Note: Descriptions are shown in the official language in which they were submitted.
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EXTRUSION METHOD AND APPARATUS THEREFOR
FIELD OF THE INVENTION
This invention relates to an extrusion method and apparatus
therefor.
BACKGROUND OF THE INVENTION
Extrusion lines for producing extruded thermoplastic products
formed by forcing heated thermoplastic material through a die and then
calibrating same to produce a product stream having a desired cross sectional
shape and size or profile require the employment of equipment requiring a
very substantial outlay of capital.
Each extrusion line requires the use of an extruding machine or
extruder to force the heated plastic through the requisite die, a series of
vacuum operated profile sizers or calibrators for finally forming and cooling
the product stream so that it has precisely the profile desired, a puller
mech~ni~m to pull the product stream through the calibrators, a cutoff or saw
mech~ni~m to cut off a~propliate lengths of the product, and a receiving table
to receive the cut product lengths.
Each such extruder line occupies a substantial area of plant floor
2 5 space and requires its own utilities and operator.
Extrusion manufactures usually extrude products having a range of
sizes from small profile products having a small volume of material per foot,
to large profile products having a substantial volume of material per foot.
The smaller profile products are conventionally produced on
extrusion lines having smaller capacity extruders while the large profile
products require extrusion lines with extruders of much higher capacity.
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The smaller capacity extruders which having a somewhat lower
cost than the high capacity extruders are not capable of delivering a sufficientvolume of heated material at a sufficient pressure to render them practical to
produce the large profiles. On the other hand, it is not practical to take
5 advantage of the capacity of the large capacity extruders to produce the
~m~ller profiles since if they were operated at capacity they would have to
deliver a product stream at such high velocity that it would be impractical to
properly calibrate same and obtain a precision profile.
As a result, at present, the production of small and large extrusion
profiles has required a proliferation of extrusion lines occupying a large plantfloor area with each line requiring its own operator and service utilities such
as electrical power and cooling water lines.
BREF DESCRIPTION OF THE INVENTION
The present invention resides in a method and a~p~atus whereby a
high capacity extruder can be operated efficiently to not only produce
2 o precision small profiles as well as precision large profiles but will produce
such small profiles at an output rate substantially matching the output of at
least two separate small capacity extruder lines thereby reducing or
elimin~ting the need of multiple extrusion lines to provide important cost
savings in plant space and utility and manpower costs.
More particularly, the invention resides in dividing the output flow
of an extruder into separate stream flows, delivering each stream through a
profile forming die to produce a profiled stream ,and individually pulling
each profiled stream through its associated calibrators at a speed so that the
30 profiled stream emerging or exiting from its profile forming die is pulled
away thererlolll at the same speed with which it emerges.
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BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of the front portion of an extrusion
line embodying the invention;
Figure 2 is a perspective view of the end portion of the extrusion
line of Figure l;
Figure 3 is a broken away perspective view illustrating a flow
10 divider assembly attached to the output of the extruder;
Figure 4 is a horizontal cross-sectional view of the flow divider of
Figure 3 and showing it feeding separate die assemblies;
Figure 5 is a front elevational view of typical profile forming dies
for forming typical profiled products which can be extruded simlllt~neously
according to the invention;
Figure 6 a broken away perspective view illustrating the profiled
2 o product streams being pulled through the system by independent pullers;
Figure 7 is a schematic perspective view illustrating the
independent drive of the separate pullers;
2 5 Figure 8 is a broken away perspective view illustrating the
independent saws for cutting off the desired lengths of the separate
simultaneously produced profiled product streams;
Figure 9 is a perspective view of an alternative form of flow
3 o divider having provision for selectively closing off one or other of the
divergent branch leg portions of the flow dividing Y passage;
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Figure 10 is a diagr~mm~tic horizontal cross sectional view
showing the shutter member in its middle position with both divergent
branches of the Y passage open;
Figure 11 is a view similar to Figure 10 but showing the shutter
bar moved to block off the right hand branch of the Y passage while the left
hand branch is fully open;
Figure 12 is a view similar to Figure 11 but showing the shutter
bar moved to block off the left hand branch of the Y passage while the right
hand branch is fully open;
Figure 13 is a broken away perspective view of the use of the
parallel pullers pulling a large profiled product stream through the system
when the flow divider is removed and the extruder feeds a single die of a
large proffle requiring the extruder to be operated at full capacity.
Extruders for extruding heated thermoplastic material through a
2 o profile forming die to produce a thermoplastic product stream having a
predetermined cross sectional configuration or profile are available with
different capacities. The capacity of an extruder in measured in terms of the
quantity of thermoplastic material it can deliver at extrusion pressures per
unit of time.
Extruders normally, in addition to heating the thermoplastic
material to an appr~liate temperature normally of the order of 170 to 180
C for flowing through the extrusion die, employ a feed screw to deliver the
heated material to the die under extruding pressure and at a feed rate
3 o dependent upon the speed of rotation of the feed screw operated by a variable
speed drive.
For an example, extruders capable of delivering from about 200 to
300 kilogr~ms or from about S00 to 700 pounds of heated thermoplastic
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material per hour and at an extrusion pressure of the order of about 3,000 to
S,000 pounds per square inch would be considered in the higher capacity
extruder range for profiles.
If an extruder with a capacity of 600 pounds per hour were used at
capacity to produce a proffled product having a weight of one pound per foot,
then the product would be produced in a stream flow of lO feet per minute.
A proffled product having a weight of one-half pound per foot would be
produced at a stream flow of 20 feet per minute.
The product stream exiting from the proffle die is relatively soft
and does not have the proffle precision required in the ffnal product being
usually about l to l l/2% bigger than the ffnal proffle. This rough profile
stream then is required to be pulled through sizers or calibrators having the
applopliate internal conffgurations corresponding to the profile die where the
stream is subjected to vacuum to pull same forcefully against the calibrator's
walls while at the same time it is subject to the cooling effect of water being
circulated within the calibrators so that the product exiting thererloll~ has a
precise and accurate profile.
If the product stream from the forming die exits or emerges too
fast because the extruder is operating at or near capacity, the speed at which
the product stream must be pulled through the calibrators will be too high to
provide the requisite cooling and sizing so that the product stream exiting the
calibrators will not have the requisite accuracy. It is then necessary to slow
down the feed of the extruder so that it is operated at a reduced capacity and
its value as a high capacity machine is lost.
In attempting to solve the problem and enable the extruder to be
3 0 used at or near full capacity for extrusion products with smaller proffles, the
output flow of the extruder was split into separate equal flow passages and the
material in these passages forced through forming dies of the same
configuration to produce two product streams of the same profile. However,
when these two streams were pulled through their calibrators, the products
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formed were unacceptable and did not have the requisite profile precision or
accuracy. Allem~ts to solve the problem by adjusting the relative heating of
the profile forming dies to alter the flow characteristics thereof were
unsuccessful.
It was finally discovered however that product streams with
precisely accurate profiles could be sim~llt~neously produced from one
extruder by pulling each product stream individually with its own puller
whose speed could be precisely controlled so that each separate product
0 stream exiting each die could be pulled through its associated calibrators at
precisely the right speed so that it was pulled away from its die at the same
rate it exited or emerged therefrom thereby elimin~tin~ all of the variable
thermoplastic flow characteristics in the divided passages, the dies, and
calibrators which it had not been previously possible to balance.
By pulling each product stream individually and adjusting the speed
of pull to accommodate the flow characteristics of the thermoplastic material
through the extrusion system of each product stream, it was found possible to
produce precision products with significantly different profiles so that
2 o profiled products having the either the same or different profiles could be
produced simultaneously.
DETALED DESCRIPTION ACCORDING TO THE PREFERRED
EMBODIMENTS OF THE PRESENT INVENTION
With reference to Figure 1, there is shown a conventional extruder
3 o 1 having a hopper 2 for inputting thermoplastic material to be heated to an
extrusion tem~rature which may be of the order of 170 to 180 C and then
delivered under high pressure. eg. of the order of 5000 p.s.i., through a
nozzle 3 to a flow divider unit generally designated at 4 which divides the
flow stream and feeds same to separate die assemblies generally design~ted at
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S and 6. As shown, separate coextruders 7 and 8 are arranged to feed into
the die assemblies 5 and 6 as desired. The coextruders 7 and 8 have feed
hoppers 9 for introducing desired coextrusion thermoplastic material which is
normally heated to a slightly lower teml?elature than the material extruded by
5 the extruder which may be of the order of 140 to 160 C and delivered at a
somewhat lower pressure, eg. of the order of 2000 p.s.i., than the material
being extruded by the extruder 1. While two coextruders are shown, it will
be understood that if each profiled product is to be coextruded with the same
m~çrial a single coextruder could be used and its output appropliately split to
lo feed into the die assemblies S and 6.
The somewhat soft and rough profiled product streams 10 and 11
emerging from the die assemblies S and 6 respectively are drawn through a
series of calibrating or sizing units to cool and precisely form same into the
15 final precisely profiled product streams.
As shown in Figure 1, the product stream 10 is drawn through a
series of calibrators or sizers 12a, 12b and 12c while the product stream 11 is
pulled through calibrators or sizers 13a, 13b and 13c.
As will be understood in the art, these sizers or calibrators 12a, 12b
and 12c and 13a, 13b and 13c have internal configurations corresponding to
the die configurations 5 and 6 respectively and operate under high vacuum to
pull the walls of the product streams against the internal walls of the
25 calibrators providing a progressive sizing and cooling of the product streams as they are pulled through the successive calibrating units.
The required vacuum to the calibrators is provided by vacuum
pumps 14 which are connected to the calibrators by lines 14' and air
30 withdrawn from the calibrators is aided in its exhausting to the atmosphere by
cyclones lS.
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As will be understood, the calibrators are water cooled to cool the
profiled product stream as it is calibrated and this cooling is provided by
waterlines 16 circulating cooling water therethrough.
The calibrated product stream emerging from calibrator 12c which
started out as a somewhat roughly profiled product stream 10 issuing from
die assembly 5 is designated as calibrated product stream lOc which now has a
precise profile. Similarly, the calibrated product stream issuing from
calibrator 13c is designated as calibrated product stre~m llc.
The product streams lOc and llc are pulled through the calibrators
by individual pullers 17 and 18 respectively.
As hereinafter more fully explained, the speeds of the pullers 17
and 18 are individually controlled to the precisely correct speeds so that
puller 17 operates to pull product stream lOc at precisely the right speed so
that the product stream 10 is pulled away from its die assembly 5 at precisely
the rate it emerges thel~rlolll. Similarly the speed of puller 18 is set so that it
pulls the profiled product stream l lc at precisely the right speed so that the
product stream 11 is pulled away from its die assembly 6 at the speed it
emerges therefr~lll.
The pullers 17 and 18 which, as will be understood, are capable of
exerting high pulling forces, eg. providing a torque of the order of 50,000 to
60,000 foot lbs., deliver the profiled product streams lOc and llc to a saw
station generally de~i~n~ted at 19 where a pair of saws 20 and 21 cut off the
proper lengths of the profiled product streams lOc and llc after they have
been delivered to a dumping table station 22.
With reference to Figures 3 and 4, the flow divider unit 4 has a
barrel portion 23 provided with a clamping flange 24 having slots 25 to
receive bolts 26 projecting from the nozzle 3 of the extruder 1. Nuts 27
applied over washers 28 engaging the bolts 26 clamp the unit 4 to the face of
the nozzle 3.
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A flange 29 is formed at the forward end of the barrel portion 23.
The flow divider 4 is bored to provide a Y passage formation generally
designated at 30.
The leg portion 31 of the Y formation is arranged to register with
the discharge outlet 32 of the extruder nozzle 3 to receive the heated
thermoplastic material delivered by the feed screw 33.
0 The divergent branch or leg passages 34 of the Y passage formation
are preferably equal in diameter and of the order of half the diameter of the
leg portion 31 whereby material forced under pressure out of the discharge
outlet 32 of the extruder is directed to divide equally between the two
divergent passages 34.
A converter block 35 fastened to the face of the flange 29 by bolts
36 is bored to provide outwardly flared passages 37 to register with the
outlets of the divergent passages 34 to convert the divergent flow through
these passages into parallel flow streams for delivery to the die assemblies S
and 6 which include adaptor blocks 38 and 39 with feed passages 38' and 39'
for inputting coextruding material and profile forming dies 40 and 41 for
forming the profiled product streams lO and 11 respectively.
Figure S illustrates the profile 42 formed by die 40 and profile 43
formed by die 41.
In the extrusion process the heated thermoplastic m~teri~l is
delivered out of the extruder orifice or outlet 32 and into the leg passage 31
of the Y passage formation under high pressure at a predetermined fixed rate.
This material flow is then divided between the divergent leg passages 34
which between them must accept all of the material moving through the
passage 31. With the passages 34 being of equal diameter, the volume flow
therethrough is basically equ~li7~d but may be effected to some extent by the
differences in resistance in flow impediment offered by the dies 40 and 41
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placed in the path of flow. Basically, however, the rate at which the
somewhat roughly profiled product streams 10 and 11 emerge from the dies
40 and 41 will principally depend upon the volume of thermoplastic material
involved per linear unit or foot of the emerging profiled product stream.
5 The profile requiring the greater volume of material per linear unit will
emerge at a slower rate than the profile requiring a lesser volume of
thermoplastic material per linear unit.
Whatever the precise flow characteristics in the divided stream are
lo it has been found that even when dies such as dies 40 and 41 are formed as
essentially identical dies the rates at which the product streams emerge
thereîlom identical dies are not precisely equal and they cannot be
successfully pulled away at the same speed as by a single puller to produce
two acceptably profiled products
The schematic diagram Figure 7 diagr~mm~ically illustrates the
pullers 17 and 18 and shows how their pulling speeds are individually
controlled. The puller 17 comprises the usual upper endless belt or track 44
stretched between a driving pulley wheel 45 and a corresponding idler pulley
20 46. The belt or track 45 is provided with transverse bars or ribs 47 of
suitable yieldable gripping material such as neoprene rubber or rubberized
material. The drive pulley wheel 45 is driven by a stepper motor 48 whose
speed can be accurately controlled from control panel 49. Immediately below
the upper endless belt or track 44 is a similar endless belt or track 50
25 extending between a drive pulley wheel 51 and a idler pulley wheel not
shown. A separate stepper motor 52 drives the lower endless belt or track 50
with the motors 48 and 52 being driven in synchronism so that the lower
reach 53 of the upper endless track 44 and the upper reach 54 of the endless
track 50 travel at precisely the same speed in the pulling direction.
It will be understood that as usual the upper and lower puller tracks
44 and 50 are relatively adjustable to change the spacing therebetween to
receive and grip the profiled stream being pulled thereby, for example, the
profiled product stream lOc as shown in Figure 6.
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Puller 18 corresponds to puller 17 comprising an upper endless
track 55 in the form of an endless belt having transverse resilient bars or ribs56 and an endless lower track 57 comprising an endless belt having transverse
5 bars or ribs 56.
Again each endless track is driven by its own stepper motor with
stepper motor 58 driving the upper endless track and stepper motor 59
driving the lower endless track with the stepper motors 58 and 59 being
o driven in synchronism and controlled from the control panel 49.
To enable the stepper motors 58 and 59 to be arranged at the same
side of the pullers as the stepper motors 48 and 52, the motors 58 and 59 are
provided with drive shafts 60 and 61 respectively which extend through the
15 pullers and drive sprocket wheels 62 and 63 respectively which drive through
chain drives 64 and 65 respectively sprocket driven pulley wheels 66 and 67.
Again the endless tracks 55 and 57 are driven in synchronism so that the
lower reach 69 of the upper endless track 55 travels at precisely the same
speed as the upper reach 70 of the lower endless track 57 with these track
20 reaches moving in the same direction to pull the profiled product stream
through the calibers. Again it will be understood that the upper and lower
endless tracks 55 and 57 are moveable relative to one another to control the
spacing thereof to tightly engage and firmly grip the profiled product s~e~m
such as the product stream l lc as shown in Figure 6.
By controlling the speed of the stepper motors driving the endless
~acks of the pullers, the pullers 17 and 18 can be controlled so that they pull
the profiled product s~eams lOc and l lc through the calibrators 12a, 12b,
12c and 13a, 13b and 13c respectively at precisely the right speed to pull the
30 profile streams 10 and 11 away from the dies 40 and 41 at precisely the rate
at which these streams emerge therefrom.
The profiled product streams lOc and l lc are delivered by the
pullers 17 and 18 to the sawing station 19 at speeds which can differ
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substantially depending on the profiles of the streams. It is therefore
necessary to provide separate reciprocal saw assemblies 71 and 72 for the two
streams lOc and l lc.
The saw assemblies 71 and 72 are of the same constructions and, as
illustrated in Figure 8, each comprises a reciprocal carriage 73 slidable on
guides 74 and driven by a reciprocating ram 75.
The carriage 73 is provided with a product stream hold down
clamp 76 which is arranged to move down into clamping position during the
cutting operation.
The carriage 73 also carries a motor driven saw blade 77 which is
moveable up and down into the cutting position by a ram 78.
It will be understood that when the requisite length of the profiled
product stream has moved past the carriage 73 the ram 75 will move the
carriage in the direction of the product stream flow at the rate of the product
stream flow while the hold down clamp engages the product stream and the
saw blade is swung into the sawing position to effect the cut off of the productstream. Thereafter the hold down clamp will be released and the carriage
will be returned to its original position awaiting passage of a further requisite
length of the profiled product stream to be fed thereby whereupon the sawing
process is repeated.
With the thermoplastic flow division arrangement of Figure 4, if it
is desired to change one of the profile forming dies 40 or 41, it would be
necessary to shut down the extruder while the die and its corresponding
calibrators are replaced unless the passage 34 thereto was blocked during this
replacement in which case the extruder could be operated at a slower speed.
that is, below capacity to feed the rem~ining die.
The flow divider 79 illustrated in Figures 9 to 12 provides for
selectively closing off one of the branches of the divided flow when desired.
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In this case, the flow divider is provided with a mounting flange
80, a body portion 81 having a transverse passage of square cross section 82
extending therethrough and a flange portion 83. A shutter bar or plunger 84
5 is slidably mounted in the transverse passage 82 and is operated by a threaded drive 85 actuated by a hand wheel 86.
With reference to Figures 10, 11 and 12, it will be seen that the
flow divider is provided with a central passage 87 extending inwardly
lo through the mounting flange 80 to the transverse passage 82 to receive the
heated thermoplastic m~tçri~l being delivered by the extruder 1.
The flange portion 83 is provided with divergent passages 88
diverging outwardly from the transverse passage 82 to the outer face of the
15 flange 89.
The shutter bar 84 is provided with central diverging passages 90
forming a truncated V passage formation which when the shutter bar is in its
central position connect the central passage 87 in the mounting flange portion
20 to the divergent passages 88 in the front flange portion 83 to provide a Y
passage formation, of which the passages 90 form the apex of the diverging
passages.
The shutter bar 84 is also provided at the left hand side as viewed
25 in Figures 10 to 12 with a passage 91 which is angled inwardly from the rear
of the shutter bar 92 to the front of the shutter bar 93.
A passage 94 corresponding to the passage 91 is arranged at the
right hand side of the shutter bar as viewed in Figures 10 to 12 and again this
30 passage 94 is angled inwardly from the rear face 92 of the shutter bar 84 to
the front face 93.
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As shown in Figure 11, when the shutter bar is moved to the right,
the passage 91 connects the central inlet passage 87 with the right hand
passage 88 while blocking off any flow to the left hand passage 88.
As shown in Figure 12, when the shutter bar is moved to the left,
passage 94 in the shutter connects the central inlet passage 87 to the left handpassage 88 while the right hand passage 88 is blocked off.
With this arrangement when the flow is not being divided as
illustrated in Figures 11 and 12 and one of the passages 88 is shut off, flow
takes place only in the one open passage 88 so that no material can go to the
closed off passage 88 to be trapped therein and hardened which would
necessitate the difficult task of cle~ning out that passage before it could be
used again.
The flow divider 79 is provided with a converter block 95 secured
to the front flange 83 and provided with passages 96 registering with the
outlets of passages 88 to convert divergent flow into parallel flow.
The extruder 1 is of course capable of extruding a single product
having a large profile such as the product 97 illustrated in Figure 13 which
requires a large volume of material per linear unit so that it takes the full
output capacity of the extruder for its production.
In this case, the extruder would simply feed directly into the
requisite profile forming die and its associated calibrators (not shown) as in
the conventional extrusion line. In this case, as illustrated in Figure 10, the
product stream 97 would be pulled by the combined pulling power of the
pullers 17 and 18 driven in synchronism at the applopliate pulling speed as
controlled from the control panel 49.
It will be appreciated that in principle the output of the extruder 1
could be divided into more than 2 stream flows each with its own extrusion
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die calibrators and pullers provided the extruder had the capacity to run
same.
Also it will be appreciated that the divergent passage of the flow
5 dividers, eg. the passages 34 of the flow divider unit 4 need not be of the
same diameter since the pullers for each product line can be adjusted to a
pulling speed to compensate for the different diameters so that the profile
stream emerging from each die can be pulled away at the rate it emerges
therefrom.
It will be understood that variations or modifications may be made
in the various components at the various stations along the extrusion line
without departing from the scope of the appended claims.
