Patent Description:
In general, it is extremely important for a ball valve, used, for example, to shut off a gas or water supply line, to be able to maintain a closed condition between the inlet and outlet even in the event of a fire.

In this regard, the problem is mainly due to the sealing rings provided between the shutter and the valve body, which are made of polymeric materials usually with poor resistance to high temperatures. It often happens that, even if the valve is in the closed configuration, due to the high temperatures reached during a fire, the sealing rings lose consistency or even melt, causing the passage of fluid from the inlet to the outlet.

It is for this reason that some industry regulations require that, even in the event of a fire, ball valves continue to maintain a closed condition between the inlet and outlet for at least thirty minutes, which is estimated as the time required for operators, such as firefighters, to intervene and close the general supply valves of the systems. <CIT> discloses a prior art valve.

The object of this invention is to provide a ball valve which is capable of satisfying the aforesaid requirements.

Said object is achieved by a ball valve according to claim <NUM>. The dependent claims identify additional advantageous embodiments of the invention.

The features and advantages of the ball valve according to this invention will become apparent from the following description, given by way of non-limiting example in accordance with the figures in the accompanying drawings, wherein:.

With reference to <FIG>, a ball valve according to one embodiment of the invention is collectively denoted with <NUM>.

The ball valve <NUM> comprises a valve body <NUM> comprising an annular wall <NUM> delimiting an internal compartment <NUM>, in which an inlet <NUM> and an outlet <NUM> for the fluid are defined.

The ball valve <NUM> further comprises a ball shutter <NUM>, housed in a space <NUM> of the internal compartment <NUM>, located between the inlet <NUM> and the outlet <NUM>. The shutter <NUM>, having an external surface 12a, is provided with a typically diametral hole <NUM> between the inlet side and the outlet side.

The shutter <NUM> is rotatable about a rotation axis Z between an angular resting position (<FIG>), wherein it closes the fluidic connection between the inlet <NUM> and the outlet <NUM> (closed configuration of the valve), and an angular opening position, in which the hole <NUM> re-establishes the fluidic connection between the inlet <NUM> and the outlet <NUM> (open configuration of the valve).

Usually, the angular opening position is set at <NUM>° to the angular closing position.

Preferably, moreover, the valve body <NUM> comprises a neck <NUM> coaxial to the rotation axis Z, which delimits a stem passage <NUM>.

The valve <NUM> further comprises a stem <NUM> engaged with the shutter <NUM>, protruding outside of the valve body <NUM> through the neck <NUM>; the stem <NUM> is sealingly rotatable in said stem passage <NUM> to maneuver the valve from the closed configuration to the open configuration and vice versa.

The space <NUM> wherein the shutter <NUM> is received is defined between a first shoulder <NUM> on the inlet side <NUM> and a second shoulder <NUM> on the outlet side <NUM>. Said shoulders <NUM>, <NUM> each comprise an annular prominence projecting from the annular wall <NUM> into the internal compartment <NUM>.

The valve <NUM> further comprises at least one sealing device <NUM>, <NUM> and preferably a first sealing device <NUM> on the inlet side <NUM> and a second sealing device <NUM> on the outlet side <NUM>.

Each sealing device <NUM>, <NUM> is placed within the space <NUM>, abutting against the respective shoulder <NUM>, <NUM>, and forms a seal with the external surface 12a of the shutter <NUM>.

The sealing device <NUM>, <NUM> comprises a continuous sealing ring <NUM> made of a polymeric material and placed in contact with the outer surface 12a of the shutter <NUM>. For example, the sealing ring <NUM> is made of PTFE (polytetrafluoroethylene), POM (polyoxymethylene), nylon (polyamide).

The sealing device <NUM>, <NUM> further comprises a continuous support ring <NUM> made of a metal material, which is connected to the sealing ring <NUM>. For example, the support ring <NUM> is located between the sealing ring <NUM> and the shoulder <NUM>, <NUM>.

For example, the support ring is made of steel, such as stainless steel or carbon steel.

In general, the sealing ring is made of a first material having a first melting temperature and the support ring is made of a second material having a second melting temperature, and the first melting temperature is less than the second melting temperature.

Preferably, the sealing ring <NUM> has a shaped cross section and the support ring <NUM> has a counter-shaped cross section with respect to a portion of the cross section of the sealing ring <NUM>, so as to achieve a shape coupling therebetween so that the support ring <NUM> is fixed to and supports the sealing ring <NUM>.

In particular, the sealing ring <NUM> has a frustoconical contact surface <NUM> in contact with the outer surface 12a of the shutter, and a front face <NUM> in the form of a circular crown, coaxial to the contact surface <NUM>.

Preferably, the sealing ring <NUM> also has an annular foot <NUM>, delimited by a portion of said front face <NUM>, which protrudes radially internally with respect to said contact surface <NUM>.

The support ring <NUM> comprises a continuous annular engagement portion <NUM> connected to the sealing ring <NUM> and a continuous annular influencing portion <NUM> joined to the coupling portion <NUM> and preferably elastically bendable relative thereto to provide an elastic lever between the sealing ring <NUM> and the shoulder <NUM>, <NUM>.

According to the invention, the coupling portion <NUM> comprises a contact portion 44b that is annular and comprises a frustoconical wall.

For example, the coupling portion <NUM> comprises an annular connecting portion 44a and the annular contact portion 44b, preferably contiguous, inclined towards each other, and resembling the shape of the foot, to which the coupling portion <NUM> is coupled. For example, the connecting portion 44a comprises a cylindrical wall defining the axis of the support ring <NUM>, while the contact portion 44b comprises a frustoconical wall divergent from the first portion. The connecting portion 44a is connected at one end to the contact portion 44b and at the other end is connected to the influencing portion <NUM>.

For example, the influencing portion <NUM> comprises a frustoconical wall converging towards the coupling portion <NUM>.

Preferably, the sealing device <NUM>, <NUM> is configured so that, inserted into the space between the shoulder <NUM>, <NUM> and the external surface 12a of the shutter, the influencing portion <NUM> is elastically deformed with respect to the resting condition, e.g., by bending, with respect to the coupling portion <NUM>, so that the sealing ring <NUM> is pushed towards the external surface 12a of the shutter <NUM> and the contact surface <NUM> operates effectively for fluid sealing.

Following a fire, it is possible for the sealing ring, being made of polymeric material, to melt, leaving only the support ring between the shoulder and the external surface of the shutter (<FIG>).

In said emergency condition, due to the pre-tensioning of the support ring <NUM>, the support ring <NUM> tends to return to the resting condition, so that, under the thrust action of the influencing portion <NUM>, at least one section of the coupling portion <NUM> comes into contact with the external surface 12a of the shutter <NUM>, forming a fluid seal.

According to the invention, the contact portion 44b of the coupling portion <NUM> is brought into contact with the outer surface 12a, forming the fluid seal.

In other words, in a normal operating condition, the support ring <NUM> is at least partially deformed elastically with respect to a resting condition so as to push the sealing ring <NUM> towards the external surface 12a of the shutter <NUM>, and in an emergency condition wherein the sealing ring <NUM> is absent, at least one section of the support ring <NUM> is in contact with the external surface 12a of the shutter <NUM>, forming a fluid seal.

Furthermore, the valve according to this invention has a particularly advantageous behavior in case of sudden overpressure on the inlet side or outlet side (<FIG>).

An overpressure on one side of the valve, for example on the outlet side, causes a crushing and advancing of the sealing ring <NUM> located on that side (for example, outlet <NUM>) and a partial release of the pre-tensioning of the corresponding support ring <NUM> and, on the opposite side, for example on the inlet side, a crushing and retraction of the corresponding sealing ring <NUM> and an increase in the pre-tensioning of the corresponding support ring <NUM>.

This behavior facilitates the absorption of the overpressure and, once this overpressure condition is over, the elasticity of the support ring allows the preceding condition to be easily re-established.

According to one embodiment of the invention (<FIG>), the sealing device <NUM>, <NUM> comprises an O-ring <NUM> arranged in an annular seat <NUM> formed in the sealing ring <NUM>.

For example, the seat <NUM> is open radially outward from the O-ring <NUM> so that the O-ring <NUM> is in contact with the side surface of the annular wall <NUM> of the valve body <NUM>, within the space <NUM>.

According to further embodiments of the invention (<FIG>), the sealing ring <NUM> is connected by interference to the support ring <NUM>.

According to another aspect, the coupling portion <NUM> is a cylindrical wall <NUM>' arranged radially internally to the sealing ring <NUM>, which is fitted with interference onto said coupling portion <NUM>.

According to another aspect (<FIG>), the support ring <NUM> comprises an influencing portion <NUM> made up of a wall in the form of a circular crown <NUM>', lying in an imaginary plane orthogonal to the axis of the support ring <NUM>. In said embodiments, even in the valve assembly configuration, the influencing portion <NUM> does not exert any thrust action on the sealing ring. In the absence of the sealing ring, for example as a result of a fire, the sealing contact between the support ring <NUM> and the outer surface 12a of the shutter <NUM> is achieved by the clearance with which the shutter is housed in the space <NUM> and the displacement that the shutter undergoes by the pressure of the fluid.

According to further embodiments (<FIG>), the coupling portion <NUM> is arranged radially outwardly to the support ring <NUM> and is connected to an external surface <NUM>' of the sealing ring <NUM>. In said embodiments, the foot <NUM> of the sealing ring <NUM> protrudes radially outwardly from the contact surface <NUM>, and the coupling portion <NUM> couples to the sealing ring <NUM> with shape coupling.

According to another aspect (<FIG>), the support ring <NUM> is devoid of the influencing portion <NUM>. In the absence of the sealing ring, for example as a result of a fire, the sealing contact between the support ring <NUM> and the outer surface 12a of the shutter <NUM> is made by the clearance with which the shutter is received in the space <NUM> and the displacement that the shutter undergoes by the pressure of the fluid.

Innovatively, the valve according to this invention solves the aforesaid problem in that following a fire, in the event that the sealing ring should melt, it is able to maintain the seal to the fluid.

Advantageously, the valve according to the invention is also able to easily withstand overpressure, for example due to water hammer, and to easily restore the condition of the seals when the overpressure has been exhausted.

Advantageously, the contact portion consisting of a frustoconical wall, in the emergency condition wherein the sealing ring is absent, allows for a fluid seal to be made without damaging and scratching the ball shutter since the support surface is flat and tangent thereto.

According to an advantageous aspect, moreover, the valve according to the invention tolerates scale formation very well, as the elastic deformation of the support ring is able to absorb dislocations caused by scale particles.

According to a further advantageous aspect, the valve according to the invention exhibits excellent sealing even at low temperatures. In said conditions, in effect, the sealing ring tends to shrink, but the support ring, relaxing, tends to compensate for the shrinkage, maintaining the fluid seal.

According to a still further advantageous aspect, the valve according to the invention manifests excellent operation in combination with actuators, for example electric actuators, as the torque required to rotate the shutter is significantly lower than solutions of the prior art.

Claim 1:
A valve (<NUM>) for intercepting a fluid in a duct, comprising:
- a valve body (<NUM>) comprising an annular wall (<NUM>) which delimits an internal compartment (<NUM>), in which a fluid inlet (<NUM>) and outlet (<NUM>) are defined, and a first shoulder (<NUM>) and a second shoulder (<NUM>), internally radially protruding from the annular wall (<NUM>), between which a space (<NUM>) is defined;
- a ball shutter (<NUM>), accommodated with clearance in the space (<NUM>) of the internal compartment (<NUM>), having an external surface (12a) and being rotatable about a rotation axis (Z) between an angular closing position and an angular opening position;
- a sealing device (<NUM>, <NUM>) placed inside the space (<NUM>), abutting against the respective shoulder (<NUM>, <NUM>), suitable for obtaining a fluid seal with the external surface (12a) of the shutter (<NUM>);
- wherein said sealing device (<NUM>, <NUM>) comprises a continuous sealing ring (<NUM>), made of polymer material, placed in contact with the external surface (12a) of the shutter (<NUM>), and a continuous support ring (<NUM>), made of metal material, coupled to the sealing ring (<NUM>) and placed between said sealing ring (<NUM>) and the shoulder (<NUM>, <NUM>);
- wherein the support ring (<NUM>) comprises a continuous annular coupling portion (<NUM>) connected to the sealing ring (<NUM>) and a continuous annular influencing portion (<NUM>) joined to and elastically bendable with respect to the coupling portion (<NUM>) to provide an elastic lever between the sealing ring (<NUM>) and the shoulder (<NUM>, <NUM>);
- wherein the coupling portion (<NUM>) comprises an annular contact portion (44b) formed by a frustoconical wall;
- wherein an outer wall of the sealing ring (<NUM>) is at least partially in contact with the side surface of the annular wall (<NUM>); and
- wherein, in an emergency condition, in which the sealing ring (<NUM>) is absent, said contact portion (44b) is in contact with the external surface (12a) of the shutter (<NUM>) at least due to the pressure of the fluid, thus obtaining a fluid seal.