JP2769988B2 - Thermal fire prevention structure of wooden fire door - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing a wooden fire door from being bent and deformed due to a fire or a difference in temperature or humidity between a room and the outside during normal use. Warpage prevention structure ".

[0002]

2. Description of the Related Art In order to enhance fire resistance, a conventional wooden fire door has a structure in which a wooden core material constituting a door body is surrounded by an inorganic fiber plate, or a core material constituting the door. In addition to injecting flame retardant chemicals into the wood itself,
Some were simply thickening the door. In this way, conventional wooden fire doors increase the heat insulation by blocking oxygen, increase the non-combustibility of the material constituting the door itself, and increase the time by increasing the thickness of the door. To ensure fire resistance.

[0003]

However, the conventional wooden fire door has a problem that when a fire occurs, the cross section of the high-temperature flame side shrinks and the door is bent and deformed toward the flame side. FIGS. 9A and 9B are conceptual diagrams showing this phenomenon. FIG. 9A is a longitudinal sectional view, and FIG. 9B is a transverse sectional view. As shown in this figure, the door 3 is rotatably provided on the hanging side door frame 44 via the hinge 41. And now,
As shown by an arrow in the figure, if a fire occurs on the side where the door opens (for example, when the door 3 is an outdoor door that opens to the outdoor OUT), the door is opened from the surface of the flame FIRE side. There is a possibility that the wood composing 3 starts to carbonize and contracts in cross section, and the door 3 warps to the flame side as shown by the two-dot chain line in FIG. Also, because the door 3 is warped,
There is a problem that a gap is formed between the door 3 and the door frames 42 to 45, and the flame FIRE penetrates the inside and outside of the room from the gap.

[0004] Further, the conventional wooden fire door has a problem in that even during normal use, warpage occurs due to a difference in temperature and humidity between the inside and outside of the room. Furthermore, in the conventional wooden fire doors, it was necessary to attach an inorganic fiber board, inject a flame retardant solution, increase the thickness of the door, etc., so that the weight of the door becomes heavy and the price becomes expensive. There was also a problem that would. In addition, with conventional wooden fire doors, the thickness of the door could not be reduced to about the thickness of steel fire doors, so general steel fire doors that are mass-produced and widely distributed on the market It cannot be applied to a steel door frame for a door, and requires a specially made door frame, thereby causing a problem that the cost is increased. The present invention has been made to solve these problems.

[0005]

In order to solve the above-mentioned problems, a structure for preventing a wooden fire door 3 from being warped according to the present invention comprises:
It has a plate-shaped core material 31 and a door-side aggregate 35 provided on the door-end side of the core material 31, and includes a door-side end surface of the core material 31.
At the joint between the door end side aggregate 35 and the hanging side end face,
A wooden fireproof door 3 provided with a metal reinforcing member 30 extending downward , wherein a cut end is provided at an end surface of the core member 31 on the door end side.
A concave groove 15 having a rectangular surface is formed to be recessed on the hanging side, and
A convex portion 25 having a rectangular cross section is formed on the hanging side end surface of the front aggregate 35.
The metal reinforcing member 30 is formed so as to protrude toward the hanging side,
The metal reinforcing member 30 includes a U-shaped member 30.
Is fitted to the projection 25 of the door-side aggregate 35,
Further, it is characterized in that it is fitted into the concave groove 15 of the core material 31 .

[0006] In addition, the heat resistance of the wooden fire door 3 according to the present invention.
The anti-slip structure comprises a plate-shaped core material 31 and a door
And a door end side aggregate 35 provided on the side,
Between the door end side end surface and the hanging side end surface of the door end side aggregate 35
A metal reinforcing member 30 extending in the vertical direction is provided at the joint of
A wooden fire door 3 which is made of
A concave groove 15 having a rectangular cross section is formed in the front end face so as to be recessed in the hanging side.
And a rectangular section on the hanging side end surface of the door-side aggregate 35.
A concave groove 25A is formed so as to be recessed on the side of the door, and
The reinforcing member 30 is made of a rod 30A having a rectangular cross section.
The metal reinforcing member 30 is provided in the groove 25A of the door-side aggregate 35.
And fitted into the concave groove 15 of the core material 31.
It is characterized by becoming.

[0007]

More preferably, a plate-shaped core material 31 and four aggregates 32 to 3 provided on the upper, lower, left and right sides of the core material 31 are provided.
5. A wooden fire door 3 comprising: a core material 31;
The upper aggregate 32 provided on the core 31 has a width dimension equal to the width of the core 31. The particle board is formed of a particle board having concave grooves 12 to 15 recessed inward on the upper, lower, left, and right sides. Consisting of hardwood or parallel plywood with
The lower aggregate 33 provided at the lower part of the core 31 is made of a parallel plywood having a width dimension equal to the width of the core 31, and the suspension aggregate provided at the suspension side of the core 31. 3
4 are the upper and lower aggregates 32, 33 above and below the core 31;
Is formed of a parallel plywood having a height dimension equal to the height dimension of the state where the core material 31 is provided, and the door-side aggregate 35 provided on the door-end side of the core material 31 is disposed above and below the core material 31. It is made of a parallel plywood having a height dimension equal to the height dimension in a state where the aggregates 32 and 33 are provided, and at least the core 3
The metal reinforcing material 30 is interposed at a joint between the door end side end surface of the first member 1 and the hanging side end surface of the door end side aggregate 35, and the bone is inserted into the concave grooves 12 to 15 of the core member 31. A wooden fire door 3 characterized in that the metal reinforcing material 30 fitted to the members 32-35 or the projections 22-25 protruding from the side end surfaces of the aggregates 32-35 are fitted. This is a heat warpage prevention structure.

[0009]

When a fire occurs, the wood constituting the door 3 starts to carbonize from the surface on the high-temperature flame side and contracts in cross section, whereby the door 3 tends to warp to the flame side. Since the metal reinforcing member 30 extending in the vertical direction is provided at least at the joint between the door end side end surface of the core material 31 and the hanging end side end surface of the door end aggregate 35, The metal reinforcing member 30 attempts to warp in the direction opposite to the wood, thereby preventing the door 3 from warping. That is, as shown in FIG. 9, when a fire occurs on the side (OUT) where the door 3 opens, as shown by the two-dot chain line in FIG. 9, the door 3 is opposite to the flame (FIRE) side where the temperature becomes high. The metal reinforcing member 30 made of a metal material such as a steel material
However, contrary to wood, the flame side expands and tends to warp to the anti-flame side. Therefore, the warp of the wood and the warp of the metal reinforcing material 30 are balanced, and the warp of the door 3 is suppressed. Also, in normal use, even if the door 3 warps due to a temperature difference or humidity difference between the inside and outside of the room, the warpage is increased by the metal reinforcing member 30 provided on the door 3 increasing the rigidity of the door 3. Is prevented.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the "warp preventing structure of a wooden fire door" of the present invention will be described in more detail. FIG. 1 is a front view showing a wooden fire door 3 to which an embodiment of the thermal warpage prevention structure according to the present invention is applied, and shows a state where the door 3 is viewed from the outside of the room. As shown in FIG.
Is provided on the door frame 4 via a hinge 41 so as to be openable and closable. That is, the door 3 is connected to the hanging side end by the door frame 44 on the hanging side.
, Is rotatably provided via three hinges 41, and is an open door which opens to the outdoor side.

FIG. 2 is an exploded perspective view of the door 3 of this embodiment. The front plate 36 is provided at the front of the door 3 (outside, OUT), and the rear surface of the door 3 is provided at the inside of the door. The back plate 37 is omitted. This figure shows the door 3
Is shown from the indoor side. The door 3 has a plate-shaped core material 31 provided at the center thereof, an upper aggregate 32 provided above the core material 31, a lower aggregate 33 also provided below the core material 31, Upper and lower aggregates 3
2 and 33 are provided on the hanging side, and the door end is provided with the upper and lower aggregates 32 and 33 on the core 31 similarly to the hanging side aggregate 34. And the metal reinforcing material 30 is provided between the core material 31 and the door end aggregate 35, so that the heat warpage preventing structure of the present invention is applied. Become.

FIGS. 3 and 4 are a longitudinal sectional view and a transverse sectional view, respectively, of the door 3 of FIG. 1, with some parts omitted. As shown in these figures, the plate thickness of the core material 31 and each of the aggregates 32 to 35 surrounding the four sides thereof are all formed in the same size. The plate thickness is not particularly limited, but is, for example, 30 mm in this embodiment. The core material 31 is made of a particle board or the like formed by hot compression molding using wood chips as a main raw material and using an adhesive, and has concave grooves 12 to 15 having a rectangular cross section depressed inward on the upper, lower, left and right side end surfaces. It becomes.
These concave grooves 12 to 15 are formed at the center in the thickness direction of the core material 31 and are formed continuously at each corner where adjacent side end surfaces intersect by forming the same width dimension. Be done. In addition, the depth of the concave groove 15 formed on the door end side end surface is the same as the concave groove 12 formed on the other side end surface.
14 is formed slightly deeper than the depth of the metal reinforcing member 30 in the groove 15 on the door end side, as described later.
Is interposed and assembled.

The upper aggregate 32 is formed of hard wood made of relatively hard natural wood or parallel plywood. Also,
The width of the upper aggregate 32 in the left-right direction is formed to be the same as the width of the core 31, and concave grooves 14 a, 15 a are formed on both left and right side surfaces so as to be recessed inward. Also,
On the lower end surface, a convex portion 22 having a rectangular cross section is formed so as to protrude downward, and the size of the convex portion 22 depends on the size of the core material 3.
1 has a size compatible with the concave groove 12 formed on the upper end surface. The lower aggregate 33 is formed by a general parallel plywood. Similarly to the upper aggregate 32, the lower aggregate 33 has the same width in the left-right direction as the width of the core 31, and has concave grooves 14b,
15b is formed to be depressed inward. A convex portion 23 having a rectangular cross section is formed on the upper end surface thereof so as to protrude upward, and the convex portion 23 has a size adapted to the concave groove 13 formed on the lower end surface of the core material 31.

The suspension side aggregate 34 is made of a parallel plywood formed to have the same vertical dimension as the upper and lower aggregates 32 and 33 provided on the core 31. And on the door end side end face,
A convex portion 24 having a rectangular cross section is formed so as to protrude toward the door top,
The size of the convex portion 24 is the same as that of the core 31 and the upper and lower aggregates 3.
2, 33 formed in the hanging side end surface,
14b. Doorside aggregate 35
Is made of a parallel plywood formed in the same manner as the hanging-side aggregate 34 in the upper and lower dimensions when the upper and lower aggregates 32, 33 are provided on the core material 31, and its hanging-side end surface has a rectangular cross section. A convex part 25 having a shape is formed so as to protrude toward the hanging side, and the size of the convex part 25 is formed to be slightly smaller than the concave groove 15 formed on the door end side end surface of the core material 31. Become. The metal reinforcing material 30 provided at the joint between the convex portion 25 formed on the door end side aggregate 35 and the concave groove 15 formed on the door end side end surface of the core material 31 is made of a metal material. It is formed of a member having a U-shaped cross section. Metal reinforcement 30 of this embodiment
Is made of a channel material made of a hot-dip galvanized steel sheet, the inner size of the channel material is adapted to the convex portion 25 formed on the door-side aggregate 35, and the outer size of the channel material is The size is adapted to fit into the concave groove 15 formed on the side end surface.

Next, the assembly of the wooden fire door 3 of this embodiment will be described. 5 to 7 are enlarged perspective views showing the X portion, the Y portion, and the Z portion in FIG. 2 in an enlarged manner.
When assembling the wooden fire door 3 of this embodiment, first, as shown in FIG.
2 is fitted with the protruding portion 22 protruding from the lower end surface of the upper aggregate 32 so that the upper aggregate 32 is
And, similarly, as shown in FIG.
The lower aggregate 33 is inserted into the groove 13 formed on the lower end surface of the core 31.
The lower aggregate 33 is joined to the lower part of the core material 31 by fitting the protruding portion 23 protruding from the upper end surface of the core material 31.

Then, as shown in FIGS. 5 and 6, in the state where the aggregates 32 and 33 are joined to the upper and lower portions of the core material 31, the hanging end side surfaces of the core material 31 and the upper and lower aggregates 32 and 33 are formed. The core member 31 and the upper and lower aggregates 32, 33 are fitted into the concave grooves 14, 14a, 14b formed in Suspended side aggregate 34
To join. Then, after fitting a metal reinforcing member 30 having a U-shaped cross section into the center of a convex portion 25 protrudingly formed on the hanging side end surface of the door end side aggregate 35, the convex portion 25 is connected to the core material 31. Grooves 1 formed in the door end side end surfaces of upper and lower aggregates 32, 33
5, 15a, 15b, the core material 31
The door-side aggregate 35 is joined to the upper and lower aggregates 32, 33.
When the metal reinforcing member 30 is provided, the metal reinforcing member 30 may be screwed to the door-side aggregate 35 or the like with a steel screw to further firmly integrate the two.

In this embodiment, the vertical dimension of the metal reinforcing member 30 is equal to or slightly shorter than the vertical dimension of the core member 31. However, the length of the metal reinforcing member 30 is
Groove 15 of the upper and lower aggregates 32, 33 longer than the length of
a, 15b. At the time of assembling the door 3, all the grooves 12 to 15, 14a, 14b, 15a, and 15b of the core 31 and the aggregates 32 to 35 are provided.
The projections 22 to 25 of the aggregates 32 to 35 and the metal reinforcing material 3
It is preferable that 0 is fitted. Therefore,
As in the above embodiment, the metal reinforcing member 30 is used as the door-side aggregate 3.
In the case of a configuration provided only at the joint between the core material 5 and the core member 31, the concave grooves 15 on the door end side end surfaces of the upper and lower aggregates 32 and 33 are provided.
The upper and lower portions of the convex portion 25 of the door-side aggregate 35 to be joined to the a and 15b are formed to be slightly larger in diameter than the central portion, so that the convex portion 25 of the door-side aggregate 35 has upper and lower aggregates 32. , 33 concave grooves 15a,
It is preferable to adopt a configuration in which the connector 15b is securely fitted.
In this case, it goes without saying that the shapes of the concave grooves 15a and 15b may be reduced instead of increasing the shape of the convex portion 25.

As shown in FIGS. 3 and 4, a front plate 36 and a back plate 37 are provided on the front and back surfaces of the door 3 thus formed. Front plate 36 and back plate 3
Numeral 7 is a plywood in which veneers 36A, 37A each made of a decorative plate having a thickness of about 0.5 mm are bonded to one surface, and the other surface having no veneers 36A, 37A is used as a core 31 or an aggregate 32. To 35 on the front and back surfaces of the door body composed of an epoxy-based adhesive or the like. The thickness of the front plate 36 and the rear plate 37 is about 3 mm in this embodiment. Further, preferably, the door 3 formed in this manner is provided on all of the upper, lower, left, and right side end faces.
A veneer 38 made of a decorative board having a thickness of about 0.5 mm is attached, and a foam material mounting groove 39 made of a relatively shallow rectangular groove is formed at the center in the thickness direction of each side end face. It is preferable to provide a foam material 40 in the groove 39 to prevent a gap between the end face of the door 3 and the door frame 4 when the door 3 is closed.

The door 3 thus provided is provided with a door frame 4
Is provided rotatably. The door frame 4 includes an upper frame 42 and a lower frame 43 that receive the upper and lower portions of the door 3, and a hanging side vertical frame 44 and a doorside vertical frame 45 that receive the left and right sides of the door 3. The door frame 4 is formed by bending a metal plate. In this embodiment, the upper frame 42 and the left and right vertical frames 44 and 45 are made of a hot-dip galvanized steel plate, and the lower frame 43 is made of SUS304 or the like. It is formed from a steel plate. The door frame 4 of this embodiment is
Airtight packing mounting groove 4 with a U-shaped cross section along the inner circumference
Airtight packings 42A to 45A made of chloroprene rubber are mounted in the airtight packing mounting grooves 42a to 45a. The hermetic packings 42A to 45A are continuously mounted along the inner periphery of the door frame 4 and, when the door 3 is closed, come into contact with the rear surface plate 37 on the indoor side of the door 3 to provide airtightness. Keep.

Next, the use state of the door 3 of this embodiment will be described. As shown in FIG. 1, the door 3 provided on the door frame 4 is provided with a door closer 5, security glasses 6, a door guard 7, a lock 8, and the like. Now, for example, when a fire occurs on the outdoor side, the door 3 starts to carbonize from the heated outdoor surface and contracts in cross section, so that the door 3 warps toward the heating side. Since the extending metal reinforcing member 30 is formed of a metal material, the heating side expands and tends to warp in the opposite direction to the wood. As a result, the contraction of the wood and the expansion of the metal cancel each other out, and the warpage of the door 3 is suppressed. In addition, even during normal use, even when the door 3 warps due to a temperature difference or humidity difference between the inside and outside of the room, the metal reinforcing member 30 provided to extend inside the door 3 in the up-down direction is used. Suppress warpage. As described above, when the thermal warpage prevention structure of the present invention is applied to the wooden fire door 3, the penetration of the flame can be effectively prevented by the action of the metal reinforcing member 30, and the thickness of the door 3 can be reduced. But it can withstand practical use. That is, in the door 3 of the above embodiment, the thickness can be reduced to 36 mm, which is equivalent to the thickness of the steel fire door, so that the steel frame for the steel door mounted on the mass production base is applied. And production costs can be reduced.

FIG. 8 is a cross-sectional view showing a wooden fire door 3A to which another embodiment of the thermal warpage preventing structure according to the present invention is applied. The door 3A of this embodiment has a structure in which four aggregates 32 to 35 are fitted around a core material 31 and a gap between the core material 31 and the door-side aggregate 35 as in the above-described embodiment. Is provided with a metal reinforcing material 30, but the joining method is different. That is, in this embodiment, a recessed groove 25 </ b> A recessed toward the door-end side is formed on the hanging side end surface of the door-side aggregate 35, and the metal reinforcing member 30 has a metal rod having a rectangular cross section. 30A
Will be used. Then, the metal rod 3 having a rectangular cross section is
0A fits into the groove 25A of the door-side aggregate 35 and is fitted into the groove 15 formed in the door-side end surface of the core material 31. Then, preferably, at the time of assembling, the metal reinforcing material 30 is fixed integrally with the door-side aggregate 35 by screws.

Incidentally, the thermal warpage preventing structure of the present invention is not limited to the configuration of the above-described embodiment, but can be variously modified. For example, in each of the above-described embodiments, the configuration in which the metal reinforcing material 30 is provided only at the joint between the core material 31 and the doorside aggregate 35 has been described. Needless to say, it may be provided to the user. For example, the core material 31 and the doorside aggregate 3
5, between the core material 31 and the upper aggregate 32,
All joints between the core 31 and the lower aggregate 33 and between the core 31 and the suspension-side aggregate 34 may be joined via the metal reinforcing member 30.

In each of the above embodiments, the core material 31
In this embodiment, the grooves 12 to 15 are formed, and the projections 22 to 25 are formed in each of the aggregates 32 to 35. On the contrary, the projections are formed in the core 31 and each bone is formed. Lumber 32-3
5 may be configured to have a concave groove. Further, the shape of the metal reinforcing member 30 provided at the joint portion is not limited to the U-shape or the rectangular shape, and may be another shape such as an H shape.
Further, the door 3 is not limited to the configuration of the above-described embodiment in which the aggregates 32 to 35 are provided on the upper, lower, left, and right sides of the core 31, and the suspension 3 and the upper and lower aggregates 32 to 34 are omitted. 31 and a door-side aggregate 35 provided on the door-side end surface thereof,
The metal reinforcing material 30 may be provided at the joint, or all the aggregates 32 to 35 may be omitted, and the core material 31 may be simply provided.
In the configuration consisting of only the metal member, a metal reinforcing member 30 extending in the up-down direction may be built inside the door tip side.

[0024]

As described above, according to the thermal warpage prevention structure of the present invention, even if a fire occurs, the metal reinforcing member 30 provided inside the door 3 expands on the heating side and the anti-flame By warping to the side, the door 3 made of wood contracts on the heating side and cancels the effect of warping to the heating side, thereby preventing the door 3 from bending and deforming. Therefore, door 3
The prevention of the penetration of the flame generated due to the warpage can enhance the fire prevention performance. Further, in the thermal warpage prevention structure of the present invention, since the metal reinforcing member 30 is provided inside the door 3, the rigidity of the door 3 can be increased, and the temperature difference and humidity between the inside and outside during normal use. The door 3 is also prevented from warping due to the difference.

Further, according to the heat warpage prevention structure of the present invention, it is not necessary to attach an inorganic fiber plate, inject a flame retardant solution, or increase the thickness of the door, so that the weight of the door 3 can be reduced. But not only can it be cheaper. In addition, according to the thermal warpage prevention structure of the present invention, fire prevention performance can be exhibited without increasing the thickness of the door 3, so that the thickness of the door 3 can be reduced to about the thickness of a steel fire door. can do. Therefore, a steel door frame for a general steel fire door that is mass-produced and widely distributed in the market can be applied, thereby reducing costs.

[Brief description of the drawings]

FIG. 1 is a front view showing a wooden fire door to which an embodiment of a thermal warpage preventing structure according to the present invention is applied, as viewed from the outside of a door.

FIG. 2 is an exploded perspective view of the door of FIG. 1, in which a front plate, a back plate, and the like are omitted.

FIG. 3 is a longitudinal sectional view of the door of FIG.

FIG. 4 is a cross-sectional view of the door of FIG.

FIG. 5 is an enlarged perspective view showing an X part in FIG. 2;

FIG. 6 is an enlarged perspective view showing a Y part in FIG. 2;

FIG. 7 is an enlarged perspective view showing a Z portion in FIG. 2;

FIG. 8 is a cross-sectional view of a wooden fire door to which another embodiment of the thermal warpage prevention structure of the present invention is applied.

9A and 9B are conceptual diagrams showing deformation of a wooden door in a fire, where FIG. 9A is a longitudinal sectional view, and FIG. 9B is a transverse sectional view.

[Explanation of symbols]

 Reference Signs List 3 wooden fire door 12-15 concave groove 22-25 convex portion 25A concave groove 30, 30A metal reinforcing material 31 core material 32 upper aggregate 33 lower aggregate 34 hanging aggregate 35 door aggregate 41 hinge

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) E06B 5/16 E06B 3/70-3/88

Claims (3)

(57) [Claims] 1. A plate-shaped core material, and a core material provided on a door end side.
Door end side aggregate, and the door end side end face of the core material and the front end
At the joint between the door end side aggregate and the hanging side end face,
Wooden fire doors with metal reinforcements extending to
There are, on the door leading end-side end face of the core material, rectangular cross-section groove is formed recessed Tsumoto side, the Tsumoto side end face of the door end side aggregate, hanging convex portions of the rectangular cross-section The metal reinforcing member is formed to protrude toward the base side, and the metal reinforcing member is formed of a member having a U-shaped cross section. The metal reinforcing member is fitted to the convex portion of the door end side aggregate, and thermal warpage prevention structure of a tree made fire door characterized by comprising fitted into the groove. 2. A plate-shaped core material, and a core material provided on a door end side of the core material.
Door end side aggregate, and the door end side end face of the core material and the front end
At the joint between the door end side aggregate and the hanging side end face,
Wooden fire doors with metal reinforcements extending to
There are, on the door leading end-side end face of the core material, rectangular cross-section groove is formed recessed Tsumoto side, the Tsumoto side end face of the door end side aggregate, the rectangular cross section of the groove door The metal reinforcing member is formed of a bar having a rectangular cross section, and is formed in a concave shape on the front side. The metal reinforcing member is fitted in the concave groove of the door end side aggregate, and the core material is formed. wood made fire doors thermal warpage prevention structure characterized in that fitted into the groove formed by. 3. A wooden fire door comprising a plate-shaped core material and four aggregates provided on the upper, lower, left and right sides of the core material, wherein the core material is recessed inward on each of the upper, lower, left and right side end surfaces. The upper aggregate provided on the upper part of the core is made of hardwood or parallel plywood having a width dimension equal to the width of the core, and the lower part of the core is provided at the lower part of the core. The lower aggregate provided is made of a parallel plywood having a width dimension equal to the width dimension of the core material. The suspension side aggregate provided on the suspension side of the core material has the upper and lower sides above and below the core material. It is made of a parallel plywood having a height dimension equal to the height dimension of the state in which the aggregate is provided, and the door-side aggregate provided on the door-end side of the core is provided with the upper and lower upper and lower sides of the core. It is made of parallel plywood having a height equal to the height of the aggregate provided. At least a metal reinforcing material is interposed at the joint between the door end side end surface of the core material and the hanging side end surface of the door end side aggregate,
The metal fireproof member fitted to the aggregate or the protrusion formed to protrude from a side end surface of the aggregate is fitted into the concave groove of the core material. Thermal warp prevention structure.