Fluid couplings.

The coupler is negative pressure distribution system, comprising a distributing assembly, wherein taking and cover is sealed the barrel or similar liquid container, and with the valve for controlling gas inlet, and a blocking device for liquid flows out. Assigns assembly and connection head with each other, the sealing to distribute component of the device for preventing liquid flows out independent. To distribute cover and connection head on the joint mechanism through the coupling pin head to distribute to the rotary for cover, layers are matched to each other. And a to prevent device for liquid flows out, is matched with the connection head and to distribute cover, such to prevent the device and connection head part of the liquid flows out with each other, thus of preventing device according the liquid flows out, to distribute cover and connection head can with the thread of each structure, or a certain angle fixing block joint part.