U.S. patent application number 11/294956 was filed with the patent office on 2006-04-20 for sizer for forming shaped polymeric articles and method of sizing polymeric articles.
This patent application is currently assigned to CertainTeed Corporation. Invention is credited to Thomas A. Gates, Thomas G. Gilbert, Kevin D. Hartley, Robert C. McEldowney.
Application Number | 20060082011 11/294956 |
Document ID | / |
Family ID | 33310355 |
Filed Date | 2006-04-20 |
United States Patent
Application |
20060082011 |
Kind Code |
A1 |
Hartley; Kevin D. ; et
al. |
April 20, 2006 |
Sizer for forming shaped polymeric articles and method of sizing
polymeric articles
Abstract
A sizer assembly for providing a shaped polymeric article in an
extrusion process comprises a sizer body having a product profile
channel corresponding to the shaped polymeric article formed
therethrough. The sizer body comprises a plurality of cooling
liquid inlet slots forming an opening substantially around the
product profile channel and a plurality of vacuum slots forming an
opening substantially around the product profile channel for
removing cooling liquid expelled from said cooling liquid inlet
slots.
Inventors: |
Hartley; Kevin D.;
(Clarklake, MI) ; McEldowney; Robert C.; (Jackson,
MI) ; Gilbert; Thomas G.; (Clarklake, MI) ;
Gates; Thomas A.; (Parma, MI) |
Correspondence
Address: |
DUANE MORRIS, LLP;IP DEPARTMENT
30 SOUTH 17TH STREET
PHILADELPHIA
PA
19103-4196
US
|
Assignee: |
CertainTeed Corporation
Valley Forge
PA
|
Family ID: |
33310355 |
Appl. No.: |
11/294956 |
Filed: |
December 6, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10428227 |
May 2, 2003 |
7001165 |
|
|
11294956 |
Dec 6, 2005 |
|
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|
Current U.S.
Class: |
264/151 ;
264/210.1 |
Current CPC
Class: |
B29K 2901/00 20130101;
B29C 48/07 20190201; B29C 48/3003 20190201; B29C 48/919 20190201;
B29C 48/12 20190201; B29C 48/903 20190201; Y10S 425/06 20130101;
B29C 48/08 20190201; B29C 48/908 20190201 |
Class at
Publication: |
264/151 ;
264/210.1 |
International
Class: |
B29C 47/00 20060101
B29C047/00 |
Claims
1. A method of manufacturing a non-hollow, shaped polymeric
article, comprising the steps of: providing a generally flat
extruded sheet of hot polymeric material having an outer surface to
a sizer assembly for cooling and shaping said polymeric sheet into
a non-hollow, shaped polymeric article, wherein said sizer assembly
comprises: a sizer body having a product profile channel
corresponding to said shaped polymeric article formed therethrough,
said sizer body further comprising a plurality of cooling liquid
inlet slots each forming an opening substantially around said
product profile channel, said cooling liquid inlet slots being in
open communication with said product profile channel, and a
plurality of vacuum slots each forming an opening substantially
around said product profile channel for removing cooling liquid
expelled from said cooling liquid inlet slots, said vacuum slots
being interspersed among, and fluidly insulated from said cooling
liquid inlet slots, except in said product profile channel, and
being coupled to at least one vacuum source; controlling at least
one of vacuum and cooling liquid levels at said product profile
channel such that a substantial portion of said outer surface of
said sheet of polymeric material is maintained away from said sizer
body as said sheet of polymeric material passes through said sizer;
and severing a length of said sheet after exiting said sizer to
produce said shaped polymeric article.
2. The method of claim 1, further comprising the step of cooling
said sheet after said providing step in a quenching tank.
3. The method of claim 1, further comprising the step of cooling
said sheet after said providing step in a spray bath.
4. The method of claim 1, wherein the product profile channel has a
substantially uniform shape along its longitudinal axis and is
sized less than 0.012 inches greater than a nominal thickness of
said shaped polymeric article.
5. The method of claim 1, wherein the product profile channel has a
substantially uniform shape along its longitudinal axis and is
sized between about 0.004-0.008 inches greater than a nominal
thickness of said shaped polymeric article.
6. The method of claim 5, wherein said method provides at least
3900 lb/hr of polymeric product.
7. The method of claim 1, wherein said sizer body is formed from a
polymeric material selected from the group consisting of
heat-resistant epoxy, polyoxybenzlene, polymide, polyamide-imide,
silicone, polyether-imide, polyetheretherketone, acrylics and
phenolics.
8. The method of claim 1, wherein, for a sizer approximately 4.0
inches in length, said sizer pulls at least about 800 BTUs/minute
from said extruded sheet at a product speed of about 1800 inches
per minute, or proportionate amounts of BTUs/minute for different
sized sizers.
9. The method of claim 1, wherein said controlling step comprises
providing to and removing from said product profile channel at
least 9 gallons per minute of said cooling liquid.
10. The method of claim 1, wherein said controlling step comprises
providing to and removing from said product profile channel between
about 9-36 gallons per minute of said cooling liquid.
11. The method of claim 1, wherein said cooling liquid inlet slots
are generally orthogonal to the longitudinal axis of said product
profile channel and said vacuum slots are interspersed among said
cooling liquid inlet slots.
12. The method of claim 1, wherein said sizer body has an top and
bottom surfaces and a pair of side surfaces, wherein at least some
of said vacuum slots are formed completely through said sizer body
from said top surface to said bottom surface intermediate said side
surfaces, and wherein at least some of said cooling liquid inlet
slots are formed only partially through said sizer body between
said top and bottom surfaces, said sizer body further comprising a
plurality of cooling liquid inlet ports formed in said sizer body
for providing access to said cooling liquid inlet slots formed only
partially through said sizer body.
13. The method of claim 12, further comprising top and bottom
manifold sections coupled to said sizer body, each of said top and
bottom manifold sections including at least one input port coupled
to said at least one source of cooling liquid and at least one
vacuum port coupled to said at least one vacuum source, said
manifold sections further being configured to place said at least
one source of cooling liquid in communication with said cooling
liquid inlet ports of said sizer body and to place said at least
one vacuum source in communication with said at least some of said
vacuum slots.
14. A method of manufacturing a non-hollow, shaped polymeric
article, comprising the steps of: providing a generally flat sheet
of hot polymeric material having an outer surface to a sizer
assembly for cooling and shaping said polymeric sheet into a
non-hollow, shaped polymeric article, said polymeric sheet being
above its glass transition temperature, wherein said sizer assembly
comprises: a sizer body having a product profile channel disposed
in a first generally horizontal direction, a plurality of
longitudinally spaced cooling liquid inlet and outlet apertures
disposed through said sizer body and in open communication with
said product profile channel, said cooling liquid outlet apertures
being interspersed among, and fluidly insulated from said cooling
liquid inlet apertures, except in said product profile channel,
said cooling liquid outlet apertures being coupled to at least one
vacuum source; controlling at least one of vacuum and cooling
liquid levels at said product profile channel such that a
substantial portion of said outer surface of said sheet of
polymeric material is maintained away from said sizer body, thereby
reducing drag on said sheet of polymeric material as it passes
through said sizer; and severing a length of said sheet after
exiting said sizer to produce said shaped polymeric article.
15. The method of claim 14, wherein said outlet apertures are
alternatingly arranged with said inlet apertures.
16. The method of claim 14, wherein a portion of said plurality of
cooling liquid inlet and outlet apertures are disposed orthogonal
to said generally horizontal product profile channel.
17. A method of manufacturing a non-hollow, shaped polymeric
article, comprising the steps of: providing a generally flat
extruded sheet of hot polymeric material having an outer surface to
a sizer assembly for cooling and shaping said polymeric sheet into
a non-hollow, shaped polymeric article, said sizer assembly
comprising a sizer body having a product profile channel
corresponding to said shaped polymeric article formed therethrough;
providing at least one source of cooling liquid for said sizer
assembly; providing at least one vacuum source for said sizer
assembly; and controlling the vacuum and cooling liquid levels at
said product profile channel such that a substantial portion of
said outer surface of said sheet of polymeric material is
maintained away from said sizer body as said sheet of polymeric
material passes through said sizer.
18. The method of claim 17, wherein the product profile channel has
a substantially uniform shape along its longitudinal axis and is
sized less than 0.012 inches greater than a nominal thickness of
said shaped polymeric article.
19. The method of claim 17, wherein the product profile channel has
a substantially uniform shape along its longitudinal axis and is
sized between about 0.004-0.008 inches greater than a nominal
thickness of said shaped polymeric article.
20. The method of claim 19, wherein said controlling step comprises
providing to and removing from said product profile channel at
least 9 gallons per minute of said cooling liquid
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional application of U.S. patent
application Ser. No. 10/428,227 filed May 2, 2003, entitled
"Improved Sizer for Forming Shaped Polymeric Articles and Method of
Sizing Polymeric Articles" now U.S. Pat. No. ______, the entirety
of which is hereby incorporated by reference herein.
FIELD OF THE INVENTION
[0002] The present invention relates to extrusion techniques, and
more particularly to sizers used in shaping extruded polymeric
articles.
BACKGROUND OF THE INVENTION
[0003] FIG. 1A illustrates a side elevational view of a prior art
sizer 40 used in an extrusion system described in U.S. Pat. No.
6,319,456 to Gilbert et al., entitled "Method for Continuous Vacuum
Forming Shaped Polymeric Articles," issued Nov. 20, 2001, the
entirety of which is hereby incorporated by reference. An extruded
sheet 10 is subjected to a sizer 40 for mechanical deforming and
shaping an extruded sheet. One or more pre-sizers (not shown) may
precede the sizer 40. A cross-section of the final sizer is shown
in FIG. 1B. This device includes a series of adjustable blocks and
plates. The final sizer 40 includes a pair of lateral forming block
mechanisms 48 and 52 which can be lever operated for a variety of
products and sizes. The final sizer 40 also includes top and bottom
forming plates 54 and 56 to maintain the planar nature of the
product while the edges are being formed.
[0004] Cooling water 42 from the final quench tank 46 is allowed to
leak back into the final sizer 40 in order to cool the sheet 10
during sizing. The cooling water 42 quickly quenches the product
below its heat deflection temperature to hold its shape. Excess
cooling water 42 is removed from the sizer 40 by a vacuum pump 34
and is either removed from the system or recycled back into the
quench tank 46.
[0005] Following the final sizer operation, the now fully formed
extruded sheet 10 is immersed in a quench tank 46 to reduce its
temperature to about that of ambient air. The continuous sheet is
then removed from the quench tank 46. Following the removal of the
product from the quench tank 46, the product can be pulled with the
puller machine (not shown) to a cut-off station which severs the
now cooled, formed extruded sheet into individual lengths of shaped
polymeric articles.
[0006] Some prior art sizers additionally include water cavities
therein for cooling the steel forming sections. These cavities are
isolated from the extruded profile and serve to draw heat
dissipated form the extruded profile into the steel shaping
sections.
[0007] Market and manufacturing pressures are beginning to demand
higher output capacities from extrusion processes, and thus sizers,
in excess of 3000 lbs/hr of product. While these prior art extruder
designs have proved reliable in the past, they have proved
ineffective at meeting these increased output demands without
sacrificing production quality. Prior art extruders generally
require that the product profile cutout within the sizer be
oversized at least between about 0.012-0.014 inches with respect to
the nominal part thickness of the final cooled product. The sizer's
channel must be oversized because it is unable to pull enough heat
from the product before the product exits the sizer and is cooled
in the quenching tank. The steel sizer also heats up, preventing
effective removal of heat from the product. The oversize is
necessary to prevent drag between the hot product against the steel
sizer. The significant oversize leads to poor dimension control,
and ultimately, poor product.
[0008] Therefore, there remains a need for a new sizer capable of
improving product cooling to allow proper product shaping at higher
output rates.
SUMMARY OF THE INVENTION
[0009] A sizer assembly for providing a shaped polymeric article in
an extrusion process comprises a sizer body having a product
profile channel generally corresponding to the shaped polymeric
article to be formed therethrough. The sizer body comprises a
plurality of cooling liquid inlet slots forming an opening
substantially around the product profile channel and a plurality of
vacuum slots forming an opening substantially around the product
profile channel for removing cooling liquid expelled from said
cooling liquid inlet slots.
[0010] A method of manufacturing a shaped polymeric article is also
provided. A sheet of extruded hot polymeric material is provided to
the sizer for cooling. A length of the sheet is severed after
exiting the sizer to produce the shaped polymeric article.
[0011] The sizer provides improved cooling of the polymeric article
being sized. This potentially allows for faster production speeds
in excess of the limits of current sizers. Faster production speeds
improve production output. These higher output speeds are
accomplished even using a tighter, tapered or non-tapered, product
channel. More even and consistent cooling of the product improves
product performance through the presence of fewer cooled-in
stresses. These cooled-in stresses are known to effect the impact,
distortion and shrinkage qualities of the product. More accurate
dimensioning and reduced product dimension variation, more
consistent product faces, crisper angles and less product
relaxation can also be achieved.
[0012] Further, because the cooling liquid pumped into the sizer is
the primary means of removing heat from the product, the sizer body
itself is not relied upon as the primary heat removal vehicle. It
is believed that this will allow for the sizer to be manufactured
out of lighter, cheaper and/or more wear resistant materials as
well as make the sizer easier to manufacture. Still further,
because the sizer need not pull the cooling liquid from a quench
tank, more efficient post-sizer cooling mechanisms may be used,
such as a shower or spray tank. Spray bath cooling is more
efficient than submersion cooling and reduces the length of the
cooling section of the extrusion line.
[0013] Even further, it is believed the that cooling water pumped
into the sizer occupies the tight (e.g., 0.004-0.008 inch) space
between the product and the sizer channel. The water acts as a
lubricant or bearing mechanism that separates the polymeric product
and the channel. This prevents drag between the product and the
sizer and reduces wear on the sizer, thereby permitting the sizer
to be manufactured from materials less wear resistant than steel,
if desired.
[0014] In still a further embodiment of this invention, a sizer
assembly for shaping a polymeric article, which is above its glass
transition temperature, that is being drawn or extruded is
provided. The sizer assembly comprise a sizer body having a product
profile channel disposed in a first generally horizontal direction,
a plurality of cooling liquid inlet and outlet apertures disposed
through the sizer body and in open communication with the product
profile channel.
[0015] The above and other features of the present invention will
be better understood from the following detailed description of the
preferred embodiments of the invention that is provided in
connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The accompanying drawings illustrate preferred embodiments
of the invention, as well as other information pertinent to the
disclosure, in which:
[0017] FIG. 1A is a side elevational view of a prior art sizer
coupled to a quenching tank;
[0018] FIG. 1B is a cross-sectional view of the prior art sizer of
FIG. 1A taken along lines 1B-1B;
[0019] FIG. 2 is a side, cross-sectional view of an exemplary sizer
according to the present invention;
[0020] FIG. 2A is a cross-sectional view of the sizer of FIG. 2
taken along lines 2A-2A;
[0021] FIG. 2B is a cross-sectional view of the sizer of FIG. 2
taken along lines 2B-2B;
[0022] FIG. 3 is a perspective view of an assembled sizer according
to the present invention; and
[0023] FIG. 3A is an exploded view of the sizer of FIG. 3
illustrating the components thereof.
DETAILED DESCRIPTION
[0024] FIGS. 2-3A illustrate an exemplary embodiment of a sizer
(also know as a fixture or calibrator) and sizer assembly for
providing a shaped polymeric article in an extrusion process. The
polymeric article can be any shaped polymeric article originating
from a flat sheet or non-flat sheet (e.g., having one or more legs
or fins formed therein) exiting an extruder having a profile of
uniform or non-uniform thickness or having pre-formed and cooled
sections. In an exemplary embodiment, the sizer is shaped to form a
siding panel formed from a thermoplastic or thermosetting
compositions, such as polyvinyl chloride ("PVC"), polyethylene,
polypropylene, polyurethane, epoxy, polyester, or composites
thereof (e.g., PVC and wood flour composite), etc. or other similar
materials.
[0025] FIG. 2 is a side, cross-sectional view of a sizer 100. An
extruded sheet of polymeric material 200 is shown disposed within
the sizer 100. As used herein, "sheet of polymeric material" means
a sheet of polymeric material of uniform or non-uniform thickness.
The sheet may be of uniform temperature or may be partially
preformed and cooled in two dimension or three dimensional form, as
taught, for example, in U.S. Pat. No. 6,319,456 to Gilbert
discussed in the "Background of the Invention" section. The sizer
has body 102 preferably made from steel, although other metals,
ceramic materials, wood, plaster, or polymeric materials such as
heat-resistant epoxy, polyoxybenzlene, polymide, PAI
(polyamide-imide), silicone, PEI (polyether-imide), PEEK
(polyetheretherketone), acrylics, phenolics, and wear surface
treated materials (e.g., a diamond coated acrylic), or composites
are also contemplated, as analyzed in more detail below. The sizer
100 has a product profile channel formed through body 102 (shown
occupied by polymeric article 200) corresponding generally to the
shape of polymeric article 200.
[0026] The extruded sheet of polymer enters the sizer at a
temperature above ambient. More specifically, portions of the sheet
that are to be formed by the sizer are above the polymer's glass
transition temperature. A material's glass transition temperature
(Tg) is the temperature below which molecules have very little
mobility. On a larger scale, polymers are rigid and brittle below
their glass transition temperature and elastic above it. Glass
transition temperature is usually applicable to amorphous phases
and is commonly applicable to glasses and plastics. By way of
example, PVC is generally formable above 170.degree. F.
[0027] In an exemplary embodiment, the portions of the product
profile channel used to size and shape the polymeric product are
sized less than 0.012'', preferably between about 0.001-0.012'',
and more preferably between about 0.004-0.008'', greater than the
nominal part thickness of the final profile size of the shaped
polymeric article. This is a reduction from the standard
0.012-0.014'' oversize described in the "Background" section. As
described in more detail below, it is believed that this reduction
is made possible by the improved heat removal abilities of the
sizer 100. Further, the reduced size allows for the cooling liquid
to act as a bearing mechanism between the product and the sizer
profile channel.
[0028] In an exemplary embodiment, the sizer 100 includes a
plurality of cooling liquid inlet apertures, such as slots 106,
holes or combinations thereof, forming an opening partially, or
substantially around, and preferably entirely around, the product
profile channel. These apertures may be isolated to specific areas
of the panel profile, if desired, to allow individual control of
cooling liquid flows in contact with specific regions of the
polymeric article. Each slot 106 is preferably coupled to a
plurality of upper and lower cooling liquid inlet ports 104 that
provide access to slots 106 for a cooling liquid, such as water. As
best shown in the cross-sectional view of FIG. 2B taken along lines
2B-2B of FIG. 2, an exemplary sizer 100 includes six inlet ports
104 disposed around each slot 106. As best shown in FIG. 2, a sizer
100 having a length L of approximately 4.0'' has three spaced slots
106 formed therein.
[0029] Cooling liquid inlet slots and ports should be sized to
allow for adequate cooling liquid volumes and the desired liquid
distribution over the product, which depend on such factors as the
shape of the product, the speed of the product and the temperature
of the product. In an exemplary embodiment, cooling liquid inlet
slots 106 have a width W.sub.1 between about 0.020''-0.500'' and
preferably at least about 0.25''. Inlet ports 104 have diameters
between about 0.250''-1.00'', and preferably at least about
0.5''.
[0030] Sizer 100 preferably includes a plurality of spaced outlet
apertures, such as vacuum slots 108, forming an opening partially,
or substantially around, and preferably entirely around, the
product profile channel for draining and/or removing cooling liquid
expelled from the cooling liquid inlet slots 106. The vacuum slots
108 are preferably disposed before, in between and/or after the
cooling liquid inlet slots 106, as best seen in FIG. 2. The
cross-section view of FIG. 2A taken along lines 2A-2A of FIG. 2
illustrates a slot 108 forming an opening entirely around the
product profile channel. The direction of the product profile
through the sizer 100 is illustrated by directional arrows in FIG.
2. The first vacuum slot 108 disposed closest to the entrance of
the sizer 100 helps to ensure that cooling liquid does not escape
through the entrance of the sizer.
[0031] Vacuum slots 108 are preferably sized to achieve relative
even distribution of vacuum forces. In an exemplary embodiment of
sizer 100, vacuum slots 108 have a width W.sub.2 between about
0.010''-0.250'', and preferably at least 0.04''.
[0032] FIG. 3 is a perspective view of an exemplary sizer assembly
300, and FIG. 3A is an exploded view showing the components
thereof. The sizer body is formed from one or more sections
defining the product profile channel. In the illustrated
embodiment, sizer assembly 300 includes a sizer 100 including four
steel sections 306, 308, 310, 312 that mate together to define the
product profile channel through the sizer 100. The inlet ports 104
can be seen in top section 306 of sizer 100. Similar inlet ports
(not shown) may be found on the underside of bottom section 308.
The vacuum slots 108 and water slots 106 are visible in the
exploded view of FIG. 3A.
[0033] The sizer assembly 300 includes top and bottom aluminum
manifolds 302 and 304, respectively. Although shown as separate
parts of a sizer assembly 300, it is contemplated that the manifold
can be formed integrally with the sizer 100. The top manifold 302
is shown secured to the top sizer section 306 via bolts disposed
within holes 318, but the manifold sections may be coupled to the
sizer by other means, such as by piping sections. Bolting plates
316 are bolted to bottom manifold 304. Rectangular side panels 314
are bolted to intermediate sizer sections 310, 312. Holes 324 are
shown drilled for insertion of toggle handles (not shown in FIGS.
3, 3A) as described in connection with prior art FIGS. 1A, 1B for
securing sections 310, 312 in sizer 100.
[0034] It should be understood that manifold sections 302, 304 may
be designed in any number of configurations. The only requirement
for manifolds 302, 304 is that the vacuum/suction chambers and
cooling liquid chambers be isolated within the manifold so that
there is no interchange therebetween. In an exemplary embodiment,
manifold sections 302, 304 have essentially the same connection
system formed therein.
[0035] An exemplary manifold section 302, 304 includes cooling
liquid (e.g., water) inlet ports 320 drilled therein from the top
side, each corresponding to a group of three inlet ports 104 formed
into a top or bottom section 306, 308. Ports 320 preferably have a
diameter of at least about 1/2''. Water slots 328 are machined into
the manifolds 302, 304 to a depth of about 3/4''. The water slots
328 are connected to the inlet ports 320 by side channels 326
drilled into the manifolds 302, 304. Although side channels 326 are
shown open, the ends of these channels are plugged when the sizer
is in use in order to prevent liquid from escaping and air from
entering. Each inlet port 320 on the manifolds 302, 304 can be
connected to a separate water pump and be individually controlled
if desired. Individual control may be desirable if more or less
cooling is required or desired at specific locations of the
polymeric article. This control may also be achieved by isolating
inlet slots or inlet ports to specific regions of the polymeric
article as noted above.
[0036] An exemplary manifold section 302, 304 also includes three
draining, vacuum and/or suction ports 322 drilled therein. Suction
ports 322 preferably have a diameter of at least about 1/2''.
Vacuum slots 330 are machined about 1/4'' into the manifolds 302,
304 and correspond to vacuum slots 108 formed in the sizer 100.
Side channels 323 are drilled across the manifolds 302, 304 and
intersect vacuum ports 322. Although the channels 323 are shown
open, the ends of these channels 323 are plugged when the sizer is
in use in order to prevent liquid from escaping during removal of
the liquid. Twelve connection holes 325 are drilled through the
manifolds 302, 304 in vacuum slots 330 to intersect side channels
323, thereby coupling ports 322 to slots 330. In an exemplary
embodiment, each port 322 on top manifold 302 and each port 322 on
bottom manifold 304 are coupled to a single suction source (e.g., a
pump) for removal of cooling liquid, e.g., water. However, it is
contemplated that the vacuum slots or apertures may be configured
for individual control.
[0037] In operation, the sizer 100 primarily utilizes a large
volume of cooling liquid, preferably water, to cool the polymeric
product profile as it moves through the sizer. The product profile
200 typically has a temperature of between about 240-260.degree. F.
as it enters the sizer 100. Water is pumped into the sizer assembly
through ports 320, where it enters channels 326 and then enters
water slots 328 of manifolds 302, 304. It is preferred to utilizes
a water slot configuration (i.e., water slots 328) in order to
balance water flows and pressure around the product and to prevent
flow from "short cutting" through the system. The water slots 328
overlap inlet ports 104 of sizer 100, which connect to cooling
liquid inlet slots 106 so that water contacts the product 200,
removing heat therefrom. The water cools the product and provides a
bearing layer between the product 200 and the product profile
channel defined through the sizer 100. The water is then removed
via vacuum slots 108 as described below.
[0038] The amount of cooling liquid injected into cooling liquid
inlet slots 106 is preferably individually controlled for each port
320, but preferably ranges between about 1.5-6.0 GPM (gallons per
minute) per port 320. In the embodiment shown in FIGS. 2-3A, this
range amounts to between about 0.5-2 GPM per inlet port 104. The
suction placed on vacuum slots 108 is preferably evenly distributed
across the vacuum slots and from the entry to exit points of the
sizer.
[0039] As mentioned, water is removed from the sizer 100 via vacuum
slots 108 of sizer 100. The vacuum slots 108 overlap slots 330
machined into the manifolds 302, 304 of the sizer assembly 300. The
water enters holes 325 from slots 330 and is pulled into channels
323 through to vacuum ports 322, where it is removed from the
assembly 300. In operation, each vacuum port 322 preferably operate
at a force or vacuum level sufficient to suction water from the
vacuum slot opening at a rate equal to or above the rate the
cooling liquid is fed through the inlet ports. In one embodiment,
each vacuum port 322 operates at a force greater than 10''
vacuum.
[0040] As mentioned, the sizer 100 and sizer assembly 300 may be
used in the formation of a shaped polymeric article in an extrusion
process. The details of the extrusion process and the components
therein should be familiar to those of ordinary skill and are
summarized hereafter. A flat sheet of a polymeric material, such as
PVC, is extruded. A wood grain finish or other finish may
optionally be applied to the extruded sheet in a press roller or
areas may be pre-formed and cooled via other means, such as those
described in U.S. Pat. No. 6,319,456 to Gilbert. A cooling roller
or other method is used to reduce the PVC temperature from about
400.degree. F. to about 250.degree. F. The PVC sheet is then
optionally applied to one or more pre-sizers to shape the product.
After the pre-sizer, the PVC sheet is provided to the sizer 100 of
sizer assembly 300. After the sizer, the shaped polymeric article
is typically pulled through a quenching tank. After exiting the
quenching tank, the shaped polymeric article is cut into
appropriate lengths for a final product.
[0041] The improved heat removal capabilities of the new sizer
design as described above were verified using finite element
analysis (FEA) using approximately a 200,000 element model for a
prior art sizer and the new sizer design. The velocity of the PVC
sheet, the conductivity of water and air, the cooling water
temperature and convection coefficient, and the thermal
conductivity and heat capacity of the polymer were all variables in
the analysis. Observation of thermal isobars for the prior art
sizer design and new sizer design, as well as the product moving
through the designs, revealed more uniform increased BTU removal in
the product sized with the new design and less heat dissipation
from the product into the new sizer body. This indicates that the
cooling water served as the primary heat removal vehicle.
[0042] The sizer 100 described above was also built and tested.
Test results indicated that the tested sizer design was capable of
pulling over 800 BTUs per minute from the product, based on tests
on the cooling water during a product run where the input product
surface temperature was measured at 245.degree. F., the output
product surface temperature was measured at 140.degree. F. and the
product speed was about 1800 inches per minute.
[0043] The sizer 100 provides several advantages. The sizer
provides improved cooling of the polymeric article being sized.
This allows for faster production speeds in excess of the estimated
3900 lb/hr limit of current sizers. Faster production speeds
improve production output. These higher output speeds are
accomplished even using a tighter, non-tapered product channel,
which provides more accurate dimensioning and reduced product
dimension variation. Indeed, more consistent product faces, crisper
angles and less product relaxation were observed using the
sizer.
[0044] It should be understood that the channel of the sizer
described herein has a substantially uniform shape, but may be
implemented with all, portions or none of the channel being
tapered. Still further, portions of the channel may be oversized
with respect to the product while other portions are characterized
by less or little oversize. This configuration may be utilized, for
example, when various portions of the product are pre-formed and
cooled prior to the sizer.
[0045] Further, because the cooling liquid pumped into the sizer is
the primary means of removing heat from the product, the sizer body
itself is not relied upon as the primary heat removal vehicle. Put
another way, the thermal conductivity of the steel is not required
to remove heat from the product. It is believed that this will
allow for the sizer to be manufactured out of lighter, cheaper
and/or more wear resistant materials, such as polymeric materials
such as heat-resistant epoxy, polyoxybenzlene, polymide, PAI
(polyamide-imide), silicone, PEI (polyether-imide), PEEK
(polyetheretherketone), acrylics, phenolics, composites, and wear
surface treated materials (e.g., a diamond coated acrylic). Other
metals, ceramic materials, wood, plaster, or composites are also
contemplated. Cooler water can also be used to cool the product
because a source of water other than the quenching tank can be
used. Higher volumes of water are used to cool the product, leading
to improved cooling. Still further, because the sizer 100 need not
pull the cooling liquid from a quench tank, more efficient
post-sizer cooling mechanisms may be used, such as a shower or
spray tank. Spray bath cooling is more efficient than submersion
cooling and reduces the length of the cooling section of the
extrusion line.
[0046] Even further, it is believed the that cooling water pumped
into the sizer occupies the tight (e.g., 0.004-0.008 inch) space
between the product and the sizer channel. The water acts as a
lubricant or bearing mechanism that separates the polymeric product
and the channel. This prevents drag between the product and the
sizer and reduces wear on the sizer, thereby permitting the sizer
to be formed from materials that are less wear resistant than
steel, if desired.
[0047] Although the invention has been described in terms of
exemplary embodiments, it is not limited thereto. Rather, the
appended claims should be construed broadly to include other
variants and embodiments of the invention that may be made by those
skilled in the art without departing from the scope and range of
equivalents of the invention.
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