Note: Descriptions are shown in the official language in which they were submitted.
--W~92/~0~40 20~6.~8 PCr/US91/04673
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INSERT MOLDIN& FOR Nl)N-RIGID ENCAPSULATED CO~PON3 :NTS
Teehnie~l Field
This inven~on relates to methods and ~a.~lus for plas~c
injection mol~lin~, and, more particularly, ~o molded plas~c pl~lu~l~ wi~ non-
5 rigid e...i~ t~y3 CO.I.1X"~ and m~thodc o making such pro~ucts.
R~srl~ l of t~e I~ ;DI-
It is well lmown to çn~ps~ t~ cc l.pc,l1e~ thin a plas~c
mol~ling die ca~rity by rigidly affi~ng such cY"..l~o~ c to or ~rough ~e wa~ls of
~e c~ . It is also hlown to avoid ~e ~yy~aace of holding devioes at ~e
10 surfau of the molded product by pro~riding retractable holding deYic~s which
retrac~ out of ~e mol lin~ ca~ity while ~e m~'1in~ m~to.ri~l iS l'setting Up." An
f - .'C of ~e latter t~chnillue is show~ in L. H. Moqin patent 3,420,929,
gra~ted January 7, 1969. It is also possible for ~e holding devices to retract into
the oen~er of the molded product, as shown in R. X. PiuLlv~y pa~ent
15 4,470,784, gran~ed September 11, 1984. Such p~ior art holding deYi~s and
te~hn;q~lP.S, however, do not hold ~e ~n~rs~ ted c~ rne~t iIl a precisely
de~ined posi~on, and hence are of limited ~ F.~ In some ~prlic~ ?n~> for
.nl le, ~e P.nc~ tP~l c~ rl~ must ~ pqecise po~iiions Tela~ve to
o~her e~ Sed c~ or with respect to the e~tenor (~UlliUU~:i of the
20 molded product.
The ~ Y~ of ~lecis~ oning enr~ tP11
within an inje~;liun m~' 1ing cavity can be further cnml lic~f~l by two ~dtlitir~n~l
facto~s. If ~e ~~ on l to be en~ tPfl is not rigid, the problem of holding
it in a precise ~Sion is far more rliffi~llt Fu~ e~l--ul~, ~e ~e tlimP.nci~m Of
25 ~he ~e molded product may be such that very li~e leeway e~s~; for pC~citiC-nin~
~e en~ll~tPA co...~n~.l away from the surfaces of ~e mold. If ~e
l is not precisely and firmly pociti~np~l in the interior of a ~in mr'1in~
cavity, for e~mrle, a },.~blt;~l called "cu~ l breakout" occurs in which
some or all of the enc~rsnl~tP~ co ,l~onelll is visible at ~e surface o~ the molded
30 product. Such bqe~Xout is normally grounds for rejecting the product.
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Su~ o~ the l~ liu~
In a~.dallce wi~ the ii~ dliVe emhQ~ r~ of the present
i~lvt;lllio~ nr~pyll~t~A cr..~ o.,~ d particularly non-rigid ~nr~ tP~
cu~ ne~ , are ;al~tu~;d at a precise position in the interior of the mold cavityS by means of l~d~ble ~hin, flat, rigid '~lades" or "forks" ha~ing one end
fab~icated with a contour which mates with and ~turcs the e~ ;l3~d
cc"l,~ne~t. The blade or fork rigidly holds the enr~ tP~ at a
precise position in the interior of ~he mold cavity during the plastic illj~lionprocess. Just before the last "packing'l portion of the injection mol~lin~ cycle, ~e
10 blades or forks can be rel~d~d to allow ~e molllin~ material to flow and fill ttle
thin voids left by ~e blades or forks. To assist in rrlldcLio~ he blades are
made as ~in as possible and yet m~;..l;.;~- s~ Pnt ngidity to hold the
enr~I sul~t~i component in the precise posi~on desired. ~1 lr.l . .~;v~l~, the blades
can be left in the mold uultil after the plastic mo! lin~ m~trri~l has set up, and
15 then wi~drawn, leaving very small, thin voids in the rnolded prcduct. This
latter procedule is possible only if ~in slots left by ~e blades or forks do notadversely afEect ~e Il~P.r~ r~ or a ~ of ~e molded product.
~ ce wi~ one feat.ure of ~e invention, the blade or fork
can be biased into ~e interior of ~e mol~ling cavity with a spring ~e force o~
20 which is ~vt~ e only by the higher ~ of ~e fimal "paeking" portion of
~e mnl-lin~ cycle. The blades or forks will ~en be a~ltom~ lly ejected from
~e mo~ ling cavity at ~lec.sely the correct time to permit filling the voids left
behind by ~e ~ Ling ~lades during ~e packing period.
For conveDience~ ~e present invention w~ll be described in
25 c~ i;on wi~ ~e m~rling of an ultra thin el~trical plug in which the ~1r~l, ;ç~l
wires mus~ lP~ in a precise position within ~e mold cavi~r to avoid
'~eakout" of ~e ~nres to the su~ce of the molded plug. Such a plug is
described, for ~ , in ~rplir~nt's patent 4,927,376, granted May 22, 1990,
and ~ n~ to applicant's ~ccignP~ is to be understood, however, th2t the
30 methofls and appa~lus of the present invention can be applied to ~e injec~on
mrl~lin~ of many o~er products, particularly ~JlOdU~ 4Uilillg the
r~ tiQn and precise pocitif)ning 0~ non-rigid c~.l,.pcl.~
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WO 92/00840 2 0 8 6 a ~ ~ P~/US91~04673
Brief De~cri~tion o~ $he D~
A ~ rlr~ g of the present invention may be gained
by conci~1ering the foll~wing detailed d~liyli~l~ in ~ ;on with the
~ c(~ .yi~g L~wii~gs, in which: .
FIG. 1 shows a par~ally cut-a~ay pe ~ e view of the lower die
of a plastic inj~ n mold showing the all ~ of both ngid and non-rigid
~o~.pn~m~ in~ cavity, and ~l~uwil~g the use of thin blades to
hold elp~ wires in place du~ing the i ;ol~ opera'don;
FIG. 2 shows a p~ial cro~s-~chon~l ~riew of ~e injection mold ~f
10 FIG. 1 showing ~e posi~on-holding blades in the P,~en-le~l position holding
non-rigid wires in a precise location l~lwæll the upper and lower surfaces of the
mold cavi~;
FIG. 3 shows a par~al cross-sectional view of ~e molded product
produced by the mold of Fl~. 2, showing one posi~on-holding blade;
FIG. 4 shows another partial cross-se~i~n~l view of ~e injection
mold of FIG. 1 showing the position-holding blade l~l~d~ t;d;
FIG. S shows a par~al cross-se~iQn~l ~qew of ~e molded p~oduct
u~d by ~e mold of FIG. 4 with ~e posi~on-holding blade l~tldCIl;d;
FIG. 6 shows a ~~ iV~ par~al se~inn~l ~ew of a molàed
20 ~ree-prong el~i~l plug molded ~ usi~g the position-holding blades of the
present invention and tab clips on one of the ~lP~ir~ ongs to assist in holding
the e~ nres in position dwing ~ie mol~lin~ process;
FIG. 7 sh~ws a ~oss-~ion~l view of ~e cavi~y mold used to
p~oduce the molded product of lFlG. 6~ uwillg the posi~on-holding blades in
25 their i~P.n(lerl position; and
FIG. 8 is a ~,~iiv~ view of ~e tab clips on ~e electric~
iground prong of ~G. 6 usecl to assist in holding the el~ l wire in posi~on
du~ing ~e mr'1ine lprocess.
To fi~irili~te reader ~ in~ iden~ ert;lellce numerals are
30 used to fl~P~ te el~mPnts commcm to the figures.
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Det~iled Des~
~ FIG. 1 there is shovvn a ~ial pr,~ i;v~ view of the lowerdie 10 of a eavity injection mold c~ a mold half eavity 11 in ~e shape of
a thin he~g~n~l electrical plug. Electrical prongs or c~ pins c~ n~ A to
5 5t~hili7inr lands 12 and 13 e~tend out of caYity ~ rough slots 14 and 15,
ely. S;lots 14 and 15 have bottoms located so as to precisely position
lands 12 and 13 in the interior of mold cavity 11. Tn~ ted wires 16 and 17 join
~oge~er in sleeve portio~l 18 of mold cavity 11 to farrn line oord 19. One end ~f
~nre 16 is elec~ically a~ rl~r~ to land 12 while one end of wire 17 is electrically
10 ~ rhP~l to land 13. In addition, wire 1~ is physically ~ hPA to land 12 by
crimp 20 while wire 17 is physically ~ r~ to land 13 by crimp 21. An upper
die, not shown in FIG. 1, has a half cavity ~ ul;ng cavity 11 in die 10, but
without the slots for the electrical plugs. An inje~ion runner or half gate 22,
together with the mating half gate on the upper die, forms a en~y ps~rt for
15 inj~ing a molten plastic such as polyvirlylchloride (PVC) into ~e ~c~.m~
mold.
~ practice, the two half cavities are r;~ r~A ti~dy t~gether in the
core of a mol-lin~v m~rhin~-. Molten plastic is injected under high pl~lllG (5
150 tons per squa~e inch) to entirely fill all of the voids in the ~e mold cavi~.
20 At ~e very end of ~e n~ lin~ cycle, ~e injec~ion pl~U~t iS raised even higherfor a brief period to ensure eomr1ete filling of all voids in ~he cavity. This
higher ~e5~UI~ at ~e end of the injec~on ~ycle is called ~e "packing' por~on of
the injPrtion r~ol(lin~ cycle. After the plas~c Jn~tPn~l has cooled, possible
assisted by cold w~ter arcula~ng in ~e inte~ior of ~e mold body, ~e mold is
2~ opened and the moldPA product is eje~ed from ~e mold by m~s of an ejection
piston 26.
In a~u~ ~ wi~ the present invention, the wir~ 16 and 17 and
the line cord 19 are ~u~ d in ~e interior of the mold cavity by a plurality of
~in metallic blades23, 24 and 25. As can be be~ter se~n in FI(:;. 3, the
30 blades 23-25 have a contour ~ormed into their upper edge which mates wi~h andes ~vire 16. That is, the upper edge of blade 24 has a contour which is
slightly more than a haU of the periphery of wire 16 and ~us is able to "grab"
~e soft insulation of wire 16 and hold it in posi~on. Blade 23 has a conto~ in
its upper edge which ma~es with the double wire line c~d 19 and also ~ nds
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WO 92/008413 2 0 8 ~ 3 ~ 8 PCr/U~91/04673
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beyond the ~ lar ~ y of ~e ~wo wire of line cord 19 to hold the line
cord in position.
It will be noted that the caYity fs~ned by the two dies is ~ .ely
~in and henoe very little leeway is available for ~e ~ 1 of wires 16 and 17
S alld line cord 19 Wi~iIl the ca~ 11. If these wires are not placed I,l~ sely in
the -,o~ g ca~ity, and held in ~at position during ~e enffre injec~on process,
the wires will be moved by the a-lv~ci~g moltcn plastic and possibly end up
being in contact wi~ ~e exterior surace of the mold cavity 11. When the
molded plug is ~e~uvt;d from the mold cavity (by piston ~6, ~fG. 2) after the
10 molten plastic has hardened, any wires pushed to the surfac~ c)f the mold cavity
are visible at the surface of ~e completed plug. This result is called 'wire
brealcout" and is sl-ffir~ntly l-n~sthPtic to result in rejection of molded p~oducts
exhibi~ng such ~nre breakout.
In accol~ce with ~e present inven~don, retractable p~i1inni
15 blades 23, 24 and 25 position the no~-rigid wires 16 and 17 and line cord 19
isely within the mold ca~ity and ~ - these non-rigid c~ r~ at th~t
precise po~ition throughout ~e mol~lin~ process. The number ~d p~ nn~ of
the blades such as blades 23-25 are direc~y s1e~ on ~e desired ~li~cff;itic~n
of the wires wi~hin the ca~ and ~e length of the ~ivire runs ~U~illg support.
20 The ~ree blades 23-25 in FIG. 1 are s~ffirip.nt for the wires in ~e elPct~ir~l plug
depicted ~erein.
Blades ~3-25 can be retrac~d, for PY~mpl~P. by hydraulic pistons,
not shown, just before the pasking por~on of ~e m~ ing cycle so that ~e voids
formed by the retracted blades can be, filled by ~he still flowing plastic matenal.
2~ ~AhPrn~tPly, and preferably, the blades 23-2S can be spring-loaded such that ~ey
are held in ~e position-st~hiliring position for ~e ini~al portion of the injec~on
cycle, but are pushed out of the mold cavity 11 by $he higher ~ e ~xerted
d~ing ~e pacl~ng portion o~ ~e inj~ion cycle. As a ~er ~ ;Ye, the
blades 23-25 can be retracted after ~e entire mnl~lin~ ~ycle is ~ ,ted, leaving
30 the ~in slots ~om which the blades are l~.lWVI~ in ~e ~ni~hPA molded product. If blades 23-25 are ~in enough and ~ocitionp~ so as to ~ , the a~ce
- of such slots, it may not be llec~ y to fill ~e voids left by blades 23-25 at a:ll.
Indeed~ ~e surface of ~e finished product can be dec~,~Ced with slo$-iike
dec~rations in ~e midst of which the actual blade slots become virtually
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invisible.
In FIG. ~ there is sh~n a partial cross-se~ion~l view of '~he
~cc~mhl~A mold cc.,..~ lower die 10 and a ma~ng upper die 27 forming the
mold cavity 11 ~h~reb~ . The rl~ ong ~8 ~thched to land 12
S SU~ > land l2 in ~e interior of c~vity 11 while blades ~4 and 25 support
wire 17 in the interior of cavity 11. FIG. 3 is a pardal cross-section of ~e
molded plug 29 ~huwi~g the wire 17 s~ e~l therein and su~w~d by
bl~de 24.
~ FIG. 4 there is shown a par~al cross-sechnn~l view of the same
lQ ~ m~ l mold of FIG. 2, but with the positioning blad~ 23-25 retracted out of
the mo' 1in~ cavity 11. In FIG. S t:here is shown a partial cross-section of ~hemolded plug 29 with the wire 17 sus~n-1pt~l in ~e hardened plastic and wi~ the
~7.~ g blades 23-2S removed, leaving cavi~ void 30. As noted above,
void 30 can be filled by retrac~ng the blade p~ior to the packing por~on of the
15 iniection cycle, or the void 30 can ~e left unfllled by retrac~ng ~e blade after
the end of ~e injection cycle and after the plas~c has hardened.
Al~ough ~e me~od and ay~ of the p~esent inven~on for
pc~ innin~ non-rigid cc,~ b in ~e interior of molded ~l~lu~, is shown in
FIGS. 1-5 in c~ inn wi~ molded ele~rical plugs, it will be a~ i to
20 persons of olJin~ skill in the injection mollling art ~at this method and
a~p~dlus can be used for positioning ~ in ~e int~or of many o~er
molded products, whether rigid or non-ngid. Thin blades or forks are ~d
having ~e edge interior to ~e mold cavity colllouled to match the exterior
surface of the c~l"~nc~t to be positioned. Such blades or forks can be used to
253 ~e~i~ly position a large number of enc~rs~ ed c~n.l~n~ wi~in ~e interior
of molded plas~c products without d~alLing from the spirit or scope of ~is
inven~don.
~ 4hhnllgh the technique d~ in co~ with FIGS. 1-5
san be used to position many S~ir~ ~ pes of C~ X wi~in the interior
30 molded products, it is also possible to make use of one or more of the
enr~lll~t~i cnmrnPnt~ itself to assist in positioning a .liff~.e~ nr~rS~ t~d
c~ r.~t Such and elrtt.n-led positioning techni~que is r~ o~d in FIG. 6-8 in
co,llle-;lion with a ~ree-pronged, grounded molded elec~ica~ plug.
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In FIG. 6 there is shown a ~livt; view, in par~al section, of a
three-prorlg el~;Llieal plug ~l~rir2~çrl by inir~hon mol~ing techniques in
aecolda~ce with ~e present il~v~lllion. The plug body 40 enr~psul~t~c the ~ee
wires of ~e three-wsre line ~ord 41 as well as st~hili7ing lands for ground pin 42
S and power pins in~ tlin~ pin 43 and a second power pin, not visible in FIG. 6.The upper por~on of ground pin 42 has two channel-formitlg l:abs 44 and 45
used to assist in ~uling the el~1~ical wire 46 cn.~ ~i to power pin 43. Thin
blades with a~lu~ lcl~ col~uurt;d upper edges ~re also used to assist in
po~itioning wire 46 in other portions of the mbld ~vit~. The mold cavity is
10 shown in cross-s~tion in PIG. 7.
In FIG. 7, the two half molds 50 and S1 define a mold cavity 52
îL.,Ic;belween in which wire 46 is positioned in par~ by bladP~ 53 and ~4 and inpart by the upper por~on of ground pin 42, shown in perspective view in FIG. B.
The tabs 44 and 45 capture wire 46 to hold wire 46 in position during the
15 m~ing process. Since wire 46 is fully in~ tPIl, the contact by tabs 44 and 45 does not i~ r~.e wi~ the PhP~i~l circuit. A çrimpi~ land 56 is also
~chion~d on grou~d pin 42 to provide a pl2Ce to e~ ly alnd me~h~ni~11y
connect ~e ground wire of line cord 41 to ~e ground pin 42.
It should be clear to ~ose skilled in ~e art that further
20 emho~limp~rts of ~e present invention may be made by ~ose sldlled in ~e art
without d~ g from ~e tP~in~ of the presP~nt invention.
