Patent ID: 7541556

Claim:
An apparatus for checking the quality of preforms ( 10 ) each having a body made of plastics material having an internal cavity ( 12 ) communicating with the exterior through an end opening ( 14 ) of the body, the apparatus comprising: a conveyor device ( 20 ) for transporting the preforms ( 10 ) along a predetermined path, an optical device ( 22 ) disposed along the path and suitable for forming an image of each of the preforms ( 10 ), a pneumatic device ( 24 ) disposed along the path and suitable for putting the internal cavity ( 12 ) of each of the preforms ( 10 ) under partial vacuum for a predetermined period of time, an electronic control unit ( 28 ) suitable for comparing the images of the preforms ( 10 ) with a standard reference image and/or for checking whether the value of the partial vacuum remains unchanged during the said period of time, a selector device ( 26 ) disposed along the path and capable of separating the preforms ( 10 ) on the basis of the result of the comparison and/or checking operations performed by the control unit ( 28 ), a carousel ( 76 ) mounted for rotating about its central axis ( 50 ) and supporting on its periphery a plurality of tubular rods ( 78 ) mounted so as to be movable along axes parallel to the axis ( 50 ), each rod ( 78 ) having a longitudinal internal cavity ( 80 ), a lower end provided with a closure element ( 82 ) with a protuberance ( 84 ) with a rounded head having a through-hole ( 86 ) which is connected to the cavity ( 80 ) and with which a pressure sensor ( 88 ) is associated, and an upper open end ( 90 ) which is connected to suction means ( 94 ) and in which a pin ( 96 ) projects radially inwardly from the lateral surface of each rod ( 78 ) and extends into a corresponding groove ( 98 ) formed on the outer surface of a stationary cylindrical body ( 100 ) mounted coaxially around the axis ( 50 ) of the carousel ( 76 ).