Note: Descriptions are shown in the official language in which they were submitted.
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MODULAR EXTRUDER
FIELD
[0001] This disclosure relates generally to extruders, and more
specifically
to extruders for extruding a plastic or thermoplastic material. This
disclosure also
relates to using one or more extruders to produce an extruded or molded
plastic
part.
INTRODUCTION
[0002] Extruders are typically used to heat and melt a solid input
material
(e.g. a plastic, or thermoplastic material) and extrude the material in a
flowable, or
melted state. The extruded, or output, material may be directed through a form
or
die while it cools and solidifies to form an elongate plastic component having
a
cross-sectional profile defined by the form or die. Alternatively, the output
material
may be directed into a mold where it is then cooled and solidifies to form a
molded
component having a shape defined by the mold.
[0003] One source of the heat provided to raise the temperature of
the
conveyed plastic material as it passes through the extrusion or injection
barrel is
mechanical shear heating. In shear heating, the plastic material is subjected
to
shearing or stretching between a rotating screw and a stationary barrel, often
while under relatively high pressures (e.g. 2,000 pounds per square inch
(psi), up
to 30,000 psi or higher), causing heat to develop in the material. Typically,
shear
heating is a significant source of heat. For example, shear heating may
provide
about 70% or more (e.g., 80%, 90%) of the heat required to melt the plastic
material.
SUMMARY
[0004] The following introduction is provided to introduce the reader
to the
more detailed discussion to follow. The introduction is not intended to limit
or
define any claimed or as yet unclaimed invention. One or more inventions may
reside in any combination or sub-combination of the elements or process steps
disclosed in any part of this document including its claims and figures.
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[0005] In
accordance with one aspect of this disclosure, a feed block for an
extruder is configured to promote an increased mass transport rate of
feedstock
material through the feed block and into the barrel of the extruder. An
increased
mass transfer rate through the feed block may allow more material to be
transferred into the barrel for a given unit of time. Accordingly, more
material per
unit time can be output from the extruder.
[0006] In
accordance with this aspect, the geometry of the feeder inlet of
the feed block may be configured to promote compression, e.g. tangential
compression, of the material as it is directed into and along the length of
the feed
flow passage. Accordingly, plastic material being conveyed through the feed
block
may be subjected to increasing pressures as it travels towards and into the
extrusion barrel. An advantage of this design is that there may be less hold-
up of
material in the feed block and a more uniform flow of material into the
extrusion
barrel.
[0007] Optionally, the feed block may removably receive different feeder
inserts. Providing a removable feeder insert may have one or more advantages.
For example, a first feeder insert may have a first inlet passage and the
second
feeder insert may have a second inlet passage having a different configuration
to
the first inlet passage. Thus, a particular feeder insert may be selected
based on
the composition of the input material being extruded and/or based on operating
parameters (e.g. temperature, screw RPM, barrel pressure) of the extrusion
process.
[0008] In
accordance with this broad aspect, there is provided a feeder for
an extruder, the feeder comprising:
(a) a feed flow
passage, the feed flow passage extending in an axial
direction from a feeder inlet to a feeder outlet;
(b) an
axially extending rotatable screw provided in the feed flow
passage, wherein rotation of the screw draws a feedstock in a direction of
flow to the feeder outlet; and,
(c) the feeder
inlet has an inlet passage that overlies the screw, the inlet
passage has an upper end, a lower end adjacent the screw, a length in the
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axial direction, a width in a plane transverse to the axial direction, and a
depth extending between the upper and lower ends of the inlet passage,
wherein the width decreases in the direction of flow.
[0009] In some embodiments, the feeder may further comprise a hopper
having a hopper outlet and the feeder inlet may be provided below the hopper
outlet.
[0010] In some embodiments, the feeder may further comprise a cooling
member.
[0011] In some embodiments, the cooling member may comprise cooling
channels provided in thermal communication with the feed flow passage.
[0012] In some embodiments, the feeder may further comprise a feeder
insert that may be removably mounted in a feed throat of the feeder, wherein
the
feeder insert has the inlet passage.
[0013] In some embodiments, the feeder may removably receive
different
feeder inserts, wherein a first feeder insert may have a first inlet passage
and the
second feeder insert may have a second inlet passage wherein the second inlet
passage may have a different configuration to the first inlet passage.
[0014] In some embodiments, each inlet passage may have an upstream
end in the direction of flow through the feed flow passage and a downstream
end
in the direction of flow through the feed flow passage and the second inlet
passage may have a narrower width at the downstream end of the inlet passage
than the first inlet passage.
[0015] In some embodiments, the lower end of the inlet passage may
have
an inner wall facing the screw and the inner wall may be spaced from the outer
end of the screw by a distance, wherein the distance may decrease in the
direction of rotation.
[0016] In some embodiments, the width may decrease at a constant rate
in
the direction of flow.
[0017] In some embodiments, the width may decrease at an increased
rate
in the direction of flow.
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[0018]
Additionally or alternatively, in accordance with this aspect, the
geometry of an internal feed flow passage of the feed block may be configured
to
promote an increasing volumetric compression as material is directed into and
along the length of the feed flow passage. Accordingly, plastic material being
conveyed through the feed block may be subjected to increasing pressures as it
travels towards and into the extrusion barrel.
[0019] In
accordance with this broad aspect, there is provided a feeder for
an extruder, the feeder comprising:
(a) a feed flow passage, the feed flow passage extending in an axial
direction from a feeder inlet to a feeder outlet;
(b) an axially extending rotatable screw provided in the feed flow
passage, wherein rotation of the screw draws a feedstock in a direction of
flow to the feeder outlet; and,
(c) the feeder inlet has an inlet passage that overlies the screw, the
inlet
passage has an upper end, a lower end adjacent the screw, a length in the
axial direction, a width in a plane transverse to the axial direction, and a
depth extending between the upper and lower ends of the inlet passage,
wherein the lower end of the inlet passage has an inner wall facing the
screw and the inner wall is spaced from the outer end of the screw by a
distance, wherein the distance decreases in the direction of rotation.
[0020] In
some embodiments, the feeder may further comprise a hopper
having a hopper outlet and the feeder inlet may be provided below the hopper
outlet.
[0021] In
some embodiments, the feeder may further comprise a cooling
member.
[0022] In
some embodiments, the cooling member may comprise cooling
channels provided in thermal communication with the feed flow passage.
[0023] In
some embodiments, the feeder may further comprise a feeder
insert that may be removably mounted in a feed throat of the feeder, wherein
the
feeder insert may have the inlet passage.
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[0024] In some embodiments, the feeder may removably receive
different
feeder inserts, wherein a first feeder insert may have a first inlet passage
and the
second feeder insert may have a second inlet passage wherein the second inlet
passage may have a different configuration to the first inlet passage.
[0025] In some embodiments, the width may decrease in the direction of
flow and each inlet passage may have an upstream end in the direction of flow
through the feed flow passage and a downstream end in the direction of flow
through the feed flow passage and the second inlet passage may have a narrower
width at the downstream end of the inlet passage than the first inlet passage.
[0026] In some embodiments, the distance may decrease at a constant rate
in the direction of flow.
[0027] In some embodiments, the distance may decrease at an increased
rate in the direction of flow.
[0028] In accordance with another aspect of this disclosure, two or
more
extruders may be used to concurrently fill a mold in a molding process.
Plastic
material output from the extruders, which is in a flowable or melted state, is
directed into a common mold, either directly or via a manifold or heated flow
conduit connected to the mold and to at least some of the extruders.
[0029] By concurrently using the output from two or more extruders, a
relatively large total flow rate of material may be provided to a mold without
requiring an extruder with a relatively high operating pressure and/or flow
rate. For
example, a molding process using smaller, light weight extruders (e.g., bench
top
extruders each weighing under 500 lbs, 400 lbs, or 300 lbs) may be 'scaled up'
to
provide higher molding volumes (e.g. for use with molds for relatively large
molded components) by providing more extruders, e.g. without having to 'scale
up' the flow rate and/or operating pressure of any one extruder.
[0030] To facilitate the concurrent use of two or more extruders, in
some
embodiments it may be advantageous to provide apparatus in which the feed
inlets of two or more extruders are not axially aligned with each other. For
example, two or more of a plurality of extruders may have a different
respective
axial length. Additionally, or alternatively, one or more extension conduits
may be
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provided between the output nozzle of at least one of the extruders and the
common mold. Alternatively, or in addition, the outlet nozzles of two or more
extruders may be provided at staggered locations axially along the length of a
flow
conduit, which is optionally heated, in communication with a mold.
[0031] In accordance with this broad aspect, there is provided a molding
apparatus comprising:
(a) a plurality of axially extending extruders wherein each of the
extruders is fluidly connectable with a common mold whereby the mold is
concurrently filled from each of the extruders; and,
(b) each of the extruders has a feed inlet,
wherein the feed inlets are axially spaced from each other.
[0032] In some embodiments, at least two of the extruders may have
different axial lengths.
[0033] In some embodiments, the extruders may feed into a common
manifold and the manifold may be connectable to the mold.
[0034] In some embodiments, the plurality of axially extending
extruders
may comprise two extruders that have a common axial length, each extruder may
have a nozzle outlet and one of the two extruders may further comprise a
conduit
extending from the nozzle outlet to the manifold.
[0035] In some embodiments, the at least two of the extruders may further
comprise an axially extending conduit extending from the extruder to the
manifold
and the conduits may have differing axial lengths.
[0036] In some embodiments, the molding apparatus may further
comprise
a plurality of hoppers in flow communication with the feed inlets.
[0037] In some embodiments, each extruder may have a hopper.
[0038] In some embodiments, a common hopper may be provided for at
least two of the extruders.
[0039] In some embodiments, a first extruder may be provided with an
additive and the common manifold may further comprise a mechanical member
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for blending the output of the first extruder with the output of at least one
other of
the extruders.
[0040] In another broad aspect, to facilitate the concurrent use of
two or
more extruders, a common manifold or conduit may be provided between each of
a plurality of extruders and a common mold. Optionally, such a conduit is
heated
to maintain the flowable plastic material within the conduit at an elevated
temperature so that the plastic material remains in a flowable state until it
exits the
conduit.
[0041] In accordance with this broad aspect, there is provided a
molding
apparatus comprising:
(a) a plurality of axially extending extruders, each extruder having
longitudinally extending axis; and,
(b) a heated conduit in flow communication with the plurality of
extruders, wherein the heated conduit is connectable to a mold, whereby
the mold is concurrently fillable from each of the extruders.
[0042] In some embodiments, the heated conduit may have a length
extending in a direction of flow from an upstream end of the heated conduit to
a
downstream end of the heated conduit and at least some of the extruders are in
flow communication with the heated conduit at different locations along the
length
of the heated conduit.
[0043] In some embodiments, the axis of at least some of the
extruders
may extend at an angle to the direction of flow in the heated conduit.
[0044] In some embodiments, an included angle located between the
axis
of at least some of the extruders and the direction of flow in the heated
conduit
may be up to 900
.
[0045] In some embodiments, an included angle located between the
axis
of at least some of the extruders and the direction of flow in the heated
conduit
may be an acute angle, such as between 15-75 or 30-60 .
[0046] In some embodiments, the molding apparatus may further
comprise
a plurality of hoppers in flow communication with the extruders wherein at
least
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some of the hoppers may be spaced apart from each other along the direction of
flow.
[0047] In some embodiments, each extruder may have a hopper.
[0048] In some embodiments, the molding apparatus may further
comprise
a common hopper in flow communication with at least two of the extruders.
[0049] In some embodiments, a first extruder may be provided with an
additive and the heated conduit may further comprise a mechanical member for
blending the output of the first extruder with the output of at least one
other of the
extruders.
[0050] In some embodiments, the heated conduit may be provided with a
feedstock ejection assist member.
[0051] In some embodiments, the feedstock ejection assist member may
comprise a plunger at an upstream end of the heated conduit.
[0052] In another broad aspect, an extruder may have a modular
design,
which may allow an extruder to be assembled from (and preferably disassembled
into) a relatively low number of parts or modules. The modular design may
enable
the modules to be connected together without the need of skilled tradespeople.
For example, the modules may be designed to be connected to each other by
inserting bolts provided on one module into mating holes provided in another
mating module and securing the modules together using the bolts and nuts.
[0053] A modular extruder design may have one or more advantages. For
example, assembly of such an extruder may be relatively simple, which may
reduce time and/or cost required to install the extruder on site. Also, a
modular
design may allow one or more modular components to be provided in different
variations, which may allow a large number of extruder configurations to be
provided by selecting desired combinations of modular components.
[0054] A further advantage is that an extruder may be able to be
repaired
by detaching a broken module and inserting a new or refurbished module, which
may be shipped e.g., by commercial courier. For example, each module may
weigh under 175 lbs, 150 lbs, 135 lbs, or 100 lbs. Accordingly, the modules
may
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be shipped by commercial courier. Further, they may be manipulatable by a few
people without the need of heavy equipment, such as a forklift.
[0055] In
accordance with this broad aspect, there is provided an extruder
comprising:
(a) an axially
extending extruder barrel module having a feedstock inlet
end and a feedstock outlet end axially spaced from the feedstock inlet end
in a direction of flow through the extruder barrel module, the extruder barrel
module comprising an axially extending barrel in which an extruder barrel
screw is removably receivable;
(b) an axially
extending extruder feeder module removably connectable
to the feedstock inlet end of the extruder barrel module, the extruder feeder
module having an axially extending flow passage aligned with the direction
of flow when the extruder feeder module is connected to the barrel module,
the axially extending flow passage having a feedstock outlet end and a
screw motor module mounting end axially spaced from the feedstock outlet
end of the extruder feeder module in a direction of flow through the axially
extending flow passage;
(c) a screw motor module removably connectable to the screw motor
module mounting end of the extruder feeder module, the screw motor
module having a motor drivingly connectable with a screw in the flow
passage of the extruder feeder module; and,
(d) an electronics module electrically connectable with the screw motor
module and mechanically removably mounted as part of the extruder.
[0056] In
some embodiments, each module may be shippable by a
commercial courier company.
[0057] In
some embodiments, each module may weigh under 175 lbs, 150
lbs, 135 lbs, or 100 lbs.
[0058] In
some embodiments, the screw in the flow passage may be
drivingly connectable with the extruder barrel screw when the extruder is
assembled.
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[0059] In
some embodiments, the screw in the flow passage and the
extruder barrel screw may comprise a single integrally formed screw.
[0060] In
some embodiments, the screw in the flow passage and the
extruder barrel screw may be removable as a unitary member from the extruder
barrel module and the extruder feeder module.
[0061] In
some embodiments, the electronics module may be also
electrically connectable with the extruder barrel module.
[0062] In
some embodiments, the electronics module may be also
electrically connectable with the extruder feeder module.
[0063] In some embodiments, the electronics module may be automatically
electrically connectable with the screw motor module when the electronics
module
is mounted as part of the extruder.
[0064] Also
in accordance with this broad aspect, there is provided an
extruder comprising:
(a) an axially
extending extruder barrel module having a feedstock inlet
end and a feedstock outlet end axially spaced from the feedstock inlet end
in a direction of flow through the extruder barrel module, the extruder barrel
module comprising an axially extending barrel in which an extruder barrel
screw is removably receivable;
(b) an axially
extending extruder feeder module removably connectable
in flow communication with the feedstock inlet end of the extruder barrel
module, the extruder feeder module having an axially extending flow
passage aligned with the direction of flow when the extruder feeder module
is connected in flow communication with the barrel module, the axially
extending flow passage having a feedstock outlet end and a screw motor
module end axially spaced from the feedstock outlet end of the extruder
feeder module in a direction of flow through the axially extending flow
passage;
(c) a
screw motor module removably drivingly connectable to an end of
a screw located at the screw motor module end of the extruder feeder
module; and,
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(d) an electronics module electrically connectable with the screw
motor
module and mechanically removably mounted as part of the extruder.
[0065] In some embodiments, each module may weigh under 175 lbs, 150
lbs, 135 lbs, or 100 lbs.
[0066] In some embodiments, the screw in the flow passage may be
drivingly connectable with the extruder barrel screw when the extruder is
assembled.
[0067] In some embodiments, the screw in the flow passage and the
extruder barrel screw may comprise a single integrally formed screw.
[0068] In some embodiments, the screw in the flow passage and the
extruder barrel screw may be removable as a unitary member from the extruder
barrel module and the extruder feeder module.
[0069] In some embodiments, the electronics module may be also
electrically connectable with the extruder barrel module.
[0070] In some embodiments, the electronics module may be also
electrically connectable with the extruder feeder module.
[0071] It will be appreciated by a person skilled in the art that a
method or
apparatus disclosed herein may embody any one or more of the features
contained herein and that the features may be used in any particular
combination
or sub-combination.
[0072] These and other aspects and features of various embodiments
will
be described in greater detail below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0073] For a better understanding of the described embodiments and to
show more clearly how they may be carried into effect, reference will now be
made, by way of example, to the accompanying drawings in which:
[0074] Figure 1 is a perspective view of an extruder in accordance
with one
embodiment;
[0075] Figure 2 is a perspective view of the extruder of Figure 1,
with
portions of a controller housing removed;
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[0076] Figure 3 is a front view of the extruder of Figure 1;
[0077] Figure 4 is a rear view of the extruder of Figure 1;
[0078] Figure 5 is an end view of the output end of the extruder of
Figure 1;
[0079] Figure 6 is an end view of the end longitudinally opposed to
the
output end of the extruder of Figure 1;
[0080] Figure 7 is a top view of the extruder of Figure 1;
[0081] Figure 8 is a bottom view of the extruder of Figure 1;
[0082] Figure 9 is a front view of components of the extruder of
Figure 1 in
a partially disassembled configuration;
[0083] Figure 10 is a perspective view of an extruder barrel, feed block,
hopper, and output nozzle of the extruder of Figure 1;
[0084] Figure 11 is a perspective cross-section view of the extruder
barrel,
feed block, hopper, and output nozzle of the extruder of Figure 10;
[0085] Figure 12 is a cross-section view of the feed block of the
extruder of
Figure 10 in a vertical plane through the feed block;
[0086] Figure 12B is a cross-section view of an alternative
embodiment of
an extruder feed block in a vertical plane through the feed block;
[0087] Figure 13 is a perspective section view of the extruder
barrel, feed
block, hopper, and output nozzle of the extruder of Figure 10, taken along
line 13-
13 in Figure 10;
[0088] Figure 14 is a perspective section view of the extruder
barrel, feed
block, and hopper of the extruder of Figure 10, taken along line 14-14 in
Figure
10;
[0089] Figure 15 is another perspective section view of the extruder
barrel,
feed block, and hopper of the extruder of Figure 10, taken along line 14-14 in
Figure 10;
[0090] Figure 16 is a rear perspective view of the extruder barrel,
feed
block, feed block insert, and extrusion screw of the extruder of Figure 1
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[0091] Figure 17 is an exploded view of the extruder barrel, feed
block, feed
block insert, and extrusion screw of Figure 16;
[0092] Figure 18 is an exploded view of the extruder barrel, feed
block, and
feed block insert of Figure 17;
[0093] Figure 19 is a perspective view of the extruder barrel, feed block,
and feed block insert of Figure 18;
[0094] Figure 20 is a perspective cross-section view of the extruder
barrel,
feed block, and feed block insert of Figure 19;
[0095] Figure 21 is a top view of the feed block, feed block insert,
extruder
barrel, and extrusion screw of Figure 16;
[0096] Figure 22 is a perspective section view of the feed block,
feed block
insert, extruder barrel, and extrusion screw of Figure 21, taken along line 22-
22 in
Figure 21;
[0097] Figure 23 is a rear perspective view of the feed block insert
of Figure
21;
[0098] Figure 24 is an end view of the barrel facing end of the feed
block
insert of Figure 21;
[0099] Figures 25 is an end view of the end opposite the barrel
facing end
of the feed block insert of Figure 21;
[00100] Figure 26 is a bottom view of the feed block insert of Figure 21;
[00101] Figure 27 is a perspective view of two extruders coupled to a
common mold, in accordance with one embodiment;
[00102] Figure 28 is a perspective view of two extruders coupled to a
common mold, in accordance with another embodiment;
[00103] Figure 29 is a perspective view of the output ends of three
extruders,
in accordance with one embodiment;
[00104] Figure 30 is a top view of the extruders of Figure 29;
[00105] Figure 31 is a perspective view of the output ends of two
extruders,
in accordance with one embodiment;
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[00106] Figure 32 is a top view of the extruders of Figure 31;
[00107] Figure 33 is an end view of the output ends of the extruders
of
Figure 31;
[00108] Figure 34 is a perspective view of six extruders connected to
a
heated conduit in accordance with one embodiment;
[00109] Figure 35 is a top view of the six extruders and heated
conduit of
Figure 34;
[00110] Figure 36 is a perspective section view of the heated conduit
of
Figure 34, taken along line 36-36 in Figure 35;
[00111] Figure 37 is a perspective section view of one of the extruders and
the heated conduit of Figure 34, taken along lines 37-37 and 37'-37' in Figure
35;
[00112] Figure 38 is a perspective view of six extruders connected to
a
heated conduit in accordance with another embodiment;
[00113] Figure 39 is a top view of the six extruders and heated
conduit of
Figure 38;
[00114] Figure 40 is a perspective view of six extruders connected to
a
heated conduit in accordance with another embodiment; and,
[00115] Figure 41 is a top view of the six extruders and heated
conduit of
Figure 40.
[00116] The drawings included herewith are for illustrating various
examples
of articles, methods, and apparatuses of the teaching of the present
specification
and are not intended to limit the scope of what is taught in any way.
DESCRIPTION OF EXAMPLE EMBODIMENTS
[00117] Various apparatuses, methods and compositions are described
below to provide an example of an embodiment of each claimed invention. No
embodiment described below limits any claimed invention and any claimed
invention may cover apparatuses and methods that differ from those described
below. The claimed inventions are not limited to apparatuses, methods and
compositions having all of the features of any one apparatus, method or
.. composition described below or to features common to multiple or all of the
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apparatuses, methods or compositions described below. It is possible that an
apparatus, method or composition described below is not an embodiment of any
claimed invention. Any invention disclosed in an apparatus, method or
composition described below that is not claimed in this document may be the
subject matter of another protective instrument, for example, a continuing
patent
application, and the applicant(s), inventor(s) and/or owner(s) do not intend
to
abandon, disclaim, or dedicate to the public any such invention by its
disclosure in
this document.
[00118] The apparatuses, methods and compositions may be used to
extrude and/or mold various materials, such as a plastic material and
optionally a
thermoplastic material. The thermoplastic material may be one or more of
acrylonitrile butadiene styrene (ABS), polyvinyl chloride (PVC), chlorinated
polyvinyl chloride (CPVC), polyethylene (PE), low molecular weight PE, high
density PE, ultra high molecular weight PE, polyethylene terephthalate (PET),
polystyrene (PS), polycarbonate (PC), acrylic, polypropylene (PP),
polybutylene
terephthalate (PBT), polyvinyl acetate, ethylene-vinyl acetate (EVA), or the
like.
Optionally, the thermoplastic material is one or more of PVC and CPVC.
General description of preferred embodiments utilizing combinations of
various aspects
[00119] Figures 1 to 9 exemplify an extruder, referred to generally as
1000.
Extruder 1000 may be used to heat and melt an input material (e.g. a plastic,
or
thermoplastic material which may be solid) and extrude the material in a
flowable,
or melted state. The extruded, or output, material may be used to fill a mold
in a
molding process, as will be discussed further subsequently, or with an
extrusion
die. It will be appreciated that extruder 1000 may receive any input material
known in the extruder art.
[00120] Extruder 1000 may include one or more user input devices that
allow
a user to initiate and/or control the operation of the extruder. For example,
user
input devices may include one or more of power switches 1012, which may be a
main on/off switch, and a display 1018, which may be a touch screen display
for
enabling user input. Extruder 1000 may also include one or more user output
devices that allows a user to monitor the operation of the extruder. For
example,
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the user output device may be display 1018, and/or one or more audio and/or
visual output devices, such as lights, buzzers, speakers, and the like (not
shown).
[00121] As shown in Figures 1 to 9, at least some of the user input
devices
and/or control electronics of extruder 1000 may be enclosed in a control
housing
or cabinet 1010, which in the illustrated embodiment includes a plurality of
solid
panels 1015 and an access door 1017 secured via, e.g., hinges 1019 to provide
access to components inside the cabinet. It will be appreciated that the
housing
may be made from any suitable material (e.g. metal, plastic, and the like),
and that
in alternate embodiments the cabinet may be formed of more or fewer panels. In
some embodiments, a control cabinet may not be provide.
[00122] Extruder 1000 also includes an input member for introducing
the
material into the extruder. The input member may be an input hopper 1020 for
receiving the input material (e.g. a solid pelletized plastic). As perhaps
best seen
in Figure 11, material received in hopper 1020 is directed through a feed
throat
.. 1062 in a feed block 1600 where it is introduced into the channels of an
extrusion
screw 1300. Rotation of the screw 1300 advances or conveys the pelletized
input
material from a first, or input, end 1302 of the extrusion screw towards a
second,
or output, end 1304 of the extrusion screw 1300, thereby conveying the
material
through an extrusion barrel 1100 from a first, or input, end 1102 of the
barrel to a
second, or output, end 1104 of the barrel.
[00123] As the material is conveyed through the extrusion barrel 1100
by the
screw 1300, heat from one or more (e.g., a plurality of) heating elements 1110
positioned about the outer surface 1108 of the extrusion barrel 1100 is
transferred
through the extrusion barrel wall to the conveyed material via the inner
barrel
surface 1106, raising the temperature of the material and thereby causing the
material to transition to a flowable, or melted state. It will be appreciated
that
heating elements 1100 may be positioned along a portion of, or all of, the
length
of the barrel. Each heating element may surround a portion of the outer
perimeter
of the barrel or they may surround most or all of the outer surface of the
barrel. In
the example illustrated in Figures 1 to 9, eight spaced apart heating elements
1110, each of which is annular and surrounds the outer surface of the barrel,
are
shown. In the example illustrated in Figure 11, five heating elements 1110 are
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shown. It will be appreciated that more or fewer heating elements 1110 may be
provided in alternative embodiments.
[00124] The input material continues to be conveyed by the extrusion
screw
1300 towards the output end 1104 of the extrusion barrel 1100, where it is
ejected
as a flowable liquid material. In the example illustrated in Figures 1 to 9,
the
material is ejected from the extruder via an ejection nozzle 1200. More
specifically, the flowable material exits the output end 1104 of the extruder
barrel
1100 and enters the input end 1202 of the nozzle 1200, flows through the
nozzle,
and is ejected from the output end 1204 of the nozzle.
[00125] Optionally, a nozzle heating element (not shown) may also be
positioned about the outer surface of output nozzle 1200. Heat from such a
nozzle
heating element may be transferred through the nozzle body to the conveyed
material via the inner nozzle surfaces, and may be used to control the
temperature of the material flowing within the output nozzle 1200. It will be
appreciated that zero, one, or two or more nozzle heating elements may be
provided in alternative embodiments.
[00126] The extrusion screw 1300 is rotated by screw drive motor 1030.
Screw drive motor 1030 is preferably an electric motor, such as an alternating
current (AC) motor (asynchronous or synchronous), a direct current (DC) motor,
and the like. In the illustrated example, electric motor 1030 is driven by an
adjustable-speed drive 1035, such as a variable-frequency drive (VFD),
adjustable-frequency drive (AFD), variable-voltage/variable-frequency (VVVF)
drive, and the like.
[00127] The screw drive motor 1030 may be drivingly coupled to the
.. extrusion screw directly or via a drive transmission member, e.g., an
optional
gearbox 1040, which is preferably a reduction gearbox. The use of a reduction
gearbox may allow the use of a higher-speed, lower power motor, which may be
more efficient and/or less expensive to purchase and/or operate than a lower
speed, higher power motor.
[00128] In the example illustrated in Figures 1 to 9, the input and output
to
gearbox 1040 are at right angles, allowing motor 1030 to be positioned at an
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angle to extrusion screw 1300. Alternatively, the input and output to gearbox
1040
may be on opposite sides of the gearbox, allowing motor 1030 to be positioned
generally in-line with extrusion screw 1300. Alternatively, the input and
output to
gearbox 1040 may be at right angles, but motor 1030 may be positioned beside
or
below extrusion screw 1300. It will be appreciated that gearbox 1040 and/or
one
or more mechanical or viscous couplings may be provided to allow any suitable
relative position of motor 1030 and extrusion screw 1300.
[00129] Extrusion screw 1300 may be rotationally supported within
extrusion
barrel 1100 by the gearbox 1040 (or motor 1030, if a gearbox is not provided)
and/or by one or more bearings. For example, at least one end thrust bearing
configured to allow rotation of screw 1300, and to resist the expected axial
forces
exerted on screw 1300 in a direction towards the input end 1302 of the
extrusion
screw (e.g. due to backpressure of the material being conveyed by screw 1300,
and/or a partial or complete obstruction of output nozzle 1200) may be
provided.
[00130] As exemplified, extrusion screw 1300 may be substantially solid.
Alternatively, the extrusion screw may be partially or substantially hollow.
In the
illustrated example, the output end 1304 of extrusion screw 1300 is provided
with
a nose cone 1310 (see for example Figure 11). Nose cone 1310 may assist with
directing the output material from the output end 1104 of the extruder barrel
1100
to the input 1202 of nozzle 1200. Nose cone 1310 may optionally be mounted to
extrusion screw 1300 in a manner that allows it to be axially advanced and
retracted relative to screw 1300, e.g. using an optional knockout rod 1042
that
extends through a hollow extrusion screw. The ability to axially advance nose
cone 1310 using knockout rod 1042 may be useful when clearing a blockage of
output material (e.g. when removing a clogged nozzle 1200).
Extrusion barrel
[00131] Extrusion barrel 1100 preferably has a relatively thin wall
thickness,
particularly in comparison to barrels used in typical extrusion or injection
molding
machines. For example, extrusion barrel 1100 may have a wall thickness of from
between 0.015 to 0.375 inches, or from between 0.04 to 0.25 inches, or from
between 0.08 to 0.1875 inches.
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[00132] Providing a relatively thin-walled extrusion barrel may have
one or
more advantages. For example, the rate of heat transfer through the extrusion
barrel wall may be proportional to the wall thickness of the barrel, such that
a
decrease in the barrel wall thickness results in a higher heat transfer rate
through
the barrel wall. An extrusion barrel 1100 having a relatively high heat
transfer rate
through the barrel wall may have one or more advantages. For example, an
increased thermal transfer rate allows more heat to be transferred through the
barrel wall for a given unit of time. Accordingly, more heat per unit time can
be
transferred to the plastic material being conveyed through the extrusion
barrel.
Thus, it follows that the plastic material needs to spend less time in the
extrusion
barrel to have the necessary amount of heat transferred to it to melt the
plastic
material and/or less shear heating is required. As a consequence, if the
material is
liquefied or the feed material is of a size that seats within the threads of a
screw,
the extrusion screw 1300 may be rotated at a higher speed (i.e. a higher RPM)
to
convey the material through the extrusion barrel in a shorter amount of time
without incurring excessive pressures that may inhibit the use of thinner
walled
barrels.
[00133] Extrusion barrel 1100 is optionally made from a material that
has a
relatively high thermal conductivity, such as copper or aluminum. Using such a
material may further increase the heat transfer rate through the barrel wall,
which
may provide or enhance one or more of the advantages noted above.
Me/find plastic
[00134] As discussed previously, in typical extrusion or injection
molding
machines, the heat provided to raise the temperature of the conveyed plastic
material as it passes through the extrusion or injection barrel is provided
primarily
by mechanical shear heating. Further, the barrel wall thickness required to
contain
the operating pressures required for significant shear heating may reduce the
maximum heat transfer rate through the barrel wall, reducing the amount of
energy that can be conveyed to the plastic material via barrel heaters. For
example, in some prior art machines, approximately 90% of the total energy
supplied to operate the machine may be supplied to the drive motor, with the
remaining 10% being supplied to one or more barrel heaters.
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[00135] In contrast, during the operation of extruder 1000, a
majority, and
preferably a substantial majority, of the heat provided to raise the
temperature of
the conveyed plastic material as it passes through the extrusion barrel may be
provided by non-mechanical heat sources.
[00136] For example, extruder 1000 preferably includes an extrusion barrel
1100 having relatively high heat transfer rate through the barrel wall, which
increases the amount of heat barrel heaters 1110 can provide to the plastic
material in a given amount of time. This may allow barrel heaters 1110 to
provide
at least 60%, 65%, 70%, 75%, 80%, 85%, 90%, or at least 95% of the total
.. amount of heat provided to the conveyed material during its time in the
extrusion
barrel 1100, with the remaining heat being provided as a result of mechanical
shear heating.
Feed block
[00137] In accordance with an aspect of this disclosure, various
different
features of a feed block for an extruder are provided. The shape of the flow
passage into and through the feeder may be adjusted. For example, the width of
the inlet passage to the screw in the feed block (in a direction transverse to
the
screw axis) may decrease along part or all of the length of the inlet in the
axial
direction, the height of the feed flow passage may decrease along part or all
of the
.. inlet passage, and the decrease in height may be constant or it may occur
in
downward steps and/or the shape of the outlet of the feeder in a vertical
plane
located at the interface of the feeder and the barrel may be adjusted to
provide a
reduced clearance between the screw and the outlet along a downstream portion
of the upper end of the outlet. Alternatively, or in addition, a removable
feeder
block may be provided. One or more of these features of the feed block may be
used in a feed block, and any such feed block may be used by itself or in any
combination or sub-combination with any other feature or features described
herein.
[00138] In accordance with this aspect, a feed block, which may also
be
referred to as a feeder, includes a feed flow passage, a rotatable screw
positioned
in the passage, and a feed block inlet that overlies at least a portion of the
screw.
By rotating the screw, a feedstock (e.g. a pelletized input material) may be
drawn
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towards a feed block outlet, and from there the feedstock may pass into an
extrusion barrel of the extruder.
[00139] An example of a feed block 1600 will be discussed with
reference
primarily to the examples illustrated in Figures 10 to 22. Figure 10
illustrates a
feed block 1600 connected to an extruder barrel 1100, and to an optional feed
hopper 1020.
[00140] With reference to Figure 11, feed hopper 1020 is optionally
positioned above and in communication with the feed block inlet 1620, so that
as
feedstock in a feed flow passage 1630 is drawn towards the feed block outlet
1604 in the direction of flow 1625, feedstock (e.g. a pelletized input
material)
loaded in the hopper may be gravity fed into the feed flow passage 1630 via
the
inlet passage 1620.
[00141] Referring to Figure 21, viewed from above inlet passage 1620
has a
length Linlet in a direction generally parallel to the axis of screw 1300,
which may
also be referred to as an axial direction 1625 of the feed flow passage 1630.
Inlet
passage 1620 also has a width W
inlet in a direction generally perpendicular to the
axial direction. As exemplified, the width W
inlet of the inlet passage may decrease
along the length of the inlet in the axial direction (i.e. W
147in1et2)= The width
may decrease at a constant rate or the width may decrease at an increased rate
in the direction of flow 1625.
[00142] In the illustrated example, viewed from above a first side
1606 of the
inlet passage is generally parallel to the axial direction 1625, and most of
the
opposite side 1608 is at an angle 0 to the first side. Notably, the width of
the inlet
passage 1620 decreases along the length of the inlet in the axial direction at
a
substantially constant rate, with the exception being at the 'narrow' end of
the inlet
passage 1620 (e.g. proximate W
in(et2), where the sides 1606, 1608 of the inlet
passage 1620 converge towards each other at an increasing rate (due to the
rounding of corners 1607 and 1609). Alternatively, corners 1607 and/or 1609
may
not be rounded, and the width of the inlet passage 1620 may decrease along the
entire length of the inlet in the axial direction at a constant rate.
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[00143] As a further alternative, the width of the inlet passage may
decrease
along the length of the inlet in the axial direction at an increasing rate.
For
example, side 1606 of the inlet passage may be generally linear, and the
opposite
side 1608 of the inlet passage may have a substantially arcuate or parabolic
shape, when viewed from above.
[00144] An advantage of this design is that the inlet passage may
preferentially direct feedstock material towards one side of the feed flow
passage,
with this preference increasing in the feed flow direction 1625. Preferably,
the side
of the feed flow passage towards which feedstock is preferentially directed is
the
side at which the feed screw 1300 is moving downward when the crew is rotated.
For example, referring to Figure 13, when feed screw 1300 is rotated in
direction
1325, feedstock material from hopper 1020 will be directed by surface 1603
preferentially towards downwardly-travelling portions of screw 1300. This may
advantageously facilitate a greater portion of feedstock material passing
through
the inlet 1620 to be directed and preferably compressed into the volume
between
the flights 1308 of the screw and the outer surface of screw shaft 1306. For
example, feedstock material may undergo radially inward (e.g. tangential)
compaction and/or compression towards the outer surface of the screw shaft
1306
between the screw flights 1308 at the region proximate the side of the feed
flow
passage and the rotating screw 1300 (see e.g. Figure 15).
[00145] Additionally, as the width of the inlet passage 1620 decreases
along
the length of the inlet in the axial direction 1625, a greater portion of the
feed flow
passage 1630 may be covered. With reference to Figure 14, lower surface 1639
is
positioned over upwardly-travelling portions of screw 1300. This inner surface
1639 of feed flow passage 1630 may inhibit or prevent material from exiting
from
between the flights 1308 of screw 1300, and/or may inhibit or prevent de-
compaction and/or decompression of material between the flights of screw 1300.
Advantageously, this may result in a greater mass of material being introduced
and/or retained between the screw flights, which may result in a greater mass
flow
rate of material in the feed flow direction for a given rate of rotation (e.g.
RPM) of
screw 1300.
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[00146] Referring to Figure 12, in addition to portions of the feed
block
overlying the feed flow passage along the axial length Linlet of the inlet
1620, an
inner surface 1639 of the feed block downstream of the inlet 1620 in the
direction
of flow 1625 may completely overlie the screw 1300 to define a downstream or
undercut portion 1634 of the feed flow passage 1630.
[00147] Alternatively, or in addition to reducing the width of the
passage, the
height of the feed flow passage 1630 may be reduced in the downstream
direction.
[00148] As exemplified in Figure 12, the height of the feed flow
passage may
remain constant as the width decreases. As exemplified, surface 1639 extends
longitudinally generally parallel to the axis of feed screw 1300, and
generally
parallel to the lower surface 1631 of feed flow passage 1630, resulting in the
downstream portion 1634 having a generally constant volume per unit length in
the direction of flow 1625, until a step 1637 proximate the inlet end 1102 of
barrel
1100.
[00149] Alternatively, or additionally, the height of the feed flow
passage may
decrease along part or all of the inlet passage, and the decrease in height
may be
constant or it may occur in downward steps. The height of the passage may be
reduced, with or without reducing the width. For example, the surface 1639 may
be angled downwardly towards the lower surface 1631 of feed flow passage 1630.
As exemplified in Figure 12B, the height of the feed flow passage Hpassage
decreases along the length of the feed flow passage in the axial direction
1625
from H1 at the inlet end to H2 towards the outlet end. Decreasing the height
of the
feed flow passage 1630 in the axial direction 1625 results in the downstream
portion 1634 having a decreasing volume per unit length in the direction of
flow
1625, which may result in increased compaction and/or compression of material
as it is drawn by screw 1300 towards the feed block outlet 1604.
[00150] This increased compaction and/or compression may
advantageously
result in a greater mass of (e.g. pelletized) input material being introduced
and/or
retained between the screw flights, which may result in a greater mass flow
rate of
material in the feed flow direction for a given rate of rotation (e.g. RPM) of
screw
1300.
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[00151] In some embodiments, surface 1639 may be angled towards the
lower surface 1631 of feed flow passage 1630 such that the height of the feed
flow passage Hpassage may decrease along the length of the feed flow passage
in
the axial direction 1625 at a substantially constant rate (e.g. as illustrated
in
Figure 12B).
[00152] Alternatively, surface 1639 may be curved (e.g. a parabolic
curve)
towards the lower surface 1631 of feed flow passage 1630 such that the height
of
the feed flow passage Hpassage may decrease along the length of the feed flow
passage in the axial direction at an increasing rate.
[00153] Alternatively, or additionally, surface 1639 may have one or more
discrete 'step-downs' where the height of the feed flow passage Hpassage may
decrease sharply. For example, in the example illustrated in Figure 12, a step
1637 is located proximate the inlet end 1102 of barrel 1100. Optionally, step
1637
(or any other step-down along surface 1639) may be chamfered, beveled, or
curved to decrease the sharpness of the transition.
[00154] Alternatively, or additionally, the shape of the outlet of the
feeder in a
vertical plane located at the interface of the feeder and the barrel may be
adjusted
to provide a reduced clearance between the screw and the outlet along a
downstream portion of the upper end of the outlet. For example, as perhaps
best
seen in the example illustrated in Figures 24 and 25, the inner surface 1639
may
have a generally planar portion 1643 and a radially curved portion 1641.
Curved
portion 1641 results in the radial gap between the outer diameter of screw
1300
and the inner surface 1639 to decrease in the direction of rotation 1325 of
the
screw 1300. This arrangement may result in increasing tangential compression
of
input material as it is conveyed towards the extrusion barrel by the rotating
screw.
[00155] For an extrusion screw and barrel used in typical extrusion or
injection molding machines, the radial gap between the outer screw flight
diameter
and the inner surface of the extruder barrel is relatively small, for example,
between about 0.001" and 0.002". This relatively stringent tolerance may be
required to maintain an increased compression of the material being extruded
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(e.g. to facilitate shear heating), and/or to prevent mixing at the barrel
wall, which
may be considered undesirable in a typical extrusion process.
[00156] In contrast, in extruder 1000, the radial gap between the
outer
diameter of screw 1300 and the inner surface 1106 of extrusion barrel 1100 may
be between 0.002" to 0.125", optionally from between 0.004" and 0.045", and
optionally about 0.006 to 0.020".
[00157] In the downstream or undercut portion 1634 of feed flow
passage
1630, the gap between the outer diameter of the upper portion of screw 1300
and
the inner surface 1639 is preferably between 0.020 to 0.750" more preferably
from
between 0.060 and 0.375", and most preferably about 0.125 to 0.250".
Accordingly, the radial volume between the screw 1300 and the inner surface of
the surrounding feed block is greater than the radial volume between the screw
1300 and the inner surface 1106 of extrusion barrel 1100. As a result, the
input
material may be compressed radially inwardly as it is conveyed by the screw
through the feed block 1600 towards the extrusion barrel 1100.
[00158] Adjusting the feed flow passage in one or more of the ways
exemplified here may result in less hold-up of the material and a more even
flow
into the barrel.
[00159] Increasing the compaction and/or compression of the input
material
within the feed block may result in increased shear heating of the material.
While
shear heating is effective at raising the temperature of the feedstock (e.g.
plastic)
material, there may be one or more disadvantages. For example, excessive
shearing of the plastic material may lead to a physical and/or chemical
degradation of the polymer molecules within the plastic material. It will be
appreciated that while the barrel is optionally of a thin wall design as
discussed
herein, the feeder and feed block insert may have thicker wall to enable
shearing
of the feedstock prior to its introduction to the barrel.
[00160] Also, if the temperature of feedstock material within feed
block
increases too much, there may be a decrease in the mass flow rate for a given
screw RPM. Without intending to be bound by theory, excessive heating of the
material may result in liquefied material with a lower viscosity, which may
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negatively affect the screw's ability to convey the material efficiently
through the
barrel and may damage the molecular structure of the material.
[00161] For example, for an ABS feedstock material, the material in
the feed
block may preferably have a temperature of between about 10 C and 35 C. At
temperatures of between about 40 C and 50 C, the mass flow rate for a given
screw RPM may decrease, and at temperatures above about 55 C, the flow rate
may decrease substantially. It is preferred to maintain a feed block
temperature of
0 C and 50 C, more preferably 5 C and 40 C and most preferably 10 C and
35 C.
[00162] For example, for a Polyether ether ketone (PEEK) feedstock
material, the material in the feed block may preferably have a temperature of
between about 10 C and 50 C. At temperatures of between about 65 C and 75 C,
the mass flow rate for a given screw RPM may decrease, and at temperatures
above about 85 C, the flow rate may decrease substantially. It is preferred to
maintain a feed block temperature of 0 C and 70 C, more preferably 5 C and
60 C and most preferably 10 C and 50 C.
[00163] Optionally, to regulate the temperature of feedstock material
that is
compressed as it travels through the feed flow passage, feed block 1600 may
include a cooling system. Accordingly, a cooling member may be provided. The
cooling member may comprise one or more flow channels provided in the feeder.
[00164] As exemplified in Figure 12, the cooling system includes a
number
of conduits or coolant flow channels 1690 extending through the feed block.
Flow
channels 1690 extend between inlet and/or outlet ends 1692, and are configured
to allow the circulation of a cooling fluid through the coolant flow channels
1690.
As exemplified, coolant flow channels 1690 may be each generally linear, and
may extend generally transverse to the material flow direction 1625. It will
be
appreciated that any suitable configuration of coolant flow channels may be
provided in one or more alternative embodiments.
[00165] Optionally, the cooling system may include one or more pumps
(not
shown) to circulate cooling fluid through the coolant flow channels. The
cooling
system may also optionally include one or more heat sinks or other passive or
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active heat exchangers (not shown) through which the cooling fluid may be
circulated to remove heat from the fluid before recirculating it through the
coolant
flow channels.
[00166] In the example illustrated in Figures 10 to 22, feed block
1600
includes a main feed block body 1610 and feed block insert 1605. With
reference
to Figures 17 to 20, feed block insert is preferably removably mounted in a
feed
throat 1062 of the feed block body 1610. In the illustrated example, feed
block
insert 1605 is secured to main feed block body 1610 using a plurality of bolts
1698. However, any other securing means or removable securing means may be
.. used.
[00167] Referring to Figures 23 to 26, feed block insert 1605 has a
downstream end 1654, an upstream end 1652, and a lower mounting surface
1653 that is configured to be secured against main feed block body 1610.
Optionally, one or more sealing members (not shown) may be positioned between
main feed block body 1610 and feed block insert 1605.
[00168] As perhaps best seen in Figures 24 and 25, surface 1639 has a
substantially planar portion 1643 and a curved portion 1641. As discussed
above,
curved region 1641 may result in the radial gap between the outer diameter of
screw 1300 and the inner surface 1639 decreasing in the direction of rotation
1325 of the screw, which may promote increased tangential compression of input
material in and/or proximate this region.
[00169] Referring to Figures 18 and 20, the main feed block body 1610
includes a channel defining a lower surface 1631 of feed flow passage 1630.
When feed block insert 1605 is mounted to the main feed block body 1610, this
.. channel and feed block insert 1605 may cooperatively define at least a
portion of
the feed flow passage 1630. Alternatively, the feeder block may define the
entire
feed flow passage 1630.
[00170] In the illustrated example, the inlet passage 1620 of feeder
1600 is
defined by feed block insert 1605 and a surface 1611 of feed throat 1062. An
advantage of this design is that different feed block inserts 1605 may have
inlet
passages with different geometries. For example, a first feed block insert
1605
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may have an inlet passage 1620 having a first length Linlet, a first width
Winlet, a
first depth Diniet (see e.g. Figure 25) and one side of the inlet passage may
be at
a first angle 0 to the opposite side. A second feed block insert may have a
length
Linlet that is different than the first length Linlet, a width W
inlet that is different than
the first width W
¨ inlet, a depth Dinlet that is different from the first depth Dinlet,
and/or one side of the inlet passage may be at an angle 0 to the opposite side
that is different than the first angle 0.
[00171] Providing feed block inserts 1605 with different geometries
may
have one or more advantages. For example, this may allow the geometries of the
feed flow passage 1630 and/or the feeder inlet 1620 of a feed block 1600 to be
reconfigured by simply replacing the feed block insert with a different feed
block
insert.
[00172] Optionally, the geometry of a feed block insert 1605 may be
designed to provide improved and preferably optimized performance for a
particular feed stock material (e.g. plastic composition, particle size,
particle
shape, elasticity in solid form, etc.) and/or process condition (e.g. screw
RPM).
Accordingly, a particular feed block insert 1605 may be selected and mounted
to
feed block body 1610 based on the extrusion process to be performed. For
instance, a feed stock material that is provided in the form of a flat flake
may feed
.. better when the distance between the outer diameter of the upper portion of
screw
1300 and the inner surface 1639 is reduced to 0.080 to 0.165" and the arc
towards the side wall may be reduced at a greater rate to improve feeding.
Conversely, a feed stock material that is provided in irregular pieces from
0.002 to
0.375" (e.g. typical of regrind material) may feed better when the distance
between the outer diameter of the upper portion of screw 1300 and the inner
surface 1639 is increased to 0.300 to 0.425" and the arc towards the side wall
may be reduced at a lesser rate to improve feeding.
[00173] It will be appreciated that some of the embodiments disclosed
herein
may not use any of the features of the feed block insert disclosed herein and
that,
.. in those embodiments, a feed block of any kind known in the art may be
used.
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Use of multiple extruders
[00174] In accordance with another aspect of this disclosure, which
may be
used with one or more of the aspects of an extruder disclosed herein, two or
more
extruders may be used concurrently to fill a mold in a molding process or with
an
.. extrusion die.
[00175] In accordance with this aspect, the plastic material output
from a
plurality (i.e. two or more) extruders, which is in a flowable or melted
state, is
directed into a common mold, either directly or via a manifold, which may be a
longitudinally flow conduit, connected to the mold and to at least some of the
extruders.
[00176] As discussed above, flowable plastic material may exit each
extruder 1000 at a relatively low pressure compared to the typical pressures
used
in commercial extruders, e.g., typically below 650 psi for filling molds,
below 1,250
psi for packing molds, whereas typical injection molding machines typically
inject
at 2,500 to 20,000 psi and pack at 2,500 to 20,000 psi.
[00177] As discussed above, a flowable plastic material may exit
extruder
1000 at a relatively low pressure, typically below 2,500 psi for producing
extruded
profiles, sheets or films through a die, and preferably below 1,500 psi,
whereas
typical machines operate at 3,500 to 20,000 psi for producing extruded
profiles,
sheets or films through a die.
[00178] A further advantage of 'ganging' two or more extruders
together,
preferably about one extruder per foot of width of sheet material that is to
be
formed, is that it may reduce the operating pressure within the system
enabling
lighter, smaller, lower cost dies and molds and reducing the material shearing
within nozzles, gates, runners and other die or mold areas, thereby minimizing
material degradation and minimizing retrained stress within the final material
or
part. For example, a typical "coat hanger die" to make a 4 foot wide sheet
will be
large and complex and the pressures to operate it will be in excess of 5,000
psi
because of the long distance that the material must travel within the die,
whereas
an extrusion die with one extruder per foot of die length (product width) can
operate at 1,500 psi or lower and enables a smaller, far less complex die,
faster
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startup and shut down of the process, less material shearing within the
nozzles,
gates, runners and die, thereby minimizing material degradation and minimizing
retained stress within the final material or part.
[00179] In the example illustrated in Figure 27, extruders 1000a and
1000b
.. are each in fluid communication with a single mold 1500. More specifically,
the
output ends of the nozzles 1200a, 1200b are each fluidically coupled to a mold
inlet port 1502a, 1502b. Mold inlet ports 1502 each provide fluid
communication to
at least one interior mold cavity within mold 1500, which in the illustrated
example
is defined by opposing mold halves 1506 and 1508.
[00180] In the example illustrated in Figure 27, the extruder nozzles
1200a,
1200b are positioned on opposite sides of mold 1500. Alternatively, the
extruder
nozzles 1200 may be positioned on opposite ends of mold 1500. For example, as
shown in Figure 28, mold inlet ports 1502 are each positioned proximate the
junction of the opposing mold halves 1506 and 1508.
[00181] In the examples illustrated in Figures 27 and 28, extruders are
positioned on opposite sides of mold 1500. Alternatively, two or more
extruders
may be positioned on the same side of a common mold.
[00182] Positioning two or more extruders on the same side of a common
mold may pose one or more challenges. For example, depending on the size of
the mold, it may be preferable to have two or more mold inlet ports positioned
in
relatively close proximity to each other. However, positioning multiple
extruders in
close proximity to each other (so that their respective output nozzles are in
close
proximity to each other) may present one or more challenges. For example, the
overall widths of the extruders may prevent their respective output nozzles
from
.. being in relatively close proximity to each other. Additionally, or
alternatively,
positioning three or more extruders in a side-by-side-by-side arrangement may
inhibit or prevent access to the 'middle' extruder(s).
[00183] In one embodiment, extruders having the same length may be
utilized wherein the feeders are staggered. Using extruders having the same
length may permit the use of identical extruders that are used in unison. In
such a
case, one or more of the extruders may be provided with an extension conduit
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1700 on the output nozzle 1200 such that each extruder may communicate with
the common mold or extrusion die. In such a case, it will be appreciated that
the
extension conduit 1700 may be heated to maintain the fluidity of the plastic
therein.
[00184] For example, as exemplified in Figures 29 and 30, extruders 1000a,
1000b, and 1000c, each having substantially the same axial length LAxiai
between
their feed inlet 1620 and their output nozzle 1200, are positioned relative to
each
other such that extruders 1000a and 1000c are positioned side-by-side, and
extruder 1000b is offset rearwardly in an axial direction from extruders 1000a
and
1000c. In the illustrated example, the output of extruder 1000b feeds into an
inlet
end 1702 of an extension conduit 1700 positioned between extruders 1000a and
1000c. In this arrangement, a nozzle 1720 at the output end 1704 of extension
conduit 1700 is axially and vertically aligned with the outputs 1200a, 1200c
of
extruders 1000a and 1000c. This may facilitate the connection of the outputs
1200a, 1200c, and 1720 to a common mold (not shown).
[00185] Extension conduit 1700 is optionally configured to maintain
the
temperature of flowable material traveling through the conduit from the output
nozzle 1200b of extruder 1000b to the nozzle or output 1720 of extension
conduit
1700. Optionally, the extension conduit 1700 is thermally insulated, and may
.. optionally include one or more heating or cooling elements to control the
temperature of material within the conduit 1700.
[00186] In an alternative embodiment, the extruders may be of
different
lengths to enable the feeders to be at staggered locations. In such a case, an
extension conduit 1700 may not be utilized.
[00187] For example, as exemplified in Figures 31 to 33, two extruders
1000a, 1000b, with different axial lengths LAxiai between their feed inlet
1620 and
their output nozzle 1200, are positioned side-by-side. In this arrangement,
the
outputs 1200a, 1200b of the extruders are axially and vertically aligned with
each
other. This may facilitate the connection of the outputs 1200a, 1200b to a
common mold (not shown).
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[00188] Alternatively, or in addition to staggering the position of
the feeders,
with or without using an extension conduit 1700, the plastic material output
from a
plurality (i.e. two or more) of extruders, which is in a flowable or melted
state, may
be directed into a heated manifold, which may itself be connected to a mold.
[00189] For example, as exemplified in Figures 34 to 37, six extruders
1000a-f are each in fluid communication with a common manifold 1800. As
exemplified, the output 1820 of the common manifold 1800 is directly connected
to a common mold (not shown). Thus, each of the six extruders 1000a-f may be
in
fluid communication with a common mold via common manifold 1800.
[00190] More specifically, the output ends of the nozzles 1200a-f are each
fluidically coupled to a respective manifold inlet port 1812a-f. Manifold
inlet ports
1812a-f each provide fluid communication to at least one interior conduit 1830
within manifold 1800, which in the illustrated example is perhaps best shown
in
Figures 36 and 37.
[00191] In the illustrated example, the extruders 1000a-f are arranged
relative to the common manifold 1800 such that the direction of flow of
material
through the extruder barrels is approximately perpendicular to the direction
of flow
of material through the manifold 1800. In other words, with reference to
Figure 35,
the angle 9 between the direction of material flow 1625 through extruder 1000b
.. and the axial direction of material flow 1825 through manifold 1800 is
about 90 .
Alternatively, one or more extruders may be arranged relative to the manifold
1800 such that the angle 9 is an acute angle (e.g. between about 80 to 10 ,
or
between about 60 to 30 , or between about 50 to 40 , or about 45 ).
Providing
an acute angle 9 between an extruder 1000 and manifold 1800 may have one or
more advantages. For example, this allows the flowing material to undergo a
change of direction of less than 90 , which may reduce backpressure through
the
manifold conduit 1830 and/or the extruder barrel 1100.
[00192] Using a manifold 1800 with the extruders positioned along part
or all
of the length of the manifold enables the extruders to be spaced apart for
ease of
maintenance. In addition, it permits the feeders to be spaced apart such that
each
may have a separate hopper or, as discussed subsequently, it may permit some
of the feeders to use a common hopper.
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[00193] Manifold 1800 is optionally configured to maintain the
temperature of
flowable material traveling through the one or more conduits 1830. As the
plastic
material exiting the extruders 1000 is in a flowable state due to its elevated
temperature, if the flowable material is allowed to cool, it will begin to
solidify,
which may not be desirable.
[00194] Accordingly, manifold 1800 optionally includes one or more
heating
elements 1850 that are operable to maintain the flowable plastic material
within
the manifold at an elevated temperature (which may be the same or different
than
the temperature at which the material exits the extruder(s) 1000) so that the
plastic material remains in a flowable state until it exits the manifold. In
the
example illustrated in Figures 36 and 37, band heaters 1850 are positioned
along
the length of conduit 1830.
[00195] Also, the manifold 1800 is optionally thermally insulated. In
the
example illustrated in Figures 36 and 37, an insulating layer 1860 is
positioned
around the length of conduit 1830 and the band heaters 1850.
[00196] In the illustrated examples, flow through the heated conduit
1830 is
induced by the pressure of the flowable plastic material exiting each of the
extruders 1000. Optionally, the conduit 1830 may be provided with one or more
ejection assist members to increase the pressure and/or flow for material
flowing
through the conduit.
[00197] For example, a rotatable delivery screw (e.g. similar to screw
1300)
may be provided within conduit 1830, and rotation of such the delivery screw
may
assist in advancing flowable plastic material towards the output 1820 of the
conduit 1830.
[00198] Alternatively, or in addition, a retractable piston or plunger may
be
provided within conduit 1830 (e.g. at the end 1832 of the conduit 1830
opposite
the conduit output end 1834). Advancement of such a plunger towards the
conduit
output 1834 (e.g. via one or more mechanical, hydraulic, or pneumatic
actuators)
may increase the pressure of material in conduit 1830 (e.g. by reducing the
effective volume of conduit 1830).
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[00199] Providing conduit 1830 with an ejection assist member may have
one or more advantages. For example, once a cavity of a mold connected to the
output of conduit 1830 is filled (or almost filled) with flowable plastic
material (e.g.,
75%, 80%, 85%, 90%, 95% or more filled), the ejection assist member may be
actuated to increase the pressure of material in conduit 1830, which may
increase
the pressure of the material in the mold. Such an arrangement may allow for
large
and/or complex mold cavities to be filled using a relatively low-pressure
output
from an extruder, and subsequently subjected to higher pressures that may be
required or desirable to properly fill the mold and/or to compress the
flowable
material within the mold cavity to improve one or more physical properties of
the
molded component.
[00200] Another possible advantage of this approach relates to the
production of molded components with relatively complicated geometries, and/or
the production of relatively large molded components. In this respect, since
the
molding process outlined above does not rely on the output or operating
pressure
of the extrusion barrels to provide the maximum pressure on the flowable
material
within the mold cavity (instead relying on one or more ejection assist members
within the conduit 1830), such a molding process may be 'scaled up' to provide
higher molding pressures (e.g. for use with molds with relatively complex
internal
cavities and/or with molds for relatively large molded components) without
having
to 'scale up' the operating pressure of the extruders.
[00201] In some embodiments, where multiple extruders are in
communication with a common mold (e.g. via a heated manifold or conduit 1830),
the input material for each extruder may be the same. For example, pelletized
feedstock of the same polymer may be fed in to each extruder, such that the
output from each extruder and the output from the common manifold generally
has the same composition.
[00202] Optionally, one or more extruders in communication with a
common
manifold may be provided with a different input material than the other
extruder(s).
For example, one or more extruders may be fed a different polymer feedstock
than one or more of the other extruders. This can enable the production of an
inner core of material with a glass filed material for strength and an outer
layer
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without any filler to create a lubricious outer surface. Similarly, one
extruder can
provide a colour for a stripe of a product while the second extruder provides
the
core colour for the product. Additionally, or alternatively, one or more
extruders
may be concurrently fed with both a polymer feedstock and one or more
additives
(e.g. a color dye, a stabilizing agent, an antioxidant, a flame retardant,
etc.) while
one or more of the other extruders may only be fed with a polymer feedstock.
[00203] Providing an apparatus that allows an additive to be provided
in one
or more extruders may have one or more advantages. For example, providing
color dye(s) in only some of the extruders in communication with a common
manifold may result in an aesthetically different molded or extruded component
than if the output from each extruder was similarly dyed (e.g. the color of
the
material output from the conduit may not be homogenous). As another example,
if
an additive is no longer used (e.g. if the apparatus is transitioned to
produce
different components), only the extruder(s) in which the additive was used may
need to be cleaned out before transitioning to the new input material.
[00204] Optionally, a mechanical mixing or blending member (not shown)
may be provided in flow communication between the heated manifold 1800 and a
mold to be filled by the material exiting the heated manifold. For example, a
static
mixer and/or a driven gear mixer (not shown) may be provided at the output end
1834 of the conduit 1830, either upstream or downstream of output nozzle 1820.
[00205] Providing a mechanical mixer downstream of the output of each
extruder connected to the common manifold 1800 may have one or more
advantages. For example, such a mixer may promote a relatively homogenous
output material from the conduit 1830, even where some of the extruders 1000
connected to the common manifold are provided with a different input materials
and/or additives.
[00206] If two or more extruders are utilized, then a common hopper
may be
used for at least two of the feeders. For example, extruders that have feeders
positioned proximate each other may use a common hopper. An advantage of
such a design is that it may maintain a common head pressure of material above
the different screws so as to maintain a more consistent feed rate. Also, it
may
make filing of the system easier.
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[00207] For example, as exemplified in Figures 34 to 37, input
material is
loaded into the inlet hopper 1020 of each extruder 1000. However, the 'middle'
extruders 1000b and 1000e ¨ and particularly their inlet hoppers 1020b and
1020e ¨ may be at least somewhat challenging to access, particularly as
.. compared to the inlet hoppers of extruders 1000a, 1000c, 1000d, and 1000f.
Optionally, the feed inlets of two or more extruders may be connected to a
common feed hopper.
[00208] Figures 38 and 39 illustrate an example apparatus in which
pairs of
extruders 1000 provided on an opposite side of a manifold are provided with a
common feed hopper. In the illustrated example, a common hopper 2020a is
connected to the inlet passages 1620a, 1620f of extruders 1000a, 1000f, such
that input material loaded into the common hopper 2020a may be directed to one
of the two extruders 1000a, 1000f. Also, a common hopper 2020b is connected to
the inlet passages 1620b, 1620e of extruders 1000b, 1000e, and a common
hopper 2020c is connected to the inlet passages 1620c, 1620d of extruders
1000c, 1000d.
[00209] Figures 40 and 41 illustrate an example apparatus in which
pairs of
extruders 1000 on the same side of a manifold are provided with common feed
hoppers. In the illustrated example, a common hopper 2020a is connected to the
inlet passages 1620a, 1620f of extruders 1000a, 1000f, a common hopper 2020b
is connected to the inlet passages 1620b, 1620c of extruders 1000b, 1000c, and
a
common hopper 2020c is connected to the inlet passages 1620d, 1620e of
extruders 1000d, 1000e.
[00210] Providing a common hopper for two or more extruders may have
one or more advantages. For example, it may allow two extruders to be loaded
from a single feed location.
[00211] It will be appreciated that some of the embodiments disclosed
herein
may not use any of the features of the heated conduit disclosed herein and
that, in
those embodiments, a conduit of any kind known in the art may be used.
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Modular extruder
[00212] In accordance with another aspect of this disclosure, a bench
scale
extruder as disclosed herein may be of a modular design. Using modular
components that are readily assemblable and disassemblable permits an extruder
to be shipped as individual components and assembled on site without the need
of a skilled tradesperson. These features may be used by themselves or in any
combination or sub-combination with any other feature or features described
herein.
[00213] In accordance with this aspect, an extruder 1000 may be
assembled
from (and preferably disassembled into) a relatively low number of parts or
modules. A modular extruder design may have one or more advantages. For
example, assembly of such an extruder may be relatively simple, which may
reduce time and/or cost required to install the extruder on site.
[00214] Optionally, in some embodiments, extruder 1000 includes at
least
four modular components. Specifically, a modular extruder may include an
extruder barrel module, an extruder feeder module, a screw motor module, and
an
electronics module. Advantageously, a design including these modular
components may allow one or more of these modular components to be provided
in different variations, which may allow a large number of extruder
configurations
to be provided by selecting desired combinations of modular components. For
example, a different screw motor module (e.g. a module with a 5 hp motor, or a
module with a 2.5 hp motor, etc.) may be selected based on a desired operating
speed and/or torque of the feed screw 1300 of extruder 1000. As another
example, a different barrel length (e.g. 36", or 48", etc.) may be selected
based on
the material to be extruded. By providing at least these four main components
of
extruder 1000 in a modular configuration, a number of possible extruder
configurations may be assembled.
[00215] With reference to Figure 9, in the illustrated example
extruder 1000
is shown in a partially disassembled configuration. A barrel module may
comprise
barrel heaters 1110 and output nozzle assembly 1200 that are provided on
barrel
1100. Optionally, the screw 1300 may be part of the barrel module or may be a
separate element. For example, if the screw 1300 extends into the flow passage
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of the feeder and the barrel, then the screw may be part of the barrel module,
the
feeder module, the screw motor module, or a separate component.
[00216] Barrel module is removably connectable to an extruder feeder
module to provide flow communication between the interior of barrel 1100 and
an
internal flow passage 1630 of the feed block 1600. As exemplified in Figure 9,
extruder 1000 includes a feed block 1600 (which, as discussed above, may
optionally include a feed block insert 1605), and a hopper 1020. In this
example,
feed block 1600 may be characterized as an extruder feeder module.
Alternatively, the hopper 1020 may be secured to feed block 1600, and the
combined hopper and feed block may be characterized as an extruder feeder
module.
[00217] The barrel module may be coupled, and optionally releasably
coupled, to the extruder feeder module using a threaded connection.
Specifically,
barrel 1100 may have an external threaded section 1103 at the inlet end 1102
and
extruder feed block 1600 may include a threaded port 1613 positioned at the
outlet end 1604 of the internal flow passage 1630 of the feed block 1600.
Threaded port 1613 is configured to receive the threaded barrel end 1103.
[00218] An extruder feeder module may also be removably connectable to
a
screw motor module. The screw motor module is the module that provides motive
force to the screw 1300 and, optionally, may include the screw 1300. As
exemplified in Figure 9, extruder 1000 includes a combined or integrated gear
box
1040 and drive motor 1030, and an adjustable-speed drive 1035. In this
example,
the gearbox 1040 and motor 1030 may be characterized as a screw motor
module. Alternatively, adjustable-speed drive 1035 may be secured to the
combined gear box 1040 and drive motor 1030, and the combined motor drive,
motor, and gearbox may be characterized as a screw motor module.
[00219] In the illustrated example, a screw motor module may be
coupled to
an extruder feeder module using a plurality of bolts 1699 (see e.g. Figures
17, 21,
and 22). Optionally, with reference to Figures 12 and 22, screw 1300 may be
positioned in the internal flow passage 1630 of the feed block 1600 such that
a
drive engaging end 1344 of the screw 1300 is accessible from the motor
mounting
end 1684 of the extruder feeder module. The drive engaging end 1344 of screw
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1300 may be coupled to a screw motor module using any suitable method known
in the art, such as a threaded coupling, a keyed joint, and the like.
[00220] As exemplified in Figure 9, extruder 1000 includes user input
devices and/or control electronics enclosed in a control housing or cabinet
1010.
In this example, housing 1010 and the control electronics housed therein may
be
characterized as an electronics module. In the illustrated example, the
electronics
module may be mechanically secured to one or more other modules and/or to an
extruder base 1005 (as discussed subsequently), and may be configured to
'straddle' the extruder barrel 1100. Notably, in the illustrated example this
allows
lower portions of housing 1010 to act as a housing or shroud for barrel 1100.
[00221] The electronics module is optionally electrically connectable
with the
barrel module, e.g. to power and/or control the operation of band heaters
1110.
The electronics module is also optionally electrically connectable with the
screw
motor module (e.g. with drive motor 1030 and/or adjustable-speed drive 1035)
to
control the operation of motor 1030, thereby controlling the rotation of screw
1300.
Optionally, the electronics module may be indirectly electrically connectable
with
the screw motor module via electrical wiring associated with the extruder
feeder
module (e.g. a wiring harness mounted internally or externally to feed block
1600).
[00222] Optionally, the electronics module may be automatically
electrically
connectable with the barrel module and/or the screw motor module (e.g. with
drive
motor 1030 and/or with adjustable-speed drive 1035) when the electronics
module
is mounted as part of the extruder 1000.
[00223] For example, an electrical connector (not shown) operatively
connected to electronic components of the screw motor module may be provided
adjacent the mounting location between the screw motor module and the extruder
feeder module. A mating electrical connector (not shown) operatively connected
to the electronics module may also be provided adjacent this mounting
location. In
such an arrangement, aligning and mechanically coupling the extruder feeder
module and the screw motor module may result in engagement of the electrical
connectors of the screw motor module and the extruder feeder module (e.g., one
connector may be 'female', and the other may be `male'). Aligning and
mechanically coupling the electronics module to the extruder feeder module may
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result in engagement of the electrical connectors of the electronics module
and
the extruder feeder module and, indirectly, connect the electronics module
with
the screw motor module.
[00224] Additionally, or alternatively, the barrel module may be
automatically
electrically connected to the feeder module in a similar way. Aligning and
mechanically coupling the electronics module to the barrel module may result
in
engagement of the electrical connectors of the electronics module and the
barrel
module and, indirectly, connect the electronics module with the screw motor
module via the feeder module.
[00225] The extruder 1000 may be secured to any base. For example, the
extruder 1000 may be mechanically secured to an extruder base 1005, which in
the illustrated example is a length of C channel steel. This may facilitate
the
installation of extruder 1000 within a workplace. For example, base 1005 may
be
secured to a floor surface or other mounting location, and the modular
components of extruder may be installed on the base. It will be appreciated
that
one or more of the modules, e.g., the barrel module, may be secured to base
1005 (with the other modules being secured directly or indirectly to the
module(s)
that are secured to the base 1005), and base 1005 may subsequently be secured
to a floor surface or other mounting location.
[00226] Optionally, screw 1300 may be a single integrally formed screw.
Alternatively, an extrusion screw 1300 may be made from two or more parts. For
example, an extrusion screw 1300 may include a feeder screw body section and a
barrel screw body section. Feeder and barrel screw body sections may be joined
using any suitable method, such as a threaded coupling, a keyed joint, welding
and the like. In such embodiments, a feeder screw body section may be secured
to extruder feed block 1600 or to the screw motor module, and a barrel screw
body section may be coupled to the feeder screw body section before, after, or
concurrently to coupling the barrel module to the extruder feeder module.
[00227] Providing a multi-part screw with a feeder screw body section
secured to an extruder feeder module or to a screw motor module may have one
or more advantages. For example, such an arrangement may facilitate proper
alignment of screw 1300 within feed flow passage 1630 and/or barrel 1100,
and/or
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reduce the time needed to assemble extruder 1000. It may also permit the screw
to be shipped internal of the modules and thereby be protected during
shipment.
[00228] As noted above, a modular extruder design may have one or more
advantages. For example, the overall weight and dimensions of each module may
result in their being shippable by a commercial courier company (e.g. FedEx,
UPS, etc.) without excessive overweight and/or oversize surcharges. For
example, each module may weigh less than under 175 lbs, 150 lbs, 135 lbs, or
100 lbs.
[00229] It will be appreciated that some of the embodiments disclosed
herein
may not use any of the features of the modular extruder disclosed herein and
that,
in those embodiments, an extruder of any suitable construction may be used.
[00230] As used herein, the wording "and/or" is intended to represent
an
inclusive - or. That is, "X and/or Y" is intended to mean X or Y or both, for
example. As a further example, "X, Y, and/or Z" is intended to mean X or Y or
Z or
.. any combination thereof.
[00231] While the above description describes features of example
embodiments, it will be appreciated that some features and/or functions of the
described embodiments are susceptible to modification without departing from
the
spirit and principles of operation of the described embodiments. For example,
the
various characteristics which are described by means of the represented
embodiments or examples may be selectively combined with each other.
Accordingly, what has been described above is intended to be illustrative of
the
claimed concept and non-limiting. It will be understood by persons skilled in
the art
that other variants and modifications may be made without departing from the
scope of the invention as defined in the claims appended hereto. The scope of
the
claims should not be limited by the preferred embodiments and examples, but
should be given the broadest interpretation consistent with the description as
a
whole.
[00232] This specification also includes the subject matter of the
following
clause sets:
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Clause Set A:
1. A feeder for an extruder, the feeder comprising:
(a) a feed flow passage, the feed flow passage extending in an
axial
direction from a feeder inlet to a feeder outlet;
(b) an axially extending rotatable screw provided in the feed flow
passage, wherein rotation of the screw draws a feedstock in a direction of
flow to the feeder outlet; and,
(c) the feeder inlet has an inlet passage that overlies the screw,
the inlet
passage has an upper end, a lower end adjacent the screw, a length in the
axial direction, a width in a plane transverse to the axial direction, and a
depth extending between the upper and lower ends of the inlet passage,
wherein the width decreases in the direction of flow.
2. The feeder of clause 1 further comprising a hopper having a hopper
outlet
and the feeder inlet is provided below the hopper outlet.
3. The feeder of clause 1 further comprising a cooling member.
4. The feeder of clause 3 wherein the cooling member comprises cooling
channels provided in thermal communication with the feed flow passage.
5. The feeder of clause 1 further comprising a feeder insert that is
removably
mounted in a feed throat of the feeder, wherein the feeder insert has the
inlet
passage.
6. The feeder of clause 5 wherein the feeder removably receives different
feeder inserts, wherein a first feeder insert has a first inlet passage and
the
second feeder insert has a second inlet passage wherein the second inlet
passage has a different configuration to the first inlet passage.
7. The feeder of clause 6 wherein each inlet passage has an upstream end in
the direction of flow through the feed flow passage and a downstream end in
the
direction of flow through the feed flow passage and the second inlet passage
has
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a narrower width at the downstream end of the inlet passage than the first
inlet
passage.
8. The feeder of clause 1 wherein the lower end of the inlet passage has an
inner wall facing the screw and the inner wall is spaced from the outer end of
the
screw by a distance, wherein the distance decreases in the direction of
rotation.
9. The feeder of clause 1 wherein the width decreases at a constant rate in
the direction of flow.
10. The feeder of clause 1 wherein the width decreases at an increased rate
in
the direction of flow.
11. A feeder for an extruder, the feeder comprising:
(a) a feed flow passage, the feed flow passage extending in an axial
direction from a feeder inlet to a feeder outlet;
(b) an axially extending rotatable screw provided in the feed flow
passage, wherein rotation of the screw draws a feedstock in a direction of
flow to the feeder outlet; and,
(c) the feeder inlet has an inlet passage that overlies the screw, the
inlet
passage has an upper end, a lower end adjacent the screw, a length in the
axial direction, a width in a plane transverse to the axial direction, and a
depth extending between the upper and lower ends of the inlet passage,
wherein the lower end of the inlet passage has an inner wall facing the
screw and the inner wall is spaced from the outer end of the screw by a
distance, wherein the distance decreases in the direction of rotation.
12. The feeder of clause 11 further comprising a hopper having a hopper
outlet
and the feeder inlet is provided below the hopper outlet.
13. The feeder of clause 11 further comprising a cooling member.
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14. The feeder of clause 13 wherein the cooling member comprises cooling
channels provided in thermal communication with the feed flow passage.
15. The feeder of clause 11 further comprising a feeder insert that is
removably
mounted in a feed throat of the feeder, wherein the feeder insert has the
inlet
passage.
16. The feeder of clause 15 wherein the feeder removably receives different
feeder inserts, wherein a first feeder insert has a first inlet passage and
the
second feeder insert has a second inlet passage wherein the second inlet
passage has a different configuration to the first inlet passage.
17. The feeder of clause 16 wherein the width decreases in the direction of
flow
and each inlet passage has an upstream end in the direction of flow through
the
feed flow passage and a downstream end in the direction of flow through the
feed
flow passage and the second inlet passage has a narrower width at the
downstream end of the inlet passage than the first inlet passage.
18. The feeder of clause 11 wherein the distance decreases at a constant
rate
in the direction of flow.
19. The feeder of clause 11 wherein the distance decreases at an
increased
rate in the direction of flow.
Clause Set B:
1. A molding apparatus comprising:
(a) a plurality of axially extending extruders wherein each of the
extruders is fluidly connectable with a common mold whereby the mold is
concurrently filled from each of the extruders; and,
(b) each of the extruders has a feed inlet,
wherein the feed inlets are axially spaced from each other.
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2. The molding apparatus of clause 1 wherein at least two of the extruders
have different axial lengths.
3. The molding apparatus of clause 1 wherein the extruders feed into a
common manifold and the manifold is connectable to the mold.
4. The molding apparatus of clause 1 wherein the plurality of axially
extending
extruders comprises two extruders that have a common axial length, each
extruder having a nozzle outlet and one of the two extruders further comprises
a
conduit extending from the extruder nozzle outlet to the manifold.
5. The molding apparatus of clause 1 wherein the at least two of the
extruders
further comprise an axially extending conduit extending from the extruder to
the
manifold and the conduits have differing axial lengths.
6. The molding apparatus of clause 1 further comprising a plurality of
hoppers
in flow communication with the feed inlets.
7. The molding apparatus of clause 6 wherein each extruder has a hopper.
8. The molding apparatus of clause 6 wherein a common hopper is provided
for at least two of the extruders.
9. The molding apparatus of clause 3 wherein a first extruder is provided
with
an additive and the common manifold further comprises a mechanical member for
blending the output of the first extruder with the output of at least one
other of the
extruders.
10. A molding apparatus comprising:
(a) a plurality of axially extending extruders, each extruder having
longitudinally extending axis; and,
(b) a heated conduit in flow communication with the plurality of
extruders, wherein the heated conduit is connectable to a mold, whereby
the mold is concurrently fillable from each of the extruders.
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11. The molding apparatus of clause 10 wherein the heated conduit has a
length extending in a direction of flow from an upstream end of the heated
conduit
to a downstream end of the heated conduit and at least some of the extruders
are
in flow communication with the heated conduit at different locations along the
length of the heated conduit.
12. The molding apparatus of clause 10 wherein the axis of at least some of
the extruders extends at an angle to the direction of flow in the heated
conduit.
13. The molding apparatus of clause 10 wherein an included angle located
between the axis of at least some of the extruders and the direction of flow
in the
.. heated conduit is up to 900
.
14. The molding apparatus of clause 10 wherein an included angle located
between the axis of at least some of the extruders and the direction of flow
in the
heated conduit is an acute angle.
15. The molding apparatus of clause 11 further comprising a plurality of
hoppers in flow communication with the extruders wherein at least some of the
hoppers are spaced apart from each other along the direction of flow.
16. The molding apparatus of clause 15 wherein each extruder has a hopper.
17. The molding apparatus of clause 11 further comprising a common hopper
in flow communication with at least two of the extruders.
18. The molding apparatus of clause 10 wherein a first extruder is provided
with an additive and the heated conduit further comprises a mechanical member
for blending the output of the first extruder with the output of at least one
other of
the extruders.
19. The molding apparatus of clause 10 wherein the heated conduit is
provided
with a feedstock ejection assist member.
20. The molding apparatus of clause 10 wherein the feedstock ejection
assist
member comprises a plunger at an upstream end of the heated conduit.
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