Patent GB-908650-A (GB)
Title: Improvements in or relating to a display transmitter
IPC: H04L17/02
Filed: 1960-09-06
Abstract: 908,650. Typewriters. TELEPRINTER CORPORATION. Sept. 6, 1960 [Sept. 28, 1959], No. 30708/60. Class 100 (4). [Also in Group XL (b)] A telegraph apparatus comprises means for printing on a tape a line of characters and for simultaneously forming on the tape a plurality of code symbols which represent the characters. In the embodiment described an operator types the characters on to the tape, each character forming operation also forming a code signal on the tape either as perforations or as ink dots. Character selection is performed under the control of contacts closed by code bars associated with a keyboard. Closure of one or more of the contacts energizes certain of six electromagnets 40, 42, 44, 80, 82, 84, Fig. 5. The cores of these magnets carry wheels 34, 36, 38, 74, 76, 78, and are such that wheels 34 and 74, 36 and 76, 38 and 78 have movements of 1: 2: 4. Cords 32, 92 are anchored at 50, 90 and pass round the wheels on the cores and round various guide wheels, such as 52, 94, to control the movement of a type cylinder 30. The cylinder is octagonal in cross-section and has eight characters on each face. Energization of any of the magnets 40, 42, 44 will move the cylinder axially to one of eight positions, and energization of any of the magnets 80, 82, 84 will rotate the cylinder so that each face can be brought to any of eight positions. Means are provided for returning the cylinder to a rest position with the cords 32, 92 tight. Code combination selection.-Beneath the type cylinder 30 are two relatively horizontally movable plates 104, 106, Figs. 10 and 11. Plate 104 moves with the type cylinder 30 when the latter moves axially, and plate 106 is moved by means of a cord when the cylinder rotates. Both plates have projections 126, 128, 130, 138, 140, 142. The paper tape 20 is sufficiently wide to extend across both plates and over the forward face of the type cylinder, see Fig. 9, so that, when the tape is struck by the printing hammer a character and the corresponding code combination are printed on the tape, the code combination appearing by the presence or absence beneath the hammer of the projections on the plates. The print hammer 160, Fig. 5, is carried by a lever 162 which is pivoted at 164. The lever is connected to the core of an electromagnet 172 so that the hammer strikes when the magnet is energized. The hammer may comprise a rigid bar, but preferably comprises self-adjustable hammer faces 178, 180, 182, Fig. 9, which strike against the type cylinder 30, the upper code plate 104, and the lower code plate 106, respectively. Tape feed.-The tape 20 is supplied from a reel 200, Fig. 5, and is guided to pass between the type cylinder 30 and the hammer 160. The tape then passes on through a reader 210, round a driving drum 212 against which the tape is frictionally held by means of a releasable spring 242, and along guide means to pass out of the apparatus at 218. The tape is stepped forward as the hammer returns after each printing action. A lever 232, Fig. 13, carries a pawl which engages with a ratchet wheel 230 and upon de-energization of the printing magnet 172 the ratchet wheel, and the drum 212 with it, are stepped forward by one increment. Reverse movement is prevented by a stop dog 234. Ribbon feed.-The ribbon spools 250, 252, Fig. 5, are mounted on the same shaft and are driven by a motor 254. A switch is tripped when an eyelet positioned near either end of the tape reaches it, in order to reverse the ribbon motion. Spool 250 is driven positively, while spool 252 is driven via a slip clutch which is prevented from reverse motion by means of a ratchet and pawl. When spool 250 is driving the ribbon, take-up spool 252 must stop on its clutch because of its larger diameter. On reversal the slip clutch drive cannot move because of the ratchet so spool 250 pulls the ribbon from spool 252 which slips against the clutch. The ribbon passes the printing position at a small angle. Use as a receiver.-Both the transmitter and receiver use for transmission a number of conductors, one for each element of a code combination and a further one for clock synchronizing signals. Received signals are amplified and used to energize the character selection magnets and to operate the printing hammer. A record of the received code combinations and the corresponding characters is therefore printed on the tape. Specifications 786,831, 892,222 and 906,774 are referred to.