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You are an expert at summarizing long articles. Proceed to summarize the following text: 
FIELD OF THE INVENTION 
       [0001]    The present invention relates to automotive window regulators. More specifically, the present invention relates to a lift plate for a window regulator that resists backdrive forces. 
       BACKGROUND OF THE INVENTION 
       [0002]    Automotive window regulators are required to resist backdrive in order to prevent a partially opened window from being forced down from the outside of the vehicle, such as in a break-in attempt. Current industry practice is to resist backdrive by using a torsion spring clutch in a manual window regulator, and by the electric motor gear ratio in a power window regulator. The disadvantages of both these systems is that the complete window regulator must be robust enough to withstand the backdrive force since the transmitted load path extends all the way from the window glass to the lift plate to the drive assembly (either a manual crank assembly or a power motor). In addition, the traditional methods of resisting backdrive create inefficiencies when the window regulator is operated normally. In a manual system the clutch torque, which could be as high as 20% of the total operating torque, must be overcome before motion is transmitted to the lift plate. In a power system, single-start worms are required in the motor gearset to ensure suitable backdrive gear efficiency, but single-start worms also create a very low driving efficiency for normal operation of the window regulator. 
         [0003]    It is therefore desired to provide a window regulator that resists backdrive in a manner that mitigates or obviates at least one of the above-described disadvantages. 
       SUMMARY OF THE INVENTION 
       [0004]    The present invention provides a window regulator that resists backdrive forces directly at the lift plate and rail, rather than by the drive assembly. A locking shoe is mounted within the lift plate and selectively frictionally engages the rail while the drive assembly is at rest. Thus, any backdrive forces are transmitted from the window glass to the lift plate, and then directly to the rail, avoiding the drive assembly. A release fork that is coupled to the drive cable automatically disengages the locking shoe when the drive assembly is activated, and engages the locking shoe when the drive assembly disengages. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    Preferred embodiments of the present invention will now be described, by way of example only, with reference to the attached Figures, wherein: 
           [0006]      FIG. 1  shows a perspective view of a portion of a window regulator in accordance with an aspect of the invention; 
           [0007]      FIG. 2  shows a perspective view of a lift plate located on the window regulator shown in  FIG. 1 ; 
           [0008]      FIG. 3  shows a perspective view of a locking shoe and a nipple housing located on the window regulator shown in  FIG. 1 ; 
           [0009]      FIG. 4  shows a perspective view of the nipple housing shown in  FIG. 3  with the locking shoe removed; 
           [0010]      FIG. 5  shows a perspective view of a the locking shoe shown in  FIG. 3  from an alternate angle; 
           [0011]      FIG. 6  shows a perspective view of the nipple housing shown in  FIG. 4  from an alternate angle; and 
           [0012]      FIG. 7  shows a perspective view of the nipple housing shown in  FIGS. 4 and 6  from an alternate angle. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0013]    Referring now to  FIG. 1 , a portion of a window regulator  10  is shown. Window regulator  10  includes a rail  12  that slidably mounts a lift plate  14 . Lift plate  14  is operable to traverse rail  12  using a drive cable  16  that is wound around a conventional drive and pulley assembly  18  (not shown). A locking shoe  20  is slidably mounted to rail  12  and retained within a cutout on lift plate  14 . Additionally, a nipple housing  22  floats within the cutout on lift plate  14 . 
         [0014]    Rail  12  is preferably formed from a unitary piece of metal or plastic and can be manufactured by conventional molding, stamping or roll forming techniques. Rail  12  is attached to a substructure (not shown) of a vehicle door frame via conventional fasteners. Alternatively, rail  12  can be attached to or otherwise formed as part of the substrate of a door hardware module. Rail  12  provides an opposing first surface  21  and second surface  23  (not shown), and further includes a parallel first edge  24  and a second edge  26  that run longitudinally along rail  12 . An arcuate flange  28  is integrally formed from first edge  24  and curves away from first surface  21  of rail  12 , providing a mounting surface for lift plate  14  (described in greater detail below). Proximate to the second edge  26  is a semicircular groove channel  30  that runs parallel to second edge  26 . 
         [0015]    Lift plate  14  is raised or lowed by drive and pulley assembly  18  (not shown). As known to those of skill in the art, drive and pulley assembly  18  typically includes a pulley mounted at each end of rail  12 , and a cable drum mounted to window regulator  10  between the two pulleys, but displaced away from rail  12 . Other arrangements of pulleys and cable drums will occur to those of skill in the art, and are within the scope of the invention. For example, the pulleys or the cable drum could be mounted directly to a door hardware module, instead of rail  12 . Drive cable  16  is threaded around the cable drum and pulleys, and is described in greater detail below, terminates with a nipple  17  at each end inside nipple housing  22  located within lift plate  14 . The cable drum is further coupled to a conventional manual crank system or an electric motor to move the lift plate along rail  12 . 
         [0016]    Referring now to  FIG. 2 , lift plate  14  is shown in greater detail. Lift plate  14  is preferably formed from a unitary piece of metal or plastic and can be manufactured by conventional casting or molding techniques. Lift plate  14  is adapted to mount a window glass (not shown) on a first surface  29  using conventional fasteners, tabs or the like. As described earlier, lift plate  14  is slidably mounted to rail  12 . An arcuate quadrant slot  32  is provided in an opposing second surface  31  of lift plate  14  and is complementarily fitted over arcuate flange  28 . This mounting configuration provides a degree of axial freedom of rotation of lift plate  14  around rail  12  without affecting the locking or unlocking action of lift plate  14  (described in greater detail below). Axial freedom of rotation provides for correct glass tracking and alignment of the window glass with the glass run channels in the door frame (not shown). As mentioned earlier, lifting plate  14  further includes a cutout  34  between first surface  29  and second surface  31 . In the current embodiment, cutout  34  includes a generally rectangular area  36  in communication with a generally oval area  38 . As can be seen in  FIG. 1  and is described in greater detail below, locking shoe  20  is retained against the sidewalls of rectangular area  36  and nipple housing  22  floats more loosely within oval area  38 . Two cable passages  40  coaxial with rail  12  extend from opposing side walls  33  of lifting plate  14  into oval area  38  and provide means to thread drive cable  16  through to nipple housing  22 . 
         [0017]    Referring now to  FIGS. 3 to 5 , locking shoe  20  is described in greater detail. Locking shoe  20  is generally ‘C shaped’ piece of metal or plastic and is fitted over both surfaces of rail  12  at the second edge  26 . Locking shoe  20  includes a sidewall  44  that abuts second edge  26  of rail  12 , a retaining wall  46  that extends around a portion of first surface  21  that includes groove channel  30 , and a retaining wall  48  extending around a portion of second surface  23  that includes the under-surface of groove channel  30 . A flange  50  with a central cutout  52  depends from retaining wall  46 . Locking shoe  20  is located around the second edge  26  of rail  12  by two resiliant balls  54  ( FIG. 4 ) that are retained between groove channel  30  in the rail and two symmetrically oriented grooves  56  formed on the interior surface of retaining wall  46  of locking shoe  20 . Preferably, balls  54  are metal bearing. A lip  58  is formed between the edge of grooves  56  and the inner surface of sidewall  44 . A fin  60 , acting as a fulcrum is integrally formed on the inner surface of sidewall  44  and retaining wall  46  midway between the two grooves  56 . Both flanges  50  and lip  58  slope away from first surface  21  on rail  12  as they extend outwards from a centerline defined by central cutout  52  and fin  60 . An opposing pair of ramps  62  are situated on the inner surface of retaining wall  48  and provide a reaction force against the underside of groove channel  30  on second surface  23 . On each side of fin  60 , ramps  62  are sloped inversely to flange  50  and lip  58 . 
         [0018]    Referring now to  FIGS. 4 ,  6  and  7 , nipple housing  22  is described in greater detail. Nipple housing  22  is located in oval area  38  of cutout  34 . A chamber  64  provided inside nipple housing  22  is adapted to retain the one or two nipples  17  located at the ends of drive cable  16 . A slot  66  is provided in a portion of the sidewalls of nipple housing  22  for drive cable  16  to pass through into chamber  64 . Additionally, a gap  68  is provided in the sidewall of nipple housing  22  to fit nipples  17  into chamber  64  through during assembly of window regulator  10 . 
         [0019]    Floating nipple housing  22  further includes an integrally molded release fork  70 . Release fork  70  includes a central finger  72  disposed between two spring fingers  74 . The ends of spring fingers  74  are generally parallel to central finger  72 . Central finger  72  passes through central cutout  52  into locking shoe  20 . A slot  76  on the end of central finger  72  locates nipple housing  22  on fin  60  ( FIG. 5 ) and allows nipple housing  22  to partially pivot there around. The range of pivotal motion of nipple housing  22  is limited by the sidewalls of central cutout  52  in flange  52 . Spring fingers  74  abut against lip  58  and urge release fork  70  into a neutral, “locked” position equidistant between the two grooves  56  and perpendicular to the axis of motion in locking shoe  20 . Additionally, spring fingers  74  preload spherical balls  54  into full contact with grooves  56  and groove channel  30  when lift plate  14  is stationary, locking lift plate  14 . Release fork  70  has two cam faces  78  that are aligned with the longitudinal centerline of groove channel  30  and with the center of balls  54  ( FIG. 4 ). The ratio of the overall length of central finger  72  to the distance from its base against sidewall  46  to the center of cam faces  78  provides a mechanical advantage which reduces the effort required to release spherical balls  54 . 
         [0020]    The rotation of release fork  70 , due to the movement of drive cable  16  locks and unlocks lift plate  14 . At rest, lift plate  14  is effectively locked. The relationship between the angle subtended by groove channel  30  on rail  12  and grooves  56  (formed by flange  50  and lip  58 ) on locking shoe  20 , together with the operating coefficient of friction in the locking shoe  20  and rail  12 , are such that locking shoe  20  is locked in place to rail  12  by a wedging action by the leading ball  54  generally perpendicular to first surface  21  on rail  12 . Backdriving of window regulator  10  is resisted directly at lift plate  14 —force is transmitted from the window glass to the lift plate, and subsequently to locking shoe  20 . The backdrive force wedges the leading balls  54  between its groove  56  and groove channel  30 . The opposing ramp  48  provides a reaction force against the underside of groove channel  30  on rail  12 . Force is then transmitted directly to rail  12 , and not down drive cable  16  to the drive assembly. A small clearance is provided between cam faces  78  and balls  54  to ensure release fork  70  does not dislodge the locking ball  54 . 
         [0021]    Lift plate  14  is effectively unlocked by engaging drive and pulley assembly  18 . The initial movement of drive cable  16  causes nipple housing  22  to rotate slightly in lift plate  14  around fin  60 , bringing the leading cam face  78  of release fork  70  into contact with the leading ball  54 . This contact pushes the leading ball  54  out of secure engagement between groove channel  30  and groove  56 . At this point, lift plate  14  is still stationary. Continued movement of drive cable  16  then rotates nipple housing  22  further until the leading sidewall of nipple housing  22  comes into contact with the side face of rectangular area  36  on cutout  34  so that nipple housing  22  reacts against lip plate  14 . Then, drive cable  16 , locking shoe  20 , nipple housing,  22  and lift plate  14  then move together as a single unit. Additionally, as nipple housing  22  is rotated around fin  60 , the trailing spring finger  74  is restrained by the slope of lip  58  and flange  50 , placing the trailing spring finger  74  under tension. When the movement of drive cable  16  stops, the release of tension forces in drive cable  16  and the trailing spring fingers  74  combine to return nipple housing  22  and balls  54  to a locked position between groove channel  30  and grooves  56 , as is described above. Only the leading ball  54  needs to be released by release fork  70  as the trailing ball  54  has no influence on the motion of lift plate  14 . 
         [0022]    The above-described embodiments of the invention are intended to be examples of the present invention and alterations and modifications may be effected thereto, by those of skill in the art, without departing from the scope of the invention which is defined solely by the claims appended hereto.

Summary:
A window regulator that resists backdrive forces directly at the lift plate and rail, rather than by the drive assembly. A locking shoe mounted within the lift plate and selectively frictionally engages the rail while the drive assembly is at rest. Thus, any backdrive forces are transmitted from the window glass to the lift plate, and then directly to the rail, avoiding the drive assembly. A release fork that is coupled to the drive cable automatically disengages the locking shoe when the drive assembly is activated, and engages the locking shoe when the drive assembly disengages.