Abstract: A variable capacity hydraulic constant stroke piston apparatus has an annular rotor rotatably mounted for rotation around an axis of rotation and having a plurality of radial cylinder bores therein spaced at intervals therearound with working liquid inlets and outlets at the radially outer ends thereof, a rotor drive for rotating said rotor around the axis of rotation, an eccentric cam positioned within the rotor and movable along a circular locus of eccentric positions concentric with said axis of rotation; a device for fixing the eccentric cam at one of the plurality of eccentric positions and for moving the eccentric cam around the axis of rotation between said positions; a plurality of pistons radially reciprocally movably mounted in corresponding cylinder bores in the rotor, the pistons having heads normally contacting an outer periphery of the eccentric cam and moving through a constant length stroke at each position of the cam; and working liquid current rectifying means connected between the inlets an

Abstract: A root pass bead welding method for joining two metal base members includes forming a dike bead by welding on a rear surface of one metal base member, and placing the dike bead against or in the vicinity of a distal end of a rear surface of another metal base member to define a groove open at the front surface of the same. Then welding is performed from the front surface of the other metal base member at the groove to form a root pass bead extending between the dike bead and the rear surface of the other metal base member.

Abstract: In the manufacture of welded pipes, edge buckling or waving of the strip is prevented by heating. In one method, during the process for bending the strip into a tubular form, the edges of the strip are heated so that tensile stress exerted thereon is reduced to a minimum and, thereafter, before the edges are abutted against each other, the strip is wholly heated so that the compressive stress exerted on the edges is reduced to a minimum. According to another mode, during the process for bending the strip gradually into a tubular form or during the process in which the edges of the strip are held in abutment against each other, the strip except its portions of the edges is substantially or partially heated so that the strip except its portions of the edges is subjected to compressive stress while the portions of the edges are subjected to tensile stress, and under these conditions the edges are welded together.

Abstract: An apparatus for continuous production of seam-welded steel tubing is proposed. The apparatus includes a series of shaping rolls for shaping a strip taken out from a strip coil into a tubular intermediate product, the roll series including a finpass roll group. The tubular product is subjected to seam welding under the action of a seam welder. Before arrival at the welder, a substantial main part of the preformed tubing with exception of opposing edge zones thereof is subjected to heating by a heater compensate for excess compressive stresses induced in the edge zones, while these zones are subjected to cooling by a cooler for avoiding otherwise formation of disadvantageous edge wavings which would otherwise occur.

Abstract: In the manufacture of welded pipes, edge buckling or waving of the strip is prevented by heating. In one method, during the process for bending the strip into a tubular form, the edges of the strip are heated so that tensile stress exerted thereon is reduced to a minimum and, thereafter, before the edges are abutted against each other, the strip is wholly heated so that the compressive stress exerted on the edges is reduced to a minimum. According to another mode, during the process for bending the strip gradually into a tubular form or during the process in which the edges of the strip are held in abutment against each other, the strip except its portions at the edges is substantially or partially heated so that the strip except its portions at the edges is subjected to compressive stress while the portions of the edges are subjected to tensile stress, and under these conditions the edges are welded together.