U.S. patent number 3,712,743 [Application Number 05/103,973] was granted by the patent office on 1973-01-23 for apparatus for detecting and measuring yarn defects and irregularities.
Invention is credited to James Harris, Robert L. Watson.
United States Patent |
3,712,743 |
Harris , et al. |
January 23, 1973 |
APPARATUS FOR DETECTING AND MEASURING YARN DEFECTS AND
IRREGULARITIES
Abstract
Apparatus for detecting light reflections from yarn
irregularities, such as broken filaments, fluffs, loops and the
like which extend from the normal body of a moving yarn strand. The
yarn strand is directly illuminated, and a shadowbar is positioned
outside the path of light illumination between the yarn strand and
the detection apparatus. The shadowbar is of such dimension as to
be larger than the normal body diameter of the yarn strand so as to
block reflection from the normal body of the yarn strand from the
detection apparatus but enables reflected light from any yarn
irregularities extending from the normal body of the yarn strand to
be detected by the detection apparatus, such as a photomultiplier
tube.
Inventors: |
Harris; James (Bristol, TN),
Watson; Robert L. (Bluff City, TN) |
Family
ID: |
22298014 |
Appl.
No.: |
05/103,973 |
Filed: |
January 5, 1971 |
Current U.S.
Class: |
356/430; 28/227;
356/238.2 |
Current CPC
Class: |
B65H
63/065 (20130101); G01N 21/8915 (20130101); G01N
21/8901 (20130101); B65H 2701/31 (20130101) |
Current International
Class: |
G01N
21/89 (20060101); G01N 21/88 (20060101); B65H
63/00 (20060101); B65H 63/06 (20060101); G01n
021/18 (); G01n 002/30 () |
Field of
Search: |
;356/102,103,199,200,237,238 ;250/219S |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Wibert; Ronald L.
Assistant Examiner: Webster, Jr.; R. J.
Claims
We claim:
1. An apparatus for detecting reflected light from yarn
irregularities in a moving yarn strand as the yarn strand moves
along a predetermined path and comprising:
wall means defining a light-tight chamber;
means for guiding the moving yarn strand through the wall means
into, across and out of the light-tight chamber;
means including a light source for directing a collimated light
beam from said light source into the light-tight chamber, to
illuminate the yarn strand when the yarn strand is moving through
the chamber;
one of the wall means defining therethrough a viewing slit that is
located outside the path of the light beam and perpendicular to the
axis of the collimated light beam and directly opposite the yarn
strand path;
a shadowbar positioned outside the path of the collimated light
beam and between the yarn strand when moving through the
light-tight chamber and the viewing slit, the shadowbar being of
such dimension as to be larger than the normal body diameter of the
yarn strand so as to block reflected light from the normal body of
the yarn strand from the viewing slit, but enabling reflected light
from any yarn irregularities extending from the normal body of the
yarn strand to enter through said viewing slit; and
means on the opposite side of said viewing slit and responsive to
reflected light entering through said viewing slit from said yarn
irregularities to generate a predetermined electrical signal
proportional to said reflected light.
2. An apparatus as defined in claim 1 and wherein said means for
guiding the moving yarn strand include light baffle means to
exclude light from entering into the light-tight chamber along the
path of the yarn strand as it enters and leaves said light-tight
chamber.
3. An apparatus as defined in claim 1 and wherein said means
responsive to reflected light include a photomultiplier tube.
4. An apparatus as defined in claim 1 and further comprising an
electrical counting system responsive to each electrical signal
generated for registering and recording each said electrical
signal.
5. An apparatus as defined in claim 1 and wherein the wall means
defines through one of said wall means an opening through which
said collimated light beam enters into the light-tight chamber, the
wall means opposite said one of said wall means defining a recessed
light absorbing well for shielding any undesired reflected light
from entering through said viewing slit.
6. An apparatus as defined in claim 5, and wherein the opening
through said one of said wall means is defined by at least one
collimating diaphragm.
7. An apparatus as defined in claim 1, and wherein a second viewing
slit is provided between the viewing slit and the last recited
means.
Description
BACKGROUND OF THE INVENTION
The present invention is directed to an apparatus for detecting
light reflections from yarn irregularities, such as broken
filaments, fluffs, loops and the like which extend from the normal
body of a moving yarn strand.
Broken filaments in the production of continuous filament yarns,
fluffs and other surface irregularities extending from yarn strands
being processed are a major quality control problem.
One method for determining this quality parameter involves visual
analysis sometimes known as "fluff counting." Although the method
is accurate, it is extremely slow since individual packages of yarn
selected on a predetermined basis must be taken to a testing
location, be creeled, threaded and analyzed by trained operators at
a rate not greater than 50 yards per minute.
Another method for detecting such yarn irregularities involves the
use of apparatus such as disclosed in the Denyssen U.S. Pat. No.
2,413,486 wherein a light beam is directed against a shadow casting
strip and in a manner so that it will not reach a photocell, and a
yarn travels within the field of the photocell through a shadowed
region of the light beam on the opposite side of the shadow casting
strip. The shadowed region of the beam is controlled by the shadow
casting strip so that the yarn normally travels in the dark. Any
irregularities projecting from the yarn extend out of the shadowed
region and into the path of the light beam, thereby reflecting
light to the photocell. A disadvantage of this arrangement,
however, is that diffracted light will pass around the shadow
casting strip and will illuminate the body of the yarn, and the
reflection from such illumination will be picked up in part by the
photocell. Any variation in yarn shape or size will thus be falsely
interpreted as a yarn defect or yarn irregularity.
Still another method for detecting such yarn irregularities
involves the use of apparatus such as disclosed in the Duncan et
al. U.S. Pat. No. 2,841,048 wherein a source of light is directed
to illuminate a non-reflecting shadow bar, behind which a funicular
structure (small cord or small rope structure) moves parallel to
the shadow bar as the funicular structure passes through a
light-tight closure. The funicular structure or yarn thus is to be
shielded from light and only broken filaments, strip backs or
fluffs balls extending from the yarn will protrude into the
illuminate area and result in reflected light from such protrusions
passing through a phototube triggering aperture. Although the
shadowbar is said to be non-reflecting, it has been found by
experimentation that there is still some reflection necessarily
from the shadowbar as it is being directly focused upon by the
light beam. This renders the apparatus somewhat less sensitive to
the reflections from broken filaments and the like because such
reflections as there are from the shadowbar will also be received
through the phototube aperture and acted upon.
Applicants eliminate the light diffraction problem by directly
illuminating the yarn body, and by positioning the shadowbar so
that it lies outside the path of the light beam between the yarn
and the viewing slit in front of a photomultiplier tube so that the
photomultiplier tube will only see light reflections from yarn
irregularities extending from the normal body of the yarn and
beyond the light shielding effect of the shadowbar. Since the
shadowbar is positioned outside the path of the light beam, the
shadowbar will not be illuminated by the light beam, and hence
there will be no diffraction or reflection of light effects such as
is possible in the above described U.S. Pat. Nos. 2,413,486 and
2,841,048.
A further method employed in the prior art is that disclosed by the
Van Dongeren U.S. Pat. No. 2,991,685 wherein light reflections from
bulked yarn are continuously received by a photo-receiver unit
mounted behind a screen, and any temporary interruptions of such
continuous recording, due to the detection of the absence of such
bulkiness, are recorded in order to indicate quality of the yarn
being tested. In his arrangement a light source directly
illuminates the moving yarn but is also directly in alignment with
the screen and photo-receiver behind the screen. Light, therefore,
is being transmitted directly into the photo-receiver. Such
arrangement would not be suitable for detecting broken filaments
for instance because any broken filament extending from the mass of
bulked filaments being detected would cause such small signal
change as to be not noticed. In applicants' invention, on the other
hand, a relatively large signal results upon receipt of reflection
of light from a single filament extending from the normal body of
the yarn strand being examined. The invention therefore is far more
sensitive to detection of such single filaments.
BRIEF SUMMARY OF THE INVENTION
The invention therefore is directed to an apparatus wherein a
moving yarn strand is directly illuminated, and reflected light
from broken filaments and the like which extend from the surface of
the normal body of the yarn strand are detected and measured or
counted as desired. Reflected light from the normal body of the
yarn strand is prevented from being detected by a shadowbar which
is positioned between the moving yarn strand and the light
reflection detection apparatus. The shadowbar is positioned so as
to be located beyond the path of illumination that is illuminating
the yarn strand, and is of such dimension as to be larger than the
normal body diameter of the yarn strand so as to block off
reflected light from the normal body of the yarn strand.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a perspective view of the overall apparatus including the
detection apparatus and the registering apparatus with the cover
assembly of the detection apparatus shown in closed portion in
phantom line and in the open position in solid line and
illustrating the yarn passing in front of the shadowbar and viewing
slit;
FIG. 2 is a cross-sectional view in side elevation of the detection
apparatus taken along line 2--2 of FIG. 1;
FIG. 3 is a diagrammatic illustration of the detection apparatus
and illustrating the path that light would follow from the light
source through the collimating diaphragms for subsequent
illumination of the yarn strand and into the light absorbing well,
and further illustrating the path reflected light from a defect
extending from the normal body diameter of the yarn strand follows
in passing the shadowbar and entering through the viewing slits to
the photomultiplier tube, and still further illustrating reflected
light from the edge of one of the collimating diaphragms being
trapped by one of the wall members defining a viewing slit; and
FIG. 4 is a cross-sectional view taken along line 4--4 of FIG.
1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In reference to the drawings, 10 designates the detection apparatus
and 12 designates the registering apparatus that may be operatively
connected to the detection apparatus. It will be appreciated that
apparatus having functions other than a registering function may
also be used without departing from the scope of the invention.
The detection apparatus 10 has a housing 14 that is divided into
three main light-tight compartments. Compartment 16 (FIG. 2) has
housed therein a light sensitive photomultiplier tube 18 which is
electrically coupled through an appropriate circuit to the
registering apparatus 12. Compartment 20, adjacent to compartment
16, houses the light source 22, suitably supported by a light
support bracket 24, and a lens 26, suitably supported by a lens
support 28. The third compartment 30 is also adjacent to
compartment 16 and is located above compartment 20. This third
compartment is formed by light shield walls 32 and a hinged cover
assembly 34 that closes over the top of the light shield walls to
form with the light shield walls a light baffled entryway for the
yarn strand 36 being inspected. The entryway consists of a pair of
opposed slots 38 formed in the light shield walls and a pair of
opposed slots 40 in the hinged cover assembly, the slots 40 being
offset (FIG. 4) with respect to the slots 38 so as to prevent light
from entering with the yarn strand. Each pair of slots is provided,
respectively, with wear resistant yarn guides 42, 44.
The third compartment 30 houses a shadowbar 46 that is positioned
parallel to the path to be followed by the yarn strand 36 when it
passes through compartment 30. The shadowbar is of such dimension
as to be larger than the normal body diameter of yarn strand that
is to be inspected. This dimension can be changed if larger or
smaller yarn strands are to be inspected. The dimension of the
shadowbar also bears a relation to the distance the shadowbar is
spaced from the path of the yarn strand, for reasons which will
become evident from subsequent description.
An aperture 48 is provided between compartments 30 and 20 so that
light from light source 22 may be beamed into compartment 30 for
illuminating the yarn strand 36 when it passes along its path
through compartment 30. The beam of light is collimated or made
parallel-like by at least one collimating diaphragm 50. Although
the detection apparatus could be operated with one such collimated
diaphragm, the use of a second collimating diaphragm 52 serves to
minimize stray light reflection and to render the light beam more
parallel. The diagrammatic illustration in FIG. 3 serves to show
how part of the light that has spread (as indicated at X) is
blocked by collimating diaphragm 52.
An aperture 54 is provided between compartments 30 and 16 so that
desired reflected light can pass therethrough, and at least one
diaphragm member 56 defining a viewing slit 58 is provided across
aperture 54 between compartments 30 and 16. The viewing slit is
located perpendicular to the light beam from the light source 22
and is directly opposite the yarn strand path. Although the
detection apparatus has been operated effectively with a single
such diaphragm member, a second diaphragm member 60 with viewing
slit 62 serves to minimize stray light reflection such as might be
reflected from the edge of the aperture in the collimating
diaphragm 50, as demonstrated in FIG. 3 at Y. Diaphragm member 60
blocks off light reflection Y and thus serves to render the
photomultiplier tube 18 more effective in performing its desired
function.
The hinged cover assembly 34 is further provided with a recessed
light-absorbing well 64 which when the cover assembly is in
operative position, as shown in FIGS. 2 and 3, will be in direct
alignment with the light source 22. The light that extends beyond
the yarn strand will be absorbed in the light absorbing well, which
is deep enough to prevent any stray light reflection from reaching
the photomultiplier tube 18.
In operation, as yarn strand 36 passes through the light-tight
chamber defined by compartment 30, the yarn strand is directly
illuminated by light source 22. Any light reflection directly abeam
of and from the normal body diameter of the yarn strand is blocked
by the shadowbar 46, which is spaced outside the path of the
collimated light beam and is between the yarn strand, when moving
through the light-tight chamber, and the viewing slit 58.
Any yarn irregularities, such as broken filaments, fluffs, loops
and the like which extend from the normal body diameter of the
moving yarn strand will reflect light beyond and behind the
shadowbar and will be picked up or detected through the viewing
slit or slits by the photomultiplier tube 18. Yarn defect 66 is
shown as reflecting light through the viewing slits for reception
by the photomultiplier tube 18. The photomultiplier tube will
respond in turn and generate a predetermined electrical signal and
actuate the registering apparatus or whatever apparatus happens to
be operatively connected to the photomultiplier tube for
registering and counting each electrical signal.
The registering apparatus may be a solid state instrument having a
pulse counting and integrating module which will process the signal
from the photomultiplier tube in order to count and integrate
voltage peaks due to yarn defects or irregularities. The signal,
for instance, may first pass through a gain control and filter and
then into a voltage follower which would prevent loading of the
photomultiplier tube. A diode could be used to clip the
positive-going portion of the signal, following which the signal
could then be fed into both an integrating amplifier and a one-shot
multi-vibrator which would trigger an electrical impulse counter.
The one-shot multivibrator could have an adjustable triggering
threshold which would allow a choice of the pulse height to be
counted.
It will now be evident that with the arrangement disclosed the
photomultiplier tube 18 will receive essentially zero light
illumination until a defect protrudes beyond the normal body
diameter of the yarn strand and beyond the shielding effect of the
shadowbar 46. In this manner the photomultiplier tube will be
rendered more sensitive to a single broken filament, loop and the
like. This apparatus, therefore, will be able to measure staple
yarn fuzz density or detect broken filaments in continuous filament
yarn.
Tests run on this apparatus have established that 55 and 150 denier
acetate yarn, for example, may be inspected at speeds up to 2,100
feet per minute. Thus the apparatus may be a high speed detector of
defects in single ends of acetate yarn.
The invention has been described in detail with particular
reference to preferred embodiments thereof, but it will be
understood that variations and modifications can be effected within
the spirit and scope of the invention.
* * * * *