| 摘要 |
A lever, pivoted intermediate its ends, rotatably mounts a roller at one end engaging the material being wound off a core. In one embodiment, the lever is spring biased in a direction to bias the roller against the material, and changes in the position of the opposite end of the lever are effective to adjust a potentiometer forming the control element of an asynchronous single phase variator. In another embodiment of the invention, the spring is omitted, and a pressure-resistance detector is mounted between the opposite end of the lever and a frame. In a third embodiment of the invention, the opposite end of the lever carriers a shutter cooperable with a photoelectric control, the lever being spring biased in this embodiment. The pressure-resistance detector can be substituted in the variator for the potentiometer. The variator controls the speed of an induction motor effecting angular displacement of the core, and the speed of the induction motor is controlled by micro-displacements of the lever carrying the roller engaging the material being wound off. The induction motor can be stopped substantially instantaneously, upon breaking of the material, by injection of a D.C. voltage into the induction motor.
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