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EP-4739485-A1 - APPARATUS AND METHOD FOR MAKING A BELL JOINT WITH GASKET

EP4739485A1EP 4739485 A1EP4739485 A1EP 4739485A1EP-4739485-A1

Abstract

Forming apparatus (1) for forming a bell joint with a sealing gasket on an end of a plastic pipe comprises a mandrel (2) provided with a front portion (4), insertable longitudinally into a pipe end (51) of a plastic pipe (50), and a rear portion (5) for receiving a sealing gasket (10). Sectors (3) provided between the front and rear portions (4, 5) can move radially between an extended configuration (E) and a retracted configuration (F in fig.4). In the extended configuration, the sectors (3) have an external radial dimension (D1) equal to or greater than the external radial dimension (D2) of the sealing gasket (10). In use, the sectors (3) abut and radially expand a front edge of said pipe end (51) and guide it over said sealing gasket (10), preventing it from being crushed when the mandrel (2) is inserted in said pipe end (51).

Inventors

  • ARGNANI, CLAUDIO

Assignees

  • IPM S.R.L.

Dates

Publication Date
20260513
Application Date
20240703

Claims (12)

  1. 1. Forming apparatus (1) for making by hot plastic deformation on an end (51) of a pipe (50) made of plastic material a bell joint (60) provided with a sealing gasket (10), comprising a mandrel (2) provided with a front portion (4), which can be inserted along a longitudinal direction (A) inside said end (51), and with a rear portion (5) suitable to receive and support said sealing gasket (10; 20), said mandrel (2) comprising a plurality of protection sectors (3) interposed between said front portion (4) and said rear portion (5), adjacent to, and in contact with, the rear portion and the sealing gasket (10; 20 ) and transversely movable, in particular almost orthogonally to said longitudinal direction (A), between an extended configuration (E) and a retracted configuration (F), said protection sectors (3) in said extended configuration (E) having a first external transverse dimension (DI) that is equal to or greater than a second external transverse dimension (D2) of said sealing gasket (10; 20) so as to abut and transversely expand a front edge (51a) of said end (51) and guide a side wall (51b) thereof above said sealing gasket (10; 20) thus avoiding its compression and/or crushing when said mandrel (2) is inserted in said end (51).
  2. 2. Forming apparatus (1) according to claim 1, comprising a compression flange (6) movable along said longitudinal direction (A) between an abutment position (R), in which it blocks said sealing gasket (10; 20) against said protection sectors (3) that are arranged in the extended configuration (E) for the insertion of said sealing gasket (10; 20) inside the end (51), and a disengagement position (D), in which said compression flange (6) is spaced apart from said sealing gasket (10; 20) to allow forming a portion of said bell joint (60) around said sealing gasket (10; 20).
  3. 3. Forming apparatus (1) according to claim 1 or 2, wherein said compression flange (6) is slidably mounted on, and coaxial with, said rear portion (5) and comprises a shaped end (6a) adapted to abut a front portion (10a) of said sealing gasket (10; 20).
  4. 4. Forming apparatus (1) according to any preceding claim, wherein said front portion (4) and said rear portion (5) of the mandrel (2) are movable along said longitudinal direction (A) with respect to each other between a first operating configuration (B), in which said front (4) and rear (5) portions are spaced apart and said front portion (4) abuts said protection sectors (3) arranged in the extended configuration (E), and a second operating configuration (C), in which said front portion (4) and said rear portion (5) abut to each other, in particular in order to compress and push the plastic material of the side wall (50b) over the sealing gasket (10; 20), with said protection sectors (3) arranged in the retracted configuration (F).
  5. 5. Forming apparatus (1) according to any preceding claim, wherein said protection sectors (3) comprise respective outer walls (13) which form an abutment surface (23) inclined and converging towards said front portion (4), adapted to abut said front edge (51a) and said lateral wall (51b) of said end (51).
  6. 6. Forming apparatus (1) according to any preceding claim, comprising compression means (9) configured to externally exert a compression on said lateral wall (50b) at said sealing gasket (10; 20) so as to form on said bell joint (60), in cooperation with said rear portion (5) and with the same sealing gasket (10; 20), an annular seat (62) for the sealing gasket.
  7. 7. Method for making by hot plastic deformation on an end (51) of a pipe (50) made of plastic material a bell joint (60) provided with a sealing gasket (10; 20) integrated therein using an forming apparatus (1) according to any preceding claim, comprising the following steps: - positioning an end (51) of said pipe (50) on which to make the bell joint (60) and blocking said end (51); - arranging a front portion (4) and a rear portion (5) of the mandrel (2) spaced apart to each other in a first operating configuration (B) and a plurality of protection sectors (3) of the mandrel (2), interposed between the front portion (4) and the rear portion (5), in an extended configuration (E), the rear portion (5) supporting the sealing gasket (10; 20); - moving said mandrel (2) along a longitudinal direction (A) and inserting the mandrel inside said end (51) so as to widen a side wall (51a) thereof and form the bell joint (60), said protection sectors (3) arranged in the extended configuration (E) having a first external transverse dimension (DI) substantially equal to or greater than a second external transverse dimension (D2) of said sealing gasket (10; 20) so as to abut and transversely expand a front edge (51a) of said end (51) and guiding said side wall (51b) over said sealing gasket (10; 20) avoiding its crushing; - moving said plurality of protection sectors (3) of said mandrel (2) transversely and internally from the extended configuration (E) to the retracted configuration (F); - moving said front portion (4) and said rear portion (5) to abut each other along said longitudinal direction (A) in the second operating configuration (C) in order to push the plastic material of the side wall (50a) above the sealing gasket (10; 20) so as to form an annular seat (62) thereof on said bell joint (60); - disengaging the pipe (50) having on the end (51) a bell joint (60) provided with the sealing gasket (10; 20).
  8. 8. Method according to claim 7, comprising after said moving said front portion (4) and said rear portion (5) in the second operating configuration (C), externally compressing said side wall (5 lb) at said sealing gasket (10; 20) so as to cooperate to form said annular seat (62) on said bell joint (60).
  9. 9. Method according to claim 7 or 8, comprising during said arranging said front (4) and rear (5) portions in the first operating configuration (B), moving a compression flange (6) along said longitudinal direction (A) in a abutment position (R) so as to block the sealing gasket (10; 20) against the protection sectors (3) arranged in the extended position (E).
  10. 10. Method according to claim 9, comprising after moving said front portion (4) and said rear portion (5) in the second operating configuration (C), moving said compression flange (6) in a disengagement position (D), in which the compression flange is spaced apart from said sealing gasket (10; 20).
  11. 11. Method according to any of claims 7 to 10, wherein said blocking said end (51) comprises blocking said pipe (50), at least along said longitudinal direction (A), by means of stopping means (30) and wherein said disengaging said pipe (50) comprises disengaging said stopping means (30) from said pipe (50) and moving said mandrel (2) along a longitudinal direction (A) away from said pipe (50).
  12. 12. Method according to any of claims 7 to 11, comprising, before said positioning said end (51), heating the end, in particular to a temperature close to the softening temperature of said plastic material.

Description

Apparatus and method for making a bell joint with gasket The invention relates to apparatuses and methods for making bell joints on ends of pipes made of plastic material. In particular, the invention relates to an apparatus and a method for making by hot plastic deformation on ends of plastic pipes bell joints provided with integrated sealing gasket. In the plastic piping field, the type of connection which includes the junction between two successive pipes by means of sleeves or what is known as “bell” joints is widespread. Bell joint refers to the portion of the so-called “female” end of the pipe which has an enlargement of the cross section (external and internal diameters) such as to form a sort of enlarged tubular sleeve capable of receiving and coupling with the so-called “male” end, normal and not enlarged, of the successive pipe. An annular groove is generally made inside the joint which forms an annular seat capable of housing a gasket which ensures the hydraulic seal, once the connection between the two pipes of the piping has been made. The gasket can be a shaped gasket provided with a sealing lip or a ring gasket with a square or circular section. Bell joints are typically made directly on the end of the pipe by hot plastic deformation of the aforementioned end (socketing process) by means of appropriate forming apparatuses. Known forming apparatuses typically comprise a metal mandrel or pad configured to be forcibly inserted in the axial or longitudinal direction inside the pipe so as to make the bell joint by plastic deformation. In the pipes intended to convey pressurized fluids, for example to make piping for the supply of pressurized water, the sealing gasket (Rieber gasket) can be integrated during the forming step in the bell joint (so-called “socketing with integrated gasket”) to ensure a firmer positioning of the gasket and therefore reduce the risks of its accidental displacement during the assembly of the piping. In particular, this procedure ensures stability of the gasket, ease of pipe mounting and hydraulic seal over time. In conventional PVC pipes (PCV-U), widely used for pressurized water piping, special lip seals (Rieber type) are used that comprise an elastomer sealing ring fixed to an anchoring and stiffening ring, made of metal or reinforced plastic material. The stiffening ring comprises a peripheral or leading edge suitably shaped to facilitate the sliding of the pipe over the gasket. In the forming process the bell joint is hot formed on the mandrel and on the gasket. More precisely, the gasket is positioned on the mandrel in such a way that the end of the pipe into which the mandrel is inserted is positioned above the gasket thanks to adequate lubrication and by virtue of the plasticity and malleability of the heated plastic material. In this way, the sealing gasket itself forms its own annular seat on the joint, which allows to minimize the existing tolerances between the gasket and the seat and guarantee mounting stability. They are also used to make piping for pressurized fluids in oriented or bi-oriented PVC pipes (PCV-O), i.e. pipes in which the plastic material, after the extrusion process, undergoes a molecular orientation process that gives it particular physical-mechanical characteristics. In particular, as is known, the pipes in rigid PCV-U after extrusion are heated up to the glass transition temperature and made to expand in radial direction and in longitudinal/axial direction (bi-orientation). This deformation results in a molecular orientation that produces a significant increase in pipe elasticity, better resistance to shocks, a lower crack propagation capacity and a greater resistance to water hammering. In addition, the pipe can be made with about 50% less material (with the same diameter) than a PVC-U pipe, with the same mechanical performance. The PVC-0 pipe with the same diameter is therefore thinner and guarantees a greater water flow, it is lighter, so there are lower transport costs and ease of application even for larger diameters. However, the greater stiffness of the PVC-0 makes problematic the socketing with integrated gasket, i.e. the insertion of the sealing gasket while forming the bell joint, since the material, sliding over the mandrel and over the gasket, tends to press, deform and crush the gasket. In fact, as is known, the bi-oriented material when heated tends to contract radially and axially (to take up again the initial configuration before orientation) making the entire socketing procedure complex and difficult. US 4218208 discloses a socketing machine for internal gaskets in which a plastic pipe is received in a locking device that can be inclined and is inclined thereon to receive a heating bell on an end portion of the pipe. The heated fluid is directed onto the end portion of the pipe inserted into the bell. The heating bell may be withdrawn from the pipe in intermittent steps to allow a temperature gradient along the end port