GB1436992A - Selective printer - Google Patents

Abstract

1436992 Control of printers INTERNATIONAL BUSINESS MACHINES CORP 12 March 1974 [26 March 1973] 10868/74 Heading G4H A chain printer comprises means for varying the hammer energization time in dependence on the supply voltage level so as to maintain a constant print hammer force. A buffer 26 is scanned under the control of a subcycle gating ring 34 to provide three subscans (1, 4, . . . ; 2, 5, . . . ; 3, 6, . . . ) as in 919,653; a hammer select circuit 175 sets. latches 36 whose outputs are fed to the hammer drivers 21 via gates 38 enabled by a control 40 which comprises the circuitry of Fig. 2 in triplicate, once for each subscan. The printer belt 12 is driven by a motor 44 controlled by a voltage-dependent circuit 46, Fig. 3, (not shown), timing marks 16 being sensed by a transducer 18 to produce a pulse train 185 whose period T p depends on the motor speed. A potentiometer 42 provides a signal 186 which indicates the thickness of the document 22 to be printed. Each circuit of Fig. 2 receives signals 185, 186 and a SUBSCAN signal (motor speeddependent width) from ring 34. Signal 185 causes a monostable 62 to produce a train of pulses of width T s determined by signal 186. The remainder of the circuit produces FIRE pulses of width T f = T s + 3/2 T p which enable gates 38 for a time sufficient to keep the voltagetime product (i.e. the print force) constant for the selected hammers. Specification No. 1,250,104 and (Specification Nos. 1,421,474 and 1,435,846) are referred to.