First stage pressure regulator with threshold actuation

Abstract

A first reducing stage of two-stage regulators includes a first chamber that receives a high pressure breathable gas, a second chamber for the breathable gas at an intermediate pressure, and a pressure reducing valve that connects the first and the second chamber. The valve includes a valve seat with an opening for communication between the first and the second chamber, and a plug cooperating with the valve seat and movable between closed and open positions and vice versa. The plug, dynamically connected to a sensor exposed to the outer pressure, includes a transmission mechanism of the mechanical stress due to the outer pressure on the plug, which has a member that stops and starts the kinematic transmission chain according to the mechanical stress due to the outer pressure. Such member includes mechanical stress sensors that stop the kinematic transmission chain when the mechanical stress is below a predetermined threshold value and that restart the kinematic transmission chain when the mechanical stress is equal or above the threshold value.

Claims

1. A first stage pressure reducer for two-stage breathing groups, comprising: a first chamber adapted to receive a high pressure breathable gas, the first chamber being connected to or configured to be connected via an inlet to a source of the high pressure breathable gas; a second chamber adapted to receive the breathable gas at an intermediate pressure, the second chamber having an outlet for the breathable gas at the intermediate pressure and being connected or configured to be connected to a user of an intermediate pressure breathable gas; and a pressure reducing valve connecting the first chamber to the second chamber and comprising a valve seat with a communication opening between the first and the second chamber and a shutter cooperating with the valve seat and movable from a closed position of a passage opening to an open position of the passage opening and vice versa, wherein the shutter is dynamically connected to a sensing member of a pressure of an external environment outside the first and the chamber, the sensing member comprising a transmission mechanism configured to transmit a mechanical load applied on the sensing member by the pressure of the external environment outside the shutter, and wherein the transmission mechanism is provided with a suspension/restoration member of a transmission kinematic chain acting based on the mechanical load applied thereon by the pressure of the external environment, the suspension/restoration member being provided with sensors of the mechanical load suspending the transmission kinematic chain when the mechanical load is below a predetermined threshold value and restoring the transmission kinematic chain when the mechanical load is equal to or exceeds the predetermined threshold value.

2. The first stage pressure reducer according to claim 1, wherein the transmission mechanism has two elements movable relatively between each other between the sensing member of the mechanical load applied by the external environment pressure and the shutter, the two elements being connected by a joint coupling actuated by a sensor of the mechanical load of the pressure of the external environment and dynamically connecting the two elements together when the mechanical loads exceeds the predetermined threshold value and being idle when the mechanical load is below the predetermined threshold value.

3. The first stage pressure reducer according to claim 2, wherein the two elements are sliders that move between each other between stop positions, one of the stop positions providing maximum mutual spacing and another one of the stop positions providing mutual abutment to stops, wherein in the mutual abutment position the two elements rigidly move together along an additional stroke in a direction parallel to a direction of reciprocal approach, elastic means of a calibrated force being provided and interposed between the two elements and opposing a movement in the direction of reciprocal approach of the two elements from a position of maximum distance to the mutual abutment position of the stops, and wherein the two elements reach the mutual abutment of a corresponding stop only upon exceeding an opposing force of the elastic means.

4. The first stage pressure reducer according to claim 1, wherein the sensing member of the pressure of the external environment comprises two movable wall elements which are spaced apart from each other with connection means arranged parallel to a sliding direction and are sealingly slidable in a housing chamber, one of the two movable wall elements being an interface with the external environment and another one of the two movable wall elements being an interface between the housing chamber and the second chamber and sealing, respectively, towards the external environment and towards the second chamber an interposition chamber that is isolated from the external environment and from the second chamber, the interposition chamber comprising a segment of the housing chamber and having a variable position and an extension in the sliding direction of the two movable wall elements that is essentially corresponding to a distance between the two movable wall elements, and wherein the connection means between the two movable wall elements introduce at least one degree of freedom between the two movable wall elements with reference to a relative position thereof, the connection means having, a spatially limited free travel state, in which a force of the external environment is not transferred to at least one of the movable wall elements, a state of mutual rigid coupling, in which at least part of the force exerted by the external environment on an external one of the movable wall elements is transferred to another one of the movable wall elements interfacing with the intermediate pressure chamber only when the external environment applies a force exceeding a predetermined level of force, and at least one or a combination of elastic pre-loaded members acting on the external one of the movable wall elements and applying an action in contrast with the force that the external environment applies on the external one of the movable wall elements.

5. The first stage pressure reducer according to claim 4, wherein the at least one or the combination of elastic pre-loaded members comprises a mechanical member.

6. The first stage pressure reducer according to claim 4, further comprising an elastic pre-loading element associated with one of the movable wall elements interfacing with the intermediate pressure chamber, the elastic preloading element being positioned inside the interposition chamber.

7. The first stage pressure reducer according to claim 4, further comprising a stationary abutment, located inside the housing chamber and interposed between the two movable wall elements, the stationary abutment being configured as an adjustable ring nut and being provided with a surface operating as a stop for the elastic preloading element.

8. The first stage pressure reducer according to claim 4, wherein an axis of the passage opening of the valve seat is coincident or parallel to an axis of a chamber housing the sensing member, wherein the shutter comprises a sealing element mounted on a piston sliding in a guide seat, and wherein the valve seat, or a sliding direction of the shutter, are parallel or coincident with the axis of the passage opening of the valve seat and/or with the axis of the chamber housing the two movable walls elements.

9. The first stage pressure reducer according to claim 8, wherein the first chamber, the second chamber, the housing chamber, the valve seat and/or the passage opening in the valve seat, the shutter, the guide seat of the piston, the movable wall elements, a connecting rod between the sensing member and piston shutter have rotational symmetry and are coaxial with each other.

10. The first stage pressure reducer according to claim 4, further comprising a preloading elastic element associated to the shutter.

11. The first stage pressure reducer according to claim 4, wherein, in the interposition chamber, an air pressure is set to a predetermined value and is substantially invariable with respect to conditions of pressure of the external environment and of the first and the second chamber.

12. The first stage pressure reducer according to claim 4, wherein one or more elements forming the housing chamber and/or the sensing member of the pressure of the external environment pressure are made of a material or a combination of materials having thermal conductivity lower than a thermal conductivity of metallic materials, and wherein the material or the combination of materials have mechanical properties that do not compromise a correct functioning of the first stage pressure reducer.

13. The first stage pressure reducer according to claim 4, wherein the sensing member of the pressure of the external environment pressure and the housing chamber are of a cylinder/plunger type, the sensing member comprising at least one rigid element, wherein the transmission mechanism connects one of the movable wall elements interfacing the second chamber with the shutter, and wherein the two movable wall elements have variable spacing elements between a minimum and a maximum distance position, abutments being provided in the minimum distance position that cooperate between guide elements so as to generate a rigid translation coupling of the interposition chamber in a direction of the force exerted by the external environment.

14. The first stage pressure reducer according to claim 13, wherein each of the movable walls is configured as a piston housed in the housing chamber, which operates as a cylinder, both pistons being sealingly guided along walls of the cylinders via peripheral seals.

15. The first stage pressure reducer according to claim 14, wherein both of the movable wall elements are movable inside the cylinder parallel to one another and in a direction of an axis of the cylinder, the axis of the cylinder being at least parallel or coaxial to a direction of movement of the shutter between the open and closed positions of the passage opening of the valve seat, the transmission members comprising a connecting rod of the sensing member to the shutter.

16. The first stage pressure reducer according to claim 4, wherein a flexible membrane is disposed between the one of the movable wall elements forming the interface with the external environment and the external environment and mounted sealingly to an end of a cylindrical chamber housing the one of the movable wall elements.

17. The first stage pressure reducer according to claim 16, wherein the one of the movable wall elements forming the interface to the external environment is free of sliding sealing gaskets cooperating with the wall housing the one of the movable wall elements and is free to slide guided along the wall substantially without friction interference.

18. The first stage pressure reducer according to claim 4, wherein one of the movable wall elements forming the interface to the second chamber and the second chamber comprises a flexible compensation membrane sealingly mounted at an end of a cylindrical chamber housing the one of the movable wall elements forming the interface to the second chamber, the flexible compensation membrane acting on the transmission mechanism of the mechanical load applied by the external environment external on the shutter.

19. The first stage pressure reducer according to claim 18, wherein the one of the movable wall element forming the interface to the second chamber is free of sliding sealing gaskets cooperating with the wall housing the one of the movable wall element forming the interface to the second chamber and is free to slide guided along the wall substantially without friction interference.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Further advantages and features of the device according to the present invention will become evident from the following description of an embodiment thereof, carried out for purposes of non-limiting example, with reference to the tables of the attached drawings, in which:

[0049] FIG. 1 shows a cross-sectional view according to a plane passing through the axis of symmetry parallel to the direction of movement of the shutter of the pressure reducing valve and which view relates to an embodiment of the known art which uses two pistons as movable wall elements;

[0050] FIG. 2 shows a view similar to the previous one of first embodiment of the invention which defines an improvement of the first embodiment according to the known art illustrated in FIG. 1;

[0051] FIG. 3 shows a cross-sectional view according to a plane passing through the axis of symmetry parallel to the direction of movement of the shutter of the pressure reducing valve and which view relates to a different embodiment of the prior art which uses a pair of flexible membranes to define the interposition chamber between the intermediate chamber and the external environment;

[0052] FIG. 4 shows a perspective view similar to the previous ones of a second embodiment of the invention which defines the improvement of the embodiment according to the known art illustrated in FIG. 3;

[0053] FIGS. 5 and 6 comprise two diagrams relating to the intermediate pressure trend according to the known art and according to the invention for two different applications.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0054] In FIG. 1, is designates with the reference number 1 the body of said first stage, which has a high-pressure chamber 101, equipped with a plurality of high-pressure outlets, for example for connecting pressure gauges or other utilities, and is connected in a way not shown in the figure and known per se to a high pressure breathing gas supply cylinder. The seat 301 of the reduction valve is located in the chamber, which opens into the intermediate pressure chamber 201, and whose flow is regulated by the obturator 311. Also in this embodiment the obturator is coupled to the rod 321, which ends at the opposite end, inside the chamber 201, with a plate 331. The intermediate pressure chamber is provided with a plurality of outlets towards the intermediate pressure gas ducts.

[0055] At the top of the intermediate pressure chamber 201, a threaded opening 401 is formed in the body 1 of the first stage, in which the block 2 is screwed tightly thanks to the gasket 411. Inside the block 2 a cylindrical chamber 102 is formed for housing a pressure sensor member of the external environment

[0056] The said chamber 102 is provided with two ground cylindrical seats 112 and 122, respectively facing the intermediate pressure chamber 201 and the external environment and separated by a threaded section in which a stop ring 302 is screwed for a coil spring 312 for elastic preload of the sensor member of the pressure of the external environment.

[0057] Two movable wall elements 4021 and 4022 are inserted into both seats 112, 122 respectively as a piston. The two movable wall elements illustrated in FIG. 1 are identical to each other particularly with respect to the surface of the two faces perpendicular to the direction of translation or to the central axis of the same.

[0058] This configuration is not intended to be limiting but is only a choice between possible variants in which said movable walls 4021 and 4022 can have different diameters: once the threshold value has been exceeded, if the diameters are the same, the intermediate pressure increase will be equal to the increase in ambient pressure, if the diameter of the upper mobile wall 4022 is smaller than the diameter of the mobile wall 4021 this increase, even if linear, will be less than the increase in ambient pressure, while if the diameter of the upper mobile wall 4022 is greater of the diameter of the mobile wall 4021 this increase, albeit linear, will be greater than the increase in ambient pressure.

[0059] The two movable wall elements 4021 and 4022, i.e. the two pistons, can be displaced together and are coupled together presenting on the opposite faces, respectively, the movable wall element 4022 which constitutes the separation wall towards the external environment a coupling stem 482, and the second movable wall element 4021 which interfaces with the intermediate pressure chamber 201 a coupling seat of said stem in the form of a bushing 452 axially coinciding with said stem 482, in particular coaxial to the same.

[0060] A preferred embodiment may further provide that the stem has a base segment 492 with which it is connected to the corresponding movable wall element 4022. This base segment has a diameter greater than a coaxial, terminal segment which is intended to engage in a hole 462 of the coupling seat 452 and to be locked therein. The axial length of the hole 462 is commensurate with the axial length of the said terminal segment of the stem 482.

[0061] According to a further possible feature, and as also illustrated, the coupling seat 452 is in the form of a cylindrical bushing and has an external diameter corresponding to the external diameter of the said base 492 of the stem 482. The coaxial hole 462 has a diameter corresponding to that of the terminal segment of the stem 482.

[0062] The base 492 of the stem 482 is connected with a conically tapered portion 442 to the terminal segment, while the seat 452 has an inlet portion 472 which tapers conically from the insertion end towards the bottom of the hole 462, starting from external diameter of the bush which forms said coupling seat 452 towards the internal diameter of the same and with an opening angle corresponding to that of the tapered portion 442 of the stem 482.

[0063] The coupling seat 452 in the form of a bushing is associated with the wall element 4021, or with the piston interfacing with the intermediate pressure chamber 201 and constitutes a central support element of the elastic element 312, for example of a coil spring.

[0064] The rigid, integral connection of the two movable wall elements 4021 and 4022, or of the two pistons, can take place thanks to removable and/or separable mechanical coupling means which allows the two pistons i.e., the two movable wall elements, to be separated from each other.

[0065] In relation to the rigid connection of the two movable wall elements it is possible to provide other alternative solutions. According to a variant embodiment, the two piston-like movable wall elements 4021 and 4022 are rigidly coupled to each other by means of a pin screwed with the two ends respectively in a threaded cup formed coaxially to the same in the faces facing each other of the other of the two movable wall elements 4021 and 4022.

[0066] The pistons 4021 and 4022, of substantially cylindrical shape, have a toroidal groove 412 formed on the lateral surface, in which a sealing element 422 is housed. On one face of the movable wall 4021 interfacing with the intermediate pressure chamber 201 an annular groove 432 is formed which surrounds the coupling seat 452. The end of a preload spring 312 is inserted into said annular groove, the opposite end of which abuts against the stop ring nut 302 which is screwed to the block 2 inside the chamber 102 in an intermediate position between the rectified cylindrical portions 112 and 122.

[0067] Due to this embodiment, an intermediate insulation chamber is generated in the cylindrical chamber 102 of block 2 and between the intermediate pressure chamber and the external environment, which remains sealed both towards the intermediate pressure chamber and towards the external environment. This isolation chamber translates correspondingly to the translation together of the two pistons 4021 and 4022 rigidly connected to each other. The translation of said pistons is delimited in both directions by annular, radial internal shoulders which define the translation limit switches, one of which in the outward direction is constituted by the shoulder 130 cooperating with the piston 4021 interfacing with the intermediate pressure chamber 201, while the other in the direction towards said intermediate pressure chamber consists of a stop of the shutter in the high pressure chamber and/or of the head side of the cylindrical chamber 102 cooperating with the plate 331.

[0068] It is clear that this ring nut 302 and said coil spring 312 always remain inside the isolation chamber and therefore separated from the external environment and from that of the intermediate pressure chamber. Different fluids can be used as fluid, but ambient air at atmospheric pressure is preferred, which is generated automatically in the assembly phase in the factory.

[0069] However, this does not mean that different types of fluids or mixtures thereof and different pressure conditions can be provided in the said isolation chamber and that the said isolation chamber is possibly accessible through an inlet which is provided with closing means. removable type seal.

[0070] It is possible that the intermediate insulation chamber between the two movable wall elements is filled with argon or an argon-containing gas mixture since this inert gas has excellent thermal insulation qualities, improving safety against the formation of ice on the wall of the “upper piston” facing the environment.

[0071] The coil spring and the area in which it is housed remain free from the dangers of ice formation and also from the dangers of infiltration of impurities, dirt or other that could mechanically limit or completely prevent the operation of the spring.

[0072] According to a further feature, which is entirely optional and could also be omitted, at the end of the block 2 in which the seat 122 is formed, a flexible membrane 212 is arranged by means of a threaded ring nut 202, which adheres to the face of the movable wall element 4022 facing the external environment and interfacing with it. The pressure of the external environment acts on the mobile wall element 4022 through said membrane 212 which deforms under the action of said pressure and the membrane has the sole and sole purpose of isolating the chamber 102 only from the point of view of fluid circulation which can generate effects of wear or degradation of the sealing gaskets of the movable wall 4022 against the wall of the cylindrical chamber 122 in which it is housed both from the chemical point of view and due to the transport of material granules.

[0073] The embodiment illustrated in FIG. 1 therefore represents a solution that isolates the compensation chamber 102 from the external environment, and the membrane 212, leaning directly on the movable wall element, actually transmits the pressure variations of the external environment to the piston 4022, while avoiding direct contact of the fluid of the external environment with the piston 4022 and the seals, protecting them. Advantageously, especially from the manufacturing point of view, with regard to the illustrated embodiments, the movable wall element 4021 interfacing with the intermediate pressure chamber can be identical for both embodiments, making it only necessary to provide the other movable wall element to realize the embodiment of FIG. 1.1.

[0074] The piston inserted in the seat facing the intermediate pressure chamber is elastically preloaded thanks to the spring 312, as was the case for the membrane used in the state of the art. The rigid connection between the two pistons 4021 and 4022 guarantees the action of the two movable walls in fact like that of a monolithic entity, which transfers the pressure variations detected in the external environment directly to the rod 321 which operates on the shutter of the reducing valve.

[0075] A variant embodiment of the embodiment according to FIG. 1 can provide that the movable wall element, i.e. the piston 4022 which constitutes the interface with respect to the external environment and which is in contact with the membrane 212, slides freely and does not seal in the cylindrical section 122 and that the seal towards the external environment of the intermediate insulation chamber delimited by the two mobile wall elements 4022 is entrusted to the side facing the external environment only by the membrane 212. This reduces sliding friction and in any case the upper membrane is the least stressed since it only senses the pressure difference between the surface and the environment.

[0076] FIG. 2 shows an embodiment according to the present invention. In this embodiment, a possible realization of the inventive step is contextualized which is translated into the modification of the known art of FIG. 1 with the aim of obtaining the benefits and overcoming the technical problem, already described in detail, of delivering gas with a constant pressure up to at a preset depth and subsequently, i.e. as the depth further increases, the pressure in the intermediate chamber increases according to a trend directly proportional to the depth itself.

[0077] In this figure the numerical references of FIG. 1 are reused for the parts present in both figures and performing the same function, possibly unless particular conformations that do not affect the general economy of the system presented.

[0078] FIG. 2 therefore shows a first delivery stage operating by means of a valve comprising shutter 311 and seat 301, where the transfer of the force exerted by the external environment to the shutter involves elements of sealed movable wall 4021 and 4022 through the plate 331 which is in cooperation with rod 321.

[0079] As in the previous figure, the shutter 311 is in the closed position when it abuts the valve seat 301; in this condition, the high pressure gas cannot flow towards the intermediate pressure chamber 201 and therefore towards the outlets to which the ducts are connected to the second stage and therefore towards the user.

[0080] The opening of the valve, understood as the condition other than closing and in which more or less breathable gas can pass towards the chamber 201, is guided by the force resulting from the forces resulting from the high pressure in the chamber 101, to the pre-charge of the shutter 341, to the pressure of the intermediate chamber 201 and to the force that the movable wall element 4021 transfers by contact with the plate 331 and the rod 321 to the shutter itself.

[0081] While in known devices this last force increases linearly with increasing depth, in the present invention a series of expedients are introduced to adapt the transfer function and make it such as to overcome the technical problems already described.

[0082] In this embodiment, which must be considered as an example and not as limiting as other embodiments can lend themselves to putting the same inventive concept into practice, the two movable wall elements 4022 and 4021, or the two pistons, have on the mutually opposite faces, respectively a coupling stem 482, and a coupling seat of said stem in the form of a bushing 452 axially coinciding with said stem 482, in particular coaxial thereto.

[0083] The two movable wall elements 4021 and 4022 are provided with a degree of freedom in the reciprocal movement, provided along the axis of the chamber 102 in turn parallel to the axis of the shutter 311, such that the distance between the two varies according to the operating conditions between a position of minimum stroke and a position of maximum stroke.

[0084] Furthermore, the ring nut 302, already acting as a stationary stop for the preloading element 312, is modified to act as a further base for a second coil spring 313 positioned coaxially to the spring 312 and exerting a force contrary to the force of the external environment.

[0085] In rest conditions, i.e. non-diving, the two elements are kept at a predefined distance as a consequence of the action that the two preloading elements 312 and 313 perform in opposite directions, the ring nut being a stationary reference interspersed with both.

[0086] In particular, the spring 313 counteracts the approach of the mobile element 4022 in the direction of the element 4021 with an elastic force proportional to the excursion of the element itself with respect to the initial position.

[0087] As the external pressure increases, the greater force resulting from the pressure on the head of the element 4022 will counteract the spring load by reducing the distance between 4021 and 4022.

[0088] However, as long as a minimum value of this distance is not reached, the effect of the environment is substantially transferred to the ring nut 302 rather than to the shutter 311. The resulting behavior is of constant intermediate pressure of the breathable gas in the chamber 201, as shown in FIGS. 5 and 6, in particular in the plateau marked with the references 521 and 621. In reality, the gradual approach of the mobile element 4022 towards the mobile element 4021 causes a reduction in the internal volume and consequently a small pressure increase, which consequently leads to a small deviation of the intermediate pressure from a perfectly constant value. However, this variation is to all intents and purposes to be considered negligible.

[0089] When said minimum stroke position is reached, the two elements 4021 and 4022 are in mutual contact, the stem 482 is in the position of maximum penetration inside the seat 452 and, through contact between the respective opposite surfaces 442 and 472, the force exerted on the wall of the element 4022 by the environment is at least partially transmitted to the shutter in favor of its translation away from said closed position.

[0090] Under such conditions, the pressure regulation of the breathable gas is therefore comparable to that resulting from a first stage of the prior art: as the depth increases, the balance of the forces on the shutter changes, which therefore offers pressure in the intermediate chamber proportional to this depth in accordance with the increasing trend 523 and 623 of the respective FIGS. 5 and 6.

[0091] FIG. 3 shows a configuration of the first dispensing stage of the membrane type, from which the difference with respect to the known art of FIG. 1 can be observed, whereby the elements that seal off the interposition chamber are two membranes rather than rigid elements.

[0092] In particular, this figure shows in section a first reducing stage of a two-stage dispensing unit according to the prior art in which an isolation chamber 70 is delimited towards the external environment by a first membrane 11 which is retained at held along its peripheral edge by the perimeter shell walls of said chamber 70. Towards the intermediate pressure chamber 10, the said isolation chamber 70 is separated from the intermediate pressure chamber by a second membrane 40, which is also held tightly along a perimeter band from the shell walls of the isolation chamber. A plate 20, to which a pin 21 is integrated, is connected to another plate 22, loaded by the spring 30 calibrated with the ring nut 31; the plate 22 insists on the membrane 40, which faces the intermediate pressure chamber and transfers the motion of the plate 22 to a plate 52 connected to the stem 51 of the dispensing valve 50. The membrane 11 isolates the chamber interposed between the plates 20 and 22 from the environment. In this way it is actually possible to isolate the chamber which houses the preload spring of the membrane 30 and the ring nut 31 for adjusting the preloading from the external environment, avoiding the drawbacks of the previous solutions of the prior art and at the same time allowing the variations to be detected. of pressure by means of the plates 20, 22 which communicate them to the membrane 40.

[0093] FIG. 4 shows a second embodiment of the invention which constitutes a possible improvement of the known art illustrated in FIG. 3, that is of a first regulator stage which uses a membrane to transfer the effect of the external pressure on the pressure reduction. The numerical references of the figure have been reused when consistent with the previous descriptions and it is possible to note how this second embodiment has a membrane 4023, whose operation is borrowed from the membrane 40 of the previous figure, which delimits the interposition chamber and the intermediate pressure 201 transferring the pressure received by the mobile element 4021 ‘towards the plate 331 and consequently to the shutter 311.

[0094] Unlike the first embodiment, the mobile element 4021 ‘does not work tightly with the housing chamber 102, a role entrusted to the aforementioned membrane 4023, but similarly to the first embodiment this embodiment also implements at least part of the inventive step by introducing suspension/reactivation members of the transmission kinematic chain as a function of the mechanical stress exerted on it by the pressure of the external environment, which suspend the transmission kinematic chain when the mechanical stress is below a predetermined threshold value and they restore the kinematic transmission chain when said mechanical stress is equal to or exceeds said threshold value.

[0095] The behavior already described in relation to the shape of FIG. 2 is then replicated, with the two movable wall elements 4022 ‘and 4021’ which have on their opposite faces, coupling seats/stems and a degree of freedom in movement reciprocal such that the distance between the two varies according to the operating conditions between a position of minimum stroke and a position of maximum stroke. The achievement of the minimum stroke condition coincides with the reactivation condition of the transmission kinematic chain between the force exerted by the external environment and the shutter 311 of the pressure reduction valve.

[0096] La The ring nut 302 already acting as a stationary stop for the preloading element 312, is modified to act as a further base for a second coil spring 313 positioned coaxially to the spring 312, and exerting on the movable wall element 4022′ a force contrary to the force of the external environment.

[0097] The ring nut 302 has a special stop 3021, annular in shape, operating as a stop and possibly a coupling seat for the base of the spring 313.

[0098] The device according to the present invention therefore solves the problems highlighted with respect to the state of the art with a constructively simple, operationally effective and reliable solution from the point of view of safety and wear resistance.

[0099] The embodiment of the present invention refers to a preferred configuration which, however, must not be considered limiting with respect to the combinations of features indicated in the various embodiments in the introductory part of the present description. For example, the choice of a rotationally symmetrical configuration of the device is a preferred choice but should not be construed in a limiting form. Also, the use of coil springs as elastic means of preloading and the particular solution of the adjustable stops by screwing to modify the preloading force is a preferred solution but should not be considered limiting.