AU2012258441B2

AU2012258441B2 - Pressure control valve

Info

Publication number: AU2012258441B2
Application number: AU2012258441A
Authority: AU
Inventors: Carlo Medina
Original assignee: Bome SRL
Current assignee: Bome SRL
Priority date: 2012-07-06
Filing date: 2012-11-28
Publication date: 2015-01-22
Anticipated expiration: 2032-11-28
Also published as: NZ603911A; AU2012258441A1; ITMI20121186A1

Abstract

PRESSURE CONTROL VALVE Abstract 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) being configured in such a manner that the closed position (C) is reached at a set limit pressure value (VL) 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 (DI) and the plug (5) comprises an intermediate portion (11) that is slidable on guiding and sealing means (12) and having an external transverse dimension that is equal to a second value (D2) less than the first value (DI). 2a 5a L 8 ~ 14 60 2b pA 4 Fig. 1 53 7 Sb 56 Fig. 2

Description

S&F Ref: P054830 AUSTRALIA PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT Name and Address B6me S.R.L., of Strada Comunale dello Strego 1, 1 of Applicant: 28010, Cavallirio, Italy Actual Inventor(s): Carlo Medina Address for Service: Spruson & Ferguson St Martins Tower Level 35 31 Market Street Sydney NSW 2000 (CCN 3710000177) Invention Title: Pressure control valve The following statement is a full description of this invention, including the best method of performing it known to me/us: 5845c(6909245_1) 1 PRESSURE CONTROL VALVE Technical Field [000 1] The present invention relates to a pressure control valve, that is suitable for controlling, in particular for limiting, the pressure inside a circuit in which a fluid flows, for example water, such as a cooling and/or heating circuit of residential or industrial type. Background of the Invention [0002] Valves are known that are mounted along a circuit to prevent the pressure of the corresponding fluid, in a zone downstream of the valve, exceeding a certain limit. Valves of this type are for example known from AU602199 and from EP1509714. [0003] AU602199 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, comprising a piston provided with a through opening that extends along a longitudinal axis of the valve. [0004] The plug is movable between a closed position, in which an upstream end thereof nearer the inlet presses 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 of the fluid downstream reaches a particular pressure value. [0005] The movable plug comprises a first cylindrical portion, having a first external 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 of the first cylindrical portion. The first external diameter has a constant value along the entire first cylindrical portion.

2 In other words, the first cylindrical portion has an external profile that does not have dimension variations transversely to the longitudinal axis. [0006] The second cylindrical portion, or head of the piston, comprises a downstream end surface, 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 of the second cylindrical portion with respect to the first cylindrical portion, is such as to generate a resulting longitudinal force that acts to push the plug to the closing washer. [0007] If pressure in the outlet zone increases, consequently also the force exerted by the aforesaid end surface downstream increases, thus compressing the spring and, if the pressure reaches an excessive value, the first cylindrical portion reaches the closing washer, thus interrupting the flow of fluid. [0008] A drawback of this 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 of the 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 upstream to downstream occur that are due to the greater fluid pressure upstream. Thus in this situation it is experimentally observed that the pressure value detected downstream of the 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 of a non stable and perfect closure of the 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 subjected in one direction to the action of the spring, which tends to open the passage, and, in an opposite direction, is subjected to a resultant of pressure forces that acts to push the plug to the closed position, in which the value of the force exerted by the spring and the value of the aforesaid resultant of pressure forces are substantially equal. This is a source of vibration and throbbing during valve operation, particularly near the pressure value limit. [0009] It is clear that if the pressure upstream increases progressively, there will be a condition in which the plug comes into contact with the closing washer, but the contact force that they 3 exchange is weak, such that it is unable to prevent fluid leaking from upstream downstream, especially in the event of a sudden and drastic pressure increase in the circuit upstream. [0010] 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 relation 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 smaller cylindrical portion, nearer the inlet, in which the smaller cylindrical portion has a constant external diameter along the entire longitudinal extend thereof, i.e. has an external profile that has not variations in dimensions transversely to the longitudinal axis, and the external cylindrical surface of which 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 of fluid is interrupted, in a slidable manner with a closing washer. In other words, the external surface of the smaller cylindrical portion of the piston, in excessive pressure conditions, is arranged in contact with the closing 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 of the upstream end of the plug rests frontally on the closing washer, in the valve disclosed in EP1509714 it is the side surface of the 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 discussed for AU602199. In the valve disclosed in EP1 509714, 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 of the passage of the fluid and thus ineffective limiting action of the pressure when it is required. [00 11] There is a need to improve prior-art pressure control valves and to provide a solution that is able to overcome the drawbacks inherent in known valves. [0012] In particular, there is a need to provide a more reliable pressure control valve with great effectiveness and operating precision.

4 [0013] 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 of the valve. Object of the Invention [0014] It is an object of the present invention to substantially overcome or at least ameliorate one or more of the disadvantages of the prior art, or to at least provide a useful alternative. Summary of the Invention [0015] 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 provided with a longitudinal through-opening for said fluid and movable along said longitudinal axis between a closed position, in which it couples with sealing closing means for interrupting the flow of said 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 counteracting 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 outlet, an enlarged portion suitable for receiving 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 dimension, measured 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 conveying chamber between said guiding and sealing means and said sealing 5 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 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 proportional to the pressure of the fluid upstream and able to ensure that said plug-means is stably in said closed position when the pressure of the fluid downstream is equal to said set limit pressure value. Brief Description of the Drawings [0016] The invention can be better understood and implemented with reference to the attached drawings, which illustrate an embodiment thereof by way of non-limiting example, in which: [0017].Figure l is a longitudinal section of the pressure control valve in an open position; [0018] Figure 2 is an enlarged detail of Figure 1; [0019] Figure 3 is a longitudinal section of the pressure control valve in a closed position; [0020] Figure 4 is an enlarged detail of Figure 3; [0021] Figure 5 shows schematically the flow of a fluid along the pressure control valve; [0022] Figure 6 is an exploded view of the pressure control valve; [0023] Figure 7 shows in detail a part of plug means included in the pressure control valve, in particular an obstruction-control-portion is shown; [0024] Figures 8 and 10 are respectively a side view and a longitudinal section view of the pressure control valve; [0025] Figure 9 is a first cross section of the valve taken along a plane IX-IX in Figure 8; [0026] Figure I I is a second cross section of the valve taken along a plane XI-XI in Figure 10; [0027] Figure 12 is a third cross section of the valve taken along a plane XII-XII in Figure 10; 6 [0028] Figures 13 and 14 are two different perspective views of a first receiving and conveying element of the valve; [0029] Figures 15 and 16 are two different perspective views of a second receiving and conveying element of the valve; [0030] Figures 17 to 19 show three different operating positions of the pressure control valve, in particular of the plug means, respectively an open position, an intermediate position and a closed position; [0031] Figure 20 is a diagram that illustrates the operation of a prior-art valve; and [0032] Figure 21 is a diagram that illustrates the operation of the pressure control valve. Detailed Description [0033] With reference to the attached Figures, a pressure control valve 1 is shown that is suitable for being fitted, in general, in a circuit in which a fluid runs, for preventing the pressure of the fluid in a zone downstream of the fluid with respect to an advance direction overcoming a set potentially harmful pressure limit value. The pressure control valve 1 thus has the function of limiting the pressure of the fluid downstream. [0034] The pressure control valve I 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 of two pieces, in particular a first piece of housing body 2a and a second piece of housing body 2b that are connected together by a first threaded coupling 13. [0035] 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 of fluid. 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.

7 [0036] The closing washer 27 is in particular of the "O-ring" type but can also be of a different type, for example flat with a square section, etc. [0037] The pressure control valve I is provided with contrast-means 8, or elastic counteracting means 8, comprising in particular a helical compression spring 8 that is arranged for exerting an opening force FA that 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 of the fluid that is found downstream of the plug 5 with respect to the advance direction of the fluid. [0038] The plug 5 comprises, at an end 9 thereof nearer the outlet 4, an enlarged portion 10 configured for receiving from the fluid downstream a thrust action that determines a closing force Fc acting in an opposite direction to the aforesaid opening force FA and tending to take the plug 5 to the closed position C. [0039] The enlarged portion 10 is slidably housed in the first piece of housing body 2a, in which a respective seal ring 31, for example of the "O-ring" type, is housed, to prevent leaks of the fluid to the exterior. [0040] In the open position A, the enlarged portion 10 is maintained abutting on a stop surface 70. [0041] The enlarged portion 10 extends transversely to the longitudinal axis L with an external dimension having a first value DI. In particular, the enlarged portion 10 is bounded externally by a cylindrical surface and has an external diameter equal to the aforesaid first value D1 (Figure 17, 18). [0042] In particular, on the enlarged portion 10 an 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 of the fluid downstream. The annular cavity enables a zone to be defined that is sheltered from the turbulences of the fluid, to prevent the enlarged 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 of the static pressure or laminar and non-turbulent operating pressure of the 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 locally dampening the movement of the fluid to 8 prevent the actual pressure value being altered by the turbulences of the fluid. In this manner, driving of the plug 5, which is very precise, depends on the actual pressure downstream and is not disturbed by local turbulent phenomena of the fluid. [0043] The plug 5 comprises an intermediate portion 11 that projects to a zone upstream of the 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 D1 mentioned above. In particular, the intermediate portion 11 is bounded externally by a respective cylindrical surface and has an external diameter equal to the aforesaid second value D2. [0044] The plug 5 comprises, upstream of the 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 of the 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 arranged for moving in a receiving and conveying chamber 30 defined between the guiding and sealing means 12 and the sealing 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 guiding and sealing means 12 and configured for receiving from the fluid in the receiving and conveying chamber 30 an auxiliary closing thrust SA that is proportional to the fluid pressure upstream, in particular 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 of the fluid measured downstream of the plug 5, is equal to the set limit pressure value VL. [0045] 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 5a of plug that includes the enlarged portion 10, and by a second piece of plug 5b that includes the intermediate portion 11 and the obstruction-control-portion 14. The first piece 5a of plug and the second piece 5b of plug are connected together by a second threaded coupling 17. In particular, the first piece 5a of plug is made of brass, which is a material that during manufacture enables the first piece 5a to be machined easily on the machine tools and that ensures good resistance to water or fluid in 9 general with which it interacts. The second piece 5b of plug is made of a material with great mechanical resistance, which is in particular resistant to wear and is able to resist critical conditions that may be generated by the speed and/or pressure of the circulating fluid, in particular near the obstruction-control-portion 14 where the stress exerted by the fluid is greater. In a non-limiting embodiment, the second piece 5b of plug is made of a material comprising steel. [0046] 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 contrast surface 18 for the spring 8, and, at an opposite end, a step surface 19 configured for promoting a flow of fluid against the closure 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 of the "O-ring" type, housed in an internal seat of the toroidal element and suitable for coming into contact with the intermediate portion I1 of the plug 5, and an external seal ring 21, for example of the "O-ring" type, housed in an external seat of the toroidal element 56 and suitable for resting on a side wall 22 of the second housing body 2b. [0047] The contrast-surface 18, together with a boundary wall 54 of the first housing body 2a define a containing chamber 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. [0048] The obstruction-control-portion 14 comprises internally an opening-control-surface 23, arranged transversely to the longitudinal axis L, which interacts with the flow-forces of the fluid advancing from the receiving and conveying chamber 30 to the outlet 4 to maintain in the open position A the plug 5 until the pressure of the fluid downstream 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 longitudinal axis L, results in the dynamic thrust of the fluid thereupon giving rising to a force having a component parallel to the aforesaid axis, which tends to keep the plug 5 open. [0049] The closure promoting surface 16 and the opening-control-surface 23 are suitably configured and cooperate to obtain a snap movement of the plug 5 from the open position A to the closed position C when the pressure of the fluid downstream reaches precisely the aforesaid pressure limit VL value. In other words, the combined action of the closure promoting surface 16 10 and of the opening-control-surface 23 interacting with the fluid-flow-forces is such as to cause a sudden movement of the 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 of the moving fluid exert on the opening-control-surface 23. [0050] 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 of the plug 5 to the closing washer 27, thus preventing vibration phenomena arising. Thus advantageously, an operation of the valve I is obtained that is more stable, clear and precise than with prior-art devices. [0051] If the pressure of the fluid increases until it reaches 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 between the transverse head 15 and the closing washer 27 has a speed that is greater than the speed of the fluid near the closure promoting surface 16; thus the pressure exerted by the fluid on the closure promoting surface 16 is greater 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 reduction 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 of sucking phenomenon is obtained that suddenly causes the plug 5 to close completely. In other words, on the obstruction control-portion 14 auxiliary closing thrust SA of the fluid upstream remains to act and continues to act on the closure 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 detected that is equal to the limit value VL. If with the plug 5 in closed position C peaks or overpressure that may be significant should occur upstream of the plug 5, such peaks or overpressure, owing to the closure promoting surface 16, would translate into a corresponding increase of the auxiliary closing force Fcaux, in a manner proportional to the value thereof. This would cause even greater tightening of the 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 S1I downstream of the valve I from possible damages. When pressure again falls to acceptable values, the action of the counteracting spring 8 returns the plug 5 to the open position A. Thus the area of the closure promoting surface 16 is carefully chosen to obtain both the effect of increasing closing stability of the plug 5, whilst at the same time ensuring that once pressure downstream stabilises at acceptable levels, the valve 1 is able to restore the passage of the fluid. [0052] The closure promoting surface 16 and the head-surface 23 have an annular shape and are arranged transversely to the longitudinal 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. [0053] 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 of the second piece 2b of housing body, and a blind protrusion 43 that projects from a first side 44 of the first disc-shaped part 42 intended for facing the plug 5. The blind protrusion 43 and the first disc shaped 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 guiding and distributing walls 47 for directing the fluid into the first through openings 45. [0054] The first through openings 45 comprise openings such as circular holes and are distributed evenly and angularly spaced apart from one another. Openings of different shape can nevertheless be provided, for example openings with circular sectors or other shapes that are suitable for performing the same function in an equivalent manner. [0055] With reference to figures 15 and 16, the second receiving and conveying element 41 comprises a second disc-shaped part 48, shaped for resting on the toroidal element of the guiding and sealing means 12, on which second through openings 49 for the fluid are obtained. A hollow cylindrical 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 of the 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 obstruction control-portion 14.

12 [0056] The second through openings 49 comprise openings, such as holes, of circular 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. [0057] The first receiving and conveying element 40 and the second receiving and conveying element 41 are reciprocally coupled and clamped between the toroidal element 56 and the abutting surface 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 upstream of the receiving and conveying chamber 30. [0058] In the following, with reference to Figures 17 to 19 the operation of the pressure control valve 1 in function of the pressure of the 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 FAI determined by the counteracting spring means 8 but also by the interaction of the opening-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 FAI and the first closing force Fci have an equal value but in opposite directions, determining a balance of the plug means 5 in the open position A, with the enlarged portion 10 that is maintained abutting on the stop surface 70. [0059] In Figure 18 a second position is shown in which the plug 5, in a position 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 subjected to a second opening force FA 2 of the spring 8 and to a second closing force Fc 2 generated by the thrust of the fluid on the enlarged portion 10. [0060] 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 of the spring, an equal and opposite third closing force Fc 3 generated by the fluid, and moreover an auxiliary closing force Fcaux generated by the thrust that the fluid upstream exerts on the closure promoting surface 16. The auxiliary closing force Fcaux is proportional to the fluid pressure upstream. [0061] In the description just made with reference to Figures 17 to 19 in a manner emphasised by the growing arrows FA I, FA2, FA3, a substantial increase has been considered of the force 13 generated by the spring 8. Nevertheless, the following 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 position A, is already at an important compression 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 of the order of one or a few millimetres and consequently so is also the further 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 deemed, 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 position 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 of the valve I of the present invention. [0062] In particular, in the diagram in Figure 21, the trend can be noted of opposite forces that act on the plug 5 according to a progressive increase in the pressure PM of the fluid located upstream of the plug means 5. [0063] If the pressure upstream of the fluid increases, the closing force Fc exerted by the fluid on the plug also increases proportionally, as shown by the first tilted line TI, until it arrives at a point in which the closing force Fc is equal to the opening force FA, as the respective and equal quantities show that are indicated by y [0064] 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 affected 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 Fc continues to grow due to the increasing component represented by the auxiliary closing force Fcaux, which, as said, is the effect of the thrust that the fluid upstream exerts on the closure promoting surface 16. The closing force Fc assumes at this point the growing trend schematised by the second portion of tilted line T2 and has a different tilt from the first line portion T1.

14 [0065] This particular pattern of the results of forces acting on the plug 5 in function of the increase in the pressure of the fluid is presented, in schematic mode and by way of example, by the line R 1 . The fact that the line R, has a value equal to zero for a portion included from the origin of the axes of the diagram to the pressure value VL represents a condition of balanced forces to which the plug 5 is subjected, which is not affected by instability vibration phenomena. The sudden change of pattern of the line R 1 , with a virtually or almost discontinuous method, shown by the portion W, is due to the action of the 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. [0066] When the valve 1 is already in the closed position, a possible further pressure increase of the fluid upstream has the sole effect of causing a corresponding and proportional 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 determines nothing other than a corresponding force increase that keeps the plug 5 closed, preventing fluid leaks from an upstream 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 pattern of the line R, shows. [0067] In other words a closure in stable equilibrium is obtained, with Fc > FA. [0068] This is made possible owing to the conformation of the obstruction-control-portion 14, in particular owing to the presence of the closure promoting surface 16 that enables a closing 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 of the fluid that act only in a direction that is orthogonal to the longitudinal axis and which has no effect on the longitudinal movement of the plugs. In particular, the pattern of the prior-art pressure limiting valve is schematised in the diagram in Figure 20. In other words, the prior-art valve, in the closed position C, creates a precarious equilibrium, due to the fact that the closing force Fc, from a certain point, i.e. from the value VL onwards, is kept the same as the constant opening force FA, regardless of even a very high increase in the pressure upstream PM. This pattern is represented by the horizontal portion To of the closing force Fe and by the horizontal line R 2 which represents the resultant of forces acting on the plug 5 and which takes on a null value. Thus, whilst the 15 plugs of the prior-art valve in the closed position C is in an unstable equilibrium with FA =Fc and in this situation continues to be maintained even with the increase of the upstream pressure PM with the clearly greater risk of fluid leaks, in valve 1 of the 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 of the obstruction control portion 14, and more specifically to the closure promoting surface 16. [0069] The particular shape of the closure promoting surface 16, combined with a particular shape of the head-surface 15, and with a particular shape of the 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. of the "ON-OFF" type and less of the progressive type, and to obtain an "over-closure" action of the plug 5 that makes the plug 5 free of instability and vibrations. [0070] From what has been disclosed and shown in the attached drawings, it is thus clear that the invention is directed to a pressure control valve that has improved operation and is suitable for achieving the previously mentioned objects and advantages. [0071] What has been said and shown in the attached drawings has been provided merely by way of example of the innovative features of the pressure control valve of a preferential embodiment; thus other modifications can be made to the entire valve or parts thereof without thereby falling outside the protective scope of the claims. [0072] In practice, the materials, 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 of the requested requirements and in function of the available prior art. [0073] It is possible to configure and dimension the valve 1 and adopt materials in a desired method in function of the multiple applications for which the apparatus 1 can be intended and variants and/or additions are possible to what has been disclosed and illustrated in the attached drawings.

Claims

1. 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 provided with a through longitudinal opening for said fluid and movable along said longitudinal axis between a closed position, where it couples with sealing closing means to interrupt the flow of said 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 counteracting spring means being configured so that said closed position is reached at a set pressure limit value of the 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 dimension, 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 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 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, transversely 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 respect to said longitudinal axis, shaped for interacting with the flow forces of the fluid that from said receiving 17 and conveying chamber advances to the outlet, to maintain in an open position said plug means when the pressure of the 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 of said plug means from said open position to said closed position when the pressure of the fluid downstream reaches said set limit pressure value.

3. Pressure control valve according to claim 1 or 2, wherein said enlarged portion, said intermediate portion, and said obstruction-control-portion are bound externally respectively by a first cylindrical surface, by a second cylindrical surface and by a third cylindrical surface, which respectively have a first external diameter, a second external diameter that is less than said first external diameter, and a third external 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 respective planes that are parallel to one another and are arranged orthogonally to said longitudinal axis.

4. Pressure control valve according to any one of the preceding claims, further comprising a first receiving and conveying element and a second receiving and conveying element that cooperate to define said sealing closing 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 upstream 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 disc shaped part, shaped for resting on an abutting surface of said 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 guiding 18 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 resting on said first disc-shaped 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 any one of the 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 plug-piece being mutually connected by a threaded coupling, on said enlarged portion an annular cavity being obtained having a thrust surface shaped for receiving a thrust of the fluid, said annular cavity being configured for locally damping the movement of the fluid to prevent alterations to the actual pressure value due to turbulence of the fluid.

8. Pressure control valve according to any one of the 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 comprising a boundary wall that cooperates with said guiding and sealing means to define a containing chamber for said counteracting spring means, on said boundary wall a vent opening being made for said containing chamber.

9. Pressure control valve according to any one of the preceding claims, wherein said guiding and sealing means comprises 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 of fluid 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 guiding and sealing means comprises an internal sealing ring housed in an internal seat of said 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 suitable for resting on a side wall of said second housing body, said toroidal element, said first receiving and conveying element and said second receiving and conveying element being clamped together between said abutting surface and an edge of said boundary wall. 19

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

12. Pressure control valve according to claim 10, or according to claim I I as appended to claim 10, further comprising a further seal ring housed in said housing body for acting on said enlarged portion, said internal sealing ring, said external seal ring, said closing washer and said further seal ring each being of the 0-ring type.

13. Pressure control valve, substantially as hereinbefore described with reference to Figures 1 to 19 and 21 of the accompanying drawings. Dated 27 November 2012 Bome S.R.L. Patent Attorneys for the Applicant/Nominated Person SPRUSON & FERGUSON