Abstract:
To provide an on-failure blind stopper system that allows reduction of depth of a head box and can be surely activated, A slider capable of moving vertically is disposed in a head box. The slider is pressed by a lifting/lowering cord and prevented from moving upward to permit a rotation shaft to rotate when the lifting/lowering cord is under tension. On the other hand, the slider moves upward to engage with the rotation shaft to prevent the rotation of the rotation shaft when the lifting/lowering cord sags.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to an on-failure blind stopper system that stops rotation of a rotation shaft when a failure occurs during lifting or lowering of a bottom part of a blind whose shielding member(s) is lifted or lowered by that a lifting/lowering cord lifts or lowers the bottom part.  
         [0003]     2. Description of the Related Art  
         [0004]     A known conventional on-failure blind stopper system of this kind is described in Japanese Utility Model Publication No. H3-51516. In this publication, a roller for guiding a lifting/lowering cord is disposed at an opening in a side plate of a support main unit for supporting a take-up drum, and a claw is disposed in the support main unit. The claw has a contact member adapted to abut against the lifting/lowering cord on one side thereof, and is pivoted at one end thereof, and is urged upward at the other end thereof by a spring so that the claw can abut against a ratchet wheel. If a shielding member of the blind bumps against an obstacle, the lifting/lowering cord sags, and the pressing force from the lifting/lowering cord on the contact member is removed. Thus, the claw rotates about the pivot point to engage with the ratchet wheel, thereby stopping the rotation of the take-up drum and stopping the movement of the lifting/lowering cord.  
       SUMMARY OF THE INVENTION  
       [0005]     However, in the type where the claw rotates as described in Japanese Utility Model Publication No. H3-51516, a problem is that the ratchet wheel and the claw cannot be sufficiently spaced apart from each other, and the stroke of the rotation of the claw is short, so that malfunctions are likely to occur.  
         [0006]     In order to sufficiently separate the ratchet wheel and the claw from each other to provide a long stroke, the depth of the head box has to be increased. Thus, the head box disadvantageously becomes large. In particular, when incorporating the blind in a double glazing, the blind having the head box of the increased depth, cannot problematically be assembled into the double glazing because the spacing between the sheets of glass of the double glazing is typically limited to a small dimension, such as within a range of 12 mm to 20 mm.  
         [0007]     The present invention has been devised in view of such problems, and an object of the present invention is to provide an on-failure blind stopper system that allows reduction of depth of a head box and can be surely activated.  
         [0008]     In order to attain the object described above, an on-failure blind stopper system according to the present invention for a blind in which a lifting/lowering cord that vertically moves in response to rotation of a rotation shaft in a head box has a lower end hanging from the head box and connected to a bottom part disposed at the bottom of shielding members, and the shielding member (s) is lifted or lowered by lifting or lowering the bottom part by the lifting/lowering cord, comprises a on-failure stopper assembly that stops rotation of the rotation shaft when a failure occurs in lifting or lowering of the bottom part. The on-failure stopper assembly has a restriction member that is vertically movable in the head box. The restriction member is pressed by the lifting/lowering cord and prevented from moving upward or downward to permit the rotation shaft to rotate when the lifting/lowering cord is under tension and moves upward or downward to engage with the rotation shaft to prevent the rotation of the rotation shaft when the lifting/lowering cord sags.  
         [0009]     Since the restriction member moves in the vertical direction to engage with the rotation shaft to stop the rotation thereof, the stroke can be long, and malfunctions thereof can be prevented. The on-failure stopping operation does not affect the depth of the head box, so that the depth of the head box can be reduced.  
         [0010]     The on-failure stopper assembly can comprise a ratchet that rotates together with the rotation shaft, the restriction member having an engaging part that is movable in a vertical direction and capable of engaging with the ratchet, an elastic member that urges the restriction member upward or downward, and a guide part that is movable in a vertical direction together with the restriction member and with which the lifting/lowering cord is in contact in a slidable manner.  
         [0011]     The engaging part and the guide part may be respectively located on the vertically opposite sides of the rotation shaft. Since the engaging part that engages with the ratchet rotating together with the rotation shaft and the guide part are located on the vertically opposite sides of the rotation shaft, the space in the head box can be used efficiently in the height direction.  
         [0012]     A take-up drum capable of rotating together with the rotation shaft can be provided on the rotation shaft, and the lifting/lowering cord capable of being wound around and unwound from the take-up drum can extend from the take-up drum, subsequently, be guided upward in the head box, be directed in the longitudinal direction of the head box, pass over the guide part of the on-failure stopper assembly, be directed to below the head box and extend to the bottom part. Since the lifting/lowering cord passes over the guide part, unlike the prior art, the lifting/lowering cord does not have to pass through a narrow space, and arrangement of the lifting/lowering cord is facilitated.  
         [0013]     The blind can be incorporated in a double glazing, and a failure may occur in lifting or lowering of the bottom part because of a deformation of the glass of the double glazing, Even in the case where a failure occurs in lifting or lowering of the bottom part because of deformation of the glass of the double glazing incorporating the blind, the movement of the bottom part can be stopped without fail, so that malfunctions or damage to the product can be prevented.  
         [0014]     The present disclosure relates to subject manner contained in Japanese Patent Application No. 2005-324119, filed on Nov. 8, 2005, which is expressly incorporated herein by reference in its entirety. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is a front view of a blind to which an on-failure blind stopper system according to the embodiment of the present invention is applied;  
         [0016]      FIG. 2  is a front view of the blind in the case where an on-failure blind stopper system is activated;  
         [0017]      FIG. 3  is a cross-sectional view taken along the line  3 - 3  in  FIG. 1 ;  
         [0018]      FIG. 4  is a cross-sectional view taken along the line  4 - 4  in  FIG. 3 ;  
         [0019]      FIG. 5  is a cross-sectional view taken along the line  5 - 5  in  FIG. 2 ; and  
         [0020]      FIG. 6  is a cross-sectional view taken along the line  6 - 6  in  FIG. 5 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]     In the following, an embodiment of the present invention will be described with reference to the drawings.  
         [0022]      FIG. 1  is a front view of a blind to which a non-failure blind stopper system according to the embodiment of the present invention is applied.  
         [0023]     A blind  10  shown in this drawing is a double glazing-incorporated type and incorporated in a double glazing  1 . The blind  10  is disposed in a space between the surfaces of two sheets  2 ,  2  of glass of the double glazing  1  as shown in  FIG. 3 . The on-failure blind stopper system according to the present invention is suitable for such a blind disposed in a narrow space in the double glazing  1 . However, the application of the on-failure blind stopper system is not limited thereto, and the on-failure blind stopper system can be applied to a blind that is not incorporated in the double glazing  1 .  
         [0024]     The blind  10  has a head box  12 . Shielding members  14  hang down from the head box  12 , and a bottom part  16  is provided on the lowermost end of the shielding members  14 . Lifting/lowering cords  18  hang down from the head box  12  and are connected to the bottom part  16  at the lower end thereof.  
         [0025]     In the head box  12 , a rotation shaft  20  that extends in the longitudinal direction is rotatably supported, and one end of the rotation shaft  20  is coupled to a manipulation unit  22 . Manipulating the manipulation unit  22  causes the rotation shaft  20  to rotate in either direction  
         [0026]     In addition, a plurality of take-up drums  24  adapted to rotate together with the rotation shaft  20  are attached to the periphery of the rotation shaft  20 , and the upper end of each lifting/lowering cord  18  is connected to its corresponding one of the take-up drums  24 . The lifting/lowering cord  18  can be wound around and unwound from the take-up drum  24 , and winding or unwinding the lifting/lowering cord  18  makes the lower end thereof move upward or downward.  
         [0027]     The lifting/lowering cord  18  extends from the take-up drum  24 , is guided upward in the head box  12 , is directed in the longitudinal direction of the head box  12  by a pulley  26 , passes over on-failure stopper assembly  30  described later and then is redirected to below the head box  12  by a second pulley  28  disposed at the end of the head box  12  so that the lower end of the lifting/lowering cord  18  is directed to the bottom part  16 .  
         [0028]     The on-failure stopper assembly  30  disposed in the head box  12  is preferably provided for each lifting/lowering cord  18 . Specifically, as shown in  FIGS. 3 and 4 , the on-failure stopper assembly  30  comprises a case  32  fixed in the head box  12  through which the rotation shaft  20  passes, a ratchet  34  that is mounted on the rotation shaft  20  in the case  32  so as to rotate together with the rotation shaft  20 , a slider 36  (restriction member) capable of sliding vertically relative to the case  32 , a compression spring  40  (an elastic member) that urges the slider  36  upward, and a guide roller  38  (a guide part) that is supported on the upper end of the slider  36  and is capable of vertically moving together with the slider  36 .  
         [0029]     The slider  36  has vertically elongated openings  36   a ,  36   a  formed in opposite side walls thereof, and the rotation shaft  20  passes through the elongated openings  36   a ,  36   a . An empty space  36   b  is formed between the opposite wide walls, in which the ratchet  34  is disposed. In a lower part of the empty space  36   b , an engaging part  36   c  capable of engaging with the teeth of the ratchet of the ratchet  34  is disposed. In addition, the slider  36  has an engaging bar  36   d  disposed in the upper portion of the empty space  36   b . A stopper  32   a  formed in the case  32  interferes with the engaging bar  36   d  and restricts the vertical movement of the slider  36 .  
         [0030]     The slider  36  has a spring receiving recess  36   e  in the lower part thereof. The compression spring  40  is inserted between the top of the spring receiving recess  36   e  and the bottom of the case  32  and constantly urges upward the slider  36 .  
         [0031]     The guide roller  38  is rotatably supported at the upper end of the slider  36 . The lifting/lowering cord  18  is in contact with the top of the guide roller  38  in a slidable manner, and the guide roller  38  is pressed downward by the tension of the lifting/lowering cord  18 . Alternatively, the guide roller  38  and the slider  36  may be integrally formed as one piece.  
         [0032]     Thus, the guide roller  38  of the on-failure stopper assembly  30  and the engaging part  36   c  of the slider  36  are respectively positioned on the vertically opposite sides of the rotation shaft  20 .  
         [0033]     In the blind arranged as described above, when the rotation shaft  20  and the take-up drums  24  rotate in response to manipulations of the manipulation unit  22 , the lifting/lowering cords  18  are wound around or unwound from the take-up drums  24  depending on the direction of the rotation. The lower end of the lifting/lowering cord  18  is lifted or lowered with the lifting/lowering cord  18  stretched by the weight of the bottom part  16 , and accordingly the bottom part  16  and the shielding members  14  are lifted or lowered.  
         [0034]     During such a normal operation, in the on-failure stopper assembly  30  of the on-failure blind stopper system according to the present invention, the slider  36  is pressed downward against the force of the spring  40  by the tension of the lifting/lowering cord  18 , as shown in  FIGS. 3 and 4 . Therefore, the engaging part  36   c  and the ratchet  34  are separated apart from each other, so that the movement of the lifting/lowering cord  18  is not hindered.  
         [0035]     On the other hand, for example, downward movement of the bottom part  16  may be hindered because the spacing between the sheets of glass  2 ,  2  of the double glazing  1  decreases. Otherwise, even in a case of the blinds other than those disposed in the double glazing  1 , the bottom part  16  may bump against an obstacle during downward movement and thus be hindered from moving. In such cases, if the lowering operation continued, the lifting/lowering cord  18  would sag, and when the lifting/lowering cord  18  becomes able to move again, the sag lifting/lowering cord  18  would be reversely wound around the take-up drum  24 , thereby causing malfunctions or damage to the product. Thus, the movement of the lifting/lowering cord  18  has to be stopped.  
         [0036]     In the on-failure blind stopper system according to the present invention, when the failure described above occurs, the weight of the bottom part  16  and thus the tension are removed from the lifting/lowering cord  18  Thus, the slider  36  moves upward by the operation of the spring  40 , and the engaging part  36   c  engages with the ratchet  34  as shown in  FIGS. 5 and 6 . Then, the rotation shaft  20  becomes unable to rotate in the direction corresponding to the direction of the lowering of the lifting/lowering cord  18 , and the lowering of the lifting/lowering cord  18  stops. In this way, the movement of the lifting/lowering cord  18  can be hindered, thereby preventing malfunctions and damage to the product.  
         [0037]     In the on-failure stopper assembly  30  according to the present invention, since the slider  36  moves in the vertical direction, the stroke can be long, and malfunctions thereof can be prevented. In particular, since the engaging part  36   c  of the slider  36  and the guide roller  38  are respectively disposed on the opposite sides of the rotation shaft  20 , the space in the head box  12  can be used efficiently in the height direction, and as a result, the depth of the head box  12  can be reduced.  
         [0038]     In the example described above, the slider  36  is normally located at the lower position and moves upward when the on-failure blind stopper system is activated. However, the present invention is not limited thereto, and the slider  36  may be normally located at the higher position and move downward by the action of a spring or gravity when the on-failure blind stopper system is activated, as in the case where the lifting/lowering cord  18  is in contact with the bottom of the guide roller  38  in a slidable manner.  
         [0039]     However, passing the lifting/lowering cord  18  over the guide roller  38  as shown eliminates the need for passing the lifting/lowering cord  18  through a narrow space, so that arrangement of the lifting/lowering cord  18  is facilitated.  
         [0040]     While the principles of the invention have been described above in connection with specific embodiments, and particular modifications thereof, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of invention.