JP2000318020A - Head for blow molding of two-layer hollow molded product - Google Patents

Abstract

(57) [Summary] [PROBLEMS] A flow path between an inner resin flow path and an outer resin flow path is provided.
Control (management / adjustment) of thickness, uniformity, ratio and sharpness of inner layer resin and outer layer resin by interposing a cylindrical sliding mandrel that can slide in the vertical direction
The present invention provides a blow molding head for a two-layered hollow molded article, which can easily perform molding and can switch the molded article in a short time. SOLUTION: An inner layer resin flow path 4 and an outer layer resin flow path 6 are formed with a cylindrical sliding mandrel 3 slidable in the vertical direction interposed therebetween, and the cylindrical sliding mandrel 3 is formed in the vertical direction. By sliding, the inflow of the inner layer or the outer layer resin is increased or decreased in a short time with high precision, and a molded article having a good thick inner layer or a thick outer layer and a thin outer layer or a thin inner layer can be easily formed. It can be formed into a shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a head for blow molding a two-layer hollow molded article.

[0002]

2. Description of the Related Art As an apparatus for blow molding a two-layered hollow molded article, an inner peripheral side of a fixedly provided inner cylinder is provided.
An inner cylindrical body fixedly provided with a main mandrel having a passage for a pressurized gas supply formed at the center and formed movably in the vertical direction with respect to the inner cylindrical body. On the side, a blow molding device and the like in which a flow path for the outer layer resin is formed and a die body is provided are known.

[0003]

In the two-layered hollow molded article, various joints made of thermoplastic synthetic resin, containers of various shapes such as bottles, and the like are found in large numbers. A colored layer is provided and a transparent or transparent matte layer is provided on the outer layer to obtain a color effect, and the rigidity, flexibility and barrier properties are obtained by different types of synthetic resin used in the inner layer and the outer layer. , Flexibility by changing the layer thickness between the inner layer and the outer layer,
Some of them seek the effect of curving.

When these two-layer hollow molded articles are molded by a conventionally known blow molding apparatus, the layer state of the inner layer and the outer layer, more specifically, the thickness ratio of the inner layer resin and the outer layer resin is arbitrarily adjusted. In some cases, the thickness ratio cannot be obtained in a wide range, it is difficult to control (manage / adjust) the sharpness of the portion where the thickness changes, and it may take time to switch to a molded product of another type.

[0005]

The blow molding head for a two-layer hollow molded article of the present invention has a cylindrical sliding mandrel that can slide vertically between the inner resin flow path and the outer resin flow path. By sliding the cylindrical sliding mandrel downward, the inflow of the outer layer resin is reduced to form a thinner inner layer, and the inflow of the inner layer resin is increased to form a thicker inner layer, Also, by sliding the cylindrical sliding mandrel upward, the inflow of the outer layer resin is increased to form a thick outer layer, and the inflow of the inner layer resin is reduced to form a thin inner layer. The inflow of the outer layer resin and the inner layer resin can be changed with high accuracy in a short time, and the thickness ratio of the inner layer and the outer layer of the parison is 1% to 99% or 99%.
It can be adjusted arbitrarily in a wide range of 1% to 1%, and a molded article having a predetermined outer layer and inner layer can be easily formed.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be specifically described below based on embodiments. FIG. 1 shows an embodiment of a blow molding head according to the present invention. The blow molding head comprises a cylindrical inner layer mandrel 1, a mandrel shaft 2, a cylindrical sliding mandrel 3, an inner layer resin flow path 4, and a cylinder. An outer layer mandrel 5, an outer layer resin flow path 6, a die body 7, and the like are provided.

[0007] Each of the inner resin inlet 4a and the outer resin inlet 6a communicating with the inner resin flow path 4 and the outer resin flow path 6 formed inside the blow molding apparatus has an extruding screw having a built-in screw. Machine (not shown) is provided. The predetermined synthetic resin is melted by the screw and flows to the resin flow paths 4 and 6.

The inner layer mandrel 1 is cylindrical and formed so as to be fixed vertically to the main body of the apparatus. A mandrel shaft 2 is provided on the inner peripheral surface of the cylindrical inner layer mandrel 1. It is fitted to the mandrel 1 so as to be slidable in the vertical direction. A through hole 2a for supplying a pressurized gas sent from a compressor or the like (not shown) into the parison P is formed in the center.

On the outer peripheral side of the cylindrical inner layer mandrel 1, an inner layer resin flow path 4 is formed, and a cylindrical sliding mandrel 3 is arranged. The cylindrical sliding mandrel 3 includes a servo motor 8, a timing pulley 9, a timing belt 9a, a ball screw 1
0, the guide shaft 20, the shaft 11 connected to the guide bearing 21, and the guides 12a and 12b,
It is provided so as to be slidable in the vertical direction.

A cylindrical outer mandrel 5 is fitted on the outer peripheral surface of the cylindrical sliding mandrel 3, and an outer layer resin flow path 6 is formed on the outer peripheral side of the cylindrical outer mandrel 5 to provide a die body 7. It is. The cylindrical outer layer mandrel 5 is fitted to the outer peripheral surface of the cylindrical sliding mandrel 3 without hindering the sliding of the cylindrical sliding mandrel 3 and formed in a state fixed to the apparatus main body. is there.

The shapes of the cylindrical sliding mandrel 3, the cylindrical inner layer mandrel 1, the die body 7, and the inner layer resin flow path 4 and the outer layer resin flow path 6 formed by these are shown in FIGS. It is formed. That is, the tip of the cylindrical sliding mandrel 3 has a form inclined downward toward the center of the mandrel shaft 2. Along with this, the portion corresponding to this portion of the cylindrical inner layer mandrel 1 and the die body 7 also has a downwardly inclined form.

With these configurations, the degree of opening of the inner resin flow path 4 and the outer resin flow path 6 can be suitably adjusted by sliding the cylindrical sliding mandrel 3 in the vertical direction. I can do it. The inclination angle, inclination length, etc. of the tip of the cylindrical sliding mandrel 3 may vary depending on the shape of the molded product, the type of resin used, molding conditions, etc. The angle of the resin flow path, in other words, the inclination angle of the tip of the cylindrical sliding mandrel is in the range of 40 ° to 80 ° depending on the appropriate molding conditions depending on the gap of the path and the resin used, and more rationally than those. It is selected as appropriate from the length of the slope determined. For this purpose, it is preferable that the tip of the cylindrical sliding mandrel 3 is screwed so as to be replaceable.

The inner resin flow path 4 has one end communicating with the inner resin inlet 4a and the other end communicating with the other end of the outer resin flow path 6. In addition, the outer resin layer flow path 6
Is formed so that one end thereof communicates with the outer resin flow inlet 6a and the other end communicates with the other end of the inner resin flow path 4. As a result, as shown in FIG. 2, the inner resin flow path 4 and the outer resin flow path 6 join at the tip of the cylindrical sliding mandrel 3, and are formed by the resin joining flow path 15, the die 13, and the core 14. Connected to the die opening for resin ejection. The molten resin is discharged and molded as a parison P having a predetermined shape through these passages.

Below the die 13 and the core 14, a molding die (not shown) for accommodating the discharged and molded parison P and performing blow molding by supplying a pressurized gas is provided. It is.

The operation of the blow molding head according to the present invention is shown in FIG.
DPE), the inner layer 31 is made of, for example, low-density polyethylene resin (LDPE), and the plug portion 32 is made of the outer layer 3.
0 is thick and the inner layer 31 is thin.
At the point 33 extending from the base to the shoulder, the outer layer 30 gradually changes to a thinner shape and the inner layer 31 changes to a thicker shape. This will be described by molding a bottle 36 formed in a shape.

The plug 32 of the bottle 36, in which the outer layer 30 is thick and the inner layer 31 is thin, is formed by sliding the cylindrical sliding mandrel 3 upward. The amount of inflow of the outer layer resin flowing into the inner layer 6 increases to form a thick outer layer, and the amount of inflow of the inner layer resin flowing into the inner layer resin flow path 4 decreases to form a thin inner layer.

Next, the outer layer 30 is gradually thinned into the inner layer 31.
Is formed from the base portion of the plug portion 32, which is gradually thick, to the shoulder portion by forming the portion 33 by sliding the cylindrical sliding mandrel 3 gradually downward. The amount of inflow of the outer layer resin flowing into the inner layer 6 decreases to form the outer layer 30 which is thinly inclined toward the bottom, and the amount of inflow of the inner layer resin flowing into the inner layer resin flow path 4 increases to increase the bottom portion. 3
The inner layer 31 becomes thicker toward 5.

The outer layer 30 is formed thin and the inner layer 31 is formed thick, and the body 34 and the bottom 35 are formed by sliding the cylindrical sliding mandrel 3 downward so that the outer layer resin flow is formed. The amount of inflow of the outer layer resin flowing into the passage 6 decreases to form a thin outer layer, and the amount of inflow of the inner layer resin flowing into the inner layer resin flow path 4 increases to form a thick inner layer.

In order to slide the cylindrical sliding mandrel 3 in the vertical direction, in other words, to form the thick outer layer and the thin inner layer by changing them, the servo motor 8, the timing pulley 9, the timing belt 9a, The shaft 11 and the guide 12 connected to the ball screw 10 are operated to slide the cylindrical sliding mandrel 3 in the vertical direction, and the extruder (provided at the outer resin inlet 6a communicating with the outer resin flow path 6) (Not shown) and an operation of increasing or decreasing the rotation speed of an extruder (not shown) provided at an inner resin inlet 4a communicating with the inner resin flow path 4 or an extruder (not shown) and an outer layer The opening / closing of a shut-off valve (not shown) interposed between the resin inlet 6a and the inner resin inlet 4a increases or decreases the inflow of the resin for the inner layer and the outer layer. It is carried out by.

A series of operations such as a sliding operation of the cylindrical sliding mandrel 3 in a vertical direction, a change in the rotation speed of an extruder (not shown) and an opening degree of a shut-off valve (not shown) are performed. For example, the resin pressure is detected by a resin pressure gauge 16 attached to the outer layer resin inlet 6a, and control is performed so that the resin pressure is always kept constant using microcomputer control means. Alternatively, an operation pattern corresponding to the characteristics of the resin used is programmed and stored, and the rotation speed and the opening degree are changed, so that it is possible to improve the quality of the molded product, not to mention automation, which is preferable.

FIG. 6 shows an example of an operation for changing the thickness of a molded product, showing the relationship between the rotation speed of the extruder screw and the opening degree of the cylindrical sliding mandrel. The number of rotations of the extruder screw that flows, the middle is the number of rotations of the extruder screw that flows the resin for the outer layer, the lower is the degree of opening of the cylindrical sliding mandrel, the vertical axis is the amount of change, and the horizontal axis is
Time.

As is clear from this, in the example of FIG.
At the start, the number of rotations of the extruder screw for flowing the resin for the outer layer (hereinafter, referred to as the screw for the outer layer) and the extruder screw for flowing the resin for the inner layer (hereinafter, referred to as the screw for the inner layer) are substantially the same. Thus, the rotation speed of the inner layer screw is slightly reduced, and the rotation speed of the outer layer screw is rapidly increased accordingly. At that time, the cylindrical sliding mandrel is raised (indicated by a minus sign) to increase the opening degree of the outer resin flow path, and the opening degree of the inner resin flow path is decreased, thereby increasing the thickness of the outer layer and increasing the thickness of the inner layer. Is made thin.

Next, after a predetermined time has elapsed, the rotation speed of the inner layer screw is increased and the rotation speed of the outer layer screw is decreased. At that time, the cylindrical sliding mandrel is lowered (indicated by plus) to lower the opening degree of the outer layer resin flow path,
Increasing the degree of opening of the inner layer resin flow path so that the outer layer is thinner,
The thickness of the inner layer is made thick.

Subsequently, the rotation speed of the inner layer screw is decreased, and the rotation speed of the outer layer screw is increased accordingly. At that time, the cylindrical sliding mandrel is raised (indicated by a minus sign) to increase the opening of the outer resin flow path, and the opening of the inner resin flow path is reduced to increase the thickness of the outer layer and the inner layer. Is made thin.

These series of operations are controlled manually or by using microcomputer control means while detecting, for example, the pressure and flow rate of the resin attached to the extruder or the thickness of the molded product.

Here, the sliding operation of the cylindrical sliding mandrel 3 in the vertical direction, in other words, the relative opening degree of the inner layer resin flow path 4 and the outer layer resin flow path 6 in the resin resin merging path 15. Is adjusted by using a servomotor or the like, and adjusting the inflow amount of the resin for the inner and outer layers by adjusting the number of revolutions of the extruder.
It is possible to take a wide range such as 1% to 99% and to switch between the inner layer and the outer layer to be extremely sharp (a change in the layer thickness can be made a short distance).

As shown in FIG. 2, the cylindrical sliding mandrel 3
When a vertical groove having a semicircular shape is formed as shown by a dotted line at the end of the outer layer resin flow path 6 as shown by a dotted line, a rib-like projection 37 can be formed from the plug 32 to the bottom 35 as shown in FIG. The rigidity of each part can be increased. In addition, this vertical groove is formed in a shallow dish shape, and the cylindrical sliding mandrel 3 is slid downward to move to the outer layer resin flow path 6 side, so that the outer layer resin flow path other than the shallow dish vertical groove is formed. 5 by closing block 6
Bottle 3 in which only predetermined portions 38 have two layers as shown in FIG.
6b can be formed. Further, the semicircular vertical groove and the shallow dish-shaped vertical groove may be formed by the ring die 19 facing the tip of the cylindrical sliding mandrel 3.

The size and shape of the molded product can be changed by changing the core 14 at the tip of the mandrel shaft 2 to one having a different size and shape. Also,
By sliding the mandrel shaft 2 in the vertical direction by operating the ball screw 17 or the servo motor 18 provided at the other end of the mandrel shaft 2, the entire thickness of the molded product, for example, the thickness of the parison is reduced from 0.5 mm to It can be varied within a range of 5 mm, preferably 1 mm to 3 mm.

As described above, the blow molding head of the present invention has different rigidities by using different types of synthetic resin for the inner layer and the outer layer.
As described in the molding of bottles for which the effects of flexibility and barrier properties were sought, a colored article was provided for the inner layer, and a transparent or transparent matting layer was provided for the outer layer. It is also possible to form a molded product or the like in which the effects of flexibility and curability are obtained by changing the layer thickness. Furthermore, by changing the shape of a molding die for performing blow molding, molded articles such as containers of various shapes other than various joints and bottles can be molded.

[0030]

According to the blow molding head of the present invention, when the layer state of the inner layer and the outer layer is formed, the thickness ratio of the inner layer resin to the outer layer resin can be adjusted arbitrarily and arbitrarily. Control (management / adjustment) of sharpness etc. becomes easy. Further, switching to a molded product of another type can be completed in a short time.

[Brief description of the drawings]

FIG. 1 is a sectional view of a blow molding head for a two-layer hollow molded article.

FIG. 2 is a partially enlarged cross-sectional view of a blow molding head of a two-layer hollow molded product.

FIG. 3A shows a bottle 36 having a two-layer structure.
(A) is a cross-sectional view of FIG.

4A is a cross-sectional view taken along line bb of FIG. 4B, and FIG. 4B is a vertical cross-sectional view of another bottle 36a having a two-layer structure.

5A is a cross-sectional view taken along line cc of FIG. 5B, and FIG. 5B is a vertical cross-sectional view of still another bottle 36b having a two-layer structure.

FIG. 6 is a diagram showing the relationship between the screw speed of an extruder and the opening degree of a flow passage of a cylindrical sliding mandrel.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Cylindrical inner layer mandrel 2 ... Mandrel shaft 2a ... Pressurized gas supply hole 3 ... Cylindrical sliding mandrel 4 ... Inner layer resin flow path 4a ... Inner layer resin inlet 5 ... Cylindrical outer layer mandrel 6 ... Outer layer resin Channel 6a ... Outer layer resin inlet 7 ... Die body 8 ... Servo motor 9 ... Timing pulley 9a ... Timing belt 10 ... Ball screw 11 ... Shaft 12 ... Guide 13 ... Die 14 ... Core 15 ... Resin merging channel 16 ... Resin pressure gauge 17 ... Ball screw 18 servo motor 19 ring die 20 guide shaft 21 guide bearing 30 outer layer 31 inner layer 36, 36a, 36b bottle P parison

Claims (3)

[Claims] 1. Separately melted synthetic resins are merged and integrated in a resin flow path to flow out from a die opening.
A blow molding apparatus for a layered hollow molded product, wherein a mandrel shaft having a through-hole for supplying a pressurized gas at a central portion is provided on the inner peripheral surface of a fixedly provided cylindrical inner mandrel with respect to the cylindrical inner mandrel. A cylindrical sliding mandrel that fits slidably in the vertical direction and is slidable in the vertical direction on the outer peripheral side of the cylindrical inner mandrel is used for the inner layer resin between the cylindrical inner mandrel and the cylindrical sliding mandrel. While forming and distributing the flow path,
The cylindrical outer mandrel is fixedly fitted to the outer peripheral surface of the cylindrical sliding mandrel so that the cylindrical sliding mandrel can slide,
A blow molding head for a two-layer hollow molded product, characterized in that a die body is provided by forming a channel for an outer layer resin on the outer peripheral side of the cylindrical outer layer mandrel. 2. A vertical sliding groove having various shapes is formed in a tip portion of a cylindrical sliding mandrel on an outer resin flow path side or a ring die on a die body side opposed thereto, and these are easily replaced. A blow molding head for a two-layer hollow molded article according to claim 1. 3. The two-layer hollow molding according to claim 1, further comprising a control device for synchronizing a vertical sliding motion of the cylindrical sliding mandrel with an inflow amount of resin in each layer. For blow molding of products.