Spool driving and braking

In combination with a spool upon which elongated stock such as ribbon, wire, thread etc. is to be wound and from which the elongated stock is to be unwound;

• an electromagnetic device including an electromagnet and a cooperating armature, further including a yoke that is part of the electromagnet, the device is to be used selectively as a brake and as a clutch, the improvement comprising:
• a shaft connected to the electromagnet for rotation therewith, the spool being rotatably arranged around the shaft;
• means for connecting the armature to the spool for rotation with the spool, while permitting axial displacement of the armature relative to the spool;
• means defining a permanent, magnetically effective gap between said yoke and said armature to remain effective as a gap in the energized state of the electromagnet;
• means for applying a first, predetermined and relatively high voltage to the electromagnet so that positive coupling obtains between the electromagnet and the armature and therefore between said shaft as connected to the electromagnet;
• and the armature as being connected to the spool, whereby rotation of the shaft rotates the spool, and
• means for applying a second predetermined voltage, lower than the first voltage, to the electromagnet so that a brake force becomes effective between the electromagnet and the shaft on one hand, and the armature with the spool on the other hand.