JPH0626847B2 - Blow molding method for bent products - Google Patents

Description

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

(B) Prior Art and Problems to be Solved by the Present Invention Conventionally, in the case of manufacturing a bent product by blow molding, for example, a spoiler attached to the rear part of the body of a passenger car, it is shown in FIGS. 7 and 8 of the drawings. The pair of left and right molds (1) and (1 ') provided with mold surfaces (2) and (2) corresponding to the outer shape of the spoiler to be processed are mounted on the blow molding machine, and the pair of left and right molds are mounted. (1) With the (1 ') opened, the parison (P) extruded from the gap between the die (6) and the core (7) in the blow molding machine is moved to the left and right dies (1) (1). After lowering to a predetermined position during ′),
The spoiler is manufactured by closing the left and right molds (1) (1 ') and supplying air from the air discharge holes (8) into the parison (P). With such a method, As shown in Fig. 8 of the drawing, it is necessary to use a parison (P) having a diameter corresponding to the entire width of the mold surface (2) having a shape corresponding to the outer shape of the spoiler to be processed, so material loss at the time of molding However, the so-called drawdown, because it is necessary to discharge a material that is several times as many as the material actually used in the product as a parison (P),
In other words, the thickness of the material injected later than the thickness of the material injected first tends to become thinner due to its own weight, which exceeds the adjustment range of the thickness adjuster, resulting in a uniform thickness. It is difficult to mold a product, and there is a problem that a molding machine having a plasticizing ability for a material more than necessary must be used and a molding time is spent more than necessary.

In view of the above conventional problems, the present invention has a uniform wall thickness of a molded product, and also enables the use of a molding machine having a plasticizing ability of a material substantially corresponding to the size of the product,
However, it is intended to provide a blow molding method that can significantly shorten the molding time.

(C) Means for Solving the Problem In order to achieve the above-mentioned object, the present invention is a bending work as a working thread provided on the mating surfaces of a pair of left and right molds (1) and (1 ') mounted on a blow molding machine. The guide plates (4) and (5) of the parison (P) are provided in a curved shape along the outside of the bent edges (a) and (b) having a shape corresponding to the outer shape of the product, and the pair of left and right molds (1) are provided. With the (1 ') open, the parison (P) pushed out from the gap between the die (6) and the core (7) in the blow molding machine is guided by the guide plates (4) and (5). As a result, it is forcibly bent and lowered to a predetermined position and then molded according to a normal blow molding sequence.

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

That is, a pair of left and right molds (1) mounted on the blow molding machine
The bending surface (3) is provided along the outside of the bending edge (c) having a shape corresponding to the outer shape of the bending product to be machined provided on the mold matching surface of (1 ′). One end of a guide plate (4 ') having flexibility larger than the bending surface (3) corresponding to the outside is fixed to the extension of the bending surface (3), and the pair of left and right molds (1 ) (1 ') is opened, and the parison (P) pushed out from the gap between the die (6) and the core (7) in the blow molding machine is guided by the guide plate (4'). After being forcibly bent while being lowered to a predetermined position, the guide plate (4 ') is pressed by the pressing means (9) to move the guide plate (4') to the molds (1) (1 '). ), The parison (P) is further forcibly bent by closely contacting it with the bending surface (3) provided in
Molding is performed according to a normal blow molding sequence.

(D) Working The parison (P) extruded in 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 is flexible, and has a certain weight. Since the pushing force works together with the guide plate (4) or (5) during the descending process, the guide plate (4) or (5) does not come into close contact with the guide plate (4) or (5) and easily bends. While descending, it descends along the curved surface. As shown in FIG. 2 of the drawing, the parison (P) is bent into a shape similar to the mold surface (2) formed on the mold (1) in correspondence with the contour of the bent product to be processed. Since it is stable at the position corresponding to the mold surface (2),
Subsequently, if molding is carried out according to a normal blow molding sequence, the resin will be spread evenly on the entire surface of the mold (2), and a product having a uniform wall thickness will be molded.

As shown in FIG. 5, the parison (P) is the same as above.
The guide plate (4 ') is forcibly bent and lowered to a predetermined position, and then the outside of the guide plate (4') is pressed by the pressing means (9) as shown in FIG. Then, when the guide plate (4 ') is brought into close contact with the bending surface (3) provided in the mold, the parison (P) corresponds to the outer shape of the bending product in which the degree of bending to be processed is remarkable. Thus, it is bent into a shape similar to the mold surface (2) formed on the mold (1) and is stabilized at a position corresponding to the mold surface (2).

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

A bent product to be processed, that is, a spoiler attached to the rear part of the passenger's body, on the mold matching surfaces of a pair of left and right molds (1) and (1 ') mounted on a blow molding machine (partly omitted in the figure). The mold surface (2) corresponding to the outer shape of the mold is provided, and as shown in FIG. 2, the mold surface (2) has a shape in which the upper end portion and the lower end portion are respectively bent to the right side. There are two bending edges (a) and (a ') or (b) and (b') on the upper side and the lower side of the surface (2), respectively, of which the bending edges located on the lower side, that is, In the upper two bent edges (a) and (a ') of the mold surface (2), the right bent edge (a),
In the lower two bending edges (b) and (b ') of the mold surface (2), a bending surface (3) is provided along the outside of the left bending edge (b), respectively. As shown in FIGS. 1, 3 and 4, one side edge of the guide plates (4) and (5) of the parison, which are provided along the curved surface along the line (3), respectively, as shown in FIGS. 1) It is superposed on the curved surface (3) and fixed by screws (not shown) etc., and the widths of the guide plates (4) and (5) are left-right paired as shown in FIGS. 1 and 3. Of the guide plates (4) and (5) when the molds (1) and (1 ') are opened so that they slightly overlap the bending surface (3) of the right mold (1'). It is set. However, overlapping is not always necessary. However, since it is a guide plate for guiding the parison (P), it needs a width capable of supporting the parison (P).

Now, with the pair of left and right molds (1) (1 ') opened as shown in FIGS. 1 and 3, the middle of the pair of left and right molds (1) (1'). When a parison (P) made of a thermoplastic material is extruded into a tubular shape from the gap between the die (6) and the core (7) located above the part, the parison (P) first comes to the upper part as shown in FIG. It is guided by the guide plate (4) to be forcibly bent to the left side, and subsequently guided by the lower guide plate (5) to be forcibly bent to the right side and descended. A so-called pre-pinch (sealing the lower end of the parison and supplying air to the inside to adjust the diameter of the parison in advance) may be performed in the same manner as above, but in this way the parison (P) is forced. While bending it, lower it to the vicinity of the lower end of the mold (1) (1 '). After the usual blow molding order,
That is, as shown in FIG. 4, the left and right molds (1)
By closing (1 ') and supplying air into the parison (P) from the air discharge hole (8), the parison (P) is expanded and brought into close contact with the mold surfaces (2) and (2), and is left as it is. After cooling and solidifying in the state, the left and right molds (1) and (1 ') are opened to complete the molding.

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

FIGS. 5 and 6 correspond to FIG. 2 in the above-described embodiment, and the spoiler in which the degree of bending to be processed is remarkable on the die matching surface of the die (1). A mold surface (2) corresponding to the outer shape of the mold is provided. Since the mold surface (2) has a shape in which the upper end portion is bent to the right side at a substantially right angle, two left and right bent edges ( Although there are c) and (c '), a bending surface (3) is provided along the outside of the right bending edge (c) located on the lower side, and corresponds to the outside of this bending surface (3). The lower end of the metal guide plate (4 ') having a larger radius of curvature than the bent surface (3) is fixed to the extension of the bent surface (3).

Now, as in the above embodiment, a pair of left and right molds (1)
When the parison (P) is extruded from the gap between the die (6) and the core (7) located above the middle part of the parison (P) in the state in which (1 ') is opened, the parison (P) is shown in FIG. As shown in the figure, it is guided by the guide plate (4 ') and descends while being forcibly bent to the left side. Therefore, after descending to a predetermined position, the outside of the guide plate (4') is pressed by an arbitrary pressing means ( 9), for example, by pressing with a hydraulic cylinder or the like to bring the guide plate (4 ') into close contact with the curved surface (3) provided on the mold (1) as shown in FIG. 6, the parison (P). Is further forcibly bent and then molded in the usual blow molding sequence.

(F) Effect of the Invention As described above, the present invention is a mold in which a parison extruded from a gap between a die and a core in a blow molding machine is formed in a mold in accordance with the outer shape of a bent product to be processed. The parison used for molding is the product of the molded product because it is forcibly bent into a shape close to the surface and stabilized at the position corresponding to the mold surface, and then molded according to the normal blow molding sequence. Since the amount of parison that substantially corresponds to the size is sufficient, material loss during molding is reduced and the drawdown due to the weight of the parison can be reduced due to the weight reduction of the parison, so the wall thickness is uniform. It is possible to mold high quality products. However, since the minimum amount of material required for molding can be discharged as a parison, the molding time can be greatly shortened, and as a result, a significant cost reduction can be realized. In addition, with conventional molding methods, it is possible to easily mold bent products with a wide width, which was difficult to mold without using a molding machine with a considerably large molding capacity, with a molding machine with a relatively small capacity. Therefore, it has a great effect such as saving the capital investment.

[Brief description 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. Fig. 1 shows a molding method, and Fig. 1 is a front view in which the left and right dies are opened. FIG. 2 is a sectional view taken along the line AA shown in FIG. FIG. 3 is a sectional view taken along line BB shown in FIG. FIG. 4 is a cross-sectional view in which the left and right molds are closed. FIG. 5 is a cross-sectional view showing the state of the first stage when the parison is forcibly bent. FIG. 6 is a cross-sectional view showing a second stage state of the above. FIG. 7 is a sectional view showing a state where the left and right molds are opened. FIG. 8 is a sectional view taken along the line CC of FIG. In the figure, (1) and (1 ') are molds. (2) is the mold surface. (3) is a curved surface. (4), (4 ') and (5) are parison guide plates. (6) is a die. (7) is the core. (8) is an air discharge hole. (9) is a pressing means. (A), (b) and (c) are bent edges. (P) is a parison.

Claims (2)

[Claims] 1. A parison guide plate is curved along the outside of a bending edge having a shape corresponding to the outer shape of a bending product to be processed provided on the die matching surfaces of a pair of left and right molds mounted on a blow molding machine. And the pair of left and right molds are opened, the parison pushed out from the gap between the die and the core in the blow molding machine is guided by the guide plate and forcedly bent at a predetermined position. A blow molding method for bent products, in which the product is lowered until it is molded according to the normal blow molding sequence. 2. A bending surface is provided along the outside of a bending edge having a shape corresponding to the outer shape of a bending product to be processed provided on the die matching surfaces of a pair of left and right molds mounted on a blow molding machine. One end of a guide plate having flexibility larger than the bending surface and having a larger radius of curvature corresponding to the outside of the bending surface is fixed to the extension portion of the bending surface, and the pair of left and right molds are opened to blow. The parison extruded from the gap between the die and the core in the molding machine is guided to the guide plate to forcibly bend and descend to a predetermined position, and then the outer side of the guide plate is pressed by a pressing means. By further forcibly bending the parison by bringing the guide plate into close contact with the bending surface provided in the mold, and molding in accordance with the usual blow molding sequence.
Blow molding method for bent products.