US2802960A

US2802960A - Brush holder assembly

Info

Publication number: US2802960A
Application number: US536089A
Authority: US
Inventors: Marvin A Baker
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1955-09-23
Filing date: 1955-09-23
Publication date: 1957-08-13
Anticipated expiration: 1974-08-13
Also published as: JPS334263B1

Description

Aug. 13, 1957 M. A. BAKER BRUSH HOLDER ASSEMBLY Filed Sept. 23, 1955 I I IIIIHI l'] [27 van far"; Marv/i7 /4 Bea/re);

HA; Attorney United States Patent BRUSH HOLDER ASSEMBLY Marvin A. Baker, Erie, Pa., assignor to General Electric Company, a corporation of New York Application September 23, 1955, Serial No. 536,089

17 Claims. (Cl. 310-246) This invention relates to dynamo-electrical machinery and more particularly to brush assemblies for use on electrical motors and generators.

The use of a coiled compression spring for maintaining motor and generator brush contact is known in the art. Previously, brush holders incorporating coiled compression springs which are pre-stressed prior to assembly and have one end attached to fixed members with the distal ends terminating in a spiral coil adapted to engage the outer ends of the brushes have been suggested. This type of spring has been acceptable due to its inherent property of exerting a force on brushes which is substantially constant throughout the (life of brushes, even though the brushes are long when installed and their length is decreased by wear until they are worn extremely short.

This type of spring as heretofore applied to brushes of the type discussed may apply a force to the brush in a manner which may cause the brush to be drawn away from the brush holder reaction surface by the force of the commutator thereon. The effect of the movement of the brush away from the reaction surface may result in brush chatter, sparking at the commutator, or rapid brush wear.

One feature of the present disclosure is a constant tension spring which applies a force to the brush at a point spaced from and on the side of the central axis of the brush remote from the reaction surface with the force having a sense inclined toward the commutator and toward the reaction surface. The resultant of the force applied by the spring and the frictional force of the rotating commutator on the opposite end of the brush produces a wedging action which holds the brush firmly against the reaction surface in either direction of rotation, thus inhibiting any tendency of the brush to chatter with the inherent undesirable results.

Furthermore, when springs are applied to brushes in the manner old in the art as aforesaid, the end engaging the brush has a tendency to creep across the surface of the end of the brush toward the reaction surface as the volute rolls up, until it reaches a point Where it will slip. As it slipped, it would tend to pull the brush with it away from the reaction surface.

To overcome the tendency of the volute to creep over the surface of the brush, this invention discloses a restraining surface on the brush for engaging the spring. This surface may take the form of a flanged plate attached to the brush as disclosed in one embodiment or it may be a notch properly located to receive the brush end as disclosed in another embodiment herein. According to this invention, the restraining means could be any form of stop for the spring.

Under conditions of severe shock, brushesv may jump out of the holder., To overcome. this tendency and to prevent the brushes from jumping out of the holder, a keeper isv disclosed. The keeper also preventsv negligent operators from; over-stressing the. spring when replacing brushes, etc.

2,802,960 Patented Aug. 13, 1957 Another important feature of the present invention is an improved shape of spring which insures proper uniform pressure and force sense as the brush wears and, consequently, the brush helix re-rolls itself with the resulting tendency not to lose its tension. This action may be facilitated by an improved brush mounting disclosed herein as Well as by a reinforcing element shown in combination with the spring.

Still another feature is a guard or keeper disposed parallel to the spring with a portion overlying the brush to keep the spring from jumping out and to protect the spring.

With the above and other advantages in view, the present invention consists of the combination and arrangement of parts hereinafter more fully described, illustrated in the accompanying drawing and more particularly pointed out in the appended claims, it being understood that changes may be made in the form, size, proportions, and minor detail of construction without departing from the spirit or sacrificing any of the advantages of the invention.

In the drawing:

Fig. 1 is a side elevational view partly in section of the improved brush holder and coiled spring assembly of this invention showing the reaction surface engaged by the brush;

Fig. 2 is a top view of the assembly shown in Fig. 1;

Fig. 3 is a side elevational view similar to Fig. 1 showing another embodiment of the invention;

Fig. 4 is a view similar to Figs. 1 and 2 of still another embodiment of the invention;

Fig. 5 is still another view similar to Figs. 1, 3 and 4 showing another embodiment of the invention; and

Fig. 6 shows another embodiment of the invention.

Referring now to the embodiment of the invention shown in Figs. 1 and 2, the commutator of a dynamoelectric machine such as a motor or generator is shown at 10. The longitudinal axis of a brush 12 is disposed generally parallel to the vertical center line of the commutator 10 and spaced on the leading side therefrom. The brush 12 will be provided with the usual pigtail or other suitable electrical connection to connect the brush 12 to a suitable electrical terminal conductor.

A brush casing 11 has

ends

17 and 18 connected by side members 19 which join the end members 17 land 18 together and are also joined to a bottom 21. The bottom 21 has an opening 22 therethrough adjacent the reaction surface to receive the lower end 23 of the brush 12. A commutator engaging surface 24 of the brush 12 will be formed in a general contour to conform to the peripheral surface of the commutator 10. The upper end 26 of the brush 12 is relieved at 27 and an outer plate 28 extends over the upper surface and bends over the outer leading edge corner and is attached thereto. The upper end 26 of the brush 12 terminates in a surface 30 preferably inclined at an angle to the transverse axis of the brush 12.

The plate 28 is attached to the upper end of the brush 12 by a suitable means. A flange 32 is attached to the plate 23 at an intermediate point thereon and extends upwardly therefrom generally perpendicular thereto.

A bracket is integrally attached to the brush casing 11 and has -a bore 41 which receives a stud 42. The stud 42 is rigidly attached to the fixed frame of the machine and insulated therefrom. The bracket 40 has a slot. 43 cut therein which has a continuation 44 on the opposite side of the bore 41. A bolt 45 threa-dably engages the end of the bracket 40, clamping the bracket 40 to the stud 42 in the usual manner. This makes it possible to loosen the bolt 45 and thereby rotate the bracket 40 on the stud 42 to bring the brush 12 into alignment with respect to the commutator and, at the same time, the bracket 40 may be slid along the stud 42 to properly locate the brush 12 relatively to the axis of the commutator 10.

A spring 14 is substantially a constant pressure spring and is made of a material flat in cross section and prestressed along its length so as to naturally assume a free self-winding volute coil 15 of a diameter which will nest well into the space between the flange 32 and the end 63 of the plate 28. The spring 14 is attached to the inner surface 74 of the end 18 and is attached thereto by means of rivets 16; however, it could be attached by any other suitable fastening means. The spring 14 is bent toward the brush 12 at 75 and the force on the coil 15 puts an inverse bend in the spring 14 as shown. As the commutator 10 rotates and wears away the lower end 23 of the brush 12, the brush 12 will be urged downward by the force of the coil 15 on the top of the plate 28 and, at the same time, the upper end of the brush 12 will be urged toward the reaction surface 29. The lower end of the brush 12 will be urged toward the reaction surface 29 by reason of the frictional force on the lower surface thereof by rotation of the commutator 10. Therefore, the brush 12 will be bodily moved toward the reaction surface 29 and held in firm relation thereagainst. As the brush 12 wears away and shortens, the volute coil 15 will rewind and the frictional force of the portion thereof engaging the plate 28 will tend to cause the volute to climb toward the reaction surface 29. This tendency will be opposed by the flange 32 which will hold it in the position shown throughout the life of the brush 12, thereby causing the spring 14 to exert a resultant force on the outer end of the brush 12 which will do its part in holding the outer end in firm engagement with the reaction surface 29.

In order to obtain the optimum pressure on the brush 12 toward the reaction surface 29, a leaf spring 72 may be used. The use of such a spring is made possible by the positive stops provided which consist of the flange 32. The leaf spring 72 is attached to the brush casing 11 by the rivets 16 or other suitable means and is disposed between the spring 14 and the casing 11. The leaf spring 72 may be bent to pre-stress it to exert the optimum pressure on the brush 12 toward the reaction surface 29.

In the embodiment of the invention shown in Fig. 3, a spring and brush assembly is shown in some respects similar to that shown in Fig. 1. The corresponding parts in Fig. 3 to the corresponding parts in Fig. l are sometimes numbered with the same number having one hundred added thereto to distinguish between the two embodiments. Fig. 3 shows a brush casing 111 supporting a brush 112. The brush casing 111 has end 117 and a spring supporting reaction end 118 and sides 119. Brush surface 124 engages the outer periphery of a commutator 110. A constant pressure spring 114 having a volute end 115 is attached to the inner surface 144 of the end 118. The surface 144 tapers outwardly and toward the brush 112, thereby causing the spring 114 to incline toward the brush 112. A keeper 150 is attached to the surface 144 between the spring 114 and the surface by means of rivet 116 and rivet 116 passes through both the keeper 150 and the spring 114. The spring 114 could be attached to the surface 144 by other suitable means than the rivet 116.

A slot 133 is formed in the outer end 126 of the brush 112 at the side thereof remote from reaction surface 129 and the side portion thereof is nested in the slot 133. As wear reduces the length of the brush 112, the volute 115 winds itself up and the edge 132, as well as the inclined edge 130, holds the volute 115 in positive relationship with the brush 112 and insures a resultant force applied by the spring 114 in a direction to force the brush 112 downward in opening 122 as well as toward the reaction surface 129 so that the resultant force applied to the brush 112 by means of the spring 114, when combined with the frictional force of the rotating commutator on the lower end of the brush 112, holds the brush 112 firmly against the reaction surface 129.

In the embodiment of the invention shown in Fig. 4, a brush casing 211 is disclosed having a reaction end 217, spring end 218, sides 219, and a bottom 221. The bottom 221 has an opening 222 therethrough. The commutator end 223 of brush 212 extends through the opening 222 and the commutator end surface 224 of the brush 212 engages the peripheral surface of the commutator 210. The brush casing 211 has the sides 219 which connect the ends and bottom 221 together.

Upper surface 230 of the brush 212 has a plate 228 thereon which bends over at 227 into a relief therein whereby it is firmly fixed to the brush 212. The opposite end of the plate 228 from the end 227 has a volute receiving saddle 1230. A constant pressure spring 214 is attached at its lower end by means of rivet 216 or other suitable means to the inner face of spring support end 218 and is supported against the spacer 260 which is disposed between a keeper or backing member 250 and the lower end of the spring 214. The spring 214 is bent at 245 toward the brush 212 whereby the spring 214, when urged to the stressed position shown, exerts a force downward and toward reaction surface 229.

The keeper 250 serves the dual purpose of forming a guard to prevent the spring 214 from coming out of place during disassembly and also forms a convenient means for holding the spring 214 in place while the rivet 216 is put into position.

It will be noted that as the brush 212 wears away and shortens, volute 215 will reroll but will be held in position nested in the saddle 1230 whereby a resultant force will be exerted on the brush 212 toward the commutator 210 and toward the reaction surface 229. This resultant force, in combination with the frictional force between the commutator 210 and the surface 224, will urge the brush 212 bodily toward the reaction surface 229, thereby holding it in position.

The embodiment of the invention shown in Fig. 5 discloses a brush casing 311 which has ends 317 and 318 connected by sides 319 and having a bottom portion 321. The outer peripheral surface of commutator 310 is engaged by conforming surface 324 of lower end 323 of a brush 312. The upper surface 330 of the brush 312 is inclined downwardly at an angle A. It has been discovered that the angle A must be between twenty-five degrees and forty-five degrees. If the angle is greater than forty-five degrees, the effective length of the brush is reduced since the beveled surface takes up an appreciable percentage of the length and thus shortens its life. If it is less than twenty-five degrees, the force toward the reaction surface will not be sufficient for desirable results and the volute will tend to slip on the upper end surface of the brush with the resulting undesirable effects.

The volute 315 of the spring 314 engages the surface and, due to the large angle of the surface 330, the brush volute 315 will be restrained against its natural inclination to climb upward on the surface 330 as the brush 312 shortens due to wear and the volute 315, therefore, rerolls.

The brush 312 is attached to the inner surface 344 of the end 318 by means of a rivet 316 or other suitable means which extends through the lower end 325 of the constant pressure spring 314 and through a keeper 350. The spring 314 is bent at 345 toward the brush 312. The keeper 350 protects the spring 314 against damage and also provides a means for preventing the brush 312 from jumping out of its casing 311 in case of shock due to explosion on shipboardand due to similar shocks.

During operation, the commutator 310 preferably rotatesin thedirection indicated and the frictional force on the surface 324, when combined with the resultant force of the volute 315 toward the reaction' surface 329,

holds the brush 312 against the reaction surface 329 in positive relation thereto.

In the embodiment of the invention shown in Fig. 6, a brush 412 is supported in a brush holder 411 and rests against the reaction surface 429. The lower end of the brush holder 411 at 417 engages the surface 422 of the brush 412. The inner end surface 424 of the brush 412 engages the outer peripheral surface of commutator 410. A spring 414 is attached to the brush holder 411 at 475 and terminates at the upper end thereof in a tightly wound volute 415 which engages the upper tapered surface 463 of the brush 412 and engages the flange or pin 430 at 432. The flange or pin 430 could be molded into the brush 412 or tamped or pressed thereinto. The flange 430 restrains the brush 412 against movement over the end of the brush 412 toward the reaction surface 429 and, therefore, provides a positive stop.

An auxiliary spring 470 is fastened to the brush holder 411 at 474 and the upper end 472 engages the volute 415 at 471, exerting an additional force toward the flange 430 which adds to the force in that direction exerted by the volute 415 and urges the brush 412 toward the reaction surface 429. The tension on the spring 470 can be adjusted to obtain the optimum force toward the flange 434) and, because of the flange or pin 430, a positive stop is provided to prevent the volute 415 from climbing up the brush 412.

The foregoing specification sets forth the invention in a practical form but the structure shown is capable of modification within a range of equivalents without departing from the invention which is to be understood is broadly novel as is commensurate with the appended claims.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A commutator brush holder comprising a brush casing, and an elongated spring, the commutator end of said spring being attached to said casing and the distal end of said spring terminating in a self-winding volute arranged to engage the upper end of a brush in said casing, said casing having an opening therethrough with a reaction surface on the inside edge thereof, one end of said brush being adapted to engage a commutator, the other end of said brush having a stop member afiixed thereon to restrain said volute against movement toward said reaction surface, said spring being adapted to apply a force to said brush to urge said brush toward said reaction surface and toward said commutator adapted to be engaged by the commutator end of said brush.

2. The brush holder recited in claim 1 wherein said means to restrain movement of said volute comprises a flange attached to said brush inwardly from the edge adjacent said spring, said volute engaging said means including said flange.

3. The brush holder recited in claim 1 wherein said i means to restrain movement of said volute comprises a plate attached to the end surface of said brush remote from said commutator end and extending outward therefrom, said end surface being inclined toward said spring, said plate extending outwardly beyond the edge of said brush adjacent said spring, and means on said plate to restrain said volute against movement over said plate toward said reaction surface.

4. The brush holder recited in claim 3 wherein said plate has a flange attached thereto intermediate the ends thereof, said volute of said spring being disposed against the overhanging ends of said plate and said flange.

5. In combination, a dynamo-electric machine having a commutator and a brush holder comprising a brush casing having a spring engaging end and a reaction surface portion, an opening through said casing, one inside edge of said opening comprising a reaction surface, means to attach said brush holder to a fixed member adjacent the commutator on said dynamo-electric machine, an elongated brush adapted to extend through said opening engagement with an inner surface of said reaction surface, the commutator end of said brush being disposed outside said casing and the end of said brush opposite said commutator end being inclined toward said commutator end and away from said-inside surface, a plate attached to and lying along said end of said brush opposite said commutator end, said plate overhanging said brush remote from said reaction surface, the other end of said plate extending into a notch in said brush, and a flat elongated spring having one end coiled into a self-winding volute engaging said plate and a flange, the other end of said spring being attached to said brush holder, said spring being adapted to urge said brush into engagement with said reaction surface, said brush being displaced from the transverse center line of said commutator parallel thereto on the side thereof toward said reaction surface.

6. The combination recited in claim-5 wherein said casing has two sides and a bottom attached to said sides and end, said opening being formed'in said bottom on the side thereof adjacent said reaction surface, said spring being attached to said brush holder at a point spaced from said brush.

7. A brush holder for a dynamo-electric machine having a commutator comprising a brush casing having a spring supporting end and a reaction surface end, a bottom on the commutator end of said brush holder, an opening in said bottom adjacent said reaction surface end, an elongated brush disposed in said opening and lying along said reaction surface, an elongated spring attached to said spring supporting end and extending therefrom, the distal end of said spring being in the form of a self-winding volute, and a notch formed in said brush in the upper portion thereof where the side remote from said reaction surface engages the end remote from said commutator end, said volute being disposed in said notch and adapted to urge said brush toward said reaction surface and toward said commutator.

8. The brush holder recited in claim 7 wherein said spring supporting end has a surface adjacent said brush inclined away from said commutator and toward said brush, said spring attached to said spring supporting surface having its attached end inclined upwardly and toward said brush.

9. The brush holder recited in claim 8 wherein an elongated handle is attached to said inclined spring supporting surface between said spring and terminating in a hook member overlying said volute.

10. In combination, a dynamo-electric machine having a commutator and a brush holder attached thereto comprising a brush casing having a spring supporting end and a reaction surface end, a bottom on the commutator end of said reaction surface end, an opening in said bottom, an elongated brush disposed in said opening and lying along said reaction surface, an elongated spring attached :to said spring supporting end and extending therefrom, a distal end of said spring being in the form of a self-winding volute, a notch formed in said brush in the corner thereof where the side remote from said reaction surface engages the end remote from said commutator end, said volute being disposed in said notch and adapted to urge said brush toward said reaction surface and toward said commutator, said spring supporting end having a surface adjacent said brush inclined away from said commutator and toward said brush, said spring attached 10 said spring supporting surface having its at tached end parallel to said inclined surface, and an elongated handle attached to said inclined surface between said spring and said surface, said handle extending along said spring and terminating in a hook member overlying said volute, said brush being displaced from the center line of said commutator in a direction toward said reaction surface.

11. A commutator brush holder comprising a brush casing, an elongated spring in said casing, the commuta- 7 tor end of said spring being attached to said casing and the distal end of said spring terminating in a self-winding volute, said casing having an opening therethrough with a reaction surface On the inside edge thereof, and a brush adapted to engage a commutator, the other end of said brush having means thereon to restrain said volute against movement toward said reaction surface, said means comprising a plate attached to the end of said brush remote from said commutator, said plate overhanging the edge of said brush adjacent said spring and said plate having a concave surface :there-on, said volute of said spring engaging said concave surface whereby said spring urges said brush toward said commutator and toward said reaction surface.

12. The brush holder recited in claim 11 wherein said brush is offset from the center line of said commutator on the side thereof toward said reaction surface.

13. The brush holder recited in claim 12 wherein said spring is attached to said brush casing by means on the inside of one end surface of said casing, and a keeper extends co-extensive with said spring and upwardly therefrom and terminates in a curved portion overlying the volute of said spring disposed thereon with a spacer between said spring and said keeper.

14. In combination, a dynamo-electric machine having a commutator and a brush holder attached to said machine adjacent said commutator, said brush holder having a casing comprising an elongated spring, the commutator end of said spring being attached to said casing and the distal end of said spring terminating in a selfwinding volute, said casing having an opening therethrough with a reaction surface on the inside edge thereof, and a brush adapted to engage a commutator, the other end of said brush having means thereon to restrain said volute against movement toward said reaction surface, said means comprising a plate attached to the end of said brush remote from said commutator and having a second plate attached to said first plate and extending generally perpendicular thereto, said first plate overhanging the edge of said brush adjacent said spring and having a concave surface thereon, said spring engaging said concave surface whereby said spring urges said brush toward said commutator and toward said reaction surface, said brush being offset from the center line of said commutator on the side thereof toward said reaction surface, and a keeper extending co-extensive with said spring and upwardly therefrom and terminating in a portion overlying the volute of said spring disposed thereon with a spacer between said spring and said keeper, said cornmutator adapted to rotate in a direction to urge said brush toward said reaction surface.

15. In combination, a dynamo-electric machine having a commutator, a brush holder attached to said machine adjacent said commutator, said brush holder having a casing and an elongated spring attached to said casing, the commutator end of said spring being attached to said casing and the distal end of said spring terminating in a self-winding volute, said casing having an opening therethrough with a reaction surface on the inside edge thereof, and a brush adapted to engage a commutator, the other end of said brush having means thereon to restrain said volute against movement toward said reaction surface, said means comprising a member embedded in the outer end of said brush intermediate there of whereby said volute urges said brush toward said commutator and toward said reaction surface.

16. The combination recited in claim 15 wherein an auxiliary spring is attached to said brush casing and is generally coextensive with said elongated spring and urges the volute end of said elongated spring and said brush toward said reaction surface.

17. The combination recited in claim- 15 wherein said member embedded in the outer end of said brush comprises a pin having one end embedded in said brush and the other end extending above the surface of said brush.

McDonald July 1, 1952 Welch Nov. 30, 1954