Brush holder
BACKGROUND OF THE INVENTION 
     The present invention relates to a brush holder for holding brushes opposite to a motor commutator and, more particularly, to a brush holder in which brush arm can be easily formed and which can hold the brush correctly in its proper position relative to the motor commutator and can be easily assembled. 
     Generally the motor case of a small-sized motor consists of a large case and a small case joined together, the large case being provided with fixed permanent magnets on its internal surface to form a motor stator, and the small case having a brush holder for holding brushes in the proper position relative to the motor commutator. The brush holder used in such a motor consists of brush arms each having a brush at its tip, a mount on which the brush arms are placed, and a part of the small case to which the brush arm mount is attached. However, the above-mentioned conventional brush holder has the disadvantage in that its brush arm becomes complicated in shape in order to firmly hold the brush and therefore requires troublesome forming operations. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a brush holder which can eliminate the above-mentioned disadvantages of the prior art. 
     It is another object of the present invention to provide a brush holder which can be easily formed. 
     It is still another object of the present invention to provide a brush holder which can firmly hold its brush arm and can be easily assembled. 
     These and other objects and advantages of the invention will be best understood from the following detailed description taken in conjunction with the accompanying drawings wherein like reference numerals and characters designate corresponding parts throughout the views. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1(A) is a perspective view of a brush arm according to a preferred embodiment of the present invention; 
     FIG. 1(B) is a side elevational view of the brush arm shown in FIG. 1(A) thereof; 
     FIG. 1(C) is an enlarged sectional side view of the main part of the brush arm shown in FIG. 1(A); 
     FIG. 2(A) is a perspective view of a brush arm mount according to a preferred embodiment of the present invention; 
     FIG. 2(B) is an end elevational view of the brush arm mount shown in FIG. 2(A); 
     FIG. 2(C) is a sectional side elevational view of the brush arm shown in FIG. 2(A) taken along line X--X in FIG. 2(B); 
     FIG. 3(A) is an elevational view illustrating two brush arms and a brush-arm mount of the present invention as they appear when assembled; 
     FIG. 3(B) is a sectional side elevational view thereof taken along line Y--Y in FIG. 3(A); and 
     FIGS. 4a and 4b are exploded perspective view illustrating the relationship between the brush arm mount comprising the present invention and a typical small motor-case. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference is first made to FIGS. 1(A), 1(B) and 1(C) which show a brush arm according to a preferred embodiment of the present invention. 
     Reference numeral 1 generally designates a brush arm, which is composed of a brush 2, a brush support 3, and a brush arm base 4 having a first ridge section 5, recesses 6 and 7, and a terminal section 8. The brush arm 1, composed mainly of the brush support 3 and the brush arm base 4, is made of conductive and resilient material, such as BeCu. The brush 2 is provided at the tip of the brush support 3, and is adapted to be held opposite to and in contact with a motor commutator (not shown). The brush arm base 4 is connected to the brush support 3 so that they form the letter T. The brush arm base 4 has, at its right and left upper edges, that are bent portions 4&#39; and 4&#39; bent substantially at right angles thereto. The first ridge section 5 is formed in the vicinity of the center of the brush arm base 4. The recesses 6 and 7 are provided at the side edges of the brush arm base 4. The terminal section 8 is provided on the top of the brush arm base 4. A lead wire (not shown) is adapted to be connected to the terminal section 8. 
     Reference is now made to FIGS. 2(A), 2(B) and 2(C), which show a brush arm mount according to a preferred embodiment of the present invention. 
     Reference numeral 9 generally designates a brush arm mount made of an insulating material, such as polyacetal. Reference numeral 10 designates the front edge portion of the brush arm mount 9, reference numeral designates 11 the rear edge portion thereof and reference numerals 12 and 13 designate the side edge portions thereof, respectively. Reference numerals 14 and 15 generally designate slits provided in the brush arm mount 9 and having therein first grooves 16 and 17, respectively. These slits 14 and 15 and first grooves 16 and 17 are adapted to receive the brush arm base 4 and the first ridge section 5, respectively, shown in FIGS. 1(A) to 1(C). Reference numerals 18 and 19 designate second grooves provided on the side edges of the brush arm mount 9. Reference numeral 20 designates a third groove provided on the front edge of the brush arm mount 9 and having a cross-sectional shape corresponding to the shape of the recesses 6 or 7 shown in FIG. 1(A). Reference numeral 21 designates a plate member projecting from the rear edge of the brush arm mount 9. Relief grooves 22 and 23 are provided on the bottom of the brush arm mount 9 for preventing the brush support 3 from inadvertently coming into contact with the brush arm mount 9. Projections 24 are provided in the slits 14 and 15, corresponding in cross section to the recesses 6 and 7 shown in FIG. 1(A), respectively. 
     In mounting the brush arm 1 shown in FIGS. 1(A) to 1(C) on the brush arm mount 9 shown in FIG. 2(A) to FIG. 2(C), the brush arm 1 is pushed into the slit 14 or 15 until the side edge surface (where the recess 6 or 7 is provided) of the brush arm base 4 engages one of the projections 24 (see FIG. 3(B)). 
     FIGS. 3(A) and 3(B) illustrate the brush arms 1 and the brush arm mount 9 as they appear when they have been assembled together in the above-mentioned manner. 
     Reference is now made to FIGS. 3(A) and 3(B), in which the reference numerals designate corresponding parts shown in FIGS. 1(A) to 1(C) and 2(A) to 2(C). 
     The brush arm base 4 of each brush arm 1 is resiliently held in the slit 14 or 15 by the action of the resilience of the ridge section 5. As shown in FIG. 3(B), the brush arm 1 has a positional relationship with the brush arm mount 9 such that one recess 7 of the brush arm 1 is mated with the projection 24 provided in the slit 14 or 15 and the other recess 6 thereof coincides with the third groove 20 of the brush arm mount 9, when assembled. 
     Next, reference is made to FIG. 4, which is an exploded perspective view illustrating the relationship between a small case 25 of the invention and the brush arm mount 9 to which the brush arms are attached. 
     Reference numeral 25 generally designates a small motorcase to be coupled with a large motor-case (not shown). The small case 25 has a base 26, sides 27, a bearing section 28 for supporting a motor shaft (not shown), second ridge sections 29 and 30 provided thereon in the vicinity of the upper edges of the internal surfaces of the sides 27 respectively, and a third ridge section 31 provided thereon in the vicinity of the upper edge of the internal surface of the base 26. Other reference numerals designate corresponding parts shown in FIGS. 1(A) to 1(C) and 2(A) to 2(C). 
     In the small case 25 shown in FIG. 4, the second ridge sections 29 and 30 have a cross-sectional shape corresponding to that of the second grooves 18 and 19 of the brush arm mount 9. In addition, the third ridge section 31 has a cross-sectional shape corresponding to that of the groove 20 of the brush arm mount 9. 
     In attaching the brush arm mount 9 to the small case 25, the brush arm mount 9 to which a pair of brush arms 1 have been attached is pushed into the small case 25 while the second grooves 18 and 19 of the brush arm mount 9 engage the second ridge sections 29 and 30, respectively. When the brush arm mount 9 is attached to the small case 25, the second grooves 18 and 19 are mated with the second ridge sections 29 and 30, and thereby the brush arm mount 9 is elastically held on the small case 25. Also, the third groove 20 of the brush arm mount 9 and the recess 6 or 7 of the brush arm 1 are both mated with the third ridge section 31 of the small case 25. Thus the brush arm mount 9 is firmly held on the small case 25. 
     According to the brush holder of the present invention, as mentioned above, the brush arms 1 are firmly held on the brush arm mount 9 by the slits 14 and 15 of the brush arm mount 9, the projections 24 thereof, and the third ridge section 31 of the small case 25. In addition, the brush arm mount 9 is firmly held on the small case 25 by the second ridge sections 29 and 30 of the small case 25 and the third ridge section 31 thereof. 
     According to the present invention, the brush arm 1 is very simple in shape as clearly shown in FIGS. 1(A) to 1(C) and therefore is very easy to form. 
     According to the present invention, the plate member 21 is provided on the brush arm mount 9. Therefore, in attaching the brush arm mount 9 to the small case 25, the brush arm mount 9 may be pushed by applying, for instance, the inner surface of a thumb to the plate member 21. Thus the mounting operation becomes very easy. 
     According to the present invention, if the brush arm mount 9 is mounted on the small case 25 when the brush arm 1 is incompletely inserted in the brush arm mount 9, the brush arm 1, after reaching the third ridge section 31, is further inserted into the slit 14 or 15 of the brush arm mount 9 by the action of the third ridge section 31 to reach the proper position. Thus, on completion of this mounting operation, the brush arm 1 is properly positioned with respect to the brush arm mount 9. Consequently, the assembly of the brush holder of the present invention becomes very easy to perform and the brush arm 1 can be correctly held in position. 
     Having described the preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied without departing from the spirit of the invention.