US1520280A - Mining machine - Google Patents

Description

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CHARLES E. DAVIS, OF CHICAGO, ILLINOIS, ASSIGNOR T0 GOODMAN MANUFACTURING COMPANY, 015 CHICAGO, ILLINOIS, A CORPORATION OF ILLINOIS.

MINING MACHINE.

Application filed April 17, 1920. Serial No. 374,746.

To all whom it may concern:

Be it known that I, CHARLES E. DAVIS, a citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented an Improvement in Mining Machines, of which the following is a specification.

My invention relates to mining machines, and more particularly to mining machines of the type commonly known as the continuous cutter coal mining machine, whichis adapted to be moved laterally across the wall of the mine to cut a horizontal kerf thereunder.

The object of the present invention, generally stated, is to provide improved means for feeding and guiding a mining machine of the above description for performing the cutting operation.

Mining machines of the continuous cutter type are particularly adapted for use in the room and pillar system of mining. They are usually fed to the work by means of a flexible draft device, such as a rope, chain, or the like, which is anchored at its free end in the desired direction of travel, and wound on a drum driven by the motor. A second draft device is anchored in the opposite direction to the first, and paid out from the rear end of the machine frame as the machine advances. A suitable retardingmeans is provided for the purpose of controlling the second draft device in order to maintain a proper position in relation to the mine wall.

In the embodiment herein described, which illustrates one of several forms which my invention may take, I have shown two rope drums, one of which is adapted to be normally driven, and the other of which is provided with a retarding means comprising a friction-controlled releasing device. However, I find that certain additional advantages in the guiding and manipulation of the machine are obtained by a construction in which the normal functions of the two drums may be mutually reversed at certain times, particularly as the machine is approaching and leaving the normal cutting position. Accordingly, in the present invention, I provide means whereby the drum which is normally the tail-rope drum may be positively driven by the motor, while the other drum is simultaneously disconnected from the motor, and allowed to be released with the ordinary type of machine, thereby affording a more continues movement of the machine. A distinction must therefore be made between the temporary reversal of the functions of the drums for the purpose stated above, anda complete reversal of the direction of cutting. As is well known to those skilled in the art, the normal direction of cutting is determined by the direction of movement of the cutter chain; that 1 to say, the side of the cutter chain in cutting engagement with the work, always moves towards the machine, and drags the cuttings out of the kerf- In the event that it is desired to reverse the direction of movement of the machine, and cut from left to right instead of right to left, it is necessary to reverse the direction of movement of the cutter chain, which op eration usually involves reversing the cutter bits, (or the chain), rearranging the control ropes, and reversing the direction of rotation of the motor and driving mechanism. Altho one of the secondary features of the present invention is the provision of mechanism whereby such a complete reversal may be accomplished if desired, yet it will be seen that for the primary purpose stated above, the functions of the drums are re versed temporarily without aflecting any change in the normal direction of movement of the cutting operation.

Furthermore, the present invention should be distinguished from that class of machines which also have driving connections with bothfeed and tail-rope drums, but in-Whicli the drums are simultaneously driven in opposite directions so that the tail-rope is paid out at the same rate that the feed rope is wound in, for the purpose of maintaining a right-angled relation of'the machine to the face during the cutting operation. As will appear in the description of the operation of the present invention, the manipulation of the machine while approaching and leaving the work, usually requires respective rates of movement of the two drums which vary so greatly, that a device in WlllOh the drums are'driven simultaneously as above described would be useless and inoperative for the purpose of the present invention. I

Other objects of the invention will appear from time to time as the descrlption proceeds.

The invention consists in the combination, construction, and arrangement of parts-as will hereinafter be described in connection with the accom anging drawings, and more.

particularly de I e in the appended claims In the drawings, Figure 1 1s a plan view of the machine in normal cutting posltron.

Figure 2 is a rear elevation of the driving mechanism, drawn to a larger scale than Figure 1.

Figure 3 is a right side elevatlon of the driving mechanism drawn to the same scale as Figure 2.

Figure 4 is an enlarged plan view of the mechanism shown in Figure 3, showing some of the details in section.

Figure 5 isa vertical transverse cross section of a rope drum taken on line 55 of Figure 4.

Figure 6 is a cross section taken on lme 6-6 of Figure 5.

Figure 7 is another cross section taken on line 77 of Figure-5.

' Figure 8 is a cross section taken on line 8-8 of Figure 4.

Figures 9 and 10 are detailed views of the friction ring pawl.

Figures Hand 12 are detailed views of the gear ring pawl.

Figures 13 to 18 inclusive, are diagrammatic views showing the machine and control ropes in various positions during the cutting o'peration.

My invention is shown as applied to a mining machine having a main frame A, and a cutting element 1 projecting therefrom. This cutting element is preferably provided with an endless cutter chain of the usual pattern, which is driven by the motor B, to cut a horizontal kerf in the mine wall as the machine advances. Figure 1 shows the arrangement of the machine ..nd control ropes during the normal cutting operation across the working face. A rope 2 is adapted to be wound on a drum 3, mounted on the left side of the machine frame A. Said rope passes from said drum over a ulley 4 adjacent the front end of the mac ine frame, and thence to a suitable anchor 5, fixed at a distance from the machine, and near the working face along which the machine is to be moved. A second rope 6 is anchored at the opposite end of the workin face, and is led over suitably arranged leys-7 and 8', at the rear end of -the mac e frame, tov a second drum 9, on the right sideof the machine. The arrangement is such that in the normal cutting position illustrated in this figure, the rope drum 2 is connected thru driving mechanism, to be hereinafter described, to the motor B The opposite drum 9 is disconnected from the driving mechanism, and during the normal cut across the face, is released at a rate substantially the same as the rate of take-up on the rope 2, by means of an adjustable friction band device 10 on the drum 9. The purpose of the rope 6 is to restrain the movement of the rear end of the machine, and maintain construction.

The main elements of the driving mechanism for drums 3 and 9 comprise a longitudinal-shaft 12 geared to the motor B, a worm gear 13 actuated by said longitudinal shaft, a variable speed mechanism 14, and anendwise movable shaft 15 driven by said variable speed mechanism, and provided with interlocking clutches 16 and 17 on opposite ends thereof. The driving connection between clutch l6 and the drum 3, comprises a shaft 18, driving pinion 19 and gear ring 20 on said drum. The driving'connection between clutch 17 and the drum 9, comprises a pinion 21, idler gear 22, and a gear ring 23 on the latter drum. The gear 22 is to drive said opposite to that of the other drum 3.

The variable s ed mechanism 14; illustrated, is prefera l y of the planetary type which may be of any provided with an external friction band 14', and a friction adjusting handle 14", for the purpose of transmitting variable. speeds to the shaft 15. Details of this gear need not be described excepting to indicate a clutch member 24 feathered on the shaft 15, and provided with clutch jaws 25, 25 adapted to be engaged either with a hi h speed member 26, or low s member 2% of the planetary gear 14. T e clutch member=24is provided with a shifter yoke 28, and a control handle 29 attached thereto. Altho I have shown a planetary gear variable speed mechanism, it will be understood that so far as the broad features of my invention are concerned any equivalent variable speed device may be urpose of the idler substituted therefor.

The endwise movable shaft 15 extends rum in a direction approved construction,

thru the speed reducing mechanism 14 and worm gear 13 to form an axial bearing therewith. The clutch 16 on the left end of said shaft comprises an annular flange 30 on said shaft, provided with clutch. jaws 31, 31 adapted to engage with corresponding clutch jaws 32, 32 on the connecting shaft 18 extending to the left hand drum 3. The shaft 15 is also provided with a recess 33 in which a reduced portion 34 of the connecting shaft 18 extends, for the purpose of maintaining the two shafts in alignment with each other.

The clutch 17 for connecting the shaft 15 to the right hand drum 9 is located adjacent the interior face of the pinion 21 on the right hand side of gthe machine. Said clutch comprises a sleeve fixed to the shaft 15 and extending thru the pinion 21 to form an axial bearing therewith clutch jaws 36, 36 are carried by said sleeve, and are adapted to engage corresponding clutch jaws 37, 37, preferably formed integral with the pinion 21. Means for shifting the shaft 15 comprises a shifter yoke 38 mounted on the sleeve 35, provided with a shifter arm 38*, which is operated by a suitable control handle 39, (see Fig. 2). In the position shown in Figures 2, 3 and 4, the shaft 15 is in neutral position, that is to say, clutches 16 and 17 are 'both disengaged. It will be seen that if the control handle 39 is moved downwardly, the shaft 15 will be moved longitudinally so as to engagelhe clutch 16 to form a driving connection with the rope drum 3. 0n the other hand, if the control handle is moved upwardly, the shaft will be moved in the opposite direction, clutch 16 will be disengaged, and the opposite clutch 17 will become engaged to form a' driving connection with drum 9.

The rope drums 3 and 9, as hereinbefore pointed out, are preferably identical in construction, so that a detailed description of one of the drums will apply to both. Means whereby each drum is automatically engaged and disengaged from its respective driving gear and friction device, comprise a pair of ratchet and pawl devices, details of which appear in Figures 5 to 12 inclusive. Drum 3 for instance, comprises a rim or body portion 3, a web 3", and a hub 3 mounted on a suitable bearing pin 3f, fixed on the machine. A driving gear ring 20 is loosely mounted on the drum body 3, and is provided with a plurality of notches 40, 40, s aced about the interior surface thereof. (gee Figs. 7 and 8.)v A pawl 41 is mounted on a rocking pin 42, and extends thru aesuitable aperture inthe drum rim 3 to engage with the notched surface of the gear ring 20. The rocking pin 42 hears at one end in a lug 43 projecting inwardly from the periphery of said drum body 3, and extends thru the web 3 of the drum. A dog 45 is fixed on the pin 42 adjacent the lug 43, said dog having an arm 45 extending over said lug and being adapted to engage the pawl 41. A handle 46 is fixed on the outer end of the rocking pin 42, and in a position suitable to be manipulated by hand. A spring 47 is attached atone end of said handle, and at'the other end to the periphery of the drum at a point on the radial line assing thru the axis of the pin 42. The (0g 45 and handle 46 are substantially in longitudinal alignment with each other on the rocking shaft 42, so that the tension of the spring 47 is transmitted to the pawl 41 thru the dog 45, which serves to maintain the pawl in engaged relation against the notched surface of gear ring 20. "lhe friction device 11 is mounted adjacent the gear ring 20, and comprises the friction ring 50, friction band 48 and friction adjusting handle 49 of the usual type. In the form illustrated, the friction ring 5t) is loosely mounted on the drum rim 3, and is provided with a ratchet and pawl device similar to that hereinbefore described in association with the gear ring 20. Said ratchet and pawl device comprises notches 51, 51, on the friction ring, pawl 52, dog 53, rocking pin 54, handle 55- and spring 56.

It will be observed that the friction pawl 52 is normally inclined to the friction ring 50 in the same direction as the driving pawl 41, as shown in Figure 5. When the pawls are in this position, and gear ring 20 is driven by the motor in the direction indicated by the arrow, the pawl 41 becomes engaged in one of the notches 40, (see Fig. 8') and the drum is carried with the gear ring to wind up the rope 2. When the driving connection to the motor is disengaged, the drum may move in the opposite direction until the friction pawl 52 engages with a notch 51 in the friction ring 50. The ro e 2 can then be paid off the drum ony against friction imposed by the friction band 48, which may be regulated by the handle 49 in the usual manner. If power is again applied to the gear ring 20, it will move in a direction to wind up t-he rope. The friction pawl becomes released as the drum is rotated in the opposite direction, so that the drum is driven independent of the friction device, in the same manner as before. It will thus be seen, that the drum may alternately be driven by the motor in one direction, or be released against friction in the opposite direction.

Whenever it is desired to reverse the direction ofdriving the drum 3, either to re verse the direction of cutting, or for any other purpose, the pawls41 and 52 may opposite ends of the pawls are moved into engaging relation with the driving gear ring 20 and friction ring 50, respectively. The springs 47 and 56 are rocked over the centers of their respective pins, so as to exert the desired tension in each pawl in either position thereof. I

The purpose of the ratchet and pawl device axoci'ated with the driving gear as above described, is to provide means whereby the drum may be rotated by hand in the same direction as the direction of driving, when desired. Altho the drum may also be rotated by hand when the driving clutch is disengaged, I prefer to provide the ratchet and pawl device so as to disengage the gearing intermediate the drum and its re-- spective clutch mechanism, thereby reducing the friction to a minimum when the drum is rotated in this manner.

The ratchet and pawl device associated with the friction ring 50 allows the drum to be rotated freely by 'the driving means in the direction to wind the rope on the drum, but engages the drum with said friction device as the rope is unwound or withdrawn fro-m said drum.

An extensible handle 60 is provided on each drum, which handle is normally re- .tained in retracted position by a spring 61 and plunger 62, but which may be pulled out beyond the face of the drum whenever itis desired to wind or unwind the drum by hand. When it is desired to actuate the drum by hand, the clutch 17 is disengaged, and the friction band 48 released, so that the drum is free to be rotated in either direction.

Some of the advantageous features of a mining machine constructed in accordance with my invention, may be best understood by reference to Figures 13 to 18 inclusive, which illustrate a so-called room and pillar mine, and show the machine in various positions incident to the cutting operation The mining machine is usually brought into a room on a truck, and is unloaded at a point a short distance from the working face 63 as shown in Figure 13. From this position it is drawn to one corner of the room under its own power by means of the .rope 6, associated with the right hand drum 9, which rope is anchored in a suitable position, as for instance, point 64 in the right hand corner of the room adjacent the side wall or face 65. In the present description, the cut is shown as proceeding from right to left along the workin face 63, but it will be understood that t e cutting operation may be from the opposite corner, and proceed from left to right, if desired. With the rope 6 anchored in position as described, it is led over pulley 66, or a similar appropriate arrangement of pulleys for guiding the machine to the face, and is wound on drum 9 to drag the machine into position. The machine is then ready for making its initial cut into the face, which cut is usually made in a direction substantially longitudinal of the cutter bar, and is known as the sumping out. In making the sumping out, it is necessary to project the machine forwardly into the face by means of the power ropes, and at the same time control the movement of the machine so that the machine will be maintained at the desired angle to the wall. Rope 2 may therefore be anchored at some point to the left of the machine, preferably at point 5, which position is also suitable for the anchor when the transverse cut is thereafter made across the face. In this position, the rope 2 may be led around pulley 67, if desired. When the ropes are thus anchored and the sumping cut is progressing, it will be seen that the rope 6 tends to swing the rear end of the machine to the right. Therefore, the friction device 10 on the drum 3 is adjusted so that the rope 2 restrains this lateral movement of the machine, and gives the desired line of advance into the face.

'IVhen the sumping cut is completed, and the machine is in position ready to make the transverse, or lateral cut, as shown in Figure 1, the rope 6 is changed to its normal position about pulleys 7 and 8 at the rear end of the frame, the rope 2 is changed to its normal position about pulley 4 at the front end of the frame, and the transverse cut is then made across the face, as shown in Figure 1, using rope 2 as the feed-rope, and rope 6 as the tail-rope.

It will be understood however, that the procedure in making the sumping cut as above described, may be deviated from in several details, particularly in regard to the arrangement of the ropes about the pulleys, depending upon the working conditions encountered as each cut is made. For instance, it may be desirable to place the anchor 64 somewhat farther away from the face, in which case the rope 6 would be changed to the rear pulleys 7 and 8 at the beginning of the sumping out instead of at the completion of this out. It also may be possible under some conditions, to train the rope 2 about the front pulley 4 at the beginning of the sumping cut, and thus dispense with the necessity of changing the feed r0 e when the transverse cut is commenced. The most convenient arrangement of ropes may be chosen by the operator as he desires. The essential and novel feature however, is that whereby the rope '2 may be anchored in one position, to act first as a restraining, or tailrop'e, during the sum ing cut, and may then be used in its norma function as a pulling, or feed rope during the transverse cut, without changing the position of the anchor 5 anchor 64 to a second position farther removed from the face in order to withdraw the machine rearwardly and thus finish the cut in a line with the left hand wall 68. With my machine, it is not necessary to replace the anchor in this manner, as it will be seen that by the application of power to the rope 6, when the machine is ositioned at the. end of the cut as shown in igure 16, the rear end of the machine will be swung to the right. The right hand front corner of the machine frame will then fulcrum at point X on the mine face 63, while the friction device on the rope 2 may be mani ulated so that the cutter arm 1 will comp ete the out along the left wall 68, and finally be withdrawn therefrom. This cut may tend to be slightly curved, somewhat as shown in Figures 17 and 18 but by proper manipulation of the friction device 10, I find that the out along the side face may be made straight enough for practical purposes. When the finishing cut illustrated in Figure 17 is completed, the tail-rope 6 is still in position to continue its pull on the machine to withdraw it substantially to the center of the room, from where it may be again loaded on the truck to be withdrawn from the room. As pointed out in connection with the fore going description of the sumping cut, it will also be seen that the specific arrangement of ropes over the pulleys may be changed during the finishing cut, dependin rope drum as it is upon working conditions, but the essentia feature afforded by a machine constructed in accordance with my invention, is that whereby the finishing cut may be made without replacing either of the anchors, and furthermore, the machine ma be withdrawn to the center of the room iiy means of the rope 6, which is an added saving in time ordinarily required when the rope 2 must be re-anchored and used for this purpose:

It will be borne in mind that all of the above operations may be accomplished at any desired speed, by means of the speed reducing mechanism 14, which is adapted to provide a widerang: of'speeds to either ing driven. Such a combination of a pair-of drums, both of which are provided with a variable speed 1 driving connection and an inde endently controlled friction device, aifor s an arrangement wherebythe machine may pull itself to the face, make the sumping cut, make the transverse cut, and the finishing cut and be withdrawn to the center of the room, with a minimum number of settin s of the anchors, and aifords thereby a su stantially continuous progress of the ma chine from the beginning to the end of the entire cutting 0 eration.

A further a vantage is the construction in which the functions of the feed and tailrope may be reversed at any time during the normal cut across the face, for the purpose of dislodging or cutting around extremely hard material which often forms an obstruction to the progress of mining machines of this class. By suitable whipsawing or rocking movement of the machine when such obstructions are encountered, it 1:; often possible to out behind or around such obstructions, and in some cases entirely remove them.

Another advanta e of this machine is the construction where y the movement of the machine is capable of being completely reversed, so that the cutting operation may be carried thru either from rlght to left, or from left to right. Such a complete reversal may be accomplished by reversing the'cutting elements on the cutter bar, rocking the pawls 41 and 52 on both rope drums, and reversing the direction of rotation of the motor.

Having described my invention what I claim as new and desire to cover by Letters Patent, is:

1. In a mining machine of the class described, the combination of a motor, and two flexible draft devices, each adapted to be driven in one direction by said motorand having means independent of said driving means for retarding each of said draft devices when moved in the other direction.

2. In a mining machine of the class described, the combination of a motor, two flexible draft devices, mechanism including a clutch aifording an operative connection between said motor and each of said draft devices, and means for retarding each of said draft devices when its respective clutch is disengaged.

3. In a mining machine of the class described, the combination of a motor, two flexible draft devices, mechanism including interlocking clutches, each affording an operable connection between said motor and one of said draft devices, and means for retarding each of said draft devices when its respective clutch is disengaged.

4. In a mining machine of the class described, the combination of a motor, a flexible draft device having operative connection with said motor whereby said draft dcvce may be driven in one direction, a retarding device, and means ,for automatically connecting said retarding device with said draft device when the latter is moved in the opposite direction.

5. In a mining machine of the class described, the combination of a motor, two flexible draft devices each having operative connection with said motor whereby said draft device may be driven in one direction, a retarding device associated with each draft device, and means for automatically connecting said retarding devices with their respective draft devices when the latter are moved in the direction opposite to that in which they are driven.

6. Inamining machine of the class described, the combination of a motor, two

control devices, each associated with a draft means, and a driving connection between each of said control devices and said motor including interlocking clutches whereby onefree to move independent of said driving I drum, a driving connection .between said.

site direction. 9. Ina machine of the class described, the.

mechanism when the opposite drum is bein driven, a retarding device associated wit each of said drums, and means forautomatically engagin each retarding device with ,its respective rum when the latter ismoved in adirection o posite to that in which said drum' is adapte to be driven. jv

8. Ina machine of the class described,-the combination of a motor, a drum, a flexible draft device adapted to be wound on said motor and said drum comprising a chan speedmechanism and a clutch, whereby saiddrum may be driven in-one direction, a retarding device and means for automatically engaging said retarding device with said drum when the latter is moved in the oppocombination of a motor, two drums, each associated with a flexible draft means, a

variable speed mechanism connected with said motor, a clutch interposed between each of saiddrums and said variable speed mechamsm, means for actuating said clutches simultaneously and a retarding device asso-- ciated with each of said drums.

10. In .a machine of the class described,

the combination of a motor, a variable speed mechanism connected with said motor, two drums each associated with a flexible draft means, dIlVlIlg mechanism intermedibearing .in, said pinion, a clutch ate each of said drums and said variable speed mechanism including interlocking clutches, and a retarding device independent of said driving means associated with each of said drums.

11. In a machine of the class described, the combination of a motor, two drums, each associated with a flexible draft means, a

variable speed mechanism connected with said motor, a longitudinall movable shaft driven by said variable 'spee mechanism and provided with two clutch members, each adapted to form a driving connection with one of said drums, and means for moving said shaft into a plurality of positions.

12. In a machine of the class described, the combination of a motor, two drums, each associated with a flexible draft means, driving mechanism for said drums, comprisan1sm, and a longitudlnally movab e shaft ing a planetary gear speed reducin mechconcentric with, and extending thru, said speed reducing mechanism, a; plurality of clutch members on said shaft, corresponding clutch members connected with each of said drums, and means for moving said shaft longitudinally intoa pluralit of ositions.

13. In a machine of the c ass the combination of aframe, a motor, two

ascribed,

drums, each associated with a flexible draft I means, a pinion having driving connection with one of said drums and -supported b mounted concentrically with and having on said shaft affording operative connection .with said said frame, a longitudinally movable sha t driven by said motor, said shaft bein'g pinion, a second clutch on said shaft hav- V mg operative connection with the, other. of 881d. drums, and means for moving said shaft longitudinally to actuate'saidclutches. 1 4. In a machine of the class described, the combination of a motor, two drums,

each associated with a flexibledraft means,

agiinion having driving connection with one 0 said drums, a bearing for said inion -mounted on said frame, a lon 'tu inall movable shaft mountedconcentrlcally wit 1 said pinion, a sleeve fixed on said shaft having an external bearing in said pinion,

clutchmeans associated. with said sleeve ad a ted to have drivin engagement with sea inion, a second 0 utch on said shaft afi o i a driving connection with the other 0 vsaid drums,- and means for shifting said shaft longitudinall 15. In a' machine of thee as described, a

combination of a frame, a motor, two drums, each associated with a flexible draft means,

a longitudinally movable shaft having driving connection with said motor, a second shaft having operative connection with one of said drums, clutch means inter osed be-- tween said 'shafts,'a second clutc afi'orda i naaoaeo ing driving connection with the other of said drums, and means for moving said shaft longitudinally.

16. In a machine of the class described, the combination of a driving means, a drum associated with a flexible draft means having operative connection with said driving means, a clutch, a frictionally controlled device adapted to rotate with said drum, and means automatically affording an operative connection between said frictionally controlled device and said drum in one direction of movement of the latter.

17. In a machine of the class described, a combination of driving means, a drum associated with a flexible draft means having operative connection with said driving means, a clutch, a frictionally controlled deviceadapted to rotate with said drum, and a ratchet and pawl device affording an operative connection in one direction between said drum. and said friction device.

18. In a machine of the class described, a.

combination of a driving means, a drum associated with a flexible draft means having operative connection with said driving means, a clutch, a frictionally controlled device adapted to rotate with said drum, and a reversible ratchet and pawl device affording an operative connection between said drum and said friction device in either direction.

19. In a machine of the class described, the combination of a driving means, a drum associated with a flexible draft means, a gear loosely mounted on said drum and ada ted to have operative connection with said riving'means, a ratchet .and pawl device associated with said drum whereby said drum I may be driven in one direction, a frictionally controlled member also loosely mounted on said drum, and a second ratchet and paw] device afl'ording an operative connection between said drum and said friction device in the opposite direction.

20. In a machine of the class described,

the combination of a driving means, a drum associated with a flexible draft means, a gear loosely mounted on said drum and adapted to have operative connection with said driving means, a reversible ratchet and pawl device associated. with said drum whereby said drum may be driven in either a direction, a frictionally controlled member also loosely mounted on said drum, and a second reversible ratchet and pawl device affording an. operative connection between said drum and said friction device in either direction.

21. In a mining machine, the combination of a motor, a variable speed mechanism having operative connection with said motor, a rotatable member driven by said variable speed mechanism, two draft-memrotatable member and both of said draft members comprising a pair of interlocking clutches, and means for retarding each of said draft members.

23. In a mining machine, the combination of a motor, a variable speed mechanism having operative connection with said motor, a rotatable member driven by said variable speed mechanism, two draft members each adapted to have operative connection with said rotatable member to be driven in one direction, and means for automatically retarding said draft members when moved in the opposite direction.

24. Ina mining machine, the combination of a motor, a variable speed mechanism having operative connection with said motor, a rotatable member driven by said variable speed mechanism, two draft members each adapted to have operative connection with said rotatable member to be 'driven in one direction, means for automatically retarding said draft members when moved in the opposite direction, and means for manually controlling said retarding means.

25. In a mining machine of the class described, the combination of a motor, a flexible draft device having operative connection with said motor whereby said draft device may be driven in one direction, a retarding device, means said retarding device with said draft device when the latter is moved in the opposite direction, and means for manually controlling said retarding device."

26. In a mining machine of the class described, the combination of a motor, two flexible draft devices each having operative connection with said motor whereby said draft device may be driven in one direction, a retarding device associated with each draft device, means for automatically connecting said retarding device with their respective draft device when the latter is moved in the direction opposite to that in which it is driven, andmeans for manually controlling each of said retarding devices.

27 In a mining machine, the combination of a frame, a motor, a variable speed mechanism having operative connection with said motor, a rotatable member driven at different speeds by said variable speed mechafor automatically connecting nism,'two rotatable draft members on 0 posite sides of said frame, each. adapte to have operative connection with said r0- tatable member to be driven in op osite directions with respect to each 0t er, and

means for retarding each of said rotatable draft means when moved in a direction opposite to that in which it is driven.

28. In a mining machine, a frame pro vided with a longitudinally extending cutting element, a motor on; said frame, variable speed mechanism havin'g-operative con nection with said motor, a shaft driven selectively b said variable speed mechanism at a plurality of speeds and extending transversely of said frame, two rotatable draft 7 members arranged at opposite sides of said frame and rotatable on transverse axes, each having operative oonn'ectlon w1th said shaft,

and means for retarding said rotatable draft members;

29. In a mining machine, a frame pr0vid-,

ed with a longitudinally extending cutting element, a motor on said frame, variable speed mechanism j having operative connection with saidmotor, a shaft driven seleotively b said variable speed mechanism at a pluraity of speeds and extendin transversely of said frame, two rotatab e draft said rotatable draft members.

CHARLES E. DAVIS.

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