Blow molding die and method for manufacturing molded products

Abstract

To simplify the manufacturing process for molded products.SOLUTION: The blow molding die comprises a first die (10) and a second die (20), and is a die for performing blow molding. The first die (10) and the second die (20) each have a clamping portion (16, 26) for clamping a parison (P). The clamping portion (16) of the first mold (10) includes an opposing surface (162) facing the second mold (20) and a connecting surface (164) connected to the opposing surface (162) and facing outward. The clamping portion (26) of the second mold (20) includes a receiving surface (262) inclined relative to both the opposing surface (162) and the connecting surface (164), such that only the corner portion (163) where the opposing surface (162) and the connecting surface (164) connect can make contact.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a blow molding mold and a method for manufacturing a molded article. [Background technology]

[0002] The following Patent Documents 1 to 3 disclose blow molding techniques. In blow molding, resin softened by heat is extruded into a pipe (tube), and the pipe-shaped resin parison is sandwiched between a pair of molds. Furthermore, while the parison is sandwiched between the pair of molds and the resin is in a soft state, air is blown into the parison. The blown-in air presses the resin against the molds and cools it, solidifying the resin to obtain a molded product. Blow molding can produce molded products at lower pressures than injection molding, so the molds and other equipment are relatively simple and inexpensive. However, molded products obtained by blow molding have unwanted parts called flash, and these unwanted parts must be removed from the molded product before it can be commercialized.

[0003] There is also an injection blow molding method in which a preform is prepared by injection molding beforehand and then blow molding is performed. This injection blow molding method is highly accurate, does not require a post-process of deburring, and is highly productive, so it is used to produce a large number of products such as hollow containers or bottles. However, it is only applicable to cylindrical product shapes and requires equipment and molds for injection and blow molding, so it is used for very large-scale production. To distinguish it from the injection blow molding method, the above-mentioned molding method that does not prepare a preform is called the direct blow molding method. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-1314 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-74001 [Patent Document 3] Japanese Patent Application Laid-Open No. 2013-111839 Summary of the Invention [Problem to be solved by the invention]

[0005] The present disclosure provides a blow molding mold useful for simplifying the manufacturing process of a molded article, and a manufacturing method of the molded article. [Means for solving the problem]

[0006] [1] A blow molding die comprising a first die and a second die for performing blow molding, wherein the first die and the second die each have a clamping portion for clamping a parison, the clamping portion of the first die including an opposing surface facing the second die and a connecting surface connected to the opposing surface and facing outward, and the clamping portion of the second die including a receiving surface inclined with respect to both the opposing surface and the connecting surface so that only the corners, which are the connection points between the opposing surface and the connecting surface, can abut.

[0007] [2] The blow molding die according to [1] above, wherein the angle between the opposing surface and the connecting surface is 60° or more.

[0008] [3] A blow molding mold as described in claim 1 or 2, wherein the clamping portions of each of the first mold and the second mold are configured so that, when the parison is clamped, a gap g1 is formed between the clamping portions inside the corner portion, and the size of the gap g1 at the end on the inside of the clamping portion is 0.5 mm or more.

[0009] [4] The blow molding mold according to any one of [1] to [3] above, wherein the clamping portions of the first mold and the second mold are configured so that, when the parison is clamped, a gap g2 is formed between the clamping portions outside the connecting surface and the receiving surface, and the size of the gap g2 is 0.5 mm to 5 mm.

[0010] [5] A method for producing a molded product, comprising a molding step of performing blow molding by a direct blow method using the blow molding mold according to any one of the above [1] to [4].

[0011] [6] The method for producing a molded article according to [5] above, wherein the molded article produced by the method is a tube having an asymmetric shape with respect to the central axis. [Effects of the Invention]

[0012] According to the present disclosure, a blow molding mold useful for simplifying the manufacturing process of a molded article and a manufacturing method of a molded article are provided. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram showing an example of a blow molding apparatus. [Figure 2] FIG. 2 is a schematic diagram showing an example of a blow molding device. [Figure 3] 3(a) and 3(b) are schematic diagrams showing an example of a molded product produced using a blow molding device. [Figure 4] FIG. 4 is a schematic diagram showing an example of a pair of molds. [Figure 5] FIG. 5 is a schematic diagram showing an example of a cross section of a clamping portion of a pair of molds. [Figure 6] FIG. 6 is a schematic diagram showing an example of a cross section of a clamping portion of a pair of molds. [Figure 7] Fig. 7(a) is a schematic diagram illustrating the positional relationship between the mold and the parison when the mold is clamped, and Fig. 7(b) is a schematic diagram illustrating an example of an intermediate product immediately after molding by a blow molding machine. [Figure 8] 8(a), 8(b), 8(c), and 8(d) are schematic diagrams illustrating other molds. DETAILED DESCRIPTION OF THE INVENTION

[0014] An embodiment will be described below with reference to the drawings. In the description, the same elements or elements having the same functions are designated by the same reference numerals, and redundant description will be omitted.

[0015] [Blow molding equipment] 1 and 2 schematically show a blow molding apparatus equipped with a blow molding mold according to one embodiment. The blow molding apparatus 1 shown in FIGS. 1 and 2 is an apparatus that performs blow molding to produce a molded article made of resin. A worker may perform a predetermined operation on the molded article produced by the blow molding apparatus 1 to produce a molded article that is shipped as a finished product. The blow molding performed by the blow molding apparatus 1 is a molding that does not require the production of a preform, and the blow molding apparatus 1 performs molding by a direct blow method. Molding by the direct blow method is also called direct blow molding or extrusion blow molding.

[0016] In conventional blow molding techniques, in order to prevent burrs from occurring, molds are used that precisely contact the cavity when the molds are mated, eliminating any gaps other than the cavity portion, and sharp blades are used to remove the burrs. After further investigation, the inventors came up with the idea of ​​cutting off the burrs by contacting a corner of the mold, not a sharp blade, with the receiving surface. After further investigation, they came up with the idea of ​​creating a gap when the molds are mated and cutting off the burrs at a contact point with an angle of 60° or more (e.g., a right angle or obtuse angle). Surprisingly, the inventors found that these ideas could stably prevent burrs from occurring, and after investigating the appropriate values, they came up with the present invention.

[0017] The following describes a specific example of the blow molding apparatus 1. The blow molding apparatus 1 includes, for example, an extrusion section 2, a molding die 4, a driving section 6, and a driving section 8.

[0018] The extrusion unit 2 is a device that applies heat to raw materials to obtain molten resin and extrudes the molten resin in a pipe shape as a parison P. The extrusion unit 2 extrudes (sends) the parison P vertically downward, for example, as shown in FIG. 2. In FIGS. 1 and 2, the up-down direction is indicated by "Z." The parison P extruded vertically downward by the extrusion unit 2 may have a cavity along the up-down direction. The parison P extruded by the extrusion unit 2 may be a two-fold sheet of molten resin instead of a pipe shape.

[0019] The molding die 4 (blow molding die) is a device that performs blow molding using a pair of dies. Hereinafter, for ease of explanation, one of the pair of dies included in the molding die 4 will be referred to as the "upper die 10" and the other will be referred to as the "lower die 20." When blow molding is performed by the direct blow method using the molding die 4, the upper die 10 (first die) does not necessarily have to be placed above the lower die 20 (second die). The upper die 10 and the lower die 20 are arranged opposite each other so that the parison P can be sandwiched between them. For example, the upper die 10 and the lower die 20 are arranged so as to face each other in one horizontal direction.

[0020] The upper mold 10 and the lower mold 20 are provided so as to be movable in directions opposite to each other. In Figures 1 and 2, the upper mold 10 and the lower mold 20 face each other in direction D1. Direction D1 is, for example, a direction perpendicular to direction Z, which is the up-down direction. A drive unit 6 is connected to the upper mold 10, and a drive unit 8 is connected to the lower mold 20.

[0021] The drive unit 6 is a device that moves the upper mold 10 along the direction D1. The drive unit 8 is a device that moves the lower mold 20 along the direction D1. As shown in FIG. 2, the drive units 6 and 8 drive the upper mold 10 and the lower mold 20 so as to sandwich the parison P extruded from the extrusion unit 2. With the parison P sandwiched between the upper mold 10 and the lower mold 20, the drive units 6 and 8 clamp the molding die 4 (the upper mold 10 and the lower mold 20). The drive units 6 and 8 include, for example, hydraulic cylinders or air cylinders.

[0022] The blow molding apparatus 1 includes a blowing unit 9. The blowing unit 9 is a device capable of introducing air into the interior of the parison P when the upper mold 10 and the lower mold 20 are clamped together. The blowing unit 9 may introduce compressed air into the interior of the parison P. By introducing air from the blowing unit 9, the portion of the parison P sandwiched between the upper mold 10 and the lower mold 20 expands, and a molded product corresponding to the shape of the interior (cavity) of each of the upper mold 10 and the lower mold 20 is produced.

[0023] 3(a) and 3(b) show an example of a molded article 90 produced using the molding die 4. The molded article 90 shown in FIGS. 3(a) and 3(b) is a pipe for circulating a fluid. The molded article 90 is, for example, a pipe having an asymmetric shape with respect to a central axis. The molded article 90 may also be a pipe having a branched portion, and in one example, is a pipe formed in a T-shape or a Y-shape. FIGS. 3(a) and 3(b) show a T-shaped pipe as the molded article 90. Hereinafter, the contents of the present disclosure will be described using an example in which a T-shaped pipe is produced as the molded article 90 using the molding die 4.

[0024] The molded article 90 includes a first portion 90a and a second portion 90b. The flow path in the first portion 90a and the flow path in the second portion 90b are connected to each other. The first portion 90a is formed to extend along a central axis Ax1. The central axis Ax1 is an imaginary axis passing through the center of the flow path formed by the first portion 90a in a cross section of the first portion 90a. The second portion 90b is formed to extend along a central axis Ax2 that intersects with the central axis Ax1 and is connected to an intermediate portion of the first portion 90a in a direction along the central axis Ax1. The central axis Ax2 is an imaginary axis passing through the center of the flow path formed by the second portion 90b in a cross section of the second portion 90b. The central axis Ax2 may be perpendicular to the central axis Ax1.

[0025] When there are multiple central axes passing through the center of the flow path, such as in a T-shaped or Y-shaped pipe, a pipe having an asymmetric shape with respect to the central axes means that it is asymmetric with respect to at least one of the multiple central axes (not axially symmetric). Molded product 90 is produced, for example, by removing unnecessary parts of a molded product molded by blow molding apparatus 1 by an operator. Hereinafter, to distinguish between these molded products, the molded product immediately after being molded by blow molding apparatus 1 will be referred to as an "intermediate product 96" (see FIG. 7(b)). Intermediate product 96 is an intermediate product of molded product 90.

[0026] 4 shows a schematic diagram of the portions of the upper mold 10 and the lower mold 20 where the cavities are formed. When the upper mold 10 and the lower mold 20 are clamped, the portions of the upper mold 10 and the lower mold 20 where the cavities are formed face each other. The upper mold 10 includes a cavity 12, an air injection section 14, and a clamping section 16. The lower mold 20 includes a cavity 22, an air injection section 24, and a clamping section 26.

[0027] The cavities 12 and 22 are portions having a shape corresponding to the intermediate product 96. That is, when the upper mold 10 and the lower mold 20 are clamped, the surfaces of the cavities 12 and 22 correspond to the shape of the intermediate product 96. The air injection sections 14 and 24 are portions that form a space (passage) for introducing air into the interior of the parison P when the upper mold 10 and the lower mold 20 are clamped.

[0028] The clamping portion 16 and the clamping portion 26 are portions that clamp the parison P. The clamping portion 16 is a portion of the upper mold 10 that faces the lower mold 20 and is located around the cavity 12, for example, a portion other than the cavity 12 and the air injection portion 14. The clamping portion 26 is a portion of the lower mold 20 that faces the upper mold 10 and is located around the cavity 22, for example, a portion other than the cavity 22 and the air injection portion 24.

[0029] When the upper mold 10 and the lower mold 20 are clamped, at least a portion of the clamping portion 16 contacts the parison P, and at least a portion of the clamping portion 26 contacts the parison P. When the upper mold 10 and the lower mold 20 are clamped, a portion of the clamping portion 16 may contact a portion of the clamping portion 26. The portion of the parison P that is clamped by the clamping portion 16 and the clamping portion 26 may not remain in the molded article 90 as a product.

[0030] FIG. 5 shows a schematic example of a cross section of the clamping portion 16 and the clamping portion 26 when the upper mold 10 and the lower mold 20 are clamped. The cross section in FIG. 5 is a cross section taken along the line VV shown in FIG. 4. In FIG. 5, the shapes of the cavities 12 and 22 are simplified, and the direction perpendicular to the direction D1 is indicated by "D2." The direction D2 corresponds to the direction in which the line VV in FIG. 4 extends. Some parts included in the upper mold 10 and the lower mold 20 will be described below, but the positional relationship between one part and other parts and the positional relationship of one part in a certain direction refer to the relationship when the molds are clamped.

[0031] The clamping portion 16 of the upper mold 10 includes an opposing surface 162, a connecting surface 164, and a gap forming surface 166. The opposing surface 162, the connecting surface 164, and the gap forming surface 166 are arranged in this order from the inside to the outside. "Inside" or "inside" refers to the direction toward the center (centre) of the molding die 4 when the mold is clamped, and "outside" or "outside" refers to the direction away from the center (centre) of the molding die 4 when the mold is clamped.

[0032] The facing surface 162 is a surface connected to the cavity 12. The facing surface 162 is a flat surface. The facing surface 162 faces the clamping portion 26 of the lower mold 20. When viewed from the direction D1, at least a portion of the facing surface 162 overlaps with the clamping portion 26 of the lower mold 20. The facing surface 162 may be perpendicular to the direction D1, or may be inclined (for example, slightly inclined) with respect to a plane perpendicular to the direction D1. The angle formed between the plane perpendicular to the direction D1 and the facing surface 162 is, for example, 0° to 45°, 0° to 30°, or 0° to 15°.

[0033] The connecting surface 164 is connected to the opposing surface 162 and faces outward. The connecting surface 164 is a flat surface. The connecting surface 164 is inclined with respect to the opposing surface 162 and is also inclined with respect to a plane perpendicular to the direction D1. The angle formed by the connecting surface 164 and the plane perpendicular to the direction D1 is, for example, 45° to 90°, 50° to 90°, or 60° to 90°. The gap forming surface 166 is a surface connected to the connecting surface 164. The gap forming surface 166 is a flat surface. The gap forming surface 166 may be perpendicular to the direction D1.

[0034] The portions of the clamping portion 16 that form the opposing surface 162 and the connecting surface 164 protrude further toward the lower mold 20 than the gap forming surface 166. In the direction D1, at least a part of the portions of the clamping portion 16 that form the opposing surface 162 and the connecting surface 164 may be located between the central plane CP and the end of the lower mold 20 (the end farther from the upper mold 10) in the direction D1. The central plane CP is an imaginary plane that is perpendicular to the direction D1 and passes through the center in the direction D1 of the space formed by the cavity 12 and the cavity 22.

[0035] The clamping portion 26 of the lower mold 20 includes a receiving surface 262 and a gap forming surface 266. The receiving surface 262 and the gap forming surface 266 are arranged in this order from the inside to the outside. The receiving surface 262 is a surface connected to the cavity 22. The receiving surface 262 is a flat surface. In the direction D2, the receiving surface 262 is disposed at the same position as the opposing surface 162 and at least a part of the connecting surface 164. The receiving surface 262 is a surface that is inclined with respect to both the opposing surface 162 and the connecting surface 164 so that only the corner portion 163, which is the connection point between the opposing surface 162 and the connecting surface 164, can abut. "Only the corner portion 163 abuts" means that the only portion that abuts against the receiving surface 262 is the corner portion 163.

[0036] The receiving surface 262 may be inclined with respect to a plane perpendicular to the direction D1. The angle between the receiving surface 262 and the plane perpendicular to the direction D1 is, for example, 20° to 80°, 30° to 70°, or 40° to 60°. When the central plane CP is used as the angle reference, the angle (inclination angle) of the receiving surface 262 differs from the angle of the opposing surface 162 and also differs from the angle of the connecting surface 164. In the direction D1, the receiving surface 262 may be located between the central plane CP and an end of the lower mold 20 (the end farther from the upper mold 10). When the molds are clamped, only the corners 163 abut, so that a part (contact point) of the clamping portion 16 of the upper mold 10 comes into line contact with the receiving surface 262. When the upper mold 10 and the lower mold 20 are clamped together so that the corners 163 abut against the receiving surfaces 262, the parison P is cut (separated) at the locations where the corners 163 abut against the receiving surfaces 262.

[0037] FIG. 5 shows an enlarged view of the vicinity of the corner 163. The angle between the opposing surface 162 and the connecting surface 164 is indicated by "θ," and the angle θ may be 60° or greater. From the viewpoint of preventing wear of the corner 163 and escape of the parison P to be cut (movement of the parison P due to contact with the corner), the angle θ may be 70° or greater, 80° or greater, 90° or greater, 100° or greater, or 110° or greater. The angle θ may be greater than 90°. The angle θ may be smaller than 180°. From the viewpoint of facilitating the production of the upper mold 10 and the lower mold 20, the angle θ may be 170° or less, 160° or less, 150° or less, 140° or less, or 135° or less. In one example, the angle θ is greater than 90° and less than 135°.

[0038] The corner 163 contacts a portion of the receiving surface 262 other than both ends (for example, a central portion). In this case, a gap (hereinafter referred to as "gap g1"; see the enlarged view of FIG. 5) is formed between the clamping portion 16 and the clamping portion 26 inside the corner 163. In the example shown in FIG. 5, the gap g1 is the gap between the portion of the receiving surface 262 inside the corner 163 (contact portion) and the opposing surface 162. As described above, the clamping portions (clamping portion 16 and clamping portion 26) of the upper mold 10 and the lower mold 20 are configured such that, when the parison P is clamped, a gap g1 is formed between the clamping portion 16 and the clamping portion 26 inside the corner 163. The size of the gap g1 may be increased from the corner 163 toward the inside.

[0039] The size of the gap g1 at the inner ends of the clamping portions 16 and 26 may be 0.5 mm or more. The size of the gap g1 at the inner ends of the clamping portions 16 and 26 is defined as the distance in the direction D1 between the boundary portion of the clamping portion 16 with the cavity 12 (for example, the corner that is the boundary between the opposing surface 162 and the cavity 12) and the boundary portion of the clamping portion 26 with the cavity 22 (for example, the corner that is the boundary between the receiving surface 262 and the cavity 22). As a result of studies by the present inventors, it was found that by providing a gap inside the contact point between the clamping portions 16 and 26 and setting the size of the gap g1 at the inner ends of the clamping portions 16 and 26 to 0.5 mm or more, the possibility of the parison P not being able to be cut due to contact at the corners can be reduced. The size of the gap g1 at the inner ends of the clamping portion 16 and the clamping portion 26 may be greater than 0.5 mm, 0.6 mm or more, 0.7 mm or more, 0.8 mm or more, or 1.0 mm or more.

[0040] The gap forming surface 266 is a surface connected to the receiving surface 262. The gap forming surface 266 is a flat surface. The gap forming surface 266 may be perpendicular to the direction D1. The angle of the gap forming surface 266 with respect to the central plane CP is different from the angle of the receiving surface 262 with respect to the central plane CP. The gap forming surface 266 may coincide with the central plane CP. In the direction D2, at least a portion of the gap forming surface 266 is disposed in the same position as at least a portion of the gap forming surface 166. A gap (hereinafter referred to as "gap g2") is provided between the gap forming surface 166 and the gap forming surface 266. When the upper mold 10 and the lower mold 20 are clamped, the gap forming surface 166 and the gap forming surface 266 do not contact each other. As described above, the clamping portions (clamping portion 16 and clamping portion 26) of the upper mold 10 and the lower mold 20 are configured so that, when the parison P is clamped, a gap g2 is formed between the clamping portion 16 and the clamping portion 26 outside the connection surface 164 and the receiving surface 262.

[0041] By forming the gap g2, it is possible to prevent the parison P from being compressed in portions other than the contact points before the parison P is cut by the contact of the corner portion 163 with the receiving surface 262. The size of the gap g2 may be 0.5 mm to 5 mm. From the viewpoint of more reliably preventing the parison P from being compressed before cutting, the size of the gap g2 may be 0.6 mm or more, 0.7 mm or more, 0.8 mm or more, 0.9 mm or more, or 1 mm or more. From the viewpoint of facilitating the production of the mold, the size of the gap g2 may be 4.5 mm or less, 4 mm or less, 3.5 mm or less, or 3 mm or less. The size of the gap g2 is defined as the shortest distance in the direction D1 between the gap forming surface 166 and the gap forming surface 266.

[0042] The clamping portion 16 and the clamping portion 26 may be configured to form a space larger than the gap g2 outside the gap forming surfaces 166 and 266. The clamping portion 16 and the clamping portion 26 may be configured to contact each other at a location outside the gap forming surfaces 166 and 266 that does not sandwich the parison P.

[0043] The opposing surface 162, connecting surface 164, gap forming surface 166, receiving surface 262, and gap forming surface 266 form a "biting-off structure" that cuts off a portion of the parison P that is not required for the product. This biting-off structure may be provided on a portion of the periphery (outer edge) of cavity 12 and cavity 22 other than the pinch-off portion, or on the entire periphery other than the pinch-off portion.

[0044] FIG. 6 schematically shows another example of the cross section of the clamping portion 16 and the clamping portion 26 in a state in which the upper mold 10 and the lower mold 20 are clamped. Unlike the example shown in FIG. 5, the clamping portion 16 further has a second connecting surface 165. The second connecting surface 165 is disposed between the connecting surface 164 and the gap forming surface 166 and is connected to both the connecting surface 164 and the gap forming surface 166. The second connecting surface 165 is a flat surface, and the inclination angle of the second connecting surface 165 with respect to the central plane CP is different from the inclination angle of the connecting surface 164 with respect to the central plane CP. The angle θ may be 80° to 100° or 85° to 95°. In the example shown in FIG. 6, the angle θ is 90°.

[0045] The clamping unit 26 further has a second receiving surface 263. The second receiving surface 263 is disposed inward of the receiving surface 262 and is connected to the cavity 22. The second receiving surface 263 is a flat surface, and the inclination angle of the second receiving surface 263 with respect to the central plane CP is different from the inclination angle of the receiving surface 262 with respect to the central plane CP. The second receiving surface 263 may be parallel to the central plane CP or may be slightly inclined with respect to the central plane CP. When the opposing surface 162 and the second receiving surface 263 are parallel to the central plane CP, the size of the gap g1 at the inner end of the clamping unit 16 and the clamping unit 26 is determined by the shortest distance in the direction D1 between the opposing surface 162 and the second receiving surface 263.

[0046] [Manufacturing method for molded products] Next, a manufacturing method (manufacturing method for a molded product) for manufacturing a molded product 90 using a blow molding apparatus 1 equipped with a molding die 4 will be described. This manufacturing method includes a molding step and a finishing step. The finishing step is carried out after the molding step.

[0047] The molding process is a process of performing blow molding by a direct blow method using a molding die 4 (blow molding device 1). In the molding process, for example, a parison P is extruded from the extrusion unit 2 while the upper die 10 and the lower die 20 are separated from each other. Then, the drive units 6 and 8 clamp the upper die 10 and the lower die 20 so that they sandwich the parison P. FIG. 7(a) illustrates an example of the parison P spread within the molding die 4 after clamping. The parison P spreads so as to cover at least the entire cavity 22.

[0048] In the molding process, with the molds clamped, air is supplied by the blowing unit 9 to the inside of the parison P sandwiched between the upper mold 10 and the lower mold 20. This causes the parison P to expand and cool in the cavity 12 and the cavity 22. After that, the upper mold 10 and the lower mold 20 are opened by the driving units 6 and 8, and the intermediate product 96 is then removed from the molding die 4 by, for example, an operator.

[0049] FIG. 7(b) schematically illustrates an intermediate product 96. The intermediate product 96 includes a product portion 97 and a flash portion 98. The product portion 97 is a portion that includes the entire molded product 90, which is the product, and is formed to correspond to the shapes of the cavity 12 and the cavity 22. The flash portion 98 is a portion of the parison P sandwiched between the upper mold 10 and the lower mold 20 that is arranged around the cavity 12 and the cavity 22 and is a portion that is unnecessary for the molded product 90. In FIG. 7(b), a portion of the boundary (boundary line) between the product portion 97 and the flash portion 98 is indicated by "L1." This line L1 is already separated by the aforementioned bite-off structure when the intermediate product 96 is removed from the molding die 4.

[0050] The finishing process is a process in which a worker performs predetermined operations to produce a molded product 90 from an intermediate product 96. In the finishing process, for example, the worker cuts off the portion that will become the end of the pipe. In FIG. 7(b), the point (line) where the worker cuts in the finishing process is indicated by "L2." For example, by cutting line L2, the product portion 97 and the flash portion 98 are physically separated (completely separated), and a pipe with an open end is produced.

[0051] The manufacturing process including the above-described molding and finishing steps is repeated to produce a plurality of molded products 90. As described above, the molded product 90 produced by this manufacturing method is a tube having an asymmetric shape with respect to the central axis.

[0052] Although an example of a blow molding apparatus and an example of a method for manufacturing a molded product have been described above, the technology of the present disclosure is not limited to the above-described example. Various modifications are possible within the scope of the gist of the present disclosure.

[0053] Summary of this disclosure The blow molding mold (4) is a mold for performing blow molding, and includes a first mold (10) and a second mold (20). The first mold (10) and the second mold (20) each have a clamping portion (16, 26) for clamping the parison (P). The clamping portion (16) of the first mold (10) includes an opposing surface (162) facing the second mold (20) and a connecting surface (164) connected to the opposing surface (162) and facing outward. The clamping portion (26) of the second mold (20) includes a receiving surface (262) inclined with respect to both the opposing surface (162) and the connecting surface (164) so ​​that only a corner (163) that is a connecting portion between the opposing surface (162) and the connecting surface (164) can abut. When one mold contacts the other mold in a surface-to-surface contact manner, the parison is compressed or stretched, making it impossible to separate. In contrast, in the blow molding mold (4), the corners (163) contact the receiving surface (262), so that the parison (P) is more reliably cut as the mold is closed. This simplifies the work required by an operator to cut off the parts required for the product from the parts not required after the intermediate product (96) is removed from the blow molding mold (4). Therefore, the blow molding mold (4) is useful for simplifying the manufacturing process of molded products.

[0054] The angle (θ) between the opposing surface (162) and the connecting surface (164) may be 60° or more. In this case, it is possible to suppress the progression of wear of the corners 163 that occurs with repeated production of the molded product 90. In addition, the parison P is less likely to move away (movement of the parison due to contact with the corners) when the mold is closed, allowing for stable production of the molded product 90.

[0055] The clamping portions 16, 26 of the first die 10 and the second die 20 may be configured such that, when the parison P is clamped, a gap g1 is formed between the clamping portions 16, 26 on the inside of the corner 163. The size of the gap g1 at the end on the inside of the clamping portions 16, 26 may be 0.5 mm or more. In this case, the parison (P) can be cut more reliably by the corners (163) coming into contact with the receiving surface (262).

[0056] The clamping portions (16, 26) of the first mold (10) and the second mold (20) may be configured such that, when the parison (P) is clamped, a gap (g) is formed between the clamping portions (16, 26) outside the connecting surface (164) and the receiving surface (262). The size of the gap (g) may be 0.5 mm to 5 mm. In this case, it is possible to prevent the parison P from being compressed in areas other than the contact points before the parison P is cut by the contact of the corners 163 with the receiving surface 262. Therefore, it is possible to reduce the possibility that the parison P will not be cut due to the contact of the corners 163 with the receiving surface 262.

[0057] The above-described method for producing a molded product includes a molding step of performing blow molding by a direct blow method using a blow molding die (4). In this manufacturing method, a blow molding die (4) is used, which is useful for simplifying the manufacturing process of molded products.

[0058] The molded product produced by the above-described production method may be a pipe (90) having an asymmetric shape with respect to the central axis (Ax1, Ax2). When a pipe that is not axially symmetrical is produced by blow molding, many unnecessary parts such as burrs are generated. As a result, the work performed by the worker on the intermediate product obtained by blow molding can become cumbersome. However, in the above-described manufacturing method, when the mold is closed, the corner 163 abuts against the receiving surface 262, so that some of the unnecessary parts can be separated from the part that will become the product. Therefore, it is more advantageous to manufacture the above-described pipe 90 using the blow molding mold 4.

[0059] Next, the usefulness of the blow molding die (4) will be further explained with reference to Figures 8(a), 8(b), 8(c), and 8(d). Figure 8(a) shows a conventional molding die different from the molding die 4, which includes an upper die 310A and a lower die 320A. The upper die 310A and the lower die 320A do not have abutting portions formed in the clamping portion. Therefore, the parison P is not cut when the die is closed, and cutting work must be performed by an operator.

[0060] In the direct blow molding process, methods for removing unnecessary portions of the parison P, such as pars, have been proposed. One such proposal involves the installation of so-called "biting blades" (see, for example, Patent Document 1). Figure 8(b) shows a schematic diagram of an upper mold 310B and a lower mold 320B equipped with biting blades. In a half-molded mold equipped with such biting blades, contact between the sharp-angled biting blades makes it difficult to achieve airtightness. Even if the mold is airtight enough to allow air to be blown into the mold at the start of molding, repeated contact can wear down the cutting edge, making it difficult to immediately cut and / or maintain airtightness. Furthermore, relief is likely to occur in at least one of the blade and the parison, resulting in dimensional deviations and large biting marks remaining in the product.

[0061] FIG. 8(c) shows a schematic representation of upper and lower dies 310C and 320C, each having a flat-tipped protrusion offset from the other. Interlocking protrusions, such as those of upper and lower dies 310C and 320C, are incapable of separating the parison. FIG. 8(d) shows a schematic representation of upper and lower dies 310D and 320D, each having a sharp-angled cutting edge offset from the other. Interlocking cutting edges, such as those of upper and lower dies 310D and 320D, are incapable of separating the parison.

[0062] There have also been proposals for interlocking biting blades that can withstand repeated use by applying them only to the pinch-off portion (see, for example, Patent Document 2). Even with these proposed methods, it is difficult to continue biting with a sharp, symmetrical interlock. Various patent documents also propose methods for removing burrs or performing biting as a separate process after molding. However, performing this as a separate process requires a separate mold or device, which necessitates a complex mold structure, and therefore has not yet become widespread as a molding technology for actual machines.

[0063] As a result, for non-cylindrical shapes that have a lot of unnecessary parts such as burrs, and for cylindrical combination shapes such as Y-shaped and T-shaped pipes, workers must stand by and remove the unnecessary parts during molding, or expensive and low-productivity post-processing equipment such as laser processing machines or cooling-blast machines is used.

[0064] To solve these problems, the inventors worked to develop a new mold that could easily remove unwanted parisons, resulting in the blow molding mold (4) described above. In the blow molding mold (4), after the parison (P) is injected, the corner (163) of the first mold (10) makes line contact with the receiving surface (262) of the second mold (20), cutting (cutting off) before molding with air blow. The parison (P) is pressed into the mold by the air blow, and the two molds are maintained airtight by line contact. Using a sharp-angled cutting blade can cause significant wear at the tip or lead to chipping of the blade or parison. Therefore, it is preferable that the angle (θ) at the corner (163) be 60° or greater. This allows for repeated cutting that can be applied to actual machines. Furthermore, repeated use causes the die to wear, which gradually changes from line contact to surface contact, making it impossible to cut through the material. This requires maintenance such as padding and polishing the contact area, but the blow molding die (4) can be used at least several thousand times, making it a practical die.

[0065] Furthermore, in the blow molding device (1), it is preferable that the contact portion of the molds for the gnawing (the portion near the contact point) be designed taking into account the thickness of the parison (P). The unnecessary portion of the parison (P) removed by the gnawing is a thick cylindrical object or a folded sheet when extruded as the parison (P). If the molds are brought into contact with each other while ignoring this, the molds will compress the parison (P) before they come into contact with each other. As a result, there is a concern that the gnawing contact (contact of the corners with the receiving surface) will not function properly.

[0066] In contrast, in the blow molding device (1), when the molds are mated without a parison (P), a gap (g) is formed in areas other than the contact points. The optimum value of this gap (g) varies depending on the material and viscosity of the parison (P) before mating. If it is too small, mating contact will be insufficient, but if it is too large, the receiving surface will be deep, making mold mating difficult and resulting in large flash. The size of the gap (g2) is preferably at least 0.5 mm to 5 mm. When a so-called hard parison (P) is used, the size of the gap (g2) is preferably 1.2 mm or more.

[0067] The parison (P) sandwiched in the appropriate gap (g2) can be easily removed after being clipped off, reducing the amount of labor required for post-processing. If the clipping is sufficient, the unnecessary portion will naturally separate from the molding section, and any small amount of flash remaining near the clipped area in the molding section will shrink and become smaller due to residual heat. This significantly reduces post-processing work such as separation and deburring. The product (90) molded by the blow molding device (1) is inexpensive and has good dimensional accuracy. [Explanation of symbols]

[0068] 1...blow molding device, 2...extrusion section, P...parison, 4...molding mold, 10...upper mold, 16...clamping section, 162...opposing surface, 163...corner section, 164...connecting surface, 166...gap forming surface, 20...lower mold, 26...clamping section, 262...receiving surface, 266...gap forming surface, g1, g2...gap, 90...molded product

Claims

1. A blow molding die having a first mold and a second mold for blow molding, Each of the first mold and the second mold has a clamping portion that clamps a parison, The clamping portion of the first die includes an opposing surface facing the second die and a connecting surface connected to the opposing surface and facing outward, A blow molding mold, wherein the clamping portion of the second mold includes a receiving surface that is inclined with respect to both the opposing surface and the connecting surface so that only the corner portion, which is the connection point between the opposing surface and the connecting surface, can abut.

2. The blow molding die according to claim 1 , wherein the angle formed between the opposing surface and the connecting surface is 60° or more.

3. the clamping portions of the first die and the second die are configured such that, when the parison is clamped, a gap g1 is formed between the clamping portions on the inner side of the corner portion, 3. The blow molding die according to claim 1, wherein the size of the gap g1 at the inner end of the clamping portion is 0.5 mm or more.

4. the clamping portions of the first die and the second die are configured such that, when the parison is clamped, a gap g2 is formed between the clamping portions on the outer side of the connecting surface and the receiving surface; 3. The blow molding die according to claim 1, wherein the size of the gap g2 is 0.5 mm to 5 mm.

5. A method for producing a molded product, comprising a molding step of performing blow molding by a direct blow method using the blow molding mold according to claim 1 or 2.

6. The method for producing a molded product according to claim 5 , wherein the molded product produced by the method is a tube having an asymmetric shape with respect to a central axis.

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