Hydraulic apparatus for casting and molding of liquid polymer

Trelease, R. B.

English

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REPLY T O  
A T T N O F  GP 
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 
WASHINGTON, D.C. 20546 
March 29, 1971 
TO : USI/Scientific & Technical Information Division 
Attention: Miss Winnie M. Morgan 
FROM: GP/Office of Assistant General 
Counsel for Patent Matters 
SUBJECT: Announcement of NASA-Owned 
U,S. Patents in STAR 
In accordance with the procedures contained in the Code GP 
to Code US1 memorandum on this subject, dated June 8 ,  1970, 
the attached NASA-owned U.S. patent is being forwarded for 
abstracting and announcement in NASA STAR. 
The following information is provided: 
U.S, Patent No. : 3,381,339 
Corporate Source : Arrowhead Products 
Supplementary 
Corporate Source 
NASA Patent Case No.: XNP-07659 
Gafle Parker 
NASA-HQ 
https://ntrs.nasa.gov/search.jsp?R=19710013499 2020-03-17T02:52:45+00:00Z
. .  
, .  . 
R. 8. .?RELEASE 
IYDMIJLSC CASTING OF’ LKQUID POLYMERS 
‘>, Or5giaal Filed Seept, 4. 1 W  
- - -*---  
__. 
CT OF B~WWIs 
This invent ik  relates to improvements in apparatus for 
casting mareriafs, such as Iiquified polymers, under 
elevated presssres. More specifically, the invention pro- 
vides, in a pressurized, closed-mold system, a core mem- 
ber which incfudes channcled and outwardly tapered or 
Conical end portions adapted to h mated or received id 
conicd' supporiing surfices disposed within the cavity 
of the mold. These surfaces are arranged adjacent 
opposed trzinsfer and exit Buid conducting ports. The 
channels of the conical end portions are uniformly dis- 
tributed and exlend radially from lie apex to iorm s p e s  
terminating about fhe circumference of the end portions 
of a cylindrical body of the core so that as viscous mate- 
rial is fed or forced from a first isobting valve into the 
mold cavity, through'the sprue% it is caused to be in- 
jected from one end of the cavity in a substantially uni- 
fora manner. The injected maferial is caused to progiGss 
akmg the exterior surface of the body of the core to be 
discharged from the cavity to a second isolating valve, 
through the converging channels or sprues of the opposite 
The isolating valves are provided at either side of 
cavity in order to Isolate the mold to thus assure that 
red presslire and material dirtributian is established 
and maintained wittin the mold during the injection and 
curing stages of the casting p w s s  in order to achieve 
substaniial uniformity in the resulting products or 
castings. . 
ORIGIN OF THE INVENTION 
The invmtion described herein was made in the per- 
formance of work under a NASA contract and is subject 
to ibe provisions of Seciion 305 of the National 
Aer6nkutics end Space Act of 1958, Public Law 85-568 
:.(72 Statute 435; 42 U.S.C. 2 4 9 ) .  Tbk a p ~ ~ ~ c ~ ~ o n  i s  a 
diVisional of application Serial No. 220,982, filed Siept. 
4, 1962. 
In recent 3wm, rnolded,plas:ic objects have found Wide 
application in a great naciber cf gelds. With continued 
devefoijment of new plastic materials, provijiag a diver- 
sity of physical and chemical propeenies to meet various 
product reyoirements, there is e y r y  indication teat the 
range of usefui applications of molded plastic qrticles 
x i I i  expand at a3 ever Cncreas: ; rata. 
The molding of plastic articles i s  accomplished by 
specific type af plastic material employed. 
Generally, thermoplastic materials, e.g. those w b f f  
fiuidh- u p n  heating knnd resolidify upon cooling, are 
molded by injection molding techniques, wherein &e 
plastic material is meter3d into a heated cylinder. From 
the fatter cytinder, the m o k n  p1as:ic is forced by a ram 
into a ciosed, fluid-cooled. mold. The plastic material 
solidifies upon cooling within the mold and i s  readily 
withdrawn in its solid state when the mold is opened 
Compression and transfer molding techniques are gena 
erally reserved for thermosetrisg pfadics which irreversi- 
bly set or cure with the application of heat. In both of 
those molding processes, the plastic material is metered 
kto a mold cavity between two half sections of tht? mold 
qi'hich are held between the platens of a press. The mold 
is heated, and pressure Is appiicd by the press to brkg 
the two sections of the mold togeher. Ibe heat and prts- 
sure cause. the fluidized plastic to sdid& in the shape of 
the meId cavity. 
Plas-tic materials can also be cast in open mo?& in a 
manner similar to that used for casting molten rnekak, but 
most of the aforedescribed therrnopladfc and them& - - 
setting materials are Rot  sufficiently i'fuidized heir 
decomposition femperatures to fill molds the 
application af external pressure. However, there is a class 
of rpbber and plastic materials, hueinafter referre6 ta 
3s piasfics, which are normally in a liquid state and which 
are capable 3f being polymerized or react&d,into a solid 
state by means of an added catalyst. In some cases, polym- 
erization may also require beating, as well as the addiikm 
af a catalyst. In this class of materials, e.g. Iiqlrid mon- 
omer or  paflially polynerized solutions utilizing a mm- 
omer as the solvent, a definite predetermined quantity of 
the catalyst used to promote sdidificaiioa iq usuafly added 
to the plastic just prior to 
Liquid polymer plastics ar 
the casting liquid onto open 
castjog liquid is usuafly low 
flot; and fili the mold cavity 
by the liquid level withh t 
adjusted so that polynierization takes pia& relathel$ 
sfucvly at room temperatures, or, with some plastics, tbe 
mold may be heated to promote cur& of the plastic 
§UTfXe Of the pQaed GQWWRd'* 
Altbcugh casting of &$6d pofyarS ~ z I  d d s  
is satisfactory for man37 applicasitons, a nurn3er of cases 
exist where it i s  necessary 'to precisely meld such liquid 
polymers Info complex cipfiprations +having extreme& 
c t w  diensiom, e.g, as in the case: of coating' another 
article with a precise thickam of a s-wci&d IkpkI 
polymer material. Such stringent requirements can gm- 
erally be satisfied only within clast& h 
'Hence, those concerned wit! the deve: 
tecbnirjties and apparatus have long recognized 'the need 
for improved. means for n&ng Iiquid polymer p M m  
in ais manner. The present invention fuifikk His D& 
Moreover, in potting arti;CIes w@n liquid 
plastic materi3ls;it has been f ~ l ~ n d  that tfre ad 
. 

for renovhg eutsapped air babbles 
e apparatus of FIGURE 3 is as folio= 
Bo& tbe inlet valve 39. atxi the ouSet v a l e  33 are opened. 
Ihe pliston 27 is &en  loved downyard& in the tank 18 6 
to drive the ffutfuid body 22 t h w g h  the trassfer pipe 16 
d 25, where the liquid passes tbroa& the 
to the mold cavity 28. When the mold is 
filled, as b&cated by a sight glass 61 in the side of the 
e s t  pip 35, the outlet valve 33 is closed. Pumping of 
liq&d into the mold 25 is then continued =ti! @e de- 
sir& bychdic pressure level is attained w i t h  the m o a  
lftir hydradie pressare is indicated by a pressure gauge 
63 communicaling with the transfer pipe 16 a? the base 
of the mold. Upon reachkg the desired pressure level, 13 
the inlet v d y  31 is closed. The cure cyc!e for the liquid 
pdyser pl;iscic then prcrceeds Fo compktion, eithet with 
or wilhout &e use of efevated mold t.empera?ures depend- 
ing upan tbe specific piastic material employed. At the 
end of the cure cycle, the elmping pressure upon the mold 20 
secsioas 37, 39 is removed to release the sections, and 
the mold 25 is then opened to remove the cured article. 
be appreciated that the waste waterid remaining 
the SprrteS 59 may be removed or severed so that 
the end portions or caps §4 may be removed from the 2s 
core 42 to facilitate disassociatior? of the core from the 
prodact in a conventional manner. 
AIthough the invention bas been illustrated and de- 
Scribed for molding a simple cbse dimension, cylindrical 
sleeve or Coating of uniform wall thickness about the core 30 
42, it is to be understood that olber, more complex, con- 
figrations can be as readily molded by varying the shape 
of the core 42 and the inner wail surfaces of the mold 
sections 37, 
The core 
$le- If, however, it is desired to remove ,the core from the 
CUT& zrtfcfe, then it is necessary to cot sway the pIastic 
material depqsited in t5e sprues. Since the caps of thi: 
core are threaded onto the center portion 42 they may b 
now screwed and the center portion 42 of the core can 40 
then be removed iezving a cylindrical article. 
The apparatus of the present invention is also useful 
y be left in  place within the cured arti- 35 
. 
d 
cataIyst material *or to pumping the liquid plastic iato 
the moid. 
The ptesent invent& sa&Ees a long existing ue& in 
the pldstics industry for an apparatus capable of p ~ c h l y  
casting liquid polymer materials into cornpjex configurn- 
Gon having extreniely close dimensions 
It will be apparent from the foregoing that, while pap 
titular foras of my invention have been illlrsfmtmi a d  
dexiibcd, *:aarious modifimtions can be made without ds- 
parttng from &e spirit and scope bf my inventioa Ace 
cordingly, 3 do no1 inteqd that my inkention be &&t& 
except s ~ 4  by the appended claims. 
1 claim: 
1. A casting apparatus fbr use in & Squid plas:ic Easrlag 
system comprising: 
a dosed, two sectioned mold inchiding a m o M  cay&$' 
therein; 
an inlet and an outlet pipe comntcnkating with said 
mold cavity, said inlet pipe being proui*;M for in- 
jecting liquid polymers kt0 said cavity and said ouS- 
le% pipe being provided foi hjschargiq liquid pMy- 
mers from said cavity; 
vaIves on said inlet and mt!et pipes for selectively i%ck 
iathg said mold cavity from system pressur-; 
a three-sectional core centrally disposed witbin &id 
cavity, said core inch cential section an? QP' 
posed conical .ends p with means forming 
s p a s  therein and which mate with corresponding 
portions of said rndd cavity; said rorresponding 
portion nf said mold cavity comprising mans defin- 
ing conical bearing surfaces arranged adjacent the 
inlet and nutlefpipes fo thereby'achieve a centmi dis- 
position of the core within the cavhy and n-*aintain 
the core centrally disposed during the foilowing fill- 
ing of the mold cavity wiih liquid polymers; 
means for pumping a liquid plastlc into said mold carity 
through said inlet p&e and raising fie pressure of 
said liquid withh the system to a selected pressure 
leve1;- 
and means for evacuating a i i  fmm said &id cavitg. 
through said outlet pipe. 



Hydraulic casting of liquid polymers Patent

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