Abstract:
A ground color main extruder  9  which supplies a ground color resin that is to cover a strand conductor  3  is disposed. Plural stripe sub extruders  21  and  31  which supply a colored resin in a strip-like manner in a longitudinal direction of the strand conductor  3  simultaneously with extrusion of the ground color resin are disposed. Insert molds  16  and  17  are multiply disposed. While alternatingly switching over the stripe sub extruders  21  and  31  each time when a colored resin to be supplied is changed, a colored resin of a predetermined color is supplied through a path which is disposed for each of the stripe sub extruders  21  and  31.

Description:
BACKGROUND OF INVENTION 
     1. Field of Invention 
     The present invention relates to a crosshead for producing a stripe electric wire in which, when a conductor is covered with a synthetic resin of the ground color in a wire cover extrusion line, colored resins of a color different from the ground color are supplied in a stripe manner from stripe sub extruders, and more particularly to a crosshead in which a mixed color area (color change loss) that is produced when the color of a colored resin covering in a stripe manner, or that of a skin layer colored resin is changed can be reduced. 
     2. Related Art 
     Usually, an electric wire has a structure in which the outside of a conductor is covered with an insulator of a synthetic resin. In order to prevent erroneous connection from occurring, such an electric wire is configured as a stripe electric wire in which the insulator is covered in a strip-like manner with a resin of a color different from the ground color so as to identify the wire. In such a stripe electric wire, the stripe coloring on the insulator is performed by using a stripe sub extruder  13 , a covering resin supplied from a ground color main extruder  9  is used as a ground color resin, and the covering resin is covered with a colored covering resin in a stripe manner. 
     Conventionally, the stripe electric wire is produced by using a crosshead such as shown in FIG.  7 . 
     The crosshead body  2  of the crosshead  1  is formed into a cylindrical shape. A cylindrical nipple  4  in which the tip end is tapered and a strand conductor  3  runs through the center is fitted into the crosshead body  2  so as to maintain a predetermined gap between the nipple and the inner face of the crosshead body  2 . An insert mold  5  which is formed into a cylindrical shape is fittingly attached to the tip end portion of the crosshead body  2 . A hole through which a covered wire  6  in which the strand conductor  3  is covered with a resin is to run is formed in the center of the insert mold  5 . A die  7  which is tapered toward the center is fixedly attached to the mold. The die  7  and the nipple  4  are placed at the same center. 
     A ground color resin supply path  8  is opened in the crosshead body  2 . A ground color main extruder  9  is attached to the body so as to communicate with the ground color resin supply path  8 . A ground color resin is supplied from the ground color main extruder  9  into the crosshead body  2  via the ground color resin supply path  8 . The reference numeral  10  denotes a seal for attaching the ground color main extruder  9  to the crosshead body  2 , and  11  denotes a switch cock for, when the color of the ground color resin from the ground color main extruder  9  is to be changed, stopping the supply of the resin therefrom. 
     A stripe resin supply path  12  is opened in the crosshead body  2 . A stripe sub extruder  13  is attached to the body so as to communicate with the stripe resin supply path  12 . A colored resin for a stripe is supplied from the stripe sub extruder  13  into the crosshead body  2  via the stripe resin supply path  12 . 
     The reference numeral  14  denotes a seal for attaching the stripe sub extruder  13  to the crosshead body  2 , and  15  denotes a switch cock for, when the color of the colored resin from the stripe sub extruder  13  is to be changed, stopping the supply of the resin therefrom. 
     The switch cock  15  is used for stopping the supply of the stripe covering resin to the crosshead body  2 , and discharging a part of the stripe covering resin of a new color which is continuous to that of the old color that has been used before the color change. In the switch cock  15 , in order to smoothly supply the colored resin to the crosshead body  2 , a heater is internally disposed to heat the colored resin to an appropriate temperature. 
     The switching by means of the switch cock  15  is performed in the following manner. The supply route from the stripe sub extruder  13  to the crosshead body  2  is changed to a discharge route from the stripe sub extruder  13  to the outside by an adequate method. In the case where the switching of the switch cock  15  is to be conducted, before the switching of the switch cock  15 , the production line is stopped, and a hopper storing a coloring material is switched to another one so that the colored stripe covering resin to be supplied to the stripe sub extruder  13  is replaced with a resin of another color. Thereafter, the switch cock  15  is switched over from the supply route from the stripe sub extruder  13  to the crosshead body  2 , to the discharge route from the stripe sub extruder  13  to the outside. As a result of the switching of the switch cock  15 , the stripe colored resin which has been extruded by the stripe sub extruder  13  is discharged through a discharge port of the switch cock  15 . 
     A stripe electric wire is produced by using the thus configured crosshead  1  in the following manner. The ground color resin supplied from the ground color main extruder  9  is sent via the ground color resin supply path  8  to the tip end of the nipple  4  with passing through the gap between the inner peripheral face of the crosshead body  2  and the outer peripheral face of the nipple  4 . The surface of the strand conductor  3  is covered with the resin at a predetermined thickness by means of the tapered tip end portion of the crosshead body  2  and the tapered portion of the die  7 . When the surface of the strand conductor  3  is to be covered with the resin at the predetermined thickness, the stripe colored resin is extruded from the stripe sub extruder  13  with passing through the stripe resin supply path  12 , into the ground color resin passing through the gap between the inner peripheral face of the crosshead body  2  and the outer peripheral face of the nipple  4 , so as to be longitudinally added in a stripe manner. The colored resin is then sent together with the ground color resin, and the surface of the strand conductor  3  is covered with the colored resin in a stripe manner by means of the tapered tip end portion of the crosshead body  2  and the tapered portion of the die  7 . 
     In the production of a stripe electric wire by using the crosshead  1 , the color of the stripe is sometimes changed although the ground color resin is not changed. In this case, the ground color resin is continued to be supplied from the ground color main extruder  9 . In the stripe sub extruder  13 , by contrast, the running of the strand conductor  3  is temporarily stopped, the supply of the colored resin from the stripe sub extruder  13  to the crosshead body  2  is temporarily stopped, and the color of the colored resin in the stripe sub extruder  13  is changed. When the color change of the colored resin in the stripe sub extruder  13  is performed, the covering resin of the old color which is used before the color change is discharged through the discharge port (not shown) of the switch cock  15 . When the discharge of the covering resin of the new color is checked and it is judged that the output of the covering resin of the new color is completely attained, the switch cock  15  is returned to the resin supplying position to restart the extrusion covering on the strand conductor  3 . When the new colored resin is supplied from the thus configured stripe sub extruder  13 , the colored resin of the old color remains in the stripe resin supply path  12  or the like, and hence the colored resin of the old color is initially supplied, and the colored resin for forming a stripe which is supplied as a result of the color changing is then extruded in succession and continuously with the colored resin of the old color. The colored resin of the old color is mixed with that of the new color, and then replaced with that of the new color. 
     The resin which is initially discharged from the discharge port of the switch cock  15  is the colored resin of the old color which is used before the color change, and after a short time a resin in which the stripe covering resin of the old color is mixed with that of the new color is discharged. After a further short time elapses, only the stripe covering resin of the new color is discharged. At the timing when the discharge of only the stripe colored resin of the new color is checked, the switch cock  15  is switched over to change the discharge route from the stripe sub extruder  13  to the outside, to the supply route from the stripe sub extruder  13  to the crosshead body  2 . As a result of the switching of the switch cock  15 , the stripe colored resin of the new color is supplied to the crosshead body  2 . At the same time when the switch cock  15  is switched over, the production line is restarted. In this way, the switching from the stripe covering resin of the old color to that of the new color is performed. 
     However, the conventional crosshead has the following problems. In the case where the color of the stripe colored resin with which the surface of the strand conductor  3  is covered is to be changed, the hopper storing a coloring material is switched to another one to change the colored resin, the covering resin of the old color which has been used before the color change and which remains in the stripe sub extruder is then discharged, and it is checked that the covering resin of the new color is discharged. Therefore, the changing operation requires much labor, and, when the switching by means of the switch cock is delayed, the covering resin is lost in a larger amount. Particularly, the resin of the old color remains in the range “from the switch cock to the insert mold,” and a mixed color area is produced in a subsequent extrusion of the resin of the next color, with the result that a color change loss is caused. 
     SUMMARY OF INVENTION 
     It is an object of the invention to prevent a mixed color area from being produced in a process of changing from the old color to the next color, thereby eliminating a color change loss (color failure of an electric wire). 
     In order to attain the object, the crosshead of a first aspect of the invention is configured so that a ground color main extruder which supplies a ground color resin that is to cover a strand conductor is disposed, plural stripe sub extruders which supply a colored resin in a strip-like manner in a longitudinal direction of the strand conductor simultaneously with extrusion of the ground color resin are disposed, insert molds are multiply disposed, and, while alternatingly switching over the stripe sub extruders each time when a colored resin to be supplied is changed, a colored resin of a predetermined color is supplied through a path which is disposed for each of the stripe sub extruders. 
     According to the first aspect of the invention configured as described above, production of a mixed color area in a process of changing from the old color to the next color can be largely reduced, and a color change loss (color failure of an electric wire) can be greatly decreased. 
     In order to attain the object, the crosshead of a second aspect of the invention is configured so that stripes are formed are formed by pairing symmetrical positions on an outer periphery of a covered wire, and separating the positions by a predetermined angle for each of the stripe sub extruders. 
     According to the second aspect of the invention configured as described above, the resin pressure in the crosshead can be uniformalized, and a stripe electric wire in which the stripe is positioned in balance can be produced. 
     In order to attain the object, the crosshead of a third aspect of the invention is configured so that one or plural skin layer sub extruders which form a skin layer on a covered wire covered with an inner layer resin by the ground color main extruder are attached to the crosshead, and a skin layer insert mold for forming the skin layer is singly or multiply disposed. 
     According to the third aspect of the invention configured as described above, an inner layer resin can be thinly covered with a resin of a preferred color so that the ground color of the covered electric wire can be freely changed without being affected by the color of the inner layer resin. 
     In order to attain the object, the crosshead of a fourth aspect of the invention is configured so that, in middles of supply paths through which the colored resins of the stripe sub extruders are supplied to the insert molds, switch cocks which allow and stop the supplies of the colored resins from the stripe sub extruders to the insert molds are respectively disposed, and resin discharge paths which respectively elongate from positions where the switch cocks are attached, and which are opened to an outside are disposed. 
     According to the fourth aspect of the invention configured as described above, during an operation of changing the color of the stripe colored resin, it is possible to prevent a mixed color area from being produced in a process of changing from the old color to the next color, whereby a color change loss (color failure of an electric wire) can be prevented from occurring. 
     In order to attain the object, the crosshead of a fifth aspect of the invention is configured so that, in middles of supply paths through which colored resins of the skin layer sub extruders are supplied to the skin layer insert molds, switch cocks which allow and stop the supplies of the colored resins from the skin layer sub extruders to the skin layer insert molds are respectively disposed, and resin discharge paths which respectively elongate from positions where the switch cocks are attached, and which are opened to an outside are disposed. 
     According to the fifth aspect of the invention configured as described above, during an operation of changing the color of the colored resin for the skin layer, the colored resin of the old color which remains in the range from the skin layer sub extruder to the switch cock can be surely discharged to the outside, and hence it is possible to prevent a mixed color area from being produced in a process of changing from the old color to the next color, whereby a color change loss (color failure of an electric wire) can be prevented from occurring. 
     In order to attain the object, the crosshead of a sixth aspect of the invention is configured so that each of the switch cock is a cock which is formed into a columnar shape, and in which a resin path that radiately communicates with a center is formed, and a discharge path elongates from a position where the resin path is formed, toward a center axis and so as not to communicate with the resin path, and is opened in an end portion. 
     According to the sixth aspect of the invention configured as described above, during an operation of changing the color of the stripe colored resin or that of changing the color of the colored resin for the skin layer, it is possible to prevent a mixed color area from being produced in a process of changing from the old color to the next color, whereby a color change loss (color failure of an electric wire) can be prevented from occurring. 
     In order to attain the object, the crosshead of a seventh aspect of the invention is configured so that, when the colored resins are to be supplied from the stripe sub extruders to the insert molds, the switch cocks cause sub-extruder supply paths through which the colored resins from the stripe sub extruders are supplied, to communicate with insert mold supply paths through which the colored resins are supplied to the insert molds, and, when the supplies of the colored resins from the stripe sub extruders are to be stopped, cause the sub-extruder supply paths through which the colored resins from the stripe sub extruders are supplied, to communicate with the resin discharge paths, and the insert mold supply paths to communicate with the discharge paths. 
     According to the seventh aspect of the invention configured as described above, during an operation of changing the color of the stripe colored resin, it is possible to prevent a mixed color area from being produced in a process of changing from the old color to the next color, whereby a color change loss (color failure of an electric wire) can be prevented from occurring. 
     In order to attain the object, the crosshead of an eighth aspect of the invention is configured so that, when the supplies of the colored resins from the stripe sub extruders are stopped, resins remaining in the sub-extruder supply paths elongating from the stripe sub extruders to the switch cocks are discharged to the outside through the resin discharge paths, by extruding the colored resins of a new color supplied from the stripe sub extruders, and resins remaining in the insert mold supply paths elongating from the switch cocks to the insert molds are discharged by a pressure of the ground color resin extruded from the ground color main extruder into the crosshead body, to the outside through the discharge paths of the switch cocks. 
     According to the eighth aspect of the invention configured as described above, during an operation of changing the color of the stripe colored resin, it is possible to prevent a mixed color area from being produced in a process of changing from the old color to the next color, whereby a color change loss (color failure of an electric wire) can be prevented from occurring. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a section view showing a first embodiment of the crosshead of the invention. 
     FIG. 2A is a transverse section view of a switch cock shown in FIG. 1, and FIG. 2B is a longitudinal section view of the switch cock shown in FIG.  1 . 
     FIG. 3 is a section view of a stripe electric wire which is produced by using the crosshead shown in FIG.  1 . 
     FIG. 4 is a section view showing a second embodiment of the crosshead of the invention. 
     FIG. 5 is a section view of a stripe electric wire which is produced by using the crosshead shown in FIG.  4 . 
     FIG. 6 is a section view showing a third embodiment of the crosshead of the invention. 
     FIG. 7 is a section view showing a crosshead of the conventional art. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Hereinafter, embodiments of the crosshead of the invention will be described. 
     FIG. 1 is a section view showing a first embodiment of the crosshead of the invention. 
     Referring to FIG. 1, a cylindrical nipple  4  in which the tip end is tapered and a strand conductor  3  runs through the center is fitted into the crosshead body  2  of a crosshead  1  formed into a cylindrical shape, so as to maintain a predetermined gap between the nipple and the inner face of the crosshead body  2 . Two insert molds  16  and  17  which are formed into a cylindrical shape are overlappingly fittingly attached to the tip end portion of the crosshead body  2 . A hole through which a covered wire  6  in which the strand conductor  3  is covered with a resin is to run is formed in the center of the insert mold  16 . A die  7  which is tapered toward the center is fixedly attached to the mold. The die  7  and the nipple  4  are placed at the same center. 
     A ground color resin supply path  8  is opened in the crosshead body  2 . A ground color main extruder  9  is attached to the body so as to communicate with the ground color resin supply path  8 . A ground color resin is supplied from the ground color main extruder  9  into the crosshead body  2  via the ground color resin supply path  8 . The reference numeral  10  denotes a seal for attaching the ground color main extruder  9  to the crosshead body  2 , and  11  denotes a switch cock for, when the color of the ground color resin from the ground color main extruder  9  is to be changed, stopping the supply of the resin therefrom. 
     A sub-extruder supply path  18  which is formed into an L-like shape and which serves as a path for supplying a stripe colored resin is formed in the crosshead body  2 . A switch cock  19  is disposed at the tip end of the sub-extruder supply path  18 . An insert mold supply path  20  for supplying the colored resin which has been supplied to the switch cock  19 , from the switch cock  19  to the insert mold  16  is disposed in the crosshead body  2 . A stripe sub extruder  21  is attached to the body so as to communicate with the sub-extruder supply path  18 . The stripe colored resin supplied from the stripe sub extruder  21  is passed through the sub-extruder supply path  18 , then passed through the insert mold supply path  20  via the switch cock  19  to be supplied to the insert mold  16 , and then supplied into the crosshead body  2  from the insert mold  16 . 
     A resin discharge path  22  which elongates from the switch cock  19  to be opened to the outside is disposed in the crosshead body  2 . 
     The switch cock  19  has the configuration shown in FIG.  2 . As shown in FIG. 2A, the switch cock  19  has the body  23  which is formed into a columnar shape, and a resin path  24  which radiately communicates with the center of the body  23  is formed in the body  23 . As shown in FIG. 2B, the resin path  24  is formed so as to be bent at the center axis by about 90°. A discharge path  25  is formed in the body  23 . The discharge path elongates from the outer peripheral face of the body  23  corresponding to the position where the resin path  24  is formed, toward the center axis and so as not to communicate with the resin path  24 , and then advances in the axial length at the center. The discharge path is opened in an end portion of the body  23 . 
     As shown in FIG. 1, when the switch cock  19  is rotated to a position where the supply of the colored resin from the stripe sub extruder  21  is stopped, therefore, the sub-extruder supply path  18  is caused to communicate with the resin discharge path  22  via the resin path  24 , and the insert mold supply path  20  is caused to communicate with the discharge path  25 . 
     The reference numeral  26  denotes a seal for attaching the stripe sub extruder  21  to the crosshead body  2 , and  27  denotes a hole for forming the sub-extruder supply path  18 . 
     A sub-extruder supply path  28  which is formed in a position opposed to the sub-extruder supply path  18  and into an L-like shape, and which serves as a path for supplying the stripe colored resin is formed in the crosshead body  2 . A switch cock  29  is disposed at the tip end of the sub-extruder supply path  28 . An insert mold supply path  30  for supplying the colored resin which has been supplied to the switch cock  29 , from the switch cock  29  to the insert mold  17  is disposed in the crosshead body  2 . A stripe sub extruder  31  is attached to the body so as to communicate with the sub-extruder supply path  28 . The stripe colored resin supplied from the stripe sub extruder  31  is passed through the sub-extruder supply path  28 , then passed through the insert mold supply path  30  via the switch cock  29  to be supplied to the insert mold  17 , and then supplied into the crosshead body  2  from the insert mold  17 . Therefore, the stripe sub extruder  21  and the stripe sub extruder  31  are disposed in symmetrical positions, i.e., positions which are separated from each other by 180°, respectively. 
     In the embodiment, the stripe sub extruder  21  and the stripe sub extruder  31  are placed in symmetrical positions (positions which are separated from each other by 180°), respectively. The positional relationship between the stripe sub extruder  21  and the stripe sub extruder  31  is not required to that in which the extruders are placed in symmetrical positions. The stripe sub extruder  21  and the stripe sub extruder  31  may be placed at positions which are separated from each other by any predetermined angle (for example, 90°, 60°, or 45°), as far as the conditions that the extruders can be placed are satisfied. 
     A resin discharge path  32  which elongates from the switch cock  29  to be opened to the outside is disposed in the crosshead body  2 . 
     The switch cock  29  has the configuration shown in FIG.  2 . As shown in FIG. 2A, the switch cock  29  has the body  33  which is formed into a columnar shape, and a resin path  34  which radiately communicates with the center of the body  33  is formed in the body  33 . As shown in FIG. 2B, the resin path  34  is formed so as to be bent at the center axis by about 90°. A discharge path  35  is formed in the body  33 . The discharge path elongates from the outer peripheral face of the body  33  corresponding to the position where the resin path  34  is formed, toward the center axis and so as not to communicate with the resin path  34 , and then advances in the axial length at the center. The discharge path is opened in an end portion of the body  33 . 
     As shown in FIG. 1, when the switch cock  29  is rotated to a position where the colored resin from the stripe sub extruder  31  is supplied, therefore, the sub-extruder supply path  28  is caused to communicate with the insert mold supply path  30  via the resin path  34 , and the discharge path  35  does not communicate with any path. 
     FIG. 1 shows a state where the colored resin from the stripe sub extruder  31  is supplied and the stripe sub extruder  21  is preparing for the next color. 
     The reference numeral  36  denotes a seal for attaching the stripe sub extruder  31  to the crosshead body  2 , and  37  denotes a hole for forming the sub-extruder supply path  28 . 
     A stripe electric wire is produced by using the thus configured crosshead  1  in the following manner. The ground color resin supplied from the ground color main extruder  9  is sent via the ground color resin supply path  8  to the tip end of the nipple  4  with passing through the gap between the inner peripheral face of the crosshead body  2  and the outer peripheral face of the nipple  4 . The surface of the strand conductor  3  is covered with the resin at a predetermined thickness by means of the tapered tip end portion of the crosshead body  2  and the tapered portion of the die  7 . When, in the formation of a stripe in the ground color resin covering the surface of the strand conductor  3 , the colored resin for forming a stripe and supplied from the stripe sub extruder  21  is to be changed to a resin of another color, the switch cock  19  is rotated to stop the supply of the colored resin supplied from the stripe sub extruder  21 , and at the same time the switch cock  29  is rotated to be opened and the stripe sub extruder  31  which has been already prepared for the next color is driven to start the supply of the resin of the next color from the stripe sub extruder  31 . 
     When the switch cock  19  is rotated to stop the supply of the colored resin from the stripe sub extruder  21 , the sub-extruder supply path  18  is caused to communicate with the resin discharge path  22  via the resin path  24 , and at the same time the insert mold supply path  20  is caused to communicate with the discharge path  25 . 
     When connections are performed as described above, the stripe sub extruder  21  is prepared for the colored resin of the next color, and the resin extrusion is further performed. Then, the colored resin remaining in the range from the stripe sub extruder  21  to the sub-extruder supply path  18  is passed through the sub-extruder supply path  18  and the resin discharge path  22  via the resin path  24  to be discharged to the outside. The stripe sub extruder  21  continues the resin supply until the color of the colored resin discharged through the resin discharge path  22  is changed from the old color to the newly set color, and stops the resin supply at the timing when the color of the colored resin discharged through the resin discharge path  22  is changed from the old color to the newly set color. As a result, a state where the sub-extruder supply path  18  is filled with the new color resin is attained. 
     On the other hand, the insert mold supply path  20  communicates with the discharge path  25  to be in a state where the path is opened to the outside. After switching to the stripe sub extruder  31 , therefore, the ground color resin is supplied from the ground color main extruder  9  to the insert mold supply path  20  which is opened in the interior of the crosshead body  2 , and the interior of the crosshead body  2  is in the pressurized state. Consequently, the ground color resin reversely flows via the insert mold  16  to cause the colored resin of the old color remaining in the insert mold supply path  20  to be discharged to the outside through the discharge path  25 . As a result, the insert mold supply path  20  is filled with the ground color resin. 
     When the supply resin is switched from the stripe sub extruder  21  to the stripe sub extruder  31 , therefore, the sub-extruder supply path  18  communicates with the insert mold supply path  20  via the resin path  24  of the switch cock  19 . Consequently, the colored resin of the new color supplied from the stripe sub extruder  21  pushes the new color resin filling the sub-extruder supply path  18 , and first pushes the ground color resin filling the insert mold supply path  20 , into the crosshead body  2 . When the ground color resin filling the insert mold supply path  20  is completely pushed out therefrom, the colored resin of the new color is pushed out. 
     FIG. 3 shows the stripe electric wire which is produced as described above. In the stripe electric wire  38 , the strand conductor  3  is covered with the ground color resin  39 , and the stripe resin  40  is formed at symmetric positions of the outer peripheral face of the ground color resin  39 . 
     FIG. 4 is a section view showing a second embodiment of the crosshead of the invention. 
     In FIG. 4, components which are identical with those of the crosshead  1  of FIG. 1 are denoted by the same reference numerals. 
     The second embodiment of FIG. 4 is different from the first embodiment of FIG. 1 in that a skin layer sub extruder for forming a skin layer is disposed in the crosshead body  2 . The skin layer is used in the following manner. The ground color is configured by a two-layer structure, and only the outer layer (skin layer) is colored. 
     An insert mold  41  which is formed into a cylindrical shape is fittingly attached to the interior of the rear end side of the crosshead body  2 . The nipple  4  is fittingly attached into the insert mold  41 . 
     A sub-extruder supply path  42  which is formed into an L-like shape and which serves as a path for supplying a colored resin for forming the skin layer is formed in the crosshead body  2 . A switch cock  43  is disposed at the tip end of the sub-extruder supply path  42 . An insert mold supply path  44  for supplying the colored resin which has been supplied to the switch cock  43 , from the switch cock  43  to the insert mold  41  is disposed in the crosshead body  2 . A skin layer sub extruder  45  is attached to the body so as to communicate with the sub-extruder supply path  42 . The skin layer colored resin supplied from the skin layer sub extruder  45  is passed through the sub-extruder supply path  42 , then passed through the insert mold supply path  44  via the switch cock  43  to be supplied to the insert mold  41 , and then supplied into the crosshead body  2  from the insert mold  41 . 
     The reference numeral  46  denotes a seal for attaching the skin layer sub extruder  45  to the crosshead body  2 , and  47  denotes a hole for forming the sub-extruder supply path  42 . 
     A resin discharge path  48  which elongates from the switch cock  43  to be opened to the outside is disposed in the crosshead body  2 . 
     The switch cock  43  is configured in the same manner as the switch cock  19  ( 26 ) shown in FIG.  2 . 
     FIG. 4 shows a state where the colored resin for forming the skin layer is supplied from the skin layer sub extruder  45 . When the switch cock  43  is set to the position shown in FIG. 4, the sub-extruder supply path  42  and the insert mold supply path  44  are caused to communicate with each other via the resin path  24 . 
     A stripe electric wire is produced by using the thus configured crosshead in the following manner. The ground color resin supplied from the ground color main extruder  9  is sent via the ground color resin supply path  8  to the tip end of the nipple  4  with passing through the gap between the inner peripheral face of the crosshead body  2  and the outer peripheral face of the nipple  4 . The surface of the strand conductor  3  is covered with an inner layer resin  49  at a predetermined thickness by means of the tapered tip end portion of the crosshead body  2  and the tapered portion of the die  7 . The colored resin for forming a skin layer  50  and supplied from the skin layer sub extruder  45  is extruded onto the inner layer resin  49 , thereby forming a covered electric wire  1  shown in FIG.  5 A. At the same time as the extrusion formation of the skin layer  50 , covering by the colored resin for forming a stripe and supplied from the stripe sub extruder  31  is conducted to form a stripe  52  as shown in FIG. 5B, thereby forming a stripe electric wire  53 . 
     FIG. 6 is a section view showing a third embodiment of the crosshead of the invention. 
     In FIG. 6, components which are identical with those of the crosshead  1  of FIG. 4 are denoted by the same reference numerals. 
     The third embodiment of FIG. 6 is different from the second embodiment of FIG. 4 in that a skin layer sub extruder for forming a skin layer is disposed in the crosshead body  2 . In the interior of the rear end side of the crosshead body  2 , an insert mold  54  is fittingly attached in a stacked manner to the inside of the insert mold  41  which is formed into a cylindrical shape, so as to constitute a double structure. The nipple  4  is fittingly attached into the insert mold  54 . 
     A sub-extruder supply path  55  which is formed into an L-like shape and which serves as a path for supplying a colored resin for forming the skin layer is formed in the crosshead body  2 . A switch cock  56  is disposed at the tip end of the sub-extruder supply path  55 . An insert mold supply path  57  for supplying the colored resin which has been supplied to the switch cock  56 , from the switch cock  56  to the insert mold  54  is disposed in the crosshead body  2 . A skin layer sub extruder  58  is attached to the body so as to communicate with the sub-extruder supply path  55 . The skin layer colored resin supplied from the skin layer sub extruder  58  is passed through the sub-extruder supply path  55 , then passed through the insert mold supply path  57  via the switch cock  56  to be supplied to the insert mold  54 , and then supplied into the crosshead body  2  from the insert mold  54 . 
     The reference numeral  59  denotes a seal for attaching the skin layer sub extruder  58  to the crosshead body  2 , and  60  denotes a hole for forming the sub-extruder supply path  55 . 
     A resin discharge path  61  which elongates from the switch cock  56  to be opened to the outside is disposed in the crosshead body  2 . 
     As shown in FIG. 6, when the switch cock  43  is rotated to a position where the skin layer colored resin supplied from the skin layer sub extruder  45  is supplied, therefore, the sub-extruder supply path  42  and the insert mold supply path  44  are caused to communicate with each other via the resin path  34 , and the discharge path  35  of the switch cock  43  does not communicate with any path. 
     FIG. 6 shows a state where the skin layer colored resin is supplied from the skin layer sub extruder  45  and the skin layer sub extruder  58  is preparing for a colored resin of the next color for the skin layer. 
     A stripe electric wire is produced by using the thus configured crosshead  1  in the following manner. The ground color resin supplied from the ground color main extruder  9  is sent via the ground color resin supply path  8  to the tip end of the nipple  4  with passing through the gap between the inner peripheral face of the crosshead body  2  and the outer peripheral face of the nipple  4 . The surface of the strand conductor  3  is covered with the resin at a predetermined thickness by means of the tapered tip end portion of the crosshead body  2  and the tapered portion of the die  7 . When, in the formation of the skin layer on the inner layer resin covering the surface of the strand conductor  3 , the colored resin for forming the skin layer and supplied from the skin layer sub extruder  58  is to be changed to a resin of another color, the switch cock  56  is rotated to stop the supply of the colored resin for forming the skin layer and supplied from the stripe sub extruder  58 , and at the same time the switch cock  42  is rotated to be opened and the skin layer sub extruder  45  which has been already prepared for the next color is driven to start the supply of the colored resin of the next color from the skin layer sub extruder  45 . 
     When the switch cock  56  is rotated to stop the supply of the skin layer colored resin from the skin layer sub extruder  58 , the sub-extruder supply path  55  is caused to communicate with the resin discharge path  61  via the resin path  24 , and at the same time the insert mold supply path  54  is caused to communicate with the discharge path  25  of the switch cock  56 . 
     When the skin layer sub extruder  58  is prepared for the colored resin of the next color and the resin extrusion is further performed, the skin layer colored resin remaining in the range from the skin layer sub extruder  58  to the sub-extruder supply path  55  is passed through the sub-extruder supply path  55  and the resin discharge path  61  via the resin path  24  of the switch cock  56  to be discharged to the outside. The skin layer sub extruder  58  continues the resin supply until the color of the colored resin discharged through the resin discharge path  61  is changed from the old color to the newly set color, and stops the resin supply through the sub-extruder supply path  55  at the timing when the color of the colored resin discharged through the resin discharge path  61  is changed from the old color to the newly set color. As a result, a state where the skin layer sub extruder  58  is filled with the new color resin is attained. 
     On the other hand, the insert mold supply path  57  communicates with the discharge path  25  of the switch cock  56  to be in a state where the path is opened to the outside. After switching to the skin layer sub extruder  45 , therefore, the ground color resin is supplied from the ground color main extruder  9  to the insert mold supply path  57  which is opened in the interior of the crosshead body  2 , and the interior of the crosshead body  2  is in the pressurized state. Consequently, the ground color resin reversely flows via the insert mold  64  to cause the skin layer colored resin of the old color remaining in the insert mold supply path  57  to be discharged to the outside through the discharge path  25  of the switch cock  56 . As a result, the insert mold supply path  57  is filled with the ground color resin. 
     When the supply resin for the skin layer is switched from the skin layer sub extruder  45  to the skin layer sub extruder  58 , therefore, the sub-extruder supply path  57  communicates with the insert mold supply path  55  via the resin path  24  of the switch cock  56 . Consequently, the skin layer colored resin of the new color supplied from the skin layer sub extruder  58  pushes the new color resin filling the sub-extruder supply path  55 , and first pushes the ground color resin filling the insert mold supply path  55 , into the crosshead body  2 . When the ground color resin filling the insert mold supply path  55  is completely pushed out therefrom, the skin color colored resin of the new color is pushed out. 
     In the crosshead  1 , the switch cocks  43  and  56  are operated in the following manner. When the colored resins are to be supplied from the skin layer sub extruders  45  and  58  to the insert molds  41  and  54 , the sub-extruder supply paths  42  and  55  through which the colored resins from the skin layer sub extruders  45  and  58  are supplied are caused to communicate with the insert mold supply paths  44  and  57  through which the colored resins are supplied to the insert molds  41  and  54 , respectively. When the supplies of the colored resins from the skin layer sub extruders  45  and  58  are to be stopped, the sub-extruder supply paths  42  and  55  through which the colored resins from the skin layer sub extruders  45  and  58  are supplied are caused to communicate with the resin discharge paths  48  and  61 , and the insert mold supply paths  44  and  57  are caused to communicate with the resin discharge paths  48  and  61 , respectively. 
     According to this configuration, during an operation of changing the color of the skin layer colored resin, a mixed color area can be prevented from being produced in a process of changing from the old color to the next color, whereby a color change loss (color failure of an electric wire) can be prevented from occurring. 
     In the crosshead  1 , when the supplies of the colored resins from the skin layer sub extruders  45  and  58  are stopped, the resins remaining in the sub-extruder supply paths  42  and  55  elongating from the skin layer sub extruders  45  and  58  to the switch cocks  43  and  56  are discharged to the outside through the resin discharge paths  48  and  61 , by extruding the colored resins of the new color supplied from the skin layer sub extruders  45  and  58 , and the resins remaining in the insert mold supply paths  44  and  57  elongating from the switch cocks  43  and  56  to the insert molds  41  and  54  are discharged by the pressure of the ground color resin extruded from the ground color main extruder  9  into the crosshead body  2 , to the outside through the resin discharge paths  48  and  61  of the switch cocks  43  and  56 . 
     According to this configuration, during an operation of changing the color of the skin layer colored resin, a mixed color area can be prevented from being produced in a process of changing from the old color to the next color, whereby a color change loss (color failure of an electric wire) can be prevented from occurring. 
     As described above, when the color of the skin layer formed on the ground color resin is to be changed, the switch cock  43  and the switch cock  56  are switched so that the operations of the skin layer sub extruder  45  and the skin layer sub extruder  58  are switched, whereby the changing can be easily realized in the same manner as the case where the stripe sub extruder  21  and the stripe sub extruder  31  are switched. 
     According to the first aspect of the invention, a mixed color area can be prevented from being produced in a process of changing from the old color to the next color, and a color change loss (color failure of an electric wire) can be prevented from occurring. 
     According to the second aspect of the invention, the resin pressure in the crosshead can be uniformalized, and a stripe electric wire in which the stripe is positioned in balance can be produced. 
     According to the third aspect of the invention, an inner layer resin can be thinly covered with a resin of a preferred color so that the ground color of the covered electric wire can be freely changed without being affected by the color of the inner layer resin. 
     According to the fourth aspect of the invention, during an operation of changing the color of the stripe colored resin, it is possible to prevent a mixed color area from being produced in a process of changing from the old color to the next color, whereby a color change loss (color failure of an electric wire) can be prevented from occurring. 
     According to the fifth aspect of the invention, during an operation of changing the color of the colored resin for the skin layer, the colored resin of the old color which remains in the range from the skin layer sub extruder to the switch cock can be surely discharged to the outside, and hence it is possible to prevent a mixed color area from being produced in a process of changing from the old color to the next color, whereby a color change loss (color failure of an electric wire) can be prevented from occurring. 
     According to the sixth aspect of the invention, during an operation of changing the color of the stripe colored resin, it is possible to prevent a mixed color area from being produced in a process of changing from the old color to the next color, whereby a color change loss (color failure of an electric wire) can be prevented from occurring. 
     According to the seventh aspect of the invention, during an operation of changing the color of the stripe colored resin, it is possible to prevent a mixed color area from being produced in a process of changing from the old color to the next color, whereby a color change loss (color failure of an electric wire) can be prevented from occurring. 
     According to the eighth aspect of the invention, during an operation of changing the color of the stripe colored resin, it is possible to prevent a mixed color area from being produced in a process of changing from the old color to the next color, whereby a color change loss (color failure of an electric wire) can be prevented from occurring.