JPH0446901Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a resin thermal decomposition prevention device for an injection molding machine, and particularly to a resin thermal decomposition prevention device for a screw-in-line injection molding machine.

[Prior art] Conventionally, there are many types of resins used for molding in screw-in-line injection molding machines, but among them, crystalline resins such as nylon, polycarbonate, and vinyl chloride are Overheating tends to cause thermal decomposition, and in open-nozzle injection molding machines, for example, during the pressure holding and cooling process, the injection nozzle tip is pressed against the mold and the mold is filled with resin, so some abnormalities may occur. If the molding machine stops due to this, gas will not only be generated from the resin accumulated in the heating cylinder, but also the internal pressure of the heating cylinder will rise abnormally, causing resin material to eject from the hopper, creating a dangerous situation for workers. It may become.

In addition, in injection molding machines equipped with a shut-off valve in the injection nozzle, the injection nozzle is closed except during the injection and pressure-holding processes, so if the resin material is squirted from the hopper or the shut-off valve is opened inadvertently. There is a particularly high risk of molten resin suddenly spewing out from the injection nozzle. Therefore, in the case of molding operations using resin materials that are prone to thermal decomposition, the residual resin must be discharged manually in advance to prevent thermal decomposition of the resin due to overheating.

[Problem to be solved by the invention] However, if an abnormality is detected during semi-automatic or fully automatic operation of the injection molding machine, or if the molding machine stops after completing the scheduled number of moldings, the above-mentioned problem will occur. There is a risk of resin material ejecting.
Particularly in molding machines equipped with a shut-off valve in the injection nozzle, there is a problem that the danger is high.

This invention focuses on the above-mentioned conventional problems, and has a simple structure. Even if the injection molding machine stops during unattended operation, the internal pressure of the heating cylinder increases due to volume expansion due to overheating of the resin retained in the heating cylinder, resulting in a dangerous situation. It is an object of the present invention to provide a device that can prevent this from occurring by opening the tip of the injection nozzle.

[Means for Solving the Problem] In order to achieve the above object, the resin thermal decomposition prevention device for an injection molding machine according to the present invention has the following features in claim 1:
In an injection molding machine consisting of an open nozzle type injection device in which the injection nozzle is not equipped with a shut-off valve and a mold device, the injection device includes a drive device that moves the injection device back and forth with respect to the mold device, and a drive device that moves the injection device back and forth with respect to the mold device, and a drive device that moves the injection device back and forth with respect to the mold device. A detector detects that the mold device is being pressed, a detector detects that the mold device is closed, and the resin is sealed in a heating cylinder that constitutes the injection device by these two detectors. a timer that is activated upon detecting that the heating cylinder is in the sealed state and continues counting while the heating cylinder continues the sealed state; and a timer that inputs a time-up signal from the timer to separate the injection nozzle from the mold device. The present invention is characterized by comprising a control device that outputs a signal for retracting the injection device from the mold device to the drive device.

According to a second aspect of the present invention, in an injection molding machine comprising a closed injection device having a shut-off valve in an injection nozzle and a mold device, a drive device for moving the injection device back and forth with respect to the mold device; A valve driving device, a detector that detects that the injection nozzle is pressed against the mold device, and a detector that detects that the mold device is closed, and by these two detectors. A timer is activated upon detecting that the resin is sealed in the heating cylinder constituting the injection device, and continues counting while the heating cylinder remains in the sealed state, and a time-up signal from the timer is input. Then, in order to separate the injection nozzle from the mold device, a signal for retracting the injection device from the mold device is output to the drive device of the injection device, and a signal to open the shut-off valve is output to the drive device for the shut-off valve. It is characterized by comprising a control device that outputs output to the drive device.

[Operation] According to the above configuration, by detecting that the mold device is closed while the injection nozzle is pressed against the mold device, it is detected that the resin is sealed in the heating cylinder. When the timer starts counting, and the heating cylinder continues to be in the sealed state for a certain period of time, the timer's time-up signal determines that the molten resin in the heating cylinder has been overheated, and the injection device is turned off. By retreating from the mold device and separating the injection nozzle from the mold device, the volume-expanded molten resin in the heating cylinder is automatically discharged to the outside from the injection nozzle, so that the resin is not thermally decomposed. This can prevent the liquid from spewing out from the hopper or nozzle.

Further, in claim 2, when it is detected that the resin is sealed in the heating cylinder by detecting that the mold device is closed while the injection nozzle is pressed against the mold device; When the timer starts counting and the heating cylinder continues to be in the sealed state for a certain period of time, the timer's time-up signal determines that the molten resin in the heating cylinder has been overheated, and the injection device is inserted into the mold. By retreating from the apparatus, pulling the injection nozzle away from the mold apparatus, and opening the shut-off valve, the volumetrically expanded molten resin in the heating cylinder is automatically discharged to the outside. It is possible to prevent thermal decomposition and spouting from the hopper or nozzle.

[Example] Hereinafter, an example of the resin thermal decomposition prevention device for an injection molding machine according to the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an embodiment of an open nozzle injection molding machine, in which an injection device front end limit switch 1a and an injection device rear end limit switch 1b are provided near the forward and backward stroke ends of the injection device 1, and inside the controller 2. is timer 2
A is provided. Further, the movable platen 21 is provided with a mold closing detection sensor 22 that detects that the mold 4 is closed.

When the injection device 1 is advanced to press the injection nozzle 3 of the injection molding machine against the mold 4, the front end limit switch 1a of the injection device is turned on, and the mold closing state is detected by the mold closing detection sensor 22. In this state, a signal is sent to start the timer 2a in the controller 2 as shown in FIG.
The solenoid is energized, the injection device forward and backward movement cylinder 6 is operated, and the injection device 1 is moved backward until the injection device rear end limit switch 1b is turned on, and the tip of the injection nozzle 3 is separated from the mold 4, so that the inside of the heating cylinder 1c is When the molten resin that has been staying in the injection nozzle 3 expands in volume due to overheating, it is naturally discharged from the injection nozzle 3. If the injection device 1 is retracted before the timer set time has elapsed and the front end limit switch 1a of the injection device is turned OFF, or if the mold is opened and the mold closing detection sensor 22 is turned OFF, the timer 2
a is reset at that point.

Fig. 3 shows an example of an injection molding machine with a shut-off valve.
A rotary shut-off valve 3b is provided which is opened and closed by a servo motor 7 via a, and the servo motor 7 is connected to the controller 2 via a servo amplifier 8. The rod 3a is connected to an output shaft provided with a ball screw in the servo motor 7, and an open end limit switch 7a, a closed end limit switch 7b, and a shut-off position limit switch 7c shown in FIGS. 4 and 5 are attached to the output shaft. and is connected to the valve opening sensor 9 and the tacho generator 10,
The wiring of the valve opening sensor 9 is connected to the controller 2.
The wiring of the tacho generator 10 is connected to the servo amplifier 8, respectively. Further, as in the embodiment of the open nozzle injection molding machine, an injection device front end limit switch 1a and an injection device rear end limit switch 1b are provided near the forward and backward stroke ends of the injection device 1, respectively. The controller 2 includes the shut-off position limit switch 7c.
It has a built-in timer 2a that starts when turned on.

In normal molding operations, the controller 2 instructs the servo amplifier 8 to open and close the shutter-off valve 3b based on the molding conditions, and operates the shutter while receiving feedback signals from the valve-opening sensor 9 and the tacho generator 10. The opening degree and opening/closing speed of the to-off valve 3b are controlled.

Now, when the shut-off valve 3b is closed and the shut-off position limit switch 7c is turned on, the timer 2a in the controller 2 is started, and when the timer set time has elapsed, the controller 2 issues an injection device retraction command and the injection device forward/backward movement valve 5 is activated. The solenoid is energized, the injection device forward and backward movement cylinder 6 is operated, and the injection device 1 is moved backward until the injection device rear end limit switch 1b is turned on, and the tip of the injection nozzle 3 is separated from the mold 4, and the shutter off valve 3b is turned on. A signal is given to the servo amplifier 8 to open the valve at a constant speed, and the servo motor 7 is operated until the open end limit switch 7a is turned on, fully opening the shut-off valve 3b, as shown on the right side of Fig. 6, and the retained resin that has expanded in volume is discharged. Excrete naturally.

Even when the shutoff valve 3b is open, the injection nozzle 3 is pressed against the mold 4, the front end limit switch 1a of the injection device is turned on, and the mold closing state is detected by the mold closing detection sensor 22. When the timer 2a starts and the timer set time has elapsed, the injection device 1 is moved backward until the rear end limit switch 1b is turned on, and the tip of the injection nozzle 3 is inserted into the mold, as in the case of the open nozzle injection molding machine described above. After separating from 4,
The shutoff valve 3b is fully opened to discharge the molten resin in the heating cylinder 1c.

Before the timer set time is reached, the shut-off valve 3b opens and the shut-off position limit switch 7c is turned off, and the injection device 1 is moved back and the front end limit switch 1a of the injection device is turned off.
OFF, and when the mold closing detection sensor 22 is OFF and the mold is open, the timer 2a is reset at that point.

In this embodiment, a limit switch is used to detect the forward and backward movement position of the injection device, the opening/closing detection of the shutoff valve, and the mold closing detection, but the present invention is not limited to this, and potentiometers, encoders, etc. may also be used. In addition, the injection nozzle shut-off mechanism may be a rotary variable valve or a needle valve, and the present invention is also applicable to systems that use hydraulic or mechanical link mechanisms in addition to servo motors as means for opening and closing the shut-off valve. I can do it.

[Effects of the invention] As explained above, according to the invention, the resin that is sealed in the heating cylinder and expands in volume is naturally discharged by opening the injection nozzle after a certain period of time has elapsed. Even during operation, jetting from the hopper or nozzle due to thermal decomposition of the resin can be prevented, resulting in the effect of improving the safety of the injection molding machine.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional explanatory diagram of an open nozzle injection device of an injection molding machine according to an embodiment, FIG. 2 is a timer-related block diagram of the open nozzle injection device, and FIG.
The figure is a cross-sectional explanatory diagram of an injection device equipped with a shut-off valve in the injection nozzle. Figure 4 is an explanatory diagram of the arrangement of a limit switch that is installed in a servo motor and inputs the opening and closing of the shut-off valve to a timer. Figure 5 is an explanatory diagram of the limit switch. FIG. 6 is a timing chart showing the relationship between the shut-off valve and the timer operation. 1... Injection device, 1c... Heating cylinder, 2a
...Timer, 3...Injection nozzle, 3b...Shut-off valve, 6...Actuator (injection device forward and backward movement cylinder).

Claims (1)

[Claims for Utility Model Registration] (1) In an injection molding machine consisting of an open nozzle type injection device in which the injection nozzle is not equipped with a shut-off valve and a mold device, a drive for moving the injection device back and forth with respect to the mold device. a detector for detecting that the injection nozzle is pressed against a mold device; and a detector for detecting that the mold device is closed; A timer is activated when it detects that the resin is sealed in the heating cylinder constituting the heating cylinder, and continues counting while the heating cylinder remains in the sealed state, and a time-up signal from the timer is input, and the timer is activated. A resin thermal decomposition prevention device for an injection molding machine, comprising a control device that outputs a signal to the drive device to cause the injection device to retreat from the mold device in order to separate the injection nozzle from the mold device. (2) In an injection molding machine comprising a closed injection device with a shut-off valve in an injection nozzle and a mold device, a drive device for moving the injection device back and forth with respect to the mold device, and a drive device for driving the shut-off valve. a detector for detecting that the injection nozzle is pressed against a mold device; and a detector for detecting that the mold device is closed; A timer is activated when it detects that the resin is sealed in the heating cylinder constituting the heating cylinder, and continues counting while the heating cylinder remains in the sealed state, and a time-up signal from the timer is input, and the timer is activated. A signal for retracting the injection device from the mold device in order to separate the injection nozzle from the mold device is output to the drive device of the injection device, and a signal to open the shut-off valve is output to the drive device for the shut-off valve. A resin thermal decomposition prevention device for an injection molding machine, comprising a control device that outputs an output.