Patent GB-783577-A (GB)
Title: Improvements in or relating to apparatus for the automatic control of the air supplyin a burner installation
IPC: F23D14/60
Filed: 1955-08-30
Abstract: 783,577. Fluid-pressure servomotor-control systems. NAAMLOOZE VENNOOTSCHAP DE BATAAFSCHE PETROLEUM MAATSCHAPPIJ. Aug. 30, 1955 [Sept. 1, 1954], No. 24928/55. Class 135. Apparatus for automatically controlling the air supply to a burner installation which may be fed with liquid and gaseous fuel either separately or simultaneously, comprises a device to which the pressures of the fuel supplies are applied to determine the pressure of an auxiliary fluid which operates a servo system controlling the air supply. As shown, the burner 1, Fig. 1, has gaseous and liquid fuel supply conduits 5, 3 respectively and is supplied with air through a conduit 7 containing a valve 8 adjusted by a servo piston 77. The pressure of the liquid fuel is transmitted through a conduit 10 to the interior of a bellows 23, Fig. 3, whilst the gaseous fuel pressure passes through a conduit 11 to a chamber 25 whereby both fuel pressures act in conjunction with a spring 22 in a downward direction on a diaphragm 19. The diaphragm 19 is connected to a diaphragm 20 which carries a seating 36 for a valve 35, the valve also having a head 34 which coacts with a seating in the housing. The valve 35 is loaded by an adjustable spring 33. The auxiliary fluid enters the housing through the conduit 43 and passes out to the servo-mechanism through a conduit 44. The arrangement is such that pressure of either or both of the fuels supplied to the burner depresses the diaphragm assembly 19, 20 to move the valve head 34 off its seating and admit auxiliary fluid to a chamber 28 until the pressure therein returns the diaphragm assembly to its original position allowing the valve head 34 to close. Should the pressure in the chamber 28 exceed that corresponding to the fuel pressure the diaphragm assembly is raised to cause the seating 36 to move away from the valve 35 to vent the chamber 28 through passages 39, 40. The pressure from the conduit 44 may be applied directly to the servo piston 77 but, preferably, acts through an amplifier, as shown, in which the conduit 44 is connected to a spring-loaded bellows 50 whose free end is pivotally connected at 54 to a lever 57 having an abutment 56 to engage a plate 85 pivoted at 68 and co-operating with a nozzle 67. The nozzle 67 is fed with compressed-air from conduits 47, 69 containing a restriction 70 whereby the position of the plate 85 determines the pressure in a flexible chamber 71 which actuates a valve 73 controlling the pressure of compressed-air supplied through a conduit 75 to the servo-piston 77. The plate 85 is held against the abutment 56 by a spring 66 whilst the lever 57 has its lower end held against an abutment 62 by a spring 58. The abutment 62 is carried by a lever 60, 61 pivoted at 59 and biased by a spring 65 so that a roller 63 is held in engagement with a conical body 64 movable by the servo-piston 77 thereby providing a followup connection between the servo-piston and the valve constituted by the plate 85 and nozzle 67. To enable the apparatus to be used with liquid fuels consisting of heavy oils &c. which are highly viscose except when heated by being in proximity to the burner the conduit 10 contains an intermediate liquid such as glycerine which does not mix readily with the liquid fuel and which has an interface with that fuel in a container 9. Specifications 654,303 and 703,721, [both in Group XI], are referred to.