units wherein all press units are always required to have the same distance from one another from this it follows that the travel distance of each individual unit is different a conceivable configuration is that a continuous threaded spindle extends from the first press unit to the last press unit parallel to the travel rail and is fixed in place for each press unit a running nut is arranged on the threaded spindle and can be rotated from the press unit and thereby displaces the press unit the rotational direction of the drive motors on the left hand side is then opposite to the rotational directions of the drive motors on the right hand side furthermore the travel distance of the outer press units is three times as great as the travel distance of the next inner press units these differences must be taken into account by correct actuation of the drives the control would therefore be comparatively complicated the only advantage of this arrangement is that sheet pile profiles of changeable width can always be gripped in the centre by the collets in the interest of a simplified and reliable and therefore forced control of the adjustment movement the invention prefers that the running nuts of each press unit are.