Abstract:
A motor brush lead frame having one end that is folded upon itself to form a pair of pinching surfaces which are adapted to pinch an electrical terminal to establish electrical contact with the electrical terminal. By folding the lead frame member upon itself to form a pair of pinching surfaces, the problems and costs associated with crimping or otherwise attaching a conventional electrical connector to the lead frame member are eliminated.

Description:
TECHNICAL FIELD 
     This invention generally relates to electric motors and more particularly relates to fractional horsepower electric motors. 
     BACKGROUND OF THE INVENTION 
     Fractional horsepower electric motors are used in numerous automotive applications. For example, electric motors are used in automotive seat adjustment mechanisms, side-view mirror adjustment assemblies, and windshield wiper control mechanisms. 
     In the last several years, significant engineering effort has been expended on reducing the cost, and increasing the reliability of fractional horsepower electric motors used in automotive applications. One way to reduce cost and to increase motor reliability is to reduce or eliminate as many components as possible. The present invention provides both these advantages in that it eliminates a separate electrical connector which is commonly used in prior art designs and which is often a cause of motor failure. An additional benefit of the present invention is that it provides more precise electrical terminal positioning than that of the prior art. 
     SUMMARY OF THE INVENTION 
     The present invention provides a motor lead frame including a brush holder assembly and a lead frame member. The brush holder assembly can include a plurality of brushes. The lead frame member can be formed from a single piece of electrically conductive material. The lead frame member can include at least one end that forms a pair of pinching surfaces. The pinching surfaces can pinch an electrical connector to establish an electrical contact between the lead frame member and the electrical connector. The lead frame member can also include a plurality of holes to accommodate the flow of plastic therethrough during an assembly process of the brush holder assembly. The assembly of the lead frame member in situ with respect to the brush holder assembly can provide a durable marriage between the lead frame member and the brush holder assembly. 
     The invention can also include a second lead frame member and a third lead frame member. The second and third lead frame members can be similar to the lead frame member in that the all three lead frame members can be formed from a single piece of electrically conductive material and have at least one end that forms a pair of pinching surfaces to pinch an electrical connector and establish an electrical contact with the electrical connector. The pinching surfaces of the second and third lead frame members can be substantially parallel the pinching surfaces to the pinching surfaces of the lead frame member. In addition, the second and third lead frame members can also include a plurality of holes to accommodate the flow of plastic therethrough during an assembly process of the brush holder assembly. 
     Other applications of the present invention will become apparent to those skilled in the art when the following description of the best mode contemplated for practicing the invention is read in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an exploded view of a motor which employs the brush holder lead frame of the present invention. 
     FIG. 2 is an elevational view of the lead frame and brush members of the brush holder assembly of FIG.  1 . 
     FIG. 3 is an enlarged, cross-sectional view taken substantially through lines  3 — 3  of FIG.  2 . 
     FIG. 4 shows the electrical connector of FIG. 3 in operational engagement with a male spade terminal. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows a exploded view of a typical motor assembly employing the improved lead frame of the present invention. The motor depicted in FIG. 1 is specifically designed to operate the windshield wiper drive mechanism of a vehicle; however, it is to be understood that the improved lead frame design of the present invention is applicable for any electrical motor application even applications which are not confined to motor vehicles. 
     The motor assembly of FIG. 1 includes motor housing  10  and gear housing  16 . Motor housing  10  includes permanent magnets mounted therein (permanent magnets not shown) and is adapted to cover rotor  12  and brush holder assembly  17 . Gear housing  16  houses gear  18  and protects gear  18  from dirt and other contaminates by way of gear cover  20 . Gear  18  includes working shaft  22  which is attached to link arm  24  by way of threaded nut  26 . Link arm  24  is the arm which is attached to the windshield wiper linkage of the vehicle (not shown). Seal  28  prevents dirt and other contaminates from entering the opening (not visible in FIG. 1) of gear housing  16  through which shaft  22  exits. 
     Brush holder assembly  17  includes at least two brushes  30  (only one brush is shown in the exploded view of FIG.  1 ). It is well understood by those skilled in the design of DC motors, that a plurality of brushes  30  engage the commutator  32  portion of rotor  12  in order to electrify one or more windings carried by rotor  12 . Brushes  30  are urged against commutator  32  by way of a respectively associated spring  34 . A flexible braided wire  36  joins each brush  30  to a respectively associated lead frame member  38 . Brush  30 , flexible wire  36 , and lead frame member  38  are all made from electrically conductive material such that they conduct electrical current without introducing significant electrical power loss. 
     Now referring to FIGS. 1 and 2, lead frame assembly  44  is shown in FIG. 1 as it exists in brush holder assembly  17 ; however, in FIG. 2, brush holder  17  is removed. Also, in FIG. 2, flexible wire  36  and brush  30  are shown attached to lead frame member  38  for purposes of clarity and illustration; however, the term lead frame member used throughout this application does not include flexible wire  36  or brush  30 . 
     At end  46  of lead frame member  38  flexible wire  36  is fastened. Any number of fastening techniques can be used such as crimping, soldering, welding, or the like. The only critical aspect of the fastening is that it should not introduce any significant electrical resistance. 
     Now referring to FIGS. 2 and 3, end  48  of lead frame member  38  terminates into an electrical connector. This electrical connector is formed from the lead frame member  38  and accordingly, no fastening step is necessary. Specifically, end  48  of lead frame member  38  is folded upon itself to form a pair of pinching surfaces  50 ,  52 . Pinching surfaces  50 ,  52  are closely adjacent to one another such that they frictionally engage male spade electrical connector  54  when it is forced between pinching surfaces  50 ,  52 . In prior art designs, electrical connectors were crimped or soldered to the ends of lead frame member  38 . The drawbacks associated with crimping electrical connectors include failure due to vibration, the ingress of contaminants, and fatigue failure based on excessive crimping forces used during the crimping operation. All of these disadvantages are eliminated from the current design. Specifically, because the electrical connector is formed from the lead frame member, it is integral therewith, and no crimping operation takes place. Because there is no crimping, there is no opportunity for the ingress of contaminants to compromise the electrical connection between the connector and lead frame member  38  and also, because no crimping operation takes place, there is no opportunity for fatigue failure due to the application of excessive force during the crimping operation. 
     Preferably, lead frame member  38  includes a plurality of holes  56  which pass through the body of the lead frame member. Holes  56  accommodate the flow of plastic therethrough during the assembly process wherein lead frame members  38 ,  40 , and  42  are joined to plastic brush holder assembly  17 . By allowing plastic to flow through holes  56  during the assembly process, a secure and durable marriage is accomplished between lead frame members  38 ,  40 ,  42  and brush holder assembly  17 . Lead frame members  40  and  42  can be similar to lead frame member  38  in that each of the lead frame members  40  and  42  can be formed from a single piece of electrically conductive material and having at least one end that forms a pair of pinching surfaces to pinch an electrical connector and establish an electrical contact with the electrical connector such that the pair of pinching surfaces of the lead frame member are substantially parallel the pinching surfaces of each of the second and third lead frame members. In addition, each of the second and third lead frame members can include a plurality of holes to accommodate the flow of plastic therethrough during an assembly process of the brush holder assembly. This structure is shown in FIGS. 2-4. 
     An additional benefit provided by forming the electrical connector directly from lead frame member  38  is that it provides for a fairly precise orientation of the connector. This is especially important if the male spade terminals which are to engage the connector descend down from gear cover  20 . This will be the case in some embodiments of the present invention wherein electrical male spade terminals are integrally cast into plastic gear cover  20 . If the prior art technique for crimping electrical connectors to the ends of the lead frame members was used, the orientation of the crimped on connectors would be critical in order that the proper mating alignment would be established between the connectors formed on the end of lead frame members  38 ,  40 ,  42  and their respectively associated male spade terminals descending from plastic cover  20  (male spade terminals descending from plastic cover  20  not shown). 
     The foregoing detailed description shows that the preferred embodiments of the present invention are well suited to fulfill the objects of the invention. It is recognized that those skilled in the art may make various modifications or additions to the preferred embodiments without departing from the spirit of the present invention. Accordingly, it is to be understood that the subject matter sought to be afforded protection hereby should be deemed to extend to the subject matter defined in the appended claims including all fair equivalents thereof.