US 3308321 A
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Description (OCR text may contain errors)
March 7, 1967 J. R. PROVOST, JR 3,308,321
REVERSIBLE BRUSH AND BRUSH HOLDER ARRANGEMENT Original Filed May 7, 1964 2 Sheets-Sheet 1 IO 50 FIG. FIG; 2
INVENTOR JOHN R. PROVOSZ JR.
ATTORNEY March 7, 1967 PRQVQST, JR 3,308,321
REVERSIBLE BRUSH AND BRUSH HOLDER ARRANGEMENT I Original Filed May 7, 1964 v v 2 Sheets-Sheet 2 INVENTOR. JOHN R. PROVOSZ JR.
ATTORNEY United States Patent 3,308,321 REVERSIBLE BRUSH AND BRUSH HOLDER ARRANGEMENT John R. Provost, .lr., Turners Falls, Mass., assignor to Miller Falls Company, Greenfield, Mass., a corporation of Massachusetts Continuation of application Ser. No. 365,727, May 7, 1964. This application Oct. 12, 1966, Ser. N0. 586,305 8 Claims. (Cl. 310-239) This case is a continuation of Serial No. 365,727, now abandoned.
This invention relates to electric power tools and motors and more particularly to a reversible brush and a brush holder.
Heret-ofore, power tools and motors required brushes and brush holder arrangements which would frequently wear out after a relatively short period of use.
Furthermore, the brush arrangements presently being used are so constructed that when the brush Wears out damage may occur to the commutator because the spring used to hold the brush in position will rub and scrape against the commutator.
It is the general object of the present invention to avoid and overcome the foregoing and other difficulties of and objections to prior art practices by the provision of a reversible brush and holder which has a long life without sacrificing space.
Another object of the present invention is to provide an automatic stop on the brush thereby eliminating damage to the tool.
Still another object of the present invention is to provide a brush and brush holder which will be easily changed thereby reducing the shut down period.
A further object of the present invention is to provide a brush holder which will allow a reversing of the brush.
Yet anotherobject of the present invention is to provide an increased exterior design potential because of the reduced space needed.
The aforesaid objects of the present invention, and other objects which will become apparent as the description proceeds, are achieved by providing a frame having a longitudinal hole therethrough and a retainer insertable therein. A stop means is provided on the retainer and a brush is insertable in the retainer which is to contact a commutator. An abutment means is fixed on the brush which cooperates with the stop means to prevent excessive wear of the brush, while a resilient means urges the brush toward the commutator. A set screw is provided and is connected to the frame for holding the retainer and resilient means within the frame.
For a better understanding of the present invention reference should be had to the accompanying drawings, wherein like numerals of reference indicate similar parts throughout the several views and wherein:
FIGURE 1 is a cross sectional view of the holder and the brush,
FIGURE 2 is a cross sectional view of the holder and the brush where the brush is worn down,
FIGURE 3 is a cross sectional view of the holder and the brush after the brush has been reversed,
FIGURE 4 is a perspective view of the brush,
FIGURE 5 is a cross sectional view of an alternative embodiment, and
FIGURE 6 is a brush used in the alternative embodiment and specifically showing the shunt wire.
Although the principles of the present invention are broadly applicable to 'means'for holding elements in contact with a rotating commutator, the present invention is particularly adapted for use in conjunction with brush holders and brushes used in electric motors and hence it has been so illustrated and will be so described.
3,308,321 Patented Mar. 7, 1967 "ice With specific reference to the form of the present invention illustrated in the drawings, and referring particularly to FIGURE 1, a brush holder is indicated generally by the reference numeral 10.
In order to hold a brush 12 in contact with a commutator 14, a frame 16 is provided. The frame 16 is provided with an enlarged top portion 18 which forms a cap 20.
The frame 16 is provided with a longitudinal hole 22 which runs through the frame 16, and will take the same general cross sectional shape as the brush 12. It can be seen that the brush 12 can take a cylindrical, rectangular or oval shape, whichever may be suited for a particular use.
It may be seen that the frame 16 may be connected to a motor in any convenient manner such that the brush 12 may contact the commutator 14.
The brush 12, herein described as cylindrically shaped,
may take other shapes, has a first cylindrical portion 24 and a second cylindrical portion 26. The first cylindrical portion 24 and second cylindrical portion 26 are separated by an abutment means 28, the abutment means 28 being in the form of an annular raised portion which forms a first abutment surface 30 for the first cylindrical portion 24 and a second abutment surface 32 for the second cylindrical portion 26.
' In order to align and hold the brush 12 within the frame 16, a cylindrical retainer 34 is provided which fits into the hole 22. It should be noted that the retainer 34 will take the general shape of the hole 22 and brush 12, and is not restricted to a cylindrical shape.
The retainer 34 is provided at its upper end 36 with an outwardly flared portion 38 which seats on an annular lip 40 in the cap 20 of the frame 16. When the flared portion 38 contacts the annular lip 40, the retainer 34 is prevented from sliding out through the hole 22.
The lower end 42 of the retainer 34 is provided with a stop means 44 which may be formed by having the lower end 42 of the retainer 34 flared inwardly, or a series of inwardly directed projections (not shown). The inwardly flared portion or stop means 44 creates an aperture 46 through which the first portion 24 or the second portion 26 of the brush 12 may pass, but is not large enough to allow the abutment means 28 to pass therethrough.
In order to hold the brush 12 against the commutator 14, a resilient means or spring 48 is disposed within the retainer 34 and encircles the first portion 24 of the brush 12 as shown in FIGURE 1. The spring 48 rests upon the abutment means 28 and forces the brush 12 downwardly and against the commutator when a set screw 50 is threadedly inserted into the cap 20 of the frame 16. In this manner the spring 48, encircling the first portion 24 of brush 12 pushes on the abutment means 28 forcing the second portion 26 of the brush 12 out the aperture 46 and against the commutator 14. When the second portion 26 of the brush is worn down, as shown in FIG- URE 2, the abutment means 28 will have its first abutment surface 30 resting against the stop means 44 thereby preventing any further feeding of the brush 12 against the rotating commutator 14.
As shown in FIGURE 3, the worn brush 12 may be reversed so that the spring 48 encircles the remainder of the second portion 26 of the brush 12 and pushing the first portion 24 thereof, through the aperture 46 and into contact with the commutator 14.
The reversing of the brush 12 is accomplished by removing the set screw 50. and pulling the spring 48 and brush 12 out of the frame 16 through the cap 20. By placing the spring 48 on the remainder of the worn portion of the second portion 26 of the brush 12 and placing the first portion 24 of the brush 12 into the retainer 34,
3 the first portion 24 of the brush 12 will protrude through theaperture 46 when the set screw 50 is screwed into the cap 20 of the frame 16.
It should be noted (see FIGURE 2) that when the brush 12 is worn down from contact with the rotating commutator, the cooperation of the abutment means 28 and the stop means 44 will prevent further contact of the brush 12 with the commutator thereby automatically warning an operator that the brush 12 should be either changed or reversed. Also this cooperation of elements prevents the damaging of the commutator 14 because no metallic element can contact the commutator when the brush 12 (either portion) has worn down,
Alternatively, a brush holder A and assembly therefor may be provided which employs a shunt wire arrangement 56. The purpose of the shunt wire arrangement 56 is to carry current, to or from the brush 12A. The entire retainer 34A is housed with an nonconductive housing 51 so that no electrical contact is made between the retainer and the frame of the motor, which is not shown.
As shown in FIGURE 6, the abutment means 28A or the annular raised portion is provided with a recess 54 such that one end 53 of a current carrying means or wire 56 may be corrected to the brush 12A at a point which would not interfer with the operation of the brush holder 10A.
In order to make a good electrical contact with the retainer 34A, the other end of the wire 56 is connected to a contact means 58 which, as shown in FIGURE 6, is a disc 60 made of a conducting material well known to those skilled in the art, such as copper and the like.
A resilient means or spring 48A is disposed within the retainer 34A and encircles the first portion 24A of the brush 12A. As shown in FIGURE 5, the diameter of the spring 48A is smaller than that of the disc 60. With this configuration of elements, the disc 60 is always assured to be forced upwardly against the set screw 50A.
In order to reverse the bush 12A, the set screw 50A is removed and the disc 60 is pulled outwardly, thus pulling the brush 12A out of the retainer 34A. The spring 48A may be pulled up against the disc 60 and depressed so that it will clear or slide over the first portion 24A of the brush 12A.
As shown in FIGURE 6, the dash lines, the shunt wire 56 may be reversed and now the spring 48A will be fitted over the worn down second portion 26A of the brush 12A. In this manner the reversing of the brush 12A is seen to be identical with the brush 12 in the main embodiment, except for the operation of the disc 60 and the spring 48A.
It will be recognized by those skilled in the art that the objects of the present invention have been achieved by providing a brush and brush holder which will last longer and prevent damage to the commutator, while further providing and automatic stop when the brush wears excessively.
While in accordance with the patent statutes a preferred embodiment of the present invention has been illustrated and described in detail, it is to be particularly understood that the invention is not limited thereto or thereby.
What is claimed is:
1. A brush and brush holder therefore for holding the brush in contact with a commutator comprising:
stop means disposed on said retainer;
brush means inserta-ble in said retainer for contacting said commutator;
abutment means on said brush cooperating with said stop means for limiting the amount of wear of said brush means;
resilient means urging said brush means toward said commutator; and
means for holding said resilient means within said retainer;
said brush means having upper and lower parts on the opposite sides of said abutment means and being reversibly insertable in said retainer so that either part may contact said commutator.
2. The combination of claim 1 wherein said resilient means is in contact with said abutment means.
3. The combination of claim 2 wherein said stop means is an inwardly flared portion of said retainer at one end of said retainer.
4. The combination of claim 3 further including a frame having a longitudinal hole t-herethrough and means for preventing said retainer from sliding through said hole.
5. The combination of claim 4 wherein said frame has an annular lip on the upper portion thereof and said means for preventing said retainer from sliding through said hole is an outwardly flared end of said retainer engaging said annular lip.
6. The combination of claim 5 wherein said holding means is a set screw connected to said frame for holding said retainer and resilient means within said frame.
7. The combination of claim 3 further including insulating means surrounding said retainer, a shunt wire having one end connected to said brush means, and a disc connected to the other end of said shunt wire and resting on said retainer, said holding means connected to said insulating means for holding said disc and resilient means in place.
8. The combination of claim 7 further including a frame having a longitudinal hole therethrough, said insulating means being positioned between said retainer and said frame.
References Cited by the Examiner UNITED STATES PATENTS MILTON O. HIRSHFIELD, Primary Examiner. D, F, DUGGAN, Assistant Examiner.