Abstract: A seam tracker in which a shaft containing a position-indicator-member, e.g., a ferromagnetic portion, is attached to a probe, and is mounted on a ball joint and the ball joint is pivotally mounted on a pin the ends of which extend through slots in a housing. Spring means urge the pin ends against one end of the respective slots. A mechanical null position spring urges the shaft to a mechanical null position off of the longitudinal axis of the housing. A means responsive to changes in position of the shaft from an electrical null position along the longitudinal axis of the housing gives an output to drive a control apparatus to correspond to changes in position of the probe represented by changes in position of the shaft.

Abstract: An arc welding apparatus is disclosed wherein an electrode carriage is mounted to occupy two positions relative to a lead screw-threaded sleeve assembly which carries the electrode carriage toward or away from a workpiece. Direction of lineal movement of the lead screw-threaded sleeve assembly is determined by the direction of rotation of a motor which rotates the lead screw. The electrode carriage is moved from its first position relative to the lead screw-threaded sleeve assembly to its second position substantially simultaneously with the contact of the electrode with the workpiece. An electric switch is operatively associated with the electrode carriage to be tripped when the electrode carriage moves from the first position to the second position. Tripping of the switch causes a control unit to reverse rotation of the motor for a predetermined time whereby the electrode is carried to be a predetermined distance from the workpiece.

Abstract: An improved welding apparatus having an electric motor driven electrode carriage assembly, is disclosed. The carriage assembly is capable of carrying the electrode either towards or away from a workpiece depending upon the direction of rotation of the electric motor. An electric switch and a control unit is operatively associated with the electrode carriage assembly for the switch to be tripped when the electrode in its movement toward the workpiece physically contacts the workpiece. Tripping of the switch sends an appropriate signal to the control unit to reverse rotation of the electric motor for a predetermined time period whereby the electrode is carried to a predetermined distance from the workpiece.