US1959056A - Brush holder - Google Patents

Description

M. F. JONES May 15, 1934.

BRUSH HOLDER Filed Aug. 20, 1932 2 Sheets-Sheet 1 INVENTOR Maw-ice F Jones.

ATTORNEY May 15, 1934.

M. F. JONES BRUSH HOLDER 1932 2 Sheets-Sheet 2 Filed Aug. 2O

INVENTOR Mal/770a F. Jones.

ATTORNEY WITNESSES:

Patented May 15, 1934 UNITED STATES PATENT OFFlCE BRUSH HOLDER Pennsylvania Application August 20, 1932, Serial No. 629,646

8 Claims.

My invention relates to brush holders which are particularly adapted for use on railway motors, where the space requirements are very difficult to meet, and where vibrational difiiculties are I particularly pronounced. My invention has particular relation to alternating current commutator railway motors where the requirements for brush holders of rugged construction, compact outline and operating characteristics with respect to commutation are particularly hard to meet.

My invention consists particularly in numerous improvements, hereinafter described and claimed, relative to the brush holder frame, the construction and composition of the pressure-finger member and other improvements hereinafter described and claimed and illustrated in the accompanying drawings wherein Figure 1 is a full-scale view of a pair of brush holders mounted in place on the commutator of an alternating current railway motor.

Fig. 2 is an enlarged double-scale view of a pressure-finger member, partly in section through its supporting shaft, with only a part of the brush holder frame being shown, most of the frame being broken away.

Fig. 3 is a cross-sectional view on line III--III of Fig. 2, and

Fig. 4 is a full-scale view, in side elevation, showing one of my brush holders complete, and

indicating a slight modification in the supporting pin for the pressure-finger member.

In Fig. 1, two of my brush holders 6 and 7 are shown mounted in back-to-back relation, supported by suitable insulators .3 and 9 from a supporting arm 11 of a brush-holder rocker ring orother supporting member on an alternating-current railway locomotive motor having a commutator cylinder which is indicated at 12. Each brush holder comprises a frame 13 which is provided with one or more slots or holes constituting brush boxes 14 for receiving one or more brushes 15. The brush-holder frame constitutes a simple, light-wei ht brush-holder body and box combined, cast from bronze, the casting being so simply and cheaply machined that it may be replaced, as a whole, when the box is worn, about as cheaply as the ordinary renewable box of a brush holder such as heretofore been widely used. This design has advantages over one utilizing an aluminum body and a bronze box, in the ease of soldering to my all-bronze body and bythe smaller cost of manufacture. The brush-holder frame carries a removable shaft 17 for supporting one or more pressure-finger members 18.

The portion of the pressure-finger member 18 which journals on the shaft 17 comprises a tubular bearing member 19 which is journaled on the shaft and which is made as long as possible, in order to afford the best possible bearing support, so as to avoid all bending or twisting. On one end of the tubular bearing member 19 is pressed a shouldered spring support 21 provided with a flange or shoulder 22 to which is silver soldered a cylindrical spring-enclosing housing 23 to be subsequently described, so that this cylindrical enclosing housing is supported at one of its ends from the shoulder 22 of the spring support 21. The spring support 21 is provided with a cylindrical seat 24 which engages the last convolution, or the last two convolutions, of a helical spring 25, the rest of which is free of contact with any portion of the pressure-finger member, so as to avoid all possible friction, thus enabling the brush-holder finger to exert as uniform a pressure as possible, on the brush, as it rides over the commutator. The end of the spring 25 may have an outwardly bent end which hooks into a perforation 26 in the shoulder 22 of the spring support 21.

It has been mentioned that the tubular bearing member 18 is as long as possible in order to obtain as much bearing surface as possible. The cylindrical enclosing member 23 is of equal length, in order to completely enclose the spring and protect it from dust. The spring, however, extends out beyond the tubular bearing member 19 and the enclosing cylindrical member 23, so as to be engaged by a novel spring-tension adjusting member which I make in the form of a worm wheel 28 having a cylindrical surface 29 in which worm gear teeth 30 are cut. The worm wheel 28 closes the open end of the annular recess which is provided between the tubular bearing member 19 and the cylindrical enveloping member 23 of the pressure finger member. The lateral surface of the worm wheel 28 is provided with an annular recess 32 which provides a seat 33 for the end of the spring 25. The spring is preferably further locked in the worm wheel by means of an outwardly bent end which engages a perforation 34 in the worm wheel.

The worm wheel 23 is rotatably adjusted by means of a short worm shaft 35 which is provided with worm teeth 36 operatively engaging the worm teeth 30 of the worm wheel 28. The worm shaft 35 is supported in a hole 38 drilled in the main brush-holder frame or casting 13. Although the worm-wheel driving-connection for effecting the spring-tension adjustment is ordinarily regarded as a non-reversible gearing, it is not strictly nonreversible in the presence of such vibration as it is subjected to in a brush holder. I provide, therefore, some means for shifting the worm shaft longitudinally in its supporting hole 38, utilizing for this purpose the end thrust which is produced by the tension of the spring trying to turn the worm wheel 28, and I provide some sort of locking means for locking the worm shaft against rotation when it is in its end-thrust position. A convenient means to this end is a slightly tapered fit of the worm shaft 35 in its hole 38, so that when it is thrust endwise it will wedge into a tight, nonrotating fit.

The worm shaft 35 and its hole 38 may also be very slightly elliptical, instead of exactly circular, in cross-section, the ellipticity being so slight that it could not be illustrated without exaggeration, yet sufiicient, in conjunction with the slight degree of tapering above described, to afford a very positive locking means for the worm shaft.

The end of the worm shaft 35 is provided with a screw-driver slot 40, so that a screw driver may be placed therein and utilized to first press the worm shaft axially, so as to disengage it from its locking fit, and then adjust it by a rotational movement in whichever direction may be necessary.

The pressure-finger member 18 is provided with an improved form of pressure-finger element 41 of very light sheet-metal construction which is made integral with the cylindrical spring-enclosing housing member 23. A piece of very thin sheet metal is bent, in its middle portion,tc form the cylindrical housing 23, the two ends of the sheet being brought together to form a tapering arm 42 extending out from the housing 23, the sheet-metal stock comprising the upper half of this arm being provided with an elevated portion or enlarged corrugation 43 for securing greater strength and rigidity. This outwardly extending arm 42 extends over the brush box 14 of the brush holder.

In order that the pressure finger of a brush holder may vibrate up and down at a very rapid rate while pressing the brush 15 (Fig. 1) down against the commutator 12, thus keeping the brush in firm contact with the commutator, notwithstanding inevitable unevennesses in the surface of the latter, it has long been recognized that the brush holder fingers must be made as light as possible. To this end, such a finger has commonly been made of aluminum or of aluminum alloys in an effort to utilize a material having as low a specific gravity as possible. Aluminum and aluminum alloys have presented real difficulties, however, in connection with soldering operations, and the thinness of the stock which could be utilized has been distinctly limited by the impossibility of obtaining a suitable temper in the aluminum or aluminum alloy available.

In accordance with my present invention, I have found that material advantages may be obtained by resorting to a material having a higher specific gravity than any aluminum alloy, and specifically I prefer to utilize a temperable copper alloy which is hardenable by heat treatment. A suitable alloy'for this purpose is a so-called tempaloy consisting of 4.2% nickel, 1.0% silicon and the remainder copper, with the exception of small quantities of so-called permissible impurities,

as described, for example, in a Corson article in the Electrical World for January 15, 1927. This material is obtained in sheet form which is first annealed so that it can be drawn and shaped. After having been shaped, as shown in Figs. 2

and 3, it is placed in a furnace, with silver solder ready in place for joining the flange 44 all around the finger arm extension 42, and for joining the cylindrical housing 23 to the shoulder 22 of the spring-support 21. This structure, thus formed, is put in a furnace at 850 C., and when it reaches about the temperature of the furnace it is taken out and quenched in wa-.

ter, but before it reaches the water it cools enough to set the silver solder, which hardens at about 720 C. The pressure-finger member is then put in a molten salt bath at some 400 or 450 C., in which it is heated without causing oxidation, and it is then permitted to cool slowly, while still in the salt bath, so that it finally becomes resilient and much harder than copper, and about as hard as bronze can be made by cold working, with the exception that the tempaloy material which I utilize becomes hard by heat treatment alone, without cold working. I have found that considerable advantage results from adopting this process and this material in the manufacture of the light pressurefinger members which are needed for brush holders.

After the pressure-finger member has been made, as above described, the tubular bearing member 19 is pressed into place, with a pressed fit, and the whole brush-finger element is then ready for assembly on the supporting shaft 17.

In some instances, it is desirable to utilize a light auxiliary spring for making the actual contact with the top of the brush 15. When this is utilized, it is placed on the under surface of the arm extension 42, as indicated at 50, being secured at its rear end by. a bolt 51 located close to the hub member of cylindrical housing 23. The front end of the aux liary spring 50 is biased to normally lie away from the bottom surface of the finger arm 42, and the extreme front end of the auxiliary spring carries a finger tip 52 of .a cadmium alloy of copper, for pressure against the top of the brush 15, said material being described and claimed in a patent of H. F. Hartman, No. 1,820,699, granted August 25, 1931 and assigned to the Westinghouse Electric and Manufacturing Company. By reason of the particular method of supporting and mounting the auxiliary spring 50, as above described, it follows that, as the finger tip 52 is pressed upwardly, the lateral surface of the auxiliary spring rolls up against the under surface of the rigid arm extension 42, so as to come into contact therewith at points further and further out along the arm, thereby adequately protecting the light auxiliary spring against breakage.

My brush holder is provided with a short flexible shunt 54, the top end of which is connected to the under side of the pressure-finger member 18, at a point 55 as close as possible to the hub member 23. The lower end of the shunt is joined to the brush holder body at a nearby point 55, as shown in Fig. 4, so that the shunt will be as short as possible and yet will be protected from undue bending stresses.

I have found it desirable to prevent substantially all current-flow across the journal bear-- ing surface on which the pressure-finger member is journaled. In order to provide the necessary insulation at this point in a manner which will take up as little room as possible, I prefer to utilize a special construction of the tubular bearing member 19 as shown in Fig. 2, utilizing, for this purpose, a pair of concentric metallic tubes 60 and 61 with a thin layer of insulation 62 between them. The inner one, 60, of these two tubes is originally a solid brass rod, around which is wound a thin layer of asbestos paper or other insulating material. A thin brass tube of slightly larger inner diameter is then slipped over the insulation, after which the whole is put through a machine which hammers down the outer tube 61 into a tight gripping engagement with the inner member 60, with the insulation 61 in between. To make possible this hammering operation, it is desirable to utilize a solid inner core 60, as just mentioned. After the hammering operation is completed, the inside hole may be bored out, producing the tubular, construction heretofore described.

An alternative means for securing the insulating effect for preventing any substantial current flow across the journal bearing is shown in Fig. 4 herein. The necessity for a special construction of the tubular bearing member 19 is avoided by making the surface of the supporting shaft 1'7 of insulating material such as a molded graphitized fibrous material 65 such as is described in the above-mentioned patent of H. F. Hartman. In this form of construction, I prefer to utilize a solid metallic core 66 for the rod 17, with only a thin tubular covering of insulating material 65, so as to obtain the necessary mechanical strength and freedom from warping.

My brush holder has been developed to meet, as nearly as possible, the following specifications which delineate the requirements for producing a brush holder of simpler and more rugged construction, more compact outline, and better operating characteristics which materially improve the commutation of large single-phase commutator motors such as are used on the locomolives of a main-line electrification.

1. The brush holders 6 and '7 must be mounted back-to-back in the space limitations shown in Fig. 1 in the particular motor illustrated in the drawings. Similar space limitations apply in other alternating-current railway motors, and to a somewhat less extent in all directand alter,- nating-current railway motors.

2. The finger length must be at least 2 inches from the center line of the brush box 14 to the center line of supporting shaft 17. The spring must be able to exert 4 pounds working force on the brush and it must not be overstressed when the finger is lifted to its maximum extent, in the process of replacing brushes. The working force of the spring should not vary more than one pound through the normal range of brush wear, which is 1%; inches on a brush 2 inches long. The working force should be adjustable, and such adjustment should be easy to make with the holder in place in the motor, and the adjusting means must be self looking or easily locked against vibration.

3. The finger should be free from any binding action and its bearing friction should be reduced to a minimum. The finger should have as low a moment of inertia about the shaft as is 1 possible, without sacrificing ample strength.

The finger should preferably be of resilient construction or it should have a resilient member between the contact tip and the remainder of the finger, although this resilient contact member may be frequently omitted,'if the finger is sufiiciently light.

4. The fingers should be insulated so as to prevent rapid wear caused by current pitting the bearing surfaces at the journal bearing support of the finger on the shaft 1'7.

' 5. The flexible shunt should have ample current-carrying capacity and should be so placed and flexed as to favor long life and minimum risk of breakage. In case of breakage, neither part of a broken shunt should be able to reach the commutator, the next adjacent brush holder, or any grounded parts of the motor.

6. The holder must have moderate cost and must require only reasonable manufacturing facilities. All wearing parts should be renewable with reasonable expense.

'7. The spring should be enclosed, in order to exclude dirt and to retain the broken parts in case of spring breakage.

It will be observed, from the foregoing de-' scription, that my new brush holder admirably meets each of these design requirements.

In constructions utilizing my auxiliary contact-making spring 50, it is quite desirable to arrange the design of the rigid arm-extension 42 of the fingers so that when a finger-lifting tool '70 (Fig. 3), is inserted in the brush holder by an operator desiring to lift the brush-holder fingers preparatory to changing brushes, the tool will not come in contact with the delicate auxiliary spring 50, thus avoiding all danger of overstressing this auxiliary spring. This is'done by providing a hole 71 in the rigid part of the finger 42 for receiving the lifting hook- '70, said hole being so placed that the hook cannot readily engage the auxiliary spring or the finger tip 52.

While I have described my invention in con siderable detail, and have explained the restric tions, materials and method of construction at present preferred, it will be understood that many changes may be made within the spirit of my invention. I desire, therefore, that the appended claims be accorded the broadest interpretation consistent with their language and the prior art.

I claim as my invention:

1. A brushholder for electrical machines comprising a brushholder frame having a brush box and a removably mounted shaft; a pressurefinger member comprising a laterally extending pressure finger extending over the brush box and adapted to engage the top of the brush, said pressure-finger member also having a tubular bearing member journaled on said shaft, a shouldered tubular spring-support secured over one end of said tubular bearing member, a helical spring having one end secured to said shouldered tubular spring-support and having the remainder thereof free, at all times, of contact with any part of said pressure-finger member, and an enclosing cylindrical housing secured at one end to the shoulder of said spring-support, said enclosing housing and said bearing member being of about the same axial length such that the helical spring extends axially beyond them at the end furthest from the spring-support, a cylindrical worm wheel mounted on said shaft for independent rotation at the end of the pressure-finger member from which said spring extends, said worm wheel having worm threads in its cylindrical surface and having means including an annular groove in its side face for receiving and securing the extending'end of said spring, and a worm shaft journaled in the brushholder frame,

said worm shaft having worm threads op'eraon the worm shaft by the spring-tension on the Worm wheel normally moves the worm shaft axially into a position in which it is locked against rotation.

2. Ln a brushholder, the combination with a supporting shaft and a helical biasing spring, of a brushholder finger member of the type having an enlarged hub mounted for journaled movement around said shaft and having an annular recess open at one end for receiving the major portion of said helical spring, so that one end of the spring extends therefrom, and a cylindrical worm wheel mounted on said shaft for independent rotation at the open end of the annular recess in said hub, said worm wheel having worm threads in its cylindrical surface and having means for securing the extending end of said spring, and a worm shaft journaled in the brushholder frame, said worm shaft having worm threads operatively engaging said worm wheel, said worm shaft further having a combined turning means and axial-thrust means at one end, and having a locking construction whereby the axial thrust exerted on the worm shaft by by the spring-tension on the worm wheel normally moves the worm shaft axially into a position in which it is locked against rotation.

- 3. In a brushholder, the combination with a supporting shaft and a helical biasing spring, of a brushholder finger member of the type having an enlarged hub mounted for journaled movement around said shaft and having an annular recess open at one end for receiving the major portion of said helical spring, so that one end of the spring extends therefrom, and a cylinjdrical worm wheel mounted on said shaft for independent rotation at the open end of the annular recess in said hub, said worm wheel having worm threads in its cylindrical surface and having means for securing the extending end of 1 said spring, and a worm shaft journaled in the brushholder frame, said worm shaft having worm threads operatively engaging said worm wheel, said worm shaft further having a com bined turning means and axial-thrust means at one end, and having a tapered fit in the brush: holder frame whereby the axial thrust exerted on the worm shaft by the spring-tension on the worm wheel normally moves the worm shaft axially into a-position in which it is'locked against rotation.

4. In a brushholder, the combination witha supporting shaft and a helical biasing. spring, of a brushholder finger member of the type having an enlarged hub mounted for journaled movement around said shaft and having an annular recess openat one end. for receiving the major portion of said helicalspring, so that one end' of the spring extends therefrom, and a cylindrical worm wheel mounted on said shaft for independent rotation at the open end of the an nular recess in said hub, said worm wheelhaving worm threads in its cylindrical surface and having means for securing the extending end of said spring, and a worm shaft journaled in the brushholder frame, said worm shaft having worm threads operativelyengaging said worm wheel, said worm shaft further having a combined turning means and axial-thrust means at one end, and having a tapered, slightly elliptical, fit in the brushholder frame whereby the axial'thrust exerted on the worm shaft by the spring-tension on the worm. wheel normally moves the worm shaft axially into a position in which it is locked against rotation. j

5. A brushholder for electrical machines come prising a brushholder frame having a brush box and a removably mounted shaft; a pressurefinger member comprising a laterally extending pressure finger extending over the brush box and adapted to engage the top of the brush, said pressure-finger member also having a tubular bearing member journaled on said shaft, a shouldered tubular spring-support secured over one end of said tubular bearing member, said springsupport having a flange or shoulder at .its'end and a short cylindrical seat adjacent to said flange or shoulder, a helical spring having one end secured to said cylindrical seat and having the remainder thereof free, at alltim es, of contact with any part of said pressure-finger member, and an enclosing cylindrical housing having one end disposed over, and secured to, the flange or shoulder of said spring-support, said enclosing housing and said bearing member being of about the same axial length such that the helical spring extends axially beyond them at the end furthest from the spring-support, a toothed Wheel mounted on said shaft for independent rotation at theend of the pressure-finger member from which said spring extends, and means for rotatably adjusting and locking said toothed wheel. 7 V a g 6. A brushholder adapted to support a brush in operative relation to a commutator cylinder of a dynamo-electric machine, said brushholder comprising a brushholder frame having a brush box and a removably mounted shaft; a pressurefinger member comprising a laterally extending pressure finger extending over the brush box and adapted to engage the top of the brush, said pressure-finger member also having an insulating tubular bearing member journaled on said shaft for supporting said pressure-finger member from the shaft and for substantially preventingcur rent-flow across the journal bearing, a shoul-. dered tubular spring-support secured over one end of said tubular bearing member, said spring, support having a flange or shoulder at its end and a short cylindrical seat adjacent to said flange or shoulder, a helical spring having one end secured to said cylindrical seat and having the remainder thereof free, at all times, of contact with any part of said pressure-finger mem ber, and an enclosing cylindrical housing having one end disposed over, and secured to, said flange or shoulder of said spring-support, said enclosing housing and said bearing member being of about the same axial length such that the helical spring extends axially beyond them at the end furthest from the spring-support, a toothed wheel mountedon'said shaft for independent rotation at the end of the pressure-finger member from which said spring extends, means for rotatably adjusting and locking said toothed wheel, and a flexible shunt having one end connected to the pressure- 5 finger member and having its other end connected to the brushholder frame, characterized by said insulating tubular bearing member comprising a pair of concentric metallic. tubes with a thin layer of insulation between them.

7. In a brushholder adapted to support a brush in operative relation to a commutator cylinder of a dynamo-electric machine, the combination with a supporting shaft and a helical biasing spring, of a brushholder finger member of the type hav- 145 ing an enlarged hub mounted for journaled movement around said shaft and having an annular recess open at one end for receiving the major portion of said helical spring, so that one end of the spring extends therefrom, means for sub ,59

stantially preventing current-flow across the journal bearing, a toothed Wheel mounted on said shaft for independent rotation at the end of the pressure-finger member from which said spring extends, means for rotatably adjusting and looking said toothed wheel, and a flexible shunt having one end connected to the pressure-finger member and having its other end connected to the brushholder frame, characterized by said means for substantially preventing current-flow across the journal member comprising an inner metallic core-member, a thin layer of insulation therearound, and a thin metallic tube tightly embracing said layer of insulation.

8. In a brushholder adapted to support a brush in operative relation to a commutator cylinder of a dynamo-electric machine, the combination comprising a brushholder frame having a brush box and a removably mounted shaft; a pressurefinger member comprising a tubular bearing member journaled on said shaft, a shouldered tubular spring-support carried by said tubular bearing member at one end thereof, said springsupport having a flange or shoulder at its end and a short cylindrical seat adjacent to said flange or shoulder, a helical spring having one end secured to said cylindrical seat and having the remainder thereof free, at all times, of contact with any part of said pressure-finger member, and a separate, light, hollow finger portion having a cylindrical part and an integral arm extension, the cylindrical part of said finger portion constituting an enclosing cylindrical housing having one end disposed over, and silver-soldered to, the flange or shoulder of said spring-support, said finger portion comprising a metallic material which is hardenable by heat treatment at a tem perature below the melting point of silver solder.

MAURICE F. JONES.

Images