Patent GB-842980-A (GB)
Title: Improvements in or relating to apparatus for converting analogue values to digital values
IPC: H03M1/00
Filed: 1956-09-04
Abstract: 842,980. Recording-apparatus. DEGEN, A. A. C. Dec. 4, 1957 [Sept. 4, 1956 (2)], Nos. 26969/56 and 26970/56. Class 106 (4). Apparatus for converting the analogue reading of an instrument into a digital value comprises a stepped cam 30, continuously adjustable by a needle 16, a probe 36 movable step-by-step into contact with the cam so that the position of the probe when contacting one of the steps represents a digital value corresponding to the analogue reading, and a number wheel adjustable in accordance with the position of the probe to indicate the digital value. Alternatively stepped probes may sense the needle direct. A toothed sector 28 with a fork 24 embracing the needle 16 carries units, tens and hundreds cams 30, 34, 32. The tens cam 34 has ten steps 43 arranged in two cascades for each of the three steps of the cam 32, similarly the units cam 30 has ten steps in two cascades 37 for each of the 30 steps 43 and both the units and tens cams 30, 34 have on their inner edges a recess and projection 39, 40; 44, 45; corresponding to each five steps on their outer edges. Three probes 36 co-operate with the steps of the 3 cams, respectively, and two probes 42 with the inner recesses and projections. A reading cycle is initiated by applying a pulse to an electric circuit, Fig. 11 (not shown). The electromagnetically-driven shaft 46 controls the cycle through 4 cams, the first causing a pawl to clamp the toothed sector 28, the second 74 through five steps lifting the 3 probes 36 in stages until each encounters a step of a cam 30, 34, 32, whereupon a corresponding lever 102 rocks to close its set of contacts 108, thereafter the third cam allows the two probes 42 to sense a recess or a projection of the cams 30, 34; if a recess is sensed an arm 123 moves to hold the contacts 108 closed so that when the fourth cam subsequently moves the lever 102 free from the contacts 108 they will open immediately only if a projection was sensed. In the final part of the cycle the system is reinstated, any closed pairs of contacts 108 are opened and the needle 16 is unclamped. Thus three electric signals are produced, the units signal, e.g., beginning at one time for 0 and 5, later for 1 and 6 and so on and ending earlier for 5, 6, 7, 8 and 9 than for 0, 1, 2, 3 and 4. The signals are transmitted to a receiver where they are caused to set type-wheels for printing the digital value. The receiver comprises three type-wheels 128, Fig. 8, each secured to a ratchet-wheel 132 and toothed wheel 134 and free on a shaft 130, the type following the sequence 0, 5, 1, 6, 2, 7 .... An electromagnetically-driven shaft 138, Fig. 7, synchronized with the control-shaft 46 of the transmitter controls type-setting through 3 cams 146, 196 and 222, the first, 146, having steps followed by a lever 148, allows a stirrup 156 to rise in stages. Tails 162 of 3 sectors 160 follow the stirrup under the stress of springs 166 and turn their corresponding type-wheels from 0 to 1, 1 to 2 ... until each is stopped individually by a pawl 184 engaging its ratchet 132 upon receipt of a signal by its electromagnet 168, a latch 186 slipping under projection 188 to lock pawl 184 in action. When the cam follower 152 engages the lowest part of the cam 146, a lever 192 enters the recess 194, Fig. 9, of the second cam 196 and rocks a stirrup 206, causing 3 pawls 210 to strike their ratchet wheels 132 midway between teeth. At the same time a lever 218, Fig. 10, moves on to the high of the third cam 222 and rocks a stirrup 226 removing the latches 186 from the pawls 184, leaving them under the control of their electromagnets 168. If in the transmitter a digit in the range 0, 1, 2, 3, 4 has been selected, the contacts 108 will remain closed, keeping electromagnet 168 energized and the appropriate digit of the wheel 128 in printing position. If a digit in the range 5, 6, 7, 8, 9 has been selected, the contacts 108 open, electromagnet 168 is deenergized and pawl 184 unlocks the type-wheel 128 which is then allowed to be turned half a tooth by spring 166 bringing the appropriate digit 5, 6, 7, 8 or 9 into printing position. A printing impulse then causes a printing hammer 236 to press a paper strip 238 and ink ribbon 240 against the three type-wheels 128, thus printing the digital value corresponding to the analogue value indicated by the needle 16. A transmitter with an alternative arrangement for probing and generating the required signals is described with reference to Figs. 12 to 14 (not shown), and another arrangement is suggested, in which stepped, concentric, cylindrical probes sense the instrument needle. For an instrument with a non-linear scale the distance between the steps on the cams 30, 32, 34 would have to be appropriately varied. More than one receiver may be operated by one transmitter. Specification 842,981 is referred to.