A method and an apparatus for detecting cracks in the mouth zone of a transparant container

Abstract: The invention provides a method and apparatus for detecting cracks, if any, in the mouth zone of a transparant container, e.g. a glass bottle. Such apparatus comprises: means for positioning a transparant container (9) in a desired position; illuminating means (1),(2),(5),(6),(7) for illuminating the outer surface of the mouth zone (8) to be inspected; sensing means (11),(12),(13),(14) for sensing the image of the inner surface of said mouth zone, said illuminating means being designed such that in case of a good container the sensing means do not sense reflected light.

Description: The invention relates to a method and an apparatus for detecting cracks in the mouth zone of a transparent container, e.g. a glass bottle according to claims 1 and 2 respectively. The embodiment in which the light source and the mouth zone of the container are shaped similarly is very practical. A prior art apparatus according to US-A-3 735 144 has a structure such that in order to allow a full inspection of the relevant inner of the bottle under inspection a scanning must take place. Furthermore this prior art apparatus is not particularly suited for detecting cracks in the mouth zone of a transparent container. EP-A-0 209 077 discloses an apparatus for detecting defects on a bottle mouth in which the bottle mouth is illuminated from the side by an annular source and a conical mirror positioned above the mouth directs reflected light to a detector. The invention will now been explained with reference to the accompanying drawing. In the drawing: Figure 1 is a schematic view of an arrangement according to the invention; and Figure 2 is a detail on an enlarged scale of the arrangement according to figure 1 for explaining the inspection according to the invention. Figure 1 shows a light source 1, in this case a stroboscopic light source, to which a conical light conductor 2 is added, the front edge 3 of which is a secondary annular light source. Such an arrangement is described in Dutch patent application 8800866, not published before, in the name of Thomassen & Drijver-Verblifa N.V., a firm of which the present applicants have recently divided off. The light 4 emitted by the annular light source is reflected by a flat mirror 5 and via a lense 6 directed to a conical mirror 7 illuminating in the way shown the mouth zone 8 of a glass bottle 9. It will be clear that the upper edge 10 of the bottle is not illuminated. This is important in view of the inspection to be described hereinafter. A video-camera 11 with an objective lens 12 senses via a flat mirror 13 and a conical mirror 14 the inner wall of the mouth zone 8 of the bottle 9. As a result of the presence of the conical mirror an effective image magnification takes place, resulting in a more detailed video-image and a better use of the resolution. In case of a perfect mouth zone, i.e. a not-cracked mouth zone, no reflection in the direction of the video-camera takes place. In that case the picture is dark. If, however, as is shown in figure 2, in the mouth zone 8 a crack 16 is present, this crack will reflect the impinging light, which reflected light, referred to with 15, reaches via conical mirror 14 camera 11 for forming a picture there. It should be noted that the drawing is not exactly drawn in scale. For safeguarding the optical parts of the inspection system against external influences the optical parts are enclosed by a closed housing. The upper side of a container to be inspected is sensed and illuminated through a glass plate 17, which also serves for supporting the conical mirror 7 and the conical mirror 14. By means of a support not-shown, the glass plate 17 also carries the flat mirror 13. It should be noted that the conical mirrors can also exhibit curved shapes, by means of which a desired magnification or reduction may be realized.

Claims: A method for detecting cracks (16), if any, in the mouth zone (8) of a transparent container, e.g. a glass bottle (9), said method comprising the steps of providing the transparant container (9); illuminating the mouth zone (8) to be inspected; sensing the image of said mouth zone (8); characterized by illuminating the mouth zone (8) such that the outer surface of the mouth zone (8) is illuminated without illuminating the upper edge (10) of the container (9); by sensing the image of said mouth zone (8) such that the image of only the inner surface is sensed so that in the case of a good container (9) the surface of the mouth zone (8) does not give a detectable reflection. An apparatus for carrying out the method according to claim 1 for detecting cracks (16), if any, in the mouth zone (8) of a transparant container, e.g. a glass bottle (9), comprising means for positioning the transparant container (9); illuminating means (1 to 7) including an annular light source (3) for illuminating the mouth zone (8) to be inspected and sensing means (11, 12, 13) including a first conical mirror (14) for sensing the image of said mouth zone (8); characterized by said illuminating means including a second conical mirror (7) arranged to illuminate the outer surface of said mouth zone (8) without illuminating the upper edge (10) of the container and in that said first conical mirror (14) of the sensing means is arranged such that the inner surface of said mouth zone (8) is sensed so that the sensing means do not sense reflected light in the case of a good container (9). Apparatus according to claim 2, characterized in that the first conical mirror (14) inspects the inner surface of said mouth zone (8) with an increased opening angle.

Inventors: MORSKIEFT MARIA GERTRUDIS, MORSKIEFT, MARIA GERTRUDIS
Applicants: HEUFT SYSTEMTECHNIK GMBH
Application year: 1989
Main classification: G01N21
IPC codes: G01N21