Abstract: The present invention refers to a liftable brush holder system (9) able to operate as fixed, comprising a motor (1) that drives a speed reducer (2) that drives a shaft (3) that moves a disc with eccentric slot (4), wherein the disk with eccentric slot (4) closes the short-circuit bushing (6) and independently moves the sides (9r, 9l) of the brush holder (9). The present invention further refers to a rotating electric machine equipped with a system according to the invention.

Abstract: Disclosed is an excitation device which includes a brush holder base. The brush holder base is provided with a plug. The plug is provided with a brush holder shaft. The front end of the brush holder shaft is provided with a brush box. A horizontal taper dovetail groove is formed in the brush holder base. A horizontal taper dovetail lug boss is disposed on the plug. The dovetail groove is matched with the dovetail lug boss. The present invention solves the problem of potential safety hazard in locking, and ensures safe and smooth operation of a unit.

Abstract: An electric motor arrangement, comprising a brush holder housing which has a plurality of brush elements which are coupled with a respective spring element, the spring element being configured to press the respectively associated brush element against a commutator of the electric motor arrangement, and the spring element having a first portion with a barbed hook for hooking or catching into a recess in the brush holder housing.

Abstract: Systems, methods, and apparatus associated for lifting brushes and shorting slip rings are provided. One embodiment may include a shaft in operable communication with a WRIM rotor; multiple slip rings positioned radially around the shaft and in electrical communication with rotor windings of the WRIM; multiple brushes adapted for selective contact with a respective one of the plurality of slip rings. In addition, the system may include multiple selectively activating electrical contacts in electrical communication with respective terminals of the rotor windings of the WRIM; and an actuating mechanism in operable communication with the brushes and the electrical contacts. When the actuating mechanism is actuated, the electrical contacts create electrical shorts between the slip rings and the rotor windings of the WRIM and the plurality of brushes are lifted from contacting the plurality of slip rings.

Abstract: Systems, methods, and apparatus associated for lifting brushes and shorting slip rings are provided. One embodiment may include an actuating mechanism in operable communication with multiple brushes and a plurality of electrical contacts. Each of the brushes may be adapted for selective contact with a respective slip ring of an induction motor. The electrical contacts may be in electrical communication with respective terminals of rotor windings of the induction motor. When the actuating mechanism is actuated, at least a portion of the electrical contacts create electrical shorts between at least a portion of the slip rings and the rotor windings of the induction motor. When the actuating mechanism is actuated, at least a portion of the brushes are lifted from contacting the plurality of slip rings.

Abstract: Systems, methods, and apparatus associated for lifting brushes and shorting slip rings are provided. One embodiment may include an actuating mechanism in operable communication with multiple brushes and a plurality of electrical contacts. Each of the brushes may be adapted for selective contact with a respective slip ring of an induction motor. The electrical contacts may be in electrical communication with respective terminals of rotor windings of the induction motor. When the actuating mechanism is actuated, at least a portion of the electrical contacts create electrical shorts between at least a portion of the slip rings and the rotor windings of the induction motor. When the actuating mechanism is actuated, at least a portion of the brushes are lifted from contacting the plurality of slip rings.

Abstract: An apparatus for holding a brush in contact with a moving conductive surface, the apparatus includes: a rotatable member disposed adjacent to the brush; and a spring coupled to the brush and to the member and configured to bias the brush towards the moving conductive surface; wherein the rotatable member in a first position makes contact with the brush to secure the brush from movement and in a second position releases the brush from the contact to allow the spring to hold the brush in contact with the moving conductive surface.

Abstract: A brush holder assembly for a dynamo-electric machine includes a brush fixture snap-fittingly secured to a shielding fixture. A brush member is moveably mounted within the brush fixture and includes a recessed region, and a shunt member. The shunt member includes a first end operatively connected to the brush member at the recessed region that extends through an intermediate region to a second end. A constant force spring is operatively connected between the second end section of the brush and the brush fixture. The brush holder assembly also includes a shunt retainer mounted in the brush fixture abutting the brush member. The shunt retainer includes a first leg portion, a second leg portion and a base portion. The shunt retainer is configured to maintain proper alignment of the constant force spring and prevent entanglement of the shunt member.

Abstract: An apparatus for holding a brush in contact with a moving conductive surface, the apparatus includes: a rotatable member disposed adjacent to the brush; and a spring coupled to the brush and to the member and configured to bias the brush towards the moving conductive surface; wherein the rotatable member in a first position makes contact with the brush to secure the brush from movement and in a second position releases the brush from the contact to allow the spring to hold the brush in contact with the moving conductive surface.

Abstract: A power tool has an electric motor that includes a commutator, with which at least one commutator brush is acted upon with spring force via at least one commutator spring in the direction of a non-rotatable collector of the commutator. At least one auxiliary tool for adjusting the commutator spring is located on a component of the power tool.

Abstract: The invention relates to an electric motor (10) and to a method for producing said electric motor, especially for adjusting mobile parts in a motor vehicle. Said electric motor comprises a collector (36), arranged on an armature (38) and electrically contacted via hammer brushes (12). The armature (38) is surrounded by a lower housing part (32) and an upper housing part (34) which can be assembled in a radial direction (50) in relation to the armature (38). The hammer brushes (12) comprise one fastening element (26) each which engages directly in a seat (30) of the lower or upper housing part (32, 34).

Abstract: A brush holder includes a base member and a retaining member mounted on the base member. The retaining member includes a first brush retaining portion and a first coil retaining portion. A first choke coil is electrically connected to a first brush. The first choke coil includes a first coil terminal extending to the outside of the first coil retaining portion. The base member includes a connector portion, a first conductive member, and a first coil terminal support portion. The first conductive member extends from the connector portion and is electrically connected to the first coil terminal at a first connecting portion. The first coil terminal support portion supports the first coil terminal between the first connecting portion and the first coil retaining portion.

Abstract: Devices and methods of use for brush holder assemblies are disclosed. Brush holder assemblies including a mounting block and a brush holder are disclosed. Also illustrated is a brush holder assembly including a first portion in sliding engagement with a second portion. In some embodiments the brush holder includes a channel, such that at least a portion of the mounting block is disposed within the channel of the brush holder.

Abstract: A manufacturing method for a brush that can reduce contact surface area between a commutator and the brush, thereby reducing frictional noise, is provided. Specifically, a method to manufacture a brush, which provides one surface with contact surfaces that make sliding contact with the commutator, involves a step to mold a molded body and a step to cut the molded body. In the molding process, carbon powder containing copper powder is sintered to form a molded body having a groove on the top surface along the direction of the axis of rotation of the commutator, and curved surface margins in the margins of the top surface in the direction of the axis of rotation. In the cutting step, the central part of the top surface of the molded body is cut by a grinding stone along the cutting direction to form contact surfaces between the margins of the top surface.

Abstract: A brush assembly for an alternator includes a brush, a brush holder holing the brush, and a slip ring cover for covering a slip ring on a rotary shaft of the alternator. The brush holder and the slip ring cover respectively have first and second through-holes that can be brought into alignment with each other by application of a mechanical force. The alignment allows a retainer to be placed through both the first and second through-holes to retain the brush in the brush holder against the spring force of a spring, thereby permitting installation of the brush assembly onto the rotary shaft to be carried out without interference between the brush and the slip ring. The first and second through-holes are brought out of the alignment by removal of the mechanical force and the retainer, thereby blocking foreign matters from entering inside through both the first and second through-holes.

Abstract: Brush holder assemblies are detailed. The assemblies permit on-line brush replacement and are interchangeable with devices currently provided by original equipment manufacturers. As well, they allow use of brushes longer than those employed in existing on-line replacement assemblies.

Abstract: Devices and methods of use for brush holder assemblies are disclosed. Brush holder assemblies including a mounting block and a brush holder are disclosed. Also illustrated is a brush holder assembly including a first portion in sliding engagement with a second portion. In some embodiments the brush holder includes a channel, such that at least a portion of the mounting block is disposed within the channel of the brush holder.

Abstract: Devices and methods of use for brush holder assemblies are disclosed. Brush holder assemblies including a mounting block and a brush holder are disclosed. Also illustrated is a brush holder assembly including a first portion in sliding engagement with a second portion. In some embodiments the brush holder includes a channel, such that at least a portion of the mounting block is disposed within the channel of the brush holder.

Abstract: Brush holder assemblies are detailed. The assemblies permit on-line brush replacement and are interchangeable with devices currently provided by original equipment manufacturers. As well, they allow use of brushes longer than those employed in existing on-line replacement assemblies.

Abstract: Brush holder assemblies are detailed. The assemblies permit on-line brush replacement and are interchangeable with devices currently provided by original equipment manufacturers. As well, they allow use of brushes longer than those employed in existing on-line replacement assemblies.

Abstract: A brush holder assembly that cannot be assembled incorrectly includes a brush inserted into a brush holder, a block attached to the top of the brush, a spring engaging the block that applies radial pressure to the block and brush, and a hook pin that holds the spring onto the block. The block includes a semicircular indentation that cradles a coiled portion of the spring and includes a slotted hole for receiving a portion of the hook pin as the block is glued to the top of the brush. The hook pin is a loop terminating at a first end that is a straight pin and terminating at a second end that is a hook-shaped loop in which the straight pin end is inserted. Alternatively, a U-shaped spool assembly can be used to engage the coiled portion of the spring to lock it in the indentation in the block.

Abstract: Devices and methods of use for brush holders are disclosed. A brush holder assembly including a brush catch and a brush release is disclosed. Also illustrated is a brush holder assembly including a first portion in sliding engagement with a second portion. Sliding engagement of the first portion with the second portion may selectively engage and/or disengage a brush catch with a brush. In some embodiments the brush catch is disengaged from the brush when the brush holder is in a locked position and is engaged with the brush when the brush holder is in an unlocked position. Methods and devices for selectively placing a brush holder in a locked or unlocked position are also disclosed.

Abstract: Devices and methods of use for brush holders are disclosed. A brush holder assembly including a brush catch and a brush release is disclosed. Also illustrated is a brush holder assembly including a first portion in sliding engagement with a second portion. Sliding engagement of the first portion with the second portion may selectively engage and/or disengage a brush catch with a brush. In some embodiments the brush catch is disengaged from the brush when the brush holder is in a locked position and is engaged with the brush when the brush holder is in an unlocked position. Methods and devices for selectively placing a brush holder in a locked or unlocked position are also disclosed.

Abstract: Devices and methods of use for brush holders are disclosed. A brush holder including an over-center locking device is disclosed. Also illustrated are methods and devices for maintaining brush pressure against a moving conductive surface using a spring without a back plate. Methods and devices for routing current from a brush to an output location without conducting through a brush box are shown. A system for ready removal and replacement of brushes, contacts and springs is disclosed. Also included are mechanisms and methods for preventing a brush from falling downward or out during removal of the brush. Methods and devices for cutting off current flow without creating arcing or shorting between a brush and collector ring or other moving conductive surface are presented as well.

Abstract: A brush support jig for use during mounting of a brush assembly on a rotary electric machine having slip rings, to restrain the brushes against contact with the slip rings during the mounting operation, is of pin configuration having a linear portion formed of a linear portion made of a metal such as steel and a coating portion made of a material such as synthetic resin, having a lower degree of hardness than the slip rings, which covers the linear portion and thereby prevents damage to the slip rings in the event that that brush support jig comes into contact with the slip rings during the mounting operation.

Abstract: A brush box assembly for use in an electric motor and an electric motor having a brush biasing mechanism that also retains the brushes to allow installation of a sliding electrical contact assembly is described. The brush box assembly has a plurality of brush holders each with a brush retention slot, a plurality of brushes each adapted to fit in the brush retention slots, the brushes having a contact face and a non-contact face, and a plurality of torsion springs each having a spring loading arm and a spring retention arm, each spring loading arm contacting one brush on the non-contact face and adapted to bias the brush against a sliding electrical contact after installation of the sliding electrical contact assembly, each spring retention arm adapted to contact one brush on the front side and retain the brush in the brush retention slot during installation of the sliding electrical contact assembly. A method of manufacture of a device having brushes with the biasing and retention mechanism is also disclosed.

Abstract: A motor has a motor housing, a brush mechanism having a substrate, and a pair of electricity supply lines extending from the substrate. A first support portion, a second support portion and a third support portion are located about the central axis of the substrate. The substrate is supported by the housing with vibration absorbing members, each of which provided at one of the first to third support portions. The first support portion is located between the electricity supply lines. The second and third support portions are symmetrically located on both sides of a straight line that extends through the first support portion and the axis of the substrate. Therefore, the brush mechanism is prevented from being inclined, and vibration of the brush mechanism is effectively absorbed.

Abstract: A multi-brush cage assembly for a subfractional horsepower electric motor has two brushes 22, 23 received in separate chambers 24, 25 of the cage and urged by springs 26, 27 towards a commutator 15 of the motor. An L-shaped changeover lever 30 is located on a pivot 33 between the chambers and keeps one brush 23 retracted until the other brush 22 has worn out.

Abstract: A brush box assembly for use in an electric motor and an electric motor having a brush biasing mechanism that also retains the brushes to allow installation of a sliding electrical contact assembly is described. The brush box assembly has a plurality of brush holders each with a brush retention slot, a plurality of brushes each adapted to fit in the brush retention slots, the brushes having a contact face and a non-contact face, and a plurality of torsion springs each having a spring loading arm and a spring retention arm, each spring loading arm contacting one brush on the non-contact face and adapted to bias the brush against a sliding electrical contact after installation of the sliding electrical contact assembly, each spring retention arm adapted to contact one brush on the front side and retain the brush in the brush retention slot during installation of the sliding electrical contact assembly. A method of manufacture of a device having brushes with the biasing and retention mechanism is also disclosed.

Abstract: A brush holder (100) for carrying a brush (102) and for providing adjustment of the brush relative to the commutator (104) of a dynamoelectric machine (105). The brush holder provides for adjustment of the gap (110) between the commutator and the brush, and for adjustment of the brush in the axial direction along the commutator. The brush holder also locks the brush at the desired position for operation in the dynamoelectric machine.

Abstract: An external connection structure for an electric motor in which basic members are able to be commonly used in an electric fan motor for which either a lead wire or a direct coupler are prepared as an external connection member. Tip end portions of first and third conductor plates and the tip ends of the second and fourth conductor plates are caused to extend between respective brushes which are adjacent to each other in the circumferential direction of the holder stay, and the tip end portions can be made visible through through-holes provided at the body portion of the end cover.

Abstract: A brush holding apparatus for at least one carbon brush includes a support plate with at least one brush guide, a spring element constructed and arranged for urging a carbon brush having a longitudinal axis mounted in the brush guide in a direction towards a commutator or slip ring, and a retaining element constructed and arranged for retracting the carbon brush against a force exerted by the spring element or for releasing the brush. The retaining element is slidably supported by the base plate in a direction perpendicular to the longitudinal axis of a carbon brush mounted in the brush guide.

Abstract: It is to provide a brush-equipped motor enabled to be used for a long time without performing operations and without interruption even when the brush wears out. When a rotor is caused to perform a turning operation, cam projections similarly start to perform a turning operation. Then, an abutting part, at which each of the cam projections contacts with a spring piece part of a corresponding one of the first brushes, gradually moves to an end of the first brush. Thus, the spring piece part of each of the first brushes is gradually and elastically deformed in a direction in which brush bodies come away from a commutator. When the turning operation continues still more, an end of each of the second brushes comes off a corresponding one of the cam projections, so that the brush bodies thereof contact with the surface of the commutator.

Abstract: A miniature electric motor comprises a housing, a cover plate fitted in an opening portion of the housing, a stator fixed to an inner circumferential surface of the housing, a rotor supported rotatably to one and the other bearing portions mounted on the housing and the cover plate, respectively, the rotor being disposed in the housing, and a brush holder holding brushes slidingly engaging with a commutator of the rotor, the brush holder being mounted on the cover plate. A first projection is formed in the vicinity of a center of the brush holder, and the first projection is forcibly pressed at a predetermined pressure against the cover plate. According to the present invention, without using any vibration proof elastic member, it is possible to reduce a noise of the miniature motor and keep the motor quiet. This motor is used for driving an air conditioner of an automobile, or the like.

Abstract: A manual electric machine tool (10), having an electric motor (16), whose commutator (20) can be connected to a voltage source via at least one carbon brush (22) pressed against the commutator (20) by spring means (26), wherein the carbon brush (22) includes a head part (34) and a foot part (35) and has an electric pigtail lead (40) and a turn-off device (38), which at a certain wear of the foot part (35) of the carbon brush (22) automatically disconnects the electrical connection between the voltage source and the commutator (20), gains a longer useful life between service intervals for changing carbon brushes in that the carbon brush (22) is lengthened in the region of its head part (34) by a single axial continuation (36), which serves as a socket for the turn-off device (38) and is dimensioned such that the spring (26) enter flush and integrally into the outer contour of the carbon brush (22) between the outermost outer edges of the head part (34) and of the continuation (36), inside these outer edges.

Abstract: A positive-side brush and a negative-side brush are held by a motor frame and contact the sliding-contact surface of a commutator. A displacement member switches the state of one brush connected with a starting power source from an ON state in which the brush contacts the commutator to an OFF state in which the brush is separated from the commutator or vice versa. The displacement member comprises a slide rail holding the brush movably, a return spring which returns the brush to the OFF state, and a push button which is manually operated to press the brush against the commutator so as to turn on the brush. A starting electric circuit can be opened or closed by operating the push button.

Abstract: In a starter, an armature is covered with a cylindrical yoke. A rear end opening portion of the yoke is spread perpendicularly outward so as to form a flange. A disc portion having a larger outer circumferential portion than the outer diameter of the cylindrical portion of the yoke is formed. A spigot portion provided in the outer circumference of the disc portion is fitted to a spigot portion provided in the frontmost of a cylindrical portion of a metal rear bracket so that the yoke and the rear bracket are fixedly connected to each other. Therefore, a brush device not limited by the outer diameter of the yoke can be provided. Accordingly, a long-life starter can be obtained by using sufficiently long brushes.

Abstract: Power supply is accomplished via two rails, which are arranged in one plane and which in each case have lugs, which can be bent out from the rail plane. In this case, contact arm of at least one lug is run away over a rail. In this way, a system which is quick to install and which, moveover, is quickly extended in the axial direction is produced.

Abstract: A brush holder assembly comprises a non-conductive brush holder body covered by a printed wiring board cover. The brush holder body includes a brush cavity for holding a brush, a spring cavity for holding a spring and a shunt wire cavity for holding a shunt wire. The spring is configured to hold the brush in contact with a commutator at a constant brush pressure throughout the entire length of brush travel. The brush holder body and printed wiring board cover are configured to enclose the brush, spring and shunt wire thus protecting the brush, spring and shunt wire.

Abstract: Brush holder for a DC motor is disclosed as having at least one brush box for housing a brush biased radially toward an opening through the brush holder. A brush retainer is provided for preventing the brush from entering the opening of the brush holder until the rotor of the DC motor is assembled to the stator, where the brush retainer is releasably attached to an annular wall defining the brush holder opening. The brush holder also includes means for capturing the brush retainer once it is displaced axially during assembly of the rotor to the stator, as well as means for retaining a printed circuit board in position between the brush holder and the stator end cap.

Abstract: A brush system for providing an electric connection to a rotating commutator wheel of an electric machine is disclosed. The brush system has a switched brush selectively switchable between an engaged position and a disengaged position and a switch connected to the switched brush and formed of a shape-memory-alloy. The switch attains an extended state at a first temperature and attaining a retracted state at a second temperature, for switching the switched brush alternately to the respective engaged position and the respective disengaged position. The switch includes a temperature conditioner for varying a temperature at the switch between the first temperature and the second temperature. The temperature condition may be an electric network wherein the internal resistance of the switch allows for heating of the switch to the second temperature.

Abstract: A short-circuiting and brush-lifting device comprises a rotatable actuating ring having with brush-actuating rods levers cause the brushes of the motor to lift up via the rotating actuating after the slip rings have been short-circuited as a result of the axial displacement of a short-circuiting ring. To make the device wear-resistant and insensitive to contamination, the actuating ring supports three rollers, with which it abuts in the starting position on the spring-loaded short-circuiting ring. The actuating ring is guided exactly in parallel by three axial guide rods, which are disposed perpendicularly to the brush-actuating rods. The configuration of all articulated joints of these rods is adjusted so as to allow the points of maximum excursion of the deflection of the articulated joint of the axial guide rods and the brush-actuating rods are exhibited at staggered times.

Abstract: A brush holding assembly comprises two elements: a body element semi-permanently secured to the machine housing and a cartridge element detachably secured to the body element. The cartridge element includes at least one brush compartment having upper and lower faces with brush openings through which an elongated brush element can be inserted. The face of the cartridge element which is adapted to be secured to the body element has a service opening for spring insertion. At the time of servicing, a twin coiled spring is inserted into the compartment via the service opening and the new brush is inserted into the compartment via the lower face brush opening. As the brush is more fully inserted, it engages the spring element between its coils, and the end of the brush eventually emerges through the upper face brush opening, unwinding the spring coils which are retained within the compartment by the upper face of the cartridge element.

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 brush holder device for an electric motor has a brush holder, a brush movably received in the brush holder, and a spring which acts between the bottom of the brush holder and the outer end of the brush so as to resiliently press the brush into contact with a commutator. The surface of the bottom of the brush holder on which one end of the spring acts and the outer end surface of the brush on which the other end of the spring acts are inclined in opposite directions along the axis of the motor such that the distance between the surfaces is greater at one axial end than at the other axial end of the brush holder. As a result, the spring is naturally urged to and stably held in the axial end where the distance between these two surfaces is greater. In addition, or alternatively, the bottom surface of the brush holder includes a recessed portion for containing the spring at one axial end of the brush holder.

Abstract: Apparatus for visually indicating a worn brush condition for carbon brushes arranged in a gang-type brush holder. A strip of red Teflon tape, or other distinctive marking, is positioned on the linear spring having a coiled top portion which biases the brush into contact with the collector ring. As the brush wears down, the marking on the spring becomes visible as the spring coils more and more. The tape is positioned on the spring such that, when the exposed top portion of the spring shows completely red (i.e., the color of the marking), it is indicated to the operator that a worn brush is to be replaced.

Abstract: An electric generator organization, particularly adapted for small vehicles such as motorcycles, is described in which a rectifier mechanism electrically disposed between the stator and the rotor is mechanically connected to the rotor for rotation therewith during engine startup and disconnected therefrom during periods of normal engine operation. An operating circuit enables efficient transmission of electric current from the battery to starting coils in the generator only during the period of engine startup. During periods of normal engine operation, the transmission of electric current is from generating coils in the generator to the battery. Included in the operating circuit is an engine operation detector that prevents excessive current feed from the generator coils to the rectifier mechanism.

Abstract: A method and a device for controlling a brush-commutator assembly of a machine under application of an electrical processing and control unit, by sensing one or more operating parameters of the electric machine, the sensing values being processed and converted into one or more control signals controlling the operation of the brush-commutator assembly to provide an optimal commutation process of the machine current. The machine current is sensed and the pressing exerted on the brushes is controlled by a fluid under pressure; the brush tracks, moreover, being engaged and disengaged upon increase and decrease of the machine current respectively in order to maintain an optimal current density in the brushes. One or more sensors for sensing operating parameters of the electric machine are used and a processing and control unit to process the signals sensed by the sensors and to supply control signals to one or more control means controlling the operation of the brush-commutator assembly.

Abstract: A commutator motor specifically designed for incorporation into portable machine tools such as a hand drill includes a stator winding in a machine housing, and a rotor winding including a rotor shaft with a commutator ring journalled in the housing. Electrical connection between the commutator and current supply is ensured by multiple pairs of diametrically opposed carbon brushes of opposite polarity, the brushes being supported in the machine housing such that each respective pair of brushes can be separately brought into contact with the commutator by a setting means capable of engaging the respective pairs of brushes. Various holder configurations for supporting the brushes include sliding cams.

Abstract: A reversible electric motor has two pairs of brushes, a separate pair for each direction of rotation. The mean diametrical positions of the two pairs are fixed with respect to the motor's stator and angularly offset. The brushes of the one or the other pair, exclusively, are selected for application against the commutator as a function of the selected direction of rotation. Preferably a rotatable cam is arranged to lift the brushes of the non-selected pair from the commutator and insulating segments are inserted between the lifted brushes and the commutator. To simplify wiring, adjacent brushes, one from each pair, may be electrically connected together. Both pairs of brushes may advantageously be lifted from the commutator during motor reversal to eliminate risk of short-circuiting the commutator and also to interrupt supply of power thereto.