JPH0528973B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to blow molding machines, and particularly to improvements in blow molding molds for molding so-called long objects such as ducts.

Conventional technology This type of conventional blow molding mold is
Various types are available, one of which is generally known as the so-called extrusion type, which is used to form intake ducts for automobile internal combustion engines, as shown in FIG.

In the molding method using this blow molding machine, first, a thermoplastic resin is plasticized by an extruder 1, and the plasticized cylindrical molten resin (parison) is extruded, and this extruded parison 2 is transferred to a lower mold 3. It flows from one end 5a side into the meandering cavity 5 formed on the upper surface 4 and has a long center line with a sharp bend, and is extruded and filled along the intricately curved inner wall surface 5b of the cavity 5. . Subsequently, an upper mold 6 having a meandering cavity corresponding to the cavity 5 on the lower surface is closed in a mold clamp state, and then air is blown into the inside of the parison 2 to expand it before solidifying, and both molds 5, It is pressed against the inner wall surface 5b of the cavity 5 of No. 6 and cooled and solidified. still,
In this blow molding machine, parison 2 is cavity 5.
While being extruded inward, the rear end side of the lower mold 3 is moved up and down and placed in an inclined state, thereby preventing so-called drawdown.

Problems to be Solved by the Invention In the conventional blow molding mold described above, the parison 2 extruded from the extruder 1 into the cavity 5 of the lower mold 3 is affected by the extrusion force from the extruder 1, the flow rate, The straightness becomes stronger due to the temperature or the accuracy of the vertical movement of the lower mold 3. Therefore, the behavior within the complicatedly shaped cavity 5 becomes unstable, and the material is pushed out while being biased towards the inner periphery 5c near each corner portion C, C. Therefore, in some cases, it may protrude slightly from the edge of the inner periphery 5c. As a result,
As shown in FIG. 4, the wall thickness at the bent portion of the parison 2 is thinner on the inner circumference 5c side than on the outer circumference 5d, resulting in uneven thickness and burrs.

Therefore, there has been proposed an invention disclosed in, for example, Japanese Patent Application Laid-open No. 18328/1983, in which a guide member is provided at each corner portion to regulate the flow position of the parison. However, in this invention, since the guide member is installed upright inside each corner of the cavity, it not only obstructs the flow of the parison and makes it impossible to obtain a smooth flow, but also causes the parison to bump into the guide member and flow. There is a risk that it will prevent itself.

Furthermore, there is a risk that this guide member may guide the parison not toward the center of the cavity but toward the rear side of the guide member, that is, the inner peripheral side of the corner portion.

Means for Solving the Problems The present invention was devised in view of the problems of the conventional blow molding molds described above, and in particular, the guide member is provided upright on the inner peripheral edge of the corner portion of the cavity. The guide member is characterized in that it is formed into a substantially arcuate shape in the peripheral direction, and the inner peripheral surface of the guide member is formed to have the same curvature as the curvature of the inner wall surface of the cavity.

Effects According to the present invention having the above configuration, the parison extruded from the extruder is rectified toward the center in the axial direction of the cavity by the guide member near the corner portion while flowing inside the cavity. For this reason, deviation toward the inner peripheral side of the corner portion is prevented. In particular, since the guide member is provided on the outside of the cavity and its inner circumferential surface is continuous with the inner wall surface of the cavity, it is possible to smoothly guide the parison without hindering its flow. .

Embodiments Hereinafter, embodiments of the blow molding mold according to the present invention will be described in detail based on the drawings. Note that the same reference numerals are given to the same components as in the above-mentioned conventional art.

FIG. 1 shows one embodiment of the present invention, in which 1 is an extruder that plasticizes thermoplastic resin and extrudes a parison 2; 3 is a lower mold that moves up and down centering on the front edge; The lower mold 3 has an elongated meandering cavity 5 formed on the upper surface 4, and two corner portions C, an inner periphery 5c of the cavity 5,
Guide members 11, 11 for guiding the flow of the parison 2 are detachably provided near 5c.

To be more specific, the guide member 11 is as follows:
As shown in FIGS. 2A and 2B, a rising portion 4a is formed by bending a metal material having a rectangular cross section into an arc shape, and is provided on the lower surface of the fixing base end portion 12 at the periphery of the cavity 5. A step portion 12a that engages with the cavity 5 is provided, and the tip portion 13 extends in the circumferential direction to a position substantially opposite to the center position of the inner wall surface 5b of the cavity 5. In addition, the inner peripheral surface 11 of the guide member 11
A is formed to have the same curvature as the curvature of the inner wall surface 5b of the cavity 5, and is formed to be a continuous surface with the inner wall surface 5b when installed. Further, the guide member 11 is removably attached to the lower mold 3 via a piston rod 15, an inclined pin, or an inclined block of the hydraulic cylinder 14 that engages in a groove 11b near the base end 12.

In addition, when the upper mold 6 is clamped and closed with the lower mold 3,
A storage groove (not shown) for storing the guide member 11 is formed.

Hereinafter, in order to mold the intake duct 21 using the blow molding mold of this embodiment, first the guide member 1
1 is pushed out by the piston rod 15 to obtain engagement between the rising portion 4a and the stepped portion 12a, and is then installed in the lower mold 3 in advance. That is, the guide member 11 is attached to the inner peripheral edge of each corner portion C, C of the cavity 5, that is, to the outside of the cavity 5. Incidentally, it is also possible to mount the guide member 11 using an inclined pin or an inclined block assembled into the mold. Next, in the process described above, the parison 2 is attached to one end 5 of the cavity 5.
When pushed inward from the a side, the parison temporarily stretches along the outer circumferential side of the corner parts C, C, but at the same time, due to its strong straightness, the parison stretches in the vicinity of the corner parts C, C. The parison 2 behaves as if it is biased toward the inner circumference 5c side and even climbs over the edge of the inner circumference 5c side, but here, the parison 2
While slidingly contacting the inner circumferential surface 11a of the cavity 5, the flow is rectified toward the axial center of the cavity 5 and pushed back toward the center. Therefore, the entire parison 2 is cavity 5.
flows along the center of the

Moreover, the guide member 11 is provided on the outside of the cavity 5 as described above, and the inner circumferential surface 11a and the inner wall surface 5b of the cavity 5 form a continuous surface, so that the cavity 5 has a sufficient flow path cross-sectional area. is ensured. Therefore, the parison 2 does not hit the guide member 11 inside the cavity 5.
It is always smoothly guided in a fluid manner and is smoothly guided in a sliding manner that fits the inner peripheral surface 11a of the guide member 11. Next, with the guide member 11 still attached, the upper mold 6 is closed, air (approximately 5 kg/cm ² ) is blown into the parison 2 to expand it, and the parison 2 is cooled and solidified to form a uniform wall thickness. It is possible to mold the intake duct 21 without generating burrs.

Further, when the upper mold 6 is removed after molding the intake duct 21, the guide member 11 is removed using an inclined pin, an inclined block, or a cylinder.

In the above embodiment, the guide member 11 is attached to the lower mold 3 using the hydraulic cylinder 14 or the like, but it is possible to change the shape of the base end 12 and the rising portion 4a so that it can be attached and detached by hand. It is also possible to configure Further, the shape of the guide member 11 is not limited to that of this embodiment; for example, if the width dimension is increased, the guiding effect will be even better.

Effects of the Invention As is clear from the above explanation, the present invention has
According to the blow molding mold, the guide member is provided upright along the inner peripheral edge of the corner portion and formed in a substantially arc shape toward the outer peripheral edge, and the inner peripheral surface of the guide member is aligned with the cavity inner wall surface. Since the flow path is formed with the same curvature to ensure a sufficient cross-sectional area, the parison is not only always guided toward the center of the cavity, but also smoothly guided without obstructing or blocking the flow of the parison. At the same time, it is possible to smoothly slide and guide the guide member in a manner that fits the inner circumferential surface of the guide member. As a result, the entire wall thickness of the molded product can be made uniform, and the occurrence of burrs can be sufficiently prevented. Furthermore, the molding conditions and control range such as the temperature and extrusion force of the parison become larger.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of essential parts showing an embodiment of a blow molding machine and a mold according to the present invention, and FIGS.
FIG. 3 is a perspective view of essential parts showing a conventional blow molding machine and mold, and FIG. 4 is a sectional view taken along the line - in FIG. 3. DESCRIPTION OF SYMBOLS 1... Extruder, 2... Parison, 3... Lower mold, 4... Upper surface, 5... Cavity, 5b... Inner wall surface, 5c... Inner periphery, 11... Guide member, 11
a...Inner peripheral surface, C...Corner part.

[Claims]

1 A double-sided vacuum forming method is used to form a foamed polypropylene resin sheet using a male and female mold that can be vacuum formed, and the foamed polypropylene resin sheet is a laminated sheet with a thermoplastic resin film adhered to both sides with an expansion ratio of 5.5 times or less. A double-sided vacuum forming method for a laminated sheet, characterized in that the gap between the molds is set to 1.0 to 2.5 times the thickness of the laminated sheet after being heated and softened.