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TECHNICAL FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to a suspension cord control mechanism suitable for use with a window covering, and more particularly a top-down style window covering.  
       BACKGROUND OF THE INVENTION  
       [0002]     Window coverings including light blocking elements, such as honeycomb panels, have long been used to control or block the amount of light entering through a window and to provide privacy. Light control is obtained by controllable opening and closing of the light blocking element.  
         [0003]     A common method for controlling the opening and closing of a light blocking element is to employ a weight actuated suspension cord lock system in a bottom-up configuration, so called because the covering is raised towards the head rail from the bottom up for retraction. A suspension cord is threaded through a cord lock in the head rail and connected to the bottom rail of the window covering at one end. To retract the light blocking element, a user pulls on the suspension cord, causing the bottom of the light blocking element to rise towards the head rail. The light blocking element is gathered according to a predetermined orderly pattern such as by folding, stacking or pleats as it is opened. The light blocking element can be fully or partially retracted. When the suspension cord is released, the cord lock in the head rail arrests the cord, holding the light blocking element in its state of deployment.  
         [0004]     A top-down control mechanism found in window coverings operates in a similar fashion except that the position of the top portion of the light blocking element is adjusted by lowering and raising the top portion relative to a head rail. Top-down window coverings are preferred in certain situations, e.g. where it is desirable to let in light from the upper portion of the window while maintaining privacy and blocking outside light in the lower portion of the window. The use of both a bottom-up and top-down control mechanisms in a window covering provides maximum versatility.  
         [0005]     A problem in the prior art results from arresting mechanisms utilized, such as cord locks. When a suspension cord is released, a certain amount of the suspension cord slips through the arresting mechanism on account of the weight of the light blocking element before the cord lock engages the suspension cord. Although this amount of slippage is relatively small, typically around ¼ inch to ½ inch, in a top-down window covering, this distance is sufficient to cause an undesirable gap between the light blocking element and the head rail. In addition to defeating the primary function of the window covering to block light, the unbridged gap is aesthetically unappealing.  
         [0006]     Thus there is a need for a mechanism to reduce or eliminate the aforementioned problem by counteracting the drop in height between the release of the suspension cord and its arrest by the cord lock mechanism. Preferably, this mechanism substantially closes the gap normally left between the head rail and the top end of the light blocking element to block light.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention is related to a suspension cord control mechanism for a window covering. A suspension cord is attached on one end to a light blocking element such as a honeycomb panel, Roman shade panel, or Venetian blind slats. The suspension cord passes through a suspension cord control mechanism in the head rail, comprising a biasing mechanism and an arresting mechanism. The arresting mechanism can be a cord lock or cord arresting device such as those known in the art, which serves to arrest the movement of the suspension cord when a user is not pulling on the suspension cord.  
         [0008]     In one preferred embodiment, the biasing mechanism includes a sliding plate. The plate is capable of movement along a portion of the length of the head rail and is attached to an end of the head rail by a spring. The suspension cord is guided around a roller on the sliding plate. When the suspension cord is drawn by a user, the cord is pulled through the suspension cord control mechanism, thereby raising the top portion of the light blocking element towards the head rail. The force on the suspension cord exerted by the user also causes the plate to slide away from the end of the head rail, thereby loading or tensioning the spring. When the cord is released, the arresting mechanism moves into engagement with the cord to secure its relative position. In addition, the potential energy stored in the spring is released as the spring contracts to its natural state, causing the plate to slide back and pull the suspension cord, further raise the light blocking element towards the head rail.  
         [0009]     In an alternate preferred embodiment, the biasing mechanism comprises a pivoting bar with spools around which the suspension cord is engaged. In its natural position, the bar is perpendicular to the suspension cord. When the suspension cord is drawn, the bar pivots to a position substantially parallel to the length of the head rail thereby compressing a coil spring secured with the bar. As the user releases the suspension cord, the spring unloads and reverts to its natural position causing the pivoting bar to rotate to its position perpendicular to the suspension cord. The movement of the pivoting bar causes the suspension cord to retract such that the light blocking element is further urged towards the head rail.  
         [0010]     In yet another preferred embodiment, the biasing mechanism includes two plates linked by a spring that slide transverse to one another other. The suspension cord is engaged around spools on each of the plates. When the suspension cord is drawn taut, the plates slide transversely to one another and compress the spring between them. When tension on the suspension cord is released and the cord is locked by the arresting mechanism, the spring reverts the plates to their natural rest state, pulling the suspension cord and urging the light blocking element towards the head rail. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     In the drawings,  
         [0012]      FIG. 1  is a front view of a preferred embodiment of the present suspension cord control mechanism with a top-down style light blocking element;  
         [0013]      FIG. 2  is a top view of the suspension cord control mechanism of  FIG. 1  in a rest state;  
         [0014]      FIG. 3  is an exploded perspective view of the suspension cord control mechanism of  FIG. 1 ;  
         [0015]      FIG. 4  is a top view of the suspension cord control mechanism of  FIG. 1  in a loaded state;  
         [0016]      FIG. 5  is a front view of the suspension cord control mechanism of  FIG. 1  in the loaded state;  
         [0017]      FIG. 6  is a front view of an alternative embodiment of a suspension cord control mechanism with a top-down style light blocking element and head rail;  
         [0018]      FIG. 7  is a top view of the suspension cord control mechanism of  FIG. 6 ;  
         [0019]      FIG. 8  is a cross sectional elevated side view of the suspension cord control mechanism of  FIG. 6  in the rest state;  
         [0020]      FIG. 9  is a perspective cutaway view of the suspension cord control mechanism of  FIG. 6  in the rest state;  
         [0021]      FIG. 10  is a perspective cutaway view of the suspension cord control mechanism of  FIG. 6  in the loaded state;  
         [0022]      FIG. 11  is a front view of an another alternative embodiment of a suspension cord control mechanism with a top-down style window covering and head rail;  
         [0023]      FIG. 12  is a top view of the suspension cord control mechanism of  FIG. 11 ;  
         [0024]      FIG. 13  is a perspective cutaway view of the suspension cord control mechanism of  FIG. 11 ;  
         [0025]      FIG. 14  is a perspective cutaway view of the suspension cord control mechanism of  FIG. 11  in the loaded position; and  
         [0026]      FIG. 15  is a perspective cutaway view of the suspension cord control mechanism of  FIG. 11  in the rest position. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0027]     Referring now to the drawings,  FIGS. 1 and 2  depict a top down style window covering comprising a head rail  15  and a light blocking element  18 . The light blocking element  18  may include one or more closure panels movable to allow and block light passage, and which may take the form of a honeycomb panel, a Roman style shade, a Venetian blind, or the like. The light blocking element  18  also includes a top portion, such as top rail  16  and a bottom portion, such as bottom rail  17 . It should be recognized that while the depicted embodiments show a top rail  16  and bottom rail  17 , they are not strictly necessary and can simply be the top and bottom portions of the light blocking device. A suspension cord  19  for controlling the deployment of light blocking element  18  is connected at one end to the top rail  16  and passes through openings  30  in the head rail  15 . The suspension cord  19  also operatively engages the suspension cord control mechanism. The suspension cord control mechanism comprises of a biasing mechanism  20  and arresting mechanism  10 .  
         [0028]     The arresting mechanism  10  is configured to engage the suspension cord  19  such that the position of the suspension cord  19  is maintained and may take the form of a window cord lock mechanism, clutch or other device for this purpose known in the art. When a user pulls on the suspension cord, the arresting mechanism disengages from the suspension cord  19  such that the cord  19  is permitted to slide freely therethrough. When the user releases the cord  19 , the arresting mechanism  10  again engages the cord  19 .  
         [0029]     In the embodiment depicted in  FIGS. 2 and 3 , biasing mechanism  20  comprises a sliding plate  22 , spring  24  and rotary roller  26 . Sliding plate  22  is slidable along at least a portion of the length of the head rail  15 . Rotary roller  26  is fixably connected to sliding plate  22 . The suspension cord  19  is operatively engaged with rotary roller  26 , although it is understood that roller  26  may be a pin or other apparatus connected or integral to sliding plate  22  that permits the suspension cord  19  to move somewhat freely. One end of spring  24  is connected to sliding plate  22  and another end of spring  24  is connected to head rail  15 . Spring  24  can be replaced with other elastic means capable of storing potential energy under tension or compression.  
         [0030]      FIGS. 4 and 5  show the operation of the biasing mechanism  20 . When a downward force is applied to the free end of suspension cord  19  by a user, the cord  19  raises top rail  16  of light blocking element  18  towards the head rail  15 . Since cord  19  is operatively engaged with roller  26  on sliding plate  22 , the action of pulling cord  19  by the user (shown by the downward arrow in  FIGS. 4 and 5 ) also causes sliding plate  22  to move laterally down the length of and away from the end of head rail  15 . In doing so, the movement of slidable plate  22  relative to the end of head rail  15  tensions spring  24  from its rest state. Spring  24  should be selected to be of an appropriate stiffness so that the spring  24  does not prevent the motion of sliding plate  22  but stiff enough that the spring  24  can overcome the weight of light blocking element  18 .  
         [0031]     When the suspension cord  19  is released by the user, the weight of light covering element  18  will cause the suspension cord  19  to fall and slide in a reverse direction. This action is prevented by arresting mechanism  10 , which locks the cord  19  in place and prevents movement. As the arresting mechanism  10  moves from an open position where the cord  19  is free to move to an engaged position where the position of cord  19  is maintained, a small amount of cord  19  slides such that the top rail  16  moves away from the head rail  15 . When cord  19  is arrested such that there is no longer an force tensioning spring  24 , the spring  24  returns to its relaxed state and returns sliding plate  22  to its initial starting position. Since the length of cord  19  between the arresting mechanism  10  and top portion  16  of the light blocking element  18  is fixed once the cord  19  is arrested by the arresting mechanism  10 , the movement of sliding plate  22  towards the end of the head rail  15  has the effect of urging top portion  16  of the light blocking element towards the head rail  15 . This movement counteracts and compensates for the downward movement of the light covering element  18  under its own weight when the cord  19  was initially released by the user prior to being engaged by arresting mechanism  10 .  
         [0032]     It should be noted that the biasing mechanism of the suspension cord control mechanism can take any number of variant forms. One such alternative preferred embodiment is shown in  FIGS. 6-10 . Cord  119  is connected to the top portion  116  of the light blocking element through openings  130  and is operatively engaged with biasing mechanism  160  and arresting mechanism  110 . In this embodiment, the biasing mechanism  160  comprises a rotary plate  165  pivotably mounted to the head rail  115 . One end of torque spring  170  is fixably connected to rotary plate  165  while the other end of spring  170  is fixably connected to the head rail  115 . Fixably mounted or integral to the rotary plate  165  are at least two projections  180  around which the cord  119  is engaged.  
         [0033]     In its rest state, torque spring  170  positions the rotary plate  165  transversely across the width of head rail  115 . In operation, when cord  119  is pulled, the force on cord  119  is in a direction substantially parallel to the length of the head rail  115 . This force causes the rotary plate  165  to rotate from its rest state into a position substantially parallel to the length of the head rail  115 . The rotation of rotary plate  165  deforms and loads torque spring  170 . When the cord  119  is released and arrested by arresting mechanism  110 , the loaded spring  170  rotates the plate  165  back to its rest state, pulling on the cord  119  and raising top portion  116  closer towards head rail  115 .  
         [0034]     Yet another preferred embodiment of a biasing mechanism sutiable for the present suspension cord control mechanism is shown in  FIGS. 11-15 . Suspension cord  219  is connected to the top rail  216  of the light blocking element, which may also have a weighted bottom rail  217  so that the light blocking element hangs freely. The cord  219  is threaded through head rail  215  via openings  230  and is operatively engaged with the biasing mechanism  260  and arresting mechanism  210 .  
         [0035]     As more clearly shown in  FIG. 13 , the biasing mechanism  260  located in head rail  215  includes two sliding plates  265   a  and  265   b.  Mounted on each sliding plate  265   a  and  265   b  are projections  280   a  and  280   b,  which may be fixably mounted or integral to the sliding plate. In the rest state, projections  280   a  and  280   b  are situated offset relative to each other across the width of the head rail  215 . The plates  265   a  and  265   b  are slidable in a lateral direction relative to each other and longitudinally down a portion of the length of head rail  215 . Plates  265   a  and  265   b  are further connected by a spring  270  interactively engaged between them.  
         [0036]     In operation, when suspension cord  219  is pulled, the cord  219  causes the top rail  216  to move in the direction of head rail  215 . Simultaneously, the component of the force parallel to the longitudinal length of the head rail  115  pulls the offset projections  280   a  and  280   b.  This force causes projection  280   a  and plate  265   a  to slide laterally relative to projection  280   b  and plate  265   b,  loading spring  270  by compression.  
         [0037]     When the cord  219  is released, the light blocking element falls of its own weight a short distance before its movement is arrested when the arresting mechanism  210  arrests the movement of suspension cord  219 . When the cord  219  has been arrested, loaded spring  270  unloads to drive plates  265   a  and  265   b  back into their original position. This movement results in lengthening the distance of cord  219  between projections  280   a  and  280   b  and-pulls on the cord  219 , lifting the top portion  216  towards head rail  215 .  
         [0038]     While the various descriptions of the present invention are described above, it should be understood that various features can be used singly or in combination thereof. Therefore, this invention is not to be limited to the specific preferred embodiments depicted herein. Further, it should be understood that variations and modifications within the spirit and scope of the invention may occur to those skilled in the art to which the invention pertains. Accordingly, all expedient modifications readily attainable by one versed in the art from the disclosure set forth herein that are within the scope and spirit of the present invention are to be included as further embodiments of the present invention. The scope of the present invention is accordingly set forth in the appended claims.

Summary:
A suspension cord control mechanism composed of an arresting mechanism and a biasing mechanism operable to move a light blocking element after the user has released a suspension cord. The biasing mechanism is loaded when the suspension cord is drawn by a user to lift the window covering. When the suspension cord is released, movement of the cord is stopped by the arresting mechanism and the biasing mechanism unloads to further move the light blocking element.