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D E S C R I P T I O N

TECHNICAL FIELD

The present invention refers to a backflow pre vention device with reduced pressure zone.

More specifically, the present invention refers to a new technical solution for an uncontrollable, AC-type backflow prevention device, check valve, or backflow preventer with reduced pressure zone, typ ically, however in a non-limiting way, useable in drinking water supplying systems.

STATE OF THE ART

Anti-pollution backflow prevention devices or check valves, also known as preventers with reduced pressure zone or with zones at different pressures are widely known in the hydraulic and thermotech nical fields.

The preventers with reduced pressure zone or with zones at different pressures are hydraulic protection devices adapted to prevent polluted wa ters to backflow to a water supply system. Such backflowing fluid, typically water, can be caused by variations and fluctuations of the pressure in the supply system, which are such to cause the flu id to revert its flow direction. Typically, the preventer is installed in the water supply systems between the public waterworks and the user system and defines a separation and safety zone preventing the fluids contained in the two systems to come in contact with each other.

In the public waterworks or drinking water sup ply systems connected to non-industrial or indus trial users of hydraulic and thermohydraulic sys tems, there are temporary drops of the fluid pres sure. When the pressure of the fluid in the public waterworks or water supply system is less than the fluid pressure in the user hydraulic system, the fluid or water of this latter has the tendency to backflow into the public waterworks.

The fluid or water supplied to the hydraulic or thermohydraulic systems of users can come in con tact with contaminating, pathogen, or polluting substances which can be dangerous for and can con taminate the water supply system itself where there is a backflow, as for example when a hose of a non industrial user is connected to a tap and is placed in a dirty water container which, in case of a flu id pressure drop, can withdraw the contaminated fluid into the public waterworks.

In the same way in the industrial hydraulic and thermohydraulic systems, the fluid can come in con tact with oils, fuels or harmful, corrosive and/or radioactive substances which, when the fluid back- flows into the water supply system, would cause substantial damages.

Consequently, it is easily understandable that in a user water supply systems connected to the public waterworks for distributing the drinking wa ter, it is particularly important to use these backflow prevention devices, which can be also re quired by regulations in effect in many countries.

The standard preventers with reduced pressure zone, of the type object of the present invention, generally can be controllable or uncontrollable and are implemented by an outer body advantageously di vided in two sections, provided with an inlet open ing and an outlet opening, typically the interior thereof houses two monostable, serially-arranged check valves and defined by two check assemblies slidingly placed upstream and downstream said open ings, in order to enable a fluid to flow in a di rection and to prevent it from flowing in the oppo site direction. In the zone comprised between the two valves, typically there is an intermediate ex haust or vent opening adapted to discharge the flu id returning from the upstream check assembly and directly towards the supply system into the atmos phere, said exhaust opening being typically opened or closed by a mobile diaphragm or membrane.

During the normal operation, when the fluid pressure is such to overcome the opposing force of the elastic elements of the check valves, the check assemblies of the valves themselves open enabling the fluid to flow only in one direction from the inlet opening, connected to the supply system, to wards the outlet opening, connected to the user. The pressure of the moving flow simultaneously acts on the mobile diaphragm or membrane system in order to simultaneously keep closed the exhaust opening.

In the traditional backflow prevention devices or preventers with reduced pressure zone of the type object of the present invention, generally there is a mobile diaphragm or membrane seal dis posed in the flow direction of the fluid and tradi tionally defined by a shaped disc of an elastomeric material having a circular shape with a central hole. The shaped cross-section of said mobile mem brane has one or more elbows developing from the central hole towards the outer edge, typically de fining a circular link integrally developed on all the circumference.

The operation of the backflow prevention device or preventer with pressure zone can be generally summarized by three conditions:

- an operative state under standard or normal conditions, in which the upstream and downstream check assemblies are both open and the exhaust opening is closed by the mobile diaphragm or mem brane. During the normal or standard operative con dition, the part of the diaphragm in proximity of the central hole opens by elastically deforming un der the pressure of the fluid in the flow direc tion, so that the liquid is linearly conveyed into the central chamber of the valve body and the up stream check assembly is pushed to an open posi tion. Simultaneously, the deformed portion of the diaphragm, in the greatest amount opening condi tion, tightly obstructs the toroidally shaped outer exhaust chamber made outside and coaxially with the sliding central chamber, so that the fluid is pre vented from outflowing towards the exhaust. In creasing the pressure of the fluid entering the in termediate zone opens the check assembly of the valve downstream the preventer under the fluid pressure enabling the fluid to flow through the outlet opening.

- stationary flow or no-flow operative state, in which the upstream and downstream check assem blies are held in a closed position by the spring elastic elements. Under this condition, there is no liquid flow towards the two directions and the mo bile diaphragm or membrane does not close the fluid passage towards the toroidal outer chamber connect ed to the outlet opening.

- Operative state in the presence of a backflow from the downstream outlet opening, in which the check assemblies are held in a closed position by the spring elastic elements and the pressure of the liquid trying to flow in the opposite direction. However, the upstream check assembly operates only if there is an incomplete or partial closure of the downstream check assembly, this condition is typi cal and can occur often when this types of devices are used, and is generally caused by solid materi als, as debris or dirtiness from the user.

The closing upstream check assembly thrusts, against the valve body, the diaphragm portion in proximity of the central hole, by means of the plate of the check assembly which is held com pressed on the mobile diaphragm or membrane itself, in order to stop the return flow from the partially closed downstream check assembly, towards the inlet opening. The mobile diaphragm or membrane disposed in a closed position, together with the upstream check assembly, opens the return flow passage in the outer chamber towards the fluid exhaust opening placed in the intermediate zone between the two check assemblies.

An example of these known backflow prevention devices, of the preventer with reduced pressure zone type, is described in the Chinese utility pa tent CN 201787144 U which refers to a device with a double check valve comprising an outer valve body and an inner part, wherein the valve body is pro vided with a seat; while the inner part of the valve is movably disposed in the valve body; the valve seat is provided with a water inlet and out let and with an outlet at the ends. The mobile in ner 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 provided with an exhaust port; when the first inner part of the valve opens the water in let, the exhaust port is closed and when the first inner part of the valve closes the water inlet, the discharge port is opened. The second inner part of the valve opens or closes the water outlet by mov ing with respect to the valve seat. In the cited utility patent, the valve body is internally pro vided with two inner parts, the second check valve prevents the fluid backflow from entering through the outlet of the valve and is exhausted directly from the exhaust port instead of flowing again through the inlet in order to prevent the pollu tion .

A further example of these known types of back- flow prevention devices, of the preventer with re duced pressure zone type, is described in the in ternational patent application WO 2016/105583 which refers to a backflow prevention device comprising a body with an inlet and outlet and adapted to be in stalled in order to have a fluid connection in a liquid supply system. An upstream check plate as sembly is positioned in the body downstream the in let and comprises an upstream control plate sup porting a downstream diaphragm. A second upstream check assembly is positioned downstream the dia phragm and is integrally formed with an upstream stem and is disposed in an opening made in a cen tral hub formed in the body in order to move be tween a normally open flow position and a closed position preventing the liquid from backflowing through the inlet. A downstream plate assembly is positioned in the housing downstream the upstream control plate assembly. A vent discharges the back- flow liquid in the atmosphere upstream the down stream check plate assembly.

Said known backflow prevention devices or pre venters with reduced pressure zone, or with zones at different pressures, however, have disadvantages and operative limits.

In the cited backflow prevention devices pre sent in the state of the art, the check assemblies defining the check valves are generally and advan tageously formed, for the sake of the simplicity and cost-effectiveness, by a disc-shaped plate bored in the central part and stabilized integrally with the end of a cylindrical stem or shaft typi cally by plastically deforming the metal of said stem, e.g. by heading or damping the metal of the stem end.

Referring firstly to Figures 4 and 5, the pro cess of assembling the check assembly, which can generally comprise also a flat seal having a perfo rated circular shape and disposed on the abutment face of the plate, has a typical shortcoming of these devices, because while is capable of mechani cally stabilizing the plate to the stem, unfortu nately it does not provide any fluid tightness be tween said stem and said plate and does not elimi nate the possibility of seepages or leakages of the fluid F between the same, as illustrated in Figure 4. In backflow conditions of the contaminated flu id, therefore, a small quantity of fluid can leak age between the mechanical coupling surfaces de fined between the plate hole and the free end of the stem of said check assembly and can leakage be tween the coupling surfaces of the stem and central hole of the hub made in the body, with respect to this the check assembly being slidingly disposed. In order to enable the stem of said check assembly to freely slide, the coupling between said stem and said central hole of the hub must inevitably have a free space or a mechanical clearance, unfortunately the contaminated fluid can leakage through it up stream the device and can contaminate the water works, particularly if the coupling surfaces slid ingly in contact with each other are substantially worn .

The mechanical clearance between the stem and the hub central hole, besides causing a leakage be tween the coupling surfaces, causes a further in convenience and operative limit typical of this known backflow prevention devices, said mechanical clearance being subjected to worsen due to the use and operative wear.

In standard operative conditions, indeed, the check assembly embodies a fluid dynamic obstruction to the fluid flow. This obstruction generates tur bulences I in the stationary laminar flow of the fluid such to generate angular oscillations and vi brations of the check assembly in a direction gen erally radial to the fluid motion, as shown in Fig ure 5 by a double dotted broken line. These angular oscillations and vibrations are greater at the plate and they are the wider the more open the check is and consequently the greater the flow is, so that the turbulences of the fluid motion are in creased and an increase of the flow resistances, efficiency of the valve is determined, and also cavitation phenomena and anticipated wear of the components of the backflow prevention device are caused . Another disadvantage of these known backflow prevention devices occurs during the step of clos ing the upstream valve because the plate of the check assembly contacts the mobile diaphragm or membrane by an edge contact consequently by a small surface and an uneven and not constant pressure, all this causes an incomplete and not centered buckling of the portion adjacent the central hole of the diaphragm itself against the valve body. Moreover, this condition could be worsened by the transversal oscillations and vibrations of the check assembly so that the check assembly plate is substantially offset from the central hole of the diaphragm or membrane, determining a less-than- perfect fluid tight closure and contributing to an anticipated wear of the elastomeric material of the diaphragm and disc-shaped seal of the plate.

Another disadvantage is that the swirling fluid motion can also be such to unevenly warp the mobile diaphragm or membrane consequently promoting its wear or an anticipated downtime of the device be sides a substantial decrease of the fluid dynamic efficiency of the backflow prevention device.

OBJECTS OF THE INVENTION

The object of the present invention consists of at least partially overcoming and preventing the above-cited operative inconveniences and limits.

More particularly, the object of the present invention consists of providing a backflow preven tion device with reduced pressure zone, adapted to ensure an increased safety of the systems and a better tightness against the polluting fluids.

A further object of the present invention con sists of making available to the user a backflow prevention device with a reduced pressure zone hav ing a higher efficiency and a better flow uniformi ty, without hydrodynamic turbulences and cavitation phenomenons .

A still further object of the present invention consists of providing a backflow prevention device with reduced pressure zone capable of ensuring a high resistance and reliability over time, so that to be in addition easily and cost-effectively manu facturable .

These and other objects are met by the backflow prevention device with reduced pressure zone object of the present invention according to the independ ent claim.

The constructive and operative characteristics of the backflow prevention device with reduced pressure zone could be better understood from the following detailed description, in which it is made reference to the attached drawings representing some preferred non-limiting embodiments, in which:

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 is a schematic representation of a longitudinal cross-section view of a preferred em bodiment of the backflow prevention device with re duced pressure zone object of the present inven tion;

Figure 2 is a schematic and partial representa tion of a longitudinal cross-section view of the operation of the backflow prevention device with reduced pressure zone object of the present inven tion, under the counterpressure and backflow condi tion of the fluid from the downstream check assem bly (not shown) and with the upstream check assem bly in the closed position;

Figure 3 is a schematic partial representation of a longitudinal cross-section view of the opera tion of the backflow prevention device with reduced pressure zone object of the present invention, un der the standard operative condition having the flow moving towards the downstream check assembly

(not shown) and with the upstream check assembly in the greatest opening limit position;

Figure 4 is a schematic partial representation of a longitudinal cross-section view of a backflow prevention device with reduced pressure zone ac cording to the prior art, under the counterpressure and backflow condition of the fluid from the down stream check assembly (not shown) and under a leak age condition of the contaminated fluid through the upstream check assembly in the closed position;

Figure 5 is a schematic partial representation of a longitudinal cross-section view of a backflow prevention device with reduced pressure zone ac cording to the prior art in the standard operative condition when the fluid flows towards the down stream check assembly (not shown) and with the presence of hydrodynamic turbulence phenomena caused by the transversal oscillations and vibra tions of the upstream check assembly placed in the greatest opening limit position.

DE TAILED DESCRIPTION OF THE INVENTION

Figures from 1 to 3 describe a preferred embod iment of the backflow prevention device with re duced pressure zone 10 object of the present inven tion .

Particularly, it is made reference to Figure 1, which shows a backflow prevention device with re duced pressure zone 10, or with zones at different pressures, suitable for or configured to be in stalled in water supply systems, comprising:

a internally hollow body 11 traditionally made of a metal material adapted to hydraulic ap plications, such as for example brass, generally divided, for the sake of assembly simplicity, in an upstream portion 11 and in a downstream portion 11' separable from each other, said body 11 being pro vided with a fluid inlet opening 12 from the water system, a fluid outlet opening 13 towards the user and a backflow fluid exhaust opening 14 from the user;

- at least a check valve assembly 20, typically an upstream check assembly and a second downstream check assembly 40, said check assembly 20 being a check valve, and comprising a stem 21 generally made of a metal material, a coil spring type elas tic element 22, and a plate 24 generally having a perforated disc shape, said check assembly 20 being housed in said body 11 and adapted to interrupt the upstream fluid connection between said inlet open ing 12 and said outlet opening 13 of the body 11.

Further, said backflow prevention device 10 comprises :

- a deformable mobile diaphragm or membrane 30 made of an elastomeric material and having an oper atively disc-shaped form with a central opening 31, an outer diametral portion 32 and an elbow radial section 33, said mobile diaphragm or membrane 30 being disposed in the flow direction in the body 11 and being adapted to interrupt, in a closed posi tion, the fluid connection between the outlet open ing 13 and inlet opening 12; and, in an open posi tion, to interrupt the fluid connection between said inlet opening 12 and exhaust opening 14.

Referring only to Figure 1, the backflow pre vention device 10 is preferably sold with, and gen erally comprises also standard-type connectors 70 provided with known mobile fixing means at the in let 12 and outlet openings 13 and adapted to a flu id connection with the standard hydraulic systems, said connectors 70 typically can comprise a flanged bush 71, a nut 72, and a seal 73. Moreover, the de vice 10 can be advantageously provided with a fil ter 80 disposed in the upstream portion 11' of the body 11 and adapted to prevent solid particles to flow through the inlet opening 12.

Still referring to the cited Figures, the main novel characteristic of the backflow prevention de vice 10 is embodied by the fact that said stem 21 of the check assembly 20 is fixedly stabilized and integral with said body 11 and by the fact said plate 24 is slidingly disposed along said stem 21 and is cooperatively placed in surface contact with said mobile diaphragm or membrane 30, in such a way to interrupting, in a closed position, the fluid connection between said inlet opening 12 and said outlet opening 13 of the body 11.

Referring again to the same Figures, moreover the stem 21 can also be inserted and stabilized by an end thereof, with known fixing means, in a hole of the hub 17 made in a central portion 18 defining an appendage formed in the central part of the per forated partition 15 of said body 11. Said known fixing means can be mobile, such as threads or sim ilar means or can be fixed as interference fits, welds and similar. In an alternative embodiment (not shown) , said stem can be also integrally made with the same body 11.

The central portion 18, in which said hub hole 17 is made, being formed on said perforated parti tion 15 of the upstream portion 11' of the body 11, can advantageously project in a flow direction to- wards said inlet opening 12 of said body 11, in or der to enable to obtain a sufficient longitudinal development of the hole 17 itself of the hub, which preferably is a blind hole, however can be also a through hole crossing all the perforated partition 15.

Advantageously, said hub hole 17 can be thread ed and adapted to be screwed to a corresponding threading formed on an end of said stem 21, and in case of a through embodiment of the hub hole 17, the threading can be advantageously fluid tight, such as for example a cylindrical or conical GAS or BSP type threading tight sealed on the thread.

A further novel characteristic (not shown) is given by the fact that the free end of said central portion 18 facing the inlet opening 12 can have a hydrodynamic shape developing towards the same in let opening 12, such as for example a pin or nosecone shape.

By particularly referring only to Figure 1, al so the diaphragm or membrane 30 and plate 24 of the check assembly 20 can advantageously be provided with features adapted to improve the seal efficien cy and safety of the backflow prevention device 10.

Particularly, a tooth 35 or projection can be advantageously formed on said mobile diaphragm or membrane 30, which defines a lobed-section profile having a complete annular development, with an in creased thickness with respect to the cross-section thickness of the mobile diaphragm or membrane 30, said tooth 35 being disposed in proximity of said central opening 31 of said mobile diaphragm or mem brane 30 and being adapted to cooperate, under flu- id-tight conditions, with said check assembly 20 and body 11. Said annular lobed-section with an in creased thickness defining said tooth 35 is prefer ably developed on both sides or faces, however it can also project towards only a side or can define several thicknesses between the two faces or sides of said diaphragm or membrane 30.

Still referring to the preferred embodiment of Figure 1, the tooth 35 can be advantageously adapted to be arranged, in a fluid-tight coopera tion, in a first annular recess 16 conjugated to the same tooth 35, said annular recess 16 being made in the central portion of a perforated parti tion 15 of the body 11 outside the central hub hole 17 in which slides the stem 21.

Particularly, referring again to Figure 1, said tooth 35 of the mobile diaphragm or membrane 30 can be also advantageously adapted to be disposed, with a fluid-tightness cooperation, in a second conju gated annular recess 25 made in the outer diametral portion of the plate 24 of the check assembly 20, in order to form a diametral projection in the axi al flow direction.

In a further simplified embodiment (not shown) , said tooth 35 can be adapted to be disposed, in a fluid-tightness cooperation, with a further stand ard sealing element, typically of an elastomeric material, coaxially to and in contact with a face of a standard not-shaped plate 24. Indeed, said tooth 35 can be advantageously made of a harder elastomeric material and adapted to deform and pen etrate a contact surface of said standard sealing element in order to improve the fluid-tightness .

Referring again to Figure 1, said diaphragm or membrane 30 can be also provided with at least one rib 36 formed in said elbow radial section 33 in the portion comprised between said central opening 31 and the outer diametral edge 32, said rib 36 be ing adapted to improve the elastic deformability of said mobile diaphragm or membrane 30 in the pres ence of dishomogeneous deformations caused by fluid turbulences. Preferably, the rib is formed in said elbow radial section 33 between said central open ing 31 and the elbow itself of said diaphragm or membrane 30 and has a transversal section with a substantially semicircular shape or shaped in an other way as a function of the required elastic ri gidity.

In a further possible alternative embodiment, not shown, said rib 36 can also extend or project on both the faces of said mobile diaphragm or mem brane 30 with a substantially circular shaped transversal section.

The description of the backflow prevention de vice 10 with a reduced pressure zone, object of the present invention, enables to understand the opera tion described in the following.

Referring particularly also to Figures 2 and 3, the backflow prevention device 10 with reduced pressure zone object of the present invention is an advantageous technical solution with respect to the standard backflow prevention devices with reduced pressure zone or zones at different pressures of the prior art.

In the presence of a counter pressure condition of a fluid returning from an user, schematically shown in Figure 2, both the upstream 20 and down- stream check assemblies 40 (not shown) , are actuat ed in a closed position by the return fluid pres sure and by the force exerted by the elastic ele ments 22.

Referring again to Figure 2, when the down stream check assembly 40 is prevented from being closed in a tightness condition due to impurities, debris and other waste, the fluid returning from the user flows again in the intermediate zone be tween the two check assemblies 20 and 40. In this case, only the plate 24 of the upstream check as sembly 20 moves towards the closed position by com ing in contact with the mobile diaphragm or mem brane 30 in order to prevent the fluid to flow up stream, towards the inlet opening 21, while the stem 21 remains fixed with respect to the body 11.

Referring particularly to Figure 3, in the flu id passage condition when the check 20 is open, the transversal clearance of the plate 24, slidingly disposed on the stem 21, is advantageously held constant and contained and does not increase as the opening stroke of the check assembly 20 increases due to an increase of the fluid flow, so that the same flow is held constant and as much as possible in a laminar state, limiting the generation of tur- bulences and cavitation phenomena, as opposed to a standard device as illustrated in Figure 5.

Referring particularly again to Figure 1, the tooth 35 formed on the mobile diaphragm or membrane 30 further enables a better locally distributed contact by the plate 24 preferably pressing on the tooth 35 by buckling it against the central portion of the perforated partition 15 of the body 11, so that a stably and accurate seal is ensured as op posed to the standard backflow prevention devices of the prior art, having an edge contact between the plate and the mobile diaphragm or membrane.

In the preferred embodiment of Figure 1, advan tageously the tooth 35 formed on the diaphragm or membrane is further made to cooperate also with the first annular recess 16 made in the central part of the perforated partition 15 of the body 11, in or der to increase the sealing contact surface and al so the centering of the central portion of the mo bile diaphragm or membrane 30 in a closed position. In the same embodiment of Figure 1, said tooth 35 is further made to cooperate with the second conju gated annular recess 25, which, by forming a fur ther outer toothed profile on the flat surface of the plate 24, causes, besides an increase of the contact sealing surface, a self-centering of the plate 24 with respect to the mobile diaphragm or membrane 30, also when the plate 24 is not perfect ly coaxial with the central opening 31 of the mo bile diaphragm or membrane 30, due to clearances or oscillations of the check assembly 20, enabling a better and efficient tightness between the plate 24, mobile diaphragm or membrane 30 and body 11 of the backflow prevention device 10.

In the alternative simplified embodiment (not shown) , the check assembly 20 with a known type flat plate 24 provided with a further known flat sealing element, presses the tooth 35 of said mo bile diaphragm or membrane 30 by the same sealing element 50 which, by deforming and adapting to the tooth 35 itself, provides the compression of the same on the body 11 and a greater contact surface for improving the tightness.

Referring again to Figure 1, the rib 36 formed on said diaphragm or membrane 30 at said elbow ra dial section 33, provides a more uniform and pro portional deformation of the diaphragm itself both in a closed condition and in a normal operative condition as the fluid flows. Indeed, the rib 36 prevents an uneven irregular deformation of the central opening 31 of the mobile diaphragm or mem brane 30 itself also in the presence of flow turbu lences, enabling a better operation and a longer life of the diaphragm itself both in an open condi tion and in a closed condition. The size and thick ness of the rib, and also the development thereof on one or both sides of said mobile diaphragm or membrane 30, can change as a function of the supply pressure at which the backflow prevention device 10 is subjected, in order to change the elastic rigid ity of the mobile diaphragm or membrane itself.

The absence of a through hole in which the stem 21 slides or the presence of a tight threading in the hub hole 17 ensure to seal off the contaminated fluid between the fixed coupling surfaces between the stem 21 and body 11 without requiring further fluid sealing elements.

As it is understood from before, the advantages which the backflow prevention device 10 with re duced pressure zone object of the present invention obtains, are evident.

The backflow prevention device 10 with reduced pressure zone object of the present invention is particularly advantageous since enables to provide an user a backflow prevention device having a bet- ter and increased tightness against polluting flu ids in backflow conditions of the fluid from the user, and a greater safety in the water supply sys tems .

The backflow prevention device 10 with reduced pressure zone object of the present invention is further particularly advantageous since enables to provide the user a backflow prevention device with a better fluid dynamic efficiency.

Still another advantage of the backflow preven tion device 10 with reduced pressure zone is the provision of a backflow prevention device having a greater operative life and an increased resistance to wear.

Even though the invention has been hereinbefore described referring particularly to a preferred em bodiment given in an exemplifying and non-limiting way, several changes and variants will be apparent to a person skilled in the art by considering the above discussed description. Therefore, the present invention intends to encompass all the modifica tions and variants falling into the scope of the following claims.