U.S. patent application number 11/711674 was filed with the patent office on 2007-09-13 for method and system for agglomerating chopped fiber strand and product.
This patent application is currently assigned to Johns Manville International, Inc. Invention is credited to John A. Cooper, Richard J. Kindle.
Application Number | 20070210470 11/711674 |
Document ID | / |
Family ID | 32107663 |
Filed Date | 2007-09-13 |
United States Patent
Application |
20070210470 |
Kind Code |
A1 |
Kindle; Richard J. ; et
al. |
September 13, 2007 |
Method and system for agglomerating chopped fiber strand and
product
Abstract
A new system and method for making agglomerates of chopped glass
fiber strand segments is disclosed as are the agglomerates
produced. The agglomerates, made by feeding wet chopped fiber
strand segments into a wave chamber having a vibrating curved
surface that produces a wave-like flow pattern in the segments and
agglomerates, have a substantially higher bulk density and greatly
improved flow characteristics than conventional chopped strand
reinforcements. The wet agglomerates are usually dried in any
conventional dryer.
Inventors: |
Kindle; Richard J.; (Bowling
Green, OH) ; Cooper; John A.; (Swanton, OH) |
Correspondence
Address: |
JOHNS MANVILLE
10100 WEST UTE AVENUE
LITTLETON
CO
80127
US
|
Assignee: |
Johns Manville International,
Inc
|
Family ID: |
32107663 |
Appl. No.: |
11/711674 |
Filed: |
February 28, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11149162 |
Jun 10, 2005 |
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11711674 |
Feb 28, 2007 |
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10291322 |
Nov 8, 2002 |
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11149162 |
Jun 10, 2005 |
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Current U.S.
Class: |
264/71 |
Current CPC
Class: |
C03C 25/12 20130101;
B01J 2/18 20130101; D04H 1/72 20130101; D04H 1/4318 20130101; B29B
9/14 20130101; C03B 37/14 20130101; D04H 1/732 20130101; C03C 25/26
20130101 |
Class at
Publication: |
264/071 |
International
Class: |
B29C 43/22 20060101
B29C043/22 |
Claims
1-36. (canceled)
37. A method of agglomerating chopped bundles of wet fiberglass
strands into uniform segments, comprising: providing a container
having a curved inner surface disposed about a generally
horizontally extending longitudinal axis, mounting the container on
a plurality of springs to resiliently support the container above a
base surface therefore, placing a plurality of chopped bundles of
wet fiberglass strands to be agglomerated onto the curved inner
surface at an input end of the container, producing vibratory force
to cause the chopped bundles of wet fiberglass strands to move from
the input end to an output end of the container, the vibratory
force causing the chopped bundles of wet fiberglass strands to be
directed in a rising and falling path of rolling movement, whereby
the rolling movement of the chopped bundles produces uniform
segments by causing agglomeration of the wet fiberglass
strands.
38. The method of claim 37 wherein the container is in the form of
a cylindrical drum and a dimpled liner is provided within the
cylindrical drum to define the curved inner surface upon which the
chopped bundles of fiberglass strands undergo rolling movement.
39. The method of claim 38 wherein the curved inner surface defined
by the dimpled liner within the cylindrical drum includes a
plurality of generally elongated dimples projecting inwardly in
relation to the cylindrical drum so as to be staggered in adjacent
rows.
40. The method of claim 39 wherein the generally elongated dimples
of the curved inner surface defined by the dimpled liner are
generally elliptical and are elongated in the direction of the
generally horizontally extending longitudinal axis of the
container.
41. The method of claim 37 wherein the vibratory force which is
produced is directed along a linear path displaced from the
generally horizontally extending longitudinal axis and also
displaced from the center of gravity of the container.
42. The method of claim 37 wherein the plurality of springs upon
which the container is mounted resiliently support the container
above the base surface for
Description
[0001] This application is a continuation of, and claims priority
benefit under 35 U.S.C. .sctn.120 to, parent U.S. patent
application Ser. No. 11/149,162, filed Jun. 10, 2005, which is a
continuation of, and claims priority benefit under 35 U.S.C.
.sctn.120 to, parent U.S. patent application Ser. No. 10/291,322,
filed Nov. 8, 2002, the contents of which is incorporated by
reference herein for all purposes.
[0002] This invention includes a method and system for
agglomerating wet chopped glass, polymer, etc. fiber strand
segments into pieces that are denser and more free flowing than
normal chopped strand. The resultant product is useful in processes
for making fiber reinforced plastics and in processes for making
other fiber containing products.
[0003] Chopped strand reinforcement products such as chopped strand
for thermoplastics are typically made by pulling fibers from a
plurality of fiberizers while the material is in a molten state,
cooling the fibers, coating the fibers with water and a chemical
sizing, gathering the fibers into strands, chopping the strands
into segments of desired lengths and drying the wet chopped strands
in a vibrating flatbed oven and sorting the resultant dry chopped
strand to remove undesirable lumps and fuzz. A typical process can
be seen in U.S. Pat. No. 3,996,032. These types of processes
produce chopped strand segments having a wide range of diameters
and containing a wide range of numbers of fibers, e.g. from just a
few fibers to 4000 or more fibers per segment.
[0004] Hundreds of millions of pounds of chopped strand products
have been produced in the above described processes and while these
products worked well in making fiber reinforced products of a wide
variety. However, for several years there has existed a desire for
a product that has a higher density, flows better through small
openings in cone shaped bins and feeders and that contains fewer
small diameter segments that tend to produce fuzz balls in the
customers system.
[0005] Several processes have been disclosed for pelletizing or
agglomerating chopped strand. These include U.S. Pat. Nos.
3,984,603, 4,107,250, 4,164,534, 4,840,755, 5,002,827, 5,185,204,
5,269,993, 5,578,535, 5,585,180, 5,639,807, 5,693,378, 5,868,982,
5,945,134 and WO 01/05722. While at least one of these processes
produces chopped strand reinforcement segments that meet most or
all of the desired improvements, there are still system and process
improvements and efficiencies desired such as less costly, simpler
and lower operating cost systems and processes.
SUMMARY OF THE INVENTION
[0006] The present invention includes a system and method for
making agglomerated reinforcing fiber strand segments, such as
agglomerated chopped strand for reinforcing plastics and products
made by the method. The system comprises a chopper for chopping one
or a plurality of wet strands of fibers having a chemical sizing on
the circumferential surfaces of the fibers into segments, and
agglomerator and a dryer for drying agglomerates of wet chopped
strand segments, the improvement being an agglomerator comprising a
non-rotating wave chamber having a generally horizontal,
non-rotating, elongated, vibrating curved surface, working surface,
for contacting the wet chopped strand segments, the working surface
being generally concave in cross section in a plane perpendicular
with the length of the working surface. The term "wave chamber"
designates the type of action that the working surface produces in
the chopped strand segments and agglomerates, moving the material
upward on the working surface like an ocean wave and curling it
over the top to slide back downwardly inside the chamber to the
working surface where the wave action is repeated again and again
until the agglomerates exit the wave chamber.
[0007] By generally horizontal is meant horizontal plus or minus up
to about 10 degrees. Preferably the working surface declines from
an upstream end to a downstream end by a variable amount up to
about 6 degrees. By non-rotating is meant that the wave chamber
does not rotate a full revolution, preferably doesn't rotate more
than 180 degrees and most preferably doesn't rotate more than about
10 degrees. The preferred embodiments disclosed herein rotate, if
at all, only due to the amplitude of vibration and spring action
and any rotation is reciprical, i.e., back and forth. By generally
concave surface is meant that the working surface in cross section
can have a constant radius or a changing radius of two or more
radii. By wave action is meant a type of action similar to a
breaking wave.
[0008] Preferably, but not necessarily, the contacting or working
surface has a textured or non-stick surface to reduce tendency of
the wet chopped strand segments to stick to said surface and to aid
in achieving a wave action in the chopped strand segments and
agglomerates. The frequency and/or amplitude of vibration can
preferably be varied to produce and optimize the wave like movement
of the wet chopped strand segments and agglomerates.
[0009] Preferably the dryer is a vibrating, flat bed dryer known
for drying wet chopped strand segments. The system can have
additional equipment at the dryer's downstream end or downstream of
the dryer for sorting the agglomerated chopped strand segments to
remove oversize and undersize pieces. The system can also have
conveyor means for collecting the wet chopped strand segments from
the chopper and delivering said segments to the vibratory wave
chamber.
[0010] The method of the present invention includes chopping one or
a plurality of strands of wet fiber into chopped strand segments,
the segments also containing a chemical sizing on circumferential
surfaces of the fibers, forming the wet segments into agglomerates
and drying the agglomerates to form agglomerates of chopped fiber
strands, the improvement comprising forming agglomerates by
subjecting a layer of the wet chopped strand segments to vibration
against the generally concave working surface of an elongated
curved surface, the working surface comprising at least about a 60
degree arc circle with at least about 45-60 degrees of the arc
being on one side of an imaginary vertical line extending through
the lowest point on the working surface and the remainder, if any,
lying on the opposite side of the vertical line. Preferably, the
frequency and/or amplitude of the vibrators can be changed to
optimize the wave action and quality of agglomerates at different
feed rates and/or with different size or type of chopped strand
segments. The front to exit of the vibrating curved surface can be
declined to affect the retention time the segments and agglomerates
are in the wave chamber and the capacity of the wave chamber.
[0011] The general appearance of the agglomerates in shape and size
is similar to that of wild rice or grains of wheat. The
agglomerates are about 1/8 to about 1/2 inch long and typically
about 1/8 to about 1/4 inch long. The diameter of the agglomerates
can vary and can be changed to address the needs of different
applications, but typically are less than about 3/16-1/4 inch in
diameter. The agglomerates of chopped fiber strand segments
produced by the system and method of the invention have
substantially reduced fuzz content and segments of only a few
fibers. The agglomerates have substantially improved density and
flow characteristics compared with conventional, non-agglomerated,
dry chopped strand products, and equal or improved performance
characteristics as reinforcements in various plastics and other
matrices. Agglomerates run through conventional sorting devices to
remove fuzz clumps, fines or lumps are further improved a small
amount, because the agglomeration tends to eliminate fines and fuzz
and the above method and system produces hardly any oversized
lumps.
[0012] When the word "about" is used herein it is meant that the
amount or condition it modifies can vary some beyond that so long
as the advantages of the invention are realized.
[0013] Practically, there is rarely the time or resources available
to very precisely determine the limits of all the parameters of
ones invention because to do would require an effort far greater
than can be justified at the time the invention is being developed
to a commercial reality. The skilled artisan understands this and
expects that the disclosed results of the invention might extend,
at least somewhat, beyond one or more of the limits disclosed.
Later, having the benefit of the inventors disclosure and
understanding the inventive concept and embodiments disclosed
including the best mode known to the inventor, the inventor and
others can, without inventive effort, explore beyond the limits
disclosed to determine if the invention is realized beyond those
limits and, when embodiments are found having no further unexpected
characteristics, the limits of those embodiments are within the
meaning of the term about as used herein. It is not difficult for
the artisan or others to determine whether such an embodiment is
either as expected or, because of either a break in the continuity
of results or one or more features that are significantly better
than those reported by the inventor, is surprising and thus an
unobvious teaching leading to a further advance in the art.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a front view of a prior art system for making
agglomerates of wet chopped strand.
[0015] FIG. 2 is a front view of a system for making agglomerates
of wet chopped strand in accordance with the present invention.
[0016] FIG. 3 is a front view of one device for agglomerating
chopped strand segments in accordance with the present
invention.
[0017] FIG. 4 is an exit end view of the device shown in FIG. 3
with the end cap with exit port removed to see the
agglomerates.
[0018] FIG. 5 is a cross section of a wave chamber of another
agglomerating device suitable for the invention.
[0019] FIG. 6 is a cross section of a wave chamber of still another
agglomerating device suitable for the invention.
[0020] FIG. 7 is a cross section of a wave chamber of yet another
agglomerating device suitable for the invention.
[0021] FIG. 8 is a partial cross section of the wave chamber shown
in FIGS. 3 and 4 and shows a working surface producing the wave
like action that agglomerates chopped strand segments in the
present invention.
[0022] FIGS. 9 and 10 show optional working surfaces having two or
more radii.
DETAILED DESCRIPTION OF THE INVENTION
[0023] FIG. 1 shows a prior art system used to manufacture
agglomerated chopped strand products with different process
portions labeled as A, B, C and D. Portion A is the fiber forming
part of the system. Portion B is the chopping part of the system.
Portion C is the agglomerating part of the system and portion D is
the drying, sorting and packaging part of the system.
[0024] Fibers 1, such as glass or polymer fibers, are formed by
passing the molten form of the material through nozzles 2 in the
bottom of bushings 4, fiberizers, in a known manner and the fibers
1 are pulled rapidly to attenuate the fibers to the desired
diameter and to quickly cool the fibers 1 with air to below their
softening point. A fine mist of water is sprayed on the fibers to
help cool them and the fibers 1 are rapidly pulled into contact
with the roller of a chemical sizing applicator 6 where the
surfaces of the fibers are coated with any one of numerous chemical
sizings. The sizings are usually water based and typically contain
a resinous film former, a silane and one or more surfactants or
wetting agents, cross linkers etc. The type of sizing used is
determined by the type of polymer or other matrix that the fibers
will be used to reinforce as is well known. The present invention
is applicable to a broad range of sizing compositions. The sizing
composition is not a part of the present invention but rather the
present invention is applicable to many known sizings.
[0025] The chemically coated, wet fibers are next pulled around a
grooved pulley 8 that gathers all of the fibers 1 from the bushing
4 into a single strand 9. The fiber strands 9 can contain any
number of fibers from a few hundred to more than 4000. The fibers 1
and the fiber strands 9 are usually pulled at the desired speed by
the chopper in part B of the system, which in this case is a
chopper 10. The strands 9 may be pulled over a strand guide roll 11
that keeps individual strands 9 separated. Chopper 10 is a known
fiber strand chopper comprising a backup roll 12, a blade roll 13,
a knurled idler roll 14, a strand moving finger 15, a strand
starting roll 16, a roll starting switch 17, and a new strand
grooved roll, 18. The chopper 10 and its operation are disclosed in
detail in U. S. Pat. No. 6,148,640, the disclosure of which is
hereby incorporated herein by reference.
[0026] The chopper 10 separates the fiber strands 9 into segments
19 of desired length. The fiber strand segments 19 are collected on
a belt conveyor 22 and transported to part C of the prior art
system, which is an agglomerator for chopped strand segments 19.
The agglomerator 24 shown here is disclosed in detail in U.S. Pat.
No. 5,945,134 and therefore will not be described further here.
Other devices for agglomerating or pelletizing chopped strand
segments have been disclosed in other U.S. patents such as U.S.
Pat. Nos. 3,984,603, 4,107,250, 4,164,534, 4,840,755, 5,002,827,
5,185,204, 5,269,993, 5,578,535, 5,639,807,5,693,378, 5,585,180,
5,868,982, however many of the devices and methods disclosed in
these additional patents have not always met all of the current
requirements of the customers for agglomerated chopped strand
products, or have been costly to operate for making glass and/or
polymer fiber segments.
[0027] Following agglomeration, the agglomerated chopped strand
agglomerates 26 (agglomerates), which are still wet, must be dried.
This is accomplished by feeding the agglomerates 26 into part D, a
dryer. Many types of dryers have been used and one of the
frequently used dryers is a vibrating fluid bed dryer 28. This type
of dryer 28, also used to dry chopped fiber strand segments 20 to
form conventional chopped strand reinforcement products, transports
the agglomerates 26 on or above a perforated flat bed 30. The
transporting force is supplied by an eccentric motor 30 acting on
the dryer 28 which is mounted on springs 32. The drying and
suspension of the agglomerates 26 in the dryer 28 is accomplished
with hot air forced through ports 34 into a chamber 33 and on
through perforations in the perforated flat bed 30 and a layer of
the agglomerates 26 and finally through one or more exhaust stacks
35 in a hood 36 of the dryer 28. The chemical sizing in the
agglomerates provides a weak bond in the agglomerates 26 that keeps
them from breaking apart with handling, but allows the fibers to
break apart and disperses in the plastic to which the agglomerates
are later added.
[0028] The dry agglomerates 37 can be packaged immediately as they
exit the dryer 28, or they can be run through an optional part E
which is a sorter screen of any of various known types, such as the
inclined multi deck sorter screen 38 comprising a top screen 40 to
remove any lumps or clumps of fuzz that might be in the
agglomerates through a side exit 39, a lower screen 42 which allows
any fines in the dry agglomerates 37 to pass through to a bottom
chamber and funnel 44 to a scrap bin (not shown). The sorted
agglomerates 37 pass out of the sorter screen and into any package,
such as a kraft board box 45. Known automatic packaging equipment
can be included in part E but is not necessary.
[0029] The known system described above produces acceptable
agglomerated or pelletized chopped strand reinforcement products,
but it is desirable to simplify the agglomeration part of the
system. The inventors have surprisingly found that when wet chopped
fiber strand segments are vibrated in a wave like action by an
elongated vibrating curved working surface, the desired
agglomeration takes place in a very simple device with no large
rotating parts, reduced wearing surfaces and with low energy usage.
The inventors have also found that a device well known for milling
hard minerals and stone to fine powder surprisingly provides the
above described wave action needed to produce the desired
agglomerates from ordinary wet chopped fiber strand segments.
[0030] FIG. 2 shows the present inventive system. Parts A, B, D and
the optional part E are just like the prior art system shown in
FIG. 1, but part C, the wave chamber agglomerator 46 is a device
that provides an elongated vibrating curved surface causing a wave
like action described above which causes the wet chopped fiber
strand segments 19 to agglomerate into wet, slightly flattened,
shaped agglomerates 26 of desired size to form the desired
agglomerated product 48. Typically, the agglomerates 26 will be
about 1/8 inch to about 1/4 inch long with the majority of the
agglomerates having diameters of from about 0.06 inch to about 0.2
inch, but longer agglomerates up to about 1/2 inch are suitable for
some applications. Preferably, at least 75 weight percent of the
agglomerated product is in agglomerates of this diameter, more
preferably at least 85 weight percent and most preferably at least
90 weight percent.
[0031] The method of agglomeration of the wet chopped strand
segments 19 in the inventive system shown in FIG. 2 is the same as
the method used with the conventional system shown in FIG. 1 except
that the agglomeration takes place on or near a non-rotating
curved, vibrating surface instead of on or near a series of
rotating curved surfaces. In the present invention it is not
necessary to add additional moisture or hydrating fluid to the
chopped strand segments prior to agglomeration, nor is it necessary
to add a binder or second sizing composition to the wet chopped
strand prior to agglomeration. The moisture content of the wet
chopped fiber strand coming from the chopper varies from about 10
wt. percent to about 16 wt. percent. Generally, the greater the
moisture content the faster the chopped strand will agglomerate and
the larger will be the agglomerates with the same residence time
and vibration frequency. Preferably the moisture content is within
the range of 12-15 percent, and in production units of 36 inches
inside diameter of the vibrating drum or larger, the moisture
content should not exceed about 15 wt. percent. When using a 36
inch diameter unit, the most preferred moisture content is in the
range of about 12-13.5 wt. percent in the chopped fiber strand
coming from the chopper and entering the wave chamber
agglomerator.
[0032] Any vibrating elongated, concave, curved, surface is
suitable for agglomerating the wet chopped strand segments 19. It
is preferred that the non-rotating curved surface be a side of a
cylinder or a segment or arc of a cylinder having a cross section
of a circle, a portion of a circle, a semi-circle, or less than a
semi-circle. However, curved surfaces having two or more radii are
also suitable.
[0033] While a smooth inner curved surface is acceptable, it is
preferred that the working surface be textured such as with small
spaced apart dimples, ridges, X shaped or some other spaced apart
raised forms to present reduced contact which prevents sticking of
the wet chopped strand segments or partial agglomerates from
sticking on the curved surface, yet providing a better gripping
surface to enhance a lifting of the segments and agglomerates up
the curved surface to optimize the wave action. Various "Toe
Plates", sized and formed into a curved surface with the raised
texture on the concave surface, are suitable. The preferred
material is stainless steel, but other metals coated with
non-corrosive coatings or various plastics, reinforced or not
reinforced would also be suitable as would be various types of
rubber known for use in wear resistant applications. A preferred
dimpled material for the working surface is 304 stainless (#4) 5.WL
product available from the Rigidized Metals Corp. of Buffalo,
N.Y.
[0034] While the curved portion can be 360 degrees it need not be.
A curved portion containing about 210 degrees is suitable as are
smaller portions, but the capacity might be reduced somewhat.
[0035] Surprisingly, one type of device found by the inventors to
be particularly suitable as the agglomerating device 46 in the
present invention is shown in FIGS. 3 and 4. This type of device is
available from General Kinematics Corp. of Barrington, Ill. under
the name of Vibra-Drum.RTM., a device normally used as a milling or
grinding device for stone and minerals.
[0036] A Vibra-Drum.RTM. 50 is shown in front view in FIG. 3 and in
an end view looking at the exit end with a front panel removed in
FIG. 4. The device 50 is comprised of a generally horizontal
cylindrical wave chamber 52 (chamber) having a feed port 54 in an
entrance end cap end and an exit port 56 at the bottom or 6 o'clock
position on a downstream end cap 51. The wave chamber 52 can be of
various diameters depending upon the capacity desired and the
length of the wave chamber. Generally horizontal means that the
cylindrical wave chamber 52 can be horizontal, but preferably
several degrees from horizontal such as less than 10 degrees from
horizontal. Diameters of about 2-3 feet are known to be
satisfactory and it is believed that other diameters would also be
satisfactory, such as 42 inch diameter or larger.
[0037] Normally the cylindrical wave chamber 52 will decline from
an entrance end to an exit end. The angle of declination will
affect the retention time of the wet chopped strand segments 19 and
wet agglomerates 26 in the cylinder 52 and preferably is
adjustable. The chamber 52 has a working surface 53 on its
interior.
[0038] The chamber 52 is mounted on a frame piece 57A attached to
one side of the chamber 52 and on a second frame piece 57B attached
to an opposite side of the chamber 52. The frame piece 57A is
supported by an array of coil springs 58. The array of coil springs
58 comprises a plurality of coil springs 59, preferably arranged in
two spaced apart and parallel rows. Each of the coil springs 59 are
attached on their top ends 60 to an underside of the frame piece
57A. Bottom ends 61 of the coil springs 59 are attached to the top
of an elongated box like frame structure 62 having a length at
least as long as the length of an array of the coil springs 58.
[0039] Mounted on opposite sides of said structure 62 and generally
straddling an end-to-end vertical imaginary centerline of said
structure 62 are two eccentric vibrators 64. The structure 62 and
pair of vibrators 64 are supported on an underneath side by two
pairs of coil springs 65. Each pair of coil springs 65 is located
close to each end of the box channel member 62 as shown in FIG. 3.
The two pairs of coil springs 65 are attached on their lower ends
67 to a frame 68. The frame 68 is comprised of a bottom member or
plate 70 with a foot 71 on the underneath side at each corner of
the bottom member 70 and two spaced apart upright legs 73 attached
to the top of the bottom member 70. The upright legs 73 can be
spaced apart about as much as the two pairs of coil springs 65 with
each leg 73 being aligned with each coil spring in the pair of coil
springs 65, but spaced apart such that each of the legs 73 is on
the opposite side of the bottom member 70 from the pair of coil
springs 65 it is aligned with.
[0040] The second frame piece 57B is supported on its bottom side
by at least two spaced apart coil springs 75 with the top 76 of
each coil spring 75 being attached to the underneath side of the
frame piece 57B and the bottom 77 of each coil spring 75 being
attached to the top 78 of one upright leg 73. The upright legs 73
can be further supported by arm braces 79 attached at one end close
to an upper end of each leg 73 and at the other end to a spot on
the upper side of the bottom member 70 spaced from the upright leg
73 as shown in FIG. 4.
[0041] The generally horizontally wave chamber 52 is therefore
totally supported by coil springs which produce a wave like action
on the wet chopped strand segments 19 that are fed through the feed
port 54 and also on the wet agglomerates 26 as they approach the
exit port 56. A particular advantage of the VibraDrum.RTM. device
shown above is that because of the array of coil springs 58 located
between the vibrators 64 and said wave chamber 52, the vibrators 64
are smaller, requiring less electrical energy usage than if the
vibrators were attached rigidly to said wave chamber 52. The wave
chamber 52 on VibraDrum.RTM. equipment can arranged to be on either
the right of the vibrators 64 or on the left, looking from the feed
end, usually dictated by the orientation of the equipment feeding
the chopped strand segments to the wave chamber 52. The unit shown
in FIGS. 3-4 is a right hand unit. Vibrating wave chamber equipment
are advantageous compared the tumbling devices used in the past
because they are easier to operate and maintain.
[0042] FIG. 4 shows a typical position of the wet agglomerates 26
and wet chopped strand segments 19 in an operating VibraDrum.RTM.
with the array extending from about 5 o'clock to about 9 o'clock on
the curved working surface 53. Thus, about 120 degrees of the
curved surface inside the wave chamber 52 is a "working" surface
and the remainder of the curved surface, at this feed rate, does
not necessarily contact the wet chopped strand segments 19 or the
wet agglomerates 26 and therefore can be modified in many ways. The
feed rate will vary depending upon the size and length of the
generally horizontal wave chamber. Also, even fewer degrees of the
curved surface will be a "working" surface at reduced feed rates or
if a longer wave chamber at greater declination is used. For
example, as little as about 45-70 degrees of contact with the
working surface is suitable, as is about 45 to about 120 degrees,
but about 90 to about 100 degrees or about 90 to about 110 degrees
is preferred. A working surface of at least about 60 degrees with
at least about 45 degrees being on a working side of a vertical
centerline running through the wave chamber is also suitable.
[0043] The important thing is to obtain a wave like movement inside
the wave chamber, as shown in FIG. 8 on or adjacent a portion of a
wave chamber having a working surface 53. The wet chopped fiber
strand segments 19 are moving in a wave like pattern as shown by
the arrows, working their way up the curved working surface 53
until they reach a maximum height based on the feed rate and the
vibration frequency, then curling over and flowing down the inside
over the upwardly moving segments 19 until they again contact the
working surface 53 and repeat the pattern. This occurs many times
down the length of the wave chamber 52 until the now agglomerates
26 reach the exit. Preferably one or more rubber dampers supplied
by the manufacturer can be used between adjacent coils of one or
more of the coil springs if the vibrating tube tends to rock back
and forth from side to side in operation.
[0044] At any given feed rate, the angle of declination of the wave
chamber is adjusted to give the residence time needed to form the
agglomerates described above. Typically, a residence time of up to
about 120 seconds, preferably about 40-60 seconds is preferred, but
this can change depending on the type of segments being processed,
other machine variables and the desired size and/or shape of the
finished agglomerates. While declinations up to 10 degrees are
possible, lower declinations of up to about 5 or 6 degrees are more
typical. With a 36 inch diameter VibraDrum.RTM., a preferred
declination angle is about 4.5 degrees. The vibration frequency can
be varied to produce the wave action by changing the RPM's of the
vibrator motors that are typically variable speed motors. Vibration
frequencies in the range of about 500 to about 1200 RPM are
normally suitable to achieve the wave action. A typical vibration
frequency on a 36 inch diameter unit is in the range of about
875-925 RPM with a range of about 885-905 RPM, such as about
890-895. A frequency of 893 RPM proved especially effective with a
moisture content of 12.5-13.5 wt. percent and a declination angle
of about 4:5 degrees on a 36 inch diameter by 10 foot long
VibraDrum.RTM. unit.
[0045] One possible modification is shown in FIG. 5 which is a
partial cross section down the length of an elongated curved wave
chamber 80. A concave working surface 83 is vibrated to act on wet
chopped strand segments to agglomerate them. The chamber 80 has a
cover 82 that can be a straight plate or a slightly curved convex
plate as shown in FIG. 5 or can be slightly curved concave. The
wave chamber 80 also has a frame piece 84A attached to a top of one
side and a second frame piece 84B attached to the top of the other
side. The wave chamber 80 and frame pieces 84A and 84B are
supported and vibrated in a same or similar manner as the
cylindrical wave chamber 52 shown in FIGS. 3 and 4.
[0046] Another possible modification is shown in FIG. 6 which is a
partial cross section taken along the length of an elongated curved
wave chamber 86. A concave working surface 87 is vibrated to act on
wet chopped strand segments to agglomerate them. The chamber 86 has
a cover 88 that has at least two straight pieces 89 and 90 that
intersect and join at an angle 91 as shown in FIG. 6. The wave
chamber 86 also has a frame piece 92A attached to a top of one side
and a second frame piece 92B attached to the top of the other side.
The wave chamber 86 and frame pieces 92A and 92B are supported and
vibrated in a same or similar manner as the cylindrical wave
chamber 52 shown in FIGS. 3 and 4.
[0047] A still further modification is shown in FIG. 7, a partial
cross section along the length of an elongated curved wave chamber
94. A concave working surface 95 is vibrated to act on wet chopped
strand segments to agglomerate them. The wave chamber 94 has no
cover, but instead is open to the atmosphere. An optional hood (not
shown) could be mounted over the open top of the wave chamber 94 to
catch and remove any fibers or moisture escaping out of the open
top of the wave chamber 94 if desired. The wave chamber 94 also has
a frame piece 96A attached to a top of one side and a second frame
piece 96B attached to the top of the other side. The wave chamber
94 and frame pieces 96A and 96B are supported and vibrated in a
same or similar manner as the cylindrical wave chamber 52 shown in
FIGS. 3 and 4.
[0048] The radius of the curved working surface need not be
constant as FIGS. 9 and 10 illustrate. A working surface 97 in FIG.
9 has two radii and a working surface in FIG. 10 has more than two
radii.
[0049] On all of the many wave chamber devices disclosed above, the
location of the vibrators and the array of coil springs between the
vibrators and the wave chamber can be changed. For example, the
elongated curved surface wave chamber can be supported on each side
with coil springs mounted on a supporting frame and the array of
coil springs, box channel and opposed vibrators can be attached to
the wave chamber near the top of the wave chamber. The only
critical requirement is an elongated curved working concave surface
acted upon to produce a wave-like motion on chopped strand segments
and agglomerates contacting the concave surface.
[0050] To practice the present invention using a system of the
present invention as disclosed above, including the disclosure of
FIGS. 2-4, conventional wet chopped fiber strand segments
containing a conventional sizing for a plastic material and a
moisture content in the range of about 10 to about 16 wt. percent,
on a dry basis, and chopped into segments with any conventional
chopper, such as shown in parts A and B of FIGS. 1 and 2, are fed
into an entry port of an agglomerator containing an elongated
curved surface wave chamber such as the VibraDrum.RTM. device shown
in FIGS. 3 and 4. The angle of declination and the feed rate are
adjusted to produce a retention time in the agglomerator of between
about 1-3 minutes. The actual feed rate, angle of declination and
frequency will vary depending on the size of the wave chamber and
the type of wet chopped strand segments being agglomerated and the
agglomerate size desired.
[0051] The amplitude of vibration of the wave chamber can also be
varied to produce the desired wave action and agglomerate size.
Typically, an amplitude of about 0.625 inch is used, but this can
be varied up or down as desired.
[0052] A retention time longer than about 120 seconds, more
typically longer than about 40-60 seconds could be used, but the
minimum retention time to achieve the agglomerate size desired is
best to avoid possible damage to the fibers, especially on the
outside layer of the agglomerates. The length of the chamber will
also affect retention time and capacity of the wave chamber.
Normally, the length of the wave chamber is fixed once a unit is
installed. Wave chambers about 4 feet long and about 8 feet long
are known to be satisfactory and no reason is known why other
lengths, within reason, would not also be suitable.
[0053] If the agglomerates are larger than desired, several things
can be done to reduce the agglomerate size as discussed above.
Another thing that can be done to reduce agglomerate size is to
reduce the moisture content of the chopped strand segments before
they are fed into the wave chamber. This may require some drying of
the segments between the chopper and the wave chamber because the
addition of more water and/or sizing to the segments after chopping
is not required in the present process.
[0054] The wet agglomerates 26 are fed into a dryer such as the
conventional vibrating, fluid bed dryer shown in part D of FIGS. 1
and 2, and preferably processed with a conventional screen sorter
shown as part E in FIGS. 1 and 2 to produce finished agglomerated
chopped fiber strand reinforcement product. Typical moisture
contents of the wet chopped fiber strand segments coming from the
chopper are in the range of about 10 to about 15 wt. Percent, on a
dry basis, i.e. based on the wt. of the dried segments.
[0055] The agglomerated chopped fiber strand reinforcement product
produced in the present system and by the present method had
substantially improved bulk density and flow characteristics
compared with conventional non-agglomerated chopped fiber strand
reinforcement products, and apparently similar characteristics as
competitive agglomerated chopped fiber strand reinforcement
products.
[0056] For example, conventional wet chopped fiber strand segments
having a moisture content of 12 to 13.5 wt. percent, on a dry
basis, were passed through the wave chamber device having an
internal diameter of about 24 inches, shown in FIGS. 3 and 4, at
vibration frequencies of 700 to 900 RPM and then run through parts
D and E of the process shown in FIG. 2 to form dry agglomerated
chopped fiber strand reinforcement products. The residence time in
the wave chamber device was about 2 minutes, plus or minus 1 minute
and the angle of declination was about 2 degrees. Two conventional
agglomerated products were made as described just above, one from
1/8 inch long chopped strand containing a first conventional sizing
and one from 3/16 inch long chopped strand containing a second
conventional sizing. The resultant agglomerated products were
labeled Product XA and Product XB respectively. Some key
characteristics of these agglomerated products were measured and
compared with results from the same tests on products made by
passing the same conventional wet chopped fiber strand segments
through parts D and E of the system shown in FIG. 2 and labeled CSA
and CSB respectively.
[0057] The test results are shown below. TABLE-US-00001 Product
Bulk Volume* Tapped Volume* Flow (Seconds)** XA 170 132 67 CSA 226
144 248 XB 160 128 111 CSB 196 140 328 *Volume in cubic centimeters
per 500 gram sample. **Flow was determined by timing how long it
took a 2000 gram sample to flow through an FMC FM-T01-A-1 vibrating
hopper having a 11/2 inch diameter .times. 6 inch straight
outlet.
[0058] The higher bulk density of the agglomerated products result
in being able to either place more weight in the standard sized box
or other package or allow a smaller package to be used to ship the
same weight as used for the conventional chopped fiber strand
products and also allow more product to be stored in available
space in the manufacturer's plant and in the customer's plant. The
faster flow of the agglomerated products result in fewer plug-ups
in the customers' hoppers and feed tubes and in increased flow
rates through existing customer equipment thus removing this
equipment where that is the barrier to increased production
rates.
[0059] While only preferred embodiments have been disclosed in
detail above, many additional embodiments are possible and obvious
to one of ordinary skill given the above disclosure and the claims
are intended to include such embodiments and obvious equivalents
thereof. Agglomerating parameters may have to be changed with some
sizing compositions, but it will be within the skill of an ordinary
artisan, given the above disclosure, to use the above disclosed
invention to agglomerate wet chopped strands having all kinds of
sizing compositions on the surface of the fibers.
* * * * *