Machine for piercing a taphole for a shaft furnace

Machine for piercing a taphole for a shaft furnace, comprising:

• a mounting for supporting either a piercing rod or a drill bit, the said mounting comprising a front end which may be arranged facing the taphole and a rear end axially opposite the front end,
• a drilling apparatus with a coupling which is designed the receive and rotationally drive the drill bit, the said drilling apparatus being mounted so as to slide on the mounting,
• a driver mounted on the mounting so as to develop a traction force or thrust force respectively, parallel to the mounting,
• a clamp mounted on the mounting between the front end of the latter and the drilling apparatus and connected to the driver, the said clamp comprising a body which is traversed axially by a channel which has a diameter slightly greater than the rod and the drill bit, and movable jaws which are arranged around the channel so as to be able to grip the rear end of the rod engaged in the channel in order to transmit to it a large traction force when the clamp is moved in the direction of the rear end of the mounting,
• wherein the clamp can be moved by the said driver along the mounting over a length which corresponds approximately to the length of the rod, and wherein
• a key can be engaged in a housing in the body of the clamp so as to block the channel axially and to be able to transmit, to the rear end of the rod engaged in the channel, an axial thrust force when the clamp is moved in the direction of the front end of the mounting,
• and wherein the said key, when it is withdrawn from its housing, frees the channel in the clamp so as to be able to pass through this channel
• with the drill bit and to couple the latter to the coupling of the drilling apparatus located between the clamp and the rear end of the mounting,
• and wherein intermediate guides are mounted on the mount between the front end of the latter and the clamp, the said guides having, on the mounting, operating positions in which they surround the rod at several axially spaced-apart places during its insertion into the taphole blocked beforehand with the taphole clay, and parked positions in which they do not hinder the advance of the said clamp towards the front end of the mounting, and
• wherein these intermediate guides are capable of moving, as the clamp advances towards the front end of the mounting, from the said operating positions into the said parked positions.