Patent GB-1252388-A (GB)
IPC: B41J23/26
Filed: 1970-04-16
Abstract: 1,252,388. Printer control arrangements. CREED& CO. Ltd. 16 April, 1970 [24 April, 1969], No. 18196/70. Heading. G4H. In a printer of the kind having a printing head having a continously rotating circular type magazine 1, Fig. 1, in which all the types are mounted on radial levers 2, the head being guided along the line of print for printing successive characters, the rotary and lateral motion both being derived from the same motor M and the lateral position being indicated by a coder WC and compared at VE with a desired position, the speed and direction of the lateral motion being determined by the difference value, the motion serving to bring the head to a-standby position from which it advances to make a printing operation moving in synchronism with the magazine. The type to be printed is selected as the magazine 1 rotates by a selector AS which deflects the selected type lever from the rest position lying on rim 4a, into a working position determined by a guide (not shown) above rim 4a. As the magazine rotates the extension 2a of the selected type lever engages a cam 9 and the type is thrown against the platen 10 to make a printing impression. The lever then rebounds and is returned to the rest position. The magazine is rotated through a gear 5 by shaft 6 connected to the motor. Shaft 6 may be connected by speed selector SG, Fig. 3, to shaft 7 displacing the head laterally through a thread and nut. One revolution of shaft 7 displaces the head 16 printing columns. On the other end of shaft 7 is mounted a shaft encoder and a gear driving a coarse shaft encoder. The two encoders provide signals on lines L1 defining the printing column in which the printing head is positioned. Each character has associated with it the number of the column in which it is to be printed. For each printing operation the character is applied from input unit AE to store DS and the corresponding column number is applied to comparator VE, also receiving the actual printing head position. The difference signal on lines L3 is applied to control logic EL. As the magazine rotates pulses are generated and applied to counter ZS. When the counter agrees with the number in store DS the selector AS is operated over line L13. The magazine has the types arranged uniformly round its circumference except for a gap which serves as a datum point. An inductive transducer JG gives a datum pulse in the middle of the gap which is applied over line L9 to logic unit EL, and to the unit AE to cause the next character to be passed to store DS and its column to comparator VE. If the last character printed was in column N the printing head comes to rest in the next column (N + 1). The indication given by the encoders WC is offset compared with the actual column position (Fig. 4, not shown) so that the column indicated is N which agrees with the value applied to the comparator VE from unit AE. The difference signal is zero and logic device EL accordingly selects brake GS4 over line L7. If printing is to recommence in column N + 1 this value is applied to the comparing device with the next character in DS. The difference +1 between this and the actual position causes logic EL first to energize fast return motion GS2 over line L5 thereby driving the printing head backwards until the difference is + 2. This causes logic to apply the brake GS4 and the head comes to rest in column N - 1. The slow advance motion GS3 is then selected and the head advanced until the column code changes to N, the difference +1 causing the brake to be applied bringing the head to rest just inside column N. This is the standby position from which the printing movement takes place by selection of the normal advance motion GS5. The head then advances in synchronism with the rotation of the magazine. If the column to be reached is more than 5 columns away the fast forward motion GS1 is energized and the printing head moves at high speed until it approaches the desired position.