| 摘要 |
<p>The invention relates to a welding device (10) for welding the opening (16) of a plastic bag (12) in order to seal same hermetically, which comprises: a lower jaw (18) and an upper jaw (20) between which the bag (12) is clamped; at least one heating wire (22); and means (30) for clamping the upper jaw (20) against the lower jaw (18) which comprise a plurality of magnetic elements (32) with permanent magnets, and in which each magnetic element (32) comprises a first stationary permanent magnet (34) and a second permanent magnet (36) which is mounted so as to be movable relative to the first permanent magnet (34) between a locking position in which the combination of the magnetic fields produced by the two permanent magnets (34, 36) produces a high-intensity magnetic field in the upper jaw (20) and a released position in which the combination of the magnetic fields produced by the two permanent magnets (34, 36) produces a low-intensity magnetic field in the upper jaw (20), allowing an operator easily to separate the two jaws after welding the bag.</p> |
