US 2874248 A
Description (OCR text may contain errors)
United Stat$ Patent 0.
MULTIPLE FUSE Julius J. Tondat, Penfield, and Oscar H. Goldman, Pittsford, N. Y., assignors to General Dynamics Corporation, Rochester, N. Y., a corporation of Delaware Application September 11, 1956, Serial No. 609,270v
'5 Claims. (Cl. 200-125) This invention relates to multiple fuses, and is particularly directed to structures for economically replacing fusible elements in an electrical circuit.
The usual cartridge fuse comprises a cylinder of insulating material with metal caps at each end and with the fusible element suspended in the cylinder between the caps. The conventional cartridge fuse block has strong clips for receiving the capped ends of the cartridge. By necessity, the clips are usually strong to make suflicient pressure contact with the caps to insure against open circuiting because of corrosion or vibration. The standard automobile fuse and fuse block are good examples of this type of fusing element. Unfortunately, the clips are usually so tight that the cartridge is often broken when being removed or inserted.
Multiple fuses for power purposes heretofore have elaborate structures to move the new fuse element into circuit and to then tighten the newly made contacts. Such structures usually require the power source to be disabled when dangerous voltages are involved, and are much too costly and heavy for communication equipment.
The objective of this invention is to provide an improved multiple fuse structure.
A more specific object of this invention is an improved multiple fuse which is easy to replace, requires no interruption of the power source, is simple and inexpensive in construction, and yet obviates the possibility of loose contacts.
The objects of this invention are attained by printing the fusible elements on an insulating board, cutting a slot through the board across the fusible elements, and then selectively and successively connecting the fuse elements in circuit by a speed nut threaded on the end of a stud bolt through the slot. By loosening the bolt the speed nut can be shifted along the slot to selectively make contact with the fusible elements.
Other objects and features of this invention will become apparent as the following description proceeds, and the features of novelty which characterize this invention will be pointed out with particularity in the claims annexed to and forming a part of this description. The following description is made in connection with the accompanying drawing, in which:
Fig. 1 is a plan view of a multiple fuse block embodying this invention,
Fig. 2 is a sectional view taken on line 2-2 of Fig. 1, and
Fig. 3 is an enlarged detail view of a blank of one speed nut embodied in this invention.
In Fig. 1 is shown the sheet 1 of thin insulating board which may comprise any of the commercially obtainable insulating boards, of which polyethylene, polystyrene, and Teflon are examples. Bonded to the face of the board, shown in Fig. 1, is a pattern of a thin metal lamina or sheet of the type familiar to the printed circuit art. The printed circuit may be made by spraying a paint containing powdered metal through a suitable mask to produce the desired outline on the board. When dried and baked,
' minal members 2 and 3 which make electrical contact with posts 4 and 5 staked into the board, making good electrical contact with members 2 and 3, respectively, as
shown. Connected with member 3 are a plurality of printed lines comprising elongated, narrow fusible elements 6a, 6b, 6c, etc., terminating at one end in element 3 and at the other end, respectively, in contact plates 7a, 7b, 7c, etc. The fusible elements are preferably spaced and parallel and the contact plates 7 are arranged in a line parallel to one edge of element 2. To increase the electrical length of the fusible elements without increasing-the overall distance between their ends, the elements may be printed in a zig-zag form. Increased length, further, serves to reduce end cooling effects.
According to an important and characteristic feature of this invention, the slot 8 is cut, as by die stamping, through the board and between the opposed edges of element 2 and terminal plates 7. As better shown in Fig. 2, the stud bolt 9, with the shoulder 10 and knurled head 11, extends through the slot 8. t
The threaded end of the bolt engages a bridging contact element which selectively connects the plates 7 to the common terminal plate 2. In the example shown, the bridging element comprises the speed nut 13 with a center hole 12 for receiving the threaded end of bolt 9. The speed nut is preferably of the commercially available Tinnerman type. Such a nut is stamped from thin metal, the stamping being of the outline best shown in Fig. 3, and
- being, desirably, of spring steel. The stamping comprises two ears 14 and 15, formed centrally on opposite sides of the elongated body of the blank. Two parallel slots 16 and 17 are lanced tangentially with the hole 12 as shown, thus producing two inwardly extending opposed tongues 18 and 19. The diameter of the hole 12 and the distance between the opposed edges of tongues 18 and 19 is slightly less than the root diameter of the threaded stud bolt to be used. When the bolt is forced into the nut, tongues 18 and 19 flex outwardly as shown in Fig. 2. In operation when the threads draw the tongues, the outer ends of the sheet 13 are forcibly biased against the engaging surface of the sheet 2 and plate 7. It is found that an unusually good contact can thus be made with the printed circuit metal.
As shown in Fig. 2, cars 14 and 15 are bent to a position substantially normal to the plane of the speed nut, and extend into slot 8 to keep the nut in the proper rotational position across the slot.
Preferably the outer end of the stud bolt is cast in a knurled head 11 of insulating material of sufiicient strength to manipulate the stud bolt, and of sufficient electrical insulating properties to protect the operator from any dangerous operating voltages. When one of the fusible elements 6 is fractured by an overload current, it is merely necessary to loosen the nut and stud bolt and shift to a new fusible element. Markings or indicia on the panel under the knurled head 11 may be employed to indicate the proper lateral position to which the bolt must be shifted to engage a new contact plate 7. The markings may be supplemented with detents to aid in finding the proper position.
Where the printed circuit plating is of standardized thickness, it is comparatively easy to control the width of fuse strips 6 to carry a maximum predetermined current before fracturing. Conveniently, several fuses of difierent current capacities may be printed on a single board as suggested in Fig. 1. The groups of multiple fuses are arranged side-by-side opposite the common terminal plate 2 and the several slots are cut end-to-end. The knobs '11, then, are orderly arranged on the reverse .or front of the panel and may be marked to indicate the circuits they serve. It is to be noted no metal parts of the fuses are exposed to the front of the panel. Such a panel is small, compact and very serviceable in communication equipment where fuses of many sizes are required. In automobile wiring systems is another highly useful application of the multiple fuses of this invention.
While we have shown and described a specific embodiment of our invention, other modifications will readily occur to those skilled in the art. For example, many substitutes can be devised for performing the switching function of the detachably secured nut 13 and bolt 9. We do not, therefore, desire our invention to be limited to the specific arrangement shown and described, and we intend in the appended claims to cover all modifications Within the spirit and scope of our invention.
What is claimed is:
1. A multiple fuse comprising a board of electrical insulating material, a two-dimensional conductive printed circuit pattern bonded to said board, said pattern consisting of a plurality of parallel spaced printed fuse lines of predetermined current carrying capacity, said capacity being less than the current capacity of connected lines, a slot through said board and normal to said fuse lines, a bridging contactor across said slot and a bolt slidable along said slot and threadably engaging said bridging contactor to releasably tighten said contactor on selected fuse lines.
2. A multiple fuse comprising a board of electrical insulatiug material, an elongated slot through the board, printed circuit contacting plates aligned along oneside of said slot, printed fuse elements of predetermined crosssection and current-carrying capacity communicating, respectively, with said plates, the opposite ends of said elements communicating with a common terminal plate, a second common terminal plate along the opposite side of said slot, and means extending through and slidable along said slot to selectively electrically connect said contacting plates to said common plate.
3. A multiple fuse comprising an insulated board, an elongated slot through said board, a threaded bolt, with a nut, extending through, slidable along, and detachably engaging the sides of said slot, a first terminal plate along one side of said slot and underlying said nut, a plurality of fusible elements bonded to said board with connected terminals spaced along the other side of said slot and underlying said nut, .the other ends of each element being connected to a second terminal plate.
4. A multiple fuse comprising an insulating board, an elongated straight slot in said board, a shouldered stud bolt extending through said slot, a knurled knob of insulating material on one end of said bolt, a nut threadably engaging the other end of said bolt, a terminal plate bonded to the side of the board underlying said nut, a plurality of fusible elements bonded to said side of the board, one end of each element being connected to a common terminal and the other end of each element being disposed along said slot and selectively engageable by said nut.
5. 'In printed circuit devices, a plurality of side-by-side printed metallic'lines bonded to an insulating board, said lines terminating at an end, respectively, in printed contact plates, and terminating at their other ends in a series of printed common terminal strip, said lines being of predetermined width and current carrying capacity, said capacity beingless than the capacity of said contact plates or of said common terminal strip, and a slot through said board parallel to said series of printed contact plates.
References Cited in the file of this patent UNITED .STATES PATENTS 427,548 Brush May 13, 1890 1,902,613 Blumberg Mar. 21, 1933 2,066,511 Arlt Jan. 5, 1937 2,263,752 Babler Nov. 25, 1941 2,678,982 Sundt May 18, 1954 FOREIGN PATENTS 337,963 France May 4, 1904 695,436 France Sept. 30, 1930 901,549 France July 30, 1945