JPH0218017A - Molding equipment of plastic material - Google Patents

Abstract

PURPOSE:To prevent the breakage of a material holding mechanism and the like from occurring and further deliver the exact amount of material by a method wherein the speed of the driving motor of a material fluidizing mechanism is decreased in response to the pressure at the material inlet of a cylinder. CONSTITUTION:After a piston 10 compresses a compression spring, the spring pressure increases as the compression spring 17 is compressed, resulting in increasing the pressure at the material inlet of a cylinder 8. Thus, the speed of a driving motor 3 lowers in response to the pressure at the material inlet of the cylinder 8, resulting in stopping the driving motor 3 at a pressure just before the maximum compression of the compression spring 17. Further, the fluidizing mechanism 2 is controlled by both a servo motor and a digital switch. Furthermore, a relief valve 27 is provided at the delivery port 25 of a delivery mechanism 4. The relief pressure of the valve 27 is set higher than the vapor pressure of the material at the delivery port at its melting temperature so as to make the delivery pressure of the material higher than its vapor pressure, resulting in eliminating bubbles developing through vaporization in the material and consequently delivering the exact amount of the material.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a plastic material molding apparatus, and particularly to a plastic material molding apparatus having a material holding mechanism and a material metering and discharging mechanism.

(Prior Art) Fig. 3 shows a conventional plastic material molding device having a plastic material holding mechanism and a metering and discharging mechanism, where ■ is a plastic material supply hopper, 2 is a plastic material fluidization mechanism, 3 is its drive motor 4 9.10 is a material measuring and discharging mechanism for the material; 5 is a material holding mechanism inserted between the fluidization mechanism 2 and the measuring and discharging mechanism 4 via HALPRO and 7; 8 is a cylinder of this material holding mechanism 5; Cylinder pistons on the material side and the pressurizing chamber side, respectively; 11 is a piston rod that connects both pistons to each other; 12 is a pressurized fluid supply hole opened to the pressurizing chamber side in the cylinder 8; 13 is a material holding mechanism 5 14 is a mold that sequentially receives and takes the material intermittently discharged from the measuring and discharging mechanism 4; 15 is its transfer conveyor; 16 is a drive motor for the material and discharging mechanism 4; shows.

In the above-mentioned plastic material molding apparatus, the plastic material is heated and fluidized by the fluidization mechanism 2 and then turned into pulp 6.
The material in the cylinder 8 is metered by opening the pulp 7 and sending pressurized air to the pressurizing chamber in the cylinder 8 of the material holding mechanism 5. It is sent out to the discharge mechanism 4, and the driving Mogoo 1
Mold 1 on conveyor 15 by driving 6
4 intermittently.

(Problems to be Solved by the Invention) In such a plastic material molding device, material is introduced into the material holding mechanism 5, and the cylinder 8 of the material holding mechanism 5 is
If the pressure at the material inlet of the cylinder 8 increases beyond the pressure inside the pressurized chamber of the cylinder 8 as a result of the interior being filled with material, the pressure detector 13 detects this and stops the drive motor 3 of the fluidization mechanism 2. It looks like this.

However, even if the drive motor 3 is stopped, the drive motor 3
The operation of the fluidizing mechanism 2 is not stopped due to the stability of the fluidizing device 2 and the material is continuously fed into the cylinder 8 even after the pressurizing side piston 10 of the material holding mechanism 5 comes into contact with the rear wall of the cylinder 8. Therefore, as shown in FIG. 3, the pressure at the material inlet of the cylinder 8 increases shockingly, and there is a risk that the cylinder 8 and other parts may be destroyed.

Further, the amount of material that is intermittently supplied from the plastic material metering and discharging mechanism is determined by the product of the rotational speed of the drive motor 16 and the driving time, and this driving time is generally set by a timer.

However, the timer itself not only varies in operating time but is also affected by the ambient temperature, and the rotational speed of the drive motor varies greatly depending on the size of the load, fluctuations in the power supply voltage, etc.

The variation in the timer operating time is ±0.0 of the maximum setting time.
Many have a range of 3 to ±2%. In actual use, the maximum setting time is often set to about 173, and in that case, the variation in operating time will be three times the above, or ±0.9 to ±6%.
Become.

The influence of ambient temperature is approximately ±2% of the maximum setting time.

Therefore, for example, if you use a 120 second timer and set it to 60 seconds, the variation in operating time will be ±120 x O,02=2.
The influence of temperature for 4 seconds is ±120×0.02=2.4 seconds, so the variation becomes a large value of ±4.8150=9.6%.

Furthermore, in a metering and dispensing mechanism that intermittently dispenses a plastic material, such as a high-temperature molten polymer, the weight of each shot varies no matter how accurately the rotation of the dispensing pump is controlled.

The biggest cause of this variation is that moisture contained in the molten material vaporizes and becomes bubbles, which increases the volume of the material.Even if the discharge pump is controlled accurately and the discharge volume is accurate, The problem is that the weight is reduced by the amount of foam.

Therefore, in order to solve this problem, it is most effective to suppress the generation of water vapor, and for this purpose it is sufficient to maintain the pressure of the molten polymer above its vapor pressure.

(Means for Solving the Problems) The plastic material molding apparatus of the present invention is designed to eliminate the above-mentioned drawbacks, and includes a material fluidization mechanism, a material holding mechanism, and a material for the cylinder of this material holding mechanism. The material holding mechanism has an elastic body compressed by a piston in its cylinder, and the piston compresses the elastic body. When the pressure at the material inlet of the cylinder increases as a result of this, the speed of the drive motor of the material fluidization mechanism is reduced accordingly, and the plastic material metering and dispensing mechanism and the plastic material metering and dispensing mechanism are a servo motor for intermittently driving the servo motor, a pulse generator provided on the servo motor, a mechanism for setting the rotation speed of the servo motor, a digital mechanism for setting the total rotation speed, and a It has a control mechanism that controls the servo motor according to the total number of rotations and the number of pulses from the pulse generator, and is further inserted between the material discharge port and the discharge nozzle of the flexible material metering and discharge mechanism. , characterized in that it has a relief valve that opens when the material pressure at the material discharge port becomes greater than a relief pressure, and the relief pressure is made higher than the vapor pressure at the temperature of the material at the material discharge port.

(Function) According to the plastic material molding device of the present invention, other damage to the material holding mechanism due to material feeding due to the inertia of the drive motor and material fluidization mechanism can be prevented, and furthermore, it is possible to prevent material measurement and Variations in the operating time of the discharge mechanism can be greatly reduced, and furthermore, the discharge amount can be made accurate without creating bubbles due to vaporization in the material.

(Example) The present invention will be explained in detail below with reference to the drawings.

In the plastic material molding apparatus of the present invention, as shown in FIG. A variable speed motor is used as the motor 3, and the analog signal from the pressure detector 13 is changed to a digital signal via the A/D converter 18, and compared with the digital signal from the pressure setting value 19. Based on the result of this comparison, Via the controller 20, the speed of the drive motor 3 is caused to decrease in response to the increase in pressure at the material inlet of the cylinder 8.

In the present invention, a servomotor having a pulse generator 21 that generates, for example, 1000 to 4000 pulses per rotation is used as the drive motor 16, and instead of using a timer, the drive motor 16 is operated for a total time of the drive motor 16 within that time. The rotation speed of the drive motor 16 is specified using the volume 23 using a digital switch 22 that digitally specifies the rotation speed.
The signals from the digital switch 22 and volume 23 are processed by the control device 24 together with the signal from the pulse generator 21 to digitally control the servo motor.

Furthermore, in the present invention, a relief valve 27 is inserted between the discharge port 25 and the discharge nozzle 26 of the material metering and discharge mechanism 4, and a pressure sensor 28 is connected to the discharge port 25.
5 is higher than the relief pressure of the relief valve 27, the relief valve 27 opens so that the material is discharged from the discharge nozzle 26, and the relief pressure of the relief valve 27 is adjusted to the melting temperature of the material at the discharge port. Set higher than steam pressure.

Since the plastic material molding apparatus of the present invention has the above-mentioned configuration, from the time when material is introduced into the cylinder 8 until the pressurization chamber side piston 10 comes into contact with the tip of the compression spring 17, as shown in FIG. The pressure at the material inlet of the cylinder 8 is equal to the fluid pressure in the pressurizing chamber of the cylinder 8 and is approximately constant, but after the piston 10 starts compressing the compression spring, the spring pressure increases as the compression spring 17 is compressed. , which causes the pressure at the material inlet of the cylinder 8 to gradually increase. However, in the device of the present invention, the speed of the drive motor 3 is gradually reduced in response to this, and if the drive motor 3 is stopped at a pressure just before the compression spring 17 is compressed to the maximum, then the drive motor 3 may be Even if such inertia is taken into account, a sudden pressure increase does not occur at the material inlet of the cylinder 8 unlike in the conventional device.

Furthermore, in the present invention, the fluidization mechanism 2 is controlled by a servo motor and a digital switch, so for example, in order to rotate the drive motor 16 at 1000 revolutions per minute for 60 seconds, the number of pulses per revolution of the pulse generator 21 is set to 4000. The total number of pulses generated by the pulse generator 21 is 1000x60/60x4000 = 4xlOh, and since the rotational error of the drive motor 16 can be suppressed to 1 pulse, the variation is ±1/4x10' =
±0. OOOO25%.

In addition, a relief valve 2 is installed at the discharge port 25 of the material measurement and discharge mechanism 4.
7 is inserted to set this relief pressure higher than the vapor pressure at the melting temperature of the material at the discharge port, so that the material discharge pressure is always higher than the vapor pressure, and the material is discharged without creating bubbles in the material due to vaporization. There is a great benefit in being able to make the quantities accurate.

(Effects of the Invention) As described above, the present invention has the great advantage of being able to eliminate the conventional drawbacks.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the plastic material molding apparatus of the present invention, FIG. 2 is an explanatory diagram of its operation, FIG. 3 is an explanatory diagram of a conventional plastic material molding apparatus, and FIG. 4 is an explanatory diagram of its operation. 1... Plastic material supply hopper 2... Fluidization mechanism, 3... Drive motor, 4... Measuring and discharging mechanism, 5
...Material holding mechanism, 6.7...Pulp, 8...Cylinder 9.10...Cylinder piston, 11...
・Piston rod 12...pressurized fluid supply hole, 13...
・Pressure detector, 14...Mold, 15...Transfer conveyor, 16...Drive motor 17...Compression spring, 18...A/D converter, 19...Pressure setting value, 20 ...Controller, 21...Pulse generator, 22...Digital switch, 23...Volume, 24...Control device 25...Discharge port, 26...
Discharge nozzle, 27... relief valve, 28... pressure detector.

Claims (1)

[Claims] 1. A material fluidization mechanism, a material holding mechanism, and a mechanism for detecting the pressure at the material inlet of a cylinder of this material holding mechanism;
a variable speed mechanism of the fluidization mechanism, the material holding mechanism having an elastic body compressed by a piston in the cylinder, and the piston compressing the elastic body to increase the pressure at the material inlet of the cylinder. If the increase occurs, the speed of the drive motor of the material fluidization mechanism is reduced accordingly, and a servo motor for intermittently driving the plastic material metering and discharging mechanism and the plastic material metering and discharging mechanism is provided. , a pulse generator provided in this servo motor, a mechanism for setting the rotation speed of the servo motor, a digital mechanism for setting the total rotation speed, and the rotation speed and total rotation speed of these servo motors and pulses from the pulse generator. and a control mechanism for controlling the servo motors according to the number of plastic material measuring and discharging mechanisms. 1. An apparatus for molding a plastic material, comprising a relief valve that opens when the pressure increases, and the relief pressure is higher than the vapor pressure at the temperature of the material at the material discharge port. 2. The plastic material molding apparatus according to claim 1, wherein the elastic body is a compression spring of a predetermined length provided to protrude from the rear wall of the cylinder. 3. The plastic material molding apparatus according to claim 1, wherein the material is a molten polymer.