JP3636247B2 - Blow molding machine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a blow molding machine that molds a plastic product such as a bottle by direct blow molding, and more particularly to a blow molding machine that can accurately mold the inner surface and top surface of a mouth of a hollow container.
[0002]
[Prior art and problems to be solved by the invention]
As shown in FIG. 5, blow molding is performed by sandwiching a cylindrical molten resin 101 called a parison from a extruder and sandwiching it between molds 102 and 103, and then using a blow pin 104 to cool compressed gas for parison. The desired hollow container finished product is obtained by blowing into the inside and inflating the parison to give a mold cavity shape, cooling, and then exhausting the compressed gas for cooling.
[0003]
As described above, in blow molding, a hollow container is formed by blowing a compressed compressed gas into the parison from the tip of the blow pin 104 to give a mold cavity shape. The tip shape is transferred and formed.
[0004]
When finishing the mouth portion of the hollow container with the tip shape of the blow pin 104, the finish accuracy of the mouth portion varies greatly depending on molding conditions such as the driving speed and blowing timing of the blow pin 104. Therefore, until now, many have relied on the experience and experience of skilled workers and lacked reproducibility.
[0005]
The main cause is that the transferability becomes poor because the portion of the molten resin 101a corresponding to the mouth portion is small. In particular, since polyethylene resin (PE resin) is a resin that easily traps gas (air), as shown in FIG. 5, as shown in FIG. 5, air A accumulates between the molds 102, 103 and the blow pin 104 corresponding to the mouth portion, The amount of the molten resin 101a in the portion is reduced. For this reason, sink marks, scallops, or chips are likely to occur on the top surface of the mouth or the inner surface of the mouth that is regulated by the lower end surface of the cut ring 106 that contacts the strikers 104, 105 provided on the upper end surfaces of the molds 102, 103. .
[0006]
Accordingly, an object of the present invention is to provide a blow molding machine capable of accurately molding the mouth top surface and the mouth inner surface of a hollow container.
[0007]
[Means for Solving the Problems]
According to the first aspect of the present invention, the tip of the blow pin is inserted into the mold provided with the striker, and the cut ring provided on the blow pin is brought into contact with the striker to cut the parison supplied into the mold. In the blow molding machine which regulates the top of the mouth of the hollow container formed by the parison, blows gas from the tip of the blow pin, and inflates the parison to form the hollow container having the mouth The striker at a portion facing the cut ring has a straight portion provided in parallel to the outer peripheral surface of the cut ring and provided at a predetermined interval from the outer peripheral surface of the cut ring. The above object is achieved by providing a blow molding machine.
[0008]
The invention according to claim 2 is the blow molding according to claim 1, wherein the length of the straight portion is 3 mm to 10 mm, and the interval is 1/3 to 2/3 of the thickness of the parison. By providing a machine, the above object has been achieved.
[0009]
The invention according to claim 3 is characterized in that the surface roughness of the outer peripheral surface of each of the tip of the blow pin and the cut ring facing the mold is 10 μm to 50 μm at the maximum height Rmax. The above object is achieved by providing the blow molding machine described.
[0010]
According to a fourth aspect of the present invention, in the blow molding machine according to the first aspect, the straight portion of the blow pin corresponding to the portion that becomes the mouth of the hollow container has a length of 3 mm to 15 mm. By providing this, the above-mentioned object is achieved.
[0011]
The invention according to claim 5 is characterized in that a gap is provided between the cut ring and the blow pin on the lower end surface side of the cut ring that regulates the top surface of the mouth of the hollow container. The above object is achieved by providing a blow molding machine.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the blow molding machine of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a cross-sectional view of an extruder for forming a parison, FIG. 2 is a cross-sectional view sequentially showing a process of forming a hollow container having a mouth portion at the top, and FIG. 3 is an enlarged cross-sectional view of a main part of the blow molding machine of this embodiment. It is.
[0013]
Before describing the blow molding machine of the present embodiment, a blow molding method will be briefly described.
In order to form a hollow container having a mouth portion at the top, first, as shown in FIG. 1, the thermoplastic resin 1 is plasticized by an extruder 2 and extruded into a tube shape to form a parison 3.
[0014]
Then, as shown in FIGS. 2 (a) and 2 (b), the parison 3 is added to the molds 4 and 5 which are divided into two before being cooled and solidified, and the upper end and the lower end thereof are connected to the mold 1 as described above. , 2 bite by the bite cutting blade. In addition, the upper part of the parison 3 is cut at a position indicated by a one-dot chain line.
[0015]
Then, as shown in FIG. 2 (c), the tip of the blow pin 6 is inserted into the closed molds 4 and 5, gas is blown from the tip of the blow pin 6, and the parison 3 is inflated to form a mold cavity shape. Is granted.
[0016]
Thereafter, the cooling compressed gas inside the hollow container 7 is exhausted from the tip of the blow pin 6. When evacuation is completed, as shown in FIG. 2D, the molds 4 and 5 are opened, and the finished product 9 of the hollow container 7 having the opening 8 at the upper portion is taken out. Blow molding is completed through the above steps.
[0017]
Next, the blow molding machine of this embodiment will be described. As shown in FIG. 3, the blow molding machine of this embodiment inserts the tip of the blow pin 6 into the molds 4 and 5 provided with the strikers 10 and 11 on the upper end surfaces 4 a and 5 a, The cut ring 12 is brought into contact with the strikers 10 and 11 and the parison 3 supplied into the molds 4 and 5 is cut, whereby the top surface of the mouth of the hollow container 7 formed by the parison 3 is removed. The gas is blown from the tip of the blow pin 6 and the parison 3 is inflated to form a hollow container 7 having a mouth at the top.
[0018]
Furthermore, the blow molding machine of this embodiment will be described in detail. The cut ring 12 abuts against the strikers 10 and 11 and cuts the parison 3 supplied into the molds 4 and 5, thereby opening the mouth top surface 8 a of the hollow container 7 formed by the parison 3. 2 (see FIG. 2 (d)), and is provided around the outer periphery of the blow pin 6 as an annular ring having a rectangular cross section.
[0019]
A gap portion 13 is provided between the cut ring 12 and the blow pin 6 on the lower end surface 12 a side of the cut ring 12 that regulates the mouth top surface 8 a of the hollow container 7. In other words, the gap 13 is provided at the lower edge portion of the cut ring 12 on the inner peripheral surface 12c side. The gap 13 is formed as an annular groove in the blow pin 6.
[0020]
Air that exists between the parison (hereinafter referred to as the mouth parison 3 a) and the blow pin 6 that becomes the mouth 8 of the hollow container 7 enters the gap 13. There is a gap of several tens of microns between the lower end surface 12a of the cut ring 12 and the blow pin 6 due to the surface roughness when these parts are processed, and air enters the gap portion 13 from the gap. In this way, air existing between the mouth parison 3a and the blow pin 6 can be trapped in the gap portion 13, so that the sink top, the emboss or the chip of the mouth top surface 8a and the mouth inner surface 8b of the hollow container 7 can be obtained. Can be eliminated.
[0021]
The strikers 10 and 11 are provided on the upper end surfaces 4a and 5a of the respective dies 4 and 5 divided into two. The strikers 10 and 11 in the portion facing the cut ring 12 are provided with straight portions 10a and 11a provided in parallel with the cut ring outer peripheral surface 12b and spaced apart from the cut ring outer peripheral surface 12b by a predetermined interval W. Have.
[0022]
By providing the straight portions 10a and 11a having the shapes described above on the strikers 10 and 11, a parison (hereinafter referred to as an upper burrison 3b) that becomes an upper burr when the blow pin 6 is inserted into the molds 4 and 5, The straight portions 10 a and 11 a and the cut ring 12 are compressed and pushed into a portion that becomes the mouth portion 8 of the hollow container 7. Therefore, a large amount of thermoplastic resin (mouth parison 3 a) is supplied between the molds 4, 5 and the blow pin 6 which are portions corresponding to the mouth 8 of the hollow container 7.
[0023]
As a result, the mold shape corresponding to the mouth portion 8 of the hollow container 7 and the transferability of the tip shape of the blow pin are improved, and the accuracy of the mouth top surface 8a and the mouth inner surface 8b of the hollow container 7 is improved. Or Ekbo or chipping disappears.
[0024]
The length L ₁ and the interval W of the straight portions 10 a and 11 a are preferably as follows so that the upper Baliparison 3 b can be supplied to the portion that becomes the mouth portion 8 of the hollow container 7. The lengths L ₁ of the straight portions 10 a and 11 a are preferably 3 mm to 10 mm, and the interval W is preferably 1/3 to 2/3 of the thickness of the parison 3.
[0025]
When the length L ₁ is more than 10 mm and the interval W is less than 1/3 of the thickness of the parison 3, the upper bali parison 3b enters the inside of the mouth too much, and the parison 3 is easily sagged, and the length L ₁ is When the distance W is less than 3 mm and the interval W is more than 2/3 of the thickness of the parison 3, the amount of resin in the portion that becomes the mouth portion 8 is reduced and transferability is poor, and the mouth top surface 8a and the mouth of the hollow container 7 are poor. The accuracy of the inner surface 8b is deteriorated.
[0026]
The tip of the blow pin 6 facing the molds 4 and 5 and the outer peripheral surfaces 6a and 12b of the cut ring 12 improve the dispersibility of the air existing between the mouth parison 3a and the blow pin 6. In order to improve the transferability of the resin, the surface roughness is 10 μm to 50 μm at the maximum height Rmax.
[0027]
When the surface roughness of the tip of the blow pin 6 and the outer peripheral surfaces 6a and 12b of the cut ring 12 is more than 50 μm at the maximum height Rmax, the surface roughness inside the mouth is deteriorated, leading to the occurrence of liquid leakage, When the thickness is less than 10 μm, air dispersibility is deteriorated, and sink marks and embles are easily generated.
[0028]
The surface roughness within the above range is roughened by, for example, sandblasting (about # 60). As described above, by roughening the tip of the blow pin 6 and the outer peripheral surfaces 6a and 12b of the cut ring 12, an air vent is formed, so that the air dispersibility is improved and the resin transfer property is improved.
[0029]
In addition, the straight portion of the blow pin 6 corresponding to the portion that becomes the mouth portion 8 of the hollow container 7 is to reduce the drag of the parison 3 when the blow pin 6 is inserted into the molds 4 and 5. the length L ₂ is a 3Mm～15mm.
[0030]
When the length L ₂ is a 15mm greater, too upper Bariparison 3b is Hikizurikomi the mouth portion, it parison 3 tends inclusive sag is less than 3 mm, will compromise the liquid sealing function, leading to the leak detected.
[0031]
According to the blow molding machine configured as described above, the upper variparison 3b can be compressed and sufficiently supplied to the portion that becomes the mouth 8 of the hollow container 7, and the air dispersibility can also be improved. Therefore, the transferability at the mouth portion 8 of the hollow container 7 becomes good, the accuracy of the mouth top surface 8a and the mouth inner surface 8b can be improved, and sink marks and eruptions can be eliminated. Therefore, according to the blow molding machine of this embodiment, the mouth top surface and the mouth inner surface of the hollow container can be molded cleanly and accurately.
[0032]
Further, according to the blow molding machine of the present embodiment, it is only necessary to change the shape of each of the conventional striker, cut ring, and blow pin, so the number of parts is the same as the conventional one and the cost is low. .
[0033]
The blow molding machine of the present embodiment is not limited to the above-described embodiment, and can be variously modified without departing from the gist of the present invention. For example, in the above-described embodiment, the strikers 10 and 11 are integrally formed. However, as shown in FIG. 4, the strikers 10 and 11 may be divided into two upper and lower parts 10b and 10c and 11b and 11c. Good.
[0034]
【The invention's effect】
As is clear from the above description, according to the present invention, it is possible to provide a blow molding machine capable of accurately molding the mouth top surface and the mouth inner surface of the hollow container.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of an extruder for forming a parison.
FIGS. 2A and 2B are cross-sectional views sequentially showing a process of forming a hollow container having a mouth portion at the top.
FIG. 3 is an enlarged cross-sectional view of a main part of a blow molding machine.
FIG. 4 is an enlarged cross-sectional view of a main part showing another example of a blow molding machine that divides a striker into two parts.
FIG. 5 is an enlarged cross-sectional view of a main part of a conventional blow molding machine.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Thermoplastic resin 3 Parison 4, 5 Mold 6 Blow pin 7 Hollow container 8 Mouth part 10, 11 Striker 12 Cut ring 13 Crevice part

Claims (5)

Formed by the parison by inserting the tip of the blow pin into the mold provided with the striker and cutting the parison supplied into the mold by bringing the cut ring provided on the blow pin into contact with the striker In the blow molding machine that regulates the top surface of the mouth of the hollow container to be blown, blows gas from the tip of the blow pin, and inflates the parison to form the hollow container having the mouth, the portion facing the cut ring The striker according to claim 1 has a straight portion provided in parallel with the outer peripheral surface of the cut ring and provided with a predetermined distance from the outer peripheral surface of the cut ring.   2. The blow molding machine according to claim 1, wherein the length of the straight portion is 3 mm to 10 mm, and the interval is 1/3 to 2/3 of the thickness of the parison.   2. The blow molding machine according to claim 1, wherein a surface roughness of each of the outer peripheral surfaces of the blow pin tip and the cut ring facing the mold is 10 μm to 50 μm at a maximum height Rmax.   The blow molding machine according to claim 1, wherein a length of the straight portion of the blow pin corresponding to a portion to be a mouth portion of the hollow container is 3 mm to 15 mm.   The blow molding machine according to claim 1, wherein a gap is provided between the cut ring and the blow pin on the lower end surface side of the cut ring that regulates the top surface of the mouth of the hollow container.

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