US2475276A - Brush lifting mechanism - Google Patents

Description

July 5, 1949 E. c. BRIGGS 2,475,276

BRUSH LIFT ING MECHANISM Filed Oct. 1, 1947 2 Sheets-Sheet l 37 3O l l INVENTOR- ATTORNEYS July 5, 1949. E. c. BREGGS 2,475,276

BRUSH LIFTING MECHANISM Filed Oct. 1, 1947 2 Sheets-Sheet 2 INVENTOR.

B BY 0 WZMMQM AT TOBNE YS Patented July 5, 1949 BRUSH LIFTING MECHANISM Eugene C. Briggs, Dayton, Ohio, assignor to The Leland Electric Company, Dayton, Ohio, a corporation of Ohio Application October 1, 194:7, Serial Nm 777,200

10"Claims. I

This invention relates. to brush lifting mechanisms for electric motors and the like.

One. of the principal. objects of the invention is to provide a brush lifting mechanism of simple construction having a minimum number of component parts, and particularly a minimum number of moving parts, which may be readily assembled and mounted for use in. a motor and which will operate efi'ectively to lift the brushes when the. motor reaches a desired speed.

Another object is to provide a brush lifting mechanism wherein the movement of the brush-es out of and into contact with the commutator takes place with a snap action, preventing arcing and. resultant damage to the parts and thus assuring a long useful. life for the. brushes.

It. is. also an. object of the invention to provide a brush liftingmechanism wherein the same spring is effective in. one position of the parts to urge a brush into contact with the commutator and another position of the parts to lift the brush out of contact with the commutator.

A- further object is to provide such a brush lifting mechanism wherein a single spring having an over center action is utilized to-efiect' both the raising and lowering movements of the brush carrying arm.

Other objects and advantages of the invention will be apparent from. the. following description, the accompanyin drawings and the appended claims.

In. the drawings Fig, l is a view in sideelevation showing a brush lifting mechanism in accordance with the invention mounted in an" electric motor, the motor being shown fragmentarily to illustrate the operation of the mechanism;

Fig. 2-. is a top. plan view of the mechanism shown. in Eig. 1;

Fig. 3 is a somewhat simplified. and diagrammatic view partly in; side elevation and partly broken away and. in section, showing the opera.- tion. ofone of the brush arms and associated parts of. the-mechanism shown in Fig. 1,. with the brush armbeing shown as in. its down or contact position;

Fig. 4 is a view in vertical section taken on the; line i'--- ioi- Fig:v 3 and also showing frag.- ments of) the: commutator Fi 5 is a view similar to: Fig. 3 but showing the brush arm in: its lifted positions; and

Fig. 6: is a sectional view similar to Fig. 4 but taken. on the line. 6-6; of. Fig. 5.

Referring, to. the drawings. which illustrate a preferred embodiment. of. the. present. invention,

' ling the: brush lifting mechanism in accordance with the speed of the motor. This. device comprises aseries of weightsit. which are so connected with the short-circuiting device that they will be controlledby the spring l5. Each weight has at its outer edge: a laterally extending flange [1, these flanges being. so. arranged as to form av practicaliy continuousannular flange. When the motor is started,v outward movement or the weights L2 and. id is resisted by a shoulder on a retaining plate t8 (Fig.4.) which engagesthe spring [5 and prevents outward movement oi the weights until the centrifugal force has become sufficient to overcome; that resistanceand then move the weights quickly to their operative or short-circuiting. positions shown i n-Fig 6..

The brush lifting. device includes a supporting plate 20 adapted to be mounted on the motor casii'lgby means 0t suitable bolts in the elongated slots 2-l these slots providing for adjustable mounting. of the plate Zll. The plate 20 carries a supporting stud. 22: parallel to but spaced radially tromthe axis ot armature shaft H5, and. this stud serves as a pivotal mounting. for the. pair of brush supporting arms 25,v each of which is provided. at its outer end with. a spring clip 25 adapted to holdone oi the. pair of brushes 2-1. As best seen in. Figs-.. 1. and. 2, each arm 25 is formed somewhat like a stirrupand includes spaced. parallel portions 351- and 3| each pivotally mounted on stud 22:. In addition, each arm portion Sllformspartof. avbell crank whichincludes a lever portion 32: extending an the opposite. side of stud 22 from thebrushl carrying part ofthe arm and including a rearwardly bent portion 3-3 extending. generally parallel to stud 22.

It-w ill accordingly be seenlthat each brush arm 25' is mounted. to pivot as a unit on stud 22. This pivotal movement is limited by a pair of pins 35:01 like abutmentor stopmembers which are carried by plate 20 and. engage in enlarged apertures. 36 formed. in the brush arms 25. Stops 35 may be. separately formed. and secured. toplate 2%, but it is desirable from the standpoint of mi inizing manufacturing operations to form them by extrusion from the body of plate 29. If the maximum length of such extruded stops 35 is insufficient to reach the brush arm more remote from plate 20, the portion 3b of this arm may be provided with an offset 31, as shown in Fig. 2, extending axially inwardly of the adjacent end of the portion 3| of the other or left-hand brush arm as viewed in Figs. 1 and 2. Since it is convenient to form both brush arms of identical configuration, the portion 3i! of the left-hand arm 25 has a similar ofiset 31 but it serves no function in the operation of the device as shown, the holes 38 being formed also in the portions 3| of each brush arm.

A link member 40 is loosely mounted on the stud 22 for movement thereon, and this link includes a looped portion 4| engaging a pin 42 carried by one end of a lever 44, the other end of which is pivotally mounted at 45 on the supporting plate 20. The lever 44 is also provided with an operating arm 46 of non-conducting material which is formed to provide a channel 4i adapted to receive the flanges IT on the centrifugal weights I6. An eccentric rivet 48 is journaled in the lever 44 and lever arm 46 for adjusting the angular relation between these parts about the pivot point 45.

Two generally U-shaped springs 50 are mounted between the lever portions 33 of the brush arms and the link 40 for movement between positions in which they urge the arms 25 in directions to carry brushes 21 into contact with the bars l3 of the commutator and positions in which they urge the arms 25 to move the brushes out of contact with the commutator. The arrangement and operation of these springs is illustrated most clearly in Figs. 3 to 6, which show the device with one brush arm removed for greater clarity of illustration. Referring particularly to Figs. 3 and 5, it will be noted that the lever portion 33 of the brush arm includes an upwardly extending tab portion 5| formed to provide a retaining groove for receiving one end of its cooperating spring 50. The opposite or inner end of this spring is similarly received in one of a pair of grooves or notches 52 formed in the sides of the link 49, the relative dimensions and spacing of these parts being such that each spring 50 is under compression between link 40 and the lever portion 33 of one of the brush arms.

As shown in Figs. 3 and 5, this arrangement of springs 50 is such that when the link 49 is at its radially inner position with respect to the motor axis, the end of each spring 50 will lie radially inwardly of its center position defined by a line connecting its outer end and the axis of stud 22. Each spring will accordingly exert tension outwardly of shaft II on the arm portion 33 connected therewith in such manner as to urge the brush carrying arm portions -3l inwardly towards shaft H, in clockwise direction as viewed in Fig. 3, and thus to move the brush 2'! carried by the arm into contact with the commutator, this position of the brush arms being also shown in Fig. 1.

When the link is moved to its radially outer position, this will result in shifting the end of each spring 5!] carried thereby to a position radially outward of its center position. Each spring will accordingly then exert tension on the lever portion 33 of the brush arm in the opposite direction from that in the position shown in Fig. 3 and will act to urge the arm to swing in a direction carrying the brush out of contact with the commutator, this position of the parts being shown in Figs. 5 and 6. Furthermore, this shift the position of the arms will take place with a snap action as the inner end of each spring 50 crosses over its center position. Movement of the arms in each direction is limited by the engagement of stops 35 in apertures 36 as described.

In operation, the shifting of the link 40 and springs 5i? is carried out in accordance with the speed of the motor by the centrifugal weights l6. Referring particularly to Fig. 4, when the motor is operating below the critical speed, the spring holds the weights IS in their inner positions, the flanges I? engage in the channel 41 in arm 26 and thus hold lever 44 and pin 42 in their inner positions. As shown in Fig. 1, the parts are so adjusted that when the arms 25 are in this position, the stops 35 will be out of engagement with the edges of apertures 36 so that the springs 5% thus act to urge the arms and the brushes 2? carried thereby resiliently into contact with the commutator bars [3, providing for starting the motor.

When the speed of the motor exceeds the critical value, the centrifugal force on weights 5.? and H3 overcomes the tension of spring l5 and these Weights move outwardly to the positions shown in Fig. 6. During this movement, the flanges ll will move the lever arm 46 outwardly, in counterclockwise direction as viewed in Fig. 1, thus sim-- ilarly moving lever 44 and carrying pin 42 and link lll to their outer positions. During the first part of this movement, the springs 59] will be further compressed, but as their inner ends in th notches 52 pass over their center positions, they will then snap to the positions indicated in Fig. 5 wherein they urge the arms 25 to move brushes 2'! out of contact with the commutator. This lifting movement of arms 25 is limited by engagement of stops 35 with the sides of the apertures 36, and as pointed out the lifting movement takes place with a snap action effectively preventing arcing and thus substantially prolonging the effective life of the brushes.

During subsequent operation of the motor, the springs 59 will hold the brush arms in their out of contact positions so long as the speed of the motor remains above th critical value at which the tension of the spring 15 will overcome the centrifugal force on weights l2 and It. When the motor slows down below that speed, the weights IE will again move inwardl and act through lever 44 to move link 4!! similarly inwardly until springs 59 are caused to return to the positions shown in Fig. l. and this return movement will also take place with a snap action as the inner ends of the springs cross over their center positions, thus causing the brushes to snap back into contacting relation with the commutator.

It will be seen that with the device constructed and arranged as described and shown, each brush arm and its associated spring 50 operate as a mechanically independent unit from the other brush arm and spring, although of course both units are necessary for proper operation of the motor. It should also be noted that the arrangement of the parts is such that when link 4!! is at either of its iimiting positions shown in Figs. 3 to 6, either brush arm may be moved to the full ex tent permitted by engagement between the hole 36 therein and its cooperating stop 35 without affecting the off-center positioning of its spring 59. Thus with the parts positioned as shown in Fig. 3, the brush arm 25 can be swung against the action of spring 50,, in counterclockwise direction, to: its position, as shown in Fig. 5 without, changing the: efiectives position of the: spring: or causing it to shift over: center. Similarly when. the: parts are positioned as shown in: 5,, the brush, arm: 25 can: be swung in clockwise direction to'its position as shownain Fig. 3; without affecting. the spring which will return the brush: arm to the. position of Fig. 5; when pressure the arm is released;

While the form of apparatus: herein described constitutes a; preferred: embodiment of the invert tiom. it. is: tobe understood that the; iiwention: is not limited to.= this precise form of apparatus, and; that changes may he: made therein. without departing; from the: scope: of the: inventionwhich is defined. in the. appended claims;

What is claimed is:

1:. A. brush liiiting: mechanism adapted for use in an electric motor having a commutator, comprising an arm: adapted to supportla brush, means supporting said. arm adjacent the commutator of said motor for rocking movement to carry said brush into and out of contact with said commutator, a single spring mounted for shifting movement between a position at. one side of center for urging said arm in a direction tomove said brush into contact with said commutator and a position on the other side of center for urging said arm in a direction to move said brush out of contact with said commutator, and means responsive to the speed of said motor for shifting said sprin be" tween said positions.

2. A brush lifting mechanism adapted for use in an electric motor having a commutator, com-- prising an arm adapted to support a brush, means for plvotally mounting said arm adjacent the commutator of said motor, a single spring, means for mounting said spring in position to urge said arm in a direction to cause said brush to contact the commutator of said motor when said motor is below a critical speed, and means efiective when the speed of said motor exceeds said critical speed to shift said spring to a position urging said arm in a direction to move said brush out of contact with said commutator.

3. A brush lifting mechanism adapted for use in an electric motor having a commutator, comprising an arm adapted to support a brush, means for pivotally mounting said arm adjacent said commutator, a single spring, means for mounting said spring in position to urge said arm in a direction to cause said brush to contact said commutator when the speed of said motor is less than a predetermined critical speed, and means effec tive when the speed of said motor exceeds said predetermined speed to shift said spring to a position urging said arm in a direction to move said brush out of contact of said commutator.

4. A brush lifting mechanism adapted for use in an electric motor having a commutator, comprising an arm adapted to support a brush, a stud mounting said arm for pivotal movement in such directions as to carry said brush into and out of contact with said commutator, a member loosely mounted on said stud for predetermined movement substantially radially of the axis of said motor between two limiting positions, a spring, and means connecting said spring to said arm and to said movable member for urging said arm in a direction to cause said brush to contact said commutator when said member is at one of said limiting positions and for urging said arm in a direction to move said brush out of contact with said commutator when said member is at the other said limiting position.

- 5.. A brush lifting; mechanism adapted: for use in an. electric. motor comprising an arm, means adjacent one end. of said arm for carrying a.

brush, a supporting. plate, a stud carried. by said plate: and. mounting said arm for pivotal movement about. an, axis located intermediate the ends of said. arm, av member loosely mounted on said stud. fior movement generally radially thereof, a spring; having; one end connected tothe end. of said arm. opposite said brush carrying end and theoth-er end. thereof connected to said movable member,. said. spring being under compression to exert tension on said arm to cause said arm? to. swing about. said stud, and means for shifting; said movable member on said stud to carry said spring over center between a position wherein said springv urgessaid arm to swing in one direction aboutsaid stud and. apposition wherein said springv urges said arm. to. swing in the opposite; direction ahoutsaid studr 6. brush. lifting mechanism adapted for use in an electric motor having a commutator; comprising; an. arm, means adjacent one end of said arm for carrying a. brush, a stud for mounting. said, armadjacent: said commutator, said arm beingmounted on: said stud for pivotal movement about an axis located intermediate the ends thereof, a link mounted on said stud for movement generally radially of the axis of said motor, a spring having the inner end thereof connected to said link and the outer end thereof connected to the end of said arm opposite said brush carrying end, and means responsive to the speed of said motor for shifting said link from a position wherein said inner spring end is located radially inwardly of a line connecting the axis of said stud and said outer spring end and a position wherein said inner spring end is located radially outwardly of said line.

7. A brush lifting mechanism adapted for use in an electric motor having a commutator, comprising an arm adapted to support a brush, means for pivotally mounting said arm adjacent said commutator, a spring, means for connecting one end of said spring to said arm, means for mounting the other end of said spring adjacent said pivotal axis of said arm with said spring under compression to exert tension on said arm outwardly of said axis, and means for shifting said other end of said spring over center relative to said axis to shift the direction of said tension between a direction urging said arm to carry said brush into contact with said commutator and a direction urging said arm to move said brush out of contact with said commutator.

8. A brush lifting mechanism adapted for use in an electric motor having a commutator, comprising an arm adapted at one end to support a brush, a stud providing a pivotal mounting for said arm adjacent said commutator, said arm including a portion extending on the opposite side of said stud from said brush carrying end, a link loosely mounted on said stud for limited movement radially thereof, a U-shaped spring, means connecting one end of said spring to said link for movement therewith, means connecting the other end of said spring to said extending portion of said arm with said spring under compression to exert tension between said link and said arm, and means for shifting said link between an inner position wherein the end of said spring connected therewith lies radially inwardly of said stud with relation to the axis of said m0- tor and an outer position wherein said spring end lies radially outwardly of said stud to cause corresponding shifting of said arm between a position holding said brush in contact with said commutator and a position wherein said brush is out of contact with said commutator.

9. A brush lifting mechanism adapted for use in an electric motor having a, commutator, comprising a supporting plate adapted for mounting adjacent said commutator, a stud carried by said plate, a pair of arms mounted for pivotal movement on said stud and extending in generally opposite directions therefrom, means on each of said arms for carrying a brush, a link loosely mounted on said stud for movement radially thereof, a pair of springs each providing a connection between one of said arms and said link, and means for causing relative movement of said stud and link between a position wherein said springs urge said arms in directions to move said brushes into contact with said commutator and a position wherein said springs urge said arms in directions to move said brushes out of contact with said commutator.

10. A brush lifting mechanism adapted for use in an electric motor having a commutator, comprising a supporting plate adapted to be mounted adjacent said commutator, a supporting stud carried by said plate, a pair of arms pivotally mounted on said stud, each said arm including a brush carrying portion and a lever portion extending on the opposite side of said stud from said brush carrying portion thereof, a link loosely mounted for movement radially of said stud, a pair of springs each mounted under compression in position to connect said link with said lever portion of one of said arms to exert tension outwardly Of said stud against said lever portion, and means for moving said link from an inner position wherein said springs urge said arms in directions to move said brushes into contact with said commutator to an outer position wherein said springs urge said arms in directions to move said brushes out of contact with said commutator.

EUGENE C. BRIGGS.

REFERENCES CITED UNITED STATES PATENTS Name Date Jeannin Sept. 12, 1916 Number

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