EP2631517A1

EP2631517A1 - Load holding valve

Info

Publication number: EP2631517A1
Application number: EP13156196.1A
Authority: EP
Inventors: Christian Storci; Karel Rozenhart
Original assignee: Atlantic Fluid Tech SRL
Current assignee: Atlantic Fluid Tech SRL
Priority date: 2012-02-22
Filing date: 2013-02-21
Publication date: 2013-08-28
Anticipated expiration: 2033-02-21
Also published as: EP2631517B1; ITMO20120042A1

Abstract

A load-holding valve (1) comprises: a body (2) provided with a plurality of openings (3, 4, 5) through which a pressurised fluid can enter, or exit, the valve (1); a main piston (30); throttling means (50) intended for being traversed by the pressurised fluid; the valve comprises piloting means (10) that can alternatively assume an open configuration (O), in which the piloting means (10) enables a portion of pressurised fluid to pass into a piloting chamber (68) for moving the main piston (30) along a direction (X) that is substantially parallel to a longitudinal axis (A), and a closed configuration (I) in which the piloting means (10) prevents the passage of the fluid and the main piston (30) is moved in the direction (X) by the pressurised fluid that reaches the piloting chamber (68) after traversing the throttling means (50).

Description

The invention relates to a load-holding valve traversed by a pressurised fluid.
Load-holding valves are piloted valves that are typically used in the field of earth-moving machines. These valves are arranged for supporting even very high suspended loads, such as, for example, an articulated arm of an excavator, and for maintaining the aforesaid suspended loads in a desired position for a preset interval of time.
These valves are supplied and traversed by a pressurised fluid, which is sent to an actuator, usually a double-action hydraulic piston, which is in turn connected to the arm to be supported.
Known valves comprise a main channel, extending longitudinally along a body of the valve, within which various known valve components are received - amongst which a main piston that is movable longitudinally - arranged for permitting or preventing the passage of the pressurised fluid according to the mutual arrangement thereof.
In the valve body a plurality of openings is made, each of which is in communication with the main channel through a respective conduit and is arranged for enabling the pressurised fluid to enter or exit the valve. Known valves thus comprise a first opening and a second opening through which, in a load-lifting step, the pressurised fluid respectively enters the body of the valve, and leave the valve to reach the actuator. On the other hand, in a load-lowering step, the pressurised fluid enters the valve from the second opening and exits from the valve through the first opening. The flow of pressurised fluid from the second opening to the first opening would, however, not be allowed, by the reciprocal arrangement of the aforesaid known components. When it is desired to lower the suspended load, the valve is thus piloted so as to enable the fluid reaching the valve from the actuator to exit through the first opening.
In the piloting step, further pressurised fluid is delivered inside the valve body through a piloting opening. From the piloting opening the pressurised fluid reaches the main channel, where the pressurised fluid is passed through a throttle before reaching a piloting chamber. Here, the further pressurised fluid acts on the main piston and pushes the main position into a position that is such as to enable the aforesaid fluid to flow from the second opening to the first opening.
The throttle is, for example, achieved by a threaded connection between a piloting element and the walls of a portion of said main channel. In this case, the further pressurised fluid flows through the helical channel defined by the space left free between the thread of the piloting element and a complementary thread of the wall of the main channel. In a head portion of the piloting element that projects outside the body of the valve an adjusting device is obtained by means of which an operator can adjust the screwing of the piloting element inside the main channel. In this manner the operator can adjust the length of the helical channel defined between the thread and the complementary thread and through which the further pressurised fluid flows. In particular, greater screwing of the piloting element inside the main channel correspond to a greater length of the helical channel, through which the further pressurised fluid accordingly takes longer to flow.
The flowrate of the further operating fluid to the piloting chamber is proportional to the length of the helical channel.
Alternatively, the throttle can consist of a dowel that considerably restricts the volume through which further pressurised fluid can flow.
One drawback of known valves is the fact that throttling delays driving in the execution of the operation (i.e. in this case the lowering of the load) controlled by the operator piloting the valve. In use, a few seconds elapse between the instant in which the operator commands the load to lower (by driving, for example, a manual joystick of normal type) and the instant in which the load actually starts to lower.
This delay is particularly unwelcome for operators because, beyond causing the operation of the machine to slow, the delay makes it more inconvenient to control and command the machine.
Further, it should be noted that this delay is further accentuated when the pressurised fluid is more viscous, as typically occurs when there are very low external ambient temperatures (for example in winter).
The driving delay is thus considered to be a serious drawback by the operators, especially at low winter temperatures.
In order to overcome this drawback, in theory the throttle could be eliminated so that the further pressurised fluid that enters the valve through the piloting opening reaches the piloting chamber for moving the main piston directly.
Nevertheless, this causes another serious drawback for the valve, which would not be appropriately stable without a throttle. When the valve is not stable, an irregular or turbulent flow of pressurised fluid can, for example, be generated that then causes instability also in the machine with which the valve is associated. In particular, this can lead to sudden and/or uncontrolled movements of the suspended load, for example of the articulated arm, and occurs above all when the valve opens and closes frequently over a short period.
The piloting element of the known valves disclosed above thus has to be screwed in such a manner as not to cause the valve an excessive driving delay or instability.
This is achieved by adjusting screwing of the piloting element during fitting of the valve. A further drawback of known valves arises from the fact that the adjusting operation is extremely delicate and laborious. This complex adjusting is performed by the operator substantially empirically inasmuch as the operator adjusts the screwing of the piloting element by trial and error. It is clear that the aforesaid adjusting operation takes a long time to be performed and terminates only when the operator obtains a driving delay and instability that are acceptable.
One object of the invention is to improve known piloted valves.
Another object is to provide a load-holding valve that is substantially devoid of an actuation delay between the instant in which the operator drives the piloting and the instant in which the suspended load starts to move.
A further object is to provide a load-holding valve that is stable and is at the same time simple and fast to adjust.
According to the invention, a load-holding valve as defined in claim 1 is provided.
The invention can be better understood and implemented with reference to the attached drawings, which show an embodiment thereof by way of non-limiting example, in which:

Figure 1 is a longitudinal section of a valve according to the invention, shown in a first operating configuration;
Figure 2 is a section like the one in Figure 1, in which the valve is shown in a second operating configuration;
Figure 3 is an enlarged portion of Figure 1;
Figure 4 is an enlarged portion of Figure 2.

Figures 1 and 2 show a piloted valve 1 in a first operating configuration K (Figure 1) and in a second operating configuration J (Figure 2).
The valve 1 comprises a body 2 provided with a plurality of openings through which the pressurised fluid can enter or exit the valve 1. These openings thus enable the valve 1 to be connected to a hydraulic circuit of a machine (not shown), for example an earth-moving machine. In particular, a first opening 3, a piloting opening 4 and a second opening 5 are visible, the function of which will be explained in detail below.
In the body 2 a first through cavity 8 is made that extends between two opposite walls of the body 2 in a manner that is substantially parallel to a first longitudinal axis A of the valve 1. The first cavity 8 comprises a plurality of portions having, for example, a substantially cylindrical cross section. The portions have diameters that are different from one another and are made in succession along the axis A.
The first opening 3 is connected to the first cavity 8 by means of a first channel 3a, the piloting opening 4 is connected to the first cavity 8 by means of a piloting channel 4a and the second opening 5 is connected to the first cavity 8 by means of a second channel 5a. In the body 2 a second cavity 9 is further made that extends substantially parallel to a second longitudinal axis B of the valve 1, which is in turn substantially parallel to the axis A. The first cavity 8 and the second cavity 9 are thus parallel to one another.
As shown with greater detail in Figures 3 and 4, the valve 1 comprises piloting means 10 that can alternatively assume an open configuration O (Figure 3), in which the piloting means 10 permits the passage of a portion of fluid, and a closed configuration I (Figure 4), in which the piloting means 10 prevents the aforesaid passage.
The piloting means 10 is provided with a screw element 11 that in turn comprises a first portion 11a - projecting outside the body 2 - and a second portion 11b received in the cavity 8. The screw element 11 is coaxial to the axis A and is provided, on an external wall thereof facing the walls of the first cavity 8, with a thread arranged for coupling with a respective complementary thread, made on the walls of the first cavity. In this manner, a threaded connection 7 is formed that enables the piloting means 10 to be removably connected to the body 2. The threaded connection 7 is made at a zone of the second portion 11b near the first portion 11a.
The piloting means 10 comprises an elastic element 14, for example a coil spring that is received in a cavity 13 extending inside the screw element 11 substantially parallel to the axis A (Figure 3; Figure 4).
The elastic element 14 acts by pressing on an abutting element 15, for example a T-shaped abutting element 15, the head of which contacts a shutting element 45, for example with a spherical shape. The shutting element 45 is positioned inside the cavity 13 in such a manner as to face a through hole 46 with a lower cross section than the cross section of the cavity 13. The hole 46, which is symmetrical to the axis A and thus coaxial to the cavity 13, extends in a terminal end of the portion 11b from a part opposite the portion 11a, and connects the cavity 13 to a piloting chamber 68 defined in the first cavity 8.
Inside the hole 46 is received, at least partially, a piloting piston 37, for example a T-shaped piloting piston 37. The piloting piston 37 comprises a body 47, which extends prevalently inside the hole 46, and a head portion 57, received in the aforesaid piloting chamber 68.
In the screw element 11, a side hole 48 is further made, having an axis that is substantially orthogonal to the axis A. The side hole 48 enables the cavity 13 to be connected to the piloting channel 4a, and is made in a position that is near the hole 46. The side hole 48 is arranged for being traversed by a portion of piloting fluid entering the body 2 through the piloting opening 4 and flowing through the piloting channel 4a. This portion of piloting fluid enters the side hole 48, leads into the cavity 13 and flows through the hole 46 and finally reaches the piloting chamber 68.
On the outer wall of the screw element 11, downstream of the side hole 48, a seat is obtained in which a first seal element 58 is housed, for example an O-ring made of a polymeric material. The first seal element 58 causes the entire portion of piloting fluid entering the piloting means 10 to flow along the path disclosed above (through the side hole 48, the cavity 13 and the hole 46), preventing part of this flow from reaching the piloting chamber 68 by flowing through the first cavity 8, i.e. outside the screw element 11.
The first portion 11a comprises first adjusting means 6 that an operator can use to adjust the preload of the elastic element 14. The adjusting means 6 can comprise a dowel 6a in contact with the elastic element 14. The operator can thus adjust the adjusting means 6 in such a manner that the elastic element 14 always maintains minimum pressure on the piloting piston 37.
Around the first portion 11a a locking element 59 is screwed, for example a nut, which prevents the screw element 11 from being accidentally unscrewed from the body 2.
The valve 1 comprises a containing element 16 received, at least partially, inside the first cavity 8 and fixed to the body 2 of the valve 1 by a threaded connection 17. On an external side wall portion of the containing element 16 a thread is made, arranged for coupling with a respective thread made on an internal side wall of the first cavity 8. The containing element 16 is internally hollow, in such a manner as to define a chamber 61 therein (which will be disclosed with greater detail below).
The containing element 16 comprises an internal portion 18, received in the first cavity 8, and an external portion 19, that projects outside the body 2 of the valve. Between the internal portion 18 and the external portion 19 a second sealing element 20 is arranged, for example an O-ring made of polymeric material, that annularly surrounds the containing element 16. The second sealing element 20 is housed in a seat obtained on the external side wall of the containing element 16 and enables the first cavity 8 to be sealingly closed. The internal portion 18 is provided with an end 21 (opposite the external portion 19), on which a plurality of passages are made. The latter are shaped as semicircular recesses and are made in succession on a terminal edge of the end 21, which is shaped as a hollow cylinder.
On the containing element 16 a passage 62 is made that conduit-shaped and connects the internal cavity of the containing element 16, i.e. the chamber 61, to the first channel 3a.
The valve 1 further comprises a main piston 30, that extends substantially parallel to the first longitudinal axis A and is received inside the first cavity 8. The main piston 30 is movable bidirectionally according to the directions indicated by the arrows X and Y, parallel to the axis A. The main piston 30 is thus substantially aligned on the screw element 11 as both are coaxial to the axis A. The main piston 30 comprises a head portion 32 that is cylindrical and enclosed inside the containing element 16, an intermediate portion 33 and an end portion 34, the intermediate portion 33 having a radial extension (i.e. a diameter) that is less than the head portion 32 and the end portion 34. Between the head portion 32 and the intermediate portion 33 a connecting portion 52 is interposed, arranged in use substantially at the end 21, and comprising a first zone 52a with a cylindrical section and a second zone 52b with a hemispherical section.
The containing element 16 further encloses a spring 41 acting on a centring element 42 that presses on the main piston 30, in particular on a base wall of the head portion 32. The centring element 42 has a substantially conical shape, which is complementary to the shape of the aforesaid base wall, and ensures that the force exerted by the spring 41 on the main piston 30 is balanced, i.e. is substantially directed along the axis A. The spring 41 is preloaded and is maintained compressed by a pushing element 43 that is fixed to the internal side wall of the containing element 16 by a threaded coupling 67. On the pushing element 43 a cover 44 is screwed by acting on which an operator can adjust the preload of the spring 41.
In the first cavity 8 a movable seat 22 is also received that has the shape of a bushing (and is thus internally hollow), arranged near the end 21 of the containing element 16. The movable seat 22 comprises a pair of annular ridges 23 that contact the walls of the first cavity 8, so as to separate the first channel 3a and the second channel 5a. A third sealing element 24 is interposed between the annular ridges 23 to ensure a sealing closure. The movable seat 22 is movable bidirectionally according to the directions X and Y, parallel to the axis A. In particular, as will be explained in greater detail below, the movable seat 22 is moved along the direction Y by the pressurised fluid and is moved along the direction X owing to the presence of a spring 25 arranged outside the movable seat 22 and acting on the pair of annular ridges 23.
The position of the spring 25, which is outside the movable seat 22, is advantageous as in this manner the spring 25 is less subject to stress - and thus to wear - than is the case in which the spring 25 is arranged inside the movable seat 22. This is due to the fact that in the latter case the spring 25 is always immersed in the fluid that traverses the first cavity 8. On the other hand, the spring 25 is more protected - as it is only partially affected by the flow of fluid - when it is positioned outside the movable seat 22.
The end portion 34 of the main piston 30 is received in a portion of the first cavity 8 having substantially the same radial dimension. In the operating configuration K of the valve 1, the end portion 34 abuts on a shoulder 60 of the first cavity 8, which is visible enlarged in Figures 3 and 4. On the external side wall of the end portion an annular groove is made that acts as a seat for a fourth sealing element 35, for example an O-Ring. Between the end portion 34 and the screw element 11 the piloting chamber 68 is interposed, where the head portion 57 of the piloting piston 37 is arranged that contacts the end portion 34.
A connecting channel 26 arranged transversely to the first cavity 8 and to the second cavity 9 leads into the piloting chamber 68. The connecting channel 26 connects the first cavity 8 and the second cavity 9 and leads onto an outer wall of the body 2 of the valve. The connecting channel 26 is closed by a threaded cap 27 provided with a sealing washer 27a.
The valve 1 further comprises throttling means 50 that is received inside the second cavity 9. The throttling means 50 comprises a closing element 70, which is fixed to the body 2 by a threaded connection 71. The latter comprises a thread that is made on an external side wall portion of the closing element 70, and a complementary thread, which is made on an internal side wall of the second cavity 9. With the closing element 70 a second locking element 72 is associated, for example a nut, which annularly surrounds the closing element 70 and prevents the latter from being accidentally unscrewed from the body 2. The closing element 70 comprises second adjusting means 53 - comprising a through hole made in a portion of the closing element 70 outside the body 2 - by means of which an operator can adjust (by means of a suitable instrument) the degree of screwing of the throttling means 50 inside the second cavity 9.
The throttling means 50 further comprises a threaded connection 49 between the outer wall of the closing element 70 and the internal walls of the second cavity 9. The threaded connection 49, which throttles the flow of fluid, is crossed by the remaining portion of the piloting fluid that does not enter the side hole 48. In particular, this portion of piloting fluid flows through the helical channel defined by the space left free between the thread of the closing element 70 and the complementary thread on the wall of the second cavity 9.
In one version, the threaded connection 49 can be replaced by any other suitable throttling device, as for example a dowel.
In another version, throttling can be achieved by two elements that are coaxial and partially penetrate one another in such a manner that between the internal element and the external element a passage is defined through which the fluid can flow. The aforesaid two elements can be shaped in such a manner that the walls defining the meatus are conical or cylindrical.
Inside the closing element 70 a check valve 51 of known type is housed that enables the fluid in the connecting channel 26 to flow to the piloting channel 4a, whereas the check valve 51 prevents the fluid from flowing in the opposite direction. When, in fact, the operator terminates the piloted operation, the connecting channel 26 (together with the piloting chamber 68) has to empty rather rapidly in such a manner that the main piston 30 again obstructs the passage between the first channel 3a and the second channel 5a, as will be explained in greater detail below. Further, it should be noted that the check valve 51 can also act as a safety valve that enables the fluid to flow from the connecting channel 26 to the piloting channel 4a when inside the connecting channel 26 the pressure of the fluid exceeds a set threshold temperature.
The check valve 51 comprises a spherical element 54 that is maintained pressed by a spring 55 against an axial hole 56 (coaxial to the axis B), as shown in Figure 1. The spring 55 is preloaded in such a manner as to ensure that it always exerts minimum pressure on the spherical element 54 to close the axial hole 56. When the pressure of the fluid in the connecting channel 26 is greater than the pressure exerted by the spring 55 on the spherical element 54, the flow of the fluid moves the latter and compresses the spring 55 in such a manner that the fluid can reach the piloting channel 4a.
The operation of the valve 1 is disclosed below, with particular reference to the case in which the latter is comprised in an earth-moving machine.
When it is desired to lift a load, the pressurised fluid, for example an oil provided with suitable chemical and physical properties, enters the valve 1 through the first opening 3 communicating with the first cavity 8 via the first channel 3a.
The pressurised fluid reaches the movable seat 22 and moves the latter in the direction Y, thus moving the movable seat 22 away from the end 21 of the containing element 16. This is due to the high pressure of the fluid, which is able to overcome the elastic force of the spring 25. In the absence of fluid, on the other hand, the spring 25 acts on the movable seat 22, maintaining the latter abutting on the second hemispherical zone 52b of the connecting portion 52 of the main piston 30.
The pressurised fluid then traverses the passage that is defined between the movable seat 22 and the connecting portion 52 and can then flow, inside the movable seat 22, to the second channel 5a. Through the second opening 5, the fluid exits the body 2 and moves to actuating means, which is comprised in the machine and is in this manner driven to lift the load.
When it is desired to lower the load, the valve 1 is initially in the first operating configuration K and the pressurised fluid exiting the actuating means enters the valve 1 through the second opening 5. The flow of this fluid causes the seat 22 moving in the direction X until it abuts on the end 21 of the containing element 16 (Figure 2). Simultaneously, via the piloting opening 4 a volume of piloting fluid enters the body 2 and flows along the channel 4a. A portion of this piloting fluid enters the side hole 48, flows through the hole 46 and reaches the piloting chamber 68, where it starts to push the main piston 30.
The latter starts to move in the direction X, whilst the second hemispherical zone 52b is still in contact with the seat 22. After the main piston 30 has performed this initial movement, also known as the pre-stroke movement, the valve 1 is in the second operating configuration J. The pre-stroke is typically of a very limited size, the pre-stroke is, for example, equal to 0.8 mm, and ensures that undesired detachments between the main piston 30 and the seat 22 do not occur sooner than required. Whilst the main piston performs the pre-stroke, the remaining piloting fluid continues to flow through the piloting channel 4a as far as the throttling means 50. In the latter, the fluid flows through the helical channel defined by the threaded connection 49 and leads into the connecting channel 26, then reaching the piloting chamber 68. In the latter the fluid exerts a pushing action that enables the main piston 30 to be pushed further in the direction X.
The main piston 30 subsequently moves inwards the containing element 16, in such a manner that the connecting portion 52 no longer abuts on the end 21 of the containing element 16 (and the second hemispherical zone 52b is no longer in contact with the seat 22). In this manner, the passages of the end 21 are no longer closed by the connecting portion 52 and the pressurised fluid entering from the second opening 5 can traverse the aforesaid passages after flowing through the second channel 5a, a portion of the first cavity 8 (inside the seat 22), and the first channel 3a, so as to exit the body 2 of the valve 1 through the first opening 3.
When the main piston 30 starts to move owing to the action of the pressurised fluid that reaches the piloting chamber 68 from the connecting channel 26, the piloting means 10 closes. In particular, the pressure of the portion of piloting fluid that passes into the hole 46 is no longer able to counteract the pushing action exerted by the elastic element 14 on the abutting element 15. Accordingly, the shutting element 45 is pressed by the abutting element 15 against the hole 46, so as to close the latter and prevent other piloting fluid from passing from the side hole 48 to the piloting chamber 68. From this instant onwards the main piston 30 is moved further in the direction X only by the portion of piloting fluid that has traversed the throttling means 50.
The piloting means 10 can close both at the instant in which the second hemispherical zone 52b and the seat 22 are detached from one another and at an instant that slightly precedes or follows the detachment. This is set by the operator by acting on the first adjusting means 6 during a step of fitting and testing the valve 1 so as to adjust the piloting means 10 in the desired manner.
When lowering of the load has to be interrupted, the pressurised fluid is no longer supplied to the piloting opening 4 and the residual pressurised fluid inside the piloting chamber 68 and the connecting channel 26 is made to exit the body 2 of the valve through the check valve 51 of the throttling means 50 and, subsequently, the piloting channel 4a. The main piston 30 is moved in the direction Y by the pushing action of the spring 41, the elastic force of which is no longer counteracted by the pressurised fluid present in the piloting chamber 68. In this manner the connecting portion 52 of the main piston 30 abuts again on the end 21 of the containing element 16 and the second hemispherical zone 52b is in contact with the movable seat 22, thus interrupting the connection between the first opening 3 and the second opening 5.
The valve 1 can be associated with any machine or apparatus, also different from an earth-moving machine.
Owing to the invention, a load-holding valve 1 is provided that is substantially devoid of actuation delay between the instant in which the operator drives piloting and the instant in which the load starts to move. This is achieved owing to the piloting means 10 that enables a portion of piloting fluid to enter a screw element 11 through a side hole 48 and flow through a hole 46 as far as a piloting chamber 68, where this portion of piloting fluid makes the main piston 30 execute an initial pre-stroke in the direction X. This occurs whilst the remaining part of the piloting fluid flows through the throttling means 50, in particular the helical channel defined between the thread and the complementary thread of a threaded connection 49, then reaching the piloting chamber 68 after flowing through the connecting channel 26. Thus the portion of piloting fluid that traverses the piloting means 10 reaches the piloting chamber 68 by flowing substantially longitudinally along the axis A (along the hole 46 inside the screw element 11), this path being shorter than the path of the remaining portion of piloting fluid that traverses the throttling means 50. Accordingly, the main piston 30 starts to move earlier than valves of known type, without having to wait for the time taken by the piloting fluid to flow through the throttling means 50, i.e. along a U-shaped path which comprises a part of the channel 4a, the threaded connection 49 and the connecting channel 26.
The valve 1 thus has the advantage of not having a delay between the instant in which the operator commands lowering of the load and the instant in which the load actually starts to be lowered.
Further, the throttling means 50 can be adjusted in such a manner that throttling is very marked, such that the valve also has the advantage of being very stable.
Also, the valve 1 has the advantage of not requiring complex and delicate adjustment by trial and error to prevent the valve from being unstable, or from having excessive actuation delay, as is by contrast required in known valves.
In the valve 1, in fact, the piloting means 10 and the throttling means 50 can be adjusted in simple and rapid manner by an operator acting respectively on the first and second adjusting means 6, 53 during the step of fitting and testing the valve. This enables the piloting means 10 and the throttling means 50 to be adjusted independently, which results in a valve 1 adjusting time (to obtain a valve provided with both the desired ready response and the desired stability) that are significantly shorter than that of known valves. Variations on and/or additions to what has been disclosed and/or to what has been shown in the attached drawings are also possible.

Claims

Load-holding valve (1), comprising:
- a body (2) provided with a plurality of openings (3, 4, 5) through which a pressurised fluid can enter, or exit, said valve (1);

- a main piston (30);

- throttling means (50) intended for being traversed by said pressurised fluid; characterised in that it comprises piloting means (10) that can alternatively adopt an open configuration (O), in which said piloting means (10) enables a portion of pressurised fluid to pass into a piloting chamber (68) for moving said main piston (30) along a direction (X) that is substantially parallel to a longitudinal axis (A) of said valve (1), and a closed configuration (I), in which said piloting means (10) prevents the passage of said portion of said fluid and in which said main piston (30) is moved in said direction (X) by said pressurised fluid that reaches said piloting chamber (68) after traversing said throttling means (50).
Valve (1) according to claim 1, wherein said piloting means (10) comprises a screw element (11) that is substantially coaxial with said longitudinal axis (A).
Valve (1) according to claim 2, wherein said piloting means (10) comprises an elastic element (14) received in a cavity (13), said cavity (13) extending inside said screw element (11) substantially parallel to said longitudinal axis (A).
Valve (1) according to claim 3, wherein said piloting means (10) comprises a through hole (46) having a cross section that is less than a cross section of said cavity (13) and connects said cavity (13) to said piloting chamber (68).
Valve (1) according to claim 4, wherein said piloting means (10) comprises a shutting element (45) positioned inside said cavity (13) such as to face said hole (6) to close said hole (46) in said closed configuration (I).
Valve (1) according to claim 4, or 5, wherein a piloting piston (37) is received, at least in part, inside said hole (46).
Valve (1) according to any one of claims 3 to 6, wherein said piloting means (10) comprises a side hole (48), having an axis that is substantially orthogonal to said longitudinal axis (A), said side hole (48) connecting the outside of said screw element (11) with said cavity (13) and being arranged for being traversed by said portion of pressurised fluid.
Valve according to any one of claims 3 to 7, wherein said piloting means (10) comprises first adjusting means (6) arranged for adjusting the preloading of said elastic element (14).
Valve according to any one of claims 2 to 8, wherein said main piston (30) extends substantially parallel to said longitudinal axis (A) and is received inside a first cavity (8) wherein it is movable bidirectionally according to opposite directions (X, Y) parallel to said longitudinal axis (A).
Valve according to any preceding claims, wherein said throttling means (50) comprises a closing element (70) received in a second cavity (9) parallel to a first cavity (8) which extends between two opposite walls of said body (2) substantially parallel to said first longitudinal axis (A).
Valve according to claim 10, wherein said closing element (70) comprises second adjusting means (53) arranged for adjusting screwing of said throttling means (50) inside said second cavity (9).
Valve according to claim 10, or 11, wherein said closing element (70) is connected to said second cavity (9) by a threaded connection (49) through which said pressurised fluid passes.
Valve according to any one of claims 10 to 12, wherein inside said closing element (70) a check valve (51) is housed that enables said pressurised fluid to flow from said piloting chamber (68) to an opening (4) of said plurality of openings (3, 4, 5).