U.S. patent application number 09/159071 was filed with the patent office on 2002-06-06 for apparatus and method for detecting metallized containers in closed packages.
Invention is credited to GOLDBERG, IRA B., MAYS, DAVID L..
Application Number | 20020067163 09/159071 |
Document ID | / |
Family ID | 22570964 |
Filed Date | 2002-06-06 |
United States Patent
Application |
20020067163 |
Kind Code |
A1 |
GOLDBERG, IRA B. ; et
al. |
June 6, 2002 |
APPARATUS AND METHOD FOR DETECTING METALLIZED CONTAINERS IN CLOSED
PACKAGES
Abstract
An apparatus and method used to detect metallized containers or
other objects in closed packages traveling in a conveyor stream.
The apparatus includes a pair of coil units mounted in association
with a packaging conveyor such that the closed packages will pass
therebetween. Appropriate field generation circuitry are connected
to the coil units for producing a magnetic field. When the
metallized containers pass through the magnetic field, the
impedance across the coils will vary. The varying impedance is
measured continuously, thus giving an indication as to whether the
metallized object has been detected. If the package is
nonconforming, steps can be taken to automatically remove it from
the conveyor stream.
Inventors: |
GOLDBERG, IRA B.; (THOUSAND
OAKS, CA) ; MAYS, DAVID L.; (WOODSTOCK, GA) |
Correspondence
Address: |
JOHN J HORN
ALLEN BRADLEY COMPANY INC
PATENT DEPT 704P FLOOR 8 T 29
1201 SOUTH SECOND STREET
MILWAUKEE
WI
53204
|
Family ID: |
22570964 |
Appl. No.: |
09/159071 |
Filed: |
September 21, 1998 |
Current U.S.
Class: |
324/234 |
Current CPC
Class: |
G01V 3/105 20130101 |
Class at
Publication: |
324/234 |
International
Class: |
G01N 027/72 |
Claims
What is claimed is:
1. An apparatus used in conjunction with a packaging conveyor to
detect metallized objects in respective packages moving along a
conveyor stream, said apparatus comprising: at least one coil unit
mounted in association with the packaging conveyor such that the
respective packages pass adjacent thereto; field generation
circuitry electrically connected to said coil unit and operative to
apply a signal thereto for generating a magnetic field through
which the respective packages will pass; and measurement circuitry
operative to measure electrical changes in said coil unit due to
the metallized objects and produce an output indicative
thereof.
2. An apparatus as set forth in claim 1, wherein said at least one
coil unit comprises a pair of coil units respectively mounted in
association with the packaging conveyor such that the respective
packages will pass therebetween.
3. An apparatus as set forth in claim 1, wherein said at least one
coil unit comprises a coil of wire wrapped about a nonferrous
core.
4. An apparatus as set forth in claim 1, wherein said field
generation circuitry includes an oscillator and a coil driver, said
coil driver operative to inhibit fluctuations in an output
frequency of said oscillator due to variations in an impedance of
said at least one coil unit.
5. An apparatus as set forth in claim 1, wherein said measurement
device is operative to measure impedance across said at least one
coil unit.
6. An apparatus as set forth in claim 1, further comprising a
weighing device mounted in association with the packaging conveyor
and operative weigh the respective packages.
7. An apparatus as set forth in claim 1, further comprising a
presence detector operative to sense physical presence of the
respective packages adjacent to said at least one coil unit.
8. An apparatus as set forth in claim 1, further comprising output
driver circuitry operative to receive said output of said
measurement circuitry and produce a scaled output signal.
9. An apparatus as set forth in claim 8, further comprising: a
control system operative to receive said scaled output signal and
responsively produce a control output if a nonconforming package
has been detected; and an ejector mechanism operative to remove the
nonconforming package from the conveyor stream.
10. An apparatus according to claim 9, wherein said control
mechanism is operative to determine a number of metallized objects
in said package and compare said number of metallized objects with
predetermined conformance criteria.
11. An apparatus according to claim 9, wherein said ejector
mechanism comprises a lateral pushing mechanism.
12. A method of detecting metallized objects in a closed package,
said method comprising steps of: generating a magnetic field having
a predetermined frequency; passing the closed package through the
magnetic field; detecting a change in the magnetic field due to
presence of the metallized object; and producing an output
indicative of the change in the magnetic field.
13. A method as set forth in claim 12, further comprising steps of:
comparing the output signal to predetermined levels; and signaling
the results of the comparison.
14. A method as set forth in claim 13, wherein said predetermined
levels are indicative of a number of said metallized objects in
said closed package.
15. A method as set forth in claim 12, wherein the magnetic field
is generated by a pair of spaced apart coil units between which the
closed package is passed.
16. An apparatus for detection of a metallized object in a package,
said apparatus comprising: a pair of coil units mounted in parallel
planes such that the packages can be passed therebetween; field
generation circuitry electrically connected to said coil units and
operative to apply a signal thereto for generating a magnetic field
in a region between said coil units; and measurement circuitry
operative to measure changes in an impedance of said coil units due
to the metallized object.
17. An apparatus as set forth in claim 16, wherein each of said
coil units comprises a coil of wire wrapped about a nonferrous
core.
18. An apparatus as set forth in claim 17, wherein said field
generation circuitry includes an oscillator and a coil driver.
19. An apparatus as set forth in claim 18, further comprising a
presence detector operative to sense physical presence of the
package between said coil units.
20. An apparatus as set forth in claim 19, further comprising
output driver circuitry operative to receive an output of said
measurement circuitry and produce a scaled output signal.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates generally to quality control
systems used with packaging conveyors in factory environments. More
particularly, the invention relates to an apparatus and method for
determining whether a closed package actually contains the desired
contents.
[0002] In the packaging of dry food products and the like, it is
important to determine whether each box contains all of the desired
contents. One approach used in industry to address this problem has
been to weigh each closed package as it moves past a weighing
station on a conveyor. If a particular package weighs less than a
known threshold, it is assumed that all of the contents are not
present. Appropriate action can then be taken, such as activation
of an ejector mechanism to remove the defective product from the
conveyor stream.
[0003] While prior art weighing systems have been generally
effective, they are not without disadvantages. For example, many
dry food products, such as rice or pasta, will contain small
seasoning packets having a weight less than the variance of the
weighing system or the variance of the weight of one or more of the
major components in the package. In this case, a weighing system
would be unable to distinguish between a package with or without
the small packet. In addition, it is often difficult to weigh
individual packages that are constantly moving in a high-speed
conveyor system. Weighing techniques are also unable to determine
the position of the packed contents without opening the
package.
SUMMARY OF THE INVENTION
[0004] The present invention recognizes and addresses the foregoing
disadvantages, and others of prior art constructions and methods.
Accordingly, it is an object of the present invention to provide
improvements in quality control techniques used with packaging
conveyors.
[0005] It is a further object of the present invention to provide
an apparatus and method for use in detecting the contents of a
closed package.
[0006] It is an additional object of the present invention to
provide an apparatus and method for detecting metallized containers
in a closed package.
[0007] It is a more particular object of the present invention to
provide an apparatus and method for detecting metallized containers
in closed packages moving rapidly in a conveyor stream.
[0008] Some of these objects are achieved by providing an apparatus
used in conjunction with a packaging conveyor to detect metallized
objects in respective packages moving along a conveyor stream. The
apparatus comprises at least one coil unit mounted in association
with the packaging conveyor such that the respective packages pass
adjacent thereto. Field generation circuitry is also provided,
electrically connected to the coil unit. The field generation
circuitry is operative to apply a signal to the coil unit for
generating a magnetic field through which the respective packages
will pass. Measurement circuitry is operative to measure electrical
changes in the coil unit due to the metallized objects and produce
an output indicative thereof.
[0009] Other objects of the present invention are achieved by a
method of detecting metallized objects in a closed package. One
step of the method involves generating a magnetic field having a
predetermined frequency. Next, the closed package is passed through
the magnetic field. A change in the magnetic field due to presence
of the metallized object is then detected. An output signal is then
produced, indicative of the change in the magnetic field. In
exemplary methodology, the output signal may be compared to
predetermined levels. The results of the comparison can then be
signaled for further use or processing.
[0010] Still further objects of the present invention can be
achieved by an apparatus for detection of a metallized object in a
package. The apparatus comprises a pair of coil units mounted in
parallel planes such that the packages can be passed therebetween.
Field generation circuitry is also provided, electrically connected
to the coil units. The field generation circuitry is operative to
apply a signal thereto for generating a magnetic field in a region
between the coil units. Measurement circuitry is operative to
measure changes in an impedance of the coil units due to the
metallized object.
[0011] Other objectives, features and aspects of the present
invention are provided by various combinations and subcombinations
of the disclosed elements, as well as methods of practicing same,
which are discussed in greater detail below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] A full and enabling disclosure of the present invention,
including the best mode thereof, to one of ordinary skill in the
art, is set forth more particularly in the remainder of the
specification, including reference to the accompanying figures, in
which:
[0013] FIG. 1 is a perspective view showing an apparatus for
detecting metallized objects in a closed package in accordance with
the present invention, installed in a packaging conveyor
system;
[0014] FIG. 2 is an elevational view taken along line 2-2 of FIG.
1;
[0015] FIG. 3 is a cross-sectional view taken along line 3-3 of
FIG. 1;
[0016] FIG. 4 is an exploded view showing the construction of a
single coil unit used in the apparatus of FIGS. 1-3;
[0017] FIG. 5 is a perspective view of a detection apparatus in
accordance with the present invention installed in an alternative
conveyor system;
[0018] FIG. 6 is a diagrammatic representation of a packaging
conveyor system showing various additional features of the present
invention;
[0019] FIG. 7 is a block diagram of components of a detection
system in accordance with a preferred embodiment of the invention;
and
[0020] FIG. 8 is a graph showing a continuous output of a detection
system in accordance with a preferred embodiment of the
invention.
[0021] Repeat use of reference characters in the present
specification and drawings is intended to represent same or
analogous features or elements of embodiments of the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0022] It is to be understood by one of ordinary skill in the art
that the present discussion is a description of exemplary
embodiments only, and is not intended as limiting the broader
aspects of the present invention, even though broader aspects are
embodied in the present invention.
[0023] FIG. 1 shows a stream of closed packages 10 moving down a
conveyor 12 as in a typical factory setting. Often, each of the
packages 10 may themselves includes several different types of
contents. For example, dry food product such as rice or pasta will
often be included within each of the packages 10. Various
metallized objects, such as metal cans 14 or foil seasoning packets
16, may also be included.
[0024] In order to ensure that adequate quality control standards
are met, the conveyor includes an apparatus 18 for detecting
whether the desired number of metallized objects are contained
within each of the packages 10. As will be described more fully
below, packages 10 pass through a magnetic field generated by the
apparatus 18 as they move down the conveyor (in the direction
indicated by arrow A). The metallized objects cause known
fluctuations in the magnetic field, the effects of which can be
detected. If a particular package is found to be nonconforming, a
suitable ejector mechanism, such as cylinder 20, can be used to
remove it from the product stream. In presently preferred
embodiments, cylinder 20 may be a fluid-actuated cylinder, such as
a hydraulic or pneumatic cylinder mechanism. It should be
appreciated, however, that other suitable types of ejector
mechanisms, such as magnetically and mechanically actuated
cylinders, as well as various types of gates, may also be used to
remove nonconforming product.
[0025] Referring now also to FIG. 2, apparatus 18 may have a
suitable device, such as a roller 24, to determine whether a
package 10 is physically present. Roller 24 pivots between a first
lowered position and an upper raised position when a package 10
moves into the detection station of apparatus 18. When roller 24
moves in this manner, a signal may be sent to indicate the presence
of package 10. One skilled in the art will appreciate that other
mechanisms, such as a photoelectric cell, may also be used to
signal the presence of an individual package.
[0026] As can be seen in FIG. 3, apparatus 18 includes a pair of
coil units 26 and 28 between which packages 10 will pass. As shown,
the coil units are situated in parallel planes on opposite sides of
conveyor 12. Preferably, package 10 will pass approximately
centered between coils 26 and 28. As can be seen, coil units 26 and
28 will preferably have a size approximate to the size of packages
10.
[0027] In operation, coil units 26 and 28 generate a magnetic field
30 of a predetermined frequency. When the metallic object passes
between coil units 26 and 28, eddy currents are generated. The
magnetic field produced by the eddy currents opposes the magnetic
field produced by the coils 26 and 28. These eddy currents cause a
measurable fluctuation in the impedance of coil units 26 and 28.
Preferably, sensor electronics continuously measure the coil
impedance to determine whether metallic objects have been
detected.
[0028] The use of two opposed and substantially identical coils in
preferred embodiments of the invention will advantageously produce
a magnetic field through package 10 that is nearly constant. As
such, the output signal from apparatus 18 will show less dependence
on the exact position of the package. Prior art metal detectors
used by hobbyists, in contrast, have a single coil. These devices
provide little information on the size, position or quantity of
metallic objects.
[0029] Referring to FIG. 4, one exemplary construction of coil unit
26 can be more easily explained. As can be seen, coil unit 26
includes a wire coil 32 wrapped around a core 34. Often, it will be
desirable to use a wire of at least 24 gauge, wound about core 34
by no more than about 200 turns. A pair of parallel plates 36 and
38 are situated on each axial end of core 34 to retain the coil 32
in position. Preferably, core 34, as well as plates 36 and 38, will
be made from a suitable nonconductive and nonferrous material, such
as LEXAN plastic or the like. The respective ends (collectively 40)
of wire coil 32 are connected to appropriate circuitry to detect
the presence of metal objects in packages 10 as they pass. While
only coil unit 26 has been described in detail for purposes of
brevity, it will be appreciated that coil unit 28 will be
substantially identical.
[0030] As used herein, the terms "conveyor" and "conveyor stream"
should be construed broadly to include package travel paths
generally, in addition to "conveyor belts" of the traditional type.
For example, FIG. 5 illustrates an embodiment wherein coil units 26
and 28 are mounted on opposite sides of a vertical conveyor 42.
Vertical conveyor 42 moves packages 10 in the direction of arrow B,
such that packages 10 pass between coil units 26 and 28. As can be
seen, conveyor 42 includes a pair of parallel belts 44 and 46 set
apart from each other by a distance slightly less than the width of
packages 10. Belts 46 and 48 each have a plurality of deformable
nubs, such as deformable nub 48, which thus compress to retain
packages 10 securely in position.
[0031] FIG. 6 diagrammatically illustrates an overall control
system constructed in accordance with the present invention. As
shown, a weighing apparatus 50 measures the weight of package 10
and sends a signal to a control unit 52. Weighing apparatus 50 is
useful to determine whether the weight of package 10 is, within
predetermined limits, what it should be. For example, dry food
product, such as rice or pasta, will often constitute the bulk of
the weight of package 10. If the dry food product is not present,
this will be detected immediately by weighing apparatus 50.
[0032] After being weighed, each of the packages 10 will travel
along conveyor 12 to apparatus 18. As described above, apparatus 18
will signal control unit 52 regarding the extent to which package
10 causes fluctuations in the magnetic field. If the particular
package is found to be nonconforming, control unit 52 will send an
actuation signal to ejector mechanism 20. As a result, the package
will be removed from the conveyor stream.
[0033] FIG. 7 illustrates a block diagram of the electronics
employed in an exemplary embodiment of apparatus 18. As shown,
apparatus 18 includes field generation circuitry 54 electrically
connected to one or more coils 56 of the respective coil units.
Field generation circuitry 54 applies a signal to coil 56 for
generating a magnetic field through which the respective packages
will pass.
[0034] In this case, field generation circuitry 54 includes an
oscillator 58 and a coil driver 60. Oscillator 58 generates an
electrical signal of the desired frequency of the magnetic field.
Coil driver 60 receives the output of oscillator 58, and applies it
the coil units. The driving frequency, which will typically fall in
a range from about 10 KHz to about 100 KHz, should preferably be
optimized based on the specific characteristics of the coil unit
and the packages to be detected. Coil driver 60 prevents the
varying impedance of the coil unit from affecting the output
frequency of oscillator 58.
[0035] As shown, apparatus 18 further includes measurement
circuitry 62 for measuring electrical changes in the coil units due
to the metallized objects. In the illustrated embodiment,
measurement circuitry 62 includes an impedance measurement device
64 and an output driver 66.
[0036] Measurement circuitry 62 continuously measures impedance
changes in the coil due to the generation of eddy currents in the
metallized objects. Preferably, measurement circuitry 62 should
respond rapidly to the change in impedance produced in the coils.
Toward this end, numerous methods may be used. One example is an
electronic bridge technique as used in proximity sensors. This
technique generally requires a constant frequency, but high
frequencies can be used. Another detection circuit is the Colpits
oscillator which is often used in commercial metal detectors. Since
the frequency in the absence of metal is fairly low, and the
presence of metal is detected by a frequency shift, the response
tends to be slow. By using a higher frequency, the Colpits
oscillator can be made to respond more rapidly.
[0037] Output driver 66 scales the output of impedance measurement
device 64 to a convenient form for transmission to the control
system. For example, output driver 66 may produce an output in the
range of 0-10V or 4-20 ma, thus conforming to accepted industry
standards. As described above, control unit 60 takes a continuous
signal from the output driver 66 and determines whether the package
is conforming or nonconforming to predetermined requirements.
[0038] An example of a continuous output signal 68 from output
driver 66 is depicted in FIG. 8. As can be seen, it has been
predetermined that an output of less than about 8.270V (represented
by line 70) corresponds to more than two foil seasoning packets.
Fewer than two foil packets are present if the output is more than
about 8.285V (represented by line 72). Output voltages between
these thresholds correspond to exactly two foil packets.
[0039] Each of the substantial peaks in signal 68 corresponds to
the passage of one package 10. As can be seen, this example
recorded four packages of greater than two packets, as shown by the
peaks 74. Exactly two packets were also noted in four packages, as
indicated by the peaks 76. The remainder of the packages each
contained fewer than two packets. While a negative peak was used in
this example to note the presence of metallized objects, this is
merely a matter of convention. It should be understood that
positive peaks may also be used in accordance with the present
invention to determine the presence or absence of various
metallized objects.
[0040] While preferred embodiments of the invention have been shown
and described, modifications and variations may be made thereto by
those of ordinary skill in the art. For example, the above example
used a physical detector (e.g., roller) to determine whether a
package was present in apparatus 18. It should be understood,
however, that the presence of a peak from an impedance measurement
may also indicate the presence of a package to the system control
unit.
[0041] In addition, the apparatus of the preferred embodiment
operates to detect the presence or absence of the metallized
object. In other embodiments, however, it is contemplated that more
sophisticated analysis of the impedance information can be
performed. For example, it is believed that the techniques
described herein can also determine whether a metallized object is
in the correct orientation in the closed package.
[0042] Accordingly, it should be understood that these and other
variations of the disclosed embodiments are intended to be included
within the scope of the appended claims. In addition, aspects of
the various embodiments may be interchanged both in whole or in
part. Furthermore, those of ordinary skill in the art will
appreciate that the foregoing description is by way of example
only, and is not intended to be limitative of the invention so
further described in such appended claims.
* * * * *