U.S. patent number 3,766,606 [Application Number 05/245,350] was granted by the patent office on 1973-10-23 for apparatus for forwarding tow.
This patent grant is currently assigned to E. I. du Pont de Nemours and Company. Invention is credited to Woodrow W. Piper, Arthur Michael Porter.
United States Patent |
3,766,606 |
Piper , et al. |
October 23, 1973 |
APPARATUS FOR FORWARDING TOW
Abstract
A fluid jet apparatus for receiving a ribbon of parallel
continuous filaments, then heating and spreading the filaments for
deposit on a moving surface as a nonwoven web includes an
adjustable diffuser connected to the outlet end of the jet. The
diffuser comprises a pair of spaced plates, adjustable with respect
to each other, mounted to the outlet end of the jet. The plates are
arranged to form aspiration slots at one end between the jet and
the plates. The slots open into a central converging passage formed
by the plates for confining and diverting gas out the open sides of
the diffuser. The particular structural arrangement of the plates
with respect to the jet permits development of static pressure in
the diffuser which in turn causes a large percentage of jet fluid
to exit from the open edges of the diffuser, generally parallel to
the moving laydown surface, while less fluid accompanies the
filaments to the laydown surface to reduce web disturbance.
Inventors: |
Piper; Woodrow W. (MT. Juliet,
TN), Porter; Arthur Michael (Madison, TN) |
Assignee: |
E. I. du Pont de Nemours and
Company (Wilmington, DE)
|
Family
ID: |
22926319 |
Appl.
No.: |
05/245,350 |
Filed: |
April 19, 1972 |
Current U.S.
Class: |
28/283; 28/250;
226/97.4; 19/299 |
Current CPC
Class: |
D01D
10/0481 (20130101); D04H 3/03 (20130101) |
Current International
Class: |
D04H
3/02 (20060101); D01D 10/04 (20060101); D01D
10/00 (20060101); D04H 3/03 (20060101); D01d
011/02 () |
Field of
Search: |
;19/65T,66T ;34/10,156
;226/7,97 ;425/464 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Newton; Dorsey
Claims
What is claimed is:
1. In a filament forwarding apparatus including a jet having inlet
and outlet ends connected by a filament passage of generally
rectangular cross section, a diffuser comprising: a pair of spaced
plates mounted to the outlet end of the jet, one end of the plates
extending above said outlet end and being spaced therefrom to form
two generally rectangular slots, the other end extended below said
outlet said plates forming an open sided diffuser passage in axial
alignment with said jet filament passage, said slots being in
communication with said diffuser passage and the outside of the
jet, said diffuser passage having successive curved, straight and
converging lengths, said curved length being adjacent the outlet
end of the jet, said converging length terminating at said exit
slot, the filaments being forwarded through the jet and diffuser
passages by a gas, said gas developing static pressure in the
diffuser; and means for pivotally mounting one of said plates to
the outlet end of the jet for swinging movement toward and away
from the other plate to change the size of the said exit slot.
2. The apparatus as defined in claim 1, said exit slot having a
width less than the combined widths of said two rectangular
slots.
3. The apparatus as defined in claim 1, including means for moving
said pivotally mounted plate according to the static pressure in
the diffuser passage.
4. The apparatus as defined in claim 3, said means for moving
according to the forwarding conditions in the diffuser passage
comprising: a pressure sensor in communication with said passage;
an air cylinder engaging said one plate adjacent said exit slot; a
source of pressurized air connected to said cylinder; and means for
cutting air off from said cylinder, said means being actuated by
said sensor.
5. In a filament forwarding apparatus including a jet having inlet
and outlet ends connected by a filament passage of generally
rectangular cross section, a diffuser comprising: a pair of spaced
plates mounted to the outlet end of the jet, said plates forming an
open sided diffuser passage in axial alignment with said jet
filament passage, said diffuser passage terminating in an exit
slot; means for pivotally mounting one of said plates to the outlet
end of the jet for swinging movement toward and away from the other
plate to change the size of the exit slot; a pressure sensor in
communication with said diffuser passage; an air cylinder connected
to said one plate adjacent said exit slot; and a control means
connected to said cylinder for admitting and releasing air to said
cylinder for operating said cylinder to move said one plate, said
control means being actuated by said sensor.
Description
BACKGROUND OF THE INVENTION
This invention concerns an apparatus for receiving a ribbon of
parallel continuous filaments, heating to promote shrinkage and
spreading for deposit on a moving surface as a nonwoven web.
Kinney, U.S. Pat. No. 3,338,992, describes a process for preparing
a uniform nonwoven web by forwarding a multifilament strand and
applying an electrostatic charge to the filaments while under
tension supplied by a fluid jet to promote separation of the
filaments when tension is released. The separated filaments are
deposited as a nonwoven web on a moving collecting surface and may
later be subjected to a heating operation to promote bonding. A
particularly useful nonwoven web may be prepared in this way using
filaments which develop spontaneous elongation in the heating
operation. Kitson and Reese in U.S. Pat. No. 2,952,879, describe a
method for preparing such filaments, which comprises passing
polyethylene terephthalate filaments having a crystallinity of less
than about 35 percent through a zone at a temperature of at least
90.degree. C. for a time sufficient to shrink the filaments between
20 percent and 70 percent and thereafter cooling before the
crystallinity reaches the maximum level achievable in the zone. In
the preparation of nonwoven webs, the heating zone may consist of a
fluid jet device where the filaments are subjected to rapid heating
by a hot gas usch as air or steam where the filaments undergo the
required 20 to 70 percent shrinkage. The jet device is preferably
the slot type, i.e., a device wherein the filament passage is
rectangular in cross section. The flow of gas through the jet
provides a sufficient tension on the filaments to forward them but
insufficient to prevent shrinkage. This tension is at least
partially released as the filaments pass out of the jet and the
filaments then become more susceptible to handling in a
diffuser.
The filaments emerging from the jet require particular treatment to
avoid sticking in the diffuser and must be spread out into wider
ribbons to promote uniformity in the webs which are collected.
Franke, U.S. Pat. No. 3,325,906 and De Gusman, U.S. Pat. No.
3,334,161, describe diffusers of the prior art. Both of these
disclosures relate to use of a diffuser attached to a jet of
rectangular cross section. The diffusers operate by providing four
diverging walls which allow the gas to expand and slow down as it
travels through the diffuser. Filaments may also be spread in a gas
stream by use of converging diffuser plates. Apparatus for such
purpose has been described in Isakoff, U.S. Pat. No. 3,593,074.
SUMMARY OF THE INVENTION
The present invention provides a jet and diffuser combination with
adjustable diffuser plates, the jet having inlet and outlet ends
connected by a filament passage of generally rectangular cross
section. The diffuser comprises a pair of spaced plates mounted to
the outlet end of the jet, one end of the plates extends above the
outlet end of the jet and is spaced therefrom to form two generally
rectangular slots. The other ends of the plates extend below the
outlet end of the jet to form a converging diffuser passage in
axial alignment with the jet filament passage. The slots are in
communication with the diffuser passage and the outside of the jet
for introducing air by aspiration into the primary fluid stream,
and the diffuser passage terminates in an exit slot. In the
preferred embodiment, the diffuser passage has open sides and from
the jet outlet to th diffuser exit, the passage is formed of
successive curved, straight and converging lengths.
One of said plates is pivotally mounted to the outlet end of the
jet for swinging movement toward and away from the other plate to
change the size of the exit slot. Means are also provided for
moving the pivotally mounted plate according to the forwarding
conditions or static pressure existing in the diffuser passage.
Preferably, the exit slot has a width less than the combined widths
of the two rectangular slots formed near the outlet of the jet. The
particular structural arrangement of the plates with respect to the
jet permits development of static pressure in the diffuser which in
turn causes a large percentage of jet air to exit from the open
edges of the diffuser, parallel to the moving laydown surface,
while less air accompanies the filaments to the laydown surface to
disturb web formation.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of the fluid jet and diffuser
combination of thei invention.
FIG. 2 is a schematic diagram showing relative placement of the
diffuser plates with respect to the jet walls and the pressure
control system for adjusting the diffuser exit slot.
FIG. 3 is a schematic of the controller of FIG. 2.
FIGS. 4 and 5 are elevation and end views of diffuser plates with
an edge control seal.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
Referring to FIGS. 1 and 2, a ribbon of continuous filament fibers
10 is forwarded by means of a fluid slot jet 12 through a diffuser
14 toward an impervious flexible belt 16 moving in the direction of
the arrow and covering a suction means (not shown) for collection
as a nonwoven web. The fluid jet 12 has a filament inlet 11 and a
filament outlet 13 both of rectangular cross section and the
diffuser 14 has a rectangular filament entrance 15 for receiving a
ribbon of filaments from the jet. Although only one jet apparatus
position has been illustrated, multiple positions may be provided
wth the jet diffuser combination of the invention, these being
diagonally placed across a collecting belt as described by Knee in
U.S. Pat. No. 3,402,227 (FIG. 9).
The diffuser is characterized by two diffuser plates 18 which at
their upper ends are located in close proximity to the lower
outside surfaces 17 of each of the two wide walls of the jet at the
outlet 13, sufficient space being provided for aspiration of air
through rectangular aspiration slots 20 between upper inside
surface 19 of the diffuser plates and the outside surface 17 of the
jet and the plates form a diffuser exit slot 22 which is
rectangular in cross section. the inside surfaces of the diffuser
plates converge from the aspiration slots 20 to the diffuser exit
22. At least one of the diffuser plates 18 is adjustable, pivoting
on pins 24 to provide an exit slot 22 which at its narrowest
setting has a width less than the combined widths of the two
aspiration slots 20. The two diffuser plates 18 form passage 26 to
confine the escaping gas from the jet and spread the gas stream,
thereby promoting spreading of the filaments into a wider ribbon.
Excess gas is discharged through escape opening 28 on one or both
sides of the diffuser 14. The upper inside surfaces 19 of the
diffuser plates in the aspiration gaps 20 are inwardly curved to
form with the lower outside surface 17 of the wide jet walls a
generally converging-diverging channel.
In the preferred apparatus, the diffuser passage 26 is
characterized by a smooth curve starting at the upper inside
surfaces 19 of the diffuser plates. Downstream, the surfaces become
straight, as designated by length 30, and continue to inflection
point 32. The lower surfaces of the two diffuser plates converge in
a length 34 and terminate in exit slot 22. Because of the reduced
area at the exit slot, air flow is reduced and a considerable
portion of the air is diverted out the gas escape openings 28
between the two plates (FIG. 1).
Several variations of the diffuser contour are possible. One
important point, however, is that the contours of the two plates
should converge. The two plates 18 preferably have areas of
parallelism (defined by lengths 30 in FIG. 2). There must be no
areas of divergence from jet outlet slot 13 to diffuser exit slot
22.
The diffuser is fastened to the jet device by means of a bracket 42
which is mounted to jet end plate by means of bolts 40. The
mountinj bracket 42 is keyed for accurate placement underneath the
jet by tab 44 which assists in providing accurate placement with
jet end plate 46. One diffuser plate 18 is rigidly attached to
mounting bracket 42 by means of bolts 43. The other diffuser plate
is mounted for swinging movement around pivot 24. The width of
diffuser exit slot 22 is adjusted by means of air cylinder 25 and
piston 23. An air supply provides pressure against piston 23 which
in turn pushes against the pivotally mounted diffuser plate 18
which it engages. An opposing pressure is exerted by air coming
through the jet 12. The width of diffuser exit slot 22 is widened
by reducing pressure in the air supply and narrowed by increasing
pressure in th air supply.
When the diffuser plates are quite thin, pivot pins 24 may pass
through a bracket 49 attached to the outside of the plate.
FIGS. 2 and 3 illustrate a combination swath width control system
which is adapted for release of fiber plugs which may develop in
the exit of the diffuser. In this system, a sensor 50 is placed in
the fixed diffuser plate 18. This sensor is connected by tubing 56
to a pressure control device 52 such as the Corning Schmitt trigger
Model 191456. The Schmitt trigger is a fluidic control element
which is very sensitive to pressure differential and has a low
switching hysteresis. It may be biased to operate at a prescribed
pressure level and will switch when the control is slightly higher
or lower than this prescribed level. Air from a regulated supply
flows to the pressure control device 52 and valve 54 such a a
Corning Fluid Amp Interface Valve Model 192621-LP (5-40 psig)
through pipes 51 and 53. Air for the three-way valve 54 passes
first through valve air restrictor 55.
The controller 52 includes Schmitt trigger 70, connected between
air supply line 51 and valve 54 and a pressure biasing system
connected to the trigger 70, line 51 and the sensor 50. The
pressure biasing system includes pipe loops 80 and 81 between line
51 and trigger 70 with loop 80 connected to a variable restrictor
83 and loop 81 connected to tubing 56 leading to sensor 50. Guage
82 is connected parallel to loops 80 and 81. In operation, the
trigger 70 is biased by balancing loops 80, 81 so that air flows
straight through trigger 70 from inlet 71 to outlet 72 and on
through pipe 57 to valve 54. This pressure applied to valve 54
holds the valve open admitting air to cylinder 25. Pressure in
loops 80 and 81 is adjusted via restrictor 83 to maintain a higher
pressure in loop 80 than in loop 81 to keep the main air stream
flowing through the trigger 70 as described. In addition, the
pressure in loop 80 is somewhat higher than the pressure in the
diffuser passage so that there is a flow of air through sensor 50
into the diffuser. In the event a plug develops in the exit 22 of
the diffuser, pressure will build up in the diffuser to an extent
to cause pressure to build in loop 81 and switch the air stream
flowing through the trigger 70 from the outlet 72 to outlet 73.
This in turn diverts the air from valve 54 which closes cutting off
air to cylinder 25. With air pressure cut off from the cylinder,
the pressure build up in the diffuser 14 causes pivotally mounted
plate 18 to swing outwardly releasing the plug. Once the plug is
released, the pressure drops to normal allowing the trigger 70 to
reset.
The sensor 50, which is 3/32 inch diameter hole in the upper
section of the fixed diffuser plate, is supplied, by the feedback
circuit, with 0.5 psig air so that bleed occurs into the diffuser.
When a plug forms a change of internal pressure equivalent to as
little as 1 inch of water is enough to trigger release. An
over-pressure of 3 inches of water is a reasonable working level so
as to allow for string up and swath adjustment by an operator
without accidentally causing release.
Additional features are needed for diffusers which are located at
either edge of the collecting belt 16. FIGS. 4 and 5 show a
suitable design for these edge diffusers. Essentially, one edge of
the diffuser plate 60 is cut at 90.degree. to the top edge and a
flexible edge control seal is added to prevent air from carrying
filaments off the edge of the belt. This is seen in detail in FIG.
5 where the edge is partially closed by a flexible sheet 62 held by
clamps 64. The flexible material and the clamps are fastened to the
two diffuser plates 60 by bolts 66.
In operation of the invention, a ribbon 10 of electrostatically
charged filaments of polyethylene terephthalate and polyethylene
terephthalate copolymers is drawn into the jet 12 by aspiration and
is carried through the jet by means of hot air introduced through
air duct 8 of FIG. 1. The construction of the jet is similar to
that of Cope, U.S. Pat. No. 3,302,237. Under the influence of the
hot air stream, th filaments shrink while passing through jet
apparatus. The temperature of the air in the jet is between
225.degree. and 235.degree. C. Upon issuing from the jet, the
filaments pass from filament outlet 13 of the jet into the filament
entrance 15 of the diffuser. Air is aspirated through aspiration
slots 20.
Typically, a ribbon 10 is about 6 inches wide. The exit of the
diffuser 4 is about 19 inches above belt 16 and is about 121/2 to
13 inches in length (L, FIG. 1). The degree of spreading at the
diffuser exit depends partially upon the charge level. With a
charge of about 2 microcoulombs/gram the swath width may be varied
for example from about 23 inches to about 32 inches by changing the
diffuser exit gap from 0.280 inch to 0.150 inch. With a charge of
about 4 microcoulombs/gram the swath width may be varied from about
31 to about 50 inches using the same exit gap range. Each
aspiration gap 20 is typically set with an 0.250 inch width at the
narrowest point.
* * * * *