U.S. Philips Corporation

Reinhold Winter

Horst Kringe

Hartmut Korn

Martin Crevecoeur

Heinz M Grevecoeur

A control device for a matrix printer in which the mechanical printing elements of the matrix printer are selectively triggered by the control device a certain time before they reach the desired printing spot on the information carrier in order to compensate for the fact that the printing head will move further over a certain distance between the triggering moment and the moment that the printing element actually hits the information carrier. This distance depends on the speed of the printing element. If the print signal, however, is always generated a constant distance before the printing element reaches the desired printing spot, this signal must be delayed as a function of the speed of the printing element if the printing head is to print accurately also during its run-up and slow-down. To this end, a delay device is provided which delays the print signal for the relevant printing element by a time interval which depends on the printing head speed. A preferred embodiment of the delay device uses a counter, which is also used for determining the energizing time of the magnet and an interval time. Furthermore a correction device for determining the delay time in dependence on the speed is provided. This device works with two adjustable counters, in which one counter counts a constant pulse frequency and the other counter counts position pulses which depend on the movement of the printing element. The constant needle stroke time thus is converted into a speed-dependent path by which the lead distance of the print signal is corrected.

Control device for a matrix printer

A circuit arrangement generates a preset number of output pulses each time between two consecutive input pulses, the distance between the input pulses being subject to variation. The output pulses should be approximately evenly distributed, which even distribution, however, cannot be maintained when the cycle of the input pulses changes. To achieve first and foremost that the total number of output pulses is reached as quickly as possible in the case of a change in the input pulse cycle, the circuit includes a first counter device, which supplies a measure for the cycle duration of the input pulses in relation to a clock pulse, and this measure is used as a preset value for the next cycle for a further counter, which counts down the preset value in period with the clock pulses. The carry pulses of the further counter essentially indicate the output pulses, the number thereof is counted in each cycle by means of a third counter, which ends the further generation in the relevant cycle after the preset number has been reached, while in the case of a shortening of the input pulse cycle, any deficiency in the number of generated pulses is additionally inserted in the next cycle. As a result, the total number of the output pulses is made equal to the preset number in the shortest possible time, albeit to the detriment of an even distribution.

Preset number of pulses generated within given time period even when

In matrix printers, the printing elements in the printing head are frequently arranged so that they do not correspond to the printing raster of the characters to be printed so that the informations delivered for each time a printing column at the same time must be delayed a time. For this purpose, a delay device is assigned to each printing element of a matrix printer, the delay times for each device representing paths mutually depending upon the orientation and spacing of the printing elements in the printing head and being determined by the time interval between a common writing pulse and individual element read-out pulses, which are produced by a shift register, in which the writing pulse is shifted at a relatively high rate depending upon the head position, the read-out pulses for the elements being produced by tappings on the shift register. By, by variation of the time intervals between the writing pulses, the density of the printing raster can readily be changed over from one character or one printing column to the other. By changing the tappings on the shift register, and thus the delays to the print elements, the inclination of the printing raster can be adjusted, for example, for printing in italics. More particularly for printing in opposite directions of movement of the printing head, the delay devices are preceded and followed by a switch matrix, which reverses the assignment of the delay information of the respective printing devices to the delay elements.

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Wilnsdorf, Germany

Reinhold Winter