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 conversion and dispersion of three or four line elements. The method comprises a step of forming a conversion section of the unit structure where the three or four line elements converge by twisting the three or four line elements together.

Description:
This application is a divisional application of Ser. No. 09/557,518, filed Apr. 25, 2000 which claims the priority under 35 U.S.C. §119 of Japanese Applications Serial Nos. 119213/1999, filed Apr. 27, 1999 and 044241/2000, filed Feb. 22, 2000. 
    
    
     BACKGROUND OF THE INVENTION 
     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. 
     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. 
     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. 22, 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. 
     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. 22 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. 
     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. 
     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 
     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 conversion 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 twisting the three line elements together. 
     According to the invention, 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 conversion and dispersion of three line elements, said method comprising steps of: 
     (A) preparing a packing manufacturing space by forming a predetermined number of hypothetical channels of a regular triangular cross-section without leaving spaces between them so that six hypothetical channels having one common apex of a triangle form a regular hexagon, said hypothetical channels consisting of hypothetical channels C 1  which share one apex of a triangle but do not share a side of a triangle with adjacent hypothetical channels and hypothetical channels C 2  which share a side of a triangle with the hypothetical channels C 1 , and disposing, in the packing manufacturing space, a plurality of rotors each having a circular shape in the radial section, being formed with three recesses in the periphery thereof at an interval of 120° for respectively receiving a line element and being connected to a rotor control unit and rotatable by a predetermined angle by operating the rotor control unit, said rotors consisting of rotors R 1  each being disposed in one of the hypothetical channels C 1 , rotors R 2  each being disposed in one of the hypothetical channels C 2  and rotors R 3  each being disposed in a space defined by three of the rotors R 1  disposed in three of the hypothetical channels C 1  which share one apex of a triangle and three of the rotors R 2  disposed in three of the hypothetical channels C 2 , in such a manner that the line element can be moved between the recess of the rotor R 3  and the recess of the rotor R 1 , and between the recess of the rotor R 3  and the recess of the rotor R 1  and that the rotors R 1  do not contact the rotors R 2 , 
     (B) inserting the line elements unwound from bobbins in the respective recesses of the rotors R 1  and thereafter rotating the rotors R 1  by one revolution or over to twist the three line elements inserted in the respective recesses of each of the rotors R 1  and thereby forming a first knot K 1  in each of the hypothetical channels C 1  downstream of the rotors R 1  in a feeding direction of the line elements, 
     (C) feeding the line elements by a predetermined length, moving the line elements from the recesses of the rotors R 1  to the recesses of the rotors R 3  and thereafter rotating the rotors R 3  by one revolution or over to twist the three line elements inserted in the recesses of the rotors R 3  and thereby forming a second knot K 2  upstream of the first knot K 1  in each of the spaces in which the rotors R 3  are disposed, 
     (D) feeding the line elements by a predetermined length, rotating the rotors R 3  and the rotors R 2  respectively by 60° in opposite directions to each other, moving the line elements from the recesses of the rotors R 3  to the recesses of the rotors R 2  and thereafter rotating the rotors R 2  by one revolution or over to twist the three line elements inserted in the recesses of the rotors R 2  and thereby forming a third knot K 3  downstream of the rotors R 2  and the upstream of the second knot K 2  in each of the hypothetical channels C 2 , 
     (E) feeding the line elements by a predetermined length, moving the line elements from the recesses of the rotors R 2  to the recesses of the rotors R 3  and thereafter rotating the rotors R 3  by one revolution or over to twist the three line elements inserted in the recesses of the rotors R 3  and thereby forming a fourth knot K 4  downstream of the rotors R 3  and upstream of the third knot K 3  in each of the spaces in which the rotors R 3  are disposed, and 
     (F) feeding the line elements by a predetermined length, rotating the rotors R 3  and the rotors R 1  respectively by 60° in opposite directions to each other and thereafter moving the line elements from the recesses of the rotors R 3  to the recesses of the rotors R 1 . 
     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 unit structures  22  which are arranged continuously in vertical and horizontal directions of the three-dimensional net-like structure, each of the unit structures  22  being formed by conversion and dispersion of three line elements. As shown in FIG. 2, this unit structure  22  is a combination of two triangular pyramids having a common apex  22   a  and bottom surfaces disposed in opposite directions. Three line elements  23  constitute three sides  22   b  of each triangular pyramid. The apex  22   a  of the two triangular pyramids and the sides  22   b  of the two triangular pyramids are formed by conversion and diversion of the three line elements  23  about a knot  24  which is formed by twisting the thee line elements  23 . Accordingly, no element corresponding to the horizontal threads in the prior art X-packing is used at all in this unit structure  22 . 
     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 redistribution of the liquid at the apex  22   a  (i.e., knot  24 ) of each unit structure  22  are performed uniformly. 
     In another 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 conversion 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 twisting the four line elements together. 
     According to the invention, 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 conversion and dispersion of four line elements, said method comprising steps of: 
     (A) preparing a packing manufacturing space by forming a predetermined number of hypothetical channels of a regular square cross-section so that these hypothetical channels align in columns and rows without leaving spaces between them, said hypothetical channels consisting of first hypothetical channels CA and second hypothetical channels CB which are disposed alternately in columns and rows of the hypothetical channels, and disposing, in the packing manufacturing space, a plurality of rotors each having a circular shape in the radial section, being formed with four recesses in the periphery thereof at an interval of 90° for respectively receiving a line element and being connected to a rotor control unit and rotatable by a predetermined angle by operating the rotor control unit, said rotors consisting of rotors RA each being disposed in one of the first hypothetical channels CA and rotors RB each being disposed in one of the second hypothetical channels CB in such a manner that the line element can be moved between the recess of the rotor RA and the recess of the rotor RB, 
     (B) inserting the line element unwound from bobbins in the respective recesses of the rotors RA and thereafter rotating the rotors RA by one revolution or over to twist the four line elements inserted in the respective recesses of each of the rotors RA and thereby forming a first knot KCA in each of the hypothetical channels CA downstream of the rotors RA in a feeding direction of the line elements, 
     (C) feeding the line elements by a predetermined length, moving the line elements from the recesses of the rotors RA to the recesses of the rotors RB and thereafter rotating the rotors RB by one revolution or over to twist the four line elements inserted in the recesses of the rotors RB and thereby forming a second knot KCB upstream of the first knot KCA in each of the hypothetical channels CB, and 
     (D) feeding the line elements by a predetermined length and moving the line elements from the recesses of the rotors RB to the recesses of the rotors RA. 
     According to the 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 is obtained. This packing  40  is made of a plurality of unit structures  41 . The unit structure  41  is a combination of two quadruple pyramids having a common apex  41   a  and having bottom surfaces disposed in opposite directions. The three-dimensional net-like structure is made by arranging these unit structures  41  in vertical and horizontal directions. 
     In the unit structure  41 , respective sides  41   b  consist of line elements  23 . That is to say, four line elements  23  constitute four sides  41   b  and the apex  41   a  is formed by conversion and dispersion of the four line elements  23 . In this unit structure  41  either, there is no element corresponding to the horizontal threads at all and, therefore, the advantageous result of the unit structure  22  can be obtained also in the unit structure  41 . In other words, the liquid flows in the direction of arrow D in FIG.  3  and collection and downward redistribution of the liquid at the apex  41   a  of each quadruple pyramid of the unit structure  41  is performed uniformly. 
     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. 
     In one 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 conversion 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 twisting the three line elements together. 
     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 conversion and dispersion of three line elements, said method comprising steps of: 
     (A) preparing a three-dimensional net-like structure manufacturing space by forming a predetermined number of hypothetical channels of a regular triangular cross-section without leaving spaces between them so that six hypothetical channels having one common apex of a triangle form a regular hexagon, said hypothetical channels consisting of hypothetical channels C 1  which share one apex of a triangle but do not share a side of a triangle with adjacent hypothetical channels and hypothetical channels C 2  which share a side of a triangle with the hypothetical channels C 1 , and disposing, in the three-dimensional net-like structure manufacturing space, a plurality of rotors each having a circular shape in the radial section, being formed with three recesses in the periphery thereof at an interval of 120° for respectively receiving a line element and being connected to a rotor control unit and rotatable by a predetermined angle by operating the rotor control unit, said rotors consisting of rotors R 1  each being disposed in one of the hypothetical channels C 1 , rotors R 2  each being disposed in one of the hypothetical channels C 2  and rotors R 3  each being disposed in a space defined by three of the rotors R 1  disposed in three of the hypothetical channels C 1  which share one apex of a triangle and three of the rotors R 2  disposed in three of the hypothetical channels C 2 , in such a manner that the line element can be moved between the recess of the rotor R 3  and the recess of the rotor R 1 , and between the recess of the rotor R 3  and the recess of the rotor R 1  and that the rotors R 1  do not contact the rotors R 2 , 
     (B) inserting the line elements unwound from bobbins in the respective recesses of the rotors R 1  and thereafter rotating the rotors R 1  by one revolution or over to twist the three line elements inserted in the respective recesses of each of the rotors R 1  and thereby forming a first knot K 1  in each of the hypothetical channels C 1  downstream of the rotors R 1  in a feeding direction of the line elements, 
     (C) feeding the line elements by a predetermined length, moving the line elements from the recesses of the rotors R 1  to the recesses of the rotors R 3  and thereafter rotating the rotors R 3  by one revolution or over to twist the three line elements inserted in the recesses of the rotors R 3  and thereby forming a second knot K 2  upstream of the first knot K 1  in each of the spaces in which the rotors R 3  are disposed, 
     (D) feeding the line elements by a predetermined length, rotating the rotors R 3  and the rotors R 2  respectively by 60° in opposite directions to each other, moving the line elements from the recesses of the rotors R 3  to the recesses of the rotors R 2  and thereafter rotating the rotors R 2  by one revolution or over to twist the three line elements inserted in the recesses of the rotors R 2  and thereby forming a third knot K 3  downstream of the rotors R 2  and the upstream of the second knot K 2  in each of the hypothetical channels C 2 , 
     (E) feeding the line elements by a predetermined length, moving the line elements from the recesses of the rotors R 2  to the recesses of the rotors R 3  and thereafter rotating the rotors R 3  by one revolution or over to twist the three line elements inserted in the recesses of the rotors R 3  and thereby forming a fourth knot K 4  downstream of the rotors R 3  and upstream of the third knot K 3  in each of the spaces in which the rotors R 3  are disposed, and 
     (F) feeding the line elements by a predetermined length, rotating the rotors R 3  and the rotors R 1  respectively by 60° in opposite directions to each other and thereafter moving the line elements from the recesses of the rotors R 3  to the recesses of the rotors R 1 . 
     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 conversion 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 twisting the four line elements together. 
     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 conversion and dispersion of four line elements, said method comprising steps of: 
     (A) preparing a three-dimensional net-like structure manufacturing space by forming a predetermined number of hypothetical channels of a regular square cross-section so that these hypothetical channels align in columns and rows without leaving spaces between them, said hypothetical channels consisting of first hypothetical channels CA and second hypothetical channels CB which are disposed alternately in columns and rows of the hypothetical channels, and disposing, in the three-dimensional net-like structure manufacturing space, a plurality of rotors each having a circular shape in the radial section, being formed with four recesses in the periphery thereof at an interval of 90° for respectively receiving a line element and being connected to a rotor control unit and rotatable by a predetermined angle by operating the rotor control unit, said rotors consisting of rotors RA each being disposed in one of the first hypothetical channels CA and rotors RB each being disposed in one of the second hypothetical channels CB in such a manner that the line element can be moved between the recess of the rotor RA and the recess of the rotor RB, 
     (B) inserting the line elements unwound from bobbins in the respective recesses of the rotors RA and thereafter rotating the rotors RA by one revolution or over to twist the four line elements inserted in the respective recesses of each of the rotors RA and thereby forming a first knot KCA in each of the hypothetical channels CA downstream of the rotors RA in a feeding direction of the line elements, 
     (C) feeding the line elements by a predetermined length, moving the line elements from the recesses of the rotors RA to the recesses of the rotors RB and thereafter rotating the rotors RB by one revolution or over to twist the four line elements inserted in the recesses of the rotors RB and thereby forming a second knot KCB upstream of the first knot KCA in each of the hypothetical channels CB, and 
     (D) feeding the line elements by a predetermined length and moving the line elements from the recesses of the rotors RB to the recesses of the rotors RA. 
     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 conversion 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 twisting the three line elements together. 
     In another aspect of the invention, there is proivded 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 conversion 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 twisting the four line elements together. 
     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 conversion 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 twisting the three line elements together. 
     In still 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 conversion 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 twisting the four line elements together. 
     Preferred embodiment of the invention will be described below with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings, 
     FIG. 1 is schematic perspective view showing an example of a three-dimensional net-like structure; 
     FIG. 2 is a perspective view showing a unit structure used in this example; 
     FIG. 3 is a schematic perspective view showing another example of a three-dimensional net-like structure; 
     FIG. 4 is a perspective view showing a unit structure used in this example; 
     FIG. 5 is a perspective view schematically showing a principal portion of a device for manufacturing the three-dimensional net-like structure; 
     FIG. 6 is a perspective view schematically showing a bobbin section of the device; 
     FIG. 7 is a prespective view showing a three-dimensional net-like structure manufacturing space; 
     FIG. 8 is a perspective view showing rotors disposed in the three-dimensional net-like structure manufacturing space; 
     FIG. 9 is a perspective view showing a shape of the rotor; 
     FIG. 10 is a perspective view showing a manner of disposing rotors R 1 , R 2  and R 3 ; 
     FIG. 11 is a perspective view showing connection between the rotors and the rotor control section; 
     FIG. 12 is a plan view showing a part of a three-dimensional net-like structure manufacturing space 
     FIG. 13 is a perspective view showing a process of forming a first knot K 1  in the method of manufacturing the three-dimensional net-like structure; 
     FIG. 14 is a perspective view showing a process of forming a second knot K 2  in the same method; 
     FIG. 15 is a perspective view showing an example of a means for moving a line element from a recess of one rotor to a recess of another rotor; 
     FIG. 16 is a perspective view showing a process for forming a third knot K 3  in the same method; 
     FIG. 17 is a perspective view showing a process for forming a fourth knot K 4  in the same method; 
     FIG. 18 is a perspective view showing a process for moving the line element to the rotor R 1 ; 
     FIG. 19 is a perspective view showing the manufactured three-dimensional net-like structure; 
     FIG. 20 is a plan view showing an example of a three-dimensional net-like structure manufacturing space used in another embodiment of the method for manufacturing a three-dimensional net-like structure according to the invention; 
     FIG. 21 is a plan view showing rotors disposed in the manufacturing space; 
     FIG. 22 is a perspective view showing connection between the rotor and the gear of the rotation controller in this embodiment; 
     FIG. 23 is a perspective view showing a process for forming a first knot KCA in this embodiment; 
     FIG. 24 is a perspective view showing a process for forming a second knot KCB in this embodiment; 
     FIG. 25 is a perspective view showing an example of means for preventing twisting of line element on the bobbin side; 
     FIG. 26 is a perspective view showing the prior art method for manufacturing an X-packing; 
     FIG. 27 is a plan view showing another manner for controlling rotation of the rotors; 
     FIG. 28A is a plan view showing structure of a rotor; 
     FIG. 28B is a side view showing the structure of the rotor; 
     FIG. 29 is a partial enlarged view showing meshing of wheels; 
     FIG. 30 is a plan view showing a wheel section and lower rotor section of rotors RX, RY and RZ; 
     FIG. 31A is a plan view of a drive wheel G; 
     FIG. 31B is a side view of the drive wheel G; 
     FIG. 32 is a plan view showing another manner of moving the line elements from the rotors RA to the rotors RB; and 
     FIG. 33 is a plan view showing another manner of moving the line elements from the rotors RA to the rotors RB. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Embodiment 1 
     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 conversion and dispersion of three line elements. 
     (1) Step of Preparing a Three-dimensional Net-like Structure Manufacturing Space 
     In this embodiment, three line elements  23  are transferred among first rotors and second rotors disposed respectively in two types of hypothetical channels in the form of a pipe of a regular triangular cross section and third rotors which are disposed in spaces defined between the first and second rotors, and thereafter the transferred line elements are twisted by rotating the rotors to cause conversion and dispersion of these line elements whereby the three-dimensional net-like structure as shown in FIGS. 1 and 2 is manufactured. 
     For this purpose, in the present embodiment, a three-dimensional net-like structure manufacturing device  25  shown schematically in the perspective views of FIGS. 5 and 6 is used to perform transfer of the line elements  23  among the three types of rotors and rotation of the rotors and thereby cause conversion and dispersion of the line elements  23 . 
     In FIG. 5, a hexagonal pillar schematically represents a three-dimensional net-like structure  21  which has been manufactured in a three-dimensional net-like structure manufacturing space  26  in the form of a hexagonal pillar consisting of a plurality of hypothetical channels shown in FIG.  7 . 
     The three-dimensional net-like structure manufacturing space  26  shown in FIG. 7 is formed by disposing a predetermined number (24 in the illustrated example) of hypothetical channels in the form of a pipe of a regular triangular cross section without leaving a space between them in such a manner that six of these hypothetical channels which have a common apex (i.e., one of their apexes contact one another) in their cross section will form a regular hexagonal cross section. The hypothetical channels consist of a plurality (12 in the illustrated example) of hypothetical channels C 1  which share one apex of a triangle (i.e., their apexes contact one another) but do not share a side of a triangle (i.e., their sides do not contact each other in a parallel state) in their cross section with adjacent hypothetical channels, and a plurality (12 in the illustrated example) of hypothetical channels C 2  which share a side of a triangle (i.e., their sides contact each other in a parallel state) in their cross section with the hypothetical channels C 1 . 
     Alternatively stated, the hypothetical channels C 1  share one edge but do not share a lateral face with adjacent hypothetical channels C 1  and th hypothetical channels C 2  are disposed between the hypothetical channels C 1  and share a lateral face with adjacent hypothetical channels C 1 . Alternatively stated further, these hypothetical channels C 1  and C 2  are disposed side by side about the center of the hexagonal pillar formed by these hypothetical channels C 1  and C 2 . 
     In this three-dimensional net-like structure manufacturing space  26  are disposed, as shown in FIG. 8, three types of rotors R 1 , R 2  and R 3  which constitute a part of the manufacturing device  25 . In the present embodiment, the rotors R 1 , R 2  and R 3  are formed in the form of a disk as shown in FIG.  9  and are formed in their periphery with U-shaped recesses  27  at an interval of 120° for receiving three line elements  23 . 
     In the hypothetical channels C 1  of the manufacturing space  26  are disposed the rotors R 1 , in the hypothetical channels C 2  are disposed the rotors R 2  and in spaces defined by the three rotors R 1  disposed in the hypothetical channels C 1  which share one apex of a triangle in cross section and the three rotors R 2  disposed in the hypothetical channels C 2  are disposed the rotors R 3 . 
     These rotors R 1 , R 2  and R 3  are of an equal diameter and these rotors R 1 , R 2  and R 3  are disposed in such a manner that the line elements  23  can be moved (transferred) between the recesses  27  of the rotors R 3  and the recesses  27  of the rotors R 1  and also between the recesses  27  of the rotors R 3  and the recesses  27  of the rotors R 2  and that the rotors R 1  do not contact the rotors R 2 . The mutual contact between the rotors R 1  and the rotors R 2  is prohibited because it is unnecessary to have them contact each other since the line elements  23  are not moved (transferred) between the rotors R 1  and the rotors R 2  and, besides, since the rotors R 1  and the rotors R 2  are rotated in the same direction, contact between these two types of rotors will cause rotation of the entire rotors R 1 , R 2  and R 3  to stop. 
     For satisfying these conditions, a small gap which is smaller than the diameter of the line element  23  may be provided between each rotor R 3  and each rotor R 1  and between each rotor R 3  and each rotor R 2  for preventing falling of the line element and a gap of the same size may be provided between each rotor R 1  and each rotor R 2 . Alternatively, as shown in FIG. 10, mutual contact between the rotors R 1  and the rotors R 2  can be prevented by adopting a structure according to which the rotors R 3  and the rotors R 1  are rotated in mutual contact and the rotors R 3  and the rotors R 2  are rotated in mutual contact but height of the plane of contact between the rotors R 3  and the rotors R 1  is made different from height of the plane of contact between the rotors R 3  and the rotors R 2 . In the illustrated embodiment, the former arrangement is adopted and a small gap which is smaller than the diameter of the line element  23  is provided between the rotors R 1 , R 2  and R 3 . 
     For enabling movement of the line elements  23  between the rotors R 3  and the rotors R 1  and between the rotors R 3  and the rotors R 2 , the rotors R 3  and the rotors R 1 , and the rotors R 3  and the rotors R 2  are disposed at relative positions where their recesses  27  are in alignment at a position where the rotors R 3  and the rotors R 1 , and the rotors R 3  and the rotors R 2  are in mutual contact or in the closest proximity witch each other. Further, the rotors R 1 , R 2  and R 3  are disposed in such a manner that, at the position where the recesses  27  of the rotors R 3  and the rotors R 1  are in alignment with each other, the two recesses  27  of the rotor R 2  are distant by 60° from the position where the rotor R 2  and the rotors R 3  are in mutual contact or in the closest proximity with each other and that, at the position where the recesses  27  of the rotors R 3  and the rotors R 2  are in alignment with each other, the two recesses  27  of the rotor R 1  are distant by 60° from the position where the rotor R 1  and the rotors R 3  are in mutual contact or in the closest proximity with each other. Accordingly, by rotating the rotor R 3  and the rotor R 2  by 60° from the position where the recess  27  of the rotor R 3  is in alignment with that of the rotor R 1 , the recesses  27  of the rotors R 3  and R 2  are brought into alignment. 
     As shown in FIGS. 5 and 11, the rotors R 1 , R 2  and R 3  are fixedly connected to gears  29  of a rotation controller  28  which constitutes the rotor control unit of the invention and is provided upstream of these rotors in the feeding direction of the line elements  23  (i.e., the direction of arrow F in FIG. 5) by means of connection shafts  30  which are coaxial with the rotors R 1 , R 2  and R 3  and also with the gears  29 . The gears  29  of the rotation controller  28  are made of spur gears having the same or substantially the same diameter as the rotors R 1 , R 2  and R 3  and the gears  29  have the same diameter and same number of teeth. The gear  29  corresponding to the rotor R 1  or R 2  is formed in its peripheral portion with line element insertion openings  31  for inserting three line elements  23  at an interval of 120°. The gear  29  having the line element insertion openings  31  has only a function of guiding three line elements  23  unwound from bobbins to be described later and has no function of transferring the line element  23  between the adjacent gear  29 . 
     In the gears  29  of the rotation controller  28 , the contact rotation mechanism of the rotors R 1 , R 2  and R 3  shown in FIG. 10 is adopted so that the gear  29  corresponding to the rotor R 3  meshes with the gear  29  corresponding to the rotor R 1  and the gear corresponding to the rotor R 3  meshes with the gear  29  corresponding to the rotor R 2  but height of the plane on which the gear  29  corresponding to the rotor R 3  meshes with the gear  29  corresponding to the rotor R 1  is made different from height of the plane on which the gears  29  corresponding to the rotors R 3  meshes with the gear  29  corresponding to the rotor R 2  whereby mutual contact between the gear  29  corresponding to the rotor R 1  and the gear  29  corresponding to the rotor R 2  is prevented. The gears  29  which do not have the line element insertion openings  31  among the group of gears  29  of the rotation controller  28  have only a function of transmitting rotation in the gear train described above. Accordingly, by transmitting rotation of the motor to one of the gears in the group of gears  29 , the rotation is transmitted to the entire gears  29  of the gear group. 
     The gears  29  of the rotation controller  28  are disposed at positions corresponding to the rotors R 1 , R 2  and R 3  in a space upstream of the three-dimensional net-like structure manufacturing space  26 . The rotation controller  28  has a sequence control unit which transmits rotation of the motor to the gears  29  by a desired rotation angle in accordance with the set sequence operation. Accordingly, by rotating the gears  29  by a desired angle, the rotors R 1 , R 2  and R 3  can be rotated by the same angle. 
     As shown in FIG. 5, the manufacturing device  25  includes a pair of conveyers  32  provided at both sides of the three-dimensional net-like structure  21  produced (only a right side conveyer is shown in FIG.  5 ). Each of the pair of conveyers  32  moves in the direction of arrow C by means of a pair of pulleys  33  disposed vertically in FIG. 5. A plurality of plates  34  are provided at a predetermined interval between the pair of conveyers  32  and these plates  34  are fixed at both ends thereof to the pair of conveyers  32 . Spacers  35  functioning also as a hanger in the form of a rod are detachably mounted on the plates  34 . By disposing these spacer/hangers  35  so that they penetrate the three-dimensional net-like structure  21  produced in the manufacturing space  26 , the produced three-dimensional net-like structure  21  is pushed by the spacer/hangers  35  in the direction of the arrow C while retaining the predetermined configuration whereby the three-dimensional net-like structure  21  is continuously manufactured. An arrangement is made so that the spacer/hangers  35  are automatically mounted to the plates  34  at the upper end portion of the conveyers  32  and are automatically detached from the plates  34  at the lower end portion of the conveyers  32 . 
     A bobbin section  37  having bobbins  36  is provided upstream of the rotation controller  28  in the feeding direction of the line elements  23 . The line elements  23  stored in the respective bobbins  36  are wound from the bobbins  36  and passed through the line element insertion openings  31  of the gears  29  among the gear group of the rotation controller  28  and fed to the recesses  27  of the corresponding rotors among the rotors R 1 , R 2  and R 3 . 
     (2) Step of Forming a First Knot K 1   
     The three-dimensional net-like structure  21  is manufactured in the manufacturing space  26  in the following manner. First, the line elements  23  unwound from the bobbins  36  are passed through the line element insertion openings  31  of the gears  29  of the rotation controller  28  and the recesses  27  of the rotors R 1  and then the foremost ends of the line elements  23  are fixed to line element fixing positions  39  corresponding to the recesses  27  of the rotors R 1  in a line element fixing plate  38  (FIG. 13) provided at a position in the manufacturing space  26  which is downstream of the rotors in the feeding direction. 
     In the following description, for convenience of explanation, five rotors R 1 , three rotors R 2  and three rotors R 3  shown in FIG. 12 among twelve rotors R 1 , twelve rotors R 2  and seven rotors R 3  shown in FIG. 8 are designated by reference characters R 1 - 1  to R 1 - 5 , R 2 - 1  to R 2 - 3  and R 3 - 1  to R 3 - 3  and operation of the line elements  23  by these rotors R 1 - 1  to R 1 - 5 , R 2 - 1  to R 2 - 3  and R 3 - 1  to R 3 - 3  will be described. Operation of the line elements  23  by the other rotors shown in FIG. 8 is entirely the same as the operation by the rotors shown in FIG.  12 . 
     The line elements  23  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 twisting, the material for the line element must be capable of plastic deformation and have sufficient rigidity to maintain their shape after twisting. 
     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  23 . 
     For convenience of explanation, fifteen line elements  23  inserted in the recesses  27  of the rotors R 1 - 1  to R 1 - 5  are distinguished from one another by reference characters No.  1  to No.  15 . In the step shown in FIG. 13, the line elements No.  1  to No.  3  are received in the rotor R 1 - 1 , the line elements No.  4  to No.  6  are received in the rotor R 1 - 2 , the line elements No.  7  to No.  9  are received in the rotor R 1 - 3 , the line elements No.  10  to No.  12  are received in the rotor R 1 - 4  and the line elements No.  13  to No.  15  are received in the rotor R 1 - 5 . 
     In the state shown in FIG. 13, the recess  27  of the rotor R 1 - 1  is in alignment with the recess  27  of the rotor R 3 - 1 , the recesses  27  of the rotor R 1 - 2  are in alignment with the recesses  27  of the rotors R 3 - 1  to R 3 - 3  and the recess  27  of the rotor R 1 - 5  is in alignment with the recess  27  of the rotor R 3 - 3 . 
     By rotating the gears  29  in the rotation controller  28  corresponding the rotors R 1 - 1  to R 1 - 5  in the above described state by one revolution or over (preferably by two revolutions, i.e., 720°), the rotors R 1 - 1  to R 1 - 5  are rotated by the same rotation angle. The three line elements inserted in the recesses  27  of each of the rotors R 1 - 1  to R 1 - 5  are twisted in a middle position between the rotors R 1 - 1  to R 1 - 5  and the line element fixing plate  38  and, as a result, a knot K 1  which is of the same shape as the knot  24  shown in FIG. 2 which is formed by twisting is formed. Thus, first knots K 1  are formed downstream of the rotors in the feeding direction of the line elements  23  in the respective hypothetical channels C 1 . 
     (3) Step of Forming a Second Knot K 2   
     The line elements  23  are fed in the feeding direction by a predetermined length (in the present embodiment, length between the first knots K 1  and the recesses  27  of the rotors R 1 - 1  to R 1 - 5 ) and then the line elements  23  are moved, as shown in FIG. 14, from the recesses  27  of the rotors R 1 - 1  to R 1 - 5  to the recesses  27  of the adjacent rotors R 3 - 1  to R 3 - 3  which are in alignment. More specifically, the line element No.  3  is moved from the recess  27  of the rotor R 1 - 1  to the recess  27  of the rotor R 3 - 1 , the line element No.  4  is moved from the recess  27  of the rotor R 1 - 2  to the recess  27  of the rotor R 3 - 1 , the line element No.  5  is moved from the recess  27  of the rotor R 1 - 2  to the recess  27  of the rotor R 3 - 3 , the line element No.  6  is moved from the recess  27  of the rotor R 1 - 2  to the recess  27  of the rotor R 3 - 2 , the line element No.  7  is moved from the recess  27  of the rotor R 1 - 3  to the recess  27  of the rotor R 3 - 2 , the line element No.  12  is moved from the recess  27  of the rotor R 1 - 4  to the recess  27  of the rotor R 3 - 3 , the line element No.  13  is moved from the recess  27  of the rotor R 1 - 5  to the recess  27  of the rotor R 3 - 3 . 
     For moving the line elements  23  between the rotors R 3  and R 1  and between the rotors R 3  and R 2 , for example, as shown in FIG. 15, an arm  49  which is provided above (or below) a position in which the rotor R 3  and the rotor R 1  (or rotor R 2 ) are in the closest proximity to each other is operated by a sequence control to push the line element  23  from the recess  27  of one rotor to the recess  27  of the other rotor. Alternatively, a solenoid may be provided in the inside of the respective recesses  27  and its plunger may be actuated to push the line element  23  from the recess  27  of one rotor to the recess  27  of the other rotor. Various other means may also be employed for moving the line element  23  from the recess  27  of one rotor to the recess  27  of the other rotor. 
     After the line elements  23  have been moved from the recesses  27  of the rotors R 1 - 1  to R 1 - 5  to the recesses  27  of the rotors R 3 - 1  to R 3 - 3 , the rotors R 3 - 1  to R 3 - 3  are rotated by one revolution or over (two revolutions in the present embodiment) to twist-the three line elements  23  inserted-in the. recesses  27  of the respective rotors R 3 - 1  to R 3 - 3  (two line elements only are illustrated with respect to the rotors R 3 - 1  and R 3 - 2 ) and thereby form second knots K 2  downstream of the rotors R 3 - 1  to R 3 - 3  and upstream of the first knots K 1  in each of the spaces in which the rotors R 3 - 1  to R 3 - 3  are disposed. 
     (4) Step of Forming a Third Knot K 3   
     After the line elements  23  are fed by the predetermined length, as shown in FIG. 16, the rotors R 3 - 1  to R 3 - 3  are rotated counterclockwise by 60° and the rotors R 2 - 1  to R 2 - 3  are rotated clockwise by 60°. Then, the line elements  23  are moved from the recesses  27  of the rotors R 3 - 1  to R 3 - 3  to the recesses  27  of the rotors R 2 - 1  to R 2 - 3 . More specifically, the line element No.  3  is moved from the rotor R 3 - 1  to the rotor R 2 - 1 , the line element No.  5  is moved from the rotor R 3 - 1  to the rotor R 2 - 1 , the line element No.  6  is moved from the rotor R 3 - 2  to the rotor R 2 - 2 , the line element No.  12  is moved from the rotor R 3 - 3  to the rotor R 2 - 3  and the line element No.  13  is moved from the rotor R 3 - 3  to the rotor R 2 - 2 . 
     Then, the rotors R 2 - 1  to R 2 - 3  are rotated by one revolution or over (two revolutions in the present embodiment) to twist the three line elements  23  inserted in the recesses  27  of the rotors R 2 - 1  to R 2 - 3  and third knots K 3  are thereby formed downstream of the rotors and upstream of the second knots K 2  in the hypothetical channels C 2 . 
     (5) Step of Forming Fourth Knots K 4   
     After the line elements  23  are fed by the predetermined length, as shown. in FIG. 17, the line elements  23  are moved from the recesses  27  of the rotors R 2 - 1  to R 2 - 3  to the recesses  27  of the adjacent rotors R 3 - 1  to R 3 - 3  which are in alignment. More specifically, the line element No.  3  is moved from the rotor R 2 - 1  to the rotor R 3 - 1 , the line element No.  5  is moved from the rotor R 2 - 1  to the rotor R 3 - 3 , the line element No.  6  is moved from the rotor R 2 - 2  to the rotor R 3 - 2 , the line element No.  12  is moved from the rotor R 2 - 3  to the rotor R 3 - 3  and the line element No.  13  is moved from the rotor R 2 - 2  to the rotor R 3 - 2 . 
     Then, the rotors R 3 - 1  to R 3 - 3  are rotated by one revolution or over (two revolutions in the present embodiment) to twist the three line elements  23  inserted in the recesses  27  of the rotors R 3 - 1  to R 3 - 3  (one line element only is illustrated with respect to the rotors R 3 - 1  and R 3 - 2 ) and fourth knots K 4  are thereby formed downstream of the rotors and upstream of the third knots K 3  in the spaces in which the rotors R 3 - 1  to R 3 - 3  are disposed. 
     (6) Step of Moving the Line Elements to the Recesses of the Rotors R 1   
     The line elements  23  are fed by the predetermined length and the rotors R 3 - 1  to R 3 - 3  are rotated counterclockwise by 60° and the rotors R 1 - 1  to R 1 - 3  are rotated clockwise by 60° to bring the recesses  27  of the rotors R 3 - 1  to R 3 - 2  in alignment with the recesses  27  of the rotors R 1 - 1  to R 1 - 3 . Then, the line elements  23  are moved from the recesses  27  of the rotors R 3 - 1  to R 3 - 3  to the recesses  27  of the rotors R 1 - 1  to R 1 - 3 . More specifically, the line element No.  3  is moved from the rotor R 3 - 1  to the rotor R 1 - 1 , the line element No.  5  is moved from the rotor R 3 - 3  to the rotor R 1 - 2 , the line element No.  6  is moved from the rotor R 3 - 2  to the rotor R 1 - 2 , the line element No.  12  is moved from the rotor R 3 - 3  to the rotor R 1 - 2  and the line element No.  13  is moved from the rotor R 3 - 3  to the rotor R 1 - 5 . 
     Thus, the initial state (the state of Step (2) described above) is restored in which the line element No.  1  to No.  3  are inserted in the recesses  27  of the rotors R 1 - 1 , the line elements No.  4  to No.  6  are inserted in the recesses  27  of the rotor R 1 - 2 , the line elements No.  7  to No. 9  are inserted in the recesses  27  of the rotor R 1 - 3 , the line elements No.  10  to No.  12  are inserted in the recesses  27  of the rotor R 1 - 4  and the line elements No.  13  to No.  15  are inserted in the recesses  27  of the rotor R 1 - 5 . By rotating the rotors R 1 - 1  to R 1 - 5  in this state, the first knots K 1  are formed again. 
     By repeating the steps (2), (3), (4), (5) and (6) sequentially, as shown in FIG. 19, knots where the three line elements  23  converge and disperse are sequentially formed in the order of the first knots K 1  formed in the hypothetical channel C 1 , the second knots K 2  formed in the spaces in which the rotors R 3  are disposed, the third knots K 3  formed in the hypothetical channels C 2 , the fourth knots K 4  formed in the spaces in which the rotors R 3  are disposed. By repeating this cycle by a desired number of times, the three-dimensional net-like structure  21  of a desired size can be manufactured. 
     Embodiment 2 
     This embodiment relates to a method for manufacturing the three-dimensional net-like structure  40  shown in FIGS. 3 and 4 which the unit structure is formed by conversion and diversion of four line elements. 
     (1) Step of Preparing a Three-dimensional Net-like Structure Manufacturing Space 
     In this embodiment, four line elements  23  are transferred between two types of rotors disposed in two types of hypothetical channels of a regular square cross section and the transferred four line elements  23  are twisted to perform conversion and dispersion of the four line elements  23  whereby the three-dimensional net-like structure shown in FIGS. 3 and 4 is manufactured. 
     For this purpose, in this embodiment also, a manufacturing device similar to the three-dimensional net-like structure manufacturing device  25  is employed to perform transfer of the line elements  23  between the two types of rotors and rotaion of the rotors and thereby perform conversion and dispersion of the four line elements  23 . 
     An example of a three-dimensional net-like structure manufacturing space  42  used in this embodiment is schematically shown in the plan view of FIG.  20 . 
     The three-dimensional net-like structure manufacturing space  42  shown in FIG. 20 consists of a predetermined number (36 channels in the illustrated example) of hypothetical channels each having a regular square cross section which are aligned in columns and rows without leaving spaces between them. These hypothetical channels consist of first hypothetical channels CA which are disposed alternately in each column and in each row of hypothetical channels and second hypothetical channels CB which are disposed alternately in each column and each row of hypothetical channels and disposed between two adjacent first hypothetical channels CA. In the illustrated example, the manufacturing space  42  consists of eighteen first hypothetical channels CA and eighteen second hypothetical channels CB. 
     In this manufacturing space  42 , as shown in FIG. 21, two types of rotors RA and RB which constitute a part of the manufacturing device  25  are disposed. The rotors RA and RB are constructed in the form of a disk as in the rotors used in the embodiment  1  and are formed in their periphery with U-shaped recesses  43  at an interval of 90° for receiving four line elements  23 . 
     The rotors RA are disposed in the first hypothetical channels CA of the manufacturing space  42  and the rotors RB are disposed in the second hypothetical channels CB of the manufacturing space  42 . These rotors RA and RB are of equal diameter. The rotors RA and RB are disposed in such a manner that adjacent ones of the rotors RA and RB are rotated in contact with each other and that the recesses  43  of the rotors RA are in alignment with the recesses  43  of the rotors RB at a position where the rotors RA contact the rotors RB so that the line elements  23  are transferred between the recesses  43  of the rotors RA and the recesses  43  of the rotors RB. 
     As shown in FIG. 22, each of the rotors RA and RB is connected to a gear  45  of a rotation controller  44  provided upstream of the rotors RA and RB in the feeding direction of the line elements  23  by means of a coaxial shaft  46 . The gear  45  is of the same diameter and has the same number of teeth as the rotors RA and RB and adjacent gears  45  mesh each other. The gear  45  is formed with line element insertion openings  47  at an interval of 90° for inserting four line elements  23 . The gear  45 , in the same manner as the gear  29  of the embodiment 1, has only a function of guiding the four line elements  23  unwound from bobbins. In the gear  45 , by transmitting rotation of the motor to one of the gears  45 , rotation is transmitted to the entire gears  45  and rotation is thereby transmitted to the entire rotors RA and RB. The rotation controller  44  has a sequence control unit for transmitting rotation of the motor to the gears  45  by a desired rotation angle in accordance with a predetermined sequence operation and, therefore, by rotating the gears  45  by a desired angle, the rotors RA and RB can be rotated by the same angle. 
     (2) Step of Forming a First Knot KCA 
     The three-dimensional net-like structure  40  is manufactured in the manufacturing space  42  prepared in the above described manner. First, the line elements  23  unwound from bobbins  36  are passed through the line element insertion openings  47  of the gears  45  of the rotation controller  44  corresponding to the rotors RA and the recesses  43  of the rotors RA and then the foremost ends of the line elements  23  are fixed to line element fixing positions corresponding to the recesses  43  of the rotors RA in a line element fixing plate (not shown) provided at a position in the manufacturing space  42  which is downstream of the rotors RA, RB by a predetermined distance in the feeding direction of the line elements  23 . 
     In the following description made with reference to FIGS. 23 and 24, for convenience of explanation, six rotors RA and four rotors RB among eighteen rotors RA and eighteen rotors RB are designated by reference characters RA- 1  to RA- 6  and RB- 1  to RB- 4  and operation of the line elements  23  by these rotors RA- 1  to RA- 6  and RB- 1  to RB- 4  will be described. Operation of the line elements  23  by the other rotors RA and RB shown in FIG. 21 is entirely the same as the operation by the rotors shown in FIG.  24 . 
     For conveniecen of explanation, twenty line elements  23  inserted in the recesses  43  of the rotors RA- 1  to RA- 6  are distinguished from one another by reference characters No.  1  to No.  20 . In the step shown in FIG. 23, the line elements No.  1  to No.  4  are received in the rotor RA- 1 , the line elements No.  5  to No.  8  are received in the rotor RA- 2 , the line elements No.  9  and No.  10  are received in the rotor RA- 3 , the line elements No.  11  to No.  14  are received in the rotor RA- 4 , the line elements No.  15  to No.  18  are received in the rotor RA- 5  and the line elements No.  19  and No.  20  are received in the rotor RA- 6 . The shaded plane P in FIG. 23 represents positions where the line elements  23  are received in the rotors RA and RB. 
     By rotating the gears  45  of the rotation controller  44  by one revolution or over (two revolutions (720°) in the present embodiment) in the above described state, the rotors RA- 1  to RA- 6  are rotated by the same rotation angle. The four line elements  23  inserted in the recesses  43  of the rotors RA- 1  to RA- 6  are twisted in a middle position between the rotors RA- 1  to RA 6  and the line element fixing plate and knots KCA which are similar to the knot  41   a  shown in FIG. 4 which is formed by twisting are formed. Thus, the first knots KCA are formed downstream of the rotors in the hypothetical channels CA in the feeding direction of the line elements  23 . 
     (3) Step of Forming a Second Knot KCB 
     The line elements  23  are fed in the feeding direction by a predetermined length (in the present embodiment, length between the first knots KCA and the recesses  43  of the rotors RA- 1  to RA- 6  in FIG.  23 ). Then, as shown in FIG. 24, the line elements  23  are moved from the recesses  43  of the rotors RA- 1  to RA- 6  to the recesses  43  of adjacent rotors RB- 1  to RB- 4  which are in alignment. More specifically, the line element No.  3  is moved from the rotor RA- 1  to the rotor RB- 1 , the line element No.  4  is moved from the rotor RA- 1  to the rotor RB- 3 , the line element No.  5  is moved from the rotor RA- 2  to the rotor RB- 3 , the line element No.  7  is moved from the rotor RA- 2  to the rotor RB- 2 , the line element No.  8  is moved from the rotor RA- 2  to the rotor RB- 4 , the line element No.  9  is moved from the rotor RA- 3  to the rotor RB- 2 , the line element No.  10  is moved from the rotor RA- 3  to the rotor RB- 4 , the line element No.  13  is moved from the rotor RA- 4  to the rotor RB- 3 , the line element No.  15  is moved from the rotor RA- 5  to the rotor RB- 3 , the line element No.  17  is moved from the rotor RA- 5  to the rotor RB- 4  and the line element No.  19  is moved from the rotor RA- 6  to the rotor RB- 4 . 
     Then, the rotors RB- 1  to RB- 4  are rotated by one revolution or over (two revolutions in the present embodiment) to twist the four line elements  23  inserted in the recesses  43  of the rotors RB- 1  to RB- 4  (two line elements only are illustrated with respect to each of the rotors RB- 1  and RB- 2 ) and second knots KCB are thereby formed downstream of the rotors and upstream of the first knots KCA in the hypothetical channels CB. 
     (d) Step of Moving the Line Elements to the Recesses of the Rotors RA 
     The line elements  23  are fed by the predetermined length and then the line elements  23  are moved from the recesses  43  of the rotors RB- 1  to RB- 4  to the recesses  43  of the adjacent rotors RA- 1  to RA- 6  which are in alignment. 
     Thus, the initial state (the state of Step (2) described above) is restored in which the line elements No.  1  to No.  4  are inserted in the rotors RA- 1 , the line elements No.  5  and No.  6  are inserted in the rotor RA- 2 , the line elements No.  9  and No. 10  are inserted in the rotor RA- 3 , the line elements No.  11  to No.  14  are inserted in the rotor RA- 4 , the line elements No.  15  to No.  18  are inserted in the rotor RA- 5  and the line elements No.  19  and No.  20  are inserted in the rotor RA- 6 . By rotating the rotors RA- 1  to RA- 6  in this state, the first knots KCA are formed again. 
     By repeating the steps (2), (3) and (4) sequentially and repeatedly, the first knots KCA formed in the hypothetical channels CA and the second knots KCB formed in the hypothetical channels CB are sequentially formed and, by repeating this cycle by a desired number of times, the three-dimensional net-like structure  40  as shown in FIG. 3 can be manufactured in a desired size. 
     In the embodiments 1 and 2, when the gears  29  ( 45 ) of the rotation controller  28  ( 44 ) of the three-dimensional net-like structure manufacturing device  25  are rotated by one revolution or over, twisting is caused in the three or four line elements at a position between the gears  29  ( 45 ) and the bobbins  36  and, therefore, some means must be provided for preventing occurrence of such twisting in the line elements  23 . For this purpose, in a case, for example, where a three-dimensional net-like structure having a unit structure consisting of three line elements is manufactured, as shown in FIG. 25, three bobbins  36 - 1 ,  36 - 2  and  36 - 3  from which the three line elements  23  inserted through the gears  29  are unwound may be fixed to a common bobbin rotating disk  48 . By rotating the bobbin rotating disk  48  by a bobbin rotating disk drive mechanism (not shown) provided in the bobbin section  37  in synchronism with rotation of the gears  29  by the same rotation angle as the rotation of the gears  29  in the same direction, twisting of the line elements  23  can be prevented. 
     In the above described embodiments of the invention, the rotor are made in the shape of a disk. The shape of the rotors is not limited to the disk but rotors which have a circular shape in the radial direction such as a cylindrical shape may also be used. 
     In the above described embodiments, the rotors which transfer the line elements are rotated by the gears  29  or  45  of the rotation controller  28  or  44 . The rotors may be rotated by other methods. An example of such other methods for rotating the rotors will be described with reference to FIGS. 27 to  30  with respect to a case where a three-dimensional net-like structure is manufactured by using three line elements. 
     FIG. 27 is a plan view showing arrangement of rotors in practicing this method in the manufacturing space shown in FIG. 8, FIG. 28A is a plan view of adjacent rotors RX, RY and RZ in FIG. 27, FIG. 28B is a side view thereof, FIG. 29 is a partially enlarged view showing alignment of recesses in gear portions of the rotor RX and the rotor RY (or RZ), FIG. 30 is a plan view showing gear sections and lower rotor sections of the rotors RX, RY and RZ with the rotor RX being placed in the center, FIG. 31A is a plan view of a drive gear G and FIG. 31B is a side view thereof. 
     In FIG. 27, the rotors RX perform the function of the rotors R 3 , the rotors RY the function of the rotors R 1  and the rotors RZ the function of the rotors R 2  of FIG.  8 . The rotors RX, RY and RZ have, as shown in FIGS. 28A and 28B, upper rotor sections RXa, RYa and RZa, gear sections RXb, RYb and RZb, and lower rotor sections RXc, RYc and RZc with the gear sections RXb, RYb and RZb being sandwiched between the upper rotor sections RXa, RYa and RZa and the lower rotor sections RXc, RYc and RZc. The upper rotor section of the rotors RX, RY and RZ has an equal diameter to the lower rotor section thereof In the same manner as in the embodiment of FIG. 8, a small gap is provided between the upper rotor sections of the respective rotors and between the lower rotor sections of the respective rotors. 
     The periphery of the gear section RXb of the rotor RX projects radially outwardly by a predetermined length from the peripheries of the upper rotor section RXa and the lower rotor section RXb. On the other hand, the peripheries of the gear sections RYb and RZb are withdrawn by the same length from the peripheries of the upper rotor sections RYa and Rza and the lower rotor sections RYc and RZc. Accordingly, the rotors RA, RB and RZ are supported by one another in such a manner that the gear section of the rotor RX is held by the upper rotor sections and the lower rotor sections of the rotors RY and RZ and the rotors RY and RZ are supported by the gear sections of the rotors RX which are adjacent to each of the rotors RY and RZ at three positions which are distant by 120°. All of the rotors RX, RY and RZ in FIG. 27 are supported by one another in mutually fitted state without being supported by outside means except for drive gears G. The number of teeth of the gear section RXb of the rotor RX is equal to the number of teeth of the gear sections RYb and RZb of the rotors RY and RZ. 
     As will be apparent from FIG. 29, in the gear section RXb of the rotor RX, a recess  50  for receiving and transferring a line element is formed in a manner to extend radially in the central portion of a tooth  51  and reaches a position which is radially inside of the root circle of the tooth  51  and also radially inside of the outer peripheries of the upper rotor section RXa and the lower rotor section RXc. The portion of the recess  50  which is radially inside of the root circle extends vertically to the upper rotor section RXa and the lower rotor section RXc so that a vertically continuous recess is formed in the rotor RX. Three recesses  50  are formed at an interval of 120° in the tooth  51 . 
     In the gear section RYb of the rotor RY and the gear section RZb of the rotor RZ, a recess  53  is formed in a manner to extend radially inside of the root  54 . Three recesses  53  are formed at an interval of 120° in the rotors RY and RZ. The recess  53  extends vertically to the upper rotor section RYa and the lower rotor section RYc in the rotor RY and to the upper rotor section RZa and the lower rotor section RZc in the rotor RZ so that a vertically continuous recess is formed in the rotors RY and RZ. In the illustrated state, the recess  50  of the rotor RX is in alignment with the recess  53  of the rotor RY. 
     The meshing state of the rotors RX, RY and RZ as viewed from one rotor RX being placed in the center is shown in FIG.  30 . This is a plan view in which, for convenience of understanding, illustration of the upper rotor sections of the respective rotors is omitted and the lower rotor sections only are illustrated. As will be apparent from FIG. 30, the gear section of the rotor RX meshes with the gear sections of the rotors RY and RZ but the gear sections of the rotors RY and RZ do not mesh with each other. Therefore, rotation is transmitted between the rotor RX and the rotors RY and RZ but rotation is not transmitted between the rotor RY and the rotor RZ. 
     The drive gears G which are dispoded along the outer periphery of the rotors RX, RY and RZ are constructed in the manner shown in FIGS. 31A and 31B. The drive gear G has, as the rotor RX, an upper rotor section Ga, a lower rotor section Gc and a gear section Gb which is sandwiched between the the upper rotor section Ga and the lower rotor section Gc and projects radially outwardly from the peripheries of these sections Ga and Gc by a predetermined length. The gear section Gb, however, does not have a recess for receiving and transferring a line element. The drive gear G is rotatably supported by a frame of the device through a gear shaft Gd and is driven and rotated by an unillustrated drive unit. The gear sections Gb of these drive gears G mesh with the gear sections RYb and RZb of the rotors RY and RZ. Accordingly, the rotors RY and RZ whose gear sections mesh with the gear section of the drive gears G are supported by the drive gears G and rotation of the drive gears G is transmitted to the entire rotors RX, RY and RZ of FIG.  27  through the rotors RY and RZ. In this embodiment, therefore, the entire gear group except for the drive gears G which are disposed outside does not require any support but necessary rotation can be transmitted to the entire gear group. Accordingly, the gears  29  of the rotation controller  28  in the embodiment 1 are not necessary and the line elements can be supplied directly from bobbins to the rotors RX, RY and RZ. The method for manufacturing the three-dimensional net-like structure is the same as the ones of the embodiments 1 and 2 and description thereof will be omitted. 
     In manufacturing the three-dimensional net-like structure using four line elements, the structure of the rotor RX can be applied to the rotor RA and the structure of the rotor RY (or RZ) can be applied to the other rotor RB so that support and rotation of the rotors RA and RB can be realized without using the gears  45  of the rotation controller  44 . 
     In the example of FIG. 15, the line element is pushed to move by operating the arm  49 . An alternative method for moving the line element from a recess of one rotor to a recess of another rotor will be described with reference to FIGS. 32 and 33. 
     FIG. 32 is a plan view showing an example in which this method has been applied to the embodiment fo FIGS. 20 to  24  for manufacturing the three-dimensional net-like structure by using four line elements. In the illustrated state, the line elements  23  are inserted in the recesses  43  of the rotors RA. For moving the line elements  23  from this state to the recesses  43  of the adjacent rotors RB, a firs comb  61  and a second comb  62  which can move up and down and left and right as viewed in the figure on one side of the rotor group and also over the surfaces of the rotors RA and RB. The comb  60  has comb teeth  60   a  in the form of rods which are arranged in parallel. The comb  61  likewise has comb teeth  61   a  in the form of rods which are arranged in parallel. 
     The combs  60  and  61  are moved in the direction of arrow M so that the comb teeth  60   a  are placed on the upper side as viewed in the figure of the lower two recesses  43  as viewed in the figure in the four recesses  43  of each rotor RA and the comb teeth  61   a  are placed on the lower side as viewed in the figure of the upper two recesses  43  as viewed in the figure in the four recesses  43  of each rotor RA. Then, by moving the comb  60  in the direction of arrow O and the comb  61  in the direction of arrow P, the line elements  23  are moved from the recesses  43  of the rotors RA to the recesses  43  of the rotors RB. Upon completion of movement of the line elements  23 , the combs  60  and  61  are moved in the direction of arrow N to remove the comb teeth  60   a  and  61   a  from the surfaces of the rotors RA and RB. 
     Then, for moving the line elements  23  from the recesses  43  of the rotors RB to the recesses  43  of the rotors RA, as shown in FIG. 33, the combs  60  and  61  are moved in the direction of arrow M so that comb teeth  60   a  are placed on the lower side as viewed in the figure of the upper two recesses  43  as viewed in the figure in the four recesses  43  of each rotor RB and the comb teeth  61   a  are placed on the upper side as viewed in the figure of the lower two recesses  43  as viewed in the figure in the four recesses  43  of each rotor RB. Then, by moving the comb  60  in the direction of arrow P and the comb  61  in the direction of arrow O, the line elements  23  are moved from the recesses  43  of the rotors RB to the recesses  43  of the rotors RA. Upon completion of movement of the line elements  23 , the combs  60  and  61  are moved in the direction of arrow N to remove the comb teeth  60   a  and  61   a  from the surfaces of the rotors RA and RB. 
     This method for moving the line elements can be applied also to manufacturing of the three-dimensional net-like structure using three line elements by disposing combs  60  and  61  in three directions at an interval of 60° and operating the combs  60  and  61  in a manner similar to the above described operation.