US3146365A

US3146365A - Electrical machinery brush holder

Info

Publication number: US3146365A
Application number: US68731A
Authority: US
Inventors: Neal A Millar
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1960-11-14
Filing date: 1960-11-14
Publication date: 1964-08-25
Anticipated expiration: 1981-08-25

Description

Aug. 25, 1964 Filed Nov. 14 1960 ELECTRICAL MACHINERY BRUSH HOLDER 2 Sheets-Sheet 1 INVENTOR.

ATTORNEY Aug. 25, 1964 N. A. MILLAR ELECTRICAL MACHINERY BRUSH HOLDER 2 Sheets-Sheet Filed Nov. 14, 1960 INVENTOR. 77ml 77/111121 ATTORNFY United States Patent 3,146,365 ELECTRICAL MACHINERY BRUSH HOLDER Neal A. Miller, La Grange Park, Ill., assignor to General Motors Corporation, Detroit, Micln, a corporation of Delaware Filed Nov. 14, 1960, Ser. No. 68,731 3 Claims. (Cl. 310-246) This invention relates generally to a structure associated with the brushes of electric motors and generators and more particularly to means for holding one or more brushes in contact with a commutator.

In designing a brush holder for the brushes of electrical machinery there are several factors which must be considered. First, a simple but effective means must be provided to engage the brush held by the brush holder and press the brush against its associated commutator. As the brushes wear, this brush engaging means must maintain the brush in contact with the commutator and it is desirable that the pressure applied to the brush by such means be non-variable irrespective of brush length.

Since these brushes are replaced from time to time as they wear out, the means normally holding the brushes in contact with the commutator must be capable of being retracted so that the old brush can be removed and a new one inserted. Brush engaging means previously available have not been made to be easily retractable. Furthermore, such prior constructions have required that the service personnel hold the brush engaging means in the retracted position with one hand while removing and replacing the brushes with the other hand. The above procedure is awkward because when the removal and replacement of brushes requires both hands of the person servicing the electric machine he has great difficulty holding the brush engaging means in a retracted position while replacing the brushes. Naturally, the stiffer the springs holding the brushes in contact with the commutator, the more awkward and diflicult changing the brushes becomes. The present invention provides novel means for holding the brush holding means retracted to thereby facilitate removal and replacement of brushes.

In prior brush engaging construction, the fingers which were biased by the springs against the brushes to hold them in contact with the commutator were commonly pivoted at one end, usually by means of a rivet, pin or the equivalent. Such construction, however, resulted in considerable rivet or pin and spring breakage. While such rivets are still used, the present construction additionally provides for sliding movement of the pivoted ends of the fingers. This sliding movement allows the springsto locate the fingers so that the brush spring functions normally and without restriction. The sliding arrangement also allows shock and vibrating loads applied to the motor armature to produce a slight sliding action instead of an impact action as was produced when the ends of the fingers were pivotally anchored by rivets, etc. It has been found that this sliding feature practically eliminates rivet and spring failures.

' Because of operational and functional difiiculties which sometimes occur in electrical machinery of the kind concerned with here, there is always the possibility that socalled fiashovers (arcing) may occur in the vicinity of the brush holders. It is important that the functioning parts associated with the brush holder such as the means holding the brushes against the commutator be protected from these flashovers or arcing so that they continue to be operable after a flashover occurs. The present invention includes as an important part thereof a case which encloses the main functioning part of the means which holds the brushes against the commutator, i.e., the spring. In tests carried out utilizing the brush engaging means,

3,146,365 Patented Aug. 25, 1964 it has been found that after severe flashovers there was no damage to the spring or other parts of the brush .the utilization of split brushes in combination with means individually biasing each brush wafer against the commutator. This latter feature has the advantage of providing positive contact at all times of each brush wafer with the commutator thereby eliminating erratic commuation and reducing or eliminating commutator maintenance.

It is an object of this invention to provide means associated with an electrical brush holder which will hold the brushes against a commutator with constant nonvariable pressure regardless of brush length.

It is a further object of this invention to provide means for locking the brush engaging means in a retracted position to facilitate the removal and replacement of commutator brushes.

It is a further object of the invention to provide a unique pivotal means in which the brush engaging means is slidable when retracted to engage in a detent against which it is yieldably held by the spring also acting to apply the pressure to the brushes.

For a fuller understanding of the above and other ob jects of this invention, reference may be made to the accompanying detailed description and the drawings in which:

FIGURE 1 is a view in elevation with certain parts in section of a brush holder including the brush holder stud mounting the brush holder on an electrical machine and with the means for holding the brushes against the commutator shown in the retracted position.

FIGURE 2 is a View similar to FIGURE 1 except that the brush engaging fingers are shown holding the brushes against the commutator.

FIGURE 3 is a top view of the brush holder including the brush engaging means.

FIGURE 4 is a sectional view taken substantially on the line 4-4 of FIGURE 2 illustrating details of the novel sliding pivot means for the brush engaging fingers.

FIGURE 5 is a View taken substantially on the line 5-5 of FIGURE 2 showing details of the constant pressure springs which serve to bias the brush engaging fingers thereagainst and which also serve to yieldably hold the fingers in their retracted position when it is desired to change out the brushes.

FIGURE 6 is an end view of an electric motor showing how the brush holders are mounted on the motor frame and the brushes engage the commutator of the motor.

Referring first to FIGURE 6, there is shown an electric motor indicated generally by the numeral 2 which includes a frame 4. Mounted for rotation within the frame 4 is the motor armature which includes its commutator 6. Mounted at circumferential locations about the armature 6 are four brush holders each indicated by the numeral 8. These brush holders 8 are secured to the motor frame 4 by insulating brush holder studs 10.

Referring now to FIGURES 1, 2 and 3 it will be observed that each brush holder 8- has provided at one end thereof an opening 12 for mounting it on its brush holder stud 10. At its opposite end there is provide a slot 14 in which is slidably mounted a split brush consisting of two wafers each indicated by a numeral 16. The brush wafers 16 as noted in FIGURES 1 and 2 engage and make electrical contact with the commutator 6 at their ends 18. The opposite ends of waters 16 have electrically secured thereto the usual shunt leads 20 in turn secured at their opposite ends to a common terminal (see particularly FIGURE 3).

Mounted on each brush holder 8 is a brush holder spring cell'which is indicated generally by a numeral 22. This cell 22 may be secured to the brush holder in any suitable manner. ,In the present instance it may be done. by passing a bolt, stud or spindle 23through the rivet 50 and" the brush holder; The cell 22 includes a frame or case 24 having a base 26,

opposite sides

28 and 30, and a longitudinally extending detent tab 32 forming an extension of the base 261' Mounted'side byside between the opposite sides 28 and; 30-of case 24on rollers or spools 34 are a-pair of non-cumulative force springs 36 which resemble rolls of metal tape woundon spools 34. This is the force utilized to;hold the brush wafers 16 against thecommutator andiis of the-same magnitude regardless of extended length as long as there is at least one turn of the coil remaining on the spools 34. The

outsiderends 38' of each spring 36 areriveted to a brush engaging finger intermediate the ends of the associated finger. E'ach'fingewttlisprovided with a brush engaging portion 42 at one end thereof and a straight portion 4-4 which .is pivotally but slidably anchored in a pivoting assembly 46. Eachpivoting assembly 46 includes two blocks 4'8whichare pivotally secured'side by side betweenthe

sides

28 and 30 by a rivet 50. E'ach'block 48 is provided with" a guide. track 52in which an end 44 of the associated finger 40 is longitudinally slidable.

The operation of the brush engaging means is as follows: Referringto FIG. 2, it will be observed that the spring 36 by reason of its tendency to wind on the roller or spool 34 causes the finger 40, including the brush engaging portion 42",. to engage the outer ends of the brush wafers 16 16', each finger 40 may be individually retracted by pulling, back on its brush engaging end 42' so that the'end 44 of finger 40 slides in its guide 52 until it engages the detent 32 against which it'will be yieldably held by the tension, in spring 3,6. These fingers 40 are shown in their retractedtposition in FIGURE 1. After the brush has beenremoved and replaced, the fingers may again be moved to their operative position against thev outer ends of the brush wafers by simply pulling outwardly on the brush engaging portions'42 so that the end 44 nov longer engages in the detent, 32. I

From the foregoing. descriptiomit may be appreciated that a simple but extremely effective brush holder spring cell has been provided whichlis easily adaptable to many brush holders for electrical machinery. It also has the desirablefeature of providing constant and uniform pressure to hold the brushes against the commutator, As previously emphasized, the brush engaging fingers are easily retractable to a locked position to facilitate changing out of the motor brushes;

I claim:

1. Cellular means for holding a brush in contact with a commutator comprising a supporting case, a brush engaging finger mounted in said case and having a free brush engaging portion extending therefrom, a spring secured to said finger and to said case adaptedvto cause. said finger to exert a non-variable pressure on the brush it is adapted to contact when said case is secured in juxtaposed relation thereto, and means to lock said finger in a retracted position in order to remove and replace the brush normally engaged thereby including guide means slidably guiding said finger and pivotally secured to said case and a detent on the opposite side of the point of pivotal connection of said guide means to saidcase from" said brush engaging portion to which anend of said finger is movable and against which said end is yieldably held by said spring when said finger is retracted.

2. Cellular meansfor holding a brush in contact with a commutator comprising asupporting case, a brush engaging finger mounted in said case and having a free brush engaging portion extending therefrom, a spring whose bias is the same irrespective of its deflection secured to said finger and to said case adapted to cause said finger to exert a constant pressure on the brush it is adapted to contact when said case is secured in juxtaposed relation thereto, and means to lock said finger in a retracted position in order to remove and replace the brush normally engaged thereby including guide means slidably guiding said finger and pivotally secured to said case, and a detent'on the opposite side of the point of piovtal connection of said guide means to said case from said brush engaging portion to which'an end of said finger is movable and against which said end is yieldably held by said spring when said finger is retracted.

3. In combination with an electrical machine havinga commutator, a brushholder mounted adjacentsaid commutator, a brush mounted in said brush holder and engaging said commutator, means for holding said brush incontact With said commutator comprising a brush engaging finger having a free brush engaging portion extending therefrom, a guide for said finger slidably supporting said finger intermediate the ends thereof, and a springadapted to bias said finger to cause said finger to exert a constant presure on said brush, said finger being retractable against the bias of said spring, and means to lock said finger in aretracted position including a detent to which the end of said finger opposite said free brush engaging portion may be retracted and against which said end is yieldably held by said spring when said finger is retracted.-

References Cited in the file of this patent UNITED STATES PATENTS

Claims

1. CELLULAR MEANS FOR HOLDING A BRUSH IN CONTACT WITH A COMMUTATOR COMPRISING A SUPPORTING CASE, A BRUSH ENGAGING FINGER MOUNTED IN SAID CASE AND HAVING A FREE BRUSH ENGAGING PORTION EXTENDING THEREFROM, A SPRING SECURED TO SAID FINGER AND TO SAID CASE ADAPTED TO CAUSE SAID FINGER TO EXERT A NON-VARIABLE PRESSURE ON THE BRUSH IT IS ADAPTED TO CONTACT WHEN SAID CASE IS SECURED IN JUXTAPOSED RELATION THERETO, AND MEANS TO LOCK SAID FINGER IN A RETRACTED POSITION IN ORDER TO REMOVE AND REPLACE THE BRUSH NORMALLY ENGAGED THEREBY INCLUDING GUIDE MEANS SLIDABLY GUIDING SAID FINGER AND PIVOTALLY SECURED TO SAID CASE AND A DETENT ON THE OPPOSITE SIDE OF THE POINT OF PIVOTAL CONNECTION OF SAID GUIDE MEANS TO SAID CASE FROM SAID BRUSH ENGAGING PORTION TO WHICH AN END OF SAID FINGER IS MOVABLE AND AGAINST WHICH SAID END IS YIELDABLY HELD BY SAID SPRING WHEN SAID FINGER IS RETRACTED.