PURPOSE: To carry out the automatic direct coupling and releasing operation by a method wherein a plurality of fitting members are radially abutted against or separate from both the flange parts of the receiving pipe of ready mixed concrete and of its feed pipe from outside with an actuator under the condition that both of the flange parts are brought into contact with each other coaxially.

CONSTITUTION: At the projected end part of a receiving pipe 2 of ready mixed concrete, which is projected outside at the under side of a secondary product form, a receiving side flange part 17 is provided. Further, at the tip surface of the feeding side flange 18 of a feed pipe 3 of ready mixed concrete, an annular packing groove 19 is provided so as to fit a U-cap packing 20 therein. When the flange parts 17 and 18 are set coaxially so as to bring their respective tip surfaces into contact with each other, a disc shape having a wedge-like outer periphery is formed with the slant surfaces of the flange parts 17 and 18. Fitting members 22, which fit from three outside directions of both the flanges 17 and 18 radially to both the flanges 17 and 18, are provided so as to be connected abuttingly against or separably from both the flanges 17 and 18 with the rods of cylinders 23. Accordingly, the attaching and detaching of both the flanges 17 and 18 can be automated.