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BACKGROUND OF THE INVENTION  
       [0001]     (a) Field of the Invention  
         [0002]     The present invention relates to a single cord activation mechanism for collecting a window blind, and more particularly to a mechanism which is used to operate a release of slats of a window blind by a method of single cord activation. The mechanism includes primarily a reel which is connected to the slats through a lifting cord, and whose one end is operated by an activation shaft with a smaller diameter, through a single activation cord. The slats can be opened by themselves with their deadweights, whereas they are collected through acting on the activation shaft and the reel associated therewith by the single activation cord, thereby achieving purposes of enlarging speed and collecting with safety.  
         [0003]     (b) Description of the Prior Art  
         [0004]     An operation of opening slats of a horizontal window blind can be performed manually or electrically. The manual operation is shown in  FIG. 1 , wherein pluralities of slats  10  are located below a top rail  1 . A pull cord  2  links with each slat  10  and passes through a penetration  15  on the top rail  1 , and then reeves on an arresting member  100  to extend with an active pull cord  20 . There are at least two active pull cords according to the quantity of pull cords. Therefore, two cords extended from the pull cord  2  will be accumulated at the position of active pull cord  20 . The arresting member  100  creates a locking function to lock on any position of a section of the active pull cord  20 , so as to position the slats  10  in a half-open or full-open status.  
         [0005]     The slats  10  can be dropped down by the deadweight effect associated with the gravity of earth. However, upon collecting slats  10 , the active pull cord  20  is used to pull up the slats  10  to stack them upward to achieve a purpose of collecting.  
         [0006]     As the active pull cord  20  is made by two cords  200 , a tangle will usually be formed between them. In addition, since an activation stroke of the active pull cord  20  is the same as a collecting/releasing stroke of the slats  10 , a certain length will be dropped down for the active pull cord  20  after collecting the slats  10 , thereby forming a free hanging cord and causing a danger of winding and tying limbs of kids due to playing.  
         [0007]     Referring to  FIG. 2 , a recent method of electrically operating a window blind is to use a motor  13  to drive a reel  11  through a polygonal driving shaft  12 . An inner hole of the reel  11  provides for the driving shaft  12  to rotate radially, and the reel  11  is supported by a sliding seat  14  which is movable. The entire mechanism is installed inside a top rail  1  and can slide longitudinally. An outer surface of the reel  11  provides for a winding of a lifting cord  16  which passes through each slat  10  and combines with a ladder string  160  to position the slats  10  in an equal distance. As the motor  13  requires electricity, the mechanism will lose its convenience under a blackout condition.  
       SUMMARY OF THE INVENTION  
       [0008]     In lieu of the aforementioned inconvenience of conventional collecting mechanisms, the present invention uses a single cord operation method to open and close the slats, whereas the slats can be dropped down by using the deadweight effect of slats themselves. In addition, the reel is driven to collect the slats by acting on the activation shaft through the single activation cord. The working principle is to use a shear force between strands of lifting cord to form a horizontal component of force, which in turn drives the reel to shift longitudinally, during the process of collecting the slats. In addition, the diameter of reel is larger than that of the activation shaft, therefore a linear velocity (length) of the activation cord can be enlarged by an enlargement of the reel, thereby providing a fast operation and shortening a length at lower end of the activation cord.  
         [0009]     To enable a further understanding of the said objectives and the technological methods of the invention herein, the brief description of the drawings below is followed by the detailed description of the preferred embodiments. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  shows a perspective view of an activation mechanism of a conventional horizontal window blind.  
         [0011]      FIG. 2  shows a perspective view of a conventional method of collecting slats electrically.  
         [0012]      FIG. 3  shows a side view of the present invention.  
         [0013]      FIG. 4  shows a schematic view of operation of a lifting cord of the present invention.  
         [0014]      FIG. 5  shows a force diagram of  FIG. 4 .  
         [0015]      FIG. 6  shows a schematic view of a release shaft driving a lifting cord of the present invention.  
         [0016]      FIG. 7  shows a force diagram of  FIG. 6 .  
         [0017]      FIG. 8  shows an end view of a relationship between a release shaft and an activation shaft of the present invention.  
         [0018]      FIG. 9  shows a side view of  FIG. 8 .  
         [0019]      FIG. 10  shows a schematic view of a release shaft after dropping down slats of the present invention.  
         [0020]      FIG. 11  shows a comparison between a stroke of lifting cord and a stroke of activation cord.  
         [0021]      FIG. 12  shows a side view of screws of another implementation of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0022]     Referring to  FIG. 3 , a release shaft  3  is located on a sliding seat  30  which is installed in a top rail  1 . The release shaft  3  is coaxially connected to an activation shaft  4  with a smaller diameter. The activation shaft  4  is supported by another corresponding slide seat  40 . An outer surface of the release shaft  3  provides for winding a lifting cord  31  whose free end passes through a shed  18  installed in the top rail  1  and which is linked downward to slats  10 , with a terminal free end connected to a bottom rail  17 . The activation shaft provides for winding an activation cord  41  which passes through an arresting member  100  located on the top rail  1 . The arresting member  100  is a conventional arresting member and its function is to lock on any position of a section of the activation cord  41 , such that when pulling down the activation cord  41 , it should be shifted by an angle to escape from the arresting member  100 . As the operation of arresting member  100  is an ordinary design, it will not be described further.  
         [0023]     The activation cord  41  wound around the activation shaft  4  will move up and down alternatively, relative to the lifting cord  31  on the release shaft  3 . Therefore, when dropping down the slats  10 , the release shaft  3  will be rotated accordingly, which in turn Will drive the activation shaft  4  to rotate in a same direction simultaneously.  
         [0024]     When the slats  10  drop down due to their deadweights, the lifting cord  31  will be limited by the position of shed  18 . Therefore, when the release shaft  3  is pulled by the lifting cord  31 , it will be pushed rightward according to its sidelong component of force, which will in turn extend the activation shaft  4  rightward. In addition, as the activation cord  41  located on the activation shaft  4  will be collected when dropping down the slats  10 , and the release shaft  3  will move rightward, hence there will be no overlapping between each strand of activation cord  41 , thereby constituting a spiral shape collection.  
         [0025]     Referring to  FIG. 4 , when the lifting cord  31  is collected on the outer surface of release shaft  3 , a series of strands  310  aligned next to each other will be formed between a last strand  310  and the lifting cord  31 . During a process of collection, as the lifting cord  31  is positioned by the shed  18  and when an upper end of lifting cord  31  is wound on an initial position of the release shaft  3 , a sidelong shear will be formed at a previous strand  310 , resulting in a distance P 2  before shearing and a distance P 1  after shearing. Pluralities of strands  310  are aligned with an equal distance P 1 , and a position of point of action P will be changed into a position on an upper surface of release shaft  3 , due to a sidelong shear.  
         [0026]     Referring to  FIG. 5 , during a process of shifting the point of action P, a sidelong force of action F will be formed, which is composed of a vertical component of force F 1  and a horizontal component of force F 2  caused by the lifting cord  31 . The horizontal force of action F 2  branched out from the sidelong force of action F will be acting on a left side. Therefore, as shown in  FIG. 4 , the force of action F 2  will push a previous strand  310 . As each strand  310  is winding on the outer surface of release shaft  3  which can freely slide as a free body in a longitudinal direction, the release shaft  3  will be pushed leftward by subjecting to the horizontal force of action F 2 .  
         [0027]     Referring to  FIG. 6 , when the lifting cord  31  is pulled down by an external force, a sidelong angle θ will be formed at the lifting cord  31  between the shed  18  and release shaft  3 , due to a positioning of shed  18  and a resistance force resulted from a horizontal shifting of release shaft  3 .  
         [0028]     Referring to  FIG. 7 , a downward vertical force of action F of the lifting cord  31  will be decomposed into a sidelong component of force F 1  and a horizontal component of force F 2  due to the aforementioned factors. Similarly, the horizontal component of force F 2  will result in a rightward force through the sidelong component of force F 1  and the force of action F, so as to push the release shaft  3  rightward.  
         [0029]     Referring to  FIG. 8 , the activation shaft  4  is coaxially connected to the release shaft  3 . Therefore, when the activation cord  41  is winding on the activation shaft  4  clockwise, the lifting cord  31  will be winding on the outer surface of release shaft  3  counterclockwise.  
         [0030]     Referring to  FIG. 9 , as the release cord  31  and the activation cord  41  are winding on the release shaft  3  and the activation shaft  4  in different direction, when the release shaft  3  is rotating counterclockwise and the lifting cord is moving downward, the activation cord  41  will be pulled up and collected. On the contrary, if the activation cord  41  is pulled down, the release shaft  3  will collect the lifting cord  31 .  
         [0031]     Referring to  FIG. 10 , it shows a schematic view of dropping down the slats. Similarly to dropping down the slats  10  due to the deadweight effect as shown in  FIG. 3 , a locking status of the activation cord  41  by the arresting member  100  must be removed, so as to enable the activation cord  41  to freely move up. Whereas, the lifting cord  31  will pull the release shaft  3  through a downward movement of slats  10 , and push the release shaft  3  rightward according to the working principle depicted in  FIG. 6 , which will in turn extend the activation shaft  4  rightward. Moreover, due to the working principles depicted in  FIG. 8  and  FIG. 9 , the activation shaft  4  will collect the activation cord  41 . On the other hand, upon collecting the slats  10 , the activation cord  41  will be escaped from the arresting member  100  and pulled, and simultaneously rotate the release shaft  3  through the activation shaft  4 , such that the release shaft  3  can collect the lifting cord  31  in a reverse direction, thereby pulling up the slats  10  and achieving a purpose of collecting the slats  10 .  
         [0032]     Referring to  FIG. 11 , a lifting stroke L 1  of the lifting cord  31  driven by the release shaft  3  is determined by multiplying a diameter D 1  of release shaft  3  by the ratio of the circumference of a circle to the diameter and a rotational speed (L 1 =π D N). As the release shaft  3  and the activation shaft  4  are connected coaxially, their rotational speeds will be identical. As the diameter D 1  of release shaft  3  is larger than the diameter D 2  of activation shaft  4 , the operation stroke L 1  of lifting cord  31  must be greater than a pulling stroke L 2  of activation cord  41 . If the diameter D 1  of release shaft  3  is twice as much as the diameter D 2  of activation shaft  4 , then the stroke L 1  will also be twice as much as the activation stroke L 2  of activation cord  41 . By taking an advantage that the strokes are not the same, a user can operate the activation cord  41  in a short range to operate a height of opening and closing of a large stroke lifting cord  31 . Correspondingly, an operation speed can be enlarged to operate an upward and downward movement of the slats  10 .  
         [0033]     A stem  410  is fastened to the free end of activation cord  41 , so as to facilitate a grab with hands for activation. As the activation cord  41  can be extended downward, and its operation stroke L 20  is also located below, therefore for a window blind hanged up in a high position, a user can operate at a position close to a ground, by using this concept.  
         [0034]     The concept of providing a grab with the stem  410  at the free end of activation cord  41  can be further applied to a terminal cord winder  42  which is connected to the free end of activation cord  41 . A shape of the cord winder  41  is used to provide for grabbing and the cord winder  41  can be an ordinary tool for winding cords, which will not be described further. By using the cord winder  42  to perform collection, the position of stem  410  can be at any height.  
         [0035]     Referring to  FIG. 12 , a sliding friction exists between the release shaft  3  and the sliding seat  30 , such that the release shaft  3  can move rightward and leftward in a longitudinal direction. To further specify that the release shaft  3  can collect the lifting cord  31  in a full pitch, male threads  32  with a pitch equal to the diameter of lifting cord  31  are located on the outer surface of release shaft  3 . The male threads  32  are acting on female screws  300  located in the sliding seat  30 . By a high sliding rate between the female screws  300  in the sliding seat  30  and the male threads  32 , the release shaft  3  can easily move longitudinally according to a specification of male threads, when pulling down the lifting cord  31 . The female screws  300  are located in a position with respect to a sliding hole  301 . By using the male threads  32  located on the release shaft  3 , the lifting cord  31  can be collected in an equal pitch, which in turn can move the activation shaft  4  axially with a uniform pushing velocity.  
         [0036]     In addition to the aforementioned implementation of male threads  32  on the outer surface of release shaft  3 , the present invention can further install male threads  43  on the outer surface of activation shaft  4 . The male threads  43  fit with female screws  400  located at a position of sliding hole  401  of a sliding seat  40 , such that the activation cord  41  can be wound on the male threads  43  according to the threads, wherein the activation cord  41  and the lifting cord  31  have the same diameter. If both the release shaft  3  and activation shaft  4  are provided with the male threads  43 , their pitch must be identical. However, the diameter of release shaft  3  is larger than that of activation shaft  4 .  
         [0037]     It is of course to be understood that the embodiments described herein is merely illustrative of the principles of the invention and that a wide variety of modifications thereto may be effected by persons skilled in the art without departing from the spirit and scope of the invention as set forth in the following claims.

Summary:
A single cord activation mechanism for collecting a window blind, especially a mechanism which uses a single cord to collect slats of a window blind, is primarily composed of a release shaft with a larger diameter which is connected coaxially with an activation shaft. The entire structure is located in a top rail longitudinally. The release shaft provides for winding a lifting cord for opening and closing the slats. The activation shaft provides for winding an activation cord through an arresting member. A linear length of releasing operation can be enlarged by increasing the diameter of activation shaft, and a height of operation can be safely and easily acquired according to opening and closing the slats with the single activation cord.