| 摘要 |
<p>1392532 Fusible cut-outs ROBERT BOSCH GmbH 28 April 1972 [29 April 1971] 19755/72 Heading H2G An excess temperature fuse for electrical windings comprises a fuse element made of metal or an alloy of metals with a melting point between 70‹ C. and 250‹ C. and a flux in contact with the fuse element which expands or gives off gas when the metal melts, the fuse element being in good thermal contact with the windings to be protected. The metal or metal alloy and flux are chosen according to their melting temperatures and the desired cut off temperature. The melting temperature of the metal alloy can be adjusted, e.g. by mixing eutectic alloy with the fuse element and using a flux with a melting temperature greater or equal to that of the eutectic. When a metal eutectic alloy made from non- eutectic metals is used for the fuse element, a flux may also be used which has a melting temperature higher than that of the eutectic but within the softening range or over the upper limit of the softening range of the alloy used. Non-eutectic "surface alloys" may also be used for fuse elements. Examples of fluxes suitable for the fuse are urea, alietic acid and natural colophony with melting temperatures of 133‹ C., 173‹ C. and 110 to 130‹ C. respectively. Details of six compositions of various alloys used for fuse elements, their softening ranges, suitable fluxes and the flux melting points are given in the Specification. In one embodiment of the invention the element comprises a metal strip made from an alloy, of e.g. Bi, Pb and Sn in equal proportions by weight, which softens in the range 95‹ C. to 140‹ C. Wires are welded to the element and urea, melting temperature 133‹ C., is deposited on part of the surface of the element either directly or by placing a piece of urea enriched material on a surface portion of the element. The whole element is then sealed between two transparent synthetic sheets welded together around their perimeter. In a second embodiment of the invention the fuse element comprises a tube made from an alloy of 60% Sn and 40% Bi, proportions by weight, that softens in the range 138‹ C. to 170‹ C., that contains passages filled with alietic acid. Connecting wires are clamped to the ends of the passages. The tube is enclosed by a plastic insulating coating. In a third embodiment of the invention the fuse element is made from solid wire formed from an alloy of 50À5% Bi, 27À8% Pb, 12À4% Sn, and 9À3% Cd, preportions by weight that softens in the temperature ranges 158‹ C. to 163‹ C., the element being welded to connecting wires. Alietic acid flux surrounds the element and the whole is inserted in a heat resistant insulating tube, e.g. of polycarbonate. Alternatively the fuse elements of the above embodiments may be provided with a solid casing, e.g. by moulding or coating thermo or duroplastic synthetic materials around them.</p> |
