Manufacturing apparatus for a tube body

Abstract

To provide a pipe body manufacturing device that enables stable molding by preventing molding defects due to drawdown by quickly attaching a resin extruded from a resin discharge port to an inner wall of a mold block.SOLUTION: A pipe body manufacturing device includes: a resin discharge part (resin outlet 47) that discharges a cylindrical molten resin into mold blocks 36, 38; a shape adjusting part (shape adjusting attachment 50) that expands a diameter of the cylindrical molten resin discharged from the resin discharge part; and a pressure-retaining part (pressure-retaining jig 60) that can retain an internal pressure of the cylindrical molten resin discharged from the resin discharge part.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a manufacturing apparatus for a tubular body such as a resin liner of a high-pressure tank (also referred to as a pressure vessel), and more particularly to a manufacturing apparatus for forming a tubular body by extrusion corrugated tube forming.

Background Art

[0002] As a method for manufacturing this type of tubular body, for example, Patent Document 1 describes a method in which a plurality of mold blocks connected in a belt shape surround a mandrel, and a resin material is extruded into a cavity space formed between the mold block and the mandrel, and the mold block is sequentially fed out to form a tubular body (synthetic resin tube).

[0003] Further, Patent Document 2 describes a method of supplying a corrugated protective layer having ridges and valleys on the outer peripheral surface to an extrusion molding section, and in the extrusion molding section, spreading the tubular protective layer in a state where the protective layer is in contact with the molten resin constituting the outer covering to extrude the outer covering.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In such an extrusion corrugated tube forming process, the cylindrical molten resin (hereinafter sometimes referred to as the molten resin tube) extruded from the resin discharge port sags due to the influence of gravity (also called drawdown). In particular, when the diameter expansion ratio is about several times, the distance between the molten resin tube extruded from the resin discharge port and the mold block becomes longer, and the upper part of the molten resin tube is difficult to contact (stick) with the mold, and it is difficult to shape along the mold. That is, as the diameter of the molded product increases, it sags due to gravity before the molded product hardens, and there is a risk of molding defects.

[0006] In view of the above circumstances, an object of the present invention is to provide a manufacturing apparatus for a tubular body that can prevent molding defects due to drawdown and enable stable molding by quickly attaching the resin extruded from the resin discharge port to the inner wall of the mold block.

Means for Solving the Problems

[0007] To achieve the above object, a manufacturing apparatus for a tubular body of the present invention is a manufacturing apparatus for a tubular body formed in a cylindrical or tubular shape, comprising a mold block, a resin discharge part that can change the relative position in the axial direction with respect to the mold block while discharging a cylindrical molten resin into the mold block, a shape adjusting part that expands the diameter of the cylindrical molten resin discharged from the resin discharge part, and a pressure holding part that can hold the internal pressure of the cylindrical molten resin discharged from the resin discharge part.

[0008] In a preferred embodiment, the shape adjusting part is configured to include a gas discharge path that discharges gas in a direction inclined radially outward inside the cylindrical molten resin discharged from the resin discharge part.

[0009] In another preferred embodiment, the gas discharge path includes a central supply path extending in the axial direction and a plurality of inclined supply paths that branch off from the central supply path in a direction inclined radially outward and open into the inside of the cylindrical molten resin discharged from the resin discharge part.

[0010] In another preferred embodiment, the shape adjusting part is configured to include a guide surface that guides the cylindrical molten resin discharged from the resin discharge part radially outward as it flows downstream.

[0011] In another preferred embodiment, the shape adjusting part is provided at the discharge side end of the resin discharge part.

[0012] In another preferred embodiment, the pressure holding part is composed of a pressure holding jig that extends axially within the mold block.

[0013] In another preferred embodiment, the pressure holding part is connected to and held by the shape adjusting part.

[0014] In another preferred embodiment, the shape adjusting part is configured to include a gas discharge path that discharges gas in a direction inclined radially outward inside the cylindrical molten resin discharged from the resin discharge part, and the pressure holding part is composed of a pressure holding jig that extends axially within the mold block and passes through the inside of the smallest diameter portion of the cylindrical resin pressed against the mold block by the pressure of the gas.

[0015] In another preferred embodiment, the clearance area between the small diameter portion and the pressure holding jig passing through the inside of the small diameter portion is equal to or less than the minimum flow path cross-sectional area of the gas discharge path.

Advantages of the Invention

[0016] According to the present invention, when forming a tubular body by extrusion corrugated tube molding, since the pressure holding part imparts internal pressure to the cylindrical molten resin while shaping it, the resin extruded from the resin discharge part is quickly attached to the inner wall of the mold block, thereby preventing molding defects due to drawdown and enabling stable molding.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0019] First, a resin liner (hereinafter simply referred to as a liner) 10 of a high-pressure tank to be manufactured in the present embodiment will be described, and then a manufacturing apparatus 30 for the liner 10 will be described. Thereafter, a manufacturing method for the liner 10 will be described. Note that an arrow CL appropriately shown in FIGS. 1 to 5 indicates the central axis of the liner 10. In addition, when simply described as the axial direction, it indicates the direction along the central axis CL, and when described as the radial direction, it indicates the direction along the radial direction of the liner 10.

[0020] (Configuration of Liner) In FIGS. 1 and 2, cross-sectional views of the liner 10 during molding are shown. Since the completed liner 10 also has the same configuration in principle, the configuration of the liner 10 will be described with reference to these figures.

[0021] The liner 10 is configured as a tubular body having an overall cylindrical or annular shape. The liner 10 includes a substantially cylindrical body portion 12, dome portions 14 formed at both axial ends of the body portion 12 and gradually narrowing (reducing in diameter) toward the opposite side (axially outward) of the body portion 12, and a substantially cylindrical neck portion 16 formed at the axial end of the dome portion 14 on the side opposite to the body portion 12 and having a smaller diameter than the body portion 12. In the present embodiment, the neck portion 16 is the thinnest portion having the smallest diameter in the liner 10.

[0022] The liner 10 is, as an example, the container body of a high-pressure tank used as a hydrogen tank mounted on a fuel cell vehicle, and constitutes the innermost layer of the high-pressure tank. The liner 10 is formed of a resin material (such as nylon or polyethylene), and a reinforcing layer (for example, a fiber-reinforced resin layer) (not shown) is formed on its outer peripheral surface to form the high-pressure tank.

[0023] The neck portion 16 of the liner 10 has an axially open end on the side opposite to the dome portion 14 (not shown), and a plug (not shown) is configured to be fitted from this open end. The high-pressure tank is sealed by a seal ring (not shown) that forms part of the plug being in close contact with the inner surface 16A of the neck portion 16.

[0024] (Configuration of the manufacturing apparatus for the liner) Next, with reference to FIGS. 1 to 5, the manufacturing apparatus 30 for the liner 10 of the present embodiment will be described.

[0025] FIG. 1 schematically shows the overall configuration of the manufacturing apparatus 30 for the liner 10 according to the present embodiment. As shown in this figure, the manufacturing apparatus 30 for the liner 10 includes a first outer mold part 32 and a second outer mold part 34. In this figure, the lower half of the first outer mold part 32 and the second outer mold part 34 that have been cut in the horizontal direction are shown, but the nozzle 40 (outer die 44), the portion immediately after the discharge of the molten resin tube 48, and the pressure holding jig 60, which will be described later, are shown in an uncut state. The first outer mold part 32 is a caterpillar-shaped mold in which a plurality of mold blocks 36 are connected and circulate in the first direction R1 at a constant speed. Similarly, the second outer mold part 34 is a caterpillar-shaped mold in which a plurality of mold blocks 38 are connected and circulate in the second direction R2, which is the opposite direction of the first direction R1, at the same speed as the first outer mold part 32.

[0026] The first outer mold part 32 and the second outer mold part 34 are configured to travel in a straight line in the same direction in a straight running area P where a part of each running path is straight, that is, in a state where a plurality of mold blocks 36 and a plurality of mold blocks 38 are in contact with each other, namely, in a state where the mold is closed. That is, the first outer mold part 32 and the second outer mold part 34 merge at the upstream start end (hereinafter, appropriately referred to as the "start end") in the running direction of the straight running area P, and the first outer mold part 32 and the second outer mold part 34 branch at the downstream end (hereinafter, appropriately referred to as the "end") in the running direction of the straight running area P. Note that FIG. 1 schematically shows the overall configuration of the manufacturing apparatus 30 and does not show the individual shapes of the plurality of mold blocks 36 and the plurality of mold blocks 38 in detail. Therefore, the configuration of the plurality of mold blocks 36 and the plurality of mold blocks 38 will be described below with reference to FIG. 2.

[0027] As shown in FIG. 2, the plurality of mold blocks 36 of the first outer mold part 32 and the plurality of mold blocks 38 of the second outer mold part 34 are configured to mold the liner 10 from the outside. In the longitudinal sectional view of FIG. 2, the side of the plurality of mold blocks 36 constituting the first outer mold part 32 is shown, but the plurality of mold blocks 38 constituting the second outer mold part 34 are the same as the plurality of mold blocks 36 constituting the first outer mold part 32. Specifically, the plurality of mold blocks 36 (38) include a cavity having a substantially semi-circular cross section, and include a body forming part 22 for forming the body part 12 of the liner 10, a dome part forming part 24 for forming the dome part 14, and a neck part forming part 26 for forming the neck part 16. The body forming part 22 is composed of a relatively large-diameter semi-cylindrical surface that is long in the axial direction. The dome part forming part 24 is formed at the axial end of the body forming part 22 and is composed of a tapered surface that gradually decreases in diameter toward the side opposite to the body forming part 22. The neck part forming part 26 is formed at the axial end of the dome part forming part 24 and is composed of a relatively small-diameter (smaller than the body forming part 22) semi-cylindrical surface. In the present embodiment, the neck part forming part 26 is a small-diameter part with the smallest inner diameter. The body forming part 22, the dome part forming part 24, and the neck part forming part 26 constitute the molding surfaces (inner surfaces) of the plurality of mold blocks 36 and 38.

[0028] Since the straight running region P is the region where molding is performed, in this region, as shown in FIG. 2, a plurality of adjacent mold blocks 36 run in contact with each other, and a plurality of adjacent mold blocks 38 run in contact with each other.

[0029] Note that the sizes and shapes of the plurality of mold blocks 36 and 38 are not limited to the examples shown in FIG. 2. For example, the dome portion 14 and the neck portion 16 may be composed of only one mold block 36 or 38 (in other words, the boundary between the body portion 12 and the dome portion 14 and the boundary between the dome portion 14 and the neck portion 16 may be configured to coincide with the boundary of the plurality of mold blocks 36 and 38), or the dome portion 14 and the neck portion 16 may be configured to span two or more mold blocks 36 and 38.

[0030] Also, a plurality of mold blocks 36 of the first outer shape portion 32 and a plurality of mold blocks 38 of the second outer shape portion 34 are provided with suction openings (not shown) for sucking the molten resin tube 48 described later and transferring the mold at a plurality of locations on their inner surfaces (molding surfaces).

[0031] Returning to FIG. 1, a nozzle 40 as a resin discharge device constituting a part of the extrusion molding machine is provided in the region upstream of the straight running region P. The nozzle 40 includes a substantially cylindrical outer die 44 and a substantially cylindrical inner die 42 (see FIGS. 2 and 3) having a smaller diameter than the outer die 44 and disposed inside the outer die 44 (hollow portion).

[0032] As shown in FIGS. 2 and 3, the outer die 44 and the inner die 42 are concentrically arranged with their tips (downstream ends) substantially coinciding, and the longitudinal direction is directed in the traveling direction of the first outer profile portion 32 and the second outer profile portion 34 in the straight traveling region P. The (substantially cylindrical) gap between the outer die 44 and the inner die 42 constitutes a resin supply path 46 through which the molten resin heated and melted in a resin supply device (not shown) passes, and an opening (substantially annular) formed at the tip of the outer die 44 (downstream end portion in the resin supply direction) and the tip of the inner die 42 (downstream end portion in the resin supply direction) serves as a resin discharge port (resin discharge portion) 47. The molten resin heated and melted in a resin supply device (not shown) is continuously extruded at a constant speed as a substantially cylindrical molten resin tube 48 from the resin discharge port 47 through the gap between the outer die 44 and the inner die 42 (that is, the resin supply path 46). At this time, the molten resin tube 48 is a substantially cylindrical resin in an unfrozen state, and its extrusion direction S is substantially the same as the traveling direction of the first outer profile portion 32 and the second outer profile portion 34 in the straight traveling region P. Further, the interior (hollow portion) of the inner die 42 constitutes a gas supply path 49 (specifically, its upstream portion) through which gas (for example, nitrogen gas) (also called blow air) supplied from a gas pressure applying device (not shown) passes.

[0033] At the tip (downstream end portion or discharge side end portion) of the inner die 42 of the nozzle 40, a shape adjustment attachment (hereinafter simply referred to as an attachment) 50 is attached as a shape adjustment portion.

[0034] The attachment 50 is formed in a stepped cylindrical shape, and its outer peripheral surface 52 guides the molten resin tube 48 extruded (discharged) from the resin discharge port 47 toward the radially outer side (in other words, the inner surfaces of the mold blocks 36 and 38), and constitutes a guide surface for expanding the diameter of the molten resin tube 48.

[0035] As can be clearly understood by referring to FIGS. 4 and 5 together with FIGS. 2 and 3, the outer peripheral surface (guide surface) 52 of the attachment 50 is composed of a substantially cylindrical surface that is substantially the same as the outer diameter of the inner die 42, and includes a start end surface portion 52A that is continuous with the outer peripheral surface of the inner die 42 and extends axially, and an intermediate widening portion 52B that is formed at the axial end of the start end surface portion 52A and is composed of a tapered surface or a frustum surface that gradually expands (increases in diameter) toward the side opposite to the inner die 42 (the downstream side in the resin supply direction), and a terminal end surface portion 52C that is formed at the axial end of the intermediate widening portion 52B on the side opposite to the inner die 42 and is composed of a substantially cylindrical surface having a larger diameter than the inner die 42.

[0036] Therefore, the molten resin tube 48 extruded (discharged) from the resin discharge port 47 in the extrusion direction S passes through the start end surface portion 52A that is continuous with the resin discharge port 47 (resin supply path 46) in the extrusion direction S, and is guided by the intermediate widening portion 52B to the radially outer side (in other words, in a direction inclined outward with respect to the extrusion direction S) as it goes downstream, so that its diameter expands (see the solid arrows in the mold blocks 36 and 38 in FIG. 3).

[0037] Also, as shown in FIGS. 2 to 5, a gas discharge path 54 is formed inside the attachment 50 to discharge (introduce) the gas supplied through the inside of the inner die 42 into the inside of the molten resin tube 48 and expand the diameter of the molten resin tube 48 (to the inner surfaces of the mold blocks 36 and 38). The gas discharge path 54, together with the inside (hollow portion) of the inner die 42 described above, constitutes a gas supply path 49 through which the gas supplied from a gas pressure applying device (not shown) passes. In other words, the gas discharge path 54 constitutes the downstream portion of the gas supply path 49.

[0038] The above-described gas release path 54 includes a relatively large-diameter central supply path 54A that extends axially (linearly) from the end on the inner die 42 side (the upstream end in the gas supply direction), and a plurality of relatively small-diameter inclined supply paths 54B that extend in a direction inclined radially outward while branching from the axial end on the side opposite to the inner die 42 of the central supply path 54A (the downstream end in the gas supply direction). In the present embodiment, four inclined supply paths 54B are arranged at 90-degree intervals around the central supply path 54A (in the circumferential direction). The tip of the inclined supply path 54B (the end on the side opposite to the inner die 42 (the downstream end in the gas supply direction)) opens to the terminal surface portion 52C (in the vicinity of its downstream end in the illustrated example) of the outer peripheral surface (guide surface) 52 of the attachment 50 described above, and the openings at the tips (a total of four openings in the circumferential direction in the present embodiment) serve as gas supply ports 55.

[0039] Therefore, the gas supplied through the inside of the inner die 42 is discharged from the gas supply port 55 through the gas release path 54 (the central supply path 54A and the inclined supply paths 54B) in a direction inclined radially outward (in other words, in a direction inclined outward with respect to the extrusion direction S), and is discharged into the inside of the molten resin tube 48 guided by the outer peripheral surface (guide surface) 52 of the attachment 50, so that the diameter of the molten resin tube 48 expands (see the broken-line arrows in the mold blocks 36 and 38 in FIG. 3).

[0040] Note that the inclined supply path 54B only needs to extend in a direction inclined radially outward. For example, it may be formed to be substantially parallel to the intermediate widened portion 52B on the outer peripheral surface (guide surface) 52 of the attachment 50 (in other words, it may be formed so that the inclination angle of the inclined supply path 54B and the inclination angle of the intermediate widened portion 52B are substantially the same), or it may be formed at different angles.

[0041] Also, the outer peripheral surface 52 of the attachment 50, the position, shape, size, etc. of the gas release path 54 are of course not limited to the illustrated example.

[0042] At the center of the axial end on the inner die 42 side of the attachment 50, a fastening portion 51 with a small diameter having a male thread 51A formed on its outer periphery is formed (projecting axially). By screwing the male thread 51A of the fastening portion 51 into the female thread 41A of the receiving portion 41 provided on the inner periphery of the inner die 42, the attachment 50 is attached and fixed to the tip of the inner die 42 of the nozzle 40. It is a matter of course that the attachment configuration of the attachment 50 to the nozzle 40 is not limited to the illustrated example.

[0043] At the center of the axial end on the side opposite to the inner die 42 of the attachment 50, a stepped small-diameter fastening portion 59 having a male thread 59A formed on its outer periphery is formed (projecting axially). By screwing the male thread 59A of this fastening portion 59 into the female thread 69A of the receiving portion 69 provided on the inner periphery of the pressure-holding jig 60, which will be described in detail later, the pressure-holding jig 60 as a pressure-holding portion is attached and fixed to the tip (downstream end) of the attachment 50.

[0044] The pressure-holding jig 60 attached to the tip of the attachment 50 has a substantially cylindrical shape extending axially (linearly), is disposed inside the molten resin tube 48 extruded (discharged) from the resin discharge port 47, and holds (maintains) the internal pressure of the molten resin tube 48 extruded (discharged) from the resin discharge port 47 inside the plurality of mold blocks 36, 38, specifically, inside the plurality of mold blocks 36, 38.

[0045] The axial length of the pressure-holding jig 60 has a length that can be inserted into the neck portions 16 formed at both axial ends of the liner 10 during molding (in other words, the two neck forming portions 26 of the plurality of mold blocks 36, 38). In other words, the axial length of the pressure-holding jig 60 is set to be equal to or slightly smaller than the axial length (interval) between the neck portions (small-diameter portions) 16 formed at both axial ends of the liner 10 during molding. Also, the outer diameter of the pressure-holding jig 60 is formed to be equal to or slightly smaller than the inner diameter of the neck portions 16 formed at both axial ends of the liner 10 during molding (in other words, the molten resin tube 48 pressed against the two neck forming portions 26 of the plurality of mold blocks 36, 38).

[0046] Therefore, the pressure maintaining jig 60 is inserted into the necks 16 formed at both axial ends of the liner 10 during molding, and the opening (area) of the neck 16 becomes narrower (decreases) by the cross-sectional area of the pressure maintaining jig 60. Therefore, the flow resistance in the neck 16, which is a small-diameter portion, increases, and the gas discharged from the gas supply port 55 into the interior of the molten resin tube 48 through the gas discharge path 54 (central supply path 54A, inclined supply path 54B) is less likely to escape from the neck 16 of the liner 10 during molding, stays in the molten resin tube 48 during molding, and it becomes easier to maintain (hold) the internal pressure of the molten resin tube 48.

[0047] In the present embodiment, the (annular) clearance area between the pressure maintaining jig 60 and the neck 16 of the liner 10 during molding (in other words, the molten resin tube 48 pressed against the two neck forming portions 26 of the plurality of mold blocks 36, 38) is set to be the same as or smaller than the minimum flow path cross-sectional area (the minimum value of the flow path cross-sectional area) of the gas discharge path 54 formed in the attachment 50 described above. As a result, the amount of gas escaping (being discharged) from the (annular) clearance between the pressure maintaining jig 60 and the neck 16 of the liner 10 during molding (in other words, the molten resin tube 48 pressed against the two neck forming portions 26 of the plurality of mold blocks 36, 38) is surely less than the amount of gas being discharged (supplied) from the gas supply port 55 through the gas discharge path 54 (central supply path 54A, inclined supply path 54B). In other words, the amount of gas discharged from the inside of the molten resin tube 48 is surely less than the amount of gas supplied to the inside of the molten resin tube 48. Therefore, it becomes easier to surely maintain (hold) the internal pressure of the molten resin tube 48.

[0048] Near the axial end on the attachment 50 side of the pressure maintaining jig 60, a receiving portion 69 having a female thread 69A formed on the inner circumference is attached to the inner circumference. By screwing the female thread 69A of the receiving portion 69 with the male thread 59A of the fastening portion 59 of the attachment 50 described above, the pressure maintaining jig 60 is attached and fixed to the tip of the attachment 50. In the present embodiment, the pressure maintaining jig 60 is connected to the tip of the attachment 50 and is supported in a cantilever manner.

[0049] In addition, in the present embodiment, the outer diameter of the pressure holding jig 60 is formed to be substantially the same as the outer diameter of the attachment 50 (the large-diameter portion having the terminal surface portion 52C). The pressure holding jig 60 is attached to the tip of the attachment 50 in a state where the axial end on the attachment 50 side is in contact with the attachment 50 (the large-diameter portion having the terminal surface portion 52C). It goes without saying that the attachment configuration of the pressure holding jig 60 to the attachment 50 is not limited to the illustrated example.

[0050] (Manufacturing method of the liner) Next, with reference to FIGS. 1 to 3, the manufacturing method of the liner 10 of the present embodiment will be described. The liner 10 is continuously manufactured by sequentially repeating the following steps.

[0051] First, as shown in FIGS. 2 and 3, the molten resin heated and melted in a resin supply device (not shown) disposed upstream of the straight running region P passes through the gap (resin supply path 46) between the outer die 44 and the inner die 42 of the nozzle 40 and is continuously extruded from the resin discharge port 47 as a substantially cylindrical molten resin tube 48 at a constant speed. At this time, the molten resin tube 48 is a substantially cylindrical resin in a non-solidified state, and the extrusion direction S is substantially the same as the running direction of the first outer shape portion 32 and the second outer shape portion 34 in the straight running region P.

[0052] The extruded molten resin tube 48 flows over the outer peripheral surface (guide surface) 52 of the attachment 50 disposed downstream of the nozzle 40 from the start end surface portion 52A to the intermediate widened portion 52B. At this time, it is guided radially outward (in other words, in a direction inclined outward with respect to the extrusion direction S) as it goes downstream by the intermediate widened portion 52B, and its diameter gradually increases as it goes downstream of the straight running region P (in other words, downstream of the resin supply direction).

[0053] The molten resin tube 48 guided by the outer peripheral surface (guide surface) 52 of the attachment 50 is continuously supplied at a constant speed without solidifying between the plurality of mold blocks 36 of the first outer mold part 32 and the plurality of mold blocks 38 of the second outer mold part 34 in a state where the first outer mold part 32 and the second outer mold part 34 are circulating and running in the first direction R1 and the second direction R2, respectively, from the upstream side of the linear running region P toward a direction inclined radially outward with respect to the extrusion direction S.

[0054] Also, simultaneously with the supply of the molten resin tube 48, gas supplied from a gas pressure applying device (not shown) passes through the gas supply path 49 (including the gas discharge path 54) inside the inner die 42 and inside the attachment 50 and is supplied (pumped) from the gas supply port 55 to the inside of the molten resin tube 48. At this time, by the plurality of inclined supply paths 54B of the gas discharge path 54, the gas is supplied (pumped) to the inside of the molten resin tube 48 in a direction inclined radially outward (in other words, in a direction inclined outward with respect to the extrusion direction S). When the gas is supplied, the gas pressure in the hollow portion of the molten resin tube 48 rises, gas pressure is applied to the molten resin tube 48 from the inside, and the molten resin tube 48 is pressed against the plurality of mold blocks 36 of the first outer mold part 32 and the plurality of mold blocks 38 of the second outer mold part 34 (the molding surface where the suction openings for mold transfer are opened). Also, when the gas is supplied to the inside of the molten resin tube 48 in a direction inclined radially outward, gas pressure is applied to the molten resin tube 48 from the inside in the radially outward direction (in other words, the molten resin tube 48 is pressed radially outward by the gas pressure), and thereby, as it goes toward the downstream side of the linear running region P (in other words, the downstream side in the resin supply direction), the diameter of the molten resin tube 48 gradually expands, and the molten resin tube 48 is pressed against the plurality of mold blocks 36 of the first outer mold part 32 and the plurality of mold blocks 38 of the second outer mold part 34 (the molding surface where the suction openings for mold transfer are opened).

[0055] Here, when the pressure-holding jig 60 of the present embodiment is not present, the gas supplied inside the molten resin tube 48 is sequentially discharged to the outside through the neck portion 16 of the liner 10 being molded, etc., and it becomes difficult to maintain the gas pressure in the hollow portion of the molten resin tube 48.

[0056] In the present embodiment, as shown in FIGS. 1 and 2, the pressure-holding jig 60 held by the attachment 50 is inserted into the neck portions 16 formed at both axial ends of the liner 10 being molded, and the opening (area) of the neck portion 16 becomes narrower (decreases) by the cross-sectional area of the pressure-holding jig 60. Therefore, the flow resistance in the neck portion 16, which is a small-diameter portion, increases, and the gas supplied inside the molten resin tube 48 is less likely to be discharged from the neck portion 16 of the liner 10 being molded, stays in the molten resin tube 48 being molded, and it becomes easier to maintain the gas pressure in the hollow portion of the molten resin tube 48 (that is, the pressure-holding effect can be enhanced).

[0057] Here, in order to efficiently enhance the pressure-holding effect, the (annular) clearance area between the pressure-holding jig 60 and the neck portion 16 of the liner 10 being molded (in other words, the molten resin tube 48 pressed against the two neck-forming portions 26 of the plurality of mold blocks 36, 38) is set to be equal to or less than the minimum flow path cross-sectional area of the gas discharge path 54 formed in the attachment 50 described above.

[0058] Due to this pressure-holding effect, the molten resin tube 48 is quickly pressed against the plurality of mold blocks 36 of the first outer mold portion 32 and the plurality of mold blocks 38 of the second outer mold portion 34 (the molding surface where the suction openings for mold transfer are opened).

[0059] Note that suction openings (not shown) for sucking and mold-transferring the molten resin tube 48 are opened at a plurality of locations on the inner surfaces of the plurality of mold blocks 36, 38. Therefore, between the plurality of mold blocks 36 of the first outer mold portion 32 and the plurality of mold blocks 38 of the second outer mold portion 34, the downstream side of the molten resin tube 48 is at a positive pressure and the upstream side is at a negative pressure.

[0060] As a result, a substantially cylindrical liner 10 is formed. During this forming process, the first outer die part 32 and the second outer die part 34 continue to circulate (i.e., the relative positions of the plurality of mold blocks 36 of the first outer die part 32, the plurality of mold blocks 38 of the second outer die part 34, the nozzle 40, etc. continue to change), and while forming the molten resin tube 48 in the linear travel region P, they are sequentially transported from upstream to downstream.

[0061] When the liner 10 continuously formed as described above is pressed against the plurality of mold blocks 36 of the first outer die part 32 and the plurality of mold blocks 38 of the second outer die part 34, it is cured by cooling means (not shown) provided in the mold blocks 36 and 38, transported to the downstream side of the linear travel region P as shown in FIG. 1, and cut by a cutter (not shown) at the axial ends (between the heads 16) of the individual liners 10 to obtain the liner 10.

[0062] (Function and Effect) As described above, in the extrusion corrugated tube forming, the molten resin tube 48 extruded from the resin discharge port 47 is drawn down under the influence of gravity. Therefore, the upper part of the molten resin tube 48 is difficult to contact (stick) with the mold, and it is difficult to shape along the mold.

[0063] The manufacturing apparatus 30 for the liner 10 of the present embodiment includes the mold blocks 36 and 38, a resin discharge part (resin discharge port 47) that can change the relative position in the axial direction with respect to the mold blocks 36 and 38 while discharging a cylindrical molten resin into the mold blocks 36 and 38, a shape adjustment part (shape adjustment attachment 50) that expands the diameter of the cylindrical molten resin discharged from the resin discharge part, and a pressure holding part (pressure holding jig 60) that can hold the internal pressure of the cylindrical molten resin discharged from the resin discharge part.

[0064] Further, the shape adjustment part (shape adjustment attachment 50) is configured to include a gas discharge path 54 that discharges gas in a direction inclined radially outward inside the cylindrical molten resin discharged from the resin discharge part (resin discharge port 47), and the pressure holding part (pressure holding jig 60) is a pressure holding jig 60 that extends axially within the mold blocks 36 and 38 and passes through the inside of the smallest diameter portion of the cylindrical resin pressed against the mold blocks 36 and 38 by the pressure of the gas.

[0065] Further, the clearance area between the small diameter portion and the pressure holding jig 60 passing through the inside of the small diameter portion is equal to or less than the minimum flow path cross-sectional area of the gas discharge path 54.

[0066] That is, when manufacturing the liner 10 by extrusion corrugated tube molding, the manufacturing apparatus 30 of the liner 10 of the present embodiment uses the pressure holding jig 60 to shape the liner 10 while applying internal pressure thereto. By supplying gas (blow air) from the gas pressure applying device and reducing the clearance between the small diameter portion of the formed liner 10 and the pressure holding jig 60, the gas (blow air) stays inside the liner 10 (inside the molten resin tube 48) during molding, and static pressure is applied inside the liner 10 (inside the molten resin tube 48). Since the molten resin tube 48 extruded from the resin discharge port 47 is attached to the mold by internal pressure, stable molding becomes possible.

[0067] Thus, according to the present embodiment, when molding a tubular body by extrusion corrugated tube molding, since the pressure holding part (using the pressure holding jig 60) shapes the cylindrical molten resin while applying internal pressure thereto, the resin extruded from the resin discharge part (resin discharge port 47) is quickly attached to the inner walls of the mold blocks 36 and 38, thereby preventing molding defects due to drawdown and enabling stable molding.

[0068] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments, and various modifications are possible without departing from the gist thereof. For example, in the above-described embodiment, an example is shown in which the relative position in the axial direction between the mold blocks 36, 38 and the nozzle 40 (resin discharge port 47 thereof) is changed by moving the plurality of mold blocks 36 of the first outer mold part 32 and the plurality of mold blocks 38 of the second outer mold part 34. However, the relative position in the axial direction between the mold blocks 36, 38 and the nozzle 40 may be changed by moving the nozzle 40 (resin discharge port 47 thereof).

Explanation of Reference Numerals

[0069] 10 Liner (tubular body) 12 Body part 14 Dome part 16 Head part 30 Manufacturing apparatus 32 First outer mold part 34 Second outer mold part 36 Plurality of mold blocks 38 Plurality of mold blocks 40 Nozzle 42 Inner die 44 Outer die 46 Resin supply path 47 Resin discharge port (resin discharge part) 48 Molten resin tube 49 Gas supply path 50 Shape adjustment attachment (shape adjustment part) 52 Outer peripheral surface (guide surface) 54 Gas discharge path 55 Gas supply port 60 Pressure holding jig (pressure holding part) P Linear travel region R1 First direction (circulation direction of the first outer mold part) R2 Second direction (circulation direction of the second outer mold part)

Claims

1. An apparatus for manufacturing a tubular or pipe-shaped body, comprising: a mold block; a resin discharge unit that discharges a tubular molten resin into the mold block and is capable of changing a relative position in the axial direction with respect to the mold block; a shape adjustment unit that enlarges the diameter of the tubular molten resin discharged from the resin discharge unit; a pressure holding unit that is capable of holding the internal pressure of the tubular molten resin discharged from the resin discharge unit, wherein the shape adjustment unit includes a gas discharge path that discharges gas in a direction inclined radially outward inside the tubular molten resin discharged from the resin discharge unit; the gas discharge path includes a central supply path extending in the axial direction, and a plurality of inclined supply paths that branch from an axial end of the central supply path and linearly extend in a direction inclined radially outward to the outer peripheral surface and open inside the tubular molten resin discharged from the resin discharge unit in the inclined direction at the outer peripheral surface, and is characterized by the manufacturing apparatus.

2. The apparatus for manufacturing a tubular body according to claim 1, wherein the outer peripheral surface is composed of a cylindrical surface extending in the axial direction around the axis, and is characterized by the manufacturing apparatus.

3. The apparatus for manufacturing a tubular body according to claim 1, wherein the shape adjustment unit includes a guide surface that guides the tubular molten resin discharged from the resin discharge unit radially outward as it flows downstream, and is characterized by the manufacturing apparatus.

4. The apparatus for manufacturing a tubular body according to claim 1, wherein the shape adjustment unit is provided at a discharge side end of the resin discharge unit, and is characterized by the manufacturing apparatus.

5. The apparatus for manufacturing a tubular body according to claim 1, wherein the pressure holding unit is composed of a pressure holding jig extending along the axial direction inside the mold block, and is characterized by the manufacturing apparatus.

6. The apparatus for manufacturing a tubular body according to claim 1, wherein the pressure holding unit is connected to and held by the shape adjustment unit, and is characterized by the manufacturing apparatus.

7. The apparatus for manufacturing a tubular body according to claim 1, wherein the pressure holding unit is composed of a pressure holding jig that extends inside the smallest diameter portion of the tubular resin pressed against the mold block by the pressure of the gas along the axial direction inside the mold block, and is characterized by the manufacturing apparatus.

8. The apparatus for manufacturing a tubular body according to claim 7, The manufacturing apparatus is characterized in that a clearance area between the small-diameter portion and the pressure-holding jig passing through the inside of the small-diameter portion is equal to or less than a minimum flow path cross-sectional area of the gas discharge path.

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