Patent ID: 8701968

Claim:
A friction stir welder comprising: a stage on which at least two material pieces to be welded are mounted and stacked, each of the material pieces having opposed broad face portions and a plurality of narrow end faces which surround the broad face portions, the broad face portions of the material pieces are engaged together and the end faces extend in a direction which is substantially perpendicular to a surface of the stage which supports the material pieces when the material pieces are mounted and stacked on the stage; a pressing member that is configured to fully cover the end faces on one side of the stacked material pieces along a full length of the material pieces on the one side and to press the covered end faces in a direction which is substantially parallel to the surface of the stage which supports the material pieces to prevent escape of the softened material from between the engaged end faces during a welding operation; a rotary tool that is inserted into the stacked material pieces to be welded while rotating such that the rotary tool extends substantially fully through the stacked material pieces in a stacked direction, so that a plastic flow of the material pieces to be welded is generated at an interfacing portion as well as in a vicinity thereof between the rotary tool and the material pieces to be welded, thereby to joint the material pieces to be welded to each other; a base portion that is configured to fully cover the covered end faces on one side of the material pieces to be welded that are mounted and stacked on the stage and to press the covered end faces of the material pieces in the direction which is substantially parallel to the surface of the stage which supports the material pieces; and a pressing portion that is configured to press one of the broad face portions of at least one of the stacked material pieces to be welded in a stacked direction thereof which is substantially perpendicular to the direction in which the base portion is configured to press the covered end faces, wherein the base and pressing portions of the pressing member are connected together in a substantially right-angle shape in cross section, and a length of the base portion in the stacked direction is greater than a length of the pressing portion which is substantially parallel to the surface of the stage.