GB1441007A - Hammer flight time aligning system for impact printers - Google Patents

Abstract

1441007 Control of printers COMPAGNIE HONEYWELL BULL 25 Oct 1973 [26 Oct 1972] 49792/73 Heading G4H A printer incorporates means which allow for variations in the flight time t v of individual hammers, where t v is the interval (t 3 -t 1 ) between the time when an actuator 2 is ordered to release a hammer 3 and the time when the hammer strikes the character support. Since t v varies uncontrollably, the "mean fictitious flight time" T = t vm +t fi (t vm = flight time averaged over n test "strikes", t d = interval (t 1 -t 0 ) between the strike command and reception of hammer-actuating energy by the actuator) is made the same for all hammers by controlling t d . The test strikes are initiated by pulse DEP which sets flip-flop 82 to open gate 83 for n clock pulses H1. During each strike, H1 sets a flip-flop 15 which is reset by pulse CAR 2 to produce pulse DEL which triggers actuator 2. The duration of DEL is equal to the (uncorrected) time td and is determined by presetting counter 14 with a value PP during each strike, PP is passed to counter 13 which is incremented to its maximum by pulses UT1 from clock 85. The actuator output MART fires hammer 3 whose impact is detected (after time t v ) at 41, 42 to produce pulse IMP which resets a flip flop 51 set by the leading edge of H1. Each output TVM from 51 opens gate 52 so that pulses UT1 pass to counter 53. The accumulated counts from the n strikes are divided by n at 54 so as to produce T= t vm +t d . A reference value T R is subtracted from T at 6 to produce an "error" signal Te=T -T R (or its complement if Te < 0). After the nth pulse H 1 , flip flop 82 is reset and its output BIS triggers monostable 76 which outputs pulse TRANSF to open gates 72, 74. Te is transferred to counter 75 which is then decremented by pulses E (UT2) from clock 85, which pulses also pass to storage counter 14 where they are used to alter the preset value transferred to counter 13 to PP+Te (Te#0). Subsequent printing operations proceed as above, except that PPŒTe replaces PP whereby t d (i.e. duration of DEL) has been modified in accordance with the monitored value of t v . Signal DEL may be divided into a "fixed delay" time DELF and a "variable delay" time DELV; a modification of Fig. 4 is described for dividing DEL and for correcting DELV (Fig. 7, not shown).