JPH022688B2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is equipped with a screw breakage prevention device that starts the screw of an injection molding machine when the resin melted by the heating cylinder is in an unmolten state. Regarding injection molding machines.

(Prior art) Conventionally, injection molding machines have been designed to prevent excessive torque from being applied to the rotating screw due to unmelted resin remaining in the heating cylinder, which could cause damage to the screw head. A device is installed to prevent screw damage.

This screw damage prevention device measures the temperature of the heating cylinder with a temperature sensor, inputs the data into a temperature controller to control the temperature, and starts the screw after the resin in the heating cylinder has sufficiently melted. It has a circuit configuration with a safety protection circuit.

However, since it is difficult to directly measure the temperature of the resin inside the heating cylinder, the temperature sensor measures the temperature of the heating cylinder itself. Therefore, even if the sensor temperature reaches the set temperature of the temperature controller, the resin in the heating cylinder remains A situation may occur in which the temperature has not yet risen to the set temperature. For this reason, the safety protection circuit has a timer, and the screw can only be operated after the timer period (approximately 10 to 20 minutes) has elapsed.

(Problems to be Solved by the Invention) In the screw breakage prevention device having the safety protection circuit as described above, it takes a considerable amount of time from turning on the power to actually producing injection molding work.

For this reason, the present applicant has developed a circuit that allows the screw to rotate as quickly as possible without having to elapse the timer time set by the safety protection circuit, even if the heater circuit is turned off for a predetermined period of time after the power is turned on. We are also developing equipment that incorporates

However, the above-mentioned device is only a measure to improve the start-up time of the injection molding operation once the heating tube is heated, and it is not possible to truly shorten the start-up time from turning on the power to starting injection molding in the first injection molding operation. I haven't reached it yet.

In other words, with conventional equipment, after the injection molding operation, the residual resin that has solidified once in the heating cylinder must be heated to a molten state, and the resin temperature cannot be accurately measured, so extra timer time is required. Sufficient solutions have not been made for these two points.

The present invention was made in view of the above circumstances, and its purpose is to always move the forward end of the screw to the front of the heating cylinder at the end of molding to reduce the amount of residual resin to be melted as much as possible. An object of the present invention is to provide an injection molding machine which can shorten the start-up time of injection molding work and prevent damage to the screw.

(Means for Solving the Problems) In order to achieve the above object, the injection molding machine of the present invention includes a detection means for detecting that the forward end of the screw is located in the front part of the heating cylinder; a detection display circuit having a display that is connected to and displays an alarm when the forward end of the screw is not at the position, and a switch that enables the detection display circuit to operate when the power to the heater circuit is turned off. The structure is equipped with a screw breakage prevention device characterized by providing means.

(Function) With this configuration, if the forward end of the screw is not located at the front of the heating cylinder when the power to the heater circuit is turned off, the detection display circuit is activated and the display alerts the operator. will be issued.

Therefore, in order to cut off the alarm output from the display, the operator is forced to move the forward end of the screw to the front of the heating cylinder before turning off the heater circuit.

As a result, there is only a minimum amount of resin remaining in the heating cylinder at the start of the injection molding operation, and only a short amount of time is required to melt the resin, so that the start-up time in the injection molding operation can be shortened.

(Example) Embodiments of the present invention will be described based on the drawings.

FIG. 1 is an electrical control circuit diagram of an injection molding machine including the circuit configuration of the screw breakage prevention device of this embodiment.

Reference numeral 1 denotes a wiring circuit breaker for the power supply, and the power is turned on by turning on the lever, which lights up the power indicator lamp 2 and turns on the electromagnetic contactor 3 to operate the pump 4 as the hydraulic drive source of the injection molding machine. let

5 is an overcurrent relay, 6 is a preheat timer,
Further, 7 is a pilot lamp indicating that it is in a preheating state.

Furthermore, in this embodiment, a heater circuit 10 is connected to the power line 8 via a breaker 9, a control circuit 12 is connected from the line of the heater circuit 10 via another breaker 11, and a power indicator lamp 2 is connected in parallel. A connected detection and display circuit 13 is provided.

Here, the temperature control device includes a heater circuit 10, a preheat timer 6, and a part of a control circuit 12.

The detection display circuit 13 is the normally closed contact 1 of the relay _R1 .
4 and a limit switch for detecting the forward position of the screw
Normally closed contacts 15 of LS ₁ are connected in series, and a buzzer 16 and a lamp 17 connected in parallel are connected to the output terminals.

The relay R ₁ as a switching means is connected between the breaker 9 on the line of the heater circuit 10 connected to the power supply line 8 and the heater circuit 10,
When the heater circuit 10 is turned on, the coil of relay _R1 is energized. Further, a current flowing through a line 18 drawn out from the line of the heater circuit 10 is guided to a control circuit 12 via a breaker 11 to perform various controls necessary for injection molding.

Next, the operation of this embodiment will be explained based on the drawings.

By turning on the power circuit breaker 1 and the breaker 9, power is supplied to the heater circuit 10, and the coil of the relay _R1 is energized, and the normally closed contact 14 of the relay _R1 is opened, and the detection display circuit 1 is turned on.
3 is OFF. On the other hand, the control circuit 12 is activated by the input from the line 18, and normal injection molding operations are performed.

When molding is completed, when breaker 9 is opened to turn off the power to heater circuit 10, normally closed contact ₁ of relay R1 is opened.
4 is closed, and the detection display circuit 13 is activated.
As shown in FIG. 2, when the screw 21 in the heating cylinder 20 is at a position 2 to 5 mm before the screw advancement limit, the actuator of the limit switch LS ₁ is pressed and the normally closed contact 15 opens, so it can be used as an indicator. The current to the buzzer 16 and lamp 17 is cut off. In FIG. 2, 30 is a temperature sensor, 31 is a heater section of a heating tube, and 32 is a hopper.

However, when the forward end 22 of the screw is not at the front inside the heating cylinder 20 and the breaker 9 is opened, the relay
Since the normally closed contact 14 of R ₁ is closed and the limit switch LS ₁ is not operating, the normally closed contact 15 of the limit switch LS ₁ also remains closed.
The buzzer 16 sounds and the lamp 17 continues to be lit to notify the operator.

To cancel this alarm, the operator moves the forward end 22 of the screw to the front part 23 of the heating cylinder, and activates the limit switch LS ₁ to activate the detection display circuit 13.
input must be cut off.

Therefore, the operator turns on the power to the heater circuit again, moves the forward end of the screw to the front of the heating cylinder, and then turns off the power.

Therefore, by providing a screw breakage prevention device that operates as described above, the screw can be rotated safely and reliably as quickly as possible without setting an extra timer time.

Note that although a buzzer and a lamp are used together here as an indicator for displaying an alarm, either one of them may be used, or other display means may be used.

In addition, when the forward end of the screw is located at the front of the heating cylinder, that is, 2 to 5 mm from the forward limit of the screw, the limit switch LS ₁ is activated. A proximity switch may be used, or a sensor, rotary encoder, potentiometer, linear scale, etc. may be used to detect the position of the forward end of the screw by setting a program in an internal memory.

(Effects of the Invention) As is clear from the above explanation, the present invention displays a warning depending on whether or not the forward end of the screw is located at the front of the heating cylinder when turning off the power to the heater circuit. , the operator can suppress the residual resin in the heating cylinder to the minimum necessary, and since there is less residual resin melted before rotating the screw, the start-up time of injection molding work is shortened and damage to the screw is prevented. be able to.

[Brief explanation of drawings]

FIG. 1 is an electric circuit diagram showing the circuit configuration of an embodiment according to the present invention, and FIG. 2 is a partially sectional configuration diagram illustrating the relationship between the heating cylinder and the screw portion in this embodiment. 10... Heater circuit, 12... Control circuit, 13... Detection display circuit, {16..., 17...} (indicator), 20
...Heating cylinder, 22...Advanced end of screw, 23...Front part inside heating cylinder, _LS1 ...Limit switch (detection means), _R1 ...Relay (switching means).