Die head and hollow molding machine having said die head
The die head design with a vertically centered inlet and throttling channels ensures uniform resin flow and thickness in the cylindrical channel, addressing non-uniformity issues in existing technologies.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- TAHARA KK
- Filing Date
- 2024-12-04
- Publication Date
- 2026-06-16
AI Technical Summary
The existing die head for hollow molding machines results in non-uniform resin flow rates in the circumferential direction of the cylindrical flow path, leading to difficulties in extruding molten resin with uniform thickness.
The die head design includes a cylindrical channel with a flattened cross-section and an inlet located vertically above the channel center, combined with throttling channels and adjustable thickness mechanisms to ensure uniform resin flow and thickness.
This design achieves uniform resin flow rates and thickness across the circumference of the cylindrical channel, enhancing the consistency of the extruded parison.
Smart Images
Figure 2026096983000001_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to a die head and a hollow molding machine having the die head.
Background Art
[0002] Patent Document 1 discloses a die head for a hollow molding machine that extrudes molten resin as a cylindrical parison. This die head has a cylindrical body and a mandrel disposed inside the body, and a cylindrical flow path that forms part of a resin flow path through which molten resin flows is formed between the two. Further, the cylindrical flow path is formed such that a cross section orthogonal to the flow direction of the molten resin is flat. Furthermore, the resin flow path has an inlet through which the molten resin flows, and this inlet is connected to one end in the longitudinal direction of the cylindrical flow path.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] In the die head of Patent Document 1, since the molten resin flows in such a way that it wraps around from one end in the longitudinal direction of the cylindrical flow path to the other end in the longitudinal direction through the inlet, the flow rate of the molten resin is higher on the inlet side of the cylindrical flow path, that is, on one end side in the longitudinal direction of the cylindrical flow path, than on the other end side in the longitudinal direction of the cylindrical flow path. For this reason, there is a problem that the flow rate of the molten resin becomes non-uniform in the circumferential direction of the cylindrical flow path, and it is difficult to extrude molten resin with a uniform thickness. Further, in Patent Document 1, no consideration is given to making the flow rate of the molten resin uniform in the circumferential direction of the cylindrical flow path.
[0005] This invention was devised in view of conventional circumstances, and one of its objectives is to provide a die head and a hollow molding machine having said die head that can make the flow rate of molten resin uniform in the circumferential direction of a cylindrical flow path and extrude molten resin of uniform thickness. [Means for solving the problem]
[0006] The present invention relates to a die head for extruding molten resin from an extruder as a cylindrical parison, the die head comprising a body opening vertically downward, a mandrel disposed within the body, and a resin channel provided between the inner circumferential surface of the body and the outer circumferential surface of the mandrel, having a cylindrical channel through which the molten resin flows vertically from upper to lower. The cylindrical channel is formed such that its cross-section perpendicular to the direction of molten resin flow is flattened. The resin channel further has an inlet for supplying molten resin to the cylindrical channel. The inlet is located vertically above the cylindrical channel at the center of the longitudinal direction of the cylindrical channel in a cross-sectional view perpendicular to the direction of molten resin flow. [Effects of the Invention]
[0007] When the inlet is located vertically above the cylindrical channel, the molten resin flows vertically from the top to the bottom and into the cylindrical channel. Therefore, compared to the case where the molten resin flows in from one end of the longitudinal direction of a flat cylindrical channel, the flow rate of the molten resin can be made uniform in the circumferential direction of the cylindrical channel, and molten resin of uniform thickness can be extruded. [Brief explanation of the drawing]
[0008] [Figure 1] This is a front view of a hollow molding machine having a die head of a first embodiment, with a portion cut out. [Figure 2] This is a perspective view of the hollow molding machine of the first embodiment. [Figure 3] This is a cross-sectional view of a hollow molding machine cut along line AA in Figure 2. [Figure 4] This is a cross-sectional view of a hollow molding machine cut along line BB in Figure 2. [Figure 5] This is a cross-sectional view of the hollow molding machine cut along line CC in Figure 3. [Figure 6] This is a top view of the first throttling member of the first embodiment. [Figure 7] This is a cross-sectional perspective view of the first throttling member of the first embodiment. [Figure 8] This is a cross-sectional perspective view of the second throttling member of the second embodiment. [Modes for carrying out the invention]
[0009] Hereinafter, embodiments of a hollow molding machine having the die head of the present invention will be described based on the drawings.
[0010] As shown in Figure 1, the hollow molding machine has a hopper 1 into which solid resin pellets are fed, an extruder (not shown) that softens and melts the resin pellets with a screw and sends them forward, an extrusion head 4 connected to the tip of the extruder that pushes the molten resin sent from the extruder out of the die 3 at the tip via a die head 2 as a flat cylindrical (flat tube-shaped) parison P and lets it hang down, a molding die 5 that holds the parison P pushed out from the extrusion head 4, a molded product holder 7 attached to the platen 6, a mold clamping device 8 equipped with an electric motor for opening the platen 6 and the molding die 5, a parison cutting device (not shown) for cutting the parison P to a predetermined length, a mold transfer device 9 for moving the molding die 5 by a predetermined stroke, and a nozzle insertion device 11 equipped with an air blowing nozzle 10 for blowing compressed air into the parison P. Reference numeral 12 in Figure 1 indicates the base.
[0011] Furthermore, the hollow molding machine shown in Figure 1 is equipped with a handling device 13. This handling device 13 has an openable / closable gripper section 14 at its tip and has the function of receiving the hollow molded product S held in the molded product holder 7 and transporting it to the outside.
[0012] As shown in Figures 3 and 4, the die head 2 includes a head body 15, a first upper body 16, a throttling channel forming member (hereinafter referred to as the "first throttling member") 17, a second upper body 18, a first lower body 19, a second lower body 20, a die 3, a die flange 21, a first mandrel 22, a second mandrel 23, and a core 24. These components, such as the head body 15, are made of metal.
[0013] The head body 15 is formed in a rectangular parallelepiped shape and has an inlet 27a for supplying molten resin to the cylindrical flow channel 28, which will be described later. As shown in Figure 3, this inlet 27a is located in the center of the head body 15.
[0014] The first upper body 16 is formed in the shape of a rectangular parallelepiped and is positioned below the head body 15. As shown in Figures 3 and 4, the first upper body 16 is suspended by being fixed to a plurality of fixing shafts 25. As shown in Figure 3, the length along the left-right direction of Figure 3 (the length along the longitudinal direction L described later) is greater than the length of the head body 15 along the left-right direction of Figure 3. A recessed portion 16b is formed on the lower surface 16a of the first upper body 16, recessed toward the head body 15 from this lower surface 16a. A first mandrel 22, which is in the shape of an elongated plate, is positioned in this recessed portion 16b.
[0015] The first diaphragm member 17 is a rectangular plate-shaped object corresponding to the outer shape of the first upper body 16, and is positioned below the first upper body 16 and the first mandrel 22. The first diaphragm member 17 will be described in detail later.
[0016] The second upper body 18 is in the shape of a rectangular square tube and is disposed below the outer peripheral portion of the first throttle member 17. The second upper body 18 has a square tube portion 18a and a flange portion 18b that projects outward from the end of the square tube portion 18a on the side of the first throttle member 17. An inclined surface 18c is formed at the end of the square tube portion 18a opposite to the first throttle member 17, and this inclined surface 18c is inclined outward as it moves away from the first throttle member 17. As shown in FIGS. 3 and 4, the outer shape of the flange portion 18b corresponds to the outer shapes of the first upper body 16 and the first throttle member 17.
[0017] The first lower body 19 is formed in a rectangular frame shape and is slidably disposed on the outer periphery of the square tube portion 18a of the second upper body 18.
[0018] The second lower body 20 is formed in a rectangular square tube shape and is disposed below the flange portion 18b of the second upper body 18. As shown in FIG. 4, a first recess 20b for accommodating the first lower body 19 is formed on the inner peripheral side of the upper surface 20a of the second lower body 20. On the other hand, a second recess 20d for accommodating a part of the die 3 is formed on the inner peripheral side of the lower surface 20c of the second lower body 20. Further, a portion of the inner peripheral portion of the second lower body 20 adjacent to the first lower body 19 is slidably disposed on the outer periphery of the flange portion 18b of the second upper body 18.
[0019] The die 3 is in the shape of a rectangular square tube, and as shown in FIGS. 3 and 4, the inner peripheral surface 3a of the die 3 is formed such that the upper and lower sides in the vertical direction are enlarged more than the central portion.
[0020] The die flange 21 is formed in a rectangular frame shape and is disposed around the die 3. As shown in FIGS. 3 and 4, the die flange 21 is fastened to the second lower body 20 by a plurality of bolts 26. In this fastened state, the die 3 is fixed between the die flange 21 and the second lower body 20 by being sandwiched therebetween.
[0021] The second mandrel 23 is formed in a generally rectangular parallelepiped shape and is positioned within the second upper body 18 and the second lower body 20. As shown in Figure 3, the length of the second mandrel 23 along the left-right direction in Figure 3 is set such that the side facing the flange portion 18b of the second upper body 18 is the shortest, while the side facing the second lower body 20 is the longest. Similarly, as shown in Figure 4, the length of the second mandrel 23 along the left-right direction in Figure 4 is set such that the side facing the flange portion 18b of the second upper body 18 is the shortest, while the side facing the second lower body 20 is the longest. The second mandrel 23, the first throttling member 17, and the first mandrel 22 are fastened together via a plurality of bolts (not shown).
[0022] The core 24 is formed in a roughly rectangular shape and is placed inside the die 3.
[0023] The first upper body 16, the outer peripheral portion D1 of the first condensing member 17, the second upper body 18, and the second lower body 20 constitute body B, which forms the outer wall of the resin channel 27 through which the molten resin flows. The die 3 also forms the outer wall of the resin channel 27.
[0024] Furthermore, the first mandrel 22, the central portion D2 of the first constricting member 17, and the second mandrel 23 constitute a mandrel M that forms the inner wall of the resin flow channel 27. This mandrel M is positioned within the body B, which opens vertically downward. The core 24 also forms the inner wall of the resin flow channel 27.
[0025] Between the inner circumferential surface of body B and the outer circumferential surface of mandrel M, a cylindrical channel 28 is formed, which constitutes part of the resin channel 27 and allows molten resin to flow from the upper vertical side to the lower vertical side. The cylindrical channel 28 has a first cylindrical channel section 28A and a second cylindrical channel section 28B. The first cylindrical channel section 28A and the second cylindrical channel section 28B are in communication via a plurality of first throttling channels 42, described later, formed in the first throttling member 17.
[0026] The first cylindrical flow channel 28A is formed adjacent to the lower surface 16a of the first upper body 16. As shown in Figures 3 and 4, the first cylindrical flow channel 28A extends along the vertical direction. Here, the direction from the upper side to the lower side in the vertical direction is defined as the flow direction F of the molten resin flowing through the first cylindrical flow channel 28A. As shown in Figure 5, the first cylindrical flow channel 28A is formed to have a flattened shape, more specifically, a flattened shape that is generally a continuous rectangular frame shape, when viewed in a cross section perpendicular to the flow direction F of the molten resin. Note that this flattened shape may be other shapes, such as an ellipse or an oblong, rather than a rectangular frame shape. As shown in Figure 5, the first cylindrical flow channel 28A has a constant thickness (the distance between the inner circumference of the first upper body 16 and the outer circumference of the first mandrel 22) around its entire circumference. Note that Figure 5 is a schematic example illustrating that the thickness of the first cylindrical flow channel 28A is constant, and the actual shape of the first cylindrical flow channel 28A corresponds to the shape of the first groove 40 shown in Figures 6 and 7.
[0027] For the sake of convenience in the following explanation, in Figure 5, the direction of the longer side of the first cylindrical channel section 28A is defined as the longitudinal direction L of the cylindrical channel 28 (the first cylindrical channel section 28A and the second cylindrical channel section 28B). This longitudinal direction L corresponds to the left-right direction in Figure 3.
[0028] As shown in Figure 5, the first cylindrical flow channel 28A has a pair of long sides 29 extending in the longitudinal direction L of the first cylindrical flow channel 28A, a pair of short sides 30 extending in a direction perpendicular to the longitudinal direction L of the first cylindrical flow channel 28A, and four arc-shaped connecting parts 31 connecting the pair of long sides 29 and the pair of short sides 30.
[0029] The second cylindrical flow channel section 28B is formed between the inner circumferential surface Ba of body B (the inner circumferential surfaces of the second upper body 18 and the second lower body 20) and the inner circumferential surface 3a of die 3, and the outer circumferential surface Ma of mandrel M (the outer circumferential surface of the second mandrel 23) and the outer circumferential surface 24a of core 24. The second cylindrical flow channel section 28B has a much longer vertical length than the first cylindrical flow channel section 28A in order to gain a distance for stably flowing molten resin with a uniform flow rate in the circumferential direction of the cylindrical flow channel 28. The second cylindrical flow channel section 28B is also formed to have a flattened shape, or more specifically, a flattened shape that is generally connected in a rectangular frame shape, when viewed in a cross section perpendicular to the flow direction F of the molten resin. As shown in Figures 3 and 4, the thickness of the second cylindrical channel section 28B is approximately the same as the thickness of the first cylindrical channel section 28A at the upper part of the second mandrel 23, and decreases towards the lower part of the second mandrel 23. Furthermore, the thickness of the second cylindrical channel section 28B is relatively large at the upper part of the core 24 to form a molten resin reservoir 32, and gradually decreases towards the outlet 33 of the cylindrical channel 28 located at the lower part of the core 24.
[0030] Furthermore, as shown in Figure 4, the second lower body 20 is fixed to a plurality of rod-shaped members 34 that can be raised and lowered by a motor (not shown). When the rod-shaped members 34 are raised and lowered, the second lower body 20 moves together with the die 3 and die flange 21, thereby adjusting the thickness (opening width) of the outlet 33 of the cylindrical flow path 28.
[0031] Furthermore, as shown in Figure 3, a pair of thickness adjustment bolts 35 are provided on the outer circumference of the die 3 in the longitudinal direction L of the cylindrical flow path 28, which press on this outer circumference from both sides to adjust the thickness of the molten resin in the reservoir 32.
[0032] Furthermore, the resin channel 27 has a wide channel 36 that flows the molten resin supplied from the inlet 27a to the first cylindrical channel section 28A of the cylindrical channel 28. As shown in Figure 3, the wide channel 36 has a longitudinal channel 36a that extends along the longitudinal direction L of the cylindrical channel 28, and a pair of inclined channels 36b that slope from both longitudinal ends of the longitudinal channel 36a toward the first cylindrical channel section 28A. The longitudinal channel 36a is formed approximately in the center of the first upper body 16 in the vertical direction. The thickness of the longitudinal channel 36a along the vertical direction is set to be greater than the thickness of the first cylindrical channel section 28A along the longitudinal direction L of the cylindrical channel 28. The pair of inclined channels 36b have a similar shape and are connected to the first cylindrical channel section 28A, gradually tapering toward the first throttling member 17 side.
[0033] Furthermore, as shown in Figure 4, the wide channel 36 further comprises a pair of gradient channels 36c that branch off from the longitudinal channel 36a and incline toward the first cylindrical channel section 28A. The pair of gradient channels 36c have similar shapes and gradually taper toward the first throttling member 17, and are connected to the first cylindrical channel section 28A.
[0034] Furthermore, as shown in Figure 3, the longitudinal channel 36a is connected to an intermediate channel 37 formed in the first upper body 16. The intermediate channel 37 extends vertically upward from the longitudinal channel 36a at the central position in the longitudinal direction L of the cylindrical channel 28 and communicates with an introduction channel 38 formed in the head body 15. As shown in Figures 3 and 4, the introduction channel 38 has a first channel 38a that communicates with the intermediate channel 37 and extends vertically, and a second channel 38b that is perpendicular to the first channel 38a and connects to the inlet 27a of the molten resin. As shown in Figure 3, when viewed in a cross-section perpendicular to the flow direction F of the molten resin, the inlet 27a is located vertically upward from the cylindrical channel 28 and the wide channel 36 at the longitudinal center of the cylindrical channel 28.
[0035] Furthermore, as shown in Figure 4, a connector 39 is attached to the head body 15, and this connector 39 has a connector channel 39a that forms part of the resin channel 27. The outlet of this connector channel 39a is connected to an inlet 27a provided on the head body 15. Molten resin is fed into this connector channel 39a from an extruder (not shown).
[0036] In the resin channel 27, molten resin flows into the first cylindrical channel section 28A via the connector channel 39a, inlet 27a, introduction channel 38, relay channel 37, and wide channel 36. The molten resin in the first cylindrical channel section 28A flows to the second cylindrical channel section 28B via a plurality of first throttling channels 42 formed in the first throttling member 17, which will be described later. The molten resin in the second cylindrical channel section 28B is then extruded into the molding die 5 as a flat cylindrical parison P with a uniform thickness around its entire circumference.
[0037] Furthermore, the first throttling member 17 is provided to eliminate the difference in flow rate between the longitudinal center side of the cylindrical channel 28 and both longitudinal ends of the cylindrical channel 28 for the molten resin flowing through the flattened first cylindrical channel section 28A. More specifically, the molten resin flows through the longitudinal channel 36a along the longitudinal direction L of the cylindrical channel 28, and then flows into the first cylindrical channel section 28A via a long first path R1 (shown as two dashed arrows in Figure 3) to both longitudinal ends of the first cylindrical channel section 28A. At the same time, the molten resin flows into the longitudinal channel 36a and immediately into a pair of gradient channels 36c, and then flows to the longitudinal center side of the first cylindrical channel section 28A via a second path R2 (shown as two dashed arrows in Figure 4) which is shorter than the first path R1. Therefore, when molten resin flows into the first cylindrical flow channel 28A, the flow rate of molten resin is greater towards the longitudinal center of the first cylindrical flow channel 28A than towards both longitudinal ends. Thus, the first throttling member 17 is provided to eliminate the difference in the flow rate of molten resin between the longitudinal center and both longitudinal ends of the first cylindrical flow channel 28A and to ensure a uniform flow rate of molten resin in the circumferential direction of the second cylindrical flow channel 28B.
[0038] As shown in Figures 3, 4, 6, and 7, an annular first groove 40 corresponding to the flattened shape of the first cylindrical flow channel 28A is formed on the upper surface 17a of the first throttling member 17. The first groove 40 is in communication with the first cylindrical flow channel 28A. As shown in Figure 7, the depth of the first groove 40 gradually increases from the center to both ends in the longitudinal direction L of the cylindrical flow channel 28, with the shallowest point being in the center and the deepest points being at both ends in the longitudinal direction L of the cylindrical flow channel 28.
[0039] Furthermore, as shown in Figures 3, 4, and 7, an annular second groove 41 corresponding to the flattened shape of the upper part of the second cylindrical flow channel 28B is formed on the lower surface 17b of the first throttling member 17. The second groove 41 has the same shape as the first groove 40 and is formed to be symmetrical with the first groove 40 in the vertical direction (thickness direction of the first throttling member 17). As shown in Figure 7, the depth of the second groove 41 gradually increases from the center to both ends in the longitudinal direction L of the cylindrical flow channel 28, with the shallowest point being in the center and the deepest points being at both ends in the longitudinal direction L of the cylindrical flow channel 28.
[0040] As shown in Figures 6 and 7, a plurality of first throttling channels 42, which are circular through-holes penetrating vertically, are formed between the bottom of the first groove 40 and the bottom of the second groove 41. As shown in Figure 6, the plurality of first throttling channels 42 are formed at approximately equal intervals along the circumferential direction of the first groove 40 and the second groove 41, that is, along the circumferential direction of the cylindrical channel 28. The plurality of first throttling channels 42 are formed by machining using a drill. The plurality of first throttling channels 42 are circular in shape with the same diameter, but their lengths along the vertical direction differ due to the difference in depth of the first groove 40 and the second groove 41 as described above. More specifically, as shown in Figure 7, the plurality of first throttling channels 42 are formed such that their length along the vertical direction increases as they get closer to the center in the longitudinal direction L of the cylindrical channel 28. In other words, the plurality of first throttling channels 42 are formed such that the flow resistance to the molten resin increases as they get closer to the center in the longitudinal direction L of the cylindrical channel 28.
[0041] Furthermore, as shown in Figure 7, a pointed protrusion 43a is formed at the upper end of the wall portion 43 separating the two first throttling channels 42 adjacent to each other in the circumferential direction of the cylindrical channel 28, tapering toward the upper surface 17a of the first throttling member 17. This protrusion 43a helps to suppress the accumulation of molten resin flowing from the first cylindrical channel portion 28A into the first groove 40 compared to when the protrusion 43a is not formed on the first throttling member 17.
[0042] Furthermore, as shown in Figures 2 to 5, multiple heaters 44 are provided on the outward-facing surfaces of the head body 15, the first upper body 16, the first throttling member 17, the second lower body 20, the first lower body 19, and the second lower body 20, in order to appropriately heat these components and promote the flow of molten resin in the internal resin flow path 27.
[0043] Furthermore, the first throttling member 17, the second mandrel 23, and the core 24 are formed with air passages 45 for pre-inflating the parison P discharged from the outlet 33. As shown in Figures 3 and 4, the air passage 45 has a first passage section 45a, a second passage section 45b, a third passage section 45c, a fourth passage section 45d, a fifth passage section 45e, and a plurality (six in this embodiment) sixth passage sections 45f.
[0044] As shown in Figure 3, the first passage portion 45a extends along the longitudinal direction L of the cylindrical flow path 28, penetrating the walls 43 of the first groove 40 and the second groove 41 (see Figure 7) from one longitudinal end face of the first throttling member 17 and entering into part D2 of the first throttling member 17. The first passage portion 45a is connected to an air supply source (not shown). Also, as shown in Figure 3, the second passage portion 45b extends vertically downward from the inner end of the first passage portion 45a. Also, as shown in Figure 4, the third passage portion 45c is formed as a groove formed on the lower surface 17b of the first throttling member 17 and communicates with the second passage portion 45b. As shown in Figures 3 and 4, the fourth passage portion 45d is formed at the central position of the second mandrel 23 and is a through hole that penetrates the second mandrel 23 vertically. As shown in Figure 4, the upper end of the fourth passage 45d is connected to the central position of the third passage 45c in the longitudinal direction L of the cylindrical flow channel 28, while the lower end of the fourth passage 45d is connected to the fifth passage 45e, which is a groove formed in the core 24. Each sixth passage 45f is formed as a through-hole extending vertically downward from the fifth passage 45e and penetrating the core 24, and is in communication with the inside of the molding die 5 shown in Figure 1. The six sixth passages 45f are arranged at equal intervals in the longitudinal direction L of the cylindrical flow channel 28.
[0045] As described above, in the first embodiment, the resin channel 27 has an inlet 27a that supplies molten resin to the flat cylindrical channel 28. As shown in Figure 3, when viewed in a cross section perpendicular to the flow direction F of the molten resin, the inlet 27a is located vertically above the cylindrical channel 28 at the longitudinal center of the cylindrical channel 28. As described above, in the prior art, the molten resin flows in from one longitudinal end of the flat cylindrical channel, and the molten resin flows around from one longitudinal end to the other longitudinal end of the cylindrical channel through the inlet. Therefore, the flow rate of the molten resin is greater at one longitudinal end of the cylindrical channel than at the other longitudinal end. However, as in the first embodiment, if the inlet 27a is located vertically above the cylindrical channel 28 at the longitudinal center of the cylindrical channel 28, the molten resin flows from vertically above to vertically below the cylindrical channel 28 without the difference in flow rate between one end and the other end of the cylindrical channel in the longitudinal direction that occurs in the conventional technology. Therefore, compared to the conventional technology, the flow rate of the molten resin (and the wall thickness of the parison P) can be made uniform in the circumferential direction of the cylindrical channel 28.
[0046] Furthermore, in this embodiment, the resin channel 27 has a wide channel 36 that flows the molten resin supplied from the inlet 27a to the first cylindrical channel section 28A of the cylindrical channel 28. The wide channel 36 has a longitudinal channel 36a that extends along the longitudinal direction L of the cylindrical channel 28. This longitudinal channel 36a not only distributes the molten resin to the longitudinal center of the cylindrical channel 28, but also efficiently distributes the molten resin to both longitudinal ends of the cylindrical channel 28 that are far from the longitudinal center.
[0047] Furthermore, in this embodiment, the first throttling member 17 has a plurality of first throttling channels 42 arranged along the circumferential direction of the cylindrical channel 28. The wide channel 36 communicates with the second cylindrical channel section 28B via the first cylindrical channel section 28A and the plurality of first throttling channels 42. The plurality of first throttling channels 42 are formed such that their length in the vertical direction increases as they approach the longitudinal center of the cylindrical channel 28. Therefore, when molten resin flows into the longitudinal central portion of the first cylindrical channel section 28A via the short second path R2 passing through the longitudinal channel 36a and gradient channel 36c of the wide channel 36, it flows slowly through the long first throttling channels 42, i.e., the first throttling channels 42 with high flow resistance. At the same time, when the molten resin flows into the longitudinal ends of the first cylindrical flow channel 28A via the long first path R1 through the longitudinal flow channel 36a and inclined flow channel 36b of the wide flow channel 36, it flows rapidly through the short first throttling flow channel 42, i.e., the first throttling flow channel 42 with low flow resistance. Therefore, when viewed in the circumferential direction of the cylindrical flow channel 28, the flow rate of molten resin flowing from each first throttling flow channel 42 into the second cylindrical flow channel 28B is almost constant. Thus, the flow rate of molten resin can be made uniform in the circumferential direction of the cylindrical flow channel 28.
[0048] Furthermore, the cross-section of the first throttling channel 42, which is perpendicular to the flow direction F of the molten resin, is circular. Since this circular first throttling channel 42 is formed by drilling, the processability of the first throttling channel 42 can be improved compared to the case where a throttling channel with a cross-section other than circular is formed.
[0049] Figure 8 is a cross-sectional perspective view of the second throttling member 47 of the second embodiment. In the second embodiment, the depths of the first groove 40 and the second groove 41 are formed to be constant in the circumferential direction of the cylindrical flow path 28. Furthermore, a plurality of second throttling flow paths 48, which are circular through holes penetrating vertically, are formed between the bottom of the first groove 40 and the bottom of the second groove 41. The plurality of second throttling flow paths 48 have the same length along the vertical direction, but are formed so that their diameter decreases as they approach the center in the longitudinal direction L of the cylindrical flow path 28. Molten resin is less likely to flow into the second throttling flow paths 48 with a smaller diameter compared to the second throttling flow paths 48 with a larger diameter, so the flow resistance of the second throttling flow path 48 in the center in the longitudinal direction L of the cylindrical flow path 28 is higher than that of the second throttling flow paths 48 located at both ends in the longitudinal direction L of the cylindrical flow path 28. In addition, the plurality of second throttling flow paths 48 are arranged at equal intervals in the circumferential direction of the cylindrical flow path 28.
[0050] As described above, in the second embodiment, the multiple second throttling channels 48 are formed such that their diameter decreases as they approach the longitudinal center of the cylindrical channel 28. Therefore, when molten resin flows into the longitudinal central portion of the first cylindrical channel section 28A via the short second path R2 passing through the longitudinal channel 36a and gradient channel 36c of the wide channel 36, it flows slowly through the second throttling channels 48 with smaller diameters, i.e., the second throttling channels 48 with high flow resistance. At the same time, when molten resin flows into the longitudinal ends of the first cylindrical channel section 28A via the long first path R1 passing through the longitudinal channel 36a and gradient channel 36b of the wide channel 36, it flows rapidly through the second throttling channels 48 with larger diameters, i.e., the second throttling channels 48 with low flow resistance. Consequently, when viewed in the circumferential direction of the cylindrical channel 28, the flow rate of molten resin flowing from each second throttling channel 48 into the second cylindrical channel section 28B is almost constant. Therefore, the flow rate of the molten resin can be made uniform in the circumferential direction of the cylindrical flow path 28.
[0051] In the second embodiment described above, an example was given in which the diameters of the multiple second throttling channels 48 were different. However, the multiple throttling channels may have the same diameter, and the inner surfaces of the throttling channels located at both ends in the longitudinal direction of the cylindrical channel 28 may be surface-treated to increase their slipperiness. This surface treatment is, for example, fluorine treatment, but is not limited to this. Even with throttling channels located at both ends in the longitudinal direction of the cylindrical channel 28, the molten resin can be flowed more quickly than with a throttling channel located in the center in the longitudinal direction of the cylindrical channel 28, making the flow rate of molten resin flowing into the second cylindrical channel section 28B uniform in the circumferential direction of the cylindrical channel 28.
[0052] Furthermore, while the above embodiments disclose an example in which a parison P having a flat, cylindrical cross-sectional shape is extruded to produce a similarly flat, cylindrical hollow molded product S, the flat, cylindrical parison P may also be molded into multiple ampoule containers having different cross-sectional shapes, such as cylinders, using a molding die for ampoule container manufacturing. [Explanation of Symbols]
[0053] 2. Die head 15. Head body 16.. First upper body 17. Constriction channel forming member (first constriction member) 18...2nd upper body 19...First lower body 20...Second lower body B...body 22. First Mandrel 23. Second Mandrel M... Mandrel 27. Resin channel 28...Cylindrical channel 28A...First cylindrical flow channel 28B...Second cylindrical flow channel 36. Wide channel 27a...Inlet 42...First aperture channel 47. Constriction channel forming member (second constriction member) 48...Second aperture channel
Claims
1. A die head that extrudes molten resin from an extruder as a cylindrical parison, A body with an opening on the lower vertical side, A mandrel placed inside the body, A resin channel is provided between the inner circumferential surface of the body and the outer circumferential surface of the mandrel, and has a cylindrical channel through which the molten resin flows from the upper side to the lower side in the vertical direction, Equipped with, The cylindrical channel is formed such that the cross-section perpendicular to the flow direction of the molten resin is flattened. The resin channel further has an inlet for supplying the molten resin to the cylindrical channel side, The die head is characterized in that the inlet is located vertically above the cylindrical flow channel at the longitudinal center of the cylindrical flow channel in the cross-sectional view.
2. The resin channel has a wide channel that allows the molten resin supplied from the inlet to flow into the cylindrical channel. The die head according to claim 1, characterized in that the wide channel extends along the longitudinal direction of the cylindrical channel.
3. The wide channel and the cylindrical channel are in communication via a plurality of throttling channels arranged along the circumferential direction of the cylindrical channel. The die head according to claim 2, characterized in that the plurality of throttling channels are formed such that their length in the vertical direction increases as they approach the longitudinal center of the cylindrical channel.
4. The wide channel and the cylindrical channel are in communication via a plurality of throttling channels arranged along the circumferential direction of the cylindrical channel. The die head according to claim 2, characterized in that the plurality of throttling channels are formed such that their diameter decreases as they approach the longitudinal center of the cylindrical channel.
5. The wide channel and the cylindrical channel are in communication via a plurality of throttling channels arranged along the circumferential direction of the cylindrical channel. The die head according to claim 2, characterized in that the inner surfaces of the aperture channels located at both longitudinal ends of the cylindrical channel among the plurality of aperture channels are surface-treated to improve slipperiness.
6. The wide channel and the cylindrical channel are in communication via a plurality of throttling channels arranged along the circumferential direction of the cylindrical channel. The die head according to claim 2, characterized in that the cross-sections of the plurality of throttling channels perpendicular to the flow direction of the molten resin are circular.
7. A hollow molding machine having a die head according to any one of claims 1 to 6.