GB757001A - Improvements in or relating to automatically regulated fuel supply systems - Google Patents

Abstract

757,001. Fluid-pressure servomotor-control systems. BAKER PERKINS, Ltd. July 9, 1954 [July 10, 1953], No. 20125/54. Class 135. A regulating system for adjusting the supply of fuel to an oven manifold 10 supplying a number of burners 20 comprises a fuel control valve 14 operated by a fluid-pressure actuator 67 supplied with pressure fluid from an independent constant-pressure source through a control line 64, 66 controlled by an auxiliary valve 59 controlled by a governor S responsive to the fuel pressure in the manifold 10 and to the pressure in a branch line 37 from the source and con. trolled by a controller 23 responsive to the heat condition in the oven. As shown, the controller 23 is responsive to changes in the oven temperature as sensed by a bulb 25 and controls the air pressure in the branch line 37 leading to a governor S. In the governor, the control pressure in the line 37 is balanced against the pressure of the fuel mixture in the manifold 10. The governor S operates the auxiliary valve 59 controlling the air pressure acting on the actuator 67 which is operatively connected to valves 14, 15 in the fuel and air lines 11, 12 respectively. The bulb 25 is connected through a spiral tube 27 to a flapper arm 29 which controls the escape of air under pressure from the nozzle 30 of an adjustably-pivoted bleeder tube 31 supplied through a restriction 34 and a pipe 24 with air from the constant pressure source. The governor S has casings 40, 41 divided by a diaphragm 42 into a chamber 44 open to the manifold pressure through a pipe 46 and a chamber 47 vented at 47a. A further chamber 55 is bounded by diaphragms 50, 53 of unequal effective area clamped between the casing 41 and rings 49, 52. The diaphragms are centrally connected to a stem 43 with an adjusting screw 58 at its upper end. The line 37 is connected to the chamber 55 and thus the control pressure therein is effective on a small area compared with the larger area of the diaphragm 42 on which the pressure of the fuel mixture acts. The screw 58 is adapted to engage a shaft 63 projecting from the relay assembly 59 and carrying therein two horizontal tappets which operate respectively spring-closed inlet and exhaust valves controlling a pipe 66 leading to the actuator 67. The actuator comprises a spring- loaded bellows 79 within an outer casing. The bellows is connected through a linkage including a stem 80 and a bell-crank lever 84 to rotary valves 14, 15 in the fuel and air lines 10, 11. By this arrangement, the manifold pressure is maintained substantially constant for a given heat demand of the oven regardless of the number of burners in operation so that when the oven is idling at a predetermined low datum temperature, a number of the burners 20 may be turned off by means of the cocks 22 without the manifold pressure rising. The burners may be lit individually for as another burner is turned on and the manifold pressure tends to drop the governor S operates to open the valves 14, 15 further and so restore the manifold pressure,