Patent GB-1069931-A (GB)
Title: Drum printer
IPC: G06K15/07
Filed: 1963-07-30
Abstract: 1,069,931. Selective printing. SCM CORPORATION. July 30, 1963 [Oct. 25, 1962], No. 30196/63. Heading B6F. [Also in Divisions F2 and H2] Type-wheel machines; power-assisted actions; line and like multiple-surface type-selection.- A selective printer receiving printing information coded in the form of electrical telegraphic code signal groups comprises a continuously rotating type carrier drum 52, Fig. 1, having a plurality of sets of identical types, each set extending along a print line and an associated clock-wheel 58, having peripheral character reference notches 124, which in conjunction with monitor heads 90, 92, generate appropriate current pulses which in turn are fed with the telegraphic code signal groups to a comparator circuit, the outgoing coincidence signal controlling the operation of print hammer or hammers 410-1, 410-2, Fig. 20. Hammer impression arrangements. Single hammer function.-The hammer 410-2, Fig. 18, is mounted on a pivot pin 412 in a hammer carriage 240 and when a character is selected and coincidence determined in the comparator circuit, the coincidence signal is applied to a coil 424-2 of an electromagnet 416-2 pulling an associated armature 438-2 towards the core 422-2, whereby a print hammer lever 448-2 integral with the armature imparts momentum to the print hammer 410-2, which moves to impact with an ink ribbon 69, paper 65 and drum 52 to print the selected character. A print hammer return spring 476-2 restores the print hammer and armature to the reset position after the coil has been de-energized. In the operated position a small air gap between armature 438-2 and core 422-2 may be maintained by placing a thin strip 466-2 of a dielectric on the lower surface of the armature. The hammer 410-2 comprises a thin square head 472-2 mounted integrally on a thin lever arm 470-2, the lower end of which is reinforced by a sector 480-2 to reduce wear. Rebound of hammer after impact is dampened by provision of an armature spring 462-2. Double hammer function.-The carriage 240 can include two or more hammers 410-1, Fig. 20, in which case the carriage spacing movement will be a correlated number of character spaces and the electronic control modified accordingly. Letter-spacing arrangements.-The print hammer carriage 240, Fig. 1, is advanced in letterspacing direction on energization of a solenoid 60, which through the intermediary of its armature 260 and operating arm 262 pivots a bail 256, which engages a bail follower roller 266 journalled at the end of space pawl 374 disengaging the latter from co-operation with rack teeth on a space rack 254. When the pawl 374 is forced out of engagement a carriage spacing drum 246, operated by a spring wound up during carriage return, through a belt 248 displaces the carriage to the right and the pawl 374 engages the next tooth space, the width of the space being correlated to the number of hammers provided on the carriage 240. Carriage-return mechanism; carriage stops; key actions.-The carriage return mechanism may be actuated on receipt of a coded carriage return character, operation of an automatic carriage return switch S21, Fig. 1, or depression of a manual switch S19 (Fig. 26, not shown), which results in the energization of a magnetic carriage return clutch 62, whereby a carriage return belt drum 282 is engaged by a continuously driven clutch pulley 122 to return the carriage 240, through the intermediary of a belt 284, to the starting position. During the carriage return movement the spacing pawl 374 is disengaged from the rack teeth of rack 254. As the carriage approaches the starting position it strikes a spring-loaded nylon rod 316, which moves into a notch 318, Fig. 13, on the belt drum 282. Concurrently the carriage also actuates a switch S22, which causes the abrupt and simultaneous deenergization of the carriage retuin clutch mechanism 62 and spacing solenoid 60 so that the pawl 374 may re-engage the rack 254. The switch S22 is actuated by a magnetic projection 324 on the distal end of the carriage 240. The rod 316 may serve as a damping plunger to prevent excessive rebound of the carriage. The disposition of the rod 316 in the drum 282 prohibits excessive rebound rotation of the drum and prevents belt 284 from unwinding. To assist the tensioning of the belt 284 a light coil spring 320 is anchored at one end to the printer frame and has its other end secured in a small groove between a collar 210 and drum 282. After the first few carriage spacing operations the nylon rod 316 retracts and the belt 284 can continue to feed out against the bias of spring 320. Alarms.-A switch S23, Fig. 1, is located several character spaces ahead of the last character position and may be used to ring a bell to monitor an operator. Line-spacing arrangements; matrix sheet, web feeding and guiding arrangements; detents.- To effect line spacing a line-feed solenoid 146, Fig. 1, is energized which pivots a stop lever 150 to unblock a clutch plate 158. The clutch plate permits clutch 142 to engage continuouslydriven shaft 121 with a cam 144, whose cam follower arm 168, Fig. 8, pivotally mounted on a post 172, rocks a pawl bail 200, attached to a line-feed shaft 186, in a counter-clockwise direction causing a line-feed pawl 198, which is always biased into engagement with the teeth of a feed ratchet wheel 194, to rotate the feed shaft against the detent action of a line-feed detent 196. The rotation of shaft 186 is translated to gears 192, 193, Fig. 6, meshing with gears 100, 102, respectively, the latter being integral with feed rollers 96 and 98. The feed rollers 96, 98 are provided with high friction wheel bands 110 and cooperate with pressure rollers 180, 181 mounted on flat springs 182, which are fixed to a spring- urged pressure roller release shaft 183. The line-spacing increments may be varied by rotation of a knob 206, a cylinder 208, Fig. 1, attached to the knob presenting various high surfaces to a bell-crank spring arm 174. The surfaces determine the point at which the cam follower 166 engages the line-feed cam dwell 164. Carriage guides and races.-The hammer carriage 240 is provided with two spigots 338, Fig. 18, having coaxial bores which carry split nylon slide bushings for the reception of a fixed carriage rail 242, Fig. 1. An eccentrically, adjustably mounted bottom carriage guide roller 244 rides between guide rails 68, spaced above and fastened to a frame base-plate (not shown). Type-sheets.-The print drum 52, Fig. 6, is assembled from a plurality of discs, preferably double type row wheels 76. A desired number of the wheels is placed on a drum shaft 74 indexed to align all characters and clamped together by two clamping end-plates 78 and spacers and nuts (Fig. 4, not shown).