The present invention relates to the fields of valves and manually operable valves, for instance gate valves, control or regulation valves or chokes valves.

Valves are used in a variety of industries to control the flow o f fluids. In particular, gate valves are used extensively in the oil and gas industry to control the flow of produced fluids at various stages o f production. Mo st gate valves used in this industry comprise a valve body having a longitudinal flow bore and a transverse gate cavity that intersects the flow bore. A gate having a gate opening extending transversely therethrough is dispo sed in the gate cavity. A valve stem is provided for moving the gate between an open po sition, in which the gate opening is aligned with the flow bore, and a clo sed po sition, in which the gate opening is offset from the flow bore. The gate cavity o f the valve body is covered by a bonnet having an axial bore transverse to the flow through which passes the valve stem.

Such a gate valve is associated to a valve operator assembly for selectively driving the valve stem up and down in order to clo se and open the gate valve. The valve operator assembly generally comprises a transmission mechanism to convert the rotational motion of a drive input into axial motion of the valve stem. To quickly open and clo se the gate valve with a minimum number of turns, the transmissio n mechanism may be a ball screw mechanism or a planetary roller screw mechanism in order to reduce the operating torque, for instance manual hand-wheel torque or powered with electric, hydraulic or pneumatic drive for surface valves or with remote operating vehicle (ROV) torque tool or electric or hydraulic actuation for subsea valves . For more details, it is po ssible for example to refer to the patent EP- B l - 1 419 334 (S KF) .

Generally, such valve operator assembly is used in harsh environment (desert, high temperature or cold, etc. ) and in remote locations. When the transmission screw mechanism and/or rolling bearing s dispo sed into the assembly wear off, the friction torque increases. This also leads to contamination of the lubricant introduced into the valve operator assembly with undesirable metal particles . Accordingly, the optimum lubrication effect is not retained which reduces maintenance intervals.

One aim of the present invention is to overcome these drawbacks.

In one embodiment, the valve operator assembly is provided for a valve comprising a valve body and a valve translating member axially moveable. The assembly comprises a housing adapted to be mounted on the valve, an input member rotatably mounted with respect to said housing, and a transmission mechanism comprising a screw provided with an outer thread, and a nut surrounding and coaxial with said screw, said nut being provided with an inner thread. One of said screw and nut acts as a translating element adapted to be connected to the valve translating member of the valve, the other acting as a rotating element connected to the input member. S aid transmissio n mechanism is adapted to convert applied rotation of the input member into axial translation of said translating element. Magnetized means are dispo sed inside the valve operator assembly.

The magnetized means provided within the assembly enable to catch metallic particles generated during the operation of the valve operator assembly, for example during the running-in phase. Metallic particles are caught and trapped by the magnetic means instead o f being spread and mixed with the lubricant introduced into the valve operator assembly. The lubricant may be grease or oil. This improve s lubricant cleanliness and extends maintenance intervals. This also increases the service life of the valve operator assembly and stabilize s the required operating torque for a long time.

Preferably, said magnetized means may be connected to the transmission mechanism. Said magnetized means may be connected to the screw and/or the nut. In one embodiment, the transmission mechanism further comprises rollers radially dispo sed between the screw and the nut and each provided with outer gear teeth meshing with synchronization gear teeth provided on the screw, or the nut.

Said magnetized means may be dispo sed inside the transmission mechanism and adjacent to at least one of the synchronization gear teeth. In one embodiment, said magnetized means are secured to the outer surface of the screw and located axially between the outer of said screw and one of the synchronization gear teeth. Alternatively, said magnetized means may be connected to the nut and located axially between the inner thread of said nut and one o f the synchronization gear teeth. Said magnetized means may be secured to the bore of the nut or secured to at least one of the gear wheels o f said mechanism which are provided with the synchronization gear teeth.

In one embodiment, the valve operator assembly comprises at least two magnetized means dispo sed inside the transmissio n mechanism and each dispo sed adj acent to the associated synchronization gear teeth.

Alternatively or in combination, said magnetized means may be secured to the bore of the housing .

The invention also relates to a valve comprising a valve body, a valve translating member axially moveable and a valve operator assembly as previously defined.

The present invention and its advantages will be better understood by studying the detailed description of specific embodiments given by way of non-limiting examples and illustrated by the appended drawings on which:

Figure 1 is a cro ss- section of a valve operator assembly for gate valve according to a first example of the invention,

Figure 2 is a detail view of Figure 1 ,

Figure 3 is a front view of a permanent magnet of the assembly of Figure 1 , Figure 4 is a front view of a permanent magnet according to another example,

Figure 5 is a cro ss- section of a valve operator assembly according to a second example of the invention,

- Figure 6 is a detail view of Figure 5 , and

Figures 7 to 9 are cro ss- sections of valve operator assemblies according to third, fourth and fifth examples of the invention.

A valve operator assembly 10 as shown on Figure 1 is adapted for a gate valve 12 provided with a bonnet 14, a valve body (not shown) covered by said bonnet and a moveable valve stem 16 with an axis 16a. Conventionally, the valve body has a flow bore and a transverse gate cavity that intersects the flow bore. The gate valve also comprises a gate having a gate opening extending transversely therethrough which is dispo sed in the gate cavity. For more detail o n such a gate valve, it could be referred to EP-B l - 1 419 334 (SKF) .

The valve operator assembly 10 comprises a tubular housing 1 8 mounted on the bonnet 14 of the gate valve, here directly, an input member having an operable wheel 20 rotatably mounted with respect to said housing, and an inverted roller screw mechanism 22 interpo sed between said wheel and the valve stem 16 of said valve to convert a rotational motion of the wheel 20 into axial motion of the valve stem. The inverted roller screw mechanism 22 is mounted into a bore 18a o f the housing and is connected to the wheel 20. One axial end of the housing 18 is secured to the bonnet 14, for example by threads or bolts. In the illustrated example, the bore 18a has a stepped form. Alternatively, the bore 18a may have different shape.

As shown more clearly on Figure 2 and as will be described later, the valve operator assembly 10 further comprises two permanent magnetized magnets 24, 26 in order to trap metallic particles generated during the operation. In this example, the magnets 24, 26 are mounted inside the roller screw mechanism 22.

The mechanism 22 comprises a screw 28 , with an axis 28 a coaxial with the axis 16a of the valve stem, provided with an outer thread 30, a nut 32 mounted coaxially about the screw 28 and provided with an inner thread 34, the internal diameter of which is greater than the external diameter of the outer thread 30, and a plurality of longitudinal rollers 36 arranged radially between the screw 28 and the nut 32. The screw 28 extends longitudinally through a cylindrical bore of the nut 32 on which the inner thread 34 is formed. The lead of the outer thread 30 of the screw is constant. The nut 32 has a tubular form and is elongated to accommodate the full extent of screw travel. The nut 32 is made in one part. The nut 32 extends axially inside the housing 1 8 and axially protrudes outwards (Figure 1 ) . The operable wheel 20 is supported by the nut 32.

The rollers 36 are identical to each other and are distributed regularly around the screw 28. Each roller 36 extends along an axis 36a which is coaxial with the axis 28 a of the screw and comprises an outer thread 38 engaging the thread 30 of the screw and the thread 34 of the nut. Each roller 36 also comprises, at each axial end, outer gear teeth 40, 42 extending axially outwards the outer thread 38. The outer gear teeth are themselves extended axially by a cylindrical stud 44, 46 extending outwards. Each gear teeth 40, 42 are axially located between the associated stud 44, 46 and the outer thread 38. The outer thread 38 of each roller is axially located between the two gear teeth 40, 42.

The roller screw mechanism 22 also comprises two outer gear teeth 48 , 50 provided on the outer surface of the screw 28 and meshing the gear teeth 40, 42 respectively of the rollers 32 for the synchronization thereof. The gear teeth 48 , 50 are identical to one another and axially dispo sed on either side of the outer thread 30. In the disclo sed embodiment, the gear teeth 48 , 50 are formed directly on the outer surface of the screw 28. Alternatively, the mechanism 22 may comprise annular gear wheels fixed on the outer surface of the screw 28 and each comprising the synchronization gear teeth 48 , 50.

The mechanism 22 further comprises two annular guides or spacer rings 52, 54 dispo sed on the outer surface of the screw 28. Said spacer ring s 52, 54 are radially dispo sed between the screw 24 and the inner thread 34 of the nut without contact with said thread. Each spacer ring 52, 54 is mounted on the outer surface of the screw 24 axially next to the associated gear teeth 48 , 50. Each spacer ring 52, 54 is axially offset towards the outside of the nut 32 with regard to the associated gear teeth 48 , 50. Each spacer ring 52, 54 comprises a plurality of cylindrical through-recesses (not referenced) which are distributed regularly in the circumferential direction and inside which the studs 44, 46 of the rollers are housed. The spacer rings 52, 54 enable the rollers 36 to be carried and the regular circumferential spacing thereof to be kept. The mechanism 22 further comprises elastic retainer ring s (not referenced) each mounted in a groove formed on the outer surface of the screw 28 in order to axially hold the corresponding spacer ring 52, 54.

Referring once again to Figure 1 , axially on the side oppo site to the wheel 20, a recess 28b is formed on a frontal radial surface o f the screw 28 and into which is mounted an end of the valve stem 16 o f the gate valve. The valve stem 16 is connected to the screw 28 by any appropriate means, for example by threads and/or a pin and/or a clamping means and/or a T- slot.

The valve operator assembly 10 also comprises rolling bearing s 56 to 58 to guide the rotation of the nut 32 of the inverted roller screw mechanism. The rolling bearing s 56 to 58 are radially mounted between the outer surface 32a of the nut and the stepped bore 18 a o f the housing . The rolling bearing s 56 to 58 are mounted radially in contact with said outer surface and said bore. A retaining ring 59 is secured on the outer surface 32a of the nut and axially bears against the rolling bearing 56. Axially on the oppo site side, the rolling bearing 58 is axially mounted against a radial shoulder (not referenced) of the outer surface 32a of the nut. Sealing means (not referenced) , which are axially located between the rolling bearing 58 and the wheel 20, are radially provided between the outer surface of the nut 32 of the bore of housing 18. Sealing means (not referenced) are also provided between the stem 14 and the bonnet 14.

The rotational drive wheel 20 is directly mounted on the nut 32 of the transmission mechanism. The wheel 20 is mounted on a part of the outer surface 32a which is located outside of the housing 1 8. The wheel 20 may be secured on the nut 32 by any appropriate means, here by key( s) and screws, or alternatively press-fitting, gluing, welding , pins, or clamping system etc. In the illustrated example, the wheel 20 is adapted to be manually operated. Alternatively, the wheel 20 may be automatically operated with electric, hydraulic or pneumatic drive.

In the disclo sed example, the rotational drive wheel 20 is directly mounted on the nut 32 of the mechanism with no interpo sitio n of additional element therebetween. Alternatively, the input member may comprise an adapter sleeve mounted on the screw 28 and the drive wheel 20 secured to said sleeve. The input member is mounted on the nut 32 and secured to said nut.

Referring once again to Figure 2, the magnets 24, 26 are mounted inside the roller screw mechanism 22 as previously mentioned. In this example, the magnets 24, 26 are mounted on the screw 28. The magnets 24, 26 are mounted on the outer surface of the screw 28. The magnets 24, 26 are secured to the screw 28. The magnets 24, 26 are radially located between said outer surface and the rollers 36. The magnet 24 is axially located between the outer thread 30 of the screw and the synchronization gear teeth 48. The magnet 26 is axially located between said outer thread 30 and the other gear teeth 50. Each magnet 24, 26 is mounted adj acent to the associated gear teeth 48 , 50. In the disclo sed example, each magnet 24, 26 is fitted inside a groove 28c, 28d formed on the outer surface of the screw 28. Each magnet 24, 26 is radially offset inwards with respect to the adjacent gear teeth 48 , 50. In the disclo sed example, the magnets 24, 26 are identical to each other. As shown on Figure 3 , the magnet 24 may comprise two identical C- shaped magnetized parts which are dispo sed on the screw to obtain a magnet having an annular form centred on the axis 28 of said screw. Alternatively, as shown on Figure 4, the magnet 24 may comprise a plurality of magnetized parts regularly spaced apart in the circumferential direction. For example, the magnet material may be neodymium, alnico , strontium ferrite, etc. When an operator applies a torque on the wheel, this torque is transmitted to the nut 32 of the inverted roller screw mechanism. With the rotation of the nut 32, the rollers 36 rotate on themselves about the screw 28 and move axially and additionally rotate in said nut. The rollers 36 are rotationally guided by outer gear teeth 48 , 50 provided on the screw and meshing with the gear teeth of the rollers. Both the rollers 36 and the screw 28 are axially or longitudinally moveable into the nut 32. Accordingly, the rotational motion of the wheel 20 is converted into a displacement of the valve stem 16.

During the running-in phase of the valve operator assembly 10, contacts between the synchronization gear teeth 48 , 50 and the gear teeth 40, 42 of the rollers generate metallic particles due to sharp edges. Such generation of particles also exists after the running- in phase.

Since the magnets 24, 26 are dispo sed proximate the gear teeth

48 and 50, the metallic particles are generated near to said magnets. The particles are thus attracted and trapped by the magnetic field emitted by the magnets 24, 26 as soon as they are produced. Accordingly, the generated metallic particles are caught by the magnets 24, 26 before to be spread and mixed with the lubricant (not shown) introduced into the valve operator assembly 10. The attractive force of each magnet 24, 26 is cho sen in order that the flow o f lubricant inside the assembly 10 is insufficient to dislodge particle s from said magnets.

Otherwise, the wear of the outer threads 38 of the rollers and the threads 30, 34 of the screw and nut also cause metal particles to be broken away. These particles are carried by the flow of lubricant which passes through the transmission mechanism 22 and which is oriented towards the magnet 24, or the magnet 26, according to the direction of rotation of the screw 28. By the screw effect, the metallic particles carried by the lubricant pass proximate the magnet 24, or 26, and are thus trapped. The action of the magnets 24, 26 increase s lubricant life, reduces the wear and consequently increases the lifetime of the roller screw mechanism 22 as well as the service life of the valve operator assembly.

In this first illustrated example, the invention has been illustrated on the basis of a valve operator assembly 10 for gate valve comprising an inverted roller screw mechanism 22. The invention can also be applied to a valve operator assembly having other type o f roller screw mechanism such as standard planetary roller screw mechanism as shown on Figure 5.

In this example, in which identical parts are given identical references, the valve operator assembly 10 is provided with a planetary roller screw mechanism 60 interpo sed between the wheel 20 and the valve stem 16 of the valve gate. The mechanism 60 comprises a nut 62 mounted coaxially about the screw 28 and provided with an inner thread 64, and the rollers 36 dispo sed radially between the screw 28 and the nut 62. In this example, the outer thread 30 of the screw has an elongated length.

As shown more clearly on Figure 6, the mechanism 60 also comprises two annular gear wheels 66, 68 mounted in a non-threaded part of the bore of the nut 62. Each gear wheel 66, 68 comprise inner gear teeth 70, 72 meshing the gear teeth 40, 42 respectively of the rollers for the synchronization thereof. Each gear wheel 66, 68 axially bears against a radial surface of the nut 62 provided between the inner thread 64 and the associated non-threaded part of said nut. The gear wheels 66, 68 are identical to one another. In this example, the spacer ring s 52, 54 are each mounted radially between the screw 28 and the associated gear wheel 66, 68. Alternatively, the mechanism 60 may be deprived of gear wheels 66, 68 fixed in the bore of the nut 16. In this case, the synchronization gear teeth 70, 72 are directly formed on the nut 16.

The mechanism 60 also comprises an outer sleeve 74 having an axial bore 74a inside which are housed the nut 62 and the rollers 36. The nut 62 is secured to the sleeve 74. The gear wheel 68 axially bears against a radial annular shoulder of the bore 74a of the nut. Axially on the oppo site side, a retaining ring (not referenced) is secured into said bore and axially comes into contact against the other gear wheel 66 of the mechanism. The rolling bearing s 56 to 58 are mounted on the outer surface of the sleeve 74 (Figure 5) . The sleeve 74 is radially interpo sed between the nut 62 and said rolling bearing s. Alternatively, it could be po ssible to make the nut 62 and the sleeve 74 in one single part.

In this example, the magnets 24, 26 are mounted on the nut 62. The magnets 24, 26 are mounted in the non-threaded part of the bore of the nut 62. The magnets 24, 26 are secured to the nut 62. The magnets 24, 26 are radially located between said non-threaded part and the rollers 36. In the disclo sed example, each magnet 24, 26 radially surrounds the gear teeth 40, 42 of the rollers. The magnet 24 is axially located between the inner thread 64 of the nut and the synchronizatio n gear teeth 70. The magnet 26 is axially located between said inner thread 64 and the other gear teeth 72. Each magnet 24, 26 is mounted adjacent to the associated gear teeth 70, 72. In the disclo sed example, each magnet 24, 26 axially abuts against the associated gear wheel 66, 68. In the disclo sed example, each magnet 24, 26 is fitted inside a groove 64a, 64b formed in the bore of the nut. Each magnet 24, 26 is radially offset outwards with respect to the adjacent gear teeth 70, 72.

Alternatively, each magnet may be secured in a groove formed in the bore of the associated gear wheel or may be provided on the spacer ring s.

The example illustrated on Figure 7 , in which identical parts are given identical references, differs from the second example in that the valve operator assembly 10 comprises a permanent magnet 80 dispo sed outside the roller screw mechanism 22. The magnet 80 is dispo sed on the outer surface of the screw 28 and located outside the nut 62 and the sleeve 74. In the disclo sed example, the magnet 80 is dispo sed on the part of the screw 28 comprising the recess 28b. The magnet 80 is here axially located between the sleeve 74 and the bonnet 14.

Alternatively, it could be po ssible to foresee another dispo sition of the magnet 80. For instance, as shown on Figures 8 and 9, in which identical parts are given identical references, the magnet 80 could be secured to the outer surface of the sleeve 74 or secured to the bore 18a of the housing . In the examples shown on Figures 7 to 9, with the dispo sition of the magnet 80, the metal particles generated by the rolling bearing s 56 to 58 are also caught. Alternatively, the magnet 80 may be secured on the retaining ring 59 or on a spacer provided between two of the rolling bearing s 56 to 58.

In another variant, it could be po ssible to combine the dispo sition of the permanent magnets 24, 26 inside the roller screw mechanism 22 as disclo sed in the first or second example with the arrangement of the permanent magnet 80 outside said mechanism as shown in the third, fourth or fifth disclo sed example.

The illustrated examples deal with an inverted roller screw mechanism and a standard planetary roller screw mechanism. The invention can also be applied to a valve operator assembly having other type of roller screw mechanism, for example a recirculating roller screw. In this case, the magnetic means may be provided on the retaining cage for maintaining the rollers circumferentially spaced apart. Alternatively, the magnetic means may be dispo sed on wipers fixed in the bore of the nut.

The invention can also be applied to a valve operator assembly having a standard or an inverted ball screw mechanism. Otherwise, the invention can also be applied to a valve operator assembly having other type of transmission mechanism adapted to convert a rotation into a linear movement, for instance a direct threaded connection. In this case, the outer thread of the screw engages directly the inner thread of the nut without interpo sition of rolling elements. However, such transmission mechanism requires large actuation forces.

Although the invention has been illustrated on the basis of a valve operator comprising a screw connected to the valve stem of the gate and a nut connected to the input member, it should be understood that the invention can be applied with a screw connected to the input member and a nut connected to the valve stem. In this case, the nut acts as the translating element and the screw acts as the rotating element.

Although the invention has been illustrated on the basis of a valve operator assembly for gate valve, it should be understood that the invention can also be used with other types of valves, for instance control or regulation valves or choke valves. The wheel may be operable manually or automatically for example with electric, hydraulic or pneumatic drive. The valve operator assembly may be used for instance with a surface gate or a subsea valve gate which may be actuated by a remote operating vehicle (ROV) torque tool or an actuator.