JPH0356510Y2 - - Google Patents

Description

【考案の詳細な説明】 〈産業上の利用分野〉 この考案はアイスクリーム等の冷菓子、その他
を断熱して収容するための組立式断熱箱に関す
る。[Detailed Description of the Invention] <Industrial Field of Application> This invention relates to an assembly type insulating box for insulating and storing frozen sweets such as ice cream and others.

〈従来の技術〉 発泡樹脂で箱の展開状態の薄板を成形し、これ
を積み重ねて保管し、必要に応じ折り曲げて箱に
組立てる組立式断熱箱は実公昭54ー9559号公報で
公知である。<Prior Art> A prefabricated heat insulating box is known from Japanese Utility Model Publication No. 54-9559, in which thin plates are formed from foamed resin in the unfolded state of the box, which are then stacked and stored, folded as necessary, and assembled into a box.

〈考案が解決しようとする問題点〉 上記従来例は４つの側板がＶ形切欠きを介して
一連に接続した周囲壁板の一つの側板の上下に同
様なＶ形切欠きを介して底板と、蓋とを一連に接
続してある。<Problems to be solved by the invention> In the above conventional example, four side plates are connected in series through V-shaped notches, and one side plate is connected to the bottom plate through similar V-shaped notches at the top and bottom of one side plate. , and the lid are connected in series.

このため箱を展開状態に発泡成形する金型には
成形キヤビテイを第１０図に示すように十字状に
彫らねばならないので無駄になる面積が多くな
り、その分だけ金型は大型化してコスト高にな
り、製品も高価になる。更に、第１０図の左（又
は右）端の側板Ｂと、右（又は左）端の側板Ｆを
直角に接続して四角筒形の周囲壁を組立てるには
側板Ｂの先端を、側板Ｆに形成した溝に嵌めるだ
けなので、側板Ｆの内側に外向きの力が加わると
側板Ｆの溝は側板Ｂの先端から抜け、側板Ｆは外
向きに開き、簡単に分解してしまう。 For this reason, the mold for foam-molding the box in its unfolded state must have a molding cavity carved in a cross shape as shown in Figure 10, which results in a large amount of wasted area, which increases the size of the mold and increases costs. and products become more expensive. Furthermore, in order to assemble a rectangular cylindrical peripheral wall by connecting the side plate B at the left (or right) end and the side plate F at the right (or left) end in FIG. Since it is simply fitted into a groove formed in the side plate F, when an outward force is applied to the inside of the side plate F, the groove of the side plate F comes out from the tip of the side plate B, and the side plate F opens outward and easily disassembles.

〈問題点を解決するための手段〉 本考案は、上述した問題点がない断熱式断熱箱
に関するもので、４つの側板Ａ，Ｂ，Ｃ，Ｄが折
曲用のＶ形切欠き４を介して一連に接続した断熱
薄板製の周囲壁板１と、上記周囲壁板１をＶ形切
欠き沿いに折り曲げて構成される角筒の底部を塞
ぐ周囲壁板とは別体の断熱薄板製の底板２、及び
上記角筒の上に被さる断熱薄板製の蓋３とからな
り、 上記周囲壁板１は一端部に折曲用のＶ形谷５を
介して接続した厚さの薄い延長片６を備え、前記
Ｖ形谷の周囲壁板側の斜面は、該周囲壁板の厚さ
よりも薄い幅の溝８を上縁沿いに有し、前記周囲
壁板は他端部に、上記延長片６が重なると共に、
先端が前記Ｖ形谷の斜面の溝８に突入する薄肉部
７を有し、前記延長片６をＶ形谷８で直角に折曲
したときに互いに重なる延長片６と薄肉部７の重
合面の一方に凹部１０、他方には上記凹部に係合
する凸部９を設けたのである。<Means for solving the problems> The present invention relates to a heat-insulating box that does not have the above-mentioned problems, and the four side plates A, B, C, and D are connected through V-shaped notches 4 for bending. A surrounding wall plate 1 made of a thin heat insulating plate connected in series with a thin heat insulating plate, and a surrounding wall plate made of a thin heat insulating plate separate from the surrounding wall plate closing the bottom of a rectangular tube formed by bending the surrounding wall plate 1 along a V-shaped notch. It consists of a bottom plate 2 and a lid 3 made of a heat insulating thin plate that covers the square tube, and the peripheral wall plate 1 has a thin extension piece 6 connected to one end via a V-shaped valley 5 for bending. The slope of the V-shaped valley on the side of the peripheral wall plate has a groove 8 along its upper edge with a width thinner than the thickness of the peripheral wall plate, and the peripheral wall plate has the extension piece at the other end. As 6 overlaps,
A thin wall portion 7 whose tip end enters a groove 8 on the slope of the V-shaped valley, and an overlapping surface of the extension piece 6 and the thin wall portion 7 that overlap each other when the extension piece 6 is bent at a right angle at the V-shaped valley 8. A concave portion 10 is provided on one side, and a convex portion 9 that engages with the concave portion is provided on the other side.

〈実施例〉 第１〜第４図の第１実施例において、１は周囲
壁板、２は底板、３は蓋を示し、これらはともに
例えば６mm厚で、発泡スチロールから成形する。<Embodiment> In the first embodiment shown in FIGS. 1 to 4, reference numeral 1 indicates a peripheral wall plate, 2 indicates a bottom plate, and 3 indicates a lid, all of which have a thickness of, for example, 6 mm and are molded from styrofoam.

周囲壁板１は同じ高さの４つの側板Ａ，Ｂ，
Ｃ，Ｄを一連に有し、相互に隣接した側板の境界
には角度90°のＶ形切欠き４が内面に形成してあ
る。 The surrounding wall plate 1 has four side plates A, B, and the same height.
C and D are arranged in series, and a V-shaped notch 4 with an angle of 90° is formed on the inner surface at the boundary between adjacent side plates.

右端の側板ＤにはＶ形切欠きと同じＶ形谷５を
介して延長片６が接続する。この延長片６の外面
は各側板の外面と同一面であるが、外面からの厚
さは例えば側板の1/2である。 An extension piece 6 is connected to the right end side plate D via a V-shaped valley 5 that is the same as the V-shaped notch. The outer surface of this extension piece 6 is the same as the outer surface of each side plate, but the thickness from the outer surface is, for example, 1/2 that of the side plate.

側板ＡとＣ、ＢとＤは箱に組立たときに夫々対
向するため、ＡとＣの幅、及びＢとＤの幅は同じ
にすべきであるが、同じなのはＢ，Ｄで、Ｃの幅
Ｗに対してＡの幅は−αだけ短く、且つこの側板
Ａの左端側、つまり周囲壁板１の他端側は、前記
延長片６の厚さだけ外面から凹んで薄肉部７にな
つている。延長片６の厚さは、この実施例では側
板の厚さの1/2であるため、薄肉部７の厚さも側
板の厚さの1/2である。 Side plates A and C and B and D face each other when assembled into a box, so the widths of A and C and the widths of B and D should be the same. The width of A is shorter than the width W by -α, and the left end side of this side plate A, that is, the other end side of the peripheral wall plate 1, is recessed from the outer surface by the thickness of the extension piece 6 to become a thin wall portion 7. ing. Since the thickness of the extension piece 6 is 1/2 of the thickness of the side plate in this embodiment, the thickness of the thin portion 7 is also 1/2 of the thickness of the side plate.

そして、前記Ｖ形谷５の周囲壁板側の斜面に
は、斜面上縁に沿つて上記薄肉部の先端が突入す
る溝８が形成してある。従つて、薄肉部７の幅
は、先端を上記溝８に突入した状態で、その外面
に延長片６を重合することができる様に定める。
この互いに重なつて接触する延長片６の内面６′
と、薄肉部７の外面７′には重なつたときに係合
する凸部９と凹部１０を設ける。この実施例では
薄肉部７の外面７′に凸部９として凸条を、延長
片６の内面６′に凹部１０として上記凸条が係合
する溝条を設けてあるが、逆に薄肉部７に凹部、
延長片６に凸部を設けてもよいし、凹部と凸部を
この実施例の様に高さ方向に一連にせず、点々と
設けてもよく、この場合は薄肉部７に凹部と凸
部、延長片６には薄肉部７とは逆の配置で凸部と
凹部を設けてもよい。 A groove 8 is formed on the slope of the V-shaped valley 5 on the side of the peripheral wall plate along the upper edge of the slope into which the tip of the thin portion enters. Therefore, the width of the thin part 7 is determined so that the extension piece 6 can be superimposed on the outer surface of the thin part 7 with the tip thereof inserted into the groove 8.
The inner surface 6' of the extension pieces 6 that overlap and contact each other
The outer surface 7' of the thin portion 7 is provided with a convex portion 9 and a concave portion 10 that engage when overlapped. In this embodiment, a protrusion 9 is provided on the outer surface 7' of the thin-walled portion 7, and a groove is provided on the inner surface 6' of the extension piece 6 as a recess 10, with which the protrusion engages. 7 has a recess,
The extension piece 6 may be provided with convex portions, or the concave portions and convex portions may not be arranged in a row in the height direction as in this embodiment, but may be provided in spots. , the extension piece 6 may be provided with a convex portion and a concave portion in an arrangement opposite to that of the thin portion 7.

この実施例では各側板Ａ，Ｂ，Ｃ，Ｄの内面下
部には、各Ｖ形切欠き４を直角に折つて側板Ａ，
Ｂ，Ｃ，Ｄで角筒を形成したときに四角に連なる
底板２の周縁部の嵌合溝１１が形成してある。 In this embodiment, each side plate A, B, C, and D have V-shaped notches 4 bent at right angles at the lower part of their inner surfaces.
When B, C, and D form a rectangular tube, a fitting groove 11 is formed at the peripheral edge of the bottom plate 2 that is continuous in a square manner.

従つて、組立てるには例えば側板Ａの嵌合溝１
１に底板の一辺の周縁部を嵌め込み、側板ＢをＡ
に対して直角に折る際にＢの嵌合溝１１を底板の
他の一辺の周縁部に嵌め、この様にして底板２を
底部に取付けた状態で４枚の側板により角筒を形
成し、最後にＶ形谷５で延長片６を直角に折りな
がら薄肉部７の先端を溝８に突入させ、同時に凸
部９と凹部１０を係合させて延長片６を薄肉部７
の外面に重ねる。これにより側板Ｄに連接した延
長片はＶ形谷５で直角に折れ、側板Ｄと直角に接
続する側板Ａの薄肉部７の外面上に重なり、延長
片６の外面は薄肉部以外の側板Ａの外面と同一面
になる（第４図の拡大部参照）と共に、側板Ｄを
外向きに開こうとする力が加わつた場合、該側板
Ｄに連接し、直角に曲がつて側板Ｄと直角な側板
Ａの薄肉部７上に重なり、凸部９と凹部１０の係
合で該薄肉部７と連結した延長片６が側板Ｄを外
向きに開こうとする力に対抗するため側板Ｄは開
くことがない。同様に側板Ａを外向きに開こうと
する力が加わつた場合、側板Ａの薄肉部７の先端
は、側板Ａと直角な側板Ｄの溝８に突入している
と共に、側板Ｄに連接して直角に曲がり、凸部９
と凹部１０を係合して薄肉部７上に延長片６が重
なるので、この薄肉部の先端と溝８の係合、及び
延長片６とが側板Ａを外向きに開こうとする力に
対抗するため側板Ａも開かない。 Therefore, in order to assemble, for example, the fitting groove 1 of the side plate A is
Insert the peripheral edge of one side of the bottom plate into 1, and attach the side plate B to A.
When folding at right angles to the bottom plate, the fitting groove 11 of B is fitted into the peripheral edge of the other side of the bottom plate, and with the bottom plate 2 attached to the bottom part, a rectangular cylinder is formed by the four side plates, Finally, while folding the extension piece 6 at a right angle at the V-shaped valley 5, the tip of the thin wall portion 7 is inserted into the groove 8, and at the same time, the convex portion 9 and the recess portion 10 are engaged, and the extension piece 6 is folded into the thin wall portion 7.
Lay it on the outside surface of. As a result, the extension piece connected to the side plate D is bent at a right angle at the V-shaped valley 5, and overlaps the outer surface of the thin wall portion 7 of the side plate A that is connected at right angles to the side plate D, and the outer surface of the extension piece 6 is bent at a right angle to the side plate A other than the thin wall portion. (see the enlarged part in Figure 4), and when a force is applied to open the side plate D outward, it connects to the side plate D, bends at a right angle, and becomes perpendicular to the side plate D. The extension piece 6 overlaps the thin wall portion 7 of the side plate A and is connected to the thin wall portion 7 by the engagement of the convex portion 9 and the concave portion 10, so that the side plate D resists the force that tends to open the side plate D outward. It never opens. Similarly, when a force is applied to open the side plate A outward, the tip of the thin wall portion 7 of the side plate A protrudes into the groove 8 of the side plate D, which is perpendicular to the side plate A, and is connected to the side plate D. bend at a right angle, and the convex part 9
Since the extension piece 6 overlaps the thin part 7 by engaging the concave part 10, the engagement of the tip of the thin part with the groove 8 and the extension part 6 are applied to the force that tries to open the side plate A outward. In order to counteract this, side plate A also does not open.

周囲壁板１を構成する発泡樹脂板は或る程度の
圧縮性を有するため薄肉部７の先端と溝８及び凸
部９と凹部１０は互いに圧縮し合つて突入ないし
係合する様に定めることにより組立強度を一層高
めることができる。 Since the foamed resin plate constituting the surrounding wall plate 1 has a certain degree of compressibility, the tip of the thin wall part 7 and the groove 8, and the convex part 9 and the concave part 10 should be determined so that they compress and protrude into or engage with each other. This allows the assembly strength to be further increased.

そして、周囲壁１を角筒に組立たとき、上面に
は角筒よりもひとまわり外形が小さい角筒形突出
部１２が生じる様に各側板Ａ，Ｂ，Ｃ，Ｄ及び延
長片６の外面上端部に段を形成して置き、蓋３に
は上記角筒形突出部１２に嵌合する窪み３′を形
成してこれに被せればよい。勿論、これに限定さ
れず、角筒形突出部１２を省略し、周囲壁で構成
した角筒の内周に嵌合する嵌合部を蓋の下面に設
けて嵌合する様にしてもよい。 When the surrounding wall 1 is assembled into a rectangular tube, the outer surfaces of the side plates A, B, C, D and the extension piece 6 are arranged so that a rectangular tube-shaped protrusion 12 whose outer diameter is one size smaller than that of the rectangular tube is formed on the upper surface. A step may be formed at the upper end, and a recess 3' may be formed in the lid 3 to fit into the prismatic cylindrical projection 12, and the lid 3 may be placed over the recess 3'. Of course, the present invention is not limited to this, and the square tubular protrusion 12 may be omitted, and a fitting portion that fits into the inner periphery of the square tube formed by the surrounding wall may be provided on the lower surface of the lid. .

第５〜７図は本考案の他の一実施例を示す。 5 to 7 show another embodiment of the present invention.

前述の実施例では延長片６と薄肉部７を箱の高
さの全長に設けたが、この実施例では延長片６と
薄肉部７を箱の上下端から離した途中に設けてあ
る。従つて、前述の実施例と同じ構成部分には同
じ符号を付して説明を省略する。 In the embodiment described above, the extension piece 6 and the thin wall portion 7 were provided along the entire height of the box, but in this embodiment, the extension piece 6 and the thin wall portion 7 are provided halfway away from the top and bottom ends of the box. Therefore, the same reference numerals are given to the same components as in the previous embodiment, and the explanation thereof will be omitted.

薄肉部７を有する側板Ａの上下の各端部a′にお
ける幅は、これと対向する側板Ｃと同じＷであ
り、この上、下各端部の左端には側板ＤのＶ形谷
５の斜面５′と接触する角度45°の斜面が形成して
ある。そして、薄肉部７の上下と、上下の各端部
a′の境界沿いに横方向のスリツト１３を設け、上
下の各端部a′に阻害されることなく薄肉部７の先
端を側板ＤのＶ形谷５の斜面上縁沿いにある溝８
に突入できる様にしてある。このスリツト１３の
横方向の長さは溝８の深さにほゞ等しければよ
い。 The width at each upper and lower end a' of the side plate A having the thin wall portion 7 is the same W as that of the opposing side plate C, and at the left end of each of the upper and lower ends, there is a V-shaped valley 5 of the side plate D. A slope with an angle of 45° is formed to contact the slope 5'. Then, the upper and lower ends of the thin section 7 and the upper and lower ends
A lateral slit 13 is provided along the boundary of a', and a groove 8 along the upper edge of the slope of the V-shaped valley 5 of the side plate D is formed so that the tip of the thin wall part 7 is provided without being obstructed by the upper and lower ends a'.
It is designed so that you can enter. The length of the slit 13 in the lateral direction only needs to be approximately equal to the depth of the groove 8.

これにより前記実施例と同様に箱に組立ること
ができ、側板Ａの薄肉部７上に重なつた延長片６
は、側板Ａを外から見たときに見えるが、箱を上
下から見たとき延長片６、薄肉部７は側板Ｄの斜
面５′に突き合わさつている側板Ａの上、下各端
部がかくされて見えず、体裁が良い。更に、薄肉
部７上に重なつた延長片６の上下面は側板Ａの上
端部下面、下端部上面と接触するので、その摩擦
によつて延長片が薄肉部から剥れるのをより確実
に防止でき、箱の組立強度は向上する。 As a result, it can be assembled into a box in the same way as in the previous embodiment, and the extension piece 6 overlapped on the thin wall part 7 of the side plate A.
are visible when side plate A is viewed from the outside, but when the box is viewed from above and below, the extension piece 6 and thin wall portion 7 are the upper and lower ends of side plate A that butt against slope 5' of side plate D. It's hidden so you can't see it and it looks good. Furthermore, since the upper and lower surfaces of the extension piece 6 overlapping the thin-walled portion 7 come into contact with the lower surface of the upper end and the upper surface of the lower end of the side plate A, the friction makes it possible to more reliably prevent the extension piece from peeling off from the thin-walled portion. This can be prevented and the assembly strength of the box can be improved.

尚、この実施例では側板の上面に角筒形突出部
を設けず、蓋３の下面には側板が囲む内部にピツ
タリと嵌合する嵌合部３〃を設けてある。 In this embodiment, a rectangular cylindrical protrusion is not provided on the upper surface of the side plate, but a fitting portion 3 is provided on the lower surface of the lid 3, which fits snugly into the interior surrounded by the side plate.

又、第８図に示した様に箱の高さが高い場合な
ど、延長片６と薄肉部を上下方向に離して複数設
け、側板Ａを上、下の各端部a′だけでなく、高さ
の途中でも側板Ｄの斜面５′に突き合わせてもよ
い。 In addition, when the height of the box is high as shown in Fig. 8, a plurality of extension pieces 6 and thin-walled parts are provided vertically apart from each other, and the side plates A are attached not only to the upper and lower ends a' but also to the upper and lower ends a'. It may abut against the slope 5' of the side plate D even in the middle of the height.

〈考案の効果〉 本考案によれば４つの側板を有する周囲壁板は
底板や蓋と分離しているため、その成形キヤビテ
イを金型面に適切に配列し、金型の面積に無駄が
生じることを防止できる。<Effects of the invention> According to the invention, since the peripheral wall plate having four side plates is separated from the bottom plate and the lid, the molding cavities must be properly arranged on the mold surface, resulting in wasted area of the mold. This can be prevented.

第９図と第１０図はこのことを示すもので、
夫々一辺が20cmの正方形で、高さ15cmの箱を同時
に２個宛成形する金型である。 Figures 9 and 10 show this.
This mold is used to simultaneously form two square boxes each measuring 20 cm on a side and 15 cm in height.

第９図は本考案の箱用の金型で、周囲壁板１の
成形キヤビテイ１′を二列に並べ、この列と平行
に底板の成形キヤビテイＥを２つと、蓋の成形キ
ヤビテイＦを２つ一列に並べて設けてあり、金型
の外形寸法は長辺が95cm、短辺が63cmの長方形で
ある。これに対し、従来の箱を成形する第１０図
の金型は箱を十字状の展開状態に成形するため、
外形は長辺95cm、短辺80cmの長方形となり、短辺
の長さを約20cm程多く要し、且つキヤビテイ以外
のデツドスペースが多い。この様に本考案では金
型面積の有効利用度が頗る高い。 Figure 9 shows a mold for a box according to the present invention, in which the molding cavities 1' of the surrounding wall plate 1 are arranged in two rows, and parallel to these rows, two molding cavities E of the bottom plate and two molding cavities F of the lid are arranged. The external dimensions of the mold are rectangular with a long side of 95 cm and a short side of 63 cm. On the other hand, the conventional box molding mold shown in Fig. 10 molds the box into a cross-shaped unfolded state.
The external shape is a rectangle with a long side of 95cm and a short side of 80cm, which requires about 20cm more length on the short side and a lot of dead space other than the cavity. In this way, the present invention makes effective use of the mold area extremely high.

そして、周囲壁板１を角筒形に組立てたとき、
直角に接続する側板ＡとＤの接続強度は頗る高
く、側板Ａを外に開く力が加わつても、側板Ｄを
外に開く力が加わつても、側板Ａ、側板Ｄは共に
外に開くことがない。 When the surrounding wall plate 1 is assembled into a rectangular tube shape,
The connection strength between side plates A and D, which are connected at right angles, is extremely high, and even if a force is applied to open side plate A outward, and a force to open side plate D outward is applied, both side plates A and D will open outward. There is no.

【図面の簡単な説明】[Brief explanation of the drawing]

第１図は本考案の第１実施例による断熱箱の組
立状態の斜視図、第２図は第１図の箱の周囲壁板
の内面側から見た展開平面図、第３図は第２図の
端面図、第４図は第１図の箱の組立状態の一部を
断面にし、且つ要部を拡大して示した平面図、第
５図は本考案の第２実施例による断熱箱の組立状
態の斜視図、第６図は第５図の箱の周囲壁板を内
面側から見た展開平面図、第７図は第６図の端面
図、第８図は本考案の他の一実施例による断熱箱
の組立状態の斜視図、第９図は本考案の箱を成形
する金型の一例の平面図、第１０図は従来の箱を
成形する金型の平面図で； 図中、１は周囲壁板、２は底板、３は蓋、４は
Ｖ形切欠き、５はＶ形谷、６は延長片、７は薄肉
部、８は溝、９は凸部、１０は凹部、Ａ，Ｂ，
Ｃ，Ｄは側板を示す。 FIG. 1 is a perspective view of the assembled state of the heat insulation box according to the first embodiment of the present invention, FIG. 2 is a developed plan view of the box shown in FIG. 4 is a partially sectional view of the assembled box of FIG. 1 and an enlarged plan view of the main parts; FIG. 5 is a heat-insulating box according to a second embodiment of the present invention. FIG. 6 is a developed plan view of the surrounding wall plate of the box shown in FIG. 5 viewed from the inner side, FIG. 7 is an end view of FIG. 6, and FIG. FIG. 9 is a plan view of an example of the mold for molding the box of the present invention; FIG. 10 is a plan view of a conventional mold for molding the box; Inside, 1 is a surrounding wall plate, 2 is a bottom plate, 3 is a lid, 4 is a V-shaped notch, 5 is a V-shaped valley, 6 is an extension piece, 7 is a thin wall part, 8 is a groove, 9 is a convex part, 10 is a Recess, A, B,
C and D indicate side plates.

Claims (1)

【実用新案登録請求の範囲】 ４つの側板Ａ，Ｂ，Ｃ，Ｄが折曲用のＶ形切欠
き４を介して一連に接続した断熱薄板製の周囲壁
板１と、上記周囲壁板１をＶ形切欠き沿いに折り
曲げて構成される角筒の底部を塞ぐ周囲壁板とは
別体の断熱薄板製の底板２、及び上記角筒の上に
被さる断熱薄板製の蓋３とからなり、 上記周囲壁板１は一端部に折曲用のＶ形谷５を
介して接続した厚さの薄い延長片６を備え、前記
Ｖ形谷の周囲壁板側の斜面は、該周囲壁板の厚さ
よりも薄い幅の溝８を上縁沿いに有し、前記周囲
壁板は他端部に、上記延長片６が重なると共に、
先端が前記Ｖ形谷の斜面の溝８に突入する薄肉部
７を有し、前記延長片６をＶ形谷８で直角に折曲
したときに互いに重なる延長片６と薄肉部７の重
合面の一方に凹部１０、他方には上記凹部に係合
する凸部９を設けたことを特徴とする組立式断熱
箱。[Claims for Utility Model Registration] A surrounding wall plate 1 made of a heat insulating thin plate in which four side plates A, B, C, and D are connected in series via a V-shaped notch 4 for bending, and the above-mentioned surrounding wall plate 1. It consists of a bottom plate 2 made of a thin heat insulating plate that is separate from the surrounding wall plate that closes the bottom of a square tube formed by bending the square tube along a V-shaped notch, and a lid 3 made of a thin heat insulating plate that covers the top of the square tube. The surrounding wall board 1 is provided with a thin extension piece 6 connected to one end via a V-shaped valley 5 for bending, and the slope of the V-shaped valley on the side of the surrounding wall board is A groove 8 having a width thinner than the thickness of the surrounding wall plate is provided along the upper edge thereof, and the extension piece 6 overlaps the other end of the peripheral wall plate, and
A thin wall portion 7 whose tip end enters a groove 8 on the slope of the V-shaped valley, and an overlapping surface of the extension piece 6 and the thin wall portion 7 that overlap each other when the extension piece 6 is bent at a right angle at the V-shaped valley 8. A prefabricated heat insulating box characterized in that a concave portion 10 is provided on one side of the box, and a convex portion 9 that engages with the concave portion is provided on the other side.