Information
-
Patent Grant
-
6214143
-
Patent Number
6,214,143
-
Date Filed
Friday, May 13, 199430 years ago
-
Date Issued
Tuesday, April 10, 200123 years ago
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Inventors
-
Original Assignees
-
Examiners
Agents
-
CPC
-
US Classifications
Field of Search
US
- 428 224
- 428 59
- 428 299
- 156 628
- 156 147
- 156 158
- 156 265
- 156 3096
- 156 311
- 156 324
- 156 325
- 156 166
- 156 169
- 156 176
- 156 181
-
International Classifications
-
Abstract
A tubular fibrous blanket is formed using a rotary fiberizer which produces a tow of substantially continuous thermoplastic fibers and a suction chamber with an annular, vertically extending, collection surface spaced from and surrounding the rotary fiberizer. The fibrous tow is collected on the annular, vertical collection surface or on a foraminous backing sheet passing over the collection surface in a spiral of very low pitch with succeeding portions of the tow at least partially overlapping and preferably, substantially completely overlapping preceding portions of the tow to form the tubular blanket. The tubular fibrous blanket and the backing sheet, when used, can then be slit longitudinally and unfolded to form a flat blanket having continuous fibers extending substantially perpendicular to the longitudinal axis of the blanket.
Description
BACKGROUND OF THE INVENTION
The present invention is directed to a method of and an apparatus for forming a uniform blanket of fibers and the blanket formed by the method and apparatus which is initially tubular in configuration and may be slit longitudinally and unfolded to form a blanket having fibers predominately oriented perpendicular to the longitudinal axis of the blanket.
In the manufacture of fibrous blankets using a rotary fiberization process, fibers are produced by the extrusion of a thermoplastic material, including glass and polymeric materials such as polypropylene and polyester through a large number of holes in a peripheral, annular wall of a fiberizing disc or rotor. The disc is rotated at a high rate of speed about a vertical axis causing the thermoplastic material within the disc to be extruded through the holes of the disc to form continuous fibers. The continuous fibers are issued from the holes of the disc in a substantially horizontal direction. These continuous fibers are directed downwardly toward a horizontal collection surface beneath the fiberizing disc by a substantially continuous, downwardly directed air stream which encircles the fiberizing disc. The horizontal collection surface is normally a foraminous conveyor belt passing over a suction chamber which draws air through the conveyor belt to draw the fibers onto the upper surface of the conveyor belt where a blanket of the fibers is formed. One such process of fiberization is described in connection with the manufacture of glass fibers in U.S. Pat. No. 4,058,386, issued Nov. 15, 1977, to D. H. Faulkner et al, and entitled “Method and Apparatus for Eliminating External Hot Gas Attenuation in the Rotary Fiberization of Glass (hereinafter the “386 patent”). The disclosure of this patent is hereby incorporated herein in its entirety by reference.
Several problems have been experience in the formation of fibrous blankets from substantially continuous fibers by the above referenced process. As the continuous fibers are directed downwardly toward the horizontal collection surface, the fibers twist beneath the fiberizing disc into a loosely twisted rope of fibers. In addition, the loosely twisted rope of fibers tends to snake back and forth across the moving collection surface in an irregular fashion and this results in the nonuniform, non-directional collection of the continuous fibers on the collection surface.
Accordingly, the blanket formed by this process is not uniform in thickness or density and has thin spots and/or holes which are undesirable when using the blanket as insulation or air filtration media. The problem of non-uniformity is magnified when thin blankets about one thirty-second of an inch to one inch thick are produced for air filtration or similar uses. Such blankets must have a uniform thickness and density throughout to prevent the passage of dirt or other matter through the filtration media. In addition to the above, the edges of the blanket produced by this process are irregular and this results in edge loss or scrap due to the need to trim the irregular edges from the blanket.
The blankets formed by this process are sometimes further processed by passing the blanket through a chopper to produce short length fibers (e.g. fibers from ¼ to 3 inches in length) for use in processes, such as, paper making, carding, air layering, etc. For these products, it is desired to have the short length fibers produced in the chopping operation uniform in length. With the twist imparted to the continuous fiber tow in the collection process and the irregular collection of the fibers on the collection surface to form the blanket, the orientation of the fibers in the blanket is not unidirectional. Accordingly, when the blanket is chopped to form short length fibers, the fibers vary in length and manufacturing tolerances for fiber length are difficult to maintain. Thus, it would be desirable to manufacture a blanket wherein the fibers are highly directional in their orientation to facilitate the formation of uniform length fibers in the chopping operation.
SUMMARY OF THE INVENTION
The method of the present invention forms a uniform tubular blanket of substantially continuous thermoplastic fibers. The fibers are produced on a rotary fiberizer which issues a tow of continuous thermoplastic fibers, such as polymeric or glass fibers. The tow is collected to form the tubular blanket in a low pitch spiral either directly on a vertically extending, annular collection surface surrounding the rotary fiberizer or on a foraminous backing sheet passing over the annular collection surface. Succeeding portions of the tow at least partially overlap and preferably, substantially completely overlap preceding portions of the tow as the tow is collected. The tubular blanket formed has a uniform thickness and density without thin spots or holes. In addition, the fibers of the tow remain essentially untwisted and parallel so that fibers in the blanket are directionally oriented. The tubular blanket and its foraminous backing sheet, if used, are normally slit and unfolded to form a flat blanket.
The flat blanket thus formed performs well as an air filtration media or as an insulation. The blanket is uniform in thickness having no holes or thin spots. In addition, since the lateral edges of the blanket are formed by the slitting of the tubular blanket, there is no trim loss.
The fibers of the flat blanket are not twisted and are directionally oriented extending substantially perpendicular to the longitudinal axis of the blanket. While a relatively few of the fibers may have some breakage, essentially all of the individual fibers of the blanket are continuous for and extend the width of the blanket. With its unique continuous fiber orientation, the blanket of the present invention can be further processed into short uniform length fibers by passing strips of the blanket through a conventional chopper. The strips are cut to a width that corresponds to the width of the chopper and are fed through the chopper in a direction essentially parallel to the orientation of the continuous fibers in the blanket strips. The short length fibers formed by the chopping operation are quite uniform in length.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1
is a side elevation of the apparatus of the present invention with a portion of the annular suction chamber omitted to show the fiberizing disc.
FIG. 2
is a front elevation of the apparatus of the present invention with a portion of the annular suction chamber, the cantilevered fiberizer support and the drive omitted for clarity.
FIG. 3
is a top view taken substantially along lines
3
—
3
of FIG.
1
.
FIG. 4
is a perspective view of the fiberizing disc.
FIG. 5
is a perspective view of the binder application ring.
FIG. 6
is a perspective view of the annular suction chamber.
FIG. 7
shows the tubular blanket of the present invention with a portion of the blanket and its backing sheet broken away to show the spiral tow of fibers forming the tubular blanket.
FIG. 8
is a transverse section of the flat blanket of the present invention.
FIG. 9
is a top view of the upper forming ring and the rollers for overlapping the lateral edges of the backing sheet to form a tube.
FIG. 10
is a top view of a portion of the lower forming ring and the ultrasonic slitting wheel.
FIG. 11
is a perspective view of the apparatus of the present invention, with portions broken away and no backing sheet passing through the apparatus, to better show the components of the apparatus.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The apparatus
20
of the present invention is shown in
FIGS. 1-3
and
11
. The apparatus
20
comprises a rotary fiberizing unit
22
, an annular suction chamber
24
, a binder application ring
26
, forming rings
28
and
30
, a backing sheet supply roll
32
and a blanket wind-up
34
.
The rotary fiberizing unit
22
comprises a drive motor
36
, a cantilevered fiberizing disc support
38
and a fiberizing disc
40
. When glass is being fiberized, a rotor or fiberizing disc heater unit, such as disclosed in the '386 patent, can be used to maintain the glass within the fiberizing disc and the area immediately adjacent the fiberizing disc at the proper temperature for fiberization of the glass. When a polymeric material is being fiberized, the polymeric material and the area adjacent the fiberizing disc is maintained at the proper temperature for fiberizing the polymeric material by the use of hot air, preferably heated by gas combustion and having a low oxygen content to minimize oxidation of the organic material. Since the drive motor
36
and the drive train of the fiberizing disc are conventional, these components are not shown in detail to better illustrate the overall relationship of the apparatus components. The cantilevered fiberizing disc support
38
employs a conventional framework for supporting the fiberizing disc
40
.
The fiberizing disc
40
, which can be of the type disclosed in the '386 patent, has thousands of small diameter holes in an annular sidewall and is rotated at several thousand revolutions per minute i.e. between 2,500 and 12,000 rpm. The fiberizing disc can be about two feet in diameter and have a sidewall about two and one-half inches high. A thermoplastic material
62
, such as, glass or a polymeric material, is deposited within the fiberizing disc
40
and extruded out through the holes
64
in the sidewall of the disc to form thousands of continuous microfibers having diameters ranging from about 0.4 to about 20 microns. The continuous microfibers are projected outwardly from the fiberizing disc in a substantially horizontal direction as a tow
60
.
The annular suction chamber
24
encircles the fiberizing disc
40
and for a fiberizing disc two feet in diameter, the inner diameter of the suction chamber is about three feet. Thus, the spacing between the fiberizing disc and the collection surface
42
of the suction chamber is about six inches. With a fiberizing disc having a two and one-half inch high sidewall, the inner annular surface is typically about fourteen inches high. The central seven inch portion of the inner annular surface is positioned directly opposite the sidewall of the fiberizing disc
40
, is foraminous, and forms the collection surface
42
of the annular suction chamber. The annular suction chamber is connected to a conventional suction fan (not shown) which creates a partial vacuum within the annular suction chamber and draws air into the chamber through the foraminous collection surface
42
. The flow of air into the annular suction chamber through the foraminous collection surface
42
draws the tow toward the collection surface where the tow is collected to form a tubular blanket
44
either directly on the annular collection surface
42
or on a foraminous backing sheet
50
passing over the collection surface.
The tubular blanket
44
of the present invention can be formed of glass fibers and/or glass microfibers or polymeric fibers and/or polymeric microfibers such as polypropylene, polyethylene, nylon or polyester fibers. The tubular blanket
44
comprises three embodiments with or without a foraminous backing sheet
50
. The backing sheet
50
is normally a spunbonded backing sheet material such as, a polyester backing sheet like REMAY fabric or CEREX fabric.
In a first embodiment, layers of the tow
60
of continuous thermoplastic fibers are collected to form the tubular blanket without bonding the continuous fibers together. In this embodiment, succeeding portions of the tow are collected in layers on preceding portions of the tow to form the tubular blanket
44
.
In a second embodiment, the temperature of the space between the fiberizing disc
40
and the annular collection surface
42
is maintained at a level which keeps the continuous fibers of the tow
60
tacky on their surface as they are collected to form the tubular blanket
44
. Thus, succeeding portions of the continuous fibers in succeeding portions of the tow are directly bonded to preceding portions of the continuous fibers in preceding portions of the tow as the succeeding layers of tow are collected on preceding layers of the tow to form the tubular blanket
44
.
In a third embodiment, a resinous binder or other suitable binder is applied to the tow
60
as it passes from the fiberizing disc
40
toward the collection surface
42
. Thus, as succeeding layers of the tow are collected on preceding layers of the tow, succeeding portions of the continuous fibers of the tow are bonded by the binder to preceding portions of the continuous fibers in preceding layers of the tow to form the tubular blanket
44
.
As shown in
FIGS. 1-3
and
11
, the binder application ring
26
is located just beneath the fiberizing disc
40
and is supported by a cantilevered support
46
of conventional construction. A pressurized liquid binder, such as, a resinous bonding agent, is supplied to the binder application ring
26
through the cantilevered support
46
. The binder application ring
26
is about thirty inches in diameter and is provided with a plurality of upwardly directed spray nozzles
48
for applying the binder to the continuous fibers of the tow as the tow of continuous fibers is drawn from the fiberizing disc
40
toward the collection surface
42
of the annular suction chamber.
As best shown in
FIGS. 1
,
2
and
11
, the forming rings
28
and
30
are supported by the cantilevered fiberizing disc support
38
and the cantilevered binder application ring support
46
respectively. The tubular forming ring
28
functions to form the foraminous backing sheet
50
from the supply roll
32
into a tubular configuration and to guide the tubular foraminous backing sheet down between the fiberizing disc
40
and the annular collection surface
42
of the annular suction chamber. The outside diameter of the forming ring
28
is substantially equal to the inside diameter of the annular suction chamber. Accordingly, the tubular foraminous backing sheet
50
, formed by passing the backing sheet over the forming ring
28
, passes over the collection surface
42
of the annular suction chamber
24
.
As shown in
FIGS. 1
,
2
and
9
, as the foraminous backing sheet
50
is formed into a tubular configuration by passing the sheet over the forming ring
28
, the lateral edges
51
of the foraminous backing sheet are overlapped. The overlapped edges of the foraminous backing sheet
50
pass between and are held in overlapping relationship by the tubular forming ring
28
and rollers
52
which are urged against the forming ring
28
by a pneumatic cylinder
54
. The rollers
52
can be resistance heated or otherwise heated to thermally bond the edges
51
of the backing sheet together at the forming ring
28
as the edges pass between the rollers and the annular forming ring. It is also contemplated that the overlapping edges of the foraminous backing sheet
50
can be secured together by applying an adhesive to the edges as the overlapping edges pass between the rollers
52
and the forming ring
28
and while not specifically shown, it is contemplated that the overlapping edges of the foraminous backing sheet can be secured together by stitching the edges together as the overlapping edges pass from between the rollers and the annular forming ring
28
.
The annular forming ring
30
, shown in
FIGS. 1
,
2
and
10
, guides the tubular blanket
44
and the backing sheet
50
, when used, downstream of the fiberizing and collection portion of the apparatus
20
. The annular forming ring
30
, in cooperation with the annular forming ring
28
, assures that the blanket
44
and backing sheet
50
, when used, are maintained in a tubular configuration for the formation of the tubular blanket
44
. The forming ring
30
also cooperates with an ultra sonic slitting wheel
56
to longitudinally slit the blanket
44
and the backing sheet
50
. The ultrasonic wheel, which is pressed against the forming ring
30
by the pneumatic cylinder
57
, vibrates at a high frequency generating heat which melts and severs the fibers of the blanket and the backing sheet. Branson Ultrasonics Corp. of Danbury Conn., markets ultrasonic slitting wheels which can be used for slitting the blanket
44
of the present invention.
After the blanket
44
is slit, the blanket is unfolded into a flat blanket
58
and wound into a roll on the blanket wind-up assembly
34
. The wind-up assembly
34
is a conventional driven wind-up assembly which also functions to pull the blanket
44
, with or without a backing sheet
50
, through the apparatus
20
.
After the process is initiated, the tubular blanket
44
of the present invention can be made with or without the foraminous backing sheet
50
. When the process is initiated, the foraminous backing sheet
50
is passed over the forming ring
28
and formed into the tubular configuration with overlapping lateral edges
51
. The tubular backing sheet
50
is next passed down between the rotary fiberizing disc
40
and the annular suction chamber
24
passing over the annular collection surface
42
of the suction chamber where the tow
60
is collected on the backing sheet to form the tubular blanket
44
. The tubular blanket
44
and backing sheet
50
are then passed over the forming ring
30
where the blanket and backing sheet are normally cut and unfolded from a tubular configuration into a flat blanket
58
which is wound onto the driven wind-up assembly
34
. When the blanket
44
being produced requires a backing sheet, the backing sheet continues to be fed into the process from the supply roll or rolls
32
until the production run is completed. When the blanket
44
being produced does not require a backing sheet, the backing sheet
50
is used only to initiate the manufacturing process and is no longer used once the blanket
44
can be pulled through the apparatus
20
by the wind-up
34
.
In the production of a blanket
44
, a molten thermoplastic material
62
, such as, glass or a polymeric material, is delivered from a suitable source (not shown) such as, a forehearth or other conventional glass or polymeric material melting and refining means, to the fiberizing disc
40
. The fiberizing disc
40
and the surrounding space intermediate the fiberizing disc and the collection surface
42
of the annular suction chamber are maintained at the appropriate temperature for fiberization of the glass of polymeric material.
As the fiberizing disc
40
is rotated at several thousand revolutions per minute, the molten thermoplastic material within the disc is extruded through the thousands of holes
64
in the peripheral sidewall of the disc to form a tow of continuous filaments. The tow
60
of fibers is projected substantially horizontally from the fiberizing disc. As air is drawn into the annular suction chamber
24
through the foraminous collection surface
42
or through the foraminous backing sheet
50
, when used, and the foraminous collection surface
42
, the tow of continuous fibers is drawn toward the collection surface and is deposited directly on the foraminous collection surface or, when used, on the foraminous backing sheet
50
to form the tubular blanket
44
.
The rate of cooling of the continuous fibers issued from the fiberizing disc
40
is controlled by controlling the temperature of the ambient air being drawn by the annular suction chamber
24
into the space between the fiberizing disc and the annular suction chamber. When the continuous fibers in the tow forming the blanket
44
are not to be thermally bonded together, the ambient air being drawn by the annular suction chamber into the space between the fiberizing disc and the annular suction chamber is maintained at a temperature to cool the fiber surfaces below the softening point of the thermoplastic material forming the fibers so that the surfaces of the fibers are no longer tacky when the fibers are collected to form the blanket. Thus, the continuous fibers do not become bonded directly together in the blanket.
When the continuous fibers in the tow forming the blanket
44
are to be thermally bonded together, the ambient air being drawn by the annular suction chamber into the space between the fiberizing disc and the annular suction chamber is maintained at a temperature to keep the fiber surfaces above the softening point of the thermoplastic material forming the fibers so that the surfaces of the fibers will be tacky when the fibers are collected to form the blanket
44
. Thus, the fibers become thermally bonded together at their points of contact and/or intersection when the surfaces of the fibers cool. The temperature of the ambient air can be controlled by cooling the air directed into the space between the fiberizing disc
40
and the annular suction chamber
24
with a conventional industrial air conditioning system and by heating the air directed into the space between the fiberizing disc
40
and the annular suction chamber
24
by conventional gas combustion heaters.
As the tow
60
of continuous fibers passes from the fiberizing disc toward the collection surface
42
, a binder can be applied to the tow from the binder application ring
26
when is it desired to produce a blanket having more integrity. The binder is sprayed up into the area between the fiberizing disc and the collection surface
42
by the spray nozzles
48
coating the continuous fibers as the continuous fibers pass from the fiberizing disc to the blanket. The binder can cure under ambient conditions or if required, the blanket
58
can be passed through a conventional convection heated oven to cure the binder.
The foraminous backing sheet
50
and/or the blanket
44
is pulled over the collection surface by the wind-up assembly
34
at between ten and one hundred feet per minute. Since the fiberizing disc is rotating a several thousand revolutions per minute, succeeding portions of the tow substantially completely overlap and are collected on preceding portions of the continuous tow. Thus, while the tow is collected in a spiral to form the blanket
44
, the spiral has an extremely low pitch.
Since the tow
60
of continuous fibers is collected on a collection surface located radially outward and opposing the sidewall of the fiberizing disc and the tow is collected in a very low pitch spiral, the tow remains untwisted and the fibers of the tubular blanket
44
are highly, directionally oriented in a substantially circumferential direction within the blanket. The thickness of the tubular blanket
44
formed is determined by the output of the fiberizing disc and the speed with which the tubular blanket is pulled through the apparatus. When no backing sheet is being used and the blanket is being formed directly on the collection surface
42
, the blanket must be thick enough to have the integrity required to be pulled through the apparatus
20
by the wind-up
34
without separating or pulling apart. At a particular thickness, the suction of the air into the annular suction chamber
24
through the blanket is not great enough to draw the tow onto the surface of the blanket being formed. At this point, the tow spirals down below the fiberizing disc and becomes wrapped about the fiberizing disc. The process then has to be interrupted to clear the entangled tow from the disc. Thus, the tubular blanket
44
formed by the process of the present invention can not exceed that thickness at which the air flow through the blanket (including the backing sheet when used) into the suction chamber is sufficient to draw the tow onto the blanket surface for collection.
After the tubular blanket
44
is formed on the annular collection surface
42
or on the foraminous backing sheet
50
as the backing sheet is pulled over the collection surface, the blanket passes over the forming ring
30
. As the tubular blanket
44
passes over the forming ring
30
, the tubular blanket with its backing sheet, when used, is slit longitudinally by the ultrasonic slitting wheel
56
. Since the ultrasonic slitting wheel melts and severs the continuous fibers, no dust is created by the slitting process and the lateral edges of the flat blanket
58
formed from the tubular blanket
44
are sealed or encapsulated. After the tubular blanket
44
is slit, the tubular blanket
44
is unfolded and wound into a roll on the blanket wind-up
34
.
FIG. 7
shows the tubular blanket
44
with its backing sheet
50
. A portion of the tubular blanket is broken away to show the spiral layers of continuous fiber tow
60
which form the tubular blanket. The spiral is exaggerated for illustrative purposes. However, as discussed above, with the fiberizing disc rotating between 2,500 and 12,000 revolutions per minute and with the blanket moving over the collection surface
42
at about ten to one hundred feet per minute, the continuous fiber tow
60
extends in a substantially circumferential direction within the tubular blanket with a spiral pitch that is extremely low. As discussed above, the layers of continuous fiber tow in the blanket may not be bonded together; the layers of continuous fiber tow may be directly bonded together through thermal bonding; or the continuous fiber tow may be indirectly bonded together through the use of a binder when the blanket requires more integrity.
The flat blanket
58
is shown in
FIG. 8
with a backing sheet
50
. Since
FIG. 8
is a section perpendicular to the longitudinal centerline of the flat blanket
58
, the continuous fibers of the tow
60
in the blanket are shown extending across the width of the blanket. Since the continuous fibers are highly, directionally oriented, the processing of strips of the blanket
58
in a chopper, to produce short length fibers, produces fibers which are very uniform in length.
In describing the invention, certain embodiments have been used to illustrate the invention and the practices thereof. However, the invention is not limited to these specific embodiments as other embodiments and modifications within the spirit of the invention will readily occur to those skilled in the art on reading this application. Thus, the invention is not intended to be limited to the specific embodiments disclosed, but is to be limited only by the claims appended hereto.
Claims
- 1. A method of forming a fibrous blanket comprising:providing a foraminous backing sheet; forming said foraminous backing sheet into a tubular foraminous backing sheet; passing said tubular foraminous backing sheet between a rotary fiberizer for producing fibers and an annular suction chamber encircling said rotary fiberizer; producing fibers with said rotary fiberizer; and forming a tubular blanket of said fibers on an inner surface of said tubular foraminous backing sheet by drawing air into said annular suction chamber through said tubular foraminous backing sheet to thereby draw said fibers toward said tubular foraminous backing sheet and collect said fibers on said inner surface of said tubular foraminous backing sheet.
- 2. The method of claim 1, wherein: said fibers are substantially continuous thermoplastic fibers.
- 3. The method of claim 1, including: slitting said tubular blanket and said tubular foraminous backing sheet longitudinally, and opening said tubular blanket and said tubular foraminous backing sheet to form a flat blanket.
- 4. The method of claim 1, including: applying a bonding agent to said fibers prior to the collection of said fibers on said tubular foraminous backing sheet to bond said fibers together and to bond said fibers to said tubular foraminous backing sheet at an interface between said tubular blanket and said tubular foraminous backing sheet; and curing said bonding agent.
- 5. The method of claim 4, including: slitting said tubular blanket and said tubular foraminous backing sheet longitudinally; and opening said tubular blanket and said tubular foraminous backing sheet to form a flat blanket.
- 6. The method of claim 5, wherein: said fibers are continuous thermoplastic fibers.
- 7. The method of claim 2, including: maintaining surfaces of said fibers at a temperature above the softening point of said fibers until the collection of said fibers on said tubular foraminous backing sheet whereby said surfaces of said fibers are tacky and bond to each other and to said tubular foraminous backing sheet at an interface between said tubular blanket and said tubular foraminous backing sheet.
- 8. The method of claim 7, including: slitting said tubular blanket and said tubular foraminous backing sheet longitudinally; and opening said tubular blanket and said tubular foraminous backing sheet to form a flat blanket.
- 9. The method of claim 7, wherein: said fibers are glass fibers.
- 10. The method of claim 7, wherein: said fibers are polymeric fibers.
- 11. The method of claim 2, including: reducing the temperature of surfaces of said fibers below the softening point of said fibers prior to collection of said fibers on said tubular foraminous backing sheet.
- 12. The method of claim 2, including: collecting said continuous fibers as a tow on said tubular foraminous backing sheet in a low pitch spiral with succeeding portions of said tow substantially, completely overlapping preceding portions of said tow to form said tubular blanket.
- 13. The method of claim 12, including: slitting said tubular blanket and said tubular foraminous backing sheet longitudinally; and opening said tubular blanket and said tubular foraminous backing sheet to form a flat blanket having continuous fibers extending substantially perpendicular to a longitudinal axis of said flat blanket.
- 14. The method of claim 13, including: applying a bonding agent to said continuous fibers prior to the collection of said continuous fibers.
- 15. The method of claim 13, including: maintaining surfaces of said continuous fibers at a temperature above the softening point of said continuous fibers until the collection of said continuous fibers.
- 16. The method of claim 13, including: reducing the temperature of surfaces of said continuous fibers below the softening point of said continuous fibers prior to the collection of said fibers.
- 17. The method of claim 13, wherein: said continuous fibers are glass fibers.
- 18. The method of claim 13, wherein: said continuous fibers are polymeric fibers.
US Referenced Citations (9)