Patent GB-721721-A (GB)
Title: Printing mechanism
IPC: G06K15/06
Filed: 1952-09-22
Abstract: 721,721. Printing mechanisms. NATIONAL CASH REGISTER CO. Sept. 22, 1952 [Sept. 29, 1951], No. 23692/52. Class 100 (4). A printing mechanism of the kind in which the characters to be printed are selected by the sensing of discriminating potentials applied to a series of points corresponding to the type characters on a printing member, comprises a source of motive power to which the printing member is coupled when a discriminating potential is absent and an electrical device responsive to the sensing of the discriminating potential which effects uncoupling and causes the printing mechanism to execute a printing cycle. An interlocking arrangement prevents the printing mechanism from operating during sensing and vice versa. As shown, the printing members comprise a series of type wheels 21, Fig. 6, directly coupled to a series of visual indicator drums 20 by gears 40, 41, the latter being internally toothed to engage a sprocket 44 rotating in a recess in a bearing disc 42 which supports the gear 41. Each sprocket 44 is arranged in a different recess in each of the discs 42 so that each of the shafts 25 are connected to the appropriate type-wheels. The shafts are connected at the other end of the machine to the indicator drums 20, Fig. 3, by a similar mechanism. The simultaneous rotation of the type-wheels. 21 and indicator drum 20 is effected by gearing 35, 78, 72, 74, 73, 56, a one revolution clutch mechanism 95, and gearing 55, 62, 61 driven by a motor. The shaft of the gear 72 rotates a carrier of a sensing. brush 108 in a sensing unit 50 which connects in turn a potential from a series of contact plates 107 to a slip ring 106 leading to the electrical device, Fig. 10A. When a start key 263, or the equivalent contacts operated from some other computing or analysing apparatus, is operated, relay R5 operates which in turn energizes relay R2 having contacts which cause the operation of the motor 60 rotating the gears on the driving side of the clutch 95. If the brush 108 is in contact with a plate 107 not having a distinguishing potential the potential on the left grid of a double triode valve 266 remains negative and no current passes in the anode circuit in which case the right grid, which is coupled to the anode circuit of the left triode, remains in a condition to pass anode current in the right-hand triode. This causes the operation of the clutch 95 and one revolution is given to the gearing driving the type-wheels and indicator drum which are stepped one character. Similar action is repeated until a more positive potential is detected by the brush 108 which causes conduction in the left triode and non-conduction in the right. The clutch 95 is thus de-energized with the type wheels &c. in correct position. If, as an alternative, a more negative potential is used for selection, the left triodes are not used and the control grids of the right triodes are connected to the slip rings 106. There is one double triode 266 and one clutch 95 for each type wheel and clutch contacts 95b are serially connected so that when all clutches are de-energized a relay R6 operates which releases the holding circuit to relay R5 thus preventing further setting operation. A pair of contacts R1a1 in this series circuit is closed by a valve circuit to give a certain delay after the operation of the start key 263, to ensure that the clutches 95 and their contacts 95b operate before R6 becomes effective. The release of relay R5 also releases relay R2, and contacts R262 operate relay R3. Relay R3 operates a solenoid 241 to effect printing operation. Aligning for impression.-The operation of the solenoid 241 initiates a rotation of a shaft 121, Fig. 6, and through cam mechanism rocks a lever 118 causing an aligner 117 to engage the type wheels. When the lever 118 is away from resting position it allows interlocking contacts 122 to open. Hammer-impression arrangements.-Solenoid 241, Fig. 5, in operation moves a slide 239 downwardly and its hooked end 238 releases a lever 235, pulled by a spring 236, and allows an arm 245 to close contacts 250. This operates a motor (215, Fig. 10B) driving gearing 216-218 and a clutch ratchet 220. Movement of the lever 235 also moves an arm 230 counterclockwise releasing a pawl 221 which engages the now rotating ratchet 220. The pawl is connected to a disc which drives gears 223, 224 to rotate the shaft 121. At the end of a revolution a cam on the shaft 121, Fig. 9, actuates link 209, toggle 205-208, and levers 203 to which is connected a platen 195 mounted on arms 197, slidably mounted on fixed pivots 130 and on studs 199, Fig. 6. Line-spacing arrangements.-End plates 125, 126 rock about the pivots 130 secured in left and right plates 131 (and 132, not shown), which, together with a cross rod on which they are mounted, form a removable rocking framework for a strip-positioning and feed mechanism, and the platen 195. Plates 131, 132 are held in position by latches, and support a rod 127 on which pivot levers 148, 149 carrying a strip supply roll 145. The ends of levers 148, 149 are connected together by a rod 150 supported by links 151, 152, and a second rod 153, carried by bell-cranks 154, 155 whose other arms have rollers engaging in slots in the end plates 125, 126 so that the cranks are rocked relative to them as the plates 125, 126 are rocked to printing position; the rocking is effected by means of levers 162, 163 operated by mechanism 164, 166, 168 and a pitman 169 coacting with a cam on the shaft 121. The strip is guided from the roll 145 over the rods 150, 153 and as the end plates 125, 126 are rocked, line spacing movement of the strip is effected by either of a pair of pawls 178, 179, Fig. 7 (displaced relative to each other by half a ratchet tooth), engaging a ratchet wheel 176 on the hub of a strip-receiving roll 165 mounted between the end plates. The pawls are mounted on a feeding plate 177, urged clockwise by a spring 180 against a stop 186 which is automatically positioned, according to the diameter of the strip, on the receiving roll, so that the line-spacing stroke of the plate 177, caused by a roller engaging an arm 190 during movement of the rockable framework to printing position, is altered accordingly. Interlocking devices.-During a printing operation the aligner 117, Fig. 6, allows the contacts 122 to open and disconnect the anode potential from all the values 265, 266 and thus prevent operation of the sensing mechanism. The arrangement of the clutches 95, their contacts 95b and relay R6 described above prevent a printing operation during a sensing operation.