JP2009241947A - Blow-molded container - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively suppress a sink formed in a flat wall part of a barrel adjacent to a corner of a bottom part due to accumulation of a molten resin at both ends of a pinch-off part, in a direct-blow-molded container having a quadrangular tube shaped barrel section. <P>SOLUTION: The synthetic resin molded product manufactured by a direct-blow molding process has a quadrangular tube shaped barrel consisting of four flat walls connected at four corners and having a quadrangular plane cross sectional shape, and a parting line formed by splitting molds is formed along a pair of opposing corners. A cutting line formed by the pinch-off part of the split molds formed along the parting line of the split molds positioned on a diagonal line at the bottom surface of a bottom part is formed into a bent line shape formed by connecting three linear lines of two end linear lines and one central linear line part formed at the parting line in a crossing manner. The two end linear lines are connected to the parting line near the corner while the end part of the central linear line is applied as a base end. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

A technique for directly blow-molding a blow-molded container having a cylindrical body is disclosed in Patent Document 1, for example.
FIG. 7 is a schematic explanatory view of this direct blow molding method, in which a cylindrical parison P is extruded from a extruder 21 through a die, and the parison P is divided into two perpendicularly to the clamping direction by a split mold 23. The mold is clamped and sandwiched, and the lower part of the molten resin is cut and thermally welded by a pinch-off part 24, which is a blade part disposed at the bottom of the cavity of the split mold 23, and a cylindrical shape is formed by a parison cutter 25 at the upper part. The upper part of the molten resin is cut to form a bottomed cylindrical parison P, and blow air is blown into the parison P from the top of the split mold 23 by an air nozzle.
The burr that protrudes below the pinch-off part 24 is cut and removed by the pinch-off part 24, but the bottom line of the bottom of the container to be molded is cut by a cutting line that is a cut mark by the pinch-off part 24. It is formed on the parting line by the mold.
Japanese Patent Laid-Open No. 07-016912

  Here, in the case of a container having a cylindrical body, it is generally possible to smoothly open the split mold, and to avoid the problem that the appearance is impaired due to the formation of parting lines on the flat wall portion of the body. For this reason, the split mold is divided in the diagonal direction of the quadrangle as viewed in a flat cross section for reasons such as the above. As a result, the parting lines formed by the split surfaces of the split mold are formed along the opposite corners in the longitudinal direction in the body portion and along the diagonal lines in the bottom surface of the rectangular shape.

  However, as described above, in the direct blow molding, the molten resin is sandwiched by the pinch-off portion at the lower end portion of the parison and the bottom portion is sealed, and at this time, a molten resin pool is formed particularly at the end portion of the pinch-off portion. Depending on the shape of the quadrangle, the appearance of sink marks in the flat portion of the trunk portion adjacent to the corner portion of the bottom due to the accumulation of the meat becomes a serious problem in appearance.

That is, since both end portions of the pinch-off portion are adjacent to the corner portion and close to the flat wall of the trunk portion, the flat wall portion is not sufficiently cooled and solidified by the split mold due to the accumulation of meat. Therefore, the so-called sink is generated due to the depression due to the post-shrinkage due to the progress of the cooling after the release.
In addition, the flat wall forming the body portion is flat, so that the concave deformation due to post-shrinkage is likely to proceed, and even a slight dent is conspicuous due to light reflection and the like, and the appearance is greatly impaired. End up.

  Accordingly, the present invention provides a direct blow molded container having a quadrangular cylindrical body portion, which causes sink marks at the flat portion of the body portion adjacent to the corners of the bottom portion due to the accumulation of molten resin at both ends of the pinch-off portion. It is a technical problem to effectively suppress the above.

The main configuration according to the means for solving the problems of the present invention is as follows:
It is obtained by a direct blow molding method using a split mold that is divided perpendicularly to the clamping direction, and a flat cross-sectional shape formed by connecting four flat walls with four corners above the bottom is square. It has a square cylindrical body part, and a mouth cylinder part is provided upright above this body part via a shoulder, and parting lines by split molds are formed along a pair of opposite corners. In a synthetic resin molded product,
The cutting line by the pinch-off part of the split mold formed along the parting line by the split mold located diagonally on the bottom surface of the bottom is formed at both ends of the central straight section formed to intersect the parting line. Each of them is formed in a bent line shape composed of three straight portions connecting the straight portions at the ends,
The straight portions at both ends are connected to the parting line in the vicinity of the corners with the end of the central straight portion as the base end.

  The basic idea of the above configuration is that the bottom line of the container is formed in a bent line shape along the parting line on the diagonal line as a whole, so that the barrel close to the corner part of the bottom part is formed. Adjust the position and orientation of the edge of the cutting line near the corner corresponding to both ends of the pinch-off part, which is the main cause of sinking in the flat wall part, using the bent shape of the bending line, This is to suppress the occurrence of this kind of sink.

  That is, by making the cut line into a bent line shape in which the end straight portions are connected to both ends of the central straight portion, the length of the central straight portion and the intersection angle with the parting line, the end straight portion and the central straight portion By changing the bend angle and the length of the end straight part, the position and orientation of the end of the cut line near the corner or the distance between the end and the flat wall can be adjusted in various ways. In addition, it is possible to effectively suppress the occurrence of sink marks in the trunk flat wall portion adjacent to the corner portion of the bottom portion.

  On the other hand, the cut-off line is formed by a central straight portion formed in a crossing manner with the parting line, and both end straight portions connected to the parting line in the vicinity of the corner with the end of the central straight portion as the base end. As a result, the cutting line can be formed along the parting line on the diagonal as a whole, and good mold opening of the split mold can be secured. It can be formed along the corners so as not to impair the appearance.

  Other configurations of the present invention, in addition to the main configuration described above, the trapezoidal cross-sectional shape of the body portion, the central straight portion is formed in the middle middle position of the upper side and lower side of the trapezoid, parallel to these upper side and lower side, It is said.

  The above configuration specifies the trapezoidal cross-sectional shape of the torso, but by forming the central straight portion at the center intermediate position of the upper and lower sides of the trapezoid and parallel to the upper and lower sides, By changing the length of the central straight line, the bending angle between the end straight part and the central straight part, and the length of the end straight part depending on the shape, the straight line along the parting line on the conventional diagonal line can be changed. As compared with a container having a cutting line, it is possible to effectively suppress the occurrence of sink marks in the body flat wall portion close to the bottom corner.

  Still another configuration of the present invention is that the end straight portion is formed in a direction that substantially bisects the angle of a corner portion close to the end straight portion.

In a container having a straight cutting line along a parting line on a diagonal line, depending on the shape of the quadrangle, the end of the cutting line forms the corner in the vicinity of the corner. Of the flat walls, the flat wall may be located close to one flat wall, and the occurrence of sink marks in the flat portion becomes significant.
Therefore, by forming the end straight portion in the above-described configuration in a direction that substantially bisects the angle of the corner that the end straight portion is close to, the end portion of the cut-off line is biased as described above. The occurrence of sink marks due to the position can be effectively suppressed.
In addition, it is not necessary to bisect the corner accurately with the above configuration, and the occurrence of sink marks can be suppressed by bisecting the corner more nearly equally compared to the direction of the parting line. Here, it is configured to be “substantially” divided into two equal parts.

Since the blow molded container of the present invention has the above-described configuration, the following effects are exhibited.
In the case of the main structure, by setting the cutting line to a bent line shape connecting the central straight line portion and the two end straight line portions, it is possible to improve the mold opening property of the split mold in blow molding. Use this bent shape without damaging it, and adjust the position and orientation of the edge of the cut line near the corner to effectively generate sink marks in the flat part of the trunk near the bottom corner. Can be suppressed.

  In the case where the flat cross section of the body is trapezoidal, and the central straight line is formed at the central middle position of the upper and lower sides of the trapezoid and parallel to these upper and lower sides, the parting line on the conventional diagonal line As compared with a container having a straight cutting line along the bottom, it is possible to effectively suppress the occurrence of sink marks in the trunk flat wall portion adjacent to the corner portion of the bottom portion.

  In the case where the end straight portion is formed in a direction that substantially bisects the angle of the corner that the end straight portion is close to, the formation position where the end of the cutting line is biased in the vicinity of the corner It is possible to effectively suppress the occurrence of sink marks on the trunk flat wall due to the above.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below along the examples with reference to the drawings.
1 to 3 show one embodiment of a blow molded container of the present invention, FIG. 1 is a front view, FIG. 2 is a plan view, and FIG. 3 is a bottom view.
In this blow molded container, four flat walls 3f (3f1, 3f2, 3f3, 3f4) are connected by four corners 3c (3c12, 3c23, 3c34, 3c41), and the flat cross-sectional shape is trapezoidal. A cylindrical barrel portion having a rectangular cylindrical barrel portion 3, a bottom portion 4 at the lower end of the barrel portion 3, and a thread formed on the outer peripheral surface of the upper end via a shoulder portion 2. 1 is constructed by standing upright.

  This blow molded container is formed by the direct blow molding method shown in the schematic explanatory diagram of FIG. 7, and as described above, the cylindrical parison P is extruded from the extruder 21 through a die, and the parison P is The mold is clamped and clamped by a split mold 23 that is divided in two perpendicularly to the mold clamping direction, and the lower part of the molten resin is cut by a pinch-off portion 24 that is a blade portion disposed at the bottom of the cavity of the split mold 23. At the top, the upper part of the cylindrical molten resin is cut by a parison cutter 25 to form a bottomed cylindrical parison P, and then blow air is blown from the top of the split mold 23 by an air nozzle inserted into the parison. B is blow-molded into P.

  FIG. 4 is a schematic explanatory view of the split mold 23 used for blow molding of the container according to the present embodiment. The split surface 23a of the split mold 23 is an opposite angle of the blow molded container that is the molded product M. It is formed along a diagonal line connecting the part 3c (here, the corner part 3c12 and the corner part 3c34). And the parting line PL is formed in the outer surface of a container by this division surface 23a. The white arrow in FIG. 4 indicates the mold opening direction of the split mold 23.

  The bottom surface 5 of the bottom portion 4 is slightly depressed in a gentle curve, and a grounding portion 7 is formed on the periphery thereof. In addition, the bottom surface 5 has a biting mark by the pinch-off portion of the parison along the parting line PL located in the diagonal direction of the corner portions 3c12 and 3c34 by the dividing surface 23a of the split mold 23 described above. The cut line 8 is formed in a bent line segment.

  As shown in FIG. 3, the cut line 8 is composed of a central straight portion 8cs and three straight portions called two end straight portions 8es connected to both ends of the central straight portion 8cs. Yes. The central straight line portion 8cs is formed so as to intersect the parting line PL, and is substantially parallel to the flat surface 3f1 and the flat surface 3f3 parallel to each other, which form the substantially central portion of the bottom surface 5 and the upper and lower sides of the trapezoid. It is located in the middle center between both flat surfaces 3f1, 3f3.

  The two end straight portions 8es are connected to the parting line PL in the vicinity of the corner portions 3c12 and 3c34 with the end portion of the central straight portion 8cs as a base end. Further, the end straight portion 8es located in the vicinity of the corner 3c12 is in a direction that bisects the angle of the corner 3c12, and the end straight portion 8es located in the vicinity of the corner 3c34 determines the angle of the corner 3c34. The direction is approximately bisected.

FIG. 5 is a bottom view of a blow molded container as a comparative example of the above embodiment.
The container of this comparative example is the same as the above embodiment in other shapes, and is formed by forming the cutting line 8 by the pinch-off portion in a straight line along the parting line PL as in the prior art.

In the blow molded container of this comparative example, the position of the end portion of the cutting line 8 is close to the flat surface 3f3, particularly in the vicinity of the corner portion 3c34 having a relatively acute angle. Due to the influence of the accumulation in the vicinity of the end portion of the pinch-off portion corresponding to the end portion position of the cut-off line 8, noticeable sink marks appear in the region indicated by the white arrow in FIG. 5 in the vicinity of the bottom portion 4 of the flat wall 3f3. Occurrence was seen. In addition, the occurrence of sink marks was observed in the region indicated by the white arrow on the flat surface 3f1 in the vicinity of the corner 3c12, though it was minute.
These sink marks are caused by the fact that the cooling solidification by the mold does not proceed sufficiently due to the accumulation of the wall near the end of the pinch-off part, but the flat wall easily deforms into a concave shape due to minute post-contraction, Even a small dent is conspicuous due to light reflection and the like, so that the appearance is greatly impaired.

  Moreover, since one corner | angular part 3c23 and the corner | angular part 3c41 are located away from the cutting line 8, there also exists a problem that the thickness of the trunk wall near the said corner | angular part 3c23 and 3c41 will become thin in the vicinity of the bottom part 4. is there.

  In this respect, in the container of the embodiment shown in FIGS. 1 to 3 in which the cut line 8 is formed in a bent line shape, the two end straight portions 8es of the cut line 8 are respectively connected to the corners 3c12 and the corners. 3c34 is formed in a substantially bisecting direction, and it is possible to alleviate that the end portion of the cut-off line 8 is biased and close to the flat wall 3f1 and the flat wall 3f3 located in the vicinity of the corners. The occurrence of sink marks in the regions of the flat walls 3f1 and 3f3 indicated by the white arrows in FIG. 5 as seen in the example can be eliminated.

  Further, by forming the cutting line 8 in a bent line segment, it is possible to effectively relieve the thinning of the wall thickness at the corners 3c23 and 3c41 in the vicinity of the bottom 4.

Next, FIG. 6 is a bottom view schematically showing another embodiment of the blow molded container of the present invention. Thus, in the container having a fairly irregular rectangular flat cross-sectional shape, according to the conventional straight cutting line 8, the end of the cutting line 8 is near the corners 3c23 and 3c14, with white arrows. Significant sink marks are observed at the indicated flat wall 3f3 and flat wall 3f1.
Therefore, as shown in FIG. 6, along the parting line PL, by forming a cutting line 8 composed of a central straight line portion 8cs and two end straight line portions 8es into a bent line segment, these white arrows The occurrence of sink marks in the flat wall 3f3 and the flat wall 3f1 pointed at can be effectively suppressed.

As mentioned above, although embodiment of this invention and its effect were demonstrated along the Example, embodiment of this invention is not limited to this Example.
For example, in the above embodiment, the body section has a trapezoidal cross-sectional shape, but the effects of the present invention can be exhibited with various forms of rectangular shapes.
In addition, by changing the length of the central straight line, the crossing angle with the parting line, the bending angle between the end straight part and the central straight part, and the length of the end straight part, The distance between the peripheral walls can be adjusted in various ways.

  As described above, the blow-molded container having the rectangular cylindrical body portion of the present invention effectively suppresses the occurrence of sink marks near the bottom and the occurrence of thin portions due to the shape of the pinch-off portion. A wide range of usage can be expected as a container having a characteristic body shape such as a trapezoidal cylinder.

It is a front view which shows one example of embodiment of the blow molding container of this invention. It is a top view of the container shown in FIG. It is a bottom view of the container shown in FIG. It is a schematic explanatory drawing of the split mold used for shaping | molding of the container shown in FIG. It is a bottom view of the blow molding container of a comparative example. It is a bottom view which shows other embodiment of the blow molding container of this invention roughly. It is a schematic explanatory drawing of the direct blow molding method.

Explanation of symbols

1; mouth tube part 2; shoulder part 3; trunk part 3f (3f1, 3f2, 3f3, 3f4); flat wall 3c (3c12, 3c23, 3c34, 3c41); corner part 4; bottom part 5; bottom face 7; Cutting line 8cs; central straight part 8es; end straight part 21; extruder 23; split mold 23a; split surface 24; pinch-off part 25; parison cutter P; parison PL;

Claims (3)

It is obtained by a direct blow molding method using a split mold that is divided perpendicular to the clamping direction, and four flat walls (3f) are connected by four corners (3c) above the bottom (4). A square cylindrical body (3) having a rectangular cross-sectional shape, and a mouth cylinder (1) standing upright above the body (3) via a shoulder (2) In the synthetic resin molded product formed along the pair of corners (3c) facing each other, the parting line (PL) by the split mold is diagonal to the bottom (5) of the bottom (4). The cutting line (8) by the pinch-off portion of the split mold formed along the parting line (PL) by the split mold located on the top is formed to intersect the parting line (PL). It is assumed that the both ends of the central straight portion (8cs) are formed in a bent line shape composed of three straight portions connecting the end straight portions (8es) to the both ends. ( A blow-molded container having a configuration in which the end portion of 8cs) is connected to the parting line (PL) in the vicinity of the corner portion (3c) with the end portion as a base end. The blow-molded container according to claim 1, wherein the body section (3) has a trapezoidal cross-sectional shape, and a central straight section (8cs) is formed at a central intermediate position between the upper and lower sides of the trapezoid, parallel to the upper and lower sides. The blow molded container according to claim 1 or 2, wherein the end straight part (8es) is formed in a direction that substantially bisects the angle of the corner (3c) with which the end straight part (8es) is adjacent.

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