CA1061385A - Miniature plug-in fuse and method of making same - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

The specification describes a plug-in fuse assembly consisting solely of a fuse-gripping body made of insulating material and an all metal plug-in fuse element secured within the body, the plug-in fuse element having a pair of juxtaposed laterally spaced terminal portions to be received by pressure clip terminals on a mounting panel, and the terminal portions having current-carrying extensions the inner end portions of which are interconnected by a fuse-forming link portion. The gripping body has a portion which closely receives the current-carrying extensions of the plug-in fuse element and wall surfaces spaced from the fuse forming link portion of the plug-in fuse element form a shield for spewing blown fuse metal of the fuse forming link portion of the plug-in fuse element when the current-rating thereof is exceeded.

Description

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i BACKGROUND OF TEIE INVENTION

¦ The present invention relates to miniature current overload fuses which, whether they are rated to carry only a few ~mperes or as much as 30 amperes, occupy a space which is only a fraction of the space occupied by the conventional glass envelope cylindrical fuses.

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j An overload fuse capable of carryin~ currents of the above range of magnitudes commonly comprise a sealed cylindrical I .
glass envelope wit'h cylindrical terminals projecting from the I, ends thereof and a fuse link extending between the fuse terrninals within the sealed cylindrical envelope. Fuses of this type having current ratings of 10-30 amperes commonly 'have :Lengths of the , I, !order of magnitude of over one inch and, together with the l ,, mounting terminals with ~hich they are associated, an overall jwidth of approximately one quarter inch and higher. Some of .
the disadvantages of this type of fuse are the large space I, requirements for mounting t'he same and difficulty in removing .
~hem from mountiny clips. ' A marked improvement in overload current fuses of the rating referred to have been made in that the fuse has a l length well under 3/4 inch and a width of under 1~4 inch. Such a fuse is disclosed in U.S. Patent No. 3,436,711. Also, t'he .
terminals of the improved fuses plug into socket openings extending ;transversely to the length of the fuse body, 50 the socket ~.
jconnector can be a much less expensive and less bulky support jmeans than that needed for convent.ional high current rated fuses.

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While the miniature fuses heretoEore developed 1 have been a substantial improvement over the conventional cylindrical glass envelope fuses, they still left much to be desired from the standpoint of their cost of manu-facture and protection to the user. For example, in some of the miniature fuses heretofore developed, the fuse link was exposed so that the insertion thereof into a shorted circuit would blow the same and spew fuse mater-ial onto the person inserting the fuse. Also, it was possible for a person inserting or removing such a fuse to make contact with the exposed fuse link which created a shock hazard if he engaged the fuse negligently.
While in one form of miniature fuse herètofore develop- ~ ~-ed, the ~use link was enclosed in a transparent housing having a handle extending from the outer walls thereof, the fuse was relatively expensive to manufacture, it had less reliability than the fuse of the present inven-tionr and the fuse link was only visible on the side of the housin~ because the handle obstructed a frontal view thereof, so the ~use link could not be seen when the fuse ~as mounted between another pair of similar closely s~paced fuses on a mounting panel. Also, the handle could not be easily grasped due to the small clearance between adjacent fuses.

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It is, accordingly, one of the objects of the invention to provide a miniature fuse with or withou-t an enclosed fuse link and which is capable of carrying currents where desired well in excess of 10 amperes, such as up to 30 amperes, and can be manufactured at a ,m,uch smaller cost than the miniature fuses heretofore designed.
A related object of the lnvention is to pro-vi,de a miniature fuse having a housing providing an i~sulated gripping surface and a shield protecting the user from being contacted by the fuse material as an in$erted fuse is blown, and which further can be easily in~serted into or remoyed from an appropriate female 1, connector on a mounting panel where the connectors are yery closely spaced, and also preferably wherein the ,f,use link thereof is readily visible when the fuse is mounted on such a mounting panel.
In the miniature fuses here-tofore developed, the design of the fuses were such that the external con- , 20 f~iguration and dimensions of the fuses were ldentical for 'l ~idely yarying current ratings thereof. It was, therefore, ', ~eadily possible for a fuse having a very high current ,, rating, such as 20-30 amperes, to be inadvertently placed ~nto a connector associated with a circuit where the ' current rating may be from 5-15 amperes, creating a very hazardous operating condition. While these fuses were , generally marked or color coded to indicate their fuse ' rat~ngs~ the user could readily make a mistake by mis- '' , reading the usually small current rating markings or com-30 plic~ted color codes.

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~06~385 Accordingly, another object of the invention is to provide a fuse design where, although the different fuse assemblies have substantially identical configurations and size, the difference between relatively high and relatively low current rated fuses can be readily detected.
In most of the miniature fuse designs heretofore pro-posed, the terminals have cylindrical pin-like configurations molded into bases of insulating material, and the fuse links were soldered between the inner ends of these terminals. The presence of solder connections sometimes created problems of reliability resulting from corrosion or hot spots due to. poor solder connections or deterioration with age. Thus, another .:.
object of.the present invention is to provide a miniature fuse having features satisfying one or more of the objectives pre-viously discussed and, in addition, are devoid of the corrosion .
or hot spot problems referred to.
SUMMARY OF THE FUSE LINK INVENTION
Canadian Patent Application Serial No. 217,~29, filed January 13, 1975, describes and claims one aspect of the~fuse link invention and a method of making a plug-in fuse element.
The present invention relates to another aspect of the plug-in fuse element disclosed in that application. Basically, the present inven-tion relates to a fuse assemhly consisting solely of a fuse-gripping body made of insulating material and an all metal plug-in fuse elemént secured within the body.
The present invention is, therefore, defined as a plug-in fuse assembly consisting solely of a fuse-gripping body made of insulating material and an all metal plug-in ~use element secured within the body, the plug-in fuse element having a pair of .~k s .
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`` ~06~385 ju~taposed laterally spaced terminal portions to be received by pressure clip terminals on a mounting panel, the terminal portions havin~ current-carrying extensions the inner end portions of which are interconnected by a fuse-forming link portion, and the gripping body having a portion which closely receives the current-carrying extensions of ~he plug-in fuse element and wall surfaces spaced from said fuse-forming link portion of the plug-in fuse element and forming a shield for spewing blown fuse metal of the fuse-forming link portion of the plug-in fuse element when the current rating thereof is exceeded.
For completeness, the description which follows describes both aspects of the plug-in fuse as well as the method of making same.

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GENERAL DESCRIPTION OF THE PLUG-IN FUSE

The smaller cross sectional area of the fuse link-forming portion of the plug-in fuse element is mos-t advanta-geously achieved by reducing both the width and thickness thereof relative to that of the other current carrying portions of the plug-in fuse elementO Reduction in thickness of the fuse link-forming portion can be achieved in a number of ways, such as by milling and/or com~ressing the metal, the combination of the two methods being preferred. (The method by which the present plug-in fuse assembly is made constitutes a joint invention of only the applicants Williamson and Aryamane.) The just described plug-in fuse element can be used as a fuse by merely plugging it into pressure clip terminals or the like without any additional elements added thereto, or can be mounted within a housing in a manner to be described, which is the preferred f~rm of the invention. The plug-in fuse element just described with or without a housing can be readily mass produced by simply stamping the same from the end of a strip of such fuse metal, after selected areas thereo~ have been milled and/or !

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` 1061385 compressed to reduce the cross sectional area of the portions ', of the strip which are to constitute the fuse link portion of the plug-in fuse elements to be severed therefrom. (Such a one pieca plug-in fuse element as described is to be con- I ;
trasted with a combination fuse and terminal member attached to an insulating base which has been manufactured and sold in ~urope for many years, which member has an elongated and compressed C-shaped configuration. The end portions of the member are on the exterior of the base and are received bet~
ween a pair of spaced support clips. Also, U. S. Patent No.
3r500~463 to Gregory and U. S. Patent No. 2,468,351 to Vail I I -show one piece fuse and term~nal elements of a different and more costly construction than that of the present invention ' ~ust described. Also, in the fuse of the Vail patent, the one piece fus~ and terminal element forms a subcomponent of a con~entional screw socket type fuse and thus is not a plug- j in unit insertable directly into a mounting panel, In accordance with the most preferred form of the plug-in fuse element of the invention, the terminal-forming blade portions of the plug-in fuse element are provided with transversely projecting ~ings when the fuse has a relatively high current rating, giVing the terminals the appearance of a, relatiyely massive and, therefore, high current carrying capacity terminals, and preventing their insertion into low current fuse-receiving sockets.
In accordance with another feature of the invention, the above one piece plug-in fuse element or one similar to the same, forms an assembly with a housing made of insulating mater- ~-ial which provides insulated gripping surfaces for the assembly 30 and forms a shield which prevents the spewing of fuse metal into , the surrounding atmosphere when the fuse is blown. In the Il . .
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~6~385 most preferred form of the invention, although the housing can be comprised of two confronting housing halves snapped around the plug-in fuse element, the housing is most advan-tageously a one piece molded element having an opening in the inwardly facing side thereof into which the plug-in fuse element is inserted into the housing. Also, the hous-ing is most advantageously a narrow elongated shape defined by relatively closelyspaced side walls bridged by narrow end walls and a narrow outer wall. The plug-in fuse element may be anchored in place in the housing by forming projecting proportions in the housing which extend into apertures in the plug-in fuse element, the projections being most advan-tageously formed by a cold staking or ultrasonic material softening-operation. At least the aforementioned outer wall of the housing ~i.e. the wall which faces outwardly when the ~use assembly is mounted on a mounting panel), and preferably the entixe housing, is most advantageously made of a trans-parent material. The fuse link portion of the plug-in fuse element ls positioned at a point contiguous to this trar.s-20 parent outer wall where it can be readily seen at all times. ~ ;
At least the longitudinal end portions of the outer wall preferably overhang the rest of the housing to provide con-yenient gripping surfaces at the ends of the housing, so that the plug-in fuse assembly can be readily grasped for insertion into and removal from any point in a mounting ;
pAnel~ despite smlll clearances between adjacently mounted plug-in fuse assemblies.
In accordance with still another aspect of the invention the housing is preferably provided with a pair of terminal access openings in the outer wall thereof, cb/ - 8 - ~

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which openings preferably taper inwardly to a point in alignment with the innermost ends of the terminal extensions, so resistancemeasuring test probes are guided into contact with the terminal-forming blade portions of the plug-in fuse element to test for continuity on the assumption that the fuse link might have a crack in it which is not readily visible through the above described transparent housing outer wall. The defining-walls of the access openings preferably haye skirt portions extending there-from which act as shield walls to prevent blown fuse material from reaching the terminal access openings.
With a plug-in fuse assembly consisting of a single stamping forming both the terminal-forming blade portions and the fuse-forming link portions of a plug-in fuse element, and a housing into which such single piece stamping may be readily inserted and locked into place, the design of the fuse assembly lends itself to a low cost mass production assembly thereof wherein various stamping and milling operations forming attached blanks ~or making many plug-in fuse elements are first performed on longitudinally spaced areas of a fuse metal strip.
Then, a plug-in fuse assembly is completed by applying a housing over the end of the strip, securing each hous- , in~ in place and severing a completed plug-in fuse assembly from the strip, the housing applying and sever-ance operations on the strip being repeated in sequence 27 to mass produce the plug-in fuse assemblies.

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GENERAL DESCRIPTION OF THE METHOD

The terminal forming blade portions and current carrying extensions preferably extend longitudinally of the strip. ~ile the fuse-forming link poxtion could be formed in a direction extending longitudinally of the kerminal forming blade portions and the stxip, it is most preferably formed in the direction extending between ' .

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the current carrying longitudinal extensions of the terminal forming blade portions, that is, in a direction extending transversely or laterally there-between. The blanking operation described also forms a relatively, strong, rigid web paralleling the portion of the body of fuse metal which forms the fuse-forming link portion thereof. A rigid body of insulating material is then anchored between the porti.ons of the body of fuse metal between which the fragile fuse forming link portion extends, to act as an insula-ting . : ¦
rigid supporting interconnection between the portions of the blank connected by the fragile fuse forming link portion thereof. In the most preferred form of the invention, this body of insulating material is extended over and around the fuse-forminy link portion of the blank, so it fully encloses the same except for portions through which the terminal forming blade portions project. The transverse web adds rigidity to the blank and securely maintains the relative positions of the terminal 1. :
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ljr:kb l()G~385 forming blade portions and the current carryiny extensions thereof before the body of insulating material is anchored thereto. Thus, distortion, breaka~e or other damage of the blank is effectiYely prevented during these operations.
The transverse web is most advantayeously left exposed after application of the body of insulating material, so that the txansverse web may then be most conveniently severed rom the blank to eliminate a short circuit between the ~use forming link portion of the blank.
The blanking of the exposed transverse web interconnecting the terminal blade portions may be such as to proyide the pair of exposed laterally spaced coplanar t~rminal portio~s with selected widths coxresponding to th~. ampere xating o~ the plug-in fuse asse~bly. Also, the outer end portlons of the e~posed pair of terminal forming blade portions may be coined to form tapers thereon to facilitate insertion thereof into the clip terminals in ~ou~ting paneI.
The blank of fuse metal is preferably initially proyided with a central portion of reduced thickness so that, when the blank is blanked, the interconnecting fuse~
~orming link portion of the blank is of less thickness tha~ the spaced coplanar terminal forming blade portions and the current carr~ing extensions. By controlling the thickness of the fuse-forming link portion and the width thereof desired selected ampere ratings for the fuse ¦ .
asae~bly may be ootained. The central portion of reduced th~ckness of t~e blank of fuse metal may be reduced by 29 ~lling or by milling and subsequent squeezing.

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While the method aspects of the invention are most advantageiously carried out using a strip of fuse metal where the previously desired coplanar plug-in fuse elements can most .
¦easily be blanked and severed from the end of the advancing strip .
¦of fuse metal, the broader aspects of the invention do not so require.

Further objects of this inven-tion reside in the particular method steps and in the cooperative relationship between the method steps in making the aforementioned plug-in fuse assembly.

DESCRIPTION OP TEIE DRAWINGS

. Fig. 1 is a perspective view of a preferred form of the plug-in fuse assembly of the invention;

Fig. 2 is an exploded view of the housing and plug-in ~fuse element making up the plug-in fuse assembly of Fig. l;

Fig. 3 is a top plan view of the plug-in fuse assembly of Fig. l; -;

Fig. 4 is a vertical longitudinal sectional view through the fuse assembly shown in Fig. 3, taken along section line 4-4 ~therein; j;

Pig. 5 is an enlarged hottom view of the plug-in fuse i _ I
assembly of Fig. l;

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Fig. 6 is an enlarged transverse vertical sectional view through the fuse assembly shown in E`ig. 4, taken along section line 6~6 thereof;
Fig. 7 is an enlarged vertical transverse sectional view through the center portion of the fuse assembly sho~n in Fig. 4, taken along section line 7-7 thereof;
Flg. 8 is a greatly enlarged fragmentary sectional yiew through the fuse link portion of the plug-in fuse assembly shown in Fig. 2, taken along section line 8-8 thereof, and showing the manner in which the fuse-forming link portion thereof is reduced in thickness by a combina-7 tion milling and pressing operation;
Fig. 9 illustrates the insertion of the housing of the fuse assembly of ~igs. 1-8 onto the end of a pre- ~ , milled and pre-stamped strip of fuse metal from which numbers of plug-in fuse elements like that shown in these figures are formed;
Fig. 10 shows the separation of a completed plug-in fuse assembly from the strip shown in Fig. 9, after a strip staking and severing operation has been carried out; ,' , Fig. 11 illustrates a fragmentary longitudinal sectional view through a portion of a plug-in fuse assembly ~ i like that shown in Figs. 1-10 but which has been modified by adding a magnifying lens to the outer wall of the housing thereof;
Fig. 12 illustrates a fragmentary side elevational vlew of a plug-in fuse ass~mbly modified from that shown in ~~ '!
Figs. 1-11 in that the wings on the terminal-forming blade

3~ portions of the plug-in fuse element have been removed to indicate a lower current rated fuse. I -Fig. 13 illustrates tha milling of the strip Cb/ - 14 _ .. ... .. . . . .

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Fig. 14 illustrates the milled strip of Fig. 13 after it is squeezed or compressed and before it is blanked or stamped as illustrated in Figs. 9 and 10;
~ ig. 15 illustrates the milled and squeezed strip of Fig. 1~ after it has been partially blanked or sta~ped and before it is completely blanked or stamped as illustrated in Figs. 9 and 10 in the event that it should be desirable to utili~e two progressive stages of blanking or stamping instead of a single stage.

DESCRIPTION O~ THE PREFERRED EMBODIMENT
OF THE INVENTION
Referring now more particularly to Figs. 1~
there is shown a plug-in fuse assembly 2 made of only two component parts, namely a plug-in fuse element 4 which most advantageously is a single stamping from a strip of fuse metal, and a housing 6 which most advantageously is a single piece synthetic plastic molded part defining a space therein into which portions of the plug~in fuse element 4 extend and are secured ln any suitable way, but most preferably by a cold staking operation to be described. ~ ;
The plug-in fuse element 4 has terminal-forming -blade portians 8-8 extending in spaced parallel relationship from the inner or bottom margin of the housi~g 6 in what Will be referred to as a downward or inwardly extending direction, The ends of the ~erminal-forming blade portions 8~8 of the plug-in fuse element are most advantageously tapered at 9-9 to form pointed end portions which readily $1ip lnto place between the confronting walls of conuentional sprtng clip terminals ~not shown) supported in mounting panel apertures. The terminal-forming blade portions 8-8 cb~ - lS - , ;
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of the plug-in fuse element 4 have inwardly extending rough current rating indicating wings or projections 10-10, to pro~ide a more massive appearance to the exposed terminal-forming portions 8-8 of the plug-in fuse element 4, identify-ing the act that the ~use assembly is one having a rela-tively high current rating, such as in the range of from 20 to 30 amps. ~The exact current rating is indicated by indicia 13 on the outer walls of the housing as shown in Figs. 1-3. Where a plug-in fuse element has a relatively low current rating such as 5 to 15 amperes, the wings 10-10 are eliminated so the user knows immediately that the plug-in fuse element which does not have any wings is for a lower current rated application. Such a plug-in fuse element is shown in Fig. 12).
The plug-in fuse element 4 is s-tamped from a strip 4' of fuse metal (Figs, 9 and 10 and 13 to 15). Prior to the plug-in fuse element being severed from the strip 4' the wings 10-10 are interconnected to form a transverse rigidifying web 10' for the strip 4', and so a narrow ,~ 20 piece of material is stamped from the transverse web 1~' to form the terminal-forming blade portions 8-8 and a gap 12 between the same. The tapered portions 9-9 of the terminal-forming blade portions ~-8 may be formed by coin-ing dies (not shown) during the operation which severs the plug;in fuse element from the strip or preferably thereaEter.
The terminal-forming blade portions 8-8 have current carrying extensions 14-14 projecting into the afore-mentioned space formed by the housing 6, which current-carrying extensions project well up into the upper or outer 30 extremities of the housing 6, to be contiguous to the front or outer wall of the h~using to be described. The outer end portions of the current-carrying extensions 14-14 are inter-cb~ - 16 -.

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connected by a fuse-forming link portion 20 which is prefer-ably both narrower in width and much smaller in thickness than the other current-carrying portions of the plug-in fuse element 4. ~he current-carrying capacity of the fuse-forming link portion 20 may be varied by varying the fuse metal composition or by varying the width and~or the thick-ness of the fuse-forming link portion. In the particular configuration of the plug-in fuse element 4 shown in the drawings the current carrying extensions 14-14 join the - 10 fuse-forming link portion 20 of the plug-in fuse element

4 by tapered portions 22-22. ~11 of the various parts of the plug-in fuse element are substantially in coplanar relation so no metal bending operations need be performed 1' in the process of making the same. I
It was found that a reduction of the thickness of the metal of the fuse-forming link portion 20 is pre~er-ably achieved by a milling operation which mills away the metal on one side thereof to form a generally curved depression 24 best shown in Fig. 8. The outer portions of this depression 24 are identified by reference numerals 24a-29a and may represent the milled surfaces. The flattened intermediate portion 24b of the depression 24 may be obtained by squee~iDg or pressing the metal to further reduce this thickness thereo~. On the other hand, following an initial milling step, both the curved outer portions 24a-24a and the flattened intermediate portion 24b of the depression 24 may be obtained by squee~ing or pressing. For example, ~t was found that in one plug-in fuse element, the thick- ;
~ess o~ the fuse metal was reduced from an initial thick-ness of 0.027 inches to about .005 inches by a milling oper- - ~, . atio~, and a further reduction of .002 inches was achieved by a pressing operation, ending up with a minimum thickness cb~ 17 -' .

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While -the plug-in fuse element 4 may be used as a fuse element without its incorporation in the housing 6, for safety reasons it is preferred to incorporate the plug-in fuse element 4 in the housing 6. ~o this end, and for reasons to be explained, the outer end portions of the terminal extensions 14-14 are provided with outwardly or upwardly projecting tabs 18-18 adapted to make contact with test probes to test for the continuity of the fuse-forming link portion 20 of the plug-in fuse element 4.
Also, to anchor the plug-in fuse element 4 within the housing 6, anchoring apertures 26-26 and 28-28 are res-pectiyely formed in the terminal extensions 14-1~ to receive anchoring projections to be described formed in the housing wall,s.
While the housing 6 could be made in two separate parts snappable together, the housing is most advantageously a single piece molded part as previously indicated. Also, it preferably has a narrow elongated configuration formed by relatively closely spaced side walls generally indicated by reference numeral 30-32, the side walls having end portions 30a-3~a and 30a~32a which are spaced together much more closely than the central or intermediate portions 30b-32b thereof, The side walls 30-32 are inter~onnected at their end margins by narrow end walls 34-34, and at their outer or top margins by an outer wall 38 whlch overhangs the rest o~ the housing to form downwardly facing shoulders 40-40 at the longitudinal ends of the outer wall 38 and downwardly Paclng shoulders 40'-40' along the longitudinal side margins cb~ - 18 -(' ~ : ' . ~; .......... .

1~6~3~35 of the housing 6. The shoulders 40'-40' are coplanar continuations of the shoulders 40-40 at the ends of the housing 6.
Terminal access openings 42-42 are provided in the outer wall 38 adjacen-t the opposi.te end portions thereof in alignment with the location of the test pro~e-receiving tabs 18-18 of the plug-in fuse element 4. The walls of the terminal access openings 42-42 taper down to an inner dimension which approximates the width of the test probe- ¦
receiving tabs 18-18 so that test probes can be guided into contact with the tabs 18-18. The terminal access openings 42-42 communicate with the aforementioned plug-in fuse element receiving space in the housing 4. The portions 44-44 of this space immediately beneath the access openings 42-~2 are relatively small because of the close spacing of the side wall por-tions 30a-32a of the housing at these points, the Width of the space portions 44-44 as viewed in Fig. 6 taperinq from the bottom open end of the housing upwardly toward the terminal access openings 42-42, reaching a narrow dimension about equal to the thickness of the plug-in fuse element 4. ht the inner margins of the terminal access open-ings 42-42 the upper wall 38 is p~.ovided with downwardly sxtending skirts 46-46 which act as shield walls preven-ting spewing fuse metal from gaining entrance to the terminal access openings 42-42. These shield forming skirts 46-46 .
also act as stop or abutment shoulders for the current-carr~ing extensions 14-14 of the terminal forming blade portions 8-8 of the plug-in fuse element.
The fuse-forming link portion 20 of the fuse element 4 is positioned in a relatively wide portion 44' .-7) of the housing interior, to provide for free . circulation of air around the center portion of the fuse-, '.
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~06~3~35 forming link portion, which is the par-t thereof which first melts under excessive current flow, so heat does not accumu-late which would adversely affect the current at which the fuse will blo~.
The narrow and wide portions 44-44 and 44' of the space within the housing 6 open onto the bottom of the housing for the full extent thereof through an entry open-ing 48 The opening 48 permits the housing to be pushed over the end portion or end blank of the pre-stamped and milled strip ~' from which a completed fuse element is punched immediately following the securing of the housing 6 to the end portion or end blank of the strip as previously indicated.
The housing 6 is preferably a molded part made of a transparent synthetic p}astic material so that the fuse-forming Eilament portion 20 of the plug-in fuse element 4 is readily visible through the intermediate portion of the outer wall 38, to which the fuse-Eorming link portion 20 is in spaced but relatively contiguous relation. The housing is preferably molded of a high temperature transparent nylon made by Belding Chemical Industries of New York City, New York ~Product Code No. LX-3330).
While the housing interior 6 could be made with resilient projections which snap into the anchoring apertures 26-26 and 28-28 in the plu~in fuse element 4, it is preferred to secure the housing in place by forming projections 52 and 54, by a cold staking operation, ultrasonic melting or other operation, which enter the anchoring apertures 26-26 and 28-28 of the plug-in fuse element 4, The depressions 56 and 58 left by a staking operation are shown in the side wall 30 in Figs. 1 and 6.
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6~3l35 link portion 20 of the plug-in fuse element, the outer wall of the housing of the fuse assembly can be modified as shown in Fig. 11 where the housing outer wall 38' of a modified fuse assembly 2' is thickened and curved to form a magnifying lens. Also, as shown in Fig. 12, the fuse assembly 2' is a low current rated fuse assembly as evidenced by the absence of wings on the terminal-forming blade portion ~'-8' on the plug-in fuse element 4'.
The exemplary embodiments of the invention just described have thus provided an exceedingly reliable, compact and inexpensive to manufacture plug-in Euse assembly which can be readily inserted into and removed from suitable closely spaced spring clip terminal connectors in a mounting ~, i panel by grasping the shoulders 40-40 at the longitudinal ends of the housing 6. The transparent material out of which the housing 6 is made forms a convenient window in the outer wall through which the fuse-forming link portion of the plug-in fuse element can be viewed when the plug-in fuse assembly iS mounted on the mounting panel. The terminal access open-20 ings enable test equipment to test the continuity of the fuse if the user does not desire to rely solely on a visual observation of the fuse-forming link portion of the fuse.
The presence or absence of wings on the terminal-forming blade portion of the plug-in fuse element immediately informs the user whether he has selected a relatively high or low cuxren-t rated fuse, although the indicia 13 should be examined to determine the actual current rating.
The preferred method of making the plug-in fuse assembly is illustrated in Figs.13, 14, 15, 9 and lO. It 30 includes providing a continuous strip 4' of a fuse metal which ~ , ' is sequentiall~ advanced the distance of a blank 4" between ,~ distances 4"' as indicated in dotted lines in these figures.

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:: ~ . . ~ , . . .- . , ~C~61385 In Fig. 13 the strip 4' is provided at spaced intervals with a milled portion 60, the milled portion 60 being pro-vided in the appropriate place in each blank 4". There-after, at each milled portion 60 each blank is squeezed or compressed as indicated at 62 in Fig. 14 to provide by squeezing or pressing a depression in the blank having curved surfaces 24a-24a and a flattened intermediate portion 24b as referred to above in connection with Fig. 8.
After the appropriate depression is formed in each blank 4", the advancing strip 4' is then blanked to ~:
form the terminal portions 8, the current carrying extensions 14 thereof and the further extensions 18 thereof. This may be accomplished in one blanking operation or in a plural- , -ity of blanking operations. As illustrated herein, the blanking operation is accomplished in two steps. The first blanking step in the sequentially advancing strip 4' is illustrated in Fig. 15 wherein each blank 4" is sequentially blanked as indicated at 64 to provide the ex-tensions 18 and a portion af the fuse link 20 having the tapered portions 22. Thereafter, each blank is seguentially blanked as illustrated in Fig. 9 at 66 to provide the current carrying extensions 14 and the other part of the fuse link 20 extend-ing between the current carrying extensions 14 having the tapered portions 22. During this same blanking operation the interlocking holes 26 and 28 are also blanked. In this blanking operation the transverse web 10' still remains between the terminal forming blade portions 8 of each blank.
As shown in Fig. 9, the housing 6 is inserted over ,, the end blank 4" to receive the current carrying extensions 14 and the fuse link 20 within the housing and with the terminal forming blade portions 8 still interconnected by the transverse web 10' extending from the housing. The housing cb~ - 22 -, . . . .

, ' .

~1~6~385 i5 then cold staked and/or ultrasonically secured in the interlock openings 26 and 28 of the end blank 4" as indicate~
at 56, 58 in Figs. 6 and 10. Preferablyr the placing of the housing 6 over the end blank ~" and securing the housing to the end blank occurs before severing the end blank from the strip at the blank edge 4 " '. In Fig 10 the end blank ,~
4" and its housing 6 ~re severed from the strip 4' at the blank edge 4 " ' of the end of the blank 4 " ' to form the substantially completed plug-in fuse assembly, but with ¦
the transverse web 10' still intact. Thereafter, the transverse web 10' is blanked at 12 to provide the spaced apart terminal forming blade portions 8 as indicated at ~ig. 10. Here, the blanking of the transverse web may provide wings 10 as illustrated in Fig. 10 or the wings may be eliminated as illustrated in Fig. 12. Thereafter, the ends of the terminal forming blade portions e may be coined as illustrated at 9 to form tapered ends for the blade portions. In this way, the complete plug-in fuse as~embly as illustxated in Figs. 10 and 1 may be provided.
While fox purposes of illustration herein one preferred specific method of making the plug-in fuse assembly has been disclosed herein, other methods may become appar-ent to those skilled in -the art and therefore this invention is to be limited only by the scope of the appended claims.

This is a division of Canadian Patent Application Serial No. .217,829 filed January 13, 1978.
'' ' cb~ - 23 -, .. . . .

Claims (6)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A plug-in fuse assembly consisting solely of a fuse-gripping body made of insulating material and an all metal plug-in fuse element secured within said body, said plug-in fuse element having a pair of juxtaposed laterally spaced terminal portions to be received by pressure clip terminals on a mounting panel, the terminal portions having current-carrying extensions the inner end portions of which are interconnected by a fuse-forming link portion, and said gripping body having a portion which closely receives the current-carrying extensions of said plug-in fuse element and wall surfaces spaced from said fuse-forming link portion of the plug-in fuse element and form-ing a shield for spewing blown fuse metal of said fuse-forming link portion of the plug-in fuse element when the current rating thereof is exceeded.

2. The plug-in fuse assembly of claim 1 wherein said all metal plug-in fuse element is a stamping from a blank of fuse metal, so that all portions thereof are formed of fuse metal.

3. The plug-in fuse assembly of claim 1 or 2 wherein said terminal portions of the plug-in fuse element are in alignment.

4. The plug-in fuse assembly of claim 1 wherein said gripping body is a housing unit which completely encloses but is spaced from said fuse-forming portion of said plug-in fuse element.

5. The plug-in fuse assembly of claim 4 wherein said housing is open along one entire side so as to initially be insertable over said plug-in fuse element in the process of assembly thereof, and means for interlocking the housing with the plug-in fuse element after the housing has been placed thereover.

6. The plug-in fuse assembly of claim 1, 2 or 4 wherein all portions of said plug-in fuse element are in sub-stantially the same plane.