Device and method for severing a thread

Abstract

The invention relates to a device ( 1 ) for severing a thread that comprises two blades ( 2, 3 ). An electric drive ( 4 ) enables said blades to be moved counter to the action of leaf springs ( 6, 7; 9, 10 ) and into a ready position, from which the blades can be moved back by means of the force of the leaf springs in order to execute a severing process.

1 . A device ( 1 ) for severing a thread (A), which has two blades ( 2 ,  3 ) at least one of which is movable relative to the other by means of an electric drive ( 4 ), characterized in that the at least one movable blade ( 2 ,  3 ) is movable by the drive ( 4 ) counter to the action of at least one spring element ( 6 ,  7 ;  9 ,  10 ) into a ready position from which, by means of the force of the at least one spring element, it can be moved back again for executing a severing operation.  
   
   
       2 . The device of  claim 1 , characterized in that both blades ( 2 ,  3 ) can be moved into a ready position with contrary motion by means of electric drives ( 4 ) and can be moved back again by means of spring elements ( 6 ,  7 ;  9 ,  10 ).  
   
   
       3 . The device of  claim 1 , characterized in that the blade or blades ( 2 ,  3 ) are each retained by respective pairs of leaf springs ( 6 ,  7 ;  9 ,  10 ), which are oriented transversely to the direction of motion of the associated blade ( 2 ,  3 ) and are disposed spaced apart from and parallel to one another.  
   
   
       4 . The device of  claim 1 , characterized in that the blade or blades ( 2 ,  3 ) are connected to an armature ( 5 ,  8 ) which contains at least one permanent magnet ( 24 ,  25 ;  26 ,  27 ) and with which an electromagnet ( 19 ,  20 ,  21 ) is associated.  
   
   
       5 . The device of  claim 4 , characterized in that the armature ( 5 ,  8 ) includes two permanent magnets ( 24 ,  25 ;  26 ,  27 ), which contact one another with unlike poles.  
   
   
       6 . The device of  claim 4 , characterized in that both blades ( 2 ,  3 ) are provided with armatures ( 5 ,  8 ), whose permanent magnets ( 24 ,  25 ;  26 ,  27 ) are disposed such that they face one another with like poles in the ready position and with unlike poles in the severing position.  
   
   
       7 . The device of  claim 1 , characterized in that the length of the permanent magnets ( 24 ,  25 ;  26 ,  27 ) of the armatures ( 5 ,  8 ) in the direction of motion of the blades ( 2 ,  3 ) approximately equals to the magnitude of the relative motion between the blades.  
   
   
       8 . The device of  claim 1 , characterized in that one common electromagnet ( 19 ,  20 ,  21 ) is provided for the armatures ( 5 ,  8 ) of both blades ( 2 ,  3 ); and that the permanent magnets ( 24 ,  25 ;  26 ,  27 ) of the two armatures ( 5 ,  8 ) are oriented in opposite directions.  
   
   
       9 . The device of  claim 1 , characterized in that the two units comprising a blade ( 2 ,  3 ), an armature ( 5 ,  8 ), and leaf springs ( 6 ,  7 ;  9 ,  10 ) are designed for different natural frequencies.  
   
   
       10 . The device of  claim 1 , characterized in that for a control unit ( 17 ) of the electric drive or drives ( 4 ), a CAN bus system is provided.  
   
   
       11 . A method for severing a thread (A) by means of two blades ( 2 ,  3 ), at least one of which is moved relative to the other by means of an electric drive ( 4 ), characterized in that the electric drive ( 4 ) moves the at least one blade ( 2 ,  3 ) into a ready position counter to spring force; and that this blade ( 2 ,  3 ), for executing a severing operation, is moved back again from the ready position at least by means of the spring force.  
   
   
       12 . The method of  claim 11 , characterized in that the electric drive ( 4 ) is activated while the associated blade ( 2 ,  3 ) is being moved back from the ready position by means of spring force.  
   
   
       13 . The method of  claim 11 , characterized in that the electric drive ( 4 ) brakes the associated blade ( 2 ,  3 ) during the motion back from the ready position, particularly after the severing operation has been performed.  
   
   
       14 . The method of  claim 11 , characterized in that a signal dependent on the motion of an armature ( 5 ,  8 ) of the electric drive ( 4 ) is formed, by means of which the course of motion of the associated blade ( 2 ,  3 ) is monitored.