Patent GB-712866-A (GB)
Title: Improvements in or relating to printing mechanisms
Inventor: WOODHEAD JAMES
Filed: 1952-03-24
Abstract: 712,866. Typewriters &c. BRITISH TABULATING MACHINE CO., Ltd. March 24, 1952, No. 7525/52. Class 100 (4) Cyclically operable printing apparatus comprises a constantly rotating driving shaft 1, Fig. 1, a character bearing type wheel 7, a lever 27 for yieldingly retaining the type wheel stationary, a gear train interconnecting the type wheel and the driving shaft including a sun and planet gear mechanism, first means, individual to each type wheel and operable at any of a plurality of times in the cycle, for stopping a member of the sun and planet gear mechanism to effect driving of the type wheel, second means subsequently operable at any of a plurality of points in the cycle for releasing the stopped gear member to bring the type wheel to rest with a selected character at a printing position and means for effecting printing from the character whilst the type wheel is stationary. Sun and planet gear mechanism.-The driving shaft 1 is formed longitudinally with teeth which are engaged by planet gears 2 mounted on pins 3 on a gear wheel 4. The gears 2 engage internal teeth on a ring gear 5 external teeth 6 of which engage the type wheel 7. A series of shallow indexing teeth on the ring gear 5 are engaged by the spring-loaded lever 27 whereby the type wheel is yieldingly retained against movement. The lever 27 is displaced on movement of the gear 5 by a tooth 28 and thereafter is held in the inoperative position by a pin 35 on lever 32 until the type wheels are reset. The gear wheel 4 meshes with a gear 39 on which is fixed a ratchet wheel 40. Type wheel driving mechanism.-A pawl 43 has an arm 46 adapted to engage the ratchet and prevent its rotation the gear 4 being locked in consequence to cause the sun and planet gear to drive the type wheel. The period of the cycle during which the ratchet wheel is arrested by the pawl determines the rotation of the type wheel and consequently the character presented by it at printing position. The pawl 43 is normally retained out of engagement with the ratchet by a lever 47 abutting an arm 44. The lever 47 is tripped by a lever 48 one arm of which is pulled downwardly by a rod 51 on energization of a solenoid 54, the armature 53 of which. is connected to the rod 51. The timing of the impulse is such that the pawl when tripped falls on top of a ratchet tooth and does not arrest the ratchet wheel until a few degrees later in the cycle ; this is shown in Fig. 7 where for example a " 6 " impulse to solenoid 54 occurs at 45 degrees causing the ratchet to stop at 57¢ degrees. There are twelve index points at which an impulse may be sent to the solenoid 54, these occupying half the cycle ; the other half of the cycle is used for printing and returning the type wheels to their initial positions. The type wheel carries numeric characters (up to eleven for printing pence values), the letters of the alphabet and various symbols making 48 in all. The twelve index points correspond to the numbers 0-11 and the other characters are arranged in three zone positions between the index points and are selected by a zoning mechanism now described. Zoning mechanism.-The pawls 43, Fig. 1, are mounted on a bar 42 supported so as to be swingable about the shaft 41 on which the ratchet wheels rotate. A link 61 attached to bar 42 is connected to a lever 62 carrying a roller 63 engaged in a cam groove in a cam 65 rotated once each cycle The cam 65 is formed so that between 145 degrees and 200 degrees (Fig. 7) the bar swings clockwise at a speed corresponding to three quarters of a ratchet tooth during each index point and then swings back to normal position. Clockwise rotation of the ratchet wheel causes anti-clockwise rotation of gear 4 which causes a reduction of speed of the type wheel to a quarter of the normal speed. Zoning impulses termed " O," " X," and " Y," are made during the period of reduced speed to select the intermediate characters. A zoning impulse to solenoid 54 causes the lever 48 to turn anticlockwise as before to engage a lever 72 and turn it into hooking engagement with the end of a lever 74. The lever 74 is pivoted in a combed bar 76 and supported by a cam 75 which, as shown in Fig. 7, allows the lever to fall at 132¢ degrees of the cycle and to remain in the operative position during the zoning period, and then lifts it clear again. The lever 72 is pivoted on the tail of a trip lever 69 pivoted on a combed bar 67 and formed with three lobes for engagement with a nose 45 of pawl lever 43. The engagement of lever 72 with hooked lever 74 and a retaining pawl 70 prevents movement of trip lever 69. As the bar 42 and the pawl swing clockwise, the nose 45 engages the first lobe of the trip lever and, if this has been secured against rotation by a zoning impulse " O," the pawl is tripped at 147¢ degrees of the cycle, i.e. after an angle corresponding to a quarter of the angle between index points. This selects the first character of the four characters selectable in the index division. A zoning impulse at "X" will energize the solenoid after the nose 45 has passed the first lobe, the lever 69 being free to swing against its spring 68 to allow this and becoming locked by the latching of levers 70, 72, 74, before The nose reaches the second lobe. Engagement between nose 45 and the second lobe trips the lever, the bar 42 having moved an angle corresponding to half the angle between index points, so that the second character of the four is selected. Similarly a " Y " impulse will cause the pawl 43 to tnp on the third lobe, selecting the third character. If no zoning impulse is made the trip lever remains unlatched and the nose 45 contacts a fixed trip bar 85 and is tripped after the type wheel has been driven at quarter speed over an angle equal to the angle between index points and therefore selects the corresponding character, which as stated above is a numeral. A spring-loaded yielding pawl 79 is allowed, by rotation of cam 81, to retain the ring gear 5 at 147¢ degrees, zoning movements being made against the action of the pawl. All type wheels are set by 195 degrees and printing takes place between 202 degrees and 215 degrees. After printing the pawl releases the gear. Special setting for symbol selection.-The symbols " ú ," " -," and " * " are arranged to correspond with an index position " 0 " (Fig. 7) and are selected by a special setting of the zoning mechanism. Normally an impulse in the " 0 " index position will not arrest the ratchet wheel because the " 0 " impulse locks the trip lever 69 and releases the pawl 46 at the same time so that the pawl is immediately tripped again. A setting lever 74 is therefore moved to a full line position where it extends the cam follower shoulder 84 and delays the movement of the lever 74 to operative position until 147¢ degrees. The pawl may therefore be tripped by an "x" or "Y" zoning impulse or by the action of the fixed stop 85, selecting " ú ," "-," " *," respectively. A type wheel for which the lever 77 is set in the operative position will only print one of these three symbols. Two-digit codings.-The two index positions corresponding to numeric characters "10" and " 1 are set by two-digit coding viz. " 7 " and " 3 and " 7 " and 4." The occurrence of either of these codings causes an impulse to be made towards the end of the previous cycle by the sensing mechanism operating through a translator relay. As shown in Fig. 7, the impulses are made at 330 degrees and 345 degrees releasing the pawl 46 at 342¢ degrees and 375¢ degrees. In the cycle after (called the second cycle) the impulses at "7" and "4" (or " 3 ") will not affect the pawl 46 since this is already released. The pawl will be tripped by a zoning impulse as before but the type wheel will have been driven (in the case of " 7 " and " 4 " coding) from 342¢ degrees of the previous cycle to (in the case of an " 0 " zoning impulse) 147¢ degrees of the second cycle selecting the forty-fifth character, i.e. " %." Type wheel resetting.-After printing, the type wheels are all reset to their initial positions. For this purpose the shaft 41 on which the ratchet wheels are mounted is rotated by a cam 95 acting through a follower lever 92, link 91, and arm 90. A cam mechanism at the end of shaft 41 causes re'ative rotation of an inside spindle 89 which has a flat thereon. A pawl 86 normally held in inoperative position by spindle 89 is permitted, when the flat is under one end, to engage either of a pair of notches 88 in the ratchet wheel. Backward movement of the ratchet wheel causes twice the movement of the type wheel 7 all the ratchet wheels being picked up and moved forward in line, the type wheels all being in the same relative position. The shaft 41 then starts moving in the other direction so that the type wheels slow down and the ratchet wheels are released for free clockwise rotation as all the type wheels return to their initial positions. This is effected by 325 degrees of the cycle. A reset bail 106 then moves against levers 32 to release retaining levers 27 which drop back into contact with the teeth of gear 5. Printing from the type wheels.-The shaft 17 carrying each type wheel is mounted on a plate 8 pivoted at 9 to a combed bar 10 and urged by a spring 12 in an anticlockwise direction. The ree ends of the plates 8 are supported on a cam shaft 11 having a fall part to allow the plates to rotate at the correct point in the cycle. As the plates 8 rotate the type wheels roll on gears 6 into contact with a paper sheet 19 passing round a cylindrical platen 20. Selected type wheels may be prevented from printing by a hammer-lock mechanism. Two mechanisms are provided for preventing a type wheel printing, one manually operable and another optionally under electromagnetic control. The first means comprise spring blades 19 displaceable by manually operable cam levers 127 into the path of the plates 8, the levers being retained by a spring plung