Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~06~3s5 ' :;;
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.
~' ' I . ' ~'"' ' '
.
. . .
.
'' " ' :'
' ' ' ' '' " ' ~ ' '. ' .
.
', '' ' ' ' ~ ":
' ~
: . ' , ' ' ' '
.j ' .
", ,, , , , ---~r !
l~
i ~
10~:13~35 .
il, ' . ,.
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.
- 2 -
".1
,. . .. , .. . ., . . . . . . ~ , . ~, .. . ~ ,
- ~ , . .. ~:
~, , ' -
.
' ' ' ' .~ . ~
.
~)6~38~
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.
'' ' .
,
cb! r 3 ~ j
`.
. . , ~ J
', ' . ( ,
.. , . ~. , ~ . . . . . ..
, ~ ~ , . , :. . ~ :
- , . ,, , .. .:
- . . . . . . . . . ...
1~6~3~35 ~ ;
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.
! ¦
,
cb/ 4
. . , ~ . , , :
: .. . , ~ ,
. . . ,j '
., ,
:-: . , , :
~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
.
: ~'~, ' ' . ~ '. .. .
`` ~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.
- 5a -
kh/~
. . . ;
.
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
!
, . ~
~'. .
:' .' . ' ' ' :
.
` 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 . .
cb/ 7
, . : . : :
'' ': . : .,:
~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 - ~
.`,, , ' ` ' ' , . ' ' '
~ "' . ' . ,
`, '' '
~0~3t3S
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.
,
I
cb~ _ g _
:. : .: ': ' : ' . , :
6138S
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
'
.
- 10 -
kh/
. .
, ,. ~ . - ., : . . . , . . . . . . . . :
. . . . .
. . . . . .
:
.
~.
~6~L38S
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. :
.. , ' I .
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.
cb~ - 12 ~
~,- ,
; . . : , : ; ' . ' .
' "' `' " ' ' ' : ~' .: ., : .
~' ~ :" ' , ' ' ' ' ' . "
"' .' ' ' . ' . : ~ ' :~ , .''; '
1061385
I
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;
, I ', I
~: -13- ' j 1~ ~
~ .
106~3i35 ~:
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 _
.. ... .. . . . .
.
,, . .:
: .. ' : . ~ ~ ,,
~06~385
before it is blanked or stamped as illustrated in Figs. 9
and 10;
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 - , ;
.. I ,'
' ~, , ' . ", ' ' ' : . " , . . ' ' ' ' .
~a~613~5;
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 -
.
`~ . ,: .:
'' ~ .
,
3~
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 -
' .
. .
~ ~, . ' ', ' . , , . , ,.. . , ' ' ' , , . ' '
106~3~35
of the fuse-forming link portion 20 of .003 inches. Of
course, the precise thickness of the fuse metal depends upon
the fuse metal composition, the width of the fuse-forming
lin~ portion 20 and the desired current rating of the fuse.
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-
, '.
~ cb/ - 19 -
'- , . , I "
~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.
To lmprove the visibility of the fuse-forming
,, ' ~
cb/ - 20 - I
. . . . . .. .
., ., ~ .
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.
'` i' :.
' ob/ - 21 - ~
:: ~ . . ~ , . . .- . ,
~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 -
,
.. . . .
