Note: Descriptions are shown in the official language in which they were submitted.
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HIC~i SPEED FUSE
This invention relates :a generel to :uses arc ..°.ore
pa=zicu:a:~y to h~gn speed fuses.
High spaced fuses have bean used ~or a numasr of years nor
the protec:i.:r. or isolation of sQ.miconauctor devices suc: as
dioaes and thy: atora. There is vary l:~~lo safety ractc_ ~n
these saaicordzc=a: devices anc they can ta:: ~:.:l:ly wnen
sua~ected to overc::rrants. Therefore, a fLSe assigned to protect
semiconductor aevicee must open quickly. each rpeed fuses nave
vary ltitle thermal capacity, and in general open in the order c:
. ool to . ooa aeconda when inser:,:~.ting s.~.crt ci-c::_tc.
Proolems exist with high apsed fuses currently on the marxet
because these tunes have been developed over time to meet
apaeific applications, result=ng .n a large number of different
:uses made in di~terent aizea and shapes to satisfy the voltage
and amperage ranges expec=ed to be eneourtered. Several hunared
different parts and subasaamb3les for these fuses may ce
reqt:::ad. T:~us, =t would be dssirable to be able to manu:act::re
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fuses having standardized parts to reauce the total numaer c:
parts that need to be stocked in ord4r to manufacture a complete
'ins of high speed :uses.
Many applicaticna for high speed fuses require the uss o. a
plurality cf =uses usually mounted side by side .n close
prcxiaity o: one another. Many users wish to mount nultip-a
!uses a. close together ss possible. Pro: art hiQn speea =uses
nave metal end bells wriic.'~ are mscranically and thus electrical?y
connectad to tho mounting terminals hale LD tile ln~Lltt~:lg tl:D6
with metal pins which are exposed flush with the tube sur;ace and
are not sealed. Conseguently) when in use in an elec;.rical
csrcuit, the pins are at the same elect::cal potential as she
terminals and end bells. Typically, trrae phase electrical
appliCatioris use a :use iri each phase mounted adjacent to each
other and as close es possible to conserve space wit:::n the
equipment. Ihduasrial standaras govern minimum spacing between
slectrically rot parts and dictate the minimum distance between
live or "siectrically hot" parts tsrough air as a :::::c~_o.~. c.
stand~otf voltage. Since the pins era elect=:tally hot ant
exposed to the tuba surface, th~s minimum distance is measured
between adjaosnt tube su::aces, as opposed to terminal distances.
Yet another C:=:iculty is encountered in manu:acturing high
spaced iusea in that the end bell moat bs joined to the terminal
!or mechanict3 s~:sagth o! the fuse package and, in most assigns,
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for the alect~:cal connection between the currant carryinc
fusible nlamsnts within the ruse and the n~ountirg termi:.al.
Prior art high speed tutee accoWplishod whir by brazing, welG~ng
or soldering the to Final to t.~e end ball or Wacraning the end
bell and terz:nal °rom a solid piece o. metal cr by pressing the
moral pins tn:oug:~ the tubs and end bell and into the nount:ng
terminal. AlI theas techniques are labor intensive.
A further prcblam it anco~unterad with and bells in t~az
tress cisc::lar places of metal era mos= often forged or mac'.~.:ned
from rod stock aad coined, e:i:lad, and sized. :ras again
requires exits time and add~t~onal la~cr a-c is :.:ZUS more
expensive.
Yet another manufacturing p=oblem is encountered in mak_n;
high speed fuses. Thaee fuses, in general, are Zi?led with sand
or other arc quaacz:nq materials. Tha motor=al is added tr.:ough
a hole 1n the end ball after .:~.e end ball is assembled tc tho
tugs tubo. Various methods o! pluggi~sg she hole have peen used,
but all suffer ::om various l:witations. For exempla, cosily
knurled plugs are used which require excessive pressure to insert
the plug into the hole in the end ball. A more economical means
to close tae sand hole is required.
Ths present invention satploya ecamped end balls and
terminals rather than forQsd cr nac.~inec parse. A slot for the
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tenainal is punched through tho and bell. The terminal .s
inaertea irtta the alo: in the end bill and staked in posa:o:..
Ttis insures a st=ang tiCat fa wit :cut raqu~ring weld=rg o_-
soidering. One end of eacz termina'_ has coined =:dges to
'acil i rate automat'_c welding c_' the :use link to trie terminals .
Round balls a~z usec to seal the _'..1 holes for the a=c quencr.~r.~
material. Altarnativaly, Lrie end bells may bn molded o'_ plastic.
Petal pins secLre the end bells within the fuse housing but are
not electrically connected to the zerminnls because of t:~e
insulative end bells.
FiCUre 111 snows a porspoctwe view pa= t_tlly cut away o. a
prior art ~usa~
FigLre =~ aiiows a parcep:we view partially in section anG
axplode6 0: N :use accorGing to ~ho present invertio:::
Figure 2 shawa a tap view o: a zarm,inal o. the iusa shown i:.
Figure 18 ~
Figure 3 shows a front viow along the lines 3-3 0~ the
tarainal shown is !'i~;ure 2 t
Figure 4 shows a complete end bell assamblyt
Fic~urs 5 scows a side cross-sectional vi,w of fns assembled
ruse o: Figure 1 g;
Figure 6 is a zap cross-seet:onal ~r:ew o. the lure cnown ir.
Figure 1$~
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Figure 7 is a par:ial cross~esc~~onal view o. the
installaticn o_" the ball in a sand hole na shown in Fiqurs 5:
Figure a is a c=oss-sect=:..:a_ view along t:~e lines e-o _..
FiSura 7t and
Figure 9 snows tae cross section o: LWO ad]acan~ fuses
illuszrat-ng positioning discnnce.
Figure 171 si~ows a prior art high speed :use 9. M~tal erc
balls 13 with terminals 15 are housed witt~.in the ends of an
insulating tune <C. ;t is seen .:.Lt LhB to winal 15 is walGcd c:
brazes at 17 onto the metal end bell .3. Tbus the and ball =~ is
elect=_cally hot when ~~c fuse is moon=ed i:. an olac:r:cally
energized c:~cua. Tho and b~11 is held in place in insulating
tubs ~0 by mszal pins di which are aiso.a' the same voltage level
as the and boll 13. Thus, as shown in Figure 9, the minimum
distance "°" that prior art rigZ spud fuses can ae placed
ad~ao~nz too aaoh other, as dictazad by induarial scanaards, is
governed by the distance between the electrically l~.ot ping 41 0:
an~scent ruses.
In the fuse according to the present invention shown in
Figures 18) 5 and 6 and raiarred to generally by numeral e, an
sad ball assembly o. an sad ball lZ anc =or~irta= 14 are adapted
co ba rscaivad in aacn end of is~sulatinQ housinr~ or tuba ao. The
and bell =Z enc Lerinal 14 era s=rmped ::am a piece c. material
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and a slot 16 is punched in the end bell 12, The to~inal 14 is
inserted into the slot 16 until shoulders 48 engage the end bell
12. The tee=nal 14 is then staked at 46 or coined c.
mechanically upset in position as shown in Figure 4 to at:ach
terminal 14 to end bell 12. '1':~us the terminal and the end boll
are joined witroL= braz:nQ, we=Cing or solder~:~g, anc witraut
complicated mecranical assembly using add:.tional components.
is more cost et_=cient to proauce the parts by stamping ratrer
than by forging. Stamping provides a scrap rsauct~on over
making the parts from lorQing and also allows the celection of
appropriate materials for the and ball 12 and terminal 14 whic:~
can be of dissimilar materials such as plastic and metal.
11s shown in Figures 2 and 3 ( a series of small rectangular
cross-sectioned ricgea, weld pads or psojec~ions 44 are emcossed
on tho inner end a: terminal 34 during labrication for welding
terminal 14 to one end o! a fuse element 30, preferably by
resistance welding. These weld projec=ions <4 may bs coined or
machined into terminal 14. The height of sack of weld
projections 44 is the same over the entire weld area. The
nums~sr of projections ad is dszs~ained by the width of terminal
1G. Tha size and shape of the pads may vary from terminal to
terminal depending upon the size of hiss element 30 and end bell
:2. ~ saw toot. pattern may also ba used in soma applications.
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Tha pitc.'~ and depth o! the saw tooth will vary wit : 1! :.k
=h-ckness.
1~n advantage to using wale p:o~actions 44 on the te=-urinal
19 1s that it improves the welding of the fusible element 3 o to
the terminal 14. Meld p:ajoct~cas 44 provide consistent welt
quality and walaed surface area rasua:ng in consistent heat
traneter and e3ect=_cal caacuc:.wity t.::ough the welded joi:~t
betwaon the ~us3ble element 30 ana the terminal 1~ o~ :use e.
This results in pore reliable fuss perfozance and reauction in
costs because al. welds can be mace simultaneously. T::!s
p:oceaure also -enuces maintenarca of ttie weld electroces becnuse
bat: elect=ooes are flat bla6as as compared ~o smal= poirttd
eleotrodes. This type o! const~:ct:on ig also very useful for
automating welding arid results in a mo:e consistent weld than
that at=ordad by ps_a: tit spot weld3ag tecrniques. D=:act labar
is roauoed because multiple welas can be mode with each eleetrece
closure. Thus, the time required to weld t:~e st:-p to tae
terminal is recucad, the eansistency of the weld arse is
improved, and tae elect:ical coac~_=t:vity and heat tranaier from
terminal strip to fuss clement is consistent.
The fuse alsment 30 1s preferably of a stanearc_zed planar
design using an aeea:Cion shape which allows for the use of an
element having a substantially longer overnll effective length
than can be ac~ieved with a straigh t t:..ough element as in mos t
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prior art high speed fuses. The increase in effective leng~~
ennnncea the abili:y of the fuse to clear lower level overcu-:ent
situations, aspscia'_ly on DC c=:~~=~s. As shown in Figures 5 and
6, a ruse element 30 may be welded to born sides of terminals 14
to provide a mLlt_rle element fuse.
Referring noW to Figures 9) since the te_~_::..~.al .4 pro3ec~s
through the trc::: face and back :ace a: t.~a end bell 12, the
:LSibla aiament 30 may be elect:=cally connectea cirertly to the
terminal 14. Thus, the end bell 12 does »ot need to be mass or
eiact-iCally corcucr:ng mazar:al, and may' ba made of pleat=c o.
zznar non-elect=:cally conduc:iva materials. Fed bells 12 ci
insulat,ng material, such as plastic, era less expensive than
metal end bells and can be molCed instead of machined allowinc
for the use o. more in=::ca=a shapes when necessary. The
insulating end bells 12 not only serve their normal turc~ion o:
closing off the ands o! tits insulating tube 40 of fuss a and
provide the re~~~ od st:uctL:a1 integrity to the fuse package,
their use results In the mesas p-ns 41) vetch sec::=a the end bell
12 within the tube 40, being insulated from tea elect=:gal
circuit passing through terminal 14 and fusible element 30.
Jan advantage o= using plestic or other non-electrically
concuctwo mata:ial for the end ball iZ is that pins 41,
designed to project through the insulating tune 40 into the and
ball 12, are not anergized~since the end ball is nom alact:~ca:ly
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conauctive. Since holding pine 41 acv not "electr,:cally hot~~
when mounted side by side, fuses can be positioned closer
together thus conserving panel board space in equipment. In the
prior err :use where the moral pin is elac;.r:cally hot, the
adjacent !uses car..zo:~ be taaan:.ed side by side in close proxi~~;y
more titan the distance "F" shown in Fi~~re 9. The separation
between the fuses is governed by the distance between t.~e
terminals which are electrically hot. Howwer) when mounted in
an electrical circ;at, high speea fuses manutacturea according
to the prsaen~ invent~on may be positioned closer to one anotzer
since the miniaum distance "F" is measured between t!:e
electr!cally hot terainals 14 aid not the pins 41 as shown 'r.
~iQura 9.
As she !uses are assuabled, t ~irsz terminal is ~o~nea to a
:tier end bell, a second terminal is joined to a socona end
bell, ana the fusible element 3o is welded between the twc
tezminala. Because at the weld projoctions 4d on the terminal
14, the welding o: zhs fusible elament may be done by projection
welding.
Re=erring now to Figures 5-8, the assembly of the and bell
assemblies welded to the ends of the lusible element ~o is
slipped into the insula::ng tuba 40 and the end bsilc are held in
position within tuna <o by p:nr .t1 which are inserted into
aligned aperruras fn tube 40 and end bells 12. Aligned
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apertures era placed in the and bells 12 and tuba 4o by dr?1=irg
just prior to insertion of pins 41. An arc quenching matariel
«, shown in Figures 5 and 6, typically special sand, is poured
into sand holes ZO in the end ball lZ. Altnr trio high speed fuss
8 is tilled with sand, the holes ZO are closed using a so=_C
spherical ball 18. These round balls 18 may be steal or attar
material and are slightly larger than the hole 2o in the end bell
12. The ball 18 is prevented :raga misaliQnmsrt because it is
guided by its cwn natural radio= irtc the hole 20. The balls .8
are thus self-centering and are held in place by =r:ctional
:once. Alternatel y, pa:z:cularly where end belle 12 are metal,
suc:. as.braas, the sand hots ZO may be coined after insertion of
the bail 18 to hold the ball in. Tho balls 18 are iorcea or
press4d into tba end ball 12 by an insert~on tool 45. The bail
18 is trapped between three smr=1 pins 47 which displace t::e
metal 49 of the metal and bet= .2 over the ball 18 while the
final insertion is boinQ accomplished. The =tat bottom of the
insertion tool 45 p:oviaos autaaatic insertion doptn. over
insertion is prevented by the design of the insertion tool a5.
Using balls 18 has several advantages. The harasnea steel ball
18 provides a low cost, salt-el'_QninQ, easily inserted means of
plugging the l:11 hole ZO in the end bell 12 0= a fuse 8. The
steel ball l8 requires leas lorce to insert and tanns to be selt-
locking. This a significantly easier than prier art processes
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which often us.d p:na, hollow cloesc-end cylinders, or screws to
seal trig bolos.
Zt 1s scan that high spood :uses ~nsn~::ac:Lraa eccarc:.~.g ;,o
zee present inven:ian ars easier to const ~~~, reguire less laic:
anc are consequent3y less expensive to manu:t=;~_ro ar.,:, '_:z cae
emaodimsnt, can De used closor t~ga-,.rier, Whan mounted acjacenL Lo
ons another, wir: recucad danger o_~ short:.ng rrcm to:e to fuss.
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