Method of monitoring a telescopic bore rod

摘要

The method involves measuring the required holding force for the rotary drive holder (8). This is compared with the theoretical pulling force based on the weight of the tubes (2,6,7). This force starts with the total weight of the tubes and is successively reduced to the weight of at least a further tube in dependence on the stroke distance covered. A signal is generated when the measured holding force falls to a predetermined value below the force corresponding to the respective stroke distance. Independent claims also cover a protective device for a telescopic tube.