Patent Description:
Prior art patent document published <CIT> discloses a pressure regulator device for compressed gas according to the preamble of claim <NUM>, comprising a pressure-sensing assembly, or regulator, defining an internal volume filled with an auxiliary gas and closed by a plug, said pressure sensing assembly being elastically deformable and located in the gas passage downstream of a seat and actuating a shutter cooperating with a seat for regulating the gas pressure. The pressure-sensing assembly comprises a series of bellows formed by a series of annular members or diaphragms that are alternately secured at radially inner and outer regions (in double weld fashion) to define an accordion-like arrangement. The internal volume is presumably sealed by the plug but how the gas pressure inside that internal volume is set is not detailed. The use of such a pressure-sensing assembly forming a sealed internal volume filled with gas is interesting in that the resulting regulation of the gas pressure is independent of the ambient or atmospheric pressure. This is particularly interesting for applications where the pressure regulator is located inside the gas cylinder where there is no access to the ambient. The adjustment and control of the stiffness of the pressure-sensing assembly or pressure sensing assembly is however challenging.

<CIT> discloses valve assembly comprising a fluid flow passage to permit the flow of a fluid through the valve assembly; a valve seat; and an actuator assembly. The actuator assembly comprises a valve member moveable relative to the valve seat between a first position in which the valve member is at least partially engaged with the valve seat to at least partially block the fluid flow passage, and a second position in which the valve member is remote from the valve seat; an actuator body in a fixed position relative to the valve seat; and a metal bellows that is attached to the valve member and to the actuator body and is disposed within the fluid flow passage. The valve member of the actuator assembly is moveable relative to the actuator body and extends around the actuator body such that the actuator body is disposed within the valve member.

The invention has for technical problem to overcome at least one of the drawbacks of the above-mentioned prior art. More specifically, the invention has for technical problem to provide a pressure regulator for compressed gas that is reliable and can be easily adjusted and/or calibrated.

The invention is directed to a pressure regulator for compressed gas, comprising: a body with a gas inlet, a gas outlet and a gas passage interconnecting said gas inlet with said gas outlet; a shut-off device comprising: a seat located in the gas passage; a shutter configured for cooperating the seat; a pressure sensing assembly defining an internal volume filled with an auxiliary gas and closed by a plug, said pressure sensing assembly being elastically deformable and located in the gas passage downstream of the seat, said pressure sensing assembly being configured for actuating the shutter relative to the seat depending on a gas pressure downstream of the seat; wherein the pressure regulator further comprises a port fluidly connected, via the plug, to the internal volume of the pressure sensing assembly, and configured for fluidly connecting an external source of the auxiliary gas to said internal volume for adjusting a pressure of the auxiliary gas in said internal volume. The port is a connecting port.

According to a preferred embodiment, the port is external to the pressure regulator.

According to a preferred embodiment, the port shows a main axis that is transversal to a longitudinal axis of the pressure regulator.

Advantageously, the port shows a main axis that is radial relative to a longitudinal axis of the pressure regulator.

Advantageously, the port opens outs at an external surface of the body, said external surface being preferably cylindrical.

The capacity of port to be fluidly connect an external source of the auxiliary gas to said internal volume of the pressure sensing assembly can be achieved by a contact surface on the body, through which the port opens out, said contact surface can, for example, be planar and circular, or a portion of cylinder, allowing a gas tight contact with the external source of the auxiliary gas.

According to a preferred embodiment, the plug comprises a threaded portion engaging with a fixed portion of the pressure sensing assembly, and a conical needle portion engaging with an auxiliary seat formed in said fixed portion.

According to a preferred embodiment, the plug is entirely located in the fluid connection between the port and the internal volume of the pressure sensing assembly.

According to a preferred embodiment, the plug comprises an internal passage for the auxiliary gas between the threaded portion and the conical needle portion.

According to a preferred embodiment, the plug comprises, at an end opposed to the internal volume of the pressure sensing assembly, an engagement surface for engaging with a tool by insertion of said tool into the port.

According to a preferred embodiment, the engagement surface of the plug shows an insertion direction for the tool that is aligned with the port.

According to a preferred embodiment, the engagement surface of the plug is configured such that the engagement with the tool is in rotation so that rotation of the tool rotates the plug.

According to a preferred embodiment, the plug comprises a conical pin axially press fitted into an auxiliary seat formed in a fixed portion of the pressure sensing assembly, said conical pin having an outer smooth surface free of thread.

According to a preferred embodiment, the plug further comprises a weld plug welded to the fixed portion of the pressure sensing assembly and fluidly located between the conical pin and the port.

According to a preferred embodiment, the pressure sensing assembly comprises a fixed portion, a movable portion and at least one flexible wall attached to said fixed portion and said movable portion in a gas-tight fashion, the internal volume of the pressure sensing assembly being delimited by said at least one flexible wall, said fixed portion and said movable portion.

According to a preferred embodiment, the shutter is mechanically linked, preferably fixed, to the movable portion of the pressure sensing assembly.

According to a preferred embodiment, the at least one flexible wall is circular, bellow-shaped and metallic.

According to a preferred embodiment, the fixed portion of the pressure sensing assembly is rigidly attached to, or is part of the body.

According to a preferred embodiment, the shutter comprises a poppet on an upstream side of the seat and a stem extending from the poppet through the seat until the pressure sensing assembly.

According to a preferred embodiment, the stem of the shutter is attached to the movable portion of the pressure sensing assembly.

According to a preferred embodiment, the port is located on cylindrical outer surface of the body, said cylindrical outer surface being able to engage in a gas-tight fashion with an adjustment tool.

According to a preferred embodiment, the body comprises at the gas inlet and/or at the gas outlet, respectively, a connector preferably with a face seal and a rotatable nut.

According to a preferred embodiment, the body comprises at the gas outlet a male-threaded portion configured for engaging with a neck of a gas cylinder.

The invention can also be directed to a pressure sensing assembly, for a pressure regulator for compressed gas, defining an internal volume filled with an auxiliary gas and closed by a plug, said pressure sensing assembly being elastically deformable and configured for actuating a shutter relative to a seat depending on a gas pressure downstream of the seat; wherein the pressure sensing assembly further comprises a port fluidly connected, via the plug, to the internal volume, wherein the plug comprises a conical pin axially press fitted into an auxiliary seat formed in a fixed portion of the pressure sensing assembly, said conical pin having an outer smooth surface free of thread.

According to a preferred embodiment, the port is a connecting port.

According to a preferred embodiment, the conical pin has a maximal outer diameter of less than <NUM>.

According to a preferred embodiment, the port is configured for fluidly connecting an external source of the auxiliary gas to said internal volume for adjusting a pressure of the auxiliary gas in said internal volume.

The invention is particularly interesting in that it provides a reliable and easy to adjust and control pressure regulator.

<FIG> is a sectional view of an in-line pressure regulator according to a first embodiment of the invention.

The pressure regulator <NUM> comprises a body <NUM> which is for instance constituted of a first body part <NUM>, a second body part <NUM> attached at one end of the first body part <NUM>, a third body part <NUM> attached at an opposed end of the first body part <NUM>, and a fourth body part <NUM> attached to the third body part <NUM>, at an end thereof opposed to the first body part <NUM>. It is however understood that the body <NUM> can be constituted of less or more than four body parts as in this specific example. The first, second, third and fourth body parts <NUM><NUM>, <NUM> and <NUM> are attached to each other by welding being understood that other attaching means like screwing or clamping can be considered. On the body <NUM> are formed a gas inlet <NUM>, a gas outlet <NUM> and a gas passage <NUM> fluidly interconnecting the gas inlet <NUM> with the gas outlet <NUM>.

For instance, the second body part <NUM> comprises a tubular port forming the gas inlet <NUM> and to which a connector <NUM> is attached. The connector is for instance of the face seal type with a freely rotatably nut, commonly commercially available. The connector <NUM> comprises a tubular port which is instance attached by welding to the tubular port of the second body portion <NUM>. A first portion <NUM> of the gas passage <NUM> extends longitudinally through the tubular port of the second body part <NUM>. The first body part <NUM> comprises a bore-shaped cavity housing a shut-off device <NUM> and forming a second portion <NUM> and a third portion <NUM> of the gas passage <NUM>.

The third body part <NUM> is arranged next the first body part <NUM>, opposite to the second body part <NUM> and the gas inlet <NUM>. A fourth portion <NUM> of the gas passage <NUM>, directly downstream of the third portion <NUM> thereof, is formed in that third body part <NUM>. The fourth body part <NUM> is attached to the third body part <NUM> and comprises a tubular port forming the gas outlet <NUM> and to which a connector <NUM> is attached. The connector is for instance of the face seal type with a freely rotatably nut, commonly commercially available. The connector <NUM> comprises a tubular port which is instance attached by welding to the tubular port of the fourth body portion <NUM>.

The shut-off device <NUM> is located in the gas passage <NUM>. The shut-off device <NUM> comprises a seat <NUM>, a shutter <NUM> cooperating with the seat <NUM>, and a pressure sensing assembly, or regulator, <NUM> defining an internal volume <NUM> filled with an auxiliary gas and closed by a plug <NUM>, said pressure sensing assembly <NUM> being elastically deformable and located in the gas passage <NUM> downstream of the seat <NUM>, said pressure sensing assembly <NUM> being configured for actuating the shutter <NUM> relative to the seat <NUM> depending on a gas pressure downstream of the seat.

The shutter <NUM> comprises for instance a poppet <NUM> located on an upstream side of the seat <NUM> and configured for cooperating with that side of the seat <NUM>. In the present case, a gasket <NUM>, e.g. an O-ring, is fitted around the poppet <NUM> and held against said poppet <NUM> by a sleeve <NUM> engaging with the poppet <NUM>, e.g. by screwing. The gasket <NUM> is configured for contacting the seat <NUM> in a gas tight-fashion. It is understood that the gasket is optional, depending on the material of the seat and of the poppet. Also, the gasket can be provided on the seat. The shutter <NUM> further comprises a stem <NUM> extending longitudinally from the poppet <NUM> to the pressure sensing assembly <NUM> through the seat <NUM>. For instance, the stem <NUM> shows a free end with a male-thread engaging with a corresponding female thread on the pressure sensing assembly <NUM>. It is understood that another fixation means between the stem and the pressure sensing assembly can be considered.

As this apparent, the seat <NUM> is formed on a disk-shaped part that is formed in the body <NUM>, for instance the first body part <NUM>. It is however understood that other constructions can be considered. As a matter of example, the seat can be attached to the body <NUM> or first body part <NUM>.

The pressure sensing assembly <NUM> comprises a fixed portion <NUM>, a movable portion <NUM> and a flexible wall <NUM> attached in a gas-tight fashion to both fixed portion <NUM> and movable portion <NUM>. The flexible wall <NUM> is preferably metallic and attached to both the fixed portion <NUM> and the movable portion <NUM> by welding. The flexible wall <NUM> is generally circular and shows a bellows- or accordion-shaped profile. The internal volume <NUM> is delimited by the flexible wall <NUM>, the fixed portion <NUM> and the movable portion <NUM> of the pressure sensing assembly <NUM>.

The fixed portion <NUM> of the pressure sensing assembly <NUM> is for instance formed on the third body part <NUM> being however understood that the fixed portion of the pressure sensing assembly can be distinct form the body of the pressure regulator <NUM>, or at least be distinct from the body part that comprises the gas outlet <NUM>.

The pressure sensing assembly <NUM> is elastically deformable in the longitudinal direction in that the movable portion <NUM> can move in that direction relative to the fixed portion <NUM> against the elastic deformation force of the flexible wall <NUM> in addition to the compression force of the auxiliary gas contained in the internal volume <NUM>. It follows that the stiffness in compression of the pressure sensing assembly is directly dependent on the auxiliary gas pressure in said internal volume <NUM>.

In operation, the compressed gas flows through the gas inlet <NUM>, the first portion <NUM> and the second portion <NUM> of the gas passage <NUM> until the shut-off device <NUM>. It then flows between the reduced cross-section between the shutter <NUM> and the seat <NUM> and is thereby laminated and reduced in pressure when reaching the regulation chamber formed by the third portion <NUM> of the gas passage <NUM> and containing the pressure sensing assembly <NUM>. The reduced pressure on the pressure sensing assembly <NUM> urges the movable portion <NUM> towards the fixed portion <NUM>, against the combined resilient force of the flexible wall and the pressure of the auxiliary gas contained in the internal volume <NUM>. Upon such a compression movement of the pressure sensing assembly <NUM>, the movable portion <NUM> moves the shutter <NUM> upwardly closer to the seat <NUM> and thereby reduces the cross-section therebetween, leading to a more intense gas lamination and reduction in pressure. This mechanism provides a controlled pressure regulation of the compressed gas contained in the gas cylinder. The principle of such a pressure regulation is as such well-known from the skilled person and does not need to be further detailed.

The internal volume <NUM> of the pressure sensing assembly <NUM>, filled with the auxiliary gas, is closed by the plug <NUM> that is in fluid connection with a port <NUM> configured for fluidly connecting an external source <NUM> of the auxiliary gas to the internal volume <NUM> for adjusting a pressure of the auxiliary gas in the internal volume.

The plug <NUM> and the port <NUM> are configured for allowing, via the external source <NUM> of the auxiliary gas and a tool <NUM> for operating the plug <NUM>, to adjust and control the auxiliary gas pressure in the internal volume <NUM>. Upon opening of the fluid connection <NUM> by operating the plug <NUM> via engagement of the tool <NUM> with the plug <NUM>, the external source <NUM> of auxiliary gas can adjust the pressure of said gas and once a desired pressure is achieved, the plug <NUM> can be operated for closing the fluid connection <NUM> and thereby closing the internal volume <NUM>.

A protective cap <NUM> can be placed on the port <NUM> so as to close it with regard to dust. It can be mode of plastic or any other material, preferably softer than the material of the body.

For instance, the plug <NUM> is entirely located in the fluid connection <NUM> between the internal volume <NUM> of the pressure sensing assembly <NUM> and the port <NUM>. This means that during pressure adjustment by means of the external source <NUM> of auxiliary gas and of the tool <NUM>, the latter <NUM> will be in contact with the auxiliary gas during adjustment and needs therefore to be in gas-tight connection relative to the auxiliary gas passage <NUM> of the external source <NUM> in fluid connection with the port <NUM>. Such a rotating gas-tight connection between the tool <NUM> and a body of the external source <NUM> can be achieved using one or more gaskets or seals mounted around a cylindrical surface portion of the tool and allowing a combined translational and rotation movement of said tool while providing gas-tight sealing.

The plug <NUM> comprises an outer threaded portion <NUM> engaging with a corresponding inner thread formed in the fluid connection <NUM>, and a needle portion <NUM> that is advantageously conical and that is configured to engage in a gas-tight fashion with an auxiliary seat formed in the fluid connection <NUM> between the internal volume <NUM> and the port <NUM>. The plug <NUM> further comprises at an end opposed to the needle portion <NUM>, an engagement surface <NUM> for engaging with a tool <NUM> by insertion of said tool into the port <NUM>. The plug <NUM> can further comprise an internal passage <NUM> for the auxiliary gas between the threaded portion <NUM> and the conical needle portion <NUM>.

Alternatively, the plug <NUM> can be only partly located in the fluid connection <NUM> between the internal volume <NUM> of the pressure sensing assembly <NUM> and the port <NUM>. More specifically, the engagement surface <NUM> can be fluidly located outside of the fluid connection <NUM>, whereby the plug <NUM> can be in a gas-tight sealed connection with the fixed portion <NUM> or third body part <NUM> forming said fluid connection <NUM>. In such a configuration, the tool <NUM> does not need to be in gas-tight connection with the body of the external source <NUM> of auxiliary gas.

The above-described pressure regulator with the shutter comprising a poppet on the high-pressure side of the seat, i. e, on the upstream side thereof, can be normally closed, i.e. closed when the gas pressure at the gas outlet is at the atmospheric pressure. In that case, the pressure regulator can function as a sub-atmospheric pressure regulator that opens when the pressure at the outlet is below the atmospheric pressure, i.e. some level of vacuum. In such a situation, the gas pressure in the chamber formed by the third portion <NUM> of the gas passage <NUM> is reduced from the atmospheric pressure, thereby reducing the resulting compressive force acting on the pressure sensing assembly <NUM>. The latter will then expand by moving the movable portion <NUM>. <NUM> away form the first portion <NUM> until the auxiliary gas pressure in the internal volume, in combination with the resilient force of the flexible wall, equilibrates with the reduced pressure in said chamber.

Alternatively, the above-described pressure regulator can be normally opened, i.e. opened in the absence of pressure at the inlet in order to allow gas to flow until a pressure threshold in the chamber <NUM> is reached above which the shut-off device closes. In such a configuration, a manual shut-off valve can be foreseen upstream and/or downstream of the shut-off device <NUM>.

Contrary to the above configuration where the shutter comprises a poppet on the high-pressure side of the seat, the shutter can be exclusively located on the low-pressure or downstream side of the seat. In such a case, the pressure sensing assembly needs to be inverted so that the gas pressure in the chamber <NUM> compresses the pressure sensing assembly <NUM> towards the seat and moves the shutter towards the seat so as to reduce the cross-section therebetween.

A filter, e.g. of the fritted type, can be placed in the first portion <NUM> of gas passage, i.e. upstream of the shut-off device <NUM>. Similarly, a filter, also possibly of the fritted type, can be placed in the fifth portion <NUM> of gas passage, i.e. downstream of the shut-off device <NUM>.

The above-described pressure regulator is particularly advantageous in that its pressure sensing assembly can be easily controlled and adjusted, not only in static conditions, i.e. in the absence of gas flow but also in dynamic conditions, i.e. when a flow of gas is outputted.

<FIG> is a sectional view of a pressure regulator according to a second embodiment of the invention. The reference numbers of the first embodiment in <FIG> are used for designating the same or corresponding elements of the second embodiment in <FIG>, these numbers being however incremented by <NUM>. It is referred to the description of these elements in connection with the first embodiment. Specific reference number(s) comprised between <NUM> and <NUM> is/are used for designating specific element(s).

The pressure regulator <NUM> in <FIG> differs from the in-line pressure regulator in <FIG> essentially in that it is located in inside a gas cylinder <NUM>. To that end, the construction of the body <NUM> is different in that the second body part with the tubular port at the gas inlet <NUM> is not provided. The body <NUM> comprises a second body part <NUM> corresponding to the third body part <NUM> of the first embodiment, and a third body part <NUM> adjacent the second body part <NUM> and corresponding to the fourth body part <NUM> of the first embodiment. The body <NUM> further comprises a fourth body part <NUM> adjacent the third body part <NUM>, with a male-threaded portion <NUM>. <NUM> being provided on the fourth body part <NUM>. The male-threaded portion <NUM>. <NUM> engages with an inner thread of the neck <NUM> of the gas cylinder <NUM>. It is understood that the third and fourth body parts <NUM> and <NUM> can be unitary and also can be unitary with the second body part <NUM>.

Apart from the change of position of the male-threaded portion on the body <NUM> of the pressure regulator <NUM>, the construction and functions thereof are identical to those of the pressure regulator of the first embodiment.

Similarly to the first embodiment, it can comprise a filter at the gas inlet <NUM> and/or at the gas outlet <NUM>. In the present embodiment, a filter is provided in the fifth portion <NUM> of the gas passage <NUM>.

<FIG> is a sectional view of a pressure regulator according to a third embodiment of the invention. The reference numbers of the second embodiment in <FIG> are used for designating the same or corresponding elements of the third embodiment in <FIG>, these numbers being however incremented by <NUM>. It is referred to the description of these elements in connection with the second embodiment and also, by reference, with the first embodiment.

The pressure regulator in <FIG> differs from the pressure regulator in <FIG> essentially in that it is a two-stage pressure regulator. The pressure regulator <NUM> comprises a first stage formed essentially by the first shut-off device <NUM> comprising the first pressure sensing assembly <NUM> and the first port <NUM>, and a second stage formed essentially by the second shut-off device <NUM> comprising the second pressure sensing assembly <NUM> and the second port <NUM>.

As this is apparent, the second shut-off device <NUM>, including the second pressure sensing assembly <NUM> and the second port <NUM>, is essentially identical to the shut-off device <NUM> of the pressure regulator <NUM> in <FIG>.

The first shut-off device <NUM>, including the first pressure sensing assembly <NUM> and the first port <NUM>, is similar but not identical to the second shut-off device <NUM> and the shut-off device <NUM> of the pressure regulator <NUM> in <FIG>. The functioning principle is however identical. The differences are essentially due to the difference in pressure values to be regulated.

The shutter <NUM> is different in that it does not comprise a gasket and a sleeve for holding said gasket as in second shut-off device <NUM>, but rather solely comprises a poppet <NUM>. <NUM> and a stem <NUM>. The seat <NUM> is formed by a washed made of non-metallic material that is press-fitted in a cavity of the body and gas-tight sealed therewith by a gasket, for instance an O-ring. The poppet <NUM> made of a harder material like a metallic material can cooperate in a gas-tight fashion with a seat <NUM> made of softer material like a non-metallic material. The first shut-off device <NUM> thereby provides a first-stage pressure reduction whereas the second shut-off device <NUM>, arranged directly downstream of the first shut-off device <NUM>, provides a second-stage pressure reduction.

The pressure-regulator <NUM> of the third embodiment can be set-up as a sub-atmospheric pressure regulator or not, similarly to the first and second embodiments.

A filter, for instance of the fritted type, is placed in the gas passage at the gas inlet <NUM>. A further filter, also preferably of the fritted type, is placed in the gas passage between the two stages. A still further filter, also preferably of the fritted type, is placed in the gas passage downstream of the second stage of the pressure regulator and upstream of the gas outlet <NUM>.

<FIG> is a detail sectional view of the port portion of an in-line pressure regulator, according to a fourth embodiment of the invention.

The reference numbers of the first embodiment in <FIG> are used for designating the same or corresponding elements of the fourth embodiment in <FIG>, these numbers being however incremented by <NUM>.

The plug <NUM>, instead of comprising an outer threaded portion engaging with a corresponding inner thread formed in the fluid connection, is a conical pin <NUM> that is axially inserted or press-fitted into an auxiliary seat formed in the fluid connection. The conical pin <NUM> shows an outer lateral surface that is smooth along its all extent. It is intended to be inserted by a tool integrated in an external source of auxiliary gas, like the one <NUM> in <FIG>. The advantage of this conical pin <NUM> is that it can be more easily put in place than the threaded plug <NUM> which is likely to grip by forming metallurgical bonds at the thread, in particular in the absence of mounting grease. This is particularly true when the parts in play are made of stainless steel. The use of grease is indeed to be avoided in many applications, in particular when the pressure regulator is to be in contact with aggressive gases.

The plug <NUM> can further comprise a weld plug <NUM> which is inserted in the fluid connection between the internal volume and the port <NUM>, fluidly between the conical pin <NUM> and the port <NUM>. That weld plug is made of metal, preferably of the same metal as the fixed portion of the pressure sensing assembly. It can then be welded to the fixed portion, preferably without any filler material, the weld plug playing basically the role of filler material during welding. The welding can be made by TIG method (Tungsten Inert Gas) or the like.

After adjustment of the pressure of the auxiliary gas in the internal volume, using an external source of auxiliary gas, the conical pin <NUM> can be inserted, using a tool integrated with the external source of auxiliary gas, thereby providing a gas tight barrier. The conical pin <NUM> can be provided with grease which is as such not incompatible with the auxiliary gas being for example Helium. Thereafter, the weld plug <NUM> is put in place and welded. It forms then a second and secure gas tight barrier that additionally prevents any contact of the ambient gas, being for example aggressive semi-conductor gases, with the grease that can be provided on the conical pin <NUM>.

Claim 1:
Pressure regulator (<NUM>; <NUM>; <NUM>) for compressed gas, comprising:
a body (<NUM>; <NUM>; <NUM>) with a gas inlet (<NUM>; <NUM>; <NUM>), a gas outlet (<NUM>; <NUM>; <NUM>) and a gas passage (<NUM>; <NUM>; <NUM>) interconnecting said gas inlet (<NUM>; <NUM>; <NUM>) with said gas outlet (<NUM>; <NUM>; <NUM>);
a shut-off device (<NUM>; <NUM>; <NUM>, <NUM>) comprising:
a seat (<NUM>; <NUM>; <NUM>, <NUM>) located in the gas passage (<NUM>; <NUM>; <NUM>);
a shutter (<NUM>; <NUM>; <NUM>, <NUM>) configured for cooperating the seat (<NUM>; <NUM>; <NUM>, <NUM>);
a pressure sensing assembly (<NUM>; <NUM>; <NUM>, <NUM>) defining an internal volume (<NUM>; <NUM>; <NUM>.<NUM>, <NUM>.<NUM>) filled with an auxiliary gas and closed by a plug (<NUM>; <NUM>; <NUM>, <NUM>; <NUM>, <NUM>), said pressure sensing assembly being elastically deformable and located in the gas passage downstream of the seat (<NUM>; <NUM>; <NUM>, <NUM>), said pressure sensing assembly being configured for actuating the shutter (<NUM>; <NUM>; <NUM>, <NUM>) relative to the seat (<NUM>; <NUM>; <NUM>, <NUM>) depending on a gas pressure downstream of the seat;
characterized in that the pressure regulator (<NUM>; <NUM>; <NUM>) further comprises:
a port (<NUM>; <NUM>; <NUM>, <NUM>; <NUM>) fluidly connected, via the plug (<NUM>; <NUM>; <NUM>, <NUM>; <NUM>, <NUM>), to the internal volume (<NUM>; <NUM>; <NUM>.<NUM>, <NUM>.<NUM>) of the pressure sensing assembly (<NUM>; <NUM>; <NUM>, <NUM>), and configured for fluidly connecting an external source (<NUM>) of the auxiliary gas to said internal volume (<NUM>; <NUM>; <NUM>.<NUM>, <NUM>.<NUM>) for adjusting a pressure of the auxiliary gas in said internal volume.