Abstract: The invention is a drive system for folding blades for the folding of flat material, preferably paper, in folding devices working by the principle of blade folding, consisting of one or several universal joints interposed between the drive and output shafts of the folding-blade drive. Universal joints may be used so that the shafts are in different planes and the angle of intersection of the shafts is greater than zero. The irregularity of the angular velocity achieved will cause an extreme displacement of the point of return, so that the folding blade will contact the sheet with a small velocity and will then be considerably accelerated to reach the velocity of the folding rollers prevailing at the moment of transferring the sheet to be folded to the folding rollers. The drive and output shafts may also be telescopic shafts.

Abstract: A rotary folder has a folding cylinder provided on its periphery with a plurality of grippers open and closable by radial displacement of respective cam followers. A pack of different release cams is axially displaceable adjacent the cylinder through positions in each of which a respective one of the cams is aligned with the cam followers. Mechanism is provided for pulling the followers radially away from the cams during adjustment, and for rotating the cams themselves for fine adjustment of the closing position in accordance with paper thickness.

Abstract: A sheet feeding unit includes a stack elevator which raises the top of a supported stack of sheets to infeed height. A sensor senses the position of the top sheets of the stack, to ascertain whether these exhibit improper left or right offset. Depending upon the magnitude and size of the sensed offset, the stack elevator is correctively shifted, to minimize offset at the top of the stack. Although the sensor is located to only one side of the stack, not at both sides of the stack, it is capable of sensing offset in both left and right directions. When the elevator is lowered, for the laying in of a fresh stack, it is automatically brought to a centered position.

Abstract: Grippers pull the leading ends of sheets along a sheet transport path, and a guidance structure facilitates sheet travel. The guidance structure comprises a plurality of longitudinally extending guide bars provided with suction openings, the ribs spaced apart transverse to the sheet-transport direction. Intermediate the bars are large-surface-area plates having suction openings. When guiding sheets printed on only one side, the intermediate suction plates are at about the same level as the longitudinally extending guide bars, and the entire face of the sheet is engaged, with the help of suction force. When guiding sheets printed on both sides, the imtermediate suction plates all drop down out of contact with the sheet, leaving only the spaced apart and narrow longitudinal guide bars to engage the sheet. The guide bars are furthermore transversely shiftable, so that they can be brought into engagement with parts of the sheets bearing no printing.

Abstract: Sheets are displaced from a supply to a continuously rotating receiver drum in a printing machine by means of a transfer drum having at least two angularly spaced grippers. The drum carrying the gripper is rotated at a relatively slow speed, and each of the grippers can be angularly displaced on the transfer drum and relative to the other gripper. Thus each gripper is accelerated after it picks up a sheet at the pickup station so that when it reaches a transfer station where it passes the sheet off to the receiver drum it is moving at the same speed as the receiver drum. Thereafter each gripper is uniformly decelerated so that when it has returned to the pickup station it is moving at the same speed as the sheet thereat.

Abstract: A printing machine has a plurality of printing stations which print images on both major surfaces of each sheet passing through the printing machine. A reversing arrangement turns the respective sheet between two of the printing stations so that the major surface of the respective sheet having a fresh image thereon faces downwardly. A support arrangement is provided which supports this sheet during its advancement to the next following printing station, and includes a blow casing having upwardly oriented passages through which air issues in upward direction to create an air cushion between the respective sheet and the blow casing for supporting the respective sheet during its advancement. An elongated bracket is arranged upwardly of the blow casing and supports a region of the respective sheet which is devoid of the image, during the advancement of the sheet in a path portion located upwardly of the blow casing.