US2159087A - Drilling machine - Google Patents

Description

May 23, 1939. R. K. JEFFREY DRILLING IACHINB Original vFiled May 14, 1934 5 Sheets-Sheet l m M M.

AT'T'Y R. K. JEFFREY DRILLING IACHINE y Original Filed lay 14, 1954 5 Sheets-Sheet' 2 May 23, 1939. R. K; JEFFREY DRILLING MACHINE Original Filed lay 14, 1934 /NVENTOR Rober-7" /f Jeff/*eyl ATT'Y May 23, 1939. R. K. JEFFREY 2,159,087

DRILLING IACHINE v 'Original Filed lay 14, 1934 5 Sheets-Sheet 4 'Ell. 73I f @bmw-MM.

Patented May 23, 1939 UNITED STATES PATENT f OFFICE Company, a corpora- Application May 14, 1934, Serial No. 725,504

, Renewed Octo ,26, 1938 .-7 Claims. (Cl. 172-46) 'lhe present invention relates to portable drilling units of the manually supported type and although particularly adapted for use in drilling operations in coal mines, it may have a general application.

One of the objects of the present invention is the provision of improved and eilicient mechavnism for a portable manually supported drilling machine to reduce the weight thereof to a minimum,-

More particularly it is the object of the present invention to provide a drilling machine sutilciently light in weight to enable it to be eiiciently handled by a single operator without necessitatl5 ing mounting of the drilling machine on any support.

Another object of the invention is the provision of drill operating mechanism compactly ar- 'ranged in a dame-proof casing in a drilling ma.-

chine capable of being manually supported during operation. g

Another object of the invention is the provision of controlling mechanism for the motor of a drilling machine, operable by means of a. lifting handle to eect starting of the machine, combined with means for automatically stopping the machine upon release of the handle.`

A further object of the invention is the provision of improved and efficient electric switch mechanism for controlling an electric motor of a drilling machine, including means for holding the switch closed until opened with a snap action to reduce the arcing to a'minimum.

A still further object of the invention is to provide a portable manually supported drilling machine with the center of gravity placed behind the axis of lifting handles to effect such counterbalancing of the weights of the parts of themachine as to facilitate free handling oi' the machine. Another object of the invention is the provision of improved and emcient air circulating mechanism about the operating motor of a drilling machine within an enclosing casing to increase the heat radiating capacity of thelatter and thereby eil'ect cooling of the motor to prevent overheating thereof during operation ofthe drilling machine.

Other objects of the invention will appear hereinafter, the novel features and combinations being set forth in the appended claims.

In the accompanying drawings: Fig. l is a plan view of my improved drilling machine with a drill connected thereto in drilling position;

Fig. 2 is an elevational view taken on the line 2 2 of F18. 1 with the drill removed from its socket and the cover for the switch housing removed to show in elevation the electric switch for controlling the operating motor;

Fig. 3 is a view taken on the line 3 3 of Fig. 2, looking in the direction of the arrows; showing mechanism for clamping to thelcasing of a machine a power cable of electric wires leading from the source of power to the electric motor of the l0 machine;

Fig. 4 is a longitudinal sectional elevational view of the motor and power transmission mechanism enclosed -by a flame-proof casing;

Fig. 5 is a sectional view taken on the line 5 5 15 of Fig. 4, looking in-the direction of the arrows;

Fig. 6 is a sectional plan view of the drilling machine including the air circulating mechanism and the heat radiator `for the electric motor;

Fig. 7 is a fragmentary sectional elevation of 90 the switch mechanism and the mechanism for effecting the operation thereof manually to closed position and automatically to open position;

Fig. 8 is a sectional view taken on the line 8 8 of Fig. 7, looking in the direction of the arrows, 25 and showing the relative positions of the switch operating handle and the switch yoke when the switch is closed;

Fig. 9 is a view similar to Fig-i8, but showing the relative positions of the switch operating hana dle and switch yoke when the switch is in open position; I

Fig. 10 is a sectional view taken on the line lli-Ilot Fig. '7, looking in the direction of the aITOWS; 3

Fig. 11 is a sectional view taken on the line Il ll of Flg.8;

Fig. 12 is a sectional view similar to Fig. '7, with certain parts broken away to show more clearly the elements of the switch mechanism;

Fig. 13 is a wiring diagram to illustrate the electrical connections from the source ofpower to the motor and the electric switch; and

Fig. 14 is a view similar to Fig. l0, but showing the electric switch in closed position.

Referring more particularly to the drawings, it will be observed that the drilling machine shown in plan in Fig. 1 comprises a motor, power transmission mechanism and an electric controlling switch very compactly arranged in a flame-proof 50 casing as shown in Fig. 6. The casing or housing comprises a plurality of compartments detachably connected and arranged and designed for maximum compactness and minimum weight to facilitate handling of the machine during operation. As shown in Fig. 6, A designates the motor compartment. B the power transmission compartment, and C the motor switch compartment. The casing or housing comprising the three compartments or sections A, B and C is preferably constructed except the motor field frame by an assembly oi' castings offmagnesium-aluminum alloy which has the advantage of being very light in weight, easily machined, and having high thercylindrical radiator i9 designated By means of cap screws 23 spaced circumferentially around the flange lili, the latter together with the cover 22 may be detachably secured to the end lli of the radiator i9. Y

It should he particularly noted that the cover 22 is provided with a. cylindrical inwardly extending flange M2 to fit against the annular shoulder i3 with its inner surface iiush with the inner cylindrical surface of the radiator I9 which also serves as a casing for the motor as herein-s after more fully explained. The flange ||2 is of suiilcient length to effect a flame-proof closure for the end iii of the casing |9 because of the length of the tortuous passageway between the interior of the casing and the outside atmosphere. Consequently, when the drilling machine is used ina gaseous mine and there should be anv explosion of a gaseous mixture within the casing no flame can reach the atmosphere outside ci' the casing even though there should be a gaseous passageway or crevice along the annular spaces between the ilange |l2 and the end of the radiator iii. As will appear more fully hereinafter, all of the parts enclosing the motor, power transmission mechanism and the switch are so assembled as to provide tortuous surfaces of suiiicient length to cool ignited gases before a flame can reach the atmosphere outside of the enclosure.

As shown in Figs, e and 5 the compartment E; is provided with flanges tid and H5 similar to flanges il@ and M2 respectively. The cornpartu ment B is detachably secured to the compartment A by means of circurnierentially spaced screws i lo. A {dame-proof connection between the compartment B and the compartment A is thus provided with the inner surface of the ange |65 iiush with the inner surface of the motor casing.

The compartment B comprises two sections 3&5 and ii'l, the latter being provided with a cylindrical ilange lll and a peripheral flange il'l detachably secured to the section 34 hy means or the circumierentially spaced screws i i8 to form a flame-proof connection between the sections 3G and lll similar to the flame-proof connections at lili-H5 and Elli, M2.

The motor compartment A is provided with screw-threaded covers |36, |161 threaded at 'dit and t? respectively into the section 34 as shown in Fig. e. -When these covers are closed theyr may be locked in closed position by means of the seals shown at |06 and |31 in `Figi. 2. When these seals are broken a Spanner wrench may loe used to open the covers to provide access to the brushes |103 and lila of the *electric motor it as shown in Fig. The screw threads at di and when the covers are closed aiord alsace? tortuous lines of contact of suiiicient length to maire the covers iBS and |31 flame-proof between the interior oi the casing and the exterior atmosphere.

In a tubular extension |31 of the section ||1 of the compartment B is mounted on the roller thrust bearings 40 and 4|)a a shaft 31 which is preferably hollow to lessen the weight of the drilling machine While being manually supported for operation. Between the shaft 31 and the drill socket 21 which is mounted at the outer end of the hollow shaft 31 is an annular collar |38 to provide an annular seat for the ring 4| which is held in place against such annular seat when the inner race of the roller thrust bearing 40 is secured to the outer surface of the hollow shaft 31 as shown in Fig. 4. By means of a resilient snap ring 4|c a ring shaped plate 4|b is held against an annular seat in the outer end of the tubular support |31 with the inner edge of the ring Mb spaced from the peripheral surface of the collar |38 but in contact with the rear end of the annular surface of the drill socket diV as shown in Fig. 4. When the drill socket rotates the ring 4 |0- rotates with it but this ring does not engage either the ring Mb or the tubular support |31 since it is spaced from both of them. This arrangement provides not noly a seal to prevent the ingress of coal dust or other material into .the interior of the compartment B but also affords a tortuous passageway between the interior of the support |31 and the exterior atmosphere of suiiicient length to serve as a dame-prooi closure in a gaseous mine during operation of the drilling machine. The outer end of the hollow shaft 3l may, if desired, he entirely closed at 63S. The inner end is screwthreaded to receive the screw plug 38 which is provided with a head 3Ba which is so constructed as to enable the lock washer 39 to cooperate therewith and with the hub of the gear 36 to lock the screw plug 38 securely to the hollow shaft 31 to rotate therewith and with the gear do which is keyed at 36 to the hollow shaft 31.

IThe outer races of the roller thrust hearings 40 and tiill iit against annular shoulders 4Gb and idc as shown in Fig. 4. The inner race of the roller thrust hearing l is secured to the outer surface of the hollow shaft 31 in position for one end of the huh of the gear 36 to abut against the same. it will thus be seen that the screw plug 3S and. the loclr washer mechanism mounted thereon and associated with the hub of the gear 36, lock the latter against longitudinal displacement relative to the hollow shaft 31. The thrust bearings serve to resist longitudinal displacement of the drill socket relative to the tubular support |l3i both when the drill is fed into the mine vein and when it is pulled out of the drill hole.

By referring to Figs. e and 6, it will he seen that the drill socket of the shaft 31 is axially alined with the tubular armature shaft 29 which is mounted :for rotation in the ball hearing 28 and the section 34 of the compartment E. The shaft dii on which the armature of the motor is mounted is made hollow throughout almost its entire length so as to assist in reducing the weight of the drilling machine. One end of this hollow Shaft is screw-threaded to receive the screwthreaded extension 30a while the extension 46 at the other end may be solid and integral with the hollow shaft as shown in Fig. 4. The extensions Sile and do serve respectively as shafts for the pinion 3U and the fan i5 hereinafter more fully described.

Mounted on the shaft 29 is a collar 29 adjacent to an annular flange |48 on the outer side of which there is located 'a washer |4| between the hub of the collar 29l and the inner race of the ball bearing 28. This arrangement serves as a flame-proof connection between the interior chamber in the compartment A and the interior chamber in the compartment B. If the flameproof connection at |48 is omitted, reliance may be had on the name-proof connection at 4|* but itis preferred to use both of the name-prooi' connections shown in Fig. 4 at |48 `and 4I so that double assurance may be had that any flame produced by an explosion of a gaseous mixture in the compartment A will not find its way through the compartment B to the outside atmos' phere. It will also be noted that the hub of the ring collarv 29 serves to space the motor armature in a predetermined position relative to the section 34 of the compartment B. Inasmuch as the end thrust on the armature shaft of the motorr is small during rotation, the ball bearings 2| and 28 held'in place as shown in Fig. 4 are suiiicient to prevent longitudinal movement of the armature shaft 29 relative to the enclosing casing. The ball bearing 2| is mounted ln a cup shaped seat at the center of the inner side of the cover 22. The ball bearing 28 is mounted in a cup shaped seat 34 and it is held in place by the resilient snap ring 28'. The brush holder support 29b is ring shaped and secured to the bosses 29 as shown in Fig. 6, in spaced relation to the collar 29* which, together with the washer |4|, rotates with the hollow shaft 29. The inner race of the ball bearing 28 fits against an annular seat formed by the collar 28 mounted at the inner end of the pinion 30 on the pinion shaft 38' which is screw-threaded into the hollow shaft 29 as shown in Fig. 4.

The .pinion 38 meshes with a gear 3| mounte on a shaft 32 the ends of which are mounted on the ball bearings 33, 33. The shaft 32 carries a pinion 35 which meshes with a gear 36. It will thus be seen that reduction gearing is provided in the section 34 of the compartment B to serve as power transmission mechanism between the armature shaft 29 and the hollow tool socket shaft 31 with the shafts 29 and 31 in axiall alinement l with each other.

In Figs. 4 and 6 the tool socket 21 is shown as being provided with interior lugs |36, |38 which are adapted to cooperate with the drill shank to hold the latter in position in the socket during the drilling operation. 'I'he lugs |36 may be formed of rivet heads welded or otherwise secured in place as shown in Fig. 4. In Fig. 2 a modified form of drill socket is shown at |34 for receiving the standard type of tapered drill shanks.

In order to support the drilling machine manu-7, ally during operation with its center of gravity back of the alined hollow handles 41 and |32 or away from the drill socket 21, said.I handles are connected to the casing of the machine so as to extend in opposite directions as shown in Fig. l at right angles to the axis of the motor shaft and of the drill. The handle |32 as shown in Fig. 6

` is screw-threaded into the socket |33 of comhandle |32 remains rigidly connected tothe supporting casing but the handle 41 is mounted for limited rotation.

Mounted in the tubular extension 48 of the compartment C is a bushing 52 to serve as a journal bearing for the cup shaped sleeve 49 which is secured by means of the pin 50 to the inner end portion of the hollow handle 41. The bushing 52 is secured to the tubular extension 48 by means of the pin shown at 48. A portion of the bushing 52 extends inwardly to form ixed abutments 52* and 52h as shown in Figs. 8 and 9, which abutm'ents'are stationary relative to the supporting casing or irame of the drilling machine.

The outer end of the sleeve 49 is provided with an annular ange 49n which is adapted to abut against the outer end of the bushing 52 as shown in Fig. 6. A retaining washer H9* and a snap ring ||9 serve to hold the annular flange 49 in its position against the outer end of the bushing 52 as shown in Fig. 6.

'I'he outer end of the tubular support 48 is recessed not only to provide annular seats for the washer ||9l and the snap ring 9 but also the inner end of the coll spring 51 which inner end is secured at 58 to the tubular support 48 as shown in Fig. 2. The outer end of the spring 51 is secured at 58 to the tubular handle 41 as shown in Figs. 2 and 6. 'Ihe inner end 5| of the sleeve 49 is provided with an extension 49' which is provided with a spring seat 5|* and a movable abutment 5|b. When theihandle 41 is released the spring 51 acts to move the abutment carrier 49 to a position shown in Fig. 9.

Projecting axially from the center of the plate 5| as shown in Fig. 6, is a bearing 54 about which is coiled the intermediate portion of the spring 68, one end of which at iii)b rests against the seat 5| and the other end of which at 60 bears against the yoke 53 one end of which is journaled on the bearing 54 and the other end of which is provided with a shaft 54a which is journaled in the bearing 55 as shown in Fig. 6. The shaft 54 is in axial alinement with the bearing 54.

The yoke 53 is connected to electric switch mechanism for controlling the starting and stopping of the electric motor by means of the circuits and connections diagrammatically illustrated in Fig. 13. When the handle 41 is turned in one direction the switch will be closed and the motor started to operate the drill 4| while the drilling machine is supported manually and fed manually into the coal vein. The rotatlonvof the handle 41 to close the switch places such tension in the spring 51 that when the handle 41 is released by the operator the spring 51 will act automatically to restore the switch to its open position and thereby effect stopping of the motor.

Inasmuch as it is desirable to open the switch with a snap a'ction or eiect very quick separation of the contacts of the electric switch in order 'to reduce the arcing to a minimum when the circuit of the electric motor is broken, compactly arranged automatic switch operating mechanism is mounted in the compartment C and connected to Ithe handle 41 as shown in Figs. 6, 8 and 9. The switch mechanism is mounted between blocks of insulating material 11 and 93 which are secured to the bosses 96a and 99 by means of the screw-threaded ends of the cap screws 96 and 98 and the insulating spacing tubes 91 and 66 as shown in Figs. 10, 11 and 14.

The spacers 66 may be integral with the insulating block 11 and each provided with a depending support 66 provided with alined openings for receiving the inner ends of laterally projecting bearings 65, 65 which may be pinned to the support 66' as indicated at 65*L in Fig. 12.

As shown in Figs. 10, 1l, 12 and 14, insulating blocks 6| are provided with upwardly opening slots or recesses 64 to lit over the bearings 65 from the underside of the latter. The insulating blocks 6| are rigidly connected by the transverse insulating cross-piece 6|'. Between the blocks 6| and parallel to the crosspiece 6|' is mounted a transverse pin 69 having a groove 10 intermediate its ends for receiving the lower end 10' of thespring 88, the upper end of which is hooked at 1| through the opening 12 at the upper central portion of the yoke 53.

Each of the insulating blocks 6| carries a metallio strip or iinger 62 the lower end of which ls pinned at 83 to the copper contact 63. At the upper end oi each metal strip 62 is a square hole adapted to iit loosely over the squared head 18 of a screw inserted in the upper portion of the block 6i as shown in Figs. l0 and 14. This arrangement prevents the contact carrying strips or fingers 52 from swiveling in its own plane but a limited movement of the strip 62 transversely ol its own plane is permitted to secure a wiping action of the contact 63 against the metal plate 13 when the switch is moved from its open position in Fig. 10 to its closed position in Fig. 14.

A pin 19 secured to each block 6| projects through a hole in the strip 62 intermediate its ends. Each pin 19 is provided with a collar.80 with a spring 8| between the same and the outer surface of the strip 62 as shown in Figs. 10 and 14. A cotter pin 82 holds the collar 80 in piace. When the block 6| is moved to the position shown in Fig. 14 the spring 8| holds the contact 63 yieldingly against the metal plate 13. As shown in Figs. l and 14, the metal plate 13 is secured by means of the cap screw 14 to the base block 16 of insulating material which may be integral with the insulating block 11.

By referring to Fig. 12, it will be seen that spaced-apart electric terminals may be aiiorded by the metal plates 15, 15 secured to the metal plates 13, 13 by means of the screws 15', 15. Electric terminals 62B, 62a are riveted to the contact carrying strips 62 as shown at 62D, 62". As shown in Fig. 13, the switch is two-pole in that one electric conductor extends through the contacts 63, 13 and another conductor extends through the contacts 63', 13', said conductors being respectively connected to the supply mains.

In order to minimize arcing during operation of the switch mechanism, there is mounted between the insulating blocks 11 and 93 within the space between the base blocks 16, 16, a blow-out coil 84 having an iron core 84B the ends of which project through openings into insulating blocks 84h, 84b so as to occupy positions closely adjacent to the points of engagement between the contacts 63 and the plates 13. As shown in Fig. 13 the winding of the blow-out coil 84 is connected in the motor circuit and in series with the two sides of the double-pole switch. When the switch is open the blow-out coil acts to lengthen the arcs between the contact 63 and the plate 13 aiding the disruption of such arcs.

As a precaution against the burning of any of the parts when such arcs are formed upon the breaking of the circuitsiat the switch contacts in the compartment C, plates |35, |35 of asbestos or other non-inhammable material are secured at |45, |45 to the outer surfaces of the base blocks 16 at the sides of the switch mechanism as shown in Fig. 12. The securing means at |45, |45 may be screws extending into the blocks 16 as shown in Figs. 10 and 14. The end blocks 84h, 84b of the blow-out coil are also preferably made of asbestos or other non-inflammable material.

A safety fuse 9| is mounted between clips 92, 92 and connected in the motor circuit as shown in Fig. 13.. The compartment C in which the switch mechanism is mounted is provided with a cover screw-threaded to closed position and sealed in closed position as illustrated at |20 in Fig. 6. Access may be had to the interior of the compartment C for renewal of the blown-out fuse 9| by removing the cover |05 but not until the seal |20 has been broken.

Secured to the insulating block 93 by means of the screws |0I, |0| is a plate of insulating material provided with upper and lower extensions |02 and |03 at right angles to the block 93 and extending across the outer ends of the clips 92, 92`as shown in Fig. 1 so as to prevent any possibility of grounding of the clips 92, 92 through the heads of the screws 96, 98 to the metal frame or casing of the drilling machine.

A connector |04 as shown in Fig. ll for the conductor |26 shown in Fig. 13 may be mounted bach of a curved portion |43 of the shield |44 for protection thereby.

In order properly to space the ends of the iron core 94 of the blow-out coil 84 from the switch contacts 63, 13 a retaining block 95 of insulating material is riveted at 94 to the inner surface of the insulating block 93 as shown in Fig. 1l. The lower corners of the block 95 are suitably notched to fit over the beveled upper edges 84c of the rectangular end insulating blocks 84|. The latter are also clamped by means of the screws 96 and 98 between the insulating blocks 93 and 11.

It should be particularly noted that when the cover |05 is removed the entire switch unit may be removed and taken apart for the purpose of repair or replacement. This is particularly true with respect to the contact carrying mechanism because the open slots 64 permit the insulating block 6| together with the crosspiece 6| to be removed from the bearings 65, 65 against the action of the spring 68. If desired, the contact carrier may be readily detached from the hook at the lower end of the spring 68. When the retaining ring ||9 shown in Fig. 1 is removed the handle 41 may be removed from the journal bearnig 52 thus disconnecting the handle from the yoke 53 and permitting the removal of the latter from the bearing 55.

When all of the parts of the drilling machine are in assembled relation ready for operation, the electric switch may be closed to effect starting of the motor by rota-tion of the handle 41 against the action of the spring 51 in an anticlockwise direction as viewed in Fig. 9. When the switch is open the yoke 53 occupies the position shown in Fig. 9 or the position shown in iull lines in Fig. 1l.

When the handle 41 is rotated in an anticlockwise direction as viewed in Fig. 9 the abut-,.1

ment 5|b will engage the yoke 53 to swing the same from its full line position shown in Fig. 11 toward its dotted line position. In doing so, the outer central portion of the yoke 53 engages the free end of the spring clip |2| which is secured to the inner surface of the compartment C as shown in Figs. 7 and l1. However, the yoke .53 clears the spring clip |2I by the time that the spring 88 moves to a position to the left of the axis of the bearing as viewed in Fig. 11 whereupon the spring 69 is free to act to eiect closure of both of the sets of contacts designated 63, 13 and 63', 13' in Fig. 13. When the switch is closed the yoke 53 is held against the fixed abutment 52n with the abutment 5|h held manually against the other side of the yoke 53 as shown in Fig. 8. Furthermore, when the switch is closed the spring 60 has one 'arm 60h resting against the seat 5|n and the other arm 50l engaging that side of the yoke 53 remote from the abutment When it is desired to open the switch the handle 41 is` released whereupon the stored tension in the spring 51 will act automatically to move the carrier 49' in a clockwise direction as viewed in Fig. 9 thereby continuing to move the abutment 5|'J away from the yoke 53. The yoke 53 moves through asmall angle to a position in engagement with the spring clip |2| due to tension in spring 00. At such time the spring 00 does not have suiiicient tension to move the yoke 53 past the clip |2|. In other words, the clip |2| prevents continued movement of the yoke 53 until a predetermined amount of tension is stored in the spring 60. The purpose of the retarding action of the spring clip |2| is to hold the yoke 53 in such position that the spring 50 may be at the left of the axis of the bearings 65 so that the switch will be held positively closed until it is ready to open with a snap action. That .is to say, in order to prevent initial movement of the handle 41 towards switch opening position from causing the contacts 53 and 63' from separating from the plates 13, 13' the spring clip |2| causes the spring 60 to hold the switch positively closed thereby preventing arcing which would occur when the contacts 63, 03' are moved only a short distance from the plates 13, 'I3'. As rotation of the handle 41 continues in a clockwise direction as viewed in Fig. 8, the abutment 5|b moves farther away 'om the yoke 53, but the latter being held by the spring clip |2| causes incrcasingtension to be stored in the spring 60 until such tension is sufiicient to overcome the holding yeffect of the spring clip |2|. Then the spring 60 moves the yoke 53 from u nder the spring clip |2| whereupon the spring 69 moves to the right of the center of the bearing 05 as viewed in Fig. 11, whereupon the contacts 63, 03' would be suddenly and quickly withdrawn from the contact plates 13, 13'. When the switch is in open position the yoke 53 will rest against the abutment 52b as shown in Fig. 9 and the crosspiece 6| of the switch contact carrier will abut against the back of the insulating block 95 as shown in Fig. l1;

Fig. 13 shows diagrammatically the circuits and connections for the electric drill motor and the switch for controlling the same. The terminal l hook |28 may be connected to a trolley wire in a mine to serve as the connector to the positive supply main |21 which is connected to the plate 13. The hook`|22 may be attached to the rail |3| of the mine track to serve as the connector to the negative supply main |23 which is connected to the contact plate 13. The motor is preferably compound wound so that it will not race under substantially no load and yet be capable oi.' withstanding heavy overloads without overheating.

When the switch is closed the motor circuit may be traced in Fig, 13 to the conductor |21 through contacts 13', 63', fuse 9|, conductor |25, series motor winding 85, motor armature I4, conductor |25, blow-out coil 04, contacts 03, 13 and thence to the negative conductor |23. The shunt field coil 35 is also energized as it is shunted across series winding 05 and armature |4 In order to protect the operator of the drilling machine the casing or frame thereof is grounded by a conductor |30 connected at its outer free end to the rail |3| and at its inner end to the frame or casing of the machine as illustrated diagrammatically at |29 in Fig. 13. This grounding connection may be effected by connecting the conductor |30 to the head of the screw 95 as shown in Fig. 2, which screw is of metal and in metallic contact with the metal frame of the machine.

It should be particularly noted that the cable 00 carrying the three conductors |23, |21 and |30 is connected by means of the connectors shown in Fig. 3 to the compartment C with an airtight nt so that no gas can enter the compartment C or escape therefrom either through the connector or the cable, the latter being impervious to air since it is composed of insulating material with the three separate wires imbedded therein i'or insulation from each other.

The connector shown in Fig. 3 comprises a tube 83 which is screw-threaded into the socket 90 which may be integral with the casing of comlpartment C. By screwing the tube 00 into the screw-threaded portion 09 of the socket 90 it engages the packing gland b which is located above the packing 90c in the lower cup portion of the socket 90. By means oi' a split sheath 01 surrounding the cable 90 and extending into the `tubular member 39, and a clamp 90|, the cable may be secured against longitudinal movement relatively to the housing oi.' the compartment C. After the connector has been assembled and the cable 09 locked in adjusted position relative to the housing, a seal 9|* may be used as shown in Fig. 3 to prevent tampering with the connector.

One of the principal features oi' the construction shown in Figs. 5 and 6 is the provision of means for effecting internal air circulation about the motor amature for the purpose of cooling the motor or preventing overheating thereof.- A multi-stepbladed centrifugal fan |5isconnected to the shaft 46 to rotate therewith immediately inside of the cover 22. Batlle vplates I0, |6, each having the shape of a segment of a cylinder as shown in Fig. 5 and composed of iiber or other light insulating material, are mounted between the pole pieces 24 and between the field coils 25. At those ends of the baiiie plates 6 near the cover 22 are mounted the plane baille plates IiiB which are secured to the inside of the cover 22 by means of brackets |49, and the rivets |61. The inner edges of the baille plates 5'L are in such positions that they will clear the outer periphery of the fan i5 when the cover 22 is removed.

It will be seen by referring to Figs. 5 and 6 that the baille plates I0"L co-operate with the pole pieces 24 and the windings 25 thereon to close the outer ends of the spaces between the motor armature and the baille I6 so that when the fan I5 rotates a circulation of air on opposite sides of the motor will be produced in the direction of the arrows |1 and i0. 'I'hat is to say, when. the fan rotates the baiiie 6 co-operates with the pole pieces 24 and the windings 25 thereon to compel the air to move into the intake openings of the fan within the periphery thereof so that the air will be thrown out by centrifugal force for inward circulation as indicated by the arrows I9, thus causing the air which has absorbed heat from the armature. to come in contact with the inner surface of the cylindrical radiator I9. The

outer surface is provided with circumferential ribs 20 .to increase the outer heat radiating surface.

Theradiator i9 constitutes the field frame of the electric motor and is therefore made of iron or steel but the cover 22 and the various other parts of the casing or frame of the machine together with the handles 41 and |32 are preferably made of a light alloy, such as magnesium-aluminum heat-treated. In a drilling machine of the construction shown and described having a compound wound electric motor oL'one and one-half to two horsepower operated at an applied voltage of 250, the weight of the entire drilling machine, excluding the drill, need be no greater than 38 pounds. The center of gravity in a drilling machine is located back of the handles, or away from the drill socket, to assist in counterbalancing the weight of the auger while a single operator supports the drilling machine during operation and by leaning against it or pushing it feeds the drill into a coal vein.

One of the handles is rotated by the operator who effects starting of the drilling machine and when this handle is released the motor is automatically stopped with a minimum amount or arcing at the switch contacts. Notwithstanding the operation oithe interior controlling switch from without the machine the enclosing structure is entirely flame-proof and the electrically operated drill is therefore permissible for operation in gaseous mines. All detachable parts by the removal of which access could be had to the interior of the enclosing structure are preferably locked and sealed against opening by the operator while using the machine for operation in a gaseous mine. It will also be noted that the complete closure of the motor, power transmission mechanism and the motor controlling switch prevents access of dust and dirt to the interiorn relatively movable parts.

Obviously those skilled in the art may make various changes in the details and arrangement of parts without departing from the spirit and scope of the invention as defined by the claims hereto appended, and I therefore wish not to be restricted to the precise construction herein disclosed.

Having thus described and shown an embodiment of my invention, what I desire to secure by Letters Patent of the United States is:

l. In a drilling machine, the combination with an electric motor, of means for controlling the operation of said motor, communicating enclosures for said motor and said controlling means, means affording a corrugated exterior surface for that portion of said motor enclosure surrounding the armature of the motor and constituting the field frame thereof, a fan connected to one end of the motor armature, and means comprising baille plates serving as partitions between said armature and the interior of said casing to provide chambers parallel to the motor axis, said plates being so constructed and arranged as to cooperate with said fan to direct air rst across the face of said armature and then across the interior of said casing to dissipate heat generated by said motor, and to circulate air within said controller enclosure. y

2. In a drilling machine, the combination with an electric motor, of an enclosure for said motor, means affording a radiating exterior surface for that portion of said enclosure surrounding the i armature of the motor and constituting the eid frame thereof, a ian connected to one end of the motor armature, and means comprising baille plates having their edges extending along the field coils of said motor and serving as partitions between said armature and the interior of said casing to provide chambers parallel to the motor axis, said plates being so constructed and arranged as to cooperate with said fan to direct air nrst across the face of said armature and then across the faoesof said field coils and the interior of said casing to dissipate heat generated by said motor.

3. In a portable tool, the combination with a ame proof casing, of a motor in said casing, operating mechanism driven by said motor, a

switch for controlling said motor, a iiame proof casing for said switch, said two casings having communication whereby the air in each may circulate in the other, and fan means driven by said motor for circulating the air in both of said casings.

4. In apparatus for use in a gaseous mine, the combination with a casing formed into a motor compartment and a gear compartment by a partition, of a motor in said motor compartment, gears in said gear compartment, a shaft extending between said motor and said gears, a drive shaft extending from said casing and driven by said gears, a flame seal between said drive shaft and said casing to provide for rotation of said shaft while restricting egress of any flame from said casing, and a second flame seal between said first named shaft and said partition.

5. In mining apparatus, the combination with a flame proof casing, partition means forming said casing into motor, gear and switch compartments, a motor in said motor compartment, gears in said gear compartment and a switch in said switch compartment, a pair of rotatable shafts, one extending from said gear compartment and operated by said gears and the other extending from said switch compartment and controlling said switch, ilame seals for each of said shafts to provide for their turning While resisting egress of any iiame from said casing, means connecting said motor and gears, and electrical circuits connecting said switch and motor.

6. In a mining drill, the combination with a flame proof casing, of a motor in said casing, a drill shaft extending from said casing, reduction means interconnecting said motor and drill shaft, a motor control switch in said casing, an operating shaft for said switch extending into said casing, a flame seal forsaid drill shaft, and a :flame seal for said switch operating shaft, said name seals providing for rotation of 'said shafts while resisting the egress of any iiame from said casing.

7. In a drilling machine, the combination with an electric motor, of a casing for said electric motor, said motor including a stationary eld structure attached to said casing and a rotating armature, a fan rotor connected to said armature to be rotated thereby, baiiie means in said casing constructed and arranged to guide circulating air across said armature in one direction and in a reverse direction across the casing in terior, said baffle means including a portion adjacent the ian rotor to provide a restricted fan inlet leading to said fan rotor through which fan rotor substantially all of the circulated air must pass.

ROBERT'K. JEFFREY.

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