Patent GB-243013-A (GB)
Title: Improvements in or relating to automatic control systems for steam boilers
IPC: F23N1/02
Filed: 1925-11-13
Abstract: 243,013. Bailey Meter Co., (Assignees of Bailey, E. G.). Nov. 13, 1924, [Convention date]. Regulating combustion.-An automatic control system for one or more steam boilers comprises mechanism for initially regulating the supply of fuel and air when the steam pressure departs from the normal and mechanism to prevent further regulation of the fuel and air until time has elapsed to test the initial regulating. During changes in the demand for power, the fuel and air supply are correspondingly varied in such a manner that the air supply is increased at a greater rate than the fuel supply upon an increased demand for steam and reduced at a lesser rate than the fuel supply on a decreased demand. The primary control instrument 2, Figs. 1 and 2, comprises a Bourdon tube 3 communicating with the boiler and operating a pointer 5 carrying a.t its extremity an indicator 6, Fig. 8, adapted to engage with a stepped recess 16 in a continuously reciprocating feeler 7 driven at slow speed in one direction by a cam 10, gearing 12, 13, and shaft 14 of a motor 15, Fig. 2, and in the, opposite direction by springs 36. When the steam pressure is normal, the indicator 6 coincides with the deepest part of the recess 16 but upon a fall of steam pressure, a step 18 of the recess engages with the indicator, during the forward movement of the feeler, and carries it forward with a frame or slide 20 which subsequently engages with the arm 24 of an electric circuit closer 22, the arm 23 of which is held by friction upon a continuously rotating shaft driven by gearing 29 from the shaft 14. The closing of the electric circuit energizes solenoids adapted to actuate clutches for connecting continuously driven shafts to gearing for actuating means for increasing the fuel and air supply or draught. The circuit is broken upon the return movement of the frame 20 but is again closed on the successive forward movement of the frame unless the indicator 6 and the pressure in the boiler have in the meantime returned to normal. Should the pressure in the boiler increase above normal, the frame 2000 is actuated to operate a circuit closer similar to 22 and effect a decrease in the fuel and air supply or draught. The secondary control instrument 40 comprises a flow meter, Figs. 6 and 7, actuated by the differential pressure of steam on opposite sides of an annular diaphragm at the joint 218 of the pipe 215 and by the differential pressure of the furnace gases on opposite sides of a baffle. The levers 41, 44 which respond to charges in air flow and steam flow respectively are connected by links 47, 48 to a floating link 49 carrying a projection 50 adapted to engage with a stepped recess in a reciprocating feeler 51, driven by a. cam 52, and similar to the feeler 7 described above. The circuit closers 60, 61 are operated when the pointers 43 46 indicate any departure from the normal relation between steam and air flow and cause an increase or decrease in the air supply draught. The damper 201 and rheostat 206 controlling the speed of the motor 207 actuating the fuel feeding apparatus 208 are operated by gearing comprising a motor 110 driving continuously a series of shafts 111 - - 116 through a train of gear wheels 117, each shaft being provided with a clutch 118 provided with gears of which those on the shafts 111, 112 may be caused to engage with a gear 119 on the shaft 120 to rotate it in either direction. Similarly the clutches on the shafts 113, 114 and 115, 116 may be engaged to rotate the shafts 124, 126 in either direction. Motion is transmitted from the shafts 120, 124 to differential gear 121, 122, 130 on a shaft 131 so as to operate through gearing 132 and shaft 205 the damper 201. The shaft 126 operates the rheostat 206. When the pressure in the boiler rises or falls above or below the normal, the circuit closer 22 or 220 of the primary control instrument allows current to pass from the positive main 500 to energize the solenoid 141 or 142 and the solenoid 145 or 146 and operate the corresponding clutch members to increase or decrease the fuel and air supply or draught. Any change in relation of the steam and air flow causes one or other of the circuit closers 60, 61 of the secondary control instrument to energize the solenoid 143 or 144 and operate the corresponding clutch member to vary the air supply or draught. Switches and push buttons are provided on the primary and secondary control instruments whereby the apparatus may be controlled by hand instead of automatically to vary the fuel and air supply. Instead of electric transmission means, pneumatic or mechanical means may be employed. The apparatus is also applicable to liquid or gaseous fuel furnaces.