Mandrel monitor for cold pilger mills

A roll mandrel monitoring device in cold pilger mills with a coil which surrounds the rolled tube concentrically and is arranged on the delivery side after the rolling mill for detecting longitudinal movement of a coil core which is fastened inside the tube to a bar extending between the mandrel and coil coaxially to the tube. In order to achieve faster reaction times and accordingly to stop the rolling mill when the mandrel breaks, the bar is connected with the mandrel rod holding the mandrel so as to penetrate the mandrel concentrically and is constructed in the region of the mandrel as a tension bar which can be pretensioned against the end of the mandrel on the delivery side with the intermediary of an energy accumulator.