JPH0757517B2 - Rotary-type hollow molding method and apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Field of Application> The present invention relates to a rotary hollow molding method and apparatus for obtaining a plastic bottle efficiently and with simple equipment, which does not require a bottle mouth finish process. Is.

<Prior Art> A method for obtaining hollow molded articles such as bottles, containers, and industrial materials using a plastic material such as polyethylene or vinyl chloride is generally a molten parison extruded from an extruder. After biting the plastic tubular body with the mold,
A blow molding method is used in which compression air is blown from the outside to form the same shape as the mold cavity.

The blow molding method includes a reciprocating method and a rotary method. Among them, the rotary method is excellent in productivity and is therefore widely used for mass-produced products.

What is the rotary system? The plastic material melted and kneaded by an extruder is continuously extruded from a die for obtaining a parison of a desired shape, and a plurality of this parison is mounted on the wheel and consists of a pair of left and right dies. It is a method of blowing the compressed air into the parison through a cylindrical blow-in port built in the mold, and molding it into the same shape as the cavity of the mold. Here, the wheel rotates in the same direction as the extrusion direction of the parison like a water wheel, and the left and right dies on the wheel start clamping immediately before the parison is bitten, and during the blow of air and the cooling of the molded product. , Mold clamping is continued, mold is opened after cooling is completed,
In this molding method, the molded product is taken out of the mold.

The molded product thus obtained is not generally in the final shape, and the mouth of the bottle is often finished in the next step.

As described above, the rotary system described above has excellent productivity and is used for mass-producing bottles of detergents, foods and the like.

On the other hand, the reciprocating method continuously extrudes a plastic material melted and kneaded by an extruder through a die for obtaining a parison of a desired shape, and this parison is a single type or multiple types on the side (one side or both sides) of the parison. The parison extruded to a predetermined length by the attached left and right pair of dies is intermittently bited, and the dies are returned to the blow station as they are.

Next, the blow pin descends and the tip of the blow pin is driven into the upper end of the parison. At the same time when the blow pin is driven, air is blown from the blow pin nozzle, and the parison that is bitten in the mold is formed into the same shape as the mold cavity. In this method, the blow pin outer diameter has the same shape as the inner diameter of the desired molded product mouth, and by driving the blow pin into the parison,
Regulate the mouth shape of molded products. The reciprocal blow molding method is called post-molding, which is because there is a method in which the blow pin is driven into the parison after the parison is cut to a predetermined size.

The reciprocating method described above has the advantage that the final product shape can be obtained only by the molding process, and is used in the manufacture of many plastic bottles, but it is mass-produced because the number of molds attached to one molding machine is small. It is not suitable for use.

<Problems to be solved by the invention> Summarizing the advantages and disadvantages of the rotary method and the reciprocating method described above, the rotary method is excellent in high-speed moldability, but needs a mouth finish in the next step, The equipment becomes complicated.

On the other hand, the reciprocating method does not require a bottle mouth finish process, but is inferior in high-speed moldability.

<Means for Solving Problems> The present invention has been described above by utilizing the advantages of the two methods and compensating for the disadvantages, that is, a plastic hollow molding method, that is, a molding method excellent in high-speed moldability that does not require a potter mouth finish process. And a device used for the implementation, in which molten thermoplastic resin is continuously extruded as a parison from a die head, the parison is bitten by a mold, and then a blow pin is driven into the upper part of the parison to form the mouth of the molded product. At the same time that the compressed air is blown into the parison at the same time as molding, it is performed at a position along the circumference of a horizontally rotating wheel to obtain a hollow molded product of the desired shape. A wheel that rotates horizontally about the wheel, and a cam follower at the inner end that reciprocates in the radial direction of the wheel via bearings that are fixed at equal intervals on the wheel. Have rods,
The mold clamping mechanism is provided at the outer end of the rod, and a vertically movable blow pin is provided above the mold clamping mechanism. The mold clamping mechanism includes a pair of platens provided at the outer ends of the rod. It consists of a mold inside each platen,
One of the pair of platens, which is closer to the fixed cam, is configured to open and close the mold by advancing and retracting with respect to the other platen by reciprocal movement of the rod due to rotation of a wheel. Is.

<Operation> The present invention is configured as described above, and the operation of the apparatus will be described. First, a thermoplastic resin is kneaded and melted by an extruder and continuously downwards as a parison from a die attached to the tip of the extruder. Extrude into.

The parison of a certain length extruded by the extruder is bitten by the mold which is clamped as the wheel rotates. At the same time, the upper part of the parison is cut by the cutter installed directly under the die.

The mold is generally attached to the platen with the bottle mouth at the top and the bottle bottom at the bottom. At the time of biting the parison, that is, at the timing when the mold is located directly below the die, the blow pin has a structure that escapes to the outside of the mold so as not to contact the parison.

The mold holding the parison rotates to the next step as the wheel rotates. Since a plurality of molds are mounted on the wheel, the next mold rotates directly below the die, bites the parison that has already been extruded to a certain length, and repeats the above operation. At this time, the mold must be sufficiently opened so as not to come into contact with the parison until just before the mold is clamped, that is, immediately before the mold is positioned immediately below the die.

Further, when the parison is bitten and the parison is further cut, the rotation of the wheel is stopped by an intermittent drive by a rotary index system using a roller cam mechanism and a Geneva mechanism to ensure the operation. The mold holding the parison rotates to the next step, where the blow pin attached to the platen advances to the center of the mold and is then driven to the upper end of the parison. The blow pin is driven by a hydraulic cylinder.

A desired bottle mouth shape is molded by driving the blow pin, but at the same time, blown air is blown from the blow pin to mold the parison into the same shape as the mold cavity and mold the desired bottle. The blow pin continues to rotate in synchronization with the mold as the wheel rotates while being driven into the parison even after air blowing. After the molded product is sufficiently cooled in the mold, the blow pin is separated from the parison, the mold is further opened, the molded product is taken out of the mold, and the series of molding steps is completed.

<Example> As an example, a method and apparatus for molding a polyethylene 220 ml capacity shampoo bottle will be described.

Polyethylene is kneaded and melted by an extruder having a φ65 screw (L / D = 25) and continuously extruded as a parison (2) from the tip die of the die head (1). The diameter of the die is φ15, the outer diameter of the parison after swell is φ19, the extrusion speed of the parison (2) is about 120 mm / sec, and the total length of the bottle is
The length of the parison (2) cut by the cutter (12) to a fixed length of 180 mm is 230 mm, and the platen (4) on the wheel (3) has eight dies (5) attached. The rotation of the wheel (3) is 4 rpm, and the pair of left and right dies (5) are clamped and opened by a link mechanism described below. A platen (4) mounted on the wheel (3) rotates around a fixed cam (6). The fixed cam (6) and the cam follower (7) are always in contact with each other, the mold is opened at the valley portion of the fixed cam (6), and the mold is clamped at the mountain portion. The details will be described below.

The link A advances when the fixed cam (6) is on the mountain,
The platen (4) operates in the mold clamping direction. At the same time, the forward movement of the link A causes the link B to turn around the fulcrum D as an axis. When the link B turns, the link and the tie bar (8) turn or retreat, and the platen (4) operates in the mold clamping direction. The mold is clamped by the series of operations described above. On the other hand, in the valley portion of the fixed cam (6), each unit operates in the opposite manner to that at the time of mold clamping, and the mold is opened. A blow pin (9) driving device is attached to the platen (4), and immediately before biting the parison (2), the air cylinder (10) is actuated to retreat to the opposite side of the mold (5) and bite the bite. Then move forward. The blow pin driving device is composed of the hydraulic cylinder for driving (11) and the blow pin (9), and after the bite of the parison (2) bites, the blow pin (9) turns into the hydraulic cylinder (11) when the wheel (3) rotates 15 °. It is driven into the upper part of the parison by the operation, and at the same time, compressed air is blown into the mold from the nozzle in the blow pin (9) to mold the parison (2) into the same shape as the mold. Driving the blow pin (9) and air blow are the rotation angle of the wheel.
It can be continued for 260 °. When the molded product is cooled, the blow pin (9) is removed from the mold (5) by the operation of the hydraulic cylinder (11), and the molded product rises while biting. Next, the molded product is removed from the blow pin (9) by the stripper plate and discharged from the molding machine. The rotation of the wheel (3) is driven by a motor, but since the roller cam type index mechanism is adopted, the peripheral speed is not constant, and the speed is extremely low immediately before the die is located directly under the die (1), and When the parison (2) is bitten, it stops for a moment, and after cutting the parison (2) with the cutter (13), it speeds up and rotates.

By the above molding method, the desired plastic bottles could be obtained at an efficiency of 32 bottles / minute.

<Effects of the Invention> Since the present invention is configured as described above, it has the following excellent practical effects.

(B) Since it is a rotary method, it uses a blow pin driving method.
There is no need to finish the mouth shape as a separate process, and it has the advantages of both rotary productivity and good reciprocating mouth finish.Shampoo, liquid detergent, seasonings, drinking water, pharmaceuticals. It can be used in a wide range of packaging bottles for toiletries, cosmetics, etc.

(B) Since the wheel rotates horizontally, it is easy and easy to take a space for discharging the molded container and collecting burrs.

(C) The opening and closing of the mold is accurately performed by a simple mechanism such as a combination of a cam and a cam follower and a link mechanism.
The entire mechanism is the same as the conventional molding machine, and it is a simple mechanism.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a mold part of an embodiment of the present invention, and FIG.
FIG. 3 is a plan view showing the mold clamping mechanism, and FIG. 3 is a schematic sectional view showing the entire device. (1) ... die head, (2) ... parison (3) ... wheel, (4) ... platen (5) ... die, (6) ... fixed cam (7) ... cam follower, (8) ... tie bar (9) … Blow pin, (10) (11)… Air cylinder (12)… Rod A, B, C… Link, D… Support point

Claims (2)

[Claims] 1. A molten thermoplastic resin is continuously extruded from a die head as a parison, the parison is bitten by a mold, and then a blow pin is driven into the upper part of the parison to mold the mouth of the molded product and at the same time the parison. A rotary hollow molding method, characterized in that a series of steps until blown with compressed air are carried out at positions along the circumference of a horizontally rotating wheel to obtain a hollow molded product having a desired shape. 2. A wheel that horizontally rotates about a fixed cam, a rod having a cam follower at its inner end that reciprocates in the radial direction of the wheel via bearings fixed on the wheel at equal intervals, and the rod. A mold clamping mechanism provided at the outer end of the rod, and a vertically movable blow pin provided above the mold clamping mechanism. The mold clamping mechanism includes a pair of platens provided at the rod outer ends and each platen. Of the pair of platens, the platen closer to the fixed cam moves forward and backward with respect to the other platen by the reciprocating movement of the rod by the rotation of the wheel. A rotary type hollow molding machine characterized by being opened and closed.