This invention relates generally to an apparatus for the machining of a tubular workpiece, and more particularly to such an apparatus having a work implement, such as a metal cutting burner or a metal welding tool, capable of a wide variety of unobstructed movements relative to the workpiece.
The free end of the workpiece implement is capable of being longitudinally adjusteed along its central axis, the work implement is mounted on a support arm for movement therealong, the support arm is mounted on the apparatus for movement about a vertical swivel axis lying perpendicular to the support arm, and the work implement is capable of movement about a tilting axis lying at a right angle to the swivel axis.
A known apparatus of the general type aforedescribed is set forth in a publication entitled: "RB-Elektron 650/1200 AGD". The support arm of such apparatus is cantilevered horizontally from a support frame capable of being moved in a vertical direction and in a direction of the longitudinal axis of the tubular work-piece. The support arm is mounted on the frame for movement about a swivel axis which lies horizontally. Tilting movement of the burner is effected by parallelogram guiding. By swivelling the burner arm about its horizontal swivel axis and tilting the burner about the tilting axis of the burner arm, the burner is capable of being adjusted throughout almost 360.degree.. Only angular areas of adjustment with approximately a horizontal burner position are excluded since such positions cannot be achieved, due to the geometry of the parallel guiding. In other words, from a central vertical position, the burner cannot be swivelled completely through .+-.90.degree. therefrom. And, the central point of the angular adjustability of the burner is located by almost an angle of 360.degree. on the intersection of the swivel and burner axes.
This known burner apparatus presents drawbacks in that the burner arm has too much play whih can only be corrected by additional and extensive mechanical arrangements. The parallelogram guiding system, necessarily includes a large number of joints which must be capable of movement without interference so that the tilting may be carried out with essentially the same ease independent of the initial tilting angle, and which must be adjusted in such a precise manner that, when the burner is swivelled through its vertical position, no dead angles occur. These requirements cannot be achieved in practice with the known burner arm arrangement. Instead, burner arm swivelling becomes unstable during repeated and extensive use and, in practice, it makes jerk-like movements since the tolerances of the swivel angles are too high. Thus, precise cutting requirements are not capable of being achieved.