JP2000351150A - Parison molding apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for molding which can mold a parison which can provide a hollow molded article with a uniform thickness and a method for molding it. SOLUTION: An extrusion die 10 is constituted in such a way that an outer mold 16 for forming an annular lip gap 46 between it and the circular outer peripheral face 36 of a core mold 14 is arranged so as to be outward inserted movably in the radial direction of the core mold 14 to the core mold 14 with the circular outer peripheral face 36 and moving means 54, 68 and 82 for moving the outer mold 16 so as to partially change the width of the annular lip gap 46 in the peripheral direction are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a parison molding apparatus and a parison molding method, and more particularly to an apparatus and a method capable of advantageously extruding a cylindrical parison.

[0002]

2. Description of the Related Art Generally, when blow molding a hollow resin molded product such as a tube or a pipe, first, through a circular lip gap which is an outlet of a molten resin in an extrusion die attached to a tip of an extruder. By extruding the molten resin, a cylindrical parison is preformed, and then
This preformed parison is housed in a molding cavity of a blow molding die in a thermoplastic state, and
Thereafter, the target hollow molded article is formed by blowing compressed air or the like into the inside of the parison.

[0003] In the blow molding of a hollow molded article as described above, when a mold composed of an upper mold and a lower mold which are opened in a vertical direction is used as a molding mold, the extruded parison is used as a lower mold. It is housed in the molding cavity while being placed on the cavity surface of the mold.
Therefore, when using such a blow molding die to obtain a hollow molded product, before blowing compressed air into the interior of the parison, the contact portion of the parison with the lower mold cavity surface is formed on the cavity surface. Heat may be deprived and solidified, and at the time of expansion and deformation of the parison due to blowing of compressed air, contact resistance occurs between the contact surface with the lower mold cavity surface of the parison and the cavity surface, The amount of deformation of the portion of the parison in contact with the lower mold cavity surface (the amount extending along the lower mold cavity surface) is smaller than the amount of deformation of the other portions, thereby increasing the thickness of the molded hollow molded product. However, the portion located on the upper mold side inevitably becomes thinner than the portion located on the lower mold side in the molding cavity.

When molding a hollow molded article having a complicated shape such as being bent two-dimensionally or three-dimensionally, a molding cavity having a bent shape corresponding to the hollow molded article is formed. In a state in which the parison is bent and housed, blow compressed air into the parison,
In recent years, so-called multi-dimensional blow molding has been widely adopted, but when performing this multi-dimensional blow molding,
The thickness of the bent parison becomes thicker at the inner part of the bent part and becomes thinner at the outer part thereof. In addition, a blow molding die composed of an upper die and a lower die is used. For this reason, it was inevitable that the thickness of the formed hollow molded article became more uneven.

[0005] Therefore, when a blow molding die composed of an upper die and a lower die is used, or when a hollow molded product having a complicated shape is formed by a multidimensional blow molding method, a hollow molded product is usually used. The parison is formed by using an unnecessarily large amount of resin material so that the thin portion inevitably formed has a specified thickness, and therefore, the weight of the parison and, consequently, the hollow molded product is more than necessary. In addition to the increase in the size of the resin material, there is a problem that the material cost is increased due to the extra use of the resin material. Moreover,
In multi-dimensional blow molding, more molten resin accumulates in the thick part of the inner part of the bent part of the parison, and thereby, the thick part of the bent part having a relatively small bending angle among those bent parts. In addition, there is also a problem that molding defects such as so-called dowels and the like occur where molten resins are self-adhering due to undulation, and the quality of a finally obtained hollow molded product is significantly reduced.

[0006]

The present invention has been made in view of the circumstances described above, and an object of the present invention is to provide a parison capable of providing a hollow molded article having a uniform wall thickness. To provide a simple molding apparatus. In the present invention, a parison molding method capable of advantageously molding such a parison is also an object to be solved.

[0007]

According to the present invention, there is provided an apparatus for forming a cylindrical parison which is attached to a tip of an extruder to solve the above-mentioned problem. A core having a cylindrical circular outer peripheral surface, and having a cylindrical shape, the core having a circular outer peripheral surface that is disposed so as to be movable in the radial direction of the core and is externally movable. An extrusion die having an outer die forming an annular lip gap for molding the cylindrical parison, and (b) the extrusion die formed between the outer die and the core die of the extrusion die. Moving means for moving the outer die so that the width of the annular lip gap partially changes in the circumferential direction, and eccentrically positioning the outer die. The gist of the present invention is a parison molding apparatus.

[0008] In short, in the parison molding apparatus according to the present invention, the outer die of the extrusion die attached to the tip of the extruder, which is extrapolated to the core die having a circular outer peripheral surface, is moved by the moving means. An annular lip formed between the core mold and the outer mold as an outlet from the extrusion die to the outside of the molten resin extruded from the extruder by being moved so as to be positioned eccentrically with respect to the mold. The width of the gap is configured to be partially changed in the circumferential direction.Thus, the molten resin extruded to the outside through the annular lip gap has a thickness partially changed in the circumferential direction. Different cylindrical parisons are to be formed.

Therefore, in such a parison molding apparatus, for example, when housed in a molding cavity of a blow molding die composed of an upper die and a lower die, the lower die is brought into contact with the cavity surface of the lower die. A parison having a thin side portion and a thick upper portion, and an inner portion of a bent portion bent in accordance with a bent shape of a molding cavity have a thinner thickness, and an outer portion thereof has a thicker portion. The thickness of the part that gives a part that inevitably becomes thicker in a conventional blow-molded hollow molded product such as a parison that is made into a wall is thin, and the thickness that gives the part that inevitably becomes thinner A thick parison can be formed very easily. Then, by blow-molding such a parison, a target hollow molded article can be molded with a wall thickness as uniform as possible.

[0010] Therefore, by using such a parison molding apparatus according to the present invention, a parison capable of providing a hollow molded article having a uniform wall thickness can be extremely advantageously molded. Then, as a result, the need to use an excessive amount of resin material in order to make the thickness of the partially thin portion of the hollow molded product to be formed a prescribed thickness can be advantageously eliminated, whereby It is possible to effectively reduce the weight of the hollow molded product to be molded and reduce the material cost due to the saving of the resin material used, and also due to the excessive accumulation of the resin material at the bent part of the parison It is possible to effectively prevent the occurrence of molding defects and the resulting deterioration of the quality of the hollow molded article.

According to one preferred embodiment of the parison molding apparatus according to the present invention, the moving means is arranged so as to be capable of rotating or reciprocating while being brought into contact with the outer peripheral surface of the outer mold. At least one cam member,
A drive mechanism for rotating or reciprocating the cam member, and the outer die is formed by the cam member by the rotation or reciprocation of the at least one cam member by the drive mechanism. It is configured to be pressed and moved in the radial direction of. In the parison molding apparatus having such a configuration, the structure for moving the outer die of the extrusion die in any radial direction of the circular outer peripheral surface of the core is a generally simple structure,
Since it is configured using a cam mechanism capable of giving various movements to a driven body (here, corresponding to an outer mold), the structure of the entire molding apparatus can be relatively simply configured. .

In the parison molding apparatus according to the present invention, when the moving means includes at least one cam member, it is advantageous that the cam member is provided with the core mold. Are positioned in pairs so as to contact the outer peripheral surface of the outer mold on an extension of the diameter of the outer mold. With the rotation or reciprocation of one of the paired cam members, While the mold is pressed and moved in one radial direction of the core by the one cam member, the other cam member rotates or reciprocates,
The outer die is configured to be moved by being pressed by the other cam member in a direction opposite to a moving direction of the one cam member. According to such a configuration, not only the structure for moving the outer mold in one radial direction of the core mold, but also the moved outer mold at a position before being moved or at a predetermined position during the movement. Can be configured utilizing a relatively simple cam mechanism, whereby the structure of the moving means and thus the forming device can be more advantageously simplified.

Preferably, the pair of cam members are paired with each other such that the pair of cam members contact the outer peripheral surface of the outer die on extensions of two diameters of the core that are orthogonal to each other. In contrast, it will be positioned. In the parison molding apparatus having such a configuration, if the operation amounts of the rotation or reciprocation of the two pairs of cam members are separately adjusted, the outer mold can be freely moved in all radial directions of the core mold. Can be moved.

According to another advantageous aspect of the parison forming apparatus according to the present invention, the moving means includes:
A control mechanism for controlling the driving mechanism is further included. By the control mechanism, the cam member is rotated or reciprocated at an arbitrary operation amount during the molding of the cylindrical parison, and Mold in the radial direction of the core,
By moving by an amount corresponding to the operation amount of the cam member, the width of the annular lip gap formed between the outer mold and the core mold is increased during the molding of the cylindrical parison. It is configured such that it can be partially and arbitrarily changed in the circumferential direction. In the parison forming apparatus having such a configuration, the thickness of the cylindrical parison to be formed can be continuously changed not only in the circumferential direction of the parison but also in the axial direction thereof, This makes it possible to more effectively suppress or eliminate the occurrence of thickness variations in the finally obtained hollow molded article.

Further, according to another preferred embodiment of the parison molding apparatus according to the present invention, the outer die is formed of a cylindrical body, and the cam member is rotated by the rotation thereof. The outer mold is configured to have a sliding convex portion that is slid against the outer peripheral surface of the outer mold and presses and moves the outer mold in the radial direction of the core mold. The contact portion of the cam member with the sliding convex portion is a flat contact surface.
In the parison molding apparatus having such a configuration,
Unlike the case in which the sliding convex portion of the cam member is rotated under the state of being brought into contact with the outer peripheral surface formed of the cylindrical surface of the outer die, the sliding convex portion of the cam member on the outer peripheral surface of the outer die is Is advantageously prevented from changing with the rotation of the cam member, so that the amount of movement of the outer die relative to the predetermined amount of rotation of the cam member is always maintained at a constant amount. You will get.

In the present invention, when the molten resin is extruded through an annular lip gap formed on an extrusion die attached to the tip of an extruder to form a cylindrical parison, The gist of the present invention also relates to a parison molding method characterized in that the molten resin is extruded while the width of the lip gap is partially changed in the circumferential direction.

In other words, in such a parison molding method, the cylindrical parison has a wall thickness partially changed in the circumferential direction corresponding to the width of the annular lip gap formed in the extrusion die. It is molded, and thereby, the thickness of the part which gives the part which becomes inevitably thick in the conventional hollow molded article formed by blow molding is thin, and the part which becomes inevitably thin A parison having a thicker portion to be applied can be formed very easily. By performing blow molding on such a parison in the same manner as in the related art, a hollow molded article having a thickness as uniform as possible can be formed.

Therefore, according to the parison molding method according to the present invention, a parison capable of providing a hollow molded article having a uniform thickness can be surely molded. And, as a result, in the related art, since the thickness variation of the hollow molded article to be molded is large, various problems caused when molding such a hollow molded article can be solved at once. It is.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, in order to clarify the present invention more specifically, the configuration of a parison forming apparatus and a parison forming method according to the present invention will be described with reference to the drawings.
It will be described in detail.

First, FIGS. 1 and 2 schematically show an apparatus for molding a cylindrical parison used in blow molding a resin tube as an example of a parison molding apparatus according to the present invention. ing. As is clear from these figures, the parison forming apparatus of the present embodiment is configured to include the crosshead type extrusion die 10.

More specifically, the extrusion die 10 includes:
It comprises a die body 12, a mandrel 14 as a core, and an outer die 16. And the die body 12
It has a thick, substantially cylindrical shape.
The mandrel fixing bush 18 and the spacer bush 20 are coaxially inserted. Of the two bushes 18, 20, the mandrel fixing bush 18
Has a substantially cylindrical shape having an outer diameter that is one size smaller than the inner hole 17 of the die body 12.
2 (extrusion die 10) is disposed so as to protrude from the opening of the inner hole 17 on the end face on the base side (right side in FIG. 2). On the other hand, the spacer bush 20 has a thin cylindrical shape having a length shorter than the mandrel fixing bush 18 and an outer diameter slightly smaller than the inner hole of the die main body 12. The inner hole 17 of the die body 12 is
It is positioned so as to fill the gap between the outer peripheral surface of the fixed bush 18 and the inner peripheral surface of the die body 12.

The mandrel fixing bush 18
An outward flange 22 integrally formed at one end of the spacer bush is fixed to an end face on the base side of the die body 12 by bolts with an outward flange portion 23 of the spacer bush 20 interposed therebetween. In addition, an inner hole 1 of the die body 12 is provided on the end face on the tip side (the left side in FIG. 2) of the die body 12.
In a state where the thick mounting bush 25 having the inner hole 24 having a diameter larger than the predetermined size by 7 is coaxially positioned,
It is fixed with a plurality of mounting bolts 21. As a result, the openings of the inner holes 17 on both end surfaces on the base side and the tip side of the die body 12 are opened to the outside through the opening on one end side of the mandrel fixing bush 18 and the inner hole 24 of the mounting bush 25, respectively. It has been impatient.

Further, a circular hole 26 is provided at a predetermined depth on the outer peripheral surface of the cylindrical wall of the die body 12. In the center of the bottom surface of the circular hole 26, a through hole 28 that penetrates the cylindrical wall of the die body 12 is provided.
The inner hole 17 of the die body 12 is
It is communicated to the outside. Then, as shown by the phantom line in FIG. 2, the tip portion 30 of the extruder is attached to the circular hole 26,
Thus, the molten resin extruded from the tip portion 30 of the extruder is supplied into the inner hole 17 of the die body 12 through the through hole 28, and further, the inside of the inner hole 17 is moved to the tip side of the die body 12. It is being led. 1 to 3,
Reference numerals 32 and 34 denote band heaters for heating the molten resin guided into the die body 12 and the inner hole 17 thereof.

On the other hand, the mandrel 14 has a generally cylindrical rod shape that is longer than the die body 12 by a predetermined dimension, and the outer peripheral surface of the distal end portion has a tapered cylindrical shape whose diameter gradually decreases toward the distal end. Is formed as a circular outer peripheral surface 36. And this mandrel 14 is the die body 1
2 is positioned by inserting the inner hole 17 from the base side to the distal end side of the die body 12, and under the inserted state, at the distal end portion having a circular outer peripheral surface 36, The mounting bush 25 fixed to the die body 12 is inserted into the inner hole 24 so as to be positioned coaxially, while being protruded from the opening at one end of the mandrel fixing bush 18 to the outside at the base. Further, at an intermediate portion thereof, the mandrel fixing bush 18 is inserted through an inner hole so as to be slidable in the axial direction. Here, the mandrel 14 is
By a known moving mechanism (not shown) using hydraulic pressure or the like,
It can be moved forward and backward in the axial direction by a predetermined amount.

The outer mold 16 has a thick, substantially cylindrical shape having an outer diameter smaller than the inner diameter of the mounting bush 25 fixed to the die body 12 by a predetermined dimension. With a size one size larger than the tapered cylindrical circular outer peripheral surface 36 at the distal end of the mandrel 14, and having a tapered cylindrical inner peripheral surface that gradually decreases in diameter from the base opening side toward the distal opening side, In addition, the large-diameter base-side opening of the inner hole 35 has substantially the same diameter as the opening of the inner hole 17 on the front end surface of the die body 12. Further, at the outer peripheral portions at both ends in the axial direction of the outer die 16, step portions 38, 38 for making the outer diameters of the outer peripheral portions at both ends smaller by a predetermined dimension than those at the intermediate portion extend continuously in the circumferential direction, respectively. In addition, annular bearings 40, 40 are formed on the two steps 38, 38.
, Respectively, are externally fitted. In addition, this bearing 4
Numeral 0 indicates that a plurality of steel balls are interposed between two coaxially arranged ring plates, and the rotation of the plurality of steel balls limits the radial movement of the two ring plates to a predetermined size. It is configured to allow only.

Thus, in the outer die 16, the inner hole 35 is communicated with the inner hole 17 of the die body 12 at the base-side opening, and the outer peripheral surface and the inner surface of the mounting bush 25 are formed. An annular gap 41 extending in the axial direction between itself and the peripheral surface
Is formed, and the inner hole 2 of the mounting bush 25 is formed.
4 are inserted and arranged. In such an arrangement, the mounting bush 25 is provided in the inner hole 35 of the outer die 16.
The distal end portion of the mandrel 14 which is inserted into the inner hole 24 is inserted. As a result, the molten resin guided to the distal end opening of the inner hole 17 of the die body 12 is provided between the inner peripheral surface of the inner hole 35 of the outer die 16 and the circular outer peripheral surface 36 of the distal end of the mandrel 14. A flow passage 44 is formed to allow the fluid to flow from the base side opening of the inner hole 35 of the outer die 16 to the distal end side opening thereof.
Between the inner peripheral surface of the outer die 16 and the outer peripheral surface of the distal end of the mandrel 14 at the opening on the distal end side of the annular shape, which serves as an outlet for the molten resin flowing through the flow passage 44 from within the outer die 16. A lip gap 46 is formed. Then, the outer mold 16 is mounted on the base side of a mounting ring 42 fixed to a distal end surface of the mounting bush 25 by a plurality of fixing bolts 43 via two bearings 40 fitted to both ends of the outer die 16. It is sandwiched in the axial direction between the end face and the front end face of the die body 12.

Thus, the outer die 16 is fixed between the mounting ring 42 and the die body 12, and the two bearings 4 fitted externally to the outer die 16 under such fixing.
0, 40, the linear movement of the outer die 16 in the radial direction or the mandrel 1 within the width of the annular gap 41 formed between the inner bush 25 and the inner peripheral surface of the mounting bush 25.
The movement in the circumferential direction while being eccentric with respect to the axis of No. 4 is allowed. As a result, the width of the flow passage 44 and the lip gap 46 provided in the inner hole 35 of the outer mold 16 can be partially changed in the circumferential direction according to the movement of the outer mold 16. I have. Further, in the present embodiment, as described above, the mandrel 14 can be moved forward and backward in the axial direction. Therefore, when the mandrel 14 is moved forward and backward in the axial direction, these flow paths 44 and lip gap 46
Are uniformly changed in the circumferential direction. Here, a slight gap is provided between the base end surface of the outer die 16 and the tip end surface of the die body 12 so that the outer die 16 can be smoothly moved as described above. , A seal ring 4
8 is provided, so that the molten resin is prevented from leaking from the flow passage 44 through the gap.

By the way, in the extrusion die 10 having such a configuration, as shown in FIGS. 2 and 3, the outer die 16 is provided between the two step portions 38, 38 on the outer peripheral surface thereof. Three flat contact surfaces 53a, 53b, 53c, 53
d are provided at equal intervals in the circumferential direction. In other words, the four flat contact surfaces 53a, 53b, 53
c, 53d are provided on the outer peripheral surface of the outer mold 16 by the outer mold 16;
Mandrel 14 coaxially inserted into inner bore 35 of
Are formed at four portions located on two extension lines 55, 57 of two diameters orthogonal to each other.

On the other hand, in the inner peripheral portion of the mounting bush 25,
Four notches 50 that open toward the formation portions of the four contact surfaces 53 of the outer die 16 are provided with a length extending to the axially intermediate portion of the mounting bush 25. Further, in such a notch portion 50, extension lines 55, 57 of two diameters of the mandrel 14, which are orthogonal to each other, are formed on the bottom surface of the mounting bush 25 extending in the radial direction.
The mounting bush 25 is axially penetrated at a position deviated by a predetermined dimension in the circumferential direction of the mandrel 14 from the mandrel 14, and through holes 52 that are open to the outside at the tip end surface of the mounting bush 25 are each one. Is provided.

Further, each of the notches 50 and the through holes 52
Inside, cam members 54 each including a cam plate 56 and a rotating shaft 58 are arranged one by one. The cam plate 56 of the cam member 54 has a thick plate shape, a substantially rectangular shaft hole 60 is formed at one end in the length direction, and the other end has a tip end surface. A sliding convex portion 62 is formed as a sliding surface 61 formed of an arc surface. The rotation shaft 58 has a round bar shape as a whole, and substantially rectangular mounting protrusions 64, 64 are integrally formed at both ends thereof.

Then, such four cam plates 5
6 are rotatably disposed in the respective notches 50, and under such an arrangement, the one end having the shaft hole 60 is connected to the mandrel 14 in each of the notches 50. Extension lines 55,5 of two orthogonal diameters
7 is located at a predetermined distance in the circumferential direction of the mandrel 14, and the tip of the sliding projection 62 extending from one end of the mandrel 14 is formed with four contact surfaces 53 of the outer die 16. , Which protrude from the opening of each notch 50, and slide surface 61 of the distal end portion.
, The contact surfaces 53 are respectively brought into contact with each other. Further, each of the rotating shafts 58 is inserted into each of the four through holes 52, and is rotatably supported by bearings 66, 66 arranged two by two in each of the through holes 52. Two mounting projections 64,
One of the cam plates 64 is irremovably inserted into the shaft hole 60 of each cam plate 56. Thus, the four cam members 54a, 54b, 54c, 54d
Are paired with each other on two mutually perpendicular extension lines 55 and 57 of the mandrel 14 (FIG. 3).
Here, the cam member 54a and the cam member 54c form a pair, and the remaining cam member 54b and the cam member 54d form a pair here. The two contact surfaces 53a, 53b, 53c, 53d are rotatably positioned in contact with each other.

As is clear from FIGS. 1 and 4, in the two pairs of cam members 54 having such a configuration, the rotating shaft 58 is opposite to the side on which the rotating shaft 58 is attached to the cam plate 56. In the mounting protrusion 64 on the side, two pairs of drive arms 68
, Respectively, are fixed so that they cannot rotate. This 2
The pair of drive arms 68 are made of a long plate material, and at one end in the longitudinal direction, an insertion hole 70 through which the attachment protrusion 64 of the cam member 54 is inserted and fixed is provided, and at the other end, a long hole 72 is provided. Are formed and configured. And
In each of the two pairs of drive arms 68, one pair is positioned so as to extend in parallel with two mutually perpendicular extension lines 55 and 57 of the mandrel 14, respectively. In this case, the respective rotating shafts 58 of the two cam members 54b and 54d forming a pair correspond to two cam members 54a and 54a forming a pair.
54c are longer than the respective pivot shafts 58 by a predetermined dimension, so that the two pairs of cam members 5
The two pairs of drive arms 68 each having the fixed 4 are vertically crossed at predetermined intervals in the axial direction of the rotation shaft 58 without contacting each other.

On the other hand, on the outer peripheral surface of the mounting bush 25 on which the two pairs of cam members 54 are disposed, two mounting brackets 74,
74 are fixed with a phase difference of 90 ° so as to be located on two extension lines 55, 57 of two diameters orthogonal to each other of the mandrel 14, and the two mounting brackets 74, 74 include: Each of the hydraulic cylinders 76
The mounting bush 25 is mounted so as to extend in a direction perpendicular to the axial direction. This hydraulic cylinder 7
6 has two piston rods 78a, 78b extending from both sides in the axial direction and configured to perform operations opposite to each other in the projecting and retracting operations with respect to the hydraulic cylinder 76. ing.

Further, mounting sleeves 80, 80 are fixed to the ends of the two piston rods 78a, 78b of each such hydraulic cylinder 76, respectively.
Both ends of a connection arm 82 having a U-shape are fitted into the two mounting sleeves 80, 80. That is, this connecting arm 82 is connected to each piston rod 78a,
A flat plate portion 84 extending in the direction of extension of the second member 78b, that is, in a direction parallel to the direction in which they protrude and retract.
And two legs 86, 86 extending in one direction in the thickness direction from both ends of the two mounting sleeves 80, 8 at the tips of the two legs 86.
0 and is fixed. As a result, in each connecting arm 82, one of the two piston rods 78a and 78b of each hydraulic cylinder 76 is caused to protrude and the other is retracted, so that the flat plate portion 84 is formed. Are moved in one direction of the extension direction, and are moved in the opposite direction to the one direction in response to the one being retracted and the other being protrudingly moved. ing.

The two pairs of drive arms 68, which are non-rotatably fixed to the two pairs of cam members 54, are arranged at the respective positions of the two connecting arms 82, 82 having the above-described structure. At the end where the elongated hole 72 is provided, the flat plate portion 8 of each connecting arm 82.
4 are positioned so as to be superimposed on both ends of each drive arm 4, and in each of the long holes 72 of the respective drive arms 68,
A round bar-shaped pin 88 provided one at each end of the flat plate portion 84 of each connecting arm 82 is inserted so as to be movable in the length direction of the long hole 72. As a result, the two pairs of cam members 54 are connected via the two pairs of drive arms 68 to the respective piston rods 78a, 78 of the two hydraulic cylinders 76, 76.
b, and is connected to the two connecting arms 82, 82 fixed to the hydraulic cylinder 76, so that the two piston rods 78a, 78b in each hydraulic cylinder 76 project and retreat.
The drive arm 68 is swung about the rotation shaft 58 of each cam member 54, and each cam member 54 is turned so that the sliding surface 61 is about 3 mm in the radial direction of the outer die 16. It can be displaced.

Thus, in this embodiment, as shown in FIG. 4, the projecting positions of the two piston rods 78a and 78b in each hydraulic cylinder
And two pairs of drive arms 68 are provided with two pairs of mutually perpendicular extension lines 55, 55 of the mandrel 14 as shown by solid lines in FIG.
While it is positioned to extend parallel to 57,
The two pairs of cam members 54 are prevented from rotating from the rotating position shown by the solid line in FIG. And two pairs of cam members 54
As a result, the outer mold 16 is held at a coaxial position with respect to the mandrel 14, so that the outer mold 16 and the mandrel 1
The width (the dimension indicated by w in FIG. 2) of the annular lip gap 46 formed between the lip gap 4 and the lip gap 46 is uniformly maintained in the circumferential direction. Further, from this state, the two piston rods 78a and 78b of each hydraulic cylinder 76 are protruded or retracted, and the two pairs of cam members 54 are rotated as shown by phantom lines in FIG. As a result, the outer mold 16
The sliding surfaces 61 of the pair of cam members 54 are pressed and moved in the radial direction of the circular outer peripheral surface 36 of the mandrel 14 according to the rotation direction. And it is positioned eccentrically with respect to the mandrel 14, so that the width of the annular lip gap 46 is 3 mm in the circumferential direction.
The degree can be partially changed up to the upper limit.

In this case, two hydraulic cylinders 7
The supply of pressurized oil to the hydraulic cylinders 6 and 76 is controlled by a computer (not shown), and the control of the supply of pressurized oil by the computer causes the amount of protrusion or retraction of the two piston rods 78 a and 78 b in each hydraulic cylinder 76. Is always adjusted to the desired amount.
Therefore, in the parison forming apparatus of the present embodiment, the outer die 16 is moved by a desired amount in any radial direction of the circular outer peripheral surface 36 of the mandrel 14 so that the lip gap 4
The width of the lip gap 46 is such that the width of the lip gap 46 can be freely changed at any time in the circumferential direction at any part thereof. It is like that. As is apparent from this, in the present embodiment, a drive mechanism for rotating the cam member 54 is constituted by the hydraulic cylinder 76, the piston rods 78a and 78b, the connection arm 82, and the drive arm 68. A control mechanism for controlling the driving mechanism is constituted by a computer (not shown). Then, the moving mechanism for moving the outer mold is constituted by the driving mechanism including the above-described members and the cam member 54.

When a cylindrical parison is formed by using the parison forming apparatus having such a structure, first, the circular hole 26 of the extrusion die 10 is
While attaching the tip portion 30 of the known extruder, the computer supplies the hydraulic oil to each hydraulic cylinder 76 so that the two piston rods 78a and 78b project from the hydraulic cylinder 76 with the same length. To maintain the two pairs of cam members 54 in the rotational position shown by the solid line in FIG. Then, after that, a predetermined molten resin is extruded from the tip portion 30 of the extruder and supplied into the inner hole 17 of the die body 12 of the extrusion die 10, so that the lip gap 46 having a uniform width is formed in the circumferential direction. The parison having a uniform thickness is extruded.

On the other hand, when the thickness of the extruded parison is partially changed in the circumferential direction, for example, first, the computer control of the two piston rods 78a and 78b in each hydraulic cylinder 76 is performed. As shown in FIG. 1, the two connecting arms 82 and 82 and the two pairs of driving arms 68 connected to the two connecting arms 82 and 82 are moved in the directions indicated by arrows A and A, respectively, as shown in FIG. By moving or swinging by the same amount, the two pairs of cam members 54 are rotated by the same amount in the directions indicated by arrows A and A in FIG. Thereby, as shown by the imaginary line in FIG. 3, the sliding surfaces 61 of the cam members 54a and 54c forming a pair are slid with respect to the contact surfaces 53a and 53c of the outer die 16 while drawing. 3) Displace upward by the same dimension. At the same time, another pair of cam members 54
b and the sliding surface 61 of the cam member 54d are also the outer mold 1
6 while sliding with respect to the contact surfaces 53b and 53d of FIG.
Displace by the same size in the middle and right directions. Thus,
The outer die 16 is pressed by two pairs of cam members 54 in the directions indicated by arrows A and B in FIG. An annular lip gap 46 formed with the mandrel 14
5 is changed so that the upper right portion in FIG. 5 is thick and the lower left portion in the opposite direction is thin. Then, the molten resin extruded from the tip portion 30 of the extruder is further extruded through the lip gap 46 having the width as described above, whereby the upper right oblique portion in FIG. 5 is made thicker, and vice versa. The parison 90 whose left lower part is thinner is formed.

When the thickness of the parison 90 is further changed in the circumferential direction, for example, first, the two piston rods 78a, 78b
As shown in FIG. 1, the two connecting arms 8 are extended by the computer-controlled projection or retraction movement.
The two pairs of cam members 54 are moved or rocked by the same amount in the directions indicated by arrows C and D, respectively, to move the two pairs of cam members 54, respectively. 3
In the directions indicated by arrows c and d, respectively. As a result, as shown by the phantom line in FIG.
4c is replaced with the contact surface 53 of the outer mold 16.
a and 53c, while being displaced downward by the same dimension in FIG. At the same time, the respective sliding surfaces 61 of the cam member 54b and the cam member 54d forming another pair are also slid with respect to the contact surfaces 53b and 53d of the outer die 16 while moving leftward in FIG. Displace by the same dimension. Thus, the outer die 16 is pressed by the two pairs of cam members 54 in the directions indicated by arrows D and E in FIG. 5, the width of the annular lip gap 46 formed between the mandrel 16 and the mandrel 14 is changed so that the lower left diagonal portion in FIG. 5 is thicker and the opposite upper right diagonal portion is thinner. By further extruding the molten resin extruded from the tip portion 30 of the extruder through the lip gap 46 having the width as described above, the lower left diagonal portion in FIG. A parison 90 whose upper right portion is thinner is formed.

Further, in the same manner, the two connecting arms 82, 82 and the two pairs of driving arms 68 are moved or rotated by the same amount in the directions indicated by arrows A and D, respectively. The two pairs of cam members 54 are rotated by the same amount in the directions indicated by arrows A and D in FIG. As a result, the outer die 16 is pressed by the two pairs of cam members 54 in the directions indicated by the arrows G and H in FIG. 5C, and is moved in the direction of the arrow I. 5, the width of the lip gap 46 is changed so that the upper left portion in FIG. 5 is thicker and the lower right portion in the opposite direction is thinner. And the tip 3 of the extruder
5 is further extruded through the lip gap 46 having the width as described above.
A parison 90 is formed in which the middle and diagonally upper left portions are thick, and the opposite diagonally lower right portion is thin.

Further, similarly, the two connecting arms 82, 82 and the two pairs of driving arms 68 are moved or rotated by the same amount in the directions indicated by arrows A and C. Then, the two pairs of cam members 54 are rotated by the same amount in the directions indicated by arrows A and C in FIG. Thereby, the outer die 16 is moved in the direction indicated by arrows J and K in FIG.
Pressed by the pair of cam members 54 and moved in the direction of arrow L, the width of the lip gap 46 is made thicker in the diagonally lower right part in FIG. 5 and thinner in the diagonally upper left part in FIG. To change. Then, the molten resin extruded from the tip portion 30 of the extruder is further extruded through the lip gap 46 having the width as described above, so that the lower right diagonal portion in FIG. 5 is made thicker, and vice versa. A parison 90 whose upper left portion is thinner is formed.

The two piston rods 78a, 78b in each of the two hydraulic cylinders 76, 76
When the cam members 54 are projected or retracted by different amounts, the rotation amounts of the two pairs of cam members 54 rotated via the two connecting arms 82 and 82 and the two pairs of drive arms 68 are: The direction and amount of movement of the outer mold 16 by the two pairs of cam members 54, and consequently the width of the lip gap 46, are changed over a wider range by one pair at a time. A parison 90 having a thickness different from that shown in a) to (d) will be formed. During the molding of the parison 90, the amount of protrusion or retraction of each of the two piston rods 78a and 78b is adjusted to a desired amount, and the rotation direction and the amount of rotation of the two pairs of cam members 54 are adjusted. , The width of the lip gap 46 may be arbitrarily changed. That way, not only in the circumferential direction,
The parison 90 having a partially different wall thickness in the axial direction can be formed.

When the thus-formed parison 90 whose wall thickness is partially different in the circumferential direction is blow-molded, for example, a blow-molding die composed of an upper die and a lower die is used. When the parison 90 is housed in the molding cavity of the blow molding die so that the thin portion contacts the cavity surface of the lower die in the molding die, the contact portion with the cavity surface of the lower die is formed. Solidifies faster than other parts, or when the parison 90 expands and deforms due to blowing of compressed air, contact resistance occurs between the cavity surface of the lower mold and the contact portion of the parison 90 with the cavity surface. Then, even if the amount of deformation of such a contact part is not smaller than the other parts,
Since the contact portion is thin, the finally obtained hollow molded article is molded with a substantially uniform thickness.

Even when the parison 90 is multi-dimensionally blow-molded, the parison 90 is bent and deformed so that the thin part is located inside and the thick part is located outside, and the multi-dimensional blow molding is performed. If it is accommodated in the molding cavity of the blow molding die, the bent parison 90
The difference in wall thickness between the inner portion and the outer portion of the bent portion is eliminated or reduced as much as possible, so that the finally obtained hollow molded product is formed with a substantially uniform thickness. Become.

As described above, in the parison forming apparatus according to the present embodiment, since the cylindrical parison 90 is formed to have a partially different desired thickness in the circumferential direction, the blow is performed. A parison 90 in which a portion providing an inevitably thick portion in a hollow molded product obtained by molding has a small thickness and a portion providing an inevitably thin portion has a thick wall, in other words. Then, a parison 90 capable of providing a hollow molded product having a uniform thickness can be obtained.
Can be formed very easily.

Therefore, when the parison forming apparatus of this embodiment is used, when the parison 90 is formed, the thickness of the partially thin portion of the hollow molded product obtained from the parison 90 is set to the specified thickness. It is possible to advantageously eliminate the need to use an unnecessarily large amount of resin material, whereby the material cost can be advantageously reduced, and the parison 90 and, consequently, the hollow molded article can be effectively reduced in weight. In addition, when performing multi-dimensional blow molding, molding defects caused by excessive accumulation of the resin material at the bent portion of the parison 90, which have conventionally occurred, and further, deterioration of the quality of the hollow molded product due to the molding defect And the like can be solved very advantageously.

Further, in the parison forming apparatus of the present embodiment, the outer die 16 is moved in the radial direction by the rotation of the cam member 54, so that the mandrel 14 is inserted into the inner hole 35 of the outer die 16. A structure for changing the width of the lip gap 46 because the width of the annular lip gap 46 can be partially changed in the circumferential direction. In other words, the structure for partially changing the thickness of the formed parison 90 in the circumferential direction can be configured with a relatively simple structure using only a cam mechanism.

Further, in this parison forming apparatus, two pairs of cam members 54 for moving the outer die 16 are provided, and the amount and direction of rotation of the two pairs of cam members 54 are adjusted. Since the moving direction and the moving amount of the outer mold 16 can be freely changed, excellent operability or usability can be advantageously exhibited.

Further, in this parison molding apparatus, the amount of protrusion or retraction of the two piston rods 78a, 78b in each of the hydraulic cylinders 76 is controlled by controlling the pressure oil to each of the hydraulic cylinders 76 by the computer. By changing the width of the lip gap 46 arbitrarily during the molding of the parison 90, the thickness of the parison 90 to be molded can be partially varied not only in the circumferential direction but also in the axial direction. Therefore, the parison 90 that can more effectively suppress or eliminate the occurrence of thickness variation of the finally obtained hollow molded article can be formed extremely easily.

Further, in the parison forming apparatus of the present embodiment, the width of the lip gap 46 can be changed uniformly in the circumferential direction by moving the mandrel 14 in the axial direction. From, parison 90,
There is also an advantage that it can be molded with a variety of thicknesses.

Further, in this parison molding apparatus, since the contact surface 53 of the outer die 16 with which the arc-shaped sliding surface 61 of the cam member 54 comes into contact is formed as a flat surface, the contact surface 53 is formed. Unlike the case where the outer surface of the outer die 16 is formed by a cylindrical surface, the contact position of the outer surface of the outer die 16 with the sliding surface 61 of the cam member 54 is different from the rotation position of the cam member 54. Is advantageously prevented, so that the amount of movement of the outer die 16 with respect to the amount of rotation of the cam member 54 can always be maintained at a constant amount.

Furthermore, in the parison forming apparatus of the present embodiment, the driving force for rotating the cam member 54 is such that the piston rods 78a and 78b project or protrude from the hydraulic cylinder 76 having excellent high-temperature durability. The normal operation can be advantageously ensured even in a high-temperature environment, since it is generated by the retraction movement.

In order to confirm that the parison molding apparatus according to the present invention has the above-mentioned excellent features, the present inventors have conducted a parison molding having a structure as shown in the present embodiment. After the parison was actually molded using the apparatus, a hollow molded article was molded from the parison, and the molded hollow molded article was subjected to the following measurement tests.

That is, first, a resin material in which a polyamide resin (6-nylon) contains 20% of glass fiber and an upper mold and a lower mold capable of forming a resin tube 92 having a bent shape as shown in FIG. A mold for three-dimensional blow molding comprising a mold was prepared. Then, using a parison molding apparatus having a structure as shown in FIGS. 1 to 4 and a known extruder, a parison is molded from the prepared resin material while the prepared three-dimensional blow molding metal is formed. The formed parison was bent and accommodated in the molding cavity having the bent shape of the mold. At this time, the outer die of the extrusion die in the parison molding device is moved in an arbitrary radial direction of the mandrel with an upper limit of 3 mm, and the width of the lip gap is partially changed in the circumferential direction within a range of 3 mm. As a result, the portion brought into contact with the cavity surface of the lower mold and the inner portion of the bent portion become thinner, and the portion opposite to the contact portion with the cavity surface of the lower mold, and the bent portion, A parison whose wall thickness was partially changed in the circumferential direction with an upper limit of 3 mm was formed so that the outer portion became thicker. After that, blow molding was performed in a three-dimensional blow molding die to obtain a target resin tube (example of the present invention).

Next, using the thus obtained resin tube (Example of the present invention), predetermined seven measurement sites (No. 1 to No. 7 in FIG. 6) in this resin tube.
), The thickness of each of the four parts, upper, lower, left and right, which are located on the extension of two diameters extending in the horizontal direction and the vertical direction, was measured. From the measurement values thus obtained, the average value of the thickness of the four portions at the seven measurement sites and the difference between the maximum value and the minimum value of the thickness of the four portions (thickness difference) are calculated. Each was calculated. Table 1 below shows the measured values, average values, and wall thickness differences of the wall thicknesses. The unit of each of the measured value, the average value, and the thickness difference in Table 1 is mm.

[0057]

For comparison, a cross-head type extrusion die and an extruder having the same structure as the conventional one were used.
The width of the lip gap of the extrusion die is not changed at all, and the prepared three-dimensional blow molding die is formed from the prepared resin material while forming a parison having a uniform thickness in the circumferential direction. The molded parison was bent and housed in a molding cavity having the bent shape of. Thereafter, blow molding was performed in a three-dimensional blow molding die to obtain a target resin tube (comparative example). Next, using the thus obtained resin tube (Comparative Example), the same measurement operation as described above was performed on this resin tube, and a predetermined seven measurement sites (in FIG. 6,
No. 1 to No. 7), the average of the thickness of the four portions at the seven measurement sites and the maximum value of the thickness of the four portions from the measured values of the thickness of the four portions at the top, bottom, left and right And the minimum value (thickness difference) were calculated. Table 2 below shows the measured values, the average value, and the difference in the wall thickness. The unit of the measured value, the average value, and the thickness difference in Table 2 is also mm.

[0059]

As is clear from the results in Tables 1 and 2, the resin tube (example of the present invention) obtained from the parison molded by using the parison molding apparatus according to the present invention was
The difference (thickness difference) between the maximum value and the minimum value of the thickness of the four portions of the upper, lower, left and right at the seven measurement sites is about 1.0, whereas the conventional crosshead type extrusion die The resin tube obtained from the parison molded by using the resin (Comparative Example) has the largest difference (thickness difference) between the maximum value and the minimum value of the wall thickness of the four upper, lower, left, and right portions at the same seven measurement sites. The small value is 1.07 and the largest value is 4.25
It has become. From this, it can be clearly recognized that by using the parison forming apparatus according to the present invention, a parison having a small thickness variation in the circumferential direction can be obtained.

Although the specific configuration of the present invention has been described in detail above, this is merely an example, and the present invention is not limited by the above description.

For example, in the above-described embodiment, the outer peripheral surface of the distal end of the mandrel 14 as a core is formed by the tapered cylindrical circular outer peripheral surface 36. Annular lip gap 4 between the peripheral surface
The shape is not particularly limited as long as it can form 6, and it does not matter at all if it is constituted by a cylindrical circular outer peripheral surface.

The shape of the outer peripheral surface of the mandrel 14 excluding the circular outer peripheral surface 36 is, of course, not limited to the one shown in the above embodiment.

Further, in the above embodiment, the mandrel 1
Although 4 is configured to be movable in the axial direction, it is of course good that it is not movable.

In the above embodiment, the outer mold 16 has a cylindrical shape. However, the outer mold 16 has a cylindrical shape that can be inserted into the mandrel 14 as a core, and at least a part of the inner peripheral surface has The overall shape of the outer die 16 and the shape of the inner hole 35 are not limited as long as an annular lip gap 46 can be formed with the circular outer peripheral surface 36 of the mandrel 14. Absent.

Further, in the above embodiment, the extrusion die 1
0, in addition to the mandrel 14 and the outer mold 16 as a core,
Although it is configured to include the die body 12 and the mounting bush 25 and the like, the outer mold 16 is arranged so as to be inserted outside the mandrel 14 and is positioned eccentrically with respect to the mandrel 14. If it is configured to be movably held, the extrusion die 10 can be configured by omitting the die body 12, the mounting bush 25, and the like, or by adding other members.

Further, in the above embodiment, the cam member 5
The driving force for rotating the hydraulic cylinder 4 is generated by the projecting or retracting movement of the piston rods 78a and 78b in the hydraulic cylinder 76. Instead of such a hydraulic cylinder 76, for example, a servo It is also possible to use an electric motor such as a motor and rotate the cam member 54 by the driving force of the electric motor.

In the above embodiment, the cam member 54
However, with the rotation, the outer die 16 is slid on the outer peripheral surface of the outer die 16 to press the outer die 16 in the radial direction of the mandrel 14,
Although it was configured to move linearly in this direction,
The cam member may be configured to move in the circumferential direction of the mandrel 14 while rotating the outer die 16 in the radial direction of the mandrel 14 by rotating the cam member. The outer mold 1 is composed of a cam or the like, and slides on the outer peripheral surface of the outer mold 16 with the reciprocating movement.
6 may be configured to be pressed and moved in the radial direction of the mandrel 14.

Further, the arrangement position of the cam member 54 with respect to the extrusion die 10, the arrangement structure, and the number of arrangements are not limited to those shown in the above embodiment.

Further, in the above embodiment, such a cam member 54, a hydraulic cylinder 76, a piston rod 78
The moving means for moving the outer mold 16 so as to be positioned eccentrically with respect to the mandrel 14 as a core is constituted by the a, 78b, the connecting arm 82, and the driving arm 68. Is not particularly limited to this structure.

In the above embodiment, the extrusion die 10
However, the cross-head type is used, but other known forms such as a straight head type and an offset type may be used.

Further, the circular outer peripheral surface 36 of the mandrel 14
The moving distance of the outer mold 16 in the radial direction is not limited to the one shown in the above-described embodiment, and is appropriately determined depending on the thickness variation of the finally obtained hollow molded product. It is determined by

In addition, in the above embodiment, the present invention is applied to a molding apparatus for molding a cylindrical parison used for blow molding a resin tube and a method for molding the parison. Although an example was shown, the present invention is intended to mold a cylindrical parison used as a preform when blow molding, regardless of the shape and use of the finally obtained hollow molded product. It is needless to say that the present invention can be advantageously applied to any of the molding apparatus and the parison molding method.

In addition, although not enumerated one by one, the present invention
Based on the knowledge of those skilled in the art, various changes, modifications, improvements and the like can be implemented in an embodiment,
It is to be understood that any such embodiments are within the scope of the present invention without departing from the spirit thereof.

[0075]

As is clear from the above description, in the parison molding apparatus according to the present invention, a parison capable of providing a hollow molded article having a uniform wall thickness can be formed extremely advantageously. As a result, when molding the parison, it is possible to advantageously eliminate the use of an excessive amount of resin material, thereby reducing the weight of the hollow molded article to be molded and the resin material used. It is possible to effectively reduce material costs due to savings, and it is also possible to reduce the parison molding defect due to excessive use of resin material, and eventually, the occurrence of poor quality of the finally obtained hollow molded product. Can be prevented.

Further, according to the method for molding a parison according to the present invention, a parison capable of providing a hollow molded article having a uniform wall thickness can be surely molded. Due to the large variation in the wall thickness of the product, various problems caused when molding such a hollow molded product can be eliminated at once.

[Brief description of the drawings]

FIG. 1 is an explanatory front view showing an example of a parison molding apparatus according to the present invention.

FIG. 2 is an explanatory cross-sectional view of a main part showing a main part of a II-II cross section in FIG. 1;

FIG. 3 is an explanatory sectional view taken along the line III-III in FIG. 2;

FIG. 4 is an explanatory diagram viewed from an arrow IV in FIG. 1;

FIG. 5 is an explanatory view showing an example of a step of forming a parison by using the apparatus of the present invention, wherein (a) to (d) show that the outer mold is moved in different radial directions of the core mold, The state where the parison is formed under the state where the width of the lip gap is partially changed in the circumferential direction is shown.

FIG. 6 is a perspective explanatory view showing a resin tube obtained by performing three-dimensional blow molding on a parison molded using the apparatus of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Extrusion die 12 Die main body 14 Mandrel 16 Outer die 25 Mounting bush 36 Circular outer peripheral surface 46 Lip gap 53 Contact surface 54 Cam member 62 Sliding convex part 68 Drive arm 76 Hydraulic cylinder 78 Piston rod 82 Connecting arm 90 Parison

[Procedure amendment]

[Submission date] April 24, 2000 (200.4.2
4)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Name of invention

[Correction method] Change

[Correction contents]

[Title of the Invention] Parison molding machine

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

2. A pair of cam members, each pair of which is in contact with the outer peripheral surface of the outer die on two orthogonally extending lines of two diameters of the core die, and two pairs of positions are provided. The parison molding apparatus according to claim 1 , wherein the parison molding apparatus is provided.

3. The moving means further includes a control mechanism for controlling the driving mechanism, and the control mechanism rotates the cam member at an arbitrary operation amount during the molding of the cylindrical parison. The outer mold is formed between the outer mold and the core by moving or reciprocating to move the outer mold in the radial direction of the core by an amount corresponding to the operation amount of the cam member. The parison molding according to claim 1 or 2 , wherein the width of the annular lip gap can be partially and arbitrarily changed in a circumferential direction during the molding of the cylindrical parison. apparatus.

Wherein said outer die is one that is composed of a cylindrical body, said cam member, with its rotation, is slid relative to the outer mold the outer peripheral surface of the outer mold The core mold is configured to have a sliding convex portion that is pressed and moved in the radial direction, and furthermore, a contact portion of the outer peripheral surface of the outer mold with the sliding convex portion of the cam member has a flat contact surface. parison forming apparatus according to any one of claims 1 to 3 there is a.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Shigehisa Takahashi 1-7-38 Kanage, Minami-ku, Nagoya City, Aichi Prefecture Inside Takahashi Seiki Kogyo Co., Ltd. (72) Inventor Noboru Kanie Kanage, Minami-ku, Nagoya City, Aichi Prefecture 1-7-38 Takahashi Seiki Co., Ltd. F-term (reference) 4F207 AA29 AR12 KA01 KA17 KL57 KL63 KL76 KL77 KL80 KL83 KL88 KM15 4F208 AA29 AR12 LA01 LA08 LB01 LG25

Claims (7)

[Claims] An apparatus for forming a cylindrical parison attached to a tip of an extruder, comprising: a core having a cylindrical or tapered cylindrical outer peripheral surface;
A circle which has a cylindrical shape, is arranged outside the core mold so as to be movable in the radial direction of the core shape, and is formed between the core shape and the circular outer peripheral surface to form the cylindrical parison. An extrusion die having an outer mold forming an annular lip gap; and a width of the annular lip gap formed between the outer mold and the core mold of the extrusion die is partially increased in a circumferential direction thereof. Moving means for moving the outer mold so as to change the outer mold so as to be eccentrically positioned with respect to the core mold. 2. The method according to claim 1, wherein the moving unit is rotatable or reciprocally movable in a state of being brought into contact with the outer peripheral surface of the outer die. And a driving mechanism for reciprocating, wherein the at least one cam member is rotated or reciprocated by the driving mechanism, and the outer die is pressed and moved in the radial direction of the core by the cam member. The parison forming apparatus according to claim 1, wherein the apparatus is configured to cause the parison forming. 3. The cam members are positioned in pairs such that the cam members contact the outer peripheral surface of the outer die on an extension of the diameter of the core mold, and one of the paired cam members is provided. With the rotation or reciprocation of the outer mold, the outer mold is pressed and moved in one radial direction of the core mold by the one cam member, while the rotation or reciprocation of the other cam member is performed. The parison molding according to claim 2, wherein the outer die is moved by being pressed by the other cam member in a direction opposite to a moving direction of the one cam member with the movement. apparatus. 4. A pair of cam members, each pair of which is in contact with the outer peripheral surface of the outer die on two mutually perpendicular extensions of the diameter of the core die, and two pairs of positions are provided. 4. The parison molding apparatus according to claim 3, wherein the apparatus is provided. 5. The moving means further includes a control mechanism for controlling the drive mechanism, and the control mechanism rotates the cam member at an arbitrary operation amount during the molding of the cylindrical parison. The outer mold is formed between the outer mold and the core by moving or reciprocating to move the outer mold in the radial direction of the core by an amount corresponding to the operation amount of the cam member. The width of the annular lip gap can be partially and arbitrarily changed in the circumferential direction during the molding of the cylindrical parison. Parison molding equipment. 6. The outer die is constituted by a cylindrical body, and the cam member is slid with respect to the outer peripheral surface of the outer die with the rotation thereof, thereby forming the outer die. The core mold is configured to have a sliding convex portion that is pressed and moved in the radial direction, and furthermore, a contact portion of the outer peripheral surface of the outer mold with the sliding convex portion of the cam member has a flat contact surface. The parison molding apparatus according to any one of claims 2 to 5, wherein: 7. Extruding the molten resin through an annular lip gap formed on an extrusion die attached to a tip of an extruder to form a cylindrical parison, wherein the width of the annular lip gap is A method for molding a parison, wherein the molten resin is extruded in a state where the molten resin is partially changed in the circumferential direction.