Apparatus and method for making a bell joint with gasket

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).

Description

[0001] Apparatus and method for making a bell joint with gasket

[0002] 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.

[0003] 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.

[0004] 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.

[0005] 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.

[0006] 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.

[0007] 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.

[0008] 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.

[0009] 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.

[0010] 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 portion of the pipe. The pipe is then inclined into a horizontal arrangement for insertion of a socketing mandrel with gasket into the heated end portion of the pipe. A gasket magazine is supported adjacent to the mandrel to automatically position an annular gasket on the mandrel for insertion into the end portion of the pipe. The mandrel includes an outer housing and a portion of the mandrel body received telescopically within the outer housing. The outer housing has a stop shoulder and a gasket positioning sleeve extended forward from it. The portion of the mandrel body has an expansion portion of the flared pipe and a portion that carries the gasket rearwardly of the latter. After insertion of the flared portion into the heated end of the pipe, the outer housing collapses onto the portion of the mandrel body for precise positioning of the gasket within the end portion of the pipe. Upon removal of the gasket positioning sleeve from said end portion of the pipe, the end portion of the pipe is collapsed by vacuum means on the portion of the mandrel body and cooled prior to removal of the portion of the mandrel body from the bell end portion of the pipe.

[0011] US 4597149 discloses a mandrel device that guides the end of a pipe to a position external to the path of an expander body, with a cam mechanism for forcing the expander body from an internal position to an external position, and maintaining said external position so as to obtain the desired enlargement for receiving the gasket of the tubular object to be processed. In a subsequent step, another cam mechanism forces the expander body radially inwards, to allow the tubular object to be processed, which is now bringing the sealing ring into a position that would result in interference from the expander body, to be released on the end of the mandrel. The two cam mechanisms are supported by subassemblies axially movable with respect to fixed parts of the mandrel and are interconnected to have both movement together and a movement with respect to each other, obtaining the effects of outward and inward cam in a sequence of multi-stage movement.

[0012] An object of the present invention is to improve known forming apparatuses and methods for making on pipes made of plastic material bell joints with integrated sealing gaskets.

[0013] Another object is to provide a forming apparatus and method that allow on mono- or bioriented PVC pipes too to form by hot plastic deformation a bell joint and at the same time insert a sealing gasket, that is, to carry out a socketing with integrated gasket.

[0014] A further object is to provide a forming apparatus and method that allow bell joints with integrated gaskets to be made using lighter and simpler gaskets, in particular without a stiffening and anchoring ring.

[0015] Another further object is to make a forming apparatus having simple, reliable and economical structure.

[0016] In a first aspect of the invention, a forming apparatus according to claim 1 is provided. In a second aspect of the invention, a forming method according to claim 7 is provided.

[0017] The invention can be better understood and implemented with reference to the attached drawings which illustrate an exemplifying and non -limiting embodiment thereof, in which: figure 1 is a schematic cross-section of the forming apparatus of the invention associated with a lip gasket and a pipe on which to form a bell joint and mount the gasket; figures 2 to 7 are schematic cross-sections of the apparatus of figure 1 and of the pipe illustrating respective subsequent operating steps of the process of forming the bell joint on an end of the pipe and inserting the gasket; figure 8 is a section of the forming apparatus of the invention in an operating step of forming the bell joint on the end of the pipe and inserting a gasket with a rectangular section.

[0018] With reference to figures 1 to 7, the forming apparatus 1 according to the invention for making by hot plastic deformation on an end 51 of a pipe 50 a bell joint 60 provided with a sealing gasket 10 integrated therein is illustrated.

[0019] The pipe 50 is made of plastic material, for example polyolefin or rigid PVC (PVC) or mono- or bi-oriented PVC (PVC-O).

[0020] The forming apparatus 1, or apparatus 1, includes a mandrel 2 movable along a longitudinal direction A and which can be inserted inside the end 51 of the pipe 50 so as to form the bell joint 60. The longitudinal direction A is parallel to a longitudinal extension axis X of the pipe 50.

[0021] The mandrel 2 is, for example, a metal pad having the shape of an inner surface of the bell joint 60 and comprises a front or head portion 4 adapted to be inserted inside the end 51 and shaped to form the bell joint 60 and a rear portion 5 adapted to support a sealing gasket 10 to be integrated into the bell joint 60 during its forming. The sealing gasket 10 is for example an annular lip gasket comprising an externally convex annular body 11 to facilitate its insertion into the pipe 50 and an annular lip 12 extending from the annular body 11 towards the inside of the pipe.

[0022] The sealing gasket 10 may further comprise a stiffening and anchoring ring of known type, made of metal or reinforced plastic material, fixed to the annular body 11 and intended to abut the lateral wall 5 lb of the end 51 of the pipe 50.

[0023] The sealing gasket 10 is inserted coaxially on the rear portion 4 of the mandrel 2, having for example a cylindrical tubular shape.

[0024] The forming apparatus 1 comprises first moving means of mandrel 2, of known type and not illustrated in the figures, configured to move the mandrel 2 along the longitudinal direction A.

[0025] The mandrel 2 is also provided with a plurality of protection sectors or inserts 3, for example also metallic, interposed between the front portion 4 and the rear portion 5, in particular adjacent to, and in contact with, the rear portion and with the sealing gasket 10 mounted thereon, and movable transversely, in particular orthogonally to the longitudinal direction A, i.e. radially with respect to the longitudinal axis X, between an extended configuration E and a retracted configuration F. In particular, the protection sectors or sectors 3 in the extended configuration E have a first external transverse dimension DI, in particular a first external diameter, which is substantially equal to or greater than a second external transverse dimension D2, in particular a second external diameter, of the sealing gasket 10 so as to abut and expand or widen transversely a front edge 51a of the end 51 and then slidably guide a lateral wall 51b thereof above the sealing gasket 10 avoiding its compression, deformation and crushing when the mandrel 2 is progressively inserted in the end 51.

[0026] The sectors 3 in the retracted position F are inside the mandrel 2 between the two front 4 and rear 5 portions to allow the mandrel 2 to be disengaged from the pipe 50.

[0027] The sectors 3 are moved radially between the extended configuration E and the retracted configuration F by second moving means, of known type and not illustrated in the figures.

[0028] The forming apparatus 1 also comprises a compression flange 6 movable along the longitudinal direction A between an abutment position R, in which it blocks the sealing gasket 10 against the sectors 3 that are arranged in the extended configuration E for the insertion of the sealing gasket 10 inside the end 51 , and a disengagement position D, in which the compression flange 6 is spaced apart from the sealing gasket 10 to allow forming a portion of the bell joint 60 around the sealing gasket 10.

[0029] The compression flange 6 is for example slidably mounted on, and coaxial with, the rear portion 5 and comprises a shaped end 6a adapted to abut a front portion 10a of the sealing gasket 10.

[0030] The compression flange 6 has for example a cylindrical shape and is linearly moved along the longitudinal direction A between the abutment position R and the disengagement position D by third moving means, of known type and not illustrated in the figures.

[0031] The front portion 4 and the rear portion 5 of the mandrel 2 are movable with respect to each other along the longitudinal direction A between a first operating configuration B, in which the front portion 4 and the rear portion 5 are spaced apart from one another (fig. 1 - 3) and the front portion 4 abuts the sectors 3 arranged in the extended configuration E, and a second operating configuration C, in which the front portion 4 and the rear portion 5 abut to each other, in particular to compress and push the plastic material of the lateral wall 50b of the end 51 onto the sealing gasket 10, with the sectors 3 arranged in the retracted position R.

[0032] In the illustrated embodiment, the front portion 4 is movable with respect to the rear portion 5 and in particular is linearly moved along the longitudinal direction A by fourth moving means, of known type and not illustrated in the figures.

[0033] The protection sectors 3 comprise respective outer walls 13 which form an abutment surface 23 inclined and converging in the direction of the front portion 4 and adapted to abut the front edge 51a and the lateral wall 5 lb of the end 51. More precisely, the outer walls 13 form an abutment surface 23 having an substantially truncated cone shape so as to abut and “deviate” over the sealing gasket 10 the front edge 51a of the end 51 of the pipe 50 while the mandrel 2 is progressively inserted along the longitudinal direction A inside the end 51. The forming apparatus 1 of the invention may optionally comprise compression means 9 configured to externally exert a compression on the lateral wall 50b at the sealing gasket 10 so as to form on the bell joint 60, in cooperation with the rear portion 5 and with the sealing gasket 10 itself, an annular seat 62 for the latter.

[0034] The compression means 9 may comprise a bell of known type adapted to enclose and contain the bell joint 60 and which is internally pressurized, for example by air or by other fluid capable of compressing the lateral wall 50b.

[0035] Alternatively, the compression means 9 may comprise mould means arranged to externally enclose the end 51 of the pipe 50 and provided with a forming cavity adapted to cooperate with the mandrel 2 to form the bell joint 60 and the seat 62 of the sealing gasket 10.

[0036] The forming apparatus 1 further comprising stopping means 30 arranged to abut and block, at least along the longitudinal direction A, the pipe 50 during the forming of the bell joint 60. The stopping means 30 comprise, for example, a cylindrical portion made of rubber or similar material and ensure that the pipe 50 is stopped and blocked during the insertion of the mandrel 2 and during the forming of the bell joint 60.

[0037] As illustrated in figure 8, the forming apparatus 1 of the invention, thanks to the protection sectors 3, allows hot forming on the end 51 of a pipe, for example made of PVC-U, a bell joint 60 that integrates a sealing gasket 20 with a quadrangular section provided with an annular inner lip and devoid of an outer stiffening and anchoring ring.

[0038] The sectors 3 arranged in the extended configuration E allow, in fact, even with a sealing gasket 20 not of the Rieber type to prevent it from being crushed by the front edge 51a while the mandrel 2 is inserted inside the end 51.

[0039] The operation of the forming apparatus 1 of the invention comprises the steps below described.

[0040] In an initial step the end 51 of the pipe 50 is suitably positioned at the forming apparatus. The pipe 50 is blocked, at least along the longitudinal direction A by the stopping means 30. Before positioning, the end 51 is heated, in particular to a temperature close to the softening temperature of the plastic material.

[0041] In a subsequent step, the front portion 4 and the rear portion 5, on which the sealing gasket 10 is positioned, are arranged spaced apart from one another in the first operating configuration B and the protection sectors 3, interposed between the front portion 4 and the rear portion 5, are arranged in the extended configuration E.

[0042] In addition, the compression flange 6 is moved along the longitudinal direction A into the abutment position R so as to block the sealing gasket 10 against the protection sectors 3 arranged in the extended position E.

[0043] The mandrel 2 is then moved along the longitudinal direction A so as to be progressively inserted into the end 51 of the pipe to enlarge the lateral wall 5 lb thereof and form the bell joint 60.

[0044] While the mandrel 2 is progressively inserted inside the end 51, the protection sectors 3, which in the extended configuration E have a first external transverse dimension DI (first diameter) that is substantially equal to or greater than a second external transverse dimension D2 (second diameter) of the sealing gasket 10, abut and expand transversely, i.e. radially, a front edge 51a of the end 51 and guide the lateral wall 51b above the sealing gasket 10, avoiding its crushing.

[0045] In particular, the outer walls 13 of the inserts 3 form the abutment surface 23 inclined and converging in the direction of the front portion 4 and able to abut and “deviate” above the sealing gasket 10 the front edge 51a of the end 51 and therefore the lateral wall 51b while the mandrel 2 is progressively inserted along the longitudinal direction A inside the end 51. Subsequently, the sectors 3 are moved transversely and internally, in particular radially with reference to the longitudinal axis X of the pipe 50, from the extended position E to the retracted position F to allow moving towards each other along the longitudinal direction A the front portion 4 and the rear portion 5 of the mandrel 2 from the first operating configuration B to the second operating configuration C.

[0046] In the second operating configuration C, the front portion 4 abuts the rear portion 5 to compress and push the plastic material of the lateral wall 5 lb above and against the sealing gasket 10. More precisely, in the illustrated embodiment, the front portion 4 is moved and approached to the rear portion 5 along the longitudinal direction A so as to facilitate the complete covering of the sealing gasket 10 by the lateral wall 61 of the end 51.

[0047] In this step, in order to allow the plastic material of the lateral wall 5 lb to slide towards the sealing gasket 10, the blocking means 30 are partially released. In this way the pipe 50 can be moved slightly along the longitudinal direction A from the front portion 4 towards the rear portion 5.

[0048] Alternatively or additionally, the mandrel 2, i.e. the rear portion 5, can be moved further into the end 51.

[0049] Concurrently with the movement of the front portion 4 and of the rear portion 5 of the mandrel 2 into the second operating configuration D, the compression flange 6 is moved into the disengagement position D, in which it is spaced apart from the sealing gasket 10 to allow the front edge 51a and the lateral wall 5 lb of the end 51 to overlap the sealing gasket 10 and pass beyond it forming the collar 61 of the bell joint 60. Thanks to the malleability of the plastic material of the pipe 50, previously heated, the sealing gasket 10 made on the bell joint 60 has its own annular housing seat 62.

[0050] In this step it may optionally be provided to compress externally, by means of the compression means 9, the lateral wall 51b of the end 51 at the sealing gasket 10 so as to facilitate the forming on the bell joint 60, in cooperation with the rear portion 5 and with the sealing gasket 10, of the seat 62

[0051] After forming is completed on the end 51 of the bell joint 60 that includes the sealing gasket 10, the mandrel 2 can be disengaged from the pipe 50.

[0052] For this purpose, the stopping means 30 release the pipe 50 and the mandrel 2 is moved along the longitudinal direction A away from the pipe 50.

[0053] The method according to the invention 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 integrated therein using the forming apparatus 1 of the invention above described comprising the following operational steps: positioning an end 51 of the pipe 50 on which to make the bell joint 60 and blocking said pipe 50; arranging the front portion 4 and the rear portion 5 of the mandrel 2 spaced apart from one another in a first operating configuration B and the 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 the mandrel 2 along the longitudinal direction A and inserting it inside the end 51 so as to widen a lateral wall 5 lb thereof and form the bell joint 60, the protection sectors 3 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 the gasket 10 so as to abut and transversely expand a front edge 51a of the end 51 and guiding the lateral wall 51b over the sealing gasket 10 avoiding its crushing; moving the plurality of protection sectors 3 of the mandrel 2 transversely and internally from the extended configuration E to the retracted configuration F; moving the front portion 4 and the rear portion 5 towards each other along the longitudinal direction A to abut each other in the second operating configuration C in order to push the plastic material of the lateral wall 50a over the sealing gasket 10 so as to form on said bell joint 60 an annular seat 62 for the sealing gasket 10; disengaging the pipe 50 having on the end 51 the bell joint 60 provided with the integrated sealing gasket 10; 20.

[0054] The method further optionally comprises, after moving the front portion 4 and rear portion 5 into the second operating configuration C, externally compressing the lateral wall 50b at the sealing gasket 10, in particular by means of compression means 9 so as to cooperate to form the annular seat 62.

[0055] The method further comprises, during said arranging the front 4 and rear 5 portions in the first operating configuration B, moving the compression flange 6 along the longitudinal direction A in the abutment position R so as to block the sealing gasket 10 against the protection sectors 3 arranged in the extended position E.

[0056] According to the method after moving the front portion 4 and the rear portion 5 into the second operating configuration C, it is provided to move the compression flange 6 in the disengagement position D, in which it is spaced apart from the sealing gasket 10.

[0057] According to the method positioning the end 51 comprises blocking the pipe 50, at least along the longitudinal direction A, by means of the stopping means 30 and disengaging the pipe 50 comprises disengaging the stopping means 30 from the pipe 50 and moving the mandrel 2 along the longitudinal direction A away from the pipe 50 itself.

[0058] The method comprises, before positioning the end 51 at the forming apparatus, to heat the end, in particular to a temperature close to the softening temperature of said plastic material. The apparatus and method of the invention therefore make it possible to quickly and precisely make on pipes made of plastic material bell joints provided with an integrated sealing gasket. More precisely, they allow to make on oriented or bi-oriented PVC pipes, by hot plastic deformation, bell joints with an integrated sealing gasket. The sealing gasket 10 can be a Rieber type gasket normally used for socketing with an integrated gasket PVC-U pipes.

[0059] Thanks to the protection inserts 3 provided in the forming apparatus 1 of the invention, in the step of inserting the mandrel 2 into the end 51 of the pipe 50 the sealing gasket 10 is protected by the abutment with the front edge 51a and therefore is not deformed or crushed. The lateral wall 51a of the end 51, although more rigid and less malleable in the case of PVC-0 pipes, is in fact widened and “deviated” by the inserts 3 so as not to abut and act on the sealing gasket 10 during the movement of the mandrel 2 and that of the front portion 4, but slides and is arranged above the sealing gasket 10 so as to adhere externally to the latter, forming the annular seat 62 during radial and axial cooling and retraction. This process of hot forming the seat 62 around the sealing gasket 10 also allows in the PVC-0 pipes to minimize the existing tolerances between the gasket and the seat and to guarantee mounting stability. Furthermore, thanks to the forming apparatus and method of the invention it is advantageously possible to use during the socketing with integrated gasket of more malleable pipes, for example PVC-U pipes, instead of the expensive Rieber gaskets, lighter and simpler gaskets, in particular without a shaped leading edge and / or external reinforcement ring. For example, as illustrated in figure 8, it is possible in the forming apparatus 1 of the invention to hot form on the end 51 of a pipe a bell joint 60 that integrates a sealing gasket 20 with a quadrangular section with an annular inner lip and devoid of an outer stiffening and anchoring ring.

Claims

CLAIMS1. 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. 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. 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. 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 theretracted configuration (F).

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. 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. 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. 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. 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. 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. 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. 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.

Images