Patent GB-276976-A (GB)
Title: Improvements in or relating to furnace regulators
IPC: F23N1/02
Filed: 1927-08-17
Abstract: 276,976. Roucka, E. Aug. 31, 1926, [Convention date]. Void [Published under Sect. 91 of the Acts]. Regulating combustion.-In a furnace regulator in which the air or draught and fuel supply are automatically regulated in accordance with the load, the ratio of the regulated quantities is varied by a " compensation " device having a curved surface forming a cam track, the configuration of which is chosen to give the correct ratio of fuel to air supply or draught at all loads. Fig. 2 shows a regulator in which a diaphragm 74 under the action of the air or draught moves a lever 76 which operates the valve 98 of a servomotor 100, the movement of the piston 82 of which varies the ratio of a variable speed friction drive 94 and hence the speed of the shaft 96 which drives the fuel feed mechanism. The lever 76 is balanced by a spring 78 and pivots about a roller 80, connected by pivoted links to the piston 82 so as to move horizontally with it. After a definite movement of the piston 82 the roller 80 reaches a position which causes the lever 76 to re-balance, so preventing further movement of the system until the pressure on the diaphragm 74 alters. In order to cause the desired variation in the ratio of the air or draught pressure to the feed of uel, the links connecting the piston 82 and roller 80 carry a roller 84 moving in contact with a track 86, the curvature of which causes the movements of the roller 80 to deviate from those of the piston 82 and so effect the desired correction. The track 86 is flexible and carried by rods 88 adjustably mounted in a support 90, so that the form of the track may be adjusted to the desired contour. Fig. 1 shows an apparatus for controlling the draught and fuel supply in accordance with the boiler pressure. A servomotor 16 adjusts a roller 30 horizontally under control of the boiler pressure, which acts on a diaphragm 2, a compensation device similar to that above described being interposed and comprising pivoted links 21 carrying a roller 17 which moves in contact with a curved track formed on member 15, the member 15 being rotatably mounted in order that different parts of its surface which provide tracks of different forms, may be brought into play. The roller 30 forms the pivot of a lever 26 which controls the valve of a servomotor 38 operating the damper 22 in the flue 20, opposite ends of the lever 26 being connected to a bell 24 subjected to the flue pressure and to a spring. Movement of the roller 30 upsets the balance of the lever 26 and causes the servo-motor 38 to re-adjust the damper 22. The apparatus may control the air supply. Two mechanisms for controlling the fuel supply are shown, one comprising a variable speed friction gear 62, 64 in which a driven member 64 is moved by the piston 18 radially across the face of a disc 62 rotated at constant speed. The other comprises a fan 58 driven by the motor 50 which operates the fuel supply device, the pressure of this fan acting on a diaphragm 48 connected to the lever 44 of a eervo-motor mechanism similar to those already described, and the servo-motor operating the speed control 54 of the motor 50. Movements of the roller 42 consequent on variations of boiler pressure unbalance the lever 44 and cause the servo-motor 56 to vary the speed of the motor 50, the system being re-balanced by the change of pressure on the diaphragm 48 consequent upon the altered speed of the fan 58. A compensation device similar to those described may be employed between the roller 42 and piston 18.