Patent Publication Number: US-6664697-B2

Title: Electrical slip ring apparatus having multiple spaced apart support structures

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to a method of manufacturing an electrical slip ring assembly and to an electrical slip ring apparatus. More particularly, the present invention relates to a method and apparatus of constructing an electrical slip ring assembly using a plurality of spaced apart comb-like structures for supporting multiple electrically conductive slip rings. 
     BACKGROUND OF THE INVENTION 
     Electrical slip rings are well known devices for communicating electrical signals from one structural member to another where one of the structural members is rotatable with respect to the other. Such a slip ring assembly, for example, may comprise a relatively stationary annular base member which has a plurality of conductive rings extending around an outer circumferential face thereof. Each of the rings extends around a substantial portion of the circumference of the slip ring base. A series of electrically conductive brushes are arranged on a relatively rotatable structural member to rotate about the slip ring base, and each of the brushes is arranged to contact a surface of one of the conductive rings thereby forming a series of electrical connections between the two structural members. 
     Heretofore, the methods of manufacturing slip ring bases of the type discussed herein above have included either molding the conductive rings as a part of the base while the base itself is being molded or plating the conductive rings into previously completed slip ring bases having grooves formed therein for the conductive rings. Both techniques require expensive tooling and machining operations which are now proving to be prohibitively expensive. 
     In connection with the molding process mentioned above, it is necessary that conductive rings be positioned within a mold so that, for example, epoxy can be cast around the rings to produce the slip ring base. Expensive tooling is required to support and maintain the rings at the proper position as the molding process is carried out. These rings are then plated, once the molding process has been completed, and this requires additional tooling. Using this technique, if the casted epoxy happens to have voids or otherwise does not properly bond to the conductive ring materials, it is not unusual to find that plating solutions can be trapped in the epoxy or around the rings. After a short period of use of the slip ring, these solutions can migrate to the ring surfaces and cause excessive wear and intermittent electrical contact problems. 
     Using those techniques where plating occurs after molding, it is not unusual to find that the plating does not adhere properly to the base member. In this event, the conductive rings must be removed, remachined and replated. It can readily be seen that these will be expensive and time consuming operations. In many cases it is not possible to repair the damage and at least the entire slip ring based must be discarded. This loss is a significant one. 
     A prior art method for manufacturing an electrical slip ring is described in U.S. Pat. No. 5,054,189 to Bowman et al. (hereinafter “the &#39;189 patent”, entitled “Method of Manufacturing An Electrical Slip Ring Assembly”. The difficulty with the method described in the &#39;189 patent is that there is expensive tooling and machining required to fabricate the electrical slip ring assembly. More specifically, the annular base member 10 in the &#39;189 patent, grooves 12 and 16 are machined and conductive strips 12 are placed therein. Further, rolling the conductive rings 12 into the grooves 12 and 16 is time consuming and expensive. Accordingly, a need exists in the art for a method and apparatus which overcomes the need for expensive tooling and machining and reduces manufacturing as compared to current electrical slip ring manufacturing methods. 
     SUMMARY OF THE INVENTION 
     It is, therefore, an object of the present invention to provide an electrical slip ring assembly which does not require expensive tooling and machining to fabricate the assembly and reduces manufacturing costs. 
     It is another object of the present invention to provide an electrical slip ring assembly which eliminates the need for an annular base member. 
     Another object of the present invention is to provide a plurality of comb-like structures which support a plurality of electrically conductive slip rings. 
     The present invention is directed to an electrical slip ring assembly having a plurality of conductive rings held in place by multiple spaced apart comb-like structures advantageously eliminates the need for molding the conductive rings as part of the base or plating the conductive rings into completed bases. Further, the present invention eliminates the need to machine an annular base or perform expensive and time consuming operations to roll conductive strips into a machined base member. 
     These and other objects of the present invention are achieved by an electrical slip ring assembly. The electrical slip ring assembly includes a first plurality of annular conductive rings spaced from each other and a second plurality of circumferentially spaced electrically non-conductive support structures. The non-conductive support structures each have inwardly extending slots. The first plurality of conductive rings are each mounted in the inwardly extending slots in one of each of the second plurality of support structures such that each of conductive rings is spaced from adjacent ones of the conductive rings. 
     The foregoing and other objects of the present invention are achieved by an electrical slip ring assembly. The electrical slip ring assembly includes a first plurality of annular conductive rings spaced from each other and a second plurality of circumferentially spaced electrically non-conductive support structures. The non-conductive support structures each have inwardly extending slots. The first plurality of conductive rings are each mounted in the inwardly extending slots in one of each of the second plurality of support structures such that each of conductive rings is spaced from adjacent ones of the conductive rings. The conductive rings are vertically spaced from each other when mounted to the second plurality of support structures. 
     The foregoing and other objects of the present invention are achieved by an electrical slip ring assembly. The electrical slip ring assembly includes a first plurality of annular conductive rings spaced from each other and a second plurality of circumferentially spaced electrically non-conductive support structures. The non-conductive support structures each have inwardly extending slots. The first plurality of conductive rings are each mounted in the inwardly extending slots in one of each of the second plurality of support structures such that each of conductive rings is spaced from adjacent ones of the conductive rings. The conductive rings are horizontally spaced from each other when mounted to the second plurality of support structures. 
     Still other objects and advantages of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein the preferred embodiments of the invention are shown and described, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly, the drawings and description thereof are to be regarded as illustrative in nature, and not as restrictive. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention is illustrated by way of example, and not by limitation, in the figures of the accompanying drawings, wherein elements having the same reference numeral designations represent like elements throughout and wherein: 
     FIG. 1 is a perspective view of a comb-like support structure according to the present invention; 
     FIG. 2 is a perspective view of the comb-like support structure including a barrier and an electrically conductive ring installed in a slot of the comb-like structure; 
     FIG. 2A is a cross-sectional view of a portion of the comb-like structure including the barrier and electrically conductive ring mounted to the comb-like support structure; 
     FIG. 3 is a top plan view of a pancake type slip ring according to the present invention; 
     FIG. 4A is a side elevational view of a second embodiment according to the present invention in which each of the slip rings have the same diameter; and 
     FIG. 4B is a top plan view of the embodiment shown in FIG.  4 A. 
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     Referring first to FIG. 1, a perspective view of a comb-like structure  10  is illustrated. As described below, the comb-like structure advantageously eliminates the need for molding the conductive rings as part of the base or plating the conductive rings into completed bases. Further, the present invention eliminates the need to machine an annular base or perform expensive and time consuming operations to roll conductive strips into a machined base member. The comb-like structure  10  has an upper surface  12  and a lower surface  14 . The electrically non-conductive comb-like structure  10  can be machined or molded from a suitable material. The comb includes a series of relatively narrow grooves  20  extending from a top surface  16 . Although the grooves  20  appear to terminate at approximately same height as upper surface  12 , the grooves  20  can extend downwardly below upper surface  12  as depicted in FIG. 1. A series of relatively wider grooves  22  are located between grooves  20 . As depicted in FIG. 1, there are two adjacent relatively narrow grooves  20 ′ and  20 ″, the purpose of which will be explained in detail below. 
     Extending inwardly from the lower surface  14  are a plurality of relatively wider grooves  24  which are aligned with grooves  22 . A through hole  26  extends from bottom surface  28  of grooves  22  through to each bottom surface  30  of grooves  24 . 
     Turning now to FIG. 2, the comb-like structure  10  is shown with a barrier  50  and an electrically conductive slip ring  52  installed in slots  20 ,  22 , respectively. For simplicity, only one barrier  50  and conductive ring  52  are illustrated although each slot  20 ,  22  would include a corresponding barrier  50  or conductive ring  52 . Depending on the voltage, there may not be a requirement for barriers or more than one barrier may be necessary. UL has standards for voltage creapage paths. The low power or signal circuits may have no barriers because they may have only millivolts of potential. The high voltage circuits, which could be as high as 500 volts or more, would need multiple barriers to stop arcing from one circuit to another. 
     The barrier  50  and the conductive ring  52  are engaged with the comb  10 , although it should be understood, particularly with reference to FIGS. 3 and 4, that the rings  50 ,  52  are circular, annular rings and can be machined or formed in one or several sections to be made into a full 360° annular ring. The cross-sectional shapes of rings  50 ,  52  are selected to substantially conform to the shapes of the grooves  20 ,  22  to be mounted therein. 
     As depicted in FIG. 2A, the barrier  50  is mounted in the slot  20  by means such as press-fit, epoxy or the like. The ring  52  has a plurality of studs  54  which are welded or otherwise affixed to the ring  52 . The stud  54  extends through a corresponding hole  28  in the comb-like structure  10 . A washer and nut  56 ,  58 , respectively, are positioned in each groove  24  and secure the respective section of ring  52  to the comb-like structure  10 . As depicted in FIGS. 2 and 2A, the ring  52  is shallower than the corresponding slot  20  such that a top surface  60  of the ring  52  is positioned below the top surface  16  of the comb-like structure  10 . By contrast, the barrier  50  extends upwardly from the top surface  16 . In this manner, brushes (not shown) are kept electrically isolated from adjacent brushes and rings during the rotatable structural member (not shown). 
     A pancake type embodiment is depicted in FIG. 3 whereas an annular slip ring assembly is depicted in FIGS. 4A and 4B. In FIG. 3, a plurality of comb-like structure  10  are fastened to a base or bracket  70  through holes  32  and  34  in comb-like structure  10 , using any type of known fastener. The comb-like structures  10  are circumferentially spaced from each other. The number of combs around the circumference is controlled by the mechanical stiffness of the conductive rings  52 . A sufficient number of comb-like structures  10  must be installed on the rings  52  to maintain electrical contact as the brush moves over the non-supported area between comb-like structures  10 . As depicted in FIG. 3, the rings  52  and barriers  50  are mounted to the comb-like structure  10 . Electrical connections are made to each of the rings and the electrical connections exit the comb-like structures  10  to the inner diameter of the slip ring. The electrical barriers  50  between the conductive rings  52  can be epoxied or mechanically locked in place. The barriers are manufactured from a suitable, flexible, non-conductive material that can be easily installed in the slots  20  in the comb-like structures  10 . The comb-like structures  10 , rings  50 ,  52  can be secured to an epoxy base, either on the face as depicted in FIG. 3 or around the circumference as depicted in FIG.  4 . As depicted in FIG. 3, each of the rings  50 ,  52  has a different diameter. 
     As depicted in FIG. 4, the individual comb-like structures  10  are mounted to a base or to individual brackets to support the comb-like structures. As depicted in FIG. 4B each of the electrical rings  52  has the same diameter. In all other respects, the FIG. 4 embodiment is identical to the FIG. 3 embodiment. 
     It will be readily seen by one of ordinary skill in the art that the present invention fulfills all of the objects set forth above. After reading the foregoing specification, one of ordinary skill will be able to affect various changes, substitutions of equivalents and various other aspects of the invention as broadly disclosed herein. It is therefore intended that the protection granted hereon be limited only by the definition contained in the appended claims and equivalents thereof.