摘要 |
PURPOSE:To realize favorable uniform heating of pot or the like by a structure wherein a bored hole, the diameter of which is larger than that of the outer peripheral wall of a burner, is provided at the center of a spider holder. CONSTITUTION:A bored hole, the diameter of which is made larger than that of the outer peripheral wall 10 of a burner 1, is provided at the center of a spider holder 26 having a supporting part to fixedly support the claws 25 of a spider 7. Further, a plate is provided in the spider holder 26 between the bored hole and the supporting part 29. A burner 1 is faced to the bored hole so as to provide a vena contracta part or a shut-off part in a secondary air flow passage 8 formed by the outer peripheral wall 10 of the burner 1 and the spider holder 26 by means of the spider 7 so as to make the flow resistance at the vena contracta part larger than that at a secondary air hole 4 in order to let the drafting force developed due to combustion apply larger to the secondary air hole 4 than to the vena contracta part. A part of the spider holder 26 is interposed in the secondary air passage in order to add a catch plate function. Consequently, the quantity of secondary air supplied through the secondary air hole 4 can be increased and yet the cleaning of the catch plate is facilitated when boiling- over occurs. |