Patent Publication Number: US-2023132827-A1

Title: Hanging device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This non-provisional application claims priority under 35 U.S.C. § 119(a) to Patent Application No. 110140166 filed in Taiwan, R.O.C. on Oct. 28, 2021, the entire contents of which are hereby incorporated by reference. 
    
    
     BACKGROUND 
     Technical Field 
     The instant disclosure relates to a hanging device, in particular, to hanging device with a spiral spring. 
     Related Art 
     Many products tend to be hung on the wall surface in order to save space, to improve aesthetic feelings, to increase safety, or to achieve other requirements upon using the products. For example, a surveillance camera may be hung on the wall surface of different places (e.g., a kinder garden, an office, or a store), thus the surveillance camera can be a communication media between the indoor space and the outdoor space. Moreover, in another example, a doorbell device may be assembled on the wall surface at the entrance or exit of a building (which may be a residence, an office, or a commercial building), so that the doorbell device can perform the security surveillance function or record personnel activities. 
     SUMMARY 
     In general, in order to prevent the product from falling off the wall surface, upon assembling a wall-hanging product known to the inventor, a plate is firstly fixed on the wall surface, and the product is then locked on the plate with bolts. As a result, upon assembling the product on the wall or detaching the product from the wall, a hand tool is applied to rotate the bolts which is timing consuming and inconvenient. Moreover, the space between the product and the plate is very narrow, thus further increasing the difficulty upon assembling the product on the wall or disassembling the product from the wall. 
     In view of this, in one embodiment, a hanging device is provided. The hanging device comprises a wall fixing plate, a wall hanging element, and a spiral spring. The wall fixing plate comprises a fixing portion, an abutting portion, and a first fitting portion. The wall hanging element comprises a housing and fixing member. The housing has a back surface. The back surface has a spring installation region and a second fitting portion. The second fitting portion is detachably fitted with the first fitting portion. The fixing member protrudes from the back surface and is detachably assembled on the fixing portion. A distance between the fixing member and a bottom edge of the spring installation region is greater than a distance between the fixing portion and the abutting portion of the wall fixing plate. The spiral spring is disposed in the spring installation region. The spiral spring comprises an inner arc section, an outer arc section, and an arc connecting section. A radius of the outer arc section is greater than a radius of the inner arc section, the arc connecting section is connected between the inner arc section and the outer arc section, and a radius of curvature of the arc connecting section gradually increases from the inner arc section to the outer arc section. 
     Based on the above, in the hanging device according to one or some embodiments of the instant disclosure, the wall hanging element can be quickly assembled on the wall fixing plate through the fixing member and the second fitting portion. Furthermore, after the fixing member is detached from the wall fixing plate, the elastic force stored in the spiral spring drives the wall hanging element to move with respect to the wall fixing plate, so that the wall hanging element can be detached from the wall fixing plate easily and conveniently. Moreover, when the spiral spring is compressed, the inner stress applied to the spiral spring can be distributed over the entire spring properly, thereby increasing the yield strength and the service life of the spiral spring. Furthermore, owing to the snail-like structure of the spiral spring, after the spiral spring is released, the spiral spring can have a longer actuation movement to provide a greater elastic force. Hence, even in a narrow space, the elastic force generated by the spiral spring and the actuation movement of the spiral spring can be ensured enough to drive the wall hanging element to move from the fixed position to the released position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure will become more fully understood from the detailed description given herein below for illustration only, and thus not limitative of the disclosure, wherein: 
         FIG.  1    illustrates a perspective view of a hanging device according to an exemplary embodiment of the instant disclosure; 
         FIG.  2    illustrates an exploded view of the hanging device of the exemplary embodiment; 
         FIG.  3    illustrates an enlarged partial exploded view of the hanging device of the exemplary embodiment; 
         FIG.  4    illustrates an enlarged partial plan view of the hanging device of the exemplary embodiment; 
         FIG.  5    illustrates a cross-sectional view of the wall hanging element at the fixed position along line  5 - 5  shown in  FIG.  1   ; 
         FIG.  6    illustrates an enlarged partial plan view of the wall hanging element at the fixed position; 
         FIG.  7    illustrates a cross-sectional view of the wall hanging element at the released position; and 
         FIG.  8    illustrates an enlarged partial plan view of the wall hanging element at the released position. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments are provided for facilitating the descriptions of the instant disclosure. However, the embodiments are provided as examples for illustrative purpose, but not a limitation to the instant disclosure. In all the figures, the same reference numbers refer to identical or similar elements. 
       FIG.  1    illustrates a perspective view of a hanging device according to an exemplary embodiment of the instant disclosure.  FIG.  2    illustrates an exploded view of the hanging device of the exemplary embodiment. As shown in  FIG.  1    and  FIG.  2   , the hanging device  1  comprises a wall fixing plate  10 , a wall hanging element  20 , and a spiral spring  30 . The wall fixing plate  10  is adapted to be fixed on a wall surface W. For example, in this embodiment, the wall fixing plate  10  has two lock holes  101 , so that the wall fixing plate  10  can be locked on the wall surface W through bolts, but embodiments are not limited thereto. In some embodiments, the wall fixing plate  10  may be fixed on the wall surface W through other manners (such as attaching or riveting). In some embodiments, the wall surface W may be the surface of the wall, the surface of the ceiling, or the surface of any articles. 
     As shown in  FIG.  1    and  FIG.  2   , in this embodiment, the wall fixing plate  10  comprises a top portion  11 , a bottom portion  12 , a fixing portion  13 , a first fitting portion  14 , and an abutting portion  16 . The fixing portion  13  and the abutting portion  16  are between the top portion  11  and the bottom portion  12 . In this embodiment, the fixing portion  13  is a through hole adjacent to the top portion  11 , and the abutting portion  16  is adjacent to the bottom portion  12 . The wall fixing plate  10  has a via hole  15 . The via hole  15  is adjacent to the bottom portion  12  and is defined through two opposite surfaces of the wall fixing plate  10 . The abutting portion  16  may be the hole edge of the via hole  15  to abut against the spiral spring  30 . As shown in  FIG.  2   , the two opposite surfaces of the wall fixing plate  10  are respectively a front surface  18  and a rear surface  19 . 
     However, it is understood that, the foregoing embodiments are illustrative examples. In some embodiments, the fixing portion  13  of the wall fixing plate  10  may be a slot and not defined through the two opposite surfaces of the wall fixing plate  10 , and the abutting portion  16  may be a protruding flange disposed on the surface of the wall fixing plate  10 . 
     As shown in  FIG.  1    and  FIG.  2   , the wall hanging element  20  may be any product which has to be hung on. For example, the wall hanging element  20  may be a surveillance camera, a doorbell, a remote controller, a charger, or the like. The wall hanging element  20  comprises a housing  21  and a fixing member  29 . The housing  21  has a back surface  22 . The back surface  22  has a second fitting portion  23  and a spring installation region  24 , and the housing  21  further has a top end  211  and a bottom end  212 . The second fitting portion  23 , the spring installation region  24 , and the fixing member  29  may be disposed on any portion between the top end  211  and the bottom end  212 . For example, in this embodiment, the second fitting portion  23  and the fixing member  29  are adjacent to the top end  211  and respectively correspond to the first fitting portion  14  and the fixing portion  13 , and the spring installation region  24  is adjacent to the bottom end  212  and corresponds to the abutting portion  16 , but embodiments are not limited thereto. 
     As shown in  FIG.  2   , the fixing member  29  is disposed in the housing  21  and shiftably protrudes from the back surface  22 . Please refer to  FIG.  5   . In this embodiment, the fixing member  29  comprises an elastic member  291  and a rod member  292 . Moreover, in this embodiment, the elastic member  291  is an elastic arm, but embodiments are not limited thereto; in some embodiments, the elastic member  291  may be a spring, an elastic piece, or an elastic rubber. One of two ends of the elastic member  291  is connected to other parts inside the housing  21 , and the other end of the elastic member  291  is connected to and pushes against the rod member  292  to protrude from the back surface  22  of the housing  21 . Therefore, when the rod member  292  is forced by the elastic member  291 , the rod member  292  is in a movable and shiftable state so as to protrude from the back surface  22  or not to protrude from the back surface  22 . The spring installation region  24  of the housing  21  is a region on the back surface  22  for assembling with the spiral spring  30  (for example, in  FIG.  2   , the region enclosed by the dot-and-dash line). The spring installation region  24  has a limiting member  25  for assembling with the spiral spring  30 . Moreover, a distance (in this embodiment, the distance in the Y-axis direction) between the fixing member  29  and the bottom edge of the spring installation region  24  is greater than a distance (in this embodiment, the distance in the Y-axis direction) between the fixing portion  13  and the abutting portion  16  of the wall fixing plate  10 . 
     Further, as shown in  FIG.  2   , the second fitting portion  23  on the back surface  22  of the housing  21  is provided for being fitted with the first fitting portion  14  of the wall fixing plate  10 . For example, the first fitting portion  14  and the second fitting portion  23  may be fitted with each other through clearance fit, interference fit, transition fit, or the like. In this embodiment, the first fitting portion  14  is the edge portion of the top portion  11  of the wall fixing plate  10  (in this embodiment, an arc edge), and the second fitting portion  23  is a buckling flange disposed on the back surface  22 . Moreover, in this embodiment, the second fitting portion  23  is an arc flange, and the shape of the arc flange corresponds to the shape of the first fitting portion  14 , so that the second fitting portion  23  can be fitted with the first fitting portion  14  of the wall fixing plate  10 . 
       FIG.  3    illustrates an enlarged partial exploded view of the hanging device of the exemplary embodiment.  FIG.  4    illustrates an enlarged partial plan view of the hanging device of the exemplary embodiment. As shown in  FIG.  2    to  FIG.  4   , the spiral spring  30  is formed by winding a wire, from the inside out, into a spiral structure. In some embodiments, the wire may be flat wire or a plat-shaped wire. The material of the wire may be carbon steel, alloy steel, stainless steel, or other metal alloys, but embodiments are not limited thereto. 
     As shown in  FIG.  2    to  FIG.  4   , the spiral spring  30  is disposed on the spring installation region  24  and comprises an inner arc section  31 , an outer arc section  33 , and an arc connecting section  35 . The inner arc section  31 , the outer arc section  33 , and the arc connecting section  35  may be arranged on a same plane. Moreover, a radius of the outer arc section  33  is greater than a radius of the inner arc section  31 . For example, the radius of the outer arc section  33  may be 1.5 to 2.5 times of the radius of the inner arc section  31 . The arc connecting section  35  is connected between the inner arc section  31  and the outer arc section  33 . Specifically, in this embodiment, the inner arc section  31  is an initial section of the spiral spring  30  which has the smallest radius of curvature, and the outer arc section  33  is a terminal section of the spiral spring  30  which has the largest radius of curvature. The radius of curvature of the arc connecting section  35  gradually increases from the inner arc section  31  to the outer arc section  33 , so that the spiral spring  30  forms a continuous spiral line segment (as shown in  FIG.  4   ). 
     It is understood that, in  FIG.  4    the dash line on the spiral spring  30  is provided for indicating the borders among the inner arc section  31 , the outer arc section  33 , and the arc connecting section  35 , but not for limiting the arc length of the inner arc section  31 , the arc length of the outer arc section  33 , and the arc length of the arc connecting section  35  to a certain embodiment. In some embodiments, the inner arc section  31  of the spiral spring  30  may be a circular arc, and the central angle of the inner arc section  31  may be in a range between 45 degrees and 210 degrees. For example, in the embodiment shown in  FIG.  4   , the central angle of the inner arc section  31  is about 180 degrees, but embodiments are not limited thereto. In some embodiments, the inner arc section  31  may be configured as a non-circular arc and has an incremental radius of curvature. Similarly, the outer arc section  33  of the spiral spring  30  may be a circular arc, and the central angle of the outer arc section  33  is in a range between 45 degrees and 210 degrees. For example, in the embodiment shown in  FIG.  4   , the central angle of the outer arc section  33  is about 75 degrees, but embodiments are not limited thereto. In some embodiments, the outer arc section  33  may be configured as a non-circular arc and has an incremental radius of curvature. 
     As shown in  FIG.  2    to  FIG.  4   , the spiral spring  30  leans against the limiting member  25  on the spring installation region  24 . The limiting member  25  comprises at least one block protruding from the back surface  22  and between the arc connecting section  35  and the inner arc section  31 , so that the arc connecting section  35  and the inner arc section  31  respectively lean against the block, thereby limiting the movement of the spiral spring  30 . In this embodiment, the limiting member  25  comprises a first limiting block  26  and a second limiting block  27  spacedly arranged along the X-axis direction. The first limiting block  26  has a first top edge  261  and a first bottom edge  262 . The first top edge  261  is nearer to the top end  211  of the housing  21 , as compared with the first bottom edge  262  (in other words, in this embodiment, a distance between the first top edge  261  and the top end  211  of the housing  21  is less than a distance between the first bottom edge  262  and the top end  211  of the housing  21 ). The second limiting block  27  has a second top edge  271  and a second bottom edge  272 . The second top edge  271  is nearer to the top end  211  of the housing  21 , as compared with the second bottom edge  272  (in other words, in this embodiment, a distance between the second top edge  271  and the top end  211  of the housing  21  is less than a distance between the second bottom edge  272  and the top end  211  of the housing  21 ). Moreover, an indentation G is between the first limiting block  26  and the second limiting block  27 . In this embodiment, the first limiting block  26  and the second limiting block  27  are spaced arranged with each other to form the indentation G. 
     Furthermore, as shown in  FIG.  4   , the arc connecting section  35  of the spiral spring  30  leans against the first top edge  261  and the second top edge  271 , and the inner arc section  31  leans against the first bottom edge  262 . Moreover, an end portion of the inner arc section  31  has an extension section  311 , and the inner arc section  31  is connected between the extension section  311  and the arc connecting section  35 . In this embodiment, the extension section  311  integrally extends and bends from the end portion of the inner arc section  31 , and the extension section  311  is inserted into the indentation G. Accordingly, in this embodiment, since the arc connecting section  35  leans against the first top edge  261  and the second top edge  271  as well as the inner arc section  31  leans against the first bottom edge  262 , the arc connecting section  35  is limited from moving downwardly and the inner arc section  31  is limited from moving upwardly. Hence, the upward and downward movements of the spiral spring  30  are limited. Moreover, since the extension section  311  is inserted into the indentation G, the leftward and rightward movements of the spiral spring  30  are also limited. The outer arc section  33  of the spiral spring  30  is not limited, so that the outer arc section  33  can be forced to move toward the inner arc section  31  radially. 
     As shown in  FIG.  4    again, the first bottom edge  262  of the first limiting block  26  may be an arc edge, and the radius of curvature of the first bottom edge  262  corresponds to the radius of curvature of the inner arc section  31 , so that the leaning area between the inner arc section  31  and the first bottom edge  262  increases to provide a better limiting performance. The first top edge  261  of the first limiting block  26  and the second top edge  271  of the second limiting block  27  may be arc edges respectively. The arc connecting section  35  comprises a first arc section  351  and a second arc section  352 , and the radius of curvature of the first arc section  351  is greater than the radius of curvature of the second arc section  352 . The first arc section  351  leans against the first top edge  261 , and the radius of curvature of the first top edge  261  corresponds to the radius of curvature of the first arc section  351 . The second arc section  352  leans against the second top edge  271 , and the radius of curvature of the second top edge  271  corresponds to the radius of curvature of the second arc section  352 . Therefore, the leaning area between the first arc section  351  and the first top edge  261  as well as the leaning area between the second arc section  352  and the second top edge  271  can be increased to provide a better limiting performance. 
       FIG.  5    illustrates a cross-sectional view showing that the wall hanging element is at the fixed position along the line  5 - 5  shown in  FIG.  1   .  FIG.  6    illustrates an enlarged partial view showing that the wall hanging element is at the fixed position. As shown in  FIG.  5    and  FIG.  6   , the wall hanging element  20  can be assembled on the wall fixing plate  10  and at a fixed position (as the position shown in  FIG.  5   ). For example, during assembling the wall hanging element  20  on the wall fixing plate  10 , the spiral spring  30  is inserted into the via hole  15  of the wall fixing plate  10  (at this moment, the spiral spring  30  does not abut against the abutting portion  16 ), so that the second fitting portion  23  of the housing  21  is above the first fitting portion  14  and the fixing member  29  abuts against the surface of the wall fixing plate  10  (as shown in  FIG.  7   ). Next, the wall hanging element  20  can be moved to the fixed position based on the gravity force or user operation, so that the fixing member  29  is buckled with and assembled in the fixing portion  13  and the second fitting portion  23  is fitted with the first fitting portion  23 . Therefore, the wall hanging element  20  is fixed on the wall fixing plate  10  and hung on the wall surface. 
     Furthermore, as shown in  FIG.  5    and  FIG.  6   , when the wall hanging element  20  is moved to the fixed position, the abutting portion  16  (in this embodiment, the hole edge of the via hole  15 ) pushes the outer arc section  33  of the spiral spring  30  to move toward the inner arc section  31 . Therefore, the spiral spring  30  is compressed to store the elastic force. In this embodiment, the outer arc section  33  is nearer to the bottom end  212  of the housing  21 , as compared with the inner arc section  31 ; in other words, in this embodiment, the distance between the outer arc section  33  and the bottom end  212  of the housing  21  is less than the distance between the inner arc section  31  and the bottom end  212  of the housing  21 . When the wall hanging element  20  is moved to the fixed position, the abutting portion  16  pushes the outer arc section  33  of the spiral spring  30  to move toward the top end  211  of the housing  21  (that is, in this embodiment, along the Y-axis direction) to come toward the inner arc section  31 . Therefore, the outer arc section  33  is compressed toward the inner arc section  31  to further drive the arc connecting section  35  and the inner arc section  31  to have elastic deformation to store the elastic force. Moreover, when the outer arc section  33  of the spiral spring  30  is released, the elastic force stored in the spiral spring  30  can provide a force along the Y-axis direction. Accordingly, in one or some embodiments of the instant disclosure, owing to the snail-like structure of the spiral spring  30  and the operation of the spiral spring  30 , the internal stress in the spiral spring  30  can be distributed over the whole spring when the spiral spring  30  is compressed. For example, as shown in  FIG.  6   , when the spiral spring  30  is compressed, several sections of the spiral spring  30  (such as the sections filled with dots shown in  FIG.  6   ) together suffer the internal stress, thereby increasing the yield strength of the spiral spring  30 . Therefore, the spiral spring  30  can sustain the weight of the wall hanging element  20  to prevent from the breaking of the spiral spring  30  due to fatigue, thus increasing the service life of the spiral spring  30 . 
       FIG.  7    illustrates a cross-sectional view showing that the wall hanging element is at the released position.  FIG.  8    illustrates an enlarged partial plan view showing that the wall hanging element is at the released position. As shown in  FIG.  7    and  FIG.  8   , when the wall hanging element  20  is to be detached off, the user can operate the fixing member  29  to be detached from the fixing portion  13 . For example, the user can operate the fixing member  29  to be detached from the fixing portion  13  by hands or by hand tools. Then, the elastic force stored in the spiral spring  30  thus drive the wall hanging element  20  to move toward the top portion  11  of the wall fixing plate  10  to a released position (as indicated in  FIG.  7   ) along the Y-axis direction (as the arrow A shown in  FIG.  7   ). Specifically, in this embodiment, when the wall hanging element  20  is moved from the fixed position to the released position, the second fitting portion  23  of the wall hanging element  20  can be moved upwardly to detach from the first fitting portion  14  of the wall fixing plate  10 . Hence, at this moment, the wall hanging element  20  is not fixed and can be detached from the wall fixing plate  10  easily. Moreover, according to one or some embodiments of the instant disclosure, after the spiral spring  30  is released, the actuation movement of the spiral spring  30  is long, thus providing a higher elastic force. Therefore, even in a narrow space (for example, in the space of the via hole  15 , where the thickness of the via hole  15  is approximately the thickness of the wall fixing plate  10 ), the elastic force generated by the spiral spring  30  and the actuation movement of the spiral spring  30  can be ensured enough to drive the wall hanging element  20  to move from the fixed position to the released position. 
     As shown in  FIG.  2   , in this embodiment, the back surface  22  of the housing  21  further comprises two side flanges  221 . The two side flanges  221  are spacedly arranged and connected to the second fitting portion  23 . The wall fixing plate  10  has two side portions  17 , the two side portions  17  are connected between the top portion  11  and the bottom portion  12 . During moving the wall hanging element  20  between the fixed position and the released position, the wall fixing plate  10  can be disposed between the two side flanges  221 , and the two side portions  17  are close to or in contact with the two side flanges  221 . Therefore, during the movement, the wall fixing plate  10  can be guided and limited by the two side flanges  221  to prevent the deflection or wobbling. 
     As shown in  FIG.  4   , the limiting member  25  further comprises a third limiting block  28 . The second limiting block  27  is between the first limiting block  26  and the third limiting block  28 , and a portion of the arc connecting section  35  is between the second limiting block  27  and the third limiting block  28 . In this embodiment, the second arc section  352  of the arc connecting section  35  is connected between the first arc section  351  and the inner arc section  31 , and a portion of the second arc section  352  is between the second limiting block  27  and the third limiting block  28 . Accordingly, as shown in  FIG.  4    and  FIG.  6   , during the process that the spiral spring  30  is released and compressed, the arc connecting section  35  can be limited between the second limiting block  27  and the third limiting block  28 , thus preventing the unexpected movements of the spiral spring  30 . 
     As shown in  FIG.  3    to  FIG.  5   , the spring installation region  24  on the back surface  22  of the housing  21  further comprises a stopping plate  40  and a limiting post  41 , so that the spiral spring  30  can be limited in the spring installation region  24 . In this embodiment, the limiting post  41  is connected between the stopping plate  40  and the housing  21 . In this embodiment, one of two ends of the limiting post  41  is fixed on the housing  21  through attaching, locking, engaging or the like, and the other end of the limiting post  41  is integrally connected to the stopping plate  40 , so that the stopping plate  40  is kept spaced from the back surface  22  of the housing  21  by a spacing. The inner arc section  31  surrounds the limiting post  41 , and the stopping plate  40  covers the spiral spring  30  to limit the axial movement of the spiral spring  30 , thus preventing the spiral spring  30  from leaving the spring installation region  24  easily. 
     Further, as shown in  FIG.  5   , when the wall hanging element  20  is at the fixed position, a portion of the wall fixing plate  10  is further inserted into the spacing between the stopping plate  40  and the back surface  22 . Therefore, after the wall hanging element  20  is assembled with the wall fixing plate  10 , the wall hanging element  20  can be stably fixed and is not wobbled easily. Moreover, as shown in  FIG.  7   , when the wall hanging element  20  is at the released position, the stopping plate  40  corresponds to the via hole  15  of the wall fixing plate  10 . Therefore, the spiral spring  30 , the stopping plate  40 , and the limiting post  41  can be detached from the wall fixing plate  10  through the via hole  15 . 
     As shown in  FIG.  4    and  FIG.  8   , the spiral spring  30  has a longitudinal center line L passing through a center of circle C of the inner arc section  31 . The outer arc section  33  has a terminal portion  331  and a connection end  332 . The connection end  332  is connected to the arc connecting section  35 . The terminal portion  331  extends away from the connection end  332 , and the terminal portion  331  of the outer arc section  33  is adjacent to the longitudinal center line L. The term “adjacent to”, in this embodiment, may indicate that, the angle θ between the connection line of the terminal portion  331  and the center of circle C and the longitudinal center line L is in a range between 0 degree and 45 degrees or between 15 degrees and 30 degrees. Moreover, in this embodiment, the connection end  332  and the terminal portion  331  of the outer arc section  33  are respectively at two opposite sides of the longitudinal center line L. Therefore, when the wall hanging element  20  is at the fixed position, the abutting portion  16  can be ensured to abut against the outer arc section  33  of the spiral spring  30  to move toward the inner arc section  31 . However, it is understood that, the foregoing embodiment are provided as illustrative purposes; in some embodiments, the connection end  332  and the terminal portion  331  of the outer arc section  33  may be at the same side of the longitudinal center line L. In another embodiment, alternatively, the terminal portion  331  of the outer arc section  33  may be on the longitudinal center line L. 
     Based on the above, in the hanging device according to one or some embodiments of the instant disclosure, the wall hanging element can be quickly assembled on the wall fixing plate through the fixing member and the second fitting portion. Furthermore, after the fixing member is detached from the wall fixing plate, the elastic force stored in the spiral spring drives the wall hanging element to move with respect to the wall fixing plate, so that the wall hanging element can be detached from the wall fixing plate easily and conveniently. Moreover, when the spiral spring is compressed, the inner stress applied to the spiral spring can be distributed over the entire spring properly, thereby increasing the yield strength and the service life of the spiral spring. Furthermore, owing to the snail-like structure of the spiral spring, after the spiral spring is released, the spiral spring can have a longer actuation movement to provide a greater elastic force. Hence, even in a narrow space, the elastic force generated by the spiral spring and the actuation movement of the spiral spring can be ensured enough to drive the wall hanging element to move from the fixed position to the released position. 
     While the instant disclosure has been described by the way of example and in terms of the preferred embodiments, it is to be understood that the invention need not be limited to the disclosed embodiments. On the contrary, it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims, the scope of which should be accorded the broadest interpretation so as to encompass all such modifications and similar structures.