1. Field of the Invention
This invention relates to an auto-threading method and apparatus suited to receive film and transfer the film to a tentering machine (crosswise stretching machine) in a biaxial stretching line.
2. Description of the Prior Art
In general, the threading of band-like material such as film has hitherto been effected manually. This manual threading has to be done during a film-manufacturing operation, which leads to a highly dangerous situation. A velocity at which the film is manufactured has to be decreased to secure safety during the threading operation. This deteriorates the working efficiency. An additional drawback is that two or more workers are required. Immediately after the film is threaded, it cannot be connected but remains in a split state. In the meantime, a scrap process has to be performed at a stenter outlet. The split scrap films are non-uniformly discharged from the stenter outlet while being seized by the clips. Especially when manufacturing thick films, the films gather formlessly. It is required that the gathered films be released from the clips and then treated.
An apparatus disclosed to obviate the conventional defects described above is shown in FIGS. 10 to 12. Referring to these Figures, the numerals 03, 05 represent guide rolls; 04 a nip roll; 06, 07 draw-off rolls for drawing off the film; and 08, 09 guide plates, formed of a material exhibiting a small frictional coefficient, for guiding the film. An upper edge 010 of a cutter is attached to the front end of the guide plate 09 so that the upper part of the upper edge coincides with the upper face of the guide plate 09, or alternatively, the upper edge is separately fixed from the guide plate. Another guide plate 011 formed of the material exhibiting the small frictional coefficient is movable up and down with the aid of an air cylinder 013, wherein the rotational axis of the guide roll 03 serves as the center of movement for plate 011. A lower edge 012 of the cutter is adjustably secured to the top end of the other guide plate 011 so that the upper part of the lower edge coincides with the upper face of the other guide plate 011. A sprocket wheel 014 functions to drive a clip chain 018 and clips 02. A disk 015 pushes blades of the clips to bite the film. Reference numeral 016 denotes a shaft, and 017 a nut.
The film 01 is carried via the guide rolls 03, 05 to the draw-off rolls 06, 07 by some means, e.g., a carrier rope, wherein the film is drawn off. The air cylinder 013 is operated to move upwards toward the other guide plate 011. The film is cut off by the cutter fitted to the top end of the guide plate 011 in cooperation with the cutter of the guide plate 09. The film is held in such a position that the upper face of the other guide plate 011 coincides with the upper face of the guide plate 09, or the other guide plate 011 is positioned slightly higher than the plate 09.
Next, the film 01 fed by the guide roll 03 and the nip roll 04 passes between the guide plates 08, 09. The film 01 reaches the clips 02 and is caught by these clips, and then the normal operation begins. Thereafter, the air cylinder 013 reverts to its original position preparatory to film threading.
In the prior art apparatus depicted in FIGS. 10 to 12, the film 01 passes between the guide plates 08, 09 with the help of the guide roll 03 and the nip roll 04, and both side edges at the end of the film are caught by the clips 02. However, when the soft or incompletely smooth film passes between the guide plates 08, 09, the end thereof remains free. Hence, if the film is pushed from behind, the film is bent, or creases are formed. It is therefore difficult for the clips to properly uniformly catch the film.