Patent Publication Number: US-11047172-B2

Title: Cord-resistance adjusting device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority of Chinese Utility Model Patent Application No. 201921849211.7, filed on Oct. 30, 2019. 
     FIELD 
     The disclosure relates to cord-resistance adjusting device, more particularly to a cord-resistance adjusting device for installing on a venetian blind. 
     BACKGROUND 
       FIG. 1  shows a conventional blind driving device  8  adapted for installing on a venetian blind (not shown) with hidden cords. The venetian blind includes an upper beam, a lower beam opposite to the upper beam, a plurality of slats disposed between the upper and lower beams, and two lift cords interconnecting the slats. The conventional blind driving device  8  includes a casing  81 , a spring driving mechanism  82  disposed on the casing  81 , and two cord reels  83  rotatably mounted to the casing  81 . The casing  81  has two casing bodies  811  connected to each other. The spring driving mechanism  82  includes a spool set  821  and a scroll spring  822 . The spool set  821  has a drive spool  823  and a take-up spool  824  each rotatably mounted to the casing  81 . The drive spool  823  and the take-up spool  824  are meshingly connected to each other through their gear portions  823   a ,  824   a . The scroll spring  822  is connected between the drive spool  823  and the take-up spool  824 . One end of the scroll spring  822  is mounted to the drive spool  823  and the other end of the scroll spring  822  is sleeved around the take-up spool  824 . The scroll spring  822  is mainly wound around the take-up spool  824  when no forces are applied thereto. The lift cords are respectively wound around the cord reels  83 , and extend through the slats to connect with the lower beam. One of the cord reels  83  is meshingly connected with the drive spool  823 , the other one of the cord reels  83  is meshingly connected with the take-up spool  824 . 
     When a user wishes to expand the venetian blind, they may use both hands to pull the lower beam downward so as to pull the lift cords from the cord reels  83 . The cord reels  83  drive the take-up spool  824  and the drive spool  823  to rotate such that the scroll spring  822  winds around the drive spool  823 . When the user releases the lower beam, a restoring force of the scroll spring  822  balances the weight of the lower beam and the slats such that the lower beam may be kept at any desirable height. 
     When the user wishes to retract the venetian blind, they may use both hands to push the lower beam upward so that restoring force of the scroll spring  822  drives the drive spool  823  to rotate and causes the scroll spring  822  to re-wind around the take-up spool  824 . In turn, rotation of the drive spool  823  drives the cord reels  83  to rotate and re-wind the lift cords. 
     However, as the venetian blind needs to be fitted according to window size in practical use and therefore may have a range of size and weight, the conventional blind driving device  8  must also be provided with the scroll spring  822  having different restoring forces. This is inconvenient, and also makes the conventional blind driving device  8  difficult to standardize and mass produce. 
     SUMMARY 
     Therefore, the object of the disclosure is to provide a cord-resistance adjusting device that can alleviate the drawback of the prior art. 
     According to the disclosure, a cord-resistance adjusting device is adapted for installing on a venetian blind which includes two lift cords. The cord-resistance adjusting device includes a casing unit, a spring driving unit, two cord reels and at least one limiting block. 
     The casing unit is adapted for mounting to the venetian blind and includes an upper casing part, a lower casing part opposite to the upper casing part in a first direction, and two side casing parts spaced-apart in a second direction which is transverse to the first direction and cooperating with the upper and lower casing parts to define a receiving space. 
     Each of the side casing parts includes a side casing part body, a first cord-exit hole extending through the side casing part body in the second direction and in spatial communication with the receiving space, and a limiting column set mounted to the side casing body inside the first cord-exit hole. 
     The spring driving unit is disposed in the receiving space. 
     The cord reels are rotatably disposed in the receiving space, and respectively and meshingly connected with two opposite sides of the spring driving unit. 
     The at least one limiting block is disposed in at least one of the side casing parts. 
     Each of the limiting column sets of the side casing parts includes an inner limiting column proximal to a respective one of the cord reels, and an outer limiting column distal to the respective one of the cord reels. The inner and outer limiting columns are adapted for a respective one of the lift cords to bend therearound in a frictionally contacting manner. 
     For the at least one of the side casing parts, the at least one limiting block is movably disposed in the first cord-exit hole between the inner and outer limiting columns such that the first cord-exit hole is provided with a cord-exit path consecutively passing through the inner limiting column, the at least one limiting block and the outer limiting column, whereby the respective lift cord frictionally contacts the at least one limiting block when moving from the inner limiting column to the outer limiting column along the cord-exit path. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the disclosure will become apparent in the following detailed description of the embodiment with reference to the accompanying drawings, of which: 
         FIG. 1  is an exploded perspective view of a conventional blind driving device; 
         FIG. 2  is a side view of an embodiment of a cord-resistance adjusting device according to the disclosure adapted for installing on a venetian blind; 
         FIG. 3  is a perspective view of the embodiment; 
         FIG. 4  is a partly exploded perspective view of the embodiment; 
         FIG. 5  is a fragmentary top view of the embodiment illustrating a limiting block of the embodiment at a position of maximum resisting force; 
         FIG. 6  is a fragmentary top view of the embodiment illustrating a limiting block of the embodiment at a position of minimum resisting force; 
         FIG. 7  is a fragmentary perspective view of the embodiment, illustrating the limiting block at the position of maximum resisting force; 
         FIG. 8  is a fragmentary perspective view of the embodiment, illustrating the limiting block and a fixing frame of the embodiment being removed for adjusting the position of the limiting block; 
         FIG. 9  is similar to  FIG. 8  but illustrating the limiting block moved to a different position; and 
         FIG. 10  is similar to  FIG. 7  but illustrating the limiting block at the position of minimum resisting force. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 2 to 4 , an embodiment of a cord-resistance adjusting device is adapted for installing on a venetian blind  9 . The venetian blind  9  includes an upper beam  91 , an lower beam  92  opposite to the upper beam  91 , a plurality of slats  93  disposed between the upper and lower beams  91 ,  92 , and two lift cords  94  interconnecting the slats  93 . The cord-resistance adjusting device includes a casing unit  2 , a spring driving unit  3 , two cord reels  4 , two fixing frames  5  and two limiting blocks  6 . 
     The casing unit  2  is adapted for mounting to the venetian blind  9  and includes an upper casing part  21 , a lower casing part  22  opposite to the upper casing part  22  in a first direction (I), and two side casing parts  24  spaced-apart in a second direction (II) which is transverse to the first direction (I) and cooperating with the upper and lower casing parts  21 ,  22  to define a receiving space  23 . 
     The upper casing part  21  has two upper limiting slots  211  opposite to each other in the second direction (II) and disposed corresponding to the side casing parts  24 , and two pairs of upper engaging grooves  212 . Each of the pairs of upper engaging grooves  212  are respectively disposed on two opposite sides of a respective one of the upper limiting slots  211  along a third direction (III) which is transverse to both the first and second directions (I, II). 
     Each of the side casing parts  24  includes a side casing part body  241 , a first cord-exit hole  242  that extends through the side casing part body  241  in the second direction (II) and that is in spatial communication with the receiving space  23  to be adapted for a respective lift cord  94  to extend therethrough, a side limiting slot  243  extending in the first direction (I) through the side casing part body  241  in spatial communication with the first cord-exit hole  242 , a limiting column set  244  that is mounted to the side casing body  241  inside the first cord-exit hole  242 , and a casing teeth portion  245  (see  FIG. 5 ) that protrudes into the side limiting slot  243  from a side thereof which is distal from the respective cord reel  4 . The limiting column set  244  of each side casing part  24  includes an inner limiting column  246  proximal to the respective cord reel  4 , and an outer limiting column  247  distal to the respective cord reel  4  (best shown in  FIGS. 5, 6 ). The inner and outer limiting columns  246 ,  247  are adapted for the respective lift cord  94  to bend therearound in a frictionally contacting manner. Each side limiting slot  243  is disposed between the inner and outer limiting columns  246 ,  247 . The upper limiting slots  211  of the upper casing  21  respectively correspond in position with the side limiting slots  243 . 
     The spring driving unit  3  is disposed in the receiving space  23  and includes a spool set  31  and a scroll spring  32 . The spool set  31  has a drive spool  311  and a take-up spool  312  meshingly connected to each other and each rotatably mounted to the lower casing  22 . One end of the scroll spring  32  is mounted to the drive spool  311  and the other end is sleeved around the take-up spool  312 . When no forces are applied to the scroll spring  32 , the scroll spring  32  is in a relaxed state and is mainly wound around the take-up spool  312 . 
     The cord reels  4  are rotatably disposed in the receiving space  23  on two opposite sides of the spring driving unit  3 , and are meshingly connected with the spring driving unit  3 . The cord reels  4  are adapted for the lift cords  94  to wind therearound and connect thereto, respectively. 
     The fixing frames  5  are mounted to the upper casing part  21  and may be removed by taking it outward in the first direction (I). Specifically, each fixing frame  5  partially and engagingly extends into the respective upper limiting slot  211  and the respective side limiting slot  243  of a respective side casing part  24 . Each fixing frame  5  includes a sliding slot  51  that extends in the third direction (III), and two engaging portions  52  that are disposed on opposite sides of the sliding slot  51  and that respectively engage two of the upper engaging grooves  212  proximal to the respective upper limiting slots  211 . 
     The limiting blocks  6  are respectively coupled with the fixing frames  5 . Specifically, the limiting blocks  6  are partially and slidably inserted into the sliding slots  51  of the fixing frames  5 , respectively (see  FIGS. 7, 8 ). Each limiting block  6  has an engaging element  65  slidably engaging the respective sliding slot  51 . The limiting blocks  6  are also respectively and removably inserted into the side limiting slots  243  of the side casing parts  24  in the first direction (I). Each limiting block  6  has a block body  61 , a second cord-exit hole  62  that extends in the second direction (II) through the block body  61  and in communication with the first cord-exit hole  242  for the respective lift cord  94  to exit therethrough, a limiting block column  63  disposed in the second cord-exit hole  62  along the first direction (I) for the respective lift cord  94  to bend therearound in a frictionally contacting manner, and a block teeth portion  64  formed on a side of the block body  61  which is distal to a corresponding one of the cord reels  4 . The block teeth portions  64  of the limiting blocks  6  mesh with the casing teeth portions  245  of the side casing parts  24 , respectively. Each of the casing teeth portions  245  have more teeth than one of the block teeth portions  64  such that each block teeth portion  64  can mesh with the respective casing teeth portion  245  at different selected sections of the respective casing teeth portion  245  for adjustment of the position of each block teeth portion  64  relative to the respective casing teeth portion  245 . 
     For each of the side casing parts  24 , a respective one of the limiting blocks  6  is movably disposed in the first cord-exit hole  242  between the inner and outer limiting columns  246 ,  247  such that the first cord-exit hole  242  is provided with a cord-exit path (see P in  FIG. 5 ) consecutively passing through the inner limiting column  246 , the limiting block  6  and the outer limiting column  247 , whereby the respective lift cord  94  frictionally contacts the limiting block  6  when moving from the inner limiting column  246  to the outer limiting column  247  along the cord-exit path. 
     To install the cord-resistance adjusting device onto the venetian blind  9 , first each of the lift cords  94  is wound around the respective cord reel  4 , bended sequentially around the respective inner limiting column  246 , limiting block column  63 , and outer limiting column  247 , and is caused to exit through the respective first cord-exit hole  242 . 
     When a user wishes to expand the venetian blind  9 , they may use both hands to pull the lower beam  92  downward so as to pull the lift cords  94  respectively from the cord reels  4 . The cord reels  4  respectively drive the take-up spool  312  and the drive spool  311  to rotate such that the scroll spring  32  is unwound from the take-up spool  312  and wound around the drive spool  311 . 
     When the user releases the lower beam  92  at a desired height, the weight of the lower beam  92  and the slats  93  is balanced by the restoring force of the scroll spring  32  so that the lower beam  92  is kept at the desired height. This mechanism is conventional in the arts, details of which is omitted for the sake of brevity. 
     When the user wishes to retract the venetian blind  9 , they may use both hands to push the lower beam  92  upward, so that the restoring force of the scroll spring  32  drives the drive spool  311  to rotate and causes the scroll spring  32  to re-wind around the take-up spool  312 . Rotation of the drive spool  311  in turn drives each of the cord reels  4  to rotate and re-wind the respective lift cord  94 . 
     Referring to  FIGS. 5, 6, and 7 , each fixing frame  5  and the respective limiting block  6  may be pulled upward so as to be removed from the casing unit  2 . Once removed, the limiting block  6  is changeable in position relative to the inner and outer limiting columns  246 ,  247  for adjustment of a frictional resisting force against a movement of the respective lift cord  94 . 
     At a position of largest resisting force, as shown in  FIG. 5 , the limiting block  6  is disposed relative to the side casing body  24  in such a way that the limiting block column  63  is at a maximum distance away from the inner and outer limiting columns  246 ,  247 . When the limiting block  6  is at the position of largest resisting force, the lift cord  94  moving along the cord-exit path (P) bends the largest amount around the limiting block column  63 . At this position, the cord-exit path (P) is the most tortuous, and the lift cord  94  experiences a maximum frictional resisting force due to its large contact surface area with the limiting block column  63  and/or the inner and outer limiting columns  246 ,  247 . 
     At a position of smallest resisting force, as shown in  FIG. 6 , the limiting block  6  is disposed relative to the side casing body  24  in such a way that the limiting block column  63  is at a minimum distance away from the inner and outer limiting columns  246 ,  247 . When the limiting block  6  is at the position of smallest resisting force, the lift cord  94  moving along the cord-exit path (P) ( FIG. 5 ) of the first cord-exit hole  242  bends the smallest amount around the limiting block column  63  and experiences a minimum frictional resisting force. 
     By adjusting the limiting block  6  between the position of maximum resisting force and the position of minimum resisting force, the frictional resisting force against a movement of the respective lift cord  94  may be adjusted. The adjustable cord resisting force is incorporated with the restoring force of the scroll spring  32  and the combined weight of the lower beam  92  and the slats  93  of the venetian blind  9  for balancing and keeping the lower beam  92  at any desirable height without needing to apply external force. This adjustment facilitating standardization of the restoring force of the scroll spring  32  and/or other relating components for use with the venetian blind  9  of different dimensions. 
     As shown in  FIGS. 5 and 6 , the block teeth portion  64  of the limiting block  6  is adjusted in position by being displaced from one section of the side casing teeth portion  245  to another section of the side casing teeth portion  245 . Referring to  FIGS. 8, 9 and 10 , to adjust the position of the limiting block  6 , the engaging portions  52  of the respective fixing frame  5  are first respectively disengaged from the two engaging grooves  212  to allow the limiting block  6  to be removed from the respective upper and side limiting slots  211 ,  243  along with the respective fixing frame  5 . Then, the limiting block  6  may be slid along the sliding slot  51  of the fixing frame  5  to a desired position and then reinserted into the upper and side limiting slots  211 ,  243  to let the block teeth portion  64  remesh with the casing teeth portion  245 . 
     In sum, by adjusting the position of the limiting blocks  6 , the configurations of the cord-exit paths in the first cord-exit holes  242  may be respectively adjusted which changes the frictional resisting forces experienced by the lift cords  94 . This allows the frictional resisting forces experienced by the lift cords  94  to be adjusted, which is advantageous for facilitating standardization of the restoring force of the scroll spring  32  and/or other relating components. 
     In this embodiment, the number of the limiting blocks  6  is two, but in other embodiments, the cord-resistance adjusting device may only include one limiting block  6  in association with one fixing frame  5  and still achieve the same advantage as this embodiment. 
     In the description above, for the purposes of explanation, numerous specific details have been set forth in order to provide a thorough understanding of the embodiment. It will be apparent, however, to one skilled in the art, that one or more other embodiments may be practiced without some of these specific details. It should also be appreciated that reference throughout this specification to “one embodiment,” “an embodiment,” an embodiment with an indication of an ordinal number and so forth means that a particular feature, structure, or characteristic may be included in the practice of the disclosure. It should be further appreciated that in the description, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of various inventive aspects, and that one or more features or specific details from one embodiment may be practiced together with one or more features or specific details from another embodiment, where appropriate, in the practice of the disclosure. 
     While the disclosure has been described in connection with what is considered the exemplary embodiment, it is understood that this disclosure is not limited to the disclosed embodiment but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.