GB1309050A - Printing arrangement - Google Patents

Abstract

1309050 Line printers PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 15 July 1971 [17 July 1970] 33201/71 Heading G4H [Also in Division B6] In a line printer variations in the print intensity upon the visual record caused by differing surface areas of the various printing characters are accommodated by varying the time during which a constant current is allowed to flow through the associated hammer energizing coils. The printer is of the type having a rotatable drum having a plurality, e.g. 16, axial lines of type characters each line having, e.g. 20 print positions of the same characters wherein one or more hammers may be activated on any one line and activations on all lines produces the complete line of print. As shown, data corresponding to a print operation is fed to and stored in a shift register consisting of two portions 17<SP>1</SP> and 17<SP>11</SP>, the former comprising 20 positions each corresponding to one of the hammer coils L 1 -L 20 and the latter having 4 positions and providing a code determining the particular tone. Upon insertion of the word in the register, a stepping motor 12 is caused to rotate the print drum and a photo-electrically sensed position encoding scale 18, the output of which is fed to a comparator 20 together with the word stored at 17<SP>11</SP>, and also to a device 30 which provides an output on 1 to 16 lines l 1 -l 16 in accordance with the code sensed. The lines l 1 -l 16 are grouped into groups of 4 by OR gates G 1 -G 4 and passed to 4 AND gates P 1 -P 4 which are enabled by a coincidence signal of the comparator, which also stops the motor 12. The groups each correspond to those characters requiring similar hammer pressure for satisfactory printing each group requiring a different pressure, and the output from one of the gates P 1 -P 4 causes activation of a corresponding monostable T 1 -T 4 each having different pulse lengths. The output pulse is taken to enable AND gates g 1 -g 20 via which particular coils are energized according to the position of one or more "1's" in the register 17<SP>1</SP>. Constant current generators I 1 -I 20 supplied from a storage capacitor C are employed and the duration of the current pulse in any event is less than the flight time of the hammers and hence each will possess a momentum proportional to the pulse duration.