A venetian blind includes a headrail, a storage rail, a covering unit and a retainer. The storage rail has front and rear sidewalls, each of which is formed with a horizontal rib. The storage rail further has two ends and an upper end opening disposed between the two ends. The retainer is configured as an inverted U-shaped plate, and bridges the front and rear sidewalls. The covering unit includes a plurality of horizontal slats. Lowermost ones of the slats are received within the storage rail, and are capable of being removed from the storage rail through the upper end opening. The retainer includes front and rear retaining-plate portions with open-ended slots engaging respectively the ribs of the storage rail, and is capable of being removed forcibly and upwardly from the storage rail.

BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     This invention relates to a venetian blind, and more particularly to a venetian blind that includes a plurality of horizontal slats and a storage rail that receives some of the slats to adjust the length of the venetian blind.  
         [0003]     2. Description of the Related Art  
         [0004]     U.S. Pat. No. 5,765,621 discloses a window blind that includes a storage rail or bottom rail, which defines a channel for receiving and storing unnecessary or unused slats of the window blind to enable the ready customization of the window blind to fit windows of different heights. Although the length of the window blind can be adjusted by receiving a selected number of the slats within the storage rail, it is difficult to perform such length adjustment of the window blind.  
       SUMMARY OF THE INVENTION  
       [0005]     The object of this invention is to provide a venetian blind, the length of which can be adjusted with ease.  
         [0006]     According to this invention, a venetian blind includes a headrail, a storage rail, a covering unit and a retainer. The storage rail has two ends, front and rear sidewalls, each having a horizontal rib, and an upper end opening disposed between the two ends. The retainer is configured as an inverted U-shaped plate, and bridges the front and rear sidewalls. The covering unit includes a plurality of horizontal slats. Lowermost ones of the slats are received within the storage rail, and are capable of being removed from the storage rail through the upper end opening. The retainer includes front and rear retaining-plate portions with open-ended slots engaging respectively the ribs of the storage rail, and is capable of being removed forcibly and upwardly from the storage rail. As such, the length of the venetian blind can be adjusted with ease. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]     These and other features and advantages of this invention will become apparent in the following detailed description of a preferred embodiment of this invention, with reference to the accompanying drawings, in which:  
         [0008]      FIG. 1  is an assembled perspective view of the preferred embodiment of a venetian blind according to this invention;  
         [0009]      FIG. 2  is a partly exploded fragmentary perspective view of the first preferred embodiment;  
         [0010]      FIG. 3  is a sectional side view of the preferred embodiment; and  
         [0011]      FIG. 4  is a sectional side view of the preferred embodiment, illustrating how the length of a covering unit is adjusted. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0012]     Referring to  FIGS. 1, 2  and  3 , the preferred embodiment of a venetian blind according to this invention is shown to include a headrail  1 , a covering unit  2 , a cord-winding device  3 , a storage rail  4 , two retainers  5  and two end caps  6 .  
         [0013]     The headrail  1  is mounted fixedly on a wall (not shown), and includes a rail body  11 , two covers  12  press-fitted respectively within two opposite ends of the rail body  11 , and two supporting members  13  disposed within the rail body  11  between the covers  12 . The rail body  11  includes a pair of vertical front and rear walls  111 , a horizontal bottom wall  112 , and an accommodating space  113  defined among the front and rear walls  111  and the bottom wall  112 . The front and rear walls  111  extend respectively, integrally, and upwardly from opposite front and rear sides of the bottom wall  112 .  
         [0014]     The covering unit  2  is disposed between the headrail  1  and the storage rail  4 , and includes a light-adjusting rod  21  disposed rotatably on the supporting members  13 , two cord-connecting elements  22  connected respectively and fixedly to two opposite ends of the light-adjusting rod  21 , a driving member  23  disposed within the accommodating space  113  in the headrail  1  and driven to rotate the light-adjusting rod  21  by a selected angle, a vertical controlling rod  24  connected to the driving member  23  and operable to drive the driving member  23 , two ladder cords  25  fastened respectively to the cord-connecting elements  22  at upper ends thereof, and a plurality of horizontal slats  26  disposed on said ladder cords  25 . Each of the ladder cords  25  has a vertical front cord portion  251  disposed in front of the slats  26 , a vertical rear cord portion  252  disposed behind the slats  26 , and a slat-supporting cord portion  253  interconnecting the front and rear cord portions  251 ,  252 . The slat-supporting cord portions  253  support the slats  26  respectively thereon. When the controlling rod  24  is operated, the light-adjusting rod  21  and the cord-connecting elements  22  rotate, as described above. This causes the slat-supporting cord portions  253  and therefore, the slats  26  to tilt. Since the process involved in adjusting the angle of the slats  26  is known in the art and is not pertinent to the claimed invention, a detailed description thereof will be omitted herein for the sake of brevity. Lowermost ones of the slats  26  can be received within the storage rail  4 , as shown in  FIG. 3 , to adjust the maximum length of the covering unit  2 , i.e., the length of the covering unit  2  in a completely lowered state.  
         [0015]     The cord-winding device  3  includes a winding unit  31  disposed within the accommodating space  113 , and two lifting cords  32 . The lifting cords  32  extend respectively through two holes  261  (see  FIG. 1 ) in each of the slats  26 . Each of the lifting cords  32  extends through the storage rail  4 , and has a lower end  321  (see  FIG. 2 ) and an upper end  322  (see  FIG. 1 ) that is connected to the cord-winding unit  31  in a known manner. The winding unit  31  imparts a spring force to balance the total weight of the covering unit  2  and the storage rail  4  so as to maintain the storage rail  4  at any position with respect to the headrail  1 . Since the structure and operation of the cord-winding device  3  are known to those skilled in the art, further description thereof will be omitted herein for the sake of brevity. The number of the lifting cords  32  and the ladder cords  25  can be changed according to the size and weight of the covering unit  2 .  
         [0016]     The storage rail  4  is disposed under the covering unit  2 , and is longer than the slats  26 . The storage rail  4  includes a pair of upright front and rear sidewalls  41 , and a horizontal bottom wall  42  having two opposite sides formed respectively and integrally with lower ends of the front and rear sidewalls  41  to define a storage space  43  among the bottom wall  42  and the front and rear sidewalls  41 . The storage space  43  is slightly wider than the slats  26 . Each of the lifting cords  32  extends through the bottom wall  42  of the storage rail  4 , and is formed with a stop element  45  (see  FIG. 2 ) at the lower end  321 , which abuts against a bottom surface of the bottom wall  42  so as to retain the lifting cords  32  on the bottom wall  42 .  
         [0017]     Each of the front and rear sidewalls  41  has an upright plate portion  411  and a horizontal rib  412  formed on an outer surface of the upright plate portion  411 . The storage rail  4  further includes two top cover portions  44  extending respectively and integrally from upper ends of the front and rear sidewalls  41  toward each other. The lowermost slats  26  are disposed between the bottom wall  42  and the top cover portions  44 . The top cover portions  44  are spaced apart from each other by a distance that is smaller than the width of each of the slats  26 . As such, in order to move one of the slats  26  through a space between the top cover portions  44 , it is necessary to tilt the same.  
         [0018]     The retainers  5  are made of a plastic material, and bridge the front and rear sidewalls  41  of the storage rail  4 . Each of the retainers  5  is configured as an inverted U-shaped plate, and includes a pair of front and rear retaining-plate portions  51  and a top plate portion  52 . The top plate portion  52  has two opposite sides that are formed respectively and integrally with upper ends of the front and rear retaining-plate portions  51 . Each of the front and rear retaining-plate portions  51  has an inner surface that is formed with a slot  511 , which has two open ends and which engages the corresponding rib  412  of the storage rail  4 . As such, the retainers  5  are retained on the storage rail  4  so as to prevent removal of the lowermost slats  26  from the storage rail  4 . The top plate portion  52  of each of the retainers  5  has an outer periphery  521  that is formed with a lifting-cord notch  522  and two ladder-cord notches  523 . The lifting-cord notch  522  is disposed between the ladder-cord notches  523 . The lifting cords  32  extend respectively through the lifting-cord notches  522  in the retainers  5 . Therefore, the lifting cords  32  can be guided to move on the storage rail  4  along a straight path. The front and rear cord portions  251 ,  252  of the ladder cords  25  extend respectively through the ladder-cord notches  523  in the retainers  5 . Therefore, the ladder cords  25  can be guided to move along a straight path. The retainers  5  can be pulled upwardly to separate from the storage rail  4 .  
         [0019]     The end caps  6  are sleeved respectively and fixedly on two opposite ends of the storage rail  4 . The end caps  6  are provided for aesthetic reasons and to provide rigidity to the storage rail  4 . An upper end opening  431  (see  FIG. 2 ) is defined between the top cover portions  44  of the storage rail  4  and between the end caps  6 . Each of the retainers  5  covers a portion of the upper end opening  431 . The upper end opening  431  is longer than the slats  26  so as to allow for movement of the same therethrough.  
         [0020]     In use, when the venetian blind is initially mounted to a window (not shown), it is completely lowered and opened, as shown in  FIG. 4 . Subsequently, the lowermost ones of the slats  26 , which are disposed below a bottom edge of the window, are received within the storage rail  4 . As such, the venetian blind of this invention can fit windows of different heights. Preferably, one of the slats  26  is clamped between the top plate portions  52  of the retainers  5  and the top cover portions  44  of the storage rail  4 . This prevents dust from entering into the storage rail  4 .  
         [0021]     The advantages of the venetian blind of this invention can be summarized as follows: 
    (1) The length of the venetian blind can be adjusted with ease.     (2) The structure of the venetian blind is relatively simple. Therefore, the manufacturing costs of the venetian blind are reduced.     (3) The lifting cords  32  are fastened to the storage rail  4  by means of the stop elements  45 , which are disposed under the bottom wall  42  of the storage rail  4  and not within the storage space  43 . Thus, efficient use of the storage space  43  in storing the slats  26  is realized.    
 
         [0025]     With this invention thus explained, it is apparent that numerous modifications and variations can be made without departing from the scope and spirit of this invention. It is therefore intended that this invention be limited only as indicated by the appended claims.