MECHANICAL FITTINGS FOR CPVC

Abstract

A mechanical coupling for connecting pipes or for securing a pipe is provided. The mechanical coupling comprises: a main body (10; 210) extending axially between a body end and an open end (11) defining an insertion space for a pipe, a gripping ring (30; 130; 230) adapted to close over a pipe, and a nut (40; 240) movably mounted on the main body for tightening the gripping ring. The gripping ring (30) has a ring outer surface (34) and a ring inner surface (35), the ring inner surface (35) having an internal friction coefficient for defining an internal friction interface between the pipe and the gripping ring (30), the ring outer surface (35) having an external friction coefficient for defining an external friction interface between the gripping ring (30) and one of the main body and the nut, the internal friction coefficient being higher than the external friction coefficient.A set and assembly method are also proposed. Figure for abstract: Figure 1.

Description

Title of the invention: MECHANICAL FITTINGS FOR CPVC Technical field

[0001] The present invention relates to a mechanical fitting for connecting pipes or for fixing a pipe, a water supply network, an assembly of a mechanical fitting with a pipe, and a method of assembling a fitting. PREVIOUS ART

[0002] Compression fittings, also called press-fit or crimp fittings, which allow pipes to be connected by compression and deformation using one or two sleeves, are well known in the field of installation of tubes, pipes and piping systems, for example for water, gas or heating.

[0003] Press fittings are used to connect not only metal pipes, but also plastic pipes or metal-plastic composite pipes. They are used to connect suitably arranged pipe sections, with their fitting parts being inserted into the ends of the pipes to be connected, where they are then deformed, crimped or pressed. They are fixed in certain areas, for example with the help of pressure sleeves on the parts, using so-called system compression tools which usually have interchangeable pressure jaws.

[0004] Pipe, tubes or conduit systems are assembled in several steps: the pipes are first inserted into a fitting, then the fitting is crimped to ensure good mechanical strength and a watertight installation. Compression is essentially pressure exerted on the fitting sleeve - also called a pressure or crimping sleeve - which causes the fitting to deform or shape into the pipe inserted into it. The pressure is usually applied to the fitting using a pressure jaw acting as a compression tool. These pressure jaws exert radial pressure on the fitting material to cause interaction with the surface of the pipe(s) to be connected, thus achieving a reliable connection and a reliable seal.

[0005] Other fittings, such as those used for example for hoses such as in gardening equipment, use a threaded engagement to allow crimping of the hose and rely on a portion of the fitting engaging the hose.

[0006] In both cases, the connection is based on a deformation of the tube to be connected, in most cases, using an insert placed inside the tube to be connected.

[0007] For different pipe arrangements, pressure fittings can be designed as curved, angular or T-shaped pieces, with typically one, two or three fitting pieces provided.

[0008] The pipe or conduit may be mono-material and composed of thermoplastic materials, including but not limited to PE, PB, PEX, PERT, PER ... or Composite (multi-material pipe structure) with different layers of functional materials (PEX, PERT, PVDF, aluminum ...).

[0009] It is known to use crimp fittings made entirely of plastic, or crimp fittings whose fitting body is made of metal (brass, stainless steel, etc.), or thermoplastic (PVC, PPSU, PVDF, PPS), which can also be reinforced with a fiberglass reinforcement.

[0010] However, with the introduction of c-PVC material pipes, compression fittings relying on the deformation of the pipe material for connection do not give good results. This is because c-PVC has different properties and is more brittle than other materials and c-PVC is more brittle over time.

[0011] One solution that has been proposed is solvent bonding. However, regulations are evolving and it will be necessary to avoid adding solvents.

[0012] It is therefore necessary to find another solution for compression fitting, in order to avoid the use of solvent.

[0013] An object of the present disclosure is to provide a mechanical fitting for connecting CPVC, PVC and PVC-U piping systems for hot and cold water installations, in particular, pressure installations. Summary of the invention

[0014] To this end, the present invention provides a mechanical fitting for connecting pipes or for securing a pipe, comprising: a main body extending axially between a body end and an open end defining an insertion space for the pipe, a gripping ring adapted to close over a pipe, and a nut movably mounted on the main body for tightening the ring. The gripping ring has a ring outer surface and a ring inner surface, the ring inner surface having an internal friction coefficient for defining an internal friction interface between the pipe and the gripping ring, the ring outer surface having an external friction coefficient for defining an external friction interface between the gripping ring and one of the main body and the nut. The internal friction coefficient is 1.7 to 7.1 and being greater than the external friction coefficient.

[0015] The present invention provides a mechanical fitting designed to use friction instead of compression to provide a connection between the mechanical fitting and a pipe inserted therein. This is advantageous in particular for pipes which are fragile, such as PVC pipes or pipes made of materials in the PVC range, such as c-PVC, PVC-U, etc. By providing two different friction coefficients for the grip ring, it is possible to ensure that the grip ring fulfills its assembly function with the pipe. In fact, the external, lower friction coefficient allows the nut to slide or move on the grip ring, while the internal friction coefficient allows the pipe to be tightened, which prevents the pipe from slipping during assembly.

[0016] In one aspect, internal circumferential recesses extending radially within the ring are provided on the inner ring surface, and the outer ring surface is smooth, to allow sliding of the nut or main body relative to the friction ring. These arrangements on the inner and outer ring surfaces provide the required internal and external friction coefficients for a friction-based mechanical connection.

[0017] In one aspect, the nut includes a first nut portion for mounting on the main body and a second nut portion extending axially between the first nut portion and a free nut end, the second nut portion extending axially away from the open end of the main body, wherein the gripping ring is received under the second nut portion. The nut and the gripping ring may extend axially away from the open end of the main body when compactness of the fitting is not an issue.

[0018] In one aspect, the gripping ring has an external conical shape that is intended to deform as the nut is moved over the main body to secure the pipe, in particular one of the main body or the second nut portion has a corresponding conical shape. A conical shape assists in tightening the fitting by gradually increasing the load on the gripping ring as the nut slides over the main body or the gripping ring.

[0019] According to one aspect, the attachment ring is an open ring, the attachment ring comprises at least one longitudinal slot from an axial end, the defined compression capacity is ensured by the dimensioning of the opening or slots of the attachment ring, so that the attachment ring cannot deform the pipe more than an ovality of the pipe.

[0020] According to one aspect, the attachment ring has a defined compression capacity and / or is provided with at least one of the following characteristics: - the hanging ring is an open ring, - the hanging ring has longitudinal slots which extend to from the same axial end or from both axial ends of the attachment ring, - the defined compression capacity is ensured by the dimensioning of the opening or slots of the gripping ring, so that the gripping ring cannot deform the pipe more than ovalization of the pipe.

[0021] A mechanical connection based on friction aims not to deform the pipe during assembly, but to create a friction interface at the interface of the pipe and the gripping ring, capable of resisting the tearing force during operation. Therefore, the gripping ring is designed to close on the pipe, but without deforming the pipe. In other words, the gripping ring, when fully closed, has a diameter that is not less than the diameter of the pipe, taking into account the ovalization of the pipe. In addition, the longitudinal slots of the gripping ring allow for good distribution of the load on the pipe.

[0022] The ovality of the pipe is defined as the difference between a maximum and minimum diameter of the pipe along its length. For example, for a c-PVC pipe with a nominal diameter of 63 mm, the ovality is approximately 0.1 to 0.15 mm depending on the pipe storage conditions. The maximum diameter can therefore be 63.15 mm.

[0023] The attachment ring may comprise a reinforcing element such as a metal open ring, in particular for pipes of larger diameter.

[0024] According to one aspect, the outer ring surface is provided with longitudinal grooves or recesses. The external longitudinal grooves on the outer ring surfaces compensate for ovality of the rigid pipe.

[0025] In one aspect, the gripping ring has an external radial projection configured to abut a flange formed at the open end of the main body. With this design, the gripping ring can be positioned in the mechanical connection.

[0026] In one aspect, a gasket is provided within a gasket housing in the main body located adjacent the flange. In one aspect, the gasket has an internal triangle shape, to facilitate insertion of the pipe within the mechanical fitting.

[0027] In one aspect, the gripping ring includes an extension rib that extends axially away from the radial projection toward the inner end of the fitting. In other words, the gripping ring can push against the gasket when tightening the fitting onto a pipe to create a seal.

[0028] In one aspect, the nut is positioned on a nut receiving portion of the main body extending between the open end and an outer radial projection on an outer body surface of the main body, the outer radial projection forming a stop for the nut. This projection allows the nut to be moved between an open position and a closed position of the mechanical connection.

[0029] According to one aspect, the nut is made of fiber-reinforced polymer, the main body is made of polymer or composite, the ring is made of polymer, composite or metal.

[0030] The present invention also provides an assembly of such a mechanical coupling and a pipe, wherein the ring and the pipe have a minimum axial contact length according to the following equation:

[0031] The contact length between the pipe and the ring is the contact length necessary to create enough friction to hold the pipe with the mechanical connection against pull-out forces.

[0032] According to one aspect, after assembly, the pipe exhibits a pipe diameter reduction of the order of an ovalization of the pipe, in particular of a maximum of 0.5% of the initial pipe diameter. In other words, there is no deformation of the pipe, unlike prior art compression fittings which rely on pipe deformation, with a diameter reduction of up to 10%. The frictional interaction with the pipe is a surface interaction, within the ovalization of the pipe.

[0033] According to one aspect, only elastically deformable portions are deformed and the pipe remains undeformed after tightening the fitting onto the pipe.

[0034] The present invention also provides a method of assembling such a mechanical connection and a pipe, which comprises the following steps:

[0035] insert the pipe into the main body of the fitting, preferably up to the internal radial projection,

[0036] moving the nut onto the main body, by sliding and / or screwing the nut onto the main body to close the gripping ring around the pipe, including sliding the nut or main body onto the ring while the pipe remains stationary against the ring,

[0037] in which the pipe remains undeformed after closing the gripping ring, with a reduction in the pipe diameter of no more than 0.5% of the initial pipe diameter.

[0038] According to one aspect, upon closing of the gripping ring, the extension rib of the ring axially pushes the seal to deform against the main body on one side and against the rigid pipe on the other side.

[0039] In one aspect, upon closing the grip ring, the grip ring is first pushed by the nut and closes around the pipe and, once the nut has reached a final position, the friction ring pushes against the seal. DESCRIPTION OF THE DRAWINGS

[0040] Other characteristics and advantages of the invention will appear more clearly on reading the description of several currently preferred embodiments, provided by way of example only, with reference to the attached drawings 1 to 13, in which:

[0041] [Fig.l] shows an exploded sectional view of a mechanical connection according to a first aspect of the present disclosure,

[0042] [Fig.2] shows a hanging ring of a mechanical connection according to one aspect of this disclosure,

[0043] [Fig. 3] shows a gripping ring of a mechanical connection according to one aspect of the present disclosure,

[0044] [Fig.4] shows a ring for attaching a mechanical connection according to another aspect of this disclosure,

[0045] [Fig.5] shows a gripping ring of a mechanical connection according to another aspect of the present disclosure,

[0046] [Fig. 6] shows a mechanical connection with the hooking ring of Figures 4 and 5 according to another aspect of the present disclosure,

[0047] [Fig.7] shows a mechanical connection with the pipe inserted inside, after assembly, according to the present disclosure,

[0048] [Fig.8] is a drawing of a mechanical connection of [Fig.7] according to another aspect of the present disclosure,

[0049] [Fig.9] shows a ring usable in the mechanical connection of [Fig.7],

[0050] [Fig. 10] shows a ring usable in the mechanical connection of [Fig.7],

[0051] [Fig. 11] shows a ring usable in the mechanical connection of [Fig.7],

[0052] [Fig. 12] shows a seal usable in the mechanical connection of [Fig.7],

[0053] [Fig. 13] shows a seal usable in the mechanical connection of [Fig.7]. DETAILED DESCRIPTION

[0054] In the figures, identical elements are identified by the same reference numbers.

[0055] [Fig.l] shows a mechanical coupling 1 for connecting a pipe (not shown in [Fig.l]) according to one aspect of the present disclosure, and [Fig.2] shows the mechanical coupling 1 with the pipe 2 after assembly.

[0056] The pipe 2 may be, for example, a pipe for / in a piping system for fluid installations inside buildings. The pipe may be made of CPVC, PVC and PVC-U for hot and cold water installations.

[0057] The connector 1 may form one side of a connector having a similar or other type of connector at its other end or side. The connector may also be placed at an orifice of a fluidic device to connect a hose thereto.

[0058] The mechanical connection 1 comprises a main body 10 intended to receive the pipe.

[0059] The main body 10 has a body outer surface 14 and a body inner surface 15. The main body 10 defines a pipe insertion space extending in an axial direction, between an open end 11, i.e., the end where the pipe is inserted, and an inner radial projection 12 extending radially inward from the body inner surface 15. The inner radial projection 12 is intended to stop the pipe inserted in the main body 10.

[0060] A nut 40 is provided to be mounted on the main body 10 when the pipe is inserted into the main body, in order to hold the pipe in place. As can be seen, the nut 40 is not provided on the entire main body 10, but only on a nut receiving portion 18 of the main body 10 which extends between the open end 11 and an outer radial projection 16 on the outer surface of the body 15. The outer radial projection 16 forms a stop for the nut 40.

[0061] Furthermore, the nut 40 comprises a first nut portion 42 for mounting on the nut receiving portion 18, in particular threaded on the nut receiving portion of the main body 10. According to one aspect, the first nut portion 42 is threaded on the nut receiving portion 18. To achieve this, the nut receiving portion 18 has external threads 17 extending between the external radial projection 16 and the open end 11. The external threads 17 are provided for screwing the nut 40 onto the main body 10 when the pipe is inserted and positioned in the main body 10. The nut 40 therefore has corresponding nut threads 47. However, the thread is only an example, and the nut could slide on the main body.

[0062] As can be seen in the figure, the outer radial projection 16 is axially spaced from the inner radial projection 12. In other words, the entire length of the pipe inserted into the fitting 1 will not be below the nut 40 and the free end of the pipe abutting against the inner radial projection 12 is not provided below the nut 40. This allows for taking into account possible variations during the installation of the pipe, which may not be completely inserted or whose cross-section may be slightly inclined. Indeed, it may happen that during the installation of a pipe system, the user cuts the pipe and the cut is not perfectly straight. This free space between the inner radial projection 12 and the outer radial projection 16 ensures that the entire pipe end is compressed, even if the pipe end is not straight.

[0063] The nut 40 also includes a second nut portion 44 extending axially between the first nut portion 42 and a free nut end 48. The second nut portion 44 extends axially away from the open end 11 of the main body.

[0064] The second nut portion 44 defines a ring receiving portion 44, adapted to accommodate a catch ring 30. The catch ring 30 is illustrated in the Figures 2 and 3 in a first aspect, and another example of a hooking ring 130 is illustrated in Figures 4 and 5 in another aspect.

[0065] The attachment ring 30 is housed inside the second nut part 44.

[0066] As will be understood from reading the present disclosure, the gripping ring 30 is a friction ring designed to hold the pipe against a tearing force due to internal pressure or an external load.

[0067] The gripping ring 30 extends axially and has an external conical shape which is intended to deform when the nut 40 is screwed onto the main body 10.

[0068] The second nut portion 44 has an inner nut surface 45 having a corresponding conical shape, with a decreasing diameter from the nut threads 47 to the free end 48, designed to cooperate with the conical ring shape.

[0069] The conical shape facilitates the closing of the fitting on the pipe. When the nut slides or is screwed onto the nut receiving portion 18, the gripping ring 30, under the effect of the load, closes on the pipe.

[0070] The attachment ring 30 has an outer ring surface 34 and an inner ring surface 35. Those skilled in the art understand that the inner ring surface 35 defines an internal friction interface between the pipe and the attachment ring 30, and that the outer ring surface 34 defines an external friction interface between the attachment ring 30 and the nut 40.

[0071] These inner and outer surfaces of the gripping ring 30 are friction surfaces, and it is important to note that the pipe must not deform under the effect of the fastening force. In fact, the mechanical connection 1 is designed to reduce the load on the pipe, in order to prevent the pipe from breaking under the load.

[0072] In other words, instead of relying on compression to connect the pipe, the present disclosure proposes to rely on friction.

[0073] Indeed, prior art compression fittings for PE pipes are based on pipe deformation and diameter reduction in order to hold the pipe against a pull-out force generated by internal operating pressure. For example, the inventors measured pipe deformation with different existing designs. They measured a pipe diameter reduction from 63 to 55 mm, which is equivalent to a pipe diameter reduction of 8 mm in a first design, a pipe diameter reduction from 63 to 57 mm, which is equivalent to a pipe diameter reduction of 6 mm in a second design, and a pipe diameter reduction from 63 to 58 mm, which is equivalent to a pipe diameter reduction of 5 mm. Thus, on average, in the prior art, the pipe diameter is reduced by 6.3 mm, which is equivalent to 10% pipe deformation or diameter reduction.

[0074] On the other hand, PVC, c-PVC or PVC-U pipes are brittle and do not withstand deformation. It is therefore not possible to rely on compression and deformation of the pipe to deform the pipe and fix the fitting, as was the case with the mechanical fitting of the known prior art. It should be noted that this document focuses on c-PVC, as it is the material most resistant to high pressures and temperatures. The brittleness is, however, similar for all PVC-based materials.

[0075] Similar measurements were made for a c-PVC pipe with a nominal diameter of 63 mm and an ovality, which is the difference between the maximum and minimum diameter of the pipe, of about 0.1 to 0.15 mm depending on the storage conditions of the pipe. Thus, the maximum diameter can be 63.15 mm. With the mechanical fitting of the present disclosure, which is based on friction, the pipe diameter is reduced from 63 to 62.81 mm, which is equivalent to a diameter reduction of 0.19 mm or 0.33 mm if ovality and a possible maximum diameter are taken into account. This is equivalent to 0.30% pipe deformation or diameter reduction. Instead of a conventional compression fitting where the pipe diameter is reduced by at least 10% to create a secure connection, the mechanical fitting of the present disclosure has a pipe surface deformation of no more than 0.5%.This deformation is negligible and is considered as a surface deformation only, without deformation of the pipe itself.

[0076] In one aspect, internal circumferential recesses 33 extending radially within the ring 30 are used to provide a roughened surface between the pipe 2 and the friction ring 30. A roughened surface instead of a smooth surface helps to hold the pipe and prevent slippage or translation of the pipe relative to the friction ring.

[0077] Indeed, it is important to note that the pipe must not slip relative to the friction ring during tightening of the fitting and subsequently.

[0078] On the other hand, the interface between the outer ring surface and the nut must allow the nut 40 to slide relative to the friction ring 30. The outer ring surface 34 is therefore as smooth as possible.

[0079] In other words, the surface between the nut and the pipe is designed to minimize the coefficient of friction, while the friction between the pipe and the gripping ring is optimized to be greater than the tear-off force applied to the pipe.

[0080] The steady-state friction coefficient can be given by the equation next:

[0081] where L represents the contact length, therefore the contact surface, m is the mass, and therefore also represents the load due to internal pressure.

[0082] A minimum friction force is required to hold the pipe against the pull-out force due to internal pressure and external force. The pull-out force on the pipe is generally a function of the operating pressure and the pipe diameter.

[0083] Therefore, a minimum contact length is required to be considered to create a frictional force to hold a pipe against a pull-out force, and the crimp area must be determined to ensure an acceptable stress distribution on the CPVC, PVC or PVC-U.

[0084] There is therefore a relationship between the steady-state friction coefficient, which depends on the load or pressure level exerted on the pipe, and the contact surface between the pipe and the gripping ring. The inventors have determined that the minimum axial contact length L at the interface between the pipe and the gripping ring, necessary to distribute the pressure generated by a tearing force between the pipe and the ring acting on the pipe, must satisfy the following equation:

[0085] where Pd is the pressure, L is the axial contact length and DN is the nominal diameter of the pipe.

[0086] For example, according to NF EN ISO 15877-5 2009-05, the design pressure generated on the c-PVC pipe of any Type II class must be less than or equal to 2.86 MPa. Under an operational pressure of 25 bar, a fitting with a diameter of 63 mm must resist a pull-out force generated by a pressure of 4.7 MPa. Applying the equation, 1.25.88 mm is the minimum length of the surface to not generate a load greater than 2.86 MPa on the pipe. On the other hand, the minimum axial contact length is required to be considered as creating a friction force to hold the pipe against a pull-out force.

[0087] For example, the inventors manufactured a friction ring with a diameter of 63 mm and a contact length of 26.59 mm between the nut 40 and the ring 30. The outer ring surface roughness was measured at 0.15 micrometers. The insertion force was measured at 1804 N. The insertion force is considered equivalent to the friction force. The friction coefficient of the outer ring surface is as follows:

[0088] For the same friction ring, with a contact length of 28.5 mm between the ring and the pipe, the friction ring surface roughness on the pipe was 1 mm. The pipe pull-out force is measured = 11,837 N for an operating pressure of 25 bar, and the friction coefficient is as follows: / 4 orinaZ. strength)= 11837 / (WormaZ / orc'e)

[0089] The tear-off force is approximately 5000 N for an operating pressure of 10 bars, and 3000 N for an operating pressure of 6 bars, while the insertion force is independent of the operating pressure.

[0090] The internal friction coefficient is more than 6 times higher than the external friction coefficient. Preferably, the internal friction coefficient is 1.7 to 7.1 times higher than the external friction coefficient, depending on the operating pressure 4, 6, 8, 10, 16 or 25 bars.

[0091] The second nut portion 44, which accommodates the ring, must have a length at least equal to the minimum axial ring length L. The first nut portion 42 may have a length which depends on the requirements of the material and the detent teeth.

[0092] To distribute the load evenly along the pipe and avoid local concentration of the load, the gripping ring 30 may not be a complete closed ring and may be an open ring, with one or more opening slots 37 provided to distribute the clamping load of the gripping ring 30.

[0093] The attachment ring 30 comprises longitudinal slots 38 which make it possible to compensate for the ovalization of the rigid pipe. The longitudinal slots 38 give a certain flexibility to the ring which is also made of a rigid material.

[0094] In Figures 2 and 3, all the longitudinal slots 38 extend from the same axial end, namely the axial end of the side where the pipe is inserted.

[0095] However, as required, longitudinal slots may extend from one axial end 31 or the other axial end 32, as shown in Figures 4 and 5, where the friction ring 130 has longitudinal slots 138A extending from one axial end and a longitudinal slot 138B extending from the other axial end. Having longitudinal slots extending from both axial ends of the gripping ring 30 creates a gap that promotes relaxation of the material under load and generates less force on the nut. A mechanical connection 101 with the friction ring 130 is shown in [Fig.6].

[0096] Furthermore, to better compensate for the ovalization of the rigid pipe, the outer surface of ring 34 may be provided with longitudinal grooves or recesses 36. In doing so, care should be taken to ensure that the outer surface in contact with the nut remains as smooth as possible for the sliding of the nut 40 when tightening the fitting onto the pipe.

[0097] The gripping ring 30 comprises an external projection 39 adapted to bear against a flange 19 formed at the open end 11 of the main body 10.

[0098] A seal 20 is provided inside a seal housing 21 in the main body.

[0099] In the example of figures 2 and 3, the attachment ring 30 comprises an extension rib 29 which extends axially away from the stop 39. When the nut 40 is tightened on the main body 10, the attachment ring 30, and more precisely the extension rib 29, pushes the seal 20 axially towards the main body.

[0100] The pipe simultaneously provides the functions of attachment and clamping by the internal recesses 32 and by the extension rib 34, the extension rib 34 pushing the rubber 20 to deform against the body 10 on one side and against the rigid pipe on the other side.

[0101] By means of an interface between the seal 20 and the pipe, the seal 20 deforms against the main body on one side and against the rigid pipe on the other, thus ensuring the clamping function.

[0102] The seal 20 may have an internal triangle shape to facilitate pipe insertion.

[0103] The seal 20 also participates in friction. As such, the seal is a gasket in rubber, preferably reinforced polymer.

[0104] The nut 40 is preferably made of polymer.

[0105] It should be understood that when closing the fitting on the pipe inserted therein, the friction ring 30 is first pushed and closes around the pipe, then the friction ring 30 pushes against the seal 20.

[0106] As mentioned previously, [Fig. 6] shows a mechanical connection 101 with the friction ring 130, having longitudinal slots extending from both axial ends. The mechanical connection 101 has a main body 210 which extends between an open end 211 and a pipe stop 112. A seal 120 is provided in a seal housing 121, the position of which in the connection differs from the mechanical connection of [Fig. 1]. Indeed, in [Fig. 1], the seal 20 is located at the open end 11 of the main body 10 and the seal 20 is pushed by the extension rib 29 of the gripping ring 30 to deform the rubber to ensure sealing.

[0107] In the mechanical fitting 101, the seal 120 is not located at the open end but further inside the main body 101, somewhere between the open end 211 and the pipe stop 112. Therefore, there is no need for the gripping ring 130 to push the seal 120 because watertightness can occur during pipe insertion. There is sufficient interface between the pipe and the rubber 120. Furthermore, the gripping ring 130 does not have an extension rib.

[0108] It should be noted that it is possible to have a gripping ring with both an extension rib and longitudinal slots extending from both ends of the gripping ring. Figures 7 and 8 show another embodiment of a mechanical connector 201 allowing the connection of a pipe 2 (not shown in [Fig.8]) according to another aspect of the present disclosure.

[0109] The mechanical connection 201 comprises a main body 210 intended to receive the pipe 2 (visible in [Fig.7]).

[0110] As with the mechanical fitting 1 of [Fig.l], the main body 210 has a body outer surface 214 and a body inner surface 215. The main body 210 defines a pipe insertion space extending in an axial direction, between an open end 211, i.e., the end where the pipe is inserted, and an inner radial projection 212 extending radially inside the body inner surface 215. The inner radial projection 212 is intended to stop the pipe inserted into the main body 210.

[0111] A nut 240 is provided to be mounted on the main body 210 when the pipe is inserted into the main body, in order to close the connection after insertion of the pipe. The nut 240 is not provided on the entire main body 210 but only on a nut receiving portion 218 of the main body 210 extending between the open end 211 and an outer radial projection 216 on the outer surface of the body 215. The outer radial projection 216 forms a stop for the nut 240.

[0112] Further, the nut receiving portion 218 has external threads 217 that extend between the outer radial projection 216 and the open end 211. The external threads 217 are provided for threading the nut 240 onto the main body 10 when the pipe is inserted and positioned in the main body 10. The nut 240 therefore has corresponding nut threads 247.

[0113] As can be seen in [Fig.8], the outer radial projection 216 is axially spaced from the inner radial projection 212. In other words, the entire length of the pipe inserted into the fitting 1 will not be below the nut 240 and the free end of the pipe abutting the inner radial projection 212 is not provided below the nut 40.

[0114] The nut 240 is designed to accommodate a gripping ring 230. The gripping ring 230 is illustrated in Figures 9 and 10.

[0115] As with the mechanical connection of [Fig.l], the gripping ring 230 is a friction ring designed to hold the pipe against a pull-out force due to internal pressure or an external load.

[0116] The attachment ring 230 extends axially.

[0117] While in the embodiment of [Fig.l], the nut 40 had an internal conical shape cooperation with the external conical shape of the grip ring 30, in this aspect, the main body 210 has an internal conical shape to cooperate with the external conical shape of the grip ring 230.

[0118] The conical shape of the main body has a diameter that decreases from the open end 211 to the interior of the main body. The conical shape stops at an axial point located approximately below the radial projection 216.

[0119] The conical shape facilitates the closing of the fitting on the pipe. When the nut is moved onto the nut receiving portion 218, the gripping ring 30, under the effect of the load, closes on the pipe.

[0120] The gripping ring 230 has an outer ring surface 234 and an inner ring surface 235. Those skilled in the art understand that the inner ring surface 235 defines an internal friction interface between the pipe and the gripping ring 230, and that the outer ring surface 234 defines an external friction interface between the gripping ring 230 and the main body 210.

[0121] These inner and outer surfaces of the gripping ring are friction surfaces, and it is important to note that the pipe must not deform under the effect of the fastening force. In fact, the mechanical fitting 1 is designed to reduce the load on the pipe in order to prevent the pipe from breaking under the load.

[0122] In other words, instead of relying on compression to connect the pipe, the present disclosure proposes to rely on friction. Indeed, the pipe is fragile and does not support deformation. It is therefore not possible to rely on compression and deformation of the pipe to deform the pipe and fix the fitting, as was the case with the mechanical fitting of the known prior art.

[0123] As can be seen best in Figures 9 and 10, internal circumferential recesses 233 extending radially within the ring 30 are used to provide a roughened surface between the pipe 2 and the friction ring 230. A roughened surface instead of a smooth surface helps to hold the pipe and prevent slippage or translation of the pipe relative to the friction ring.

[0124] Indeed, it is important to note that the pipe must not slip relative to the friction ring during tightening of the fitting and subsequently.

[0125] In other words, the inner ring surface has an internal friction coefficient to define an internal friction interface between the pipe and the grip ring, the outer ring surface has an external friction coefficient to define an external friction interface between the grip ring and one of the main body and the nut, and the internal friction coefficient is greater than the external friction coefficient.

[0126] The gripping ring 230 is an open ring with longitudinal slots 38 to help compensate for the ovality of the rigid pipe. Longitudinal slots 38 provide flexibility to the ring, which is otherwise made of a rigid material. This helps distribute the load evenly along the pipe and avoids local concentration of the load.

[0127] The attachment ring 230 comprises an external radial projection 239 intended to bear against the open end 211 of the main body.

[0128] A reinforcing element 262 is provided for the friction ring 230. In the illustrated example, the reinforcing element 262 is an open ring. The open ring may be a metal open ring, inserted inside the ring 230.

[0129] The reinforcing element 262 is provided with internal circumferential recesses 263 which extend radially inside the reinforcing element 262. The internal circumferential recesses 263 provide a roughened surface between the pipe 2 and the friction ring 230. A roughened surface instead of a smooth surface helps to hold the pipe and prevent slippage or translation of the pipe relative to the friction ring.

[0130] The gripping ring 30 has an external projection 39 designed to bear against a flange 19 formed at the open end 11 of the main body 10.

[0131] As shown in [Fig.8], a seal 220 is provided within a seal housing 221 in the main body. The seal 220 is best shown in Figures 12 and 13.

[0132] Thanks to an interface between the seal 220 and the pipe, the seal 220 deforms against the main body on one side and against the rigid pipe on the other side, thus ensuring the clamping function.

[0133] The seal 220 may have an internal triangle shape to facilitate pipe insertion.

[0134] As shown in [Fig. 13], the gasket has a pipe contact surface 222 with the pipe opposite a fitting contact surface 223, connected by a circular joining section 224. The pipe is pressed between the pipe and the fitting, the pipe contact surface 222 and the fitting contact surface 223 being moved towards each other. The shape of the circular joining section 224 ensures sealing when the gasket is compressed.

[0135] The seal 220 also contributes to friction. As such, the seal is a rubber seal, preferably made of reinforced polymer.

[0136] This technology has a significant impact on the replacement of solvent cement connections for CPVC, PVC and PVC-U pipes.

[0137] Once closed, the gripping rings 30, 130 do not deform the pipe 2. The mechanical connection, taking into account the coefficient of friction and the minimum contact surface required to resist the tearing force, provides a well-defined contact both in terms of dimensions but also so as not to put too much stress on the c-PVC.

[0138] The advantage of the friction mechanical connection is that it is easy to connect and the network system becomes operational quickly.

[0139] The foregoing description of preferred embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired by practice of the invention. The embodiment has been selected and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to use the invention in various embodiments suited to the particular use contemplated. The scope of the invention is defined by the claims appended hereto and their equivalents. Reference numbers

[0140] Pipe 2

[0141] main body 10, 210

[0142] open end 11,211

[0143] internal radial projection 12, 212

[0144] external surface of body 14, 214

[0145] internal surface of body 15, 215.

[0146] external radial projection 16, 216

[0147] nut receiving part 18, 218

[0148] flange 19

[0149] joint 20, 120

[0150] joint housing 21, 221

[0151] extension rib 29

[0152] hanging ring 30, 130, 230

[0153] axial end 31, 32

[0154] outer surface of ring 34, 234

[0155] inner surface of ring 35, 235

[0156] longitudinal grooves or recesses 36

[0157] opening of ring 35

[0158] longitudinal slots 38, 138, 238

[0159] external projection 39

[0160] nut 40, 240

[0161] first part of nut 42

[0162] second part of nut 44

[0163] nut threads 47, 247

[0164] free end of nut 48, 248

[0165] internal surface of nut 45, 245

[0166] the reinforcing element 262

[0167] recesses 263

Claims

Claims

1. A mechanical coupling for connecting pipes or for securing a pipe, comprising: a main body (10, 210) extending axially between a body end and an open end (11) defining an insertion space for a pipe, a gripping ring (30, 130, 230) adapted to close over a pipe, a nut (40, 240) movably mounted on the main body for tightening the gripping ring (30), wherein the gripping ring (30) has a ring outer surface (34) and a ring inner surface (35), wherein the ring inner surface (35) has an internal friction coefficient for defining an internal friction interface between the pipe and the gripping ring (30), the ring outer surface (34) has an external friction coefficient for defining an external friction interface between the gripping ring (30) and one of the main body and the nut (40), wherein the internal friction coefficient is 1.7 to 7,1 times higher than the external friction coefficient.,

2. A mechanical connection according to claim 1, wherein internal circumferential recesses (33) extending radially inside the gripping ring (30) are provided on the inner ring surface (35, 235), and wherein the outer ring surface (34, 234) is smooth, to allow sliding of the nut (40) or the main body (210) relative to the friction ring (30, 230).

3. A mechanical connection according to claim 1 or 2, wherein the nut (40) has a first nut portion (42) for mounting on the main body (10) and a second nut portion (44) extending axially between the first nut portion (42) and a free nut end (48), the second nut portion (44) being arranged to extend axially away from the open end (11) of the main body, wherein the gripping ring is housed below the second nut portion.

4. Mechanical connection according to one of claims 1 to 3, in which the gripping ring (30) has a conical external shape intended to deform when the nut (40) is moved on the main body to fixing the pipe, in particular one of the main body or the second nut part (44) has a corresponding conical shape.

5. A mechanical connection according to any preceding claim, wherein the gripping ring (30, 230) has a defined compression capacity, and / or is provided with at least one of the following features: the gripping ring (30, 130, 230) is an open ring, the gripping ring (30, 130, 230) has at least one longitudinal slot (38, 138, 238) from one axial end, preferably a plurality of longitudinal slots extending from the same axial end or extending from both axial ends of the gripping ring, the defined compression capacity is ensured by dimensioning the opening or slots of the gripping ring, so that the gripping ring cannot deform the pipe more than an ovality of the pipe.

6. A mechanical connection according to any preceding claim, wherein the gripping ring is provided with a reinforcing element such as an open metal ring.

7. A mechanical connection according to any preceding claim, wherein the outer ring surface (34) is provided with longitudinal grooves or recesses (36).

8. A mechanical connection according to any preceding claim, wherein the gripping ring (30) has an external radial projection (39) adapted to bear against a flange (19) formed at the open end (11) of the main body.

9. A mechanical connection according to the preceding claim, wherein a seal (20) is provided within a seal housing (21) in the main body located adjacent the flange (19).

10. Mechanical connection according to the preceding claim, in which the seal (20) has an internal triangle shape.

11. A mechanical connection according to any preceding claim, wherein the gripping ring (30) comprises an extension rib (29) extending axially away from the radial projection (39), towards the inner connection end.

12. A mechanical connection according to any preceding claim, wherein the nut (40) is provided on a nut receiving portion (18) of the main body (10) extending between

13.

14.

15.

16.

17.

18.

19. the open end (11) and an outer radial projection (16) on an outer body surface (14) of the main body (10), the outer radial projection (16) forming a stop for the nut (40). A mechanical connection according to any one of claims 1 to 12, wherein the nut (40) is made of fiber-reinforced polymer. A mechanical coupling according to any one of claims 1 to 13, wherein the main body is made of polymer or composite, and the gripping ring is made of polymer, composite or metal. An assembly of a mechanical coupling according to any one of the preceding claims and a pipe, wherein the gripping ring and the pipe have a minimum axial contact length (L) according to the following equation: L = (DN / 4* stress) * Pd; where Pd is the pressure and DN is the nominal diameter of the pipe. An assembly according to claim 15, wherein, after assembly, the pipe exhibits a reduction in pipe diameter of the order of an ovalization of the pipe, in particular of a maximum of 0.5% of the initial pipe diameter. An assembly according to claim 15 or 16, wherein only elastically deformable portions are deformed and the pipe remains undeformed after tightening the fitting onto the pipe. A method of assembling a fitting according to any one of claims 1 to 14 and a pipe, comprising the following steps: inserting the pipe into the main body of the fitting, preferably up to the internal radial projection (12), moving the nut (40) on the main body, sliding and / or screwing the nut onto the main body to close the gripping ring (30) around the pipe, comprising sliding the nut or the main body onto the gripping ring (30) while the pipe remains stationary against the ring (30), wherein the pipe remains undeformed after closing the gripping ring (30) with a pipe diameter reduction of up to 0.5% of the initial pipe diameter. A method according to the preceding claim, wherein the fitting is a fitting according to claim 11 and wherein, upon closing of the gripping ring (30), the extension rib (29) of the ring (30) axially pushes the seal (20) to deform against the main body (10) on one side and against the rigid pipe on the other side. 20

20. A method according to the preceding claim, wherein, during closing of the gripping ring (30), the gripping ring (30) is first pushed by the nut (40) and closes around the pipe, and, once the nut has reached a final position, the gripping ring (30) pushes against the seal (20).

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