| 摘要 |
A device on a drafting mechanism of a spinning room machine, for drafting one or more fibre slivers, comprising at least two roll pairs arranged one after another. The upper rolls are arranged to be pressed against the lower rolls by spring loading. At least one cylinder containing a piston 18 is arranged so as to be axially movable within the cylinder housing 9, from which a piston rod 19 extends towards the upper roll. A sensor arrangement 24, 25 is provided for determining the position of the piston, with a switching element connected to the piston. To allow self-adjusting lap recognition with a desired spacing of the switching element from the switch, there is arranged, between the switching element and the piston, a magneto rheological substance, such as a magnetorheological elastomer (MRE) 26, or fluid, which co-operates with an electromagnetic coil 27. The MRE is able to modify its viscoelastic properties when exposed to the field of the coil, which, when activated, hardens the MRE. If a lap starts to form around the rolls, the piston 18 presses against the MRE 26, which in turn presses the switching screw 25 upwards, triggering the sensor.
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