The invention relates to a method of manufacturing a pipe from thermoplastic material, in particular a single or multi-wall pipe produced by helical winding designed especially for applications in wastewater pipeline systems and tor transporting fluids, including water, and a thermoplastic strip for manufacturing such pipe.

For example, the European patent description EP 0816050 discloses a method and a device for producing plastic pipes used in wastewater and stormwater systems. According to said method, a flat strip is extruded from thermoplastic material and directly after extruding, while being in a molten state, said strip is spirally wound on rotating rollers of the device until a base pipe is formed, and after that reinforcing ribs are put on and attached to the external surface of the pipe, wherein said ribs contain a layer made from the same material as die base pipe and the internal filling from recycled plastics.

Another example of a method for producing a spirally wound pipe from a hollow thermoplastic profile with a rectangular cross section is disclosed in the Polish patent description PL 194867 Bl. According to said method, the thermoplastic profile is wound onto a drum, the adjacent coils are bonded together by means of extrusion welding, the external seam is then smoothed by means of special heating and a smoothing unit leaning against the seam, after that the pipe is fed axially towards freely rotating elements, radial pressing rollers working on the thermoplastic profile during the first winding on the drum. While the thermoplastic profile is being led onto the drum, it passes through a first stationary section comprising spaced sliding elements located along the circumference thereof, where extrusion welding is carried out and after which the shaped internal seam is positioned in such a way that it runs along the spiral furrow around the first stationary section, where the internal seam and the external seam are machined with the use of special heating and a stationary smoothing unit leaning against said seams, and that said pipe with simultaneously smoothened extrusion welded surfaces is led to the section of a rotary drive drum which turns the pipe and induces the winding movement of the thermoplastic profile.

Furthermore, a method of manufacturing spirally wound plastic pipes is known from the Polish patent description application P-377750. Said method consists in forming a strip-shaped profile with a rectangular cross section which has a recess on one side in the shape of a semi-circle and/or an open polygon along the horizontal edges, and on the other side said profile has a spline in the shape corresponding with the formed recess. Moreover, inside the profile there are formed parallel channels of arbitrary shape, thus leading to the hollowing thereof. The hollowed profile is wound onto a rotary sleeve, thus a spiral tube is shaped, and the adjacent horizontal spirally wound edges are connected by means of a catch fastener formed on the borders of the profile. The manufactured plastic pipe is continuously axially shifted by the wound profile. Additionally, the catch fastener, in the place of the recess is preferably filled with the molten material of the profile. The manufactured pipes are used in construction of water and wastewater pipeline systems.

In the above descriptions of methods a term 'spiral winding' was used, which can be understood as winding along a helical path as shown in the presented embodiments and attached drawings. For the needs of the present invention the term helical winding shall be used, which should be understood accordmg to the common meaning of the term, which means winding along a helical path, along the formed cylinder or conic line. Tt also encompasses the meaning used in the state of the art described above.

The invention relates to a method of manufacturing a pipe from thermoplastic material, which method consists in helical winding of an element from thermoplastic material onto a drum with the use of rotary rollers and bonding together adjacent coils. The essence of the invention is that the pipe is manufactured from a pre-manufactured strip from thermoplastic material, wherein before winding said strip onto the drum, said strip is shaped into a U or L profile in cross section, and after that the so shaped profile is wound onto the drum with simultaneous bonding of the adjacent coils in such a way that a wall or walls of the L or U profile create an external, helical reinforcement ri b of the pipe.

The pre-manufactured strip from thermoplastic material means a strip manufactured from known material by known methods, for example by extrusion, fully formed. Said strip may also contain a reinforcing element or elements from another material. Said reinforcing element or elements may be located inside the strip or attached to the surface thereof. Furthermore, said reinforcing clement or elements may be located in the whole width of the strip or, alternatively, only in a part of the width thereof, for example, in the part corresponding with the base of the U or L profile.

Tn a preferred embodiment the segments of the strip making up the rib are partially or whol ly corrugated in such a way that before forming of the U or L profile there is a longitudinal flat segment and one or two longitudinal corrugated segments located along one or both longitudinal edges of the strip, wherein before winding said strip onto a drum, the strip is formed into the U or L profile in cross section, along the separation line between a flat segment and a corrugated segment or segments.

It is also envisaged that the strip is formed into the L or U profile along the separation line in the form of a notch, preferably in the form of a groove.

Tt is an option that an additional profile with closed section, preferably circular, is attached to the upper edge of the rib of the pipe manufactured in such a way.

Tt is also an option that an additional pre-manufactured thermoplastic strip is wound around a pipe manufactured in such a way and attached to the upper edges of side walls of the adjacent coils of the rib in such way that said strip covers the space between the adjacent coils of the pipe rib. it is also recommendable that the adjacent coils made from the IJ profile are bonded both in the upper and in the lower part of the side walls of the U profile.

It is also intended that the manufacturing of pipes beginning with the forming of the strip into a U or L profile is carried out as a continuous process.

Another benefit is achieved when a fiat strip is created by cutting a prefabricated thermoplastic sheet. It relates to a strip for forming the U or L profiles and a strip used as an external shell of the pipe.

Jt is also an option that a pipe is manufactured with the use of a mobile device, preferably in the area of construction of wastewater or water pipeline systems.

A strip for manufacturing a pipe from thermoplastic material designed to be helically wound onto a drum and bonding the adjacent coils in order to form the pipe is characterised by that it comprises a longitudinal flat segment and one or two longitudinal partially or, preferably, wholly corrugated segments located along one or both longitudinal edges of said strip, designed to form a helical rib of the pipe. The term 'partially corrugated' means that only a part of the segment surface in question is corrugated, whereas the term 'wholly cormgated' means that the whole surface of the segment in question is corrugated.

It is advisable that between the flat segment and the corrugated segment Of segments there is a separation line in. the form of a notch, preferably a groove, which facilitates the forming of the strip into a U or l profile.

The corrugated segment or segments may be wave-like, wherein the surfaces of the strip are alternately convex and concave or concertina-like, wherein the surfaces of the strip are planes inclined to each other and to the flat segment of the strip.

A method according to the invention allows to manufacture light weight large diameter pipes with high stiffness with the use of a mobile device, providing the possibility to manufacture said pipes in the area of construction site of a pipeline. The presented method is very simple and effective, consumes low amounts of energy and the application thereof does not require sophisticated devices. Large diameter pipes due to their volume are difficult to transport or store, therefore the possibility to manufacture them from pre-manufactured strips at any chosen location with the use of a mobile device is an important aspect. Such strips occupy little space and the transport thereof does not cause any problems. The manufacturing method requires low amounts of energy, thus the process may be run from a local electrical network or even a mobile generator. Moreover, said method al lows to manufacture pipes in many options, according to clients' specific requirements, for short production series and special applications such as silos or tanks. The manufacturing stresses are virtually limited to the weld regions, thus the pipes maintain their shape after cutting and further joining and assembly of the pipes is uncomplicated.

Furthermore, the volume of used materials was reduced due to the optimized structure, the amount of material waste from starting and stopping production is minimal. By using composite materials and reinforcing elements for the strips it is very simple to change the strength parameters. What is more, it is possible to obtain a dual wall, closed structure of a pipe wall by attaching an additional thermoplastic strip to the external edges of the ribs, wherein said strip covers the space between the adjacent coils of the pipe rib, which contributes to increase the pipe stiffness. The stiffness can also be enhanced by attaching an additional profile with closed cross section to the upper, free edge of the rib. In a most preferred embodiment the reinforcing ribs are made up of corrugated, longitudinal segments of the strip, owing to which, after forming them into a pipe, they arc stretched and are free of stresses, and a pipe formed in such a way has good strength parameters and is durable. The strip according to the invention allows to manufacture a pipe with helical ribs, free from stresses.

The invention is presented in greater detail in the following embodiments and in the attached drawing, where fig. 1 is a schematic perspective view of the manufactured pipe in the first embodiment, fig. 2 is a schematic cross section of a pre-manufactured flat strip used in the production of the pipe in fig. 1 , fig, 3 is a schematic longitudinal section of a fragment of the pipe after bonding the adjacent coils of the U pro file in the area of the base of the profile, fig. 4 - a schematic longitudinal section of a fragment of the pipe after bonding the adjacent coils of the U profile both in the area of the base of the profile and in the area of the upper edges of the side walls of the profile, fig. 5— a schematic cross section of the L profile formed from the strip as in fig. 2, fig. 6 - a schematic longitudinal section of a fragment of the pipe after bonding the adjacent coils of the L profile, fig.7 - a schematic longitudinal section o f a fragment of the pipe after bonding the adjacent coils of the U profile and attaching an additional strip to the upper edges of the side walls, fig. 8 - a schematic perspective view of the process line for manufacturing pipes, fig, 9 - a schematic perspective view of the device for realisation of the method of manufacturing a pipe with highlighted working elements of the used device, fig. 10 shows a cross section of a thermoplastic strip in another embodiment, fig. 10a and 10b - a schematic A- A section of fig. 10 in two possible embodiments, fig. 1 1 - a schematic elevated view of the strip shown in fig. 10, fig. 12 ~ a schematic cross section of the strip shown in fig. 10 and 1 1 after forming into an L profile, fig. 13 - a schematic partial longitudinal section of the pipe formed from the L profi le shown in fig. 1 2, fig. 14 - a schematic partial longitudinal section of the pipe formed from the L profile shown in fig. 12 with an additional closed profile attached to the upper edge of the rib, fig. 15 - a schematic cross section of the thermoplastic strip in yet another embodiment, fig. 16 - a schematic elevated view of the strip shown in fig. 1 5, fig. 17 - a schematic cross section of the strip shown in fig. 1 5 and 16 after forming into the U profile, fig. 1 8 - a schematic partial longitudinal section of the pipe formed from the U profile shown in fig, 17, fig. 1 9 - a schematic partial longitudinal section of the pipe formed from the U profile shown in fig. 17 with an additional closed profile attached to the upper edge of the rib. The method of manufacturing a pipe from thermoplastic material consists in manufacturing the pipe from a pre-manufactured strip from thermoplastic material. The concept of the thermoplastic strip was explained in the description of the essence of the invention above, wherein it is possible to pre-manufacture a strip as such or, alternatively, to cut a pre-manufactured thermoplastic sheet into strips of required width. As was said before, the strips may contain reinforcing elements and be manufactured from various thermoplastic materials depending on the needs. A helically wound light weight pipe is manufactured with the use of rotary rollers making up a drum onto which a pre-manufactured strip, formed before winding into a U or L profile, is helically wound, and adjacent coils are bonded by known methods, for example by extrusion welding which means forcing in the material extruded from an extruder or other known methods of welding of thermoplastic materials. It is also possible to use glue for bonding. The walls of the U or L profile make up an external helical rib on the surface of the manufactured pipe and said rib ensures the circumferential stiffness of the pipe. Furthermore, a dual-wall, closed structure of the pipe wall may be obtained by attaching an additional thermoplastic strip to the external edges of the ribs in such a way that said strip covers the space between the adjacent coils of the pipe rib. The profile should preferably be wound onto the rollers of the drum with the lower base thereof. The adjacent coils made from the U profile may be bonded only in the lower part of side walls as well as in the lower and upper parts of the side wall of the U profile. Hie manufacturing of the pipe beginning with forming a strip into a U or L profile may be carried out in a continuous process with the use of a mobile device, preferably in the area of construction of a pipeline, for example wastewater or water pipeline systems.

Referring in detail to the attached drawing, a pipe 1 is manufactured from a pre-manufactured flat strip 2 ( fig. 2 ), which strip 2 is formed into a U-shaped profile 3 and helically wound by the base thereof on rollers 4 making up a drum 5 ( fig. 1 , fig. 8, fig. 9 ). The adjacent coils of the profile 3 are bonded together by the above mentioned methods in the area of the base ( tig. 3 ). Alternatively, it is possible to make an additional bonding of the adjacent coils of the profile 3 in the area of the upper edges of the side walls of the profile 3 ( fig. 4 ). The side walls of the profile 3 make up a rib 6 which is an integral part of the pipe 1 .

In a preferred embodiment an additional pre-manufacturcd thermoplastic strip 7 may be attached to the pipe 1 described above (fig. 1, fig. 9 ). The strip 7 constituting the external layer of the pipe 1 is attached by methods described above to the upper edges of the side walls of the profile 3 ( fig. 7 ).

It is also possible to manufacture the pipe 1 by forming the strip 2 into an T, -shaped profile 8 ( fig. 5, fig. 6 ). Such structure of the base pipe allows for alternative attachment of an additional strip constituting the external layer of the pipe and covering the space between the ribs created by one arm of the profile 8. Such external strip is attached to the upper edges of the adjacent coils of the rib created by an arm of the profile 8. Fig. 8 shows a schematic perspective view of the process line for manufacturing pipes by the method according to the invention. The pre-manufacturcd strip 2 is led from a reel 9 and through a feeder 10 it is fed into a shaping unit 1 1 , where the strip 2 is shaped into a U profile 3 or an L profile 8. The forming into the U or L profiles, depending on the designed structure of the pipe, is done by conventional methods, for example by, separate or combined, bending, cutting, incision, heating and/or welding. The strips may be of uniform or composite structure. Then, a formed U or L profile is wound onto a reel 5 made up of power driven rollers 4 (fig. 8, fig. 9 ). The helical winding is performed by means of self-propelled rotary pressing roller gages 12 and shaping rollers 13. The strip is wound helically in a similar way as in the process of the "Drostholm" system for manufacturing fibreglass pipes in a continuous process. The difference is that there is a gap between the profiles which allows for making a weld for bonding the adjacent coils of the profile together. After winding the adjacent coils they are internally bonded together with help of a pressing elements by a suitable method, for example extrusion welding with the material from an extruder. Moreover, in the case of the U profile it is possible to bond the external edges of the adjacent side walls making up the rib 6 when it is required for the stability of the rib.

The so manufactured open profile pipe 1, the so called base pipe may be used in the construction of pipelines where lower circumferential stiffness is permitted or it is required by other aspects of the design. In order to increase the circumferential stiffness and/or ensure higher strength and safety, an additional external layer may be attached to the base pipe in the same continuous process. To do this, an additional strip 7 of suitable width is provided from a reel 9a by means of a feeder 1 0a. The speed of the feeder 10a is regulated to adjust it to the otational speed of the external surface of the rib 6 of the base pipe. The additional strip 7 is attached to the helical surface of the rib 6 on at least one of the edges or on two edges. Additional tightening and reinforcement is passible by additional welding. External scams may also be made with internal seams with the use of special welding heads or a set of welding heads from the same extruder. The so manufactured helically wound pipe I is then cut while passing through a cutting device 14. The ready pipe is cut in radial direction across the centre axis to required length. The cut lengths of the pipe are then transported to a storage location 1 5 or. loaded on wagons and taken away to a client.

The internal and/or external surface of the pipe I in the area of seams may be smoothened by methods known from the state of the art.

Fig. 9 shows in detail the method of winding the profile 3 on a winder which is a drum 5 comprising power driven rollers 4. The profile 3 is led on the drum 5 and helically wound until a base pipe is created. By means of the rollers or shaping elements 13 the rib 6 is placed in the suitable position for bonding the adjacent coils of the profile 3. Furthermore, the pressing rollers 12 support the profile 3 during winding and provide the necessary friction between the profile and the rollers 4 of the drum 5. Bonding of the external strip 7 Ixom the inside is carried out after said strip 7 has passed through the feeder 10a by providing the molten rruiterial to the space between the sheets of the rib 6 in order to stabilize the original form with the use of supports and pressing elements 16. An additional external weld 17 may be added from the external side in order to ensure proper bonding.

In another embodiment the pipe is manufactured from a pre- manufactured strip 21 made from thermoplastic material, for example by extrusion. The strip 21 ( fig. 10, fig. 1 1 ) comprises a longitudinal flat segment 22 and a longitudinal corrugated segment 23 located along the edge of the strip 21. The corrugated segment 23 may be wave-like as shown in fig. 10a or have a concertina-like shape as shown in fig. 10b. The segment 23 may be partially corrugated or, preferably, wholly corrugated along the length and width thereof. Prior to winding said strip 21 onto a drum, for example made up of rotary rollers, analogically as shown in fig. 8 and fig. 9, the strip 21 is shaped to an L profile in cross section along a separation line 24 between the flat segment 22 and the corrugated segment 23. The separation line 24 in a preferred embodiment may have the form of a notch, for example a groove 24a which facilitates the forming of the strip 21 into the profile L ( fig. 12 ). Such a separation line may also be present in the strips presented in the previous embodiments, in particular in fig. 2 to fig. 6. After forming the strip 21 into the L profile along the groove 24a, said profile is wound onto a drum and at the same time the adjacent coils are bonded in such a way that the wall of the L profile made from the corrugated segment 23 creates an external helical reinforcement rib 25 of the pipe 26 ( fig. 13 ), which rib 25 is an integral part of the pipe 26.

In another embodiment ( fig. 14 ) an additional closed cross section, preferably circular profile 27 is attached to the upper edge of the rib 25. The profile may be solid or ring-like, hollow inside. Such a profile may also be added to the profiles presented in the previous embodiments, in particular in fig. 2 to fig. 6.

In another possible embodiment, not shown in the drawing, an additional strip covering the space between the subsequent coils of the helical rib is attached to the upper edge of the adjacent coils of the rib of the pipe shown in fig. 13, identically as shown in the previous examples, in particular in fig. 7.

In another embodiment of the method of manufacturing a pipe from thermoplastic material the pipe is manufactured from a pre- manufactured thermoplastic strip 21 ', for example by extrusion. The strip 21 ' ( fig. 1 5, fig. 16 ) comprises a longitudinal flat segment 22' and two longitudinal corrugated segments 23 ' located along the two edges of the strip 2Γ. The corrugated segments 23' may be wave-like or concertina-like. The segments 23 ' may be partially corrugated or, preferably, whol ly corrugated along the length and width thereof. Before winding of said strip 21 ' onto a drum, for example made up of rotary rollers, analogically as shown in fig. 8 and fig. 9, the strip 21 ' is formed into a IJ profile in cross section, along a separation line 24' between the flat segment 22' and the corrugated segments 23 '. The separation line 24' in a preferred embodiment may have the form of a notch, for example a groove 24'a which facil itates the forming of the strip 21 ' into the shape of the U profile ( fig. 1 7 ). After forming the strip 21 ' into the U profile it is subsequently wound onto a drum along the groove 24'a and at the same time the adjacent coils are bonded in such a way that the walls of the U profile made from the corrugated segments 23' create an external helical reinforcement rib 25' of the pipe 26' ( fig. 18 ), which rib 25' is an integral part of the pipe 26'.

In another embodiment ( fig. 19 ) an additional closed cross section, preferably circular profile 27' is attached to the upper edge of the rib 25'. The profile may be solid or ring-like, hollow inside.

In another possible embodiment, not shown in the drawing, an additional strip covering the space between the subsequent sheets of the helical rib is attached to the upper edge of the adjacent coils of the rib of the pipe shown in fig. 18, identically as shown in the previous embodiments, in particular in fig. 7.

With reference to the above described embodiments, the strip for manufacturing the pipe according to the invention may comprise reinforcement and be manufactured from various thermoplastic materials, depending on the need. A helically wound light weight pipe is manufactured with the use of rotary rollers making up a drum, onto which a prc-manufaetured strip, shaped into an L or U profile prior to winding, is helically wound and the adjacent coils are bonded together by conventional methods, for example by extrusion welding or other known methods of welding thermoplastic materials. Bonding by glue is also possible. The walls of the L or U profile create a helical external rib on the surface of the manufactured pipe, wherein said rib ensures the circumferential stiffness of the pipe and is virtually free from stress. Moreover, a dual, closed structure of the pipe wall can be obtained by means of attaching an additional thermoplastic strip to the external edges of the ribs in such a way that said strip covers the space between the adjacent coils of the pipe rib. The additional strip making up the external layer of the pipe is attached by methods described above to the upper edges of the adjacent coils of the rib. The adjacent coils made from the U profile may be connected only in the lower part of the side walls as well as in the lower and upper part of the side walls of the U profile. The manufacturing of the pipe beginning with forming of the strip to the L or U profile may be carried out as a continuous process with the use of a mobile device, preferably in the area of assembly of the pipeline, for example wastewater or water pipeline systems.

The method shown in fig. 10 to fig. 19 may be realised with the use of process lines presented in detail in fig. 8 and fig. 9.

With reference to all of the above embodiments, the pre- manufacturcd strip may be formed into the L or U profile, depending on the designed structure of the pipe, along the notch as was described above or by other known methods, for example by, separate or combined, bending, cutting, incision, heating and/or welding.

With reference to the embodiments presented above in fig. 10 to fig.19 a separation line between a flat segment and corrugated segments may be without a notch. With reference to all of the above embodiments, it is possible to provide the coils of the rib with a metal sheet plate, for example in the form of a U-shaped profile or a profile folded on the coils of the rib, wherein said plate is put on the coils of the rib or folded thereon and overlaps with the rib partially or wholly. Such a plate protects the rib against damage and/or destruction. The plate may be attached to the rib with the use of mechanical fasteners, for example screws, rivets, clamps or by various types of glue, polymers or other fasteners and means.