Abstract: An apparatus for controlling a first fluid cylinder and a second fluid cylinder includes an operational pressure source and a fluid control circuit. The fluid control circuit includes a pilot valve assembly having a first valve position and a second valve position. Moreover, the fluid control circuit (1) delivers pressure from the operational pressure source to the first fluid cylinder when the pilot valve assembly is positioned in the first valve position, (2) isolates the second fluid cylinder from the operational pressure source when the pilot valve assembly is positioned in the first valve position, (3) delivers pressure from the operational pressure source to the second fluid cylinder when the pilot valve assembly is positioned in the second valve position, and (4) isolates the first fluid cylinder from the operational pressure source when the pilot valve assembly is positioned in the second valve position. A method for controlling a first fluid cylinder and a second fluid cylinder is also disclosed.

Abstract: A method for sensing and controlling the weld quality of gas metal arc welding employs sampling of the welding current and voltage signals and making determinations of the weld quality state based on information embedded in those signals. The signals are processed such that the quality of the weld can be determined and the appropriate steps are taken to respond to the detected quality level. If the quality level is deemed unacceptable the process is terminated and the operator is alerted. The method includes determinations based on the standard deviation of the electrical signal, the summed power spectrum of the electrical signal, and/or the average absolute value of the time derivative of the electrical signal.