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RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Application Ser. No. 61/589,912 filed Jan. 24, 2012 and incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     A. Field of Invention 
     This invention relates to window treatment operating apparatus including a bi-directional drive, and, more particularly, to a cycloidal drive providing rotation of an output member in either direction at a predetermined mechanical advantage in response to rotation from an input member while resisting rotational forces from the output member. The input member is preferably a pulley operated by a beaded chain and the output member includes a sleeve supporting and rotating a mandrel of window treatment. 
     B. Description of the Prior Art 
     Roller shades are often used as window treatment and provide both a practical and an aesthetic function. Typically, a roller shade includes a tubular mandrel and a decorative panel wound on the mandrel. The mandrel can be selectively rotated by a user either in one direction or the other causing the panel to be either raised or lowered, depending on how it is wound on the mandrel. The roller shade is provided at its two ends with mounting means so that it can be mounted on a window frame or other similar location, using suitable brackets. Normally, one end of the roller shade is a simple rotatable coupling that allows the roller shade to rotate with respect to the bracket. The other end is provided with a bi-directional clutch that provides a mechanical advantage during the operation of the roller shade. Bi-directional clutch mechanisms of this type are disclosed in U.S. Pat. Nos. 4,433,765, 4,372,432 and 6,685,592, all incorporated herein by reference. These references disclose clutch mechanisms in which the mechanical advantage is developed between a pulley and a small shaft. One or more springs are also provided as a means for locking the mandrel to prevent undesirable rotation. Other clutch mechanisms are also known which are based on frictional braking. U.S. Pat. Nos. 3,135,369 and 3,920,106 also disclose bi-directional clutches useable for roller shades. 
     Recently there has been an increased need for roller shades having larger sizes and/or weights which in turn require stronger clutch mechanisms with a larger mechanical advantage, normally requiring more space. However, in the existing roller blinds, since mechanical advantage is dependent on the relative diameters of a pulley and a small shaft, and since the shaft has already been minimized, the mechanical advantage can be increased by increasing the size of the pulley. However, this is not a practical solution because space is too limited to accommodate a larger pulley, and in addition, a larger pulley may not be esthetically acceptable. 
     In addition, a stronger clutch mechanism requires more springs for locking the roller blind to prevent its undesirable rotation. However, more springs complicate the structure of the clutch mechanism, and increase the force required to operate the same. 
     U.S. Pat. No. 6,685,592, also incorporated herein by reference, discloses a clutch mechanism incorporating planetary gears as a means of developing a mechanical advantage. However, planetary gears require several parts that have to made with very precise dimensions. These gears are more expensive to make and assemble thereby adding significantly to the cost of the clutch. Furthermore the mechanical advantage obtainable with such mechanisms may not be sufficient for all purposes. 
     Many other window dressings, such as awnings, also rely on a rotating mechanism for activation. 
     SUMMARY OF THE INVENTION 
     Briefly, a window treatment operation control apparatus for operating a window treatment, the apparatus including a guard for supporting an end of the window treatment, said guard being stationary during the operation of the window treatment; an input member selectively activated by a control member; a rotor coupled to said input member; and an output member connected to said window treatment for operating said window treatment when said input member is activated by the control member; wherein said rotor and said guard cooperating with said guard to form a cycloidal drive that transmits rotational motion form said input member to said output member. 
     In one aspect of the invention, the control member is operable in a first mode to rotate said pulley in a first direction and in a second mode to rotate said pulley in a second direction, and wherein said cycloidal drive is adapted to rotate said output member in corresponding first and second directions respectively. 
     In one aspect of the invention, the cycloidal drive resists torsional forces from said output member and does not transmit the same to said input member. 
     In one aspect of the invention, the input member is a pulley having a disc-shaped body and a motion transmission element transmitting rotational motion of said pulley to said rotor. 
     In one aspect of the invention, the motion transmission element on the pulley is a circular rib disposed in an off-center position with respect to a rotational axis of the pulley. 
     In one aspect of the invention, the guard includes projections and said rotor includes motion control elements cooperating with said pins to impart a cycloidal motion to said rotor. 
     In one aspect of the invention, the guard has m projections and said rotor has n control elements where m is larger than n, wherein n and m define the mechanical advantage of the cycloidal drive. 
     In one aspect of the invention, the input element is a pulley, further comprising a gear disposed between said pulley and said rotor. 
     In one aspect of the invention, the input element is a pulley, further comprising a first gear coupled to said input element, and a second gear coupled between said first gear and said rotor. 
     In one aspect of the invention, the input element is a pulley and said output element is a drum, said pulley and said drum being coaxial. 
     In another aspect of the invention, the input element is a pulley and said output element is a drum, said pulley and said drum having axially offset axes of rotation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further features and advantages of the invention will become apparent upon consideration of the following detailed description of preferred, but nonetheless illustrative embodiments, when considered in conjunction with the following drawings, in which: 
         FIG. 1  shows an exploded view of a prior art clutch for a window dressing; 
         FIG. 2  shows a side elevational view of the present window treatment activating apparatus incorporated into a window treatment; 
         FIG. 3  shows an exploded view of apparatus of  FIG. 2 ; 
         FIG. 4  shows an orthogonal view of the guard; 
         FIG. 5  shows an orthogonal view of one side of the rotor; 
         FIG. 6  shows an orthogonal view of one side of the pulley; 
         FIG. 7  shows an orthogonal view of the back of the output member; 
         FIG. 8  shows the rotor engaging the guard; 
         FIG. 9  shows the rotor engaging the pulley; 
         FIG. 10  shows an isometric view of the assembled apparatus; 
         FIGS. 11A ,  11 B show isometric exploded views of a first alternate embodiment of the invention; 
         FIG. 11C  shows an isometric view of the pulley for the apparatus of  FIGS. 11A ,  11 B. 
         FIG. 12A , shows an isometric exploded view of a second alternate embodiment of the invention; and 
         FIG. 12B  shows an interior view of the guard of the apparatus of  FIG. 12A . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a prior art clutch as described in commonly owned U.S. Pat. No. 6,685,592. The clutch includes a base or guard  12 , a ring  30  with a plurality of circumferential pockets  32  and inner circumferential teeth  36 , a pair of brake springs X and Y and an output member  40  with a mandrel  44  and a barrel S. The barrel S fits into the mandrel W of a window dressing such as window shade. Different sized and shaped barrels S may be used for different window dressings. 
     The mechanism further includes a plurality of gears  48  rotatably mounted on shafts  46  of output member  40 . Rotation of the ring  30  is transferred at a mechanical advantage by the gears  48  to the output member  40  which then rotates the mandrel W through a barrel S. However, any rotational forces from mandrel W, for example, due to the weight of the window dressing, are opposed by the springs X and Y which act as a brake and stop the output member from rotating. 
       FIG. 2  shows a window dressing support  11  (as described in more detail in commonly assigned U.S. Pat. No. 6,935,401) including a clutch  15  operated by an elongated chain  25 , a headboard  13  and end brackets  31 . The window dressing itself has been omitted for the sake of clarity however it has a mandrel which fits over the barrel  15 A of clutch  15 . Pulling chain  25  causes the barrel  15 A of the clutch  15  to rotate in one direction or another thereby raising or lowering the window shade in a known manner. However pulling on the window shade or any other rotational force on the barrel  15 A (due, for example, to the weight of the window shade) is resisted by the internal brake of the clutch (e.g., the springs X,Y). 
     An improved clutch  100 , also referred to herein as a cycloidal drive, that can be used in the dressing support  11  (by replacing clutch  15 ) is shown in  FIGS. 3-10 . The clutch  100  includes a stationary guard  110 , a rotor  140 , a pulley  170  and an output member  190 . The guard  110  (shown in more detail in  FIG. 4 ) includes a flat, circular disc  112  with a circumferential wall  114  extending axially as shown. The disc  112  also supports a central boss  116  concentric with disc  112  and terminating with two axially extending fingers  118 A,  118 B. Also on disc  112  there are a plurality of driving projections  120  disposed at equal distances around the boss  116 . In  FIG. 3 , eight such projections  120  are shown, however, this number may change as discussed in more detail below. Each of the driving projection has an arcuate wall  122  arranged as shown. The walls  122  may be circular with a radius r 1  and are oriented axially inwardly toward boss  116 . The projections  120  have a radially outward wall  124  as well. Walls  124  are also circular with a radius much larger than the radius r 1 . Moreover, the walls  124  are arranged on disc  112  to define an imaginary circle having a diameter D 1  and concentric with boss  116 . Finally, the guard  110  further includes depressions  130  sized and shaped to mount the clutch  100  to a stationary bracket or other support means (not shown). The guard  110  is preferably molded as a single unitary piece and is made a plastic material. 
     Rotor  140  is disc-shaped and has base  142  with two flat surfaces  143 A,  143  B defining its two sides. The base  142  is circular with a diameter D 2  (see  FIG. 5 ) that is smaller than D 1 . The base  142  is formed with a central circular opening  144  disposed concentrically within the base  142  with a diameter D 3 , and seven smaller circular openings  146  disposed evenly around the central opening  144  and each having a diameter D 4 . At least between each opening  146 , there is an arcuate wall  148  defining lobes  149  therebetween. Preferably walls  148  and lobes  149  have a continuous wave-like curvature defined to provide a cycloidal movement to the rotor. The walls  148  define a cavity  150  receiving one of the projections  120 , each having a wall  122  at least partially contacting the wall  148 , as shown in  FIG. 8 . In  FIG. 5 , rotor  140  is shown with seven lobes  149 . The number of lobes  149  and the number of projections  120  define the mechanical advantage of the drive. More specifically, with m projections and n lobes, the mechanical advantage of the resulting drive is m−n/m, in this case 1:8. 
     As also shown in  FIGS. 5 and 8 , attached to the base  142  is shaped as an annular ring  151  formed by an inner circular wall  152  and an outer circular wall  154 . The inner wall  152  is circular and has a diameter D 5 . 
     Pulley  170  is essentially disc shaped with a plurality of outer teeth  172  forming a channel to receive and engage with a conventional operating cord or bead chain (not shown). A circular concentric hole  174  is formed at the center of the pulley  170 . On one side  173 , the pulley  170  is formed with a circular rib  176  having an outer circular wall  178 . Wall  178  is not concentric with the hole  174  or pulley  170  and has a diameter D 6  that is equal to, or slightly smaller than D 5 . As a result, when the pulley  170  is placed adjacent to the rotor  140 , the outer wall  178  of rib  176  fits within the inner surface  152  of ring  151  on rotor  140 , as shown in  FIG. 9 . 
     The output member  190 , is the output member, as can be seen in  FIGS. 3 and 10 . Includes a disc-shaped member  192  and a hollow drum  194 . The drum  194  has an outer surface  196  that is essentially cylindrical and is formed to accept and drive the mandrel of a window dressing (not shown). The tip of the drum  194  is formed with a concentric circular hole  198 . 
     On the side  200  opposite the drum  184 , the member  190  is formed with a central cavity  202  extending through drum  194  extending to hole  198 . The side  200  is further provided with a circular concentric platform  204  with seven pins  206  extending axially. The platform  204  has a diameter that is equal to or slightly smaller than the diameter of hole  174  of pulley  170 . 
     The clutch is assembled by putting the elements just described in the relative positions shown in  FIG. 3 , with the pulley  170  being mounted rotatably on the platform  204 , the rotor  140  mounted with its inner wall  152  riding on the wall  178  of the pulley  170  and two or three of its outer walls  148  receiving respective projections  122 . A cord or beaded chain is trained around and engages some of the circumference if the pulley  170 . 
     The elements described are pressed together with the boss  116  extending into the drum  194  and the arms  118 A,  1188  extending through the hole  198 . Preferably the arms  118 A,  1188  have slightly enlarged heads so that they can be inserted into and through the hole  198  thereby capturing and holding the elements together. Each of the pins  206  on output member  190  extend through one of the respective holes  146  of the rotor  140 . The assembled drive  100  is shown in  FIG. 10 . 
     With the possible exception of pins  206 , all the elements described can be made of a plastic material by molding or other materials by well-known techniques. At least some of these elements, e.g., the elements that come in contact with each other can be either lubricated or can be made of a self-lubricating material. 
     The clutch or cycloid drive  100  operates as follows. Pulling the cord or chain in one direction causes the pulley  170  to rotate coaxially around the stationary boss  116 . The rotation of the pulley  170  causes the rotor  140  to rotate eccentrically on wall  178  of rib  176  in a precessing motion to contact between successive projections  122  of the guard  110  entering into successive cavities  150  formed by valleys  149  and the sliding contact between walls  178  on the pulley  170  and wall  152  on the rotor  140 . It should be noted that since the number of projections  122  are different then the number of walls  156  and the rotor is smaller in diameter then the pulley  170 , the pulley  170  and rotor  140  are rotating at different rates. Since each pin  206  extends into a hole  146  of rotor  140 , as the rotor  140  rotates, it causes the output member  190  to rotate as well through pins  206 . The output member  190  then rotates the mandrel (or other similar elements) of the window dressing in the appropriate direction. 
     The clutch described herein provides a speed reduction defined by the number of projections on the guard and the number of external surfaces on the rotor. Moreover, the structure of the clutch is such that torque can be transferred inherently from the input member—the pulley—to the output member but not in the other direction. 
       FIGS. 11A and 11  B show an alternate embodiment. There are several differences between this embodiment and the embodiment previously described as shall become apparent from the following description. Drive  300  includes a stationary guard  310  that gets mounted on a wall or the frame of a window and supports one end of the window dressing (not shown). The drive  300  further includes a pulley  370 , which is the power input member, a rotor  340  and an output member  340 . As seen in  FIG. 11A , guard  310  is formed with an inner boss  312  formed with a central socket  313 , a circular protective wall  314 , an outer wall  316 , and a plurality of pins  320 . 
     Rotor  340  has on one surface (see  FIG. 11B ) a central hole  342 , and a plurality of lobes  344  forming valleys  346  therebetween. On the other side, the rotor  340  has a plurality of circular holes  350  ( FIG. 11B ). 
     Pulley  370  has on one side a plurality of somewhat circular indentations  372  arranged concentrically around a hole  374 . On the other side, the pulley  370  has a circular boss  376  that is set at a predetermined distance from the center of pulley  370  and hole  374 . The boss  376  is sized and shaped to fit into hole  342  in the rotor  340 . 
     The output member  390  includes a disc  392  and a drum  396  concentric with the disc  392 . On the inner side, disk  392  is formed with several pins  394 . The pins are sized and arranged to fit through holes  350  of the rotor  340 . The disc  390  also includes a central concentric pin  398  long enough to pass through the rotor  340 , pulley  370  and enter into hole  313  in guard  310 . 
     Drive  300  is assembled by placing the rotor  340  adjacent to disc  392  with each of the pins  396  being disposed in one of the holes  350 , and the pin  398  extending through hole  342 . Next, the pulley  370  is placed next to the rotor  370  with the boss  376  entering into hole  372  and pin extending through the hole  374 . A Belleville washer  394  is inserted on pin  398  to keep all these parts in place and the parts thus assembled are placed adjacent to the guard  310  with the end of the pin  398  being received by hole  313  and some, but not all the pins  320  contacting the walls of the valleys  346 . In the Figures, there are five pins  320  and four lobes  344  and valleys  346 . A chain is trained around the pulley  370  and its beads (if any) are engaged by the indentations  372  so that when the chain is pulled in either direction, the pulley  370  turns accordingly around the pin  398 . The chain (not shown) is maintained in position by the inner wall  314 . 
     As in the previous embodiment, the drive  300  is a cycloidal drive with the pulley  370  and guard  310  (through its pins  320 ) causing the rotor  340  to turn off centrically and precessing. The movement of the rotor  340  is transmitted by the walls of holes  350  to pins  396  thereby causing the output member to rotate as well. 
     The mechanical advantage of this arrangement is 5:1. 
     Another embodiment of the invention is shown in  FIGS. 12A-12B . 
     In this embodiment, a drive  400  is provided including a guard having two shells  411 A,  411 B that close to form a cavity for the remaining element so of the drive. These elements include a first gear  430 , a second gear  436 , a rotor  440  and an output member  490 . The output member  490  and the rotor  440  have the same shape as the corresponding members  390  and rotor  340  described above. 
     The output member  490  includes a drum  496  with a wheel bearing  414 . The drum  496  passes through an opening  416  in shell  411 B and the wheel bearing  414  is used to support the drum  496  within this opening  416  Output member  440  also has pins  496 A similar to pins  396 . 
     As shown in more detail in  FIG. 12B , shell  411 A is shaped to define two sections, an upper section  415 A and a lower section  415 B. The upper section  415 A includes five pins  420  having the same structure and function as pins  320  in  FIGS. 11A ,  11 B. An inner wall  417  defines a space for receiving second gear  436 , with a shaft  435  supported at one end by a hole  419 . 
     Lower section  415 B has a similar hole  502  receiving the end of a shaft (not shown) supporting the pulley  470 . The cord or bead chain trained around the pulley  470  is protected by a wall  504 . 
     Between the two sections  415 ,  415 B, a shaft  423  is used to support first gear  430 . 
     Gear  430  is provided with a plurality of standard gear teeth  432  that mesh with similar teeth on the pulley  470  and second gear  436 . 
     Second gear  436  has a structure similar to the structure of pulley  370  except that it has gear teeth  438  replacing the indentations  372 . Thus, second gear  436  includes a round boss  439  that is off center from shaft  435  and is received in a hole of rotor  440 . Rotor  440  also has circular holes  496  receiving pins  496 A of output member  490 . 
     Pulley  470 , shown in detail in  FIG. 11C  includes a central disc  471 . On one side of the disc, a boss  473  is provided with a plurality of indentations  472  receiving the beads of a bead chain (not shown), On the other side of the disc there are a plurality of gear teeth  472 A. 
     Once the drive  400  is assembled, a bead chain (not shown) is trained around pulley  470 . Pulling the chain in either direction causes the pulley  470  to rotate in a respective direction. The rotation of the pulley  470  is transmitted through gear teeth  472 A and  432  to first gear  430 . First gear  430  in turn causes second gear  436  to turn. The number of gear teeth on pulley  470 , gear  430  and gear  436  are selected to obtain a predetermined mechanical advantage, e.g., 4:1. The rotation of second gear  436  then causes the rotor  440  and the output member  490  to turn in a cycloid motion as described above. It should be appreciated that in all three drives described, any torque on the drum is resisted by the respective drives and is not transmitted back to the input member, e.g., the pulley. Accordingly, there is no need for springs or other brake mechanisms. 
     Numerous modifications may be made to this invention without departing from its scope as defined in the appended claims.

Summary:
An apparatus for selectively activating a window treatment includes an input member, such as a pulley activated by a bead chain, an output member such as a sleeve activating a mandrel, a stationary guard for mounting the window treatment and a rotor. The rotor, pulley, and stationary base are coupled to form a cycloid drive, wherein rotation of the pulley causes the rotor to precess with respect to the pulley.