JPH068310A - Blow molding machine parison length control method - Google Patents

Abstract

(57) [Abstract] [Purpose] It is possible to quickly obtain the control constants corresponding to the resin used, improve the precision of parison length control, improve the precision of product thickness distribution, and respond well to high-speed molding. To do. [Constitution] In the parison length control method of the blow molding machine 10, the relationship between the parison length of the resin to be used and the number of revolutions of the extruder screw 28 is previously obtained in the test molding step, and the current parison length is calculated in the normal molding step. Is detected and the difference in the parison length between the current parison length and the target parison length is calculated.From the relationship between the parison length and the extruder screw rotation speed that was obtained in advance, the extruder screw rotation speed is corrected according to the parison length difference. The target parison length is obtained by calculating the amount and controlling the screw speed of the extruder screw.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a parison length control method for a blow molding machine.

[0002]

2. Description of the Related Art In a blow molding machine, a parison extruded from an extruder is hung, and the parison is clamped by a pair of molds to close both ends of the parison and blow it into the closed parison. The product is obtained by injecting gas and inflating the parison until it matches the cavity of the mold.

However, it is necessary to control the length of the parison extruded from the extruder to a constant length for the following reasons.

The thickness of the parison extruded from the extruder is
In order to give a desired wall thickness distribution to the product after blow molding, it is controlled at a constant cycle with respect to the target parison length. Therefore, in order to obtain a highly accurate product wall thickness distribution by the parison wall thickness control which is operated in a constant cycle, it is necessary to secure a constant parison length at the mold clamping timing.

If the length of the parison is too large, the length of the lower end of the parison, which protrudes from the mold and becomes burrs, becomes too large, resulting in a large material loss.

If the length of the parison is too small, the lower end of the parison cannot be clamped by the mold, which makes blow molding impossible.

Therefore, as a conventional method for controlling the length of the parison, the method described in USP 3759648 and JP-A-51
-41061 is proposed.

According to US Pat. No. 3,759,648, the length of the parison is long or short depending on whether or not the parison reaches the position where the photocell is shielded from light at a specific detection timing defined with reference to the mold clamping timing. To determine. Then, based on this determination result, the rotation speed of the extruder screw is changed to try to secure a constant parison length at the mold clamping timing.

The device disclosed in Japanese Patent Laid-Open No. 51-41061 has two pairs of upper and lower photocells arranged below the extruder. If the parison does not block both photocells, the length of the parison is too short. When only the upper photocell is shielded from light, the parison length is appropriate. When the parison shields both photocells, it is determined that the parison length is too long. Based on the result of this determination, the mold clamping timing is changed so as to ensure a constant parison length at the mold clamping timing.

[0010]

However, the prior art has the following problems. In both USP3759648 and Japanese Patent Laid-Open No. 51-41061, the relationship between the monitored object (parison length) and the controlled object (extruder screw rotation speed or mold clamping timing) is unclear,
The determination of the control constant must depend on the trial and error of the operator. Therefore, it takes time to find the optimum value of the control constant, and the reproducibility of control is low.

In both USP 3759648 and Japanese Patent Laid-Open No. 51-41061, it is only determined whether the current parison length is long or short, and the amount of deviation from the target value (parison length difference) is ignored. Therefore, the control is not performed according to the parison length difference, and the control accuracy is low. When the amount of deviation is small, hunting is easy, and when the amount of deviation is large, it takes time to converge.

In Japanese Patent Laid-Open No. 51-41061, the object to be controlled is to change the mold clamping timing, which makes it difficult to synchronize with the parison thickness control which is operated at a constant cycle, and the accuracy of the product thickness distribution is improved. It is easy to get worse. In addition, changing the mold clamping timing requires adjusting the operation timing and operation speed of the mechanical system, which impairs high-speed moldability.

According to the present invention, a control constant corresponding to a resin to be used is rapidly obtained, the parison length control is highly accurate, the product thickness distribution is highly accurate, and high-speed molding can be well coped with. With the goal.

[0014]

According to a first aspect of the present invention, a parison extruded from an extruder is hung and the parison is clamped by a mold to close and close both ends of the parison. In the parison length control method of the blow molding machine, which injects blowing gas into the parison, the relationship between the parison length of the resin to be used and the screw speed of the extruder is obtained in advance in the test molding process. In the process, the current parison length is detected, the parison length difference between the current parison length and the target parison length is determined, and the parison length is determined from the relationship between the pre-determined parison length and the extruder screw rotation speed. A target parison length is obtained by calculating a correction amount of the extruder screw rotation speed to control the extruder screw rotation speed.

According to the present invention of claim 2, in the present invention of claim 1, further, a variation of the current parison length within a relatively short time is obtained, and the extrusion is performed according to the magnitude of the variation. The width of the dead zone is set so that the machine screw speed is not corrected.

According to a third aspect of the present invention, in the present invention according to the first or second aspect, the parison light-shielding time measured by a photoelectric tube provided below the extruder is used as a current parison length equivalent value. It is the one.

[0017]

According to the present invention described in claim 1, the following (1)
There is an action of (5). (1) Control constants are automatically calculated. Therefore, the reproducibility of the control is high because the determination is made quickly without depending on the trial and error of the operator.

(2) The control constant is obtained corresponding to the resin used, and the control accuracy is high. (3) The parison length is controlled based on the amount of deviation (parison length difference) between the current parison length and the target parison length, and the control accuracy is high. Since the control is performed according to the difference in parison length, hunting is unlikely to occur and the time until convergence is shortened.

(4) The object to be controlled is the screw speed of the extruder and does not change the mold clamping timing. Therefore, it is easy to synchronize with the parison thickness control that operates at a constant cycle, and since the parison length is controlled to be constant,
Highly accurate product thickness distribution.

(5) Since the mold clamping timing is not changed,
High-speed molding is possible without the need to adjust the operating timing and operating speed of the mechanical system.

According to the present invention of claim 2,
There are (6) and (7). (6) The dead zone can be set from the variation data of the current parison length obtained by actual molding by the molding apparatus itself used for molding. Therefore, the dead zone can be set within an appropriate range to prevent hunting.

(7) The dead zone is automatically calculated. Therefore, the setting is promptly performed without depending on the trial and error of the operator, and the control reproducibility is good.

According to the invention described in claim 3,
It has the function of (8). (8) The current parison length is calculated from the parison shading time, and the parison length can be detected reliably and easily.

[0024]

1 is a block diagram showing a parison length control system according to an embodiment of the present invention, FIG. 2 is a flow chart showing a basic control procedure of the present invention, and FIG. 3 is a parison light-shielding time and a screw rotation speed. 4 is a flow chart for determining a control constant representing the relationship between the parison light-shielding time and the screw rotation speed, FIG. 5 is a diagram showing a dead zone, and FIG. 6 is a correction of the screw rotation speed from the parison light-shielding time. FIG. 7 is a flow chart for obtaining the correction amount of the screw rotation speed from the parison light-shielding time, FIG. 8 is another flow chart for obtaining the correction amount of the screw rotation speed from the parison light-shielding time, and FIG. 9 is blow molding. FIG. 10 is a plan view showing the machine, and FIG. 10 is a side view showing the blow molding machine.

The rotary blow molding machine 10 is shown in FIGS.
As shown in (1), it has an extruder 12 for vertically extruding a tubular molten parison 11 made of a thermoplastic resin. The blow molding machine 10 clamps the parison 11 on a turntable 15 rotatably supported by a support shaft 14 on a base 13 arranged in front of the extruder 12, and closes both ends of the parison 11. Six pairs of opening / closing dies 16 are placed via each base plate 17, and each pair of the dies 16 of the six sets is placed.
While intermittently rotating the section from the station A to the station F in FIG. 9 to make a circuit, injecting a blowing gas into the parison 11 closed by the mold 16, the parison 1
The product is obtained by inflating 1 until it matches the cavity of the mold 16.

The extruder 12 includes a lower base 21, an upper base 23 provided on the lower base 21 so as to be horizontally rotatable by a swivel drive device 22, and a vertical drive device 24 for vertically moving the upper base 23. It is composed of an extruder main body 25 which supplies the parison 11 into the pair of molds 16 when the parison 11 moves in the direction and descends.

The extruder main body 25 has a hopper 26 for introducing a pellet-shaped thermoplastic resin, and a screw 2 which is rotated by a motor 27 under the hopper 26.
It has a cylinder 29 which houses 8 and whose outside is heated by a heater (not shown). The thermoplastic resin heated and melted in the cylinder 29 is supplied to the side of the pair of molds 16 as the tubular parison 11 by the tubular pushing die head 30 provided at the tip of the cylinder 29. The parison cutting device 31 is provided below the die head 30.
The cutter 32 of the cutting device 31 cuts into a fixed length so that the upper end of the parison 11 supplied into the pair of molds 16 slightly projects from the upper surface of the pair of molds 16. To do.

However, in the blow molding machine 10, the lower end of the parison 11 supplied into the mold 16 is slightly lower than the lower surface of the pair of molds 16 at the timing of clamping the pair of molds 16. In order to obtain a constant parison length so as to project, a controller 40 as shown in FIG. 1 is provided, and parison length control as shown in FIG. 2 is performed.

In the blow molding machine 10, the photoelectric tube 41 is installed below the die head 30 of the extruder 12, and the parison 1
The light-shielding timing of 1 can be detected. The controller 40 additionally includes an input device 42, a monitor device 43, and a motor driver 44.

The controller 40 executes (A) control constant calculation mode, (B) dead zone calculation mode, and (C) normal operation mode as follows.

(A) Control constant calculation mode (see FIGS. 1 to 4) This mode shows the relationship between the parison length of the resin used (parison shading time t) and the extruder screw rotation speed N in the test molding process. It is obtained in advance.

At this time, the counter 5 of the controller 40
1 obtains the cutting timing of the parison 11 by the parison cutting device 31 and the light-shielding timing at which the parison 11 passes through the phototube 41, and obtains the timing difference between them as the parison light-shielding time t.
Is used as a parison length (current parison length) equivalent value at the mold clamping timing of the parison 11.

Therefore, the relational expression between the parison light-shielding time t and the screw rotation speed N is determined by the following equations (1) to (6). That is, when the resin extrusion amount (weight of resin extruded per unit time) Q, resin pressure (screw tip part) P, parison weight M, constants A, B, C, D, E Equation (1) of
Eliminating the term P ⁿ from equation (2) gives equation (3). Q = A × N−B × P ⁿ (1) Q = C × P ⁿ (2) Q = D × N (relationship between extrusion amount and screw rotation speed)
… (3) D = A × C / (C + B)

The relationship between the extrusion amount and the parison light-shielding time is (4)
It is an expression. Since it is N and t that can be actually measured,
Eliminating Q from equations (3) and (4), we obtain equation (5). Q = M / t (4) N = a × (1 / t) (5)

According to the equation (5), 1 / t and N are in a proportional relationship, and as shown in FIG.
It is recognized that the target parison length can be secured by changing the screw rotation speed by ΔN with respect to t.

The control constant a in the equation (5) is N ₁ , N
By obtaining the parison shielding time t _1, t ₂ corresponding to the two screw rotation speed of _2, is determined as follows (6). Incidentally, this determination of a is normally performed once when changing the resin.

Two points (1 / t ₁ , N ₁ ), (1 / t ₂ , N 1
₂ ) is substituted into the straight-line general formula Y = aX + b, N ₁ =
_{a × (1 / t 1)} + b, N 2 = a × (1 / t 2) + b , and the result as equation (6) is determined.

[0038]

[Equation 1]

Therefore, in the test molding process, the controller 40 issues a physical property measurement request command as shown in FIGS. 1 and 2, and the input device 42 rotates the physical property measurement screw speed N.
₁ and N ₂ and then ₂ by motor driver 44
The motor 27 of the screw 28 is driven by _two N ₁ and N ₂ . The rotation speed of the motor 27 is the pulse generator 33.
And is fed back to the motor driver 44. Then, the controller 40 connects the output end of the counter 51 to the control constant calculation circuit “1” (see FIG. 1) and sets the parison light-shielding times t ₁ and t ₂ corresponding to the _two N ₁ and N ₂ respectively. Then, the control constant a is calculated by using the physical property values N ₁ , N ₂ , t ₁ and t ₂ in the equation (6), and this a is stored in the data memory 52.

Specifically, the controller 40 sets N ₁ as shown in FIG. 4, measures the parison light-shielding time t 6 times after the screw 28 reaches N _1, and calculates the average value thereof. Be t ₁ . Further, after setting N _2, and after the screw 28 reaches N ₂ , the parison light-shielding time t is measured 6 times, and the average value thereof is taken as t ₂ . When calculating t ₁ and t ₂ , the parison shading time t is set to 6 times (or n
The measurement is performed in order to ignore the variation in the measured values in the dead zone described later.

(B) Dead zone calculation mode (FIGS. 1, 2 and 5)
This mode is used for the current parison length (parison shading time t).
Is obtained within a relatively short time, and the width of the dead zone where the extruder screw rotation speed N is not corrected is set according to the magnitude of the variation.

Generally, the parison length varies with the elapse of extrusion time, but as shown in FIG. 5 (A), the average value varies greatly and gradually, and the dispersion of each measuring point is fine around this average value. It's scattered. This fine variation is due to the shape of the cut in the cutter 32 and the fluctuation of the parison, and should not be considered as variation in the extrusion amount itself. That is, the object of control is a large variation in the parison length (solid line), and fine variation (dotted line) may cause hunting, so it should be ignored.
Therefore, in the present invention, this fine variation (dotted line)
The width of is automatically measured and calculated, and it is set as the dead zone. It suffices to perform control so that the parison length control result is as shown in FIG.

Specifically, the parison length is as shown in FIG.
Since it fluctuates as shown in, the total fluctuation range is W ₂ . When the data is actually taken in units of one hour as shown in FIG. 5A, the result of W ₂ is obtained.
However, in an extremely short time (about 1 to 5 minutes), that is, a short time that is not affected by a large loose fluctuation, only the variation of W ₁ can be obtained. Therefore, if this data is collected after the start of molding and before obtaining a non-defective product, the dead zone can be set by using this data for the subsequent molding.

The variation in the parison length may be obtained by using the statistical standard deviation σ, and if 3σ is set as the dead zone, 99.7% of theoretically fine variation is ignored and a larger variation is caused. Sometimes, control can be performed to correct the extruder screw rotation speed.

Therefore, after the molding is started, the controller 40 issues a dead zone automatic measurement command as required, as shown in FIGS. 1 and 2, and causes the output end of the counter 51 to output the dead zone calculation circuit.
Connect to "2" (see Fig. 1), measure the parison shading time t many times (for example, 60 times), find the average and σ, and calculate the σ
The dead zone is set based on the above, and the dead zone is stored in the data memory 52.

(C) Normal operation mode (FIGS. 1, 2 and 6-
In this mode, the current parison length (parison light-shielding time t) is detected in the normal molding process, and the current parison length (reciprocal of the parison light-shielding time t) and the target parison length (target parison light-shielding time t) are detected. The reciprocal of ₀ ) and the parison length difference (parison shading time difference T) are obtained, and the control constant a of the above (A) is obtained in advance.
Using, the correction amount (ΔN) of the extruder screw rotation speed according to the parison length difference (parison shading time difference T)
Is calculated to control the extruder screw speed (N) to obtain the target parison length.

Therefore, in the normal molding process, the controller 40 obtains the control constant a and the dead zone from the data memory 52 and sets the output end of the counter 51 to the correction amount calculation circuit "3" as shown in FIGS. Connected (see FIG. 1), the reciprocal of the parison light-shielding time t is obtained as a difference T from the reciprocal of the target parison light-shielding time t ₀ , and the control constant a is used on condition that the parison light-shielding time difference T is out of the dead zone. Then, a correction amount ΔN of the extruder screw rotation speed according to the parison light-shielding time difference T is calculated. Then, the motor driver 44 is used to drive and control the motor 27 of the screw 28 to obtain the target parison length.

Incidentally, the controller 40 can employ various control correspondences (C-1) to (C-3) below for the parison light-shielding time difference T.

(C-1) Control Mode of FIG. 6A This control mode goes through a dead zone proportional correction area and an abnormal correction area as the parison light-shielding time difference T increases. In FIG. 6A, PN is the upper limit value of the correction amount of the extruder screw rotation speed. If the calculated correction amount α exceeds PN, only the correction for PN is applied. Specifically, the control is as shown in the following (1) to (6) (see FIG. 7).

(1) The parison shading time t is 60 after the molding is started.
Measure the number of times, find the average and σ, and set a dead zone with a width of 3σ, for example. This (1) may be omitted.

(2) The parison light-shielding time t is measured, and Δτ = 1 / t −1 / t ₀ is calculated with respect to the target parison light-shielding time t ₀ .

[0052] For (3) each extrusion shot, monitors .DELTA..tau, When .DELTA..tau ₀ is out of the dead zone, an average of Δτ ₁ ~Δτ ₆ subsequent 6 extrusion shot as parison shading time difference T. this

[Equation 2] If is out of the dead zone, the correction shall be applied for the first time.
Here, after Δτ ₀ described above, whether or not to adopt the correction is determined by obtaining the average T of Δτ _{1 to} Δτ ₆ by correcting the sudden fluctuation (measurement error) of only one extrusion shot. This is to prevent it from being lost.

(4) From (3) above, the extruder screw rotation speed correction amount absolute value

[Equation 3] Ask for.

(5) If α> PN is not satisfied, it is determined that it is in the proportional correction region, the screw rotation speed is accelerated and corrected by ΔN = α under the condition of T <0, and the screw rotation is performed under the condition of T> 0. The number is corrected by deceleration with ΔN = −α.

(6) If α> PN, it is determined that it is in the abnormal correction region, the screw rotation speed is accelerated and corrected by ΔN = PN on condition that T <0, and the screw rotation is executed on condition that T> 0. The number is corrected by deceleration by ΔN = −PN.

(C-2) Control Mode of FIG. 6B This control mode narrows the dead zone (for example, the width of the dead zone is reduced).
If you want to control (2σ), the proportional correction area is extended. This control mode also goes through the dead zone proportional correction area and the abnormal correction area in accordance with the increase in the parison light-shielding time difference T. The specific control is the same as in FIG. 7.

(C-3) Control Mode of FIG. 6 (C) This control mode is to extend the minimum correction amount of the proportional correction region as it is when it is desired to control the dead zone by narrowing it as in (C-2). is there.

This control mode is effective in the following cases. That is, the minimum correction amount cannot be reduced when the resolution is rough in controlling the screw speed of the extruder. In such a case, the dead zone cannot be further narrowed in the control mode of FIG. 6 (B), but the dead zone can be narrowed in the control mode of FIG. 6 (C). At this time, in the quantitative correction, a correction larger than that in FIG. 6B is applied and the target value is exceeded, so that the correction that exactly matches the target value cannot be applied.
By adjusting the dead zone so that it does not protrude, it is possible to narrow the dead zone as a result.

This control mode goes through a dead zone, a quantitative correction area, a proportional correction area, and an abnormal correction area as the parison light-shielding time difference T increases. In FIG. 6C, LB is the range of deviation of the parison light-shielding time difference T for quantitative correction, and LN is the absolute value (manual input) of the correction amount for quantitative correction. Further, PN is the upper limit value of the correction amount of the extruder screw rotation speed. If the calculated correction amount α exceeds PN, only the correction for PN is applied. Specifically, the control is as described in (1) to (7) below (see FIG. 8).

(1) After the molding is started, the parison light-shielding time t is set to 60.
The measurement is performed twice, the average and σ are obtained, and the dead zone and LB with a width of 2σ are set, for example.

(2) The parison light-shielding time t is measured, and Δτ = 1 / t −1 / t ₀ is calculated with respect to the target parison light-shielding time t ₀ .

[0062] For (3) each extrusion shot, monitors .DELTA..tau, When .DELTA..tau ₀ is out of the dead zone, an average of Δτ ₁ ~Δτ ₆ subsequent 6 extrusion shot as parison shading time difference T. this

[Equation 4] If is out of the dead zone, the correction shall be applied for the first time.
Here, after Δτ ₀ described above, whether or not to adopt the correction is determined by obtaining the average T of Δτ _{1 to} Δτ ₆ by correcting the sudden fluctuation (measurement error) of only one extrusion shot. This is to prevent it from being lost.

(4) According to (3) above,

[Equation 5] If so, it is determined to be in the quantitative correction region, the extruder screw rotation speed correction amount absolute value α = LN, and the screw rotation speed is accelerated and corrected by ΔN = LN under the condition of T <0, and T> 0. The screw rotation speed is ΔN = -L
Correct the deceleration at N.

(5) By the above (3),

[Equation 6] If so, the extruder screw rotation speed correction amount absolute value

[Equation 7] Ask for.

(6) If α> PN is not satisfied, it is determined that it is in the proportional correction region, the screw rotation speed is accelerated and corrected by ΔN = α under the condition of T <0, and the screw rotation is performed under the condition of T> 0. The number is corrected by deceleration with ΔN = −α.

(7) If α> PN, it is determined that it is in the abnormality correction region, the screw rotation speed is accelerated and corrected by ΔN = PN on the condition of T <0, and the screw rotation is on the condition of T> 0. The number is corrected by deceleration by ΔN = −PN.

The operation of this embodiment will be described below. (1) The control constant a is automatically calculated. Therefore, the reproducibility of the control is high because the determination is made quickly without depending on the trial and error of the operator.

(2) The control constant a is obtained corresponding to the resin used, and the control accuracy is high. (3) The parison length is controlled based on the amount of deviation (parison length difference) between the current parison length and the target parison length, and the control accuracy is high. Since the control is performed according to the difference in parison length, hunting is unlikely to occur and the time until convergence is shortened.

(4) The object of control is the extruder screw rotation speed, and does not change the mold clamping timing. Therefore, it is easy to synchronize with the parison thickness control that operates at a constant cycle, and since the parison length is controlled to be constant,
Highly accurate product thickness distribution.

(5) Since the mold clamping timing is not changed,
High-speed molding is possible without the need to adjust the operating timing and operating speed of the mechanical system.

(6) The dead zone can be set from the variation data of the current parison length obtained by actual molding by the molding apparatus itself used for molding. Therefore, the dead zone can be set within an appropriate range to prevent hunting.

(7) The dead zone is automatically calculated. Therefore, the setting is promptly performed without depending on the trial and error of the operator, and the control reproducibility is good.

(8) The current parison length is calculated from the parison light-shielding time, and the parison length can be detected reliably and easily.

(9) The setting items for the operator's input device 42 are only the target parison length and the mounting position of the photoelectric tube 41, and the control accuracy does not depend on the individuality of the operator.

(10) Since the controller 40 monitors the parison length difference, it is possible to provide an alarm function for the occurrence of an abnormal parison length by defining the allowable range of the parison length difference.

(11) Even if the screw rotation speed is arbitrarily set, the parison length is automatically controlled to the target value. That is, even if the screw rotation speed is arbitrarily set, the screw rotation speed quickly converges to the desired rotation speed and becomes stable, so that the screw rotation speed can be easily set.

(12) From the start of molding operation to the stabilization of the parison, the screw is rotated at a slower speed than usual to prevent the uneven thickness of the parison and the parison from being caught in the guide pins of the mold. Although it is actually practiced to raise the rotation speed to a normal rotation speed after it stabilizes, if the present invention is adopted and a low rotation speed is set to start, the above-mentioned problems can be avoided and the molding operation can be smoothly started. Can be raised.

In the practice of the present invention, the current parison length is not limited to being detected by the parison light-shielding time measured by the phototube, but may be detected by other means such as an image processing camera. .

[0079]

As described above, according to the present invention, the control constant corresponding to the resin to be used is rapidly obtained, the parison length control is highly accurate, and the product thickness distribution is highly accurate.
In addition, it is possible to cope with high-speed molding well.

[Brief description of drawings]

FIG. 1 is a block diagram showing a parison length control system according to an embodiment of the present invention.

FIG. 2 is a flow chart showing a basic control procedure of the present invention.

FIG. 3 is a diagram showing a relationship between a parison light-shielding time and a screw rotation speed.

FIG. 4 is a flow chart for determining a control constant representing the relationship between the parison light-shielding time and the screw rotation speed.

FIG. 5 is a diagram showing a dead zone.

FIG. 6 is a control diagram for obtaining a correction amount of a screw rotation speed from a parison light-shielding time.

FIG. 7 is a flow chart for obtaining a correction amount of the screw rotation speed from the parison light-shielding time.

FIG. 8 is another flow chart for obtaining the correction amount of the screw rotation speed from the parison light-shielding time.

FIG. 9 is a plan view showing a blow molding machine.

FIG. 10 is a side view showing a blow molding machine.

[Explanation of symbols]

 10 Blow Molding Machine 11 Parison 12 Extruder 16 Mold 28 Screw 40 Controller 41 Photoelectric Tube

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[Procedure amendment]

[Submission date] October 20, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0028

[Correction method] Change

[Correction content]

However, in the blow molding machine 10, the lower end of the parison 11 supplied into the mold 16 is slightly lower than the lower surface of the pair of molds 16 at the timing of clamping the pair of molds 16. In order to obtain a constant parison length (target parison length: in this embodiment, a desired parison length measured from the cutter 32) is provided with a controller 40 as shown in FIG. Then, the parison length control as shown in FIG. 2 is performed.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0046

[Correction method] Change

[Correction content]

(C) Normal operation mode (FIGS. 1, 2 and 6-
In this mode, the current parison length (parison light-shielding time t) is detected in the normal molding process, and the current parison length (reciprocal of the parison light-shielding time t) and the target parison length (target parison light-shielding time t) are detected. The reciprocal of ₀ ) and the parison length difference (parison shading time difference T) are obtained, and the control constant a of the above (A) is obtained in advance.
Using, the correction amount (ΔN) of the extruder screw rotation speed according to the parison length difference (parison shading time difference T)
Is calculated to control the extruder screw speed (N) to obtain the target parison length. The target parison light-shielding time t ₀ can be obtained by l ₀ / L = t ₀ / molding cycle (l ₀ : parison length from the cutter 32 to the phototube 41, L: target parison length, see FIG. 1. ).

[Procedure 3]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 1

[Correction method] Change

[Correction content]

[Figure 1] ─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] January 22, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0002

[Correction method] Change

[Correction content]

[0002]

2. Description of the Related Art A blow molding machine hangs down a parison extruded from an extruder, closes both ends of the parison, injects a blowing gas into the closed parison, and puts the parison into a mold capity. The product is obtained by inflating until matched.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

[0014]

According to the present invention, a parison extruded from an extruder is suspended, both ends of the parison are closed, and a blowing gas is injected into the closed parison. In the method for controlling the parison length of the blow molding machine, in the test molding step, the relationship between the parison length of the resin to be used and the extruder screw rotation speed is obtained in advance, and in the normal molding step, the current parison length is detected, The difference in parison length between the current parison length and the target parison length is calculated, and from the relationship between the parison length and the screw speed of the extruder, which is calculated in advance, the correction amount of the extruder screw speed corresponding to the difference in the parison length is calculated. By controlling the screw speed of the extruder, the target parison length is obtained.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0078

[Correction method] Change

[Correction content]

In the practice of the present invention, the current parison length is not limited to being detected by the parison light-shielding time measured by the phototube, but may be detected by other means such as an image processing camera. . Further, in the present embodiment, a blow molding machine is used in which both ends of the parison are closed by sandwiching them with a mold, and a blow gas is injected into the closed parison. It is closed by sandwiching one end with a mold, and a blowing gas is injected into the closed parison (when the blowing gas is injected, the other part of the parison of the other of the parison is formed by a blowing gas injection means configured in a structure different from that of the mold). It can also be applied to blow pin type blow molding machines.

[Procedure Amendment 5]

[Document name to be corrected] Drawing

[Correction target item name] Figure 9

[Correction method] Change

[Correction content]

[Figure 9]

Front page continuation (72) Inventor Masayuki Akimoto 2166 Kamamomo, Kami-Mikawa-cho, Kawachi-gun, Tochigi Prefecture 1-509 Kao-Kami-Mikawa Shrine House (509) Inventor Mitsuo Yamanoi 117 Koshitocho, Utsunomiya-shi, Tochigi Prefecture No. 205 (72) ) Inventor Minoru Oizumi 6-12-12 Minamikasai, Edogawa-ku, Tokyo Omiya Miyako 5-505

Claims (3)

[Claims] 1. A blow molding in which a parison extruded from an extruder is hung, and the parison is clamped by a mold to close both ends of the parison, and a blowing gas is injected into the closed parison. In the parison length control method of the machine, in the test molding step, the relationship between the parison length of the resin to be used and the screw speed of the extruder is obtained in advance,
In the normal molding process, the current parison length is detected, the parison length difference between the current parison length and the target parison length is calculated, and the parison length difference is calculated from the relationship between the pre-determined parison length and the extruder screw rotation speed. A parison length control method for a blow molding machine, characterized in that a target parison length is obtained by calculating a correction amount of the extruder screw rotation speed according to the control and controlling the extruder screw rotation speed. 2. The width of the dead zone at which the extruder screw rotation speed is not corrected is set according to the variation of the current parison length within a relatively short time. A parison length control method for the blow molding machine described. 3. The method for controlling a parison length of a blow molding machine according to claim 1, wherein the parison light-shielding time measured by a photoelectric tube provided below the extruder is used as a value corresponding to the current parison length.