JP7658223B2 - How to check the electrical insulation of a heat sealer - Google Patents

Description

This disclosure relates to a method for checking the electrical insulation of a heat sealer that heat seals conductive objects.

The following Patent Document 1 discloses an impulse type heat sealer. In an impulse type heat sealer, a relatively large current is passed through the heater only during heat sealing, and the heater is instantly heated to a temperature at which heat sealing is possible. The impulse type heat sealer disclosed in Patent Document 1 has a transformer inside. When current is passed through the primary coil of the transformer, the heater connected to the secondary coil is heated by the power generated by electromagnetic induction.

JP 2009-6604 A

There is a demand for heat sealing conductive objects with a heat sealer. For example, there are cases where the object to be sealed is a sheet member made of a thermoplastic resin containing a conductive filler. In such cases, it is necessary to insulate the heater so that the current passing through it does not flow inside the object to be sealed. For example, during heat sealing, the heater is pressed against the object to be sealed, and it is possible to perform heat sealing with an insulating sheet between the heater and the object to be sealed. Here, if a hole is made in the insulating sheet, the current passing through the heater may flow inside the object to be sealed, which may cause the object to be sealed to burn or result in poor sealing. For this reason, it is desirable to check the electrical insulation state of the insulating sheet.

The objective of this disclosure is to provide a method for checking the electrical insulation of a heat sealer to check the electrical insulation state of an electrically conductive object to be sealed in the heat sealer.

In the method for checking the electrical insulation of a heat sealer according to the present disclosure, the heat sealer includes a transformer having a primary coil and a secondary coil, a heater electrically connected to the secondary coil, an insulating sheet disposed between the heater and an electrically conductive object to be sealed, and a mounting table having a conductive surface on which the object to be sealed is placed, the conductive surface of the mounting table is electrically connected to a reference potential part of the heat sealer, and the resistance between the heater and the reference potential part is measured in a state in which the heater is in contact with the object to be sealed placed on the conductive surface via the insulating sheet without supplying power to the primary coil, and the insulation of the insulating sheet is checked based on the measured resistance value.

The heat sealer may further include a resistance meter connected between the secondary coil and the reference potential portion for measuring the resistance value, and a switch electrically connected in series to the resistance meter, and the switch may be closed when the resistance value is measured and opened when the heater is heated.

The insulating sheet may be attached to the heat sealer so as to cover the heater.

The heater may be brought into contact with the object to be sealed via the insulating sheet, and if the resistance value measured by the resistance meter with the switch closed is equal to or greater than a reference value, the switch may be opened and then current may be passed through the primary coil to heat the heater and heat seal the object to be sealed.

FIG. 2 is a schematic diagram of a heat sealer that performs the electrical insulation checking method according to the embodiment. FIG. 4 is an enlarged cross-sectional view showing the flow of electricity during heat sealing. 2 is a flowchart of the method.

Below, an embodiment of a method for checking the electrical insulation of a heat sealer will be described with reference to the drawings. The heat sealer 1 used in this embodiment is an impulse type heat sealer, and is intended to heat seal an electrically conductive object 10 to be sealed. The object 10 to be sealed in this embodiment is, for example, a sheet member made of a thermoplastic resin containing an electrically conductive filler. For this reason, the heat sealer 1 in this embodiment has special mechanisms such as an insulating sheet 8, which will be described later, but it is also possible to heat seal an object that is not electrically conductive without using these mechanisms.

First, the configuration of the heat sealer 1 will be described. Figure 1 is a simplified diagram of the heat sealer 1, with the housing and other parts omitted. As shown in Figure 1, the heat sealer 1 is equipped with a transformer 2 that generates a current in a heater 4 that heats the object 10 to be sealed when heat-sealing it. The configuration with this transformer 2 is the same as that of a normal heat sealer. The transformer 2 has a primary coil 21 and a secondary coil 22. The primary coil 21 is electrically connected to an AC power source 3.

The heater 4 described above is specifically a nichrome wire, and is electrically connected to the secondary coil 22. When a current is applied to the primary coil 21 by the AC power source 3, a current flows through the secondary coil 22 by electromagnetic induction, causing the heater 4 to heat up. In the heat sealer 1, a current is applied to the heater 4 only during heat sealing, and the heater 4 is instantly heated to a temperature at which heat sealing can be performed. The heater 4 is normally raised, and during heat sealing it is lowered and pressed against the object 10 to be sealed via an insulating sheet 8, which will be described later. The heater 4 can be raised and lowered automatically or manually, and the raising and lowering mechanism is configured in the same way as a normal heat sealer.

The AC power supply 3 is connected to the controller 5, which controls the supply of electricity to the primary coil 21, i.e., the heating of the heater 4. When the heater 4 is raised and lowered automatically by the heat sealer 1 rather than manually, the raising and lowering of the heater 4 and the time the heater 4 is pressed against the object 10 to be sealed are also controlled by the controller 5. When the raising and lowering is performed manually, the controller 5 controls the AC power supply 3 so that current flows through the heater 4 while the heater 4 is pressed against the object 10 to be sealed. The controller 5 is composed of, for example, a CPU and a memory in which programs and data are stored.

The controller 5 is electrically connected to the reference potential portion G of the heat sealer 1. The reference potential portion G is the frame ground of the heat sealer 1. The heater 4 is also electrically connected to the reference potential portion G via the resistance meter 6 and the switch 7. More specifically, the heater 4 is electrically connected to the reference potential portion G via the resistance meter 6 and the switch 7 at the electrical connection portion with the secondary coil 22. The switch 7 is electrically connected in series to the resistance meter 6, and when the switch 7 is closed, the resistance meter 6 can perform measurements. The resistance value measured by the resistance meter 6 will be described in detail later. The switch 7 is opened when the transformer 2 is energizing the heater 4. The resistance meter 6 and the switch 7 are also connected to the controller 5, and their operations are controlled by the controller 5.

In the heat sealer 1 of this embodiment, an insulating sheet 8 is attached so as to cover the heater 4 from below. When the heater 4 generates heat, a current flows through the heater 4 itself, and the insulating sheet 8 is provided to prevent this current from flowing from the heater 4 into the conductive object 10 to be sealed. The insulating sheet 8 of this embodiment is provided as a cover for the heater 4, and can be replaced. The insulating sheet 8 is made of a heat-resistant insulating material, for example, a heat-resistant insulating resin sheet. Therefore, during heat sealing, the insulating sheet 8 is sandwiched between the heater 4 and the object 10 to be sealed, and transmits heat from the heater 4 to the object 10 to be sealed, but prevents current leakage from the heater 4 to the object 10 to be sealed.

The heat sealer 1 also includes a mounting table 9 on which the object to be sealed 10 is placed. The mounting table 9 may be an automatic device such as an electric conveying device that automatically conveys the object to be sealed 10, or an electric stacking device that automatically stacks the object to be sealed 10. The mounting table 9 in this embodiment is an automatic device that operates with such power, and its reference potential part G is electrically connected to the reference potential part G of the heat sealer 1 described above. Specifically, the frame ground of the heat sealer 1 is electrically connected to the frame ground of the automatic device as the mounting table 9. That is, the reference potential of the automatic device as the mounting table 9 of the heat sealer 1 is equal to the reference potential of the heat sealer 1 itself. In addition, the upper surface of the mounting table 9 on which the object to be sealed 10 is placed is formed as a conductive surface 91 having conductivity. And the conductive surface 91 is electrically connected to the reference potential part G described above. That is, the potential of the conductive surface 91 is equal to the potential of the reference potential part G.

Now, referring to FIG. 2, a case will be described in which the insulating sheet 8 is damaged and the current flowing through the heater 4 leaks into the object to be sealed 10 during heat sealing. FIG. 2 shows a state in which two holes 11 have been created in the insulating sheet 8. In such a case, a closed circuit is formed during heat sealing as shown by the dotted lines in FIG. 2, and current flows from the heater 4 into the object to be sealed 10. In this case, heat is generated due to the internal resistance of the object to be sealed 10, which may damage the appearance of the product. In addition, part of the current that should flow through the heater 4 flows into the object to be sealed 10, which may result in poor sealing due to insufficient heat generation by the heater 4.

For this reason, in the heat sealer 1 of this embodiment, it is checked whether or not insulation breakdown has occurred in the insulating sheet 8 before heat sealing. This electrical insulation check may be performed after each heat sealing operation, after a certain number of heat sealing operations, or once a day. Even if only one hole 11 is formed, electricity may flow from the heater 4 through the object to be sealed 10 to the conductive surface 91, depending on the potential difference between the heater 4 and the conductive surface 91 and whether or not a closed circuit is formed.

Next, the above-mentioned electrical insulation checking method will be described with reference to the flowchart shown in FIG. 3. Here, the case where the heater 4 is raised and lowered and heated automatically by the controller 5 will be described, but electrical insulation can be checked similarly even when it is performed manually. First, when heat sealing, the object 10 to be sealed is placed on the conductive surface 91 of the mounting table 9. In FIG. 1 and FIG. 2, the sheet-like objects 10 to be sealed and made of the same material to be heat sealed are placed on the conductive surface 91 in a stacked state.

First, the heater 4 is lowered by the controller 5, and the heater 4 is pressed against the object to be sealed 10 via the insulating sheet 8 (step S1), and the switch 7 is closed by the controller 5 (step S2). Here, the switch 7 is closed (step S2) after the heater 4 is lowered (step S1), but these steps may be performed simultaneously, or the switch 7 may be closed before the heater 4 is lowered. Also, the switch 7 may be closed before the heater 4 is pressed against the object to be sealed 10 via the insulating sheet 8, or after it is pressed. At this time, power is not yet supplied from the AC power source 3 to the primary coil 21 by the controller 5, so no power is generated by the secondary coil 22.

As described above, the potential of the conductive surface 91 is equal to the reference potential of the reference potential portion G described above, and one end of the resistance meter 6 is electrically connected to this reference potential portion G. On the other hand, when the switch 7 is closed, the other end of the resistance meter 6 is connected to the heater 4, forming a closed circuit for measuring the resistance value. The resistance meter 6 measures the resistance value on the secondary side of the transformer 2, that is, between the heater 4 and the conductive surface 91, and at this time, the insulating sheet 8 and the object to be sealed 10 are interposed between the heater 4 and the conductive surface 91.

In this embodiment, the insulating sheet 8 is attached to the heat sealer 1 so as to cover the heater 4. Therefore, the insulating sheet 8 can be interposed between the heater 4 and the object to be sealed 10 simply by lowering the heater 4, and the process of setting the insulating sheet 8 between the heater 4 and the object to be sealed 10 is performed automatically.

Following steps S1 and S2, the resistance value is measured by the resistance meter 6 (step S3). If no holes 11 are formed in the insulating sheet 8 and electrical insulation is ensured, the measured resistance value will be sufficiently large. On the other hand, if holes 11 are formed in the insulating sheet 8 and electrical insulation is not ensured, current flows from the heater 4 through the object to be sealed 10, and the resistance value of this path is measured by the resistance meter 6. The resistance value at this time is sufficiently smaller than the resistance value when the electrical insulation of the insulating sheet 8 is ensured. A reference value for judging electrical insulation is set between these two. Then, it is judged whether the measured resistance value is equal to or greater than the judgment reference value (step S4).

If the measured resistance value is less than the judgment reference value (NO in step S4), it can be determined that the electrical insulation of the insulating sheet 8 has been destroyed, and a warning is issued (step S5). On the other hand, if the measured resistance value is equal to or greater than the judgment reference value (YES in step S4), it can be determined that the electrical insulation of the insulating sheet 8 has been secured, and heat sealing is then performed. Specifically, first, the switch 7 is opened (step S6), and the closed circuit for the resistance measurement described above is also opened. At this time, the primary circuit and secondary circuit of the transformer 2 are electrically separated.

Then, power is supplied from the AC power source 3 to the primary coil 21 by the controller 5, and power flows to the secondary coil 22 by electromagnetic induction, causing the heater 4 to heat up. The time required to heat seal the object 10 to be sealed is preset, and the power supply from the AC power source 3 automatically ends after the specified time, and heating by the heater 4 also ends (step S7). This completes the heat sealing. After the above-mentioned step S5 or step S7, the controller 5 raises the heater 4 together with the insulating sheet 8 (step S8). In this way, the electrical insulation of the heat sealer 1 is confirmed.

The heat sealer 1 in the electrical insulation confirmation method according to this embodiment includes a transformer 2, a heater 4 electrically connected to the secondary coil 22 of the transformer 2, an insulating sheet 8 arranged between the heater 4 and the object to be sealed 10, and a mounting table 9 having a conductive surface 91. The conductive surface 91 is electrically connected to a reference potential portion G. Then, the resistance value between the heater 4 and the reference potential portion G is measured in a state in which the heater 4 is in contact with the object to be sealed 10 placed on the conductive surface 91 via the insulating sheet 8 without supplying power to the primary coil 21. The insulation of the insulating sheet 8 is confirmed based on the measured resistance value. Therefore, since the insulation of the insulating sheet 8 can be reliably confirmed, it is possible to reliably avoid poor appearance and poor sealing of the heat-sealed object to be sealed 10. In other words, even if the object to be sealed 10 has conductivity, heat sealing can be reliably performed.

In this embodiment, the heat sealer 1 further includes a resistance meter 6 connected between the secondary coil 22 and the reference potential portion G, and a switch 7 electrically connected in series to the resistance meter 6. The switch 7 is closed when measuring the resistance value, and is opened when the heater 4 is heated, i.e., when heat sealing. This allows the above-mentioned resistance value to be measured when checking the insulation, while the primary and secondary circuits of the transformer 2 are separated when heat sealing, ensuring the safety of the device.

Furthermore, in this embodiment, the insulating sheet 8 is attached to the heat sealer 1 so as to cover the heater 4. Therefore, when checking the insulation and when heat sealing, the insulating sheet 8 can be automatically interposed between the heater 4 and the object to be sealed 10, making the work more efficient.

Here, according to the electrical insulation checking method of this embodiment, the heater 4 is brought into contact with the object 10 to be sealed via the insulating sheet 8, and the resistance value is measured by the resistance meter 6 in the above-mentioned state with the switch 7 closed. Then, if the measured resistance value is equal to or greater than the reference value, the switch 7 is opened and then electricity is passed through the primary coil 21 to heat the heater 4, thereby heat-sealing the object 10 to be sealed. Therefore, if the insulation of the insulating sheet 8 is checked and it is determined that the insulation is ensured, the heater 4 can be lowered and the heat sealing operation can be started directly, which makes it possible to improve the efficiency of the work, including the heat sealing operation.

The present disclosure is not limited to the above-described embodiment. For example, the electrically conductive object 10 to be sealed is limited to a shape that can sufficiently transmit the heat required for heat sealing, but is not limited to a sheet-like object as in the above-described embodiment. In addition, the electrically conductive object 10 to be sealed in the above-described embodiment is a sheet member made of a thermoplastic resin containing an electrically conductive filler, but it may also be a CFRP sheet such as a CFRTP sheet.

Reference Signs List 1 Heat sealer 2 Transformer 21 Primary coil 22 Secondary coil 3 AC power source 4 Heater 6 Resistance meter 7 Switch 8 Insulating sheet 9 Mounting table 91 Conductive surface 10 Sealing object G Reference potential portion

Claims (4)

A method for checking electrical insulation of a heat sealer, comprising the steps of:
the heat sealer comprises a transformer having a primary coil and a secondary coil, a heater electrically connected to the secondary coil, an insulating sheet disposed between the heater and an electrically conductive object to be sealed, and a mounting table having a conductive surface on which the object to be sealed is placed;
the conductive surface of the mounting table is electrically connected to a reference potential portion of the heat sealer;
measuring a resistance value between the heater and the reference potential portion while the heater is in contact with the object to be sealed placed on the conductive surface via the insulating sheet without supplying power to the primary coil;
A method for checking the electrical insulation of a heat sealer, comprising: checking the insulation property of the insulating sheet based on the measured resistance value. The heat sealer is
a resistance meter connected between the secondary coil and the reference potential portion for measuring the resistance value;
a switch electrically connected in series with the ohmmeter,
2. The method for checking electrical insulation of a heat sealer according to claim 1, wherein the switch is closed when the resistance value is measured, and the switch is opened when the heater is heated. The method for checking the electrical insulation of a heat sealer according to claim 2, wherein the insulating sheet is attached to the heat sealer so as to cover the heater. The method for checking the electrical insulation of a heat sealer according to claim 2 or 3, in which the heater is brought into contact with the object to be sealed via the insulating sheet, and if the resistance value measured by the resistance meter with the switch closed is equal to or greater than a reference value, the switch is opened and then current is passed through the primary coil to heat the heater and heat seal the object to be sealed.

Images