throttle free region of the annular groove 2 which has the maximum annular gap for unimpeded throughflow to reduce the flow resistance the surface area of the magnet armature 1 is provided with at least one longitudinal groove 10 which extends from the upper guide collar 8 via the annular groove 2 and the oblique shoulder 9 to the lower end facing the valve closing member not depicted of the magnet armature 1 so that the vertical throughflow of the longitudinal groove 10 takes place directly as free of deflection as possible as a function of the size of the annular gap 14 in each case released by the throttle disk 4 as may be gathered from the previous description and the drawings the two end faces on the throttle disk 4 are acted upon hydraulically in each case opposite to the lifting direction of the magnet armature 1 so that the action upon the throttle disk 4 or the lifting movement of the latter always takes place opposite to the lifting movement of the magnet armature 1 correspondingly in fig1 3 as a result of the hydraulic action upon the upper end face of the throttle disk 4 opposite to the upward movement of the magnet armature 1 the throttle disk 4 remains in the lower position at the housing stop 5 since the pressure medium is displaced out of the interspace 13 in the direction of the housing stop 5 whereas in fig4 and 5 after the interruption in electromagnetic.