US3722144A

US3722144A - Method and machine to de-bur commutator bars

Info

Publication number: US3722144A
Application number: US00131642A
Authority: US
Inventors: C Rickrode; C Becker
Original assignee: CAM Industries Inc
Current assignee: CAM Industries Inc
Priority date: 1971-04-06
Filing date: 1971-04-06
Publication date: 1973-03-27
Anticipated expiration: 1990-03-27

Abstract

This invention comprises a method and one embodiment of a machine for automatically deburring the opposite sharp edges of commutator bars of the armatures of electric motors and generators by the use of an abrading brush rotatably driven in opposition to the direction of rotation of the commutator while the brush traverses the bars thereof longitudinally. At the completion of deburring one similar edge of each bar, the rotary directions of the brush and commutator are reversed to deburr the opposite edges of the bars.

Description

United States Patent Rickrode et a]. 51 Mar. 27, 1973 [5 METHOD AND MACHINE TO DE-BUR 3,556,752 1 1971 Wilson ..51 295 COMMUTATOR BARS 789,917 5/1905 Jordan t ..51/244 2,784,537 3/1957 Schinske ..51/244 [751 Gym New 0mm; 1 727 112 9/1929 Munday ..51/244 Charles A. Becker, Hanover, both of Primary Examiner-Donald G. Kelly [73] Assignee: Cam Industries, Inc., Hanover, Pa. Attorney-C. l-lercus Just [22] Filed: Apr. 6, 1971 ABSTRACT 21 A l.N.:131642 1 pp 0 This invention comprises a method and one embodiment of a machine for automatically deburring the op- U-S- Cl. R, posite sharp edges of commutator bars of the arma- [51] l- 1,001 1324b 5/04 324d 13/02 tures of electric motors and generators by the use of [58] Fleld of Search ..5 l/34 G, 34 R, 34 C, 34 D, an abrading brush rotatably driven in opposition to h 51/34 34 50 105 289 direction of rotation of the commutator while the 295 brush traverses the bars thereof longitudinally. At the completion of deburring one similar edge of each bar, [56] References C'ted the rotary directions of the brush and commutator are UNITED STATES PATENTS reversed to deburr the opposite edges of the bars.

1,968,550 7/1934 Barnes ..5 H289 R X 14 Claims, 6 Drawing Figures PATENTEDHARNIQB SHEET 10F 2 INVENTORS. CWARLES ,4. bake z 'm/L JI [PICK/2017+:

PATENTEBHARZ? I975 SHEET 2 OF 2 INVENTORS. ("Hues ,4. Baa/am Cm/L JI RIC/(ROBE TORNiY METHOD AND MACHINE TO DE-BUR COMMUTATOR BARS BACKGROUND OF THE INVENTION Commutators comprise a circular series of radially extending bars of predetermined length which are provided on one end of armatures of many types of electric motors and generators. The bars are insulated from each other by relatively thin sheets of mica. The overall exterior surface of a commutator of this type is substantially cylindrical and the inner ends of said bars are appropriately connected electrically to the windings of the armature. The commutatorsare engaged by carbon brushes which slidably engage the bars of the commutator in order to establish certain successive momentary electrical contacts therewith. The brushes normally are spring-pressed toward the commutator so that there is continual, gradual wearing of the outer surfaces of the commutator bars and the ends of the carbon brushes which engage the same.

When commutators are being manufactured, the outer surface thereof usually is machined to establish a uniform overall cylindrical configuration. At this stage, the outer edges of the mica insulation strips normally are coextensive with the outer surfaces of the commutator bars which usually are made of copper. It is necessary to cut away the outer edge portions of the mica strips to a predetermined depth because it is harder than the copper and causes undue wear of carbon brushes if they are permitted to engage the same. Such cutting away of the outer edges of the mica strips is known as undercutting the same. Such undercutting is performed on specialized machines adapted to that purpose and provided with narrow cutters capable of effectively cutting or milling the outer edges of the mica sheets without materially disturbing the adjacent surfaces of the copper bars.

Further, when commutators become worn to such extent that the outer edges of the insulating strips are substantially even with the worn outer surfaces of the copper bars, it is necessary to machine the commutators to reestablish a desired operative surface. When in such worn condition, it is not uncommon that the surfaces of the bars which are engaged by'the carbon brushes actually have shallow grooves worn therein by said brushes and it is necessary to restore the outer surface of the commutator to a substantially cylindrical shape and thereby remove said grooved effects. This is done by machining the outer surface of the commutator in an appropriate cutting lathe and, as in regard to when the armature is newly manufactured, it then is necessary to undercut the insulating strips of mica to dispose the outer edges thereof at a level below the overall cylindrical outer surface of the commutator.

Following such machining operations, either during the restoration of a worn commutator the operative condition or when manufacturing a new commutator initially, the machining of the commutator on a lathe, or the like, produces opposite edges on the outer peripheral surfaces of the copper commutator bars which are very sharp and frequently actually include small laterally projecting burs which result from the cutting of the bars by the cutter of such lathe. In order to suitably finish such outer surfaces of the commutator bars, and preferably polish the same prior to completing the manufacturing or repairing operation so that the commutator is adapted; to be engaged operatively by carbon brushes, it is necessary to remove such sharp edges and burrs, or deburrsuch commutator bars, before the commutator is placed in operation.

In accordance with current practice, such deburring and polishing of commutators, as now practiced, is a manual operation and comprises the use of special scraping or cutting tools, usually hand made by the individual workman who is to perform the operation, so as to suit his particular technique. One common type of relatively crude tool presently used comprises grinding a hooked arrangement on one end of a discarded hack saw blade. One edge of the hook is sharpened and is adapted to be drawn along the sharp, machined edge of each commutator bar, longitudinally, to cut therefrom a small thread or ribbon, or shavings, of copper constituting the outermost corner portion of each bar. This operation must be done carefully so as to uniformally bevel or round off the outer edges of the commutator bars. In shop parlance, such operation is similar to what is known as breaking an edge of a work piece or object.

By performing such deburring operation by manual means as described above, it is obvious that care must be exercised by the mechanic undertaking the operation to besure that similar edges of successive commutator bars are substantially equally rounded, cut-away or deburred for the full length of each bar, and being sure that such deburring of any bar is not omitted. Usually, the similar edge of each bar (left or right side) is deburred in succession and then the opposite edges of bars are successively deburred by such manual operations. Particularly in regard to deburring commutator bars of armatures of relatively large size, whereby the amount of metal removed from each edge of the bars comprises a small ribbon of noticable size, an appreciable amount of manual pulling force is required to achieve the removal of such edges.

' Particularly if such bars are of substantial length,

such as of the order of four or five inches, or more, it can be appreciated that, on occasions, the cutting or shaving tool conceivably will slip and, due to the substantial manual force being exerted, the edge of the tool will be drawn, inadvertently and accidentally, diagonally across the faces of adjoining bars and this results in the commutator having to be refinished upon a lathe, for example, to remove the cut or scratch if the same is of sufficient depth to require it, followed by performing a complete additional deburring operation.

As a result of the manual refinishing or deburring operations as now practiced, it is not uncommon for such deburring operation on a commutator of substantial size to require as much as several hours to complete the same, following which it is necessary to polish the deburred, outer surfaces of the commutator bars with relatively fine grades of non-metallic abrasive cloth or the like. Accordingly, it can be seen that deburring either new or refinished commutators by the foregoing means is time consuming and, correspondingly, it is costly, especially if accidental cutting or scratching of the commutator occurs during the deburring operations, as described above, whereby additional time is required to complete the deburring and polishing of an acceptable commutator, whether on a newly manufactured or refinished, used armature.

BACKGROUND OF THE INVENTION It is the principal object of the present invention to provide a method, and a machine to perform the same, by which the aforementioned manual operations, as presently employed to deburr commutator bars, are eliminated and, instead, uniform deburring of the opposite edges of machined outer surfaces of the commutator bars is achieved automatically by power means, without the possibility of accidentally damaging the commutator during the deburring operation, except possibly through the exercise of gross negligence, and the entire deburring operation of commutators of even relatively large sizes is accomplished in a matter of relatively few minutes as compared with hours required to effect corresponding deburring by manual operations. The maximum width of the commutator bars also is preserved so as to provide maximum commutation.

It is another object of the invention to perform such deburring of the opposite edges of commutator bars by utilizing an abrasive brush mounted for rotation while peripherally engaging the outer surfaces of the commutator bars, the rotary direction of the brush being the same as that of the commutator to produce opposite peripheral directions at the line of engagement. The commutator during such operation, is rotated very slowly, while the abrading brush is rotated at a relatively high speed, thereby not only deburring the bars but also removing any thin side mica strips from either side of the bars which may result from improper undercutting of the mica.

It is a further object of the invention to provide means by which the aforementioned abrading brush, which is narrower than the length of the commutator bars, may be moved in opposite axial directions parallel to the axis of the commutator, through a distance substantially equal to the length of the commutator bars, whereby after a few minutes, the leading edge of each commutator bar has been buffed and thereby deburred by the abrading brush sufficiently to break" the corresponding edges of the bars, uniformally, to render them capable of normal engagement by carbon brushes, following which the directions of rotation of both the armature and abrading brush are reversed in order to debur the opposite edges of each bar in similar manner to that described above, after which the uniformally deburred commutator bars may be polished appropriately by conventional means.

It is still another object of the invention to mount the abrading brush upon a head supported for movement in two directions respectively transverse to each other, one of said directions being parallel to the axis of the armature and the other one being perpendicular thereto, whereby said brush may be reciprocated to traverse the commutator bars as described above and movement of said head in said aforementioned transverse direction is possible to effect desired abrasive engagement of the abrading brush with the edges of the commutator bars which are to be deburred thereby, such transverse movement usually being of limited extent according to the width of the brush selected for any given operation.

Still further objects of the invention are to provide simple but effective power-operated driving means to rotate the armature and the commutator carried thereby, provide relatively slow speed power means to reciprocate the head which carries the abrading wheel relatively slowly to traverse the commutator bars, and relatively high speed power means carried by said head which supports the brush and is directly connected to said brush to rotate the same at relatively high speed.

A still further object of the invention is to provide an abrading brush which is of smaller diameter than that of the commutator in order to achieve effective abrading of substantially only the leading edges of the commutator bars as the commutator is slowly rotated in opposition to the direction of rotation of the abrading brush.

Details of the foregoing objects and of the invention,

as well as other objects thereof, are set forth in the following specification and illustrated in the accompanying drawings comprising a part thereof.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of an exemplary machine adapted to deburr the commutators of armatures supported by the machine and thereby perform a deburring method comprising part of the invention.

FIG. 2 is a vertical elevation, partly in section, of portions of the machine shown in FIG. I as seen on the line 2--2 of said figure.

FIG. 3 is an enlarged, fragmentary elevation, partly in vertical section, showing an abrading brush comprising part of the invention and illustrating a preferred means for mounting the same upon a drive shaft therefor.

FIG. 4 is a fragmentary side elevation of portions of an abrading brush and a section of a commutator being abraded thereby, generally as seen from the line 4-4 of FIG. 2.

FIG. 5 is a fragmentary, enlarged end elevation, generally as seen on the line 5-5 of FIG. 4, and showing an exemplary manner of engagement of the abrading wheel with the commutator bars of an armature.

FIG. 6 is a fragmentary end elevation of an exemplary pair of commutator bars, the opposite edges of which have been deburred in accordance with the principles of the present invention.

DETAILED DESCRIPTION Referring to FIG. 1, an exemplary machine is illustrated therein capable of performing a preferred method by which the opposite edges of commutator bars are deburred in accordance with the principles of the invention. Said machine includes a base 10 supportably mounted upon a suitable surface, such as a floor 12. A pair of vertically extending standards or supports 14 and 16 are mounted on base 10 by appropriate means and are capable of being fixed in desired operative positions thereon. The supports 14 and 16 respectively support headstocks l8 and 20 which respectively support tapered centers 22 and 24 adapted to be adjusted longitudinally within the headstocks, respectively for rotatable engagement with the opposite ends of a shaft 26 of an armature 28 having an exemplary commutator 30 on one end thereof.

The upstanding support 16, rearwardly of the headstock 20, as viewed in FIG. 1, supports a head 32 having a substantial. number of different elements and mechanisms thereon. For example, vertically extending means 34 thereon has bearings 36 at opposite ends thereof, as shown in FIG. 2, respectively supporting the opposite end portions of a shaft 38 having driving pulleys 40 at the upper end thereof and the lower end thereof supporting a small milling cutter, not shown, by which the mica strips of the commutator 30 may be undercut. Accordingly, it will be seen that the present invention which comprises means for deburring the opposite edges of commutator bars is adapted to be supported upon a so-called undercutting machine to which various items have been added by means of which such deburring operations may be performed, as described in detail hereinafter.

The head 32 is supported upon the upper end of vertical support 16 for movement in two directions respectively transverse to each other. As seen in FIG. 1, the upper end of support 16 carries a relatively broad, dove-tailed guideway 42 which is intended to be exemplary of any suitable guide means by which the head 32 may be moved transversely to the axis of the armature 28. The lower portion of the head 32 is provided with a base member 44, the lower end of which is slidably complementary in shape to the dove-tailed guideway 42. As seen from FIG. 2, the guideway 42 is supported by a heavy-duty type laterally extending bracket 46. Conventional, preferably hand-operated means comprising a screw 48 and hand wheel 50, see FIG. 2, are interconnected between the guideway 42 and base member 44 in such manner that the entire head 32 and all elements carried thereby may be moved toward and from the axis of the armature 28 and commutator 30, for purposes to be described.

Fixed to and extending upward from base member 44 of head 32 is a vertical bracket 51, best shown in FIG. 2, which, at its upper end, supports a horizontally extending guideway 52 provided with a guide groove 54 which is dove-tail shape in cross-section, as can be seen from FIG. 2. The guideway 52 supports a longitudinally extending plate 56 having a pair of

parallel guide members

58 and 60 thereon which have opposing surfaces that are complementary to the dove-tail shaped configuration of guide groove 54. The lower edge of guide member 58 is provided with a row of gear teeth to constitute an elongated rack 62 or, if desired, a separate rack may be provided .which is fixed to the guide member 58 by appropriate means.

Mounted upon the horizontal guideway 52, which is stationary with respect to the base member 44 of head 32, is a flange-mounted gear head type electric motor 64 having a shaft which projects toward plate 56. The outer end of said shaft has a pinion gear 66 fixed thereto which meshes with the rack 62. The motor 64 is of the reversible type, operation of which is controlled by appropriate switches contained in control box 68 shown in FIG. 2 and located appropriately for easy access to anoperator so that he may control and observe the deburring operation described in detail hereinafter.

Referring to FIG. 1, the plate 56, which is horizontally reciprocable in opposite directions with respect to the relatively stationary horizontal guideway 52 also supports a vertical mounting plate 70 which, for purposes of simplifying the view, has been omitted in FIG. 2. It will be understood that the same is substantially in line with the shaft 38 if it were illustrated in said figure. Said plate 70, at its upper end, supports an electric motor 72 having pulleys 74 on the upper end thereof to accommodate driving belts 76 which also extend around the pulleys 40 on the upper end of shaft 38 and serve to drive the same when undercutting operations are to be performed.

Particularly to adapt the present invention to the structure which is also adapted to perform undercutting operations, as described hereinabove, the longitudinally extending plate 56 is provided with an elongated supporting plate 78 which is connected by a plurality of bolts or screws 80 to the face of plate 56 which is nearest the axis of the commutator 30. Connected to the lower edge of and extending along the plate 78 for the full length thereof is an elongated bearing 82 through which a drive shaft 84 extends, the opposite ends of said shaft projecting respectively beyond the opposite ends of the bearing 82.

Referring to FIG. 1, it will be seen that the right-hand end of shaft 84, as viewed in said figure, is provided with a driven pulley 86. Supported on the forward face of plate 56, as viewed in FIG. 1, is another electric motor 88 which is of a relatively high speed type. The shaft thereof supports a drive pulley 90 and a belt 92 extends around the same and also around the driven pulley 86 for purposes of rotating the drive shaft 84.

Referring particularly to FIG. 3, the end 94 of drive shaft 84 which is opposite that to which the driven pulley 86 is connected extends sufficiently beyond the adjacent end of the bearing 82 that the socket of a short head shaft 96 may be disposed upon the end 94 of shaft 84 and is secured thereto by an exemplary set screw 98. Relative rotation between the end 94 of the drive shaft and the head shaft 96 may further be prevented by means of a short radial key 100 on shaft 84 which is received within a longitudinally extending notch 102 in the head shaft 96, as clearly shown in FIG. 3.

The head shaft 96 supports an abrading brush 106 which, in appearance and construction, somewhat resembles a conventional abrading wire brush. Preferably however, the circular flanged central portion 108 of the brush supports radially extending bristles 110 which, in accordance with the preferred type that is well adapted to perform the method comprising part of the present invention, are formed from durable synthetic resin, such as sold under the commercial trade name Nylon. To render the same even more effective for abrading purposes in accordance with the present invention, it is additionally preferred that the bristles be coated or impregnated with abrading material such as aluminum oxide. Brushes 106 are obtainable in various diameters and widths or thickness.

The diameter of the brush 106 preferably is selected in accordance with the diameter of the commutator 30 which is to be deburred thereby. Preferably, the diameter of the brush 106 should be appreciably smaller than the diameter of the commutator 30 with which it is to be used. The relative proportion of brush and commutator as illustrated in FIG. 2 has been found to be highly satisfactory. The preferred method of deburring to be performed by the machine described and illustrated herein, and in accordance with the preferred method comprising the present invention, is as follows.

Referring to FIG. 5, a fragmentary portion of the commutator 30, otherwise illustrated in FIGS. 1 and 2, is shown in enlarged manner. It will be seen that the commutator comprises a plurality of commutator bars 112 which are slightly wedged-shaped. Successive bars 1 12 are separated in insulated manner by strips of mica 1 14 which are of uniform thickness and are firmly compressed between adjacent commutator bars 1 12. As

shown in FIG. 5, the outer edges of the mica strips 1 14 have been undercut, or cut away at the outer edges, so as to space said outer edges of the mica strips radially inward from the outer surfaces 1 16 of the commutator bars 112.

The commutator bars 112 are of conventional type and generally are made from an appropriate copper alloy. Therefore, they are of a softer nature than the strips of insulating mica 114. The brush 106 is firmly clamped to the outer end of head shaft 96 by means of a clamping bolt 118 which is threaded axially into the outer end of said head shaft 96, as shown in FIG. 3. The commutator 30 is rotated at a relatively slow speed, such as of the order of between about 50 and 55 rpm, in the direction of the arrow shown in FIG. 5, while the deburring or abrading brush 106 is rotated in the same rotary direction, as indicated by the directional arrows shown in FIG. adjacent the periphery of bristles 110 of the brush in order to produce opposite peripheral directions of movement at the line of contact thereof.

The relatively radial position of the periphery of the bristles 110 of the brush 106 and the outer peripheral surfaces 1 16 of the commutator is such that the tip portions of the bristles 110 will be slightly flexed, as shown in exemplary manner in FIG. 5, at the portion thereof engaging successively the leading edges 120 of the commutator bars 112. It has beenfound that there is a greater tendency for the abrasive bristles 110 of the brush 106 to attack the sharp edges of the outer surfaces of the bars 112 than the peripheral surfaces 116 thereof. Such abrasive engagement of the bristles 110 of the high speed brush with the leading edges 120 of the commutator bars 112 quite rapidly removes a limited amount of the material at the edges of the bars incident to the commutator being rotated a limit number of revolutions while engaged by the brush 106, while both' are'rotating, as well as traversing the bars of the commutator.

To provide effective deburring of the leadingedges 120 of the commutator bars 112, the brush 106 is rotated at relatively high speed, such as of the order of between 3,400 and 4,000 rpm. The motor 88, which drives the brush, is selected to deliver that range of speed. While this is occurring, the armature to which the commutator 30 is connected is rotated at relatively slow speed by means comprising a gear head motor 122. Preferably, such motor is supported in outboard manner upon a mounting plate 124 which is pivotally connected at one end to a bracket 126 connected to base of the machine, as best shown in FIG. 2, but also illustrated in FIG. 1.

The motor shaft has a pulley 128 connected thereto and the driving belt 130 extends around pulley 128 and also around the armature 28. By operating the pulley 128 at speeds within the range of approximately 160 rpm, and considering the fact that the diameter of the pulley 128 is very substantially smaller than that of the armature 28, it will be seen that the actual speed thereof and, correspondingly, the speed of the commutator 30, will be approximately between about 50' and 55 rpm.

Without restriction thereto, it will be seen that the arrangement shown in FIG. 2 with respect to the mounting of the motor 122 and especially with the weight thereof being outboard with respect to the pivot by which the mounting plate 124 is connected to the bracket 126, such weight. of the motor will provide adequate tension of the belt 130 which extends around the pulley 128 and armature 28 that adequate driving friction will be provided between the motor 122 and armature 28.

Referring to FIG. 6, there is'illustrated a fragmentary side elevation of the outer portions of a pair of adjacent commutator bars 112 on which the outer edges 132 of the opposite sides of the outer peripheral surfaces 116 of the contact bars have been deburred adequately so that when the surfaces 116 are engaged by carbon brushes or the like, there will be no tendency for the brushes to sustain unusual wear as would be occasioned in the event the sharp opposite edges of the commutator bars 112 were not deburred.

It will be seen from the exemplary illustration shown in FIG. 6, which is intended to be illustrative only, rather than restrictive, that only a very limited amount of metal has been removed from the corners along the opposite outer side edges of the commutator bars 1 12. However, the amount of metal removed by the abrading brush 106 is uniform for each bar and for each of said opposite edges of the commutator bars, which amount is adequate to operatively condition the bars in a manner which equals or exceeds deburring operations which are effected manually in accordance with current practice.

OPERATION OF THE MACHINE The preferred manner of effecting the method of deburring commutator bars in accordance with the invention and the operation of the machine illustrated in the drawings and described hereinabove is as follows. Either a newly manufactured armature 28 and its commutator 30 or a used armature and its commutator is mounted in the machine between the centers 22 and 24 so as to be freely rotatable thereon. Appropriate control means for the gearhead motor 122 is contained within the control box 68 and is initiated to energize reversible slow speed motor 122 after driving belt 130 has been mounted around the armature 28 and pulley 128.

The direction of rotation of the armature 28 is also established by such operation and it will be assumed that the armature is rotated clockwise, as viewed in FIG. 2. An appropriate switch means also provided in control box 68 is closed to energize the reversible motor 88 which rotates the abrading brush 106 in the direction of the arrow shown in FIG. 2, at a relatively high rate of speed in contrast to the relatively slow speed at which the armature 28 and commutator 30 are rotated in the same rotary direction with respect to the brush to produce opposite peripheral directions thereof at the line of contact.

Manually adjustable hand wheel 50 then is actuated in the desired direction to move the base member 40 of head 32 horizontally toward the axis of the armature 28, as viewed in FIG. 2, until the bristles of the abrading brush 106 are brought into peripheral engagement with the outer surfaces 116 of the commutator bars 112, such movement being of such extent that the tip portions of the bristles 110 are slightly flexed by engagement thereof with the leading corners or edges 120 of the commutator bars 112 as illustrated in exemplary manner in FIG. 5.

When the foregoing relationship between the brush 106 and commutator 30 has been established, reversible slow speed gear head traversing motor 64 then is energized by actuation of a push button switch means also provided therefor on the control box 68. Timing and switch means in the control box not only will initiate actuation of the reversible motor 64 in the desired directions but, a suitable adjustable timing switch 133 also is provided in the control box assembly 68, which is automatically reversible in accordance with a desired setting of the timing switch. This will cause the longitudinal plate 56, which carries the bearing 82 and rotatable shaft 84 which drives the abrading brush 106 in the desired direction, to traverse the full length of the commutator bars 112 and will automatically reciprocate in such traversing movements in opposite directions, as illustrated by the exemplary arrow shown in FIG. 4, for a distance substantially equal to the length of said commutator bars 1 12.

If desired, a suction fan unit 134, shown in FIG. 2, which has an inlet adjacent one surface of the brush 106, also may be provided and energized to withdraw and either contain abraded material removed from the edges 120 of the commutator bars 112 in a suitable receptacle. or discharge such removed material into a removal conduit, as desired. Such reciprocating abrad ing movement is continued for an interval of several minutes while the commutator 30 is slowly rotated a number of revolutions so that the traversing of the brush 106 occurs for a limited number of reciprocations. Such operation is timed and set so as to be adequate to remove sufficient metal to produce substantially uniform deburred outer edges 132 upon the leading edges 120 of the commutator bars as illustrated in FIGS. Sand 6. In addition, due to improper undercutting of the mica strips, such as by a narrow saw or cutting tool not cutting the mica for the full width thereof, thin strips of mica occasionally mayremain along one or the other sides of the commutator bars. The above-described deburring operation also removes at least any objectionable portions of such mica which is known as side-mica, when the same exist.

After leading edges of each of the commutator bars have been deburred while the commutator is rotating in a predetermined direction, the motors 88 and 122 then are momentarily de-energized by means of operating the control switches therefor'in control box 68, followed by either such switches being reversed orby additional switches being closed which will energize both of said motors respectively to revolve in opposite directions, whereby the opposite side edges of the commutator bars 112 become the leading edges under such circumstances and the bristles of the abrading brush 106 will effect removal of the metal comprising the sharp edges thereof until a desired deburred configuration 132 is provided on such opposite edges and thereby produce outer peripheral surfaces 116 on the commutator bars which will terminate along the opposite edges thereof in deburred edge surfaces 132 which are substantially equal to each other and to all ill other corresponding deburred edges on all of the other commutator bars. Following such deburring operation, the outer surfaces 116 of the bars 112 may be polished by conventional means such as fine grade non-metallic abrasive cloth.

The foregoing operation is capable of being achieved within the matter of a few minutes, even when the diameter and length of the commutator are relatively large, whereby such operation may be accomplished uniformly and automatically in a period of time which is approximately of the order of only 2 or 3 percent of the amount of time required to achieve the same or even more inferior deburring by manual means of the type described above.

Upon the tip portion of the bristles 110 of the brush 106 becoming worn to limited extents, full operative abrading engagement of the brush with an armature may be accomplished by slightly adjusting the manually operable hand wheel 50 in the desired direction so as to move the axis of the brush a small distance radially toward the axis of the armature and thereby establish the desired maximum efficient abrading action of the brush with respect to the commutator bar.

From the foregoing, it will be seen that the method and apparatus comprising the present invention enables a commutator undercutting machine additionally to deburr machined bars on the commutator, followed by final polishing of the commutator. In particular, the

extraneous side-mice which may remain between the commutator bars is relieved and is either removed au-' tomatically during the process or easily is removed by an air hose or pick. Final inspection time also is minimized.

While the invention has been described and illustrated in its several preferred embodiments, it should be understood that the invention is not to be limited to the precise details herein illustrated and described since the same may be carried out in other ways falling within the scope of the invention as illustrated and described.

We claim:

1. A method of deburring the metal bars of the commutator of an armature of electric motors and generators which have been machined to provide an operating surface thereon, said process comprising the steps of mounting the shaft of said armature for rotation about a fixed axis, mounting a brush having flexible abrading bristles for rotation about an axis parallel to the axis of said armature, adjusting the periphery of said brush relative to the periphery of said commutator of said armature to effect abrading contact with the leading edges of the commutator bars by said bristles being slightly flexed, rotating said armature in one rotary direction at a predetermined relatively slow speed, rotating said brush in the same rotary direction at a substantially higher rotary speed than said armature to produce opposite peripheral directionsof movement 'at the line of engagement, and continuing such rotations of said brush and armature until the sharp corners of the leading edges of said commutator bars have been removed to a sufficient extent that no sharp contact with a coacting brush will occur when the armature is placed in use, and reversing the directions of rotation of both said brush and armature to remove the sharp corners of the opposite edges of said commutator bars similarly to that of said aforementioned leading edges.

2. The method according to claim 1 including the ad ditional step of traversing said armature commutator with said brush successively in opposite axial directions for substantially the full length of the commutator bars while abrading the same with said brush.

3. The method according to claim 1 wherein the diameter of said brush is less than that of said armature commutator and the range of rotary speed of said armature is between about 45 and 60 rpm and the range of rotary speed of said brush is substantially between 3,000 and 4,000 rpm.

4. The method according to claim 1 wherein said abrading of said armature commutator respectively in each direction of rotation of the commutator and brush is continued for a period of not appreciably greater than 2 minutes.

5. A machine operable to de-burr the opposite sharp edges of machined commutator bars of an electric armature comprising in combination, means adapted to support an electric armature and commutator for rotation upon a predetermined axis, power means connectable to said armature to rotate the same in desired rotary directions, a rotary abrading brush having bristles, means to support said brush and flex the bristles thereof when in peripheral rotary engagement with the outer surfaces of the bars of a commutator to be deburred, power means operable to rotate said brush in the same rotary directions to that in which said armature is rotated to produce opposite peripheral directions of movement at the line of engagement of said brush and armature, and means operable to maintain the tips of the bristles of said brush due to such flexed condition substantially in uniform abrading contact with the leading edges of the bars of a commutator to be de-burred as they are rotatably moved into engagement with said brush.

6. The deburring machine according to claim 5 further including means operable to reverse the rotary directions of said power means which effect rotation of said armature and abrading brush, thereby to deburr the opposite edges of commutator bars from those deburred by said brush while said armature and brush were rotating to deburr the first-mentioned edges of said commutator bars.

7. The deburring machine according to claim 5 in which the width of said deburring brush is less than the length of the commutator bars of an armature to be deburred thereby, and said machine further including a head upon which said abrading brush is mounted rotatably, and reversible power means interconnected to said head and operable to reciprocate said head and the abrading brush carried thereby in opposite axial directions parallel to the axis of said armature.

8. The deburring machine according to claim 7 further including control means for said reversible power means operable automatically to reciprocably move said head successively in opposite directions for distances substantially equal to the lengths of commutator bars to be deburred bysaid brush.

9. The deburring mac me according to claim 7 further including a toothed rack connected to said head and extending thereon longitudinally parallel to the axis of a commutator to be deburred, and said reversible power means comprising a gearhead electric motor having a spur gear driven thereby and engaging said rack to reciprocate said head and deburring brush carried thereby as aforesaid.

10. The de-burring machine according to claim 5 further including base means, upright supports carried by said base in spaced relationship to each other and respectively having centers operable to engage the opposite ends of the shaft of an armature to be de-burred and support the same rotatably, said power means connectable to said armature to rotate it comprising a reversible gearhead electric motor supported by said base of said machine, a rotary driving member connected to the shaft of said motor and having a diameter substantially less than that of said armature to be deburred, and an endless flexible driven member extending around said rotary driving member and also around said armature to rotate the same in selected rotary directions at relatively slow speed compared to the rotary speed of said brush.

11. The de-burn'ng machine according to claim 10 in which said gearhead motor is connected to a support pivotally connected at one end to said base means, and said motor being connected in outboard manner to said support, whereby the weight of said motor tends to move the same away from the axis of said motor and thereby tension said belt into driving engagement with said pulley and an armature adapted to be driven thereby. I

12. The deburring machine according to claim 5 further including a head, a shaft rotatably supported thereby, means on one end of said shaft adapted to have said abrading brush connected thereto for rotation thereby, a base for said head, guide means for said head on said base extending transversely to the axis of said shaft, and hand operated means interconnected to said head and operable to move said head upon said transverse guide means in opposite directions to adjust the abrading engagement of said brush with commutator bars to be abraded thereby.

13. The deburring machine according to claim 12 in which said power means for said brush comprises a reversible electric motor interconnected to the opposite end of said rotatable shaft for said brush and operable to rotate said shaft and drive said brush at rotary speeds substantially higher than those at which a commutator is rotated while being deburred.

14. The deburring machine according to claim 5 in which the diameter of said abrading brush is substantially less than that of a commutator to be deburred thereby.

Claims

1. A method of deburring the metal bars of the commutator of an armature of electric motors and generators which have been machined to provide an operating surface thereon, said process comprising the steps of mounting the shaft of said armature for rotation about a fixed axis, mounting a brush having flexible abrading bristles for rotation about an axis parallel to the axis of said armature, adjusting the periphery of said brush relative to the periphery of said commutator of said armature to effect abrading contact with the leading edges of the commutator bars by said bristles being slightly flexed, rotating said armature in one rotary direction at a predetermined relatively slow speed, rotating said brush in the same rotary direction at a substantially higher rotary speed than said armature to produce opposite peripheral directions of movement at the line of engagement, and continuing such rotations of said brush and armature until the sharp corners of the leading edges of said commutator bars have been removed to a sufficient extent that no sharp contact with a coacting brush will occur when the armature is placed in use, and reversing the directions of rotation of both said brush and armature to remove the sharp corners of the opposite edges of said commutator bars similarly to that of said aforementioned leading edges.

2. The method according to claim 1 including the additional step of traversing said armature commutator with said brush successively in opposite axial directions for substantially the full length of the commutator bars while abrading the same with said brush.

5. A machine operable to de-burr the opposite sharp edges of machined commutator bars of an electric armature comprising in combination, means adapted to support an electric armature and commutator for rotation upon a predetermined axis, power means connectable to said armature to rotate the same in desired rotary directions, a rotary abrading brush having bristles, means to support said brush and flex the bristles thereof when in peripheral rotary engagement with the outer surfaces of the bars of a commutator to be de-burred, power means operable to rotate said brush in the same rotary directions to that in which said armature is rotated to produce opposite peripheral directions of movement at the line of engagement of said brush and armature, and means operable to maintain the tips of the bristles of said brush due to such flexed condition substantially in uniform abrading contact with the leading edges of the bars of a commutator to be de-burred as they are rotatably moved into engagement with said brush.

8. The deburring machine according to claim 7 further including control means for said reversible power means operable automatically to reciprocably move said head successively in opposite directions for distances substantially equal to the lengths of commutator bars to be deburred by said brush.

9. The deburring machine according to claim 7 further including a toothed rack connected to said head and extending thereon longitudinally parallel to the axis of a commutator to be deburred, and said reversible power means comprising a gearhead electric motor having a spur gear driven thereby and engaging said rack to reciprocate said head and deburring brush carried thereby as aforesaid.

10. The de-burring machine according to claim 5 further including base means, upright supports carried by said base in spaced relationship to each other and respectively having centers operable to engage the opposite ends of the shaft of an armature to be de-burred and support the same rotatably, said power means connectable to said armature to rotate it comprising a reversible gearhead electric motor supported by said base of said machine, a rotary driving member connected to the shaft of said motor and having a diameter substantially less than that of said armature to be de-burred, and an endless flexible driven member extending around said rotary driving member and also around said armature to rotate the same in selected rotary directions at relatively slow speed compared to the rotary speed of said brush.

11. The de-burring machine according to claim 10 in which said gearhead motor is connected to a support pivotally connected at one end to said base means, and said motor being connected in outboard manner to said support, whereby the weight of said motor tends to move the same away from the axis of said motor and thereby tension said belt into driving engagement with said pulley and an armature adapted to be driven thereby.