US2737605A - Brush shift governor - Google Patents

Description

March 6, 1956 E. J. WAGNER ETAL BRUSH SHIFT GOVERNOR Filed April 29, 1953 w m M my mwa 27er QQ/ of brush shift mechanism is the United States Patent BRUSH lSHIFT yGOVERNOR Edward J. Wagner, Berwyn, and vFred C. Schwaneke, Chicago, Ill., assignors to Dormeyer Corporation, Chicago, Ill., a corporation of Illinois Application April -29, 1953, Serial No. 351,939 6 Claims. "(Cl. S10-241) This invention relates to a speed control mechanism for electric kitchen mixers and the like, and more Vparticularly to brush shift mechanism 'wherein control of the motor speed of the mixers is achieved by selective manual shifting of the axis of Vthe motor brushes.

It is customary in electric household appliances such as kitchen beaters or mixers to provide a manually adjustable speed control so that the motor speed and the speed of the beaters driven thereby can be selectively regulated to meet the specialized requirements ofparticular mixing operations. In a whipping operation, .for example, best results are obtained when the beaters rotate lat a relatively high speed, while .for stirring or folding the material a low speedis most desirable.

Numerous means have been employed Vfor providing speed control in electric mixer apparatus; y'among these are the variable resistance, governor and tapped field type of control. The most promising from the standpoint of economy, operating efliciency and providing an infinitely variable speed control is a brush shift arrangement. Shifting of the motor brushes as a means for achieving speed control, however, creates vspecial problems of wear, alignment, mounting, assembly, tolerances, arcing, etc., that have heretofore seriously discouraged the `use of speed control "by such means.

Important among the yproblems encountered in the use iprevention of uneven and rapid brush wear. Since the brushes ride upon .the motor commutator and are shifted-thereabout to effectuate the speed control, it is essential that Athe'brusheslie in a plane perpendicular to 'the rotational axis of the commutator and not be canted or angularly disposed relative thereto. If the 'brushes-are canted, the face of the brushes riding upon the peripheral surface of the commutator willengage the surface at v.a constantly changing angle as the brushes are shifted thereabout. It is apparent that the entire brush Vface will not then at all times engage the commutator and instead, only a portion of the brushface 'will ride upon fthe commutator and the effective contact area will change with each change in the position of the brushes about the commutator. The brushes will, therefore, have a short :life particularly because of the frequent changing of the speed setting that is required as the mixer is used in the numerous mixing operations.

The same result, Inamely, uneven and rapid wearing Vof the brushes wil occur if the 'brush holders move in a circular path not concentric with the commutator surface, as is the 'case with conventional constructions where manufacturing tolerancesinc'idental in the nature of conventional arrangements cause such result. This wear occurs because the brushes have their relative angulation with the peripheral surface ofthe commutator continually changing with their shifting and therefore the effective contact area between each brush and the commutator is reduced and is shifted from one .side to the .other side of Lthe brush as the'brushes arefshifted about the commutator. Whether the effective contact area be- ICC tween the brushes and the commutator is reduced due to non-concentricity of the rpath of brush movement about the commutatorfperiphery or canting of the brushes relative to the commutator periphery, brush wear is accelerated by a reduction in the effective contact area because arcing between the brushes and commutator segments is thereby greatly increased and arcing results in rapid brush deterioration.

Itis, accordingly, an object of this invention to provide a 'brush shift speed control for electric food mixers and the like that overcomes the difficulties set out above.

Another 'object of the invention is to provide a manually adjustable speed control for electric food or kitchen mixers wherein the speed control is effectuated by shifting the axis of the motor brushes while maintaining the brushes at a determined constant angular relationship relative to the rotational axis of the commutator and while insuring shifting of the brushes in an unconstrained arc that is concentric with the peripheral surface of the commutator.

Still another object is vto provide a brush shift speed control for mixers and the like wherein a brush support plate kis mounted within the mixer housing for pivotal movement about an axis coaxial with the rotational axis 'of the commutator and located in a plane substantially normal thereto whereby brushes carried by the plate have a constant angulation relative to the rotational axis of the commutator irrespective of the position to which the brushes are shifted, and irrespective of manufacturing tolerances.

A further object is the provision of a guide formed integrally with the bearing support for the motor shaft and providing a race or bearing surface for a brush sup- ,port yplate to maintain the same in substantially perpendicular relation to the motor shaft; the plate being urged against the race by spring switch contacts; and the periphery of the plate providing a portion, preferably arcuate, that is urged into engagement with the mixer housing by an alignment spring arranged with the plate and housing to prevent transversemovement of the plate during the pivoting thereof, whereby the pivotal axis of the plate is coaxial with the rotational axis of the commutator and the path of movement of the brushes in the shifting thereof to effect speed control is concentric with the periphery of the commutator.

Still a further object is to provide an annular guide formed integrally with the bearing support for the motor shaft that is operative to maintain the brush shift plate in proper alignment relative to the motor shaft and thereby the rotational axis of the commutator; the formation of the race integrally with the bearing support necessitating consideration of but a single manufacturing tolerance in providing proper plate alignment. Additional objects and advantages will appear as the specication proceeds.

An embodiment of the invention is illustrated in the accompanying drawing, in which- Figure l is a side view in elevation showing a mixer and in which portions are broken away and shown in section; Fig. 2 is a transverse sectional View taken on the line 2 2 of Fig. l; Fig. 3 is a transverse sectional View taken on the line 3-3 of Fig. 1; Fig. 4 is an end View in elevation of the contact plate; and Fig. 5 is a side view in elevation of a spring contact member.

Illustrated in the drawing is a mixer, or beater, A equipped with a handle B (shown in broken form), shafts C having beaters at oneend and being connected at their opposite end to the motor drive, lever D, that provides a release for removing andinserting the beater shafts C, base stand fins E, and an electric cable F for connecting the mixer `motor to a suitable source of power. The general structure ofthe mixer is well known in the art and for purposes of this invention a detailed discussion thereof is believed unnecessary.

The beater A is equipped with a housing that may be formed in two parts and provides a rear housing portion 11 and a front housing portion 12. Mounted within the rear housing portion '11 is a motor (not shown) that is equipped with a commutator 13 and the shaft 14 that is supported in a suitable bearing in the end of the rear casing portion 11. As is seen best in Fig. 1, the shaft 14 is supported adjacent its forward end within a bearing 15 that provides free rotationlof the shaft 14 therein. The bearing 15 is supported within a bearing support member 16 that is equipped centrally with a hub 17 having a suitable opening therein for receiving the bearing 15. The snap retainer 18 locks the bearing 15 within the hub 17 of the bearing support member. lf desired, a suitable gasket 19 may be provided within the opening of the hub 17 and may bear against the forward portion of the bearing 15; any conventional type of gasket may be employed and it will be understood that the gasket member may be lled with oil to provide lubrication for the bearing shaft. Y

Formed integrally with the bearing support member 16 is a guide 2t) that provides an annular race upon which a brush support plate 21. may ride; preferably the annular guide 2t? is formed integrally with the bearing support member 16 so that a single manufacturing tolerance exists between the hub 17 and the guide 20. Conveniently the bearing support 16 is a cast member and may be formed of any metal. I have found that aluminum provides excellent results.

r,The brush support plate 21 can best be seen by referring to Figs. 2 and 3. lt is seen in Fig. 2 that the brush support plate 21 has arcuate peripheral portions 22 and 23 that have substantially the same radius of curvature as the radius of the cylindrical casing portion 11 in which the support plate 21 is rotatably mounted. Between the arcuate portions 21 and 22 the plate is cut away to permit elongated bolts to extend through the casing portions to draw the same together. Threaded apertures within the casing portions 11 are illustrated in Fig. 2 and are designated by the numeral 24. An alignment spring 25 is secured to the plate 21 by rivets 26 or any other suitable means and has a V-shaped end 27 that bears against the inner surface of the casing. When in the position illustrated in Fig. 2, the V-shaped portion 27 is received within a recess 28 provided by the casing and this position indicates the off position of the manual motor control as will be described later. Also secured to the plate 21 by the rivets 26 is manually adjustable speed control lever 29 that extends outwardly from the casing 1t) and'may be easily gripped. The edge of the rear casing portion 11 is equipped with an elongated recess 30 in which the lever 29 rides. The walls at each end of the recess 3i) provide stop members to limit the movement of the lever 29.

T he plate member 21 isequipped with a central opening therethrough, having a considerably larger diameter than the diameter of the commutator 13, and receives the commutator therein. On its opposite side, the plate 21 is equipped wih a pair of brush holders 31 that are secured to the plate by rivets 32 or other suitable fastening devices. The brush holders 31 slidably receive brushes 33 therein and helical springs 34 resiliently urge the brushes 33 against the peripheral surface of the commutator 13.

Also carried by the plate 21 are a pair of spring switch contact members 35 secured to the plate by rivets. The contact members 35 are electrically connected to the brush holders 31, and through these members to the brushes 33. in the specic embodiment the electrical contact between the contacts 35 and the brush holders 31 is accomplished by using one of the rivets 32 to secure the brush holders to the plate 21. TheA forward casing portion 12 is also equipped with openings 36 adapted to receive the elongated bolts for drawing the rear and forward casingportions together.

As is best seen in Fig. 5, the contact members 35 are generally U-shaped and are equipped at their ends with a generally V-shaped contact point 37 that bears against the elongated contact strips 3S secured by rivets 39 to the contact mounting plate 40; the plate 40 is provided with an enlarged central opening 41 therethrough that receives the commutator 13, the member 40 being mounted within the rear casing portion 11 in spaced relation with the plate 21. Stop members 42 that may be formed integrally with the rear casing portion 11 align the support member 40 within the casing portion 11.

It is understood that the electric leads provided by the cable F extend through the rear casing portion 11 and are connected to the contact strips 38 mounted upon the support member 4t). The contact strips 38 and the spring contact members 3S are formed of a material having a relatively high electrical conductivity and thereby connect the brushes 33 and the commutator 13 to the electrical supply with negligible power loss.

Operation in the operation of the mixer, the electric cable F is connected to a source of power and upon gripping the lever 29 and moving the same about the casing 11 and within the limits provided by the recess 36, the plate 21 is shifted and the spring contact members 35 move into engagement with the contact strips 38 and the motor is electrically connected to the power source. lt is noted that shifting of the plate 21 rotates the brushes 33 about the commutator 13, and the axis of the brushes 33 relative to the axis of the field windings of the motor is shifted. It is well known that shifting of the brush axis will provide a change in operational speed of a motor; therefore, by shifting the plate 21 the brushes 33 carried thereby are rotated about the commutator 13, and the motor speed is determined by the particular setting of the brushes 33. In the view shown in Fig. 2, the speed of the motor is increased as the control lever 29 is moved clockwise, or to the right, about the housing portion 11.

It is seen, particularly in Fig. 1, that the contact plate 43 is held rigidly Within the casing by the stop members 42 and that the spring contact members 35 bear against the support plate 40 and thereby urge the brush-equipped plate 21 into engagement with the guide or race 20. The plate 21 is urged against the guide 20 irrespective of the rotated position of the plate and while the plate is rotated. Since the guide member is formed integrally with the bearing support 16 and the shaft 14 which provides the rotational axis of the commutator 13 is supported by the bearing support member, the guide 20 may be readily related thereto so that it defines a plane substantially perpendicular to the shaft 14 and thereby the rotational axis of the commutator 13. By insuring that the plate 21 is at all times in engagement'with the race or guide member 20, the plate is, therefore, maintained in the position that is substantially normal to the rotational axis of the commutator 13 and there will be no canting of the brushes carried by the plate relative to the commutator axis and peripheral surface. The spring contact members 35 serve the dual purpose of connecting the brushes 33 electrically to the power supply source and of urgingv the plate 21 into engagement with the race 20.

The bearing support member 16 being a cast piece and the race or guide 20 being formed integrally there with, only a single manufacturing tolerance is involved in providing the guide and the hub of the bearing support member. The plane defined by the guide 20 is therefore readily established at substantially right angles to the axis of the hub 17.

As seen in Fig. 2, the arcuate portion 22 of the plate 21 is urged into seating engagement upon the inner surface upon the cylindrical casing by the alignment spring 25. The alignment spring prevents transverse movement of the plate 21 during shifting thereof and maintains the path of movement of the brushes concentric with the periphery of the commutator 13. It is relatively unimportant in fabricating the plate 21 if permissible manufacturing tolerances result in irregularities in the plate periphery or cause plate dissymmetry relative to the center thereof, because the brushes will move in a path concentric with the periphery of the commutator during shifting of the plate and there will be therefore no change in the angularity of brushes respective to the commutator as the plate is shifted. Once the brushes are run in, the entire arcuate brush face will at all times engage the commutator regardless of the position to which the plate is shifted.

It is seen that the arc of movement of the brushes 33 about the periphery of the commutator 13 is concentric therewith, While the plate 21 is not canted and remains normal to the rotational axis of the commutator as the plate is shifted thereabout. Once that the brushes are run in, the arcuate face formed in each brush engages the commutator 13 throughout the entire area thereof irrespective of the position of the plate 21. No irregular or excessive wear of the brushes results from the brush shift speed control provided, and at the same time proper aligning of the brush-carrying plate 21 is easily accomplished in that a single manufacturing tolerance is involved in maintaining the plate substantially normal to the axis of the commutator 13, and the arcuate movement of the brush holders 31 is substantially concentric with the periphery of the commutator 13 irrespective of irregularities in the plate 21 and periphery thereof incidental in the manufacturing tolerances of the plate.

While in the foregoing specification an embodiment of the invention has been set out in considerable detail for purposes of illustration, it will be apparent to those skilled in the art that changes may be made in these details without departing from the spirit of the invention.

We claim:

l. In a mixer or the like having a housing and a commutator-equipped motor mounted therein, a plate rotatably mounted in said housing and being equipped with brushes resiliently urged against the peripheral surface of said commutator, means for rotating said plate to shift said brushes about said commutator, and resilient means operatively arranged to urge said plate against a suitably located guide element on said casing for maintaining the axis of rotation of said plate substantially concentric with the rotational axis of said commutator as said plate is rotated.

2. In a mixer or the like having a cylindrical housing and a commutator-equipped motor mounted therein, a plate rotatably mounted in said housing and being equipped with brushes resiliently urged against the peripheral surface of said commutator, means for rotating said plate to shift said brushes about said commutator, and at least one alignment spring carried by said plate and engageable with the inner surface of said housing for maintaining the axis of rotation of said plate substantially concentric with the rotational axis of said commutator as said plate is rotated.

3. In a mixer having a cylindrical housing and a commutator-equipped motor mounted therein, a plate rotatably mounted in said housing and having a central opening therethrough of greater diameter than said cornmutator and receiving said commutator therein, said plate being equipped with brushes resiliently urged against the* peripheral surface of said commutator, an alignment spring carried by said plate adjacent the periphery thereof and engageable with the inner surface of said housing, said plate having at least one arcuate peripheral portion opposite of said spring and having a radius substantially the same as the radius of saidA cylindrical housing, and

6 means for rotating said plate to shift said brushes about said commutator, said spring being operative to urge said arcuate portion of said plate into engagement with said housing to maintain the rotational axis of said plate subtantially concentric to the rotational axis of said commutator.

4. In a mixer or the like having a housing and a commutator-equipped motor mounted therein, a plate rotatably mounted in said housing and being equipped with brushes resiliently urged against the peripheral surface of said commutator, means for rotating said plate to shift said brushes about said commutator', resilient means operatively arranged to urge said plate against a suitably located guide element on said housing for n'raintaining the axis of rotation of said plate substantially concentric with the rotational axis of said commutator as said plate is rotated, guide means mounted within said housing and adapted to engage said plate and defining a plane substantially normal to the rotational axis of said commutator, and means for urging said plate into engagement with said guide means.

5. In a. mixer having a cylindrical housing and a commutator-equipped motor mounted therein, a plate rotatably mounted in said housing and being equipped with brushes resiliently urged against the peripheral surface of said commutator, means for rotating said plate to shift said brushes about said commutator, at least one alignment spring carried by said plate and engageable with the inner urface of said housing for maintaininT the axis of rotation of said plate substantially concentric to the rotational axis of said commutator as said plate is rotated, a bearing support member carried in said housing and equipped with a bearing providing a support for the shaft of said motor, said bearing support member providing a guide formed integrally therewith and adapted to engage said plate, said guide defining a plate substantially normal to the rotational axis of said commutator, and spring means urging said plate against said guide.

6. In a mixer, a cylindrical housing, a motor mounted within said housing and being equipped with a commutator and a motor shaft extending outwardly therefrom, a plate pivotally mounted within said housing and equipped with an enlarged central opening therethrough receiving said commutator therein, said plate being equipped with brushes and means resiliently urging said rushes into engagement with the peripheral surface of said commutator, said plate being equipped adjacent a peripheral edge thereof with a spring member resiliently engaging the inner surface of said cylindrical housing and with an arcuate peripheral portion substantially opposite to said spring member and having a radius substantially equal to the radius of said cylindrical housing, a bearing support member mounted within said housing and equipped with a bearing receiving an end of said motor shaft, said bearing support member being equipped with an integral guide providing an annular race adapted to engage said plate and defining a plane substantially normal to the rotational axis of said commutator, a contactequipped member mounted within said housing and being spaced from said plate, resilient contact members carried by said plate and adapted to engage the contacts carried by said member and resiliently biasing said plate against said annular race, and means for pivoting said plate within said housing to shift the brushes carried thereby about `said commutator.

References Cited in the le of this patent UNITED STATES PATENTS 761,985 Norris June 7, 1904 1,301,922 Endorf Apr. 29, 1919 1,744,998 Wisler Ian. 28, 1930 1,887,675 Brown Nov. 15, 1932

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