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Title:
Brush lifting mechanism
United States Patent 2475276
Abstract:
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,...


Inventors:
Briggs, Eugene C.
Application Number:
US77720047A
Publication Date:
07/05/1949
Filing Date:
10/01/1947
Assignee:
LELAND ELECTRIC COMPANY
Primary Class:
International Classes:
H02K23/66
View Patent Images:
US Patent References:
1198235N/A1916-09-12
Description:

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 effectively 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 brushes 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 lifting mechanism wherein the same spring is effective in one position of the parts to urge a brush into contact with the commutator and in 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 effect 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 accompanying drawings and the appended claims.

In. the drawingsFig. 1, is a view in side: elevation 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 Fig. 1; Fig. 3 is a somewhat simplified, and diagrammatic view partly in side elevation and partly broken away and in. section, showing the operation. of one of the brush arms! and associated parts of the mechanism shown in Fig. 1, with the brush arm being shown as in. its down or contact position,; Fig. 4 is a view in vertical section taken on the, line 4-4 of Pig: 3 and also showing fragments of the- commutator;: Fig. 5 is a view similar to: Fig. 3- but showing the brush arm in its lifted position; 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, Figs. 1, 4 and 6 show fragments of the commutator I a and armature shaft .I upon which the commutator is mounted. The shaft I also carries a short-circuiting device comprising an annular series of weights 12 controlled by centrifugal force and movable into and out of short-circuiting engagement with the, ends of segments 113 of the commutator.. A contractile band or annular spring 15 engages the outer edges, of the weights 12t to. retain these weights in their retracted and inoperative positions when the motor is at rest.

A centrifugal device is provided for controlling the brush lifting mechanism in accordance with the speed of the motor. This device comprises a: series of weights, I6. which are so connected with. the short-circuiting device that they will be controlled by the spring 15. Each weight has at its. outer edge: a laterally extending flange IT, these flanges being so. arranged, as to form- a practically continuous annular flange. When the motor is started, outward movement of the weights 1;l and 1.6 is, resisted by a shoulder on a retaining plate 18 (Fig.. 4). which engages the spring 15 and prevents outward movement of the weights until the centrifugal force has become sufficient to overcome that resistance- and then move the weights quickly to their operative or short-circuiting positions shown in Fig. 6.

The brush lifting, device includes a supporting plate 2.0 adapted, to be mounted on the motor easing, by means of suitable bolts, in the elongated slots 2-1, these slots providing for adjustable mounting, of the plate 20. The plate 20 carries a supporting stud 22: parallel to but spaced radially from the- axis of armature shaft II;, and. this stud serves as, a pivotal mounting for the pair of brush, supporting arms. 25, each of which is provided at its- outer end with. a spring clip 25 adapted to hold one of the. pair of brushes 27. As best seen in Figs. 1. and- 2 each- arm 25 is, formed somewhat, like a stirrup, and includes spaced parallel portions 30- and- 31 each pivotally mounted on stud, 22.. In addition, each arm portion 30. forms part, of. a bell crank which includes a lever portion 32; extending on the, opposite, side' of stud 22 from the brush: carrying part of the arm and including a rearwardly bent portion. 33 extending generally parallel, to stud 22.

It- will, accordingly be seen that 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, or like abutment or stop- members, 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 to plate 20, but it is desirable from the standpoint of minnimizing manufacturing operations to form them by extrusion from the body of plate 20. If the maximum length of such extruded stops 35 is insufficient to reach the brush arm 25 more remote from plate 20, the portion 30 of this arm may be provided with an offset 37, as shown in Fig. 2, extending axially inwardly of the adjacent end of the portion 31 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 30 of the left-hand arm 25 has a similar offset 37 but it serves no function in the operation of the device as shown, the holes 36 being formed also in the portions 31 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 41 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 47 adapted to receive the flanges 17 on the centrifugal weights 16. 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 27 into contact with the bars 13 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 51 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 40, the relative dimensions and spacing of these parts being such that each spring 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 40 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 30-31 inwardly towards shaft II, in clockwise direction as viewed in Fig. 3, and thus to move the brush 27 carried by the arm into contact with the commutator, this position of the brush arms being also shown in Fig. 1.

When the link 40 is moved to its radially outer position, this will result in shifting the end of each spring 50 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 in 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 50 is carried out in accordance with the speed of the motor by the centrifugal weights 16.

Referring particularly to Fig. 4, when the motor is operating below the critical speed, the spring 15 holds the weights 16 in their inner positions, and the flanges 17 engage in the channel 47 in arm 46 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 5S thus act to urge the arms and the brushes 27 carried thereby resiliently into contact with the commutator bars 13, providing for starting the motor.

When the speed of the motor exceeds the critical value, the centrifugal force on weights 12 and S1 overcomes the tension of spring It and these weights move outwardly to the positions shown in Fig. 6. During this movement, the flanges 17 will move the lever arm 46 outwardly, in counterclockwise direction as viewed in Fig. 1, thus similarly moving lever 44 and carrying pin 42 and link 40 to their outer positions. During the first part of this movement, the springs 50 will be further compressed, but as their inner ends in the 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 27 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 50 will hold the brush arms in their out of contact positions so long as the speed of the motor remains above the critical value at which 60 the tension of the spring 15 will overcome the centrifugal force on weights 12 and 16. When the motor slows down below that speed, the weights 16 will again move inwardly and act through lever 44 to move link 40 similarly inwardly until springs 50 are caused to return to the positions shown in Fig. 1, 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 40 is at either of its limiting positions shown in Figs. 3 to 6, either brush arm may be moved to the full extent permitted by engagement between the hole 36 therein and its cooperating stop 35 without af-fecting the off-center positioning of its spring 50.

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, effective; position of the; spring or causing it to shift over center. Similarly when' the parts are positioned as shown; in Fig. 5, the' brush, arm: 25 can be swung in clockwise direction toits positionas shownin Fig: 3 without affecting the spring - , which will return the' brush arm. to, the: position. of Fig. 5 when, pressure, on the- arm is released.; While the form of apparatus; herein described- l( constitutes a preferred embodiment of the invention,. it is& to be understood that the invention is not. limited to this precise form of apparatus,. aa- d that changes may be made therein, without departing; from the scope: of the inventiaon which is 1, defined, in the. appended claims.

What is claimed is: 1. A brush lifting mechanism adapted for use in an electric motor having a commutator, comprising an arm adapted tc supporta brush, means 2 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 2 urging said arm in a direction to. move 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 spring between said positions.

2. 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 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 effective 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 effective 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,, a member loosely mounted on said stud; for movement generally radially thereof, a spring, having one end connected to- the end, of O' said arma opposite said brush: carrying end and the: other 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 spring urges said arm to swing in one direction about.said stud, and a position wherein said spring urges said arm, to. swing in the: opposite: direction 0 about said, stud..

6. A 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 i5 said. arm adjacent said commutator, said arm being mounted 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, 30 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 35 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.

40 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 45 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 50 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 55 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 60 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 65 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 70 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 motor and an outer position wherein said spring 70 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.

20 REFERENCES CITED The following references are of record in the file of this patent: UNITED STATES PATENTS 25 Number 1,198,235 Name Date Jeannin _--------- Sept. 12, 1916