In the exemplary embodiment shown in FIG 1, the relief opening is connected with a return line 41 that leads to pressure medium reservoir 39, and {HEAD ~ a 2/2 way magnetic valve} 42 having a spring return mechanism is used as {TAIL ~ shutoff valve} 40 
In the exemplary embodiment shown in FIG 1 , the relief opening is connected with a return line 41 that leads to pressure medium reservoir 39 , and { HEAD ~ a 2/2 way magnetic valve } 42 having a spring return mechanism is used as { TAIL ~ shutoff valve } 40
OTH OTH OTH OTH OTH 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 HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH