Patent GB-889031-A (GB)
Title: Improvements in or relating to control mechanisms for aircraft jet propulsion engines
Inventor: KEEN JOHN MICHAEL STORER
IPC: F02K1/15
Filed: 1958-04-02
Abstract: 889,031. Combined thrust reversal and throttle control of aircraft jet propulsion engines. ROLLS-ROYCE Ltd. March 23, 1959 [April 2, 1958], No. 10702/58. Class 4. A control mechanism for an aircraft jet propulsion engine including thrust reversing means, comprises engine fuel supply control means adjustable between idling and full power settings, means operative in a low power setting of the control to permit selection of and initiate operation of the jet thrust reversing means, and means actuated by the jet thrust reversing means as it moves from one position to the other to limit adjustment of the fuel control away from the low power setting except when the jet thrust reversing means is substantially in the selected position. Fig. 1 shows jet thrust reversing means in the exhaust system of a gas turbine engine of the by-pass type, having an exhaust duct 10 defined by wall 11 and an exhaust cone 12, and a by-pass duct 13 defined by walls 11 and 14. Ports 17 in wall 14 lead to apertures 21 in a nacelle 22 through ducts containing vanes 23. A pair of jet reversal doors 18 are pivotable about an axis C between the positions shown in full lines, blanking off ports 17, and the position shown in broken lines, blanking off the nozzle (not shown) and diverting the gas flow through the ports to have a forward component of velocity. Doors 25 each mounted on two forward swinging links 26a (one shown) and one rearward swinging link 26b can close apertures 21 when the jet reversing means is not operative. Fig. 2 shows the combined throttle and jet reversal control mechanism. A pilot's throttle lever 27 controlling the engine fuel supply by means not shown, works in a gate 28 comprising two slots 29, 30, connected by a step 28a which is the engine idling position. Increased forward thrust is obtained by moving the lever from the step in slot 29, and increased reversed thrust by moving the lever from the step in slot 30. The lever is connected by belt and pulley drive 31 to a gear 34 engaging a quadrant 35 connected by a linkwork to a rod 43. Gears 34, 35 are mounted in a frame 37 pivoted about the axis of gear 34 and connected by arm 38 and rod 39 to an anchorage 40 on the jet pipe casing, to compensate for control errors due to thermal expansions. Rod 43 is pivoted to a selector valve cam 44, this and other cams being shown also in greater detail in Fig. 3. Cam 44 is pivoted on an axis A, and has faces 44a, 44b, 44c co-operating with rollers 45, 46 on an anchor shaped member 47 pivoted on an axis B and connected by rod 48 to a spool 49a of a selector valve 49. High pressure air from the engine compressor is led to valve 49, through filter 51, pressure reducing valve 52, and ports 49c. Ports 49d lead to pipe 61, and ports 49e to pipes 71, 72, and 73. The valve chamber is open at its right hand end, and vented at its left through bores 49f. The spool is urged to the position shown by spring 49b. Each thrust reversing door 18 in Fig. 1 is operated by two twin rams 54 (one shown), one on each side of the jet pipe. The ram pistons divide the rams into spaces 54a connected to branches 61a of pipe 61, and spaces 54b, and the piston rods 55a of a twin ram are connected together by a crosshead 56 pivoted to a lever 57 connected to rotate a door 18, so that if, for example, the apertures 17, Fig. 1, lie port and starboard, the port door is operated by a lever 57 extending starboard from axis C, and vice versa. As seen in Fig. 2, the upper lever 57 operates the lower door 18 and vice versa. The two levers 57 are connected by rods 58 to a head 59 running in a guide 60. A rod 75 is connected to head 59 and runs in a bushing 77 in guide 60, and co-operates with an abutment 78 on a lever 79 pivoted on an axis D. Lever 79 is connected by rod 81 to an interlock cam 82 described below, and by link 80 to the spool 63a of a sequence valve 63. Referring to Fig. 3, cam 44 is provided with two rollers 84, 85 co-operating with a feed back cam 83 secured to one lever 57. Cam 44 also has a projection 86 adapted to enter a slot 82a in the interlock cam 82, which is pivoted about axis C. Cam 82 also has faces 82b, 82c and 82d, with a nose 82e. A plunger 92 pivoted to cam 82 enters a housing 93 pivoted to fixed structure 94, and is urged to the left by a spring in the housing. Referring to Fig. 2, each door 25 of Fig. 1 is operated by two rams 64 (one shown for each door) the piston rods of which are connected to the swinging links 26a through links 102 and arms 103. The pistons 66 divide the rams 64 into spaces 64a connected to pipes 65 leading from the sequence valve 63, and spaces 64b connected to pipes 71, 72. Each ram piston rod 67 is hollow, and has a port 69 which in the contracted position of the ram is aligned with a port 70 in the ram cylinder. Tubes 68 are a sliding fit in the piston rods 67. Port 70 of the upper ram is connected to branch 71a of pipe 71, and the tube 68 of this ram is connected by pipe 88 to port 70 of the lower ram. The tube 68 of this ram is connected by pipe 89 to a space 63b in the sequence valve 63. The spool 63a divides the valve chamber into spaces 63b, 63d and 63e of which space 63d is vented to atmosphere through bores 63f and the interior of the spool. All parts are shown in the position for forward thrust at idling setting. The operation will now be described. When obtaining increased forward thrust, the pilot moves lever 27 along slot 29. This rotates cam 44 clockwise, Fig. 3, and does not rock lever 47, rollers 45 and 66 moving along faces 44c, 44b respectively. Valve 49. thus remains in the position shown while lever 27 is moved in slot 30. Valve 63 and abutment 78 also remain as shown. High pressure air is fed through pipe 50, ports 49c and 49d of valve 49, pipe 61 and branches 61a at spaces 54a of rams 54, and through pipe 61, chamber 63e of valve 63, and pipes 65 to spaces 64a of rams 64. Spaces 54b of rams 54 are vented to atmosphere through pipes 62 and space 63d of valve 63. Spaces 64b of rams 64 are vented to atmosphere through pipes 71, 72 and ports 49e and bores 49f of valve 49. Thus the doors 18 and 25 are held in the forward thrust positions. Further, rod 75 attached to head 59 contacts abutment 78 on lever 76, thus preventing the levers 57 from rotating and doors 18 from moving, even if pneumatic failure occurs. Also, for forward thrust above the idling setting projection 86 on cam 44, Fig. 3, enters slot 82a in cam 82, locking the cam. This immobilizes the valve spool 63a through linkage 81, 79, and 80, and thus prevents the valve from causing thrust reversal in the manner explained below, even in the event of malfunctioning of the system. To obtain reversed thrust, lever 27 is moved through the idling step 28a to a position in slot 30 corresponding to some figure in the range 20 to 50% reverse thrust, the exact figure depending on cam 83. The movement of lever 27 is limited to this position by the clockwise rotation of cam 44 by the lever and the consequent abutment of roller 84 on cam 83. This rotation of cam 44 also moves rollers 46, 45 on member 47 on to cam faces 44c, 44a, respectively, rocking the member, and thus moving valve spool 49a to the left by rod 48. The spaces 54a of rams 54 are now vented to atmosphere through pipes 61a and 61, and ports 49d of valve 49. The spaces 64a of rams 64 are vented through pipes 65, space 63e of valve 63 and pipe 61. Air under pressure is admitted through pipe 50, ports 49c and 49e of valve 49, and pipes 71 and 72 to spaces 64b of rams 64, thus contracting the rams and removing doors 25 from the apertures 21 in Fig. 1. When the rams 64 are fully contracted, air under pressure is admitted through pipes 71 and 71a, ports 70 and 69 and tube 68 of the upper ram, pipe 88, ports 70 and 69 and tube 68 of the lower ram, and pipe 89, to the space 63b in valve 63, moving the valve to the left. This rocks lever 79, removing abutment 78 from the path of rod 75, and rotates cam 82 so that face 82b opposes projection 86 on cam 44, and prevents the pilot from moving lever 27 into the forward thrust slot 29. Movement of spool 63a to the left also connects space 63b to pipe 73 fed with air under pressure through ports 49c and 49e of valve 49, and to pipes 62 which convey air under pressure to spaces 54b of rams 54. The rams thus contract, moving doors 18 to the reversed thrust position. This moves rod 75 into the path of abutment 78, and locks spool 63a in the left hand position. When doors 18 approach their final thrust reversal position, cam 83 moves out of the path of roller 84, and into that of roller 85. The pilot is now free to move lever 27 into an increased reversed thrust position. To revert to forward thrust, the pilot places lever 27 in the idling position, (in which roller 85 abuts cam 83). The cam surfaces 44a, 44c on cam 44 then rock member 47 anticlockwise, and valve 49 returns to the position shown. The spaces 54b of rams 54 are thus vented through pipes 62, space 63b of valve 63, pipe 73, and ports 49e and bores 49f of valve 49. The spaces 54a of rams 54 are fed with air under pressure through pipes 61a and 61, and ports 49d and 49c of valve 49. The rams expand and return doors 18 to the forward thrust position. Cam 83 is rotated with levers 57 to clear roller 85 and enter the path of roller 84 on cam 44. The pilot is now free to select increased forward thrust by lever 27. In valve 63, space 63b is vented through pipe 73, and space 63e is pressurized through pipe 61. As soon as rod 75 is withdrawn from the path of abutment 78 as doors 18 approach their final forward thrust position, spool 63a moves back to the position shown. The spaces 64b of rams 64 are vented through pipes 71, 72 and ports 49e and bores 49f of valve 49, and the spaces 64a are pressurized through pipe 65, space 63e of valve 63 and pipe 61. The rams expand, and doors 25 are moved to cover apertures 21. When fully expanded the rams operate catches 96 to lock the