Abstract: An improved welding apparatus and method of use including a pair of opposed electrodes mounted on arms which are fixed against outward displacement during the application of the welding current. One of the arms includes a cylinder for moving an electrode to and away from the work piece. The cylinder includes a pilot operated check valve which permits a one-way flow of hydraulic fluid while the weld current is applied. The check valve prevents movement of the electrode away from the work piece during expansion of the weld nugget, however, permits inward movement of the electrode after the nugget is softened.

Abstract: An improved welding apparatus and method of use including a pair of opposed electrodes mounted on arms which are fixed against outward displacement during the application of the welding current. One of the arms includes a pneumatic cylinder for moving an electrode to and away from the work piece. The cylinder includes a piston rod attached to a clutch by a ball screw mechanism. A brake assembly is connected to the unidirectional clutch to prevent outward displacement of the electrodes during expansion of a weld nugget and permitting inward movement of the electrodes to provide indentation of the weld after the nugget softens.