JP2817447B2 - 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 blow molding machine for forming a hollow body.

[0002]

2. Description of the Related Art In general, a blow molding machine injects a molten resin into the atmosphere from the lower end of a die to form a tubular parison, and stores the parison in a cavity of a mold disposed below the die. The high pressure gas is blown into the parison housed in the cavity. However, since the parison is formed from the molten resin, the state of sagging (drawdown) due to the weight of the parison differs significantly depending on the type of resin, the temperature of the resin, and the surrounding temperature, and the length and thickness of the parison to be molded are large. Variations occur, molding defects occur, and burrs increase, resulting in increased material loss and reduced molding efficiency. Therefore, conventionally, in order to keep the length of the parison constant, the following method has been adopted.

As shown in FIG. 6A, a mold 10a,
A lamp 14 such as a light emitting diode is attached to a predetermined position of one of the platens 12a and 12b to which the 10b is fixed, and a photoelectric tube 16 is attached to a position corresponding to the other lamp 14, and the parison 20 emitted from the dice 18 by the photoelectric tube 16 is attached. Detect the lower end of the parison 2
0 and the time at which the photoelectric tube 16 detects the lower end of the parison 20 is obtained, and this time difference is fed back to the die gap control unit or the resin metering unit supplied to the die 18 to obtain the die gap. The parison length is controlled to be constant by adjusting or adjusting the measured value of the resin.

Further, as shown in FIG.
A lamp 14 and a phototube 16 are provided below the 0a and 10b, and when the lower end of the parison 20 is detected by the phototube 16, the mold clamping operation of the molds 10a and 10b is started.
The parison 20 to be molded is designed to have a constant length.

[0005]

However, FIG.
In both methods (A) and (B), parison 2
Even if the time from the start of injection of 0 to the time when the phototube 16 detects the parison 20 can be made constant, the dies 10a, 10
It takes a long time for the mold closing of b to be completed, and the parison 20 does not follow the movement of the parison 20 during the mold clamping operation. It is difficult to improve the molding efficiency because the parison 20 is stretched by drawdown and the parison length to be formed becomes large, and large burrs are generated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned drawbacks of the prior art, and it is an object of the present invention to provide a blow molding machine capable of performing proper molding even when a resin having a severe drawdown is used. The purpose is.

[0007]

In order to achieve the above object, a blow molding machine according to the present invention introduces a parison injected from a die into a cavity of a mold, and supplies high-pressure gas to the parison in the cavity. In a blow molding machine that blows and forms a predetermined shape, a parison receiver that is disposed below the die and supports a lower end of the parison that has reached a predetermined length, and is attached to the parison receiver,
A parison sensor for detecting that the parison has come into contact with the parison receiver, an injection sensor for detecting the end of injection of the parison from the die, and a detection signal of the injection sensor and the parison sensor. Calculating a detection time difference, comparing the detection time difference with a predetermined reference time, and, in accordance with a deviation between the reference time and the detection time difference, a parison control device that outputs a correction signal of the parison injection time of the die; It is characterized by having.

[0008]

According to the present invention constructed as described above, since the parison receiver supports the lower end of the parison injected from the die, even if a resin having a severe drawdown is used, the parison falls apart and falls, and it is impossible to mold. It is possible to prevent the occurrence of such a situation, and to reduce the generation of burrs by keeping the parison length to be formed constant, thereby improving the forming efficiency.

In addition, a parison sensor is provided in the parison receiver, and the measured value of the resin supplied to the die, the parison injection speed, or the die gap is determined in accordance with the time difference between the end of the parison injection by the die and the detection of the parison by the parison sensor. Since the injection time of the parison is adjusted by the correction, the parison length can be controlled to a predetermined value according to the drawdown, and more appropriate molding can be performed.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a blow molding machine according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is an explanatory diagram of a blow molding machine according to an embodiment of the present invention.

In FIG. 1, a parison receiver 22 is provided below the die 18. The parison receiver 22 has, for example, a fluororesin or the like having heat insulating property disposed on the upper surface of an aluminum plate, and is mounted on the parison receiver 22.
In addition to preventing cooling of the parison 20, the parison 20 has an upwardly curved shape and prevents the parison 20 from dropping from the parison receiver 22. A parison sensor 24, which is formed of, for example, a vibration detector and detects that the lower end of the parison 20 has contacted the parison receiver 22, is attached to a lower part of the parison receiver 22.

Further, the parison receiver 22 includes the dies 10a, 1
Ob is opened and closed by an elevating cylinder 28 provided on a mold clamping frame 26 of the mold clamping device that opens and closes. That is, the cylinder rod 30 of the lifting cylinder 28
A connecting member 32 is fixed to the tip (upper end) of the connector (see FIG. 2).
), And a support member 34 for supporting the parison receiver 22 is mounted on the connecting member 32.

The support member 34 comprises a cylindrical body 36 and a receiving seat 38 to which the parison receiver 22 is fixed. The body 36 is inserted into the connecting member 32 so as to be movable in the axial direction. A flange (not shown) is formed at the lower end to prevent the support member 34 from detaching from the connector 32. The compressed spring 4 is provided inside the body 36.
Numeral 0 is provided to push up the support member 34 and absorb vibration from the lift cylinder 28 side, thereby preventing the vibration on the lift cylinder 28 side from affecting the parison sensor 24. Reference numeral 42 shown in FIG. 2 is a sensor code for extracting an output signal of the parison sensor 24.

On the other hand, the die 18 has a die slip 46 disposed inside a housing 44. Die slip 4
6 has a substantially truncated conical shape, a lower end portion having a larger diameter than an upper end portion, and a parison control rod (hereinafter simply referred to as a rod) 48 is connected to the upper end portion. The die slip 46 is moved up and down by a rod 48 to change the opening degree of a die gap 50 formed between the die slip 46 and the housing 44 and adjust the thickness of the parison 20.

That is, the rod 48 is connected to the housing 44
Penetrates through a plunger 54 for discharging the molten resin 52 disposed inside the housing and an upper end portion of the housing 44, and is connected to a piston 57 of a parison control cylinder 56 for controlling the position of the die slip 46 via a rod 48. I have. The parison control cylinder 56 includes
A servo valve 60 controlled by a gap controller 58 is connected and controls the position of the piston 57. And, on the piston 57,
A detection rod 62 projecting outside the parison control cylinder 56 is fixed, and a gap sensor 64 for detecting the opening degree of the die gap 50 is attached to the tip of the detection rod 62. The data is input to the controller 58.

A measuring device 66 and an injection cylinder 68 are connected to the die 18. The weighing device 66 is controlled by the weighing controller 70 and supplies a predetermined amount of the molten resin 52 to the die 18. On the other hand, the injection cylinder 68 is controlled by an injection cylinder controller 72 and drives the plunger 54 in the die to inject the molten resin 52 from the die gap 50 to form the parison 20. The injection cylinder 68 is provided with an injection sensor 74 such as a position detector, which detects the stroke amount of the injection cylinder 68 and the end of injection of the parison 20 and inputs a detection signal to the injection cylinder controller 72. , Together with the detection signal of the parison sensor 24, to the parison injection control device 76.

The parison injection control device 76 obtains a time difference between the input of the two detection signals from the detection signals of the injection sensor 74 and the parison sensor 24, as will be described in detail later. 70, outputting a correction signal to the injection cylinder controller 72; Further, the parison injection control device 76 receives the detection signal of the parison sensor 24 and outputs a mold clamping start command to the mold clamping controller 78. The mold clamping controller 78 operates the mold clamping cylinders 80a and 80b to which the platens 12a and 12b are attached, and
0b is opened and closed. In addition, near the lower end of the die 18,
A pre-pinch blade 82 for taking out a molded product from the mold is provided with the upper end of the parison 20 after the injection is completed.

As shown in FIG. 3, the parison injection control device 76 includes a timer 84 for outputting a signal at a constant cycle,
A detection signal from the parison sensor 24 and the injection sensor 74 is input, and a time measuring device 86 that counts the output signal of the timer 84, a time discriminator 88 that compares the time measured by the time measuring device 86 with a predetermined time, It has a weighing correction circuit 90, an injection correction circuit 92, and a gap correction circuit 94 that receive signals from the time discriminator 88, and receives a detection signal of the parison sensor 24 and outputs a mold clamping command to the mold clamping controller 78. A mold clamping command device 96 is provided.

In the embodiment constructed as described above, according to the type of the molds 10a and 10b, the type of the molten resin 52 to be used, etc., the molten resin to be supplied to the die 18 obtained from conventional experience or trial molding is used. Initial values such as the measured value of 52, the die gap 50, and the injection speed of the parison sensor 24 (the molten resin 52) are measured by the metering controller 70, the gap controller 58,
This is set in the injection cylinder controller 72. Further, a reference time and a criterion to be described later are set in a time discriminator 88 of the parison injection control device 76, and a correction value obtained in advance is measured in a weighing correction circuit 90, an injection correction circuit 92, and a gap correction circuit 94. It is memorized.

The parison injection controller 76 outputs an injection start command for the parison 20 to the injection cylinder controller 72 as in step 100 of FIG. Injection cylinder controller 7
2 injects the parison 20 in accordance with a preset injection speed curve shown, for example, by a solid line in FIG. 5A, and the gap controller 58 outputs a predetermined value, for example, in FIG.
According to the curve shown by the solid line in FIG.
The dice gap 50 is changed in accordance with the stroke amount. When the parison 20 ejected from the die gap 50 of the die 18 reaches a predetermined length, the lower end contacts the parison receiver 22 and vibrates the parison receiver 22.

When the parison receiver 22 vibrates, the vibration is detected by a parison sensor 24 comprising a vibration detector, and the parison sensor 24 outputs a parison detection signal to the time measuring unit 86 and the mold clamping command unit 96 of the parison injection control unit 76. To enter. When a detection signal is input from the parison sensor 24, the mold clamping command unit 96 outputs a signal to start mold clamping to the mold clamping controller 78, and the mold clamping controller 78 outputs the signal to the mold clamping cylinder 8.
0a and 80b are activated to start closing the molds 10a and 10b.

On the other hand, the time measuring device 86 is provided with the injection sensor 74.
When either one of the injection end detection signal from the parison sensor 24 and the parison detection signal from the parison sensor 24 is received, the timer 84 counts the output signal and starts measuring the time. When the other detection signal is received, the time measurement is terminated, and the measured time is indicated by the time discriminator 8 together with information on which detection signal was input first.
Send to 8.

When the time discriminator 88 receives from the time measuring device 86 the information of the sensor that previously output the detection signal and the measurement time, the parison detection signal of the parison sensor 24 (the lower end of the parison 20 contacts the parison receiver 22). It is determined whether or not the detected signal is after the injection of the parison 20 by the die 18 is completed (step 102). When the end of the injection of the parison 20 by the dice 18 is before the detection of the parison 20 by the parison sensor 24, the time discriminator 88 outputs an injection end detection signal by the injection sensor 74 based on the time measured by the time measuring device 86. It is determined whether the time t _A from the output to the detection signal output by the parison sensor 24 is within a predetermined first reference time T ₁ (for example, 1 second) (step 104).

When t _A ≦ T ₁ , the time discriminator 88 outputs a signal requiring no correction to the weighing correction circuit 90, the injection correction circuit 92, and the gap correction circuit 94, and these correction circuits output the next parison signal. Also in the injection of 20, a control signal is sent to the corresponding controller so as to maintain the initial resin measured value, the injection speed, and the die gap 50.

If t _A > T ₁ , the time discriminator 88 determines whether t _A is within a _second reference time T ₂ (for example, 3 seconds) (step 106), and t _A > T ₂ if outputs a correction request signal to increase the weight value weighed correction circuit 90, an injection correction circuit 92, gap correction circuit 9
4 outputs a signal which does not need to be corrected. Therefore, the weighing correction circuit 90 increases the weighing value of the molten resin 52 supplied to the dice 18 according to the request of the time discriminator 88, and
8 to increase the parison injection time so that t _A ≦ T ₁ (for example, if the initial weighing value was 60% of the volume of the die 18, the weighing value would be 65% of the die volume).
Is sent to the weighing controller 70 (step 10).
8). Then, the parison injection control device 76 outputs a command to start the next injection (step 112), and the metering controller 7
The weighing device 66 is controlled so that 0 becomes the corrected weighing value.

On the other hand, the time discriminator 88 determines in step 106
In the case where t _A ≦ T _2, that is, T ₁ <t _A ≦
If it is T _2, and outputs the modified request signal to reduce the injection speed in the injection correction circuit 92, and outputs the unnecessary signal modification to another correction circuit. As a result, the injection correction circuit 92 calculates t _A
As shown by a dashed line in FIG. 5 (A), an injection correction signal for making the injection speed smaller than the initial value is output so that ≦ T ₁ (step 110). When the parison injection control device 76 outputs the next injection start command (step 112), the injection cylinder controller 72 controls the injection cylinder 68 at the injection speed corrected by the injection correction circuit 92.

If the detection of the parison 20 by the parison sensor 24 is earlier than the end of the parison ejection from the die 18, the time discriminator 88 proceeds from step 102 to step 114, and after the parison sensor 24 outputs a detection signal, The time t _B until the injection sensor 74 outputs the injection end detection signal is a predetermined third reference time T ₃
(For example, 1 second). And
When t _B ≦ T ₃ , the time discriminator 88 outputs a gap correction request signal for increasing the dice gap 50 to the gap correction circuit 94, and the weighing correction circuit 90
A correction unnecessary signal is output to the injection correction circuit 92.

The gap correction circuit 94 includes a time discriminator 88
When a correction request signal is input from the
A correction signal for increasing 0 is output to the gap controller 58 (step 116). Then, the parison injection control device 76 outputs the next injection start command, and the gap controller 5
8 is based on the correction signal of the gap correction circuit 94, and FIG.
As shown by the broken line in (B), the parison control cylinder 56 is controlled via the servo valve 60 so as to increase the die gap 50, the wall thickness of the parison 20 is increased, and the parison injection end time of the die 18 is reduced. The end of the injection of the parison 20 by the die 18 is set earlier than the detection of the parison 20 by the parison sensor 24.

On the other hand, if t _B > T ₃ , the time discriminator 88 determines that t _B is the fourth reference time T ₄ (for example, 3 seconds).
Is determined (step 118), and t _B ≦
If T _4, a correction request signal for increasing the injection speed is output to the injection correction circuit 92 (step 120). If t _B > T ₄ , a correction request signal for reducing the measurement value is output to the measurement correction circuit 90 (step 122). ).

Upon receiving the correction request signal from the time discriminator 88, the injection correction circuit 92 outputs a correction signal for increasing the injection speed to the injection cylinder controller 72, and the injection cylinder controller 72 performs the next injection. For example, the injection cylinder 68 is controlled so that the injection speed is as shown by the broken line in FIG.
Is controlled so that the injection end time of the parison 20 by the die 18 is advanced, and the injection is ended before the parison sensor 24 outputs the detection signal. Also, the weighing correction circuit 90
For example, when the correction command to decrease the weighing value is input from the time discriminator 88, the injection of the parison 20 is completed before the parison sensor 24 outputs the detection signal. A correction signal is output to the weighing controller 70 so that the weighed value, which was 60% of the above, is set to 55% of the dice capacity. Then, the metering controller 70 controls the metering device 66 so that the metered value of the molten resin 52 to be injected next time becomes the value given by the metering correction circuit 90.

As described above, in the embodiment, the parison 20 ejected from the die 18 by the parison receiver 22 is used.
Since the lower end of the parison 20 is supported, it is possible to prevent a situation in which the parison 20 is torn and falls and becomes unusable even if the drawdown of the parison 20 is severe. Also, since the parison receiver 22 supports the parison 20, even if there is some detection error, the mold 10
The length of the parison 20 to be formed can be kept substantially constant by the steps a and b, so that proper molding can be performed, and the occurrence of burrs on the molded product is reduced, and the molding efficiency can be improved.

In the embodiment, the parison receiver 22
Provided that the parison 20 reaches a predetermined length (the lower end of the parison 20 is
Is detected, and the difference between the detection time of the parison sensor 24 and the parison injection end time of the die 18 is compared with the reference time to adjust the injection time. Can be controlled so that the parison length becomes constant in accordance with the state of.

In particular, in the embodiment, the difference between the detection time of the parison sensor 24 and the parison ejection time of the die 18 is divided into six steps, and the correction of the measured value of the molten resin 52 and the adjustment of the injection speed are performed in each step. Since the correction and the die gap 50 are corrected, the parison length can be controlled more accurately. In the embodiment, since the parison receiver 22 uses a heat-resistant heat-insulating material such as a fluororesin,
The portion of the parison 20 in contact with the parison receiver 22 is cooled, so that the thickness of the molded product can be prevented from being partially increased, and the parison sensor 24 can be prevented from being thermally affected. Moreover, since the fluororesin is used, parison 2
0 can be prevented from sticking to the parison receiver 22.

The alternate long and short dash line shown in FIG. 5B shows a modified example of the die gap 50 in the case where the die gap 50 is reduced and the injection time of the parison 20 is lengthened. In the above embodiment, the molten resin 5
Although the so-called in-die type blow molding machine in which the molten resin 52 is stored in the die 18 has been described,
It can also be applied to a so-called die-external blow molding machine that stores outside the machine. In the above embodiment, the case where the vibration detector is used as the parison sensor 24 has been described, but the parison sensor 24 may use a differential transformer or the like. Further, in the above embodiment, the case where the parison sensor 24 is provided below the parison receiver 22 has been described.
May be provided on the upper surface.

[0035]

As described above, according to the present invention, since the parison receiver supports the lower end of the parison ejected from the die, even if a resin having a severe drawdown is used, the parison may be cut off. It is possible to prevent occurrence of a situation in which the molding falls and the molding cannot be performed, and it is possible to reduce the generation of burrs by keeping the length of the parison to be molded constant, thereby improving molding efficiency.

In addition, a parison sensor is provided in the parison receiver, and the measured value of the resin supplied to the die, the parison injection speed, or the die gap is determined in accordance with the time difference between the end of the parison injection by the dice and the detection of the parison by the parison sensor. Since the injection time of the parison is adjusted by the correction, the parison length can be controlled to a predetermined value according to the drawdown, and more appropriate molding can be performed.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a blow molding machine according to an embodiment of the present invention.

FIG. 2 is a detailed explanatory view of a parison receiver of the embodiment.

FIG. 3 is a configuration block diagram of a parison injection control device according to the embodiment.

FIG. 4 is a flowchart illustrating an operation of the parison injection control device according to the embodiment.

FIGS. 5A and 5B are illustrations of a method for adjusting the injection time of the parison according to the embodiment, wherein FIG. 5A is an explanatory diagram in the case of correcting the injection speed of the parison, and FIG. FIG.

FIG. 6 is an explanatory diagram of a conventional method for controlling the parison length.

[Explanation of symbols]

 18 dice 20 parison 22 parison receiver 24 parison sensor 50 die gap 74 injection sensor 76 parison injection control device

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiroaki Furuya 1980, Kogushi-ji, Obe, Ube City, Ube City, Yamaguchi Prefecture Ube Industries, Ltd. Ube Resin Processing Machine Research Laboratory (56) References JP-A-56-95650 (JP, A) JP-A-63-104802 (JP, A) JP-A-61-244523 (JP, A) JP-A-53-74569 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) ) B29C 49/04 B29B 11/10 B29C 49/28-49/42 B29C 49 / 78,49 / 80 B29L 22:00

Claims (1)

(57) [Claims] 1. A blow molding machine for introducing a parison injected from a die into a cavity of a mold, and blowing a high-pressure gas into the parison in the cavity to form the parison into a predetermined shape. A parison support that supports the lower end of the parison that has reached a predetermined length,
A parison sensor attached to the parison receiver, for detecting that the parison has contacted the parison receiver, an injection sensor for detecting the end of injection of the parison from the die, and a detection signal of the injection sensor and the parison sensor. Receiving the detection time difference between the two detection signals, comparing the detection time difference with a predetermined reference time, and outputting a correction signal of the parison injection time of the die according to the deviation between the reference time and the detection time difference. And a parison control device.