Pyrotechnic actuator with a deformable membrane

Details Pyrotechnic actuator with a deformable membrane Pyrotechnic actuator with a deformable membrane

2001-05-17

2002-06-04

Nguyen, Hoang (Department: 3748)

Power plants

Fluid within expansible chamber heated or cooled

Having means within the working chamber to effect the...

C060S508000, C137S067000

Reexamination Certificate

active

06397595

ABSTRACT:

DESCRIPTION
1. Technical Field
The invention relates to a pyrotechnic actuator with a deformable membrane, i.e. a device able to actuate an external member, such as a valve or a jack, under the action of gases under high pressure produced by pyrotechnic means and acting on a deformable membrane.
The pyrotechnic actuator according to the invention can be used in numerous fields and in particular in the aeronautical and space industries for actuating members of different types such as valves, jacks, etc.
2. Prior Art
As is more particularly illustrated by FR-A-2 561 743, a pyrotechnic actuator conventionally comprises a body internally defining a cavity in which is placed a deformable membrane. More specifically, the deformable membrane subdivides the cavity into two chambers which are tight with respect to one another. A first of these chambers communicates with the pyrotechnic means in such a way that the operation of said means has the effect of filling said first chamber with pyrotechnic combustion gases under high pressure. The second chamber contains an actuating member. The deformation of the membrane brought about by the admission of combustion gases into the first chamber has the effect of displacing the actuating member on moving away from the first chamber. In FR-A-2 561 743, which describes a pyrotechnic actuator applied to the actuation of a valve, the effect of this displacement is to break apart bringing about the opening or closing of a tube integrated into the actuator body and forming part of a fluid circuit.
In a pyrotechnic actuator of this type, the membrane is inoperative in a non-prestressed state, which generally gives it an essentially planar shape. When the pyrotechnic combustion gases are admitted into the first chamber, the membrane deforms in the direction of the second chamber. To ensure sealing between the pyrotechnic combustion gases admitted into the first chamber and the fluid of the circuit, it is necessary to maintain the integrity of the membrane. Thus, the deformation of the membrane must take place on a limited functional path. To this end, a bearing surface is provided in the second chamber, so as to limit the deformation of the membrane within said second chamber.
This feature, more particularly described in FR-A-2 561 743, leads to the limitation of the functional travel of the actuating member placed in the second chamber. However, it is this functional travel which determines and limits the action of the actuating member. Thus, in the example described where the actuator is used for controlling a valve, the functional travel of the actuating member defines the dimensions of the part, which must be broken by the control member during the operation of the actuator. For an actuator of given dimensions, this leads to a limitation in the diameter of the tube in which the fluid circulates within the valve.
In order to obviate this disadvantage, it is possible to consider increasing the functional travel by increasing the membrane diameter. However, this very rapidly leads to giving the actuator large dimensions and a high weight. This is generally unacceptable, particularly in the most current applications of such actuators, namely the aeronautical and space industries.
SU-A-1 721 360 discloses a pyrotechnic actuator with a deformable membrane in which the membrane has, in the inoperative state, an undulating shape obtained by the compression of said membrane between a perforated disk, placed in a first chamber and provided for receiving the pyrotechnic combustion gases, and an actuating member placed in the second chamber. Said actuating member then bears, by means of damping elements, on a wall of the second chamber positioned facing the membrane. When the pyrotechnic means are actuated, the combustion gases penetrate the first chamber and drive back the actuating member against the aforementioned wall of the second chamber, whilst deforming the damping elements. At the end of its travel, the actuating member acts on a sealing device and destroys a bursting disk by which said device was initially linked with the actuator body. A spring then displaces the sealing device released in this way, which has the effect of opening a fluid circuit.
Said actuator is designed to limit the effects of impact during the operation of the pyrotechnic means in such a way as to increase the reliability thereof.
This result is obtained by limiting the functional travel for controlling the opening of the fluid circuit, which is in opposition to the aim of the present invention.
DESCRIPTION OF THE INVENTION
The invention specifically relates to a pyrotechnic actuator having a deformable membrane, whose original design makes it able to double the functional travel of the actuating member and therefore the diameter of the tube in which the fluid circulates when said member controls the opening or closing of a valve, but without increasing the size and weight of the actuator.
According to the invention this result is obtained by means of a pyrotechnic actuator comprising a body internally defining a cavity, a deformable membrane tightly subdividing said cavity into two chambers, a first of said chambers being able to receive pyrotechnic combustion gases in order to bring the membrane into an actuating position determined by a bearing surface limiting the deformation of the membrane within the second chamber, said second chamber containing a control member displaceable by said membrane over a distance corresponding to an actuating travel of said actuator when the combustion gases are admitted into the first chamber, characterized in that said membrane occupies in the inoperative state a prestressed position on moving away from the bearing surface.
In the invention defined in this way, due to the fact that the membrane occupies a prestressed position on moving away from the bearing surface when the actuator is inoperative, the operation of the actuator has the effect of deforming the membrane over a distance which is increased compared with the deformation of the membrane of a prior art pyrotechnic actuator, but without said deformation being prejudicial to the sealing of said membrane. This brings about a significant increase in the displacement of the member actuatable by the actuator and e.g. the size of a tube which can be severed by the actuator, but without increasing the size and weight thereof.
In a preferred embodiment of the invention, the prestressed position of the membrane is substantially symmetrical with respect to its actuating position. The functional travel is then doubled compared with a prior art pyrotechnic actuator.
Preferably, the prestressed position of the membrane is defined by its maintenance in abutment against the control member, normally bearing against a part able to break or move when the combustion gases are admitted into the first chamber.
Advantageously, said part is an integral portion of a fluid circuit, so that its breaking has the effect of changing the state of said circuit, i.e. either the opening or closing thereof.
Preferably, the membrane is planar when in its non-prestressed state.


REFERENCES:
patent: 3106131 (1963-10-01), Barr et al.
patent: 3315748 (1967-04-01), Merdinyan et al.
patent: 4091621 (1978-05-01), Patrichi
patent: 4111221 (1978-09-01), Olsen
patent: 4619284 (1986-10-01), Delarue et al.
patent: 5489072 (1996-02-01), Gordon et al.
patent: 6106008 (2000-08-01), Clackshire et al.
patent: 2 561 743 (1985-09-01), None
patent: 1 721 360 (1992-03-01), None

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