Patent Publication Number: US-2022235608-A1

Title: Blind lifting device and a blind lifting control module thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority of Taiwanese Patent Application No. 110103296, filed on Jan. 28, 2021. 
     FIELD 
     The disclosure relates to a blind, and more particularly to a blind lifting device for controlling lifting of a blind, and a blind lifting control module thereof. 
     BACKGROUND 
     A variety of blinds including roller blinds, Roman blinds, honeycomb shades, Venetian blinds, pleated blinds, etc. are commercially available for use on a window. A conventional roller blind generally uses a loop cord-driven controller for controlling lifting of a blind body. The pull cords of some controllers are suspended outside, which may easily be entangled with objects nearby and cause inconvenience in use. In addition, young children may reach and be entangled by the pull cords, hence causing danger. 
     SUMMARY 
     Therefore, an object of the disclosure is to provide a blind lifting device and a blind lifting control module thereof that can alleviate at least one of the drawbacks of the prior art. 
     According to the disclosure, the blind lifting control module is connectable with an end of a horizontal axle for controlling rotation of the axle, and includes a supporting unit, a transmitting wheel, an anti-backward unit and a driving unit. The supporting unit includes a base seat and a mounting shaft which is securely connected with the base seat and which extends parallel to the horizontal axle from the base seat. The mounting shaft has a shaft portion. The transmitting wheel is rotatably sleeved on the mounting shaft, and includes an axle connecting body which is securely connectable with the end of the horizontal axle, and a flange disc which is connected with a side of the axle connecting body proximate to the base seat and which extends radially and outwardly from the axle connecting body. The axle connecting body has a receiving groove which extends from the side for receiving the shaft portion, and a first ratchet portion which is formed in the receiving groove and faces the base seat. The flange disc has a second ratchet portion which is formed on a surface that faces the base seat and surrounds the receiving groove. The anti-backward unit includes an anti-backward wheel and a biasing returning member which are received in the receiving groove. The anti-backward wheel has a movable wheel body which is movably sleeved on the shaft portion, and a third ratchet portion which is formed on a surface of the movable wheel body and faces the first ratchet portion. The anti-backward wheel is movable relative to the shaft portion between an anti-backward position, where the third ratchet portion meshes with the first ratchet portion to permit a uni-directional rotation of the transmitting wheel, and a released position, where the third ratchet portion is disengaged from the first ratchet portion. The biasing returning member is disposed to bias the anti-backward wheel to the anti-backward position. The driving unit includes a driving reel which is rotatably sleeved on the shaft portion, a transmitting member which is connected between the driving reel and the anti-backward wheel to transmit a rotation of the driving reel to move the anti-backward wheel to the released position, a thrust member which is movably disposed to the base seat, a hindering member which is pivotably disposed to the base seat, a pull cord which has an end secured to the driving reel and which winds on a periphery of the driving reel to have a free end for pulling operation, and a reel biasing member. The driving reel has a fourth ratchet portion which faces the second ratchet portion, and is movable relative to the shaft portion between a driving position, where the fourth ratchet portion meshes with the second ratchet portion, and a normal position, where the fourth ratchet portion is disengaged from the second ratchet portion. The thrust member is movable relative to the base seat between an initial position, where the thrust member is free from action with the driving reel, and a thrusting position, where the thrust member provides a thrust force to move the driving reel to the driving position. The hindering member is turnable relative to the base seat between a hindering position, where the hindering member is kept to position the thrust member in the initial position, and a keeping-off position, where the thrust member is allowed for movement to the thrusting position. The free end of the pull cord passes through the hindering member to receive a pulling force to turn the hindering member. The reel biasing member is disposed to bias the driving reel to rotate to reel the pull cord. 
     According to the disclosure, the blind lifting device includes a rail, a blind lifting control module described previously, a rotating support module and a horizontal axle. The rail extends in an axial horizontal direction and has first and second ends opposite to each other. The base seat of the supporting unit is connected with the first end of the rail to have the shaft portion extending toward the second end. The rotating support module is connected with the second end of the rail. The horizontal axle for reeling a blind thereon has two ends which are respectively connected with the blind lifting control module and the rotating support module so as to be controlled for its rotation by the blind lifting control module to lift and lower the blind. 
     The pull cord is reeled on the driving reel in a non-operated state, which can avoid entangling children and objects nearby. The operation of lifting the blind is convenient to conduct. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other features and advantages of the disclosure will become apparent in the following detailed description of the embodiments with reference to the accompanying drawings, of which: 
         FIG. 1  is a perspective view illustrating a first embodiment of a blind lifting device according to the disclosure; 
         FIG. 2  is an exploded perspective view of the first embodiment; 
         FIG. 3  is an exploded perspective view of the first embodiment taken from another angle; 
         FIG. 4  is an exploded perspective view of the first embodiment, a rail thereof being removed; 
         FIG. 5  is an exploded perspective view similar to  FIG. 4 , but taken from another angle; 
         FIG. 6  is a perspective view illustrating a blind lifting control module of the first embodiment; 
         FIG. 7  is a partly-exploded perspective view of the blind lifting control module; 
         FIG. 8  is an exploded perspective view of the blind lifting control module; 
         FIG. 9  is an exploded perspective view similar to  FIG. 8 , but taken from another angle; 
         FIG. 10  is a perspective view of an anti-backward unit of the blind lifting control module; 
         FIG. 11  is a sectional view of the anti-backward unit; 
         FIG. 12  is a perspective view of a rotating support module of the first embodiment; 
         FIG. 13  is an exploded perspective view of the rotating support module; 
         FIG. 14  is an exploded perspective view similar to  FIG. 13 , but taken from another angle; 
         FIG. 15  is a side view illustrating the blind lifting control module in a non-operated state; 
         FIG. 16  is a front view of  FIG. 15 ; 
         FIG. 17  is a side view illustrating the blind lifting control module in a blind-lowering operated state; 
         FIG. 18  is a front view of  FIG. 17 ; 
         FIG. 19  is a side view illustrating the state where a pull cord is pulled to the end; 
         FIG. 20  is a front view of  FIG. 19 ; 
         FIG. 21  is a perspective view illustrating the state where a blind is lowered; 
         FIG. 22  is a side view illustrating the state where the pull cord is released; 
         FIG. 23  is a front view of  FIG. 22 ; 
         FIG. 24  is a side view illustrating the blind lifting control module in a blind-lifting operated state; 
         FIG. 25  is a front view of  FIG. 24 ; 
         FIG. 26  is a perspective view illustrating the state where the blind is lifted; 
         FIG. 27  is a perspective view of the blind lifting control module of a second embodiment; 
         FIG. 28  is a side view of the blind lifting control module of the second embodiment; 
         FIG. 29  is a front view of the blind lifting control module of the second embodiment; 
         FIG. 30  is a perspective view of the blind lifting control module of a third embodiment; 
         FIG. 31  is a side view illustrating a hindering member in a hindering position; 
         FIG. 32  is a side view illustrating the hindering member in a keeping-off position; 
         FIG. 33  is a perspective view of the blind lifting control module of a fourth embodiment; 
         FIG. 34  is an exploded perspective view of the fourth embodiment; 
         FIG. 35  is a perspective view illustrating a transmitting wheel of the blind lifting control module; 
         FIG. 36  is a perspective view illustrating a supporting unit, a thrust member and a hindering member of the blind lifting control module; 
         FIGS. 37 and 38  are exploded perspective views of  FIG. 36 ; 
         FIG. 39  is a perspective view of the blind lifting control module of a fifth embodiment; 
         FIG. 40  is a perspective view illustrating a supporting unit, a thrust member, a hindering member, a transmitting ring and a driving reel of the blind lifting control module; and 
         FIG. 41  is an exploded perspective view of  FIG. 40 . 
     
    
    
     DETAILED DESCRIPTION 
     Before the disclosure is described in greater detail, it should be noted that where considered appropriate, reference numerals or terminal portions of reference numerals have been repeated among the figures to indicate corresponding or analogous elements, which may optionally have similar characteristics. 
     Referring to  FIGS. 1 to 3 , a first embodiment of a blind lifting device  100  according to the disclosure includes a rail  1 , a blind lifting control module  2 , a rotating support module  3  and a horizontal axle  4 . 
     The rail  1  extends in an axial horizontal direction, and has first and second ends  11 ,  12  opposite to each other. In one embodiment, the rail  1  includes a top wall  13  and a front wall  14  extending downwardly from a front edge of the top wall  13 , and the first and second ends  11 ,  12  are formed at two opposite end edges of the top and front walls  13 ,  14 . The blind lifting control module  2  is connected with the first end  11 . The rotating support module  3  is connected with the second end  12 . The horizontal axle  4  for reeling a blind  9  thereon has two ends which are respectively connected with the blind lifting control module  2  and the rotating support module  3  so as to be controlled for its rotation by the blind lifting control module  2  to lift and lower the blind  9 . The blind  9  may be a fabric blind, Roman blind, honeycomb shade, Venetian blind, pleated blind, etc. 
     With reference to  FIGS. 4 and 5 , the horizontal axle  4  is in the form of a tubular shaft, and has a blind engaging portion  41  which is punched and concaved from an outer surrounding wall thereof and which is elongated horizontally to the two ends to define an elongated slot  42  for securely engaging with the blind  9  (see  FIG. 1 ). 
     With reference to  FIGS. 6 to 9 , the blind lifting control module  2  includes a supporting unit  5 , a transmitting wheel  6 , an anti-backward unit  7  and a driving unit  8 . 
     The supporting unit  5  includes a base seat  51  which is connected with the rail  1  (see  FIG. 1 ), and a mounting shaft  52  which is securely connected with the base seat  51 . The base seat  51  has a mounting plate  511  which extends in an upright direction transverse to the axial horizontal direction, a positioning pin portion  512  which projects horizontally from the mounting plate  511 , a supporting portion  513  which projects horizontally from the mounting plate  511  and which is disposed upwardly of the positioning pin portion  512 , and two first locking holes  514  formed in the mounting plate  511  and at upper and lower sides of the positioning pin portion  512 . The mounting shaft  52  has a shaft portion  521  extending parallel to the horizontal axle  4 , and a protrusion  522  which projects radially and outwardly from the shaft portion  521  to serve as a cam surface. In one embodiment, the shaft portion  521  includes a larger-diameter segment ( 521   a ) abutting against the mounting plate  511 , and a smaller-diameter segment ( 521   b ) extending horizontally from the larger-diameter segment ( 521   a ). The larger-diameter segment ( 521   a ) has an insert hole  523  for insertion of the positioning pin portion  512 , and two second locking holes  524  respectively aligned with the first locking holes  514  for screw fasteners (not shown) or hot-pressed rivets to extend through the first and second locking holes  514 ,  524  to secure the mounting shaft  52  to the mounting plate  511 . The shaft portion  52  further includes a pair of elastic pawls  525  extending from a terminate end of the smaller-diameter segment ( 521   b ), and a spring positioning protrusion  526  projecting radially and outwardly from the smaller-diameter segment ( 521   b ) and adjacent to the larger-diameter segment ( 521   a ). 
     The transmitting wheel  6  is rotatably sleeved on the mounting shaft  52  and is retained by the elastic pawls  525  to prevent from removal, and includes an axle connecting body  61  which is securely connectable with the end of the horizontal axle  4 , and a flange disc  62  which is connected with a side of the axle connecting body  61  proximate to the base seat  51  and which extends radially and outwardly from the axle connecting body  61 . The axle connecting body  61  has a receiving groove  611  which extends from the side for receiving the shaft portion  521 , and a first ratchet portion  612  which is formed in the receiving groove  611  and which faces the base seat  51 . The flange disc  62  has a second ratchet portion  621  which is formed on a surface that faces the base seat  51  and surrounds the receiving groove  611 . The axle connecting body  61  of the transmitting wheel  6  is inserted into the one end of the horizontal axle  4 , and has a first retaining slot  613  which is retainingly connected with the blind engaging portion (see  FIG. 4 ) so as to rotate with the horizontal axle  4 . 
     With reference to  FIGS. 7, 8, 10 and 11 , the anti-backward unit  7  includes an anti-backward wheel  71  and a biasing returning member  72  which are received in the receiving groove  611 . The anti-backward wheel  71  has a movable wheel body  711  which is movably sleeved on the shaft portion  521 , and a third ratchet portion  712  which is formed on a surface of the movable wheel body  711  and faces the first ratchet portion  612 . The anti-backward wheel  71  is movable axially relative to the shaft portion  521  between an anti-backward position (see  FIG. 16 ), where the third ratchet portion  712  meshes with the first ratchet portion  612  to permit a uni-directional rotation of the transmitting wheel  6 , and a released position (see  FIG. 20 ), where the third ratchet portion  712  is disengaged from the first ratchet portion  612 . The biasing returning member  72  is interposed between the anti-backward wheel  71  and the transmitting wheel  6  to bias the anti-backward wheel  71  to the anti-backward position. In one embodiment, the anti-backward wheel  71  is also rotatable relative to the shaft portion  521 , and has a groove  713  which is cut in the movable wheel body  711  and engaged with the protrusion  522  so as to convert a rotation of the anti-backward wheel  71  into an axial movement between the anti-backward position and the released position. The biasing returning member  72  is in the form of an O-ring which is disposed on an outer peripheral surface of the movable wheel body  711  to provide a biasing returning force to the anti-backward wheel  71  by a friction with the inner peripheral surface of the transmitting wheel  6 . In another embodiment (such as the fourth embodiment mentioned below), the biasing returning member  72  may be a coil spring sleeved around the shaft portion  521  and axially disposed between the anti-backward wheel  71  and a driving reel  81  of the driving unit  8 . 
     With reference to  FIGS. 7 to 9  again, the driving unit  8  includes a driving reel  81 , a transmitting member  82 , a thrust member  83 , a hindering member  84 , a pull cord  85 , a reel biasing member  86  and an elastomeric biasing ring  87 . 
     The driving reel  81  is rotatably sleeved on the shaft portion  521 , and has a fourth ratchet portion  811  facing the second ratchet portion  621 . The driving reel  81  is movable axially relative to the shaft portion  521  between a driving position (see  FIG. 25 ), where the fourth ratchet portion  811  meshes with the second ratchet portion  621 , and a normal position (see  FIG. 16 ), where the fourth ratchet portion  811  is disengaged from the second ratchet portion  621 . The transmitting member  82  is connected between the driving reel  81  and the anti-backward wheel  71  to transmit a rotation of the driving reel  81  to move the anti-backward wheel  71  to the released position. The thrust member  83  is movably disposed to the base seat  51  to be movable relative to the base seat  51  between an initial position (see  FIG. 16 ), where the thrust member  83  is free from action with the driving reel  81 , and a thrusting position (see  FIG. 25 ), where the thrust member  83  provides a thrust force to move the driving reel  81  to the driving position. The hindering member  84  is pivotably disposed to the base seat  51  to be turnable relative to the base seat  51  between a hindering position (see  FIG. 17 ), where the hindering member  84  is kept to position the thrust member  83  in the initial position, and a keeping-off position (see  FIG. 24 ), where the thrust member  83  is allowed for movement to the thrusting position. The pull cord  85  has an end secured to the driving reel  81 , and winds on a periphery of the driving reel  81  to have a free end passing through the hindering member  84  for pulling operation. Specifically, the free end of the pull cord  85  is disposed to receive a pulling force to turn the hindering member  84 . The reel biasing member  86  is disposed to bias the driving reel  81  to rotate to reel the pull cord  85 . The elastomeric biasing ring  87  is frictionally interposed between the transmitting wheel  6  and the driving reel  81  to bias the driving reel  81  back to the normal position. 
     In one embodiment, the driving reel  81  includes first and second reel halves  812 ,  813  coupled with each other. The first reel half  812  has an annular plate portion ( 812   a ), an annular wall portion ( 812   b ) extending from the annular plate portion ( 812   a ) toward the second reel half  813 , a plurality of engaging studs ( 812   c ) formed on the annular wall portion ( 812   b ), and an annular grooved portion ( 812   d ) formed in the annular plate portion ( 812   a ) and opposite to the annular wall portion ( 812   b ). The fourth ratchet portion  811  is formed on the annular plate portion ( 812   a ) and surrounds the annular grooved portion ( 812   d ). The second reel half  813  has a plurality of engaging holes ( 813   a ) respectively engaged with the engaging studs ( 812   c ) to couple the first reel half  812  with the second reel half  813 . The annular plate portion ( 812   a ), the annular wall portion ( 812   b ) and the second reel half  813  cooperatively define an accommodation space for receiving the reel biasing member  86 . The pull cord  85  is reeled on the periphery of the annular wall portion ( 812   b ) and is confined between the annular plate portion ( 812   a ) and the second reel half  813 . The annular wall portion ( 812   b ) has a notch  8121  for passing of the pull cord  85 , and a spring positioning slot  8122  for securing of an end of the reel biasing member  86 . The end of the pull cord  85  is secured to the inner side of the annular wall portion ( 812   b ). The reel biasing member  86  is a coil spring which is sleeved around the shaft portion  521 , and has an inner end secured to the spring positioning protrusion  526 , and an outer end secured to the spring positioning slot  8122  so as to provide a returning force to rotate and return the driving reel  81  and to reel the pull cord  85 . 
     In one embodiment, the transmitting member  82  is in the form of a string having two ends which are respectively secured to the movable wheel body  711  and the driving reel  81 , and a middle portion which winds on the shaft portion  521 . Thus, the transmitting member  82  is tensed by a pulling force applied to the pull cord  85  to the end through the driving reel  81  to move the anti-backward wheel  71  to the released position. Specifically, the movable wheel body  711  has a string slot  714  (see  FIG. 10 ). The annular plate portion ( 812   a ) is formed with a string hole  8123 . The two ends of the transmitting member  82  are secured to the string slot  714  and the inner side of the annular plate portion ( 812   a ), and the middle portion is received in the annular grooved portion ( 812   d ). The transmitting member  82  surrounds the shaft portion  521  in a loosened state when it is not driven by the driving reel  81 . With the pulling force applied to the pull cord  85  to the end, the transmitting member  82  is pulled through the driving reel  81  to be in a fully tensed state so as to move the anti-backward wheel  71  to the released position. When the transmitting member  82  is returned back to the loosened state, the anti-backward wheel  71  is returned back to the anti-backward position by means of the biasing returning member  72 . 
     In one embodiment, the thrust member  83  is pivotably disposed to the supporting portion  513  of the base seat  51 , and has a forced portion  831  through which the pull cord  85  passes to be turned by a pulling action of the pull cord  85 , and a thrust portion  832  which is disposed at an opposite side of the driving reel  81  relative to the fourth ratchet portion  811  to thrust the driving reel  81  such that the thrust member  83  is activated by the pulling action of the pull cord  85  to turn from the initial position to the thrusting position. Specifically, the thrust member  83  has a pivot axle  836  which is pivotably journalled on the supporting portion  513  and which extends transverse to both the axial horizontal direction and the upright direction such that the forced portion  831  is turnable about the pivot axle  836 . 
     In one embodiment, the hindering member  84  is in the form of a lever which extends in the upright direction and which has a fulcrum portion  841  that is pivotably connected to the mounting plate  511  of the base seat  51 , a hindering portion  842  that is disposed upwardly of the fulcrum portion  841  to engage with the thrust portion  832  of the thrust member  83  for hindering turning of the forced portion  831 , and a pull portion  843  that is disposed downwardly of the fulcrum portion  841 . The pull cord  85  passes through the pull portion  843 . As shown in  FIG. 17 , when an outwardly-inclined downward pulling force is applied to the pull cord  85 , the hindering portion  842  is turned to abut against the thrust member  83 . Specifically, the thrust portion  832  of the thrust member  83  has an engaging notch ( 833   a ) cut from an end edge  833  thereof that is close to the hindering portion  842  of the hindering member  84  such that, in the hindering position, the hindering portion  842  is engaged and restricted in the engaging notch ( 833   a ). 
     With reference to  FIGS. 5 and 12 to 14 , the rotating support module  3  includes a mounting wall  31  which extends in the upright direction to be connected with the rail  1  (see  FIG. 1 ), a support axle  32  which is secured to the mounting wall  31  and which extends horizontally toward the blind lifting control module  2 , and a rotary seat  33  which is rotatably sleeved on the support axle  32 . The rotary seat  33  has an axle connecting portion  331  which is inserted into the other end of the horizontal axle  4  and which has a second retaining slot ( 331   a ) that is retainingly connected with the blind engaging portion  41  so as to be rotated with the horizontal axle  4 . 
     In one embodiment, the rotating support module  3  further includes a speed-reducing sleeve  34  and a coil member  35 . The rotary seat  33  further has a tubular portion  332  which extends horizontally from the axle connecting portion  331  toward the blind lifting control module  2  to spacedly surround the support axle  32  and which has a diameter smaller than that of the axle connecting portion  331 . The support axle  32  has an axle body  321  and at least one frictional ring  322  (two frictional rings  322  are shown). The axle body  321  has a secured end portion ( 321   a ) which is secured to the mounting wall  31 , and a free end portion ( 321   b ) which is opposite to the secured end portion ( 321   a ) and exposed from the rotary seat  33 . The frictional rings  322  surround the free end portion ( 321   b ), and are elastic  0 -rings to generate a frictional resistance with the speed-reducing sleeve  34 . 
     The speed-reducing sleeve  34  has a sleeve body  341  which is sleeved on the free end portion ( 321   b ), and a plurality of elastic plates  342  which are arranged around the axle body  321  and which extend from the sleeve body  341  toward the rotary seat  33  and have terminate ends interposed between the tubular portion  332  and the axle body  321 . The coil member  35  is sleeved around the speed-reducing sleeve  34 , and has two ends which are respectively secured to the rotary seat  33  and the sleeve body  341 . Specifically, a first connecting hole ( 331   b ) and a second connecting hole  343  are formed in the axle connecting portion  331  of the rotary seat  33  and the sleeve body  341 , respectively, to securely engage with two ends of the coil member  35 . The coil member  35  is a compression spring. Alternatively, the coil member  35  may be a string or wire. 
     As shown in  FIG. 1 , the horizontal axle  4  is rotated forwardly to lift the blind  9  and a clockwise rotational direction of the horizontal axle  4  is defined. The horizontal axle  4  is rotated rearwardly to lower the blind  9  and a counterclockwise rotational direction of the horizontal axle  4  is defined. During rotation of the horizontal axle  4  in the counterclockwise rotational direction, the speed-reducing sleeve  34  is in frictional contact with the frictional rings  322  to have a rotational speed slower than that of the rotary seat  33 , and to shrink the coil member  35  to compress the elastic plates  342  toward the axle body  321  so as to reduce the rotational speed of the rotary seat  33  and to slowly lower the blind  9 . When the horizontal axle  4  is rotated with the blind lifting control module  2  in the clockwise rotational direction to lift the blind  9 , the coil member  35  is returned back to its original position and the elastic plates  342  loosely surround the axle body  321 . In this state, the rotating support module  3  generates a relatively small torque to permit an operator to operate the pull cord  85  of the blind lifting control module  2  with less effort. 
     The operation of the blind lifting control module  2  is described in detail as follows. 
     With reference to  FIGS. 1, 7, 15 and 16 , when the blind  9  is in a non-operated state, the pull cord  85  is reeled on the driving reel  81 , and the anti-backward wheel  71  is in the anti-backward position such that, with the meshing engagement of the first and third ratchet portions  612 ,  712 , the transmitting wheel  6  is only permitted to perform a uni-directional rotation (i.e., a rotation in the clockwise rotational direction to rotate the horizontal axle  4 ) and the horizontal axle  4  is kept from lowering the blind  9 . At this stage, the thrust member  83  is in the initial position and the driving reel  81  is in the normal position. 
     With reference to  FIGS. 7, 17 and 18 , the pull cord is applied with an outwardly-inclined downward pulling force (remote from the driving reel  81 ) to turn the pull portion  843  outward, and the hindering portion  842  is turned to abut against the thrust member  83  so as to position the thrust member  83  in the initial position such that the driving reel  81  is in the normal position and free from action with the transmitting wheel  6 . Thus, the driving reel  81  is rotated through the pulling force applied to the pull cord  85  without rotation of the transmitting wheel  6  and the horizontal axle  4 . Rotation of the driving reel  81  brings about winding of the transmitting member  82  on the shaft portion  521  and movement of the anti-backward wheel  71  to the released position. With reference to  FIGS. 19  to  21 , when the pulling force is applied to the pull cord  85  to the end, the anti-backward wheel  71  is moved to the released position. At this stage, the transmitting wheel  6  is rotatable freely such that the blind  9  on the horizontal axle  4  is lowered by virtue of its weight. With the speed reducing means of the rotating support module  3  to reduce the rotational speed of the horizontal axle  4 , the blind  9  is lowered slowly. With reference to  FIGS. 22 and 23 , when the pulling force is released from the pull cord  85 , the driving reel  81  is rotated in an opposite rotational direction by means of the reel biasing member  86  to reel the pull cord  85  and the transmitting member  82  is released (see  FIG. 7 ) so as to return the anti-backward wheel  71  to the anti-backward position to stop rotation of the transmitting wheel  6  and position the blind  9  at a desired height position. In other words, the anti-backward wheel  71  is kept in the anti-backward position until the pull cord  85  is pulled to the end. 
     With reference to  FIGS. 24 to 26 , the operator applies an uprightly downward pulling force to the pull cord  85  to lift the blind  9 , the hindering member  84  is turned to the keeping-off position where the hindering portion  842  is remote from the thrust portion  832 , and the thrust member  83  is moved to the thrusting position so as to move the driving reel  81  to the driving position. With the meshing engagement of the fourth and second ratchet portions  811 ,  621 , the driving reel  81  drives rotation of the transmitting wheel  6  and the horizontal axle  4  in the clockwise rotational direction so as to reel and lift the blind  9 . When the pull cord  85  is released, as shown in  FIG. 16 , the driving reel  81  is returned to the normal position by means of the elastomeric biasing ring  87 , the thrust member  83  is returned to the initial position, and the pull cord  85  is reeled on the driving reel  81 . Similarly, the transmitting wheel  6  is interfered with the anti-backward wheel  71  and is not rotated backward by means of the horizontal axle  4  so as to keep the blind  9  at an appropriate height position. In case of a long blind  9 , the operations of pulling downward and releasing of the pull cord  85  should be repeated so as to lift the blind  9  with a relative long distance. 
     As mentioned above, the pull cord  85  is reeled on the driving reel  81  in the non-operated state, which can avoid entangling children and objects nearby. The operation of lifting the blind  9  is convenient to conduct. 
     With reference to  FIGS. 27 to 29 , in a second embodiment, an elastic leaf portion  834  is formed on and extends from the forced portion  831  of the thrust member  83 . The elastic leaf portion  834  has a terminal end which abuts against the top wall  13  of the rail  1  (see  FIG. 2 ) so as to generate a counteracting force when the thrust member  83  is in the thrusting position, which urges the thrust member  83  back to the initial position once the thrust member  83  is free from action with the pull cord  85 . 
     With reference to  FIGS. 30 to 32 , in a third embodiment, the thrust portion  832  of the thrust member  83  has a keeping-off notch  835  cut from a lower edge  839  thereof that is close to the hindering portion  842  of the hindering member  84 . As shown in  FIG. 31 , when an uprightly downward pulling force is applied to the pull cord  85 , the pull portion  843  of the hindering member  84  is turned slightly inwardly so as to turn the hindering member  84  to the hindering position, where the hindering portion  842  abuts against the lower edge  839 , and thus the thrust member  83  is positioned in the initial position. As shown in  FIG. 32 , when an outwardly-inclined downward pulling force (remote from the driving reel  81 ) is applied to the pull cord  85 , the pull portion  843  of the hindering member  84  is turned slightly outwardly so as to turn the hindering member  84  to the keeping-off position, where the hindering portion  842  is received in the keeping-off notch  835 , and thus the thrust member  83  is moved to the thrusting position to move the driving reel  81  to the driving position. 
     With reference to  FIGS. 33 to 35 , in a fourth embodiment, the biasing returning member  72  is a coil spring sleeved around the shaft portion  521  and axially disposed between the anti-backward wheel  71  and a driving reel  81  of the driving unit  8 . 
     The axle connecting body  61  of the transmitting wheel  6  has an inner surrounding wall extending axially and defining the receiving groove  611  therein, and a plurality of elastomeric muffling members  614  formed on the inner surrounding wall and adjacent to the first ratchet portion  612 . In this embodiment, the axle connecting body  61  has three pairs of the muffling members  614  (only one pair is shown) angularly spaced from one another by 120 degrees, and slightly inclined toward the rotational direction of the anti-backward wheel  71 . The muffling members  614  may be made from silicone or rubber material to retard the returning rotation of the anti-backward wheel  71  such that, during the lifting of the blind  9 , a buffering action is applied to the anti-backward wheel  71  to decrease impact to the first ratchet portion  612  so as to provide muffled sound effects. 
     With reference to  FIGS. 36 to 38 , in this embodiment, the mounting shaft  52  is integrally formed with the base seat  51 , and the mounting plate  511  of the base seat  51  has a plurality of annular grooves  515  which surround the shaft portion  521  and are angularly spaced from each other. The base seat  51  further has a positioning frame  516  which is disposed on the mounting plate  511 , a stop block  517  which is angularly spaced apart from the positioning frame  516  and proximate to the hindering member  84 , and a slope block  518  which extends angularly to have an end connected with the stop block  517 . As shown in  FIG. 37 , each annular groove  515  has a depth which is gradually reduced in a clockwise direction. The thrust portion  832  of the thrust member  83  has an annular portion  837  which is rotatable about and sleeved on the shaft portion  521 , and a plurality of sliding protrusions  838  which project from the annular portion  837  and which are respectively and slidably engaged in the annular grooves  515 . The annular portion  837  has an engaging notch ( 837   a ) cut from an outer periphery thereof that is close to the hindering portion  842  of the hindering member  84  so as to be engaged with the hindering portion  842  when the hindering member  84  is turned to the hindering position. The forced portion  831  of the thrust member  83  has an extension segment ( 831   a ) which extends radially and outwardly from an outer periphery of the annular portion  837 , a cord-pulling segment ( 831   b ) which extends from the extension segment ( 831   a ) and through which the pull cord  85  (see  FIG. 33 ) passes, and a positioned segment ( 831   c ) which extends from the extension segment ( 831   a ) and transverse to the cord-pulling segment ( 831   b ). As shown in  FIG. 36 , when the thrust member  83  is in the initial position, the positioned segment ( 831   c ) passes through and is positioned to the positioning frame  516 , the extension segment ( 831   a ) abuts against the positioning frame  516 , the annular portion  837  is attached to the mounting plate  511 , and the sliding protrusions  838  are respectively engaged in deeper areas of the annular grooves  515 . When an uprightly downward pulling force is applied to the pull cord  85  to turn the hindering member  84  to the keep-off position, and to rotate the forced portion  831  in the clockwise direction, the sliding protrusions  838  slide along the annular grooves  515  toward shallower areas to move the annular portion  837  away from the mounting plate  511  so as to thrust the driving reel  81  to the driving position. The extension segment ( 831   a ) abuts against and is stopped by the stop block  517  when the thrust member  83  is moved to the thrusting position for preventing excess rotation of the thrust member  83 . During the rotation of the thrust member  83  from the initial position to the thrusting position, the extension segment ( 831   a ) is supported on the slope block  518  and is moved steadily with the annular portion  837  away from the mounting plate  511 . Similar to the hindering member  84  in the first embodiment, an outwardly-inclined downward pulling force (remote from the driving reel  81 ) applied to the pull cord  85  brings about turning of the hindering member  84  to the hindering position, where the pull portion  843  is turned outward, and the hindering portion  842  is turned to engage in the engaging notch ( 837   a ) to position the thrust member  83  in the initial position. Moreover, in this embodiment, the hindering member  84  is made from a plastic material, and further has a returning post  844  deformably abutting against the stop block  517  such that, the returning post  844  is elastically bent when the hindering member  84  is turned by a pulling force from the keeping-off position to the hindering position, and is returned back its posture when the pulling force is released so as to keep the hindering member  84  in the keeping-off position. 
     With reference to  FIGS. 39 to 41 , in a fifth embodiment, the forced portion  831  of the thrust member  83  is in the form of a tube which extends axially from an inner periphery of the annular portion  837  and which is inserted into the driving reel  81 . The driving unit  8  further includes a transmitting ring  88  which is sleeved on the forced portion  831  and frictionally interposed between the forced portion  831  and the driving reel  81  so as to transmit rotation of the driving reel  81  to rotate the forced portion  831 . The transmitting ring  88  may be made from silicone, rubber and other elastomeric material. Further, the annular portion  837  has two elongated grooves ( 837   b ) extending along the inner periphery. The base seat  51  further has two studs  519  which are disposed on the mounting plate  511  and respectively and movably engaged in the elongated grooves ( 837   b ) so as to limit the rotation of the thrust member  83 . Alternatively, only one elongated groove ( 837   b ) and one stud  519  may be disposed to be movably engaged with each other. In this embodiment, the hindering member  84  has a simple structure and is of an elongated bent shape. The base seat  51  further has a side wall  510  extending transverse to the mounting plate  511  and having a through slot ( 510   a ) for passing of the pull portion  843  of the hindering member  84  so as to limit the turning of the hindering member  84 . 
     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 embodiments. 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. 
     While the disclosure has been described in connection with what are considered the exemplary embodiments, it is understood that this disclosure is not limited to the disclosed embodiments 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.