Patent GB-358737-A (GB)
Title: Improvements in keyboard mechanisms for printing telegraph apparatus
IPC: H04L17/04
Filed: 1930-10-18
Abstract: 358,737. Punching telegraph tapes. TRIGGS, W. W., 57, Lincoln's Inn Fields, London.-(Teletype Corporation; 1410, Wrightwood Avenue, Chicago, U.S.A.) Oct. 18, 1930, No. 31318. [Class 31 (ii).] Selective punching machines.-In a telegraph keyboard perforator each code element is represented by a pair of bars, and on the operation of a key lever the individual bars of each pair are moved transversely of their lengths in opposite directions. The bars are moved vertically in opposite directions, and levers associated with each pair of code bars are selectively positioned so that a tape is perforated according to the code elements of a combination. The key levers 26, mounted on a shaft 27, engage six pairs of code bars a, b, associated with six levers 37 connected to further levers 16 which are selectively moved into an operative position with respect to a hammer 15 operated by an electromagnet 18. Each bar a, b is formed near one end with a U-shaped slot 30 engaged by a roller 31 mounted on a shaft 32, and at the opposite end is similarly mounted except that the U slot is replaced by a shallow slot. Associated with each pair of code bars are two T-shaped members 34 mounted on the shafts 32 and each formed with forward and rear lugs 36 extending laterally into slots in the lower edges of the a and b bars respectively. The T members are connected at their lower ends to the levers 37. The upper edges of the bars are formed with notches so positioned that a notch on an a bar corresponds to an unnotched part of its associated b bar and vice versa. When, on depression, a key lever 26 engages a raised portion of an a bar, the latter is depressed and effects the rotation of the associated T members in an anticlockwise direction about the shafts 32, thus moving the associated lever 37 towards the right. At the same time the bar b is raised by the opposite lug on the member 34. If a key engages a raised portion on a b bar the connecting member 34, rotated in a clockwise direction, raises the a bar, and moves the associated lever 37 towards the right, withdrawing the corresponding member 16 from an operative position with respect to the hammer 15. On the depression of any key an auxiliary bar 40 corresponding in operation to an a bar operates T members 34<1>, 341 having only forward lugs, and moves to the right a lever 41 to close at contacts 44 the circuit of the electromagnet 18, the circuit being broken subsequently by the opening of the contact 44 under the action of a spring 42. The armature, rotatably mounted on a shaft 17, carries the hammer 15, and when operated drives code pins 10 through the tape 14 in accordance with the rods 16 selectively moved into the zone of operation. At the same time an auxiliary pin forms a feed-hole in the tape and a pawl 22 is moved idly over a ratchet wheel 21 having pin teeth engaging in the feed-holes of the tape. On the release of the armature the ratchet wheel is moved a step to position the tape for the next set of perforations. The bars a, b remain on their operated positions until reset by subsequent depression of a letter key 29. Interlocking arrangement. On account of the complementary nature of the notched and unnotched portions of the code bars a, b, the operation of a key lever 26 prevents the simultaneous operation of any other key lever. The series of raised portions and notches on the a, b bars corresponding to the code combination for a letter or signal and simultaneously engaged by the corresponding key lever 26 will differ for each letter on at least one pair of code bars. The raised portion of an a bar causes the b bar of that pair to be raised on depression of a key lever, and the unnotched part on that b bar will be raised under another key and so prevent the latter key from being operated since the operation of the first key raises the unnotched part of its b bar, whilst to operate the second key the same projection would have to be depressed.