US2072551A

US2072551A - Portable electric tool

Info

Publication number: US2072551A
Application number: US80311A
Authority: US
Inventors: Frithiof P Forss
Original assignee: Independent Pneumatic Tool Co
Current assignee: Independent Pneumatic Tool Co
Priority date: 1936-05-18
Filing date: 1936-05-18
Publication date: 1937-03-02
Anticipated expiration: 1954-03-02
Also published as: FR809145A

Description

March 2, 1937. k oRss 2,072,551

PORTABLE ELECTRIC TOOL Filed May 18, 1936 2 Sheets-Sheet l mvmox. fkITH/Of P .FORJ'S rd mn ATTORNEY.

March 1937. F. P. FORSS PORTABLE ELECTRIC TOOL Filed May 18, 1936 2 Sheets-Sheet 2 INVENT OR. EilfH/Offi F0555 W My 6 ATTORNEY.

Patented Mar. 2, 1937 PATENT OFFICE PORTABLE ELECTRIC TOOL' Frithiof 1. Fans, Aurora, 111.. amignor to Independent Pneumatic Tool 00., Chicago, 111., a corporation of Delaware Application May 18,

1: Claims.

This invention relates to portable electrically operated hand tools for drilling, screw driving. grinding, and the like.

The tool to which my invention relates is relatively small in size and light in weight and has a pistol grip handle at its rear end whereby the operator may hold and operate the tool in one .hand: The spindle of the tool is at its front end and is provided with a chuck or other device, whereby a drill bit. screw driving attachment, grinding wheel, or other desired working element may be attached to the spindle for rotation thereby. The handle of the. tool may be made hollow to accommodate the electric supply cable for the motor, and, if desired, provide an air duct for the intake of air for the cooling system for the motor.

The general purpose and object of my invention is to support the brush assembly and the supply cable for the motor entirely by the motor casing go of the tool and not by the grip handle, thereby enabling the grip handle to be made in one piece and be removed in its entirety from the motor case without disturbing the brush assembly or the cable connections with the motor. The advantage of this is that the brush holders, brushes and commutator of the motor may on removal of the handle be inspected while the motor is running and the commutator cleaned with a piece of sand paper as done with large stationary motors.

A further object of my invention is to support the supply cable from the motor case by providing the bearing cup at the rear end of the motor with a depending bracket to which the cable may be conveniently clamped or secured. This construction also provides open spaces above and below the cup and on opposite sides of the bracket to give an unobstructed view of the commutator and the brush assembly on the removal of th handle.

A further object of my invention is to provide a motor for the tool of the regular universal type with a distributed stator winding, thereby assuringhigh power and emciency with a stator of small diameter, and also to provide a space between the stator and the motor casing for the switch device and the manually operable parts therefor without adding size to the tool.

A further object of my invention is to employ a cam and lever combination for operating the switch device. By the use of this combination the operating cam and lever can be placed in a position most convenient for the thumb of the operator's hand holding the tool for turning on and off the electrical current to the motor.

1936, Serial No. 30,311

The invention consists further in the features hereinafter described and claimed.

Fig. l is a side view of the improved tool, the pistol grip handle member being shown in full lines removed from' the tool;

Fig. 2 is an enlarged longitudinal, vertical sectional view of the tool with the handle member in place at the rear end of the motor casing, parts being shown in elevation;

Fig. 2a shows the interlocking connection be- 10 tween the upper end of the handle member and the top part of the motor casing;

Fig. 2b shows the interlocking connection between the lower portion of the motor casing and the handle member;

Fig. 3 is a rear view of the tool with the handle removed and on approximately the scale of Fig. 2;

Fig. 4 is a horizontal sectional view taken on line 4-4 of Fig. 3;

Fig. 5 is a similar sectional view taken on line 5-5 of Fig. 2, with parts in elevation. to show the cam and lever combination for operating the switch device for the motor;

Figs. 6 and 7 show the action of the cam means referred to; and

Fig. 8 is a sectional view taken on line 8-8 oi Fig. 2.

In the drawings, I indicates the outer casing of the tool enclosing the electric motor which rotates the chuck shaft or spindle 2 at the front end of the tool. The motor, as shown, is of the regular type having its armature 3 rotatable in and encircled by a stator 4. The motor assembly is located in the lower portion of the casing I, providing a space 5 above the motor for the switch device 6 and its combination cam and lever actuating mechanism to be later described.

The armature shaft I is Journaled at its ends in

ball bearings

8, 9, one located at the front end of the motor case I and the other located at the rear end of said case. The forward bearing 8 is supported in a plate Ill which closes the front end of the-motor case I and forms the rear wall of a gear housing to be presently described. The rear bearing is supported in a cup I I located between and cast integral with'a pair of lugs l2, l2 extending rearwardly from the'side walls of the motor case as shown in Fig. 3.

The cup I I is provided with a depending bracket I! cast integral with the cup and comprised of a pair of arms I3a, I3b spaced axially of the tool and connected at their lower ends on one side by a curved yoke piece II. The latter accommodates the end of the cable ii at the tool, said cable containing electric supply wires I i, ll

for the motor of the tool. The cable is clamped in the yoke piece by a clamp plate or strip I8, which as shown in Figs. 2 and 3, spans the open side of the yoke piece and is secured to the arms by fastening screws I9.

The commutator 20 of the motor is located within the motor casing I adjacent its rear end and is engaged by a pair of carbon brushes 2I, 22. These brushes are also located wholly within the motor casing I, being supported therein by a ring-shaped plate 23 of suitable insulating material. The ring 23 surrounds or encircles the commutator 26 and is held in place in the motor case I against a seat 24 by one or more fastening screws 25, as indicated in Figs 3 and 4. In the particular embodiment shown, the ring23 is located adjacent the inner end of the commutator, the brushes being disposed on the outer side of the ring and slidably mounted in

brush holders

26, 21, one for each brush.

Each

brush holder

26, 21 is preferably in the form of a metal strip, shaped to provide a channel section 28 intermediate its ends to receive a brush and anchored at its ends to the ring 23 by

fastening elements

29, 30 which may be of the screw type as shown. The element 29 provides an anchor for one end of a spiral spring 3|, the other end of the spring bearing against the outer end of the associated brush to press the brush against the commutator, as shown. The other element 30 at each brush holder provides a binding post for connecting the brushes in the motor circuit.

The handle member 32 for the tool is releasably secured to the rear end of the motor casing I by a number of

fastening screws

33, 34. The screw 33 takes into a tapped lug 35 at the upper edge of the motor case, while the screw 34 screws into a tapped hole in the cable supporting bracket' I3, as shown in Fig. 2. The handle member provides a cover for the rear end of the motor casing and has recesses 36, 36 in its side walls to receive the similarly shaped projections I2 on the motor-case.

The lug 35 at the top of the motor case interlocks with a recess 31 in the top portion of the handle member, while a lug 38 on the handle member interlocks with a recess 39 in the lower edge of the motor case, as shown in Figs. 2a and 2b, respectively. The lugs and projections referred to interlock the handle with the motor case and also serve as means for centering the parts when assembling them, I

The lower portion 40 of the handle member 32 extends below the motor case I in substantially normal relation thereto and is made tubular in shape, as shown in Fig. 2b, to provide a pistol grip for the fingers of the hand of the operator holding and operating the tool. The portion 46 is made hollow to accommodate the cable I5 and the supporting bracket I3, when the parts are assembled. The lower end of the portion 46 may be closed by a fiber plate 4| set in a recess in the edge of the handle as shown. This plate centers the cable with respect to the handle and may be provided with one or more air intake openings 42 in addition to the central opening 43 for the cable.

The motor is equipped at its forward end with a rotary fan having a disc 44 fixed to the armature shaft 1 between the armature 3 and the plate I0. The disc 44 is provided with fan blades 45 which in the rotation of the motor draws air through the motor from its rear end and discharges such air out of the case through a number of vent openings 46. The latter are provided in the motor casing I adjacent the periphery of the fan and may be disposed in tangential relation to the fan as disclosed in my patent No. 1,652,401, granted December 13, 1927.

Air intake openings 41 may also be provided in the motor case I in advance of the brush plate 23 as shown in Fig. l.

The spindle 2 is arranged on the side of the armature shaft 1 opposite the grip portion 40 of the handle member 32. Said spindle is driven from the shaft I by a reducing gear 48 in mesh with gear teeth 49 provided in the forward end of the shaft 1. The gear 48 is fixed to the spindle 2 and is located in the gear housing, the front cover plate 50 of which is secured to the forward end of the motor casing I by a number of screws 5| as shown. The spindle 2 is journaled in ball bearings 52, 53, one carried by the plate In and the other carried by the gear housing cover 50. The spindle 2 in the particular tool shown is equipped with a chuck 54 for holding a drill bit.

The switch device 6 is of the conventional snap type obtainable on the market and is supported in the motor case I by a metal strip 55 extending across the motor case in the space 5 beneath the switch block or housing 56. The latter seats against the cover plate I6 in a socket formed by a U-shaped flange 51 provided on said plate. The strip 55 has one or more

upturned lugs

58, 58 to hold the switch in place, as shown in Fig. 8. The top wall of the motor case may be provided with

recesses

59, 59 to receive the upper corners of the switch block as shown in said figure. The ends of the strip 55 are engaged in

apertures

60, 60 in the motor case as shown.

The actuator 6I of the switch 6 extends toward the rear of the tool and is engaged by the forked end 62 of a lever 63 fulcrumed intermediate its ends on a screw 64 depending from the top wall of the motor case as shown in Fig. 2. The rear end of the lever 63 is engaged by the inner end of a second lever 65 arranged at right angles to the main lever 63 and fulcrumed in the motor case I on a pivot pin 66 between a pair of lugs or ears 61, 61a as shown in Fig. 5. The free or outer end of the supplemental lever 65 extends out of the motor case through a. slot 68 therein as shown in Figs. 6 and 7. This slot is located adjacent the rear end of the motor case, thus positioning the outer end of the supplemental lever 65 in a position to be readily engaged by the thumb of the hand of the operator holding and operating the tool. The tool is grasped and held with the thumb of the hand on the side of the motor case from which the lever 65 extends. I

The inner end of the lever 65 is provided with a cam slot 69 to move the main lever 63 to actuate the switch 6 as the outer end of the supplemental lever 65 is moved to the opposite ends of the slot 68. In the particular embodiment shown, the switch is off when the outer end of the lever 65 is at the upper end of the slot 68, whereas the switch is on when the outer end of the lever 65 is at the lower end of said slot, as indicated in Figs. 7 and 6, respectively. The free end of the lever 63 works in said cam slot, which by its angularity to the lever 63 swings the latter back and forth in the up and down movement of the lever 65. One edge of the cam slot moves the lever 63 in one direction, while the other edge of the slot moves the lever in the opposite direction. The upward movement of the lever 65 is limited by its inner end striking the top wall 01' the motor case. The downward movement of the lever 65 is stopped by the closed end of the cam slot 69 striking the engaged end of the main lever 63. The lever 63 enables the switch device 6 to be seated against the plate III at the front end of the motor, yet be operated from adjacent the rear end of said case by the thumb of the operator's hand holding and using the tool.

The handle member 32 is in one piece, being die cast. The motor case I, bearing cup ii and cable bracket i3 are also in one piece being die cast, as are the other casing parts of the tool. Light metal is used to provide a tool which is relatively light in weight. The motor and other parts are so proportioned as to provide a tool smaller in size and lighter in weight than ordinary tools with equal power. The advantages of such construction are that the tool can be held in and operated by one hand and be usable in close or confined quarters.

With the support for the brush assembly and the supply cable i5 confined to the motor case I, the handle member 32 is relieved of this duty,

and thus may be removed in its entirety from the tool without disturbing the brush assembly or the connection of the supply cable to thetool.

This permits running of the motor for inspection of the brush assembly and the commutator while the handle is removed from the tool as indicated in Figs. 1 and 3. Also an unobstructed view of the brush assembly and the commutator is provided on removing the handle member as the entire rear portion of the motor case is opened on taking oil. the handle member. The upper brush and the commutator is accessible in the large open space above the bearing cup ll, while the lower brush is accessible below the cup through the open spaces on opposite sides of the cable bracket i 3, as clearly shown in Fig. 3. The space 5 above the motor enables the upper brush 2i to be replaced when worn, said brush being placed on an angle to clear the lug 35. With the pistol grip section 40 of the handle member removed, the lower brush 22 may be replaced through the recess or notch 39 provided in the lower edge of the motor case for the lug 38 on the grip section 40. The large space provided above the cup ll enables the commutator to be readily and easily reached for cleaning, as by the use of a piece of sand paper as used for large stationary motors.

The particular tool shown has a universal motor, for either A. C. or D. C. current and has a free speed of approximately 2500 revolutions per minute.

The electrical circuit of the tool is as follows: The cable wire I6 is connected to one of the field coil leads 10. The other field coil lead II is connected to the binding screw 30 of the lower brush holder. The cable wire I! is connected to one of the switch wires 12. The other switch wire 13 is connected to the post 33 of the upper brush holder.

The handle member 32 on being released from the motor case I to view the brush assembly, etc. is dropped down the cable It. On assembling the tool in the first instance, the cable I5 is inserted into the handle member 32 through the opening 43 in the closure disc, whereupon the cable is clamped to the bracket I3 and the connections made with the motor. On completion of the motor switch and gear assembly, the handle is secured in place over the rear end of the motor case. On assembling the motor, the

stator 4 is inserted into the casing I through the open front end thereof, and is fastened in place by a number of set screws carried by the case I, one screw being shown at N in Fig. 1. All of the wiring for the motor circuit has tight connections which avoid faulty electrical contacts. It will be noted that the switch device 6 is not screwed in place, the clamping arrangement shown enabling a single snap switch to be used and mounted.

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

I claim as my invention:

1. In a portable electric tool of the character described, a motor case, an electric motor in said case, a spindle at the forward end of the case and driven by said motor, a brush assembly and a supply cable for the motor at the rear end of said case, and a handle member releasably secured to the rear end of the motor case over the brush assembly and the supply cable and providing a closure therefor, said handle member having a pistol grip portion extending below the motor case, said brush assembly and the supply cable being supported wholly by the motor case, whereby the handle member including the whole of its pistol grip portion may be removed from the motor case without disturbing the brush assembly or. the supply cable.

2. In a portable electric tool of the" character described, a motor case, an electric motor in said case, a spindle at the forward end of the case and driven by the motor, a bearing cup and a brush' assembly for the motor at the rear end of said case, a supply cable for the motor secured to said cup, and a handle member releasably secured to the rear endof the motor case over the bearing cup and the supply cable and providing a closure therefor, said handle member having a pistol grip portion extending below the motor case, said brush assembly and bearing cup being wholly supported by the motor case, whereby the handle member including the whole of its pistol grip portion maybe in one piece and be removable as a unit from the motor case without disturbing the brush assembly or the supply cable.

3. In a portable electric tool of the character described, a motor case, an electric motor in said case, a spindle at the forward end of the case and driven by said motor, a brush assembly and a supply cable for the motor at the rearend of the motor case, a handle member releasably secured to the rear end of the motor case over the brush assembly and the supply cable and providing a closure therefore, said handle member having a pistol grip portion extending below the motor case, said brush assembly and the supply cable being wholly supported by the motor casing, whereby the handle member including its pistol grip portion may be removed from the motor case without disturbing the brush assembly or the supply cable, and interfitting means on the handle member and the motor case to interlock the handle member to'the motor case when the handle member is secured to the motor case.

4. In a portable electric tool of the character described, a motor case, an electric motor in said case, a spindle at the forward end of the case and driven by the motor, a brush assembly having upper and lower brushes and a supply cable for the motor at the rear end of the motor case, a handle member releasably secured to the rear end of the motor case over the brush assembly and the supply cable and providing a closure therefor, said handle member having a pistol grip portion extending below the motor case, said brush assembly and the supply cable being supported wholly by the motor case, whereby the 'handle member including its pistol grip portion may be removed from the motor case without disturbing the brush assembly or the supply cable, said motor case having a space above the motor for the removal of the upper brush and a recess in the lower rear edge of the motor case below the motor for the removal of the lower brush.

5. In a portable electric tool of the character described, a motor case, an electric motor in said case, a spindle at the forward end of the case and driven by the motor, said case'having a pair of rearwardly projecting, laterally spaced lugs at its rear end, a bearing for the rear end of the motor, a cup for the bearing between and supported by said lugs, a bracket depending from said cup, a supply cable for the motor clamped to said bracket, and a handle member releasably secured to the rear end of the motor case over said cup and said bracket and providing a closure therefor, said handle member having a pistol grip portion extending below the motor case,-said handle member having rceesses to receive and interfit the lugs on the motor case when the handle member is secured thereto.

6. In a portable electric tool of the character described, a motor case, an electric motor in said case and having its commutator adjacent the rear end of the case, a spindle at the forward end of the case and driven by the motor, a brush assembly forthe commutator and a supply cable for the motor, both located at the rear end of the motor case, and a handle member at the rear end of the motor case having a pistol grip portion extending below the case, said brush assembly and the supply cable being wholly supported by the motor case, said handle member providing a closure for the rear and of the motor case and being releasably secured thereto, whereby an unobstructed view and access may be had to the brush assembly and the commutator on removing the handle member including its pistol grip portion from the motor case.

7. In a portable electric tool of the character described, a motor case, an electric motor in said case, a spindle at the forward end of the case and driven by the motor, a handle member secured to the rear end of the case and having a pistol grip portion extending below the case, said motor being disposed in the lower portion of the case to provide a space between the motor and the top wall of the motor case, a switch device for the motor, said switch device being located in said space adjacent the spindle, and means disposed in said space and connected with the switch device for actuating the same, said means extending along the space toward the handle member and operable from the exterior of the motor case adjacent the handle member.

8. In a portable electric tool of the character described, a motor case, an electric motor in said case, a spindle at the forward end of the case and driven by the motor, a handle member secured to the rear end of the case and having a pistol grip portion extending below the case, said motor being disposed in the lower portion of the case to provide a space between the motor and the top wall of the motor case, a switch device for the motor, said switch device being 10- cated in said space adjacent the spindle, a lever pivoted in the space adjacent the handle member and operable from the exterior of the case adjacent the handle member, a second lever pivoted in the space between the switch device and the first lever, said second lever extending along the space from the switch device to the first lever and having one end at the first lever and its other end engaged with the switch device for operating the same, and a cam connection between the first and the second levers for actuating the second lever by the first lever.

9. In a portable electric tool of the character described, a motor case, an electric motor in said case, a spindle at the forward end of said case and driven by the motor, a handle member secured to the rear end of the case and having a. pistol grip portion extending below the case, said motor being disposed in the lower portion of the case to provide a space between the motor and the top wall of the motor case, a switch device for the motor, said switch device being located in said space adjacent the spindle, a lever pivoted in the space adjacent the handle member and operable from the exterior of the case adjacent the handle member, and a second lever pivoted in the space between the switch device and the first lever, said second lever extending along the space from the switch device to the first lever and having one end at the first lever and its other end engaged with the switch device for operating the same, said first lever being disposed substantially normal to the second lever and having a cam slot cooperable with the second lever for operating the same.

10. In a portable electric tool of the character described, a motor case, an electric motor in said case, a spindle at the forward end of the case and driven by the motor, a cover plate closing the front end of the case, a handle member closing the rear end of the case and having a pistol grip portion extending below the case, said motor being disposed in the lower portion of the case to provide a space between the motor and the top of the case, a switch device for the motor, said switch device being located in said space adjacent the cover plate and supported thereby, means for holding the switch device in place with respect to the cover plate, and means in said space and connected with the switch device for operating the same, said means extending along the space toward the handle member and being operable from the exterior of the motor case adjacent the handle member.

11. In a portable electric tool of the character described, a motor case, an electric motor in said case, a spindle at the forward end of the case and driven by the motor, brushes for the motor at the rear end of the case, a handle member releasably secured to the rear end of the motor case over the brushes and providing a closure therefor, said handle member having a pistol grip portion extending beyond the motor case, said brushes being supported by the motor case, whereby the handle member including the whole of its pistol grip portion may be removed from the motor case without disturbing the brushes with respect to the motor, and a supply cable associated withthe handle member for the motor.

12. In a portable electric tool of the character described, a motor case, an electric motor in said case, a spindle at the forward end of the case and driven by the motor, brushes at the rear end of the motor case, a handle member releasably secured to the rear end of the motor case over the brushes and providing a closure therefor;

said handle member having a grip portion extending outwardly from the motor case, said brushes being supported by the motor case, whereby the handle member including the whole of its grip portion may be removed from the motor case without disturbing the brushes with respect to the motor, and a cooling system for the motor comprising a fan member at the front end of the motor and driven thereby, and air intake and discharge openings in the motor case, the intake openings being adjacent to and in advance of the brushes and the discharge openings being adjacent to the periphery oi the fan.

13. In a portable electric tool of the character described, a motor case, an electric motor in said case, a spindle at the forward end of the case and driven by the motor, brushes for the motor at the rear end of the motor case, a. handle member releasably secured to the rear end of the motor.

FRI'I'HIOP P. FORSS.