JP2020131654A - Double facer - Google Patents

Abstract

To provide a double facer that has a simple structure and that can be operated with high accuracy.SOLUTION: There is provided a double facer 90 that comprises a heating plate having an upper surface for heating a belt-shaped single-sided corrugated paper sheet P1 and a liner paper sheet P2 while feeding them in a traveling direction, in which a heating plate 92 is formed with: a plurality of base plates that are made of a first material and extend in a plate shape and are stacked in the traveling direction with a gap between each other; and a unit structure having a plurality of beams made of a second material and connecting adjacent base plates to each other, and a linear expansion coefficient of the first material is larger than the linear expansion coefficient of the second material.SELECTED DRAWING: Figure 1

Description

The present invention relates to a double facer.

In the process of manufacturing the corrugated cardboard sheet, each device called a single facer and a double facer is used. The single facer forms a single-sided corrugated cardboard sheet by attaching a corrugated plate-shaped core paper to a flat plate-shaped back liner. The double facer attaches a flat plate-shaped front liner to this single-sided corrugated cardboard sheet from the core paper side. As a specific example of this type of device, the one described in Patent Document 1 below is known.

The double facer described in Patent Document 1 is provided on a single-sided corrugated board sheet supplied from a single facer, a pair of preheaters for preheating a front liner unwound from a base paper roll, and a top of a core paper in the single-sided corrugated board sheet. A gluing device that applies raw starch, which is the raw material for glue, a hot plate that heats a single-sided corrugated cardboard sheet and a front liner in a bonded state, an upper belt conveyor that conveys the completed double-sided corrugated cardboard sheet, and a lower belt conveyor. And have. By heating with a hot plate, the raw starch applied to the core paper is gelatinized, and the core paper and the front liner are fixed to each other. A steam chamber through which steam for heating flows is formed inside the hot platen. The single-sided corrugated cardboard sheet that touches the upper surface (heat dissipation surface) of the hot plate is heated by the heat of this steam.

The hot plate is, for example, a large plate material having a width of 1900 to 2600 mm. Further, the corrugated cardboard sheet passes on the hot plate at a high speed of about 300 m / min. That is, the time that the corrugated cardboard sheet is in contact with the hot plate is about several seconds. Therefore, in order to spread heat uniformly over the entire area of the single-sided corrugated cardboard sheet on the hot plate in a short time, the hot plate is required to have extremely high flatness. In order to satisfy such a requirement, in the apparatus described in Patent Document 1, a reinforcing rib is attached to the lower surface of the hot plate for the purpose of improving rigidity and heat dissipation. It is said that the provision of the reinforcing ribs not only increases the rigidity but also balances the amount of heat radiated from the upper and lower surfaces of the hot platen to suppress the thermal deformation of the hot platen.

Japanese Unexamined Patent Publication No. 2008-200961

However, in the apparatus described in Patent Document 1, it is necessary to normally control the flow rate and temperature of steam in order to balance the amount of heat radiated from the upper surface of the hot plate and the reinforcing ribs. In addition, it is inevitable that the weight and cost of the heating plate will increase due to the provision of the reinforcing ribs.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a double facer capable of operating with high accuracy while having a simple configuration.

The double facer according to one aspect of the present invention includes a heat plate having an upper surface that heats a strip-shaped single-sided corrugated cardboard and a liner paper while feeding them in a traveling direction, and the heat plate is made of a first material and extends like a plate. It is composed of a plurality of base plates laminated at intervals from each other and a unit structure having a plurality of beams made of a second material and connecting the base plates adjacent to each other, and the coefficient of linear expansion of the first material is It is larger than the coefficient of linear expansion of the second material.

According to the above configuration, the hot plate is composed of a base plate laminated at intervals and a unit structure having a plurality of beams connecting the base plates. The first material forming the base plate has a larger coefficient of linear expansion than the second material forming the beam. Therefore, when heat is applied to the hot platen, the base plate undergoes thermal deformation in the direction of its own surface, while the thermal deformation generated in the beam becomes small. As a result, the amount of thermal deformation in the stacking direction of the base plate becomes zero or a very small value. Therefore, the thermal deformation of the hot plate in this stacking direction is zero or extremely small. As a result, the flatness of the hot plate can be maintained even in a state of being exposed to high heat.

In the double facer, the heat plate may be formed with a heat medium flow path that penetrates the inside of the heat plate and through which a heat medium flows.

According to the above configuration, the heat plate can be efficiently heated by the heat medium flowing through the heat medium flow path formed in the heat plate. In particular, since a material that does not easily cause thermal deformation is used for the hot plate itself, such a heat medium flow path can be directly formed in the hot plate. As a result, it is possible to avoid distortion and deformation of the hot plate while keeping the size and physique of the hot plate small.

The double facer further includes a skin covering the outer surface of the heat plate, and the space between the plurality of beams inside the heat plate may be a heat medium flow path through which the heat medium flows.

According to the above configuration, the outer surface of the hot plate is covered with the skin, so that a closed space (flow path) is formed inside the skin. By supplying a heat medium to this space, the hot plate can be heated efficiently. Further, since the flow path can be formed without processing in the hot plate, the manufacturing cost can be reduced. In addition, since the space exists uniformly inside the hot platen, the hot platen can be heated even more uniformly as compared with the case where the pipeline is provided inside the hot platen, for example.

The double facer may be provided along the lower surface, which is a surface opposite to the upper surface of the hot plate, and may further include a heat generating portion for heating the hot plate.

According to the above configuration, since the heat plate is less likely to undergo thermal deformation, the heat generating portion can be provided only on the lower surface of the heat plate without considering the balance between the amount of heat radiation and the temperature on the upper surface and the lower surface. As a result, the heating plate can be heated more efficiently by the heat generating portion.

In the double facer, at least one of the base plate and the beam may be formed of a metal material having a high electric resistance value.

According to the above configuration, by forming at least one of the base plate and the beam with a metal material having a high electric resistance value, an electric current can be passed through the material to generate heat. As a result, the temperature of the heat plate can be efficiently raised without using another heat source.

In the double facer, at least one of the base plate and the beam may be formed of a nickel-chromium alloy.

According to the above configuration, by using the nickel-chromium alloy, the temperature of the hot plate can be efficiently raised by passing an electric current under a high electric resistance value.

According to the present invention, it is possible to provide a double facer capable of operating with high accuracy while having a simple configuration.

It is a schematic diagram which shows the structure of the corrugator which concerns on 1st Embodiment of this invention. It is sectional drawing which shows the hot disk which concerns on 1st Embodiment of this invention. It is a perspective view which shows the non-thermal expansion member which comprises the hot disk which concerns on 1st Embodiment of this invention. It is explanatory drawing which shows the behavior of the non-thermal expansion member. It is sectional drawing which shows the structure of the hot disk which concerns on 2nd Embodiment of this invention. It is sectional drawing which shows the structure of the hot disk which concerns on 3rd Embodiment of this invention. It is sectional drawing which shows the modification of the hot disk which concerns on 3rd Embodiment of this invention. It is sectional drawing which shows the structure of the hot disk which concerns on 4th Embodiment of this invention.

[First Embodiment]
The first embodiment of the present invention will be described with reference to FIGS. 1 to 4. FIG. 1 shows the configuration of the corrugator 100 including the double facer 90 according to the present embodiment. The corrugated board 100 is an apparatus for manufacturing corrugated cardboard P3 (double-sided corrugated cardboard P3). As shown in the figure, the corrugator 100 according to the present embodiment includes a first preheater 11, a second preheater 12, a gluing device 13, and a double facer 90. Specifically, in the corrugator 100, the first preheater 11, the second preheater 12, the gluing device 13, and the double facer 90 are arranged in this order. In the following description, the side on which the double facer 90 is arranged as viewed from the first preheater 11 and the second preheater 12 is referred to as a downstream side, and the opposite side is referred to as an upstream side. Further, the direction from the upstream side to the downstream side is called a traveling direction.

The strip-shaped single-sided corrugated cardboard P1 supplied from the preceding single facer is sent to the first preheater 11. The single-sided corrugated cardboard P1 is a paper material in which a corrugated plate-shaped core paper P4 is attached to one side of a flat plate-shaped back liner paper. The first preheater 11 preheats the single-sided corrugated board P1.

The paper material (front liner P2) unwound from the base paper roll is sent to the second preheater 12. As will be described in detail later, the corrugated cardboard P3 is formed by attaching the front liner P2 to the single-sided corrugated board P1. The second preheater 12 preheats the front liner P2. The first preheater 11 and the second preheater 12 are provided at the same position in the traveling direction. That is, the preheating of the single-sided corrugated cardboard P1 and the preheating of the front liner P2 are performed in parallel on different lines. Further, the first preheater 11 is arranged above the second preheater 12. The single-sided corrugated cardboard P1 passing through the first preheater 11 is conveyed while the side to which the core paper is attached faces downward.

A gluing device 13 is arranged on the downstream side of the first preheater 11. The gluing device 13 applies raw starch, which is a precursor material of glue, to the top of the core paper P4 of the single-sided corrugated cardboard P1. That is, the gluing device 13 is arranged on the lower side of the single-sided corrugated cardboard P1 sent out from the first preheater 11. Although not shown in detail, the gluing device 13 has an application tool such as a roll brush and a drive unit for rotationally driving the application tool, and continuously and uniformly applies the raw starch to the core paper.

A double facer 90 is arranged on the downstream side of the gluing device 13. The double facer 90 is a device for attaching the front liner P2 to the single-sided corrugated cardboard P1 coated with the above-mentioned raw starch. The double facer 90 has an upper belt conveyor 91, a plurality of heating plates 92, a pressurizing device 93, and a lower belt conveyor 94. The upper belt conveyor 91 conveys the single-sided corrugated cardboard P1 that has passed through the gluing device 13 to the downstream side by frictional force in a state of being in contact with the upper belt conveyor 91 from above. A plurality of heating plates 92 are arranged below the upper belt conveyor 91 with a gap.

The hot plate 92 heats the single-sided corrugated board P1 to gelatinize the raw starch applied to the top of the core paper. In this embodiment, a plurality of heat plates 92 are arranged without gaps in the traveling direction. The pressurizing device 93 applies pressure downward to the single-sided corrugated board P1 via the upper belt conveyor 91. The lower belt conveyor 94 faces the upper belt conveyor 91 on the downstream side of the heating plate 92 with a gap. That is, the single-sided corrugated cardboard P1 and the front liner P2 are bonded together in a pressurized state between the upper belt conveyor 91 and the hot plate 92 to form corrugated cardboard P3 (double-sided corrugated cardboard P3), and then on the upper side. It is conveyed downstream by the belt conveyor 91 and the lower belt conveyor 94.

Next, the configuration of the heating plate 92 will be described with reference to FIGS. 2 to 4. As shown in FIG. 2, the heat plate 92 is formed with a plurality of heat medium flow paths F that penetrate the inside and circulate the heat medium. As an example, each heat medium flow path F extends in a direction orthogonal to the traveling direction. The plurality of heat medium flow paths F are arranged at equal intervals in the traveling direction. In forming the heat medium flow path F, specifically, a method of inserting a pipe material having a constant diameter into a through hole formed inside the heat plate 92 can be considered.

As the heat medium, high-temperature saturated steam supplied from the outside is used as an example. As the steam flows through the heat medium flow path F, the heat plate 92 itself is heated, and the heat propagates to the front liner P2 and the single-sided corrugated cardboard P1 carried on the upper surface S1 of the heat plate 92. The raw starch applied to the single-sided corrugated cardboard P1 is gelatinized by this heat, and the front liner P2 and the single-sided corrugated cardboard P1 are bonded together.

Here, the hot plate 92 is, for example, a large plate material having a width of 1900 to 2600 mm. Further, the front liner P2 and the single-sided corrugated cardboard P1 pass on the hot plate 92 at a high speed of about 300 m / min. That is, the time that the front liner P2 is in contact with the heat plate 92 is about several seconds. Therefore, in order to uniformly distribute heat on the hot plate 92 over the entire area of the front liner P2 in a short time, the hot plate 92 is required to have extremely high flatness. In other words, it is desirable that the hot plate 92 does not undergo thermal deformation or is made of a material having an extremely small amount of thermal deformation.

Therefore, in the present embodiment, the heat plate 92 is made of a material showing zero thermal deformation (or extremely small thermal deformation). Specifically, the heating plate 92 is composed of a non-thermal expansion member M.

FIG. 3 shows an example of the configuration of the non-thermal expansion member M. Any material can be used as the non-thermal expansion member M as long as the material exhibits zero thermal deformation (or extremely small thermal deformation). As shown in FIG. 3, the non-thermal expansion member M is formed in a plate shape, and a plurality of base plates 1 arranged in parallel with each other at intervals in the thickness direction, and these base plates 1 are placed on each other. It has a three-dimensional truss structure 2 to be connected. Both the base plate 1 and the three-dimensional truss structure 2 are made of a metal material. The coefficient of linear expansion of the first material forming the base plate 1 is relatively large with respect to the coefficient of linear expansion of the second material forming the three-dimensional truss structure 2. As the first material and the second material, stainless steel (SUS304, SUS310, SUS316, SUS410), Ti6Al4V, Ni-based alloy (Inconel 600, 718), high chrome steel (9Cr, 12Cr), 2.25Cr-1Mo A material selected from materials and the like is appropriately used. More specifically, it is conceivable to use SUS304 as the first material and SUS410 as the second material having a coefficient of linear expansion smaller than that of SUS304. It is also possible to use SUS304 as the first material and Ti6Al4V as the second material. In addition, aluminum alloy, copper, and carbon steel can be used as the first material or the second material. The plurality of base plates 1 face each other at equal intervals over the entire extending area.

The three-dimensional truss structure 2 has a plurality of beams 21 extending in directions intersecting each other. Each beam 21 has a rod shape. In this three-dimensional truss structure 2, the four beams 21 are one of a plurality of support points (first) in which the four beams 21 are arranged in a grid pattern on the surface of the base plate 1 on one side of the pair of base plates 1 facing each other. The support points 31) and the four support points (second support points 32) arranged in a grid pattern on the surface of the base plate 1 on the other side are connected to each other.

The base plate 1 has a support portion 41 that forms a first support point 31 by connecting a plurality of (four) beams 21 and a plurality of support portions that are adjacent to each other in the spreading direction (plane direction) of the base plate 1. It has a connecting portion 42 for connecting 41. As a result, the base plate 1 is formed with a plurality of (four) quadrangular holes (base plate hole portions 6) having a plurality of (four) first support points 31 as vertices. That is, the base plate 1 has a grid pattern that connects the first support points 31 to each other.

When viewed from the direction orthogonal to the base plate 1, the first support point 31 and the second support point 32 are arranged so that their positions do not overlap each other, and are arranged in a grid pattern at equal intervals from each other. There is. That is, the four beams 21 form a quadrangular pyramid having one first support point 31 as an apex and a quadrangle formed on the base plate 1 by the four second support points 32 as a bottom surface. .. The plurality of beams 21 have the same length as each other.

The three-dimensional truss structure 2 as described above is arranged so as to be mirror image symmetric in the stacking direction with the base plate 1 interposed therebetween. In other words, the other first support point 31 is located on the opposite side of one first support point 31 on one side surface of the base plate 1 (on the other side surface of the base plate 1). In the example of FIG. 3, the unit structure composed of the base plate 1 and the three-dimensional truss structure 2 is laminated over four layers.

Next, the behavior of the non-thermal expansion member M will be described with reference to FIG. FIG. 4 typically shows only a pair of base plates 1 and a one-layer three-dimensional truss structure 2 provided between the base plates 1. When heat is applied to the non-thermal expansion member M, the base plate 1 and the three-dimensional truss structure 2 behave as follows. First, the base plate 1 expands in the direction of its extending surface (expands in the direction of the arrow Da in FIG. 4: base plate 1a). Therefore, the distance between the above-mentioned first support points 31 is widened (first support point 31a in FIG. 4). Here, since the coefficient of linear expansion of the beam 21 is smaller than the coefficient of linear expansion of the base plate 1, the amount of thermal expansion of the beam 21 is smaller than the amount of thermal expansion of the base plate 1. As a result, the distance between the first support points 31 is widened, and the pair of beams 21 are pulled in the expanding direction of the base plate 1 (beams 21a in FIG. 4). As a result, a force is applied to the base plate 1 on one side to displace the base plate 1 on the other side in the approaching direction. Due to this force, the base plate 1 on the other side is displaced in the direction of arrow Db in FIG. As described above, while the base plate 1 expands in the spreading plane direction, the thermal deformation becomes zero (or an extremely small value) in the thickness direction (stacking direction) orthogonal to the plane direction. In the example of FIG. 5, the behavior of the base plate 1 is exaggerated for the sake of explanation. That is, in reality, the base plates 1 do not displace in the direction of approaching each other, and the thermal deformation in the stacking direction becomes zero (or an extremely small value).

On the other hand, when heat is applied to a solid plate made of a uniform material, which is different from the non-thermal expansion member M as described above, thermal expansion occurs in both the surface direction and the thickness direction. It ends up. That is, the non-thermal expansion member M can realize characteristics that have not been obtained in the past.

In the hot plate 92 according to the present embodiment, as an example, the stacking direction of the base plate 1 is the traveling direction of the corrugated cardboard P3. Therefore, the dimensions of the hot plate 92 in the traveling direction do not change or show a very small change. As a result, the distortion of the heating plate 92 is suppressed. The stacking direction of the base plate 1 on the heating plate 92 is not limited to the rearward phase. As another example, the base plate 1 may be laminated in the thickness direction or the width direction of the heating plate 92, or the base plate 1 may be laminated in the diagonal direction intersecting the thickness direction, the width direction, and the traveling direction. You may.

As described above, according to the above configuration, the heating plate 92 is composed of a base plate 1 laminated at intervals and a unit structure having a plurality of beams 21 connecting the base plates 1 to each other. ing. The first material forming the base plate 1 has a larger coefficient of linear expansion than the second material forming the beam 21. Therefore, when heat is applied to the heating plate 92, the base plate 1 undergoes thermal deformation in its own surface direction, while the thermal deformation generated in the beam 21 becomes small. As a result, the amount of thermal deformation of the base plate 1 in the stacking direction becomes zero or a very small value. In the above configuration, as an example, the stacking direction of these base plates 1 is the traveling direction of the single-sided corrugated cardboard P1 and the front liner P2 (liner paper). Therefore, the thermal deformation of the heating plate 92 in this traveling direction becomes zero or an extremely small value. As a result, the flatness of the heating plate 92 can be maintained even in a state of being exposed to high heat.

Further, according to the above configuration, the heat plate 92 can be efficiently heated by the heat medium flowing through the heat medium flow path F formed in the heat plate 92. In particular, since the heat plate 92 itself is made of a material that does not easily undergo thermal deformation, such a heat medium flow path F can be directly formed in the heat plate 92. As a result, it is possible to avoid distortion and deformation of the heat plate 92 while keeping the size and physique of the heat plate 92 small.

The first embodiment of the present invention has been described above. It should be noted that various changes and modifications can be made to the above configuration as long as the gist of the present invention is not deviated. For example, in the above embodiment, an example in which the heat medium flow path F is formed of a pipe material has been described. However, the configuration of the heat medium flow path F is not limited to this, and the heat medium flow path F may be formed by forming a through hole in the heat plate 92 and then applying a thin film coating to the inner peripheral surface thereof. It is possible. Further, in the above embodiment, an example in which the stacking direction of the base plate 1 is the traveling direction of the corrugated cardboard P3 has been described. However, the stacking direction of the base plate 1 is not limited to the above, and the stacking direction can be set to the thickness direction of the hot plate 92 as needed.

[Second Embodiment]
Subsequently, the second embodiment of the present invention will be described with reference to FIG. The same components as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted. As shown in FIG. 5, the double facer 90B according to the present embodiment includes a heat plate 92 and a skin 95 that covers the outer surface of the heat plate 92. The skin 95 has a film shape that covers the outer surface of the heating plate 92 without gaps, and is formed of a material having a small coefficient of linear expansion and a high thermal conductivity. Graphene and Invar alloys are examples of materials that form the skin 95.

Further, the space (above) between the beams 21 inside the non-thermal expansion member M forming the heat plate 92 is a heat medium flow path F2 through which the heat medium flows. High-temperature saturated steam is supplied from the outside to the heat medium flow path F2 as a heat medium.

According to the above configuration, the outer surface of the heating plate 92 is covered with the skin 95, so that a closed space (flow path) is formed inside the skin 95. By supplying a heat medium to this space, the heat plate 92 can be efficiently heated. Further, since the flow path can be formed in the heating plate 92 without processing, the manufacturing cost can be reduced. In addition, since the space exists uniformly inside the hot plate 92, the hot plate 92 can be heated even more uniformly as compared with the case where the pipeline is provided inside the hot plate 92, for example. ..

The second embodiment of the present invention has been described above. It should be noted that various changes and modifications can be made to the above configuration as long as the gist of the present invention is not deviated.

[Third Embodiment]
Next, the third embodiment of the present invention will be described with reference to FIG. The same components as those of the above embodiments are designated by the same reference numerals, and detailed description thereof will be omitted. As shown in FIG. 6, the double facer 90C according to the present embodiment has a heating plate 92 and a heat generating portion 96 provided along the lower surface S2 (the surface opposite to the upper surface S1) of the heating plate 92. I have. The heat generating portion 96 extends in a plate shape over the entire lower surface S2 of the heating plate 92. As the heat generating portion 96, for example, an electric heater that discharges internal resistance as heat energy by passing an electric current is preferably used.

According to the above configuration, since the heat plate 92 is formed by the non-thermal expansion member M, thermal deformation is unlikely to occur. Therefore, the balance of heat dissipation and temperature between the upper surface S1 and the lower surface S2 is not considered. The heat generating portion 96 can be provided only on the lower surface S2 of the heating plate 92. As a result, the heating plate 92 can be heated more efficiently.

The third embodiment of the present invention has been described above. It should be noted that various changes and modifications can be made to the above configuration as long as the gist of the present invention is not deviated. For example, as shown in FIG. 7, a plurality of ribs 8 (reinforcing materials) are arranged at equal intervals on the lower surface S2 of the heating plate 92, and a heat generating portion 96B is attached between the ribs 8 respectively. Is also possible.

[Fourth Embodiment]
Subsequently, the fourth embodiment of the present invention will be described with reference to FIG. The same components as those of the above embodiments are designated by the same reference numerals, and detailed description thereof will be omitted. In the present embodiment, the material of the non-thermal expansion member M forming the heating plate 92 is different from that of each of the above embodiments. Specifically, in the non-thermal expansion member M, at least one of the base plate 1 and the beam 21 is formed of a metal material having a high electric resistance value. As such a metal material, a nickel-chromium alloy is preferably used as an example.

According to the above configuration, by forming at least one of the base plate 1 and the beam 21 with a metal material having a high electric resistance value, an electric current can be passed through the material to generate heat. As a result, the heat plate 92 can be efficiently heated without using another heat source.

The fourth embodiment of the present invention has been described above. It should be noted that various changes and modifications can be made to the above configuration as long as the gist of the present invention is not deviated.

100 ... Corrugated board 90, 90B, 90C ... Double facer 1 ... Base plate 2 ... Three-dimensional truss structure 6 ... Base plate hole 8 ... Rib 11 ... First preheater 12 ... Second preheater 13 ... Gluing device 21 ... Beam 31 ... No. One support point 32 ... Second support point 41 ... Support part 42 ... Connection part 91 ... Upper belt conveyor 92 ... Heat plate 93 ... Pressurizing device 94 ... Lower belt conveyor 95 ... Skin 96, 96B ... Heat generation parts F, F2 ... Heat Medium flow path M ... Non-thermal expansion member P1 ... Single-sided corrugated cardboard P2 ... Front liner P3 ... Corrugated cardboard P4 ... Core paper S1 ... Top surface S2 ... Bottom surface

Claims (6)

It is equipped with a hot plate having an upper surface that heats the strip-shaped single-sided corrugated paper and liner paper while feeding them in the traveling direction.
The hot plate is
It is composed of a unit structure composed of a plurality of base plates made of a first material and extending in a plate shape and laminated at intervals from each other, and a unit structure having a plurality of beams made of a second material and connecting the adjacent base plates to each other.
A double facer in which the coefficient of linear expansion of the first material is larger than the coefficient of linear expansion of the second material. The double facer according to claim 1, wherein the heat plate has a heat medium flow path that penetrates the inside of the heat plate and through which a heat medium flows. Further provided with a skin covering the outer surface of the hot plate
The double facer according to claim 1, wherein the space between the plurality of beams inside the hot plate is a heat medium flow path through which the heat medium flows. The double facer according to claim 1, which is provided along a lower surface which is a surface opposite to the upper surface of the hot plate and further includes a heat generating portion for heating the hot plate. The double facer according to claim 1, wherein at least one of the base plate and the beam is made of a metal material having a high electric resistance value. The double facer according to claim 5, wherein at least one of the base plate and the beam is made of a nickel-chromium alloy.