JPH06315972A - Continuous and stable injection of parison in blow molding machine - Google Patents

Abstract

PURPOSE:To stabilize the viscosity of a resin and to make the length of a parison constant by measuring the temp. of the molten resin in an extruder to calculate the difference with the previous resin temp. and integrating a proportionality factor with this difference to calculate the correction number of rotations and setting this correction number of rotations to the corrected set number of rotations of a screw to perform temp. correction. CONSTITUTION:The pellet like resin in a hopper 36 is supplied to the inner hole 33a of an extruder 33 and melted under heating while a screw 35 is rotated and the molten resin 15 is stored in an accumulator 32 while a plunger 38 is allowed to retreat. Next, when the plunger 38 is allowed to advance, the resin 15 is supplied to a die 10 through a resin passage 31 to be molded as a parison 50. At this time, the temp. of the molten resin 15 extruded from the extruder 33 is measured to calculate the difference with the previous resin temp. and a proportionality factor preliminarily obtained on the bases of a rule of thumb is integrated with this difference to calculate the correction number of rotations. The correction of the set number of rotations of the screw is performed on the basis of this correction number of rotations and the temp. of the molten resin is controlled so as to become desired temp. until the next extrusion supply.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous and stable parison injection method in a blow molding machine.

[0002]

2. Description of the Related Art Conventionally, when blow molding is performed by a blow molding machine, molten resin supplied from an extruder is stored in an accumulator in an amount corresponding to the amount of a molded product, and then a die is moved by moving a plunger in the accumulator. The desired product was obtained by injecting air into the parison by ejecting the resin in a tube shape from the ejection port.

[0003]

However, in the conventional extruder, the resin temperature when the resin melted in the extruder is accumulated in the accumulator may fluctuate for each extrusion supply. Once the temperature of the resin accumulated in the accumulator begins to change, the extrusion melting of the next extrusion supply and the accumulated load on the accumulator change, and the resin temperature also changes and may not stabilize to a constant resin temperature value. The length of the parison changes as the resin temperature changes,
Alternatively, there is a problem in that the weight of the molded product fluctuates and a defective molded product is likely to occur.

The present invention has been made in view of the above problems, and an object thereof is to obtain a parison of a constant length by controlling the temperature in the vicinity of the exit of the extruder so that the molten resin temperature becomes constant between each extrusion supply. To do.

[0005]

In order to achieve the above object, in the present invention, a blower equipped with an accumulator having a front end resin passage joined to a die and an extruder having the front end resin passage joined to this accumulator. Using the feeder of the molding machine, the temperature sensor attached near the exit of the extruder is used to measure the temperature of the molten resin extruded from the extruder, and the difference in resin temperature between the pre-extrusion supply and the current extrusion supply is measured. In addition to the calculation, the corrected rotation speed calculated by integration with the predetermined proportionality constant was taken into consideration, and the temperature was corrected as the correction set rotation speed of the screw at the time of the current extrusion feed.

[0006]

[Function] When the resin is supplied from the hopper to the extruder and the screw is rotated while heating the resin, the resin is melted and the molten resin is stored in the accumulator while the plunger is retracted. The temperature of the resin extruded from the extruder is measured by a temperature sensor installed near the machine outlet, and the temperature difference between the pre-extrusion feed and the current extrusion feed is multiplied by a preset constant of proportionality to perform arithmetic processing and extrusion. The rotation speed of the extruder screw is adjusted so that the resin extruded from the machine and directed to the accumulator has a desired resin temperature. Therefore, the resin temperature can be controlled to a stable temperature that does not vary for each extrusion supply by quantifying the resin temperature.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments of a parison continuous stable injection method in a blow molding machine according to the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a schematic cross-sectional view of a resin supply device for a die according to the present invention, and FIG. 2 is a diagram showing the relationship between the temperature of molten resin for each supply extruded from an extruder and the screw rotation speed of the extruder. . In FIG. 1, the blow molding machine 1 is provided with a pair of platens 21 which are erected on the floor, and dies 22 and 23 having vertical joint surfaces are fixed to each platen 21. Mold open / close cylinders are fixed to the cylinders (not shown) provided outside the left and right platens 21, and the molds 22 and 23 are mounted on the piston rods of these mold open / close cylinders, respectively. The molds 22 and 23 are opened and closed by advancing and retracting the piston rod.

A vertical die 10 equipped with a controller (not shown) is provided directly above the joining surfaces of the molds 22 and 23. The die 10 has a die housing 12 made of a rectangular block, and a mandrel 16 having a diameter smaller than that of the through hole 14 is inserted into the through hole 14 having a substantially circular cross section along the longitudinal center line. , The mandrel 1
The cylindrical passage 18 is provided between the outer peripheral surface of 6 and the inner peripheral surface of the through hole 14.
Is formed. A parison control mandrel 20 is attached to the lower end of the mandrel 16 so as to be able to go in and out, and this faces the opening of the through through hole 14 and
A mandrel lip 24 that forms a ring-shaped resin discharge port 25 is integrally provided with the opening. Also,
A passage 26 for supplying the molding resin to the tubular passage 18 is formed on the upper side wall of the mandrel 16, and the tubular passage 18 is filled from the inside of the resin introducing chamber 27 formed in the upper portion of the mandrel 16 through the passage 26. I have to.

The die 10 is additionally provided with a resin supply device indicated by reference numeral 30. This resin supply device 3
0 has an accumulator 32 formed in a cylindrical shape and having a resin passage 31 at the front end portion joined to the die 10.
The accumulator 32 has an extruder 3 which is orthogonal to the accumulator 32.
The resin passage 34 formed at the tip of the No. 3 is joined. A shut-off valve 41 is provided at the outlet of the extruder 33, and a shut-off valve 42 is provided at the outlet of the accumulator 32.
4 is cut off.

The screw 35 is rotatably engaged with the inner hole 33a of the extruder, and the extruder 33 is provided with a hopper 36 as a supply port for supplying pelletized resin to the inside thereof. Has been. Furthermore, accumulator 3
A plunger 38 which is driven by an injection cylinder (not shown) and moves back and forth is fitted in the second inner hole 32a. A thermocouple 40 is arranged on the way of the resin passage 34 near the outlet of the extruder 33, and the temperature of the molten resin immediately after being extruded from the extruder 33 can be measured. This is because the mounting position of the thermocouple 40 is set to a location where the molten resin passage area is small and the molten resin does not stay, and the temperature change of the molten resin extruded from the extruder 33 is detected as quickly as possible.

A heating heater 37 such as a band heater or a sheath heater is wound around the resin passages 31 and 34, the accumulator 32, and the extruder 33 so that the temperature of each device can be controlled. That is, a heater 37a is wound around the resin passage 31, a heater 37b is wound around the accumulator 32, a heater 37c is wound around the resin passage 34, and a heater 37d is wound around the extruder 33.

The blow molding machine having such a structure is used to continuously and stably inject the parison.
This is supposed to be done as follows. When the shut-off valve 41 is opened and the shut-off valve 42 is closed, the pellet-shaped resin is supplied from the hopper 36 to the inner hole 33a of the extruder 33 and the screw 35 is rotated while heating the resin. The molten resin 15 (hereinafter, simply referred to as resin 15) is melted by the plunger 38
Is stored in the accumulator 32 while retreating.
Next, when the shutoff valve 41 is closed and the shutoff valve 42 is opened to move the plunger 38 forward, the resin 15 is supplied to the die 10 through the resin passage 31.

The resin 15 supplied to the die 10 is injected toward both cavities of the opened molds 22 and 23 to form a parison 50 which is a resin cylinder. The length of the parison 50 is adjusted. The temperature of the resin 15 is adjusted depending on the rotation speed of the screw 35 of the extruder 33.
It becomes possible by adjusting the viscosity of. That is, resin 1
5 When the temperature is high, the viscosity is generally low, and the length of the parison 50 injected from the die 10 is longer than the desired length due to drawdown. Conversely, when the temperature of the resin 15 is low, the viscosity is integrally increased and the die is The length of the parison 50 ejected from 10 is shorter than the desired length.

As described above, regarding the relationship between the temperature and the viscosity of the resin 15, it is important to obtain the resin 15 having a constant viscosity while keeping the temperature of the resin 15 constant, and as a result, the stable injection of the parison 50 is performed. Will be done. From this, in order to obtain a constant viscosity, in this embodiment,
The above-mentioned adjustment of the rotational speed of the extruder screw 35 is performed. When the rotation speed of the screw 35 is increased, the shear heat insulation of the resin between the inner hole 33a of the extruder 33 and the screw 35 is increased and the temperature of the resin 15 is increased. Conversely, when the rotation speed of the screw 35 is decreased, the shear heat insulation is increased. Is decreased and the temperature of the resin 15 is decreased. In this case, the resin passage 3
1, 34, the accumulator 32, and the heaters 37 wound around the extruder 33 do not perform adjustment.

In this embodiment, the resin temperature (T _n ) of the pre-extrusion supply extruded from the extruder 33 under the condition of the set rotational speed (R _m ) of the screw 35 set during the pre-extrusion supply,
Now, by calculating the resin temperature (T _{n + 1} ) of the extrusion feed, and multiplying this by the proportional constant α obtained beforehand based on the empirical rule, the corrected rotation speed (converted to the corrected rotation speed) is obtained. , Set rotation speed of screw 35 rotation speed (R _{m + 1} ) at this time of extrusion supply
Is corrected and the molten resin temperature is controlled to reach the desired temperature T by the next extrusion supply (hereinafter referred to as the next shot). These are performed based on the following Equation 1.

[0017]

## EQU1 ## R _{m + 1} = R _m −α (T _{n + 1} −T _n ).

In the above formula, T _n is the resin temperature at the time of pre-extrusion supply, T _{n + 1} is the resin temperature at the time of pre-extrusion supply, R _m is the set rotational speed of the screw at the time of pre-extrusion supply, R _{m + 1} Is the corrected set rotational speed of the screw at the time of extrusion supply.

If T _{n + 1} > T _n , the set rotational speed of the screw 35 is lowered until the next shot.
Conversely, when _{n + 1} <T _n , the screw 3
The number of rotations set in 5 is increased. In this embodiment, the resin temperature converges to the desired temperature T while the above operation is repeated several times. After the parison 50 thus obtained is sandwiched between the molds 22 and 23, gas such as air is blown into the parison 50, and then the resin 15
When is fixed by cooling, a hollow molded article is obtained.

[0020]

As is apparent from the above description, according to the present invention, there is provided the accumulator having the front end resin passage joined to the die and the extruder having the front end resin passage joined to the accumulator. The temperature of the molten resin extruded from the extruder is measured by a temperature sensor mounted near the exit of the extruder using the blower feeder, and the difference in resin temperature between the pre-extrusion feed and the current extrusion feed is measured. Is calculated, and the correction speed calculated by integrating with the predetermined proportional constant is taken into consideration, and the temperature is corrected as the corrected set speed of the screw at the time of the current extrusion supply. Since the temperature of the molten resin can be kept constant during the period, the resin viscosity is stable and the parison length is always constant, enabling continuous stable molding. In addition, the resin temperature is constant and a stable surface texture is obtained. Furthermore, since the conditions can be easily set, the resin loss (waste) until the injection becomes stable can be reduced, and it becomes easy to deal with different molded products (measured values).

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a resin supply device for a die according to the present invention.

FIG. 2 is a diagram showing the relationship between the temperature of the molten resin for each supply extruded from the extruder and the screw rotation speed of the extruder.

[Explanation of symbols]

 1 Blow Molding Machine 10 Die 12 Die Housing 15 Molten Resin 16 Mandrel 22,23 Mold 30 Resin Supply Device 31,34 Resin Passage 32 Accumulator 33 Extruder 35 Screw 37 (37a, 37b, 37c, 37d) Heater 38 Plunger 40 Thermocouple 41,42 Shut-off valve

Claims (1)

[Claims] 1. A blow molding machine supply device equipped with an accumulator having a front end resin passage joined to a die and an extruder having a front end resin passage joined to the accumulator, which is mounted near an exit of the extruder. The temperature sensor measures the molten resin temperature for each feed extruded from the extruder, calculates the resin temperature difference between the pre-extrusion feed and the current extrusion feed, and calculates it by integrating with the pre-specified proportional constant. A parison continuous stable injection method in a blow molding machine, characterized in that the temperature is corrected as a corrected set rotational speed of the screw at the time of feeding the extrusion now, taking into account the corrected rotational speed.