GB497112A - Improvements in control means for fluid fuel burners - Google Patents

Abstract

497,112. Fluid-pressure servomotor - control systems. MAJOR FURNACE & COMBUSTION ENGINEERS PROPRIETARY, Ltd. Oct. 29, 1937, No. 29618. Convention date, Dec. 18, 1936. [Class 135] [Also in Group XI] In a fluid burner in which the fuel and air supplies are regulated automatically to maintain a constant temperature in a furnace &c., the fuel-air ratio is determined at the minimum setting by the adjustment of a tubular valve body formed with a metering face relatively to a metering pin formed with a tapered groove or flat, and the fuel discharge at the maximum setting is determined by the adjustment of a main fuel valve. Fig. 1 shows a liquid fuel burner comprising a fuel jet 8 and air nozzle 5 secured to the stem 4 of a piston 3 fitted leakily in the burner casing C. The pressure of the air supplied to the main air nozzle 20 forces back the piston 3 until it is balanced by the pressure of a spring 6 on the nozzle 5 and the pressure on the rear side of the piston, which is connected by a pipe 37 to a vent valve 40, Fig. 9, operated by a thermostat 50 in the furnace. A tube 9 extends from the jet 8 into a tubular valve body 22 which is adjustable by a differentially threaded sleeve 32 in a boss 31 on the burner casing C. The fuel passes through a valve 68 controlling the maximum supply to a chamber 29 formed between the sleeve 32 and a screwed cap 25. A metering pin 21 formed with a tapered flat 27 or groove 27a communicating with an end bore 28ispressed against the jet tube 9 by a spring 23. The valve body 22 has a metering face 30 and is adjustable relatively to the pin 21 to determine the fuel-air ratio by turning the sleeve 32 which is formed with a hand wheel 33. Alternatively, the sleeve 32 may engage abutments on the valve body 22 instead of being threaded thereon. The air supply to the nozzle 5 may be adjusted by means of a rotatable vane 59 in the pilot air duct 58 and the movement of the piston 3 may be limited by a pin 57 adjusted by a hand operated cam wheel 55. The piston may be caused to leak in the cylinder 1 of the casing C by forming the cylinder with tapered bore or with a tapered groove. In large burners the pipe 37, instead of being directly connected to the vent valve 40, is connected to the bottom of a cylinder 41 fitted with a leaky piston 39 operating a vent valve 42. The upper part of the cylinder 41 is connected to the vent valve 40 so that when the thermostat 50 operates the lever 45 to relieve the pressure on the valve 40, the piston 39 rises and opens the valve 42. In an alternative arrangement shown in Fig. 10, the pipe 37 is fitted with a tapered valve 74 which is moved to allow air to escape through outlets 75 when a piston 74a subject on one side to the pressure in the pilot air duct 58 is moved by the pressure on its other side being released by the opening of the vent valve 40. In another arrangement, a spring-closed ball valve is opened to vent the space behind the piston 3 by a solenoid having a thermostatically-controlled circuit.