Patent GB-823136-A (GB)
Title: Proportional letter feed mechanism
IPC: B41J19/32
Filed: 1956-01-20
Abstract: 823,136. Typewriters. UNDERWOOD CORPORATION. Jan. 20, 1956 [April 1, 1955], No. 1941/56. Class 100(4) In a typewriter wherein the carriage is given letter spacing movements proportional to the widths of the characters typed, the escapement mechanism includes a wheel having equally spaced teeth and driven by carriage movement, a dog normally engaged with the wheel but released by actuation of a type lever and moved in one direction by a spring and then re-engaged with the wheel, stop means to limit movement of the dog in the opposite direction after re-engagement, a series of stops, selectively projectable parallel to the wheel axis by actuation of certain type keys, for variably limiting the movement of the dog in the first direction and causing the reengagement of the dog, and a member normally positioned to limit movement of the dog in the first direction to a less amount than that permitted by one or more of stops, but which is moved out of the range of the dog by the projection of those stops. The type bars 10 are power operated by power roll 15 via actuators 13 and case shift is brought about by means of a power operated rocker 52. Carriage 25 is urged leftwardly by spring motor 28 under control of escapement dog 32 and wheel 33 on shaft 34. Dog 32 normally engages wheel 33 and is pivoted on an arm 45 swingable on shaft 34, branch 46 normally resting against abutment 47 on arm 48. Dog 32, after release from wheel 33 at a type action, is re-engaged with the wheel, by a spring 55, the appropriate number of teeth, i.e. feed increments, away from abutment 47 to permit the carriage to advance the number of feed increments proportional to the width of the character typed. To give a spacing of three increments in the lower case and four in the upper case a pivoted stop arm 49 is positioned by the caseshift body so that stop face 53 or 54 is in the path of finger 56 on dog 32 so as to effect reengagement of the dog to control three and four tooth advances respectively. Carriage advances of one to five increments, other than those controlled by arm 49, are controlled by stop pins 61-65 which are movable into the path of the dog, such operation pivoting arm 49 downwardly to a position in which it has no controlling effect on dog 32. Operation of a type bar 10 acts through universal bar 76, rocker 78, lever 85, and a pin and slot connection to disengage dog 32, finger 56 moving from branch 46, arm 45 being moved by spring 55 until finger 56 engages stops 53 or 54 or pins 62-65. If fingers 56 encounters face 53 or 54 arm 45 travels further and pivots dog 32 into mesh with wheel 33 which returns the dog to the position shown in Fig. 2. Operation of a type key 22 requiring other than this 3/4 increment feed, acts through 110, 111 to close corresponding contacts 107, 108, and the corresponding electromagnet 92-95 then pivots lever 102 to move the required pin 62-65 into operative position. Operation of space bar 151 acts through 154, 155 (Fig. 8), to lower pin 61 into range of dog 32, and through 160, 161, 162 draws actuator 163 into contact with power roll 15 and hence through 164, 165, 166 operates lever 85 to disengages dog 32, which is re-engaged with wheel 33, one tooth later, by pin 61. Operation of space bar 152 acts through 169, 171, 161 and actuator 163 &c. to free dog 32, and through 169, 172, 173, 174 to close contacts 175 which are in circuit with magnet 92 and cause pin 62 to be projected to control a twoincrement spacing. Operation of space bar 153 acts through 176, 177 and actuator 163 &c. to free dog 32, and through 176, 178, 180 to close contacts 183 of magnet 93 so that pin 63 is actuated. Snatch pawl 185 having initial idle movement ensures that pins 61-63 are selected in advance of operation of lever 85. To ensure that wheel 33 comes to rest before the next release of dog 32 a secondary escapement dog 188 is engaged with a wheel 42 unitary with wheel 33 by an arm 190, at each typing or spacing action. Arm 48 may be conditioned, by means of a. knob 195, for movement, following . the next escapement operation, to the position shown in Fig. 2, or to one in which abutment 47 is removed rearwardly from between abutment 193 and branch 46, arm 45 then making step movement which is one increment greater. A pawl lever 210 normally co-operates with an arm 212 integral with arm 45 to hold the latter against movement from abutment 47 or 193, but is freed, to permit movement of dog 32, by a pin 214 when dog 188 is operated. To permit manual positioning of carriage 25, dog 32, but not dog 188, may be released by operation of a bail 215 which acts through 220, 221, 85. When tabulating key 248 is operated it acts via an actuator 258 (not shown), shaft 15, and rocking assembly 261 to raise link 250 (Fig. 12) and through arm 268 to actuate lever 85 and so release dog 32 for carriage tabulating travel. Link 250 lifts arm 243 and via spring 254 raises an element 235 into position to co-operate with keysettable, tabulation terminating elements 228. As rocker 261 reaches its operative position actuator 258 is disengaged by its tail and returned by spring 259 (not shown) independently of the rocker which is held in operative position by latch 272 (Fig. 1). Lever 277 held by latch 280 holds stop slide 226 from wheel 225 which is fast on shaft 34 and has teeth at intervals corresponding to three teeth of wheel 33. When any set element 228 advances against and displaces element 235 the latter frees latch 280 and lever 277 is swung by spring 282 and moves slide 226 into engagement with wheel 225 to terminate tabulating movement. As element 235 moves further arm 243 is carried clear of link 250 and spring 245 returns arm 243 and element 235. The upper end of link 250 is adjustable relatively to arm 243 by screwing guide stud 238. Arm 291 follows lever 277, and arm 294 brings cam roll 296 into contact with driven wheel 298. The roll is then driven through a single turn and swings arm 294 counterclockwise (Fig. 1), first causing arm 290 to actuate latch 272 to free rocker 261, and then. through pins 292 on arm 291, restoring lever 277 and retracting slide 226. Spring- 293 returns arms 290, 291, 294. A carriage run may be terminated by leftward displacement of stop 336 by a key settable line end margin stop 357, a pin 358 on stop 336 moving element 235 to release latch 280 &c. Element 235 is cut-out at 360 so that it is operative range of latch 280 only when projected for tabulation termination. Depression of the carriage return key 324 acts through 325, 326, 328 to release latch 322 from lever 316, whereupon spring 321 moves arm 315 to close the clutch so that drum 312 is driven by motor 308, through a reduction gear, and by means of draw band 313 returns the carriage to a limit, determined by the key-adjustable stop 333. When lever 316 moves with arm 315 it acts through 335, 337 to move the counter stop 336 leftwardly, Fig. 11, and when the latter is displaced by stop 333 lever 316 is swung clockwise to open the clutch. Lever 316 is temporarily detained by latch 342 if latch 322 is withheld as a result of continued depression of key 324. Depression of key 324 also acts via 330, 331, 343, 344, 346 to operate lever 85 and so remove dog 32 from wheel 33, lever 85 being latched in operative position by latch 348. Movement of lever 316 to open the clutch also acts through 350, 351 to release latch 280 so that stop slide 226 snaps into engagement with wheel 225. Cam roll 296 also becomes active, whereupon arm 290 releases latch 348 so that dog 32 again engages wheel 33, and through arm 354, lever 277 is again latched. A rod 355 linked to latch 348 lifts link 344 at each release of latch 348 to ensure that lever 346 is free to return if key 324 is held depressed after carriage return is completed. To bring an element 228 automatically into register with setter 230, and therefore in accord with the teeth of wheel 225, the latter is back spaced, i.e. in three-increment steps, by a pawl 361, Fig. 2. Operation of key lever 375, Fig. 19a, acts via dog 374 to free pawl 371 for engagementwith wheel 368, fast on shaft 367 of roll 15, so that cam 366 is coupled for rotation with the wheel, and via 365, 364, 363 actuates cam 361, the time lever 375 is held determining the number of reciprocations of the pawl. At the conclusion of back spacing stud 376 acts on pawl 361 to prevent movement thereof. Operation of back space key 388 acts via a pawl 384 (not shown) to back space wheel 33 a single movement. The proportional feed mechanism may control a type supporting carrier for movement with respect to a paper support. Specifications 823,137, 823,138, 823,139 and 823,140 are referred to.