It is well known in the field of aircraft gas turbine engine propulsion systems to provide a thrust reversing system to slow the aircraft down when it has contacted the landing field and the brakes have been applied to the wheels of the aircraft. These thrust reversing systems are deployable to reverse the fan air of a by-pass fan type aircraft gas turbine jet engine and in some instances to reverse the combined flow of the fan air and main thrust gases issuing from the nozzle of the core engine. Generally speaking, a target type thrust reverser system is used for smaller aircraft gas turbine jet engines, a pivoting door thrust reverser system is used for larger aircraft gas turbine jet engines and a cascade type thrust reverser system is used for the largest high by-pass fan aircraft gas turbine jet engines. Each thrust reversing system has its advantages and limitations for the particular size of aircraft gas turbine engine with which it is used.
An early example of a translating sleeve thrust reverser system, which was the forerunner of the cascade type thrust reverser system, is seen in U.S. Pat. No. 3,036,431 which shows a translating sleeve which forms the fan duct being translated aft by translating actuator means. As the translating sleeve is translated aft a plurality of blocker doors positioned forwardly of the translating sleeve in a fixed cowl structure are rotated inwardly into abutting contact with the core cowl of the aircraft gas turbine engine in order to block the fan air and reverse its flow forwardly through the opening created by the translated sleeve structure and the fixed cowl structure.
U.S. Pat. No. 3,262,270 illustrates a later translating sleeve thrust reverser system in which a lower translating sleeve carries a plurality of circumferentially arranged blocker doors on its inner forward edge, the blocker doors being hingedly connected to the core cowl so that translation of the lower translating sleeve causes the blocker doors being drawn inwardly by such hinged connections into abutting contact with the core cowl and to reverse the fan air through the ii- opening created by an upper translating sleeve portion and a fixed cowl structure. The sleeve structure of this thrust reverser system actually comprises two sleeve portions, one being translatable and another being fixed which carries a fixed cascade structure through which the reversed fan air flow flows.
The most common type of cascade type thrust reverser system in use today for an aircraft fan gas turbine jet engine employs a forward fixed cowl portion and a translating sleeve which carries a plurality of circumferentially arranged blocker doors on its inner skin surface. The blocker doors are hingedly connected to the translating sleeve and are also hingedly connected to the core cowl of the jet engine so that aft translation of the translating sleeve causes the blocker doors to be drawn inwardly into fan air blocking abutment with the core cowl and cause the reversed fan air to flow through the opening provided by the translated sleeve and the fixed cowl portion A plurality of cascades are either fixedly positioned in the exposed opening or are translated into such opening by the translation of the sleeve structure. While such a thrust reversing system is in common use in the art, it is still possible to improve upon such an arrangement.
Characteristically, such an arrangement provided for the inner sleeve to be constructed by adhesively bonding a number of detail parts together to provide for openings for such blocker doors and the requisite hinged connections. Also, to preclude any tendency for air to leak through the multiplicity of bonded parts a backing layer in the form of a honeycomb core panel termed a "pressure shelf" was bonded to the inner side of the inner skin of the translating sleeve structure. Such a arrangement was expensive to manufacture. Also, this arrangement provided for the blocker doors to be provided at the leading edge of the translating sleeve structure and did not take into account the deleterious effect of fluid being expelled, from time to time, at an elevated pressure and temperature though bleed ports provided in the core cowl to alleviate undesired buildup of pressures associated with the core engine. Such expulsions when they occur could be very injurious to the blocker doors and their hinged link connections.
Also, since the blocker doors were positioned at the leading edge of the inner skin of the translating sleeve the sizing of such blocker doors to accommodate the fan air duct was limited in that only a certain level of efficiency of limitation of blow-by of fan gases past the closed blocker doors could be achieved. A mid frame stiffening structure was also characteristically interposed between the inner and outer skins of the translating sleeve and added to the weight and manufacturing complexity of such a sleeve.
U.S. Pat. No. 4,545,199 is directed to a fan cascade thrust reverser particularly adapted for a military aircraft where it was desirable to substantial eliminate the problems of engine ingestion of reversed gases and of the dust and blowing about of foreign objects when landing, taking off or ground maneuvering. This thrust reverser provides a lower non-translating sleeve section and an upper translatable sleeve section that could be translated to expose an opening between such translating sleeve section and a fixed cowl structure. The blocker doors include a first set that rotatably attached to the upper translating sleeve section and a second set of blocker doors that are circumferentially arranged around the core cowl and are connected to the fixed lower sleeve portion and to the upper sleeve portion Both sets of blocker doors were suitably rotated inwardly to block the fan air and direct it upwardly and outwardly from the thrust reverser. No thought was given to the location of the bleed port means in the core cowl in this arrangement.
U.S. Pat. No. 4,858,430 is directed to a pivoting door arrangement in which a plurality of large pivoting blocker doors have their inner and outer skins forming part of the inner and outer flow surfaces of a fixed cowl portion. Such pivoting doors are pivoted outwardly to cause their inner trailing surfaces to contact the core cowl of an aircraft engine and reverse the fan air flow. This patent shows that the each pivoting door may be provided at its leading edge with an opening to assist the reversed fan air in flowing forwardly by increasing the space available for such fan air flow.
U.S. Pat. No. 4,914,905 is a variation of the pivoting door thrust reverser arrangement described above and also teaches the provision of an air deflector positioned at the trailing edge of the fixed cowl portion of the thrust reverser. Characteristically, such a pivoting door arrangement is provided with a "pit" formed by the leading edge of each blocker door and the trailing edge of such door to enhance the thrust reversing capability of the pivoting door when opened. This patent also teaches that the air deflector could also be attached to an actuator for each door in the immediate vicinity of the fixed cowl structure.
While the aforesaid and other thrust reverser arrangements have been generally satisfactory for thrust reversing purposes a general need continues to exist for improvements in thrust reversing arrangements to decrease their cost, increase their reliability and performance, to reduce their weight, and to increase the ease of manufacture.
Accordingly, it is a general object of this invention to provide a cascade type thrust reversing arrangement which decreases the cost of manufacture of the translating sleeve structure and which provides for the positioning of the blocker doors in a position which precludes damage to such doors from fluid emanating from bleed ports in the core cowl.
It is another object of the invention to provide an improved translating sleeve structure which accommodates blocker doors all having the same size and being positioned to increase the efficiency of the thrust reverser to an optimum blow-by fan air percentage.
It is still another object of the invention to provide an improved translating sleeve structure which eliminates a mid fame structure therein and that precludes a build up of pressure of the reversed fan air in the interior of the translating sleeve structure.
It is yet another object of the invention to provide an improved translating sleeve structure that provides improved fan air flow through the opening provided the deployment of such sleeve structure.
It is a further general object of this invention to provide pressure seal means that cooperates with the translating sleeve structure in its stowed position to preclude outward leakage of the fain air during thrust and which is optimally positioned to preclude interference with the reversed fan air and to enhance the service life of such seal means
The foregoing has outlined some of the more pertinent objects of the invention. These objects should be construed to be merely illustrative of some of the more prominent features and application of the intended invention Many other beneficial results can be attained by applying the disclosed invention in a different manner or by modifying the invention within the scope of the disclosure. Accordingly, other objects and a fuller understanding of the invention may be had by referring to the summary of the invention and the detailed description of the preferred embodiment in addition to the scope of the invention defined by the claims taken in conjunction with the accompanying drawings.