Pipe breakage control valve device

A hose rupture control valve unit (200) comprising:

• a poppet valve member (5) slidably disposed within a housing (3) between a supply/drain port (102a) of a hydraulic cylinder (102) and a hydraulic hose (105), said housing (3) being provided with a cylinder connection chamber (8) connected to said supply/drain port, a hose connection chamber (9) connected to-said hydraulic hose, and a back pressure chamber (10), said poppet valve member serving as a main valve for selectively cutting off and establishing communication between said cylinder connection chamber and said hose connection chamber;
• and
• a spool valve member (6) disposed in pilot passages (15a, 15b) connecting said back pressure chamber and said hose connection chamber, and operated by the external signal to selectively cut off and establish communication through said pilot passages,
• said poppet valve member having throttle passages (50a, 50b, 51) for communicating said cylinder connection chamber and said back pressure chamber with each other,
• wherein said hose rupture control valve unit further comprises pressure control means (39;
• 40, 41) for preventing a pressure from being generated in said back pressure chamber (10) to such an extent as impeding opening of said poppet valve member (5) when a hydraulic fluid is introduced from said hydraulic hose (105) to said hose connection chamber (9) before said spool valve member (6) is closed.