JP5057524B2 - Blow molded product opening forming method - Google Patents

Description

  The present invention relates to a method for forming an opening of a blow molded product formed of a thermoplastic synthetic resin.

Conventionally, the structure of a hollow body such as a fuel tank for automobiles has been made of metal. However, in recent years, the weight of the vehicle is reduced, rust is not generated, and it is easy to mold into a desired shape. For example, those made of thermoplastic synthetic resin have been used.
For the production of a hollow body made of a thermoplastic synthetic resin, a blow molding method has been often used because of the ease of molding the hollow body. In the blow molding method, a melted thermoplastic synthetic resin member parison is formed into a cylindrical shape, extruded from a die of a blow molding machine, the parison is sandwiched between molds, and air is blown into the parison to form a hollow body such as an automobile fuel tank. Was producing blow molded products.

In this blow molded product, an opening is formed for taking in and out a component to be mounted inside the hollow body. The opening is formed by integrally forming the opening 110 at the same time that the blow molded article 101 is formed by blow molding.
For example, as shown in FIGS. 8 to 10, the opening 110 is formed by providing a slidable blade tool 130 on the blow molding die 120 and punching the outer wall of the blow molded product 101 (for example, , See Patent Document 1).

As shown in FIGS. 8 and 9, the opening 110 is formed by forming a cutting edge 131 at the tip of the bladed tool 130 and inserting the cutting edge 131 into the inside of the mold surface of the blow molding die 120 in advance. In this state, blow molding is performed, and the resin parison is brought into close contact with the cutting edge 131 to form the blow molded product 101. Thereafter, as shown in FIG. 10, the bladed tool 130 is slid into the blow mold 120, and the opening 110 is punched with the blade edge 131.
However, in this method, the cutting edge 131 is simply slid, and the cut portion of the opening 110 of the blow molded product 101 is not necessarily smooth. Moreover, when the outer wall of the fuel tank or the like is thick, it was sometimes difficult to punch.

Moreover, as shown in FIG. 11, there is also a method in which the blow molding die 220 is provided with a rotary blade 230 to form the opening 210 (see, for example, Patent Document 2).
That is, after the blow molded product 201 is molded in the blow molded mold 220, a part of the slide part 221 of the blow molded mold 220 is slid, and the rotary blade 230 forms the opening 210 of the blow molded product 201. In some cases, the opening 210 is formed by rotating the rotary blade 230.

However, when forming the opening 210 of the blow molded article 201 having a thick outer wall such as a fuel tank, the inside of the outer wall is often not sufficiently solidified within the normal molding time. When the opening 210 is formed by rotating the blade 230, the periphery thereof may be deformed. Moreover, when it waits for the inside of an outer wall to solidify completely, the cycle time of a shaping | molding process will become long and productivity will fall remarkably.
JP 11-34811 A JP 2003-220840 A

  Therefore, the present invention provides a method for forming an opening of a blow-molded product, which can easily form an opening even in a blow-molded product having a thick outer wall such as a fuel tank and can accurately form the shape of the opening. This is the issue.

The present invention of claim 1 for solving the above-described problems is a synthetic resin blow-molded product opening forming method for forming an opening of a molded product formed by blow molding in a blow molding die.
The blow molding die is provided with a cylindrical rotary blade that is slidable in and out of the cavity and rotatable with respect to the opening surface at a portion corresponding to the opening of the blow molded product. Forming a protruding part protruding from the tip part in the part,
The tip of the rotary blade is slightly extended and positioned in the cavity, and the parison is sandwiched between blow molding dies to perform blow molding.
After at least the surface of the synthetic resin of the parison is solidified, the rotating blade is slid from the inside of the cavity to the outside, and then the rotating blade is slid into the cavity while rotating so that the protrusion is the outer wall of the blow molded product. Is an opening forming method for a blow-molded product, characterized in that the opening is formed by cutting.

  According to the first aspect of the present invention, the blow molding die is a cylindrical rotary blade that can slide in and out of the cavity and can rotate in parallel with the opening surface at a portion corresponding to the opening of the blow molded product. Is provided. For this reason, the opening part of a blow molded product can be formed by rotating a cylindrical rotary blade inside the blow molding die, and the opening part can be formed simultaneously with the blow molding.

  Since the protruding part that protrudes from the tip part is formed on a part of the tip part of the rotary blade, when the rotary blade is rotated in the blow molding die to form the opening, only the protruding part is the outer wall of the blow molded product. The cutting resistance between the outer wall of the blow molded product and the rotary blade can be reduced, and the rotation can be made smoothly and easily. Moreover, since the opening is cut by the rotation of the rotary blade, the cutting surface can be smoothed.

  The tip of the rotary blade is positioned slightly overhanging in the cavity, and the parison is sandwiched between blow molding dies to perform blow molding. Can be formed, the rigidity around the opening can be increased, and in the case of a fuel tank, for example, a fuel supply pipe or a vent valve can be easily welded or attached to the opening. Become.

  After at least the surface of the synthetic resin of the parison is solidified, it is slid from the inside of the cavity to the outside. For this reason, a gap is formed between the tip of the rotary blade and the opening so that the rotary blade can rotate smoothly, there is no contact between the tip of the rotary blade and the synthetic resin wall of the opening, and the protrusion The part can freely rotate, and only the protruding part comes into contact with the synthetic resin of the part forming the opening and can be easily cut. Moreover, since an excessive stress is not applied to the cut portion of the opening, the opening can be cut without waiting until the opening is completely solidified.

  Next, while rotating the rotary blade, the projecting part cut the outer wall of the blow molded product to form an opening, so when at least the surface of the parison synthetic resin solidifies to some extent, the rotary blade is slid and rotated. The opening is formed by cutting, and blow molding and formation of the opening can be performed simultaneously. When the blow molded product is solidified to some extent, the opening can be formed, there is no deformation of the opening, the molding cycle can be accelerated, and the productivity is good.

  The present invention of claim 2 is a blow molded product opening forming method in which after the rotary blade forms the opening, the blow molding die is opened and the blow molded product is taken out.

  According to the second aspect of the present invention, after the rotary blade forms the opening, the blow molding die is opened and the blow molded product is taken out. Therefore, the blow molded product is held by the blow molding die during the formation of the opening. It is easy to cut the opening.

  The present invention of claim 3 is a blow molded product opening forming method in which the opening is formed with a flange around the opening, and the flange protrudes inward of the blow molded product.

  In the present invention of claim 3, since the flange portion is formed around the opening portion, the strength around the opening portion can be increased to absorb the impact of the opening portion. Even if it is attached by hot plate welding or the like, the opening is not deformed. Furthermore, since the flange portion is formed so as to protrude in the inner direction of the blow molded product, the upper surface of the opening portion can be smoothed, and it is easy to attach a component to the opening portion.

  The present invention of claim 4 is a blow molded product opening forming method in which the rotary blade is blow-molded by causing the tip portion to protrude 2 mm to 7 mm into the cavity of the blow-molding mold.

  In the present invention of claim 4, since the rotary blade is blow-molded by projecting the tip portion into the cavity of the blow-molding die, the flange portion formed in the opening is 2 mm to 7 mm or more. It can be formed so as to protrude in the inner direction of the blow-molded product at a height, and the opening can have sufficient strength.

  The present invention of claim 5 is a method for forming an opening of a blow molded product in which one or two protrusions of a rotary blade are formed.

  In the present invention of claim 5, since one or two protrusions of the rotary blade are formed, the portion that forms the opening of the blow molded product is cut at one or two protrusions, so the cutting force is small. And the opening 10 can be formed smoothly.

  According to the present invention of claim 6, after the outer wall of the blow molded product is cut to form an opening, the portion of the outer wall cut for the opening is held in a blow mold and taken out. It is a part formation method.

  In the present invention of claim 6, after the outer wall of the blow molded product is cut to form the opening, the portion of the outer wall cut for the opening is held and taken out by the blow molding die. The portion of the outer wall cut off can be automatically discharged.

  The present invention of claim 7 is a blow molding product opening forming method in which the tip and the protrusion of the rotary blade rotate and slide along the inner surface of the flange of the opening.

  According to the seventh aspect of the present invention, since the tip of the rotary blade and the projecting portion slide and slide along the inner surface of the flange portion of the opening portion, the inner surface of the flange portion of the opening portion is smooth and smooth. The post-processing of the opening is not necessary, and when a part is attached to the opening, the sealing performance of the opening can be improved.

In the present invention, after at least the surface of the synthetic resin of the parison is solidified, the tip of the rotary blade is slid outward from the inside of the cavity until at least the protrusion is located at the portion where the tip is located. A gap is created between the opening and the opening, so that the rotary blade can rotate smoothly, and only the protrusion comes into contact with the synthetic resin of the portion forming the opening and can be easily cut.
When the surface of the parison synthetic resin is solidified, the rotary blade can be slid, rotated and cut to form the opening, and then the blow molded product can be taken out, and blow molding and opening can be formed simultaneously. When the blow molded product is solidified to some extent, the opening can be formed, the molding cycle can be accelerated, and the productivity is good.

A blow molded product opening forming method according to an embodiment of the present invention will be described with reference to FIGS. 1 to 7 by taking an example of an automotive fuel tank opening forming method as a blow molded product.
FIG. 1 is a perspective view of a fuel tank 1 having an opening 10 formed in the embodiment of the present invention. FIG. 2 is a cross-sectional view of the blow molding die 20 used in the embodiment of the present invention. FIG. 3 is a bottom view of the rotary blade 30 assembled to the blow molding die 20 used in the embodiment of the present invention. 4-7 is sectional drawing of the opening shaping | molding part of the blow molding die 20 which shows the process of forming the opening part 10 with the rotary blade 30 in formation of the opening part of a blow molded product.

In the embodiment of the present invention, as shown in FIG. 1, the fuel tank 1 has an opening 10 for taking in and out a fuel pump (not shown) and the like.
The fuel tank 1 is formed by blow molding, and its outer wall is composed of only one layer or three layers of an outer layer, an inner layer, and an intermediate layer formed between the outer layer and the inner layer. In blow molding, a parison composed of one or three layers is used.
In the case of three layers, the outer layer and the inner layer are formed from a thermoplastic synthetic resin that has high strength and maintains strength against fuel oil, and the intermediate layer is formed from a thermoplastic synthetic resin that has very little permeation of fuel oil. Has been.

  As shown in FIG. 1, the opening 10 is formed on the upper surface of the fuel tank 1, and the opening 10 is left as it is for attaching a fuel pump or the like, and the lid is attached after the assembly. In some cases, the fuel supply pipe 4 and the vent valve 3 are welded to the opening 10.

Next, a blow mold 20 for molding the fuel tank 1 which is a blow molded product will be described with reference to FIGS.
The blow-molding mold 20 usually sandwiches a synthetic resin parison that is discharged in a molten state from a nozzle of a blow-molding machine (not shown) located above the blow-molding mold 20. It is formed by a blow molding die body 21 divided into left and right parts so as to be molded.

  The portion of the blow molding die 20 used in the present invention that forms the opening 10 is a blow molding die main body 21 on the side that forms the upper portion of the fuel tank 1 and has a diameter substantially the same as that of the opening 10. The opening 26 is formed, and the mold body opening 26 is provided with a cylindrical opening forming mold portion 24 substantially perpendicular to the surface of the cavity 25. A blade edge space 22 is formed between the opening forming mold portion 24 and the mold body opening 26 so that a blade edge at the tip of a rotary blade 30 described later can slide and rotate.

  A slide space 23 that is a space on a cylinder having a slightly larger diameter than the mold body opening 26 is formed in the back of the mold body opening 26 of the blow molding mold body 21. A space between the slide space 23 and the mold body opening 26 is formed in a step shape.

A rotary blade 30 is attached to the slide space 23 and the mold body opening 26 so as to be slidable in the axial direction and rotatable in the circumferential direction of the rotary blade 30.
The rotary blade 30 is formed in a cylindrical shape, and a root portion is formed from a thick-walled rotary blade main body 31 and a rotary blade blade portion 32 extending from the rotary blade main body 31 in the axial direction and formed thin. Is done. The rotary blade main body 31 and the rotary blade blade portion 32 are formed in a hollow shape without any step so that the periphery of the opening forming mold portion 24 can rotate, and the outer surface is between the rotary blade main body 31 and the rotary blade blade portion 32. Are stepped.

The rotary blade edge portion 32 has a tip that is circumferentially formed on the same plane without a step, and a pointed rotary blade tip 33 is formed. As for the rotary blade front-end | tip part 33, it is preferable that the cross section of the blade edge | tip is formed in the outer peripheral side being sharp.
The rotary blade portion 32 is attached in a cavity 25 of the blow molding die 20 from between the blade space 22 by means of a slide mechanism (not shown).

  A rotary blade protrusion 34 protruding from the rotary blade tip 33 is formed on a part of the rotary blade tip 33. Therefore, as will be described later, when the rotary blade 30 is rotated in the blow molding die 20 to form the opening 10, only the rotary blade protrusion 34 can scrape the outer wall of the fuel tank 1. Cutting resistance between the outer wall of the tank 1 and the rotary blade 30 is reduced, and rotation can be made smoothly and easily.

One or a plurality of rotary blade protrusions 34 can be provided.
When one or two rotary blade protrusions 34 are formed, the cutting force is reduced because the rotary blade protrusion 34 cuts the portion that forms the opening 10 of the fuel tank 1 at one or two locations. Thus, the opening 10 can be formed smoothly.

Next, a method for forming the opening 10 will be described with reference to FIGS.
First, as shown in FIG. 4, the rotary blade tip portion 33 of the rotary blade 30 protrudes into the cavity 25 of the blow molding die 20 by 2 mm to 7 mm. At this time, the rotary blade protrusion 34 protrudes further into the cavity 25 than the rotary blade tip 33.

  Then, the parison discharged from the blow molding machine is sandwiched between blow molding dies 20, and air is blown into the parison in the cavity 25 so that the parison is brought into close contact with the wall surface of the cavity 25. Then, as shown in FIG. 4, the tank body outer wall 2 of the fuel tank 1 is formed along the surface of the cavity 25. At this time, since the rotary blade tip 33 and the rotary blade protrusion 34 protrude into the cavity 25, the tank main body outer wall 2 is the rotary blade tip at the portion where the opening 10 of the tank main body outer wall 2 is formed. It protrudes to the height which added the thickness to the dimension which 33 and the rotary blade protrusion part 34 protrude.

  Then, as shown in FIG. 5, after at least the surface of the tank body outer wall 2, which is a parison, is solidified, the rotating blade 30 is moved until at least the rotating blade protrusion 34 is positioned at the position where the rotating blade tip 33 is positioned. Slide the cavity 25 outward. The tank body outer wall 2 need not be completely solidified, as long as the surface is solidified and its shape can be maintained. The rotary blade 30 is preferably slid to a portion where the rotary blade protruding portion 34 is positioned, but may be slid beyond that.

  When the surface of the synthetic resin forming the tank body outer wall 2 which is a parison is solidified to some extent, the rotary blade 30 is slid, rotated and cut to form the opening 10. As will be described later, after the opening 10 is formed, the fuel tank 1 can be taken out from the blow molding die 20, and the blow molding of the fuel tank 1 and the formation of the opening 10 can be performed simultaneously. Before the tank main body outer wall 2 is completely solidified, the opening 10 can be formed, the molding cycle can be accelerated, and the productivity is good.

  When the rotary blade 30 is slid, a gap 15 is generated between the rotary blade tip 33 of the rotary blade 30 and the outer surface of the protruding portion for forming the opening 10 of the tank body outer wall 2. Both the tip 33 and the rotary blade protrusion 34 can smoothly rotate without contacting the tank body outer wall 2. Then, next, the rotary blade protrusion 34 is slid inward until it comes into contact with the tank body outer wall 2 of the portion forming the opening 10.

  Next, as shown in FIG. 6, the rotary blade 30 is rotated in the circumferential direction and gradually lowered toward the inside of the fuel tank 1 while cutting the tank body outer wall 2 by the rotary blade protrusion 34. Then, since only the rotary blade protruding portion 34 of the rotary blade 30 is in contact with the tank main body outer wall 2, the rotary blade 30 is smoothly rotated, and the opening 10 can be easily cut and formed. Further, since the tank body outer wall 2 is cut by the rotation of the rotary blade 30, excessive stress is not applied to the opening 10, and deformation of the opening can be prevented without taking a long parison cooling time.

  Next, as shown in FIG. 7, after the rotary blade protrusion 34 cuts the tank body outer wall 2 to form the opening 10 while rotating the rotary blade 30, the rotary blade 30 is slid outward and blown. The molding die 20 is opened and the fuel tank 1 is taken out. At this time, it is preferable that the opening excision part 14 of the trace where the opening 10 is formed is held by the opening forming mold part 24 of the blow molding die 20. This holding may be performed by sucking or closely adhering the opening cut-out portion 14 from the opening forming mold portion 24, or by forming an undercut portion in the opening forming mold portion 24 and making the opening cut-out portion 14 It may be locked.

  In this case, after the opening cut portion 14 is held in the blow molding die 20 and the fuel tank 1 is taken out from the blow molding die 20, suction is stopped, or the opening forming die portion 24 is pushed out by an extrusion pin. Since the opening excision 14 is removed, automatic molding is possible, and the opening excision 14 can be automatically discharged. Further, since the opening cut portion 14 does not remain inside the fuel tank 1, no post-processing is necessary.

  When the opening 10 is formed as described above, the blow molded parison is formed to protrude into the cavity 25 by the rotary blade tip 33 and the rotary blade protrusion 34. A flange portion 11 is formed around the periphery. Because of the flange 11, the strength around the opening 10 is increased to prevent deformation when a component or the like is welded by a hot plate, and when the shock is applied to the opening 10 from the outside, the shock is absorbed. be able to. Further, since the flange portion 11 is formed so as to protrude in the inner direction of the fuel tank 1, the upper surface 13 which is the outer surface of the opening portion 10 can be smoothed, and components can be attached to the opening portion 10 or the lid can be screwed. It is easy to do.

  The rotary blade 30 is preferably blow-molded by projecting the tip 33 of the rotary blade into the cavity of the blow molding die 20 by 2 mm to 7 mm. In this case, the flange portion 11 formed in the opening 10 can be formed to protrude in the internal direction of the fuel tank 1 at a height of 2 mm to 7 mm or more, and the opening 10 has sufficient strength. it can.

  The rotary blade 30 of the blow molding die 20 can slide on the inner wall surface 12 of the flange portion 11 corresponding to the opening portion 10 of the tank body outer wall 2 and slide parallel to the inner wall surface 12 of the opening portion 10. It is provided as possible. The rotary blade tip 33 and the rotary blade protrusion 34 of the rotary blade 30 are formed so that the outside of the blade edge is sharpened, and the blade edge rotates and slides along the inner surface of the flange portion 11 of the opening 10. Thus, the inner surface of the flange portion 11 of the opening 10 can be made flat and smooth. Therefore, post-processing of the opening 10 is unnecessary, and when a part is attached to the opening 10, the sealing performance of the opening 10 can be improved. Moreover, the hot plate welding of components is also easy.

It is a perspective view of a fuel tank which has an opening which is an embodiment of the present invention. It is sectional drawing of the blow molding die used for embodiment of this invention. It is a bottom view of the rotary blade assembled | attached to the blow molding die used for embodiment of this invention. It is sectional drawing of the opening shaping | molding part of the blow molding die used for embodiment of this invention, and is a figure which shows the state by which the rotary blade was inserted in the cavity and was blow-molded. It is sectional drawing of the opening shaping | molding part of the blow molding die used for embodiment of this invention, and is a figure which shows the state which the rotary blade carried out cavity sliding after blow molding. It is sectional drawing of the opening shaping | molding part of the blow molding die used for embodiment of this invention, and is a figure which shows the state which the rotary blade rotated and excised the opening part. It is sectional drawing of the opening shaping | molding part of the blow molding die used for embodiment of this invention, and is a figure which shows the state which removed the opening part and took out the blow molded product. It is sectional drawing of the opening shaping | molding part of the conventional blow molding die. It is an expanded sectional view of the tool part with a blade of the opening shaping | molding part of the conventional blow molding die. It is an expanded sectional view in the state where a tool with a blade cut off an opening in a tool with a blade of an opening molding portion of a conventional blow molding die. It is sectional drawing of the opening shaping | molding part of the other conventional blow molding die.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel tank 2 Tank main body outer wall 10 Opening part 11 Opening flange part 20 Blow molding die 24 Opening part forming part 25 Cavity 30 Rotary blade 32 Rotary blade blade part 33 Rotary blade front-end | tip part 34 Rotary blade protrusion part

Claims (7)

In the method of forming an opening of a synthetic resin blow-molded product in which an opening of a molded product formed by blow molding is formed in a blow molding die,
The blow molding die is provided with a cylindrical rotary blade at a portion corresponding to the opening of the blow molded product so as to be slidable in and out of the cavity and rotatable with respect to the opening surface. Forming a protruding part protruding from the tip part in a part of the part,
The tip of the rotary blade is slightly extended and positioned in the cavity, and the parison is sandwiched between blow molding dies to perform blow molding,
After at least the surface of the synthetic resin of the parison is solidified, the protruding portion is formed by sliding the rotating blade from the inside of the cavity to the outside and then sliding the rotating blade into the cavity while rotating the rotating blade. Cutting the outer wall of the blow molded product to form the opening.   2. The blow-molded product opening forming method according to claim 1, wherein after the rotary blade forms the opening, the blow-molding die is opened to take out the blow-molded product.   The blow-molded product opening forming method according to claim 1 or 2, wherein the opening is formed with a flange around the opening, and the flange is formed so as to protrude in an inner direction of the blow-molded product. .   The blow-molded product opening according to any one of claims 1 to 3, wherein the rotary blade performs blow molding by projecting a tip portion of the rotary blade into a cavity of the blow molding die by 2 mm to 7 mm. Forming method.   The blow-molded product opening forming method according to any one of claims 1 to 4, wherein the rotary blade has one or two protrusions.   6. The blow molding product according to claim 1, wherein after the outer wall of the blow molded product is cut to form an opening, a portion of the outer wall cut for the opening is held and taken out by the blow molding die. The method for forming an opening of a blow molded product according to claim 1.   The opening of the blow-molded product according to any one of claims 3 to 6, wherein the tip and the protruding portion of the rotary blade slide along the inner surface of the flange portion of the opening. Part formation method.

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