A charging installation of a shaft furnace typically comprises a stationary feed channel arranged vertically in the center of the furnace throat, centered on the vertical axis of the furnace, and a distribution spout for distributing the charged materials arriving via said channel in the furnace. In order to enable appropriate distribution of the charged material, the distribution spout may be rotated about said vertical axis and pivoted about a horizontal axis. To this end, the spout is typically mounted pivotably about said horizontal axis, in a shell mounted coaxially around said feed channel, and rotatably about the vertical axis. The spout is mounted pivotably in the shell by means of trunnions of a generally cylindrical shape with a horizontal axis, to which the spout is secured and which are mounted revolvably about said horizontal axis in bearings integral with the shell. In general, the shell is rotated and the spout pivoted by gear means located in an annular chamber surrounding the shell.
The spout is fixed on either side on radially inner ends, directed towards the vertical axis of the furnace, of the trunnions, which are driven pivotably by means of geared drive means located in said chamber surrounding the shell. Said drive means may act directly on the trunnions by meshing, or by means of arms or levers.
To ensure good operation of the spout, the latter must be joined integrally and rigidly to the trunnions. However, in particular to enable easy replacement of the spout, the latter is supported and fixed detachably to the trunnions.
To meet these two requirements of a rigid but nevertheless detachable connection, it is known to use a connection such as that illustrated in FIG. 1, where the spout 1 comprises towards its upper part fixing lugs 11 capable of engaging in receptacles 21 of a corresponding shape formed at the ends of the trunnions 2. It will be noted that the shapes of the lugs and of the receptacles are specifically designed to allow the lugs to engage in the receptacles, then, by relative pivoting, to apply the lugs at the bottom of the receptacles. Maintenance of this position is ensured by an immobilizing pin 3 which is removable to allow the spout lugs to be disengaged from the receptacles on the trunnions, but which has also to ensure that the lugs are mounted on the trunnions securely and without play.
Typically, the immobilizing pins comprise a cylindrical body mounted to slide and revolve in a bore formed in the trunnion and having an axis parallel to that of the trunnion, an eccentric nipple 31 formed at the end of the body located towards the spout, and rotation control and rotational locking means located at the opposite end of the pin body and accessible at the level of the outer, front end of the trunnion which is located in the annular chamber surrounding the shell. When the spout is put in place, once the lugs thereof have been positioned in the receptacles of the trunnions, the immobilizing pins are pushed axially into the bores in the trunnions until the eccentric nipples are inserted into holes formed to this end in the lugs of the spout. By pivoting the pins, and thanks to the eccentric nature of the nipples, the latter act on the lugs of the spout, pushing against the walls of the lug holes to push the latter into the bottom of their receptacles, so ensuring that the spout is mounted on the trunnions without play. To prevent the pin from being able to become disengaged by sliding axially, and to ensure also that the pin does not subsequently revolve during operation of the furnace, which could cause the spout to become detached, locking means are provided at the level of the opposite end of the pin from the nipple, to block any displacement of the pin both axially and in rotation. One particular problem is that rotational locking of the pin has to be ensured in various angular positions thereof, because this angular position is determined by cooperation of the eccentric nipple with the hole in the spout lug and, owing to the dimensional differences between the receptacles in the trunnion ends, the spout lugs, the nipples and the holes in which they engage, or indeed deformation or wear of these elements, said angular position of the pin, capable of ensuring correct immobilization of the spout, is variable from one instance of mounting to another, and/or must be capable of adjustment to ensure play-free maintenance of the assembly.
To respond to this issue, a known embodiment of these locking means consists of an arm secured to the end of the pin, which comprises at its end a screw and an adjusting and immobilizing nut, which makes it possible to immobilize said arm on the front end of the trunnion in various positions, thus immobilizing the pin in the desired position. In another embodiment, the arm is replaced by a flat lug which may be clamped on the front end of the trunnion in a plurality of positions.
One disadvantage of these systems for locking the immobilizing pins is that they take up a major part of the front end surface of the trunnion, while said surface is also occupied by the cooling duct connections formed in the trunnions for cooling the latter, as well optionally as the spout. Typically, these connections are additionally bulky because they comprise revolving joints, which are needed to join the pivoting trunnions to the stationary ducts for supplying cooling water. The result is that it is necessary to disassemble these revolving joints in order to access the locking means of the pins when it is necessary to act thereon, in particular when the spout is replaced. Consequently, in particular when a pressurized cooling system is used, it is then necessary to purge the circuit prior to disassembly, then to refill it. Errors may be made then and when the cooling system is being restarted. Furthermore, cooling of the trunnions is stopped during the entire spout replacement operation, while the trunnions remain exposed to the intense heat prevailing in the furnace.