Patent Description:
The use of remotely controlled actuators for controlling shut-off members, i.e. control valves, at the service of ducts for carrying fluids in multiple industrial fields such as oil, petrochemical, manufacturing, food, etc., is known in the art.

Several actuators, belonging to the known art, have as their control component a cylinder/piston assembly with hydraulic or pneumatic actuation which, once activated, allows the piston/cylinder assembly to carry out its stroke thus creating a translatory motion that is converted, in various and different ways, to a rotary motion that is integral with the adjusting stem of the shut-off member. The dimensions and size of such actuators can vary between different configurations since the cylinder/piston assembly can be arranged in a position that is coaxial or transversal to the axis of the stem of a shut-off member, thus creating "I"- or "T"-like configurations, respectively. The so-called compact actuators are actuators with "I"-like configuration, substantially cylindrical in shape without projections or protrusions that are present instead in "T"-like configurations.

Patent document <CIT>) depicts an actuator with compact configuration that makes the conversion of the stroke of the cylinder/piston assembly to a proportional rotation of the stem of the shut-off member through a coaxial arrangement of three cylindrically shaped hollow bodies coupled through helical threads.

This type of solution has some disadvantages.

First of all, the necessary construction complexity due to making high precision, helical, threaded shapes with significant manufacturing costs and times.

Secondly, a degree of mechanical strain which, over time, can lead to early wear of the threads and seizure of the three coaxial cylindrical bodies.

In fact, in the event of failure to operate the control cylinder, for example due to a lack of oleodynamic pressure and the need to act on the shut-off member, the independent mechanical control system, present in this device and which constitutes the emergency actuation system, must be used.

Such system produces the rotation of the outermost coaxial cylindrical hollow body in the presence of said inactive control cylinder, which is axially locked and which therefore inhibits each displacement of the coaxial cylindrical bodies in the axial direction.

The rotation of the outermost coaxial cylindrical body, through the helical threads, consequently drags with it the other two innermost coaxial cylinders.

A solution of this type is described in <CIT>.

The aforesaid integral movement of the three coaxial cylinders causes axial thrusts between the various engaged elements and, since no relative axial displacement can be made as previously specified, the integral rotation of the three coaxial cylinders will cause a mechanical strain condition on the mentioned threads with a sort of "packing" effect.

This type of mechanical strain, which is repeated over time, can be a source of micro fractures of small thread portions, resulting in material detachments and subsequent seizure of the threaded couplings.

Another device of the known art is that depicted in patent document <CIT>) in which the stem for actuating the plug of a fluid control valve acts with an axial translational movement, thanks to a threaded nut, and is connected, through a special shaft, to a lower "T"-like head, which in turn has two opposite pins that are perpendicular to the axis of the shaft.

The "T"-like head is inserted in a first rotatable inner cylindrical sleeve, which is in turn contained in a second fixed outer cylindrical sleeve that is integral with the valve casing.

Each pin engages, through a proximal portion thereof, with a respective first longitudinal through slit, which is parallel to the axis of the shaft and is formed in the wall of the inner sleeve and, through an end portion thereof, with a second slit, which is inclined with respect to the axis of the shaft and which is formed in the inner wall of the outer sleeve.

The first hollow cylinder is integrally connected to the stem of the valve plug, and causes this plug to be activated through its rotation.

As the actuator stem moves forward, thanks to the mechanical or fluidically assisted rotation of the threaded nut, it transmits the same axial translatory motion to the "T"-like head which, by axially translating, is rotated by the second inclined slits of the fixed outer sleeve and in turn rotates, thanks to the longitudinal slits, the rotatable inner sleeve.

As said, the rotatable inner sleeve is kinematically connected to the valve plug, so as to cause the relative closing or opening rotation of the same valve.

<CIT> does not describe the presence of a manually operable safety mechanism in the event of a jam in the axial movement of the stem and therefore of the "T"-like head.

Moreover, the solution described above of the patent document <CIT> has the problem of having a technical structure that makes it unsuitable for housing an independent actuation system of mechanical type.

Furthermore, the fact that the <CIT> solution requires that the "T"-like head is caused to rotate, together with the inner sleeve, by the inclined slits of the fixed outer sleeve, involves a certain complexity in the transmission of motion from the actuation stem, which please remember it is subject to an axial motion of the valve and that of the same "T"-like head, in addition to the fact that the rotation of at least two bodies constrained to each other, that is the "T"-like head and the inner sleeve, can easily lead to jams during the actuator operation.

Therefore, an object of the present invention is to solve the above-mentioned technical problems through an actuator which has a high mechanical efficiency in the transformation of the actuation motion of the various components of the device. Another object of the present invention is to make an improved high-efficiency alternative mechanical intervention system, called "override", and which can effectively complement the main actuation system.

Finally, a further object of the invention is to provide a simple embodiment with low manufacturing costs.

These and other purposes are achieved by an actuator for control valves according to claim <NUM>.

An advantage of the invention is constituted by a high mechanical efficiency associated with the limited number of sliding components constituted only by pins acting inside the longitudinal flutes.

Another advantage of the invention is the possibility of defining the overall degree of rotation and performance of the drive torque that the actuator can operate on the plug, by varying the inclination of the helical flutes formed in the inner sleeve.

A further advantage is given by the possibility of a fine adjustment of the position of the pins in the helical flutes of the inner sleeve in order to guarantee a uniform contact between each pin and the respective flute and a torque equally distributed between the pins.

Furthermore, such invention minimises the possibility of jams during its actuation. The present invention is particularly applicable to oil and petrochemical control valves in offshore and underwater installations.

Further characteristics of the invention can be deduced from the dependent claims.

Further characteristics and advantages of the invention will become clear from reading the following description provided by way of non-limiting example, with the aid of the figures depicted in the accompanying drawings, wherein:.

The present invention will now be described with particular reference to the accompanying figures.

In particular, <FIG> depicts an actuator according to an embodiment of the invention, denoted by the reference numeral <NUM> as a whole, said actuator <NUM> comprising at least one fluidic actuation - constituted by a device known per se - contained inside a casing <NUM>, where the aforesaid actuator <NUM> is configured to operate on a plug of a control valve.

From this figure, the compact construction of the substantially cylindrical actuator can be observed.

It can also be observed that the actuator <NUM> further comprises an alternatively operating emergency mechanical device <NUM>, which will be better described in greater detail below, positioned at the base of the actuator <NUM> with an input shaft <NUM> of the mechanical device <NUM> that is easily accessible for its actuation from the outside through a suitable tool.

<FIG> shows the inside of the casing <NUM> and its main components, according to a cross section of the actuator <NUM> taken along the B-B line denoted in <FIG>.

In particular, it is visible that inside the casing <NUM> having a longitudinal axis X, there is a cylinder <NUM> which, as a result of a fluidic actuation according to modes known per se that include remote control, can axially slide inside the aforesaid casing <NUM>.

The axial sliding of the cylinder <NUM>, along a piston <NUM>, compresses a spring <NUM>, while keeping the position of the piston <NUM> unchanged.

A single-acting fluidic actuator with return spring has been described herein. Alternatively, as it will be known to those skilled in the art, it is possible to use any other known fluidic actuator such as, for example, a dual-chamber jack.

As it can be seen from <FIG>, said cylinder <NUM> has a support <NUM> for at least one pin <NUM>, where each of the aforesaid pins <NUM> acts on an inner sleeve <NUM> through corresponding helical flutes <NUM> formed in the same inner sleeve <NUM>.

The pins <NUM> may preferably be three in number.

Axial sliding involves the action of each pin <NUM>, through a suitable roller <NUM>, on the respective helical flute <NUM> so as to rotate the inner sleeve <NUM> around the longitudinal axis of said casing <NUM>, since the outer sleeve <NUM> does not rotate and constrains the aforesaid pins <NUM> to an axial translation thanks to the action of the three sliding blocks <NUM>, which are also mounted on the pins <NUM> and coaxial with the rollers <NUM>, which act on axial flutes <NUM> formed in the outer sleeve <NUM>.

In fact, as shown in <FIG> and <FIG>, the outer sleeve <NUM> is connected, for example through dowels <NUM> or other known connecting elements, integrally to the crown <NUM> in turn coupled to a worm screw <NUM>.

De facto this worm screw <NUM>, which ensures rotational irreversibility, forces the outer sleeve <NUM> to remain in position despite the rotational torque transmitted by the system of rollers <NUM> and sliding blocks <NUM>, thus guiding the movement in the longitudinal direction of the sliding blocks <NUM> and of the rollers <NUM> and achieving the consequent rotation of the inner sleeve <NUM>.

Finally, the rotation of the aforesaid inner sleeve <NUM> integrally connected to the plug, causes the plug of the control valve to rotate.

In the absence of pressure in the cylinder <NUM>, the spring <NUM> can extend again, thus returning the cylinder <NUM> of the aforesaid actuator <NUM>, as well as the plug, to the initial position.

In place of the actuation described above, carried out by the actuator <NUM>, it is possible to perform an intervention from the outside, for example in the case of no pressure on the cylinder <NUM> or for other reasons, with said cylinder <NUM> in its initial position and the aforesaid spring <NUM> in extended configuration, through the alternatively operating mechanical device <NUM> which acts by rotating the aforesaid outer sleeve <NUM>.

As shown in <FIG> and in <FIG>, the aforesaid alternatively operating mechanical device <NUM> comprises a bevel gear pair <NUM> or other gear systems (such as for example epicyclic gears or gears with parallel axes) configured to transmit a rotational motion coming from the input shaft <NUM> of the aforesaid mechanical device <NUM> to a worm screw <NUM>.

In particular, by acting on the input shaft <NUM>, for example through a dedicated tool, the bevel gear pair <NUM> rotates the worm screw <NUM> which in turn actuates the rotation of the crown <NUM>, which consequently causes the outer sleeve <NUM> integral therewith to rotate.

The rotation of the outer sleeve <NUM> rotates the sliding blocks <NUM> engaged in the longitudinal flutes and consequently the rollers <NUM> which, by acting on the helical flutes of the inner sleeve <NUM>, transmit the rotation to the inner sleeve <NUM> integrally connected to the plug, a movement that consequently causes the valve plug to rotate.

It should be specified that the rotation of the entire outer sleeve <NUM>/inner sleeve <NUM> assembly is made possible by the presence of bearings <NUM> mounted between the cylinder <NUM> and the seats <NUM> of the pins <NUM>, so as to prevent the transmission of the rotary motion to the cylinder <NUM>.

It should be noted that some embodiments provide for other gear systems, in place of the bevel gear pair <NUM>, such as for example epicyclic gears or gears with parallel axes depending on the sizing requirements of the mechanical device <NUM> and to the desired reduction ratio between the number of revolutions of the input shaft <NUM> and the degree of rotation of the valve plug.

Finally, in the detail of <FIG>, a support pin <NUM> is shown.

The support pin <NUM> is configured to ensure the fine adjustment of the respective rollers <NUM> on the respective helical flutes <NUM> present in the inner sleeve <NUM>.

Said pin <NUM> can have an eccentric outer portion to allow the position of said pin <NUM> to be adjusted radially.

Other known means for adjusting the respective rollers <NUM> on the respective helical flutes <NUM> can be alternatively used.

In the operation of the actuator <NUM>, as a result of a fluidic actuation according to modes known per se, the cylinder <NUM> slides axially inside the casing <NUM>.

The axial sliding of the cylinder <NUM>, along the piston <NUM>, compresses the spring <NUM>, while keeping the position of the piston <NUM> unchanged.

Such axial sliding of cylinder <NUM> involves the action of each pin <NUM> through the respective roller <NUM>, on the respective helical flute <NUM> so as to rotate the inner sleeve <NUM> around the longitudinal axis X, with the outer sleeve <NUM> which does not rotate, thus remaining in a fixed position by virtue of its coupling with the mechanical device <NUM>. Said outer sleeve <NUM>, during the rotation of the inner sleeve <NUM>, constrains the pins <NUM> to an axial translation thanks to the action of the sliding blocks <NUM> mounted on the pins and coaxial with the rollers <NUM>, which act on the axial flutes <NUM> formed in the outer sleeve <NUM>.

The rotation of the inner sleeve <NUM>, integrally connected to the plug, consequently rotates the valve plug.

In the absence of pressure in the cylinder <NUM>, the spring <NUM> extends again, thus returning the cylinder <NUM> to the initial position as well as the valve plug.

In case of need and/or emergency situation, with the cylinder <NUM> in its initial position and the spring <NUM> in extended configuration, it is possible to carry out an operation from the outside through the alternatively operating emergency mechanical device <NUM>.

Operating the mechanical device <NUM> requires acting on the input shaft <NUM>, the rotation of which moves the bevel gear pair <NUM> which, in turn, rotates the worm screw <NUM>.

Such worm screw <NUM> operates the rotation of the crown <NUM>, which consequently rotates the outer sleeve <NUM>.

Such outer sleeve <NUM> rotates the sliding blocks <NUM> engaged in the longitudinal flutes and consequently the rollers <NUM> which, by acting on the helical flutes of the inner sleeve <NUM>, transmit the rotation to the inner sleeve <NUM>.

The assembly of the sliding blocks and rollers is constrained to maintain the longitudinal position thanks to the reactive action of the spring <NUM>, which keeps the cylinder <NUM> and all the elements integral therewith during the whole manoeuvre through the mechanical device <NUM>.

It should be observed that alternative means with elastic behaviour for retaining the cylinder <NUM> and the respective elements integral therewith during the actuation of the mechanical device <NUM>, can be used peacefully without departing from the protection scope required herein.

The inner sleeve <NUM> is integrally connected to the plug, which consequently causes the valve plug to rotate.

Claim 1:
Actuator (<NUM>) for a control valve, where a plug of said actuator (<NUM>) can be operated by fluidic actuation and alternatively by an operating mechanical device (<NUM>), wherein said actuator (<NUM>) comprises a case (<NUM>) having a longitudinal axis, a cylinder (<NUM>), an inner sleeve (<NUM>) and an outer sleeve (<NUM>), wherein inside said case (<NUM>) there is said cylinder (<NUM>), which, as a result of the fluidic actuation, can axially slide inside said case (<NUM>), wherein said cylinder (<NUM>) has at least one support (<NUM>) for a pin (<NUM>), wherein each of said pins (<NUM>) can act on said inner sleeve (<NUM>) by means of corresponding helical flutes (<NUM>) formed in the inner sleeve (<NUM>) in order to rotate said inner sleeve (<NUM>) around the longitudinal axis of said case (<NUM>), while said outer sleeve (<NUM>) constrains said pins (<NUM>) to an axial translation and wherein the rotation of said inner sleeve (<NUM>) acts on the plug of the valve, characterized in that said alternatively operating mechanical device (<NUM>) can act by rotating said outer sleeve (<NUM>) in such a way that said pins (<NUM>) act on said helical flutes (<NUM>) of the inner sleeve (<NUM>) by rotating said inner sleeve (<NUM>), which acts on the movement of the plug.