Patent GB-759519-A (GB)
Title: Improvements in or relating to typewriters
Inventor: THOMSON JAMES EDWIN
IPC: B41J29/02
Filed: 1953-12-21
Abstract: 759,519. Typewriters &c. WESTERN STAMPING CO. Dec. 21, 1953, No. 35555/53. Class 100 (4). Carriage-shift mechanism; platen mounting and operation.- A platen 125 is mounted on a carriage 115 which is mounted for slidable horizontal movement on a carriage assembly comprising a rail 113 and frame members 106 pivotally supported on the main frame of the typewriter at a position substantially above the lower position of the type faces of the type levers and at a substantial distance from the plane of engagement of the type faces with the , platen whereby pivotal movement to raise and lower the platen and carriage assembly occurs in a plane approximately parallel to the type faces when in their striking position. The platen 125, Fig. 13, is mounted between the bent-up ends 123 of the carriage 115 slidingly mounted by rollers 122 and roller cage 117, Fig. 2, to the carriage assembly rail 113 formed from stamped metal. Shifting to upper case for an intermediate case position is effected by two links 226, one at either side of the machine coupled by a torsion bar 228. The bar 228 is pivoted in a support 229 and its crank ends 225 engaged in the links 226. On operation of a case shift key 222 or 236 to effect an intermediate or full case shift, the ends of the key levers 232 or 239 respectively engage the ends 225 and lift the links 226 until the lever strokes are limited by a stop 234 on a support 233. To lock the platen in case shifted position the key is slid backwardly upon its pivot 39 or 237 and the ends slide into an aperture in the support 233. Balancing arrangements. A spring 241 (Fig. 4, not shown), too weak to lift the platen on its own, assists in lifting the carriage when a case shift key is operated. Main frame. The various parts of the typewriter are fabricated of pressed or stamped parts. The main frame, Fig. 3, is channel shaped having sides 28, and a base 31 secured to a main base 22. A cover 26 with sloping sides alongside the keyboard fit over the channel member. Bearings and hangers.-The type levers 53, Fig. 2, are mounted on a continuous wire pivot disposed within a groove 65 in a hanger comprising two upright plates 56 and 57 joined by welding. The end circular guide portion 63 of each type lever is guided by two vertical plate slots 67, 68 kept in alignment by pins in pilot holes in the plates. Touch regulating.-Uniformity of touch is arranged by the arcuate shape of the universal bar 89, Fig. 3. The keys at the extremity of the machine are thus spaced slightly downwardly from the bar 89 than those towards the centre to allow sufficient momentum to be imparted to the outer type bars to lessen the effect required to counteract the springs 93. Notches 97 are provided on the edge 96 of the bar 89 for the engagement of the front bank of keys 43. Paper feed-rollers.-Feed rollers 132, Figs. 2 and 3, are mounted on shafts 135 supported by bent-out ears 134 of a feed roller frame 133 pivoted at 137 and urged clockwardly by a wire spring 138, clipped on the platen carriage and engaging in a loop 143 formed at the upper rear end of the frame. Paper-bail.-The loop 143 of the frame 133 also carries a paper bail 144. Letter-spacing.-The escapement mechanism comprises a pawl 162, Fig. 7, rocking on a pin 161 carried on a cage 155 pivotally attached to the carriage track. Attached to the pawl 162 is an outwardly bent spring 163 forming a resilient pawl. A notch 169 on the pawl 162 is normally in alignment with the teeth of an escapement rack 145 attached to the carriage, but the carriage is held by the upper edge of the spring 163. When the pawl 162 and spring 163 are rocked by the bail 174 to effect a letter-space the spring 163 slides across the tooth of the rack 146 until its own notch 168 comes into alignment with this tooth, which thereupon falls on the edge of pawl 162 since the notch 169 is now displaced. Spring 163 is now released an amount limited by aperture 164, a distance equal to the pitch of the rack 145. Upon release of the actuated key the bail 174 rocks a pawl 162 and a spring clockwise, Fig. 6, and when notch 169 is in alignment with the rack the latter moves in a letter-spacing direction. During carriage return the inclined teeth of the rack 145 ride over the edge of the spring 163 which is urged upwardly by a spring. Driving arrangements.-The carriage is pulled in a letter-spacing direction by a mechanical spring 147 (Fig. 4, not shown) attached at one end to the typewriter frame and at the other end to a pulley slot around which runs a drawband 152. Carriage -release, tabulation control.-The cage 155, Fig. 7, has an extension 179 which may be depressed to release the pawl 162 and spring 163 from the rack 145. Space-bar mechanism.-An easy-to-operate space-bar 244, 245, Fig. 2, is pivoted on a spindle 37 and has a rear extension 248 which has an amount of free travel to collect momentum before it engages the universal bar 89. Line-spacing.-The platen is axially urged by a spring 128, Fig. 3, so that axially directed teeth of a ratchet wheel 127 resiliently engaged a pawl 129 which comprises a projection inwardly pressed from the left-hand platen end bearing 123. Line-spacing is effected by rotation of the platen by knobs 131. Margin stops.-Stops 214, 215, Figs. 14, 3 respectively, are formed by lugs on the carriage 115 and the carriage rail 112 which simultaneously engage with the carriage or cage 118. Ink-ribbon mechanism.-Vibrator mechanism. The ribbon guide 103, Fig. 6, is slidably mounted on a U-shaped bracket 184 attached to the underside of the carriage rail 112. It is separate from the type-lever guide, so that when it is actuated by a bell-crank lever 187 rotated by the side of the spring 171 during operation of the bail 174, there is constant throw of the ribbon guide irrespective of the position of the platen for case shift. The throw is limited by a stop 193 on the lever 187 when it engages the bracket 184. Ribbon-feeding and manual reversing. Ribbon spools 194 are alternately clutched to driving shaft 195, Fig. 2, by snap-over flat springs 202 so that one of them is coupled to the ratchet driver actuated from an arm 92 of the universal bar mechanism. A link 211 from the arms 92 is loosely attached to a stamp-out pawl 206 having a bent-down end for engaging a ratchet wheel 204.