Patent GB-905506-A (GB)
Title: Gas turbine engine thrust reversal control
IPC: F02K1/76
Filed: 1960-01-28
Abstract: 905,506. Gas turbine engine thrust reversal. UNITED AIRCRAFT CORPORATION. Jan. 28, 1960 [Feb. 2, 1959], No. 3083/60. Class 4. Gas turbine engine thrust reverser control apparatus comprises reverser locking means operable by an actuator responsive to the flow of a motive fluid, and a pilot valve connected with the actuator and operable to actuate the thrust reverser sequentially with respect to operation of the locking means by the actuator. In the Fig. the pilot's throttle control 37 is connected by shaft 36 to a bell crank lever 38, one arm 50 of which is connected by rod 52 to the control arm 54 of the engine fuel control mechanism 20. The other bell crank arm 40 is connected by rod 42 to the spool 46 of a valve 18, which can connect either of conduits 56, 58 to compressor discharge pressure through conduits 34 and 32, and vents the other of conduits 56, 58, to atmosphere. This operates the thrust reverser locking actuator, which is a ram comprising a casing 22 and piston 62 connected through bell crank 70 to a control ring 26 surrounding the rear of the engine. A part 84 connected to the thrust reversing elements, e.g., clam shell doors, has a recess 82 cooperating with a roller 80 on a bell crank 78 biased by a spring 86 so that roller 80 is normally in recess 82. This locks the associated thrust reverser element against movement to the thrust reversing position. When piston 62 moves to the right, however, an abutment 74 on ring 26 rotates bell crank 78 and frees the thrust reversing element. The spool 96 of the pilot valve 24 is connected to piston 62 by a lost motion connection 92. Spring loaded balls 100 prevent spool 96 being moved by friction in the lost motion connection. The spool can connect either of conduits 104, 106 with compressor discharge pressure through conduit 32, and vents the other of conduits 104, 106, to atmosphere. These conduits are connected to a ram 28 operating the thrust reversal elements. One element 16 has a boss 114 slidable between abutments 130, 132 on a rod 116, the displacement of which is limited by stops 134, 138, and 136, 140. An over centre spring device 142, 146 prevents the rod being displaced from either extreme position merely by the friction between boss 114 and rod 116. The rod is connected to a bell crank 118 freely rotatable on shaft 36 and providing limit stops 124, 126 for lever arm 50, the stops being adjustable, as by screw 128. The parts are shown in their normal forward thrust positions. To reverse thrust, the throttle lever 37 is moved to and along an idle range to a position in which arm 50 abuts stop 124, preventing further movement of lever 37 which would increase the thrust again. Valve 18 is changed over, and compressed air is admitted to conduit 58. Piston 62 is moved to the right, and abutment 74 rotates lever 78 to unlock the thrust reverser elements. After the lost motion between pistons 62 and spool 96 is taken up, the spool moves to the right, and compressed air is admitted to conduit 106 to operate the ram 28 of the thrust reverser elements. When element 16 approaches its final thrust reversing position, boss 114 contacts abutment 132, and moves rod 116 to rotate bell crank 118 and displace stop 124, to permit further displacement of lever 37 to obtain full reverse thrust. To revert to forward thrust, lever 37 is moved to and along the idling range until arm 50 abuts stop 126. A similar operational sequence then occurs, the spring 88 returning roller 80 to a position in which it re-engages recess 82 when the thrust reverser elements attain their normal position.