JPH05104524A - Die head for blow molding machine - Google Patents

Abstract

PURPOSE:To mold using resin of poor thermal stability such as PVC by means of a parison program device by fixing a core at the lower end of a spider, providing a shell which can deform to the core, deforming the shell by means of control of parison program device and adjusting the wall thickness of parison. CONSTITUTION:A fixed die 3 communicated with a molten resin passage 2 of a die head main body 1 is provided with a tapered space and formed in a manner of encircling the end outside measurement of the molten resin passage 2. Then, a slide die 4 is fitted on the outer periphery, and bushes 5 and 6 coated with ceramic are force fitted into fitting sections to prevent the burning and leakage of resin and make the die slidable. A shell 7 is fixed at the lower end of slide die 4, and a parison outlet is formed between the end of shell and a core 17. A rod 9 is fixed on the outer face of slide die 4 and moved up and down by a driving device for controlling the parison to control the thickness of parison. The core 17 is supported by the spider 15 and the stop section 16 is formed into an conical shape.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a die head of a blow molding machine, and more particularly to a die head for molding a resin such as vinyl chloride resin which is easily deteriorated by heat.

[0002]

2. Description of the Related Art Conventionally, as shown in FIGS. 2 and 3, a single layer die head for blow molding of polyethylene resin or polypropylene resin is known. The die head has a stick 33 penetrating a spider 31 supported by a die head main body 29 so as to be positioned above the space of the shell 30, and the stick is driven by a cylinder to move up and down, whereby the core at the tip of the stick is 34 moves up and down to change the gap a at the parison outlet formed by the shell tip 35 and the core tip to control the thickness of the parison. Conventionally, a parison programming device has been used as a device for moving the core up and down to control the parison wall thickness.By programming the parison wall thickness in advance, the core automatically moves up and down to change the parison outlet gap. The wall thickness is controlled (Japanese Patent Laid-Open No. 47-713).
No. 7, JP-A-49-53657, JP-B-63
-See 28766, etc.).

However, since the conventional die head blocks the flow of resin by the spider, in the case of a resin having poor thermal stability such as vinyl chloride resin (PVC), charring occurs and fluidity deteriorates, and the core is It became difficult to move up and down, and the thickness of the parison could not be automatically controlled by the parison programming device. Therefore, in the conventional PVC blow molding machine, the parison program device has not been used. Most PVC bottles can be molded without parison programming,
In the case of a bottle that needs to have a thick nozzle portion, it can be molded only by a post-casting molding machine, resulting in poor production efficiency.

[0004]

DISCLOSURE OF THE INVENTION The present invention is intended to solve the drawbacks of the conventional blow molding die heads and to obtain a die head which can be molded by using a parison plug rama even with a resin which is easily deteriorated by heat. Provided is a blow molding die head which improves the flow of resin in a die head of a blow molding machine and enables good molding using a parison program device without causing charring even with a resin having poor thermal stability such as PVC. The purpose is.

[0005]

In order to solve the above problems, as a result of various studies, the present inventor moved a conventional core as a method that can be controlled by a parison plug rama without interrupting the flow of resin. Instead of the above, the present invention has been accomplished by finding a method of fixing the core and moving the shell, and a good resin sealing method in that case. That is, the die head of the blow molding machine of the present invention is configured such that the core is fixed to the lower end of the spider and the shell is slidably provided so that the shell can be displaced with respect to the core, and the shell is displaced by the control of the parison program device. The parison outlet gap was adjusted. The shell is fixed to the lower end of a slide die, which is slidably provided on a fixed die fixed to the die head main body, and is displaced together with the slide die.

By pressing a ceramic-coated bush into the slide surface of the slide die with the fixed die, the resin can be reliably sealed on the slide surface, and the occurrence of charring and rust can be prevented. be able to. Further, by making the top of the spider into a conical shape and pressing the molten resin from above the apex thereof, the resin can be extruded from the parison outlet with a uniform pressure without interrupting the flow of the resin.

[0007]

[Function] The resin extruded into the die head body passes through the molten resin passage to reach above the center of the conical top of the spider, and from there to a cylindrical resin passage formed by the die inner peripheral surface and the spider outer peripheral surface. A parison is formed by flowing in and being extruded from the parison outlet gap formed by the inner peripheral tip of the shell and the outer peripheral tip of the core. At that time, the shell driving means is driven according to a preset parison program, and the slide die fixed to the shell is slid to change the gap at the parison outlet,
Controls the thickness of the parison. Since the core is fixed, it is not necessary to provide a stick for sliding the core, there is no obstruction to the resin flow, and the resin can be extruded from the upper center part of the spider into the cylindrical resin passage. As a result, the molten resin was evenly extruded into the cylindrical resin passage, the fluidity was improved, and the PVC resin, which is easily thermally deteriorated, did not cause charring. In addition, since a ceramic-coated bush is press-fitted onto the slide surface of the slide die, there is no occurrence of resin scorching or rust on the slide surface, and the resin sealing property is high. Moreover, since the slidability is good, the shell can be displaced more reliably than in the case of displacing the conventional core, and it becomes possible to control the thickness of the parison by the parison program device in PVC molding, which was impossible in the past. Can be controlled accurately and production efficiency can be improved.

[0008]

Embodiments of the present invention will be described in detail below with reference to FIG. FIG. 1 shows a die head according to an embodiment of the present invention. In the figure, 1 is a die head main body, and has a molten resin passage 2 inside. Reference numeral 3 denotes a fixed die having an upper space communicating with the molten resin passage of the die head main body that expands in a tapered shape, and is arranged so as to surround the outer end of the molten resin passage 2 and the outer peripheral portion of the fixed die 3. The slide die 4 is slidably fitted in the. Ceramic-coated bushes 5 and 6 are press-fitted into the fitting portion of the slide die with the fixed die to prevent rust and scorching of the resin at the portion and to completely remove the resin on the slide surface. I made it possible to slide by sealing. 7
Is a shell fixed to the lower end of the slide die by bolts 8 or the like, and the inner peripheral edge of the lower end of the shell forms a core outer peripheral lower end described below and a parison outlet for controlling the thickness of the parison. A rod 9 is fixed at an appropriate position on the outer peripheral portion of the slide die 4, guided by a bracket 10 provided on the die head main body, and connected to a drive rod 11 that moves up and down by a drive means such as a servo cylinder for parison control (not shown). The slide die (shell) can be slid up and down by driving the driving means. Reference numeral 15 is a spider that is fixedly supported concentrically in the internal space of the fixed die and the slide die and supports the core 17, and its top 16 is conical so as to be concentric with the tapered surface of the fixed die. Has become. The core 17 is fixed to the lower end of the spider 15, and the thickness of the parison is controlled by the size of the gap formed between the outer peripheral surface 18 of the lower end and the inner peripheral surface of the lower end of the shell. Reference numeral 19 is a parison air passage, which extends from the outer peripheral surface of the fixed die through the spider to the center of the lower end of the core.

The die head of this embodiment is constructed as described above, and the resin extruded into the die head main body passes through the molten resin passage 2 and reaches above the central portion of the conical top portion 16 of the spider, and from there, in the die. The parison is formed by flowing into a cylindrical resin passage formed by the peripheral surface and the outer peripheral surface of the spider, and being extruded from the clearance formed by the shell inner peripheral tip and the core outer peripheral tip. At that time, the shell driving means (not shown) is driven according to preset parison programming to slide the slide die 4 to which the shell 7 is fixed with respect to the fixed die 3 so that the tip of the inner peripheral surface of the shell and the outer peripheral surface of the core are separated. The wall thickness of the parison is controlled by changing the position to change the gap at the parison outlet.

As a result of molding a PVC bottle using the die head of the present embodiment having the above-mentioned structure, no resin leakage or scorching of resin from the slide surface of the slide die was found. Further, the displacement of the shell based on the control of the parison program device can be surely performed, the wall thickness of the parison can be accurately controlled, and a bottle having a desired wall thickness can be obtained. And since the molding has become possible with the rotary blow molding machine with many molds, the production efficiency is about 5 times that of the conventional post-casting molding machine that has only two molds. Rose to.

[0011]

The present invention has the following special effects. There is no need to provide a stick for sliding the core, there is no obstruction to the flow of the resin, and even if the resin has good fluidity and is easily thermally deteriorated, no charring occurs.
In addition, since the bush coated with ceramic is press-fitted on the slide surface of the slide die, there is no occurrence of resin scorching or rust on the slide surface, the resin sealing property is high, and resin leakage does not occur even if the shell is displaced. It never happens. And you can surely displace the shell,
The parison thickness can be controlled by the parison program device in the molding of a resin such as PVC that is easily deteriorated by heat, which is impossible in the past, and the thickness of the parison, that is, the thickness of the bottle can be accurately controlled. In addition, production efficiency can be improved.

[Brief description of drawings]

FIG. 1 is a schematic side sectional view of a blow molding machine die head according to an embodiment of the present invention.

FIG. 2 is a side sectional view of a conventional single-layer die head for polyethylene resin or polypropylene resin.

FIG. 3 is an enlarged view of a main part of FIG. 2, where (a) is a state in which the core is raised and the parison outlet gap is minimized, and (b) is a state in which the core is lowered and the parison outlet gap is increased. is there.

[Explanation of symbols]

1 Die Head Main Body 2 Resin Passage 3 Fixed Die 4 Slide Dies 5 and 6 Bushing 7 Shell 15 Spider 16 Spider Top 17 Core 18 Parison Exit Gap

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Claims (4)

[Claims] 1. In a die head of a blow molding machine, a core is fixed to a lower end of a spider, a shell is slidably provided so as to be displaceable with respect to the core, and the shell is displaced by control of a parison program device, thereby arranging a parison outlet. A die head for a blow molding machine, characterized in that the gap is adjusted. 2. The die head of a blow molding machine according to claim 1, wherein the shell is fixed to a lower end of a slide die provided slidably on a fixed die fixed to a die head main body. 3. The die head of a blow molding machine according to claim 2, wherein a bush coated with ceramic is press-fitted on a slide surface of the slide die with the fixed die. 4. The top of the spider is conical,
The die head of the blow molding machine according to claim 1, 2 or 3, wherein the molten resin is press-fitted from above the conical apex.