Method of and device for reducing the static friction between a reel and a coil
The invention relates to a method of releasing a reel awe, which is hydraulically restrained by a self-locking effect by means of inwardly located wedge surfaces of expansion elements. Removal of a coil from a reel awe is achieved, without problems, by lifting off the self-locking effect of the expansion elements at least partially or completely by applying longitudinal vibrations acting in an axial direction. The invention also relates to a correspondingly formed device.
1. A method of reducing static friction between a reel mandrel and a strip wound thereon during unwinding of the strip, the reel mandrel being restrained by self-locking effect produced by inwardly located wedge surfaces of a plurality of axially displaceable expansion elements arranged in a row inside the mandrel, the method comprising the step of providing a vibrator at an end of the reel mandrel and including an axially reciprocating body; and passing fluid through the vibrator for exciting the reciprocating body to apply longitudinal vibrations to the reel mandrel in an axial direction of the reel mandrel.
2. The method according to claim 1 , wherein the vibration applying step includes applying vibrations having different frequencies.
3. A reel assembly, comprising a reel mandrel for winding up a strip; a plurality of expansion elements located in a row inside the mandrel and having wedge surfaces for restraining the mandrel as a result of a self-locking effect between the wedge surfaces of the expansion elements; and a vibrator provided at an end of the reel mandrel and having means providing for flow of fluid through the vibrator, and a body axially reciprocating in response to flow of the fluid through the vibrator for applying longitudinal vibrations to the mandrel in the axial direction of the mandrel.
4. The reel assembly according to claim 3 , wherein the vibrator is formed as a pneumatic turbovibrator or a pneumatic impact vibrator.