Abstract: A main spindle of an air saw is reciprocated by sliding a piston in a cylinder chamber with the pressure of air supplied to the cylinder chamber via an air supply path so as to alternately apply the air pressure to pressure-receiving surfaces of a back plate and a front plate, wherein a rear air-cushion chamber is formed in a portion for fixing a return spring for urging the back plate toward the center of a cylinder while a front air-cushion chamber is formed in a portion for fixing a return spring for urging the front plate toward the center of the cylinder, so that the front and rear balance is maintained.

Abstract: A main spindle of an air saw is reciprocated by sliding a piston in a cylinder chamber with the pressure of air supplied to the cylinder chamber via an air supply path so as to alternately apply the air pressure to pressure-receiving surfaces of a back plate and a front plate, wherein a rear air-cushion chamber is formed in a portion for fixing a return spring for urging the back plate toward the center of a cylinder while a front air-cushion chamber is formed in a portion for fixing a return spring for urging the front plate toward the center of the cylinder, so that the front and rear balance is maintained.

Abstract: A reduction process and apparatus wherein the flow of the reducing fluid through the fixed bed of iron ore, oxidized pellet or the like to be reduced is reversed in direction so that the iron ore, oxidized pellet or the like, at any place in the bed, may be reduced uniformly.

Abstract: An arc furnace for quickly and continuously melting directly reduced iron ore so as to make steel, wherein the furnace wall above the hearth line and the furnace roof have partly spherical inner surfaces, the spherical surface defining these inner surfaces having the center located adjacent to the point equidistantly spaced apart from the lower ends of electrodes, and the electrodes are inclined at an angle to the vertical so that the distance between the lower ends thereof may be reduced to a minimum.

Abstract: Disclosed is a furnace wall structure which is placed in opposed relation with electrodes of a electric arc furnace and is made of copper or copper alloy in order to ensure a long service life, improved safety and a minimum thermal loss and in which a front plate which defines a heat-receiving surface exposed within the furnace is cooled by the forced circulation of cooling water.