Piston-diaphragm assembly for a valve and manufacturing method

Abstract

Piston-diaphragm assembly for a valve and manufacturing method Piston-diaphragm assembly, for a valve (3), with a piston (50), comprising a rod (52) and a needle (90). The rod (52) comprises a piston groove (58), with a proximal groove edge (56). The needle (90) is fixed on a distal end of the rod (59). The assembly comprises a diaphragm (80), with a peripheral annular ring (81), an internal annular ring (82), received in the piston groove (58) to attach the diaphragm (80), and an annular membrane (83), connecting the annular rings. The needle (90) comprises a crown (93), which surrounds the rod (52) by externally covering the internal annular ring (82) and which comprises a crown edge (95), which terminates the crown (93) at the height of the proximal groove edge (56). The diaphragm (80) is radially interposed between the proximal edge of the groove (56) and the crown edge (95), in contact with the crown edge (95).Figure for abstract: Figure 3.

Description

Title of the invention: Piston-diaphragm assembly for a valve and manufacturing method

[0001] The present invention relates to a piston-diaphragm assembly, a valve comprising such an assembly and a method of manufacturing such an assembly.

[0002] FR3108378A1 describes a coating product spray projector, which comprises a base, with an internal channel, into which an inlet conduit and an outlet channel open for coating product. A seat is formed in the internal channel, at the outlet of the outlet channel. A valve is mounted in the internal channel so as to close it from the outside, so that a coating product chamber is delimited by the valve and the internal channel, into which the inlet conduit and the outlet channel open. The valve comprises a valve body, by means of which the valve is attached to the base, a stem movable in translation in the valve body and a needle fixed to the end of the stem. Depending on the position of the stem, the needle can bear on the seat to close the outlet channel and be distant from the seat so as not to close the outlet channel.To prevent the coating product present in the coating product chamber from rising through the valve body along the stem, the valve has a membrane, sometimes called a diaphragm, surrounding the stem, secured to the valve body by an O-ring and to the stem by another O-ring, an elastically deformable web being deployed between the rings.

[0003] While this type of valve is generally satisfactory for handling coating products or other pressurized fluids, a common failure consists of a leak of pressurized fluid at the level of the snap ring attaching the diaphragm to the stem, under the effect of a progressive accumulation of fluid residue between the diaphragm and the needle, tending to deform or damage the snap ring. Indeed, by elastic deformation of the diaphragm during use of the valve, a gap is likely to be accidentally opened between the diaphragm and the needle. This open gap then allows the introduction of debris between the diaphragm and the needle, this debris keeping the gap open, then allowing more debris to accumulate at this location, until the snap ring is deformed or damaged enough to create a leak of pressurized fluid.

[0004] The aim of the invention is then to propose a new piston-diaphragm assembly for which the risk of leakage at the level of an internal annular ring of the diaphragm is reduced.

[0005] To this end, the invention relates to a piston-diaphragm assembly for a valve. The assembly comprises a piston, comprising a rod, which extends parallel to a distal direction, the rod being intended to be received in a central conduit of a body of the valve, in a sliding manner relative to the body parallel to the distal direction, the rod comprising a piston groove, surrounding the rod and being open radially outwards, the piston groove comprising a proximal groove edge and a distal groove edge between which the piston groove is delimited, the distal groove edge being offset in the distal direction relative to the proximal groove edge. The piston comprises a needle, which is fixed on a distal rod end, belonging to the rod, and which is configured to bear against a closure seat in the distal direction to close a pressurized fluid conduit.The assembly includes a diaphragm, including a peripheral annular ring, for attaching the diaphragm to the valve body, the peripheral annular ring surrounding the piston, an inner annular ring, which surrounds the piston and is received in the piston groove to thereby attach the diaphragm to the piston, and an annular membrane, which connects the peripheral annular ring to the inner annular ring.

[0006] The needle comprises a crown, which surrounds the rod by externally covering the internal annular ring and which comprises a crown edge, which terminates the crown in the opposite direction to the distal direction, the crown edge being arranged at the height of the proximal edge of the groove, the diaphragm being radially interposed between the proximal edge of the groove and the crown edge, being in contact with the crown edge.

[0007] An idea underlying the invention is to provide that the crown of the needle covers the internal annular ring to a large extent, to prevent a gap from opening between the diaphragm and the crown, in particular regardless of the elastic deformation imparted to the diaphragm by a pressurized fluid during use of the valve. The crown of the needle covers the internal annular ring to a large extent in that the crown edge is arranged at the height of the proximal edge of the groove. The needle advantageously covers the internal annular ring over its entire height, or even also covers a portion of the annular membrane, unlike the prior art which does not provide for a covering, or provides only a marginal covering, of the internal annular ring by the needle.

[0008] According to other advantageous aspects of the invention, the invention implements one or more of the following characteristics, taken in isolation or in all technically possible combinations.

[0009] Preferably, the crown comprises a base, which is adjacent to the distal groove edge.

[0010] Preferably, the crown comprises an inner conical surface, which connects the base to the crown edge, which converges in the distal direction, the crown being in oblique support in the opposite direction to the distal direction against the diaphragm by means of the inner conical surface.

[0011] Preferably, the crown comprises an internal concave curved surface, which connects the base to the crown edge, which converges in the distal direction, the crown being in oblique support in the opposite direction to the distal direction against the internal annular ring by means of the internal concave curved surface.

[0012] Preferably, the crown comprises an internal chamfer which converges in the distal direction, and which is adjacent to the distal edge of the groove.

[0013] Preferably, the needle comprises a proximal fixing interface, forming an internal conduit, by means of which the needle is fixed to the rod, preferably by fitting the distal end of the rod into the proximal fixing interface in the distal direction, the crown extending from the proximal fixing interface, in the opposite direction to the distal direction.

[0014] Preferably, the proximal groove edge is radially wider than the distal groove edge.

[0015] Preferably, the piston groove has a radial section in the form of a portion of a circle, from the distal edge of the groove to the proximal edge of the groove.

[0016] The invention also relates to a valve, comprising the piston-diaphragm assembly as defined above. The valve comprises a body, having a central conduit coaxial with a central axis and opening at a distal body end belonging to the body. The piston is slidable relative to the body along the central axis, between a distal position and a proximal position, the distal direction of the piston being parallel to the central axis. The rod is received in the central conduit, protruding from the central conduit from the distal body end when the piston is in the distal position. The needle is arranged outside the central conduit, being offset in the distal direction relative to the distal body end, whether the piston is in the proximal position or in the distal position. The peripheral annular ring attaches the diaphragm to the distal body end.The diaphragm separates the central conduit from a pressurized fluid chamber defined beyond the diaphragm in the distal direction, and is configured to be elastically deformed between: an initial shape, when the piston is in the distal position and no overpressure occurs in the pressurized fluid chamber relative to the central conduit, and stretching shapes, under the effect of an overpressure occurring in the pressurized fluid chamber relative to the central conduit. The crown edge is in contact with the diaphragm, whether the diaphragm is in the initial shape or in one of the stretching shapes, and whether the piston is in the distal position or in the proximal position.

[0017] The invention also relates to a method for manufacturing the piston-diaphragm assembly as defined above. The method comprises: threading the ring inner annular ring on the rod, while the needle is not yet fixed on the rod, the threading of the inner annular ring being carried out via the distal end of the rod and until the inner annular ring is received in the piston groove to attach the diaphragm to the rod. The method comprises, while the inner annular ring is received in the piston groove, fixing the needle on the distal end of the rod, so that the crown surrounds the rod by externally covering the inner annular ring, and so that the diaphragm is radially interposed between the proximal edge of the groove and the edge of the crown, being in contact with the edge of the crown.

[0018] Preferably, the method comprises positioning a temporary cap on the distal end of the rod, while the needle is not yet fixed on the rod and the internal annular ring is not yet threaded onto the rod, the temporary cap covering the distal end of the rod, the threading of the internal annular ring onto the rod being carried out by means of the temporary cap, with sliding of the internal annular ring along an external tapered surface of the temporary cap, the external tapered surface being convergent in the distal direction. Preferably, the method comprises removing the temporary cap, while the internal annular ring is received in the piston groove and before fixing the needle on the distal end of the rod.

[0019] The invention will appear more clearly on reading the description which follows, given solely by way of non-limiting example, and made with reference to the drawings in which:

[0020] The invention will appear more clearly on reading the description which follows, given solely by way of non-limiting example, and made with reference to the drawings in which:

[0021] [Fig-1] [Fig. 1] is a longitudinal sectional view of a pressurized fluid apparatus comprising a valve with a piston in a distal position and a diaphragm in an initial shape;

[0022] [Fig.2] [Fig.2] is a view similar to that of [Fig.l], with the piston in the distal position and the diaphragm in a distally stretched shape;

[0023] [Fig.3] [Fig.3] is an enlarged view of a detail of [Fig.2];

[0024] [Fig.4] [Fig.4] is a view similar to that of Figures 1 and 2, with the piston in a proximal position and the diaphragm in a proximally stretched shape;

[0025] [Fig.5] [Fig.5] is a view similar to that of Figures 1, 2 and 4, showing a step in a manufacturing process of a piston-diaphragm assembly belonging to the valve.

[0026] Figures 1 to 4 show part of an apparatus for applying a coating product. This apparatus is, for example, a sprayer for paint, varnish, anti-corrosion coating, or any other type of coating product that can be envisaged. The apparatus is a particular type of pressurized fluid apparatus, implementing at least two pressurized fluids, namely the coating product or other products used in the context of the coating, for example a solvent or constituents of the coating product, and a control fluid, for example compressed air. The coating product is a pressurized fluid in that it is implemented under a pressure of between 1 and 16 bar, preferably between 2 and 10 bar, in the apparatus. This also applies in the case of a solvent or a coating product constituent. The control fluid is a pressurized fluid in that it is implemented under a pressure of between 1 and 10 bar, preferably between 2 and 6 bar in the apparatus.

[0027] The apparatus comprises a valve 3. The valve 3 is particularly suitable for installation in a coating product application apparatus as described herein, but can also be used with other types of pressurized fluid apparatus, such as pneumatic or hydraulic apparatus, implementing one or more pressurized fluids other than those described herein. In the present example, the valve 3 is intended to selectively interrupt and allow a flow of pressurized fluid which is a coating product. In the other cases of application of the valve 3 mentioned above, this particular pressurized fluid can be replaced by another.

[0028] A base 2, which belongs to the apparatus or to the valve 3, forms a bore 20 and two pressurized fluid conduits, including an inlet conduit 21 for the coating product, and a discharge conduit 22 for the coating product. The conduits 21 and 22 open into the bore 20. The bore 20 opens onto an exterior 24 of the apparatus, that is to say is advantageously open to the open air. The valve 3 is fixedly received in the bore 20 by closing the bore 20. The valve 3 and the bore 20 define a common central axis X3. The central axis X3 passes through the bore 20 from the opening to the bottom of the bore 20. In the present case, the discharge conduit 22 is centered on the axis X3. A distal direction X50 is also defined, directed parallel to the axis X3, towards the bottom of the bore 20.Unless otherwise stated, terms such as "distal", "proximal", "radially" and "axially" are indicated with reference to the X3 axis and the X50 direction.

[0029] The conduits 21 and 22 open into a zone of the bore 20 which delimits a chamber of pressurized fluid 25, here the coating product. A closure seat 27 is formed at the outlet of the conduit 22 into the chamber 25, here coaxially with the axis X3. As shown in [Fig. 4], a flow F21 of pressurized fluid, which is here the coating product, is intended to circulate successively in the conduit 21, the chamber 25 and the conduit 22, via the seat 27, when the valve 3 is in an open configuration. When the valve 3 is in a closed configuration as shown in FIGS. 1 to 3, the flow F21 is interrupted by the valve 3, which closes the seat 27.

[0030] A control fluid conduit, not shown, opens into an area of ​​the bore 20 which delimits a chamber 26, called the “peripheral control chamber”, which extends between the chamber 25 and the outlet of the bore 20 to the exterior 24. A flow of control fluid circulates between the control fluid conduit and the peripheral control chamber 26 to mechanically control the valve 3. The control fluid may be pressurized air.

[0031] The valve 3 comprises a body 30. The central axis X3 is fixed relative to the body 30. Along the axis X3, the body 30 has a distal end 31 called the “distal end of the body” and a proximal end 32 called the “proximal end of the body”, opposite and crossed by the axis X3.

[0032] The valve 3 is received and fixed in the bore 20, by means of the body 30. To be fixed to the bore 20, the body 30 advantageously comprises an external thread 34, here centered on the axis X3, or any other suitable fixing means, cooperating with a complementary fixing means belonging to the base 2, here an internal thread complementary to the external thread 34, formed inside the bore 20 near the opening. In the example, the thread 34 is arranged at the proximal end 32.

[0033] Thus received in the bore 20, the valve 3 delimits, with the bore 20, the pressurized fluid chamber 25, at the bottom of the bore 20, in the distal direction X50 relative to the valve 3.

[0034] The proximal end of the body 32 is arranged at the opening of the bore 20, opening onto the exterior 24. The control chamber 26 is delimited radially between the body 30 and the bore 20 of the base 2. Preferably, a peripheral chamber 28, called the “vent chamber”, is delimited radially between the body 30 and the bore 20 of the base 2, axially between the chamber 25 and the chamber 26. In particular, the thread 34 is arranged between the proximal end 32 and the control chamber 26.

[0035] The body 30 forms a central conduit 33, which is coaxial with the axis X3 and crossed by the axis X3 over its entire length. The conduit 33 passes through the body 30 from one side to the other. The central conduit 33 opens at the distal end of the body 31 and at the proximal end of the body 32.

[0036] At the distal end of body 31, the central conduit 33 defines a distal end of conduit 36, which terminates the central conduit 33 and which opens at the distal end of body 31. In the opposite direction to the distal direction X50, from the distal end of conduit 36, and successively along the axis X3, the central conduit 33 advantageously delimits, inside the body 30, an intermediate chamber 37, a control chamber 38 and a proximal chamber 39. These chambers 37, 38 and 39 are crossed by the axis X3.

[0037] The valve 3 further comprises a piston 50.

[0038] The piston 50 is received in the central conduit 33 and is configured to slide by relative to the body 30 along the axis X3, being guided by the central conduit 33 for this sliding. The piston 50 slides between a distal position, which is a closing position, to thus obtain the closing configuration of the valve 3 shown in Figures 1 to 3, and a proximal position, which is an opening position, to thus obtain the opening configuration of the valve 3 shown in [Fig.4]. In the distal position, the piston 50 is offset in the direction X50 relative to the proximal position. In these positions, the piston 50 protrudes out of the central conduit 33 along the direction X50, from the distal end of conduit 36 ​​and, therefore from the distal end of body 31, into the chamber 25.

[0039] The valve 3 further comprises a diaphragm 80. The diaphragm 80 is an elastically deformable part, unlike other parts such as the piston 50 and the body 30, which are rigid.

[0040] The diaphragm 80 comprises a peripheral annular ring 81, for attaching the diaphragm 80 to the distal end of body 31 and surrounding the piston 50. The diaphragm 80 comprises an internal annular ring 82, attaching the diaphragm 80 to the piston 50 and surrounding the piston 50. The diaphragm 80 comprises an annular membrane 83, radially connecting the peripheral annular ring 81 to the internal annular ring 82, forming a continuous surface all around the piston 50. Thus, the diaphragm 80, in particular thanks to the membrane 83, separates the central conduit 33 from the pressurized fluid chamber 25, delimited beyond the diaphragm 80 in the direction X3. The rings 81 and 82 are preferably both centered on the axis X3. Each ring 81 and 82 is preferably circular in shape around the axis X3 and extends in a respective plane perpendicular to the axis X3.The ring 82 is movable at the same time as the piston 50 by being attached to the piston 50, while the ring 81 is fixed whatever the position of the piston 50 by being attached to the body 30. The membrane 83 deforms elastically so as to always connect the rings 81 and 82, whatever the position of the piston 50 relative to the body 30.

[0041] The diaphragm 80 has a geometry of revolution around the axis X3, that is to say that it advantageously has an identical or similar radial section all around the axis X3.

[0042] The diaphragm 80 is crossed by the piston 50, which crosses the internal annular ring 82 to protrude into the chamber 25. The diaphragm 80 and the bottom of the bore 20 together delimit the chamber 25. In other words, the diaphragm 80 borders the chamber 25. The diaphragm 80 ensures dynamic sealing to the pressurized fluid around the piston 50, between the chamber 25 and the distal end of the body 31, in particular between the chamber 25 and the central conduit 33. Preferably, it is also the diaphragm 80 which closes the bore 20, around the body 30, with respect to the exterior 24, as detailed below.

[0043] Preferably, the distal end of the body 31 forms an annular cradle 43 and, preferably, a body groove 40. The annular cradle 43 is formed around the distal end of the conduit 36. The body groove 40 is formed around the cradle 43, and therefore, around the distal end of the conduit 36. The groove 40 extends all around the body 30, around the axis X3, along a plane perpendicular to the axis X3. The groove 40 borders the cradle 43 over the entire outer periphery of the cradle 43, so as to delimit the cradle 43. Preferably, the body groove 40 is open towards the outside.

[0044] Advantageously, the peripheral annular ring 81 is received in the body groove 40, to be securely positioned on the body 30. Preferably, the ring 81 is held in a slightly deformed state by the body groove 40, in that the body groove 40 bears radially outwardly on the ring 81, relative to the central axis X3. The ring 81 is thus held in the deformed state, where the ring 81 is elastically stretched radially outwardly, relative to the central axis X3. In an undeformed state, the ring 81 preferably has a circular radial section, i.e. is toric. In the deformed state shown in Figures 1 to 4, the ring 81 is preferentially slightly flattened by the body groove 40 for a portion of the peripheral annular ring 81 against which the body groove 40 bears radially outwards.The ring 81 is thus slightly held on the body by the groove 40, in particular during assembly when the body 30 is not yet received in the bore 20.

[0045] Preferably, to fix the peripheral annular ring 81 to the body 30 while delimiting the chamber 25 in a manner that is sealed to the coating product, the peripheral annular ring 81 is radially interposed between the body 30 and the bore 20. The ring 81 thus separates the chamber 25 from the rest of the bore 20 and is held in the groove 40 by the bore 20. Pressurized fluid present in the chamber 25 cannot then escape to the outside 24 along the body 30. In particular, the bore 20 comprises an internal conical surface 29, which is centered on the axis X3 and which converges along the direction X50. The surface 29 bears obliquely, along the axis X3, in the opposite direction to the direction X50, against the peripheral annular ring 81. Thus the ring 81 is interposed radially between the surface 29 and the groove 40 to ensure the sealing of the chamber 25.In particular, the ring 81 fluidly separates the chamber 25 from the vent chamber 28, which are adjacent to said ring 81. The ring 81 therefore prevents a leak of coating product from the chamber 25 to the vent chamber 28, or even to the control chamber 26. Alternatively, it is provided that it is not the ring 81 which ensures this sealing, but a static seal distinct from the diaphragm, radially interposed between the body 30 and the bore 20.

[0046] Preferably, to facilitate the mounting of the ring 81 in the body groove 40, the body groove 40 is open, not only outwards, but also in the distal direction X50. The ring 81 is nevertheless held in place in the groove 40 thanks to the bore 20 pressing against the ring 81.

[0047] In more detail, as best seen in [Fig. 3], the body groove 40 comprises a proximal groove edge 41 and a distal groove edge 42, between which the body groove 40 is delimited. The edge 41 forms a circular projecting edge which extends around the axis X3, along a plane perpendicular to the axis X3. The edge 42 is offset in the direction X50 relative to the edge 4L. The edge 42 forms a circular projecting edge which extends around the axis X3, along a plane perpendicular to the axis X3. The edge 42 marks the boundary between the groove 40 and the annular cradle 43.The edge 41 is of larger diameter than the edge 42, and the edge 42 is arranged in the direction X50 relative to the edge 4L. Preferably, the groove 40 has a radial profile which, from the edge 42, is first parallel or almost parallel to the axis X3, then which turns outwards to the edge 4L. In other words, the groove 40 is hollow in the opposite direction to the distal direction X50, but is not or only slightly hollow radially inwards, which facilitates the introduction of the ring 81 into the groove 40 in the opposite direction to the distal direction X50.

[0048] To delimit the control chamber 26 in a manner that is sealed to the control fluid, the valve 3 advantageously comprises a static seal 72 and a static seal 73, which are for example O-rings. The chamber 26 is axially delimited by the seals 72 and 73, extending axially between the seals 72 and 73. Each seal 72 and 73 surrounds the body 30 over its entire periphery, around the axis X3. Each seal 72 and 73 is interposed between the body 30 and the bore 20, radially relative to the axis X3. In particular, the seal 72 is axially disposed between the ring 81 and the seal 73. The seal 72 fluidly separates the chamber 26 from the vent chamber 28, which are adjacent to the seal 72, to prevent control fluid from the chamber 26 from escaping to the vent chamber 28, or even to the chamber 25, by flowing along the body 30. The seal 73 separates the chamber 26 from the opening of the bore 20.The seal 73 therefore prevents a leak of control fluid from the chamber 26 towards the thread 34, or even towards the exterior 24.

[0049] The annular cradle 43 of the body 30 extends radially between the central duct 33 and the peripheral annular ring 81, in particular between the body groove 40 and the distal end of the duct 36. More precisely, the cradle 43 is delimited, internally, by the distal end of the duct 36 and, externally, by the distal edge of the groove 42. The annular cradle 43 advantageously has a shape of revolution around the axis X3. Preferably, the annular cradle 43 has a rounded radial section, hollow in the opposite direction to the direction X50. More precisely, the rounded radial section has a hollow curvature without undulation. More generally, as shown in the figures, the annular cradle 43 is concave towards the annular membrane 83. Preferably, the end 36, which forms a circular edge bordering the cradle 43 from the inside, is arranged in the direction X50 relative to the edge 42, which borders the cradle 43 from the outside. The edge 42 is advantageously of larger diameter than the end 36. The rounded radial section connects the end 36 to the edge 42.

[0050] The piston 50 advantageously comprises a rod 52 and a needle 90.

[0051] The rod 52 extends parallel to the direction X50 and is coaxial with the axis X3. The rod is received in the central duct 33. In particular, the rod 52 emerges in the chamber 25, then successively passes through the distal end of the duct 36 and the intermediate chamber 37, and emerges in the control chamber 38. Preferably, the piston 50 is guided in sliding by radial sliding of the rod 52 along a wall of the intermediate chamber 37. In other words, the piston 50 is guided in sliding by means of the rod 52, by the central duct 33 of the body 30.

[0052] The rod 52 comprises, successively along the direction X50, a part 51, a piston groove 58 and a distal rod end 59.

[0053] It is advantageously provided that the part 51 cooperates with the conduit 33 so that the rod 52 guides the sliding of the piston 50. In the distal position of the piston 50 as shown in FIGS. 1 to 3, the part 51 protrudes outside the conduit 33 in the direction X50, that is to say extends beyond the end 31 and the end 36. In the proximal position of the piston 50 as shown in [Fig. 4], the part 51 is retracted inside the conduit 33, preferably entirely, or almost entirely.

[0054] The piston groove 58 is arranged so as to be outside the central duct 33, whatever the position of the piston 50. The piston groove 58 surrounds the rod 52 over its entire circumference around the central axis X3 and is open radially outwards relative to the central axis X3. The piston groove 58 advantageously extends along a plane perpendicular to the axis X3.

[0055] As best seen in [Fig. 3], the piston groove 58 comprises a proximal groove edge 56 and a distal groove edge 57, between which the piston groove 58 is delimited. The edge 57 is offset in the distal direction X50 relative to the edge 56. The edge 56 advantageously forms a circular projecting edge which extends around the axis X3, along a plane perpendicular to the axis X3. The edge 56 preferably has a rounded radial fillet profile so as not to be sharp. The edge 56 marks the boundary between the groove 58 and the part 51. The edge 57 is offset in the direction X50 relative to the edge 56. The edge 57 forms a circular projecting edge which extends around the axis X3, along a plane perpendicular to the axis X3. The edge 57 marks the boundary between the groove 58 and the distal end of the rod 59. Preferably, the piston groove 58 has a radial section in a portion of a circle, in hollow, of the edge 56 to the edge 57. In other words, the groove 58 describes a portion of a torus around the axis X3.

[0056] For the diaphragm 80 to be attached to the piston 50, the internal annular ring 82 is received in the piston groove 58. Preferably, the ring 82 is maintained in a slightly deformed state by the piston groove 58, in that the piston groove 58 bears radially outwardly on the ring 82, relative to the central axis X3. The ring 82 is thus maintained in the deformed state, where the ring 82 is elastically stretched radially outwardly, relative to the central axis X3. In an undeformed state, the ring 82 preferably has an elliptical radial section, obliquely, converging in the direction X50. In the deformed state shown in Figures 1 to 4, the ring 82 is preferentially rounded by the piston groove 58 for a portion of the annular ring 82 against which the groove 58 bears radially outwards.The ring 82 is thus attached to the rod 52 by the groove 58, in particular during assembly when the needle 90 is not yet fixed to the rod 52.

[0057] Advantageously, the proximal edge of groove 56 is radially wider than the distal edge of groove 57, which facilitates the mounting of the ring 82 on the rod 52 by threading in the opposite direction to the direction X50, via the distal end 59 as explained below. However, unlike the groove 40, it is advantageously provided that the groove 58 is hollow radially inwards, so that the ring 82 is attached to the rod by the groove 58, even when the needle 90 is not yet in place.

[0058] The membrane 83 is of constant thickness, or with slight variations from the ring 81 to the ring 82. The diaphragm 80, in particular the membrane 83, is configured to be elastically deformed as a function of the current position of the piston 50 and the occurrence of an overpressure of pressurized fluid in the chamber 25 with respect to the central conduit 33. Preferably, the membrane 83 has a shape of revolution around the axis X3.

[0059] By "occurrence of an overpressure", it is meant that pressurized fluid 25 is present in the chamber 25 with a pressure of a value greater than that of the pressure of a fluid, which may be air, present on the other side of the diaphragm 80, in particular in the central conduit 33. In this case, the difference in value between the pressure of the pressurized fluid in the chamber 25 and in the conduit 33 is greater than a certain pressure differential threshold, which is not negligible. When the difference in value between the pressure of the pressurized fluid in the chamber 25 and in the conduit 33 is less than a given pressure differential threshold, tending towards zero, it is considered that there is no overpressure.

[0060] In particular, the diaphragm 80 adopts an initial shape, shown in [Fig.l], when no overpressure occurs in the chamber 25 relative to the central conduit 33 and the piston is in the distal position. The initial shape can be considered as a rest position of the diaphragm 80, to which the diaphragm returns naturally by elasticity when the pressures in the chamber 25 and in the conduit 33 are of close or identical value. In this initial form, the annular membrane 83 is distant from the cradle 43, preferably over the entire surface of the annular membrane 83. Preferably, the annular membrane 83 is also distant from the rod 52, in particular from the part 51 of the rod 52. Optionally, the membrane 83 is in contact with the rod only at the edge 56 and in contact with the cradle 43 only at the edge 42. An annular volume is thus formed between the annular membrane 83 and the cradle 43, between the edges 42 and 56. In this initial form, as shown in [Fig.l], the membrane 83 preferably has a general flared or conical shape, possibly curved in the direction of the cradle 43, preferably without undulation.

[0061] As shown in Figures 2 to 4, when an overpressure occurs in the chamber 25 relative to the conduit 33, the diaphragm 80 is elastically deformed towards a stretched shape. Depending on the situation, and in particular, depending on the position of the piston 50, the stretched shape may be different. In all the stretched shapes that can be adopted, the annular membrane 83 comes into contact with, and matches, the annular cradle 43, under the effect of the overpressure, which presses the annular membrane 83 against the annular cradle 43. Matching the cradle 43, the membrane 83 takes a shape that is complementary to that of the cradle. To obtain one of the stretched shapes, it is necessary for the overpressure to be sufficiently intense to elastically deform the membrane 83 until the membrane 83 bears against the annular cradle 43 in the opposite direction to the direction X50.The cradle 43 thus receiving the membrane 83 in support in the opposite direction to the X50 direction, it retains the membrane 83 against the effect of the overpressure, so that the membrane 83 is not excessively stretched. This prevents deterioration of the membrane in the event of excessive overpressure. Furthermore, the shape of the cradle 43 ensures that the membrane 83 is deformed exactly according to the desired shape, given by the cradle 43, since the membrane 83 fits the cradle 43. This also reduces the risk of deterioration of the membrane 83.

[0062] The diaphragm 80 can be elastically deformed towards a particular stretched shape, called "distal stretched shape" and shown in Figures 2 and 3, not only when an overpressure occurs in the chamber 25, but also when the piston 50 is in the distal position. In this distal stretched shape, only a proximal portion 86 of the membrane 83 is in contact with, and matches, the cradle 43, while a distal portion 87 is in contact with, and matches the rod 52, for the portion 51 which protrudes from the end 36 of the conduit 33. Given the distal position of the piston 50, the portion 51 then extends axially between the annular cradle 43, in particular the end 36, and the internal annular ring 82, in particular the groove 58.

[0063] In more detail, the proximal portion 86 is annular in shape and extends from the ring 81 to the distal portion 87. The distal portion 87 is annular in shape and extends from the proximal portion to the ring 82. Preferably, the distal portion 87 and the proximal portion 86 each represent approximately half the area of ​​the membrane 83. Preferably, almost all of the distal portion 87 is in contact with the portion 51 of the rod 52. Preferably, almost all of the proximal portion 86 is in contact with the cradle 43. Similarly, almost all of the cradle 43, from the edge 42 to the end 36, is in contact with the membrane 83. Similarly, almost all of the portion 51 of the rod 52 which emerges from the conduit 33, from the end 36 to the edge 56, is in contact with the membrane 83. Optionally, a portion of the membrane 83 located at the border between the distal 87 and proximal 86 portions is not pressed against the cradle 43 or the rod 52, at the end 36.

[0064] The fact that the membrane 83 fits both the part 51 of the rod 52 and the cradle 43 in this situation reduces the risks of deterioration of the membrane 83.

[0065] The diaphragm 80 can be elastically deformed into a particular stretched shape, called the "proximal stretched shape" and shown in [Fig. 4], not only when an overpressure occurs in the chamber 25, but also when the piston 50 is in the proximal position. In this case, the portion 51 of the rod 52 is retracted inside the conduit 33. Preferably, in this case, almost the entire membrane 83 is in contact with the cradle 43. Similarly, almost the entire cradle 43, from the edge 42 to the end 36, is in contact with the membrane 83. In particular, the proximal 86 and distal 87 portions are both in contact with the cradle 43, preferably almost entirely. The fact that the membrane 83 almost entirely fits the cradle 43 in this situation reduces the risks of damage to the membrane 83.

[0066] In its initial form, it is preferred that the annular membrane 83 be convex in the direction of the annular cradle 43, that is to say, have a curvature whose back is directed towards the annular cradle 43 as shown in [Fig.l]. This initial curvature ensures that the membrane 83 will adopt the other shapes described above when an overpressure occurs. It is advantageously provided that, when the diaphragm 80 is in the initial form, none of the parts 86 and 87 are in contact with the cradle 43 and the rod 52, except possibly with the edges 42 and 56.

[0067] Preferably, in all the shapes that the diaphragm 80 can take when using the valve, or at least for the stretched shapes, it is advantageously provided that no surface of the annular membrane 83 comes into contact with another surface of the annular membrane 83. In other words, the annular membrane 83 is not folded to the point of coming into contact against itself, which makes it possible to reduce the risk of deterioration of the membrane 83. More generally, it is possible provide that no folding of the membrane 83 occurs, thanks to the initial and stretching shapes mentioned above, in particular by pressing the membrane 83 against the cradle 43 for the stretching shapes, the shape of the cradle 43 being specifically configured to avoid a sharp folding of the membrane 83.

[0068] In the absence of overpressure and while the piston 50 is in the proximal position, the membrane 83 advantageously adopts the same shape as the proximal stretched shape. However, it is possible to provide for the membrane 83 to adopt a different intermediate shape, in particular in which the membrane 83 does not come entirely into contact with the cradle 43.

[0069] Still other stretched shapes can be obtained, when the overpressure occurs and the piston 50 is in an intermediate position between the distal position and the proximal position. Furthermore, in all intermediate situations where either too low an overpressure occurs, or the piston 50 is not in the distal position, or both, the diaphragm 80 can adopt a respective intermediate shape, which is neither the initial shape nor one of the stretched shapes as described above.

[0070] Whether the piston 50 is in the proximal or distal position, the needle 90 is arranged, preferably entirely, in the chamber 25, outside the central conduit 33, being offset in the distal direction X50 relative to the distal end of the body 31. The needle 90 is fixed to the rod 52, by the distal end of the rod 59. The needle 90 is a separate part of the rod 52, which is fixed to the rod 52 by being attached to the rod 52. The distal end of the rod 59 starts from the piston groove 58, in the direction X50 and is advantageously coaxial with the axis X3. In the proximal position of the piston 50, the needle 90 is distant from the seat 27 to allow the flow F21 to circulate, and, in the distal position of the piston 50, is in axial support against the seat 27 to close the conduit 22 and prevent the circulation of the flow F21.

[0071] In more detail, the needle 90 advantageously comprises a distal sealing end 91, a proximal fixing interface 92 and a crown 93, which together advantageously constitute a single-piece part.

[0072] The needle 90 is fixed to the distal end of the rod 59 by the proximal fixing interface 92. Preferably, the proximal fixing interface 92 is in the form of an internal conduit centered on the axis X3, opening in the opposite direction to the distal direction X50, receiving within it the distal end of the rod 59 in a fitted manner along the distal direction X50. Preferably, the fixing is obtained by a force fitting of the needle 90 onto the rod 52, in particular of the interface 92 onto the distal end 59. As shown in the figures, it is advantageously provided that the distal end 59 has claws, arranged at the periphery of the end 59, and which are radially implanted in the interface 92 to retain the needle 90 in the opposite direction to the distal direction X50. Alternatively, instead of a fitting of the needle 90 on the distal end of rod 59, it is possible to provide for screwing of the needle 90 onto the distal end of rod 59. Then, the proximal fixing interface 92 carries an internal thread and the distal end of rod 59 carries an external thread complementary to the internal thread so that this screwing can be carried out.

[0073] The closure end 91 extends in the distal direction from the interface 92 and the end 59. The closure end 91 is preferably convex in shape, or plug-shaped in the direction X50. When the rod 52 is in the distal position as shown in FIGS. 1 to 3, the end 91 bears in the distal direction X50 against the closure seat 27, thereby closing the closure seat 27. The conduit 22 is then fluidically separated from the chamber 25, preventing the establishment of the flow F21. When the rod 52 is in the proximal position as shown in [Fig.4], the end 91 is set back from the closure seat 27 in the opposite direction to the direction X50, thereby releasing the closure seat 27. The conduit 22 is then fluidly connected to the chamber 25, so that the fluid flow F21 can be established.

[0074] The crown 93 is formed at a proximal end of the needle 90, that is to say axially opposite the closing end 91. The bottom of the internal conduit of the interface 92 is arranged between the crown 93 and the end 91. The crown 93 surrounds the rod 52 over its entire periphery, at the height of the groove 58, and externally covering the internal annular ring 82, while the internal annular ring 82 is radially interposed between the crown 93 and the groove 58.

[0075] In more detail, the crown 93 comprises a base 94 and a crown edge 95. Preferably, the crown 93 forms, on the inside of the crown 93, successively in the opposite direction to the distal direction X50, an internal chamfer 96, an internal concave curved surface 97, then an internal conical surface 98, as indicated in [Fig. 3]. These surfaces 96, 97 and 98 together constitute a continuous flared internal wall, surrounding the rod 52.

[0076] The base 94 advantageously begins at a proximal end of the interface 92. In other words, the crown 93 extends in the opposite direction to the direction X50 from the internal conduit formed by the interface 92. The crown edge 95, arranged in the opposite direction to the distal direction X50 relative to the base 94, advantageously constitutes a proximal end of the needle 90 and of the crown 93.

[0077] The base 94 connects the crown 93 to the distal end of the closure 91 and begins at a proximal end of the interface 92. The base 94, which is annular in shape, surrounds the rod 52. In the opposite direction of the X50 direction, the base 94 begins by being adjacent to the distal edge of the groove 57, and extends in the opposite direction of the X50 direction away from the rod 52, radially outwardly, to the edge of the crown 95, which terminates the crown 93 in the opposite direction of the X50 direction by being radially distant from the rod 52. The crown edge 95, preferably of circular shape, extends all around the rod 52, in a plane orthogonal to the axis X3. The crown edge 95 is arranged at the height of the proximal edge of groove 56, that is to say, at the same level as the proximal edge of groove 56 along the axis X3, or even beyond the proximal edge of groove 56 in the opposite direction to the direction X50. The crown 93 thus completely covers the groove 58 by extending radially at a distance from the groove 58, from the distal edge 57 where the crown 93 is adjacent to the distal edge 57.

[0078] The inner chamfer 96 converges along the distal direction X50 and is adjacent to the distal edge of the groove 57. The chamfer 96 prevents a cutting edge from being formed at the boundary between the needle 90 and the rod 52, thus avoiding a risk of damage to the snap ring 82 during use.

[0079] The inner concave curved surface 97, of rounded hollow shape, connects the base 94 to the crown edge 95, in particular connects the chamfer 96 to the inner conical surface 98. The surface 97 starts from the chamfer 96, so that the distal edge of the groove 57 is offset in the direction X50 relative to the start of the surface 97. The inner concave curved surface 97 converges along the distal direction X50.

[0080] The inner conical surface 98 connects the base 94 to the crown edge 95, in particular connects the inner concave curved surface 97 to the crown edge 95. The surface 98 converges along the distal direction X50.

[0081] The internal annular ring 82 being received in the groove 58, it is interposed between the crown 93 and the rod 52, radially relative to the axis X3, being in contact with the crown 93, preferably over all or most of its height. In particular, the ring 82 is in contact with the surfaces 97 and 98. The crown 93 bears obliquely in the opposite direction to the distal direction X50 against the internal annular ring 82 by means of the internal concave curved surface 97. This oblique support allows the ring 82 to be held by the needle 90 in the groove 58, so that the ring 82 is kept fixed to the rod 52. The crown 93 bears obliquely in the opposite direction to the distal direction X50 against the diaphragm 80, in particular against the ring 82, by means of the internal conical surface 98. This contributes to holding the ring 82 in the groove 58.

[0082] The distal portion 87 of the membrane 83, by means of which the membrane 83 is attached to the ring 82, is interposed between the proximal edge of the groove 56 and the edge of the crown 95, radially relative to the axis X3, being in contact with the edge of the crown 95. More generally, the diaphragm 80 is radially interposed between the proximal edge of the groove 56 and the edge of the crown 95, being in contact with the edge of the crown 95.

[0083] In other words, the diaphragm 80 bears against the crown 95 for the entire surface of the diaphragm 80 which is radially interposed between the crown 95 and the rod. 52, in particular at the crown edge 95, and possibly except at a distal end of the ring 82 at the edge 57. Preferably, the crown edge 95 is maintained in contact with the diaphragm 80, whether the diaphragm 80 is in the initial shape, in one of the stretched shapes, or in any other shape during its use. Preferably, the crown edge 95 is maintained in contact with the diaphragm 80, whether the piston 50 is in the distal position, in the proximal position, or in any intermediate position. Maintaining this support between the crown edge 95 and the diaphragm 80, all around the axis X3, prevents the opening of any annular gap between the diaphragm 80 and the needle 90, which prevents the introduction and accumulation of residues or other materials between the diaphragm 80 and the crown 93.To ensure that contact is maintained between the crown edge 95 and the diaphragm 80 in all these situations, it is provided that, when the needle 90 is fixed, the crown 93 is pressed onto the diaphragm 80 so as to apply a force in the opposite direction to the direction X50, so as to maintain the diaphragm 80 in an elastically deformed configuration, in compression in the opposite direction to the direction X50. In particular, it is provided that the ring 82 and the part 87 of the membrane 83 are maintained in this elastically deformed state by oblique support of the surfaces 96 and 97 and the edge 95 against the ring 82 and the part 87 of the membrane 83.

[0084] Preferably, the rod 52 comprises a proximal base 53 and a collar 55, which are at a proximal end of the rod 52, opposite the part 51 and the needle 90. Between, on the one hand, the base 53 and the collar 55 and, on the other hand, the part 51 and the needle 90, the rod 52 passes through the intermediate chamber 37 and the control chamber 38 of the central conduit 33. The collar 55 separates the control chamber 38 from the proximal chamber 39. The proximal base 53, formed at a proximal end of the piston 50, is opposite the needle 90. The proximal base 53 is arranged in the proximal chamber 39.

[0085] The valve 3 advantageously comprises a spring 54, which exerts an elastic return force on the piston 50, here via the proximal base 53, by bearing on the body 30. The elastic return force tends to move the piston 50 in the direction X50, from its proximal position to its distal position. Preferably, the spring 54 is arranged inside the body 30, here in the proximal chamber 39, around the piston 50.

[0086] The control chamber 26, delimited by the base 2, is fluidically connected to the control chamber 38 formed inside the body 30. For this, the body 30 provides one or more conduits, not shown, connecting the chambers 26 and 38 when the body 30 is mounted on the base 2. The control fluid can therefore invade the control chambers 26 and 38, and thus exert a pressure force on the collar 55 by pressurizing the chamber 38, tending to move the piston 50 from the distal position to the proximal position, against the force developed by the spring 54. The application of the pressure force by pressurizing with control fluid puts the piston 50 in the proximal position and the release of the pressure force by lowering the control fluid pressure allows the spring 54 to return the piston 50 to the distal position. The opening and closing of the valve 3 can thus be controlled.

[0087] Like the peripheral chamber 28, the intermediate chamber 37 also constitutes a vent chamber. Preferably, the peripheral chamber 28 is fluidically connected to the intermediate chamber 37 by one or more conduits provided in the body 30, so that these chambers 28 and 37 together constitute the vent chamber. In the event of failure of one of the seals, or of the ring 81, pressurized fluid or control fluid can escape to the chambers 28 and 37 through the faulty seal to avoid invading the rest of the valve 3.

[0088] The piston 50 and the diaphragm 80 can be considered as a group, as a piston-diaphragm assembly, belonging to the valve 3. During the manufacture of the valve 3, the piston-diaphragm assembly is preferably installed in the body 30 whereas, in the piston-diaphragm assembly, the snap ring 82 is already received in the groove 58 of the rod 52 and whereas the needle 90 is already fixed on the rod 52. This involves introducing the piston 50 into the central conduit 33 then fixing the snap ring 81 in the groove 40. The body 30 is then installed in the bore 20 of the base 2. Similarly, for maintenance, it is possible to replace the entire piston-diaphragm assembly, by removing the worn piston-diaphragm assembly from the body 30 in one piece, then reassembling the assembly repaired piston-diaphragm assembly, or a new piston-diaphragm assembly, as a single unit in the body 30.

[0089] To manufacture the piston-diaphragm assembly, a manufacturing method is implemented which comprises several steps described below.

[0090] Firstly, the rod 52, the needle 90 and the diaphragm 80 are provided in a configuration where these parts are separated from each other.

[0091] Then, as shown in [Fig.5], the method advantageously comprises positioning a temporary cap 100 on the distal end of rod 59. At this stage, the needle 90 is not yet fixed on the rod 52 and the internal annular ring 82 of the diaphragm 80 is not yet threaded onto the rod 52.

[0092] The temporary cap 100 advantageously comprises a proximal base 102, by means of which the cap 100 is fixed to the distal end of the rod 59. Preferably, the proximal base 102 comprises a bore open in the opposite direction to the direction X50 to receive the end 59 within it, the end 59. The proximal base 102 thus covers the end 59, preferably entirely, in particular by covering the claws possibly provided at the end 59. Preferably the base 102 extends to the distal edge 57 of the groove 58, when the cap 100 is positioned. Externally, the base 102 preferably has a cylindrical shape with a circular base, centered on the axis X3.

[0093] The temporary cap 100 advantageously comprises a distal end 101 of tapered shape along the distal direction X50, centered on the axis X3, and of which an extreme tip is advantageously rounded. Preferably, the end 101 forms an external tapered surface 103, which is here conical. The surface 103 is convergent along the distal direction X50. The end 101 converges in the direction X50. The end 101 extends the external shape of the base 102, so that, externally, the cap 100 is entirely tapered, for example with a general cylindro-conical shape.

[0094] The method then comprises threading the inner annular ring 82 onto the rod 52, while the needle 90 is still not fixed on the rod and while the cap 100 is in place on the rod 52. The threading of the inner annular ring 82 is carried out via the distal end 59, until the inner annular ring 82 is received in the piston groove 58, in order to attach the diaphragm 80 to the rod 52. Since the cap 100 is installed, this threading of the inner annular ring 82 onto the rod 52 is carried out via the temporary cap 100, with sliding of the inner annular ring 82 along the external tapered surface 103 of the temporary cap, in the opposite direction of the X50 direction.The use of this cap 100 facilitates the threading of the ring 82, in that the ring 82 can easily be crossed by the pointed end of the temporary cap 100, then be progressively elastically separated as it progresses along the external tapered surface 103, then finally elastically return to a tighter shape once the cap 100 has passed through, to be received in the groove 58. The cap 100 also advantageously prevents the claws carried by the end 59 from damaging the ring 82.

[0095] The method then comprises removing the temporary cap 100, while the internal annular ring 82 is received in the groove 58, and before fixing the needle 90 on the distal end of the rod 59.

[0096] The method then comprises, while the internal annular ring 82 is received in the groove 58 and the temporary cap 100 has been removed, fixing the needle 90 on the distal end of the rod 59. For this, the needle 90 is fitted onto the rod 52, by force-fitting the proximal fixing interface 92 onto the end of the rod 59, in the opposite direction to the direction X50. The claws of the end of the rod 59, if they are provided, then prevent removal of the needle 90. The fixing of the needle 90 is carried out so that the crown 93 surrounds the rod 52 by externally covering the internal annular ring 82, that the base 94 is adjacent to the distal edge of the groove 57, and that the diaphragm 80 is radially interposed between the edge proximal groove 56 and crown edge 95, being in contact with crown edge 95, as described above.

[0097] Any feature described above for one of the embodiments or variants can be implemented for the other embodiments and variants described above, as far as technically possible.

Claims

Claims

1. Piston-diaphragm assembly, for a valve (3), the assembly comprising: • a piston (50), comprising: • a rod (52), which extends parallel to a distal direction (X50), the rod (52) being intended to be received in a central conduit (33) of a body (30) of the valve (3), in a sliding manner relative to the body (30) parallel to the distal direction (X50), the rod (52) comprising a piston groove (58), surrounding the rod (52) and being open radially outwards, the piston groove (58) comprising a proximal groove edge (56) and a distal groove edge (57) between which the piston groove (58) is delimited, the distal groove edge (57) being offset in the distal direction (X50) relative to the proximal groove edge (56), and • a needle (90), which is fixed on a distal end of the rod (59), belonging to the rod (52), and which is configured to come into contact with a closure seat (27) in the distal direction (X50) to close a pressurized fluid conduit (22); and • a diaphragm (80), comprising: • a peripheral annular ring (81), for attaching the diaphragm (80) to the body (30) of the valve (3), the peripheral annular ring (81) surrounding the piston (50), • an internal annular ring (82), which surrounds the piston (50) and which is received in the piston groove (58) to thereby attach the diaphragm (80) to the piston (50), and • an annular membrane (83), which connects the peripheral annular ring (81) to the internal annular ring (82); characterized in that the needle (90) comprises a crown (93), which surrounds the rod (52) by externally covering the internal annular ring (82) and which comprises a crown edge (95), which terminates the crown (93) in the opposite direction to the distal direction (X50), the crown edge (95) being arranged at the height of the proximal groove edge (56), the diaphragm (80) being radially interposed between the proximal groove edge (56) and the crown edge (95), being in contact with the crown edge (95).

2. A piston-diaphragm assembly according to claim 1, wherein the crown comprises a base (94), which is adjacent to the distal groove edge (57).

3. Piston-diaphragm assembly according to claim 2, in which the crown (93) comprises an inner conical surface (98), which connects the base (94) to the crown edge (95), which converges in the distal direction (X50), the crown (93) being in oblique support in the opposite direction to the distal direction (X50) against the diaphragm (80) via the inner conical surface (98).

4. Piston-diaphragm assembly according to any one of claims 2 or 3, in which the crown (93) comprises an internal concave curved surface (97), which connects the base (94) to the crown edge (95), which converges in the distal direction (X50), the crown (93) being in oblique support in the opposite direction to the distal direction (X50) against the internal annular ring (82) by means of the internal concave curved surface (97).

5. A piston-diaphragm assembly according to any one of claims 2 to 4, wherein the crown (93) comprises an internal chamfer (96) which converges in the distal direction (X50), and which is adjacent to the distal groove edge (57).

6. Piston-diaphragm assembly according to any one of the preceding claims, in which the needle (90) comprises a proximal fixing interface (92), forming an internal conduit, by means of which the needle (90) is fixed to the rod (52), preferably by fitting the distal end of the rod (59) into the proximal fixing interface (92) in the distal direction (X50), the crown (93) extending from the proximal fixing interface (92), in the opposite direction to the distal direction (X50).

7. A piston-diaphragm assembly according to any preceding claim, wherein the proximal groove edge (56) is radially wider than the distal groove edge (57).

8. A piston-diaphragm assembly according to any preceding claim, wherein the piston groove (58) has a cross-section radial in portion of circle, from the distal edge of groove (57) to the proximal edge of groove (56).

9. Valve (3), comprising the piston-diaphragm assembly according to any one of the preceding claims and in which: • the valve (3) comprises a body (30), having a central conduit (33) coaxial with a central axis (X3) and opening at a distal end of the body (31) belonging to the body (30); • the piston (50) slides relative to the body (30) along the central axis (X3), between a distal position and a proximal position, the distal direction (X50) of the piston (50) being parallel to the central axis (X3); • the rod (52) is received in the central conduit (33), protruding from the central conduit (33) from the distal end of the body (31) when the piston (50) is in the distal position; • the needle (90) is arranged outside the central conduit (33), being offset in the distal direction (X50) relative to the distal end of the body (31), whether the piston (50) is in the proximal position or in the distal position; • the peripheral annular ring (81) attaches the diaphragm (80) to the distal end of the body (31); • the diaphragm (80) separates the central conduit (33) from a pressurized fluid chamber (25) delimited beyond the diaphragm (80) in the distal direction (X50), and is configured to be elastically deformed between: • an initial shape, when the piston (50) is in the distal position and no overpressure occurs in the pressurized fluid chamber (25) relative to the central conduit (33), and • stretched shapes, under the effect of an overpressure occurring in the pressurized fluid chamber relative to the central conduit (33); and • the crown edge (95) is in contact with the diaphragm (80), whether the diaphragm (80) is in the initial shape or in one of the stretched shapes, and whether the piston (50) is in the distal position or in the proximal position.

10. Method of manufacturing the piston-diaphragm assembly according to one of

11. any of claims 1 to 8, the method comprising: • threading the internal annular ring (82) onto the rod (52), then that the needle (90) is not yet fixed on the rod (52), the threading of the internal annular ring (82) being carried out via the rod distal end (59) and until the internal annular ring (82) is received in the piston groove (58) to attach the diaphragm (80) to the rod (52); and • while the internal annular ring (82) is received in the piston groove (58), fixing the needle (90) on the distal end of the rod (59), so that: • the crown (93) surrounds the rod (52) by externally covering the internal annular ring (82), and • the diaphragm (80) is radially interposed between the proximal edge of the groove (56) and the crown edge (95), being in contact with the crown edge (95). The method of claim 10, comprising: • positioning a temporary cap on the distal end of the rod (59), while the needle (90) is not yet fixed on the rod (52) and the internal annular ring (82) is not yet threaded onto the rod (52), the temporary cap covering the distal end of the rod (59), the threading of the internal annular ring (82) onto the rod (52) being carried out by means of the temporary cap, with sliding of the internal annular ring (82) along an external tapered surface of the temporary cap, the external tapered surface being convergent in the distal direction (X50); and • removal of the temporary cap, while the internal annular ring (82) is received in the piston groove (58) and before fixing the needle (90) on the distal end of the rod (59).

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