Means for automatic closing and opening of the air intake duct of an oil burner

Apparatus for opening and closing the air intake duct of an oil burner having a motor provided with a shaft which extends through said air intake duct and which drives a fan and an oil pump which feed air and oil to a mixer, said apparatus comprising a duct section having a wall surrounding said shaft, said duct section being reduced in cross sectional area in one axial direction with reference to said shaft to provide a plurality of section portions of increasingly reduced cross sectional area in said direction, a plate, a hub carried by said plate for movement therewith, interengageable threaded means on said hub and on said shaft for mounting said plate on said shaft for movement in the direction of the axis thereof, the construction and arrangement being such that under the influence of a deceleration of said shaft said plate moves in said one axial direction and to abut said duct section wall to close said duct section upon stopping of said shaft and such that under the influence of an acceleration of said shaft said plate moves in a direction opposite to said one axial direction and to move away from said wall to open said duct section upon start up of said shaft.