Patent GB-1312769-A (GB)
Title: Printing apparatus
IPC: G06K7/14
Filed: 1971-06-22
Abstract: 1312769 Printer NATIONAL CASH REGISTER CO 22 June 1971 [30 June 1970 (2)] 29164/71 Heading G4H [Also in Division B6] Printing apparatus for printing on a record medium coded data in the form of a series of contiguous areas of equal width in the direction of the series, each area having one of three possible colours and no two adjacent areas having the same colour, includes drive means arranged to move the record medium in a series of steps, each equal to the width of one of the areas, past two printing stations in sequence, the two printing stations being for printing areas of the first and second colours respectively, the third colour being the background of the record medium, printing control signals being supplied to the two printing stations in accordance with input data, those applied to the second printing station being suitably delayed to compensate for the distance between the two stations. A series of tags forming a strip of paper are each to be printed so as to each have a series of contiguous bars each white (i.e. unprinted), black or green with no two adjacent bars alike, such that a transistion from white to black, or from black to green, or from green to white represents 1, and each of the reverse transitions represents 0, the series of bars on the tag being a left end code, binary coded decimal data, a block check charac - ter, and a right end code. The left end code is a direction bit (the first bar being green), a size code specifying the number of decimal data digits, and a parity bit, and the right end code is similar, the last bar being black and the size code being the bit-by-bit inverse of the left size code. Each parity bit specifies that the number of 0 bits is equal modulo 3 to the number of 1 bits. The block check character ensures that the sum of 1 bits in each binary order is even. In Fig. 5, the data is entered from a decimal keyboard 22 (or computer or tape), converted to binary-coded-decimal form by NAND gates at 154, and passed via a buffer store 160 to a recirculating shift register 164, together with the block check character generated at 166 using a bi-stable per binary order. A code converter 168 (see below) co-operates with NAND gates at 172 to generate the parity bits from the contents of shift register 164 and store them in left and right end code registers 170a, 170b which also receive presetting signals, and the size code from a counter 152 which counted the decimal data digits entered at keyboard 22. The contents of the left end code register 170a, the shift register 164 and the right end code register 170b are shifted out in turn to code converter 168 to produce green and black print pulses which are supplied directly and via a shift register 176 (providing a delay corresponding to the distance between the two printing stations) respectively to print solenoids 46 66 controlling the print hammers at the green and black printing stations respectively. The stations have green and black print ribbons respectively, advanced by pulses associated with the print pulses. An adjustment screw is provided at each station to adjust the distance between the print bars (against which the hammers strike the ribbons) at the two stations. Before the data is entered, the keyboard 22 is used to enter the number of tags required, via converter 154 into a tag counter 156. Code converter 168 (Fig. 10C).-The bits to be converted to the bar code are supplied via a bi-stable 410 which provides them in true and complement form, to NAND gates 412-422 also controlled by the true and inverse outputs of two bi-stables 424, 426, the set inputs J of which are controlled by NANDS 420, 422 and the set outputs Q of which provide the black and green print pulses B, G. The reset inputs K of the two bi-stables 424, 426 are controlled by the respective set outputs Q.