Machine for straightening and stress-relieving steel rails

A stretching machine for straightening and stress-relieving steel rails, including a first longitudinal axis, a stretching head and a fixing head, each head being attached to a hydraulic command piston having an associated shaft and supported on a motorized carriage for displacement along the first longitudinal axis, each head including grip-carrying jaws, the hydraulic command piston of the stretching head being secured at one end of the machine to a frame by a cross head, the hydraulic command piston of the fixing head being secured at the other end of the machine to a frame by means of a cross head, the improvement comprising:

• (a) a ball-joint coupling connecting the shaft of one hydraulic command piston to the stretching head for permitting the stretching head to move freely in all directions relative to the coupling;
• (b) a ball-joint coupling connecting the shaft of the other hydraulic command piston to the fixing head for permitting the fixing head to move freely in all directions relative to the coupling;
• (c) the stretching and fixing heads each include a fixed jaw carrying a lower grip, a mobile jaw carrying an upper grip, a hydraulic jaw piston including an associated shaft carried by the fixed jaw for moving the mobile jaw between open and closed positions relative to the fixed jaw, a return mechanism for disposing the mobile jaw in the open position when the hydraulic jaw position is deactivated, a transverse rest supporting the fixed jaw for rotation about a second longitudinal axis, a system linking the transverse rest to the fixed jaw, and a separating systme for rotating the fixed jaw about the second longitudinal axis;
• and
• (d) wherein the ball-joint couplings permit self-alignment of the heads and a rail disposed therebetween along the first longitudinal axis during initial stretching of the rail and further permit the rail to be stretched along the first longitudinal axis.