Brush Holder Assembly

Abstract

The invention disclosed is a brush holder assembly for use in electric motors. It may be of any general shape and is characterized by suitable structure that provides an interference fit between the brush and its holder whereby the spring-biased brush is wedged in the holder as a preassembly and is then easily released by a slight pressure to permit the brush to smoothly reciprocate in the brush holder against the commutator.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention pertains to a brush holder assembly as used in an electric motor frame wherein the assembly has means by which the brush may be wedged in the brush holder for easy preassembly and placement in position in the frame and the brush may then be easily released for smooth slidable movement in the holder for biased contact against the commutator.

2. Description of the Prior Art

Many types of brush holder assemblies have been devised for different specific applications and these have generally been directed to easily removable assemblies and are generally directed to improvements of individual parts or reducing the cost and number of parts of the assembly in order to adapt it for machine assembly as opposed to manual assembly and to improve the repairability of the device. Such improvements may prevent rotation, expelling, or twisting movement of the brush or other parts and are all aimed at simplifying the brush assembly structure.

None of the prior art has successfully overcome the inherent tendency of the outwardly-biased brush from interfering with the commutator during assembly or replacement. Various clamping means must be used to hold the brush back in the brush holder so that it does not interfere or strike the commutator until it is in position.

SUMMARY OF THE INVENTION

Briefly described, the invention is directed to a brush holder assembly that is used in an electric motor frame which is designed for holding a rotating commutator. The brush holder assembly is improved for easy assembly or replacement by providing a tubular holder in the frame with its spring-biased brush member in the holder and slidable longitudinally thereof. Integral fixed means is provided on one of the members and is disposed between them as a permanent part to provide a frictional restraint of the sliding movement between the brush and holder. This restraint may be a dimple in the holder whereby the brush is pushed back in the holder and jammed or wedged by the dimple so the brush is held in the holder and not expelled by the spring. The location of the holding means is predetermined and is generally in the half of the assembly that is away from the commutator for free movement in operation. A suitable means such as an opening in the brush holder is provided so that a tool may be put through the opening to push the brush away from its frictional restraint and allow it to freely slide in the normal fashion, once it is in the desired operating position. Thus, the main object is to provide an improved brush holder assembly that ensures that the brush and holder stay together as a compact assembly without other external means even though the brush is biased by an internal spring. The assembly is then placed in position and the brush easily released or freed for normal operation.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a partial perspective view of a typical motor frame showing a brush holder assembly removed for convenience;

FIG. 2 is a detailed perspective view of a brush holder showing frictional modifications;

FIG. 3 is a partial cross-sectional view through a brush holder showing a different frictional modification with the brush in two positions;

FIG. 4 is a cut-away perspective showing carried a preferred modification; and

FIG. 5 is a partial sectional view showing still another modification.

DESCRIPTION OF THE PREFERRED EMBODIMENT

While the invention is applicable to any brush holder assembly, regardless of its shape, it will be convenient to describe it in the more common rectangular shape as used on many motors.

Referring to FIG. 1, there is shown an electric motor frame 10 that is designed to support a rotating armature 12 with the usual commutator 14. The frame may be of any material such as a die casting or molded plastic and is supplied with upstanding brush holder lugs 16 having openings 18 therethrough for the reception of a brush holder assembly generally indicated at 20.

In the assembly of such electric motors, whether by automated machinery or manual labor, it is generally desired to preassemble the brush holder assembly 20 with its internal carbon brush and spiral spring as a package. This is then inserted into opening 18 so the brush contacts commutator 14 in the normal manner. One of the troublesome assembly or repair problems is the tendency of the brush, because of its outward spring-bias, to interfere or get in the way of the commutator or just plain drop out of the assembly. It is the purpose of this invention to provide a convenient and useful brush holder assembly wherein the parts stay together until they are conveniently and easily released once the assembly is in position on the motor frame.

Referring next to FIG. 2, a typical brush holder assembly is shown. This generally comprises a tubular holder member 22 that will usually be made of a flat piece of brass that is machine folded to provide a tube open at one or both ends. Any form of tubular member of different materials and formed in any suitable manner or cross section may be used. The tubular holder 22 is provided with lug 24 for connection with the motor wiring. In order to retain the holder in the frame, any suitable retention means well-known in the art may be employed. Typically, as shown in FIG. 2, tubular holder 22 may be folded from a flat piece of sheet material to provide a rectangular opening 26 centered on a slit extending down one side of the holder with the free ends or four corners formed at the intersections of the slit and the rectangular opening being bent outwardly of the holder to form resilient tabs 28. When the holder is slidably positioned in opening 18 of the frame as seen in FIG. 1, forward flexible tabs 28 are forced down and past an abutment 30 to drop into slot 32. The rear tabs 28 lock on the other surface of abutment 30 and the holder is then locked against longitudinal movement in opening 18. It may be released by insertion of a suitable tool to depress the forward tabs 28 and withdraw the holder.

In accordance with the invention, it is desired to provide means whereby the brush can be retained within the holder so the entire holder containing the spring-pressed brush can be handled as an integral preassembly without external clamps or the like and without fear of losing the brush or having it interfere with any assembly or repair operation or, in other words, with just the use of the operating parts themselves to keep the brush in its holder and out of the way. To this end, as best seen in FIG. 4, it is necessary to provide means to retain brush 34 within the holder since the brush is constantly urged out of the end of the holder under the bias effect of spring 36 which bears against spring bearing surface 38 which may be on the closed end surface 40 remote from the commutator as seen in FIG. 1. In order to restrain the brush from being slidable longitudinally of holder 22, a suitable means is provided as part of the brush or holder whereby the brush can be wedged or jammed in position and held. This is most easily accomplished by an indented fixed ridge or rib portion 42 that is integral with and punched or pressed into the tubular holder 22 a distance substantially equal to the clearance between the brush and holder and at a predetermined location in the holder as shown. Generally, this location is in the rearward half of the holder or that portion that is remote from the commutator end to restrain movement over a portion of the tube holder and allow the brush to slide freely at the other end. The indentation is merely sufficient in depth generally substantially equal to the clearance between the parts, for the brush to be wedged when it is pushed under the indentation as shown in FIG. 4. Of course, any suitable fixed and integral indentation such as dimple 44 or a similar rib 46 may be used as shown in FIG. 2 and these are merely modifications. Additionally, as shown in FIG. 3, the frictionally restraining means may comprise a punched-in portion 48 that can be an actual cut in the holder. FIG. 3 also shows the brush 34 in its wedged or solid line position to the right where it is entirely held within the holder and its extended or released dotted line position to the left where it is against commutator 14 in operation.

In all these modifications it is essential that means be provided for releasing the wedged or jammed brush once the assembly is in position. To this end the holder is provided with an access opening means which, in the closed end surface 40 modification of tubular holder shown, may comprise a convenient central aperture 50 through which any suitable pointed tool may be inserted through the opening and inner spring to free or release the brush 34 by a slight push on its center to snap it into its dotted line operating position of FIG. 3.

Referring next to FIG. 5, a modification that is substantially the reversal of those previously described is shown. In this modification the tubular holder 22 may have a fixed integral portion 52 extending inwardly a suitable distance for wedging over a portion of the holder. To cooperate with this portion, brush 54 may have a raised rib 56 that extends toward the tubular holder 22 and may ride in a suitable track 58. The track may be omitted if the extending rib 56 is circumferentially spaced around the brush 54 or plural portions 52 are used as will be apparent. Again, the wedging or frictionally restraining means is released by a suitable tool through aperture 50.

It will be apparent that the punched-in or restraining portions may be provided as an integral part of either the holder or the brush or both, the preferred embodiment being on the holder because of ease of formation and cost. Thus, the frictional restraint must be formed by a wedging or jamming action between the members regardless of how it is obtained. The distance of the punched-in portion is substantially equal to the clearance between the members so it depends on the actual parts. Also, the aperture opening means obviously can be located any place it is desired to gain access to the wedged brush to free it and several embodiments are shown by way of example. It will be apparent that the simple expedient of wedging the brush in the holder eliminates all separate clamps and parts and provides for an easy preassembly whereby the brush is firmly held within the holder solely by action between the two for either manual or machine assembly or subsequent repair without the usual difficulty of the spring-biased brush tending to drop or hang out the end of the holder. It is also conveniently snapped free or released with a slight push to break the wedging action whereby the brush is then snapped against the commutator for normal operation.

While there have been shown preferred forms of the invention, obvious equivalent variations are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practised, otherwise than as specifically described, and the claims are intended to cover such equivalent variations.

Claims

I claim:

1. In combination with an electric motor having a frame and openings therein for brushes to contact a commutator, the improvement in a brush holder assembly comprising,

a tubular holder member in said frame,

a spring-biased brush member disposed in and slidable longitudinally of said holder,

integrally fixed means on one of said members predeterminedly disposed between said brush and tube and frictionally and wedgingly restraining said slidable movement therebetween over a portion of said tube, and

opening means in said assembly for access to free said frictional restraint whereby said brush is held in the tube during assembly of said motor and then released for contact with the commutator.

2. Apparatus as described in claim 1 wherein the predeterminedly disposed means is located in substantially the half of said assembly remote from said commutator.

3. Apparatus as described in claim 1 wherein said tubular member has an end surface remote from said commutator as a spring bearing surface, and

said opening means is disposed in said end face.

4. Apparatus as described in claim 2 wherein said tubular member is closed at one end thereof remote from said commutator,

said spring bearing on said one end, and

said opening means in an aperture centrally of said end and brush member.

5. Apparatus as described in claim 1 wherein said restraining means is a portion pressed into said tube toward said brush a distance substantially equal to the clearance between said members.

6. Apparatus as described in claim 1 wherein said restraining means is a longitudinally extending rib pressed into said tube toward said brush a distance substantially equal to the clearance between said members.

7. Apparatus as described in claim 1 wherein said restraining means is a raised portion extending from said brush toward the tube,

said tube having a portion extending inwardly for cooperative wedging therewith over a portion of said tube.

8. Apparatus as described in claim 5 wherein said tubular member is closed at one end thereof remote from said commutator,

said spring bearing on said one end, and

said opening means is an aperture centrally of said end and brush member.

9. Apparatus as described in claim 6 wherein said tubular member is closed at one end thereof remote from said commutator,

said spring bearing on said one end, and

said opening means is an aperture centrally of said end and brush member.

10. Apparatus as described in claim 7 wherein said tubular member is closed at one end thereof remote from said commutator,

said spring bearing on said one end, and

said opening means is an aperture centrally of said end and brush member.