PVC-O pipe

Abstract

A pipe made of PVC-O type thermoplastic material has an axis of symmetry (101); the pipe (100) has a main longitudinal extension from a first end (102) to a second end (103) in a direction parallel to the axis of symmetry (101); the pipe (100) has an inner cavity (104) extending from the first end (102) to the second end (103); the pipe (100) includes a seal (200) located in a corresponding receptacle (111) and having a circumferential extension relative to the axis of symmetry (101); the seal (200) has an inner surface (201) facing the inner cavity (104) and an outer surface (202) facing the receptacle (111); the outer surfaces (202) of the seal (200) have each other The first portion (203) and the second portion (204) are arranged adjacently, thereby defining the tip (205); the first portion (203) and the second portion (204) are inclined at corresponding acute angles (θa; θp) relative to the direction parallel to the axis of symmetry (101); the inner chamber (104) has a tapered portion (108) at the first end (102) of the tube (100) that guides the external environment and has a diverging shape; the inclination of the tapered portion (108) relative to the direction parallel to the axis of symmetry (101) is equal to the acute angle (αf), the value of which is related to the value of the acute angle (θp) of the inclination of the first portion (203) of the outer surface (202) of the seal (200) relative to the direction parallel to the axis of symmetry (101) of the tube (100).

Description

Technical Field

[0001] This invention relates to a pipe made of PVC-O (oriented polyvinyl chloride). Background Technology

[0002] Starting in the late 1990s, a process was developed for the industrial production of solid-walled pipes made of non-plasticized polyvinyl chloride, which are known as biaxially oriented PVC or PVC-O.

[0003] The production process of PVC-O pipes can orient the long molecular chains of PVC obtained from the pipe extrusion process. Orientation in both the longitudinal and circumferential directions allows for improvements in the physical properties of PVC.

[0004] Orientation is achieved by increasing the temperature above the glass transition temperature Tg (75℃-80℃) of PVC and then applying large forces in both the axial and circumferential directions to increase the diameter of the pipe and reduce its wall thickness.

[0005] The production process for PVC-O pipes is much more complex and labor-intensive than the production process for extruded unplasticized polyvinyl chloride (PVC-U) pipes.

[0006] Compared to PVC-U, PVC-O material has higher tensile strength, fatigue resistance, and impact resistance. Therefore, although its production cost is higher than PVC-U, PVC-O pipes have significant advantages over PVC-U pipes in certain applications. For example, in the field of pipe technology for pressurized fluid supply, PVC-O pipes can operate at pressures up to 25 bar, compared to the well-known PVC-U pipes; it should be noted that the operating pressure of PVC-U pipes typically does not exceed 16 bar.

[0007] Similarly, for piping systems with pressures below 25 bar, PVC-O pipes have significant advantages over PVC-U pipes, at least when the operating pressure reaches 12.5 bar.

[0008] In fact, under the same working pressure, PVC-O pipes have a smaller wall thickness; therefore, PVC-O pipes are lighter pipes with a larger transmission cross-section, which means they have a greater flow capacity.

[0009] Similar to PVC-U pipes, in PVC-O pipes, the joint between pipes is an integral flared section, that is, an enlarged shape at the end of one pipe, into which the end of another pipe is inserted to form a pipe. This joint shape is uniform and is currently the most common.

[0010] Typically, the flared section has a base in its wide shape, and the base houses a seal made of elastic material to ensure the sealing of the flared joint.

[0011] One system that forms the flare is the so-called Rieber system. In the Rieber system, the flare is made with the seal being sealed and integrated with the flare wall, making the seal non-removable and non-replaceable.

[0012] The Rieder system includes a flared section formed by a metal gasket, and a lower section pre-installed on the metal gasket for sealing.

[0013] During the forming of the flared section, the seal remains attached to and integrated with the flared section wall. Then, the gasket is removed from the flared section, ultimately forming a pipe with an integral flared section and a non-removable seal.

[0014] Unlike PVC-O pipes, in PVC-U pipes, the method of integrating the seal with the flared wall is through internal negative pressure and / or overpressure on the outer surface of the flared section (e.g., using a pressurized fluid such as compressed air).

[0015] According to the Rieber system, in PVC-O pipes, the relative seating of the flared end and the seal is due to the spontaneous shrinkage of the molecular orientation on the molded gasket and the seal. This shrinkage occurs when the thermal state of the PVC-O material is above the glass transition temperature (Tg) of PVC.

[0016] In fact, at temperatures above Tg, the molecular structure of PVC releases enormous forces that are applied during the pipe manufacturing process, which are used to achieve the axial and circumferential orientation of the pipe.

[0017] The currently known methods for expanding PVC-O pipes using the Rieber system, as described and illustrated in existing technical documents WO97 / 33739, WO99 / 42279, WO97 / 10942, EP0930148, EP2614952 and IT0130598, have several drawbacks.

[0018] A drawback found in existing methods is the irreversible collapse of the seal during pipe insertion into the seal housed in the gasket.

[0019] When the pipe end impacts the seal held by the contact flange during flaring, the force generated by the pipe end causes considerable deformation of the seal until it adversely affects the structure of the seal. The seal is mainly made of elastic material and is easily deformed.

[0020] The tubing has a flat front end perpendicular to the gasket axis. The contact area between the front end of the tubing and the seal is very small. The edge of the tubing impacts the seal, creating contact pressure, which causes the seal to deform and subsequently break.

[0021] Another drawback is that during the entire process of inserting the pipe into the seal, the axial orientation of the material in the flared section is canceled or reduced due to the significant axial compression of the pipe wall, until the resistance to the hydrostatic pressure generated by the circulating fluid in the pipe during use is adversely affected.

[0022] This drawback involves the resistance generated by the shape of the seal protruding from the cylindrical gasket, as well as the frictional resistance generated by the surface of the resilient seal, which are much greater than the resistance generated by the shape and surface of the metal gasket. Furthermore, these resistance effects due to the presence of the seal are exacerbated as the pipe wall impacts and passes over the seal, with the seal's shape gradually changing.

[0023] In this case, it is necessary to manufacture a PVC-O pipe, as described in independent claim 1, which allows for limiting the deformation of the seal during flaring. Summary of the Invention

[0024] The purpose of this invention is to overcome the above-mentioned requirements by providing a PVC-O pipe that can limit the deformation of the seal when it is inserted during flaring, allowing for high-quality products.

[0025] The present invention also relates to a method and system for manufacturing PVC-O pipes, which can prevent deformation of the seal during flaring. Attached Figure Description

[0026] The advantages of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings, which provide preferred embodiments of the invention by way of example only and do not limit the scope of the inventive concept, and wherein:

[0027] - Figure 1 This is a partial front view of a flaring machine, which is part of the forming system according to the present invention;

[0028] - Figure 2A The invention illustrates thermoplastic pipes made of PVC-O to be processed using a flaring machine;

[0029] - Figure 2B and 34 The image shows a PVC-O thermoplastic pipe at the end of a process performed in the conizing station of a flaring machine according to the present invention;

[0030] - Figure 2C and 36 A thermoplastic pipe made of PVC-O with flared ends according to the present invention is shown, produced by the flaring machine and method according to the present invention;

[0031] - Figure 2D yes Figure 2C A magnified view showing the details;

[0032] - Figure 3 A cross-section of a seal is shown, which can be used to manufacture... Figure 2C The deformed flared thermoplastic pipe shown;

[0033] - Figure 4A It is formed according to the present invention Figure 1 A partial cross-section of the flared unit of a part of the machine shown;

[0034] - Figure 4B It shows Figure 4A Enlarged view (where the pipe seals are not shown);

[0035] - Figures 5 to 22 This schematically illustrates the different sequential steps in creating a flared end on a pipe. Figure 4A The flaring machine and pipe shown;

[0036] - Figures 23 to 33 Further details of the flared portion forming a tube according to the present invention are shown;

[0037] - Figure 35 and 37 The image shows a magnified detail of the moment of first contact between the first end of the pipe and the seal during pipe flaring. Detailed Implementation

[0038] Reference Figure 2A The number 400 indicates a pipe made of PVC-O type thermoplastic material, which will be processed by the machine and method according to the invention.

[0039] Pipe 400 has a symmetrical axis 401.

[0040] The pipe 400 has a main longitudinal extension from the first end 402 to the second end 403 in a direction parallel to the axis of symmetry 401.

[0041] The first end 402 and the second end 403 are respectively defined by the edge of the pipe 400.

[0042] The pipe 400 has two end portions E1 and E2, each located at the first end 402 and the second end 403, respectively.

[0043] The tube 400 has an outer surface 409 extending about an axis of symmetry 401.

[0044] Pipe 400 has an annular cross section.

[0045] The pipe 400 has an inner cavity 403 that extends from the first end 402 to the second end 404.

[0046] Pipe 400 has a nominal diameter value “dn” and a nominal wall thickness value “en”.

[0047] The actual outer diameter at any point on the 400mm pipe is marked as "de".

[0048] The actual wall thickness at any point on the 400mm pipe is marked as "e".

[0049] At the second end 403, the outer surface 409 of the tube 400 has a chamfer 410, the chamfer being inclined relative to a direction parallel to the axis of symmetry 401 at an acute angle β, specifically between 10° and 25°, including 10° and 25°, and more specifically the angle β being equal to 15°.

[0050] The chamfer 410 is characterized in that the longitudinal extension “k” is parallel to the axis of symmetry 401, and the lateral extension “h” of the first end 402 is perpendicular to the direction of the axis of symmetry 401.

[0051] The first end 402 of the pipe 400 does not contact the chamfer 410.

[0052] Preferably, the longitudinal extension value "k" of the chamfer 410 is related to the actual minimum outer diameter of the pipe 400, referred to as "demin", with the following relationship: k ≥ 0.05demin.

[0053] Preferably, the lateral extension value "h" of the second end 403 is related to the actual wall thickness value measured at the second end 403 of the pipe, and the relationship is as follows: h≥0.5e.

[0054] Reference Figure 2B The number 400 indicates a pipe made of PVC-O type thermoplastic material, which is processed by the machine and method according to the invention and is in the state at the end of the processing step of the conical station SV.

[0055] Except for the inner tapered portion 412 at the first end 402 of the pipe 400, the above-mentioned reference Figure 2A All the characteristics described remain unchanged in the pipe.

[0056] The inclination of the tapered portion 412 is equal to the acute angle "αi" or the initial acute angle, and the longitudinal extension is equal to "Li" or the initial longitudinal extension.

[0057] The value of the angle "αi" of the extension "L1" will be defined below.

[0058] Reference Figure 2CThe number 100 indicates a pipe made of PVC-O type thermoplastic material according to the present invention.

[0059] Figure 2C The pipe 100 shown constitutes a finished pipe according to the present invention for all purposes and intentions.

[0060] Pipe 100 has an axis of symmetry 101.

[0061] The pipe 100 has a main longitudinal extension from the first end 102 to the second end 103 in a direction parallel to the axis of symmetry 101.

[0062] It should be noted that the two ends 102 and 103 of the pipe 100 correspond to the two ends 402 and 403 of the pipe 400 during the previous processing steps.

[0063] The first end 102 and the second end 103 are respectively defined by the edge of the pipe 100.

[0064] The pipe 100 has two end portions E1 and E2, each end portion E1 and E2 being located at a first end 102 and a second end 103, respectively.

[0065] The tube 100 has an outer surface 109 extending about an axis of symmetry 101.

[0066] Pipe 100 has an annular cross section.

[0067] At the second end 103, the outer surface 109 of the tube 100 has a chamfer 110, the chamfer being inclined relative to a direction parallel to the axis of symmetry 101 at an acute angle β, specifically between 10° and 25°, including 10° and 25°, and more specifically the angle β being equal to 15°.

[0068] The chamfer 110 is characterized in that the longitudinal extension “k” is parallel to the axis of symmetry 101, and the lateral extension “h” of the second end 103 is perpendicular to the direction of the axis of symmetry 401.

[0069] The first end 102 of the pipe 100 does not contact the chamfer 110.

[0070] Preferably, the longitudinal extension value "k" of the chamfer 110 is related to the actual minimum outer diameter of the pipe 100, referred to as "demin", with the following relationship: k≥0.05demin.

[0071] Preferably, the lateral extension value "h" of the second end 103 is related to the actual wall thickness value measured at the second end 103 of the pipe, and the relationship is as follows: h≥0.5e.

[0072] The pipe 100 has an inner cavity 104 that extends from the first end 102 to the second end 103.

[0073] The inner cavity 104 includes a first segment 105 having a first diameter and a second segment 106 having a second diameter at least larger than the first diameter, and a third segment 107 for connecting the first segment 105 to the second segment 106, having a converging shape from the second segment 106 to the first segment 105.

[0074] The second diameter of the second section 106 is greater than the outer diameter "de".

[0075] The convergence tendency of the third segment 107 is inclined relative to the direction parallel to the axis of symmetry 101, which is determined by the convergence angle. The value of the convergence angle is limited to ±5° from the value of the acute angle β of the inclination of the chamfer 110 relative to the direction parallel to the axis of symmetry 101.

[0076] The third section 107 and the second section 106 define the flared portion 113 of the pipe 100.

[0077] The first segment 105 of the inner chamber 104 extends from the second end 103.

[0078] In a direction parallel to the axis of symmetry 101, the length of the first segment 105 is greater than the length of the second segment 106.

[0079] The inner chamber 104 has a fourth section 108 which is adjacent to the second section 106 and leads to the external environment at the first end 102 of the tube 100, having a diverging tendency from the second diameter of the second section 106 to the external environment.

[0080] The fourth segment 108 has an inclination relative to the direction parallel to the axis of symmetry 101 equal to an acute angle "αf", i.e., the final acute angle, and the longitudinal extension is equal to "Lf", i.e., the final longitudinal extension.

[0081] The value of the angle "αf" of the extension "Lf" will be specified below.

[0082] In other words, the fourth section 108 takes the form of the inner tapered portion of the tube 100 or the first end 102.

[0083] The pipe 100 includes a seal 200 located in a corresponding reservoir 111.

[0084] The seal 200 has a circumferential extension relative to the axis of symmetry 101 of the pipe 100.

[0085] like Figure 2D As shown, the seal 200 has an inner surface 201 facing the inner cavity 104 of the tube 100 and an outer surface 202 facing the receptacle 111.

[0086] The seal is positioned along the second section 106 of the inner cavity 104.

[0087] The inner surface 201 has protrusions 207 designed to limit the sealing performance of the seal 200.

[0088] The outer surface 202 has a first portion 203 and a second portion 204, such as Figure 3 As shown, these two sections are adjacent to each other, thereby defining the tip 205.

[0089] Part 203 is also known as the rear shoulder of seal 200.

[0090] Part 204 is also known as the front shoulder of seal 200.

[0091] The first part 203 and the second part 204 are inclined at corresponding acute angles with respect to the direction parallel to the axis of symmetry 101 of the tube 100, as indicated by θp and θa respectively in the figure. Figure 2D As shown.

[0092] The acute angle θp of the inclination of the first portion 203 of the outer surface 202 of the seal 200 relative to the direction parallel to the axis of symmetry 101 of the pipe 100 is preferably between 25° and 35°, and particularly equal to 30°.

[0093] The acute angle θa of the inclination of the second portion 204 of the outer surface 202 of the seal 200 with respect to the direction parallel to the axis of symmetry 101 of the pipe 100 is preferably between 25° and 40°, and particularly equal to 30°.

[0094] The seal 200 includes a reinforcing element 206 located at the first portion 203 of the seal 200.

[0095] The reinforcing element 206 has a first end 206a and a second end 206b, such as Figure 3 As shown.

[0096] Preferably, the reinforcing element 206 is at least partially annular in shape.

[0097] More specifically, the reinforcing element 206 is made of metal or plastic material.

[0098] Advantageously, the reinforcing element 206 makes the relative seal more resistant to internal hydrostatic pressure during use, and thus also more resistant to the flared joint 113 of the pipe 100.

[0099] The reinforcing element also ensures the integrity of the seal when it is subjected to the force generated when the seal 200 is loaded on the gasket 2 of the flare unit 1, and when it is subjected to the force generated when it is subjected to the impact of the pipe wall and the force generated when it surmounts the seal 200 during the formation of the flare 113.

[0100] Reference Figure 37 Relative to the direction parallel to the axis of symmetry 101, the reinforcing element 206 includes an extension “C1”, which will be explained in detail below.

[0101] like Figure 1 As shown, the invention also includes a flaring machine 300, which is designed to be installed in a unit for producing pipes 100 made of thermoplastic materials.

[0102] The unit includes a processing unit configured to form an outer chamfer 410 at the second end portion E2 of the tube 400.

[0103] As described above, the unit also includes a flaring machine 300 for producing finished PVC-O pipes 100.

[0104] Specifically, the machine 300 includes a flaring unit 1, which is capable of producing a flared portion 113 starting from at least one end portion E1 of the PVC-O pipe 400, particularly from the first end 402 of the pipe 400.

[0105] The flaring machine 300 for use with pipes 400 made of PVC-O type thermoplastic material according to the present invention includes a unit 304 for processing pipes 400 to remove material or plastic deformation.

[0106] The processing unit 304 is used to process the PVC-O pipe 400, so that the first end 402 of the pipe 400 forms an inner tapered portion 412.

[0107] The processing unit 304, designed to manufacture the inner tapered portion 412 of the first end 402 of the pipe 400, is located upstream of the unit 301 that heats the pipe to a predetermined heating temperature and the flaring unit 1 (which will be described in detail below).

[0108] Advantageously, since the pipe 400 has not yet been flared, the processing unit 304 forms an inner tapered portion 412 on the wall of the partially processed pipe 400, such that when the first end 402 of the pipe 400 collides with the seal 200, the taper angle of the tapered portion is equal to or close to the taper value of the seal 200 designed for insertion into the first portion 203 of the pipe 400.

[0109] Advantageously, this shape of the first end 402 of the pipe 400 greatly increases the contact surface when the first end 402 of the pipe 400 collides with the seal 200, thereby reducing the contact pressure and local deformation of the seal 200.

[0110] For example, machining unit 304 is in the form of a planetary machine tool.

[0111] As for the length of the inner tapered portion 412, a compromise must be made between ensuring the structural and functional integrity of the seal 200 and the wall thickness of the edge of the flared portion 113 made on the first end portion E1 of the tube 400, so that it does not adversely affect the stability of the flared portion edge.

[0112] The sturdiness of the edge of the flared portion 113 is necessary to prevent damage to the pipe 100 during transport and installation operations.

[0113] In the type of seal 200 under consideration, the size of the extension of the inner tapered portion 412 is determined such that, in the first collision between the first end 402 of the tube 400 and the seal 200, the surface of the tapered portion 412 contacts the rear shoulder 203 of the seal 200, the rear shoulder 203 being at least partially facing the reinforcing ring 206.

[0114] Typically, if the wall thickness of the finished pipe 100 and the size and construction of the seal 200 allow, the dimensions of the extension of the conical surface of the inner conical portion 412 of the pipe 400 are advantageously determined such that, in the first collision between the first end 402 of the pipe 400 and the seal 200, the inner conical portion 412 of the pipe 100 and the first portion 203 of the seal 200 are in complete contact, both vertically and horizontally, on the portion facing the reinforcing element 206.

[0115] Advantageously, these standards for determining the dimensions of the inner tapered portion 412 of the pipe 400 are applicable to certain types of seals 200, equivalent to the standards used when making Rieber flares in PVC-U pipes. These standards can serve as guiding principles for designing new seals optimized specifically for Rieber flares in PVC-O pipes, which have different wall thicknesses and diameters when flared using the Rieber system.

[0116] These design criteria are intended to define the shape and size of the seal, and at least involve: the cone angle of the first portion 203; the extension of the first portion 203; the shape of the reinforcing element 206; and the relative position of the reinforcing element 206 to the elastic matrix of the seal 200.

[0117] When determining the geometry of the inner tapered portion 412 to be fabricated on the pipe 400 that will still be heated, the effects of diameter and axial shrinkage on the wall of the PVC-O pipe at temperatures above the glass transition effect must be taken into account; these effects depend primarily on the circumferential orientation, axial orientation, and wall thickness of the pipe 400.

[0118] These parameters are all known and are characteristics of the processed pipe 100.

[0119] The magnitude of the shrinkage effect depends on the thermal state of the pipe 400 during its processing.

[0120] When the heated pipe 400 is used for flaring, these effects will change the cone angle and cone length of the inner cone 412 initially formed on the cold pipe 400, but only a few experiments are needed to determine the values ​​of the cone angle and cone length that must be formed on the cold pipe 400 in order to obtain the optimal values ​​of the cone angle and cone length when the pipe is heated for flaring.

[0121] Moreover, since the orientation, thickness parameters, and processing temperature of the pipe are fixed, the direct relationship between the geometric features of the initial tapered portion 412 formed on the cold pipe 400 and the geometric features that change during the forming of the flared portion can be successfully determined experimentally.

[0122] The Rieber flare is formed integrally with the PVC-O pipe 100 using the equipment and process described in detail below.

[0123] The flared section 113 formed by the pipe 100 meets the following functional requirements: it is compatible with the pipe, has a sealing function, and can resist hydrostatic pressure at the joint.

[0124] Compared to traditional Rieber glass, this Rieber flare formed in PVC-O pipes has more advantages.

[0125] Specifically, the inner tapered portion 108 of the tube 100 remains shaped within the edge of the flared portion in the finished product.

[0126] The tapered portion 108 of the finished pipe 100 originates from the inner tapered portion 412 of the pipe 400, which is formed before the heating and flaring process steps.

[0127] The conical surface of the inner conical portion 108 does not maintain the same dimensions as the surface 412 formed before the flaring process because the surface changes during the flaring process, during the various steps of heating and forming the flared portion, due to the effect of spontaneous shrinkage of the PVC-O pipe caused by heating to a temperature above temperature Tg, and the different effects of the flaring equipment and the seal 200 on the edge of the pipe 400 at the same time.

[0128] It is precisely because of the special characteristics of the flaring equipment and processing method that a conical surface is maintained in the first end 102 of the finished pipe 100. The cone angle and cone length of this conical surface can be correlated with the cone angle and cone length formed on the cold pipe 400 before the heating and flaring steps by a simple proportional coefficient.

[0129] Therefore, relative to the cone angle of the first portion 203 of the seal 200 integrally formed in the flared portion 113 of the pipe 100, the cone angle of the inner tapered portion 108 of the finished pipe 100 retained on the end edge of the flared portion 113 is appropriately formed.

[0130] In fact, the process and flaring unit according to the invention allow for convenient formation of the flared portion in a relatively low (95°C-105°C) thermal state of the pipe, thereby reducing the influence of the plastic behavior of the pipe. That is, although the equipment for forming the flared portion has a mechanical function, it is insufficient to change the tapered shape of the first end 402 of the pipe 400.

[0131] In other words, during the production of PVC-O pipes, the following product parameters must be determined and stabilized:

[0132] - Pipe diameter (de);

[0133] - Pipe wall thickness (e);

[0134] -Circumferential orientation degree;

[0135] - Axial orientation.

[0136] Under these necessary repeatable conditions, if the flared portion is made in a hot state at a relatively low and controllable temperature (approximately 95°C–105°C) on the processed PVC-O pipe, the tapered portion 412 of the first end 402 of the pipe 400 formed on the pipe 400 in the cold state will remain unchanged. Even if there are variations in the angle and the size of the extension, it will always have a constant and repeatable size, and it is directly related to the size of the tapered portion formed in the cold state.

[0137] The machine and method according to the invention allow the forming process of the flared portion to be carried out at a specified temperature, giving it an advantage.

[0138] If the manufacturing process of the tube 100 and the flared portion 113 is repeatable, then the length Lf and the cone angle αf determined in the first end 102 of the flared portion 113 that is finally formed and cooled are also repeatable.

[0139] On the other hand, if the production process and flaring process of the pipe 100 are not performed correctly, or if the pipe 400 to be processed does not have the established physical and dimensional characteristics, then the taper regularity of the inner tapered part 108 will not be performed correctly.

[0140] For example, if the flared section is made in a hot state at a temperature above 105°C, the softening of the material will cause the initial conical shape formed on the edge of the pipe 400 before the pipe is heated to disappear in the final shape of the flared section, and the orientation of the material on the wall of the flared section cannot be maintained, which is necessary to ensure that the pipe 100 resists hydrostatic pressure.

[0141] Therefore, during the production of the flared section, by monitoring the regularity of the conical surface on the edge of the flared section, defects in the flaring process can be detected, which facilitates the diagnosis of the production process and the control of product quality.

[0142] Not only during the production of the pipe, but also during subsequent operations such as pipe laying, the inner tapered portion 108 of the first end 102 of the pipe 100 serves as a clear visual indicator of the process of forming the flared portion.

[0143] The flared end edge of the 113 has a marked inner tapered portion 108, which facilitates the installation of the pipe.

[0144] In fact, the flared portion 113 has a tapered inlet, which facilitates the insertion of a pipe into the flared portion of another pipe to be formed, for joining in the flared joint. In practice, even if the operating conditions make it difficult to align the axes of the pipes to be joined in the flared joint, the tapered inlet allows the joining operation.

[0145] Figure 34 The geometric dimensions of the inner tapered portion 412, which was fabricated on the first end 402 of the tube 400 prior to the heating process of the tube 400, were confirmed.

[0146] The term “αi” refers to the cone angle of the inner tapered portion 412 of the first end 402 of the tube 400 before heating the tube 400.

[0147] The term "Li" refers to the longitudinal extension of the inner tapered portion 412 of the first end 402 of the tube 400 before the heating process.

[0148] Figure 35 The geometric features of the inner tapered portion 412 formed at the first end 402 of the pipe 400 were confirmed at the moment of first contact between the first end 402 of the pipe 400 and the first portion 203 of the seal 200 mounted on the gasket 2.

[0149] The term "αp" refers to the moment when the first end 402 of the pipe 400 collides with the first portion 203 of the seal 200 mounted on the gasket 2, and the cone angle of the inner tapered portion 412 at the first end 402 of the pipe 400.

[0150] The term "Lp" refers to the longitudinal extension of the inner tapered portion 412 of the first end 402 of the pipe 400 at the moment when it collides with the first portion 203 of the seal 200 mounted on the gasket 2.

[0151] Figure 36 The geometric features of the inner tapered portion 108 after the first end 102 of the tube 100 is fully formed and finally cooled are shown.

[0152] The term "αf" refers to the cone angle of the inner tapered portion 108 of the first end 102 of the finished pipe 100.

[0153] The term "Lf" refers to the longitudinal extension of the inner tapered portion 108 of the first end 102 of the finished pipe 100.

[0154] Figure 37 The extension and positioning of the reinforcing element 206 at the first part 203 of the seal 200 were confirmed.

[0155] In this figure, the extension and positioning of the reinforcing element 206 are compared with the geometry 200, which describes the feature of the inner tapered portion 412 formed at the first end 402 of the tube 400 during the formation of the flare, at the moment of first contact between the first end 102 of the tube 100 and the first portion 203 of the seal 200 mounted on the gasket 2.

[0156] In the direction parallel to the axis 401 of the pipe 400, we have:

[0157] C0 = the distance between the vertex of the first part 203 of the seal 200 and the first end 206a of the reinforcing element 206.

[0158] C1 = Longitudinal extension of reinforcing element 206

[0159] C2 = the longitudinal extension of the first part 203 of the seal 200.

[0160] Experimental tests show that, in order to make the inner tapered portion of the pipe end edge more advantageous, the relationships (1) and (2) described below must be followed.

[0161] αp = θp ± 10° (1)

[0162] C2 > Lp ≥ C0+0.1C1 (2)

[0163] After defining the values ​​of αp and Lp, experimental tests confirmed that the values ​​of αi and Li corresponding to the generation of αp and Lp met the conditions (1) and (2). A unique relationship between the values ​​of αi and Li and the values ​​of αp and Lp was established.

[0164] αi=mαp

[0165] Li = n Lp

[0166] The final flared portion 113 will maintain the inner tapered portion of the end edge, which is defined by the values ​​of αf and Lf, and is different from αp and Lp but has a unique correlation with the values ​​of αp and Lp.

[0167] αf=rαp

[0168] Lf = s Lp

[0169] The coefficients m, n, r, and s depend on the characteristic parameters of the PVC-O pipe being processed, such as: pipe diameter (de); pipe wall thickness (e); circumferential orientation of the pipe; and axial orientation of the pipe.

[0170] These are all known fixed parameters, and their deviations are within the nominal tolerance range of the predetermined pipe production process.

[0171] Referring to condition (1), the best case is: αp = θp.

[0172] Therefore, the following type of correspondence applies: αf=rθp.

[0173] For the various but defined industrial pipes involved in this invention, we have: αf=rθp,2.5≥r≥0.75.

[0174] Regarding the extension Lf of the inner tapered portion 108 retained in the end edge of the flared portion, for various but already determined industrial pipes involved in the present invention, it is convenient to select the value of Li such that not only can an Lp value that meets condition (2) be generated, but also an Lf value that meets the following conditions.

[0175] LF≥0.1C1.

[0176] Downstream of processing unit 304 are unit 301 and flaring unit 1 (which will be described in detail below) for heating the tube to a predetermined heating temperature.

[0177] Machine 300 includes a unit 302 for cooling tubing, which is associated with the flaring unit 1 for cooling tubing 400 adapted to the molding pad 2 (e.g., ...). Figure 20 As shown, this will be described in detail below and forms part of the flared unit 1.

[0178] The molded pad 2 is configured to engage with the end portion E1 of the tube 400 starting from the first end 402.

[0179] Therefore, the flaring machine 300 includes multiple stations that operate sequentially on the pipe 400 (especially on the end portion E1 of the pipe 400 starting from the first end 402).

[0180] Station ST1 for receiving tubing is configured to pick up tubing 400 (with end edges 403 properly cut and chamfered) from the extrusion line.

[0181] Therefore, the station for receiving the tubing includes a pick-up unit 305.

[0182] Downstream of the station ST1 for receiving the tubing, machine 300 includes a tapering station SV, wherein a unit 304 for processing the tubing 400 is operatively activated at a first end 402.

[0183] The machine includes a preheating station ST2, in which a unit 303 for preheating pipe 400 is operatively activated, the pipe 400 being located in the preheating station after a station for tapering the pipe.

[0184] In the preheating station ST2, the pipe 400 is preferably heated to a temperature below the glass transition temperature (Tg) of PVC.

[0185] The machine also includes a heating station ST3, in which a unit 301 for heating the tube 400 is operatively activated.

[0186] Pipe 400 is located in the heating station after the preheating station.

[0187] In heating station ST3, the pipe 400 is heated to a temperature higher than the glass transition temperature of PVC, and in any case, to a temperature higher than the heating temperature.

[0188] The presence of the preheating station ST2 is optional; that is, machine 300 may also include only one heating station ST3.

[0189] Optionally, the machine 300 includes a preheating unit 303 located upstream of the heating unit 301 and configured to heat the pipe 400 to a predetermined preheating temperature, which is lower than the heating temperature.

[0190] Preferably, the preheating unit 303 includes an oven.

[0191] Preferably, the heating unit 301 includes an oven.

[0192] Preferably, the oven is a contact oven.

[0193] The oven heats the end portion E1 of the tube 400 in different ways along the longitudinal direction of the tube 400.

[0194] The heating station ST3 also includes an internal contact element located inside the tube to internally support the end portion E1 of the tube 400 during heating and to prevent the diameter of the tube from shrinking.

[0195] At the end of the heating step, the temperature at the end of the pipe 400 is about 100°C, while in the section forming the connecting wall between the pipe and the flared section, the temperature drops to 80°C.

[0196] This invention relates to a unit 1 (part of a forming machine 300) for expanding a pipe T made of PVC-O type thermoplastic material. The unit 1 includes a forming pad 2 for deforming an end portion E1 of the pipe 400 into a flared shape B. The pad 2 has a symmetrical longitudinal central axis X1 and a region 3 for receiving an annular seal 200, which is designed to internally connect with the pipe 400. See [link to relevant documentation]. Figure 4A .

[0197] It should be noted that the inner tapered portion 412 of the pipe 400 can significantly reduce the contact pressure between the rear shoulder 203 of the seal 200 and the first end 402 of the pipe 400.

[0198] As described in the prior art, the collapse problem of the seal 200 occurs during the step of inserting the pipe 400 into the seal 200 housed in the gasket 2.

[0199] Under the force of the wall of the pipe 400, the seal 200 is compressed by the first end 402 of the pipe 400 and abuts against the contact element 4 and the gasket 2.

[0200] In the subsequent deformation of the seal 200, the cone angle of the first part 203 tends to increase significantly, in contrast to the gradual insertion of the pipe 400.

[0201] Advantageously, in the machine according to the invention, the distribution of force on the sealing element 200 can prevent damage to the sealing element 200, especially in the discontinuous region that separates the reinforcing element 206 from the elastomeric body of the sealing element 200, that is, the boundary region between the reinforcing element 206 and the elastomeric body on the first portion 203 of the sealing element 200.

[0202] The annular contact element 4 is slidably adapted to the pad 2 to move between the forward position P1 and the backward position P2 along the direction of the longitudinal central axis X1.

[0203] Unit 1 includes a first heating device 6 configured to heat the annular contact element 4 to a certain temperature (above the glass transition temperature) and thereby heat the inner surface of the end portion E1 of the tube 400 adapted to the annular contact element 4 by contact heating.

[0204] The second heating device 5 is configured within a predetermined area of ​​the molding pad 2 for external heating of the tube 400 made of thermoplastic material adapted to the molding pad 2 (more specifically, the predetermined area extends from the proximal region of the region 3 designed to accommodate the seal 200 to the first end 402 of the tube 400).

[0205] It should be noted that the assembly consisting of the second heating device 5 and the first heating device 6 can define a hot (cylindrical) chamber 21.

[0206] Regarding the second heating device 5, it should be noted that the device preferably includes an annular heating element 12.

[0207] The annular heating element 12 is preferably made of a metallic material, and more preferably of an aluminum alloy.

[0208] The second heating device 5 may include a plurality of heating elements 20 located in (around or embedded in) the annular heating element 12, for generating heat from multiple different zones.

[0209] According to one variation, the second heating device 5 may include a single resistor located in (around or embedded in) the annular heating element 12.

[0210] One or more resistors are configured to uniformly heat the annular heating element 12.

[0211] The second heating device 5 heats the end portion E1 of the external heating pipe 400, preferably starting from the first end 402 and continuing to the area 3 for accommodating the seal 200.

[0212] The annular heating element 12 is configured to form a thermal chamber (cylindrical) 21 with the annular contact element 4 heated by the first heating device 6.

[0213] The size of the hot chamber 21 is preferably designed to encompass a portion of the end tube 400 adapted to the annular contact element 4.

[0214] Therefore, the wall of the end portion E1 of the tube 400 is contained in the hot chamber 21, the corresponding inner surface is in contact with the surface of the annular contact element 4, and the adjacent outer surface is separated from the inner surface of the annular heating element 12.

[0215] It should be noted that the predetermined distance between the outer surface of the wall of the tube 400 and the inner surface of the annular heating element 12 allows the tube wall to be inserted into the hot chamber 21 without interfering with (not contacting) the annular heating element 12.

[0216] Experimental tests have concluded that the optimal distance between the wall of the tube 400 and the inner surface of the annular heating element 12 is between 0.5 and 10 mm; more preferably between 1 and 8 mm; and even more preferably between 2 and 6 mm.

[0217] The position of the annular heating element 12 is such that the distance between the wall and the inner surface of the pipe 400 makes the convection effect of the hot air negligible, which would interfere with the transfer of heat to the pipe 400.

[0218] Heat transfer from the annular heating element 12 to the tube 400 is mainly carried out by irradiation.

[0219] Preferably, the second heating device 5 heats the end portion E1 of the pipe 400 without contact (the position of the pipe is preferably not in contact with the annular heating element 12).

[0220] Preferably, the second heating device 5 heats the end portion of the tube 400 by irradiation.

[0221] Experimentally and advantageously, it has been found that during the flaring process, the end portion E1 of the pipe 400 adapted to the annular contact element 4 is heated from the inside by contact with the annular contact element 4 (heated by the first heating device 6), and heated from the outside by the heating element 12 heated by the second heating device 5. More specifically, the fact that uniform heating is performed at a predetermined temperature allows for a significant improvement in the flaring effect of PVC-O, thereby allowing the formation of a flared portion in the PVC-O pipe with a larger size (diameter and wall thickness) than that of pipes processed according to conventional techniques.

[0222] Therefore, the unit 1 according to the present invention can process PVC-O pipes with large diameter / wall thickness.

[0223] According to another aspect, the molded pad 2 is equipped with a first annular seat S1 for accommodating at least a portion of the seal 200.

[0224] According to another aspect, the annular contact element 4 is equipped with a second seat S2 for receiving the seal 200, which receives at least a portion of the seal 200.

[0225] Advantageously, the shapes of seats S1 and S2 are designed to receive corresponding portions of seal 200, especially portions of the inner surface 201 of seal 200.

[0226] Specifically, the shapes of seats S1 and S2 are designed to allow the adhesive force between the seal and the molded pad 2 and the annular contact element 4, respectively, to reach its maximum.

[0227] The technical effects of the presence of the second seat S2 for accommodating the seal 200 and the first annular seat S1 for accommodating the seal 200 will be described below.

[0228] The applicant has discovered through experiments that the presence of the second seat S2 of the seal 200 facilitates the insertion of the pipe 400 into the gasket 2 and the seal 200, and to a certain extent (as much as possible) reduces the risk of serious damage to the seal 200 due to stress caused by contact with the pipe 400.

[0229] In fact, the second S2 restricts the deformation of the seal by housing a portion of it, which occurs when the pipe 400 is fitted onto the seal.

[0230] Preferably, the second seat S2 has a concave shape toward the distal portion of the pad 2 (i.e. toward the clamping member 10).

[0231] The first annular housing seat S1 has essentially the same technical effects as the second seat S2.

[0232] Therefore, by receiving a portion of the seal within it, the first annular housing seat S1 helps limit the deformation of the seal 200 during flaring, thereby reducing the risk of excessive deformation of the seal 200.

[0233] According to yet another aspect, unit 1 includes control and operation unit 7 (electronic unit, including hardware and / or software).

[0234] According to yet another aspect, unit 1 includes a first (temperature) sensor 9 configured to measure the temperature at the first heating device 6 (more precisely, to measure the temperature of the annular contact element 4).

[0235] According to another aspect, unit 1 includes a second (temperature) sensor 8 configured to measure the temperature at the second heating device 5.

[0236] Preferably, but not necessarily, the first sensor 9 is a thermocouple.

[0237] Preferably, but not necessarily, the second sensor 8 is a thermocouple.

[0238] The control and operation device 7 is configured to adjust the second heating device 5 according to the temperature value measured by the second sensor 8 to heat a portion of the area 3 in the pipe 400 used to accommodate the seal 200 to a predetermined temperature up to the first end 402 of the pipe 400.

[0239] The control and operation device 7 is configured to adjust the first heating device 6 according to the temperature value measured by the first sensor 9 to heat the annular contact element 4 to a predetermined temperature (above the glass transition temperature).

[0240] According to yet another aspect, the device 1 includes a clamping element 10 for clamping the tubing.

[0241] The clamping member 10 is provided with clamping clamps (10A, 10B) that can move relative to each other between the closed and open configurations (particularly, preferably the first and second clamping clamps).

[0242] The clamping member 10 fixes the tube 400 in a horizontal position, so that the longitudinal axis 401 of the tube 400 coincides with the axis X1 of the forming pad 2.

[0243] On the other hand, the molded pad 2 and the annular contact element 4 are supported by the bracket 11.

[0244] More specifically, the molding pad 2, the annular contact element 4, the second heater 5, and the first heater 6 are supported by a bracket 11 (movable relative to the machine frame).

[0245] It should be noted that the annular contact element 4 is configured to move relative to the support 11, that is, to move relative to the molded pad 2.

[0246] More specifically, the annular contact element 4 is supported by the bracket 11, but can move independently of the bracket 11.

[0247] Preferably, the annular contact element 4 and the second heater 5 are connected as one unit to each other during the movement relative to the pad 2 (i.e., they always move as a whole).

[0248] According to another embodiment, the annular contact element 4 can move independently of the second heating device 5 during relative movement with respect to the pad 2.

[0249] The advantage of this last embodiment is that it can better adapt to changes in operating conditions; more specifically, when the annular contact element 4 is withdrawn and separated from the tube 400, the second heating device 5 can remain in the heating position to provide heating for a portion of the tube that forms on the seal and gasket in the event of spontaneous shrinkage.

[0250] As a result, the spontaneous shrinkage effect of the pipe end wall was enhanced.

[0251] The support 11 can move between a position P4 near the pipe 400 and a position P5 away from the pipe 400.

[0252] The support 11 is driven by a corresponding actuator device (not shown).

[0253] Regarding the annular contact element 4, it should be noted that, preferably, the annular contact element 4 is a hollow cylindrical body (preferably made of metal).

[0254] More specifically, it should be noted that the annular contact element 4 is mounted on the support 11 and is movable relative to the molding pad 2: in other words, the molding pad 2 and the annular contact element 4 are configured to move independently.

[0255] The annular contact element 4 can slide on the molded pad 2; more precisely, the inner surface of the annular contact element 4 can slide on the outer surface of the molded pad 2.

[0256] Regarding the adaptation of the seal to the molded gasket 2, unit 1 may include a device for picking up and moving the seal 200, which is of a conventional type and therefore not described.

[0257] Regarding the seal 200, it should be noted that the seal 200 is located in the area 3 for receiving the gasket 2 before the pipe 400 is fitted onto the gasket 2.

[0258] The receiving area 3 is defined by the lower section formed on the outer surface of the pad 2.

[0259] Regarding the pad 2, it should be noted that unit 1 includes a heater for heating and molding the pad 2.

[0260] According to a non-limiting example, the pad 2 can be heated by an internal loop labeled 13 for circulating a heating fluid (e.g., water).

[0261] Preferably, the pad 2 is heated to a temperature between 40°C and 65°C (below the glass transition temperature of PVC-O).

[0262] More preferably, the pad 2 is heated to a temperature between 45°C and 60°C (or alternatively, a temperature between 45°C and 55°C).

[0263] Regarding the annular contact element 4, it should be noted that, preferably, it is heated (by the first heating device 6) to a temperature between 85°C and 105°C (more preferably between 90°C and 100°C, and even more preferably between 92°C and 100°C).

[0264] For example, the first heating device 6 is defined by resistor 22.

[0265] Resistor 22 is controlled by control and operation device 7.

[0266] The present invention provides a method for expanding a pipe 100 made of PVC-O type thermoplastic material according to the present invention.

[0267] The method includes the following steps:

[0268] - The step of feeding the pipe 400 into station ST1 for receiving the pipe 400;

[0269] - In the tapering station SV, the step of making an inner tapered portion 412 at the first end 402 of the end portion E1 of the tube 400;

[0270] -After the step of making the inner tapered part 412, the end portion E1 of the tube 400 is heated in the heating station ST3;

[0271] - After the step of heating the end portion E1 of the tube 400, the step of expanding the end portion E1 of the tube 400.

[0272] Advantageously, the shape of the end portion E1 with an inner tapered portion at the first end 402 of the pipe 400 significantly increases the contact surface when the first end 402 of the pipe 400 collides with the seal 200, thereby reducing the contact pressure and local deformation of the seal.

[0273] Advantageously, the extension of the tapered portion is at least equal to the extension when it comes into contact with the reinforcing element 206, which facilitates contact between the first portions 203 of the seal 200 without damaging the seal 200.

[0274] The flaring step includes preparing a molding pad 2, which is designed to deform the end portion E1 of the tube 400 made of thermoplastic material into a flared shape, starting from the first end 402; preparing an annular contact element 4, which is mounted on the molding pad 2 and is movable along the molding pad 2 between a forward position P1 and a retracted position P2; and preparing an annular seal 200 on the molding pad 2 in a predetermined area 3, the annular seal 200 being designed to be stably located in the flared portion B to be formed (integrated with the finished tube 100). The annular contact element 4 is positioned in the forward position P1 to contact the seal 200 disposed in region 3. The tube 400 is prepared, and the end portion E1 of the tube 400 is heated to a predetermined temperature (greater than the glass transition temperature Tg) to allow deformation. In the direction of the axis of symmetry 401 of the tube 400, the end portion E1 of the tube 400 and the gasket 2 are moved toward each other to a predetermined distance to adapt the end portion E1 to the assembly of the end gasket 2, the seal 200, and the annular element 4.

[0275] The method further includes the following steps: heating the annular contact element 4 to a predetermined temperature (above the glass transition temperature) such that the inner surface of a portion of the end tube 400 adapted to the annular contact element 4 is heated by contact, while the tube 400 made of thermoplastic material adapted to the molded pad 2 is heated from the outside in a predetermined region of the pad 2, the predetermined region extending from the proximal region of the region 3 for receiving the seal 200 to the first end 402 of the tube 400.

[0276] Move the annular contact element 4 from the forward position P1 to the exit position P2, so that the annular contact element 4 is released from the seal 200 and the pipe 400 (no longer in contact with them).

[0277] According to yet another aspect, the molded pad 2 is provided with a first annular seat S1 for receiving the seal 200, the first annular seat S1 being radially oriented toward the outside of the molded pad 2, and the step of adapting the end portion E1 of the tube 400 to the assembly of the molded pad 2 and the annular seal 200 includes the step of receiving at least a portion of the seal 200 into the first seat S1 for receiving the molded pad 2.

[0278] According to yet another aspect, the annular contact element 4 is provided with a second seat S2 for receiving a portion of the seal 200, and the step of positioning the annular contact element 4 in the forward position P1 includes the step of receiving at least a portion of the seal 200 into the second seat S2.

[0279] According to another aspect, the step of preparing an annular seal 200 on the molded pad 2 at a predetermined position includes adapting the seal 200 to the molded pad 2, and moving the annular contact element 4 from the exit position P2 to the advance position P1 to contact the seal 200 and move it to the predetermined position of the molded pad 2.

[0280] According to yet another aspect, the method includes the step of clamping the pipe by closing clamp 10 before moving the end portion E1 of the pipe 400 and the pad 2 relative to each other to a predetermined distance.

[0281] According to another aspect, the method includes, after the following steps, releasing the tube 400 by opening the clamp 10 for a predetermined time: moving the end portion E1 of the tube 400 and the molding pad 2 toward each other to a predetermined distance in the direction of the longitudinal central axis 401 of the tube 400; positioning the annular contact element 4 in the forward position P1 for contacting the tube 400 and the seal 200 of the tube; and simultaneously heating the end portion E1 of the tube 400, made of thermoplastic material, to a predetermined temperature from the inside and outside in a region extending from the receiving area 3 where the seal 200 is disposed to the first end 402 of the tube 400 for a predetermined time.

[0282] According to yet another aspect, the step of releasing the tubing by opening the clamp 10 is performed before, or partially superimposed on, the step of moving the annular contact element 4 from the forward position P1 to the exit position P2, so as to release it from the seal 200 and the tubing 400.

[0283] According to another aspect, the method includes, after the step of releasing the pipe 400 by opening the clamp 10 for a predetermined time, the step of further clamping the pipe 400 by closing the clamp 10.

[0284] According to yet another aspect, the method includes, after moving the annular contact element 4 from the forward position P1 to the retracted position P2 to release it from the seal 200 of the pipe 400, moving the annular contact element 4 from the disengaged retracted position P2 to the engaged forward position P1, until an intermediate position P3 where the annular contact element 4 engages with the end 402 of the pipe 400 between the seal 200 and the end edge 402 of the pipe 400.

[0285] Advantageously, this allows for the obtaining of the flared portion B, in which the seal 200 has the desired final inner diameter, because the end of the tube 400 is stressed by the annular element 4 while it is still in its extended stage (not fully cooled), thus allowing the seat of the tube 400 and the seal 200 to be modeled so that once the finished tube 100 has cooled, the seal 200 has the correct final diameter and can properly accommodate the connection of another tube 100.

[0286] During the formation of the flared section, when the wall of the pipe 400 is fully formed on the seal 200 and the gasket 2, but the cooling and final stabilization steps of the flared section have not yet been initiated, the response of the wall of the flared section to mechanical stress, even if it is mainly an elastic response, is generally an elastoplastic response.

[0287] In particular, the plasticity is more pronounced in the area from the front shoulder of the flared portion to the end edge of the flared portion, adjacent to the seal 200.

[0288] In fact, this section is constantly subjected to heat transfer from the hot chamber, and due to this heating, it maintains residual plasticity.

[0289] If, during this step of the process for forming the flare, the annular contact element 4 is advanced toward the edge of the flare of the tube 400, so that the annular contact element 4 moves to a predetermined height where the edge of the flare is pressed, the radial pressure of the flare wall will be beneficially released onto the seal 200.

[0290] During this step, the seal 200 is compressed and flattened by the wall of the flared portion toward the gasket 2.

[0291] The seal 200 is elastic; therefore, even if the inner wall of the flared portion within the seal region expands, the seal 200 maintains adhesion to the inner wall of the flared portion, meaning it can elastically recover the previously flattened portion. Simultaneously, the inner wall of the flared portion of the pipe 400 continues to cool gradually, allowing the elastic relaxation portion of the seal 200 to be partially retained when the contact action between the annular contact element 4 and the edge of the pipe 400 ends, i.e., when the annular contact element 4 moves from the intermediate position P3 to the exit position P2. This is because the mechanical response of the flared portion to the stress induced by the annular contact element 4 is not perfectly elastic, but rather elastoplastic.

[0292] This partial loosening of the seal 200 is sufficient to ensure that the inner diameter of the tube 100 at the seal is the required inner diameter after the gasket 2 is removed from the finally cooled flared section (which is necessary for the proper functioning of inserting the next tube into the flared section while maintaining a seal).

[0293] The following is a brief introduction Figures 5 to 22 The method of the present invention is illustrated in detail in the figure.

[0294] Figures 5 to 22 The steps of the flaring process are shown.

[0295] Figure 5 The steps for positioning the tube 400 within the clamp 10 are shown.

[0296] As shown in the figure, when the tube 400 is positioned, its axis 401 is aligned (coincident) with the axis X1 of the forming pad 2 (and the axis of the contact element 4).

[0297] Figure 6 The steps for closing the clamp 10 are shown. The tube 400 is locked between the clamping jaws (10A, 10B) of the clamp 10.

[0298] Figures 7 to 14 The bracket 11 is shown being advanced toward the tube 400 at different forward positions. During these steps, the tube 400 is gradually inserted into the molding pad 2 (the tube is fitted onto the molding pad 2, inserted into the seal 200, and finally inserted into the annular contact element 4, that is, into the hot chamber 21).

[0299] During these steps, the stent 11 is moved from the distal position P5 to the proximal position P4.

[0300] Figure 14 A step is shown in which the support 11 is in the proximal position P4 and the annular contact element 4 is in the forward position P1.

[0301] During this step, the clamping member 10 is in an open configuration, that is, each clamping clamp (10A, 10B) is open.

[0302] The figure shows the beginning of the extension step of the forming flared portion, wherein the clamps 10A and 10B of the clamping member 10 remain open for a predetermined time.

[0303] Figure 15 The extension step of the flared section is shown.

[0304] During this step, the clamp 10 is in the open configuration, the bracket 11 is in the closed position P4, and the annular contact element 4 begins to move from the forward position P1 toward the exit position P2.

[0305] From the moment the pipe 400 is inserted into the seal 200 until the extension step is completed, the first heating device 6 is activated to heat the inside of the pipe, while the second heating device 5 is activated to heat the pipe 400, which is made of thermoplastic material, from the outside. Both heating devices (5, 6) contribute to heating the end portion E1 of the pipe 100, which extends from the seat 111 of the seal 200 to the first end 102 of the pipe 100.

[0306] Figure 17 This shows the end of the extension step of the flared section.

[0307] During this step, the clamp 10 is in a closed configuration.

[0308] Figure 18 A step is shown in which the annular contact element 4 moves toward the tube 400 (towards the forward position P1), that is, the annular contact element 4 moves to the intermediate position P3 (between the forward position P1 and the exit position P2), in which the annular contact element 4 engages with the edge of the flared portion of the tube 400.

[0309] In this way, the annular contact element 4 impacts and compresses the edge of the flared portion.

[0310] The annular contact element 4 is held in a predetermined position in the middle position where it engages with the edge of the tube 400 for a predetermined time to allow the seal 200 to relax elastically and the edge of the tube 400 to adapt.

[0311] This step defines the elastic relaxation of seal 200 and the fit of the edge of pipe 400.

[0312] Figure 19 This illustrates the end of the elastic relaxation of seal 200 and the edge fit of tubing 400.

[0313] The annular contact element 4 moves away from the pipe 100 and toward the exit position P2.

[0314] Figure 20 The annular contact element 4 is shown in the disengaged, withdrawn position P2 (without any engagement with the seal 200 and / or the tubing 400).

[0315] The flared section is still hot, and during this step, cooling of the first end E1 of the pipe 400 begins (using cooling unit 302).

[0316] Figure 21 The flared portion 113 of the tube 100, manufactured while the clamp 10 remains closed, is shown. In this step, the bracket 11 is moved to the distal position P5 to disengage the pad 2 from the tube 100.

[0317] Figure 22 The clamping member 10 is shown in the open configuration. During this step, the tube 100 (with the fabricated flare 113 and the seal 200 inserted into the tube) is pulled out from the unit 1.

[0318] Figures 23 to 33 The process of forming the flared portion of the tube 100 according to the invention is shown in more precise detail (time).

[0319] exist Figures 23 to 25 In the middle, the support 11 moves toward the pipe 400; Figure 30 In the middle, the ring element 4 moves toward the exit position P2.

[0320] like Figure 26 As shown, the first impact between the end edge of the pipe and the shoulder of the seal occurs on the surface of the end edge of the flared pipe, with its cone angle αp being equivalent to the tilt angle θp of the shoulder 203 of the seal 200.

[0321] exist Figure 32 In the middle, the annular element 4 moves toward the closed position P1, more specifically, until it reaches the predetermined intermediate contact position P3 with the edge of the tube 400 (before which it moves again toward the exit position P2).

[0322] It should be noted that, according to the above method and unit 1, the seal 200 is permanently locked inside the tube 100 (for the form connection and the connection established between the material of the tube 100 and the seal 200 during processing).

[0323] Using the machine and method described above, prior to the heating process, especially through the aforementioned embodiment of the inner tapered portion 412 of the first end portion E1 of the tube 400, the axial compressive stress of the wall is significantly reduced, and the design defines the flared portion 113 of the finished tube 100.

[0324] The internal action generated during the entire process of inserting the pipe 400 into the seal 200 offsets or significantly reduces the initial axial orientation of the PVC-O pipe in the first end portion E1 of the flared portion 113 of the finished pipe 100.

[0325] The presence of these stresses is related to the increase in the wall thickness of the flared portion 113 of the finished pipe 100 relative to the wall thickness of the pipe 400 without a flared portion.

[0326] In fact, this thickening is essentially a permanent deformation caused by axial compressive load.

[0327] In fact, through the machine 300 and method, the shape of the seal 200 installed in the gasket 2 remains basically unchanged throughout the entire step of inserting the pipe 400 into the seal 200, so the resistance that creates an axial contrast with the wall of the pipe and causes it to thicken is not significant, and therefore the resistance of the flared part 113 to hydrostatic pressure is not adversely affected.

[0328] Indirectly, the flaring unit 1 according to the invention is already advantageous in achieving the correct shape of the last part of the flaring portion 113, that is, in locking the seal 200 in the wall of the flaring portion 113. It also helps to limit the phenomenon of generating axial compressive stress, which would have an adverse effect on the orientation of the material in the flaring portion 113.

[0329] In fact, the unit 1, designed to perfectly form the final part of the flare 113 on the seal 200, can limit the heating state of the tubing, which is necessary to start and complete the flare forming process.

[0330] The cooler tubing is more elastic and rigid, resulting in less permanent plastic deformation due to axial compression during the insertion of tubing 400 into gasket 2, seal 200, and flange 4.

[0331] Advantageously, and according to the appended claims, the RIEBER method allows for the creation of flared sections in PVC-O pipes even with considerable wall thickness.

[0332] This flaring unit 1 and method are extremely effective and allow for the production of high-quality flared sections in PVC-O pipes (both in terms of the size and structural features of the flared section, as well as the connection between the seal and the pipe and the relative seal during the connection of the pipe with other pipes).

[0333] Furthermore, according to the appended claims, PVC-O pipes suitable for operating pressures of 25 bar and with diameters up to 630 mm can also be manufactured.

Claims

1. A pipe made of PVC-O type thermoplastic material, the pipe having an outer surface (109) extending about an axis of symmetry (101); the pipe (100) having a main longitudinal extension from a first end (102) to a second end (103) in a direction parallel to the axis of symmetry (101); At the second end (103), the outer surface (109) of the tube (100) has a chamfer (110) with an inclination of β relative to a direction parallel to the axis of symmetry (101). The pipe (100) has an inner cavity (104) extending from the first end (102) to the second end (103). The tubing (100) includes a seal (200) located in a corresponding receptacle (111) and having a circumferential extension relative to the axis of symmetry (101); The seal is located in the housing (111) in a non-removable manner; The seal (200) has an inner surface (201) facing the inner cavity (104) and an outer surface (202) facing the receptacle (111); the outer surface (202) of the seal (200) has a first portion (203) and a second portion (204) arranged adjacent to each other, thereby defining a tip (205); the first portion (203) and the second portion (204) are inclined at corresponding acute angles θp, θa with respect to a direction parallel to the axis of symmetry (101); The inner cavity (104) includes a first segment (105) having a first diameter and a second segment (106) having a second diameter at least larger than the first diameter, and a third segment (107) for connecting the first segment (105) to the second segment (106), the third segment (107) having a converging shape from the second segment (106) to the first segment (105); The tubing (100) is characterized in that the inner chamber (104) has a tapered portion (108) adjacent to the second segment (106) and directed towards the external environment at the first end (102) of the tubing (100), the tapered portion (108) having a diverging tendency from the second diameter of the second segment (106) toward the external environment; The inclination of the tapered portion (108) relative to the direction parallel to the axis of symmetry (101) is equal to an acute angle αf. The value of the acute angle αf is related to the value of the acute angle θp of the inclination of the first portion (203) of the outer surface (202) of the seal (200) relative to the direction parallel to the axis of symmetry (101) of the tube (100), with a factor "r" between 0.75 and 2.5, inclusive. αf=r θp.

2. The pipe according to claim 1, characterized in that, The value of the angle β of the chamfer (110) is between 10° and 25°, including 10° and 25°.

3. The pipe according to claim 1 or 2, characterized in that, The acute angle θp of the inclination of the first portion (203) of the outer surface (202) of the seal (200) relative to the direction parallel to the axis of symmetry (101) of the tube (100) is between 25° and 35°, including 25° and 35°.

4. The pipe according to claim 1, characterized in that, The acute angle θa of the inclination of the second portion (204) of the outer surface (202) of the seal (200) relative to the direction parallel to the axis of symmetry (101) of the tube (100) is between 25° and 40°, including 25° and 40°.

5. The pipe according to claim 1, characterized in that, The seal (200) includes a reinforcing element (206) located in the seal (200) at the first portion (203) of the outer surface (202).

6. The pipe according to claim 5, characterized in that, The reinforcing element (206) is made of metal or plastic material.

7. The pipe according to claim 5, characterized in that, The tapered portion (108) of the inner chamber (104) has an extension that is proportional to the extension of the reinforcing element (206) in a direction parallel to the axis of symmetry (101) of the tubing, and the extension of the tapered portion (108) is at least equal to the extension of the reinforcing element (206) multiplied by a factor of 0.

1.

8. The pipe according to claim 2, characterized in that, The convergence tendency of the third segment (107) is inclined relative to the direction parallel to the axis of symmetry (101), determined by the convergence angle. The convergence angle is defined as follows: The value is within ±5° of the acute angle β, which is the angle of inclination of the chamfer (110) relative to the direction parallel to the axis of symmetry (101).

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