JPH0564576B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a blow molding method and a molding apparatus.

Conventional technology In conventional blow molding, for example, parison A is sandwiched between a pair of split molds consisting of a male mold A and a female mold B, and air is blown into the parison A that has been flattened by mold clamping. Since it can be molded with air, the manufacturing cost of the split mold is low, and it is easy to mold, so it is widely used.In terms of materials, even ultra-high molecular polyethylene and engineering plastics are suitable for blow molding. has also been developed and used as a useful molding method.

Problems to be Solved by the Invention However, due to the characteristics of the molding method, hollow bodies and double-walled structures can be easily molded, but on the other hand, complex shapes such as plate-like double-walled structures cannot be formed. There were technical problems in molding, such as the following difficulties and low molding pressure, which resulted in poor transferability of the mold from the inner surface shape of the cavity to the parison.

(i) A parison loaded into a split mold will cause a welding phenomenon when the mold is clamped, and a tearing phenomenon will occur when blowing.

For example, the upper and lower walls are double and R as shown in Figure 6.
Problems in the process of molding a molded product with a long cover shape are explained with reference to Fig. 9 a, b, and c. When the double-walled parison A is set in the part 2 and the mold is being clamped, the parison A becomes bowl-shaped when viewed in cross section along the convex part 2, and the side walls 1 and 2 are not yet in close contact with each other. I'm there.
Then, as shown in Fig. 9b, as the female mold B approaches the male mold A and the internal corners E and E of the female mold B come into contact with one side wall T of the parison A, the center of the side wall T changes to the corner E, It is pressed by E and begins to adhere to the other side wall and weld, and as the mold tightening progresses further, the 9th
As shown in Figure c, the side wall G is pulled in the horizontal direction by the pressure of both corner parts E and E, and the part corresponding to the convex part D is cut and damaged. The welded part did not separate, and the welded part at the convex part D of the male mold A sometimes broke.

As described above, the side wall of the parison A sometimes has welding or tearing on the other side wall, does not expand even when blown, and sometimes breaks locally.

In order to solve these problems, a convex part D is formed on the core body and is slidable toward the female mold B side, and the convex part D is retracted before mold clamping. There was a structure that prevented the occurrence of welded parts of the parison and made the final mold clamping by protruding the convex part 2 after mold clamping, but the structure became complicated and the production cost of the split mold increased. However, depending on the shape of the molded product, it may not be possible to apply it.
There was also a problem in that it was a major constraint when using the blow molding method.

(ii) Furthermore, air tends to remain between the parison A and the wall of the cavity, and removal of the remaining air is a major problem.

In other words, since the parison A is inflated after the mold is clamped during molding, air remains on the wall of the cavity, creating avatar-like irregularities on the surface of the molded product, resulting in a quality that is significantly inferior to injection molding or vacuum molding. It was on. To solve this problem, methods have been used to roughen the cavity wall surface with sandblasting to evenly disperse the residual air, and to create holes for air vents, but these methods cannot be said to be sufficient and their effectiveness is limited. It was also extremely small.
A particular problem is that even if air is sucked from the cavity after the mold is clamped, there are always burrs from the parison above and below the split mold, making it impossible to maintain an airtight state. Evacuation was also insufficient, and even if a hole for vacuum suction was partially opened in a part of the wall, it was not an effective method because it could not be sealed unless the parison was in close contact with the surrounding wall. In the present invention, a parison is inserted into a split mold, and as mold clamping progresses, the space formed by the cavity surface in the split mold is evacuated by a vacuum device, and the outer circumferential surface of the parison is tightly attached to the cavity. At the same time, by maintaining the airtightness between the part in the burr relief part, the parison, and the parison itself, it is possible to prevent incomplete airtightness and avatar-like unevenness caused by welding or damage to the parison or burrs on the parison. The purpose of this invention is to eliminate the occurrence of molding and obtain a molded product with good appearance.

Means for Solving the Problems The present invention brings a pair of split molds 1, 1 close to each other and brings opposing elastic members 7, 7 into close contact with each other.
Inside the parison A, the outer surface B of the parison A is brought into close contact with the cavities 2, 2 while the space surrounded by the inner cavities 2, 2 is airtight and evacuated, and the mold is clamped. When molding is performed by blowing, and when the pair of split molds 1, 1 are clamped, the elastic materials 7, 7 laid in the burr relief parts 4, 4 of the split mold 1 and the arcuate passage 5 for the blowing mandrel,
Before crimping the parison A in the burr relief parts 4, 4 and the arcuate passage 5, the ends 7a, 7a on both sides of the opposing elastic members 7, 7 are brought into contact with each other, and the elongated hole part 11,
This is a molding method in which the burr of the parison A, which is pressed into a flat shape by the approach of the elastic materials 7, 7, is surrounded by the elongated holes 11, 11 to make it airtight. A long groove 8 is continuously formed along the mating surface 6 of the mold 1, the burr relief parts 4, 4, and the arcuate passage 5 for the blowing mandrel, and the part of the split mold 1 An elastic material 7 that can be crushed when the mold is clamped is laid so as to protrude from the mating surface 6, the burr relief parts 4, 4, and the arcuate passage 5, and an exhaust passage 9 is formed inside the split mold 1. The exhaust passage 9 is opened into a cavity 2 within the split mold 1.

Effect Next, the function and operation of the present invention will be explained.

As shown in Fig. 4a, there is a parison injection head (not shown) above between the split molds 1 and 1 facing each other at a distance, and a head (not shown) for parison injection is located below when the split molds 1 and 1 are clamped. A pipe F for injecting gas into the blow mandre is placed at a position opposite to the arc-shaped passage 5 constituting the hole for the blow mandre, and the parison A is poured out from the head and split in a hanging state as shown in Fig. 4b. When the molds 1, 1 are brought close to each other, the elastic members 7, 7 of the upper and lower pinch parts 3, 3 and the burr relief parts 4, 4 that face each other come into contact with the left and right outer surfaces B of the parison A,
Eventually, as shown in FIG. 4c, the elastic members 7, 7 planted on the mating surfaces 6 of the split molds 1, 1 begin to come into contact with each other, and as the split molds 1, 1 further approach, the elastic members 7, 7 are inserted into the long grooves 8.
It begins to be crushed inside. At this stage, the parison A between the upper opposing pinch parts 3, 3 and burr relief parts 4, 4 as shown in FIG. The ends 7a, 7a, 7a, 7a on both sides of the elastic members 7, 7 are pressed into a substantially flat shape by the elastic members 7, 7 of 4, 4.
The elongated elliptical long hole portion 1 is formed in close contact with each other.
1 begins to be surrounded by the flat parison A.
Gaps E, E, E remain between the inner surface C of the parison A or between the ends D, D of the parison A and the elastic members 7, 7, respectively, and the mating surfaces 6, 6 of the split molds 1, 1 are still in close contact with each other. I haven't. Further, as shown in FIG. 8, the parison A located between the pinch portions 3, 3, burr relief portions 4, 4, and arcuate passages 5, 5 facing each other at the bottom has an elastic outer surface B as shown in FIG. 8a. Although the parison A is pressed by the members 7, 7, the inner surface C at the center of the cross section of the parison A is in close contact with the outer periphery of the pipe F for the blowing mandre, and the other side parts of the parison A are almost flat. After that, as mentioned above, the upper elastic members 7 and 7 and the parison A
Due to the same operation as in the relationship, a gap E remains. Then, when the split molds 1, 1 are brought closer together, the upper elastic members 7, 7 are exposed to the long grooves 8, as shown in Fig. 7b.
At the same time as it begins to be crushed inside, Parison A
is further pressed and becomes flat, and the inner surfaces C and C of the parison A are brought into close contact with each other, and the outer surfaces B and B of the parison A are brought into close contact with the elastic members 7 and 7, respectively. Furthermore, as the lower elastic members 7, 7 begin to be crushed into the long grooves 8 as shown in FIG. , C are in close contact with each other, and the outer surfaces B, B of the parison A are in close contact with the elastic members 7, 7. At this stage, the mating surfaces 6, 6 of the split molds 1, 1 are not yet in close contact, but the elastic materials 7, 7 of the mating surfaces 6, 6 are in close contact, and the parison in the upper burr relief parts 4, 4 is in close contact with each other. A and the elastic materials 7, 7 in this part are in close contact with each other [Fig. 7c], and the inner surface C of the parison A in the lower burr relief parts 4, 4, the central part of C is a pipe. [Fig. 8b], the inner surfaces C, C of other parts of the parison A are in close contact with each other, and the outer surfaces B, B
is in close contact with the elastic members 7, 7, and the ends 7a, 7a of the elastic members 7, 7 in this portion are in close contact with each other,
The interior of the split molds 1, 1, ie, the space surrounded by the cavities 2, 2, becomes airtight. When the vacuum equipment is operated in this state and the space surrounded by the cavities 2, 2 is started to be exhausted through the plurality of exhaust passages 9, the outer surface B of the parison A is
At the same time, the molds 1 and 1 are brought into close contact with each other and the molds are clamped. And arcuate passage 5,
5 are combined to form a hole, and the blowing mandre is actuated to inject gas into the parison A through the pipe F of the blowing mandre, which is sandwiched between the parison A and the elastic members 7, 7. At this time, parison A
The outer surface B of the parison firmly adheres to the surface of the cavity 2 due to the combination of the effect of exhausting the space and the effect of blowing into the parison, and the shape and surface formed by the opposing cavities 2 and 2 are The pattern cut into the parison A is faithfully transferred to the parison A.

After blow molding, the split molds 1 and 1 are separated and the molded product is taken out from inside.

Embodiment An example of the implementation of the present invention will be explained with reference to a drawing illustrating one of the split molds. 1 is one of the split molds forming a mold, and as shown in FIG. 1, a cavity 2 is formed inside. Then, the pinch parts 3, 3 are left in the upper and lower central parts of the split mold 1, and the concave burr escape parts 4, 4 are formed.
is drilled, and further from the lower burr relief parts 4, 4 to the pinch part 3, when the pair of split molds 1, 1a are clamped, they combine to form a hole and communicate the outside and the inside of the split mold. An arcuate passage 5 is formed for the blowing mandrel. The mating surface 6 of the split mold 1, the burr relief parts 4, 4, and the arcuate passage 5 are covered with elastic materials 7, 7, which will be described later, during mold clamping.
A continuous long groove 8 having a cross-sectional volume that can be crushed and accommodated is bored, and an elastic material 7 is implanted in the long groove 8 so as to slightly protrude from the mating surface 6 of the split mold 1. The elastic material 7 is composed of such a material that it can overcome the melt tension of the parison A and be crushed into the long groove 8 when it collides with the elastic material 7 provided on the mating surface 6 of the opposing split mold 1 during mold clamping. Use resin material. The long groove 8 is formed so that the volume of a cross section cut in a direction intersecting the long groove 8 is large enough to accommodate the crushed elastic material 7. Reference numeral 9 denotes a plurality of exhaust passages bored in the split mold 1, and one opening 9a of the exhaust passage 9 is formed by burning the burr relief part 4 and the mating surface 6 inside the elastic material 7, and the inner surface or corner of the cavity 2. Clamp metal piece 1
0, and the other opening 9b is connected to a vacuum device (not shown).

Effect According to the present invention, opposing elastic members in the mating surfaces and burr relief areas are brought into close contact by bringing opposing split molds close together, and elastic members in the arcuate passage are brought into close contact with the outer surface of the parison. At this stage, the inside of the split mold is kept airtight, and blow molding is performed while evacuating air and clamping the mold while keeping the parison in close contact with the cavity. The parison will not be cut due to pressure from the protrusions or corners of the cavity in the mold, or avatar-like unevenness will occur due to residual gas between the outer surface of the parison and the cavity. Since the pattern can be faithfully transferred, the transferability is improved and a product with a good appearance can be obtained.

In addition, an elastic material and a long groove are provided in the upper and lower burr relief parts, and the parison in the burr relief part is flattened by the opposing elastic materials when the mold is clamped.
By enclosing the elongated hole formed by the elastic material and making it airtight, the seal at the burr escape area is ensured before the mold clamping is completed, and as a result, the inside of the split mold is airtight before mold clamping. This makes it possible to achieve a breakthrough in blow molding, which was previously unachievable, by ensuring reliable molding and faithful transferability, and allowing the blow molding method to be widely used for molding complex shapes. This produces a significant effect.

[Brief explanation of the drawing]

The figures show an embodiment of the present invention, in which Fig. 1 is a perspective view of one of the split molds, Fig. 2 is a sectional view taken along line AA in Fig. 1, and Fig. 3 is a sectional view taken along line BB in Fig. 1. Figure 4 is a side view showing the position and operation of the split molds, parison, and blowing mandre pipes, where a shows the parison starting to hang down from the head between the opposing split molds;
b shows a state in which the parison has finished hanging down, and C shows a state in which the split molds are brought close together and the elastic material is in close contact with each other. Figures 5a and 5b are cross-sectional plan views of the central part of the split mold showing the process of molding the molded product shown in Figure 6 by the method and apparatus of the present invention; , b shows a state in which the parison starts to come into close contact with the cavity surface due to exhaust air in the split mold, and b shows a state in which after the split mold is clamped, the mating surfaces come into close contact and the parison is completely brought into close contact with the cavity. FIG. 6 is a perspective view of a long, roof-shaped molded product. Figures 7a, b, and c are cross-sectional views taken along the line CC in Figure 1, and a is a state in which the elastic material in the upper burr relief part begins to contact the cylindrical parison due to the clamping operation of the split mold. , b shows a state in which the parison is deformed into a flat shape as the mold clamping progresses and the opposing elastic materials come into contact, and c shows a state in which the mold clamping progresses further and the opposing elastic materials and the parison are in airtight contact. It shows. Figure 8 a, b
1 is a sectional view taken along line DD in FIG. 1, where a shows a state in which the opposing elastic material, parison, and pipe are in contact, and b shows a state in which the elastic material, parison, and pipe are in airtight contact. Figures 9a, b, and c are cross-sectional plan views showing the state in which the molded product shown in Figure 5 is molded using a conventional molding device; A state in which one of the split molds is in contact with the parison after the start is shown, and c shows a state in which the parison is broken during mold clamping. Code, 1, 1... split mold, 2... cavity,
3, 3... Pinch part, 4, 4... Burr escape part, 5
...Arc-shaped passage, 5a...Hole, 6...Matching surface, 7...
...Elastic material, 7a... End, 8... Long groove, 9... Exhaust path, 9a, 9b... Opening, 10... Sintered metal piece, 11... Elongated hole, A... Parison, B... ...Outer surface, C...Inner surface, D...End, E...Gap, F...
...Pipe, A...Male type, B...Female type, C...Cover (molded product), D...Protrusion, E, Ho...Corner, H...Cavity, G, CH...Side wall. Ri...melting,
Nu...cut.

Claims (1)

[Scope of Claims] 1. An elastic material 7 that is stronger than the melt tension of the parison A and can be crushed is applied to the mating surface 6 of the split mold 1, the burr relief parts 4, 4, and the arcuate passage 5 for the blow mandrel.
The mating surface 6, the burr relief parts 4, 4, and the arcuate passage 5 are laid in a long groove 8 formed continuously, and the pair of split molds 1, 1 are brought close to each other so that the opposing elastic members 7, 7 are connected to each other. The outer surface B of the parison A is brought into close contact with the cavities 2, 2 while the molds are clamped while the space surrounded by the cavities 2, 2 in the split molds 1, 1 is airtight and evacuated. The split molds 1 and 1 are inserted through the hole formed by combining the passage 5.
A blow molding method characterized by blowing into the inner parison A. 2. A long groove 8 is continuously formed along the mating surface 6 of the split mold 1, the burr relief parts 4, 4, and the arcuate passage 5 for the blowing mandrel, and a parison A is formed in the long groove 8.
An elastic material 7 that can overcome the melt tension of the split mold 1 and can be crushed when the split mold is clamped is laid so as to protrude from the mating surface 6, the burr relief parts 4, 4, and the arcuate passage 5, and A blow molding apparatus characterized in that an exhaust passage 9 is formed inside and an opening 9a is formed in the area surrounded by the elastic material 7 around the split mold 1. 3 When the pair of split molds 1, 1 are clamped, the elastic materials 7, 7 laid in the burr relief parts 4, 4 of the split molds 1, 1 and the arcuate passage 5 prevent the parison A in the burr relief parts 4, 4. Before crimping, the ends 7a, 7a on both sides of the opposing elastic members 7, 7 are brought into contact with each other, and the elongated hole 1 is closed.
1 and 11, and the parison A, which is pressed into a flat shape by the approach of the elastic materials 7 and 7, is inserted into the elongated hole part 1.
1. The blow molding method according to claim 1, wherein the blow molding method is made airtight by enclosing the molded material by means 1 and 11.