Abstract:
A method for manufacturing a packing made of a three-dimensional net-like structure which constitutes an internal structure of device which performs material transfer, heat exchange or mixing between gases, liquids or gas and liquid, the internal structure being divided in a plurality of chambers or channels connected to one another is provided. The three-dimensional net-like structure is made of a plurality of unit structures which are arranged continuously in vertical and horizontal directions of the three-dimensional net-like structure. Each of the unit structures is formed by converging and dispersion of three or four line elements. The method comprises a step of forming a converging section of the unit structure where the three or four line elements converge by binding the three or four line elements together.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates to a column packing filled in a device which is divided in a plurality of chambers or channels connected to one another and performs material transfer, heat exchange or mixing between gases, liquids or gas and liquid. The invention relates also to a method for manufacturing such column packing.  
           [0002]    Japanese Patent Application Laid-open Publication No. Hei 3-203976 discloses a column packing of this type. This column packing is made up of a plurality of permeable sheets which are disposed in parallel to one another and extend in the direction of a main stream of fluid. Projecting portions of these permeable sheets are disposed in the direction that crosses the main stream of fluid and these projections function as spacers between the adjacent permeable sheets. This packing (hereinafter referred to as “X-packing” because the cross section of a joint portion between two adjacent permeable sheets assumes the shape of the letter X) is beneficial in that fluid flowing down along the permeable sheets is repeatedly joined, mixed, horizontally dispersed and redistributed at each joint of the permeable sheets. Thus, fluid flow which was not uniform when it was charged in the device gradually becomes uniform resulting in an optimum material transfer or heat exchange. Moreover, gas charged in the device passes through the liquid flowing along the inclined surfaces of the permeable sheets and necessary contact between the gas and the liquid is achieved by contacting the gas with the liquid while the gas passes through the permeable sheets, so that material transfer or heat exchange can be effected efficiently with a minimum pressure loss.  
           [0003]    For manufacturing this X-packing, the inventor of this application proposed the method described in U.S. Pat. No. 5, 673,726. According to this method, as shown in FIG. 24, permeable sheets  51  in plural layers and joints  51   b  of adjacent permeable sheets  51  are simultaneously produced and a three-dimensional woven packing  50  thereby is produced.  
           [0004]    In a case where this X-packing manufactured by the above described prior art method is used as a packing loaded in, e.g., a gas-liquid mixing device, the packing  50  of FIG. 24 is erected in the device and liquid from a distributor is caused to flow from the top to the bottom, i.e., in the direction of arrow A. It is, however, actually difficult to maintain the packing  50  strictly horizontally in the device by reason of an error in installation or other causes and, as a result, the threads that run crosswise of the separated portions  51   a  and the joints  51   b  of the packing  50  are disposed in a somewhat inclined relationship to the horizontal direction. For this reason, when the operation of the device is started and liquid is caused to flow in the direction of the arrow A, the liquid flows concentrically along a lower portion of the threads that run crosswise with the result that collection, horizontal distribution and downward redistribution of the liquid are not performed uniformly but flow of the liquid tends to concentrate on the lower portion of the inclined threads running corsswise.  
           [0005]    It is, therefore, an object of the invention to provide an X-packing capable of accurately achieving uniform collection and redistribution of liquid at joints of the X-packing.  
           [0006]    It is another object of the invention to provide a method for manufacturing such X-packing at a low cost and in a large scale.  
         SUMMARY OF THE INVENTION  
         [0007]    For achieving the above described objects of the invention, there is provided a method for manufacturing a packing made of a three-dimensional net-like structure which constitutes an internal structure of a device which performs material transfer, heat exchange or mixing between gases, liquids or gas and liquid, said internal structure being divided in a plurality of chambers or channels connected to one another and said three-dimensional net-like structure being made of a plurality of unit structures which are arranged continuously in vertical and horizontal directions of the three-dimensional net-like structure, each of the unit structures being formed by converging and dispersion of three line elements, said method comprising a step of forming a converging section of the unit structure where the three line elements converge by binding the three line elements together.  
           [0008]    There is also provided a method for manufacturing a packing made of a three-dimensional net-like structure which constitutes an internal structure of a device which performs material transfer, heat exchange or mixing between gases, liquids or gas and liquid, said internal structure being divided in a plurality of chambers or channels connected to one another and said three-dimensional net-like structure being made of a plurality of unit structures which are arranged continuously in vertical and horizontal directions of the three-dimensional net-like structure, each of the unit structures being formed by converging and dispersion of three line elements, said method comprising steps of:  
           [0009]    (A) forming a unit structure with three line elements, said unit structure consisting of a plurality of basic units each of which is a combination of two triangular pyramids having a common bottom surface and apexes disposed in opposite directions, said basic units being arranged continuously in vertical direction of the three-dimensional net-like structure with apexes of each of the basic units being in contact with apexes of adjacent basic units, and a converging section of the three line elements being formed by binding the three line elements at a point of contact of the apexes of the adjacent basic units, and  
           [0010]    (B) disposing a plurality of said unit structures in such a manner that adjacent ones of the unit structures come into contact with each other so that the adjacent one of the unit structures are in a position to form the converging section of the three line elements at each apex of the common bottom surface of the two triangular pyramids constituting the basic unit, and forming the converging section of the three line elements by binding the three line elements at each point of contact of the adjacent ones of the unit structures.  
           [0011]    According to the manufacturing method of the invention, a packing  21  consisting of a three-dimensional net-like structure as shown in the schematic perspective view of FIG. 1 can be produced. This packing  21  is made, as shown in the partial perspective view of FIG. 2, of a plurality of basic units  22  which are arranged continuously in vertical direction of the three-dimensional net-like structure with apexes  22   a  of each basic unit being in contact with the apexes of adjacent basic units  22  to constitute a unit structure  25 , each of the basic units  22  being formed by converging and dispersion of three line elements. As shown in FIG. 2, this basic unit  22  is a combination of two triangular pyramids having a common bottom surface  22   d  and apexes  22   a  disposed in opposite directions. Three line elements  23  constitute three sides  22   b  of each triangular pyramid. The apexes  22   a  of the two triangular pyramids and the sides  22   b  of the two triangular pyramids are formed by converging and dispersion of the three line elements  23  about a converging section  24  which is formed by binding the thee line elements  23 . In the example of FIG. 2, the three line elements  23  are bound by wire  27 . Accordingly, no element corresponding to the horizontal threads in the prior art X-packing is used at all in this unit structure  25 .  
           [0012]    By disposing, as shown in FIG. 1, a plurality of these unit structures  25  in such a manner that horizontally adjacent ones of the unit structures  25  come into contact with each other so that the adjacent one of the unit structures  25  are in a position to form a converging section  26  of the three line elements  23  at each apex  22   c  of the common bottom surface  22   d  of the two triangular pyramids constituting the basic unit  22 , and forming the converging section  26  of the three line elements  23  by binding the three line elements  23  at each point of contact of the horizontally adjacent ones of the unit structures  25 , the packing  21  made of a three-dimensional net-like structure is formed.  
           [0013]    Accordingly, by using the packing  21  manufactured by the method of the invention in a device such as a gas-liquid contact device, liquid from a distributor flows in the direction of arrow B in FIG. 1 and, since no element corresponding to the horizontal threads is used in the packing  21 , the liquid which has fallen upon the top of the packing  21  does not produce a drift which is caused by flow of the liquid toward a laterally lower portion even if there is an error in installing the packing  21  in the device and, therefore, collection and downward reditribution of the liquid at the apex  22   a  (i.e., converging section  24 ) and  22   c  (converging section  26 ) of each unit structure  22  are performed uniformly.  
           [0014]    The three line elements may be bound by means of wire, clip or the like fastening means or by adhering the three line elements together by means of adhesive.  
           [0015]    For achieving the objects of the invention, in one aspect of the invention, there is provided a method for manufacturing a packing made of a three-dimensional net-like structure which constitutes an internal structure of a device which performs material transfer, heat exchange or mixing between gases, liquids or gas and liquid, said internal structure being divided in a plurality of chambers or channels connected to one another and said three-dimensional net-like structure being made of a plurality of unit structures which are arranged continuously in vertical and horizontal directions of the three-dimensional net-like structure, each of the unit structures being formed by converging and dispersion of four line elements, said method comprising a step of forming a converging section of the unit structure where the four line elements converge by binding the four line elements together.  
           [0016]    There is also provided a method for manufacturing a packing made of a three-dimensional net-like structure which constitutes an internal structure of a device which performs material transfer, heat exchange or mixing between gases, liquids or gas and liquid, said internal structure being divided in a plurality of chambers or channels connected to one another and said three-dimensional net-like structure being made of a plurality of unit structures which are arranged continuously in vertical and horizontal directions of the three-dimensional net-like structure, each of the unit structures being formed by converging and dispersion of four line elements, said method comprising steps of:  
           [0017]    (A) forming a unit structure with four line elements, said unit structure consisting of a plurality of basic units each of which is a combination of two quadruple pyramids having a common bottom surface and apexes disposed in opposite directions, said basic units being arranged continuously in vertical direction of the three-dimensional net-like structure with apexes of each of the basic units being in contact with apexes of adjacent basic units, and a converging section of the four line elements being formed by binding the four line elements at a point of contact of the apexes of the adjacent basic units, and  
           [0018]    (B) disposing a plurality of said unit structures in such a manner that adjacent ones of the unit structures come into contact with each other so that the adjacent one of the unit structures are in a position to form the converging section of the four line elements at each apex of the common bottom surface of the two quadruple pyramids constituting the basic unit, and forming the converging section of the four line elements by binding the four line elements at each point of contact of the adjacent ones of the unit structures.  
           [0019]    According to the manufacturing method of the invention, a packing  40  consisting of a three-dimensional net-like structure as shown in the schematic perspective view of FIG. 3 can be produced. This packing  40  is made, as shown in the partial perspective view of FIG. 4, of a plurality of basic units  41  which are arranged continuously in vertical direction of the three-dimensional net-like structure with apexes  41   a  of each basic unit  41  being in contact with the apexes of adjacent basic units  41  to constitute a unit structure  45 , each of the basic units  41  being formed by converging and dispersion of four line elements. As shown in FIG. 4, this basic unit  41  is a combination of two quadruple pyramids having a common bottom surface  41   d  and apexes  41   a  disposed in opposite directions. Four line elements  23  constitute four sides  41   b  of each quadruple pyramid. The apexes  41   a  of the two quadruple pyramids and the sides  41   b  of the two quadruple pyramids are formed by converging and dispersion of the four line elements  23  about a converging section  44  which is formed by binding the four line elements  23 . In the example of FIG. 4, the four line elements  23  are bound by wire  47 . Accordingly, no element corresponding to the horizontal threads in the prior art X-packing is used at all in this unit structure  45 .  
           [0020]    By disposing, as shown in FIG. 3, a plurality of these unit structures  45  in such a manner that horizontally adjacent ones of the unit structures  45  come into contact with each other so that the adjacent one of the unit structures  45  are in a position to form a converging section  46  of the four line elements  23  at each apex  41   c  of the common bottom surface  41   d  of the two quadruple pyramids constituting the basic unit  41 , and forming the converging section  46  of the four line elements  23  by binding the four line elements  23  at each point of contact of the horizontally adjacent ones of the unit structures  45 , the packing  40  made of a three-dimensional net-like structure is formed.  
           [0021]    Accordingly, by using the packing  40  manufactured by the method of the invention in a device such as a gas-liquid contact device, liquid from a distributor flows in the direction of arrow B in FIG. 3 and, since no element corresponding to the horizontal threads is used in the packing  40 , the liquid which has fallen upon the top of the packing  40  does not produce a drift which is caused by flow of the liquid toward a laterally lower portion even if there is an error in installing the packing  40  in the device and, therefore, collection and downward reditribution of the liquid at the apex  41   a  (i.e., converging section  44 ) and  41   c  (converging section  46 ) of each unit structure  41  are performed uniformly.  
           [0022]    The four line elements may be bound by means of wire, clip or the like fastening means or by adhering the four line elements together by means of adhesive.  
           [0023]    The present invention can be applied not only to the column packing used in devices such as a gas-liquid mixing device but also to manufacturing of other three-dimensional net-like structure such as ones used for a mist eliminator, a multi-layer filtering film and aggregate.  
           [0024]    In one asepect of the invention, there is provided a method for manufacturing a three-dimensional net-like structure including a mist eliminator and a multi-layer filtering film made of a plurality of unit structures which are arranged continuously in vertical and horizontal directions of the three-dimensional net-like structure, each of the unit structures being formed by converging and dispersion of three line elements, said method comprising a step of forming a converging section of the unit structure where the three line elements converge by binding the three line elements together.  
           [0025]    In another aspect of the invention, there is provided a method for manufacturing a three-dimensional net-like structure including a mist eliminator and a multi-layer filtering film made of a plurality of unit structures which are arranged continuously in vertical and horizontal directions of the three-dimensional net-like structure, each of the unit structures being formed by converging and dispersion of three line elements, said method comprising steps of:  
           [0026]    (A) forming a unit structure with three line elements, said unit structure consisting of a plurality of basic units each of which is a combination of two triangular pyramids having a common bottom surface and apexes disposed in opposite directions, said basic units being arranged continuously in vertical direction of the three-dimensional net-like structure with apexes of each of the basic units being in contact with apexes of adjacent basic units, and a converging section of the three line elements being formed by binding the three line elements at a point of contact of the apexes of the adjacent basic units, and  
           [0027]    (B) disposing a plurality of said unit structures in such a manner that adjacent ones of the unit structures come into contact with each other so that the adjacent one of the unit structures are in a position to form the converging section of the three line elements at each apex of the common bottom surface of the two triangular pyramids constituting the basic unit, and forming the converging section of the three line elements by binding the three line elements at each point of contact of the adjacent ones of the unit structures.  
           [0028]    In another aspect of the invention, there is provided a method for manufacturing a three-dimensional net-like structure including a mist eliminator and a multi-layer filtering film made of a plurality of unit structures which are arranged continuously in vertical and horizontal directions of the three-dimensional net-like structure, each of the unit structures being formed by converging and dispersion of four line elements, said method comprising a step of forming a converging section of the unit structure where the four line elements converge by binding the four line elements together.  
           [0029]    In another aspect of the invention, there is provided a method for manufacturing a three-dimensional net-like structure including a mist eliminator and a multi-layer filtering film made of a plurality of unit structures which are arranged continuously in vertical and horizontal directions of the three-dimensional net-like structure, each of the unit structures being formed by converging and dispersion of four line elements, said method comprising steps of:  
           [0030]    (A) forming a unit structure with four line elements, said unit structure consisting of a plurality of basic units each of which is a combination of two quadruple pyramids having a common bottom surface and apexes disposed in opposite directions, said basic units being arranged continuously in vertical direction of the three-dimensional net-like structure with apexes of each of the basic units being in contact with apexes of adjacent basic units, and a converging section of the four line elements being formed by binding the four line elements at a point of contact of the apexes of the adjacent basic units, and  
           [0031]    (B) disposing a plurality of said unit structures in such a manner that adjacent ones of the unit structures come into contact with each other so that the adjacent one of the unit structures are in a position to form the converging section of the four line elements at each apex of the common bottom surface of the two quadruple pyramids constituting the basic unit, and forming the converging section of the four line elements by binding the four line elements at each point of contact of the adjacent ones of the unit structures.  
           [0032]    In another aspect of the invention, there is provided a packing made of a three-dimensional net-like structure which constitutes an internal structure of a device which performs material transfer, heat exchange or mixing between gases, liquids or gas and liquid, said internal structure being divided in a plurality of chambers or channels connected to one another and said three-dimensional net-like structure being made of a plurality of unit structures which are arranged continuously in vertical and horizontal directions of the three-dimensional net-like structure, each of the unit structures being formed by converging and dispersion of three line elements characterized in that a converging section of the unit structure where the three line elements converge is formed by binding the three line elements together.  
           [0033]    In another aspect of the invention, there is provided a packing made of a three-dimensional net-like structure which constitutes an internal structure of a device which performs material transfer, heat exchange or mixing between gases, liquids or gas and liquid, said internal structure being divided in a plurality of chambers or channels connected to one another and said three-dimensional net-like structure being made of a plurality of unit structures which are arranged continuously in vertical and horizontal directions of the three-dimensional net-like structure, each of the unit structures being formed by converging and dispersion of three line elements, said three-dimensional net-like structure being formed of a plurality of unit structures each of which consists of a plurality of basic units each of which is a combination of two triangular pyramids having a common bottom surface and apexes disposed in opposite directions, said basic units being arranged continuously in vertical direction of the three-dimensional net-like structure with apexes of each of the basic units being in contact with apexes of adjacent basic units, said plurality of unit structures being disposed in such a manner that adjacent ones of the unit structures come into contact with each other so that the adjacent one of the unit structures are in a position to form a converging section of the three line elements at each apex of the common bottom surface of the two triangular pyramids constituting the basic unit, a converging section of the three line elements formed at a point of contact of the apexes of the adjacent basic units and the converging section formed at a point of contact of adjacent unit structures being respectively formed by binding the three line elements.  
           [0034]    In another aspect of the invention, there is provided a packing made of a three-dimensional net-like structure which constitutes an internal structure of a device which performs material transfer, heat exchange or mixing between gases, liquids or gas and liquid, said internal structure being divided in a plurality of chambers or channels connected to one another and said three-dimensional net-like structure being made of a plurality of unit structures which are arranged continuously in vertical and horizontal directions of the three-dimensional net-like structure, each of the unit structures being formed by converging and dispersion of four line elements characterized in that a converging section of the unit structure where the four line elements converge is formed by binding the four line elements together.  
           [0035]    In another aspect of the invention, there is provided a packing made of a three-dimensional net-like structure which constitutes an internal structure of a device which performs material transfer, heat exchange or mixing between gases, liquids or gas and liquid, said internal structure being divided in a plurality of chambers or channels connected to one another and said three-dimensional net-like structure being made of a plurality of unit structures which are arranged continuously in vertical and horizontal directions of the three-dimensional net-like structure, each of the unit structures being formed by converging and dispersion of four line elements, said three-dimensional net-like structure being formed of a plurality of unit structures each of which consists of a plurality of basic units each of which is a combination of two quadruple pyramids having a common bottom surface and apexes disposed in opposite directions, said basic units being arranged continuously in vertical direction of the three-dimensional net-like structure with apexes of each of the basic units being in contact with apexes of adjacent basic units, said plurality of unit structures being disposed in such a manner that adjacent ones of the unit structures come into contact with each other so that the adjacent one of the unit structures are in a position to form a converging section of the four line elements at each apex of the common bottom surface of the two quadruple pyramids constituting the basic unit, a converging section of the four line elements formed at a point of contact of the apexes of the adjacent basic units and the converging section formed at a point of contact of adjacent unit structures being respectively formed by binding the four line elements.  
           [0036]    In another aspect of the invention, there is provided a three-dimensional net-like structure including a mist eliminator and a multi-layer filtering film made of a plurality of unit structures which are arranged continuously in vertical and horizontal directions of the three-dimensional net-like structure, each of the unit structures being formed by converging and dispersion of three line elements characterized in that a converging section of the unit structure where the three line elements converge is formed by binding the three line elements together.  
           [0037]    In another aspect of the invention, there is provided a three-dimensional net-like structure wherein the three-dimensional net-like structure is formed of a plurality of unit structures each of which consists of a plurality of basic units each of which is a combination of two triangular pyramids having a common bottom surface and apexes disposed in opposite directions, said basic units being arranged continuously in vertical direction of the three-dimensional net-like structure with apexes of each of the basic units being in contact with apexes of adjacent basic units, said plurality of unit structures being disposed in such a manner that adjacent ones of the unit structures come into contact with each other so that the adjacent one of the unit structures are in a position to form a converging section of the three line elements at each apex of the common bottom surface of the two triangular pyramids constituting the basic unit, a converging section of the three line elements formed at a point of contact of the apexes of the adjacent basic units and the converging section formed at a point of contact of adjacent unit structures being respectively formed by binding the three line elements.  
           [0038]    In another aspect of the invention, there is provided a three-dimensional net-like structure including a mist eliminator and a multi-layer filtering film made of a plurality of unit structures which are arranged continuously in vertical and horizontal directions of the three-dimensional net-like structure, each of the unit structures being formed by converging and dispersion of four line elements characterized in that a converging section of the unit structure where the four line elements converge is formed by binding the four line elements together.  
           [0039]    In still another aspect of the invention, there is provided a three-dimensional net-like structure wherein the three-dimensional net-like structure being formed of a plurality of unit structures each of which consists of a plurality of basic units each of which is a combination of two quadruple pyramids having a common bottom surface and apexes disposed in opposite directions, said basic units being arranged continuously in vertical direction of the three-dimensional net-like structure with apexes of each of the basic units being in contact with apexes of adjacent basic units, said plurality of unit structures being disposed in such a manner that adjacent ones of the unit structures come into contact with each other so that the adjacent one of the unit structures are in a position to form a converging section of the four line elements at each apex of the common bottom surface of the two quadruple pyramids constituting the basic unit, a converging section of the four line elements formed at a point of contact of the apexes of the adjacent basic units and the converging section formed at a point of contact of adjacent unit structures being respectively formed by binding the four line elements. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0040]    In the accompanying drawings,  
         [0041]    [0041]FIG. 1 is schematic perspective view showing an example of a three-dimensional net-like structure;  
         [0042]    [0042]FIG. 2 is a perspective view showing a unit structure used in this example;  
         [0043]    [0043]FIG. 3 is a schematic perspective view showing another example of a three-dimensional net-like structure;  
         [0044]    [0044]FIG. 4 is a perspective view showing a unit structure used in this example;  
         [0045]    [0045]FIG. 5A is a front view showing a state in which line elements are arranged for forming a unit structure;  
         [0046]    [0046]FIG. 5B is a plan view of the state shown in FIG. 5A;  
         [0047]    [0047]FIG. 6A is a front view showing a state in which line elements of a unit structure are bound with wire;  
         [0048]    [0048]FIG. 6B is a plan view of the state shown in FIG. 6A;  
         [0049]    [0049]FIG. 7 is a perspective view showing wire used for binding line elements;  
         [0050]    [0050]FIG. 8 is a perspective view showing a state in which wire is engaged with line elements:  
         [0051]    [0051]FIG. 9 is a front view showing a step of forming a knot in the wire;  
         [0052]    [0052]FIG. 10A is a front view showing hooked portions of line element openers are placed about line elements;  
         [0053]    [0053]FIG. 10B is a view taken along arrows B-B in FIG. 10A;  
         [0054]    [0054]FIG. 11A is a front view showing line elements in a spread apart state;  
         [0055]    [0055]FIG. 11B is a view taken along arrows C-C in FIG. 11A;  
         [0056]    [0056]FIG. 12 is a perspective view showing a converging section bound with a wire;  
         [0057]    [0057]FIG. 13 is a perspective view showing a flat steel wire used for binding line elements;  
         [0058]    [0058]FIG. 14 is a perspective view showing a flat steel wire engaged with line elements;  
         [0059]    [0059]FIG. 15 is a plan view showing the flat steel wire enclosing line elements being caulked with cutting pliers;  
         [0060]    [0060]FIG. 16 is a plan view showing a step of cutting the flat steel wire with the cutting pliers;  
         [0061]    [0061]FIG. 17 is a perspective view showing the converging section bound with the flat steel wire;  
         [0062]    [0062]FIG. 18 is a plan view showing pliers enclosing line elements;  
         [0063]    [0063]FIG. 19 is a perspective view showing a foremost end portion of the pliers;  
         [0064]    [0064]FIG. 20 is a perspective view showing a converging section bound with a flat steel wire;  
         [0065]    [0065]FIG. 21 is a perspective view showing a converging section consisting of four line elements bound with a wire;  
         [0066]    [0066]FIG. 22 is a perspective view showing a converging section consisting of four line elements bound with a flat steel wire;  
         [0067]    [0067]FIG. 23 is a perspective view showing a converging section consisting of four line elements which adhere together by means of adhesive; and  
         [0068]    [0068]FIG. 24 is perspective view showing an example of the prior art X-packing. 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0069]    Embodiments of the invention will now be described with reference to the accompanying drawings.  
       Embodiment 1  
       [0070]    This embodiment relates to a method for manufacturing a three-dimensional net-like structure shown in FIGS. 1 and 2 in which the unit structure is formed by converging and dispersion of three line elements.  
         [0071]    Line elements used in the manufacturing method of the invention may be made of metal or plastic. There is no particular limitation in the material used for line element and wire, twine or monofilament may be used as the line elements. Since the line element is formed to a three-dimensional net-like structure by alternately repeating opening and converging of the three line elements, the material for the line element must be capable of plastic deformation and have sufficient rigidity to maintain their shape after twisting.  
         [0072]    The line element may be made of a monofilament or a single piece of wire but a line element made of wire or twine which is made by twisting thin steel lines or plastic lines is preferable because liquid flows along the space between the lines which constitute the wire or twine due to the capillary action and thereby enhance transfer of the liquid. In the present embodiment, seven steel lines each having a diameter of 0.1 mm are twisted together to form a single steel wire and two of this steel wire are further twisted to a single wire and this wire is used as the line element  3 .  
         [0073]    (1) Step of Producing a Unit Structure  
         [0074]    For producing the unit structure  25  of the three-dimensional net-like structure shown in FIGS. 1 and 2, three line elements  23  are first disposed in parallel to one another and in contact with one another as shown in the front view of FIG. 5A and the plan view of FIG. 5B. Then, for forming converging sections  24  of the unit structure  25 , the three line elements  23  are bound together at a predetermined interval with wires  27  as shown in the front view of FIG. 6A and the plan view of FIG. 6B.  
         [0075]    For binding the three line elements  23  with the wires  27 , as shown in FIG. 7, a wire  27  made of steel wire is bent in U-shape in its foremost end portion  27   a  by means of a known wire tip bending machine (not shown). Then, as shown in FIG. 8, this wire  27  is disposed in such a manner that its bent foremost end portion  27   a  enclose the three line elements  23  and are engaged with these line elements  23  and then, as shown in FIG. 9, the foremost end portion  27   a  of the wire  27  and a portion of the wire  27  adjacent to the foremost end portion  27   a  are held by cutting pliers  50 . By turning the cutting pliers  50  by predetermined times (e.g., three times), a knot (shown by reference numeral  27   b  in FIG. 12) is formed in the wire  27 . Then, the cutting pliers  50  are withdrawn by a predetermined distance and the wire  27  and its foremost end portion  27   a  are cut off with the cutting pliers  50 .  
         [0076]    Then, the three line elements  23  which have been bound at converging sections  24  formed at the predetermined interval in the longitudinal direction are spread apart at each middle position between the adjacent converging sections  24  in a manner shown in FIGS. 10A, 10B,  11 A and  11 B. First, as shown in FIGS. 10A and 10B, an opening spreader  51  having three hooks  51   a  which are disposed at an interval of 180 degrees is disposed in such a manner that the respective hooks  5 l a  are engaged with respective three line elements  23  at middle positions between the respective converging sections  24 . Then, by pulling the hooks  51   a  in the direction of arrow A in FIG. 10B, the three line elements  23  are spread apart at the middle positions of the converging sections  24  as shown in FIGS. 11A and 11B. Thus, when the hooks  51   a  have been withdrawn, the unit structure  25  which consists of a plurality of basic units  22  each of which is a combination of two triangular pyramids having a common bottom surface  22   d  and apexes  22   a  disposed in opposite directions, the basic units  22  being arranged continuously in vertical direction, is formed. The converging section  24  of this unit structure  25  is shown in the perspective view of FIG. 12.  
         [0077]    (2) Step of Binding a Plurality of the Unit Structures  
         [0078]    A plurality of the unit structures  25  are disposed in such a manner that, as shown in FIG. 1, horizontally adjacent ones of the unit structures  25  come into contact with each other so that the adjacent one of the unit structures  25  are in a position to form the converging section  26  of the three line elements  23  at each apex  22   c  of the common bottom surface  22   d  of the two triangular pyramids constituting the basic unit  22 . By binding the converging section  26  of the three line elements  23  at each point of contact of the adjacent ones of the unit structure  25  in a manner shown in FIGS.  7  to  9 , i.e., by binding with wire  27 , the packing  27  made of a three-dimensional net-like structure is formed.  
         [0079]    In the above described steps (1) and (2), forming of plural unit structures  25  and binding of these unit structures  25  can be achieved all at once by arranging and operating a plurality of cutting pliers  50  and opening spreader  51 .  
         [0080]    Another example of binding three line elements  23  together is shown in FIGS.  13  to  17 . In this example, as shown in FIG. 13, flat steel wire  52  in the form of a flat sheet is bent in U-shape in its foremost end portion  52   a  . This flat steel wire  52  is disposed, as shown in FIG. 14, in such a manner that its bent foremost end portion  52   a  substantially encloses the three line elements  23  and is engaged with the line elements  23 . Then, as shown in FIG. 15, the foremost end portion  52   a  of the fiat steel wire  52  is caulked against the three line elements  23  with cutting pliers  53  and then, as shown in FIG. 16, by cutting the flat steel wire  52  with a cutting tipe of the pliers  53 , a clip ring  59  as shown in FIG. 17 is formed and the three line elements  23  are thereby bound together. The converging section  24  of the unit structure formed in this manner is shown in the perspective view of FIG. 17.  
         [0081]    Another example of binding the three line elements  23  is shown in FIGS.  18  to  20 . In this example, as shown in FIG. 18, pliers  54  are disposed in such a manner that an annular portion  54   a  encloses the three line elements  23  with a predetermined gap  55  defined between the annular portion  54   a  and the three line elements  23 . The pliers  54  are made of hollow pipes and, as shown in FIG. 19, a foremost end portion  54   b  of the annular portion  54   a  is formed in its inner side portion with an opening  54   c . The pliers  54  are connected to an adhesive supply tank (not shown) storing adhesive such as a quick setting adhesive through a connecting hose (not shown). By supplying liquid quick setting adhesive under pressure into the pliers  54  in FIG. 19, the liquid quick setting adhesive flows into the gap  55  between the line elements  23  and the annular portion  54   a  and the three line elements  23  adhere to one another to form an adhered section  56  (FIG. 20) whereby binding of the three line elements  23  is achieved. After completion of adhesion, the pliers  54  are withdrawn. The converging section  24  of the unit structure made in this manner is shown in the perspective view of FIG. 20.  
       Embodiment 2  
       [0082]    This embodiment relates to a method for manufacturing a three-dimensional net-like structure  40  shown in FIGS. 3 and 4 in which the unit structure is formed by converging and dispersion of four line elements.  
         [0083]    In this embodiment also, the line element which can be used in the Embodiment 1 can be used. In forming of the unit structure  45  and binding of the unit structures  45  together, the same steps as described with respect to the Embodiment 1 can be used except that four line elements  23  instead of three line elements  23  are used and the opening spreader  51  shown in FIGS. 10 and 11 has four hooks  51   a  instead of three. Detailed description about these steps will therefore be omitted. For binding converging sections  44  and  46  of the four line elements  23 , the same methods employed in the Embodiment 1 can be employed.  
         [0084]    [0084]FIG. 21 is a perspective view showing an example of a converging section  44  ( 46 ) formed by binding four line elements  23  with wire  60  in the same manner as illustrated in FIGS.  7  to  9 . FIG. 22 is a perspective view showing an example of a converging section  44  ( 46 ) formed by binding the four line elements  23  with a clip ring  62  in the same manner as illustrated in FIGS.  13  to  16 . FIG. 23 is a perspective view showing an example of a converging section  44  ( 46 ) formed by forming an adhered section  64  with quick setting adhesive in the same manner as illustrated in FIGS. 18 and 19.  
         [0085]    In the same manner as in Embodiment 1, forming of plural unit structures  45  and binding of these unit structures  45  can be achieved all at once by arranging and operating a plurality of cutting pliers  50  and opening spreader  51 .