BLADE TERMINAL FUSES WITH INTEGRITY INDICATOR

Abstract: An integrity indicator formed as an illuminable bead (27) is combined with the pair of flat terminal blades (31) of a miniature plug-in fuse and is positioned in a central window (23a) provided in the top wall (23) of the insulator housing (21) thereof, the housing defining a chamber (21a) having an open bottom and a central section (24a) with relatively narrow lateral sections (24b) in which upper portions of the blades are secured. A fuse-wire (35) extends across the central section conductively interconnecting the blades. The illuminable bead has a pair of wire leads (29) extending oppositely into the lateral sections (24b) of the chamber, each wire lead conductively contacting the upper portion of one of the blades for connecting the bead in parallel circuit with the fuse-wire, clamping components (26) being formed on the interior of the top wall and on the upper portion of each terminal blade (31) to secure each wire lead in operative position.

Description: BLADE TERMINAL FUSES WITH INTEGRITY INDICATOR FIELD OF THE INVENTION This invention relates generally to miniature, blade terminal fuses currently used in motor vehicle electrical systems and described in U.S. Patent No. 3,909,767 granted to H. L. Williamson et al and more particularly to a light indicating capability for identify¬ ing a blown, open circuit condition of such, fuses. BACKGROUND ART Recent models of motor vehicles have electrical systems equipped with- fuse panels which utilize miniature parallel blade terminal fuses, replacing the familiar cartridge type panels and fuses. These blade terminal fuses, a representative construction of which is described in said Williamson et al patent, provide two methods for identifying a blown, open circuit condition without removal of the fuse from the panel, namely, by a test instrument which may be applied to two test points accessible through openings in the top exposed surface of the fuse housing, or by visual inspection of the fuse-wire through the trans¬ parent housing. The requirement of a test instrument, per se, is a considerable disadvantage. Other disadvan¬ tages include the difficulty in making visual and test in- strument inspection due to the often limited accessibility of the panel and fuses and the failure of visual inspection even after removal of the fuse from the panel when the failure of the fuse is due to a substantially invisible hair-line open circuit resulting from a slight circuit over- load. There is, therefore, a present need for provide ing such miniature, hlade terminal fuses with a visible indicator of a blown, open circuit condition of the fuse which will make the blown fuse readily distinguishable from the other operating fuses in a fuse block. SUMMARY OF THE " INVENTION Among the objects of the invention is to satisfy the hereinbefore described need by providing a miniature, plug-in blade terminal fuse incorporating an illuminable bead positioned in the top wall of the fuse and comprising solid state elements including an LED for providing the illumination. The several embodiments of the invention shall comprise few and simple parts and be inexpensive to manufacture in quantity production using methods of assembly compatible with existing production procedures and which shall be dependable and efficient in operation. With the foregoing in mind we provide in accordance with the invention a blade terminal fuse having an integrity indicator comprising a insulator housing formed with a top wall, an interior chamber having relatively narrow lateral sections on opposite sides of a central section and an open bottom, a pair of flat terminal blades in coplanar spaced relation having upper portions located in said chamber lateral sections and lower portions projecting downwardly from said open bottom, a fuse-wire extending through said chamber central section conductively connected in series with said terminal blades, characterized in that said top wall is formed with a central window above said chamber central section and, on the interior side thereof on opposite sides of said window, with a component of a clamp¬ ing means, an illuminable bead comprising said integrity indicator located in said chamber central section in reg¬ ister with said top wall window and having wire leads ex¬ tending oppositely into said chamber lateral sections con- ductively contacting said terminal blade upper portions whereby said illuminable bead is in series with said blades and in parallel with said fuse-wire, said terminal blade upper portions each being formed with a companion component of said clamping means, the clamping means se¬ curing each of said wire leads in said conductive contact with each terminal blade upper portion. Upper portions of the terminal blades are ad¬ vantageously retained, as by snap-in engagement, in the lateral sections of the interior chamber with the lower portions of the blades projecting downwardly from the open housing bottom providing the exposed fuse terminals for removably engaging the socket of a fuse block. The clamping means for securing each wire lead in conductive contact with each terminal blade upper portion includes a component integrally formed on the interior of the top wall of the housing, one component being located on each side of the central window for coacting with the com¬ panion component formed on the upper end portion of each of the terminal blades. The snap-in engagement between an opening in the upper portion o-f each terminal blade and in¬ dentations provided in the housing which secures the blades in assembly with the housing also serves to retain the clamping engagement of the wire leads between the top wall of the housing and the ends of the upper portions of the blades. In an embodiment of the invention, in which the fuse-wire is integrally formed with the terminal blades as a unitary coplanar element, the clamping means component on each side of the window is formed as a rib extending from the top wall of the housing into the lateral section of the chamber and into a V-shaped cutout formed in the end of the upper portion of the blade as the companion component of the clamping means. A section of each wire lead of the illuminable bead is thus formed with a loop and clamped in the V-shaped cutout by the downwardly ex¬ tending rib. In another embodiment, the fuse-wire is also inte¬ grally formed with the terminal blades which are substantially in coplanar relation except for the clamping means companion components which are incorporated in integral tabs extending from the ends of the upper portion of the blades and dis¬ posed perpendicular to the plane of the blades. The clamping means component of the top wall is formed as a groove or cradle along which each wire lead of the illuminable bead extends, side portions of the groove being recessed to accommodate the integral tab which is formed with a central U-shaped cutout through which a portion of the wire lead ex¬ tends for engagement and clamping retention by the tab. Other modifications contemplate a five-piece assembly in which the fuse-wire and terminal blade unitary element is formed in three separate parts, namely, a pair of separate terminal blades and a fuse-wire. The two clamp¬ ing means embodiments hereinbefore described for the three- piece constructions may also be used to secure the opposite ends of a separate fuse-wire in conductive engagement with each of the terminal blades. Thus, the wire leads of the illuminable bead is positioned- in the window of the top wall' of the housing as in the other embodiments while the fuse-wire is formed with a looped midportion extending down¬ wardly from the top wall and through the central section of the housing chamber. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of a miniature blade terminal fuse constructed with an integrity indicator embody¬ ing the invention. Fig. 2 is a top plan view as seen along line 2-2 in Fig. 1. Fig. 3 is a bottom view as seen along line 3-3 in Fig. 1. Fig. 4 is a side elevation view as seen along either of the lines 4-4 in Fig. 1. Fig. 5 is a sectional view taken on line 5-5 in Fig. 2 showing interior structure of the fuse. Figs. 6 and 7 are transverse sectional views taken on lines 6-6 and 7-7, respectively, in Fig. 5. Fig. 8 is a perspective view of the integrity indi¬ cator shown prior to assembly with the leads thereof preformed in accordance with the invention. Figs. 9 and 10 illustrate two steps in the assembly of the molded plastic housing with the other components com¬ prising the fuse shown in Fig. 1. Fig. 11 is a schematic of the electronic components of the integrity indicator shown in parallel circuit with the fuse-wire in accordance with the assembly shown in Fig. 5. Fig. 12 is a sectional view similar to Fig. 5 but showing a modified assembly construction in which three sepa¬ rate parts comprise the fuse-wire and terminal blade compo¬ nent. Fig. 13 is .an exploded perspective view of the inte¬ grity indicator, fuse-wire and pair of blades removed from assembly in the housing shown in Fig. 12. Fig. 14 is a sectional view similar to Figs. 5 and 12 but showing a modified construction of the three-piece fuse shown in Fig. 5. Fig. 15 is an exploded perspective view of the integrity indicator and combined fuse-wire and terminal blade element removed from the assembly in the housing shown in Fig. 14. Figs. 16 and 16A are enlarged sectional views taken on lines 16-16 and 16A-16A, respectively, in Fig. 14 showing structural details. Fig.. 17 is a sectional view similar to Fig. 12 show¬ ing a five-piece modification of the structure and assembly shown in Fig. 14. Fig. 13 is an exploded perspective view of the inte¬ grity indicator, fuse-wire and pair of blades removed from as¬ sembly in the housing shown in Fig. 17, and Fig. 19 is a fragmentary perspective view of the up- per end of one of the terminal blades showing a modified form of clamping component for the integrity indicator lead wire. DESCRIPTIQN OF THE PREFERRED EMBODIMENTS Referring in detail to Figs. 1 to 7, inclusive, of the drawings, 2O denotes a three-piece minature, plug-in, blade terminal fuse-with an integrity indicator embodying the invention comprising an insulator housing 21^ a combined blade terminal and fuse-wire element 30_ an< an integrity indicator in the form of an illuminable bead 2T_. As seen in Figs. 5 and 7, element 30_ is formed of sheet metal as a pair of spaced parallel blades 33-_ integrally interconnected at a midportion thereof by a link fashioned as a fuse-wire 35.. Each blade 31 has a centralized opening 3^ providing the female component of a snap-in connection between the element 30_ and housing 2L and an inner or upper end formed with a generally V-shaped cutout 33_ providing for the securing of illuminable bead 27 ^ in position in housing l_ and making electrical contact there¬ with. Each blade 3^ has a lower or outer end portion 34_ ex¬ tending beyond the bottom 22 as a blade terminal or male con¬ tact for engaging a cooperating female contact of a fuse sock¬ et (not shown) . - . • • Housing 2_1, molded of suitable plastic material having electrical insulating properties, such as, nylon, polystyrene or the like, comprises a relatively long and narrow top wall 23_ and a pair of opposite sidewalls 24_ connected along opposite lateral margins by end walls 25_, all forming an interior chamber which is open along bottom 22 ^ . Top wall 2_3 is formed with a central opening 23a providing a window in which illuminable bead 27_ is located and end walls 25 each have a vertical rib 25a for engagement by means provided in the fuse socket (not shown) for resilient reten- tion therein of fuse 2CL Sidewalls 24 are each contoured to provide a pair of lateral panels 24b symmetrically arranged on opposite sides of a central panel 24a, the latter being out¬ wardly stepped to provide a relatively wide central chamber portion 21a therebetween which communicates with top wall opening 23a. The opposing lateral panels 24b are relatively more closely spaced to accommodate blades 3_1 therebetween and have aligned indentations 24c which engage openings 32 ^ as male components of the snap-in connection between housing 21 ^ and element 3). Each of a pair of interior ribs 2 _ extends downwardly from top wall 23_ between lateral panels 24b of the opposite sidewalls 24_ into the V-shaped cutout 33_ of each blade 3JL. Illuminable bead 27., as seen in Fig. 11, may com¬ prise a pair of LEDs 28 ^ arranged in parallel in opposite po¬ larity and in series with a protecting resistor 27a all en¬ cased in suitable transluscent material, such as, epoxy, glass or the like, in accordance with conventional solid state technology and has a pair of oppositely extending wire leads 2£. Each lead 2 is sized in length and shaped to extend between the medial leg 33a of V-shaped cutout 33^ and top wall 23_, along the curved edge of leg 33a and into the bottom of cutout 3_3_ for locking engagement therein by rib 2j3. One of the advantages of the construction embodying the invention is the close parallel of the method of assem¬ bling the three components of fuse 20_ to the production method disclosed in said 'Williamson et al patent and currently in use. It will be apparent that in practice the assembly is performed in a downwardly vertical direction, namely, with the strip 3_6_ and housing 2!L rotated clockwise 90° from the posi¬ tion shown in Figs. 9 and 10. Strip 36 ^ , being made of a metal having properties suitable for fuse-wire use, as seen in Fig. 9, is precut with a series of centrally located rectangular openings 3_7_ separa¬ ted by transverse portions 38 ^ connecting longitudinally ex¬ tending border portions which when suitably die cut, as here¬ inafter described, form the spaced parallel blades 31_. Like- wise, a looped wire structure 35a extends through each opening 37 properly aligned with respect to a small opening in each border portion of strip 36_ providing fuse-wire 35_ and openings 32, respectively, in assembled fuse 20_. The leading end of each border portion of strip 3_6 > as seen in Fig. 10, is formed with a V-shaped cutout 3_3_ having a longer medial leg 33a and a shorter lateral leg 33b. Assembly may be performed as a continuous process whereby housing 2 _ is orientated in an inverted position. Illuminable bead 27_, having oppositely extending wire leads 29 preshaped as shown in Fig. 8, is also inverted and fed by gravity into the upfacing open bottom of the interior chamber to seat in central opening 23a in top wall 23 with wire leads 29 extending between lateral panels 24b and across interior ribs 26 ^ . The leading end of strip 36_ is then inserted into the interior chamber so that wire leads 29_ are clamped by V-shaped cutouts 3_3_ against interior ribs 26 In fully in¬ serted position, reached when medial legs " 33a of blades 31 engage a portion of wire leads 2 adjacent illuminable bead 27 which portions in turn abut the interior surface of top wall 23^ indentations 24c simultaneously snap into engagement in openings 32_ for retention of the three components in operative assembly as fuse 2j3. Die cutting means (not shown) then severs the leading, assembled, section from strip 3_ in the region of the adjacent transverse portion 3J3, cutting out the latter and forming both the beveled ends of blade portions 34_ of the assembled fuse 2_0_ and the V-shaped cutouts 33 as a new leading end of strip 36. A modification shown in Figs. 12 and 13 contemplates a five-piece fuse 40_ comprising a housing 41 ^ , a pair of spaced parallel blades 5 ~ L_, the upper ends of which clampingly engage both wire leads 49_ of illuminable bead 47_ and end portions 55a of fuse-wire 5_5. Housing 41_ may be substantially identical to housing 2 _ of fuse 2_0_ and is shown to include a top wall 43 having a central opening 43a, opposite sidewalls 44 formed with lateral panels having indentations 44c for engaging open- ings 5_2 ^ in blades 5_1, an interior chamber open at bottom 42 and a pair of interior ribs 46 ^ extending downwardly from top wall 43_. Each blade 51 ^ has the upper end formed with a V- shaped cutout 5_3 also provided with longer medial leg 53a and a shorter lateral leg 53b similar to V-shaped cutout 33_ of blades TL . A modified structure for securing the illuminable bead in position in electrical conductive engagement in series circuit with the terminal blades is shown in Figs. 14, 15, 16 and 16A for a three-piece fuse and in Figs. 17 and 18 for a five-piece construction. Fuse Q_, shown in Figs. 14 and 15, comprises a housing 61_, a combined blade terminal and fuse-wire element 70 and an illuminable bead 67_ having oppositely extending wire leads £. Element 70_ is similar to element 30 of fuse 20 in the provision of fuse-wire 7_5 integrally connecting parallel blades 7_1 having openings 72 ^ for snap-in engagement by indentations 64c and an outer end portion 74_ extending beyond the bottom (2 of housing 61_ but differs from the complete coplanar configuration of element 30 in the formation of an integral tab 73_ extending from the inner end of each blade 7_1 and disposed in a plane perpendicular to that of blades 7_1 and fuse-wire 7_5, tabs 73_ being formed with U-shaped cutouts 73a. Housing 61^, likewise, is a modified form of housing 21, having the interior surface of top wall 63 ^ formed with thickened portions 63b (see Figure 16A) extending longitu- dinally from opposite sides of central opening 63a, each portion 63b having a medial groove 63c which may have inclined walls, as seen in Fig. 16A. A relatively deep depression or recess (6> terminates each groove 63c and has a central longi¬ tudinal projection 66a seen in Figs. 14 and 16 as a clamping component for wire lead 6_9_ coacting with a respective integral tab 1 _ and cutout 73a. The lateral panels 64b of housing sidewalls 64_ are slightly narrower than lateral panels 24b of housing 21_ providing a central chamber portion 61a which is wider than central chamber portion 21a for inclusion of tabs 3_ therein enabling insertion of element 7_0 through the open bottom of the chamber during assembly. Grooves 63c and the clamping afforded by tabs 7_3_ and recesses 6β_ enable use of wire leads ^9_ of bead 67_ disposed in a straight line configuration. Fuse 80_, shown in Figs. 17 and 18, is a five-piece structure similar to fuse 4(3 in that parallel terminal blades 91 are separate from fuse-wire 9_5_. Otherwise fuse 8) embodies the modifications of fuse ( L Thus, housing 8JL is similar to housing 61^ having a top wall 8_3_ formed with interior grooves terminating in recesses 86 ^ and projections 86a, sidewalls 84_ formed to provide an enlarged central chamber portion, an open bottom 8_2 through which outer end portions 34_ of blades 91 project and indentations 84c for snap-in engagement with openings £2 of blades 91_. The upper ends of blades £1 are also formed with tabs 93 and U-shaped cutouts 93a which co- act with recesses 8_6 and projections 86a to simultaneously clampingly secure both the wire leads 8_9_ of bead 87_ and the end portions 95a of fuse-wire 95. Fig. 19 shows a modified upper end of a blade 5_6 " having a tab 5_7_ cutout and offset from the plane of the blade instead of the perpendicular configuration between tabs 73, 9_3_ and blades 71_, 9_1, respectively, or the coplanar relation of V-shaped cutouts 33_ and 53 ^ . Wire leads 29_, 49_, 69_ or 8£ and fuse wire end portions 55a and 95a may thus be retained between end portions 56a and tab 57_ to clampingly engage suit¬ ably provided clamping components in top walls 23 ^ , 43_, 62_ or 83.. It is to be understood that instead of molding the indentations 24c, 44c, 64c s.nd 84c in housings 21_, 4.., 61_ and 81 for snap-in engagement with blade openings 32_, f)2_, JA an d 92, respectively, assembly between the respective housings and blades may be accomplished utilizing cold staking or ultrasonic melting means and methods in the well known manner. Illuminable beads 27_, 47_, 67_ and 8_7_ may be of any desired shape other than that shown in the drawings and the windows provided in top walls 23_, 43_, 63_ and 83_ appropriately shaped and may be closed rather than open or formed with a magnifier to intensify the light emitted by the LED. The il¬ luminable beads may also include a single LED requiring orien¬ tation means between the fuse housing and the socket recepta¬ cle for proper polarity in the D. C. circuits of motor vehi- cles. Also, in accordance with LED technology, the resistor 27a may be an active P-N junction properly polarized with re¬ spect to the LED whereby each LED has a P-N junction in series therewith. The LED and P-N junction combinations are in turn in parallel to achieve the universal polarity of the circuit shown in Fig. 11. In use, any opening of the fuse-wire 3^5, 55_, 7_5 or 95_, as by blowing or otherwise, results in the lighting of the respective illuminable bead while the load remains in the circuit. The blade terminal fuses with the integrity indica¬ tor herein disclosed are seen to achieve the several objects of the invention and to be well adapted to meet conditions of practical use. As various possible embodiments might be made of this invention, and as various changes might be made in the disclosed fuses, it is to be understood that all matters herein set forth or shown in the accompanying drawings are to be interpreted as illustrative and not in a limiting sense.

Claims: CLAIMS 1. A blade terminal fuse having an integrity indicator comprising an insulator housing formed with a top wall, an interior chamber having relatively narrow lateral sections on opposite sides of a central section and an open bottom, a pair of flat terminal blades in coplanar spaced re¬ lation having upper portions located in said chamber lateral sections and lower portions projecting downwardly from said open bottom, a fuse-wire extending through said chamber cen¬ tral section conductively connected in series with said ter¬ minal blades, characterized in that said top wall (23) is formed with a central window above said chamber central section (24a) and, on the interior side thereof on opposite sides of said window, with a component (26) of a clamping means, an illuminable bead (27) comprising said integrity indicator located in said chamber central section in register with said top wall window and having wire leads (29) ex¬ tending oppositely into said chamber lateral sections (24b) conductively contacting said terminal blade upper portions whereby said illuminable bead is in series with said blades (31) and in parallel with said fuse-wire (35) , said terminal blade upper portions each being formed with a companion component (33) of said clamping means, the clamping means securing each of said wire leads in said conductive contact with each terminal blade upper portion. 2. The blade terminal fuse defined in claim 1, characterized in that said pair of flat terminal blades (.31) and fuse-wire (35) are formed as an integral structure of a fuse metal. 3. The blade terminal fuse defined in claim 1, characterized in that said pair of flat terminal blades (51) are separate components and said fuse-wire (55) is a discrete element having opposite ends extending into said chamber lateral sections, said clamping means (46,53) also securing said fuse-wire opposite ends in conductive contact with each terminal blade upper portion as said series connection with the terminal blades. 4. The blade terminal fuse defined in claim 1, characterized in that said housing clamping means components are interior ribs (26,46,66a) having free ends extending toward said open bottom, said clamping means companion component being a cutout (33,53,73a,93a) formed in each terminal blade upper portion, said wire leads being retained in said cutouts in said conductive contact by said rib free ends. 5. The blade terminal fuse defined in claim 4, characterized in that said cutouts have medial (33a) and lateral legs (33b) bordering said cutouts, said medial legs being longer than the lateral legs and serve to clamp por¬ tions of said wire leads adjacent the illuminable bead against said top wall. 6. The blade terminal fuse defined in claim 4, characterized in that said cutouts each includes a tab (57) attached to the bottom of the cutout and extending in offset parallel relation to the plane of said blades. 7. The blade terminal fuse defined in claim 1, characterized in that said clamping means companion components each comprise a tab (73,93) extending perpendicularly to the plane of said blades and formed with cutouts (73a,93a), said top wall clamping means component each including a depression recessed (66) from the interior surface of the top wall in registered alignment to receive one of said tabs therein, each of said illuminable bead lead wire (69,89) extending along the interior surface of said top wall, across the de¬ pression and being engaged in the cutout (73a,93a) of one of said tabs as said conductive contact. 8. The blade terminal fuse defined in claim 7, characterized in that said pair of terminal blades (71) , perpendicular tabs (73) and fuse-wire (75) are formed as an integral structure of a fuse metal. 9. The blade terminal fuse defined in claim 7, characterized in that said fuse-wire (.95) is a discrete element having opposite ends extending into said chamber lateral sections, said clamping means also securing said fuse-wire opposite ends in conductive contact with each of said tabs (93) as said series connection with the terminal blades (91).

Inventors: GREENBERG M BARRY, GREENBERG, M., BARRY
Applicants: VISUAL FUSE INC, VISUAL FUSE, INCORPORATED
Application year: 1985
Main classification: H01R3
IPC codes: H01H85