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BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a foldable honeycomb structure and the method for making the same, and particularly relates to a foldable honeycomb structure made through a simple process and the method for making the same. 
     2. Description of the Related Art 
     Referring to  FIG. 1 , a schematic sectional view of a first kind of conventional foldable honeycomb structure is shown. The conventional foldable honeycomb structure  1  is applied to thermal insulation devices such as window curtain, and can be texture or non-texture, as shown in  FIG. 2 . Referring to  FIG. 1 , the honeycomb structure  1  is a double cell row structure, in which the reference numbers  11   a ,  11   b ,  11   c ,  12   a ,  12   b  and the like refer to a cell, the cells  11   a ,  11   b ,  11   c  refer to a first row, and the cells  12   a ,  12   b  refer to a second row. 
     Referring to  FIGS. 3   a  to  3   d , schematic views of a method for making the conventional foldable honeycomb structure in  FIG. 1  are shown. First, a flat strip  13  with a length extending longitudinally is provided as shown in  FIG. 3   a . The strip  13  has a first surface  131  and a second surface  132 . 
     Next, referring to  FIG. 3   b , a first longitudinal crease  14  and a second longitudinal crease  15  are formed on the strip  13 , so as to define a first longitudinal margin  16 , a central portion  17  and a second longitudinal margin  18  on the strip  13 . Then, the first longitudinal margin  16  of the strip  13  is folded towards one side (upside) of the strip  13  along the first longitudinal crease  14 , and the second longitudinal margin  18  of the strip  13  is folded towards the other side (underside) of the strip  13  along the second longitudinal crease  15 , thereby forming an approximate Z-shape appearance. The first longitudinal margin  16  has a first surface  161  and a second surface  162 ; the central portion  17  has a first surface  171  and a second surface  172 ; and the second longitudinal margin  18  has a first surface  181  and a second surface  182 , wherein the first surfaces  161 ,  171 ,  181  are the same as the first surface  131  of the strip  13 , and the second surfaces  162 ,  172 ,  182  are the same as the second surface  132  of the strip  13 . 
     Next, referring to  FIG. 3   c , a first glue line  191 , a second glue line  192  and a third glue line  193  are applied longitudinally to the folded strip  13 . The first glue line  191  is applied on the inside surface where the first longitudinal margin  16  and the central portion  17  are overlapped, i.e. between the first surface  161  of the first longitudinal margin  16  and the first surface  171  of the central portion  17 , and the first glue line  191  is at the free end of the first longitudinal margin  16 . The second glue line  192  is applied to the second surface  172  of the central portion  17  at the position where the central portion  17  and the second longitudinal margin  18  are not overlapped, and the second glue line  192  is usually at the position corresponding to half of the width of the first longitudinal margin  16 . The third glue line  193  is applied to the first surface  181  of the second longitudinal margin  18 , and is at the free end of the second longitudinal margin  18 . 
     Next, referring to  FIG. 3   d , the glued strips  13  are stacked; the first glue line  191  is used for adhering the free end of the first longitudinal margin  16  to the central portion  17 ; the second glue line  192  is used for adhering the central portion  17  to a first longitudinal margin of another adjacent (underlying) strip; and the third glue line  193  is used for adhering the second longitudinal margin  18  to a central portion of another adjacent (underlying) strip. The expanded view after adhering is as shown in  FIG. 1 . 
     Referring to  FIG. 4 , a schematic sectional view of a second kind of conventional foldable honeycomb structure is shown. The conventional foldable honeycomb structure  2  is a four-cell row structure. 
     Referring to  FIGS. 5   a  to  5   d , schematic views of a method for making the conventional foldable honeycomb structure in  FIG. 4  is shown. First, referring to  FIG. 5   a , a flat strip  23  with a length extending longitudinally is provided. The strip  23  has a first surface  231  and a second surface  232 . 
     Then, referring to  FIG. 5   b , a first longitudinal crease  24  and a second longitudinal crease  25  are formed on the strip  23 , so as to define a first longitudinal margin  26 , a central portion  27  and a second longitudinal margin  28  on the strip  23 . After that, the first longitudinal margin  26  of the strip  23  is folded towards one side (upside) of the strip  23  along the first longitudinal crease  24 , and the second longitudinal margin  28  of the strip  23  is folded towards the other side (underside) of the strip  23  along the second longitudinal crease  25 , thereby forming an approximate Z-shape appearance. The first longitudinal margin  26  has a first surface  261  and a second surface  262 , the central portion  27  has a first surface  271  and a second surface  272 , and the second longitudinal margin  28  has a first surface  281  and a second surface  282 , wherein the first surfaces  261 ,  271 ,  281  are the same as the first surface  231  of the strip  23 , and the second surfaces  262 ,  272 ,  282  are the same as the second surface  232  of the strip  23 . 
     Then, Referring to  FIG. 5   c , a first glue line  291 , a second glue line  292 , a third glue line  293 , a fourth glue line  294  and a fifth glue line  295  are applied longitudinally to the folded strip  23 . The first glue line  291  is applied to the inside surface where the first longitudinal margin  26  and the central portion  27  are overlapped, i.e. between the first surface  261  of the first longitudinal margin  26  and the first surface  271  of the central portion  27 , and the first glue line  291  is at the location corresponding to the free end of the first longitudinal margin  26 . The second glue line  292  is applied to the second surface  272  of the central portion  27  at the location where the central portion  27  and the second longitudinal margin  28  are not overlapped, and the second glue line  292  is usually at the location corresponding to half of the width of the first longitudinal margin  26 . The third glue line  293  is applied to the first surface  281  of the second longitudinal margin  28 , and is at the free end of the second longitudinal margin  28 . The fourth glue line  294  is applied to the inside surface where the second longitudinal margin  28  and the central portion  27  are overlapped, i.e. between the second surface  282  of the second longitudinal margin  28  and the second surface  272  of the central portion  27 , and the fourth glue line  294  is two thirds of the width of the second longitudinal margin  28  away from the second longitudinal crease  25 . The fifth glue line  295  is applied to the first surface  281  of the second longitudinal margin  28 , and is one third of the width of the second longitudinal margin  28  away from the second longitudinal crease  25 . 
     Next, referring to  FIG. 5   d , the glued strips  23  are stacked, wherein the first glue line  291  is used for adhering the free end of the first longitudinal margin  26  to the central portion  27 . The second glue line  292  is used for adhering the central portion  27  to a first longitudinal margin of another adjacent (underlying) strip. The third glue line  293  is used for adhering the second longitudinal margin  28  to a central portion of another adjacent (underlying) strip. The fourth glue line  294  is used for adhering the second longitudinal margin  28  to the central portion  27 . The fifth glue line  295  is used for adhering the second longitudinal margin  28  to a central portion of another adjacent (underlying) strip. The expanded view after adhering is as shown in  FIG. 4 . 
     The first kind of conventional double cell row honeycomb structure  1  of  FIG. 1  and the second kind of conventional four cell row honeycomb structure  2  of  FIG. 4  and other methods of making the same have been disclosed in U.S. Pat. Nos. 5,482,750, 5,670,000, 5,702,552, 6,319,586. The most important problem of the honeycomb structure and method for making the same described above resides in that the glue lines are between the central portions and the longitudinal margins. Taking the double cell row honeycomb structure  1  of  FIG. 3   c  for example, the first glue line  191  is applied to the inside surface where the first longitudinal margin  16  and the central portion  17  are overlapped. During practical production process, since the first longitudinal margin  16 , the central portion  17  and the second longitudinal margin  18  are very close when the strip  13  is folded as an approximate Z-shape as shown in  FIG. 3   b . Therefore, when the first glue line  191  is to be applied, a strip opener is required to be interposed between the first longitudinal margin  16  and the central portion  17  to open the first longitudinal margin  16 , such that the gluing nozzle can go deep into the gap between the first longitudinal margin  16  and the central portion  17  to apply the first glue line  191 . In this way, the strip  13  will be subjected to a force, which results in the bending deformation of the central portion  17 , and thus the precision of gluing position is affected, as well as the aesthetic appearance of the final products. 
     Similarly, taking the four cell row honeycomb structure  2  of  FIG. 5   c  for example, the first glue line  291  is applied to the inside surface where the first longitudinal margin  26  and the central portion  27  are overlapped, and the fourth glue line  294  is applied to the inside surface where the second longitudinal margin  28  and the central portion  27  are overlapped. The above-mentioned problem of requiring a strip opener is not yet eliminated. 
     Furthermore, another problem of the above honeycomb structure and method for making the same resides in that it employs the same strip, and if a manufactured honeycomb structure is desired to have two sides of different colors, the difficulty in dyeing will be increased; or if a manufactured honeycomb structure is desired to have two sides with different material properties, it is very difficult to manufacture the strip. 
     Consequently, there is an existing need for a foldable honeycomb structure and method for making the same to solve the above-mentioned problems. 
     SUMMARY OF THE INVENTION 
     The main object of the present invention is to provide a method for making a foldable honeycomb structure, wherein the gluing positions are on at least one of exposed outside surfaces. As a result, it need not open the longitudinal margins during the process of applying the longitudinal glue lines, which can avoid the deformation of the strip and have a precise gluing position. Moreover, since the conventional trip opener is omitted, the manufacture equipment can be more simplified, thus reducing the cost and the process time. 
     Another object of the present invention is to provide a method for making a foldable honeycomb structure, wherein two strips of different materials, colors or made through different processes are used to improve the combined functionality. 
     In order to achieve the above objects, the present invention provides a method for making a foldable honeycomb structure, which comprises the steps of: 
     (a) providing a plurality of flat strips each of which has a length extending longitudinally; 
     (b) forming a first longitudinal crease and a second longitudinal crease on each strip, so as to define a first longitudinal margin, a central portion and a second longitudinal margin on each strip; 
     (c) folding the first longitudinal margin of each strip towards one side of the strip along the first longitudinal crease, and folding the second longitudinal margin of each strip towards the other side of each strip along the second longitudinal crease, so that each folded strip has a first exposed outside surface and a second exposed outside surface opposite to the first exposed outside surface; 
     (d) applying a first glue line, a second glue line and a third glue line longitudinally on the first exposed outside surface or the second exposed outside surface of each folded strip; and 
     (e) stacking the glued strips, wherein the first glue line is used for adhering a central portion of a strip to a second longitudinal margin of an adjacent strip; the second glue line is used for adhering a first longitudinal margin of a strip to a second longitudinal margin of an adjacent strip; and the third glue line is used for adhering a first longitudinal margin of a strip to a central portion of an adjacent strip. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a schematic sectional view of a first kind of conventional foldable honeycomb structure; 
         FIG. 2  shows a schematic view of the conventional foldable honeycomb structure of  FIG. 1  applied to the window curtain; 
         FIGS. 3   a - 3   d  show schematic views of a method for making the conventional foldable honeycomb structure of  FIG. 1 ; 
         FIG. 4  shows a schematic sectional view of a second kind of conventional foldable honeycomb structure; 
         FIGS. 5   a - 5   d  show schematic views of a method for making the conventional foldable honeycomb structure of  FIG. 4 ; 
         FIG. 6  shows a schematic sectional view of a foldable honeycomb structure in the first embodiment of the present invention; 
         FIGS. 7   a - 7   d  show schematic views of a method for making the foldable honeycomb structure in the first embodiment of the present invention of  FIG. 6 ; 
         FIG. 8  shows a schematic sectional view of a foldable honeycomb structure in the second embodiment of the present invention; 
         FIGS. 9   a - 9   d  show schematic views of a method for making the foldable honeycomb structure in the second embodiment of the present invention of  FIG. 8 ; 
         FIG. 10  shows a schematic sectional view of a foldable honeycomb structure in a third embodiment of the present invention; 
         FIGS. 11   a  and  11   b  show schematic views of a method for making the foldable honeycomb structure in the third embodiment of the present invention of  FIG. 10 ; 
         FIG. 12  shows a schematic sectional view of a foldable honeycomb structure in a fourth embodiment of the present invention; 
         FIGS. 13   a - 13   e  show schematic views of a method for making the foldable honeycomb structure in the fourth embodiment of the present invention of  FIG. 12 ; 
         FIG. 14  shows a schematic sectional view of a foldable honeycomb structure in the fifth embodiment of the present invention; 
         FIGS. 15   a - 15   e  show schematic views of a method for making the foldable honeycomb structure in the fifth embodiment of the present invention of  FIG. 14 ; 
         FIG. 16  shows a schematic sectional view of a foldable honeycomb structure in a sixth embodiment of the present invention; and 
         FIGS. 17   a  and  17   b  show schematic views of a method for making the foldable honeycomb structure in the sixth embodiment of the present invention of  FIG. 16 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIG. 6 , a schematic sectional view of a foldable honeycomb structure in a first embodiment of the present invention is shown. The foldable honeycomb structure  3  is applied to the thermal insulation devices such as window curtain or shield curtain, and can be texture or non-texture. The honeycomb structure  3  is of a double cell row structure, in which reference numbers  31   a ,  31   b ,  31   c ,  32   a ,  32   b  refer to a cell respectively, the cells  31   a ,  31   b ,  31   c  refer to a first row, and the cells  32   a ,  32   b  refer to a second row. 
     Referring to  FIGS. 7   a  to  7   d , schematic views of a method for making the foldable honeycomb structure in the first embodiment of the present invention of  FIG. 6  are shown. First, referring to  FIG. 7   a , a plurality of flat strips  33  each has a length extending longitudinally are provided. It is to be noted that one strip  33  is illustrated in the embodiment. The strip  33  has a first surface  331  and a second surface  332 . 
     Next, referring to  FIG. 7   b , a first longitudinal crease  34  and a second longitudinal crease  35  are formed on the strip  33 , so as to define a first longitudinal margin  36 , a central portion  37  and a second longitudinal margin  38  on the strip  33 . After that, the first longitudinal margin  36  of the strip  33  is folded towards one side (upside) of the strip  33  along the first longitudinal crease  34 , and the second longitudinal margin  38  of the strip  33  is folded towards the other side (underside) of the strip  33  along the second longitudinal crease  35 , thereby forming an approximate Z-shape appearance. The total width of the first longitudinal margin  36  and the second longitudinal margin  38  is slightly larger than that of the central portion  37 . Preferably, the widths of the first longitudinal margin  36  and the second longitudinal margin  38  are the same, and both of them are slightly larger than half of the width of the central portion  37 . 
     The first longitudinal margin  36  has a first surface  361 , a second surface  362  and a free end  363 . The central portion  37  has a first surface  371  and a second surface  372 . The second longitudinal margin  38  has a first surface  381 , a second surface  382  and a free end  383 . The first surfaces  361 ,  371 ,  381  are the same as the first surface  31  of the strip  33 , and the second surfaces  362 ,  372 ,  382  are the same as those of second surface  332  the strip  33 . However, the folded strip  33  has a first exposed outside surface and a second exposed outside surface opposite to the first exposed outside surface, wherein the first exposed outside surface comprises the second surface  362  of the first longitudinal margin  36  and the surface where the first surface  371  of the central portion  37  and the first longitudinal margin  36  are not overlapped (i.e. the right side of the first surface  371 ); the second exposed outside surface comprises the first surface  381  of the second longitudinal margin  38  and the surface where the second surface  372  of the central portion  37  and the second longitudinal margin  38  are not overlapped (i.e. the left side of the second surface  372 ). 
     Then, referring to  FIG. 7   c , a first glue line  391 , a second glue line  392  and a third glue line  393  are applied longitudinally to the exposed outside surface of the folded strip  33 . In the embodiment, the first glue line  391 , the second glue line  392  and the third glue line  393  are all applied to the first exposed outside surface, wherein the first glue line  391  is applied to the surface where the first surface  371  of the central portion  37  and the first longitudinal margin  36  are not overlapped (i.e. the right side of the first surface  371 ); the second glue line  392  and the third glue line  393  are applied to the second surface  362  of the first longitudinal margin  36 , wherein the second glue line  392  is applied to the free end  363  of the first longitudinal margin  36 ; and the third glue line  393  is applied to the central position of the first longitudinal margin  36 . It is understood that the first glue line  391 , the second glue line  392  and the third glue line  393  can all be applied to the second exposed outside surface; or the first glue line  391 , the second glue line  392  and the third glue line  393  can be applied to different exposed outside surfaces respectively. 
     Since the first glue line  391 , the second glue line  392  and the third glue line  393  are all applied to the exposed outside surface, it is not necessary to open the first longitudinal margin  36  during the process of applying the glue lines, which can avoid the deformation of the strip  33  and have a precise gluing position. Moreover, the conventional strip opener can be omitted, thus simplifying the manufacturing equipment. 
     Then, Referring to  FIG. 7   d , the glued strips  33  are stacked, wherein the first glue line  391  is used for adhering the central portion  37  of the strip  33  to a longitudinal margin of an adjacent (upper) strip. The second glue line  392  is used for adhering the free end  363  of the first longitudinal margin  36  of the strip  33  to the free end of a longitudinal margin of the adjacent (upper) strip. The third glue line  393  is used for adhering the first longitudinal margin  36  of the strip  33  to a central portion of the adjacent (upper) strip. The expanded view of the strips after adhering is as shown in  FIG. 6 . 
     Returning to  FIG. 6 , the foldable honeycomb structure  3  is stacked by a plurality of folded strips  33 , and each of the folded strip  33  comprises a first longitudinal crease  34 , a second longitudinal crease  35 , a central portion  37 , a first longitudinal margin  36 , a second longitudinal margin  38 , a first glue line  391 , a second glue line  392  and a third glue line  393 . The central portion  37  is between the first longitudinal crease  34  and the second longitudinal crease  35 . The first longitudinal margin  36  is folded towards one side (upside) of the central portion  37  along the first longitudinal crease  34 . The second longitudinal margin  38  is folded towards the other side (underside) of the central portion  37  along the second longitudinal crease  35 . The total width of the first longitudinal margin  36  and the second longitudinal margin  38  is slightly larger than that of the central portion  37 . Preferably, the widths of the first longitudinal margin  36  and the second longitudinal margin  38  are the same, slightly larger than half of the width of the central portion  37 . 
     The folded strip  33  has a first exposed outside surface and a second exposed outside surface opposite to the first exposed outside surface. The first glue line  391  is on the first exposed outside surface of the folded strip  33  and the central portion  37 , which is used for adhering the central portion  37  to a longitudinal margin of an adjacent strip. The second glue line  392  is on the first exposed outside surface of the folded strip  33  and the free end of the first longitudinal margin  36 , which is used for adhering the free end of the first longitudinal margin  36  to the free end of a longitudinal margin of the adjacent strip. The third glue line  393  is on the first exposed outside surface of the folded strip  33  and the first longitudinal margin  36 , which is used for adhering the first longitudinal margin  36  to of a central portion of the adjacent strip. 
     Referring to  FIG. 8 , a schematic sectional view of a foldable honeycomb structure in a second embodiment of the present invention is shown. The foldable honeycomb structure  4  is a four-cell row structure. 
     Referring to  FIGS. 9   a  to  9   d , schematic views of a method for making a foldable honeycomb structure in the second embodiment of the present invention are shown. The method for making the present embodiment is substantially the same as that of the first embodiment, except that two more bonding lines are formed during the gluing step of the present embodiment. First, referring to  FIG. 9   a , a plurality of flat strips  33  each has a length extending longitudinally are provided. It is to be noted that one strip  33  is illustrated in the embodiment. The strip  33  has a first surface  331  and a second surface  332 . 
     Next, referring to  FIG. 9   b , a first longitudinal crease  34  and a second longitudinal crease  35  are formed on the strip  33 , so as to define a first longitudinal margin  36 , a central portion  37  and a second longitudinal margin  38  on the strip  33 . After that, the first longitudinal margin  36  of the strip  33  is folded towards one side (upside) of the strip  33  along the first longitudinal crease  34 , and the second longitudinal margin  38  of the strip  33  is folded towards the other side (underside) of the strip  33  along the second longitudinal crease  35 , thereby forming an approximate Z-shape appearance. The folded strip  33  is the same as the strip  33  of  FIG. 7   b , and both of them have a first exposed outside surface and a second exposed outside surface opposite to the first exposed outside surface, wherein the first exposed outside surface comprises the second surface  362  of the first longitudinal margin  36  and the surface where the first surface  371  of the central portion  37  and the first longitudinal margin  36  are not overlapped (i.e. the right side of the first surface  371 ); the second exposed outside surface comprises the first surface  381  of the second longitudinal margin  38  and the surface where the second surface  372  of the central portion  37  and the second longitudinal margin  38  are not overlapped (i.e. the left side of the second surface  372 ). 
     Then, referring to  FIG. 9   c , a first glue line  391 , a second glue line  392  and a third glue line  393  are applied longitudinally, and a fourth bonding line  394  and a fifth bonding line  395  are formed. In the present embodiment, the first glue line  391 , the second glue line  392  and the third glue line  393  are all applied to the first exposed outside surface, wherein the first glue line  391  is applied to the first surface  371  of the central portion  37  which is not overlapped by the first longitudinal margin  36  (i.e. the right side of the first surface  371 ), and the first glue line  391  is two fifths of the width of the second longitudinal margin  38  away from the second longitudinal crease  35 . The second glue line  392  and the third glue line  393  are applied to the second surface  362  of the first longitudinal margin  36 , wherein the second glue line  392  is applied to the free end  363  of the first longitudinal margin  36 , and the third glue line  393  is two fifths of the width of the first longitudinal margin  36  away from the first longitudinal crease  34 . 
     It is understood that the first glue line  391 , the second glue line  392  and the third glue line  393  can all be applied to the second exposed outside surface; or the first glue line  391 , the second glue line  392  and the third glue line  393  can be applied to different exposed outside surfaces respectively. 
     In the present embodiment, the fourth bonding line  394  is a fourth glue line  394 , and the fifth bonding line  395  is a fifth glue line  395 . The fourth bonding line  394  is on the inside surface where the first longitudinal margin  36  and the central portion  37  are overlapped in the folded strip  33 , and it is four fifths of the width of the first longitudinal margin  36  away from the first longitudinal crease  34 . The fifth bonding line  395  is on the inside surface where the second longitudinal margin  38  and the central portion  37  are overlapped in the folded strip  33 , and it is four fifths of the width of the second longitudinal margin  38  away from the second longitudinal crease  35 . It should be noted that the fourth bonding line  394  and the fifth bonding line  395  can also be bonded by using other bonding methods such as ultrasonic bonding or the like. In other applications, the fourth bonding line  394  and the fifth bonding line  395  can be formed previously, and the gluing operation (the first glue line  391 , the second glue line  392  and the third glue line  393 ) is then carried out. 
     Next, referring to  FIG. 9   d , the glued strips  33  are stacked, wherein the first glue line  391  is used for adhering the central portion  37  of the strip  33  to a longitudinal margin of an adjacent (upper) strip; the second glue line  392  is used for adhering the free end  363  of the first longitudinal margin  36  of the strip  33  to the free end of a longitudinal margin of the adjacent (upper) strip; the third glue line  393  is used for adhering the first longitudinal margin  36  of the strip  33  to a central portion of the adjacent (upper)strip; the fourth bonding line  394  is used for bonding the first longitudinal margin  36  to the central portion  37 ; and the fifth bonding line  395  is used for bonding the second longitudinal margin  38  to the central portion  37 . The expanded view of the strips after adhering is as shown in  FIG. 8 . 
     Returning to  FIG. 8 , the foldable honeycomb structure  4  is stacked by a plurality of folded strips  33 , and each folded strip comprises a first longitudinal crease  34 , a second longitudinal crease  35 , a central portion  37 , a first longitudinal margin  36 , a second longitudinal margin  38 , a first glue line  391 , a second glue line  392 , a third glue line  393 , a fourth bonding line  394  and a fifth bonding line  395 . The central portion  37  is between the first longitudinal crease  34  and the second longitudinal crease  35 . The first longitudinal margin  36  is folded towards one side (upside) of the central portion  37  along the first longitudinal crease  34 . The second longitudinal margin  38  is folded towards the other side (underside) of the central portion  37  along the second longitudinal crease  35 . The total width of the first longitudinal margin  36  and the second longitudinal margin  38  is slightly larger than that of the central portion  37 . Preferably, the width of the first longitudinal margin  36  is the same as that of the second longitudinal margin  38 , and both of the widths are slightly larger than half of the width of the central portion  37 . 
     The folded strip  33  has a first exposed outside surface and a second exposed outside surface opposite to the first exposed outside surface. The first glue line  391  is on the first exposed outside surface of the folded strip  33  and the central portion  37 , which is used for adhering the central portion  37  to a longitudinal margin of an adjacent strip. The second glue line  392  is on the first exposed outside surface of the folded strip  33  and on the free end of the first longitudinal margin  36 , which is used for adhering the free end  363  of the first longitudinal margin  36  to the free end of a longitudinal margin of the adjacent strip. The third glue line  393  is on the first exposed outside surface of the folded strip  33  and the first longitudinal margin  36 , which is used for adhering the first longitudinal margin  36  to a central portion of the adjacent strip. 
     The fourth bonding line  394  is on the inside surface where the first longitudinal margin  36  and the central portion  37  are overlapped in the s folded strip  33 , which is used for bonding the first longitudinal margin  36  to the central portion  37 . The fifth bonding line  395  is positioned on the inside surface where the second longitudinal margin  38  and the central portion  37  are overlapped in the folded strip  33 , which is used for bonding the second longitudinal margin  38  to the central portion  37 . 
     Referring to  FIG. 10 , a schematic sectional view of a foldable honeycomb structure in a third embodiment of the present invention is shown. The foldable honeycomb structure  40  is a four-cell row structure. 
     Referring to  FIGS. 11   a  and  11   b , schematic views of a method for making the foldable honeycomb structure in the third embodiment of the present invention of  FIG. 10  are shown. The method for making the present embodiment is substantially the same as that of the second embodiment, except that in the present embodiment the width of the first longitudinal margin  36  is different from that of the second longitudinal margin  38 , and the fifth bonding line  395  is in a different position. Preferably, in the present embodiment, the ratio of width of the first longitudinal margin  36  to the width of the second longitudinal margin  38  is approximately more than 3:2. In the present embodiment, the fifth bonding line  395  is on the second surface  362  of the first longitudinal margin  36  of the first exposed outside surface. Therefore, the fifth bonding line  395  is a fifth glue line  395 . It should be noted that the corresponding positions of the first glue line  391 , the second glue line  392 , the third glue line  393  and the fourth glue line  394  are the same as that in the second embodiment, but they need to be adjusted slightly along horizontal direction. Referring to  FIG. 11   b , after the glued strips  33  are stacked, the fifth glue line  395  is used for adhering the first longitudinal margin  36  of the strip  33  to a central portion of an adjacent (upper) strip. The expanded view of after adhering is as shown in  FIG. 10 . 
     Returning to  FIG. 10 , the foldable honeycomb structure  40  is substantially the same as the foldable honeycomb structure  4  in the second embodiment, only except that in the present embodiment the width of the first longitudinal margin  36  is different from that of the second longitudinal margin  38 , and the fifth bonding line  395  is in a different position. Preferably, in the present embodiment, the ratio of the width of the first longitudinal margin  36  to the width of the second longitudinal margin  38  is approximately more than 3:2. In the present embodiment, the fifth bonding line  395  is on the second surface  362  of the first longitudinal margin  36  of the first exposed outside surface. Therefore, the fifth bonding line  395  is a fifth glue line  395 . The fifth glue line  395  is used for adhering the first longitudinal margin  36  of the strip  33  to a central portion of an adjacent (upper) strip. 
     Referring to  FIG. 12 , a schematic sectional view of a foldable honeycomb structure in a fourth embodiment of the present invention is shown. The foldable honeycomb structure  41  is a double-cell row structure. 
     Referring to  FIGS. 13   a  to  13   e , schematic views of a method for making the foldable honeycomb structure in the fourth embodiment of the present invention of  FIG. 12  are shown. First, referring to  FIG. 13   a , a plurality of first strips  5  and a plurality of second strips  6  are provided. It is to be noted that one first strip  5  and one second strip  6  are illustrated in the embodiment. Both of the first strip  5  and the second strip  6  are flat and have a length extending longitudinally. In the present embodiment, the color or material of the first strip  5  is different from that of the second strip  6 . 
     Next, referring to  FIG. 13   b , a first longitudinal crease  53  is formed on the first strip  5  and the first strip  5  is folded along the first longitudinal crease  53 , thereby defining a first region  54  and a second region  55  on the first strip  5 . The first region  54  has a first surface  541 , a second surface  542  and a free end  543 . The second region  55  has a first surface  551 , a second surface  552  and a free end  553 . 
     A second longitudinal crease  63  is formed on the second strip  6  and the second strip  6  is folded along the second longitudinal crease  63 , thereby defining a third region  64  and a fourth region  65  on the second strip  6 . The third region  64  has a first surface  641 , a second surface  642  and a free end  643 . The fourth region  65  has a first surface  651 , a second surface  652  and a free end  653 . 
     Next, referring to  FIG. 13   c , the free end  553  of the second region  55  is connected to the free end  643  of the third region  64 , so as to form a combined strip  42 . In the combined strip  42 , the total width of the first region  54  and the fourth region  65  is larger than that of the second region  55  and the third region  64  after combination. In the present embodiment, a glue line  43  is used to connect the free end  553  of the second region  55  to the free end  643  of the third region  64 . However, it can be understood that the free end  553  of the second region  55  can be connected to the free end  643  of the third region  64  by any other conventional methods. 
     The combined strip  42  has a first exposed outside surface and a second exposed outside surface opposite to the first exposed outside surface. The first exposed outside surface comprises the first surface  541  of the first region  54  and the first surface  641  of the third region  64 . The second exposed outside surface comprises the second surface  552  of the second region  55  and the second surface  652  of the fourth region  65 . 
     Next, referring to  FIG. 13   d , a first glue line  431 , a second glue line  432  and a third glue line  433  are applied longitudinally to the same exposed outside surface of the combined strip  42 . In the present embodiment, the first glue line  431 , the second glue line  432  and the third glue line  433  are all applied to the first exposed outside surface, wherein the first glue line  431  is applied to the third region  64 , preferably, on the central portion of the third region  64 . The second glue line  432  is applied to the free end  543  of the first region  54 . The third glue line  433  is applied to the first region  54 , preferably, on the central portion of the first region  54 . It can be understood that the first glue line  431 , the second glue line  432  and the third glue line  433  can also be applied to the second exposed outside surface; or the first glue line  431 , the second glue line  432  and the third glue line  433  can be applied to different exposed outside surfaces respectively. 
     Next, referring to  FIG. 13   e , the glued combined strips  42  are stacked, wherein the first glue line  431  is used for adhering the third region  64  to a fourth region of an adjacent (above) combined strip. The second glue line  432  is used for adhering the free end  543  of the first region  54  to the free end of a fourth region of the adjacent (above) combined strip. The third glue line  433  is used for adhering the first region  54  to a second region of the adjacent (above) combined strip. The expanded view after adhering is as shown in  FIG. 12 . 
     Returning to  FIG. 12 , the foldable honeycomb structure  41  is stacked by a plurality of combined strips  42 , and each combined strip  42  comprises a first strip  5 , a second strip  6 , a first glue line  431 , a second glue line  432  and a third glue line  433 . 
     The first strip  5  comprises a first longitudinal crease  53 , a first region  54  and a second region  55 . The first region  54  is folded towards the second region  55  along the first longitudinal crease  53 , and the first region  54  and the second region  55  each has a free end. The second strip  6  comprises a second longitudinal crease  63 , a third region  64  and a fourth region  65 . The third region  64  is folded towards the fourth region  65  along the second longitudinal crease  63 , and the third region  64  and the fourth region  65  each has a free end. The free end of the third region  64  is connected to the free end of the second region  55  by using a glue line  43 , so as to form a combined strip  42  which has a first exposed outside surface and a second exposed outside surface opposite to the first exposed outside surface. 
     The first glue line  431  is on the first exposed outside surface of the combined strip  42  and the third region  64 , which is used for adhering the third region  64  to a fourth region of an adjacent combined strip. The second glue line  432  is on the first exposed outside surface of the combined strip  42  and the free end  543  of the first region  54 , which is used for adhering the free end  543  of the first region  54  to the free end of a fourth region of the adjacent combined strip. The third glue line  433  is on the first exposed outside surface of the combined strip  42  and the first region  54 , which is used for adhering the first region  54  to a second region of the adjacent combined strip. 
     It can be understood that the first glue line  431 , the second glue line  432  and the third glue line  433  can also be applied to the second exposed outside surface; or the first glue line  431 , the second glue line  432  and the third glue line  433  can be applied to different exposed outside surfaces respectively. 
     The material or manufacturing process of the first strip  5  can be different from those of the second strip  6 , such that the combined functionality can be increased. 
     Referring to  FIG. 14 , a schematic sectional view of a foldable honeycomb structure in a fifth embodiment of the present invention is shown. The foldable honeycomb structure  7  is a four-cell row structure. 
     Referring to  FIGS. 15   a  to  15   d , schematic views of a method for making the foldable honeycomb structure in the fifth embodiment of the present invention of  FIG. 14  are shown. The method for making the present embodiment is substantially the same as that of the fourth embodiment, only except that two more bonding lines are formed in the gluing step of the present embodiment. 
     First, referring to  FIG. 15   a , a plurality of first strips  5  and a plurality of second strips  6  are provided. It is to be noted that one first strip  5  and one second strip  6  are illustrated in the embodiment. Both of the first strip  5  and the second strip  6  are flat and have a length extending longitudinally. 
     Next, referring to  FIG. 15   b , a first longitudinal crease  53  is formed on the first strip  5  and the first strip  5  is folded along the first longitudinal crease  53 , thereby defining a first region  54  and a second region  55  on the first strip  5 . The first region  54  has a first surface  541 , a second surface  542  and a free end  543 . The second region  55  has a first surface  551 , a second surface  552  and a free end  553 . 
     A second longitudinal crease  63  is formed on the second strip  6  and the second strip  6  is folded along the second longitudinal crease  63 , thereby defining a third region  64  and a fourth region  65  on the second strip  6 . The third region  64  has a first surface  641 , a second surface  642  and a free end  643 . The fourth region  65  has a first surface  651 , a second surface  652  and a free end  653 . 
     Next, referring to  FIG. 15   c , the free end  553  of the second region  55  is connected to the free end  643  of the third region  64 , so as to form a combined strip  42 . In the combined strip  42 , the total width of the first region  54  and the fourth region  65  is larger than that of the second region  55  and the third region  64  after combination. In the present embodiment, a glue line  43  is used to connect the free end  553  of the second region  55  to the free end  643  of the third region  64 . However, it can be understood that the free end  553  of the second region  55  can be connected to the free end  643  of the third region  64  by any other conventional method such as ultrasonic bonding or the like. 
     The combined strip  42  has a first exposed outside surface and a second exposed outside surface opposite to the first exposed outside surface. The first exposed outside surface comprises the first surface  541  of the first region  54  and the first surface  641  of the third region  64 . The second exposed outside surface comprises the second surface  552  of the second region  55  and the second surface  652  of the fourth region  65 . 
     Next, referring to  FIG. 15   d , a first glue line  431 , a second glue line  432 , and a third glue line  433  are applied longitudinally to the combined strip  42 , and a fourth bonding line  434  and a fifth bonding line  435  are formed on the combined strip  42 . The first glue line  431 , the second glue line  432  and the third glue line  433  are all applied to the first exposed outside surface, wherein the first glue line  431  is applied to the third region  64 , preferably, the first glue line  431  is about two fifths of the width of the third region  64  away from the second longitudinal crease  63 . The second glue line  432  is applied to the free end  543  of the first region  54 . The third glue line  433  is applied to the first region  54 , preferably, the third glue line  433  is about two fifths of the width of the first region  54  away from the first longitudinal crease  53 . 
     It can be understood that the first glue line  431 , the second glue line  432  and the third glue line  433  can also be applied to the second exposed outside surface; or the first glue line  431 , the second glue line  432  and the third glue line  433  can be applied to different exposed outside surfaces respectively. 
     In the embodiment, the fourth bonding line  434  is a fourth glue line  434 , and the fifth bonding line  435  is a fifth glue line  435 . The fourth bonding line  434  is on the inside surface where the first region  54  and the second region  55  are overlapped in the combined strip  42 , i.e. the second surface  542  of the first region  54  or the first surface  551  of the second region  55 . The fourth bonding line  434  is about four fifths of the width of the second region  55  away from the first longitudinal crease  53 . The fifth bonding line  435  is on the inside surface where the third region  64  and the fourth region  65  are overlapped in the combined strip  42 , i.e. the second surface  642  of the third region  64  or the first surface  651  of the fourth region  65 . The fifth bonding line  435  is about four fifths of the width of the fourth region  64  away from the second longitudinal crease  63 . It should be noted that the fourth bonding line  434  and the fifth bonding line  435  can also be bonded by other bonding methods such as ultrasonic bonding or the like. In other applications, the fourth bonding line  434  and the fifth bonding line  435  can be formed previously, and the gluing operation (the first glue line  431 , the second glue line  432  and the third glue line  433 ) is then carried out. 
     Next, referring to  FIG. 15   e , the glued combined strips  42  are stacked, wherein the first glue line  431  is used for adhering the third region  64  to a fourth region of an adjacent (upper) combined strip. The second glue line  432  is used for adhering the free end  543  of the first region  54  to the free end of a fourth region of the adjacent (upper) combined strip. The third glue line  433  is used for adhering the first region  54  to a second region of the adjacent (upper) combined strip. The fourth bonding line  434  is used for bonding the first region  54  to the second region  55 . The fifth bonding line  435  is used for bonding the third region  64  to the fourth region  65 . The expanded view after adhering is as shown in  FIG. 14 . 
     Returning to  FIG. 14 , the foldable honeycomb structure  7  is stacked by a plurality of combined strips  42 . Each combined strip  42  comprises a first strip  5 , a second strip  6 , a first glue line  431 , a second glue line  432 , a third glue line  433 , a fourth bonding line  434  and a fifth bonding line  435 . 
     The first strip  5  comprises a first longitudinal crease  53 , a first region  54  and a second region  55 . The first region  54  is folded towards the second region  55  along the first longitudinal crease  53 , and the first region  54  and the second region  55  each has a free end. The second strip  6  comprises a second longitudinal crease  63 , a third region  64  and a fourth region  65 . The third region  64  is folded towards the fourth region  65  along the second longitudinal crease  63 , and the third region  64  and the fourth region  65  each has a free end. The free end of the third region  64  is connected to the free end of the second region  55 , so as to form a combined strip  42  which has a first exposed outside surface and a second exposed outside surface opposite to the first exposed outside surface. 
     The first glue line  431  is on the first exposed outside surface of the combined strip  42  and the third region  64 , which is used for adhering the third region  64  to a fourth region of an adjacent combined strip. The second glue line  432  is on the first exposed outside surface of the combined strip  42  and the free end  543  of the first region  54 , which is used for adhering the free end  543  of the first region  54  to the free end of a fourth region of the adjacent combined strip. The third glue line  433  is on the first exposed outside surface of the combined strip  42  and the first region  54 , which is used for adhering the first region  54  to a second region of the adjacent combined strip. The fourth bonding line  434  is on the inside surface where the first region  54  and the second region  55  are overlapped in the combined strip  42 , i.e., the second surface  542  of the first region  54  or the first surface  551  of the second region  55 , and the fourth bonding line  434  is used for bonding the first region  54  to the second region  55 . The fifth bonding line  435  is on the inside surface where the third region  64  and the fourth region  65  are overlapped in the combined strip  42 , i.e., the second surface  642  of the third region  64  or the first surface  651  of the fourth region  65 , and the fifth bonding line  435  is used for bonding the third region  64  to the fourth region  65 . 
     Referring to  FIG. 16 , a schematic sectional view of a foldable honeycomb structure in a sixth embodiment of the present invention is shown. The foldable honeycomb structure  70  is a four-cell row structure. 
     Referring to  FIGS. 17   a  and  17   b , schematic views of a method for making the foldable honeycomb structure in the sixth embodiment of the present invention of  FIG. 16  are shown. The method for making the present embodiment is substantially the same as that of the fifth embodiment, only except that in the present embodiment the width of the first strip  5  is different from that of the second strip  6  (i.e. the width of the first region  54  is different from that of the third region  64 ), and the fifth bonding line  435  is in a different position. Preferably, in the present embodiment, the ratio of the width of the first region  54  to the width of the third region  64  is approximately larger than 3:2. In the embodiment, the fifth bonding line  435  is on the first surface  541  of first region  54  of the first exposed outside surface. Therefore, the fifth bonding line  435  is a fifth glue line  435 . It should be noted that the corresponding positions of the first glue line  431 , the second glue line  432 , the third glue line  433  and the fourth glue line  434  are the same as those of the fifth embodiment, but they need to be adjusted slightly along horizontal direction. Referring to  FIG. 17   b , after the glued combined strips  42  are stacked, the fifth glue line  435  is used for adhering the first region  54  to a second region of an adjacent combined strip. The expanded view after adhering is as shown in  FIG. 16 . 
     Returning to  FIG. 16 , the foldable honeycomb structure  70  is substantially the same as the foldable honeycomb structure  7  of the fifth embodiment, only except that in the present embodiment the width of the first strip  5  is different from that of the second strip  6 , and the fifth bonding line  435  is in a different position. Preferably, in the present embodiment, the ratio of the width of the first region  54  to the width of the third region  64  is approximately more than 3:2. In the present embodiment, the fifth bonding line  435  is on the first surface  541  of the first region  54  of the first exposed outside surface. Therefore, the fifth bonding line  435  is a fifth glue line  435 . The fifth glue line  435  is used for adhering the first region  54  to a second region of an adjacent combined strip. 
     While several embodiments of the present invention have been illustrated and described, various modifications and improvements can be made by those skilled in the art. The embodiments of the present invention are therefore described in an illustrative but not restrictive sense. It is intended that the present invention may not be limited to the particular forms as illustrated, and that all modifications which maintain the spirit and scope of the present invention are within the scope as defined in the appended claims.

Summary:
The present invention relates to a foldable honeycomb structure and method for making the same. The method comprises (a) providing a plurality of flat strips; (b) forming a pair of longitudinal creases in each strip thereby defining the first two longitudinal margins of each strip and a central portion of each strip between the creases; (c) folding each strip along said creases so that each folded strip has two exposed outside surfaces; (d) applying at least three longitudinal glue lines to the exposed outside surface of each folded strip; and (e) stacking the glued strips. As a result, it need not open the longitudinal margins during the process of applying the longitudinal glue lines, which can avoid the deformation of the strip and have a precise gluing position.