In a development of the invention, the positioning unit is configured in the manner of an armature which is rigidly attached to {HEAD ~ the piston} and is axially displaceable in a specified manner by {TAIL ~ means} of a proportional magnet 
In a development of the invention , the positioning unit is configured in the manner of an armature which is rigidly attached to { HEAD ~ the piston } and is axially displaceable in a specified manner by { TAIL ~ means } of a proportional magnet
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH