JP3948810B2 - Thermal insulation for residential joists using lightweight section steel - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heat insulating material used for a floor joist of a house using a lightweight section steel. Specifically, a lightweight section steel that is used to cover and insulate with good workability without dropping a C-shaped steel material used as a floor joist of a house using lightweight section steel with a foamed resin insulation. It is related with the heat insulating material for the joist of the house which uses.
[0002]
[Prior art]
Traditionally, timber was used for the floor joists for wooden houses, so these wooden joists are hard to transfer heat and have some thermal insulation, so there is no need to cover them with thermal insulation. It was thought.
On the other hand, in the floor joist in a house using a lightweight steel, a steel frame made of a steel material 4 such as a light groove steel having a C-shaped cross section or a lip groove steel is used, but as shown in FIG. In addition, it is considered that it is not always necessary to further lay a heat insulating material because a wooden discard plate 11 and a finishing material 12 are laid on the upper surface of the joist made of the steel material 4.
Further, when it is necessary to lay a heat insulating material for improving the heat insulating property, it is not easy to cover the frame material itself such as joists, and therefore, it is made of the steel material 4 on the lower surface side of the discard plate 11. The heat insulating materials 10a and 10b were laid and covered only on the portions excluding the joists.
However, in this case, since the steel joist 4 for flooring is directly exposed to the outside air temperature, the floor is easy to rot because it is easy to condense, and it cannot be said that the heat insulation is sufficient.
Therefore, when it is necessary to insulate the floor joist steel 4 itself in order to improve heat insulation, there is a method in which a glass fiber mat or the like is wrapped around the steel 4 itself and attached with an adhesive to insulate. Tried.
However, wrapping a glass fiber mat or the like around the floor joist steel 4 itself and sticking it with an adhesive to insulate the material significantly increases the amount of the heat insulating material used, and the heat insulating material falls off. Since it takes time and effort, from the viewpoint of saving construction costs and the like, it has not been generally performed to cover and heat-insulate the floor joist steel 4 itself, which is a frame material.
[0003]
[Problems to be solved by the invention]
However, in recent years, due to the global warming caused by carbon dioxide gas, further energy efficiency has been demanded for energy saving, and the frame material itself, which has not been insulated at all so far, is covered with a heat insulating material. As a result, it has become necessary to save energy.
Therefore, the glass fiber mat was wrapped around the frame material itself to insulate it, but because the frame material itself has a special cross-sectional shape, it was wrapped with glass wool insulation material without any gaps. It was not easy to do, and it was difficult to insulate with good workability.
[0004]
[Means for Solving the Problems]
As a result of intensive research in view of the above problems, the present inventor can coat the heat insulating material without dropping off, and in addition, in order to perform heat insulation with good workability, the cross-sectional shape of the steel material having a C-shaped cross section is reduced. The sandwiching protrusion 3b and the steel material 4 of the support cover member 3 having a substantially L-shaped covering member 2 and a support covering member 3 having a substantially U-shaped cross section are covered with the support cover member 3 having a substantially U-shaped cross section. The substantially L-shaped covering member 2 is removed by supporting and fixing the substantially L-shaped covering member 2 with the bottom surface covering projection 2b of the substantially L-shaped covering member 2 interposed between the lower surface portion 4a and the lower surface portion 4a. The present invention has been completed based on the knowledge that it can be prevented. That is, the heat insulating material for house joists using the lightweight section steel of the present invention is made of a foamed resin for heat insulation by covering a steel material having a C-shaped cross section used as a floor joist for houses using light weight steel. In the heat insulating material, the foamed resin heat insulating material is composed of at least two members, a covering member having a substantially L-shaped cross section and a substantially U-shaped supporting covering member having a cross-sectional shape that is extremely thick on the upper surface. is configured, the covering member of the substantially L type, the vertical portion with forming the flat portion covering portion covering the flat portion of the side surface of the steel material, the horizontal portion covering the lower surface side of the steel is obtained by Na and lower surface portion covering the protrusion, the supporting cover member of said substantially U-type, with forms a fitting protrusion for fitting the upper surface portion in the groove side of the steel, the lower surface portion of the support covering member the projects steel lower surface portion covering the substantially L-shaped covering member Across the protruding portion between the lower surface portion of the steel material is characterized in that it without a narrow wear projections for supporting and fixing the cover member substantially L-shaped.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
[I] Foamed resin insulation for residential joists using lightweight steel
(1) Structure As shown in FIG. 1, the structure of the heat-insulating material 1 for a house joist using the lightweight steel of the present invention has a covering member 2 having a substantially L-shaped cross section and a support having a substantially U-shaped cross section. The covering member 3 is composed of at least two members.
Further, if the cross-sectional shape is only to cover and insulate the steel material 4 having a C shape, even if the shape of the combined heat insulating material 1 is a simple shape having a substantially square cross section as shown in FIG. Although it is good, as shown in FIGS. 4 to 5, the underfloor heat insulating materials 10 a and 10 b can be formed to be supportable, or as shown in FIGS. 6 to 8, the underfloor heat insulating materials 10 a and 10 b are integrated. It can also be formed.
[0006]
(A) Cover member 2 having a substantially L-shaped cross section As shown in FIG. 1, the cover member 2 having a substantially L-shaped cross section has a vertical portion as a flat portion side cover portion 2a and a horizontal portion as a lower surface portion. and covering protrusion 2b ungated.
[0007]
(a) Flat part side covering part The flat part side covering part 2a whose cross-sectional shape forms a vertical portion of the substantially L-shaped covering member 2 has a C-shaped cross section used as a floor joist for a house using lightweight steel. The flat portion 4b side of the steel material 4 such as a light groove steel and a lip groove steel is covered. As shown in FIG. 2, when the underfloor heat insulating materials 10 a and 10 b are laid on the upper portion of the flat portion side covering portion 2 a adjacent to the joist heat insulating material 1 using the lightweight steel of the present invention. The step portion 2c can be formed so that the underfloor heat insulating materials 10a and 10b do not fall off. As shown in FIGS. 4 to 5, the step portion 2 c has a depth until the underfloor heat insulating materials 10 a and 10 b come into contact with the flat portion 4 b side of the steel material 4, and is used for the underfloor on the entire upper portion of the flat portion side covering portion 2 a. It is also possible to support the heat insulating materials 10a and 10b and prevent them from falling off.
[0008]
(b) Lower surface covering protrusion The lower surface covering protrusion 2b, which forms the horizontal portion of the covering member 2 having a substantially L-shaped cross section, protrudes toward the steel material 4 side and is used as a floor joist for a house using lightweight steel. Is formed so as to cover the lower surface portion 4a side of a steel material 4 such as a C-shaped light groove steel or lip groove steel.
[0009]
(B) Support covering member 3 having a substantially U-shaped cross-section The support covering member 3 having a substantially U-shaped cross-section has a fitting projection 3a protruding toward the steel material 4 as shown in FIG. A pinching protrusion 3b protruding to the 4 side is formed.
[0010]
(a) the fitting projection portion and the cross section has fitting projections 3a ungated fitting the upper surface of the support covering member 3 substantially U type grooves 4c of steel 4, the fitting protrusion 3a is steel 4 is supported by the bottom portion 4a of the steel material 4 from below and prevents the support covering member 3 having a substantially U-shaped cross section from falling off. As shown in FIG. 2, a recess 5 can be formed on the steel projection 4 side of the fitting projection 3a for cost reduction. Further, as shown in FIG. 2, an underfloor heat insulating material 10a, adjacent to the heat insulating material 1 for a house joist using the lightweight steel of the present invention, is provided on the upper portion of the support covering member 3 having a substantially U-shaped cross section. It is also possible to form the stepped portion 3c so that the underfloor heat insulating materials 10a and 10b do not fall off when laying 10b. As shown in FIGS. 4 to 5, the step portion 3 c has a depth until the underfloor heat insulating materials 10 a and 10 b come into contact with the steel material 4, or as shown in FIG. 4, than the upper end of the fitting projection 3 a. Accordingly, it is possible to support the underfloor heat insulating materials 10a and 10b by the entire support covering member 3 and prevent the falling off.
[0011]
(B) clamping wear projections the cross section has narrow wear protrusion 3b ungated projecting the lower surface of the support covering member 3 of substantially C-type steel material 4 side, the lower surface of the steel material and the clamping wear protrusion 3b The covering member 2 having a substantially L-shaped cross-section is supported and fixed by sandwiching the lower surface covering projection 2b of the covering member 2 having a substantially L-shaped cross-section with the portion 4a. The covering member 2 of the mold is prevented from falling off. As shown in FIG. 4, the pinching protrusion 3 b supports the entire bottom 2 d of the covering member 2 having a substantially L-shaped cross-section and prevents the covering member 2 having a substantially L-shaped cross-section from falling off. You can also. Or as shown to (a) and (b) of FIG. 10, height (depth) 4 mm or less to the contact surface of the said lower surface part coating | coated protrusion part 2b and the pinching protrusion part 3b , Preferably it is 3- It is also possible to prevent the covering member 2 having a substantially L-shaped cross-section from coming off and falling off easily by forming the fitting uneven portions 2e and 3e having 2 mm.
[0012]
(2) Shape The covering member 2 having the substantially L-shaped cross section and the supporting covering member 3 having the substantially U-shaped cross section may be solid or hollow. Alternatively, as shown in FIGS. 2, 6 and 8, a recess 5 may be formed.
The shape of the steel member 4 is a light grooved steel or lip grooved steel having a C-shaped cross-section used as a floor joist. The covering member 2 has a substantially L-shaped cross-section and a substantially U-shaped cross-section. In order to cover and insulate by combining the support covering member 3, it is possible to select and adopt an appropriate size depending on the size and shape of the steel material 4 to be used. It can also be used by cutting into a size.
[0013]
In general, the covering member 2 having a substantially L-shaped cross section and the supporting covering member 3 having a substantially U-shaped cross section generally have a thickness of 20 to 90 mm, preferably 20 to 90 mm in order to maintain appropriate heat insulation and appropriate strength. Is 20 to 50 mm, particularly preferably 20 to 40 mm. Further, the length of the covering member 2 having a substantially L-shaped cross section and the supporting covering member 3 having a substantially U-shaped cross section is about 900 mm, and a house using the lightweight section steel of the present invention in a state where both members are combined. It is preferable that the outer appearance of the heat-resisting material 1 is approximately 600 to 2,000 mm in length, 300 to 600 mm in height, and 30 to 200 mm in width. Moreover, as shown in FIG. 1, the heat-insulating material 1 for a house joist using these light-weight shaped steels covers and insulates the entire steel material 4 such as a light-grooved steel having a C-shaped cross section or a lip groove-shaped steel. Therefore , when connecting several heat insulating materials 1 for joist according to the present invention in accordance with the length of the steel material 4, the substantially L-shaped covering member 2 and Step portions can also be formed at both ends of the substantially U-shaped support covering member 3.
[0014]
The heat-insulating material 1 for residential joists using the lightweight steel of the present invention is foam-molded with foamed resin in the mold, and therefore has a shape that can be easily punched by the mold in terms of manufacturing cost. It is preferable from the viewpoint.
Basically, it is preferable that the covering member 2 has a substantially L-shaped cross-sectional shape and the support covering member 3 whose cross-sectional shape is a substantially U-shaped, but each of these is divided into two or more members. It can also be formed.
In addition, the shape of the covering member 2 having a substantially L-shaped cross-section and the support covering member 3 having a substantially U-shaped cross-section in the heat insulating material 1 for a house joist using the lightweight steel of the present invention is formed by resin foam molding. Since it is molded, if it cannot be die-cut, the cost cannot be reduced by mass production. Therefore, the structure needs to be die-cut like the above-described structure.
[0015]
(3) Material
(A) Foamed resin The material constituting the heat-resisting material 1 for residential joists using the lightweight steel of the present invention is a polystyrene resin foam, a polyolefin resin foam such as polyethylene or polypropylene, or a styrene modified polyolefin. Examples thereof include foamed resins such as resin foams.
Specifically, the foamed resin is made by foaming a synthetic resin such as a polystyrene resin, a polyolefin resin such as polyethylene or polypropylene, or a styrene modified polyolefin resin at a foaming ratio of 25 to 80 times. In addition, a foamed resin having a high closed cell ratio and usually having a density of 0.0125 to 0.04 g / cm ³ can be mentioned.
[0016]
[II] Floor joists for houses using lightweight sections Steel floor joists that use lightweight sections covered with foamed resin heat insulating material 1 for houses joists using lightweight sections are cross-sectionally shaped C Steel materials 4 such as light groove steel and lip groove steel are used.
The steel material 4 such as a light-grooved steel having a C-shaped cross section or a lip groove-shaped steel is used for a so-called light steel prefab house or steel house, and specifically, shown in FIG. In the lip channel steel, the height (H) is 300 mm, the width (W) is 50 mm, the lip length is 20 mm, the thickness (t) is 1.6 mm, or the height (H) is 235 mm and the width ( W) 40 mm, lip length 20 mm, thickness (t) 1.6 mm, or height (H) 184 mm, width (W) 40 mm, lip length 20 mm, thickness (t) There are types such as 1.0 mm, or in light channel steel, height (H) is 304 mm, width (W) is 40 mm, thickness (t) is 1.6 mm, or height (H) is 238 mm, width (W) 40 mm, thickness (t) 1.2 mm, or height (H) 92 mm, width (W) is 40 mm, the thickness (t) is the type of 1.2mm or the like.
[0017]
[III] Construction To cover and insulate the steel material 4 having a C-shaped cross-section as a joist of a house using the above light-weight steel, first, as shown in FIG. The fitting protrusion 3 a that forms the upper surface of the substantially U-shaped support covering member 3 is fitted into the groove 4 c to cover the groove 4 c side of the steel material 4. Next, a substantially L-shaped covering member 2 is brought into contact with the flat portion side 4b of the side surface of the steel material 4, and the lower surface portion covering projection 2b formed on the lower side thereof is cross-sectioned with the lower surface portion 4a of the steel material 4. The steel cover 4 is fitted between the substantially U-shaped support covering member 3 to cover the lower surface portion 4a side of the steel material 4, and the cross-sectional shape of the support covering member 3 and the lower surface portion 4a of the steel material 4 The covering member 2 sandwiched between them and having a substantially L-shaped cross section is supported and fixed. Then, underfloor heat insulating materials 10a and 10b are laid adjacent to the heat insulating material 1 for residential joists using the lightweight steel, and further, the heat insulating material 1 for residential joists using the C-shaped steel material 4 and the lightweight steel. After the discard plate 11 is laid on the surface, the finishing material 12 is laid on the discard plate 11.
[0018]
[Action]
The heat-dissipating material 1 for a house joist using the lightweight steel of the present invention is composed of at least two members, a covering member 2 having a substantially L-shaped cross section and a supporting covering member 3 having a substantially U-shaped cross section. A flat portion side covering portion 2a that forms a vertical portion of the covering member 2 having a substantially L-shaped cross section covers a flat portion 4b side of a steel material 4 such as a light groove shape steel or lip groove shape steel having a C shape cross section. The lower surface portion 4a side of the steel material 4 is covered with a lower surface portion covering projection 2b forming a horizontal portion. Further, the fitting projection 3a forming the upper surface portion of the support cover member 3 having a substantially U-shaped cross-section is fitted into the groove 4c of the steel material 4 having a C-shaped cross-section, and the support cover having a substantially U-shaped cross-section. A covering member having a substantially L-shaped cross section that prevents the member 3 from falling off and sandwiches the bottom surface covering projection 2b between the sandwiching projection 3b forming the bottom surface and the bottom surface 4a of the steel material 4. 2 is supported and fixed.
[0019]
【Example】
An example of the foamed resin heat insulating material for residential joists using the lightweight section steel of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a perspective view of a foam resin heat insulating material for a house joist using a lightweight section steel of the present invention that is covered with a C-shaped steel material and insulated, and FIG. 2 is a C-shaped cross-sectional shape. FIG. 3 to FIG. 5 are cross-sectional views of a foam resin heat insulating material for a house joist using a lightweight section steel according to the present invention, which is covered with a steel material, and further has an underfloor heat insulating material, a waste plate and a finishing material applied thereto. FIG. 6 is a cross-sectional view of another embodiment of a foam resin heat insulating material for a house joist using the lightweight section steel of the invention, and FIG. 6 is a house joist using the light section steel of the present invention formed integrally with the under floor heat insulating material. Is a cross-sectional view of a floor structure using a foamed resin heat insulating material, in which FIGS. 7 to 8 are integrally formed with a covering member having a substantially L-shaped cross section and an underfloor heat insulating material used in the floor structure of FIG. 9 represents the dimensions (unit: mm) of the support covering member whose cross-sectional shape is substantially U-shaped, and FIG. 9 is a cross-sectional shape of FIG. Member and underfloor insulation and the dimensions of the covering member of the cross-sectional shape is substantially L-type disconnecting the underfloor heat-insulating material than thermal insulation material formed integrally (unit: mm) represents, FIG. 10 and the lower surface portion covering protrusion The partial enlarged view of the contact surface of a pinching projection part is represented.
[0020]
1 has a cross-sectional shape made of expanded polystyrene having a length of 909 mm, a width of 285 mm, and a thickness of 90 mm shown in FIG. 8 and a foaming ratio of 50 times, a density of 0.02 g / cm ³ , and a closed cell ratio of about 100%. U-shaped support covering member 3 and expanded polystyrene having a length of 909 mm, a width of 285 mm, and a thickness of 90 mm shown in FIG. 9 with an expansion ratio of 50 times, a density of 0.02 g / cm ³ and a closed cell ratio of about 100%. It is a foam resin heat insulating material for a joist of a house using a lightweight section steel made of two members, a covering member 2 having a substantially L-shaped cross section. Lip groove shape with a cross-section of C-shaped height (H) 235mm, width (W) 40mm, lip length 20mm, thickness (t) 1.6mm, length (L) 3,600mm the groove 4c of steel 4, FIG sectional shape shown in 8 by fitting the fitting projections 3 a forming the upper surface of the support covering member 3 of substantially U-type, is the cross-sectional shape in the steel 4 substantially U Four support covering members 3 of the mold were connected and fixed in the length direction of the steel material 4. Next, a flat portion side covering portion 2a that forms a vertical portion of the covering member 2 having a substantially L-shaped cross section is in contact with and covered with the flat portion 4b side of the side surface of the steel material 4, and then the horizontal surface of the covering member 2 is covered. the lower surface portion covering the protrusion 2b which forms a part for covering the lower surface portion 4a side of the steel 4, clamping said cross-sectional shape and the lower surface portion 4a of the steel 4 forms the lower surface of the support covering member 3 substantially U-type Inserted in the recess between the wearing projection 3b and sandwiched between the lower surface 4a of the steel material 4 and the sandwiching projection 3b forming the lower surface of the support covering member 3 having a substantially U-shaped cross section. The bottom surface covering projections 2b were connected in the length direction of the steel material 4 and fixed.
[0021]
Then, underfloor insulation materials 10a and 10b having a thickness of 50 mm are laid on the step portion 2c of the covering member 2 having a substantially L-shaped cross section and the step portion 3c of the supporting covering member 3 having a substantially U-shaped cross section. After laying a 12 mm thick discard plate 11 on the heat-resisting material 1 for a house joist using a C-shaped steel material 4 and a light-weight shape steel, a finishing material 12 having a thickness of 12 mm is laid on the discard plate 11. To do. The heat-insulating material 1 for residential joists using the lightweight section steel of the present invention thus formed has extremely good workability during construction, can be easily constructed, can be insulated at low cost, and can be used for flooring. Since the cross-sectional shape used as a joist can be covered without falling off from the C-type steel material 4, and since the heat retaining property is sufficient and there is no condensation, the floor is difficult to rot.
[0022]
【The invention's effect】
The heat-insulating material for residential joists using the lightweight section steel of the present invention configured as described above can cover and insulate the cross-sectional shape used as floor joists without dropping into a C-type steel material, and Since the workability is extremely good, heat insulation can be performed at a low cost.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a perspective view of a foam resin heat insulating material for a house joist using a lightweight steel of an embodiment of the present invention which is insulated by covering a lip groove steel material having a C-shaped cross section.
FIG. 2 is a foam resin for a joist of a house using the lightweight section steel of the present invention, which is coated with a lip groove steel having a C-shaped cross section and further has an underfloor heat insulating material, a waste board and a finishing material. It is sectional drawing of the floor structure using a heat-insulating material.
FIG. 3 is a view showing a house using a lightweight section steel according to another embodiment of the present invention, in which a lip groove steel material having a C-shaped cross section is coated, and further, an underfloor heat insulating material, a waste board and a finishing material are applied. It is sectional drawing of the floor structure using the foamed resin heat insulating material for joists.
FIG. 4 is a view of a house using a lightweight section steel according to another embodiment of the present invention, in which a lip groove steel material having a C-shaped cross section is coated, and further, an underfloor heat insulating material, a waste board and a finishing material are applied It is sectional drawing of the floor structure using the foamed resin heat insulating material for joists.
FIG. 5 is a view of a house using a lightweight section steel according to another embodiment of the present invention, in which a lip groove steel material having a C-shaped cross section is coated, and further, an underfloor heat insulating material, a waste board and a finishing material are applied. It is sectional drawing of the floor structure using the foamed resin heat insulating material for joists.
FIG. 6 is a view of a floor of an embodiment of the present invention using a foamed resin heat insulating material for a house joist using a lightweight section steel in which a covering member having a substantially L-shaped cross section is formed integrally with an underfloor heat insulating material. It is a partially cutaway sectional view of the structure.
7 is a front view (a) and a plan view (b) of a heat insulating material in which a covering member having a substantially L-shaped cross section and an underfloor heat insulating material used in the floor structure of FIG. 6 are integrally formed. Represents a side view (c), and the numbers represent the dimensions (unit: mm).
8 shows a front view (a), a bottom view (b), and a side view (c) of the support covering member 3 having a substantially U-shaped cross section used in the floor structure of FIG. The dimension (unit: mm) is represented.
FIG. 9 is a covering member having a substantially L-shaped cross-sectional shape in which the under-floor heat insulating material part is separated from a heat insulating material in which the cross-sectional shape of FIG. A front view (a), a plan view (b), and a side view (c) are shown, and the numbers represent the dimensions (unit: mm).
Figure 10 is a bottom part covering projection and clamping joists foam plastic insulation housing using lightweight shape steel cross-sectional shape of FIG. 1 has thermal insulation to cover the C-shaped lip interposition steel It is the elements on larger scale of the contact surface of a wear projection part .
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Heat-resisting material for house joists using lightweight steel 2 Cover member 2a having a substantially L-shaped cross section Flat portion side covering portion 2b Lower surface portion covering projection portion 2c Step portion 2d Bottom portion 2e Fitting convex portion 3 Sectional shape is substantially U-shaped support covering member 3a Fitting projection 3b Clamping protrusion
3c Step
3e Fitting recess 4 Steel material 4a having a C-shaped cross section 4a Steel lower surface 4b Steel flat portion 4c Steel groove 5 Recess 10a, 10b Floor insulation 11 Discarding plate 12 Finishing material

Claims (4)

In a heat insulating material made of foamed resin for covering and covering a C-shaped steel material used as a floor joist for a house using lightweight steel, the heat insulating material made of foamed resin has a substantially cross-sectional shape. L-shaped covering member and the cross-sectional shape is constituted by at least two members of the support covering member substantially U type was extremely bold the upper surface, the covering member of the substantially L type, the vertical portion together form a flat portion side cover portion covering the flat portion of the side surface of the steel material, the horizontal portion is obtained by Na and lower surface portion covering protrusion covering the lower surface side of the steel, of the substantially C-type support covering member, together with the forms and the fitting protrusion for fitting the upper surface portion in the groove side of the steel, for the lower surface portion covering the support covering member covering member lower surface portion protrudes steel side of the substantially L-shaped A substantially L-shaped covering member sandwiching the protrusion between the lower surface of the steel material Characterized in that it without a narrow wear projections for supporting and fixing, joist insulation for residential use of lightweight shape steel.   The lightweight section steel according to claim 1, wherein stepped portions are formed at the corners on the opposite side of the steel material on the upper surface portion of the covering member having a substantially L-shaped cross section and the support covering member having a substantially U-shaped cross section. Insulation for residential joists. The heat insulating material for a joist of a house using the lightweight section steel according to claim 1 or 2, wherein a concave portion is formed in a fitting projection that is fitted to a groove portion side of the steel material. The heat insulating material for a joist of a house using the lightweight section steel according to any one of claims 1 to 3, wherein a concave and convex portion for fitting is formed on a contact surface between the bottom surface covering projection and the pinching projection .

Images