BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

[0001] This invention relates to a valve and more particularly to a solution enabling efficient flow control to be implemented without generating unwanted cavitation or noise.

DESCRIPTION OF PRIOR ART

[0002] Previously there is known a valve having a flow channel between an inlet opening and an outlet opening. A closure member, which may be e.g. a plug, disc or segment (of a sphere), is arranged in the flow channel such that it can be moved between a closed position and an open position. In the rotary valves, the valve is fully open or closed when the closure member is rotated e.g. a quarter turn. Valves may have eccentric design, wherein the closure member of the valve comes into contact with a seat only in a completely closed position of the valve, thus, preventing excess contact torque between the seat and the closure member.

[0003] A challenge relating to valves is to restrict flow without generating unwanted cavitation and noise. When flow is restricted the pressure difference over the valve increases which may result in an increase in the amount of cavitation and noise.

[0004] Previously there are known many solutions to reduce cavitation and noise. In one known solution there is arranged in the flow channel a noise reduction device, which comprises a plurality of openings dividing a flow entering the openings of the noise reduction device from the fluid channel into a plurality of subflows, which exit the openings of the noise reduction device. In the eccentric rotary valves, such noise reduction devices may be placed before or after a closure member.

[0005] A problem relating to known noise reduction devices, is that they work optimally in valves having non-spherical closure member only when the valve is fully open. However, once the closure member is in an intermediate position, which is typical in control applications, the noise reduction device does no longer work optimally. SUMMARY OF THE INVENTION

[0006] An object of the present invention is to solve the above mentioned drawback and to provide a valve in which cavitation and noise can be more efficiently prevented also while the flow through the valve is restricted. This object is achieved with the valve according to independent claim 1 .

[0007] The use of a flow guide member which can be moved between a closed position restricting flow through a noise reduction device and an open position allowing maximum flow through the noise reduction device, makes it possible to adjust the size of the cross-sectional flow area of the noise reduction device simultaneously as opening of the closure member of the valve is adjusted. Therefore the cross-sectional flow area of and, thus, pressure differential over the noise reduction device can always be kept optimal for the flow which at that moment passes through the valve. By the pressure differential over the noise reduction device, the pressure differential over the closure member can be lowered and, thus, less cavitation and noise is generated. Further, the use of the flow guide member makes it possible to optimize the noise reduction capability of eccentric valves and valves with non- spherical closure members (both eccentric and centric) throughout the operating range i.e. between minimum and maximum openings of the valve.

[0008] Preferred embodiments of the invention are disclosed in the dependent claims.

BRIEF DESCRIPTION OF DRAWINGS

[0009] In the following the present invention will be described in closer detail by way of example and with reference to the attached drawings, in which

[0010] Figure 1 illustrates a cross-sectional view of a valve in a closed position,

[0011] Figure 2 illustrates a cross-sectional view of the valve of Figure 1 in an intermediate position, and

[0012] Figure 3 illustrates the closure member, axle and flow guide member of Figures 1 and 2.

DESCRIPTION OF AT LEAST ONE EMBODIMENT

[0013] Figure 1 illustrates a cross-sectional view of a control valve 1 with a closure member 2, an axle 3 for moving the closure member 2, and a flow guide member 4. The valve 1 is in a closed position in Figure 1 . Figure 2 shows the valve of Figure 1 in an intermediate position, in other words in a position where the flow path through the valve is not totally closed and not fully open, but between these extremes. Figure 3 shows a side view of the closure member 2, the axle 3 and the flow guide member 4.

[0014] The valve 1 illustrated in the figures is typically a control valve adjusting flow of fluid, such as liquid or gas, flowing in a pipe, for instance. The valve comprises a flow channel extending between the inlet opening 5 and outlet opening 6. The closure member 2 is arranged in the flow channel such that it is freely movable between a closed position stopping flow through the flow channel and a fully open position allowing maximum flow through the channel. Figure 1 illustrates the closure member 2 in the closed position, where it blocks the inlet opening 5 to prevent any fluid flow through the flow channel of the valve 1 . Figure 2 illustrates the valve 1 in a partially open position, where flow of fluid is restricted by the closure member 2.

[0015] In the illustrated example it is assumed that the closure member 2 is movable by rotating around the longitudinal center axis 7 of the shaft 3, though also other ways of moving the closure member 2 are possible.

[0016] A noise reduction device 8 is arranged at the outlet opening 6 of the valve 1 . Thereby in the illustrated example, the closure member 2 is not provided with a noise reduction device, but instead the noise reduction device 8 is located separately from the closure member 2. The term "noise reduction device" refers in this connection to an arrangement which reduces vibration, of which a part usually has a frequency that can be heard as noise, and which in addition may reduce cavitation. For simplicity, however, the term "noise reduction device" is used. Flow of fluid out of the valve 1 therefore occurs through the noise reduction device 8. The noise reduction device 8 comprises a plurality of openings 9 dividing the flow entering the openings 9 from the fluid channel of the valve into a plurality of subflows exiting the openings 9 of the device 8. Previously there are known a plurality of different noise reduction devices which can be utilized with the invention as such or as appropriately modified. It is therefore to be understood that noise reduction devices of any suitable design can be used. One example of a suitable flow reduction device is disclosed in WO 2012/136890 A1 , for instance.

[0017] The flow guide member 4 is arranged in a connection with the noise reduction device 8. The flow guide member 4 is movable between the closed position illustrated in Figure 1 , the intermediate position illustrated in Figure 2, where it restricts the flow through the noise reduction device 8, and a fully open position, where flow through the openings 9 of the noise reduction device 8 is not restricted. In the illustrated closed and intermediate positions the flow guide member 4 is preferably located very close to the noise reduction device 8. It is, however, not necessary that the flow guide member 4 seals off the openings 9 of the noise reduction device totally to prevent any flow through them. Instead, a small gap may be allowed between the flow guide member 4 and the noise reduction device 8 such that operating torque of the closure member 2 is not increased due to friction between the flow guide member 4 and the noise reduction device 8. Shape of the flow guide member 4, which is shown in figures for illustrative purposes only, has an impact on flow characteristics of the noise reduction device and, thus, its noise reduction performance.

[0018] The flow guide member 4 is operatively connected to the shaft 3 and/or closure member 2 for moving it between the closed position and the open position. In this connection the term "operatively connected" refers to a solution where the flow guide member 4 moves in conjunction with simultaneously as the closure member 2 moving between the closed position and the open position no matter whether they are physically attached to each other or not. In this way it can be ensured that as the opening of the closure member 2 at a specific moment allows certain amount of fluid to flow through the flow channel of the valve, a suitable part of the cross-sectional flow area of the noise reduction device 8 at that moment is open, in other words not covered by the flow guide member 4. Therefore the reduction in cavitation and noise obtained with the noise reduction device 8 can be optimized throughout the operating range of the valve 1 , as the free cross-sectional flow area of the noise reduction device 8 may be adjusted with the flow guide member 4 in accordance with the flow allowed by the closure member 2.

[0019] In the illustrated example the flow guide member 4 and the closure member 2 are operatively connected to each other via the shaft 3. Thus both the flow guide member 4 and the closure member 2 turn around the longitudinal center axis 7 of the shaft 3 once the shaft is rotated. Although a fixed installation (e.g. by welding) is possible, the flow guide member 4 is preferably easily attachable to/removable from the closure member 2 and/or the shaft 3 (e.q. with bolts), which makes assembling of the valve easier or possible, especially with valves with jointless bodies 12, wherein the closure member 2 is installed through the inlet opening 5 or outlet opening 6. Also, an interchangeable flow guide member 4 makes it easy to obtain noise reduction characteristics depending on needs (e.g. different flow guide members for different application or flow rates). For the attachment of the flow guide member 4, an attaching arrangement in between the member 4 and the closure member and/or the shaft 3 may be used (not shown in figures).

[0020] In Figure 1 it is by way of example illustrated that the valve 1 is an eccentric valve, which refers to a valve having an eccentric closure member 2.

[0021] Consequently when the closure member 2 is in the closed position of Figure 1 , a center axis 10 of the closure member 2, in a plane intersecting perpendicularly the center axis 7 of the shaft 3 (in other words when seen from above in the direction of the shaft 3 in Figure 1 ), is offset with a distance D from the longitudinal center axis 7 of the shaft 3. It should, however, be observed that the present invention can be utilized also in valves which are centric, in other words in valves where the offset distance D of Figure 1 is zero, such that the center axis 10 of the closure member 2 and the longitudinal center axis 7 of the shaft 3 intersect.

[0022] Though the valve is an eccentric valve with an eccentric closure member 2, the flow guide member 4 is preferably centric. Consequently a center axis 1 1 of the flow guide member 4, in a plane intersecting perpendicularly with the center axis 7 of the shaft (in other words when seen from above in the direction of the shaft 3 in Figure 1 ), substantially intersects the longitudinal center axis 7 of the shaft. In this connection the term "substantially intersects" refers to the fact that in the optimal case the center axis 1 1 of the flow guide member intersects the longitudinal center axis 7 of the shaft, however, due to practical reasons a tolerance is allowed, in which case these axis 1 1 and 7 do not intersect each other, but they are located close to each other.

[0023] As illustrated in the figures, the flow guide member 4 may have a convex surface facing the noise reduction device 8, and the noise reduction device 8 may have a concave surface facing the flow guide member 4. In this way and with a suitable dimensioning, these surfaces facing each other remain sufficiently close to each other all the time irrespectively of in which position the closure member 2 and flow guide member 4 are.

[0024] The the convex surface of the flow guide member 4 may be a spherical surface and the concave surface of the noise reduction device 8 may be a spherical surface. In that case the the convex surface of the flow guide member 4 and the concave surface of the noise reduction device 8 may both be curved along a common center point P4 which is located at or in close proximity to the longitudinal center axis 7 of the shaft 3. In Figure 1 the radius R4 of the curved shape of the flow guide member 4 is illustrated by way of example.

[0025] Alternatively it is possible that the convex surface of the flow guide member 4 is a cylindrical surface and the concave surface of the noise reduction device 8 is a cylindrical surface. In that case the convex surface of the flow guide member 4 and the concave surface of the noise reduction device 8 are both curved around an axis located at or in close proximity to the longitudinal center axis 7 of the shaft 3. Also in this case the radius R4 of the curved shape of the flow guide member 4 is as illustrated in Figure 1 .

[0026] The surface of the closure member 2 facing the inlet opening 5 in the closed position illustrated in Figure 1 may be convex. In that case the surface may be at least partially spherical and curved around a point P2 which is offset from the center point P4. Alternatively, the surface of the closure member 2 may be cylindrical, in which case it may be curved around an axis located at point P2 and which is parallel with the longitudinal center axis 7 of the shaft 3.

[0027] It is to be understood that the above description and the accompanying figures are only intended to illustrate the present invention. It will be obvious to a person skilled in the art that the invention can be varied and modified without departing from the scope of the invention.