Abstract:
A ladder tape includes two pairs of warp strings, and two weft strings repeatedly passing through the warp strings in a predetermined way to form two cords and a plurality of bridge sections between the cords. The weft strings respectively are wound around one section of each pair of the warp strings only to form an opening between the warp strings that the ladder tape may engage with the rotary drum of the window blind in a fast and easy way. The weft strings are wound around the warp strings in a way that the ladder tape will not get entangled with other objects unexpectedly.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates generally to a cord and its application, and more particularly to a ladder tape for a window covering and a slat adjusting apparatus of a window blind using the ladder tape. 
         [0003]    2. Description of the Related Art 
         [0004]    There are lots of ways to weave cords for various purposes of a ladder tape.  FIG. 1  and  FIG. 2  show a conventional ladder tape  1  for a window blind. The ladder tape  1  includes two parallel cords, each of which has a weft string la and two warp strings  1   b,    1   c . The weft string  1   a  winds around the warp strings  1   b ,  1   c  in a specific way. The weft string  1   a  forms several transverse coupling sections  1   d  to support slats  2  of the window blind (as shown in  FIG. 1 ) and an unwound section  1   e  (as shown in  FIG. 2 ). The unwound section  1   e  lets the warp strings  1   b ,  1   c  having an unbounded section that an opening  1   f  is formed between the warp strings  1   b ,  1   c.    
         [0005]    As shown in  FIG. 2 , a pin  3  passes through a gap  1   g  between the unwound section  1   e  and the weft string  1   b , and then passes through the opening  1   f  through a path L. The pin  3  has a neck  3   a  that will be arranged to be located between the warp strings  1   b ,  1   c  so that the warp strings  1   b ,  1   c  may hold the pin  3 . Next, the pin  3  is inserted into a rotary drum  4 . The rotary drum  4  has a plate  4   a  to cover and press the pin  3  thereunder so to fix the pin  3  with the rotary drum  4 . The rotary drum  4  is rotated to move the ladder tape  1  and tilt the slats  2 . 
         [0006]    The conventional apparatus for controlling the slats  2  has the following drawbacks: 
         [0007]    1. The ladder tape  1  are fastened to the rotary drum  4  using an additional pin  3  that is difficult to assemble and the ladder tape  1  may be disengaged with the rotary drum  4  easily if the pin  3  becomes loose within the rotary drum  4 . 
         [0008]    2. The pin  3  is inserted into the gap  1   g  between the unwound section  1   e  and the warp string  1   b  and the opening  1   f  that will have a risk of breaking the unwound section  1   e.    
         [0009]    3. The unwound section  1   e  may be entangled with other objects unexpectedly because it is exposed without any protection. 
       SUMMARY OF THE INVENTION 
       [0010]    The primary objective of the present invention is to provide a ladder tape, which is not easily entangled with other objects unexpectedly. 
         [0011]    According to the objective of the present invention, a ladder tape includes a first warp string, a second warp string, a third warp string, a fourth warp string; and at least two first weft strings repeatedly passing through the warp strings in a predetermined way. The first warp string and the second warp string are wound by a first weft string to form a first cord, and the third warp string and the fourth warp string are wound by the other first weft string to form a second cord. The first weft strings respectively have a plurality of first sections alternately wound around the first warp string and the second warp string, a plurality of second sections alternately wound around the third warp string and the fourth warp string. The first weft strings have a plurality of bridge sections between the first cord and the second cord, and opposite ends of each bridge sections respectively connect to the corresponding first section and the corresponding second section. The first weft strings respectively have a winding section wound around the first warp string to form a first opening between the first warp string and the second warp string, and wound around the third warp string only to form a second opening between the third warp string and the fourth warp string. 
         [0012]    The present invention further provides a slat adjusting apparatus of a window blind, including a rotary drum and a ladder tape. The ladder tape has a first warp string, a second warp string, a third warp string, a fourth warp string, and at least two first weft strings repeatedly passing through the warp strings. The first weft strings respectively have a winding section wound around the first warp string to form a first opening between the first warp string and the second warp string, and wound around the third warp string only to form a second opening between the third warp string and the fourth warp string. 
         [0013]    In an embodiment, the first warp string and the second warp string are interlaced with each other at a region above and under the first opening, and the third warp string and the fourth warp string are interlaced with each other at a region above and under the second opening. 
         [0014]    In an embodiment, the first warp string and the second warp string respectively have a high knitting density section at a region around the first opening, and the third warp string and the fourth warp string respectively have a high knitting density section at a region around the second opening. 
         [0015]    In an embodiment, the ladder further includes at least two second weft strings repeatedly passing through the warp strings in a way opposite to the first weft strings, wherein the second weft strings have a plurality of first sections alternately wound around the first warp string and the second warp string, a plurality of second sections alternately wound around the third warp string and the fourth warp string, and a plurality of bridge sections between the first cord and the second cord; wherein opposite ends of the bridge section respectively connect to the corresponding first section and the corresponding second section; and wherein the second weft strings respectively have a winding section wound around the second warp string within the first opening and the fourth warp string within the second opening. 
         [0016]    The present invention overcomes the drawbacks of the conventional device. It has no hanging string to get entangled unexpectedly. When the ladder tape of the present invention is mounted on a window blind, it may engage the first and the second openings to the coupling portion of the rotary drum in an easy and fast way. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is a perspective view of the conventional window blind; 
           [0018]      FIG. 2  is a perspective view of the conventional ladder tape and the pin; 
           [0019]      FIG. 3  is a perspective view of the first preferred embodiment of the present invention; 
           [0020]      FIG. 4  is a sketch diagram of the ladder tape of the first preferred embodiment of the present invention; 
           [0021]      FIG. 5  is a sketch diagram of the ladder tape of a second preferred embodiment of the present invention; 
           [0022]      FIG. 6  is a sketch diagram of the ladder tape of a third preferred embodiment of the present invention; and 
           [0023]      FIG. 7  is a sketch diagram of the ladder tape of a fourth preferred embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    As shown in  FIG. 3 , a ladder tape  10  of the first preferred embodiment of the present invention is incorporated in a window blind. The window blind has a top rail  30 , in which a rotary drum  20  is provided to be turned. In the present invention, the rotary drum  20  is a barrel has a protrusion  22  to form a coupling portion, and the protrusion  22  has a neck  22   a.  The neck  22   a  is a thinner portion of the protrusion  22 . 
         [0025]    As shown in  FIG. 4 , the ladder tape  10  of the first preferred embodiment has a first warp string  11 , a second warp string  12 , a third warp string  13 , a fourth warp string  14 , and two first weft strings  15 ,  16 . The first weft strings  15 ,  16  repeatedly pass through the warp strings  11 - 14  to be wound around the warp strings  11 - 14  in a predetermined way to form the ladder tape  10 . The first weft string  15  repeatedly passes through the first and the second warp strings  11 ,  12  for a predetermined length, and then goes to the third and the fourth warp strings  13 ,  14  to repeatedly pass through them for a predetermined length, and then goes back to the first and the second warp strings  11 ,  12  for the same. The first weft string  16  is opposite to the first weft string  15 , it starts from the third and the fourth warp strings  13 ,  14 , goes to the first and the second warp strings  11 ,  12 , and then goes back to the third and the fourth warp strings  13 ,  14 . The first weft strings  15 ,  16  go between the first and the second warp strings  11 ,  12  and the third and the fourth warp strings  13 ,  14  for several times. The first and the second warp strings  11 ,  12  are wound by the first weft strings  15 ,  16  to form a first cord  10 A, and the third and the fourth warp strings  13 ,  14  are wound by the first weft strings  15 ,  16  to form a second cord  10 B. The first weft string  15  has a plurality of first sections  15   a  and second sections  15   b,  in which the first sections  15   a  are the parts of the first weft string  15  being wound around the first and the second warp strings  11 ,  12 , and the second sections  15   b  are the parts of the first weft string  15  being wound around the third and the fourth warp strings  13 ,  14 . The first weft string  16  has a plurality of first sections  16   a  and second sections  16   b,  in which the first sections  16   a  are the parts of the first weft string  16  being wound around the first and the second warp strings  11 ,  12 , and the second sections  16   b  are the parts of the first weft string  16  being wound around the third and the fourth warp strings  13 ,  14 . Therefore, on the first cord  10 A has alternate the first sections  15   a,    16   a,  and on the second cord  10 B has alternate the first sections  15   b,    16   b.  The first weft strings  15 ,  16  form several bridge sections  15   c,    16   c  between the first cord  10 A and the second cord  10 B to support slats  40 . 
         [0026]    The first weft string  15  further has a winding section  15   d  which is wound around the first warp string  11  only, and the first weft string  16  further has a winding section  16   d  which is wound around the third warp string  13  only. Consequently, the first cord  10 A has a first opening  10   a  between the first and the second warp strings  11 ,  12  beside the winding section  15   d,  and the second cord  10 B has a second opening  10   b  between the third and the fourth warp strings  13 ,  14  beside the winding section  16   d.  The first cord  10 A and the second cord  10 B are fastened to the rotary drum  20  by engaging the first and the second openings  10   a,    10   b  of the first cord  10 A and the second cord  10 B to the protrusion  22  of the rotary drum  20 . The first cord  10 A and the second cord  10 B will be rested in the neck  22   a  of the protrusion  22 . 
         [0027]    The present invention has the following advantages: 
         [0028]    1. No fastener (such as the pin of the prior art) is needed to connect the ladder tape to the window blind. It only needs to fit the first and the second openings  10   a,    10   b  of the ladder tape  10  to the protrusion  22  of the rotary drum  20 . 
         [0029]    2. The first weft strings  15 ,  16  have the winding sections  15   d,    16   d  wound around the corresponding warp strings within the first and the second openings  10   a,    10   b.  It will help the first and the second cords  10 A,  10 B to form the first and the second openings  10   a ,  10   b,  and furthermore, there is no hanging string besides the opening that the ladder tape  10  of the present invention will not get entangled unexpectedly. 
         [0030]    3. The first and the second openings  10   a,    10   b  are not formed by cutting the cords  10 A,  10 B. They are formed naturally after the warp strings  11 - 14  being wound by the first weft strings  15 ,  16 . Besides, the first and the second openings  10   a,    10   b  are between the warp strings that the ladder tape  10  is strong enough to hold the slats when the first and the second openings  10   a,    10   b  are fit to the protrusion  22  of the rotary drum  20 . 
         [0031]    The following embodiments provide different structures to enhance the strength of the first and the second openings  10   a,    10   b  of the ladder tape  10 . 
         [0032]      FIG. 5  shows a ladder tape of the second preferred embodiment of the present invention. The warp strings  11  to  14  have different knitting intensities in different parts. The warp strings  11  to  14  respectively have a high knitting density section around the first and the second openings  10   a,    10   b,  in other words, the knitting densities around the first and the second openings  10   a,    10   b  are higher than the rest pars of the warp strips  11  to  14 . Also, the first weft strings  15 ,  16  can have longer sections, thus denser knitting, wound around the high density sections, and therefore, the strengths around the first and the second openings  10   a,    10   b  increase. As a result, the portions around the openings  10   a,    10   b  are stronger. 
         [0033]      FIG. 6  shows a ladder tape of the third preferred embodiment of the present invention. The first warp string  11  and the second warp string  12  are interlaced with each other at a region above and under the first and the second openings  10   a,  and the third warp string  13  and the fourth warp string  14  are interlaced with each other at a region above and under the first and the second openings  10   b.  It enhances the strength of the first and the second openings  10   a,    10   b  as well. 
         [0034]    As shown in  FIG. 7 , a ladder tape of the fourth preferred embodiment of the present invention further includes a pair of second weft strings  17 ,  18 . The second weft strings  17 ,  18  repeatedly pass through the warp strings  11 - 14  to be wound around the warp strings  11  to  14  in a way opposite to the first weft strings  15 ,  16  respectively. Therefore, the sections of the warp strings  11  to  14  within the first and the second openings  10   a,    10   b  are respectively wound by the first and the second weft strings  15  to  18 . Precisely, the first and the second warp strings  11  and  12  within the first opening  10   a  are wound by the winding sections  15   a  and  17   a  of the first weft strings  15  and the second weft strings  17 , and the third and the fourth warp strings  13  and  14  within the second opening  10   b  are wound by the winding sections  16   a  and  18   a  of the first weft strings  16  and the second weft strings  18 . It enhances the total strength of the ladder tape. 
         [0035]    The description above is a few preferred embodiments of the present invention and the equivalence of the present invention is still in the scope of claim construction of the present invention.