JP2833870B2 - Molding method for hollow resin products - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[Object of the invention]

[0002]

BACKGROUND OF THE INVENTION The present invention relates to a method for forming a deep groove-shaped cavity surface in at least one of a pair of split molds, introducing a parison between the pair of split molds, clamping the mold, and forming a parison. The present invention relates to a method for molding a hollow resin product, which blows air into the interior to form a hollow resin product having a deep portion on the surface.

[0003]

2. Description of the Related Art A split mold has conventionally been used for molding a hollow product made of a thermoplastic resin such as an air spoiler for an automobile. A parison is introduced into the split mold, the mold is clamped, and air is filled in the parison. Is blow-molded.

In this method, since the parison partially contacts the inner surface of the clamped split mold, during the blow molding,
The portion not in contact with the inner surface of the mold is locally stretched. That is, the parison has portions that are freely stretched and portions that are not stretched. In particular, when a product having a sharp corner is formed, the corner comes into contact with the inner surface of the mold last, so that the thickness of the parison corresponding to this corner becomes the thinnest. May be damaged.

As described above, in order to prevent the corners of the molded product from being thinned or damaged, Japanese Patent Application Laid-Open No.
A method disclosed in Japanese Patent No. 40224 is known.

[0006] However, in this method, an acute angle 1
A parison corresponding to most of the sides is stretched while being adhered and restrained to the inner surface of the mold. In other words, there are many portions in contact with the inner surface of the parison, and few portions are freely stretched. Accordingly, the time required for freely extending the parison is shortened, and the portion that is freely extended, such as a sharp decrease in the temperature of the parison, is limited, and the parison is locally extended. This causes a problem such as the occurrence of the above-described thin portion in an acute angle portion where some burrs do not protrude. In other words, this technology considers that the burr is projected to prevent thinning at a closed acute angle,
No consideration is given to preventing the thinner portions from being made thinner.

In addition, the mold surface of one mold used in the above method and the core surface of the core provided in the one mold eventually become the same surface. The line at the boundary of the line appears, which degrades the quality of the product. In addition, in order to move the core forward and backward, another power such as a cylinder mechanism must be provided, which is different from that for mold clamping, and the device becomes complicated and large.

[0008]

As described above, it is difficult to reliably prevent the occurrence of a thin portion at an acute angle portion, a line is formed on a molded product, and the structure of the apparatus is complicated and large. There is also a problem.

It is an object of the present invention to provide a method for molding a hollow resin product, which can reliably prevent the occurrence of a thin portion at a corner and obtain a high quality molded product.

[Structure of the Invention]

[0011]

SUMMARY OF THE INVENTION The present invention provides a pair of split molds.
Deep groove-shaped cavity surface 14a on at least one of 13 and 14
, 14b are formed, a parison 11 is introduced between the pair of split molds 13 and 14, the mold is clamped, and air is blown into the parison 11 to form a resin hollow having a deeply drawn portion on the surface. The present invention relates to a method of molding a product, wherein one of the split molds 14 having the deep groove-shaped cavity surfaces 14a and 14b is
It is divided at the bottoms of the deep groove-shaped cavity surfaces 14a and 14b, and one side of the split mold 14 is movable as a movable portion 14c and advances and retreats in the mold clamping direction with respect to the other side as a fixed portion 14d. The movable part 14c and the fixed part 14d of the split mold 14 are brought into contact with the parison 11 with a time difference. .

[0012]

According to the present invention, one of the split molds 14 is provided with a movable portion 14c and a fixed portion 14d at the bottoms of the deep groove-shaped cavity surfaces 14a and 14b.
Since the movable part 14c of the split mold 14 is advanced by elastic force in advance, there is a time difference between the parison 11 and the inner surface of the split mold 14 when the mold is clamped. Since the parison 11 can be extended freely, the parison 11 can be extended sufficiently even to corners where burrs do not protrude to the outside, and good molded products can be obtained by blow molding by blowing air into the parison 11. No thin portion is generated.

[0013]

An embodiment of the present invention will be described below with reference to the drawings.

In this embodiment, a spoiler 11 for an automobile shown in FIG. 4 will be described as an example of a resin hollow product to be molded. This spoiler 11, as shown in FIG.
It is a hollow molded article made of resin having a substantially triangular cross section, and is molded according to the procedure shown in FIGS. FIG.
In FIG. 3 to FIG. 3, a parison which is a hollow resin material (polypropylene or polyester) before molding is denoted by the same reference numeral 11 as the spoiler which is a product after molding.

Reference numeral 12 denotes a mold, and the mold 12 is a first split mold 13.
A cavity surface 13a corresponding to the upper surface shape of the spoiler 11 shown in FIG. 5 is formed on the lower surface of the first mold half 13, and the second mold half 14 is formed. In the spoiler 14, deep groove-shaped cavity surfaces 14a and 14b corresponding to both lower slopes of the spoiler 11 are formed.

The second split mold 14 is divided into right and left portions at the bottom of the deep groove-shaped cavity surfaces 14a and 14b, that is, at the boundary between the lower slopes of the spoiler 11 having a substantially triangular cross section. The right side portion is configured as a movable portion 14c so as to be able to advance and retreat in the vertical direction in the drawing, that is, in the mold clamping direction of the pair of split molds 13 and 14 by a guide pin 16 which stands vertically from the back plate 15. The left side of the figure is fixed to the back plate 15 as a fixing portion 14d.

The movable portion 14c receives an elastic force by a spring 17 in a direction (ascending direction in the figure) moving forward with respect to the mold clamping direction. Therefore, when the pair of split molds 13 and 14 are open, as shown in FIG.
In the closed position (during molding) when the mold is closed by the elastic force of the spring 17 and the mold is closed, as shown in FIG. 3, the original mold position (the retreat limit by a not-shown stopper that contacts the back plate 16). ) To retreat.

In the above-described configuration, when molding is performed, first, as shown in FIG. 1, the parison 11 is connected to a pair of split molds 13 and 14.
Then, in this state, the pair of split molds 13 and 14 are closed and the molds are clamped.

In this case, the movable part 14c of the second split mold 14
Is in the forward position by the elastic force of the spring 17, the first split mold 13 first comes into contact with the movable portion 14c with a part of the parison 11 (upper right portion in the figure) interposed therebetween with the above-described mold clamping operation. . For this reason, a part of the parison 11 is restrained, but the other part remains in a free state. Therefore, as shown in FIG.
It extends along 14b and then along the other cavity surface 14a. For this reason, the parison 11
It extends near the valley by a and 14b.

Next, the first split mold 13 is brought into contact with the fixed portion 14d of the second split mold 14 with the upper left portion of the parison 11 shown in the drawing interposed therebetween. When the mold clamping operation is further continued in this state, the movable portion 14c retracts (moves downward in the figure) while compressing the spring 17, stops at the retreat limit position determined by the back plate 15 and the stopper, and enters the maximum mold clamping. 3 is blow-molded by blowing air into the parison 11. As shown in FIG.

Here, each of the acute angle portions on the upper left and right sides in the figure shows the first split mold 13 and the corresponding second split mold 14 when the mold is clamped.
The parison 11 is partially sandwiched between the movable part 14c and the fixed part 14d, and is molded in a state of protruding to the outside as burrs.Therefore, it is not locally stretched, and a thin-walled part or damage due to this is prevented. Will not occur.

Further, the parison 11 corresponding to the acute angle portion at the lower part of the drawing without such projection as a burr to the outside.
When the mold is clamped, as described above, the parison 11 first extends along one cavity surface 14b, and then extends along the other cavity surface 14a, thereby extending the extension time of the parison 11, The contact time with the cavity surfaces 14a and 14b is delayed, and the movable portion 14c having the one cavity surface 14b is moved backward, so that the movable portion 14c is extended to near the valley formed by the cavity surfaces 14a and 14b.
Therefore, there is no local extension, and no thin-walled portion or breakage occurs at the acute angle portion after blow molding.

Further, each of the cavity surfaces 13a, 14a, 14b
Since each is composed of one surface, unlike a conventional mold in which the inner surface and the core surface are arranged so as to be on the same surface, lines formed by these boundaries may not occur on the product surface after molding. And the quality of the product can be kept high.

Further, the movable part 14 of the second split mold 14
The operation of c is performed by compressing the spring by the mold clamping force.There is no need to provide a power mechanism for driving the core separately from the mold clamping power as in the past. Therefore, the device configuration can be simplified.

In the above embodiment, the deep groove-shaped cavity surfaces 14a and 14b formed on one of the pair of split molds 13 and 14 (the second split mold 14 in the illustrated example) are substantially as shown in the drawing. Although it was a V type, it may be a semicircular groove type, a square groove type, an oblique V type, or the like. In either case, a split mold is used to split the cavity surfaces. Further, both of the pair of split dies may have a cavity surface having a deep groove shape. In this case, in order to divide each cavity surface, a split die is used for both of the split dies.

[0026]

As described above, according to the present invention, it is possible to reliably prevent a thin wall portion due to local expansion of a parison and breakage caused by the local wall portion even at a corner portion formed without projecting burrs to the outside. And a high quality molded product having a uniform thickness can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a pair of split molds used in an embodiment of a method for molding a resin hollow product according to the present invention.

FIG. 2 is a sectional view showing an operation process of the device shown in FIG.

FIG. 3 is a sectional view showing a final operation state of the device shown in FIG. 1;

FIG. 4 is a perspective view showing an example of a product produced by the method of the present invention.

5 is a cross-sectional view of the product shown in FIG.

[Explanation of symbols]

 11 Parison 13, 14 Split mold 14a, 14b Cavity surface 14c Movable part 14d Fixed part 17 Spring that gives elastic force

Claims (1)

(57) [Claims] 1. A deep groove-shaped cavity surface is formed on at least one of a pair of split molds, a parison is introduced between the pair of split molds, molds are clamped, and air is blown into the parison. In a method of molding a resin hollow product having a deep portion with a drawn surface, one of the split molds having the deep groove-shaped cavity surface is divided at the bottom of the deep groove-shaped cavity surface, and the divided portion is divided. One side of the split mold is a movable part, and the other side as a fixed part is configured to be able to advance and retreat in the mold clamping direction and to provide an elastic force for advancing in the mold clamping direction. Wherein the movable part and the fixed part are brought into contact with the parison with a time difference.