this mechanism offers a simple solution wherein an axial movement of a grooved piece brings about a radial movement of rigid balls that grip and deform a pipe that is initially in a plastic state . depending on the geometry of the channels of the grooved piece , a variable grip is achieved . this gripping operation is simply released as the grooved piece returns to its initial position , the pipe itself now being in a solid state , so that the balls are returned to their initial position . the correct position for gripping the plastic pipe can be detected by a detector . the pressurization of the plastic pipe can be achieved thanks to an elastic joint on the piece that surrounds the pipe .