US2383325A - Opposed-angle brush holder - Google Patents

Description

1945. a. P. LESSMANN 3 OPPOSED-ANGLE BRUSHHOLDER Filed NOV. 6,,1943

WITNESSES:

INVENTOR g 4' Gerhard/716 5509900.

ATTORNEY Patented Aug. 21, 1945 UNITED ,s'rnrss PATENT 1 OFFICE 2 Claims. (Cl. 171- 324) My invention relates to brushhoiders for holdlDIlt'WO brushesin operative relation to a rotating commutator, at opp sed angles with respect to theradial direction, so that the brushholdersacan be used, without change or adiustment, 'on dynamin-electric machines having both directions of rotation.

*Bmshholders having two (or more) :brushes *(two in the circumferential direction), have a guest ::advantage over single-brush brushholders, in that any roughness or elevation in the commutator surface will not strike two circumferentially displaced brushes simultaneously, and hence the entire -:current will be carried, inomentarllmiby one brush while the other ibrush jumps off of the commutator-surface due to roughness.

Heretofore, two-brush brushholders have been of two "types, and both have suffered disadvantages. In one .type, the two brushes have been parallel to each other, the brushholder had to be taken off and remounted to accommodate a reversed direction of rotation, two 'springsrwere required for the two brush-fingers, the springpressure was not well compensated against changes due to the :a'mount of brush-wear, and the number of parts, andihence the cost, were excessive. In the other type, the two brushes were at opposed 'angleaso that the maohineoould rotate in either direction, a single spring was sometimes used for the two hrush-fingers, and the number of parts was reduced, but the spring was not compensated against the efiects of brushwear, so that the pressure on the brush decreased excessively as the length of the brush became smaller because of wear, and there were also other disadvantages, such as excessive lateral pressure on the brushes.

It is an object of my present invention to provide an improved V-type or opposed-angle up, only one spring is used, to provide pressure double-brush brushholder utilizing a linearly acting spring which is connected to the brushfinger, or to both-brush-fingers', at such a position and angle that the change in the leverage or moment-alarm of the spring automatically compensates the finger-pressure for practically constant brush-pressure against the commutator, within very narrow limits, during the entire life of the brush. No spring-adjustment is required, therefore, during the life of the brush, to make up for wear or to compensate for the reduced spring-pressure or for altered angle of application of the brush-finger pressure, as the brushfinger follows up the brush as the brush wears away.

Other objects of my invention are to provide-a new double-brush brushholder which can be manufactured at less cost than eitherof the lpl'esent or previously known'common types of doubilebrush brushholders, and which has numerous other important advantages, among which may be mentioned: I

(a/l A design suitable tor either-casting or inbricatiOn rom sheet-metal.

-(b) Only one shape of finger is required, not a separate finger for rightand left-"hand mounting.

(c) The compensating leverage previously mentioned.

(d) The arrangement permits the removal and exchange of either brush without disturbing the other brush. a i

(a) One old brush and :one new brush may he used, without choice of position.

(f) In replacing a. worn or defective brush, the brush-finger pulls over-center when lifted off of the brush, and thus locks itself in its elevated position, freeing one hand for the exchange 'of brushes.

(9) The new brushholder fits old brush-rigging interchangeably with ol holders.

:(h) The center part of the new holder can :be made the same for all sizes of brushes, thus reducing the number of patterns or tools.

(i) It has a reduced number of parts.

' (1') For (brush-to-radius) angles of 25 and for both brush-fingers.

Three exemplary forms of embodiment of:my new brushholder are shown in the drawing, wherein Fig. 1 is a 'top'plan viewof a two-gang V-type brushholder utilizing only one spring .for the two "opposed-angle brushes, one of the gangs or brushholders being shownempty; Fig. 2-is a side-elevationa-l view of the brushholder shown in Fig. 1.; Fig. 3 is a side-elevational view of a V-ty-pe brushholder "having an angle ofless than 25" and consequently utilizing two springs for the two brush-fingers; and Fig. 4 is .a view similar to Fig. -3, illustrating the equivalence of a compression spring in place of a tension spring.

In the form shown in Figs. 1 and 2, two brushholders l and 2 are placed side-by-side, with only one mounting-pad 6, in what is known as a twogang brushholder. To facilitate the illustration, one brushholder, l, is shown bare, in Fig. 1, without any loose or movable parts. Each brushholder proper comprises a V-shaped center part I, having an angularly disposed or inclined brushbox 8 on each side, and having upstanding fingersupporting arms l which are notched at l2 to receive the pivot-pins 14.

Associated with each brushholder proper, are two identical brush-fingers l6, of which only one will be described, and the reference-numerals will be applied only to it, so that its outline may be more readily traced. It has a U-shaped mounting-portion carrying the laterally extending pivot-pins I4. From one side or leg of the U, there extends a downwardly curving finger-arm Hi, the tip IQ of which is bent, for engagement with the top of the brush 2|. Each finger |6 has its pivot-pins l4 seated in the notches |2 in one side of the brush-holder, and it has its finger-arm |8 extending over to the far brush 2|, so as to obtain as long a finger-arm as possible.

It is an important feature of my invention that I utilize a linearly acting spring 23, which is so connected to the brush-fingers l6 that its leverage changes, as the finger swings in following up the brush as it wears on the commutator 24, thus automatically compensating for brush-wear} as previously mentioned.

In the form of my invention shown in Figs. 1 and 2, only one spring 23 is used for the two brush-fingers l6, and the spring is a tensionspring. Each finger l6 has an upstanding rearportion 25 of the U-shaped mounting-portion l1, and said upstanding rear-portion 25 is provided with two notches 26 and 21, either one of which may be utilized to seat a cross-pin 28 which carries one end of the spring 25, in one notch or the other according to the spring-tension desired.

It will be noted that the center-line of the spring 23 lies above the pivot-point H of each finger l6, thus providing a moment-arm for the linearly applied spring-force, tending to rotate the finger-arm I8 downwardly. It will further be noted that the lever-arm, from M to' 26, extends backwardly, as well as upwardly, so that, as the finger-arm |8 swings downwardly, following the top of the brush 2| as the brush wears on the commutator 24, the rear end 26 of the spring 23 swings upwardly, increasing the spring-moment or vertical distance between the center-line of the spring and the finger-pivot l4. This is the automatic pressure-compensating feature of which I have spoken. Without it, the brush-pressure would fall off quite considerably as a result of brush-wear.

When the finger |8-| 9 is lifted ofi of the brush 2|, as for the purpose of replacing the brush, the rearwardly inclined spring-lever-arm 26-14 again makes itself felt, because the springterminal 26 swings downwardly until the center'- line of the spring falls slightly below the finger-' pivot l4, thus locking the finger in its elevated position, as shown in dotted lines at I9, so that the operator will not need to use one hand to hold up the finger while he replaces the brush. At the same time the spring is only slightly extended, so that the spring-tension on the other finger is only slightly increased while the first finger is in its locked elevated position l9, thus not interfering with the operation of the other brush, while the defective brush is being replaced.

In common with modern practice, reaction-type brushes 2| are utilized, having inclined or wedgeshaped top-pieces 29 so that the pressure of the finger-tip l9 will have a component or reaction tending to hold one side of the brush against one side of the box 8, thus avoiding rattling or chattering of the brush.

By utilizing a construction in which the fingerarm IB is long, I reduce the length of arc through which the finger must swing during the useful life of the brush, and I avoid obtaining excessive lateral pressures on the brush at either extreme position of th finger.

Other advantageous features of the operation of my brushholder will be obvious from the construction shown in Figs. 1 and 2, and from the statement of the nature and objects of my invention.

In Figs. 3 and 4, I illustrate a manner in which my invention may be applied to V-type brushholders in which the brush-to-radius angle is too small to readily provide room for'the overlying brush-fingers and single-spring construction of Figs. 1 and 2. In Figs. 3 and 4, the fingers l6 are mounted on laterally extending arms 3| on the brush-boxes 8', the finger-pivot being indicated at M. Because of this arrangement, a separate spring 32 is provided for each brush-finger i 6. As in the single-spring design of Figs. 1 and 2, the spring may be either a tension spring 32, as shown in Fig. 3, or a compression-spring 32, as shown in Fig. 4. In either case, the line of action and the spring-lever-arm are so chosen as to have the pressure-compensating advantages, and the over-center, locked, elevated finger position feature already described. i

While I have illustrated my invention in three preferred forms of embodiment, these forms are nevertheless only illustrative, as many changes may be made without departing from some of the broader features and advantages of my invention. I desire, therefore, that the appended claims shall be accorded the broadest construction consistent with their language.

I claim as my invention:

1. An opposed-angle double-brush brushholder comprising a V-shaped center part, an inclined brush-box on each side thereof, two upstanding finger-supporting arms, one on each side of the brushholder, two fingers, each finger being pivot ed on the finger-supporting arm on one side of the brushholder and extending over to the brushbox on the other side of the brushholdeneach finger having an extended, downwardly curved finger-arm having a finger-tip adapted to engage the top of a brush, and a linearly acting spring having its respective ends in engagement with the respective fingers for biasing the fingers toward the respective brushes.

2. The invention as defined in claim 1, characterized by said two fingers being identical and GERHARD P. LESSMANN.

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