Patent GB-642090-A (GB)
Title: Keyboard impulse transmitter for step-by-step printing telegraph
IPC: H04L19/00
Filed: 1946-08-14
Abstract: 642,090. Impulse transmitters MECANIQUE ET TRANSMISSION METRAN. Aug. 14, 1946, No. 24097. Convention date, June 15, 1945. [Class 40 (iv)] [Also in Group XL (b)] In a keyboard transmitter for a start-stop telegraph system, the impulses representing a character are transmitted during the backward rotation of a shaft, and a set of contacts which, in the rest position of the transmitter, prepare an energizing circuit for the backward rotation of the motor, are temporarily operated by a bar controlled by the depression of a key to close a circuit for the forward rotation, at the end of which the contacts are returned to a position to effect the backward rotation when a finger on the shaft encounters an abutment positioned by the key corresponding to the selected character. Circuit arrangement. When contact operating member 7 is moved to the left by the operation of the universal bar, a circuit is completed from the input terminals 1, 2 through the field windings 3, 4 and rotor 5, 6 of the motor. A cam 15 operated by the transmitter shaft closes contacts 24, 26 for the transmitting circuit, opens the receiving circuit at contacts 24, 25 and closes contacts 17, 18 so that when the universal bar is released at the end of the forward movement of the transmitter shaft and moves the member 7 to the right a circuit is completed for the backward rotation during which the impulses corresponding to a character ,are transmitted by a cam 20 operating an arm 21 between contacts 22, 23. A resistance 27 reduces the speed of backward movement. Each key 28, Fig. 3, is provided with an extension 29 carrying rollers 30, 31 engaging a slotted front plate 32 and having its rear portion guided in a slot in a back-plate 33. On the depression of a key, a pivoted hook 34 engages a universal bar member 9 carried by a pivoted shaft member 40 with which is associated a spring-biassed locking member 41 rotating on pivots 42 and engaging above the projection 43 of the depressed key lever and with notches 44 of the key levers which have not been actuated. The hook 34 is pivotally connected to an extension 36 carrying an abutment 39 and guided by a stud 37 on the extension 29. The downward movement of the bar 9 on the actuation of a key rotates a disc 46, Fig. 5, connected to the shaft 40 and carrying a stud 45 acting on a spring 47 attached to a contact block 48 carrying the contact members 11, 12, 13, 14, 16, 19, Fig. 1, the block being released for rotation when a spring arm 52 is released from a hook 50 operated by an extension of a lever member 53 rotated with the shaft 40. The transmitting shaft 61 is then rotated in an anti-clockwise direction and a cam 76 operates a roller 77 carried by a pivoted lever 78 so that contacts 17, 18 are closed in preparation for the reversed, i.e. operative, rotation of the shaft 61. The lever is looked by a spring-biassed hook 82, and a link 85, secured to the opposite end of the rod, rotates a hook 86 against the end 88 of a second arm of the lever 53. A spring arm 72 connected to the contact block 73 is operated by a cam 71 so that the contact member is brought into operative relation with the impulsing wheel 75, corresponding to the cam 20, Fig. 1, mounted on a shaft 96. The extent of angular anticlockwise rotation of the shaft 61 is selectively determined by the engagement of one of a number of fingers 62, Fig. 3, with the abutment 39 of the key which has been depressed and the leftward movement of the abutment against a stop-plate 63 rotates the hook 34 to release the universal bar 9. The hook 86 thereupon latches underneath the extension 88 of the lever 53 and the contact assembly carried by the block 48 returns to its normal position. During the forward movement of the shaft 61 a pawl 67 slides idly over a ratchet 69 and during the return movement the wheel 69 is driven and rotates gears 91, 92 to drive shaft 96 carrying the impulse wheel 75. The return movement is regulated by a governor device 95. If a key is depressed during the transmission of a character, the universal bar 9 and the locking bar 41 are operated, but transmission is withheld until a pin 103 on the cam 76 has released the hook 82 from the bar 78 which in turn releases the hook 86 so that the lever 53 is freed to rotate and to remove the hook from extension 52 of the contact block 48.