US2158228A - Electric drill - Google Patents

Description

Patented May 16, 1939 UNITED STATES PATENT OFFICE ELECTRIC DRILL Application March 30,

9 Claims.

This invention relates to portable motor driven hand tools for drilling, screw driving, reaming and other rotary operations.

Tools of this character of the larger capacities by reason of the increased power requirements are equipped with side handles so that the operator may hold the tools against the torque strains developed by these more powerful motors. The end handles with which these tools are also provided can not alone be used to overcome these torque strains.

These tools, as heretofore constructed, due to their greater power requirements, have been relatively large in size and relatively heavy in weight. These factors, aside from increasing the manufacturing costs of these machines, have fatigued the operator holding the tools over long working periods and have limited the use of these tools to more freely accessible places.

In accordance with my invention, I propose to make these tools lighter in weight and shorter in overall length so that they can be handled more easily without tiring the operator and be usable in more confined or crowded quarters.

In accomplishing the objects of my invention, I lessen the length of the tool by terminating the motor case short of the rear bearing for the motor and have the rear end handle come up to the rear end of the motor case. Hence, this handle member does not project wholly beyond the end bearing as in the previous constructions and the toollength is materially reduced.

- Also, in accordance with my invention, the end bearing is exteriorly oi the motor case, thus permitting the use of a bracket on the motor case as a support for this bearing and providing a space for the handle member and the commutator and brush assembly of the motor.

A further object of my invention is to cast the bracket and the motor case in one piece and provide a space above and below the bracket so that access may be readily and easily had tothe brush assembly and the commutator on removing the cover element which is provided at the rear end of the tool.

A further object of my invention is to connect the end handle and this cover element together,

preferably integrally, so that these parts provide a single unit for ease in applying and removing them to and from the motor case.

Other and further objects of my invention will appear from the following specification taken in connection with the accompanying drawing, in which- Fig. 1 is a side view of my improved drill;

1938, Serial No. 198,915

Fig. 2 is a top plan view of the end handle and cover element and adjacent portion of the motor case at the rear end of the tool;

Fig. 3 is a view, partly in section, showing the end handle and cover unit removed from the motor case; and

Fig. 4 is a top plan view of the bracket which provides a support for the motor bearing at the rear end of the tool. v

The drill shown in the drawing is of a one-half inch capacity or size. It is equipped with a universal electric motor operable on either a D. C. or an A. C. current cycles or less) of volts. The motor isof the distributed winding type as used in tools of this character and is housed within the motor case l of the tool. This case encloses the stator and the armature of the mo-' tor, the armature shaft extending beyond the op posite ends of the motor case and being journaled in bearings, one in the nose end section 2 of the tool, and the other bearing being in a bracket 3 at the rear end of the motor case.

The nose end section 2 is releasably bolted to the front end of the motor case and comprises a casing section 4 which supports the tool spindle 5 and the reducing gearing which connects the spindle to the armature shaft for rotation thereby. The nose end section also includes a plate 6 which supports the front bearing for the armature shaft and provides a closure'for the open front end of the motor case. The securing means referred to is disposed about the motor case and includes bolts and nuts some of which are shown at I in Fig. 1.

The bracket 3 is integral with the motor case I, the latter and the bracket being cast in one piece. The bracket is yoke-shaped and straddles the open rear end of the motor case and has a recess or socket 8 in its mid-portion 9 to accommodate the rear bearing assembly ID for the armature shaft II. The commutator l2 of the armature l3 and the upper and lower brushes l4, [4 therefore are disposed in the space provided by the bracket. The brush holders are above and below the commutator as shown at i5, I6 in Fig. 3. The closed end of the socket 8 in the embodiment shown mm the form of a protuberance I! in th mid-portion of the bracket as shown.

Terminating the motor case short of the rear bearing and providing a bracket on the motor case for the bearing enables the end handle [8 of the tool to be secured to the motor case inwardly of the bearing. This is an important feature of my invention, in that the overall length of the tool isconsiderably shortened as compared to the previous tools in which the motor case extends to and encloses the rear bearing and the end'handle extends that much farther beyond the rear of the motor case. In the embodiment shown, the cross-portion [9 of the end handle is relatively close to the rear bearing, and thus the tool is shorter and may be used in more confined quarters than with the previous tools.

Also, by the structure disclosed, the cover element 20 for the rear end of the motor case may be carried by the handle member l8 and thus these parts may be applied to and be removed from the motor case as a single unit without disturbing other parts of the tool. As illustrated, the cover 26 is cup-shaped and fits over and about the bracket 3 and the brush assembly of the motor. The edge of the cover fits against the opposed edge of the motor case, a screw element 2| taking into a lug 22 on the bracket 3 to releasably secure the cover element in place. The lug 22 is cast integral with the bracket 3 on its under side and has a threaded hole 23 to receive the screw 2|.

The edge of the cover, where it fits against the motor case, is provided with a number of openings or slots 24 providing air intake openings for the cooling system for the motor. This system includes .a fan (not shown) at forward end of the motor case and discharge ports 25 in the motor case about the periphery of the fan.

The cover 20 is interlocked with the motor case through lugs 26, 26 on the cover fitting in notches 27, 21 in the rear edge of the motor case. These lugs and notches are diametrically disposed, one set above the motor axis and the other set below said axis.

The end handle l8 and the closure cup 20 are cast integral with the exception of the crosspiece 19, which is fastened between the side arms 28, 28 of the handle by screws: or other fasteners 29. The handle and cover assembly is additionally secured to the motor case by a screw element 30 which takes into a lug 3| in the motor case at the upper notch 21. The screw 30 extends through a hole in the cover section at the upper lug 26 as indicated in Fig. 3.

The side handle 32 for the tool extends below the motor case and is of the longitudinally divided type, one portion being cast integral with the motor case and the other part constituting a removal cover plate 33 for the switch assembly (not shown) located in the handle, which is hollow to mount and house said switch. The latter has an actuating lever 34 on the forward side of the handle 32 for controlling the supply of electric current to the tool motor, a current supplying cable 35, being attached to said handle and extending into the same at its lower end as shown.

The gear case section 4 at the front end of the tool is relatively narrow axially and thus cuts down the length of the tool at its front end. The chuck 33 on the tool spindle is relatively close to this gear case section as shown in Fig. 1, thus also shortening the length of the tool. The end handle I8 is secured to the motor case in general axial alignment with the tool spindle 5 and thus the operator may guide the tool to the work and apply the needed pressure on the spindle in the use of the tool.

. The tool is relatively light in weight comparedto its size and power and with the handle member l8 secured to motor case inwardly of the rear bearing the tool is, relatively short. axially and may be used in confined quarters. With the cover 20 carried by the handle and the rear bearing supported by the motor case, the cover and the rear handle may be removed from the tool without disturbing the motor and, moreover, the tool may be operated with the handle and cover removed, thus permitting inspection of the motor, cleaning the commutator and renewing the brushes. The stator for the motor is indicated in dotted lines at 3'! in Fig. 3.

The details of construction and arrangement of parts may be variously changed and modified without departing from the spirit and scope of my invention, except as pointed out in the appended claims.

I claim as my invention:

1. A portable motor driven tool having a motor-enclosing case, a bearing for the motor at the rear end of said case, a support for the bearing carried by said case, said case having an open rear end terminating short of said bearing, a side handle secured to the motor case, a cover element for the rear end of the motor case and secured thereto over the bearing and its support, and an end handle secured to and projecting rearwardly from said cover element.

2. A portable motor driven tool having a motor-enclosing case having an open rear end, a bearing for the motor beyond the rear end of said case, a bracket secured to the motor case and providing a support for said bearing, a side handle secured to the motor case, a cover element for the rear end of the motor case and secured thereto over said bracket, and an end handle carried by the cover element and projecting rearwardly therefrom from a point spaced inwardly from the bearing.

3. A portable motor driven tool having a motor-enclosing case, having an open rear end, a yoke-shaped bracket secured to and straddling the open rear end of the motor case, said bracket projecting rearwardly from the motor case and providing a support for the motor bearing at the rear end of the case, a side handle secured to the motor case, a cup shaped cover element for the rear end of the motor case and secured thereto over the bracket, and an end handle carried by and projecting rearwardly from the cover element from adjacent the joint between the cover element with the rear end of the motor case.

4. A portable motor driven tool having a motor-enclosing case, having an open rear end, a yoke-shaped bracket secured to and straddling the open rear end of said case, said bracket extending rearwardly from the case and providing a support for the motor bearing at the rear end of the case and a space to accommodate the commutator of the motor and the brush assembly therefor, a side handle secured to the motor case, a cup-shaped cover element secured to the m0- tor case over the bracket to enclose the same and associated parts of the motor at the rear end of the motor case, and an end handle carried by and projecting rearwardly from the cover element from adjacent the joint between the cover element and the rear end of the motor case.

5. A portable motor driven tool having a motor-enclosing case having an open rear end, a yoke-shaped bracket secured to and straddling the open rear end of said case, said bracket extending rearwardly from the motor case and providing a support for the motor bearing at the rear end of the case, a cup-shaped cover element secured. to the motor case overthe bracket to I enclose the same, an end handle carried by and projecting rearwardly from the cover element from adjacent the meeting edges of the cover and the motor case, and air intake openings at said edges.

6. A portable motor driven tool having a motor-enclosing case having an open rear end, a yoke-shaped bracket secured to and straddling the open rear end of said case, said bracket extending rearwardly from the motor case and providing a support for the motor bearing at the rear end of the case, a cup-shaped cover element secured to the motor case over the bracket to enclose the same, and an end handle carried by and projecting rearwardly from the cover element from adjacent the meeting edges of the cover and the motor case, the motor case and the cover element having an interlocking connection at their meeting edges.

'7 A portable motor driven tool having a motor-enclosing case having an open rear end, a yoke-shaped bracket secured to and straddling the open rear end of said case, said bracket extending rearwardly from the motor case and providing a support for the motor hearing at the rear end of the case, a cup-shaped cover element for the rear end of the motor case, said cover eleviding a support for the motor bearing at the rear end of the case, a cup-shaped cover element for the rear end of the motor case and enclosing the bracket when in closing relation to said case, means for securing the cover element to the bracket comprising a lug on the bracket and a fastening element engaging the lug through the cover element, and an end handle carried by and projecting rearwardly from the cover element.

9. A portable motor driven tool having a motor-enclosing case having an open rear end, a motor bearing at the rear end of said case, a cover element for the rear end of the case and secured thereto over and enclosing said bearing, and a handle member carried by the cover element and projecting rearwardly therefrom.

FRITZ V. FORSS.

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