The present invention is directed to a device for sidewise or lateral alignment of flat workpieces on a feeding table of a die-cutting machine or platen press. On a feeding table, the flat workpiece is forwarded by means, such as a belt or a roller track, toward one or several front lays or stops and then carried by a second means, which is the object of the present invention, toward one or several positioning side marks or stops prior to the front edge of the workpiece being seized by a series of grippers fitted on a gripper bar of the platen press.
The device is used for the accurate sidewise alignment of flat workpieces that have already been printed with one or several printed patterns or motifs for the subsequent operation, which, possibly, may be either an additional printing in the platen press or a cutting and/or waste-ejecting process in the platen press. This subsequent operation must be achieved in a rigorous concordance with the previous printed patterns.
The devices for sidewise alignment used up to now include, first of all, a lower roll which is positively rotated as well as arranged to extend crosswise to the travelling direction of the workpiece close to the side stops, which are usually located on the left-hand side of the table when looking along the travelling direction of the workpiece, and which left-hand side is usually called the operator's side. These devices then include an upper roller which is fitted vertically to roll on an end of an arm which, at rest, is in the upper position. This arm is regularly lowered each time a flat workpiece reaches the front stops in such a way that the upper roller will press the flat workpiece against the driven lower roll, which action generates a corrective shift laterally to the side stops to position the workpiece.
A complementary device located at an inlet of the aligning device verifies the uniqueness of the workpiece which is taken into consideration. This device consists of a lower roll and an upper roll, which are situated on the same vertical plane oriented in the travelling direction of the workpiece and whose spacing is set so as to correspond to the thickness of only a single workpiece.
The proper alignment of the flat workpiece is verified owing to the motion of a spring plate arranged in front of the stop, which motion is established by means of a metallic flag that is part of the spring plate and that moves close to a magnetic detector.
Working satisfactorily with sheets of paper or cardboard with standard characteristics, these devices, however, reach their limits as soon as the basic weight becomes too heavy for the pulling power available. Moreover, such devices are not easily used for corrugated cardboard, because the pressure between the roller and the roll tends to flatten out the flutes. Finally, the application point for the pulling power is intangible, since it is defined by the dimensions of the device, which fact might be inconvenient dependent on the size of the flat workpiece to be processed and/or on the designs to be given a run.
These problems are actually partially overcome owing to another device which is arranged on the right-hand side of the table, i.e., the side opposite the operator, and includes an element which pushes crosswise on the side edge of the flat workpiece. However, this device works properly only if the workpiece is sufficiently rigid to offer resistance to such a rapid pushing over its whole width. Moreover, the mounting of the device, the special adjustment of the device and the subsequent dismantling of this expensive complementary device generate a long production down-time between each run.