1. A releasing device for releasing a locking mechanism in a catching device which is intended to connect the wire with the inner core tube in wire line core drills in order to enable lifting and also lowering of the inner core tube, the locking mechanism having a gripper head connected with the wire, the gripper head being provided with a locking shoulder behind which a latch connected with the inner core tube is intended to engage and lock to perform said connection, characterized by a releasing sleeve which in its normal rest position is brought back a distance from the locking shoulder of the gripper head to release the locking shoulder, the releasing sleeve being retainable in this position by means of a positioning mechanism which is releasable by applying a predetermined pulling force to the wire, said pulling force having a direction away from the inner core tube and exceeding the weight of the inner core tube, the releasing sleeve upon such releasing of the positioning mechanism being provided to be displaced unobstructedly towards the gripper head and to engage the locking shoulder of the gripper head, thereby moving away the latch and said positioning mechanism including a torsion spring, one end of which is fastened to a gripper head rod attached to the gripper head, the releasing sleeve being slidably mounted on said rod, and the other end of which is fastened to the releasing sleeve, the upper end edge of the releasing spring is provided with a locking recess in which a positioning means attached to the gripper head rod is intended to be accommodated for the positioning of the releasing sleeve after same in its brought back position is rotated to provide the desired biasing of the torsion spring, an axially active compression spring is provided on the gripper head rod in order to retain the positioning means in fixed position in the recess and to give way for enabling the removal of the positioning means from the recess and thereby to unbias the torsion spring upon a wire pulLing force which is directed away from the inner core tube and which substantially exceeds the weight of the inner core tube.

2. A releasing device for releasing a locking mechanism in a catching device which is intended to connect the wire with the inner core tube in wire line core drills in order to enable lifting and also lowering of the inner core tube, the locking mechanism having a gripper head connected with the wire, the gripper head being provided with a locking shoulder behind which a latch connected with the inner core tube is intended to engage and lock to perform said connection, characterized by a releasing sleeve which in its normal rest position is brought back a distance from the locking shoulder of the gripper head to release the locking shoulder, the releasing sleeve being retainable in this position by means of a positioning mechanism which is releasable by applying a predetermined pulling force to the wire, said pulling force having a direction away from the inner core tube and exceeding the weight of the inner core tube, the releasing sleeve upon such releasing of the positioning mechanism being provided to be displaced unobstructedly towards the gripper head and to engage the locking shoulder of the gripper head, thereby moving away the latch and said positioning mechanism including an O-ring provided in a groove in the releasing sleeve and positioned in an inactive position by engagement in a shallow groove in a housing in which the wire is fastened, said O-ring giving way to enable the displacing of the sleeve towards the shoulder of the gripper head upon a certain wire pulling force which is directed away from the inner core tube and which substantially exceeds the weight of the inner core tube.