Note: Descriptions are shown in the official language in which they were submitted.
214~237
Title: "EX~RUSION DIE AND ME3[HOD OF CON~OLLING FLOW THROUGH THE DIE"
D~
This invention relates generally as indicated to an extrusion die and also to
a method of controlling flow through the die, which flow in turn affects the shape or
profile of the item being extruded.
B~ ~IN~ OF ~F Tl~vF~N
In the extrusion process a plastic or resin melt is formed under heat and pressure.
l~e melt is usually formed continuously by a rotating screw in a barrel which converts
solid pellets of the resin or plastic into the flowable melt. A wide variety of additions may
be i~ ,old~d into the melt such as extenders or blowing agents for foam products. The
nozzle of the extruder is of necessity restricted to eate the required high pressure. From
the nozzle the melt flows through a pipe into the die which usually includes a plenum
chamber PYr:~nr~in~ to the width of the die opening. The relatively wide die opening may
have adjustable die lips as in a sheet, film or board die, or it may have a series of equal
circular fixed openings as in a strand die. The dies themselves are heated or cooled and
may have straight, circular, or arcuate die openings. Moreover, the die openings may not
be uniforrn across the die lips. One such die, known as a bow-tie die, is illustrated in US
Patent 4,364,722. Other such dies are illustrated in prior US patents 3,871,812 and
4,201,534.
One of the major problems in extrusion is to achieve complete ho,l,og~ y of the
melt. This is difficult to do, particularly with regard to ~ .,Id~UI~ hOm~lgl"tU'ity,
T~ C~d~UI~, of course, affects viscosity. Even if uniform viscosity is achieved at some
point in the process, it may be lost before the extrudate exits the die lips. The lower the
viscosity, the faster the flow rate, and the more difficult it is to control volume
u~ u~ and the shape or profile of the product being formed. The problem is
.,1 by the .~,..L~u~ ioll of the die. The flow path for the extrudate is not in
25 every instance identical. For example, with fan-shape or coat hanger dies having arcuate
adjustable die lips such as shown in the noted prior patents, it has been found that higher
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viscosity or flow is usually ~ 1 at the center of the die with the die lips in an
adjusted position. This, of course, makes the product such as a foam board, bulge in the
middle. To remedy this situation, the die lips need to be readjusted to be brought closer
together at the center and spread further at the lateral ends or edges. This must be done
5 with multiple ~j .~l... .l~ which are made even more difficult by the fact that the die
may be inside a Yacuum chamber. Since tbe die lip ~lj.. ~ .. l is plel~ l~ly a vernier dial
or fine ~ ......... l, it takes longer to achieve, resulting in more out of tolerance product
and removal of the die lips from an ideal setting for a giYen product. It would be
preferable if the excess Lllluu~ u~ at the center of the die could be corrected
10 ~y~ l;~lly by a gross ~ lC~m.ont without moving the die lips from an ideal setting for
a given product.
In some relatively wide dies internal choker bars have been employed to achieve
some form of ~.1j.. ~l.. 1 apart from the die lips. These bars are somewhat flexible or
dl~vl~lc and are usually supported by a plurality of ~ lju~ l screws. By
15 ~ l :.... of the screws the profile of a window or opening within, the die may be
controlled. Each screw has to be eYtended locally to restrict the opening or retracted
locally to enlarge the opening. Without very expensive drives or controls, it is ~ r
to shift an e~ lb lll.llL or restridion in the window laterally of the extrudate path and
s~ : lI y maintain the cross sectional area of the window. This is especially true if the
20enlargement or restriction is to be divided and moved ~... - l. ;. ~lly from the center to
the ends or edges, or vice versa.
Also, a common form of flow control is to machine a diversion delta or control
into a plenum of a die body or part, and then replace that body or part when thepal~ la change. Die changes in a large extrusion line are, needless to say, costly. It
25 would ~...u 1;lll51y be desirable to duplicate numerous types of die plenums with a simple
~rljllctm~nt
It is also desirable to have a simple gross ,-lj~,.l .... l within the die, apart from the
die lips, which will form an enlargement in a window within the die and enable that
e.~ to be moved Ll~ cly of the flow path for the eYtrudate along the die
30 lips, whether from one end to the other, or preferably, ~llull~LI;~.~lly from the center to
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' . ~
the edges and vice versa. It would also be desirable that such gross - ~; be made
quickly and cc.~ ly from a single point or power source. It is also desirable that the
ability to make such ~ be ~--- ",~ ,r~1 without sharp profile or ~i~nifir~n~
pressure drops within the die, which in a foam process may result in ~ICIIId~UIC foaming
5 within the die.
S1'MMARY OF THE INVENnON
An extrusion die and flow control method il~C~.IJUld~ a flow control in the formof a flow diverter which extends ~ldi~a~la~ly across the flow path. The diverter forms
part of a window upstream of the die lips and provides a slight tapering ~llldl~10 which may be moved along the window across the flow path from one side to the other
or preferably, from the center a~...lll.ll l~lly outwardly, or vice versa, to divert flow from
the center proportionally to the edges without changing the total cross sectional area of
the window. The window is formed by at least one axially rotatable cylindrical bar
recessed in the die body which has a flat forming the c.~ld.~,_.,._.,~. In the preferred form
15 the flat is helical. Movement of the .IIIdl~,_lll.l,~ across the flow path is obtained by axial
rotation of the bar.
In the preferred form two opposed parallel bars are provided forming the long ortransverse edges of the window which may nûrmally be rather wide an~ narrow. Thewidth may correspond to the width of the die lip opening, or be ~IIIIII~ dl therewith
2û about the machine direction or extrusion axis. The helical flats are opposed or matched
so that as the bars contra-rotate ayll~ unuualy the l ~ will move across the
window. Where the ~UV~ is ay~u~ ; dl from the center or axis to each transverse
edge and vice versa, the helical matching flats on each bar have a turn or twist in opposite
directions on each end of the middle of each bar. Where the C~lldl~;.l...ll~ simply moves
25 from one transverse end of the window to the other the turn of the helix of each flat is
the same from end to end of the bar, although for each of the pair, in the opposite
direction.
The helical flats have a relatively small helix angle so that the ~llldl~,_ll,.ll~ moves
its entire extent along the window upon relatively little of rotation of the bar. The
3û circular bars are recessed within the die body in circular slots to pro~ect only slightly into
27 ~3~
. -- .
the plenum of the die. Each bar may also be provided with a linear flat which forms a
Iinear c~-ntinl.~t;on of the plenum in one rotational position of the bar. The bar then is
effectively recessed from the plenum. Each bar may be axially hollow to accommodate
an electrical heater to facilitate rotation and not adversely affect viscosity. A plurality of
pairs of bars may be positioned in tandem in the plenum to be used concurrently or
separately as a gross flow control in the die. The tandem pairs may be used separately or
in conj~nrtion with each other to obtain a variety of controls. Especially useful with the
tandem ~ gC.l~ are bars with inclined flats.
To the ~ccOlll~l;al~ of the foregoing and related ends the invention, then,
comprises the features hereinafter fully described and particularly pointed out in the
claims, the following description and the annexed drawings seKing forth in detail certain
illustrative embodiments of the invention, these being indicative, however, of but a few
of the various ways in which the principles of the invention may be employed.
BR~EP DEsc~PTIoN OF lHE DRAWINGS
In said annexed drawings:
Figure 1 is a top plan view partially broken away and in section of a die in
.~oldal~cc with the present invention;
Figure 2 is a vertical section of the die of Figure 1 taken on the lines 2-2 of Figure
l;
Figure 3 is a somewhat enlarged side elevation of the flow control drive at one side
of the die;
Figure 4 is a s~ction ~ of the single drive point as seen from the line 4-4
of Figure 3;
Figure S is a side elevation of one of the rotatable flow control bars of the die
illustrated in Figures 1 and 2;
Figure 6 is an end view of the bar seen from the right hand end of Figure 5;
Figure 7 is a top plan view of the bar of Figure 5 seen from the top thereof;
Figure 8 is an end view of the bar of Figure 7 seen from the right hand end
thereof;
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' ~.
Figure 9 is an elevation of a pair of bars such as shown in Figures s and 7 forming
the transverse edges of the window and showing the ~ in the center of the
window;
Figure 10 is a top plan view of a die similar to that shown in Pigure 1, but
5 illustrating three sets of flow control bars in the die;
Figure 11 is a view similar to Figure 2, but taken on the lines 11-11 of Figure 10
illustrating such tandem - ~- h' "'"~;
Figure 12 is a side elevation of another form of bar;
Figure 13 is a top plan view of the bar of Figure 12;
Figure 14 is a view simi~ar to Figure 9, but illustrates a pair of bars such as shown
in Figures 12 and 13 forming the transverse edges of the window;
Figures 15 through 18 are schematic sequential views foreshortened and somewhat
CA~ d~ld illustrating various rotational positions of the bar set seen in Figure 9
plUgl~ lllg from the bars in a retracted position to the cnl..l~ t in the center, to the
clll.. l~;~.ll.l.L moving ~.. - l. ;- -11y to the ends, and finally at the ends;
Figures 19-22 are schematic sequential views rul~allûl L~ d and somewhat
~A ~,gc..-Lt:d illustrating various rotational positions of the bar set seen in Figure 14
pl~ >;llg from the bars in a retracted position, to the cnl.~ at one end, the
~nl~rgem,nt in the middle, and finally at the opposite end;
Figures 23 and 24 are similar schematic views of a set of bars having a linear flat
on one side and parabolic or axially inclined flats on the other, the bars of figure 24 being
contra-rotated from the position of Figure 23;
Figures 25 and 26 are sirnilar schematics of the similar two positions of a bar set
having parabolic flats but axially inclined in the opposite direction; and
Figure 27 is a some what top plan view of one of the bars of the set of Figure 26
as seen from the line 27-27 thereof.
DErAILED Dr~ v~ OF ~ ~I~ EMsQD~
Referring initially to Figures 1 and 2, there is illustrated an extrusion die shown
generally at 30. The die comprises an upper die body 31 and a lower die body 32, which
30 parts are clamped between upper retainer 33 and lower retainer 34. It will be ~pl~ cd
.
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. ~
that the clamp fasteners and various oil heating passages which extend through the die
body parts are not illustrated. The upper and lower die bodies form a sizable inlet
indicated at 36 which extends into a coat hanger-shaped plenum indicated generally at 37.
The plenum is closed at the transverse edges by end caps 39 and 40. The plenum also has
5 horizontal top and bottom walls indicated at 42 and 43 which between the end caps
provides a relatively wide and vertically narrow chamber for the plenum. The chamber
is elongated in the horizontal or transverse direction, sometimes referred to as the Y axis.
The chamber is relatively narrow in the vertical or Z axis direction. The machine
direction or machine aYis is sometimes referred to as the extrusion axis or the X axis. The
10 chamber 37 v - -~ ` with a similar chamber between the upper die lip 45 and the
lower die lip 46. The flexible die lips 45 and 46 are mounted to the front of the die body
parts 31 and 32 by the fasteners indicated at 48. Further detail of the construction and
mounting of the die lips may be seen in the noted prior US Patent 4,364,722.
As seen, the upper and lower retainers project beyond the die body parts to extend
15 above and below the die lips 45 and 46, ~ .Li~.ly. The front edge of the upper and
lower retainers is arcuate as indicated at 50, as is the front edge of the die lips. The
;d forward extensions of the die retainers each support three die ~
the upper ~ being seen at 53, 54, and 55. The P ~j- ~l - .1~ are obtained by
hollow externally geared nuts threaded in the retainers as seen at 57. The nuts bear on
20 adjusting bolts 58 which are threaded within spherical adjusting nuts 59 secured by the
spherical washer assembly illustrated in the die lip. The rotation of the nuts from a
remote location may be used to bring the die lips closer together, when tightened, or
further apart when loosened with the pressure of the melt separating the flexible die lips.
Referencemaybehadtopriorpatents4,211,739and4,234,529forthe.l1vil~,lllllcllL
25 of a foam board die as one of a number of applications in which the present inYention
may be utilized. As indicated, the ~ l.". t of the die lips is rather complex having a
least six ~ points, three at the top and bottom, although additional ~ C~mPrlt
points may be provided. The adjustment of the die lips for a given product parameter is
designed to control the flow through the die lips which in turn controls the shape or
profile of the product. Because of the problem of C~ g excess ~ u~ u~ or flow
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. ~
in the center of the die lip opening, there is provided a gross flow ~1; ,l.. ~ shown
generally at 62. The gross - ~; comprises circular cylindrical bars 63 and 64
mounted in circular cylindrical recesses 65 and 66 in the upper and lower die bodies 31
and 32, rc.~..Li~ .Iy. As illl-str It~, the circle of thc cylindrical bars projects only slightly
5 into the plenum. The cylindrical bars form the parallel long dillllsiolls of a relatively
narrow rectangular window which extends Ll ~li7~ .ely of the machine direction. In the
die illllctr~t.-,i the window has the same width as the transverse width of the die opening.
The window should, at least, b~ ~IIllll~L~i~l with the die opening about the machine axis.
As indicated in Figure 9, each bar 63 and 64 has a reduced diameter projection on
one end as seen at 70 and 71~ Ic.~ L;~cly. As seen in Figure 3, the projections are keyed
to helical gears 73 and 74, ~c.~..L~.ly, mounted on outside of end cap 40. The gears are
driven by respective right and left-hand worms 73 and 74 mounted on shaft 75. Rotation
of the shaft 75 will drive the gears and thus the cylindrical bars in opposite directions of
rotation. The shaft 75 is mounted in bushing 76 and 77 secured by respective brackets
78 and 79 to the exterior of the end cap 40. The motor drive for the shaft 75 may be
located remotely from the die. The shaft and motor constitute a single point ~lju5tm.ont
for the cylindrical bars.
Referring again to Figure 9~ it will be rloted that each cylindrical bar 63 and 64 has
a hollow or open interior seen at 82 and 83, I~ . ly, which opens at the ends 84 and
85 opposite the drive 70 and 71. Electrical heaters may b~ positioned inside
the hollow interior of each cylindrical bar and the electrical connection 86 for such heaters
is seen in Figure 1 on the exterior of the end cap 39.
The bars 63 and 64 are a mirror image of each other and only the bar 64 is
described in detail as illustrated in Figures 5-8. When COlllp~iillg Figures 5 and 7, it is
important to note that the top plan view of Figure 7 is as though the bar of Figure 5 has
been rotated 90 about its axis with the top moving toward the viewer. In ~ lg
Figures 6 and 8, the bar itself has rotated 90 in a counter clockwise direction from Figure
6 to Figure 8.
It will be seen that the bar has two flats which extend from end to end. One flat
shown at 88 in Figures 6 and 8 is linear and does not axially twist. In one position of
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. ~.
rotation of the bar the nat can be aligned with the surface of the plenum 37 so that no
portion of the bar projects into the plenum.
The other flat is indicated at 90 has a turn or twist in one direction to the
midpoint 92 of the bar and then turns or twists in the opposite direction. The flat is, of
5 course, ~y~.LIl..l.;~l with respect to the midpoint of the bar and each end of the nat has
a very low but opposite helix angle. The oppositely twisting ends of the flat on each side
of the midpoint are shown at 93 and 94.
The flat 90 in its illustr~ted co..rig,~ n~ then provides a profile deviation in the
form of a depression shown generally at 95. The depression in the profile along the top
10 of Figure 5 can thus be seen by viewing the top edge of the bar from the right or left-
hand side of the sheet. The depression has its deepest point at the center 96 and extends
from the point 97 on the left-hand side of the view to the point 98 on the right-hand side.
When the bar has been rotated 90 with the top moving toward the viewer as seen in
Figure 7, the depression has d;~ d from the edge. The depression is a very gradual
15 tapering depression formed by the helix of the flat. As an example, the bar may be
L~ L~ly 1.125 inches in diameter while the flat 90 is 0.10 inches deep.
When the two bars 63 and 64 are positioned as seen in Figure 9 to form the
window 100 th.~ ll, the helical flats 90 of each bar will form an e~ l...l.L in
that window as seen at 102. The ~l ' b` ~ 1 102 is then centered and ~ ic. l with
20 the machine axis which runs through the center of the die.
Referring now ~ ition~lly to Figures 15-18, it will be seen that by contra-rotating
the bars, in the direction of the arrows indicated in Figures 16, 17 and 18, theenlargement is divided equally and moYed to the outer ~ of the window. In
Figure 15, the linear flats 88 are opposite each other and flush with the wall of the
25 plenum so that the bar does not project at all into the plenum. In Figure 16, the bars
have been rotated to form the .l~la~ 102 in the center of the window on the
machine axis. Continued rotation of the bars in the directions of the arrows 104 and 105
causes the enlargement in the window 100 to divide into the two enl.,L~;.l...l.L~ seen at 106
and 107. Continued rotation in the direction of the arrows 104 and 105 causes the
enl.. l~;.l.. L.~ to move to the .,.L-~I~,L~ of the transverse window 100 as seen at 108 and
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109 in Figure 18. ~ontinllr-l rotation in the opposite directions as shown will cause the
~nlqrg~-nn--nt to disappear altogether. It is noted in moving from the Figure 16 to the
Figure 18 position, where the opposed helical flats have gone from the center to the edges
of the window, the bars have only rotated only 68. A..o~ ly, by rotating the bars
5 through a rdatively small arc, the cl~ .l....lL moves from the center to the c,.LlcllPl~i.s
in the window uniformly and ~y- . l. . -lly.
Referring now to Figures 10 and 11, there is illustrated a die assembly 120 which
is in most respects identical to the die assembly 30 seen in Figures 1 and 2. The upper
and low die bodies 122 and 123 have been somewhat elongated as have the upper and
lower retainers 124 and 125, to form a plenum 126 which is elongated in the machine
direction or X axis. The end caps 128 and 129 are also somewhat elongated.
The reason for the elongation of the plenum 126 is to provide tandem flow control
bar sets as seen generally at 130, 131 and 132. The bar sets are mounted for contra-
rotation in the identical manner as the flow control described above. Each bar of each
15 set has a linear flat enabling the bar to be positioned to be flush with the plenum surface.
Also, each bar may have a different ~ullrih.~ ion of flat or flats to enable the bar sets to
be operated in conjunction with each other or individually to obtain a variety of flow
control characteristics.
Referring now to Figures 12,13,14 and 19-22, there is illustrated another form of
20 bar with a helical flat and the pairing of bars with a mirror image of the Dat in order to
form a flow control where the ~lllal~,.lll.ll~ in the window may be moved from one end
of the window to the other, but not to both and ~Il.. L.;c.,lly.
Referring initially to Figure 14, it will be seen that the opposed bars 140 and 142
form a window 144 th.. b.~.. Each bar is provided with a helical flat as seen at 145
25 and 146, I~i,,u..~;vcly. The helix of each flat has the same low helix angle as in the Figure
7 . ..l o-li...- .l, but instead of changing its direction of twist or turn, at the center or
midpoint of the bar, the helix angle continues from one end to the other of the bar. As
seen in Figure 12, the flat 145 forms a depression 148 in the profile ~yllllll-~ lly to each
side of the center of the depression. The depression extends from the center 149 to the
ends 150 or 151. A~ain by rotating the bar the profile depression will move from one end
21 ~237
' ~.
to the other of the edge of the bar. When the opposed bars with the mirror image flats
145 and 146 are positioned to form the long edges of the window 144, and in the position
illustrated an ~ ;c~ 153 is formed in the center of the window. With the bar andflat dimensions the same, the window 153 is identical in ~ .r;~ol..Lion to the window 102
seen in Figure 9. However, when the bars 140 and 142 are contra-rotated synchronously,
the e.iL..~ will move across the window, but not divide and move symmetrically.
A..ol.l;ll~ly, the enlargement 153 may be placed in the center or anywhere along the
length of the window.
Because of the reversal of the turn at the midpoint of the bar of the flats of the
10 Figure 9 embodiment, the total arc of the circle of the cylindrical bar taken up by the flat
is only 68. Because the helix continues in the Figure 14 ~-mho~lim~ n~ the total arc taken
up by the helical flat is twice that or 136. Thus the bars 140 and 142 need only be
rotated 136 to move the enlargement from one end or extreme of the window to the
other. In the embodiment of Figure 14, the angle of ~ is still less than 180
15 while the angle of 3-~ju~ in the Figure 9 ~ l-o~ is less than 90, and well less
than 75. In both helical flat .. l.o.l;.. l~ illustrated the helix angle is slightly less than
5, and it is preferred to be less than 10.
The bars 140 and 142 are also provided with a linear flat opposite the helical flat.
Again, the linear flat is designed to bring the surface of the bar flush with the wall of the
plenum. Such linear flats are illustrated at 155 and 156 in Figure 19. In such Figure the
flow control bars are effectively retracted. However, contra-rotation of the bars as
indicated by the arrows 158 and 159, will cause the ~ 153 to appear first at oneend of the window as indicated in Figure 20. Continued rotation in the direction of the
arrows causes the window ~ L to move to the center as seen in Figure 21 and
finally to the opposite end as seen in Figure 22.
In Figures 23 and 24 there is illustrated another embodiment of the invention. The
bar set indicated at 160 and 161 is provided with opposed linear flats 162 and 163 in
Figure 23. Offset from the linear flats are axially inclined flats seen at 164 and 165 for
the bar 160, and 166 and 167 for the bar 161. When the bars are contra-rotated in the
direction of the arrows 168 and 169, they will form an enlargement 170 in the window
2~44237
172. The flats 164 through 167 are axially inclined so that they are closest to the axes of
the respective bars at the midpoints thereof. In the ~ -o~ of Figures 23 and 24,the window 170 may be made to gradually appear and disappear and cannot be shifted
~ldll,v.la,ly across the window.
In the cl.lbo~;lll.ut of Figures 25, 26 and 27, the bars 180 and 181 forming thewindow have linear flats 182 and 183 as seen in Figure 25. Offset from those flats are
inclined flats 184 and 185 for the bar 180, and 186 and 187 for the bar 181. Unlike the
flats illustrated in Figure 24, the flats of the, ~ - ' of Figure 26 are closest to the
axis of the respective bar at the ends thereof. Such flats form the parabolic ~ ld~ion
seen in Figure 27
By contra-rotating the bars in the directions of the arrows 188 and 189,
les~c.~ivcly, e~ .gcll...l~a 192 and 193 may be formed at each transverse end of the
window 194. By contra-rotating the bars the enl ~ may be made gradually to
appear and disappear. Again, they cannot be moved I~ tllw;ae of the window. However,
15 by using the bar sets illustrated in the ~..lbod of Figures 24 and 26 in the tandem
d~.dil~C.ll..l~ of Figure 11, and by operating the bar sets in conjl-nrtirn with each other,
it will be seen that an enlargement in the center of the window may be convertcd to
a~llull~ dl enldl~;..ll..l~ at each end of the window. It will be d~Jpl~;d~d that any of
the various bar set flat ~ullf~;uld~i~nls illustrated and described may be used in the tandem
20 or single bar set .~ g....l In the tandem ...~ , the bar sets may be used
individually or in conjunction with each other to control the aOw of melt through the
die.
It can now be seen that there is proYided an extrusion die which forms a
rectangular window having an enlargement therein along the long side of the window,
25 and by ddjlla~lll -.t, that ~ may be moved uniformly across the flow path of the
eYtrudate. The method of the present invention provides upstream of the die lip or
opening a flow path window ayllull~l;~l with the die opening, and providing an
C.ll~.~,~.ll..l~ in the window, the position of which is then adjusted to control the flow
through the die lip.
Il
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' .~,
With the present invention, there is achieved and ~ r~l the desired product
profile without die changes or complex set up time or trial and error costs.
Although the invention has been shown and described with respect to certain
preferred ~ .o~ , it is obvious that equivalent alterations and modifications will
5 occur to others skilled in the art upon the reading and und..aL~ g of this sp~rifir~ti~ln.
The present invention includes all such equivalent alterations and mr.~lifir~tirln~, and is
litt~it~d OAIy b~ dhe scope ~f the ClAittt .
