JP2776048B2 - 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 blowing a high-pressure gas into a cylindrical parison in a mold to obtain a hollow molded article having a predetermined shape.

[0002]

2. Description of the Related Art In a blow molding machine, a parison having a predetermined length corresponding to a molded article is formed by a parison forming apparatus, and the formed parison is housed in a mold for blow molding. The conventional parison is formed by controlling the amount of resin supplied to the parison forming apparatus and the injection speed of the parison in consideration of the appropriate drawdown of the parison (dropping due to its own weight) generally based on experience. Thus, a parison of a predetermined length can be obtained.

[0003]

However, it is extremely difficult to obtain an optimum parison for molding by control on the premise that the above-described proper drawdown occurs. That is, since the viscosity of the resin forming the parison changes due to changes in the external environment such as temperature changes and the non-uniformity of the resin, the drawdown characteristics of the parison change. Different length. In addition, since the mold clamping timing is conventionally kept constant, the parison length is too early or too late due to the effect of drawdown, etc., and the parison is too short to reach the mold. Also, the parison is too long, and the molded product has many burrs, which lowers the molding efficiency.

The present invention has been made to solve the above-mentioned drawbacks of the prior art.
It is an object of the present invention to provide a blow molding machine capable of obtaining a parison having a length suitable for molding.

[0005]

To achieve the above object, a blow molding machine according to the present invention comprises: a parison sensor for detecting that a parison injected by a parison forming apparatus has reached a predetermined length; An injection sensor that detects that the parison has been completely injected by the parison forming device; a mold clamping sensor that detects the completion of mold clamping of a mold clamping device that opens and closes a mold that houses the parison; and an output of the parison sensor. The difference between the time from the start of injection of the parison to the predetermined length obtained based on the signal, and the time of injection of the parison obtained based on the output signal of the injection sensor is determined. An injection time correction circuit for comparing with a predetermined first reference value and outputting a correction value of the parison injection time of the parison forming apparatus according to a difference between the two; Time and up to the point that has become a constant length of,
The difference between the time from the start of injection of the parison to the completion of mold clamping of the mold clamping device, which is obtained based on the output signal of the mold closing sensor, is determined, and this difference is compared with a predetermined second reference value. And a mold closing command correction circuit for correcting the mold closing start time according to the difference between the two.

[0006]

According to the present invention constructed as described above, the parison sensor detects that the parison has reached a predetermined length, and the injection sensor detects completion of the parison injection of the parison forming apparatus. Then, the injection time correction circuit calculates the difference between the time when the parison has reached a predetermined length from the start of injection and the injection time of the parison, which is obtained based on the detection signals of both sensors. The injection time of the parison forming device is corrected so as to be a value. Due to the drawdown of the parison, for example, the injection speed of the parison forming device or the resin supply amount is adjusted by keeping the injection speed constant, the parison injection time is adjusted, and the parison forming device performs the injection. The parison length is controlled so as to be constant.

Further, the mold closing sensor 58 detects that the mold has been closed, and the mold closing command correction circuit determines the difference between the time when the parison has reached a predetermined length and the time required for mold closing. In comparison with the second reference value, the mold closing timing of the mold is adjusted so that the mold clamping is completed a fixed time after the parison sensor detects the parison. Thereby, the length of the parison molded by the mold can be made constant, the occurrence of burrs is reduced, the loss of material is reduced, and the molding efficiency can be improved.

[0008]

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. 2 is an explanatory diagram of the blow molding machine according to the embodiment of the present invention.

In FIG. 2, a blow molding machine 10 has a parison forming apparatus 12 having a die 14 and an injection mechanism 16 connected to the die 14 as main components. A discharge port (not shown) for ejecting the parison 18 is formed in the lower part of the die 14, and a parison control cylinder 20 for adjusting the opening degree (opening area) of the discharge port is formed in the upper part.
Is provided.

The injection mechanism 16 includes a resin accumulator 22 for temporarily storing resin supplied from an extruder (not shown), and an injection cylinder 24 for injecting the resin in the resin accumulator 22 and supplying the resin to the die 14. . A pipeline 28 that communicates between the injection cylinder 24 and a hydraulic source 26 that supplies hydraulic oil to the injection cylinder 24 includes:
A hydraulic pressure adjusting device 30, a pressure gauge 32, and a switching valve 34 are provided so that the operation of the injection cylinder 24 can be controlled, and the injection speed of the injection cylinder 24 can be changed by adjusting the oil pressure.

The injection cylinder 24 is provided with an injection sensor 36 such as a position detecting device, for example, to detect the completion of injection of the resin (parison 18) by the injection cylinder 24. Then, the detection signal of the injection sensor 36 is input to the control device 40, which will be described in detail later, together with the detection signal of the pressure gauge 32. In addition, the control device 40 outputs a control signal to the hydraulic pressure adjustment device 30 and the switching valve 34.

Below the parison forming device 12, a pair of molds 42 and 44 are arranged. These molds 42, 4
4 is connected to mold clamping cylinders 50 and 52 constituting a mold clamping device via platens 46 and 48, and the mold closing cylinders 50 and 52 perform mold closing and mold opening.

A light-emitting body 54 such as a light-emitting diode and a light-receiving element 56 such as a photoelectric tube are mounted below the molds 42 and 44, that is, under the cavity of the mold. The light emitting body 54 and the light receiving element 56 constitute a parison sensor, and the light receiving element 56
Is detected by a change in the amount of light, and a detection signal is sent to the control device 40. The mold clamping cylinders 50 and 52 are provided with a mold clamping sensor 58 such as a pressure gauge and a position detecting device.
0 is input. And the control device 40
Outputs a control signal to a switching valve or the like (not shown) to control the operation of the mold clamping cylinders 50 and 52. The control device 40
Is connected to a display device 60 so that an error display or the like described later can be performed.

As shown in FIG. 1, the control device 40 includes a timer 62 for outputting a signal at a constant cycle,
And a counter 64 for counting the output signal of The output signal of the light receiving element 56 is received at the output side of the counter 64, and the time from the start of the emission of the parison 18 to the detection of the parison 18 by the light receiving element 56, that is, the parison 1
A t ₁ output circuit 66 for outputting a time t _{1 at} which the signal 8 becomes a predetermined length, receives an output signal of the injection sensor 36,
T ₀ the output circuit 68 for outputting a parison injection time t ₀ to the exit completion from the start of injection, receives the output signal of the clamping sensor 58, the time from the start of injection of the parison 18 until the completion of mold clamping of the mold 42, 44 t ₃ output circuit 70 for outputting the t ₃ is is connected.

The control device 40 further includes a parison 18
T from the start of injection of the mold to the start of mold closing of the molds 42 and 44
And t ₂ setting circuit _{72 2} is set, t ₂ setting circuit 72
Read the set time t ₂ in, t ₂ counting circuit 74 for counting the t ₂ receives a signal of the timer 62 is provided.
Further, the control device 40 has a mold clamping device driving circuit 76 that receives the output signal of the t ₂ counting circuit 74 and drives the mold clamping cylinders 50 and 52.

The output side of the t ₀ output circuit 68 and the t ₁ output circuit 66 is connected to an α operation circuit 73 for obtaining a difference α between the two.
1 is input. The α operation circuit 73
To the display device 60, and outputs an error display signal to the display device 60 when the value of α is negative.

The injection time correction circuit 71 includes an α ₀ setting circuit 7
5, α ₀ which is a first reference value to be described later is input, and α output from the α operation circuit 73 is compared with α _0, and the injection of the parison forming device 12 is performed according to the difference between the two. The correction value for adjusting the time is output to the injection control circuit 77.
The injection control circuit 77 controls the operation of the injection cylinder 24 of the parison forming apparatus 12 and outputs a reset signal to the counter 64 and the t ₂ counting circuit 74.

On the other hand, at the output side of the t ₃ output circuit 70, β
The arithmetic circuit 78 is connected. The β operation circuit 78
The output of the t ₁ output circuit 66 is also input,
The difference β between t ₃ and t ₁ is obtained and sent to the mold closing command correction circuit 80. The mold closing command correction circuit 80 reads a second reference value β ₀ described later set in the β ₀ setting circuit 82, compares β with β _0, and calculates a correction value of t ₂ according to the difference between the _two . To t
₂ outputs the setting circuit 72, to correct the value of t ₂ which gives the timing of the mold closing.

The operation of the embodiment constructed as described above is as follows. First, as shown in step 100 of FIG. 3, the time t ₂ from the start of injection to the mold clamping start of the mold 42, 44 of the parison 18, injection time t ₀ of the parison 18
And the time from the start of the injection of the parison 18 to the length of the parison 18 (the time from the start of the injection of the parison 18 to the detection of the parison 18 by the light receiving element 56) t.
₁ the difference between the alpha _0, and the difference beta ₀ between times t ₃ and t ₁ from the start of injection until the clamping of the mold 42, 44 is completed parison 18 is set through a keyboard or the like (not shown). However, the above times t ₀ , t ₁ , t ₃ , t ₂ are:
It is a value determined based on the results of molding in the past, test punching, and the like, and varies depending on the resin used, the size of the mold, and the like. For example, when t ₀ = 20 seconds, t ₁ = 18 to
About 19 seconds, t ₂ = 18 seconds young to about 20 seconds, t ₃ = 20
２０20 seconds or so, α ₀ = 1 to 2 seconds, β ₀ = 2
~ 5 seconds, α-α ₀ = ± (0.1-0.5) seconds,
β−β ₀ = ± (0.1 to 0.5) seconds.

When t ₂ , α ₀ , and β ₀ are set as described above and the start button is pressed, the control device 40
The injection control circuit 77 outputs a control signal to the switching valve 34 to start injection of the parison 18 (step 101). At this time, the injection control circuit 77 outputs a reset signal to the counter 64 and the t ₂ counting circuit 74,
Is counted from zero.

In the parison forming apparatus 12, the injection cylinder 24 injects the resin stored in the resin accumulator 22 to the die 14 by driving the switching valve 34 by the control device 40. As a result, the parison 18 is ejected from the lower end of the die 14. The control device 40
The t ₂ counting circuit 74 reads t ₂ set in the t ₂ setting circuit 72, and counts the mold closing start time t ₂ based on the output signal of the timer 62. Then, the t ₂ counting circuit 74
Outputs the mold closing start signal to the mold clamping device driving circuit 76 when the counting of t ₂ is completed (step 102). And
The mold clamping device driving circuit 76 operates the mold clamping cylinders 50 and 52 to start closing the molds 42 and 44.

On the other hand, the parison 18 injected by the die 14
Enters the space between the light emitter 54 and the light receiving element 56 constituting the parison sensor, the light receiving element 56 inputs a parison detection signal to the t ₁ output circuit 66 of the control device 40. When a signal is input from the light receiving element 56, the t ₁ output circuit 66 reads the count value (time) of the counter 64 at that time, and continues until the injection of the parison 18 starts or the light receiving element 56 detects the lower end of the parison 18. Send time t ₁ to the α calculating circuit 73 (step 103).

On the other hand, when the injection cylinder 24 completes the injection of the resin in the resin accumulator 22 (injection of the parison 18), this completion is detected by the injection sensor 36,
Detection signal is sent to t ₀ the output circuit 68 of the control device 40. Upon receiving the signal from the injection sensor 36, the t ₀ output circuit 68 reads the time counted by the counter 64 at that time, and sends the time to the α operation circuit 73 as the injection time t ₀ of the parison 18 (step 104). ). Further, the t ₃ output circuit 70 outputs a signal from the mold clamping sensor 58 to the mold 4.
When a signal indicating that the mold clamping has been completed in steps 2 and 44 is input, the count value of the counter 64 is read, and the time t ₃ from the start of injection of the parison 18 to the completion of mold clamping is calculated by the β operation circuit 78.
(Step 105).

The α operation circuit 73 includes a t ₀ output circuit 68 and a t
_{When the} emission time t ₀ and the detection time t ₁ of the light receiving element 56 are input from the _one output circuit 66, a difference α = t ₀ −t ₁ is obtained (step 106). Then, the α operation circuit 73
It is determined whether or not the difference α is equal to or greater than zero (step 10).
7) If α <0, that is, if the light receiving element 56 detects the parison 18 after the injection of the parison 18 is completed, the length of the parison 18 is not sufficient for blow molding. Is determined to be wrong, the device is stopped, an error is displayed on the display device 60 (step 108), the above is notified by a buzzer, voice, or the like, and the settings of t ₂ , α ₀ , and β ₀ are reset. To instruct.

If α ≧ 0, the α operation circuit 73 sends the obtained α (= t ₀ −t ₁ ) to the injection time correction circuit 71.
Injection time correction circuit 71, when the alpha from alpha arithmetic circuit 73 comes to enter, reads alpha ₀ from alpha ₀ setting circuit 75 calculates the alpha-alpha ₀ as shown in step 109. Then, an injection time correction circuit 71, alpha-alpha ₀ is within a predetermined value (eg, ± within 0.01 seconds) to determine whether (step 110), alpha-alpha ₀ is equal to within a predetermined value, The same injection time as the previous time is maintained without performing the correction for adjusting the injection time of the parison 18.

On the other hand, the injection time correction circuit 71 calculates α-α ₀
Is larger than the predetermined value, it is determined whether α-α ₀ is positive or negative to adjust the injection time (step 11).
1). That is, when α-α ₀ exceeds the predetermined value on the positive side, the time from when the light receiving element 56 detects the parison 18 to when the injection is completed is long, and the drawdown of the parison 18 is large. Is shown. Therefore, in this case, the injection time correction circuit 71 increases the injection speed of the injection cylinder 24, increases the swell ratio, and increases the thickness of the parison 18, or the die 1
A correction signal for reducing the amount of resin to be supplied to No. 4 is output to the injection control circuit 77 (step 112) to shorten the injection time.

The injection speed is increased to shorten the injection time,
When α-α ₀ is set within a predetermined value, the injection control circuit 7
7 outputs a control signal to the hydraulic adjustment device 30 to increase the oil pressure and increase the injection speed of the injection cylinder 24. When the injection time is shortened by reducing the supply amount of the resin to the die 14, the injection amount is adjusted by setting the next stroke amount to _{Sn + 1} as the following equation (1).

S _{n + 1} = {1− (| α−α ₀ | / t ₀ )} × S _n where _Sn is the stroke amount of the injection cylinder 24 this time.

Conversely, when α-α ₀ exceeds a predetermined value on the negative side, the drawdown of the parison 18 is small,
Since the parison 18 is formed short, the process proceeds from step 111 to step 113 so that the parison 18 to be ejected next time becomes long. That is, the injection time correction circuit 71 provides the injection control circuit 77 with a correction signal for decreasing the injection speed of the injection cylinder 24 or the die 14
And outputs a correction signal that increases the amount of resin supplied to the controller.

When increasing the resin amount, step 1
As in the case of reducing the resin amount of No. 12, the adjustment is performed by adjusting the stroke amount of the injection cylinder 24. That is, the next stroke amount S of the injection cylinder 24
_{n + 1} is

S _{n + 1} = {1+ (| α−α ₀ | / t ₀ )} × S _n

When the control device 40 completes the correction of the injection time of the parison 18, the β arithmetic circuit 78 sets the difference β between t ₃ and t ₁ , that is, the mold 42, from the start of injection of the parison 18.
The time t ₃ to complete the mold clamping of 44 and the parison 1
8 obtains the difference between the time t ₁ until the predetermined length from the start of injection (step 114) to the mold closing command correction circuit 80.

The mold closing command correction circuit 80 reads out β ₀ set in the β ₀ setting circuit 82, calculates β-β _0, and determines that β-β ₀ is within a predetermined value (for example, ± 0.01 seconds). Is determined (steps 115 and 116). Then, the control device 40 determines that the mold closing command correcting circuit 80
When it is determined that β ₀ is within the predetermined value, the process proceeds to step 120 to count the number of blow molding shots, and displays on the display device 60 that the injection of the parison 18 and the mold clamping of the dies 42 and 44 are good. Then, the process returns to step 101 to eject the next parison 18.

However, when β-β ₀ is equal to or larger than the predetermined value, the mold closing command correcting circuit 80 determines whether β-β ₀ is positive or negative (step 117). If β-β ₀ exceeds the predetermined value on the positive side, the drawdown of the parison 18 is large, and it takes time from the detection of the parison 18 by the light receiving element 56 to the completion of the mold clamping, and the length of the parison 18 is long. is longer than necessary, in order to generate a large burr when blow molding, the next mold clamping start time t ₂

## EQU3 ## t ₂ = t ₂ − (β−β ₀ ) (step 118), and the new t ₂
It was set to t ₂ setting circuit 72, to shorten the time until the mold clamping completion in earlier than this time the mold clamping start time, the parison 18
Is prevented from becoming unnecessarily long. Then, after finishing the adjustment of t ₂ , the control device 40 proceeds to step 120.

When β-β ₀ exceeds the predetermined value on the negative side, the mold closing command correction circuit 80 sets the next mold closing timing t ₂

Equation 4] _{t 2 = t 2 + (β} -β 0) as determined ,, set and the so calculated t ₂ to t ₂ setting circuit 72, the time until the clamping delays the mold clamping start time is completed Is adjusted so that the length of the parison 18 is longer than the current time, and the process proceeds to step 120.

As described above, in the embodiment, the time t ₁ from the start of the injection of the parison 18 to the predetermined length of the parison 18 and the injection time t ₀ of the parison 18 are obtained from the following equation.
The difference α between the two times is compared with a first reference value α _0, and α−
The length variation due to the drawdown of the parison 18 is detected according to the magnitude of α ₀ , and the parison injection time is adjusted so that the injection parison length becomes constant, so that when the material having a large drawdown or the external environment changes. Even so, a parison 18 of a certain length can be obtained.

[0035] Moreover, the time t ₃ and the parison 18 to mold clamping completion compared to beta ₀ is a second reference value the difference beta between the time t ₁ to a predetermined length, the mold clamping start time t ₂ Is corrected so that t ₃ -t ₁ is constant, and the parison 18 having a constant length is always blow-molded. Therefore, the defective rate of the product can be reduced, and the amount of burrs under the parison is minimized. Material loss can be reduced.

In addition, the luminous body 5 serving as a parison sensor
4. By changing the position of the light receiving element 56, the parison length corresponding to the shape of the product (die) can be easily set, and the molding conditions can be easily set, so that the efficiency of the blow molding operation can be improved. Improvement can be achieved.

In the above embodiment, the case where the hydraulic pressure is adjusted to change the injection speed of the injection cylinder 24 has been described. However, the amount of hydraulic oil supplied to the injection cylinder 24 may be changed. Further, in the above-described embodiment, the case where the light emitter 54 and the light receiving element 56 are used as the parison sensor has been described. However, a magnetic detector, an ultrasonic sensor, a capacitance sensor, or the like may be used as the parison sensor. In the above-described embodiment, the case where the amount of the injected resin is controlled by Expression 1 or 2 has been described. However, the control of the amount of resin may be performed by another method.

[0038]

As described above, according to the present invention, by keeping the difference between the injection time of the parison and the time when the parison has a predetermined length constant, the external environment can be changed, Even if the resin is not uniform, the length of the parison can be kept constant. In addition, by keeping the difference between the time to complete the mold clamping and the time for the parison to reach the predetermined length constant, the length of the parison molded by the mold can be kept constant, minimizing material loss and improving molding efficiency. Can be improved.

[Brief description of the drawings]

FIG. 1 is a detailed block diagram of a control device of a blow molding machine according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a blow molding machine according to an embodiment of the present invention.

FIG. 3 is a part of a flowchart illustrating an operation of the control device of the embodiment.

FIG. 4 is a part of a flowchart illustrating an operation of the control device of the embodiment.

[Explanation of symbols]

 Reference Signs List 10 blow molding machine 12 parison forming device 14 dice 16 injection mechanism 18 parison 36 injection sensor 40 control device 56 parison sensor (light receiving element) 58 mold clamping sensor 71 injection time correction circuit 80 mold closing command correction circuit

Continuation of the front page (56) References JP-A-63-262212 (JP, A) JP-A-61-244523 (JP, A) JP-A-59-29131 (JP, A) , A) (58) Field surveyed (Int.Cl. ⁶ , DB name) B29C 49 / 04,49 / 78 B29L 22:00

Claims (1)

(57) [Claims] 1. A parison sensor for detecting that a parison ejected by a parison forming device has reached a predetermined length; an ejection sensor for detecting that the parison of the parison forming device has been ejected; and a parison. A mold clamping sensor that detects the completion of mold clamping of a mold clamping device that opens and closes a mold for storing the mold, and obtained from an output signal of the parison sensor, from a time point at which the parison starts injection to a time point at which a predetermined length is reached. Of the parison injection time obtained on the basis of the output signal of the injection sensor,
An injection time correction circuit that outputs a correction value of the parison injection time of the parison forming apparatus in accordance with the difference between the two, and a time from the start of injection of the parison to the time when the parison reaches a predetermined length. And the difference between the time from the start of injection of the parison and the completion of mold clamping of the mold clamping device, which is obtained based on the output signal of the mold closing sensor, and determines this difference as a predetermined second reference value. And a mold closing command correction circuit for correcting the mold closing start time according to the difference between the two.