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Патент USA US2061042

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Nov. 17, 1,936.
2,061,042
F. A. PARKHURST
MACHINE FOR EXTRUDING PLASTIC MATERIALS
Filed Oct. 16, 1934
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¿cette
Patented Nov. 17, 1936
PATENT OFFICE
UNITED STATES
2,081,042
MACHINE FOR EXTRUDING PLASTIC
MATERIALS
Frederic A. Parkhurst, Bethesda, Md., assigner to`
The Fibel-leid Corporation, Indian Orchard,
Mass., a corporation of Massachusetts
A Application october 1s, 193'4, serial No. '148,459
3 Claims.
This‘invention relates to apparatus for form
ing a. web or sheet by extruding plastic material,
such as a cellulose ester, under heavy pressure
through a slot orifice having a length and width
5 corresponding substantially to the desired width
and thickness of the sheet to be formed.
Heretoi'ore, the commercially successful appa
ratus for the extrusion of plastic material under
heavy pressure to form a web or sheet has been
10 one having a circular orifice adapted to extrude
the plastic material in the form of a tube which
had to be slit subsequently to form a web or
sheet. Attemptstë Aform a web or sheet, here
tofore, by extrusion through a straight slot die
15 have failed because of lack of uniformity in _thick
ness of the sheet formed, particularly transverse
ly of the sheet.
y
'
'
The invention will be moreclearly understood
from the following description in conjunction
with the accompanying dra'wing inwhich.
Fig. 1 is an end elevational view, partly in sec
tion taken upon the line'I--~I of Fig. 2, of an
,
Fig. 2 is a' longitudinal sectional elevational
view of the apparatus. 1
30
I5 and surrounded by ducts or passages 2I in lI5
which a temperature controlling fluid is circu
lated. The end ofthe casing I1 adjacent the
casing IE is provided with a recess to receive and
hold an obstruction, such a's a partition or Bridge .
22 having a plurality of apertures'23, adapted 10
to extend across the passages I5 and _20 at. their
point of communication. ‘ If desired, a screen 2l
may also be interposed between the bridge 22
and the casing III.
A plate or die lip 25 having .- -
a slot orifice 26 adapted to register with the pas- 15
sage 20 is secured upon the casingy I1 by a plu
ings 28 in the plate 25. A plurality of adjust
2.0 iice which is so constructed as to overcome the
apparatus embodying the invention; and ,
registering with the adjacent elongated'passage y,
rality of bolts 21 passing through enlarged open
'
It is an object of the present invention to pro
vide an apparatus having a straight or slot ori
above mentioned diñlculties.
ably secured to the other end of the casing I0
by bolts I8 and I9 and is provided with a pas
sage 2II having- an inlet end of elongated shape
'
Before explaining in detail the present inven
tion it is to be understood that the invention is
v*not limited in its application to the details of
construction- and arrangement of parts illustrated
in the accompanying drawing, since the invention
is capable of other embodiments and of being
ing screws 20 are mounted in thev casing I1 so
as to engage and adjustably position the plate or
die lip 25. Each of the screws 30 is provided with
a lock nut Il for locking it in its adjusted po
sition. Thus, it will be noted that the passages
the
I5 and
extrusion
2Ii provide
pressa and
continuous
the orifice
passage
26, the
between
width 25
and depth of which gradually increases and de
creases respectively so as to progressively ap
proach that of the oriiice.
'i `
The passage I5 adjacent the feed screw Il is _
of circular shapefand gradually changes to a long 30
narrow and horizontal opening adjacent the cas
ing I1 and the bridge 22, so as to conform in
shape with the elongated inlet opening of the
passage 20. While the area of the circular inlet
opening of the passage I5 is substantially the v35
practiced or carried out in various ways.~ Also 5 same as the elongated end of this passage, the
it is to be understood that the phraseology or width of the elongated opening is more than twice
l tei-ninology employed herein is for the purpose as long as the diameter of the circular inlet while
vof description and not of limitation, and it is the depth of the elongated opening is only about
one third offthis diameter. Thus, a large cylin40 not intended to linut the invention claimed here
drical mass of material may be transferred to a
in beyond the requirements of the prior art.
An apparatus embodying the invention, as thinner elongated horizontal cross-section prep
illustrated in the accompanying drawing, com ‘ aratory to further reduction of> the area of the
prises a casing I0 which is suitably secured to mass of material as the stock is conveyed to the
passage 20 where it is further reduced in thick45 the end of a source of supply shown herein as
an extrusion press II by bolts I2. The extrusion ness until it issues through the discharge 26 in
the form of the thin web W. The bridge 22 is
press II is of the usual construction and is pro
vided with a substantially cylindrical passage Il of oblong shape and is provided‘with a sufiicient
in which a feed screw I4 is rotatably movable for number of openings 23 so that the total area of
50 feeding the plastic stock through the press. The these openings will be about one third of the inicasing I0 is provided with a passage- I5 which tial or inlet opening of the passage I5 adjacent
`the screw I4. Similarly, the inlet opening of the
communicates with the passage I3 of the ex
passage 20' which is a continuation of the elon
trusion press and is surrounded by ducts or pas
sages I6 in which a temperature controlling fluid, gated discharge opening of the passage I5, grad
ually increases in width and decreases in depth
5 such as water, is circulated. A casing I1 is suit
40
45
50
56
2
2,061,042
or thickness as it approaches the lip 25. As the
film of stock passes through the lip 25, it is re
duced to the desired thickness of the web W which
may vary in accordance with the class or kind
of material required. As the stock passes through
the chamber i5, its flow is retarded due to the
restriction of the openings 23 in the bridge 22.
During the travel of the material through the
passage 20, it is thinned down and brought to uni
10 form temperature preparatory to its flnal extru
sion through the oriilce 26 in the lip 25.
In the operation of the apparatus any desired
plastic material, such as a cellulose ester, is fed
under heavy pressure by the screw conveyor il
through the passage I5 and the apertures 23 in
the obstruction 22 into and through the passage
20 and is extruded through the slot orifice 26
in the form of a. continuous sheet or web W. The
obstruction 22 tends to increase the resistance
to the passage of the plastic material and, con
sequently, the pressure of the plastic material
near the obstruction on the side thereof adjacent
the extrusion press tends to build up and be con
siderably greater than the pressure of the plas
25 tic material between the obstruction and the ori
fice 26. This increase in pressure of the plastic
material in this region causes the plastic mate
rial to be spread out under uniform pressure
across the passage 20 and into and through the
30 orifice 26 thus assuring uniformity in the thick
ness of the web W.
The source of pressure of the material for rea
sons which need not be explained fluctuates sub
stantially. If this fluctuation in pressure pro
duced corresponding fluctuation at the orifice, ex
cessive Variations in gauge would result. The
bridge or obstruction 22 is a baille or construc
tion beyond which there is a sudden drop in pressure. The space I5 before the obstruction is
reached forms a sort of pressure reservoir in
the whole of which the pressure is more or less
uniform, the fluctuations being somewhat dis
tributed through a large mass of material.
Be
yond the obstruction 22, i. e. in` the space 2li,
there is only a relatively small mass of material
and the pressure is much lower, perhaps half
that in the space I5, and accordingly the fluctua
tions in the space 20 are correspondingly dimin
ished.
50
I claim:
1. In lan apparatus for forming a web from
plastic material, a casing providing a passage for
the plastic material having an inlet opening of
substantially circular shape and terminating in
an elongated straight discharge oriilce, means
adjacent the inlet opening for feeding plastic
material through said passage under high pres
sure, the diameter of said inlet opening being less
than the width of said discharge orifice, and
a perforated pressure-distributing baille within
said passage and remote from the inlet opening
and feeding means so as to form a chamber be
tween the end of the feeding means and the pres
sure distributing baille, said baille serving to in
crease the resistance to the flow of the material 10
through the passage so as to cause the pressure
of the material to be greater on the inlet side of
the passage than on the outlet side thereof, the
width of said passage gradually increasing and
its depth gradually decreasing so as to approach 15
that of said discharge orifice, said passage be
tween the orifice and the inlet opening being un
obstructed except by said perforated baille and
the passage at the orifice side of the baille con
stituting an uninterrupted pressure reservoir 20
whereby when the material issues from the per
forated baille any fluctuations in pressure are
substantially reduced and the material is uni
formly distributed across the passage and at the
discharge orifice to form an elongated thin sheet
of uniform thickness.
.
2. In an apparatus for forming a web from
plastic material, means for feeding the plastic
material under pressure, a casing providing a
passage from the feeding means and terminat 30
ing in a slot orifice, pressure-distributing means
in said passage spaced substantially from said
feeding means so as to form a chamber between
the end of the feeding means and the pressure
distributing means, the width and depth of said 35
passage progressively approaching that of said
orifice from said feeding means to said orifice,
and said passage from said feeding means to the
oriñce being unobstructed except by said pres
sure-distributing means.
3. Inlan apparatus for forming- a web from
plastic 'material, a casing providing a passage
for the plastic material terminating in a slot ori
flce, means for feeding plastic material through
said passage under high pressure, and a per
45
forated pressure-distributing baille in said pas
sage spaced substantially from said feeding means
so as to form a chamb'er between the end of the
feeding means and the pressure distributing
means, the width of said passage progressively 50
increasing and the depth decreasing so as to ap
proach that of said orifice and said passage from
said feeding means to the orifice being unob
structed except by said perforated baille.
55
FREDERIC A. PARKHURST.
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