JP2795292B2 - Method and apparatus for controlling parison thickness of blow molding machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for controlling the thickness of a parison of a blow molding machine, and more particularly to a method and an apparatus for controlling the thickness of a parison of a blow molding machine for partially controlling the thickness of the parison in the circumferential direction. About.

[0002]

2. Description of the Related Art In a blow molding machine, a molten resin supplied from an extruder is formed into a cylindrical molten resin cylinder called a parison by a die having a ring-shaped resin discharge port, and this is sandwiched between molds. Thereafter, a gas such as air is blown into the parison and cooled to form a hollow product. A parison injection die used in such a blow molding machine, wherein a die with a built-in accumulator forms a cylindrical resin passage by inserting a mandrel into a die housing, and a ring plunger is formed in the cylindrical passage. A hollow parison is injected from a resin discharge port opened at the lower end surface of the housing by press-fitting the inserted and filled molten resin by the plunger.

[0003] Such a parison injection die with a built-in accumulator has a structure in which the wall thickness of the parison in the circumferential direction as well as in the hanging axis direction is changed in accordance with the blow ratio, especially when a large product is molded. Proposed. For example, Japanese Patent Publication No. Sho 62-5815 discloses that a part of the periphery of a resin discharge port is cut out, a block capable of changing a die gap is attached thereto, and the part is moved in a parison thickness direction by a cylinder or the like. A method for performing a typical wall thickness adjustment is shown. Further, as disclosed in JP-A-2-15883-8, a method has been proposed in which a resin temperature difference is given in the circumferential direction by controlling the temperature of each part of the die lip at the resin discharge port, and the thickness is adjusted by the difference in viscosity. ing.

[0004]

However, in the former method, there is a problem in that a step is generated in a portion where the die gap is changed, and there is a problem of strength due to a notch effect, and a streak remains in a parison. In the latter case, there is a problem that local variable control cannot be performed, and effective control cannot be performed because of lack of responsiveness.

SUMMARY OF THE INVENTION An object of the present invention is to focus on the above-mentioned conventional problems and to perform a blow-molding machine capable of controlling the thickness of a parison with excellent responsiveness without fear of strength instability or occurrence of scratches. To provide a parison control method and apparatus.

[0006]

In order to achieve the above object, a method for controlling the thickness of a parison of a blow molding machine according to the present invention comprises inserting a ring plunger into a cylindrical passage of a parison injection die and filling the same. In the method of injecting a cylindrical parison from a resin discharge port by pressurizing a molten resin by the plunger, the ring plunger is divided in a circumferential direction and individually moved to control a thickness in a parison circumferential direction. It was done.

The parison thickness control device for a blow molding machine according to the present invention is characterized in that a ring plunger is inserted into a cylindrical passage of a parison injection die, and the filled molten resin is pressurized by the plunger so that a resin discharge port is formed. In the apparatus for injecting a cylindrical parison from the above, the ring plunger is divided in the circumferential direction, and a plunger drive mechanism is connected to each of the divided plungers.

[0008]

According to the above construction, after the molten resin is filled in the cylindrical passage in the die, the ring plunger is moved downward to eject the hollow parison from the resin discharge port. And a descending operation for injection can be individually performed. Therefore, when the descending speed of the split plunger is partially increased in the cylindrical passage, the swell ratio of the resin extruded from the resin discharge port (the ratio between the die gap and the resin thickness immediately after exiting the die) increases. And the wall thickness can be increased. As a result, by controlling the speed of an arbitrary split plunger, the circumferential wall thickness of the parison can be locally changed. Such a change in wall thickness does not directly change the gap between the resin discharge ports, so that the parison is not scratched or notched. Moreover, since the moving speed of the split plunger can be quickly changed by the plunger drive mechanism, the responsiveness is good, and not only the thickness control in the circumferential direction but also the thickness control in the length direction can be realized with high accuracy. it can. In addition, it is possible to correct the non-uniformity of the parison discharge state when the resin discharge port has an elliptical or oval shape.

[0009]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a parison thickness control method for a blow molding machine according to the present invention.

FIGS. 1 and 2 are cross-sectional views of a parison injection die 10 provided with a parison thickness control device according to a first embodiment. The die 10 is for injecting a parison corresponding to a large product, and has a die housing 12 formed of a rectangular block, and a through-hole 14 having a substantially oval cross section is formed along a vertical center line thereof. Have been. Such a through-hole 14 is opened at the lower end surface of the housing 12 in a state where the inner diameter is gradually reduced from the middle to the lower end surface of the housing 12.

A through-hole 14 is provided in the housing 12.
A mandrel 16 having a smaller diameter is inserted therethrough, and a cylindrical passage 18 is formed between the outer peripheral surface of the mandrel 16 and the inner peripheral surface of the through hole 14. The upper end of the mandrel 16 is provided with a flange 20 having a diameter larger than the outer diameter of the main body.
The opening of the through-hole 14 is sealed by being engaged with an engaging step portion 22 formed on the upper surface of the second member 2. Further, the lower end of the mandrel 16 is formed with a narrowed end in accordance with the diameter-reduced portion of the through-hole 14. Particularly, the mandrel 1 is formed at the front end.
Parison Control Mandrel 2 for access from 6
6 is mounted. A die lip 29 is formed integrally with the tip of the parison control mandrel 26 so as to face the opening of the through-hole 14 and form an oval ring-shaped resin discharge port 28 with the opening of the through-hole 14. . Therefore, the die gap t can be arbitrarily changed by changing the amount of movement of the parison control mandrel 26.

The die gap t can be changed by driving a control cylinder 30 mounted on a support plate 24 holding the die housing 12, and thus connecting the control cylinder 30 and the parison control mandrel 26. A rod 32 extends through the mandrel 16.

In order to allow the molten resin from the extruder to flow into the cylindrical passage 18, a supply path 34 connected to the extruder is formed at the center of the mandrel 26. The inlet 36 is opened to the cylindrical passage 18 by being branched right and left.

Such a dice has a dice structure with a built-in accumulator. Therefore, a ring plunger 40 is inserted into the cylindrical passage 18 so as to be slidable therein.
The ring plunger 40 extrudes the resin filled in the cylindrical passage 18 through the resin inlet port 36 under pressure from the resin discharge port 28 by downward movement thereof, thereby injecting a hollow parison.

Here, a parison thickness control device is incorporated in the parison injection die 10 as follows. That is, although the ring plunger 40 has an elliptical cross section in conformity with the cylindrical passage 18,
In this embodiment, the ring plunger 40 is divided into four parts in the circumferential direction. As shown in FIG.
A, 40C and a pair of plate split ring plungers 40
B, 40D. An L-shaped step groove 42 is formed at each of the divided joining edges. They are engaged with each other so as to be able to move up and down in the cylindrical passage 18 while sliding at the joint. Such split ring plungers 40A to 40D can be independently moved, and therefore, a drive mechanism is connected to each of the split plungers 40A to 40D. This is composed of the hydraulic cylinders 44A to 44D arranged around the die gap adjusting control cylinder 30 as a center,
The drive rods 46A to 46D that are extended and retracted by the cylinders 44A to 44D are connected to the respective split ring plungers 40A.
-40D. The plunger drive cylinders 44 </ b> A to 44 </ b> D are installed on a pedestal 50 attached to the control cylinder 30 using a support base 48. When the plunger drive cylinders 44A to 44D installed on the pedestal 50 are arranged so as not to interfere with the control cylinder 30 side, when the cylinder expansion / contraction axis direction does not coincide with the sliding direction line of each of the split ring plungers 40A to 40D, As shown, the drive rod 46
A-46D is bent in the middle and attached.

The thickness control of the parison thus constructed is performed as follows. When a deep drawn portion is present at the center of both the male and female molds when molding a large product, an oval flat parison 52 is injected and, as shown in FIG. In 52F, since the blow ratio is large, it is necessary to make the thickness relatively thicker than the arc portion 52T at both ends. In addition, burrs are generated at the arc portions at the left and right ends of the parison because they correspond to the joining portions of the mold. Since it is desirable to suppress the generation of burrs from the viewpoint of improving the yield, similarly, it is necessary to control the thickness of the parison at the arc portion to be thin and the other portions to be relatively thick. In this case, since the ring plunger 40 is divided in the circumferential direction as described above, a pair of flat plate divided ring plungers 40B,
Increased the descent speed of 0D, and semicircular split ring plunger 4
Control adjustment is made so that the descending speed of 0A and 40C is decreased. This is easily achieved by controlling the amount of pressurized oil supplied to the hydraulic cylinders 44A to 44D connected to the split ring plungers 40A to 40D. For example, a servo valve is connected to the hydraulic piping to each of the hydraulic cylinders 44A to 44D. And can be realized by this valve control.

In the parison injection die 10, if the descending speed of the plunger 40 is increased, the thickness of the parison 52 can be increased due to the dependence of the swell characteristic of the resin on the shearing speed. As a result, as shown in FIG. Further, the parison 52 having a thick flat plate portion 52F and a thin arc portion 52T can be injected. In this case, the required thickness dimension of each part of the parison 52 is set in the design stage of the mold, and the relationship between the descent speed of the plunger 40 and the swell ratio is determined by the factors including factors such as the type of the resin material and the resin temperature. It can be obtained by a rule. Therefore, the resin used and the cylindrical passage 1
The relationship between the plunger descent speed and the swell ratio is determined in advance in accordance with the temperature of the resin supplied to 8, and the descent speed of each of the split plungers 40A to 40D is set based on this relationship, so as to match this set value. It controls.
At this time, since the resin temperature is a large factor affecting the parison thickness control during the actual operation, the resin temperature is monitored, and the descending speed of each of the split plungers 40A to 40D is determined according to the temperature change and the temperature distribution in the circumferential direction. May be individually feedback controlled.

FIG. 5 shows a flowchart of such parison thickness control. First, the relationship between the swell ratio at the resin discharge port 28 and the descending speed of the ring plunger 40 or the die gap is calculated (step 100). This is determined using the die gap, the resin used, and the set resin temperature as factors. At the same time, the thickness of each part in the parison injection direction determined by the shape of the molded product is set (step 1).
10). And when locally changing the parison thickness,
Calculate the swell ratio from the thickness and die gap value,
The plunger descent speed calculated in step 100 is determined so as to obtain the swell ratio of the die gap control, and the hydraulic cylinder 4 of each of the split ring plungers 40A to 40D is determined.
The output is set to the servo valve controllers 4A to 44D (step 120). After such processing is completed,
The valve controller detects the position of the plunger 40 (step 130), and drives the plunger for injection (step 140). At the time of this injection, it is monitored whether or not the descending speed of the plunger 40 is within an allowable range (step 150). If the descending speed is out of the range, feedback control is performed by the valve controller to adjust the plunger 40 to an appropriate descending speed. Also monitors the resin temperature,
If the resin temperature is out of the allowable range and the temperature is lowered, the process returns to step 100 to reset the plunger descending speed (step 160), and if the temperature is within the appropriate temperature range, the injection is continued (step 160). 170). Such processing is performed for each of the divided ring plungers 40A to 40D.
Let me do it every time.

In the example shown in FIG. 4 (2), the cylindrical passage 18 inside the die is made cylindrical, the plunger 40 is inserted as a two-part structure, and the cylindrical parison 54 is injected. It is. This is because when a product having a convex cross section is formed, the parison portion facing the convex portion is deep drawn, so that this portion is a thick parison 54F.
Also in such a case, the descending speed of the split plunger corresponding to the thick portion 54F is controlled to be higher than the speeds of the other split plungers.

As described above, according to the present embodiment, the dice 10
The ring plunger 40, which is inserted into the cylindrical passage 18 and pressurizes and injects the filled resin, is divided in the circumferential direction, and the descending speed is changed and controlled for each of the divided plungers 40A to 40D to thereby control the divided plungers 40A to 40D. The swell ratio at each portion of the resin discharge port 28 facing the 40D can be directly controlled, and the parison thickness can be arbitrarily adjusted in the circumferential direction.

In particular, in this embodiment, since the gap of the resin discharge port 28 is not locally adjusted, the thickness change portion of the parison changes smoothly, and no cut or streak occurs. The descending speeds of the split plungers 40A to 40D can be quickly changed by the hydraulic cylinders 44A to 44D, so that the thickness control with excellent responsiveness can be performed, and the advantage can be applied to the drawdown suppression control. is there. As a result of the thickness control in the above-described embodiment, the difference in the amount of resin at the divided portion (the amount of resin injected into the thick portion increases) can be obtained by changing the measurement value in each of the split plungers 40A to 40D. It can be easily dealt with by adjusting the rising ends of the plungers 40A to 40D.

In the above embodiment, an example is shown in which the resin supply passage 34 to the cylindrical passage 18 is formed in the mandrel 16, but FIG.
It is needless to say that the present invention can also be applied to a die formed in the die housing 12 and having the inflow port 36 opened in the inner surface of the through-hole 14 of the die housing 12 as shown in FIGS. Other configurations are the same as those of the embodiment of FIGS. 1 and 2, and the same components are denoted by the same reference numerals and description thereof will be omitted.

In the above embodiment, an example of controlling the wall thickness of the parison in the circumferential direction has been described.
In the above-described dice 10 having the above, the length of the parison can be controlled. That is, the parison length is corrected by the extrusion speed of each of the split plungers 40A to 40D. This allows the length of the parison to be detected by a photoelectric sensor, a magnetic sensor, an ultrasonic sensor, or the like arranged along the parison hanging direction. This may be arranged below each of the split plungers 40A to 40D to detect the partial length of the parison extruded by each of the split plungers 40A to 40D. And
When it is detected that the parison length of each part is shorter than a predetermined value, the extrusion speed of the plungers 40A to 40D corresponding to this part is reduced to partially reduce the parison wall thickness and increase the droop speed. Adjust with. Conversely, if it is determined that the length of the parison is partially long, the corresponding plungers 40A to 40D are selected to increase the extrusion speed, increase the thickness of the parison, and partially reduce the droop speed. You do it. This makes it possible to control the parison length so that the lower end of the parison is made uniform over the entire circumference.

FIGS. 8 and 9 show flowcharts of such parison length control. In the example shown in FIG. 8, the parison length is controlled by replacing and defining the length from the injection start time to the time when the sensor detects the lower end of the parison. That is, when there is an injection start command (step 200), measurement is started (step 210), and this is counted until the photoelectric sensor detects the lower end of the parison (step 220). Exit measured when the photoelectric sensor detects the parison bottom (step 230), defining the parison length as t = t ₁ (step 240). This is compared with the length at the time of the previous shot (t = t ₀ ).
_{When 1} is small, it can be determined that the parison is long,
A command to increase the injection speed of the corresponding plungers 40A to 40D is output (step 260). Conversely, when t ₁ is large, it can be determined that the parison has become short, and in such a case, a command to reduce the injection speed is output (step 2).
70). By increasing the injection speed, the swell ratio can be increased to increase the wall thickness, and by decreasing the injection speed, the swell ratio can be reduced to reduce the wall thickness. The thickness control controls the parison length. The injection speed is reset as described above, and a command for starting the next injection is issued (step 280). If t ₁ = t ₀ in step 250, the process may be shifted directly to the next injection start.

According to such an embodiment, the length of the parison portion corresponding to each of the divided ring plungers 40A to 40D can be detected and set and controlled to be uniform over the entire circumference. It is possible to prevent the lower ends from being uneven, thereby improving the yield.

The example shown in FIG. 9 is a flowchart of a method in which the time from the detection of the lower end of the parison by the photoelectric sensor to the completion of the injection is replaced with the parison length and defined and controlled. That is, after the injection start command (step 300), the process waits until the photoelectric sensor detects the lower end of the parison (step 310), and starts measurement when the photoelectric sensor detects the lower end of the parison (step 320). When the injection completion signal from the injection machine has been output (step 330) to exit the measurement (step 340), defining the parison length as t = t ₁ by the measurement time (step 350). This is compared with the length of the previous shot (t = t ₀ ) (step 360). When t ₁ is smaller than the time of the previous shot, it can be determined that the parison is longer, so that the injection speed of the corresponding plungers 40A to 40D is determined. Is output (step 370). Conversely, t
_{When 1} is large, it can be determined that the parison has become short, and in such a case, a command to reduce the injection speed is output (step 380). By increasing the injection speed, the swell ratio can be increased to increase the wall thickness, and by decreasing the injection speed, the swell ratio can be reduced to reduce the wall thickness. The thickness control controls the parison length. The injection speed is reset as described above, and a command for starting the next injection is issued (step 390). If t ₁ = t ₀ in step 250, the process may be shifted directly to the next injection start.

In the control of the parison length, the die gap may be adjusted at the same time as the injection speed of the split plunger 40 is controlled. In this gap adjustment, when the rate of change of the die gap is α, it is desirable that the injection speed be the square root thereof.

As described above, according to the present embodiment, the swell ratio can be controlled by individually changing the extrusion speed of the split plungers 40, so that the parison length can be controlled to be uniform over the entire circumference, thereby improving the yield. The advantages that can be achieved are obtained.

[0029]

As described above, according to the present invention,
The plunger inserted in the cylindrical passage of the die is divided in the circumferential direction, the injection movement speed is individually controlled to perform parison injection, and the circumferential thickness is arbitrarily adjusted by controlling the swell ratio at each part As a result, the thickness of the parison can be controlled with excellent responsiveness without fear of occurrence of anxiety and scratches on the strength, and uneven parison discharge of the elliptical and elliptical dies can be corrected. An excellent effect is obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional configuration diagram of a parison injection die including a parison thickness control device of a blow molding machine according to an embodiment.

FIG. 2 is a longitudinal sectional view of FIG.

FIG. 3 is a schematic view of a parison thickness control device of a blow molding machine.

FIG. 4 is a sectional view of a parison whose wall thickness is controlled.

FIG. 5 is a flowchart of a parison thickness control of the blow molding machine.

FIG. 6 is a cross-sectional view of a modified example of the die provided with the parison thickness control device of the blow molding machine according to the embodiment.

FIG. 7 is a longitudinal sectional view of FIG.

FIG. 8 is a flowchart of parison length control.

FIG. 9 is a flowchart showing another embodiment of parison length control.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 parison injection die 12 die housing 18 cylindrical passage 28 resin discharge port 40 ring plunger 40A-40D split ring plunger 44A-44D hydraulic cylinder 46A-46D drive rod

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // B29L 22:00 (72) Inventor Hiroaki Furuya 1980 No. Oki, Kogushi-ji, Obe, Ube City, Yamaguchi Prefecture Ube Industries, Ltd. Ube Resin Processing Machine In-house (56) References JP-A-62-174128 (JP, A) JP-A-4-286605 (JP, A) JP-A-62-116112 (JP, A) JP-B-63-38285 (JP, A) B2) (58) Investigated field (Int.Cl. ⁶ , DB name) B29C 49 / 02,49 / 04,49 / 42,49 / 78 B29B 11/10 B29C 47/20-47/26 B29L 22:00

Claims (2)

(57) [Claims] In a method of inserting a ring plunger into a cylindrical passage of a parison injection die and injecting the filled molten resin into a cylindrical parison from a resin discharge port by pressurizing the plunger, the ring plunger is rotated around the ring plunger. And split the plunger corresponding to the thickness change area.
A method for controlling the thickness of a parison in a blow molding machine, wherein the thickness of the parison in a circumferential direction is controlled by individually moving the parison at a descent speed according to the thickness adjustment amount . 2. An apparatus for inserting a ring plunger into a cylindrical passage of a parison injection die and injecting the filled molten resin into a cylindrical parison from a resin discharge port by pressurization by the plunger. dividing direction, Pariso corresponding to each of the split plunger
A wall thickness control device for a parison of a blow molding machine, wherein a plunger drive mechanism capable of controlling a descent speed according to a wall thickness adjustment amount is connected.