Aeronautics and astronautics – Aircraft structure – Ice prevention
Reexamination Certificate
1998-11-12
2001-02-27
Swiatek, Robert P. (Department: 3643)
Aeronautics and astronautics
Aircraft structure
Ice prevention
Reexamination Certificate
active
06193192
ABSTRACT:
The present invention relates to the deicing of air inlet cowls of jet engines, especially aircraft engines.
It is known that, if need be (to prevent the formation of ice or to remove ice that has already formed), the leading edge of the air inlet cowl of such engines is deiced by heating with pressurized hot air tapped from said engine and conveyed to said leading edge by a pressurized hot air circulation circuit.
To this end, such an air inlet cowl comprises:
a hollow leading edge delimiting an internal peripheral chamber, closed by an internal partition (or frame) and equipped with at least one orifice placing said internal chamber in communication with the outside; and
a pipe which can be connected, at the rear end away from said leading edge, to said pressurized hot air circulation circuit and, at the front end toward the leading edge, to an injector injecting said pressurized hot air into said internal chamber.
The known devices for providing the connection between the injector and the pipe are generally of the piston or stuffing box type. However, given that the pressurized hot air tapped from the engine and conveyed by said circuit is at a high temperature, of the order of 400° C., it is necessary to use special-purpose sealing products (high-temperature seal) which entail:
the joint being, by nature, extremely stiff,
a system for controlling the compression of the seal, and
a bearing surface for said seal which has a specific surface finish and a specific rigidity.
What this means is that these known connection devices are cumbersome and complicated and that they require costly special-purpose maintenance, entailing the provision of an access hatch in the engine cowl and intervention tooling which are specially reserved for maintaining said connection devices.
Furthermore, the rigidity of these connection devices entails perfect alignment between the pipe and the injector in order to avoid any risk of leaks. However, the thermal expansions and structural flexing of the engine nacelle affect this alignment and give rise to stresses in the surrounding structures.
The object of the present invention is to overcome these drawbacks.
To this end, according to the invention, the connection device that is airtight to pressurized hot air, for an air inlet cowl of a jet engine, particularly for an aircraft, said air inlet cowl being equipped with means for deicing its leading edge and comprising for this purpose:
a hollow leading edge delimiting an internal peripheral chamber closed by an internal partition and equipped with at least one orifice placing said internal chamber in communication with the outside; and
a pipe which can be connected, at its rear end away from said leading edge, to a pressurized hot air circuit and, at its front end toward said leading edge, to an injector injecting said pressurized hot air into said internal chamber,
said airtight connection device being designed to connect said pipe to said injector, is noteworthy in that it consists of a ball joint allowing variations in the longitudinal and angular positions of said pipe with respect to said injector.
Thus, as said connection device is no longer rigid, it is no longer necessary to ensure perfect alignment between the pipe and the injector, and the mechanical stresses are avoided.
In an advantageous embodiment, said connection device comprises:
a cylindrical chamber, open at both ends and secured to said injector at its front end; and
a hollow ball, secured to the front end of said pipe and tightly fitted into said cylindrical chamber through the rear end thereof.
It can be seen that in this way the front end of said pipe and said hollow ball can pivot and be translated axially with respect to said cylindrical chamber and to said injector, in order to accept the tolerances, the thermal expansions, the relative moments and the structural deformations. It will also be noted that said pipe connects to the injector simply by being push-fitted into said cylindrical chamber.
In order to ensure good airtightness in the ball joint in accordance with the present invention, while at the same time avoiding excessive wear, said joint may additionally have the following particular features:
the cylindrical internal wall of said chamber, against which said ball is pressed, is coated with an antifriction coating, which may be borne by a ring, preferably mounted removably in said cylindrical chamber so that it can be replaced;
the hollow ball may be made of a slightly elastic metallic material, or alternatively may be made of a rigid metallic material and bear an elastic external coating. This elastic coating may hug the exterior surface of said ball or alternatively be separated therefrom by a clearance, increasing its elasticity. As an alternative, said hollow ball may bear a diametral seal cooperating with the internal wall of said cylindrical chamber;
the hollow ball may form part of a piece, attached to the front end of said pipe, for example by welding; and
the cylindrical chamber may comprise means for attaching it and said injector to said internal partition, it being possible for this attachment to be rigid or alternatively allow said cylindrical chamber to float longitudinally with respect to said internal partition.
Furthermore, the present invention relates to an air inlet cowl for a jet engine, particularly for an aircraft, said air inlet cowl being equipped with means for deicing its leading edge and comprising for this purpose:
a hollow leading edge delimiting an internal peripheral chamber closed by an internal partition and equipped with at least one orifice placing said internal chamber in communication with the outside; and
a pipe which can be connected, at its rear end away from said leading edge, to a pressurized hot air circuit and, at its front end toward said leading edge, to an injector injecting said pressurized hot air into said internal chamber,
this air inlet cowl being noteworthy in that, in order to connect said injector to said pipe, it comprises a connection device which consists of a ball joint allowing variations in the longitudinal and angular positions of said pipe with respect to said injector.
Of course, this connection device may have all the features described hereinabove.
Advantageously, in the air inlet cowl in accordance with the present invention, the rear end of said pipe, which can be connected to said hot air circuit, is fixed in position on another internal partition (or frame) of said cowl. Thus, said rear end occupies a precise position making it easy to connect to the hot air circuit secured to the engine. Such attachment of said end to said other internal partition may be rigid. It may, as an alternative, allow said rear end of the pipe to slide longitudinally with respect to said other internal partition.
In a particular embodiment, the rear end of said pipe is secured to another attached piece comprising means of attachment to said other partition and means of connection to said hot air circuit.
From what has just been described it can be seen that, by virtue of the present invention, there is obtained a deicing circuit for an engine air inlet cowl, the design of which is practically isostatic and eliminates thermal and structural stresses while being durably airtight to pressurized hot air. This deicing circuit has only a few parts and its mass and cost can be optimized. What is more, it readily adapts to the tolerances and to the structural deformations of the environment.
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patent:
Aerospatiale - Societe Nationale Industrielle
Fisher Christen & Sabol
Swiatek Robert P.
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