| 摘要 |
For manufacturing cross bottom valve sacks, the ends of continuously transported tubular sections are opened out with the formation of so-called "bottom squares" with triangular corner folds lying opposite each other. A valve leaf or a valve tube is tacked onto one side of an opened-out bottom square in such a way that, after the side folds of the opened-out bottom have been folded-in with a mutual overlap, the leaf forms a valve tube leading into the inside of the sack, and with its outer end freely accessible at one side of the sack bottom. For checking the correct position of the valve leaves or of the valve tube, the valve leaf or the valve tube, or the zone of the corner fold, covered thereby when the leaf is tacked in its correct position, is provided with a mark that can be registered by a photocell device fixed to the frame. The photocell device is activated by a reference pulse when, in the manufacturing installation, the sack bottom has reached its predetermined position to be checked. Sacks with an incorrect position of their valve tubes or leaves are eliminated. |
