JPH0140904Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to plywood for concrete formwork that reduces weight and increases strength. Conventionally, hardwood veneer or plywood, such as plywood made from lauan wood, is often used as plywood for concrete formwork, but lauan wood is convenient when used as formwork because it has no knots. Although it is heavy, there is a desire for a lightweight one from the viewpoint of workability at the site where it is handled. The present invention is an attempt to improve the conventional veneer or plywood made of hardwood. This was achieved by providing plywood made by arranging softwood boards between both front and back boards and adhering them to each other. That is, the plywood for formwork according to the present invention will be further disclosed in detail with reference to the illustrated embodiments. As shown in the figure, the concrete formwork plywood CP according to the present invention has hardwood boards, such as lauan wood boards, arranged on the front and back sides, and softwood boards, such as pine wood boards, between both front and back boards 1 and 2. Boards made of Japanese pine, Japanese fir, Japanese larch, Japanese larch, etc. are arranged, and these are glued together.
For example, they are firmly adhered to each other using a thermosetting resin, such as a fuphenol resin adhesive. Here, the hardwood boards 1 and 2 on the front and back surfaces are simply veneers made from the respective hardwoods, but plywood can be used as appropriate. Furthermore, the intermediate softwood board 3 may be made of veneer or plywood as opposed to the front and back boards 1 and 2 made of hardwood, as appropriate. In the illustrated example, the front and back plates 1 and 2 are made of veneer, and the intermediate plate 3 made of softwood is made of plywood. Usually, this coniferous wood board 3 is made of pine wood such as pine wood or Japanese pine wood, so there are many knots, and when these appear on the surface, these knots, especially when there are many loose knots, are removed. Problems such as creating uneven parts or transferring patterns on the surface of poured concrete,
By arranging the boards 1 and 2 made of hardwood on the front and back sides and the board 3 made of softwood in between, it becomes possible to eliminate the problems of the softwood itself. In manufacturing, the front or back surfaces of these plates CP, selectively both the front and back surfaces, are impregnated with a thermosetting synthetic resin, such as fueru resin or melamine resin, using thermosetting synthetic resin-impregnated paper 4 and an adhesive. Boards 1 and 2 made of hardwood and board 3 made of softwood
The plywood CP for concrete formwork according to the present invention is manufactured by simultaneously heat curing the whole. In addition, the peripheral end surface 5 of these concrete formwork plywood CP is coated with a suitable synthetic resin, and if the purpose is to be able to be treated at the same time from the manufacturing process, phenolic resin or melamine resin is applied as described above and dried. By curing the plywood, it is possible to prevent rainwater, moisture, etc. from penetrating into the interior of the plywood from the cut end of the peripheral end surface 5 of the plywood while it is being used as a formwork. As described above, the plywood for concrete formwork according to the present invention has hardwood boards arranged on the front and back sides, and softwood boards arranged between the front and back boards, which are glued together. A board made of heavy hardwood only exists on the front and back surfaces, and a board made of softwood, which is light in weight and has many knots, is easy to twist due to its material. This provides a plywood for concrete formwork that combines the advantages of both, solving the problem of weight on the one hand and the problems of knots and twisting on the other, although it is lightweight. be. In addition, as an example to which the present invention is applied, by pasting thermosetting synthetic resin-impregnated paper on at least one surface of the front and back plates, the surface can be flattened and the strength can be increased, and both sides can be When used, the number of uses of the plywood for concrete formwork can be increased, and when a synthetic resin is applied to the peripheral end surface, water resistance can be imparted. Next, a comparison between the formwork flannel according to the present invention and conventional panels is shown in the table below.

[Table] As can be seen from the above table, the specific gravity of the panel according to the present invention is about 0.14 lower than that of the panel using conventional lauan. Although the bending Young's modulus also increases and the weight can be reduced to a large extent, the strength is actually higher than that of conventional ones, and it is cheaper in terms of cost and can be used for softwoods that have many knots such as loose knots. Even when used for this intermediate plate, it is still possible to provide a panel that is lighter, has improved strength, and is lower in cost than panels using conventional lauan materials.

[Brief explanation of the drawing]

The drawing is a perspective view of a plywood for concrete formwork according to the present invention. CP: Plywood for concrete formwork, 1: Surface board,
2: Back plate, 3: Intermediate plate, 4: Thermosetting synthetic resin impregnated paper, 5: Peripheral end surface.

Claims (1)

[Scope of Claim for Utility Model Registration] 1. Plywood for concrete formwork, which is made by placing hardwood boards on the front and back sides, and placing softwood boards between the front and back boards and adhering them to each other. 2. Plywood for concrete formwork according to claim 1, wherein the front and back plates are hardwood veneers, and the intermediate plate is softwood plywood. 3. Plywood for concrete formwork according to claim 1 or 2 of the utility model registration claim, which is made by pasting thermosetting synthetic resin-impregnated paper on at least one surface of the front and back plates. 4. Plywood for concrete formwork as set forth in claim 1 or 2 of the utility model registration claim, comprising thermosetting synthetic resin-impregnated paper adhered to both sides of the front and back plates. 5. Plywood for concrete formwork as set forth in claim 1 or 2 or 3 or 4 of the utility model registration claim, which is obtained by coating the peripheral end surface of the plywood with a synthetic resin.