US449090A - Ingee - Google Patents

Description

(No Model.) GSheets-Sheet 1.

W. M. SOHLESINGER.

ELECTRIC ROCK DRILL.

No. 449,090. Patented Mar. 24,1891.

WITNESSES: JNVE/VTOR/ gumxmww 7C3 WW7?! SW70,

A TTORNE V (.No Model.) 6 Sheets-Sheet 2.

W. M. SOHLESINGER.

ELECTRIC ROCK DRILL.

No. 449,090. Patented Mar. 24, 1891.

W! TNESSES: [NVEN TOR/ mmnosmufi zwym'wfl' A TTORNE V v m; m, mare-LIT (No Model.) 6 Sheets-Sheet 3. W. M. SOHLESINGER.

ELECTRIC ROCK DRILL.

No. 449,090. Patented Mar. 24, 1891.

WITNESSES: r [NI EN T OR Qmwwoflwb fmz m a. JM

ATTORNEY m5 Norms pnzns cm, wow-mun. msmm-rcu, o. c

(No Model.) 6 Sheets-Sheet 4. W. M. SGHLESINGER.

ELECTRIC ROCK DRILL.

No. 449,090. PatentedMar. 24, 1891.

[NVENTOR W ATTORNEY WITNESSES. WW

(No Model.) 6 Sheets-Sh6et 5.

- W. M. SGHLESINGER.

ELEG'IRIG ROCK DRILL.

N0. 449,090. Patented Mar. 24, 1891.

INVENTOR/ mm 046 SW allllllllllllilllllll'l ATTORNEY (No Model.) 6 Sheets-Sheet 6. W. M. SOHLESINGER. ELECTRIC ROCK DRILL.

No. 449,090. Patented Mar.'24,1891.

WITNESSES: INVENTOR,

A TTOR/VE V UNITED STATES PATENT OFFICE.

\VI'LLIAM ML SCIILESINGER, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO GIIARLFS F. VAN HORN, OF SAME PLACE.

ELECTRIC ROCK DRlLL.

SPECIFICATION forming part of Letters Patent No. 449,090, dated March 24, 1891. Application filed November 17, 1888. Serial No. 291,140. (No model.)

To all whom it may concern.-

Be it known that I, \VILLIAM ll. SCHLES- INGER, a subject of the Queen of Great Britain, residing at Philadelphia, in the county of Philadelphia and State of Pennsylvania,

have invented certain new and useful Improvements in Electric Rock-Drills, of which the following is a specification.

My invention has relation to power rotary io rock-drills in general, and particularly to portable rock-drills; and it has for its object to so construct the drill that it can be electrically operated, to provide an economical form of construction of e1eotrically-rotated rock-drill I 5 which is exceedingly durable and efficient, and to provide a simple and durable drill-rod feed-regulator of the form which, when predeterminedly adjusted automatically, acts to vary the degree of feed for the drill or anger to correspond with or suit the varying hardness of material through which the anger is working or penetrating, so as to avoid damaging or injurying the anger as it suddenly passes from a soft to a hard substance, and,

furthermore, to enable one and the same feed mechanism and drill-rod to be used for working in materials of varying hardness.

My invention accordingly consists of the combinations, constructions, and arrange- 3o ments of parts, as hereinafter described in the specification, and pointed out in the claims, reference being had to the accompanying drawings, wherein- Figure 1 is a longitudinal section of a portable rotary rock-drill embodying my im pro vements, the supporting-coluinn therefor not being shown. Fig. 2 is a horizontal section of part of same, showing more plainly the horns or lugs projecting from the ends of the motor field-magnet poles and connection between the same and the ends of the casing therefor. Fig. 3 is an end view, partly sectional, on the line 11 11, Fig. 1, showing partof the supporting-column and connection between the column and drill-casing. Fig. 4 is a like view,

partly sectional, on line 2 2 2", Fig. 1, the supporting-column not being shown. Fig. 5 is an elevation of the feed-nut for the drillrod. Fig. 6 is an end view of same. Fig. 7 is an inverted plan of the drilland supporting-column, the latter being in section. Fig.

8 is an elevation of preferable form of holders for the brushes for the commutator for the electric motor. Fig. 0 is a plan of same. Fig. 10 is a sectional elevation, partly broken away, of the supporting-column for the drill. Fig. 11 is a section, partly in plan, through the hand-wheel on the supporting-column. Fig. 12 is a section drawn to an enlarged scale on the line 2 2", Fig. 1. Fig. 13 is an elevation of the handle or turning end of electric switch for the motor and resistance-box with spring-pawl and ratchet-locking mechanism therefor. Fig. 1% is a diagrammatic plan showing more plainly the circuit-connections between the switch, resistances, and electric motor. Fig. 15 is a sectional elevation of part of the motor-armature shaft and feed-rod, showing a modified form of feed mechanism for the drill-rod; and Fig. 1c is a detail ele- 7o vation of part of the same, partly in section.

A represents a casing or box, composed of, preferably, a base-plate a, ends a a and a sheet-metal cap or cover a forming the top and sides of casing. The ends a a are preferably screwed to the base-plate, as indicated at o or they may otherwise be fastened to the plate, as desired.

On the under side of the base-plate a, near its front end, is a tubular bearing I3, in which is journaled a tubular sleeve 1, having in its bore keys K), at one end a collar Z1 fitting or engaging with a slot 1/ in the base-plate a, and at its other end a gear-wheel Z)", which wheel and sleeve, if desired, may be integral, as shown. Through the sleeve Z) passes the drill-rod C, (indicated in dottedlines, Fig. 1,) which has longitudinally-arranged peripheral key-slots c for engagement with the keys Z) in the bore of sleeve Z) to provide for rota- 0 tion of the drill or feed rod with the sleeve Z), and at the same time admit of the drill-rod sliding or feeding longitudinally through the sleeve when actuated by the feed mechanism.

The latter consists of a two-part cylindrical 5 or tubular nut D, smooth on its exterior surface, interiorly threaded at (Z, and having between its parting edges springs d, which tend to normally spread the sections of the nut D apart. The nut D is loosely supported between two sliding dogs or jaws E E, curved to conform to the nut and having end flanges e overlapping the ends of the nut to prevent endwise movement of the nut-sections when they are out of contact or engagement with the drill-rod C. The dogs or jaws E have at their upper extremities ends or feet e',-which fit and slide in transverse ways-or guides e in the bed-plate a. The feet e have threaded openings e ,the threads in one being right and the other left handed, which respectively engage with right and left screw-threads on adjusting-rod e, which may be mounted upon the bed-plate a, as shown more plainly in Fig. 12, or otherwise swiveled on the bedplate, as desired, in order that when the rod is turned it will not have a lengthwise movement, so that by turning rod e in one direction the jaws E E approach each other until they contact with the sections of nut D, and close them together until their parting edges meet, to effect engagement between the nut and drill-rod, and, further, to produce a frictional clamping between the nut and the jaws, and by more or less reversely turning said rod 6 the clamping or frictional pressure between the jaws and nut is decreased, or the jaws E E are drawnapart to admit of the springs 01' spreading the nut-sections apart to totally release the engagement between the drill-rod and the nut to enable the drill-rod to be manually pulled backward or forward rapidly for adjustment or exchanging of angers. As the parting edges of the nut-sections meet when the sections are closed into engagement with the drill-rod, the pressure of the jaws on the nut-sections impart no pressure of the nut-sections on the drill-rod. Consequently the full power exerted by the motor is employed for drilling and not for overcoming useless frictional contact between the nut and drill-rod.

Secured to or formed on the top of the baseplate a are the cores and pole-pieces for the field-magnets f of a form of electric motor F, having a rotating armature G and armatureshaft g, and to admit of more readilyv winding the helices f on the field-magnets I prefer to longitudinally divide the base-plate, as indicated at 00, Fig. 7, in which case the tubu lar bearing 13 is also correspondingly divided and the bed-plate sections are connected by transverse bolts a and the sleeve-sections B by a yoke or bar b The motor-armature G may be of any suitable construction, and its shaft g is mounted in bearings g, secured to or formed on the casing ends a a One end of said armature-shaft projects beyond end a of the casing, and upon it is mounted a pinion 9 which gears with wheel b for transmitting power to the sleeve 17 and in turn to the drill-rod for rotating it. From the ends of the pole-pieces of the field-magnets f project horns or lugs f (see more plainly Fig. 2,) the outer ends of which have a screw or bolt connection f with the ends of the casing to stiffen and strengthen the same against the side thrust of the motor. The lugs at the commutator end of the armature-shaft, which commutator is shown at f, form supports for the brush-holders H.

Any suitable form of brush -holder and brushes may be used. In the drawings, Figs. 8 and 9, I have shown a preferable form of same, wherein the holder H is secured to but insulated from the lugs f and consists, essentially, of a frame or bracket h, having at its forward end a transverse slot h, preferably opened at one'end to admit of easy replacement of brushes and secure compactness of parts. Said slot is closed at its open end by a screw b to keep the brushes in position. Through slot 71' vertically passes the brush h the thickness of which is less than that of the slot, so that. the brush will have lateral play in the slot to assume a slightlyinclined vertical position for contact with the commutator-segments, being maintained in such contact by means of a presser-bar 72, bearing upon the outer end of the brush. The

be connected to a spiral or other spring h by a set-screw mechanism h so that the degree of pressure upon the brushes to maintain their contact with the commutator may be regulated as desired. The vertical position of the brushes is due to the location of the neutral line of the motor as it is constructed, and in this position they are easy of access for replacement or adjustment through openings h in the casing end a which are covered by doors or slides h The brushes are inclined, so as to give a softer contact with and have a more even pressure on the commutator. The slot h is made wider than the width of the brush to enable the brush to take up oppositely-inclined positions in case of reversal from the outside.

The. sheet-metal casing-cap a is preferably made of brass or other non-magnetic materesser-bar h ma beas rin -bar or it ma IIO rial for the purpose of preventing short circuiting of the magnet-circuit, and within the casing, near the top of the same, and secured to said cap, is a resistance-box L, having circuit-connections with a suitable electric controlling-switch K for the motor. The movable part K of said switch, the resistancebox L, the contact-fingers between the switch and resistance-box, and the line-wire bindingposts or couplings are all mounted on or secured to cap a while the contact-fingers between the switch and motor are secured to the end a of the casing, so that the casingcap a canbe removed and replaced without necessitating dismantling any of said parts. The binding-posts for the line-wire 1 l are shown in the form of a coupling-section N, as described and claimed in a pending application filed by me on the 2d day of October, 1888, Serial No. 286,979, so that the ends of the line-wire secured to a mate coupling-section can easily and safely be connected to and disconnected from coupling-section N.

The switch K, as shown in the drawings,

consists of a rotating cylinder K, of insulating material, suitably mounted in hearings in the sides of cap a having an outside knob or turning-handle 7;. (See more plainly Figs. 3, at, '7, and 14.) Upon said cylinder are oppositely-located segmental contact-plates 7t" 7t, electrically connected, as indicated at 7t", and 7c" 7r? are the respective contact-fingers therefor. (See more plainly Fig. ll.) k is another segmental contact-plate, having steps 7.1 it 76, which is in electrical contact, as indicated at with a segmental contact-plate 7t on said cylinder in line with the step it of plate 7;.

7& is the contact-finger for contact-plate 7t, and 113 7.1 and 7.9 are the respective contactfingers for the steps 71: 7f, and it of plate 7;. One side of the line-circuit lends to contactfinger 7& and the other side of said line is connected to contaet-finger 7.1 and the latter and the fingers 7t 7.; are in circuit with the resistance-box L. The electric motor F is in circuit with the contact-fingers 71;" 7. \Vhen the cylinder K is in the position shown in Fig. let, the circuit from the line 1 1 to the motor is by way of contact-finger 73 through the resistance-box L and finger 7; to contactfinger 7e, and all the resistances in said box are included in the circuit, thence by wayof plate 705 or its step 75 and connection 7.1 to plate 7;, and thence by way of finger 73 to and through the motor to finger 7e" and plate 7t, and finally by connection 7r to plate 7; and finger 7; to the other side of the line. This described position of the switch is the one in which the motor is started and all the resistances L are included in the circuit to enable the motor to be started slowly and the work adjusted before drilling full speed.

turning the cylinder or switch part K in the direction of the arrow, Fig. 14., until the finger 7d contacts with step b of plate 7t part of the resistance in box L is cut out, and a further turning of said cylinder until the finger 75 contacts with the plate-step it cuts the resistance L out of circuit and the motor is then doing its maximum work. By reversely turning said cylinder the resistances are included in the circuit, and when the cylinder is turned until all the fingers pass off of the contact-plates the motor is cut out of the line-circuit. If desired, a suitable reactingspringt (see Fig. 1) may be used for re versely turning cylinder K. To maintain the cylinder K in the position to which it is adjusted, a collar Z is secured to its sliaftl outside of the casing, (see more plainly Fig. 13,) which collar has a number of peripheral notches Z corresponding to the number of fixed positions desired for the cylinder, and these as the cylinder is turned come into successive engagement with a spring-pawl Z to lock the cylinder in its adjusted position.

Adjacent to one side of the bed-plate a and to its under side, or otherwise suitably located, is formed a socket m, into which screws a bolt m, swiveled in sleeve or ring M on a column or support P. The sleeve M rests upon a collar 0, secured to column Pbya setscrew 0, so that the drill, sleeve M, and collar 0 can be adjusted vertically on said column. The sleeve M is parted or split at m and has a clamping-screw in thereat, so that by loosing said screw on the drill may be rotated horizontally to any desired position, and by tightening said screw on" the sleeve M is clampedto the column to secure the drill in its adjusted position. The bed-plate socket m is secured to the screw m, swiveled to sleeve M to admit of placing the drill-rod in a vertical, horizontal, or angular positionfor work or drilling.

Any suitable form of vertical or horizontal or other column P may be used. In the drawings I have shown a form of vertical column comprising a two-prong or other numbered prong-base p, to which is jointed a plug 11, secured in the bottom end of a tube 12 which has at its upper end a tubular plugp the bore of which is threaded to receive a screw 1), having a hand-wheel p and a swiveled pointed top p. By manipulating hand-wheel p the length of the column may be increased, as desired, and the prongs onthe base 1) prevent twisting or rotation of the column P when the drill is in operation.

hen the drill is in proper position for working, the coupling-connection at the end of the line-wire is connected to coupling-section N on the casing A, and the screw-rod c" is turned to move jaws E E to cause the sections of nut D to come together and engage with the drill-rod, and also to produce between the jaws E and said nut the frictional pressure desired therefor, which pressure in practice depends upon the strength of the drill and the power of the motor thereon. The switch K being manipulated to the position shown in Fig. ll, the drill-rod is slowly rotated and as there is no baclepressure on the drill-rod, or, in other words, as there is no pressure between the nut and drill-rod opposing or overcoming that between the nut and jaws E, the nut remains stationary and feeds the drill-rod forwardly at full speed to bring the auger up to the work. As soon as the auger meets the material and begins to drill or to work therein, the back-pressu re, due to the resistance which the auger meets with on penetrating the materials, falls on the nut D. If this back-pressure is not powerful enough to overcome the frictional pressure between the nut D and jaws E E, then the nut still remains stationary and feeds the drill-rod forwardly at full speed. As soon, however, as the back-pressu re is strong enough to overcome such frictional pressure between the nut and jaws the nut revolves with the drill-rod and automatically varies the feed of the drill-r0d. The degree of variation in the feed of the drill depends upon the speed of rotation of the nut D, and the speed of rotation of nut depends upon the back-pressure or the resistance the auger meets with. Thus the harder the material in which the auger is IIO worked the greater the back-pressure, the faster the speed of rotation of the nut D, and the slower the feed of the drilLrod. On the other hand, the softerthe materhl the less the back-pressure and the slower the speed of rotation of the nut and faster the drill-rod is fed forwardly.

As the variation in the feed of the drill-rod, as above described, is due entirely-to the variation of the back-pressure on the rod, it follows that as the back-pressure varies as the auger penetrates or bores through materials of dilferent degrees of hardness the variations in the feed of the drill-rod are automatically effected. Only one and the same drill-rod and feeding mechanism, therefore, is required for use, and all danger of injury to the anger or drill, due to too rapid feedingof the drill-rod as the auger suddenly passes from a soft to a hard material, is avoided.

In Figs. 15 and 16 I have shown a modified form of feed mechanism for the drill-rod 0, wherein the sections of the nut D are hinged to ether and pivoted to a disk R, which finds 9 its bearing on the top of the screw-threads on rod 0, being loose thereon, and said nut-sections have an adjusting-screw r for engaging them with and disengaging them from the drill-rod O. The disk or wheel R is in frictional engagement with one or more like disks S S, rotating with the armature-shaft g,bein9 keyed thereon, so as to have a movement along the shaft 9 when adjusted by means of a right and left screw-bolt r to vary the frictional contact between disks S and disk R. In this case, as shown, the threads on the drill-rod are of a reverse pitch to that for the threads .shown in Fig. 1, or are left-handed to avoid interposing idler-disks between the disks S and R. In this construction the disk R and nut D are continuously revolved by the armature-shaft, or the nutis always in motion, and the faster the nut revolves the greater the feed of the drill-rod. As the backpressure on the drill-rod falls on the disk It, such pressure opposes the frictional pressure between the disk It and disks S S on the armature-shaft to effect a variation in the speed of rotation of nutD and consequent variation in the feed of rod 0. To withdraw the rod 0 from the nut D, the screw '1" thereon is adjusted to spread the nut-sections apart until their threads disengage from those on the drill-rod.

As it is obvious that the novel constructions and arrangements of parts may be greatly varied without departing from the spirit of my invention, I do not confine myselfv to the same, as shown and described. Thus, for instance, while I have illustrated a preferable form of feed mechanism for the drill-rod it is obvious that any other suitable or the wellknown hand or other feeds can be substituted.

From the foregoing it will be noted that as all the parts of the electric motor, as well as the electrical resistance-box, switch, and their circuit-connections, areinclosed in the casing A said parts are preserved from injury by careless handling of the 'drill or by falling rock or debris. Dust and dirt are excluded from the working parts of the motor and from the terminals of the switch, so that they are always bright or clean to obtain perfect contact when necessary changes of circuit are made for controlling the operations of the motor and in turn those of the drill-rod. Furthermore, as the casing A is closed the operators or attendants cannot inadvertently catch hold of any live wires or other current-conducting parts in said casing, and, lastly, access of fire-damp or explosive gases to the sparks at the commutator-brushes or switchterminals, and consequent explosion of same by said sparks when the drill is used in mines, is prevented, and greater safety of working electrically-actuated drills is obtained. As the casing A has the removable cap a with part of the electrical devices secured thereto, all of said parts are easy of access for making quick repairs and replacement. As all the electrical devices are secured to the bed-plate a, as is also the drill-rod O, and as the sectional feeding-nut D is applied directly to the drill-rod, the number of parts are very much diminished and the drill is lighter and more compact, so that it can be easily and quickly handled in shafts of mines or other confined places. As the sectional nut D is loose on the drill-rod and has an adjusting clamping device which does not impose any friction on the drill-rod, the full power of the motor is used for drilling and is not wasted in overcoming needless friction,and, further, as said nut is in sections it can be readily separated to disengage its sections from the drill-rod, so that it can quickly be pulled back out of the drilled opening. These described advantages, in conjunction with the minor advantages hereinbefore set forth, afford a portable drill of extreme usefulness and durability, as it can easily and quickly be handled under all conditions of service. and its parts are correspondingly repaired or replaced, and great safety in working or operating it is assured.

What I claim is 1. The combination of a rotating and longitudinally-feeding drill-rod, as'upport there for, an electric motor havingarotating armature-shaft on said support, gearing betwe said armature shaft and drill-rod, feeding mechanism for the'drill-rod, and devices for disengaging said feeding mechanism from the drill-rod to admit of a quick return of the drill-rod independently of said feeding mechanism, substantially as set forth.

2. The combination of a rotating and 1ongitudinallyfeeding drill-rod, a support therefor, an electric motor having a rotating armature-shaft on said support, gearing between said armature-shaft and drill-rod, an electric switch, resistance-box, and circuit-connections for the electric motor, substantially as set forth.

3. The combination, with a rotating and IOO ITO

longitudinallyfeeding drill-rod, a support] therefor, an electric motor having a rotating armaturesl'iaft and the field-magnets of the motor forming a part of said support, gearing between said armature-shaft and the drill rod, feeding mechanism for the drill-rod, de-

vices for disengaging said feeding mechan= ism from the drill-rod to admit of a quick returnof the drill-rod ii'idependently of said feeding mechanism, and a casing for said motor, substantially as set forth.

4. In combination with a support or column I the casing A, an electric motor, electrlcal switch, resistance-box, and circuit-eonneetions therefor, all supported on and located within said casing, a rotating drill-rod O, mounted on said casing and in gear with the motor, and feeding mechanism for the feed-rod, substantially as set forth.

5. In combination with a column or support P, a base-plate a, swiveled to said support and composed of sections, each section having an eleetro-niagnet secured thereto, a casing on said bed-plate, an armature forsaid magnets, an armature-shaft suitably mounted in said casing, a drill-rod supported on the bed-plate, and gear connection between the drill-rod and the armature'shaft, substantially as set forth.

0 (i. The combination of bed-plate a, ends a w, secured thereto, cap a", connecting said ends and bed-plate and forminga closed casing A, electromotor F within said casing A, and a drill-rod C, supported on said bed-plate and having gear connections with said motor, substantially as set forth.

7. The combination of bed-plate (I, ends a a metal cap a openings ii in end a doors or covers for said ends and forming a casing A, electric motor F within said casing A,a drill-rod C, and gear connection between said motor and rod, substantially as set forth.

8. In combination with a drill-rod support, a closed casing A, made in sections, one of which is removable from the other, an electric motor within said casing, an electric switch, one part of which is secured to the fixed casing-section and the other part to the removable easing-section, substantially as set forth.

9. In combination with drill-rod C, a support therefor, electric motor F in gear with said drill-rod, resistance-box L, switch K, circuit-connections for said motor, switch, and resistance-box, and a closed casing A for said motor, switch, and resistance-box, substantially as set forth.

10. In combination with the base-plate at, having ends a a drill-rod 0, metal cap (t having secured theretoa resistance-box, part of an electric switch, and a coupling-section for the ends of the line-wire, the other part of said switch being connected to one of the ends a a an electric motor within said cap and ends, and a drill'rod O in gear with said motor, substantially as set forth.

11. In combination with the sectional bedplate (1, having sectional sleeve l3, drill-rod C in said sleeve, field-magnets f, secured to said bed-plate sections, ends a a secured to said plate, an armature mounted in said ends, drill-rod C, and gearing between the rod and armature-shaft, substantially as set forth.

1?. In combination with bed-plate a, drill red C, ends a a secured to said bed-plate, an electric motor the field-magnet poles of which have end horns or lugs f connected to ends a (t cap a and gearing between said feed-rod and motor, substantially as set forth.

13. In combination with a drill-rod C, an electric motor in gear with said rod, a switchbar K, having ratchet-wheel Z, a spring-pawl Z engaging with said ratchet-wheel, resistance-box L, eircuit-coiniections, and a closed casingri, substantially as set forth.

14c. The combination of a rotating and longitudinally-feeding drill-rod having exterior screw-threads, a sectional threaded nut on said drill-rod, and adjustable jaws for supporting said sectional nut for engaging the latter with the drill-rod, and for imposing an adjustable friction or clamping contact between the sectional nut and the jaws, substantially as set forth.

15. The combination of a rotating and longitudinally-feeding screw-threaded drill-rod, a sectional SG1GW1llll) on said rod, friction de vices for said nut, which act to hold the sectional nut stationary to feed the drill-rod when there is no back-pressure on it, and which permit the nut to rotate to vary the feed of the drill-rod when subject to backpressure, substantially as set forth.

16. The combination of a rotating and longitudiually-feedingdrill-rodexteriorlythreaded, a sectional nut on the drill-rod, adjustable jaws for supporting said nut, and spring-actuated devices between the nut-sections for spreading them apart out of engagement with the threads on the drill-rod when the adjustable jaws are moved apart, substantially as set forth.

17. In a rock-drill, the combination of a 1'0- tating and longitudinally-feeding drill-rod O, the sectional feedingnut D, loose upon and engaging with said rod, and adjustable clamping devices for said nut to hold it in a fixed position and admit of said nut rotating with the red C to vary its feed, substantially as set forth.

18. In a rocledrill, the combination, with a rotating and longitudinally-feeding red C, the sectional nut D, loose on said red C, clamping and supporting jaws E E, and adjusting devices for moving said jaws to impart a clamping-friction between the jaws and nut without creating friction or clamping contact between the nut and drill-rod, substantially as set forth.

19. In combination with bed-plate a, the rotating and longitudinally-sliding drill-rod G, sliding jaws E E, having adjusting mechanism, and sectional nut D, interposed between the jaws and rod, which nutis stationary for feeding'the red at a given feed and rotates with the rod to vary said feed, subsantially as set forth.

20. In a rock-drill, the combination of the drill-rod C, the sectional nut D, springs in-' terposed between the meeting edges of the nut-sections, movable jaws E E for supporting said nut-sections on rod 0, and adjusting mechanism for said jaws, substantially as set forth.

21. In a rock-drill, the combination of a motor-shaft, a feeding drill-rod separate from and driven by the motor-shaft, a feeding device for the drill-rod, a clamp for said feeding device to hold the latter stationary to feed the drill when there is no back-pressure on it to permit the feeding device to rotate for varying the feed of the drill-rod when sub-

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