Patent GB-816761-A (GB)
Title: Improvements relating to sound recording and reproducing apparatus
IPC: G11B25/04
Filed: 1957-06-25
Abstract: 816,761. Electric motors. ATELIERS DE CONSTRUCTIONS ELECTRIQUES DE CHARLEROI. June 25, 1957 [June 25, 1956; Aug. 29, 1956], No. 19968/57. Class 35. [Also in Group XXXVIII] Magnetic locating, advancing and reversing devices 13... 15, for actuating the driving- shaft 5 of a sound record required to be advanced step-by-step (see Group XXXVIII), may be in the general form of a pair of wheels such as 40, 41 coupled by a sleeve 42 on the shaft 5, and a pair of fixed arcuate-ended cheek-plates such as 44, 45 separated by a magnet 43, the wheels, sleeve and cheek-plates being of magnetically permeable material; one or both wheels 40, 41 and the end of the corresponding cheek-plate are toothed, Fig. 5, the wheels being so arranged on the shaft 5 that with the teeth of the wheels and cheek-plates of the locating device 13 in alignment, those of the advancing and reversing devices 14, 15 are offset less than one toothwidth in the appropriate direction to produce the required movement of the shaft 5 upon energization of their electromagnets 43, 40<SP>1</SP>. The locating device 13 may have a permanent magnet, or an electromagnet excited continuoulsy or only when the magnets 43, 40<SP>1</SP> are not excited. Its toothed wheels and sleeve are fast on the shaft 5, but those of the devices 14, 15 are free thereon and one wheel 41 has a slot 48 providing lost-motion for a peg 49 projecting thereinto from the shaft 5 and connected by a spring 50 to the wheel 41, the spring tending to rotate the shaft 5 in the required direction; energization of the magnet 43 or 40<SP>1</SP> then immediately aligns the teeth of the wheel 41 and cheek-plate 45, tensioning the spring 50 whereby the shaft 5 with the record are driven until the peg 49 strikes the side of the slot 48; the magnet 43 or 40<SP>1</SP> is at this point de-energized, and the impact of the peg 49 carries the parts on past the position of maximum offset of the teeth of the locating device 13 so that the latter then locates the record one step further on or back accordingly. The materials of the wheel 41 and peg 49 are chosen for minimum noise of impact. To eliminate impact entirely, the mechanical lost-motion device 48 ... 50 may be omitted, the devices 14, 15 then comprising two alternately-energized internally-toothed annular electromagnets 101, 102, the top half of the latter being cut away in Fig. 14 to show the offsetting of the teeth, the number of which on the rotor 105 and magnets is identical, being half that in the locating device 13; with the rotor located by the latter in the position shown, energization of the magnet 101 moves it anti-clockwise almost one step of the device 13, which step is thereby completed as soon as the magnet 101 is de-energized; for the next step the magnet 102 is energized. A similar but oppositely arranged device may be provided for reverse drive, or a single device may be used with magnets adjustable between two positions (either mark A or mark B on the magnets being in line with a fixed index C). The advancing device magnet or magnets may be controlled by two end-of-travel contacts closed by the oscillating tone arm 4, those for the magnet 43, Fig. 1, being in parallel, while those for the magnets 101, 102, Fig. 14, are each individual to one magnet. The circuit of the reversing device 15 may be closed by a push-button, while for rapid advance or re-wind of the record using a single device as in Fig. 14, a commutator, Fig. 16, may be used : similar but offset conductive spiders, having the ends of their legs 89, 90 bent over the edge of an insulating disc 88 fixed on the shaft 5, are fed with current by brushes 91, 92, via a manual switch and engage twin-brush contactors 81, 82 feeding the magnets 102, 101, respectively.