WO2013136136A1

WO2013136136A1 - Venting plug, particularly for electrolytic cells of electric batteries and the like

Info

Publication number: WO2013136136A1
Application number: PCT/IB2012/051279
Authority: WO
Inventors: Folco Gibellini
Original assignee: Accuma S.P.A.
Priority date: 2012-03-16
Filing date: 2012-03-16
Publication date: 2013-09-19

Abstract

A venting plug (1, 101), particularly for electrolytic cells of electric batteries and the like, comprising a main body (2) adapted to be inserted in an opening (4, 104) between a volume (22), in which at least one gas can be generated, and an external environment. The main body (2) has a first axially extended portion (2a, 103) provided with a first radial gasket (9) around it which is coaxial to the longitudinal axis (11) of the first portion (2a, 103). The first radial gasket (9) has a transverse cross-section with a lip-like profile along at least one arc of the circumference of the first radial gasket (9). Moreover, the venting plug comprises a second radial gasket (10) around the first portion (2a, 103) coaxially to the longitudinal axis (11) in a position comprised axially between the first radial gasket (9) and a second portion (2b, 102) of the plug (1, 101) intended to interface with the external environment. The second radial gasket (10) has a thickness which is substantially constant or in any case capable of preventing the venting of the gas toward the external environment.

Description

VENTING PLUG, PARTICULARLY FOR ELECTROLYTIC CELLS OF ELECTRIC BATTERIES AND THE LIKE

The present invention relates to a venting plug particularly for electrolytic cells of electric batteries and the like.

Venting plugs for electrolytic cells of electric batteries are known which are of the type comprising a rubber safety valve which is applied by assembly or molded directly with a multipart injection system.

These conventional plugs are fitted in the adapted seats provided within the covering element of the electric battery, one for each electrolytic cell, and the safety valve is adapted to ensure hermetic closure of the electrolytic cells in normal operating conditions.

In greater detail, the safety valve is deformed elastically as the internal pressure of the electric battery increases, until it opens and allows the gases to escape when a given internal pressure is exceeded.

As the internal pressure of the electrolytic cell being considered decreases below the opening value, the safety valve closes again, ensuring hermetic closure again.

The_. value of this pressure is determined by the geometry of the safety valve and by the material of which it is made. It is therefore possible to provide safety valves that can be switched with different pressures as a function of the requirements by varying the cited parameters.

More specifically, the plug in which the safety valve is integrated can be used in all electric batteries requiring hermetic closure and the assurance that when a given pressure is exceeded the gas inside the battery has a way to escape.

For example, conventional plugs can be constituted by three or more components which are mutually assembled and one of which acts as a safety valve. One drawback of this type of plug is that it requires a plurality of components to be assembled in order to perform the functions for which it is intended; these conventional plugs suffer the drawback of having an assembly quality that is not always satisfactory and depends on the number of components by which they are constituted.

Another example of application provides for safety valves, which typically consist of cap-shaped or disk-like valves, which at the end of the process for the production of the electric battery are placed in adapted seats which are defined by the covering element of the electric battery and are arranged at each electrolytic cell. Finally, a locking device is fitted which is adapted to keep in position each safety valve.

Conventional plugs are not devoid of drawbacks, among which is the fact that the covers of electric batteries, by requiring a large opening for filling with acid and for all the top-up and leveling operations, and by requiring dimensions sufficient for easy handling and assembly by an operator and by automatic machines, have geometries and structures which entail a high production cost, which is linked to the need to manufacture separately the individual components to be assembled manually or by means of automatic machines.

Moreover, in order to limit production costs, the individual elements to be assembled and the seats of the safety valves cannot have large dimensions. This aspect clashes with the fact that this reduction in size causes the holes used for , filling, leveling and top-up with acid to be excessively small, causing problems for the use of the equipment required for these operations and of the automated machines intended to assemble the safety valves and the corresponding covers on the finished electric batteries.

The aim of the present invention is to provide a venting plug, particularly for electrolytic cells of electric batteries and the like, which solves and overcomes the above mentioned drawbacks and limitations of the background art.

Within this aim, an object of the present invention is to provide a venting plug which allows to keep constant the pressure inside the electrolytic cells of an electric accumulator at a predefined value. Another object of the invention is to provide a venting plug that is particularly adapted for use in covers of electrolytic batteries in which a gas manifold is optionally present which passes along the cover, is connected to the electrolytic cells and leads, on one side of the cover, into a chamber for collecting any liquid electrolyte carried by the gases.

Another object of the present invention is to provide a venting plug which is structurally simple and economically competitive with respect to those of the known type, both from the point of view of production costs and from the point of view of costs linked to the maintenance and assembly of electric batteries.

This aim and these and other objects that will become better apparent hereinafter are achieved by a venting plug, particularly for electrolytic cells of electric batteries and the like, comprising a main body adapted to be inserted in an opening between a volume in which at least one gas can be generated and an external environment, said main body having a first axially extended portion provided with a first radial gasket around said first portion and coaxial to the longitudinal axis of said first portion, characterized in that said first radial gasket has a transverse cross-section with a lip-like profile along at least one arc of the circumference of said first radial gasket and in that said venting plug comprises a second radial gasket around said first portion coaxially to said longitudinal axis in a position comprised axially between said first radial gasket and a second portion of said plug intended to interface with said external environment, said second radial gasket having a thickness which is substantially constant or in any case capable of preventing the venting of the gas toward said external environment.

The aim and objects of the invention are also achieved by a covering element for electric batteries with electrolytic cells, comprising at least one shaped body which has at least one through seat, characterized in that it comprises said venting plug inserted axially in said at least one seat so that said first radial gasket and said second radial gasket engage with a radial seal against the inner wall of said at least one seat.

Further characteristics and advantages of the present invention will become apparent from the description of preferred but not exclusive embodiments of the invention, illustrated by way of nonlimiting example in the accompanying drawings, wherein:

Figure 1 is a perspective view of a first embodiment of a venting plug, particularly for electrolytic cells of electric batteries and the like, according to the invention;

Figure 2 is a sectional view of the venting plug shown in Figure 1, taken along an axial plane;

Figure 3 is an enlarged-scale detail view of the first radial gasket of the venting plug shown in Figure 1 ;

Figure 4 is a perspective view of an electric battery provided with venting plugs according to Figure 1 ;

Figure 5 is an enlarged-scale detail view of the electric battery shown in Figure 4;

Figure 6 is a sectional view, taken along a plane which passes through the longitudinal axes of the venting plugs of the electric battery shown in Figure 5;

Figure 7 is a side view of a venting plug according to a second embodiment of the invention;

Figure 8 is an axial sectional view of the venting plug of Figure 7 inserted in the corresponding seat of a cover of an electric battery;

Figure 9 is an enlarged-scale detail view of the cross-section of Figure 8 during operation.

With reference to the figures, the venting plug, particularly for electrolytic cells of electric batteries and the like, generally designated by the reference numeral 1, comprises a main body 2, which has a first axially extended portion 2a, which preferably has a cylindrical shape with a circular base, and a second portion 2b, which is contiguous to the first portion 2a and is preferably disk-shaped with a larger radius than the first portion 2a, and is coaxial to said first portion 2a, so as to define an overall shape of the main body 2 which is substantially T-like, the first portion 2a thereof constitutes the stem and the second portion 2b constitutes the head. For this reason, the portions 2a and 2b are also referenced herein as stem and head respectively.

In greater detail, the first portion 2a is internally hollow and can have, at its end which lies opposite the end that is contiguous to the second portion 2b, a threaded shank 3, which is adapted to allow the venting plug 1 to be screwed into a seat 4 of a covering element 5 of a battery 6, which also is threaded.

Of course, the fixing in the seat 4 of the venting plug 1 can be achieved in a manner other than threaded coupling.

In order to allow the screwing of the venting plug 1 in the respective seat 4, on the face 7 of the second portion 2b of the main body 2, which is directed away from the first portion 2a, it is possible to provide grip means 8 which are adapted to engage suitable tools. For example, a cross-shaped notch can be provided which is adapted to be engaged by means of a Philips-head screwdriver.

Advantageously, the first portion 2a of the main body 2 is provided with a first radial gasket 9 and a second radial gasket 10, both of which are annular and surround externally the first portion 2a around its longitudinal axis 1 1.

In greater detail, the first radial gasket 9 and the second radial gasket 10 are annular and are arranged along the longitudinal axis 1 1 at a preset distance, with the second radial gasket 10 arranged proximate to the second portion 2b of the main body 2 and the first radial gasket 9 arranged proximate to the threaded shank 3.

In other words, the second radial gasket 10 is arranged between the second portion 2b and the first radial gasket 9. Depending on the particular use, the venting plug 1 according to the invention can comprise both gaskets 9 and 10 as described above or only the first radial gasket 9. In the second case, the first gasket 9 is arranged proximate to the second portion 2b of the main body 2, so as to ensure the outward gas-tightness of the battery.

According to the invention, the first radial gasket 9 has, along at least one arc of its circumference and optionally along its entire circumference, a transverse cross-section with a lip-like profile. The lip of the first radial gasket is deformable by the pressure of the gases generated by the electrolytic reactions inside the battery, thus performing the function of valve for venting the gases in the region affected by said profile. The transverse cross-section of the lip-like profile can have a thickness, in an axial direction, which is substantially constant along a first portion 9a which is radially internal and along which a lip 9b protrudes.

More specifically, the lip 9b is delimited upward and downward by two curved surfaces in which the centers of curvature are arranged on opposite sides with respect to the threaded shank 3 : the lip 9b is thus inclined and directed toward the head 2b of the plug 1.

Differently, the remaining circular arc of the first radial gasket 9 is instead adapted to ensure a seal for the gases generated inside the battery, in contrast with the arc having a lip-like profile. Therefore, the thickness of the first radial gasket 9 along the arc affected by a center angle which is explementary to the center angle of the arc with lip-like profile can be substantially constant along the radial direction or can in any case have a consistency capable of preventing the passage of gases at the pressures that cause venting through the deformation of the lip 9b : for example, the transverse cross-section of the gasket along the arc that is not affected by the lip-like profile may be substantially rectangular or have a D-shaped profile or in any case a shape adapted to offer greater resistance to the pressure of the gases than the cross-section having a lip-like profile 9a-9b of the complementary circular arc described above.

As regards the second radial gasket 10, it has the purpose of ensuring a seal for the gases generated inside the battery, preventing their venting toward the external environment, and it can have along its entire perimeter a thickness which is substantially constant along the radial direction or in any case capable of preventing the passage of gas at the pressures that cause venting by means of the deformation of the lip 9b: for example, the transverse cross-section of the gasket can be substantially rectangular or D- shaped or in any case of a shape adapted to offer greater resistance to the pressure of the gases than the cross-section having a lip-like profile 9a-9b of the first radial gasket 9.

The gaskets 9 and 10 can be made of a thermoplastic elastomer (TPE), for example Santoprene®, SEBS or Thermolast®, and can be formed advantageously directly on the stem 2a of the plug 1 , for example by means of a coextrusion or coinjection molding process together with the main body 2.

The correct positioning of the two radial gaskets 9 and 10 can be achieved by means of two respective annular grooves 12 and 13 which are provided directly on the first portion 2a of the main body 2 and in which the radially internal portions of the gaskets 9 and 10 are accommodated respectively. The annular grooves 12 and 13 are particularly useful also in the above cited process for forming by comolding, since they contribute to define the volume in which the injected thermoplastic elastomer accumulates.

As a result of the injection process, an axially extended connecting segment 14, provided monolithically with the first radial gasket 9 and the second radial gasket 10, can be comprised between the first radial gasket 9 and the second radial gasket 10.

Advantageously, in order to stabilize the position of the main body 2 in the respective seat 4 and have optimum centering between the venting plug 1 and said seat 4, between the first radial gasket 9 and the second radial gasket 10 at least one centering element 15 is provided, which protrudes radially from the first portion 2a with respect to the longitudinal axis 1 1 and along the entire circumference of the first portion 2a.

As shown in the figures, the centering element 15 can be divided into a plurality of segments.

Conveniently, in order to provide a correct seal of the radial gaskets 9 and 10 in the seat 4, the first radial gasket 9 and the second radial gasket 10 have an external radius which is comprised between the maximum radius of the centering element 15 and the external radius of the second portion 2b, the latter being larger than the maximum radius of the centering element 15.

According to the invention, the venting plug 1 can be used in covering elements 5 particularly for electric batteries with electrolytic cells, comprising at least one shaped body 21 which has a plurality of seats 4, one for each electrolytic cell 22 of the battery, and each arrangeable above the respective electrolytic cell 22.

In greater detail, it is possible to use a plurality of venting plugs 1 which are inserted axially in the respective seats 4, are arranged above the electrolytic cells 22 and are connected to them.

Advantageously, each centering element 15 of each venting plug 1 has such an extension as to interfere with the inner walls 4a of the respective seat 4, in order to ensure position stability and axial centering of the main body 2 in said seat 4. Moreover, both the first radial gasket 9 and the second radial gasket 10 of each venting plug 1 are in contact with said inner walls 4a of the seat 4 for the hermetic sealing of said electrolytic cell 22 against the escape of the fluids, such as acid gases or liquid acids, contained in the respective electrolytic cell 22.

Thanks to the shape mating between each venting plug 1 and the respective seat 4, at least one venting chamber 24 is defined for each seat 4 and is defined respectively in a lower region by the first radial gasket 9, in an upper region by the second radial gasket 10 and laterally by the inner walls 4a of the seat 4 and by the outer walls of the first portion 2a.

More precisely, as shown in Figure 6, in the first embodiment of the invention each venting chamber 24 can be connected to a manifold 25 which passes radially through the seats 4 and is arranged at an intermediate level between the first gasket 9 and the second gasket 10, in order to collect at least part of the pressurized gases that originate from the electrolytic cells 22 and have escaped into the venting chamber 24 as a consequence of the elastic yielding of the circular arc with lip-like profile 9a-9b due to the reaching of a preset value of the internal pressure of at least one of the electrolytic cells 22.

The manifold 25, of a known type, leads to at least one side of the covering element 5 in a chamber for collecting the liquid electrolyte that is optionally carried by the gases (Figure 5).

Conveniently, for each venting chamber 24 at least one passage 26 is provided which is defined between the inner walls 4a of the respective seat 4 and the outer walls of the first portion 2a and is limited in an upward region by the circular arc with lip-like profile 9a-9b of the first radial gasket 9.

In the illustrated embodiment, in order to provide the passage 26, the female thread of each seat 4 is interrupted in portions.

Operation of the venting plug 1, particularly for electrolytic cells of electric batteries and the like, and of the covering element 5, particularly for electric batteries with electrolytic cells, provided with one or more venting plugs 1 , is clear and evident from what has been described.

In particular, when the internal pressure of the individual electrolytic cell 22 rises above a preset threshold, the circular arc with lip-like profile of the respective first radial gasket 9 is deformed elastically until it allows the escape of the gas toward the manifold 25, as shown in Figure 6. Typically, this escape occurs with a spacing of at least 0.2-0.3 mm of the lip 9b of the radial gasket from the inner wall 4a of the seat 4.

As the internal pressure of the electrolytic cell 22 produced by the escape of the gas decreases, the first radial gasket 9 recovers its initial position and shape, ensuring the seal again.

The fact that the first radial gasket 9, at least along an arc of its circumference, is a lip-like gasket in which the lip 9b is inclined toward the head of the plug 1 allows to obtain a venting valve which not only can be operated even with low internal pressures (for example 70 mbar) but also has a good resistance to high external pressures (for example 700 mbar).

In applications in which a manifold 25 is provided, preference is given to the use of the second radial gasket 10 in combination with the first radial gasket 9, in the arrangement shown in the drawings, in order to ensure the correct hermetic outward closure of the individual electrolytic cell 22 but allow at the same time the venting of the gases in the manifold 25.

The circular arc of the first radial gasket 9 affected by the lip-like profile covers a center angle that is preferably smaller than 90° and even more preferably comprised between 10° and 20°. Preferably, the lip-like profile is limited only to an arc of the circumference of the first radial gasket 9 so that the first radial gasket 9 has, on most of its circumference, a stronger structure than the thin and flexible one constituted by the arc affected by the lip-like profile, thus allowing greater uniformity in the manufacture of the gaskets of the several plugs and lower variability of the opening pressures of the valve constituted by the first radial gasket 9 as well as a better centering of the plug in the corresponding seat.

With reference to a second embodiment of the invention, the venting plug 101 comprises a head 102 and a stem 103, the latter being threaded at one end in order to fix it in a respective opening 104 of a covering element 105 of an electric battery, the openings 104 being connected to a respective electrolytic cell. The thread of the stem 103 can have missing portions in order to allow the passage of gases. As in the first embodiment, the stem 103 of the plug 101 has a first radial annular gasket 9 which has, for at least an arc of its circumference, a lip 9b which is inclined toward the head 102 and can be deformed due to the pressure of the gases that form inside the electric battery as a consequence of the electrolytic reactions.

The circular arc that is optionally not affected by the lip-like profile maintains gas tightness together with inner wall of the opening 104 of the covering element 105 during use. In this case also, the circular arc of the first radial gasket 9 that is affected by the lip-like profile covers a center angle of preferably less than 90° and even more preferably comprised between 10° and 20°.

Also on the stem 103, between the head 102 and the first radial gasket 9, a second radial gasket 10 is also provided, which is also annular and has exclusively the function of a seal against the gases generated by the electrolytic reactions.

The gaskets 9 and 10, being identical in terms of shapes and materials to the ones of the first embodiment and being obtainable in the same manner, have the same characteristics described earlier with reference to the first embodiment, to which reference is made. The plug 101 can further comprise, between the gaskets 9 and 10, a centering element 1 15, which is coaxial to the stem 103 and is divided into multiple segments in order to allow the passage of the gases.

The venting plug 101 is adapted to be used in a covering element 105 for electric batteries which does not have a common manifold 25 for conveying outwardly the gases generated inside the battery as a consequence of the electrolytic reactions.

For this purpose, the venting plug 101 is internally hollow and has two cavities separated by a wall 109. A step 107 is present in a cavity 110 that is open toward the head 102, and a porous flamebreaker pad 106, also known as frit and of a per se known type, is fixed on the step 107 and is intended to prevent any sparks that occur outside the electric battery from propagating inside it, causing the explosion of the hydrogen that is usually present inside the battery and also so as to retain the droplets of liquid electrolyte that might be carried by the gases generated by the electrolytic reactions inside the battery. The flamebreaker pad 106 can be locked in position by a riveting 108. A perforated cover 1 1 1 can also be fixed onto the head 102 so as to protect the flamebreaker pad 106.

The stem 103 further has a transverse opening 112 between the first radial gasket 9 and the second radial gasket 10 in order to connect the cavity 1 10 to the venting chamber defined by the interspace between the stem 103, the inner wall of the opening 104 of the covering element 105 and the two radial gaskets 9 and 10.

Operation of the second embodiment is as follows.

During the initial charging of the battery or during its normal operation, the pressure of the gases generated due to the electrolytic reactions, if it exceeds a preset threshold, causes the elastic deformation of the lip 9b, such as to allow the escape of the gases toward the opening 1 12, as shown in Figure 9. Typically, this escape occurs with a spacing of at least 0.2-0.3 mm of the lip 9b from the inner wall of the opening 104 that surrounds the first radial gasket 9. The gases are thus conveyed toward the internal cavity 1 10, from which they vent outward, passing through the flamebreaker pad 106.

As the internal pressure of the electrolytic cell decreases due to the escape of the gas, the first radial gasket 9 recovers its initial position and shape, ensuring again tightness to fluids, such as low-pressure acid gases or liquid acids contained in the respective electrolytic cell.

In practice it has been found that the venting plug, particularly for electrolytic cells of electric batteries and the like, as well as the covering element, particularly for electric batteries with electrolytic cells, provided with one or more venting plugs according to the present invention, fully achieve the intended aim and objects, since they allow to make safe an electric accumulator with electrolytic cells with respect to the escape of the gas contained in the electrolytic cells, with a small number of components which are geometrically simple. The venting plug is easy to provide and assemble and is perfectly compatible with the seats for valve plugs of covers for batteries that are already available on the market.

Another advantage of the venting plug according to the present invention resides in that thanks to the particular geometry the first radial gasket, in order to ensure hermetic closure of the respective electrolytic cell up to a preset maximum value of internal pressure, if necessary, i.e., when this value is exceeded, acts as a safety valve for gas venting, which can occur through a common manifold provided on the cover or through the plug itself.

A further advantage of the venting plug and of the covering element provided with one or more venting plugs according to the present invention resides in that it is economically competitive with respect to the background art, both from the point of view of production costs and from the point of view of costs related to the maintenance and assembly of the electric batteries.

The venting plug, particularly for electrolytic cells of electric batteries and the like, as well as the covering element, particularly for electric batteries with electrolytic cells, provided with one or more venting plugs, thus conceived, are susceptible of numerous modifications and variations, all of which are within the scope of the appended claims.

For example, instead of the threaded shank of the stem adapted to fix the venting plug in the respective seat of the covering element, it is possible to provide detachable interlocking means or any other detachable fixing means known to the person skilled in the art.

All the details may further be replaced with other technically equivalent elements. In practice, the materials used, so long as they are compatible with the specific use, as well as the contingent shapes and dimensions, may be any according to requirements and to the state of the art.

Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

1. A venting plug (1, 101), particularly for electrolytic cells of electric batteries and the like, comprising a main body (2) adapted to be inserted in an opening (4, 104) between a volume (22), in which at least one gas can be generated, and an external environment, said main body (2) having a first axially extended portion (2a, 103) provided with a first radial gasket (9) around said first portion (2a, 103) which is coaxial to the longitudinal axis (1 1) of said first portion (2a, 103), characterized in that said first radial gasket (9) has a transverse cross-section with a lip-like profile along at least one arc of the circumference of said first radial gasket (9) and in that said venting plug comprises a second radial gasket (10) around said first portion (2a, 103) coaxially to said longitudinal axis (11) in a position comprised axially between said first radial gasket (9) and a second portion (2b, 102) of said plug (1, 101) intended to interface with said external environment, said second radial gasket (10) having a thickness which is substantially constant or in any case capable of preventing the venting of the gas toward said external environment.

2. The venting plug (1 , 101) according to claim 1, wherein said liplike profile extends along only an arc of the circumference of said first radial gasket (9) so as to allow the venting of the gas toward the external environment only along said circular arc.

3. The venting plug (1, 101) according to claim 1 or 2, wherein said first radial gasket (9) comprises, along said arc, an inclined lip (9b) which can be deformed due to gas pressures exceeding a certain threshold, said first radial gasket (9) having, along the optional circular arc that is not affected by said lip (9b), a thickness which is substantially constant or in any case capable of preventing the venting of gases at said pressures.

4. The venting plug (1 , 101) according to one or more of the preceding claims, characterized in that said circular arc with lip-like profile of said first radial gasket (9) is affected by a center angle of less than 90° and preferably comprised between 10° and 20°.

5. The venting plug (1) according to one or more of the preceding claims, characterized in that it comprises at least one centering element (15) protruding radially from said first portion (2a) with respect to said longitudinal axis (1 1).

6. The venting plug (1) according to claim 5, characterized in that said first radial gasket (9) and said second radial gasket (10) have an external radius that is greater than the external radius of said at least one centering element (15).

7. The venting plug (1) according to one or more of the preceding claims, characterized in that said first radial gasket (9) and said second radial gasket (10) are provided by means of a co-molding process together with said main body (2).

8. The venting plug (1) according to one or more of the preceding claims, characterized in that at least one between said first radial gasket (9) and said second radial gasket (10) is made of thermoplastic elastomer.

9. The venting plug (101) according to one or more of the preceding claims, wherein said main body has an internal cavity (1 10) which is open toward said external environment and a transverse opening (1 12) which leads from said internal cavity (1 10) between said first radial gasket (9) and said second radial gasket (10), so as to define a passage for the venting of the gas through said second portion (102) of the plug (101).

10. The venting plug (101) according to the preceding claim, wherein said second portion (102) of the plug (101) comprises a flamebreaker pad (106).

1 1. A covering element (5, 105) for electric batteries with electrolytic cells, comprising at least one contoured body (21) which has at least one through seat (4, 104), characterized in that it comprises the venting plug (1, 101) according to one or more of the preceding claims, inserted axially in said at least one seat (4, 104) so that said first radial gasket (9) and said second radial gasket (10) engage with a hermetic radial seal against the inner wall (4a) of said at least one seat (4, 104).

12. The covering element (5) according to claim 11, characterized in that said at least one centering element (15, 1 15) of said venting plug (1) is in contact with the inner walls (4a) of said seat (4, 104) for the axial centering of said main body (2) in said seat (4, 104).

13. The covering element (5) according to one or more of claims 1 1 and 12, characterized in that said covering element (5) comprises internally a gas manifold (25), which is directed transversely to said at least one seat (4) and is connected to said at least one seat (4) and exits at one end of the covering element (5), said first radial gasket (9) and said second radial gasket (10) being arranged on opposite sides with respect to said manifold (25), so that said first radial gasket (9) is directed upstream of said manifold (25) with respect to the gas venting direction.