JPH068028B2 - Rotary hollow molding method and device - Google Patents

Description

The present invention relates to a rotary hollow molding method and apparatus for plastic containers.

[Prior Art] A method for obtaining a hollow molded article such as a bottle, a container, and an industrial material by using a plastic material such as polyethylene or polyvinyl chloride is generally a melted parison extruded from an extruder. A method is used in which a plastic cylinder is bitten by a mold, and then compression air is blown from the outside to mold it into the same shape as the mold cavity.

The above method is called a blow molding method, and there are a reciprocating method and a rotary method. Of these methods, the latter method is widely used for mass production because of its excellent productivity.

What is the rotary blow molding method, the plastic material melted and kneaded by an extruder is continuously extruded from a die,
Get the parison.

This parison is bitten one after another by a pair of left and right molds mounted on the wheel, and then compressed air is blown into the parison from the cylindrical blow port built in the mold,
This is a method of molding this 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. , Mold clamping is continued, the mold is opened after cooling is completed, and the molded product is taken out of the mold.

Here, as the mold clamping mechanism of the mold, the direct pressure type and the toggle type have been conventionally used. As a general direct pressure method, a cam mounted on a frame of a molding device directly operates a cam roller attached to a mold mounting mold plate by rotating a wheel to perform mold clamping. That is, the mold clamping force directly presses the frame as a reaction force.

The toggle type general method uses the rotation of the frame, the cam template, the cam roller, and the wheel in the above direct pressure type similarly, but adopts the toggle mechanism consisting of two links or three links between the frame and the cam, By expanding and contracting, the mold clamping force is increased. That is, the mold opening is performed when the toggle is contracted, and the mold clamping is performed when the toggle is fully extended. By doing so, the mold opening / mold clamping speed is increased, and
The pressure applied to the molding device frame during mold clamping is small, and a strong mold clamping force can be obtained with the lightweight frame.

[Problems to be Solved by the Invention] The features of the direct pressure type and the toggle type are summarized.

The direct pressure type has a simple mold-clamping mechanism, but in order to obtain a strong mold-clamping force, a frame structure of a molding device corresponding to it is required. Not suitable for molding.

The toggle type can speed up mold closing and mold opening and can lengthen trokes. Also, a strong mold clamping force can be obtained with a molding device having a relatively lightweight structure. However, since the toggle just before the completion of mold clamping is just before reaching the end,
The speed becomes extremely slow, and theoretically, the mold clamping speed becomes "0" when the toggle is fully extended, that is, when the mold clamping force is maximum. It is said that if the mold clamping speed is low just before the completion of mold clamping, the cutting suitability for punching the parison with the mold is poor and molding is impossible, or the moldability of the pinch-off part deteriorates.However, the toggle type causes this defect. It could not be molded sufficiently.

The present invention relates to a mold clamping mechanism for solving the disadvantages of each of the above two methods in combination and obtaining a highly productive rotary hollow molding method.

In other words, a molding machine with a lightweight structure exerts a strong mold clamping force, the mold clamping speed immediately before the completion of mold clamping is fast, and
The present invention relates to a mold clamping mechanism having many advantages such as a high mold opening speed.

[Means for Solving the Problems] As an apparatus constituting the present invention, an extruder for continuously extruding a parison, a molding apparatus having a wheel that rotates like a water turbine, and a pair of left and right attached to a plurality of sets on the wheel. Is a molding die or the like. The mold clamping mechanism, which is the subject of the present invention, is included in the molding apparatus, but the problems in the previous term were solved by adopting a toggle mechanism and a hydraulic cylinder for this mechanism.

The following is a description with reference to the drawings. FIG. 1 is a schematic side view of a molding apparatus of the present invention, and FIG. 2 is a side view of a mold clamping unit. The right side of the drawing shows the mold opening, and the left side shows the mold closing. Bed (7)
A hole (19) corresponding to the thickness of the cam shaft is provided at the joint between the fulcrum support (17) and the fulcrum support (17).
The fulcrum support (17) provided with the fulcrum (20) is attached,
The link (15) is connected to the fulcrum (20), and the other end of the link (15) is connected to the link (16) through the fulcrum (21).
At the other end of (16), a mold (5) and template (11) are placed via a fulcrum (22).
Is connected to a hydraulic cylinder (12). Further, a fulcrum (24) is provided substantially in the center of the link (15), the link (14) is connected via the fulcrum (24), and the other end of the link (14) is Through a fulcrum (23) provided on a connecting portion (18) attached to an inner end of the camshaft (13), which is slidable in the opening / closing direction of the mold in the hole (19). It is connected to a link (14), and a cam roller (9) is attached to the outer end of the cam shaft (13). The cam roller (9) is attached integrally to the frame (8). Clamping unit with a structure that slidably contacts the cam (10) and an extruder
(1), a die head mounted on the extruder (1)
(2) The die head comprises a parison (3) and a parison guide (4) mounted on the tip of the die head (2).

In addition, when explaining the molding method, kneading by rotating the screw, continuously extruding the melted thermoplastic resin as a parison from the die head, and biting it with a split mold that constantly rotates along the extrusion direction of the parison, This is a molding method in which compressed air is blown into the parison from a needle incorporated in the mold, and when the mold is clamped, a toggle mechanism having a plurality of nodes and a hydraulic cylinder are used together to mold the mold.

[Operation] The mold clamping mechanism according to the molding method of the present invention will be described.

A plurality of mold clamping units are mounted on the wheel of the blow molding apparatus according to the present invention.

The mold clamping unit is a bed for mounting the entire unit on a wheel, a mold plate for mounting a mold, a toggle mechanism consisting of three links, a cam roller for activating the toggle, a hydraulic cylinder and a mold that operate just before the completion of mold clamping. It is composed of a slide shaft for moving the plate.

The mold clamping principle and operation will be described below. The rotation of the wheel causes the cam mounted on the frame of the molding apparatus to press the cam roller, and the movement of the cam roller causes the cam shaft on which the cam roller is mounted to slide. By this operation, the link (14) attached to the camshaft and the link (1) attached to the bed side fulcrum
5), the links (16) attached to the template act so as to widen the space between the bed-side fulcrum and the template.
Due to the characteristics of the link mechanism, the link (15) and the link (1
When 6) is contracted, the operation amount of the cam roller is increased and is transmitted to the template. On the contrary, when the cam roller is fully extended, the operation of the template is delayed. Link with link (15)
The cam roller is pressed until (16) is fully extended, but when it is fully extended, the cam roller maintains the state and slides on the cam. In this state, the mold is not completely clamped, there is a gap of 5 to 15 mm between the left and right molds, and the parison is held by the mold edge. Next, the hydraulic cylinder built into the template operates to completely clamp the die and cut the parison.

After completion of the mold clamping, the mold clamping unit and the mold continue to rotate while maintaining the state, and air blows into the parison to mold a desired container. When the molded product is cooled, the cam roller operates in the direction opposite to that during mold clamping due to the spring reaction force built in the cam shaft, and this movement links the link (15)
(16) operates in the contracting direction to open the mold.

Furthermore, when the mold is clamped, the hydraulic cylinder is also used to clamp the mold.

[Examples] As an example, a method for molding a polyethylene 3-volume liquid detergent bottle will be described.

A parison is continuously extruded by an extruder having a φ120 screw (L / D = 22), and 12 sets of a mold clamping unit and a mold are set in a molding device. Wheel is 3.5r
Rotate at a speed of pm.

It is estimated that the projected area of the molded product is 470 cm ² , the blow pressure is 7 kg / cm ² , and the pressure required to bite the parison is 3 tons.

From these figures, the required mold clamping force is estimated to be 9.6 tons.
(Formula projected area × blow pressure × safety factor + Pariso bite have outright pressure ^{= 470cm 2 × 7kg / cm 2} × 2 + 3000Kg ≒ 9600Kg), mold opening stroke 120mm on one side, the hydraulic cylinder φ120
With a stroke amount of 5 mm, the hydraulic pressure is 100 kg / cm ² when the mold is clamped.

With the above specifications, a good bottle could be molded at a speed of 42 bottles per minute.

[Effect] As described above, the toggle mechanism and the hydraulic mechanism are adopted as the mold clamping mechanism, and the mold clamping is performed by using both of them together, so that the mold clamping force is weak when only the hydraulic mechanism is clamped. Can be supplemented by using the toggle mechanism together, and when the mold clamping is performed only by the toggle mechanism, the mold clamping speed was slow just before the completion of the mold clamping. , All the drawbacks of both can be overcome. At the same time, since the forces of both are added together, a strong mold clamping force of 10 tons or more can be easily obtained. Therefore, molding of two or more large bottles, hollow molded articles for industrial materials, etc. becomes easy. Also, since the operation at the time when the mold is completely closed is performed by the hydraulic cylinder, the mold clamping speed can be freely selected, and it is possible to improve the formability of the parison's scissoring pinch-off part. Moldability is obtained.

Further, since the toggle mechanism is adopted as the molding device, the weight can be relatively reduced and the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic side view of a molding apparatus according to the present invention, and FIG. 2 is a side view of a mold clamping unit. The right side of the drawing shows the mold opening and the left side shows the mold closing. (1) ・ ・ ・ Extruder (2) ・ ・ ・ Die Head (3) ・ ・ ・ Parison (4) ・ ・ ・ Parison Guide (5) ・ ・ ・ Mold (6) ・ ・ ・ Wheel (7) ・ ・・ Bed (8) ・ ・ ・ Frame (9) ・ ・ ・ Cam roller (10) ・ ・ ・ Cam (11) ・ ・ ・ Template (12) ・ ・ ・ Hydraulic cylinder (13) ・ ・ ・ Camshaft (14) ) ・ ・ ・ Link (15) ・ ・ ・ Link (16) ・ ・ ・ Link (17) ・ ・ ・ Support point support (18) ・ ・ ・ Connecting part (19) ・ ・ ・ Hole (20) to (25) ···fulcrum

Claims (2)

[Claims] 1. A thermoplastic resin, which is kneaded and melted by rotating a screw, is continuously extruded as a parison by a die head, and is bitten by a split mold that constantly rotates along the extrusion direction of the parison, and then is formed into a mold. Compressed air is blown into the parison from the built-in needle to obtain the desired hollow product.In the rotary hollow molding method, a toggle mechanism consisting of multiple nodes and a hydraulic cylinder are used together to perform mold clamping. A rotary blow molding method, characterized in that a molded product is obtained. 2. A die head for continuously extruding a kneaded and melted thermoplastic resin as a parison, a split mold for constantly rotating along the extruding direction of the parison, and a mold for blowing compressed air into the parison. A rotary hollow molding device comprising a needle and a needle, wherein a toggle mechanism having a plurality of nodes and a hydraulic cylinder are used together as a mold clamping mechanism.