Abstract:
A thrust reverser blocker door assembly for use in turbofan engines includes an engine nacelle with an aft translating cowl that is movable from a stowed position to a deployed position. An engine case is disposed within the engine nacelle forming an airflow duct therebetween. A gap is uncovered when the translating cowl is moved into the deployed position, and a cascade vane set is positioned in the gap. A blocker door covers the cascade vane set while in the stowed position and blocks a portion of the airflow duct while in the deployed position. A geometrically shaped drag link is pivotally connected to the engine case at a first end and connected to the blocker door at a second end. While in the deployed position, the shape of the drag link provides clearance from the engine case.

Description:
BACKGROUND 
     This invention relates to cascade type thrust reversers for aircraft turbofan engines and, more particularly, to blocker door assemblies used in cascade type thrust reversers. 
     Modern aircraft turbofan engines have a nacelle or shroud surrounding the engine, spaced outwardly from a core engine cowl to define an annular passage or duct for flow of air rearwardly from the outer portion of a large fan or axial flow compressor. In this type of engine, a large proportion of the total thrust is developed by the reaction to the air driven rearward by the fan. The balance of the thrust results from ejection of the exhaust gas stream from the core engine. 
     Aircraft using gas turbine engines tend to have high landing speeds, placing great stress on wheel braking systems and requiring very long runways. To reduce this braking requirement and permit use of shorter runways, means are now provided in such engines for reversing a major portion of engine thrust during the landing roll. Many different types of thrust reversers have been designed. 
     With turbofan engines, it is possible to block and reverse substantially all of the fan flow without excessive stress on the system, since the core flow continues through the engine. In some cases, sufficient reverse flow can be obtained by blocking only a substantial portion of the fan flow. The most common type of thrust reverser used in turbofan engines utilizes sets of cascade vanes in the sidewalls of the engine nacelle with devices for uncovering the cascades to direct the airflow though the cascades, which turn the airflow in a reverse direction. 
     As turbofan engines become increasingly more complex and efficient, the higher their bypass ratios get. A higher bypass ratio in a turbofan engine leads to better fuel burn because the fan is more efficient at producing thrust than the core engine. As a consequence, the fan gets bigger, and the annular airflow duct between the nacelle and the core engine cowl gets taller. The introduction of a fan drive gear system for turbofan engines has also led to smaller engine cores. Smaller engine cores lead to shorter fan ducts, which are desirable so the heavy components of the engine are not hung out too far in front of the wings of the aircraft. As such, engine sub-systems are required to be packaged within smaller spaces. 
     SUMMARY 
     The present invention is a thrust reverser blocker door assembly that includes an engine nacelle with an aft translatable cowl and an engine case disposed inside the engine nacelle such that an airflow duct is formed between the engine nacelle and the engine case. The translatable cowl can translate from a stowed position to a deployed position, uncovering a gap between the translatable cowl and the nacelle. A cascade vane set is positioned in the gap, a portion of which is covered by a blocker door when the translatable cowl is in the stowed position. The blocker door moves to block a portion of the airflow duct when the translatable cowl is in the deployed position. A geometrically shaped drag link is pivotally connected to the engine case at a first end and connected to the blocker door at a second end. The blocker door and shaped drag link move with the translatable cowl. When the geometrically shaped drag link and blocker door are in the deployed position, the shape of the drag link provides clearance from the engine case. 
     In another aspect of the invention, an aircraft turbofan engine includes an engine nacelle with an aft translatable cowl and an engine core disposed inside the engine nacelle such that an airflow duct is formed between the engine nacelle and the engine core. A fan disposed at a forward portion of the engine nacelle can produce a flow of air through the airflow duct. A protrusion such as an airflow scoop for an air/oil cooler is positioned within the airflow duct. An actuator is able to extend the translatable cowl from a stowed position to a deployed position, uncovering a gap between the translatable cowl and the nacelle. A cascade vane set is positioned in the gap, a portion of which is covered by a blocker door when the translatable cowl is in the stowed position, thereby allowing a flow of air to travel through the airflow duct. The blocker door moves to block a portion of the flow of air through the airflow duct and divert the flow of air through the cascade vane set when the translatable cowl is in the deployed position. A geometrically shaped drag link is pivotally connected to the engine core at a first end and connected to the blocker door at a second end. The blocker door and shaped drag link move with the translatable cowl. When the geometrically shaped drag link and blocker door are in the deployed position, the shape of the drag link provides clearance to avoid contacting the protrusion positioned within the airflow duct. 
     In yet another aspect of the invention, a blocker door assembly comprises a geometrically shaped drag link with a first end and a second end. The first end of the geometrically shaped drag link is connected to a blocker door, while the second end of the drag link is pivotally connected to a boss. The geometrically shaped drag link may be connected to the blocker door by inserting the first end through a slot in the blocker door and securing the first end with a pin or bolt that goes through a hole in the first end of the geometrically shaped drag link. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic side view of a typical aircraft turbofan engine cowl using a thrust reverser system. 
         FIG. 2  is a fragmentary, sectional view taken along line  3 - 3  in  FIG. 1  showing a blocker door incorporating a curved drag link, illustrated in the stowed position. 
         FIG. 3  is a view similar to  FIG. 2 , showing the blocker door and curved drag link in a deployed thrust-reversing configuration. 
         FIG. 4  is view taken along line  4 - 4  in  FIG. 3  showing two blocker doors deployed in a thrust-reversing configuration. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows turbofan engine  10  that is mounted onto an aircraft by pylon  12 . Engine  10  includes segmented cowl  13  which includes nacelle body  14  and translating cowl  16  and engine core  18 . Duct  20  is formed between nacelle body  14  and core  18  for fan air flow. Translating cowl  16  is split from nacelle body  14  and translates rearwardly to produce reverse thrust. 
     With cowl  16  translated aft as seen in  FIG. 1 , a plurality of cascade vane sets  22  are uncovered. Each of cascade vane sets  22  includes a plurality of conventional transverse, curved, turning vanes which turn airflow passing out from duct  20  through the cascade sets in an outwardly and forwardly direction relative to engine  10 . Islands  24  are provided between cascade vane sets  22  to support the translation of cowl  16  and support the sides of cascade vane sets  22 . In the stowed position, cowl  16  is translated forwardly to cover cascade vane sets  22  and provide a smooth, streamlined surface for air flow during normal flight operations. 
       FIG. 2  shows a portion of an inner view of engine  10  which includes segmented cowl  13 , engine core  18 , duct  20 , air/oil cooler  26 , blocker door  28 , cascade  30 , and linkage assembly  32 . Engine core  18  is circumscribed by segmented cowl  13 . Segmented cowl  13  includes nacelle body  14  and translating cowl  16  capable of rearward translation along the longitudinal axis of engine  10 . Disposed internally of segmented cowl  13  is translating sleeve  34  slaved for movement with translating cowl  16 . Lying yet closer to the engine centerline is inner fixed structure (IFS)  36 . IFS  36  is an outer surface of engine core  18 . Duct  20  lies between translating sleeve  34  and IFS  36  and through which engine air is forced by a fan (not shown) for the operation of the engine. 
     In this particular portion of engine  10  shown in  FIG. 2 , air/oil cooler (AOC)  26  is comprised of airflow scoop  38 , intake duct  40 , exhaust duct  42  and aero faring surface  44 . AOC  26  is disposed within IFS  36  to pull airflow out of duct  20  with its airflow scoop  38 . The airflow travels through AOC intake duct  40  into AOC  26  where the relatively cool air from duct  20  is able to cool engine oil in a fluid heat exchange before it reenters duct  20  through AOC exhaust duct  42 . Scoop  38  has aero faring surface  44  to minimize the drag that it produces in duct  20 . As turbofan engines become more complex, sophisticated, and axially shorter, it becomes more common to have protrusions such as scoop  38  of AOC  26  extending from IFS  36  into duct  20 . Other types of devices that may protrude into duct  20  include heat exchangers such as precoolers, and deicers, as they, too, may utilize scoops to pull airflow from duct  20 . The considerations that go into packaging a modern turbofan engine with accessories such as heat exchangers often make it impractical or inefficient to build turbofan engines without these sorts of protrusions into duct  20 , therefore it is important to note that very seldom are modern turbofan engines equipped with perfectly smooth fan ducts  20 . 
     Annular bypass duct  46  is disposed circumferentially adjacent and radially outward of duct  20 , defined between translating cowl  16  and translating sleeve  34 . In the normal or cruise mode shown in  FIG. 2 , blocker door  28  lies generally contiguous with the surface of translating sleeve  34  and functions as a continuous extension thereof defining a forward zone of duct  20 . Forward face  48  of blocker door  28  thus constitutes an aerodynamic surface within engine  10 . Door  28  is configured to mate and cooperate with a plurality of like doors; a typical door has a general form of an arcuate wedge segment of a circle with a radius corresponding generally to the radius of curvature of translating sleeve  34 . When door  28  is associated with a plurality of like doors disposed with side edges in mating engagement, an annular ring is formed as shown in  FIG. 4 . 
     Cascade  30  is disposed within bypass duct  46  secured by forward and aft brackets  50  and  52  respectively. Cascade  30  includes a plurality of vanes  54  curved with a forward aspect to divert air in that direction through duct  46 . In the cruise mode shown in  FIG. 2 , cascade  30  is surrounded by blocker door  28  and translating cowl  16 . Therefore, as airflow passes through duct  20 , blocker door  28  and its forward face  48  prevent airflow from passing through bypass duct  46  and cascade  30 . Linkage assembly  32 , responsible for control in the deployment of blocker door  28 , includes drag link  56  which is pinned or otherwise secured for rotation around its proximal end. In the embodiment shown, this is achieved by securing drag link  56  by pin  58  to boss  60  secured to IFS  36  by flange  62 . Both drag link  56  and boss  60  are provided with suitable bushings or bearings within this pin joint for improved dynamic performance. The distal end of drag link  56  is inserted through slot  64  in blocker door  28  and is secured with pin  66 . Any other means of securing drag link  56  to blocker door  28  can also be used, such as a bolt for example. 
     Cascade  30  shown in  FIG. 2  is just one of many cascade vane sets  22  disposed circumferentially around engine  10  as shown in  FIG. 1 . Actuator  68  is disposed between these sets of cascades in order to drive cowl  16  and translating sleeve  34  rearward by means of connection  69  on translating sleeve  34 . After a thrust reversing operation is completed, actuators  68  return blocker door  28  to the stowed position. Actuator  68  can be a ball-screw actuator, hydraulic actuator, or any other actuator known in the art. In one embodiment, multiple actuators  68  are spaced around engine  10  in between cascade vane sets  22 . 
     Blocker door  28  is engaged with translating sleeve  34  through bracket means  70 . Pivot  72  is a hinge attachment between blocker door  28  and bracket means  72 . In an alternative embodiment, blocker door  28  can be engaged directly to translating sleeve  34  through a hinge attachment. Pivot  72  allows blocker door  28  to rotate as cowl  16  and translating sleeve  34  move from a stowed position to a deployed position. 
     With the increased fan duct dimensions currently employed in the state-of-the-art designs for turbofan engines, as well as with the potential protrusions in the duct  20 , blocker door  28  must be deployed over large radial distances. Moreover, door  28  and linkage assembly  32  must be able to avoid interfering with other components and protrusions within duct  20  and engine  10  in order to effectively play a part in producing reverse thrust. 
       FIG. 3  shows engine  10  in a reverse thrust mode. Blocker door  28  and its associated linkage system  32  are responsive to translation of cowl  16  and translating sleeve  34  during a thrust reversing sequence. As noted above,  FIG. 2  shows a normal or cruise mode where fan air is directed through duct  20 . When in reverse thrust mode or deployed position, shown in  FIG. 3 , duct  20  is blocked by a ring of blocker doors  28 , interposed within duct  20  and collectively having a complementary geometric configuration with respect thereto, for diversion of fan air into bypass duct  46 . The reverse thrust mode is achieved by aft or rearward movement of cowl  16  and translating sleeve  34  by actuator  68  such as a ball-screw actuator, thereby exposing outlet port  74  for airflow to escape through after the air passes into bypass duct  46 . Concomitantly, blocker doors  28  are translated aft due to attachment with bracket means  72  borne on sleeve  34 . Pivot  72  is a hinge attachment between blocker door  28  and bracket means  70 . Alternatively, blocker door  28  can be directly hinged to translating sleeve  34 . As actuator  68  drives cowl  16  and translating sleeve  34  rearward into the deployed position, blocker door  28  is pivoted downwardly into duct  20 . Air that formerly passed through duct  20  now strikes face  48  of door  28  and is diverted radially outwardly, through cascade  30  which, by virtue of the forward aspect on vanes  56 , directs the flow forwardly and out through outlet port  68  to achieve reverse thrust. Blocker door  28  has trailing edge  76  that is configured to fit over or mate with scoop  38  when engine  10  is in reverse thrust mode. A clearer illustration of the relationship between trailing edge  76 , IFS  36 , and scoop  38  can been seen in  FIG. 4 . 
     Drag link  56  is shaped or contoured in such a way that when blocker door  28  moves from the stowed position shown in  FIG. 2  to the deployed position in  FIG. 3 , it does not interfere with scoop  38  of AOC  26 . In other words, drag link  56  can be fashioned so that it has a clearance with respect to IFS  36  due to the shaping of drag link  56  when blocker door  28  is in the deployed position. Further, it is possible to fashion drag link  56  so that it has a clearance with respect to scoop  38  while it is in the deployed position, and it is also possible to fashion drag link  56  so that it rests on scoop  38  while it is in the deployed position. Blocker door  28  is fashioned to fit tightly over aero faring surface  44  of scoop  38  such that when it joins the plurality of blocker doors to form an annular ring, duct  20  is still substantially blocked, forcing the air through cascade  30  and bypass duct  46 . 
     There are a number of possible geometric shapes into which drag link  56  can be fashioned. Drag link  56  can be fashioned into a smooth curve, it can be bent, or it can have multiple bends. A drag link  56  that is shaped into a smooth curve is an especially desirable embodiment because it can result in a decrease in air drag through duct  20  during cruise mode. 
       FIG. 4  is a front view of two blocker doors  28  in a deployed position. Blocker doors  28  have tapered side edges  78  to mate with each other to form an annular ring. This annular ring makes a wall of blocker door forward faces  48  that deflect the airflow through duct  20  through cascades  30 . In  FIG. 4 , only two blocker doors  28  are shown forming part of the annular ring so as to show translating sleeve  34  to which they are engaged, either by bracket means  70  and pivot  72 , or another attachment hinged directly to translating sleeve  34  (not illustrated in  FIG. 4 ). Blocker doors  28  also have trailing edges  76  configured to mate with IFS  36  and scoop  38 . Blocker doors that do not line up with scoop  38  can have trailing edges  76  configured to mate with only IFS  36 . 
     Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the scope of the invention. The implementations described above and other implementations are within the scope of the following claims.