JPH02269608A - Method of controlling heater for welding band in packing machine - Google Patents

Abstract

PURPOSE:To obviate a means of sensing the temperature of the heater by passing to the heater, when a packing machine is in action, a compensated current which is larger than a constant current passed when the packing machine is not in action. CONSTITUTION:In using a packing machine, power is applied to a heater 14 which is connected to the secondary coil 13 of a transformer 3; the temperature of the heater 14 instantaneously rises to a specified point and, to maintain the specified temperature of the heater 14, a constant current is passed to the heater 14 continuously. Under this condition, when the packing machine is put in action, a compensated current which is larger than the constant current is passed to the heater 14 so that the temperature of the heater 14 increases in order to insure a desirable temperature. In other words, a constant current flows to the heater 14 when the packing machine is not in action but, every time the packing machine works, a compensated current larger than the constant current flows to the heater 14. This method obviate a thermocouple for sensing the temperature of the mobile heater 14.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a heating method for a band welding heater in a packaging machine. Specifically, the present invention relates to a method of heating a heater in a packaging machine for welding both ends of a band of thermoplastic resin such as polypropylene wrapped around a packaged item to phase n.

(Prior art) As a heater for band welding in a packaging machine, both ends of a band wrapped around the packaged item and tightened are brought into contact with each other vertically, and a heater is inserted between these facing surfaces. After applying pressure to melt the opposing surfaces of the upper and lower bands, a heater is used to press and bond the melted surfaces of the upper and lower bands.

As a heating method for such a band welding heater, the method shown in Japanese Patent Publication No. 11279/1984 is known. In this method, a triac is inserted in the primary winding circuit of the transformer that supplies excessive current to the nichrome plate of the heater, and a thermocouple interlocking switch that senses the temperature of the heater is placed in the bias circuit of the triac. The device is designed to raise the heater to a desired temperature in an extremely short period of time and maintain this temperature using heat sensing.

[Problem to be solved by the invention]

In the above conventional method A3, the temperature of the moving heater is sensed by a thermocouple, which increases the cost, and since the thermocouple is used in the moving part, the thermocouple is easily damaged. There is.

The present invention has been made in an attempt to solve such problems.

(Means for Solving the Problems) In order to solve the above problems, the present invention instantaneously heats the heater to a predetermined temperature after commuting, and thereafter, when the packaging machine is not in operation, a constant current is passed through the heater, and the packaging machine The present invention provides a heating method for a band welding heater connected to a packaging machine, characterized in that a correction current larger than the constant current is passed through the heater during operation.

[For production]

In the method of heating a heater for band welding in a packaging machine according to the present invention, electricity is first applied to the heater when the packaging machine is used. Then, the temperature of the heater instantly rises to a predetermined temperature, and a constant current continues to flow through the heater to maintain the heater temperature at this predetermined temperature. When the packaging machine is operated in this state, a correction current larger than the constant current flows through the heater, raising the temperature of the heater and ensuring the desired temperature. That is, the constant current flows through the heater when the packaging machine is not in operation, but a correction current larger than the constant current J flows through the heater each time the packaging machine operates.

〔Example〕

Next, embodiments of the present invention will be described with reference to the accompanying drawings.

(Primary side of transformer) A timer T-1 is connected between power circuits 1 and 2, and relays R-1 and R-3 are connected in parallel between timer T-1 and power circuit 2. 1.2, the primary coil 4 of the transformer 3 is connected to the coil end 5.6. In the power supply circuit 1, a contact R3 of a relay R-3 and a RIAC 7 are arranged, and a capacitor C and a DIAC 8 are arranged between a contact R3 of the relay R-3 and a gate G of a RIAC 7. Connect in series.

A switching contact R2 of a relay R-2 interlocked with the packaging machine is provided between the capacitor C side of the diac 8 and the lower terminal 2 side of the triac 7. The switching contact R2 includes one movable contact 9a and two fixed contacts 9b and 9C.
b, 9C are variable resistors 10 with different resistance values set.
．． 11 respectively. 15-2 is a packaging machine connection switch. Furthermore, the relay R- at 33 in the power supply circuit 1
The timer T-1 side of the contact R3 of No. 3 is connected to the intermediate tap 12 of the primary coil 4 of the transformer 3 via the contact R1 of the relay R-1.

(Secondary side of transformer) A heater 14 is connected to the secondary coil 13 of the transformer 3.

In the above circuit, when the power is turned on, the timer T
Contact R1 of relay R-1 closes for the set time of -1 (an extremely short time required to heat the heater 14 to a predetermined temperature), and the middle tap 12 of the primary coil 4 connected to the transformer 3 a3 connects to one side. A circuit passing through the coil end 6 is constructed. In this case, since the number of turns of the secondary coil 4 is reduced, the heater 14 connected to the secondary coil 13 is instantaneously heated to a high temperature. The above set time elapses, timer T-
1 listens to contact R1 of relay R-1 and also connects relay R-3.
Close contact R3. When covered, capacitor C is charged,
When the terminal voltage rises and reaches the breakover voltage of the triac 8, the diac 8 becomes conductive, and a pulse current flows due to its negative resistance characteristic, causing the gate G of the triac 7 to flow.
Trigger current flows through. This causes triac 7 to become O.
NL, a circuit passing through both coil ends 5.6 of the primary coil 4 at d3 in the transformer 3 is constructed. On the other hand, at the switching contact R2 of the relay R-2 that is linked to the packaging machine, when the packaging machine is not operating, the movable contact 9a is connected to one variable resistor "F51".
When the packaging machine is in operation, the movable contact 9a is in contact with the other fixed contact 9C connected to the variable resistor 11. Different resistance values are set for the resistors 10 and 11. Therefore, diac 8 is the gate G of triac 7
The pulse width applied to the packing machine is different when the packaging machine is not operating and when it is operating. In this way, the triac 7 geto G
The conduction angle of the triac 7 can be changed by changing the pulse width applied to the triac 7.

By controlling the conduction angle in this manner, it is possible to cause the constant current to flow through the heater when the packaging machine is not in operation, and to flow a correction current larger than the constant current through the heater when the packaging machine is in operation. In other words, a correction current flows through the heater each time the packaging machine operates.

〔Effect of the invention〕

As explained above, in the present invention (d), there is no need for a means for sensing the temperature of the moving bitter, so it is advantageous in terms of cost and eliminates problems such as damage to the means. When the machine is not operating, a constant current is applied to keep the heater temperature constant, and when the packaging machine is operating, a correction current larger than the constant current is applied to raise the heater temperature, which improves the stability of the heater temperature. is extremely high.

[Brief explanation of drawings]

Figure 1 is a circuit diagram for implementing the method of the present invention, Figure 2 is a circuit diagram for implementing the method of the present invention.
The figure is a circuit diagram showing a packaging machine connection switch and relay. 1.2...Power supply circuit 3...Transformer 4...Next coil 5.6...Coil end 7...Triac 8...Diac 9a...Movable contacts 9b, 9C...・Fixed contact 10.11...Variable resistor 12...Intermediate tap 13...Secondary coil 14...Heater T1...Timer R-1, R-2, R-3... Relays R1, R2, R3...occupied

Claims (1)

[Claims] 1. After energizing, the heater is instantly heated to a predetermined temperature, and thereafter, when the packaging machine is not operating, a constant current is passed through the heater, and when the packaging machine is operating, a correction current larger than the constant current is passed through the heater. A heating method for a band welding heater in a packaging machine.