Patent GB-214665-A (GB)
Title: Improvements in and connected with telephone systems
IPC: H04M1/57
Filed: 1924-04-22
Abstract: 214,665. Howell, T. H., and Ferguson, R. G. April 18, 1923, [Convention date]. Electric type-wheel machines; aligning for impression; letter-spacing mechanism.-In an automatic telephone system, a subscriber on leaving his telephone may operate a switch 16, Fig. 16, so that when he is called, ringing current operates a relay 12, and after a definite interval, direct current is connected to the line 14. The calling subscriber may then by means of his impulse transmitter cause his number to be printed on a ribbon 95, Figs. 5 and 15, at the called substation. A digit magnet 33 responds to the impulses of each train to step a type quadrant 38 to the correct position, and after an interval a magnet 54 is energized to effect printing of the digit. The ribbon 95 is fed by a drum 53 connected by a spiral spring to the spindle 28, which is driven by a motor 26. The relay 12 intermittently connects up the motor 26 and the digit magnet 33, which become connected in an independent circuit over springs 76, 73 when the spindle 28 is slightly rotated to bring the uninsulated part. of a flange 69 on a drum 68, Fig. 9, in contact with the spring 73. The spindle is thus driven through 1“ revolutions until a pin 124 on the gear 31, Fig. 7, strikes a flange 127 on a rocking lever 120. The flange 127 normally lies out of the path of the pin 124, but the T- shaped lever 120 is rocked by the engagement of a gravity pawl 123 with a flange 121 on the other end thereof. The feed drum 53 is normally locked by a detent 103, Figs. 4 and 13, which cooperates with two teeth 102 on a flange 101 on the drum, and is released therefrom during the rotation of the spindle 28 by the movement of an annular cam 107 on the drum 68 which allows two lateral movements of the detent 103. A pawl 111, Figs. 12 and 13, pivoted on a spring-pressed lever 110, co-operates with a ratchet 99 on the feed drum when the detent 103 is withdrawn, and controls the rotation. The ribbon is thus fed distances a, b during the rotation of the spindle 28, while the operating pawl 36 on the upper end of the armature 34 of the magnet 33 is held away from the type quadrant 38 by engagement with a projection 52 on the feed drum 53 until this movement is completed. A cam 79 on the spindle 28 allows a lever 80, Fig. 16, to descend under control of a. dash-pot 83 to make contact with a post 88 to shunt the condenser 15 and connect direct current to the line 14, the motor circuit being broken at the spring 76. In response to the first digit dialled by the calling subscriber, the type quadrant is stepped by the engagement of the pawl 36 on the armature 34 of the digit magnet 33 with the upper ratchet 37, a. detent being provided to prevent backward movement. An arm 43 pressed against a pin 46 on the quadrant is moved until it strikes a pin 143 on the armature 34. A bell-crank lever 58 is withdrawn by a stud 65 on the first de-energization of the magnet 33, and returns under control of a dash-pot 61 and makes contact between a screw 62 and the arm 43, connecting up the printing magnet 54. The lever 39 which carries the type quadrant is raised by a loop 57 on the armature 55 and prints the digit on the ribbon 95 on the feed drum, inking being effected by a ribbon or otherwise. The quadrant is held during printing by the engagement of the pawl 36 with the lower ratchet 37, and then drops slightly so that the pawl is between the two ratchets and returns to normal under the action of a spring 49. The arm 43 also returns and releases the magnet 54. The feed drum is locked during printing by the engagement of the ratchet 99 by a detent 117, Fig. 12, on a slotted plate 115 raised by the lever 39. The plate 115 also lifts the lever 110 and the pawl 111, so that on its return, the feed drum is fed a distance c through one tooth of the ratchet 99. The remaining digits are printed in the same way, and the spacing on the ribbon is governed by the lengths of the teeth of the ratchet 99. In the example given, the first digit designates the exchange of the calling subscriber, and is separated by an extra long space c from the subsequent digits. The circuit of the motor 26 is momentarily broken when the calling subscriber hangs up, and the spindle 28 is driven backwards by the spring in the feed drum through a quarter of a revolution until a pawl 90, Fig. 4, engages a flange 89, since in this case the gravity pawl 123. Fig. 7, strikes the other end of the rocking lever 120 and moves the flange 127 out of the path of the pin 124. The spring 73, Fig. 9, which rests against a pin 140 just beyond the flange 69 during printing, engages first an insulated flange 71 to hold the circuit open, and then the insulated end of the flange 69. The cam 79 returns the lever 80 to normal, and the cam 107 moves the detent 103 into the path of the teeth 102 and the lever 110 and pawl 111 are raised, so that the feed drum moves through a distance g until the first tooth 102 strikes the detent 103. The projection 52 then engages the operating pawl 36, and the printed number is displayed through an opening in the casing of the apparatus. Part of the winding of the relay 12 may be shunted by the condenser 15, and the motor 26 may be connected up over a contact of the magnet 33 independently of the contacts of the relay 12.