JP2016129943A - Opening formation method of blow molding article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an opening formation method of a blow molding article, capable of easily cutting an opening on an external wall of a fuel tank or the like, and in which cut sediments are hardly left on the opening.SOLUTION: The invention relates to the opening formation method of a blow molding article, in which an opening 10 comprises an opening cylindrical part 11 and an opening cut part 12. A blow molding die 20 comprises an opening cylindrical part molding part 24, a cut part holding part 22, and a blow pin 23. After a parison 5 is tightly brought into contact with the blow molding die 20, the blow pin 23 is slid, then after the parison 5 is cooled, an opening cutting blade 27 is slid from a cutting gap part 29, for removing the parison 5 on the opening cut part 17. The opening cutting blade 27 has an opening cutting blade contact face 27c, and forms an arc-state curve face on a side where the cross sectional shape contacts the opening cylindrical part 11 in a salient-state, and a curvature radius of the opening cutting blade contact face 27c is smaller than that of an inner face of the opening cylindrical part 11.SELECTED DRAWING: Figure 13

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 and extruded from a die of a blow molding machine. Was producing blow molded products.

In this blow molded product, as shown in FIG. 1, an opening 110 is formed for taking in and out a component to be mounted inside the hollow body. The opening 110 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 FIG. 15, the opening 110 is formed by providing a slidable rotary blade 130 on a blow molding die 120 and cutting the outer wall 102 of the blow molded product 101 (for example, a patent). Reference 1).

As shown in FIGS. 15 to 17, the opening 110 is formed by forming a cutting edge 133 at the tip of the rotary blade 130, projecting the cutting edge 133 slightly into the cavity 126 and positioning the cutting edge 131 in advance. Blow molding is performed in a state of entering the inside of the mold surface of the blow molding die 120, 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. 16, the rotary blade 130 is rotated to cut away the cut portion 118 of the opening 110 to form the opening 110.
Then, as shown in FIG. 17, the blow molded product 101 is removed from the blow molding die 120 while leaving the cut portion 118 in the blow molding die 120.

However, in this method, when the cut portion 118 of the opening 110 is cut, the surface of the resin parison is cut little by little while the rotary blade 130 rotates. The remaining may fall into the hollow body. Furthermore, there was a problem that chips were generated on the cut surface and could not be cut cleanly.

Further, as shown in FIGS. 18 and 19, in order to form the opening 210 of the blow molded product 201, the tip 227 b of the opening cutting blade 227 is held by the cut piece holding part 222 of the blow molding die 220. There are some which are made to enter between the opened opening excision part 217 and the opening cylindrical part 211 and rotate the opening part cutting blade 227 to excise the opening excision part 217.

However, in this case, as shown in FIG. 20, the opening cutting blade contact surface 227 c that comes into contact with the inner surface of the opening cylindrical portion 211 of the tip end portion 227 b of the opening cutting blade 227 is the opening cylinder of the opening 210. It rotates while contacting the inner surface of the shaped portion 211. At this time, the opening portion cutting blade side portion cutting edge 227d formed on the side surface of the tip portion 227b of the opening portion cutting blade 227 also rotates while contacting the inner surface of the opening tubular portion 211.

At this time, as shown in FIG. 21, the position of the tip 227 b of the opening cutting blade 227 is shifted or the size of the opening 210 varies, so that the opening cutting blade side blade edge 227 d becomes the side wall of the opening cylindrical portion 211. The part 211a is cut too much, or as shown in FIG. 22, the opening cutting blade side blade edge 227d cuts the protruding part 211b of the opening cylindrical part 211.

In this case, the side wall part 211a and the overhanging part 211b become chips and enter the blow molded product. This chip needs to be taken out from the blow molded product, and it takes time and effort to take it out, resulting in an increase in manufacturing time and cost.

JP 2010-76297 A

  Therefore, an object of the present invention is to provide a method for forming an opening of a blow molded product that facilitates cutting of an opening of an outer wall of a fuel tank or the like and does not leave a notch in the opening.

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 blow-molded product formed by blow molding in a blow mold.
The opening is extended from the outer wall of the blow molded product, and is formed by bending the outer wall integrally from the outer wall to the outside of the blow molded product. Part
The blow molding die is provided with an opening cylindrical part forming part that forms an opening cylindrical part and a cut part holding part that forms an opening cutting part at a part corresponding to the opening part of the blow molded product, and the opening cylindrical part. A cutting gap is provided between the molding part and the excision holding part, and an opening cutting blade that can slide inside and outside the cavity through the cutting gap is provided, and the excision holding part can be slid into and out of the cavity. Provided a blow pin,
The opening cutting blade has an opening cutting blade contact surface that comes into contact with the inner surface of the opening cylindrical portion, and the opening cutting blade contact surface has a cross-sectional shape that is convexly rounded toward the side in contact with the opening cylindrical portion. Forming a curved surface in an arc shape, the radius of curvature of the opening cutting blade contact surface is smaller than the radius of curvature of the inner surface of the opening cylindrical portion,
After closely attaching the parison to the opening cylindrical part molding part and the opening excision part, after sliding the blow pin and penetrating the parison, air is blown from the blow pin into the cavity, the parison is cooled,
After the parison is cooled, the opening cutting blade is slid from the cutting gap and rotated while the opening cutting blade contact surface is in contact with the inner surface of the opening cylindrical portion, so that the parison at the opening cutting portion is cut off. This is a method for forming an opening of a blow molded product.

In the first aspect of the present invention, the opening portion extends from the outer wall of the blow molded product, and is formed by bending the outer wall integrally from the outer wall to the outside of the blow molded product, and the opening cylindrical portion. It has an opening excision part which is excised and forms an opening. For this reason, the opening cylindrical part and opening cut part of an opening part can be integrally formed from the outer wall of a blow molded product.

The blow molding die is provided with an open cylindrical part forming part for forming an open cylindrical part and a cut part holding part for forming an open cut part at a part corresponding to the opening part of the blow molded product. For this reason, the opening cylindrical part and opening cut part of an opening part can be formed simultaneously by inflating a parison at the time of blow molding, and making it closely_contact | adhere to an opening cylindrical part shaping | molding part and an opening cutting part.

A cutting gap was provided between the opening cylindrical portion forming portion and the cut portion holding portion, and an opening cutting blade that was slidable in and out of the cavity through the cutting gap was provided. For this reason, an opening part cutting blade can be slid from the clearance gap part for cutting, and an opening cutting part can be cut out from an opening cylindrical part.
Since the blow pin slidable in and out of the cavity is provided in the excision holding part, the blow pin can break through the parison, and air can be blown into the parison, so that the parison can be brought into close contact with the blow mold.

The opening cutting blade has an opening cutting blade contact surface that comes into contact with the inner surface of the opening cylindrical portion, and the opening cutting blade contact surface has a cross-sectional shape that is convexly rounded toward the side in contact with the opening cylindrical portion. A curved surface was formed in an arc shape, and the radius of curvature of the contact surface of the opening cutting blade was smaller than the radius of curvature of the inner surface of the opening cylindrical portion. For this reason, when the opening cylindrical blade is cut by the opening cutting blade, the apex of the opening cutting blade contact surface abuts the inner surface of the opening cylindrical portion, and the side edge of the opening cutting blade and the opening cylindrical shape A gap is generated between the inner surface of the opening, and the inner surface of the opening cylindrical portion and the opening cutting blade can be smoothly rotated.

After the parison is brought into close contact with the opening cylindrical portion forming portion and the opening excision portion, the blow pin is slid to penetrate the parison, and then air is blown from the blow pin into the cavity to cool the parison. For this reason, the parison is brought into close contact with the cavity by the air blown from the blow pin, the parison can be cooled in a short time, and the parison can be set to a predetermined hardness.

After cooling the parison, the opening cutting blade is slid from the cutting gap and rotated while the opening cutting blade contact surface is in contact with the inner surface of the opening cylindrical portion, so that the parison of the opening excision is cut. For this reason, when the opening cutting blade is rotated while the opening cutting blade contact surface is in contact with the inner surface of the opening cylindrical portion and the opening cylindrical blade is cut with the opening cutting blade, the opening cutting blade A gap is generated between the side end of the opening and the inner surface of the opening cylindrical portion, and the side end of the opening cutting blade does not scrape the inner surface of the opening cylindrical portion, so that chips are not generated during cutting.

According to the second aspect of the present invention, on the side surface of the tip of the opening cutting blade, on the inner side of the opening cylindrical portion than the apex of the opening cutting blade contact surface, between the opening cylindrical portion forming portion and the opening cutting portion. Is an opening forming method of a blow molded product in which an opening cutting blade side part cutting edge is formed.

In the second aspect of the present invention, on the side surface of the distal end portion of the opening cutting blade, on the inner side of the opening cylindrical portion with respect to the apex of the opening cutting blade contact surface, the opening cylindrical portion forming portion and the opening cutting portion are provided. The opening part cutting blade side part cutting edge which cut | disconnects between was formed. For this reason, when the opening cutting blade is rotated to form the opening cylindrical portion, the opening cutting blade side portion cutting edge can have a gap with the inner surface of the opening cylindrical portion, and scrape off the opening cylindrical portion. There is no.

The present invention of claim 3 is a blow molded product opening forming method in which a plurality of opening cutting blades are used and the total of the plurality of rotation angles is about 360 degrees.

In the third aspect of the present invention, a plurality of opening cutting blades are used, and the total rotation angle of each of the plurality is approximately 360 degrees. Therefore, the rotation angle of the opening cutting blade is reduced, and the processing time is reduced. It can be shortened.

After the parison is cooled, the opening cylindrical blade is cut with the opening cutting blade in order to cut the parison of the opening cutting portion by rotating the opening cutting blade contact surface against the inner surface of the opening cylindrical portion. Sometimes, there is a gap between the side edge of the opening cutting blade and the inner surface of the opening cylindrical portion, and the side edge of the opening cutting blade does not scrape the inner surface of the opening cylindrical portion, and chips are cut during cutting. Will not occur.

It is a perspective view of the fuel tank which has the opening part of the blow molded product which is embodiment of this invention. It is sectional drawing of the opening part of the blow molded product which is embodiment of this invention. It is an expanded sectional view of the part holding the cover body of the opening part of the blow molded product which is embodiment of this invention. It is sectional drawing of the part which forms the opening part of the blow molding metal mold | die used for embodiment of this invention, an opening part cutting blade and a blow pin retreat from the front end surface of an excision part holding part, and a parison becomes a cavity. It is sectional drawing of the state before closely_contact | adhering. It is sectional drawing of the part which forms the opening part of the blow molding die used for embodiment of this invention, a clearance part opening-closing member closes the clearance gap part for cutting, and an opening part cutting blade is the front-end | tip of a cutting part holding part It is sectional drawing of the state which retracted from the surface, the parison closely_contact | adhered to the cavity, and the blow pin was inserted in the parison. It is sectional drawing of the part which forms the opening part of the blow molding die used for embodiment of this invention, an opening part cutting blade retreats from the front end surface of a cutting part holding part, and a clearance gap part opening-and-closing member is for cutting FIG. 6 is a cross-sectional view of a state in which the parison of the opening bent portion of the opening is compressed by the slide mold after the gap portion is closed and air is blown from the blow pin and the parison adheres to the cavity. It is sectional drawing of the part which forms the opening part of the blow molding metal mold | die used for embodiment of this invention, and the clearance gap opening-and-closing member has the clearance gap part opened, and the cutting-blade front-end | tip part of an opening part cutting blade is It is sectional drawing of the state which approached the inside of the cavity from the clearance gap part for a cutting | disconnection. It is sectional drawing of the part which forms the opening part of the blow molding die used for the 1st Embodiment of this invention, and the cutting-blade front-end | tip part of an opening part cutting blade enters the inside of a cavity from the clearance gap part for a cutting | disconnection FIG. 5 is a cross-sectional view showing a state in which the opening cut portion of the opening portion of the parison is cut and rotated. It is sectional drawing of the part which forms the opening part of the blow molding die used for the embodiment of the present invention, and after the opening part cutting blade, the opening part gap stop member and the blow pin cut out the opening part cutting part of the parison, It is sectional drawing of the state which retracted to the part of the front end surface of a cutting part holding part. It is a bottom view which shows the rotation state of the clearance gap for cutting of the blow molding die used for embodiment of this invention, and an opening part cutting blade, and the bottom face figure provided with one opening part cutting blade in the clearance gap part for cutting It is. It is a bottom view which shows the rotation state of the clearance gap for cutting of the blow molding die used for embodiment of this invention, and an opening part cutting blade, and the bottom part figure provided with two opening part cutting blades in the clearance gap part for cutting It is. It is a bottom view which shows the rotation state of the clearance gap for cutting of the blow molding die used for other embodiment of this invention, and an opening part cutting blade, and three opening part cutting blades were provided in the clearance gap part for cutting. It is a bottom view. It is a schematic diagram which shows the state which the opening part cutting blade used for embodiment of this invention rotates, contacting the inner surface of an opening cylindrical part, and excising an opening cutting part. It is an expanded sectional view of the part of the opening part cutting blade of the blow molding die used for an embodiment of the invention, and is a sectional view in the state where the tip of the opening part cutting blade cut off the parison. It is an expanded sectional view of the gap part for cutting of a conventional blow molding die, and the part of a gap part opening-and-closing member, and a sectional view in the state where the gap part opening-and-closing member closed the gap part for cutting. It is an expanded sectional view of the gap part for cutting and the part of a gap part opening and closing member of the conventional blow molding die, and the sectional view of the state where the gap part opening and closing member slides from the gap part for cutting and opens the gap part for cutting It is. It is sectional drawing of the state after excising the opening part of the opening shaping | molding part of the conventional blow molding die. It is an expanded sectional view of the gap part for cutting of other conventional blow molding dies, and the portion of an opening part cutting blade, and is a sectional view in the state where the tip of the opening part cutting blade entered a parison. It is an expanded sectional view of the clearance gap part and opening part cutting blade part of the other conventional blow molding die, and is an expanded sectional view of the state where the tip of the opening part cutting blade entered the parison. It is a schematic diagram which shows the state which other conventional opening part cutting blades rotate, contacting the inner surface of an opening cylindrical part, and excising an opening cutting part. It is a schematic diagram which shows the state which a chip | tip produces from the inner surface of an opening cylindrical part, when the other conventional opening part cutting blade cuts off an opening cut part. It is a schematic diagram which shows the state which a chip | tip produces from the inner surface of an opening cylindrical part, when the other conventional opening part cutting blade cuts off an opening cut part.

The opening structure of a blow molded product and its forming method according to an embodiment of the present invention will be described with reference to FIGS. First, the opening part of the fuel tank for automobiles will be described with reference to FIGS. 1 to 3, and then the method for forming the opening part of the fuel tank for automobiles will be described.

FIG. 1 is a perspective view of a fuel tank 1 having a tank opening 10 formed in the embodiment of the present invention. 2 to 3 are cross-sectional views of the tank opening 10 according to the embodiment of the present invention.
In the embodiment of the present invention, as shown in FIG. 1, the fuel tank 1 has a tank opening 10 for taking in and out components attached to the inside of the fuel tank 1 such as a fuel pump (not shown). Is formed.

The fuel tank 1 is formed by blow molding, and the tank body outer wall 2 is composed of only one layer, or five layers of an outer layer, an inner layer, an intermediate layer formed between the outer layer and the inner layer, and an adhesive layer thereof. ing. In blow molding, the parison 5 composed of the above-mentioned one layer or five layers is used.
In the case of five 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. The adhesive layer is made of a thermoplastic synthetic resin that bonds the outer layer and the intermediate layer and the inner layer and the intermediate layer, respectively.

As shown in FIG. 1, the tank opening 10 is formed on the upper surface of the fuel tank 1, and the tank opening 10 is left as the tank opening 10 so that a fuel pump or the like is assembled. There are cases where the body 40 is attached and locked, or the fuel supply pipe 4 and the vent valve 3 are welded to the tank opening 10.

As shown in FIG. 2, the tank opening 10 is formed on the upper surface of the fuel tank 1, and the tank opening 10 is locked with a lid 40 attached thereto.
As shown in FIG. 2, the locking structure of the lid 40 in the tank opening 10 includes a locking ring 14 that is a lid locking member embedded in the tank opening 10 and a lock plate that is an attachment member. 15 is sandwiched.
The lid body 40 is formed in a substantially disk shape, and a flange portion 41 protruding along the inner periphery of the tank opening 10 is formed on the lower surface to prevent the lid body 40 from shifting.

The lock plate 15 that sandwiches the lid 40 has a ring shape and a cross-sectional shape formed in a flat plate shape, and an engagement claw portion 15a is formed. The locking ring 14 embedded in the tank opening 10 is formed with a locking hole 14a at a portion corresponding to the engaging claw 15a. The engaging claw 15a is inserted into the locking hole 14a, and the lid body 40 can be locked.

The tank opening 10 of the fuel tank 1 is formed integrally and continuously from the fuel tank 1 with the same material, as will be described later in the manufacturing method. A locking ring 14 is embedded in the tank opening 10. The locking ring 14 is made of a metal plate and is formed in a bent substantially cylindrical shape.
Without using the locking ring 14, a screw portion can be formed outside the opening cylindrical portion 11 of the tank opening portion 10 and the lid body 40 can be screwed.

The lock plate 15 presses the periphery of the lid 40 that closes the tank opening 10 of the fuel tank 1 against the tank opening 10, and when the lock plate 15 is attached to the locking ring 14, The lid 40 can be brought into close contact with the tank opening 10 and the sealing property can be secured.

As shown in FIG. 3, the tank opening 10 is formed of an opening cylindrical portion 11 and an opening bent portion 12.
The opening cylindrical portion 11 is formed by extending a thermoplastic synthetic resin wall composed of an outer layer, an inner layer, and an intermediate layer constituting the outer wall of the fuel tank 1 outwardly from the fuel tank 1 in a cylindrical shape. . A locking ring 14 that is a lid locking member is embedded in the outer layer of the open cylindrical portion 11. A material constituting the thermoplastic synthetic resin wall of the outer layer enters the fixing hole or notch of the locking ring 14. For this reason, the locking ring 14 can be firmly fixed to the tank opening 10.

The opening bent portion 12 is formed integrally and continuously from the tip of the opening tubular portion 11 of the tank opening 10, and expands the diameter of the opening tubular portion 11, that is, from the tip of the opening tubular portion 11. It bends outward at a right angle, and further bends in the form of a hairpin in the center direction of the tank opening 10 so as to be folded in the vicinity of the center, and a layer of thermoplastic synthetic resin is superimposed on the top and bottom to the opening surface of the tank opening 10 It is formed to have parallel outer surfaces.

For this reason, the opening bent portion 12 is configured by two layers, with the outer layer, the inner layer, and the intermediate layer constituting the wall of the fuel tank 1 overlapping each other in the vertical direction. Accordingly, the tank opening 10 is continuously formed integrally with the same material from the fuel tank 1 and has excellent sealing performance, and the portion other than the opening compression portion 13 described later of the opening bent portion 12 is thick. It is possible to ensure the strength. Further, since the intermediate layer exists, the permeation of fuel can be prevented.

The opening bent portion 12 is formed by compressing in a substantially central portion from a direction perpendicular to the surface of the tank opening 10, and an opening compression portion 13 having a thinner thickness than other portions is formed. The groove portion 18 having a concave cross section is formed over the entire circumference of the tank opening 10. The groove portion 18 of the opening compression portion 13 is fitted with a rubber seal ring 16 having a circular cross section, and when the lid body 40 is attached to the tank opening portion 10, it comes into contact with the back surface of the lid body 40, The gap between the lid 40 and the tank opening 10 can be sealed.
In addition, when forming the opening part of the tank opening part 10, the part from which the parison 5 is excised forms the opening excision part 17. FIG.

Next, based on FIG. 4 to FIG. 14, an example of a method for forming the tank opening 10 of the fuel tank for an automobile, which is a blow molded product, is an example of the method for forming the blow molded product opening that is an embodiment of the present invention. I will explain to you.
The blow molding die 20 usually sandwiches a synthetic resin parison 5 which is discharged in a molten state from a nozzle of a blow molding machine (not shown) located at the top of the blow molding die 20, with an internal cavity. It is comprised by the blow-molding die main body 21 divided into right and left so that it may shape | mold.

As shown in FIG. 4, the portion of the blow molding die 20 used in the present invention that forms the tank opening 10 is connected to the blow molding die main body 21 on the side forming the upper portion of the fuel tank 1. An open cylindrical portion forming portion 24 for forming ten open cylindrical portions 11 is provided. A cylindrical space that is the same as the inner diameter of the opening tubular portion 11 is provided inside the tank opening 10 of the opening tubular portion forming portion 24 of the blow molding die main body 21, and a columnar slide mold at the center thereof. 25 is fitted.

A slide mold tip 25 a is provided at the tip of the slide mold 25 to form the opening compression part 13. A ring-shaped slide space 25 b is formed between the slide mold 25 and the blow mold body 21. In the slide space 25b, an elongated opening cutting blade 27 and a cylindrical opening gap stopper 28 having the same circumference as the circle around which the opening cutting blade 27 rotates are attached so that the side surface of the slide mold 25 can slide. It has been. A blow pin 23 is slidably attached to the center of the slide mold 25. The bottom part of the slide mold 25 forms a cut-out holding part 22 and holds the opening cut-out part 17 of the parison 5.

The opening cut portion 17 is a portion cut from the parison 5 at an inner portion of the tank opening portion 10 in order to form the tank opening portion 10.
In order to form the open cylindrical part 11 of the tank opening 10, an open cylindrical part forming part 24 is provided at the tip of the blow molding die main body 21. The opening tubular portion forming portion 24 is provided with a locking member holding portion 24 a for holding the locking ring 14.

When the parison 5 is sandwiched inside the blow molding die 20, as shown in FIG. 5, the blow pin 23 slides into the parison 5, and air is blown into the parison 5 through the blow pin air hole 23a. I do. When blow is performed, the parison 5 is in close contact with the cavity surface 26 at the inner surface of the cut portion holding portion 22 of the blow molding die 20, and is in close contact with the opening tubular portion forming portion 24 at the tank opening 10 portion. To do. For this reason, the opening cylindrical part 11 of the tank opening part 10 can be formed in the part of the opening cylindrical part formation part 24. FIG. At this time, the opening cutting blade tip 27 b of the opening cutting blade 27 at the tip of the opening cutting blade 27 is located inside the excision holding part 22.

Furthermore, when air is continuously blown from the blow pin air hole 23a, the parison 5 that is in close contact with the cavity surface 26 can be cooled. The time for blowing air from the blow pin air hole 23a into the cavity is preferably 30 to 60 seconds. In this case, the parison 5 initially placed on the blow mold 20 was about 200 ° C., but the parison 5 can be cooled to about 60-100 ° C.

For this reason, the predetermined hardness required for the parison 5 to cut can be obtained. If the air blowing time is less than 30 seconds, the parison 5 is too soft, and the parison may stick to the opening cutting blade 27 when cut by the opening cutting blade 27 described later, and the air blowing time exceeds 60 seconds. In this case, the parison 5 becomes too hard, and the cutting by the opening cutting blade 27 is not smooth, and the parison 5 of the opening cutting portion 17 can be reliably cut by one rotation of the opening cutting blade 27. it can.

At this time, as shown in FIG. 5, a cutting gap 29 is provided between the slide tip 25a of the slide mold 25 and the cut-out holding part 22 so that the opening cutting blade 27 can slide. Yes. A gap opening / closing member 30 is provided to open and close the cutting gap 29 so that the parison 5 does not enter. Instead of the gap opening / closing member 30, the opening cutting blade 27 can be inserted into the cutting gap 29 to prevent the parison 5 from entering.

The gap opening / closing member 30 is attached to the slide space 25b on the surface opposite to the surface with which the parison 5 of the cut portion holding portion 22 abuts. The gap opening / closing member 30 includes an opening / closing slide pin 31, an opening / closing slide pin holding portion 32 that slidably holds the opening / closing slide pin 31, and an opening / closing member cylinder 33 that slides.

When the opening / closing slide pin 31 is slid by the opening / closing member cylinder 34 of the gap opening / closing member 30, the opening / closing slide pin 31 slides in an oblique direction, moves in the direction of the cutting gap 29, and closes the cutting gap 29. Can do. At this time, the other part of the cutting gap 29 that is closed by the opening / closing slide pin 31 is closed by the opening gap stopper 28.
Instead of the gap opening / closing member 30, the cutting gap 29 can be closed by the opening cutting blade 27.

Since the tip of the open / close slide pin 31 is formed in a flat slope shape, it can reach the lower surface of the cutting gap 29. Accordingly, the lower surface of the excision holding portion 22 with which the parison 5 abuts and the lower surface of the distal end of the open / close slide pin 31 can form a flat surface without unevenness, so that the parison 5 enters the cutting gap 29. The surface of the parison 5 of the cutting gap 29 can be a flat surface.

Next, as shown in FIG. 6, the slide mold 25 is lowered to form the opening bent portion 12 of the tank opening 10 of the parison 5 at the slide mold tip 25a. Thereby, as shown in FIG. 3, the parison 5 can be bent and the opening compression portion 13 can be formed in the opening bending portion 12. Further, the locking ring 14 can be firmly attached to the tank opening 10.

Next, as shown in FIG. 7, the opening / closing slide pin 31 is moved from the cutting gap 29 by operating the gap opening / closing member 30.
In the movement, the opening / closing slide pin 31 is slid by the opening / closing member cylinder 33 of the gap opening / closing member 30. By the sliding, the opening / closing slide pin 31 is guided by the opening / closing slide pin holding portion 32 and slides in an oblique direction, and moves in a direction away from the cutting gap 29 to open the cutting gap 29.

Next, the opening cutting blade 27 is slid in the direction of the cavity (downward in FIG. 7) in the slide space 25b.
The opening cutting blade 27 has an elongated opening cutting blade tip 27b and a cutting blade cylinder 27a that slides the opening cutting blade tip 27b. When the opening cutting blade 27 is slid by the cutting blade cylinder 27a after the opening cutting portion 17 of the parison 5 is brought into close contact with the cutting portion holding portion 22, the opening cutting blade tip 27b passes through the cutting gap 29. Break through Parison 5.

The opening / closing slide pin 31 closes the cutting gap 29 during blow molding so that the parison 5 does not enter the cutting gap 29, and the parison 5 of the cutting gap 29 has a flat surface. The opening cutting blade tip 27b smoothly enters the parison 5 from the clearance 29, and the opening excision 17 can be easily excised.
At this time, the tip of the opening cutting blade tip 27b is located at a position (downward in FIG. 7) that has broken through the opening cutting portion 17 of the parison 5 held by the cutting portion holding portion 22.

Next, as shown by the arrow in FIG. 8, the opening cutting blade 27 is rotated, and the inside of the tank opening 10 is formed from the parison 5 that is in close contact with the excision holding portion 22 at the opening cutting blade tip 27 b. The opening excision part 17 which is the part is excised. Since the opening cutting part 17 is held by the cutting part holding part 22 of the blow molding die 20, the opening cutting part 17 is hardly deformed, and the opening cutting blade 27 is rotated and the opening cutting part 27 is rotated by the opening cutting blade tip 27 b. Part 17 can be excised. At this time, the opening clearance gap member 28 rotates together with the opening cutting blade 27.

As shown in FIGS. 13 and 14, the opening cutting blade 27 has an opening cutting blade contact surface 27 c that contacts the inner surface of the opening cylindrical portion 11. The opening cutting blade abutting surface 27 c forms a convex arcuate curved surface on the side where the cross-sectional shape abuts on the inner surface of the opening cylindrical portion 11. The radius of curvature of the opening cutting blade contact surface 27 c is formed to be smaller than the radius of curvature of the inner surface of the opening cylindrical portion 11.

Further, on the side surface of the opening cutting blade tip 27b of the opening cutting blade 27, on the inner side (left side in FIG. 13) of the opening cylindrical portion than the apex of the opening cutting blade contact surface 27c, the opening cylindrical portion An opening cutting blade side blade edge 27d for cutting between 11 and the opening cutting portion 17 is formed. Since the opening cutting blade 27 rotates in the direction indicated by the arrow in FIG. 13, as the opening cutting blade 27 rotates, the opening cutting blade side blade edge 27 d moves between the opening cylindrical portion 11 and the opening cutting portion 17. Disconnect.

When the opening cylindrical blade 11 is cut by the opening cutting blade 27, the apex of the opening cutting blade contact surface 27c contacts the inner surface of the opening cylindrical portion 11, and the opening cutting blade contact surface 27c is curved. Thus, a gap is generated between the opening cutting blade side blade edge 27d of the opening cutting blade 27 and the inner surface of the opening cylindrical portion 11, and the opening cutting blade side blade edge 27d scrapes the inner surface of the opening cylindrical portion 11. There is nothing.

For this reason, when the opening cylindrical part 11 is cut by the opening cutting blade 27, chips are not generated, and it is not necessary to take out the chips from the inside of the fuel tank 1 after the fuel tank 1 is formed. In order to take out the chips from the inside of the fuel tank 1, washing with water has been performed, and thus a drying process is required. However, the drying process is not necessary, and the time is shortened.

At this time, when there is one opening cutting blade 27. As shown in FIG. 10, it rotates 360 degrees which is one rotation. As described above, since the parison 5 has a predetermined hardness, the opening cutting blade 27 that is a sharp blade can cut the opening cutting portion 17 in one rotation. For this reason, no chips are generated in the tank opening 10, and in combination with the effect of the opening cutting blade contact surface 27 c, it does not take time to clean the tank opening 10 after cutting.

In addition, when there are two opening cutting blades 27. As shown in FIG. 11, each rotation is 180 degrees, and the entire rotation is 360 degrees.
When there are three opening cutting blades 27. As shown in FIG. 12, each rotation is 120 degrees, and the entire rotation is 360 degrees.
In these cases, the cutting angle can be shortened by reducing the rotation angle of the opening cutting blade 27.

Then, the opening excision part 17 held by the excision part holding part 22 of the parison 5 is cut into a disk shape.
At this time, a part of the opening excision 17 can be left to be a parison connection. In this case, as will be described later, when the fuel tank 1 which is a blow molded product is taken out from the blow molding die 20, the opening cut portion 17 can be taken out from the blow molding die 20 together with the fuel tank 1. it can.

Then, the parison 5 is further cooled, and as shown in FIG. 9, the blow pin 23 is retracted from the parison 5 and the opening cutting blade tip portion 27b is retracted toward the blow molding die 20 (upward in FIG. 9). Let
Thereafter, the blow molding die 20 is opened, the fuel tank 1 is taken out from the blow molding die 20, and the opening cut portion 17 of the cut tank opening 10 is taken out from the blow molding die 20 with an extrusion pin.

DESCRIPTION OF SYMBOLS 1 Fuel tank 2 Tank main body outer wall 5 Parison 10 Tank opening part 11 Opening cylindrical part 12 Opening part bending part 17 Opening cutting part 20 Blow molding die 22 Cutting part holding part 23 Blow pin 25 Slide type 27 Opening cutting blade 27c Opening part Cutting blade contact surface 27d Opening cutting blade side portion cutting edge 29 Cutting gap portion 30 Clearance portion opening / closing member

Claims (3)

In the method of forming an opening of a synthetic resin blow-molded product that forms an opening of a blow-molded product formed by blow molding in a blow molding die,
The opening includes an opening cylindrical portion that extends from the outer wall of the blow-molded product and is integrally bent from the outer wall to the outside of the blow-molded product, and an opening cut from the opening cylindrical portion. Having an opening excision to form
The blow molding mold is provided with an opening cylindrical part forming part for forming the opening cylindrical part and a cut part holding part for forming the opening cut part in a part corresponding to the opening part of the blow molded product, A cutting gap is provided between the opening cylindrical portion forming portion and the cut portion holding portion, an opening cutting blade that is slidable in and out of the cavity through the cutting gap portion, and the cut portion holding portion is provided. A blow pin that can slide inside and outside the cavity is provided,
The opening cutting blade has an opening cutting blade contact surface that makes contact with the inner surface of the opening tubular portion, and the opening cutting blade contact surface has a cross-sectional shape that is in contact with the opening tubular portion. A curved surface is formed in a convex arcuate shape, and the curvature radius of the opening cutting blade contact surface is smaller than the curvature radius of the inner surface of the opening cylindrical portion,
After the parison is brought into close contact with the opening cylindrical portion forming portion and the opening excision portion, the blow pin is slid and penetrated through the parison, and then air is blown from the blow pin into the cavity, and the parison Cool and
After the parison is cooled, the opening cutting blade is slid from the cutting gap, and rotated while the opening cutting blade contact surface is in contact with the inner surface of the opening cylindrical portion. 4. A method for forming an opening of a blow molded product, wherein the parison is removed.   Cut between the opening cylindrical portion forming portion and the opening excision portion on the side surface of the tip portion of the opening cutting blade and on the inner side of the opening cylindrical portion from the apex of the opening cutting blade contact surface The blow-molded product opening forming method according to claim 1, wherein the opening cutting blade side blade edge is formed. 3. The method for forming an opening of a blow molded article according to claim 1, wherein a plurality of the opening cutting blades are used, and the total of the plurality of rotation angles is about 360 degrees.