Patent Publication Number: US-2016237740-A1

Title: Ladder tape and method of making the same

Description:
The current application claims a foreign priority to application number 201510084098.8 filed on Feb. 16, 2015 in China. 
     BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention generally relates to knitted fabrics, and more particularly to a ladder tape and a method of making the ladder tape. 
     2. Description of Related Art 
     Ribbon style ladder tapes are widely used in window blinds to support slats. However, ladder tapes made by different knitting techniques usually have different disadvantages which need to be overcome. For example, while making a commonly seen ribbon style ladder tape, it needs to manually cut redundant connecting threads after completing the knitting, which leads to a time-consuming manufacturing process and a low yield. Also, as illustrated in  FIG. 1 , the front appearance of such ladder tape  1  has several discontinuous, annoying shades when exposed to light, for the portions corresponding to the threads of wefts which support slats have higher stitch density than other portions on the ribbon. 
     A China patent, of which patent number 201121234, has disclosed an improved structure for ribbon style ladder tapes, where two ends of a weaving thread are integrally connected to the front crochet ribbon and the rear crochet ribbon through a crocheting process. In this way, it is not necessary to cut any weaving threads between the front crochet ribbon and the rear crochet ribbon; therefore, the inherent problem of needing additional manpower to manually cut redundant connecting threads while making a conventional ladder tape is solved. Furthermore, the technique disclosed in said patent also avoids the unwanted opaque shades formed at where threads of wefts are connected to the ribbons. 
     However, though the problems above are solved, said patent seems to create another disadvantage. Knitting pattern  3  shown in  FIG. 2  is so loose that a lot of holes  3   a  are left therebetween. As a result, while using such a ladder tape with a window blind, light may leak in through those holes  3   a . Therefore, the conventional method of making a ladder tape and the conventional structure of a ladder tape both still have room for improvement. 
     BRIEF SUMMARY OF THE INVENTION 
     In view of the reasons mentioned above, the primary objective of the present invention is to provide a ladder tape and a method of making the ladder tape, which have no redundant connecting threads needed to be manually cut. Therefore, the time required to make a ladder tape can be shortened, and the yield can be increased as well. Also, the ladder tape provided in the present invention does not have the problem of light leakage, and the resultant knitting structure of the provided method is well-proportioned. 
     The present invention provides a ladder tape, which includes a first band, a second band, a first warp, a second warp, and at least one weft. The first band and the second band respectively have a front surface and a rear surface. The first warp and the second warp respectively interlaces the front surface and the rear surface along a long axis of the corresponding band, wherein each of the warps forms a plurality of threading segments on the rear surface; a slit is left between each of the threading segments and the rear surface. The weft shuttles between the first warp and a second warp, wherein the weft comprises a plurality of first portions following a S-shaped path to pass through the slits left between the threading segment of the first warp and the rear surface of the first band, a plurality of second portions following a S-shaped path to pass through the slits left between the threading segment of the second warp and the rear surface of the second band, and a plurality of bridging portions, each of which is connected to the corresponding first portion and the corresponding second portion with two ends thereof respectively. 
     In an embodiment, each of the warps forms a plurality of loop-shaped visible segments on the front surface of the corresponding band; the visible segments interlock one another. 
     The present invention further provides a method of making a ladder tape, which includes the following steps: a) provide a first band and a second band in parallel, wherein each of the bands has a front surface and a rear surface; the first band and the second band are adapted to be pulled downward in a vertical direction; b) control a hook portion of a first crochet needle to move forward and backwards to pass through the first band, and control a hook portion of a second crochet needle to move forward and backwards to pass through the second band; c) place a first warp on the hook portion of the first crochet needle to pull the first warp from the rear surface of the first band to the front surface thereof, wherein the first warp forms a first chain on the front surface of the first band, and forms a plurality of threading segments on the rear surface of the first band; and place a second warp on the hook portion of the second crochet needle to pull the second warp from the rear surface of the second band to the front surface thereof, wherein the second warp forms a second chain on the front surface of the second band, and forms a plurality of threading segments on the rear surface of the second band; and d) move a weft vertically along a S-shaped path to pass through a series of the threading segments of the first warp, pull the weft across a space between the first band and the second band, moving the weft vertically along a S-shaped path to pass through a series of the threading segments of the second warp, and pull the weft back to the first warp to continuously pass through another series of the threading segments of the first warp after going through a predetermined distance on the second band; wherein the weft is repeatedly pulled and moved in such manner between the first warp and the second warp until a knitting is completed. 
     In an embodiment, the first crochet needle and the second crochet needle are synchronously moved forward or backwards. 
     In an embodiment, after the first crochet needle and the second crochet needle are moved forward to pass through the corresponding band and before arriving at a first predetermined point, the weft goes beneath the first crochet needle and the second crochet needle; when the first crochet needle and the second crochet needle are continuously moved forward to arrive at a second predetermined point, and then are moved backwards, the first warp is placed on the hook portion of the first crochet needle, and the second warp is placed on the hook portion of the second crochet needle; after that, the first crochet needle and the second crochet needle respectively pull the corresponding warps backwards to leave the corresponding bands. 
     In an embodiment, the first warp passes through a first warp knitting needle, while the second warp passes through a second warp knitting needle; the first warp knitting needle and the second warp knitting needle are rotationally moved along a surrounding path on a virtual vertical plane to place the first warp on the hook portion of the first crochet needle, and to place the second warp on the hook portion of the second crochet needle. 
     In an embodiment, a guiding tube which is movable back and forth in a lateral direction is provided to feed the weft; when the first crochet needle and the second crochet needle are moved from the first predetermined point to the second predetermined point, the guiding tube is moved upward to a position higher than the first crochet needle and the second crochet needle; when the first crochet needle and the second crochet needle respectively pull the corresponding warps backwards to leave the corresponding bands, the guiding tube is laterally moved in one of two opposite directions to continuously feed the weft. 
     With the invention above, the manufacturing process can be simplified, and labor cost can be reduced. Also, the resultant ladder tape is beautiful and has no those opaque shades; the problem of light leakage can be avoided at the same time. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The present invention will be best understood by referring to the following detailed description of some illustrative embodiments in conjunction with the accompanying drawings, in which 
         FIG. 1  is a plan view of a conventional ribbon style ladder tape; 
         FIG. 2  is a perspective view of another conventional ribbon style ladder tape; 
         FIG. 3  is a perspective view of a window blind, showing the window blind includes the ladder tape of a preferred embodiment of the present invention; 
         FIG. 4  is an enlarged partial view of  FIG. 3 ; 
         FIG. 5  is a partial front view of the first band of the ladder tape of the preferred embodiment of the present invention; 
         FIG. 6  is a partial rear view of the first band of the ladder tape of the preferred embodiment of the present invention; 
         FIG. 7  is a segmental view along the  7 - 7  line in  FIG. 6 ; 
         FIG. 8  is similar to  FIG. 4 , showing the knitting path of a weft; 
         FIG. 9  is similar to  FIG. 8 , showing the knitting path of another weft; 
         FIG. 10  is a perspective view of the knitting apparatus adapted to implement the method of making the ladder tape of the present invention; 
         FIG. 11  is a simplified schematic view, showing the moving path of the warp knitting needle and the guiding tube of the knitting apparatus shown in  FIG. 10 ; 
         FIG. 12  is a plan view of  FIG. 11 ; 
         FIG. 13  is a perspective view, showing the positions of the warps and the weft while being knitted; 
         FIG. 14  is a front view, showing the first crochet needle of the knitting apparatus is moved forward; 
         FIG. 15  is a perspective view, showing first warp runs over the first crochet needle; 
         FIG. 16  is similar to  FIG. 15 , showing the first warp knitting needle is controlled to swing downward, and the first crochet needle is moved backwards; 
         FIG. 17  is similar to  FIG. 14 , showing first crochet needle is moved backwards with its hook portion hooks the first warp; and 
         FIG. 18  is similar to  FIG. 15 , showing first crochet needle is moved backwards to leave the first band. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     We are going to describe the structure of the ladder tape provided in the present invention first, and explain the method of making it afterwards. 
     A ladder tape  100  of a preferred embodiment of the present invention is illustrated in  FIG. 3  to  FIG. 7 , which is adapted to be used with a window blind, and includes a first band  10 , a second band  12 , a first warp  14 , a second warp  16 , and two wefts  18 ,  19 . It has to mention that, the number of the components above including the first warp  14 , the second warp  16 , and the wefts  18 ,  19  can be further increased to meet different practical requirements. 
     The first band  10  and the second band  12  are elongated woven bands, which are tightly woven and, therefore, opaque. The width and texture of the first band  10  and the second band  12  are not limited in the present invention, which can be decided by the manufacturers to meet different requirements. The first band  10  has a front surface  10   a  and a rear surface  10   b . Similarly, the second band  12  also has a front surface  12   a  and a rear surface  12   b . The front surfaces mentioned herein refer to the surfaces which can be directly seen when the ladder tape  100  is in use; the rear surfaces mentioned herein refer to the surfaces of the first band  10  and the second band  12  which face each other. 
     The first warp  14  and the second warp  16  are made by the same knitting method, and are respectively stitched onto the first band  10  and the second band  12 . In the following paragraphs, we&#39;ll use the first warp  14  and the first band  10  to explain the concept of the present invention. The first warp  14   a  follows a regular stitching path to interlace the front surface  10   a  and the rear surface  10   b  along a long axis of the first band  10 . As shown in  FIG. 5 , visible segments  14   a  of the first warp  14  on the front surface  10   a  are loop-shaped, wherein the visible segments  14   a  interlock one another, which are called a first chain hereafter. As shown in  FIG. 6  and  FIG. 7 , the first warp  14  forms a plurality of threading segments  14   b  on the rear surface  10   b , wherein each of the threading segments  14   b  aligns with the same oblique direction, and a slit S is left between each of the threading segment  14   b  and the rear surface  10   b . Similarly, the second warp  16  also has visible segments on the front surface  12   a  of the second band  12 , and has threading segments and slits on the rear surface  12   b  of the second band  12 . However, the visible segments, the threading segments, and slits of the second warp  16  are not shown in the figures. By following the same naming rule, the visible segments of the second warp  16  are called a second chain hereafter. 
     While stitching the first warp  14  and the second warp  16 , the wefts  18 ,  19  shuttle between the first warp  14  and the second warp  16  through a knitting technique. As shown in  FIGS. 4, 6, and 8 , the weft  18  follows an S-shaped path along the long axis of the first band  10  to passes through a series of slits S of the threading segments  14   b  of the first warp  14  on the rear surface  10   b . After being moved for a predetermined distance on the first band  10 , the weft  18  is pulled across the space between the first band  10  and the second band  12 , and then the weft  18  continues passes through a series of slits S of the threading segments of the second warp  16  on of the rear surface  12   b . Similarly, after being moved for another predetermined distance on the second band  12 , the weft  18  is pulled back to the first warp  14 , and so on. The process continues until the knitting is completed. As for the weft  19  (shown in  FIG. 9 ), similarly, it follows a S-shaped path to shuttle through the second warp  16  along a long axis of the second band  12  first, gets across the space between the second band  12  and the first band  10  to shuttle through the first warp  14 , gets back to the second warp  16  again, and so on and on. 
     In the description above, the segments of the wefts  18 ,  19  winding around the first warp  14  are respectively defined as first portions  18   a  ( 19   a ), and the segments winding around the second warp  16  are respectively defined as second portions  18   b  ( 19   b ). The cross-over segments of the wefts  18 ,  19  between the first warp  14  and the second warp  16  are defined as bridging portions  18   c  ( 19   c ). In other words, two ends of each of the bridging portion  18   c  ( 19   c ) are respectively connected to a corresponding first portion  18   a  ( 19   a ) and a corresponding second portion  18   b  ( 19   b ). Each of the bridging portions  18   c  ( 19   c ) is used to support one single slat L of a window blind. 
     It has to be mentioned that, since the wefts  18 ,  19  of the ladder tape  100  pass through the slits S left between the threading segments  14   b  of the first warp  14  and the rear surface  10   b  (or between the threading segments of the second warp  16  and the rear surface  12   b ), the wefts  18 ,  19  are bound by these threading segments to be firmly fixed onto the rear surface  10   b  (or the rear surface  12   b ) of each of the bands  10 ,  12 . In other words, the wefts  18 ,  19  in the preferred embodiment are hidden behind each of the bands  10 ,  12  and cannot be seen directly. 
     The first band  10  and the second band  12  of the ladder tape  100  in the preferred embodiment are tightly woven and opaque; the first warp  14  and the second warp  16  are stitched onto the corresponding bands  10 ,  12  by a knitting technique. In addition that the threading segments the first warp  14  and the second warp  16  can tightly bind the wefts  18 ,  19 , when exposed to light, the front surfaces  10   a ,  12   a  won&#39;t have any discontinuous opaque shade, for the bands  10 ,  12  have consistent stitch density everywhere thereon, even for the portions where the weft  18  ( 19 ) passes through the threading segments. More specifically, instead of the discontinuous opaque shades seen on a conventional ladder tape as shown in  FIG. 1 , the front surfaces  10   a ,  12   a  of the bands  10 ,  12  of the preferred embodiment only have the first chain and the second chain shown thereon. Also, since the first warp  14 , the second warp  16 , and the wefts  18 ,  19  are stitched onto the first band  10  and the second band  12  by a knitting technique, the first band  10  and the second band  12  would not be deformed or have small holes formed thereon due to the effect of gravity when the bridging portions  18   c ,  19   c  are used to supporting the slats L. As a result, the effect of blocking light for the slats L would be better. 
     The method of making the ladder tape  100  is explained in the following paragraphs. As shown in  FIG. 10 , a knitting apparatus suitable to use the method includes a needle holder  200 , a first crochet needle  201 , a second crochet needle  202 , a needle seat  203 , a first warp knitting needle  204 , a second warp knitting needle  205 , and a guiding tube  206 . The selected knitting materials include the first band  10 , the second band  12 , the first warp  14 , the second warp  16 , and the wefts  18 ,  19 . We are going to introduce the function and action of the components of the knitting apparatus first, and then explain the method of making the ladder tape afterwards. 
     The needle holder  200  is located on the front surface of each of the bands, and is fixed to its location, wherein a plurality of needle channels  200   a  are provided thereon to let the crochet needle movably received therein. In the preferred embodiment, the first warp  14  and the second warp  16  are knitted synchronously when the first crochet needle  201  and the second crochet needle  202  are placed in the needle channels  200   a  of the needle holder  200 . The first crochet needle  201  and the second crochet needle  202  are controllable to synchronously move forward or backwards in the direction of a Z axis, wherein, when the first crochet needle  201  and the second crochet needle  202  are moved forward, hook portions  201   a ,  202   a  at a front thereof pass through the bands to the rear surfaces; when the first crochet needle  201  and the second crochet needle  202  are moved backwards, the hook portions  201   a ,  202   a  at the front thereof leave the bands and are at the front surfaces. 
     The first warp knitting needle  204  and the second warp knitting needle  205   a  are both provided on the needle seat  203 , and are both located on the rear surface of each of the bands. The first warp  14  passes through a front end of the first warp knitting needle  204 , while the second warp  16  passes through a front end of the second warp knitting needle  205 . Because the needle seat  203  can be moved back and forth in the direction of an X axis and swing, the front ends of the first warp knitting needle  204  and the second warp knitting needle  205  can be rotationally moved in a clockwise manner along a surrounding path from a position PA 1 , a position PA 2 , a position PA 3 , to a position PA 4  which are on a virtual vertical plane as illustrated in  FIG. 11  and  FIG. 12 , and each of the crochet needles  201 ,  202  passes through one of the pieces of space surrounded by the positions PA 1 -PA 4 . 
     One of the wefts  18 ,  19  passes through the guiding tube  206 , which can be moved back and forth in the direction of the X axis (i.e., laterally) to feed the weft. In the preferred embodiment, the guiding tube  206  is controllable to rotationally move in a counter-clockwise manner from a position PB 1 , a position PB 2 , a position PB 3 , to a position PB 4  which are on a virtual vertical plane, wherein the first crochet needle  201  and the second crochet needle  202  can pass through the space surrounded by the positions PB 1 -PB 4 . More specifically, the virtual vertical plane having the positions PA 1 -PA 4  and the virtual vertical plane having the positions PB 1 -PB 4  are arranged one after the other in the direction of the Z axis. 
     Before we start explaining the method of making the ladder tape with the aforementioned knitting apparatus, it has to be mentioned that, since the first warp  14 , the second warp  16 , and the wefts  18 ,  19  are knitted synchronously, and the first warp  14  and the second warp  16  are knitted in the same way, we&#39;ll take the first warp  14  and one of the wefts  18  as an example for explanation. 
     As shown in  FIG. 13  to  FIG. 15 , the first band  10  is placed between the needle holder  200  and the needle seat  203 , and can be pulled and rolled in the direction of a Y axis (i.e., vertically). The first crochet needle  201  is controllable to move forward along the Z axis. After the hook portion  201   a  thereof passing through the band and before arriving a first predetermined point P 1  (see  FIG. 14 ), the guiding tube  206  has been moved from the position PB 1  to the position PB 2 ; when the first crochet needle  201  arrives at the first predetermined point P 1 , the weft  18  fed by the guiding tube  206  is just under the first crochet needle  201 . By moving the guiding tube  206  from the position PB 1  to the position PB 2 , the weft  18  is pulled from the first warp  14  to the second warp  16 . 
     After that, when the first crochet needle  201  is continuously moved toward a second predetermined point P 2 , the guiding tube  206  is moved upward to the position PB 3 , which is higher than the first crochet needle  201 . At this time, the location of the weft  18  remains unchanged due to being pressed by the first crochet needle  201 . On the other hand, the first warp knitting needle  204  is moved from the position PA 1  to the position PA 2  when the first crochet needle  201  arrives at the second predetermined point P 2 . This action makes the first warp  14  cross over the first crochet needle  201 , as shown in  FIG. 15 . At certain determined moment, the guiding tube  206  located at the position PB 3  is moved toward the position PB 4 , whereby the weft  18  is pulled from the second warp  16  back to the first warp  14 . Furthermore, the segments of the weft  18  which shuttle between the first warp  14  and the second warp  16  become the bridging portions  18   c  which are adapted to support slats as illustrated in  FIG. 4 . 
     As shown in  FIG. 16  and  FIG. 17 , when the first crochet needle  201  is controlled to move backwards, the first warp knitting needle  204  is controlled to swing downward. In other words, the front end thereof is moved from the position PA 2  toward the position PA 3 , whereby the first warp  14  can be hooked by the hook portion  201   a . When the first crochet needle  201  is continuously moved backwards to leave the first band  10 , the first warp  14  is pulled from the rear surface  10   b  of the first band  10  to the front surface  10   a  thereof (see  FIG. 18 ). By repeating the aforementioned knitting actions, and by pulling and rolling the band, the first warp  14  finally forms the first chain (see  FIG. 5 ) which is composed of the multiple loop-shaped visible segments  14   a  on the front surface  10   a  of the first band  10 , and forms the plurality of threading segments  14   b  (see  FIG. 6 ) on the rear surface  10   b  of the first band  10 . At the same time, the weft  18  is pressed by the threading segments  14   b  of the first warp  14  and bound on the rear surface  10   b  (see  FIG. 7 ). Similarly, the second warp  16  forms the same knitting structure on the front surface and the rear surface of the second band  12  by the same knitting actions, and we are not going to repeat the same description in details herein. 
     And then, after the first crochet needle  201  is moved back into the needle holder  200  (i.e., casting off the needle), the guiding tube  206  will be moved from the position PB 4  back to the position PB 1  to wait for another feeding of the weft. At the same time, the first warp knitting needle  204  will be also moved toward the position PA 4 , so that when the crochet needle is moved forward again, the first warp knitting needle  204  can be properly moved from the position PA 1  toward the position PA 2 . 
     In summary, the ladder tape  100  provided in the present invention has no discontinuous opaque shades, and the problem of light leakage can be avoided as well. Also, the method provided in the present invention can make well-proportioned and beautiful products. 
     It must be pointed out that the embodiments described above are only some preferred embodiments of the present invention. All equivalent structures and methods which employ the concepts disclosed in this specification and the appended claims should fall within the scope of the present invention.