Patent GB-531337-A (GB)
Title: Telegraph transmitters
IPC: H04L17/02
Filed: 1939-07-18
Abstract: 531,337. Type-printing telegraphy. CREED & CO., Ltd. (Teletype Corporation). July 18, 1939, No. 20876. [A Specification was laid open to inspection under Sect: 91 of the Acts, Feb. 8, 1940.] [Class 40 (iii)] [Also in Groups VIII and XXIV] A perforated strip transmitter has "sensing" elements or feelers, settable in accordance with the perforations, mounted in a carrier movable towards and away from the exit channel of - the tape perforator depending on whether the perforator is operated faster or more slowlythan the rate of transmission. When the last perforated character has been transmitted, the transmission is automatically interrupted. The complete machine comprises three main parts, viz., the perforator, the sensing unit which is mounted - in one or more movable frames, and the -transmitter proper which is of the type in which a rotary cam distributer closes contacts in-sequence when permitted to do so by the sensing elements, as in known five-unit printing telegraph transmitters. Three forms of the invention are described which differ substantially only in the construction of the sensing unit. The sensing unit is initially closely adjacent the tape exit channel of the perforator ; if tape is perforated faster than the transmitter works, the sensing unit moves, about a pivot, away from the perforator until arrested by a stop, and thereafter a loop of tape may form. Tape-feeding means for the sensing unit, separate from that of the perforator is provided, the arrangement being such that if the tape is taut when the feeding means operates, the sensing unit is moved along the tape towards the perforator. The three forms of sensing unit described differ mainly as regards the arrangement of this feeding mechanism. Perforator. The depression of any key displaces, in known manner, one or more of five pivoted members 71, Fig. 2, connected to interponents 18 one or more of which are brought between the pivoted hammer 17 and the five punchers 13. The free end of the hammer 17 is slotted to form guides for the interponents 18. The hammer 17 and a pin 38 actuating the feed-hole punch are operated by a pivoted lever 21 controlled by a cam on a shaft clutched to the power shaft when any key is depressed. The punches 13 are withdrawn by a stripper plate 44 which engages shoulders on the punches. The feed drum 47 is fed by a pawl pivoted to the hammer 17, and this pawl may be withdrawn if it is desired to back step the feed drum manually. Transmitter. In the form shown in Figs. 2, 3, 6, the sensing unit comprises five sensing pins 125 arranged in a frame 105, 106 pivoted on pins such as 109. The pins 125 co-operate with five bell-crank-levers 148, pivoted on shaft 147, and these levers 148 are associated with five bell-crank-levers 184 controlling the contacts of the transmitter. The frame 105, 106 is initially in the position shown in Figs. 2 and 6, in which the pins 125 engage the tape 43 immediately it has left the perforator. In this position, a pin 174, Fig. 3, on the frame 105 keeps contact springs 175, 176 apart, but as soon as the frame is moved, by the feed of the tape from the perforator, contact 175, 176 energizes a magnet 177, Fig. 6, which clutches the power shaft to the main cam shaft of the transmitter. If the perforator is operated faster than the transmitter, the frame 105 may move into the position shown in Fig. 3 and thereafter a loop may form as indicated. The main cam shaft has a cam drum 185 having five cams engaging the levers 178, the cams having helically-displaced notches co-operating with lugs 184 on the levers 178, so arranged that the cams sequentially close contacts, such as 183, when the free end of the lever 178 is permitted to move upwards by the lever 148 associated with the sensing pin 125, i.e., when the pin passes through a perforation in the tape. The cam shaft also carries cams 205, 206, 207 which control the feed of the tape relatively to the sensing unit, and the movement of the sensing pins towards and away from the tape. The sequence of operations is as follows : (1) As long as there is any perforated tape ready to control the transmitter, contact 175, 176 is closed and the magnet 177 clutches the power shaft to the main cam shaft ; (2) cam 205, Fig. 6, operates a link 132 having a pin 133 engaging a cam slot in a member 126, having three pins engaging feed perforations in the tape, thereby causing relative movement between the tape and sensing unit, so as to bring the next row of perforations above the sensing pins ; (3) a cam 185 permits a lever such as 178 to send a "start" impulse ; (4) cam 206 operates a comb bail 154 to permit the sensing pins to assume positions in accordance with the perforations in the tape ; (5) the cam distributer 185 allows the five levers 178 to close sequentially the contacts 183 in accordance with the position of the sensing pins; (6) cam 206 withdraws the sensing pins from the tape ; (7) cam 207 moves the member 126 downwardly, thus withdrawing the three pins thereon from the feed perforations in the tape, which is held by other pins on a spring 120 above the tape ; (8) cam 205 moves the link 132 upwardly, thereby, since the three pins are withdrawn, moving the member 126 to the right in Fig. 6, so that when the cam 207 continues its rotation the three pins enter the next set of feed perforations in readiness for the next cycle of operations. Modified transmitters. In a modification, Figs. 9 to 14 (not shown), the sensing unit comprises two frames oscillating to and from the perforator. One frame carries the sensing fingers and the other the means for advancing the tape through the sensing unit ; the two frames are interconnected by springs and tend to follow each other. The tape is fed by a cam-controlled ratchet-operated drum instead of by a rectilinear movement as in the first modification. In a further modification, Fig. 15 (not shown), the sensing unit comprises a single frame only. Clutches. In order to prevent rotation of the driven part before the clutch members are fully engaged, e.g. by frictional engagement of the tips of the clutch teeth, a drag sufficient to resist such rotation is furnished by the engagement of a roller on a cam on the driven part.