JPS584616B2 - Mold monitoring device - Google Patents

Description

Detailed Description of the Invention The present invention provides a mold monitoring device for monitoring molds used in molding machines for plastics, aluminum alloys, etc. More specifically, by monitoring only the movable side mold of the mold, Related to a mold monitoring device that can detect whether product remains in either the side mold or the fixed mold and prevent the next mold clamping from being performed with the product remaining. It is something.

Plastic injection molding machines use two molds, a movable side mold and a fixed side mold (hereinafter simply referred to as the movable side and fixed side, respectively), and the movable side is strongly pressed against the fixed side to form the mold. After tightening, molten plastic material is pressurized and filled into the mold cavity.

After the plastic material has cooled and solidified, the movable side is separated from the fixed side and the mold is opened.

At this time, the molded product remains on the movable side.

Next, after opening the mold, the ejector pin is pushed out to take out the product remaining on the movable side, and then the movable side is moved to the fixed side and the mold is clamped again.

This plastic injection molding machine has a fairly strong mold clamping force, so if the product or runner remains in the mold, the expensive mold may be destroyed when the mold is clamped. Or the product may become defective.

Therefore, a mold monitoring device is generally installed in an injection molding machine to monitor whether there is any product or runner left in the mold.

Conventionally, many of these monitoring devices have been of the weighing type.

This weighing-type monitoring device compares the total weight of dropped or removed plastic material with a preset standard weight, and if the item, runner, or part thereof is lighter than the standard weight, the item, runner, or part thereof is removed from the mold. This system is designed to send a signal to the control system of the molding machine to prevent mold clamping if the mold remains in the mold.

However, with this weighing-type monitoring device, it is difficult to confirm the difference in weight when the unit weight of the product is extremely small, and in order to prevent malfunctions due to the falling speed of the product, the weighing scale stops shaking. have to wait for
Therefore, there was a drawback that confirmation required a long time.

As is well known, in injection molding, an extremely large number of products are molded in a cycle measured in seconds, so a loss time of 1 second or 2 seconds leads to a significant increase in costs.

Furthermore, a device has been proposed in which, for example, a photoelectric switch consisting of an LED and a phototransistor is used to confirm that the product has passed between the LED and the phototransistor and then permit mold clamping. There is a risk of malfunction if part of the product remains in the mold, or if only part of the product is ejected in the case of multi-piece molding.

In view of the above-mentioned drawbacks, the present invention has been developed in such a way that the molded product or a part thereof is located on the movable side and on the movable side. It is an object of the present invention to provide a mold monitoring device that is capable of accurately and accurately detecting a mold remaining on any fixed side in a short period of time.

A further object of the present invention is to provide a mold monitoring device that can monitor both the fixed side and the movable side of a mold with one mold monitoring device.

．． 1 The mold monitoring device of the present invention uses an imaging means such as a television camera or an optical system to monitor the mold at a predetermined position when mold opening is completed (or during the mold opening process) and when product ejection is completed (or during the mold clamping process). Monitor the movable side of the mold, form an image of its inner surface onto an imaging medium such as a cathode ray tube or focus plate, and measure the brightness of the image on this imaging medium with a suitable measuring means to determine the brightness at both points. By comparing the brightness or comparing these brightness with the reference brightness, monitor whether the product remains on the movable side or the fixed side and whether the product is correctly ejected from the movable side. It is characterized by the fact that

That is, it photoelectrically detects whether a product remains in the mold based on the difference in brightness between the mold image and the product image.

If the product remains in the mold, the product image is formed on the imaging medium, and if no product remains, the mold image is formed on the imaging medium.

Therefore, the brightness will vary depending on the presence or absence of the product.
By appropriately selecting the reference brightness within the range of the brightness of the mold image and the product image and comparing the brightness of the image on the imaging medium with the standard brightness, it is possible to know whether there is any product remaining in the mold. can.

Further, since the mold is opened while the product remains on the movable side, by monitoring only the movable side, even if the product remains on the fixed side, this can be indirectly detected.

Therefore, it is possible to obtain the effect of monitoring both the movable side and the fixed side with one monitoring device.

In addition, the present invention involves once forming an image of the mold on an imaging medium,
Since the brightness of the image on the imaging medium is measured, the desired measurement area can be easily selected and changed on the imaging medium, making it extremely easy to operate during installation and convenient for practical use. It is.

As the imaging means, a television or an optical system can be used; in the former case, the imaging medium is a cathode ray tube, and in the latter case, a focus plate.

In particular, when a combination of a television, that is, a television camera and a receiver is used, (1) the contrast and brightness of the screen can be adjusted freely, and matching with the sensor (measuring means) can be performed extremely easily.

(2) By adjusting the contrast of the screen and increasing the brightness difference between the product image and the mold image, detection sensitivity can be extremely easily increased.

(3) By adding an automatic brightness adjustment device, the brightness level can be automatically adjusted following changes in external light, and the input level to the sensor can be kept constant.

(4) When a color television is used, hue adjustment, color signal level adjustment, etc. can be performed, and the difference in brightness between the product image and the mold image can be further increased.

There are advantages such as

As the measuring means, a brightness sensor such as CdS or silicon blue cell is used.

If only one product is being molded at a time, a single brightness sensor may be sufficient, but if you use multiple brightness sensors and arrange them in a matrix over the entire image plane, it will be possible to detect even if a part of the product remains. It is desirable because it can be done.

If the mold has multiple molds, it is desirable to use multiple brightness sensors to monitor each product.

Instead of monitoring the entire surface of the mold, it is possible to monitor only the areas where part of the product is likely to remain.

Various methods can be considered for holding the brightness sensor on the image of the imaging medium, for example, a suction cup may be used, or a holding frame having a plurality of insertion holes in a grid or honeycomb shape may be used. held on the imaging medium by a method of
A brightness sensor may be inserted and held within the insertion hole.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a part of the injection molding machine and a television camera.

The injection molding machine 1 has two molds on a fixed side 2 and a movable side 3.
divided.

The movable side 3 moves forward (moves to the right in the figure) guided by the tieper 4 during mold clamping, and overlaps the fixed side 2.

The cavity formed by the movable side 3 and the fixed side 2 is filled with a hot melted plastic material from a nozzle 5 attached to the fixed side 2.

After the molded product has solidified and cooled, the movable side 3 moves back (
(to the left in the figure), and the mold is opened.

When the movable side 3 moves back and hits the protrusion 7, the protrusion pin 8 provided on the movable side 3 is advanced by the protrusion 7 to eject the product from the movable side 3.

After this product is ejected, the movable side 3 moves forward again to perform mold clamping.

A television camera 9 is installed to photograph the inner surface of the movable side 3 when the movable side 3 is in a predetermined position, and monitors the state of the movable side.

In order to detect that the movable side 3 is at the predetermined position (hereinafter referred to as the monitoring position), a position detection limit switch 1 is used.
0 is provided, and when the movable side 3 is in the monitoring position, ONL sends a monitoring command signal to the monitoring device.

In addition, in the plastic injection molding machine, when the movable side 3 retreats to a certain position after the start of mold opening, that is, to the mold opening completion position, it issues a mold opening completion signal and temporarily stops, and the ejecting part 7 moves forward by hydraulic drive and closes the ejecting pin. There is a mechanism that ejects the product by pressing 8, and when 7 returns to its original position, it issues an ejection completion signal and starts mold clamping, and this is called an injection molding machine with a hydraulic ejector.

In such a molding machine with a hydraulic ejector, if the monitoring position is selected as the mold opening completion position, the monitoring command signal can be taken out from inside the molding machine as a mold opening completion signal and an ejection completion signal, and the limit switch 10 There is no need to provide a special setting.

However, even in this case, it is also possible to provide the limit switch 10 and perform the same monitoring.

FIG. 2 is a perspective view of a measuring section that measures the brightness of an image.

A video signal of the movable side 3 captured by a television camera 9 is sent to a receiver 12 having a cathode ray tube 21.

In this embodiment, the movable side 3 is an eight-cavity mold, and has eight core parts 13-20.

Brightness sensors 30 to 37 are attached above the images 22 to 29 of the eight core parts 13 to 20 on the cathode ray tube 21 to measure the brightness of these images 22 to 29, respectively.

FIG. 3 is a block diagram schematically showing an apparatus according to the present invention.

The inner surface of the movable side 3 is projected onto a cathode ray tube 21, and the light from the inner surface of the movable side 3 is measured by brightness sensors 30 to 37 using the cathode ray tube 21 as a medium.

The brightness signals measured by the brightness sensors 30 to 37 are compared with reference brightness levels by comparators 38 to 45 to determine their magnitude.

It is set by this reference brightness level setter 46.

The reference brightness level is a reference value for determining whether a product remains in the mold, and is therefore set within the range from the brightness of the mold image to the brightness of the product image.

When the standard brightness is set to the brightness of the mold image, when the brightness signal from the brightness sensor matches the standard brightness level, it is determined that there is no product in the mold, and when it does not, there is no product in the mold. It is determined that the product is present.

On the contrary, when the reference brightness is set to the brightness of the product image, it is determined that there is a product in the mold when both brightnesses match.

Furthermore, when the reference brightness is set to an intermediate value between the mold image and the product image, the presence or absence of the product is determined according to the magnitude relationship between the reference brightness level and the brightness signal from the brightness sensor.

For example, when the brightness of the product image is higher than the brightness of the mold image, it is determined that the product is present when the brightness signal from the sensor is greater than the reference brightness, and it is determined that the product is absent when it is smaller.

In this way, the presence or absence of a product is detected from the difference in brightness between the product image and the mold image, so if the brightness difference is small, it is desirable to adopt a method of enlarging this difference. There are methods such as applying paint to the surface, using a color filter, and linearly changing the input of light to the imaging means and the output of the brightness sensor, that is, varying the γ value.

The use of color filters is particularly effective when the product is colored.A filter of the same color or complementary color as the product is placed in front of the imaging means or in front of the brightness sensor.
This is a method of increasing the brightness difference between the product image and the mold image.

In addition, the method of varying the γ value is to use a television camera as the imaging means,
The imaging medium is particularly useful when using a television receiver.

The γ value is a constant defined by the relational expression E=CLr, where the light is input to the imaging means and the output of the brightness sensor placed on the imaging medium is E. Here, C is a proportional It is a constant.

When γ-1, the input and output are in a proportional relationship, and faithful brightness reproduction can be achieved.

When γ〉1, the output is compared to the input by expanding the white level, that is, the bright input, and reducing the black level, that is, the dark input, and γ〈l.
The opposite is true when .

Therefore, compare the light input of the product image and the mold image, and if the product image is even slightly brighter than the mold image, adjust the γ value by appropriate means so that γ>1. Then, the sensor output obtained from the product image and mold image will be magnified.

When the product image is darker than the mold image, the adjustment should be made so that γ<1.

Variable adjustment of the γ value as described above can be achieved very easily when a television camera and television receiver are used by processing the video signal with an appropriate electronic circuit.

In the embodiments shown in FIGS. 3 to 6, the reference brightness LO is set to the intermediate value (Ll
>LO>L2 or Ll<LO<L2).

Therefore, if the luminance from the image on the cathode ray tube 21 is L, the comparators 38 to 45 output the output terminals 1A to 8A as "1" and the output terminals 1B to 8B as "0" when L>L0. ” signal is output.

Also, when L<LO, each output terminal 1A to 8A is "0".
”, each of the output terminals 1B to 8B outputs a signal of “1”.

Signals from the output terminals 1A to 8A of the comparators 38 to 45 are input to a first logic gate 47 which is activated by the product ejection completion signal.

Further, the signals from each of the output terminals 1B to 8B are input to a second logic gate 48 which is activated by a mold opening completion signal.

These first and second logic gates 47, 48 are
It consists of a NOR gate, and all input signals are
Mold clamping is allowed only when the value is "0", and mold clamping is prevented when even one of the values is "1".

Note that when there is only one brightness sensor, these logic gates can be omitted.

The output terminals of the first and second logic gates 47 and 48 are connected to an injection molding machine control system 49, and when the output signal is "1", mold clamping is permitted (continuation of sequence control), and when the output signal is "1", mold clamping is permitted (continuation of sequence control). 0", mold clamping is prevented (sequence control is stopped).

When the product image is brighter than the mold image (L1>LO) L2), the determination circuit operates as follows.

When the movable side 3 retreats and the mold opening is completed, the product remains on the movable side 3, so the brightness sensor 30~
37 measures the brightness L1 of each product image.

Therefore, the brightness L1 of this product image is compared with the reference brightness LO by comparators 38-45.

Here, since Ll>LO, the output terminals 1A to 8A of each comparator 38 to 45 become "1" and the output terminals 1B to 8B become "0".

When the mold opening is completed, only the second logic gate 48 is operating, and since all the input signals of this second logic gate 48 are "0", its output signal becomes "1".

When the output signal of the second logic gate 48 becomes "1" and is determined to be normal, mold clamping is permitted and the injection molding machine continues to operate.

However, when any one of the cores 13 to 20 on the movable side 3 does not contain a product, that is, when one of the eight products remains on the fixed side 2 when the mold is opened, the core A brightness sensor monitoring the part measures the brightness L2 from the mold image.

Therefore, in the comparator connected to this brightness sensor, output terminal A becomes "0" and output terminal B becomes "1".

If part of the product remains on the fixed side in this way, the comparators 38 to 38
All of the output terminals 1B to 8B of 45 do not become "0", but at least one of them becomes "1".

As a result, the output signal of the second logic gate 48 becomes "0".
This prevents mold clamping.

When the product is ejected from the movable side 3 by the ejector pin 8, each brightness sensor 30-37 measures the brightness L2 of the mold image.

Therefore, when the product ejection is completed, each comparator 38 to 45
The output terminals 1A to 8A of the output terminals 1A to 8A become "0" and the output terminals 1B to 8B become "1".

When this product ejection is completed, the first logic gate 47 operates instead of the second logic gate 48, so the first logic gate 47 operates instead of the second logic gate 48.
The output signal of the logic gate 47 becomes "1" and mold clamping is permitted.

However, if a part of the product remains on the movable side 3 because the ejecting pin 8 does not operate normally, the comparator monitoring that part will indicate that the output terminal A is "1" and the output Terminal B becomes "0".

Therefore, since the input signals of the first logic gate 47 are not all "0", its output signal becomes "0", and mold clamping is prevented.

When the product image is darker than the mold image (Ll<LO<L2), the output signals of the comparators 38 to 45 are opposite to the above.

Therefore, each output terminal 1A to 8A is connected to the second logic gate 48.
Then, each output terminal 1B to 8B is connected to the first logic gate 47.

Alternatively, the mold opening completion signal may be connected to the first logic gate, and the product ejecting signal may be connected to the second logic gate.

FIG. 4 shows an embodiment of the comparator, taking a brightness sensor 30 and a comparator 38 as an example.

A CdS photoconductive element is used as the brightness sensor 30, and this brightness sensor 30 is connected in series with resistors 50 and 51.

The base of one transistor 53 constituting the current switch circuit is connected to the connection point 52 between the brightness sensor 30 and the resistor 50.

The other transistor 5 forming the current switch circuit
4 is connected to a reference brightness level setter 46 via an input terminal 1C.

This current switch circuit compares the brightness signal measured by the brightness sensor 30 with a reference brightness signal.

When the potential of the connection point 52 is higher than the potential of the IC, that is, the reference brightness level, the transistor 53 is turned ON and the transistor 54 is turned OFF.

Conversely, if the potential of the connection point 52 is lower than the potential of the IC, the transistor 54 is turned ON and the transistor 53 is turned OFF.

Therefore, if the potential at the connection point 52 that appears when the product image is measured is E1, and the potential when the mold image is measured is E2, then the reference brightness applied to the base of the transistor 54 via the input terminal IC is The level potential E0 is the potential E1
and E2.

When the product image is brighter than the mold image (E1>EO>
E2) If the product remains on the movable side 3, the brightness sensor 30 measures the brightness of the product image.

Therefore, the potential of the connection point 52 is El. (El > E
O ), so the transistor 53 is turned on and the transistor 54 is turned off.

When the transistor 53 is turned on, this transistor 53
The transistor 56 whose base is connected to the collector of is turned on.
become.

As a result, the potential of the output terminal 1A connected to the collector of the transistor 56 becomes EV.

On the other hand, since the transistor 54 is OFF, the transistor 57 connected to this transistor 54 is also OFF, and the potential of the output terminal 1B connected to the collector of this transistor 57 becomes an atmosphere (earth potential).

Furthermore, when no product remains on the movable side 3, the mold image is measured by the brightness sensor 30, so the potential at the connection point 52 becomes E2 (EO>E2).

At this time, since the transistor 53 is OFF and the transistor 54 is ON, the output terminal 1A becomes the atmosphere and the output terminal 1B becomes the EV.

Note that when the mold image is brighter than the product image, El<EO
Since <E2, the signals from the output terminals IA and 1B are reversed.

FIG. 5 shows another embodiment of the comparator.

In this embodiment, when the transistor 56 is turned on, O
A Schmitt trigger circuit is provided by providing a transistor 58 which is turned on, and when the transistor 58 is turned on, the base potential of the transistor 54 constituting the current switch circuit is lowered to turn it off.

Therefore, when one transistor 53 constituting the current switch circuit is ON, the other transistor 53
4 is always OFF, the switching operation is ensured.

FIG. 6 shows another embodiment of the comparator. In this embodiment, if the light emitted from the mold is not the same, the reference brightness level of each comparator can be changed accordingly. This is how it was done.

Transistors 59 and 60 are connected in series, and one transistor 160 has an input terminal 1C to which a reference brightness level is input to a connection point 62 between these transistors 59 and 60 whose base potential can be adjusted by a potentiometer 61. It is connected.

Therefore, by adjusting the potentiometer 61, the collector current of the transistor 60 is changed and the connection point 6
The potential of 2 changes.

This connection point 62 is connected to a transistor 6 whose emitter is connected to one transistor 54 constituting a current switch.
It is connected to the base of 3.

Therefore, by adjusting potentiometer 61, the base potential of transistor 54 can be changed.

FIG. 7 shows an embodiment of the reference brightness level setter.

A potentiometer 65 is connected to the base of the transistor 64 so that the base potential can be adjusted.

When this base potential is changed, the emitter potential of transistor 64 changes accordingly.

Therefore, the potentiometer 65 is adjusted depending on the mold and plastic material used to set the potential EO at the reference brightness level.

- The emitter of this transistor 64 is connected to input terminals 1C to 8C of comparators 38 to 45, respectively.

The reference brightness level must be corrected due to changes in external light or changes in the brightness of the cathode ray tube over time.

1. FIG. 8 shows an embodiment in which a CdS photoconductive element 70 is provided at a position where the movable side of the mold is imaged to automatically correct the reference brightness level.

Resistors 71 and 72 are connected in series with the CdS photoconductive element 70, and a potential corresponding to the light incident on the CdS photoconductive element 70 appears at a connection point 73.

The base of an amplification transistor 74 is connected to this connection point 73.

The emitter of this transistor 74 is connected to a connection point 77 of transistors 75 and 76 connected in series.

A potentiometer 78 is connected to the base of one transistor 76, and by adjusting this potentiometer 78, the level of the connection point 77 can be changed.

The luminance signal measured by the CdS photoconductive element 70 is therefore level-adjusted by the potentiometer 78.

This level-adjusted signal is applied to the base of transistor 79, and the emitter potential changes in accordance with the signal.

Each comparator 38 to 45 is connected to the emitter of this transistor 79.
are connected to input terminals 1C to 8C, and a reference luminance signal corrected according to external light and the brightness of the cathode ray tube is input to each comparator 38 to 45.

FIG. 9 shows an embodiment of a logic gate and control system for an injection molding machine.

The output terminals 1A to 8A of the comparators 38 to 45 are connected to the base of a transistor 88 via diodes 80 to 87, respectively.
The transistor 88 constitutes the first logic gate 47 .

Similarly, the output terminals 1B to 8B of the comparators 38 to 45 are also:
Transistor 9 via diodes 89 to 96, respectively.
7, and these constitute the second logic gate 48.

A switch 98 that is turned on during the mold clamping process is connected in series to the transistor 88, and a transistor 97 is connected in series to the transistor 88.
A switch 99 that is turned on during the mold opening process is connected in series to the transistors 88 and 97, and a voltage is applied to the transistors 88 and 97 depending on the process.

As mentioned above, the reference brightness is set to the intermediate value between the brightness from the mold image and the product image, so even if the state of the movable side 3 is the same, the brightness of the mold image and the product image can be compared to see which is greater. The output signal of the device becomes different.

Therefore, transistors 88.97 and switches 98.
A changeover switch 100 for switching the connection of 99 is provided.

The switches 98 and 99 are connected in parallel, and the position detection limit switch 10 shown in FIG. 1 and the abnormality detection relay 102 are connected in series.

When this relay 102 is activated, a relay switch 103 is opened and the operation of the drive section 104 of the injection molding machine is stopped.

Specifically, when the drive section 104 is a motor, its power is turned off, and when it is a hydraulic cylinder, a valve is opened to stop the movement of the movable side.

Note that once the relay switch 103 is turned on, it is self-maintained.

This self-holding is achieved by turning on the reset switch 105.
It is released by activating relay 106.

Next, the operation of the above circuit will be explained with reference to FIGS. 10 and 11.

When the product image is brighter than the mold image, the product remains on the movable side 3 when the mold is opened, so the brightness sensors 30 to 37
The luminance signal photometered in is higher than the reference luminance level.

Therefore, each comparator 38-45 outputs an EV whose output terminals 1A-8A are "1" and output terminals 1B-8B which are "0".
It is at ground potential.

During the mold opening process, the switch 99 is on and the switch 98 is off, so when the position detection limit switch 10 is turned on, only the transistor 97 is activated during this period.

However, under normal conditions with the product remaining on the movable side 3,
Since the output terminals 1B to 8B are all at ground potential, the transistor 97 is not turned on.

When the mold opening is completed and the product is ejected, mold clamping is started, and during this mold clamping process, switch 98 is turned on and switch 99 is turned off.

When the product is pushed out, the brightness sensors 30 to 37
Since the light from the mold image is incident, the comparators 38-45 are inverted, each output terminal 1A-8A is at ground potential, and each output terminal 1B-8B is at EV.

During the mold clamping process, when the holder detection limit switch 10 is turned on, the transistor 88 is activated, but since the output terminals 1A to 8A of the comparators 38 to 45 are all at ground potential, the transistor 88 is It doesn't turn on.

FIG. 11 is a time chart showing a case where an abnormality occurs during the mold opening process.

If a part of the product remains on the fixed side after the mold opening starts, the image of that part on the movable side becomes the mold image.

Therefore, since the brightness signal from the brightness sensor monitoring that part will be lower than the reference brightness level, only the comparator connected to this brightness sensor will be inverted.

In this way, if an abnormality occurs in even a part, the comparators 38 to 4
None of the output terminals 1B to 8B of No. 5 are at ground potential, and at least one is at EV.

As a result, the diode is forward biased and transistor 97 is turned on.

When this transistor 97 turns on, the abnormality detection relay 1
02 is excited, and the relay switch 103 is turned OFF to prevent mold clamping.

FIG. 12 shows a time chart when an abnormality occurs during the product ejection process.

If part of the product remains on the movable side when the product is ejected, all of the output terminals 1A to 8A of the comparators 38 to 45 will not be at ground potential, and at least one will be at EV. Transistor 88 is turned on.

As a result, the relay switch 103 is turned off and mold clamping is prevented.

If the product image is darker than the mold image, comparators 38 to 45
The output is inverted.

At this time, simply switch the changeover switch 100.
As in the case where the product image is brighter than the mold image, each circuit operates to detect an abnormality.

In the embodiment described above, the brightness signal measured by the brightness sensor is compared with a reference brightness level to detect whether the mold is normal at both times of mold opening and mold clamping.

Incidentally, when the mold is opened, the product remains on the movable side, and when the mold starts clamping, the product should be pushed out.

Therefore, when the product remains on the fixed side 2, the amount of light received by the brightness sensor will be the same when the mold opening is completed and when the product ejection is completed, and if the product remains on the movable side when the product is ejected, the amount of light received by the brightness sensor will be the same. The quantities become equal.

When operating normally, the brightness sensor measures the product image when the mold is opened, and the mold image when the product is ejected.

Table 1 shows the state of the movable side 3 and the product.

In the above state, when the product image is brighter than the mold image, the amount of light received by the brightness sensor is as shown in Table 2.

Therefore, by comparing the luminance signals at both times,
It is possible to detect mold abnormalities.

FIG. 13 shows an embodiment in which the brightness measured when the mold opening is completed and when the product ejection is completed is compared.

A brightness signal from the brightness sensor 30 is sent to a sampling hold circuit 110 and a first sampling gate 111.

The sampling hold circuit 110 operates at t0 when the mold opening is completed.
The brightness signal at that point in time is stored.

A second circuit connected to this sampling hold circuit 110
The sampling gate 112 and the first sampling gate 111 are opened between the time t2 when ejection of the product is completed and the time t3 when mold clamping is started.

The luminance signal at t0 when the mold opening is completed through these sash pulling gates 111 and 112, and the luminance signal at t2 when the product ejection is completed.
The luminance signals at are compared by a comparator 113.

Comparator 113 outputs output terminal A when there is no input signal.
, B are both “0”.

Then, at I in Table 2, that is, when the input signal from the second sampling gate 112 has a higher level, the output terminal A becomes "0" and the output terminal B becomes "1".

When both input signals are equal, output terminal A becomes "1".
become.

When this output terminal A is "1", logic gate h1
14 becomes "0", and the injection molding machine control system 49
, mold clamping is prevented.

Next, the operation of the above circuit will be explained in Figures 14 and 15.
This will be explained with reference to the figures.

FIG. 14 shows a time chart when the mold is normal.

When the product image is brighter than the mold image, the brightness from the product image is stored in the sampling and hold circuit 110 when the mold opening is completed.

On the other hand, at the time t2 when ejection of the product is completed, the brightness of the mold image is measured by the brightness sensor 30.

The first and second sampling gates 111 and 112 are simultaneously opened between the time t2 when ejecting the product is completed and the time t3 when mold clamping is started, and both luminance signals are compared by the comparator 113.

As a result, the output terminal A of the comparator 113 becomes "0", so the output terminal A of the logic gate 114 becomes "0". The number becomes "1",
Mold clamping is allowed.

FIG. 15 is a time chart showing a state in which the product remains when ejecting the product is completed.

At this time, a luminance signal obtained by measuring the product image is output from the first sampling gate 111, and since the two input signals of the comparator 113 are the same, its output terminal A becomes "1".

As a result, the logic gate 114 becomes "0" and mold clamping is prevented.

Also, if there is any product left on the fixed side, the same problem as above will occur.
Since the two input signals are equal, mold clamping is prevented.

Note that when the product image is darker than the mold image, the comparator 11
Since the output signal of No. 3 is inverted, the signal of output terminal B is used.

According to the present invention having the above configuration, the image on the movable side is monitored, it is determined whether it is a mold image or a product image,
Since it is detected whether a product remains in the mold when the mold opening is completed and the product is ejected, it is possible to accurately detect the molded product remaining in the mold in a short time.

Furthermore, by monitoring only the movable side, the status of the fixed side can also be known, so that both the movable side and the fixed side molds can be monitored with one monitoring device.

In addition, since the brightness at the time of completion of mold opening and the time of completion of product ejection is compared and the state of product removal is detected from the magnitude relationship of the brightness, there is no problem even if measurement conditions such as external light change.

In addition, the memory that stores the brightness signal when the mold opening is completed is
Since the storage time is approximately 5 seconds or less, a sample and hold circuit with a simple configuration can be used.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a television camera installed in an injection molding machine, FIG. 2 is a side view showing an embodiment of the measuring section of the present invention, and FIG. 3 is a block diagram showing a schematic diagram of the present invention. 4 to 6 are circuit diagrams showing embodiments of the comparator, respectively;
Figures 7 and 8 are circuit diagrams showing examples of the reference light level setting device, Figure 9 is a circuit diagram showing the logic gate and injection molding machine control system, and Figures 10 to 12 are time charts thereof. , FIG. 13 is a block diagram showing another embodiment of the invention, and FIGS. 14 and 15 are time charts thereof. 1...Injection molding machine, 2...Fixed side, 3
...Movable side, 8...Protrusion pin, 9.
...TV camera, 10...Position detection limit switch, 12...Television receiver, 13-20
・・・・・・Curr part, 21・・・・・・Brown tube, 22
~29...Image of the core part, 30-37...
・Brightness sensor, 102... Abnormality detection relay.

Claims (1)

[Claims] 1. A mold monitoring device that monitors whether a product remains after molding in a mold consisting of a movable side and a fixed side,
Imaging means for forming the image of the movable side onto an imaging medium; measuring means for measuring the brightness of the image formed on the imaging medium; and upon completion of mold opening of the mold measured by this measuring means. a storage means for storing brightness information of the product; and a storage means for comparing the brightness information stored in the storage means with the brightness information measured by the measuring means at the time of completion of ejection of the product to determine the product in the mold after the ejection of the product is completed. A mold monitoring device characterized in that it is provided with a determination means for determining the presence or absence of. 2. The mold monitoring device according to claim 1, wherein the storage means is a sampling and holding circuit. 3. The mold monitoring device according to claim 1, wherein the image forming means comprises a television camera and a receiver. 4. The mold monitoring device according to claim 3, wherein the measuring means is detachably attached to any position on a display surface of a cathode ray tube of a television receiver.