US1850191A - Electric drill - Google Patents

Description

March 22, 1932. G. R. WILCOX ELECTRIC DRILL Filed Aug 29, 1929 huh E A TToRA/EY Patented Mar. 22, 1932 i 1 UNITED. STAT oFFic GEORGE E. wILcox',Yo1 i GREENFIELD, MAssAcnusEr'rs, essienoia TO'IHLLERS rants COMPANY, on MILLERS FALLS, MAssAcHusE'rrs, A conrona'rron or: MASSACHU- SETTS nLEcrRIc DRILL Application filed August 29, 1929. Serial No. 389,180. V

This invention relates to the small portable type of electric'drill, and to various improve I 'ments therein whereby the drill is more convenient to handle and use.

In using a small portable electric drill of the type to which the present invention relates it, may be desirable in some cases to hold the drill with one hand during the drilling operation so that the other hand may remain free to hold the work, or to perform some other function, and in other cases'it may be desirable to use both hands in 'operatlng the electric drill so that the tool driven by the motor may be guided to the ,WOI'k with a high degree of accuracy, I

The entire electric drill of the present invention istherefore designed along the lines of a pistol or revolver and has a central cyl ndrical casing that is provided at one end w th a pistol grip handle and at the other end w th the tool holding chuck, the parts belng so arranged that the drill can be conveniently operated with one hand by grasping the pistol grip handle, or may be gulded to the won: with a high degree of accuracy by grasping the cylindrical casing in one hand while the pistol grip handle isgrasped 1n the other hand.

One of the featuresof the present invention resides in an electric drill having a mo tor enclosing casing that is small enough to be grasped between the thumb and fingers of one hand and provided with ribbed panels'at the opposite sides of the casing to afford the hand a firm grip, evenwhenthe hand is greasy; and a further feature'of the invention resides in a pistol grip handle attached to the casing and which is also provided w th ribbed panels to afford the hand a firm grip,

Another feature of the presentinvention resides in an electric drill having a motor, an enclosing casing, a hollow pistol grip handle atone end of the casing,and a'fan, driven by themotor to draw air from the atmosphere into the casing through the pistol grip handle to keep the handle-and motor cool. H

A further feature of the ,presentinvention resides in the construction whereby the brush holders are disposed at an angle of approximately 45 to the central plane of the pistol grip'handle so asnot to interfere with the useofthe drill in a corner, and a further feature resides in sleeves or ferrules that are permanently secured to the motor casing to protect the projecting portions of the-brush holders. 1

Another feature of the present invention resides in a partition located between the motor containing compartment-of the casing and the gear containing compartment and provided with afelt washersurrounding the motor shaft for preventing the grease from the gears fromreaching the motor.

Still a further feature resides in conductors extending throughthe pistol grip handle to the motor and in a bridge bar mounted in the butt of the handle to anchor the conductors therein.

Other features of the invention and novel combinations of parts in addition to the above will be hereinafter described in connection with the accompanying drawings which illustrate one good practical form of .the invention;

/ In the drawings-:-

Fig.1 is a side elevation with parts in section of an electric drill constructed in accordance with the present invention; a

Fig. 2 is a sectional View taken'on the line 2'2 of Fig.1; and J Fig. 3 is an end View of the butt of the pistol grip handle.

Referring to the drawings, the embodiment of the invention illustrated consists of a cy-" lindrical motor casing 10 adapted to enclose an electric'motor having the central shaftll and armature 12. At one end of the casing 10 is provided the pistol grip handle 13 and at the opposite end of the casing 10 is provided the gear casing 14 containing gears'for driving a spindle that rotates in the extension 15'and to the outer end of this spindle is secured a chuck 16 which is or maybe of well known construction.

The electric drill of the present invention is preferably sufficiently small to beeasily handled and the entiredevice is so. designed that it. is well balanced when supported either by thecasing 1 0 or by the pistol grip handle 13, and as above stated the casing 10 is preferably sufficiently small to permit the same to be grasped between the thumb and fingers of one hand. The opposite sides of the easing are therefore preferably provided with i the ribbed or roughened panels 17 adapted to afford the hands a firm grasp even when the hands are greasy. The opposite sides of the handle 13 are also provided with ribbed or roughened panels 18 to give the hand a firmer gri The electric motor which may be of well known construction is provided with the contact brushes 19 having the holders 20 that extend through the casing 10. These brush holders are provided at their outer ends with the cap screws 21, and since the cap screws extend outwardly beyond the outer surface of the casing 10 they are likely to be injured. In order to protect these cap screws the casing 10 is provided, in accordance with the present invention, with the sleeves or ferrules 22 which are permanently secured in sockets formed in the casing 10 about the brush holders 20 as will beapparent from Fig. 2, the

' construction of the sleeves 22 being such that they surround and extend outwardly beyond the caps 21 to protect them.

In some cases it may be desirable to use the present electric drill in a corner such as indicated by the lines C, C in Fig. 2, and when the drill is positioned as shown in this view the pistol grip handle 13 may readily be held substantially parallel to one of the walls C. Having this in mind the. brushholders 20 are preferably disposed at an angle of approximately to the longitudinal central plane of the handle 13, as will be apparent from Fig. 2 in which the dotted line .w-a indicates the central longitudinal plane of the pistol grip handle. As a result of this arrangement, when the electric drill is used in a corner the projecting sleeve 22 will extend into the corner as shown and will not prevent the cylindrical casing 10 from resting firmly against the angularly disposed walls lf the electric motor 12 is used for a con- -.-siderable length of time under heavy load it will tend to heat up so that the casing 10 and handle 13 may become uncomfortably warm to the hands. This is prevented, however, in accordance with the present invention, by providing the motor shaft 11 with a fan 23 arranged to draw air from the atmosphere inwardly through the butt end of the hollow handle 13, as shown by the arrows, and through the rear end 24 of the casing past the motor to the fan, whereupon the air is discharged from the casing by the fan through the openings .25. In this manner both the motor casing 10 and the pistol grip handle 13 are kept cool.

It is desirable to prevent the grease supplied to the gears within the gear casing 14 $5 from reaching the electric motor and this is prevented, in accordance with the present invention by providing a partition 26 which is secured between the motor compartment and the gear compartment of the casing as shown in Fig. 1. The shaft 11 extends through a central opening in the partition 26 and oil and grease are prevented from traveling along the motor shaft through this opening by providing a felt washer or the like 27 which may be confined between a face of the partition and a washer 28 secured to the disk by rivets 29.

Current for operating the motor is supplied by conductors within the insulating jacket 30, and these conductors extend inwardly through the hollow handle 13 as shown. It is desirable to anchor the insulated conductors within the handle 13 so that they will not be pulled loose from their connections, and this is done in the present construction by providing the bridge bar 31 adapted to be mounted in the butt end of the'handle as shown, and the bridge bar is conveniently secured within the handle by providing at each end of the bridge bar, the projections 32 adapted to be sprung or forced into holes 33 formed in the handle 13. The edges of the bridge bar are spaced from the inner walls of the handle as shown in Fig. 3 to permit air to enter through the spaces 34.

The conductors 30 extend through a central opening in the bridge bar .31 and are preferably protected by the coiled wire 35, the inner end of which extends under the U-shaped clamp 36 that may be forced into clamping engagement with the coiled wire 35 and insulated conductors 30 by tightening the screw 37. This causes the inner end portion of the coiled wire and the insulation upon the conductors to be flattened out suiiicientl to bind them in the annular opening in t e bridge bar .31,

Current to the motor is controlled by a pivoted switch 38 that may be readily shifted by .the thumb to either start or stop the motor, and the design of the entire device is such that it is very convenient to handle and operate and permits close drilling to a wall or other surface.

What is claimed is:-

1. A portable electric drill, comprising in combination, an electric motor having a surrounding casing that is small enough to be conveniently grasped between the thumb and fingers of onehand. and provided with ribbed side walls to afford the hand a firm grip upon the casing, a tool operating spindle driven from the motor and extending from an end of the casing at one side of the motor axis,

and a pistol grip handle secured to the opsects the handle so as to $11 port the motor drill opposite its centre gravity.

2. A portable electric drill,comprising in M combination, an electric motor having a surrounding, casing, a tool operating spindle driven from the motor and extending from an. end of the casing at one side-of the motor axis, a pistol grip handle secured to the opposite end of the casing in substantial lo alignment with said spindle and extending laterally of the casing in spaced relation thereto across the axis of the motor and beyond a side Wall of the casing, contact brushes for the motor and mounted in brushlholders that protrude from the annular walls of the casing, and the protruding brush holders being disposed at angles of approximately 45 to the central longitudinal plane of the pistol grip handle to facilitate the use of theelectric drill adjacent angularly disposed walls and to clear the surface against which the drill casing may rest when the handle is held substantially parallel to said surface during the drilling operation.

3. A portable electric drill, comprising in combination, an electric motor having a casing, a tool operating spindle driven from the motor and extending from an end of the casing, a hollow pistol grip handle secured to the opposite end of the casing and provided with recesses in its opposite Walls near the butt end of the handle, conductors extending inwardl through said handle to the motor, means or anchoring the conduc- 36 tors in the handle comprising a flattened bridge bar having a central conductor receiving opening and reduced oppositely extending ends adapted to be inserted in said opposite recesses to secure the bridge bar in the hollow handle, and an enlarged abutment secured to the conductors in position to en age the inner face of the bridge bar.

11 testimony whereof I have signed my name to this specification. GEORGE R. WILCOX.

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