Abstract: Apparatus for printing any line of characters comprises printing wheels on a common shaft, the wheels on the shaft together defining a printing line over a hammer. Each printing wheel is rotated by a respective stepping motor through a respective setting wheel. An aligner bar is inserted into notches in the wheels, prior to printing, to verify the alignment of the characters in printing position. The stepping motors are bi-directional and take the shortest path from a preceding printing position to the next printing position. The pulsing frequency may be ramped to give a higher stepping rate in the intermediate portion of each printing wheel movement.

Abstract: This invention is concerned with the high speed printing of a line of text on a sheet in very accurate registration with an edge of the sheet or another feature (for example an existing print line) on the sheet. The sheet is fed without preregistration on to a track (10, FIG. 1) which passes the printing station (20). A detector (16) adjacent the track senses the arrival of the edge or some other feature of the sheet and a printing control means (14) responsive to the detector signal initiates the firing of the printing hammer (22) when the print line reaches the printing station, a registered operation being thereby effected without stopping the sheet. The detector signal may start the operation of a counter (70, FIG.

Abstract: To print on each of a number of sheets, the sheets are advanced, preferably in underlapped form, up to registering stops. When a sheet has been registered at the stops, suction is applied to an underlying conveyor, the stops are withdrawn and the sheet is advanced in steps to a printing station, the sheet being held in register by suction during this advancement. Printing takes place while the sheet is stationary and still held in register, between steps of movement. Suction may be switched on and off at the registering station by means of a movable perforated switch plate, the perforations of which are aligned, in a first position of the switch plate, with suction-conveying perforations in another plate or belt; in a second position of the switch plate its perforations are misaligned with the perforations in the other plate or belt, preventing the application of suction to an overlying sheet.