Technical Field

[1] The present invention relates to paper formwork formed with a plurality of semi- cylindric paper tubes for easy installation and transport, and formed with a double- layered semicylindric paper tube that is reusable due to its separability from concrete.

[2]

Background Art

[3] Paper formwork refers to temporary construction material that is temporarily installed to define a concrete structure in a predetermined form and predetermined dimensions. When constructing various buildings, structures, etc., formwork of predetermined shapes are installed for columns, floors, walls, etc., and concrete or other material is filled and cured in the formwork to realize desired forms of shapes.

[4] For column formwork applied to buildings, bridges, piers, etc., while column formwork having a rectangular cross section has generally been used in the related art, cylindrical column formwork is commonly used today, due to a cylindrical column's advantages in terms of aesthetics, spatiality, and endurance of force per sectional area unit, when compared to a rectangular cross section column. However, when fabricating cylindrical formwork from plywood boards, steel plates, plastic plates, etc., formwork fabrication cost is high, and it is difficult to fabricate formwork in a proper cylindrical shape. Also, because diameters of column formwork are respectively different due to different construction applications for buildings, it is difficult to remove and reuse formwork after concrete is cured, and thus, the formwork is discarded, which is detrimental to the environment. Should the formwork be disassembled, re-fabricated, and reused, the problems of an increase in cost and the inherent difficulties involved in reuse are manifested. Further, when the diameter of a column for a building, bridge, pier, etc. is large, the column formwork must also be made large, presenting difficulties in transporting and moving of the formwork. Such difficulties of transport, unloading, etc. become greater in proportion to the increase in weight or size of the column formwork.

[5] Thus, research and development of materials for formwork to be applied to cylindrical columns for buildings, structures, bridges, piers, etc. is actively being pursued today. When paper is used for such formwork, formwork fabrication can be simplified to improve work efficiency and convenience, transporting, unloading, etc. becomes easier due to reduced weight and improved workability, and more efficient work spaces and fabrication spaces can be used due to the ability to minimize a fab- rication space and site, so that fabrication and labor costs can be reduced. Also, because paper formwork does not induce corrosion, it can be applied to various fields in addition to buildings, structures, bridges, piers, etc. Additionally, after removal of formwork, because the remaining debris is paper, not only is disposal easy, but environmental pollution can also be reduced.

[6] Korean Patent Publication No. 1992-0016680 discloses a formwork panel made of synthetic resin that can withstand high lateral pressures and thus be used to form an underground structure with cast-in-place concrete that is subject to high lateral pressure loads, and capable of being repeatedly reused.

[7] The above related art formwork is formed by fixing the respective panels with bolts and nuts. Therefore, when performing dismantling, a great number of coupled bolts and nuts must be unfastened, so that processing time and cost for installation and dismantling are increased. While reuse is possible, there is no significant improvement in cost reduction.

[8] Thus, to solve the above problems, the present inventor has completed the present invention relating to paper formwork formed of two layers using semicylindric paper tubes, in anticipation of the following advantages. After fixing of paper formwork formed using a plurality of bands to enable it to withstand lateral pressure of concrete filled therein, when it is used to built an underground structure, because its installation and dismantling are easy, working time and cost are substantially saved when compared to a related art formwork. Because it is formed as semicylindric formwork, it can be applied not only to reinforced concrete (RC) structures, but also to steel frame reinforced concrete (SRC) structures. Through a finish coating applied to the inner periphery of the semicylindric paper tube, the formwork is given excellent separability and can thus be reused many times. Due to a finish coating applied on the inner and outer peripheries of the semicylindric paper tube, the formwork has superb water resistance and strength. Because it can be used as paper material after use, the formwork is economically favorable in terms of environmental-friendliness.

[9]

Disclosure of Invention Technical Problem

[10] An object of the present invention is to provide paper formwork formed of two layers of semicylindric paper tubes that is easy to transport, install, and dismantle, that is recyclable, and that can substantially reduce working time and cost.

[H]

Technical Solution

[12] To achieve the above object in accordance with the present invention, there is provided paper formwork formed with two layers of semicylindrical tubes including a pair of semicylindric inner paper tubes, and a pair of semicylindric outer paper tubes pressed against an exterior of the inner paper tubes. Advantageous Effects

[13] The present invention provides paper formwork that is recyclable because it is fabricated using paper, thus reducing material costs and making it economical, can increase benefits for construction companies while being environmentally friendly, can improve construction quality while reducing construction time, and can be applied to RC structures as well as SRC structures.

[14]

Brief Description of Drawings

[15] FIG. 1 is a perspective view of a semicylindric paper tube that forms paper formwork according to the present invention.

[16] FIG. 2 is a schematic perspective view of a method for tightly coupling an inner periphery of a pair of semicylindric outer paper tubes to an outer periphery of a pair of semicylindric inner paper tubes.

[17] FIG. 3 is a perspective view of paper formwork formed in 2 layers using 4 semicylindric paper tubes that have been fixed with a plurality of bands.

[18] FIG. 4 is a schematic perspective view of a method for inserting a cut cylindric OPP coated sheet into paper formwork in order to couple to the inner periphery of the paper formwork, while considering the circular diameter of the inner periphery, according to the present invention.

[19] FIG. 5 is a schematic perspective view of paper formwork according to the present invention applied to an RC structure.

[20] FIG. 6 is a schematic perspective view of paper formwork according to the present invention applied to an SRC structure.

[21] FIG. 7 is an enlarged perspective view of the circular region represented by A in FIG.

6, illustrating an embodiment in which paper formwork according to the present invention is applied to an SRC structure.

[22] FIG. 8 is an enlarged perspective view of the circular region represented by A in FIG.

6, illustrating another embodiment in which paper formwork according to the present invention is applied to an SRC structure.

[23]

Mode for the Invention

[24] Below, a detailed description of the present invention is provided.

[25] The present invention provides paper formwork formed with two layers of semicylindric paper tubes including a pair of semicylindric inner paper tubes, and a pair of semicylindric outer paper tubes pressed against the exterior of the semicylindric inner paper tubes. The present invention further includes a plurality of bands provided to fix the semicylindric outer paper tubes.

[26] FIG. 1 is a perspective view of a semicylindric paper tube 10 that forms paper formwork according to the present invention. Because the paper formwork according to the present invention is formed of the above semicylindric paper tubes, in comparison with related art cylindric formwork formed with plywood boards, steel plates, or compound resin boards, it is easier to handle during transport, installation, etc., and ensures safety for workers during construction due to its light weight.

[27] Also, an oriented polypropylene (OPP) coated sheet is used to finish the inner periphery of the formwork 10 according to the present invention. While core paper for a related art paper tube is generally finished with a polyethylene (PE) coated sheet, because the semicylindric paper tube according to the present invention is finished with an OPP coated sheet, not only is water resistance improved, but improved separability for removal after concrete is cured can be realized as well.

[28] A woven sheet may be used to finish the outer surface of the semicylindric paper tube 10. By using a woven sheet to finish the outer surface of the semicylindric paper tube 10, water resistance in case of torrential rain can be improved, and the outer surface strength of paper formwork can be increased in order to reduce the likelihood of being deformed in a rough construction site environment. Further, additional finishing treatment can be performed on the outer surface of the semicylindric paper tube 10 according to the present invention by using a finish material such as a paraffin coated sheet, a PE coated sheet, an OPP coated sheet, a PE fiber coated sheet, a PP fiber coated sheet, and a tarpaulin sheet. Because the outer surface of the semicylindric paper tube 10 used in the present invention can easily be damaged during transport such as transferral or unloading and during construction, and because strength can readily be reduced from water or moisture infiltration into a damaged portion of the outer surface, the finishing agent may be used to perform finishing treatment of the outer surface of the semicylindric paper tube 10. By thus performing finishing treatment of the semicylindric paper tube 10 used in the present invention, weakening of the paper formwork according to the present invention from water or moisture infiltration can be prevented.

[29] FIG. 2 is a schematic perspective view of a method for tightly coupling an inner periphery of a pair of semicylindric outer paper tubes 30 to an outer periphery of a pair of semicylindric inner paper tubes 20, after the pair of semicylindric inner paper tubes 20 has been formed. When concrete is filled in double-layered paper formwork formed with 4 semicylindric paper tubes 10 according to the present invention, the lateral pressure generated can be well-tolerated to maintain a perfect circular shape. When the double-layered paper formwork with 4 semicylindric paper tubes 10 is thus formed, it must be coupled so that the seams of one pair of semicylindric paper tubes 10 constituting the semicylindric inner paper tubes 20 and the seams of the another pair of semicylindric paper tubes 10 constituting the semicylindric outer paper tubes 30 pressed against the outer periphery of the former pair do not align. To enable toleration of lateral pressure generated by concrete when concrete is filled in the paper formwork 1 according to the present invention, the paper formwork 1 may be formed so that the seams of one pair of semicylindric paper tubes 10 constituting the semicylindric inner paper tubes 20 and the seams of the another pair of semicylindric paper tubes 10 constituting the semicylindric outer paper tubes 30 pressed against the outer periphery of the former pair are perpendicular to each other (as shown in FIG. 3).

[30] The paper formwork 1 formed in a double layer using the 4 semicylindric paper tubes

10 according to the above-described method is fixed using a plurality of bands 40. As illustrated in FIG. 3, the paper formwork 1 according to the present invention is fixed using an adequate number and type of bands 40 that will enable it to tolerate lateral pressure generated, in consideration of the quantity of concrete to be filled in the paper formwork according to the size of a column to be constructed - that is, the diameter and length of the column. This determining of an adequate number and type of bands that will enable the paper formwork 1 to withstand lateral pressure generated according to the quantity of concrete to be filled therein will be easy for those having ordinary skill in the art. Specific examples of the band 40 include steel bands, buckle-coupled steel bands, turnbuckles, and fabric bands for transportation, of which 1 or more types can be used in combination, and which are not disposable but can be reused, thereby reducing subsidiary material costs for formwork construction.

[31] To more thoroughly treat the finished surface, the paper formwork 1 according to the present invention further includes a cylindric OPP coated sheet 70 cut and formed to attach to the inner peripheries of the semicylindric inner paper tubes 20. FIG. 4 is a schematic perspective view of a method for inserting a cut cylindric OPP coated sheet 70 into paper formwork in order to couple to the inner periphery of the paper formwork 1 , while considering the circular diameter of the inner periphery, according to the present invention. The semicylindric OPP coated sheet 70 may be attached to the inner periphery of the paper formwork using double-sided tape, etc. When the cylindrical column OPP coating sheet 70 is thus coupled to the inner periphery of the paper formwork according to the present invention, formation of vertical ridges on the surface of concrete corresponding to the seams of the semicircular inner paper tubes from concrete being filled therein can be prevented, and formation of spiral traces on the surface of concrete from the finishing agent treated on the semicylindric inner paper tubes can be prevented. Further, in order to protect the end surfaces of the semi- cylindric paper tubes, masking tape, OPP tape, PE tape, etc. may be used for finishing treatment.

[32] FIGS. 5 and 6 are schematic perspective views of 2-layered paper formwork 1 according to the present invention applied to an RC structure and an SRC structure. As illustrated in FIG. 5, 2-layered paper formwork 1 according to the present invention is inserted and fixed in a floor fixing frame 50 for paper formwork used for on-site construction, and when a column to be built is tall, a support 60 may be additionally used to easily fix the formwork. FIGS. 6, 7, and 8 illustrate various methods in which paper formwork according to the present invention can be applied to an SRC structure.

[33]

Industrial Applicability

[34] As described above, double-layered paper formwork according to the present invention can be reused many times when it is finish-treated with an OPP coated sheet on its inner periphery due to improved separability from cured concrete, is capable of increasing profit margins for construction companies due to substantially reduced costs from being formed of semicylindric paper tubes that facilitate its transportation and workability during construction, etc., has excellent water resistance and strength from treating the inner peripheries of semicylindric paper tubes with a finishing agent, is environmentally-friendly due to reduced waste brought about by using paper to fabricate the formwork, can be applied to SRC construction as well as RC construction, etc., so that it has many advantages over related art formwork.