GB826134A - Improvements in or relating to oil-firing equipment - Google Patents

Abstract

826,134. Liquid fuel supply to burners. ZIEGLER, S. Jan. 13, 1956 [Jan. 14, 1955], No. 1182/56. Class 75(1) Apparatus for minimizing the after dribble of fuel oil from a burner nozzle comprises a displacement member displaceable in a casing and in part defining. a chamber of variable volume and 'having one face which, during operation of the burner, is subjected to the action of the fuel oil under pressure to cause displacement of the displacement member in the casing in a direction to reduce the volume of the chamber, a spring acting on the member to urge it relative to the casing in the reverse direction to increase the chamber volume, and connection whereby the chamber may be placed in communication with a fuel oil supply conduit to the burner at least whilst the displacement member is moving in the reverse direction to increase the chamber volume to produce a suction effect in the fuel supply conduit. In the arrangement shown in Fig. 1 oil is supplied, on operation of a valve 49, by a pump 48 to a spring loaded inlet valve 41 which opens at a pressure in excess of 30 pounds per square inch to allow oil to enter a chamber 33 and then the nozzle 54. The oil pressure in the chainber 33 acts on the member 35 to push a differential piston 34, 35 downwards against a spring 37. The piston 34, 35 makes contact with a valve 40 to close a bore 36 in the differential piston 34, 35 leading to a chamber 31. The valve 40 when closed acts on a dashpot piston 39 the two sides of which piston 39 are connected by throttling apertures, and a spring 38 to delay the downward movement of. the piston 34, 35. Alternatively a by-pass line provided with a non-return valve may be provided to allow rapid downward movement of the piston 39. The oil displaced from the chamber 31 passes to an intermediate chamber 46 or a return pipe 51 through a non-return valve 42. If the pump 48 is stopped, the valve 49 closed or the oil supply otherwise interrupted the valve 41 closes and the pressure in the chamber 33 falls the spring 37 then moving the piston 34, 35 upwards. The upward movement of the valve 40 is restrained by the slowly moving piston 39 to open the bore 36 so that the chamber 33 is placed in communication with the larger chamber 31 to effect a sucking action on the chamber 33 and hence the burner 54. The valve 40 eventually closes the duct 36 under the action of spring 38. Upward movement of the piston 34, 35 returns the fuel in the intermediate space 46 to the return line 51. In a modification shown in Fig. 2 fuel is supplied to the nozzle 154, on operation of a valve 149, past a spring-loaded valve 141 and a chamber 171. The oil pressure in chamber 171 moves a piston 164 downwards against a spring 172 to displace a diaphragm 163 and a valve 175 downwards against a spring 180. During the downward movement a quantity of oil below the diaphragm 163 passes through passages 181 in the stem of valve 175 and through a non-return valve 142 into a return line 151 or into a chamber 185 through a throttling duct 186. If the fuel supply is stopped the pressure in the chamber 171 falls and the piston 164 and diaphragm 163 are moved upwards by the spring 172. This movement is, however, delayed by the throttling effect exerted on the fuel passing out of the chamber 185 through the duct 186. Since the valve 175 is not subjected to this delay it is moved upwards by the spring 180 to place the chambers 171 and 170 into communication and since the chamber 170 is the larger of the two a sucking effect is exerted on the chamber 171 and hence the nozzle 154. The valve 175 is closed when the piston 164 reaches the top of its stroke.