Hearth for a furnace, notably a furnace for urban waste, including a grate made up of alternately fixed and reciprocating bars, with increased flexiblity of adjustment

Furnace hearth equipped with a grate designed to support a burning mass of solid fragments, notably urban waste, and comprising, sloping downwardly between a loading area (2) at the upstream end and an ash box (3) at the downstream end, at least one bed made up of a succession of transverse bars (55, 55') with a dorsal surface (55a, etc) for supporting the mass and a frontal surface (55b, etc) with a lower edge sliding on the dorsal surface of the immediately upstream bar, the bars being attached by a downstream end alternately to a fixed frame of the hearth and a mobile frame that can be reciprocated longitudinally by control means, the hearth further comprising, under the grate, at least one draft chamber (43, 44) equipped with ventilation means for feeding combustion-supporting air to the mass through draft holes provided in the bars and, above the grate, a furnace chamber (5) connected to a fumes extractor flue (8) with extends longitudinally from the loading area to a vertical wall (7) referred to as the altar wall, the hearth being extended by a sprung roof from the altar wall to the ash box, characterized in that the grate comprises, within its length, two consecutive beds (41, 42) with substantially the same general slope joined together at a point in substantial vertical alignment with the altar wall (7), each bed having its own mobile frame (45d, 46d) with its own control means (45, 46) and its own draft chamber (43, 44) with its own ventilation means.