JP7780368B2 - Electrical heating device and cylindrical laminate manufacturing system - Google Patents

Description

The present invention relates to an electric heating device that heats a metal body by passing an electric current directly through it, and a cylindrical laminate manufacturing system equipped with this electric heating device.

Cylindrical laminates such as cartridge filters are manufactured by heating a heat-sealable sheet, such as a nonwoven fabric sheet, while winding it around a core and then heat-sealing each layer of the heat-sealable sheet (see, for example, Patent Document 1). In the method for manufacturing a cylindrical laminate described in Patent Document 1, the metal core is preheated to a temperature higher than that of the drive roller using a heat transfer medium or electric heater to improve the adhesion of the heat-sealable sheet and prevent wrinkles from forming.

On the other hand, one method for heating rod-shaped or cylindrical metal bodies such as winding cores is resistance heating, in which an electric current is passed directly through the metal body to heat it. However, in the production of cylindrical laminates, the winding core needs to be heated to about 150°C in a short period of time. Therefore, when resistance heating is used, a large current of about 500 A must be passed from the electrode to the metal winding core, which can short-circuit the winding core and electrode, making it more likely to generate sparks (arc discharge).

Conventionally, methods proposed to prevent sparks from occurring during resistance heating include, for example, providing a control unit in the resistance heating device to gradually control the current value supplied to the electrodes (see Patent Document 2), and providing a coated section on the surface of the metal body to be heated, where an antioxidant is applied, and an exposed section where no antioxidant is applied, and bringing the electrode into contact with the exposed section (see Patent Document 3).

JP 2012-245771 A Japanese Patent Application Laid-Open No. 2018-195539 JP 2018-167284 A

When sparks occur during resistance heating, the spark marks create irregularities on the surface of the metal body being heated, creating gaps between the electrodes and the metal body, narrowing the path for current and making sparks even more likely to occur. Thus, conventional resistance heating devices have the problem that once a spark occurs, it becomes even more likely to occur. In particular, in the production of cylindrical laminates, even if the irregularities created by the spark marks are only around 0.1 to 0.2 mm, scratches caused by the irregularities can appear on the inside of the cylindrical laminate when it is removed from the core, resulting in product defects. Therefore, it is necessary to reliably suppress sparks.

Meanwhile, Patent Documents 2 and 3 propose methods for suppressing spark generation during resistance heating, but neither method is suitable for applications in which electricity is repeatedly passed through a metal body. Specifically, the method described in Patent Document 2 assumes that if a spark occurs, the exposed portion will be cut off and discarded. However, in the case of metal bodies that are used repeatedly, such as the winding core of a cylindrical laminate, it is not possible to cut off and discard a portion of the metal body midway through use. Furthermore, the method described in Patent Document 2 applies an antioxidant to areas other than those that come into contact with the electrodes, but applying an antioxidant to the winding core of a cylindrical laminate can result in the antioxidant being transferred to the manufactured cylindrical laminate and becoming a foreign substance.

In addition, the method described in Patent Document 3 involves first passing a small current to intentionally short-circuit the electrodes and metal body while minimizing damage, and then increasing the current value to raise the temperature of the metal body, so it takes time to heat the metal body to the desired temperature. Furthermore, in the case of metal bodies that are used repeatedly, such as the winding core of a cylindrical laminate, even if a single short circuit causes little damage, repeated short-circuiting can result in major defects, so it is desirable to minimize the generation of sparks.

The present invention aims to provide an electric heating device and a cylindrical laminate manufacturing system that can suppress spark generation and is less likely to cause scratches on the metal object being heated even when electricity is repeatedly applied.

The inventors conducted extensive research to solve the above-mentioned problems, and discovered that by forming a groove in the electrode and placing a conductive tip made of a thin metal plate over this groove, and electrically connecting the metal body and electrode via the conductive tip, it is possible to suppress the generation of sparks even when a rod-shaped or cylindrical metal body is heated by passing a large current through it, leading to the present invention.

In other words, the electric heating device of the present invention is an electric heating device for heating a rod-shaped or cylindrical metal body, and comprises a pair of electrodes arranged spaced apart on the metal body, a power supply unit that supplies power to the pair of electrodes, and an electric tip that is arranged between the electrodes and the metal body and consists of a metal plate with a thickness of 0.05 to 1 mm, the surfaces of the pair of electrodes are metal-plated and have linear grooves extending from one end to the other end formed on the surface on which the metal body is arranged, the electric tip is arranged on each groove of the pair of electrodes, the metal body is arranged on the electric tip along the groove, and the metal body and the electrodes are electrically connected via the electric tip.
A heat sink may be attached to the pair of electrodes. In this case, the heat sink may have, for example, a plurality of fins arranged in a comb-like pattern, with the fins having a thickness of 1 to 10 mm and the spacing between the fins being 2 to 6 times the thickness.
The grooves formed in the pair of electrodes may be V-grooves having a V-shaped cross section, for example, and in this case the inner angle of the V may be 150 to 170°.
The metal plating of the electrodes is, for example, nickel plating.

The cylindrical laminate manufacturing system of the present invention includes the aforementioned electric heating device, a rod-shaped or cylindrical metal body around which a heat-sealable sheet is wound, and a winding device that winds the heat-sealable sheet around the metal body, and the metal body is electrically heated by the electric heating device.

According to the present invention, the rod-shaped or cylindrical metal body and the electrode are electrically connected via an electric tip, which suppresses sparks during electrical heating and reduces the risk of scratches on the metal body being heated, even when current is applied repeatedly.

1 is a conceptual diagram showing a configuration of a direct resistance heating device according to a first embodiment of the present invention. 1A and 1B are cross-sectional views showing the relationship between the electrode 11 and the current-carrying tip 13 of the electric heating device 1 shown in FIG. 1 and the metal body 2, where A shows the state before use and B shows the state during electric heating. 2 is a diagram showing a state in which a heat sink 14 is attached to an electrode 11 in the electric heating device 1 shown in FIG. 1 . FIG. FIG. 10 is a conceptual diagram showing an example of the configuration of a manufacturing system for a cylindrical laminate according to a second embodiment of the present invention.

The following describes in detail the embodiments of the present invention, with reference to the accompanying drawings. Note that the present invention is not limited to the embodiments described below.

(First embodiment)
First, a first embodiment of the resistance heating device according to the present invention will be described. Fig. 1 is a conceptual diagram showing the configuration of the resistance heating device of this embodiment. Also, Figs. 2A and 2B are cross-sectional views showing the relationship between the electrode 11, the current-carrying tip 13, and the metal body 2 of the resistance heating device 1 shown in Fig. 1, with Fig. 2A showing the state before use and Fig. 2B showing the state during resistance heating.

As shown in FIG. 1, the electric heating device 1 of this embodiment is a device that heats a rod-shaped or cylindrical metal body 2 by passing current directly through it, and includes at least a pair of electrodes 11, a power supply unit 12 that supplies power to each electrode 11, and an electric tip 13 that is disposed between each electrode 11 and the metal body 2. If necessary, a heat sink 14 can be attached to each electrode 11 of this electric heating device 1.

[Metal body 2]
The metal body 2 to be heated is, for example, a solid or hollow material having a circular, elliptical, or polygonal cross section. The metal body 2 may be made of any metallic material that can be heated by electrical current, and its material, shape, and size are not particularly limited. For example, when the metal body 2 is a winding core used in the manufacture of a cylindrical laminate, a relatively thick cylindrical body made of iron or stainless steel is used.

[Electrode 11]
The pair of electrodes 11 may be, for example, block-shaped electrodes, and the electrodes 11 are disposed at opposite ends of the metal body 2 at a distance from each other. Note that the "ends" referred to here do not necessarily have to be the ends of the metal body 2 in the strict sense, but may be the ends of the portion that needs to be heated. Also, although Figures 1 and 2 show a configuration in which the electrode 11 is disposed below the metal body 2 and the metal body 2 is placed on the electrode 11, the present invention is not limited to this. The electrode 11 may be composed of two members, an upper electrode and a lower electrode, and the metal body 2 may be sandwiched between the upper electrode and the lower electrode, or a ring-shaped electrode may be used as the electrode 11.

Generally, copper is used as an electrode material because it is economical and has high conductivity, but when the metal body 2 of a copper electrode is heated by electrical heating, the copper electrode is oxidized by the heat and copper oxide is formed on the surface. Because copper oxide has high electrical resistance, the formation of copper oxide creates areas of high and low electrical resistance in the electrode. Specifically, the electrical resistivity of copper (Cu) is 1.7× ^10-8 Ω·m, while the electrical resistivity of copper (I) oxide ( _Cu2O ) is ¹⁰⁶ to 107 ^Ω ·m, a difference of approximately ¹⁰¹² times.

As such, because there is a large difference in electrical resistivity between copper and copper oxide, if an electrode has both oxidized and non-oxidized parts, the difference between the maximum and minimum electrical resistivity values will be large. As a result, areas will be created where electricity does not flow, and large amounts of current will flow into areas where electricity does flow, causing sparks. Therefore, in the resistance heating device 1 of this embodiment, the entire surface of each electrode 11 is metal-plated to prevent the copper electrode material from coming into contact with oxygen. This prevents copper oxide from forming on the electrode 11.

The material for the metal plating film formed on the surface of the electrode 11 can be any metallic material that is conductive and resistant to oxidation, such as nickel, cobalt, gold, and silver. Among the various metal plating films, nickel plating is preferred from the perspective of heat resistance. Nickel plating has high heat resistance and can prevent an increase in electrical resistance due to oxidation of the electrode surface, thereby suppressing spark generation.

The thickness of the metal plating film formed on the surface of the electrode 11 is preferably 5 to 15 μm, more preferably 5 to 10 μm, from the viewpoints of preventing oxidation and improving heat resistance. If the thickness of the metal plating film is less than 5 μm, sufficient heat resistance may not be obtained, and forming a plating film with a thickness greater than 15 μm will not change the effect but will only increase costs. Furthermore, from the viewpoint of suppressing spark generation, the electrical resistivity of the metal plating layer is preferably approximately 1.6×10 ⁻⁸ to 2.2×10 ⁻⁷ Ω·m.

A groove 11a is formed linearly from one end to the other on the surface of the electrode 11 on which the metal body 2 is placed, and the metal body 2 is placed along this groove 11a. The shape of the groove 11a may be, for example, a V-groove with a V-shaped cross section, a U-groove with a U-shaped cross section, or a rectangular cross section, but is not limited to these. It is sufficient if the cross section perpendicular to the longitudinal direction has a symmetrical shape. For example, if the groove 11a is a V-groove, the inner angle of the V-shape is preferably 150 to 170 degrees. By setting the inner angle of the V-groove within this range, the contact area between the electrode 11 and the conductive tip 13 and the contact area between the conductive tip 13 and the metal body 2 can be secured, improving the conductivity from the electrode 11 to the metal body 2.

The size of the groove 11a is not particularly limited, as long as it is large enough to provide a contact area between the conductive tip 13 and the metal body 2 to ensure a sufficient amount of current flow, and can be set appropriately depending on the thickness of the conductive tip 13 and the diameter of the metal body 2.

[Power supply unit 12]
The power supply unit 12 supplies power to the pair of electrodes 11 to cause a current to flow between the electrodes 11. The power supply unit 12 in the resistance heating device 1 of this embodiment is preferably a power supply capable of flowing a large current of about 500 A, and from the viewpoint of temperature control, it is preferable that it is capable of PID control (Proportional-Integral-Differential Controller). For example, by using a transformer capable of stepping down a voltage of 200 V to about 15 V, it is possible to realize a power supply unit 12 capable of flowing a large current of about 500 A (maximum 800 A).

[Electrifying tip 13]
The current-carrying tip 13 is a thin metal plate having a thickness of 0.05 to 1 mm, and is disposed between each electrode 11 and the metal body 2, with the electrodes 11 and the metal body 2 being electrically connected via the current-carrying tip 13. If the thickness of the current-carrying tip 13 is less than 0.05 mm, it may be damaged during repeated energization. If the thickness of the current-carrying tip 13 exceeds 1 mm, the current-carrying tip 13 will not be able to conform to the curved surface of the metal body 2, reducing the contact area and making it impossible to ensure a sufficient amount of current. The thickness of the current-carrying tip 13 can be set appropriately depending on the material, etc., but when a brass plate is used, it is preferably 0.2 to 0.4 mm.

The material of the energizing tip 13 may be any metal with an electrical resistivity of approximately 1.6×10 ⁻⁸ to 2.2×10 ⁻⁷ Ω·m, such as brass, silver, copper, aluminum, nickel, or lead. However, if the rigidity of the energizing tip 13 is high, the energizing tip 13 may not be able to conform to the curved surface of the metal body 2, reducing the contact area and potentially preventing a sufficient amount of current from being passed through. Furthermore, if the rigidity of the energizing tip 13 is low, it may be damaged during repeated energization. Therefore, it is preferable that the rigidity of the energizing tip 13 be approximately 75×10 ⁹ to 120×10 ⁹ N/m ² in terms of elastic modulus (Young's modulus).

By placing the aforementioned conductive tip 13 between the electrode 11 and the metal body 2, the current flow can be improved and sparks can be suppressed. If the metal body 2 is placed on a block electrode without using the conductive tip 13, the contact between the electrode and the metal body 2 will be a line contact with a width of about 1 mm, and it will not be possible to achieve a current flow sufficient to heat the metal body 2. Furthermore, even if an electrode 11 with a groove 11a is used and the metal body 2 is placed along the groove 11a, if the shape and size of the groove 11a are not set to match the shape and diameter of the metal body 2, a sufficient contact area will not be obtained and the current flow will be reduced.

In the electric resistance heating device 1 of this embodiment, as shown in FIG. 2A, the electric-conductive tip 13 is placed on the groove 11a of the electrode 11, and the metal body 2 is placed on top of it along the groove 11a. In this state, pressure is applied to the metal body 2 from above. As a result, as shown in FIG. 2B, the electric-conductive tip 13 curves to fit the outer surface of the metal body 2, and the concave electric-conductive tip 13 and part of the metal body 2 are pressed into the groove 11a. As a result, the contact area between the electric-conductive tip 13 and the metal body 2 increases, improving the conductivity from the electrode 11 to the metal body 2 via the electric-conductive tip 13.

Here, the contact rate between the conductive tip 13 and the metal body 2 is preferably such that the conductive tip 13 contacts at least 10% of the circumference of the metal body 2 at any cross section in the longitudinal direction. This reduces the resistance R at the contact point between the conductive tip 13 and the metal body 2, making it possible to reduce the resistance R to approximately 1/15 or less of the state shown in Figure 2A.

[Heat sink 14]
When the electric heating device 1 repeatedly applies electric current to heat the metal body 2 from the electrodes 11, the temperature of the electrodes 11 may rise, increasing their resistance. For example, if the electrodes 11 are made of copper, their resistance at 160°C is approximately 1.6 times their resistance at 20°C. Since high resistance of the electrodes 11 can cause sparks to occur, the electric heating device 1 of this embodiment has heat sinks 14 attached to each electrode 11 as needed. Attaching the heat sinks 14 integrally to the electrodes 11 in this manner prevents the temperature of the electrodes 11 from rising due to the passage of current, and suppresses sparks due to increased electrical resistance.

Figure 3 shows the heat sink 14 attached to the electrode 11 of the electric heating device 1. The type of heat sink 14 is not particularly limited, but from the perspective of heat dissipation, a heat sink with multiple fins 14a arranged in a comb-like pattern as shown in Figures 1 and 3 is preferred. The material of the heat sink 14 is not particularly limited, and considering the influence of Joule heat, a material with low electrical resistance is preferred. However, from the perspectives of workability into fins, hardness, and economy, aluminum or an aluminum alloy is preferred, as it has a relatively low electrical resistance and excellent workability.

For example, if the electrode 11 is made of copper and the heat sink 14 is made of aluminum, the electrical resistance of aluminum is higher than that of copper, so the current from the electrode 11 flows toward the metal body 2 rather than the discharge plate 14. On the other hand, the heat from the electrode 11 is also transmitted to the discharge plate 14 and dissipated from the fins 14a, thereby suppressing the temperature rise of the electrode 11.

From the perspective of the surface area and mechanical strength of the heat sink 14, the thickness of each fin 14a is preferably 1 to 10 mm, and more preferably 1 to 3 mm. If the fins 14a are too thick, fewer fins 14a can be installed, resulting in an insufficient surface area for the entire heat sink 14 and reduced heat dissipation efficiency. On the other hand, if the fins 14a are too thin, the strength will be insufficient. Furthermore, the spacing d between each fin 14a is preferably 2 to 6 times the thickness of the fins 14a, and more preferably 3 to 5 times. If the spacing between the fins 14a is too narrow, heat will easily become trapped, and if the spacing between the fins 14a is too wide, fewer fins 14a can be installed, resulting in an insufficient surface area for the entire heat sink 14 and reduced heat dissipation efficiency.

The height of each fin 14a on the heat sink 14 may all be the same as shown in Figure 1, or as shown in Figure 3, several fins 14a on the electrode 11 side may be lower than the other fins 14a, or the height of the fins 14a may increase as they move away from the electrode 11. Furthermore, the fins 14a may be arranged at equal intervals, or the intervals between each fin 14a may vary.

As described above in detail, the resistance heating device of this embodiment forms a linear groove extending from one end to the other in the electrode, and a thin metal plate current-carrying tip is placed in this groove. The metal object to be heated and the electrode are electrically connected in the electrode groove via the current-carrying tip. This improves the electrical conductivity and suppresses the occurrence of sparks even when a large current is used for electrical heating. Therefore, the resistance heating device of this embodiment is less likely to cause scratches on the metal object to be heated or the electrode, even when current is passed repeatedly.

In addition, the electric heating device of this embodiment has a discharge plate integrally attached to the electrode, which suppresses temperature increases in the electrode and further enhances the effectiveness of suppressing spark generation.

Second Embodiment
Next, a cylindrical laminate manufacturing system according to a second embodiment of the present invention will be described. Fig. 4 is a conceptual diagram showing an example of the configuration of the cylindrical laminate manufacturing system of this embodiment. As shown in Fig. 4, the cylindrical laminate manufacturing system of this embodiment includes the electric heating device 1 of the first embodiment described above, a rod-shaped or tubular metal body (winding core 21) around which the heat-sealable sheet 3 is wound, and a winding device 4 that winds the heat-sealable sheet 3 around the winding core 21. In this manufacturing system, for example, the winding core 21 is electrically heated by the electric heating device 1, and then the heat-sealable sheet 3 is wound around the winding core 21 by the winding device 4, while heat-sealing each layer of the heat-sealable sheet 3.

[Heat-fusible sheet 3]
The thermal adhesive sheet 3 constituting the cylindrical laminate can be, for example, a nonwoven fabric sheet, which is a fiber assembly. The raw fibers of the nonwoven fabric sheet may be any fibers containing thermal adhesive fibers, and can be appropriately selected depending on the required heat resistance, chemical resistance, etc. The thermal adhesive fibers used in the thermal adhesive sheet can be formed from thermoplastic resins such as olefin resins, polyester resins, polyamide resins, styrene resins, cellulose resins, vinyl resins, fluorine resins, polyphenylene sulfide, polyether ether ketone, polyether ketone, and thermoplastic polyimide.

Examples of olefin-based resins include polyethylene and polypropylene. Examples of polyester-based resins include polyethylene terephthalate, polybutylene terephthalate, and aromatic polyester. Examples of polyamide-based resins include polyamide 6 and polyamide 66. Examples of styrene-based resins include polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, and acrylonitrile-butadiene-styrene copolymer.

Cellulose-based resins include cellulose acetate, cellulose propionate, and cellulose butyrate. Vinyl-based resins include polyvinyl chloride, polyvinylidene chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyvinyl alcohol, and ethylene-vinyl acetate copolymer. Fluorine-based resins include tetrafluoroethylene-perfluoroalkoxyvinyl ether copolymer (PFA) and polytetrafluoroethylene (PTFE).

The heat-fusible fibers used in nonwoven fabric sheets may be single fibers made of a single thermoplastic resin, or may be composite fibers made of two or more thermoplastic resins with different melting points. Examples of composite fibers made of two or more thermoplastic resins include core-sheath composite fibers, eccentric sheath-core composite fibers, and side-by-side composite fibers. When a nonwoven fabric is made of two or more single fibers with different melting points or composite fibers made of two or more thermoplastic resins with different melting points, from the perspective of maintaining the structure of the nonwoven fabric, it is preferable to heat the fibers at a temperature that melts the low-melting-point thermoplastic resin but not the high-melting-point thermoplastic resin, and to heat-fusibly bond the fibers only with the low-melting-point thermoplastic resin.

The nonwoven fabric sheet used in the cylindrical laminate may contain one or more types of non-thermal-bonding fibers in addition to thermally bondable fibers. Non-thermal-bonding fibers used in the thermally bondable sheet may include inorganic fibers, thermosetting resin fibers, natural fibers, and high-strength fibers. Examples of inorganic fibers include glass fibers, carbon fibers, ceramic fibers, and metal fibers. Examples of thermosetting resin fibers include epoxy resin fibers, phenolic resin fibers, unsaturated polyester fibers, polyimide fibers, and polyurethane fibers. Examples of natural fibers include cellulose fibers and silk fibers. Examples of high-strength fibers include aramid fibers, polyarylate fibers, and polyparaphenylene benzoxazole fibers.

The fibers constituting the nonwoven fabric sheet may optionally contain antioxidants, UV absorbers, light stabilizers, antistatic agents, antislip agents, antiblocking agents, lubricants, colorants, flame retardants, antibacterial agents, plasticizers, fillers, etc. The type of nonwoven fabric sheet is not particularly limited, and examples include thermally bonded nonwoven fabrics, needle-punched nonwoven fabrics, water-punched nonwoven fabrics, and melt-blown nonwoven fabrics. Furthermore, the nonwoven fabric sheet may be a wet-laid or dry-laid nonwoven fabric, and may be a short-fiber or long-fiber nonwoven fabric. The basis weight of the nonwoven fabric sheet is also not particularly limited, and may be, for example, in the range of 10 to 100 g/ ^m² .

[Core 21]
The winding core 21 is a rod-shaped or cylindrical metal body. There are no particular limitations on the material of the winding core 21, but in the case of a cylindrical metal body, it is preferably formed from a steel material such as iron or stainless steel to prevent deformation due to heating. The diameter of the winding core 21 used in the cylindrical laminate manufacturing system of this embodiment is, for example, 6 to 95 mm.

When a cylindrical metal body is used for the winding core 21, it is desirable to make it thick to prevent warping; however, if the wall thickness is too large, the volume increases, and it takes time to reach the specified temperature by electrical heating, reducing productivity. Therefore, when the winding core 21 is a cylindrical metal body, it is preferable to make the wall thickness approximately 2.5 to 4.5 mm. Note that when the diameter of the winding core 21 is 14 mm or less, the volume is small, which has little effect on electrical heating time and ease of handling, so from the perspective of preventing warping, it is preferable to use a rod-shaped metal body for the winding core 21.

[Take-up device 4]
The winding device 4 winds the heat-fusible sheet 3 onto the winding core 21 and includes a drive roller 41 that is driven to rotate about an axis parallel to the axis of the winding core 21. The drive roller 41 is composed of, for example, two rollers 41a and 41b of the same diameter, and each of the rollers 41a and 41b is driven to rotate independently. When the layers of the heat-fusible sheet 3 are heat-fused in the winding device 4, the rollers 41a and 41b of the drive roller 41 are heated by an electric heater or a heat medium, and are independently controlled so that their surfaces reach a predetermined temperature.

If necessary, the winding device 4 may be provided with a pressure unit 42 that presses the winding core 21 downward, i.e., toward rollers 41a and 41b, and a guide roller 43 that uses its own weight to press the heat-sealable sheet 3 toward roller 41a of the drive roller 41, thereby preventing wrinkles from forming in the heat-sealable sheet 3 wound around the winding core 21. The winding device 4 may further be provided with a sheet cutting device (not shown) that cuts the heat-sealable sheet 3 and a sheet unwinding machine (not shown) that unwinds the heat-sealable sheet 3.

[Other configurations]
In addition to the above-described electrical heating device 1, winding core 2, and winding device 4, the cylindrical laminate manufacturing system of this embodiment may also be provided with a cooling device (not shown) for cooling the cylindrical laminate, a drawing machine (not shown) for pulling out the winding core 21 from the cylindrical laminate, a laminate cutting device (not shown) for cutting the cylindrical laminate to a predetermined length, and the like.

[Operation]
Next, we will explain the operation of the cylindrical laminate manufacturing system of this embodiment, i.e., a method of manufacturing a cylindrical laminate using the cylindrical laminate manufacturing system shown in Fig. 4. When manufacturing a cylindrical laminate using the manufacturing system of this embodiment, first, the winding core 21 is heated to a predetermined temperature by the electrical heating device 1, and the heated winding core 21 is placed between the two rollers 41a, 41b of the drive roller 41 of the winding device 4.

When the drive roller 41 is rotated in this state, the core 21 also rotates, and the heat-sealable sheet 3, which has been unwound from a sheet unwinder (not shown), for example, is wound onto the core 21. At this time, each layer of the heat-sealable sheet 3 wound onto the core 21 is thermally fused by the heat of the core 21 and the drive roller 41. Then, once the predetermined winding diameter is reached, the heat-sealable sheet 3 is cut using a sheet cutting device (not shown) or the like, and winding is completed when the remaining sheet has been wound.

Next, the outer diameter of the cylindrical laminate is adjusted by applying pressure using the pressure unit 42 as needed, and the cylindrical laminate is then discharged while still wound around the winding core 21 and cooled to approximately room temperature by air cooling or the like. The winding core 21 is then pulled out of the cylindrical laminate using a drawing machine (not shown) or the like, and if needed, cut to a predetermined length using a laminate cutting device (not shown) or the like to produce products such as cartridge filters.

In the cylindrical laminate manufacturing system shown in Figure 4, an electric heating device 1 is provided separately from the winding device 4, and the winding core 21 heated by the electric heating device 1 is placed on the winding device 4, but the present invention is not limited to this. The winding core 21 may be heated by the electric heating device 1 while the heat-sealable sheet 3 is being wound by the winding device 4.

As described above in detail, the cylindrical laminate manufacturing system of this embodiment heats the winding core using the electric heating device of the first embodiment described above, thereby suppressing the generation of sparks during electric heating and preventing the occurrence of unevenness on the surface of the winding core. If the surface of the winding core is uneven, scratches will be made on the inside of the cylindrical laminate when the winding core is pulled out of the cylindrical laminate. However, with the manufacturing system of this embodiment, the winding core can be heated without causing unevenness, so scratches caused by the unevenness of the winding core do not occur on the cylindrical laminate. As a result, the occurrence of product defects is reduced in the production of cylindrical laminates, thereby improving yield.

The effects of the present invention will be specifically explained below using examples. In these examples, electrical heating was performed using the method and conditions shown below, and the occurrence of sparks was confirmed.

Example 1
A pair of copper block electrodes with a linear V-groove extending from one end to the other was prepared, a nickel plating film with a total thickness of approximately 10 μm was formed on the surface of each electrode, and a heat sink with multiple fins arranged in a comb-like pattern was attached to each electrode. The pair of electrodes were then arranged spaced apart so that the V-grooves were aligned linearly, and a 0.3 mm thick brass conductive tip was placed on the V-groove of each electrode.

The stainless steel cylindrical core to be heated was then placed on the current-carrying tip along the V-groove of a pair of electrodes spaced a specified distance apart, and the current-carrying tip was pressed from above with a cylinder to deform along the outer surface of the core, giving the current-carrying tip a curve similar to that of the core. The current-carrying tip, electrode, and core were then tightly attached with the cylinder, and while maintaining this state, electricity was applied at a current value of 500 A. When the core reached 150°C, electricity was stopped. This procedure was repeated 200 times, and the appearance of the electrodes and core was observed visually and by touch.

Example 2
Heating was carried out by applying current under the same method and conditions as in Example 1, except that the discharge plate attached to the electrode was removed, and the appearance of the electrode and core was checked visually and by touch.

Example 3
Heating by applying current was carried out in the same manner and under the same conditions as in Example 1, except that the shape of the groove formed in the electrode was changed to a U-shaped groove having a U-shaped cross section, and the appearance of the electrode and the winding core was observed visually and by touch.

Example 4
Heating by applying current was carried out in the same manner and under the same conditions as in Example 1, except that the shape of the grooves formed in the electrodes was changed to grooves having a rectangular cross section, and the appearances of the electrodes and winding cores were observed visually and by touch.

<Comparative Example 1>
A pair of copper block electrodes without grooves was prepared, and a nickel plating film with a total thickness of approximately 10 μm was formed on the surface of each electrode. This pair of electrodes was arranged with a predetermined distance between them, and a stainless steel cylindrical winding core to be heated was placed directly on top of them (without an electric tip), and pressed from above with a cylinder to bring the electrodes and winding core into close contact. While maintaining this state, current was increased to 500 A and current was applied, and was stopped when the winding core reached 150°C. In this comparative example, this procedure was repeated 100 times, and the appearance of the electrodes and winding core was observed visually and by touch.

<Comparative Example 2>
Resistance heating was carried out in the same manner and under the same conditions as in Comparative Example 1, except that a pair of copper block electrodes without grooves or nickel plating films was used, and the appearances of the electrodes and the core were inspected visually and by touch.

[Evaluation of spark generation]
The electric heating devices of Examples 1 to 4 and Comparative Examples 1 and 2 were evaluated according to the following criteria. The results are shown in Table 1 below.
⊚: No flaws on either the electrode or the core even after 200 cycles of current application.
◯: After 200 cycles of current application, slight scratches were observed on the electrode or core.
Δ: After 100 cycles of energization, uneven defects occurred on the electrode or the winding core.
x: After 100 cycles of current application, large irregular flaws were formed on the electrode or core, and the electrode temperature also rose significantly.

As shown in Table 1 above, the electric heating devices of Examples 1, 3, and 4 showed no defects on either the electrodes or the core, and the electrode temperature was 60-80°C, even after 200 cycles of energization and shutdown. Furthermore, with the electric heating device of Example 2, slight defects were found on the surface of the core after 200 cycles of energization, and the electrode temperature was 120-140°C, which was higher than in Example 1, but was still at a negligible level.

In contrast, with the electric heating device of Comparative Example 1, large scratches were visible on the surface of the winding core after 100 cycles of current application, and large scratches also appeared on the electrodes, creating unevenness. Furthermore, when the temperature of the electrodes in the electric heating device of Comparative Example 1 was measured, it was found to have risen to 140-160°C, even higher than that of the device of Example 2. Furthermore, when the area where the electrode winding core was placed was observed, the plating film had peeled off, exposing the copper, and some of this had turned black, suggesting the formation of copper oxide.

Similarly, with the electric heating device of Comparative Example 2, large scratches were found on the surface of the winding core after 100 cycles of current application, and numerous blackened irregularities thought to be copper oxide had appeared on the electrodes. Furthermore, when the temperature of the electrodes of the electric heating device of Comparative Example 2 was measured, it had risen to 150-170°C.

These results confirm that the present invention makes it possible to realize an electric heating device that can suppress spark generation even when repeatedly heating a metal body with a large current.

REFERENCE SIGNS LIST 1 Electric heating device 2 Metal body 3 Heat-sealable sheet 4 Winding device 11 Electrode 11a Groove 12 Power supply unit 13 Electrical tip 14 Heat sink 14a Fin 21 Winding core 41 Drive roller 41a, 41b Roller 42 Pressure unit 43 Guide roller

Claims (6)

An electric heating device for heating a rod-shaped or cylindrical metal body,
a pair of electrodes spaced apart from each other and disposed on the metal body;
a power supply unit that supplies power to the pair of electrodes;
a conductive tip arranged between the electrode and the metal body and made of a metal plate having a thickness of 0.05 to 1 mm;
and
The pair of electrodes has a surface that is metal-plated, and a linear groove extending from one end to the other end is formed on the surface on which the metal body is disposed,
the conductive tip is disposed on each groove of the pair of electrodes;
The metal body is disposed on the conductive tip along the groove, and the metal body and the electrode are electrically connected via the conductive tip. The electric heating device of claim 1, wherein a heat sink is attached to the pair of electrodes. The electric heating device described in claim 2, wherein the heat sink has multiple fins arranged in a comb-like pattern, the fins have a thickness of 1 to 10 mm, and the spacing between each fin is 2 to 6 times the thickness. An electric heating device according to any one of claims 1 to 3, wherein the grooves formed in the pair of electrodes have a V-shaped cross section, with the inner angle of the V being 150 to 170 degrees. An electric heating device according to any one of claims 1 to 4, wherein the metal plating on the electrodes is nickel plating. The electric heating device according to any one of claims 1 to 5,
a rod-shaped or cylindrical metal body around which a heat-sealable sheet is wound;
a winding device that winds the heat-sealing sheet around the metal body,
The system for manufacturing a cylindrical laminate, wherein the metal body is electrically heated by the electric heating device.