To enhance the coupling speed and accuracy of a half die by applying the constitution that a coupling stricture approaching a line for being coupled to the laterally positioned half die, and a reversal unit having an operation means, mounted on a periodical motion element and formed to be capable of following the travel of half die on the line at the same speed, are respectively arranged at both sides of the line.

The forward travel of an attached belt 22 and the motion of a line 10 are interlocked with each other for a reversal unit 20. When a reversal device 13 is turned on, the unit 20 is positioned off the line 10, together with coupling structural members 40 and 42. Then, a roller is pulled with a cam 32 for causing the coupling structural members 40 and 42 to travel toward the line 10 and to be coupled to openings 44 and 46. Also, a cam 66 reverses the coupling structure member 42 of the moving unit 20 coupled to a half die 12 by 180 degrees along the locus of a crank 52 with an arm via a follower roller 64, thereby stacking half dies 11 and 12 on top of each other, together with the coupling members 40 and 42. Furthermore, the unit 20 leaves the line 10 via a roller and a cam 32, and the coupling structural member 42 returns to an original position on the operation of the cam 66 and a roller 64.