supported on the collar face 36 is provided for the displacement of the first valve 8 also displacement of the second valve 27 into the open position depends on this movement after the switching shaft 10 has travelled the idling path or free travel relative to the actuation element the final position which is limited by the second abutment 39 can also provide a levelled flat portion portion subsequently connected to the circumference portion 37 to secure a definite position of the actuation element 5 fig6 shows a modified embodiment here the same parts which have been described in connection with the fig2 5 are provided with reference numerals which have been increased numerically by the number 100 compared to the parts of fig2 and 3 in respect to the description of these parts it is referred to the description of the embodiment of fig2 5 the deviations will be described in the following the difference between the embodiment of fig2 5 is that the second block housing 103 with its front face 132 abuts directly with the face 123 of the cover plate of the first block housing 101 a bore 46 is provided in the second block housing 103 to provide a gap for the sealing sleeve 117 an annular chamber 40 is provided to receive the sealing sleeve 117 during the displacement from the position shown in fig6 to an advanced projected position which for example corresponds to the position shown in connection with fig3 in fig7 and 8 an embodiment is.