JPH0790593B2 - Blow molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a blow molding method in which a parison is pinched by a pair of molds having a molded product shape cavity and air is supplied into the parison for molding. In particular, the present invention relates to a blow molding method suitable for producing a molded product having a reduced diameter portion such as a constricted portion.

[Conventional technology]

As shown in FIG. 8, a conventional blow molding machine for molding a resin container (molded product) 1 having a reduced diameter portion 1C in the middle as shown in FIG. The pair of molds 3 and 5 thus formed are arranged to face each other on the left and right, and the extrusion die 6 is opened from above toward the space between the molds 3 and 5, and the extrusion die 6
There is a structure in which an air supply nozzle 8 is protruded from below to a position between the molds 3 and 5 from below. Then, when the parison 7 supplied from the extrusion die 6 reaches the lower end position of the molds 3, 5, the molds 3, 5 move toward the parison 7 and move the parison 7 as shown in FIG. Pinch. At the same time, air is supplied from the air supply nozzle 8 into the parison 7,
As shown in FIG. 10, the parison 7 has the cavities 2,4.
The molded article 1 as shown in FIG. 11 is molded by being pressed against the inner peripheral surface and cooled. Reference numeral 6A is a core provided in the extrusion die 6.

[Problems to be solved by the invention]

In the conventional blow molding method described above, when the parison 7 has a small diameter, particularly the same diameter as the reduced diameter portion 1C of the molded product 1 or a diameter smaller than that, as shown in FIG. 13, the expanded diameter portion 1A (1B )
Then, the material was stretched and became significantly thinner than the wall thickness of the reduced diameter portion 1C, and there was a problem when it was used as a component requiring strength. It is also possible to adjust the wall thickness of the molded product by adjusting the gap (slit) of the extrusion die 6, but it is difficult to actually adjust the wall thickness and the wall thickness adjustment is limited.

On the other hand, if the parison 7 has a large diameter close to the expanded diameter portions 1A, 1B, the wall thickness of the expanded diameter portions 1A, 1B can be sufficiently secured.
As shown in the figure, the material is pinched in the reduced diameter portion 1C.
Moving from 7A into the cavity, a bulge 7B is formed along the pinch portion 7A. Therefore, especially when the inner diameter is small, there is a problem that the necessary inner diameter is crushed by the protrusion 7B. In addition, when the reduced diameter part has a bellows structure, it is difficult to bend the finished molded product in the direction of the raised part (upward and downward in Fig. 12), and the flexibility varies depending on the direction of the force acting on the molded product. There was a point.

Thus, in the conventional blow molding method, when molding a container having a reduced diameter portion 1C as shown in FIG. 11, crushing of the inner diameter and uneven thickness are likely to occur, so that it is required to be thin and not so durable. At present, it is used only for molding unmolded products.

The present invention has been made in view of the above-mentioned problems of the prior art, and when blow molding a molded product having a reduced diameter portion such as a constricted portion, blow molding without collapse of the inner diameter or uneven thickness It is intended to provide a way.

[Means for solving problems]

In order to achieve the above-mentioned object, in the blow molding method according to the present invention, the parison supplied between a pair of dies arranged opposite to each other is pinched from both sides by the pair of dies, and is projected into the parison. In a blow molding method in which air is supplied from the air supply nozzle into the parison, a cylindrical core with a female thread molding screw die formed on the outer peripheral surface is used so that the tip opening reaches the parison. In addition, the air supply nozzle is inserted and arranged in this core, and a predetermined reduced diameter portion of the molded product is pressure-molded by the screw mold of the core of the mold. .

Further, in the blow molding method according to claim 1, the molding surface of the mold facing the female screw portion molding screw die of the core has a male screw aligned with the female screw portion molding screw die of the core. A screw mold for forming a part is formed, so that the reduced diameter spiral bellows part of the molded product is pressure-molded by the male screw part forming screw mold of the mold and the female screw part forming screw mold of the core. It is the one.

[Action]

The parison corresponding to the position of the reduced diameter (bellows) of the constricted part of the molded product is pinched on both sides by the mold, and the internal thread of the core and the molding surface of the mold (claims) In the second term, pressure molding is performed with a male screw part forming screw die). On the other hand, the parison corresponding to the part with a large diameter other than the reduced diameter part is pinched on both sides, or even if it is not pinched, it is made to be a size close to the size of the large diameter cavity part of the cavity, and from the air supply nozzle The expansion coefficient of the parison due to the supply of air is relatively small and a sufficient wall thickness is secured.

〔Example〕

 Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of an apparatus for carrying out the blow molding method according to the present invention. As shown in FIG. 4, a molded product having a bellows structure with a reduced diameter in the central portion ( container)
FIG. 3 is a vertical sectional view of a blow molding machine for blow molding 10.

In FIG. 1, a blow molding machine 20 includes a pair of molds 23, 25 arranged facing each other in the left-right direction and slidable in the direction of arrow A, and a mold 23, 25 arranged at an upper position between the molds 23, 25. Parison between 25
Extrusion die 26 for supplying 27 and molds 23, 25
The protruding portion is arranged between the 25, the air supply nozzle 28 for supplying air into the parison 27, and the insertion is arranged in the parison 27, and cooperates with the molds 23 and 25 to partly form the molded product 10. It is composed of a core 30 for pressure molding.

A cavity 22 having a shape matching the outer peripheral surface shape of the molded product 10 is formed on each of the facing surfaces of the molds 23 and 25, and the cavity 22 has a large diameter corresponding to the expanded diameter portions 10A and 10B of the molded product 10, respectively. The hollow portions 22A, 22B and the small-diameter hollow portion 22C corresponding to the reduced-diameter bellows portion 10C. The small-diameter hollow portion 22C is formed with a female screw portion 22D that is a male screw portion forming screw die that matches the outer peripheral surface shape of the reduced-diameter bellows portion 10C of the molded product.

The parison 27 supplied between the molds 23 and 25 is the expanded diameter portion 10A, 10B.
The tip of the extrusion die 26 is adjusted so as to have a size close to the diameter of the parison, so that the parison can be pinched at the peripheral edge 21 of the cavity 22. Reference numeral 26A is a core arranged in the extrusion die 26.

At the position directly below the extrusion die 26, a cylindrical core 30 is provided
It is arranged so as to project from below to the large-diameter cavity 22A position,
An air supply nozzle 28 is inserted and arranged in the core 30.

On the outer peripheral surface of the central portion of the core 30 in the longitudinal direction, a male screw portion 32, which is a screw type for forming a female screw portion of an outer peripheral surface shape that matches the inner peripheral surface shape of the reduced diameter bellows portion 10C of the molded product 10, is formed. Thus, the reduced diameter bellows portion 10C is pressure-molded in cooperation with the small diameter hollow portion 22C of the cavity 22. A large number of small holes 34 are formed in the front end portion and the rear end portion of the core 30, and the air supplied from the air supply nozzle 28 through the small holes 34 has a large diameter hollow portion.
It can be supplied in the parison located at 22A and 22B. The root portion 31 of the core 30 has a diameter larger than the outer diameter of the male screw portion 32, and the insert member 30 can be twisted and pulled out from the opening side (downward direction in FIG. 3) of the molded product after molding. It is like this. Further, it is desirable that the molds 23, 25 and the core 30 are made of a metal having a high thermal conductivity such as iron in order to enhance the cooling effect at the time of molding.

Next, the procedure for molding the molded product 10 shown in FIG. 4 will be described by embodying the blow molding method according to the present invention with this blow molding machine 20.

First, the parison 27 is supplied from the extrusion die 26 between the molds 23 and 25. Then, as shown in FIG. 1, when the front end of the parison 27 reaches the lower ends of the molds 23 and 25 sufficiently, the extrusion die 26
Will stop supplying Parison 27 from. Molds 23 and 25 at the same time
Are brought close to each other to bring them into close contact with each other as shown in FIG. The parison protruding from the cavities of the molds 23 and 25 is pinched by the rim 21 of the cavity, while the parison at the position corresponding to the small diameter cavity 22C is located in the male screw part 32 of the core 30 and the small diameter cavity 22C of the mold. It is pressure-molded from inside and outside by the formed female screw portion 22D. The air supply nozzle 28 at the same time as the cavity peripheral portions 21 are brought into close contact with each other.
To supply air to the parison 27. Air is supplied into the parison located in the large-diameter cavities 22A and 22B through the small holes 34 of the core 30, and the parison is pneumatically molded as shown in FIG. This state is maintained until the parison cools and solidifies, and when it cools and solidifies, the core 30 is twisted and pulled out from the lower opening of the molded product, and then the molds 23, 25
And separate the molded product. In addition, the core 30 is removed from the mold
The 23 and 25 sides may be twisted, or the molds 23 and 25 may be separated and then withdrawn. Then, if necessary, burrs are removed from the molded product.

As described above, according to the blow molding method using the blow molding machine 20 according to the present embodiment, the wall thickness at the expanded diameter portions 10A and 10B is sufficiently secured, and the bulging inward at the reduced diameter bellows portion 10C. It is possible to obtain a molded product having no parts and no uneven thickness on the whole.

In the first embodiment, the blow molding of the molded product having the bellows structure has been described. However, it goes without saying that the present invention can be applied to a molded product having a flat constricted part.

5 and 6 are views showing another embodiment of the apparatus for carrying out the blow molding method according to the present invention. As shown in FIG. 7, female threads are formed on the inner peripheral surface of the constricted portion 41. FIG. 3 shows a vertical cross-sectional view of a blow molding machine for blow molding a molded product 40 having a portion 42 formed therein.

In these figures, the cavity 52 that matches the outer peripheral surface shape of the molded product 40 is provided on the facing surfaces of the pair of molds 53 and 55 that face each other.
The cavity 52 includes a large-diameter cavity 52A having an inclined surface 52B, a small-diameter cavity 52C having a uniform diameter, and a medium-diameter cavity 52D. A core 58 for pressure-molding the constricted portion 41 and the flange portion 44 of the molded product 40 is arranged directly below the extrusion die 26 in cooperation with the small diameter hollow portion 52C and the medium diameter hollow portion 52D of the cavity 52. There is.

A male screw portion 60 having a shape matching the shape of the female screw portion 42 formed on the inner peripheral surface of the constricted portion 41 of the molded product 40 is formed on the upper end surface 59 of the tip of the core 58 so as to project. The female screw portion 42 and the flange portion 44 are pressure-molded in cooperation with the portion 52C and the medium diameter hollow portion 52D. Medium cavity 52D and core 58
The gap 61 between them is set to be sufficiently smaller than the plate thickness of the parison 57, and at the time of molding, the material in this gap 61 flows toward the flange portion 44 side, and the plate thickness of the flange portion 44 becomes the ballison.
The thickness is sufficiently thicker than 57.
Further, the core 58 is hollow and has an air supply nozzle 28 inside.
Is inserted through. The size of the parison 57 supplied from the extrusion die 26 is close to that of the large diameter hollow portion 52A, and the wall thickness of the expanded diameter portion 40A of the molded product is sufficiently secured.

As described above, in this embodiment, similarly to the first embodiment described above, it is possible to mold a molded product having a sufficient thickness and no uneven thickness. Further, in the present embodiment, the upper end surface of the flange portion 44 of the molded product 40 and the female screw portion 42 of the inner peripheral surface of the constricted portion 41 are pressure-molded, so that these parts can be precisely molded. Therefore, it is possible to omit the work such as finishing of these parts after the molding.

Although the core 58 is fixed to the dies 53 and 55 in the second embodiment, the core 58 is moved upward by a force such as hydraulic pressure in a molded product which does not need to have a female screw shape. It is also possible to more effectively perform pressure molding of the flange portion 44 by performing molding while pushing up.

〔The invention's effect〕

As is clear from the above description, according to the present invention, it is possible to mold a molded product with no uneven thickness and high accuracy.

In particular, according to the present invention, a product having a complicated shape with a constriction of a spiral bellows structure, which has heretofore been considered to be impossible to be manufactured by blow molding, or a screw-fitting connection portion capable of closely contacting which requires finishing processing. It has an extremely excellent effect that it can manufacture a product requiring accuracy such as a product that the user has.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing one embodiment of a blow molding machine for carrying out the method according to the present invention, FIGS. 2 and 3 are explanatory views showing its operating state, and FIG. 4 is molded. FIG. 5 is a perspective view of a molded product, FIG. 5 is a vertical sectional view showing a second embodiment of a blow molding machine for carrying out the method according to the present invention, and FIG. 6 is an explanatory view for explaining its operating state, and FIG. The figure is a perspective view of a molded product, and FIGS. 8 to 12 are explanatory views for explaining a conventional blow molding method. FIG. 8 is a longitudinal sectional view of a conventional blow molding machine, FIG. 9 and FIG. FIG. 10 is an explanatory view for explaining its operating state, FIG. 11 is a perspective view of a molded product, and FIG.
FIG. 13 is a cross-sectional view taken along the line XII-XII shown in FIG. 10,40 …… Molded product, 10A, 10B, 40A …… Expanding part, 10C …… Reducing bellows, 20… Blow molding machine, 22,52… Cavity, 22A, 22B… Large-diameter cavity , 22C, 52C ... small-diameter cavity,
22D …… Female thread part, 23,25,53,55 …… Mold, 26 …… Extrusion die, 27,57 …… Parison, 28 …… Air supply nozzle, 30,58
...... Core, 32,60 …… Male screw part, 34 …… Small hole for air ejection, 41 …… Diameter reduction part, 52D …… Medium diameter cavity part.

Claims (2)

[Claims] 1. A parison supplied between a pair of dies opposed to each other is pinched from both sides by the pair of dies, and air is supplied into the parison from an air supply nozzle projecting into the parison. In the blow molding method of molding, a cylindrical core having a female thread molding screw die formed on the outer peripheral surface is arranged so that the tip opening reaches the parison, and the air supply is provided in the core. A blow molding method, wherein a nozzle is inserted and arranged, and a predetermined reduced diameter portion of a molded product is pressure-molded by the mold and the screw mold of the core. 2. A male screw portion forming screw die which is aligned with the female screw portion forming screw die of the core is formed on a forming surface of the die facing the female screw portion forming screw die of the core,
3. The reduced diameter spiral bellows portion of the molded product is pressure-molded by the male screw portion forming screw die of the mold and the female screw portion forming screw die of the core. The blow molding method described.