Patent Description:
A thrust reverser of the bucket/target type has doors that can be moved from a stowed position to a deployed position so as to deflect at least a portion of the gases coming out of the gas turbine engine and create a braking force slowing down the aircraft. The deflected gases come from the by-pass flow or from both the by-pass flow and the core flow of the engine.

Challenges in the design of thrust reversers include the need to minimize weight and to provide the various parts within the smallest possible space. It will be appreciated that the actuators, door pivots and pivot arms of a thrust reverser must fit within the envelope provided between the outer mold line (OML) and inner mold line (IML) of the nacelle and thrust reverser. Traditionally, these components are relatively bulky, and thus a significant envelope or space is required between OML and IML to accommodate them, resulting in a larger nacelle outer surface and increased drag, in comparison to a nacelle without a thrust reverser. Therefore, the pivots and mounting of the thrust reverser doors is one area where improvements are needed.

British Patent Specification No. <CIT> discloses an aircraft-reaction propulsion unit or installation comprising a jet-pipe, a propulsion nozzle at the outlet end of the jet-pipe, porting in the wall of the jet-pipe upstream of the propulsion nozzle leading to auxiliary ducting extending from the porting to an outlet to atmosphere and inclined forwardly to the direction of flight at its outlet end so that gas flowing through the auxiliary ducting produces a braking effect on an aircraft fitted with the unit, and at least one valve member adapted to swing about an axis at right angles to the jet-pipe axis and passing through it and adapted in one position to close off the passage through said auxiliary ducting and in a second position to block the flow through the jet-pipe to the propulsion nozzle.

British Patent Specification No. <CIT> discloses a discharge nozzle for a propulsive fluid stream having at least one wall portion extending downstreamwardly of a duct for the fluid stream, supporting means for the wall portion and a pivot attachment between the latter and the supporting means whereby the wall portion is pivotable about an axis extending transversely to the direction of fluid flow at a region upstream of the downstream end of the wall portion to vary the configuration of the nozzle and wherein the pivot attachment is movable transversely to the fluid stream independently of pivotal movement of the wall portion to vary the flow area of the nozzle.

Patent document <CIT> discloses a thrust reverser of the prior art.

According to an aspect of the present invention, there is provided a thrust reverser as specified in claim <NUM>. According to another aspect of the present invention, there is provided a thrust reverser as specified in any of claims <NUM> - <NUM>. According to a further aspect of the present invention, there is provided a method of pivotally connecting a thrust reverser door to a thrust reverser as specified in claim <NUM>.

Further details of these and other aspects of the improvements presented herein will be apparent from the detailed description and appended figures.

Referring now to <FIG>, there is shown an example of a nacelle <NUM> including a thrust reverser <NUM> in the aft section 20a of the nacelle <NUM>. The turbofan gas turbine engine is located within the nacelle <NUM> and the nacelle <NUM> is attached under the wings or on the fuselage of the aircraft using an appropriate arrangement (not shown). The thrust reverser <NUM> comprises two opposite pivoting doors <NUM>, <NUM> forming most of the exhaust nozzle of the nacelle <NUM> when they are in their stowed position. In the example illustrated in <FIG>, one door <NUM> is at the upper side and the other door <NUM> is at the bottom side. The nacelle <NUM> defines an outer aerodynamic shape, referred to herein as the outer mold line (OML) of the assembly.

Each door <NUM>, <NUM> has a trailing edge 24a, 26a adjacent to the propulsive jet outlet <NUM>. The arrows in <FIG> show the direct thrust operation of the engine. <FIG> is an enlarged view showing an example of a jet pipe <NUM> having rearwardly extending jet pipe arms <NUM> to which the doors <NUM>, <NUM> are pivotally connected. The doors <NUM>, <NUM> are in their deployed position in <FIG> is a rear view of what is shown in <FIG>. The jet pipe <NUM> is concealed inside the aft section 20a of the nacelle <NUM> when the doors <NUM>, <NUM> are in their stowed position, as in <FIG>. It will be understood that the interior of the jet pipe, together with the interior of the doors when stowed, defines an inner aerodynamic shape or nozzle for direct exhaust gases of the engine, and this inner shape is referred to herein as the inner mold line (IML) of the assembly (see <FIG>).

The arrows in <FIG> indicate the main flow path when the engine is operated during a thrust reversal. As can be seen, exhaust gases from the engine are redirected substantially forwardly when the doors <NUM>, <NUM> are in their deployed position. The gases exit the doors <NUM>, <NUM> in the vicinity of their leading edges 24b, 26b. These edges 24b, 26b are located at the front of the doors <NUM>, <NUM> and are referred to as "leading" edges with reference to the travel path of the aircraft. The redirection of the exhaust gases from the engine creates a resulting horizontal retarding force opposing the forward movement of the aircraft. Increasing the output thrust generated by the engine increases the aerodynamic decelerating force. Also, in the illustrated example, the trailing edge 24a of the upper door <NUM> is pivoted behind the trailing edge 26a of the lower door <NUM>, this resulting from the asymmetrical positioning of the pivots with reference to the horizontal medial plane of the jet pipe <NUM>, as described in <CIT>. It should be noted that most of the details about actuators, the pivots and the mechanisms provided to lock the front of the doors <NUM>, <NUM> during the direct thrust operation of the engine have been omitted from <FIG>, for clarity. It will be understood that an actuator system is to be provided on each side of the jet pipe <NUM>, for instance, generally underneath a fairing <NUM> between the longitudinal sides of the doors <NUM>, <NUM> when the doors are in their stowed position. Also, in the illustrated example a fairing <NUM> is provided for covering the door pivots when the doors are stowed. Fairings <NUM>, <NUM> of course merge smoothly with nacelle <NUM> and doors <NUM>, <NUM>, when the doors are stowed, to provide an aerodynamically smooth outer mold line (OML) to the assembly. The actuators, pivots and pivot arms of the doors must reside within the envelope defined by the outer mold line (OML) and inner mold line (IML).

<FIG> shows an example of an individual pivot fitting <NUM>. The pivot fitting <NUM> comprises a base <NUM> having a slightly arcuate shape. The curvature of the base <NUM> corresponds to the curvature of the jet pipe arm <NUM> in which the pivot fitting <NUM> will be positioned, and thus each pivot is designed to substantially follow the curvature of the space between the OML and IML and thus minimize the envelope needed therebetween. The illustrated base <NUM> is substantially rectangular. Other shapes can be used as well. The pivot fitting <NUM> also includes a shaft <NUM> projecting from one of the main sides of the base <NUM>, namely the side that will be toward the outside of the reverser assembly. The shaft <NUM> is disposed on the base so that it projects normally to the plane of door rotation, i.e. provides an axis for door rotation, and preferably all pivot shafts <NUM> will be parallel or coaxial with one another, as the case may be, when installed on the reverser. The shafts <NUM> preferably include a coaxially disposed threaded bore <NUM> defined in the free end of the shaft. This threaded bore <NUM> can be used to receive a bolt, as explained hereafter. The base <NUM> also includes holes <NUM> for receiving fasteners.

<FIG> shows an example of the interior of a jet pipe arm <NUM> in which two pivot fittings <NUM> are provided. Each pivot fitting <NUM> is inserted into a recess <NUM> that is configured and disposed so that the pivot fittings <NUM> will be flush mounted with reference to the inner surface of the jet pipe arm <NUM>, so that the aerodynamics of inner mold line (IML) of the jet pipe is not affected. The recess <NUM> is, for instance, a cut-away portion or a punched portion of the jet pipe arm <NUM>. The jet pipe arm <NUM> also includes a side opening corresponding to each pivot fitting <NUM> for receiving its shaft <NUM>. Each shaft <NUM> outwardly projects with reference to the jet pipe arm <NUM>, as shown for instance in <FIG> also shows that the illustrated pivot fittings <NUM> are connected to the jet pipe arm <NUM> using a plurality of bolts <NUM>. Other fastening arrangements are also possible. While it is possible to provide two shafts <NUM> on a same side of a single base, the illustrated example uses two distinct pivot fittings <NUM>, namely an upper door pivot fitting and a lower door pivot fitting, each having their own shaft <NUM>. This facilitates maintenance since it is possible to only remove one door at a time. Each pivot fitting <NUM> is removable from inside the jet pipe <NUM>.

<FIG> is a cross sectional view taken along line <NUM>-<NUM> in <FIG>. It shows the pivot fitting <NUM> being flush mounted inside the jet pipe arm <NUM>. Bolts <NUM> are used in the illustrated embodiment for connecting the pivot fitting <NUM> to the jet pipe arm <NUM>. The bolts heads can be hidden in chamfered holes. Also, <FIG> shows that the recess of the jet pipe arm <NUM> may require a reinforcement layer or embossed portion on the opposite side. This layer or portion is also shown in <FIG>.

<FIG> shows the arrangement of <FIG> when assembled. <FIG> shows the pivot arm <NUM> for the upper door <NUM> and the pivot arm <NUM> for the lower door <NUM>. The pivots for these pivot arms <NUM>, <NUM> are asymmetrically disposed with reference to a medial plane of the jet pipe arm <NUM>, as described in <CIT>. The pivot arms <NUM>, <NUM> are preferably overlapping or crossing one another when the doors <NUM>, <NUM> are in their stowed position, which thus allows a planar exit of the thrust reverser nozzle when the doors are stowed. Other arrangements are possible as well. <FIG> also shows that one end of the pivot arms <NUM>, <NUM> has a pivot receiving hole for coaxially mounting the door on the shaft <NUM> of the corresponding pivot fitting <NUM> (the other end of each pivot arm is mounted to, or integrated with, its associated door <NUM>, <NUM>). A bearing <NUM> (see <FIG>), preferably a spherical type, separates the pivot arm <NUM>, <NUM> from the shaft <NUM>. The bearings <NUM> lower the friction to a minimum and compensates any slight misalignment of the pivoting axis of the doors. The pivot arms <NUM>, <NUM> may be connected to the corresponding shafts <NUM> and retained via a bolt <NUM> provided in the threaded bore <NUM> of the shaft <NUM>, as best shown in <FIG>. Each bolt <NUM> is used with a set of washers <NUM>, <NUM>, one of which <NUM> is a bendable lock washer cooperating with a notch in the shaft <NUM> for preventing the bolt <NUM> from rotating once it is installed. The other washer <NUM> provides adjustment of the reverser door in the transverse direction for easier adjustment of the reverser door position. Other arrangements can also be used as well. The bolts <NUM> can be prevented from rotating using any other accepted methods in aeronautics. The shaft <NUM> is sized for adequately taking the loading conditions in direct and reverse thrust, and has an adequate diameter for supporting the bearing <NUM> installed on each shaft <NUM>. Referring to <FIG>, each pivot arm <NUM>, <NUM> has a curvature about the engine selected to follow the curvature of the space available between the OML and IML, and the hinges are configured to cross each other when the reverser doors move towards their stowed position. Lower pivot arm <NUM> is curved generally to follow the local outer profile of the jet pipe <NUM>. Upper pivot arm <NUM> is curved to follow the local outer profile of the jet pipe <NUM>, but also to avoid interference. with lower pivot arm <NUM> (since the pivots cross one another). This curvature assists in reducing the profile of the door-hinge arrangement, and allows a further reduction in the OML of the assembly. The skilled reader will appreciate that any suitable radius (or radii) of curvature may be provided, and that the "curvature" need not be continuous, nor arcuate, as depicted.

<FIG> schematically shows a prior art thrust reverser hinge arrangement. Each pivot fitting <NUM> has a clevis <NUM> that has an integral base <NUM> riveted to the jet pipe <NUM>. The jet pipe <NUM> defines an inner mold line (IML) and the nacelle or thrust reverser outer skin defines an outer mold line (OML) for the assembly. As can be seen by a comparison of <FIG> and <FIG>, the envelope required to fit the prior art configuration is significantly larger than that required to fit the arrangement described above. Relative to the present approach, the prior art has a significantly larger OML and nacelle wetted area, factors that contribute to the increase of the nacelle drag when the reverser nozzle is in its stowed position, in order to accommodate the larger apparatus of the prior art.

Referring now to <FIG> and <FIG>, to mount a thrust reverser door <NUM>, <NUM> onto jet pipe <NUM>, e.g. during assembly or after maintenance, one positions the thrust reverser doors, then inserts a pivot fitting <NUM> inside the jet pipe <NUM> through its cutout and slides its shaft <NUM> (that is outwardly projecting through a side opening of the jet pipe <NUM>) through the end of the pivot arm <NUM>, <NUM> and bearing <NUM> of the door <NUM>, <NUM>, and then mounts a nut or other fastener to the shaft for securing the reverser door arms on their respective shaft.

As can be appreciated, the pivot fittings <NUM> and pivot arms <NUM>, <NUM> provide both a low profile and light structure to which the thrust reverser doors <NUM>, <NUM> can be attached, and thereby assist in reducing the overall nacelle wetted area, as well as assembly weight.

Claim 1:
A thrust reverser (<NUM>) comprising:
first and second thrust reverser doors (<NUM>, <NUM>) surrounding a jet pipe (<NUM>) to form an exhaust nozzle (<NUM>) having aerodynamic outer and inner mold line surfaces (OML, IML),
each door (<NUM>,<NUM>) having a pair of opposed pivot arms (<NUM>, <NUM>);
the jet pipe (<NUM>) including a pair of jet pipe arms (<NUM>) having inner surfaces defining corresponding portions of the inner mold line surface (IML);
each door (<NUM>,<NUM>) being pivotally mounted at the pivot arms (<NUM>, <NUM>) to the jet pipe arms (<NUM>) by a door pivot arrangement comprising a pivot fitting (<NUM>) having a base (<NUM>), wherein said jet pipe arms (<NUM>) each have a recess (<NUM>) co-operatively receiving the base (<NUM>) substantially flush with the inner mold line surface (IML), and a shaft (<NUM>) extending outwardly from the base (<NUM>) through an opening of a said jet pipe arm (<NUM>) and pivotally connected to corresponding ones of the pivot arms (<NUM>, <NUM>), wherein the opening is sized to allow the shaft (<NUM>) to pass through the opening but to prevent the base (<NUM>) from passing through the opening.