U.S. patent number 3,829,690 [Application Number 05/392,724] was granted by the patent office on 1974-08-13 for method and apparatus for the examination of articles for defects.
Invention is credited to Ellery P. Snyder.
United States Patent |
3,829,690 |
Snyder |
August 13, 1974 |
METHOD AND APPARATUS FOR THE EXAMINATION OF ARTICLES FOR
DEFECTS
Abstract
A method for examining the upper part of a glass vessel for
defects comprises the steps of applying a fluorescent material to
selected surfaces of the upper part of the vessel while inhibiting
the introduction of the fluorescent material into voids or defects
existing in coated surfaces, irradiating the coated surface with
light having a frequency for exciting the fluorescent material,
scanning the surface for discontinuities occurring in fluorescent
radiation which corresponds to defects in the vessel, and providing
an indication of the existence of such a discontinuity. The
selected surfaces, in particular, comprise helically formed threads
and the top surfaces of screw top beverage bottle. An apparatus in
accordance with the invention is provided for effecting the
examination of a glass vessel.
Inventors: |
Snyder; Ellery P. (Norwalk,
CT) |
Family
ID: |
23551762 |
Appl.
No.: |
05/392,724 |
Filed: |
August 29, 1973 |
Current U.S.
Class: |
250/302;
250/461.1 |
Current CPC
Class: |
G01N
21/91 (20130101); G01N 21/9054 (20130101) |
Current International
Class: |
G01N
21/90 (20060101); G01N 21/88 (20060101); G01n
021/16 () |
Field of
Search: |
;250/302,458,461
;356/237,240 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Lawrence; James W.
Assistant Examiner: Willis; Davis L.
Attorney, Agent or Firm: Kaufman & Kramer
Claims
What is claimed is:
1. A method for examining articles for the detection of voids which
extend into the article from a surface of the article comprising
the steps of:
Depositing a material on the surface of an article being examined
and inhibiting the introduction of the material into voids
extending into the article from the surface, said material adapted
to fluoresce when irradiated with light energy of a predetermined
spectrum;
Irradiating the surface of said article at the predetermined
spectrum for exciting the fluorescent material and causing
fluorescent radiation therefrom; and,
Detecting discontinuities occurring in fluorescent radiation along
the surface thereof corresponding to voids in the surface.
2. The method of claim 1 wherein said fluorescent material is
deposited on the surface and inhibited from introduction into the
voids by applying the material with an applicator having a surface
hardness which inhibits the applicator surface from extending into
a void existing in the surface of the article.
3. The method of claim 2 wherein said coated surface is irradiated
by scanning the coated surface with a light beam thereby causing
sequential fluorescent radiation from the coated surface at a
radiation detection means.
4. The method of claim 3 wherein said coated surface is scanned by
providing relative motion between the light beam and the
article.
5. The method of claim 4 wherein relative motion is provided
between said article and said light beam by transporting said
article about an axis of the article past a stationary light
beam.
6. The method of claim 3 including projecting the light beam at the
coated surface through an optical filter which transmits light of a
limited frequency spectrum for exciting the coated material and
projecting the fluorescent radiation at the detection means through
an optical filter which transmits light of a limited frequency
spectrum corresponding to the spectrum of fluorescent radiation of
the excited fluorescent material.
7. The method of claim 6 wherein said fluorescent radiation is
projected at said detection means and said detection means is
scanned for generating electrical indications in digital form of
the occurrence or the absence of fluorescent radiation from a
selected surface of the article.
8. The method of claim 2 wherein said coated material comprises a
solution of quinine in a solvent.
9. The method of claim 2 wherein said applicator is formed of
rubber.
10. A method for examining a glass vessel for defects which extend
from a surface of the vessel into the vessel comprising the steps
of:
Applying a fluorescent material to a selected surface of the vessel
with an applicator having a surface dimension and firmness which
inhibit the entry of the applicator surface and the fluorescent
material into a void existing in the surface;
Irradiating the coated surface with light having a frequency
spectrum for exciting the fluorescent material and causing
fluorescent radiation therefrom;
Scanning the coated surface by providing relative motion between
the coated surface and said irradiating light;
Detecting discontinuities occurring in fluorescent radiation which
correspond to a void in the vessel surface; and,
Providing an indication of the existence of the discontinuity.
11. The method of claim 10 wherein said vessel comprises a glass
bottle and said selected surface comprises a top surface of the
bottle.
12. The method of claim 10 wherein said vessel comprises a glass
bottle and said selected surface comprises a helically shaped
integral glass thread formed in an upper part of the bottle and
which is adapted for engaging a closure cap for the bottle.
13. The method of claim 12 wherein said selected surface includes a
shoulder segment integrally formed in an upper part of the bottle
for sealing a bottle cap thereto.
14. A method for examining a glass beverage bottle for defects or
flaws in an upper portion of the bottle, said upper portion
including an integrally formed top wall surface and a helically
shaped thread for engaging a closure member for the bottle
comprising the steps of:
Coating a surface of the thread with a fluorescent material which
is deposited on said surface by an applicator having a surface area
and stiffness which inhibits the entrance of the applicator and the
introduction of coating material into voids or flaws which extend
from the surface of the thread into the body of the thread;
Projecting a narrow rectangular shaped beam of ultraviolet light at
said upper portion of said bottle thereby causing fluorescent
radiation to emanate from coated surfaces located within the
relatively narrow area of beam impingement;
Rotating the bottle about a longitudinal axis thereof, past the
light beam;
Directing the fluorescent radiation at a photo detection means for
generating an electrical signal representative of beam impingement
upon said photo detection means; and,
Analyzing an electrical output signal from said photo detection
means for sensing discontinuities occurring in fluorescent
radiation from said coated surface which correspond to a defect in
the surface.
15. The method of claim 14 wherein said rectangular shaped beam is
projected at said bottle for providing that a relatively longer
dimension of said rectangular shaped beam is generally parallel to
a longitudinal axis of said bottle.
16. The method of claim 15 wherein said photo detection means
includes a photodetector which is segmented into a plurality of
photo detector elements and said elements are sequentially
scanned.
17. An apparatus for detecting surface voids existing in an article
comprising:
Means for depositing a fluorescent material on a selected surface
of an article being examined and for inhibiting the introduction of
the material into a void extending into the article from said
surface;
Means for irradiating said coated surface at a frequency for
exciting the deposited fluorescent material thereby causing
fluorescent radiation from said surface;
and,
Means for detecting a discontinuity occurring in fluorescent
radiation along the surface corresponding to a void in the
surface.
18. The apparatus of claim 17 wherein said fluorescent material
comprises a solution of quinine in a vehicle.
19. An apparatus for examining the upper part of a glass vessel for
voids occurring therein comprising:
Means for applying a fluorescent material to selected surfaces of
the upper part of the vessel, said means including an applicator
body in contact with said surface and having a dimension which is
generally larger than the voids occurring in the vessel and having
a surface hardness for inhibiting the entry of said applicator
surface and the introduction of said material into said voids;
Means for scanning the coated surface with light having a frequency
for exciting the fluorescent material; and,
Means for detecting discontinuities in fluorescent radiation
corresponding to voids in the surface.
20. The apparatus of claim 19 wherein said means for scanning said
selected surface and detecting discontinuities in fluorescent
radiation comprises a source of ultraviolet light, means for
providing relative motion between said light source and said
vessel, means for projecting ultraviolet light from said source at
said selected surface through an optical filter which transmits
ultraviolet light and inhibits the transmission of visible light, a
photodetector, means for projecting fluorescent radiation at said
photodetector through an optical filter which transmits light
within a limited frequency spectrum corresponding to the spectrum
of the fluorescent radiation, said photodetector providing an
output signal corresponding to voids in the selected surface.
21. The apparatus of claim 20 wherein said photodetector comprises
a plurality of segmented photodetector elements and means are
provided for sequentially scanning each of said elements for
sensing the occurrence or non-occurrence of an electrical signal at
said element.
22. The apparatus of claim 19 wherein said applicator is formed of
rubber.
23. A method for examining recycled glass vessels comprising the
steps of:
Conveying the vessels to a washing and rinsing station;
Washing and rinsing the vessels;
Conveying the vessels from the washing and rinsing station to a
coating station;
Applying a fluorescent material to a selected surface of the vessel
with an applicator having a surface dimension and firmness which
inhibits the entry of the applicator surface and the fluorescent
material into voids or defects existing in the surface;
Irradiating the coated surface with light having a frequency
spectrum for exciting the fluorescent material and causing
fluorescent radiation therefrom;
Scanning the coated surface by providing relative motion between
the coated surface and said irradiating light;
Detecting discontinuities occurring in fluorescent radiation which
correspond to a void in the vessel surface;
and
Discarding the vessels in which voids in the vessel surface were
detected.
Description
This invention relates generally to an improved method and
apparatus for the examination of articles by fluorescent
techniques. The invention relates more particularly to an improved
method and apparatus for the detection with fluorescent techniques
of defects occurring in glass beverage vessels and the like.
Fluorescent examination of articles for flaws or defects therein
has principally been accomplished with a known technique referred
to as the penetration technique. Examination with this technique is
accomplished by coating a surface of an article with a fluorescent
material, rinsing the fluorescent material from the surface and
then irradiating the object with ultraviolet light. Defects in the
article, such as hairline cracks and similar flaws which extend
from the surface of the object and which are otherwise not visible
to the naked eye, trap and retain the fluorescent material. Upon
irradiation, the entrapped material fluoresces and reveals the
presence and extent of any defects.
Various other procedures for the fluorescent examination of glass
vessels are known. One such procedure requires the fabrication of a
vessel being examined from a fluorescent material. Upon irradiation
of the vessel, smooth surfaces of the vessel wall cause a uniform
internal reflection of fluorescent radiation and a resulting
confinement of the radiation within the vessel wall. The existence
of a flaw however interrupts the uniformity of reflection and
permits radiation to emanate from the flaw. This reflected
radiation which escapes from the wall is then detected.
Another fluorescent examination technique has been employed for
inspecting the interior of glass beverage bottles for residue and
foreign objects. The interior of the bottle is washed with a
fluorescent liquid and is then rinsed. Irregular surfaces of
particles or a residue remaining in the bottle will retain or trap
a portion of the fluorescent material and reveal its presence upon
irradiation with ultraviolet light.
These known flourescent examination techniques can be impractical
and costly, particularly when employed for beverage bottle
examination. The penetration technique, for example, necessitates
the removal or rinsing of the fluorescent material from the article
before the existence of the defect can be sensed. There are
instances however in which it is not feasible to rinse or remove
the major portion of the fluorescent material. This is true in the
recycling of glass beverage bottles. A large number of present day
glass beverage bottles include integrally formed threads which
engage a mating threaded bottle cap. Examination of the top surface
of the bottle and the threads of a recycled bottle for defects is
important for several reasons. The upper portion of a bottle often
comes in contact with a users mouth and sharp edged voids and flaws
can cause personal injury to the user. In addition, a defective
bottle top surface can cause an incomplete seal resulting in the
loss of carbonation and entry of bacterial growth when beverages
contain sugar. In practice, large numbers of bottles are examined
and in order to be economically feasible, the handling and
examination of the bottles should occur at a relatively high rate
such as, for example, 10 bottles per second. However, it is found
that recycling equipment which is provided for washing and rinsing
the bottles and for conveying bottles between various operating
stations at these relatively high rates can itself cause damage to
the bottles. While, in comparison with the total number of damaged
returned bottles, this process results in a relatively low
percentage of damage to bottles, nonetheless, the risk of personal
injury to a user from a defective bottle thread dictates that all
defective bottles be detected and discarded.
It is therefore preferable to examine the bottle threads after the
principal recycling and cleaning steps have been performed and
immediately before refilling of the bottles. At this stage of the
process, however, fluorescent examination by techniques such as the
penetration technique which provides for coating with a fluorescent
material and then rinsing the material from the surface of the
bottle will substantially reduce the reprocessing rate and can
render the reprocessing examination costly. Alternatively, the
fabrication of bottles from a fluorescent material is limiting and
can be prohibitively expensive. Furthermore, detection arrangements
employed with prior fluorescent sources for the examination of
articles have suffered from reflections and refractions which
interferred with the accuracy of detection.
Accordingly, it is an object of this invention to provide an
improved method and apparatus for inspecting articles by
fluorescent examination techniques.
Another object of the invention is to provide an improved method
and apparatus for examining an article by fluorescent techniques
wherein a fluorescent material which is deposited upon a surface of
the article remains on the surface during the examination.
Another object of the invention is to provide a method and
apparatus for fluorescent examination of an article wherein a
fluorescent material which is deposited upon the article for
purposes of examination of the article remains on the article after
examination.
Another object of the invention is to provide an improved method of
fluorescent examination of articles wherein the article acts as a
fluorescent light source and having an improved defect detection
arrangement which is substantially nonsusceptible to reflection of
incident exciting light.
Another object of the invention is to provide a method of
fluorescent examination of articles which are compatible with
digital information handling techniques.
Still another object of the invention is to provide a relatively
high speed and relatively low cost method and apparatus for the
examination of screw threads and upper bottle surfaces on a screw
top glass bottle.
A further object of the invention is to provide an improved method
and apparatus for the examination of recycled glass bottles for
defects which may occur in the bottle.
In accordance with the general features of this invention, a
fluorescent material is deposited on the surface of an article
being examined and is inhibited from introduction into voids or
defects extending into the article from the surface. The article
surface is subsequently irradiated at a frequency for exciting the
deposited fluorescent material and discontinuities occurring in
fluorescent radiation along the surface corresponding to defects in
the surface are detected and indicated.
In accordance with more particular features of this invention, a
method for examining the upper part of a glass vessel for defects
comprises the steps of applying a fluorescent material to selected
surfaces of the upper part of the vessel with an applicator having
a firmness which inhibits entry of the fluorescent material into
voids or defects existing in the article and extending into the
vessel from the selected surfaces, irradiating the coated surface
with light having a frequency for exciting the fluorescent
material, scanning the surface for discontinuities occurring in
fluorescent radiation which correspond to defects in the vessel,
and providing an indication of the existence of such a
discontinuity. The selected surfaces, in particular, comprise the
integrally formed threads and top surface of a screw top beverage
bottle.
In accordance with more particular features of the invention, the
fluorescent material comprises a substance which is adapted for
human consumption and which may remain on the bottle after
examination.
These and other objects and features of the invention will become
apparent with reference to the following specification and to the
drawings wherein:
FIG. 1 is a flow chart illustrating the process of this
invention;
FIG. 2a is an elevation view of an upper portion of a screw thread
glass beverage bottle illustrating an integrally formed
non-defective screw thread and top bottle surfaces.
FIG. 2b is a plan view of the bottle of FIG. 2a;
FIG. 3a is an elevation view of an upper portion of a screw thread
glass beverage bottle illustrating an integrally formed defective
screw thread and a defective top bottle surface;
FIG. 3b is a plan view of the bottle of FIG. 3a;
FIG. 4 is a diagram of a bottle recycling and examination apparatus
constructed in accordance with features of this invention;
FIG. 5 is a side view of an apparatus for depositing a fluorescent
material on a screw thread surface and a top bottle surface of a
glass beverage bottle;
FIG. 6 is a view taken along line 6--6 of FIG. 5;
FIG. 7 is a schematic plan view of a part of an examination station
of the apparatus of FIG. 4;
FIG. 8 is a schematic elevation view of another part of the
examination station of the apparatus of FIG. 4;
FIG. 9 is a view of an upper portion of a screw top glass bottle
illustrating the thread configuration for different orientations of
the bottle with respect to a detector means as the vessel is
rotated about its axis;
FIG. 10 is a view taken along lines 10--10 of FIG. 7 and
illustrating an aperture disc of the detection means of FIG. 7;
FIG. 11 is a view taken along line 11--11 of FIG. 7 and
illustrating the surface of a segmented photo-detector upon which
fluorescent radiation from the bottle impinges;
FIG. 12 is a view illustrating an alternative form of
photodetector;
FIG. 13 is a schematic diagram in block form of a circuit means for
digitally sensing and indicating a defect in a bottle under
examination;
FIG. 14 is a schematic diagram in block form of an alternative
circuit means for digitally sensing and indicating a defect in a
bottle under examination; and
FIG. 15 is a schematic diagram in block form of an alternative
circuit means for providing analog sensing and for indicating a
defect in a bottle under examination.
FIG. 1 illustrates the steps employed in accordance with features
of this invention. While the present invention will be described
with respect to the recycling of glass bottles, the invention is
also applicable to the examination of newly manufactured bottles as
well as to the examination of other types of articles. Bottles for
recycling are derived from a source 18 and are conveyed in sequence
to a cleaning and rinsing station 20, a coating station 22 at which
an upper portion of the bottles is coated with a fluorescent
material, and to an examination station 24 where the bottles coated
with fluorescent material are examined for defects. When a
determination is made that a bottle is defective, the bottle is
discarded. The discard occurs by bypassing the bottle to a discard
conduit represented by line 25 before the bottle is filled at a
subsequent station 26. Alternatively, and in view of the relatively
low proportion of defective bottles encountered, it is less costly
at times in terns of equipment and processing rate to fill a
defective bottle and then discard the bottle. Non-defective bottles
which are filled at station 26 are conveyed to a station 28 where
they are capped. The bottles are then collected for
distribution.
FIG. 4 illustrates an apparatus for carrying out the described
bottle recycling process. Recycled bottles 20 are transported by a
conventional bottle conveying means 30 from the source 18 (FIG. 1)
to the cleaning and rinsing station 20 at which location the
bottles are scoured under pressure with a detergent wash. The wash
is derived from a source and pump means 32 and is introduced into
the bottles by a suitable conduit means 34. The detergent is pumped
from the bottle through the conduit 34 at this location and the
bottle then is conveyed to a rinsing location. A clear rinse is
derived from a rinse source and pump means 36 at the rinsing
station and is pumped into and then flushed from the bottle at this
location. The equipment for performing the washing and rinsing
steps is conventional.
As indicated hereinbefore, recycling of bottles is preferably
accomplished at a relatively high transport rate. For example, the
bottles are in practice stepped past a station at a rate of about
10 bottles per second. Because of this relatively high rate and the
possibility of damage to the bottles from the equipment itself, it
is preferable to examine the bottles for defects after cleaning and
immediately prior to the beverage filling step.
The fluorescent material coating station 22 provides for depositing
a fluorescent material on the top surface 37 of the bottle wall
(FIG. 2a), on the outer surface or ridge 38 of the helical screw
threads, and on a cap locking shoulder segment 39 while inhibiting
deposition of the material in voids or defects which may exist in
the top surface 37 in the screw thread 38, in voids or defects in
the shoulder segment 39, and in valleys and spaces 40 extending
between the threads. The fluorescent material coating station of
FIG. 4 is shown to include a rotatable turntable 41 which is
mounted to a drive shaft 42. The drive shaft 42 is coupled by a
drive belt 44 to a drive shaft of a motor 46. A bottle 29 is
stepped onto the turntable 44 and is rotated at a predetermined
speed upon energization of the motor 46. Although the turntable 41
is illustrated as supporting a single bottle for rotation,
multiunit turntables can be provided which are adapted for rotating
a plurality of bottles simultaneously. The coating station 22
further includes a reservoir 48 containing a fluorescent material
50 which is conveyed by gravity feed, for example, through a
conduit 52 to a transfer applicator 54. The transfer applicator 54
is rotatably mounted on a shaft 56 and is positioned in contact
with an applicator 58 which is similarly rotatably mounted on a
shaft 60. These shafts are coupled by a drive belt 62 to a drive
shaft of a motor 46. The applicator 58 is positioned for contacting
selected surfaces 37, 38 and 39 of the bottle being coated and is
driven at a rate for providing that the outer surface of the
applicator 58 and these selected surfaces of the bottle are
transported at the same rate. Stepping of the conveyor 30 and
energization and de-energization of the drive motor 46 is
controlled and synchronized by conventional means, not
illustrated.
Reference is made to FIGS. 2, 3, 5 and 6 for a more detailed view
and description of the applicator and the bottle 29. While there is
illustrated a screw cap bottle closure, the invention is equally
applicable to "twist off," "crown caps," and other forms of bottle
closures. An upper part of a bottle 29 is shown to include an
integrally formed helically configured glass screw thread 72 having
a thread starting segment 74 and a thread terminating segment 76
which terminates at the cap shoulder 39. The valley areas or spaces
40 extending between the segments of the screw threads are
generally planar. In comparison with the non-defective bottle of
FIG. 2a, FIG. 3a illustrates a top surface 37 having a chipped out
defect 79, a screw thread 72 having defects 80 and 81 and a
shoulder 39 having a defect 81. These defects and flaws can have
relatively sharp edges and can result in personal injury. In
addition the flaw 79 in the top surface 37 can cause the loss of a
seal between a cap and the bottle and result in a loss of
carbonation in the case of carbonated beverages and in the growth
of bacteria with sugar containing beverages.
In coating the selected surfaces 37, 38 and 39, it is important for
proper detection of defects to inhibit the coating of the valley
bottle surface 40 and the defects 79, 80, 81 and 82. The applicator
is dimensioned so that the applicator body itself cannot enter
these voids or valleys. It is further achieved by providing an
applicator 58 which is formed of a material which is capable of
transporting the fluorescent material on its surface yet exhibits a
stiffness which, when in contact with selected surfaces will not
extend into voids or defects and will not contact the surface 40.
One such suitable applicator comprises a cylinder 58 which is
formed of rubber. Suitable rubbers comprise butyl, styrene
butadiene, polybutadiene, polyisoprene and natural rubber. Another
suitable applicator comprises a cloth faced rubber inking pad. The
applicator 58 (FIG. 5) is generally cylindrically shaped and
includes a segment 83 of relatively larger diameter than another
segment 84. A lower surface 85 of the segment 83 extends over,
contacts and deposits the fluorescent material 50 on the bottle top
surface 37. An outer surface of the segment 84 contacts and
deposits fluorescent material on the ridge or edge surface 38 of
the thread 72 and on the shoulder 39. The transfer applicator 54 is
fabricated of a material which is capable of receiving the
fluorescent material 50 from the reservoir 48 and applying it by
surface contact to the lower surface of the segment 83 and to the
outer surface of the segment 84 of the applicator 58. One such
material for handling a liquid fluorescent material comprises
relatively soft sponge rubber.
As indicated, the valley surfaces 40 preferably should not be
coated with the fluorescent material. Coating of this surface
undesirably increases the complexity of the detection means as will
become apparent from a consideration of particular detector means,
hereinafter. However, the planar surface 40 as well as other planar
surfaces on similar or different articles may be coated with the
fluorescent material when the detector means is adapted for an
analysis of this surface. With respect to the detector means
discussed hereinafter, this can be accomplished by presetting a
counter to an appropriate count or by establishing a digital
"signature" for a non-defective article surface.
The fluorescent material 50 preferably exists in the liquid state
although powdered fluorescent materials may also be coated in
accordance with this invention. The fluorescent material employed
for coating recycled beverage bottles preferably comprises a
substance which is suitable for human consumption and thereby
advantageously eliminates any personal hazard and the need for
washing of the material from the coated surfaces after the
detection step. While a large number of fluorescent substances
existing in the liquid state and which are suitable for human
consumption are known, liquids comprising solutions of a vehicle or
solvent and relatively small concentrations of quinine in
particular have been found to be suitable for this application. The
liquid may comprise any suitable solvent for quinine such as sodium
alginate and water. A carbonated water beverage containing quinine
and sold under the trade names of "Quinine Water" distributed by
the Schwepps Corporation and a similar beverage distributed by the
Cott Corporation comprises a liquid fluorescent material suitable
for human consumption. Other suitable materials which need not be
rinsed are eosin in water, esculin in water or alcohol, and
fluorescin in water. In addition, in those instances when it is
practical to rinse the coated material from the article other
suitable fluorescent materials comprise anthrocene in alcohol,
naphthalene-red in alcohol, resorsin blue in water and rhodamine in
water.
After coating of selected surfaces, a bottle is transported by the
conveyor 30 from the turntable 41 to the examination station 24. At
the examination station 24, the bottle is rotated past a stationary
sensing means, illustrated in FIGS. 7 and 8, which detects
discontinuities in fluorescent radiatin along the length of the
surface being examined. The sensing station is shown in FIG. 4 to
include a turntable 96 which is mounted on a rotatable drive shaft
98. The drive shaft 98 is coupled by a drive belt 100 to the drive
shaft of the electric motor 65 causing rotation at a predetermined
speed of a bottle 29 which is positioned on the turntable.
The discontinuity detection means of FIG. 7 includes means for
irradiating the upper part of a bottle 29 and for detecting a
discontinuity in the fluorescent radiation from the selected
surface as the bottle is rotated past the sensing station. The
radiation means comprises an ultraviolet light source 106 from
which a light beam 107 is projected through a slit 108 in an
aperture plate 110. The slit 108 has a principal dimension
extending in a direction substantially parallel to a longitudinal
axis 112 of the bottle 29. The light beam 107 is transmitted
through a filter 114 which is adapted for passing with minimum
attenuation those light components occurring in the UV band and for
eliminating visible light. The light beam 107 is focused by a lens
116 onto a segment of the upper bottle extending from the shoulder
39 to and including the upper surface 37. Scanning for
discontinuities is provided by rotating the bottle and sequentially
positioning segments of the bottle for impingement by the light
beam.
Coated surfaces upon which the beam 107 impinges fluoresce and the
bottle thus acts as a light source. This fluorescent radiation,
represented by the beam 120, is focused by a lens 122 on a slit 126
in an aperture plate 128. A filter 129 is positioned in the path of
this beam and is adapted for restricting the transmission of light
to those components occurring within the light spectrum of the
fluorescing material and for eliminating UV light. The use of the
filters 114 and 129 greatly enhances the signal noise
characteristic of the detection means. A photodetector 130 is
positioned behind the plate 128 and is aligned with the slit 126.
An electrical signal having an amplitude proportional to the
intensity of the impinging light beam is generated by the
photodetector and is coupled to a scanning and preamplifying means
131 discussed hereinafter. With the exceptions enumerated
hereinafter, a non-defective bottle generates substantially
continuous fluorescent radiation and provides a substantially
continuous output signal from the photodetector as the bottle is
rotated. However, defects in the selected surfaces result in an
interruption in fluorescent radiation and a corresponding
interruption in the continuity of the electrical signal. The
amplified signal is coupled, as indicated in detail hereinafter, to
circuit means for an analysis of the photodetector signal and a
determination and indication of the existence of a defect in the
bottle.
Fluorescent radiation from the top surface 37 is similarly sensed,
as illustrated in FIG. 8, by focusing the fluorescent radiation on
a photodetector 132. The photodetector 132 is positioned behind a
slit 133 in an aperture plate 134. The beam 136 of fluorescent
radiation is focused by a lens 137 onto the detector 132. An
optical filter 138 having transmission characteristics for passing
the spectrum generated by the fluorescent radiation and similar to
that of filter 129 of FIG. 7 is positioned in the path of the beam
136. An output signal from the detector 132 is coupled to a
preamplifier 139 for amplification and coupling to circuit means
for analyzing the detector signals.
The operation of the error determination circuit means of FIGS. 13,
14 and 15 will be more fully appreciated by a consideration of the
character of the fluorescing surfaces under examination. FIG. 10
which is a view of the output aperture plate 128 and the slit 126
formed therein illustrate that the coated fluorescent material is
positioned at three locations along the length of the slit. An
upper shaded segment 140 represents fluorescent radiation emanating
from the uppermost thread segments while the segments 141 and 142
represent fluorescent radiation emanating respectively from a lower
thread segment located at a different vertical position on the
bottle and from the shoulder segment 39. The pattern illustrated in
FIG. 10 represents the fluorescent radiation pattern presented to
the detector 130 for one rotational position of a bottle. As the
bottle is rotated, the helical configuration of the thread 72
causes the thread segments 140 and 141 to assume different vertical
locations in the slit. The fluorescent segments 140 and 141
therefore appear to be moving vertically within the slit. Since a
bottle is rotated at a substantially constant angular velocity, the
segments 140 and 141 will appear to move in a vertical direction at
a substantially uniform rate. However, at the thread starting
segment 74 (FIG. 2) and at the thread terminating segment 76,
discontinuities will appear to occur. The discontinuities represent
the rotational orientation of the bottle and are not indicative of
a defect in the screw thread. They must be accounted for in the
analysis of the photodetector output. In FIG. 9, the slit 126 is
superimposed on the screw threads in order to illustrate the
variations in the screw thread patterns which will be presented to
the photodetector at different rotational orientations of a bottle
about its longitudinal axis. The shoulder segment 142 and the flat
top surface segment 37 do not exhibit a variation along the length
of the slits 126 and 132, respectively, and the fluorescent
radiation emanating from these slits will remain at stationary
locations within their respective slits. It is noted that the
presentation of the fluorescing surfaces represents bits of
information which conveniently lend themselves to analysis by
digital techniques.
Defects which may occur in the selected surfaces being examined can
have varying widths along the length of the thread, depending upon
the type and severity of the defect. Typically, bottles having
defects on the order of one-half millimeter or greater along the
length of the surface in the general direction of rotation are
considered potentially dangerous and should be detected and
discarded. The width of the slit is preferably about 1/2 millimeter
at the bottle top and the length of the slit 126 extends from the
bottom of the shoulder 39 to the surface 37. The length of the slit
133 extends for about the thickness of the bottle wall near the
surface 37.
FIG. 13 illustrates a circuit arrangement for handling data
provided by the detectors 130 and 132. The photodetectors 130 and
132 are segmented along their length into a plurality of insulated
segments 150 and 151, respectively, each of which provides an
independent output voltage on an associated output line 152 and 153
respectively. The output of the photodetectors is then scanned by a
high speed electronic switch 154 which cyclically and sequentially
couples each of the photodetector segments to a preamplifier 156.
The switching operation of the electronic switch 154 is controlled
by a control and synchronizing means 158 which also synchronizes an
output signal from a pulse generator 160. The pulse generator 160
provides an output pulse which is coupled to an AND gate 162 along
with the output from the preamplifier 156. The occurrence of an
output signal from the preamplifier 156 indicates that the segment
which is coupled to the preamplifier at a particular point of time
in the scanning cycle by the electronic switch 154 is being
impinged by fluorescent radiation from a segment of the coated
surface. Upon the occurrence of an output signal from the
preamplifier 156, the pulse generator 160 will enable the AND gate
162 and provide a pulse output to a preset countdown counter 164.
This counter is preset to a value representative of the number of
counts which would be provided by a bottle having no defects in the
surface examined and therefore no discontinuities in fluorescent
radiation as the bottle is rotated. This preset count is adjusted
to account for the discontinuities caused by the thread segments 74
and 76 as discussed hereinbefore. The initial rotational
orientation of a bottle on the table 96 (FIG. 4) need not proceed
from a same reference location on each bottle in this form of
operation since the number of counts for a non-defective bottle are
known and since only the total count is being examined and compared
with the total count of a nondefective bottle. Initiation and
termination of rotation of a bottle at the examination station is
controlled by the control and synchronizing means 158 which
provides an output control signal for controlling excitation of the
motor 65 (FIG. 4) and provides an output signal, which indicates
termination of rotation and of the examination, to an AND gate 166.
The rotation of a non-defective bottle will result in the countdown
of the preset counter to a predetermined count such as a binary
zero state. An absence of one or more pulses to the counter 164
will result in a binary count differing from the predetermined
final count and will enable an AND gate 166 and initiate a bottle
reject operation. The reject operation comprises for example the
actuation of a mechanical gate, not shown, which diverts the
transport of a defective bottle either before or after filling with
a beverage to a discard bin.
FIG. 14 illustrates an alternative form of circuit means for
digitally examining the condition of coated selected surfaces of a
screw top bottle. The photodetector 130 is, similiar to FIG. 13,
divided into a plurality of segments 150, each of which is mutually
insulated and each of which has an output line 152 for coupling an
associated photodetector segment to a preamplifier strip 168. The
preamplifier strip includes a plurality of preamplifing stages 170
equal in number to the photodetector segments 150 and each of which
is associated with one of the photodetector segments. This
arrangement provides for a binary presentation in parallel of the
state of each of the photodetector segments 150 as the bottle
rotates. This information is coupled in parallel through an
input/output terminal 172 to the arithmatic section 174 of a small
scale wired program computer. The binary information presented by
the photodetector 130 at each rotational position of the bottle is
coupled to the computer and is stored in a memory system 176. There
is previously stored in the memory system 176 a pattern,
configuration or "signature" of a bottle known to be non-defective.
This information or signature is provided by examining a bottle
known to be non-defective in order to generate signal patterns
which are then stored as reference data. Data from a bottle under
examination and which is temporarily stored in memory 176 is then
transferred to the arithmetic unit 174 for comparison with the
"signature" or data from a non-defective bottle.
It is noted that the data derived from a bottle under examination
is stored without respect to a predetermined orientation. In order
to compare the sample data with the reference data, the sample data
is convolved with the reference data. The results of each signal
are added and the arithmatic unit 174 searches for a maximum value.
A starting point for comparison is then set equal to the sample
position of maximum value. Having thus established the start
position, the reference data and the sample are compared signal by
signal and any differences can be associated with bottle
defects.
FIG. 15 illustrates an analog detection circuit arrangement for
detecting discontinuities in fluorescent radiation from selected
surfaces. A photodetector suitable for use with the arrangement of
FIG. 15 is illustrated in FIG. 12. This photodetector comprises a
unitary strip 180 which is exposed to fluorescent radiation along
the entire length of the aperture slit. The total instantaneous
output power of the photodetector is proportional to the area of
the fluorescent radiation impingement on the photodetector strip.
As the bottle is rotated, the output power will vary in accordance
with the area of the coated surface which provides fluorescent
radiation. A non-defective bottle will provide substantially smooth
and gradual changes in output power. A defective bottle however
will cause relatively sharp discontinuities in the power level
which are detected by the arrangement of FIG. 15. In addition, the
discontinuities of the thread segments 74 and 76 will cause
relatively sharp discontinuities in the output power level. During
one revolution of a non-defective bottle, there will be two
relatively short discontinuities in the output power.
The output from the photodetectors 130 and 132 which are arranged
as the nonsegmented unit of FIG. 12 are coupled to preamplifiers
181 and 182, respectively. Signal outputs from these preamplifiers
are in turn coupled to differentiating and wave shaping circuit
arrangements 183 and 184, respectively. Since the change in the
power output level from the photodetectors for a non-defective
bottle is relatively smooth and gradual, there will be no output
from the differentiating and wave shaping circuit arrangements 183
and 184. However, the relatively sharp discontinuities created by
the thread segments 74 and 76 will result in two discontinuities
and thus two output pulses from the differentiating and wave
shaping circuit 183. This output is coupled through an OR gate 185
to a binary counter 186. A control means 187 controls the rotation
of the vessel by initiating and terminating the energization of the
rotating motor and in addition resets the counter 186 to a binary
zero. During a rotational cycle of a non-defective bottle, the
counter 186 will have a count of binary two, (i.e., 010). An AND
gate 188 is accordingly disabled and a reject signal is not
generated. However, the existence of defects in the bottle surfaces
being examined will result in sharp discontinuities in the
fluorescent radiation and will result in one or more additional
pulses creating a 010. This output signal along with the end of
rotation signal from the control means 186 results in a reject
signal output from the AND gate 188.
Although this specification has specifically described fluorescent
examination techniques with respect to recycling of screw thread
glass bottles, the invention is equally applicable to the
examination of defects in other types of bottles. For example, this
invention may advantageously be utilized for an inspection of
crowns on non-threaded bottle cap types of bottles. Newly
manufactured as well as recycled vessels can be examined with this
invention. Furthermore, the techniques described are applicable to
the detection of surface defects in other articles.
There has thus been described an improved method and apparatus for
examining articles for defects existing therein. These defects are
advantageously detected by coating the surface under examination
with a fluorescent material and inhibiting entry of the material
into voids or defects, irradiating the coated surface causing
fluorescence of the coated material and detecting discontinuities
in the fluorescent radiation as the article is rotated.
While there has been described particular embodiments of the
invention, it will be understood that modifications may be made
thereto without departing from the spirit of the invention and the
scope of the appended claims.
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