GB845405A - Improvements in or relating to throttle control systems for engines driving forward and reverse gears - Google Patents

Abstract

845,405. Reverse gear control. BRISTOL SIDDELEY ENGINES Ltd. Nov. 22, 1956 [Dec. 9, 1955], No. 35385/55. Class 80 (2). In engine-driven reversing gearing having forward and reverse clutches and a manual throttle control, means are provided for delaying the response to the throttle control until either of the clutches is engaged. In a marine reverse gear, wherein an engine drives a screw-propeller through an epicyclic reverse-reduction gear having hydraulic clutches or brakes, the manual throttle control 10 rotates a bell-crank lever 11 rigid with a shaft 16 actuating two supply valves 17, 18, the former 17 controlling the supply of oil to either of the clutch-operating pistons 19, 20. The valve 18 controls the supply of oil to a pressure equalizing duct 23 and a restrictor 26 leading to the ends of a servovalve 15 controlling the admission to a servopiston 13, rigid with engine throttle linkage 14, through a duct 24. The piston 13 is urged towards a throttle closed position by a spring 21, in a space 21 free to atmosphere through bleed hole 71. A rocking arm 12 is connected at its ends to the piston 13 and valve 15, and at its centre to a link 70 connected to the bellcrank 11, the linkage being arranged that when the lever 10 is in the neutral position the link 70 is in line with the arm of the bell-crank 11. When the lever 10 is moved from neutral to ahead position, the shaft 16 is rotated to move the valve 17 to supply pressure oil to the ahead clutch and also to cause valve 18 to supply oil to the restrictor 26. Throttle movement is also transmitted to the arm 12 to move the servovalve 15 to the right and allow the passage of oil through the restrictor to the piston 13 to open the engine throttle, the build-up of pressure on the piston 20 being rapid while the restrictor 26 delays the build-up on the throttle opening piston 13. Displacement of the piston 13 moves the rocking arm 12 about its pivot on the link 70 to move the valve 15 to the left until it reaches its equilibrium position when it closes the duct 24. Movement of the lever 10 to shut the throttle causes the valve 15 to move to the left to vent the piston 13 through duct 24 and drain 25, and the piston 13 is moved to the left by the spring 21 until equilibrium at the desired throttle setting is again obtained. If, when either clutch is engaged, the oil pressure should drop, the reduction of pressure on the piston 13 allows a ball-check valve 27 to open to release the pressure on piston 13, and the spring 21 operates to close the throttle. A collar 33 on the link 14 forms with the levers 34, 35 and adjustable slowrunning stop whereby the throttle may have limited opening for inspection or testing purposes.