with the face opposite them and arranged in a vertical bank set progressively in advance of one another from top to bottom to under cut the face, and a drive means for said saws.

9. In a mining machine, a carriage movable along the face to be mined, a track for the carriage movable to follow the receding face being mined, a plurality of saws mounted in said carriage to rotate in planes parallel with the face opposite them and in relative position to slice off the face to be mined, means to break away the face as it is sliced by said saws, a top cutting saw mounted to cut a horizontal kerf .adjacent the roof, and a drive means for said saws.

10. In a mining machine according to claim 9,

a conveyor means working between the mining machine and the base of the face, and a bottom cutter mounted and driven to rotate in a horizontal plane and cut a level oor for the advance of said conveyor means as it is moved to follow the receding face.

11. In a mining machine, a carriage movable along the face to be mined, a track for the carriage movable to follow the receding face being mined, a plurality of saws mounted in said carriage to rotate in planes parallel with the face opposite them and staggered to produce an undercut stepped face, a drive means for said saws, and an endless conveyor means having its working flight traveling parallel with and overhung by said undercut face.

12. In combination, a machine carrying a staggered bank of saws disposed to produce an undercut stepped mineral face, means to guide the machine along said face to cut it away in thin slices, means to break down the sliced mineral responsive to the advance of said machine along the face, and a conveyor means traveling along and parallel with the base ofthe face in position to receive the sliced off mineral as it is broken down and remove it.

13. In combination, a machine carrying a staggered bank of saws disposed to produce an undercut stepped mineral face, means to guide the machine along said face to cut it away in thin slices, means to break down the sliced mineral responsive to the advance of said machine along the face, a conveyor means working along the face in position to receive the mineral as it falls and remove it, and roof props adapted to overhang the path of said machine and support the roof in juxtaposition to the overhanging top bench of the stepped mineral face.

14. In a mining machine movable along a mineral face, a back cutting saw disposed to cut a kerf parallel with the face and juxtaposed thereto, and means to rotate said saw, said saw having teeth which project beyond its periphery and are designed with working faces disposed both to cut the saw kerf and to exert an increasing outward component of force adapted to break away the slice as it is cut from the face by the advancing saw.

15. A mining machine according to claim 14,

-in which the teeth present a slice engaging edge which is inclined in a direction outwardly and toward the saw axis.

16. In a mining apparatus, a machine, a track therefor extending along parallel with the face to be mined, means to propel the machine back and forth along said face, means to slice oil and break away the face as the machine progresses, an endless conveyor having its idle flight traveling in the same plane with its working flight, the latter flight being movable along the floor level at the base of the face being sliced through out the length thereof, and an apron over which said Working flight slides and which is interposed between the track and the face.

17. A mining apparatus according to claim 16, in which the apron is hingedly attached to and adapted to be advanced along with the track to follow the receding face.

18. A mining apparatus according to claim 16, in which the track comprises a covered housing in which the return iiight of the conveyor travels below the machine level.

ERSKINE RAMSAY.

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