WO2008082174A1

WO2008082174A1 - Method and apparatus for inserting synthetic resin-pipe in the outside-pipe and combined pipe manufactured thereby

Info

Publication number: WO2008082174A1
Application number: PCT/KR2007/006928
Authority: WO
Inventors: Tae Hwa Jeong
Original assignee: Tae Hwa Jeong
Priority date: 2007-01-05
Filing date: 2007-12-28
Publication date: 2008-07-10
Also published as: KR100887450B1; KR20070011642A

Abstract

Provided are method and an apparatus for inserting a synthetic resin pipe into an outside pipe and composite pipe manufactured thereby, comprising: manufacturing a metallic pipe and a resin pipe; reducing a diameter of the resin pipe; inserting the diameter-reduced resin pipe into an outside pipe; and restoring the diameter-reduced resin pipe. In accordance with the method and an apparatus for inserting a synthetic resin pipe into an outside pipe and composite pipe manufactured thereby, the diameter-reduced synthetic resin pipe is to have a restoring force to be in close contact with a metallic pipe, and the method of inserting the resin pipe into the metallic pipe enables the resin pipe to be inserted into the metallic with ease as well as by way of the mechanical device so that mass production can be achieved.

Description

METHOD AND APPARATUS FOR INSERTING SYNTHETIC RESIN-PIPE IN THE OUTSIDE-PIPE AND COMBINED PIPE

MANUFACTURED THEREBY

Technical Field

[1] The present invention relates to a method and an apparatus for inserting a synthetic resin pipe into an outside pipe and composite pipe manufactured thereby, and more particularly, a method for inserting a synthetic resin liner into other pipe body such as a metallic pipe, other resin pipe or a concrete pipe among a series of processes of manufacturing a lined pipe by inserting the synthetic resin pipe into the outside pipe, in particular, the metallic pipe. Background Art

[2] In order to prevent corrosion of an internal surface of the metallic pipe or a concrete pipe, etc, generally, a resin pipe is inserted into and brought in close contact with a pipe, or the resin pipe is inserted into and then adhered to the metallic pipe. A conventional method for inserting a resin pipe is disclosed in Korean Patent No. 10-0446197, entitled Method for Manufacturing Combination Pipe using Polyolefine, registered on August 19, 2004. The above Patent suggested a method; inserting a resin pipe (whose diameter is smaller than that of a metallic pipe) is inserted into the metallic pipe coated with an adhesive and then expanded into contact with the metallic pipe by using vacuum, which is formed between the metallic pipe and the resin pipe and discharges an air. This is, in case of vacuum absorption, a kind of removing blowholes by way of vacuumizing a space between the resin pipe and the metallic pipe and heating the metallic pipe into which the resin pipe, whose outer surface is coated with the adhesive, is inserted. This method has some problems; the blowholes generated in the middle of the pipe may remain inside, because air discharge paths are clogged as air existing at the pipe ends are being discharged so that a vacuum force does not reach the middle of the long pipe when the resin pipe has the length larger than its diameter; the resin pipe may be detached from the metallic pipe when the pipe is to be used for a long time, in particular, after changes in temperature, due to a restoration force of the resin pipe by which polyethylene is adhered and then is restored to its original size, i.e., the resin pipe is restored to its original diameter smaller than the metallic pipe.

[3] Other technologies are disclosed in Korean Patent No. 10-0500285, entitled

Apparatus for Manufacturing Dual Pipe, registered on June 30, 2005) and Korean Patent No. 10-0095887, entitled Lining Process for Internal Surface of Pipe, registered on February 16, 1996. The above Patent involve a method; a resin pipe is inserted into a metallic pipe (whose diameter is larger than that of the resin pipe) and thermal expansion under heating and pressure brings the resin pipe in close contact with the metallic pipe. However, due to formation of an air gap and generation of a restoration force after adhesion, there is still a problem that the resin pipe may fall apart from the metallic pipe in a long-term use.

[4] Another insertion technology is disclosed in Korean Patent No. 10-0347003, entitled A Method for Manufacturing Double Pipe by Inserting a Synthetic Resin Pipe into Inside of a Metallic Pipe, registered on July 19, 2002) and Korean Patent Application Publication No. 10-2002-0013704, entitled Manufacturing Method of Inner Surface Resin Lining Pipe, published on February 21, 2002. The above Patent and publications involve a method of adhering to the metallic pipe, by using the adhesive as an medium, the resin pipe expanded into close contact with the metallic pipe as a result of being left at the room temperature after the resin pipe, whose external surface is coated with the adhesive, is cooled and contracted, and then is inserted into the metallic pipe. In the method using an expansive force of a pipe, the unstability of the state and shape of the product make it difficult to meet adhesion conditions of the adhesive. Further, when inserting the cooled resin pipe into the metallic pipe, the blowholes may be generated between contact surfaces of the pipes as it is not easy to control moisture on the resin pipe.

[5] In all of the methods, since the inserted internal resin pipe has an internal force to be contracted and restored to its original small diameter as time elapses as much as the pipe is used, due to repeated expansion and contraction caused by temperature, an adhesive force of an adhesive becomes reduced and the resin pipe is to be slowly detached from the metallic pipe.

[6] Further, the above-mentioned methods involve the use of adhesives, which affects the life span of a composite pipe as the adhesion performance of the adhesive is limited. In particular, in Korea, where hot and cold weather recurs repeatedly according to four seasons, the adhesive gets easily superannuated due to a difference in thermal expansion coefficients between the metallic pipe and the resin pipe (i.e., approximately 10 times in case of steel and polyethylene). Thus, the adhesive is not conducive to keeping the semi-permanent life span of the metallic pipe or the resin pipe.

Disclosure of Invention Technical Problem

[7] An object of the present invention is to provide: a new insertion method for improving load conditions of expansive and contractive forces according to usage conditions, in particular, changes of temperature, so as to reduce stress generated due to a difference in thermal expansion coefficients between a metallic pipe and a synthetic resin pipe; a method for reducing the diameter of the synthetic resin pipe having an outer diameter larger than the inner diameter of the metallic pipe as well as a diameter-reduced synthetic resin pipe; a method and an apparatus for inserting the diameter-reduced synthetic resin pipe; and a composite pipe manufactured in accordance with the method. Technical Solution

[8] According to an aspect of the present invention, there is provided a method for inserting a synthetic resin pipe into an outside pipe, comprising: manufacturing a metallic pipe and a resin pipe; reducing a diameter of the resin pipe; inserting the diameter-reduced resin pipe into an outside pipe; and restoring the diameter-reduced resin pipe.

[9] The diameter of the resin pipe may be larger than the value that is obtained by adding to an inner diameter of the outside pipe the value of multiplying a combined pipe usage temperature range by a thermal expansion coefficient of the resin pipe, and may be smaller than a value that is obtained by adding 1/3 of the thickness of the resin pipe to the inner diameter of the outside pipe.

[10] The inserting of the diameter-reduced resin pipe into the outside pipe may comprise, after inserting the diameter-reduced resin pipe into the outside pipe, using a pressurizing unit so that the resin pipe is compressed into close contact with an inner circumferential surface of the outside pipe.

[11] The pressurizing unit may comprise a first compression unit compressing the resin pipe in a lengthwise direction of a pipe along a bent of the resin pipe and a second compression unit rotating and compressing the resin pipe in a circumferential direction of the pipe.

[12] The reducing of the diameter of the resin pipe may comprise reducing the diameter of the resin pipe in the center direction of the resin pipe by using a press device and inserting into the outside pipe the resin pipe having a larger diameter than the inner diameter of the outside pipe.

[13] A press force of the press device may be within an elastic force of the resin pipe.

[14] The shape of a cross-section of the press device may be one of arc, circular arc and polygonal shapes.

[15] The press device may be a press wheel or a press bar which is driven by using a hydraulic and pneumatic pressurizing unit.

[16] The press device may be disposed plurally in a radial shape from a center axis of the resin pipe to be able to press simultaneously. [17] Before the reducing a diameter of the resin pipe, the method may further comprise heating the resin pipe at a temperature within a softening point of a resin.

[18] The inserting the resin pipe into the metallic pipe may comprise transferring and inserting the diameter-reduced resin pipe into the outside pipe as one body with a press device, and the restoring the diameter-reduced resin pipe may comprise removing the press device after transferring and inserting, and pressurizing and restoring the resin pipe from which the press device is removed.

[19] The inserting the resin pipe into the metallic pipe may comprise fixing both ends of the resin pipe by using a fixing means and pushing the press device and the resin pipe formed as one body into the outside pipe in order to transfer and insert them.

[20] After the reducing the diameter of the resin pipe, the method may further comprise clamping both ends of the diameter-reduced resin pipe, wherein the inserting of the resin pipe into the metallic pipe comprises pulling one end of the clamped resin pipe to insert the resin pipe into the outside pipe, and the restoring of the diameter-reduced resin pipe comprises removing the clamp of the inserted resin pipe and pressurizing the removed resin pipe to restore it.

[21] According to another embodiment of the present invention, there is provided a method for inserting a synthetic resin pipe into a metallic pipe, comprising: manufacturing a metallic pipe and a resin pipe; reducing a diameter of the resin pipe; sealing both ends of the diameter-reduced resin pipe by using a sealing means; making an inside of the sealed resin pipe in a vacuum state; inserting the diameter-reduced resin pipe into an outside pipe; releasing the vacuum state of the inserted resin pipe; removing the sealing means of the vacuum-released resin pipe; and restoring the diameter-reduced resin pipe.

[22] The sealing means may comprise a resin pipe insertion groove that can be accommodated in the shape of the diameter-reduced resin pipe, a vacuum conduit having one end connected to a vacuum device so as to form a vacuum state, a vacuum gauge at which the vacuum state can be measured, a valve controlling pressure of the vacuum device, and a rapid separation socket to which the other end of the vacuum conduit is connected.

[23] The frame for vacuum may have the shape of the diameter-reduced resin pipe.

[24] According to another aspect of the present invention, a combined pipe may be manufactured by using any of methods for inserting a synthetic resin pipe into the outside pipe.

[25] According to another aspect of the present invention, there is provided an apparatus for inserting a synthetic resin pipe into an outside pipe, comprising: a fixing means to fix and not to move an outside pipe; and a moving carrier provided with a rail, a height adjusting means, and a driving means to move the resin pipe whose diameter has been reduced by using a press device.

[26] The apparatus may further comprise a guide wheel fixing both ends of the resin pipe at one side of the fixing means so as to prevent collision of the resin pipe with the outside pipe when the diameter-reduced resin pipe is inserted into the outside pipe.

[27] The apparatus may further comprise: a combining means to combine the diameter- reduced resin pipe with a press device as one body; and a transferring means to pull one end of the diameter-reduced resin pipe.

[28] The transferring means may comprise a rail, a moving carrier, a clamp fixed at the above-stated moving carrier, a rod connected to the clamp, and a rod transferring device.

[29] The press device may further comprise a guide wheel which can be rotated so that the resin pipe escapes from the press device when one end of the diameter-reduced resin pipe is pulled by using the transferring means.

Advantageous Effects

[30] The present invention, involving the method and the apparatus for inserting a synthetic resin pipe into a outside pipe and a composite pipe manufactured in accordance therewith, has advantageous effects: first, the diameter-reduced synthetic resin pipe is to have a restoring force to be in close contact with a metallic pipe, and the method of inserting the resin pipe into the metallic pipe enables the resin pipe to be inserted into the metallic with ease as well as by way of the mechanical device so that mass production can be achieved. As a result, the composite pipe manufactured by using the method according to the present invention can keep the adhering performance for a long time as the synthetic resin pipe is adhered tightly; and, secondly, since thermal expansion and contraction due to changes of temperature in use of the composite pipe or change of seasons are conductive to removing part of previously applied stress, that is, since thermal expansion becomes a force to come into close contact with the metallic pipe and thermal contraction becomes a force to slightly offset a restoring force against contraction applied during manufacturing, the composite pipe is used in an environment in which only one-direction stress is applied. Therefore, an adhering performance is kept for a long time and the performance of the product is improved.

Brief Description of the Drawings

[31] FIG. 1 is a flowchart illustrating a method for inserting a synthetic resin pipe into an outside pipe according to the first embodiment of the present invention.

[32] FIG. 2 is a latitudinal cross-sectional view and a longitudinal cross-sectional view illustrating a frame for vacuum with a mold and a hollow pipe attached to, which is inserted into a synthetic resin pipe, so as to reduce the diameter of the synthetic resin pipe according to the first embodiment of the present invention. [33] FIG. 3 is a schematic cross-sectional view illustrating a synthetic resin pipe installed at a diameter-reducing rod and a press device arranged in a radial shape according to the first embodiment of the present invention. [34] FIG. 4 is a schematic cross-sectional view illustrating the state of the synthetic resin pipe of Fig. 3 whose diameter is reduced with a press device (a press bar). [35] FIG. 5 is a latitudinal cross-sectional view and a longitudinal cross-sectional view illustrating a sealing cap among sealing means according to the first embodiment of the present invention. [36] FIG. 6 is a cross-sectional view in which a sealing cap and a frame for vacuum are attached to the diameter-reduced synthetic resin pipe according to the first embodiment of the present invention.

[37] FIG. 7 is a cross-sectional view illustrating an apparatus for inserting a diameter- reduced synthetic resin pipe into a metallic pipe according to the first embodiment of the present invention. [38] FIG. 8 is a schematic cross-sectional view illustrating the synthetic resin pipe which a sealing cap is removed from and is being restored to a circular shape according to the first embodiment of the present invention. [39] FIG. 9 is a schematic cross-sectional view illustrating the synthetic resin pipe which is compressed by a first compression unit in the lengthwise direction of the metallic pipe. [40] FIG. 10 is a cross-sectional view illustrating the state where the synthetic resin pipe and the metallic pipe are brought into close contact with each other by a first compression unit. [41] FIG. 11 is a schematic cross-sectional view illustrating the state of uniformly adjusting the remaining stress by compressing the synthetic resin pipe with a second compression unit in the circumferential direction of the metallic pipe. [42] FIG. 12 is a flowchart illustrating a method for inserting a synthetic resin pipe into an outside pipe according to the second embodiment of the present invention. [43] FIG. 13 is a schematic cross-sectional view illustrating the diameter of the synthetic resin pipe to be reduced with a wheel press according to the second embodiment of the present invention. [44] FIG. 14 is a schematic longitudinal cross-sectional view illustrating the synthetic resin pipe whose diameter is reduced with a wheel press and which is transferred and inserted into the metallic pipe, according to the second embodiment of the present invention. [45] FIG. 15 is a latitudinal cross-sectional view illustrating an apparatus for reducing a diameter of the synthetic resin pipe with a wheel press and transferring and inserting the pipe into the metallic pipe according to the second embodiment of the present invention.

[46] FIG. 16 is a flowchart illustrating a method for inserting a synthetic resin pipe into an outside pipe according to the third embodiment of the present invention.

[47] FIG. 17 is a cross-sectional view illustrating an apparatus for reducing a diameter of the synthetic resin pipe with a wheel press and for transferring and inserting inside into the metallic pipe a synthetic resin pipe which is pulled by using a moving carrier, according to the third embodiment of the present invention. Best Mode for Carrying Out the Invention

[48] The preferable exemplary embodiments of the present invention will now be described in details with reference to the accompanying drawings.

[49] Before describing the present invention, the terms and the words used in this specification and the claims should not be construed as being limited in general or dictionary senses, and the inventor should construe his/her own invention in senses and concepts conforming to technical ideas of the invention based on the principle of properly defining the concept of the terms so as to describe the invention in the best way.

[50] Therefore, the configuration shown in the embodiments and the drawings of the specification is only the most preferable exemplary embodiment of the present invention and does not represent all technical ideas of the present invention. Thus, it should be understood that there may be various equivalents and modified examples replacing them at the time of filing the present application.

[51] The present invention relates to a method for inserting a synthetic resin pipe into other outside pipe when manufacturing a combined pipe or a double-layer pipe having a synthetic resin pipe inside, comprising: manufacturing a synthetic resin pipe having a outer diameter larger than the inner diameter of the outside pipe; heating the resin pipe at the room temperature or within a softening point of a corresponding resin; distorting and folding the resin pipe by pressurizing with a press device with a force within a yield strength by using ductile and elastic deformation of the resin pipe; and therefore enabling the resin pipe, whose circumferential length is uniform and outward appearing diameter is reduced, to be inserted into the outside pipe having a diameter smaller than the outside diameter of the resin pipe. Restoring, after inserting, the resin pipe to its original shape by force of a pressurizing unit to press and attach the resin pipe to the outside pipe enables the resin pipe to be reduced in its diameter adjusted according to the inner diameter of the outside pipe to be in close contact with the outside pipe.

[52] The outside pipe comprises a resin pipe in its inside. An example of the outside pipe includes such general pipes as a steel pipe, a cast iron pipe, a concrete pipe, etc., and a metallic pipe is preferred.

[53] The method may be applied to line a water pipe, a gas pipe, a chemical material conveying pipe, a seawater pipe, an oil pipeline, and a drain pipe in a factory, for example.

[54] A resin pipe lined by applying the above method may be used in the lined state without performing additional processing on a liner. However, in a usage environment in which a large amount of a minus pressure is applied to a pipe, durability increases if adhering or gluing the resin pipe to the outside pipe, in particular, the metallic pipe is added to the inserting process.

[55] Gluing among the above-mentioned terms means a process in which an adhesive resin is coated between a liner (which is marked as a liner when the resin pipe is inserted in the outside pipe but the terms of the liner and the resin pipe are used as a synonym) and the outside pipe and is dried so that an adhesive force is generated. Adhesion means a process in which, since a resin such as polyethylene has an adhesive property only in a molten state even though the resin has an adhesive property as polarity is induced with the resin reforming, it is necessary to add heating and pressurizing processes to coating of an adhesive, and thus hereinafter, the process is referred to as adhesion, in particular.

[56] A method for inserting into the outside pipe a resin pipe by distorting by using ductility and elastic limits of the resin pipe may be applied in various ways under the same idea. However, several exemplary embodiments for inserting the resin pipe into metallic pipes will be described and may be applied in other ways by ordinary technicians. However, it is natural that such embodiments are within the scope of the idea of the present invention.

[57] First of all, an embodiment of the present invention will now be described by operations.

[58] FIG. 1 is a flowchart illustrating a method for inserting a synthetic resin pipe into an outside pipe according to the first embodiment of the present invention.

[59] The inserting method according to the present invention, to be described according to the process suggested in FIG. 1 as an exemplary embodiment, comprises manufacturing a metallic pipe and a synthetic resin pipe (Sl 1), reducing the diameter of the synthetic resin pipe (S 12), sealing both ends of the diameter-reduced resin pipe with a sealing means (S 13), making the inside of the sealed resin pipe be in a vacuum state (S 14), inserting the diameter-reduced resin pipe into an outside pipe (S 15), releasing the vacuum state of the inserted resin pipe (S 16), removing the sealing means of the vacuum-released resin pipe (S 17), and restoring the removed resin pipe (S 18).

[60] First of all, the manufacturing operation (Sl 1) will now be described in detail. [61] A resin pipe 10 made from any one of the synthetic resins, in particular, polyethylene (PE), polybutylene (PB), polypropylene (PP), is manufactured, according to the method as pronounced publicly, in a diameter larger by a predetermined amount than the inner diameter of a metallic pipe 20.

[62] The above-mentioned preferable predetermined amount means the range in which, while a contractile force is generated in the resin pipe due to a fall of temperature, the contractile force is smaller than a restoration force for enlarging the diameter of the resin pipe generated when the resin pipe is inserted into the outside pipe, i.e., the range between the amount that is obtained by adding to the inner diameter of the metallic pipe the result of multiplying a temperature range, in which a combined lined pipe is to be used, by a thermal expansion coefficient of the resin pipe and the amount that is obtained by adding a compression space to the inner diameter of the metallic pipe, which will be expressed as the following equation:

[63] Outer diameter of inside resin pipe = (inner diameter of metallic pipe + thermal expansion coefficient x usage temperature range) ~ (inner diameter of metallic pipe + compression space).

[64] For example, in case of a 300A steel pipe for ordinary piping, when the inner diameter of the metallic pipe is approximately 297.9mm, the thermal expansion coefficient of high-density polyethylene is 0.0000012, the thickness of the resin pipe is 10mm and the metallic pipe and the resin pipe are used in Korea exposed to the atmospheric pressure, the usage temperature range is approximately 90 degrees from - 30°to 60°. Thus, the following equation is formed.

[65] 297.9 + (0.0000012 x 90) ~ 297.9 + 10/3 = 297.900108 ~ 301.24.

[66] In this case, it is noticeable that the insertion by a small amount of force acts on the binding force effectively in one direction against to thermal contraction due to temperature.

[67] Thus, the lower limit of a predetermined amount is equal to the contraction amount in a temperature change range less than the room temperature, and an upper limit thereof, while, as a compression amount increases, a closely adhering force increases but is uneconomical, is to be preferably within the thickness of the resin pipe, more preferably, within 1/3 of the thickness of the resin pipe so that the center of the cross- section of the diameter-reduced resin pipe is positioned close to the core point of the center of the cross-section of the resin pipe before diameter-reduction. Thus, a force in which the resin pipe is to be bent (to be bounced) toward the center is prevented from being generated so as to achieve structure mechanical stability.

[68] A force in which the resin pipe is to be closely adhered to the metallic pipe is in proportion to the amount of elastic deformation. However, as the amount of elastic deformation increases, a force in which the resin pipe is to be bounced toward the center from part of the resin pipe increases simultaneously. Thus, in particular, high-density polyethylene may be easily bent due to lower flexural strength (0.95kg/mm ) than elastic strength (56~105kg/mm ). When the amount of deformed diameter-reduction is limited to 1/3 of the thickness of the resin pipe, only a restoration force to be expanded to the metallic pipe exists.

[69] Referring to a metallic pipe, its surface to be adhered to the resin pipe is, according to the method as pronounced publicly, to be processed against welding beads, etc., cleaned and blasted etc. to make fine roughness so as to get ready for an insertion of the resin pipe.

[70] When epoxy is used as a base adhesive, according to the method as pronounced publicly, the metallic pipe is coated with epoxy in a uniform thickness either by rotating the metallic pipe while moving a spray nozzle or by rotating the spray nozzle while moving the metallic pipe at a predetermined speed, so as to get ready for an insertion of the resin pipe.

[71] When epoxy or other adhesive resin is coated between the outside pipe, in particular, the metallic pipe and the resin pipe as above, its thickness should be considered previously to determine the outer diameter of the resin pipe.

[72] Next, the diameter-reducing operation (S 12) will now be described in detail. FIG. 2 is a latitudinal cross-sectional view and a longitudinal cross-sectional view illustrating a frame for vacuum with a mold and a hollow pipe attached to, which is inserted into a synthetic resin pipe, so as to reduce the diameter of the synthetic resin pipe according to the first embodiment of the present invention, and FIG. 3 is schematic a cross- sectional view illustrating a synthetic resin pipe installed at a diameter-reducing rod and a press device arranged in a radial shape according to the first embodiment of the present invention.

[73] As illustrated in FIG. 3, after the manufactured resin pipe is put on a diameter- reducing rod 160 and a frame for vacuum 200 of FIG. 2 is inserted into the resin pipe, the resin pipe is compressed and distorted by a press device (a press bar) 50 fixed at the end of the piston 42 as a piston 42 is pushed by using a hydraulic and pneumatic pressurizing unit. This operation may be carried out with the resin pipe preferably heated under a softening point like in the case of a hard resin, depending on the type of the resin, but may be carried out at the room temperature without heating in case of semi-hard resin polyethylene.

[74] The frame for vacuum 170 comprises mold 173 disposed at predetermined intervals centering on a hollow shaft 171. The mold 173 is used to prevent the resin pipe from being distorted in a non-fixed form in a vacuum state and from being excessively distorted. The mold 173 may be formed of aluminum that is light and rigid. The length of the mold 173 corresponds to the overall length of the resin pipe together with the hollow axis 171. A connection portion 174 having a screw 172 is provided at both ends of the hollow shaft 171 and is to be screw-combined with a conduit 77 of a sealing cap 70.

[75] The shape of the mold 173 is shown in the embodiment of FIG. 2 but the mold 173 may have other shapes and may be manufactured in a shape related to the shape of the press device.

[76] FIG. 4 is a schematic cross-sectional view illustrating the state of the synthetic resin pipe of Fig. 3 whose diameter is reduced with a press device (a press bar).

[77] The diameter-reduced shape should be controlled. The shape as illustrated in FIG. 4 is preferred. Other cases, for example, the case where the number of distorted portions is replaced by three or five from four shown in the embodiment or the shape of the distorted portion is replaced by a polygonal shape from an arc shape, will be naturally in the scope of the present invention.

[78] The press bar 50 as a press device may be positioned preferably in a radial shape centering on the resin pipe, and more preferably, the number of the press bar 50 may be four or more. As the diameter of the pipe becomes larger, the number of the press bar 50 may increase as many as possible. However, the number of the press bar 50 may be the number at which, when the resin pipe is inserted, the restoration force of the resin pipe is uniformly generated. In order to make no flaw on the resin pipe when contacting the press bar 50 and to induce the smoothly bent shape of the resin pipe, the shape of the portion contacting the resin pipe is to be an arc or a circular arc.

[79] All press bars 50 moved simultaneously by a pressurizing unit 60 are to compress and distort the resin pipe simultaneously in several directions in order to make its distorted shape steady.

[80] When the resin pipe has considerable ductility, an operation of pressurizing the resin pipe using a press device is omitted. The frame for vacuum 200 is inserted in the resin pipe and both ends of the resin pipe are sealed by using a sealing means having a vacuum conduit and is made in a vacuum state so that the resin pipe is distorted and is attached to the frame for vacuum 200 and the diameter of the resin pipe is reduced.

[81] Next, the sealing operation (S 13) will now be described in detail. FIG. 5 is a latitudinal cross-sectional view and a longitudinal cross-sectional view illustrating a sealing cap among sealing means according to the first embodiment of the present invention.

[82] As illustrated in FIG. 4, when the diameter of the resin pipe 11 is reduced, the sealing cap 70 is attached to each opening at both ends of the resin pipe as an embodiment of a vacuum sealing means. The shape of the sealing cap 70 is shown in the latitudinal cross-sectional view and the longitudinal cross-sectional view in FIG. 5. More specifically, the resin pipe is to be inserted into a cap body 76 with its end portion adjusted to a resin pipe insertion groove 71 of the sealing cap 70, and a conduit 77 having a valve 74, a rapid separation socket 75, and a fixing nut 73 is inserted in the cap body 76 and is screw-combined with a screw portion 172 of the frame for vacuum 200 and the resin pipe is sealed by screw-driving the fixing nut 73.

[83] Next, the vacuum operation (S 14) will now be described in detail. FIG. 6 is a cross- sectional view in which a sealing cap and a frame for vacuum are attached to the diameter-reduced synthetic resin pipe according to the first embodiment of the present invention.

[84] As illustrated in FIG. 6, if the valve 74 is opened after an end of the conduit 77 connected to a vacuum device (not shown) is connected to the rapid separation socket 75 of the sealing cap 70 which is a sealing means, the inside of the resin pipe is gradually made in a vacuum state and the resin pipe gets attached to the frame for vacuum 200. When the resin pipe is formed in a proper shape or the value of a vacuum gauge attached to a sealing cap (not shown) reaches its indication value as known by experience, the valve 74 is closed and the vacuum conduit 77 is separated and removed from the rapid separation socket 75.

[85] Now, the resin pipe is distorted and its diameter is reduced and its inside is in a vacuum state. Thus, even when the press device 50 has been removed, it is not returned to its original state and can be moved to other place.

[86] Next, the inserting operation (S 15) will now be described in detail. FIG. 7 is a cross-sectional view illustrating an apparatus for inserting a diameter-reduced synthetic resin pipe into a metallic pipe according to the first embodiment of the present invention.

[87] As illustrated in FIG. 7, when the vacuum operation (S 14) is completed, the resin pipe having a diameter larger than that of the original metallic pipe is sufficiently to be inserted into the metallic pipe. Thus, the inserting operation (S 15) will start with reference to the cross-sectional view of FIG. 7

[88] First, one-side body of the sealing cap 70 formed at both sides of the resin pipe moves on a rail 80 forwards and backwards, and a clamp 100 operated with hydraulic and pneumatic pressure is installed and fixed at a moving carrier 90 in which the height of the resin pipe is adjusted so as to adjust the center of the pipe supported by a fixing means 190, and a rod 120 is connected to the clamp 100 installed at the sealing cap 70 at the other side (forward direction) that is first inserted in the metallic pipe. The rod 120 is installed at another moving carrier and may move forwards and backwards by a rod moving device 121 which operates by hydraulic and pneumatic pressure.

[89] Several guide wheels 110 are attached to the clamp 100 being in the forward direction so that, when the diameter-reduced resin pipe 11 moves within the metallic pipe 20, the resin pipe 11 may not contact the metallic pipe 20.

[90] When the diameter-reduced resin pipe 11 is nearly inserted into the metallic pipe

20, a guide wheel receiver 123 is attached to a height adjusting unit 124 which has the same height as the inner diameter of the metallic pipe 20 on the moving carrier 90, so as to prevent the guide wheel 110 from falling out of the metallic pipe 20.

[91] Now, when the resin pipe 11 is inserted in a proper position of the metallic pipe 20, a brake attached to the moving carrier 90 is pulled to stop the inserting operation.

[92] Next, the releasing operation S 16 will now be described in detail. When a valve 74 attached to an end of the sealing cap 70 is gradually opened, the air is let in the vacuum state of the resin pipe 11 and the inside of the resin pipe 11 gets in an atmospheric pressure, the resin pipe that is contracted in a vacuum state is slightly expanded and restored to a certain degree of its original state.

[93] Next, the removing operation (S 17) will now be described in detail. After the fixing nut 73 is released, and the conduit 77 to which the valve 74 is attached is removed from the frame for vacuum 200, the sealing cap 70 is separated and removed from the rein pipe 11, and then, the frame for vacuum 200 in the resin pipe 11 is removed.

[94] Next, the restoring operation (S 18) will now be described in detail. FIG. 8 is a schematic cross-sectional view illustrating the synthetic resin pipe which a sealing cap is removed from and is being restored to a circular shape according to the first embodiment of the present invention, and FIG. 9 is a schematic cross-sectional view illustrating the synthetic resin pipe which is compressed by a first compression unit in the lengthwise direction of the metallic pipe.

[95] Referring to FIG. 8, after the sealing cap 70 is removed from the resin pipe 11 which is compressed and has a reduced diameter, a resin pipe 12 shows the shape being in process of restoration, and the resin pipe is expanded until it contacts the metallic pipe 20.

[96] However, since the outer diameter of the resin pipe is larger than the inner diameter of the metallic pipe, after the resin pipe in process of restoration 12 contacts the inside of the metallic pipe, it is not expanded any more and is bent. Hence, the resin pipe in process of restoration 12 is pressurized with a pressurizing unit into close contact with the metallic pipe 20.

[97] Another pressurizing means, except a compression roller, is such that both ends of the metallic pipe 20 are closed and the resin pipe 12 may be pressurized by the compression air, which involves a danger of explosion in case of a large-diameter pipe. Thus, an example in which a compression roller is used will now be described.

[98] As illustrated in FIG. 9, a first compression unit 140 according to the present invention comprises: attaching a forward and backward transfer means of hydraulic and pneumatic pressure to the moving carrier 90, attaching a cylinder 143 and a piston 142 to the hollow shaft 130 of FIG. 9 at an end of the transfer means, attaching a bracket 141 to an end of the piston 142, and attaching a compression roller 145 to the bracket 141.

[99] It is preferable to install the same number of compression roller 45 as the press bar

50 used for diameter-reduction, if possible. Making a reciprocal motion in the lengthwise direction of the pipe, the roller is to compress the resin pipe into close contact with the outside pipe.

[100] Further, it is desirable that the shape of the compression roller 145 of the first compression unit 140 may be similar to an arc formed by the circumference of the pipe. The angle of the compression roller 145 should be changed in a circumferential direction in the center of the pipe, and the compression roller 145 should be formed of a material having elasticity, and its surface should be coated with Teflon etc. having, if possible, no electrical and chemical affinity with the resin pipe.

[101] FIG. 10 is a cross-sectional view illustrating the state where the synthetic resin pipe and the metallic pipe are brought into close contact with each other by a first compression unit. FIG. 11 is a schematic cross-sectional view illustrating the state of uniformly adjusting the remaining stress by compressing the synthetic resin pipe with a second compression unit in the circumferential direction of the metallic pipe.

[102] Now, if the resin pipe keeps in close contact with the metallic pipe, it comes into the state as shown in FIG. 10. However, since stress caused by distortion of the resin pipe is ununiformly distributed, compression is performed once again so as to solve the problem, as illustrated in FIG. 11. In this case, bent and nonuniform stress is dispersed by a second compression unit 150 which rotates and compresses the resin pipe in a circumferential direction by changing the direction of the compression roller by 90 degrees.

[103] As the first compression unit 140, the second compression unit 150 is such: a cylinder 153 and a piston 152 is attached to the hollow shaft 130, and one end of the piston 152 is connected to a tool rest 154, and a compression roller 155 is attached to the other end of the piston 152 so that remaining stress can be uniformly adjusted in a circumferential direction by using the compression roller 155.

[104] Now, by removing the second compression unit 150 from the inside of the resin pipe when the resin pipe is completely in close contact with the metallic pipe, the resin pipe inserting operation is completed to form the compressed resin pipe 13.

[105] Now, the second embodiment of the inserting operation will be described with reference to the flowchart of FIG. 12.

[106] FIG. 12 is a flowchart illustrating a method for inserting a synthetic resin pipe into an outside pipe according to the second embodiment of the present invention.

[107] The above-mentioned first exemplary embodiment applies a method, comprising: distorting the resin pipe so as to reduce its diameter, inserting the frame for vacuum 170 into and vacuumizing the resin pipe so as not to make the distorted shape be restored. However, since a procedure to insertion is complicated, a more convenient method will now be described.

[108] According to the second embodiment of the present invention, the method for inserting a resin pipe into an outside pipe comprises manufacturing a resin pipe and a metallic pipe (S21), reducing the diameter of the resin pipe by compressing the resin pipe by using a wheel press (S22), transferring and inserting the diameter-reduced resin pipe to and into the metallic pipe (S23), removing the wheel press (S24), and restoring the resin pipe (S25).

[109] Manufacturing of the resin pipe and the metallic pipe in the manufacturing operation (S21) according to the second embodiment of the present embodiment is performed by using the same method as used in the manufacturing operation (Sl 1) according to the first embodiment of the present invention. Thus, a description thereof will be omitted.

[110] Now, the diameter-reducing operation (S22) will be described in detail. FIG. 13 is a schematic cross-sectional view illustrating the diameter of the synthetic resin pipe to be reduced with a wheel press according to the second embodiment of the present invention.

[I l l] As illustrated in FIG. 13, a plurality of press wheels 40 as a press device instead of the press wheel 40 are attached to the end of a piston 42 in a radial shape in the center of the pipe. In this case, the press wheels 40 are disposed at regular intervals in the lengthwise direction of the pipe so that, when the resin pipe is distorted, it has a required shape. The softer the material of the resin pipe is, the narrower the intervals should be.

[112] The press bar 50 as used in the first embodiment of the present invention may also be applied.

[113] Further, a slider 43 is provided between a piston 42 and a press wheel 40 , enabling the wheel to make slide movement of the wheel in a shaft direction.

[114] Other matters are similar to the diameter-reducing operation (S 12) according to the first embodiment of the present invention and thus, a detailed description thereof will be omitted.

[115] Next, the inserting operation (S23) will now be described in detail.

[116] FIG. 14 is a schematic longitudinal cross-sectional view illustrating the synthetic resin pipe whose diameter is reduced with a wheel press and which is transferred and inserted into the metallic pipe, according to the second embodiment of the present invention, and FIG. 15 is a latitudinal cross-sectional view illustrating an apparatus for reducing a diameter of the synthetic resin pipe with a wheel press and transferring and inserting the pipe into the metallic pipe according to the second embodiment of the present invention.

[117] When the diameter of the resin pipe is reduced as the press wheel 40 compresses the resin pipe, as illustrated in FIGS. 14 and 15, a cover clamp 180 is attached to each end of both sides of the resin pipe, and a height-adjustable rod 120, installed at the moving carrier 90 that moves along the rail, is to be coupled with the cover clamp 180 at a rear side (a side to be later inserted into a pipe), is combined, and a pin 45 attached to a ring 44 of a slider 43 is inserted into a pin hole 181 of the cover clamp 180.

[118] Now, when the moving carrier 90 is moved by using a driving means such as a motor, the resin pipe and the press wheel 40 being a press device are moved and inserted together as one body into the metallic pipe 20 at the speed not harmful to the slider 43.

[119] When the resin pipe and the press wheel 40 being a press device as combined as one body start to move and be inserted into the metallic pipe 20, the guide wheel 110 attached to the end of each slider 43 contacts and rolls on the inside of the metallic pipe 20 so that load of the resin pipe and the slider 43 is transmitted to the metallic pipe through the guide wheel 110.

[120] Next, the removing operation (S24) will now be described in detail. When the resin pipe is moved in a proper position of the metallic pipe 20, a brake of the moving carrier 90 is fixed, the pin 45 is removed from the ring 44 of the cover clamp 180, and the slider 43 and the press wheel 40 are moved backwards and are separated from the resin pipe.

[121] Next, when the cover clamp 180 is separated from both sides of the resin pipe, the resin pipe is expanded to a possible range and, with moving backwards the moving carrier 90 is to be removed from the resin pipe.

[122] After that, the cover clamp 180 is to be separated from the rod 120.

[123] Next, the restoring operation (S25) is the same as the restoring operation (S 18) of the first embodiment of this present invention.

[124] Another exemplary embodiment of the inserting operation according to the third embodiment of the present invention will now be described with reference to FIGS. 16 and 17.

[125] FIG. 16 is a flowchart illustrating a method for inserting a synthetic resin pipe in an outside pipe according to the third embodiment of the present invention, and FIG. 17 is a cross-sectional view illustrating an apparatus for reducing a diameter of the synthetic resin pipe with a wheel press and for transferring and inserting inside into the metallic pipe a synthetic resin pipe which is pulled by using a moving carrier, according to the third embodiment of the present invention.

[126] According to the second embodiment of the present invention, the cover clamp 180 is attached so as not to restore the shape of the diameter-reduced resin pipe and then the slider 43 is attached between the press wheel 40 and the piston 42 so that the slider 43 is transferred and inserted into the metallic pipe as one body with the diameter- reduced resin pipe. However, in a small-and-medium- diameter pipe, when the weight of the resin pipe is light and insertion should be performed right after diameter redu ction, an embodiment that is appropriate to this situation is to be presented in the third embodiment.

[127] As illustrated in FIG. 16, the third embodiment of the method and the apparatus for inserting the synthetic resin pipe into the outside pipe according to the third embodiment of the present invention comprises manufacturing operation (S31), diameter-reducing operation (S32), clamping operation (S33), inserting operation (S34), removing operation (S35), and restoring operation (S36).

[128] First, the manufacturing operation (S31) is the same as the manufacturing operation

(Sl 1) according to the first embodiment of the present embodiment and thus, a description thereof will be omitted.

[129] Next, the diameter-reducing operation (S32) is the same as the diameter-reducing operation (S22) according to the second embodiment of the present embodiment. However, the resin pipe is compressed and distorted without the slider 43 attached between the press wheel 40 and the piston 42, so as to reduce the diameter of the resin pipe.

[130] Only, the degree of distortion is more excessive so that the amount of diameter- reduction should be increased.

[131] Next, in the clamping operation (S33), when the diameter of the resin pipe is reduced, the cover clamp 180 is attached to the rear side of the resin pipe and a plurality of clamps 200 are attached to the front side of the resin pipe in a radial shape.

[132] In this case, in order to attach the front-side clamp 200, the moving carrier 90 is moved backwards, the rod 120 and the guide rod 122 are taken out to the rear side as much as possible, and the clamp 100 attached to the end of the rod 120 is to be inserted into an end portion of the resin pipe and is to be clamped manually or by hydraulic and pneumatic pressure.

[133] Further, in the inserting operation (S34), while both sides of the diameter-reduced resin pipe are fixed with fixing means such as clamps, one side of the resin pipe is pulled out of a press device and is directly inserted into the outside pipe 20. Specifically, when the moving carrier 90 is moved forwards by using an electromotive or hydraulic and pneumatic driving means in the state where the clamping operation is completed, the resin pipe escapes from the press wheel 40 and starts being inserted into the metallic pipe 20. The guide wheel 110 should be attached to the outer circumferential surface of the clamp 200 so as to transmit load of the resin pipe to the metallic pipe 20. [134] When the diameter-reducing operation is completed and the resin pipe escapes from the press wheel 40, only the end of the resin pipe is fixed with the clamp 200 and there is no device against the restoration force of the resin for the rest of the resin pipe.

Hence, when the resin pipe starts being transferred, the moving carrier 90 should be moved at a uniform speed, and the inserting operation should be completed as fast as possible, preferably, within several minutes. [135] Next, in the removing operation (S35), when the resin pipe is inserted in a proper position of the metallic pipe, the moving carrier 90 is stopped. [136] The clamp 200 is released manually or by hydraulic and pneumatic force, and the rod 120 and the guide rod 122 are moved forwards and are separated from the resin pipe. [137] Last, the restoring operation (S36) is the same as the restoring operation (S 18) according to the first embodiment of the present embodiment, and thus, a description thereof will be omitted. [138] While the present invention has been particularly shown and described with reference to limited exemplary embodiments thereof, it is needless to say that various changes and modifications in form and details are apparent to those with ordinary skill in the art to which the present invention pertains without departing from the technical idea of the present invention and within the even scope of as defined by the following claims.

Claims

[1] A method for inserting a synthetic resin pipe into an outside pipe, comprising: manufacturing a metallic pipe and a resin pipe; reducing the diameter of the resin pipe; inserting the diameter-reduced resin pipe into an outside pipe; and restoring the diameter-reduced resin pipe.

[2] The method of claim 1, wherein the diameter of the resin pipe is larger than the value that is obtained by adding to an inner diameter of the outside pipe the value of multiplying a combined pipe usage temperature range by a thermal expansion coefficient of the resin pipe, and is smaller than a value that is obtained by adding 1/3 of the thickness of the resin pipe to the inner diameter of the outside pipe.

[3] The method of claim 1, wherein the inserting of the diameter-reduced resin pipe into the outside pipe comprises, after inserting the diameter-reduced resin pipe into the outside pipe, using a pressurizing unit so that the resin pipe is compressed into close contact with an inner circumferential surface of the outside pipe.

[4] The method of claim 3, wherein the pressurizing unit comprises a first compression unit compressing the resin pipe in a lengthwise direction of a pipe along a bent of the resin pipe and a second compression unit rotating and compressing the resin pipe in a circumferential direction of the pipe.

[5] The method of claim 1, wherein the reducing of the diameter of the resin pipe comprises reducing the diameter of the resin pipe in the center direction of the resin pipe using a press device and inserting the resin pipe having a larger diameter than the inner diameter of the outside pipe into the outside pipe.

[6] The method of claim 5, wherein a press force of the press device is within an elastic force of the resin pipe.

[7] The method of claim 5, wherein the shape of a cross-section of the press device is one of arc, circular arc and polygonal shapes.

[8] The method of claim 5, wherein the press device is a press wheel or a press bar which is driven by using a hydraulic and pneumatic pressurizing unit.

[9] The method of claim 5, wherein the press device is disposed in a radial shape plurally from a center axis of the resin pipe to be able to press simultaneously.

[10] The method of claim 5, before the reducing the diameter of the resin pipe, further comprises heating the resin pipe at a temperature within a softening point of a resin.

[11] The method of claim 5, wherein the inserting the resin pipe into the metallic pipe comprises transferring and inserting the diameter-reduced resin pipe into the outside pipe as one body with a press device, and the restoring of the diameter- reduced resin pipe comprises removing the press device after transferring and inserting, and pressurizing and restoring the resin pipe from which the press device is removed.

[12] The method of claim 5, wherein the inserting the resin pipe into the metallic pipe comprises fixing both ends of the resin pipe by using a fixing means and pushing the press device and the resin pipe formed as one body into the outside pipe in order to transfer and insert them.

[13] The method of claim 5, after the reducing the diameter of the resin pipe, further comprises clamping both ends of the diameter-reduced resin pie, wherein the inserting the resin pipe into the metallic pipe comprises pulling one end of the clamped resin pipe to insert the resin pipe into the outside pipe, and the restoring the diameter-reduced resin pipe comprises removing the clamp of the inserted resin pipe and pressurizing the removed resin pipe to restore it.

[14] A method for inserting a synthetic resin pipe into a metallic pipe, comprising: manufacturing a metallic pipe and a resin pipe; reducing a diameter of the resin pipe; sealing both ends of the diameter-reduced resin pipe using a sealing means; making an inside of the sealed resin pipe in a vacuum state; inserting the diameter-reduced resin pipe into an outside pipe; releasing the vacuum state of the inserted resin pipe; removing the sealing means of the vacuum-released resin pipe; and restoring the diameter-reduced resin pipe.

[15] The method of claim 14, wherein the sealing means comprises a resin pipe insertion groove that can be accommodated in the shape of the diameter-reduced resin pipe, a vacuum conduit having one end connected to a vacuum device so as to form a vacuum state, a vacuum gauge at which the vacuum state can be measured, a valve controlling pressure of the vacuum device, and a rapid separation socket to which the other end of the vacuum conduit is connected.

[16] The method of claim 14, wherein the frame for vacuum has the shape of the diameter-reduced resin pipe.

[17] A composite pipe manufactured by using the method of any one of claims 1 through 16.

[18] An apparatus for inserting a synthetic resin pipe into an outside pipe, comprising: a fixing means fixing an outside pipe; and a moving carrier having a rail, a height adjusting means, and a driving means so as to move the diameter-reduced resin pipe by using a press device. [19] The apparatus of claim 18, further comprising a guide wheel fixing both ends of the resin pipe at one side of the fixing means so as to prevent collision of the resin pipe with the outside pipe when the diameter-reduced resin pipe is inserted into the outside pipe. [20] The apparatus of claim 18, further comprising: a combining means combining the diameter-reduced resin pipe with a press device as one body; and a transferring means pulling one end of the diameter-reduced resin pipe. [21] The apparatus of claim 20, wherein the transferring means comprises a rail, a moving carrier, a clamp fixed at the moving carrer, a rod connected to the clamp, and a rod transferring device. [22] The apparatus of claim 20, wherein the press device further comprises a guide wheel which can be rotated so that the resin pipe escapes from the press device when one end of the diameter-reduced resin pipe is pulled by using the transferring means.