JPH05104615A - Cooling method and device of blow molding - Google Patents

Abstract

PURPOSE:To perform swiftly and uniformly cooling of a parison in blow molding. CONSTITUTION:A parison P on the inside of clam molding tools 2, 3 is pierced with a blow pin 9 and leak pin 10, blow air is fed into an inner space S from the blow pin, the parison P is cooled by the blow air while molding the parison P into a fixed form and the blow air is evacuated through the leak pin 10 after that. Then at the time of feed of the blow air, an air blow-off member 14 of the tip of a blow pin is turned by making use of blow pressure of the blow air, through a rotation of which the blow air is made into a state of a turbulent flow and fed into the inner space S of the parison. With this construction, it becomes that the blow air is blown against an inner wall of the parison extending over the whole region and the parison P can be cooled swiftly and uniformly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling method for blow molding and an apparatus used for the blow molding, and in particular,
The present invention relates to a blow pin that is inserted into the parison to introduce blow air into the parison interior space.

[0002]

2. Description of the Related Art Blow molding has been known as a method for molding hollow resin molded articles. This blow molding is
With a set of split molds opened, between these split molds,
The molten cylindrical parison is introduced and then the mold is closed to position the parison in the mold. And in this state,
As shown in FIG. 5, blow pins b from the side of the parison a.
And the tip opening of the blow pin b faces the parison internal space c. Then, blow air is blown into the parison internal space c by the blow pin b to bring the internal space c to a pressure equal to or higher than the atmospheric pressure. As a result, the outer surface of the parison a is molded into a shape along the molding surface of each of the molds d and e. On the other hand, in such blow molding, a configuration is known in which a leak pin f is provided separately from the blow pin b. That is, as shown in FIG. 5, the leak pin f having the plurality of openings g, g is pierced from the side surface of the parison a, and the blow pin b is inserted as described above.
Blow air blown into the parison internal space c from the parison is appropriately exhausted to stabilize the internal pressure of the parison internal space c to a predetermined value, and new air is constantly supplied to the parison internal space c. The cooling efficiency is improved. Then, after continuously supplying and exhausting such blow air for a predetermined time, the blow air in the internal space c of the parison a is exhausted from the pins b and f, and the parison internal space c is at atmospheric pressure. Then, the mold is opened to obtain a blow molded product.

[0003]

However, in the above-mentioned operation, since the blow air flows as shown by the arrow in FIG. 5 between the blow pin b and the leak pin f, this occurs. Cooling is promoted in the parison a existing between the pins b and f, but air stays in a region that is not between the pins b and f, for example, in the region h in FIG. However, the parison a in this portion cannot be cooled sufficiently. In such a situation, not only the molding cycle time cannot be shortened, but also the molded product is deformed due to the non-uniform cooling rate in each part of the parison a, which causes a defective product. It could have been a factor.

Further, in such blow molding, the structure as disclosed in JP-A-3-9831 and JP-A-3-13313 is considered in consideration of positively cooling the parison. However, this requires a separate cooling device and a cooling process separate from the molding process, which complicates the device and significantly shortens the molding cycle time. It wasn't enough to get me to do it.

The present invention has been made in view of these points, and an object thereof is to obtain a blow molding which can cool a parison quickly and uniformly with a simple structure.

[0006]

In order to achieve the above-mentioned object, the present invention supplies blow air blown from a blow pin into a parison in a turbulent state so that the blow air is blown over the entire interior space of the parison. To supply. Specifically, in the method according to the invention of claim 1, after closing the parison with the molding die, the blow pin and the leak pin are respectively projected from the molding surface of at least one molding die at positions spaced by a predetermined distance from each other. The parison, and blow air is blown into the parison internal space from the blow pin to form the parison into a predetermined shape, and at the same time heat is exchanged between the blow air and the parison to cool the parison, and then this heat exchange is performed. The cooling method of blow molding in which the blow air that has been subjected to the above is appropriately exhausted by the leak pin is targeted. Then, the blow air is supplied from the blow pins to the internal space of the parison in a turbulent state so that the blow air is blown over the entire area of the inner wall of the parison.

In the apparatus according to the second aspect of the present invention, the parison is closed by the molding die, and the blow pin and the leak pin are respectively projected from the molding surface of at least one molding die at positions where a predetermined distance is present, and the parison is formed. And blow air from the blow pin into the parison internal space to form the parison into a predetermined shape,
The blow molding apparatus is designed to perform heat exchange between the blow air and the parison, and appropriately discharge the blow air after the heat exchange by the leak pin.
Further, the blow pin is configured such that at least a blow air blowing portion is rotatable so that blow air is supplied to the parison internal space in a turbulent state.

According to a third aspect of the present invention, in the blow molding apparatus according to the second aspect, the blow air blowing portion of the blow pin is rotated by the blow pressure of the blow air.

[0009]

The operation of the above configuration will be described below. According to the first aspect of the invention, at the time of blow molding, first, the parison is closed by the molding die, and then the blow pin and the leak pin are projected from the molding surface of the molding die and pierced into the parison. In this state, blow air is supplied from the blow pin to the internal space of the parison to mold the parison into a predetermined shape. At this time, the blow air supplied from the blow pin is in a turbulent state and is blown over the entire area of the inner wall of the parison, and heat is exchanged with the parison to cool the parison. The blow air that has exchanged heat is appropriately exhausted by the leak pin. In this way, in this method, the blow air is turbulently blown over the entire inner wall of the parison, so that the parison is cooled quickly and uniformly.

According to the second aspect of the present invention, when the blow air is blown from the blow pin, at least the blow air blowing portion of the blow pin rotates and the blow air is supplied to the parison internal space in a turbulent state. Therefore, in blow molding using this device, the parison can be cooled quickly and uniformly.

When the blow air reaches the blow air blowing portion of the blow pin, the blow air blowing portion is rotated by the blow pressure of the blow air. By this rotation, the blow air supplied to the internal space of the parison becomes a turbulent state, and the parison is cooled quickly and uniformly. As described above, since the turbulent flow state is generated by effectively utilizing the blow pressure, the device structure is simplified.

[0012]

【Example】

(First Embodiment) Next, a first embodiment of the present invention will be described. In this example, a case where an automobile fuel tank is adopted as a blow-molded product molded by the blow molding according to the present invention will be described.

FIG. 1 shows a vertical cross section around the molding die 1 in the blow molding process of the fuel tank T. The mold 1 is composed of a pair of left and right split molds 2 and 3, and the right mold 2 molds the upper half of the fuel tank T, and the left mold 3 molds the lower half of the fuel tank T. .. That is, in the mold closed state as shown in FIG. 1, the cavity formed between the molding surfaces 2a and 3a of both molds 2 and 3 constitutes a predetermined fuel tank shape.

Further, inside the left and right dies 2 and 3, pool passages 4 are formed through which cooling water for cooling the dies 2 and 3 flows during blow molding. This pool passage 4
Is equipped with a plurality of pool holes 4a, 4a, ... Bored in the direction perpendicular to the paper surface of FIG. 1, and a supply hole 4b for supplying cooling water to the pool holes 4a.
.. and the supply hole 4b communicate with each other to form the pool passage 4. In addition, each mold 2, 3
Sensor mounting holes 5 into which mold temperature sensors (not shown) for detecting the respective temperatures are inserted and arranged. Further, each mold 2 and 3 is formed with an air vent hole 6 which communicates the cavity with the outside of the mold (atmosphere), and the outer surface of the fuel tank T which is a molded product and the molding surface 2a during blow molding. The air remaining between the air and 3a is discharged into the atmosphere.

A molding machine (not shown) is connected to each of the molds 2 and 3, and in the right mold 2, the molding machine is connected via a spacer 7 and a molding machine mounting plate 8. Further, on the upper surface of the spacer 7, a hanger 7a to which a wire for suspending is attached when suspending and moving the respective molds 2 and 3 together with the spacer 7 is arranged.

The right mold 2 is provided with a blow pin 9 which will be described later and a leak pin 10 which is arranged at a position spaced apart from the blow pin 9 by a predetermined distance. The leak pin 10 will be described below. This leak pin 10
Is a tubular member that is pierced into the side surface of the parison P during blow molding so that its tip 10a faces the internal space S of the parison P and exhausts blow air. The tip end of the leak pin 10 is formed in a tapered shape to ensure the ability to pierce the parison P, and a plurality of exhaust holes 10b, 10b, ... Are formed near the tip end. Also,
The leak pin 10 has its base end portion arranged on the right side surface 2b of the right mold 2 so as to be movable between the state shown by the solid line and the state shown by the phantom line in FIG. Is connected to the air cylinder 10c. In addition, the internal space of the leak pin 10 is an exhaust pipe 10d indicated by a phantom line in FIG.
The blow air exhausted from the leak pin 10 is discharged into the atmosphere through the exhaust pipe 10d. An unillustrated openable and closable exhaust valve is provided in the exhaust pipe 10d, and the exhaust amount of blow air in the parison internal space S is adjusted appropriately by controlling the opening degree of the exhaust valve.

Next, the blow pin 9 for supplying blow air and its peripheral structure will be described. When the blow pin 9 is blow-molded, the blow pin 9 is pierced into the side surface of the parison P so that the front end portion 9a thereof faces the internal space S of the parison P to supply blow air. In addition, this blow air is also forcedly exhausted.

The blow pin 9 is attached to the right mold 2.
A blow pin insertion hole 11 for movably inserting the blow pin 9 is formed, and a driving means 12 for moving the blow pin 9 in and out is arranged on the right side surface 2b of the right mold 2. That is, the blow pin 9 has its base end portion (right end portion in FIG. 1) connected to the drive means 12, and with the drive of the drive means 12, the state shown by the solid line in FIG. It is configured so that it can move between the state shown and the inside of the blow pin insertion hole 11.

First, the drive means 12 will be described. In the drive means 12, an air cylinder 12b is attached to a support frame 12a attached to the right side surface 2b of the right mold 2, and the drive force of the air cylinder 12b is used. The blow pin 9 is moved. That is, the connecting rod 12c is screwed to the piston tip of the air cylinder 12b.
Has a space 12d opening leftward at its left end, and a female screw portion (not shown) is formed at the left end of this space 12d. A male screw (not shown) is formed on the outer peripheral surface of the base end portion of the blow pin 9, and the base end portion is screwed into the female screw portion of the connecting rod 12c so that the blow pin 9 connects the connecting rod 12c. It is attached to the air cylinder 12b through. The space 12d formed in the connecting rod 12c is open to the lower surface of the connecting rod 12c, and an air pipe 12e extending toward an air pump (not shown) is connected to the open portion. With such a configuration, the inside of the blow pin 9 is connected to the air pump via the space 12d formed in the connecting rod 12c and the air pipe 12e, and the blow pin 9 is driven as the air pump is driven. Blow air can be ejected and sucked from the tip portion 9a of the.

Next, the structure of the tip portion 9a of the blow pin 9 will be described as a characteristic structure of this embodiment. As shown in FIG. 2, the blow pin 9 is composed of a blow pin body 13 and an air blowing member 14 as a blow air blowing portion in the present invention. The tip portion of the blow pin body 13 is formed into a circular opening, and the air blowing member 14 is rotatably supported by a bearing B at the opening edge portion. This air blowing member 14 is
As shown in FIG. 3, the inside is formed in a hollow shape, and the upper end portion thereof is formed in an opening 14a facing the internal space 13a of the blow pin body 13. Further, the air blowing member 14 has a tapered portion 14 formed in a tapered shape.
b and the cylindrical portion 1 integrally formed on the upper side of the inclined portion 14b.
4c and a bearing mounting portion 14d integrally formed on the upper side of the cylindrical portion 14c. In addition, in the inclined portion 14b and the cylindrical portion 14c, a plurality of air holes 14e, 14e,
, 14f, 14f, ... Are formed. That is, the air holes 14e, 14 formed in the inclined portion 14b.
When blow air is blown out from e, ..., the blown blow air is directed obliquely downward as indicated by an arrow A in FIG. 2, while the air hole 14f formed in the cylindrical portion 14c. , 14f, ... Blow air is blown out in a horizontal direction as indicated by arrow B in FIG. Further, as shown in FIG. 3, a pair of inclined plates 14g, 14g are arranged in the inner space of the air blowing member 14 in the vicinity of the opening 14a so as to be inclined in mutually opposite directions.
Are arranged. Since such inclined plates 14g, 14g are provided, when the blow air reaching the opening 14a of the air blowing member 14 from the blow pin main body 13 flows while contacting the inclined plates 14g, 14g, air is blown out. By the blow pressure of the blow air, the member 14 is
It is configured to rotate.

Next, the blow molding process using the molding die 1 constructed as described above will be described. First, the driving means 1
2 and the air cylinder 10c, the blow pin 9 and the leak pin 10 are set to the retracted positions as shown by phantom lines in FIG.
Is in a state where there is a predetermined interval, that is, the mold opening state. And in this mold open state, both molds 2,
The molten cylindrical parison P is introduced into the space between 3. After that, the molding machine is driven to move the left and right molds 2 and 3 in a direction of approaching each other to close the mold, and the parison P is positioned in the cavity formed by the molds 2 and 3. In this state, the substantially bag-shaped parison P is located in the cavity. Then, in this state, the driving means 12 is driven to cause the blow pin 9 to project from the molding surface 2a of the right mold 2 as shown by the solid line in FIG. 1, and the tip portion 9a thereof is pierced into the side surface of the parison P at the same time. Leak pin 1 by driving the air cylinder 10c
0 is also projected from the molding surface 2a of the right mold 2 as shown by the solid line in FIG. 1, and the tip portion 10a thereof is pierced into the side surface of the parison P. As a result, the tips 9a, 10 of the pins 9, 10 are
a faces the internal space S of the parison P.

Then, the air pump is driven to blow air through the air pipe 12e, the space 12d formed in the connecting rod 12c and the blow pin 9, and then the air holes 14e, 14e, ..., 14f, 14f ,. Supply to the internal space S of. Then, the supply of the blow air causes the parison P to expand into a shape along the molding surface of each of the molds 2 and 3 to form a predetermined fuel tank shape.
At this time, the outer surface of the parison P and the molding surface 2 of each mold 2, 3
The air remaining in the space between a and 3a is discharged into the atmosphere through the air vent hole 6.

The characteristic operation of this example is as follows.
This is in the blow air supply operation described above. That is, the blow air that has reached the air blowing member 14 via the blow pin body 13 of the blow pin 9 is brought into contact with the inclined plates 14g, 14g inside the air blowing member 14. At this time, the inclined plate 14
Since blow pressure of blow air acts on g and 14g, the air blowing member 14 rotates in the direction of arrow C in FIG. 3 with respect to the blow pin body 13. In this way, the air blow-out member 14 rotates and the air holes 14
Blow air is supplied from e, 14e, ..., 14f, 14f, ... To the internal space S of the parison P (arrows A and B in FIG. 2). Therefore, the blow air blown toward the internal space S of the parison P is in a turbulent state, and heat is exchanged with the parison P while being uniformly blown over the entire area of the inner wall of the parison. That is, the entire parison P is cooled uniformly.

In such blow air supply operation, when the pressure in the internal space S of the parison P reaches a predetermined value (for example, 7 kgf / cm ² ) which is equal to or higher than the atmospheric pressure, the blow air is continuously supplied. , The leak pin 10
By adjusting the opening degree of the on-off valve of the exhaust pipe 10d connected to the, the blow air is appropriately exhausted from the leak pin 10 to maintain the pressure of the internal space S of the parison P at a constant value. Is continued for a predetermined time. Therefore, the blow air supplied from the blow pin 9 to the parison internal space S in a turbulent state is exhausted to the outside by the leak pin 10 while removing the heat of the parison P. Low (outside air temperature) blow air is constantly supplied to uniformly cool the parison P. Therefore, the parison P is efficiently and uniformly cooled in a short time. At this time, cooling water is circulated in the pool passage 4 to lower the mold temperature, which also promotes cooling of the parison P. When the mold temperature detected by a mold temperature sensor (not shown) mounted in the sensor mounting hole 5 falls below a predetermined temperature, the supply of blow air from the blow pin 9 is stopped and the blow air exhaust operation is performed. .. Explaining this exhaust operation, the on-off valve connected to the leak pin 10 is fully opened to maximize the exhaust function from the leak pin 10, and at the same time, the air pump connected to the blow pin 9 is reversed from the above. The blow pin 9 is forced to suck the blow air in the internal space S of the parison P by performing the operation. In this way, the blow air in the internal space S of the parison P is exhausted, the internal pressure of the parison internal space S is returned to the atmospheric pressure, and then the mold is opened by driving the molding machine to form a blow molded product. Obtain the fuel tank T.

As described above, according to the blow molding as in this example, since the blow air is supplied from the blow pin 9 to the parison internal space S in a turbulent state, the parison P is efficiently and uniformly cooled in a short time. As a result, the blow molding cycle time can be greatly shortened, and the occurrence of product defects due to the difference in heat shrinkage between the respective parts of the parison can be suppressed.

(Second Embodiment) Next, a second embodiment of the present invention will be described. This example is a modification of the blow pin, and since the other configurations are similar to those of the above-described first example, the description thereof will be omitted and only the characteristic portion will be described. As shown in FIG. 4, the blow pin 20 in this example
Has a tip portion 20a formed in a conical shape, and air holes 20b, 20b, ... For ejecting and sucking blow air are formed at a plurality of locations around the tip portion 20a. A first gear 21 is connected to a substantially central portion of the blow pin 20 in the longitudinal direction. An opening 21a for inserting the blow pin 20 is formed in the center of the first gear 21, and a key groove 21b is formed in a part of the opening 21a.
Are formed. On the other hand, the blow pin 20 is provided with a key 20c that is locked in the key groove 21b. Therefore, the blow pin 20 moves first in the longitudinal direction.
It can be performed without being restricted by the gear 21, and when the first gear 21 rotates, it can rotate integrally with the first gear 21. On the other hand, a drive motor 22 is arranged on the right side surface 2b of the right mold 2, and the drive shaft 22a of the drive motor 22 is
A second gear 23 that meshes with the first gear 21 is attached.

With such a structure, during blow molding, the driving force of the drive motor 22 is transmitted from the second gear 23 to the first gear 21, and thereby the blow pin 20.
Will rotate integrally with the first gear 21. Therefore, the blow air blown out from the air hole 20b of the blow pin 20 in such a state also forms a turbulent flow state as in the above-described first embodiment, and even in this example, the parison P is efficiently and short. It can be cooled uniformly over time, the cycle of blow molding can be greatly shortened, and the occurrence of product defects due to the difference in heat shrinkage between the respective parts of the parison can be suppressed.

In the above-mentioned embodiment, the case where the fuel tank for automobile is adopted as the blow-molded article has been described, but the present invention is not limited to this, and various blow-molded articles may be used. Can be adopted. The blow pin 9 and the leak pin 10 may be arranged not only on the right mold 2 but also on the left mold 3. Further, in the invention according to claim 1, as the means for making the blow air turbulent, in addition to rotating the blow pin 9, a means such as disposing a baffle plate in the vicinity of the blow air blowing portion is adopted. You can

[0029]

As described above, according to the present invention,
The following effects are exhibited. First, claim 1
According to the method of the invention described above, the blow air is supplied to the parison internal space from the blow pin in a turbulent flow state so that the blow air is blown over the entire inner wall of the parison. In addition to being uniformly cooled, this not only shortens the molding cycle time, but also avoids the occurrence of product defects caused by the uneven cooling rate in each part of the parison.

According to the device of the invention described in claim 2,
The blow pin is configured so that at least the blow air blowing portion is rotatable, and blow air is supplied in a turbulent flow state, so that the parison is cooled quickly and uniformly, as in the method according to the invention of claim 1. Therefore, the molding cycle time can be shortened and product defects can be avoided.

According to the apparatus of the invention as defined in claim 3,
Since the blow air blowing portion of the blow pin is configured to rotate by the blow pressure of the blow air, it is possible to effectively use the blow pressure to generate a turbulent flow state, shorten the molding cycle time, and reduce product defects. Avoidance can be obtained with a simple configuration.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view around a molding die according to a first embodiment.

FIG. 2 is a vertical cross-sectional view around an air blowing member.

FIG. 3 is a perspective view of an air blowing member.

FIG. 4 is a view corresponding to FIG. 1 in the second embodiment.

FIG. 5 is a vertical cross-sectional view around a molding die in conventional blow molding.

[Explanation of symbols]

 1 Mold 2 Right Mold 2a Molding Surface 9 Blow Pin 10 Leak Pin P Parison S Parison Internal Space

Claims (3)

[Claims] 1. After closing the parison with a molding die, blow pins and leak pins are respectively projected from the molding surface of at least one molding die at positions spaced apart from each other to pierce the parison, and blow air is blown from the blow pin. The parison is supplied to the internal space of the parison to form the parison into a predetermined shape, and at the same time, heat exchange is performed between the blow air and the parison to cool the parison, and then the blow air that has performed this heat exchange is appropriately exhausted by the leak pin. In the blow molding cooling method, the blow air is turbulently supplied from the blow pin to the parison internal space so as to be blown over the entire area of the parison inner wall. Cooling method. 2. A parison is closed by a molding die, and blow pins and leak pins are respectively projected from the molding surface of at least one molding die at positions spaced by a predetermined distance to pierce the parison, and blow air is blown from the blow pin. A blow molding device that supplies the internal space of the parison to form the parison into a predetermined shape and causes heat exchange between the blow air and the parison, and the blow air that has performed this heat exchange is appropriately exhausted by the leak pin. A blow molding device, wherein at least a blow air blowing portion of the blow pin is configured to be rotatable so as to supply blow air to the parison internal space in a turbulent state. 3. The blow molding device according to claim 2, wherein the blow air blowing portion of the blow pin is configured to be rotated by the blow pressure of the blow air.