JPH06190905A - Die for blow molding - Google Patents

Abstract

PURPOSE:To provide a die for blow molding which can carry out changing of materials and colors smoothly. CONSTITUTION:A core bar 16 is inserted into a die housing 12 to form resin passages 18 and 22, and a resin inflow opening 21 is opened from the extruder side in the resin passages 18 and 22, and a manifold 20 branched in the left and right in the peripheral direction from the surface of core bar 16 on the resin inflow opening 21 side and heading for the reverse resin inflow opening side of core bar 16 is formed, and a joining section 27 is formed on the manifold 20 side. A residual resin discharge hole and a plug forming a circular passage are formed movably on the die housing 12 in the position facing the resin inflow opening 21 in the resin passages 18 and 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a die capable of easily changing materials and colors in a blow molding machine, and capable of uniformly injecting a parison in the circumferential direction of the die.

[0002]

2. Description of the Related Art Conventionally, when performing blow molding by a blow molding machine, after the molten resin supplied from the extruder is stored in an amount corresponding to the quantity of the molded product, the plunger of an injection device (not shown) is moved. A parison is formed by ejecting resin in a tube shape from the die discharge port, and air is blown to obtain the desired product. On the outer peripheral surface of the core metal of the blow molding die, the resin distributed in two directions, 180 ° opposite to the resin supply port direction side of the die housing to which the discharge port of the extruder is connected, joins at the downstream part thereof. The resin distribution path was formed in the shape described above, and the molten resin was formed as a cylindrical parison.

[0003]

However, the resin distribution passage has a complicated flow passage shape, resulting in a portion where the flow of the molten resin is extremely slow or a residence portion. This stagnation is particularly noticeable on the wall surface where the cross-sectional area of the flow path is large and the flow velocity is slow, and at the corners or confluences where the shape of the flow path changes. There is a problem that a large amount of resin and working time are wasted due to the replacement of the old resin with the new resin that remains, resulting in a decrease in productivity.

Further, the resin may be deteriorated by staying in a high temperature atmosphere for a long time, and the deteriorated resin may be gradually peeled off during the molding and mixed into the hollow molded product, resulting in deterioration of the quality of the molded product. There is also a nature. Furthermore, as a conventional solution, there is a method of disassembling the die itself and directly removing the residual resin adhering to the inside, but it is necessary to stop the entire line every time the material is changed. The work was greatly affected, the operating rate of the equipment decreased, and a long work time was required.

Further, since the weld line formed in the parison is eliminated by the stagnant resin retained in the merging portion, a cleaning hole is formed in the vicinity of the merging portion, and the stagnant resin is taken out from the hole and is not cleaned. There is also a method of sealing with a plug etc. at times, that is, during normal operation. However, the effect of removing old resin adhering to and remaining in a wide retention area such as the resin passage wall in the upstream area, which is the source of the confluence, is small with only the cleaning holes locally provided at the confluence. Further, there is a problem that the resin remaining or deteriorated in the cleaning hole during the sealing plug blocks the hole itself.

It is an object of the present invention to provide a die for blow molding in a blow molding machine, which is capable of smoothly performing material change and color change in view of the above conventional problems.

[0007]

In order to solve such a problem, in a blow molding die according to the present invention, a core metal is inserted into a die housing to form a resin passage, and the resin is extruded into the resin passage. Open the resin inlet from the machine side, branch from the surface of the core metal on the resin inlet side to the left and right in the circumferential direction, reduce the passage cross-sectional area toward the side opposite to the resin inlet of the core, and bend in the extrusion direction. And forming a merging portion by merging ends of the manifold to form a merging portion, and forming a stagnation resin discharge hole in the die housing at a position where the resin inlet is open in the resin passage, A plug having a gap between the inlet opening communicating with the resin passage of the staying resin discharge hole and the inner surface of the opening is movably provided.

[0008]

[Function] During normal operation of the hollow molded product, that is, when there is no so-called material change or color change, a loose fitting state (annular passage) is kept between the plug and the inlet opening of the staying resin discharge device discharge hole, so that the resin is in the middle. The resin flow in the resin retention area is constantly formed so that it will not accumulate. On the other hand, when the hollow molded product is not molded, that is, when the material is changed or when the color is changed, the plug is retracted to completely open the inlet opening of the staying resin discharge device extraction hole. The new and old resin can be exchanged in a short time.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of the blow molding die according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a blow molding die 1 according to an embodiment.
FIG. The die 10 has a die housing 12 made of a rectangular block, and a through-hole 14 having a substantially circular cross section is bored along the vertical center line. Such a through hole 14 is opened in the lower end surface of the housing 12 in a state where the inner diameter is gradually reduced from the middle to the lower end surface of the housing 12.

A through hole 14 is formed in the housing 12.
The core metal 16 having a smaller diameter is inserted, and the core metal 1
6 between the outer peripheral surface of 6 and the inner peripheral surface of the through hole 14
Is formed. The lower end of the cored bar 16 is formed with a narrowed end corresponding to the reduced diameter portion of the through hole 14.

A core metal 16 is provided at the lower end of the die 10.
A parison control core 16b is mounted so that it can be moved in and out. A mandrel lip 29, which faces the opening of the through hole 14 and forms a circular ring-shaped resin discharge port 28 between the opening of the through hole 14 and the front end of the parison control core 16b, is integrally provided. . Therefore, the die gap of the resin discharge port 28 can be arbitrarily changed by changing the in / out amount of the parison control core 16b.

The die gap is changed by changing the die housing 1.
This is made possible by driving a control cylinder 30 fixed to a support plate 25 on a column 24 standing upright on the column 2. Therefore, a parison control rod 32 connecting the control cylinder 30 and the parison control core 16b is used as a core. It penetrates the gold 16.

Further, the molten resin supplied to the resin inlet 21 from the resin passage 22 connected to the extruder 23 provided on the peripheral wall of the die housing 12 is first measured in the circumferential direction from the surface of the core metal 16 on the resin inlet 21 side. A manifold 20 having a semicircular cross section is formed which is branched leftward and rightward, and is gradually curved in the extrusion direction with a predetermined curvature while gradually reducing the passage cross-sectional area toward the anti-resin inlet 21 side of the core metal 16 at a predetermined rate. ing. The end of the manifold 20 is formed so as to join with the symmetrical manifold 20 on the opposite surface side at a position of approximately 180 degrees from the resin inlet 21.

A dam lip portion 31 is formed corresponding to the confluence portion 27 to form a shallow passage along the circumferential direction of the core metal 16. The dam lip portion 31 is provided corresponding to the throttle passage portion of the resin passage 18, and is set so that the gap between the dam passage portion 31 and the through hole 14 of the housing 12 is narrowed so that the flow passage resistance is uniform over the entire circumference. ing.
In this case, the merging portion 27 is connected and merged so that the manifolds 20 having merging symmetry are in contact with the line along the axis of the core metal 16. As a result, the flow lines of the molten resin flowing down the manifold 20 are parallel at the merging portion.

The entire tubular passage extending from the lower edge of the manifold 20 to the dam lip portion 31 is
It is shallower than the cross-sectional depth of passage 0, and the dam lip 3
Land portion 29 forming a passage deeper than the depth of the flow passage in one portion
Is formed. This is formed by adjusting the scraping depth of the outer periphery of the cored bar 16 as described above.

In the present invention, with the above structure as a basic structure,
As shown in FIG. 1 and FIG. 2, in order to replace old resin and new resin that have stayed in the die 10 without moving, quickly and completely, in particular, a place where the resin is likely to stay,
In other words, the accumulated resin extraction hole 50 (FIG. 4) is formed in the die housing 12 in the vicinity of the resin retention portion 60 (where weld lines are likely to occur) that is the most remote from the resin inlet 21 passing through the manifold 20. .

The staying resin discharge hole 50 has an opening 50a whose one end is opened in an upper region of the resin passage 18 and is formed in the die housing 12 in a state of being bent in the shape of a dogleg. In addition, the structure has a discharge port portion 50b having the other end opened to the outer wall portion of the die housing 12.

Further, as described above, the die housing 1
2. A staying resin discharging device 3 for completely opening or loosely fitting the opening 50a of the staying resin extraction hole 50 formed in the second embodiment.
3 are provided. The accumulated resin discharging device 33 shown in FIG.
Is composed of a valve rod 34, a piston rod 34a, a joint 34b, a plug 35 and a cylinder 36.

The inner peripheral surface of the opening 50a of the staying resin discharge hole 50 and the outer peripheral surface of the plug 35 fixed to the tip of the valve rod 34 are arranged in a loose fit (annular passage) state. The space has, for example, an annular passage having a gap of 0.1 to 3 mm. On the other hand, the upper end of the valve rod 34 is connected to the cylinder 3 via the joint 34b.
6, a piston rod 34a is provided so as to be able to move forward and backward, and both are connected. Therefore, by supplying or discharging pressurized oil or compressed air to or from the cylinder 36, the plug 35 moves back and forth, and during normal operation (blow molding machine), the plug 35
Is at the position shown by the solid line in FIG.

With this structure, when molding a normal blow-molded product without material change or color change, the molten resin has an annular passage between the inner peripheral surface of the opening 50a and the outer peripheral surface of the plug 35 at the forward limit of the plug 35. The resin is continuously flown into the resin extraction hole 50 from the discharge port 50, and the inflowing resin can be discharged to the outside from the discharge port 50b communicating with the resin extraction hole 50.

On the other hand, when the material or the color is changed,
Not only the accumulated resin in a wide range from the manifold 20 to the merging portion 27, but also when it is desired to replace the old resin and the new resin remaining in the resin retaining portion 60, that is, a portion where the resin is likely to retain, the accumulated resin discharging device 33. This is made possible by supplying pressurized oil or compressed air to the cylinder 36 to move the plug 35 at the tip of the valve rod 34 to the backward limit and completely open the opening 50a.

The operation of the blow molding die portion configured as described above will be described. The resin that has flowed in from the resin inflow port 21 branches left and right in the manifold 20 and flows down to reach the merging portion 27, and simultaneously with the branching and downflow, overflows from the lower edge of the manifold 20 to the land portion 29, and the resin passes through the resin passage 18 It will flow evenly around the entire circumference. And
Since the groove cross-sectional area of the manifold 20 is set to be gradually smaller, the pressure distribution in the circumferential direction becomes uniform and the parison has a uniform thickness and flows down in a state of being readjusted by the dam lip portion 31. It is ejected.

Even during the repeated molding of the blow-molded product, the molten resin constantly flows little by little through the annular passage between the plug 35 and the opening 50a toward the resin extraction hole 50, so that the resin material is changed. , Or plug 3 with color change
Even when 5 is moved backward to the position shown by the chain double-dashed line in FIG. 4, unlike the conventional case where the opening 50a of the resin extraction hole 50 is completely opened or completely sealed by moving the needle valve or the like forward and backward, Resin that stays in the vicinity of the opening 50a or in the resin extraction hole 50 for a long time when completely sealed and the molten resin deteriorates and solidifies without causing the problem that the resin does not flow even if the needle valve and the like are opened. Can be completely discharged to the outside through the staying resin extraction hole 50. By continuously holding or intermittently repeating such a series of operations, the remaining resin at the most apt to stay is eliminated, and the old resin is replaced with the new resin conveniently and quickly and completely.

As described above, in the embodiment according to the present invention, the die housing 12 facing the confluence portion 27 of the manifold 20 is provided with one resin withdrawal hole 50, but the invention is not limited thereto. Instead, as shown in FIGS. 5 and 6, the merging portion 27 (1
If the resin withdrawal holes 50 are provided in the die housing 12 (two places) facing the manifold 20 on the upstream side of the joining portion 27 and the joining portion 27, the material and the color can be easily changed in a short time.

[0026]

As is clear from the above description,
In a blow molding die according to the present invention, a core metal is inserted into a die housing to form a resin passage, and a resin inlet from the extruder side is opened in the resin passage. A manifold is formed that is branched from the surface to the left and right in the circumferential direction, has a passage cross-sectional area that decreases toward the anti-resin inlet side of the core metal, and is curved in the extrusion direction, and joins the manifold ends to form a merging portion. A stagnation resin discharge hole is formed in the die housing at a position where the resin inflow port opens in the resin passage, and the stagnation resin discharge hole has an inlet opening communicating with the resin passage. By providing a movable plug with a gap between it and the inner surface of the opening, uniform parison injection can be performed, and the retention part of the resin flow in the die can be prevented from being generated at a fixed position. Material change And excellent effect that it is possible to perform rapid discharge of the old material during such color change is obtained. Further, the material and color can be easily changed over a wide range of the resin passage extending to the confluence portion and the upstream area, and the old resin does not stay in the newly provided staying resin extraction hole and adhere and remain. Further, the time for changing the material or the color is shortened, the productivity is improved, the resin is not wasted during the preparatory work, and the consumption of the resin is reduced.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional front view of a die showing an embodiment according to the present invention.

FIG. 2 is a partial cross-sectional side view of a die showing an embodiment according to the present invention.

FIG. 3 is a sectional view taken along line AA of FIG.

FIG. 4 is a partially enlarged cross-sectional view showing a staying resin discharging device.

FIG. 5 is another embodiment of the die having the accumulated resin discharging device according to the present invention.

6 is a cross-sectional view taken along the line AA of FIG.

[Explanation of symbols]

 10 dice 12 die housing 12a upper die housing 12b lower die housing 14 through-hole 16 core metal 16b parison control core 18,22 resin passage 20 manifold 21 resin inlet 23 extruder 27 merge part 28 resin discharge port 29 land part 30 control Cylinder 31 Dam lip part 33 Retained resin discharge device 35 Plug 36 Cylinder 50 Resin extraction hole 50a Resin extraction hole opening 60 Resin retention part

Claims (1)

[Claims] 1. A core metal is inserted into a die housing to form a resin passage, and a resin inlet from the extruder side is opened in the resin passage. A manifold having a passage cross-sectional area reduced toward the side opposite to the resin inlet of the core and curved in the extrusion direction, and the manifold ends are joined to form a joining portion. Is formed in the die housing at the opposite position opened in the resin passage, and a stagnant resin discharge hole is formed in the die housing, and an inlet opening communicating with the resin passage of the stagnant resin discharge hole is provided with an inner surface of the opening. A blow molding die characterized in that a plug having a gap between them is movably provided.