Patent Publication Number: US-8986053-B2

Title: Slip ring brush and holder for slip ring brush

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from German Patent Application No. 10 2012 203 842.6 filed on Mar. 12, 2012, the disclosure of which is incorporated by reference in its entirety. 
     TECHNICAL FIELD 
     The invention relates to a holder for a slip ring brush and a respective slip ring brush. Slip ring brushes are used in slip ring arrangements for transmitting electrical signals between mutually rotatable parts. At least one slip ring brush that includes an electrically conductive material will slide on a slideway made of electrically conductive material. As a result of the galvanic contact between the slideway and the slip ring brush it is possible to transfer electric current between them. 
     BACKGROUND 
     EP 0 662 736 A1 discloses a multi-fiber brush with a plurality of brush wires in which the individual brush wires are soldered into a sleeve. Several of such sleeves are integrated with (for example, by soldering) a carrier. This leads to a series of soldered electrical contact points. Such complex structural configuration is highly prone to various malfunctions. 
     U.S. Pat. No. 3,316,519 also discloses a multi-fiber brush, in which the individual wires are soldered into a brass body. Only one soldering point is disposed in the path of electric current. While good mechanical relief is achieved by the deep penetration of the individual brush wires into the brass body and a relatively massive soldering point, the disadvantage of this arrangement stems from its complex configuration and the relatively high complexity of the brass body. Moreover, parallel switching of several proposed brushes can be achieved only by external wiring. 
     EP 1 453 155 A2 discloses a slip ring brush in which the individual wires are soldered onto the surface of a printed circuit board. While simple parallel switching between and/or among the brushes is possible in this case, the disadvantageous aspect is the high level of operational susceptibility to malfunctions due to mechanically loaded soldering points. Moreover, this arrangement is not suitable for the use of multi-fiber brushes, which, in comparison with the use of individual brushes, could offer substantially better current transmission properties. 
     SUMMARY 
     The embodiments of the present invention are directed to an assembly including a structural cooperation between a slip ring brush and a holder for slip ring brush(es), where one or more brush wires can be used in an individual brush, where simple parallel connection of several brushes is possible, and which is characterized by increased operational reliability in combination with reduced production costs. 
     In an embodiment, a slip ring brush includes a holding device with at least one first holding plate and a second holding plate disposed above the first holding plate. Each of the two holding plates include an attachment area with at least one clamping finger. At least one clamping finger of the first holding plate is disposed opposite a clamping finger of the second holding plate and forms a cavity for holding at least one brush wire. Preferably, several such clamping fingers are arranged in parallel and disposed opposite one another in pairs to form several cavities. A single brush wire or a plurality of brush wires (forming a multi-fiber brush, for example) is held in such a cavity. For the purpose of fixing the brush wires, a clamping sleeve encompasses at least one clamping finger of the first holding plate and the respectively oppositely disposed clamping finger of the second holding plate and at least one brush wire encompassed in the cavity formed by the clamping fingers. The clamping sleeve can be crimped on by means of a crimping tool. Alternatively, it can also be arranged in a resilient manner to compress the clamping fingers by means of its spring force. 
     Instead of a single brush wire or a plurality of brush wires, a prefabricated multi-fiber brush in which the ends of the brush wires are joined by a sleeve can be held by the clamping fingers. The term of multi-fiber brush shall generally be understood in this case as a multi-wire brush with several brush wires. It is alternatively referred to as a bundle brush. 
     In a further embodiment, the clamping fingers of the first holding plate are arranged in such a way that they can be crimped around the at least one brush wire. This embodiment may require only one holding plate and the second holding plate can be omitted because the brush wires are already held by the first holding plate alone. 
     The advantage of the slip ring brushes in accordance with the embodiments over the related devices is the especially simple mechanical configuration. Consequently, an embodiment of a slip ring brush is substantially based on two holding plates which can be produced as simple punched or metal-stamped parts. The mounting of the brush wires is simple and possible without any soldering. As a result, the disadvantages of soldering processing (such as deformation or a change in the spring properties of the brush wires by high soldering temperatures) are reduced or substantially prevented. The fastening of the brush wires between the clamping fingers and the fixing of the brush wires with clamping sleeves lead to a mechanically stable structure, which is operable as a permanently reliable electrical contact even under long-term loads with high vibration amplitudes. In fact, the proposed arrangement is substantially devoid of problems with mechanically loaded soldering points, in which the crystal structure of the solder changes by mechanical loading and which then subsequently breaks up. At the same time, the proposed configuration enables optional exchange and replacement of individual brush wires of a brush when they are worn out. They could be pulled out after the withdrawing the sleeve from the clamping fingers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the following, embodiments of the invention are described based on examples, without limitation of the general inventive concept, and with reference to the drawings. 
         FIG. 1  is a perspective view of a first embodiment of a slip ring brush; 
         FIG. 2  is an exploded perspective view of a portion of the embodiment of  FIG. 1  illustrating its components; 
         FIG. 3  is a perspective view of a clamping sleeve; 
         FIG. 4  is a perspective view of a further embodiment of a slip ring brush; 
         FIG. 5  is a perspective view of a multi-fiber brush; 
         FIG. 6  is a perspective view of a brush block. 
     
    
    
     While embodiments of the invention can be appropriately modified, several of such embodiments are shown by way of example in the drawings and described below in detail. It should be understood, however, that the drawings and detailed description are not intended to limit the invention to any particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present invention as defined by the appended claims. 
     DETAILED DESCRIPTION 
       FIG. 1  shows a first embodiment of a slip ring brush assembly. The same slip ring brush is shown in  FIG. 2  in a state prior to assembly. A first holding plate  10  and a second holding plate  20  are shaped in such a substantially congruent way that they can be “pushed” into each other and/or inserted into each other to rest on each other and to form areal contact at least within a predetermined area. In reference to  FIG. 2 , the first holding plate  10  has an attachment area  11  with the first clamping fingers  12 ,  13 ,  14 ,  15 . Furthermore, the second holding plate  20  includes an attachment area  21  with the second clamping fingers  22 ,  23 ,  24 ,  25 . When the two holding plates  10 ,  20  are slid into each other as shown in the illustrations of  FIGS. 1 ,  2 , the clamping fingers  12 ,  13 ,  14 ,  15  of the first holding plate  10  and the clamping fingers  22 ,  23 ,  24 ,  25  of the second holding plate  20  are disposed opposite one another in pairs ( 12 ,  22 ); ( 13 ,  23 ); ( 14 ,  24 ); ( 15 ,  25 ) to form a cavity for accommodating brush wires  32 ,  33 ,  34 ,  35 . Preferably, the clamping fingers are shaped in such a way that they rest on the brush wires to be inserted or encompass or embrace the same as tightly as possible. In one specific case, shown in  FIG. 2 , the individual clamping fingers are preferably shaped in a semi-cylindrical manner in order to form a cylindrically-hollow opening with a circular cross-section to accommodate the brush wires. The holding plates  10 ,  20  can be produced in an especially simple and cost-effective way as punched parts. The holding plates may include copper or a copper alloy such as brass or bronze. 
     Clamping sleeves  36 ,  37 ,  38 ,  39  are provided for tightly affixing the brush wires between the clamping fingers. The position of the first holding plate  10  with respect to the second holding plate  20  can be fixed by the clamping sleeves. As shown in  FIG. 1 , the clamping sleeve  36  has not yet been slid onto and over the respective clamping fingers ( 12 ,  22 ), whereas the other clamping sleeves  37 ,  38  and  39  have already been placed on their respective clamping fingers ( 13 ,  23 ); ( 14 ,  24 ); ( 15 ,  25 ). A holding plate is bent into a U-shape to position a first portion of the first holding plate in a substantially parallel relationship to a second portion of the first holding plate. For the purpose of fixing the slip ring brush and for establishing electrical contact, a bolt or screw  42  is provided through a first fixing hole  16  and an opposite second fixing hole  17  of the U-shaped bent first holding plate  10  and a first fixing hole  26  and an opposite second fixing hole  27  of the U-shaped bent second holding plate  20 . The first and second fixing holes may be disposed substantially co-axially. Optionally, the position of the first holding plate  10  with respect to the second holding plate  20  is also determined by a fastener such as the bolt or screw secured by a nut  43 , for example. At the same time, the same fastener can be used for connecting a cable lug  40  that is further extended with the cable  41  or a connecting plug to the slip ring brush. The holding plates  10 ,  20  are bent in a U-shaped manner in this embodiment, which enables especially simple spatial coordination, cooperation, and attachment of the holding plates with respect to one another and simple mounting of the slip ring brushes thereon. Generally, the holding plates could also be provided shaped in any other way (for example, flat). The configuration of the clamping fingers, on the other hand, is relevant for the embodiments herein. 
       FIG. 3  shows a clamping sleeve  36 . It is shown shaped as a hollow cylinder having, preferably, a longitudinal slit along its wall, by means of expansion of which the diameter of the sleeve can be increased. It preferably further includes a collar  51  which facilitates inserting the clamping sleeve onto the clamping fingers. 
       FIG. 4  shows a further embodiment. In this case, only one first holding plate  60  will be used, with the brush wires  32 ,  33 ,  34  and  35  being tightly crimped along their length by the crimping fingers  62 ,  63 ,  64 ,  65  which are connected to the attachment area  61  of the first holding plate  60 . 
       FIG. 5  shows an embodiment of a multi-fiber brush or a bundle brush  70 . This brush includes several individual brush wires  72  brought in a bunch and encompassed by a sleeve  71  at one end. Preferably, the sleeve  71  is crimped onto the individual wires. Alternatively or in addition, the sleeve  71  can be soldered onto the wires  72 . The individual brush wires  72  themselves and/or the sleeve  71  can be held by the clamping fingers. 
       FIG. 6  shows a f brush block containing five slip ring brushes  81 ,  82 ,  83 ,  84 ,  85 , which are mounted on a preferably electrically insulated carrier  80 . Connecting electrical cables  91 ,  92 ,  93 ,  94 ,  95  are provided for supplying current to the brushes  81 ,  82 ,  83 ,  84 ,  85 . If several slip ring brushes are to be connected in parallel, then this can occur in an especially simple way by an electrically conductive carrier to which the brushes  81 ,  82 ,  83 ,  84 ,  85  may be attached. 
     Further modifications and alternative embodiments of various aspects of the invention will be apparent to those skilled in the art in view of this description. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the general manner of carrying out the invention. It is to be understood that the forms of the invention shown and described herein are to be taken as the presently preferred embodiments. Elements and materials may be substituted for those illustrated and described herein, parts and processes may be reversed, and certain features of the invention may be utilized independently, all as would be apparent to one skilled in the art after having the benefit of this description of the invention. Changes may be made in the elements described herein without departing from the spirit and scope of the invention as described in the following claims. 
     LIST OF REFERENCE NUMERALS 
       10  First holding plate 
       11  First attachment area 
       12 - 15  First clamping fingers 
       16  First fixing hole 
       17  Second fixing hole 
       20  Second holding plate 
       21  Second attachment area 
       22 - 25  Second clamping fingers 
       26  First fixing hole 
       27  Second fixing hole 
       32 - 35  Brush wires 
       36 - 39  Clamping sleeves 
       40  Cable lug 
       41  Connecting cable 
       42  Bolt 
       43  Nut 
       50  Clamping slit 
       51  Collar 
       60  Holding plate 
       61  Attachment area 
       62 - 65  Crimping fingers 
       70  Multi-fiber brush 
       71  Sleeve 
       72  Brush wires 
       80  Carrier 
       81 - 85  Brushes 
       91 - 95  Connecting cables