Device for controlling the travel distance of a chisel in a feeding system for an aluminium production electrolytic cell

Device for controlling the travel distance of a chisel (13) for a feeding system (12) for an electrolytic cell (1) designed for aluminium production, the said cell (1) comprising an electrolytic bath (4) covered with a crust (5), the chisel (13) being carried by a rod (14) fixed to the rod of an actuator (15) controlling vertical displacement of the chisel between a high position in which it is above the crust (5) and a low position in which the crust (5) is perforated and in which contact is made with the bath (4), the device (11) comprising means of detecting electrical contact between the chisel (13) and the bath (4), these means comprising an electrical circuit (19) capable of making an electrical measurement between the chisel (13) and a point (20) in the cell used as an electrical reference, and taking immediate action on the actuator to cause vertical upwards displacement of the chisel when a predetermined value of an electrical measurement is reached, characterised in that the said electrical circuit (19) is connected to the chisel (13), to the rod (14) of the chisel (13) or to the actuator rod through connecting means capable of creating a point contact (24) at at least one point between the circuit (19) and the chisel (13), the rod (14) of the chisel (13) or the actuator rod (17), these connecting means (23) being acted upon by elastic means (25) pushing them towards the chisel, the chisel (13) rod (14) or the actuator rod (17) respectively.