Resin pipe and method for producing resin pipe

Abstract

To provide a resin pipe from which an index is readily viewable.SOLUTION: A resin pipe 1 includes: a pipe body 11; a belt-like part 13 formed to extend across the whole length of the pipe body 11 at the outer peripheral surface of the pipe body 11; and an index 15 provided on either an exposed surface 11a, which is not covered by the belt-like part 13, of the outer peripheral surface of the pipe body 11 or the outside surface of the belt-like part 13, so as to extend across the whole length of the pipe body 11.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a plastic pipe and a method for manufacturing the same. [Background technology]

[0002] Conventionally, the use of resin pipes (pipe bodies) made of olefin-based resins such as polyethylene resins has been considered for transporting fluids such as water (see, for example, Patent Document 1). By making the resin pipes from olefin-based resins, corrosion of the resin pipes can be suppressed.

[0003] In order to distinguish between plastic pipes, the plastic pipes are colored light blue, black, etc. As the number of types of plastic pipes increases, it becomes difficult to distinguish between the plastic pipes by color alone. For this reason, the inventors are considering a plastic pipe that includes a pipe body and a band-like portion formed on the outer peripheral surface of the pipe body so as to extend over the entire length of the pipe body. The band-like portion is formed on a portion of the pipe body in the circumferential direction. By making the color of the pipe body and the color of the band-like portion different from each other, it becomes possible to distinguish between the plastic pipes by the color of the pipe body and the color of the band-like portion, even if the number of types of plastic pipes increases. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2007-268628 A Summary of the Invention [Problem to be solved by the invention]

[0005] A stencil (indicator) is provided on a plastic pipe to indicate the product name, model number, etc. of the plastic pipe. The stencil is provided so as to extend over the entire length of the plastic pipe so that the stencil can be easily seen at any position in the axial direction of the plastic pipe.

[0006] However, if the stencil is provided across both the exposed surface of the outer circumferential surface of the pipe body that is not covered by the band-shaped portion, and the outer surface of the band-shaped portion, the stencil becomes difficult to see.

[0007] The present invention has been made in consideration of such problems, and has an object to provide a resin pipe with an easily visible indicator. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention proposes the following means. The plastic pipe of the present invention is characterized in comprising a pipe body, a band-shaped portion formed on the outer peripheral surface of the pipe body so as to extend along the entire length of the pipe body, and an indicator provided on only one of an exposed surface of the outer peripheral surface of the pipe body that is not covered by the band-shaped portion or an outer surface of the band-shaped portion so as to extend along the entire length of the pipe body. According to this invention, the indicator is provided on only one of the exposed surface of the pipe body and the outer surface of the band-shaped portion, so that the indicator is not provided across both the exposed surface of the pipe body and the outer surface of the band-shaped portion, making the indicator easy to see.

[0009] In the above-described resin pipe, the indicator may be provided on either the exposed surface of the pipe body or the outer surface of the band-shaped portion, whichever has a longer circumferential length of the pipe body. According to this invention, by providing the index on the surface having a long circumferential length, the index can be made easier to see on a wide surface.

[0010] In the above resin pipe, a lead angle that is an angle that the band-shaped portion makes with respect to a plane perpendicular to the axis of the pipe body may be 85° or more. According to this invention, it is possible to prevent the band-shaped portion from being inclined with respect to the axis of the pipe body, and to prevent deterioration in the appearance of the band-shaped portion extending over the entire length of the pipe body.

[0011] In addition, in the above-mentioned resin pipe, the color difference between the exposed surface of the pipe body or the outer surface of the band-shaped portion on which the indicator is provided, and the color of each of the indicators may be 1 or more in the L*a*b* color system defined in JIS Z8781-4:2013. According to this invention, the exposed surface of the pipe body or the outer surface of the band-shaped portion on which the indicator is provided and the indicator can be easily visually recognized. Effect of the Invention

[0012] According to the resin pipe of the present invention, the indicator can be made easily visible. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a perspective view of a resin pipe according to an embodiment of the present invention. [Diagram 2] FIG. [Diagram 3] FIG. 11 is a side view of a resin pipe in a modified example of an embodiment of the present invention. [Figure 4] FIG. 2 is a diagram showing a schematic diagram of a manufacturing apparatus for the resin pipe. [Diagram 5] FIG. [Figure 6] FIG. 11 is a side view of a resin pipe in a modified example of an embodiment of the present invention. [Figure 7] 13 is a side view illustrating a method for measuring the width of the band-shaped portion of the resin pipe. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, one embodiment of a plastic pipe according to the present invention will be described with reference to Fig. 1 to Fig. 7. As shown in Fig. 1 and Fig. 2, a plastic pipe 1 of this embodiment includes a pipe body 11, four band-like portions 13, and a stencil (indicator) 15. In the following figures, in order to distinguish the pipe body 11 from the band-like portions 13, the band-like portions 13 are shown hatched with dots. The pipe body 11 is formed into a tubular shape using polyethylene resin, which is an olefin resin. The polyethylene resin may be high-density polyethylene resin, medium-density polyethylene resin, etc. The olefin resin may be polypropylene resin, polybutene resin, etc., other than polyethylene resin. The olefin resin may contain inorganic fibers such as glass fiber, carbon fiber, and wollastonite. Furthermore, the pipe body 11 may be a multi-layer pipe in which an olefin resin layer is laminated with other layers, such as a layer containing inorganic fibers or a layer containing an oxygen barrier material. When the pipe body 11 is a multi-layer pipe, a band-shaped portion 13 is formed on the outermost layer for visibility. In order to connect with an electric fusion joint, it is preferable that the olefin resin layer is located outside the other layers, and in this case, the band-shaped portion 13 is formed on the olefin resin layer that is located outside the other layers. In the following description, the circumferential direction of the pipe body 11 will be simply referred to as the circumferential direction, and the radial direction of the pipe body 11 will be simply referred to as the radial direction.

[0015] The band-shaped portions 13 are formed on the outer peripheral surface of the pipe body 11. The band-shaped portions 13 extend over the entire length of the pipe body 11. In this example, each band-shaped portion 13 is disposed along the axis C of the pipe body 11. The band-shaped portions 13 are disposed around the axis C at equal angular intervals. The thickness of each band-shaped portion 13 (the length in the radial direction of the pipe body 11) is appropriately determined according to the thickness of the pipe body 11, and is preferably 0.02 mm to 2.0 mm, more preferably 0.05 mm to 1.0 mm, and even more preferably 0.1 mm to 0.5 mm. By setting the thickness of each band-shaped portion 13 within this range, the thickness is not too large, and it is easy to confirm that the band-shaped portion 13 has disappeared and been cut by the surface cutting work of the resin pipe 1 performed when connecting with the electric fusion joint. In addition, the thickness is not too small, and the color of the pipe body 11 cannot be seen from the outside through the band-shaped portion 13, and the ability to distinguish the band-shaped portion 13 can be exhibited. The circumferential length of the band-shaped portion 13 is constant regardless of the position in the axis C direction of the pipe main body 11.

[0016] The radial width of the band-shaped portion 13 is appropriately determined according to the outer diameter of the tube body 11, and is set to 4 mm or more and 50 mm or less, and preferably 8 mm or more and 40 mm or less. The ratio of the width of the band-shaped portion 13 to the outer diameter of the tube body 11 is set to 5% or more and 30% or less, and preferably 7% or more and 25% or less. The ratio of the width of the band-shaped portion 13 to the outer diameter of the tube body 11 referred to here means 100 times the value obtained by dividing the width of the band-shaped portion 13 by the outer diameter of the tube body 11. By setting the width of the band-shaped portion 13 within this range, the width is not too narrow, so that the band-shaped portion 13 can be distinguished from any direction. In addition, since the width is not too wide, an increase in manufacturing costs can be suppressed.

[0017] The radial width of the band-shaped portion 13 can be measured using a known vernier caliper 71, for example, as shown in Fig. 7. A slider 73 is moved along a body 72 of the caliper 71, and the outer measurement surfaces 75a, 76a of a pair of jaws 75, 76 are aligned with the first boundary lines 13a of the band-shaped portion 13, respectively, when the band-shaped portion 13 to be measured is in the state shown in Fig. 7 as viewed from the radial outside. At this time, it is preferable that the outer measurement surfaces 75a, 76a are arranged so as to be aligned along the axis C of the pipe main body 11. The value or scale displayed on the display 77 of the caliper 71 is read to measure the width of the band-like portion 13. The width of the band-like portion 13 is determined by this measurement method.

[0018] 1 and 2, an exposed surface 11a of the outer circumferential surface of the pipe body 11 that is not covered by the band-shaped portion 13 is flush with the outer surface of the band-shaped portion 13. The outer surface of the band-shaped portion 13 is the surface of the band-shaped portion 13 that is exposed to the outside. In this example, the circumferential length of the exposed surface 11a of the pipe body 11 is longer than the circumferential length of the outer surface of the band-shaped portion 13. However, in the circumferential direction, the length of the exposed surface 11a of the pipe body 11 and the length of the outer surface of the band-shaped portion 13 may be equal to each other or may be different from each other. The four band-shaped portions 13 do not have to be arranged at equal angles around the axis C. The number of band-shaped portions 13 provided in the resin pipe 1 is not particularly limited, and may be one to three, or may be five or more.

[0019] The band-like portion 13 is preferably formed from the same material as the pipe body 11 . The color of the tube body 11 is different from the color of the belt-like portion 13. The color difference (ΔE) (hereinafter simply referred to as color difference) between the colors of the tube body 11 and the belt-like portion 13 in the L*a*b* color system defined in JIS Z8781-4:2013 is 1 or more. This color difference is preferably 5 or more, and more preferably 10 or more. For example, the tube body 11 is blue, and the belt-like portion 13 is red.

[0020] The color difference can be measured using a spectrophotometer (handy spectrophotometer "NF333" manufactured by Nippon Denshoku Industries Co., Ltd.). It is preferable to measure the color difference in a darkened environment such as a darkroom. Here, the color difference (ΔE) is calculated by the following formula (1). ΔE=√((L1-L2) 2 +(a1-a2) 2 +(b1-b2) 2 ) (1) In formula (1), L1, a1, and b1 respectively represent the lightness L, chromaticity a in the red direction, and chromaticity b in the yellow direction of the belt-shaped portion 13, and L2, a2, and b2 respectively represent the lightness L, chromaticity a in the red direction, and chromaticity b in the yellow direction of the tube body 11.

[0021] The stencil 15 is provided only on the exposed surface 11a of the pipe body 11 so as to extend over the entire length of the pipe body 11. The stencil 15 is arranged along the axis C of the pipe body 11. The stencil 15 indicates, for example, the product name, model number, etc. of the resin pipe 1. The stencil 15 is formed by printing or the like using ink formed from a material similar to that of the pipe body 11. For example, the stencil 15 is black, and the black stencil 15 is printed on the blue exposed surface 11a. Since the stencil 15 is not provided on the red belt portion 13 but is provided only on the blue exposed surface 11a, the stencil 15 is easy to see. The color difference between the exposed surface 11a of the pipe body 11 on which the stencil 15 is provided and the color of the stencil 15 is preferably 1 or more. This color difference is preferably 5 or more, and more preferably 10 or more.

[0022] 3, the band-shaped portion 13 may be formed in a spiral shape on the outer circumferential surface of the pipe body 11, and the lead angle (twist angle) θ, which is the angle that the band-shaped portion 13 makes with respect to a plane P perpendicular to the axis C of the pipe body 11, may be 85° or more and less than 90°. Even in this case, the stencil 15 is provided only on the exposed surface 11a of the pipe body 11 so as to extend over the entire length of the pipe body 11. When the band-shaped portion 13 is disposed along the axis C of the pipe body 11, the lead angle θ is approximately 90°.

[0023] For example, a case will be described in which the specifications of the pipe body 11, the band-like portion 13, and the stencil 15 are as follows: The outer diameter of the pipe body 11 is 216.3 mm (nominal diameter 200A), and the length is 5 m. The width (circumferential length) of the band-like portion 13 is 10 mm, and there are four portions. The width of the stencil 15 is 10 mm. In this case, the distance between the band-shaped portions 13 in the circumferential direction is about 160 mm. If the lead angle θ is less than about 88.3°, the stencil 15 will be provided not only on the exposed surface 11a of the pipe body 11 but also on the outer surface of the band-shaped portion 13, as shown by the two-dot chain line in Figure 3, making the stencil 15 difficult to see.

[0024] Next, a manufacturing apparatus for manufacturing the resin pipe 1 configured as above will be described. As shown in Fig. 4, the manufacturing apparatus 51 includes a co-extrusion molding machine 52, a cooling section 53, a printing machine 55, a take-up machine 54, and a cutting machine 56. In Fig. 4, a portion of a molding die 52a (described later) that forms a second flow path 52c is indicated by a two-dot chain line so that the inside can be easily seen. The co-extrusion molding machine 52, cooling section 53, printing machine 55, take-up machine 54, and cutting machine 56 are arranged in this order from the upstream side to the downstream side along which the resin pipe 1 (the continuous resin pipe 1A described later) is transported.

[0025] A first flow path 52b and a second flow path 52c are formed in a molding die 52a of the co-extrusion molding machine 52. In this embodiment, four second flow paths 52c are formed in the molding die 52a. The four second flow paths 52c merge with the first flow path 52b from the side of the first flow path 52b. A resin material for forming the pipe main body 11 is supplied in a molten state to the first flow path 52b. A resin material for forming the band-shaped portion 13 is supplied in a molten state to the second flow path 52c. The continuous resin pipe 1A is extruded downstream from the molding die 52a. The continuous resin pipe 1A is formed by continuously connecting the resin pipes 1 in the axial direction C. 5 shows a central axis C1 of a molding die 52a of a co-extrusion molding machine 52 as viewed from the downstream side toward the upstream side. In order to focus on the position of the central axis C1, the molding die 52a is shown by a two-dot chain line.

[0026] The cooling section 53 is composed of a water tank, etc. The cooling section 53 cools the continuous resin pipe 1A molded by the co-extrusion molding machine 52 using water, etc.

[0027] 5, the pull-off machine 54 has a plurality of endless tracks 58. The plurality of endless tracks 58 are arranged at intervals around a predetermined central axis C2. In this example, the pull-off machine 54 has four endless tracks 58. Each endless track 58 has a plurality of holding members 59. A recess 59a is formed in the center of the width direction (circumferential direction) of the holding members 59. When a drive motor (not shown) is rotated, the portion of the endless track 58 facing the central axis C2 moves downstream or upstream.

[0028] The endless track 58 is supported by support members 61 and the like via a known distance adjustment mechanism 60. Each support member 61 is fixed to a frame or the like (not shown). For example, the distance adjustment mechanism 60 is provided with a lever (not shown). When the lever is rotated, the endless track 58 approaches or moves away from the support member 61, adjusting the distance between the endless track 58 and the central axis C2. The distance adjustment mechanism 60 adjusts the position of the endless track 58 in a first direction D1 toward and away from the central axis C2.

[0029] The multiple endless tracks 58 hold the continuous resin pipe 1A on the central axis C2. At this time, a part of the outer circumferential surface of the continuous resin pipe 1A fits into the recess 59a of each holding member 59 of the endless tracks 58. This allows the multiple endless tracks 58 to securely hold the continuous resin pipe 1A. The axis C of the continuous resin pipe 1A held by the multiple endless tracks 58 is positioned on the central axis C2. When each of the endless tracks 58 rotates in a predetermined direction, the continuous resin pipe 1A is pulled downstream.

[0030] The pull-up machine 54 may be provided with a position adjustment mechanism that adjusts the position of the endless tracks 58 in the second direction D2, which is the tangent direction of a circle centered on the central axis C2. With this configuration, when the centers of the multiple endless tracks 58 deviate from the central axis C2, the position adjustment mechanism and distance adjustment mechanism 60 can be used to adjust the centers of the multiple endless tracks 58 so that they coincide with the central axis C2.

[0031] The printer 55 prints a stencil 15 on the exposed surface 11a of the continuous resin pipe 1A. The cutter 56 cuts the continuous resin pipe 1A to a predetermined length to obtain the resin pipe 1. The resin pipe 1 is manufactured by the manufacturing apparatus 51 described above.

[0032] It is preferable that the resin pipe has the band-shaped portion 13 disposed along the axis C of the pipe body 11 and the lead angle θ of the band-shaped portion 13 is approximately 90°. Possible causes of the band-shaped portion 13 being twisted in a spiral shape and the lead angle θ being smaller than 90° include the following factors (1) and (2). (1) The central axis C1 of the molding die 52a of the co-extrusion molding machine 52 and the central axis C2 of the take-up machine 54 are not arranged on the same straight line. (2) There is a difference in the contact force between each of the endless tracks 58 and the continuous plastic pipe 1A due to a difference in the distance between each of the endless tracks 58 and the central axis C2, etc.

[0033] Regarding item (1), for example, a method of measuring using a laser beam and adjusting the positions so that both central axes C1, C2 are aligned on the same line may be used. The above-mentioned distance adjustment mechanism 60 and position adjustment mechanism may be used to move the central axes C2 of the multiple endless tracks 58, and adjust both central axes C1, C2 to be aligned on the same line. For example, it is preferable that the deviation between the central axes C1, C2 is within 10 mm along the horizontal plane and within 10 mm in the vertical direction. Regarding item (2), one solution is to use a lever to adjust the distance between each endless track 58 and the central axis C2, thereby adjusting the contact force. By suppressing twisting of the band-shaped portion 13 in this manner, the residual stress in the resin pipe can be reduced.

[0034] As described above, according to the plastic pipe 1 of this embodiment, the stencil 15 is provided only on the exposed surface 11a of the pipe body 11, so that the stencil 15 is not provided across both the exposed surface 11a of the pipe body 11 and the outer surface of the band-shaped portion 13, which are different colors, making the stencil 15 easy to see. The stencil 15 is provided on the exposed surface 11a having a longer circumferential length out of the exposed surface 11a of the pipe body 11 and the outer surface of the band-shaped portion 13. By providing the stencil 15 on the exposed surface 11a having a longer circumferential length, the stencil 15 can be made easier to see on the wide exposed surface 11a.

[0035] Since the lead angle θ of the band-shaped portion 13 is 85° or more, the band-shaped portion 13 is prevented from tilting with respect to the axis C of the pipe body 11, thereby preventing the appearance of the band-shaped portion 13 extending over the entire length of the pipe body 11 from deteriorating. Since the color difference between the colors of the exposed surface 11a of the pipe body 11 and the stencil 15 is 1 or more, the exposed surface 11a of the pipe body 11 and the stencil 15 can be easily visually recognized.

[0036] Although one embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and changes, combinations, deletions, etc. of the configuration are also included within the scope that does not deviate from the gist of the present invention. For example, in the above embodiment, as in the resin pipe 3 shown in Fig. 6, the stencil 15 may be provided only on the outer surface of one band-shaped portion 13 so as to extend over the entire length of the pipe body 11. In this case, it is preferable that the color difference between the color of the stencil 15 and the outer surface of the band-shaped portion 13 on which the stencil 15 is provided is 1 or more. It is more preferable that this color difference is 30 or more.

[0037] In the manufacturing apparatus 51, the printing machine 55 may be disposed between the take-up machine 54 and the cutting machine 56. By configuring the manufacturing apparatus 51 in this manner, twisting of the band-shaped portion 13 with respect to the axis C of the pipe main body 11 can be suppressed. The lead angle of the stencil 15 is preferably 85° or more, similar to the lead angle θ of the band-shaped portion 13. In addition to the stencil 15, the indicator may be letters or symbols such as the name of the manufacturer of the plastic pipe or a warning.

[0038] In the above embodiment, the band-shaped portion 13 is integrally formed with the pipe body 11 by co-extrusion molding, but the method of forming the band-shaped portion 13 is not limited to this. For example, the band-shaped portion 13 may be formed by printing an ink containing a colorant on the outer circumferential surface of the pipe body 11 after molding the pipe body 11. In this case, it is preferable to print the stencil 15 simultaneously with or after printing the band-shaped portion 13. By manufacturing the resin pipe 1 in this manner, it is possible to prevent the band-shaped portion 13 from being printed on the stencil 15 and concealing the stencil 15. [Explanation of symbols]

[0039] 1,2,3 Plastic pipe 11 Tube body 11a Exposed surface 13 Belt 15 Stencil (Index) C axis P plane θ Lead angle

Claims

1. A pipe body to be connected to the electric fusion joint; a band-shaped portion formed on an outer peripheral surface of the pipe body so as to extend over the entire length of the pipe body; an indicator provided on only one of an exposed surface of the outer circumferential surface of the pipe body that is not covered by the band-shaped portion and an outer surface of the band-shaped portion so as to extend over the entire length of the pipe body; A resin pipe comprising:

2. The resin pipe according to claim 1 , wherein the indicator is provided on one of the exposed surface of the pipe body and the outer surface of the band-shaped portion, whichever has a longer circumferential length of the pipe body.

3. 3. The resin pipe according to claim 1, wherein a color difference in the L*a*b* color system defined in JIS Z8781-4:2013 between the exposed surface of the pipe body or the outer surface of the band-shaped portion on which the indicator is provided, and the color of each of the indicators is 1 or more.

4. A method for manufacturing a resin pipe comprising: a pipe body; a band-shaped portion formed on an outer peripheral surface of the pipe body so as to extend over the entire length of the pipe body; and an indicator provided on only one of an exposed surface of the outer peripheral surface of the pipe body that is not covered by the band-shaped portion and an outer surface of the band-shaped portion so as to extend over the entire length of the pipe body, forming a continuous resin pipe using an extrusion molding machine; cooling the continuous resin pipe; a step of taking up the continuous resin pipe by a take-up machine; printing the indicia; and cutting the continuous resin pipe to a predetermined length to manufacture the resin pipe. A method for manufacturing a resin pipe, comprising a step of printing the indicator after the cooling step.

5. The method for manufacturing a resin pipe according to claim 4, further comprising a step of printing the indicator after the step of taking out the resin pipe.

6. The method for producing a resin pipe according to claim 4 or 5, wherein the band-shaped portion is molded together with the pipe body in the molding step.

7. The method for producing a resin pipe according to claim 4 or 5, further comprising the step of forming the band-shaped portion on the outer circumferential surface of the pipe body by printing.

8. The method for manufacturing a resin pipe according to claim 7 , further comprising a step of forming the band-shaped portion by printing, the step being performed before the step of printing the indicator or simultaneously with the step of printing the indicator.

9. The take-off machine used in the take-off step is provided with a mechanism for adjusting a position and a distance, The method for producing a resin pipe according to claim 4 or 8, further comprising aligning a central axis of a metal mold used in the molding step with a central axis of the take-off machine.

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