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You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates generally to window blind assemblies and, more particularly, to a window blind assembly control crank gear. The invention relates also to a window blind assembly having such a control crank gear.  
           [0003]    2. Description of the Related Art  
           [0004]    A regular Venetian blind comprises a lifting control unit and a slat tilting control unit. The lifting control unit comprises lift cords extended to the outside for operation by the user. However, because the exposed portions of the lift cords may be hung on the body of a person accidentally, causing death. In order to eliminate this problem, a rotary driving bar is disclosed to match with a transmission mechanism instead of conventional lift cords. It is also well known to use a rotary driving rod for controlling the tilting angle of blind slats. In general, a rotary driving rod may be used in a window blind assembly to separately or concomitantly control the lifting of the blind and the tilting of the slats, thereby changing the light shading status of the window blind assembly.  
           [0005]    There is known a folding collapsible crank design for use in a window blind assembly to control the light shading status of the blind slats. This design is seen in Swiss patent No. 689234. The folding collapsible crank disclosed in the Swiss patent No. 689234 is comprised of a top rod, an intermediate rod and a bottom rod. The top rod, the intermediate rod and the bottom rod are axially connected to one another. When in use, hold the top rod and the bottom rod with the hands and turn the connections to a particular angle, and then turn the bottom rod about the top rod to further control the light shading status of the blind. According to this design, the bottom end of the top rod and the top end of the bottom rod are shaped like a flat block, and the intermediate rod has two spring members provided in the top and bottom ends thereof and respectively stopped against the flat block-like bottom end of the top rod and the flat block-like top end of the bottom rod, for enabling the top rod and the bottom rod to be respectively set in the operative position perpendicular to the intermediate rod. This design is still not satisfactory in function. Because this folding collapsible crank can only be set in one particular position (angle) for operation, it does not fit different persons of different body heights. In general, this design is not orthopedically engineered.  
         SUMMARY OF THE INVENTION  
         [0006]    It is the main object of the present invention to provide a window blind assembly control crank gear, which is orthopedically engineered.  
           [0007]    It is another object of the present invention to provide a window blind assembly control crank gear, which can be set in one of a series of operation positions to fit different persons.  
           [0008]    It is still another object of the present invention to provide a window blind assembly control crank gear, which has fine adjustment means for adjusting the position retaining force.  
           [0009]    To achieve these objects of the present invention, the window blind assembly control crank gear comprises a top rod having a bottom end terminating in a coupling block with a transverse pivot hole, an intermediate rod having a coupling lug at the top, the coupling lug having two upright sidewalls and two pivot holes respectively formed in the upright sidewalls and axially aligned, and a fastener passed through the pivot hole of the coupling block and the pivot holes of the coupling lug to pivotally secure the coupling block to the coupling lug between the upright sidewalls of the coupling lug and to impart a pressure to the upright sidewalls against the coupling block for enabling the intermediate rod to be turned relative to the top rod and quickly positioned in an adjusted angular position, and a bottom rod pivoted to a bottom end of the intermediate rod. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is a perspective view of a window blind assembly equipped with a control crank gear according to a first preferred embodiment of the present invention.  
         [0011]    [0011]FIG. 2 is a perspective view of a window blind assembly control crank gear according to the first preferred embodiment of the present invention.  
         [0012]    [0012]FIG. 3 is an exploded view in an enlarged scale of a part of the window blind assembly control crank gear according to the first preferred embodiment of the present invention.  
         [0013]    [0013]FIG. 4 illustrates the window blind assembly control crank gear of the first preferred embodiment of the present invention set in one operation position.  
         [0014]    [0014]FIG. 5 is an exploded view of a part of a window blind assembly control crank gear according to a second preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]    Referring to FIG. 1, a window blind assembly control crank gear  20  is for use in a window blind assembly  10  comprised of a headrail  11 , a bottom rail  12 , two ladder tapes  13  connected between the headrail  11  and the bottom rail  12 , a set of slats  14  arranged in parallel between the headrail  11  and the bottom rail  12  and fastened to the ladder tapes  13 , two lift cords  15  (the lift cords and the ladder tapes are overlapped in FIG. 1) each having one end affixed to the bottom rail  12  and the other end upwardly inserted through the slats  14  into the inside of the headrail  11 , a shaft  16  mounted inside the headrail  11  and adapted to roll up the ladder tapes  13  and/or the lift cords  15 , and a transmission mechanism  17  mounted in the headrail  11  and coupled to one end of the shaft  16 . The control crank gear  20  is connected to the transmission mechanism  17  and vertically suspended at one lateral side of the window blind assembly  10  for turning by hand to drive the transmission mechanism  17  to rotate the shaft  16  clockwise or counter-clockwise, so as to further lift or lower the bottom rail  12  or tilt the slats  14 .  
         [0016]    Referring to FIGS.  2 ˜ 4 , the control crank gear  20  is comprised of a top rod  21 , an intermediate rod  22 , a fastener  23 , a bottom rod  24 , an upper sleeve  25 , a lower sleeve  26 .  
         [0017]    The top rod  21  is a round rod member having a top end detachably connected (or affixed) to the transmission mechanism  17  of the window blind assembly  10 , and a bottom end terminating in a flat coupling block  211 , which has a pivot hole  212  extended through two opposite flat sidewalls thereof and a front protrusion  213  protruding from the smoothly arched front wall thereof.  
         [0018]    The intermediate rod  22  is a round rod member having a top end terminating in a coupling lug  221  and a bottom end pivoted to the bottom rod  24 . The coupling lug  221  comprises a flat base  226 , two parallel upright sidewalls  225  bilaterally upwardly extended from the flat base  226  and spaced from each other at a space slightly smaller than the thickness of the flat coupling block  211  of the top rod  21 , two pivot holes  222  respectively transversely extended through the upright sidewalls  225  and aligned in a line, an engagement portion, for example, an inner thread  223  formed in one pivot hole  222 , and a stop block  224  protruded from the flat base  226  between the upright sidewalls  225  at one side. Because the pitch between the upright sidewalls  225  is slightly smaller than the thickness of the flat coupling block  211  of the top rod  21 , the top rod  21  and the intermediate rod  22  are secured together by friction resistance when the flat coupling block  211  plugged into the coupling lug  221  in between the upright sidewalls  225 . When the flat coupling block  211  plugged into the coupling lug  221  in between the upright sidewalls  225 , the fastener  23  is installed in the pivot holes  212  and  222  to pivotally secure the top rod  21  and the intermediate rod  22  together. When connected together, the top rod  21  and the intermediate rod  22  can be set in a line where the front protrusion  213  is stopped at the stop block  224  to hold the top rod  21  and the intermediate rod  22  in the axially aligned position.  
         [0019]    The fastener  23  is comprised of a screw bolt  27  and a holding down member, for example, a spring washer  28 . The screw bolt  27  is inserted through one pivot hole  222  of the coupling lug  221  and the pivot hole  212  of the coupling block  211  and threaded into the inner thread  223  in the other pivot hole  222  of the coupling lug  221  to pivotally secure the top rod  21  and the intermediate rod  22  together. The spring washer  28  is clamped on the screw bolt  27  and stopped between the head of the screw bolt  27  and one upright sidewall  225  of the coupling lug  221  to hold down the screw bolt  27 .  
         [0020]    The bottom rod is a round rod member having a top end pivoted to the bottom end (free end) of the intermediate rod  22 . The connecting structure between the bottom end of the top rod  21  and the top end of the intermediate rod  22  may be employed to the connection between the bottom end of the intermediate rod  22  and the top end of the bottom rod  24 . However, simply pivoting the top end of the bottom rod  24  to the bottom end of the intermediate rod  22  achieves the desired functions of the present invention.  
         [0021]    The upper sleeve  25  is a round tube sleeved onto the top rod  21 . The lower sleeve  26  is a round tube sleeved onto the bottom rod  24 . The upper and lower sleeves  25  and  26  are provided for holding by the user&#39;s hands, preventing direct friction between the hands and the top and bottom rods  21  and  24  during operation.  
         [0022]    The operation of the control crank gear  20  is outlined hereinafter. Normally, the control crank gear  20  is set in a line as shown in FIG. 2. When operating the control crank gear  20 , hold the upper sleeve  25  and the lower sleeve  26  with both hands, and then apply a force to the lower sleeve  26  relative to the upper sleeve  25  and the top rod  21  to change the angle of the intermediate rod  22  from vertical to a particular angle, for example, 120° relative to the top rod  21  and the bottom rod  24  (see FIG. 4), and then turn the lower sleeve  26  and the bottom rod  24  about the axis passing through the top rod  21  to drive the transmission mechanism  17  to rotate the shaft  16  (see also FIG. 1). After operation, apply a force to the upper sleeve  25  and the lower sleeve  26  in reversed directions, pulling the control crank gear  20  back to the straight condition.  
         [0023]    This embodiment achieves the advantages as follows:  
         [0024]    1. When the protrusion  213  of the coupling block  211  stopped at the stop block  224  of the coupling lug  221 , the top rod  21  and the intermediate rod  22  are positively maintained in a line. Therefore, the user can easily return the control crank gear  20  to the straight status.  
         [0025]    2. The friction between the coupling lugs  221  and the coupling block  21  and the clamping force of the spring washer  28  of the fastener  23  enables the intermediate rod  22  to be freely adjusted to any of a series of angular positions to fit different users and quickly and positively positioned in the adjusted angular position. Therefore, the control crank gear  20  is constantly maintained in the adjusted angular position during operation.  
         [0026]    3. When the fastener  23  installed, the screw bolt  27  is meshed with the inner thread  223  in one pivot hole  222  of the coupling lug  221  to pivotally secure the top rod  21  to the intermediate rod  22 . Further, the user can rotate the screw bolt  27  inwards or backwards in the inner thread  223  to adjust the friction resistance between the two upright sidewalls  225  of the coupling lug  221  and the coupling block  211 .  
         [0027]    [0027]FIG. 5 is an exploded view of a part of the second preferred embodiment of the window blind assembly control crank gear  30  of the present invention. According to this embodiment, the coupling block  311  of the top rod  31  has a pivot hole  312  extended through two opposite flat sidewalls thereof, and two elongated ribs  313  respectively formed in the two opposite flat sidewalls and longitudinally extended from the pivot hole  312  to the front smoothly arched front end. The coupling lug  321  of the intermediate rod  32  comprises a flat base  324 , two parallel upright sidewalls  323  upwardly extended from the flat base  324  at two sides, two pivot holes  322  respectively formed in the upright sidewalls  323  and axially aligned, and two sets of radial grooves  325  respectively formed in the upright sidewalls  323  at an inner side and equiangularly spaced around the pivot holes  322 . According to this embodiment, the number of each set of radial grooves  325  is 12, and the 12 radial grooves  325  are spaced from one another at 30° around the corresponding pivot hole  322 . The fastener  33  is comprised of a pivot  34 , a screw cap  35 , and a spring washer  36 . The pivot  34  has a head  341  at one end and thread means, i.e. a screw hole  342 , at the other end. The pivot  34  is inserted through the pivot holes  322  of the coupling lug  321  and the pivot hole  312  of the coupling block  311  to pivotally secure the top rod  31  and the intermediate rod  32  together. The screw cap  35  is threaded into the screw hole  342  to secure the pivot  34  to the coupling lug  321 . The spring washer  36  is clamped on the pivot  34  and stopped between the head  341  of the pivot  34  and one upright sidewall  323  of the coupling plug  321 . When installed, the elongated ribs  313  are meshed with the radial grooves  325 . Further, the pivot  34  and the screw cap  35  can be rotated relative to each other to adjust the friction resistance between the upright sidewalls  323  of the coupling lug  321  and the coupling block  311 . According to this embodiment, the angular position of the intermediate rod  32  can be adjusted relative to the top rod  31  step by step, i.e., by shifting the elongated rib  313  from one radial groove  325  to another. Further, a screw bolt and a nut may be used instead of the pivot  34  and the screw cap  35 , achieving the same effect.

Summary:
A window blind assembly control crank gear includes a top rod, an intermediate rod and a bottom rod pivoted to the intermediate rod. The top rod has a coupling block with a transverse pivot hole. The intermediate rod has a coupling lug including two upright sidewalls and two pivot holes respectively formed in the upright sidewalls and axially aligned. A fastener is passed through the pivot hole of the coupling block and the pivot holes of the coupling lug to pivotally secure the coupling block to the coupling lug between the upright sidewalls and to impart a pressure to the upright sidewalls against the coupling block for enabling the intermediate rod to be turned relative to the top rod and quickly positioned in an adjusted angular position.