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FIELD OF INVENTION 
       [0001]    The invention generally relates to the field of window regulators, and more particularly to window regulators for automotive applications. 
       BACKGROUND OF INVENTION 
       [0002]    One of the design objectives for window regulating systems, particularly in automotive applications where the regulator controls the vehicle window, is to optimize the operating torque by maximizing the number of crank turns to the limit provided for by specification. In automotive applications, the maximum number of permissible crank turns is generally limited in manual applications to about 6-6.5 turns. Reducing the operating torque reduces the amount of power or manual effort required to raise the window. 
         [0003]    Conventionally, operating torque can be reduced by reducing the diameter of the drum which connects the crank to the cable(s) attached to the lift plate. The problem with this solution is that the cable is subject to higher stress because it is wrapped around a smaller diameter. In addition, decreasing the diameter of the drum will increase the number of turns, resulting in a wider drum. This could result in packaging problems since the width of the drum and drum housing must fit within a confined space defined between the inner and outer panels of a vehicle door. In addition, increasing the number of drum turns increases the possibility of ratcheting (i.e., noise) resulting from the cable rubbing against the grooves in the drum, particularly since the cable is routed at a greater angle between its intake position entering the drum housing and the outermost turns of the drum. 
         [0004]    An alternative approach to reducing operating torque is to employ a gear reduction system in the drum housing. The problem with this solution is that the extraneous gears typically increase the width of the drum housing, leading to the packaging constraints discussed above. Another problem with gear reduction systems is that they typically require tight tolerances, driving up costs, and backlash is a persistent problem in such systems. 
         [0005]    An alternative solution of preferably low cost is desired in order to optimize torque in window regulating systems. 
       SUMMARY OF INVENTION 
       [0006]    In general, the invention employs a pulley ‘block and tackle’ principle in order to obtain a mechanical advantage for reducing operating torque requirements. 
         [0007]    According to one aspect of the invention, a window regulator assembly is provided which has a rail on which a lift plate is mounted to slide. therealong. The lift plate is configured to mountingly receive a window thereto. A lift pulley is rotatably mounted on the lift plate. A first guide pulley and a second guide pulley are respectively mounted near first and second ends of the rail. The assembly has at least one cable that has a first end anchored near the first end of the rail and wound about the lift pulley and thence routed about the first guide pulley to operatively engage a multi-turn cable-guiding rotatable drum, and a second end anchored near the second end of the rail and wound about the lift pulley and thence routed about the second guide pulley to operatively engage the drum. Operative movement of the drum in a first sense tensions the at least one cable to move the lift plate towards the first end of the rail, and operative movement of the drum in a second sense, opposite the first sense, tensions the at least one cable to move the lift plate towards the second end of the rail. 
         [0008]    The window regulator preferably employs two cables anchored to the drum and disposed to wind around the drum. The first cable is fixed near the first end of the rail, thence wound around the lift pulley to the first guide pulley, and thence routed to the drum. The second cable is fixed near the second end of the rail, thence wound around the lift pulley to the second guide pulley, and thence routed to the drum. The motive power for rotating the drum may be provided via a hand crank or an electric actuator such as a motor. 
         [0009]    According to another aspect of the invention, a dual-rail window regulator assembly is provided having first and second rails; first and second lift plates respectively slidingly mounted to the first and second rails; first and second lift pulleys respectively slidingly mounted to the first and second lift plates; and first and second guide pulleys ( 140 A,  140 B) respectively mounted near first and second ends of the first and second rails. At least one cable has a first end anchored near the first rail end and wound about the first lift pulley of the first rail and thence routed about the first guide pulley to operatively engage a rotatable multi-turn, cable-guiding drum. A second end of the least one cable is anchored near the second rail end and wound about the second lift pulley of the second rail and thence routed about the second guide pulley to operatively engage the drum. Additional means, such as a third cable, interconnect the first and second lift plates. The operative movement of the drum in a first sense tensions the at least one cable to move the first and second lift plates towards the first rail end, and operative movement of the drum in a second sense, opposite the first sense, tensions the at least one cable to move each lift plate towards the second rail end. 
         [0010]    According to another, more general aspect of the invention, a window regulator assembly is provided which includes at least one rail, a lift plate slidingly mounted on each rail, and a lift pulley mounted to each lift plate. A first guide pulley is mounted near a first end of the at least one rail, which represents a one end of window travel (e.g., the open position). A second guide pulley is mounted near an opposing second end of the at least one rail, which represents another end of window travel (e.g., the closed position). A cable, which may be provided in one or more segments, has a first end anchored near the first rail end and wound about the lift pulley associated with the rail presenting said first rail end and thence routed about the first guide pulley. A second, end of the cable is anchored near the second rail end and wound about the lift pulley associated with the rail presenting said second rail end and thence routed about the second guide pulley. A drive means is provided for tensioning and translating the cable. Actuating the drive means in a first sense tensions the cable to move each lift plate towards the first rail end, and actuating the drive means in a second sense, opposite the first sense, tensions the cable to move each lift plate towards the second rail end. 
         [0011]    The drive means may include a multi-turn cable-guiding drum powered by a hand crank or motor. Alternatively, at least one of the guide pulleys may be connected to a hand crank or motor and include a multi-turn cable guide for winding and unwinding the cable thereon, thus reducing the part count. 
         [0012]    Another broad aspect of the invention relates to replacing a guide pulley in a window regulating system with a drive pulley having a multi-turn cable guide for winding and unwinding a cable thereon, and driving such a pulley with an external drive. 
     
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0013]    The foregoing and other aspects of the invention will become more apparent from the following description of illustrative embodiments thereof and the accompanying drawings, which illustrate, by way of example, the principles of the invention. In the drawings: 
           [0014]      FIG. 1  is a perspective view of one side of a window regulator according to a first exemplary embodiment; 
           [0015]      FIG. 2  is a perspective view of the opposite side of the window regulator shown in  FIG. 1 ; 
           [0016]      FIG. 2B  is an isolated cross-sectional view of a rivet pulley employed in the window regulator shown in  FIG. 1 ; 
           [0017]      FIG. 3  is a schematic diagram of a pulley system, shown in isolation, which is employed in the window regulator shown in  FIG. 1  to provide a 2:1 mechanical advantage; 
           [0018]      FIG. 4  is an isolated view of a cable-winding drum employed in the window regulator shown in  FIG. 1 ; 
           [0019]      FIGS. 5A and 5B  are schematic diagrams of a pulley system according to an alternative embodiment which yields a 4:1 mechanical advantage; 
           [0020]      FIG. 6  is a schematic diagram of a window regulator according to a second exemplary embodiment, which employs dual rails and dual lift plates; 
           [0021]      FIG. 7  is a schematic diagram of a window regulator according to a third exemplary embodiment, which employs conduit-less cables; 
           [0022]      FIG. 7B  is cross-sectional view of an anchor, taken in isolation, employed in the window regulator shown in  FIG. 7 ; and 
           [0023]      FIG. 8  is a schematic diagram of a window regulator according to a third exemplary embodiment, which has a reduced part count. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0024]      FIGS. 1 and 2  show a window regulator  10  according to a first exemplary embodiment. The regulator  10  comprises a rail assembly  12  which is mountable to the vehicle door structure via integrally formed brackets  14 . A lift plate  16  including a plastic guide  18  is mounted to the rail assembly  12 . More particularly, the guide  18  includes slotted tabs  20  which slidingly ride along flanges  22  formed along the edges of the rail assembly  12 . The lift plate  16  includes rubber-tipped clamps  24  for mounting the vehicle window (not shown) thereto. Stops  26  define the upper and lower limits of travel for the lift plate  16 , and hence the maximum distance traversed by the vehicle window. 
         [0025]    The lift plate  16  is regulated by a pulley system  30 , shown in isolation in  FIG. 3 , which comprises an upper cable  32   a  and a lower cable  32   b.  The upper cable  32   a  is anchored to the top of the rail assembly  12  by an anchor  34   a.  The upper cable  32   a  is routed around a pulley rivet or lift pulley  36 . The lift pulley  36  is preferably rotatably mounted to the lift plate  16  and features two independent (i.e., non-spiraling) grooves  38   a,    38   b,  as detailed in  FIG. 2B . The upper cable  32   a  is routed around one of the grooves  38   a,    38   b  and back up to an upper guide pulley  40   a  which is rotatably mounted to the top of the rail assembly  20 . From the guide pulley  40   a  the upper cable  32   a  is routed through a first conduit  42   a  and attached to a crank assembly  44 . The crank assembly  44  includes a multi-turn cable-guiding drum  445  (not explicitly shown in  FIGS. 1 &amp; 2 ) as well known in the art per se which is mounted in the housing  45  of the assembly  44 . The upper cable  32   a  is anchored to the drum and, depending on whether or not the limit of travel has been reached, partially wound around the drum. 
         [0026]    The conduit  42   a  is mounted to the rail assembly  12  by a conduit socket  46   a  mounted in a receptacle  48   a  formed in the rail assembly. Another conduit socket  50   a  is mounted to an intake tube  52   a  of the housing  45 , and a torsion spring  54   a  is provided to maintain tension on the upper cable  32   a.    
         [0027]    The lower cable  32   b  is routed in a similar manner. The lower cable  32   b  is anchored to the bottom of the rail assembly  12  by an anchor  34   b  and routed around the other of the grooves  38   a,    38   b  of the lift pulley  36 . From the lift pulley  36  the lower cable  32   b  is routed around back down to lower guide pulley  40   b  which is fixed to the bottom of the rail assembly  20 . From the guide pulley  40   b  the lower cable  32   b  is routed through a second conduit  42   b  and attached to the multi-turn cable-guiding drum of the crank assembly  44 . 
         [0028]    The second conduit  42   b  is mounted to the rail assembly  12  by a second conduit socket  46   b  mounted in a second receptacle  48   a  formed in the rail assembly. A second conduit socket  50   b  is mounted to a second intake tube  52   b  of the housing  45 , and a second torsion spring  54   b  is provided to maintain tension on the lower cable  32   b.    
         [0029]    A handle  60  (shown in phantom) is attached to the crank assembly  44 . Rotating the handle  60  causes the cable-guiding drum  445 , shown in isolation in  FIG. 4 , to rotate. The drum  445  converts rotational motion to linear motion so as the drum  445  rotates, the cables  32   a,    32   b  which are wound around the drum, are translated. More particularly, as the drum  445  rotates, one of the upper and lower cables  32   a,    32   b  spools onto the drum while the other cable correspondingly spools off the drum, i.e., one cable winds onto the drum while another cable winds off the drum. 
         [0030]    As the drum rotates, the length L u  of one of the cables  32   a,    32   b  as measured along the rail flange  22  increases with a corresponding decrease in the length L l  of the other cable as measured along the rail flange. In conjunction, the lift pulley  36  travels up or down depending on which cable increases its length along the rail. Note that as a result of the pulley system, the lift pulley  36 , and hence the vehicle window, travels at substantially half the speed of the cables, yielding a 2:1 mechanical advantage and thus a 2:1 reduction in motive torque requirements. This is shown also in the exaggerated schematic diagram of  FIG. 3 . 
         [0031]    It is desirable to have both upper and lower cables  32   a,    32   b  wrapped around the lift pulley  36  from opposing directions in a symmetrical arrangement. Note that one of the cables, e.g., cable  32   a,  is routed in a ‘block and tackle’ arrangement and, being under tension, presents a force acting upwards on the pulley rivet  36  and lift plate  16 . The other cable, e.g., cable  32   b,  is also routed in a block and tackle arrangement and, being under tension, presents a force acting downwardly on the pulley rivet  36  and lift plate  16 . The upward and downward forces are preferably selected so as to be substantially equal. 
         [0032]    The pulley block and tackle principle can be applied to yield other mechanical advantage ratios. For example,  FIG. 5A  shows, in schematic form, an alternative embodiment which provides a 4:1 mechanical advantage.  FIG. 5B  is a perspective view of the lift pulley of this embodiment, taken in isolation, showing the cable routing about the lift pulley. 
         [0033]      FIG. 6  shows, in schematic form, a second exemplary embodiment of a window regulator  100  which employs two rails  112 A and  112 B having two lifter plates  116 A,  116 B respectively glidingly connected thereto. First and second cables  132 A and  132 B are attached to and spool to/from a multi-turn cable-guiding drum (not shown) of a crank assembly  144 . In this embodiment, the first cable  132 A, which is anchored to the top of the first rail  112 A at  134 A, extends around a lift plate pulley  136 A rotatably mounted to lift plate  116 A, and thence around a pulley  140 A rotatably mounted to the top of rail  112 A to the crank assembly  144 . In a similar manner, the second cable  132 A is anchored to the bottom of the second rail  112 B at  134 B, extends around a lift plate pulley  136 B rotatably mounted to lift plate  116 B, and thence around a pulley  140 B rotatably mounted to the bottom of rail  112 B to the crank assembly  144 . Thus, the pulley rivet  36  of the first embodiment is essentially replaced by the two pulleys  136 A,  136 B. A third cable  132 C wrapped around pulleys  170 A,  170 B respectively mounted to rails  112 A,  112 B interconnects the two lift plates  116 A,  116 B together. In operation, as the crank assembly  144  is rotated, the lifter plates  116 A,  116 B and hence the window travels at half the speed of cables  132 A,  132 B yielding a 2:1 mechanical advantage. 
         [0034]    It will be understood that while the embodiments described above have employed at least two cables, a single cable could be wound around the drum and used to translate the pulley rivet or lifter plate(s). In addition, while the embodiments discussed above have shown a manually activated crank assembly, it will be understood that other drive means can be provided for tensioning and translating the cable, such as a motor operatively coupled to a multi-turn drum cable or other electromechanical actuator providing the motive torque for actuating the regulator. 
         [0035]    Furthermore, while the cable shown in the embodiments discussed above is sheathed in conduits, it will be appreciated that a conduit-less window regulator system is also contemplated. For example,  FIG. 7  shows a window regulator system  210  having a rail  212 , a lift plate  216  mounted to slide along the rail  212 ; a lift pulley  236  mounted to the lift plate  216 ; a cable  230 ; and first and second guide pulleys  240   a,    240   b  respectively mounted near first and second ends of the rail  212 . The cable  230  has a first end anchored (via anchor  234   a ) near the first end of the rail and is wound about the lift pulley  236  and thence routed about the first guide pulley  240   a.  A second end of the cable  230  is anchored (via anchor  234   b ) near the second end of the rail and wound about the lift pulley  236  and thence routed about the second guide pulley  240   b.    FIG. 7B  is a cross-sectional view of anchor  234  which includes a socket  248  mounted in an aperture of the rail. The cable  230  has a nipple  250  mounted at the end thereof. The nipple enables the cable to receive tensioning forces provided by a spring  248 . No cable conduits are employed. 
         [0036]    The cable  230  extends between the first and second guide pulleys and is preferably provided in two separate segments,  230   a  and  230   b,  each of which is anchored to or otherwise connected to a cable drive means, such as a motor-driven cable guiding drum  244 . Actuation of the drive means in a first sense tensions the cable to move the lift plate towards the first end of the rail, and actuation of the drive means in a second sense, opposite the first sense, tensions the cable to move the lift plate towards the second end of the rail. Note that in this embodiment, each cable segment is wrapped around the pulleys or drum in one direction only, thus eliminating “reverse bending” of the cable and the risk of premature fatigue. 
         [0037]    It should also be appreciated that one of the pulleys employed in any of the above-described embodiments can be replaced with a cable-guiding drum, i.e., one of the pulleys can be a drive pulley. For example,  FIG. 8  shows a conduit-less window regulator system  310  having a rail  312 , a lift plate  316  mounted to slide along the rail  312 ; a lift pulley  336  mounted to the lift plate  316 ; a cable  330 ; and first and second guide pulleys  340   a,    340   b  respectively mounted near first and second ends of the rail  312 . The cable  330  has a first end anchored (via anchor  334   a ) near the first end of the rail and is wound about the lift pulley  336  and thence routed about the first guide pulley  340   a.  A second end of the cable  330  is anchored (via anchor  334   b ) near the second end of the rail and wound about the lift pulley  336  and thence routed about the second guide pulley  340   b.  The cable  330  extends linearly between the first and second guide pulleys. In this embodiment, the second pulley has a multi-turn spiraling groove on the outside diameter thereof and is drivingly connected to a motor, thus providing an alternative drive means for translating the cable. Actuation of the drive means in a first sense tensions the cable to move the lift plate towards the first end of the rail, and actuation of the drive means in a second sense, opposite the first sense, tensions the cable to move the lift plate towards the second end of the rail. The principle advantages provided by this embodiment are a reduced part count and a very narrow lateral profile. 
         [0038]    Those skilled in the art will appreciate that a variety of other modifications may be made to the embodiments disclosed herein without departing from the spirit of the invention.

Summary:
A window regulator, e.g., for a vehicle window, which includes opposing block and pulley arrangements that interact via a lift pulley mounted to a lift plate that slides along a rail. Operative movement of a crank assembly in a first sense tensions a cable to move the lift plate towards a first end of the rail and operative movement of the crank assembly in a second sense, opposite the first sense, tensions a cable to move the lift plate towards a second end of the rail. The regulator enables the reduction of the operating torque requirements without affecting the packaging of the crank assembly.