IT201800003815A1 - IMPROVED ANTIFLUX DEVICE WITH REDUCED PRESSURE ZONE - Google Patents

Description

Description of the industrial invention entitled:

“IMPROVED ANTI-BACKFLOW DEVICE WITH REDUCED PRESSURE ZONE”.

DESCRIPTION

FIELD OF TECHNIQUE

The present invention relates to an improved backflow preventer with a reduced pressure zone.

More particularly, the present invention relates to an improved non-controllable non-controllable backflow preventer, check valve or backflow preventer with reduced pressure zone, typically but not limited to usable for drinking water distribution water systems.

STATE OF THE PRE-EXISTING TECHNIQUE

Anti-backflow devices or anti-pollution check valves, also known as backflow preventers with reduced pressure zone or with different pressure zones, are widely known in the field of hydraulic and thermotechnical systems.

Backflow preventers with reduced pressure zones or with different pressure zones are water protection devices designed to prevent the return of polluted water into the distribution water network. This return of fluid, typically water, can occur as a result of pressure variations and fluctuations in the distribution network, such as to cause an inversion of fluid flow. The backflow preventer is typically installed in water distribution systems between the public water network and the user water network and defines a separation and safety area that prevents contact between the fluids contained in the two networks. In public water networks or drinking water supply systems connected to civil or industrial users of plumbing and thermo-hydraulic systems, temporary fluid pressure shortages may occur. When the pressure of the fluid in the public water network or in the hydraulic supply system is lower than the fluid pressure of the user hydraulic system, the fluid or water of the latter tends to flow back into the public water network.

The fluid or water distributed in the plumbing or thermo-hydraulic systems of the users can come into contact with contaminating, pathogenic or polluting elements that can be harmful and contaminate the water network itself in case of flow reversal, such as in the case of a pipe hose of a civil user connected to a tap and placed in a container of dirty water which, in the event of a lack of fluid pressure, can suck contaminated fluid into the public distribution network.

Even in industrial hydraulic and thermo-hydraulic systems, the fluid can come into contact with oils, fuels or harmful, corrosive and / or radioactive substances which, in case of backflow of the fluid into the water mains, would cause considerable damage.

In the water networks of users connected to the public drinking water distribution network, the use of these anti-backflow devices is particularly important, which may also be imposed by the regulations in force in the various countries.

The traditional backflow preventers with reduced pressure area, of the type object of the present invention, can generally be controllable or not controllable and are defined by an external body advantageously divided into two sections, provided with an inlet and an outlet opening, at the inside which are typically housed two monostable check valves arranged in series and defined by two shutters slidably arranged upstream and downstream of said openings, in such a way as to allow the flow to pass in one direction and block it in the opposite direction. In the area between the two valves there is typically an intermediate discharge or vent opening suitable for discharging the return fluid from the downstream shutter into the atmosphere and directed towards the distribution network, said discharge opening being typically open or closed. by a mobile diaphragm or membrane system.

During normal operation, with initial reference to Figure 5, when the pressure of the fluid p1 is such as to overcome the resisting force of the elastic elements of the check valves, the shutters of the same valves open allowing the fluid to flow in a single direction from the inlet opening, connected to the water mains, to the outlet opening, connected to the user. The pressure of the moving flow acts simultaneously on the diaphragm or mobile membrane system while keeping the discharge opening closed.

In traditional backflow preventers or backflow preventers there is generally a diaphragm seal or mobile membrane arranged along the flow direction of the fluid and traditionally defined by a shaped disc made of elastomeric material having a circular shape with a central hole. The shaped cross section of said movable disc or membrane has one or more elbows which extend from the central hole towards the outer edge, typically defining a circular ring developed integrally over the entire circumference.

The operation of the backflow preventer or pressure zone backflow preventer can generally be summarized in three conditions:

- Operating state in standard or normal conditions, in which the upstream and downstream shutters are both open and the discharge opening is closed by the diaphragm or mobile membrane. During normal or standard operating conditions, the part of the diaphragm near the central hole opens, deforming elastically under the pressure of the fluid in the direction of the flow, conveying the liquid linearly into the central chamber of the valve body and pushing the upstream shutter. At the same time, the deformed portion of the diaphragm, in a condition of maximum opening, hermetically obstructs the external toroidal-shaped discharge chamber obtained externally and coaxially to the central sliding chamber, thus preventing the exit of fluid towards the drain. As the pressure of the fluid entering the intermediate area increases, the shutter of the valve downstream of the backflow preventer also opens under the pressure of the fluid, allowing the fluid to pass through the outlet opening.

- Operating state with steady or zero flow, in which the upstream and downstream shutters are kept in the closed position by means of the elastic spring elements. In this condition, no liquid flow occurs in either direction and the diaphragm or mobile membrane does not close the passage of fluid to the external toroidal chamber connected to the outlet opening.

- Operating state in the presence of backflow from the downstream outlet opening, in which the shutters are held in the closed position by the elastic spring elements and by the pressure p2 of the liquid that tries to flow in the opposite direction as shown in figure 4. However, the upstream shutter intervenes only in the case of incomplete or partial closure of the downstream shutter, a typical condition that can occur frequently in the use of these types of devices and generally due to solid material such as debris or dirt coming from the 'user. The upstream obturator, when closing, carries the diaphragm portion near the central hole against the valve body, by means of the obturator plate which remains compressed on the same diaphragm or mobile membrane, in such a way as to block the return flow from the downstream shutter, partially closed, towards the inlet opening. The diaphragm or mobile membrane placed in the closed position together with the upstream shutter thus frees the passage of the return flow in the external chamber towards the fluid discharge opening located in the intermediate area between the two shutters.

An example of these known backflow preventers, of the type backflow preventers with reduced pressure zone, are described in the Chinese utility model CN 201787144 U which refers to a device with a double check valve comprising an external valve body and a internal part, where the valve body has a seat; while the inner part of the valve is movably disposed in the valve body; the valve seat is equipped with a water inlet and outlet and an outlet at the ends. The movable inner part of the valve comprises a first valve part disposed at the water inlet and a second valve part disposed at the outlet. The body of said check valve is equipped with a discharge port; when the first internal part of the valve opens the water inlet, the drain port is closed, and when the first internal part of the valve closes the water inlet, the drain port is opened. The second internal part of the valve opens or closes the water outlet by moving away from the valve seat. In the utility model mentioned, the valve body has two internal parts internally, the second check valve prevents backflow of fluid entering through the valve outlet and is drained directly from the drain port instead of flowing back through the inlet in such a way as to prevent pollution.

A further example of these known types of backflow preventers, such as backflow preventers with a reduced pressure zone, are described in international application WO 2016/105583 which refers to a backflow preventer comprising a body with an inlet and an outlet and adapted to be installed to be mounted in fluid connection on a liquid distribution system. An upstream retaining plate assembly is positioned in the body downstream of the inlet and includes an upstream control plate that supports a downstream diaphragm. A second upstream retaining assembly is positioned downstream of the diaphragm and is integrally formed with an upstream stem and disposed in an opening formed in a central hub formed in the body for movement between a normally open flow position and a closed position. which prevents backflow of liquid through the inlet. A downstream plate assembly is positioned in the downstream housing from the upstream control disk assembly. A vent discharges the reflux liquid into the atmosphere upstream of the downstream retaining plate assembly.

Said known anti-backflow devices or backflow preventers with a reduced pressure zone, or with differentiated pressure zones, however, have drawbacks and operating limits.

In the aforementioned anti-backflow devices present in the state of the art, the shutter assemblies defining the check valves are generally and advantageously formed, for simplicity and cost-effectiveness of construction, of a disc-shaped plate drilled in the central part and integrally stabilized on the end of the a cylindrical stem or stem typically by means of a plastic deformation of the metal of said stem, also known as swaging or edge-wrapping of the metal of the end of the stem.

With preliminary reference to Figures 4 and 5, the assembly process, which generally also includes a flat gasket of circular shape with holes and arranged on the abutment face of the plate, has a typical drawback of these devices, since although it is such as to guarantee the mechanical stabilization of the plate on the stem, however, does not guarantee the tightness of fluid between said stem and said plate and to the possibility of infiltrations of fluid F between them, as illustrated in figure 4. Under conditions of reflux of the contaminated fluid, therefore , a small quantity of fluid can seep between the mechanical coupling surfaces identified between the hole of the plate and the free end of the stem of said shutter assembly and seep between the coupling surfaces of the stem and of the central hole of the hub obtained in the body, with respect to which the shutter assembly is slidably arranged. In fact, to ensure the free sliding of the stem of said shutter assembly, the coupling between said stem and said central hole of the hub must inevitably have a free space or mechanical play through which the contaminated fluid can seep upstream of the device and contaminate the water supply.

The mechanical play between the rod and the central hole of the hub, in addition to favoring the leakage between the coupling surfaces, determines a further drawback and operating limit typical of these known anti-backflow devices, and tends to increase with the use and exercise wear.

In fact, under normal operating conditions, the shutter unit constitutes a fluid-dynamic obstacle to the passage of the flow. This obstacle, as shown in figure 5, generates turbulences T in the laminar and stationary flow of the fluid such as to generate oscillations and angular vibrations of the shutter assembly in a generally radial direction to the motion of the fluid, as shown in figure 5 (line between two points ), thus amplifying the turbulence of fluid motion and causing an increase in pressure drops, valve efficiency as well as causing cavitation phenomena and premature deterioration of the anti-reflux device components. Another drawback of these known anti-backflow devices is due to the fact that during the closing phase of the upstream valve, the disc of the shutter unit intercepts the diaphragm or mobile membrane with an edge contact therefore with a limited surface and a non-uniform and constant pressure. , a condition that can cause an incomplete and non-centered crushing of the portion close to the central hole of the diaphragm itself, against the valve body. This condition can be further amplified by the oscillations and transverse vibrations of the obturator in such a way as to contribute to significantly offset the obturator plate from the central hole of the diaphragm or diaphragm, thus resulting in a closure that is not perfectly fluid-tight as well as wear. premature of the elastomeric material of the diaphragm and of the disc-shaped gasket of the plate.

A further drawback is also due to the fact that the turbulent motions of the fluid can also be such as to deform the diaphragm or the mobile membrane in a non-homogeneous way, contributing to its wear or to the premature outage of the device as well as to a decay of the fluid dynamic efficiency of the backwater device. AIMS OF THE INVENTION

The object of the present invention is to overcome and obviate, at least in part, the drawbacks and operating limits mentioned above.

More particularly, the object of the present invention is to provide an improved anti-backflow device with a reduced pressure zone, suitable for guaranteeing an increased safety of the networks and a better sealing of the polluting fluids.

A further purpose of the present invention is to provide the user with an improved backflow device with a reduced pressure area with better efficiency and greater uniformity of the flow, free from hydrodynamic turbulence and cavitation phenomena.

Still a further object of the present invention is to provide an improved backflow preventer with a reduced pressure zone capable of guaranteeing a high level of resistance and reliability over time, such as to be easily and economically achievable.

These and other objects are achieved by the improved backflow preventer with reduced pressure zone object of the present invention in accordance with the independent claim.

The constructive and functional characteristics of the improved backflow preventer with reduced pressure zone can be better understood from the following detailed description, in which reference is made to the attached drawings which represent some preferred and non-limiting embodiments, in which:

BRIEF DESCRIPTION OF THE FIGURES

Figures 1A and 1B are schematic representations respectively of a longitudinal section view and a side view from the inlet opening side, of a preferred embodiment of the improved backflow preventer with reduced pressure zone object of the present invention;

Figures 2A and 2B are schematic representations respectively of a longitudinal section view and a side view from the inlet opening side, of a simplified embodiment of the improved backflow preventer with reduced pressure zone object of the present invention;

Figures 3A, 3B, 3C and 3D are schematic representations of longitudinal section views of as many embodiments of fluidic seals between the upstream shutter and the body of the improved backflow preventer with reduced pressure area object of the present invention;

Figure 4 is a schematic and partial representation of a longitudinal sectional view of an anti-backflow device with a reduced pressure zone according to the prior art in the condition of back pressure and backflow of fluid from the downstream shutter (not shown) and of leakage of contaminated fluid through the upstream shutter in the closed position; figure 5 is a schematic and partial representation of a longitudinal section view of a backflow preventer with reduced pressure zone according to the prior art in the normal or standard operating condition with the onset of hydrodynamic turbulence due to the oscillations and transverse vibrations of the upstream shutter (not shown).

DETAILED DESCRIPTION OF THE INVENTION

With reference to Figures 1A to 3D, some possible embodiments of the improved backflow preventer 10 with reduced pressure zone object of the present invention are described below.

With particular reference to the preferred embodiment of Figure 1, an anti-backflow device 10 with a reduced pressure zone, or with different pressure zones, for installation on water systems is shown and comprises:

- an internally hollow body 11 and generally made of metallic material for hydraulic applications such as brass, generally divided for ease of assembly into a separable upstream portion 11 'and a downstream portion 11' ', said body 11 being provided with a' inlet opening 12 for fluid from the water mains, an outlet opening 13 for the fluid towards the user and a discharge opening 14 for the fluid returning from the user;

- at least one shutter 20, 20 'or shutter assembly, traditionally a shutter 20, 20' upstream and a second shutter 40 downstream, said shutter 20, 20 'a non-return valve, and comprising a stem 21 generally made of metallic material , an elastic element 22 of the spiral spring type and a plate 24, 24 'made of metal sheet and stabilized to said stem 21 at one of its free ends with known stabilizing means, such as for example plastic deformation or interference couplings or by means of movable fasteners such as screws and the like,

Said shutter 20, 20 'is slidably housed in said body 11 and is adapted to interrupt the upstream fluid connection between said inlet opening 12 and said outlet opening 13 of body 11.

Said anti-backflow device 10 also comprises:

- a deformable movable diaphragm or membrane 30, made of elastomeric material and having a functionally shaped discoidal shape with a central opening 31, an external diametrical portion 32 and a radial elbow section 33, said diaphragm or movable membrane 30 being arranged in the direction of flow in the body 11 and adapted to interrupt, in a closed position, the fluid connection between the outlet opening 13 and the inlet opening 12; and, in an open position, to interrupt the fluid connection between said inlet opening 12 and the discharge opening 14.

Again with reference to the aforementioned figures, the anti-reflux device 10 has the innovative characteristics represented by the fact that on said diaphragm or mobile membrane 30 there is integrally formed on it a tooth 35 or projection defining a profile with a lobed section with complete annular development, having an increased thickness with respect to the section thickness of the diaphragm or mobile membrane 30, said tooth 35 being arranged in proximity to said central opening 31 and able to cooperate in fluid sealing conditions with said shutter 20, 20 'and with said body 11. annular lobed section with increased thickness defining said tooth 35 is preferably developed on both faces or sides but can also project towards a single side or different thicknesses between the two faces or sides of said diaphragm or membrane 30.

Still with reference to the embodiments of Figures 1A, 2A, the tooth 35 is advantageously adapted to be arranged in fluid sealing cooperation in a first annular recess 16 conjugated to the same tooth 35, said annular recess 16 being formed in the central portion of a perforated septum 15 of the body 11 outside the hole in the central sliding hub 17 of the stem 20.

With particular reference to the preferred embodiment of Figure 1A, said tooth 35 of the diaphragm or mobile membrane 30 can also be advantageously adapted to be arranged, in fluid sealing cooperation, in a second conjugated annular recess 25, obtained on the external diametrical portion of the plate 24 of the shutter assembly 20, in such a way as to form a diametrical projection along the axial direction of the flow.

With particular reference now to Figure 2A, in a further simplified embodiment said tooth 35 is able to be arranged in fluid sealing cooperation with a further traditional sealing element 50, typically of elastomeric material, coaxially disposed in contact on a face of a traditional plate 24 'of a known shutter 20'. In a variant embodiment, the diaphragm or mobile membrane 30 or even just the tooth 35 can be advantageously made of a harder elastomeric material, than said sealing element 50, and capable of deforming and penetrating the contact surface of the same element seal 50 in such a way as to increase it and improve fluid sealing.

With reference again to Figures 1A and 2A, a further innovative feature of the anti-reflux device 10 object of the present invention is represented by the fact that said diaphragm or membrane 30 is provided with at least one rib 36 formed on said radial elbow section 33 in the portion comprised between said central opening 31 and the external diametrical edge 32, said rib 36 being adapted to improve the elastic deformability of said diaphragm or mobile membrane 30 in the presence of non-homogeneous deformations due to fluid turbulence. The rib 36 is preferably formed on said radial elbow section 33 between said central opening 31 and the same elbow of said diaphragm or membrane 30 and has a cross section of substantially semi-circular shape or otherwise shaped according to the required elastic stiffness.

In a further embodiment, not shown, said rib 35 can protrude or project on both faces of said diaphragm or mobile membrane 30 with a substantially circular cross section.

A further innovative feature of the non-return device 10, with particular reference also to figures 3A, 3B, 3C and 3D, is represented by the fact that said shutter assembly 20, 20 'can comprise a second sealing element 60 suitable for preventing the leakage of fluid between the coupling surfaces of the stem 21 with the plate 24, 24 '. Said further sealing element 60 can be a traditional gasket or elastic sealing ring of the O-ring type and can be advantageously arranged between said stem 21 and said plate 24 in correspondence with recesses and housing grooves formed thereon (e.g. Figure 1) , or in direct contact with a sealing element 50 coaxially arranged and facing said plate 24 'of said shutter 20' (e.g. Figure 3A), said second sealing element 60 being able to translate integrally with said stem 21 and shutter 20, 20 '. This second sealing element 60 can also be arranged between said stem 21 and said body 11 in correspondence with recesses and housing grooves formed thereon, said second sealing element being able to be housed in a groove formed in the hole of the hub 17 and a remain integral with the body 11, as shown in Figure 3C. The sealing element 60 can also be arranged in a groove formed on the same stem 21, said second sealing element 60 being able to translate integrally to said shutter 20, 20 '.

In a further alternative embodiment shown in Figure 3B, the second sealing element 60 can also be arranged in a groove formed in said hole in the hub 17 of the same body 11, said second sealing element 60 being able to remain integral with said body 11 and being able to be arranged on said stem 21 and kept pressed against said body 11 by the elastic element 22 in cooperation and by means of a washer or washer 70, said elastic element 22 and said washer 70 being coaxially arranged with respect to the same seal 60.

From the description of the improved anti-reflux device 10 with reduced pressure zone, object of the present invention, the operation described below can be deduced.

With initial reference to figures 1A to 2B, the improved anti-backflow device 10 with reduced pressure zone object of the present invention constitutes an improvement of the traditional anti-backflow devices with reduced pressure zone or with differentiated pressure zones present in the state of the art.

With reference to Figures 1A and 2A, when the back pressure condition of the return fluid from the user occurs, both the upstream shutters 20, 20 'and downstream 40, are carried into the closed position by means of the pressure of the return fluid and due to the force exerted by the elastic elements 22.

When the downstream shutter 40 is prevented from sealing due to impurities, debris and other residues, the fluid returning from the user flows back into the intermediate zone between the two shutters 20, 20 'and 40. upstream 20, 20 'by translating towards the closed position it comes into contact with the diaphragm or mobile membrane 30 in such a way as to prevent the return of the fluid upstream, towards the inlet opening 12. The tooth 35 formed on the diaphragm or mobile membrane 30 allows a better and locally distributed contact by means of the plate 20, 20 'which preferentially presses on the tooth 35, pressing it against the central portion of the perforated septum 15 of the body 11, thus ensuring a firm and precise seal unlike what happens in the conventional anti-backflow devices of the prior art with an edge contact the plate and the diaphragm or mobile membrane.

In the preferred embodiment of Figure 1A, the tooth 35 formed on the diaphragm and the membrane is advantageously placed in cooperation with the first annular recess 16 obtained in the central part of the perforated septum 15 of the body 11, in such a way as to increase the contact surface and as well as the centering of the central portion of the diaphragm or movable membrane 30 in the closed position. In the same embodiment of figure 1A said tooth 35 is further placed in cooperation with the second conjugated annular recess 25, which by forming a further toothed profile externally on the flat surface of the plate 24 guarantees, as well as an increase in the contact and sealing surface , the self-centering of the plate 24 with the mobile diaphragm or membrane 30 even in the case of imperfect coaxiality of the plate 24 with the central opening 31 of the mobile diaphragm or membrane 30, due to play or oscillations of the shutter 20, allowing thus a better and efficient watertight seal between the plate 24 and the mobile diaphragm or membrane 30 and the body 11 of the anti-backflow device 10. In the simplified embodiment of figure 2A, the shutter 20 'with a plate 24' of a known type and a further sealing element 50 presses on the tooth 35 of said diaphragm or mobile membrane 30 by means of the same sealing element 50 which, deforming and adapts ndosing on the same tooth 35, it guarantees the compression of the same on the body 11 and a greater contact surface and such as to improve its watertight seal.

With reference again to Figures 1A and 2A, the rib 36 formed on said diaphragm or membrane 30 in correspondence with said radial elbow section 33 ensures a better and proportional deformation of the diaphragm itself both in the closed condition and in the normal operating condition with the passage of fluid. The rib 36 in fact prevents an irregular and non-uniform deformation of the central opening 31 of the same diaphragm or mobile membrane 30 even in the presence of turbulence of the flow, thus allowing a better functioning and a longer duration of the same diaphragm both in the opening condition and in closed condition. The dimensions and thickness of the rib as well as its development on one or both sides of said diaphragm or mobile membrane 30, can vary as a function of the supply pressure to which the non-return device 10 is subject in such a way as to vary the elastic stiffness of the same diaphragm or moving membrane.

With reference to Figures 3A, 3B, 3C and 3D, the second sealing element 60 has the function of preventing any fluid leaks that may occur in the closed condition of the shutters 20, 20 'between the mechanical coupling surfaces of the plate 24 , 24 'and the stem 21, thus helping to ensure an increased tightness and safety of the non-return device and a damping action of any oscillations of the shutter 20, 20' inside the hole of the hub 17 due to fluid turbulence under normal operating conditions.

As can be seen from the foregoing, the advantages that the improved anti-reflux device 10 with reduced pressure zone object of the present invention achieves are evident.

The improved anti-backflow device 10 with reduced pressure zone object of the present invention is particularly advantageous because it allows to provide the user with an anti-backflow device with a better and increased tightness of the polluting fluids in conditions of backflow of the fluid from the user, as well as greater safety of water distribution networks.

The improved anti-backflow device 10 with reduced pressure area object of the present invention is also particularly advantageous because it allows to make available to the user an anti-backflow device with better fluid dynamic efficiency.

A further advantage still due to the improved anti-backflow device 10 with a reduced pressure zone is given by the fact of providing the user with an anti-backflow device with a longer operating life and resistance to wear.

Although the invention has been described above with particular reference to some preferred embodiments, given by way of non-limiting example, numerous modifications and variations will appear evident to a person skilled in the art in the light of the above description. The present invention, therefore, intends to embrace all the modifications and variations that fall within the spirit and protective scope of the following claims.

Claims (14)

CLAIMS 1. A backflow preventer (10) with reduced pressure zone for installation on water systems comprising: - a hollow body (11) equipped with an inlet opening (12), an outlet opening (13) and a discharge opening (14); - at least one shutter (20, 20 ') comprising a stem (21), an elastic element (22) and a plate (24, 24'), said shutter (20, 20 ') being slidably housed in said body (11) and adapted to interrupt the fluid connection between said inlet opening (12) and said outlet opening (13) of the body (11); - a deformable movable diaphragm or membrane (30) having a disc-shaped shape with a central opening (31) and a radial elbow section (33), said diaphragm or movable membrane (30) being arranged in the direction of flow in the body (11 ) and adapted to interrupt the fluid connection between the outlet opening (13) and the inlet opening (12) and between said inlet opening (12) and the discharge opening (14); characterized in that a tooth (35) is integrally formed on said diaphragm or mobile membrane (30) defining a lobed section profile with annular development, arranged in proximity to said central opening (31), said tooth (35) being able to cooperate in fluid tight conditions with said shutter (20, 20 ') and with said body (11). The anti-backflow device (10) according to claim 1, wherein said lobed section of said tooth (35) develops on both faces of said diaphragm or membrane (30). The anti-backflow device (10) according to claim 1, wherein said tooth (35) is able to be arranged in fluid sealing cooperation in a first conjugated annular recess (16), obtained in the central portion of a perforated septum (15) of the body (11). 4. The anti-backflow device (10) according to claim 1, wherein said tooth (35) is able to be arranged in fluid sealing cooperation in a second conjugated annular recess (25), obtained on the external diametrical portion of the plate (24) of the 'shutter (20). The non-return device (10) according to claim 1, wherein said tooth (35) is adapted to be arranged in fluid sealing cooperation with a further sealing element (50) coaxially disposed in contact on one face of the plate (24 ') of the shutter (20'), said tooth (35) being able to deform and penetrate the contact surface of said sealing element (50) in such a way as to improve fluid sealing. The non-return device (10) according to claim 1, wherein said diaphragm or membrane (30) is provided with at least one rib (36) formed on said radial elbow section (33) between said central opening (31) and the edge external diameter (32), said rib (36) being adapted to improve the elastic deformability of said diaphragm or mobile membrane (30) in the presence of fluid turbulence. The non-return device (10) according to claim 6, wherein said rib (36) is formed on said radial elbow section (33) between said central opening (31) and the same elbow of said diaphragm or membrane (30). The non-return device (10) according to claim 6, wherein said rib (36) extends on both faces of said mobile diaphragm or membrane (30). The non-return device (10) according to claim 1, wherein said shutter assembly (20, 20 ') comprises a second sealing element (60) adapted to prevent the leakage of fluid between the coupling surfaces of the stem (21) and the plate (24, 24 '). 10. The backflow preventer (10) according to claim 9, where said second sealing element (60) is arranged between said stem (21) and said plate (24) in correspondence with recesses and grooves formed thereon, said second sealing element seal (60) being able to translate integrally with said shutter (20). 11. The anti-backflow device (10) according to claim 9, wherein said second sealing element (60) is arranged between said stem (21) and said body (11) in correspondence with recesses and grooves formed thereon. 12. The non-return device (10) according to claim 11, where said second sealing element (60) is arranged in a groove formed on the same stem (21) said second sealing element (60) being able to translate integrally with said stem (21) and said shutter (20, 20 '). 13. The non-return device (10) according to claim 11, where said second sealing element (60) is arranged in a groove formed in the sliding hole of the hub of the same body (11), said second sealing element (60) being able to remain integral with said body (11). The non-return device (10) according to claim 9, wherein said second sealing element (60) is arranged on said stem (21) and is held pressed against said body (11) by the elastic element (22) and by a washer or washer (70) arranged coaxially with respect to it.