1. A stator magnetic field source (20) generates a magnetic field (N', S') that penetrates the cylinder (12), and comprises a coil that is supplied with current of alternating polarity by a control unit (24) to reciprocate the piston (16) inside the cylinder.

Eine Statormagnetfeldquelle (20) erzeugt ein Magnetfeld (N', S'), das den Zylinder (12) durchdringt.