Description

DOUBLE WALL SPIRAL TUBE WITH INNER WALL

PROTECTING STRUCTURE

Technical Field

[1] The present invention relates to a double walled spiral tube for carrying or passing waste water or domestic sewage water, and more particularly, to a double walled spiral tube with an inner wall protecting structure, which is laid under the ground and is constructed to allow the corrugations of an outer tube and the synthetic resin body of an inner tube to independently expand and contract, so that the damage to the structurally weak inner tube can be prevented. Background Art

[2] Referring to FIG. 1, a conventional double walled spiral tube includes an outer tube 1 which is formed using a coated metal plate Ia to have the configuration of a spiral cylinder having a plurality of corrugations Ib, and an inner tube 2 which is constituted by a synthetic resin body 2a integrally joined to the inner ends of the corrugations Ib of the outer tube 1 and formed to have the configuration of a straight cylinder.

[3] In the conventional double walled spiral tube, the outer tube 1 , which is formed using the coated metal plate Ia to have the configuration of a spiral cylinder, sustains load or earth pressure, and the inner tube 2, which is constituted by the synthetic resin body 2a joined inside the outer tube 1 and is formed to have the configuration of a straight cylinder, ensures smooth passage of waste water or domestic sewage water.

[4] However, the conventional double walled spiral tube has a defect in that the inner tube 2 joined inside the outer tube 1 can be easily damaged.

[5] That is to say, as shown in FIGs. 2 and 3, with the double walled spiral tube laid under the ground, if the corrugations Ib of the outer tube 1 are pressed by the load or earth pressure applied from the outside so that the pitch of the corrugations Ib increases, excessive tensile force is applied to the synthetic resin bcdy 2a of the inner tube 2 which is joined to the corrugations Ib of the outer tube 1. Consequently, the synthetic resin body 2a of the inner tube 2 is likely to be separated from the corrugations Ib of the outer tube 1 , or a portion of the synthetic resin body 2a of the inner tube 2 is likely to rupture.

[6] Also, as shown in FIG. 4, considering material characteristics that the coated metal plate Ia of the outer tube 1 has low contractibility and the synthetic resin body 2a of the inner tube has high contractibility, if the synthetic resin body 2a of the inner tube 2

repeatedly undergoes excessive contraction and expansion through a distance greater than the pitch of the corrugations Ib of the outer tube 1 due to the change of outside temperature, etc. with the double walled spiral tube laid under the ground, the junction region between the corrugations Ib of the outer tube 1 and the synthetic resin body 2a of the inner tube 2 cannot sustain the compressive and tensile force applied repeatedly thereto. As a consequence, the phenomenon occurs in which the synthetic resin body 2a of the inner tube 2 becomes separated from the corrugations Ib of the outer tube 1.

[7] As a result, with the conventional double walled spiral tube laid under the ground, the inner tube 2 structurally weak compared to the outer tube 1 can be easily damaged by external factors such as the application of load or earth pressure or changes of temperature. Thus, waste water or domestic sewage water may not smoothly pass through the inner tube 2, and the lifetime of the double walled spiral tube can be markedly shortened so that the costs incurred to maintain and administrate a sewer system excessively increase. Disclosure of Invention Technical Problem

[8] Accordingly, the present invention has been made in an effort to solve the problems occurring in the related art, and an object of the present invention is to provide a double walled spiral tube with an inner wall protecting structure, which is laid under the ground and is constructed to allow the corrugations of an outer tube and the synthetic resin body of an inner tube to independently expand and contract, so that the damage to the structurally weak inner tube can be prevented, thereby allowing the tube to be capable of appropriately performing and continuously carrying out the function of carrying or passing waste water or domestic sewage water. Technical Solution

[9] The present invention has the same technical concept as the conventional art in that a double walled spiral tube includes an outer tube 10 which is formed using a coated metal plate 11 possessing a plurality of corrugations 12 to have the configuration of a spiral cylinder, and an inner tube 20 which is placed inside the outer tube 10 and is constituted by a synthetic resin body 21 formed to have the configuration of a straight cylinder.

[10] The double walled spiral tube according to the present invention has a characterizing feature in that it further includes a flexible intermediate member 30 which is fixed to be interposed between the corrugations 12 of the outer tube 10 and the synthetic resin

body 21 of the inner tube 20 and is made of synthetic resin, such that the corrugations 12 of the outer tube 10 and the synthetic resin body 21 of the inner tube 20 can expand and contract independently of each other by the medium of the flexible intermediate member 30 made of synthetic resin. Advantageous Effects

[11] Thanks to the above-described features, the double walled spiral tube with an inner wall protecting structure according to the present invention is constructed in a manner such that the corrugations 12 of the outer tube 10 and the synthetic resin body 21 of the inner tube 20 are coupled with each other by the medium of the flexible intermediate member 30 made of synthetic resin. Therefore, when the double walled spiral tube is applied with load or earth pressure or undergoes temperature change in the state in which it is laid under the ground, the corrugations 12 of the outer tube 10 and the synthetic resin body 21 of the inner tube 20, which have different contractibilities, independently expand and contract due to the presence of the flexible intermediate member 30 made of synthetic resin. As a consequence, it is possible to prevent the synthetic resin body 21 of the inner tube 20 which is structurally weak compared to the coated metal plate 11 of the outer tube 10, from becoming separated from the outer tube 10 or ruptured.

[12] Accordingly, in the present invention, since the inner tube 20 is substantially prevented from being damaged attributable to the adverse influences exerted from the outside, waste water or domestic sewage water can smoothly pass through the inner tube 20, and the lifetime of the double walled spiral tube can be significantly extended, so that the costs incurred to maintain and administrate a sewer system can be reduced. Brief Description of the Drawings

[13] FTG. 1 is a partially broken-away front view illustrating a conventional double walled spiral tube;

[14] FIGs. 2 through 4 are enlarged sectional views illustrating the operation of the conventional double walled spiral tube;

[15] FIG. 5 is a partially broken-away and partially enlarged front view illustrating a double walled spiral tube with an inner wall protecting structure in accordance with an embodiment of the present invention;

[16] FIGs. 6 and 7 are enlarged sectional views illustrating the operation of the double walled spiral tube with an inner wall protecting structure according to the embodiment of the present invention;

[17] FIG. 8 is a partially broken-away and partially enlarged front view illustrating a double walled spiral tube with an inner wall protecting structure in accordance with a variation of the present invention; and

[18] FIGs. 9 and 10 are enlarged sectional views illustrating the operation of the double walled spiral tube with an inner wall protecting structure according to the variation of the present invention. Best Mode for Carrying Out the Invention

[19] Reference will now be made in greater detail to a preferred embodiment of the invention, an example of which is illustrated in the accompanying drawings.

[20] Referring to FIG. 5, a double walled spiral tube in accordance with an embodiment of the present invention includes an outer tube 10 which is formed using a coated metal plate 11 to have a plurality of corrugations 12, an inner tube 20 which is placed inside the outer tube 10 and is constituted by a synthetic resin body 21, and a flexible intermediate member 30 which is interposed between the outer tube 10 and the inner tube 20 and is made of synthetic resin.

[21] The outer tube 10 is a component part which sustains load or earth pressure applied thereto from the outside.

[22] As can be readily seen from FIG. 5, the outer tube 10 is formed in a manner such that both surfaces of a metal plate A are coated with cohesive synthetic resin A and the resultant coated metal plate 11 having the plurality of corrugations 12 is wound spirally to have the configuration of a spiral cylinder.

[23] Due to the fact that the outer tube 10 is formed by using the coated metal plate 11 possessing the corrugations 12 to have the configuration of a spiral cylinder, the outer tube 10 can efficiently sustain load or earth pressure applied thereto with the double walled spiral tube according to the present invention laid under the ground.

[24] Further, the coated metal plate 11 of the outer tube 10 has a pair of hook portions 13 which are formed on both ends of the outer tube 10 and are bent in opposite directions. Therefore, by hooking and thereby locking the hook portion 13 of one coated metal plate 11 bent in one direction with the hook portion 13 of another coated metal plate 11 bent in the other opposite direction, the outer tube 10 can be continuously formed to have the configuration of a spiral cylinder.

[25] Further, it is to be noted that the coated metal plate 11 can be formed by heat-fusing a separate synthetic resin covering A to the cohesive synthetic resin A coated on the outer surface of the metal plate A . The synthetic resin covering A functions to protect the metal plate A so that the metal plate A is not damaged due to friction with or

shocks from foreign matters and to block the leakage of moisture from the outside so that the metal plate A is not corroded.

[26] The inner tube 20 is a component part which is placed inside the outer tube 10 and passes waste water or domestic sewage water.

[27] As can be readily seen from FIG. 5, the inner tube 20 is constituted by the synthetic resin body 21 and is formed to have the configuration of a straight cylinder. The inner tube 20 is coupled to the inner end of the outer tube 10 by the medium of the flexible intermediate member 30 made of synthetic resin.

[28] Due to the fact that the inner tube 20 is formed to have the configuration of a straight cylinder placed inside the outer tube 10, the inner tube 20 can smoothly pass waste water or domestic sewage water introduced therein.

[29] It is preferred that the synthetic resin body 21 constituting the inner tube 20 be made of polyethylene resin having excellent tensile strength and compressive strength, so that the inner tube 20 is not damaged by the influences exerted from the outside as well as by foreign matters or earth introduced therein alongside the introduction of waste water and domestic sewage water.

[30] The flexible intermediate member 30 made of synthetic resin is a component part which joins the outer tube 10 and the inner tube 20 with each other such that they can expand and contract independently of each other.

[31] As can be readily seen from FIG. 5, the flexible intermediate member 30 is made of synthetic resin having predetermined degree of flexibility and elasticity. The outer surface of the flexible intermediate member 30 is heat-fused to the inner ends of the corrugations 12 of the outer tube 10, and the inner surface of the flexible intermediate member 30 is heat-fused to the outer surface of the synthetic resin body 21 of the inner tube 20. In this way, the flexible intermediate member 30 can be interposed between the corrugations 12 of the outer tube 10 and the synthetic resin body 21 of the inner tube 20.

[32] The flexible intermediate member 30, which is made of synthetic resin and is interposed between the corrugations 12 of the outer tube 10 and the synthetic resin body 21 of the inner tube 20, allows the corrugations 12 of the outer tube 10 and the synthetic resin body 21 of the inner tube 20 to expand and contract independently of each other, thereby preventing the structurally weak inner tube 20 from being damaged.

[33] That is to say, as shown in FIG. 6, with the double walled spiral tube according to the present invention laid under the ground, if the corrugations 12 of the outer tube 10 are

pressed by the load or earth pressure applied thereto from the outside so that the pitch of the corrugations 12 increases, the flexible intermediate member 30 made of synthetic resin absorbs the excessive tensile force applied to the synthetic resin body 21 of the inner tube 20 while being elastically deformed, whereby it is possible to prevent the synthetic resin body 21 of the inner tube 20 from being separated from the corrugations 12 of the outer tube 10 or being ruptured.

[34] Also, as shown in FIG. 7, with the double walled spiral tube according to the present invention laid under the ground, if the synthetic resin body 21 of the inner tube 20 repeatedly undergoes excessive contraction and expansion through a distance greater than the pitch of the corrugations 12 of the outer tube 10 due to the change of outside temperature, etc., the flexible intermediate member 30 made of synthetic resin absorbs and alleviates the excessive compressive and tensile force applied to the junction regions between the corrugations 12 of the outer tube 10 and the synthetic resin body 21 of the inner tube 20 while being elastically deformed between the corrugations 12 of the outer tube 10 and the synthetic resin body 21 of the inner tube 20, whereby it is possible to prevent the synthetic resin body 21 of the inner tube 20 from being separated from the corrugations 12 of the outer tube 10.

[35] In the present embodiment, the flexible intermediate member 30 is made of synthetic resin having predetermined degree of flexibility and elasticity to have the shape of a band, in a manner such that the upper surface thereof is formed as a concave junction surface 31 which is depressed inward and the lower surface thereof is formed as a flat junction surface 32 which is plane.

[36] In other words, in the present embodiment, the flexible intermediate member 30 made of synthetic resin can be flexibly and elastically deformed in the state in which the concave junction surface 31 thereof is joined with the inner ends of the corrugations 12 of the outer tube 10 and the flat junction surface 32 thereof is joined with the outer surface of the synthetic resin body 21 of the inner tube 20. Thus, the flexible intermediate member 30 alleviates not only the excessive stretching force or tensile force applied to the synthetic resin body 21 of the inner tube 20 when the pitch of the corrugations 12 of the outer tube 10 changes by the influences exerted from the outside but also the stretching force or tensile force generated in the junction regions between the synthetic resin body 21 of the inner tube 20 and the corrugations 12 of the outer tube 10 due to the change of outside temperature, etc., whereby it is possible to prevent the structurally weak inner tube 20 from being damaged.

Mode for the Invention

[37] FIG. 8 is a partially broken-away and partially enlarged front view illustrating a double walled spiral tube with an inner wall protecting structure in accordance with a variation of the present invention. In the present variation, a flexible intermediate member 30, which is made of synthetic resin having predetermined degree of flexibility and elasticity, is composed of an upper junction part 33 which is formed in the shape of a concave dish to be joined with the inner ends of corrugations 12 of an outer tube 10, a lower junction part 34 which is formed in the shape of a convex dish having a flat lower surface to be joined with the outer surface of a synthetic resin body 21 of an inner tube 20, and a middle movable part 35 which integrally connects the upper and lower junction parts 33 and 34 with each other.

[38] In the flexible intermediate member 30 made of synthetic resin according to the present variation, with the upper junction part 33 joined with the inner ends of the corrugations 12 of the outer tube 10 and the lower junction part 34 joined with the outer surface of the synthetic resin body 21 of the inner tube 20, the upper and lower junction parts 33 and 34 can be moved more flexibly and elastically due to the presence of the middle movable part 35. Therefore, as can be readily seen from FIGs. 9 and 10, when the pitch of the corrugations 12 of the outer tube 10 is changed by the influences exerted from the outside, the excessive stretching force or tensile force applied to the synthetic resin body 21 of the inner tube 20 can be alleviated, and, when the synthetic resin body 21 of the inner tube 20 repeatedly undergoes contraction and expansion due to the temperature change, the stretching force or tensile force generated in the junction regions between the synthetic resin body 21 of the inner tube 20 and the corrugations 12 of the outer tube 10 can be efficiently alleviated, whereby it is possible to reliably prevent the structurally weak inner tube 20 from being damaged.

[39] It is to be noted that an opening 36 can be defined in the middle movable part 35 of the flexible intermediate member 30 made of synthetic resin. The opening 36 allows the middle movable part 35 of the flexible intermediate member 30 made of synthetic resin to be moved more flexibly and elastically to aid in efficiently alleviating the excessive stretching force or tensile force applied to the synthetic resin body 21 of the inner tube 20. Industrial Applicability

[40] As is apparent from the above description, in the double walled spiral tube with an inner wall protecting structure according to the present invention, when the double

walled spiral tube is applied with load or earth pressure or undergoes temperature change in the state in which it is laid under the ground, the corrugations 12 of the outer tube 10 and the synthetic resin body 21 of the inner tube 20, which have different con- tractibilities, independently expand and contract due to the presence of the flexible intermediate members 30 made of synthetic resin. As a consequence, it is possible to effectively prevent the synthetic resin body 21 of the inner tube 20 which is structurally weak compared to the coated metal plate 11 of the outer tube 10, from being separated from the outer tube 10 or ruptured.

[41] Accordingly, since the inner tube 20 is substantially prevented from being damaged attributable to the adverse influence exerted from the outside, waste water or domestic sewage water can smoothly pass through the inner tube 20, and the lifetime of the double walled spiral tube can be significantly extended, so that the costs incurred to maintain and administrate a sewer system can be reduced.