DESCRIPTION

Technical field of the invention

The present invention relates to a sealing gasket for ball valves, a manufacturing process thereof, and to a product such as a ball valve comprising such sealing gasket and to an assembling method which provides to assembly such gasket in order to form a product such as a ball valve.

More specifically, the present invention refers to a sealing gasket devised to be applied to the stem of a ball valve (stem gasket) and to be made of polymer material by means of 3D printing.

Said application is particularly critical because the sealing gasket is exposed both to a static load, determined by the pressure in the body center, and to a dynamic load due to the movement of the stem.

Prior art

Figure 1 is a cross-section view of a known type of ball valve.

The operation is of the ON/OFF type, so that it is not introduced any type of flow adjustment.

In this case, the shutter is a ball, B in Figure 1 , capable of rotating by 90° due to the actuation of the stem ST.

In the configuration illustrated in Figure 1 , the valve is in an open position and enables a flow passage.

Rotating the stem by 90° switches the valve in the closed condition, wherein the sealing is ensured by the adherence between the ball B and the valve seats S.

In this type of valve, it is clear that the most critical parts forming the valve, are the pressure containment components and the gaskets placed in the main sealing areas.

The development of these latter is therefore crucial for the object of isolating the inside of the valve from the outer environment, consequently preventing in-line pressure and service fluid losses.

The technologies actually used in the Oil&Gas (O&G) field, which occupy the application field of the herein described invention, are mainly O-ring and lip seal.

The O-rings are rings made of elastic plastic materials, called elastomers, having a circular cross-section, designed to ensure a mechanical sealing by the squeezing obtained by their assembly inside a housing.

The materials commonly used in the Oil&Gas field are nitrile rubbers, hydrogenated nitrile rubbers, and fluoro-elastomers.

The sealing which it is possible to obtain by using an O-ring can be static, if there is no relative motion between the parts forming the seat, or dynamic, if there is a relative motion. The main limitations of the O-rings are represented by temperature, aging, and degradation of the rubber, extrusion and explosion risks due to decompression.

This type of gasket is generally manufactured in large numbers by moldings or, as an alternative with large diameters, by the spliced rope method.

The lip seals are the main alternative to the O-rings and are also widely used in the Oil&Gas field.

They are U-shaped rings energized by an inner spring.

The lip seals are made of thermoplastic materials, mainly reinforced PEEK or PTFE, enabling to use them in applications at pressures and temperatures which do not enable to use elastomers.

The spring placed inside the housing is necessary in order to apply a preload to the walls of the lip seal, enabling in this way to have an interference with the metal housing.

This is needed because the walls of the housing of the lip seals are generally very thin and would be easily subjected to squeezing upon the assembly without being capable of exerting a sufficient pressure against the wall and consequently yielding once, they are under stress.

As soon as the pressure reaches the slot of the lip seal, it energizes the latter by pressing mostly against the walls, contributing in this way to promote the sealing.

As with the O-rings, the application fields of the lip seals comprise static and dynamic cases.

A difference with respect to the O-rings is the sealing directionality of the lip seal which is capable of ensuring its effect only at the side where the gasket housing is present.

The lip seals are used in the Oil&Gas field in a less standardized way than the O-rings and, consequently, the manufacture thereof is not adapted to large-scale manufacturing processes.

Due to the very thin thickness of the lips forming the housing, the lip seals are often obtained by CNC machines, from solid.

This type of manufacturing method substantially increases the manufacturing costs and times, weighing on budgets and on the supply of the finished product.

Another possible traditionally used solution is the V-pack. This type of gasket has plural sealing levels ensured by overlapping several lip seals which, once coupled, work together in order to ensure the sealing.

The first lip seal of the chain is the main one and represents the first barrier of the gasket. Once energized, it is pressed by the pressure against the other rings of the V-pack which are in turn energized.

This solution is adopted for the stems of valves and has the same advantages and over- comings of the traditional lip seals which form it.

The manufacturing method and the material are the same as the ones of a traditional lip seal. Although the gasket is safer and more dependable from a technical point of view, it is often preferred a single lip seal due to cost reasons if the application is not too critical.

Moreover, the following prior art documents: EP3862599A1 , DE202012100209U1 and US10914383B2 are known.

EP3862599A1 and DE202012100209U1 disclose gaskets, the lower and upper portions thereof are configured and destined to be flattened under conditions of use of the gasket.

US10914383B2 discloses a gasket having a “U” shape.

Objects of the invention

A task of the present invention consists of manufacturing a gasket, particularly for ball valves, and a manufacturing method thereof, which overcome the disadvantages of the above cited prior art.

In the context of this task, an object of the invention consists of providing a sealing gasket and a manufacturing method thereof which enable a great flexibility in the design stage, easiness of prototyping, reduction of the supply times and costs, with respect to the actually used technologies and materials.

Another object of the invention consists of realizing a gasket and a manufacturing method thereof which enable to improve the performances and the specificity of the valve with respect to the commonly used traditional products.

Still another object consists of manufacturing a gasket ensuring several sealing points, some primary, other secondary, if the pressure is capable of passing beyond the first barrier.

Another object of the present invention consists of manufacturing a gasket and a manufacturing method thereof which enable to easily adapt the gasket inside the metal housing, in order to ensure a dynamic and a static sealings without altering the relative movement among the metal components.

A further object of the present invention consists of providing a gasket and a manufacturing method thereof which offer an easy adaptability of standard components, for the purpose of quickly converting pieces of commercial gaskets to this new solution.

Another object of the present invention consists of realizing a gasket and a manufacturing method thereof which, due to the peculiar manufacturing features, are capable of providing the greatest assurance of reliability and safety in use.

An additional object of the invention consists of providing an assembling method which comprises: reliably assembling the gasket as part of a product, particularly of a ball valve, and capable of ensuring the sealing at the housing receiving the gasket, by preventing fluid leakages among the housing and the components of the product and of the valve in contact with the gasket.

Summary of the invention

These and other objects which will better appear in the following are met by a sealing gasket comprising an annular body defining an inner diameter and having a profile (defined with reference to a cross-section of the gasket) comprising:

- an upper portion having an upper segment joined to side upper segments; an outer circular segment and an inner circular segment; an inner slot, preferably joined to or by said inner circular segment; and

- a lower portion having a lower slot formed by two lower flaps, the lower portion being a sealing portion. Preferably, the lower portion is configured to deform for preventing the passage of fluid when the gasket is in operative conditions.

Said and other objects which will better appear in the following, are further met by a product or by a valve, particularly a ball valve, comprising:

- a component, such as a stem or other elongated element, developing along a rectilinear axis, particularly a vertical axis, preferably said component being configured to rotate and/or translate, and

- said sealing gasket, and

- a housing receiving said sealing gasket, the sealing gasket cooperating with the component for ensuring sealing. Particularly, the objects are met by a ball valve comprising a containment body of a ball shutter controlled by a stem; said valve comprising a slot (the slot or housing being preferably formed by an adapter plate, by a sealing pin, and by said stem); said slot receiving (housing) said sealing gasket.

Said sealing gasket is formed by an annular body defining an inner diameter and provided with a profile defined with reference to a cross-section of the sealing gasket and comprising:

- an upper portion provided with an upper segment joined to side upper segments; an outer circular segment and an inner circular segment; an inner slot, preferably joined to or by said inner circular segment; and

- a lower portion provided with a lower slot formed by two lower flaps, the lower portion being a sealing portion. Preferably, the lower portion is configured to deform for preventing the passage of fluid when the gasket is in operative conditions.

The objects mentioned above and other ones which will better appear in the following, are further met by an assembling method and by a method of manufacturing a sealing gasket, said sealing gasket comprising an annular body defining an inner diameter and provided with a profile defined with reference to a cross-section of the gasket and comprising:

- an upper portion provided with an upper segment, joined to side upper segments; an outer circular segment and an inner circular segment; an inner slot, preferably joined to or by said inner circular segment; and

- a lower portion provided with a lower slot formed by two lower flaps, the lower portion being a sealing portion; said method comprising extruding (at least) one filament of plastic material, particularly only one filament of plastic material, by polymer additive manufacturing. Definitions and conventions

In the context of the present discussion, one or more of the following defini- tions/conventions can be applied, when appropriate and unless otherwise stated and/or where the context excluded it:

- “upper” and “lower” are terms which must be understood one in relation with the other,

- the wording “lower portion” and “upper portion” of the profile of the gasket mean portions of the profile of the gasket that are specifically shaped for, and destined to be placed under conditions of use of the gasket (in other words with reference to an assembled condition of the gasket in a product, for example in a valve), respectively below and above. The terms “lower” and “upper” are defined with reference to the axial symmetry axis of the gasket and/or to the longitudinal axis AL of the profile; in the attached figures, wherein the longitudinal axis AL is a vertical axis, the lower and upper portions are vertically offset, in other words are placed at a different height with respect to a horizontal plane. The upper and lower portions of the profile are upper and lower portions of the gasket.

- when the gasket is used in a product provided with a stem (such as a valve) or another elongated element, the upper portion is defined at a height higher than the height of the lower portion; such heights can be defined along or with reference to the stem or to the elongated element.

- the gasket has a height H defined along the longitudinal axis AL of the gasket, the “lower portion” and the “upper portion” of the gasket being defined with reference to a midline of the gasket, the midline of the gasket crossing the gasket perpendicularly to the longitudinal axis AL of the gasket, halfway the height H of the gasket (H/2).

- the gasket does not comprise any spring,

- the gasket is preferably made in one material only,

- the gasket is preferably made in one piece by polymer additive manufacturing,

- the lower portion of the profile of the gasket, due to the presence of the lower slot, is not configured to be completely squeezed on a surface of the housing which is in contact with; substantially, in use, the lower portion of the profile of the sealing gasket is not completely squeezed on a surface of the housing which is in contact with. Therefore, both in rest conditions and in use conditions, the gasket has an end housing 24 defined by the flaps 28’, 28” of the lower slot,

- the upper segment K of the upper portion of the profile of the gasket is configured to be squeezed, in use, on a surface which is in contact with it; preferably, the upper segment K does not have slots and has a width minor than a (greatest) width B of the profile, optionally the width of the upper segment K being minor than half the (greatest) width B of the profile.

Said conventions and definitions can be used, when appropriate, for limiting and/or interpreting the claims. Consequently, when appropriate, one or more of said conventions and defi- nitions can be included in one or more of the following claims, particularly when these claims use one or more expressions object of one or more conventions or definitions.

Brief description of the drawings

Further features and advantages will be better understood by the description of preferred, but not exclusive, embodiments of the invention, illustrated in an indicative and non-limiting way in the attached drawings, wherein:

Figure 1 is a cross-section view of a known type of ball valve;

Figure 2 is a perspective view of a gasket according to the present invention;

Figure 3 is a partial cross-section view of a ball valve illustrating the housing adapted to receive the gasket of Figure 2;

Figure 4 is a cross-section partial view illustrating the gasket of Figure 2 housed in the housing of Figure 3;

Figure 5 is a cross-section view of the gasket of Figure 2;

Figure 6 is a cross-section partial view, particularly illustrating the gasket of Figure 2. Figure 6 illustrates the profile of the gasket in a rest condition (undeformed condition);

Figure 7 is a cross-section view of a ball valve provided with the gasket according to the present invention, illustrated in a static condition, the ball being at 45° of rotation with respect to the completely open condition, starting from which the stem is moved by opening and closing the valve;

Figures 8 and 9 are views similar to the preceding view of Figure 7, which illustrate the opening of the valve, starting from the completely closed position, in order to enable the passage of fluid.

Detailed description of embodiments of the invention

With reference to the cited figures, the gasket (preferably for ball valves) according to the invention is generally indicated by the reference number 1 . Preferably, the gasket 1 is used in a ball valve, which is indicated by reference number 100.

The sealing gasket 1 is preferably made by polymer additive manufacturing. The fact that the gasket 1 is made by polymer additive manufacturing can be inferred by the features of the product, particularly by the layers of the gasket 1 and by the seam line of the layers. In other words, the product features which enable to identify that the gasket 1 has been made by polymer additive manufacturing, are the parallel lines determined by successive material layers overlapped by the polymer additive manufacturing due to the peculiarity of such manufacturing method.

Before describing the typical features of the gasket object of the present invention, it is pertinent to describe the 3D printing process, preferably used for manufacturing the former.

The machine selected for the prototyping and the manufacturing steps of the gaskets 1 described in this document is advantageously an Ultimaker S5®.

This machine uses the FDM (Fused Deposition Modeling) technology which exploits the layer-by-layer deposition of a plastic material extruded through a heated nozzle.

The material, at the beginning, is in the shape of a filament having a starting diameter of 2.85 mm and it is extruded to a measure corresponding to the diameter of the nozzle, for this application, 0.4 mm.

This technology enables to realize strong, long-lasting and dimensionally stable pieces, having a high degree of accuracy, reproducibility, and rapidity.

The user-friendliness and rapidity of the prototyping step enabled by the FDM machines have allowed a quick development of the gasket 1 presented in this discussion.

The definitive profile, in fact, is the result of a series of quick iterations which would not be possible without using the additive manufacturing.

However, the FDM print has also some limitations: difficult adhesion of determined materials to the print plate, impossibility of realizing too marked angles without using supports and the dimensional shrinkage of some materials after the cooling step.

One of the more important problems tied to 3D printing refers to the redesign of components adapted to this manufacturing technology, in order to simultaneously maximize the performances and ensure the highest ease of printing.

From this point of view, the gasket 1 object of the invention, was devised just from the initial designing steps to be realized by the additive manufacturing.

The operation descends from the V-pack concept: there are several contact points in order to ensure the sealing also in case of failure of the first barrier/barriers.

Lastly, the FDM technology enables to realize the product in one piece, by integrating the main features required for the end application in a complex geometry.

The gasket 1 has an annular body defining an inner diameter D. The annular body has an axial symmetry and defines an inner circular opening defining the inner diameter D; the axial symmetry axis crosses the center of the inner circular opening. The annular body has a profile defined with reference to a cross-section and is illustrated in Figures 2 and 4; the profile is provided with a width B which is defined transversally and with a height H which is defined longitudinally. The profile has an upper portion and a lower portion; such portions are aligned along a longitudinal axis (or direction) AL, which crosses the profile and is parallel to the symmetry axis of the gasket 1. In the attached figures (specifically see the Figures 4 and 6), the upper portion is shown at the top and the lower portion is shown at the bottom; in use, the gasket 1 has the orientation shown in the attached figures, wherein the upper portion is at a height greater than the one of the lower portion, the heights being defined with respect to a horizontal plane. At least the lower portion is a sealing portion; preferably, as it will be more particularly described in the following, also the upper portion is a sealing portion.

As it is visible in Figure 2 and in Figure 5, the gasket 1 is axially symmetrical, however its cross-section (therefore its profile) is substantially irregular, in other words asymmetrical; for this matter, please see Figures 4 and 6. Precisely this asymmetry is the underlying concept of the invention and is the result of a study and of an adaptation during the design step of each single sealing point in order to improve the performance of the product.

As illustrated still more specifically in Figure 4 showing the cross-section of the gasket 1 , the profile of the gasket has such asymmetry. Still more particularly, the profile has a double asymmetry. A first asymmetry of the profile is defined with reference to the longitudinal axis (or direction) AL of the profile of the gasket 1 crossing the upper portion and lower portion of the gasket profile (see Figure 6, wherein the longitudinal axis is a vertical axis). As illustrated in Figure 6, the longitudinal axis AL can cross the profile halfway the width B of the profile; the first asymmetry provides that the parts of the profile, opposite with respect to the longitudinal axis AL, are not symmetrical to each other. A second asymmetry of the profile is defined with reference to a transversal axis AT of the profile, which is transversal to the longitudinal axis AL (in Figure 6 the transversal axis AT is perpendicular to the longitudinal axis AL). As illustrated in Figure 6, the transversal axis AT can cross the profile halfway the height H of the profile; the second asymmetry is such that the parts of the profile opposite with respect to the transversal axis AT are not symmetrical to each other.

Since this type of solution is completely new, it is necessary, at the same time, a particular design of the housing 2 adapted to contain the gasket 1 .

Even though it was previously made reference to a ball valve 100, the sealing gasket 1 can be used in any product provided with a component 5 having a rectilinear and/or vertical and/or rotating and/or salient axes. Such components, which preferably has an elongated shape, can be a stem 5 configured to rotate and/or translate. Particularly, the product provides a seat or housing 2 receiving the sealing gasket 1 ; the sealing gasket 1 cooperates with the component 5 in order to ensure the sealing.

More particularly, the product can be a valve. Specifically, the product can be a valve 100 provided with a shutter and a stem 5 configured to move the shutter, wherein the gasket 1 is used as a stem gasket.

As said, this gasket 1 is devised to be advantageously used on the stem 5 of ball valves 100.

The housing 2, visible in Figure 3, in which the gasket is housed, is formed by an adapter plate 3, a gland trunnion 4 and a stem 5.

This shape of the cavity receiving the gasket 1 cannot be used with conventional gaskets and therefore it must be realized ad hoc for this application.

The shape of the housing 2, together with the fact that generally in the area of interest a lot of metal is present in an amount greater than the one required, enables to easily adapt existent components for housing the gasket 1 according to the present invention.

It is the very interaction between the gasket 1 and the housing 2 the cause of the sealing of this component. The squeezing determined by the coupling between the adapter plate 3 and the gland trunnion 4 increases the interference and therefore the sealing of the gasket 1 .

This happens both with reference to the same components and with reference to the stem 5 of the valve 100, the rotation thereof being not compromised.

Therefore, there is a design mechanical interference, where the gasket 1 is not subjected to squeezing, and one provided only after completing the mounting.

Figure 4 shows the gasket 1 housed in the described housing 2, as described hereinbefore.

Figure 4 highlights the points or portions of interference provided by design (design interference), which are indicated by the reference numbers 21 , 22, 23, and the points or portions of interference determined by the mounting (mounting interference) indicated by the reference numbers 11 , 12, 13. The design interference portions or points 21 , 22, 23 were designed for determining an interference with the housing 2 which determines a deformation, particularly a bend, of such portions 21 , 22, 23 of the gasket 1 ; such deformation in turn determines the sealing of the gasket 1 at such portions 21 , 22, 23. The deformation of the design interference portions 21 , 22, 23 determines, during the mounting (assembling) step of the gasket 1 , the contact, particularly the squeezing, of the mounting interference portions 11 , 12, 13 with the respective housing 2 portions (see Figure 4); such effect and the relationship between the design interference portions 21 , 22, 23 and the mounting interference portions 11 , 12, 13 will be detailed in the following.

There is no design interference in the mounting interference points 11 , 12 and 13.

The squeezing at point 21 determines a bend towards the stem 5 of the upper portion of the gasket 1 , which increases the pressure in the points 11 and 1 .

The provided design interference at point 22 presses the lower portion of the gasket 1 against the stem 5 and the whole contact band 13 is brought into interference.

In the area of point 23, an end housing 24 is formed, inspired by the one which is generally found in the conventional lip seals but without the use of springs, so that the performance of the gasket 1 adapts as the pressure increases.

The two walls of the end housing 24, once energized, are pressed against the gland trunnion 4 and the stem 5, ensuring an increase of the sealing under static conditions and a greater reactivity in dynamic cases.

The provided design interference at the point 23 is devised in order to apply a preload to the gland trunnion 4 and stem 5, thus simulating the effect of a spring in the lip seals, which is absent for technological reasons in this solution.

The efficacy of this gasket 1 is not only tied to maintaining the inner pressure.

Actually, the sealing points 11 and 12 have a double effect: they provide a second barrier against the pressure and enable a sealing from the outside to the inside.

The first described effect ensures a greater safety during the use of the valve 100, analo- gously to a V-pack when the sealing of the first stage fails.

The inwards sealing is important in order to ensure the highest possible purity of the fluid flowing in the valve 100.

This concept makes the gasket 1 very versatile because it can be used both with service fluids common to the O&G field and in more complex and specific applications, wherein the purity of the fluid must be maintained the highest as possible, an example being hydrogen service.

By specifically referring to Figures 5 and 6, which illustrate in detail the geometry of the gasket 1 according to the present invention, the fundamental dimension is given by the inner diameter D, which coincides with the diameter of the stem 5 of the valve 100 and determines also the height H of the section by a fixed proportionality factor. The ratio of the height H to the inner diameter D is preferably comprised between 0.2 and 0.35, particularly between 0.23 and 0.3. Preferably, the ratio H/D can be substantially equal to, or about, 0.3. The characteristic dimensionless ratios of the gasket are summarized in table 1 .

The upper portion of the gasket is formed by an upper segment K, substantially parallel to the surface of the housing 2, and suitably joined to upper side segments N and I. At the upper segment K, the design interference point or portion 21 is defined. The upper side segments N and I are opposite to and inclined with respect to the upper segment K. The segment N faces the inner circular opening of the gasket 1 (inner upper side segment N), while the segment I is defined on an outer surface of the annular body of the gasket 1 (outer upper side segment I). The outer upper side segment I has an extension greater than the one of the inner upper side segment N.

The upper side segments N and I respectively form angles G1 and G2 with respect to the vertical, where G1 coincides with the angle imposed by the housing 2 in that point and G2 enables the rotation of the whole upper portion of the gasket 1 by closing towards the surface L, representing the stem 5 of the valve 100, after the mounting. The angles G1 and G2 are acute angles; as illustrated in Figure 6, preferably, the angle G1 is minor than the angle G2.

The upper portion of the profile comprises a portion defining a radius R1. The radius R1 is tangent to the surface L and enables to form a sealing capable of adapting to the deformation, without never loosing the contact with the stem 5. At the radius R1 , the mounting interference point or portion 11 is defined.

An outer circular segment R3, besides representing the greatest transversal size of the gasket 1 , is also devised to adapt to the deformation caused by the mounting by coming in interference with the housing 2.

The upper portion of the profile has a segment F facing the inner circular opening, defined below the segment N and consecutive to it. The segment F is inclined with respect to the segment N, preferably by an angle greater than 90° (the angle formed by curvilinear portion defining the radius R1 at its concavity; inner angle), still more preferably comprised between 90° and 135°. The upper portion of the profile has further a circular segment R2 (or inner circular or concave segment R2) defined below the segment F and consecutive to this latter. The profile has a circular segment R3 (or outer circular or convex segment R3) defined below the circular segment R2. The circular segment R2 and the circular segment R3 both face the inner circular opening and respectively define a concavity and a convexity; the concavity defined by the circular segment R2 defines an inner slot. The slot inside the gasket 1 , formed by the segment F, inclined with respect to the horizontal of the angle G5 (acute angle), and by the inner R2 and outer circular segments R4 (or radius R4), is used for reducing the weight of the piece and facilitate its deformation and the adaptation following the assembly and in use when it is exposed to the pressure.

Generally, the overall upper portion of the profile is studied and devised to operate as a barrier from the outside to the inside of the valve 100 and as a second barrier against the inner pressure in case of failure of the first one.

As it can be observed in Figure 5, the axis of the slot does not coincide with the transversal axis AT of the gasket 1. Particularly, the axis of the inner slot is defined above with respect to the transversal axis AT (i.e. at a greater height).

The lower portion is the primary barrier against the pressure from the inside of the valve 100 and the secondary barrier against possible outer contaminations.

The main geometric element of this barrier formed by the lower portion of the profile is a further slot made by two lower flaps 28’, 28”, having respectively a width (or thickness) S1 and S2, which are coincident. The lower flaps 28’, 28” are deformable because they are configured to be brought closer to each other in condition of use as a consequence of the insertion into the slot 2. The lower portion of the profile forms the end housing 24, which is defined between the two lower flaps 28’, 28”.

The slot has a width at the base C, a depth P and an inclination G6 (acute angle) of the inner walls with respect to its axis E. The width at the base C can be defined with reference to the outer surfaces of the lower flaps 28’, 28”. The width at the base C can be defined with reference to an undeformed condition of the gasket 1 (condition preceding the mounting of the gasket); following the mounting, by the deformation of the gasket, the lower flaps 28’, 28” are brought closer to each other and therefore such width at the base decreases with respect to the value C which it takes in the undeformed condition.

The inner walls of the flaps 28’, 28” forming the lower slot are perfectly symmetrical with respect to the axis E, unlike the outer parts where an interference is already provided by design both on the stem 5 and on the gland trunnion 4.

An inclined end segment U, having an inclination G7 (acute angle) with a vertical segment M and a radius R4 (or a portion having radius R4) form the stem-side sealing; preferably, the inclination of the segment U is defined with respect to the development direction of the vertical segment M. The inclined end segment U and the segment M are part of the lower portion of the profile. At or in proximity of the portion defining the radius R4, a mounting interference point or portion 13 is defined. Preferably, the radius R4 is part of the lower portion of the profile.

A lower segment M is in contact with the surface L of the stem 5 and is further pressed against it once the slot is energized. The segment M is arranged between the radius R4 and the inclined end segment U. In undeformed conditions of the gasket, the inclination G7 defines an acute angle between the development direction of the segment M and the inclined direction of the lower segment M (see Figure 6). The segments M and U face the inner circular opening.

On the opposite side, an outer end segment Y, having inclination G8, behaves specularly with respect to the already cited inclined end segment U and it is the first barrier against the pressure on the side of the gland trunnion 4. At or in proximity of the segment Y, the design interference point or portion 23 is defined.

The lower portion of the profile has a protrusion formed by two suitably joined segments T and V, which are transversal (particularly perpendicular) to each other. The protrusion defines the design interference point or portion 22. The lower portion of the profile has further a segment W, which is arranged between the lower flap 28’ and the protrusion, and a segment J is arranged between the segment T and the segment I. The protrusion, besides forming by itself a sealing zone, adds a preload on the gasket 1 following the mounting (assembly) by rotating the segment W, inclined by an angle G4 (acute angle) with respect to the vertical, towards the stem 5 and the segment J, inclined by an angle G3 (acute angle) with respect to the vertical, towards the gland trunnion 4. Preferably, the angle G3 is minor than the angle G4.

This rotation affects the whole lower portion of the gasket 1 , by further squeezing the radius R4 against the stem 5 of the valve 100 and the outer end segment Y against the gland trunnion 4.

Therefore, the protrusion forms the interference portion 22 of the gasket 1 configured to bend the lower portion of the profile when the gasket 1 is in conditions of use.

The segment J is inclined with respect to the segment I, preferably by an angle comprised between 70° and 120° (angle described by the outer circular segment R3 at its concavity; inner angle), still more preferably between 80° and 110. The segment J and the segment I, both defined at the outer surface of the gasket, form the mounting interference portion 12 (see Figure 4).

The gasket 1 has some characteristic dimensionless ratios among some dimensions thereof and the inner diameter D. Some of such ratios are described in the following; the following table 1 lists the main dimensionless ratios of the gasket 1. Such dimensionless ratios are preferably maintained independently from the absolute dimensions of the gasket 1 ; substantially, gaskets 1 of different dimensions can have the same dimensionless ratios indicated herein.

The depth P of the lower slot is minor than the inner diameter D and has a ratio with the inner diameter D (ratio P/D) comprised between 0.02 and 0.05, particularly comprised between 0.025 and 0.04, preferably about 0.032. The width B of the profile of the gasket 1 is minor than the inner diameter D and has a ratio (ratio B/D) with the inner diameter D comprised between 0.05 and 0.2, particularly comprised between 0.08 and 0.15, preferably about 0.115. The width B is preferably the greatest width of the profile measured in a rest condition, in other words in an undeformed condition, of the gasket 1 . Particularly, the width B can be measured in the undeformed condition of the gasket 1 as the distance between the outer circular segment R3 and the surface L (see Figure 6), in other words as the distance between the point or portion having the greatest transversal size R3 of the gasket 1 and the contact line L with the stem 5 (the distance from the contact line 5 can be considered at the radius R1).

Table 1 : dimensionless ratios of the gasket 1

It is to be noted that such ratios are rounded to the third decimal place or, in some cases, to the second decimal place. One or more of such ratios can be used, combined with each other or also in isolation from each other, for specifying the attached claims.

Assembling method

Moreover, the invention refers to an assembling (mounting) method which provides to assemble the gasket 1 to a product. The method provides to:

- realize at least partially a slot (or housing) 2, preferably according to what is herein described, configured to house the sealing gasket 1 ,

- insert the gasket in the slot 2,

- deform the sealing gasket 1 , such step providing to: o squeeze the sealing gasket 1 against one or more surfaces of the slot 2, o bring at least partially closer the two lower flaps 28’, 28” of the lower slot.

The step which provides to bring at least partially closer the two lower flaps 28’, 28” of the lower slot is advantageous because it enables to increase the preload on the slot 2.

The step of deforming the sealing gasket 1 provides to: o determine an interference between the design interference portions 21 , 22, 23 and the respective surfaces of the slot 2, o after the step of determining the interference between the design interference portions 21 , 22, 23 and the respective surfaces of the slot 2, bring in contact and/or squeeze further interference portions 11 , 12, 13 of the sealing gasket 1 on respective portions of the slot 2.

The step of bringing in contact and/or squeezing further interference portions 11 , 12, 13 of the sealing gasket 1 on respective portions of the slot 2 comprises determining an interference between said further interference portions 11 , 12, 13 and the slot 2.

Specifically referring to a ball valve 100, the assembling method provides to realize the slot 2 by assembling the adapter plate 3, the sealing pin 4, and the stem 5.

More particularly, during the assembly of the ball valve 100, before inserting the gasket 1 , the sealing pin 4 and the stem 5 are positioned and fixed. The axis of the gasket 1 is centered with the axis of the stem 5, and the gasket 1 is made to slide on the stem 5 until it comes in contact with the sealing pin 4. The gasket 1 is “abutted” on the sealing pin 4 without stressing or compressing it. At this time, the adapter plate 3 is mounted, by “abutting” it on the gasket 1 .

The step of squeezing the sealing gasket 1 against one or more surfaces of the slot 2 is executed during the coupling between the adapter plate 3 and the gland trunnion 4; such coupling increases the interference and, consequently, the sealing of the gasket 1. Such coupling enables to deform the gasket, to rotate and/or bend the portions of the gasket according to what is beforehand described. In the following it is described the coupling between the adapter plate 3 and the gland trunnion 4.

After abutting the adapter plate 3 on the gasket 1 , the bolts constraining the adapter plate 3 and the sealing pin 4 (the number of bolts depends on the diameter or size of the valve and pressure class of the valve) are inserted and tightened, for example by hand, as much as possible. At this point, by using a torque wrench, the bolts are tightened to the tightening torque provided by design calculations, following a predetermined closure sequence and “distributing the tightening forces” in order to keep the adapter plate 3 horizontal during the operation. Maintaining the adapter plate 3 horizontal enables to prevent it from tilting and applying a greater force at a point than at another one.

The herein described assembling or mounting method can be part of a method of assembling or mounting a product such as a valve, particularly a ball valve.

Tests on the valve 100 comprising the gasket 1

Figures from 7 to 9 illustrate an example of implementation of the invention.

Before obtaining a product capable of meeting the standards provided in the design step, several tests are necessary for ascertaining its sealing and resistance when it is exposed to different fluids and pressures.

Particularly, in order to evaluate the soundness of a specific gasket with respect to another, a procedure was suitably studied. During the execution of the tests, both the static and dynamic sealing properties of the valve were tested.

The used fluids are three: water, nitrogen, and helium.

In the first case, the valve is arranged in an intermediate position between the "completely opened” one and the "completely closed” one, in order to enable the fluid to pressurize the whole body center of the valve (Figure 7).

In this way the gasket is affected by such pressure, the slot present in the lower portion and formed by the flaps 28’, 28” is energized and it is possible to check the sealing of the same under a static load condition.

With reference to the dynamic sealing, two tests were performed during the tests.

Firstly, by using water as fluid, fifteen operations of opening and closing the valve 100 at the highest pressure (Figure 7) were performed.

In this case, the system is in balance, and it is possible to evaluate the response of the gasket 1 to the relative movement between the two parts forming the cavity where it is housed in (the gland trunnion 4 and adapter plate 3 remain still and the stem 5 rotatively reciprocates by 90°).

This operation is particularly critical and the energization of the lower slot present in the gasket enables to easily adapt the contact point as the stem 5 rotates, without increasing the torque required to open the valve 100.

The second dynamic test is called “functional test” (Figures 8 and 9), the valve 100 is in a "completely closed” position and is pressurized on one side, leaving the opposite one unaltered.

At this point, the valve 100 is opened and the pressure is discharged.

During this test, the gasket 1 is not subjected to a particular load determined by the pressure, on the contrary by a mechanical load determined by the transversal displacement of the internal elements of the valve 100 with a consequent induced inclination for the stem 5. Therefore, the gasket is stressed by this load, which adds to the squeezing induced by the assembly in the cavity.

Moreover, it is possible, by repeating the static sealing test, to verify if the gasket 1 has suffered damages.

Then, the procedure provides to test the valve 100 by using as a fluid an inert gas (specifically nitrogen or helium) more critical than water.

Between the two gases, helium is particularly critical: helium is a very small molecule and is prone to easily cross through not perfect barriers. In addition, since the test is performed at only 6 bars, the energizing load on the slot of the gasket is limited and the sealing is ensured almost only by the interference provided in the designing step. Pressure-holding static tests and stem 5 movement tests were performed not only with water but also with gases.

The procedures are particularly illustrated in table 2. The results were immediately very good, and the procedure was repeated and successfully completed on a significant number of components for evaluating the reproducibility.

Table 2: procedure of testing the stem gasket 1

Further advantages of the invention

The present invention substantially differs from the prior art.

First of all, with reference to the manufacturing process, 3D printing enables a greater design flexibility and versatility, making the gasket 1 object of the present invention more adapted to the realization of products, particularly valves (ball valves or others), to order.

This invention, if compared with a lip seal or a V-pack, enables to obtain savings not only in terms of money but also in terms of time, because it reduces the delivery times from some weeks to few print hours.

This establishes a limit to the mass production of components which is less convenient just because of the manufacturing process.

The trend in the additive manufacturing field is to prevent, as much as possible, to generate an excessive stock in a physical warehouse.

It is more important to provide a “digital inventory” where it is possible to access to the files required to print the component (the gasket 1 ) directly on site, in order to enormously decrease the times.

Hence, it is clear the advantage stemming from the new stem 1 gasket in terms of spare parts, since a replacement piece will require few steps to be made, thus avoiding interruptions due to a malfunction and associated economic losses.

Another important advantage of 3D printing with respect to the conventional manufacture refers to the material selection.

Once the project is done, suitably devised from the point of view of the additive manufac- taring , the selection of the material does not constitute a limitation.

In fact, the project can be quickly adapted to different materials, suitable to the provided machine, without requiring modifying molds or tools for making it.

Moreover, the possibility to add material only where it is strictly required, enables substantial savings of raw material, with a consequent reduction of the weight of the structure of the component (gasket 1) that, simultaneously, maintains its characteristics of strength.

With reference to the operative advantages of this invention, it is immediately clear the possibility of having a multistage sealing on a single gasket 1 and, in this way, to substantially simplify the application, by reducing the risk of problems during the mounting step.

The herein described gasket 1 is self-centering due to the coupling with its housing 2 and is stronger in the mounting step than the conventional solutions which are prone to be easily damaged, because of the very small thicknesses involved.

Further, the stem 1 gasket can be easily dimensionally scaled by considering as reference the diameter of the stem 5 where it is housed (by considering that such diameter is substantially equal to the inner diameter D and by considering the previously described dimensionless ratios), so that can be quickly adapted to different dimensions of the valves in which it will be mounted.

The gasket 1 is also adapted to ensure the sealing both in low pressure conditions and in high pressure conditions, without requiring changes to its structure.

From what was hereinbefore described, it is clear that the development of this product is the result of an accurate geometric and process study, which has led to the realization of a gasket 1 having a high complexity and capable of comprising in a single component different functional features.

Besides having a substantial asymmetry with respect to the transversal plane and with respect to structures having a varying interference when pressurized, the gasket 1 is optimized to be produced by the additive manufacture and does not require the presence of supports.

Therefore, the structure is self-supporting during the printing step, enabling material and time savings and eliminating the requirement of a post-processing step.

From an applicative point of view, the gasket 1 is capable of substituting the products commonly used as barriers on the stem 5 of ball valves 100 (O-ring, lip seal, and V-pack), ensuring simplicity of assembly and safety due to the different sealing stages.

Due to its layout and the versatility of the additive manufacture, the same geometry can be easily used with different materials, as long as they have a suitable flexibility and surface hardness.

The seal 1 , according to the present invention, was devised to be printed by polyamides, polypropylene, polyurethanes thermoplastics and semi-fluorinated materials.

The material selected for this application, and used during the tests, is by itself not obvious in this field; indeed, PVDF (polyvinylidene fluoride) exhibits a high tendency to dimensional- ly shrinking during the printing step and is prone to the warping phenomenon and to deformations during the process.

In order to overcome these problems, a printing profile was developed dedicated to the use of PVDF by the Ultimaker S5®, capable of ensuring dimensional, structural stability and of helping in eliminating the requirement of a post-processing step on the finished product.

The gasket 1 , object of this invention, is studied to be capable of being adapted to be used with different fluids in order to extend the possibility of its uses in different fields or steps of a given application.

The starting point of its development is certainly constituted by the ball valves 100 for O&G applications.

Consequently, by considering that this product can be mounted on the stem of any ball valve, we can find an application in all the steps of a cycle for producing gases and hydrocarbons. From the extraction to the storage, from the transport to the refinery processes.

The valves in which the gasket 1 is mounted/assembled can be used in the long chain hydrocarbon synthesis and in processes which use fluids of different types such as hydrogen or oxygen.

Generally, by the tests performed during the validation step, it is ensured the operation of the gasket 1 also with very small particles, consequently in the limits of the chemical compatibility of the selected material with the working fluid, it is possible to develop an application for this gasket 1 .

With reference to the gasket manufacturing method, it is suitably noted that the herein described gasket 1 is optimized to be printed by the FDM (Fused Deposition Modeling) technology, however the gasket 1 object of the present invention can be obtained by other polymer additive technologies such as, for example, SLA (resin photopolymerization), SLS (selective laser sintering).

It is practically proved that the invention meets the set out tasks and objects.