METAL SEALING ARRANGEMENT FOR SEALING BETWEEN A ROTATING SHAFT AND A FIXED FRAME

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of metallic sealing assemblies dedicated to sealing rotating rods.

[0002] It finds applications in various industrial sectors, and advantageously for achieving external sealing of rotating shaft valves, at the stem level.

[0003] The invention thus relates to a metallic sealing assembly for sealing between a rotating shaft and a fixed frame. PREVIOUS STATE OF THE ART

[0004] The sealing of rotating shafts can be achieved in various ways. For applications where temperatures do not exceed 250 to 300°C, multiple solutions, including elastomers or polymers, exist and have proven their reliability.

[0005] However, beyond these temperatures, or due to contact with chemical elements incompatible with these elastomers or polymers, gland packing systems, frequently made of graphite, or mechanical seals are regularly used, the secondary seals of which are very often made of graphite. These solutions, while practical and sometimes economical, nevertheless have several drawbacks. First, their sealing performance remains limited, with the leakage rate not falling below 10⁻⁵ Pa·m³·s⁻¹, this value being a best-case scenario, which should be further qualified according to the specific service conditions. Similarly, it can happen that, despite its very broad spectrum of chemical compatibility, graphite is nevertheless incompatible with the fluid being sealed. For example, graphite is incompatible with liquid sodium.

[0006] Also, in cases where the use of graphite, polymers or elastomers is not possible, the solutions become rarer and sometimes very specific to the application.

[0007] For example, in French patent application FR 2 541 416 A1, a solution is described for sealing liquid sodium. The principle is to use a so-called "solidified" seal. Between the pipe and the graphite gland is a space cooled by external fins. The sodium, cooling in this buffer zone, creates its own sealing barrier. However, this system has drawbacks. First, the length of the required heat exchange surface necessitates a massive, heavy, and considerably bulky valve top. Furthermore, if the valve needs to be operated regularly, the area of ​​the sodium plug in contact with the shaft can quickly degrade. The still-liquid sodium can then easily bead up to the upper gland.

[0008] Another type of solution involves the use of metallic seals with at least one inner lip that contacts the shaft. This principle is also widely used with elastomers: the inner diameter of the lip is smaller than that of the shaft, and the material's hyperelasticity is used to create contact pressure between the lip and the shaft. However, extending this principle to a metallic material presents several drawbacks: since this material is not hyperelastic, the diameter tolerances of both the shaft and the lip must be very tight. There is also a high sensitivity to variations in shaft circularity, as the lip is inherently too rigid to compensate for them. Finally, sealing can only be achieved through significant contact pressure, generating a potentially substantial operating torque that is very difficult to control.

[0009] It has been proposed to address such drawbacks, as described, for example, in US patent 7,428,912 B1. This patent proposes adding a cone system, axially pushed by springs, to a V-shaped seal to maintain consistent pressure on the shaft. However, this system does not compensate for any circularity defects in either the shaft or the seal, thus limiting its sealing performance. Furthermore, the inherent rigidity of the seal lip restricts the system's adjustment range.

[0010] Furthermore, an unusual solution was presented by the Canadian company VELAN, which involves using a hydroformed bellows mounted on an angled shaft. This solution only allows a quarter-turn movement of the shaft. Despite this limitation, this system eliminates the need for any sealing between two parts moving relative to each other. However, it presents several drawbacks. First, it is a complex system requiring considerable height. Indeed, the system relies on the inherently limited flexural capacity of a mechanical bellows. This capacity can be easily increased, but this also implies increasing the length of the bellows, and therefore its overall size. Moreover, this assembly is significantly expensive and complex to manufacture: in particular, the shape of the shaft necessitates specific and delicate machining processes. In addition, the pressure resistance of this flexible element remains to be demonstrated.

[0011] Furthermore, French patent application FR 2 151 186 A1 discloses a flexible annular seal that provides optimal sealing due to its ability to conform to the surfaces against which it is applied. More specifically, the flexible metal seal comprises a core consisting of a closed, toroidal helical metal spring with tightly wound coils. A first non-ductile metal sheath, shaped like a toroid, allows the spring to be embedded, and a second ductile metal sheath, also shaped like a toroid, allows the first sheath to be embedded.

[0012] Another metallic sealing assembly, according to the preamble of claim 1, is known from FR 2 721 085 A1. DESCRIPTION OF THE INVENTION

[0013] The invention aims to remedy at least partially the needs mentioned above and the drawbacks related to prior art achievements.

[0014] In particular, it aims to offer a metal sealing assembly for rotating shafts, combining compactness, high sealing performance and easily adjustable operating force.

[0015] The invention thus relates, according to one of its aspects, to a metallic sealing assembly for sealing between a rotating shaft and a fixed frame of a receiving machine, characterized in that it comprises: a flexible metallic seal with two concentric tori of different average diameters, comprising: a first closed metallic helical spring with tightly wound coils, substantially in the shape of a torus at rest, called the inner torus; a second closed metallic helical spring with tightly wound coils, substantially in the shape of a torus at rest, called the outer torus; the outer torus having an average diameter greater than the average diameter of the inner torus; one of the inner and outer tori being positioned between a rotating part and a non-rotating part, and thus called the "dynamic torus"; and the other of the inner and outer tori being positioned between two parts not rotating relative to each other, and thus called the "static torus"; a metallic casing in which the inner and outer tori are embedded and held, substantially,in its resting state, the shape of a hollow torus comprising an inner housing and an outer housing, respectively for the embedding of the inner and outer torus, the surface of the envelope comprising an annular opening between the inner and outer housings, said envelope comprising: an inner overlap portion defining the inner housing and allowing partial covering of the inner torus, an outer overlap portion defining the outer housing and allowing partial covering of the outer torus, an intermediate portion, called inter-torus, connecting the inner overlap portion and the outer overlap portion, formed opposite the annular opening, a shaft rotating about an axis of rotation, comprising an annular shoulder against which the metallic sealing gasket bears at the static torus,the metal seal positioned around the rotating shaft being centered by means of its inner diameter, a part called the counter face, comprising a contact face, substantially flat, against which the metal seal bears at the level of the dynamic torus, a shim, positioned around the rotating shaft so that the metal seal is held between on one side the shim and on the other side the contact face of the counter face, the shim being mounted on the rotating shaft in a sliding manner along the axis of rotation of the rotating shaft, a metal part forming a cap, which may possibly be confused with the shim, covering the assembly comprising the metal seal and at least the contact face of the counter face, the cap being traversed by the rotating shaft and being fixed to the frame and / or to the counter face, on the outside of the contact face,The rotating shaft is free to rotate relative to the cap and axially fixed to the cap.

[0016] The metallic sealing assembly according to the invention may further comprise one or more of the following characteristics taken individually or in any possible technical combinations.

[0017] Advantageously, the metal sealing gasket corresponds to a particular embodiment of the sealing gasket described in French patent application FR 2 151 186 A1 described above.

[0018] According to one variant, the counter face can be a non-rotating part, intended to be fixed to the fixed frame. In this case, the assembly may include a seal, in particular a static seal, for example an O-ring, between the counter face and the frame.

[0019] According to a second variant, the counter face can be a rotating part, fixed to the rotating shaft at the shoulder. In this case, the assembly may include a seal, in particular a static seal, for example an O-ring, between the counter face and a shoulder of the rotating shaft as described below.

[0020] The contact face of the counter face can be rough, this roughness being obtained in particular through polishing.

[0021] The wedge can be locked in rotation on the rotating shaft by means of a pinned and / or keyed connection.

[0022] Furthermore, the assembly may include a shim clamping nut positioned so that the shim is located between the clamping nut and the metal seal. The rotating shaft may then include a threaded portion onto which the clamping nut can be screwed.

[0023] Furthermore, the cap may include a plurality of first smooth holes extending along the axis of rotation and passing axially through the cap, intended to be positioned opposite second threaded holes formed axially in the counter face and / or third threaded holes formed axially in the fixed frame, or intended to be positioned opposite second smooth holes formed axially in the counter face and third threaded holes formed axially in the fixed frame. The assembly may include a plurality of threaded rods, each threaded rod being suitable for insertion into a first smooth hole as well as into a second smooth or threaded hole and / or a third threaded hole. The cap may be fixed to the frame and / or the counter face by screwing nuts onto the threaded rods at the top of the cap.

[0024] According to a first variant, the cap may include, particularly at its apex, a plurality of radial holes of the same diameter, extending substantially perpendicularly to the axis of rotation of the rotating shaft and opening onto the inner diameter of the cap so as to pass radially through it. Pins, of the same diameter as the radial holes, may be inserted into the radial holes. The rotating shaft may have a groove into which the pins fit to lock the axial movement of the rotating shaft. A locking element may optionally be positioned around the cap to prevent the pins from slipping outwards.

[0025] According to a second variant, the cap may have a threaded hole on its inner diameter at the centering of the rotating shaft. The rotating shaft may have a reduced diameter section at the threaded hole to create a locking shoulder on the rotating shaft. The assembly may include a locking nut designed to fit between the rotating shaft and the cap at the threaded hole and the reduced diameter section, and to bear against the locking shoulder to axially prevent the rotation of the shaft.

[0026] Furthermore, the shim can be made in at least two parts, comprising a first part called the internal shim bearing on the internal torus, having a smooth internal diameter intended to slide on the rotating shaft and a threaded external diameter, and a second part called the external shim bearing on the external torus, having a threaded internal diameter intended to be screwed onto the internal shim.

[0027] In addition, the wedge surface of the wedge, in contact with the outer portion of the cover, may have a greater roughness than that of the contact face of the counter face.

[0028] The wedge may have a return on its outer diameter allowing the outer torus to be capped on its outer diameter.

[0029] The contact face of the counter face may have a female conical shape.

[0030] The metal sealing gasket may have a deposit of added material on its surface, including gold and / or silver.

[0031] The metallic casing may be a first metallic casing made of a material with high mechanical strength, in particular an Inconel®-type alloy. The metallic seal may include a second metallic casing wound around the first metallic casing and made of a more ductile material than that of the first metallic casing, in particular silver, intended to deform plastically when the metallic seal is crushed.

[0032] Furthermore, the counter face can consist of at least three parts joined together, comprising an internal block with the contact face against which the metal sealing gasket rests at the level of the external torus, a bellows and an external flange, the bellows providing a degree of axial freedom to the assembly so as not to block possible differential expansions, the bellows connecting the internal block and the external flange, the external flange being fixed to the fixed frame.

[0033] In addition, the cap may consist of at least two parts, including an external cap fixed to the fixed frame and an internal cap attached to the external cap by means of a screw connection.

[0034] The metallic sealing assembly according to the invention may include any of the features stated in the description, taken individually or in any technically possible combinations with other features. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The invention will be better understood upon reading the detailed description that follows, the non-limiting examples of its implementation, and upon examination of the schematic and partial figures in the attached drawing, on which: there figure 1 represents a partial cross-sectional view of a first example of a metallic sealing assembly according to the invention, the Figure 1A is an enlarged and simplified view of zone A of the figure 1 , there figure 2 represents another partial cross-sectional view of the assembly of the figure 1 allowing visualization of the cap's attachment to the back face and the frame, the figure 3represents yet another partial cross-sectional view of the assembly of the figure 1 allowing visualization of the principle of axial locking of the rotating shaft, the figure 4 is a view according to III-III of the figure 3 , there figure 5 is an enlarged and simplified view of zone B of the figure 1 , there figure 6 represents a partial cross-sectional and perspective view of a second example of a metallic sealing assembly according to the invention, comprising an expansion joint, the figure 7 is a partial view according to C of the figure 6 , there figure 8 represents a typical compression curve of the evolution of linear force as a function of crushing for a prior art metal seal, the Figures 9A and 9B represent in partial section variants of the realization of non-planar shapes of the contact face of the counter face, the Figures 10 to 12represent partial cross-sectional views of other examples of embodiments of a metallic sealing assembly according to the invention, and the figure 13 illustrates, schematically in partial section, an embodiment of a metallic sealing assembly according to the invention in which the counter face is a rotating part, fixed to the rotating shaft at the level of its shoulder.

[0036] Throughout these figures, identical references may designate identical or analogous elements.

[0037] Furthermore, the different parts represented in the figures are not necessarily shown on a uniform scale, in order to make the figures more legible. DETAILED DESCRIPTION OF SPECIFIC METHODS OF IMPLEMENTATION

[0038] Throughout this description, it is noted that the axial direction corresponds to the axis of rotation X of the rotating shaft 16. A radial direction is a direction perpendicular to the X axis. Furthermore, unless otherwise specified, the adjectives and adverbs axial, radial, axially, and radially are used with reference to the aforementioned axial and radial directions. In addition, unless otherwise specified, the terms inside (or internal) and outside (or external) are used with reference to a radial direction such that the inner part of an element is closer to the X axis of the rotating shaft 16 than the outer part of the same element. Thus, an inner diameter is closer to the axis of rotation X than an outer diameter. For a given element, the inner diameter is the portion of the diameter closest to the axis of rotation X, and the outer diameter is the portion of the diameter farthest from the axis of rotation X.Similarly, the inner torus 24 is closer to the axis of rotation X than the outer torus 25.

[0039] The present invention proposes a construction of a metallic sealing assembly 30 particularly adapted to a slow rotary movement of a shaft.

[0040] The assembly is built around two particular components, namely the metal sealing gasket 1 and the counter face 14, described below.

[0041] It should be noted that, overall figures 1 to 12 relating to a non-rotating counterface 14, the inner torus 24 constitutes the static torus, taken between two rotating parts joined in rotation, while the outer torus 25 constitutes the dynamic torus, taken between a rotating part and a fixed part.

[0042] On the contrary, in the example of the realization of the figure 13described later, relating to a rotating counterface 14, the inner torus 24 constitutes the dynamic torus while the outer torus 25 constitutes the static torus.

[0043] Thus, the figure 1 represents a partial cross-sectional view of a first example of a metal sealing assembly 30 according to the invention, and the Figure 1A is an enlarged and simplified view of zone A of the figure 1 .

[0044] The assembly 30 is intended to enable the creation of a seal between a rotating shaft 16 and a fixed frame 3 of a receiving machine, or the body of the object comprising the assembly 30.

[0045] The assembly 30 includes first of all a flexible metallic sealing gasket 1 with two concentric tori of different average diameters, this gasket corresponding in particular to a double-torus sealing gasket obtained according to the principle described in the French patent application FR 2 151 186 A1 described above.

[0046] As seen on the Figure 1A , the metal sealing joint 1 thus comprises a first metallic helical spring with contiguous coils closed upon itself and having substantially, in the rest state, the shape of a torus, called inner torus 24, and a second metallic helical spring with contiguous coils closed upon itself and having substantially, in the rest state, the shape of a torus, called outer torus 25. The outer torus 25 has an average diameter greater than the average diameter of the inner torus 24.

[0047] Furthermore, the sealing gasket 1 comprises a metal casing 26, or metal strip 26, in which the inner torus 24 and the outer torus 25 are embedded and held. This strip 26 substantially has, in its resting state, the shape of a hollow torus comprising an inner housing 27a and an outer housing 27b, respectively for the embedding of the inner torus 24 and the outer torus 25. In addition, the surface S of the strip 26 comprises an annular opening 28 between the inner housing 27a and the outer housing 27b, formed on the upper part of the surface S of the strip 26.

[0048] Thus, the strip 26 covers the inner torus 25 and outer torus 26. Three zones can be distinguished on the strip 26: First, it includes an inner overlap portion 26a defining the inner housing 27a and allowing partial coverage of the inner torus 24. This inner overlap portion 26a is wrapped around the inner torus 24, for example by flow forming, thus with a shape evoking a capital "C" open on the outer diameter of the inner torus 24.

[0049] Furthermore, the strip 26 has an outer overlap portion 26b defining the outer housing 27b and allowing partial overlap of the outer torus 25. This outer overlap portion 26b is wrapped around the outer torus 25, for example by flow forming, thus with a shape evoking a capital "C" open on the inner diameter of the outer torus 25.

[0050] Finally, the two lower ends of the two capital "C"s thus formed by the inner overlap portion 26a and the outer overlap portion 26b are connected to each other by means of an intermediate portion 26c, called inter-tores 26c, thus connecting the inner overlap portion 26a and the outer overlap portion 26b, formed opposite the annular opening 28 in the lower part of the surface S of the strip 26. This inter-tores 26c zone does not support a spring.

[0051] It should be noted that, by observation in cross-section as well as on the Figure 1A The inter-torus 26c can have a rectilinear form but also, as shown by the example of the Figure 1A , a wavy shape.

[0052] Furthermore, the assembly 30 includes a rotating shaft 16 about an axis of rotation X. This rotating shaft 16 includes an annular shoulder 7 against which the metal sealing gasket 1 bears at the level of the inner torus 24, and more precisely against the surface 16c of the shoulder 7. The gasket 1 is therefore mounted on the shoulder 7, and positioned around the rotating shaft 16, being centered by means of its inner diameter with the diametrical surface 16b of the rotating shaft 16.

[0053] It should be noted that the shoulder 7 has a width, defined along an axis perpendicular to the X axis, which is sufficient to support the inner torus 24 from below.

[0054] Furthermore, it should also be noted that the inner diameter of the metal sealing gasket 1 is large enough to allow sliding on the rotating shaft 16. It is therefore possible to position the gasket 1 on the shoulder 7. At axial contact between the gasket 1 and the shoulder 7, a first sealing line is created, once the inner torus 24 is compressed as explained later.

[0055] Furthermore, the assembly 30 includes a shim 17 which is slid axially around the rotating shaft 16 so that the metal sealing gasket 1 is held between the shim 17 on one side and the shoulder 7 of the rotating shaft 16 and the contact face 14a of the counter face 14 described below on the other. The shim 17 thus presses against the inner torus 24 from above.

[0056] This shim 17 can be prevented from rotating on the shaft by means of a pinned and / or keyed connection. In this embodiment, the shim 17 is prevented from rotating by a pin 2 fitting into two opposing grooves located on the inner diameter of the shim 17.

[0057] Furthermore, a clamping nut 18 for the shim 17 is positioned around the rotating shaft 16 so that the shim 17 is located between the clamping nut 18 and the metal sealing ring 1. To achieve this, above the shim 17, the rotating shaft 16 has a threaded portion 16d onto which the clamping nut 18 is screwed. Tightening the nut 18 pushes the shim 17 towards the shoulder 7, and the inner torus 24 is then compressed. In this example as well, the shim 17 covers the outer torus 25. Also, at the end of compression, the shim 17 is in contact or very close to the outer torus 25. Advantageously, the assembly 30 therefore allows the inner torus 24 to be compressed without it being subjected to the rotation of the nut 18, which is usually not recommended for any metal sealing joint.

[0058] In addition, the assembly 30 includes a part called counterface 14, comprising a contact face 14a, substantially flat, against which the metallic sealing gasket 1 rests at the level of the outer torus 25.

[0059] In this embodiment, the counterface 14 is a non-rotating part fixed to the frame 3 of the receiving machine. Under the counterface 14, a seal is achieved with the frame 3 by means of a static seal in the form of an O-ring 4.

[0060] The outer torus 25 is designed to make contact with the contact face 14a of the counter face 14. In this particular example, this upper contact face 14a is coated with Stellite®. This contact face 14a is generally, but not exclusively, flat. It preferably has a very low roughness, obtained, for example, by precision polishing. It is positioned so as to be opposite the underside of the outer torus 25.

[0061] The counter-face 14 is preferably metallic. However, other materials can be used, such as ceramics, including tungsten carbides and silicon carbides, among others. Similarly, the contact face 14a can be coated, particularly before polishing, with a surface coating that facilitates sliding, for example, a cernet or a Stellite® as in this example.

[0062] When the rotating shaft 16, including the metal sealing ring 1, is mounted, the geometric arrangement of the assembly causes the outer torus 25 of the ring 1 to bear against the contact face 14a. Since the ring 1 is fixed to the rotating shaft 16, the outer torus 25 will slide on the contact face 14a during the rotations of the rotating shaft 16.

[0063] To achieve an adequate level of sealing on this outer torus 25, it is preferable to compress this torus 25 axially. The system compressing the outer torus 25 should therefore preferably rotate simultaneously with the rotating shaft 16. Indeed, if a metal part compressing this torus 25 were static, the torus 25 would be severely pinched axially. Rotating the rotating shaft 16 would then risk leading to violent shearing, followed by rupture of the inter-torus 16c.

[0064] Consequently, the wedge 17 preferentially also plays a role at the level of the outer torus 25 during compression. Its geometry means that during compression of the inner torus 24, it also comes into contact with the outer torus 25, opposite the contact face 14a, or even covers it over a significant portion of its height in certain preferred embodiments of the invention described below.

[0065] The compression of the outer torus 25 will therefore take place between the movable wedge 17 on one side and the fixed counter-face 14 on the other. The compressive force on the outer torus 25 will thus be transmitted via the rotating shaft 16.

[0066] To apply this force to the rotating shaft 16, the assembly 30 advantageously includes a metal cap 15 covering the assembly comprising the shim 17, the clamping nut 18, the metal sealing gasket 1, and at least the contact face 14a of the counter face 14. The cap 15 allows the rotating shaft 16 to rotate freely. However, it is axially fixed to the rotating shaft 16 so as to create a rotational but non-translational connection between them.

[0067] At its upper part, the rotating shaft 16 passes through the cap 15 so as to allow the centering of the rotating shaft 16. On the figure 1 It should be noted that two optional O-ring seals 22 and 23 can be integrated into assembly 30 for performance testing purposes. Furthermore, a clearance J is provided between the cap 15 and the counter face 14.

[0068] Furthermore, as can be seen on this figure 1, the cap 15 has a return 38 on its outer diameter which comes to cap the outer diameter of the counter face 14. Similarly, the counter face 14 has a return 37 on its outer diameter which comes to cap the outer diameter of the fixed frame 3.

[0069] The cap 15 can be fixed to the frame 3 by bolts and / or directly to the counter face 14, and preferably in this case on the outside of the contact face 14a. This creates a connection between the rotating shaft 16 and the cap 15, at its top, which makes the axial movement of the two parts fixed, but leaves the rotating shaft 16 free to rotate, such as for example a bearing assembly.

[0070] Given the generally low speeds for the intended applications, a different assembly is preferentially chosen, as shown in the example of the implementation of the figure 1 .

[0071] Thus, the figures 2 to 4allow for a better understanding of how the assembly is tightened. As seen on the figure 2 For example, the cap 15 has a plurality of first smooth holes 51 extending along the axis of rotation X and passing axially through the cap 15. These first smooth holes 51 are positioned opposite second smooth holes 52 formed axially in the counter face 14, themselves opposite third tapped holes 53 formed axially in the fixed frame 3.

[0072] The assembly 30 further comprises a plurality of threaded rods 19 which pass through the cap 15, the counter face 14 and the frame 3 to engage in the smooth holes 51, 52 and tapped holes 53. The cap 15 is then fixed to the frame 3 by screwing nuts 6 onto the threaded rods 19 at the top of the cap 15, washers 5 being positioned between the nuts 6 and the cap 15.

[0073] Furthermore, the cap 15 includes at its apex a plurality of radial holes 8, here four, of the same diameter, extending perpendicularly to the axis of rotation X and opening onto the inner diameter of the cap 15 so as to pass through it radially. Pins 20, of the same diameter as the radial holes 8, are inserted into the radial holes 8.

[0074] The rotating shaft 16 is positioned so that the pins 20 fit into a groove 16e machined in the shaft, the width of which is equal to the diameter of the pins 20 plus a slight clearance. The pins 20 fit into the groove 16e and thus block the axial movement of the rotating shaft 16. Thanks to the slight clearance, rotation remains free.

[0075] Furthermore, a locking element 21, called a "circlip," is then positioned around the cap 15 to prevent the pins 20 from slipping out. Once this is done, the rods 19 are secured with the nuts 6. The applied torque allows adjustment of the force on the outer torus 25. This allows for simultaneous adjustment of the sealing level and the rotational resistance torque.

[0076] When the cap 15 is tightened, the assembly formed by the shaft 16, the sealing ring 1, the nut 18 and the shim 17 is therefore driven, and the outer torus 25 is crushed on the contact face 14a of the counter face 14. The assembly is then ready to rotate.

[0077] It is known that during rotation, maintaining a high degree of intimacy between the outer torus 25 and the contact face 14a is crucial for achieving a high level of sealing. Since the contact face 14a is preferably not completely flat, or generally not completely regular, the spring coils continuously follow the surface undulations, thus ensuring this intimacy at all times. Internal sealing is achieved on the static inner torus 24.

[0078] The compression force on the outer torus 25 is adjusted purely axially; therefore, there is no need to counteract the rigidity of cylindrical elements radially. Consequently, the adjustment is straightforward, and it is possible to optimize the torque formed by the sealing level and the operating force. Indeed, the operating force is directly linked to the compression force through the tangential friction force thus generated.

[0079] An industrial optimization of this principle of the invention consists of establishing a metal-to-metal contact between the cap 15 and the part onto which it is screwed, namely the counterface 14 or the frame 3, to adjust the compression of the outer torus 25. The metal sealing gasket 1 is then compressed to a predetermined dimension. This makes it possible to increase the tightening torque after contact is established and prevents any shedding during high-pressure ramp-ups. This is acceptable insofar as a typical curve of the linear force EL, expressed in N.mm⁻¹, as a function of the compression EC, expressed in mm, is shown in the diagram. figure 8 , of a metallic sealing gasket of the type described in French patent application FR 2 151 186 A1, and applicable to the metallic sealing gasket 1 of assembly 30 according to the invention, has a flat plate at the end of the compression, hence an adaptability to wide housing tolerances.

[0080] Furthermore, it is important that during rotation, the outer torus 25 can slide on the counterface 14 and not, conversely, slip at its interface with the wedge 17. Thus, the figure 5 This illustrates an improvement to the invention in which the wedge surface 17a of the wedge 17, in contact with the outer portion of the cover 26b, has a greater roughness than the contact face 14a of the counterface 14, the latter being smooth. The aim is thus to promote locking in the wedge 17 and sliding on the counterface 14.

[0081] Furthermore, when fluid pressure pushes from the inside, there is a risk of deformation of the outer torus 25, or even a risk of pushing it out. Therefore, a small return 17b formed on the outer diameter of the shim 17 allows the outer torus 25 to be capped on its outer diameter. The height of the return 17b is less than the compressed dimension of the sealing gasket 1; otherwise, the return 17b would rub against the contact face 14a and prevent proper compression of the outer torus 25. Advantageously, the assembly is thus designed to maintain, by construction, a minimal axial clearance between this return 17b and the contact face 14a.

[0082] One drawback of assembly 30 can be the presence of axial blocking of the rotating shaft 16 relative to the frame 3 of the receiving machine. This can occur in two cases: if the cap 15 is fixed directly to the frame 3; or if the cap 15 is fixed to the counterface 14, and the counterface 14 is rigidly fixed to the frame 3. During applications at high or low temperatures, differential expansion between the frame 3 and the rotating shaft 16 may then be observed. The presence of the blockage counteracts this phenomenon, which can be detrimental.

[0083] Furthermore, it is common for the axial position of the rotating shaft 16 to be determined by other mechanical elements. For example, on a ball valve, the ball, rigidly attached to the shaft, will self-adjust with internal mechanical elements. The axial position of the shaft will be a resultant to which it will have to adapt.

[0084] One solution is to link the counterface 14 to an axial bellows-type part, itself connected to the frame 3. Thus, in another embodiment of the invention, as shown with reference to the figures 6 and 7 The counterface 14 consists of three parts joined together, either machined together or welded together. The counterface 14 thus comprises an internal block 11 provided with the contact face 14a against which the metal sealing gasket 1 bears at the level of the external torus 25, a bellows 12 and an external flange 13.

[0085] The external flange 13 is fixed to the fixed frame 3 by means of bolts 60. A sealing gasket is inserted into the groove 61 to ensure a seal. The threaded rods 19 are now screwed directly onto the internal block 11, and not onto the frame 3 as before. The bellows 12 provides axial freedom to the assembly 30 to allow for potential differential expansion; the bellows 12 connects the internal block 11 and the external flange 13. The bellows 12 can be hydroformed, welded blades, or even machined from a solid block with the counter face 14.

[0086] Furthermore, the Figures 9A and 9BThese features allow visualization of the fact that the contact face 14a of the counter face 14 has a female conical shape, typically used in applications with high internal pressure. The outer torus 25 is alternately in contact with the conical contact face 14a, and the returns 65 and 66 also contribute to pressure resistance. The resulting slope inherently limits radial movement, and the returns 65 and 66 can act as a final stop if necessary.

[0087] Furthermore, the Figure 10This illustrates the fact that a shim 17 is divided into three parts. The shim 17 comprises a first part, called the internal shim 29, which rests on the internal torus 24. This shim has a smooth inner diameter and is designed to slide on the rotating shaft 16. The internal shim 29 has a threaded outer diameter. Its value lies between the outer diameter of the internal torus 24 and the inner diameter of the outer torus 25. Furthermore, the shim 17 comprises a second part, called the external shim 31, which rests on the outer torus 25. This shim has a threaded inner diameter and is designed to be screwed onto the internal shim 29. This screw connection allows adjustment of the position of the two shims, internal 29 and external 31, during assembly, which can be useful for compensating for variations in the dimensions of the different components. Furthermore, once the adjustment has been made, the shim 17 includes a lock nut 32 which allows this adjustment to be fixed.

[0088] In general, optimizations can be made to pre-set the crushing of the outer torus 25 before assembly. Another concept is illustrated with reference to the figure 11 which consists of replacing the radial pin system 20. Thus, the cap 15 has on its inner diameter, at the centering of the rotating shaft 16, a thread 34, and the rotating shaft 16 has, at the thread 34, a portion of reduced diameter 35 so as to create a locking shoulder 27 on the rotating shaft 16.

[0089] Furthermore, the assembly 30 includes a locking nut 28 designed to fit between the rotating shaft 16 and the cap 15 at the threaded hole 34 and the reduced diameter portion 35 and to bear against the locking shoulder 27 so as to axially block the movement of the rotating shaft 16. A lock nut (not shown) can be used to lock the assembly to prevent any loosening / over-tightening during rotations of the rotating shaft 16.

[0090] Furthermore, in the case where the problem of differential expansion does not arise, and we are just looking to adapt to an axial position of the shaft 16 "imposed" due to the adjustment of other components, it is also possible to separate the cap in two.

[0091] Thus, the figure 12This presents an alternative embodiment in which the cap 15 is separated into two parts. It comprises an outer cap 43 fixed to the frame 3, the outer cap 43 having openings for the passage of bolts 49 for fixing to the frame 3. The outer cap 43 is connected to an inner cap 41 by means of a threaded connection 42. The inner cap 41 includes a non-adjustable connection to the rotating shaft 16, such as a bearing assembly, a pin system, among other things. Here, it is a pin system 48. The threaded or screwed connection 42 between the inner cap 41 and the outer cap 43 allows the height of the cap 15 to be adjusted and the pins 48 to be pre-positioned to adapt to the axial position of the rotating shaft 16. Once the adjustment has been made, a lock nut 47 can be used to secure the adjustment.

[0092] Furthermore, it should be noted that in such an assembly 30 according to the invention, a torque can be generated between the inner torus 24 and outer torus 25. During the development process, the aim is therefore to limit the friction between the outer torus 25 and the contact face 14a of the counter face 14. This can be achieved, for example, by applying a coating to the sealing gasket 1, such as a gold or silver coating. This coating also has the advantage of increasing sealing performance due to its surface flexibility.

[0093] Furthermore, in certain embodiments of the invention, the metallic sealing gasket 1 may have two layers or coatings wrapped one on top of the other. The first winding or first layer 26, in contact with the springs, is for example made of a material with high mechanical strength, in particular an Inconel® type alloy, to give mechanical cohesion to the gasket 1, and the second winding is made of a more ductile material, in particular silver, intended to deform plastically in contact with the sealing surfaces to reduce leakage rates.

[0094] Of course, the invention is not limited to the examples of implementation that have just been described. Various modifications can be made to it by a person skilled in the art.

[0095] In particular, the counter face 14 can be a rotating part, fixed to the rotating shaft 16 at the shoulder 7, as illustrated by the figure 13 .

[0096] On this figure 13 , the counter face 14 is driven in rotation with the rotating shaft 16 by means of a drive pin 62 positioned in housings 70 and 71 respectively of the counter face 14 and the shoulder 7.

[0097] Furthermore, the assembly includes a secondary sealing joint 67, in particular a static sealing joint, for example an O-ring, between the counter face 14 and the shoulder 7. This sealing joint 67 may in particular correspond to a particular embodiment of the sealing joint described in French patent application FR 2 151 186 A1 described above.

[0098] In addition, a secondary locking element 63, called a "circlip", is positioned in contact with the counter face 14 and the rotating shaft 16 such that the counter face 14 is located between this locking element 63 and the sealing gasket 67.

[0099] In this example, the internal torus 24 acts as a dynamic torus. It is in contact with the surface 14a of the counterface 14.

[0100] In this example as well, the wedge 17 plays the role of the cap 15 so that the wedge 17 and the cap 15 correspond here to the same structural element.

[0101] The wedge 17 and the frame 3 also have respectively orifices 58a and 58b, in particular tapped orifices, for the passage of fixing means between the wedge 17 and the frame 3, such as a threaded rod 50. Thus, the frame 3 and the wedge 17 are fixed together and do not rotate.

[0102] Metal washers 46 and 59 are provided at the threaded rod 50 and also between the shim 17 and the nut 18, which is secured by a locknut 45 to hold the assembly in place. More specifically, a sliding metal washer 59 may be used between the nut 18 and the shim 17, while a standard metal washer 46 may be used at the threaded rod 50.

Claims

1. Metallic sealing assembly (30) for sealing between a rotating shaft (16) and a fixed frame (3) of a receiving machine, including: - a flexible metallic sealing joint (1) with two concentric tori having different average diameters, comprising: - a first metallic helical spring with contiguous turns, closed onto itself and substantially having, at rest, the shape of a torus, called inner torus (24), - a second metallic helical spring with contiguous turns, closed onto itself and substantially having, at rest, the shape of a torus, called outer torus (25), the outer torus (25) having an average diameter greater than the average diameter of the inner torus (24), one of the inner (24) and outer (25) tori being positioned between a rotating part and a non-rotating part and thus being called "dynamic torus", and the other of the inner (24) and outer (25) tori being positioned between two parts non-rotating with respect to one another and thus being called "static torus", - a metallic jacket (26) in which the inner torus (24) and the outer torus (25) are embedded and maintained, substantially having, at rest, the shape of a hollow torus comprising an inner housing (27a) and an outer housing (27b), respectively for the embedding of the inner torus (24) and of the outer torus (25), the surface (S) of the jacket (26) comprising an annular opening (28) between the inner (27a) and outer (27b) housings, said jacket (26) comprising: - an inner covering portion (26a) defining the inner housing (27a) and allowing the partial covering of the inner torus (24), - an outer covering portion (26b) defining the outer housing (27b) and allowing the partial covering of the outer torus (25), - an intermediate portion (26c), called inter-tori (26c), connecting the inner covering portion (26a) and the outer covering portion (26b), formed facing the annular opening (28), said metallic sealing assembly being characterised in that it includes: - a rotating shaft (16) rotating about an axis of rotation (X), comprising an annular shoulder (7), the metallic sealing joint (1) bearing at the static torus against said annular shoulder (7) or the frame (3), the metallic sealing joint (1) positioned around the rotating shaft (16) being centred via its inner diameter, - a part called counterface (14), comprising a contact face (14a), substantially flat, against which the metallic sealing joint (1) bears at the dynamic torus, - a wedge (17), positioned around the rotating shaft (16) so that the metallic sealing joint (1) is caught between on the one hand the wedge (17) and on the other hand the contact face (14a) of the counterface (14), the wedge (17) being mounted on the rotating shaft (16) in a sliding way along the axis of rotation (X) of the rotating shaft (16), - a metallic part forming a bonnet (15) covering the assembly comprising the metallic sealing joint (1) and at least the contact face (14a) of the counterface (14), the bonnet (15) being passed through by the rotating shaft (16) and being fastened onto the frame (3) and / or onto the counterface (14), on the exterior of the contact face (14a), the rotating shaft (16) being free in rotation with respect to the bonnet (15) and axially rigidly connected to the bonnet (15).

2. Assembly according to claim 1, characterised in that the back (14) is a non-rotating part, intended to be fastened to the fixed frame (3).

3. Assembly according to claim 1 or 2, characterised in that the contact face (14a) of the counterface (14) is rough, this roughness being in particular obtained via polishing.

4. Assembly according to any one of the previous claims, characterised in that the wedge (17) is blocked in rotation on the rotating shaft (16) via a pinned (2) and / or keyed link.

5. Assembly according to any one of the previous claims, characterised in that it includes a clamping nut (18) for clamping the wedge (17) positioned so that the wedge (17) is located between the clamping nut (18) and the metallic sealing joint (1), the rotating shaft (16) including a threaded portion (16d) onto which the clamping nut (18) is screwed.

6. Assembly according to any one of the previous claims, characterised in that the bonnet (15) includes a plurality of first smooth holes (51) extending along the axis of rotation (X) and axially passing through the bonnet (15), intended to be positioned facing second threaded holes (52) formed axially in the counterface (14) and / or third threaded holes (53) formed axially in the fixed frame (3), or intended to be positioned facing second smooth holes (52) formed axially in the counterface (14) and third threaded holes (53) formed axially in the fixed frame (3), and in that the assembly (30) includes a plurality of threaded rods (19), each threaded rod (19) being capable of being inserted into a first smooth hole (51) as well as into a second smooth or threaded hole (52) and / or a third threaded hole (53), the bonnet (15) being fastened onto the frame (3) and / or onto the counterface (14) by screwing of nuts (6) onto the threaded rods (19) in the top part of the bonnet (15).

7. Assembly according to any one of the previous claims, characterised in that the bonnet (15) comprises, in particular in in an upper portion thereof, a plurality of radial holes (8) having the same diameter, extending substantially perpendicularly to the axis of rotation (X) and opening onto the inner diameter of the bonnet (15) so as to pass through it radially, in that pins (20), having the same diameter as the radial holes (8), are inserted into the radial holes (8), and in that the rotating shaft (16) includes a groove (16e) into which the pins (20) penetrate to block the axial movement of the rotating shaft (16), a blocking element (21) being optionally positioned around the bonnet (15) to prevent sliding of the pins (20) towards the outside.

8. Assembly according to any one of claims 1 to 7, characterised in that the bonnet (15) includes on its inner diameter, at the centring of the rotating shaft (16), an inner thread (34), and in that the rotating shaft (16) includes, at the inner thread (34), a portion having a reduced diameter (35) so as to create a blocking shoulder (27) on the rotating shaft (16), the assembly (30) including a locking nut (28) capable of being housed between the rotating shaft (16) and the bonnet (15) at the inner thread (34) and the portion having a reduced diameter (35) and of bearing against the blocking shoulder (27) so as to axially block the movement of the rotating shaft (16).

9. Assembly according to any one of the previous claims, characterised in that the wedge (17) is made in at least two parts, comprising a first part called inner wedge (29) bearing on the inner torus (24), having a smooth inner diameter intended to slide on the rotating shaft (16) and a threaded outer diameter, and a second part called outer wedge (31) bearing on the outer torus (25), having a threaded inner diameter intended to be screwed onto the inner wedge (29).

10. Assembly according to any one of the previous claims, characterised in that the wedge surface (17a) of the wedge (17), in contact with the outer covering portion (26b), has a roughness greater than that of the contact face (14a) of the counterface (14).

11. Assembly according to any one of the previous claims, characterised in that the wedge (17) includes a fold (17b) on its outer diameter allowing to cover the outer torus (25) on its outer diameter.

12. Assembly according to any one of the previous claims, characterised in that the contact face (14a) of the counterface (14) has a female conical shape.

13. Assembly according to any one of the previous claims, characterised in that metallic sealing joint (1) includes, on its surface, a deposit of added material, in particular gold and / or silver.

14. Assembly according to any one of the previous claims, characterised in that the metallic jacket (26) is a first metallic jacket (26) consisting of a material with a high mechanical strength, and in that the metallic sealing joint (1) includes a second metallic jacket wound onto the first metallic jacket and consisting of a material more ductile than that of the first metallic jacket (26), in particular silver, being intended to be plastically deformed during the crushing of the metallic sealing joint (1).

15. Assembly according to any one of the previous claims, characterised in that the counterface (14) consists of at least three parts rigidly connected together, comprising an inner block (11) provided with the contact face (14a) against which the metallic sealing joint (1) bears at the outer torus (25), a bellows (12) and an outer flange (13), the bellows (12) conferring a degree of axial liberty onto the assembly (30) to not block possible differential expansions, the bellows (12) connecting the inner block (11) and the outer flange (13), the outer flange (13) being fastened to the fixed frame (3).

16. Assembly according to any one of the previous claims, characterised in that the bonnet (15) consists of at least two parts, comprising an outer bonnet (43) fastened onto the fixed frame (3) and an inner bonnet (41) rigidly connected to the outer bonnet (43) via a screwed link (42).

17. Assembly according to claim 1, characterised in that the counterface (14) is a rotating part, rigidly connected to the rotating shaft (16) at the shoulder (7).