Patent GB-491459-A (GB)
Abstract: 491,459. Fluid-pressure servomotors. ELECTROFLO METERS CO., Ltd. (Republic Flow Meters, Inc.) March 19, 1937, No. 8151. [Class 135] Automatic control of a boiler 12, or similar device, comprises a regulator 84 which controls the position of a damper 82 in the flue pipe, and a regulator 138 controlling the speed of an electric motor 30 which drives a fuel grate 28, the control being governed by the steam pressure in a header 18. Instead of controlling the valve 82, the air supply to the boiler may be regulated by the regulator 84 acting on a valve in the inlet pipe or controlling the speed of a blower 34. At a low boiler output additional control pistons 116 raise balance levers 88 and maintain proportional control of air and fuel supply to the boiler at low boiler pressures. Compressed air is supplied through a pipe 50 to boxes 48, 60, past needle valves 52, and from one of these to a chamber 58, past needle valves 72, to pipes 94, 150, which lead to air and fuel regulators 84, 138, Figs. 1, 4, respectively. A valve 54 connects either box 48 or 60 according to whether automatic or manual control is desired. Valves 46, 62 bleed air to atmosphere, the former being controlled by steam pressure acting under a diaphragm 38, and the latter by a manual control 70. Bleed valves 78 lead to atmosphere. The regulator 84 includes a lever 88 balanced about a fulcrum 90, and a diaphragm 92 connected by a pipe 94 with the chamber 74. A diaphragm 96 is connected at its upper and lower sides to boiler passes 22, 24 respectively. During normal operation a roller 106 rides on the surface of a cam 134 and maintains a fixed tension in a spring 102, which is attached to the lever 88. Fluid, such as oil, under pressure enters through a port 124 above the piston 116, passes through openings 118, 110, to a discharge port 126. When a reduction in pressure occurs in the header 18, the bar 44 tips and the valve 46 is pressed against its seat to create an increased pressure in chambers 48, 58, 74, 76. The diaphragm 92 is forced downwards to tip the lever 88 and lower valve rods 108 and restrict the openings 110 in the regulators 84, 138. This increases the pressure on the lower sides of the pistons 116 causing them to rise, to move the damper 82 and rheostat 32 (controlling the speed of the motor 30), to new settings to increase the ratio of air and fuel supply to the boiler. In the regulator 138, a speed-responsive device 140 includes a chamber 142 having a number of vanes in its bottom and which is connected to a shaft 144 driven through bevel gears from a pulley 146 which is belt-driven by the stoker. A non-rotatable disc 148 has a series of vanes on its upper surface, and is connected to the lever 88. Fluid is whirled in the chamber 142 and exerts a downward force on the disc 148 in proportion to the stoker speed. As the pistons 116 rise they tend to restore the levers 88 to a level position. Pistons 122 are vented and act as dashpot pistons. At low boiler ratings when the pistons 116 have risen, rods 130 turn cams 132 so that the tension in springs 102 is eased on the downward movement of the pistons. Manometers 80 indicate the pressures in boxes 74, 76.