Liquid container labelling machine with optical inspection device

A method for labelling containers for containing a liquid, wherein the containers are elongate along respective longitudinal axes and each of the containers has at least one seam lying in a seam plane containing the longitudinal axis, wherein the method comprises:

• transporting the containers along a path by means of a carousel;
• rotating the containers about the respective longitudinal axes while they are being transported;
• lighting a plurality of said containers positioned in a sector of the path, through an illuminator;
• capturing one or more images of each container of the plurality of containers positioned in the sector, through at least one camera, wherein the containers of said plurality of containers positioned in the sector are simultaneously illuminated by the illuminator and visible by the at least one camera;
• processing the images to derive data therefrom representing a position of the seam in a context of each container of the plurality of containers,
• wherein lighting the containers is carried out with a diffuser interposed between the illuminator and the collimator, wherein the diffuser defines a first surface directed towards the illuminator, and a second surface directed towards the collimator and diffuses the light rays that are coming from the illuminator and are directed towards the collimator, wherein collimated light rays are emitted by a lighting surface facing the sector of the path and whose inclination is less than a critical angle relative to corresponding planes which are parallel to a longitudinal direction defined by the longitudinal axes of the containers and at right angles to the lighting surface.

A labelling machine for containers for containing a liquid, each of the containers being elongate along a respective longitudinal axis and having a seam lying in a seam plane containing the longitudinal axis, wherein the machine comprises:

• a carousel which rotates about a central axis of rotation;
• a plurality of supporting elements, rotating about respective supporting axes and configured to support the containers in rotation about the respective supporting axes which operatively coincide with the longitudinal axes of the containers, the supporting elements being integral with the carousel to transport the containers along a predetermined path in rotation about the central axis of rotation;
• a plurality of actuators mounted on the carousel and connected to respective supporting elements to move them about the respective supporting axes;
• an optical inspection device having an illuminator to light at least one sector of the path, at least one camera to capture one or more images of the containers supported by the supporting elements and positioned in the sector, and a processing unit configured to process the images in order to identify the position of the respective seams on the containers,
• wherein the illuminator of the optical inspection device comprises:
• a light generator defining a light emitting surface;
• a collimator, interposed between the light generator and the carousel, defining a lighting surface which faces towards the sector of the path, and configured, for light rays generated by the light generator and incident upon the collimator, to block a portion of light the rays having an inclination that is greater than a critical angle relative to corresponding planes which are parallel to the supporting axes and at right angles to the collimator at the respective points of incidence of the incident light rays, wherein the collimator and the light generator are spaced from each other;
• and
• a diffuser, which is interposed between the light generator and the collimator, that defines a first surface directed towards the light emitting surface, and a second surface directed towards the lighting surface, in order to diffuse the light rays coming from the light generator and directed towards the collimator,
• wherein the lighting surface has a first extension along a first direction parallel to the central axis of rotation and a second extension positioned along a trajectory which is in turn positioned around the sector of the path followed by the containers, wherein the trajectory along which the second extension of the lighting surface is positioned is such that the lighting surface surrounds the sector of the path, and wherein a plurality of snapshots is taken, by the at least one camera, of each container of the containers, which is transiting in the sector of the path.