Abstract:
The present invention relates to an end cap for a showcase roller shelf. The end cap for a showcase roller shelf according to an embodiment of the present invention, in a state where roller unit bodies including casings enclosing the outer perimeter of a roller support body are arranged in a plurality of rows, is inserted into and is supported on both ends of each casing while a plurality of rollers are rotatably supported on the roller support body so as to slide a product on the inside of a showcase and move the product to a withdrawal location. The end cap for a showcase roller shelf comprises: cap bodies which are disposed on both ends of each casing so as to face each other, and are installed on locations crossing both ends of each casing disposed in a plurality of rows; and a plurality of protruding bodies which: protrude from locations where the cap bodies face each other so as to be inserted into both ends of each casing disposed in a plurality of rows, wherein the protrusion distances thereof are adjusted so that the rollers arranged in a plurality of rows in locations where the plurality of casings are inserted are positioned at locations where rotation centers are different in each row; and protrude alternately repeatedly while the protrusion distances thereof, by which an adjacent row among a plurality of row locations is supported, are different from each other.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation application of International Application No. PCT/KR2015/002258 filed on Mar. 9, 2015, which claims priority to Korean Application No. 10-2014-0187552 filed on Dec. 23, 2014, which applications are incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure relates to an end cap for a showcase roller shelf, and more particularly, to an end cap for a showcase roller shelf, in which when end cap structures installed to support both ends of the showcase roller shelf on which displayed goods slide in a contact manner are arranged in a plurality of columns, a roller unit having a plurality of standardized rollers that are rotatably installed in misalignment in each column and thus increase a contact area can be installed in each column, thereby improving productivity and assembliness. 
       BACKGROUND ART 
       [0003]    In general, a showcase is a box structure installed in a shop to display goods. The front of the showcase is transparent so that a customer may see the goods from the outside of the showcase and withdraw one from the showcase. 
         [0004]    Such a showcase is installed in a place such as a market or a convenience store. As shelves are provided to display goods by type inside the showcase, the showcase increases convenience with which a customer may identify and select goods, and facilitates the customer to withdraw goods. 
         [0005]    A plurality of items are kept on a shelf installed in the showcase. Rollers are installed on surfaces contacting with items in the showcase so that after the customer purchases an item placed on an end of the shelf, the next item may be positioned on the end of the shelf. The shelf is inclined to allow an item to move on the rollers. 
         [0006]    For a typical showcase roller shelf, the size and number of rollers are determined according to the size and width of the shelf, a frame is fabricated to support the rollers rotatably according to the determined size and number of rollers, and the fabricated roller shelf is installed at a user-intended position. 
         [0007]    Recently, showcase roller shelves have been commercialized, in which roller units are arranged in misalignment in a plurality of columns so that the roller units may have different center axes in the respective columns, and thus goods may slide down more smoothly. 
         [0008]    In such a showcase roller shelf, two types of roller units having different steps are arranged alternately so that rollers of the roller units in adjacent columns among the plurality of columns may be placed at different rotation center positions. If roller units are not arranged to alternate with each other inadvertently, a wrong roller unit should be removed and replaced with another roller unit, thereby decreasing workability. 
         [0009]    Accordingly, there is a need for a structure of a showcase roller shelf which can improve productivity. 
       SUMMARY 
       [0010]    An aspect of the present disclosure devised to solve the conventional problem is to provide an end cap for a showcase roller shelf, which is improved so as to increase a contact area by arranging a plurality of rollers rotatably in one unit to allow goods displayed on the showcase roller shelf to slide in contact with the rollers, and when end cap structures installed to support both ends of the rollers are arranged in a plurality of columns, by arranging the rollers of each column in misalignment. 
         [0011]    It will be appreciated by persons skilled in the art that the objects that could be achieved with the present disclosure are not limited to what has been particularly described hereinabove and the above and other objects that the present disclosure could achieve will be more clearly understood from the following detailed description. 
         [0012]    In an aspect of the present disclosure, an end cap for a showcase roller shelf, which is inserted supportedly into both ends of each casing in a state where a plurality of rollers are rotatably supported by each roller support to slide products inside a showcase to a withdrawal position, and roller units are arranged in a plurality of columns, each roller unit including a casing surrounding the outer periphery of a roller support, includes cap bodies disposed at facing positions at both ends of the casings, and installed at positions across both ends of the casings arranged in a plurality of columns, and a plurality of protrusions protruding at facing positions of the cap bodies, to be inserted into both ends of the casings arranged in the plurality of columns, and alternately repeated, with protrusion distances controlled to place rotation centers of the rollers, which are arranged in the plurality of columns at positions at which the casings are inserted, at different positions in the respective columns, and thus to be different in adjacent columns. 
         [0013]    The protrusions may include a first protrusion protruding for a first protrusion distance in the other direction from one portion of a cap body in one part, to be inserted into one of both ends of a casing disposed at an end of one side among the casings arranged in the plurality of columns, a second protrusion disposed in the other part facing the first protrusion, and protruding for a second protrusion distance in one direction from a cap body in the other part, to be inserted into the other end of the casing into which the first protrusion is inserted supportedly, a third protrusion disposed at the other side adjacent to the first protrusion, and protruding for a third protrusion distance in the other direction, to be inserted into one end of a casing positioned at the other side adjacent to the casing supporting the first protrusion, and a fourth protrusion disposed in the other part facing the third protrusion, and protruding for a fourth protrusion distance in the one direction from the cap body positioned in the other part, to be inserted into the other end of the casing into which the third protrusion is inserted supportedly. As the first protrusion distance is different from the third protrusion distance, and the second protrusion distance is different from the fourth protrusion distance, positions of center axes of the rollers installed in the casings supported by the first to fourth protrusions may be misaligned with each other, the first and third protrusions may alternate with each other, being extended according to a length of the cap body disposed in the one part, and the second and fourth protrusions may alternate with each other, being extended according to a length of the cap body disposed in the other part. 
         [0014]    As the first protrusion distance is larger than the third protrusion distance, and the fourth protrusion distance is larger than the second protrusion distance by a difference by which the first protrusion distance is larger than the third protrusion distance, the positions of center axes of the rollers installed in the casings supported by the first to fourth protrusions may be misaligned with each other in the columns in which the rollers are rotated. 
         [0015]    The difference by which the first protrusion distance is larger than the third protrusion distance may be equal to a difference by which the fourth protrusion distance is larger than the second protrusion distance, and the sum of the differences being the double of the difference may be smaller than a distance between rotation axes of the plurality of rollers in the casings. 
         [0016]    Further, the difference by which the first protrusion distance is larger than the third protrusion distance and the difference by which the fourth protrusion distance is larger than the second protrusion distance may be equally ¼ of the distance between the rotation axes of the plurality of rollers in the casings, and the sum of the differences may be ½ of the distance between the rotation axes of the plurality of rollers. 
         [0017]    Also, as the third protrusion distance is larger than the first protrusion distance, and the second protrusion distance is larger than the fourth protrusion distance by a difference by which the third protrusion distance is larger than the first protrusion distance, the positions of center axes of the rollers installed in the casings supported by the first to fourth protrusions may be misaligned with each other in the columns in which the rollers are rotated. 
         [0018]    The difference by which the third protrusion distance is larger than the first protrusion distance may be equal to a difference by which the second protrusion distance is larger than the fourth protrusion distance, and the sum of the differences being the double of the difference may be smaller than a distance between rotation axes of the plurality of rollers in the casings. 
         [0019]    Further, the difference by which the third protrusion distance is larger than the first protrusion distance and the difference by which the second protrusion distance is larger than the fourth protrusion distance may be equally ¼ of the distance between the rotation axes of the plurality of rollers in the casings, and the sum of the differences may be ½ of the distance between the rotation axes of the plurality of rollers. 
         [0020]    Details of other embodiments lie within the detailed description of the present disclosure and the drawings. 
         [0021]    According to an end cap for a showcase roller shelf in an embodiment of the present disclosure, as an end cap structure supporting a plurality of rollers, which are installed on the shelf to enable sliding provisioning of goods displayed on the shelf, has a different support position in each column, even though roller units each having a plurality of rotatable rollers have an equal standardized length, misalignment between the rollers in the columns can lead to an increased contact area between the rollers and goods. Therefore, the goods may make a cloud movement by contacting with rollers at an accurate position, thereby increasing movement efficiency. 
         [0022]    Further, the end cap for a showcase roller shelf according to the present disclosure is characterized in that the rotation positions of the center axes of rollers are changed in roller units by changing support positions at both ends of casings into which roller units are inserted. Since a roller unit having the same number of standardized rollers can be used in each column with a support position changed by the installation of the end cap can be used in a casing of each column, production cost can be reduced, and production efficiency can be increased. 
         [0023]    In the end cap for a showcase roller shelf according to the present disclosure, both ends of roller units arranged in a plurality of columns are supported by a single body. Since protrusions may be provided at facing positions in each of the plurality of columns, and protrusions may be arranged alternately along the columns, the center axes of rollers are misaligned in the plurality of columns, just by installing roller units of the same dimensions in the columns. The resulting decrease in a contact area can increase assembly efficiency. 
         [0024]    It will be appreciated by persons skilled in the art that the effects that can be achieved with the present disclosure are not limited to what has been particularly described hereinabove and other advantages of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]      FIG. 1  is an exploded perspective view illustrating a state in which an end cap for a showcase roller shelf according to an embodiment of the present disclosure is installed to the showcase roller shelf. 
           [0026]      FIG. 2  is a perspective view illustrating the state in which the end cap for a showcase roller shelf, illustrated in  FIG. 1 , is installed to the showcase roller shelf. 
           [0027]      FIG. 3  is a plan view illustrating the state in which the end cap for a showcase roller shelf, illustrated in  FIG. 1 , is installed to the showcase roller shelf. 
           [0028]      FIG. 4  is a perspective view illustrating a state in which a plurality of end caps for a showcase roller shelf illustrated in  FIG. 1  are installed to the showcase roller shelf. 
           [0029]      FIG. 5  is a plan view illustrating a state in which an end cap for a showcase roller shelf according to another embodiment of the present disclosure is installed to the showcase roller shelf. 
           [0030]      FIG. 6  is a perspective view illustrating the state in which the end cap for a showcase roller shelf illustrated in  FIG. 5  is installed to the showcase roller shelf. 
       
    
    
     DETAILED DESCRIPTION 
       [0031]    A preferred embodiment of the present disclosure will be described in detail with reference to the attached drawings so that those skilled in the art may readily implement the present disclosure. 
         [0032]    A description of a generally known technology with no direct relation to the present disclosure will be avoided lest it should obscure the subject matter of the present disclosure. 
         [0033]    For the same reason, some components are shown as exaggerated, omitted, or schematic in the attached drawings. Further, the size of each component does not reflect an actual size wholly. Like reference numerals denote the same or corresponding components in the drawings. 
         [0034]    Now, a description will be given of an end cap for a showcase roller shelf according to embodiments of the present disclosure with reference to the attached drawings. 
         [0035]      FIG. 1  is an exploded perspective view illustrating a state in which an end cap for a showcase roller shelf according to an embodiment of the present disclosure is installed to the showcase roller shelf, and  FIG. 2  is a perspective view illustrating the state in which the end cap for a showcase roller shelf illustrated in  FIG. 1  is installed to the showcase roller shelf. 
         [0036]    Referring to  FIGS. 1 and 2 , in the state where a plurality of rollers  11  are rotatably supported by each roller support  12  to enable goods in the showcase to slide to a withdrawal position, and roller units  10  each including a casing  13  surrounding the outer periphery of a roller support  12  are arranged in a plurality of columns, an end cap  100  for a showcase roller shelf according to an embodiment of the present disclosure is inserted into both ends of each of the casings  13 . 
         [0037]    As goods are continuously provided to a withdrawal position in cloud-contact with the plurality of rollers  11  and thus a loading position is higher than a providing position, each roller unit  10  is inclined. Thus, both ends of the casing  13  surrounding the rollers are at upper and lower positions, respectively. Accordingly, one of positions at which the end cap  100  is installed is defined as an upper part or position and the other position is defined as a lower part or position. 
         [0038]    Further, a plurality of roller units  10  which are fabricated on a unit basis are arranged according to the latitudinal sizes of goods and the latitudinal area of a showcase shelf. An initial installation position of a roller unit  10  is defined as one side, and a direction in which a plurality of roller units  10  are arranged is defined as the other side. 
         [0039]    These terms are defined for the convenience of description, and those skilled in the art will understand that the installation direction and positions of the roller units  10  are not limited. 
         [0040]    The above-described end cap  100  for a showcase roller shelf includes cap bodies  110  and protrusions  12 , which are installed at upper and lower ends of the casings  13  arranged in a plurality of columns. 
         [0041]    The cap bodies  110  are disposed at facing positions at both ends of the casings  13 , and installed at positions which are across both ends of the casings  13  arranged in the plurality of columns. The cap bodies  110  are installed at positions which are respectively across the upper and lower ends of the casings  13  arranged in the plurality of columns according to the width of the shelf, so as to support the upper and lower ends of all of the casings  13 , respectively. 
         [0042]    The cap bodies  110 , which are inclined from top to bottom, are provided at upper and lower positions of the plurality of casings  13  arranged from one side to the other side. Each of the cap bodies  110  is installed at a position which is across from the one side to the other side at the upper or lower ends of the casings  13 , so that protrusions  120  may be inserted into the casings  13 . 
         [0043]    The protrusions  120  protrude in directions in which the cap bodies  110  face each other. The protrusions  120  protrude at facing positions of the cap bodies  13 , so that the protrusions  120  may be inserted into both ends of the casings  13  arranged in the plurality of columns. The protrusions  120  are provided with controlled protrusion distances, so that rollers  11  arranged in a plurality of columns at each of positions at which the plurality of casings  14  are inserted may have different rotation center positions between the columns. That is, as protrusions  120  with different protrusion distances in adjacent columns among the plurality of columns alternate with each other repeatedly, when the protrusions  120  are inserted into the casings  13 , a plurality of rollers  11  are disposed with a different rotation center axis position in each of the plurality of columns. As a consequence, the contact area between goods and the rollers  11  is increased in each column. 
         [0044]      FIG. 3  is a plan view illustrating the state in which the end cap for a showcase roller shelf illustrated in  FIG. 1  is installed to the showcase roller shelf, and  FIG. 4  is a perspective view illustrating a state in which a plurality of end caps for a showcase roller shelf illustrated in  FIG. 1  are installed to the showcase roller shelf. 
         [0045]      FIGS. 3 and 4  illustrate one embodiment of the protrusions  120  which are important components of the end cap  100  for a showcase roller shelf according to the present disclosure. The protrusions  120  include a first protrusion  121 , a second protrusion  122 , a third protrusion  123 , and a fourth protrusion  124 . 
         [0046]    The first protrusion  121  protrudes for a first protrusion distance L 1  downwards from the end of one portion of the cap body  110  positioned in one part, so that the first protrusion  121  may be inserted into the upper end of the casing  13  at the end of the one side among the casings  13  arranged in the plurality of columns. 
         [0047]    The second protrusion  122  is disposed in the lower part facing the first protrusion  121 . The second protrusion  122  protrudes for a second protrusion distance L 2  upwards from the cap body  110  positioned in the lower part, so that the second protrusion  122  may be inserted into the lower end of the casing  13  into which the first protrusion  121  is inserted supportedly. 
         [0048]    The first protrusion  121  and the second protrusion  122  are provided to be inserted supportedly into the upper and lower ends of the casing  13  installed at the end of the one side, that is, at the first support position of the casings  13  arranged from the one side to the other side in the plurality of columns. 
         [0049]    The third protrusion  123  is disposed at the other side portion adjacent to the first protrusion  121 . The third protrusion  123  protrudes for a third protrusion distance L 3  downwards from a casing  13  at the other side adjacent to the casing  13  supporting the first protrusion  121 , so that the third protrusion  123  may be inserted supportedly into the upper end of the casing  13 . 
         [0050]    The fourth protrusion  124  is disposed in the lower part facing the third protrusion  123 . The fourth protrusion  124  protrudes for a fourth protrusion distance L 4  upwards from the cap body  110  positioned in the lower part, so that the fourth protrusion  124  may be inserted into the other end of the casing  13  into which the third protrusion  123  is inserted supportedly. 
         [0051]    The first protrusion distance L 1  is different from the third protrusion distance L 3 , and the second protrusion distance L 2  is different from the fourth protrusion distance L 4 . Therefore, the rollers  11  are misaligned with each other to have different rotation center axis positions in the casings  13  corresponding to the first to fourth protrusion distances L 1  to L 4 . 
         [0052]    That is, the first protrusion distance L 1  is larger than the third protrusion distance L 3 , and the fourth protrusion distance L 4  is larger than the second protrusion distance L 2  by the difference between the first protrusion distance L 1  and the third protrusion distance L 3 . Thus, the positions of center axes upon which the rollers  11  are rotated are misaligned with each other in the casings  13 . 
         [0053]    In other words, the first protrusion  121  protrudes downwards in a direction to the second protrusion  122 , further by Ld which is the difference by which for the first protrusion distance L 1  larger than the third protrusion distance L 3 , and the fourth protrusion  124  protrudes upwards from the lower part facing the third protrusion  123 , further by Ld. Therefore, the rollers  11  protruded upwards and downward in the casings  13  arranged in two columns may be disposed in misalignment with each other, with rotation center axis distances controlled. 
         [0054]    The degree by which the first protrusion distance L 1  is larger than the third protrusion distance L 3  and the degree by which the fourth protrusion distance L 4  is larger than the second protrusion distance L 2  are equally Ld. 2×Ld is smaller than the distance S between the rotation axes of the plurality of rollers  11  installed in the casings  13 . Therefore, the rollers  11  are disposed in the casings  13 , with the positions of their center axes misaligned with each other. 
         [0055]    That is, the first protrusion distance L 1  is larger than the third protrusion distance L 3  and the fourth protrusion distance L 4  is larger than the second protrusion distance L 2 , by the same difference Ld. Therefore, the casing  13  into which the first and second protrusions  121  and  122  are supportedly inserted shifts the center axes of the rollers  11  downwards. Further, the casing  13  into which the third and fourth protrusions  123  and  124  are supportedly inserted shifts the center axes of the rollers  11  upwards. The sum of the distances for which the roller units  10  installed in the two casings  13  supported by the protrusions  120  are shifted upwards and downwards, that is, 2×Ld is set to be smaller than the distance S between the axes of the rollers  11 . Therefore, the rollers  11  are misaligned with each other in the two columns, thereby increasing the contact area between goods and the rollers  11  during transfer. 
         [0056]    Preferably, the degree Ld by which the first protrusion distance L 1  is larger than the third protrusion distance L 3  and the degree Ld by which the fourth protrusion distance L 4  is larger than the second protrusion distance L 2  are equally set to ¼ of the distance S between the rotation axes of the plurality of rollers  11  installed in the casings  13 , so that 2×Ld becomes ½ of the distance S between the rotation axes of the rollers  11 . 
         [0057]    In the casings  13  in the two columns, the first protrusion distance L 1  larger than the third protrusion distance L 3  by Ld leads to an upward shift of the rotation center axes of the rollers  11  supported by the casing  13  at the one side by ¼ of the distance S between the axes of the rollers  11 , and the fourth protrusion distance L 4  larger than the second protrusion distance L 2  by Ld leads to a downward shift of the rotation center axes of the rollers  11  supported by the casing  13  at the other side by ¼ of the distance S between the axe of the rollers  11 . If the rollers  11  at the one side and the rollers  11  at the other side are shifted by ¼ of the distance S between axes in this manner, the rotation center axes of the rollers  11  at the other side are arranged at positions corresponding to ½ of the distance S between the axes of the rollers  11  at the one side. The resulting minimization of the gap between the rollers  11  may maximize a cloud-contact area. 
         [0058]    The first protrusion  121  and the third protrusion  123  alternate with each other, thus being extended in the upper cap body  110  according to the length of the upper cap body  110 , and the second protrusion  122  and the fourth protrusion  124  alternate with each other, thus being extended in the lower cap body  110  according to the length of the lower cap body  110 . That is, roller units  10  having different roller positions can be repeatedly installed according to the lengths of the cap bodies  110 , thereby increasing installation efficiency. 
         [0059]      FIG. 5  is a plan view illustrating a state in which an end cap for a showcase roller shelf according to another embodiment of the present disclosure is installed to the showcase roller shelf, and  FIG. 6  is a perspective view illustrating the state in which the end cap for a showcase roller shelf illustrated in  FIG. 5  is installed to the showcase roller shelf. 
         [0060]      FIGS. 5 and 6  illustrate another embodiment of the protrusions  120  which are important components of the end cap  100  for a show case roller shelf according to the present disclosure. The protrusions  120  includes the first protrusion  121 , the second protrusion  122 , the third protrusion  123 , and the fourth protrusion  124 . The positions and configurations of the protrusions  120  according to another embodiment are identical to those of the protrusions  120  illustrated in  FIGS. 3 and 4 , and thus only a different configuration will be described below. 
         [0061]    The third protrusion distance L 3  of the third protrusion  123  is larger than the first protrusion distance L 1  of the first protrusion  121 , and larger than the fourth protrusion distance L 4  of the fourth protrusion  124  by the difference Ld between the third protrusion distance L 3  and the first protrusion distance L 1 . Thus, the positions of center axes upon which the rollers  11  are rotated in the casings  13  are misaligned with each other in the respective columns. 
         [0062]    In other words, the third protrusion  123  protrudes downwards in a direction to the fourth protrusion  124 , further by the degree by which the third protrusion distance L 3  larger than the first protrusion distance L 1 , and the second protrusion  122  protrudes upwards in the lower part facing the first protrusion  121 , further by Ld. Therefore, the rollers  11  protruded upwards and downward in the casings  13  arranged in two columns may be positioned in misalignment with each other, with rotation center axis distances controlled. 
         [0063]    The degree by which the third protrusion distance L 3  is larger than the first protrusion distance L 1  and the degree by which the second protrusion distance L 2  is larger than the fourth protrusion distance L 4  are equally Ld. 2×Ld is smaller than the distance S between the rotation axes of the plurality of rollers  11  installed in the casings  13 . Therefore, the rollers  11  are disposed in the casings  13 , with the positions of their center axes misaligned with each other in the respective columns. 
         [0064]    That is, the third protrusion distance L 3  is larger than the first protrusion distance L 1  and the second protrusion distance L 2  is larger than the fourth protrusion distance L 4 , by the same difference Ld. Therefore, the casing  13  into which the first and second protrusions  121  and  122  are supportedly inserted shifts the center axes of the rollers  11  upwards. Further, the casing  13  into which the third and fourth protrusions  123  and  124  are supportedly inserted shifts the center axes of the rollers  11  downwards. The sum of the distances for which the roller units  10  installed in the two casings  13  supported by the protrusions  120  shift upwards and downwards, that is, 2×Ld is set to be smaller than the distance S between the axes of the rollers  11 . Therefore, the rollers  11  are misaligned with each other in the two columns, thereby increasing the contact area between goods and the rollers  11  during transfer. 
         [0065]    Preferably, the degree Ld by which the third protrusion distance L 3  is larger than the first protrusion distance L 1  and the degree Ld by which the second protrusion distance L 2  is larger than the fourth protrusion distance L 4  are equally set to ¼ of the distance S between the rotation axes of the plurality of rollers  11  installed in the casings  13 , so that 2×Ld becomes ½ of the distance S between the axes of the rollers  11 . 
         [0066]    In the casings  13  in the two columns, the third protrusion distance L 3  larger than the first protrusion distance L 1  by Ld leads to an upward shift of the rotation center axes of the rollers  11  supported by the casing  13  at the other side by ¼ of the distance S between axes, and the second protrusion distance L 2  larger than the fourth protrusion distance L 4  by Ld leads to a downward shift of the rotation center axes of the rollers  11  supported by the casing  13  at the one side by ¼ of the distance S between axes. If the rollers  11  at the one side and the rollers  11  at the other side are shifted by ¼ of the distance S between axes in this manner, the rotation center axes of the rollers  11  at the other side are arranged at positions corresponding to ½ of the distance S between the axes of the rollers  11  at the one side. The resulting minimization of the gap between the rollers  11  may maximize a cloud-contact area. 
         [0067]    The first protrusion  121  and the third protrusion  123  alternate with each other, thus being extended in the upper cap body  110  according to the length of the upper cap body  110 , and the second protrusion  122  and the fourth protrusion  124  alternate with each other, thus being extended in the lower cap body  110  according to the length of the lower cap body  110 . That is, roller units  10  having different roller positions can be repeatedly installed according to the lengths of the cap bodies  110 , thereby increasing installation efficiency. 
         [0068]    Preferred embodiments of the present disclosure have been disclosed in the specification and drawings. While specific terms are used, they are used in their general meaning to describe the present disclosure and assist understanding of the present disclosure, not limiting the scope of the present disclosure. It will be apparent to those skilled in the art that other modification examples than the disclosed embodiments can be implemented without departing from the scope and spirit of the present disclosure.