To energize each of a linkage holding part for holding a linking member at an initial position and a lower door locking part to be engaged with a lower door by a single energizing means.

First locking pawls 31 and 32 are assembled through a bracket 41 to the rear surface of a holding frame 7 constituting an exchange unit 3. The first locking pawl 31 is engaged with the first bracket 60 of a front surface door 6, and the first locking pawl 32 is engaged with the first bracket 61. The linking member 35 is moved by turning a key 55 inserted to a key cylinder 36 and the engagement of the first locking pawls 31 and 32, and the first brackets 60 and 61 is released. The abutting piece 38a of the holding member 38 is abutted to the pressurizing surface 35g of the linking member 35. The locking pawls 39c and 39d of a locking member 39 are engaged with the opening 66a of a third bracket 66 formed on the rear surface of the lower door 22. One end of a third coil spring 58 is attached to the attaching piece 38b of the holding member 38, and the other end is attached to the attaching piece 39f of the locking member 39.