Drive device for locking and unlocking a lock with conditional opening

A drive device for locking a conditionally opening lock, the device comprising:

• motor means with a drive element;
• a transmission member (28) provided with first and second ends, a coupling surface disposed in the vicinity of the first end, the transmission member being pivotally mounted at the second end,
• a locking block connected mechanically to the motor means by means of the transmission member, this member being operable by the motor means to cause the block to occupy an active position, in which the block opposes the displacement of a bar, and an inactive position (P2) in which the block allows displacement of the bar;
• and
• elastic means allowing the locking block to be put under bias when the block is actuated by the motor means, towards the active position and when displacement of the block is impeded by the bar, wherein the elastic means are arranged between the drive element and the transmission member, the transmission member being connected to the locking block through a rod or link which is articulated to the locking block.