The invention relates to a method and a plant for winding a ship into a coil and applies in particular to the winding of a steel band after hot rolling.
When exiting out of a hot band train, the steel band is carried generally on a roller table, towards one or several coiling machines situated at a certain distance downstream of the roller table, generally under it.
Upstream of the coiling machines, the band is driven by a clamping device, followed by guiding means which direct the band towards a rotary chuck whereon the band, driven by friction, is wound in superimposed turns.
For winding a new band, the head of the band is applied on the external face of the rotary chuck in order to be driven by friction downstream. Then, the band is guided by a curved bending plate so as to be bent while remaining applied on the chuck, along an angular sector which increases gradually, which enhances the friction driving effect. After one revolution, the head of the band passes below the internal face of the hand to form a second turn and so on. In order to keep the tension necessary for winding, the band is held upstream by a device including, usually, a deflecting roll and a pinch roll driven into rotation at an angular velocity slightly smaller than that of the chuck, wherein the band may thus be stretched along a theoretical winding plane tangent, upstream, to the deflecting roll, along a generatrix thereof, and, downstream, to the coil being winding. Usually, the chuck is retractable so as to reduce in diameter to enable the removal of the coil, once it has reached the requested diameter.
The document U.S. Pat. No. 2,918,226, for instance, describes a winding plant of such type including, downstream of a deflecting roll placed at the outlet of a roller table, a rotary chuck arranged inside a pit and associated with two winding assemblies, each comprising an application roll of the band on the cylindrical external face of the chuck and a curved bending plate for guiding the band during the winding process. In the arrangement of document U.S. Pat. No. 2,918,226, the assembly is placed on a supporting chassis mounted so that it is capable of being pivoted around an axis parallel to the axis of the chuck and actuated by a jack, so as to move between a spaced apart position and a working position for which the bending plate is substantially parallel to the external face of the chuck. On the other hand, the application roll is mounted itself on an auxiliary chassis hinged on the supporting chassis of the bending plate and pushed towards the chuck by a spring so as to exert an elastic force to apply the band on the chuck, along a pushing direction running through a back-up generatrix of the external face of the chuck and the axis thereof.
Moreover, the application roll can be driven into rotation around its axis in a reverse direction relative to the direction of rotation of the chuck, in order to apply, to the external face of the band, an additional driving friction force which is added to the main driving friction force exerted by the chuck on the internal face of the band.
At the beginning of the winding process, the head of the band may rest on the bending plate situated downstream of the application roll and is guided in the annular gap between the bending plate and the external face of the chuck so as to be winded around the chuck. After one revolution, the head of the band may run below the hand so as to form a second turn, the application roll, pushed by a spring, being capable to move apart slightly.
In a more developed embodiment described in document U.S. Pat. No. 3,587,274, an additional roll is mounted, upstream of the application roll and of the chuck, on a chassis hinged around an axis, in order to exert a pre-bending torque on the band.
Until now, such devices were satisfactory since they were used for winding steel bands with a relative small thickness, for instance ranging between 2 and 12 mm.
For such thicknesses, indeed, the band bends easily and may be guided in the annular gap provided between the chuck and the bending plate, so as to be applied on the cylindrical face of the chuck in order to be driven by friction.
However, it is now contemplated to use devices of such type for winding hot bands with increased thicknesses, up to for example 25 mm. Moreover, one may have to wind products with high elastic limits, for instance of the order of 370 MPa at the temperature of use.
Still, it has appeared that, for relatively high thicknesses, the usual arrangement of the type represented on FIG. 1 does not enable sufficient bending of the band, in particular at the beginning of its winding process.
At that time, indeed, the band is applied only on a small angular sector of the chuck, and the main driving force exerted by the chuck on the internal face of the band depends essentially of the pressure exerted by the application roll of the band to the chuck.
However, in the previous arrangements disclosed by the documents mentioned above, this pushing force, exerted by a spring system or an elastic stop, would be insufficient to enable the winding of a hot band which is relatively thick and rigid.