Electromechanical actuator for controlling a flow modulator of t

Details Electromechanical actuator for controlling a flow modulator of t Electromechanical actuator for controlling a flow modulator of t

1995-01-27

1998-07-28

Lee, Kevin

Valves and valve actuation

Electrically actuated valve

Rotary electric actuator

251 65, F16K 3102

Patent

active

057852960

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The subject of the present invention is an electromechanical actuator for controlling a flow regulator of the vane type pivoting inside a pipe.
Rapid fluctuations in flow rate encountered in industrial plant are dynamic in nature, that is to say that their behaviour involves inertia and elasticity of the fluid or of the walls of the devices. They may be the cause of particularly troublesome phenomena such as excessive vibration giving rise to fatigue of the materials, or acoustic disturbance. These fluctuations cannot be controlled using the conventional devices for shutting off pipelines (valves, cocks . . . ) which in practice require quite a long time to open them owing to their inertia or to their displacement device (screw for example).
DE-A-3,908,546 discloses a device for driving a butterfly valve for an internal-combustion engine.
Such a device includes a rotor, secured to the butterfly valve, and a stator which includes windings capable of generating a variable magnetic field acting on the rotor to make it turn.
The rotor is equipped with a return device for establishing correspondence between the strength of the electric current flowing through the windings of the stator and the angular position of the rotor.
By virtue of this drive device, the butterfly valve may be precisely positioned angularly.
However, this device is provided only for a gas inlet valve of an internal combustion engine. Such a valve is intended to assume various stable positions in succession, each position corresponding to one set of operating conditions of the engine.
Between two variations in operating conditions, the valve remains in its angular position.
In contrast, the present invention aims to provide a very low inertia device which can impart, for example to a butterfly valve, very rapid alternating movements so as to control the surges of a fluid in a pipe.
FR-A-2,613,089 makes known a method and a device for reducing such rapid fluctuations in flow rate of a fluid flowing in a pipe.
In this document, a flow regulator is provided having the appearance of a vane or of a butterfly valve mounted so that it can pivot in a pipe and the purpose of which is to create an instantaneous head loss; its dimensions, determined as a function of this last objective, may in general lead to a shape and to dimensions which do not make it possible to close off the pipeline completely. This regulator is controlled by a driving means such as a stepper motor.
However, although it allows accurate positioning of the flow regulator, a stepper motor may have too long a response time.
Furthermore, a device which controls surges in a fluid does not, a priori, include the angular position of the flow regulator as an operating parameter. Now, knowledge of this position is indispensable if a stepper motor is used.
It is therefore necessary to have use, in addition to the stepper motor, of a device for accurately identifying the angular position of the flow regulator.
In order to overcome this drawback, the use of a conventional electric motor could be envisaged.
However, the actuation of the flow regulator is then not very reliable and even detrimental to the motor itself, because the brushes of the latter wear rapidly owing to the fact that it constantly operates in the start-up region.
Bearing in mind the values of the frequencies of oscillation required to obtain effective actuation of the flow regulator, a mechanical transmission of a rotational movement of the actuator into an oscillatory movement of the flow regulator would have too high an inertia and would preclude any possibility of matching the characteristics of the alternating movement to those of the flow rate measured.


SUMMARY OF THE INVENTION

The present invention aims to provide an actuator having a low moment of inertia, of the order of 2.10.sup.-7 kg/m.sup.2, which allows it to reach very high values of acceleration, of the order of 5.10.sup.4 rad/s.sup.2, by virtue of which the flow regulator can reach frequencies of the order of several tens to

REFERENCES:
patent: 4800308 (1989-01-01), Tice
patent: 5158262 (1992-10-01), Kamerbeek et al.
patent: 5238023 (1993-08-01), Kristoffer

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