Patent GB-647722-A (GB)
Title: Engine control apparatus
IPC: F02C9/16
Filed: 1947-07-18
Abstract: 647,722. Gas turbine plant. GENERAL MOTORS CORPORATION. July 18, 1947, No. 19257. Convention date, Nov. 19, 1945. [Class 110(iii)] [Also in Groups XXIX and XXXIII] In control apparatus for internal combustion turbine engines driving an aircraft propeller, in which manually controlled means are provided for varying the load on the engine and speed responsive governor means are provided for controlling the supply of fuel to the engine to maintain a desired speed, means responsive to the engine temperature operate to reduce the load on the engine independently of the manually controlled means so as to prevent overheating of the engine. The load is adjusted by changing the angle of pitch of the propeller blades and this angle is also adjusted automatically in accordance with the torque applied by the engine to the propeller. The pilot's lever 10 operates a cam plate 13 controlling a speed governor 20 and a pitch governor 40. A cam surface 14 operates through a roller 15 on a lever 16 controlling the loading spring 31 of an engine driven governor 30 and pivoted to the rod 17 of a servopiston 18 operating the engine fuel control means and controlled by a valve 26 connected to the governor so as to maintain a desired speed. The cam 14 is shaped so as to eliminate " speed droop. " The pitch governor 40 comprises a servo-piston 42 the rod 43 of which controls the pitch of the propeller through the mechanism similar to that described in Specifications 544,580 and 545,520, [both in Group XXXIII]. The piston 42 is under the control of a valve 73 supplied by a pump 66a but a reversing valve 56 is interposed between the conduits 54, 55 and 46, 48 connecting the valve 73 with the servo-cylinder 41. The reversing valve 56 is operated by a cam surface 62 on the plate 13 and operates to reverse the connections of the conduits 54, 55 with conduits 46, 48 when the pilot's lever 10 changes over from positive pitch to negative pitch. When this change is made, a roller 120 on the piston rod 43 is constrained by a gate 123 so that the change from low positive pitch to low negative pitch is directly effected manually. Outside this range, the roller 120 operates in one of the openings 121, 122 depending on whether the pitch is positive or negative, but in either range the actual blade angle must be small before the change to the other range can be made. The plate 13 also has a cam surface 97 normally engaged by a roller 96 carried on a rod 92 bearing a spring abutment 91 at one end and a piston 93 at the other. Pressure from a pump 95a normally maintains the roller S6 against the cam 97. The control valve 73 is moved downwardly by a spring 90 adjusted by the cam 97 and upwardly by pressure on a piston 74 under the pressure from a pump 76, which pressure is modulated by a torque meter. This meter comprises a gear 81 connected to the turbine shaft. planet gears 79 carried by a ring 78 and associated with the propeller shaft, and a ring gear 80 the reaction of which is conveyed to pistons 84 in the pump circuit 75. A relief port 86 is associated with one of the pistons 84. If the engine exhaust temperature becomes too high, a thermally responsive member operates a relief valve which reduces the pressure below a spring-pressed piston 109 and so lowers the left-hand end of a lever 105 pivoted on the rod 92. Operation of the cam 97 by the lever 10 may then cause the lever 105 to descend to a point where it operates a valve 101 to vent the conduit 95 through ports 103, 102. Fur. ther movement of the cam 97 in either direction is therefore ineffective since the pressure on the piston 93 is reduced and further increase of load which would cause overheating is avoided.