Pipe made from a PVC-o material and methods of producing a PVC-o pipe

Abstract

A pipe made of a PVC-O material, with the pipe defining a longitudinal axis. The pipe has a first axially extending circumferential section having a first thickness, and a second axially extending circumferential section having a second thickness. The second thickness is greater than the first thickness. A method of producing a PVC-O pipe comprises forming a tubular preform from a PVC material, the tubular preform having a first circumferential section and a second circumferential section; and forcing the tubular preform over a mandrel to expand the tubular preform and form a PVC-O pipe with biaxially oriented PVC. The first circumferential section of the tubular preform forms a first axially extending circumferential section of the pipe having a first thickness, and the second circumferential section of the tubular preform forms a second axially extending circumferential section having a second thickness. The second thickness is greater than the first thickness.

Description

[0001] Pipe Made from a PVC-0 Material and Methods of Producing a PVC-0 Pipe

[0002] Technical Field

[0003] The present disclosure relates to a pipe from a PVC-0 material and methods of producing a PVC-0 pipe.

[0004] Background

[0005] In irrigation systems, for example for use in agriculture or forestry, a network of plastic pipes, for example made from PVC, is used to transport water under pressure from the water source to the irrigable area. Generally, irrigation systems often include supply pipes for transporting the water to the irrigable area, and pressure pipes which connect to the supply pipes to distribute the water over the irrigable area. The pressure pipes can connect to the supply pipes with a connector through the wall of the supply pipe.

[0006] For large irrigation systems, the length of the pipes can run for many kilometres, requiring large amounts of plastic to produce. This can make the pipes difficult to transport and install as well as environmentally unfriendly and expensive to produce.

[0007] There is hence a need in the art for pipes which have a reduced amount of plastic whilst maintaining the required functionality and strength to supply water in the irrigation system.

[0008] Summary

[0009] In a first aspect of the present disclosure, there is provided a pipe made of a PVC-0 material, the pipe defining a longitudinal axis. The pipe has a first axially extending circumferential section having a first thickness. The pipe further has a second axially extending circumferential section having a second thickness. The second thickness is greater than the first thickness. The first axially extending circumferential section and the second axially extending circumferential section form part of the same circumference of the Pipe. In some embodiments, this may result in result in a pipe having a reduced amount of plastic whilst maintaining the required functionality and strength to supply water in an irrigation system.

[0010] Throughout this disclosure, the term “PCV-0 material” refers to a PVC material in which the PVC molecules have been biaxially oriented.

[0011] A central angle defining the first axially extending circumferential section may be greater than a central angle defining the second axially extending circumferential section.

[0012] In some embodiments, this may reduce the amount of PVC material used in the pipe.

[0013] Throughout this disclosure, the term “central angle” is used to refer to the angle at the centre of the pipe, i.e., at the longitudinal axis, between two radii enclosing a circumferential section of the pipe.

[0014] The central angle defining the second axially extending circumferential section may be in the range of 60 to 120 degrees.

[0015] In some embodiments, this may allow for secure connection of a pressure pipe to the pipe.

[0016] The second axially extending circumferential section may have a visual indicator positioned on the outside surface of the pipe to identify the position of the second axially extending circumferential section.

[0017] In some embodiments, this may allow an operator to easily identify the second axially extending circumferential section and more easily connect a pressure pipe to the pipe.

[0018] The visual indicator may comprise a marking or a different colour.

[0019] The ratio of the second thickness to the first thickness may be in the range of 1 .2 to 1.6.

[0020] In some embodiments, this may allow for secure connection of a pressure pipe to the pipe whilst maintaining required strength and functionality in the pipe. The first thickness may be in the range of 1.0 mm to 2.5 mm.

[0021] In some embodiments, this may result in a pipe having the required functionality and strength.

[0022] The inner surface of the second axially extending circumferential section may be straight.

[0023] The inner surface of the second axially extending circumferential section may be curved.

[0024] The thickness of the second axially extending circumferential section may gradually increase in a circumferential direction from the first thickness to the second thickness.

[0025] The outer surface of the second axially extending circumferential section may be straight.

[0026] The outer surface of the second axially extending circumferential section may be curved.

[0027] The outer diameter of the pipe may be constant.

[0028] The second axially extending circumferential section may have additional material disposed on an inside surface of the pipe.

[0029] The second axially extending circumferential section may comprise a material selected from acrylic, MBS, ABS, a filler, or a combination thereof.

[0030] In some embodiments, this may help to keep the pipe straight and avoid warping. In some embodiments, this may further improve the structural characteristics of the second axially extending circumferential section to allow for improved drilling of holes and connecting of the pressure pipes.

[0031] The filler may be a mineral filler such as Mica, Talc or Calcium Carbonate (CaCO3).

[0032] The pipe may further comprise a third axially extending circumferential section having a third thickness which is greater than the first thickness. In some embodiments, this may allow a greater number of pressure pipes to be connected to the pipe.

[0033] The third axially extending circumferential section may be positioned opposite the second axially extending circumferential section.

[0034] In some embodiments, this may help to keep the pipe straight and avoid warping.

[0035] The first axially extending circumferential section and the second axially extending circumferential section may form a first axial section. The pipe may further comprise a second axial section with a uniform circumferential thickness.

[0036] In some embodiments, this may further reduce the amount of PVC material required for the Pipe.

[0037] The pipe may comprise alternating first axial sections and second axial sections.

[0038] In some embodiments, this may further reduce the amount of PVC material required for the Pipe.

[0039] The second axially extending circumferential section may extend along the length of the Pipe.

[0040] In some embodiments, this allows a greater number of pressure pipes to be connected to the pipe.

[0041] The second axially extending circumferential section may have one or more holes for connecting one or more pressure pipes.

[0042] In some embodiments, this may help to efficiently connect the pressure pipes to the pipe. In other embodiments, the holes may be drilled into the pipe on-site where the pipe is to be installed. The second axially extending circumferential section may have a plurality of holes arranged axially along the second axially extending circumferential section for connecting a plurality of pressure pipes.

[0043] The first axially extending circumferential section and the second axially extending circumferential section together may form a full circumference of the pipe.

[0044] The first axially extending circumferential section and the second axially extending circumferential section may extend straight along the longitudinal axis.

[0045] In a second aspect of the present disclosure, there is provided a method of producing a PVC-0 pipe. The method comprisesforming a tubular preform from a PVC material, the tubular preform having a first circumferential section and a second circumferential section, the first circumferential section and the second circumferential section forming part of the same circumference of the pipe. The method further comprises forcing the tubular preform over a mandrel to expand the tubular preform and form a PVC-0 pipe with biaxially oriented PVC. The first circumferential section of the tubular preform forms a first axially extending circumferential section of the pipe having a first thickness. The second circumferential section of the tubular preform forms a second axially extending circumferential section having a second thickness. The second thickness is greater than the first thickness.

[0046] In some embodiments, this may result in an effective method of producing pipe having a reduced amount of plastic whilst maintaining the required functionality and strength to supply water in an irrigation system.

[0047] The thickness of the second circumferential section of the tubular preform may be greater than the thickness of the first circumferential section of the tubular preform.

[0048] Forming the tubular preform may comprise injecting the PVC material into an extruder die to form the tubular preform.

[0049] The extruder die may be shaped to form the tubular preform having the first circumferential section and the second circumferential section.

[0050] In some embodiments, this may result in an effective method of forming the tubular preform. The extruder die may have an annular outlet with a first circumferential section and a second circumferential section, with the second circumferential section having a greater thickness than the first circumferential section.

[0051] Forming the tubular preform may further comprise injecting additional material at a circumferential section of the extruder die to form the second circumferential section of the tubular preform having a thickness greater than the first circumferential section.

[0052] In some embodiments, this may result in an effective method of forming the tubular preform.

[0053] The additional material may comprise a material selected from acrylic, MBS, ABS, a filler, or a combination thereof.

[0054] In some embodiments, this may help to keep the pipe straight and avoid warping. In some embodiments, this may further improve the structural characteristics of the second axially extending circumferential section to allow for improved drilling of holes and connecting of the pressure pipes.

[0055] The additional material may of a different colour to the PVC material.

[0056] In some embodiments, this may make it easier to identify the second axially extending circumferential section and allow an operator to more easily connect the pressure pipes to the pipe.

[0057] The method may further comprise controlling the temperature of the tubular preform at an outlet of the extruder die, with the first circumferential section of the tubular preform having a lower temperature and the second circumferential section of the tubular preform having a higher temperature.

[0058] In some embodiments, this may result in an effective method of forming the tubular preform.

[0059] Controlling the temperature of the tubular preform at an outlet of the extruder die may comprises operating a plurality of heaters positioned around the outlet of the extruder die. The higher temperature may be in the range of 10°C to 30°C higher than the lower temperature.

[0060] The method may further comprise, prior to forcing the tubular preform over a mandrel, controlling the temperature of the tubular preform to reach an orientation temperature which is suitable for biaxial stretching of the PVC material.

[0061] Prior to or during forcing of the tubular preform over the mandrel, the temperature may be controlled with a first circumferential section of the tubular preform having a higher temperature and a second circumferential section of the tubular preform having a lower temperature.

[0062] In some embodiments, this may result in an effective method of forming the first and second axially extending circumferential sections.

[0063] The temperature may be controlled prior to or during forcing of the tubular preform over the mandrel but after the extruder.

[0064] The higher temperature may be in the range of 10°C to 40°C higher than the lower temperature.

[0065] Forcing the tubular preform over a mandrel may comprise forcing the tubular preform over a mandrel having a flat surface or a circumferential groove, with the flat surface or circumferential groove forming the second axially extending circumferential section of the Pipe

[0066] The method may further comprise cooling the pipe after forcing the tubular preform over the mandrel.

[0067] A central angle defining the first axially extending circumferential section may be greater than a central angle defining the second axially extending circumferential section.

[0068] In some embodiments, this may help to reduce the amount of PVC material required for the Pipe. The central angle defining the second circumferential section may be in the range of 60 to 120 degrees.

[0069] The ratio of the second thickness to the first thickness may be in the range of 1 .2 to 1.6.

[0070] An advancement speed of the tubular preform may be set by an adjustable drawing device positioned downstream of the mandrel.

[0071] The advancement speed may be constant resulting in a constant thickness of the pipe along the axial direction.

[0072] Brief Description of the Drawings

[0073] To enable better understanding of the present disclosure, and to show how the same may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which:

[0074] FIGS. 1A to 1C show different views of a pipe made of a PVC-0 material, in accordance with one or more embodiments of the disclosure.

[0075] FIGS. 2A and 2B illustrate an apparatus for a method of producing a PVC-0 pipe, in accordance with one or more embodiments of the present disclosure.

[0076] FIGS. 3A and 3B show cross-sectional views of tubular preforms produced by the apparatus of FIG. 2A.

[0077] FIG. 3C shows a cross-sectional view of a PVC-0 pipe produced by the apparatus of FIG. 2B.

[0078] FIG. 4 shows a stripe injector for use in a method of producing a PVC-0 pipe, in accordance with one or more embodiments of the present disclosure.

[0079] FIG. 5 shows a cross sectional view of an embodiment of an extruder die for use in a method of producing a PVC-0 pipe, in accordance with one or more embodiments of the present disclosure. FIG. 6A shows a mandrel for use in a method of producing a PVC-0 pipe, in accordance with one or more embodiments of the present disclosure.

[0080] FIG. 6B shows a cross-sectional view of the mandrel of FIG. 6A along line AA.

[0081] FIG. 6C shows a cross-sectional view of an alternative embodiment of the mandrel of FIG. 6A along line AA.

[0082] FIGS. 7A to 7E show cross sectional views of alternative embodiments of a pipe made of a PVC-0 material, in accordance with one or more embodiments of the disclosure.

[0083] FIG. 8A shows a cross-sectional side view of another embodiment of a pipe made of a PVC- O material, in accordance with one or more embodiments of the disclosure.

[0084] FIG. 8B shows a cross-sectional view of the pipe of FIG. 8A along line BB.

[0085] FIG. 8C shows a cross-sectional view of the pipe of FIG. 8A along line CC.

[0086] FIGS. 9A and 9B show cross-sectional side and front views of a PVC-0 pipe with pressure pipes connected.

[0087] Detailed Description

[0088] FIGS. 1A to 1C show a pipe 100 made of a PVC-0 material. A PVC-0 material is a PVC material in which the PVC molecules have been biaxially oriented, for example, through stretching of the PVC material. PVC-0 has greatly improved structural characteristics such as impact resistance, fatigue resistance or crack propagation over standard amorphous PVC material. FIG. 1A shows an isometric view of the pipe whilst FIG. 1 B shows a cross- sectional side view of the pipe 100 along the longitudinal axis and FIG. 1C shows an axial cross-sectional view of the pipe 100. The pipe 100 may be a supply pipe for an irrigation system to which pressure pipes may be connected via a connector through the wall of the pipe 100. The pipe 100 defines a longitudinal axis L extending through a centre thereof. The pipe 100 comprises a first axially extending circumferential section 110 and a second axially extending circumferential section 120. The first axially extending circumferential section 110 and the second axially extending circumferential section 120 form part of the same circumference of the pipe 100. As illustrated in FIG. 1C, the first axially extending circumferential section 110 has a first thickness t1 and the second axially extending longitudinal section 120 has a second thickness t2, with the second thickness t2 being greater than the first thickness t1 .

[0089] This may help to provide a pipe 100 requiring a reduced amount of PVC material whilst maintaining the required functionality and strength to supply water in an irrigation system. The thicker second axially extending circumferential section 120 may be used to connect supply pipes via a connector which connects through the wall of the second axially extending circumferential section 120. The increased thickness t2 of the second axially extending circumferential section 120 provides the required strength to accommodate the connectors. The remaining first axially extending circumferential section 110 can be made with a smaller thickness t1 in order to save PVC material and make the pipe 100 lighter and easier to transport and handle.

[0090] The ratio of the second thickness t2 to the first thickness t1 , i.e., t2 / t1 , may be in the range of 1.2 to 1.6. The first thickness t1 may be in the range of 1 .0 mm to 2.5 mm and the second thickness t2 may therefore be in the range of 1 .2 mm to 4.0 mm. The first thickness t1 may be constant throughout the circumference of the first axially extending circumferential section 110. The thickness of the second axially extending circumferential section 120 may change along the circumference, however, the second thickness t2 may be taken at the centre of the second axially extending circumferential section 120. In particular, the thickness of the second axially extending circumferential section 120 may gradually increase to a maximum thickness t2 at the centre of the second axially extending section 120.

[0091] The second axially extending portion 120 may extend along the length of the pipe 100, as shown in FIG. 1 B. The second axially extending circumferential section 120 may further comprise a visual indicator 121 positioned on an outside surface of the pipe 100 to allow an operator to easily identify the position of the second axially extending circumferential section 120. The visual indicator 121 may comprise a marking including alphanumeric characters or other indices, or the visual indicator 121 may be provided as a colour which is different from the colour of the first axially extending circumferential section 110. The first axially extending circumferential section 110 and the second axially extending circumferential section 120 may extend straight along the longitudinal axis L of the pipe 100.

[0092] As shown in FIG. 1 C, the first axially extending circumferential section 110 and the second axially extending circumferential section 120 may be the only two circumferential sections present and together may form a full circumference of the pipe 100. The circumferential extent of the first axially extending circumferential section 110 and the second axially extending circumferential section 120 may be defined using a “central angle” corresponding to an angle at the center of the pipe, i.e., at the longitudinal axis L, between two radii enclosing the respective circumferential section of the pipe 100. A central angle <|) of the first axially extending circumferential section 110 may be greater than a central angle 0 of the second axially extending circumferential section 120. The central angle 0 may be in the range of 60° to 120°, whereas the central angle <|) may be in the range of 240° to 300°. By making the second axially extending circumferential section 120 smaller than the first axially extending circumferential section 110, the pipe 100 requires less PVC material to make.

[0093] The second axially extending circumferential section 120 may be formed by increasing the thickness on an inner surface 122 of the pipe 100. The inner surface 122 may be straight or flat whilst an outer surface of the second axially extending circumferential section 120 may remain curved. The outer diameter of the pipe may remain constant throughout. By having a straight inner surface 122 of the second axially extending circumferential section 120, this may help to provide a more secure connection to a pressure pipe which may be connected through the wall of the second axially extending circumferential section 120 of the pipe 100. At the points where the first axially extending circumferential section 110 and the second axially extending circumferential section 120 meet, the wall thickness of the pipe 100 may transition gradually from the first thickness t1 to the second thickness t2.

[0094] The second axially extending circumferential section 120 may, in addition to a PVC-0 material, comprise an additional material. The additional material may include one or more of an acrylic, MBS, ABS, a filler such as a mineral filler like Mica, Talc or CaCO3, or a combination thereof. The acrylic, MBS or ABS may function as an impact improver to enhance impact strength and processability of the second axially extending circumferential section 120. A filler such as a mineral filler like Mica, Talc or CaCO3 may help to prevent warping of the pipe 100 during manufacture.

[0095] FIGS. 2A and 2B illustrate an exemplary apparatus for producing a PVC-0 pipe, such as the pipe 100 of FIGS. 1A to 1C. A method of producing a PVC-0 pipe such as pipe 100 is explained in relation to the apparatus of FIGS. 2A and 2B.

[0096] FIG. 2A shows an extruder 1 with one or more extruder screws 2 and with an associated controllable drive, which creates a flow of molten plastics material, in this case a PVC material, which is fed to an extruder die 3 arranged on the extruder 1.

[0097] The extruder die 3 may have an outer ring 4 and an inner core 5 which, together with the outer ring 4, delimits an annular outlet opening, from which an extruded tubular preform 6 made from PVC material emerges in a substantially horizontal direction. In this arrangement, the inner core 5 defines an axial space in the tubular preform 6.

[0098] The extruder die 3 may have a specific shape for controlling the wall thickness of the tubular preform. Specifically, the annular outlet opening may be shaped to produce different circumferential sections of the tubular preform 6 having different thicknesses. For example, the annular outlet opening may have a first circumferential section with a smaller thickness and a second circumferential section with a greater thickness to form a tubular preform 6 having a first circumferential section with a first thickness and a second circumferential section with a second thickness, wherein the thickness of the second circumferential section is greater than the thickness of the first circumferential section. The annular outlet opening of the extruder die 3 may also be shaped to have a uniform thickness and produce a tubular preform 6 with a uniform circumferential thickness.

[0099] An internal cooling member may be attached to the inner core 5 for internal cooling of the tubular preform. The tubular preform 6 coming out of the extruder die 3 has a relatively thick wall, in order thus to allow the biaxial stretching to take place.

[0100] The extruder die 3 may further comprise a stripe injector 3A (shown in FIG. 4) for injecting additional material at a circumferential section of the die 3 to form a circumferential section of the tubular preform 6 having a greater thickness. The tubular preform 6 may then be externally calibrated with the aid of external calibration sleeve 10. Downstream of the calibration sleeve 10 there may be a first external cooling device 15, by means of which the tubular preform 6 is externally cooled. The external cooling device 15 may comprise, for example, a number of compartments which are located one behind the other, through which cooling water flows and through which the tubular preform 6 moves, coming into direct contact with the cooling water. If appropriate, the cooling water in each compartment may be at different temperatures, in order in this way to optimize the cooling of the tubular preform 6.

[0101] Downstream of the external cooling device 15 there may be a tube speed-control means 20 which acts on the cooled outer layer of the preform 6. The tube speed-control means 20 may in this case be designed as a drawing device having a plurality of tracks acting on the tubular preform 6.

[0102] As shown in FIG. 2B, a heater device 25 is arranged downstream of the tube speed-control means 20. This device 25 may comprise a plurality of heater units which are positioned around the path for the tubular preform 6, can be controlled separately and are each directed towards a sector of the circumference of the tubular preform 6. As a result, a separately controllable amount of heat can be fed to each sector of the tubular preform 6, for example six circumferential sectors each of 60°. The heater device 25 may be configured to heat the tubular preform 6 and control the temperature of the tubular preform 6, specifically a surface temperature of the tubular preform 6, to reach an orientation temperature which is suitable for biaxial stretching of the PVC material. The surface temperature of the tubular preform may be heated to be in the range of 100°C to 200°C.

[0103] The apparatus furthermore comprises an expansion mandrel 30. The mandrel 30 may be non-deformable and made from a metal. The mandrel 30 may be held in a stationary position with respect to the extruder 1 and may in this case be attached to the inner core 5 by means of an anchor member 31 .

[0104] At its upstream end, the mandrel 30 may have a run-on part 32, which in this case is of substantially cylindrical design. The said run-on part 32 is adjoined by an expansion part 33, the external surface of which substantially corresponds to the surface of a truncated cone with a diameter which increases in the downstream direction. The said expansion part 33 may be adjoined by a runoff part 34 of the mandrel 30, which part 34 may be substantially cylindrical and of substantially constant diameter. In some embodiments, the runoff part 34 may be tapering slightly in the downstream direction.

[0105] The tubular preform 6 is forced over the mandrel 30 to expand the tubular preform and form a PVC-0 pipe 6' where the PVC molecules are biaxially oriented. As a result of passage over the mandrel 30, the molecules of the plastics material are oriented, i.e., stretched, both in the axial direction and in the circumferential direction, resulting in a PVC-0 material with improved structural characteristics such as impact resistance, fatigue resistance or crack propagation over standard amorphous PVC material.

[0106] At the location of the mandrel 30, in particular of the run-off part 34, there may be a temperature control device 40, by means of which the PVC-0 pipe 6' may be externally heated or cooled. For example, the stretched tube may be cooled after it has passed the expansion part of the mandrel 30, so that as a result the changes which have been brought about in the plastics material of the tube are frozen.

[0107] A second external calibration device 45 may be arranged at a distance downstream of the mandrel 30, which calibration device 45 may reduce the external diameter of the PVC-0 pipe 6'.

[0108] The installation may also comprise a drawing device 50 which is arranged downstream of the mandrel 30 and of the external calibration device 45. The drawing device 50 is intended to exert a considerable tensile force on the PVC-0 pipe 6'. Downstream of the drawing device 50 there may be a cutting-to-length device (not shown), for example a sawing, cutting or milling device, in order to cut sections of the desired length from the PVC-0 pipe 6' which has been produced.

[0109] The tubular preform 6 is forced over the mandrel 30 under the influence of the forces which are exerted on the tubular preform 6 and the tube 6' by means of the drawing device 50 in conjunction with the tube speed-control means 20. By means of the drawing device 50 and the tube speed-control means 20, it is possible to accurately control the advancement speed both at a location up-stream of the mandrel 30 (at tube speed-control means 20) and at a location downstream of the mandrel 30 (at drawing device 50). A unit for measuring the wall thickness may be arranged between the extruder 1 and the mandrel 30, by means of which unit the thickness of the tubular preform 6 and the shape of the cross section of the tubular preform 6 can be measured.

[0110] Downstream of the mandrel 30 there may be a unit 60 for measuring wall thickness. This wall-thickness measuring unit 60 may be connected to a control unit which, on the basis of the measured cross section of the stretched tube 6', controls the operation of the drawing device 50, the device 25, and, if appropriate, the distance between the calibration device 45 and the mandrel 30.

[0111] A PVC-0 pipe, like pipe 100, having a first axially extending circumferential section 110 with a first thickness t1 and a second axially circumferential section 120 with a second thickness t2 may be manufactured with the above-described apparatus in a number of different ways. The different methods will be explained below with reference to FIGS. 2A and 2B and FIGS. 3A to 3C.

[0112] In a first method, the annular outlet opening of the extruder die 3 is shaped to have a first circumferential section with a smaller thickness and a second circumferential section with a greater thickness, such that the tubular preform 6 which is formed by the extruder die 3 comprises a first circumferential section with a first thickness and a second circumferential section with a second thickness, with the second thickness being greater than the first thickness. This tubular preform 6 is shown in FIG. 3A, with the first circumferential section having a thickness t3 and the second circumferential section having a thickness t4. When this tubular preform 6 is forced over the mandrel 30 to expand the tubular preform and form the PVC-0 pipe 6’, the first circumferential section of the tubular preform 6 forms a first axially extending circumferential section 110 of the PVC-0 pipe 6’ and the second circumferential section forms the second axially extending circumferential section 120, with the second axially extending circumferential section 120 having a thickness t2 greater than a thickness t1 of the first axially extending circumferential section 110, as shown in FIG. 3C. The PVC-0 pipe 6’ may then be cut to length to form pipe 100.

[0113] In a second method, the extruder die 3 further comprises the stripe injector 3A which injects additional material at a circumferential section of the die 3 in order to form the tubular preform 6 comprising a first circumferential section with a first thickness and a second circumferential section with a second thickness, with the second thickness being greater than the first thickness. This tubular preform 6 is shown in FIG. 3A, with the first circumferential section having a thickness t3 and the second circumferential section having a thickness t4. The additional material injected by the stripe injector 3A may be a PVC material or it may be another material such as an acrylic, MBS, ABS, a filler such as a mineral filler like Mica, Talc or CaCO3, or a combination thereof. The acrylic, MBS and ABS may function as an impact improver to enhance impact strength and processability of the second axially extending circumferential section 120. A filler such as a mineral filler like Mica, Talc or CaCO3 may help to prevent warping of the pipe 100 during the further production steps. The additional material may also have a different colour from the PVC material inserted into extruder 1 , such that the additional material forms the visual marker 121 on the second axially extending circumferential section 120. When this tubular preform 6 is forced over the mandrel 30 to expand the tubular preform and form the PVC-0 pipe 6’, the first circumferential section of the tubular preform 6 forms a first axially extending circumferential section 110 of the PVC-0 pipe 6’ and the second circumferential section forms the second axially extending circumferential section 120, with the second axially extending circumferential section 120 having a thickness t2 greater than a thickness t1 of the first axially extending circumferential section 110, as shown in FIG. 3C. The PVC-0 pipe 6’ may then be cut to length to form pipe 100.

[0114] In a third method, the extruder die 3 further comprises a plurality of heaters 7 (shown in FIG. 5) positioned circumferentially about an outlet of the extruder die 3 to control the temperature of the tubular preform as it exits the extruder die 3. Specifically, the heaters 7 may be operated to heat a first circumferential section of the tubular preform 6 to a lower temperature and a second circumferential section of the tubular preform to a higher temperature. The higher temperature may be 10°C to 30°C higher than the lower temperature and both the higher and lower temperature may be in the range of 180°C to 220°C. The higher temperature results in the PVC material flowing more quickly through the extruder die outlet thereby forming a thicker section. The tubular preform 6 exiting the extruder die 3 therefore comprises a first circumferential section with a first thickness and a second circumferential section with a second thickness, with the second thickness being greater than the first thickness. This tubular preform 6 is shown in FIG. 3A, with the first circumferential section having a thickness t3 and the second circumferential section having a thickness t4. When this tubular preform 6 is forced over the mandrel 30 to expand the tubular preform and form the PVC-0 pipe 6’, the first circumferential section of the tubular preform 6 forms a first axially extending circumferential section 110 of the PVC-0 pipe 6’ and the second circumferential section forms the second axially extending circumferential section 120, with the second axially extending circumferential section 120 having a thickness t2 greater than a thickness t1 of the first axially extending circumferential section 110, as shown in FIG. 3C. The PVC-0 pipe 6’ may then be cut to length to form pipe 100.

[0115] In a fourth method, the extruder die 3 may produce a tubular preform 6 having a constant wall thickness over its circumference. This tubular preform 6 is shown in FIG. 3B having a constant wall thickness t3. When the tubular preform reaches heater 25, which is positioned prior to the mandrel 30 but after the extruder die 3, and is heated to reach an orientation temperature which is suitable for biaxial stretching of the PVC material, different circumferential sections of the tubular preform 6 are heated to different temperatures. This is possible due to the plurality of heater units which are positioned around the path for the tubular preform 6, which can be controlled separately and are each directed towards a sector of the circumference of the tubular preform 6. As a result, a separately controllable amount of heat can be fed to each sector of the tubular preform 6, for example six circumferential sectors each of 60°. A first circumferential section of the tubular preform 6 may be heated to higher temperature and a second circumferential section of the tubular preform may be heated to a lower temperature. When this tubular preform 6 is forced over the mandrel 30 to expand the tubular preform and form the PVC-0 pipe 6’, the first circumferential section of the tubular preform 6 forms a first axially extending circumferential section 110 of the PVC-0 pipe 6’ and the second circumferential section forms the second axially extending circumferential section 120, with the second axially extending circumferential section 10 having a thickness t2 greater than a thickness t1 of the first axially extending circumferential section 110. Due to the lower temperature of the second circumferential section of the tubular preform 6, it will expand and stretch less when forced over the mandrel, therefore resulting in an increased thickness of the second axially extending circumferential section 120. The higher temperature may be 10°C to 30°C higher than the lower temperature. The temperature at the mandrel 30 may also be controlled in the same, either manner additionally or alternatively, for example using the temperature control device 40 which may comprise heaters. The PVC-0 pipe 6’ may then be cut to length to form pipe 100.

[0116] In a fifth method, the extruder die 3 may produce a tubular preform 6 having a constant wall thickness over its circumference. This tubular preform 6 is shown in FIG. 3B having a constant wall thickness t3. An alternative embodiment of a shaped mandrel 30A (shown in FIGS. 6A-C) may be used which has a runoff part 34 which has been machined or otherwise formed with a flat surface 35 or a circumferential groove 36. When this tubular preform 6 is forced over the mandrel 30A to expand the tubular preform 6 and form the PVC-0 pipe 6’, the flat surface 35 or circumferential groove 36 of the mandrel 30A causes a circumferential section of the tubular preform 6 to expand less the rest of tubular preform 6. The tubular preform 6 therefore forms a thickened section of the pipe 6’ where the mandrel 30A has the flat surface 35 or circumferential groove 36. A first circumferential section of the tubular preform 6 which comes into contact with a rounded surface of the mandrel 30A therefore forms a first axially extending circumferential section 110 of the PVC-0 pipe 6’ and a second circumferential section of the tubular preform 6 which comes into contact with the flat surface 35 or circumferential groove 36 of the mandrel 30A forms the second axially extending circumferential section 120, with the second axially extending circumferential section 120 having a thickness t2 greater than a thickness t1 of the first axially extending circumferential section 110, as shown in FIG. 3C. The PVC-0 pipe 6’ may then be cut to length to form pipe 100.

[0117] The first, second, third, fourth and fifth methods above may be performed individually or combined in a number of different ways. For example, it may be possible to combine a shaped extruder die 3 with a stripe injector 3A, or a shaped extruder die 3 with temperature control at the extruder die outlet, or a stripe injection 3A with temperature control at the extruder die outlet, or a shaped extruder die 3 with a stripe injector 3A and temperature control at the extruder die outlet. It may further be possible to combine the circumferential temperature control of the tubular preform 6 at or before the mandrel with a shaped mandrel 30A. It may also be possible to combine any of the shaped extruder die 3, stripe injector 3A and temperature control at the extruder die outlet with any of the temperature control of the tubular preform 6 at or before the mandrel and the shaped mandrel 30A.

[0118] FIG. 4 shows a side view of the stripe injector 3A. The stripe injector 3A may form part of the extruder die 3 of FIG. 2A having an outer ring 4 and an inner core 5. The additional material may be injected at a circumferential section of the die 3 through a side inlet 4A in the outer ring 4. The stripe injector may have a plurality of side inlets 4A, for example, positioned on opposite sides as shown in FIG. 4. These side inlets 4A may be used together or individually. As noted above, this may allow a tubular preform 6 to be formed with a first circumferential section having a first thickness and a second circumferential section having a second thickness, with the second thickness being greater than the first thickness.

[0119] FIG. 5 shows a cross sectional view of an outlet 3B of the extruder die 3. The extruder die 3 may have an outer ring 4 and an inner core 5. The tubular preform 6 may exit the annular outlet 3B through the annular outlet opening formed between the inner core 5 and outer ring 4. A plurality of heaters 7 may be positioned circumferentially around the outlet 3B. FIG. 5 shows eight individual heaters, however, any suitable number of heaters 7 may be used. For example, in the range of 4 to 20 heaters 7 may be used.

[0120] As noted above, the heaters 7 may be used to control the temperature of the tubular preform 6 as it exits the extruding die 3. The heaters 7 may be operated to heat a first circumferential section of the tubular preform 6 to a lower temperature and a second circumferential section of the tubular preform to a higher temperature. The higher temperature may be 10°C to 30°C higher than the lower temperature and both the higher and lower temperature may be in the range of 180°C to 220°C. The higher temperature results in the PVC material flowing more quickly through the extruder die outlet thereby forming a thicker circumferential section of the tubular preform 6.

[0121] FIG. 6A shows a cross sectional side view of an embodiment of a mandrel 30A which may be used in the apparatus for producing a PVC-0 pipe of FIG. 2A and 2B. The mandrel 30A is similar to mandrel 30 of FIG. 2B, and has a run-on part 32, expansion part 33 and run-off part 34. An anchor member 31 may be positioned within the mandrel 30A for connecting to the extruder 1.

[0122] The mandrel 30A differs from mandrel 30 in that the run-off part 34 is shaped and may either have a flat surface 35 which extends axially along the length of the run-off part 34 or a circumferential groove 36 which also extends axially along a length of the run-off part 34.

[0123] FIG. 6B shows a cross sectional view of the run-off part 34 along line AA of FIG. 6A and illustrates the flat surface 35 in more detail. The flat surface 35 may be formed, for example, by machining the run-off part 34 of mandrel 30A. When the tubular preform 6 is forced over the mandrel 30A to expand the tubular preform 6 and form the PVC-0 pipe 6’, the flat surface 35 of the mandrel 30A causes a circumferential section of the tubular preform 6 which is in contact with the flat surface 35 to expand less the rest of tubular preform 6. The tubular preform 6 therefore forms a thickened section of the pipe 6’ where the mandrel 30A has the flat surface 35.

[0124] FIG. 6C also shows a cross sectional view of the run-off part 34 along line AA of FIG. 6A and illustrates the circumferential groove 36, in an alternative embodiment. The circumferential groove 36 may also be formed, for example, by machining the run-off part 34 of mandrel 30A.

[0125] The circumferential groove 36 functions in a similar manner to the flat surface 35 in that when the tubular preform 6 is forced over the mandrel 30A to expand the tubular preform 6 and form the PVC-0 pipe 6’, the circumferential groove 36 of the mandrel 30A causes a circumferential section of the tubular preform 6 which is in contact with the circumferential groove 36 to expand less the rest of tubular preform 6. The tubular preform 6 therefore forms a thickened section of the pipe 6’ where the mandrel 30A has the circumferential groove 36.

[0126] FIGS. 7A to 7E show cross-sectional views of a number of alternative embodiments of a PVC-0 pipe.

[0127] FIG. 7A shows a pipe 200 made of a PVC-0 material having a first axially extending circumferential section 110 and a second axially extending circumferential section 220. The pipe 200 additionally has a third axially extending circumferential section 230 positioned opposite the second axially extending circumferential section. The third axially extending circumferential section 230 may have the same dimensions as the second axially extending circumferential section 220 and the same thickness t2 which is greater than the thickness t1 of the first axially extending circumferential section.

[0128] By having a third axially extending circumferential section 230, the pipe 200 allows a greater number of pressure pipes to be connected compared to pipe 100, as the pressure pipes can be connected through the walls of the second axially extending circumferential section 220 and the third axially extending circumferential section 230. Furthermore, by having the third axially extending circumferential section 230 positioned opposite the second axially extending circumferential section 220, this may help to avoid warping or bending of the pipe during manufacture due to the symmetrical cross section of the pipe 200.

[0129] Both the second axially extending circumferential section 220 and the third axially extending circumferential section 230 may be formed by including additional material on the inner surface of the pipe whilst the outer surface remains circular or curved. The inner surface of the second and third axially extending circumferential sections 220, 230 may be formed to be straight, as in pipe 100 of FIG. 1.

[0130] FIG. 7B shows another pipe 300 made from a PVC-0 material. The pipe 300 also has a first axially extending circumferential section 110 and a second axially extending circumferential section 320. The second axially extending circumferential section 320 may be defined by the same central angle as the second axially extending circumferential section 120 of pipe 100 of FIGS. 1A to 1C.

[0131] The pipe 300 differs from pipe 100 in that the second axially extending circumferential section 320 has a rounded inner surface and a substantially constant thickness along its circumference. At the edges of the second axially extending circumferential section 320 the thickness gradually tapers to the first thickness t1 of the first axially extending circumferential section 110. The outer surface 323 may be remain curved, whilst the inner surface 322 is also formed as a curved surface.

[0132] FIG. 7C shows another pipe made from a PVC-0 material having a first axially extending circumferential section 110 and a second axially extending circumferential section 420. The second axially extending circumferential section 420 may be defined by the same central angle as the second axially extending circumferential section 120 of pipe 100 of FIGS. 1A to 1C.

[0133] The pipe 400 differs from pipe 100 in that the second axially extending circumferential section 420 is formed increasing the thickness on an outside surface 423 in order to increase the thickness, for example including additional material on the outside surface 423 with the stripe injector 3A. The thickness t2 may be the same as thickness t2 of pipe 100. The outer surface 423 may be formed to be a curved surface, whilst the inner surface 422 also remains curved. FIG. 7D shows another pipe made from a PVC-0 material having a first axially extending circumferential section 110 and a second axially extending circumferential section 520. The second axially extending circumferential section 520 may be defined by the same central angle as the second axially extending circumferential section 120 of pipe 100 of FIGS. 1A to 1C.

[0134] The pipe 500 differs from pipe 100 in that the second axially extending circumferential section 520 is formed by increasing the thickness on both an inside surface 522 and an outside surface 523. The thickness t2 may be the same as thickness t2 of pipe 100. The outer surface 523 may be formed to be a curved surface, whilst the inner surface 522 may be formed as a straight surface.

[0135] FIG. 7E shows another pipe made from a PVC-0 material having a first axially extending circumferential section 110 and a second axially extending circumferential section 620. The second axially extending circumferential section 620 may be defined by the same central angle as the second axially extending circumferential section 120 of pipe 100 of FIGS. 1A to 1C.

[0136] The pipe 600 differs from pipe 100 in that the second axially extending circumferential section 620 is formed by increasing the thickness on both an inside surface 622 and an outside surface 623. The thickness t2 may be the same as thickness t2 of pipe 100. The outer surface 623 may be formed to be a straight surface and the inner surface 622 may also be formed as a straight surface. By having both the inside and the outside surfaces 622, 623 formed as straight surface, this may help to provide a secure connection with a connector for connecting to a pressure pipe.

[0137] FIGS. 8A to 8C show another alternative embodiment of a PVC-0 pipe 700.

[0138] FIG. 8A shows a cross-sectional side view of the pipe 700. The pipe 700 comprises a first axial section 701 and a second axial section 702. The first axial section 701 and second axial section 702 may repeat axially along the length of the pipe 700. In the embodiment of FIG. 8A, the pipe 700 has a first axial section followed by a second axial section 702, followed by another first axial section 701 and another second axial section 702. FIG. 8B shows a cross sectional view of the first axial section along line BB. The cross section of the first axial section 701 corresponds to the cross section of pipe 100 and comprises a first axially extending circumferential section 110 with a thickness t1 and a second axially extending circumferential section 120 with a second thickness t2 which is greater than the first thickness t1 .

[0139] FIG. 8C shows a cross sectional view of the second axial section 702 along line CC. The second axial section 702 only has one axially extending circumferential section 140 which extends around the entire circumference and has the first thickness t1.

[0140] By having the second axially extending circumferential section 120 limited to the first axial section 701 , a further reduction in the amount of PVC material required for the pipe 700 can be achieved without reducing the functionality of the pipe. The first axial section 702 and the second axial section 702 can be spaced such that each first axial section 701 can accommodate one connector and pressure pipe. The pipe 700 may comprise any suitable number of first and second axial section 701 , 702.

[0141] FIGS. 9A and 9B illustrate the pipe 100 with pressure pipes 160 connected thereto via respective connectors 150.

[0142] The connectors 150 may be connected to the second axially extending circumferential section 120 through holes in the wall of the second axially extending circumferential section 120. The holes may be formed by an operator when installing the pipes, for example, using a drill. The connectors 150 may then be inserted into the holes and the pressure pipes 160 may be connected to the connectors 150. A number of connectors and pressure pipes may be connected to the pipe 100, for example, a first connector 150A and first pressure pipe 160A and a second connector 150B and second pressure pipe 160B. The first connector 150A and second connector 150B may be axially arranged along the second axially extending circumferential section 120. The increased thickness t2 of the second axially extending circumferential section 120 may provide the required structural strength to allow the holes to be drilled therethrough and the connectors 150 to be securely connected.

[0143] Various modifications will be apparent to those skilled in the art. The central angle <|) defining the first axially extending circumferential section 110 may be smaller the central angle 0 defining the second axially extending circumferential section 120.

[0144] The central angle 0 defining the second axially extending circumferential section 120 may be less than 60° or greater than 120°.

[0145] The second axially extending circumferential section 120 may not have a visual indicator 121.

[0146] The ratio of the second thickness t2 to the first thickness t1 is not limited to the range of 1.2 to 1 .6 but may be greater than 1 .6 or smaller than 1 .2.

[0147] The second axially extending circumferential section 120 may not comprise any additional materials and may be formed only from PVC-O. The additional materials are also not limited to acrylic, MBS, ABS and a filler.

[0148] The third axially extending circumferential section 230 may not be positioned opposite the second axially extending circumferential section 220. The third axially extending circumferential section 230 may differ in shape and / or size from the second axially extending circumferential section 230.

[0149] The pipe 700 may comprise any number of repeating first and second axial sections 701 , 702. The first axial section 701 may have any of the cross sections of pipes 200, 300, 400, 500, or 600.

[0150] The second axially extending circumferential section 120 may not have any holes. The holes may be formed separately by an operator during installation of the pipe 100, for example.

[0151] The calibration sleeve 10, cooling device 15, tube-speed control means 20, heater 25, anchor member 31 , temperature control device 40, calibration device, wall-thickness measuring unit 60, and drawing device 50 are optional features of the apparatus for producing a PVC-0 pipe and not essential for producing a PVC-0 pipe. The extruder die 3 may not have a stripe injector 3A.

[0152] The extruder die 3 may not have any heaters 7. All of the above are fully within the scope of the present disclosure and are considered to form the basis for alternative embodiments in which one or more combinations of the abovedescribed features are applied, without limitation to the specific combination disclosed above. In light of this, there will be many alternatives which implement the teaching of the present disclosure. It is expected that one skilled in the art will be able to modify and adapt the above disclosure to suit its own circumstances and requirements within the scope of the present disclosure, while retaining some or all technical effects of the same, either disclosed or derivable from the above, in light of his common general knowledge in this art. All such equivalents, modifications or adaptations fall within the scope of the present disclosure.

Claims

Claims1. A pipe made of a PVC-0 material, the pipe defining a longitudinal axis, the pipe having: a first axially extending circumferential section having a first thickness; and a second axially extending circumferential section having a second thickness, wherein the second thickness is greater than the first thickness, wherein the first axially extending circumferential section and the second axially extending circumferential section form part of the same circumference of the pipe.

2. The pipe of claim 1, wherein a central angle defining the first axially extending circumferential section is greater than a central angle defining the second axially extending circumferential section.

3. The pipe of claim 2, wherein the central angle defining the second axially extending circumferential section is in the range of 60 to 120 degrees.

4. The pipe of any preceding claim, wherein the second axially extending circumferential section has a visual indicator positioned on the outside surface of the pipe to identify the position of the second axially extending circumferential section.

5. The pipe of claim 5, wherein the visual indicator comprises a marking or a different colour.

6. The pipe of any preceding claim, wherein the ratio of the second thickness to the first thickness is in the range of 1.2 to 1.6.

7. The pipe of any preceding claim, wherein the first thickness is in the range of 1.0 mm to 2.5 mm.

8. The pipe of any preceding claim, wherein the inner surface of the second axially extending circumferential section is straight or curved.

9. The pipe of any preceding claim, wherein the thickness of the second axially extending circumferential section gradually increases in a circumferential direction from the first thickness to the second thickness.

10. The pipe of any preceding claim, wherein the outer surface of the second axially extending circumferential section is curved.

11. The pipe of claim 10, wherein the outer diameter of the pipe is constant.

12. The pipe of any preceding claim, wherein the second axially extending circumferential section has additional material disposed on an inside surface of the pipe.

13. The pipe of any preceding claim, wherein the second axially extending circumferential section comprises a material selected from acrylic, MBS, ABS, a filler, or a combination thereof.

14. The pipe of any preceding claim, further comprising a third axially extending circumferential section having a third thickness which is greater than the first thickness.

15. The pipe of claim 14, wherein the third axially extending circumferential section is positioned opposite the second axially extending circumferential section.

16. The pipe of any preceding claim, wherein the first axially extending circumferential section and the second axially extending circumferential section form a first axial section, and the pipe further comprises a second axial section with a uniform circumferential thickness.

17. The pipe of claim 16, wherein the pipe comprises alternating first axial sections and second axial sections.

18. The pipe of any of claims 1 to 15, wherein the second axially extending circumferential section extends along the length of the pipe.

19. The pipe of any preceding claim, wherein the second axially extending circumferential section has one or more holes for connecting one or more pressure pipes.

20. The pipe of claim 19, wherein the second axially extending circumferential section has a plurality of holes arranged axially along the second axially extending circumferential section for connecting a plurality of pressure pipes.

21. The pipe of any preceding claim, wherein the first axially extending circumferential section and the second axially extending circumferential section together form a full circumference of the pipe.

22. The pipe of any preceding claim , wherein the first axially extending circumferential section and the second axially extending circumferential section extend straight along the longitudinal axis.

23. A method of producing a PVC-0 pipe, the method comprising: forming a tubular preform from a PVC material, the tubular preform having a first circumferential section and a second circumferential section, the first circumferential section and the second circumferential section forming part of the same circumference of the pipe; forcing the tubular preform over a mandrel to expand the tubular preform and form a PVC-0 pipe with biaxially oriented PVC, the first circumferential section of the tubular preform forming a first axially extending circumferential section of the pipe having a first thickness, and the second circumferential section of the tubular preformforming a second axially extending circumferential section having a second thickness, wherein the second thickness is greater than the first thickness.

24. The method of claim 23, wherein the thickness of the second circumferential section of the tubular preform is greater than the thickness of the first circumferential section of the tubular preform.

25. The method of claim 24, wherein forming the tubular preform comprises injecting the PVC material into an extruder die to form the tubular preform.

26. The method of claim 25, wherein the extruder die is shaped to form the tubular preform having the first circumferential section and the second circumferential section.

27. The method of claim 26, wherein the extruder die has an annular outlet with a first circumferential section and a second circumferential section, with the second circumferential section having a greater thickness than the first circumferential section.

28. The method of any of claims 25 to 27, wherein forming the tubular preform further comprises injecting additional material at a circumferential section of the extruder die to form the second circumferential section of the tubular preform having a thickness greater than the first circumferential section.

29. The method of claim 28, wherein the additional material comprises a material selected from acrylic, MBS, ABS, a filler, or a combination thereof.

30. The method of claim 28 or 29, wherein the additional material is of a different colour to the PVC material.

31. The method of any of claims 25 to 30, further comprising controlling the temperature of the tubular preform at an outlet of the extruder die, with the firstcircumferential section of the tubular preform having a lower temperature and the second circumferential section of the tubular preform having a higher temperature.

32. The method of claim 31, wherein controlling the temperature of the tubular preform at an outlet of the extruder die comprises operating a plurality of heaters positioned around the outlet of the extruder die.

33. The method of claim 31 or 32, wherein the higher temperature is in the range of 10°C to 30°C higher than the lower temperature.

34. The method of any of claims 23 to 33, further comprising, prior to forcing the tubular preform over a mandrel, controlling the temperature of the tubular preform to reach an orientation temperature which is suitable for biaxial stretching of the PVC material.

35. The method of claim 34, wherein prior to or during forcing of the tubular preform over the mandrel, the temperature is controlled with a first circumferential section of the tubular preform having a higher temperature and a second circumferential section of the tubular preform having a lower temperature.

36. The method of claim 35, wherein the higher temperature is in the range of 10°C to 40°C higher than the lower temperature.

37. The method of any of claims 23 to 36, wherein forcing the tubular preform over a mandrel comprises forcing the tubular preform over a mandrel having a flat surface or a circumferential groove, with the flat surface or circumferential groove forming the second axially extending circumferential section of the pipe.

38. The method of any of claims 23 to 37, further comprising cooling the pipe after forcing the tubular preform over the mandrel.

39. The method of any of claims 23 to 38, wherein a central angle defining the first axially extending circumferential section is greater than a central angle defining the second axially extending circumferential section.

40. The method of claim 39, wherein the central angle defining the second circumferential section is in the range of 60 to 120 degrees.

41. The method of any of claims 23 to 40, wherein the ratio of the second thickness to the first thickness is in the range of 1.2 to 1.6.

42. The method of any claims 23 to 41, wherein an advancement speed of the tubular preform is set by an adjustable drawing device positioned downstream of the mandrel.

43. The method of claim 42, wherein the advancement speed is constant resulting in a constant thickness of the pipe along the axial direction.

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