JPH04278322A - Safety door of injection molder - Google Patents

Abstract

PURPOSE:To enhance the safety of a molder by a method wherein an alarm means is actuated when the combination of signals representing the abnormality of a sensor is detected similarly by reading the output signals of the sensor again after the predetermined period of time since the detection of the combination of signals representing the abnormality of the sensor. CONSTITUTION:In order to perform the fault disgnosis of two limit switches SW1 and SW2 provided as a sensor interlocking with a safety door 10, under the open state of which an injection molder is put out of operation, a CPU 18 resets its own timer, when the system concerned is started. When the output signals of the limit switches SW1 and SW2 are read by the CPU 18, the switches SW1 and SW2 are judged as normal under the condition that said signals are ON-ON or OFF-OFF. On the other hand, when said signals are ON-OFF or OFF-ON, abnormality is judged to have occurred in the switches. And, when the generation of abnormality is judged, after the predetermined period of time, the signals of the switches SW1 and SW2 are again checked. At that time, when the generation of abnormality is judged similarly, an alarming means is actuated so as to announce fault.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to injection molding machine safety doors, and more particularly to injection molding machine safety doors that, when opened, render the injection molding machine inoperable.

0002

2. Description of the Related Art Conventionally, in an injection molding machine, for example, a mold clamping section, a very large force is applied to clamp the mold. Therefore, a safety door is provided in the mold clamping section to ensure the safety of the operator. When an operator opens the safety door for work such as mold replacement, a sensor (for example, a limit switch) outputs a signal indicating the open state of the safety door.
The CPU reads the output and detects the open state of the safety door, and even if a mold clamping instruction is input to the injection molding machine due to an erroneous operation, the mold clamping section will be rendered inoperable to protect the safety of the operator. . Two or more sensors for detecting the state of the safety door are provided to improve safety, so that even if one sensor fails, it can be detected by another sensor.

0003

However, the safety door of the conventional injection molding machine described above has the following problems. Although it has become possible to improve the accuracy of detecting the state of a safety door by providing a plurality of sensors, conventional safety doors have not been provided with any means for detecting sensor failure. If a plurality of sensors are provided, the CPU will perform control based on signals from normal sensors, making it impossible to detect sensor failure. Therefore, there is a problem that the sensor must be inspected from time to time, which is troublesome. Also, for example, one of the two sensors
There is a problem in that if one of the safety doors malfunctions, and the sensor fails while the other sensor is controlling it, the state of the safety door cannot be accurately detected, which may impair the safety of the operator. . Therefore, an object of the present invention is to provide a safety door for an injection molding machine that has a function of detecting failure of a sensor for detecting the state of the safety door.

0004

[Means for Solving the Problems] In order to solve the above problems, the present invention has the following configuration. That is, in a safety door of an injection molding machine that makes the injection molding machine inoperable in an open state, there are a plurality of sensors that output predetermined signals depending on the position of the safety door or a movable part interlocked with the safety door, and a predetermined sensor. a clock means for measuring time from the timing; an alarm means for notifying that the sensor is out of order; reading output signals of the plurality of sensors;
When a combination of signals indicating an abnormality of the sensor is detected by the combination of the output signals, the timing means starts measuring time, and when a predetermined time has elapsed, the output signal of the sensor is read again, and a signal indicating an abnormality of the sensor is generated again. and a control means for activating the alarm means when a combination of the following is detected.

[0005]

[Action] The action will be explained. When the control means detects a combination of signals indicating an abnormality in the sensor, the timing means starts measuring time, and after a predetermined time elapses, the output signal of the sensor is read again, and the combination of signals indicating an abnormality in the sensor is detected again. Then, the alarm means can be activated to notify the operator of the sensor failure.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. First, the configuration will be explained with reference to the block diagram shown in FIG. Reference numeral 10 denotes a safety door, which is installed, for example, in the mold clamping section of the injection molding machine (not shown), and when opened by moving in the direction of arrow A, the operator can work on the mold inside the mold clamping section. It is now possible to do this. SW1 and SW2 are limit switches that are examples of sensors, and are fixed to the safety door 10 or the lower part of the safety door 10, and send a predetermined signal depending on the position of the push cam 12, which is a movable part that moves together with the safety door 10. Output. That is, when the safety door 10 is closed, the switch piece 14 of the limit switch SW1 is pushed by the push cam 12 (the state shown in FIG. 1), the normally open contact closes, and a signal is output. On the other hand, when the safety door 10 moves in the direction of arrow A and is opened, the push cam 12 pushes the switch piece 16 of the limit switch SW2, opening the normally closed contact. With this configuration, when the safety door 10 is closed, the limit switches SW1 and SW2 are both in the ON state and output a signal indicating ON. On the other hand, when the safety door 10 is open, the limit switch S
Both W1 and SW2 are in the OFF state and output a signal indicating OFF. The above combination of output signals of limit switches SW1 and SW2 (ON-ON or 0FF)
-0FF) is the safety door 10 in a closed state?
Or it becomes possible to identify whether it is in the open state. Note that the output signals of the limit switches SW1 and SW2 are also sent in parallel to the detector, electromagnetic valve, etc. of the injection molding machine via an input/output circuit (not shown) and become control data. In this embodiment, two limit switches SW1 and SW2 are used as sensors, but photosensors, proximity switches, etc. can also be used as sensors, and three or more sensors can be provided.

[0007] 18 is a CPU that also serves as a time measurement means and a control means.
and consists of a microprocessor. The CPU 18 reads the combination of signals sent from the limit switches SW1 and SW2, and determines whether the combination is ON-OF.
If it is F or OFF-ON, it is determined that there is an abnormality, and time measurement is started using its own clock or software timer. If this state continues for a predetermined period of time (2 seconds in this embodiment), it is determined that the limit switch SW1 and/or SW2 is malfunctioning. A failure is determined only when the abnormal condition continues for 2 seconds or more when the safety door 10 moves and the limit switches SW1 and SW2 are activated.
When the state of the contact changes, albeit momentarily,
The combination of signals sent from limit switches SW1 and SW2 to the CPU 18 is ON-OFF or OFF.
- ON, and this is to avoid determining this state as a failure. CPU18 is limit switch S
When W1 and SW2 are determined to be malfunctioning, an alarm means to be described later is activated to notify the operator. In addition to the clock means and control means, the CPU 18 also has an input key 20, a ROM 22, and a RAM.
24, a display 26, an LED 28, a buzzer 30, etc. constitute an electronic controller of the injection molding machine to control the operation of each part of the injection molding machine. Note that an independent timer device may be provided as the time measurement means and connected to the CPU 18.

Various commands and control data can be entered through the input key 20. ROM22 has a CPU
18 operating systems, limit switch S
Application programs including programs for performing operations for determining failures of W1 and SW2, various predetermined control data, and the like are stored. RAM24
Stored therein are data input from the input keys 20, various information processed by the CPU 18, various information output to the display 26, etc. The input key 2 is on the display 26.
0, various information processed by the CPU 18, and when the CPU 18 as an alarm means determines that the limit switches SW1 and SW2 are out of order, this fact is displayed in characters. The LED 28 serves as a warning means.
When the PU 18 determines that the limit switches SW1 and SW2 are out of order, it flashes a red light to notify the operator. The buzzer 30 also serves as a warning means, and when the CPU 18 determines that the limit switches SW1 and SW2 are malfunctioning, the LE
It sounds in time with the flashing of D28 to notify the operator. In this embodiment, the display 26, L is used as an alarm means.
Although a combination of the ED 28 and the buzzer 30 is used, the present invention is not limited to this, and any means or combination may be used.

Next, the safety door 10 constructed in this way
The operation will be explained with further reference to the flowchart of FIG. Limit switch SW1 of safety door 10,
The failure diagnosis of the SW2 may be performed at a specific time (for example, when the injection molding machine is started, when inspected at regular intervals, etc.), or the diagnosis may be performed at all times. In this embodiment, an example will be described in which the process is performed continuously at all times. When this system starts (step 100), the RAM 24 is cleared and the CPU 18
resets its own timer (step 102). C
The PU 18 reads the output signals sent from the limit switches SW1 and SW2 (step 104), and first checks whether the signals are ON-ON (step 10).
6). If it is ON-ON, it is determined that the limit switches SW1 and SW2 are normal as described above, so step 1
Returning to step 04, the occurrence of an abnormality is detected. At step 106,
If it is not ON-ON, it is checked whether the signal is OFF-OFF (step 108). If the signal is OFF-OFF here, it is determined that the limit switches SW1 and SW2 are normal as described above, so the process returns to step 104 and the occurrence of an abnormality is detected. If the signals sent from limit switches SW1 and SW2 are ON-OFF or OFF-ON, the CP
U18 determines that an abnormality has occurred, starts a timer, and starts measuring time (step 110).

[0010] The CPU 18 checks whether two seconds have elapsed (step 112), and once the two seconds have elapsed, it reads the output signals sent from the limit switches SW1 and SW2 again (
Step 114). Then, it is checked whether the signal is ON-ON (step 116). If ON-ON, it is determined that the previous abnormal state is momentary and the limit switches SW1 and SW2 are determined to be normal, so the process returns to step 104 and the occurrence of an abnormality is detected. Step 11
6, if it is not ON-ON, the signal is OFF-O
It is checked whether it is FF (step 118). If the signal is OFF-OFF here, it is determined that the previous abnormal condition is momentary, and the limit switches SW1 and SW2
is determined to be normal, and the process returns to step 104 to detect the occurrence of an abnormality. The signals sent from the limit switches SW1 and SW2 read again in step 114 are ON-
If it is OFF or OFF-ON, it is determined that the abnormal state continues for 2 seconds, so the CPU 18
determines that limit switches SW1 and SW2 are faulty, and
An alarm means such as the ED 28 is activated to notify the operator of the failure (step 120). After making the announcement, C.
The PU 18 stops the fault diagnosis operation (step 122).
, control each part according to pre-programmed operations or commands input by the operator. Although various preferred embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments, and it goes without saying that many modifications can be made without departing from the spirit of the invention. .

[0011]

[Effects of the Invention] When the safety door of the injection molding machine according to the present invention is used, when the control means detects a combination of signals indicating an abnormality in the sensor, the timer starts measuring time, and when a predetermined time elapses, When the sensor output signals are read again and a combination of signals indicating sensor abnormality is detected again, the alarm means is activated and the operator is notified of the sensor failure, so the operator can immediately know if the sensor has failed. . Therefore, there is no need to inspect the sensor from time to time. In addition, since the failure is immediately notified, it is possible to avoid continuing operation in a failed state, so there is a significant effect that the operator's safety is not compromised.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of a safety door for an injection molding machine according to the present invention.

FIG. 2 is a flowchart showing the operation of a CPU.

[Explanation of symbols]

10 Safety door 12 Push cam 18 CPU 26 Display 28 LED 30 Buzzer

Claims (1)

[Claims] 1. A safety door for an injection molding machine that renders the injection molding machine inoperable in an open state, comprising a plurality of sensors that output predetermined signals depending on the position of the safety door or a movable part interlocking with the safety door. , a clock means for measuring time from a predetermined timing, an alarm means for notifying that the sensor is out of order, reading the output signals of the plurality of sensors, and detecting the sensor by a combination of the output signals. When a combination of signals indicating an abnormality in the sensor is detected, the clocking means starts measuring time, and when a predetermined time has elapsed, the output signal of the sensor is read again, and when a combination of signals indicating an abnormality in the sensor is detected again, the A safety door for an injection molding machine, comprising a control means for activating an alarm means.