Abstract:
A system for assuring removal of a cord from its wrapping in an external thread of a spool utilizes a follower having an internal thread that moves along the spool upon rotation of the spool with the follower having a slot through which the cord is passed and a catch on the internal surface of the follower adjacent to the slot in the follower that projects into the external thread of the spool to force a removal of the cord from the thread. Preferably, the catch comprises one end of the internal thread in the follower which by its very nature projects into the external thread of the spool for engagement with a cord received in the external thread.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims the benefit under 35 U.S.C. § 119(e) to U.S. Provisional Patent Application No. 60/753,520 (“the &#39;520 application”), which was filed on Dec. 22, 2005 and entitled “THREADED LIFT CORD SPOOL FOR COVERINGS FOR ARCHITECTURAL OPENINGS.” The &#39;520 application is incorporated by reference into the present application in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to retractable coverings for architectural openings and more particularly to a spool about which a lift cord can be wrapped and unwrapped while extending and retracting the covering. 
     2. Description of the Relevant Art 
     Retractable coverings for architectural openings can assume numerous forms including retractable shades, venetian blinds, vertical blinds, cellular shades, and the like. In such coverings, a lift cord is typically utilized to move the covering between extended and retracted positions and the lift cord is sometimes wrapped around a spool, rod, or the like during a retracting movement. Lift cords can become entangled on the spool thereby inhibiting error-free operation of the covering and, accordingly, systems have been devised for discouraging entanglement of a lift cord. 
     One system for preventing entanglement is to provide a thread on the lift cord spool so that the cord is confined within the thread as it is wrapped about the spool and is therefore discouraged from becoming entangled. Another system for preventing entanglement consists of providing a surrounding housing to the spool which is closely spaced from the outer winding surface of the spool whereby only a single layer of cord is allowed on the spool thereby discouraging entanglement. 
     One cause of entanglement, when using a thread to confine the lift cord, resides in the lift cord being frictionally trapped within the thread and not being readily separated from the thread as the cord is being unwrapped from the spool and accordingly a system for assuring the removal of a lift cord from the thread of a lift spool during an extending movement of the covering would be desirable. 
     SUMMARY OF THE INVENTION 
     The present invention employs a lift system for a retractable covering for architectural openings wherein the lift cord for moving the covering between extended and retracted positions is positively controlled to prevent entanglement. The lift spool has an external thread in which the lift cord is confined and the lift cord is laid into the thread with a follower that is internally threaded and adapted to move axially along the length of the threaded spool upon rotation of the threaded spool. As the follower is moved along the threaded spool, the lift cord is fed into the thread on the spool with the lift cord being fed through a cord passage in the follower. 
     When the cord is removed from the external thread in the spool, as when the spool is rotated in an opposite direction, the follower moves in an opposite axial direction and the lift cord is removed through the cord passage in the follower. To prevent the lift cord from being trapped in the thread thereby causing entanglement, the internal thread on the follower has an end provided immediately adjacent to the cord passage with the end of the internal thread extending into the external thread of the spool to lift the cord out of the external thread thereby removing any possibility the cord will become trapped or hung up in the external thread as the spool is rotating causing entanglement. 
     Other aspects, features and details of the present invention can be more completely understood by reference to the following detailed description of a preferred embodiment, taken in conjunction with the drawings and from the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a fragmentary isometric of a retractable covering for architectural openings incorporating the lift cord control system of the present invention. 
         FIG. 2  is an isometric similar to  FIG. 1  with the shade material having been removed and with the middle rail of the covering in a lowered position. 
         FIG. 3  is an isometric similar to  FIG. 2  with the bottom rail having been raised in the covering. 
         FIG. 4  is a diagrammatic isometric showing the control system of the present invention incorporated into the remainder of the covering with the shade material removed. 
         FIG. 5  is an exploded isometric of the lift cord control system of the invention. 
         FIG. 6  is an isometric similar to  FIG. 5  with the components of the lift cord control system integrated. 
         FIG. 7  is an isometric looking downwardly on the threaded spool in a first direction. 
         FIG. 8  is an isometric looking downwardly on the threaded spool from an opposite direction. 
         FIG. 9  is an end elevation looking at the left end of the spool as shown in  FIG. 8 . 
         FIG. 10  is an isometric looking downwardly on a follower used with a threaded spool in accordance with the present invention. 
         FIG. 11  is a top plan view of the follower of  FIG. 10 . 
         FIG. 12  is a front elevation of the follower of  FIG. 10 . 
         FIG. 13  is a rear elevation of the follower of  FIG. 10 . 
         FIG. 14  is an isometric looking at the rear side of the follower used on a second threaded spool for the lift system of the present invention. 
         FIG. 15  is a top plan view of the follower shown in  FIG. 14 . 
         FIG. 16  is a front elevation of the follower shown in  FIG. 14 . 
         FIG. 17  is a rear elevation of the follower shown in  FIG. 14 . 
         FIG. 18  is an isometric of the housing for the lift system of the present invention. 
         FIG. 19  is an isometric looking at one end of an end plug for a threaded spool of the lift system of the invention. 
         FIG. 20  is an isometric looking at the opposite end of the spool as shown in  FIG. 19 . 
         FIG. 21  is a section taken along line  21 - 21  of  FIG. 6 . 
         FIG. 22  is a section taken along line  22 - 22  of  FIG. 6 . 
         FIG. 23  is a section taken along line  23 - 23  of  FIG. 6 . 
         FIG. 24  is an enlarged section taken along line  24 - 24  of  FIG. 6 . 
         FIG. 25  is an enlarged section taken along line  25 - 25  of  FIG. 6 . 
         FIG. 26  is an enlarged section taken along line  26 - 26  of  FIG. 24 . 
         FIG. 27  is a section taken along line  27 - 27  of  FIG. 26 . 
         FIG. 28  is an enlarged section taken along line  28 - 28  of  FIG. 27 . 
         FIG. 29  is a section similar to  FIG. 27  with the lift cord spool having been rotated in a clockwise direction approximately 30 degrees with the catch thread of the follower engaging the lift cord. 
         FIG. 30  is a top plan view of the lift system of the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The threaded cord spool  32  of the present invention would find use in any covering for an architectural opening wherein a cord is wrapped or unwrapped about a generally cylindrical body depending upon the deployment of the architectural covering. For purposes of the present disclosure, the lift cord spool is disclosed in a top down/bottom up covering  34  of the type shown in  FIGS. 1-4 . The covering includes a headrail  36  in which the operative components of the shade are housed, a bottom rail  38  including a roller  40  to which the bottom of the shade material  42  is attached and about which the shade material can be wrapped, and a middle rail  44  connected to the top of the shade material. The middle rail is connected to a control system with lift cords  46   a  and  46   b  operatively associated with opposite ends of the middle rail and with the lift cords being operatively engaged with threaded lift cord spools  32  of the present invention. The bottom rail is supported by its own set of lift cords  48   a  and  48   b  which are operatively incorporated into a counterbalance system  50  also disposed in the headrail. The shade material, which could be most any flexible material, is shown for illustrative purposes as including a pair of spaced vertical flexible sheets  52  of translucent material which are interconnected by a plurality of horizontally disposed flexible vanes  54 . The vanes assume a generally S-shaped transverse configuration when in the open position shown in  FIG. 1  and become generally flat vertical planar sheets when the shade material is closed with the flat vanes overlapping each other. The shade material is not shown in the closed position, but a complete understanding of a covering of the general type disclosed in  FIGS. 1-3  can be found in U.S. application Ser. No. 10/642,017, now U.S. Pat. No. 7,063,122, which is of common ownership with the present application and the disclosure of which is hereby incorporated by reference. 
       FIG. 2  shows the covering  34  with the middle rail  44  fully extended in adjacent relationship with the fully extended bottom rail  38  so there is no shade material  42  extending across the opening in which the covering would be mounted.  FIG. 3  shows both the bottom rail and the middle rail in a retracted or raised position adjacent to the headrail  36 . As will be appreciated from the generic description of the covering as being a top down/bottom up covering, the top of the shade material can be lowered or the bottom can be raised depending upon the deployment of the shade material desired. 
     With reference to  FIG. 4 , the covering  34  of  FIGS. 1-3  is shown diagrammatically and with the shade material removed. Both the middle rail  44  and bottom rail  38  are shown in phantom lines. As mentioned previously, the bottom rail is supported by lift cords  48   a  and  48   b  that are operatively associated with a counterbalance system  50  described in detail in the aforenoted U.S. Pat. No. 7,063,122. In that system a lift cord  48   a  and  48   b  is associated with each end of the bottom rail and extends upwardly around a vertical pulley  56  and then horizontally until it passes around a friction pin  58  and subsequently onto one of two rotatable spools  60 . The spools are rotated in unison and are operatively associated with a constant tension spring  62  so that regardless of the direction of rotation of the spools, a constant spring bias is created sufficient to support the bottom rail. The bottom rail can therefore be manually lifted or lowered between any selected position within an architectural opening in which the covering is mounted and it will retain that position due to the counterbalance system that supports the bottom rail. Also, movement of the bottom rail relative to the middle rail causes the shade material  42  to be wrapped around or unwrapped from the roller  40  disposed within the bottom rail which is also spring biased toward a wrapped position of the shade material in a conventional manner and as described in the aforenoted U.S. Pat. No. 7,063,122. 
     A threaded lift cord spool system  64  including a pair of cord spools  32  is utilized in controlling the lift cords  46   a  and  46   b  associated with the middle rail  44  and as will be appreciated by reference to  FIG. 4 , there are two threaded lift spools  32  with one having a right-hand thread and the other a left-hand thread. Otherwise the spools are identical. The two spools are utilized in the covering  34  disclosed in the present application but it should be understood the concept of the present invention is applicable to any threaded spool and more specifically to a system for controlling the wrapping and unwrapping of a cord about a threaded spool. 
     In general, each threaded spool  32  is associated with a lift cord  46   a  and  46   b  that is in turn associated with one end of the middle rail  44 . The middle rail has first and second spaced axially extending friction pins  66   a  and  66   b  respectively at each end thereof and an anchor  68  is provided within the headrail for anchoring one end of each lift cord. The lift cord associated with each threaded spool extends from its associated anchor  68  in a horizontal direction around an arcuate block  70  and from the block vertically downwardly where it is wrapped around the second friction pin  66   b  adjacent one longitudinal edge of the middle rail and subsequently around the first friction pin  66   a  adjacent the opposite longitudinal edge of the middle rail before extending upwardly and passing around a pulley  72  from which it extends generally horizontally to the associated threaded spool  32 . As will be described in more detail later, the lift cord is wound onto the threaded spool or unwound from the spool depending upon whether or not the middle rail is raised or lowered respectively and the threaded spools are manually rotatably driven by an endless drive cord  74  at one end of the covering. The endless drive cord extends around a drive wheel  76  that is in turn operatively connected to the lift spools  32  through a two-way clutch  78  so that rotation of the drive wheel in either direction by the drive cord will rotate a drive shaft  80  associated with the threaded spools. The two-way clutch, however, allows the threaded spools to remain in any position in which they are moved until the drive wheel is again rotated by the drive cord. Again, this system as thus far described is disclosed in detail in the aforenoted U.S. Pat. No. 7,063,122. 
     It will be appreciated from the above that by rotating the drive wheel  76  with the drive cord  74 , the middle rail  44  can be raised or lowered depending upon the direction of rotation of the drive wheel. By manually lifting or lowering the bottom rail  38 , it can be moved between any selected position through its operative connection with the counterbalance system  50 . Accordingly, the shade material  42  can be extended to any desired degree between the middle rail and the bottom rail and positioned at any desired location between the headrail  36  and the fully extended position of the bottom rail  38 . 
     As is also described in detail in the aforenoted U.S. Pat. No. 7,063,122, when the drive cord  74  rotates the drive wheel  76  in a direction causing the lift cords  46   a  and  46   b  to be wrapped onto their associated threaded spools  32 , the tension placed in the lift cord between the spool and the first friction pin  66   a  directly associated therewith causes the lift cord to grip the first friction pin thereby lifting the associated edge of the middle rail  44  relative to the opposite edge of the middle rail which pivots the middle rail about a longitudinal axis, and consequently the connected flexible vanes  54  in the shade material  42 , between the open position of  FIG. 1  and a closed position (not shown) wherein the vanes are substantially vertically oriented in a flat planar configuration and slightly overlapped with each other. When the lift cords are unwrapped from the associated threaded spools due to rotation of the drive wheel in an opposite direction, the first friction pin  66   a , directly associated with the lift cord as it emanates from the threaded spool, is initially lowered until it becomes horizontally aligned with the second friction pin  66   b  so that when the middle rail is thereby pivoted, the slats in the shade material are pivoted correspondingly to the open position of  FIG. 1 . 
     The components of the threaded lift cord spool system  64  of the present invention are possibly shown best in  FIG. 5  where again it will be appreciated there are two lift cord spools  32  with one having an external left-hand thread  82  and the other an external right-hand thread  82  on a cylindrical body. The spools are otherwise identical. Each spool has hexagonal openings  84  in its opposite ends for receipt of end plugs  86  that include a cylindrical body  88  insertable into the associated end of the threaded spool and a hexagonal head  90  that fits frictionally into the hexagonal opening at the associated end of the spool. As will be described in more detail later, each spool also has a radial slot  92  at one end extending from the external thread  82  to the hexagonal opening in that end. 
     A generally L-shaped follower  94  is associated with each threaded spool  32  and has a cylindrical passage  96  therethrough with an internal thread  98  adapted to mate with the external thread  82  on the associated spool. The followers are adapted to move axially along the length of their associated threaded spools upon rotation of the threaded spools and due to the opposite threads on the threaded spools, unitary rotation of the spools in one direction causes the followers to move toward each other and in the opposite direction causes the followers to move away from each other. The followers will be described in detail later but suffice it to say each follower has a cylindrical skirt  100  with an elongated, diagonal, arcuate cord slot  102  formed in the top surface thereof and with the slot being angled relative to the axis of the cylindrical skirt so as to be aligned with the thread on the underlying spool. 
     Each end plug  86  has a square passage  104  therethrough with the proximal end plugs at the adjacent ends of the threaded spools  32  receiving a dual axle connector  106  having a pair of axles  108  of square cross section extending in opposition directions so that the threaded spools rotate uniformly and in unison. The square passage in the end cap at the opposite or distal end of one threaded spool (the right threaded spool as seen in  FIG. 5 ), is adapted to receive the square drive shaft  80  which is driven by the two-way clutch  78  described previously. In other words, it will be appreciated that by rotation of the drive wheel  76 , the square drive shaft will rotate both threaded spools in the same direction causing the followers  94  to move toward or away from each other depending upon the direction of rotation of the square drive shaft. 
     As will be described in more detail later, the threaded spools  32  and the shaft  80  and axles  108  upon which they are mounted, as well as the followers  94 , are confined within a generally U-shaped elongated housing  110  and the followers are slidably confined within the housing so they cannot rotate relative to the housing while the threaded spools on which they are mounted are rotated with the square drive shaft  80 . This arrangement assures uniform movement of each follower along its associated threaded spool upon rotation of the threaded spool. 
       FIGS. 7 ,  8  and  9  show a threaded spool  32  as above described wherein the spool has either a left or right-hand thread  82 , the hexagonal opening  84  in each end, a cylindrical inner surface  112  and a cylindrical outer surface in which the external thread is formed. The radial slot  92  at one end of the spool is seen in  FIGS. 8 and 9  to extend from the external thread  82  of the spool to the internal cylindrical surface  112 . 
     The two followers  94  are mirror images of each other with one follower illustrated in  FIGS. 10-13  and the other in  FIGS. 14-17 . Each follower has a horizontal upper leg  114  and a vertical lower leg  116  with the cylindrical skirt  100  and passage  96  extending through the vertical lower leg and the skirt. The internal thread  98  in the follower, as possibly best seen in  FIG. 28 , commences inwardly of a flat front wall or surface  118  of the follower and extends to an end location  120  just past the front surface or wall  118  of the upper leg so as to be in alignment with the rearwardmost end  124  of the lift cord slot  102 . The internal thread therefore has two ends with one end  126 , the rearmost end, being positioned inwardly of the flat front wall or surface  118  of the follower and the other end  120 , the forwardmost end, at a location commensurate with the rearwardmost end  124  of the lift cord slot  102 , i.e. the end closest to the front wall  118  of the upper leg. 
     The upper leg  114  also has a horizontal passage  128  formed therein in which a pulley  130  is adapted to be mounted. A vertical hole  132  passes downwardly through the upper leg and the passage to receive a pivot pin  134  for the pulley. The pulley can be seen for example in  FIG. 6 . The lower or vertical leg  116  of each follower has three flattened tabular corners, two  136  and  138  along its bottom and one  140  at its top, that cooperate with corresponding walls of the housing, as will be appreciated hereinafter, to prevent rotation of the follower relative to the housing. As mentioned previously, since the followers  94  are mirror images of each other, the skirt on one follower will confront the skirt  100  on the other follower and the front faces  122  of the followers will face in opposite directions when the followers are threadedly mounted on their associated spools. 
     With reference to  FIG. 18 , the elongated housing  110 , as mentioned previously, is generally U-shaped in configuration having an open upper top  142 , a front wall  144 , a rear wall  146 , and a bottom wall  148 . The bottom wall has longitudinally extending tabs  150  for anchoring the housing to the headrail  36  of the covering  34  for the architectural opening. Each end of the housing has a U-shaped bearing surface  152  and a divider  154  at the midpoint of the length of the housing which also defines a U-shaped bearing surface  156  for rotatably supporting the end plugs  86  and the dual axle connector  106  respectively. As may possibly best be appreciated by reference to  FIG. 24 , the front  144  and rear  146  walls of the housing are spaced from the bottom wall so as to define angled gaps  158  therebetween for receipt of the two lower flat tabular corners  136  and  138  of the followers  94  so that the followers are prohibited from rotating within the housing. The third flat tabular corner  140  at the top of the vertical leg of the follower overlies the front wall  144  for the same purpose. It will be appreciated, however, that the follower is allowed to slide along the length of the housing upon rotation of the lift spool  32  upon which it is threadably mounted. 
     The end plugs  86  are all identical and are illustrated in  FIGS. 19 and 20 . As mentioned previously, they include the cylindrical body  88  with the hexagonal head  90  and a hollow axle  160  protrudes axially from the hexagonal head to be rotatably seated on a U-shaped bearing surface  152  or  156  of the housing. The square passage  104  through the end plug is adapted to receive either the square drive shaft  80  or the dual shaft connector  106  so that the end plugs and consequently the threaded spools are rotated in unison with the drive shaft. 
     FIGS.  6  and  21 - 23  show the aforenoted components of the threaded lift cord spool system  64  integrated and in operative relationship with each other. As will be appreciated, and as was mentioned previously, one end of each lift cord  46   a  and  46   b  is secured to an anchor block  68  in the headrail  36  and the opposite end is secured to an associated spool  32 . The end of the cord secured to the spool is connected by passing it through the radial slot  92  provided in the proximal end of the spool and the cord is held in position by thereafter inserting an end plug  86  into the end of the spool which becomes frictionally retained within the end of the spool with the cord and rotates with the spool due to the cooperation of the hexagonal head  90  of the end plug with the hexagonal opening  84  in the end of the spool. As the lift cord radiates outwardly through the radial slot in the end of the spool, it is fed into the external thread  82  of the spool and subsequently through the diagonal cord slot  102  in the skirt  100  of the associated follower. It thereby extends out of the cord slot and then around the pulley  130  on the follower before extending to the middle rail  44  and ultimately the anchor block  68  at its opposite end. 
     As will be appreciated, as the threaded spools  32  are rotated in one direction, the lift cords  46   a  and  46   b  are either laid into the external threads  82  through the cord slots  102  in the skirts or removed from the threads when the spools are rotated in the opposite direction. In the disclosed embodiment, one direction of rotation, as when the followers move away from each other, causes the cords to be laid in the spools and the middle rail to be raised. The opposite direction of rotation causes the followers to be moved toward each other removing the cords from the spools and allowing the middle rail to be lowered. Further, the internal thread on the follower and the external thread on the spool are obviously the same, allowing the lift cord to be carefully and controllably laid into the external thread in a continuous manner when the spool is rotated in one direction. When the spool is rotated in the opposite direction, the weight of the middle rail  44  which creates a tension in the lift cord, causes the lift cord to be lifted from the external thread again in a controlled manner as the follower  94  is moved along the threaded spool. 
     As mentioned previously, and as possibly best appreciated by reference to  FIGS. 26-29 , the forewardmost end  120  of the internal thread  98  of the follower that terminates adjacent to the rearwardmost end  124  of the cord slot  102  in the skirt  100  of the follower has its termination location closely adjacent to or contiguous with the rearwardmost end of the slot. Accordingly, if during an unwinding movement of the spool, the lift cord does not easily lift out of the external thread  82  of the spool in which it is wound, the forwardmost end  120  of the internal thread as seen in  FIG. 29  will engage the lift cord and force it out of the external thread of the spool. If the forwardmost end of the internal thread were not so positioned, the lift cord might remain within the external thread of the spool passing beyond the cord slot in the skirt of the follower and become entangled within the system. As best appreciated by reference to  FIG. 29 , however, the interrelationship of the internal and external threads do not provide enough space for the lift cord to get therebetween and, accordingly, it is forced out of the external thread and through the cord slot in the follower for reliable operation. It should also be noted that the end  120  of the internal thread is shown as a radical surface relative to the cylindrical passage  96  that the surface could be inclined at an acute angle relative to the radical orientation illustrated so as to provide some lift should the surface engage the cord. An acute angle in the range of 5° to 15° has been found useful but not mandatory. An inclined alternative surface is illustrated in  FIG. 27  in dashed lines. 
     It will be appreciated from the above a system has been disclosed for controlling the wrapping and unwrapping of a cord from a threaded spool by utilization of a follower having an internal thread mated with the external thread of the spool for movement along the length of the spool. By removing the cord from the external thread through a slot in the follower at a location immediately adjacent or contiguous with an end of the internal thread of the follower, the cord is forcibly removed from the external thread of the spool. 
     It will be appreciated, however, that the end  120  of the thread would not necessarily need to be used for forcing the cord out of the thread but rather a separate catch or thread follower (not shown) could be incorporated into the follower with the internal thread of the follower actually terminating before the cord slot in the follower. Such a catch or thread follower would of course project into the external thread  82  of the lift spool  32  immediately adjacent to the cord slot  102  in the follower so as to function similarly to the first described system. The most convenient system, however, is felt to employ the internal thread  98  of the follower itself for making sure the cord is lifted from the external thread  82  of the spool. 
     Although the present invention has been described with a certain degree of particularity, it is understood the disclosure has been made by way of example, and changes in detail or structure made be made without departing from the spirit of the invention as defined in the appended claims.