Patent Publication Number: US-9850704-B2

Title: Under structure of blind apparatus and blind apparatus having the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to and the benefit of Korean Patent Application No. 10-2016-0045159, filed on Apr. 12, 2016, the disclosure of which is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to an under-structure of a blind apparatus and a blind apparatus having the same and, more particularly, to an under-structure of a blind apparatus that can adjust the length of a screen, and a blind apparatus having the under-structure of a blind apparatus. 
     Description of the Related Art 
     In general, a blind apparatus is installed in space with windows or window walls such as a dining room, a room, and an office to shut out light, hinder vision, or adjust the amount of light traveling inside. In most blind apparatuses, an end of a screen is fixed to a roll at the top and the other end is fixed to a roll bar at the bottom so the blind is pulled up or down over a window or a window wall by rolling or unrolling the screen on or from the roll bar, in which the screen is a single screen or a double screen composed of separate screens. 
     The double screen can adjust the amount of light only when fully unrolled. Accordingly, when the entire length of a window is shorter than the length of a screen fully unrolled, it is required to fully unroll the screen to adjust the amount of light and then roll back up the screen to fit to the entire length of the window. 
     Therefore, there is a need for a blind apparatus that can adjust the entire length of a screen to fit to the entire length of a window. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: Korean Patent No. 10-1357736 (2014, Jan., 24.) 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an under-structure of a blind apparatus that can adjust the length of a screen. 
     Another object of the present invention is to provide a blind apparatus that can adjust the length of a screen. 
     The objects of the present invention are not limited to those described above and other objects not stated herein may be clearly understood by those skilled in the art from the following description. 
     In order to achieve the objects of the present invention, an embodiment of the present invention provides an under-structure of a blind apparatus that includes: a first bar that holds the lower end of a screen; a plug that is coupled to an end of the first bar and has a first through-hole at the center; a second bar that receives the first bar and has a slit through which the screen comes out; a cover that is fixed to an end of the second bar and has a second through-hole communicating with the first through-hole; and a wrench plug that is coupled to the outside of the cover and is fitted in the first through-hole through the second through-hole to transmit torque. 
     The wrench bar may have a non-circular cross-sectional portion in at least a predetermined section and the first through-hole may have a non-circular cross-section the same as the cross-section of the wrench bar. 
     The wrench bar may have a prismatic first section and a cylindrical second section extending from the first section. 
     The wrench bar may have at least one projections protruding outward at the boundary between the first section and the second section. 
     The wrench bar may apply elasticity to the inner side of the first through-hole by being longitudinally divided into several parts. 
     The outer diameter at an end of the wrench bar may be larger than the inner diameter of the first through-hole. 
     At least one fixing hole may be formed at any one of the wrench plug and the cover in the contact surface of the wrench plug and the cover and a fixing protrusion inserted in the fixing hole may be formed at the other one. 
     The wrench plug may include a flange part extending outward at the end of the wrench bar and an elastic member disposed between the flange part and the plug and transmits elasticity to bring the wrench plug in contact with the cover. 
     The under-structure may further include a handle that is coupled to the wrench plug and has a grip that is larger in diameter or thickness than the wrench plug. 
     Another embodiment of the present invention provides a blind apparatus including: a screen; a roll that is fixed to the upper end of the screen to roll up the screen; and the under-structure of a blind apparatus of any one of claims  1  to  9 . 
     The screen may include: a first screen and a second screen attached to different positions on the outer side of the roll and overlapping each other; and a plurality of third screens connecting the first screen and the second screen to each other and arranged in parallel with regular intervals. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing a blind apparatus according to an embodiment of the present invention; 
         FIG. 2  is an exploded perspective view showing an under-structure of the blind apparatus shown in  FIG. 1 ; 
         FIG. 3  is an exploded perspective view enlarging a portion of the under-structure of the blind apparatus; 
         FIG. 4  is a cross-sectional view of a wrench plug; 
         FIG. 5  is a view showing a change in length of a screen by rotation of a first bar; 
         FIGS. 6 and 7  are view illustrating the operation of the under-structure; 
         FIG. 8  is a view illustrating an operation for adjusting an amount of light by the blind apparatus; 
         FIG. 9  is a view illustrating a change in length of a screen depending on the length of a window; and 
         FIG. 10  is a view illustrating the operation of a wrench plug according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED 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 describe 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 and the present invention is defined by claims. Like reference numerals denote like elements throughout the descriptions. 
     An under-structure of a blind apparatus according to an exemplary embodiment of the present invention and a blind apparatus having the under-structure will be described hereafter in detail with reference to  FIGS. 1 to 9 . 
     A blind apparatus according to an embodiment of the present invention is an apparatus for hinders vision to block the inside from the outside and adjust an amount of light form the outside. 
     The under-structure of a blind apparatus and the blind apparatus having the under-structure can adjust the entire length of a fully unrolled screen in accordance with the entire length of a window through simple operation without assembling or disassembling. Adjusting the entire length of a fully unrolled screen means adjusting the longitudinal length of the entire screen fully unrolled down. Accordingly, when it is a double screen, it is possible to remove the trouble that it is required to fully unroll down a screen to adjust the amount of light and then roll back up the screen. Further, it is possible to easily remove wrinkles or waves at the lower end or around the lower end of the screen, so the external appearance of the blind apparatus can be improved, and functional deterioration of the blind apparatus due to wrinkles or waves can be prevented. 
     Hereinafter, an under-structure  1  of a blind apparatus and a blind apparatus  100  having the under-structure will be described in detail with reference to  FIGS. 1 to 4 . 
       FIG. 1  is a perspective view showing a blind apparatus according to an embodiment of the present invention,  FIG. 2  is an exploded perspective view showing an under-structure of the blind apparatus shown in  FIG. 1 ,  FIG. 3  is an exploded perspective view enlarging a portion of the under-structure of the blind apparatus, and  FIG. 4  is a cross-sectional view of a wrench plug. 
     The under-structure  1  of a blind apparatus according to the present invention, which is connected to the lower end of a screen  2  to unroll down and fix the entire screen  2  using its own weight, includes a first bar  10 , a plug  20 , a second bar  30 , a cover  40 , and a wrench plug  50 . 
     The first bar  10 , which is a cylindrical member, holds the lower end of the screen  2 . The first bar  10 , as shown in  FIG. 2 , has at least one insertion groove  10   a  formed in the longitudinal direction of the first bar  10  and recessed inside the first bar  10 , so the lower end of the screen  2  can be inserted and fixed in the insertion groove  10   a . A plurality of insertion grooves  10   a  may be formed around the outer circumference of the first bar  10  and the screen  2  may be selectively inserted into any one of the insertion grooves  10   a . If necessary, it is possible to couple a plurality of screens  2  to the first bar  10  by inserting the screens  2  in different insertion grooves  10   a . A plug  20  is coupled to a first end of the first bar  10 . 
     The plug  20 , a part rotating the first bar using torque from the wrench plug  50  to be described below, as shown in  FIGS. 2 and 3 , has a first through-hole  20   a . The first through-hole  20   a  is formed at the center of the plug  20 , so it is aligned with the rotational center axis of the first bar  10 . The rotational center axis of the first bar  10  means a virtual axis that is arranged in the longitudinal direction of the first bar  10  and passes through the center of the first bar  10 . Since the first through-hole  20   a  is aligned with the rotational center axis of the first bar  10 , the first bar  10  can more stable rotate. That is, the first through-hole  20   a  is eccentrically positioned from the rotational center axis of the first bar  10 , the first bar  10  may unstably rotate, so the first through-hole  20   a  is positioned on the rotational center axis of the first bar  10 , that is, at the center of the plug  20  in order for the first bar  10  can smoothly rotate without eccentricity. 
     The plug  20  may be coupled to at least coupling portion  21  protruding toward the first bar  10 , and when the plug  20  is separated from the first bar  10 , the first end of the first bar  10  can be opened. Accordingly, with the first end of the first bar  10  open, the screen  2  can be more easily inserted into the insertion groove  10   a . Although a pair of protruding coupling portions  21  is formed on the plug  20  in the figures, the present invention is not limited thereto and the number and shape of the coupling portion  21  may be variously changed. 
     The first bar  10  is inserted in disposed in the second bar  30 . 
     The second bar  30  is a hollow cylinder that is larger in diameter of the first bar  10 . Accordingly, the first bar  10  can be disposed in the empty space inside the second bar  30 . The second bar  30  is not necessarily a cylinder and may be formed an elliptical space having a space inside for keeping the first bar  10 , or may be formed in other polygonal bar shapes rather than a cylindrical or an elliptical shape. Further, when there is a sufficient space inside the second bar  30 , the first bar  10  may also change in various shapes such as a polygonal bar shape other than the cylindrical shape as long as it can freely change. 
     The first bar  10  is fully inserted in the second bar  30  and the screen  2  comes out through a slit  30   a  formed through the outer side of the second bar  30 . To this end, the first bar  10  may be smaller in entire length than the second bar  30 . The slit  30   a  may be changed in length in accordance with the width of the screen  2  and may be appropriately changed in width in accordance with the thickness of the screen  2  or the number of screens  2  coupled to the first bar  10 . 
     The cover  40  is fixed to a first end of the second bar  30 . 
     The cover  40  may have a shape corresponding to the transversal cross-section of the second bar  30  and to cover the first end of the second bar  30  and to be open at the top to overlap the slit  30   a  of the second bar  30 . Accordingly, even though the cover  40  is coupled, the screen  2  can freely enter the slit  30   a  through the top of the cover  40 . 
     The cover  40  has a second through-hole  40   a  that communicates with the first through-hole  20   a . The second through-hole  40   a  may be formed in a circular shape through the cover  40 , as shown in the figures, but may be formed in shapes other than a circle, if necessary. That is, the shape of the second-through-hole  40   a  is not specifically limited as long as the second through-hole  40   a  has an appropriate width large enough for a wrench bar  51  of the wrench plug  50  to be described below can be easily inserted into the first through-hole  20   a . The minimum diameter of the second through-hole  40   a  may be larger than the maximum diameter of the first through-hole  20   a  so that the wrench bar  51  can be easily inserted into the first through-hole  20   a  through the second through-hole  40   a  even if the second through-hole  40   a  is not a circle. 
     The cover  40  is coupled to the second bar  30  such that the edge protruding toward the second bar  30  in contact with the second bar  30 , whereby it can be firmly coupled to the first end of the second bar  30 . Further, the cover  40  can be more firmly combined with the second bar  30  by at least fastening protrusions  41  and  42  protruding to the inside of the second bar  30 . A pair of first fastening protrusions  41  and a fastening protrusion  42  are formed at over and under the second through-hole  40   a , respectively, in the figures, but the present invention is not limited thereto and the positions, numbers, and shapes of the first fastening protrusions  41  and the second fastening portion  42 . 
     The wrench plug  50  is coupled to the outside of the cover  40 . 
     The wrench plug  50 , which is provided to apply torque to the plug  20  and the first bar  10 , has the wrench bar  51  that is fitted in the first through-hole  20   a  through the second through-hole  40   a  to transmit torque. In other words, when the wrench plug  50  is coupled to the outside of the cover  40 , the wrench bar  51  is fitted in the first through-hole  20   a  through the second through-hole  40   a  of the cover  40 , so torque from the wrench plug  50  can be transmitted to the plug  20  and the first bar  10 . 
     The wrench bar  51 , as shown in  FIG. 3 , protrudes from the wrench plug  50  toward the first through-hole  20   a  and has a non-circular cross-sectional portion in at least some section. Accordingly, the first through-hole  20   a  where the wrench bar  51  is fitted may have a non-circular cross-section the same as that of the wrench bar  51 . Since the cross-sections of the wrench bar  51  and the first through-hole  20   a  are not a circle, the wrench bar  51  can be firmly engaged in the first through-hole  20   a . In other words, the wrench bar  51  having a non-circular cross-section is fitted in the first through-hole  20   a  having a non-circular cross-section with corners such as a polygon, so the corners are fitted to each other, thereby firmly combining them. Accordingly, the wrench bar  51  fitted in the first through-hole  20   a  is rotated, so the torque from the wrench plug  50  can be effectively transmitted to the plug  20  and the first bar  10 . Although the first through-hole  20   a  has a hexagonal cross-section and the wrench bar  51  is formed in the shape of a hexagonal prism in the figures, the present invention is not limited thereto, and the shape of the first through-hole  20   a  and the cross-sectional shape of the wrench bar  51  may be formed in various non-circular shapes. For example, the shape of the first through-hole  20   a  and the cross-sectional shape of the wrench bar  51  may include not only rotation-symmetric shapes, but other various asymmetric shapes or nonfinite shapes that have a corner so be fitted to each other. 
     The wrench bar  51  may have a prismatic first section A and a cylindrical second section B extending from the first section A. Referring to  FIGS. 3 and 4 , in detail, the wrench bar  51  has the first section A formed in a prismatic shape at a portion connected to the wrench plug  50  and the second section B formed in a cylindrical shape at the other portion extending from the first section A. Since the wrench bar  51  has the prismatic first section A and the cylindrical second section B, it is possible to adjust rotation of the plug  20  and the first bar  10 , depending on the sections of the wrench bar  51  inserted in the first through-hole  20   a . For example, when the first section A of the wrench bar  51  is inserted in the first through-hole  20   a , the wrench bar  51  is fitted in the first through-hole  20   a , the plug  20  and the first bar  10  rotate in the same direction as the wrench plug  50 , whereby the screen  2  can be rolled on or unrolled from the first bar  10 . In contrast, when the second section B of the wrench bar  51  is inserted in the first through-hole  20   a , the wrench bar  51  is not fitted in the first through-hole  20   a , torque from the wrench plug  50  is not transmitted to the plug  20  and the first bar  10 . 
     The wrench bar  51  may have at least one projection  52  protruding outward at the boundary between the first section A and the second section B. As at least one projection  52  that protrudes perpendicular to the longitudinal direction of the wrench bar  51  (to the X-direction in  FIG. 4 ) at the boundary between the first section A and the second section B, a user can accurately recognize the first section A and the second section B even through the wrench plug  50  is coupled to the cover  40  and the plug  20 , that is, the wrench bar  51  is fitted in the first through-hole  20   a . Accordingly, it is possible to easily adjust the entire length of the screen  2  by turning the plug  20  and the first bar  10  even without separating the wrench plug  50  from the cover  40  and the plug  20 . 
     Further, the wrench bar  51  can apply elasticity to the inner side of the first through-hole  20   a  by being longitudinally divided in several parts. The longitudinal direction means the longitudinal direction of wrench bar  51 . As the wrench bar  51  is divided in several parts and applies elasticity to the inner side of the first through-hole  20   a , the wrench bar  51  and the first through-hole can be more strongly fitted, so it is possible to easily turn the plug  20  and the first bar  10  even with small force. 
     The wrench bar  51  has an outer diameter at the end larger than the inner diameter of the first through-hole  20   a , so it can prevent the wrench plug  50  from separating from the plug  20 . 
     Fixing holes  40   b  may be formed at any one of the wrench plug  50  and the cover  40  and fixing protrusions  53  may be formed at the other one. It is assumed hereafter that the fixing holes  40   b  are formed at the cover  40  and the fixing protrusions  53  are formed at the wrench plug  50 . 
     At least one fixing hole  40   b  is formed around the second through-hole  40   a  of the cover  40  through the side being in contact with the wrench plug  50 . Although four fixing holes  40   b  are formed around the second through-hole  40   a , the present invention is not limited thereto and the position, number, and shape of the fixing holes  40   b  may be changed in various ways. The fixing projections  53  are inserted in the fixing hole  40   b . The fixing protrusions  53  protrude toward the cover  40  on the side being in contact with the cover  40  and are inserted in the fixing holes  40   b , thereby fixing the wrench plug  50 . At least one fixing protrusion  53  may be formed outside the wrench bar  51 , corresponding to the position, number, and shape of the fixing hole  40   b.    
     A handle  60  is coupled to the outside of the wrench plug  50 . 
     The handle  60 , which is provided to operate the wrench plug  50 , has a third through-hole  60   a  at the center for inserting the wrench plug  50 . The handle  60  has a grip  61  outside the third through-hole  60   a  and the grip  61  may be larger in diameter or thickness than the wrench plug  50 . As described above, the wrench plug  50  is coupled to the outside of the cover  40 . Accordingly, when the wrench plug  50  has a larger diameter or larger thickness, it can be easily operated by a user, but the wrench plug  50  protrudes too much out of the cover  40 , so it is likely to be separated from the cover  40  and the external appearance of the blind apparatus  100  is deteriorated. 
     The under-structure  1  of a blind apparatus according to the present invention is characterized in that the wrench plug  50  has a small diameter and a small thickness and the separate handle  60  for operating the wrench plug  50  is provided in order to improve the external appearance of the blind apparatus  100  and enable a user to easily operate the apparatus. The handle  60  is separably coupled to the wrench plug  50 . That is, the handle  60  is coupled to the wrench plug  50  to operate the wrench plug  50 , but is separated from the wrench plug  50  and stowed after finishing the operation. 
     Fastening grooves  50   a  may be formed at any one of the handle  60  and the wrench plug  50  and fastening protrusions  62  may be formed at the other one. It is assumed that the fastening holes  50   a  are formed at the wrench plug  50  and the fastening protrusions  62  are formed at the handle  60 . 
     At least one fastening groove  50   a  is formed on the outer circumferential surface of the wrench plug  50 , that is, on the surface coming in contact with the handle  60 . The fastening hole  50   a  is recessed on the wrench plug  50  and has a stepped structure, so it can prevent separation of the fastening protrusion  62 . Although a four fastening grooves  50   a  are formed around the outer circumferential surface of the wrench plug  50  in the figures, the present invention is not limited thereto and the number and shape of fastening groves  50   a  may be variously changed. The fastening protrusions  62  are inserted into the fastening groove  50   a . The fastening protrusions  62  are formed on the surface coming in contact with the wrench plug  50 , that is, protrude toward the wrench plug  50  inside the third through-hole  60   a  and are inserted in the fastening grooves  50   a , thereby fixing the wrench plug  50  and the cover  40 . The fastening protrusion  62  may be formed to correspond to the position, number, and shape of the fastening grooves  50   a.    
     An assistant plug  70  is coupled to a second end of the first bar  10 . 
     The assistant plug  70 , which is provided to cover the second end of the first bar  10 , has a rotational hole  70   a  at the center. The rotational hole  70   a  is formed in a circular shape, unlike the first through-hole  20   a , and can hold a rotary shaft  81  formed on the assistant cover  80  such that the rotary shaft  81  can rotate. The rotational hole  70   a  may also be formed on the rotational center axis of the first bar  10  and the first bar  10  can be more stably rotated by a pair of the rotational hole  70   a  and the first through-hole  20   a  on the rotational center axis of the first bar  10 . 
     The assistant cover  80  is coupled to the second end of the second bar  30  where the cover  40  is not coupled, thereby closing the second end of the second bar  30 . The rotary shaft  81  protruding toward an end of the first bar  10  may be formed at the center of the assistant cover  80  and may be rotatably inserted in the rotational hole  70   a  of the assistant plug  70  coupled to the end of the first bar  10 . The rotary shaft  81  may be formed in the same shape as the rotational hole  70   a . The assistant cover  80  is disposed at the opposite side to the cover  40  in a pair with the cover  40 . The assistant cover  80  and the cover  40  may be the same when seen from the outside, but the rotary shaft  81  is formed inside the assistant cover  80 , so the assistant cover  80  can support the first bar  10  with the rotary shaft  81  inserted in the rotational hole  70   a  so that the first bar  10  can stably rotate. That is, the rotary shaft  81 , the rotational hole  70   a , the first through-hole  20   a , and the wrench bar  51  inserted in the first through-hole  20   a  are all positioned on the rotational center axis of the first bar  10  so that the first bar  10  can easily rotate while maintaining balance. 
     The edge of assistant cover  80  protruding toward the second bar  30 , similar to the cover  40 , is contact with the second bar  30 , so it can be firmly coupled to the end of the second bar  30 . Further, the assistant cover  80  can be more firmly combined with the second bar  30  by at least couplers  82  and  83  protruding to the inside of the second bar  30 . A pair of first fastening protrusions  82  and a fastening protrusion  83  are formed at over and under the rotary shaft  81 , respectively, in the figures, but the present invention is not limited thereto and the positions, numbers, and shapes of the first fastening protrusions  82  and the second fastening portion  83 . 
     The blind apparatus  100  according to the present invention includes the screen  2 , the roll  3 , and the under-structure  1  of a blind apparatus. 
     The screen  2  includes a first screen  2   a  and a second screen  2   b  overlapping each other and a plurality of third screens  2   c  connecting the first screen  2   a  and the second screen  2   b  and arranged in parallel with regular intervals. Referring to  FIGS. 1 and 2 , the first screen  2   a  and the second screen  2   b  overlap each other and transmit light, but the third screens  2   c  are inserted between the first screen  2   a  and the second screen  2   b  and block light. In other words, the first screen  2   a  and the second screen  2   b  are nets that at least partially transmit light and the third screens  2   c  are blinds that block light. Accordingly, the screen  2  can transmit or block light in accordance with the overlapping types of the first screen  2   a , the second screen  2   b , and the third screens  2   c.    
     For example, when the third screens are  2   c  are vertically arranged between the first screen  2   a  and the second screen  2   b , light passing through any one of the first screen  2   a  and the second screen  2   b  is blocked by the third screens  2   c , so it cannot pass through the last one. The third screens  2   c  are vertically arranged between the first screen  2   a  and the second screen  2   b , but partially overlap each other, so they can block light. In contrast, when the third screens are  2   c  are horizontally arranged between the first screen  2   a  and the second screen  2   b , light passing through any one of the first screen  2   a  and the second screen  2   b  can pass through the last one. 
     The upper end of the screen  2  is fixed to the roll  3 . The roller  3 , which fixes the upper end of the screen  2  and rolls up the screen  2 , is a bar or a rod having a length corresponding to the width of the screen  2  and is rotatably disposed in a housing  4 . The upper ends of the first screen  2   a  and the second screen  2   b  are connected longitudinally to both sides of the roll  3 , respectively, in which the connected portions of the first screen  2   a  and the second screen  2   b  may extend in parallel in the same plane. In other words, the first screen  2   a  and the second screen  2   b  are tightly connected to different positions on the roll  3 , respectively. 
     The roll  3  is rotated by a specific opening/closing unit, for example, a chain  5  to roll up the screen  2 , in which the chain  5  may be coupled to the connected portions of the first screen  2   a  and the second screen  2   b . Accordingly, when the roll  3  is rotated by pulling the chain, the first screen  2   a  is moved with respect to the second screen  2   b  and the third screens  2   c  are moved with the first screen  2   a . The third screens  2   c  moving with the first screen  2   a , as described above, may be vertically or horizontally positioned between the first screen  2   a  and the second screen  2   b , whereby they can pass or block light. 
     For example, when the chain  5  coupled to the connected portion of the second screen  2   b  is pulled down, the roll  3  is rotated and the connected portion of the first screen  2   a  is moved up than the connected portion of the second screen  2   b . Accordingly, as the first screen  2   a  moves up than the second screen  2   b , the third screens  2   c  are moved with the first screen  2   a  and vertically arranged between the first screen  2   a  and the second screen  2   b . When the third screens  2   c  are vertically arranged, light is blocked. With light blocked by the third screens  2   c , when the chain  5  coupled to the connected portion of the first screen  2   a , the roll  3  is rotated and the connected portion of the first screen  2   a  is moved into the same plane as the connected portion of the second screen  2   b . Accordingly, the first screen  2   a  returns to the initial position and the third screens  2   c  are horizontally arranged between the first screen  2   a  and the second screen  2   b . When the third screens  2   c  are horizontally arranged, light is passed. 
     Hereinafter, the operation of the under-structure  1  of a blind apparatus and a blind apparatus  100  having the under-structure will be described in more detail with reference to  FIGS. 5 to 9 . 
       FIG. 5  is a view showing a change in length of a screen by rotation of the first bar,  FIGS. 6 and 7  are view illustrating the operation of the under-structure,  FIG. 8  is a view illustrating an operation for adjusting an amount of light by the blind apparatus, and  FIG. 9  is a view illustrating a change in length of a screen depending on the length of a window. 
     Referring to  FIG. 5 , as the first bar  10  is rotated relative to the second bar  30 , the entire length of the screen  2  when it is pulled down can be appropriately adjusted. 
     The lower end of the screen  2  is fixed to the first bar  10  and the first bar  10  is disposed in the second bar  30 . The cover  40  is coupled to an end of the second bar  30 , that is, the cover  40  may be coupled to the second bar  30  by the first fastening portion  41  and the second fastening portion  42 . 
     When it is not required to adjust the entire length of the screen  2  that has been pulled down, as shown in (a) of  FIG. 5 , the first bar  10  is not rotated relative to the second bar  30 . On the contrary, when it is required to adjust the entire length of the screen  2  that has been pulled down, as shown in (b) of  FIG. 5 , the first bar  10  is rotated relative to the second bar  30 . As the first bar  10  is rotated, the lower end of the screen  2  is rolled around the first bar  10 , so the entire length of the screen  2  that has been pulled down can be adjusted. It is possible to adjust step by step the length of the screen  2  that has been pulled down in accordance with the degree of rotation of the first bar  10 . As described above, when the screen  2  is rolled around the first bar  10 , additional tension is applied to the lower end of the screen  2 , so deformation such as wrinkles or waves of the screen  2  can be removed by the additional tension. As the first bar  10  is rotated, the screen  2  can be brought in contact with the first fastening portion  41 , so the additional tension can be easily maintained. 
       FIG. 6  is a view illustrating a process when torque from the wrench plug is transmitted to the plug and the first bar and  FIG. 7  is a view illustrating a process when the torque from the wrench plug is stopped. 
     The plug  20  is coupled to the first end of the first bar  10  and the assistant plug  70  is coupled to the second end. The first bar  10  is disposed in the second bar  30 , and the cover  40  is coupled to the first end of the second bar  30  and the assistant cover  80  is coupled to the second end. The rotary shaft  81  of the assistant cover  80  is rotatably inserted in the rotational hole  70   a  of the assistant plug  70  and supports the first bar  10 , and the wrench bar  51  of the wrench plug  50  is fitted in the first through-hole  20   a  of the plug  20  through the second through-hole  40   a  of the cover  40 . 
     When the first bar  10  is not rotated relative to the second bar  30 , as shown in (a) of  FIG. 6 , the fixing protrusions  53  of the wrench plug  50  are inserted in the fixing holes  40   b  of the cover  40 . As the fixing protrusions  53  are inserted in the fixing hole  40   b , rotation of the wrench plug  50  is limited, so the plug  20  and the first bar  10  are prevented from rotating relative to the second bar  30 . The wrench bar  51  can be maintained with the prismatic first section A in the first through-hole  20   a.    
     On the contrary, in order to rotate the first bar  10  relative to the second bar  30 , as shown in (b) of  FIG. 6 , the wrench plug  50  where the handle  60  is coupled is partially pulled out of the cover  40 , thereby separating the fixing protrusions  53  of the wrench plug  50  out of the fixing holes  40   b  of the cover  40 . Since the projections  52  are formed at the boundary between the first section A and the second section B, a user can pull out the wrench plug  50  within the first section A where the wrench plug  50  can be rotated. That is, the user can pull and turn the wrench plug  50  until the projections  52  reach the plug  20 . As the fixing protrusions  53  are separated out of the fixing hole  40   b , the wrench plug  50  can be rotated and torque from the wrench plug  50  is transmitted through the wrench bar  51 , so the plug  20  and the first bar  10  can be rotated relative to the second bar  30 . As the plug  20  and the first bar  10  are rotated, the lower end of the screen  2  can be rolled on or unrolled from the first bar  10 . 
     On the other hand, as shown in (a) of  FIG. 7 , when the wrench plug  50  is further pulled out from the cover  40 , the wrench bars  51  applying elasticity to the inner side of the first through-hole  20   a  close to the center, so the projections  52  can be inserted into the first through-hole  20   a  of the plug  20 . That is, the cylindrical second section B of the wrench bar  51  can be partially inserted into the first through-hole  20   a.    
     Thereafter, when the wrench plug  50  is further pulled, the outer side at the end of the wrench bar  51  is locked to the plug  20 , in which the wrench bar  51  can be maintained with the second section B inserted in the first through-hole  20   a . As the second section B is inserted into the first through-hole  20   a , torque from the wrench plug  50  is not transmitted to the plug  20  and the first bar  10 , so the plug  20  and the first bar  10  may idle with respect to the wrench plug  50 , or the wrench plug  50  and the plug  20  may idle with respect to the first bar  10 . 
     Referring to  FIG. 8 , the blind apparatus  100  adjusts the amount of light traveling through the screen  2  by changing the degree of overlapping of the first screen  2   a , the second screen  2   b , and the third screen  2   c . For example, as shown in (a) of  FIG. 8 , when the third screens  2   c  are vertically arranged between the first screen  2   a  and the second screen  2   b  by rotating the roll  3 , light can be blocked. The first screen  2   a  and the second screen  2   b  may operate as a single screen in contact with each other. In contrast, as shown in (b) of  FIG. 8 , when the third screens  2   c  are horizontally arranged between the first screen  2   a  and the second screen  2   b  by rotating the roll  3 , light can be passed. 
     According to a blind apparatus of the related art that adjusts the amount of light traveling through the screen  2  by changing the arrangement of the third screens  2   c , as shown in (a) of  FIG. 9 , it is possible to adjust the amount of light only when the screen  2  is fully pulled down. That is, when the vertical length L 1  of a window W is smaller than the vertical length L 2  of the screen  2  that has been fully pulled down, it is required to fully pull down the screen to adjust the amount of light. 
     However, according to the blind apparatus  100  of the present invention, since it is possible to simply roll/unroll the lower end of the screen  2  on/from the first bar  10 , it is possible to adjust the vertical length L 2  of the screen  2  that has been fully pulled down to fit to the vertical length L 1  of the window W. 
     A wrench plug  50  according to another exemplary embodiment of the present invention will be described hereafter in detail with reference to  FIG. 10 . 
       FIG. 10  is a view illustrating the operation of a wrench plug according to another embodiment of the present invention. 
     A wrench plug  50  according to another embodiment of the present invention further includes a flange part  54  and an elastic member  55 . The wrench plug  50  according to another embodiment of the present invention is substantially the same as that in the previous embodiment except for further including the flange part  54  and the elastic member  55 . Accordingly, the difference is described and the above description is substituted for other configuration not specifically stated. 
     The wrench plug  50  may further include the flange part  54  and the elastic member  55 . 
     The flange part  54  is a plate extending outward at the end of the wrench bar  51 . Although the flange part  54  is thread-fastened to the wrench bar  51  in the figure, the present invention is not limited thereto and it may be modified in various structures as long as it can be fixed to the wrench bar  51 . For example, the flange part  54  may be bonded to the wrench bar  51  by an adhesive. The elastic member  55  is disposed between the flange part  54  and the plug  20 . 
     The elastic member  55 , which transmits elasticity to bring the wrench plug  50  in contact with the cover  40 , for example, may be a compression spring. That is, the elastic member  55  is longitudinally compressed when force is applied, and returns to the initial position when the force is removed. The elastic member  55  brings the wrench plug  50  in contact with the cover  40  with one end in contact with the flange part  54  and the other end in contact with the plug  20 . 
     For example, as shown in (a) of  FIG. 10 , when the wrench plug  50  is prevented from turning by inserting the fixing protrusions  53  of the wrench plug  50  in the fixing hole  40   b  of the cover  40 , the elastic member  55  is maintained in the initial position. As the elastic member  55  is maintained in the initial position, the wrench plug  50  can be in contact with the cover  40 . On the contrary, as shown in (b) of  FIG. 10 , when the fixing protrusions  53  are separated out of the fixing hole  40   b  and the wrench plug  50  is operated, the elastic member  55  is compressed. When the force for operating the wrench plug  50  is removed, the elastic member  55  returns and the wrench plug  50  can be brought in contact with the cover  40 . The wrench plug  50  prevents the screen  2  from unexpectedly unrolled, when a user does not roll or unroll the screen  2 . 
     According to the present invention, it is possible to simply adjust the entire length of a screen that has been pulled down to fit to the entire length of a window without assembling or disassembling the apparatus. Accordingly, when it is a double screen, it is possible to remove the trouble that it is required to fully unroll down a screen to adjust the amount of light and then roll back up the screen. 
     Further, it is possible to easily remove wrinkles or waves at the lower end or around the lower end of the screen, so the external appearance of the blind apparatus can be improved, and functional deterioration of the blind apparatus due to wrinkles or waves can be prevented. 
     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, it should be understood that the exemplary embodiments are not limiting but illustrative in all aspects.