Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
The invention concerns apparatus for detecting
foreign bodies in glass bottles, particularly in continuously
moving beverage bottles, using a detection system in which
light is projected through the bottom of the bottle, a first
photoelectric scanning device scans at least the edge zone of
the bottle bottom in sectors, an optical element conducts at
least the rays originating from the central region of the
bottle bottom to a second photoelectric scanning device, and
10 a separate gating device is used for each photoelectric
scanning device.
The inspection apparatus is usually used in conjunction
with automatic bottle filling machines, as they are employed
mainly in plants of the beverage industry. The function of
the bottle inspection machines is to sort out from the row of
bottles moving from the washing machine to the fil:Ling machine
those which contain impurities or foreign bodies. The in~
spection apparatus must be very reliable and sensitive.
A known type of inspection apparatus for glass
20 bottles uscs a sing]e scanning device to scan the bottle bottom
in sectors. These inspection machines may use a rotating con-
cave mirror segment as in U.S. Patent No. 3,415,370 issued
December 10, 1968 to Robert G. Husome, or a rotating glass
disk provided with opaque sectors as in U.S. Patent No.
3,133,640 issued May 19, 1964 to Frederick L. Calhoun, et al,
or with a rotating slit diaphragm as in U.S. Patent No.
3,411,009 issued November 12, 1968 to Geoffrey E. Ford, et al.
In these kinds of known apparatus wherein optical
scanning or rotating elements are used, when a clean bottle
30 bottom is scanned during one or several revolutions of the
element, the intensity of the radiation sensed by the
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photoelectric element remains constant and so does its out-
put signal. But if there is a foreign body on the bottom,
a momentary reduction of radiation intensity occurs when
the body is scanned by the rotating element thus causing a
corresponding drop in the output voltage signal from the
photoelectric elements. This voltage pulse is usually
differentiated with a capacitor and resistor and the differ-
entiated signal is fed to an a-c amplifier which is tuned
to the rotation frequency of the scanning element. The
amplified signal is used to actuate a reject mechanism.
Known apparatus is generally satisfactory. But if there is
a foreign body on the bottom of the bottle whose image
coincides with the axis of rotation of the rotating optical
scanning element, there is no sharp reduction of the radiation
intensity but only a slight linear level change. This causes
a correspondingly small drop in the output voltage of the
photoelectric element which is difficult to detect. In
practice, the result is that relatively small foreign bodies,
which can be readily detected in the edge zones or annular
20 margin of the bottom, remain undetected if they are exactly -
in the center of the bottle bottom which is generally con-
centric to the axis of rotation of the optical scanning
element. Even if the bottle performs a slight translatory
movement during the inspection period so a foreign body
located in the center moves slightly relative to the axis of
rotation, there is no substantial improvement.
In another known testing apparatus for glass bottles,
scanning of the bottle bottom in sectors is effected with a
rotating prism directing light to a stationary mosaic of
sector shaped photoelements which are read out by a switching
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device in cyclic order as in U.S. Patent No. 3,292,785. In
order to be able to detect foregin bodies in the central
region, the scanning device of this known apparatus uses the
rotating prism to obtain a circular partial image of the
bott]e bottom which is projected on the mosaic. This known
apparatus is complex and greatly limited in its performance
because the rotating prism must rotate at a substantially
lower speed than corresponds to the scanning frequency of the
photoelements to ensure complete examination of the bottle
bottom. If a foreign body lies exactly on the circle de-
scribed by the center of the mosaic relative to the bottle
bottom, the same disadvantages regarding sensitivity appear
as in the above described apparatus in the central region
of the bottle bottom.
Finally an apparatus is also known where, in
addition to a first scanning device with a rotating mirror
segment, a second scanning device is provided, particularly
for the central region of the bottle bottom as in U.S. Patent
No. 4,083,637 issued April 11, 1978 to Bernd Ellinger, et al
To this end, a light conductor such as a fiber optic bundle
is inserted coaxially in the drilled shaft of the rotor which
rotates the concave mirror segment. The fiber optic bundle
conducts the radiation falling on the central region of the
rotor to a photoelectric element. Detection of a foreign
body in the center of the bottle bottom is improved this way.
But a disadvantage is the limitation of the second scanning
device to a relative small field, since the diameter of the
light conductor is limited by the shaft diameter of the rotor.
In addition, there is a relatively sharp separation of the
inspection zones of the two scanning devices which jointly
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scan the single image of the bottle bottom projected on the
end face of the rotor. This has the effect that one half of
a relatively small foreign body which lies exactly on the
separating line falls into each scanning zone so that it can
not be reliably detected by either of the scanning devices.
SUI~IMARY OF THE INVENTION
The main object of this invention is, therefore, to
provide an apparatus for detecting foregin bodies or particles
in glass bottles, where the sensitivity is completely
independent of the position of the foreign body.
This problem is solved according to the invention by
apparatus for detecting foregin matter in bottles comprising:
means for illuminating the bottom of a bottle, lens means
arranged for its optical axis to intersect the bottom of a
bottle under examination and for projecting a beam containing
an image of the illuminated bottom of said bottle, beam
splitter means disposed on said optical axis on a side of
said lens means opposite of the side on which said bottle
is disposed, said beam splitter means being constructed and
arranged for directing said image beam into two separate
optical paths to provide corresponding images, first
photoresponsive means including a first contiguous array of
photoresponsive elements arranged in a first optical path
for intercepting the image of the central area of said
bottom of the bottle, said photoresponsive elements changing
state in response to the image of foreign matter falling on
them, respectively, from corresponding areas in said bottom,
means for detecting any changes of state of said photo-
responsive elements in said first array, second photoresponsive
means including a second contiguous array of photoresponsive
elements arranged in a second optical path for detecting
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variations in light intensity due to the image of foreign
matter in an area generally surrounding said central area,
said second photoresponsive elements changing state in
response to the image of foreign matter falling on them,
the total areas of the first and second arrays of photo-
sensitive elements being great enough for a part of the
first array to overlap a substantial part of the second
array so that the image of any dirt particle in the central
area which divides between elements in one array has a high
probability of being imaged and detected mostly by a single
element in the other array, means for detecting any changes
in state of said photoresponsive elements in said second
array, and means responsive to said changes of state and
said light variations being detected, respectively, by
producing signals for activating a bottle rejector.
The invention is based on the idea of producing
simultaneously two separate images or projections of the
bottle bottom or parts of the bottom and of checking the
two separate scanning devices separately and independently
of each other. Due to the use of a beam splitter with a
partly reflecting separating surface, either of the two
scanning devices can receive the radiation of any part of
the bottle bottom, without the formation of a separating
line that would
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reduce sensitivity. In the extreme case, each scanning
device can thus check the entire bottle bottom or its pro-
jection completely in different ways. Each scanning device
can be adapted without compromise to its special purpose,
for example, detection of foreign bodies in the central
region or in the edge zone of the bottle bottom and detection
of foreign small bodies or larger impurities. In the
simplest case, it suffices, for example, to use for the second
scanning device a single photosensitive element with an
effective area of a few square millimeters which receives
exactly the radiation originating from the center of the
bottle bottom.
It is more advantageous, however, if the second
photoelectric scanning element has, according to another
feature of the invention, a mosaic of photoelectric elements
receiving continuously the radiation originating from the
central region of the bottle bottom, preferably in the image
plane of a projection lens. This way a substantially larger
central region of the bottle bottom can be checked with
greater sensitivity, so that the first scanning devicé
working in sectors can concentrate on the edge zone for which
it is particularly suitable. "Sectorwise" in the sense of
the invention does not mean that a complete sector of the
bottle bottom must be scanned, but that the lateral separating
lines of a single scanning field extend in a substantially
radial direction and the totality of all scanning fields has
a circular circumference corresponding to the bottle bottom.
The first scanning device can work with any scanning
rotating optical element such as a concave mirror segment
and any arrangement of photoelectric detectors which have
been used for scanning of the edge zone of the bottle bottom.
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It is of particular advantage if, according to another feature
of the invention, the first photoelectric scanning device
has a mosaic of photoelectric elements receiving continuously
at least the radiation originating from the edge zone of the
bottle bottom, preferably in the image plane of a projection
lens system. It was found that a rotating optical element
can be completely eliminated in the scanning of several
partial images of the bottle bottom of substantially equal
light intensity and that the scanning Gf the edge zone can
be effected exclusively by a stationary mosaic of photo-
electric elements. The limitation of the performance by
the rotation of the optical element and the expense for the
support and drive are thus avoided.
It is of particular advantage if, according to
another feature of the invention, the photoeiectric elements
of one scanning device differ in their circumferential form
and/or arrangement and/or position of the separating lines
relative to the bottom from the photoelectric elements from
the other scanning device. This way the position of a
foreign body on the separating line of two adjacent photo-
electric elements of one scanning device can not have an
adverse effect since the foreign body then falls fully on a
photoelectric element of the other scanning device. The new
inspection apparatus thus permits inspecting glass bottles
for foreign particles exclusively with stationary photoelectric
elements and without rotating optical elements at no sacrifice
of sensitivity.
The heam splitter can be formed, according to two
other features of the invention, by a partly reflecting
mirror inclined to the center axis of the cone rays originating
from the bottle bottom or by two adjacent triangular prisms
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with a separating surface inclined to the center axis of
the cone of rays originating from the bottle bottom. In
both cases, two projections with the same light intensity can
be produced with an appropriate design of the separating
surfaces.
The beam splitter can cover a more or less large
partial region of the cone of rays originating from the '
bottle bottom depending on the purpose of the two scanning
devices. Preferably the beam splitter covers the entire
cross section of the cone or rays originating from the
bottle bottom, according to another feature of the invention.
In this case, two complete projections of the bottle bottom
are produced and the scanning devices can be adjusted in any
desired position.
The best mode of operation is obtained if, according
to another feature of the invention, a projection lens
system or a part of a projection lens system for projecting
the image of the irradiated bottle bottom is arranged
between the bottle bottom and the beam splitter. This way
particularly sharp uniform projections of the bottle bottom
can be obtained.
Another feature of the invention consists in having
one of the two photoelectric scanning devices arranged in
the field of the optical axis of the projection lens system
in the radiation transmitted by the beam splitter and that
the other scanning device is arranged laterally of the optical
axis in the field of the radiation reflected by the splitter.
This results in a particularly clear and compact design of
the apparatus.
How the above mentioned objects and other more
specific objects of the invention are achieved will appear
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in the more detailed description of embodiments of the
invention which will now be set forth in reference to the
drawings.
Description of the Drawings
FIGURE 1 shows a schematic side elevation of an
apparatus, partly in section, for checking beverage bottles;
FIGURE 2 shows a top view of the beam splitter and
the projection lens system of the apparatus according to
FIGURE l;
FIGURE 3 shows a top view of the lower end face of
the rotor of the apparatus according to FIGURE l;
FIGURE 4 shows a side elevation of the second
photoelectric scanning device of the apparatus according to
FIGURE l;
FIGURE 5 shows the position of the inspection
fields of the two photoelectric scanning devices relative to
a bottle bottom;
FIGURE 6 shows a schematic side elevation of
another embodiment of the new apparatus, partly in section,
for checking beverage bottles;
Figure 7 shows a top view of the first photoelectric
scanning device of the apparatus according to FIGURE 6.
FIGURE 8 shows a side elevation of the second
photoelectric scanning device of the apparatus according to
FIGURE 6.
Description of a Preferred Embodiment
The apparatus according to FIGURES 1 to 4 is
- desi.gned to detect foreign bodies and impurities in the
bottom area of upright empty beverage bottles 1 of glass, and
is part of an automatic bottle inspection machine not repre-
sented here. The suspended bottles to be checked are moved
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by a star wheel 2 rotating continuously about a verticalaxis of rotation in cooperation with stationary guides 3
over a stationary light source 4. The light source is
covered at the top by an opal glass disk 5 so that the
bottoms of the bottles 1 are illuminated diffusely from
the bottom. The image of an illuminated bottle bottom is
projected in a beam by a stationary pro~ection lens system,
arranged above the path of motion of the bottles, which
includes a collecting lens 6 and an aperture diaphragm 7.
1~ The light intensity over the image area is substantially
uniform if the bottle is clean, but the intensity is modulated,
usually reduced, in those areas which are occupied by foreign
matter. A rotor 8 is fastened to the shaft of a motor 9 and
is set in rapid rotation by the motor. On the bottom end
face of rotor 8 is arranged a narrow radially extending
concave mirror segment 10 which focuses the modulated or
unmodulated radiation originating from the scanned portion of
the bottle bottom on a single photoelectric cell 11. The
axis of rotation of motor 9 is slightly inclined to the
optical axis of the projection lens system 6, 7 so the concave
mirror will focus on cell 11. The concave mirror segment 10
and the photoelectric cell 11 comprise a first scanning device
that responds primarily to foreign bodies in the edge zone of
the bottle 1 bottom.
If an area of the bottle bottom is scanned during
the rotation of the concave mirror segment 10 in which a
foreign body is located, the intensity of the radiation
received by the photoelectric cell 11 diminishes monentarily
and its output voltage drops correspondingly for an instant.
This signal is processed in a connected gating circuit 12
with an amplifier 13 and a discriminator 14 and effects the
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emission of a reject initiating signal over control lines 15
to the conventional reject device of the bottle inspection
machine. Preferably, gating circuit 12 is capacitor coupled
to filter out the d-c voltage components of the signals
produced by cell 11, and amplifier 13 is preferably an a-c
voltage amplifier. This permits a very high sensitivity.
A conventional trigger mechanism (not shown) ensures
that a rejection signal can be produced only during an exactly
defined inspection interval. It starts when the center axis
of a bottle 1 is short of the optical axis of the projection
lens system 6, 7, and ends when the bottle axis is directly
behind the optical axis.
Behind diaphragm 7 of the optical projection system
there is a beam sp~itter 16 which includes two identical
abutting triangular prisms 16A and 16B which form a cube.
The interfacing surfaces 16' or hypotenuses of the two
prisms are arranged in a plane inclined to the axis of the
optical pro~ection lens system by 45 so the prism 16B
transmits one half of the impinging light rays through itself
and prism 16A and deflects the other half by 90. Thus, the
beam splitter 16 produces two identical images of the bottle
bottom of equal brightness and directs the images in separate
optical paths, one of which falls on the end face of rotor 8
and is gated in the above described manner. The other image
falls on a stationary second photoelectric scanning device 17
arranged in a corresponding distance laterally of the beam
splitter 16. This second scanning device 17 has, for example,
a mosaic or an array of three times three photoelectric cells
18 arranged concentrically to the image of the bottle bottom
as shown in FIGURE 4 in broken lines. The cells mosaic
covers the entire field of the bottle bottom as it can be
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seen from FIGURE 4, not only the central region. The radi-
ation originating from the edge zone is thus not considered.
The second scanning device 17 is connected to a second
gating circuit 19 with amplifier 20 and a pulse discriminator
21. The gating circuit 19 can be provided, as in prior
practice, with an OR-circuit (not shown). All photoelectric
cells 18 are then simultaneously scanned and as a result
of darkening of at least one cell by a foreign body in the
area of the bottle bottom a rejection signal is generated
by discriminator 21. The latter is applied to the control
lines 15 over an OR-gate 22 to which is also connected the
first gating circuit 12. Due to the use of correspondingly
small photoelectric cells 18, even relatively small foreign
bodies can be reliably detected in the central region of
the bottle bottom which could not be detected by the first
photoelectric scanning device 10, 11. If a semi-transparent,
semi transmissive mirror is used as a beam splitter 16,
it should be disposed diagonally of the optical axis at an
angle of 45 to lie along the hypotenuse plane 16' and, of
course, the prisms would not then be used with the mirror.
The second photoelectric scanning device 17 can be
realized in various ways. It could have a circular mosaic
of several annular or sector-shaped photocells and it can
likewise scan the entire image of the bottle bottom. It is
important that it scans at least the central region of the
bottle bottom. The concave mirror segment 10 of the first
scanning device, therefore, need not extend to the axis of
rotation of rotor 8, as shown in FIGURE 3, that is, up to
the center of the image of the bottle bottom, but it can be
confined to the edge zone. Such a concave mirror segment
10a is shown in FIGURE 3 in broken lines. Care must be taken
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that the square inspection field of second scanning device
17 and the circular inspection field of scanning device 10a,
11 sufficiently overlap on the bottle bottom. To illustrate,
FIGURE 5 shows the position of two different hatched inspec-
tion fields of scanning devices 17, or 10a, 11 on the bottle
bottom. A foreign body 23 which lies on the inner boundary
line of inspection field A of the first scanning device 10a,
11 is fully scanned by the second scanning device 17. Con-
versly, a foreign body 24 lying on the boundary line of
inspection field B of the second scanning device 17 is fully
scanned by the first scanning device 10a, 11.
The embodiment according to FIGURES 6 to 8 is
identical in design and arrangement of the illuminatins
device 4, 5, of the star wheel 2 and of the guides 3, the
projection lens system 6, 7 and the beam splitter 16 with the
embodiment according to FIGURE 1.
In FIGURE 6, in the range of the field along the
optical axis of the projection lens system 6, 7 is a first
scanning device 25, which thus receives the part of the
radiation penetrating the interfacing prism surfaces of beam
splitter 16. The first scanning device 25 has a mosaic of
closely arranged sector-shaped photocells consisting of two
rings arranged concentrically to the center axis of the
container image and the optical axis, respectively, of the
projection lens system 6, 7. The cells 26 are connected
individually to an electronic switching device 27 which feeds
the output signals of the cells 26 in cyclic order successively
into a a-c voltage amplifier 13. Connected to the latter is
a discriminator 14 which feeds a bottle rejection signal
over an OR-gate 22 to control lines 15 leading to the
rejection device, not shown, of the inspection machine when
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the signal voltage drops briefly due to foreign matterbeing scanned. The cells 18 each have the same effective
surface so that they all have the same output voltage with
the same illumination.
The effect of the first photoelectric scanning
device 25 is similar to the action of the scanning device
lOa, 11, that is, the outer o-r edge zone of the bottle
bottom is scanned in sectors. But the scanning device 25
has no rotating elements at all. Due to the use of a
plurality of correspondingly small photocells, in connection
with an a-c voltage amplifier 13 that is tuned to the
scanning frequency of the switching device 27, an extremely
high sensitivity is achieved.
The mosaic of the scanning device 25 can naturally
also be designed differently. For example, it can have only
one ring or it can have more than two rings composed of
different photocells of a different type. The cells can
also extend all the way or at least very close to the center
of the bottle bottom, that is, to the optical axis of the
projection lens system, so that a larger area is scanned.
Furthermore, simultaneous scanning of all individual cells by
a switching device with an OR function is possible.
Laterially of the beam splitter 16 or of the
optical axis of the projection lens system 6, 7 is arranged
a second photoelectric scanning device 29 in the image plane.
It consists of a square mosaic of a plurality of square,
closely arranged cells 30. The mosaic is arranged concen-
trically to the circumferential line of the image of the
bottle bottom represented in broken lines and extends almost
to the circumferential line. The scanning device 29 thereby
detects in the field of the second laterally deflected
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portion of the radiation originating from the bottle bottom.Its cells 30 are connected individually to a gating circuit
19 whose function has already been described. Instead a
cyclic, line-by-line scan can also be used, as it was
described on the basis of scanning device 25 and the
respective gating circuit 28. In each case, the central
range of the bottle bottom, which is not covered by the
first scanning device 25, is checked by this second scanning
device 29. The two scanning devices 25 and 29 thus make
a complete check of the bottle bottom. Their inspection
zones on the bottle bottom overlap in a similar manner as
represented in FIGURE 5.
The square photocells of the second scanning
device 29 can obviously also be arranged differently, for
example, with a circumferentical line approaching substantially
the circular form while maintaining the overlapping with the
photoelements of the first scanning device 25.
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