Abstract: A composite fusible element for electric fuses comprising a pair of spaced drawn wires substantially circular in cross-section, at least one pair of spaced plates of sheet metal in contact with said pair of wires, and electrical bonds conductively connecting each of said pair of wires and one of said pair of plates. The pair of wires is preferably of silver, and the pair of plates is preferably of copper. A fuse according to the invention includes a fusible element as described above.

Abstract: An electric fuse for elevated circuit voltages, such as, e.g. 5 to 15 KV. It includes a tubular casing or electric insulating material, terminal elements and a pulverulent arc-quenching filler. It further includes a plurality of equidistantly spaced fusible elements electrically connected in parallel, wound substantially helically in planes defining a prism and forming part of a current path conductively interconnecting the pair of terminal elements.The point of novelty consists in that the fusible elements are formed by a unitary metal stamping. That stamping also includes aligned metal bridges conductively interconnecting all the fusible elements. The preferred number of planes or sides of the aforementioned prism is four and the preferred number of bridges is n-1 for each quarter turn of the fusible elements, wherein n is the number of fusible elements connected in parallel. The bridges are arranged in spaced relation from the edges of the prism.

Abstract: Contact pressure is established by means of two screw-nuts mounted on a stud projecting from, and affixed to, a contact member. There is a first cooperating pair of screw-threads between said stud and a drive screw-nut and a second cooperating pair of screw-threads between said drive screw-nut and a driven screw-nut. All screw-threads are oriented in such a way that the axial movements of said driven screw-nut relative to said stud are the sum of the axial movements of said drive screw-nut relative to said stud plus the relative axial movements of said drive screw-nut and said driven screw-nut. Means are provided for inhibiting any relative rotary motions of said driven screw-nut and said stud.

Abstract: In fuses exceeding a certain voltage rating it is necessary to establish series multibreaks to interrupt small overload currents. An initial break is formed in the helically wound fusible elements near the center thereof where the temperature is highest. If the arc voltage along this initial break does not exceed the circuit voltage, even after a number of cycles of arcing, secondary or tertiary breaks must be formed in series to the initial break. This is achieved according to the present invention by providing one or more quarter-turns of reduced pitch where the spacing between contiguous groups of windings is reduced and a low temporary current flashover is allowed to occur which results in the formation of secondary and tertiary breaks.

Abstract: In fuses embodying this invention each of the terminal elements has a port for the passage of fluid through the casing of the fuse during normal operation thereof, i.e. while the fuse is carrying current. A tubular fusible element conductively interconnects said port in each of said terminal elements. The fuse further includes a toroidal body of quartz sand filling the space between said casing and said tubular fusible element. The fusible element has perforations covered by annular structures of electric insulating material precluding said quartz sand from penetrating into said tubular fusible element during the normal operation of said fuse. The fuse is further provided with a pair of check valves which open during normal operation of said fuse and then allow the flow of fluid through said tubular fusible element and close on occurrence of a build-up of a predetermined amount of pressure inside of said tubular fusible element and then inhibit said flow of fluid.

Abstract: Electric fuses having supports for their fusible element or elements which supports are formed of bundles of glass fibers in form of cords, rovings, or the like glass fiber structures made up of fibers which extend but in longitudinal direction, i.e. do not include fibers which extend in transverse direction. The fibers are under considerable stress in longitudinal direction, so as to form a supporting structure of considerable dimensional stability. The terminal elements of the fuse are preferably in the form of terminal plugs and provided with means to control the stress to which the glass fibers are subjected. The latter may be impregnated with chemical compounds that evolve protective and arc-quenching gases under the heat of electric arcs.

Abstract: A high-voltage fuse having a casing closed at each end thereof by a pair of composite plug terminals. Each of these composite plug terminals is made up of a pair of semi-cylindrical complementary parts. The fuse includes a pair of helically wound fusible element means whose longitudinal axes are parallel to each other and spaced from each other. One of said pair of fusible element means and one pair of semi-cylindrical terminal parts are arranged to one side of a plane of symmetry extending in a direction longitudinally of the casing of the fuse. The other of said pair of fusible element means and another pair of semi-cylindrical terminal parts are arranged to the other side of the aforementioned plane of symmetry.

Abstract: A fuse for elevated circuit voltages having a fusible element that is substantially in the shape of a helix and is, in essence, supported only by the pulverulent arc-quenching filler of the fuse, i.e. which is supported without resort to a mandrel of electric insulating material around which the fusible element is wound. The casing of the fuse is sealed to preclude the escape of hot arc products by circular disks of asbestos fibers and by ferrules mounted on the ends of the casing. Plug terminals performing that sealing function are dispensed with. The steps involved in assembling the fuse are described in detail.

Abstract: A high-voltage fuse having a pair of axially spaced paper labels at the relatively cool ends thereof remote from the plateau-like high temperature zone formed by the fuse when carrying current.

Abstract: A fuse having a composite casing. It includes a radially inner tubular portion that is circular in cross-section, of uniform wall thickness, and houses the fusible element means and a body of pulverulent arc-quenching filler. The casing structure further includes a plurality of angularly displaced rods of an electric insulating material having substantially the same length as the tubular portion of uniform wall thickness of the casing arranged parallel to the axis of said tubular portion, in abutting relation to the outer surface thereof, and adhesively affixed to said outer surface. A pair of spaced external terminal plates closes the tubular portion of the casing and is provided with fasteners having shanks projecting into the end surfaces of said plurality of rods.

Abstract: An electric fuse having a casing which has a substantially prismatic outer surface rounded at the longitudinal edges thereof. The casing is a multiply glass cloth laminate including thermosetting resin and is formed by pultrusion.

Abstract: A method for assembling fuses having casings closed by plug terminals conductively interconnected by helically wound fusible elements. The fusible elements are wound around squirrel-cage-like structures involving extremely thin and extremely stiff metal rods. These rods are withdrawn from the fusible elements and drawn out of the casings of the fuses at such time when the pulverulent arc-quenching filler filled into the casings provides sufficient support for the fusible elements so that the support thereof previously provided by the aforementioned metal rods can safely be dispensed with. The small diameter of the rods minimizes the voids initially formed by their removal which, in turn, minimizes the tendency of the fusible elements to be somewhat displaced incident to removal of their temporary metallic supporting rods.