GB1528177A - Pickup cartridges - Google Patents

Abstract

1528177 Moving coil pickups NIPPON COLUMBIA KK 12 Dec 1975 [13 Dec 1974] 51091/75 Heading H4J A pickup cartridge comprises an armature 15 (Fig. 4) of rectangular or other form but preferably of cruciform shape (Fig. 3, not shown) wound with a coil 3a and having a cantilever 1 extending forwardly from it. A suspension wire 18 presses the armature 15 rearwardly against a damper 4. A magnet arrangement to which the wire 18 is held provides a magnetic field from the centre to the outside and which the armature crosses during use to induce an E.M.F. in the coil 3a. Opposite limbs of the armature have independant but equal coils 3a, 3b (and 3c, 3d), thereby providing a substantially linear response (Fig. 6, not shown). A ring- shaped magnetic member or magnet 16 cooperates with a holder 17 which is of magnetic material or is a magnet. A projection 17a is within the ring-shaped member. The magnet 16 is of N polarity at one end and of S polarity at its other end. Projection 17a is of S polarity. The wire 18 is attached within a tube 10 in a central bore 11 of the holder 17. In a first alternative embodiment the ring shaped member 16 and holder 17 are integrally combined and are of magnetized ferrite (Figs. 7, 8, not shown). In a modification, member 16 and projection 17a are secured to a rear holder (Fig. 9, not shown). In a further modification (Fig. 18, not shown) the ring-shaped magnet 16 is divided into upper and lower half portions which are attached to the holder 17 with polarities opposite to each other, the projection 17a being of neutral polarity. Fig. 20 (not shown) shows a more complex permanent magnetization of the ring shaped magnet 16'. In another arrangement (Fig. 24, not shown) the projection (17a) has a free end surface of N polarity and the ring shaped member (30) has adjacent permanent magnets which provide induced magnetization of the free end of the ring shaped member 16 of opposite polarity to the free end of the projection 17a. In a further arrangement (Fig. 10, not shown) a member of magnetic material is formed by bending four legs (23) upwardly from a cruciform blank to provide a square base section. An apertured projection (17a) is disposed centrally between the four legs (23), the free ends of the legs (23) being of opposite polarity to the free end of the projection (17a). Alternatively (Fig. 11) four magnets 24a, 24b, 24c, 24d are arranged around a fifth magnet. They are secured at one end to a plate 25 of magnetic material. The free end of the fifth magnet is of opposite polarity to the free ends of the other magnets 24a, 24b, 24c, 24d. In a modification (Fig. 19, not shown) the end surfaces of the magnets 24a and 24c and of magnets 24b and 24d are of opposite polarity, the end surface of member 24e being neutral. In another arrangement (Figs. 12, 13, not shown) the ring-shaped magnet (16) is used without the projection (17a) but the magnet is of N polarity at its outer periphery and of S polarity at its inner periphery (Figs. 12, 13, not shown). In place of the ring-shaped magnet (16) rod-like magnets or metallized elements (26a, 26b, 26c, 26d) Fig. 15 (not shown) are glued in grooves in cross formation in an end of a ring-shaped holder (27) made of synthetic resin or non-magnetic material. All the rod-like magnets or magnetized elements (26a, 26b 26c, 26d) have the same polarity at the centre. In a modification (Fig. 21, not shown) the opposing magnets (26a, 26c) and (26b, 26d) are of opposite polarity at their facing surfaces. A cylindrical magnet (16) Fig. 16 (not shown) having an end surface facing the damper may have respective half portions thereof (16a, 16b) of opposite polarity to each other, there being a projection (17a) having neutral polarity. In yet another arrangement (Fig. 23) a magnet 16 is disposed between two magnetic plates 28a, 28b. A cantilevered holder 17 passes through an aperture in magnetic plate 28b and the vibrating system is inserted through the bore of the holder 17.