System for forming and cutting a mineral fiber tow

A system is provided for forming a continuous mineral fiber wool tow and cutting the tow into discrete lengths. The system comprises a conveying apparatus for pulling a mineral fiber wool tow from a mineral fiber pack at a first location and transporting the tow to a chopping station. A chopping apparatus is positioned at the chopping station for chopping the tow into discrete lengths. The conveying apparatus further receives the discrete lengths at the chopping station and transports the discrete lengths to a collecting station. The conveying apparatus further includes a collection device located at the collecting station for receiving the discrete lengths of mineral fiber wool material and collecting the discrete lengths for subsequent use.

TECHNICAL FIELD 
This invention relates to a system for collecting a mineral fiber wool tow 
from a forming apparatus, transporting the tow to a chopping station, 
chopping the tow into discrete lengths and packaging the chopped fibers. 
BACKGROUND AND SUMMARY 
Chopping devices for cutting glass filaments are known in the art. For 
example, U.S. Pat. No. 3,869,268 to Briar et al. teaches a device for 
chopping continuous glass filaments drawn from streams of molten glass 
into discrete segments. The device comprises a cot roll and a juxtaposed 
cutting roll, which together define a cutting nip for receiving the glass 
filaments. The cot and cutting rolls supply the attenuation forces to draw 
the streams of molten glass into filaments and further serve to chop the 
glass filaments into discrete segments. Because the filaments are 
continuous and pulled by the cot and cutter rolls towards them, conveying 
or delivering the glass filaments to the cutting nip is generally not a 
problem. Also, because the filaments are continuous and due to their 
weight, it is typically not difficult to keep the glass filaments properly 
positioned between the cot and cutting rolls during the cutting step. 
It would be desirable to use a chopping device comprising cot and cutting 
rolls to cut a light-weight mineral fiber wool tow into discrete sections. 
However, in order to do so, a conveying system must be designed which is 
capable of delivering a light-weight tow to a cutting nip between cot and 
cutting rolls. The system must also be capable of maintaining the 
light-weight tow properly positioned between the two rolls. 
In accordance with the present invention, a conveying system is provided 
which is capable of delivering a light-weight tow to a cutting nip between 
cot and cutting rolls. 
In accordance with a first aspect of the present invention, a system is 
provided for forming a continuous mineral fiber wool tow and cutting the 
tow into discrete lengths. The system comprises a conveying apparatus for 
pulling a mineral fiber wool tow from a mineral fiber pack at a first 
location and transporting the tow to a chopping station. A chopping 
apparatus is positioned at the chopping station for chopping the tow into 
discrete lengths. The conveying apparatus further receives the discrete 
lengths at the chopping station and transports the discrete lengths to a 
collecting station. The conveying apparatus further includes a collection 
device located at the collecting station for receiving the discrete 
lengths of mineral fiber wool material and collecting the discrete lengths 
for subsequent use. 
Preferably, the chopping apparatus comprises a cot roll having a generally 
smooth outer circumferential surface; a drive motor for effecting rotation 
of the cot roll; a rotatable cutting roll juxtaposed to the cot roll and 
contacting the cot roll at its circumferential surface to rotate with the 
cot roll; and a substantially air-tight enclosure surrounding the cot roll 
and the cutting roll. The rotatable cutting roll and the cot roll define a 
cutting nip for receiving the tow such that the tow is received in the nip 
and cut into discrete lengths. 
The cutting roll may comprise a cutting wheel having a plurality of cutting 
blades associated therewith and spaced apart from one another about the 
cutting wheel. 
The conveying apparatus preferably comprises a collection hood for 
receiving the mineral fiber tow; a nozzle extending into the air-tight 
enclosure for delivering the tow to the cutting nip; a first conduit 
section coupled to and extending between the hood and the nozzle; a second 
conduit section coupled to and extending between the chopping device and 
the collection device and a vacuum pump associated with the collection 
device for drawing a vacuum in the collection device, the air-tight 
enclosure, the nozzle, the first and second conduit sections, and the 
collection hood. 
In one embodiment, the conveying apparatus further comprises a third 
conduit section coupled to and extending between the collection hood and 
the second conduit section for defining a bypass path for the tow when the 
tow is to be conveyed to the collecting station without being cut into 
discrete lengths. A first valve device may be associated with the first 
conduit section for allowing the tow to pass through the first conduit 
section when the first valve device is in its open position and for 
preventing the tow from passing through the first conduit section when the 
first valve device is in its closed position. A second valve device may be 
associated with the third conduit section for allowing the tow to pass 
through the third conduit section when the second valve device is in its 
open position and for preventing the tow from passing through the third 
conduit section when the second valve device is in its closed position. 
In accordance with a second aspect of the present invention, a chopping 
device is provided for cutting a continuous mineral fiber wool tow into 
discrete lengths. The cutting device comprises a cot roll having a 
generally smooth outer circumferential surface; a drive motor for 
effecting rotation of the cot roll; and a rotatable cutting roll 
juxtaposed to the cot roll and contacting the cot roll at its 
circumferential surface to rotate with the cot roll. The rotatable cutting 
roll and the cot roll define a cutting nip for receiving the tow such that 
the tow is received in the nip and cut into discrete lengths. The cutting 
roll preferably comprises a cutting wheel having a plurality of cutting 
blades associated therewith and spaced apart from one another about the 
cutting wheel. At least one of the cutting blades has a generally V shape, 
a chevron shape or is formed in the shape of an arc. 
In one of the illustrated embodiments, the blades are spaced apart from one 
another about the cutting wheel such that at least one blade is always in 
contact with the cot roll during rotation of the cot roll and the cutting 
roll. 
It is further contemplated that the cutting roll may further comprise a 
plurality of teeth positioned about at least one of the outer 
circumferential edges of the cutting wheel. 
In accordance with a third aspect of the present invention, a method is 
provided for forming a continuous mineral fiber wool tow and cutting the 
tow into discrete lengths. The method comprises the steps of: pulling a 
continuous mineral fiber wool tow from a mineral fiber pack; conveying the 
tow to a chopping station; chopping the tow into discrete lengths at the 
chopping station; and transporting the discrete lengths from the chopping 
station to a collecting station where the discrete lengths are collected 
for subsequent use. 
Accordingly, it is an object of the present invention to provide a 
conveying system which is capable of delivering a light-weight tow to a 
cutting nip between cot and cutting rolls. It is further an object of the 
present invention to provide a conveying system which is capable of 
maintaining a light-weight tow generally centered between cot and cutting 
rolls such that the tow is cut into discrete lengths or segments. It is 
another object of the present invention to provide a method and apparatus 
for cutting a mineral fiber wool tow into discrete lengths. 
These and other objects and advantages of the present invention will be 
apparent from the following description, the accompanying drawings and the 
appended claims.

DETAILED DESCRIPTION 
A system 10 constructed in accordance with a first embodiment of the 
present invention is illustrated in FIG. 1. The system 10 comprises a 
conveying apparatus 40 for pulling a tow 20a from a mineral fiber wool 
pack 20 traveling along a take-away conveyor 30, and transporting the tow 
20a to a chopping station 50. A chopping apparatus 60 (also referred to 
herein as a chopping device) is positioned at the chopping station 50 for 
chopping the tow 20a into discrete lengths 22a. The conveying apparatus 40 
further receives the discrete lengths 22a at the chopping station 50 and 
transports the discrete lengths to a collecting station 70. The conveying 
apparatus 40 further includes a collection device 80 located at the 
collecting station 70 for receiving the discrete lengths 22a and 
collecting the discrete lengths 22a for subsequent use. 
In the illustrated embodiments, the mineral fiber wool pack 20 is formed 
from irregularly shaped glass fibers. 
The irregularly shaped fibers are entangled and require no binder. The 
fibers are formed via a rotary fiberizing apparatus (not shown). The 
take-away conveyor 30 may be positioned beneath the rotary fiberizing 
apparatus for capturing the long glass fibers and delivering the fibers to 
a first location 32 where the tow 20a of the fibers is pulled from the 
pack 20 by the conveying apparatus 40 (see FIG. 1). A description of such 
fibers and methods for producing same are set forth in commonly assigned 
U.S. Pat. No. 5,431,992 and co-pending U.S. patent application Ser. No. 
08/240,428, filed May 10, 1994; and U.S. patent application Ser. No. 
08/310,183 filed Sep. 21, 1994; all of which are incorporated by reference 
herein in their entirety. 
Referring now to FIGS. 1 and 2, the chopping apparatus 60 comprises a cot 
roll 62, a conventional drive motor (not shown) coupled to the cot roll 62 
for effecting rotation of the cot roll 62, and a rotatable cutting roll 
64. The cutting roll 64 is juxtaposed to the cot roll 62 and contacts the 
cot roll 62 at its outer circumferential surface 62c such that the cutting 
roll 64 is rotated by the cot roll 62. The rotatable cutting roll 64 and 
the cot roll 62 define a cutting nip 68 for receiving the tow 20a. As the 
tow 20a passes between the cot and cutting rolls 62 and 64, it is cut into 
discrete lengths 22a. A collecting structure 61 is positioned below the 
cot and cutting rolls 62 and 64 for collecting the chopped discrete 
lengths 22a before they are received by the conveying apparatus 40. 
The cot roll 62 comprises a metal hub 62a formed, for example, from 
aluminum, and a removable outer portion 62b mounted on the hub 62a. The 
outer portion 62b is preferably formed from polyurethane or a like 
polymeric material and has a generally smooth outer circumferential 
surface 62c. The chopping apparatus 60 further includes an air-tight 
enclosure 66 surrounding the cot roll 62 and the cutting roll 64. The 
air-tight enclosure 66 includes a pivotable access door 66a which has a 
clear side panel 66b formed from glass or a clear polymeric material (see 
FIG. 2). 
Referring now to FIG. 3, the cutting roll 64 is mounted at each end via a 
mounting assembly 65 having a rotatable inner portion 65a and a 
nonrotating outer portion 65b which is clamped within a U-shaped frame 69. 
The inner and outer portions 65a and 65b have interlocking concentric 
rings on their adjacent faces which prevent dust from reaching a bearing 
assembly (not shown) located between the portions 65a and 65b. The frame 
69 has a tongue portion 69a which is received in a groove 100 provided in 
a mounting structure 102, see also FIG. 2. Bolts 104, shown only in FIG. 
2, are provided for frictionally locking the tongue portion 69a in the 
groove 100. The mounting structure 102 and, hence, the cutting roll 64 are 
movable toward and away from the cot roll 62 by conventional apparatus not 
shown. 
In the embodiment illustrated in FIGS. 2 and 3, the cutting roll 64 
comprises a cutting wheel 67 and a plurality of cutting blades 67a which 
are integral with the cutting wheel 67. The cutting roll 64 is formed from 
a hollow, cylindrical steel section. The section is machined such that the 
blades 67a are cut into the steel section. The height of the cutting 
blades 67a preferably falls within the range of 0.20 inch to 0.30 inch 
(0.005 meter to 0.0076 meter). The machined section is heat treated. After 
the heat treating step, the blades 67a are sharpened via a grinding step. 
In this embodiment, the blades 67a are spaced apart from one another about 
the cutting wheel 67 such that at least one blade 67a is always in contact 
with the cot roll 62 during rotation of the cot roll 62 and the cutting 
roll 64. 
The blades 67a have a chevron shape (only five of the blades 67a are shown 
in FIG. 3). That is, each blade 67a comprises right and left hand helix 
portions 67b and 67c, each of which extends from a cutting wheel surface 
line L.sub.1 at an angle .THETA.. The cutting wheel surface line L.sub.1 
is parallel to the axis of rotation of the cutting wheel 67. The angle 
.THETA. preferably falls within the range of 5.degree. to 50.degree., and 
more preferably within the range of 20.degree. to 40.degree.. Each blade 
67a also includes a smooth radius transition portion 67d which extends 
between the helix portions 67b and 67c. The radius Rp of portion 67d 
preferably falls within the range of 0.5 inches to 3 inches (0.01 meter to 
0.08 meter). The larger the value of the radius R.sub.p, the less likely 
that the cot roll 62 will be damaged, i.e., gouged, by the blades 67a. 
Preferably, the cutting roll 64 is rotated such that the transition 
portion 67d of each blade 67a is the last portion of the cutting blade 67a 
to pass through the nip 68. 
Because the blades 67a are chevron shaped, airflow through the nip 68 and 
around the cot and cutting rolls 62 and 64 is controlled such that the 
light-weight tow 20a is maintained centered as it travels between the two 
rolls 62 and 64. Conventional cutting rolls oftentimes have knife blades 
wrapped about the cutting wheel portion of the cutting roll at a 
10.degree. to 30.degree. helix angle. Such a cutting roll, if used to cut 
a tow of light-weight wool material, is likely to act as a blower causing 
the tow of wool material to follow the airflow and bypass the nip between 
the cot and cutting rolls. The cutting blades 67a of the present 
invention, however, center the airflow between the cot and cutting rolls 
62 and 64 such that the tow 20a is maintained properly positioned between 
the two rolls 62 and 64. 
A cutting roll 110, formed in accordance with a second embodiment of the 
present invention, is shown in FIGS. 4 and 5. The cutting roll 110 
comprises a cutting wheel 112 and a plurality of cutting blades 114 which 
are integral with the cutting wheel 112. The blades 114 have a chevron 
shape which shape is similar to that of the blades 67a illustrated in FIG. 
3. The cutting roll 110 further includes first and second annular cutting 
blades 116a and 116b which are positioned at opposite ends 112a and 112b 
of the cutting wheel 112. The cutting blades 116a and 116b cut away any 
tow material that extends beyond the width of the cutting blades 114. 
Because of the spacing between the cutting blades 114, a cutting blade 114 
is not always in contact with the cot roll 62 during rotation of the cot 
roll 62 and the cutting roll 110. However, the cutting blades 116a and 
116b are in constant engagement with the cot roll 62 during the cutting 
operation, thereby ensuring that the cot roll 62 effects smooth and 
continuous rotation of the cutting roll 110. The cutting blades 116a and 
116b also help control airflow through the nip 68 and around the cot and 
cutting rolls 62 and 64. 
A cutting roll 120, formed in accordance with a third embodiment of the 
present invention, is shown in FIG. 6. In this embodiment, the cutting 
roll 120 comprises a cutting wheel 122 and a plurality of cutting blades 
124 which are integral with the cutting wheel 122. The blades 124 are 
V-shaped. The spacing between the blades 124 is such that a cutting blade 
124 is not always in contact with the cot roll 62 during rotation of the 
cot roll 62 and the cutting roll 120. To ensure that the cutting roll 120 
is driven in a smooth and continuous manner, the cutting roll 120 further 
includes teeth 126 which engage the cot roll 62. The teeth 126 are 
integral with the cutting wheel 122 and may be formed via a machining 
operation. The height of the teeth 126 is essentially the same as the 
height of the cutting blades 124. The teeth are closely spaced from one 
another, e.g., 0.5 inch (1.3 cm) from one another. 
It is further contemplated that cutting blades shaped in the form of a 
continuous arc having a radius ranging from, for example, three inches to 
six inches (7.5 to 15 cm), may be used in place of the cutting blades 67a, 
114, and 125. It is also contemplated that the cutting blades may be 
formed as straight blades which are substantially parallel to the axis of 
rotation of the cutting roll. It is still further contemplated that the 
cutting blades may have a helix shape such that they form an angle of 
approximately 2.degree. with a line generally parallel to the axis of 
rotation of the cutting roll. When substantially straight cutting blades 
or blades having a helix shape are used, it may be preferable to include 
annular cutting blades similar to cutting blades 116a and 116b to more 
effectively control airflow through the nip 68 and around the cot and 
cutting rolls 62 and 64. It is also contemplated that annular plates 
without cutting edges may be substituted for the annular cutting blades to 
control airflow and to ensure adequate contact between the cutting roll 
and the cot roll. Cutting blades having shapes not explicitly set out 
herein may also be employed so long as they are effective in cutting the 
tow 20a into discrete lengths 22a. 
Referring now to FIGS. 1 and 7, the conveying apparatus 40 includes a 
collection hood 42 which is positioned just above the take-away conveyor 
30 and along the path of travel of the tow 20a for pulling the tow 20a off 
the conveyor 30. As will be discussed below, the collection hood 42 
communicates with a vacuum pump 90 such that an airstream is drawn into 
the collection hood 42 which pulls with it the tow 20a. 
The collection hood 42 comprises upper and lower plates 42a and 42b and 
first side plates 42c which define an opening 44 through which the tow 20a 
passes. The size of the opening 44 may, for example, be three inches (7.5 
cm) in height and 28 inches (71.1 cm) in width. Movable entrance plates 
43a and 43b are slidably received in upper and lower tracks 43c and 43d 
which are fixedly secured to the upper and lower plates 42a and 42b and 
the side plates 42c. The movable plates 43a and 43b and the tracks 43c and 
43d define the size of an entrance 44a into the collection hood 42. The 
size of the entrance 44a can be varied by repositioning the plates 43a and 
43b within the tracks 43c and 43d. By varying the size of the entrance 
44a, the vacuum in the conveying apparatus 40 and, hence, the speed at 
which the tow 20a passes through the conveying apparatus 40, can be 
varied. The collection hood 42 further comprises second side plates 42d, 
vertical baffles 42e, an intermediate rectangular section 42f and an end 
circular section 42g. 
As shown in FIGS. 1 and 2, the conveyor apparatus 40 further includes a 
first conduit section 46, a nozzle 48 and a second conduit section 47. The 
first conduit section 46 is coupled to and extends between the collection 
hood 42 and the nozzle 48 (see FIG. 1). The second conduit section 47 is 
coupled to and extends between the chopping apparatus 60 and the 
collection device 80. The vacuum pump 90, which also forms part of the 
conveyor apparatus 40, communicates with the collection device 80 and, 
hence, draws a partial vacuum in the collection device 80, the second 
conduit section 47, the airtight enclosure 66, the nozzle 48, the first 
conduit section 46, and the collection hood 42. Consequently, an airstream 
together with the tow 20a are pulled via the vacuum pump 90 into the 
air-tight enclosure 66 of the chopping apparatus 60 after first passing 
through the collection hood 42, the first conduit section 46 and the 
nozzle 48. The vacuum pump 90 also effects movement of the discrete 
lengths 22a from the air-tight enclosure 66 and the collecting structure 
61, through the 30second conduit section 47 and into the collection device 
80. 
The take-away conveyor 30 is preferably operated at a sufficiently high 
speed, e.g., 80 feet per minute (24.4 meters per minute) such that the 
fibers deposited by the fiberizing apparatus onto the take-away conveyor 
30 are loosened sufficiently to allow the pack 20 to be easily stretched 
by the conveyor apparatus 40 and pulled into a single tow 20a. Preferably, 
the vacuum pump 90 is sufficient to pull the tow through the first conduit 
section 46 at a speed of approximately 4000 feet per minute (1220 meters 
per minute). The cot roll 62 should be driven such that the cot and 
cutting rolls 62 and 64 have outer linear surface speeds which are 
approximately the same as the speed at which the tow 20a moves through the 
first conduit section 46. The first section 46 may have an inner diameter 
of about 3 inches (0.076 meter) and the second section 47 may have an 
inner diameter of about four inches (0.1 meter). 
The nozzle 48 extends into the air-tight enclosure 66 for delivering the 
tow 20a to the cutting nip 68 after it has first passed through the 
collection hood 42 and the first conduit section 46, see FIG. 2. The 
nozzle 48 must dissipate the high-speed airstream pulling the tow 20a 
toward the cutting nip 68 before the airstream reaches the nip 68. If the 
airstream is not dissipated, the tow 20a will follow the path of the 
undissipated airstream which, after first striking the outer surface 62c 
of the cot roll 62, moves laterally out the frontside 62d or the backside 
of the cot roll 62. Hence, if the airstream is not dissipated, the tow 20a 
is likely to bypass the cutting nip 68 without being chopped. 
The nozzle 48 comprises a back section 48a facing the cot roll 62, a front 
section 48b which is opposed to the back section 48b, side sections 48c 
which extend between the front and back sections 48a and 48b, and a 
mounting plate 48d, see FIGS. 2 and 8. The front, back and side sections 
48a-48c are formed from perforated steel which, for example, has a 40% 
open area. The back section 48a extends only partially along the length of 
the front and side sections 48c and defines with the front and side 
sections 48b and 48c an outlet 48e. As can be seen in FIG. 2, the tow 20a, 
after passing through the nozzle outlet 48e, strikes the outer 
circumferential surface 62c of the cot roll 62 and then moves with the cot 
roll 62 into the cutting nip 48. 
A nozzle 148 formed in accordance with a further embodiment of the present 
invention is shown in FIG. 9. The nozzle 148 comprises a back section 148a 
facing the cot roll 62, a front section 148b which is opposed to the back 
section 148a, side sections 148c which extend between the front and back 
sections 148a and 148b, and a mounting plate 148d. The front and side 
sections 148b and 148c are formed from a perforated sheet of steel or 
other similar material. The back section 148a is formed from solid 
stainless steel. It is further contemplated that the back section 148a may 
also be formed from perforated steel. The back section 148a together with 
the front and side sections 148b and 148c define an outlet 148e. Because 
of the somewhat small size of the outlet 148e, the nozzle 148 delivers the 
tow 20a in a very controlled manner tangentially to the cot roll 62. 
A nozzle 158 formed in accordance with another embodiment of the present 
invention, is shown in FIG. 9A. The nozzle 158 is very similar in 
construction to nozzle 148 shown in FIG. 9, except that the front, back 
and side sections 158a, 158b and 158c define an outlet 158e which is 
larger than outlet 148e. The larger outlet 158e reduces the likelihood 
that the tow 20a might bunch up or become plugged within the nozzle 158. 
However, some placement control is lost because of the larger size outlet 
158e. 
The collection device 80 is provided with a flexible, breathable collection 
bag 82 formed from woven polypropylene material. The bag 82 sits within a 
metal support frame (not shown) which forms part of the collection device 
80. An intermediate conduit section 84 extends between the second conduit 
section 47 and into the collection bag 82 such that the discrete lengths 
22a are deposited in the bag 82. The collection device 80 is shown in the 
illustrated embodiment associated with a scale 86. When the bag 82 is 
filled with discrete lengths 22a such that the bag 82 reaches a 
predetermined weight as measured by the scale 86, a valve (not shown) is 
closed to deadhead the vacuum pump 90 and the bag 82 is removed from the 
collection device 80. Another bag is then inserted into the collection 
device 80 and operation is resumed. The removed bag is closed in a 
conventional manner and stored for subsequent use. It is contemplated that 
the discrete lengths 22a can be used during a wet-laid mat forming process 
or during traditional textile operations such as carding, garnetting, and 
the like. 
The conveying apparatus 40 in the FIG. 1 embodiment additionally comprises 
a third conduit section 130 coupled to and extending between the 
collection hood 42 and the second conduit section 47. The third section 
130 defines a bypass path for the tow 20a when the tow 20a is to be 
conveyed to the collecting station 70 without being cut into discrete 
lengths 22a. 
In the illustrated embodiment, a first gate valve device 140 is associated 
with the first conduit section 46 for allowing the tow 20a to pass through 
the first conduit section 46 when the first valve device 140 is in its 
open position and for preventing the tow 20a from passing through the 
first conduit section 46 when the first valve device 140 is in its closed 
position. A second gate valve device 142 is associated with the third 
conduit section 130 for allowing the tow 20a to pass through the third 
conduit section 130 when the second valve device 142 is in its open 
position and for preventing the tow 20a from passing through the third 
conduit section 130 when the second valve device 142 is in its closed 
position. When the tow 20a is to be chopped into discrete lengths 22a, the 
first valve device 140 is moved to its open position and the second valve 
device 142 is closed. When the tow 20a is not to be chopped into discrete 
lengths, the first valve device 140 is moved to its closed position and 
the second valve device 142 is moved to its open position. 
In the illustrated embodiment, the first, second and third sections 46, 47 
and 130 are provided with generally clear conduit portions 46a, 47a and 
130a which allow an operator to visually monitor tow movement through the 
first, second and third sections 46, 47 and 130. 
A system 150 constructed in accordance with a second embodiment of the 
present invention is illustrated in FIG. 10, wherein like reference 
numerals indicate like elements. The system 150 comprises a conveying 
apparatus 160 for receiving separately or simultaneously the mineral fiber 
wool tows pulled from mineral fiber packs 21a and 21b traveling along 
first and second take-away conveyors 30a and 30b, and transporting the 
tows to a chopping station 50. A chopping apparatus 60 is positioned at 
the chopping station 50 for chopping the tows into discrete lengths 22a. 
The conveying apparatus 160 further receives the discrete lengths 22a at 
the chopping station 50 and transports the discrete lengths to a 
collecting station 70. The conveying apparatus 160 further includes a 
collection device 80 located at the collecting station 70 for receiving 
the discrete lengths and collecting the discrete lengths for subsequent 
use. 
The conveying apparatus 160 includes two collection hoods 162a and 162b and 
two first conduit sections 164a and 164b. A first gate valve device 170 is 
associated with first conduit section 164a for allowing the tow from the 
pack 21a to pass through the conduit section 164a when the first valve 
device 170 is in its open position and for preventing the tow from the 
pack 21b from passing through the section 164a when the first valve device 
170 is in its closed position. A second gate valve device 172 is 
associated with first conduit section 164b for allowing the tow from the 
pack 21b to pass through the conduit section 164b when the second valve 
device 172 is in its open position and for preventing the tow from the 
pack 21a from passing through the conduit section 164b when the second 
valve device 172 is in its closed position. When it is desired to chop 
both tows simultaneously, both valve devices 170 and 172 are moved to 
their open positions. When only one of the two tows is to be chopped, only 
one of the two valve devices 170 and 172 is moved to its open position and 
the other valve device is closed. 
While not shown in the illustrated embodiment, it is contemplated that two 
or more collecting stations 70 may be provided. For example, the two 
stations 70 could be used alternatively such that when the bag 82 in one 
station 70 is completely filled, an operator could quickly switch over to 
the other collecting station 70 via a conventional gate valve device or 
like element so as to reduce downtime. 
Having described the invention in detail and by reference to the preferred 
embodiments thereof, it will be apparent that other modifications and 
variations are possible without departing from the scope of the invention 
defined in the appended claims.