Patent GB-854085-A (GB)
Title: Communication equipment
IPC: H04L17/04
Filed: 1956-11-09
Abstract: 854,085. Type-printing telegraphy. SMITH-CORONA MARCHANT Inc. Nov. 9, 1956 [Nov. 16, 1955], No. 28452/59. Divided out of 854,083. Class 40(3). The invention relates to a telegraph printer for use in the communication system described in Specification 854,083. General. The printer is a page printer employing a type wheel in which the majority of the operating mechanism is arranged to be behind the record medium. The type wheel is divided into 32 equal parts around its periphery, 26 of which bear characters and the remainder of which are employed for functions, such as line feed. The wheel is mounted on a shaft for rotation to effect character selection and the general procedure is set the shaft rotating and to stop it at the correct position to select a desired character by means of an electrical impulse which is applied to actuate an electromagnetically controlled stop-wheel mechanism. The correct timing of the impulse is effected by means of a control circuit to which are applied the five mark/space signal conditions representative of the telegraph code and which incorporates commutators driven from the type-wheel shaft. The type-wheel is located behind the recording medium, which is in the form of a paper bearing a black material which is in turn covered by light material on the operative face. A printing hammer strikes the operative face to force the medium against the type wheel and the portion of the light material over the raised character is broken exposing the black material to form the recording. The printer incorporates the customary features line feed, line return and automatic feed and return at the end of a line. Operation proceeds on a cyclic basis with a main shaft which effects a single rotation for each character in response to receipt of an electrical impulse. The main shaft drives the type wheel shaft and carries cams to bring about correctly tuned operations of character selection, printing, spacing and, if necessary or desired, line feed and return. Type-wheel mechansim, Fig. 18. The type wheel 230 is carried by a square portion of a shaft 212, which may be rotated to effect character selection, and is slidably mounted so that it may move along the shaft space-by-space to print a line of characters. The movement is effected by a cable 250 which also moves a printing hammer 316 which is similarly slidably mounted on a square shaft 314. Shaft 212 carries two tooth wheels 254, 255, which form part of the stop mechanism (see below), and a group of cams 218-221 (illustrated in exploded form) which control functions, such as line feed (see below). The precise angular positions of the cams with relation to the type wheel are illustrated in Fig. 31. Cams 218, 219 and 221 are solid with shaft 212. Cam 220 is freely rotatable on the shaft. Each end of shaft 212 carries the wiper 306 of a 16-segment commutator S801 and S802 which forms part of the control circuit (see below). Stop wheel mechanism, Fig. 27. Wheels 254 and 255 are carried by shaft 212 and have oppositely facing teeth. Wheel 254 functions as the actual stop wheel and wheel 255 functions as a cam wheel. Each wheel has 16 teeth. Associated with the wheels are two pawls 258, 259 having stopping edges 262 and 263 respectively which may engage wheel 254 and camming edges 264 and 265 respectively which engage wheel 255. The two pawls are so positioned angularly with respect to wheel 254 that one stops the wheel at positions intermediate those due to other thus permitting shaft 212 to be stopped at 32 possible positions. A pawl is operated to stop the shaft by energization of solenoid E801 or E802, the actual movement of the pawl to engage a tooth on wheel 254 being effected by the cam action of wheel 255 and the solenoid merely serving to hold the pawl in position. Control circuit, Fig. 5. In accordance with the mark/space combination of the telegraph code of a character to be printed earth is applied simultaneously to one or the other terminal of five pairs of terminals 1-6, 2-7, - 5-10. Two commutators S801 and S802, have their wipers driven by the type wheel shaft and each have 16 segments which are connected to rectifier networks CR801-CR804. A negative potential is applied to the input of network CR801 and CR802 from the junction of resistors R805, R806, and in accordance with the selective combination of earths on terminals 1-10 the potential is allowed to pass through only one of the two commutators and at only one of sixteen possible paths through the commutator. By this means, in accordance with the telegraph code combination, an impulse is produced at the correct one of 32 intervals to stop the type wheel shaft and select the corresponding character. The impulse appears at the input of either amplifier V801A or V801B and is effective to cut-off the amplifier and fire an associated thyratron V802 or V804 to energize the stop wheel solenoid E801 or E802. A cycle of printer operation is initiated by a positive impulse which appears at terminal 11 after the setting of the code potentials on terminals 1-10 is completed. The impulse renders a tube V805 conductive to energize the solenoid E803 of a start clutch on the main shaft (see below) and also produces a negative impulse via tube V803 to extinguish whichever of thyratrons V802 and V804 remains fired from the previous operation. Main shaft, timing, control of funtions, Fig. 22. The main shaft 363 is coupled to a continuously rotating shaft 357 for each character by means of a one revolution clutch 361 (see below). The clutch is actuated by an electromagnet E803 which is energized after the setting of the code potentials in the control circuit is completed. The shaft times the whole operation of the printer in the manner shown in Fig. 32. The shaft drives type wheel shaft 212 through gears 372, 481 and 226, the gear ratio being such that the type wheel is driven through a full revolution, so as to permit selection from the whole of the 36 character spaces, during only a part of the revolution of shaft 363, the remainder of the revolution being devoted to printing and function operations. Gear 372 is friction mounted on shaft 363 so that it may slip when the type wheel shaft is stopped at the selected character. Printing is effected by a cam 386 on shaft 363, the operation taking place after character selection is completed as shown in Fig. 32. The cam operates through lever system 335, 336, 331 to rock shaft 314 carrying the print hammer. A sensing lever 327 is engaged by a projection 344 on cam 218 on the type wheel shaft at each of the six positions allotted to functions to block the printing action. Type wheel spacing. The type wheel and printing hammer are moved along a line by means of a spring loaded drum, Fig. 21 (not shown), which drives cable 250, Fig. 18. The drum is held by a ratchet and pawl mechanism 392, 412, the spring being wound as the type wheel is advanced space-by-space across the printer and released to drive the wheel back at the end of a line or in response to a line return signal. The space-byspace advance of the type wheel is effected by cam 385, which, at each revolution of shaft 363, displaces a lever 486 and produces a downward movement of a feed pawl 493 engaging ratchet wheel 392. The wheel is moved through the distance of one tooth and held by pawl 414. Line return is effected by means of cam 387 which operates through lever 564 to displace feed pawl 493 and knock pawl 412 out of engagement with ratchet wheel 392. Lever 564 is pivoted at each rotation of shaft 363 but is ineffective to initiate line return unless a line return signal is received. This causes cam 219 on the type wheel shaft to be positioned so that a finger 346 engages pin 574 of a sensing lever 571. Movement of lever 564 then causes a clockwise movement of the end of sensing lever 571 to depress pawl 493. Line return at the end of a line is brought about automatically by cam 220 on the type wheel shaft. At the end of a line a stud 411 on ratchet wheel 392 engages lever 596 and slightly rotates cam 220 which is freely journalled on shaft 212, to bring finger 604 into a position to engage pin 574 of sensing lever 571. At the next printer cycle line return cam 387 then becomes effective as described above to cause depression of pawl 493 to release ratchet wheel 392. Line feed of the recording sheet is brought about by cam 368. At each revolution of shaft 363, a feed lever 549 is tripped to operate a ratchet and pawl mechanism 518, 538 on the sheet feed roller 513, the operation being ineffective however unless the type wheel shaft is positioned for line feed, where cam 221 is positioned to bring a finger 345 into engagement with the pin 559 of a sensing lever 556. Cam 221 has a second finger 345 in the line return position so that a line feed operation is made for each line return. The sensing pin 559 also extends to engage a finger 603 on cam 220 so that a line feed operation is made when automatic line return is initiated at the end of a line. Cam 374 on shaft 363 operates switches S803, S805 in the stop position, i.e. when the printer operation is completed and shaft 363 is at rest. These switches serve to prevent a code combination from being applied to the control circuit until a previous one has been dealt with. One revolution clutch, Figs. 23, 26. Continuously rotating driving shaft 357 terminates in gear 360 and is coupled to the driven member 450 by pawls 446 which are secured to the driven member on pivots 449 and urged into engagement with gear 360 by springs 462 connected between the pivot posts and pins 458 on the pawl ends. A plate 453 is carried freely between pawls 446 and the driven member and has apertures 454 about pivots 449 and further apertures 460 engaging pins 458. The plate is formed with a lug 465 which may be engaged by the pivoted armature 466 of solenoid E803. The armature is normally biased into engagement with the lug by spring