Abstrict A nep separator and detector for presenting a fiber sample having
fibers, neps, and trash. A toothed rotating cylinder receives the
fiber sample at a fiber sample receiving point, and impacts and
propels at least a portion of the trash and neps along an ejection
path. An air curtain is directed toward and passes across a portion
of the toothed surface of the rotating cylinder, at a location rotationally
after the fiber sample is received by the toothed rotating cylinder.
The air curtain crosses and is oriented transverse to the ejection
path, and draws at least a portion of the neps out of the ejection
path and onto the surface of the toothed cylinder as it rotates.
The trash propelled by impact with the toothed rotating cylinder
has sufficient momentum to pass through the air curtain along the
ejection path. A dead air space is positioned in the ejection path
and disposed adjacent the air curtain and across the air curtain
from the fiber sample receiving point. The trash propelled by the
toothed rotating cylinder passes through the dead air space. A nep
air stream draws the neps on the surface of the toothed cylinder
off the surface of the toothed cylinder at a nep release point,
and the neps are entrained in the nep air stream. A sensor detects
the neps entrained in the nep air stream, and produces a nep detection
signal upon the occurrence of each detection of a nep. An output
receives the nep detection signals produced by the sensor and produces
output signals corresponding to the nep detection signals.
Claims What is claimed is:
1. A nep separator and detector, comprising:
means for presenting a fiber sample having fibers, neps, and trash,
a toothed rotating cylinder for receiving the fiber sample at a
fiber sample receiving point, and for impacting and propelling at
least a portion of the trash and neps along an ejection path, an
air curtain directed toward and passing across a portion of the
toothed surface of the rotating cylinder at a location rotationally
after the fiber sample is received by the toothed rotating cylinder,
the air curtain crossing and being oriented transverse to the ejection
path, for drawing at least a quantity of the portion of the neps
out of the ejection path and onto the surface of the toothed cylinder
as it rotates, the trash propelled by impact with the toothed rotating
cylinder having sufficient momentum to pass through the air curtain
along the ejection path,
a dead air space disposed adjacent the air curtain and across the
air curtain from the fiber sample receiving point, and positioned
in the ejection path, through which the trash propelled by the toothed
rotating cylinder passes,
a nep air stream for drawing the neps on the surface of the toothed
cylinder off the surface of the toothed cylinder at a nep release
point and entraining the neps,
a sensor for detecting the neps entrained in the nep air stream,
and producing a nep detection signal upon the occurrence of each
detection of a nep, and
output means for receiving the nep detection signals produced by
the sensor and producing output signals corresponding to the nep
detection signals.
2. The nep separator and detector of claim 1, further comprising:
a trash removal volume disposed adjacent the dead air space and
across the dead air space from the air curtain at a location along
the ejection path, for receiving the trash passing through the dead
air space, and
a trash air stream entering the trash removal volume for entraining
the trash received in the trash removal volume, and for exiting
the trash removal volume with the trash entrained in the trash air
stream, and for conducting the trash entrained in the trash air
stream out of the trash removal volume.
3. The nep separator and detector of claim 2, further comprising
a trash sensor for selectively detecting the trash entrained in
the trash air stream.
4. The nep separator and detector of claim 1, wherein the means
for presenting the fiber sample further comprises a rotating feed
roller disposed proximate the toothed rotating cylinder, the rotating
feed roller and the toothed rotating cylinder both rotating in the
same direction, such that adjacent surfaces of the rotating feed
roller and the toothed rotating cylinder pass each other in opposite
directions.
5. The nep separator and detector of claim 1, wherein the teeth
on the toothed rotating cylinder are disposed at an angle forward
from normal relative to the direction of rotation of the toothed
rotating cylinder.
6. The nep separator and detector of claim 1, wherein the toothed
rotating cylinder has a solid surface.
7. The nep separator and detector of claim 1, wherein the speed
of rotation of the toothed rotating cylinder is about 6,000 rotations
per minute.
8. The nep separator and detector of claim 1, further comprising
a carding flat disposed adjacent the toothed rotating cylinder at
a position between the fiber sample receiving point and the nep
release point, for carding the neps drawn along the surface of the
toothed cylinder.
9. The nep separator and detector of claim 1, wherein the sensor
further comprises:
a light source disposed adjacent the nep air stream, for illuminating
in a transverse direction the neps entrained in the nep air stream,
the neps casting shadows in the illumination having an amplitude
component and a time duration component, and
a light detector disposed adjacent the nep air stream and across
the nep air stream from the light source, for detecting the illumination
and the shadows in the illumination cast by the neps, and for producing
the nep detection signals corresponding to the amplitude and time
duration components.
10. The nep separator and detector of claim 9, wherein the output
means further comprise means for comparing the amplitude and time
duration components of the nep detection signals against predetermined
limits, and for incrementing a count of neps detected when the amplitude
component of the nep detection signals is at least equal to a first
predetermined limit and the time duration component of the nep detection
signals is no greater than a second predetermined limit.
11. A nep separator and detector, comprising:
means having a rotating feed roller, for presenting a fiber sample
having fibers, neps, and trash,
a toothed rotating cylinder disposed proximate the rotating feed
roller, the rotating feed roller and the toothed rotating cylinder
both rotating in the same direction, such that adjacent surfaces
of the rotating feed roller and the toothed rotating cylinder pass
each other in opposite directions, the teeth on the toothed rotating
cylinder disposed at an angle forward from normal relative to the
direction of rotation of the toothed rotating cylinder, the toothed
rotating cylinder having a solid surface, the toothed rotating cylinder
for receiving the fiber sample at a fiber sample receiving point,
and for impacting and propelling at least a portion of the trash
and neps along an ejection path,
an air curtain directed toward and passing across a portion of
the toothed surface of the rotating cylinder at a location rotationally
after the fiber sample is received by the toothed rotating cylinder,
the air curtain crossing and being oriented transverse to the ejection
path, for drawing at least a quantity of the portion of the neps
out of the ejection path and onto the surface of the toothed cylinder
as it rotates, the trash propelled by the toothed rotating cylinder
having sufficient momentum to pass through the air curtain along
the ejection path,
a dead air space disposed adjacent the air curtain and across the
air curtain from the fiber sample receiving point, and positioned
in the ejection path, through which the trash propelled by the toothed
rotating cylinder passes,
a trash removal volume disposed adjacent the dead air space and
across the dead air space from the air curtain at a location in
the ejection path, for receiving the trash passing through the dead
air space,
a trash air stream entering the trash removal volume for entraining
the trash received in the trash removal volume, and for exiting
the trash removal volume with the trash entrained in the trash air
stream, and for conducting the trash entrained in the trash air
stream out of the trash removal volume,
a nep air stream for drawing the neps on the surface of the toothed
cylinder off the surface of the toothed cylinder at a nep release
point and entraining the neps,
a carding flat disposed adjacent the toothed rotating cylinder
at a position between the fiber sample receiving point and the nep
release point, for carding the neps drawn along the surface of the
toothed cylinder,
a sensor for detecting the neps entrained in the nep air stream,
the sensor having; a light source disposed adjacent the nep air
stream, for illuminating in a transverse direction the neps entrained
in the nep air stream, the neps casting shadows in the illumination
having an amplitude component and a time duration component, and
a light detector disposed adjacent the nep air stream and across
the nep air stream from the light source, for detecting the illumination
and the shadows in the illumination cast by the neps, and for producing
nep detection signals corresponding to the amplitude and time duration
components; and
output means for receiving the nep detection signals produced by
the sensor, and for comparing the amplitude and time duration components
of the nep detection signals against predetermined limits, and for
incrementing a count of neps detected when the amplitude component
of the nep detection signals is at least equal to a first predetermined
limit and the time duration component of the nep detection signals
is no greater than a second predetermined limit.
12. The nep separator and detector of claim 11, further comprising
a trash sensor for selectively detecting the trash entrained in
the trash air stream.
13. A method of separating and detecting neps in a fiber sample
having fibers, neps, and trash, comprising:
presenting the fiber sample with a fiber sample presenting means,
receiving the fiber sample with a propelling means at a fiber sample
receiving point,
propelling at least a portion of the trash and neps along an ejection
path with the propelling means,
orienting an air curtain transverse to the ejection path, the air
curtain crossing the ejection path,
drawing at least a quantity of the portion of the neps in the fiber
sample out of the ejection path and into a nep air stream,
the trash being propelled with sufficient momentum to pass through
the air curtain along the ejection path,
the trash thereby passing through a dead air space disposed adjacent
the air curtain and across the air curtain from the fiber sample
receiving point, and positioned in the ejection path,
detecting the neps entrained in the nep air stream with a sensor,
and
producing a nep detection signal upon the occurrence of each detection
of a nep.
14. A method of separating and detecting neps in a fiber sample
having fibers, neps, and trash, comprising:
a) presenting the fiber sample with a fiber sample presenting means,
b) receiving the fiber sample with a toothed rotating cylinder
at a fiber sample receiving point,
c) propelling at least a portion of the trash and neps along an
ejection path with the teeth of the rotating cylinder,
d) orienting an air curtain transverse to the ejection path, the
air curtain crossing the ejection path,
e) directing the air curtain toward and passing the air curtain
across a portion of the toothed surface of the rotating cylinder
at a location rotationally after the fiber sample is received by
the toothed rotating cylinder,
f) drawing at least a quantity of the portion of the neps in the
fiber sample out of the ejection path and onto the surface of the
toothed cylinder as it rotates,
g) the trash being propelled with sufficient momentum to pass through
the air curtain along the ejection path,
h) the trash thereby passing through a dead air space disposed
adjacent the air curtain and across the air curtain from the fiber
sample receiving point, and positioned in the ejection path,
i) drawing the neps on the surface of the toothed cylinder off
the surface of the toothed cylinder with a nep air stream at a nep
release point,
j) entraining the neps drawn off the surface of the toothed cylinder
in the nep air stream,
k) detecting the neps entrained in the nep air stream with a sensor,
and
l) producing a nep detection signal upon the occurrence of each
detection of a nep.
15. The method of claim 14 further comprising:
m) receiving the trash passing through the dead air space in a
trash removal volume disposed adjacent the dead air space and across
the dead air space from the air curtain in the ejection path,
n) entraining the trash received in the trash removal volume with
a trash air stream, and
o) conducting the trash entrained in the trash air stream out of
the trash removal volume.
16. The method of claim 14 further comprising:
m) carding the neps on the surface of the toothed rotating cylinder
with a carding flat disposed adjacent the toothed rotating cylinder
at a position between the fiber sample receiving point and the nep
release point.
17. The method of claim 14 wherein the step of detecting the neps
entrained in the nep air stream with the sensor and the step of
producing the nep detection signals further comprise:
illuminating in a transverse direction the neps entrained in the
nep air stream with a light source disposed adjacent the nep air
stream,
the neps thereby casting shadows in the illumination, the shadows
having an amplitude component and a time duration component,
detecting the illumination and the shadows in the illumination
cast by the neps with a light detector disposed adjacent the nep
air stream and across the nep air stream from the light source,
and
producing the nep detection signals with the light detector, corresponding
to the amplitude and time duration components.
18. The method of claim 17 further comprising:
m) comparing the amplitude and time duration components of the
nep detection signals against predetermined limits, and
n) incrementing a count of neps detected when the amplitude component
of the nep detection signals is at least equal to a first predetermined
limit and the time duration component of the nep detection signals
is no greater than a second predetermined limit.
19. A method of separating and detecting neps in a fiber sample
having fibers neps, and trash, comprising:
presenting the fiber sample with a fiber sample presenting means,
receiving the fiber sample with a toothed rotating cylinder at
a fiber sample receiving point,
propelling at least a portion of the trash and neps along an ejection
path with the teeth of the rotating cylinder,
orienting an air curtain transverse to the ejection path, the air
curtain crossing the ejection path,
directing the air curtain toward and passing the air curtain across
a portion of the toothed surface of the rotating cylinder at a location
rotationally after the fiber sample is received by the toothed rotating
cylinder,
drawing at least a quantity of the portion of the neps in the fiber
sample out of the ejection path and onto the surface of the toothed
cylinder as it rotates,
the trash being propelled with sufficient momentum to pass through
the air curtain along the ejection path,
the trash thereby passing through a dead air space disposed adjacent
the air curtain and across the air curtain from the fiber sample
receiving point, and positioned in the ejection path,
receiving the trash passing through the dead air space in a trash
removal volume disposed adjacent the dead air space across from
the air curtain along the ejection path,
entraining the trash received in the trash removal volume with
a trash air stream,
conducting the trash entrained in the trash air stream out of the
trash removal volume,
carding the neps drawn along the surface of the toothed rotating
cylinder with a carding flat disposed adjacent the toothed rotating
cylinder,
drawing the neps on the surface of the toothed cylinder off the
surface of the toothed cylinder with a nep air stream at a nep release
point,
entraining the neps drawn off the surface of the toothed cylinder
in the nep air stream,
illuminating in a transverse direction the neps entrained in the
nep air stream with a light source disposed adjacent the nep air
stream,
the neps thereby casting shadows in the illumination, the shadows
having an amplitude component and a time duration component,
detecting the illumination and the shadows in the illumination
cast by the neps with a light detector disposed adjacent the nep
air stream and across the nep air stream from the light source,
producing the nep detection signals with the light detector, corresponding
to the amplitude and time duration components,
comparing the amplitude and time duration components of the nep
detection signals against predetermined limits, and
incrementing a count of neps detected when the amplitude component
of the nep detection signal is at least equal to a first predetermined
limit and the time duration component of the nep detection signals
is no greater than a second predetermined limit. Description FIELD OF THE INVENTION
This invention relates to the field of fiber processing. More particularly
the invention relates to the field of separating and detecting neps
within a fiber sample.
BACKGROUND OF THE INVENTION
Fibers, such as cotton, are subject to entanglements called neps.
Neps are clusters of one or more fibers having a knotted mass. A
nep may be naturally occurring, such as an entanglement of fibers
on a seed shell, or may be mechanically produced during handling
or processing of the fibers.
Different articles for which the fibers are used tend to have different
tolerance levels for the number of neps within a given amount of
the fiber. For example, it is desired to have very few neps, or
no neps, in a batch of cotton fibers that are to be used for the
production of a pin-point cotton fabric, such as is used for shirts.
On the other hand, a large amount of neps may be tolerated, and
even preferred, in a sample of fibers that is to be used for the
production of a filter.
Thus, buyers, sellers, and processors dealing in fiber need to
have some method for testing and grading a sample of fibers as to
nep content. Such a method could be used to classify the fibers
as to grade at the time that they are sold, so that both the buyer
and seller would know the relative worth of the fibers as to their
intended purpose. Such a method could also be used by processors
during carding and other processes to measure the reduction of neps
through the processing. In addition, such a method could be used
to monitor the performance of processing machines, to determine
whether the machines were increasing the number of neps in the fibers.
While equipment is available which will determine the characteristics
of a fiber sample, such equipment typically analyzes the sample
for a multiplicity of characteristics, such as size and type of
neps, trash content, length of fibers, fiber color, fiber strength,
moisture content, etc. While this amount of information can be valuable
when it is all needed, the ability to analyze the fiber sample so
completely tends to increase both the size and cost of the equipment
required. In addition, extensive training may be required to master
the set-up, calibration, and operation of such equipment.
What is needed, therefore, is a low-cost, quick, simple, and readily
transportable method and apparatus for counting the number of neps
in a fiber sample.
SUMMARY OF THE INVENTION
The above and other needs are answered by a nep separator and detector.
Means are provided for presenting a fiber sample having fibers,
neps, and trash. A toothed rotating cylinder receives the fiber
sample at a fiber sample receiving point, and impacts and propels
at least a portion of the trash and neps along an ejection path.
An air curtain is directed toward and passes across a portion of
the toothed surface of the rotating cylinder, at a location rotationally
after the fiber sample is received by the toothed rotating cylinder.
The air curtain crosses and is oriented transverse to the ejection
path, and draws at least a portion of the neps out of the ejection
path and onto the surface of the toothed cylinder as it rotates.
The trash propelled by impact with the toothed rotating cylinder
has sufficient momentum to pass through the air curtain along the
ejection path.
A dead air space is positioned in the ejection path and disposed
adjacent the air curtain and across the air curtain from the fiber
sample receiving point. The trash propelled by the toothed rotating
cylinder passes through the dead air space. A nep air stream draws
the neps on the surface of the toothed cylinder off the surface
of the toothed cylinder at a nep release point, and the neps are
entrained in the nep air stream. A sensor detects the neps entrained
in the nep air stream, and produces a nep detection signal upon
the occurrence of each detection of a nep. Output means receive
the nep detection signals produced by the sensor and produce output
signals corresponding to the nep detection signals.
In this manner, trash is propelled out of the fiber sample and
away from the toothed cylinder. The air curtain tends to direct
neps and fibers of the fiber sample into the toothed cylinder, where
they are eventually conducted to the sensor for measurement. The
trash propelled out of the sample typically has sufficient momentum
to shoot through the air curtain, so that it is not brought back
into the fiber sample that goes on to the sensor. After passing
through the air curtain, the trash enters a dead air space, which
is placed in that location so that, among other purposes, as the
trash decelerates, it is not drawn back into the air curtain and
mixed back into the fiber sample.
This apparatus effectively removes the trash from the fiber sample
in a way that tends to be destructive of the fibers in the sample.
However, fiber integrity is not of the upmost importance when a
nep count is desired. Thus, this method is relatively inexpensive
when compared to other fiber, trash, and nep separation methods,
which place a higher priority on maintaining fiber integrity. In
addition, an apparatus according to the present invention is quite
simple and does not require extensive calibration. Further, it can
be made quite small, so that it can fit on a cart and be easily
transported. Additionally, because it is relatively easy to manufacture
an apparatus according to the present invention, and such an apparatus
requires relatively unsophisticated electronics, it is typically
less expensive than other units.
In the preferred embodiment a trash removal volume is disposed
adjacent the dead air space (preferably below the dead air space)
and across the dead air space from the air curtain at a location
along the ejection path. The trash removal volume receives the trash
passing through the dead air space, that has been propelled through
the air curtain. A trash air stream enters the trash removal volume,
entrains the trash received in the trash removal volume, and exits
the trash removal volume with the trash entrained. The trash entrained
in the trash air stream is thus conducted out of the trash removal
volume.
The preferred means for presenting the fiber sample includes a
rotating feed roller, which is disposed proximate the toothed rotating
cylinder. The rotating feed roller and the toothed rotating cylinder
both rotate in the same direction, meaning either clockwise or counterclockwise.
With the roller and the cylinder rotating in this manner, the adjacent
surfaces of the rotating feed roller and toothed rotating cylinder
pass each other in opposite directions.
The teeth on the toothed rotating cylinder of the preferred embodiment
are disposed at an angle forward from normal, relative to the direction
of rotation of the toothed rotating cylinder. In this manner the
teeth lean into the direction of rotation, so to speak, which tends
to aid in drawing the fiber sample along the surface of the toothed
rotating cylinder. The toothed rotating cylinder preferably has
a solid surface, and rotates at a speed of about 6,000 rotations
per minute. This speed is destructive of the fibers in the fiber
sample, but again the integrity of the fibers is not the primary
objective. This speed tends to be effective at impacting the teeth
of the cylinder against the trash of the fiber sample, and propelling
the trash through the air curtain.
A carding flat is preferably disposed adjacent the toothed rotating
cylinder at a position between the fiber sample receiving point
and the nep release point. The carding flat cards the neps on the
surface of the toothed cylinder. At the speeds mentioned above,
the carding flat is also destructive to the fibers.
The preferred sensor has a light source disposed adjacent the nep
air stream, which illuminates the neps entrained in the nep air
stream in a direction transverse to the direction of the nep air
stream. The illuminated neps cast shadows in the illumination, the
shadows having an amplitude component and a time duration component.
A light detector is disposed adjacent the nep air stream and across
the nep air stream from the light source, and it detects the illumination
and the shadows cast by the neps in the illumination. The light
detector produces nep detection signals corresponding to the amplitude
and time duration components of the shadows. The output means has
means for comparing the amplitude and time duration components of
the nep detection signals against predetermined limits. A count
of the neps detected is incremented when the amplitude component
of the nep detection signals is at least equal to a first predetermined
limit and the time duration component of the nep detection signals
is no greater than a second predetermined limit.
The neps tend to cast a larger or darker shadow than the now-fragmented
fibers in the fiber sample. By using simple predetermined thresholds
to detect the neps, rather than complex algorithms, an apparatus
according to the preferred embodiment of the present invention is
able to use less sensitive, and therefore less expensive output
means than those devices which attempt to determine the exact size
of the neps and the fibers. Thus, such an apparatus according to
the present invention will produce a count of the number of neps
in the fiber sample that was provided. An operator can feed in samples
of a given amount from several different pieces of fiber processing
equipment, or from the same piece of equipment over a period or
time, such as before and after a maintenance procedure, and know
how the normalized nep count has changed.
In a preferred embodiment of a method according to the present
invention, of separating and detecting neps in a fiber sample having
fibers, neps, and trash, the fiber sample is presented with a fiber
sample presenting means, and received at a fiber sample receiving
point with a toothed rotating cylinder. At least a portion of the
trash and neps are propelled along an ejection path by the teeth
of the rotating cylinder. An air curtain crosses and is oriented
transverse to the ejection path. The air curtain is directed toward
and passes across a portion of the toothed surface of the rotating
cylinder at a location rotationally after the fiber sample is received
by the toothed rotating cylinder. At least a portion of the neps
in the fiber sample are drawn out of the ejection path and onto
the toothed cylinder as it rotates.
The trash is propelled with sufficient momentum to pass through
the air curtain along the ejection path, thereby passing through
a dead air space disposed adjacent the air curtain and across the
air curtain from the fiber sample receiving point, in the ejection
path. The trash passing through the dead air space is received in
a trash removal volume, which is disposed adjacent the dead air
space and across the dead air space from the air curtain along the
ejection path, where the trash is entrained in a trash air stream
and conducted out of the trash removal volume.
The neps on the surface of the toothed rotating cylinder are carded
with a carding flat disposed adjacent the toothed rotating cylinder,
and are drawn off the surface of the toothed cylinder with a nep
air stream at a nep release point and entrained in the nep air stream.
The neps entrained in the nep air stream are illuminated in a transverse
direction with a light source disposed adjacent the nep air stream,
thereby casting shadows in the illumination having an amplitude
component and a time duration component. The illumination and the
shadows cast by the neps in the illumination are detected with a
light detector disposed adjacent the nep air stream and across the
nep air stream from the light source. The light detector produces
nep detection signals corresponding to the amplitude and time duration
components, which are compared against predetermined limits. A count
of neps detected is incremented when the amplitude component of
the nep detection signals is at least equal to a first predetermined
limit and the time duration component of the nep detection signals
is no greater than a second predetermined limit.
BRIEF DESCRIPTION OF THE DRAWINGS
Further advantages of the invention will become apparent by reference
to the detailed description of preferred embodiments when considered
in conjunction with the following drawings, which are not to scale,
in which like reference numerals denote like elements throughout
the several views, and wherein:
FIG. 1 is an enlarged view of a portion of an embodiment of the
invention, depicting the detail of the fiber sample receiving point
and other elements along the ejection path, and
FIG. 2 depicts an embodiment of the invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings, there is depicted in FIG. 1 an embodiment
of a portion of a nep separator and detector according to the invention.
A fiber sample is introduced to the separator with a presenting
means, which in the embodiment depicted is a feed roller 12 which
draws the fiber sample along block 18, and presents the fiber sample
at a fiber sample receiving point 13. The fiber sample preferably
includes fibers, in which an amount of trash may be mixed. There
may also be neps, or tangled masses of fibers, in with the unentangled
fibers. It is one of the objects of the invention to at least partially
separate these neps from some of the other components of the fiber
sample, and then detect and preferably count the neps.
A toothed rotating cylinder 10 receives the fiber sample at fiber
sample receiving point 13. The surface of the cylinder 10 is solid.
The cylinder 10 preferably has a diameter of about 62 cm and width
of about 26 cm. The teeth 11 on the cylinder 10 are preferably raked
at an angle of about 9 degrees forward of the direction of rotation,
which in the embodiment depicted in FIG. 1 is counter-clockwise.
In a preferred embodiment, there would be more teeth 11 on the cylinder
10 than depicted, and the teeth would be disposed closer together
around the circumference of the cylinder 10. The teeth 11 have been
so depicted in FIG. 1 so as to not unduly complicate the figure.
Preferably the teeth have a diameter of about 0.03 inches, a height
of about 0.074 inches, and a density of about 100 teeth per inch.
Preferably, the feed roller 12 is rotating in the same direction
as the cylinder 10, which in this example is counter-clockwise.
In this configuration, the surface 14 of the cylinder 10 and the
surface of the feed roller 12 are moving in opposite directions
where they pass each other at fiber sample receiving point 13. The
cylinder 10 is preferably rotating at speed of approximately 6,000
rotations per minute. At this speed, and with the fiber sample being
introduced by the feed roller 12 in a direction against the direction
of rotation of the cylinder 10, the fibers of the fiber sample may
be torn, broken, and sheared as they are presented. Thus, this apparatus,
operating at this speed, would not typically be appropriate for
a device that was used for processing sellable fibers in a production
environment. Therefore, an apparatus according to the present invention
is designed more for testing fiber samples for neps, and less for
separating good fibers from the other components of the fiber sample.
The teeth 11 of the cylinder 10 tend to engage and hold the fibers
and neps of the fiber sample, but the trash in the fiber sample
tends to be propelled away from the surface 14 of the cylinder 10
by the force of impact with the teeth 11. This impact tends to impart
sufficient momentum to the trash to propel it along a ejection path
15. It will be appreciated that even though ejection path 15 is
depicted as a line, there is no actual line, but this is merely
a representation of the approximate trajectory of a trash particle
that has been propelled by the teeth 11 on the rotating spinning
cylinder 10. Fibers and neps may also tend to follow the first portion
of the ejection path 15.
An air curtain 16 is introduced into the separator, such as between
blocks 18 and 20, and passes across a portion of the surface 14
of the cylinder 10. As depicted, the air curtain 16 blows against
the cylinder 10 at a position 17 that is rotationally after the
fiber sample receiving point 13, and the direction and orientation
of the air curtain 16 is generally transverse to the ejection path
15. The air curtain 16 tends to urge at least a portion of the neps
that are engaged in the teeth 11 and against the surface 14 of the
cylinder 10 to remain so engaged, and draws them along the surface
14 of the cylinder 10 as it rotates past block 28 at point 17. The
air curtain 16 also tends to blow back any of the neps that initially
followed ejection path 15, and draw them along the surface 14 of
the cylinder 10 as well.
However, the trash that is traveling along ejection path 15, because
it typically has a greater mass or density than the neps, tends
to have sufficient momentum to pass through the air curtain 16 and
further along the ejection path 15. The next region encountered
by the trash traveling along the ejection path 15 is a dead air
space 22, which is disposed adjacent the air curtain 16, across
from the fiber sample receiving point 13. One purpose of the dead
air space 22 is to provide a buffer, such that anything which enters
it, such as trash, will be in a relatively aerodynamically quiet
or still area, and will not be drawn back into and along the air
curtain 16.
Further along the ejection path 15, adjacent the dead air space
22 and across from the air curtain 16, is a trash removal volume
24, which receives the trash that is propelled along the ejection
path 15. A trash air stream 26 enters the trash removal volume 24,
such as through the port defined between blocks 20 and 28, and entrains
the trash received in the trash removal volume 24. The trash air
stream 26 is drawn off, such as through port 30, and exits the trash
removal volume 24, conducting the trash entrained in it out of the
trash removal volume 24 as it exits.
In this manner, the trash in the fiber sample, which tends to have
sufficient size so as to be later confused with the neps, as described
more fully below, is removed from the neps in the fiber sample.
First the trash is propelled out of the fiber sample along ejection
path 15 by the teeth 11, which occurs approximately at receiving
point 13, and passes through the air curtain 16, which tends to
blow any neps which may also be propelled along the ejection path
15, back against the surface 14 of the cylinder 10. The trash then
travels through the dead air space 22 and into the trash receiving
volume 24, where it is entrained by the trash air stream 26, and
conducted away. The dead air space 22 tends to prevent the trash
which is in the trash removal volume 24 from re-contacting and being
drawn along with the air curtain 16.
The neps, now substantially free of trash, continue along the surface
14 of the cylinder 10 as it rotates. Preferably, a carding flat
32, as depicted in FIG. 2, disposed at a position between the fiber
sample receiving point 13 and a nep release point 34, cards the
neps as they are drawn along with the rotation of the cylinder 10.
The neps are drawn off the surface 14 of the cylinder 10 at the
nep release point 34 by a nep air stream 36, such as defined between
blocks 38 and 40, which nep air stream 36 entrains the neps.
The neps in the nep air stream 36 are presented to an enclosure
41, in which a sensor detects the neps at point 43. In the preferred
embodiment depicted in FIG. 2, the sensor has a light source 42
disposed adjacent the nep air stream 36. The light source 42 illuminates
the neps entrained in the nep air stream 36 in a transverse direction.
The neps in the nep air stream 36 cast shadows in the illumination,
which shadows have an amplitude component and a time duration component.
For example, a shadow cast by a longer nep will last longer than
that cast by a shorter nep. This is the time duration component
of the shadow. Similarly, a shadow cast by a denser nep will have
a larger amplitude than that cast by a less dense nep. This is the
amplitude component of the shadow. Together, the time duration component
and the amplitude component of the shadow tend to provide an indication
of the type of entity casting the shadow.
A light detector 44 is preferably disposed adjacent the nep air
stream 36, across from the light source 42. The light detector 44
detects the illumination from the light source 42 and the shadows
cast by the neps in the illumination, and produces nep detection
signals corresponding to the amplitude and time duration components
of the shadows. Thus, the nep detection signals also have amplitude
and time duration components.
The nep detection signals are sent on lines 48 to an output means
46. Preferably, output means 46 includes a transimpedance amplifier
with a gain of about 100,000 volts/amp, a bandpass filter, a threshold
comparator with the threshold set to about 1.7 volts, a pulse width
timer with a resolution of about 0.1 microseconds, a peak detector,
an 8-bit analog to digital converter, and a microcomputer to implement
the nep detection method, count the neps, and display the result.
The output means 46 receive the nep detection signals and compare
the amplitude and time duration components of the nep detection
signals against predetermined limits. If the amplitude component
is sufficiently large to equal or exceed a first predetermined limit,
and the time duration component does not exceed a second predetermined
limit, then the output means determines that a nep has been detected.
If the amplitude component does not equal or exceed the first predetermined
limit, and the time duration component exceeds the second predetermined
limits, then the output means determines that the signals are not
associated with a nep.
In the preferred embodiment, the second predetermined limit of
the time component is between about 20-50 microseconds at the 1.7
volt hardware threshold, and the first predetermined limit of the
amplitude component is between about 2.2-2.5 volts. The predetermined
limits are preferably user adjustable so that the nep detector may
be configurable for different applications. For example, if it is
important that as many neps as possible be detected, at the risk
of possibly incorrectly identifying some of the fibers as neps,
then the first predetermined limit may be adjusted to a lower value,
or the second predetermined limit may be adjusted to higher values.
On the other hand, if it is important that no fibers be incorrectly
identified as neps, at the risk of excluding some neps from detection,
then the first predetermined limit may be adjusted to a higher value,
or the second predetermined limit may be adjusted to a lower value.
Most preferably there is a setting for the amplitude and time component
predetermined limits where all of the neps are detected, but none
of the fibers are detected.
Fibers from the fiber sample may still be mixed in with the neps
at the point 43 where the sensor takes its readings. However, the
fibers tend to not exceed the predetermined limits as described
above. There are at least two reasons for this. First, the apparatus
tends to individualize the fibers, which tend to be smaller than
the entangled mass of fibers which make up a nep. Second, the apparatus
tends to break the fibers, making them even smaller than they typically
would be. Thus, the operating conditions of the separation and detection
apparatus, as described above, aid in the detection of neps in the
fiber sample.
The output means 46 preferably increments a count of neps detected
when the output means 46 determine that a nep has been detected,
as described above. In a preferred embodiment, the output means
46 sends a tally of the count across wire 52 to a display 50, where
the nep count is presented to an operator.
The air curtain 16, nep air stream 36, and trash air stream 26
are preferably all created with a vacuum source 45, such as a vacuum
pump. The vacuum source draws the nep air stream 36 away from the
cylinder 10 and toward the vacuum source 45. This draws in an air
stream from the port defined by blocks 18 and 20. Thus, by adjusting
the amount of vacuum provided by the vacuum source 45, the flow
of the air curtain 16 can be controlled.
The vacuum source 45 is also tied to port 30, such as through adjustment
valve 49 and vacuum line 47. The vacuum applied at port 30 will
draw in the trash air stream 26 through the port defined between
blocks 20 and 28. By adjusting the relative amount of vacuum applied
on port 30 by adjusting valve 49 and the size of port 30, and by
adjusting the size of the two ports defined between blocks 18 and
20 and blocks 20 and 28, all of the air curtain 16 will flow around
the cylinder 10 at point 17, and all of the trash air stream 26
will flow out of the port 30. When these two air streams 16 and
26 flow out in separate directions as described, the dead air space
22 is created.
These air flows 16 and 26 can then be adjusted together so that
the trash propelled by the cylinder 10 has enough momentum to go
through the air curtain 16, but the neps tend to be blown back toward
the cylinder 10 by the air curtain 16. Alternately, the rotational
speed of the cylinder 10 can be adjusted to achieve the same result.
For example, if the trash in not being propelled with sufficient
momentum to travel through the air curtain 16, the speed of the
cylinder 10 can be increased until the trash does have sufficient
momentum, or the vacuum can be reduced so that the air curtain 16
does not have as much flow. If the fiber sample is being impacted
by the teeth 11 of the cylinder 10 with so much force that the neps
are tending to have sufficient momentum to cross the air curtain
16, then the rotational speed of the cylinder 10 can be decreased
until the neps are drawn along the surface of the cylinder 10, or
the vacuum can be increased so that the air curtain 16 has more
flow. Of course, as mentioned above, whenever the flow of the air
curtain 16 is adjusted, the flow of the trash air stream 26 is also
preferably adjusted, so as to maintain the dead air space 22.
Thus, there is a relationship between the amount of vacuum applied
on the nep air stream 36 and the port 30, and the rotational speed
of the cylinder 10. The relationship between the nep air stream
36 and the port 30 defines the dead air space 22, and the relationship
between the air curtain 16 and the speed of the cylinder 10 defines
how much of the trash and neps pass through the air curtain 16.
The trash conducted away through port 30 may also be sensed and
analyzed in a manner similar to that described above for the neps.
For example the trash may be sent to a sensor 54 similar to that
described, or even to the same sensor by routing the trash through
valve 51 and line 53.
While specific embodiments of the invention have been described
with particularity above, it will be appreciated that the invention
comprehends rearrangement and substitution of parts within the spirit
of the appended claims. |