JP6746248B2 - Injection molding machine safety door - Google Patents

Description

The present invention relates to a safety door provided in an injection molding machine.

As is well known, the injection molding machine is composed of a mold clamping device for clamping a mold, an injection device for melting an injection material and injecting it into the mold, and the like. In a mold clamping device of an injection molding machine, there are various maintenance works such as replacement of molds, and such maintenance work is dangerous. Therefore, safety measures are taken in the mold clamping device, the entire mold clamping device is covered with a housing, and a safety door is provided at an opening portion reserved for maintenance work. The safety door can be opened only when the injection molding machine is stopped. When the safety door is open, the servomotor is not driven because the power of the servomotor is cut off. That is, each device cannot operate. Therefore, as long as the safety door is opened, the worker can safely perform maintenance on the mold clamping device.

By the way, safety regulations for injection molding machines have been established in certain regions and countries, and according to the regulations, it is essential to provide a limit switch with a lock. And this rule will be adopted in Japan. The lock mechanism prevents the safety door from being opened while the injection molding machine is operating. For example, the lock mechanism is required to have a strength capable of withstanding a load of at least 1000 N so as not to be broken. , Various regulations have been established. FIG. 5 shows a limit switch with lock, that is, a tongue-type interlock switch 50, which is used for a safety door of a general injection molding machine based on such a predetermined regulation. The tongue-type interlock switch 50 detects whether or not the metal fitting fixed to the safety door 51, that is, the tongue-type actuator 53, the lock mechanism 55 that locks the tongue-type actuator 53, and whether or not the tongue-type actuator 53 is inserted. And a limit switch 56 that operates. The lock mechanism 55 includes a lock pin 59 that is biased forward by a spring 58, a solenoid 61 that retracts the lock pin 59 against the spring bias, and a forward/backward movement state of the lock pin 59, that is, a locked/unlocked state. And a first contact 62 for detecting The tongue type actuator 53 has a hole 53a, and the tip of a lock pin 59 is inserted into the hole 53a to lock the safety door 51. The size of the hole 53a is formed so that the lock pin 59 can be inserted therein. The limit switch 56 includes a spring 65 and a second contact 64, and the open state is detected when the tongue actuator 53 is pulled out, that is, when the safety door 51 is opened. Such a tongue interlock switch 50 is connected to the controller of the injection molding machine. When opening the safety door 51, the worker performs a predetermined operation on the controller of the injection molding machine. Then, the controller stops the servo motor and shuts off the power to the servo amplifier. Next, the controller drives the solenoid 61 in the lock mechanism 55 to retract the lock pin 59, as shown in FIG. That is, it unlocks. At this time, unlocking is detected at the first contact 62 and the controller is notified. When the safety door 51 is opened as shown in FIG. 5C, the opening of the safety door 51 is detected by the second contact 64, and the controller is notified.

A tongue type interlock switch 70 shown in FIG. 6 is also known as a limit switch with a lock provided on a safety door of an injection molding machine. The tongue-type interlock switch 70 includes a tongue-type actuator 71 fixed to a safety door (not shown), a cam 72 rotatably provided in a predetermined shape, a lock mechanism 73, and a limit switch 74. It consists of The tongue actuator 71 has a hole 71a formed therein, and a claw portion 72a formed on the cam 72 is inserted therein. The cam 72 is also formed with a lock notch 72b. The lock mechanism 73 includes a lock pin 76, a spring 77 that biases the lock pin 76, a solenoid 78 that drives the lock pin 76, and a first contact 79 that detects a locked state. It is projected forward by urging, and its tip is inserted into the lock notch 72b. This restricts the rotation of the cam 72, and the tongue-type actuator 71 is locked by the claw portion 72a. The limit switch 74 includes a pin 80, a spring 81, and a second contact 82, and the pin 80 is biased by the spring 81 so that its head is in contact with the end surface of the cam 72. When the cam 72 rotates, the contact position of the pin 80 changes and the pin 80 moves forward and backward, whereby the second contact 82 is turned on/off. When opening a safety door in an injection molding machine provided with such a tongue interlock switch 70, a worker performs a predetermined operation on the controller of the injection molding machine. Then, the controller stops the servo motor and shuts off the power to the servo amplifier. Next, the controller drives the solenoid 78 in the lock mechanism 73 to retract the lock pin 76, as shown in FIG. That is, it unlocks. At this time, unlocking is detected at the first contact 79 and the controller is notified. When the safety door is opened, the pin 80 retracts as shown in FIG. 6C, and the opening of the safety door is detected by the second contact 82, and the controller is notified.

Japanese Patent No. 4486049

Patent Document 1 describes a safety door that can be opened directly without requiring an operator to operate the controller of the injection molding machine when opening the safety door. The safety door described in Patent Document 1 is provided with a lever-shaped handle that rotates within a predetermined rotation angle range and a lock mechanism that locks the safety door in a closed state. This handle is a handle for opening and closing the safety door, and is provided with a predetermined sensor in association therewith. The operation is detected by this sensor when a worker grasps the handle and turns it slightly to open the safety door. Upon receiving the detection from this sensor, the controller of the injection molding machine stops the servo motor and stops the power supply to the servo motor. After confirming safety, the controller drives the lock mechanism to unlock. The worker holds the handle and slides it sideways. Then you can open the safety door.

The safety door provided with the conventional tongue-type interlock switches 50 and 70 is also excellent because the safety of the worker who maintains the injection molding machine is ensured. The safety door described in Patent Document 1 is also excellent because it is possible to safely stop the injection molding machine and open the safety door simply by operating the handle. However, there are some problems to be solved. First, in the case of the safety door provided with the conventional tongue-type interlock switches 50 and 70, when an operator tries to open the safety door, some operation such as operation on the controller of the injection molding machine is performed. Will be required. This is because the injection molding machine is stopped and the lock mechanisms 55 and 73 are released to unlock. When an abnormality occurs in the injection molding machine, it may be necessary to open the safety door urgently to deal with it, but opening the safety door requires a pre-operation in a controller or the like, and the operation is troublesome. That is, in the case of the safety door provided with the conventional tongue-type interlock switches 50 and 70, the operator cannot open the door without performing two types of operations, and the response is delayed in an emergency. There is. On the other hand, in the safety door described in Patent Document 1, the operation of the handle is detected, and the controller of the injection molding machine stops the injection molding machine to unlock the lock mechanism. It is good just to open the safety door. However, the safety door described in Patent Document 1 has some problems. First, there is the problem of the strength of the steering wheel. Since the safety door is relatively heavy, a large amount of force is applied to the handle in order for the worker to open it. Since the handle is designed to be rotated within a predetermined angle range, in other words, the handle is provided with a movable portion, the structure is complicated and there is a problem in strength. To ensure sufficient strength, a sturdy and large handle must be provided, which increases the cost. There is a possibility that a large shock will act on the lock mechanism. The locking mechanism is designed to withstand a load of at least 1000N as described above. However, in an emergency, when an operator tries to open the safety door in a hurry, the handle is rotated and the handle is immediately slid laterally. Immediately after turning the handle, the controller has not stopped the servo motor, so the lock mechanism is in a locked state.At this time, if you try to open the safety door, the force will be applied to the lock mechanism. There is a risk that the lock mechanism will be damaged due to shock.

Therefore, the present invention is an injection molding machine having a simple structure and a small cost, but when an operator wants to open the safety door, the operator only has to open the safety door, and there is no problem of the lock mechanism failure. The purpose is to provide a safety door.

The present invention, in order to achieve the above object, is provided in a mold clamping device of an injection molding machine, and is maintained in a closed state by being locked by a predetermined locking mechanism during operation of a servomotor that drives the mold clamping device. When the door is opened, the safety door is designed so that the lock mechanism is released after the operation stop of the servo motor is confirmed. The lock mechanism is composed of a tongue type actuator having a predetermined lock hole and a lock pin inserted into the lock hole, and the safety door is provided with a limit switch having a predetermined detection pin. When the detection pin is pushed in by the tongue type actuator, the closed state of the safety door is detected, and when the detection pin is pushed out by the spring bias, the opened state of the safety door is detected. By the way, the lock hole is formed in the shape of a long hole that is longer than the diameter of the lock pin.When the safety door in the locked state is opened by this, the safety door is opened by a small gap and the open state is detected by the limit switch. To configure. Then, the operation of the servo motor is stopped by the controller of the injection molding machine. The safety door is constructed so that the locking mechanism is unlocked after confirmation of this stop.

That is, the invention according to claim 1 is provided in a mold clamping device of an injection molding machine, and is maintained in a closed state by being locked by a predetermined lock mechanism during operation of a servomotor for driving the mold clamping device, and when opened. A safety door configured to release the lock mechanism after it is confirmed that the servomotor has stopped operating, wherein the lock mechanism is a tongue type actuator having a predetermined lock hole and is inserted into the lock hole. The safety door is provided with a limit switch having a predetermined detection pin, and when the detection pin is pushed by the tongue type actuator, the closed state of the safety door is changed to the detection pin. Is pushed out by a spring bias, the open state of the safety door is detected, and the lock hole is formed in a long hole shape longer than the diameter of the lock pin. The safety door is allowed to open by a predetermined gap in the locked state where the lock pin is inserted in the lock hole, and when the safety door in the locked state is opened, the safety door is opened by the predetermined gap. The open state is detected by the limit switch, the operation of the servo motor is stopped by the controller of the injection molding machine, and the lock mechanism is unlocked after confirmation of the stop. Configured as a safety door for the molding machine.
The invention according to claim 2 is provided in a mold clamping device of an injection molding machine, and is kept closed by a predetermined locking mechanism while a servomotor for driving the mold clamping device is in operation. A safety door in which the lock mechanism is released after it is confirmed that the servomotor has stopped operating, wherein the lock mechanism includes a tongue actuator having a predetermined lock hole, a cam having a predetermined shape, and a lock. The cam is configured to be rotatable, the pawl portion and the lock groove are formed, and when the tongue-type actuator enters the cam, the cam rotates to lock the tongue-type actuator and the pawl. When the lock pin is driven in this state, the lock pin is inserted into the lock groove and the rotation of the cam is restricted so that the cam is locked. Is provided with a limit switch having a predetermined detection pin that comes into contact with the edge of the cam by a spring bias, and when the cam rotates, the detection pin moves forward and backward depending on the shape of the cam. A limit switch is actuated so that the open/closed state of the safety door can be detected, and the lock groove is formed longer than the diameter of the lock pin, whereby the lock pin is locked by the lock groove. The cam is allowed to rotate within a predetermined range in the locked state inserted into the housing, so that the safety door is allowed to open a predetermined gap, and when the safety door in the locked state is opened , The open state is detected by the limit switch in the middle of opening the gap, the operation of the servo motor is stopped by the controller of the injection molding machine, and the lock mechanism is unlocked after confirming the stop. It is configured as a safety door for injection molding machines.

INDUSTRIAL APPLICABILITY As described above, the present invention is provided in the mold clamping device of an injection molding machine, and the servo motor for driving the mold clamping device is locked by a predetermined lock mechanism to maintain the closed state, and when opened, the servo motor is opened. It is intended for safety doors where the lock mechanism is released after it is confirmed that the motor has stopped operating. The lock mechanism is composed of a tongue type actuator having a predetermined lock hole and a lock pin inserted into the lock hole, and the safety door is provided with a limit switch having a predetermined detection pin. When the detection pin is pushed in, the closed state of the safety door is detected, and when the detection pin is pushed out by the spring bias, the opened state of the safety door is detected. In the present invention, the lock hole is formed in a long hole shape that is longer than the diameter of the lock pin, which allows the safety door to open only a predetermined gap in the locked state in which the lock pin is inserted into the lock hole. When the safety door in the locked state is opened, the open state is detected by the limit switch in the middle of opening the specified gap, the servomotor operation is stopped by the controller of the injection molding machine, and after confirming the stop, The lock mechanism is designed to be unlocked . Therefore, when the worker opens the safety door, he/she only has to perform the opening operation of the safety door, and after the opening operation is detected and the servo motor of the mold clamping device is automatically stopped to ensure the safety, the safety door is opened. Can be opened. Since the operation is simple, it is useful especially when it is desired to open the safety door in an emergency. It should be noted that although a slight gap is opened by opening the safety door, there is a problem even in the regulation of the safety door if the arm or the like cannot be inserted even if the gap of about several cm is opened. Absent. By the way, the stop of the servo motor of the mold clamping device is completed within a few seconds at the most, zero comma after the stop command is issued from the controller. It can be said that a few seconds are zero commas from the start of the opening operation until the lock mechanism is unlocked. When performing the opening operation of the safety door, even if the lock mechanism is locked, the safety door can be opened by the amount of play, but since the heavy safety door has a large inertia, keep the safety door open until the play limit is reached. It takes some time to open. Then, the lock will be released within a few seconds of this zero comma, and the lock mechanism will be completely unlocked before the play limit is reached during the opening operation, and the lock mechanism will be damaged. There is no fear. That is, since the play is provided, no shock load is generated on the lock mechanism during the opening operation of the safety door. In addition, since the safety door of the present invention does not have a movable part, it can be provided at a low cost. Since play with a simple configuration that only the locking holes into the long hole is secured, the present invention can be inexpensively implemented. According to another aspect of the invention, the lock mechanism includes a tongue-type actuator having a predetermined lock hole, a cam having a predetermined shape, and a lock pin, and the cam is rotatable and has a claw portion and a lock groove. , When the tongue type actuator enters the cam, the cam rotates and the tongue type actuator and the claw are engaged. When the lock pin is driven in this state, the lock pin is inserted into the lock groove and the cam rotation is restricted. A limit switch with a predetermined detection pin that comes into contact with the edge of the cam by spring bias is provided near the cam, and when the cam rotates, the limit switch In response, the detection pin moves forward and backward to activate the limit switch, which detects the open/closed state of the safety door, and the lock groove is formed longer than the diameter of the lock pin. The cam is allowed to rotate within a predetermined range in the locked state in which the pin is inserted into the lock groove, and thus the safety door is allowed to open by a predetermined gap. When the safety door in the locked state is opened, the limit switch detects the open state while opening the predetermined gap, the controller of the injection molding machine stops the operation of the servo motor, and after confirming the stop, the lock mechanism is released. It is supposed to be unlocked. Also in this invention, since the play can be secured only by making the lock groove a predetermined length, the invention can be implemented at a low cost.

FIG. 1 is a view showing an injection molding machine according to an embodiment of the present invention, in which (A) is a front view of the injection molding machine, and (A) is an enlarged view of a part of a safety door provided in the injection molding machine. It is a front view shown. (A) to (E) are front views showing the tongue-type interlock switch in various states when the safety door of the injection molding machine according to the embodiment of the present invention is opened. 3 is a graph showing the timing of opening operation of the safety door of the injection molding machine according to the embodiment of the present invention, the timing of operation/stop of the servo motor of the mold clamping device, and the like. It is a figure which shows the tongue type interlock switch provided in the safety door of the injection molding machine which concerns on 2nd Embodiment, The (a)-(d) are various states at the time of carrying out opening operation of a safety door. It is a front view which shows the tongue-type interlock switch. It is a figure showing a tongue-type interlock switch provided on the safety door of a conventional injection molding machine, and (a) to (d) show the tongue-type interlock switch in various states when the safety door is opened. It is a front view shown. It is a figure showing a tongue-type interlock switch provided on the safety door of a conventional injection molding machine, and (a) to (d) show the tongue-type interlock switch in various states when the safety door is opened. It is a front view shown.

Hereinafter, embodiments of the present invention will be described. Although the injection molding machine 1 according to the present embodiment is shown in FIG. 1A, it is mounted on the bed B like the conventional injection molding machine, and the injection device 2 and the mold clamping device 3 are provided. It is composed of and. The drive part of the injection device 2, that is, the drive mechanism for driving the screw is covered with a protective cover 5, and the mold clamping device 3 is entirely covered with a protective cover 6 and a safety door 8. When a worker performs maintenance on the mold clamping device 3, for example, when exchanging a mold, the safety cover 6 is opened, but the molding cycle of the injection molding machine 1 is stopped and the mold clamping device 3 is stopped. The driving servomotor cannot be opened without stopping, which guarantees the safety of workers.

The safety door 8 according to the present embodiment is provided with a tongue type interlock switch 10 according to the present embodiment, as shown in FIG. The tongue interlock switch 10 includes a tongue actuator 11, a lock device 12, and a limit switch 13. The tongue type actuator 11 is fixed to the end of the safety door 8 and is driven integrally with the safety door 8. The lock device 12 and the limit switch 13 are provided on a part of the protective cover 6, that is, on a predetermined fixing member. There is.

The tongue actuator 11 is made of a rectangular metal plate and has a lock hole 15. The lock hole 15 is formed in a long hole shape, and a predetermined play is secured even when the lock hole 15 is locked by the lock device 12. That is, the safety door 8 can be opened by a small gap, for example, 3 to 4 cm even in the locked state. Even if the safety door 8 is opened until the limit switch 13, which will be described later, detects that the play is open, this play has more allowance. Even if the safety door 8 opens such a gap while the injection molding machine 1 is in operation, there is no problem with the safety regulations required for the safety door 8.

The lock device 12 detects a lock pin 17, a spring 18 that biases the lock pin 17 forward, a solenoid 19 that retracts the lock pin 17 against the bias of the spring 18, and a locked state of the lock pin 17. And a first contact 20 that When the safety door 8 is closed, the tongue actuator 11 is inserted near the lock device 12, and the lock hole 15 is aligned with the lock pin 17. When the energization of the solenoid 19 is stopped, the lock pin 17 is driven forward by the biasing force of the spring 18, and the tip of the lock pin 17 is inserted into the lock hole 15 so that the lock pin 17 is locked. In other words, it can be said that the tongue actuator 11 having the lock hole 15 and the lock pin 17 constitute a lock mechanism. When in the locked state, this state is detected by the first contact 20. On the other hand, when the solenoid 19 is energized, the lock pin 17 retracts from the lock hole 15 and is unlocked.

The limit switch 13 includes a detection pin 22, a spring 23 that biases the detection pin 22 forward, and a second contact 24 that detects the closed state of the safety door 8. When the safety door 8 is opened, the detection pin 22 is pushed forward by the biasing force of the spring 23 and the second contact 24 is opened. However, when the safety door 8 is closed, the detection pin 22 is pushed by the tongue actuator 11 and detected by the second contact 24. That is, the closed state of the safety door 8 is detected. The tongue interlock switch 10 according to the present embodiment is connected to the controller of the injection molding machine. Signals from the first and second contacts 20 and 24 are notified to the controller, and the solenoid 19 is driven by the controller.

The operation of the safety door 8 according to this embodiment will be described. When the injection molding machine 1 is performing the molding cycle, the safety door 8 is closed and the tongue actuator 11 is locked by the locking device 12, as shown in FIG. Has become. At this time, since the safety door 8 is completely closed, the closed state of the second contact 24 is detected. From this state, the worker opens the safety door 8. The timing t1 of the opening operation is shown in the graph of FIG. Even if the tongue actuator 11 is locked by the lock pin 17 due to the play of the lock hole 15, the tongue actuator 11 is slid and the safety door 8 is slightly moved, as shown in FIG. open. The detection pin 22 is pushed out by the bias of the spring 23, the second contact 24 is opened, and the controller is notified. It is shown at timing t2 in the graph of FIG. At timing t3, the controller issues a cutoff command to the servo amplifier of the servomotor for driving the mold clamping device 3. As indicated by the timing t4 in the graph of FIG. 3, the servo motor shifts to the stop processing. The rotation speed of the servo motor decreases rapidly and stops completely at timing t5. The controller detects that the rotation of the servo motor has stopped, and issues a lock release command to the lock device 12 at timing t6. That is, electric power is supplied to the solenoid 19, and the lock pin 17 is retracted and unlocked as shown in FIG. As shown at timing t7, unlock is detected at the first contact 20 and the controller is notified. By the way, the worker starts the opening operation of the safety door 8 at the timing t1 and continues the opening operation, but since the time until the locking device 12 is unlocked is short, the tongue actuator 11 is locked. It is unlocked with some allowance for play between the hole 15 and the lock pin 17. Therefore, the lock device 12 is not damaged by the opening operation of the safety door 8 by the worker. The controller cuts off the power supply to the servo amplifier after a predetermined delay time Tx from the cutoff command to the servo amplifier at timing t3, for example, a few seconds after zero comma. When the worker continues to open the safety door 8, the tongue type actuator 11 is pulled out from the lock device 12 as shown in FIG.

A second embodiment will be described. FIG. 4A shows a tongue-type interlock switch 30 according to the second embodiment provided on the safety door 8. The tongue interlock switch 30 according to the second embodiment includes a tongue actuator 31 fixed to the safety door 8, a cam 32 that engages with the tongue actuator 31, and a lock device 33 that locks the cam 32. And a limit switch 35 for detecting the closed state of the safety door 8. The cam 32 is made of a metal plate having a predetermined shape and is rotatably provided. The cam 32 is formed with a claw portion 36 protruding by a predetermined height and a lock groove 37 having a predetermined length. The tongue-type actuator 31 has a hole 46. When the safety door 8 is closed and the tongue-type actuator 31 is inserted into the cam 32, the cam 32 rotates and the claw portion 36 is inserted into the hole 46. .. That is, it engages. At this time, the lock groove 37 is aligned with the lock device 33, but since the lock groove 37 is formed to have a predetermined length, like the tongue-type interlock switch 10 according to the previous embodiment, Even if locked, play is secured. The lock device 33 includes a lock pin 39, a spring 40 that biases the lock pin 39 forward, a solenoid 41 that retracts the lock pin 39, and a first contact 42. When the pawl portion 36 of the cam 32 is engaged with the tongue-type actuator 31, when the power supply to the solenoid 41 is stopped, the lock pin 39 is moved forward by the bias of the spring 40 and the tip of the lock pin 39 is locked by the lock groove 37. Can be put in. This puts it in a locked state. That is, in this second embodiment, it can be said that the tongue-type actuator 31, the cam 32, and the lock pin 39 constitute a lock mechanism. The limit switch 35 includes a detection pin 43, a spring 44 that biases the detection pin 43 forward, and a second contact 45. The head of the detection pin 43 is in contact with the end surface of the cam 32. Since the end surface is formed in a predetermined shape, when the cam 32 rotates, the detection pin 43 is driven back and forth. The second contact 45 is turned on when the safety door 8 is completely closed. The first and second contacts 42 and 45 and the solenoid 41 are connected to the controller of the injection molding machine 1.

During the molding cycle in the injection molding machine 1, a worker opens the safety door 8 and performs an opening operation. Then, as shown in FIG. 4A, the tongue-type actuator 31 is pulled out by a predetermined length and the cam 32 is rotated by the claw portion 36 engaging with the hole 46. Since the lock groove 37 is formed to have a predetermined length, it does not hinder the rotation of the cam 32 even when locked by the lock pin 39. At this time, the opening operation of the safety door 8 is detected at the second contact 45. The controller stops the servomotor of the mold clamping device 3. After confirming the stop, the controller drives the solenoid 41 to retract the lock pin 39 to release the lock, as shown in FIG. The worker continues to open the safety door 8. As shown in FIG. 4D, the tongue actuator 31 is completely withdrawn from the cam 32, and the safety door 8 is opened.

1 injection molding machine 2 injection device 3 mold clamping device 8 safety door 10 tongue type interlock switch 11 tongue type actuator 12 locking device 13 limit switch 15 lock hole 17 lock pin 18 spring 19 solenoid 20 first contact point 22 detection pin 23 spring 24 Second Contact 30 Tongue Type Interlock Switch 31 Tongue Actuator 32 Cam 33 Lock Device 35 Limit Switch 36 Claw 37 Lock Groove 39 Lock Pin 40 Spring 41 Solenoid 42 First Contact 43 Detection Pin 44 Spring 45 Second Contact 46 holes

Claims (2)

It was confirmed that the operation of the servomotor provided in the mold clamping device of the injection molding machine was locked and kept closed by a predetermined lock mechanism during the operation of the servomotor, and that the operation of the servomotor was stopped when the servomotor was opened. A safety door in which the lock mechanism is to be released later,
The lock mechanism includes a tongue type actuator having a predetermined lock hole and a lock pin inserted into the lock hole,
The safety door is provided with a limit switch having a predetermined detection pin, and when the detection pin is pushed by the tongue type actuator, the closed state of the safety door is pushed out by the spring biasing of the detection pin. And the open state of the safety door is detected,
The lock hole is formed in a long hole shape longer than the diameter of the lock pin, so that the safety door can be opened by a predetermined gap in a locked state in which the lock pin is inserted into the lock hole. Allowed,
When the safety door in the locked state is opened, the open state is detected by the limit switch in the middle of opening the predetermined gap , the operation of the servo motor is stopped by the controller of the injection molding machine, and the confirmation of the stop is confirmed. A safety door for an injection molding machine, wherein the lock mechanism is unlocked later. It was confirmed that the operation of the servomotor provided in the mold clamping device of the injection molding machine was locked and kept closed by a predetermined lock mechanism during the operation of the servomotor, and that the operation of the servomotor was stopped when the servomotor was opened. A safety door in which the lock mechanism is to be released later,
The lock mechanism is composed of a tongue type actuator having a predetermined lock hole, a cam and a lock pin of a predetermined shape, the cam is rotatable, and a claw portion and a lock groove are formed. When the actuator enters the cam, the cam rotates to engage the lock hole and the claw portion of the tongue actuator, and when the lock pin is driven in this state, the lock pin is inserted into the lock groove. The rotation of the cam is restricted and locked.
A limit switch having a predetermined detection pin that comes into contact with the edge of the cam by a spring bias is provided near the cam, and when the cam rotates, the detection pin moves back and forth according to the shape of the cam. The limit switch is actuated and the open/closed state of the safety door is thereby detected,
The lock groove is formed longer than the diameter of the lock pin, so that the cam is allowed to rotate within a predetermined range in a locked state in which the lock pin is inserted into the lock groove. It is allowed to open only a predetermined gap,
When the safety door in the locked state is opened, the open state is detected by the limit switch in the middle of opening the predetermined gap , the operation of the servo motor is stopped by the controller of the injection molding machine, and the confirmation of the stop is confirmed. A safety door of an injection molding machine, wherein the lock mechanism is unlocked later.

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