JPS63280614A - Blow molding method and device - Google Patents

Abstract

PURPOSE:To mold a hollow molded product having a bent section to a desired shape with good efficiency by guiding a parison into mold cavities by means of specific clamping pawls and hollow molding. CONSTITUTION:The lower end P0 of a parison is grasped by clamping pawls 11 and 12, and the parison P is guided into cavities 15 and 16. Along the bent shape of said cavities 15 and 16, the molten parison P is passed through, and the lower end P0 of the parison is positioned outside the lower end opening sections of the cavities 15 and 16 of the divided molds 13 and 14. The parison P is drawn into the cavities 15 and 16 of the divided molds 13 and 14, bent and deformed to flex mold the parison P preliminarily to a certain extent. Then, pressurized air is blown from an extrusion die head 10 into the parison P, and the preliminarily molded parison P is expanded in the cavities 15 and 16 and molded. After molding, the upper and lower ends of the parison P are cut to manufacture a S-shaped flex tube.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is applicable to blow molding of synthetic resin hollow molded products, particularly bent tubes such as synthetic resin pipes and ducts whose axes are bent in two or three dimensions. METHODS AND APPARATUS.

<Prior art and its problems> This type of device is disclosed in Japanese Patent Application Laid-Open No. 55-21239, in which two lower molds are installed on a turntable to be transferred between the die head of an extruder and a mold clamping device. This die head is placed in the
, Z. A manufacturing device is described and disclosed that can be moved forward, backward, left, right, and up and down by controlling the drive of a motor for movement in each axis direction. In this manufacturing device, the turntable of the lower mold is In addition, a large driving force is required to move the die head, and the entire manufacturing equipment has a complicated structure and is large in size. In order to copy and receive the die into a two-dimensionally or three-dimensionally carved cavity, the movement control program for the die head must be highly accurate, and the manufacturing equipment becomes expensive.

Another example of this type is disclosed in Japanese Patent Laid-Open No. 61-41522.

On the other hand, unlike the above, there is a manufacturing device in which the horizontal nozzle for the parison extruder of the extruder is completely fixed, the lower mold is freely moved back and forth, left and right, and up and down, and the parison is stored along the cavity of the lower mold. As disclosed in Japanese Patent Application Laid-Open No. 53-56262, since the nozzle is oriented horizontally, the molten parison immediately after being extruded sag downward, and the front and back films are fused to each other before blow molding. There is a risk of this, and it takes time and effort to position the parison to begin tracing into the mold cavity, which has a complex shape, and there is a feeling that there is still a time to efficiently feed the parison into the mold cavity.

Furthermore, in order to make the wall thickness of the hollow molded product having a bent part uniform, a pin for regulating the position of the parison is provided in the cavity of the lower mold so that it can be retracted from the cavity according to the mold alignment operation of the upper and lower molds. Japanese Patent Application Laid-open No. 60-18328 discloses this, but since a pin for regulating the position of the parison is provided in the cavity of the lower mold, the pin must be moved back during blow molding each time the upper and lower molds are aligned, resulting in bending. The method for forming a hollow molded product having a section is rather troublesome, and the equipment is also complicated.

In addition, the joint surface of the proportion mold for molding of male and female sets in Japanese Patent Publication No. 61-32128 is molded into a concave bent cavity and a convex bent cavity, respectively, and a parison air suction is provided in the cavity of the female mold. An appropriate number of small holes are provided in the cavity of the male mold, and an appropriate number of small holes for blowing out heated air are also provided in the cavity of the male mold, and the parison is first directed toward the female mold through the small holes for air suction. At the same time as suction, heated air is blown out from the small hole for blowing heated air while the male mold is sent forward toward the parison, and after adsorbing the parison to the female mold as if pressing the parison into the cavity of the female mold, The male and female molds are clamped and the parison is blow-molded into the cavity shape, that is, into the shape of a curved tube.In this curved tube molding method, the group of small holes must be drilled in the male and female molds. As the structure of the mold became more complex, additional equipment was required to suck air into the mold and blow out heated air, and the shape of the curved pipe that could be molded was limited to almost a dogleg shape. -There is a sense of walking.

In JP-A-61-179718, which is a prior art divided from the above-mentioned JP-B-61-32128, -
A parison is supplied hanging from a die of an extruder between a set of split molds for molding, and a guide tool having a curved surface portion at the tip having a shape that corresponds to the shape of the curved pipe to be molded is inserted from the horizontal direction. While moving the guide tool forward toward the parison and deforming the parison by following the grooves formed on the curved surface of the guide tool,
After approaching the half-split curved pipe-shaped portion of the cavity of these split molds, the guide tool is retreated, and during this time the parison, which has been transformed into a curved pipe, is placed in the cavity of one of the split molds with an appropriate number of air bubbles. Adsorb it into the cavity through the small suction hole,
In this state, a set of split molds for molding is clamped, and the parison is blow-molded into a curved pipe.
The structure of the mold is complicated, and since the guide tool has a curved surface, it has the drawback that it is not possible to accurately blow mold a parison other than a curved pipe shape convex in the forward direction.

Means for Solving Problems〉 The present invention includes a deformable string-like parison retracting device that is deformed and curved to follow the cavities of a pair of split molds.
The lower end of the molten parison extruded from the extrusion die head of the extrusion molding machine is gripped and closed by the opening/closing grip claw provided at the upper end of the shank of the drawing tool, the pair of split molds are brought together, and the molten parison is With preload applied to the inside of the parison, the lower end of the shank of the drawing tool protruding from the lower end opening of the cavity of the mold is pulled downward, and the entire gripped parison is guided and inserted into the cavity of the mold. By adopting a blow molding method characterized by ah-molding and then blowing pressurized air into the inserted parison from an extrusion die head to press and deform the parison against the inner surface of the cavity, the above-mentioned conventional problems can be solved. This is a blow molding method that solved the problem.

Another invention provides an extrusion molding apparatus for three-dimensional blow molding a parison in a molten state using a pair of split molds, including a deformable parison retracting tool that removably grips and closes the lower end of the parison. This blow molding apparatus is characterized in that the pair of split molds are formed so as to be freely inserted into a cavity formed by combining them, thereby solving the problems of the conventional blow molding apparatus.

<Operations and Effects> According to the first method invention, pressurized air is blown into the parison in the pair of split molds, and the lower end of the molten parison is extruded from the extrusion die head using the deformable parison drawing device. The divided molds are closed together with the retracting tool hanging from the lower end of the parison, and the retracting tool is elastically deformed to follow the shape of the mold cavity, and the parison is retracted from the opening at the lower end of the mold cavity. By pulling the tool downward and guiding the entire gripped parison into the cavity of the closed mold, the parison is closed by following the movement of the pulling tool prior to blow molding with pressurized air. The cavity of the mold can be preformed into a similar shape, and even if the pressure of pressurized air inside the mold is low, the molten parison can be sufficiently pressed against the inner surface of the cavity and deformed. During blow molding, the parison pulling tool is located outside of the closed molds, so blow molding of the parison using pressurized air can be carried out smoothly without being obstructed by the parison drawing tool.

The second device invention can carry out the first method invention, and also controls the position of the mold in each of the X, Y, and Z axes without making any improvements to the existing extrusion molding machine and mold opening/closing device. A deformable parison retractor that removably grips the lower end of the parison can be used to close a pair of split molds without using expensive equipment such as a drive device for tilting the device and mold or a position control device for the extrusion head die. It is formed so that it can be inserted freely into the cavity formed by fitting it together, and by the action of this retracting tool,
The uncured parison extruded from the extrusion head die can be easily drawn into the cavity and preformed.

<Example> Next, a typical example of the apparatus invention for carrying out this method invention will be described with reference to the drawings.

In Fig. 1, A is an extrusion molding machine, and a retracting tool B for gripping and closing the lower end of the parison P which is in a molten state immediately after being extruded from the extrusion die head A is in a string state and can be freely deformed and curved. A pair of clamps 11 and 12, which can be opened and closed, are attached to the upper end of the junk part 10 of the retractor B, and are always biased in the closing direction. These clamping claws 11, 12 are preferably made of spring steel, and the shank portion 10 is made of a flexible pipe formed by partially overlapping thin steel strips in a spiral shape, giving flexibility to the shank portion 10. There is.

The length of this shank portion 10 is such that, when a pair of split molds 13 and 14 for forming a three-dimensional bent pipe (duct pipe) for automobile air conditioning, such as an S-shape, are put together, the lower end thereof becomes the split mold. 1
The cavity 15.16 of 3.14 has a sufficient size to protrude downward from the lower end opening, and the clamping claw 1 of the retracting tool B
1.12 and the size of the shank part 10 are the S-shaped cavities 15.16 of this combined split mold 13.14.
It is about one-third to one-fifth of the inner diameter of the cavity 15, 16, and is dimensioned so that it can be inserted freely along the curved part of the cavity 15, 16.

A method of blow molding an S-shaped three-dimensional bent pipe for automobile air conditioning using the blow molding apparatus C of such an embodiment, that is, one aspect of the present method invention will be described below.

First, the intermediate portion of the retracting tool 3 is deformed and curved along the cavity of one of the pair of open split molds 13 and 14, and then installed. At this time, the pair of clamping claws 11.12 are positioned so as to protrude above the mold 13.14.

Next, the lower end P of the parison P in a molten state immediately after being extruded from the extrusion die head A. is gripped and closed by the pair of clamping claws 11.12 of the retracting tool B, and the pair of split molds 13.14 are brought into a closed state. At this time, even if the retracting tool 3 is inserted from above into the cavities 15.16 of a pair of closed molds 13.14, followed by deformation and attachment, the method invention is the same.

In this closed state, a pre-pressure is applied to the inside of the molten parison P, causing the parison P to expand to some extent (brib blow), thereby preventing the inner surfaces of the parison from being fused together.

In this state, the lower end of the shank portion 1o projects downward from the lower end opening of the cavity 15.16 of the combined split mold 13.14.

The protruding shank portion 10 of the retracting tool B is mechanically or manually pulled downward until the clamping claw 11.12 completely passes through the cavity 15.16 of the split mold 13.13. .

This clamping claw 11.12 is located at its lower end P. The parison P gripped is introduced into the cavity 15.16, and the molten parison P is curved and deformed along the curved shape of the cavity 15.16 to pass through the lower end P. The cavities 15 and 16 of the divided molds 13 and 14 are located outside the lower end openings. At this time, it goes without saying that the upper end of this parison P is connected to the extrusion die head A, and the parison drawing speed of the drawing tool B is the same as the extrusion speed of the parison P from the extrusion die head A.
and slow down to prevent parison P from breaking or sagging.

In this way, pull the retracting tool B downward and remove the parison P.
By drawing the parison P into the cavities 15, 16 of the divided molds 13, 14 and deforming it into a curve, the parison P is preliminarily bent to a certain extent while the main molding is still being performed.

Next, pressurized air is blown into the parison P from the extrusion die head 10 in the same manner as in the normal blow molding method, and the preformed parison P is expanded in the cavities 15.16 of the divided molds 133.14, and these inner surfaces are 13.1 After pressing the parison and deforming the parison,
4 and cut the upper and lower ends of the parison P to obtain a bent pipe for automotive air conditioning, such as an S-shape, which is three-dimensionally bent with both ends open.

During this main molding, the pair of clamping claws 11.1 of the retracting tool B
2 is opened, the retractor B is removed from the lower end of the parison P, and is reused.

<Effects Unique to the Embodiments> The apparatus and method configured as described above exhibits the functions and effects of the first and second inventions, as well as the following unique effects.

In the embodiment in which the shank portion 10 of the retracting tool B is formed by partially polymerizing thin steel strips in a spiral shape, the flexibility of the shank portion 1o can be increased, and it is possible to improve the flexibility of the shank portion 1o. A large two-dimensional or three-dimensional bent pipe can be efficiently and efficiently molded into a desired shape.

[Brief explanation of the drawing]

The figures relate to this invention, and are shown in Figures 1(a) to (e).
1 is a schematic diagram illustrating an embodiment of a method invention and an apparatus invention; FIG. Main symbol B in the diagram...Retractor.

Claims (1)

[Scope of Claims] 1) A deformable string-like parison drawing tool is attached to the mold by deforming and bending it to follow the cavities of a pair of split molds, and the lower end of the molten parison extruded from the extrusion die head of an extrusion molding machine is , the retractor is gripped and closed by the opening/closing clamping claw provided at the upper end of the shank part, the pair of split molds are brought together, and the lower end of the cavity of the mold is applied with pre-pressure applied inside the molten parison. The lower end of the shank of the pulling tool protruding from the opening is pulled downward, the entire gripped parison is guided and inserted into the cavity of the mold for preforming, and then the inserted parison is pressurized from an extrusion die head. A blow molding method characterized by blowing air to press the parison against the inner surface of the cavity and deform it by following the pattern. 2) In an extrusion molding device for blow molding a parison in a molten state using a pair of split molds, a shank portion is provided at the upper end with a pair of opening/closing gripping claws for removably gripping and closing the lower end of the parison. A blow molding apparatus characterized in that a deformable parison retracting tool is formed so as to be freely inserted into a cavity formed by combining the pair of split molds. 3) The blow molding apparatus according to claim 2, wherein the retracting tool is a whole string-like body.