JPS6219528Y2 - - Google Patents

Description

[Detailed description of the invention] [Field of industrial application] The present invention relates to the structure of the mouth end of a thick-walled injection blow molded product. It is designed to reliably prevent this from occurring.

[Conventional technology]

So-called injection blow molding, in which the primary molded product is injected and then blow molded into the final shape, is widely used for molding various molded products, especially bottles. In the long blow molding method, when molding a thick molded product, blow molding is performed with the primary molded product attached to the core for reasons such as temperature control of the primary molded product and shrinkage due to cooling of the primary molded product. A method has been adopted to do so.

That is, (see Figures 5 to 8 below)
A primary molded product 1' is formed by injecting molten synthetic resin material into the mold cavity formed by the core 6, the mouth split mold 7, and the cavity 8, and the primary molded product 1' is Once the core 6 is cooled and hardened, remove only the cavity 8, install the blow split mold 9 in place of the cavity 8, and tighten the mold.
Pressure fluid is injected into the primary molded product 1' through a passage formed therein to blow mold the body 2' of the primary molded product 1', thereby completing the molding of the molded product 1.

[Problem that the invention attempts to solve]

By the way, thick-walled injection blow-molded products molded in this way tend to shrink when cooled. In the case of synthetic resin,
Due to this cooling shrinkage, each part of molded product 1 “shrinks”.
This may occur and cause inconvenience.

In particular, due to this "shrinkage", the mouth end surface 4' of the molded product 1 forming the packing land is not located on a flat surface as shown in FIGS. The tapered surface gradually descends, causing a significant deterioration in the packing effect.

In other words, the outer periphery of the molded product 1 and the mouth part 3 that is in contact with the mouth split mold 7 is smaller than the inner periphery side that is in contact with the core 6 over the entire molding period of the injection blow molding. Since the surface side receives a stronger cooling force, the outer peripheral surface side portion of the mouth portion 3 is cooled and hardened earlier than the inner peripheral surface side portion.
For this reason, even though the outer circumferential surface side is cooled and hardened and is not deformed, the inner circumferential surface side is cooled and shrinks and deforms, so that the mouth end surface 4' deforms into a downward shape as it goes inward. be.

This tendency, that is, the tendency that the mouth end surface 4' of the thick-walled injection blow-molded product 1 inclines inward, increases as the wall thickness increases and as the shrinkage rate of the synthetic resin material increases. In addition, if a thread is formed on the outer peripheral surface of the opening 3 as in the illustrated embodiment, the contact area of the outer peripheral surface of the opening 3 with the mold device is smaller than the inner circumference due to the thread. The area of contact with the mold device on the surface side is larger, and therefore the cooling rate on the outer peripheral surface side is higher than that on the inner peripheral surface side, and the degree of inclination deformation of the mouth end surface 4' described above is even more remarkable. becomes.

In this way, in the thick-walled injection blow-molded product 1, a difference inevitably occurs in the cooling rate between the inner circumferential surface side and the outer circumferential surface side of the mouth portion 3, but conventionally, There is no technology to prevent the occurrence of tilted deformation of the mouth end surface 4' due to the difference in cooling rate. Product 1 was maintained sealed.

However, due to the difference in cooling rate, the mouth end surface 4'
The degree of inclination deformation is not constant for each molded product 1, and therefore, it is not always possible to achieve and maintain hermetic retention of all molded products 1 reliably and stably.

The reason why the inclination deformation occurs in the mouth end surface 4' due to the difference in cooling rate between the inner peripheral surface side and the outer peripheral surface side of the mouth portion 3 is as follows.
This is because the discrepancy in cooling and hardening timing due to the above-mentioned difference in cooling rate also occurs at the mouth end 4. For example, a difference in cooling rate occurs between the inner peripheral surface side and the outer peripheral surface side of the mouth part 3. Even if the entire mouth end 4 is uniformly cooled and hardened at the same time, even if deformation force is generated in the mouth portion 3 other than the mouth end 4 due to the difference in cooling rate, it will already harden into a certain shape. The shape of the mouth end 4 should not be deformed even if this deforming force is applied.

Therefore, the technical object of the present invention is to uniformly cool and harden the entire mouth end 4 before cooling and hardening the entire mouth 3.

[Means for solving problems]

The means of the present invention is to heat only the body 2' of the injection molded primary molded product 1' (see Figure 5) and then blow mold it. At this time, a circumferential groove 5 (a fourth (see figure), the upper surface 5a of this circumferential groove 5 is parallel to the mouth end surface 4', the bottom surface 5b is parallel to the inner circumferential surface of the mouth end 4, and the depth of the circumferential groove 5 is set to the bottom surface 5b. The thickness of the mouth end portion 4 is set to be equal to the distance a.

[Effect]

On the outer peripheral surface of the mouth end 4, from the mouth end surface 4' to the mouth end 4.
Since the circumferential groove 5 is provided at a position that is lowered by a predetermined distance a determined by the wall thickness of In addition, since the upper surface 5a of the circumferential groove 5 is parallel to the mouth end surface 4' and the bottom surface 5b is parallel to the inner peripheral surface of the mouth end 4, the mouth end where the circumferential groove 5 is formed is The thickness of the portion 4 is uniform, and the thickness of the portion between the mouth end surface 4' and the circumferential groove 5 is also uniform, and the depth of the circumferential groove 5 is made equal to the thickness of the mouth end portion 4 at the bottom surface 5b. Since it is set to be equal to the distance a, the natural thickness of the mouth end 4 formed with the circumferential groove 5 becomes uniform and equal to the distance a.

Furthermore, by forming the circumferential groove 5 on the outer circumferential surface of the mouth end 4, the contact area of the outer circumferential surface of the mouth end 4 with the mold device increases by an amount corresponding to the surface area of the circumferential groove 5. Therefore, the mouth end portion 4 is in a state where it is more likely to receive cooling power from the mold device than other portions of the mouth portion 3.

Therefore, the entire region of the mouth end portion 4 is uniformly cooled by the mold device, and is cooled and hardened earlier than other portions of the mouth portion 3.

In this way, the mouth end 4 is cooled and hardened by itself separately from the other parts of the mouth 3, and this cooling and hardening is performed while it is located in the mold device, that is, when the shape is not regulated. Therefore, the mouth end surface 4' is cooled and hardened in a state in which the shape is regulated by the mold device without receiving deformation force from other parts. It will be molded into the perfect flat surface shape set by the device.

Therefore, even if the other mouth parts 3 are cooled and hardened after the mouth end part 4 is cooled and hardened, and the contraction deformation force due to this cooling hardening acts on the mouth end part 4, the mouth end part 4 has already been cooled and hardened. Therefore, the mouth end surface 4' is not deformed by the applied contraction deformation force, and the flat surface shape of the mouth end surface 4' is maintained.

In addition, specific deformation due to cooling shrinkage occurs in the mouth part 3 after the molded product 1 is released from the mold apparatus, so the cooling hardening of the mouth end part 4 occurs in the molded product 1.
It would be good if the process was completed before the process was released from the mold.

〔Example〕

In the illustrated embodiment, the circumferential groove 5 has a rectangular cross-sectional shape, but the cross-sectional shape of the circumferential groove 5 is not limited to a rectangle, and the side surface 5a is parallel to the mouth end surface 4' and the bottom surface 5b is parallel to the inner peripheral surface of the mouth end 4, and the lower side surface may be a parallel trapezoid with an outwardly downward slope.

Further, the distance a is set according to the wall thickness of the mouth end 4, and strictly speaking, it is a value set according to the physical properties of the molding material of the molded product 1, but the distance a is The setting standard is the maximum wall thickness that can be quickly cooled and hardened to the center part by the cooling power from the mold device when the molding material of molded product 1 is in contact with the mold device. It is said that

Therefore, the distance a is determined by the type of molding material, the wall thickness of the mouth end 4, and the time required until the entire injection blow molding operation is completed and the molded product 1 is released from the mold. It is a value, not a constant value.

For example, if the molded product 1 is molded from polypropylene resin and the wall thickness of the mouth end 4 is approximately 2.5 mm, the specific value of the distance a is approximately 1.5 mm at the normal injection blow molding speed. About mm is appropriate.

[Effect of idea]

As is clear from the above explanation, the present invention has a simple structure in which only a circumferential groove is provided on the outer peripheral surface of the mouth end, and the present invention can be used as a conventional injection blower without requiring special temperature control. The molding operation can be applied as is to reliably prevent the deformation of the mouth end surface due to cooling shrinkage, so it is easy to implement, and as mentioned above, no special operation is required, so it is reliable and stable. It exhibits many excellent effects, such as being able to mold the mouth end surface to provide a good packing land.

[Brief explanation of the drawing]

Figures 1 and 2 are longitudinal sectional views showing the structure of a conventional thick-walled injection blow molded product. FIG. 3 is a partially enlarged view showing an inconvenient “shrinkage” phenomenon. 3 and 4 are longitudinal cross-sectional views showing the structure of an embodiment of the thick-walled injection blow molded product according to the present invention. FIG. 3 is an overall view of the product, and FIG. FIG. 2 is an enlarged view showing the mouth end. Figures 5 to 8 are longitudinal cross-sectional views showing examples of states at major points in the injection blow molding operation. Time,
FIG. 7 shows the blow split mold in an assembled state, and FIG. 8 shows the blow molding operation. Explanation of symbols, 1; Molded product, 1'; Primary molded product,
2; body part, 3; mouth part, 4; mouth end part, 4'; mouth end surface, 5; circumferential groove, 5a; side surface, 5b; bottom surface, 6; core, 7; mouth part split mold, 8; cavity , 9; Blow split mold.

Claims (1)

[Scope of utility model registration request] In a thick-walled injection-exjection blow-molded product 1 that is blow-molded after heating only the body 2' of the injection-molded primary molded product 1', a A circumference in which the upper surface 5a is parallel to the mouth end surface 4' and the bottom surface 5b is parallel to the inner peripheral surface of the mouth end surface 4 from a position lowered by a predetermined distance a set by the wall thickness of the end portion 4. A groove 5 is provided around the circumference, and the depth of the circumferential groove 5 is set to the bottom surface 5b.
The wall thickness of the mouth end surface 4 is set to be equal to the distance a.