US2078896A - Electric motor - Google Patents

Description

Pl'l 27, 1937 .1. A. HANLEY 2,078,896

ELECTRIC MOTOR Filed Dec. 17, 1954 .42 J 8f a? H @f4-Q 6.076,46@ 179.113

ATTORNEYS Patented Apr. 27, 1937 UNITED STATES PATENT OFFICE 2,078,896 ELECTRIC MOTOR poration of New York Application December 17.193,4, Serial No.^757,755

25 Claims.

My present invention relates to compact, lowpower electric motors of the type'used for driving small tools such as apparatus for shaving, hairclippirm, massaging or the like, and more especially of the type in which the motor is encased or housed within the handle of the tool.

An object of the invention is to provide an apparatus of the above type, rugged, compact and inexpensive in construction, which shall be of universal utility, both on direct and on alternating current circuits.

Another object is to provide an apparatus of the above type, which can be readily started by a simple manipulation, with the same hand that grasps the apparatus, and in which no exposed part revolves while themotor is running.

Another object is to provide an apparatus of the above type which has a minimum amount of winding, a minimum number of circuit connections and which is not subject to short circuit or shock to the operator.

Another object is to provide an apparatus of the above type which is subject neither to excessive heating nor to excessive sparking in the course Another object is to provide apparatus of the above type, the small casing of which is substantially completely illled by the largest motor capable of being accommodated therein and which motor is so designed as to admit of an armature practically the full Width of the casing.

Another object is to provide a motor of the above type, of simple stampings easily assembled, said motor of low power consumption, yet exerting substantial operating force on the tool, not easily stalled, smooth in operation and inherently non-hunting, inthe absence of any adjustment devices to that end.

' A feature of the invention is the use of an.

armature rotor operating between the poles of a ileld stator, both enclosed within an insulating 45. handle casing, there beinga contact breaker operated by a cam conformation on the amature shaft and in circuit Ywith the electromagnetic win'ding of the motor. y i y.

Another feature is the rotary armature, having three or more poles for eicient operation, 'with its transverse diameter beyond the two field poles and therefore of diameter substantially equal to themaximum width of the field.

Another feature is the arrangement whereby each pole of the eld structure is made of. a

of operation, all without resort to exposed medistinct set of L-shaped laminations, the bases of which are frictionally tted from opposite ends of an insulating spool for the field coil, which thus carries the laminations.

Another feature is the construction of the eld 5 coil in two segments with an intervening insulating plate to cause said coil to have substantial capacity effects, tending to preclude any arc at the breaker contacts; also to facilitate starting under direct current operation by neutralizing the choking effect of the`coil, and furthermore to reduce the likelihood of arcing across the insulation of 'the coil.

Another feature is the transmission for operating the tool by a lever protruding from the casing, pivoted preferably to the rotor frame and caused to oscillate by an eccentric at one end of the rotor shaft.

Another feature is the mode of mounting the motor within the casing by iit of the field between the lateral Walls of the casing and lmounting of the armature frame'upon bosses molded in the floor of the casing and affording spacefor the transmission lever.

Another featureis the disposition of the contact breaker upon the armature frame and the disposition of the breaker points in the space between the armature and the field winding.

Another feature is the connection of the breaker elements in circuit with the stationary field by flexible exposed leads accommodating the relative movement and serving as heat radiating fins.

Another feature is the use pf a starting roller protruding from the casing, normally free fromv contact with the rotor and brought into peripheral engagement therewith in the application of the starting torque, said roller remaining inactive while the motor is running.-

Another feature is the construction of the rotor4 or armature with non-magnetic segments intervening between ythe poles of one or more magynetic laminations to aiord continuous uninterrupted engagementy for the starting roller during the application of the starting torque, without reducing the magnetic effect of the rotor.

In the accompanying drawing, in which is shown one of various possible embodiments of the several features of the invention, 4

Fig. 1 is a plan view-of theapparatus with the cover removed, showing the contact breaker lust closed,

Fig. 2 is a view in longitudinal cross-section on linevZ-Z of Fig. 1, Y

v Fig. 3 is a fragmentary plan view similar to Fig. l, showing the contact breaker about to open,

Fig. 4 is a perspective viewof the amature, Fig. 5 is a detail view on a larger scale taken on the line 5 5 of Fig. 3, and

Fig. 6 is a fragmentary side elevation, showing the arrangement of the starting roller.

Referring now to the drawing, the device includes a casing i0 preferably molded of Bakelite, vulcanite or similar composition with special conformations to house the motor and parts now to be described. In particular the casing includes side walls il and I2 between which are snugly fitted the legs I3 of the laminated motor field, which is preferably of the two-pole type.

Preferably the field coil is prewound on a unitary open insulating frame or spool F of Bakelite", vulcanite or the like, said frame being preferably rectangular and having flanges Il and 92 at its ends. The coils i5 and I8 are wound about said frame in contact with the respective flanges and at their contiguous ends they contact a separating median nn Sl which is an integral part of and completely encircles the spool F.

The outer terminals of coils i5 and it are connected respectively to binding posts i1 and i8 on the tops of reinforced ribs I9' at the corners of the casing and are electrically connected to leads i! and 20 protruding at 2i from the rear of the casing through insulating bushing 22.

Unlike conventional U-eld constructions in which the eld coil is wound about and carried by the field structure, the field laminations are carriedby the coil spool unit. To render possible such assembly the U-shaped field is not made of U-shaped laminations but each lamination is made of two symmetrical L-shaped parts I3. Two stacks of laminations are inserted through opposite ends of the spool F to snugly fit and completely to fill the opening thereof, as best shown in Fig. l, with the ends of said laminations in abutting relation at 8l to form the yoke of thel field. In operation of the motor, as is obvious, the abutting ends of the field laminations are magnetically drawn together. Fastening screws 62 through the field stack and preferably near the poles, bind the field structure firmly against a shelf (not shown) in the floor of the casing.

The armature is a rotor unit comprising preferably a stack of laminations 23 having arcuate notches 24 therein to form three poles P', P and I.V The stack of laminations is secured together by pins 2! transversely through the poles thereof.` The three-pole construction of armature makes for a far smoother operation than a two-pole armature, since the torque impulses are more frequent and a relatively shorter mean magnetic path is afforded.l

For application of starting torque in manner to be set forth below. one of the magnetic iron armature segments 23 preferably near the top of the amature, has stamped thereout of key-way conformations but is otherwise identical with n the other laminations and does not present any interruption at the pole segments.

These key slots serve to mount stii! non-magnetic segments 2l, preferably of Bakelite im.

pregnated fiber, having complementary keys l1 firmly fitting the respective key-ways, and if desired also cemented in place. The segments 2U occupy the gap between the successive poles of the keyed lamination 23' so that the composite lamination presents in contour a complete circle coaxial with the armature.

The effectiveness of the armature from an electromagnetic standpoint is in no way impaired by the presence of the non-magnetic segments 2C, since the magnetic structure is continuous both axially'and transversely and of the same width and thickness throughout.

The armature has a shaft 21 tightly fitting into corresponding central holes in the laminations and having its bearings in an armature carrying frame, the latter composed of a base plate 2l and a cover plate 29 both of duralumin or the like. The plates 28 and 29 have preferably inturned apertures as at 3|! and Il extending into the corresponding central openings 30' and Il in the uppermost and lowermost laminations of the armature and affording long and eifective bearing surfaces for shaft 2l. The two plates of the frame are connected together by screws I2 encircled by'spacer sleeves I2 affording a cage for the rotor. The rotor unit just described is affixed into the casing upon upstanding bosses 3l and Il molded as unitary parts of the floor il of the casing into which are threaded respectively the lower ends of screws 56 and I2 of the armature carrying frame just described.` An additional boss 3 is disposed immediately in front of the field coils l5 and I6, the base plate 28 of the motor frame being elongated as at 28' to overlap said boss, to which it is also attached by a short screw I5, readily accessible from between the legs of the motor field.

As shown in the drawing, the armature diameter transversely of the casing extends somewhat beyond the extremities of the field poles which are rounded as at I3 to accommodate the curvature of the armature. Unlike arrangements in which the field poles are in direct facing relation to accommodate the armature therebetween, the

present arrangement admits of an armature of diameter not materially less than the maximum width of the field structure and in turn substantially equal to the effective width of the casing.

The motor therefore substantially completely fills the small handle casing without waste space and is thus of largest possible size and power to be accommodated within a casing sufficiently small to be grasped as a handle.

By the arrangement described, the motor frame is spaced by the height of the bosses 34', Il and u from the floor of the casing, said space serving to accommodate the transmission lever 3l by means of which the tool, illustratively a hair clipping head Il, is operated from the motor. The inner end of the transmission lever is pivoted abouta screw Il, threaded into the base 2l of the armature frame and the lower end of the rotor shaft 21 has an eccentric conformation I! extending into a slot Il in the transmission lever, thereby to cause the latter to make one oscillation back and forth about the pivot pin Il for each complete revolution of the motor armature. The eccentric II need be but slightly offset to operate the corresponding part of the lever through a relatively small path, in order to produce an effective displacement at the operating tool 81 by the multiplying effect of the long lever arm. The transmission lever as shown, has a double bend "-42, to offset its outer tool carrying end Il to position centrally of the front of the-casing.

Upon the upper plate 20 of the motor frame is mounted the contact breaker C now to be described. This breaker comprises a pair of arms 4i and Il. Arm "comprises a rigid bar of insulation aiiixed `by screw 41 to the plate 29, said bar having molded therein a conducting blade 48 carrying a contact point 5I) preferably of the alloy commonly employed for ignition contact breakers. 'The complementary movable contact point 5I is mounted on a similar metal blade 52 similarly molded in a rigid insulating mounting arm 46 which has a rocking mount about a pivot screw 53 in the top plate 28 of the rotor casing..

A blade of spring steel 54 aiixed at an eye 55 thereof by means of screw 56'to the top of the rotor frame urges the arm 46 about its pivot 53 for normal engagement of the contacts 50 and 5|.

The blades 49 and 52, preferably of Monel metal or other suitable alloy have their ends bent downward at right angles as at 58 into the space between the armature and the field coils and between the legs of the field, thev contacts 5I and 62 extending in vertical planes as shown in Figs. 1 and 2. v

The field coils i5 and I6 are series-connected through the contacts 50 and 5I by means of Y wire leads 64 retained by wire holding clips 60 and 6I of fiber, each secured to the field by the screw 62, whichholds the field in place. Each wire clip has an upstanding eye 63 mounting the corresponding insulated lead 64 from the field coil. Soldered to the protruding end 65 of each lead is a corresponding flexible connector 66, the free end of which is clamped between the associated contact point 5I and its mounting blade 52 as at 61 in Fig. 5. Connectors 66 are preferably of beryllium copper alloy and serve the purpose of a flexible connection to admit of relative movement of contacts C, and also vserve as heat radiating flns to prevent overheating at contacts C.

The contact breaker is operated preferably by a triangular cam conformation 16 at the upper end o f the armature shaft which clears the fixed contact arm but engages the movable contact arm 46, so that'in the revolution of the rotor,

` arm 46 is moved about its pivot 53 to break contact three times in each revolution of the armature v shaft. The spring 54 in each case closes the contact as'the flat side of the cam comes into engagement with the contact arm. vThe alternate movement of opening and closing the contact breaker will be apparent from Figs. l and 3.

It will be seen that the vrespective apices of the cam 16 registerrwith the respective poles P', P2 and i"3 of the armature, so that the contact is closed when one of the armature poles is midway between the field poles, but is open when two of the amature poles are alined with the corresponding fieldpoles.

Once the motor has been started, the opening of the contact breakers interrupts the circuit, but the inertia of the moving armature carries it on to a position where the contact breakerV again closes the circuit for further impulse, three cycles of alternate impulse and inertia advance occurring for each complete turn of the rotor. The rotation of the motor is thus uninterrupted and operation will occur regardless whether on direct current or any frequency of alternating current.

Preferably the cam is so proportioned that the circuit is alternately closed for 52 degrees and open for 68 degrees, there being thus three complete cycles of opening andv closing for each ro- 'tation of the armature. In the position of Fig. 1,

[The rotor which prior to said contact closure is still -moving under inertia, is given a sharp torque l due to the magnetic attraction of armature pole P by the field pole immediately in advance of it and of armature pole P2 by the field pole immediately in advance of it.

Each time contacts50-5I open, in the operation of the motor, arcing therebetween is effectively prevented, since the residual energy in the circuit is stored as a charge, due to the capacity effect of the coil unit, coils I5 and I6 acting as the plates of a condenser in their correlation with the intervening insulating fin 83 which serves as the dielectric thereof. The stored charge is given up when the contacts are again closed, thereby adding to that extent to the effective torque of the motor. Of course the capacity effect depends upon the thickness and material of the n 93. While the construction and arrangement of coils I5 and I6 to serve as an effective capacitor has special utility in the specific environment set forth, this feature is of more general applicability in other relations.

By the arrangement set forth, the maximum voltage existing between the ends of the field coil structure is at no time exerted on any partof the insulating carrying structure, but since the coil is in two segments separated by insulation,

at most half of the maximum voltage exists across lany insulating portion, so that the likelihood of current, for in that relation the choking effect of the field coil is partly or wholly neutralized by its capacity effect.

It will, of course, be understood that the principle of the motor set forth could be carried out in a. wide variety of manners, and that the pre- 4cise construction shown and described, while preferred, is largely illustrative..

The casing, preferably has an obliquely extending upper rim 15 which at the right end is only half the height of the assembled casing, the casing cover 16 being correspondingly wider at its rear end 11 and narrower at its forward end 18. Between registering notches 'I8 and 86 in the cover and casing respectively, the shank of bushing 22 is lodged, the cover and casing being also respectively undercut at 8| and 82 to lodge the bushing flange 83 The cover is secured to the casing preferably by screws 84, 85 and 66.

The motor is equipped with a starting appliance comprising a small insulating starting roller 81 protruding through a corresponding notch 88 at the -upp'er rim of the casing. The notch 88 is of width less than the diameter of the roller, as shown, so that the roller is effectively held from dropping out of the casing, though no between the casing wall, the armature and .the I l spacer sleeve about screw 56.

The lower rim of the casing cover It exerts a-slight longitudinal pressure on the roller, which protrudes laterally from the port in the casing dened by notch 88 and the cover. The roller is substantially in the same plane as the starting segmentv 26 of the armature, but as best shown in Fig. 1, -is normally slightly spaced therefrom.

To start the motor after plugging irithe leads 2i, the starting roller I1 is merely twirled with the thumb of the same hand holding the casing, which causes the roller to be pressed slightly inward away from the casing wall to engage the starting segment and then to start spinning the rotor, which promptly falls in step and rotates continuously in the manner above described to oscillate the transmission lever 36 and tool 31 at the exposed end of the casing. When the finger pressure is released from the starting roller 81, the rapidly revolving armature segment 26 kicks the roller 81 outward so that it becomes lodged in the notch 88 and is retained by the slight frictional hold thereon exerted by the casing cover l. ri'he starting roller therefore remains stationary during the operation of the motor and the danger of injury to the user, as for instance by the catching of hair under a rapidly spinning exposed part is precluded.

The starting appliance is thus of extremely simple construction, the starting roller in the assembling operation being simply dropped into place without any clutch, bearing or other holding appliance therefore As previously indicated there are three distinct torque impulses applied at uniform intervals for each complete rotation of the armature, which rotation, however, effects only one complete back and forth reciprccaticn of the tool Il, such as the hair clipping tc-ol. The torque impulses being thus at intervals much more frequent than those at which the tool takes its maximum load, the motor applies full momentum to its load, and the operation is therefore quite smooth and is inherently non-hunting, and the adjustment devices generally used for such purpose are dispensed with.

The power consumption of the motor is l0 watts or less, and while the torque on the armature is small, yet said torque is most efficiently applied.

It will thus be seen that there is herein described apparatus in which the several features of this invention are embodied, and which apparatus in its action attains the various objects of the invention and is well suited to meet the requirements of practical use.

As many changes could be made in the above construction, and many apparently widely different embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent, is:

l. An implement comprising a handle casing substantially closed at the forward end thereof and having an electric motor therein comprising a stator and a rotor, said rotor having a shaft with an eccentric at its end, and a pivoted lever coasting with said eccentric and protruding through a corresponding small opening in the forward end of the casing for reciprocating a v tool applied over the forward end of said casing and of area much larger than said opening and a cover abutting at its forward end the rear edge o! the substantially closed forward end of said casing.

2. A small, electrically operated implement comprising a handle casing substantially closed at' the forward end thereof and. an electric motor therein, said motor comprising a stator and a rotor, said rotor having a shaft, an eccentric integral with said shaft, a lever pivoted at one end with respect to the casing and having an aperture near said end coacting with said eccentric, the forward end of said lever protruding through a corresponding small opening in the forward end of said casing for coaction with a tool applied over the forward end of said casing and of area much larger than said opening to be reciprocated by said lever in the operation of the motor and acover abutting at its forward end the rear edge of the substantially closed forward end of said casing.

3. A universal electric motor comprising a field yoke having poles, a field coil thereon, a

vcontact breakerfin circuit with said field coil, a

rotary armature disposed between said poles, a cage therefor said armature having a cam thereon, with as many protrusions as the armature has poles, for periodically operating said Contact breaker, said armature being segmental for periodic variation of the air gaps between the field poles in the rotation of the armature, contact breaker being constructed and arranged for owning and closing the field circuit at definite phases in the rotation of the armature and carrying arms for the contact breaker mounted or. said cage, the contact elements of the contact breaker being lodged in the space between said field yoke and said armature.

' 4. A universal motor comprising a field' yoke having poles, an armature pivotally mounted between said poles and having a cage, said armature having poles of width nearly that of the field poles and with gaps therebetween and a contact breaker in circuit with the field coil having arms mounted on said cage and operated from the armature to be opened each time two amature poles pass substantially beyond a position of registry with the field poles the contacts of said contact breaker being lodged in the space between said i'ield yoke and said armature.

5. An apparatus of the character described comprising a handle casing, a universal electric motor enclosed in said casing, said motor comprising a two-pole held mounted in said casing and extending longitudinally thereof and having a field coil thereabout, an amature having a rotary shaft, bearings for said shaft, a carrying frame for said bearings and straddling said armature, said armature having three spaced about 52 degrees and opening of the circuit for` about 68 degrees of the rotation of the armature. 6. An apparatus of the character described, comprising an insulating casing constituting a handle, a universal electric motor therein, said' motor having a two-pole field structure extending longitudinally of said casing and secured therein,'

an amature rotor unit comprising a support frame having a base iixed to said casing, said base having a bearing for said rotor, said frame also having a cover piece for said rotor, a contact breaker in circuit with the field coil and carried by said trame cover piece, said amature shaft rotation of said armature.

having a cam formation for effecting periodic opening and closing of said contact breaker in the 7. An apparatus of the character described comprising an insulating casing having a fioor with integral mounting boss support means, a two-pole eld structure having an encircling coil, said field structure secured between the sides of said casing with its coil extending back of said support means, a rotary armature between the poles of said eld structure, said armature including a supporting frame secured to said support means and spaced thereby from vsaid floor, an operating lever pivoted to said frame support and extending in the space determined therebelow by said support means, and an eccentric cn the end oi' said amature shaft cooperating with said lever to oscillate the same in the rotation of said armature, the forward end of said lever being exposed through the casing for operating a tool.

8. An automatic tool comprising a handle having an electric motor incorporated therein, said motor comprising a stator and a rotor, lone of said elements having an electro-magnetic coil, means constituting a bearing mount for said rotor, spaced from the corresponding walls of said casing, operating conformations at the opposite ends of the rotor shaft, a contact breaker in said casing coacting with one of said conformations and in circuit with said coil, and a lever in said casing, cooperating with the conformation at the other end of said rotor shaft to be oscillated thereby, said lever having its free end exposed f through the forward end of lthe casing for coaction with a tool.

9. Apparatus of the character described Comprising an insulating casing, a two-pole fieldstructure extending longitudinally of, tightly fitted in engagement with the sides of said casing, and secured to the floor thereof, a coil about the end of said field structure, support boss means rising from the iioor of said casing in advance of saidy coil, an armature unit comprising a rigid support frame and a rotor having its bearings in said frame, the bottom of said support frame 4secured to the top of said support means, thereby spacing said frame from the floor of said casing, an operating lever pivoted within said casing and under the base of said frame, and an eccentric at the lower end of the armature shaft cooperating with said lever, the forward end of said lever protruding through the front of said casing.

10. Apparatus of the character described, cornprising an insulating casing, a two-pole field structure extending longitudinally of, fitted in engagement with the sides of said casing and secured to the oor thereof, a coil about the end of said field structure, boss means rising from the floor of said casing in advance of said coil, an armature unit comprising a rigid support frame and a rotor having its bearings therein, the bottom of said support frame extending beyond said rotor and secured at more than one point to said boss means,ithereby spacing said frame from-the floor of said casing. an operating lever pivoted to the base of said frame, in the space therebelow determined by said boss means, an eccentric at the lower end of the armature shaft cooperating with said lever, the forward end of said lever protruding through the front of said casing, acontact breaker in circuit with` the held coil mounted on top'of said armature frame and a cam.

formation at the upper end of the amature shaft for operating said contact breaker.

f 11. Apparatus of the character described, comprising an elongated insulating casing constituting a handle, a universal electric motor mounted therein and including a two-pole field structure fitted at its sides between the sides of said casing and secured therein, an energizing coil about the end of said field structure, a rotary armature, a. carrying frame therefor, said frame fixed to the fioor of said casing, a contact breaker including arms mounted on top of said motor carrying frame, said arms carrying contacts at the free ends thereof, said ends extending downward into the space between said field coil and said armature and between the legs of said field structure, the end of l said armature shaft having a cam for operating the contact breaker.

12. Apparatus of the character described comprising an insulating casing, a universal electric motor mounted therein, said motor including a two-pole field structure fitting and secured in said casing, an armature structure including a rotor and a carrying frame therefor, said frame affixed in said casing, a coil about said iield structure, a contact breaker carried by said armature frame and means connecting said field coil in circuit with said contact breaker, said means comprising a pair of wire holders fixed to said field structure, leads from said field coil held by said wire holder and flexible leads from the latter fixed at their opposite ends with respect to said breaker contacts.

13. An armature structure for a universal motor comprising a series of magnetic iron laminations each presenting a plurality of poles, ashaft extending through said laminations, a carrying frame comprising-a base and a cover plate turned inward into correspondingv clearances in the extreme laminations for bearing mount of said shaft and spacer means securing said frame plates together in fixed spaced relation.

14. An armature for a universal motor comprising a stack of superposed laminations, each presenting armature poles and a concentric composite circular lamination constituting part of said stack, presenting armature poles, and intervening stiff non-magnetic segments, the elements of said stack'being rigidly secured together.

15. Apparatus of the character described comprising an insulating casing constituting a han` dle, a universal electric motor therein, said motor comprising a field structure fitted in said casing,

-a rotary armature fixed in said casing between the poles of said field structure, said armature having a plurality of poles, means for imparting impulses in rapid succession for continuous operation o1' said rotor and means for starting said rotor, said latter means comprising a starting roller exposed through a corresponding port in said casing, and a rigid disk concentric with and cnstituting part of said armature and contacted by said starting roller when the latter is pressed inward,

16. Apparatus of the character described. comprising an insulating casing, a universal electric motor therein, said motor comprising a two-pole field with legs along the sides of said casing, a rotary armature structure including a carrying frame fixedin said casing, an armature rotor having'bearings in said frame and including a plurality of poles and a hand starter for said armature, said starter comprisingv a small starting roller exposed through a corresponding port in said casing, said amature including a concentric rigid circular disk, adapted to be rotated by said starting roller, said disk including nonmagnetic segments between the poles thereof.

17. Apparatus of the character described, comprising an insulating casing, auniversal motor therein comprising a two-pole tleld with legs along the sides of said casing, an amature rotor between the poles of said field structure, said rotor having a metallic carrying frame, three bosses in the floor `of said casing mounting said carrying frame, bearings for said rotor in said carrying frame, a contact breaker structure carried by said frame, a cam on the upper end of said rotor shaft for operating said contact breaker, leads from said field coil to said contact breaker, an operating lever in the space below said carrying frame determined by said bosses, said lever pivoted at one end to said carrying frame, an eccentric at the lower end of the armature shaft for operating said lever, the forward end of said lever protruding through the front end of said casing, said amature having a plurality of spaced poles, starting means for said armature comprising a starting roller exposed through a corresponding port in said casing, said armature including a rigid non-magnetic part between the poles adapted' to be engaged and rotated by actuation of said starting rolt-r.

An automatic tool comprising a handle having an electric motor incorporated therein, and starting means for 'said motor comprising a roller exposed at the exterior of the casing out of contact with the' rotor, but adapted under pressure of the thumb to be brought into engagement with a part of said rotor for effective application of starting torque thereto.

i9. In electric apparatus of the character described, an electro-magnetic coil structure comnarising two coil units in contiguous relation, a breaker contact connecting said units in series, and an insulating plate separating said coils, whereby said plate acts as the dielectric of a condenser, of which the coils are the electrodes, thereby to reduce arcing at said contacts.

20. In apparatus of the character described, a motor including a stator and a rotor, said motor having an electro-magnetic coil, a contact break.

er in circuit with said coil and including at least one contact movable relative to said coil, conductors electrically connecting said coil to said contacts, said conductors being flexible to accommodate relative movement and comprising sheets of exposed metal of substantial width, each of length Vconsiderably greater than the distance between the ends thereof and free from contact with the structure at the maior part of the length thereof and serving as heat dissipating hns.

21. An automatic tool comprising a handle casing having incorporated therein an electric` rigid non-magnetic segments between the poles.

thereof, at the region of the plane of said starting roller.

23. An automatic tool comprising a handle casing having incorporated therein an electric motor including a rotor, a starting roller exposed at the exterior of the casing, said rotor having rigid non-magnetic segments between the poles thereof, at the region of the plane of said starting roller, and means loosely retaining said roller free from contact with said rotor while the latter is operating.

24. An automatic tool comprising an insulating handle casing having incorporated therein an electric motor including a rotor, a starting roller exposed through a port in. the casing narrower than said roller, said rotor having a carrying frame and including rigid non-magnetic segments intervening between the rotor poles in the plane of the roller, said parts correlated with the roller to block the latter from dropping inward, said port exerting a friction hold on said roller releasably to retain the latter out of engagement with the rotor.

25. A small electric motor comprising a field structure and an armature, an insulating casing enclosing the same having mounting means, a tool exposed exteriorly of said casing at one end thereof, said casing having a lead inlet at the other end thereof, a transmission within said casing connected from said armature to said tool, said casing including 'complementary partsv comprising a base and a cover, said parts having contacting rims extending obliquely of the casing with the narrowest part of the cover near the tool end thereof, and the wider part of the cover lat the lead inlet, said complementary casing parts having cooperating notches at their contacting rims to accommodate the inlet leads.

JOHN A. HANLEY.

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