Production system and production of a pipe from one or more streams of thermoplastic material

Abstract

A production system for producing a pipe from one or more streams of thermoplastic material. The system comprises a distributor head which comprises at least an inlet orifice for a stream of plastics material, and an outlet orifice of annular cross section. The distributor head comprises at least one flow channel system which is connected to an inlet orifice of the distributor head by means of an inlet channel which inlet channel, in a number of stages of branchings and intermediate flow channels branches into a number of outlet channels terminating on a periphery around the centre line of the outlet orifice, which outlet channels open into the outlet orifice. The distributor head is further provided with a flow rate adjustment system which is configured to individually adjust the flow rate of the thermoplastic material in the associated channel.

Description

[0001] PRODUCTION OF A PIPE FROM ONE OR MORE STREAMS OF THERMOPLASTIC MATERIAL

[0002] The present invention relates to the production of pipe from one or more streams of thermoplastic material.

[0003] WO94 / 04341 discloses a plastic pipe production system which comprises a distributor head and at least one extruder. The distributor head comprises at least an inlet orifice connected to an extruder for a stream of plastics material, an outlet orifice of annular cross section, and a flow channel system. The flow channel system comprises an inlet channel which is at one end thereof connected to the inlet orifice, which inlet channel, in a number of stages of branchings and intermediate flow channels, branches into a number of outlet channels terminating on a periphery around the centre line of the outlet orifice, which outlet channels open into the outlet orifice.

[0004] The present invention aims to provide an improved production system for producing a pipe. In particular, the present invention aims to provide a production system which allows for a more precise production of a pipe and allows for the use of narrower tolerances, e.g. which decreases the amount of plastic that needs to be used. For example, in a multi-layer pipe having a foam core, it is desirable to enhance control of the wall thickness of the inner and / or outer layer, and / or to enhance control of the quality of the foam core, e.g. reducing the number and / or size of voids in the foam core.

[0005] A first aspect of the present invention provides a production system according to claim 1.

[0006] The branching of the flow channel system in the distributor head allows for a generally even distribution of the thermoplastic material which is introduced in the inlet orifice by an extruder over the outlet orifice from which the extruded pipe or a layer thereof in a multilayer pipe emerges. Each outlet channel opens into a particular portion of the outlet orifice, and each outlet channel thus corresponds to a respective circumferential portion of the cross-section of the outlet orifice and thus a respective circumferential portion of the extruded pipe or layer thereof.

[0007] The flow rate of thermoplastic material through the flow channel system(s) of the distributor head determines one or more characteristics of the produced pipe, e.g. the wall thickness, the uniformity of wall thickness (e.g. in cross-section of the pipe), layer thickness(es) in a multilayer pipe, the quality of a foam core in a foam core pipe (e.g. the presence of voids in the foam core), etc. By locally adjusting the flow rate in at least one stage of the distributor head, one or more of the characteristics of the pipe can be adjusted.

[0008] The local flow adjustment system allows for the individual adjustment of the flow rate in intermediate flow channels and / or outlet channels. The local flow adjustment system can thus be applied to change the flow rate in the channels that correspond to particular circumferential portions of the pipe. This allows for adjustment of one or more of the characteristics, e.g. wall thickness, layer thickness(es), etc, of the whole pipe as well as specific circumferential portions of the pipe or layer(s) of the pipe. In general, this allows for a further optimized control of the production process.

[0009] The measurement device allows data related to one or more characteristics of the pipe to be determined.

[0010] In an embodiment, the measurement device transmits the data to the controller of the local flow adjustment system. In another embodiment, or in combination, the data determined by the measurement device is displayed to a human operator. The data allows the controller, e.g. fully automatically, and / or the human operator to make appropriate adjustments of the flow adjustment elements, thereby e.g. improving overall pipe quality and reducing deviations in production.

[0011] Characteristics of the pipe that the measurement device measures are for example, wall thickness, layer-thickness(es) in a multi-layered pipe, shape, and dimensions of the crosssection, if present number, size, location of voids in the foam core of the pipe, foam cell size, etc.

[0012] It is advantageous to measure the one or more characteristics of the pipe after the pipe has been cooled by the in-line cooling device as the thermoplastic material is still relatively deformable prior to such cooling. In practice, only after the pipe has been cooled the shape of the pipe is set and will not change; measuring before the pipe has been cooled could result in unreliably and inaccurate measurements.

[0013] The inventive production system thus allows for enhanced control in the production of a plastic pipe, e.g. a multi-layered pipe, e.g. a pipe having a foam core layer, based on the measured one or more characteristics of the extruded pipe. In particular it beneficially allows for control of one or more of the characteristics, e.g. in circumferential portions of the cross section of the pipe.

[0014] For example, if the measurement device measures that the wall thickness of a circumferential portion of the cross-section of the pipe is too small and deviates from a predetermined value(s), the local flow adjustment system can be used to increase the flow rate of thermoplastic material in the intermediate flow channel and / or outlet channel which correspond to said portion of deviating wall thickness, such that the wall thickness can be locally corrected and a (more) uniform pipe which has the desired characteristic(s) can be produced.

[0015] In an embodiment, the flow adjustment elements are thermal adjustment elements which are configured to heat and / or cool the respective intermediate flow channel and / or outlet channel. By heating or cooling the thermoplastic material the viscosity of the material may be somewhat increased or decreased respectively. This increase or decrease in viscosity and / or of the wall friction will decrease or increase the flow rate of the thermoplastic material respectively.

[0016] In an embodiment, the thermal adjustment elements are configured to heat or cool the thermoplastic material by plus or minus 10 degrees Celsius, e.g. by plus or minus 5 degrees Celsius, e.g. compared to an average temperature of the distributor head during production. For example, the average temperature is set between 180 and 200 degrees Celsius, e.g. by means of an overall heating device associated with the distributor head.

[0017] In an embodiment, the thermal adjustment elements are each embodied as cartridge heater which are installed in or on or in the proximity of an associated intermediate flow channel or an associated outlet channel.

[0018] For example, multiple thermal adjustment elements are arranged around the perimeter of a channels.

[0019] For example, multiple thermal adjustment elements are arranged along the length of the channels.

[0020] For example, a thermal adjustment element extend along a majority of the length of the associated channel. In an embodiment, each thermal adjustment element is provided with an associated temperature sensor, wherein the associated temperature sensor is configured to measure local temperature data and transmit the data to the controller, e.g. wherein the temperature sensor is configured to measure the temperature of the thermal adjustment element and / or of the associated channel and / or of the thermoplastic material flowing through the respective channel.

[0021] In embodiments, the thermal adjustment elements, possibly in conjunction with the overall heater device, may be used for enhanced control of the temperature of the pipe upon leaving the die head, e.g. allowing for control of the average temperature of the pipe upon leaving the die head.

[0022] In embodiments, the thermal adjustment elements, possibly in conjunction with the overall heater device, may be used for enhanced control of the concentricity of the pipe and / or of layers of the pipe. As known in the art, this, for example, allows for control of variation in wall thickness and / or layer thickness.

[0023] In an embodiment, the distributor head comprises a number of disc-shaped bodies which are each provided with all the flow channels associated with one branching stage, wherein the flow adjustment elements are arranged in at least one of the disc-shaped bodies, preferably wherein the flow adjustment elements are arranged in one or two of the disc-shaped bodies. For example, the disc-shaped bodies are fixed in the distributor head by means of clamping rings engaging on the outer periphery thereof and a core extending through an axial bore in the bodies, e.g. as disclosed in WO94 / 04341.

[0024] In an embodiment, one or more of the disc-shaped bodies are each provided with flow adjustment element cavities, e.g. bores, in proximity to the intermediate flow channels and / or outlet channels, wherein the flow adjustment elements are housed inside these flow adjustment element cavities. Preferably, one or more flow adjustment element bores are provided in one or more of the disc-shaped bodies, which bores extend along the intermediate flow channel and / or outlet channel, wherein the flow adjustment elements are arranged inside of these bores . For example, the thermal adjustment elements are cartridge heaters arranged in the bores so as to extend along the channels.

[0025] In an embodiment, the distributor head comprises a plurality of, preferably three, inlet orifices and concentric outlet orifices, such that the distributor head is configured to produce a pipe with a multi-layered wall. For example, the wall has a foamed-core layer. For example, each inlet orifice is connected to an associated extruder, preferably wherein two extruders are arranged at an angle with respect to a central line of the system, e.g. wherein the two extruders which are arranged at an angle correspond to the inner and outer layer of the wall and wherein an extruder arranged in-line forms the middle or core layer, preferably a foamed core layer. It is also possible, for example, for one inlet orifice to be connected to two flow channel systems in order to form the inner and the outer layer of a tube profile whose wall consists of three layers. In addition, one extruder may, for example, be connected to two inlet orifices by means of a manifold. The layer thickness of each layer is proportional to the flow rate of the thermoplastic material delivered to the distributor head by the extruders, e.g. the higher the flow rate of thermoplastic material of a certain extruder will result in a larger layer thickness of the corresponding layer of the multi-layered wall of the pipe.

[0026] In an embodiment, the controller also is configured to control the operation of the one or more extruders, e.g. to send a control signal to one or more of the extruders, e.g. to in- or decrease the flow rate of the output of thermoplastic material and / or the temperature of the stream of plastic material, e.g. in order to in-or decrease a corresponding layer thickness of the pipe.

[0027] In an embodiment, a die body is attached to the distributor head, and is configured to combine the multiple, e.g. three, concentric material streams emanating from the distributor head with each other to form a pipe having a multi-layered, e.g. three-layered wall.

[0028] In a preferred embodiment, the cross-sectional areas of the flow channels downstream of a branching are generally equal to one another and together are generally equal to the cross- sectional area of the flow channel upstream of the branching. The fact the total cross- sectional area remains about equal ensures that the rate of flow of the material does not drop below a predetermined lower limit.

[0029] In an embodiment, the outlet channels are connected to the outlet orifice via a fan-shaped mouth, wherein the fan-shaped mouths adjoin one another such that the entire outlet orifice is covered by the adjoining fan-shaped mouths. In an embodiment, one or more of the flow adjustment elements are associated with one or more of the fan-shaped mouths.

[0030] In an embodiment, the distributor head is further provided with a heater device which is configured to heat the entire distributor head or a large portion thereof, e.g. the heater device being arranged around the circumference of the distributor head. This heater device is configured to simultaneously heat all channels of the flow channel system or all channels of at least one stage, while the inventive thermal adjustment elements are configured to locally adjust the temperature of the associated channel. In an embodiment, the controller is configured to also control the heater device.

[0031] In an embodiment, the flow adjustment elements are embodied as mechanical flow adjustment elements which are configured to change an effective cross-sectional area of the respective intermediate flow channels and / or outlet channels. For example, a mechanical adjustment element is located where the flow channel system branches into more flow channels, e.g. like a gate which is placed at the junction where the flow channel branches into more channels.

[0032] In an embodiment, the controller comprises an interface for a human operator, e.g. an interface screen, wherein an operator can use the interface to individually control each or all flow adjustment element(s), to adjust the flow rate in the respective intermediate flow channel and / or outlet channel.

[0033] For example, the extruded pipe has a foam core layer which is made of recycled plastic material. For example, the inner and outer layers of the pipe are made of virgin thermoplastic material.

[0034] In an embodiment, the controller is configured to compare the characteristic(s) of the pipe measured by the measurement device with one or more predetermined desired characteristic(s) of the pipe and determines if and by how much the measured characteristic(s) deviate(s) from the desired characteristic(s). If the determined deviation is higher than a predetermined threshold the controller is configured to send a control signal to the flow adjustment elements and / or to a human operator, preferably wherein the control signal is correlated to the determined deviation.

[0035] In an embodiment, the measurement device is a terahertz measurement device which is configured to measure the one or more characteristics, e.g. wall thickness and / or layer thickness(es), of the pipe. In another embodiment, the measurement device is an X-ray measurement device.

[0036] In an embodiment, the system further comprises an in-line cutting device arranged downstream of the cooling device which is configured to cut the pipe into individual pipe elements. For example, a cutting device comprises a carriage configured to move along with the pipe to be cut, wherein a cutting tool is arranged on the carriage, e.g. a chisel cutting tool. For example, the carriage is provided with one or more clamps which clamp onto the pipe so that the carriage moves at the same speed as the pipe.

[0037] In an embodiment, the measurement device is a vision measurement device which is configured to make one or more images of a cut end of the pipe. The images can be analysed, e.g. by a human operator and / or by the measurement device and / or the controller, to determine one or more characteristics of the pipe, e.g. the vision measurement device makes images of the cross-section of the cut-end of the pipe.

[0038] In an embodiment, the vision measurement device is an in-line vision measurement device which is configured to measure one or more characteristics of the cut end of the pipe, e.g. of one cut end of each individual pipe element made during production or of a selected number of the produced cut ends.

[0039] Preferably, the vision measurement device is arranged at or downstream of the cutting device. By this arrangement the in-line the vision measurement device is able to have a view of the cut-end of the pipe, e.g. immediately or shortly after the cut has been made, e.g. allowing for accurate and fast measurement of the characteristic(s) of the pipe. It also allows the measurement device to measure the characteristics of the cut end of the pipe as soon as the cutting device has made the cut, any deviations in the characteristics will thus be noticed as soon as possible allowing for a quicker adjustment of the flow rate, resulting in a more accurate production process.

[0040] In an embodiment, the vision measurement device is an off-line vision measurement device which is configured to measure the one or more characteristics of individual pipe elements produced by the system, e.g. wherein the vision measurement device is arranged in a specific test location, preferably the off-line measurement device and test location are arranged in proximity to the cutting device, e.g. parallel to the cutting device, such that the pipe element can be measured as soon as the pipe element has been cut. By arranging the vision measurement device off-line, it can be assured that the measurement conditions are optimal, e.g. lighting and position of the vision measurement device relative to the cut-end of the pipe, which increases the accuracy of the measurements.

[0041] In an embodiment, the off-line vision measurement device is embodied as flat-bed scanner measurement device, wherein a section of, or the entire individual pipe element is placed on top of the scanner. It is further envisaged that a combination of an in-line and an off-line vision measurement device is used, wherein the in-line measurement device provides continuous measurements, while the off-line measurement device provides measurements with an increased accuracy and reliability compared to the in-line measurement device.

[0042] As discussed herein with regard to all aspects of the invention, the term in-line refers to a measurement device that is integrated into the production process. This does not mean that the device must be physically aligned with specific components such as the extruder, cooling unit, or cutting station. An in-line measurement device may be positioned offset from these components, provided that the pipe element being measured remains within the production line and is not removed from the continuous manufacturing flow. Conversely, the term off-line refers to a measurement system in which the pipe element is removed from the production line for inspection or analysis. This off-line measurement may occur in a different section of the facility or in a separate room, though it may still be located in proximity to the production line.

[0043] In an embodiment, the measurement device, preferably the vision measurement device, is configured to move along the perimeter of the cut end of the pipe, e.g. wherein the measurement device is arranged in proximity to the cut end of the pipe such that the measurement device is not able to measure the entire cut end of the pipe at once. The proximity to the cut end of the pipe allows for an accurate determination of the characteristics of the pipe such as wall thickness or layer thickness. By being configured to move along the perimeter of the pipe, the measurement device is able to make an accurate measurement of the characteristics of a portion of the pipe after which it can move to a different portion of the pipe to make a measurement there.

[0044] In an embodiment, the in-line vision measurement device comprises one or more cameras, preferably just one camera which makes one image covering the entire cross-section of the pipe, e.g. of a non-bevelled cut end of the pipe. In practical embodiments, the pipe many have a diameter between 30 and 500 millimeters. In case of multiple cameras, these can be arranged to each make an image of a respective section of the cut end of the extruded pipe.

[0045] For example, the in-line vision measurement device has one or more high resolution 62 MP (Mega Pixel) camera.

[0046] In an embodiment, the line of sight of the single camera is aligned with the central axis of the extruded pipe. In an embodiment, the vision measurement device is configured to adjust the position and / or line of sight of each of the one or more cameras.

[0047] In an embodiment, the in-line vision measurement device comprises a housing having a viewing window. The one or more cameras, and preferably one or more associated lighting devices, are arranged inside of the housing. The cameras, and preferably lighting devices, are arranged to face, i.e. look out of, the viewing window. Preferably, the viewing window is covered by a transparent covering member, e.g. a glass covering member.

[0048] In an embodiment, a polarizing filter is provided, e.g. placed over the transparent covering member, wherein the polarizing filter is configured to attenuate ambient light, e.g. the ambient light in a production facility wherein the production system is arranged.

[0049] In an embodiment, the vision measurement device comprises one or more guiding rail(s), e.g. vertical and / or horizontal guiding rail(s). The one or more cameras and the one or more lighting devices being movable connected to a respective guiding rail. The vision measurement device comprising one or more actuators configured to move the camera(s) and lighting device(s) along the respective guiding rail.

[0050] In an embodiment, the at least one camera is arranged stationary in the housing and the one or more lighting devices are configured to move in the vertical direction, e.g. move along vertical guiding rails, with respect to the camera.

[0051] In an embodiment, the vision measurement device comprises a display configured to display an imaged cross-section of the pipe and / or the data related to the measured characteristic(s) of the pipe.

[0052] In an embodiment, the housing of the vision measurement device is provided, e.g. at a lower end thereof, with a vibration damping member which is configured to dampen vibrations. It is envisaged that the vision measurement device may be arranged on the production floor, e.g. an in-line vision measurement device, the heavy machinery on the production floor such as the extruders create significant vibrations. The vibration damping member reduces the vibrations of the one or more cameras of the vision measurement device allowing for consistent and high quality images. In an embodiment, the production system further comprises a socketing device, which is configured to form a socket at an end portion of each individual pipe element.

[0053] In an embodiment, the vision measurement device is configured to take an image of a cut end of the individual pipe element. The vision measurement device is arranged such that the vision measurement device is able to make an image of the cut end prior to an end portion being formed into a socket.

[0054] In an embodiment, the cutting device is configured to cut the pipe such that one end of the individual pipe element comprises a bevelled edge and the other end of the individual pipe element comprises a non-bevelled edge, i.e. straight edge. An end portion of the individual pipe element having the non-bevelled edge cut end is formed into a socket by the socketing device. The vision measurement device is arranged such that the vision measurement device takes an image of the non-bevelled cut end prior to the end portion having the non-bevelled cut end being formed into a socket.

[0055] In an embodiment, the production system further comprises a transfer device configured to transfer the individual pipe elements from the cutting device to the socketing device.

[0056] In an embodiment, the transfer device, e.g. a transfer table device, is configured to transfer the individual pipe element from the cutting device to a measurement station prior to transferring the individual pipe element to the socketing device. The vision measurement device is arranged to make an image of the cut end, e.g. the non-bevelled cut end, of the individual pipe element at the measurement station.

[0057] In an embodiment, the distributor head, in-line cooling device, and in-line cutting device are arranged along a production axis. The vision measurement system being arranged laterally adjacent to the production axis, the socketing device being arranged laterally adjacent to the vision measurement device.

[0058] In an embodiment, the vision measurement system is arranged laterally adjacent to the in-line cutting device with respect to the production axis, and the socketing device being arranged laterally adjacent to the vision measurement device.

[0059] In an embodiment, each individual pipe element comprises an upstream and a downstream cut end with respect to the production direction, wherein an upstream end portion, preferably having a non-bevelled cut end, is configured to be formed into a socket by the socketing device. The transfer device is configured to laterally transfer each individual pipe element from the cutting device to the measurement device and socketing device, while maintaining the orientation of the pipe element such that the upstream end remains upstream and the downstream end remains downstream. The measurement device is configured to capture an image of the, preferably non-bevelled, upstream end after which the transfer device is further configured to laterally transfer the pipe element to the socketing device where the upstream end portion is formed into a socket.

[0060] In an embodiment, the controller is also configured to receive data relating to production parameters. Examples of production parameters are composition of the thermoplastic material, amount and / or composition of foaming agent, diameter of pipe, set point of wall I layer thickness(es), the temperature of the distributor head during production, parameters relating to the flow adjustment elements, etc.

[0061] In an embodiment, the controller is also configured to determine one or more relations between the data relating to the one or more characteristics of the pipe as measured by the measurement device, e.g. the vision measurement device, and data relating to the production parameters during extrusion of the pipe for which the one or more characteristics were measured, e.g. using machine learning or artificial intelligence.

[0062] In an embodiment, the controller is configured to transmit the data relating to the one or more characteristics of the pipe to a central server, e.g. a remote central server, and configured to transmit data relating to production parameters during extrusion of the pipe for which the characteristics were determined to the central server, e.g. a remote central server. Preferably, the central server is configured to receive data from multiple remote controllers. The production of a pipe can take a long time, e.g. multiple hours, which makes it difficult to gather enough data from a single production line to provide meaningful insight between the relation of the pipe characteristics and the production parameters, by transmitting the data to a central server data of multiple production lines may be combined, allowing for the determination of more accurate relationships.

[0063] In an embodiment, the central server is configured to determine a relation between the one or more characteristics of the pipe and the production parameters, e.g. via statistical modelling, regression analysis, algorithms, machine learning and / or artificial intelligence.

[0064] In an embodiment, the controller is configured to receive data relating to the relation between the measured characteristics and the production parameters. In an embodiment, the controller is configured to, in response to receiving data relating to the one or more characteristics of the pipe, adjust, or display a recommended adjustment to an operator of, the production parameters based on the relation between the data relating to the one or more characteristics of the pipe and the data relating to the production parameters during extrusion of the pipe for which the characteristics.

[0065] In an embodiment, the controller is configured to receive a set of parameter adjustment rules or models from the central server and apply them locally during the pipe extrusion process.

[0066] In an embodiment, the controller is configured to display a representation of the cross-section of the cut end of the pipe comprising one or more characteristics of the pipe determined by analysing the image of the cut end of the pipe taken by the vision measurement device.

[0067] In an embodiment, the representation comprising a pipe wall represented as a horizontal profile, and variations in wall, and preferably layer, thickness are displayed along the length of the horizontal profile to reflect variations of the wall, and preferably layer, thickness around the pipe's circumference. Preferably, a reference horizontal pipe profile having the desired and constant wall, and preferably layer, thickness is overlayed over the measured horizontal profile.

[0068] In an embodiment, indicators are displayed along the horizontal profile enabling a user to identify the corresponding circumferential positions on the pipe at which the indicators are located.

[0069] In an embodiment, the representation comprises a circular cross-section of the pipe wall with a visually exaggerated wall thickness while still showing the entire cross-section.

[0070] In an embodiment, the representation maintains an outer diameter of the pipe approximately equal to the outer diameter of the image, and wherein the representation reduces an inner diameter of the pipe with respect to the inner diameter of the pipe, thereby visually exaggerating the wall thickness while still showing the entire cross-section of the pipe. The exaggerated wall thickness allows a user to more easily detect any irregularities inside of the pipe wall, e.g. voids in the foam core. In an embodiment, an inner and outer perimeter of the cut end of the pipe is determined in the representation of the cross-section of the cut end and overlayed on top of the respective displayed representation of the cross-section of the cut end of the pipe.

[0071] In an embodiment, estimated boundary layers between the different wall layers are overlayed over the displayed representation of the cross-section of the cut end of the pipe.

[0072] In an embodiment, the controller is configured to determine the maximum and minimum outer diameter of the pipe are determined, and to overlay the maximum and minimum outer diameter at the corresponding location on top of the cross-section.

[0073] In an embodiment, the controller is configured to indicate voids having an area larger than a predetermined area are the representation, e.g. an outline of the void is overlayed on top of the cross-section.

[0074] The invention further relates to a method for producing a pipe from one or more streams of thermoplastic material according to claim 8.

[0075] The features of the system used in the method can be combined with the features of the production system as described herein, and the method described herein can be used with the production system described herein.

[0076] The local flow adjustment system is used for adjustment of the flow rate in the intermediate flow channels and / or outlet, this allows for a more precise production method, e.g. as the characteristic(s) of the pipe can be adapted for different circumferential portions of the pipe.

[0077] In an embodiment, the plurality of flow adjustment elements are thermal adjustment elements which heat and / or cool the associated intermediate flow channel and / or outlet channel and / or the thermoplastic material flowing through the channel, such that the flow rate of the thermoplastic material is changed.

[0078] In an embodiment, the controller individually controls each thermal adjustment element.

[0079] In an embodiment, the controller also controls the one or more extruders, e.g. the controller sends a control signals to the one or more extruders, e.g. to in- or decrease the flow rate of the thermoplastic material delivered by the extruder to the distributor head. In an embodiment, the production system further comprises an in-line cooling device arranged downstream of the distributor head which cools the extruded pipe after it has been formed by the extruder and distributor head.

[0080] In an embodiment, the measurement device measures one or more characteristics are for example wall thickness, layer-thickness(es), shape, and dimensions of the cross-section, if present number and / or size of voids in the foam core, foam cell size, etc.

[0081] In an embodiment, the controller compares the characteristic(s) of the pipe measured by the measurement device to one or more predetermined desired characteristics of the pipe and determines if and by how much the measured characteristic(s) deviate / es from the desired characteristic(s). If the determined deviation is higher than a predetermined threshold the controller sends a control signal to the flow adjustment elements and / or to an operator, preferably wherein the control signal is correlated to the determined deviation.

[0082] In an embodiment, the controller automatically controls the flow adjustment elements based on the data relating to the one or more characteristics of the pipe transmitted by the measurement device. Alternatively, the controller provides a controller interface which allows the human operator to manually send a control signal to one or more flow adjustment elements.

[0083] In an embodiment, the system further comprises an in-line cutting device which cuts the pipe into individual pipe elements.

[0084] In an embodiment, the system further comprises a transfer device and a socketing device. The transfer device transfers the individual pipe element from the in-line cutting device to the socketing device, where the socketing device forms a socket at an end portion of the individual pipe element.

[0085] In an embodiment, the measurement device is a vision measurement device which is configured to make one or more images of a cut end of the pipe. The images may be analysed to determine data related to one or more characteristics of the pipe, e.g. by the measurement device and / or the controller and / or a human operator.

[0086] In an embodiment, the transfer device transfers the individual pipe element from the cutting device to a measurement station where the vision measurement device makes an image of a cut-end of the individual pipe element. The transfer device then transfers the individual pipe element from the measurement station to the socketing device.

[0087] In an embodiment, the in-line vision measurement device makes an image of the cut-end of the individual pipe element, wherein an end portion of the individual pipe element having the imaged cut-end is formed into a socket by the socketing device.

[0088] In an embodiment, the cutting device cuts the pipe such that one end of the induvial pipe element comprises a bevelled edge and the other end of the induvial pipe element comprises a non-bevelled edge, i.e. a straight edge. The vision measurement device makes an image of the non-bevelled end at the measurement station, and the socketing device forms an end portion having the non-bevelled cut end of the individual pipe element into a socket.

[0089] In an embodiment, each thermal adjustment element is provided with an associated temperature sensor, wherein the temperature sensor measures local temperature data and transmits the data to the controller, e.g. wherein the temperature sensor measures the temperature of the thermal adjustment element and / or the associated channel and / or the thermoplastic material flowing through the associated channel.

[0090] In an embodiment, the measurement device measures one or more characteristics along a perimeter of the cut end of the pipe, wherein the measurement device transmits data relating to the characteristics to the controller.

[0091] In an embodiment, the measurement device, preferably a vision measurement device, e.g. a camera thereof, is configured to move along the perimeter of the cut end of the pipe. For example, the measurement device measures the one or more characteristics of a certain portion of the cross-section of the pipe before moving along the perimeter such that another portion of the pipe can be measured, this is done until the entire cut end of the pipe has been measured, wherein the controller or measurement device combines the measurements of each different circumferential portion in order to determine the characteristic(s) of the entire cut-end of the pipe. The measurement device can be arranged close to the cut end of the pipe, which allows for accurate measurement of the characteristics of each portion of the cut end of the pipe. By combining the accurate measurement of each portion it is possible to provide an accurate measurement of the characteristics of the entire cut end of the pipe.

[0092] In an embodiment, the controller compares the measured characteristic(s) of the pipe, e.g. of different circumferential portions of the pipe, with one or more predetermined values for the characteristic(s), and - when necessary - adjusts or suggests an adjustment to an operator of the flow rate in the one or more intermediate flow channels and / or outlet channels to reduce or eliminate the deviation. This can be done, for example, by adjusting the flow adjustment elements for each channel that corresponds to a deviating portion. For example, if the wall thickness of one or two portions of the cut end of the pipe is locally thinner than the predetermined threshold value of the wall thickness, the controller may send a signal to the flow adjustment elements associated with the channels which correspond to the respective one or two deviating portions, e.g. the controller sends a control signal to the thermal adjustment elements such that these elements heat the channels which increases the flow rate and thus the wall thickness.

[0093] In an embodiment, the distributor head comprises a plurality of, e.g. three, inlet orifices and concentric outlet orifices, such that a pipe with a multi-layered wall is produced. In embodiments, the wall comprises a foam core layer. For example, each inlet orifice is connected to an associated extruder.

[0094] In embodiments, two extruders are arranged at an angle with respect to a central line of the production system, e.g. wherein the two extruders which are arranged at an angle corresponding to the inner and outer layer of the wall and an extruder arranged in-line forms the middle / core layer, preferably a foam core layer.

[0095] It is also possible, for example, for one inlet orifice to be connected to two flow channel systems in order to form the inner and the outer layer of a tube profile whose wall consists of three layers. In addition, one extruder may, for example, be connected to two inlet orifices by means of a manifold.

[0096] In an embodiment, the measurement device measures the layer thickness of each individual layer of a multi-layered pipe wall, and / or the foam cell size of the foamed core layer. For example, the measurement device measures one or more of the layer thickness of each layer, wall thickness, foam cell size, presence of voids, size of voids, wherein the measurement data is transmitted to the controller. Preferably, the controller sends a control signal to the extruder which corresponds to a deviating layer, and / or to the flow adjustment elements in order to correct the flow rate in a flow channel system or one or more individual channels respectively.

[0097] In an embodiment, a human operator analyses the measurements, e.g. images, made by the measurement device, preferably vision measurement device, the operator determining one or more characteristics of the pipe, and wherein the operator sends data relating to the one or more characteristics of the pipe to the controller and / or a control signal to the controller.

[0098] In an embodiment, the controller is configured to compare the characteristic(s) of the pipe measured by the measurement device to one or more predetermined desired characteristics of the pipe and to send a control signal to a haul-off device, e.g. to control the haul-off speed, e.g. allowing to control the weight per meter of the pipe.

[0099] In an embodiment, the controller is configured to compare the characteristic(s) of the pipe measured by the measurement device to one or more predetermined desired characteristics of the pipe and to send a control signal to a foaming agent dosing device for dosing foaming agent, e.g. associated with the extruder producing the foam layer(s) of the pipe. For example, a foaming agent is fed under pressure to the polymer melt in the extruder and the amount of foaming agent is controlled by a valve. In an embodiment, a foaming agent is combined with plastic granules fed into the extruder.

[0100] In an embodiment, the measurement device is an in-line vision measurement device which is arranged at or in line with the cutting device and is configured to measure the characteristic(s) of the cut end of the pipe, e.g. one or more cameras directed onto the cut end to determine one or more of the wall thickness, layer thickness(es), and / or foam cell size, etc.

[0101] For example, the in-line vision measurement device comprises a carriage configured to move along with the cut pipe end, wherein one or more cameras are arranged on the carriage. For example, the carriage is provided with one or more clamps which clamp onto the pipe so that the carriage moves at the same speed as the pipe.

[0102] For example, the one or more cameras are mounted to revolve, at least over an arc segment, about a longitudinal pipe axis, e.g. allowing to image a sector of the cut end per camera.

[0103] For example, the one or more cameras are stationary arranged at or in line with the cutting device, so not movable in axial direction of the production line. Also, in such embodiment, for example, the one or more cameras could be mounted to revolve, at least over an arc segment, about a longitudinal pipe axis, e.g. allowing to image a sector of the cut end per camera.

[0104] In an embodiment, the vision measurement device is an off-line vision measurement device arranged at a test location, wherein the individual pipe elements are transferred to the test location where the vision measurement device measures the characteristic(s) of the pipe element.

[0105] The one or more cameras of the vision measurement device may provide a high resolution image of the cut end. For example, when a pipe having a foam (core) layer is produced, the one or more cameras may be configured to have a resolution allowing to measure the foam cell size.

[0106] In embodiments, the vision measurement device has one or more associated lighting devices configured to provide illumination of the cut end, e.g. LED lighting devices. For example, the one or more lighting devices are configured to provide for a controllable illumination of the cut end, e.g. to allow for a desired, e.g. variable, intensity and / or spectrum and / or spatial position of the lighting device(s) relative to the cut end.

[0107] In an embodiment, a combination of an in-line and an off-line vision measurement device is used, wherein the in-line measurement device provides more or less continuous measurements during production, while the off-line measurement device provides measurements with an increased accuracy and reliability compared to the in-line measurement device.

[0108] In an embodiment, the controller also receives data relating to production parameters.

[0109] In an embodiment, the controller also receives control signals from an operator, e.g. an operator analyses the representation of the cross section of the cut end of the pipe and / or one or more characteristics of the pipe and on basis of the analyses sends a control signal to the controller.

[0110] In an embodiment, the controller also determines a relation between the data relating to the one or more characteristics of the pipe and the data relating to the production parameters during extrusion of the pipe for which the characteristics were measured, e.g. using machine learning or artificial intelligence.

[0111] In an embodiment, the controller also transmits the data relating to the one or more characteristics of the pipe to a central server, e.g. a remote central server, and transmits data relating to production parameters during extrusion of the pipe for which the characteristics were measured to the central server, e.g. a remote central server. Preferably, the central server is receiving data from multiple remote controllers. In an embodiment, the central server determines a relation between the one or more characteristics of the pipe and the production parameters, e.g. via statistical modelling, regression analysis, or algorithms, machine learning and / or artificial intelligence.

[0112] In an embodiment, the controller receives data relating to the relation between the measured characteristics and the production parameters.

[0113] In an embodiment, the controller, in response to receiving data relating to the one or more characteristics of the pipe, adjusts, or displays a recommended adjustment to an operator of, the production parameters based on the relation between the data relating to the one or more characteristics of the pipe and the data relating to the production parameters during extrusion of the pipe for which the characteristics.

[0114] In an embodiment, the controller receives a set of parameter adjustment rules or models from the central server and apply them locally during the pipe extrusion process.

[0115] In an embodiment, the controller displays a representation of the cross-section of the cut end of the pipe comprising one or more characteristics of the pipe determined by analysing the image of the cut end taken by the measurement device.

[0116] In an embodiment, the one or more characteristics comprise the wall thickness of the pipe along the perimeter thereof and / or the radius of the pipe along the circumference thereof.

[0117] In an embodiment, the pipe is a multi-layer pipe having a foam core, wherein the one or more characteristics comprise the layer thickness of the pipe along the perimeter thereof and / or the wall thickness of the pipe along the perimeter and / or the number and / or size of voids within the foam core and / or foam cell size.

[0118] In an embodiment, the cross-section of pipe wall is depicted as a linear profile, e.g. horizontal profile, and variations in wall thickness, e.g. also layer thickness(es) are shown along the length of the profile to reflect variations of the wall thickness, and preferably layer thickness around the pipe's circumference. Preferably, a reference pipe profile having the desired and constant wall, and preferably layer, thickness is overlayed over the measured profile.

[0119] Preferably, the estimated boundary layers between the different wall layers are overlayed over the displayed horizontal profile. Preferably, indicators are displayed along the horizontal profile enabling a user to identify the corresponding circumferential positions on the pipe at which the indicators are located.

[0120] In an embodiment, the circular cross-section is displayed with a visually exaggerated wall thickness while still showing the entire cross-section.

[0121] In an embodiment, the representation maintains an outer diameter of the pipe approximately equal to the outer diameter of the image, and wherein the representation reduces an inner diameter of the pipe with respect to the inner diameter of the pipe, thereby visually exaggerating the wall thickness while still showing the entire cross-section of the pipe. The exaggerated wall thickness allows a user to more easily detect any irregularities inside of the pipe wall, e.g. voids in the foam core. Preferably, an inner and outer perimeter of the cut end of the pipe is determined in the representation of the cross-section of the cut end and overlayed on top of the respective displayed representation of the cross-section of the cut end of the pipe.

[0122] In an embodiment, the maximum and minimum outer diameter of the pipe are determined, wherein the maximum and minimum outer diameter are overlayed at the corresponding location on top of the cross-section.

[0123] In an embodiment, voids in a foam-core layer having an area larger than a predetermined area are indicated in the representation, e.g. an outline of the void is overlayed on top of the cross-section.

[0124] The invention further relates to a distributor head for forming a pipe from one or more streams of thermoplastic material, wherein the distributor head comprises at least an inlet orifice for a stream of thermoplastic material which is configured to be connected to an extruder, and an outlet orifice of annular cross section, wherein the distributor head comprises at least one flow channel system which comprises an inlet channel which is at one end thereof connected to the inlet orifice, which inlet channel, in a number of stages of branchings and intermediate flow channels, branches into a number of outlet channels terminating on a periphery around the centre line of the outlet orifice, which outlet channels open into the outlet orifice, wherein the distributor head is provided with a local flow adjustment system which comprises a plurality of flow adjustment elements which are each configured to adjust the flow rate of the thermoplastic material in an associated intermediate flow channel and / or outlet channel.

[0125] Preferably, all intermediate flow channels and / or outlet channels of at least one stage are provided with an associated flow adjustment element.

[0126] The invention also relates to a disc-shaped body which are provided with all flow channels associated with one branching stage of the flow channel system described herein, wherein the disc-shaped body further is configured to accommodate the flow adjustment elements, preferably thermal adjustment elements.

[0127] The invention also relates to the combination of a distributor head and a controller as discussed herein.

[0128] A second aspect of the invention relates to a system for producing a pipe from one or more streams of thermoplastic material, wherein the system comprises an extruder and a distributor head, wherein distributor head comprises at least an inlet orifice for a stream of thermoplastic material which is connected to the extruder, and an outlet orifice of annular cross section, wherein the distributor head comprises at least one flow channel system which comprises an inlet channel which is at one end thereof connected to the inlet orifice, which inlet channel, in a number of stages of branchings and intermediate flow channels, branches into a number of outlet channels terminating on a periphery around a centre line of the outlet orifice, which outlet channels open into the outlet orifice, characterized in that the distributor head is provided with a local flow adjustment system which comprises a plurality of flow adjustment elements which are each configured to adjust the flow rate of the thermoplastic material in an associated intermediate flow channel and / or outlet channel.

[0129] It will be appreciated that the system of the second aspect and / or one or more components thereof can be embodied as discussed herein with reference to the first, third, fourth, fifth and sixth aspect of the invention. The flow rate of thermoplastic material through the flow channel system(s) determines certain characteristics of the produced pipe, e.g. the wall thickness, etc. By changing the flow rate, one or more of the characteristics of the pipe can be adjusted. The branching of the flow channel system allows for a generally even distribution of the thermoplastic material which is introduced in the inlet orifice over the outlet orifice. Each outlet channel opens into a particular portion of the outlet orifice; each outlet channel thus corresponds to a respective circumferential portion of the cross-section of the outlet orifice and thus a respective circumferential portion of the produced pipe.

[0130] The local flow adjustment system allows for the individual adjustment of the flow rate in intermediate flow channels and / or outlet channels. The local flow adjustment system can thus be applied to change the flow rate in the channels that correspond to particular circumferential portions of the pipe. This allows for adjustment of one or more of the characteristics, e.g. wall thickness, layer thickness(es), foam cell size, of the whole pipe as well as specific circumferential portions of the pipe. In general, this allows for a further optimized control of the production process.

[0131] In an embodiment, all intermediate flow channels and / or all outlet channels of at least one stage, e.g. the first stage, are each provided with an associated flow adjustment element.

[0132] In an embodiment, the flow adjustment elements are thermal adjustment elements which are configured to heat and / or cool, preferably to heat, the respective intermediate flow channel and / or outlet channel.

[0133] In an embodiment, wherein the local flow adjustment system comprises a controller which is configured to individually control each flow adjustment element, so as to adjust the flow rate in the associated intermediate flow channel and / or outlet channel.

[0134] The second aspect of the invention further relates to a method for producing a pipe from one or more streams of thermoplastic material, wherein use is made of a production system which comprises an extruder and a distributor head, wherein distributor head comprises at least an inlet orifice for a stream of thermoplastic material, which is connected to the extruder, and an outlet orifice of annular cross section, wherein the distributor head comprises at least one flow channel system which comprises an inlet channel which is at one end thereof connected to the inlet orifice, which inlet channel, in a number of stages of branchings and intermediate flow channels, branches into a number of outlet channels terminating on a periphery around the centre line of the outlet orifice, which outlet channels open into the outlet orifice, wherein the distributor head is provided with a local flow adjustment system which comprises a plurality of flow adjustment elements which are each configured to adjust the flow rate of the thermoplastic material in an associated intermediate flow channel and / or outlet channel, wherein the method comprises the step of operating the flow adjustment element to adjust the flow rate in the one or more of the intermediate flow channels and / or outlet channels.

[0135] In an embodiment, intermediate flow channels and / or outlet channels of at least one stage are provided with an associated flow adjustment element.

[0136] In an embodiment, the plurality of flow adjustment elements are thermal adjustment elements which are operated to heat and / or cool the associated intermediate flow channel and / or outlet channel and / or the thermoplastic material flowing through the channels, such that the flow rate of the thermoplastic material is changed.

[0137] In an embodiment, a controller controls each flow adjustment element, so as to adjust the flow rate in the associated intermediate flow channel and / or outlet channel.

[0138] A third aspect of the invention relates to a production system for producing a pipe having a multi-layered wall from streams of thermoplastic material, said wall including at least one foam layer, wherein the system comprises:

[0139] - a distributor head and extruders, wherein the distributor head comprises a plurality of, preferably three, inlet orifices and concentric outlet orifices, such that the distributor head is configured to produce a pipe with a multi-layered wall,

[0140] - a foaming agent dosing device for dosing foaming agent, which foaming agent dosing device is associated with the extruder producing the foam layer(s) of the pipe,

[0141] - an in-line cooling device arranged downstream of the distributor head which is configured to cool the extruded pipe, - an in-line cutting device arranged downstream of the cooling device which is configured to cut the pipe into individual pipe elements,

[0142] - an in-line vision measurement device which is configured to measure one or more characteristics of the cut end of the pipe, e.g. one cut of an individual pipe element, wherein the in-line vision measurement device is configured to determine data relating to the characteristic(s) of the pipe, and wherein the measurement device is configured to transmit said data to a controller, and / or to display said data to a human operator so as to allow the operator to manually control the controller, wherein the controller is configured to control the foaming agent dosing device at least in part on the basis of said data.

[0143] It will be appreciated that this system of the third aspect and / or one or more components thereof can be embodied as discussed herein with reference to the first and / or other aspects of the invention.

[0144] It will be appreciated that the third aspect of the invention allows for enhanced control of the formation of the foam layer.

[0145] For example, the one or more characteristics(s) of the pipe are one or more of: the number of voids in the foam core, the size of voids in the foam core, the foam cell size, the location of voids in the foam core.

[0146] For example, the in-line vision measurement device comprises a carriage configured to move along with the cut pipe end, e.g. along a linear guide, wherein one or more cameras are arranged on the carriage. For example, the carriage is provided with one or more clamps which clamp onto the pipe so that the carriage moves at the same speed as the pipe. For example, the one or more cameras are mounted to revolve, at least over an arc segment, about a longitudinal pipe axis, e.g. allowing to image a sector of the cut end per camera.

[0147] The third aspect of the invention also relates to a method for producing a pipe from one or more streams of thermoplastic material, wherein use is made of the production system, and wherein the measurement device transmits data relating to the characteristic(s) of the pipe to the controller, and wherein the controller controls the foaming agent dosing device, at least in part on the basis of this data.

[0148] As discussed in the context of the first aspect of the invention, data from the in-line vision measurement device may, optionally, also be used in the control of one or more other components of the system, e.g. one or more of the extruders, etc.

[0149] The third aspect of the invention also relates to the combination of a foaming agent dosing device configured for use with an extruder to form a foam layer of a pipe having a multilayered wall from streams of thermoplastic material and a vision measurement device configured to measure one or more characteristics of a cut end of the pipe, and wherein the foaming agent dosing device is configured to be controlled, at least in part, on the basis of data transmitted by the vision measurement device. Herein the vision measurement device can be an in-line vision measurement device, as preferred, or an off-line vision measurement device, e.g. as described with reference to the first aspect of the invention.

[0150] The third aspect also relates to a method for producing by extrusion of a pipe having a foam layer from streams of thermoplastic material, wherein a vision measurement device measures one or more characteristics of a cut end of the pipe, and wherein data related to said measurements are used in the control of the dosing of a foaming agent used in forming the foam layer. Herein the vision measurement device can be an in-line vision measurement device or an off-line vision measurement device, e.g. as described with reference to the first aspect of the invention.

[0151] A fourth aspect of the invention relates to a production system for producing a pipe from one or more streams of thermoplastic material, wherein the system comprises: a distributor head and one or more extruders; an in-line cooling device arranged downstream of the distributor head, wherein the cooling device is configured to cool the extruded pipe; an in-line cutting device arranged downstream of the cooling device which is configured to cut the pipe into individual pipe elements; a socketing device configured to form a socket at an end portion of the individual pipe elements, a transfer device configured to transfer the individual pipe element to the socketing device, a vision measurement device configured to take an image of a cut end of the individual pipe element, wherein the vision measurement device is arranged such that the vision measurement device is able to make an image of the cut end prior to that the end portion having the cut end being formed into a socket.

[0152] It will be appreciated that this system of the fourth aspect and / or one or more components thereof can be embodied as discussed herein with reference to the first, second, third, fifth, and / or sixth aspect of the invention.

[0153] It will be appreciated that the fourth aspect of the invention allows for an operator or the system itself, to quickly identify any irregularities or defects in the produced pipes. This visual feedback allows the system and / or operator to make timely adjustments to the production process, thereby improving overall pipe quality and reducing manufacturing errors.

[0154] In an embodiment, the cutting device is configured to cut the pipe such that one end of the individual pipe element comprises a bevelled edge and the other end of the individual pipe element comprises a non-bevelled edge, i.e. straight edge. An end portion of the individual pipe element having the non-bevelled edge cut end is formed into a socket by the socketing device. The vision measurement device is arranged such that the vision measurement device takes an image of the non-bevelled cut end prior to said end portion is formed into a socket.

[0155] In an embodiment, the transfer device is configured to transfer the individual pipe elements from the cutting device to a measurement station prior to transferring the individual pipe elements to the socketing device. The vision measurement device is arranged to take an image of the cut end, e.g. the non-bevelled cut end, of the individual pipe element at the measurement station.

[0156] In an embodiment, the distributor head, in-line cooling device, and in-line cutting device are arranged sequentially along a production axis. The vision measurement system being arranged laterally adjacent to the production axis, the socketing device being arranged laterally adjacent to the vision measurement device.

[0157] In an embodiment, the vision measurement system is arranged laterally adjacent to the in-line cutting device with respect to the production axis, and the socketing device being arranged laterally adjacent to the vision measurement device. In an embodiment, each individual pipe element comprises an upstream and a downstream cut end with respect to the production direction, wherein the, preferably non-bevelled, upstream end portion is configured to be formed into a socket by the socketing device. The transfer device is configured to laterally transfer each individual pipe element from the cutting device to the measurement device and socketing device, while maintaining the orientation of the pipe element such that the upstream end remains upstream and the downstream end remains downstream. The measurement device is configured to capture an image of the upstream end — preferably non-bevelled — after which the transfer device is further configured to laterally transfer the pipe element to the socketing device, wherein the socketing device is configured to form the upstream end portion into a socket.

[0158] In an embodiment, the system further comprises a controller configured to control one or more production parameters based on the image of the cut end of the individual pipe elements taken by the vision measurement device.

[0159] In an embodiment, the distributor head is a distributor head as described herein, e.g. as described in claim 1 or claim 15. Optionally, the controller is configured to individually control each flow adjustment element, so as to adjust the flow rate in the associated intermediate flow channel and / or outlet channel.

[0160] In an embodiment, the system is configured to produce a multi-layer pipe having a foam core layer.

[0161] The fourth aspect of the invention further relates to a method for producing a pipe from one or more streams of thermoplastic material wherein use is made of a production system as described herein. The method comprises the steps of: extruding a pipe using the one or more extruders and distributor head; cooling the pipe using the in-line cooling device; cutting the pipe into individual pipe elements using the in-line cutting device; transferring the individual pipe elements to a measurement station using the transferring device; making an image of a cut-end of the individual pipe element at the measurement station using the vision measurement device; transferring the individual pipe element from the measurement station to the socketing device using the transferring device; forming a socket at an end portion of the induvial pipe element using the socketing device. In an embodiment, the cutting device cuts the pipe such that the downstream end of the individual pipe element comprises a bevelled edge and the upstream end of the individual pipe element comprises a non-bevelled edge, i.e. straight edge. The vision measurement device makes an image of the non-bevelled upstream end at the measurement station, and the socketing device forms an end portion of the individual pipe element having the nonbevelled upstream end into a socket.

[0162] A firth aspect of the invention relates to an in-line vision measurement device configured to measure one or more characteristics of an extruded multi-layer pipe comprising a foam core.

[0163] It will be appreciated that the device of the fifth aspect and / or one or more components thereof can be embodied as discussed herein with reference to the first, second, third, fourth, and sixth aspect of the invention.

[0164] The in-line vision measurement device according to the fifth aspect of the invention provides real-time, non-contact measurement of one or more characteristics of an extruded multi-layer pipe comprising a foam core. This enables immediate detection of deviations in pipe geometry, e.g. shape, wall I layer thickness(es). Improving process control and early defect detection, which reduces material waste and downtime. As a result, overall product quality is enhanced, and production efficiency is significantly increased.

[0165] In an embodiment, the one or more characteristics comprise the thickness of each layer of the multi-layer pipe in the direction along the perimeter of the pipe and / or the size / number of voids in the foam core and / or the inner and outer diameter of the pipe along the circumference thereof.

[0166] In an embodiment, the vision measurement device comprises a camera configured to make an image of a cut-end of the pipe, e.g. a multi-layer pipe. For example, the device just has one camera. For example, the camera is a high resolution 62 MP camera.

[0167] In an embodiment, the line of sight of the camera, e.g. the single camera, is aligned with the central axis of the extruded pipe. This ensures that the cut-end is centralised in the image, minimising distortion of the section of the image comprising the cut-end. Furthermore, the position of the central axis of the extruded pipe is constant in a production line regardless of the diameter of the extruded pipe. By arranging the camera such that the line of sight is aligned with the central axis of the extruded pipe, there is no need to adjust the position and / or orientation of the camera for different diameter pipes.

[0168] In an embodiment, the vision measurement device comprises multiple cameras, each configured to make an image of a respective section of the cut end of the extruded pipe. As known in the art, the images may be stitched to achieve a complete image of the crosssection of the pipe.

[0169] In an embodiment, the vision measurement device is configured to adjust the position and / or the line of sight of each of the one or more cameras.

[0170] In an embodiment, the vision measurement device has one or more lighting devices configured to provide illumination of the cut end, e.g. LED lighting devices. For example, the one or more lighting devices are configured to provide for a controllable illumination of the cut end, e.g. to allow for a desired, e.g. variable, intensity and / or spectrum and / or spatial position of the lighting device(s) relative to the cut end. For example, by changing the spatial position of the lighting devices with respect to the camera the contrast between voids in the foam core layer with respect to the rest of the foam core layer can be increased allowing for easier detection.

[0171] In an embodiment, the vision measurement device comprises a housing having a viewing window. The one or more cameras, and preferably the one or more lighting device, are arranged inside of the housing. The cameras, and preferably lighting devices, are arranged to face, i.e. look out of, the viewing window. Preferably, the viewing window is covered by a transparent covering member, e.g. a glass covering member.

[0172] In an embodiment, a polarizing filter is provided, e.g. placed over the transparent covering member, wherein the polarizing filter is configured to attenuate ambient light, e.g. the ambient light in a production facility.

[0173] In an embodiment, the vision measurement device comprises one or more guiding rail(s), e.g. vertical and / or horizontal guiding rail(s). The one or more cameras and the one or more lighting devices being movable connected to a respective guiding rail. The vision measurement device comprising one or more actuators configured to move the camera(s) and lighting device(s) along the respective guiding rail. In an embodiment, the camera is arranged stationary in the housing and the one or more lighting devices are configured to move in the vertical direction, e.g. move along vertical guiding rails, with respect to the camera.

[0174] In an embodiment, the vision measurement device comprises a display configured to display the measured characteristics of the pipe.

[0175] In an embodiment, the housing is provided at a lower end thereof with a damping member that is configured to damp vibrations, e.g. the dampening vibrations origination from a production floor on which the housing is placed.

[0176] A sixth aspect of the invention relates to a method for displaying one or more characteristics of an extruded pipe to a user, wherein the method comprises: taking one or more images of a cut end of the pipe using a vision measurement device; determining one or more characteristics of the pipe based on the one or more images; displaying a representation of the cross-section of the cut end of the pipe comprising the one or more characteristics of the pipe.

[0177] It will be appreciated that this system of the sixth aspect and / or one or more components thereof can be embodied as discussed herein with reference to the first, second, third, fourth, and fifth aspect of the invention.

[0178] It will be appreciated that by displaying a representation of the cross-section of the cut end of the pipe, including one or more characteristics of the pipe, according to the sixth aspect of the invention. The method enables an operator to quickly identify any irregularities or defects. This visual feedback allows the operator to make timely adjustments to the production process, thereby improving overall pipe quality and reducing manufacturing errors.

[0179] In an embodiment, the one or more characteristics comprise the wall thickness of the pipe along the perimeter thereof and / or the radius of the pipe along the circumference thereof.

[0180] In an embodiment, the pipe is a multi-layer pipe having a foam core, wherein the one or more characteristics comprise the layer thickness of the pipe along the perimeter thereof and / or the wall thickness of the pipe along the perimeter and / or the number and / or size of voids within the foam core and / or foam cell size. In an embodiment, the pipe wall is represented as a horizontal profile, and variations in wall, and preferably layer, thickness are shown along the length of the horizontal profile to reflect variations of the wall, and preferably layer, thickness around the pipe's circumference.

[0181] In an embodiment, a reference horizontal pipe profile having the desired and constant wall, and preferably layer, thickness is overlayed over the displayed horizontal profile.

[0182] In an embodiment, the estimated boundary layers of the different wall layers are overlayed over the displayed representation of the cross section of the cut end of the pipe, e.g. the horizontal profile.

[0183] In an embodiment, indicators are displayed along the horizontal profile enabling a user to identify the corresponding circumferential positions on the pipe at which the indicators are located.

[0184] In an embodiment, the cross-section of the pipe is displayed with a visually exaggerated wall thickness while still showing the entire cross-section.

[0185] In an embodiment, the representation maintains an outer diameter of the pipe approximately equal to the outer diameter of the image, and wherein the representation reduces an inner diameter of the pipe with respect to the inner diameter of the pipe, thereby visually exaggerating the wall thickness while still showing the entire cross-section of the pipe. The exaggerated wall thickness allows a user to more easily detect any irregularities inside of the pipe wall, e.g. voids in the foam core. Preferably, an inner and outer perimeter of the cut end of the pipe is determined in the representation of the cross-section of the cut end and overlayed on top of the respective displayed representation of the cross-section of the cut end of the pipe.

[0186] In an embodiment, the maximum and minimum outer diameter of the pipe are determined, wherein the maximum and minimum outer diameter are overlayed at the corresponding location on top of the cross-section.

[0187] In an embodiment, voids in the foam core having an area larger than a predetermined area are indicated in the representation, e.g. an outline of the void is overlayed on top of the crosssection. In an embodiment, multiple different representations may be displayed next to and / or above and below each other.

[0188] The aspects of the invention are envisaged, for example, for the production of circular crosssection pipes for transportation of liquid or gas, e.g. water pipes, e.g. for water mains, sewer pipes, gas pipes, e.g. for natural gas. For example the diameter of the pipes are between 40 millimeter and 630 millimeter. For example, the pipe has an outer layer, inner layer, and a foam core in between.

[0189] For example, the pipes, or layer(s) thereof, are made of PVC, PE, PP.

[0190] For example, the individual pipe elements have a length of 6 meters.

[0191] The invention will now be described in reference to the figures. In the figures:

[0192] Fig. 1 shows a schematic view of the system,

[0193] Fig. 2 shows a schematic view of the distributor head,

[0194] Fig. 3 shows a schematic view of the flow channel system,

[0195] Fig. 4 shows an exploded view of the distributor head,

[0196] Fig. 5 shows a block diagram of the flow rate adjustment system,

[0197] Fig. 6 shows a schematic view of a different embodiment of the system,

[0198] Fig. 7 shows a schematic view of the in-line vision measurement system,

[0199] Figs. 8a-c show different representation of the cross-section of the cut end of an imaged pipe.

[0200] Figure 1 shows the production system 1 for producing a multi-layer pipe 2 for three streams of thermoplastic material.

[0201] The system comprises a distributor head 10 and three extruders 20a, 20b, 20c, wherein the three extruders 20a, 20b, 20c are connected to the distributor head 10.

[0202] The extruders 20a, 20b, 20c supply thermoplastic material to the distributor head 10 which distributes the thermoplastic material, resulting in three concentric annular streams of thermoplastic material. Two extruders 20b, 20c are arranged at an angle with respect to a central line 17 of the system which correspond to the inner and outer layer of the wall of pipe. The in-line extruder 20a forms a middle / core layer, preferably a foam core layer. A die body 30 is attached downstream to the distributor head 10, wherein the die body 30 is configured to combine the three concentric annular streams of thermoplastic material with each other to form a pipe 2 having a three-layered wall.

[0203] A cooling device 40 is arranged downstream of the die body 30, wherein the cooling device is configured to cool the pipe 2 after it has left the die body 30.

[0204] A haul-off device 55 is arranged downstream of the cooling device 40, for example the haul- off device having a controllable haul-off speed for the pipe 2.

[0205] An in-line pipe cutting device 70 is arranged downstream and is configured and operated to cut the extruded pipe 2 into individual pipe elements.

[0206] Figure 2 shows the distributor head 10 which comprises the inlet orifices 11a, 11 b, 11 c for a stream of thermoplastic material which are each configured to be connected an extruder 20a, 20b, 20c.

[0207] In a preferred embodiment, the cross-sectional areas of the flow channels downstream of a branching are equal and together are essentially equal to the cross-sectional area of the flow channel upstream of the branching. The fact the total cross-sectional area remains equal ensures that the rate of flow of the material does not drop below a predetermined lower limit.

[0208] In an embodiment, as shown, the outlet channels are connected to the outlet orifice via a fanshaped mouth, wherein the fan-shaped mouths adjoin one another such that the entire outlet orifice is covered by the adjoining fan-shaped mouths.

[0209] The distributor head further comprises three concentric outlet orifices of annular cross section 16a, 16b, 16c.

[0210] Each inlet orifices 11a, 11b, 11c is connected to a respective annular outlet orifice 16a, 16b, 16c by a flow channel system.

[0211] Each flow channel system comprises an inlet channel 12a, 12b, 12c which is at one end thereof connected to the inlet orifice 11a, 11 b, 11c. The inlet channel 12a, 12b, 12c, in a number of stages of branchings and intermediate flow channels 13a, 13b, 13c, branches into a number of outlet channels 14a, 14b, 14c terminating on a periphery around a centre line of the outlet orifices 17, which outlet channels 14a, 14b, 14c open into an outlet orifice 16a, 16b 16c, via a number of fan-shaped mouths 15a, 15b, 15c.

[0212] The distributor head 10 is provided with a local flow adjustment system 50 which comprises a plurality of flow adjustment elements 51 which are each configured to adjust the flow rate of the thermoplastic material in an associated intermediate flow channel 13a, 13b, 13c and / or outlet channel 14a, 14b, 14c.

[0213] For clarity only two flow adjustment elements 51 are shown in the figure, however it is envisaged that all intermediate flow channels 13a, 13b, 13c and / or outlet channels 14a, 14b, 14c of at least one of the stages or of multiple stages, possibly of all stages are provided with associated flow adjustment elements 51.

[0214] The flow adjustment elements 51 are in this example, as preferred, thermal adjustment elements which are configured to heat the respective intermediate flow channel 13a, 13b, 13c, and / or outlet channel 14a, 14b, 14c, and / or the thermoplastic material flowing through the channels. In another embodiment, the elements 51 could be configured to provide for a cooling effect, e.g. using a liquid coolant or Peltier effect. In another embodiment, the elements 51 could be configured to selectively provide for heating or cooling.

[0215] The thermal adjustment elements 51 are each embodied as cartridge heater which is installed to have an effect on the associated intermediate flow channel 13a, 13b, 13c or outlet channel 14a, 14b, 14c.

[0216] For example, the thermal adjustment elements 51 each extend along the length, e.g. a majority of the length, of the associated channel.

[0217] As shown only one thermal adjustment element 51 is arranged for an associated channel, however, it is also envisaged that multiple thermal adjustment elements 51 are arranged around the perimeter of a channels and / or arranged along the length of the channel.

[0218] The distributor head 10 may be provided with an overall heater device (not shown) which is configured to heat the entire distributor head or a large portion thereof. The overall heater device may be configured to simultaneously heat all channels of the flow channel system or all channels of at least one stage, while the thermal adjustment elements 51 are configured to locally adjust the temperature of the associated channel. For example, the overall heater device is an annular device fitted on the outer circumference of the distributor head, e.g. an electric heater device.

[0219] The local flow adjustment system comprises a controller 52 which is configured to individually control each flow adjustment element 51 so as to adjust the flow rate in the associated intermediate flow channel 13a, 13b, 13c and / or outlet channel 14a, 14b, 14c.

[0220] The controller 52 sends a control signal to each flow adjustment element 51.

[0221] The controller 50 may be configured to also control the overall heater device.

[0222] The controller 52 may comprise a user interface 53, e.g. an interface screen, wherein an operator can use the interface 53 to control each or all flow adjustment element(s) to adjust the flow rate in the respective intermediate flow channel and / or outlet channel.

[0223] The system further comprises a measurement device 60 which is configured to measure one or more characteristics of the pipe 2 after the pipe 2 has been cooled by the cooling device 40.

[0224] In an embodiment, the measurement device 60 transmits data relating to the measured characteristic(s) of the pipe to the controller 52.

[0225] The controller 52 may be configured to compare the characteristic(s) of the pipe measured by the measurement device 60 to one or more predetermined desired characteristics of the pipe and determines if and by how much the measured characteristic(s) deviate(s) from the desired characteristic(s). If the determined deviation is higher than a predetermined threshold the controller 52 is configured to send a control signal to the flow adjustment elements 51, preferably the control signal is correlated to the determined deviation, and / or to an operator.

[0226] The measurement device 60 preferably is a vision measurement device which is configured to make one or more images of a cut end of the pipe 2. The images are analysed, preferably automatically, to determine data related to one or more characteristics of the pipe, e.g. the vision measurement device makes images of the cross-section of the cut-end of the pipe.

[0227] As shown in Figure 1 , the vision measurement device is an in-line vision measurement device which is configured to c measure characteristics of the cut end of the pipe 2, wherein the vision measurement device 60 is arranged at or downstream of the cutting device 70. In an alternative not shown, the vision measurement device 60 is an off-line vision measurement device which is configured to measure characteristics of individual pipe elements produced by the system, e.g. wherein the off-line vision measurement device is arranged in a test location, preferably the off-line measurement device and test location are arranged in proximity to the cutting device, e.g. parallel to the cutting device, such that the pipe element can be measured as soon as the pipe element has been cut.

[0228] It is further envisaged that a combination of an in-line vision measurement device and an offline vision measurement device is used, wherein the in-line measurement device provides continuous measurements, while the off-line measurement device provides measurements with an increased accuracy and reliability compared to the in-line measurement device.

[0229] Each thermal adjustment element 51 is provided with an associated temperature sensor 54, wherein the temperature sensors 54 are each configured to measure local temperature data and transmit the data to the controller 52.

[0230] In an embodiment, the controller 52 may be configured to compare the characteristic(s) of the pipe measured by the measurement device 60 to one or more predetermined desired characteristics of the pipe and to send a control signal to the haul-off device 55, e.g. to control the haul-off speed, e.g. allowing to control the weight per meter of the pipe 2.

[0231] Figure 4 shows an exploded view of the distributor head 1.

[0232] The distributor head comprises a base part 3 which is configured such that three extruders 20a, 20b, 20c can be connected to it for forming a three-layered wall.

[0233] The distributor head comprises two disc-shaped bodies 4a, 4b. By means of core member 5, the disc-shaped bodies can be fastened to the base part 2.

[0234] A ring 6 is screwed onto the outer periphery of the base part 2, which ring is provided with a circular groove on its outside. By fitting a clamping ring 7 consisting of two halves in said groove and in a groove of the disc-shaped body 4, the disc-shaped bodies 4 are fastened to the base part 2.

[0235] The die body 30 may be attached to the distributor head 10 by means of clamping ring 8. It is illustrated that the flow adjustment elements 51 are arranged in the disc-shaped bodies 4a, 4b. In a practical design, such a disc-shaped body is provided with flow adjustment element cavities, e.g. bores, in proximity to the intermediate flow channels and / or outlet channels. The thermal flow adjustment elements are housed inside these cavities. Preferably, the thermal adjustment channels are cartridge heaters which extend along the channels.

[0236] Figure 5 shows a block diagram of an embodiment of the flow rate adjustment system.

[0237] The controller 52 is provided with input data by the measurement device 60, e.g. in the form of images, or data based on processing of images, of the pipe 2, e.g. images of the cut end 2a of a pipe, to determine one or more characteristics of the pipe.

[0238] For example, the in-line vision measurement device 60 comprises a carriage configured to move along with the cut pipe end 2a, e.g., along a linear guide (schematically shown in figure 1), wherein one or more cameras are arranged on the carriage. For example, the carriage is provided with one or more clamps which clamp onto the pipe so that the carriage moves at the same speed as the pipe. For example, the one or more cameras are mounted to revolve, at least over an arc segment, about a longitudinal pipe axis, e.g. allowing to image a sector of the cut end 2a per camera.

[0239] For example, the cut end 2a of the pipe 2 is scanned by one or more cameras of the device 60.

[0240] For example, the image(s) obtained by the camera or cameras of device 60 are used to determine thickness of the wall and / or of layer(s) of the wall of the pipe, and / or concentricity, and / or the presence of voids in a foam core, the foam cell size, etc.

[0241] The one or more cameras of the vision measurement device 60 may provide a high resolution image of the cut end. For example, when a pipe 2 having a foam (core) layer is produced, the one or more cameras may be configured to have a resolution allowing to measure the foam cell size.

[0242] In embodiments, the vision measurement device 60 has one or more associated lighting devices configured to provide illumination of the cut end, e.g. LED lighting devices. For example, the one or more lighting devices are configured to provide for a controllable illumination of the cut end, e.g. to allow for a desired, e.g. variable, intensity and / or spectrum and / or spatial position of the lighting device(s) relative to the cut end. In embodiments, the controller also receives data from the temperature sensors 54 in the form of local temperature data.

[0243] The controller may also receive operator generated instructions, e.g. via the interface 53.

[0244] The controller 52 sends control signals to the individual flow adjustment elements 51 and provides information to the interface 53.

[0245] The controller may also control a foaming agent dosing device 90 associated with extruder 20a which forms a foam core layer of the pipe 2 as discussed herein. For example, this allows to control the foaming level during pipe production.

[0246] The invention further relates to a method for producing a pipe 2 from one or more streams of thermoplastic material, wherein use is made of a production system 1 which comprises a distributor head 10 and an extruder, here three extruders 20a, 20b, 20c.

[0247] The method comprises the step of operating the flow adjustment elements 51 to adjust the flow rate in the intermediate flow channels and / or outlet channels. As discussed, this may be done to counter deviations in wall thickness, thickness of one or more layers, and / or foam cell size (when a foam core layer is present).

[0248] The controller 52 compares the characteristics of the pipe measured by the measurement device 60 to predetermined desired characteristics of the pipe and determines if and by how much the measured characteristics deviate from the desired characteristics. If the determined deviation is higher than a predetermined threshold the controller 52 sends a control signal to the flow adjustment elements 51 , preferably wherein the control signal is correlated to the determined deviation, and / or to an operator.

[0249] In an embodiment, the controller 52 automatically controls the flow adjustment elements 51 based on the data relating to the characteristics of the pipe transmitted by the measurement device. Alternatively, the controller has a controller interface which displays if a deviation in characteristics is present to an operator and allows the operator to manually send a control signal to one or more flow adjustment elements 51.

[0250] Figure 6 shows a different embodiment of the production system 1 for producing a multi-layer pipe 2 of three streams of thermoplastic material. The production system comprising an in-line vision measurement device 60 which is arranged laterally adjacent to the in-line cutting device 70, as seen from a top-down view.

[0251] The production system further comprising a transfer device 80, here shown as a transfer table device, which transports the individual pipe element 2b from the cutting device 70 to first a measurement station where the upstream cut end 2a is imaged by the in-line measurement vision device 60.

[0252] The transport device 80 then transports the individual pipe element 2b from the measurement station to a socketing device 95 which is arranged laterally adjacent to the in-line vision measurement device 60. The socketing machine 95 forms the upstream end portion having the upstream cut end 2a into a socket. The other end remains without socket.

[0253] Figure 7 shows the in-line vision measurement device 60. The in-line vision measurement device 60 comprises a housing 61 with a viewing window 62. A polarizing filter 66 is placed over the viewing window 62. The housing 61 is at the lower end thereof provided with a damping member 67.

[0254] The in-line vision measurement device 60 further comprises a camera 63 and a lighting device 64 which are directed to face out of the view window 62 and facing the cut end 2c of the individual pipe element 2b. The line of sight of the camera 63 being aligned with the central axis of the individual pipe element 2b. As shown the individual pipe element 3b is arranged on top of the transfer device 80 at the measurement station.

[0255] The lighting device 64 and camera 63 are movably connected to a vertical guiding rail 65 which allow both the lighting device 64 and the camera to move in the vertical direction.

[0256] Figures 8a-c show different representations of the cross-section of a cut end of a multilayered pipe 100 imaged by a vision measurement device 60. The pipe having an inner layer 101 , a foam core 102, and an outer layer 103.

[0257] Figure 8a shows the cross-section as a horizontal profile, wherein variations in the wall and layer thickness are shown along the length of the horizontal profile to reflect variations of the wall and layer thickness around the pipe's circumference. As shown the estimated boundary layers 104, 105 are overlayed over the horizontal profile. Figure 8b show the maximum diameter 106 and the minimum diameter 107 overlayed over the circular cross-section of the cut end of the pipe.

[0258] As shown in Figures 8a and 8b the representations are provided with indicators, which allow an operator to quickly identify corresponding locations of the horizontal profile and the circular cross-section.

[0259] Figure 8c shows representation of the cross-section of the pipe wherein the representation maintains an outer diameter of the pipe approximately equal to the outer diameter of the image. The representation reduces an inner diameter of the pipe with respect to the inner diameter of the pipe, thereby visually exaggerating the wall thickness while still showing the entire cross-section of the pipe. The inner and outer wall boundary layer 108, 109 of the cross-section are determined and overlayed on top of the cross-section. Voids 110 having an area larger than a predetermined area are indicated in the representation by overlaying an outline of the void on top of the cross-section.

Claims

C L A I M S1. Production system for producing a pipe from one or more streams of thermoplastic material, wherein the system comprises an extruder and a distributor head from which - in use - an extruded pipe emerges, wherein the distributor head comprises an inlet orifice for a stream of thermoplastic material which inlet orifice is connected to the extruder, and an outlet orifice of annular cross section, wherein the distributor head comprises at least one flow channel system which comprises an inlet channel which is at one end thereof connected to the inlet orifice, which inlet channel, in a number of stages of branchings and intermediate flow channels, branches into outlet channels terminating on a periphery around a centre line of the outlet orifice, which outlet channels open into the outlet orifice, wherein the production system is provided with a local flow adjustment system which comprises a plurality of flow adjustment elements provided on the distributor head, which flow adjustment elements are each configured to adjust the flow rate of the thermoplastic material in an associated intermediate flow channel and / or outlet channel, wherein all intermediate flow channels and / or all outlet channels of at least one stage of the distributor head are each provided with an associated flow adjustment element, wherein the local flow adjustment system further comprises a controller which is configured to individually control each flow adjustment element of the distributor head, so as to adjust the flow rate in the associated intermediate flow channel and / or outlet channel, wherein the production system further comprises an in-line cooling device which is arranged downstream of the distributor head and is configured to cool the extruded pipe, and wherein the production system further comprises a measurement device which is configured to measure one or more characteristics of the extruded pipe after the pipe has been cooled by the in-line cooling device, wherein the measurement device is configured to determine data relating to the characteristic(s) of the pipe,and wherein the measurement device is configured to transmit said data to the controller of the local flow adjustment system, and / or to display said data to a human operator so as to allow the operator to manually control the controller of the local flow adjustment system.

2. Production system according to claim 1 , wherein the measurement device is configured to transmit said data to the controller of the local flow adjustment system.

3. Production system according to claim 1 or 2, wherein the flow adjustment elements are thermal adjustment elements which are configured to heat and / or cool, preferably to heat, the respective intermediate flow channel and / or outlet channel, preferably wherein one or more, e.g. each, thermal adjustment element is / are provided with an associated temperature sensor, wherein the temperature sensor(s) is configured to measure local temperature data and transmit the data to the controller.

4. Production system according to any one or more of claims 1 - 3, wherein the production system further comprises an in-line cutting device arranged downstream of the inline cooling device and configured to cut the extruded pipe into individual pipe elements.

5. Production system according to any one or more of claims 1 - 4, preferably claim 4, wherein the measurement device is a vision measurement device which is configured to make one or more images of a cut end of the pipe, e.g. of an individual pipe element, and wherein the vision measurement device and / or the controller of the local flow adjustment system is / are configured to analyse said one or more images to determine one or more characteristics of the pipe.

6. Production system according to claims 4 and 5, wherein the vision measurement device is an in-line vision measurement device which is arranged at or in line with the in-line cutting device, e.g. upstream of a socketing device of the production system.

7. Production system according to any one or more of claims 1 - 6, wherein the distributor head comprises multiple disc-shaped bodies which are each provided with all the flow channels associated with one stage, wherein the flow adjustment elements are arranged in at least one of the disc-shaped bodies, preferably, wherein the distributor head comprises a plurality of, preferably three, inlet orifices and concentric outlet orifices, such that the distributor head is configured to produce a pipe with a multi-layered wall, e.g. wherein the pipe wall has a foam-core layer.

8. Method for producing a pipe from one or more streams of thermoplastic material, wherein use is made of a production system which comprises an extruder and a distributor head from which an extruder pipe emerges, wherein distributor head comprises an inlet orifice for a stream of thermoplastic material, which inlet orifice is connected to the extruder, and an outlet orifice of annular cross section, wherein the distributor head comprises at least one flow channel system which comprises an inlet channel which is at one end thereof connected to the inlet orifice, which inlet channel, in a number of stages of branchings and intermediate flow channels, branches into a number of outlet channels terminating on a periphery around the centre line of the outlet orifice, which outlet channels open into the outlet orifice, wherein the production system further comprises a local flow adjustment system which comprises a plurality of flow adjustment elements provided on the distributor head, which flow adjustment elements are each configured and operated to adjust the flow rate of the thermoplastic material in an associated intermediate flow channel and / or outlet channel, wherein all intermediate flow channels and / or outlet channels of at least one stage are provided with an associated flow adjustment element, wherein the local flow adjustment system further comprises a controller which controls each flow adjustment element, so as to adjust the flow rate in the associated intermediate flow channel and / or outlet channel, wherein the production system further comprises an in-line cooling device arranged downstream of the distributor head which cools the extruded pipe, wherein the production system further comprises a measurement device which measures one or more characteristics of the extruded pipe after the pipe has been cooled by the cooling device, wherein the measurement device determines data relating to the one or more characteristics of the pipe, and wherein said data are used to control the operation of the flow adjustment elements in order to adjust the flow rates in the associated intermediate flow channels and / or outletchannels, wherein the measurement device transmits said data to the controller of the local flow adjustment system, and / or said data are displayed to a human operator so as to allow the operator to manually control the controller of the local flow adjustment system.

9. Method according to claim 8, wherein the measurement device transmits said data to the controller of the local flow adjustment system.

10. Method according to claim 8 or 9, wherein the plurality of flow adjustment elements are thermal adjustment elements which are operated to heat and / or cool the associated intermediate flow channel and / or outlet channel and / or the thermoplastic material flowing through the channel, such that the flow rate of the thermoplastic material is changed, preferably wherein each thermal adjustment element is provided with an associated temperature sensor which measures local temperature data and transmits the data to the controller.

11. Method according to any one or more of claims 8 - 10, wherein the production system further comprises an in-line cutting device arranged downstream of the cooling device, which in-line cutting device cuts the pipe into individual pipe elements.

12. Method according to claim 11, wherein the measurement device is a vision measurement device which makes one or more images of a cut end of the pipe, preferably an in-line vision measurement device which is arranged at or in line with the in-line cutting device.

13. Method according to any one or more of claims 8 - 13, wherein the distributor head comprises a plurality of, preferably three, inlet orifices and concentric outlet orifices, such that a pipe with a multi-layered wall is produced, preferably wherein the distributor head comprises three concentric outlet orifices to form a pipe with a three-layered wall, e.g. including a foam core layer.

14. Method according to claim 12, wherein the one or more characteristics measured by the vision measurement device comprise one or more of: wall thickness, layer thickness(es) in a multilayer pipe, foam cell size in a foam layer of a multilayer pipe, presence of voids in a foam layer of a multilayer pipe, size of voids in a foam layer of the pipe.

15. Distributor head for forming a pipe from one or more streams of thermoplastic material, wherein the distributor head comprises at least an inlet orifice for a stream ofthermoplastic material which is configured to be connected to an extruder, and an outlet orifice of annular cross section, wherein the distributor head comprises at least one flow channel system which comprises an inlet channel which is at one end thereof connected to the inlet orifice, which inlet channel, in a number of stages of branchings and intermediate flow channels, branches into a number of outlet channels terminating on a periphery around the centre line of the outlet orifice, which outlet channels open into the outlet orifice, wherein the distributor head is provided with a local flow adjustment system which comprises a plurality of flow adjustment elements which are each configured to adjust the flow rate of the thermoplastic material in an associated intermediate flow channel and / or outlet channel.

16. Distributor head according to claim 15, wherein all intermediate flow channels and / or outlet channels of at least one stage are provided with an associated flow adjustment element, e.g. thermal adjustment elements.

17. Production system for producing a pipe from one or more streams of thermoplastic material, wherein the production system comprises: one or more extruders and a distributor head; an in-line cooling device arranged downstream of the distributor head, wherein the cooling device is configured to cool the extruded pipe; an in-line cutting device arranged downstream of the cooling device which is configured to cut the pipe into individual pipe elements; a socketing device configured to form a socket at an end portion of each individual pipe element, a transfer device configured to transfer the individual pipe elements to the socketing device, a vision measurement device configured to take an image of a cut end of each individual pipe element, wherein the vision measurement device is arranged such that the vision measurement device is able to make an image of the cut end prior to the end portion having said cut end being formed into a socket.

18. Production system according to claim 17, wherein the cutting device is configured to cut the pipe such that one end of the individual pipe element comprises a bevelled edge and the other end of the individual pipe element comprises a non-bevelled edge, i.e. straight edge, wherein an end portion of the individual pipe element having the non-bevelled edge cutend is formed into a socket by the socketing device, and wherein the vision measurement device is arranged such that the vision measurement device - in use - takes an image of the non-bevelled cut end prior to said end portion being formed into a socket.

19. Production system according to claim 17 or 18, wherein the transfer device is configured to transfer the individual pipe element from the cutting device to a measurement station prior to transferring the individual pipe element to the socketing device, wherein the vision measurement device is arranged to take an image of the cut end, e.g. the non-bevelled cut end, of the individual pipe element at the measurement station.

20. Production system according to any one or more of claims 17 - 19, wherein the distributor head, in-line cooling device, and in-line cutting device are arranged along a production axis, and wherein the vision measurement system is arranged laterally offset from the production axis, e.g. adjacent to the in-line cutting device, and wherein the socketing device is arranged laterally adjacent to the vision measurement device with respect to the production axis.

21. Production system according to any one or more of claims 17 - 20, wherein each individual pipe element comprises an upstream cut end and a downstream cut end with respect to a production direction, wherein the, preferably non-bevelled, upstream cut end is configured to be formed into a socket by the socketing device, wherein the transfer device is configured to laterally transfer each individual pipe element from the cutting device to the measurement device and socketing device, while maintaining the orientation of the pipe element such that the upstream end remains upstream and the downstream end remains downstream, wherein the measurement device is configured to capture an image of the, preferably non-bevelled, upstream end after which the transfer device is further configured to laterally transfer the pipe element to the socketing device, wherein the socketing device is configured to form the upstream end into a socket.

22. Production system according to any one or more of claims 17 - 21 , wherein the production system further comprises a controller configured to control one or more production parameters based on the images of the cut ends of individual pipe elements taken by the vision measurement device, e.g. of all individual pipe elements, e.g. wherein the vision measurement device is configured to determine data relating to the characteristic(s) of the pipe, e.g. wherein the vision measurement device is configured totransmit said data to the controller, and / or to display said data to a human operator so as to allow the operator to manually control the controller.

23. Production system according to claim 22, wherein the distributor head is a distributor head according to claim 15 or 16, wherein the controller is configured to individually control each flow adjustment element, so as to adjust the flow rate in the associated intermediate flow channel and / or outlet channel.

24. Production system according to any one or more of claims 17 - 23, wherein the system is configured to produce a multi-layer pipe having a foam layer.

25. Production system according to claim 24, wherein the distributor head comprises a plurality of, preferably three, inlet orifices and concentric outlet orifices, such that the distributor head is configured to produce a pipe with a multi-layered wall, wherein the production system further comprises a foaming agent dosing device for dosing foaming agent, which foaming agent dosing device is associated with the extruder producing the foam layer(s) of the pipe, wherein the controller is configured to control the foaming agent dosing device, at least in part on the basis on images made by the vision measurement device.

26. Production system according to claim 24 or 25, wherein the images allow to determine one or more characteristics(s) of the pipe, for example number of voids in the foam core, size of voids in the foam core, foam cell size, location of voids in the foam core.

27. A method for producing a pipe from one or more streams of thermoplastic material, wherein use is made of a production system according to any one or more of claims 17 - 26, wherein the method comprises the steps of: extruding a pipe using the one or more extruders and distributor head; cooling the pipe using the in-line cooling device; cutting the pipe into individual pipe elements using the in-line cutting device; transferring each individual pipe element to a measurement station using the transferring device; making an image of a cut-end of the individual pipe element at the measurement station using the vision measurement device; transferring the individual pipe element from the measurement station to the socketing device using the transferring device;forming a socket at an end portion of the induvial pipe element using the socketing device.

28. Method according to claim 27, wherein the cutting device cuts the pipe such that the individual pipe element comprises a bevelled edge and a non-bevelled edge, i.e. straight edge, wherein the vision measurement device makes an image of the non-bevelled end at the measurement station, and the socketing device forms an end portion of the individual pipe element having the non-bevelled end into a socket.

29. Method according to claim 27 or 28, wherein the distributor head produces a pipe with a multi-layered wall, wherein a foaming agent dosing device doses foaming agent, which foaming agent dosing device is associated with the extruder producing the foam layer(s) of the pipe, wherein the controller controls the foaming agent dosing device, at least in part on the basis on images made by the vision measurement device.

30. A method for displaying one or more characteristics of an extruded thermoplastic pipe, e.g. a foam-core pipe, to a user, e.g. an extruded pipe produced by a system and / or method according to any one or more of claims 1 - 14 and / or claims 17 - 29, wherein the method comprises: taking one or more images of a cut end of the pipe using a vision measurement device; determining one or more characteristics of the pipe based on the one or more images; displaying a representation of the cross-section of the cut end of the pipe, which displayed representation comprising the one or more characteristics of the pipe.

31. Method according to claim 30, wherein the displayed one or more characteristics comprise the wall thickness of the pipe along the perimeter thereof and / or the radius of the pipe along the circumference thereof.

32. Method according to claim 30 or 31 , wherein the pipe is a multi-layer pipe having a foam core, wherein the displayed one or more characteristics comprise one or more of : the wall thickness of the pipe, the layer thickness(es) of the pipe, the number and / or size of voids within the foam core, and / or the foam cell size.

33. Method according to any one or more of claims 30 - 32, wherein the cross-section of the pipe is displayed with a visually exaggerated wall thickness while still showing the entire cross-section.

34. Method according to claim 33, wherein the representation maintains an outer diameter of the pipe approximately equal to the outer diameter of the image, and wherein the representation reduces an inner diameter of the pipe with respect to the inner diameter of the pipe, thereby visually exaggerating the wall thickness while still showing the entire crosssection of the pipe.

35. Method according to any one or more of claims 30 - 34, wherein the maximum and minimum outer diameter of the pipe are determined, wherein the maximum and minimum outer diameter are overlayed at the corresponding location on top of the cross-section.

36. Method according to any one or more of claims 30 - 32, wherein the pipe wall is represented as a horizontal profile, preferably wherein a reference horizontal pipe profile having the desired and constant wall, and preferably layer, thickness is overlayed over the displayed horizontal profile, preferably, estimated boundary layers of the wall layers are overlayed over the displayed horizontal profile, preferably, indicators are displayed along the horizontal profile enabling a user to identify the corresponding circumferential positions on the pipe at which the indicators are located.

37. Method according to any one or more of claims 30 - 36, wherein voids in a foam core having an area larger than a predetermined area are indicated in the representation, e.g. an outline of the void is overlayed on top of the cross-section.

Images