US1422188A - Brush holder for electric machines - Google Patents

Description

E. DORFFEL- BRUSH HOLDER FOR ELECTRIC MACHINES. APPLICATXONFILED MAR. '10, 192 1 1 422 1 Patented July 11, 1922.

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- UNITED STATES ERNST noRrrEL, or BEBNBURG, GERMANY.

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Specification of Letters Patent.

- Patented July11, 1922.

Application filed March 10, 1921. Serial No. 451,361.

To all whom it may concern:

Be it known that I, Dr. Ing. ERNST DcRrrnL, a citizen of the German Republic, residing at Bernburg, in the State of Saxony-Anhalt, Germany, have invented certain new and useful Improvements in a Brush Holder for Electric Machines (for which. I have obtained patents in Germany, No. 312,- 218, dated February 22, 1918, and No. 311.- 993. dated March 6 1918), of which the following isa specification.

The brush holders now in use can be divided into two main groups.

Vith one of the groups the brush is movably mounted in the brush holder frame fixed upon the brush-holder bolt, the brush being pressed upon the slip-ring or collector either directly by a spring or through the intermediary of a lever pivotally mounted and influenced by a spring. i

In rough service it happens that the frame which guides the brush collects dirt so that, notwithstanding the high spring-pressure,

the brush is not always pressed tightly upon the slip ring. .The link of the pressure lever getting dirty this lever is frequently jammed in its position so that the spring is prevented from acting uponthe brush.

In order to prevent the brush from being insufficiently pressed upon the collector ring, springs are used which are very strong so that the'wear of the brush and of the collector ring becomes. great.

Vith the second group of brush holders the brush is rigidly connected with the holderwhich is adapted to revolve around 7 a sleeve surrounding the bolt, said holder being pressed upon the slip ring or commutator through the action of a spring.

The inconvenience of the brush holders known construction consists in the great wear of this revolving link with rough servbrush is caused. The strong pull spring is however not capable of preventing the jamming of the dirty holder.

According to this invention-the brush is not movably but rigidly mounted in a triotionless holder. All pivot pins which cause the above mentioned inconveniences are dispensed with and a blade spring which is bent more or less and whichis put under stress of tension, bending or compressing is substi tuted for said pivot pin, an edge being used forthe same purpose in a third form of construction.

In order that the invention may be clearly understood, I shall proceed to describe the same with reference to the example of construction shown in the accompanying drawings, wherein Figs. 1, 2 and 3 are sectional side elevations of three forms of construction of the improved brush holder.

In the first form of construction shown in Fig. l the joint isreplaced by a blade spring a, which might be composed'of several thin blade springs. The strength of this blade spring is calculated so that the blade spring actsmerely as a frictionless connecting element but not as means for pressing the brush upon the slip ring or collector.

A separate spring 6 serves for pressing the brush upon the slip ring or collector, which is arranged so that the torsional moment of the holder caused by said spring f Z) remains constant in the entire range of wear of the brush; 7 i V In the second form'of construction shown in Fig. 2 the revolving joint which causes the aforesaid objections is replaced by one or several superposed blade springs a which are bent more or less and which are almost exclusively put under' tensile stress. This blade spring can be very weak, as it is put only under tensile stress; it it therefore very flexible and opposes to the movement of the holder only a scarcelyperceptible resistance, serving in nowise for pressing the brush upon the slip ring or collector.

The torsional moment of the holder required for the uniform pressing of the brush upon the collector is produced exclusively by the pull spring I) which is mounted in such a manner that the torsional moment of the holder remains approximately constant for the entire range of wear of the brush so that it is not necessary to adjust the brush holder when the brush is worn. The abutments 0 and d limit the movement of the holder in downward direction. f is the elastic current conductor for the brush.

In the third form of construction shown in Fig. 3 the same object is attained by using, instead of a blade spring a frictionless edge 9 or points. The tension spring 6 produces at the various positions of the brush holder a constant torsional moment and presses the edge y into the bearing disk.

For securing the connection between the edge and the bearing disk a second spring h can be used which produces no torsional mo ment, the point of attachment of said spring coinciding almost with the edge. This spring it can however be omitted in most cases.

The value of the invention consists in this that the brush holders of improved construction ensure a uniform pressing on of the brush even in the dirtiest service exposed to moisture, dust and to strongly oxidizing influences, owing to the suppression of any sliding friction or of any journal friction, so that consequently the considerably excessive pressure between brush and slip ring or commutator which is indispensable with other constructions, owing to the braking effects occurring with the same, can be dispensed with.

A much less pressure can be used from the beginning than was hitherto possible this pressure never wirying even when the holder gets very dirty. The consequence hereof is that fewer brushes and slip rings are used than is the case at present so that in most cases even the expensive and complicated short-circuiting and brush-lifting devices can be dispensed with. All the interruptions of service are thus avoided which are caused at present by imperfect application of the brush or by the short-circuiting device.

There have already become known frictionless brush holders in which one or sev eral blade springs are substituted for the joint but with. such holders the torsional mo ment is either produced by the said blade spring or by a separate spring, the torsional moment of the holder in the range of wear of the brush remaining however not constant.

There have further become known brush holders with revolving oint having tension springs which are constructed and mounted so that the pressure with which. the brush is pressed upon the slip ring remains ap proximately constant in the range of wear of the brush.

The improvedbrush holders according to this invention combine the two advantages mentioned, namely the absence of friction and the approximately constant pressure of the brush without requiring any adjusting in the range of wear of the brush.

I claim:

1. In an electric machine, a brush-holder, av supporting member, a yieldable bladespring connecting the brush-holder to the supporting member and being approximately neutral in tendency with respect to the com mutator so as to exert no appreciable pressure on the commutator and at the same time serve as a frictionless pivot, and a second spring for pressing the brush upon the commutator arranged in such manner that the torsional moment exerted by said second spring remains approximately constant in the entire range of wear of the brush, for the purposes set forth.

2. In an electric machine. a bruslrholder, a supporting member, a yieldable bladespring connecting the lnush-holder to the supporting member and beingapproximately neutral in tendency with respect to the commutator so as to exert no appreciable pressure on the commutator and at the same time serve as a frictionless pivot, and a second contractile spring connecting the brushholder to the supporting member and lying between the blade-spring and the commutator and being arranged to press the brush upon the commutator in such manner that the torsional moment exerted by said second spring remains approximately constant in the entire range of wear of the brush, for the purposes set forth.

3. In an electric machine, a brush-holder, a supporting member, a yieldable bladespring connecting the brush-holder to the supporting member and being approximatcly neutral in tendency with respect to the commutator so as to exert no appreciable pressure on the commutator and at the same time serve as a frictionless pivot, a second spring for pressing the brush upon the commutator arranged in such manner that the torsional moment exerted by said second spring remains approximately constant in the entire range of wear of the brush and a knife-edge bearii'ig between the brush-holder and the supporting member.

In testimony whereof I attix my signature in presence of two witnesses.

DB. Inc. nnnsr nonrrnn Witnesses ALBERT Bonmr, PAUL FRUMBHOLE.

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