The so-called fuel sucking-up and gasifying type combustors, in which, for example, liquid fuel in the fuel tank is sucked or drawn up by the capillary action of the combustion wick and gasified and burned at the surface of the fuel gasifying portion at the upper end of the wick projecting into the gasifying chamber in the combustion section of the combustor, are popularly used for the kerosene heater, oil burners and the like. In this type of combustors, since the fuel gasifying portion of the wick is located in the gasifying chamber which is heated to a high temperature and in which oxygen is also allowed to exist, there inevitably occurs the phenomenon that a part of the liquid fuel soaked in the fuel gasifying portion of the wick is turned into a tar-like substance by dint of oxidation, polymerization reaction and/or other chemical actions during combustion and such tar-like substance deposits on the fuel gasifying portion of the wick. Formation and deposition of such tar-like substance are noticeably promoted in case small amounts of high-boiling materials are mixed in the liquid fuel (for example, in case machine oil, gas oil, salad oil or such is mixed in kerosene) or in case the liquid fuel components are partly denatured (for example, in case an doxide, peroxide, resin or such is produced in kerosene as a result of long-time exposure to a high temperature or to direct rays of the sun). Accumulation of such tar-like substance on the fuel gasifying portion of the wick causes blocking of the capillaries in the surface or the inside of said gasifying portion to impair suction or gasification of the liquid fuel, resulting in various troubles or inconveniences such as an abnormal reduction of the liquid fuel gasification rate or fluctuation of the air/fuel ratio in the combustion chamber to produce an offensive smell, soot and harmful substances such as carbon monoxide in great volumes. Also, at the time of ignition, said tar-like substance obstructs quick rise of temperature of the fuel gasifying portion or increase of the fuel gasifying rate, thus necessitating a very long time till reaching a stable combustion, and during this time, there would be generated an offensive smell, soot, carbon monoxide, etc., in volumes due to unstable overcombustion. Combustion wick is usually supported on its both sides by a draft pipe and designed such that, when igniting the wick, it is raised above said draft pipe and, when putting out fire, said wick is lowered down, but if said tar-like substance builds up on the wick, it might adhere to the draft pipe to make it unable to put out fire even if the wick is lowered, bringing about a very dangerous situation.
The present invention is to deal with the technical subject for minimizing or discouraging formation and deposition of said tar-like substance on the gasifying portion of the wick, and as a solution to such problem, the invention provides a novel structure for the fuel gasifying portion of the wick which is described in detail hereinbelow.