JP2004148718A - Mold for blow molding - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a mold for blow molding having a technical subject for suppressing the occurrence of burr from the left and right ends of the pinch-off part to a lateral direction in a bottom surface in direct blow, and providing a blow-molded container having excellent appearance which has no burr mark, gloss irregularity and color irregularity on the side surface near the bottom part of the container and is low in blow ratio. <P>SOLUTION: A split mold divided front and rear has a main body parting surface vertical to a mold clamping direction and a pinch-off part where a bite-off blade for the pinch-off of a parison is arranged to the bottom surface of the bottom part of a mold cavity. In the planar cross section in the mold closing state of the split mold, one bottom part parting line is formed from the straight line-like pinch-off line formed to the bottom surface by the bite-off blade, a pair of main body parting lines formed to left and right peripheral edge parts by a main body parting surface and a pair of connection lines for connecting the left and right ends of the pinch-off line and the left and right ends of the main body parting lines. The connection lines form a step-like bent part almost right-angled to the pinch-off line by the end part parting surfaces positioned at the left and right ends of the pinch-off part. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a mold for blow molding, and more particularly to a mold for blow molding that can control generation of burrs at a bottom pinch-off portion of a container such as a bottle.
[0002]
[Prior art]
As shown in FIG. 10, in a normal direct blow molding method, a parison P which is a cylindrical molten resin is extruded by an extruder 21, and this parison P is subjected to a mold clamping process of a split mold 1 for blow molding divided into two parts. In the lower part of the mold, the lower part of the molten resin is cut with a cutting blade provided in the bottom pinch-off part 5 of the cavity 2 of the split mold 1 and the lower part of the molten resin is sealed by heat welding. Is cut to form a parison P as a bottomed cylinder, and then blow air is blown into the parison P by an air nozzle inserted from the top of the split mold 1 to form a molded product.
[0003]
FIGS. 8 and 9 show an example of a conventional split mold. The split mold 1 has a structure in which the entire split mold 1 is divided into two by one plane (body dividing surface 11). As shown in ()), the pinch-off line 14 formed by the cutting blade 6 on the bottom surface 3 and the bottom surface 4 of the mold cavity 2 is formed by 11 on the main body division surface in a plane cross section of the split mold 1 in the mold closed state. Located on the main body dividing line 13.
[0004]
The width of the pinch-off portion 5, that is, the length of the pinch-off line 14 corresponding to the length of the cutting blade 6 in the left-right direction is a width obtained by crushing a parison having an outer diameter Dp, which is usually a cylindrical shape, into two flat shapes. It is about 1.6 Dp, and a cutting line by a cutting blade having a length of about 1.6 Dp is inevitably formed on the bottom bottom surface of the container as a molded product.
[0005]
Conventionally, with respect to the structure in the vicinity of the bottom pinch-off portion of a blow molding die, various improvements have been made from the viewpoint of improving the strength of the bottom seal portion of a container as a molded product and from the viewpoint of appearance. There is a description about a method of forming a stepped depression on both sides of the pinch-off portion to improve the strength of the bottom seal portion of the laminated container in particular, and Patent Document 2 discloses a method in which the pinch-off portion is provided below the pinch-off portion. There is a description of a method of controlling a thickness of a bottom seal portion by providing a compression plate for sandwiching the protruding resin (burr).
[0006]
[Patent Document 1]
JP-A-7-88943 [Patent Document 2]
JP-A-9-262902
[Problems to be solved by the invention]
As described above, a cut line of approximately 1.6 Dp is usually formed on the bottom surface of the bottom of a container which is a direct blow molded product. In a container having a sufficiently large blow ratio, the range of formation of the cut line is determined by the peripheral edge of the bottom surface. It is used for many applications without any problems in appearance, since it is not as good as any part. However, in the blow molding of a container having a low blow ratio, the pinch-off portion is close to or equal to the diameter of the bottom surface at the bottom surface of the mold cavity, so that the parison is crushed into a flat shape in the pinch-off process, and the pinch-off process is performed. The resin forming the parison flows laterally along the main mold split surface located on the left and right from the left and right ends of the part, or the resin forming the parison flows, resulting in the main body split not only on the bottom of the container but also on the side of the trunk just above the bottom Residual resin remains near the line, so-called burrs are formed, and burrs are left on the product container.
[0008]
For example, even in a container having a blow ratio of about 2, the width of the pinch-off portion can be made smaller than the diameter of the bottom surface of the container, but the resin forming the parison by being pinched and crushed by the pinch-off portion causes the pinch-off. It flows from the left and right ends of the part in the horizontal direction along the body dividing surface, and although there is no burr mark near the body dividing line on the side of the body just above the bottom of the molded container, no burr mark remains, Glossy spots or color spots occur due to factors such as stretch spots, orientation spots, and cooling spots due to changes in flow.
[0009]
If the parison needs to be made thicker, the above-mentioned gloss spots or color spots occur even if the blow ratio is close to 3.
[0010]
In the field of cosmetics such as mascara and eyeliner, for example, small containers having a blow ratio of 1.6 or less are often used, and the appearance of the container is an important factor of commercial value. In a container having a small blow ratio as described above, the width of the pinch-off portion that can be taken is at most the diameter of the bottom surface of the bottom of the mold cavity, and is smaller than the flattened width of the parison, 1.6 Dp. Since the parison is crushed not only on the pinch-off portion but also on the main-body division surface near the pinch-off portion, burrs are inevitably generated near the main-body division line on the side surface of the body directly above the bottom.
[0011]
These burr marks, gloss spots, color spots, and the like are a major problem in terms of their merchantability especially in containers for cosmetics and the like, but no effective solution to such a problem has been hitherto shown. Is the current situation. Even if the appearance is improved in the post-treatment process, a long process is required.
[0012]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the conventional technology, and it is a technical problem to suppress the occurrence of burrs in the lateral direction from the left and right ends of the pinch-off portion at the bottom bottom surface in direct blow. An object of the present invention is to create a blow molding die capable of providing a blow molded container having a low blow ratio and excellent appearance without burr marks, gloss spots, and color spots on the side of the container near the bottom.
[0013]
[Means for Solving the Problems]
Among the present invention for solving the above technical problem, the means of the invention according to claim 1 is as follows:
A split mold divided into front and rear, having a main body division surface perpendicular to the mold clamping direction, having a pinch-off portion in which a cutting edge for pinch-off of a parison is arranged on the bottom bottom surface of the mold cavity,
In a flat cross section of the split mold in a closed state, a straight pinch-off line formed by a cutting blade on the bottom surface, a pair of main body dividing lines formed by a main body dividing surface on left and right peripheral portions, and left and right of the pinch-off line Forming one bottom parting line from the end and a pair of connecting lines connecting the left and right ends of the body parting line,
A configuration in which the connection line forms a pinch-off line and a step-like bent portion at a substantially right angle by end division surfaces located at the left and right ends of the pinch-off portion,
It is in.
[0014]
According to the above configuration, a straight pinch-off line is formed at the center of the bottom bottom surface of the mold cavity by a cutting blade disposed at the bottom pinch-off portion of the split mold, and the split edges are formed at the left and right peripheral portions. A pair of body dividing lines are formed by a body dividing surface perpendicular to the mold clamping direction, and a connecting line connects the pinch-off line and the body dividing line, and a bottom dividing line is formed on the bottom surface. Have been.
[0015]
Further, the connecting line is configured such that a step-like bent portion substantially perpendicular to the pinch-off line is formed by end division surfaces located at the left and right ends of the pinch-off portion of the split mold. That is, the conventional mold cavity has a configuration in which a stepped bent portion is inserted between a pinch-off line and a main body dividing line which are formed in a straight line on the bottom surface of the mold cavity.
[0016]
This end part dividing surface is formed on the left and right ends of the pinch-off part substantially perpendicularly to the left-right direction of the cutting blade, and the pinch-off part left and right ends in the process of deforming the cylindrical parison into a flat shape at the pinch-off part Functions as a weir surface that stops the flow of the flattened resin in the horizontal direction due to the pressing of the cutting edge, and the deformation of the parison between the main body division surfaces And block the flow of resin.
[0017]
Due to the above-mentioned stepped bent portion, that is, the effect of the end divided surface, the range of formation of burrs at the time of mold clamping of the blow mold is from the center of the bottom bottom surface of the mold cavity to the stepped bent portion. This makes it possible to provide a container having a very good appearance with a low blow ratio and no burr marks, gloss spots, and color spots, which has been difficult with conventional molds.
[0018]
In addition, the configuration of the mold structure of claim 1 is such that the surface exhibiting a weir-like function against the deformation of the parison or the flow of the resin is formed by the configuration of the divided surface of the portion below the bottom bottom surface of the cavity of the split mold. It is formed by simply changing the method of dividing the part below the bottom of the normal mold cavity, without the need to add other components, movable parts, etc. The same productivity and durability can be exhibited as compared with the metal mold.
[0019]
As a matter of course, the shape of the mold dividing surface is configured so that the forward and backward movement of the split mold, that is, the opening of the mold closing mold is smoothly achieved.
[0020]
According to a second aspect of the present invention, in the first aspect, the step height of the step-shaped bent portion is at least twice the thickness of the parison in blow molding.
[0021]
According to the above configuration, when the blow ratio exceeds approximately 1.6, the cylindrical parison is firstly folded into a flat shape at the pinch-off portion, and its thickness is substantially equal to the thickness of the parison. It is doubled and then cut to be crushed by a cutting blade. For this reason, by setting the step height of the step-up bent portion to at least a height corresponding to this thickness, it is possible to reliably prevent the resin from flowing laterally from the left and right ends of the pinch-off portion due to the pressing force of the cutting blade. can do.
[0022]
When the blow ratio is about 1.6 or less, the width of the pinch-off portion needs to be about 1.6 Dp or less, and it is necessary to restrict the deformation of the parison in the lateral direction. The height can be determined according to conditions such as the shape, blow ratio, parison diameter, and wall thickness of the container.
[0023]
The invention according to claim 3 is the invention according to claim 1 or 2,
In a plane cross section of the split mold in the closed state, the direction of the pinch-off line passing through the center of the bottom bottom surface of the mold cavity is defined as a direction forming a predetermined center angle with the direction of the main body dividing line,
Connecting the left and right ends of the pinch-off line and the left and right ends of the body parting line in a substantially straight line to form a connection line,
Forming a bottom parting line approximately axially symmetric with respect to the center of the bottom surface,
It is in.
[0024]
According to a third aspect of the present invention, the direction in which the pinch-off line is formed is inclined from the direction of the main body dividing line, and the left and right ends of the pinch-off line and the left and right ends of the main body dividing line are positioned stepwise by this inclination. It is configured to be connected in a substantially straight line to form a step-like bent portion. Further, the step height of the step-like bent portion can be adjusted by the angle of the inclination, that is, the center angle.
[0025]
In addition, since the divided surface of the portion below the bottom surface of the mold cavity as a whole can be formed in a simple shape, the width of the pinch-off portion can be formed over substantially the entire width of the bottom surface. The mold can be adapted to a container having a specific ratio, is more excellent in durability, and has a simple flow path for resin that forms burrs, so that there is no residual resin and a mold that is easy to maintain.
[0026]
According to a fourth aspect of the present invention, in the third aspect, the central angle is set to 45 ° or less.
[0027]
The above configuration according to claim 4 determines the upper limit of the center angle. However, if the center angle is too large, that is, if the pinch-off line is too inclined from the direction of the main body dividing line, the surface that is greatly inclined in the pinch-off step of blow molding. In this case, the parison is crushed in a flat shape, and the pinch-off process cannot be achieved smoothly. Therefore, the center angle is preferably set to 45 ° or less.
[0028]
Since the step height of the step-like bent portion is adjusted by the center angle as described above, the lower limit of the center angle is the required step height, the size of the container to be formed, the thickness of the parison, etc. From, it is possible to geometrically determine a guideline value.
[0029]
According to a fifth aspect of the present invention, in the first or second aspect of the present invention, the direction of the pinch-off line passing through the center of the bottom bottom surface of the mold cavity in the plane cross section of the split mold in the closed state is determined. In other words, the step is to form the step-like bent portion substantially symmetrically from the left and right ends of the pinch-off line.
[0030]
According to the above configuration, since the parison is crushed by the pinch-off portion on a plane perpendicular to the mold clamping direction of the split mold, the pinch-off process can be more stably achieved. The step height of the bent portion can be made sufficiently high, and the deformation of the parison in the left-right direction can be reliably restricted.
[0031]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 3 show a split mold 1 according to a first embodiment of the blow molding mold of the present invention. FIG. 1 shows a rear part of a pair of split molds 1 divided into two parts in front and rear. FIG. 2 is an overall perspective view of a split mold 1b, and one front split mold 1a has a substantially axially symmetric shape of a rear split mold 1b. The split mold 1 is for molding a container having a cylindrical body with a blow ratio of 1.8.
[0032]
FIG. 8 shows an example of a conventional split mold. The split mold 1 is entirely divided into two parts by a main body dividing surface 11 perpendicular to the mold clamping direction (the direction of the white arrow in FIG. 8). The pinch-off portion 5 is formed by disposing the cutting blade 6 along the main body dividing surface 11, whereas the split mold 1 according to the first embodiment is formed as shown in FIG. In the following description, the dividing surface is formed of a stepped surface in a portion below the bottom 3 and the bottom 4 of the mold cavity 2, and the direction in which the cutting blade 6 is disposed is inclined at a certain angle from the main body dividing surface 11, and is pinched off. The part 5 is formed.
[0033]
At the left and right ends of the pinch-off portion 5, end division surfaces 12 are formed and arranged substantially perpendicular to the left and right direction of the cutting blade 6, and at the left end, the end division surfaces 12 are recessed from the main body division surface 11, At the right end, it is formed to protrude from the main body division surface 11.
[0034]
Further, in the first embodiment, a part of the mold below the bottom 3 and the bottom 4 of the mold cavity 2 is formed as a separate and substantially semi-cylindrical bottom block 7 and fitted and assembled. By making such a combination, the manufacture of the split mold becomes easy, gas can be released during blow molding along the combined surface, and the pinch-off portion including the cutting blade 6 can be formed by changing the material of the metal. There is an advantage that the wear resistance near 5 can be improved.
[0035]
Referring to FIG. 2, the details of the division of the mold in a plane cross section in the closed state of the split mold 1 will be described. A pair of straight pinch-off lines 14 formed by abutment of the cutting blades 6 and a main body dividing surface 11 formed on the left and right peripheral portions of the bottom surface 4 are formed on the bottom surface 4 of the bottom portion 3 of the mold cavity 2. From the main body dividing line 13 and a pair of connecting lines 16 connecting the left and right ends of the pinch-off line 14 and the left and right ends of the main body dividing line 13, one bottom dividing line 17 is axially symmetric with respect to the center of the bottom surface 4. Is formed.
[0036]
In the present embodiment, the connection line 16 is formed along the arc of the circular fitting line 18 formed near the periphery of the bottom surface 4 by the fitting combination surface of the bottom block body 7 described above. On the bottom surface of the connecting line 16 to make the mark of the connecting line 16 formed inconspicuous.
[0037]
The pinch-off line 14 passes through the center of the circular bottom 3 and the bottom surface 4 and is formed in a direction inclined at a predetermined center angle α from the direction of the main body dividing line 13. The connecting line 16 is formed from the end divided surfaces 12 located at the left and right ends of the pinch-off portion 5, and forms a substantially right-angled step-shaped bent portion 15 at the left and right ends of the pinch-off line 14.
[0038]
FIG. 3 is an explanatory view showing a pinch-off step by the split mold 1 of the present embodiment in a plan sectional view. The parison P is pinched by the pinch-off portion 5 provided with the cutting blade 6 in accordance with the progress of the mold clamping and crushed flat, but the step-like bent portion 15 formed at the left and right ends of the pinch-off line 14 is a pinch-off. Since the end divided surfaces 12 formed at the left and right ends of the portion 5 function as weirs, it is possible to prevent the flow of the flattened resin to the main body divided surface 11 in the left and right directions due to the pressing of the cutting blade 6. it can.
[0039]
As can be seen from FIGS. 2 and 3, the direction of the cutting blade 6 is perpendicular to the mold clamping direction of the split mold 1 (the direction of the white arrow in FIG. 3A). The center angle α is deviated from the direction described above, but if α is in the range up to 45 °, the pinch-off step is smoothly achieved.
[0040]
Further, by setting the step height h of the step-shaped bent portion 15 formed from the end part dividing surface 12 to at least twice the thickness of the parison P, the flow of the resin to the main body dividing surface 11 in the lateral direction is ensured. Can be blocked. (See FIG. 3B)
[0041]
As described above, FIG. 8 shows an example of a conventional split mold for forming a container having a cylindrical body with a blow ratio of 1.8 as in the split mold of the first embodiment. It is. As described above, in the conventional split mold 1, the whole is divided into two by the main body dividing surface 11 perpendicular to the mold clamping direction (the direction of the white arrow in FIG. 8), and along the main body dividing surface 11. The cutting blade 6 is provided to form the pinch-off portion 5.
[0042]
FIG. 9 is an explanatory view showing a pinch-off process by the split mold 1 of FIG. In the mold closed state (see FIG. 9C), the pinch-off line 14 and the main body dividing line 13 are formed in a straight line, so that the resin crushed in the pinch-off process also flows in the left-right direction and the main body is divided. In particular, in the case of a container having a low blow ratio, burr marks remain near the position of the main body division line mark on the side of the body directly above the bottom, and even if the burr marks are not reached, gloss or color spots may occur. Occurs.
[0043]
4 to 7 show a split mold 1 according to a second embodiment of the blow mold of the present invention. FIGS. 4 and 5 are overall perspective views of a rear mold half 1b and a front mold half 1a of a pair of split molds 1 divided into two in the front and rear directions, respectively. This is for molding a container having
[0044]
Also in this embodiment, the dividing surface is formed by a step-shaped bent surface in a portion below the bottom 3 and the bottom 4 of the mold cavity 2, but the disposing direction of the cutting blade 6 is changed to the conventional split mold. Similarly, the pinch-off portion 5 is formed as a direction along the main body division surface 11.
[0045]
In addition, an end division surface 12 is formed at the left and right ends of the pinch-off portion 5 so as to be substantially perpendicular to the left-right direction of the cutting blade 6, and the left and right ends of the pinch-off portion 5 are arranged as shown in FIGS. In the rear split mold 1b, an ear-shaped concave portion 8b is formed from the main body split surface, and the front split mold 1a is formed with a projection 8a. The mold clamping of the split mold 1 is achieved while fitting into the recess 8b.
[0046]
Also in the present embodiment, a part of the mold below the bottom 3 and bottom 4 of the mold cavity 2 is formed by separate block bodies 7a and 7b and fitted and assembled.
[0047]
Referring to FIG. 6, the details of the division of the split mold 1 in a closed plane in the closed state will be described. The bottom 3 of the mold cavity 2 is formed with a pinch-off line 14, a pair of main body parting lines 13, and a fitting surface of the protrusion 8a and the concave part 8b. A bottom dividing line 17 is formed so as to be symmetrical with the pair of ear-shaped connecting lines 16 connecting the left and right ends of the bottom.
[0048]
The pinch-off line 14 is in the same direction as the main body dividing line 13, and the connecting line 16 is substantially perpendicular to the left and right ends of the pinch-off line 14 and forms a step-shaped bent portion 15 having a step height h. The width of the pinch-off portion 5, that is, the length in the left-right direction of the pinch-off line 14 is approximately 1.2 Dp (Dp indicates the outer diameter of the parison P), and is shorter than the width 1.6 Dp obtained by flattening the parison.
[0049]
FIG. 7 is an explanatory view showing a pinch-off process by the split mold 1 of the second embodiment. The cylindrical parison P is flattened and deformed into an elliptical shape. When the parison P reaches a certain flat state, as shown in FIG. The end divided surface 12 which forms a part of the protruding portion 8a in the shape of a triangle serves as a weir surface, preventing further lateral deformation, and thereafter the left and right end divided surfaces. The parison P is crushed within the range of the width 12 and the excess resin is forced to flow below the cutting blade 6.
[0050]
In the split mold 1 of the second embodiment, since the parison P is crushed by the pinch-off portion 5 on a plane perpendicular to the mold clamping direction, the pinch-off process can be more stably achieved.
[0051]
In the description of the split molds of the first embodiment and the second embodiment, molding of a container having a blow ratio of 1.8 or 2 has been described. However, as described above, the width of the pinch-off portion 5 is approximately 1.6 Dp. Even in a narrower case, if the step height h of the step-like bent portion 15 is made sufficiently high, the deformation of the cylindrical parison P can be restricted to the range of the width of the pinch-off portion 5. The molding die can sufficiently cope with the molding of a container having a blow ratio of about 1.6 or less. The blow ratio ranges from about 1 to 3 and the burr formation range in blow molding is reduced to the mold cavity bottom. The range can be up to the step-shaped bent portion on the bottom surface, and a container having an extremely good appearance without burr marks, gloss spots, and color spots on the side of the body can be provided.
[0052]
【The invention's effect】
The present invention has the above-described configuration, and has the following effects.
According to the first aspect of the present invention, the end divided surfaces located at the left and right ends of the pinch-off portion restrict the deformation of the parison in the horizontal direction, and prevent the resin from flowing in the horizontal direction from the left and right ends of the pinch-off portion. It is possible to provide a container which functions as a weir surface for stopping and has extremely excellent appearance without burr marks, gloss spots, and color spots on the side face at a bottom blow ratio, which was difficult with a conventional mold.
[0053]
Even for a container having a blow ratio of about 1.6 or less, the range in which burrs are formed can be the range of the bottom surface.
[0054]
In addition, since the surface that exhibits the function of the weir surface is formed by the configuration of the mold dividing surface, it is not necessary to add other components, movable parts, and the like. As a result, the same productivity and durability can be exhibited.
[0055]
According to the second aspect of the present invention, by setting the step height of the step-bent portion to at least twice the thickness of the parison in blow molding, particularly in the case of a container having a blow ratio of more than about 1.6. In addition, it is possible to reliably prevent the resin from entering the main body dividing surface from the left and right ends of the pinch-off portion.
[0056]
According to the third aspect of the present invention, since the division surface is formed in a simple shape, the width of the pinch-off portion can be formed over substantially the entire width of the bottom surface, which corresponds to a container having a lower blow ratio. It is possible to provide a mold which is excellent in durability, has no residual resin, and is easy to maintain.
[0057]
According to the fourth aspect of the present invention, the pinch-off step can be smoothly performed by setting the angle between the body dividing line and the pinch-off line to 45 ° or less.
[0058]
In the invention according to claim 5, since the parison is crushed by the pinch-off portion on a plane perpendicular to the mold clamping direction of the split mold, the pinch-off process can be more stably achieved. Further, since the step height can be made sufficiently high, in particular, the deformation of the parison can be more reliably restricted.
[Brief description of the drawings]
FIG. 1 is an overall perspective view showing a rear split mold of a split mold according to a first embodiment of the present invention.
FIG. 2 is a plan cross-sectional view of the split mold according to the first embodiment of the present invention, taken along the line AA in FIG. 1, in a mold closed state;
FIG. 3 is an explanatory view showing a pinch-off step using a split mold according to the first embodiment of the present invention in a plan sectional view similar to FIG. 2;
FIG. 4 is an overall perspective view showing a rear split mold of a split mold according to a second embodiment of the present invention.
FIG. 5 is an overall perspective view showing a front split mold of a split mold according to a second embodiment of the present invention.
FIG. 6 is a plan sectional view taken along the line BB in FIG. 4 in a mold closed state of the split mold according to the second embodiment of the present invention.
FIG. 7 is an explanatory view showing a pinch-off step using a split mold according to a second embodiment of the present invention in a plan sectional view similar to FIG. 6;
FIG. 8 is an overall perspective view showing a rear split mold of an example of a conventional split mold.
FIG. 9 is an explanatory view showing a pinch-off step using the split mold of FIG. 8 in the same manner as FIG. 3;
FIG. 10 is an explanatory view showing a mold clamping step of blow molding.
[Explanation of symbols]
1; split mold 1a; front split mold 1b; rear split mold 2; mold cavity 3; bottom 4; bottom 5; pinch-off section 6; cutting blade 7; bottom block 7a; bottom block 7b; Bottom block body 8a; Protrusion 8b; Recess 11; Main body division surface 12; End division surface 13; Main body division line 14; Pinch-off line 15; Step-like bent portion 16; Connection line 17; Bottom division line 18; 21; extruder 22; parison cutter P; parison α; center angle h;

Claims (5)

It has a main body division surface (11) perpendicular to the mold clamping direction, and a cutting blade (6) for pinching off a parison (P) is disposed on the bottom portion (3) and the bottom surface (4) of the mold cavity (2). A split mold (1) having a pinch-off portion (5), which is divided into front and rear, and has a flat cross section in a closed state of the split mold (1), and the cutting blade (6) is provided on the bottom surface (4). ), A pair of main body dividing lines (13) formed by the main body dividing surface (11) on the left and right peripheral portions, and left and right ends of the pinch off line (14). One bottom dividing line (17) is formed from a pair of connecting lines (16) connecting the left and right ends of the main body dividing line (13), respectively, and the connecting line (16) is formed of a pinch-off portion (5). The pinch-off line (14) is formed by the end division surfaces (12) located at the left and right ends. Configuration and then blow mold the forming stepped bent portion of the substantially right angle (15). The blow molding die according to claim 1, wherein the step height (h) of the step-shaped bent portion (15) is at least twice the thickness of the parison (P) in blow molding. In the plane cross section of the split mold (1) in the closed state, the direction of the pinch-off line (14) passing through the center of the bottom (3) and the bottom (4) of the mold cavity (2) is changed to the direction of the main body dividing line (13). The left and right ends of the pinch-off line (14) and the left and right ends of the body parting line (13) are connected in a substantially straight line to form a connection line (16). The blow molding die according to claim 1 or 2, wherein the bottom parting line (17) is formed substantially axially symmetrically with respect to the center of (4). 4. The blow molding die according to claim 3, wherein the central angle (α) is 45 ° or less. In the plane cross section of the split mold (1) in the closed state, the direction of the pinch-off line (14) passing through the center of the bottom (3) and the bottom (4) of the mold cavity (2) is changed to the direction of the main body dividing line (13). The blow mold according to claim 1 or 2, wherein the step-shaped bent portion (15) is formed in the same direction as the left and right ends of the pinch-off line (14) so as to be substantially symmetrical.

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