NZ603911B - Pressure control valve - Google Patents

Abstract

Patent 603911 A pressure control valve 1 comprises a housing 2 defining a flow path P for a fluid between an inlet 3 and an outlet 4, a hollow plug 5 for the fluid, movable between a closed position C, in which the plug 5 is coupled with a closing washer 27 for interrupting the flow of fluid, and an open position A to enable the fluid to pass, a counteracting spring 8 exerting an opening force FA for pushing the plug 5 to the open position A. The plug 5 and the spring 8 are configured in such a manner that the closed position C is reached at a set limit pressure value of the fluid downstream. The plug 5 comprises an enlarged portion 10 that is suitable for receiving from the fluid downstream a closing force Fc which counteracts the opening force FA and acts towards the closed position C. The enlarged portion 10 has a transverse external dimension equal to a first value. The plug 5 further comprises an intermediate portion 11 that is slidable on guiding and sealing means 12 and has an external transverse dimension that is equal to a second value D2 less than the first value D1. nd an open position A to enable the fluid to pass, a counteracting spring 8 exerting an opening force FA for pushing the plug 5 to the open position A. The plug 5 and the spring 8 are configured in such a manner that the closed position C is reached at a set limit pressure value of the fluid downstream. The plug 5 comprises an enlarged portion 10 that is suitable for receiving from the fluid downstream a closing force Fc which counteracts the opening force FA and acts towards the closed position C. The enlarged portion 10 has a transverse external dimension equal to a first value. The plug 5 further comprises an intermediate portion 11 that is slidable on guiding and sealing means 12 and has an external transverse dimension that is equal to a second value D2 less than the first value D1.

Description

PATENTS FORM 5 Our Ref: P054830NZ PATENTS ACT 1953 Dated: 27 November 2012 COMPLETE SPECIFICAnON Pressure control valve We, Borne S.R.L., incorporated in Strada le dello Strego 1,1-28010 Cavallirio, Italy, hereby e the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: AH25(6890300_1):MLW RE CONTROL VALVE Technical Field The present invention relates to a pressure control valve, that is suitable for controlling, in particular for ng, the pressure inside a t in which a fluid flows, for example water, such as a cooling and/or heating circuit dential or rial type.

Background of the Invention Valves are known that are mounted along a circuit to prevent the pressure ofthe corresponding fluid, in a zone downstream ofthe valve, exceeding a certain limit. Valves ofthis type are for example known from AU602199 and from EP1509714. 99 discloses a valve comprising a hollow valve body, inside which an inlet and an outlet for the fluid are defined, and a passage that links the latter to one another. In the valve body a closing washer is provided that is received in a respective seat, placed near the inlet for the fluid, and a movable plug is housed, sing a piston provided with a through opening that extends along a longitudinal axis ofthe valve.

The plug is movable between a closed position, in which an am end thereofnearer the inlet s against the closing washer to close the fluid passage and interrupt the flow, and an open position, in which the plug is detached from the aforesaid washer to enable the fluid to flow to the outlet and thus to circulate in the circuit downstream. A spring is provided that acts to move the plug away from the closing washer during operation in normal operating conditions.

The spring is dimensioned in such a manner as to be compressed and to enable the plug to reach the closed position when pressure ofthe fluid downstream reaches a particular pressure value.

The movable plug comprises a first cylindrical portion, having a first al diameter, that extends to near the inlet and the external surface of which is intended for coming into contact with the incoming fluid. The movable plug comprises a second cylindrical portion, in other words the piston head, positioned nearer the outlet for the fluid, and having a second external diameter that is greater than the aforesaid first external diameter ofthe first cylindrical portion. The first external diameter has a constant value along the entire first cylindrical portion.

AH25(6890300~I):MLW In other words, the first cylindrical portion has an external profile that does not have dimension ions transversely to the longitudinal axis.

The second rical portion, or head ofthe piston, comprises a downstream end e, extending transversely to the longitudinal axis and facing the outlet for the fluid, which is suitable for receiving the outlet fluid pressure so as to generate a force counteracting the force exerted by the aforesaid spring. The downstream end surface, through the greater transverse extent ofthe second cylindrical portion with respect to the first rical portion, is such as to generate a resulting longitudinal force that acts to push the plug to the closing washer. sure in the outlet zone increases, consequently also the force exerted by the aforesaid end surface downstream increases, thus compressing the spring and, ifthe pressure reaches an excessive value, the first cylindrical portion reaches the g washer, thus interrupting the flow offluid.

A drawback ofthis valve is that it is not able to ensure appropriate precision and operating efficacy. In particular, although the spring is dimensioned with the objective of determining total closure ofthe passage by the plug at a precise theoretical pressure limit value, drawbacks are on the other hand found when, in the closed position, upstream pressure increases significantly. In this case, fluid leaks from am to downstream occur that are due to the greater fluid pressure upstream. Thus in this situation it is experimentally ed that the pressure value ed downstream ofthe plug is greater than the pressure limit value that it is desired should not be exceeded. In other words, the aforesaid pressure limit value is not respected and this is because ofa non stable and perfect closure ofthe valve. This is due to the equilibrium not being perfectly static and stable to which the plug is subjected, in particular in the closed position. In other words, the plug is ted in one direction to the action ofthe , which tends to open the passage, and, in an opposite direction, is subjected to a resultant ofpressure forces that acts to push the plug to the closed position, in which the value ofthe force exerted by the spring and the value ofthe aforesaid resultant ofpressure forces are substantially equal. This is a source of vibration and throbbing during valve operation, particularly near the pressure value limit.

It is clear that ifthe pressure upstream increases progressively, there will be a ion in which the plug comes into contact with the closing washer, but the contact force that they AH25(6890300_1 ):MLW exchange is weak, such that it is unable to prevent fluid leaking from upstream downstream, especially in the event ofa sudden and drastic pressure increase in the circuit upstream.

EP1509714 discloses a pressure control valve comprising a valve body with which an inlet and an outlet for a fluid are associated, and in which a closing piston is slidable that is provided with a longitudinal through opening and is shaped in a manner that is substantially analogous to what is disclosed above in on to the valve piston specified in document AU602199. In particular, also the piston disclosed in EP1509714 comprises a larger cylindrical portion, nearer the outlet, and a r cylindrical portion, nearer the inlet, in which the smaller cylindrical n has a constant external diameter along the entire longitudinal extend thereof, i.e. has an external profile that has not variations in dimensions ersely to the longitudinal axis, and the external cylindrical surface ofwhich is intended to come into contact with the inlet fluid. Nevertheless, the valve disclosed in EP1509714 differs from the one disclosed in AU602199 inasmuch as the smaller cylindrical portion is configured for cooperating in a closed position in which the flow offluid is interrupted, in a slidable manner with a closing . In other words, the external surface ofthe r cylindrical portion ofthe piston, in ive pressure conditions, is arranged in t with the g washer, sliding on the latter so as to close a passage connecting the inlet with the outlet for the fluid. Thus, unlike the valve disclosed in AU602199 in which a front surface ofthe upstream end ofthe plug rests frontally on the closing washer, in the valve disclosed in EP1509714 it is the side surface ofthe smaller cylindrical portion that comes into contact with the closing washer, coupling slidably with the latter with slipping. Also this solution has drawbacks, analogously to what has been sed for AU602199. In the valve disclosed in EP1509714, in particular, over time, even a minimal wear to the closing washer caused by slipping contact with the plug, determines a loss of seal and thus ineffective interrupting action ofthe passage ofthe fluid and thus ctive limiting action ofthe pressure when it is required.

There is a need to improve prior-art pressure l valves and to provide a solution that is able to overcome the drawbacks inherent in known valves.

In particular, there is a need to provide a more reliable pressure l valve with great effectiveness and operating precision.

AH25(6890300_1):MLW There is also a need to provide a pressure control valve that ensures a stable closed position for interrupting the flow of fluid, and which prevents a precise desired calibrated pressure value being exceeded even in extreme operating conditions, for example if drastic and sudden pressure increases occur upstream ofthe valve.

Object of the Invention It is an object ofthe present invention to substantially overcome or at least rate one or more ofthe disadvantages ofthe prior art, or to at least provide a useful alternative.

Summary of the Invention There is disclosed herein a pressure control valve comprising: a housing body defining a flow-path for a fluid between an inlet and an outlet aligned along a longitudinal axis; plug means ed with a longitudinal h-opening for said fluid and movable along said longitudinal axis between a closed position, in which it couples with sealing closing means for upting the flow ofsaid fluid, and an open position to enable said fluid to advance from said inlet to said outlet, counteracting spring means suitable for exerting an opening force for pushing said plug means to said open position, said plug means and said racting spring means being configured in such a manner that said closed position is reached at a set limit pressure value of the fluid downstream, said plug means comprising, near said , an enlarged n suitable for ing from the fluid downstream a thrust that generates a closing force counteracting said opening force and acting on said closed position, said enlarged portion having an external ion, ed transversely to said longitudinal axis, equal to a first value, said plug means further comprising an intermediate portion that is slidably coupled with guiding and sealing means and has a respective external transverse dimension that is equal to a second value that is less than said first value, wherein said plug means comprises upstream of said intermediate portion near said inlet an obstruction-control-portion having a respective external transverse dimension equal to a third value that is greater than said second value, said obstruction-control-portion being movable in a receiving and ing chamber between said guiding and sealing means and said sealing AH25(6890300_1):MLW closing means and comprising, transversely to said longitudinal axis, a head-surface configured for abutting on said sealing closing means, and a closure-promoting-surface, opposite said headsurface , facing said guiding and sealing means, and configured for receiving from the fluid in said receiving and ing r a thrust that generates an auxiliary closing force proportional to the pressure ofthe fluid am and able to ensure that said plug-means is stably in said closed position when the pressure ofthe fluid downstream is equal to said set limit pressure value.

Brief Description of the Drawings The invention can be better understood and implemented with nce to the attached gs, which illustrate an embodiment thereof by way ofnon-limiting example, in which: Figure 1 is a longitudinal section ofthe pressure control valve in an open position; Figure 2 is an enlarged detail ofFigure 1; Figure 3 is a longitudinal section ofthe pressure control valve in a closed position; Figure 4 is an enlarged detail ofFigure 3; Figure 5 shows schematically the flow of a fluid along the pressure control valve; Figure 6 is an exploded view ofthe pressure control valve; Figure 7 shows in detail a part ofplug means included in the pressure l valve, in particular an ction-control-portion is shown; Figures 8 and 10 are respectively a side view and a longitudinal section view ofthe pressure control valve; Figure 9 is a first cross section ofthe valve taken along a plane IX-IX in Figure 8; Figure 11 is a second cross section ofthe valve taken along a plane XI-XI in Figure 10; Figure 12 is a third cross section ofthe valve taken along a plane XII-XII in Figure 10; AH25(6890300_1):MLW Figures 13 and 14 are two different perspective views ofa first receiving and conveying t ofthe valve; Figures 15 and 16 are two different perspective views ofa second receiving and conveying element ofthe valve; Figures 17 to 19 show three ent operating positions ofthe re control valve, in particular ofthe plug means, respectively an open position, an intermediate position and a closed position; Figure 20 is a m that illustrates the operation of a prior-art valve; and Figure 21 is a m that illustrates the operation ofthe pressure control valve.

Detailed Description With reference to the attached Figures, a re control valve 1 is shown that is le for being fitted, in general, in a t in which a fluid runs, for preventing the pressure ofthe fluid in a zone downstream ofthe fluid with respect to an advance direction overcoming a set potentially l pressure limit value. The re control valve 1 thus has the function of limiting the pressure ofthe fluid downstream.

The pressure control valve 1 comprises a housing body 2 that defines a flow path P for a fluid between an inlet 3 and an outlet 4 aligned along a longitudinal axis L. In particular, the housing body 2 is made oftwo pieces, in particular a first piece ofhousing body 2a and a second piece ing body 2b that are connected together by a first threaded coupling 13.

Inside the housing body 2 a plug 5 is provided that has a through longitudinal opening 6 through which the fluid flows, the plug 5 being movable along the longitudinal axis L between an open position A, (shown in Figures 1,2, 17), in which it enables the fluid to advance from the inlet 3 to the outlet 4, and a closed position C, (shown in Figures 3, 4, 19), in which the plug 5 engages with sealing closing means 7 for interrupting the flow offluid. The sealing closing means 7 comprises a closing washer 27 and is defined by a first receiving and conveying element 40 and by a second receiving and conveying element 41 that will be disclosed in detail below.

AH2S(6890300_1):MLW The closing washer 27 is in particular ofthe "O-ring" type but can also be ofa different type, for example flat with a square section, etc.

The pressure control valve 1 is provided with contrast-means 8, or elastic counteracting means 8, comprising in particular a helical compression spring 8 that is arranged for ng an opening force F Athat tends to maintain the plug 5 in the open position A. The spring 8 and the plug 5 are configured in such a manner that the closed position C is achieved at a set calibration value, specifically a pressure limit value VL ofthe fluid that is found downstream ofthe plug 5 with respect to the advance direction ofthe fluid.

The plug 5 comprises, at an end 9 thereofnearer the outlet 4, an ed portion 10 configured for receiving from the fluid downstream a thrust action that determines a closing force Fe acting in an opposite direction to the aforesaid opening force FA and tending to take the plug 5 to the closed on C.

The enlarged portion 10 is slidably housed in the first piece ofhousing body 2a, in which a respective seal ring 31, for e ofthe "O-ring" type, is housed, to prevent leaks ofthe fluid to the exterior.

In the open position A, the enlarged portion 10 is maintained ng on a stop surface The ed portion 10 extends transversely to the longitudinal axis L with an external dimension having a first value Dl. In ular, the enlarged portion 10 is bounded externally by a cylindrical surface and has an al diameter equal to the aforesaid first value Dl (Figure 17,18).

In particular, on the enlarged n lOan annular cavity is obtained on the bottom of which a thrust surface 50 is provided, lying transversely to the longitudinal axis L, suitable for receiving the thrust ofthe fluid downstream. The annular cavity enables a zone to be defined that is sheltered from the turbulences ofthe fluid, to prevent the ed portion 10 being subjected to "false" pressure values, i.e. to act in such a way that the enlarged portion 10 receives as much as possible the action ofthe static pressure or laminar and non-turbulent operating pressure ofthe fluid. In other words, the enlarged portion 10, so configured with the annular cavity, has a function of guiding the fluid to the outlet 4 and y dampening the movement ofthe fluid to AH25(6890300_1):MLW prevent the actual pressure value being altered by the turbulences ofthe fluid. In this manner, driving ofthe plug 5, which is very precise, depends on the actual pressure downstream and is not disturbed by local turbulent phenomena ofthe fluid.

The plug 5 comprises an intermediate portion 11 that projects to a zone am ofthe enlarged portion 10 and has a respective external dimension that is transverse to the longitudinal axis L, having a second value D2 less than the first value D 1 mentioned above. In particular, the intermediate portion 11 is bounded externally by a respective rical e and has an external er equal to the aid second value D2.

The plug 5 comprises, am ofthe intermediate portion 11, thus nearer the inlet 3, an obstruction-control-portion 14 having a respective external transverse dimension equal to a third value D3 that is greater than the aforesaid second value D2 ofthe intermediate portion 11. In particular, the obstruction-control-portion 14 is externally limited by a cylindrical surface that extends around and parallel to the longitudinal axis L and has an external diameter that is equal to the third value D3. The obstruction-control-portion 14 is ed for moving in a receiving and conveying chamber 30 defined n the guiding and sealing means 12 and the g closing means 7, and is suitable for abutting on the latter in the closed position C. In particular, the obstruction-control-portion 14 comprises a head-surface 15 configured for abutting on the sealing closing means 7, in particular on the closing washer 27. The obstruction-control-portion 14 comprises a closure promoting surface 16, opposite the head-surface 15, facing the g and sealing means 12 and configured for receiving from the fluid in the receiving and conveying chamber 30 an ary closing thrust SA that is proportional to the fluid pressure upstream, in ular in the chamber 30, this auxiliary closing thrust SA acting to ensure in a stable manner that the plug 5 is in the closed position C when the pressure ofthe fluid measured downstream of the plug S, is equal to the set limit re value VL. [004S] The plug 5, in the non-limiting embodiment that is disclosed and shown in the Figures, is defined by two pieces, in particular by a first piece Sa ofplug that includes the enlarged portion , and by a second piece of plug Sb that includes the intermediate portion 11 and the obstruction-control-portion 14. The first piece Sa of plug and the second piece Sb ofplug are connected er by a second threaded coupling 17. In particular, the first piece 5a of plug is made ofbrass, which is a material that during manufacture enables the first piece Sa to be machined easily on the machine tools and that ensures good resistance to water or fluid in AH25(6890300_1):MLW general with which it interacts. The second piece 5b ofplug is made ofa material with great mechanical resistance, which is in particular resistant to wear and is able to resist al conditions that may be generated by the speed and/or pressure ofthe circulating fluid, in particular near the obstruction-control-portion 14 where the stress exerted by the fluid is greater.

In a non-limiting ment, the second piece 5b ofplug is made ofa material comprising steel.

The intermediate portion 11 is slidably coupled with guiding and sealing means 12. In particular, the guiding and sealing means 12 comprises a toroidal element 56 having a contrastsurface 18 for the spring 8, and, at an opposite end, a step e 19 configured for promoting a flow offluid against the e promoting surface 16. The step surface 19, in a region radially nearer the longitudinal axis, comprises a recessed zone positioned nearer a downstream zone. An internal seal ring 20 is also provided, for example ofthe "O-ring" type, housed in an internal seat ofthe toroidal element and suitable for coming into contact with the intermediate portion 11 of the plug 5, and an external seal ring 21, for example ofthe "O-ring" type, housed in an external seat ofthe toroidal element 56 and suitable for resting on a side wall 22 ofthe second housing body 2b.

The contrast-surface 18, together with a boundary wall 54 ofthe first g body 2a define a containing r for the spring 8. On the boundary wall 54 a vent opening 55 is made for venting the counteracting spring means 8 during the compression step.

The obstruction-control-portion 14 ses internally an opening-control-surface 23, arranged transversely to the longitudinal axis L, which interacts with the flow-forces ofthe fluid advancing from the receiving and ing chamber 30 to the outlet 4 to maintain in the open position A the plug 5 until the pressure ofthe fluid ream is less than the set limit pressure value VL. The opening-control-surface 23, as it is arranged on a plane that is transverse to the udinal axis L, results in the dynamic thrust ofthe fluid thereupon giving rising to a force having a component parallel to the aforesaid axis, which tends to keep the plug 5 open.

The closure promoting surface 16 and the opening-control-surface 23 are suitably configured and cooperate to obtain a snap movement ofthe plug 5 from the open position A to the closed position C when the pressure ofthe fluid downstream reaches precisely the aforesaid pressure limit VL value. In other words, the combined action ofthe closure promoting surface 16 AH25(6890300_I):MLW and of the g-control-surface 23 interacting with the flow-forces is such as to cause a sudden movement ofthe plug 5 once the pressure value limit VL has been reached downstream.

In particular, the opening-control-surface 23 acts by providing the plug 5 with an action that tends to maintain the plug 5 open by counteracting the closing force Fc until the pressure downstream is less than the limit value VL. In this operating condition, the push that the incoming fluid exerts on the closure promoting surface 16 is substantially compensated by an opposite thrust that the dynamic forces ofthe moving fluid exert on the opening-control-surface When the plug 5 is open, the opening-control-surface 23 is affected, through the effect of the dynamic flow forces, by a pressure that that is greater than that acting on the thrust surface 50 downstream, and consequently prevents an unstable approach ofthe plug 5 to the closing washer 27, thus preventing vibration phenomena arising. Thus advantageously, an operation ofthe valve 1 is obtained that is more stable, clear and precise than with prior-art devices.

Ifthe pressure ofthe fluid increases until it s the limit value VL, when the plug 5 is near the closing washer 27 the following phenomenon occurs: the fluid that passes into the gap n the transverse head 15 and the closing washer 27 has a speed that is greater than the speed ofthe fluid near the closure promoting surface 16; thus the pressure exerted by the fluid on the closure promoting surface 16 is r than the pressure acting on the head-surface 15. This pressure difference is the more marked the narrower said gap or slit becomes. Above all, the ion in an available passage for the fluid consequently causes a reduction in the dynamic flow forces acting on the opening-control-surface 23, thus reducing the opening action that the opening-control-surface 23 exerts on the plug 5. At this point a sort ofsucking phenomenon is obtained that suddenly causes the plug 5 to close completely. In other words, on the obstructioncontrol-portion 14 auxiliary closing thrust SA ofthe fluid upstream remains to act and continues to act on the e promoting surface 16 that results in an auxiliary closing force Fcaux intended for maintaining the plug 5 stably closed for all the time that downstream a pressure is ed that is equal to the limit value VL. Ifwith the plug 5 in closed position C peaks or overpressure that may be significant should occur upstream ofthe plug 5, such peaks or essure, owing to the closure promoting surface 16, would ate into a corresponding increase ofthe ary closing force Fcaux, in a manner proportional to the value thereof. This would cause even greater tightening ofthe head-surface 15 against the closing washer 27, thus further securing the plug 5 in the closed position C and thus effectively preserving the installations AH25(6890300_1):MLW ream ofthe valve 1 from possible damages. When pressure again falls to acceptable values, the action ofthe counteracting spring 8 returns the plug 5 to the open position A. Thus the area ofthe closure promoting e 16 is carefully chosen to obtain both the effect of increasing closing stability ofthe plug 5, whilst at the same time ensuring that once re downstream ises at acceptable levels, the valve 1 is able to restore the passage ofthe fluid.

The closure promoting e 16 and the head-surface 23 have an annular shape and are arranged transversely to the udinal axis L. In particular, the closure promoting surface 16 and the head-surface 23 lie on respective planes that are parallel to one another and are arranged orthogonally to the longitudinal axis L.

With reference to Figures 13 and 14, the first receiving and conveying element 40 comprises a first disc-shaped part 42, shaped for resting on an abutting surface 60 ofthe second piece 2b ofhousing body, and a blind protrusion 43 that ts from a first side 44 ofthe first haped part 42 intended for facing the plug 5. The blind protrusion 43 and the first discshaped part 42 define a first seat portion for the closing washer 27. On the first disc-shaped part 42 first through openings 45 for the fluid are obtained that are distributed circumferally. On a second side 46 opposite the first side 44 there are provided first g and distributing walls 47 for directing the fluid into the first through openings 45.

The first through openings 45 comprise openings such as circular holes and are distributed evenly and angularly spaced apart from one another. Openings ofdifferent shape can nevertheless be provided, for example openings with ar sectors or other shapes that are suitable for performing the same function in an lent manner.

With reference to figures 15 and 16, the second receiving and ing element 41 comprises a second disc-shaped part 48, shaped for resting on the toroidal element ofthe guiding and sealing means 12, on which second through openings 49 for the fluid are obtained. A hollow rical protrusion 51 is provided that projects from the second disc-shaped part 48 and is shaped for resting on the first disc-shaped part 42 ofthe first receiving and conveying element 40. The hollow cylindrical protrusion 51 defines a second seat portion for the closing washer 27.

On the second disc-shaped part second guiding and distributing walls 52 are obtained for directing the fluid coming from the second through openings 49 radially to the obstructioncontrol-portion AH25(6890300_1):MLW The second through openings 49 comprise openings, such as holes, ofcircular shape, and are distributed uniformly and angularly equidistant from one another. Nevertheless, openings of different shape can be provided, for example circular-sector openings or other shapes suitable for performing the same function in an equivalent manner.

The first receiving and conveying element 40 and the second receiving and conveying t 41 are reciprocally coupled and clamped between the toroidal element 56 and the abutting e 60. Between the first 40 and the second 41 receiving and conveying element there is defined an annular distributing and passage chamber 53 for the fluid located am of the receiving and conveying chamber 30.

In the following, with nce to Figures 17 to 19 the operation ofthe pressure control valve 1 in function ofthe pressure ofthe fluid in the circuit is disclosed. In Figure 17 a first operating step is disclosed in which the plug 5, in the open position A, is subjected to a first opening force FAl determined by the counteracting spring means 8 but also by the interaction of the g-control-surface 23 with the fluid flow forces, and to a first closing force FCI generated by the thrust of the fluid on the enlarged portion 10. The first opening force FAl and the first closing force FCI have an equal value but in opposite directions, determining a balance ofthe plug means 5 in the open position A, with the ed n 10 that is maintained abutting on the stop surface 70.

In Figure 18 a second position is shown in which the plug 5, in a on nearer the closing washer 27, is subject to balanced forces similar to those of Figure 17 but having greater values than them. In particular, the plug 5 is ted to a second opening force FAl ofthe spring 8 and to a second closing force FC2 ted by the thrust ofthe fluid on the enlarged portion When the obstruction-control-portion 14 is in contact with the closing washer 27 (Figure 19), on the plug 5 there act a third opening force FA3 ofthe spring, an equal and opposite third closing force FC3 generated by the fluid, and moreover an auxiliary g force Fcauxgenerated by the thrust that the fluid upstream exerts on the closure promoting surface 16. The ary closing force FCaux is proportional to the fluid pressure upstream.

In the description just made with reference to Figures 17 to 19 in a manner emphasised by the growing arrows FAt, FAl, FA3, a substantial increase has been ered ofthe force AH2S(6890300_1):MLW generated by the spring 8. Nevertheless, the ing should be taken into consideration; the spring 8, during the assembly step, is positioned in the housing body 2 in such a manner as to be already noticeably compressed. In other words, the spring 8, with the plug 5 completely in the open on A, is already at an important ssion degree that is such as to generate the opening force FA that is necessary for maintaining the plug 5 open in normal operating conditions, i.e. for pressure values that are less than the limit value VL. Moving the plug 5 from the completely open position to the completely closed position is very limited, i.e. it has a very limited value, in particular ofthe order ofone or a few millimetres and consequently so is also the r compression to which the counteracting spring means 8 is subjected when the plug 5 moves from the open position A to the closed position C. It can thus be , with good approximation, also for the purpose of exposition, that the opening force exerted by the counteracting spring means 8 is maintained almost unvaried, at a set constant value FA, between the open on A and the closed position C. This pattern is schematised by the horizontal line FA in the diagram in Figure 21, which refers to the operation ofthe valve 1 ofthe present invention.

In particular, in the diagram in Figure 21, the trend can be noted ofopposite forces that act on the plug 5 according to a progressive increase in the pressure PM ofthe fluid located upstream ofthe plug means 5.

Ifthe pressure upstream ofthe fluid ses, the closing force Fc exerted by the fluid on the plug also increases proportionally, as shown by the first tilted line Tl, until it arrives at a point in which the closing force Fe is equal to the opening force FA, as the respective and equal quantities show that are indicated by "y".

When the head-surface 15 touches the closing washer 27, at the pressure limit value VL, whilst the spring 8 continues to exert the closing force FA, which remains constant, the plug 5 is ed by the auxiliary closing force Fcaux determined by and proportional to the thrust that the fluid exerts on the closure promoting surface 16. At this point, the closing force Fe continues to grow due to the increasing component represented by the auxiliary closing force FCaux, which, as said, is the effect ofthe thrust that the fluid upstream exerts on the closure promoting surface 16.

The g force Fe s at this point the growing trend schematised by the second portion oftilted line T2 and has a different tilt from the first line portion n.

AH2S(6890300_1):MLW This particular pattern of the results of forces acting on the plug 5 in function ofthe increase in the pressure ofthe fluid is presented, in schematic mode and by way ofexample, by the line RI. The fact that the line RI has a value equal to zero for a n included from the origin ofthe axes ofthe diagram to the pressure value VL ents a condition ofbalanced forces to which the plug 5 is subjected, which is not affected by ility vibration phenomena.

The sudden change ofpattern ofthe line RI, with a virtually or almost discontinuous method, shown by the portion W, is due to the action ofthe auxiliary closing force Fcaux that suddenly subjects the plug 5 to an "over-closure", making the plug 5 stably pressed against the closing washer 27.

When the valve 1 is already in the closed on, a possible further pressure se of the fluid upstream has the sole effect ofcausing a corresponding and tional increase in the auxiliary closing force Fcaux. This means that when the valve 1 is already in a closed position for limiting the pressure downstream, an undesired pressure peak in the circuit portion upstream ines nothing other than a corresponding force increase that keeps the plug 5 closed, preventing fluid leaks from an am region to a downstream region. The more pressure increases upstream, the more the force increases that keeps the plug 5 closed against the closing washer 27, as the growing tilted n ofthe line RI shows.

In other words a closure in stable equilibrium is obtained, with Fe > FA.

This is made possible owing to the conformation ofthe obstruction-control-portion 14, in particular owing to the presence ofthe closure promoting surface 16 that enables a g force component to be generated that is parallel to the longitudinal axis L and directed to the sealing closing means 7, in particular, the closing washer 27, unlike prior-art devices in which the respective plugs, in the region more upstream, is subject the thrusts ofthe fluid that act only in a direction that is onal to the longitudinal axis and which has no effect on the longitudinal movement ofthe plugs. In particular, the pattern ofthe prior-art re limiting valve is schematised in the diagram in Figure 20. In other words, the prior-art valve, in the closed position C, creates a ious equilibrium, due to the fact that the closing force Fe, from a certain point, i.e. from the value VL onwards, is kept the same as the constant opening force--F A, regardless ofeven a very high increase in the pressure upstream PM. This pattern is represented by the horizontal portion To ofthe closing force Fe and by the horizontal line R2 which represents the resultant of forces acting on the plug 5 and which takes on a null value. Thus, whilst the AH2S(6890300_I):MLW plugs ofthe prior-art valve in the closed position C is in an le brium with FA = Fc and in this situation continues to be maintained even with the increase ofthe upstream pressure PM with the clearly greater risk offluid leaks, in valve 1 ofthe present invention, as the upstream pressure PM increases also the closing force acting on the plug 5, (i.e. the condition Fc > FA is achieved) further stabilising the closed position C. In other words the plug 5 is clamped against the closing washer 27 with a force growing proportionately to the pressure increase upstream PM and this prevents possible fluid leaks. This is made possible owing to the conformation ofthe obstruction control portion 14, and more specifically to the closure promoting surface 16.

The particular shape ofthe closure promoting surface 16, combined with a particular shape ofthe head-surface 15, and with a particular shape ofthe opening-control-surface 23 have been studied to obtain high positional stability of the plug 5, a drive from the open position A to the closed position C of"snap type" i.e. ofthe "ON-OFF" type and less ofthe progressive type, and to obtain an "over-closure" action ofthe plug 5 that makes the plug 5 free of instability and vibrations.

From what has been disclosed and shown in the attached drawings, it is thus clear that the invention is directed to a re l valve that has improved operation and is suitable for achieving the previously mentioned objects and advantages.

What has been said and shown in the attached drawings has been provided merely by way ofexample ofthe innovative features ofthe pressure l valve ofa preferential embodiment; thus other modifications can be made to the entire valve or parts thereof without thereby falling outside the protective scope ofthe claims.

In practice, the als, in the measure in which they are compatible with the specific use and with the respective single components for which they are intended, can be chosen suitably in function ofthe requested requirements and in function ofthe available prior art.

It is possible to configure and dimension the valve 1 and adopt materials in a desired method in function ofthe multiple applications for which the apparatus 1 can be intended and variants andlor additions are possible to what has been disclosed and rated in the ed AH2S(6890300_1 ):MLW

Claims (13)

We Claim

1. Pressure l valve, comprising: a housing body ng a flow path for a fluid between an inlet and an outlet aligned along a longitudinal axis; plug means provided with a through udinal g for said fluid and movable along said longitudinal axis between a closed position, where it couples with sealing closing means to interrupt the flow ofsaid fluid, and an open position to enable said fluid to advance from said inlet to said outlet, counteracting spring means suitable for ng an opening force for pushing said plug means to said open on, said plug means and said racting spring means being configured so that said closed on is reached at a set pressure limit value ofthe fluid downstream, said plug means comprising, near said outlet, an enlarged portion suitable for receiving from the fluid downstream a thrust that generates a closing force contrasting said opening force and acting towards said closed position, said enlarged portion having an external ion, measured transversely to said longitudinal axis, equal to a first value, said plug means further comprising an intermediate portion being slidably coupled with guiding and sealing means and having a respective al transverse dimension that is equal to a second value that is less than said first value, wherein said plug means ses upstream ofsaid intermediate portion near said inlet an obstruction-control-portion having a respective external transverse dimension that is equal to a third value that is greater than said second value, said obstruction-control-portion being movable in a receiving and conveying chamber between said guiding and sealing means and said sealing closing means and comprising, ersely to said longitudinal axis, a head surface configured for abutting on said sealing closing means, and a closure promoting surface, opposite said head surface, facing said guiding and sealing means, and configured for receiving from the fluid in said receiving and conveying chamber a thrust that generates an auxiliary closing force that is proportional to the fluid pressure upstream and is able to ensure that said plug means is stably in said closed position when the fluid pressure downstream is equal to said set pressure limit value.

2. Pressure control valve according to claim 1, wherein said obstruction-control- portion internally comprises an opening-control-surface, arranged transversely with t to said longitudinal axis, shaped for interacting with the flow forces ofthe fluid that from said receiving AH25(6890300_1):MLW and conveying chamber es to the outlet, to maintain in an open position said plug means when the re ofthe fluid downstream is less than said set pressure limit value, said closure promoting surface and said opening-control-surface being configured for obtaining a snap movement ofsaid plug means from said open position to said closed position when the pressure ofthe fluid downstream reaches said set limit pressure value.

3. Pressure control valve according to claim 1 or 2, wherein said enlarged n, said intermediate portion, and said obstruction-control-portion are bound externally respectively by a first cylindrical surface, by a second rical surface and by a third cylindrical surface, which respectively have a first external diameter, a second external diameter that is less than said first al diameter, and a third al diameter, which is greater than said second external diameter, and in which said closure promoting surface and said head surface have an annular shape and lye on tive planes that are parallel to one another and are arranged orthogonally to said longitudinal axis.

4. re l valve according to anyone ofthe ing , further comprising a first receiving and conveying element and a second receiving and conveying element that cooperate to define said sealing g means, and define, together with said guiding and sealing means said receiving and conveying chamber, between said first and said second receiving and conveying element there being defined an annular distributing and passage chamber for said fluid, said annular distributing and passage chamber being located am of said receiving and conveying chamber.

5. Pressure control valve according to claim 4, wherein said sealing closing means comprises a closing washer, and wherein said first receiving and conveying element comprises a first discshaped part, shaped for resting on an abutting surface ofsaid housing body, and a blind protrusion that projects from a first side of said first disc-shaped part intended for facing said plug means, said blind protrusion and said first disc-shaped part defining a first seat portion for said closing washer, on said first disc-shaped part first through openings being obtained that are circumferally distributed for said fluid, on a second side opposite said first side first guiding and distributing walls being provided for directing said fluid to said first through openings.

6. Pressure control valve according to claim 4 or 5, wherein said second receiving and conveying element comprises a second disc-shaped part, conformed for resting on said g AH25(6890300_1):MLW and sealing means and in which second through openings are obtained for said fluid, and a hollow cylindrical protrusion projecting from said second disc-shaped part and shaped for g on said first haped part and for defining a second seat portion for said closing washer, on said second disc-shaped part second guiding and distributing walls being obtained to direct the fluid coming from said second through openings radially to said obstruction-control- portion.

7. Pressure control valve according to anyone ofthe preceding claims, wherein said plug means comprises a first plug-piece that includes said enlarged portion, and a second plug-piece that includes said intermediate portion and said obstruction-control-portion, said first plug-piece and said second iece being ly connected by a ed coupling, on said enlarged portion an annular cavity being ed having a thrust surface shaped for receiving a thrust of the fluid, said annular cavity being configured for locally damping the movement ofthe fluid to prevent alterations to the actual pressure value due to turbulence ofthe fluid.

8. Pressure control valve according to anyone ofthe preceding claims, wherein said housing body comprises a first housing piece and a second housing piece, that are mutually connected by a further threaded coupling, said first housing body sing a boundary wall that cooperates with said guiding and sealing means to define a containing r for said counteracting spring means, on said boundary wall a vent opening being made for said containing chamber.

9. Pressure control valve according to anyone ofthe ing claims, wherein said g and sealing means ses a toroidal element having a counteracting surface for said counteracting spring means and, at an opposite end, a step surface configured for promoting a flow offluid against said closure promoting surface.

10. Pressure control valve according to claim 9 as appended to claim 5 or 6 or to claim 7 or 8 as appended to claim 5 or 6, wherein said g and sealing means comprises an internal sealing ring housed in an internal seat ofsaid toroidal element and suitable for coming into contact with said intermediate portion of said plug means, and an external sealing ring housed in an external seat of said toroidal element and le for resting on a side wall ofsaid second housing body, said toroidal element, said first receiving and conveying element and said second receiving and conveying element being clamped together n said abutting surface and an edge ofsaid boundary wall. AH2S(6890300_1):MLW

11. Pressure control valve according to claim 7 or according to anyone of claims 8 to 10 as appended to claim 7, wherein said first plug piece is made ofbrass or a brass alloy and said second plug piece is made of a highly wearproof material, as steel.

12. Pressure l valve according to claim 10, or according to claim 11 as appended to claim 10, further comprising a further seal ring housed in said g body for acting on said enlarged portion, said internal sealing ring, said external seal ring, said g washer and said further seal ring each being ofthe O-ring type.

13. Pressure control valve, substantially as hereinbefore described with reference to