Abstract:
A high degree of freedom from noise is possible with a simple manufacturing technique for a small commutator motor by virtue of the fact that brush boxes are permanently mounted on parts of a brush plate and lockable by molded locking pins in locking openings of a base mounted on a motor housing with a gap therebetween. Damping sleeves may be premounted into the base edgewise with through openings for locking pins.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a noise-damped brush holder, especially for small commutator motors, in which the holder includes a brush mount having brush boxes mounted in a brush plate with brushes disposed therein. 
     German Patent Document No. DE-U-81 28 614 and corresponding European Patent Document No. EP-A1-00 76 403 disclose a noise-damped brush mount for a commutator motor, in which the individual brush housings guiding the brushes are each mounted independently on a brush plate with a damping plate interposed therebetween. The brush plate accepts additional electronic and/or electrical components and is mounted directly on the motor housing. The brushes are each mounted diagonally at an angle of incidence that differs from the perpendicular to the surface of the commutator, in such fashion that in view of a leg spring pressing on one beveled end of the brush and in view of the operational frictional force between the carbon brush and the surface of the commutator on the one hand and the pressure applied by the leg spring on the other, the brush abuts one side wall of the brush housing receiving it in a fixed position over its entire radial length, regardless of the rotational direction of the commutator. 
     French Patent Document Nos. FR-A-22 49 468 and FR-A-26 27 821 (the latter of which corresponds to U.S. Pat. Document No. US-A-4,921,371 and German Patent Document No. DE-A-39 04 844) disclose mounting a brush holder plate on a motor end shield using damping elements. 
     These prior designs are complex to manufacture in that they rely on complicated arrangements of damping elements to reduce the effects of noise. 
     SUMMARY OF THE INVENTION 
     The present invention addresses this deficiency of the known systems. Accordingly, it provides a brush mount, which better ensures a high degree of noise damping, especially in small commutator motors, and is also simpler to manufacture while ensuring reliable and simple contact with terminals for an external supply line and/or additional electrical components. 
     In an embodiment of the present invention a noise damped brush mount for a small commutator motor that has a stator in a housing, includes a base permanently mounted on the stator part. Furthermore, a brush plate is mounted on the base with a damping insert therebetween. Brush boxes are mounted directly on the brush plate and a brush is mounted in each of the brush boxes. 
     The brush mount according to the present invention permits, in simple fashion, a definite immobilization, ensured even over long operating times, of the brush box and thus of the brushes relative to the commutator by mounting the brush boxes on the brush plate without an elastic damping insert. It also ensures a high degree of freedom from noise with very simple assembly during manufacture and good positioning by noise-damping mounting of the brush plate on the base which serves for permanent mounting in the motor. Connectors for supply lines and mounts for additional electrical components can be stably mounted on the base. In this way, the ability of stresses to affect the position of the brushes in an unfavorable manner during the mounting of these components and/or the plugging in of an external connector is reliably prevented. 
     To achieve an assembly that is advantageous from the manufacturing standpoint, for mutually spaced and noise-damping mounting between the brush plate on the one hand and the body on the other, opposing axially lockable locking and snap connections ensure axial spacing in particular, and opposing axially interlocking guide connections ensure preferably opposing radial and/or tangential alignment. Thus, according to one embodiment of the present invention, the brush plate is lockable and/or insertable by means of respectively axially integrally formed, laterally elastically deformable locking pins inserted into corresponding guide openings and/or by means of solid guide pins inserted into corresponding guide openings of the base, with interposition of damping sleeves fitting around the locking pins and/or guide pins. The damping sleeves are provided with through openings for the locking pins and guide pins are advantageously premountable in the locking or guide openings. 
     The damping sleeves act as axial spacers between the brush plate and the base, whereby as a result of the positive locking connection between the brush plate and the base, their axial spacing, for example over the length of the locking pins or by provision of locking means, a pretensioning of the elastic damping sleeves can be adjusted in simple fashion to produce a specific damping. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention, as well as additional advantageous embodiments of the invention, will now be explained in greater detail with reference to the drawings. 
     FIG. 1 shows an axial top view of a brush mount in an embodiment of the present invention, from the brush plate side, with a partially cutaway view of a brush box. 
     FIG. 2 shows a detailed cross section along line II--II in FIG. 1; 
     FIG. 3 shows a top view of the brush mount from the base side, with a partially cutaway view of a connector housing molded on the base; 
     FIG. 4 shows a detailed section along line IV--IV in FIG. 3; 
     FIG. 5 shows the brush mount in a cross section along line V--V in FIG. 1; 
     FIG. 6 shows the diagonal positioning of a brush in the brush box relative to the commutator. 
    
    
     DETAILED DESCRIPTION 
     A brush mount according to an embodiment of the present invention consists essentially of two components, namely a base 3 lockable in a motor housing 1 (FIG. 3) and a brush plate 2, mounted with an intermediate damping element between it and base 3. Brush plate 2 essentially has the sole purpose of holding and guiding brushes 8 and 9 which rub on a commutator 12 (brush 9 is illustrated in FIG. 1, brush 8 is illustrated in FIGS. 1, 2 and 6, and commutator is illustrated in FIG. 6). In addition, brush boxes 2.5 and 2.6, integral with brush plate 2, are made in the form of components of brush plate 2 as can be seen from the section in FIG. 1. The boxes can be injection-molded from plastic and are closable radially by a lockable lid following insertion of the brush springs. Otherwise they are closed one-piece components of brush plate 2. An annular brush mounting holder is injection-molded on brush plate 2 by means of connecting ribs that can be broken out in such manner that the brushes, which rest against its outer circumference when the commutator is inserted, are initially raised, then, following the breaking out and ejection of the brush mounting holder, they are pressed through the commutator, which pushes back axially in the opposite direction during assembly against its brush rubbing surface by the brush springs. 
     For opposing mounting of brush plate 2 and base 3, laterally elastically flexible locking pins 2.1 and 2.2 are molded on brush plate 2. These pins are lockable or snappable into corresponding locking openings 3.1 in base 3 for the purpose of axial mounting assembly. Damping sleeves 4 and 6 are interposed between the plate and base. Axially projecting guide pins 2.3 and 2.4 are also molded on brush plate 2, specifically for radial and tangential alignment between brush plate 2 and base 3, said pins in turn being insertable, using the same assembly technique, into corresponding guide openings 3.2 (FIG. 4), with interposition of damping sleeves 5 and 7 (FIG. 3). 
     Advantageously, damping sleeves 4-7 are held in premountable fashion in locking openings 3.1 and guide openings 3.2 of base 3; for this purpose, as is particularly evident in FIG. 2 and FIG. 4, undercuts in the outer edges of damping sleeves 4-7 snap into the edges of locking opening 3.1 or guide opening 3.2. 
     The minimum distance between brush plate 2 and base 3 is determined by the length of the spacing of the locking connection of locking pins 2.1 and 2.2; because damping sleeves 4-7 are provided as axial spacers between brush plate 2 and base 3, a controlled pretensioning of damping sleeves 4-7 in the area between brush plate 2 and base 3 is achieved by selecting the locking length of locking pins 2.1 and 2.2 and thus a desired specific damping is ensured between the otherwise mutually spaced components of brush plate 2 and base 3. 
     Base 3, in addition to actual mounting of the entire brush mount in motor housing 10 also serves to receive additional electronic or electrical components, especially suppression capacitors 10 and 11 insertable axially into pockets 3.6 and 3.7. Suppression capacitors 10 and 11 are connected firstly by electrical leads with brushes 8 and 9 and secondly with a connector housing 3.4 molded on base 3, said housing projecting through an opening in motor housing 1. Connector housing 3.4 therefore simultaneously serves in the manner of an approximately opposite positioning projection 3.3 for tangential and axial immobilization of base 3 and hence for the entire brush mount relative to motor housing 1. On the outer circumference of the base, a plurality of scraping ribs 3.5 are provided for premounting. The ribs ensure radially positive and axially nonpositive retention when the brush mount is inserted axially into motor housing 1. The base is mounted permanently on a stator point of the commutator motor without a damping insert. The damping insert is instead provided between the base 3 and brush plate 2. 
     As is particularly evident from FIG. 1 and shown enlarged in schematic form in FIG. 6, the brush is inclined, with respect to its perpendicular to the surface of the commutator, by an angle α, preferably equal to 30°, and with a bevel at one end, 8.1, such that it remains in a fixed position, with its commutator end abutting one (the right) side wall of brush box 2.5 and with its head end abutting the other (left) side wall of brush box 2.4, due to the force F1 of a brush spring acting an beveled end 8.1 and the frictional force between brush and commutator 12, independently of the rotational direction of commutator 12.