Abstract: Carbon segments (7) of a planar commutator are moulded over contact members (5). Anchor means (8), integral with each carbon segment (7) have an interlocking part (11) engaging the rear surface (6) of the contact member (5) and fit into a first envelope (4) in the form of a recess of uniform transverse cross-section extending. rearwardly of the front end (3) of a moulded plastic base member (1). The contact members (5) are each attached to the base member (1) by means of locking portions (15) which project into second envelopes (14) having internal surfaces which grip the locking portions (15).

Abstract: The invention is a commutator for a high speed, high power DC traction motor having a rotor with a plurality of copper commutator bars having a V-shaped groove an axial end thereof, an electrically conductive retaining ring engaging the V-shaped grooves of the commutator bar, and means for exerting an axial force between the retaining ring and commutator bars to retain the latter against radial movement during high speed rotation of the rotor. Each of the commutator bars has an axial end face with a radially inwardly extending axial depression which joins an axially extending radial depression in a radially inner axial surface thereof adjacent the retaining ring. The retaining ring has an axial end face aligned with the axial end face of the commutator bars and an outwardly radially extending axial depression which joins an axially extending radial depression in a radially outer axial surface thereof adjacent the commutator bars.

Abstract: An electric rotating machine which withstands mechanical and thermal loads applied thereto is provided. Coil arms and coil trunks are provided in roughly parallel orientation to the end faces of an armature core only through insulating rings and insulating spacers. Metal brush is disposed on coil arms constituting a commutator, whereby the overall length of the armature can be remarkably shortened. The coil arms are strongly pressed against and fixed to the side of armature core by a collar, so that the resistance to the centrifugal force can be remarkably improved. A cylindrical ring is circumferentially fitted on the upper coil trunks to prevent radially outward movement of the coil arms due to the centrifugal force. The coil arms disposed in a non-commutator side are made radially shorter than those disposed in the commutator side. Thus, electric resistance of an armature coil is reduced and radial movement caused by the centrifugal force is reduced.

Abstract: It is an object of the present invention to provide a commutator in which the making of the plate solder can be omitted.A segment 21 is arranged at one end face of the axial direction of the boss 16 with an equal spacing and is fixed in an insulating manner. Each riser bar 4 is electrically connected to each segment. Each connecting plate 6 is continuously provided at each riser bar 4. A recess 5 formed at each connecting plate 6 is engaged at a projection 10 formed at the outer circumference of each ring solder 12. Each connecting plate 6 is arranged on the outer circumferential face of each segment, which is thereby electrically connected by a solder layer 13. A boss 16 surrounds each connecting plate 6 from the outside thereof in a state which makes each riser bar 4 project.

Abstract: A two-speed direct-current electric motor with a high-speed rotation switch activated by a vehicular sensed parameter signal. The motor includes a motor shaft supported by at least one bearing for rotation, at least two sets of windings supported by the shaft, a contactor arrangement supported by the shaft to electrically couple the windings in first and second configurations based upon a sensed parameter signal having at least a first and a second state, and a commutator arrangement coupled to the contactor arrangement to apply electrical energy to the windings. The motor rotates at a first speed when the windings are coupled in the first configuration and rotates at a second speed when the windings are coupled in the second configuration. The high-speed rotation switch is coupled directly to a sensed parameter signal and is integral to the electric motor.

Abstract: A starter which optimally maintains the characteristics of a spring which presses a brush and reduces its axial direction length. A compressed coil spring is arranged around an outer circumference of a plunger of a magnet switch and the length of the spring can be set as long as the radial direction length of the magnet switch. The spring effectively uses the space around the outer circumference of the magnet switch, so the axial direction length of the spring need not be added to the axial direction length of the starter.

Abstract: The unit has an electric motor (18) with a rotor (26) which is formed of an armature (40) and a plan commutator (32) and which is at least partially encased by a plastic casing (50, 62). The plan commutator (32) has a plurality of segments (52) which are separated from one another by slots (56) extending along the longitudinal axis (28) of the rotor (26) and which are connected with the armature (40). The casing (50) extends in the direction of the longitudinal axis (28) of the rotor (26) only so far that it does not cover the slots (56). Connection wires (60) for connecting with the armature (40) are arranged at the outer surfaces (54) of the segments (52). The casing (50) has portions (62) which extend in the direction of the longitudinal axis (28) of the rotor (26) over the base of the slots (56) until the connection wires (60) are covered by the portions (62).

Abstract: A roll commutator for electric motors has a plurality of bars adjacent to one another and produced from a continuous metal section. The metal section already has projections on one of its sides before the production of the bars, which projections serve as anchoring claws after rolling up the line portions produced from the metal section. Additional tools and processing steps are not needed since it is not necessary to process the claws when manufacturing the roll commutator.

Abstract: A flat commutator includes a circular arrangement of sectorial carbon segments made of conductive carbon providing commutating surface of the commutator, metallic segments attached to respective of the carbon segments, and a hub body of synthetic resin. The metallic segments have fixing members encroaching into inner and outer peripheral surfaces of the carbon segments, thereby fixing the carbon segments to the metallic segments. The hub body encloses at least fixed portions of the inner and outer peripheral surfaces of the carbon segments that engage with the fixing members of the metallic segments.

Abstract: Each of the two brush leafs of an electric motor comprises a first resiliently flexible conductive section, attached to a terminal, and an additional resiliently flexible section extending an acute angle to the first section. The first and second ends of the first section are disposed on opposite sides of a contact portion of the additional section which engages a commutator forming part of the motor. It is therefore possible to increase the length of the first section to thereby provide robust brush leafs which are nevertheless capable of flexing sufficiently to accommodate discrepancies in the mounting of the brush leaf means and in concentricity of the commutator.

Abstract: An improved commutator anchoring system and methods of manufacturing such a system are disclosed. The system includes a wound fiberglass or other ring embedded in the internal core of the commutator to reinforce the resulting structure and enhance its thermal and mechanical stability. The reinforcing ring also functions as a form about which various anchors can be patterned, increasing their uniformity over free-form designs.

Abstract: A binded carbon brush includes a brush main portion formed mainly of carbon, and an electric conductor formed by a material, such as a copper powder, having an electric resistivity lower than that of the brush main portion and extending along a main current direction of the brush. In the cross section of the brush perpendicular to the main current direction, the diameter or the vertical and horizontal sizes of the conductor is so set as to be smaller than both the vertical and horizontal sizes of the brush main portion.

Abstract: A varistor disk assembly for mounting to a commutator base comprising a non-conductive retaining ring, a conductive member, and a varistor disk interposed between the commutator base and the distal end of the retaining ring. The retaining ring has an axial bore therethrough providing a friction fit with the motor shaft on which the commutator is mounted. A tolerance absorbing member can be interposed between the varistor disk and the retaining ring. The conductive member conducts current through its thickness from the commutator base to the varistor disk, but does not conduct current between adjacent commutator segments. To orient the varistor disk to the commutator, the proximal end of the retaining ring can have at least one planar side formed in its periphery for alignment with one of the commutator segments, while the distal end of the retaining ring also has formed in its periphery a planar side, and the varistor disk is provided with a complementary planar side in its inner diameter.

Abstract: A miniature motor including a case formed into a bottomed hollow tubular shape having a permanent magnet, an end cap fitted to an open end of the case, and a rotor having an armature iron core and a commutator. A sleeve made of a resin material and formed into a hollow cylindrical shape is fitted coaxially with the core constituting the armature iron core and the commutator, with a gap provided on at least one end face of the sleeve; a plurality of grooves facing at least an end face of the sleeve are provided on the iron core and the commutator at certain spacings in the circumferential direction; a projection for press-fitting to any one of the grooves is provided each on both end faces of the sleeve integrally with the sleeve; and a groove extending along the axial line of the sleeve is provided in the middle part of these projections.

Abstract: A miniature motor in which stators are mounted in an interior of a casing, and a preassembled commutator is provided on a rotor rotatably disposed to face the stators. The commutator has a sleeve body having a cylindrical portion provided with a flanged portion and a plurality of recesses, directed outwardly, in a side wall of the flanged portion, with the sleeve body being made of insulating material and mounted on a rotary shaft of the rotor. The commutator also has a plurality of conductive commutator pieces each having a body portion formed in an arcuate shape and mounted on an outer circumferential surface of the cylindrical portion, a terminal portion and at least one retainer portion, with each of the terminal portion and the retainer portion being received in the recesses.

Abstract: A single speed, two pole permanent magnet motor has compact brush card assembly mounted within the volume form by a plurality of ring shaped laminations forming the armature to allow the height of the motor to much less than a standard motor. In addition, there is shown a two speed, four pole permanent magnet motor having a height much less than a standard two speed motor. In each motor there are electrically connected to the supply lines a choke means and across each supply line is a capacitor for suppressing radio frequency interference.

Abstract: Core-type brushes used in dynamoelectric machines, such as electric motors, have cores which are arranged in substantially parallel planes extending at an angle with respect to the direction at which the brushes move toward the commutator as the brushes wear. As the brushes wear, the position of the cores relative to the outer surface of the commutator changes, preventing constant positioning of the cores relative to the commutator surface and reducing or preventing non-uniform commutator wear which occurs when the cores maintain a fixed position with respect to the commutator surface as the brushes wear. This arrangement of the cores eliminates the need to resurface the commutator at brush change, reduces the time required to properly seat the brushes to the commutator and increases commutator and brush life.

Abstract: A binded carbon brush includes a brush main portion formed mainly of carbon, and an electric conductor formed by a material, such as a copper powder, having an electric resistivity lower than that of the brush main portion and extending along a main current direction of the brush. In the cross section of the brush perpendicular to the main current direction, the diameter or the vertical and horizontal sizes of the conductor is so set as to be smaller than both the vertical and horizontal sizes of the brush main portion.

Abstract: A planar carbon segment commutator has contact members, with terminals, attached to the front surface of an insulating base member by means of overmoulded carbon segments formed integral with anchor pieces disposed within apertures in the base member. Each aperture has a second part disposed rearwardly of a first part having a smaller cross-section than the second part and the anchor piece disposed within the aperture has a locking portion which fills the second part of the aperture to thereby resist withdrawal of the anchor piece from the aperture. The contact members are embedded in the carbon segments and have holes filled with carbon segment material to increase interlocking between the contact members and the segments.

Abstract: Carbon commutator segments are secured to a base member by means of integral anchor pieces disposed within axially extending, cruciform-section slots formed in the outer cylindrical surface of an insulating base member. Elongate contact members having lateral edges seated in lateral parts of the slots are embedded in the anchor pieces and are each provided, at one end, with a terminal for connection to an armature winding lead wire. The carbon segments and the integral anchor pieces are formed by enclosing the base member, together with assembled contact members, in a mould and then injecting a mouldable mixture of carbon powder and carrier material into space between the mould and the assembly. When the injection moulded layer has solidified, an annular-section outer portion of this injection moulded layer is divided into segments by means of axially-extending radial cuts.

Abstract: An assembled commutator has an insulating commutator body having a cylindrical outer surface, radially extending axial support means and an axial extension on the opposite side of the axial support means to the cylindrical outer surface. Three commutator segments each have an arcuate brush-contacting portion seated on the cylindrical outer surface of the commutator body, an axial terminal stem extending through a passage formed in the axial support means, and a radial terminal stem seated in one of three equiangularly extending radial grooves formed in the axial support means. An apertured insulating clamping member which is press-fitted on a first part of the axial extension clamps an apertured varistor which is seated on a second part of the axial extension in electrically conductive engagement with the radial terminal stems.

Abstract: An electric motor has a tubular housing part, permanent magnets arranged inside the housing part, a rotatable motor armature with a collector having a running surface, a plurality of sliding brushes having sliding surfaces abutting against the running surface of the collector, and an element for loading the motor armature in direction of its rotary axis toward the sliding brushes so that the running surface of the collector which in its projection is formed as an annular surface abuts against the sliding surfaces of the sliding brushes.

Abstract: A direct current machine, such as a motor or a dynamo, has a commutator. The commutator has a contact surface which includes a generally cylindrical contact surface. The commutator is rotatable around an axis. A brush assembly of the direct current machine includes at least two brushes. Each brush has a distal surfaces which is engagable to a contact surface of the commutator. A brush holder movably holds the brushes toward the commutator. A clearance is defined between the brush and the brush holder. Each spring urges the corresponding brush against the contact surface of the commutator. Further, the spring urges the brush to be off-set toward the front side of a rotational direction of the commutator, within the brush holder.

Abstract: A dynamo assembly comprising a stator assembly and rotor assembly as shown. The preferred rotor assembly comprises two end caps, a single wire strand, a collector ring assembly and a plurality of laminants. The two end caps are preferably identical to one another, and oriented with the wire wrapped in two coils therearound. The laminants are supported between the two end caps, in a skewed manner. An advantageous arrangement for engagement between the collector ring assembly and wire held on the end caps is provided. A unique method of molding the collector ring assembly without internal inserts is also disclosed.

Abstract: A commutator has such a construction that a flange having an outside diameter larger than the outside diameter of a cylindrical body is provided integrally with the cylindrical body in the vicinity of one end of the cylindrical body; guide grooves formed in a circular arc shape in cross section are provided on the flange at the boundary of the flange to the cylindrical body; engaging pieces passing through the guide grooves are provided on one end of a commutator segment; and engaging pieces are caused to deform plastically to fixedly fit the engaging pieces to the flange.

Abstract: A commutator has a central support supporting a plurality of conductive segments separated by a plurality of insulative segments. In addition to providing an insulative function between the conductive segments, the dielectric constant, the area, and the thickness of the insulative segments are chosen so that they provide a capacitive effect, which capacitive effect suppresses current peaks during operation of the commutator. Preferably, the dielectric constant is greater than 10. The central support may include a metal shaft and an insulating ring, which insulating ring is preferably of material with a lower dielectric constant thereby to suppress-shorting between the shaft and the conductive segments. It is particularly advantageous if the conductive and insulative segments are of ceramics material since this provides good wear resistance. In further alternatives, capacitors are formed between the conductive segments by rings or other bodies of insulative materials of a suitably high dielectric constant.

Abstract: A commutator employs superconducting switches to commutate currents in the field stator of a dc machine. The switches couple the machine's stator windings to a DC link. The switches are exposed to magnetic fields of alternating strengths, turning on and off in a sequence that maintains a constant torque angle between the stator's mmf vector and the flux vector of the machine's rotor or that rectifies a current induced into the stator by the machine's rotor.

Abstract: A small d.c. motor which includes a commutator including a plurality of commutator segments, a resilient metal brush kept in contact with the commutator segments, the commutator segments being coated with a layer of a lubricating fluid.

Abstract: Dynamoelectric machines are disclosed that are characterized by lengthened ground potential leakage current paths, desirable mechanical conformations, mechanical integrity when subjected to expected centrifugal forces, and ease of manufacture. One process involves establishing an extended or elongated path for commutator leakage currents with a path extending structure, establishing a cantilevered insulation skirt about the in-board or armature coil end of a commutator, and securely fastening such skirt to the commutator. The material utilized in making the skirt is one: that has electrical properties that permit it to withstand leakage currents without tracking; that for practical purposes is non-burnable, so as to resist flashovers or sparking; and that has the ability to withstand elevated temperatures that are encountered within dynamoelectric machine.

Abstract: Four side walls surrounding a recess in the center of a commutator segment are extended to overhang toward the recess comprising claws and cut-and-raised protrusions, thereby ensuring that the commutator segment is securely engaged with the resin filled in the recess against any of the triaxial stresses due to centrifugal force, rotating force, and tensile force. The volume of cutting in the insulating resin at undercut portions is reduced. The internal and cut-and-raised protrusions are molded by cylindrically bending oriented progressive dies made of plate material.

Abstract: An assembled commutator comprises a cylindrical base and a plurality of segments glued on the base. To secure the segments on the base a loop, formed by stamping out a tang, is urged over a boss on the end of the base. A tongue is inserted in a recess at the other end of the base, as is known in the art. The loop pulls the segment down onto the base and also prevents circumferential movement.

Abstract: A brush holder plate assembly comprising a brush holder plate fabricated from electrically insulating thermoplastic material and having a plurality of sets of spaced-apart, parallel, raised guiding and support rails integrally formed on one surface of the plate. The plate further has a centrally formed aperture of sufficient cross sectional dimension to be slipped over the commutator of an electric machine after complete assembly of all the parts of the machine. The sets of spaced-apart, parallel, raised guiding and support rails project radially outward away from the centrally formed aperture like the spokes of a wheel. A plurality of snap-in-place, brush holder cartridges are removably secured by slide catches to the respective sets of spaced-apart parallel raised guiding and support rails for physically supporting commutating brushes in an array surrounding the commutator of the electric machine with one exposed end of each brush in physical and electrical contact with the commutator.

Abstract: A DC motor is provided with a brush arrangement in which two parts of the brushes are arranged around the peripheral surface of a commutator so that each line across the opposite brushes with respect to the central axis of the commutator forms an angle, thus the space between the positive and negative brushes is sufficient to mount components thereon. Each width of the brushes is determined by the number of conducting segments in contact with the brushes of the same polarity, affording sufficient current to flow in the brushes.

Abstract: The commutator comprises a commutator base and a plurality of commutator segments. The base is in two parts. One part is a pre-formed base part and the other part is moulded to the base part after the segments have been located on the base part to firmly secure the segments thereto. The commutator is of the barrel-type and the base part is tubular and has castellated ends. The segments have apertured lugs which engage with the castellated ends of the base part and extend inside opposite ends of the base part to locate the segments relative to the base part. The other part of the base forms a sleeve inside the pre-formed base part and firmly secures the lugs and hence the segments to the pre-formed base part.

Abstract: A commutator includes a plurality of commutator segments disposed in circular configuration and equally spaced from each other in a circumferential direction. Each commutator segment has a contact portion for contact with a brush and an anchoring portion which forms a recess in cooperation with the contact portion. A ball made of insulation material is disposed between each two adjacent commutator segments in such a manner that ball is partly engaged with both recesses of adjacent commutator segments. A cylindrical hub made of synthetic resin is molded with the anchoring portions of the commutator segments and the balls.

Abstract: A rotor for miniature motors having a shaft serving as a rotating shaft, a commutator having commutator segments mounted on a commutator proper fixedly fitted to the shaft, a rotor core fixedly fitted to the shaft and having rotor windings wound thereon, a plurality of positioning bosses formed in such a manner as to protrude toward the side of the rotor core on the commutator proper, and a positioning groove, formed on the side surface of the rotor core, into which the positioning bosses are inserted; the commutator being fixedly fitted by press-fitting the positioning bosses into the positioning groove, characterized in thatpositioning grooves which are formed on the side surface of the rotor core, and smaller in number than the number of the positioning bosses,a long positioning boss, among a plurality of the positioning bosses, having a sufficient length to be press-fitted into the positioning grooves,other short positioning bosses having a length at least equal to the thickness of an insulating core fitt

Abstract: An electrical commutator of the type which is formed by bending a strip of conducting material having outwardly extending and spaced apart tangs along one side into a cylindrical sleeve so that the tangs extend outwardly from one axial end of the sleeve. The strip includes at least one, and preferably two, recessed portions in the space between adjacent tangs so that these recessed portions protrude radially inwardly once the strip is formed into the cylindrical sleeve. Anchoring portions on the inner surface of the sleeve, as well as the recessed portions, are then encapsulated in an insulating material, such as phenolic resin. Thereafter, axially extending and circumferentially spaced slots are machined in the outer periphery of the sleeve and these slots extend to a midpoint in the space between adjacent tangs.

Abstract: The trailing edge of a carbon brush for commutating electric machines has a notch flanked by an ear on either side. The brush can include one or more wafers. The angular thickness of the trailing brush wafer at the notch is such that the brush does not touch more than n commutator contacts at a time. However, the brush wafer is thick enough at the ears to touch n+1commutator contacts at a time. The relatively high resistance of the ears improves commutation.

Abstract: A commutator arrangement includes a commutator member rotatably mounted on a support and including a plurality of circumferentially adjacent contact pads that are mechanically connected with one another and electrically separated from each other by respective intervening gaps, and a number of commutator brushes that are mounted on the support for only substantially radial movements toward and away from the commutator member and are biased toward the latter to establish contact between their respective contact surfaces and those of the pads. The lateral edges bounding one kind of these contact surfaces circumferentially deviate from those delimiting the other contact surface kind over at least a part of their courses such that different portions of such lateral edges are juxtaposed with their counterparts at different times during the relative rotation of the commutator member.

Abstract: A collector segment comprising a connector lug having a contact surface, to which a wire winding loop of electric machine rotor is to be welded, and extending in a direction radially outward relative to a rotational axis of the electric machine rotor, and positioning surfaces which define a position of the wire winding loop in an extension direction of the connecting lug.

Abstract: An engine starter includes a motor having a tubular armature rotation shaft, and a rotation output shaft arranged on one axial end side of the motor coaxially therewith to be axially slidably supported. A clutch mechanism is included for transmitting torque from the armature rotation shaft to a rotation output shaft and an electromagnetic switch which has a shifting member to push the aforementioned rotation output shaft by an electromagnetic force in the axial direction to slidably move it. The switch also brings movable contacts in touch with fixed contacts to supply power to the aforementioned motor. A rear part of the rotation output shaft and the front part of the shifting member are inserted into the armature rotation shaft tube from opposite directions. The shifting member of the electromagnetic switch, the armature rotation shaft and the rotation output shaft are all coaxially arranged to reduce the length of the starter.

Abstract: An assembled commutator comprises a base carrying segments. Each segment 16 has a connector portion with a wall portion having an aperture to locate the connector portion about a projection on a collar formed on the base, to locate the segment. The connector portions each have a U-shaped portion having a radially inner arm which rests on the collar and is wider than the radially outer arm, to form wings which can be used when hot forging a tang to an armature coil wire, with a first electrode bearing down on the arm and a second electrode bearing down on the wings.

Abstract: An assembled commutator has a thermoplastics base supporting segments. A ring 15 of high temperature, non-softening material, such as phenolic, fits on a shelf on the base beneath tangs which are for hot connection, particularly forging, to an armature wire. The ring is held in place by fingers on the tangs.

Abstract: An improved commutator for an electric motor and a method of making the same wherein the outer surface of a commutator sleeve molded of a synthetic resin is coated with an insulating coating layer of an electrically insulating coating material. The molded commutator sleeve thus coated is protected from oxidative degradation and cracking which would otherwise result in removal of a commutator bar and insulation failure.

Abstract: An epoxide resin moulding composition, comprising(a) a phenol or cresol novolak epoxide resin,(b) dicyandiamide as a hardener,(c) an accelerator suitable for hardening with dicyandiamide,(d) 20 to 70% by weight of calcium carbonate and(e) 10 to 60% by weight of glass fibres, the quantity of components (d) and (e) together not exceeding 80% by weight, relative to the total weight of the epoxide resin moulding composition,is suitable with advantage for the manufacture of commutators and slipring bodies.

Abstract: An electrical brush assembly for use with a d.c. dynamoelectric machine commutator 44 having a substantially cylindrical commutator contact surface 46 comprising an electrical brush element 48 having a sliding contact surface 50 engageable with the contact surface of the commutator. The brush element is slidably supported by a brush holder 54, and is urged against the contact surface of the commutator by a spring 58. The sliding contact surface of the brush element is a concave cylindrical surface having a central axis 62 substantially parallel to the central axis 45 of the commutator contact surface, and has a radius R2 about 1.2 to 2.5 times larger than the radius R1 of the commutator contact surface.

Abstract: A rotor in an electric motor comprises a shaft having a commutator and armature thereon. To prevent relative movement between the armature lamination stack and the commutator, a structural coating such as epoxy resin coats the shaft between the commutator and stack. The commutator base has a coaxial recess in the adjacent end. The base is urged towards the stack while the coating is still fluid to gather up the coating so that it is of substantial thickness on the shaft, at least partially filling the recess and a radial slot in the recess wall.

Abstract: An armature for a motor comprises a winding and a commutator. Each commutator segment has a brush contacting portion and an integral terminal portion connected to a connector portion of the winding. A commutator base includes housings which receive the terminal portions and which have slots for positioning the connector portions of the winding relative to each housing. Each terminal portion has a slot which straddles and grips the connector portion positioned relative to a respective housing. At least one and preferably all terminal portions have two slots arranged side-by-side so that the two side-by-side slots of one of the terminal portions can straddle and grip the lead end and tail end of the winding, respectively.

Abstract: An assembled commutator comprises a base carrying segments. Each segment has a tang with laterally extending arms which are folded into recesses in a collar supporting the tangs. An edge 30 of each arm abuts a wall of a recess to prevent axial movement of the segments.

Abstract: The armature of an engine starter direct current (d.c.) motor comprises a rotary shaft, an aluminum armature coil. The commutator a commutator disposed on the rotary shaft and has a plurality of copper commutator segments each including a main body portion having a sliding contact surface and a connecting portion having an aluminum connecting surface. The aluminum armature coil is electrically and mechanically connected to each of the aluminum connecting surfaces of the commutator segments to form an electrical and mechanical connection therebetween. The electrical and mechanical connection between the aluminum connecting surface and the armature coil is coated with an electrically insulating resin.