Electric actuator for control valves

Abstract

Electric actuator (10) for a process fluid control valve (30) provided with: • - an electric motor (20) configured to convert electrical energy into rotary or linear motion to operate the control valve (30), • - a gear mechanism (40) configured to transmit the motion delivered by the electric motor to a stem (50) of the valve (30), and • - a fail-safe mechanism (60, 80), configured to intervene in emergency conditions, wherein the fail-safe mechanism (60) is provided with an elastic element (70), configured to store energy during normal operating conditions and to release energy when an emergency condition occurs, so as to move the valve (30) to a predetermined position.

Description

[0001] ELECTRIC ACTUATOR FOR CONTROL VALVES DESCRIPTION

[0002] Technical Field of the Invention

[0003] The present invention relates to an electric actuator for fluid control valves. In particular, the electric actuator is provided with a fail-safe mechanism that manages emergency situations.

[0004] Background art

[0005] Electric actuators for control valves with fail-safe mechanism are critical components in automated systems, providing precise control and safety in various industrial applications. These actuators convert electrical energy into mechanical motion to operate valves and are equipped with an emergency or fail-safe mechanism that ensures that the valve moves to a safe position in the event of a power failure or system malfunction.

[0006] In the state of the art, several embodiments of electric actuators are known. For example, in US5497672A an electric valve actuator is described that is designed for efficient valve control, especially in subsea applications. It is equipped with a solenoid-actuated locking mechanism that allows precise axial movement of the valve stem, allowing rapid opening and closing of the valve. This solution improves operational efficiency and reliability in fluid flow control, especially in environments where hydraulic systems could fail due to external temperature, corrosive environment, harsh operating conditions.

[0007] W02019 / 002906A1 is a fail-safe electric gate valve actuator that integrates a simple and efficient mechanism for emergency closing. It isequipped with a housing, a movable stem, an electric motor drive assembly and a biasing assembly that ensures that the valve returns to a safe position in the event of a loss of power. The purpose of this actuator is to ensure reliable valve operation and emergency closing without the need to use hydraulic or pneumatic systems.

[0008] In W02020 / 088974A1, the object of the invention is to provide a safety device that safely blocks the output element of a linear actuator, particularly in applications such as process valves. The purpose of this device is to ensure that the connected system can be reliably transferred to a predefined safe state (e.g. a valve in the fully open or fully closed position), preventing accidental movements during power outages or system failures.

[0009] All known electric actuators, however, are characterized by complex solutions that require significant energy requirements, especially for the emergency mechanism.

[0010] There is therefore a need to define an electric actuator for control valves that is free from or at least minimizes the above-mentioned drawbacks.

[0011] Summary of the invention

[0012] In order to solve the above-mentioned technical problems, the present invention relates to an electric actuator for process fluid control valves, the actuator being provided with a fail-safe mechanism realized by means of an elastic element that stores energy during normal operation and that, in case of emergency situations, releases its energy to move thevalve to a safe position (fully open or fully closed, depending on the application).

[0013] Therefore, according to the present invention, an electric actuator for process fluid control valves is realized, provided with a fail-safe mechanism and that has the characteristics set forth in the independent claim.

[0014] Further preferred and / or particularly advantageous ways of implementing the invention are described according to the characteristics set forth in the appended dependent claims.

[0015] Brief Description of the Drawings

[0016] The invention will now be described with reference to the attached drawings, which illustrate some non-limiting examples of implementation, in which:

[0017] - figure 1 is a diagram of the operation of an electric actuator equipped with a fail-safe mechanism and used for control valves of process fluids, according to a first embodiment of the present invention, and

[0018] - figure 2 is a diagram of the operation of the electric actuator in a second embodiment of the present invention.

[0019] Detailed description

[0020] With reference to the above figures, an electric actuator for control valves is indicated with the reference 10.

[0021] The electric actuator 10 comprises:

[0022] - an electric motor 20, for example an alternating current motor or a direct current motor. Preferably, a brushless direct current motor will be used, as it is more efficient and more reliable than other types of electricmotor. The electric motor converts electrical energy into rotary or linear motion to operate a valve 30 for controlling a process fluid;

[0023] - a gear mechanism 40, of a known type and for this reason only indicated in its position, mechanically connected to the electric motor 20. The gear mechanism transforms the rotary motion into linear motion, if applicable, and in any case transmits the motion delivered by the electric motor to the stem 50 of the valve 30, regulating speed and torque according to the needs of the application. The gear mechanism may include planetary gears, worm gears or cylindrical gears, depending on the requirements of the application;

[0024] - a safety mechanism or fail-safe mechanism 60, characterized in that it comprises an elastic element 70, for example a coil spring. During normal operating conditions, the elastic element 70 stores energy, for example mechanical energy due to the compression of the coil spring. When an emergency condition occurs, for example a power failure, the elastic element 70 releases its energy (for example, the coil spring expands) to move the valve 30 to a safe position, either fully open or fully closed depending on the safety requirements of the application.

[0025] The elastic element can be a helical spring, as well as a leaf spring or a cup spring. In the following description, specific reference will be made to a helical spring 70 without losing generality. Conveniently, the helical spring 70 is housed between a first plate element 71, fixed, and a second plate element 72, mobile but integrally connected to the electric motor 20, to the gear mechanism 40 and to the valve stem 50.The accumulation of energy and its subsequent release can be achieved in different ways.

[0026] For example, according to a first preferred embodiment of the invention and with particular reference to figure 1, the energy that the spring 70 accumulates during a dedicated phase is generated by a pump element 1, for example a hydraulic pump, powered by a motor 2. The pump 1 is fluidically connected to cylinders 13, preferably two in number, and containing within them respective hydraulic pistons 14 which define the first 13' and second chambers 13" inside the cylinders 13. Along a delivery line 3 the pump 1 pressurizes the first chambers 13' of the cylinders 13. The second chambers 13" of the cylinders 13 are connected to a supply line 4 in fluidic connection with the pump 1. Pump element 1, delivery line 3, the first 13' and second 13" chambers and the supply line define a hydraulic circuit 5.

[0027] In normal operating conditions, the first chambers 13' have a higher pressure than the pressure of the second chambers 13" and, consequently, the pistons 14 exert a pressing action on the second plate element 72, which in turn compresses the helical spring 70.

[0028] In emergency conditions, a controlled valve 6, for example a solenoid valve, connects the first 13' and second chambers 13" of the cylinders 13, i.e. the delivery line 3 and the supply line 4, in fluidic connection. In this way, a pressure balance is created between the first 13' and second chambers 13". The piston 14 will then cease to exert the pressing action on the second plate element 72 which in turn will cease to compress the spring 70. The expansion energy released by the spring 70 isable to lift the entire electric motor group 20, gear mechanism 40 and stem 50 of the valve 30, bringing the valve itself to a safe condition, for example completely open as in figure 1.

[0029] Advantageously, hydraulic accumulators 11, 12 compensate for the system losses, in order to keep the pressure inside the cylinders 13 stable. In the hydraulic implementation described above, the spring 70 represents a possible implementation of the accumulation of mechanical energy necessary to carry out the safety stroke. This task can, in principle, also be achieved by means of a gas or spring-operated hydraulic accumulator, positioned in the vicinity of the valve, using the pressurized liquid contained therein to provide the hydraulic cylinders 13 with the force necessary to lift the entire electric motor unit 20, by filling the chambers 13". This alternative implementation, which requires some small modifications to the hydraulic circuit, is not directly illustrated in figure 1.

[0030] In a second and preferred embodiment of the invention and with particular reference to Figure 2, the fail-safe mechanism 80 operates via an electro-hydraulic brake 90, which releases force on demand.

[0031] Energy may be stored via the use of a hydraulic pump and hydraulic pistons as in the previous embodiment, or via a second electric motor 82, separate from the first electric motor 20. In the case of an electric motor, the electro-hydraulic brake 90 may be applied directly to the second electric motor 82.

[0032] The second electric motor 82 is mechanically connected to a transmission mechanism 83 comprising a pair of gear wheels 84 coupled to respective toothed rods 85.The electro-hydraulic brake 90 comprises an electromagnetic actuator 91 and a pair of pistons 92 hydraulically connected to the electromagnetic actuator 91 by means of a hydraulic circuit 93 (e.g., pressurized oil circuit). The pistons are respectively positioned on the opposite side to the second plate element 72.

[0033] In normal operating conditions, by operating the mechanism 83, the toothed rods 85 exert a pressing action on the second plate element 72, which in turn compresses the helical spring 70. The thrust on the second plate element 72 ends when the plate itself is aligned with the pair of pistons 92. In this condition, the electromagnetic actuator 91 is energized, compresses the oil in the hydraulic circuit and, consequently, operates the pistons 92. The pistons 92, in turn, exert a radial force on the second plate element 72, maintaining it in the position reached. The second electric motor 82 can then release the second plate element 72, reversing the motion and moving the toothed rods 85 away from the plate itself. In this way, the compression of the helical spring 70 is guaranteed exclusively by the pair of pistons 92.

[0034] In emergency conditions, the electromagnetic actuator 91 is deenergized and the pair of pistons 92 is released. Therefore, the spring 70 is able to push the second plate element 72 releasing the previously stored energy.

[0035] In conclusion, the present invention allows to have a solution for the fail-safe mechanism of an electric actuator that is simple to implement and requires very limited energy consumption.In addition to the embodiment of the invention, as described above, it is to be understood that numerous other variants exist. It is also to be understood that such embodiments are exemplary only and limit neither the scope of the invention, nor its applications, nor its possible configurations. On the contrary, although the above description allows the skilled person to carry out the present invention at least according to an exemplary embodiment thereof, it must be understood that many variants of the components described are possible, without thereby departing from the scope of the invention, as defined in the attached claims, which are interpreted literally and / or according to their legal equivalents.

Claims

AMENDED CLAIMSreceived by the International Bureau on June 11 , 2026 (11.06.2026)CLAIMS1. Electric actuator (10) for a process fluid control valve (30), comprising:- a first electric motor (20) configured to convert electrical energy into rotary or linear motion to operate the control valve (30),- a gear mechanism (40) configured to transmit the motion delivered by the first electric motor (20) to a stem (50) of the valve (30), and- a fail-safe mechanism (80), configured to intervene in emergency conditions,the electric actuator (10) being characterized in that the fail-safe mechanism (80) comprises an elastic element (70), configured to store energy during normal operating conditions and to release energy when an emergency condition occurs, so as to move the valve (30) to a predetermined position,wherein the elastic element is a helical spring (70) housed between a first plate element (71), fixed, and a second plate element (72), movable and integrally connected to the first electric motor (20),and wherein the fail-safe mechanism (80) comprises an electro-hydraulic brake (90) provided with:an electromagnetic actuator (91), configured to be energized under normal operating conditions and to be de-energized under emergency conditions, anda pair of pistons (92) hydraulically connected to the electromagnetic actuator (91) by means of a hydraulic circuit (93), wherein the pistons are respectively positioned on opposite sides of the second plate element (72)and, under normal operating conditions, are configured to exert a radial force on the second plate element (72) maintaining it in position,and wherein the fail-safe mechanism (80) comprises a second electric motor (82), separate from the first electric motor (20), mechanically connected to a transmission mechanism (83), in turn comprising a pair of toothed wheels (84) coupled to respective toothed stems (85), wherein under normal operating conditions the toothed stems (85) are configured to exert a pressing action on the second plate element (72) until the second plate element (72) is aligned with the pair of pistons (92).

2. Electric actuator (10) according to claim 1, wherein the electric motor (20) is a brushless DC motor.

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