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Патент USA US3082299

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March 19, 1963
R. w_ GORE
‘ 3,082,292
MULTICONDUCTOR WIRING STRIP
7 Filed Sept. 30, 1957
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' Inventor
jfobert WGore I
mm
United States Patent 0 “ice
3,082,292
Patented Mar. 19, 1963
1
2
3,082,292
around the circumference of the rolls, these grooves being
indexed to ?t opposite the grooves on the opposing roll if
MULTICONDUCTOR WIRING STRIP
Robert W. Gore, Newark, DeL, assignor to
grooves are cut in both rolls. One or more electrical con
ductors 13 of relatively uniform cross section are guided
W. L. Gore & Associates, Inc.
the rolls; and two sheets 14
5 into the contoured grooves
and 15 are fed ‘as shown by the arrows, between the two
Filed Sept. 30, 1957, Ser. No. 686,900
27 Claims. (Cl. 174-—117)
roll-s so that they are formed around the wires and pressed
together ibetween each wire to separate each wire into its
This invention relates to the product-ion of coated arti
capsule and seal it there. The assembly is then passed
cles. More particularly, it relates to a process for coat
ing such articles as wire with plastic materials.
10 through an oven 16 to sinter the polytetra?uoroethylene
Objects such as electrical conductors are most com
if that polymer is being used.
screw or ram extrusion operations in which a melt, paste,
The resultant assembly constitutes at least a single wire
uniformly surrounded by the plastic except at the ter
plastisol, or uncured elastomeric composition is forced
minals of the grooves where certain ribs or connecting
monly enclosed in plastic and rubber insulators by either
around the conductor as it passes through a die or forming 15 pieces ‘are. If a multitude of wires are processed, the as
ori?ce. Great mechanical dif?culties have been encoun
sembly comprises the various wires held together by the
tered in attempting to coat more than two or three con
ribs or membranes. The assembly is useful as it comes
ductors in a single assembly by these methods.
from the apparatus; regardless of the number of wires
therein, it can be used ‘directly. Frequently, separation is
Furthermore, a number of processes heretofore have
had to use the plastic in powder form. Flow rates of pow 20 desired and the assembly is passed to a cutter. The con
necting membrane sections are readily removed leaving a
der to the article to be coated had to be carefully con
trolled. Methods using powders have been used with
intractable polytetra?uoroethylen-e but such methods have
continuous, smooth-surfaced length of coated wire. As
sembly examples 20 and 22 are shown in FIGURES 4
and 5.
In FIGURE 2 there is shown the relationship of the
Accordingly, it is an object of this invention to provide 25
various parts at the nip. Wires 13 are centered in the
an economical and e?icien-t method for encapsulating ar
grooves and are uniformly surrounded by plastic 17, the
ticles. Another objective is the provision of 1a method for
connecting membrane being designated at 18. This mem
producing coatings simultaneously on a band of articles,
brane generally has a thickness less than twice the thick
such as a large number of wires. Another objective is the
production of thin coatings. A still further object is the 30 ness of the coating. The con?guration in FIGURE 3 re
lates to apparatus in which the grooves are contained en
provision of an ef?oien-t process for making polytetrailuo
tirely in one roll 19. A thicker coating at 21 results. This
roethylene coatings, These and other objectives will ap
assembly has the advantage in that it presents a ?at surface
pear hereinafter.
for mounting of ‘the assembly to ?at surfaces, the mem
The objectives of this invention are accomplished by
brane being used for holding staples and the like.
passing the article to be coated into the nip of two con
The process of this invention and the articles made
verging sheets of the coating material. The surfaces are
thereby will be further understood by reference to the fol
fed to a pressure element, for example, into the nip of two
lowing examples which are not limitative but are given
drive rolls or between two pressure plates, so that a sur
‘for illustrative purposes only.
face of the coating material lies between each roll or plate
.and ‘the article. The pressure elements, such :as the rolls,
Example I
usually contain in their surfaces cut-out portions such as
Eight
No.
22
gage
stranded wires were guided into
grooves, which correspond to the contour of the ‘article
eight sets of grooves in two opposing rolls six inches in
being coated, and the articles are fed into these sections.
diameter. The rolls were not heated. The grooves were
The rolls act as pressure or calender rolls. Thus, the
articles, such as wires, are fed into hollow sections which 45 contoured to form a circular cross section about 0.045
inch in diameter at the plane of closest approach of the
become ?lled by portions of the converging sheets of plas
rolls. The eight sets of grooves were spaced 0.075 inch
tic material as the sheets pass through the apparatus and
apart, and the rolls were adjusted so that the ungrooved
are pressed together. Generally, the articles are strung up
parts were 0.003 inch apart at the bite. Two tapes of un
prior to passing the plastic material through the apparatus
‘though this is not essential. While a single article, such 50 sintered polytetra?uoroethylene sheet 0.008 inch thick and
1.0 inch wide were guided into the bite of the rolls, one
as a wire, can be processed, this invention is advanta
tape on each side of the set of wires. The rolls were
geously used in handling a plurality of articles to be coated.
revolved so that the sheeting formed around the wires
This invention will be ‘further understood by reference
and was pressed tightly together between them to form
to the ?gures in which
a
0.003 inch thick web that appeared homogeneous and
55
‘FIGURE 1 is a perspective showing the converging
not been e?icient and economical.
sheets with a band of wires passing through the resultant
mp;
FIGURE 2 is a cross-sectional view, a section on line
2-2, showing the contours of the grooves in the rolls, the
position of the wires, the con?guration of the sheets and
one article made herein;
oven at 350° C. fora few minutes and then removed and
cooled. The assembly was tightly held together and was
tough so that it could be ?exed and twisted without harm
ing it. The coating thickness ‘around the wires was about
0.008". No electrical ?aws were found when it was im
'
FIGURE 3, similar to FIGURE 2, shows a different
groove shape and a different ‘assembly, the web construc
mersed in salt water with 3,000- volts potential between
the wires and the salt water. The conductors were sep
65 arated by slitting the web between them and tested in
tion being similar; and
FIGURE 4 is an elevation of one article made herein;
and
FIGURE 5 is an elevation of another assembly of this
invention.
showed no tendency to separate during handling of the
unsintered assembly. The assembly was placed in an
dividually by immersing them in salt water at 3,000 volts
potential. No electrical ?aws werev found in the insula
tion.
Example I]
_
The procedure of Example I was repeated using one
As shown in FIGURE 1, a set of opposing cylindrical 70
unsintered polytetra?uoroethylene tape colored with 0.1%
rolls 10 and 11 are adjusted to a small and speci?ed sep
aration from each other, and contoured with grooves 12
cadmium red pigment, the other tape being uncolored.
3,082,292
3
4
The mechanical qualities appeared unchanged from the
ethylene sheeting somewhat larger than the copper insert.
stmcture made in Example I, and no electrical ?aws
The edges around the copper sheet and the areas where
it was cut out were pressed together by going over them
with a small roller about one half inch in diameter, one
were found at 3,000 volt stress.
Example‘ 111
The procedure of Example I was repeated except that
two unsintered polytetrafluoroethylene tapes 0.004 inch
thick were guided between the wires and rolls on each
eighth inch wide. The unsintered polytetra?uoroethylene
sheets were quite ?rmly fastened together by this treat
ment. The assembly was then placed in an oven at 350°
C. for ?ve minutes. The two polytetra?uoroethylene
sheets were fused together where they had been pressed
homogeneous and strong, both before and after sintering. 10 by the roller and appeared to be completely homogeneous.
No electrical flaws were found when the assembly was
The copper sheet was tightly sealed into the polytetra
immersed in salt water and the conductors charged with
?uoroethylene envelope.
3,000 volts.
This process is a versatile way to encapsulate electrical
side of the wires. The seal between the wires appeared
Similar results are attained when screen is used instead
components or any device that needs to be protected from
of wires, the rolls being correspondingly grooved circum 15 a corrosive or harmful environment by encapsulating it
ferentially and longitudinally.
in an impervious envelope of polytetra?uoroethylene.
It is very surprising that the intractable polytetratluoro
Example IV
ethylene resin can be pressed together to form the tightly
The forming procedure of Example I was repeated ex
cept that smaller heated rolls were used and 0.005 inch
polyethylene tape was ‘used in place of polytetratluoro
ethylene. In this experiment, the forming rolls were
bound assemblies of this invention. Hitherto, no ex
trusion process was known for intractable polytetra'lluoro
ethylene resin which process would produce coatings free
from electrical flaws; such flaws caused breakdowns in
four inches in diameter, they were constructed of an
the insulation when it was subjected to an electrical stress
aluminum core with a polytetra?uoroethylene outside
of several thousand volts. Furthermore, heretofore, it
annulus, and they were heated to about 150° C. Again 25 has not been feasible to extrude coatings thinner than ,
a mechanically sound assembly was formed and no elec
about 0.008 inch. Thin coatings of good electrical quality
trical ?aws were found at 3,000 volt stress in the salt bath.
can be put on electrical conductors by wrapping them
with polytetra?uoroethylene tape and then sintering the
Example V
The procedure of Example IV was repeated using 30 wrapped tapes together. However, this is a laborious
operation that can be done only at low linear rates along
plasticized polyvinyl chloride tape. Again a mechanically
the
conductor; only single conductors can be coated by
sound assembly was formed and no electrical ?aws were
this process; and the coatings are somewhat rough where
found at 3,000 volt stress in the salt bath.
the spiral wraps overlap. This invention obviates all of
Example VI
these difficulties.
In many applications in the electrical and electronic
A sheet of unsintered polytetra?uoroethylene sheet 35
0.007” thick was laid over a section of a die with a ladder
shaped recess cut in it ‘about 0.050” deep.
Next a cop
?elds it is necessary to carry a number of conductors from
one set of terminal connections to another set some dis
tance away. In doing so, the conductors must be kept
per sheet, 0.010" thick, cleaned with a bichromate solu
tion and cut to fit the ladder-shaped recess, was placed 40 insulated from each other and from external objects, and
must be identi?ed at each set of terminals. By this in
over the polytetra?uoroethylene sheet so it indexed with
vention an assembly of numerous conductors is provided
the die recess. A second sheet of unsintered polytetra
which greatly reduces the labor of stringing out the hook
?uoroethylene was placed on top of the copper insert so
up, allows wiring to be done in smaller channels and
that it was completely covered by the two poiytetrafluoro
passageways, and greatly simpli?es the problem of iden
ethylene sheets, and the assembly was pressed with a ?at
plate so that the two sheets of unsintered polytetrafluoro 45 tifying the ‘leads, both in making the original installation
and in maintenance and alterations that may be required
ethylene were compressed together except where the
later.
copper insert lay in the die recess. No heat was applied
The sheets or tapes used can be colored differently so
to the die surfaces. The pressure was increased to the
that the assembly is made up of sections colored different
point where thickness of the web around the copper in
sert was decreased ‘from the approximately 0.014" thick 50 ly. For example, one side may be colored yellow and
the other white. Thus, if an installation is made up at
ness of the two layers of sheet to about 0.008”. The
terminals with the white side up, one need only number
assembly was lifted from the die. It was ?rmly held
the leads, from left to right, for example, and at the
together where the sheets had been pressed and the cop
distant point place the White side up and use the same
per insert was completely encapsulated in the polytetra
?uoroethylene. The assembly was placed in an oven at 55 numbering to make the connections at the distant point.
If desired, the different colored sheets may be fed run
350° C. for ?ve minutes and then removed and cooled.
ning lengthwise side by side preferably with a slight over
The polytetratluoroethylene was completely fused and
lap. By so doing, different colored sections can be ob
became very tough after this baking. No separation oc
tained on one side or on both if desired.
,
curred where the two sheets were pressed together.
With polytetra?uoroethylene, unsintered sheets of ma
One edge of the copper insert was uncovered by cut 60
terial are used and the rolls are not heated. An unex
ting away insulation. The rest of the assembly was im
pected discovery is that these unsintered sheets of poly
mersed in salt water, and 2,000 volts applied between
»tetra?uoroethylene adhere together very tightly when
the salt water and the copper insert. No breakdown
they are compressed in the bite of the rolls, and the seal
occurred in the insulation at this voltage.
This process is useful for the manufacture of “printed 65 remains strong and homogeneous when this plastic en
circuit” types of assemblies, particularly where good elec
trical properties, toughness, or very high temperature
velope around the conductors is sintered by heating it to
above 327° C. When the unsintered polytetra?uoro
ethylene sheets are used as the encapsulating material,
resistance are required. By this invention, articles of ir
the assembly must be heated to a temperature between
regular shape or assemblies of no symmetry whatsoever
can be manufactured using polytetrafluoroethylene as 70 about 330° C. and about 430° C. to sinter or coalesce the
material into a homogeneous structure that has the
the insulating material.
strength and toughness characteristic of the fused ma
Example VII
terial.
If great assurance is required that no electrical ?aws
A ladder-shaped piece of copper sheet 0.010” thick was
placed between two sheets of unsintered polytetrafluoro 75 exist in the construction, several sheets of material can
3,082,292’
6
5
be guided into the rolls on each side of the conductors.
For example, the feeds going in may comprise two tapes
one on top of the other, instead of the single tape or
sheet 14 or 15 shown in FIGURE 1. There is little pos
for example using smooth rolls. However, membrane
sibility that any flaw in one of the sheets will occur
exactly indexed with a flaw in the other sheet or sheets.
Still further, instead of the two sheets 14 and 15 one
hexagonal, diamond and other shapes.
thickness increases in such operations, and the consump
tion of polymer rises. The shapes of the contours or
grooves may be slots, circular, rectangular, square,
By this invention electrical conductors are readily en
capsulated in a sheath of plastic material. High-quality
sheaths can be produced under controlled conditions.
sheet may be used by folding it and passing it vertically
For example, it is possible to produce structures hitherto
or horizontally to the nip of the rolls with the wire inside
the fold. Also, the tapes shown in FIGURE 1 may be 10 not feasible and to manufacture from polytetra?uoro
ethylene objects that could not be made before, yet retain
ing the chemical incrtness, dielectric and other desirable
properties of the resin. Further, the weight of insula
ing the nip of resinous materials apply, of course,’ to the
thermoplastic materials also. These materials include
tion
craftisand
minimized.
missile wiring
Thisinis which
important,
thin, for
high-quality
example, wiring
in
polyethylene, tetra?uoroethylene copolymers such as tetra 15
is most essential. Such objects having no electrical ?aws
?uoroethylene/monochlorotrifluoroethylene polymer or
are produced by this invention. ‘These desirable articles
tetrafluoroethylene/hexa?uoropropylene, polymonochlo
are made efficiently and economically.
rotri?uoroethylene, polyvinyl chloride, polyamides,
fed vertically if desired.
The various types of feed or the di?Terent ways of form
polymerized epsilon-caprolactam, polyformaldehyde, poly~
While the invention has been disclosed herein in con
vinylidene chloride cellulose acetate, plasticized cellulose 20 nection with certain embodiments and certain procedural
details, it is clear that changes, modi?cations or equiva
‘acetate butyrate, polyether polymers, and poyvinyl ace
lents can be used by those skilled in the art; accordingly,
tate, among others. The thermoplastic materials, such
such changes within the principles of this invention are
intended to be included within the scope of the claims
that respect. The rolls or whatever pressure elements are 25 below.
1 claim:
used may be heated to some extent, if desired, when
as those exempli?ed, must be heated in the converging
process and are unlike the polytetra?uoroethylene in
processing the polytetrafluoroethylene but it is much
more advantageous not to heat. It should be recognized
1. A process for coating, in a continuous manner, an
article which process comprises passing along their lon
gitudinal axes at least two surfaces of a coating material
to the converging. While some sintering can be toler 30 derived from an unsintered tetrafluoroethylene polymer
and in sheet form to and through the nip of two pressure
ated in the converging of the sheets and the articles, it
rolls, the said sheets and said rolls being at temperatures
is preferred to minimize this and to effect all the sinter
that the polytetra?uoroethylene must be unsintered prior
ing in the subsequent heating step. This affords greater
control to the entire process, higher production speeds
and lower costs.
below the sintering temperature of the said polymer;
simultaneously passing the article to be coated to and
through
the resultant nip being formed by the said sheets;
35
exerting pressure on the said coating material to en
While the assemblies can be used in units, the process
close the said article in the said material and to bond the
of this invention may be used to produce single coated
said unsintered sheets together when and where they
articles. The assembly is passed to a cutter, not shown,
contact each other under pressure in said passage to form
where it is cut into smaller sections or into singles. It
is also possible to effect the separation into singles by ex 40 at least one web which contains unsintered polymer and
which extends longitudinally along the length of the re
erting su?icient pressure on the rolls so that the web, that
sultant
enclosed article and transversely away from it;
is, the sections between the coated articles almost or en
and withdrawing from the exit side of the rolls the result
tirely disappears. The plurality of articles emerge with
ant assembly which comprises the said article having a
little or no membrane polymer and they are easily sep
coating of the said unsintered polymer and at least one
arated. When asemblies are to be produced, the pres
web.
sure used will be adjusted to get the desired web thick
2; A process in accordance with claim 1 in which said
ness. Using contoured pressure surfaces for economy
coating material comprises poly(tetrafluoroethylene).
purposes, one can readily produce assemblies in which
3. A process in accordance with claim 1 in which said
the web or membrane portions have a thickness less than
coat-ed article is heated after leaving the said rolls to
twice the coating thickness.
50 sinter the said polymer in the resultant article.
The heating time need only be long enough to effect
4. A process in accordance with claim 1 in which the
the sintering of the polymer. This will depend upon the
said coated article is heated, after leaving the said rolls
size of the oven being used, the amount of coated ma
and in the absence of applied pressure, to sinter the said
terial being sintered, the type of heat and the speed
of the traveling coated article While batch sintering 55 polymer in the resultant article at a temperature of about
330° C. to about 430° C.
can be used, it is preferred to conduct the sintering on a
5. A process in accordance with claim 1 in which said
continuous basis. Usually, the time is in the order of
article is an electrical conductor.
only a few seconds but it may be as high as 30 minutes
6. A process in accordance with claim 1 in which a
or higher. All that is usually required is su?icient time
roll contains a recess corresponding to the shape of the
to get the body heated to the sintering point of the poly
article being coated.
mer. With the thermoplastics the after-heating is
omitted, the coalescing being e?ected simultaneously
with the converging.
With polytetra?uoro-ethylene, as
well as with others, one will avoid thermally or other
7. A process for coating, in a continuous manner, an
article which process comprises passing along their lon
gitudinal axes at least two surfaces of a coating material
wise degrading the polymer. This is readily done, for at 65 derived from an unsintered tetrafluoroethylene polymer
and in sheet form to and through the nip of two pres
high temperatures heating times are short. Further, par
ticularly effective kinds of heating, such as radiant heat
ing may be employed.
‘
‘sure rolls, the said sheets and said rolls being at tem~
peratures below the sintering temperature of the said
polymer; simultaneously passing the article to be coated
A variety of articles may be processed in accordance
with this invention including wires, rods, strips, screen 70 to and through the resultant nip being ‘formed by the said
and similar items. It is preferred to process axially sym
metrical ob-jects for the attendant ease with which the
rolls may be grooved. However, it is not essential that
grooved pressure elements, as grooved rolls, be used and
sheets; exerting pressure on the said coating material to
enclose the said article in the said material and to bond
the said unsintered sheets together when and where they
contact each other under pressure in said passage to form
unsymmetrical articles may be coated by this'invention, 75 at least one web which has a thickness less than the sum
3,082,292
7
of the initial thicknesses of said sheets, which contains
prising a plurality of articles coated with a polymer com
unsintered polymer and which extends longitudinally
along the length of the resultant enclosed article and
prising poly (tetra?uoroethylene) as the coating, each
article being held in said assembly by webs that extend
transversely away from it; and withdrawing [from the
between adjacent articles, said webs having a thickness
exit side of said rolls the resultant assembly which com
less than twice the thickness of the coating.
prises the said article having a coating of the said un‘sin-v
19. As an article of manufacture, an assembly com
prising a plurality of articles coated with a polymer com
tered polymer and at least one web.
8. A process in accordance with claim 7 in which said
.
prising poly(tetra?uoroethylene) as the coating, each
article being held in said assembly by webs that extend
without applying pressure to said article, to a tempera 10 between ‘adjacent articles, said assembly being of one
coated article is heated, after leaving said element and
ture of at least 327° C. to sinter the tetra?-uoroethylene
color on one side and of another color on the other side
polymer.
and said webs having a thickness less than twice the
9. A process in accordance with claim 7 in which said
thickness of the coating.
polymer is poly(tetra?uoroethylene).
>
20. A color-coded assembly comprising a plurality of
10. A process in accordance with claim 7 in which at
articles, such as conductors, coated with a polymer com
least two sheets are used, one being of one color and
prising poly(tetraiiuoroethylene); separating each article
the other being of a different color.
11. A process for coating, in a continuous manner, an
a web of said polymer which web has a portion coalesci
longitudinally along the length of the resultant enclosed
than twice the thickness of said coating, said assembly
article and transversely away from it; and withdrawing
?rom the exit side of said rolls the resultant assembly
which comprises the said article coated with polymer that
thickness.
ble into the respective adjacent polymer that coats a por
article which comprises passing along their longitudinal
tion of the adjacent article and which web has. a thick
axes at least two surfaces of a coating material derived 20 ness less than twice the coating thickness; on one side of
from an unsintered tetraiiuoroethylene polymer and in
said assembly a colored material on said side; and on
sheet form to and through the nip of two pressure rolls
the other side a different colored material.
containing recesses separated by ridges, the said sheets
21. An assembly in accordance with claim 20 in which
and the said rolls being at temperatures below the sinter
said polymer has been sintered.
ing temperature of the said polymer; simultaneously
2.2. An assembly comprising a plurality of electrical
passing the article to be coated to and through the‘result
conductors coated with a tetra?uoroethyiene polymer,
ant nip being formed by the said sheets and aligned to
each conductor being coated and being held in said as
pass through respective recesses; exerting pressure on the
sembly by webs that extend between adjacent conduc
said coating material to enclose the said article in said
tors, each of said webs having a thickness less than twice
material and to press the said sheets together, when and so, the thickness of said coating and said assembly showing
where they contact each other under pressure in said pas
no electrical ttlaws at a stress of 200 volt/mil thickness.
sage over said ridges, to‘ a thickness less than the sum
23. An assembly comprising an electrical conductor
of their initial thicknesses to bond the said sheets together
coated with a tetrai'luoroethylene polymer as the coating
in the form of a web which has the said lesser thickness,
around said conductor and extending away from said
which contains unsintered polymer and which extends 35 coated conductor a web portion having a thickness less
showing no electrical ?aws at a stress of 200 volt/mil
24. As an article of manufacture, an electrical con
40 ductor coated with a tetra?uoroethylene polymer which
is unsintered and the said web.
12. A process in accordance with claim 11 in which
is in an unsintered form and is bonded by a weld extend
said coating material comprises poly(tetra?uoroethyl
ene).
ing ‘longitudinally along the length of said conductor and
transversely away from it, said weld comprising at least
two overlapped sheets of said polymer compressed to a
thickness less than the sum of the initial thicknesses of
the elements in the overlap, the said initial thickness of
a sheet being measured by the thickness of the coating
13. A process in accordance with claim 11 in which
a plurality of articles aligned with respective recesses is
treated.
14. A process in accordance with claim 13 in which
the said pressed sheets ‘form webs which extend between
adjacent articles and which hold them together.
15. A process for coating an article‘ which comprises
passing along their longitudinal axes at least two surfaces
derived from the respective sheet.
25. A conductor in accordance with claim 24 in which
the polymer has been subsequently sintered.
26. A conductor in accordance with claim 24 in which
the polymer is poly(tetra?uoroethylene).
of a coating material derived from an unsintered tetra
?uoroethylene polymer and in sheet form to lie between
the adjacent, co-acting surfaces of a pressure element,
the said sheets and the said elements being at tempera
tures below the ‘sintering temperature of the said poly
nter; passing the article to be coated to said pressure ele
27. A conductor in accordance with claim 24 in which
the polymer is poly(tetra?uoroethylene) and the said
polymer has been subsequently sintered.
References Cited in the ?le of this patent
UNITED STATES PATENTS
ment to lie between the said sheets of said material; exert
ing pressure on the said material around the periphery
of said article between the ‘sheets of said material to en
close the said article in the said material; and at the
same time bonding by exerting pressure on at least one
246,407
665,989‘
1,291,709
portion of the said unsintened sheets where they contact
. 1,977,108
each other to form at least one homogeneous, bonded
portion and to produce thereby a self~supporting struc- '
ture, the polymeric material of which is coalescible to
form a homogeneously sintered coating of said polymer
material around said article.
16. A process in accordance with claim 15 in which
said polymer comprises poly(tetra?uoroethylene).
70
17. A process in accordance with claim ‘15 which in
cludes the step of heating the said coalesci'ble material
at a temperature of about 330° C. to about 430° C. to
sinter said polymer.
18. As an article of manufacture, an assembly com 75
2,112,723
2,361,374
2,425,294
2,533,501
2,578,522
2,710,909
2,744,041
2,749,261
2,767,113
2,786,792
2,797,729
McTighe ___________ __ Aug. 30, 1881
Bechtold ____________ __ Jan. 15, 1901
Angier et al. _________ __ Jan. 21, 1919
A-rnberg _____________ __ Oct. 16, 1934
Wisott ______________ __ Mar. 29,
Abbott ______________ __ Oct. 31,
Morgan ____________ a- Aug. 12,
Pendleton ___________ __ Dec. 12,
‘Edgar ______________ __ Dec. 11,
Logan et al. _________ __ June 14,
Balchen _____________ __ May 1,
Hardison _____________ __ June 5,
Bower ______________ __ Oct. 16,
Mikiska ____________ __ Mar. 26,
Runton ______________ __ July 2,
1938
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