Machine for attaching a tag to an infusion bag using an intermediate knotted thread

The present invention relates to machines for the automatic production of filter bags containing a product for infusion, such as tea, camomile or other similar products, the filter bags being made of filter paper, folded and closed with a knotted thread which connects them to the pick-up tag. An improved machine () for making filter bags () containing a product for infusion, with a pick-up tag () connected to the top () of the filter bag () by an intermediate thread (), comprises a wheel () which rotates with a stepping motion about its own axis of rotation () and is equipped with grippers () which are brought into contact with a series of operating stations, comprising at least one station () for folding a tubular semi-finished product () containing the product for infusion, and at least one station () for knotting the thread (). The machine () has thread () feed means () which operate on the thread () fed between consecutive pairs of the grippers () along the edge of the wheel () so as to prevent it from sliding backwards. The thread () knotting station () is equipped with needles () which have a first and second eye () positioned at different distances from the point. The needles () are moved in such a way as to pick up the thread () with the second eye (), forming a loop () in which the thread () is associated with the first eye (), interceptor elements () being moved in time with the needles () so that they passe through the first eye (), pushing a section of thread () through the loop (). The invention also relates to a method for knotting the thread ().