Method and apparatus for detecting edge cracks

Edge crack detector apparatus for detecting cracks on an edge of a travelling product, such as a continuous paper web, and the like, said detector apparatus comprising:

• an air-purged housing, said air-purged housing comprising, at least,
• an inner air chamber, said inner air chamber being relatively enclosed,
• an air receipt port defining a first opening through said housing into said inner air chamber,
• a first air delivery port defining a second opening through said housing into said inner air chamber, wherein said first air delivery port is positioned to direct air at a first surface of a travelling product, and
• a second air delivery port defining a third opening through said housing into said inner air chamber, wherein said second air delivery port is positioned to direct air at a second opposing surface of the travelling product,
• a passageway through which at least a portion of the travelling product may continuously travel,
• wherein said first air delivery port is displaced from said second air delivery port along a direction parallel to the direction of travel of the travelling product, whereby air flowing through said first air delivery port and air flowing through said second air delivery port exert relatively oppositely directed forces on adjacent portions of a travelling product sufficient to separate non-separated cracks in the portions of travelling product located within the passageway;
• and
• an optical sensor comprising, at least,
• an optical signal emitter connected to said air-purged housing and located, at least partially, within said inner air chamber so that air flowing through said inner air chamber flows across said optical signal emitter and so that light emitted from said optical signal emitter travels through said first air delivery port in a direction having a directional component which is parallel to the travelling direction of the travelling product, and
• an optical signal receiver connected to said air purged housing and located, at least partially, within said inner air chamber so that air flowing through said inner air chamber flows across said optical signal receiver and so that light received by said optical signal receiver travels through said second air delivery port.

Edge crack detector apparatus for detecting cracks on an edge of a travelling product, such as a continuous paper web, and the like, movable along a product path, said detector apparatus comprising:

• a first air means for directing air toward a first surface of a travelling product;
• a second air means for directing air toward a second opposing surface of the travelling product, wherein said second air means is displaced from said first air means along a direction parallel to the direction of travel of the travelling product;
• an optical signal emitter means for directing optical signals toward the first surface of the travelling product;
• and
• an optical signal receiver means located across a product path from said optical signal emitter means for receiving optical signals emitted from said optical signal emitter means.

Method of detecting cracks on an edge of a product travelling in a travelling direction, said method comprising the steps of:

• directing a first stream of air across an emission surface of an optical signal emitter of an optical signal device;
• directing the first stream of air in a first direction toward a first contact area on a first surface of a travelling product;
• directing a second stream of air across a receiving surface of an optical signal receiver of the optical signal device;
• directing the second stream of air in a second direction toward a second contact area on a second surface of the travelling product, wherein the first surface and second surface define opposite sides of the travelling product, and wherein the first contact area and the second contact area are displaced from one another along the travelling direction;
• transmitting optical signals from the optical signal emitter toward the travelling product;
• and
• receiving the optical signals at the optical signal receiver when a crack in the travelling product passes between the optical signal emitter and the optical signal receiver.

Method of detecting cracks on an edge of a product travelling in a travelling direction, said method comprising the steps of:

• locating a sensing unit at an edge of a travelling product, wherein the sensing unit includes a housing with a viewing aperture and an optical transceiver located inside the housing and over the viewing aperture;
• directing a stream of air across the optical transceiver to maintain cleanliness of the transceiver by purging all space between the optical transceiver and the viewing aperture;
• further directing the stream of air toward a travelling product to separate edge cracks;
• transmitting optical signals from the optical transceiver toward the travelling product to sense edge cracks;
• and
• tracking the edge of the travelling product by generating edge-sensing signals which indicate proximity to the edge of the travelling product, and moving the optical transceiver in response to the edge-sensing signals.