JP2009202925A - Blow molding container - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of an extremely thin-walled part at the foot part of a blow molding container having a cylindrical trunk portion, the foot part being a bordering part between the trunk portion and bottom portion thereof, by suppressing the extent of a local stretch deformation in the foot part while equalizing it. <P>SOLUTION: A crisscross pinched off line 9 formed as remaining on the bottom surface 6 of a bottom part 4 is positioned on a diagonal (t) of the bottom surface 6, while one of the diagonals (t) is positioned on a parting line (P), with the tip ends of respective pinched off lines 9 positioned in proximity to the foot part 7 of the bottom part 4 locally stretched for forming, thereby reducing the amount stretched in the foot part 7 for preventing occurrence of the extremely thin-walled part. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a synthetic resin blow-molded container molded by a direct blow molding method.

As a technique for direct blow molding of a blow molded container having a cylindrical body, for example, as disclosed in Japanese Patent Application Laid-Open No. 07-016912, a parison extruded from an extruder is used as a pair of split metal. It is sandwiched between molds, and the sandwiched parison is inflated in a split mold to be molded into a blow molded container.In blow molding, the leg part, which is the boundary between the body part and the bottom part, has a wall structure. Since it is bent at an acute angle, it is a portion that is easily stretched locally.
Japanese Patent Laid-Open No. 07-016912

  In the technique of this Patent Document 1, since the parison is pinched off with a pair of split molds, the bite line that is a bite cut by the pinch-off part formed at the bottom of the molded container is located on the parting line. It will be.

  In this case, since the length of the weeding line 9 is 1.6 times the outer diameter of the parison, generally, as shown in FIG. 8, the leg part 7 on the parting line P extends from the end of the weaving line 9. Therefore, even if the leg portion 7 is a portion formed by local stretching, the degree of thinning due to local stretching is small (see FIG. 7A).

  On the other hand, in the case of, for example, a square tube located in a direction intersecting with the cutting line 9, the leg part 7 positioned on the diagonal line t has a large distance from the cutting line 9, and thus local stretching deformation is concentrated. As a result, the degree of thinning due to local stretch molding becomes extremely significant (see FIG. 7B).

  For this reason, in a blow molded container having a conventional cylindrical body, the corners located on the parting line at the bottom are thin, and therefore the mechanical strength as the bottom of the container is maintained. As shown in FIG. 8, there is a problem that this tendency becomes conspicuous when the body is square.

  In addition, when giving a hardness similar to that of a glass bottle, it is only necessary to increase the overall wall thickness, but in this case, it is also necessary to increase the wall thickness of the bottom leg as described above. There is a problem that the wall thickness increases and the moldability may be lowered.

  Furthermore, in order to obtain a crystal feeling similar to that of a glass bottle, if the whole is made transparent, the extreme thickness change of the above-mentioned leg at the bottom appears as an appearance, so this extreme change in thickness is uncomfortable. There was a problem that it might cause

  Therefore, the present invention was devised to solve the above-described problems in the prior art, and it is a technical problem to suppress and equalize the extent of local stretch deformation at the bottom leg of the blow molded container, Accordingly, an object is to prevent the occurrence of thinning of the above-described leg portion.

  The direct blow molded container made of synthetic resin according to the present invention is constructed by standing up a cylindrical mouth portion through a shoulder portion at an upper end of a cylindrical body portion whose lower end is closed by a bottom portion.

  On the bottom surface of the bottom portion, at least four biting lines that are the remaining biting marks are arranged radially, and a pair of the biting lines arranged in a straight line is positioned on the parting line.

  The tip of each cutting line arranged radially is positioned close to the leg.

  For this reason, the parison part located in the vicinity of the leading edge of each cutting line will be locally stretch-molded into the leg part without being greatly stretched and displaced, and thinning due to local stretch deformation in this leg part will be sufficiently suppressed. be able to.

  Moreover, since the extent of local stretch deformation in the leg portion can be suppressed in this way, stretch molding itself can be achieved without difficulty.

  Another configuration of the present invention is that the body portion is a rectangular tube shape, four cutting lines are arranged in a cross, and each of a pair of the cutting lines arranged in a straight line is positioned on two diagonal lines. Is.

  In the case where each of the pair of straight lines of the cut-off line is positioned on two diagonal lines, the tip of each cut-off line is brought close to the leg part on the diagonal line. Will be positioned.

  In another configuration of the present invention, the whole is made thick enough to exhibit hardness that does not flex and deform.

  In the case where the whole is made thick enough to bend and deform so as not to be deformed, the extent of local stretching deformation in the leg is sufficiently suppressed, so even if the thickness increases, the leg There is no fear that the moldability of the resin will deteriorate.

  In addition, another configuration of the present invention is such that the whole is transparent or translucent.

  In the case where the whole is transparent or translucent, it is observed from the outside because the thinness of the legs is suppressed while the crystal appearance can appear in the entire container. There is no sense of incongruity in the thinning of the legs.

Since the present invention has the above-described configuration, the following effects can be obtained.
In the present invention, it is possible to sufficiently suppress the thinning due to local stretch deformation in the leg portion at the bottom, so that the mechanical strength is insufficient due to the extreme thinning in the bottom leg in the direct blow molded container. Generation | occurrence | production can be prevented reliably and sufficient mechanical strength can be obtained.

  Moreover, since the extent of local stretch deformation at the bottom leg portion can be suppressed, stretch molding itself can be achieved without difficulty, thereby enabling stable molding.

  If the body part is a square cylinder, four cut lines are arranged in a cross, and each of the pair of cut lines arranged in a straight line is positioned on two diagonal lines. Since the front end of the diagonal portion can be positioned close to the leg portion on the diagonal line, it is possible to reliably suppress the occurrence of local stretching deformation in the leg portion on the diagonal line where extreme local stretching is likely to occur.

  In the case where the whole is made thick enough to bend and deform so that it does not deform, even if the wall thickness increases, the moldability of the bottom leg will not be reduced, so the wall thickness is reduced. Larger hard containers can be formed without difficulty.

  If the whole is transparent or translucent, there is no sense of incongruity in the thickness of the leg at the bottom observed from the outside. Can do.

  Embodiments of the present invention will be described below with reference to FIGS.

  In the first embodiment shown in FIG. 1 to FIG. 3, a thread is engraved on the outer peripheral surface of the upper end of a regular rectangular cylindrical body 3 whose lower end is closed by a bottom 4 via a shoulder 2. The cylindrical mouth portion 1 is constructed by standing upright.

  The bottom 4 has a bottom surface 6 which is a lower surface of the bottom wall 5 which is a main portion thereof, and is formed into a concave curved surface which forms a leg portion 7 around the bottom surface 6 by being slightly curved and depressed. The four bit lines 9 that are the bite traces are formed in the remaining state.

  Each cut line 9 (refer to FIG. 3 hereafter) is arranged in a cross shape, and each of the pair of cut lines 9 arranged in a straight line is an imaginary separate diagonal line of the bottom face 6 having a regular square shape. It is located on t, and one diagonal line t is located on the parting line P.

  The blow-molded container in this first embodiment is obtained by a direct blow molding method, and the parison 12 is extruded from a extruder through a die, and the parison 12 is clamped by a two-part split mold. The lower part of the parison 12 is cut at the pinch-off part, which is a blade part provided at the bottom of the cavity of the split mold, and heat-sealed and sealed, and the upper part of the mold is formed of a cylindrical parison with a parison cutter. By cutting the upper part, a parison 12 having a bottomed cylindrical body is formed, and then blow air is blown into the parison 12 from the top of the split mold by an air nozzle, and blow molding is performed.

  Here, among the blow molding dies, by using a bottom split mold 10 (refer to FIG. 4) in which a portion for molding the bottom 4 of the blow molding container is divided into four, a cross-shaped biting line 9 is formed. can do. Here, as the main part mold for forming the part other than the bottom part 5 of the blow-molded container, that is, the part corresponding to the body part 3, the shoulder part 2 and the mouth part 1, the one divided into two parts is used as usual.

  FIG. 4 is an explanatory view showing in a bottom view the pinch-off process of the parison 12 by the four-part bottom split mold 10 having the pinch-off parts 11 each of which is a blade part. Each corner of the mold 10 faces the parison 12 (FIG. 4 (a)) and further moves in the direction of the central axis of the parison 12 (FIG. 4 (b)), and the parison 12 is pinched off in a cross shape (see FIG. 4). 4 (c)), as a result, a cross-shaped cut-off line 9 is formed on the bottom surface 6 of the bottom 4 of the parison 12. A parting line P is shown by a two-dot chain line in FIG.

  Thus, when the parison 12 is blow-molded in a state where the parison 12 is cut and held by the four pinch-off portions 11, four “sides” of the legs 7 to be molded that have a small distance from the virtual extension center axis are small. ”Portion, even in the corner portion 8 having a larger distance from the extending central axis than the“ side ”portion, the difference in thickness is suppressed to a small value (see FIG. 3).

  In the illustrated embodiment that is molded into a thick container using a transparent synthetic resin such as PET, the outer diameter of the mouth portion 1 engraved with a thread is 16 mm, the inner diameter is 10 mm, The height is 650 mm, the width of each side wall is 27 mm, the thickness of the central portion of each wall is 2.5 mm, the thickness of the portion close to the ridgeline of each wall is 1.5 mm, and the bottom wall of the bottom portion 6 5 The thickness of the central part was 3 mm, the thickness of the side part central part of the leg part 7 was 4 mm, and the thickness at the corner part 8 was 2 mm.

  As shown in FIG. 2, the central portion on the inner surface side of the bottom wall 5, which is located immediately above the intersection of the cross-cutting lines 9 that are cross-shaped, is formed so as to be recessed from the periphery. It seems that the delay of the cooling rate is concentrated in the central portion due to the thermal effect from the excision portion of the parison 12 that is cut off by the pinch-off portion 11 of the split mold 10, thereby causing the post-shrinkage due to the delay of cooling.

  FIG. 5 and FIG. 6 show a second embodiment of the present invention, which has a cylindrical body portion 3, and in this case as well, compared to the case where there is only one conventional cutting line. As the number of the cut-off lines 9 is increased, the local stretch deformation in the leg portion 7 which is the boundary portion between the trunk portion 3 and the bottom portion 4 is equalized, and the thinning is effectively performed as shown in FIG. Can be suppressed.

  Note that the number of the cutting lines 9 is not limited to four, and it is optimal to provide the number corresponding to the number of corners of the rectangular tube constituting the trunk portion 3.

1 is an overall external perspective view showing a first embodiment of the present invention. FIG. 4 is an oblique side view of the exemplary embodiment shown in FIG. 1, partially cut along the line AA in FIG. 3. FIG. 2 is a bottom view of the exemplary embodiment shown in FIG. 1. It is operation | movement explanatory drawing explaining the cutting-off operation | movement of a parison. It is a whole external appearance perspective view which shows the example of 2nd embodiment of this invention. FIG. 6 is a bottom view of the exemplary embodiment shown in FIG. 5. FIG. 9A is a partially cut-away side view of the conventional example, and is a cutaway view taken along the line BB in FIG. 8, and FIG. 8B is a cutaway view taken along the line CC in FIG. is there. It is a bottom view of the conventional example shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1; Mouth part 2; Shoulder part 3; Body part 4; Bottom part 5; Bottom wall 6; Bottom face 7; Leg part 8; Corner part 9; Cut-off line 10: Bottom split mold 11: Pinch-off part 12; P: Parting line

Claims (4)

A bottle-shaped synthetic resin direct blow molded product with a cylindrical mouth part standing upright at the upper end of a cylindrical body part closed at the bottom with a bottom part, remaining on the bottom of the bottom part A blow-molded container in which at least four biting lines that are the biting marks formed are arranged radially, and a pair of the biting lines arranged in a straight line is positioned on the parting line. The blow-molded container according to claim 1, wherein the body portion is formed in a rectangular tube shape, four cutting lines are arranged in a cross shape, and a pair of the cutting lines arranged in a straight line are positioned on two diagonal lines. . The blow-molded container according to claim 1 or 2, wherein the whole is made thick enough to exhibit a hardness that does not flex and deform. The blow molded container according to any one of claims 1 to 3, wherein the whole is transparent or translucent.

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