APPARATUS FOR THE FEEDING OF SOLID MATERIALS INTO FURNACE, ESPECIALLY THE UNINTERRUPTED FEEDING OF SIZE-REDUCED SOLID FUELS INTO A SLOPING GRATE FURNACEAPPARATUS FOR THE FEEDING OF SOLID MATERIALS INTO A FUNANCE, ESPECIALL Y THE UNITERRUPED FEEDING OF SIZED-REDUCEDSOLID FUELS INTO A SLOPING GRATE FURNANCE