Method and device for spreading fiber strands

Abstract

A method and a device for spreading a fiber strand to provide a strip-type fiber strand. In particular, the initial fiber strand is provided with an initial width and thickness, and is then spread to form the strip-type fiber strand having a greater final width and a smaller final thickness as compared to the initial width and thickness. The fiber strand consists of continuous multifilament fibers.

1 . A method for spreading a fiber strand with an initial width and with an initial thickness to a strip-type fiber strand with a greater final width and with a smaller final thickness, wherein the fiber strand consists of continuous multifilament fibers, comprising;
 moving the fiber strand from an unwinding unit to a winding unit in the longitudinal direction (x-direction); and   passing the fiber strand through a spreader station between the unwinding unit and the winding unit, while holding the fiber strand under an adjustable tension   wherein the fiber strand in the spreader station is placed under uniform tension during its entire passage;   wherein in the spreader station the fiber strand contacts at least one sonotrode and by means of vibrations introduced into the fiber strand from above and/or from below (z-direction) by a front-side contact surface of the sonotrode, the fiber strand is uniformly spread transverse to the longitudinal direction; and and   wherein the vibrations have a frequency is between 15 kHz and 80 kHz,   
     
     
         2 . The method according to  claim 1 , wherein the multifilament fibers of the fiber strand are surrounded by a release agent and a quantity ratio of multifilament fibers to the release agent in the strip-type fiber strand does not change with respect to the fiber strand prior to spreading. 
     
     
         3 . The method according to  claim 1 , wherein when fiber strands are made of tension-resistant fibers, the fibers strands are supplied at a work angle to a contact surface of the at least one sonotrode. 
     
     
         4 . The method according to  claim 1 , wherein the fiber strand, proceeding from the unwinding unit out to the winding unit, is moved in the fiber longitudinal direction at a speed of at least 20 m/min. 
     
     
         5 . The method according to  claim 1 , wherein the fiber strand, proceeding from the unwinding unit out to the spreader station, is moved continuously in an invariant plane (x-z-plane) deflected upward or downward in the fiber longitudinal direction, and does not undergo any lateral deflection transverse (y-direction) to the fiber longitudinal direction other than spreading. 
     
     
         6 . The method according to  claim 1 , wherein the strip-type fiber strand produced by the spreading attains an at least 2-fold greater final width in comparison to the initial width. 
     
     
         7 . The method according to  claim 1 , wherein several fiber strands are spread simultaneously and are combined into a common widely spread fiber strand. 
     
     
         8 . A device for spreading of a fiber strand with an initial width and with an initial thickness, into a strip-type fiber strand with a greater final width and with a lesser final thickness, wherein the fiber strand consists of continuous multifilament fibers, comprising:
 an unwinding device for the fiber strand for unwinding in the fiber longitudinal direction (x-direction):   a spreader station for lateral (y-direction) spreading of the fiber strand into the strip-type fiber strand;   a controllable tensioning device for uniform tensioning of the fiber strand in the fiber longitudinal direction during movement of the entire fiber strand through the spreader station; and   a winding device of the strip-type fiber strand;   wherein the spreader station contains at least one sonotrode for contacting and spreading of the fiber strand; and   wherein the sonotrode is configured to introduce along a front-side contact surface, vibrations at a frequency of between 15 kHz and 80 kHz from above and/or from below (z-direction) into the fiber strand.   
     
     
         9 . The device according to  claim 8 , wherein the front-side contact surface of the sonotrode has a width greater than the final width of the band strip-type fiber strand obtained by spreading. 
     
     
         10 . The device according to  claim 8 , wherein at least 2 sonotrodes are disposed in the spreader station, wherein two neighboring sonotrodes are arranged at a default spacing, and When in a default, are arranged with different alignment to each other, so that fiber strands of different characteristics can contact the sonotrodes with an adaptable looping. 
     
     
         11 . The device according to  claim 8 , wherein additional deflection rollers are arranged in front of and behind the spreader station to adjust an adjusted angle of the fiber strand to the contact surface of the sonotrode. 
     
     
         12 . The device according to  claim 8 , wherein the controllable tensioning device for uniform tensioning of the fiber strand consists of two dancing roller units with at least two rollers, wherein a front dancing roller unit is disposed in a direction of motion of the fiber strand in front of the spreader station, and a rear dancing roller unit is disposed behind the spreader station. 
     
     
         13 . The device according to  claim 8 , wherein a bandwidth limiter is provided which is disposed behind the spreader station in the direction of movement of the fiber strand for limiting and adjusting a consistent final width of the spread. 
     
     
         14 . The device according to  claim 8 , wherein for a continuous movement of the fiber strand in an invariant plane (x-z-plane) proceeding from the unwinding device out to the spreader station, the unwinding device comprises a rotatable unwinding spool which can be displaced transverse (y-direction) to the direction of movement of the fiber strand. 
     
     
         15 . The device according to  claim 14 , wherein the front dancing roller unit controls the rotational velocity of the unwinding spool and the winding device comprises a torque-driven winding spool. 
     
     
         16 . The device according to  claim 8 , wherein the spreader device is configured such that several fiber strands can pass through the spreader device side by side, and, a supply unit is further arranged in the direction of motion of the fiber strands behind the spreader device for combining of the individually spread fiber strands into a wide fiber strand. 
     
     
         17 . The method according to  claim 1  wherein the strip-type fiber strand produced by the spreading attains an at least 5-fold greater final width in comparison, to the initial width. 
     
     
         18 . The method according to  claim 1  wherein the strip-type fiber strand produced by the spreading attains a final width that is limited to a default value. 
     
     
         19 . The device according to  claim 16 , further comprising an additional spreader device for standardizing the wide fiber strand.