The present invention relates to an X-ray inspection method.
More particularly, the invention relates to a method of non-destructive
X-ray inspection of containers of food products.
It is known that non-destructive X-ray inspection of containers of
food products is carried out by stationary inspection apparatuses inside which the
containers to be inspected are made to pass on a horizontal conveyor belt. Said
apparatuses comprise an X-ray emitter connected with a suitable detector, and the
relevant control circuits.
Inspection of containers of food products aims at detecting the presence
of possible contaminants within the container. Indeed, it is possible that during
the working and bottling phases a particle or fragment of a foreign substance, generally
of higher specific weight than the liquid where it is by chance present, is found
within the container.
It is known that in most cases non-destructive X-ray inspection of
glass containers for food industry is carried out by individual apparatuses, located
aside the row of said containers to be inspected. Said apparatuses are substantially
equipped with an emitter and a detector between which the row of said containers
to be inspected passes.
It is also known that said individual apparatuses result in an inspection
of 90 to 95% the contained product, said limitation being due to shadow areas created
by concavities or inclined walls in the container.
In many cases said result has been wrongly considered sufficient.
In effect, a 95% validity only of the inspection has created several problems. Some
attempts to remedy such problems have been made, which however were rather complex
and expensive, and scarcely satisfactory.
Among such attempts it is worthwhile mentioning the solution proposed
in Italian Patent 1 285 008, corresponding to the European application EP 0 795
746 A1, in the name of the same Applicant, which discloses a side inspection apparatus
for glass containers and/or cans for food industry. Said apparatus comprises a static
structure consisting of two modular units arranged at 90° relative to each other
and at 45° relative to the container displacement line. One unit is equipped with
a semi-panoramic emitter and a detector, whereas the other unit is equipped with
a detector only, identical to that of the first unit
Such a solution allowed eliminating some shadow areas due for instance
to the curvature of the container bottoms. Yet it does not allow a direct inspection
of the container bottom, that is of the region where contaminants become deposited.
A design of stereoscopic X-ray imaging system having two linear parallel
detectors and one X-ray emitter for inspecting passenger baggage is disclosed in
Evans JPO et Al. "Design of a stereoscopic X-ray imaging system using a single X-ray
source" NDT & E International, Butterworth-Heinemann, Oxford, GB Vol.33, Nr.5,
Another example of X-rays inspection apparatus equipped with a single
source and a pair of linear receivers is disclosed in DE19823448.
These latter two prior art methods, however, are not suitable for
inspecting food containers having a neck and inclined walls like bottles and pots.
It is therefore an object of the present invention to obviate the
above drawbacks, by providing a method of using an inspection device allowing a
complete and direct inspection, in quick and sure manner, of the bottom of a glass
or metal container.
The above and other objects are achieved by a method of using a device
for non-destructive X-ray inspection of containers of liquid products, such as glass
jars or pots, in accordance with the invention, as claimed in the appended claims.
The method of the invention uses an inspection device with a vertically
arranged radiation emitter and at least two radiation detectors, located close to
each other, which simultaneously detect the radiation coming from the emitter according
to two slightly different directions. Thus, possible zones remaining in the shadow
with respect to one direction can generally be inspected by the other detector.
The invention will be now disclosed with reference to the accompanying
drawings, relating to a preferred but non limiting embodiment of the invention itself,
- Fig. 1 is a schematic top view of a container in a prior art inspection device;
- Fig. 2 is a schematic side view of an inspection device made in accordance with
- Fig. 3 is a top view of the inspection device shown in Fig. 2; and
- Fig. 4 is a schematic side view of a container during an inspection phase in
an inspection device made in accordance with the invention.
Fig. 1 shows, in a schematic top view, a container 2 passing, e. g.
on a conveyor belt (not shown), in a known inspection device comprising a radiation
emitter 12, located above container 2, and a linear radiation detector 4, located
below the conveyor belt. The radiation beam emitted by emitter 12 passes through
container 2 and its contents and arrives at detector 4, generating, thanks to known
electronic processing means, an image related with the transparency, relative to
the employed radiation, of the materials passed through by the beam.
Yet, as shown in the same Fig. 1, during displacement of container
2 inside the inspection device, the whole of the container bottom, where possible
contaminants are deposited, is not properly inspected. In particular, dashed areas
10a, 10b remain excluded from inspection.
This mainly occurs because, in the container portion lying between
neck 6 and external wall 8, the glass layer to be passed through is thicker, because
of the wall inclination.
Even though the radiation beam emitted by emitter 12 is a divergent
beam and penetrates into the container wholly irradiating the bottom area, linear
detector 4 can only detect radiation lying in a vertical plane passing through its
sensing surface, thus leaving lateral shadow zones 10a, 10b uncovered.
An inspection device for containers of food and other products, made
in accordance with the present invention, is instead disclosed referring to Figs.
2, 3 and 4.
In particular, Figs. 2 and 3 show a group of containers 22, e. g.
foodstuff containing glass pots, which are conveyed by a conveyor belt 20 within
a vertically arranged inspection device made in accordance with the present invention.
The inspection device comprise a radiation emitter 24, emitting a
diverging ray beam 32, e. g. an X-ray beam, and means 26 adapted to detect the radiation
emitted by emitter 24. The emitter position is vertically adjustable, e. g. between
a low position 24 suitable for small size pots, and a high position 24', suitable
for bottles or higher containers.
Actually, for an optimum operation of the device, as it will be disclosed
in detail hereinafter with reference to Fig. 4, emitter 24 is to be located slightly
above the neck of containers 22.
Radiation detecting means 26 comprise two distinct linear detectors
28, 30, slightly spaced and symmetrically located with respect to a vertical line
passing through radiation emitter 24. Detectors 28, 30 receive radiation emitted
by emitter 24 according to two different directions 32 and 32', as shown in detail
in Fig. 4.
Actually Fig. 4 schematically shows an inspection phase of a pot 22,
located between emitter 24, schematically shown above pot neck 34, and detectors
28 and 30. Reference symbol A in the drawing denotes the width of the inclined pot
portion 36, between neck 34 and external wall 40. The drawing clearly shows that,
if detectors 28, 30 are suitably spaced, the pot bottom, including the extreme bottom
corners, can be wholly inspected.
Minimum spacing B between the detectors must at least be equal to
twice the half-diameter difference A between neck 34 and external wall 40 of container
or pot 22. Indeed in this way rays 32' emitted by emitter 24 penetrate inside container
22, without passing through inclined portion 36, and can pass, without obstacles,
also through the bottom periphery, subsequently reaching detector 30. Similarly,
the other end of bottom 38 of pot 22 is properly inspected by the other detector
Moreover, to adapt the inspection device to containers with different
shapes and sizes, the spacing between sensors 28 and 30 is made variable, of course
always within the emission cone of emitter 24. Actually, to inspect wide bottom
containers, a greater spacing between detectors 28 and 30 can be suitable, whereas
in case of cylindrical container the detectors can be located closer to each other.
The method of the invention thus allows improving the inspection phase
of container of food products, ensuring a greater security and reliability.