Abstract: A laser beam machining device employs a laser for generating a laser beam, a chopper device for intermittently blocking the laser beam for intermittently irradiating the laser beam onto the surface of a work, and an assisting gas discharge device for injecting assisting gas toward the point, on which the laser beam is irradiated. By locating the chopper upstream of the primary condenser and away from the assist gas flow, the assist gas to be discharged toward the predetermined point of the work, on which the laser beam is irradiated, is not disturbed which otherwise would cause turbulence to degrade the precision of the laser beam machining operation. In addition, the assisting gas discharging device is so arranged as to direct the assist gas flow substantially along the axis of the laser beam to be irradiated onto the work surface.

Abstract: A roll cooling device for a rolling mill having rolls comprises cooling water guide plates each having a curved surface along a circumferential direction of rolls, the cooling water guide plates being provided close to the rolls, cooling water supply headers for supplying cooling water to cooling water passages defined by the cooling water guide plate and the rolls, water discharge headers for discharging the cooling water, supplied by the water supply headers, from the cooling water passages, support members supporting the cooling water guide plates, and curvature adjusting members for changing curvature of the guide plates in accordance with a diameter of the rolls. A thickness of the guide plate is increased from each edge portion to a central portion of the guide plate in the circumferential direction of the roll. In the case where the roll diameter is largely changed, the clearance between the guide plate and the roll is kept suitably, thereby sufficiently cool the rolls.

Abstract: A laser-welding apparatus including a pair of clamps at least one of which is movable reciprocally along the steel strip-feed line direction and which are adapted to clamp the edge portions of preceding and trailing steel strips, a shear which is advanceable and retractable between the pair of the clamps in a perpendicular direction to the line and cuts the edge portions of the preceding and trailing steel strips, a device for butting the cut faces of the preceding and trailing steel strips while being clamped by means of the clamps, a device for continuously feeding a filler wire at a weld zone at which the laser beam is condensed, and a laser torch adapted to condense a laser beam from a laser oscillator on an off-line at a weld zone and movable in the width direction of steel strips to be welded together.