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BR-102025008708-A2 - MACHINE AND METHOD FOR FLARING PVC PIPES

BR102025008708A2BR 102025008708 A2BR102025008708 A2BR 102025008708A2BR-102025008708-A2

Abstract

A flaring machine comprising a forming station (600), in which the PVC-O pipes (1) each have an integrated flaring socket (3) formed therein and provided with a seat (6) to receive a joint (100); the forming station (600) comprises a flaring apparatus (40) for flaring the end of the PVC-O pipe (1a) to be processed; the apparatus (40) comprises forming means (59) for forming the end of the pipe (1a) into a flaring socket, which comprise a mechanical mandrel (15) intended to be inserted into one end of the pipe (1a) and a forming flange (14) for forming at least part of the end of the pipe (1a); the forming flange (14) comprises an annular body (26) whose inner surface (27) defines, with the outer surface (36) of the mandrel (15), a forming chamber (35) to form a portion of the flare socket (3a) to be formed.

Inventors

  • Giorgio Tabanelli
  • Elisa FILIPPI

Assignees

  • SICA S.P.A.

Dates

Publication Date
20260310
Application Date
20250430
Priority Date
20240502

Claims (13)

  1. 1. Flaring machine comprising a feeding station (400) for feeding PVC-O pipes (1a) to be processed, one or more heating stations (500) for heating one end of the PVC-O pipe (1a) to be processed and a forming station (600) for forming the end of the PVC-O pipe (1a) to be processed into the shape of a flaring socket; upon exiting the forming station (600), the PVC-O pipes (1) each have an integrated flaring socket (3) formed in them and provided with a seat (6) to receive a joint (100); the forming station (600) comprises a flaring apparatus (40) for flaring the end of the PVC-O pipe (1a) to be processed; the apparatus (40) comprises forming means (59) for forming the end of the tube (1a) into a flare socket and comprising a mechanical mandrel (15), intended to be inserted into one end of the tube (1a) and a forming flange (14) for forming at least part of the end of the tube (1a); the mandrel (15) and the forming flange (14) are coaxial with each other; the forming flange (14) is disposed around part of the outer surface (36) of the mandrel (15); the mandrel (15) has a tip (16) and a cylindrical portion (65) comprising expandable segments (17) that define an annular portion (64) extending from the cylindrical portion (65) of the mandrel (15); the said annular portion (64) has an end wall (66), a front fitting (67) and a rear fitting (68), in relation to the tip (16) and the cylindrical surface (65) of the mandrel (15); movement means (41) move the forming flange (14) in relation to the mandrel (15) in translation parallel to the axis of the forming means (59) in a first feed direction and a second feed direction opposite to the first, and vice versa; characterized by: - the forming flange (14) comprising an annular body (26) whose inner surface (27) defines, with the outer surface (36) of the mandrel (15), a forming chamber (35) to form a portion of the flare socket (3a) that is being formed; the forming chamber (35) extends at least into the annular portion (64) of the mandrel (15) and has a blind end defined by a flat front end (22); the inner surface (27) of the annular body (26) is at least partially shaped to coincide with the outer surface (36) of the mandrel (15) on the end wall (66) of the annular portion (64), on the back fitting (68) and on the cylindrical surface (65) adjacent to the back fitting (68).
  2. 2. Flaring machine, according to the preceding claim, characterized in that, starting from the outside towards the flat front end (22), the inner surface (27) of the annular body (26) has a mouth (28) converging and smoothly fused with a first cylindrical surface (29), followed by a conical surface (30); a curved fitting (31) converging with the conical surface (30) connects to a second cylindrical surface (32).
  3. 3. Machine according to the preceding claim, characterized in that the second cylindrical surface (32) has a plurality of through openings (33) arranged circumferentially along the second cylindrical surface (32) itself.
  4. 4. Flaring machine, according to any of the preceding claims, characterized in that the forming flange (14) comprises a cylindrical collar (20) coaxial to the mandrel (15), whose end, considering a positioning plane orthogonal to the axis (15a) of the mandrel (15), is the flat front end (22) of the forming chamber (35).
  5. 5. Flaring machine, according to any of the preceding claims, characterized in that, to interrupt the relative movement between the mandrel (15) and the forming flange (14), a control and drive unit (60) is configured to receive an activation signal (62) from a sensor (51) configured to be activated when a relative position between the mandrel (15) and the forming flange (14) is reached; in the forming chamber (35), there is a free front (54) of a sensor (53) intended to contact the end (13a) of the edge of the flaring socket (7a) being formed, which projects from the flat front end (22) of the forming chamber (35) by a given length Y; the free front (54) of the sensor (53) is configured to create a retraction stroke of length p, which is less than Y and which is the limit for activation of the sensor (51).
  6. 6. Machine according to the preceding claim, characterized by elastic means (55) maintaining the contact sensor (53) in the rest position; the extension of the elastic means (55) being limited by cam means (52), fastened in an open groove (58) in an inner wall of the cylindrical collar (20) and arranged coaxially with the contact sensor (53); the cam means (52) define means to activate the sensor (51), whose activation signal (62) is sent to the control and drive unit (60).
  7. 7. Machine according to claim 5 or 6, characterized in that the control and drive unit (60), after receiving the activation signal (62), is configured to activate the motion means (42) that move the forming flange (14) relative to the mandrel (15); the motion means (42) move the forming flange (14) by a distance equal to the length Y mentioned above and by a defined forming stroke q.
  8. 8. Machine, according to any of the preceding claims, characterized in that, when the flaring process begins in the forming station (600), the forming flange (14) is arranged in an intermediate position relative to the mandrel (15), so that the free front (54) of the contact sensor (53) is located on the edge (7a) of the flaring socket, whose virtual length is: where E is the length of the flare socket edge (3) of a finished tube (1), q is the forming stroke and ep is the retraction limit stroke to activate the sensor (51).
  9. 9. Flaring method, for production in a flaring machine according to claim 1, comprising a step of feeding PVC-O pipes (1a) to be processed, a step of heating one end of the PVC-O pipe (1a) to be processed and a step of shaping the end of the PVC-O pipe (1a) to be processed into the shape of a flaring socket; said flaring socket (3a) being formed has a flaring socket edge (7a) with a free end (13a) and a seat (6) to receive a joint (100) with an end wall (8a) and a pair of inclined side walls (9a, 10a); the shaping step comprises the following substeps: - clamping the pipe (1a) in a horizontal position and leaving the heated end to be formed free; - insert a mechanical mandrel (15) into the heated free end so that it is coaxial with the tube (1a) until the end (13a) of the tube edge (1a) impacts a free front (54) of a contact sensor (53); characterized by comprising the steps of: - instructing the mandrel (15) to stop when the free front (54) of the sensor (53) has traveled the length of a retraction stroke p; - actuating the movement of a forming flange (14) which has a forming chamber (35) to contain the wall of the flare socket (3a) formed on the outer face of the end wall (8a) of the seat (6a) of the joint (100) and on the edge of the flare socket (7a); As the forming flange (14) travels the length of a Y section, the forming chamber (35) comes into contact with the end (13a) of the edge of the flare socket (3a) and the outer face of the inclined front wall (9a) of the seat (6a) of the joint (100).
  10. 10. Flaring method, according to the previous claim, characterized in that the forming flange (14), after traversing the length of a section Y, traverses the length of a section of the forming stroke q, where the forming chamber (35) molds the wall of the flaring socket (3a) being formed, the edge end (13a) of the flaring socket (3a) and the outer face of the inclined front side wall (9a) of the seat (6a) of the joint (100), forcing the wall of the tube (1a) to adhere to the forming chamber (35).
  11. 11. Flaring method, according to the previous claim, characterized in that, when the forming flange (14) reaches the end of the forming stroke, corresponding to the advanced position of the forming flange (14), the method comprises a cooling step of the formed flaring socket (3).
  12. 12. Flaring method, according to the previous claim, characterized in that the cooling step of the molded flaring socket (3) is carried out, at least partially, after a subsequent step of extracting the forming flange (14) from the flaring socket (3).
  13. 13. Flaring method, according to claim 11 or 12, characterized in that the cooling step of the molded flaring socket (3) is followed by a mandrel extraction step (15), thereby releasing the tube (1) which has the integral flaring socket (3) molded therein.

Description

[001] The present invention relates to a machine and a method for widening, or enlarging, PVC-O pipes. [002] In the 1970s, the use of unplasticized polyvinyl chloride, known as PVC-U, became established in the production of pressurized water supply pipes with solid walls. [003] Starting in the late 1990s, processes were developed for the industrial production of solid-walled pipes made of unplasticized polyvinyl chloride, known as biaxially oriented PVC or PVC-O. [004] PVC-O pipes are manufactured using an extrusion process that allows the long molecular chains of PVC to be oriented. The bidirectional orientation, in both the axial and circumferential directions of the pipe, improves the physical and mechanical properties of the material. [005] The orientation is obtained in an elastoplastic rheological state of the material, known technically as the leathery state, attainable at a temperature above the glass transition temperature of PVC (Tg, approximately 80 °C), but below the temperature that makes the material fully plastic (approximately 105 °C). [006] Under these thermal and rheological conditions, a high force is applied to the tube in both the axial and circumferential directions, so as to increase the diameter of the tube and, at the same time, lengthen it and reduce the thickness of the tube wall. [007] The deformation resulting from the orientation of the tube is technically known as the axial orientation factor and the circumferential orientation factor, respectively. [008] Compared to the extrusion process for producing PVC-U pipes, the production of PVC-O pipes is much more complex and expensive. [009] Compared to PVC-U, PVC-O exhibits much greater tensile, fatigue and impact resistance and therefore, despite the higher production cost compared to PVC-U, PVC-O pipes, in certain fields of application, offer significant advantages over PVC-U pipes. [0010] In fact, under equal conditions of operating pressure and outside diameter of the tube, the greater strength of the material allows for the production of tubes with thinner walls. [0011] The reduced thickness, in addition to defining a larger free-flow cross-section, results in a lighter pipe, leading to material savings. [0012] These properties allowed the production of PVC-O pipes suitable for operating pressures of 25 Bar up to diameters of 630 mm. On the other hand, with PVC-U pipes, operating pressures cannot exceed 20 Bar up to diameters of 500 mm and, in addition, the pipe walls are thicker than those of the corresponding PVC-O pipes. [0013] In general, for operating pressures above 16 bar, PVC-O pipes with a diameter greater than 160 mm are more competitive than the corresponding PVC-U pipes. [0014] For PVC-U and PVC-O pipes, the most well-established and by far the most common form of pipe joint is the bell joint integrated into the pipe. The bell joint is the socket at the flared end of one pipe, into which the end of another pipe is inserted to join them and form a duct. [0015] Typically, the bell joint has, in its wide shape, a seat in which a sealing gasket made of elastomeric material is housed. The gasket ensures that the bell joint is hermetically sealed. [0016] The integrated bell joint is formed by heating the tube in what is commonly known as a flaring machine. [0017] In a flaring machine, the tube cut from the extrusion line is softened at one end in one or more heating stations. Thus, at a thermal state above the glass transition temperature, the plastically deformable end of the tube is then shaped into a bell shape by a metal forming tool in a forming station. The bell shape of the socket is stabilized by a final process step in which the socket is cooled in the forming tool. [0018] The effectiveness of the bell joint's hermetic seal is guaranteed by the high dimensional and shape precision of the socket's inner surface; for this reason, the forming tool is normally a metal spindle, commonly known as a mandrel, which is inserted into the end of the tube. [0019] In PVC-U and PVC-O pipes, sealed seat bell joints are manufactured according to two different systems, briefly described below. [0020] The mechanical mandrel system, in which the bell joint is molded onto a metal shaft, commonly known as a mechanical mandrel; the part of the mandrel that forms the seat of the joint is provided with expandable mechanical inserts (segments) that are retracted and disappear into the shaft body when it needs to be extracted from the molded joint. [0021] The Rieber system, in which the bell joint is molded into a metal mandrel and a bell joint is previously installed in a recessed zone of the mandrel. The bell joint is applied during the molding of the socket and remains fixed to the socket wall. Once the socket is cool and the joint is fixed to it, the mandrel is extracted from the socket and the end result is a tube with an integrated socket, complete with a non-removable gasket. [0022] The hot flaring process of PVC-U pipes occurs wi