Patent Publication Number: US-6662850-B2

Title: Lift coard concealable venetian blind lift control mechanism

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to Venetian blinds and, more specifically, to a lift cord concealable Venetian blind lift control mechanism for use in a Venetian blind for lifting control that keeps the lift cords from sight and from reach of children. 
     2. Description of the Related Art 
     A regular Venetian blind is generally comprised of a top rail, a bottom rail, a plurality of slats arranged in parallel between the top rail and the bottom rail, a lift control mechanism for controlling lifting and positioning of the bottom rail to adjust the extending area of the Venetian blind, and a tilting control mechanism for controlling the tiling angle of the slats to regulate the light. The lift control mechanism comprises a lift cord suspended from the top rail at one side for operation by hand to control the elevation of the bottom rail. Because the lift cord is exposed to the outside, it destroys the sense of beauty of the Venetian blind. Further, because a child can easily reach the exposed lift cord, an accident may occur when a child pulling the lift cord for fun. 
     U.S. Pat. No. 6,024,154 discloses a Venetian blind lift control mechanism, which keeps the lift cords from sight. It is to be noted that the marked numbers described hereunder are quoted directly from U.S. Pat. No. 6,024,154. According to this design, the Venetian blind lift control mechanism comprises a T-shaped retaining member  51  mounted inside the bottom rail  22  on the middle, two lift cord take-up members  32  respectively pivoted to the T-shaped retaining member  51  at two sides and adapted to wind up the lift cords  41  of the Venetian blind, and two spring means  33  adapted to provide a torsional force to the lift cord take-up members  32  respectively. The T-shaped retaining member  51  has a rack  512 , which is forced by springs  513  into engagement with engagement means  322  of the lift cord take-up members  32  to stop the lift cord take-up members  32  from rotary motion, keeping the bottom rail  22  at the desired height. When the user pressed the T-shaped retaining member  51 , the lift cord take-up members  32  are released for free rotation. At this time, the user can lift the bottom rail  22  for enabling the torsional force of the spring means  33  to force the lift cord take-up members  32  to wind up the lift cords  41 , or pull the bottom rail  22  downward against the torsional force of the spring means  33 , so as to adjust the bottom rail  22  to the desired height. This Venetian blind lift control mechanism is complicated, resulting in high manufacturing cost and complicated installation procedure. Further, when adjusting the elevation of the bottom rail, the user has to press the T-shaped retaining member with one hand and move the bottom rail with the other hand. 
     SUMMARY OF THE INVENTION 
     The present invention has been accomplished to provide a lift cord concealable Venetian blind lift control mechanism, which eliminates the aforesaid drawbacks. It is the main object of the present invention to provide a lift cord concealable Venetian blind lift control mechanism, which keeps the lift cords of the Venetian blind from sight and out of reach of children. It is another object of the present invention to provide a lift cord concealable Venetian blind lift control mechanism, which is easy to operation. It is still another object of the present invention to provide a lift cord concealable Venetian blind lift control mechanism, which is simple and inexpensive to manufacture. To achieve these objects of the present invention, the lift cord concealable Venetian blind lift control mechanism is installed in a Venetian blind, which comprises a top rail, a bottom rail, a plurality of slats arranged in parallel between the top rail and the bottom rail, and two lift cords vertically inserted through the slats and arranged in parallel. The lift cord concealable Venetian blind lift control mechanism comprises a base installed in one of the top and bottom rails of the Venetian blind, the base comprising two screw rods axially horizontally aligned in a line between the lift cords, an axle hole axially extended through the screw rods; a revolving rod inserted through the axle hole of the base for free rotation relative to the base, the revolving rod having two distal ends respectively extended out of the screw rods; a spring member mounted in the base and adapted to impart a torsional force to the revolving rod; and two bobbins respectively threaded onto the screw rods and coupled to the ends of the revolving rod for synchronous rotation with said revolving rod and for axial movement relative to the screw rods to wind up/let off the lift cords upon forward/backward rotation of the revolving rod. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an elevational assembly view of a lift cord concealable Venetian blind lift control mechanism according to the preferred embodiment of the present invention. 
     FIG. 2 is an exploded view of the lift cord concealable Venetian blind lift control mechanism according to the preferred embodiment of the present invention. 
     FIG. 3 is a sectional view taken along line  3 — 3  of FIG.  1 . 
     FIG. 4 is similar to FIG. 3 but showing the bobbins respectively moved from the right side position to the left side position. 
     FIG. 5 is an applied view of the present invention, showing he lift cord concealable Venetian blind lift control mechanism installed in a Venetian blind. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. from  1  through  3 , a lift cord concealable Venetian blind lift control mechanism  20  is shown comprised of a base  30 , a revolving rod  40 , a spring member  50 , and two bobbins  60 . 
     The base  30  comprises a casing  31  defining a receiving chamber  32 , two screw rods  33  of same diameter and same thread design respectively horizontally extended from the left and right sides of the casing  31  and aligned in a line, an axle hole  34  of circular cross-section axially extended through the screw rods  33  and the casing  31 , two arm rods  35  respectively horizontally extended from the left and right sides of the casing  31  in parallel to the screw rods  33  at a lower elevation, and two pulleys  36  respectively provided to the free ends of the arm rods  35 . The arm rods  35  have a length approximately equal to the screw rods  33 . The pulleys  36  are disposed in such a direction that the central axis of the pulleys  36  extends perpendicular to the central axis of the arm rods  35 . 
     The revolving rod  40  is a round rod inserted through the axle hole  34  of the base  30  for free rotation in the axle hole  34 , having two plug portions  41  of non-circular cross-section respectively axially disposed at the ends. 
     The spring member  50  is, for example, a torsional spring mounted in the receiving chamber  32  of the base  30 , having one end fixedly fastened to the base  30  and the other end fixedly fastened to the revolving rod  40  for imparting a torsional force to the revolving rod  40  in one direction (at the view angle shown in FIGS. 1 and 2, the spring member  50  imparts a torsional force to the revolving rod  40  in counter-clockwise direction). 
     The bobbins  60  are cylindrical members, each comprising a threaded receiving hole  61  axially extended to one end and respectively threaded onto the screw rods  33  respectively, and a plug hole  62  of non-circular cross-section axially extended to the other end in communication with the threaded receiving hole  61  and respectively forced into engagement with the plug portions  41  of the revolving rod  40 . After installation of the bobbins  60  in the revolving rod  40 , the bobbins  60  can be synchronously rotated with the revolving rod  40 . Because the bobbins  60  are respectively threaded onto the screw rods  33 , the bobbins  60  can be rotated forwards/backwards relative to the screw rods  33 . According to the present preferred embodiment, the threads of the screw rods  33  have same pitch, and are extended in same direction. Therefore, the bobbins  60  can be moved in same direction as same speed. 
     According to the aforesaid arrangement of the screw rods  33  and the bobbins  60 , the left bobbin  60  moves gradually outwards (leftwards) relative to the corresponding screw rod  33  when rotated in counter-clockwise direction, and at the same time the right bobbin  60  moves inwards (leftwards) relative to the corresponding screw rod  33 , i.e. the bobbins  60  are respectively moved from the positions shown in FIG. 3 to the positions shown in FIG. 4 during counter-clockwise rotation. On the contrary, the left bobbin  60  moves gradually inwards (rightwards) relative to the corresponding screw rod  33  when rotated in clockwise direction, and at the same time the right bobbin  60  moves outwards (rightwards) relative to the corresponding screw rod  33 , i.e. the bobbins  60  are respectively moved from the positions shown in FIG. 4 to the positions shown in FIG. 3 during clockwise rotation. 
     FIG. 5 shows the lift cord concealable Venetian blind lift control mechanism installed in a Venetian blind  10 . The Venetian blind  10  comprises a top rail  12  fixedly fastened to the top side of the window, a bottom rail  14  disposed at a lower side in parallel to the top rail  12 , a plurality of slats  16  arranged in parallel between the top rail  12  and the bottom rail  14 , and two lift cords  18  vertically inserted through the slats  16  near the left and right sides (the slat tilting control arrangement of the Venetian blind is of the known art and not within the scope of the claims of the present invention, no further detailed description is needed in this regard). 
     The lift control mechanism  20  is installed in the middle of the top rail  12 , i.e., the base  30  is fixedly fastened to the inside of the top rail  12  on the middle, keeping the screw rods  33  respectively aimed at the left and right sides of the Venetian blind  10 . Further, the lift cords  18  each have a bottom end respectively fixedly fastened to the bottom rail  14 , and a top end inserted into the inside of the top rail  12  and turned toward the center of the top tail  12  and then extended over the bottom side of the corresponding pulley  36  and then turned upwards and fixedly fastened to the left end of the periphery of the corresponding bobbin  60  (i.e., the left-sided lift cord  18  is fixedly fastened to the outer end of the left-sided bobbin  60 ; the right-sided lift cord  18  is fixedly fastened to the inner end of the right-sided bobbin  60 ), keeping the cord body of each lift cord  18  wound round the periphery of the corresponding bobbin  60 . 
     When the Venetian blind  10  extended out (i.e., the bottom rail  14  is lowered to the bottom side) as shown in FIGS. 3 and 5, the bobbins  60  are respectively disposed at the right side of the respective movable range, and the lift cords  18  each have only a small part respectively wound round the bobbins  60 . When moving the bobbins  60  toward the left side (counter-clockwise rotation under the view angle of FIG.  1 ), the bobbins  60  are rotated to wind up the lift cords  18  (see FIGS.  3  and  4 ). On the contrary, when moving the bobbins  60  toward the right side (clockwise rotation under the view angle of FIG.  1 ), the bobbins  60  are rotated to let off the lift cords  18 . 
     As stated above, the spring member  50  imparts a torsional force to the revolving rod  40  in counter-clockwise direction, thereby causing the bobbins  60  to be rotated toward the left side (to wind up the lift cords  18 ). Because the top ends and bottom ends of the lift cords  18  are respectively fastened to the bobbins  60  and the bottom rail  14 , the gravity weight of the slats  16  and the bottom rail  14  impart a torsional force to the bobbins  60  in clockwise direction, thereby causing the bobbins  60  to be rotated toward the right side (to let off the lift cords  18 ). Because the aforesaid two reversed torsional forces are approximately equal (by means of controlling the spring power of the spring member  50  or the weight of the bottom rail  14 , the two reversed torsional forces can easily be balanced) and the bobbins  60  are respectively supported on the screw rods  33 , the stretching force of the lift cords  18  biases the axis of the bobbins  60  slightly away from the axis of the screw rods  33 , thereby causing a friction resistance to be produced between the bobbins  60  and the screw rods  33  to stop the bobbins  60  from free rotation relative to the screw rods  33 , i.e., the current length of the lift cords  18  wound round the bobbins  60  as well as the current vertical distance between the top rail  12  and the bottom rail  14  are maintained unchanged, i.e., the lift cords  18  are capable of lifting the bottom rail  12  to a predetermined height. 
     If the user holds the bottom rail  14  of the Venetian blind  10  and pulls it downwards, the downward pulling force of the lift cords  18  surpasses the torsional force of the spring member  50  (the difference between the aforesaid two reversed torsional forces surpasses the friction resistance between the bobbins  60  and the screw rods  33 ), and therefore the bobbins  60  are synchronously rotated rightwards to release the lift cords  18  at same speed, enabling the bottom rail  14  to be lowered and keeping the bottom rail  14  in horizontal when lowered. If the user releases the hand from the bottom rail  14 , the two reversed torsional forces are returned to the balanced status immediately, thereby causing the bottom rail  14  to be held at the current height. On the contrary, if the user lifts the bottom rail  14  with the hand, the downward pulling force of the lift cords  18  is reduced, and the torsional force of the spring member  50  immediately rotates the bobbins  60  toward the left side, thereby causing the bobbins  60  to wind up the lift cords  18  and to lift the bottom rail  14  until the user has released the hand from the bottom rail  14 . 
     As indicated above, the present invention provides a lift cord concealable Venetian blind lift control mechanism that stably controls closing, opening, and elevational positioning actions of the Venetian blind, and keeps the lift cords from sight. Because the lift cords are kept from sight, the Venetian blind causes a sense of beauty and, keeps the lift cords from reach of children. The structure of the lift cord concealable Venetian blind lift control mechanism is simple, resulting in low manufacturing cost and convenient installation. When adjusting the extending area (elevation) of the Venetian blind, the user needs only to pull or lift the bottom rail of the Venetian blind with the hand to the desired height. 
     The lift cord concealable Venetian blind lift control mechanism of the present invention can also be selectively installed in the bottom rail of the Venetian blind. In this case, the top ends of the lift cords are respectively fixedly fastened to the top rail, and the bottom ends of the lift cords are respectively wound round the bobbins. 
     As another alternate form of the present invention, the screw rods have threads extended in reversed directions, and the bobbins are moved axially in reversed directions when rotated in one direction, i.e., the bobbins are respectively moved toward the base when rotated in one direction, or moved away from the base in reversed directions when rotated in the other direction. 
     Furthermore, a friction member may be installed in the receiving chamber  32  of the base  30  and disposed in contact with a friction portion of the revolving rod  40  so that a friction force is produced between the revolving rod  40  and the base  30  to stop the revolving rod  40  from rotary motion relative to the base  30  when the bottom rail of the Venetian blind receives no pressure from the user.