JPH03293112A - Method for blow-molding bent product - Google Patents

Abstract

PURPOSE:To make it possible to reduce material loss and to check drawdown by a method wherein extruded parison is forcibly bent into the shape similar to the molding surface of a mold so as to conform to the outside shape of a bent product to process and, at the same time, guide plates are provided at the positions corresponding to the molding surface. CONSTITUTION:Guide plates 4 and 5 are provided along the outsides of bent edges (a) and (b), which correspond to a product on the mating mold surface of the horizontal pair of molds 1 and 1' of a blow molder. After the molds 1 and 1' are opened, parison P, which is extruded through a gap made between a die 6 and a core 7, is lowered to the predetermined position as being forcibly bent by the guide plates 4 and 5 so as to be formed. Thus, material loss is reduced and drawdown is checked, resulting in forming a product having uni form wall thickness.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a blow molding method for bent plastic products.

(b) Prior art and problems to be solved by the present invention Conventionally, when manufacturing a bendable product, such as a spoiler attached to the rear part of a passenger car body, by blow molding, As shown in J-, a pair of left and right molds (1) and (1') each having mold surfaces (2>(2)) corresponding to the outer shape of the spoiler to be processed are mounted on a blow molding machine. When a pair of molds (1) (11) are opened, the die (6) and core (7) in the blow molding machine
The parison (P) extruded from the gap between ) The spoiler is manufactured by supplying air into the parison (P) from inside the parison (P), but when using this method, the spoiler corresponds to the external shape of the spoiler to be processed as shown in Figure 8 of the drawing. Because it is necessary to use a parison (P) with a diameter that corresponds to the full width of the mold surface (2) of the shape to be shaped, there is a lot of material loss during molding, and the material is several times more than that actually used in the product. must be discharged as a parison (P), so there is a so-called drawdown, in which the thickness of the material injected later tends to be thinner than the thickness of the material injected first due to its own weight, resulting in a drop in thickness. As a result of exceeding the adjustment range of the thickness adjustment machine, it becomes difficult to mold a product with uniform wall thickness, and a molding machine that has a greater ability to plasticize the material than necessary must be used, and the molding time is also reduced. There were also problems such as spending more than necessary.

In view of the above-mentioned conventional problems, the present invention has been developed by using a molding machine that has a uniform wall thickness of the molded product and a plasticizing ability of the material that substantially corresponds to the size of the product. It becomes possible,
However, it is an object of the present invention to provide a blow molding method that can significantly shorten the molding time.

(c) Means for Solving the Problems In order to achieve the above object, the present invention provides a bend to be processed, which is provided on the mold mating surfaces of a pair of left and right molds (1>(1')) mounted on a blow molding machine. A guide plate <4) (5) of the parison (P) is provided in a curved shape along the outside of the bent edge (a>(b)) with a shape corresponding to the external shape of the product, and the pair of left and right molds (1
) (1') in the open state, the parison (P) extruded from the gap between the die (6) and the core (7) in the blow molding machine is guided to the guide plates (4) and (5). After lowering it to the specified position while forcibly bending it,
It is molded according to the usual blow molding sequence.

Further, in another invention related to the above invention, a blow molding method particularly suitable for cases where the degree of bending of the product is significant is as follows.

That is, a pair of left and right molds (1) (
A bent surface (3) is provided along the outside of the bent edge (C) of a shape corresponding to the outer shape of the bent product to be processed, which is provided on the 1N mold matching surface, and corresponds to the outside of this bent surface (3). One end of a flexible guide plate (4') with a radius of curvature larger than that of the curved surface (3) is fixed to the extension of the curved surface (3), and the pair of left and right molds (1) ( '1') in the open state, the parison (P) extruded from the gap between the pull die (6) and the core (7) is guided to the guide plate (4') in the blow molding machine. After lowering the guide plate (4') to a predetermined position while forcibly bending it, the outside of the guide plate (4') is pressed by the pressing means (9) and the guide plate (4') is pressed against the mold (1) (1). The parison (P) is further forcibly bent by bringing it into close contact with the curved surface (3) provided in the molding section (3), and then molded according to the usual blow molding sequence.

(d) Function The parison (P) extruded into a tubular shape from the gap between the die (6) and the core (7) in the blow molding machine is heated to a specified temperature and becomes flexible and has a certain amount of self-weight. Since there is also a pushing force acting on the guide plate (4) or (5), if it comes into contact with the guide plate (4) or (5) while descending, this guide plate (4)
) (5) It does not stop in close contact with the curved surface and descends along the curved surface while being easily bent. Then, the parison (P) is as shown in Figure 2 of the drawing.
A mold (1) is made to correspond to the external shape of the bent product to be processed.
The resin is bent into a shape similar to the mold surface (2) formed in the mold surface (2), and is stabilized in the position corresponding to the mold surface (2). It spreads over the entire surface and molds a product with uniform thickness.

As shown in Figure 5 of the drawings, the parison 61 (I) was lowered to a predetermined position while being forcibly bent by being guided by the guide plate (4-) in the same manner as described above.
As shown in the figure, the outside of the guide plate (4') is pressed by the pressing means (
9) to bring the guide plate (4-) into close contact with the bent surface (3) provided on the mold, the parison (P) is a bent product with a remarkable degree of bending to be processed. It is bent into a shape that approximates the mold surface (2) formed on the mold (1) corresponding to the external shape of the mold, and is stabilized in a position corresponding to and covering the mold surface (2).

(E) Embodiment An embodiment of the present invention will be described with reference to FIGS. 1 to 4 of the drawings.

The mating surfaces of the left and right molds (1) and (1') installed in a blow molding machine (parts omitted in the figure) are machined to form a bent product with a V shape, that is, to be attached to the rear of the body of a passenger car. A mold surface (2) corresponding to the external shape of the spoiler is provided, and as shown in Figure 2 of the drawing, the mold surface <2> has a shape in which its upper end and lower end are respectively bent to the right. From, the mold surface〈2
) have two bent edges (a) and (
a') or (b) and (b'), of which the two bent edges located on the lower side, that is, the two bent edges (a) and (a') on the upper part of the mold surface (2), respectively. The right bent edge (a)
, the lower two bent edges (h) and (b-) of the mold surface (2)
In this case, a curved surface (3) is provided along the outside of the left curved edge (1)), and a guide plate (4) of the parison is provided in a curved shape along each curved surface (3). ) and (5)-
As shown in Figures 1, 3 and 4 of the drawings, the side edges are overlapped with the bent surface (3) of the left mold (1) and fixed with screws (not shown), etc. When the left and right pair of molds (1)<1') are opened, the width of the plates (4) and (5) is as shown in Figures 1 and 3 of the drawings.
The right edges of 4) and (5) are set so as to slightly overlap the curved surface (3) of the right mold (1'). However, it is not necessarily necessary to overlap. However, parison (P
), it needs a width that can support the parison (P).

Now, as shown in Figures 1 and 3 of the drawings, with the pair of left and right molds (1) (1') opened, the middle of the pair of left and right molds (1) <1') The dice located above the section (
6) and the core (7), the parison (P) made of thermoplastic material is extruded into a tubular shape, and the parison (P) is first pushed into the upper guide plate (4) as shown in Figure 2 of the drawing. I was guided and forcibly bent to the left, and continued to the lower guide plate (5)
During this time, the lower end of the parison is sealed and air is supplied to the inside of the parison. In some cases, adjusting the diameter of the parison (
P) is forcibly bent and lowered to approximately the lower end of the molds (1) and (1'), and then the normal blow molding sequence is performed, i.e.,
As shown in Figure 4 of the drawing, the left and right molds (1) (1') are closed, and the air discharge hole (8) is opened into the inside of the parison (P).
By supplying air from the parison (P), the parison (P) is engraved and brought into close contact with the mold surface (2) (2), and after being cooled and solidified in that state,
The left and right molds (1) (1M) are opened to complete molding.

Next, an embodiment suitable for cases where the degree of bending of the product is significant will be described with reference to FIGS. 5 and 6.

5 and 6 of this drawing correspond to FIG. 2 of the drawing for the above-mentioned embodiment, and the degree of curvature that covers the machining hole is on the mold matching V surface of the mold (1). A mold surface (2) corresponding to the prominent spoiler external shape is provided, but this mold surface (2)
) has a shape in which the upper end is bent at an approximately right angle to the right, so there are two left and right bent edges <C> and C') bent at an approximately right angle.
However, among these, the lower right bent edge (C
) along the outside of the bending surface (3), and a metal guide plate (4') having flexibility with a radius of curvature larger than that of the bending surface (3) corresponding to the outside of the bending surface (3). The lower end of is fixed to the extension of the bent surface (3).

Now, as in the above embodiment, a pair of left and right molds (1) (1-
) in the open state, if the parison (P) is pushed out from the gap between the die (6) and the core (7) which cover the -10= position above the middle part, the parison (P) will be as shown in Figure 5. As shown in the figure J: The sea urchin is guided by the guide plate (4') and descends while being forcibly bent to the left. After descending to a predetermined position, press the outside of the guide plate (4') as desired. Means (9
), for example, by pressing with a hydraulic cylinder etc., the guide plate (4'
) as shown in Figure 6 of the drawing, the parison (P) is further forcibly bent by bringing it into close contact with the bent surface (3) provided on the mold (1), and then the parison (P) is molded according to the normal blow molding order. It is molded.

(f) Effects of the Invention As described above, the present invention is characterized in that the parison extruded from the gap between the die and the core of a blow molding machine is formed into a mold corresponding to the external shape of the bent product to be processed. The parison used for molding is forcibly bent into a shape that approximates the mold surface, stabilized in a position corresponding to the mold surface, and then molded according to the normal blow molding order. Since it is sufficient to use an amount of parison that substantially corresponds to the size of J:
Since the drawdown is reduced compared to the conventional method, it is possible to mold products with uniform wall thickness and excellent quality. However, since the minimum amount of material necessary for molding can be discharged as a parison, the molding time can be significantly shortened, and as a result, a significant cost reduction can be achieved. In addition, it is now possible to easily mold large-width bent products using a relatively small-capacity molding machine, which was difficult to mold using conventional molding methods without using a molding machine with considerably large molding capacity. Since it becomes possible to do so, it has great effects such as contributing to savings in capital investment.

[Brief explanation of drawings]

1 to 4 show a blow molding method according to the present invention, FIGS. 5 and 6 show a blow molding method according to a related invention of the present invention, and FIGS. 7 and 8 show a conventional blow molding method. This shows the molding method, and Figure 1 is a front view with the left and right molds open. FIG. 2 is a sectional view taken along line A-A shown in FIG. 1. FIG. 3 is a sectional view taken along line B-B shown in FIG. 1. FIG. 4 is a cross-sectional view of the left and right molds in a closed state. FIG. 5 is a sectional view showing the first stage of forcibly bending the parison. FIG. 6 is a sectional view showing the second stage of the same as above. FIG. 7 is a sectional view of the left and right molds in an open state. FIG. 8 is a sectional view taken along line CC shown in FIG. 7. In the figure, (1)<1') is the mold. (2) is the mold surface. (3) is a curved surface. (4) (4M) (5) is the parison guide plate. (6) is the die. (7) is the core. (8) is the air discharge hole. (9) is the pressing means. (a) (b) (c) is a bent edge.

Claims (2)

[Claims] (1) The guide plate of the parison is shaped into a curved surface along the outside of the curved edge, which is shaped to correspond to the outer shape of the curved product to be processed, which is provided on the mold matching surfaces of the pair of left and right molds installed in the blow molding machine. When the left and right pair of molds are opened, the parison extruded from the gap between the die and the core of the blow molding machine is guided by the guide plate and lowered to a predetermined position while being forcibly bent. A blow molding method for bending products, which is then molded according to the normal blow molding sequence. (2) A bent surface is provided along the outside of the bent edge of a shape corresponding to the outer shape of the bent product to be processed, which is provided on the mold matching surfaces of the pair of left and right molds installed in the blow molding machine, and this bent surface One end of a flexible guide plate having a radius of curvature larger than that of the curved surface corresponding to the outside of the curved surface is fixed to the extension of the curved surface, and the blow molding machine After the parison extruded from the gap between the die and the core is guided by the guide plate and lowered to a predetermined position while being forcibly bent, the outside of the guide plate is pressed by a pressing means to remove the parison from the guide plate. A method of blow-molding a bent product, in which the parison is further forcibly bent by bringing the parison into close contact with a bending surface provided in the mold, and then the parison is molded according to a normal blow-molding order.