JPH0645176B2 - Rotary 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 for obtaining plastic bottles efficiently and with simple equipment, and not requiring a bottle mouth finish process. .

<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. A hollow molding method is used in which a plastic cylinder is bitten by a mold and then compressed air is blown from the outside to mold it into 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 widely used for mass-produced products because of its excellent productivity.

The rotary method continuously extrudes the plastic material melted and kneaded by an extruder from a die for obtaining a parison of a desired shape, and the parison is a pair of right and left dies mounted on the wheel one after another. Bite,
After that, compression air is blown into the parison through a blow-in port of a cylinder built in the mold, and this is molded into the same shape as the mold cavity. 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. The molding method is to continue mold clamping, open the mold after cooling is completed, and take out the molded product from 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.

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 is intermittently bited by the attached left and right pair of dies, and then returns to the blow station in that state.

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 generally called post-molding, but this is because it is a method of driving a blow pin into the parison after cutting the parison to a predetermined size.

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

<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.

The present invention relates to a plastic hollow molding method that utilizes the advantages of the above two methods and compensates for the disadvantages, that is, a molding method excellent in high-speed moldability that does not require a bottle mouth finish process.

<Means for Solving Problems> The present invention relates to a method and apparatus for using a blow pin to finish a bottle mouth to a desired shape at the same time as air blowing, and to perform this hollow molding by a rotary method. As a method, kneading by rotation of a screw, a molten thermoplastic resin is continuously extruded as a parison from a die head, bite this with a split mold attached on a wheel, and then blow compressed air into the parison. In a rotary hollow molding method for obtaining a desired plastic hollow molded article, after extruding a parison and biting with a split mold,
The parison between the lower end of the die head and the upper end of the split mold is cut, then the blow pin is driven into the parison mouth, and compressed air is blown to form the desired molded product.The device is kneaded and melted. A die head that continuously extrudes a thermoplastic resin as a parison, a plurality of split dies for equipping the parison that is extruded from the die head by biting, and a wheel provided with the split die and the split die and the die head. And a blow pin for cutting the parison between, the die head is located above the split mold at the highest position of the wheel, and the split mold opens and closes in a direction orthogonal to the extrusion direction of the parison. Further, the cutter is composed of a pair of blades that sandwich the parison in the left-right direction between the lower end of the die head and the upper end of the split mold, Serial blow pin is characterized in that provided in the split die upper end to be driven into the mouth of the parison after cutting the parison is closed split mold.

<Operation> The molding method using the apparatus of the present invention will be described in detail below.

The plastic material used is polyethylene, polypropylene, polystyrene, polyvinyl chloride, or any other thermoplastic resin generally used for blow molding. These plastic materials are kneaded and melted by an extruder, and extruded downward as a parison from a die attached to the tip of the extruder. Immediately below the die, that is, in the direction in which the parison is extruded, a pair of left and right dies mounted on the wheel is located. The mold rotates continuously as the wheel rotates. The dice are located on the normal to the top of the wheel.
The pair of left and right molds is clamped by a mechanism such as a cam and a hydraulic cylinder at the top of the wheel, that is, immediately below the die, and the parison extruded to a certain length is bitten into the mold. At the same time, the upper part of the parison is cut by the cutter installed directly under the die. Here, the mold generally has a trapezoidal shape, and a bottle mouth is formed on the upper bottom portion of the mold, and a bottle bottom portion is formed on the lower bottom portion.
That is, it is attached in the direction close to the die. The mold holding the parison rotates to the next step as the wheel rotates. Since multiple molds are mounted on the wheel, as the wheel rotates, the next mold rotates to the top of the wheel, 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.

A blow pin and a counter plate are attached to the upper bottom of each mold. The mold holding the parison rotates to the next step, where the blow pin is driven into the top of the parison. The blow pin can be driven by using a hydraulic cylinder or a cam mechanism that uses the rotational force of the wheel to simplify the equipment. The desired shape of the mouth of the bottle is molded by driving the blow pin, and at the same time, the parison is molded into the same shape as the mold cavity by blowing blow air from the blow pin, and the desired bottle is molded. 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, and the molded product is taken out of the mold.

The above is a series of explanations of the present invention, but depending on the shape of the bottle to be molded, the parison may come into contact with a predetermined position of the mold immediately before the mold is clamped, or the parison may be cut and further extruded. It may not be pushed vertically due to the force of rotation. In this case, the die for extruding the parison is provided with an accumulator structure and a so-called accumulator head that extrudes the parison instantaneously is used, or the wheel is intermittently rotated by a Geneva mechanism, an index cam mechanism, etc. This problem is solved if the rotation is stopped or the speed is slowed before and after biting.

<Example> As an example, 250 m of polyethylene using the present invention
The method and equipment for forming a bottle for a shampoo with a capacity is described.

Extruder with φ65 screw (L / D = 25) (1)
The polyethylene is kneaded and melted in, and continuously extruded as a parison (4) from the tip die (3) of the die head (2).
Die diameter is φ15, parison outer diameter after swell is approximately φ1
9. The extrusion speed of the parison is about 150 mm / sec, and 10 dies are attached to the die plate (6) on the wheel (5). Wheel rotation is 3.5 rpm. The mold (7) has a trapezoidal shape with an upper bottom of 70 m / m and a lower bottom of 110 m / m and a height of 220 m / m. The pair of left and right dies are clamped and opened by sliding the die plate. Die plate (6) Cam follower on the outside
A plate cam (10), to which (8) is attached and which is assisted by a frame (9) that supports the entire molding apparatus, slides the die plate as the wheel rotates to perform mold clamping and mold opening. The rotation of the wheel is driven by a motor, but since the index cam is used, the peripheral speed is not constant, it is extremely low immediately before the mold is located directly under the die, and for a moment immediately after biting the parison (4). Stop the cutter (1
After cutting the parison (4) in 1), it rotates at high speed.

The die (7) bites the parison (4) and simultaneously cuts the parison (4) with the cutter (11). Next, when the mold (7) is rotated by 18 °, the blow pin (12) attached to the die plate is driven into the upper end of the parison. The blow pin consists of an air blow pin (13), a lever (14), a fulcrum, and a cam follower (15) .The cam follower (15) is driven by a cam (16) attached to the frame (9) as the wheel rotates. Raise,
The blow pin is driven into the upper end of the parison by this action.

Simultaneously with the blow pin driving, air is blown into the mold to mold the parison into the same shape as the mold cavity. Blow pin driving and air blow are wheels (5)
The rotation angle of is continued for 200 °. Then, the blow pin (12) is removed from the mold by the cam for operating the blow pin. Then, subsequently, the mold is opened by the mold clamping cam. After opening the mold, the molded product is taken out from the mold by the take-out robot.

With the above molding method, the desired plastic bottle is 35
I was able to obtain it with the efficiency of books / 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 adopts a method of driving a blow pin, so there is no need to finish the mouth shape as a separate step after hollow molding the bottle, and the productivity of the rotary method is good, It has both the advantages of reciprocating method and good mouth finish, and can be used in a wide range of packaging bottles for shampoo, liquid detergent, seasonings, drinking water, pharmaceuticals, toiletries, cosmetics, etc.

(B) It is a simple mechanism that only changes the direction of the mold and the position of the die head of the conventional rotary hollow molding machine, and the timing of the blow pin and the opening and closing of the mold is matched by the combination of the cam and the cam follower. Therefore, when the mold is closed, the blow pin is accurately driven into the parison mouth, and the shape of the mouth of the bottle is finished at the same time as the hollow molding.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic side view of a rotary hollow molding device according to the present invention, and FIG. 2 is a partial sectional view showing a mold clamping mechanism and a blow pin of the rotary hollow molding device according to the present invention. (1)… Extruder, (2)… Die Head (3)… Die, (4)… Parison (5)… Wheel, (6)… Die Plate (7)… Mold, (8)… Cam Follower (9) ) ... Frame, (10) ... Plate cam (11) ... Cutter, (12) ... Blow pin (13) ... Pin, (14)… Lever (15)… Cam follower, (16)… Cam

Claims (2)

[Claims] 1. A thermoplastic resin, which is kneaded and melted by rotating a screw, is continuously extruded from a die head as a parison, which is bitten by a split mold mounted on a wheel, and then compressed air is blown into the parison. In a rotary hollow molding method for obtaining a desired plastic hollow molded product, a parison is extruded, bitten by a split mold, then the parison between the lower end of the die head and the upper end of the split mold is cut, and then a blow pin is attached to the parison mouth. And a compressed air is blown into the molded product to form a desired molded product. 2. A die head for continuously extruding a kneaded and melted thermoplastic resin as a parison, and a plurality of split molds for biting and molding the parison extruded from the die head at equal intervals. A wheel, a cutter for cutting the parison between the split mold and the die head, and a blow pin, the die head is located above the split mold at the highest position of the wheel, and the split mold is The parison is configured to open and close in the direction orthogonal to the pushing direction, and the cutter is composed of a pair of blades that sandwich the parison in the left-right direction between the lower end of the die head and the upper end of the split mold. A rotary hollow forming device, characterized in that it is provided at the upper end of a split mold so as to be driven into the mouth of the parison after the mold is closed and the parison is cut.