THOMPSON, Matthew, Duane (5875 Burch Ridge Trail, Cumming, Georgia, 30040, US)
| WHAT IS CLAIMED IS:
1. A distribution manifold for transferring an air stream from an air supply
to an extrusion die in a meltspinning apparatus, comprising:
a body member having a cavity, an inlet coupling said cavity with the
air supply, and a plurality of outlet passages coupling said cavity with the
extrusion die, the air stream flowing in said cavity from said inlet to said
plurality of outlet passages; and
a plurality of metering elements disposed within said cavity between
said inlet and said plurality of outlet passages, each adjacent pair of said
plurality of metering elements being separated by a corresponding one of a
plurality of gaps, and the air stream flowing through said plurality of gaps
before entering said plurality of outlet passages.
2. The distribution manifold of claim 1 wherein said plurality of metering
elements cooperate to balance the air stream such that a mass flow of a
portion of the air stream through each of said plurality of gaps is within about
±5% of an average mass flow through said plurality of gaps.
3. The distribution manifold of claim 1 wherein said plurality of metering
elements have a side-by-side arrangement to define an aligned row, and
said plurality of gaps between have a substantially equal spacing.
4. The distribution manifold of claim 1 wherein said body member further
comprises:
a plate member including said cavity; and a cover member mounted to said plate member for closing said
cavity, said plurality of metering elements extending across said cavity
between said plate member and said cover member.
5. The distribution manifold of claim 1 wherein said cavity includes a first
compartment having a substantially triangular cross-sectional shape with an
open base and inclined side surfaces converging toward an apex, said inlet
being located proximate to said apex, and said plurality of metering
elements being located proximate to said base.
6. The distribution manifold of claim 5 wherein said cavity includes a
second compartment separated from said first compartment by said plurality
of metering elements, each of said plurality of outlet passages
communicating with said second compartment, and the air stream flowing
from said first compartment through said plurality of gaps into said second
compartment and recombining for flow into said plurality of outlet passages.
7. The distribution manifold of claim 6 wherein said plurality of metering
elements are linearly arranged between said first and second
compartments.
8. The distribution manifold of claim 6 wherein said plurality of outlet
passages are linearly arranged with a substantially uniform spacing between
adjacent pairs of said plurality of outlet passages.
9. The distribution manifold of claim 1 wherein said plurality of outlet
passages are linearly arranged with a substantially uniform spacing between
adjacent pairs of said plurality of outlet passages.
10. A meltspinning apparatus for converting a heated liquid into a plurality
of filaments and directing an air stream at the plurality of filaments,
comprising:
a liquid manifold including a liquid passage for the heated liquid;
an air distribution manifold including a cavity, a plurality of metering
elements disposed within said cavity, and a plurality of outlet passages, said
cavity having an inlet communicating with said air stream, each adjacent pair
of said metering elements being separated by a corresponding one of a
plurality of gaps through which the air stream flows through said cavity to
said plurality of outlet passages; and
an extrusion die coupled with said liquid manifold and with said air
distribution manifold, said extrusion die communicating with said liquid
passage for discharging the heated liquid received from said liquid manifold
as a plurality of filaments, and said extrusion die communicating with said
plurality of outlet passages for discharging the air stream received from said
air distribution manifold at the filaments.
11. The meltspinning apparatus of claim 10 wherein said plurality of
metering elements cooperate to balance the air stream such that a mass flow of a portion of the air stream through each of said plurality of gaps is
within about ±5% of an average mass flow through said plurality of gaps.
12. The meltspinning apparatus of claim 10, wherein said plurality of
metering elements have a side-by-side arrangement to define an aligned
row, and said plurality of gaps have a substantially equal spacing.
13. The meltspinning apparatus of claim 10 wherein said plurality of
metering elements are formed integrally with said body member.
14. The meltspinning apparatus of claim 10 wherein said at least one
plate member with said cavity includes a cover member mounted thereto to
close said cavity, said plurality of metering elements extending across said
cavity between said plate member and said cover member to define said
plurality of gaps therebetween.
15. The meltspinning apparatus of claim 10 wherein said cavity includes
a first compartment having a substantially triangular cross-sectional shape
with an open base and inclined side surfaces converging toward an apex,
said inlet being located proximate to said apex, and said plurality of metering
elements being located proximate to said base.
16. The meltspinning apparatus of claim 15 wherein said cavity includes
a second compartment separated from said first compartment by said plurality of metering elements, each of said plurality of outlet passages
communicating with said second compartment, and the air stream flowing
from said first compartment through said plurality of gaps into said second
compartment and recombining for flow into said plurality of outlet passages.
17. The meltspinning apparatus of claim 16 wherein said plurality of
outlet passages are linearly arranged with a substantially uniform spacing
between adjacent pairs of said plurality of outlet passages.
18. The meltspinning apparatus of claim 16 wherein said plurality of
metering elements are linearly arranged between said first and second
compartments.
19. A method for operating a meltspinning apparatus, the method
comprising:
flowing an air stream through a cavity from an inlet to a plurality of
outlet passages;
balancing a mass flow of the air stream into the plurality of outlet
passages with a plurality of flow constrictions positioned in the cavity
between the inlet and the plurality of outlet passages; and
communicating the air stream from the plurality of outlet passages to
an extrusion die.
20. The method of claim 19 further comprising: heating the air stream before the air stream exits the plurality of outlet
passages.
21. The method of claim 19 further comprising:
extruding a plurality of filaments from the extrusion die; and
directing the air stream from the extrusion die toward the plurality of
filaments. |
APPARATUS AND METHODS FOR DISTRIBUTING A BALANCED AlR STREAM TO AN EXTRUSION DIE OF A MELTSPINNING APPARATUS
Field of the Invention
The present invention relates generally to meltspinning apparatus
and methods and, more particularly, to meltspinning apparatus and methods
with a balanced airflow distribution to an extrusion die.
Background
Meltspinning techniques, such as spunbonding or meltblowing
techniques, for extruding fine diameter filaments of a polymer melt find
many different applications in various industries including, for example,
nonwoven material manufacturing. Spunbonded and/or meltblown materials
are used in many consumer and industrial products, including but not limited
to disposable diapers, incontinence diapers, surgical gowns and other
disposable protective attire, bedding, pillows, furnishings, geotextiles, carpet
underlayment, medical products, and fluid filters.
Meltspinning apparatus generally extrude filaments of a thermoplastic
material from an extrusion die having a relatively large width and impinge
the extruded filaments with an air stream. A spunbond extrusion die
includes a spinneret usually consisting of a flat perforated plate arranged
across the width of a production line. A polymer melt is forced through
numerous small orifices or holes in the spinneret to form a descending
curtain of continuous filaments.
A meltblowing apparatus includes an extrusion die with a die tip or
nosepiece, also referred to as a spinneret, having numerous small orifices or
holes arranged in a straight line along the crest of nosepiece. A polymer
melt is extruded from these holes to form filament strands that are
subsequently attenuated by high-velocity heated air to form fine fibers. Air
manifolds supply the high velocity heated air, also called primary air, through
slots defined in the die nosepiece for impinging the filament strands to
cause attenuation and form the fine fibers. Smaller orifices are usually
employed in meltblowing techniques compared to those generally used in
spunbonding techniques.
One problem associated with conventional meltspinning apparatus
involves the cost and complexity of the manifolds used to effectively transfer
air to the spinneret or extrusion die. For example, a large manifold is often
required to ensure that balanced distribution of the flow of air to the
extrusion die or spinneret. A balanced airflow helps to insure uniformity
among the filaments discharged across the width of the extrusion die or
spinneret. Another problem encountered in conventional meltspinning
apparatus is the inability to provide a balanced air distribution across the
width of the extrusion die or spinneret. Any deviations from balanced air
distribution may result in non-optimized characteristics and properties of the
nonwoven web formed from the collected filaments impinged by different
portions of the airflow after extrusion from the spinneret or extrusion die.
For these and other reasons, it would be desirable to provide a
meltspinning apparatus with an air distribution manifold that is easily
manufactured while providing a balanced distribution of airflow to an
extrusion die or spinneret.
Summary of the Invention
The present invention provides a distribution manifold for transferring
an air stream from an air supply to an extrusion die in a meltspinning
apparatus. The distribution manifold includes a body member having a
cavity, an inlet coupling the cavity with the air supply, and a plurality of outlet
passages coupling the cavity with the extrusion die. The air stream flows in
the cavity from the inlet to the outlet passages. The distribution manifold
further includes a plurality of metering elements disposed within the cavity
between the inlet and the outlet passages. Each adjacent pair of metering
elements is separated by a corresponding one of a plurality of gaps. The air
stream flows through the gaps before entering the plurality of outlet
passages. Because the air stream is constrained to flow through the gaps,
the metering elements restrict the airflow to create backpressure. This
backpressure helps balance the mass flow of the air through the various
gaps before the airflow enters the outlet passages.
In another aspect, a meltspinning apparatus is provided for
converting a heated liquid into a plurality of filaments and directing an air
stream at the plurality of filaments. The meltspinning apparatus comprises a
liquid manifold including a liquid passage for the heated liquid. The
meltspinning apparatus further comprises an air distribution manifold
including a cavity having an inlet communicating with the air stream, a
plurality of metering elements disposed within the cavity, and a plurality of
outlet passages. Each adjacent pair of metering elements is separated by a
corresponding one of a plurality of gaps through which the air stream flows
through the cavity to the outlet passages. An extrusion die is coupled with
the liquid and air distribution manifolds. The extrusion die communicates
with the liquid passage for discharging the heated liquid received from the
liquid manifold as a plurality of filaments. The extrusion die communicates
with the outlet passages for discharging the air stream received from the air
distribution manifold at the filaments.
In another aspect of the present invention, a method for distributing a
flow of an air stream in a meltspinning apparatus comprises flowing the air
stream through a cavity from an inlet to a plurality of outlet passages and
balancing a mass flow of the air stream into the plurality of outlet passages
with a plurality of flow constrictions positioned in the cavity between the inlet
and the plurality of outlet passages. The method further comprises
communicating the air stream from the plurality of outlet passages to an
extrusion die.
Advantageously, the air distribution manifold of the present invention
may be easily manufactured while still achieving the goal of providing a
balanced distribution of airflow directed to attenuate the extruded fibers.
The ease of manufacture, which is due at least in part to the simplicity of the
device design, reduces the cost to machine the distribution manifold of the
present invention. The present invention eliminates the need for a large
conventional external air manifold to provide a balanced air distribution to a
meltblown extrusion die or to a spin pack. The air distribution manifold of
the present invention may be used for both spunbond and meltblown
applications.
Brief Description of the Drawings
The accompanying drawings, which are incorporated in and
constitute a part of this specification, illustrate embodiments of the invention
and, together with a general description of the invention given above, and
the detailed description given below, serve to explain the principles of the
invention.
FIG. 1 is an exploded perspective view of a manifold assembly for
directing a heated liquid or air to an extrusion die;
FIG. 2 is a cross sectional view taken generally along line 2-2 in FIG.
1 ;
FIG. 3 is perspective view of a distribution manifold of the manifold
assembly shown in FIG. 1 ; and
FIG. 4 is an enlarged perspective view of a portion of the distribution
manifold shown in FIG. 3.
Detailed Description
With reference to FIGS. 1-4, a meltspinning apparatus 10 is equipped
to convert a heated liquid, such as a molten or semi-solid, melt-processable
thermoplastic polymer, into a curtain of filaments 132 and direct one or more
air streams 136 at the filaments 132 discharged or otherwise extruded from
the meltspinning apparatus 10. A collector 133 collects the filaments 132 to
form a nonwoven web 134 and mechanically supports the nonwoven web
134 as web 134 is transported in a machine direction away from the
meltspinning apparatus 10 for further processing. Generally, the nonwoven
web 134 is a flexible continuous sheet layer having a structure of individual
filaments 132 interlaid in a random manner to have an open, porous
structure. For simplicity, details of the construction of the nonwoven web
134 are omitted from Fig. 2. In certain embodiments of the invention, the
nonwoven web 134 may constitute an individual layer in a laminate
consisting of two or more individual layers.
Meltspinning apparatus 10 includes a manifold assembly 12 and an
extrusion die or spinneret 14 coupled in fluid communication with the
manifold assembly 12. The manifold assembly 12 includes a plurality of
body or plate members 16a, 16b, 16c, 16d, such as a lamellar or plate-like
construction that advantageously aids in the efficient transfer of air and
liquid to extrusion die 14. Fasteners 54 extend through registered holes 26
in plate members 16a-d to secure the plate members 16a-d in an abutting
side-by-side relation. The manifold assembly 12 may be heated to, for
example, maintain a process temperature for heated liquid flowing through
the manifold assembly or to heat the process air, or other gas, supplied to
the manifold assembly 12. Accordingly, heating elements (not shown) may
be positioned between or in the individual plate members 16a-d to heat the
liquid and/or air flowing through manifold assembly 12.
Inner plate members 16b, 16c, which are coextensive, cooperate to
define a liquid distribution manifold. Specifically, inner plate members 16b,
16c bound a feed channel or liquid passage 28 that transfers heated liquid
pumped from an extruder (not shown) to the extrusion die 14. As best
shown in FIG. 2, the liquid passage 28 is defined by respective recesses 38,
40 and inlet slots 42, 44 that align with each other in abutting surfaces of
inner plates 16b, 16c. Recesses 38, 40 generally terminate in an elongate
liquid outlet slot 48 at a top surface 50 of extrusion die 14. The liquid outlet
slot 48 communicates with liquid passageways 140 inside the extrusion die
14 that direct the heated liquid for extrusion from die 14 as filaments 132.
Although only a single liquid passage 28 is shown in the figures, a person
having ordinary skill in the art will appreciate that the manifold assembly 12
may include additional plate members each having a liquid passage for
applications that produce multicomponent filaments. Exemplary plate
arrangements are shown and described in commonly-assigned U.S. Patent
Application 2005/0046090, the disclosure of which is incorporated by
reference herein in its entirety.
Outer plate members 16a, 16d operate as air distribution manifolds
containing respective air passages 30, 32 for transferring an air stream to
the extrusion die 14. Air passage 30 includes a cavity 58 defined in the
constituent material of the outer plate member 16a and a plurality of outlet
passages 62 that extend through the thickness of the outer plate member
16a. Cavity 58, which generally has a coathanger shape, is closed off by
securing a cover member 68 to the outer plate members 16a. Similarly, air
passage 32 includes a cavity 60 defined in outer plate member 16d and a
plurality of outlet passages 64 that extend through the thickness of the outer
plate member 16d.
With continued reference to FIGS. 1-4, cavity 60, which also
generally has a coathanger shape, is closed off by securing cover member
70 to outer plate member 16d. In an alternative embodiment, either cavity
58 or cavity 60 may be closed off by securing an additional plate member
(not shown) similar to plate members 16a-d rather than cover member 68,
70, respectively. Additionally, those skilled in the art will further appreciate
that cavity 58, for example, may be formed as a compartment inside plate
member 16a so as to eliminate the need for a cover member or the like.
Extrusion die 14 may be any suitable extrusion die having liquid
passages 140 coupled with the liquid outlet slot in inner plate members
16b,c. Outlet orifices 142 of the liquid passages 140 extend along the
underside of the extrusion die 14. A descending curtain of filaments 132 is
extruded from the outlet orifices 142. Extrusion die 14 also includes air slots
138a,b each communicating at a respective open end with the outlet
passages 62, 64 for receiving the balanced air streams from cavities 58 and
60 and discharging the air streams 136 from slotted discharge outlets
144a, b, respectively, toward the filaments 132. The air streams 136
discharged from the slotted discharge outlets 144a,b impinge the filaments
132 discharged from the outlet orifices 142 for attenuating, or otherwise
affecting, the filaments 132 to form fine fibers that are subsequently
collected as nonwoven web 134 on collector 133. The air streams 136 are
illustrated in FIG. 2 as impinging two diametrically opposed sides of the
curtain of filaments 132 extruded from extrusion die 14, although the
invention is not so limited.
Holes 76 penetrate through the cover member 68 and receive
fasteners 24 that are used to secure cover member 68 with bolt holes 116
plate member 16a. Smaller fasteners 78 extend through additional holes 80
spaced along the perimeter of cover member 68 to attach cover member 68
to plate member 16a. An inlet 84 extending through cover member 68
provides an access path for process air into the cavity 58. Inlet 84 extends
through a short, flanged spool 86 coupled at one open end with a registered
opening in cover member 58. A mating flange 88 on spool 86 is configured
for attaching a supply line extending to an air supply 90 (FIG. 2). Cover
member 70 includes a similar spool 94 and mating flange 96 such that the
air supply 90 is coupled with an inlet 98 extending through cover member
70.
With continued reference to FIGS. 1-4, cavity 58 is inset into a side
surface of the plate member 16a and generally has a triangular cross-
sectional shape bounded by a base 110 and inclined side surfaces 112,
114. The side surfaces 112, 114 converge toward an apex 108 located
proximate to inlet 84. Accordingly, cavity 58 has a "coat hanger"
configuration. Outlet passages 62 are substantially linearly aligned adjacent
to base 110. Adjacent pairs of outlet passages 62 have a substantially
uniform spacing therebetween, which advantageously facilitates the transfer
of air to extrusion die 14, as will be described in greater detail below.
A plurality of flow restrictions represented by metering elements 118
are disposed within the cavity 58 at a location between apex 108 and base
110. The metering elements 118 may be disposed with a side-by-side or
linear arrangement so as to define aligned row located proximate to base
110 and outlet passages 62, although the invention is not so limited. The
metering elements 118 sub-divide or partition the cavity 58 into first and
second compartments or sections 122, 124 that are contiguous and
communicate with each other through gaps 128 between the metering
elements 118. The outlet passages 62 communicate at one open end with
the second section 124 of cavity 58. Cavity 60, which has a construction
substantially identical to cavity 58, also includes a set of metering elements
(not shown) that are equivalent in structure and function to metering
elements 118.
Metering elements 118 may be secured to the plate member 16a
within cavity 58 or, alternatively, may be integrally formed with the
constituent material of the plate member 16a. The metering elements 118
may be uniform in shape and size, each having a rectangular prism-like
configuration or parallelepiped shape, although the invention is not so
limited. For example, in one embodiment of the present invention, the
metering elements 118 may have a cross-sectional width of 0.625" and a
height of 0.225". The depth or length of metering elements 118 may be any
desired distance, but advantageously corresponds to the depth of cavity 58.
Thus, if cavity 58 is 1" deep, then metering elements 118 are
advantageously 1" long. Such a relationship enables metering elements
118 to extend across cavity 58 and abut cover member 68 when cavity 58 is
closed off. Adjacent pairs of metering elements 118 are spaced apart from
each other so as to define a corresponding one of a plurality of slots or gaps
128 therebetween. Because metering elements 118 are equally spaced
apart and uniform in size, gaps 128 have a substantially equal center-to-
center spacing. For example, each gap 128 may have a spacing of 0.25".
Metering elements 118 and gaps 128 define flow constrictions between first
and second sections 122, 124 of cavity 58.
In various embodiments of the present invention, the metering
elements 118 may other shapes and sizes. For example, the metering
elements may have circular or polygonal cross-sections viewed in a direction
normal to the side surface of plate member 16a. The metering elements
may also be dome-shaped or pyramid-shaped. One or more of these
various shapes may be utilized in any particular application, along with one
or more variations in size. Additionally, the metering elements 118 may be
arranged in a nonlinear pattern with non-uniform spacing or in some other
manner between the first and second sections 122, 124 of cavity 58. Thus,
the number, shape, size, and arrangement of the metering elements 118
may be tailored to provide constrictions supplying a desired application-
specific balanced airflow through the cavity 58.
In use and with reference to FIGS. 1-4, heated liquid is supplied to
the inlet slots 42, 44 in manifold assembly 12. The liquid flows through
recesses 38, 40 before reaching elongate liquid outlet slot 48. Extrusion die
14 then receives the liquid from elongate outlet slot 48 and discharges the
liquid from outlet orifices 142 to produce extruded filaments 132 of
thermoplastic material. A continuous stream of air is directed from air
supply 90 through inlets 84, 98 into cavities. The air stream flows in each of
the individual cavities 58, 60 from the corresponding inlet 84, 98,
respectively, toward the outlet passages 62, 64. In each of the cavities 58,
60, the associated air stream intersects the metering elements 118 with a
main velocity component approximately perpendicular to the side surface of
each of the metering elements 118. The air stream flowing in, for example,
cavity 58 in outer plate member 16a travels from first section 122 through
the gaps 128 between metering elements 118 into second section 124,
where the air stream recombines for flow into outlet passages 62. The flow
of the air stream in cavity 60 in outer plate member 16d is similar.
The metering elements 118 balance the distribution of the air stream
by constraining the air stream to flow through gaps 128. More specifically,
metering elements 118 restrict the airflow through cavities 58, 60 so as to
create backpressure that evenly distributes, or meters, a mass flow of air
through each gap 128. For example, cavities 58, 60 and metering elements
118 may be designed such that the mass flow of air through each gap 128 is
within about ±5% of the average mass flow through all of the gaps 128. The
mass flow through gaps 128 may be simulated, calculated, or experimentally
measured for the purposes of determining the balancing effect. The
balancing effect supplied by the metering elements 118 improves upon the
distribution afforded by the coat-hanger geometry of cavities 58, 60.
The balanced air stream originating from each of the cavities 58, 60 is
communicated with the corresponding one of the air slots 138a, b and is
ultimately discharged from slotted discharge outlets 144a,b to impinge the
filaments 132. The attenuated filaments 132 are then collected on the
moving collector 133 as nonwoven web 134. Supplying a balanced
distribution of air to the outlet passages 62 from each of the cavities 58, 60
ultimately improves the uniformity of filament attenuation across the length of
the extrusion die 14. The effect of the uniformity is manifested by
optimization of the characteristics and properties of the nonwoven web 134
formed from the collected filaments 132.
Persons having ordinary skill in the art will further appreciate that the
metering elements 118 may have other applications relating to balancing the
mass flow of any compressible or incompressible fluid through a cavity. In
particular, the spaced confined by the recesses 38, 40 in inner plate
members 16b, 16c may be provided with a set of metering elements similar
to metering elements 118 to assist in balancing the mass flow of the heated
liquid to extrusion die 14.
While the invention has been illustrated by the description of one or
more embodiments thereof, and while the embodiments have been
described in considerable detail, they are not intended to restrict or in any
way limit the scope of the appended claims to such detail. Additional
advantages and modifications will readily appear to those skilled in the art.
The invention in its broader aspects is therefore not limited to the specific
details, representative apparatus and methods and illustrative examples
shown and described. Accordingly, departures may be made from such
details without departing from the scope or spirit of Applicant's general
inventive concept.
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