Patent Publication Number: US-6659156-B2

Title: Screw transmission mechanism for a blind

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to Venetian blinds and, more specifically, to a screw transmission mechanism for a motor-driven blind. 
     2. Description of the Related Art 
     A regular Venetian blind comprises headrail, a bottom rail, a plurality of slats arranged in parallel between the headrail and the bottom rail, an amplitude modulation control mechanism for controlling lifting and positioning of the bottom rail to change the extending area of the blind, a frequency modulation control mechanism for controlling the tilting angle of the slats to regulate the light. The amplitude modulation control mechanism comprises an endless lift cord suspended from the headrail at one lateral side for pulling by hand to lift/lower the bottom rail. The frequency modulation control mechanism comprises a frequency modulation member disposed at one lateral side of the blind for permitting rotation by the user to regulate the tilting angle of the slats. When adjusting the elevation of the bottom rail, the user must approach the blind and pull the lift cord by hand with much effort. Further, because the lift cord is not kept out of reach of children, children may pull the lift cord for fun. In case the lift cord is hung on a child&#39;s head, a fetal accident may occur. 
     U.S. Pat. No. 5,103,888 discloses a motor-driven blind, which keeps the lift cord from sight. According to this design, a motor is mounted in the headrail or bottom rail, and controlled by a remote controller to roll up or let off the lift cord. The motor is used to control lifting of the lift cord only. When adjusting the tilting angle of the slats, the user must approach the blind and touch-control a tilting control unit. This operation manner is still not convenient. 
     SUMMARY OF THE INVENTION 
     The present invention has been accomplished to provide a screw transmission mechanism for a motor-driven blind, which eliminates the aforesaid drawbacks. It is the main object of the present invention to provide a screw transmission mechanism for a motor-driven blind, which controls lifting/lowering of the slats and bottom rail of the Venetian blind as well as tilting of the slats. It is another object of the present invention to provide a screw transmission mechanism for a motor-driven blind, which is compact, and requires less installation space. It is still another object of the present invention to provide a screw transmission mechanism for a motor-driven blind, which is inexpensive to manufacture. To achieve these objects of the present invention, the screw transmission mechanism is installed in a motor-driven Venetian blind and adapted to lift/lower the slats and bottom rail of the Venetian blind and to tilt the slats, comprising at least one cord roll-up unit and a driving unit adapted to drive the at least one cord roll-up unit. Each cord roll-up unit comprises: an amplitude modulation set, the amplitude modulation set comprising a support, an amplitude modulation lift cord connected to the slats and bottom rail of the Venetian blind and adapted to lift/lower the slats and bottom rail of the Venetian blind, and an amplitude modulation wheel threaded into the support and coupled to the driving unit for free rotation and axial movement relative to the support to roll up/let off the amplitude modulation lift cord upon operation of the driving unit, the amplitude modulation wheel comprising a longitudinal groove; a frequency modulation set, the frequency modulation set comprising a frequency modulation lift cord adapted to tilt the slats of the Venetian blind, and a frequency modulation wheel sleeved onto the amplitude modulation wheel and adapted to roll up/let off the frequency modulation lift cord, the frequency modulation wheel comprising a notch; and a linkage, the linkage comprising a link mounted in the groove of the amplitude modulation wheel and the notch of the frequency modulation wheel to couple the frequency modulation wheel to the amplitude modulation wheel for synchronous rotation, and a stop block adapted to limit the angle of rotation of the frequency modulation wheel and to force the link away from the frequency modulation wheel when the amplitude modulation wheel rotated to a predetermined position. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is an applied view of the present invention, showing the screw transmission mechanism installed in a Venetian blind. 
     FIG. 2 is an exploded view of the cord roll-up unit for the screw transmission mechanism according to the present invention. 
     FIG. 3 is an elevational assembly view of the cord roll-up unit shown in FIG.  2 . 
     FIG. 4 is a sectional view of the cord roll-up unit shown in FIG.  3 . 
     FIGS.  5 ˜ 8  are side views showing continuous action of the amplitude modulation set and the frequency modulation set according to the present invention. 
     FIGS.  9 ˜ 11  are sectional views showing the action of the amplitude modulation set and the frequency modulation set according to the present invention. 
     FIGS.  12 ˜ 14  are schematic drawings showing lift cord rolling up action of the amplitude modulation set according to the present invention. 
     FIG. 15 is a perspective view in an enlarged scale of the detector shown in FIG.  1 . 
     FIGS.  16 ˜ 18  are schematic drawings showing the action of the detector according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. From  1  through  4 , the present invention provides a screw transmission mechanism  100  mountable to a Venetian blind  10 . The Venetian blind  10 , as shown in FIG. 1, comprises a headrail  11  and a slat set  12 . The headrail  11  is mountable to the top side of the window, comprising, an inside holding chamber  111 , and two through holes  112  bilaterally disposed at a bottom side in communication with the holding chamber  111 . The slat set  12  is comprised of a plurality of slats  121  and a bottom rail  123 . Each slat  121  has two-wire holes  122  corresponding to the through holes  112  of the headrail  11 . Because the Venetian blind  10  is of the known art, no further detailed structural description is necessary. The screw transmission mechanism  100  comprises a driving unit  20  and two cord roll-up units  30 . 
     As shown in FIG. 1, the driving unit  20  comprises a reversible motor  21 , a transmission shaft  22 , a signal transmitter  23 , a signal receiver  24 , and a battery  25 . The motor  21  is mounted inside the holding chamber  111  of the headrail  11 . The transmission shaft  22  is a non-circular rod member, having one end coupled to the motor  21  for rotation by the motor  21 . The signal transmitter  23  can be a remote controller or wired controller for providing control signal to the signal receiver  24 . According to the present preferred embodiment, the signal transmitter  23  is a radio transmitter. The signal receiver  24  is electrically connected to the motor  21 , and adapted to control the operation of the motor  21  subject to the nature of the control signal received from the signal transmitter  23 . The battery  25  can be storage battery, dry battery, planar battery, cylindrical battery, or mercury battery mounted inside of the holding chamber  111  and electrically connected to the motor  21  to provide the motor  21  with the necessary working power. 
     Referring to FIGS. From  2  through  4 , the cord roll-up units  30  are respectively mounted inside the holding chamber  111  of the headrail  11  corresponding to the through holes  112 . each comprised of an amplitude modulation set  31 , a frequency modulation set  32 , and a linkage  33 . 
     The amplitude modulation set  31  comprises an amplitude modulation wheel  311 , a support  312 , and an amplitude modulation lift cord  313 . The amplitude modulation wheel  311  is a cylindrical wheel, comprising an axially extended center through hole  311   a  for accommodating the transmission shaft  22  of the driving unit  20 , the center through hole  311   a  having a cross section fitting the cross section of the transmission shaft  22 , an outer thread  311   b  extended around the periphery, and a longitudinal groove  311   c  longitudinally disposed in the periphery and extended to the two distal ends across the outer thread  311   b . The support  312  is fixedly mounted inside the holding chamber  111  of the headrail  11 , having a stepped center through hole formed of a through hole  312   a  and a recessed hole  312   b , and inner threads  312   c  extended around the center through hole  312   a . The inner diameter of the through hole  312   a  is smaller than the recessed hole  312   b  but approximately equal to the outer diameter of the amplitude modulation wheel  311 . The inner thread  312   c  is threaded onto the outer thread  311   b  of the amplitude modulation wheel  311 . As illustrated in FIG. 3, the amplitude modulation lift cord  313  has one end fixedly connected to the amplitude modulation wheel  311 , and the other end inserted through one through hole  112  of the headrail  11  and one wire hole  122  of each slat  121  and then fixedly connected to the bottom rail  123 . 
     The frequency modulation set  32  is comprised of a frequency modulation wheel  321 , and a frequency modulation lift cord  322 . The frequency modulation wheel  321 ; comprises an axially extended circular hole  321   d , a body  321   a  and a head  321   b  disposed around the periphery. The body  321   a  is provided with a notch  321   c . The outer diameter of the head  321   b  is greater than the outer diameter of the body  321   a . The frequency modulation lift cord  322  has one end fixedly connected to the frequency modulation wheel  321 , and the other end inserted through one through hole  112  of the headrail  11  and fixedly connected to each slat  121  and the bottom rail  123 . 
     The linkage  33  comprises a spring  331 , a pressure ring  332 , a stop block  333 , a link  334 , and a limiter  335 . The spring  331  is sleeved onto the amplitude modulation wheel  311  and inserted into the recessed hole  312   b  of the support  312 , having one end supported on the inside wall of the support  312  between the recessed hole  312   b  and the through hole  312   a . The pressure ring  332  is sleeved onto the amplitude modulation wheel  311  and stopped at the other end of the spring  331 . The stop block  333  is fixedly fastened to the support  312  at the outside of the recessed hole  312   b  and stopped at the opposite side of the pressure ring  332  against the spring  331 , having a semi-circular notch  333   a , and two beveled faces  332   b ;  332   c  disposed at two sides of the semi-circular notch  333   a  and respectively downwardly sloping from the top toward the recessed hole  312   b . The link  334  is a L-shaped key inserted into the groove  311   c  of the amplitude modulation wheel  311 . The frequency modulation wheel  321  is sleeved with its circular hole  321   d  onto the amplitude modulation wheel  311 . The link  334  has one part inserted into the notch  321   c  and another part inserted into the groove  311   c  of the amplitude modulation wheel  311 , enabling the amplitude modulation wheel  311  and the frequency modulation wheel  321  to be linked to each other by the link  334 . The limiter  335  is fixedly fastened to the support  312 , stopping the frequency modulation wheel  321  from falling out of the amplitude modulation wheel  311 . 
     The operation of the present invention is outlined hereinafter with reference to FIGS. from  5  through  8 , when the user operated the signal transmitter  23  of the driving unit  20  to transmit a control signal of lifting the Venetian blind, the signal receiver  24  immediately receives the signal. Upon receipt of the signal, the signal receiver  24  drives the motor  21  to rotate the transmission shaft  22 . Because the center through hole  311   a  of the amplitude modulation wheel  311  is a non-circular hole that fits the transmission shaft  22 , rotating the transmission shaft  22  causes the amplitude modulation wheel  311  to be synchronously rotated to roll up the amplitude modulation lift cord  313 , as shown in FIGS. from  12  through  14 . During rotary motion, the amplitude modulation wheel  311  moves axially in the support  312 , keeping the amplitude modulation lift cord  313  to be smoothly wound round the amplitude modulation wheel  311 . When the amplitude modulation wheel  311  rolling up the amplitude modulation lift cord  313 , the bottom rail  123  is lifted, thereby causing the slats  121  to be received and moved with the bottom rail  123  upwards toward the headrail  11  to the desired elevation. 
     Because the linkage  33  links the frequency modulation wheel  321  and the amplitude modulation wheel  311 , the frequency modulation wheel  321  is rotated with the amplitude modulation wheel  311  at this time, as shown in FIGS. 5 and 6 and FIGS. 9 and 10. During rotary motion of the frequency modulation wheel  321 , the frequency modulation lift cord  322  is moved, causing the slats  121  to be tilted. When the frequency modulation wheel  321  turned to a predetermined position (the position where the link  334  touches the beveled face  333   b  of the stop block  333 ), as shown in FIGS. 4,  7 , and  8 , the link  334  moves along the beveled face  333   b  toward the recessed hole  312   b  to push the pressure ring  332  against the spring  331  and to compress the spring  331 , enabling the link  334  to be forced out of the notch  321   c  of the frequency modulation wheel  321  to disconnect the frequency modulation wheel  321  from the amplitude modulation wheel  311 . Therefore, when the frequency modulation wheel  321  rotated to this angle, it is disengaged from the amplitude modulation wheel  311 . At this time, the transmission shaft  22  continuously rotates the amplitude modulation wheel  311  to roll up the amplitude modulation lift cord  313  and to receive the slats  121  without changing the tilting angle of the slats  121 . 
     When releasing the slats  121 , operates the signal transmitter  23  to transmit a control signal of releasing the slats to the signal receiver  24 . Upon receipt of the signal, the signal receiver  24  immediately drives the motor  21  to rotate in the reversed direction, thereby causing the transmission shaft  22  and the amplitude modulation wheel  311  to be rotated in the same direction. Reverse rotation of the amplitude modulation wheel  311  lets off the amplitude modulation lift cord  313 , and therefore the bottom rail  123  and the slats  121  are lowered to extend out the Venetian blind  10 . At the initial stage during rotary motion of the amplitude modulation wheel  311 , the beveled face  333   b  of the stop block  333  keeps the frequency modulation wheel  321 , out of the amplitude modulation wheel  311 . However, when the link  334  moved with the amplitude modulation wheel  311  to the beveled face  333   b , the spring power of the spring  331  forces the pressure ring  332  against the link  334 . When the link  334  moved to the border area of the notch  321   c  of the frequency modulation wheel  321 , it is immediately forced into the notch  321   c , thereby causing the frequency modulation wheel  321  and the amplitude modulation wheel  311  to be linked again. At this time, the frequency modulation wheel  321  is rotated with the amplitude modulation wheel  311  to tilt the bottom rail  123  and the slats  121 . When the link  334  moved to the other beveled face  333   c , the beveled face  333   c  forces the link  334  away from the frequency modulation wheel  321  (see FIG. 11) to disconnect the amplitude modulation wheel  311  from the frequency modulation wheel  321 . At this time, the transmission shaft  22  continuously rotates the amplitude modulation wheel  311  to let off the amplitude modulation lift cord  313  and to release the slats  121  without changing the tilting angle of the slats  121 . 
     With respect to the tilting of the slats  121 , the operation is described hereinafter. At first, the user operates the signal transmitter  23  to transmit a slat tilting control signal to the signal receiver  24 . Upon receipt of the control signal, the signal receiver  24  immediately drives the motor  21  to rotate the transmission shaft  22  and the amplitude modulation wheel  311 , and to further forces the link  334  into engagement with the amplitude modulation wheel  311  and the frequency modulation wheel  321 , permitting synchronous rotation of the frequency modulation wheel  321  with the amplitude modulation wheel  311  to let off the frequency modulation lift cord  322  and to further control the tilting angle of the slats  121 . In actual practice, it is not necessary to tilt the slats  121  at a wide angle, therefore the angle of rotation of the frequency modulation wheel  311  can be limited within a limited range. According to the present preferred embodiment, the frequency modulation wheel  321  is rotatable with the amplitude modulation wheel  311  within about 180°. The stop block  333  limits the angle of rotation of the frequency modulation wheel  311 . When the slats  121  tilted to the desired angle, the motor  21  is stopped. (during the aforesaid slat angle tilting control operation, the amount of upward or downward movement of the bottom rail  11  due to rotation of the amplitude modulation wheel  311  is insignificant, without affecting the reliability of the operation). 
     Referring to FIG.  1  and FIGS. 15 and 18, the screw transmission mechanism  100  further comprises a detector  60  installed in the middle of the transmission shaft  22 . When the slats  121  moved to the upper limit or lower limit position, the detector  60  is induced to stop the motor  21 . According to the present preferred embodiment, the detector  60  comprises a mounting plate  61 , a wheel  62 , two limit switches  63 ; 64 , and a locating block  65 . The mounting plate  61  is fixedly fastened to the peripheral wall of the holding chamber  111  of the headrail  11 . The locating block  65  is fixedly mounted inside the holding chamber  111  of the headrail  11 . having a center screw hole  651 . The wheel  62  is coupled to the transmission shaft  22  for synchronous rotation, having an outer thread  621  threaded into the center screw hole  651  of the locating block  65 . Rotation of the transmission shaft  22  causes synchronous rotation of the wheel  62  with the transmission shaft  22  and axial movement of the wheel  62  in the locating block  65 . The limit switches  63 ; 64  are respectively mounted on the mounting plate  61  at two sides relative to the wheel  62  (in such positions where the wheel  62  touches one limit switch  63  or  64  when the slats  121  moved to the upper limit or lower limit position), and electrically connected to the motor  21 . When the slats  121  moved to the upper or lower limit position, the wheel  62  touches one limit switch  63  or  64 , thereby causing the limit switch  63  or  64  to cut off power supply from the motor  21 . 
     The structure and function of the present invention are well understood from the aforesaid detailed description. The advantages of the present invention are outlined hereinafter. 
     1. Slat lifting and tilting dual-control function: 
     The link serves as clutch means to couple the amplitude modulation wheel, which controls lifting of the slats, and the frequency modulation wheel, which controls tilting of the slats, enabling the amplitude modulation wheel and the frequency modulation wheel to be driven by same driving source to lift or tilt the slats. 
     2. Single drive source and compact size: 
     Because the link serves as clutch means to couple the amplitude modulation wheel and the frequency modulation wheel, one single driving source is sufficient to drive the amplitude modulation wheel and the frequency modulation wheel. Therefore, the invention is compact and inexpensive, and requires less installation space. 
     3. Durable mechanical design: 
     Because the screw transmission mechanism is provided with a detector, the motor is immediately stopped when the slats moved to the upper or lower limit position, preventing damage to the parts of the mechanism.