manner that the rotary arm 172 can be horizontally positioned as shown in fig1 or vertically positioned as shown in fig1 works w11 w14 are fixed on pallets p11 to p14 respectively but each pallet has no concave member 71 as the members shown in fig1 except the pallets p11 to p14 and the rotary arm 172 are substantially identical with the corresponding members shown in fig1 and 2 respectively the members in fig1 are indicated by the reference numerals corresponding to the members in fig1 and 2 referring to fig1 the rotary arm 172 formed in an elongated plate member is provided with hydraulic cylinders 600 620 the rod 640 of the hydraulic cylinder 600 and the rod 660 of the hydraulic cylinder 620 can extend along the opposite direction one another in the longitudinal direction of the rotary arm 172 the rods 640 660 are provided with connecting means 670 680 respectively each of the connecting means 670 680 is an electromagnet the pallet p12 can be electromagnetically connected to the connecting means 670 while the pallet p11 can be electromagnetically connected to the connecting means 680 the connecting means 670 680 may be designed to mechanically catch the pallet next an.