Patent Publication Number: US-11377906-B2

Title: Cordless blind device for external power drive

Description:
TECHNICAL FIELD 
     The present invention relates to a cordless blind device for external power drive and, more particularly, a cordless blind device for external power drive, the cordless blind device being able to be conveniently operated by directly moving a screen without a cord and being able to be operated by separate external power. 
     BACKGROUND ART 
     A blind device is installed to block direct sunlight passing through a window or gaze from the outside. It is possible to make a more comfortable indoor mood from soft glow effect by appropriately adjusting the amount of light using a blind device. A blind device is installed over a window and has a structure that can be opened/closed. 
     A blind device may include a screen that is wound or unwound in a form of a roll. It is possible to open a portion or the entire of a window and adjust the amount of light by adjusting the size of the screen. In such a roll type blind device, it is possible to adjust the size of the screen using a cord (pulling string) that rotates the roll. 
     That is, existing blind devices are formed such that a user can easily rotate a roll installed at the top of a window by applying tension by pulling down a cord. However, according to this structure, force is concentrated only on the side connected with the cord, so there is a problem that blind devices are unbalanced or the joint between the roll and the cord is easily broken when it is repeatedly used. 
     Further, when a cord is hung down too long, people, particularly, careless children easily trip on it, so there is a high possibility of a safety accident. Further, it is required to rotate the entire roll while maintaining balance with a cord connected to a side of the roll, so there are many problems with the driving structure using a cord, such as an unnecessarily complicated rotation structure, and the problems need to be resolved. 
     Further, when a cord is not used to solve the problems and a blind device is installed high over a window, it may be difficult to operate the blind device due to problems such as people cannot reach the blind device, these problems also need to be resolved. 
     CITATION LIST 
     Patent Literature 
     [Patent Literature 1] 
     Korean Utility Model No. 20-0480955 (2016.07.29) 
     SUMMARY OF INVENTION 
     Technical Problem 
     The present invention has been made in an effort to solve the problems, and an object of the present invention is to provide a cordless blind device for external power drive, the cordless blind device being able to be conveniently operated by directly moving a screen without a cord and being able to be operated by separate external power. 
     The object of the present invention is not limited to those described above, and other objects may be made apparent to those skilled in the art from the following description. 
     Solution to Problem 
     A cordless blind device for external power drive of the present invention includes: a winding roll rotatably coupled to a pair of fixing brackets disposed at both ends, respectively; a screen being wound on or unwound from the winding roll; a weight connected to a lower end of the screen and applying torque in a first direction in which the screen is unwound from the winding roll by gravity; an elastic member applying torque in a second direction in which the screen is wound by applying elasticity to the winding roll; and a power conversion module disposed in at least one of the pair of fixing brackets and including a first driving shaft connected to the winding roll, a second driving shaft exposed outside the fixing bracket and connected with a driving device connector, and a gear box connecting the first driving shaft and the second driving shaft and transmitting power in two directions. 
     The first driving shaft may be coaxially disposed with the winding roll, and the second driving shaft may extend downward from the fixing bracket. 
     The first driving shaft and the second driving shaft may perpendicularly cross each other. 
     The gear box may include a pair of bevel gears. 
     The driving device connector may have a tool insertion groove recessed coaxially with the second driving shaft. 
     An end connected to the first driving shaft of the gear box may be inserted in the winding roll and the other end connected to the second driving shaft may be positioned in the fixing bracket. 
     The gear box may generate resistance that offsets a resultant force of torque applied to the winding roll in the first direction and torque applied to the winding roll in the second direction. 
     The magnitude of the resistance may be adjusted by adjusting a gap between gears in the gear box. 
     The elastic member may be a torsional elastic member keeping elastic energy by elastically deforming with rotation of the winding roll. 
     The torsional elastic member may be a coil spring fitted on an outer side of a rotary shaft connected to the winding roll. 
     The cordless blind device may further include a driving device separably coupled to the driving device connector and providing a driving force to the second driving shaft. 
     Advantageous Effects of Invention 
     According to the present invention, there is no cord for operating the screen, so it is possible to remarkably reduce the possibility of a negligent accident of children and it is possible to simply adjust the height of the screen without a cord. 
     Further, since the cordless blind device can be operated by power provided from the outside using a separate tool, it is possible to operate the screen even at a height that is not reached by a hand. In particular, since it is possible to conveniently operate the screen using common electric tools that are generally used at home, it is possible to achieve a blind device that is electrically operated without additional cost. 
     Further, since it is possible to use simple manual tools in addition to electric tools, it is possible to vary external power that is applied, depending on the situation of user. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of a cordless blind device for external power drive according to an embodiment of the present invention. 
         FIG. 2  is an exploded perspective view of a winding roll of the blind device shown in  FIG. 1 . 
         FIG. 3  is a cross-sectional view showing the internal structure of the winding roll of the blind device shown in  FIG. 1 . 
         FIG. 4  is a cross-sectional view showing the internal structure of a fixing bracket of the cordless blind device shown in  FIG. 1 . 
         FIGS. 5A-5B and 6A-6B  are views showing the operation of the blind device shown in  FIG. 1  by directly moving up/down the screen. 
         FIG. 7  is a view showing the operation of the blind device shown in  FIG. 1  using external power. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The advantages and features of the present invention, and methods of achieving them will be clear by referring to the exemplary embodiments that will be described hereafter in detail with reference to the accompanying drawings. However, the present invention is not limited to the exemplary embodiments described hereafter and may be implemented in various ways, and the exemplary embodiments are provided to complete the description of the present invention and let those skilled in the art completely know the scope of the present invention. The present invention is defined by claims. Like reference numerals indicate the same components throughout the specification. 
     Hereafter, a cordless blind device according to an embodiment of the present invention will be described in detail with reference to  FIGS. 1 to 7 . 
       FIG. 1  is a perspective view of a cordless window blind according to an embodiment of the present invention,  FIG. 2  is an exploded perspective view of a winding roll of the blind device shown in  FIG. 1 , and  FIG. 3  is a cross-sectional view showing the internal structure of the winding roll of the blind device shown in  FIG. 1 . The screen shown in  FIG. 1  is not shown in  FIG. 2  and to more clearly show the mechanical structure. 
     Referring to  FIGS. 1 to 3 , a cordless blind device  1  for external power drive according to an embodiment of the present invention (hereafter, referred to as a cordless blind device), as shown in the figures, has a very simple external shape without a cord (pulling string). The cordless blind device  1  is designed to maintain balance using its own elasticity, so it can be very simply operated in an automatic or semiautomatic type. If necessary, it has a convenient function, that is, it can be operated by a driving force provided from the outside of the device. That is, the cordless blind device  1  of the present invention can be conveniently operated even without a cord because the elasticity and the weight of the components of the device are equilibrated, and if necessary, it can be operated by a driving force provided from a separate external driving device. In particular, even if the blind device is installed high and a person has difficulties to directly touch it, the blind device has an advantage that it can be very conveniently operated using a separate driving device. 
     The cordless blind device  1  is easily operated even without a cord by rotational forces (torque) that are applied to the winding roll  100  in opposite directions. The rotational force is generated in a pair by an elastic member (see  400  in  FIGS. 2 and 3 ) connected to the winding roll  100  and the weight of a screen  200  being wound on or unwound from the winding roll  100  and a weight  300  connected to the screen  200 . The rotational forces (torque) generated in a pair are increased or decreased while maintaining balance depending on the unwound length of the screen  200 . Since the rotational forces (first-directional torque (see T 1  in  FIGS. 5 and 6 ) and second-directional torque (see T 2  in  FIGS. 5 and 6 ) generated in a pair are equilibrated but act in opposite directions, it is possible to easily break the equilibrium by applying a minimum external force (which can be easily transmitted by touching the screen or the weight) and easily restore the equilibrium by removing the external force. Accordingly, it is possible to rotate the winding roll  100  by applying external force in a desired direction or stop the winding roll  100  at the rotated position by removing the external force. 
     Further, there may be a subtle difference between the magnitudes of torque due to reasons related to the structure, design, and manufacturing process, but it is possible to solve this problem by generating resistance using a power conversion module  100  connected to the winding roll  100 . That is, it is possible to more easily maintain a stop status by offsetting the resultant force of opposite torque with resistance of the power conversion module  110 . The resistance of the power conversion module  110  acts in a direction in which a motion is stopped by friction generated in a driving structure included in the power conversion module  110 , whereby it is possible to prevent undesired rotation of the winding roll  100  and easily maintain the stop status until an appropriate external force is transmitted. As described above, by the structure using the pair of rotational forces acting in opposite directions and resistance such as friction force, it is possible to very conveniently operate the blind device even without a cord. 
     Further, since the power conversion module  110  transmits an external driving force to the winding roll  100  by connecting the winding roll  100  to an external driving device (see A in  FIG. 7 ), it is possible to automatically operate the blind device by providing a rotational force to the winding roll  100  using the external driving device. In particular, when the blind device is operated by the external driving device, it is possible to very conveniently operate the blind device by connecting a driving device, etc., to the power conversion module  110  even if the blind device is installed at a relatively high position that a person has difficulties in directly touching. The external driving device may be provided together with the blind device, but it is possible to directly use electric tools at home as the external driving device, so it is possible to more conveniently operate the cordless blind device  10  of the present invention using various tools. 
     The cordless blind device for external power drive, in detail, includes: a winding roll  100  rotatably coupled to a pair of fixing brackets  610  and  620  disposed at both ends, respectively; a screen  200  being wound on or unwound from the winding roll  100 ; a weight  300  connected to the lower end of the screen  200  and applying torque in a first direction in which the screen  200  is unwound from the winding roll  100  by gravity; an elastic member  400  applying torque in a second direction in which the screen  200  is wound by applying elasticity to the winding roll  100 ; and a power conversion module  110  disposed in at least one of the pair of fixing brackets  610  and  620  and including a first driving shaft  111  connected to the winding roll  100 , a second driving shaft  112  exposed outside the fixing bracket  610  and connected with a driving device connector  112   a , and a gear box  113  connecting the first driving shaft  111  and the second driving shaft  112  and transmitting power in two directions. The cordless blind device  1  having this characteristic is described hereafter in more detail with reference to the drawings. 
     The winding roll  100  is formed in a cylindrical shape. The winding roll  100  may be formed in a hollow cylindrical shape, as shown in  FIGS. 1 to 3 . The winding roll  100  may be disposed between fixing brackets  610  and  620  to which a rotary shaft is fixed, and the fixing brackets  610  and  620  may be combined with a housing (indicated by dotted lines in  FIG. 1 ) that keeps the winding roll  100  therein. Since the winding roll  100  is hollow, the rotary shaft can be inserted in the winding roll  100 . Further, the elastic member  400  and the power conversion module  110  can also be inserted in the winding roll  100 . However, the winding roll  100  is not necessarily limited to a cylindrical shape, and at least a portion of the winding roll  100  may be changed in an appropriate shape that easily winds or unwinds the screen  200 . The winding roll  100  may be rotatably coupled to a shaft structure having various shapes and rotatably supporting the winding roll  100 . 
     The shaft structure rotatably supporting the winding roll  100  may include the driving shaft (first driving shaft  111 ) of the power conversion module  110  and a rotary shaft  120  connected to the elastic member  400 . As in an embodiment of the present invention, these components may be coupled to and rotatably supported at both ends of the winding roll  100 . By separately coupling the shaft structure to different ends, it is possible to more efficiently use the internal space of the winding roll  100 . However, the present invention is not limited thereto, and shaft structures that can rotatably support the winding structure in various ways may be used. 
     The screen  200  is wound on or unwound from the winding roll  100 . The screen  200  can be wound on the winding roll  100  or unwound from the winding roll  100  when the winding roll  100  is rotated. An end of the screen  200  may be connected to the winding roll  10  to rotate with the winding roll  100  and the other end may be connected and fixed to the weight  300 . Assuming that the screen  200  is unwound when the winding roll  100  is rotated in a predetermined direction, the screen  200  can be wound when the roll winding  100  is rotated in the opposite direction. The screen  200  may be made of fabric, but is not limited thereto. The screen  200  may be made of various flexible materials. 
     The weight  300  is connected to the lower end of the screen  200 . As shown in  FIG. 1 , the weight  300  is connected to the lower end of the screen  200 , so the screen  200  can be unrolled. The weight  300  has appropriate mass, so it transmits tension due to gravity to the screen  200 , and the tension transmitted to the screen  200  can act as a rotational force (torque) that rotates the winding roll  100 . That is, the weight  300  is connected to the lower end of the screen  200 , so it applies torque (rotational force) to the winding roll  100  in a first direction in which the screen  200  is unwound by gravity. The weight  300  may be formed in a bar shape having a length corresponding to the width of the screen  200 , but it may be formed in other various shapes. 
     The elastic member  400  applies torque in a second direction in which the screen  200  is wound, by applying elasticity to the winding roll  100 . The elastic member  400  may be disposed in the winding roll  100 , as shown in  FIG. 2 . That is, since the elastic member  400  is provided, torque is applied to the winding roll  100  in the opposite direction to the first direction in which the weight  300  applies torque, so the winding roll  100  can be balanced. The elastic member  400  may be a torsional elastic body that keeps elastic energy by elastically deforming with rotation of the winding roll  100 , and the torsional elastic body may be a coil spring fitted on the outer side of the rotary shaft. For example, as shown in  FIG. 2 , the elastic member  400  that is a torsional elastic body may be a coil spring fitted on the outer side of the rotary shaft  120 , as shown in  FIG. 2 . 
     The more the winding roll  100  is rotated, the larger the deformation of the elastic member  400 , and accordingly, the larger the restoring force. The restoring force acts in the opposite direction to the rotation causing the deformation, so it generates a rotational force in the opposite direction. For example, when the screen  200  is unwound, as the winding roll  100  is rotated in the unwinding direction, the rotational force in the opposite direction, that is, a winding direction (the second direction described above) is increased by elasticity. Further, since the length of the screen  200  increases when the screen  200  is unwound, the rotational force in the unwinding direction (the first direction described above) due to gravity is also increased by the sum of the weights of the weight  300  and the screen  200 . Accordingly, the first-directional rotational force (torque) and the second-directional rotational force (torque) are increased while maintaining equilibrium. By the equilibrium of the rotational forces, it is possible to simply rotate the winding roll  100  and easily stop the winding roll  100  at a rotated position. Detailed operation will be described in more detail below. 
     The elastic member  400  is disposed between the rotary shaft  120  and the winding roll  100  and can generate torque. The elastic member  400 , for example, may be coupled to the winding roll  100  through a rotary block that is coupled to the winding roll  100  to rotate. The rotary shaft  120  extends to the inside of the winding roll  100 , and a rotary block  410  that is coupled to the winding roll  100  to rotate with the winding roll  100  may be formed in the winding roll  100 . The elastic member  400 , as shown in  FIG. 3 , may have both ends respectively connected and fixed to sides of the rotary block  410  and the rotary shaft  120 . The rotary shaft  120  may pass through the rotational center of the rotary block  410 , and a holder  411  formed around the outer side of the rotary block  410  is fitted on a guide rail (see  101  in  FIGS. 2 and 3 ) on the inner side of the winding roll  100 , so the winding roll  100  and the rotary block  410  can be rotated together. 
     According to this structure, when the winding roll  100  is rotated, the rotary block  410  is also rotated and the end, which is connected to the rotary block  410 , of the elastic member  400  can be twisted and deformed. The rotary shaft  120  rotatably supports the winding roll  100 , but does not rotate by itself, so the other end, which is fixed to the rotary shaft  120 , of the elastic member  400  is maintained fixed. Accordingly, torsion is generated between an end and the other end of the elastic member  400 , whereby elastic energy is stored. The elastic member  400  can be configured in this way. However, the configuration of the elastic member  400  is not limited thereto and the elastic member  400  may be configured in other ways that can apply a rotational force by applying elasticity to the winding roll  100 . 
     The rotary shaft  120  may be coupled and fixed to the fixing bracket  620 . A fixing portion  120   b  having various shapes may be formed and firmly fixed at the end, which faces the fixing bracket  620 , of the rotary shaft  120 . For example, the fixing portion  120   b  may be formed in various ways by compounding various fixing structures such as a fitting structure of a projection and a hole or a thread-fastening structure. Further, a rotary ring  120   a  is rotatably fitted on the circumference of the rotary shaft  120 , and, as shown in  FIG. 3 , may be coupled to an end of the winding roll  100 . Accordingly, the winding roll  100  can be supported by the rotary ring  120   a  to rotate. 
     The holder  411  of the rotary block  410  may be slidably coupled to the guide rail (see  101  in  FIG. 2 ) disposed in the winding roll  100 . Accordingly, the rotary block  410  can horizontally move while rotating with the winding roll  100 . The guide rail  101  extends in parallel with the rotary shaft  120 , thereby being able to guide the sliding in parallel with the rotary shaft (see  FIGS. 5 and 6 ). Accordingly, the rotary block  410  can easily cope with the length of the elastic member  400 , which contracts or stretches, by horizontally moving in the longitudinal direction of the rotary shaft  120  while rotating. Therefore, it is possible to achieve a structure that more flexibly cope with elastic deformation. 
     Hereafter, the power conversion module is described in more detail with reference to  FIGS. 1 to 4 . 
       FIG. 4  is a cross-sectional view showing the internal structure of a fixing bracket of the cordless blind device shown in  FIG. 1 . 
     The power conversion module  110  is, as described above, disposed in the fixing bracket  610 . The power conversion module  110 , as shown in  FIGS. 2 and 4 , may be disposed in one, which is not connected with the rotary shaft  120 , of the fixing brackets  610  and  620  at both ends of the winding roll  100 . The power conversion module  110  includes the first driving shaft  111  connected to the winding roll  100  and the second driving shaft  112  connected to the external driving device connector  112   a . The gear box  113  is disposed between the first driving shaft  111  and the second driving shaft  112  and transmits power in two directions between them. The first driving shaft  111 , as shown in the figures, is coaxially disposed with the winding roll  100 , and the second driving shaft  112  extends downward from the fixing bracket  610 . That is, the first driving shaft  111  and the second driving shaft  112  may not be in parallel with each other and may transmit power not in parallel with each other by the power transmission structure of the gear box  113 . 
     The first driving shaft  111  and the second driving shaft  112  particularly perpendicularly cross each other. In order to easily transmit a driving force between the driving shafts perpendicular to each other, the gear box  113  may include a pair of bevel gears  113   a  engaged between the first driving shaft  111  and the second driving shaft  112 . That is, the first driving shaft  111  is disposed at the rotational center of the winding roll  100  in parallel with the winding roll  100 , and the second driving shaft  112  is connected perpendicularly thereto through the bevel gears  113   a  and can transmit power. Accordingly, external power is provided to the first driving shaft  111  through the second driving shaft  112 , whereby the winding roll  100  connected to the first driving shaft  111  can be conveniently rotated. Since the second driving shaft  112 , as described above, extends downward from the fixing bracket  610  and has the driving device connector  112   a  at the end, it is possible to easily connect a driving device to the second driving shaft  112  extending downward and the driving device connector at the end and to operate the blind device even if the blind device is installed relatively high. 
     That is, the power conversion module  110  has a structure that can transmit power in two directions by connecting the horizontally disposed first driving shaft  111  and the second driving shaft  112  disposed perpendicular to the first driving shaft  111 . The gear box  113  may be used to transmit a driving force between the different driving shafts. The gear box  113  particularly includes the pair of bevel gears  113   a  rotating in mesh with each other, so it can freely transmit both forward and rearward rotation between the driving shafts perpendicular to each other from the winding roll  100  to the power conversion module  110  or from the power conversion module  110  to the winding roll  100 . 
     That is, as shown in  FIG. 4 , the driving device connector  112   a  and the second driving shaft  112  connected to the driving device connector  112   a  can rotate both forward and rearward, and a rotational force is transmitted through the pair of bevel gears  113   a  engaged with each other, so the first driving shaft  111  can rotate both forward and rearward. Accordingly, the winding roll  100  connected to the first driving shaft  111  can be rotated both forward and rearward (i.e., the winding direction and the unwinding direction). That is, when an external driving device is connected to the driving device connector  112   a  and the second driving shaft  112  is rotated, a rotational force is transmitted to the winding roll  100 , so the blind device can be driven. As shown in the figures, the driving device connector  112   a  has a tool insertion groove  112   b  recessed coaxially with the second driving shaft  112 , so it can be easily combined with an external driving device by putting a driving shaft of the driving device into the tool insertion groove  112   b . The tool insertion groove  112   b  may not necessarily mean a groove for inserting a tool, and may be a groove in which common tools are coupled to be able to rotate the second driving shaft  112  using the common tools. Accordingly, even though it is referred as a tool insertion groove  112   b , but it may be a special groove in which only a dedicated driving device is coupled. 
     Further, on the contrary, when a user directly touches and operates the blind device, the winding roll  100  may be rotated first and then the power conversion module  110  is correspondingly rotated. That is, when the winding roll  100  is rotated, the first driving shaft  111  connected to the winding roll rotates in the corresponding direction and a rotational force is transmitted backward through the bevel gears  113   a  engaged with each other, so the second driving shaft  112  can also be rotated in the corresponding direction. In this case, friction is generated in the power conversion module  110  while the rotational force is transmitted, so resistance that offsets the resultant force of the torque applied in the first direction and the torque applied in the second direction can be generated. Accordingly, the screen  200  can be stably maintained at various heights while more precisely maintaining balance. As described above, it is possible not only to rotate the winding roll  100  using the power conversion module  110  and external power, but also to more precisely balance the blind device, which is operated without a cord, using the resistance generated in the power conversion module  110 . 
     The tool insertion groove  112   b  of the driving device connector  112   a , for example, may be a recessed polygonal groove. It is possible to transmit a driving force by inserting a driving shaft having a polygonal outer side of an external driving device into the tool insertion groove  112   b . That is, it is possible to rotate the second driving shaft  112  by detachably coupling an external driving device having a polygonal driving shaft to the driving device connector  112   a , and as described above, a rotational force can be transmitted to the first driving shaft  111  through the bevel gears  113   a  engaged with each other. The first driving shaft  111  may be inserted and fixed in a connection block  111   a  having an end connected in the winding roll  100 . The connection block  111   a , as shown in the figures, may be a block filling the inside of the winding roll  110 , and may be inserted in the winding roll  100  and rotated with the winding roll  100 . The connection block  111   a  may have a groove on the outer surface and may be coupled to a protrusion on the inner surface of the winding roll  100 , thereby being able to be synchronized with the winding roll  100  in rotation. It is possible to fix the first driving shaft  111  to the connection block  111   a  through pressure of a fixing screw  111   b  by fastening the fixing screw  111   b  to the connection block  111   a . However, the present invention is not limited thereto, and the connection structure for connecting the first driving shaft  111  and the winding roll  100  may be changed in various types. 
     The gear box  113  has a box-shaped structure through which the first driving shaft  111  and the second driving shaft  112  protrude from the ends, and the bevel gears  113   a  connecting the first driving shaft  111  and the second driving shaft  112  are disposed therein. The gear box  113  connects the first driving shaft  111  and the second driving shaft  112  through the pair of bevel gears  113   a  disposed therein. The end connected to the first driving shaft  111  of the gear box  113  is inserted in the winding roll  100 , and the other end connected to the second driving shaft  112  is positioned in the fixing bracket  610 . The gear box  113 , for example, has an L-shaped bending structure, thereby being able to maintain the arrangement of the driving shafts (the first driving shaft  111  and the second driving shaft  112 ) perpendicular to each other and to connect the winding roll  100  and the fixing bracket  610  to each other. As described above, the first driving shaft  111  is connected with the connection block  111   a  in the winding roll  100 , thereby being able to be synchronized in rotation with the winding roll  100 . In particular, the magnitude of the resistance described above can be adjusted by adjusting the gap between the gears in the gear box  113 . For example, it is possible to adjust the engagement strength by adjusting the gap between the bevel gears  113   a  connecting the first driving shaft  111  and the second driving shaft  112  to each other in the gear box  113 , whereby it is possible to appropriately change the magnitude of the resistance generated in the power conversion module  110 . Therefore, by appropriately changing the magnitude of the resistance, it is possible to easily find a balance point and more easily maintain the screen  200  at various positions. 
     Hereafter, the operation process of the cordless blind device is described in more detail with reference to  FIGS. 5 to 7 . 
       FIGS. 5 and 6  are views showing the operation of the blind device shown in  FIG. 1  by directly moving up/down the screen and  FIG. 7  is a view showing the operation of the blind device shown in  FIG. 1  using external power. 
     The cordless blind device  1  can be very easily operated even without a cord because of the structural characteristic. The weight  300  applies torque (see T 1  in  FIGS. 5 and 6 ) to the winding roll  100  in the first direction in which the screen  200  is unwound, and the elastic member  400  correspondingly applies torque (see T 2  in  FIGS. 5 and 6 ) in the second direction in which the screen  200  is wound. Accordingly, it is possible to maintain balance of the winding roll  100  at various rotated positions, and it is possible to more easily keep the winding roll  100  stopped using the friction force generated by a friction fixing portion  500 . 
     That is, it is possible to easily break the balance and adjust the length of the screen  200  by applying a minimum external force (for example, simply touching the screen or the weight) to the cordless blind device  1  using the torque (T 1  and T 2 ) acting in opposite directions while increasing or decreasing in accordance with the unwound length of the screen  200 . Further, it is possible to easily return to the balanced status by removing the external force, whereby it is possible to maintain the changed length of the screen  200 . Even if subtle unbalance is generated between the applied torque T 1  and T 2 , the resultant force of the torque T 1  and T 2  applied in opposite directions is offset by the resistance of the power conversion module  110  generating resistance while rotating together, so the stopped status can be more easily maintained. 
     For example, the screen  200  may be unwound, as shown in  FIG. 5B . In this case, the winding roll  100  rotates, as shown in  FIG. 5A , and accordingly, the rotary block  410  coupled to the winding roll  100  also rotates. Accordingly, the elastic member  400  connected to the rotary block  410  stores elastic energy while deforming. The elastic member  400  deforms to correspond to the unwound length of the screen  200 , so a restoring force is increased. The restoring force acts as the second-directional torque T 2 , as shown in  FIG. 5B . 
     Further, the first-directional torque T also increases. In addition to the load of the weight  300 , load corresponding to the unwound length of the screen  200  increases, so the effect of gravity increases. Accordingly, the tension in the screen  200  is increased by gravity and the increased tension acts as the first-directional torque T 1 . The first-directional torque T 1  is generated in the completely opposite direction to the second-directional torque T 2 , so balance can be maintained. It may be possible to adjust the first-directional torque T 1  and the second-directional torque T 2  such that the magnitudes become the same by adjusting the elastic modulus of the elastic member  400  or the load of the weight  300 . 
     In this case, as shown in  FIG. 5A , the power conversion module  110  connected to the winding roll  100  is rotated by the rotational force from the winding roll  100  and generates resistance due to friction. The resistance acts on the winding roll  100  and keeps the winding roll  100  stopped. Since the power conversion module  110  has the gear engagement structure described above therein, resistance can be more effectively generated by friction. Even if there is a subtle difference between the magnitudes of the first-directional torque T 1  and the second-directional torque T 2 , the resistance transmitted to the winding roll  100  removes the difference and maintains a stopped status. That is, even if there is a remaining resultant force of the first-directional torque T 1  and the second-directional torque T 2  applied in opposite directions, it is offset by the resistance generated in the power conversion module  110 , so a stopped status can be effectively maintained. 
     This action is performed in accordance with the same principle also in the case when the screen  200  is wound, as shown in  FIGS. 6A-6B . As shown in  FIG. 6B , when the screen  200  is wound, the winding roll  100  is rotated in the opposite direction as shown in  FIG. 6A , the elastic member  400  returns to the initial shape while decreasing in deformation, the stored elastic energy decreases, and the restoring force also decreases. Accordingly, the second-directional torque T 2  correspondingly decreases. Further, the unwound length of the screen  200  decreases and only the load of the weight  300  acts downward, so the first-directional torque T 1  applied to the winding roll  100  also correspondingly decreases. In addition, since the driving shafts of the power conversion module  110  generate resistance using friction while rotating in opposite directions, the first-directional torque T 1  and the second-directional torque T 2  are equilibrated and resistance acts, whereby the winding roll  100  can be kept stopped. 
     That is, regardless of winding or unwinding of the screen  200 , first-directional torque T 1  and the second-directional torque T 2  increase or decrease while maintaining equilibrium. Further, since the power conversion module  110  generates resistance by operating with rotation of the winding roll  100 , it is possible to more easily stop the winding roll  100 . A user can easily adjust the length of the screen  200  by providing only a minimum external force that can break the equilibrium, and can maintain a predetermined length at a desired position by breaking the equilibrium. This operation can be very easily performed only by simply touching and moving up or down the screen  200  or the weight  300  connected to the screen  200 . As described above, it is possible to achieve a convenient use environment using the cordless blind device  1  of the present invention. 
     On the other hand, as shown in  FIG. 7 , the cordless blind device  1  can be driven using an external driving device A. It is possible to transmit a driving force from the driving device A to the cordless blind device  1  by connecting the driving device A to the power conversion module  110  by coupling a driving shaft Aa of the driving device A into the tool insertion groove  112   b  of the driving device connector  112   a . In this case, as described above, a rotational force is transmitted to the first driving shaft  111  through the bevel gears  113   a  from the second driving shaft  112 , and accordingly, the winding roll  100  connected to the first driving shaft  111  can be rotated by the driving force of the external driving device A. In particular, as shown in the figures, by simply coupling the external driving device A to the driving device connector  112   a  of the second driving shaft  112  extending downward, it is possible to very conveniently operate the blind device even if the blind device is installed relatively high. The driving device A is separably coupled to the driving device connector  112   a , so it may function as a power generation device providing a rotational driving force to the second driving shaft, that is, an electric driving device such as an electric tool. However, the present invention is not limited thereto, and for example, various rotation transmission devices that are used for a manual hand drill may be used. 
     As described above, since both forward and rearward rotation can be easily transmitted to the winding roll  100  through the engagement structure of the bevel gears  113   a , it is possible to very conveniently wind or unwind the screen  200  using the driving force of the external driving device A. As described above, it is possible to very conveniently operate the cordless blind device  1  of the present invention. 
     Although exemplary embodiments of the present invention were described above with reference to the accompanying drawings, those skilled in the art would understand that the present invention may be implemented in various ways without changing the necessary features or the spirit of the prevent invention. Therefore, the embodiments described above are only examples and should not be construed as being limitative in all respects. 
     INDUSTRIAL APPLICABILITY 
     Since the cordless blind device for external power drive of the present invention is operated without a cord, it is possible to remarkably reduce the possibility of a negligent accident due to a cord. Further, since the cordless blind device can be operated by power provided from the outside using a separate tool, if necessary, it is possible to conveniently operate the screen even at a height that is not reached by a hand. Further, since it is possible to operate the screen using common electric tools that are generally used at home, it is possible to achieve a blind device that is electrically operated without a specific cost. Further, since it is possible to use simple manual tools in addition to electric tools, it is possible to conveniently operate the entire blind device without a cord. Further, since there is no cord, the blind device can be safely used and can be conveniently operated by external power from various external devices, depending on cases, thereby securing common use and adaptability and increase industrial applicability. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1 : cordless blind device 
               100 : winding roll 
               110 : power conversion module 
               111 : first driving shaft 
               111   a : connection block 
               111   b : fixing screw 
               112 : second driving shaft 
               112   a : driving device connector 
               112   b : tool insertion groove 
               113 : gear box 
               113   a : bevel gear 
               101 : guide rail 
               120   a : rotary ring 
               120   b : fixing portion 
               120 : rotary shaft 
               200 : screen 
               300 : weight 
               400 : elastic member 
               410 : rotary block 
               411 : holder 
               610 ,  620 : fixing bracket 
             T 1 : first-directional torque 
             T 2 : second-directional torque 
             A: driving device