Abstract:
A contact assembly of an alternator comprising an interior chamber, which houses a first end of a rotor shaft having an axis of rotation, first and second bearing assemblies coaxially aligned with the rotor shaft and electrically isolated from one another; and at least one spring member coaxially positioned with respect to the rotor shaft within the chamber. The spring member(s) exerts resistive forces into at least one of the first and second bearing assemblies and support structures within the interior chamber in order to compressively sandwich the first and second bearing assemblies within the interior chamber. The contact assembly may also comprise capacitors electrically connected to the bearing assemblies.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    The present application is a continuation-in-part of U.S. application Ser. No. 09/635,811, filed Aug. 9, 2000, titled “Improved Alternator,” which is based on, and claims priority from, U.S. provisional application Serial No. 60/132,883, filed May 6, 1999, titled “Anti-Friction Brushless Alternator”, which is incorporated herein in its entirety by reference, and is a continuation-in-part of U.S. application Ser. No. 09/498,384, filed Feb. 3, 2000.  
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates generally to electrical machines commonly known as alternators. More specifically, the present invention relates to an improved alternator in which an exciting or field current is supplied to a rotor assembly so that the rotor assembly and a stator assembly may electromagnetically cooperate to generate an AC current for use by and in the operation of, for example, motor vehicles such as heavy duty and business class trucks.  
           [0003]    The basic function of an alternator is to generate the AC current. Two types of alternators, a brush-type alternator and a brushless-type alternator, have been commonly employed by the art.  
           [0004]    In brush-type alternators, the exciting (DC) current is conventionally supplied to the rotor assembly, in part, by brushes that are in physical, sliding contact with a portion of the rotor shaft of the alternator. Brushless-type alternators, as the name implies, do not use brushes in supplying the exciting current. Rather the exciting current is supplied to the fixed core or stator so that there is a stationary field.  
           [0005]    The employment of brushes is a long recognized disadvantage for brush-type alternators. The brushes tend to wear, due to the “mechanical,” brush-to-rotor shaft contact, and have a relatively short life as compared to the rest of the alternator components. Worn brushes must be replaced, and such replacement can be time consuming and expensive.  
           [0006]    Further, the brushes used in brush-type alternators can produce sparks that may damage other nearby equipment, or may create electromagnetic interference problems. Brush-type alternators also tend to be noisy and are sensitive to dusty environments.  
           [0007]    Brushless-type alternators overcome the brush related problems associated with brush-type alternators. However, compared to equivalent brush-type alternators, present brushless-type alternators are inefficient in terms of AC current output. They tend to be much larger in size and heavier than comparable output brush-type alternators. Brushless-type alternators are also more expensive than comparable output brush-type alternators.  
         SUMMARY OF THE INVENTION  
         [0008]    Accordingly, a primary object of the present invention is to provide an improved alternator that overcomes the problems related to the brush-type alternators and disadvantages of the brush-type alternators while avoiding the weight, size, cost and electrical output disadvantages inherent in present brushless-type alternators.  
           [0009]    Another object of the present invention is to provide an improved alternator in which the exciting current is supplied to the rotor assembly, as in a conventional brushtype alternator, but without employment of the conventional brushes or other structure that results in relatively high friction, high wear due to mechanical contact between a rotating member and a relatively fixed member.  
           [0010]    A further object of the present invention is to provide an improved alternator having a rotor assembly, which includes a rotatable shaft that rotates, as the rotor assembly rotates, about the shaft&#39;s longitudinal axis; a stator assembly that electromagnetically cooperates with the rotating rotor assembly so an AC current is generated upon the supply of an exciting current to the rotor assembly; and an improved contact assembly including: at least one, first, relatively fixed member that is disposed adjacent to the rotatable shaft and that is electrically conductive to the exciting current; at least one, second, moveable member that is mounted on the rotatable shaft adjacent to the first member, that rotates with the rotatable shaft, and that is electrically conductive to the exciting current and that defines, with the first member, an annular volume between the first and second members; and third, relatively moveable members that are electrically conductive to the exciting current, that are disposed between the first and second members in the annular volume, that have an electrically conductive grease which is packed in the annular volume and about the third members, and that permits the second member to rotate, relative to the first member, with relatively minimal friction between the first, second and third members.  
           [0011]    These objects are met, in whole or in part, by an improved alternator of the present invention which may employ a rotor assembly, a stator assembly and a rotor shaft like those used in brush-type alternators but which does not utilize conventional brushes for supplying exciting current to the rotor assembly. More specifically, improved alternators of the present invention comprise a rotor assembly and a stator assembly, both of which assemblies may be of conventional design, and an improved contact assembly, which is used to supply exciting current to the rotor assembly instead of the conventional brush structures previously employed in brushtype alternators. In the preferred embodiments, the contact assembly includes two relatively low friction ball bearing assemblies that are electrically isolated from each other and that have components made of an electrically conductive materials. Each of the ball bearing assemblies has an outer race that is electrically connected to an inner race. This electrical connection between each bearing assembly&#39;s respective inner and outer races is provided by a plurality of bearing balls disposed between the inner and outer races, and additionally, by a highly electrically conductive grease that is packed about the balls and between the spaces around the balls so that the balls and grease substantially fill the annular volume defined between the inner and outer races. The inner races of the ball bearings are mounted on and rotate with the rotor assembly shaft. The ball bearings&#39; outer races are held relatively stationary with respect to the inner races and are connected with field conductors, which, in turn, are connected with a source of DC exciting current such as, for example, a conventional storage battery. The contact assembly of the present invention may also be enclosed in a cartridge housing that is made of an electrical insulative material and that maintains the outer races of the bearing assemblies axially aligned with and concentric about the longitudinal axis of the rotor shaft. The rotor shaft, adjacent to the contact assembly, includes stepped diameter portions that facilitate the assembly of the bearing assemblies into and about the rotor shaft.  
           [0012]    The improved alternator of the present invention affords commercially important advantages vis-a-vis conventional brush-type and brushless-type alternators. The improved alternator eliminates brushes, and their concomitant problems, and gives the long life characteristics of a brushless-type alternator. The improved alternator also provides the output characteristics of a brush-type alternator, which includes good output at low rpms as, for example, at 5000 rpms. The improved alternator also requires less space than conventional brushless-type alternators with the same output and is more economical and lighter in weight.  
           [0013]    Certain embodiments of the present invention provide an improved alternator for use with motor vehicles and for supplying AC current for the operation of the motor vehicle in response to a DC exciting current being supplied to the alternator from a source of exciting current. The improved alternator comprises a rotor shaft and a contact assembly. The rotor shaft has first and second ends and an axis of rotation. The contact assembly comprises first and second bearing assemblies and at least one spring member. The contact assembly comprises first and second bearing assemblies that are disposed adjacent to the first end of the rotor shaft. The first and second bearing assemblies are coaxially aligned with the rotor shaft. The first and second bearing assemblies are longitudinally spaced from one another by a first spacer. The bearing assemblies are electrically isolated from one another. Each of the first and second bearing assemblies have an outer race member that is relatively fixed with respect to the rotor shaft.  
           [0014]    The first spring member is coaxially positioned with respect to the rotor shaft within the contact assembly. The first spring member exerts at least one resistive force into at least one of the first and second bearing assemblies in order to maintain a constant axial force between the first and second bearing assemblies. The improved alternator may also comprise a second spring member. The spring member(s) exerts resistive forces into at least one of the first and second bearing assemblies and support structures within said chamber in order to compressively sandwich the first and second bearing assemblies within the chamber of the contact assembly.  
           [0015]    Additionally, the improved alternator may also comprise a locating sleeve positioned over the bearing assemblies. The locating sleeve ensures and maintains proper axial alignment of the rotor shaft and the bearing assemblies.  
           [0016]    The bearing assemblies may be retained, in part, by bearing holders. Each bearing assembly is retained by a separate bearing holder. The bearing holders are separate and distinct from one another in order to allow relative motion between the first and second bearing holders.  
           [0017]    The improved alternator of may also comprise at least one capacitor in electrical communication with each of said first and second bearing assemblies. The capacitor(s) absorb electrical charges produced by arcing, sparking and the like.  
           [0018]    Certain embodiments of the present invention also provide a method of manufacturing a contact assembly of an alternator. The method comprises the steps of positioning a rotor shaft having an axis of rotation within an interior chamber of the contact assembly; coaxially positioning a slip ring over the rotor shaft; coaxially positioning two bearing assemblies over the slip ring and the rotor shaft; mechanically and electrically isolating the two bearing assemblies from one another; and compressively sandwiching the two bearing assemblies together along the axis of rotation by way of at least one spring member. The method may further comprises the step of ensuring proper axial alignment of the rotor shaft and the bearing assemblies through a locating sleeve positioned over the bearing assemblies. Additionally, the method may comprise the step of retaining each of the two bearing assemblies through separate and distinct bearing holders, each of the bearing holders moving independent of the other. Also, the method may comprise the step of electrically connecting at least one capacitor to the two bearing assemblies.  
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0019]    [0019]FIG. 1 is vertical cross-sectional view, taken along the longitudinal axis of the rotor assembly shaft, of the improved alternator of the present invention.  
         [0020]    [0020]FIG. 2 is a partially exploded, perspective view of the rotor assembly and contact assembly of the alternator of the present invention.  
         [0021]    [0021]FIG. 3 is a partially exploded perspective view of components of the contact assembly of the alternator of the present invention  
         [0022]    [0022]FIG. 4 is a schematic, partial vertical cross-sectional view of components of the contact assembly.  
         [0023]    [0023]FIG. 5 is an exploded, isometric view of another embodiment of the improved alternator of the present invention.  
         [0024]    [0024]FIG. 6 is an end elevational view of the housing of the improved alternator of FIG. 5, taken of the right end of the alternator as shown in FIG. 5.  
         [0025]    [0025]FIG. 7 is an exploded, isometric view of a portion of the cartridge housing assembly of the improved alternator of FIG. 5.  
         [0026]    [0026]FIG. 8 is an end elevational view of the cartridge housing portion, as assembled, and as shown in FIG. 7.  
         [0027]    [0027]FIG. 9 is a cross-sectional view taken along the line  9 - 9  of FIG. 8.  
         [0028]    [0028]FIG. 10 is a side elevational view of the rotary stub shaft of the improved alternator of FIG. 5.  
         [0029]    [0029]FIG. 11 is an end elevational view of the stub shaft of FIG. 10, taken of the left end of the shaft as shown in FIG. 10.  
         [0030]    [0030]FIG. 12 is a vertical cross-sectional view of a contact assembly according to an alternative embodiment of the present invention. 
     
    
       [0031]    The foregoing summary, as well as the following detailed description of certain embodiments of the present invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings, certain embodiments. It should be understood, however, that the present invention is not limited to the arrangements and instrumentalities shown in the attached drawings.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0032]    As an overview, the improved contact assembly  12 , hereinafter described, of the present invention is intended to be used with alternators which heretofore might have commonly been described as brush-type alternators. More particularly, the contact assembly  12  is intended to be employed in place of conventional alternator brush structure, that is, the structure used to supply DC exciting current to the rotor shaft of a rotor assembly of a brush-type alternator. For this reason, the conventional alternator structure, as illustrated in FIGS. 1 and 2 will be only generally described.  
         [0033]    In this regard the improved alternator  14 , illustrated in FIG. 1, has a housing  15  that includes two die-cast aluminum parts (i.e., a front housing portion  16  and a rear housing portion  18 ). A rotor assembly  22  and stator assembly  24  are enclosed within the housing  14 .  
         [0034]    Referring now to the alternator embodiment of FIGS.  1 - 4 , the rotor assembly  22  is of conventional design and structure. The assembly  22  includes a centrally disposed rotor shaft  26 , a field coil  28  disposed around an iron core  32 , and two pole pieces  34 ,  36 . The rotor assembly  22 , including the shaft  26 , rotates about the central longitudinal axis of the shaft  26 . Conventional ball bearings  38  and  42  are mounted in the housing  14  and serve to support the shaft  26  and thus the entire rotor assembly  22 , for rotation about the central longitudinal axis of the shaft  26 . The one end  44  (the left end as shown in FIG. 1) of the shaft  26  may be connected with, for instances, a pulley, not shown, that may be driven by the engine of a motor vehicle, also not shown. The contact assembly  12  is disposed adjacent to the other end  46  (the right end as shown in FIG. 1) of the shaft  26  and will be more fully described hereinafter. A cooling fan blade  48  may also be mounted on the shaft  26 , for rotation with the shaft  26 , adjacent the bearing  38 .  
         [0035]    The stator assembly  24  is of conventional design and structure. The assembly  24  is disposed between the front and rear housing portions  16  and  18 . The frame of the stator assembly  24  is formed by a number of steel stampings riveted together. Around the stator frame, three windings are arranged in layers in three slots on the frame, and the ends of the windings are connected with a conventional rectifier  52 .  
         [0036]    As illustrated in FIGS. 1 and 2, a pair of conventional electrical leads  54  and  56  extend radially inwardly from the field coil  28  to and into the shaft  26 . The leads  54  and  56  then extend longitudinally, along a longitudinal internal passage  58  in the shaft, which passage  58  generally parallels the longitudinal shaft axis, toward and out of the other end  46  of the shaft  26 . As noted, the end  46  is supported by the ball bearing  42 , which is spaced from the rotor assembly  22  by a conventional spacer ring  62 .  
         [0037]    A stub shaft  64  is coupled to and from a part of the end  46  of the shaft  26 . The end  46  and the stub shaft  64  may be coupled or inter-connected by a conventional shaft connection that will permit the stub shaft to rotate with the shaft  26 .  
         [0038]    The stub shaft  64  is preferably molded of nylon or any other suitable electrically nonconductive plastic material. It includes a distal end part  66 , a larger diameter flange part  68 , which abuts the distal end  74  of the shaft end  46 , and a shaft coupling part  72 . The leads  54 ,  56  extend longitudinally through the stub shaft  64  so that the distal ends of  5  the leads may project out of and beyond the distal end  74  of the shaft  64 .  
         [0039]    The connector assembly  12  also includes a pair of rings  76 ,  78  that fit over and are mounted on, in a longitudinal spaced relationship, on the stub shaft part  66 . The rings  76 ,  78  are preferably made of copper, are electrical conductive and may be molded with the stub shaft  64 . A pair of copper conductor poles  82 ,  84  are molded into the part  66 . The inboard ends of the poles  82 ,  84  are electrically connected with the rings  76 ,  78  respectively. The other, outboard ends of the poles  82 ,  84  are connected, preferably by soldering, to the distal ends of the leads  54 ,  56 , respectively.  
         [0040]    As illustrated in FIGS. 1, 3 and  4 , the contact assembly  12  further includes an outboard, relatively low-friction ball bearing or bearing assembly  86 , an inboard, relatively low-friction ball bearing or bearing assembly  88 , an outboard field conductor  92 , an inboard field conductor  94  and a cartridge housing  96 . A cartridge housing  96 , which is preferably made of a molded, electrically non-conductive plastic or phenolic material, encloses and supports the ball bearings  86 ,  88  and the field conductors  92 ,  94 .  
         [0041]    Except as hereinafter noted, the ball bearings  86 ,  88  may be of a conventional design and construction. The ball bearings  86 ,  88  include outer races  98 ,  102 , respectively, inner races,  104 , 106 , respectively, and a plurality of bearing balls  108 ,  112 , respectively, which are disposed between, and in the annular volume defined between, the inner and outer races. The bearing balls  108 ,  112  may be maintained between their respective inner and outer races by conventional cages not shown in FIGS.  1 - 4 . The ball bearings  86 ,  88  are made of a highly conductive material such as, for instance, high carbon chromium, low carbon steel, or a bronze/brass alloy. It is preferable that approximately one-third of the annular volume (which, as noted, is defined by and between the inner and outer race) is open, that is, not occupied by the balls. The bearings are packed in an electrically conductive grease that, with the balls and cage, completely fills the annular volume. A preferably useable grease is: Nyogel 753G, manufactured by NYE Lubricants Inc. of New Bedford, Mass. As shown best in FIG. 3, each of the annular volumes between the inner races  104 ,  106  and the outer races  98 ,  102 , respectively, is closed by conventional lip seals  114 ,  116  that close or seal both sides of the annular volumes (that is, the sides substantially perpendicular to the longitudinal axis of the rotor shaft  26 ) of each of the bearings  86 , 88 . The lip seals  114 ,  116  prevent the grease from escaping from about the balls  108 ,  112  during rotation of the ball bearing  86 , 88  which normally will be in excess of 5000 rpms. The lip seals  114 ,  116  may be made of a buna(nitride) material. The ball bearings  86 ,  88  may be manufactured by NTN USA Corporation (NTN Bearing Corporation of America) of Mount Prospect, Ill.  
         [0042]    The outer races  98 ,  102  each include a radially outwardly facing, annular copper layer. The inner races  104 ,  106  fit about, and are in surface-to-surface contact with the rings  76 ,  78 , respectively. The fit, preferably press-fit, between the inner races  104 , 106  and their respective rings  76 , 78  is such that no relative rotary movement occurs between them. Hence, both the inner races  104 , 106  and the rings  76 ,  78  rotate with the stub shaft  64 , and thus with the shaft  26 .  
         [0043]    The field connectors  92 ,  94  are made of copper and are cast or molded in the housing  96 . The connectors  92 ,  94  include annular members  122 ,  124 , respectively. The inner radial dimension of the annular members  122 , 124  is such that the ball bearings  86 ,  88 , and more particularly, their outer races  98 ,  102 , tightly fit within the members  122 ,  124 , respectively and so that there is surface-to-surface contact between the radical inner facing surfaces of the members  122 ,  124  and the radial outer facing surfaces of the outer races  98 , 102 . It is preferable that the longitudinal length or width (that is, the dimension in the longitudinal direction) of the members  122 , 124  is approximately two-thirds of the longitudinal length of the outer races  98 , 102 .  
         [0044]    The field connectors  92 ,  94  also includes radially outwardly projecting, copper arms  126 ,  128 , respectively. The radially inner ends  132 ,  134  of the arms  126 ,  128  respectively, are secured to the radially outwardly facing surface of the annular members  122 ,  124 , respectively. The other, outer ends  136 , 138  of the arms  126 ,  128 , respectively, are disposed at an angle (90° as shown in FIG. 3) with the plane of the members  122 ,  124  and are adapted to be connected to the conventional electrical leads (shown at  142 ,  44  in FIG. 1) connected with a conventional storage battery, not shown, as a source of a DC current.  
         [0045]    As noted, the outer races  98 ,  102  of the ball bearings  86 ,  88  are each electrically connected to the field conductors  92 ,  94 , respectively. More specifically, the outer race  98  of the outboard bearing  86  is electrically connected with the outboard field conductor  92 , and the outer race  102  of the inboard bearing  88  is electrically connected with the inboard field conductor  94 . The field conductors  92 ,  94  are typically oppositely electrically charged. For present, exemplary purposes, the outboard field conductor  92  is negatively charged, and the inboard field conductor  94  is positively charged. Thus, the outboard field conductor  92  is electrically connected to the negative terminal of the battery, and the inboard field conductor  92  is electrically connected to the positive terminal of the battery. However, this convention is not necessary, and the charges may be reversed.  
         [0046]    As also noted, the inner races  104 ,  106  are electrically connected to the leads  54 ,  56 , respectively, that extends from the field coil  28 . Again and more specifically, inner race  104  of the outboard bearing  86  is electrically connected with the negative lead of the field coil, and the inner race  106  of the inboard bearing  88  is electrically connected with the positive lead of the field coil. As described before, the inner races  104 ,  106  of ball  20  bearings  86 ,  88  are mechanically secured to and allowed to rotate with the stub shaft  64  while the outer races  98 , 102  of the ball bearings  86 ,  88  remain relatively stationary and with the cartridge housing  96 .  
         [0047]    The DC exciting or field current from the positive terminal of the battery passes through the inboard field conductor  94  to the outer race  102  of the inboard ball bearing  88 . From the outer race  102 , the exciting current flows through the bearing  88  to the inner race  106 . The current then flows from the inner race  106  to the ring  78 , to the pole  82 , to the positive lead  56  and ultimately to the field coil  28 .  
         [0048]    The exciting current flows through the field coil  28 , thus creating a magnetic field needed to generate AC current by the electromagnetic cooperation between the rotating rotor assembly  22  and the stator assembly  24 .  
         [0049]    The exciting current then flows from the field coil  28 , and through the negative lead  54 , the pole  84 , and the outboard ring  76  to the inner race  104  of the outboard ball bearing  86 . The exciting current is then transmitted from the inner race  104 , through the balls  108  and the surrounding grease, to the outer race  98  of the outboard bearing  86 . The exciting current then flows from the outer race  98 , to the outboard field conductor  92 , to the lead  142  and ultimately to the battery through the battery&#39;s negative terminal.  
         [0050]    Referring again to FIG. 4, a capacitor  300  is positioned between, and in electrical communication with, the bearing assemblies  86  and  88 . Similarly, a capacitor  302  is positioned between, and in electrical communication with, the bearing assemblies  86  and  88 . The capacitors  300  and  302  may be 0.1 microFarad capacitors; however, other suitable capacitors may be used depending on the magnetic field generated. The capacitors  300  and  302  may be connected in series, or in a parallel, with the bearing assemblies  86  and  88 . The capacitors  300  and  302  may be connected to the inboard field conductor  94  and/or the outboard field conductor  92 . The addition of the capacitors  300  and  302  on the inboard and outboard filed conductors  94  and  92 , respectively, of the bearing assemblies  86  and  88  absorbs excess energy such as that produced by sparking, arcing, and the like, which may develop as the alternator  14  is activated and in use. Overall, it has been found that because the capacitors  300  and  302  absorb the energy produced through arcing and sparking, electrolytic corrosion of the components of the system is reduced.  
         [0051]    As shown in FIG. 4, two capacitors  300  and  302  are positioned above the rotor shaft  26  while two capacitors  300  and  302  are positioned below the rotor shaft  26 . Optionally, only one capacitor  300  or  302  may be positioned above the rotor shaft  26 , while another conductor  300  or  302  may be positioned below the rotor shaft  26 . Additionally, more than two capacitors  300  and  302  may be used. That is, instead of using four total capacitors, as shown in FIG. 4, five or more capacitors may be used. Further, the capacitors  300  and  302  may be oriented in a variety of configurations relative to the bearing assemblies  86  and  88 .  
         [0052]    While in the foregoing description of a preferred embodiment, two ball bearings  86 ,  88  have been utilized to connect the exciting current from the battery to the electrical leads  54 ,  56  it should be recognized that a single ball bearing assembly might be used to conduct this current. If such a single ball bearing were to be used in an alternator, it would include two sets of balls and its outer and inner races would have to be divided into two, longitudinal, electrically insulated portions, so that the single bearing would function as the two bearings  86 , 88  as described above.  
         [0053]    It has been found that enhanced performance and longer bearing life will be achieved when the longitudinal axes of the rotor shaft, the stub shaft, the inner and outer races of the ball bearings are maintained axially aligned and concentric. Also manufacturing efficiencies can be achieved by making the stub shaft and ball bearings such that the I.D.&#39;s of the inner races of the two ball bearings are different, that is, where the ID of the inboard ball bearing is slightly larger than the ID of the outboard ball bearing. Also the manufacture and assembly of the alternator is improved when the cartridge housing is made in two, substantially mirror image parts or pieces.  
         [0054]    Referring now to the alternator embodiment shown in FIGS.  5 - 11 , an improved alternator  150  of the present invention, as shown in FIG. 5, is structurally and functionally identical to the alternator  14  except as noted below. More specifically, the alternator  150  includes a rear housing  152 , a stub shaft  154 , and a cartridge housing assembly  156  that are structurally and functionally identical to the housing  18 , stub shaft  64  and housing  96 , respectively, except as noted below. Otherwise (and except as noted) the alternators  14  and  150 , and their other components are substantially identical in structure and function.  
         [0055]    As best illustrated in FIGS.  5 - 6 , the right facing end (with reference to FIG. 5) of the housing  152  includes a centrally disposed, generally key-hole shaped recess  158 . This recess  158  is designed to closely receive the housing assembly  156  when the ball bearings  86 , 88  are assembled in the alternator  150 . The shape and outer dimensions of the recess  158  are selected with respect to the shape and dimensions of the housing assembly  156  so that when the housing assembly  156  (with its component parts) is fit (preferably press-fit) within the recess  158 , the fit maintains the ball bearings  86 , 88  and more particularly, the outer races  98 , 102 , in axial alignment with and concentric about the longitudinal central axis of the shaft  26 .  
         [0056]    The cartridge housing assembly  156  includes two parts  162 , 164 . The parts,  162 , 164  are generally structurally and functionally identical to each other except for the size of their recesses  166  as described below. Like the housing  96 , the parts  162 , 164  are preferably made of molded, electronically non-conductive plastics or phenolic material.  
         [0057]    When assembled, the parts  162 ,  164  are arranged as mirror images of each other as illustrated in FIG. 5. Because of this, only the inboard part  162  will be described in detail. In this regard and with reference to FIG. 5 and particularly to FIGS.  7 - 9 , the part  162  includes a head portion  168  whose outer peripheral shape and size is substantially identical to the correspondingly curved portion of the key hole recess  158 . Hence when the parts  162 , 164  are fit (preferably press-fit) within the recess  158 , they do not move with respect to the housing  152 . The head portion  168  of the part  162  includes a central recess  166 . Access to the recess  166  is through two openings  172 , 174  that are formed in axial facing sides of the head portion. The opening  172 , 174  have different diameters. The larger opening  172  is dimensioned and shaped so that the ball bearing  88  may be received within the recess  166 . Specifically, the ID of the opening  172  and recess  166  are selected so that the OD of the bearing  88  will fit tightly (preferably press-fit) within the recess  166  through the opening  172 . The smaller openings  174  is in the opposite side of the head portion  168  and is dimensioned so as to permit the stub shaft  154  to extend into and through that opening.  
         [0058]    The part  162  (and also the part  164 ) includes integral leg portion  182  that depends or extends from adjacent to the side of the head portion that includes the smaller opening  174 . The portion  182  includes a hole  184  that receives a bolt  186  that is used to secure the parts  162 ,  164  together and to the housing  152 . An annual spacer  188  also receives the bolt  186  and extends between the leg portions  182  of the parts  162 , 164 . The spacer  188  is longitudinally dimensioned so that when assembled, the head portions  168  of the parts  162 , 164  abut face-to-face and with the openings  172  facing each other and so that the longitudinal axis of the recesses  166  are aligned and coaxial. As shown in FIG. 5, a viton “0” ring  190  is disposed and clamped between the abutting head portions  168  and surrounds the openings  172 . The “0” ring  172  is made of a flor elastomer, provides heat insulation and prevents electrical shorting between the abutting adjacent head portions  168  of the parts  162 , 164 .  
         [0059]    An annular, copper field conductor ring  192 , like the members  122 , 124  of the conductors  92 ,  94 , surrounds and defines each of the recesses  166 , and electrically cooperates with the OD&#39;s of the outer races  98 ,  102 . An electrical lead, not shown, is molded in each of the parts  162 , 164  and extends between the annular conductor  192  and connectors  194  which project from the distal ends of the portions  182  of each part  162 ,  164 . The connector  194 , like the arms  126 , 128 , is adapted to be connected with a conventional storage battery via a conventional voltage regulator. As discussed below, the OD&#39;s of the outer races  98 , 102  have slightly different diameters. For this reason, the ID of the recesses  166  in the parts  162 , 164  similarly have different diameters.  
         [0060]    Specifically, the recess  166  of the part  162  is dimensioned so that the outer race  102  of the bearing  88  can be press-fit within the recess. Similarly, the recess  166  of the part  164  is dimensioned so that the outer race  98  of the bearing  86  can be press-fit within the recess. As best illustrated in FIG. 9, a conventional cage  202  maintains the balls  112  separate and circumferentially evenly spaced from each other. The cage  202  is metal and hence does electrically interconnect the balls. In each of the bearings  86 , 88 , the electronically conductive grease, which is packed about the balls  112  (and about the cage  202 ) is maintained within the annular volume (defined between the inner and outer races  102 , 106 ) by the two lip seals is  204 , 206 . In other words, the lip seals  204 ,  206  prevent the grease from escaping from the annular volume, since were any grease to escape, the grease might cause an electrical short between the adjacent ball bearing.  
         [0061]    Referring now to FIGS. 5 and 10- 11 , the stub shaft  154  has an inboard end  212  that is configured and adapted to mechanically interconnect with the distal end (or right end as in FIG. 205) of the shaft  26 . When thus interconnected, the shafts  26  and  154  are coaxially aligned and rotate together. Specifically, the end  212  includes four, evenly spaced, radially disposed shoulder portions  214 ,  216 ,  218  and  222  that interfit with corresponding, but annularly spaced shoulder portions (not shown) on the distal end of the shaft  26 .  
         [0062]    The inboard ends of the leads  54 ,  56  in the shaft  154  terminate in axially recessed, electrical fittings  224 ,  226 . As shown in FIG. 11, these fittings  224 ,  226  can be snap connected with corresponding fittings on the distal portions of the leads  55 ,  56  in the shaft  26 .  
         [0063]    The distal end portion  228  of the shaft  154  has a preselected OD that is slightly smaller than the OD of the mid-portion  232  of the shaft  154 . As with the shaft  64 , the end portion  228  and mid-portion  232  include electrically conductive rings  76  and  78 , respectively mounted (or preferably molded) about them. These rings are electrically connected with the leads  54 ,  56 , respectively.  
         [0064]    The ID&#39;s of the inner races  104 ,  106  of the ball bearings  86 ,  88  are selected so that the inner races may be press-fit about OD&#39;s of the end portion  228 ,  232  (with rings), respectively. Differentiating (that is, stepping) the DD&#39;s of the portions  228 ,  232  and the ID&#39;s of the inner races  104 ,  106  facilitates assembly of the bearings  86 ,  88  onto the shaft  154 . Hence the assembly of the entire contact assembly  156  onto the alternator  150 .  
         [0065]    [0065]FIG. 12 is a vertical cross-sectional view of a contact assembly  12 ′ according to an alternative embodiment of the present invention. The contact assembly  12 ′ is similar to the contact assembly  12  in that it is included within the rear housing  18  of the alternator  14 . The contact assembly  12 ′ includes an end cap  314  attached to the rotor  26  having an axis of rotation  315 , spacer  316 , outboard spacer  318 , inboard spacer  319 , a slip ring  320 , inboard bearing  322 , outboard bearing  323 , spacer  324 , an inboard bearing holder  326 , an outboard bearing holder  327 , a sleeve  328 , a wave spring  330 , shim spring  332 , washer  334  and cap screw  336 . The spacers  316 ,  318  and  319  may be formed of a phenolic material or any other electrically insulative material.  
         [0066]    The slip ring  320 , which is coaxially positioned with the spacer  324  and the rotor  26 , is secured to the rotor  26  by way of an interference fit with the shaft of the rotor  26 . The inboard spacer  319  is coaxially positioned over the slip ring  320  and the spacer  324 . The inboard spacer  319  assists in axially positioning the inboard bearing  322 . Additionally, the inboard spacer  319  axially clamps the inner race of the inboard bearing  322  once assembly of the contact assembly  12 ′ is complete.  
         [0067]    The inboard bearing  322  is retained by the inboard bearing holder  326 , while the outboard bearing  323  retained by the outboard bearing holder  327 . The steel sleeve  328  allows radial loading of the bearings  322  and  323  and serves as a sliding guide or skirt. The steel sleeve  328  acts as an assembly locator for the coaxial components of the contact assembly  12 ′, ensuring axial alignment and concentricity of the components of the contact assembly  12 ′. The inboard bearing holder  326  and outboard bearing holder  327  are separate and distinct from one another so as to allow relative motion between the two. That is, the bearing holders  326  and  327  may move independent of one another and each may automatically adjust to spring tension exerted by the shim spring  332  and the wave spring  330 .  
         [0068]    The outboard spacer  318  is positioned between the inboard and outboard bearings  322  and  323 , thereby separating the bearings  322  and  323  from one another. The outboard spacer  318  also mechanically interlocks the bearings  322  and  323  together by axially clamping the inner races of the bearings  322  and  323  once assembly of the contact assembly  12 ′ is complete. The end cap  314  rigidly clamps and locks the components of the contact assembly  12 ′ onto the slip ring  320  and the shaft of the rotor  26 . The inner races of the bearings  322  and  323  are securably retained so that the rotating components of the contact assembly  12 ′ remain in the same phase angle during operation.  
         [0069]    The outer race of the inboard bearing  322  is retained by the inboard bearing holder  326 . The inboard bearing  322  and inboard bearing holder  326  are axially loaded onto the slip ring  320  against the wave spring  330 , which is sandwiched between the inboard bearing  322  and the spacer  316 . The wave spring  330  has a spring tension. The spring tension of the waver spring  330  exerts a resistive force on the inboard bearing  322  in the direction of line A while simultaneously exerting a resistive force in the direction of line B. The forces exerted by the wave spring  330  in the directions of lines A and B are sufficient to compress the wave spring  330  between the outboard spacers  316 ,  318 , which are in turn compressed against the inboard bearing  323  (as discussed below) and the inboard spacer  319 . The inboard spacer  319  is in turn compressed against support structure  338 , which may be an additional bearing, or support wall within the rear housing  18 . The directions of lines A and B are generally parallel to the longitudinal axis  315  of the shaft of the rotor  26 .  
         [0070]    Similarly, the outer race of the outboard bearing  323  is retained by the outboard bearing holder  327 . The outboard bearing  323  and outboard bearing holder  327  are axially loaded onto the slip ring  320  by way of the shim spring  332 , which is sandwiched between the outboard bearing holder  327  and a support structure  340 , which may be a support wall, within the rear housing  18 . That is, the shim spring  332  exerts a resistive force on the outboard bearing holder  327  in the direction of line A, while simultaneously exerting a resistive force on the support structure  340  in the direction of line B. The forces exerted by the shim spring  332  are sufficient to compress the shim spring  332  and the outboard bearing  323  into the spacers  316  and  318 . Thus, the shim spring  332 , the outboard bearing holder  327 , the outboard bearing  323 , the spacers  316 ,  318 , the inboard bearing  322 , the inboard bearing holder  326  and the spacer  319  are all compressively sandwiched between the support walls  340  and  338  due to the forces exerted by the wave spring  330  and the shim spring  340 . That is, the wave spring  330  and the shim spring  332  ensure proper mechanical contact between components of the contact assembly  12 ′.  
         [0071]    The shim spring  332  and wave spring  330  provide sufficient force upon axial loading of the components of the contact assembly  12 ′, to ensure that the components are compressed together. The outer races of the bearings  322  and  323  are spring loaded thereby maintaining a constant axial force among the outboard bearing  323 , the spacers  316 ,  318 , the inboard bearing  322 , the spacer  319  and supporting structure within the contact assembly  12 ′.  
         [0072]    The exciting current is free to travel to and from the field coil  28  in a similar fashion as that described above with respect to FIG. 4. The separation of the bearings  322  and  323  by the spacers  318  and  316  ensures that the bearings are electrically isolated from one another, so that the outboard field conductor connected to the outboard bearing  323  remains negatively charged while the inboard field conductor connected to the inboard bearing  322  remains positively charged.  
         [0073]    While not shown in FIG. 12, capacitors, such as capacitors  300  and  302  (as shown in FIG. 4) may be positioned within the contact assembly  12 ′. As discussed above with respect to FIG. 4, the capacitors absorb electrical discharge from arcing, sparking and the like.  
         [0074]    While the preferred embodiment of the present invention has been described, it will be understood that this description has been made by way of example and that it should be recognized that modifications and changes may be made by those in this art without departing from the spirit and scope of the invention.