Title of the Invention PLASTIC PIPE OF TRIPLE LAYERS USING PLASTIC SALVAGE AND ITS MANUFACTURING METHOD AND APPARATUS Technical Field The present invention relates to a plastic pipe of triple layers using plastic salvage and its manufacturing method and apparatus, and more particularly to a plastic pipe of triple layers which comprises an intermediate waste layer of a helically overlapped multiple layer structure using common plastic waste <BR> <BR> such as waste plastic for agriculture, waste vinyl, etc. , an inner layer and an outer layer formed by extruding plastic material different from plastic waste onto the opposite surfaces of the intermediate waste layer, and thus, which can recycle resources and protect environment by using regenerated plastic, increase resisting pressure strength and airtightness properties between an inner surface and an outer surface even with a simple structure, and that have graceful appearance and excellent quality by using new plastic material in the inner layer and the outer layer.

Background Art Generally, there is well known a method of manufacturing a multilayer pipe having a thermoplastic layer helically wound wherein each layer can be wound and overlapped onto each other, and of making a large size pipe by winding various structure of a small size pipe. There is also known a method of separately 5 installing a hollow room shape each of which is formed linearly between two helically wound flat layers without forming the multilayer pipe completely. Various structures are developed as a plastic hume pipe of a multilayer structure, and their manufacturing mathods and apparatus are also developed.

10 For one example, a pressure resistant plastic pipe disclosed by Korean patent application laid-open publication No.

99-001314 is formed of a helical convex-concave wave shape, and improves a pressure resistance by laying a metal reinforcement strap into the wall thickness of a plastic pipe. Such a metal 15 reinforcement strap is overlapped or formed of a special structure, thereby achieving reinforcement over the whole wall of the pipe. However, such reinforcement structure makes the expense higher and the manufacturing method complicated.

Further, one method of a multilayer pipe is disclosed in 20 Korean patent application laid-open publication No. 99-032911,

wherein an outer surface of a multilayer pipe having almost a circular profile is not even, and adjoining side surfaces are molten and adhered to each other by making the inner face and the side face plastic after achieving a shape stabilization of the profile in a small sized pipe of a lozenge section or a ball-shaped hollow room profile in order to solve a disadvantage of being unstably expanded. Such a structure consumes little material only, but makes a process complicated and a unit cost higher because of having to form a certain structure of a small size pipe.

Still furthermore, a spiral pipe and its forming apparatus which uses a scrapped plastic waste is disclosed in Korean patent application laid-open publication No. 99-24148 (laid-open date: March 25,1999, an application No. 1998-054767), wherein mixed material of agricultural by-products such as chaff, rice straw, <BR> <BR> etc. , is used, and wherein a square shaped profile whose inside is<BR> filled with wast plastic or waste film, etc. , is formed by an extruder and through a process adhering the profile with supplying resin by opposite assistant extruders.

Such a spiral pipe is to remove the problem that proper adhesion cannot be obtained due to a temperature deviation of the prior art small-sized pipe profile and the adherence material, but it is easily severed or separated by a heavy load or an outer pressure because an interior hollow of the pipe is not effective 5 to a load and adhered portions are weak. And, strength is provided by forming a square profile with mixed material of agricultural by-products besides plastic material and forming a spiral pipe of an H beam structure with supplying resin by opposite assistant extruders. Still, it has some problems that a method and an 10 apparatus are complicate because of forming a square profile using agricultural by-products, etc. , and that, although it is formed of an H beam structure, adhered portions are still weak. Further, it is unavoidable that strength is lowered because of using agricultural by-products.

15 Still furthermore, an apparatus of manufacturing a pipe using a plastic waste, which is registered in Korean Patent No. 255842 (registration date: February 16,2000, an application No. 1997-34994), is characterized by comprising an extruder member for extruding and transporting inputted waste plastic material by 20 means of a screw shaft, a heating room in which heat is circulated for melting the material with being installed outside of the extruder member, and a material storage means in which material outputted from the extruder member is contained temporarily with being installed at the exit side of the extruder member, thereby 5 supplying material outputted from the material storage means onto a winder, and moving upward and removing an air bubble generated in material or vacancy generated during transportation of plastic waste material in the transportation portion by storing and sedimenting the molten material in the material storage means 10 before extruding. Although the pipe may have a superior quality and the apparatus for regeneration without generating an environment pollution may be provided, it is still impossible to manufacture a superior pipe with polluted plastic waste having different physical properties, in particular waste plastic for 15 agriculture by using one melting and extruding means. Further, although an air bubble or vacancy can be moved upward and removed by storing and sedimenting the molten material in the material storage means, such effect cannot be obtained satisfactorily between a highest point and a lowest point of the stored material 20 because a stable flow of material for withdrawal cannot be ensured

in the material storage means without adding a certain constant pressure. And although the molten material is maintained in a temperature at which hardening is not generated in the material storage means, the stored material is difficult to flow to a transportation roller along an inclined plate at that temperature, and reoperation of the apparatus after the apparatus stops in the state where the substantial material is stored in the material storage means is very difficult and needs a lot of time because the stored material must be remolten in the material storiage means for reoperation.

Disclosure of Invention Accordingly, the present invention is made in order to solve the above problems in the prior art Hume pipes, and methods and apparatus for manufacturing the pipes using plastic waste, and one object of the present invention is to provide a plastic pipe of triple layers which comprises an intermediate waste layer of a helically overlapped multiple layer structure using common plastic waste such as waste plastic for agriculture, waste vinyl, etc. , an inner layer and an outer layer formed by extruding plastic material different from plastic waste onto the opposite surfaces of the intermediate waste layer lb, and thus, which can recycle resources and protect environment by using regenerated plastic, increase resisting pressure strength and airtightness properties between an inner surface and an outer surface even with a simple 5 structure, and that have graceful appearance and excellent quality by using new plastic material in the inner layer and the outer layer.

To accomplish the object of this invention, a plastic pipe of triple layers using plastic waste is provided in accordance 10 with one embodiment of the invention, which comprises an intermediate waste layer helically wound by crushing, melting and extruding at least plastic waste of thermoplastic material, said plastic pipe being characterized by further comprising an inner layer of one layer formed as an inmost wall layer by extruding 15 molten plastic material onto the surface of a rotating single mandrel or multiple rotating rollers in a tensioning apparatus just prior to forming the intermediate waste layer, and an outer layer of one layer formed as an outmost wall layer by extruding molten plastic material onto the outer surface of the intermediate 20 waste layer just after forming the intermediate waste layer, said

intermediate waste layer being adhered to the outer surface of the inner layer by extruding molten plastic waste onto the outer surface of the inner layer, said molten plastic waste being made by crushing, mixing and melting plastic waste of thermoplastic material in multiple stages, said intermediate waste layer being wound with a helically overlapped multiple layer structure by the tensioning apparatus, the multiple layers of the intermediate waste layer being completely adhered by heating the surface of each layer with a heated air while said multiple layers are helically wound and inclinedly overlapped each other.

Furthermore, the present invention is to provide a method of manufacturing a triple layer plastic pipe which comprises an inner layer of at least one layer helically wound and forming a pipe by melting and extruding thermoplastic material, an intermediate waste layer helically wound and adhered to the outer surface of the inner layer by crushing, melting and extruding thermoplastic material including at least thermoplastic waste just after the inner layer is wound, and an outer layer of one layer formed as an outmost wall layer by extruding and adhering molten plastic material onto the outer surface of the intermediate waste

layer, the method being characterized by comprising the steps of: selecting and cleaning collected plastic waste (PE, Nilon, PP, <BR> <BR> etc. ) and inputting the plastic waste to a first crushing and melting apparatus through a plastic waste input opening thereof; firstly crushing and melting the inputted plastic waste by transporting the inputted plastic waste forward by means of a forwarding screw means of a twin screw means, mixing molten plastic waste and unmolten plastic waste and further melting unmolten plastic waste by transporting the forwarded plastic waste rearward by means of a rearwarding screw means, and then melting the plastic waste by transporting the plastic waste forward by means of a forwarding screw means, concurrently with heating the inputted plastic waste at a temperature around 300 C, in the first crushing and melting apparatus ; inputting the crushed/mixed/molten plastic waste to a plastic waste input opening of a second crushing and melting apparatus and transporting the inputted plastic waste by means of a twin screw means, concurrently with secondly melting the inputted plastic waste by continuously heating the inputted plastic waste at a temperature around 250 C ; inputting the molten plastic waste to a plastic waste input

opening of a third melting apparatus from the second crushing and melting apparatus and thirdly melting the inputted plastic waste by heating the molten plastic waste for inputting the molten plastic waste to a input opening of a dispensing unit ; dispensing and extruding, onto the inner layer wound on the tensioning apparatus, the molten plastic waste inputted to the dispensing unit with the extruded quantity of the molten plastic waste controlled by means of a pair of extruding rollers; forming the intermediate waste layer of a helical structure by rotation of the tensioning apparatus and extruding the plastic waste onto the inner layer; forming an outer layer by extruding molten plastic material onto the outer surface of the intermediate waste layer of a helical pipe structure pushed out from the tensioning apparatus, thereby forming the triple layer plastic pipe; and, cooling the triple layer plastic pipe into a room temperature for maintaining the triple layer plastic pipe of a desired shape and cutting the cooled triple layer plastic pipe by a desired length.

Still furthermore, the present invention is to provide an apparatus for manufacturing a triple layer plastic pipe which comprises a tensioning apparatus for forming an extruded molten

plastic material or waste into a helical pipe by means of rotation of one or more rotating rollers and helically pushing the helical pipe on the rotating rollers outward, an inside surface layer extruder for melting and extruding a thermoplastic material so as to wind the thermoplastic material on the tensioning apparatus and form one layer of an inner layer, an intermediate waste layer extruder for crushing, melting and extruding at least a thermoplastic waste so as to wind and joining the extruded thermoplastic waste on the inner layer and form an intermediate waste layer, and an outside surface layer extruder for melting and extruding a thermoplastic material so as to wind the thermoplastic material on the wound and joined intermediate waste layer and form one layer of an outer layer: wherein the intermediate waste layer extruder comprises a first crushing and melting apparatus, a second melting apparatus and a third melting apparatus separated to each other; wherein each of the first crushing and melting apparatus, the second melting apparatus and the third melting apparatus comprises a material input opening into which collected plastic waste (PE, nylon, PP, etc. , ) or molten plastic waste is inputted, a twin screw means which crushes and mixes the inputted

plastic waste, a cylinder for enclosing the twin screw means, and multiple electric heaters and/or a boiler means of one or more heating burners for heating the cylinder, at least one of said twin screw means comprising forwarding screw means and a rearwarding screw means between the forwarding screw means so that melting is ensured by passing molten plastic waste of the forwarded plastic waste by the forwarding screw means between the cylinder and the rearwarding screw means, and rearwarding unmolten plastic waste by the rearwarding screw means so as to be mixed with forwarded and molten plastic waste.

Brief Description of Drawings Fig. 1 is a longitudinal section of a part of a plastic pipe of triple layers using plastic waste according to one embodiment of the present invention.

Fig. 2 is a constructional block diagram illustrating a process according to one embodiment of a method of manufacturing a plastic pipe of triple layers using plastic waste by an apparatus of the present invention.

Fig. 3 is a constructional diagram illustrating one embodiment of an apparatus of the present invention for

manufacturing a plastic pipe of triple layers using plastic waste according to one embodiment of the present invention.

Fig. 4 is a schematic constructional diagram illustrating a third melting apparatus configuring an intermediate waste layer extruder of Fig. 3 for forming an intermediate waste layer of a helically overlapped multiple layer structure.

Fig. 5 is a schematic constructional diagram illustrating one embodiment of an inside surface layer extruder or an outside surface layer extruder for supplying plastic material and forming an inner layer or an outer layer in Fig. 3.

Fig. 6 is a constructional diagram enlarged in part and illustrating a twin screw means for crushing, heating, mixing and transporting in a first crushing and melting apparatus of an inside surface layer extruder.

Fig. 7 is a front view illustrating an outer structure of a dispensing unit of Fig. 3.

Fig. 8 is a plane view illustrating an inner structure of the dispensing unit.

Best Mode for Carrying out the Invention Now, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Fig. 1 is a longitudinal section of a part of a plastic pipe 1 of triple layers using plastic waste according to one embodiment of the present invention with an enlarged detail, and 5 Fig. 2 is a constructional block diagram illustrating a process according to one embodiment of a method of manufacturing the plastic pipe 1 of triple layers using plastic waste by an apparatus of the present invention. In Figs. 3 to 8, one embodiment of an apparatus for manufacturing a plastic pipe of 10 triple layers using plastic waste is illustrated as a schmetic constructional diagram.

In Fig. 1, the plastic Hume pipe 1 of triple layers using plastic waste comprises an inner layer (inside surface layer) la, an intermediate waste layer lb and an outer layer (outside surface 15 layer) lc, wherein said intermediate waste layer lb is adhered to the outer surface of the inner layer la by extruding molten plastic waste onto the outer surface of the inner layer la, said molten plastic waste being made by crushing, mixing and melting plastic waste of thermoplastic material in multiple stages, said 20 intermediate waste layer lb being wound with a helically overlapped multiple layer structure by a tensioning apparatus 30, the multiple layers of the intermediate waste layer lb being perfectly adhered by heating the surface of each layer with a hot air while said multiple layers are helically wound and overlapped 5 each other.

The inner layer la is formed as an inmost wall layer by extruding molten plastic material onto the surface of a rotating single mandrel or multiple rotating rollers 31 in the tensioning apparatus 30 just prior to forming the intermediate waste layer 10 lb. And, the outer layer lc is formed as an outmost wall layer by extruding molten plastic material onto the outer surface of the intermediate waste layer 1b just after forming the intermediate waste layer lb.

The intermediate waste layer lb is formed of a multilayer 15 structure having three to six layers in overlapped section by being wound so as to be inclined as shown in Fig. 1, and in case of a thickness of 10cm, each layer has a thickness of approximately 1.7 cm to 3.3 cm by being extruded with a thickness of approximately 1.5 cm to 3.0 cm.

20 Such a plastic pipe 1 of triple layers using plastic waste

is constituted by the inner layer la, the intermediate waste layer lb and the outer layer lc, which are helically wound, the intermediate waste layer lb being thickly formed of a helically overlapped multilayer structure with plastic waste, and the inner layer la and the outer layer lc being thinly formed with new plastic material. Thus, the intermediate waste layer lb has higher strength, and the inner layer la and the outer layer lc has graceful appearance without any impurity, thereby being able to use the pipe for many purposes and promoting recycle of resources and reduction in material.

A structure of an apparatus for manufacturing such a plastic pipe 1 in accordance with one embodiment of the present invention is as follows.

In Fig. 3, a tensioning apparatus 30 is constructed so as to make molten plastic waste, which is extruded from the inside surface layer extruder 20a, be wound onto a rotating single mandrel or multiple rotating rollers 31 and form a helical pipe shape by rotation of the rotating single mandrel or multiple rotating rollers 31, and so as to push out the wound pipe on the the rotating single mandrel or multiple rotating rollers 31 with

cooling by means of cooling means.

The inside surface layer extruder 20a and an outside surface layer extruder 20 are schematically shown, for example, in Fig. 5 for melting and extruding a plastic material for forming a helically wound pipe according to the prior art, each of which comprises an input opening 22 configured so as to input plastic <BR> <BR> material (PE, nylon, PP, etc. ), a first melting apparatus (24) for heating the inputted plastic material and maintaining a temperature around 300 C so that the plastic material can be extruded, a second melting apparatus 26 for transporting the molten plastic material to the tensioning apparatus 30 with heating the molten plastic material so as to maintain a temperature around 250 C, and an extruding die or a guide attached to the end of the second melting apparatus 26. More detailed explanation about such an inside or outside surface layer extruder 20a or 20 is omitted.

An intermediate waste layer extruder 10, as shown in Fig.

3, comprises a first crushing and melting apparatus 10c, a second melting apparatus 10b, a third melting apparatus 10a and a dispensing unit 18, said first crushing and melting apparatus 10c

comprising an input opening 12c for inputting selected and cleaned plastic waste after selecting and cleaning collected plastic <BR> <BR> waste (PE, nylon, PP, etc. ), as shown in detail in Fig. 6. Also, the first crushing and melting apparatus 10c further comprises a twin screw means 14c rotating in a cylinder 14'and a boiler means (a heating burner part) 14d for heating and mixing the inputted plastic waste for 3 to 7 minutes at a temperature around 3001 :.

The twin screw means 14c, as shown in Fig. 6, comprises forwarding screw means 15a and 15c and a rearwarding screw means 15b between the forwarding screw means 15a and 15c so that complete melting can be ensured by passing molten plastic waste of the forwarded plastic waste by the forwarding screw means 15c between the cylinder 14'and the rearwarding screw means 15b, and by rearwarding unmolten plastic waste by the rearwarding screw means 15b so as to be mixed with forwarded and molten plastic waste. Said forwarding screw means 15c constructs most of the twin screw means 14c, and the rearwarding screw means 15b may comprise two or three reverse-directional screws in the intermediate of the forwarding screw means 15c. Such a forwarding screw means 15c and such a rearwarding screw means 15b may be constructed variously in

a concrete structure. One example may be a separated screw structure to be installed on one axis.

Also, the second melting apparatus lOb, as shown in Fig. 6, comprises an input opening 12b for inputting heated and mixed plastic waste to be transported from the first crushing and melting apparatus 10c, and a twin screw means 14b and a boiler means (a heating burner part) 14d for further heating, crushing and mixing the inputted plastic waste once more at a temperature around 300 C. Also, the twin screw means 14b may be constructed similarly to the twin screw means 14c of the first crushing and melting apparatus 10c.

The third melting apparatus 10a, as shown in Fig. 4, is constructed so as to transport the plastic waste transported from the second crushing and melting apparatus 10b to the dispensing unit 18 with maintaining a temperature around 250 C. In the third melting step in the third melting apparatus 10a, almost all plastic waste are crushed and molten and so it is not necessary to crush and melt the plastic waste any more. However, the plastic waste is more uniformly mixed and, even if any clod remains, it can be completely crushed by a twin screw means 14a employed in

the third melting apparatus 10a as shown in Fig. 4.

The dispensing unit 18 comprises an input opening 17 for inputting the molten plastic waste to be supplied from the third melting apparatus 10a through an input pipe 16a, and for a continuous production, it is preferable to be constructed so as to extrude the molten plastic waste of a constant thickness and width to the tensioning apparatus 30 with controlling the supply amount as shown in Figs. 7 and 8. That is, the dispensing unit 18 may comprise a control handle means 19a for controlling a gap between a pair of extruding rollers 19 and the thickness of the plastic waste, as shown in Figs. 7 and 8. And, a guide means to be in contact with the extruding rollers 19 may be installed whose width can be controlled so as to controll the extruding width, or a controller of a motor means for controlling a rotation speed of the extruding rollers 19 may be included.

Further, a hot-air nozzle 35 is preferably included for applying hot air to the plastic waste just before the plastic waste extruded from the third melting apparatus 10a is wound onto <BR> <BR> the inner layer la so as to vent moisture, etc. , from the surface of the extruded plastic waste and melt the surface for joining together.

Besides, the apparatus for manufacturing the plastic pipe 1 of triple layers using plastic waste preferably comprises a cooling means for a plastic pipe 1 wound and pushed out on the 5 tensioning apparatus 30, a pressure roller means for leveling the outer surface of the plastic pipe 1 after being wound, a severing means for cutting by a predetermined length, etc. , according to the conventional technology.

A method of manufacturing the plastic pipe 1 of triple 10 layers using plastic waste by using the manufacturing apparatus of such a construction, is explained bringing a method of manufacturing the intermediate waste layer 1b into focus and referring to Fig. 2. And the inner layer la and the outer layer lc are formed according to the conventional method in main and their 15 concrete explanation is omitted. That is, the plastic material is extruded and helically wound on the tensioning apparatus 30. At this time, the wound plastic material may be adhered by filler material (which can be supplied from a assistant melting apparatus) or by overlap according to the well-known technology.

20 First, the method of manufacturing the plastic pipe 1 of

triple layers using plastic waste comprises a selecting/inputting step, a first crushing/melting step, a second melting step and a third melting step, though which steps the plastic waste becomes in the state to be able to be extruded in the melted state.

In Figs. 2 and 3, an inner layer extruding step according to the conventional technology is performed prior to extruding the plastic waste, and the inner layer la is in the state to be first wound on the rotating mandrel or rotating rollers 31. At this time, as shown in Fig. 3, the inner layer la of a helical pipe shape is formed by extruding and winding the molten plastic with a constant thickness and width on the exterior surface of the rotating rollers 31 of the tensioning apparatus 30 by means of the inside surface layer extruder 20a and by pushing out the extruded and wound plastic.

While the outer surface of the inner layer la is not solidified after the inner layer la is formed by doing as stated above, the intermediate waste layer 1b is wound with a multilayer helical overlapped structure by extruding molten plastic waste on the surface of the inner layer la right after the inner layer la is wound with a helical structure as possible, as stated above.

For the intermediate waste layer 1b to be wound as above, first in the selecting/inputting step, collected plastic waste (PE, nylon, PP, etc. ) is selected and cleaned, and then inputted to the first crushing and melting apparatus 10c through the plastic waste input opening 12c thereof, as shown in Figs 2 to 6. Then, the first crushing/melting step (step S02) is performed.

In the first crushing/melting step (step S02), the plastic waste inputted to the first crushing and melting apparatus 10c is crushed and transported forward by means of the forwarding screw means 15a of the twin screw means 14c (step S21), with being heated at a temperature around 300 C and mixed for 3 to 7 minutes by the boiler means (a heating burner means) 14d. The boiler means 14d uses gas, oil or plastic waste as a heat source.

When such forwarded plastic waste reaches the rearwarding screw means 15b, crushed, but unmolten, plastic waste clods cannot pass through a gap between the cylinder 14'and the screw means, but is transported rearward by means of the rearwarding screw means 15b, thereby being mixed with molten and forwarding plastic waste and then promoting melting of unmolten plastic waste (step S22). Then, molten plastic waste and very small plastic waste

clods pass through the rearwarding screw means 15b by forwarding pressure of the forwarding screw means 15c and are continuously transported forward by the forwarding screw means 15c, thereby being inputting to the input opening 12b of the second melting apparatus 10b after being more crushed, mixed and molten (step <BR> <BR> S23). At this time, several gases, moisture, etc. , can be vaporized into the air (step S24).

Thus, the heated/mixed plastic waste is inputted to the second melting apparatus 10b, and in the second melting step (step S02), the heated/mixed plastic waste is further crushed and mixed by means of a twin screw means 14b, and at the same time, secondly melted by being continuously heated so as to maintain a temperature around 300°C. At this time, various gases, moisture, etc. , can be vaporized into the air (step S34). Such second melting step (step S03) comprises three steps of crushing and melting (steps S31, S32 and S33), as stated in the above first crushing/melting step (step S02), by means of the twin screw means 14b comprising the rearwarding screw means 15b.

Then, in the third melting step, the molten plastic waste inputted to the plastic waste input opening 12a of the third

melting apparatus 10a is thirdly heated so as to maintain a temperature around 250 C, and the heated molten plastic waste is further mixed and has a more density and composition by means of the twin screw means 14a. Then, the molten plastic waste being inputted to the input opening 17 of the dispensing unit 18. At this time, as in the above first crushing/melting step (step S02), the twin screw means 14a comprises the rearwarding screw means 15b, therby producing further uniform mixing and melting.

In the first crushing/mixing/melting step (step S02) and the second melting step (step S03), a temperature in the outside of a cylinder or a screw case of the twin screw means 14b and 14c is maintained around 400 C. And, a temperature in the outside of a cylinder or a screw case is maintained around 300 C in the third melting step.

In the dispensing and extruding step of the plastic waste, the molten plastic waste inputted to the dispensing unit 18 is extruded onto the tensioning apparatus 30, with the extruded quantity of the molten plastic waste controlled by means of a pair of extruding rollers 19. At this time, since the inner layer la is already wound on the tensioning apparatus 30 (step S10), then the

molten plastic waste is extruded onto the outer surface of the inner layer la wound on a tensioning apparatus 30.

In order to form the intermediate waste layer 1b of a helically wound and overlapped multilayer structure shown in Fig.

1 by winding and joining the plastic waste extruded on the inner layer la, hot air is applied to opposite surfaces of the extruded plastic waste by means of a hot-air nozzle 35 after being extruded from the third melting apparatus 10a and just before being wound <BR> <BR> in step S07, thereby vaporizing moisture, etc. , from the surface of the extruded plastic waste, and further melting the surfaces of each overlapped multilayer of the intermediate waste layer 1b <BR> <BR> together. Thus, the gases, moisture, etc. , are completely removed, and the surface of the extruded plastic waste is further melted, thereby completely adhering each layer of the intermediate waste layer 1b and the inner layer la.

Then, in order to form an outer layer lc, molten plastic material is extruded onto the outer surface of the intermediate waste layer lb of a helical pipe structure and wound by the tensioning apparatus 30 (step S12).

In addition, a width and a pitch of the plastic extruded

from the inside surface layer extruder 20a and the outside surface layer extruder 20 are preferably controlled proper to a pitch of each layer of the intermediate waste layer 1b because the intermediate waste layer 1b is formed of a helically wound and overlapped multilayer structure.

Thus, on the tensioning apparatus 30, the inner layer la formed of new plastic material, the intermediate waste layer lb formed of plastic waste and the outer layer lc of new plastic material are helically wound by rotation of the tensioning apparatus 30 and pushed out of the tensioning apparatus 30, thereby forming the triple layer plastic pipe 1 with being cooled.

Then, the triple layer plastic pipe 1 having the intermediate waste layer 1b of a helically wound and overlapped multilayer structure is completely cooled to a room temperature (step S08) and maintained the triple layer plastic pipe of a desired shape. Sequently, the cooled triple layer plastic pipe 1 is cut by a desired length (step S09) for a desired product.

The plastic pipe 1 of triple layers using plastic waste manufactured by the method and the apparatus described above, has wondrous strength against outer pressure and abrasion-resistance

due to the intermediate waste layer lb of a helically wound and overlapped multilayer structure together with graceful appearance and excellent air-tightness as compared with other products using plastic waste, thereby being proper as a substitute product for a concrete Hume pipe, etc. That is, it is very cheap as compared with the existing pipes such as a water pipe, a waste pipe, a <BR> <BR> sewer pipe, etc. , is very economical in a transport expense, a construction expense, a maintenance expense. Also, it is possible to recycle resources and protect environment.

Although the present invention has been described in detail with respect to the plastic pipe 1 of triple layers comprising the intermediate waste layer lb manufactured using plastic waste only, and its manufacturing method and apparatus, the intermediate waste layer lb may contain 20 to 30wt. x of new plastic material or regenerated plastic material besides the plastic waste without lowering its strength substantially.

According to the configuration and acting of the plastic pipe of triple layers using plastic waste, and its manufacturing method and apparatus in accordance with the embodiments of the present invention described above, the plastic pipe of triple

layers having superior quality, particularly in pressure strength resistance can be inexpensively manufactured due to the intermediate waste layer lb of a helically wound and overlapped multilayer structure, and that it is possible to recycle resources and protect environment by using plastic waste with advantages of graceful appearance, complete air-tightness properties between an inner surface and an outer surface, etc.