JP3657937B2 - Method and apparatus for forming bottomed parison for hollow molding - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a bottomed parison molding method and apparatus for hollow molding a molded product.
[0002]
[Prior art and problems]
Conventionally, a molded product made of a synthetic resin is molded by hollow molding. The molded article generally consists of a container, and has a mouth portion to which a lid is attached and a bottomed container body. Such a molded product is molded by direct blow. That is, the molten resin is extruded by a crosshead of a hollow molding machine to form a cylindrical parison, the lower end of the parison is sandwiched by a pinch device and closed, and then a parison of a predetermined length is made of gold. It is formed in the mold by being guided and expanded.
[0003]
The pinch part at the lower end of the parison is pushed out from the hollow molding machine while supplying support air to the inside, and when a parison of a predetermined length is pushed out, it is pinched by the pinch blade of the pinch device. By cutting, the seal is formed. By forming the pinch portion, a bottomed parison for hollow molding is formed. By making the parison bottomed in advance and blowing the air into the bottomed parison and inflating it uniformly, the thickness of the molded product can be made uniform.
[0004]
However, in the molding method of the bottomed parison for hollow molding such a conventional molded product, the parison pinch portion is formed by crushing the lower end portion of the parison, so as shown in FIG. In the vicinity of the pinch portion 61, the cylindrical parison 60 is crushed to form a flat, divergent shape. Accordingly, the pinch width L becomes longer.
[0005]
When the parison 60 having the pinch portion 61 in this state is subjected to molding by a normal mold, in order to prevent a large amount of burrs from being generated in the molded product, the pinch portion 61 is avoided from the bite portion of the mold. It is necessary to close the mold. For this reason, the amount of lower burrs is inevitably increased, and the production efficiency is lowered.
[0006]
In addition, when the parison 60 having the pinch part 61 is received in a mold having no bite part and so-called burr-free molding is performed, the pinch part 61 for sealing the parison 60 remains thick to form a molded product. The remainder will generate a large volume of meat in the bottom of the molded product. When the meat pool is small, the strength of the molded product is lowered.
[0007]
[Means for Solving the Problems]
The present invention has been made in view of such a conventional technical problem, and its configuration is as follows.
According to the first aspect of the present invention, a cylindrical parison 2 is extruded from a hollow molding machine 1, the lower end portion of the parison 2 is closed to form a pinch-off portion 2a, and the parison 2 is blown and molded. A method of forming a bottomed parison that is hollow-molded into a molded product 10, wherein the pinch-off portion 2 a extends the parison 2 extruded from the hollow molding machine 1 to form a small-diameter portion 2 b that is reduced in diameter, and then the small-diameter portion It is a method for forming a bottomed parison for hollow molding, characterized in that it is formed by cutting and adhering 2b.
According to a second aspect of the present invention, there is provided a parison molding method for hollow molding according to the first aspect, wherein the small-diameter portion 2b is sandwiched and adhered by a pinch device 3.
According to a third aspect of the present invention, there is provided the method of forming a hollow parison according to claim 1 or 2, wherein the small diameter portion 2b is cut by stretching the parison 2.
According to a fourth aspect of the present invention, a cylindrical parison 2 is extruded from the hollow molding machine 1, the lower end portion of the parison 2 is closed to form a pinch-off portion 2a, and the parison 2 is blown and molded. A bottomed parison molding device for hollow molding into a molded product 10, a tension device 4 that stretches the parison 2 extruded from the hollow molding machine 1 to form a reduced diameter portion 2 b, and sandwiches the small diameter portion 2 b A pinch device 3 that is attached and brought into intimate contact, and the pinch-off portion 2a is pinched and sealed by the pinch device 3 sandwiching and contacting the cut small diameter portion 2b. This is a molding apparatus for a bottomed parison for molding.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 5 show an embodiment of the present invention. In FIG. 5, the code | symbol 1 shows the crosshead of a hollow molding machine, and the air blowing apparatus 25 which has the blowing nozzle 26 is attached to the side of the crosshead 1 (right side on a figure). The crosshead 1 is connected to an extruder (not shown) and can continuously supply a molten material. An air flow path (not shown) is provided at the center of the crosshead 1, and air from an air source outside the figure can be blown into the parison 2 from the tip of the air flow path. Thus, the molten material from the extruder is continuously extruded from the nozzle of the crosshead 1 in a cylindrical shape, and the parison 2 is formed.
[0009]
Below the cross head 1 and the blowing nozzle 26, a mold clamping device 30 to which the mold 24 and the pinch device 3 are attached is arranged. The mold 24 and the mold clamping device 30 are placed on the mold moving device 29 and driven to reciprocate left and right together, and a parison receiving position A below the crosshead 1 and a blowing position B below the blowing nozzle 26. Move between. The mold clamping device 30 has a known structure that opens and closes a pair of molds 24.
[0010]
Further, a molded product holding device 31 is provided on the side (right side in the drawing) of the mold 24 and the mold clamping device 30. The molded product holding device 31 is reciprocated to the left and right in conjunction with the reciprocating movement of the mold 24 and the mold clamping device 30, holds the molded product at the blowing position B below the blowing nozzle 26, and moves to the take-out position C. .
[0011]
Below the crosshead 1, a tensioning device 4 for forming a small-diameter portion 2b (shown in the second and third steps in FIG. 1) in which the parison 2 is stretched and contracted is provided. The tension device 4 is lifted and lowered by the lifting device 12 so as not to interfere with the mold 24, the pinch device 3, and the mold clamping device 30 that move to the left and right.
[0012]
The tensioning device 4 has a clamp portion that is provided at the upper end of the lifting device 12 and is opened and closed by a driving device (not shown). The tension device 4 has a function of extending the parison 2 hanging from the crosshead 1 to form the small diameter portion 2b, and further extending the parison 2 to cut the small diameter portion 2b.
[0013]
The pinch device 3 may be a well-known device that is installed on a mold mounting plate of the mold clamping device 30 and that opens and closes pinch blades arranged opposite to each other, and can be attached with a burr tension device. The burr tension device has a pair of deburring claws that are driven to open and close, and the lower burr 2c (shown in the fourth step in FIG. 1) of the parison 2 removed by the deburring claws is dropped and collected. To do.
[0014]
As shown in FIG. 4, the portion of the parison 2 pressed and compressed by the pinch device 3 forms a pinch-off portion 2 a that is tightly bonded and sealed in a state where the thickness is reduced. The pinch width l by the pinch device 3 is pinched by the cut small-diameter portion 2b, and thus becomes smaller than the diameter of the parison 2.
[0015]
Next, a method for forming a bottomed parison by the hollow molding machine will be described.
As shown in the first step (parison discharge) in FIG. 1, the molten material from the extruder is continuously extruded from the nozzle of the crosshead 1 in a cylindrical shape, and the parison 2 begins to be formed. This first step is not different from the operation of the conventional example. After the start of the discharge of the parison 2, the support air from the air flow path is continuously supplied in a small amount toward the inside of the parison 2, and the parison 2 is held in a cylindrical shape.
[0016]
If the parison 2 is properly discharged, the lower end of the parison 2 is lifted by the pulling device 4 driven up by the lifting device 12, as shown in the second step (parison pulling / tearing) in FIG. After gripping the part, the pulling device 4 is lowered at a predetermined speed by the lifting device 12. When the pulling device 4 is lowered, the parison 2 is stretched to form a small diameter portion 2 b that is locally reduced in diameter with the crosshead 1. Further, by extending the parison 2, the parison 2 is cut at the small diameter portion 2b while reducing the diameter. The tension device 4 is preferably one that grips the entire width of the crushed parison 2. In that case, the clamp part of the tension | pulling apparatus 4 has the length which hold | grips the full width of the pinch width L in the prior art example shown in FIG.
[0017]
Since the cylindrical parison 2 made of a molten resin has appropriate elasticity, it is elastically extended by lowering the tension device 4 at a speed higher than the extrusion speed from the crosshead 1, A small diameter portion 2b having a sufficiently reduced diameter is formed. The descending speed of the tension device 4 is increased after the reduced-diameter portion 2b starts to be formed, so that the time from the gripping of the parison 2 by the tension device 4 to the formation and cutting of the small-diameter portion 2b can be shortened.
[0018]
When the parison 2 is cut at the small diameter portion 2b, the parison 2 on the crosshead 1 side is elastically restored and deformed as shown in the third step (parison contraction) in FIG. Thin parts are eliminated. Such restoration deformation is remarkable when the material of the parison 2 is HDPE (High Density Polyethylene) or the like. At the same time, as shown in the fourth step (parison pinch) in FIG. 1, the pair of pinch blades of the pinch device 3 sandwiches the cut small diameter portion 2b of the parison 2 and closes it as a pinch-off portion 2a. When the lower burr 2c is generated by pinching with the pinch blade of the pinch device 3, the lower burr 2c is removed by the burr tension device. In addition, since the parison 2 is torn off in the second step, it is not usually necessary to generate the lower burr 2c. The operation itself after the fourth step is not substantially different from the conventional example. The point which adds the 2nd process (parison tension and tearing) and the 3rd process (parison contraction) is different from a conventional example.
[0019]
The pinch-off portion 2a is pinched and sealed by cutting and closely contacting the small diameter portion 2b. In this way, the pinch-off portion 2a is formed after the parison 2 is pulled by the tension device 4 and the reduced-diameter portion 2b is torn, so that the pinch-off portion 2a is larger than the diameter of the parison 2 itself as shown in FIG. Since it is thin and thin, the pinch width l of the pinch-off portion 2a is small, and particularly smaller than the diameter of the parison 2. For this reason, the pinch allowance by the pinch device 3 is reduced, and the strength of the pinch-off portion 2a can be appropriately secured by a small pinch force, and a bottomed parison with almost no meat accumulation can be formed.
[0020]
Next, the pinch blade of the pinch device 3 is opened and moved together with the mold clamping device 30 (fifth step (bottom parison) in FIG. 2), and subsequently, as shown in the sixth step (mold closing) in FIG. The mold 24 in the mold open state moves toward the lower side of the crosshead 1 (parison receiving position A).
[0021]
If the bottomed parison 2 is received between the molds 24 in the mold open state, when the parison 2 having a length necessary to form the molded article 10 composed of the container is pushed out from the crosshead 1, the mold The mold 24 is clamped by the mold clamping device 30, and the upper part 2 d of the parison 2 is clamped in an annular shape by the upper end opening 24 a of the mold mating surface of the mold 24. When the upper portion 2 d is tightened by the upper end opening 24 a of the mold 24, the parison 2 is held by the upper end opening 24 a of the mold 24. The pinch-off part 2a at the tip of the parison 2 can also be pinched by the lower part of the die mating surface of the mold 24.
[0022]
Almost simultaneously with closing the mold 24, a large amount of air is supplied from the air flow path of the crosshead 1 into the parison 2 in a short time. As a result, a relatively soft portion of the upper end portion of the parison 2 (above the upper portion 2d fastened by the upper end opening 24a of the mold 24) swells, and a large-diameter portion 2e is formed in the parison 2. The large-diameter portion 2e serves as a location where the parison 2 is cut and separated from the cross head 1 and a location where a blow nozzle 26 described later is driven. The parison 2 in this state is shown in the seventh step (blow) of FIG.
[0023]
Next, the mold 24 holding the bottomed parison 2 cut to a predetermined length is moved below the air blowing device 25 (blowing position B) as shown in the seventh step of FIG. . In parallel with moving the mold 24 holding the parison 2 to the blowing position B, the tensioning device 4 is driven up by the lifting device 12 to prepare for the next operation.
[0024]
In the air blowing device 25, the parison 2 is blown. The blow nozzle 26 is driven into the large-diameter portion 2e that is cut and gradually expands in the upward direction, the upper end portion of the parison 2 is cut off, and a relatively large amount of air is blown out from the blow nozzle 26 to perform blow molding of the parison 2. Do.
[0025]
Thus, when the molded product 10 is molded by the parison 2 and cooled sufficiently, the mold 24 is opened, and the molded product holding device 31 holds the molded product 10 as a container shown in FIG. It moves from the blowing position B to the take-out position C and takes out the molded product 10 (eighth step (molded product)). By repeating the above operation, the molded product 10 is molded one after another. The molded product 10 made of a container is used for use by attaching a lid to the mouth portion 10a as described above. The pinch-off portion 2a ′ (pinch-off portion) after pinching off remaining in the molded product 10 is small because the pinch-off portion 2a formed in the parison 2 is small. The biting 2a ′ can be made smaller than the mouth portion 10a. The molded product holding device 31 is reciprocated to the left and right in conjunction with the reciprocating motion of the mold 24 and the mold clamping device 30, holds the molded product 10 at the blowing position B below the blowing nozzle 26, and moves to the take-out position C. To do.
[0026]
By the way, in the above embodiment, the pulling device 4 stretches the parison 2 hanging from the crosshead 1 to form the small diameter portion 2b and cuts the small diameter portion 2b, and pinches the cut small diameter portion 2b. Although pinched by the device 3, the parison 2 is stretched to form the small diameter portion 2b, and before being cut, the small diameter portion 2b is pinched by the pinch device 3, and the parison 2 is cut and the pinch off portion 2a is It can also be formed.
[0027]
Also in this case, the portion of the parison 2 that has been pressed and compressed by the pinch device 3 is reduced in thickness to form a pinch-off portion 2a that is tightly bonded and sealed as shown in FIG.
[0028]
Moreover, although the parison 2 was formed with the molten material continuously supplied from the extruder 9, it is also possible to form the parison 2 with the molten material supplied intermittently. Further, it is possible to separate the pinch device 3 from the mold clamping device 30 and to move it appropriately in accordance with the parison 2 by an elevating device, a left / right driving device or the like.
[0029]
【The invention's effect】
As understood from the above description, the bottomed parison molding method and apparatus for hollow molding according to the present invention can provide the following effects.
A bottomed parison with the required pinch strength can be obtained in a state where there is no spread of meat at the end, so that it can be made into a small-looking product after biting by pinch-off, and the lower bite of the molded product The pinch-off strength is improved because cutting is minimized. As a result, the butting surface of the pinch-off portion is opened, and a problem that leads to leakage of the contents of the molded product is prevented satisfactorily.
[0030]
Further, it becomes possible to mold a specially shaped molded product. That is, for a bellows structure molded product having a contraction function in the lateral direction, a large pinch-off part is generated in the contraction direction in the conventional molding method. According to the present invention, the pinch-off portion becomes small and a good contraction function can be exhibited.
[0031]
Compared with the conventional device, it is only necessary to incorporate a parison tension device substantially, and it is not necessary to greatly change the conventional device configuration and operation. In addition, since the operation using the parison tension device and the operation not using the parison tension device can be easily selected, the range of molding conditions can be expanded at a low cost.
[0032]
Furthermore, it is possible to eliminate the need for lower cutting with a mold. In this case, the bite cutting blade at the bottom of the mold and the lower deburring device are not required, so that the mold is simple and inexpensive. Regarding the burr scattering problem, in the case of the conventional example in which the burr is processed from the mold, it is torn off by the mold, so that the burr is easily scattered and it is difficult to collect the burr. Since burrs are treated by a parison tension device or the like, recovery at a predetermined location is facilitated, and scattering of burrs is reduced. As for the molded product itself, pinch-off due to the mold does not occur, which has the effect of improving the strength of the molded product.
[Brief description of the drawings]
FIG. 1 is a diagram showing a process of a bottomed parison molding method for hollow molding according to an embodiment of the present invention.
FIG. 2 shows the same process.
FIG. 3 shows the same process, wherein (a) is a front view of the molded product, and (b) is a bottom view of the molded product.
FIG. 4 is also a diagram showing a bottomed parison.
FIG. 5 is a front view showing a hollow molding machine used in a method for forming a bottomed parison that is also hollow-molded.
FIG. 6 is a view showing a conventional bottomed parison.
[Explanation of symbols]
1: cross head (hollow molding machine), 2: parison, 2a: pinch-off part, 2b: small diameter part, 3: pinch device, 4: tensioning device, 10: molded product, 12: lifting device, 24: mold, 25 : Air blowing device, 26: Blowing nozzle, 30: Clamping device, l: Pinch width.

Claims (4)

A cylindrical parison (2) is extruded from the hollow molding machine (1), the lower end of the parison (2) is closed to form a pinch-off portion (2a), and the parison (2) is blown and molded. A method for forming a bottomed parison that is hollow-molded into a molded article (10), wherein the pinch-off portion (2a) extends a parison (2) extruded from the hollow molding machine (1) to reduce the diameter ( A method for forming a bottomed parison for hollow molding, characterized in that, after 2b) is formed, the small-diameter portion (2b) is cut and closely adhered. The method for molding a parison for hollow molding according to claim 1, wherein the small-diameter portion (2b) is sandwiched and adhered by a pinch device (3). 3. The method of forming a hollow parison according to claim 1 or 2, wherein the small diameter portion (2b) is cut by stretching the parison (2). A cylindrical parison (2) is extruded from the hollow molding machine (1), the lower end of the parison (2) is closed to form a pinch-off portion (2a), and the parison (2) is blown and molded. A bottomed parison molding device for hollow molding into a molded article (10), which is a tension device (2b) formed by stretching the parison (2) extruded from the hollow molding machine (1) to reduce the diameter (2b). 4) and a pinch device (3) that sandwiches and contacts the small-diameter portion (2b), and the pinched device (3) clamps and contacts the cut small-diameter portion (2b). By the above, the pinch-off part (2a) is pinched and sealed.

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