Patent Publication Number: US-2020291544-A1

Title: Head unit, electrospinning head, and electrospinning apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2019-044870, filed Mar. 12, 2019; the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate to a head unit, an electrospinning head, and an electrospinning apparatus. 
     BACKGROUND 
     There exists an electrospinning apparatus which deposits fine fiber on a surface of a collection body or substrate via an electrospinning method (sometimes referred to as an “electric spinning method” or “charge-induced spinning method”) to form a film of fiber. The electrospinning apparatus includes an electrospinning head, including a head body and a nozzle. The electrospinning head is provided with a hollow (head flow passage) for storing a raw material liquid inside the head body, and the nozzle on an outer circumference surface of the head body. The raw material liquid is ejected from an ejection port of the nozzle toward the surface of the collection body or substrate to deposit the fiber on the surface of the collection body or substrate, via the application of a voltage between the electrospinning head and the collection body or substrate. 
     In the electrospinning apparatus described above, when fiber is deposited on a surface of a substrate having a large size in its width direction, a film of the fiber having a large size in its width direction may be formed via the electrospinning method. Even when a film of the fiber having a large size in its width direction is formed, an electrospinning apparatus is required to appropriately deposit the fiber on a surface of a substrate or the like, and appropriately form a film of the fiber. The electrospinning apparatus is also required to suppress the complexity of its configuration and its control system, and to suppress an increase in manufacturing costs and a reduction in productivity of its electrospinning head. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram showing an example of an electrospinning apparatus according to a first embodiment; 
         FIG. 2  is a perspective diagram schematically showing an electrospinning head according to the first embodiment; 
         FIG. 3  is a schematic diagram showing the electrospinning head according to the first embodiment when viewed from a direction crossing the longitudinal axis of the head; 
         FIG. 4  is a cross-sectional diagram schematically showing the electrospinning head according to the first embodiment at a cross-section parallel or substantially parallel to the longitudinal axis of the head; 
         FIG. 5  is a cross-sectional diagram schematically showing the electrospinning head according to the first embodiment at a cross-section perpendicular or substantially perpendicular to the longitudinal axis of the head; 
         FIG. 6  is a perspective diagram schematically showing an electrospinning head according to a first modification; 
         FIG. 7  is a schematic diagram showing the electrospinning head according to the first modification when viewed from a direction crossing the longitudinal axis of the head; 
         FIG. 8  is a cross-sectional diagram schematically showing the electrospinning head according to the first modification at a cross-section parallel or substantially parallel to the longitudinal axis of the head; 
         FIG. 9  is a cross-sectional diagram schematically showing the electrospinning head according to the first modification at a cross-section perpendicular or substantially perpendicular to the longitudinal axis of the head; 
         FIG. 10  is a schematic diagram showing an electrospinning head according to a second modification in a state where head units are separated from each other; 
         FIG. 11  is a cross-sectional diagram schematically showing the electrospinning head according to the second modification at a cross-section parallel or substantially parallel to the longitudinal axis of the head; 
         FIG. 12  is a schematic diagram showing an electrospinning head according to a third modification when viewed from a direction crossing the longitudinal axis of the head; 
         FIG. 13  is a schematic diagram showing the electrospinning head according to the third modification when viewed from one side of the direction along the longitudinal axis; and 
         FIG. 14  is a schematic diagram showing an electrospinning head according to a fourth modification. 
     
    
    
     DETAILED DESCRIPTION 
     According to an embodiment, the head unit includes a unit main body and a nozzle. Inside the unit main body, a hollow configured to store a raw material liquid is formed along the longitudinal axis of the unit main body. The nozzle is formed of a conductive material and provided on an outer circumferential surface of the unit main body. The nozzle is configured to eject the raw material liquid supplied through the hollow of the unit main body. The head unit includes a coupling structure. The coupling structure is capable of coupling another head unit to the head unit, on at least one side of the head unit, in the direction along the longitudinal axis. The coupling structure couples a unit main body of another head unit to the unit main body in a state where the hollow of the unit main body communicates with a hollow of the unit main body of said another head unit. A head flow passage is then formed by the hollow of the unit main body and the hollow of said another head unit communicating with the hollow of the unit main body. 
     According to another embodiment, the electrospinning head includes a plurality of head units and a coupling structure, and the plurality of head units are arranged along the longitudinal axis. The plurality of head units are coupled to one another through the coupling structure. Each head unit includes a unit main body and a nozzle. Inside the unit main body, a hollow configured to store a raw material liquid is formed along the longitudinal axis. The nozzle is formed of a conductive material and provided on an outer circumferential surface of the unit main body. The nozzle is configured to eject the raw material liquid supplied through the hollow of the unit main body. The coupling structure connects the plurality of head units in a state where the hollows of the unit main bodies communicate with one another. A head flow passage is formed along the longitudinal axis by the hollows communicating with one another. 
     According to another embodiment, an electrospinning apparatus includes the electrospinning head, a supply source, and an electric power source. The supply source supplies a raw material liquid to the head flow passage of the electrospinning head. The electric power source applies a voltage to the electrospinning head. 
     Hereinafter, the embodiments will be described with reference to the drawings. 
     First Embodiment 
       FIG. 1  shows an example of an electrospinning apparatus  1  according to a first embodiment. As shown in  FIG. 1 , the electrospinning apparatus  1  includes an electrospinning head  2 , a supply source (supply section)  3  of a raw material liquid, an electric power source  4 , a collection body  5 , and a controller  6 . 
       FIGS. 2 to 5  respectively show the configuration of the electrospinning head  2 . As shown in  FIGS. 1 to 5 , the electrospinning head  2  has a longitudinal axis C as a central axis, and extends along the longitudinal axis C. The electrospinning head  2  includes a head main body  11  and a plurality of nozzles  12  (four nozzles in the present embodiment). In the electrospinning head  2 , as many connectors  13  as there are nozzles  12  are provided, and each nozzle  12  is connected to the head main body  11  via one corresponding connector  13 . In the present embodiment, the head main body  11 , nozzles  12  and connectors  13  are respectively formed of a conducting material. 
     The number of the nozzles  12  is not particularly limited. The connectors  13  are not necessarily provided, and each nozzle  12  may be directly connected to the head body  11 . Furthermore, each of the head main body  11 , nozzles  12 , and connectors  13  is preferably formed of a material having resistance to a raw material liquid (to be described later), for example, stainless steel. Here,  FIG. 2  is a perspective diagram and  FIG. 3  shows a state where the electrospinning head is viewed from a direction crossing (perpendicular or substantially perpendicular to) the longitudinal axis C.  FIG. 4  shows a cross-section parallel or substantially parallel to the longitudinal axis C, and  FIG. 5  shows a cross-section perpendicular or substantially perpendicular to the longitudinal axis C. 
     The respective nozzles  12  are provided on an outer circumferential surface of the head main body  11 . The outer circumferential surface of the head main body  11  extends around the longitudinal axis C and forms a part of an exterior surface of the head main body  11 . The outer circumferential surface of the head main body  11  faces the side away from the longitudinal axis C, in a direction crossing the longitudinal axis C. In the present embodiment, the plurality of nozzles  12  are arranged at the same or substantially the same angular positions with respect to one another around the longitudinal axis C. For this reason, in the present embodiment, the plurality of nozzles  12  are arranged along the longitudinal axis C to form a nozzle row  15 . Each nozzle  12  protrudes to the outer circumference side on the outer circumferential surface of the head main body  11 . 
     Inside the head main body  11 , a head flow passage  16  is formed along the longitudinal axis C. In the present embodiment, the head flow passage  16  is formed coaxially or substantially coaxially with the head main body  11 , and the central axis of the head flow passage  16  is formed coaxially or substantially coaxially with the longitudinal axis C. Also, the head flow passage  16  is formed across the entirety or the majority of the head main body  11  in the direction along the longitudinal axis C. Therefore, in the present embodiment, the head main body  11  is formed into a cylindrical shape, provided with the head flow passage  16  as an internal hollow. 
     In the electrospinning head  2 , as many nozzle flow passages  17  as there are nozzles  12  are formed, and one corresponding nozzle flow passage  17  is formed inside of each nozzle  12 . Each nozzle flow passage  17  communicates with the head flow passage  16  and extends toward the outer circumference side of the head main body  11  from the head flow passage  16 . Each nozzle flow passage  17  opens externally at its ejection port  18 . In each nozzle  12 , an ejection port  18  is formed at a projecting end from the head main body  11 . 
     Each nozzle  12  is, for example, a needle nozzle. The outer diameter of each nozzle  12  is not particularly limited; however, it is preferably as small as possible. By reducing the outer diameter of each respective nozzles  12 , an electric field concentration tends to take place in the vicinity of the respective ejection ports  18  of the nozzles  12  when a voltage is applied between the electrospinning head  2  and the collection body  5 , as described later. The generation of the electric field concentration in the vicinity of the respective ejection ports  18  of the nozzles ensures a high electric field intensity between each nozzle  12  and the collection body  5 , even when the voltage applied between the electrospinning head  2  and the collection body  5  is lowered. In an example, the outer diameter of each nozzle  12  is, for example, about 0.3 mm or larger and 1.3 mm or smaller. 
     The opening size of each ejection port  18  is not particularly limited, as long as it is within a range smaller than the outer diameter of each nozzle  12 . Each opening size of the ejection ports  18  is properly set corresponding to the type, etc. of fiber  100  to be deposited on a surface of the collection body  5 . In an example, each opening size of the ejection ports  18  is, for example, about 0.1 mm or larger and 1 mm or smaller. 
     The supply source  3  of the raw material liquid includes a reservoir  31 , a supply driver  32 , a supply adjuster  33 , and a supply pipe  35 . The reservoir  31 , supply driver  32 , supply adjuster  33 , and supply pipe  35  respectively have resistance to the raw material liquid. In an example, the reservoir  31  and the supply pipe  35  are respectively formed of an insulating material, such as a fluorine resin. 
     The reservoir  31  is a tank or the like to store a raw material liquid. In the raw material liquid, a polymer material is dissolved in a solvent. The polymer contained in the raw material liquid and the solvent to dissolve the polymer are properly determined so as to correspond to the type, etc. of the fiber  100  to be deposited on a surface of the collection body  5 . The supply pipe  35  connects the reservoir  31  and the head main body  11  of the electrospinning head  2 . A flow passage of the raw material liquid is formed inside the supply pipe  35 . 
     An inflow port  22  is formed at one end of the head flow passage  16  of the head main body  11 . The supply pipe  35  is connected to the head main body  11  at the inflow port  22 , and the head flow passage  16  communicates with the inside of the supply pipe  35  at the inflow port  22 . In the present embodiment, the inflow port  22  is formed on one end face of the head main body  11 , in the direction along the longitudinal axis C. The other end of the head flow passage  16 , i.e., the opposite end of the head flow passage  16  to the inflow port  22  in the head flow passage  16 , closes to the outside of the head main body  11 . In an example, the other end of the head flow passage  16  is closed by the head main body  11  itself, and in another example, the other end of the head flow passage  16  is closed by a lid member, etc. attached to the head main body  11 . 
     The supply driver  32  is driven to thereby supply the raw material liquid from the reservoir  31  to the head flow passage  16  of the head main body  11  through the supply pipe  35 . In an example, the supply driver  32  is a pump. In another example, the supply driver  32  pressure-feeds the raw material liquid from the reservoir  31  to the head flow passage  16  by supplying a gas to the reservoir  31 . 
     The supply adjuster  33  adjusts the rate of flow, pressure, etc. of the raw material liquid supplied to the head flow passage  16 . In an example, the supply adjuster  33  is a control valve capable of controlling the rate of flow, pressure, etc. of the raw material liquid. The supply adjuster  33  constrains the ejection of the raw material liquid from the respective ejection ports  18  of the nozzles  12  by adjusting the rate of flow, pressure, etc. of the raw material liquid. The supply adjuster  33  adjusts the rate of flow, pressure, etc. of the raw material liquid to appropriate values based on the viscosity of the raw material liquid, respective sizes of the ejection ports  18 , etc. Furthermore, in an example, the supply adjuster  33  is switchable between supplying and not supplying the raw material liquid from the reservoir  31  to the head flow rate  16 . In this case, the supply adjuster  33  is, for example, a switch valve. 
     The supply driver  32  and supply adjuster  33  need not necessarily be provided. In an example, the reservoir  31  is provided on the vertically upper side, with respect to the head main body  11  to supply the raw material liquid from the reservoir  31  to the head flow passage  16  by utilizing gravitational force. In this case, the ejection of the raw material liquid from the respective ejection ports  18  of the nozzles  12  is constrained in a state where no voltage is applied between the electrospinning head  2  and the collection body  5  by adjusting the difference in height of the reservoir  31  with respect to the head main body  11 . 
     The electric power source  4  applies a voltage between the electrospinning head  2  and the collection body  5 . In this case, in the electrospinning head  2 , a voltage with predetermined polarity is applied to the each nozzle  12  via the head main body  11  and one corresponding connector  13 . In an example, a terminal (not shown) electrically connected to each nozzle  12  is provided, and a voltage is applied to each nozzle  12  via the terminal. In a configuration where a terminal(s) is provided, the head main body  11  and the connectors  13  need not be formed of a conductive material. As described above, it suffices that the electric power source  4  is configured to apply a voltage to each nozzle  12 . 
     The nozzles  12  are electrically connected to each other. Therefore, in a state where a voltage is applied to each nozzle  12 , the nozzles  12  come to have identical or substantially identical electric potential to one another. The voltage applied to each nozzle  12  may have a positive polarity or negative polarity. In the example shown in  FIG. 1 , the electric power source  4  is a direct-current electric power source and applies a positive voltage to each nozzle  12 . 
     The collection body  5  is formed of a conductive material. The collection body  5  has resistance to the raw material liquid, and in an example, it is formed of stainless steel. The collection body  5  is disposed on the side where each of the ejection ports  18  opens with respect to the electrospinning head  2 . Therefore, the collection body  5  is disposed on the side where the raw material liquid is ejected from the ejection ports  18  with respect to the electrospinning head  2 . 
     In the example of  FIG. 1 , the collection body  5  is grounded. For this reason, in a state where a positive voltage is applied to each nozzle  12 , the voltage to ground of the collection body  5  becomes OV or substantially OV. In another example, the collection body  5  is not grounded. The electric power source  4  applies, to the collection body  5 , a voltage with counter-polarity to that of each nozzle  12 . 
     In a state where the raw material liquid is supplied to the electrospinning head  2  by the supply source  3 , the raw material liquid is ejected from each ejection port  18  of the nozzles  12  toward the collection body  5  by applying a voltage between each nozzle  12  and the collection body  5  by means of the electric power source  4 , as described above. In other words, the raw material liquid is ejected toward the collection body  5  by an electric potential difference between each nozzle  12  and the collection body  5 . The raw material liquid is ejected from each ejection port  18  of the nozzles  12  toward the collection body  5 , so that fiber  100  is deposited on the surface of the collection body  5 , and a film of the fiber  100  is formed by the deposited fiber  100 . That is, a film of the fiber  100  is formed by an electrospinning method (which may be referred to as an “electric spinning method” or “charge-induced spinning method”). 
     The voltage applied between the electrospinning head  2  and the collection body  5 , i.e., an electric potential difference between each nozzle  12  and the collection body  5 , is adjusted to a suitable size, corresponding to the kind of polymer contained in the raw material liquid and the distance from each nozzle  12  to the collection body  5 , etc. In an example, a 10 kV or higher and 100 kV or lower direct current-voltage is applied between each nozzle  12  and the collection body  5 . In an example, the direction along the longitudinal axis C of the electrospinning head  2  is identical or substantially identical to the width direction of the collection body  5 . The width direction of a formed film of the fiber  100  is identical or substantially identical to the direction along the longitudinal direction C of the electrospinning head  2 . 
     The collection body  5  is formed into a plate or sheet. When the collection body  5  is formed into a sheet, the fiber  100  may be deposited on a collection body  5  wound to the outer circumferential surface of a roll or the like. The collection body  5  may be movable. 
     In an example, a pair of rotating drums and a driving source to drive the rotating drums are provided. The rotating drums are driven by the driving source, so that the collection body  5  moves between the pair of rotating drums in a similar manner to that of a conveyor belt. In this case, for example, the moving direction (conveying direction) of the collection body  5  crosses (becomes perpendicular or substantially perpendicular to) the width direction of the collection body  5 . The movement (conveyance) of the collection body allows a region in which the fiber  100  is deposited on the surface of the collection body  5  to change depending on time. With this configuration, the fiber  100  can be continuously deposited on the collection body  5  depending on time, and a film of the fiber  100  as a deposit of the fiber  100  is efficiently manufactured. 
     The film of the fiber  100  formed on the surface of the collection body  5  is removed from the collection body  5 . The film of the fiber  100  is not limited thereto; however, it is used for an unwoven fabric, a filter, and the like. 
     In an example, the collection body  5  is not provided. In this case, a substrate formed of a conductive material is used, and a voltage is applied between each nozzle  12  and the substrate, so that the raw material liquid is ejected from each ejection port  18  of the nozzles  12  toward the substrate. A film of the fiber  100  is then formed on a surface of the substrate by depositing the fiber  100  on the surface of the substrate. In this case, the substrate may be grounded, and a voltage with counter-polarity to that of each nozzle  12  may be applied to the substrate by the electric power source  4 . 
     In another example, a substrate is placed on the collection body  5 , and a voltage is applied between each nozzle  12  and the collection body  5  as described above. The fiber  100  is deposited on a surface of the substrate placed on the collection body  5  to form a film of the fiber  100  on the surface of the substrate. In this case, even when the substrate has electrically insulating properties, a film of the fiber  100  can be formed on the surface of the substrate. 
     When the substrate is placed on the collection body  5 , the substrate may be movable on the collection body  5 . In an example, a rotating drum around which a sheet-like substrate is wound and a rotating drum which winds up the substrate in which a film of the fiber  100  is formed on the surface are provided. Each drum rotates, so that the substrate moves on the collection body  5 . At that time, for example, the moving direction (conveying direction) of the substrate crosses (is perpendicular or substantially perpendicular to) the width direction of the substrate. The movement (conveyance) of the substrate allows a region in the surface of the substrate where the fiber  100  is deposited to change depending on time. With this configuration, the fiber  100  can be continuously deposited on the substrate depending on time, and a film of the fiber  100  as a deposit of the fiber  100  is efficiently manufactured. 
     An example of forming a film of the fiber  100  on a surface of the substrate is not limited thereto and includes the manufacture of a separator integrated electrode for batteries. In this case, one of a negative electrode and a positive electrode in an electrode group is used as a substrate. A film of the fiber  100  formed on a surface of the substrate will be a separator integrated with a negative or positive electrode. 
     A controller  6  is, for example, a computer, etc. The controller  6  includes a processor or an integrated circuit (control circuit) including a central processing unit (CPU), an application-specific integrated circuit (ASIC) or a field-programmable gate array (FPGA), etc., and a storage medium, such as a memory. The controller  6  may include only one integrated circuit, etc. or a plurality of integrated circuits, etc. The controller  6  executes a program, etc. stored in the storage medium, etc. to thereby perform processing. The controller  6  controls driving of the supply driver  32 , actuation of the supply adjuster  33 , output from the electric power source  4 , etc. 
     As shown in  FIGS. 2 to 5 , the electrospinning head  2  includes a plurality of head units  21 A,  21 B (two in the present embodiment). The head units  21 A,  21 B are arranged along the longitudinal axis C. The head units  21 A,  21 B are coupled to each other. In the present embodiment, the two head units  21 A,  21 B are coupled, so that the electrospinning head  2  is formed. The other head unit  21 B is coupled to the head unit  21 A on one side in a direction along the longitudinal axis C. For this reason, in the present embodiment, the head units  21 A and  21 B are adjacent to each other in the direction along the longitudinal axis C. 
     Each of the head units  21 A and  21 B includes a unit main body  23 . Each head main body  23  extends with the longitudinal axis C as a central axis. In the electrospinning head  2 , a head main body  11  is formed of the unit main bodies  23  of the head units  21 A,  21 B. The outer circumferential surface of the head main body  11  is formed of the outer circumferential surfaces of the unit main bodies  23  of the head units  21 A,  21 B. In addition, the head units  21 A,  21 B are coupled in a state where the unit main bodies  23  of the head units  21 A and  21 B are coaxial or substantially coaxial with each other. 
     In each of the head units  21 A,  21 B, a hollow  25  is formed along the longitudinal axis C inside of the unit main body  23 . In each of the head units  21 A,  21 B, the hollow  25  is formed coaxially or substantially coaxial with the unit main body  23 , and the central axis of the hollow  25  is formed coaxially or substantially coaxial with the longitudinal axis C. In the electrospinning head  2 , the head units  21 A,  21 B are coupled in a state where the hollows  25  of the unit main bodies  23  of the head units  21 A,  21 B communicate with each other. The head flow passage  16  is then formed along the longitudinal axis C by the hollows  25  of the unit main bodies  23  of the head units  21 A,  21 B. 
     In each of the head units  21 A and  21 B, the nozzle  12  described above is arranged on the outer circumferential surface of the unit main body  23 . In an example of  FIG. 2 , etc., two nozzles  12  are provided in the head unit  21 A, and two nozzles  12  are provided in the head unit  21 B. The number of nozzles  12  provided in each of the head units  21 A,  21 B is not particularly limited, and it suffices that one or more nozzles  12  are connected to each unit main body  23  of the head units  21 A,  21 B. 
     In the example of  FIG. 2 , etc., an end face of the head main body  11  on one side in the direction along the longitudinal axis C is formed of the unit main body  23  of the head unit  21 A, and the other end face of the head main body  11  on the other side in the direction along the longitudinal axis C is formed of the unit main body  23  of the head unit  21 B. An inflow port  22  of the head flow passage  16  is formed in the head unit  21 A. 
     A sealing member  20  is provided between the adjacent head units  21 A,  21 B adjacent in the direction along the longitudinal axis C. Therefore, the sealing member  20  is placed on a coupling face P of the adjacent head units  21 A,  21 B. The sealing member  20  is, for example, a washer or ring, etc. An example of a material forming the sealing member  20  includes polytetrafluoroethylene (PTFE). The sealing member  20  maintains a space between the unit main bodies  23  of the head units  21 A and  21 B in a liquid-tight manner at the coupling face P. This configuration prevents the raw material liquid from flowing out from the head flow passage  16  to the outside of the head main body  11 . 
     The coupling face P passes by a position away from each nozzle  12 . In the present embodiment, the coupling face P is perpendicular or substantially perpendicular to the longitudinal axis C. A normal line direction (direction shown by arrows N 1  and N 2 ) of the coupling face P is identical or substantially identical to the direction along the longitudinal axis C, and is parallel or substantially parallel to the longitudinal axis C. 
     Here, a coupling structure (coupling) that couples the head units  21 A,  21 B to each other will be described. In each unit main body  23  of the head units  21 A and  21 B, one or more holes  26  are formed along the longitudinal axis C. In the present embodiment, three holes  26  are formed in each of the head units  21 A,  21 B. In each of the head units  21 A and  21 B, each hole  26  penetrates through the unit main body  23  in the direction along the longitudinal axis C. In each of the head units  21 A and  21 B, the holes  26  are respectively formed on the inner circumference side with respect to the outer circumferential surface of the unit main body  23  and nozzles  12 , and are formed between the hollow  25  and the outer circumferential surface of the unit main body  23  in the radial direction of the unit main body  23 . 
     In each of the head units  21 A and  21 B, the holes  26  are formed away from one another around the longitudinal axis C. In an example, the holes  26  are arranged at regular or substantially regular intervals around the longitudinal axis C. In addition, each hole  26  of the head unit  21 A is arranged at the same or substantially the same angular position with one corresponding hole  26  in the head unit  21 B in a direction around the longitudinal axis C. 
     In the present embodiment, as many holes  27  as there are holes  26  formed in the head unit  21 A, i.e., as many as the holes  26  formed in the head unit  21 B, are formed in the sealing member  20 . Each hole  27  penetrates through the sealing member  20  in the direction along the longitudinal axis C. Each hole  27  is arranged at the same or substantially the same angular position with one corresponding hole  26  in the head unit  21 A and one corresponding hole  26  in the head unit  21 B around the longitudinal axis C. In the head main body  11 , each hole  26  of the head unit  21 A communicates with one corresponding hole  26  in the head unit  21 B via one corresponding hole  27  in the sealing member  20 . 
     As many bolts  28  as there are holes  26  formed in the head unit  21 A, i.e., as many as the holes  26  formed in the head unit  21 B, are fixed, as fastening members, to the head main body  11 . Each bolt  28  is inserted into one corresponding hole  26  in the head unit  21 A, one corresponding hole  27  in the sealing member  20 , and one corresponding hole  26  in the head unit  21 B. In addition, respective head portions of the bolts  28  abut an end face of the head main body  11  on one side in the direction along the longitudinal axis C. A single corresponding nut  29  is fastened to each bolt  28  via screw-fitting, etc. at an end of the bolt  28  opposite the head portion. Each nut  29  abuts the head main body  11  at the end face opposite to the end face which abuts the head portion of the bolt  28 . 
     The bolts  28  and the nuts  29  are fixed to the head main body  11  as described above, so that the head main body  11  is fastened in the direction along the longitudinal axis C by the bolts  28  and nuts  29 . In other words, the head main body  11  is compressed between the head portions of the bolts  28  and the nuts  29  in the direction along the longitudinal axis C. The head units  21 A and  21 B are coupled to each other through fastening involving use of the bolts  28  and the nuts  29 . 
     In the present embodiment, since the bolts  28  and the nuts  29  are attached to the head main body  11  as described above, the bolts  28  and nuts  20  are provided on the inner circumferential side with respect to the outer circumferential surface of each unit main body  23  of the head units  21 A,  21 B and the nozzle  12 . The bolts  28  and nuts  29  are formed between the head flow passage  16  (hollow  25 ) and the outer circumferential surface of the head main body  11  according to the radial direction of the head main body  11 . Therefore, in the present embodiment, the coupling structure coupling the head units  21 A and  21 B to each other is provided on the inner circumferential side with respect to the outer circumferential surface and the nozzles  12  in each unit main body  23  of the head units  21 A,  21 B. That is, the coupling structure (coupling) is not formed on the outer circumferential surfaces of the unit main bodies  23  on which the nozzles  12  are arranged. 
     The bolts  28  and nuts  29  are formed of a conductive material. In the present embodiment, the head portion of the bolt  28  abuts one end face of the head main body  11  in the direction along the longitudinal axis C as described above. The nut  29  abuts the head main body  11  at the end face opposite to the end face which abuts the head portion of the bolt  28 . For this reason, in the present embodiment, the head units  21 A and  21 B are electrically connected to each other via the bolts  28  and the nuts  29 . Also, in each of the head units  21 A and  21 B, the unit main body  23  is electrically connected to the nozzles  12 . Therefore, when a voltage is applied to the electrospinning head  2  by the electric power source  4  as described above, the nozzles  12  in the head unit  21 A and the nozzles  12  in the head unit  21 B come to have identical or substantially identical electric potential to each other. 
     In the present embodiment, the plurality of head units  21 A and  21 B are arranged along the longitudinal axis C, and the head units  21 A and  21 B are coupled to each other. For this reason, the size of the head main body  11  in the direction along the longitudinal axis C can be increased. In the head main body  11 , which is large in size in the direction along the longitudinal axis C, a plurality of nozzles  12  are arranged along the longitudinal axis C. By configuring the head main body  11  as described above, a film of the fiber  100 , large in size in the direction along the longitudinal axis C of the head main body  11 , is appropriately formed. That is, a film of the fiber  100 , large in size in its width direction, is appropriately formed. 
     In the present embodiment, since the plurality of nozzles  12  are arranged as described above, when the film of the fiber  100  is formed as described above by the ejection of the raw material liquid from the nozzles  12 , it is unnecessary to reciprocally move the nozzles  12  in the width direction of the film of the fiber  100 , for example. Therefore, it is unnecessary to provide a driving system for moving the nozzles  12  in the electrospinning apparatus  1 . Therefore, in the electrospinning apparatus  1 , its configuration, control system, etc. will not be complicated. 
     In addition, in the present embodiment, the head units  21 A and  21 B are coupled in a state where the hollows  25  of the unit main bodies  23  of the head units  21 A and  21 B communicate with each other. A head flow passage  16  is then formed along the longitudinal axis C by the hollows  25  of the unit main bodies  23  of the head units  21 A and  21 B. Since the head flow passage  16  is formed as described above, in the present embodiment, it is unnecessary to form, in a single member, a hole (hollow), large in size in the direction along the longitudinal axis C, in the formation of the head main body  11 . Therefore, the manufacturing costs of the head main body  11  and the electrospinning head  2  are suppressed, and their productivity increases. 
     In the present embodiment, a space between the unit main bodies  23  of the head units  21 A and  21 B is maintained in a liquid-tight manner by the sealing member  20 . The outflow of the raw material liquid from the head flow passage  16  to the outside of the head main body  11  is prevented at a coupling face P by the sealing member  20 . For this reason, even with the configuration where the head flow passage  16  is formed by configuring the hollows  25  of the unit main bodies  23  of the head units  21 A and  21 B to communicate with each other, the outflow of the raw material liquid from the head flow passage  16  is effectively prevented. 
     In the present embodiment, the head units  21 A and  21 B are electrically connected to each other via the bolts  28  and the nuts  29 . In each of the head units  21 A and  21 B, the unit main body  23  is electrically connected to the nozzles  12 . Therefore, when a voltage is applied from the electric power source  4 , each nozzle  12  of the head units  21 A and  21 B comes to have an identical or substantially identical electric potential to each other by connecting the electric power source  4  to one of the unit main bodies  23  of the head units  21 A,  21 B. This prevents complication of the configuration of the power feeding system that applies a voltage to the electrospinning head  2 . 
     In the present embodiment, the bolts  28 , the nuts  29 , etc. are provided on the inner circumferential side with respect to the outer circumferential surface and the nozzles  12  in each unit main body  23  of the head units  21 A,  21 B. For this reason, even if the coupling structure for coupling the head units  21 A and  21 B is provided, protruding portions other than the nozzles  12  are not formed in the vicinity of the nozzles  12  on the outer circumferential surface of the head main body  11 . Therefore, the influence of the coupling structure on an electric field in the vicinity of the nozzles  12  is suppressed, even if the coupling structure of the head units  21 A and  21 B is provided. 
     (Modifications) 
     In a first modification shown in  FIGS. 6 to 9 , nozzles  12 A,  12 B are provided as the nozzles  12  on the outer circumferential surface of the head main body  11 . In this modification, the nozzles  12 A and  12 B are respectively provided in plural numbers. In addition, in this modification, a plurality of nozzles (first nozzles)  12 A are arranged at the same or substantially the same angular positions with respect to one another around the longitudinal axis C, and a plurality of nozzles (second nozzles)  12 B are arranged at the same or substantially the same angular positions with respect to one another around the longitudinal axis C. Therefore, in this modification, the plurality of nozzles  12 A are arranged along the longitudinal axis C to form a nozzle row (first nozzle row)  15 A. Also, the plurality of nozzles  12 B are arranged along the longitudinal axis C to form a nozzle row (second nozzle row)  15 B. Here,  FIG. 6  is a perspective diagram of the electrospinning head  2 , and  FIG. 7  shows a state where the electrospinning head  2  is viewed from a direction crossing (perpendicular or substantially perpendicular to) the longitudinal axis C.  FIG. 8  shows a cross-section of the electrospinning head  2  parallel or substantially parallel to the longitudinal axis C, and  FIG. 9  shows a cross-section of the electrospinning head  2  perpendicular or substantially perpendicular to the longitudinal axis C. 
     The nozzles  12 B are provided so as to be shifted with respect to the nozzles  12 A around the longitudinal axis C. Therefore, the nozzle row  15 B is formed so as to be shifted with respect to the nozzle row  15 A. In this modification, however, both the nozzles  12 A and  12 B are arranged on the side where the collection body  5  is positioned with respect to the longitudinal axis C. For example, the nozzles  12 A are provided so as to be shifted by about 60° from the nozzles  12 B around the longitudinal axis C. In an example of  FIG. 6 , etc., two sets of each nozzle  12 A and  12 B are provided in the head unit  21 A, and two sets of each nozzle  12 A and  12 B are provided in the head unit  21 B. Therefore, four sets of each nozzle  12 A and  12 B are provided in the head main body  11 . The numbers of the nozzles  12 A and  12 B provided respectively in the head units  21 A and  21 B are not particularly limited, and it suffices that one or more nozzles  12 A and one or more nozzles  12 B are connected to each unit main body  23  of the head units  21 A,  21 B. 
     In the electrospinning head  2 , a nozzle flow passage  17 A is formed in each nozzle  12 A, and a nozzle flow passage  17 B is formed in each nozzle  12 B. Each of the nozzle flow passages  17 A and  17 B communicates with the head flow passage  16  and extends from the head flow passage  16  toward the outer circumference side of the head main body  11 . Each nozzle flow passage  17 A opens toward the outside at an ejection port  18 A, and each nozzle flow passage  17 B opens toward the outside at an ejection port  18 B. In each nozzle  12 A, the ejection port  18 A is formed at a projecting end from the head main body  11 . In each nozzle  12 B, the ejection port  18 B is formed at a projecting end from the head main body  11 . 
     The nozzles  12 A and  12 B are arranged in a zigzag manner on the outer circumferential surface of the head main body  11 . The nozzles  12 A and the nozzles  12 B are alternately arranged in the direction along the longitudinal axis C. Therefore, one corresponding nozzle (second nozzle)  12 B is disposed between adjacent nozzles (first nozzles) in the direction along the longitudinal axis C. 
     Also in this modification, the sealing member  20  is placed on a coupling face P of the head units  21 A,  21 B adjacent to each other. The coupling face P passes by a position away from both the nozzles  12 A and  12 B. In this modification, however, the nozzles  12 A and  12 B are arranged in a zigzag manner as described above. For this reason, the coupling face P is inclined relative to the longitudinal axis C. The normal line direction of the coupling face P (the direction shown by the arrows N 1  and N 2 ) is inclined relative to the longitudinal axis C. 
     In this modification, a nozzle  12 B is disposed between nozzles  12 A adjacent to each other in the direction along the longitudinal axis C. Therefore, in the collection body or the substrate, the fiber  100  is deposited by the nozzle  12 B, even in a region between the nozzles  12 A adjacent to each other in the direction along the longitudinal axis C. This configuration effectively prevents the fiber  100  from being locally deposited on the collection body  5  or the substrate. Therefore, it is possible to effectively prevent a formed film of the fiber  100  from having uneven thicknesses. 
     The coupling face P is inclined relative to the longitudinal axis C. Therefore, the head units  21 A and  21 B can be coupled at the coupling face P passing by a position located away from both the nozzles  12 A and  12 B, even when the nozzles  12 A and  12 B are arranged in a zigzag manner as described above. 
     Furthermore, the coupling structure which couples the head units  21 A and  21 B is not limited to the above-mentioned coupling structure using the bolts (fastening member)  28  and the nuts  29 . For example, in a second modification shown in  FIGS. 10 and 11 , a male screw  41  is formed in the unit main body  23  of the head unit  21 A. A female screw  42  is formed in a unit main body  23  of a head unit  21 B. In this modification, the male screw  41  is screw-fitted into the female screw  42 , so that the head units  21 A and  21 B are coupled to each other. Therefore, a coupling structure (coupling) which couples the head units  21 A and  21 B is formed by the male screw  41  and the female screw  42 . Here,  FIG. 10  shows a state where the electrospinning head is viewed from a direction crossing (perpendicular or substantially perpendicular to) the longitudinal axis C, and the head units  21 A and  21 B are separated from each other.  FIG. 11  shows a cross-section parallel or substantially parallel to the longitudinal axis C. 
     Also in this modification, the coupling structure formed from the male screw  41  and the female screw  42  is provided on the inner circumference side with respect to the outer circumferential surface and the nozzles  12  of each unit main body  23  of the head units  21 A,  21 B. The coupling structure is formed between a head flow passage  16  (hollow  25 ) and the outer circumferential surface of a head main body  11 , in the radial direction of the head main body  11 . Therefore, also in this modification, the coupling structure which couples the head units  21 A and  21 B to each other is not formed on the outer circumferential surface of the unit main body  23  on which the nozzles  12  are arranged. For this reason, the influence of the coupling structure on an electric field in the vicinity of the nozzles  12  is suppressed. 
     Furthermore, also in this modification, the sealing member  20  is placed on the coupling face P of the head units  21 A,  21 B. In this modification, a sealing member  20  is placed on the outer circumference side of the male screw of the head unit  21 A. Also in this modification, the head units  21 A and  21 B are electrically connected to each other via the male screw  41  and the female screw  42 , and the unit main body  23  is electrically connected to the nozzles  12  in each head unit  21 A and  21 B. By virtue of the configuration described above, the electrospinning head according to this modification exerts similar function and advantageous effects to those in the first embodiment. 
     In a modification, a male screw is formed in the head unit  21 B, and a female screw to be screw-fitted into the male screw is formed in the head unit  21 A. 
     In a third modification shown in  FIGS. 12 and 13 , a flange  45  is formed on each unit main body  23  of the head units  21 A and  21 B. In each of the head units  21 A and  21 , the flange  45  protrudes to the outer circumference side in the outer circumferential surface of the unit main body  23 . The flange  45  is, however, provided away from the nozzles  12 , around the longitudinal axis C. The flange  45  is preferably provided on the opposite side to a side where the nozzles  12  are positioned, with respect to the longitudinal axis C. In an example, the flange  45  is disposed away from the nozzles  12  by about 180° around the longitudinal axis C. Here,  FIG. 12  shows a state where the electrospinning head is viewed from a direction crossing (perpendicular or substantially perpendicular to) the longitudinal axis C.  FIG. 13  shows a state where the electrospinning head is viewed from one side (the side where an inflow port  22  is positioned) in a direction along the longitudinal axis C. 
     In the head unit  21 A, a flange  45  is formed at the end of the side where the head unit  21 B is positioned in the direction along the longitudinal axis C. In the head unit  21 B, the flange  45  is formed at the end of the side where the head unit  21 A is positioned in the direction along the longitudinal axis C. In this modification, the flanges  45  of the head units  21 A,  21 B abut each other. The flanges  45  of the head units  21 A,  21 B are fastened in the direction along the longitudinal axis C by a bolt  46  and a nut  47 . The head units  21 A and  21 B are coupled to each other by the fastening of the flanges  45  of the head units  21 A,  21 B through use of the bolt  46  and the nut  47 . Therefore, in this modification, the coupling structure (coupling) which couples the head units  21 A and  21 B is formed by the flanges  45 , bolt  46  and nut  47 . 
     In this modification, the coupling structure is provided on the outer circumferential surface of each unit main body  23  of the head units  21 A,  21 B. However, the coupling structure including the flanges  45  is provided away from the nozzles  12 , around the longitudinal axis C. For this reason, in the vicinity of the nozzles  12  on the outer circumferential surface of the head main body  11 , protruding portions other than the nozzles  12  are not formed, similarly to the embodiments described above. Therefore, also in this modification, the influence of the coupling structure on an electric field in the vicinity of the nozzles  12  is suppressed. 
     Furthermore, also in this modification, the sealing member  20  is placed on a coupling face P of the head units  21 A,  21 B. In this modification, in the coupling face P, the sealing member  20  is placed on the inner circumference side of the flange  45  of the head unit  21 A. Furthermore, in this modification, the head units  21 A and  21 B are electrically connected to each other via the flanges  45 , and the unit main bodies  23  in each of the head units  21 A and  21 B are electrically connected to the nozzles  12 . By virtue of the configuration described above, the electrospinning head according to this modification exerts similar function and advantageous effects to those in the first embodiment. 
     In another modification, the sealing member  20  is formed of a conductive rubber, etc., and has conductivity. In this case, the head units  21 A and  21 B are electrically connected to each other via the sealing member  20 . 
     In the above-mentioned embodiments, the electrospinning head  2  is formed from two head units  21 A and  21 B; however, the configuration thereof is not limited to that disclosed above. In a fourth modification shown in  FIG. 14 , an electrospinning head  2  is formed from three head units  21 A to  21 C. Also in this modification, the head units  21 A to  21 C are arranged along the longitudinal axis C and coupled to one another. Also, hollows  25  of unit main bodies  23  of the head units  21 A to  21 C communicate with one another, and a head flow passage  16  is formed along the longitudinal axis C by the hollows  25  of the unit main bodies  23  of the head units  21 A to  21 C. 
     In this modification, the head units  21 A and  21 B are coupled to each other in the same manner as in any one of the above-mentioned embodiments. The head units  21 B and  21 C are coupled to each other in the same manner as in any one of the above-mentioned embodiments. When a voltage is applied to the electrospinning head  2  by an electric power source  4 , the nozzles  12  in the head units  21 A to  21 C come to have an identical or substantially identical electric potential to one another. In this modification, a sealing member  20  is placed on a coupling face of the head units  21 A and  21 B which are adjacent to each other, and the sealing member  20  is placed on a coupling face of the head units  21 B and  21 C which are adjacent to each other. Also in this modification, similar function and advantageous effects to those of the above-mentioned embodiments are exerted. 
     Furthermore, in a modification, an electrospinning head  2  is formed by coupling four or more head units  21  to one another. Also in this case, the head units  21  are coupled to one another to form a head flow passage  16 , in the same manner as in any one of the above-mentioned embodiments. 
     According to at least one embodiment or example of those described above, another head unit can be coupled to the head unit on at least one side in the direction along the longitudinal axis C by the coupling structure. The coupling structure couples a unit main body of said another head unit to the unit main body of the head unit, in a state where the hollow of the unit main body of the head unit communicates with the hollow of the unit main body of said another head unit. With this configuration, it is possible to provide a head unit capable of suppressing the complexity of its configuration and its control system in addition to an increase in manufacturing costs and a reduction in productivity of the electrospinning head, and which can appropriately form a film of fiber large in size in the width direction. 
     In addition, according to at least one embodiment or example of those described above, the plurality of head units are coupled to one another by the coupling structure. The coupling structure couples a plurality of head units in a state where the hollows of their unit main bodies communicate with one another. Thereby, it is possible to provide an electrospinning head which suppresses the complexity of its configuration and its control system in addition to an increase in manufacturing costs and a reduction in productivity of the electrospinning head, and which can appropriately form a film of fiber large in size in the width direction. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.