This invention is concerned with the final stage of the hot rolling of metal strip, that is, after the strip leaves the last stand of the rolling mill. At this stage, the hot metal strip issuing from the last stand passes along a roller table where it is supported as it moves in the direction of its length. A pair of pinch rolls serve to divert the strip from the roller table to a downcoiler where it is coiled. It is also known for a strip leveller to be positioned at the exit of a hot strip mill. The leveller consists of first and second sets of parallel spaced apart rollers with the rollers of one set being positioned in inter eshing relation with the rollers of the other set. The strip leaving the mill is threaded through the leveller between the intermeshing sets of rollers and, when the head end of the strip has been taken up by the downcoiler, tension is applied to the strip and, as it passes through the roller leveller, the strip is subjected to reverse flexing to thereby improve the shape of the strip.

When the strip is leaving the last stand of the rolling mill at a relatively modest speed, it can be threaded through the intermeshing rollers of the roller leveller with not too much difficulty but, as rolling speeds increase, it becomes increasingly difficult to thread the strip and cobbles form at the

roller leveller.

The present invention is characterised in that the roller leveller comprises first and second sets of parallel spaced apart rollers, one of said sets being able to move to a non-intermeshing position with the rollers of the other set.

In use, the two sets of rollers are moved such that they are in non-intermeshing relation and the head end of the strip leaving the last stand passes without hindrance between the two sets of rollers and is eventually taken up by the downcoiler. As soon as tension is brought into the strip, the one set of rollers is moved to its working position where the rollers of that set are intermeshed with the rollers of the other set and by doing so causes the strip to pass around part of the periphery of each roller thereby providing reverse bending to the strip as it passes through the leveller.

The roller leveller may be located upstream ot the pair of pinch rolls which divert the strip from the roller table to the downcoiler, or the roller leveller may be positioned between the pair of pinch rolls and the coiler. There is additional advantage in making the roller leveller in two parts, one of which is located upstream of the pair of pinch rolls and the other between the pair of pinch rolls and the downcoiler.

Another problem which exists in the final

stage of the hot rolling of metal strip is that the strip, moving in the direction of its length, tends to wander laterally and this makes it very difficult to produce good straight-sided coils at the downcoiler.

According to another embodiment of the invention, means are provided for steering the strip laterally relative to its direction of movement so that the strip follows a predetermined path as it enters the downcoiler thereby producing good straight-sided coils. The strip steering means may comprise a pair of steerable rolls located upstream of the pinch rolls, the pinch rolls themselves may be made steerable, or the roller leveller may be made steerable, in which case the leveller may comprise a sub-base, a frame pivotally mounted on the sub-base and carrying one of the sets of rollers, support means pivotally mounted on the frame and carrying the second set of rollers, means for pivoting the support means with respect to the frame and means for pivoting the frame with respect to the sub-base.

In order that the invention may be more readily understood, it will now be described, by way of example only, with reference to the accompanying drawings, in which:-

Figure 1 is a diagrammatic elevation of apparatus in accordance with one embodiment of the invention;

Figure 2 is a diagrammatic elevation of

apparatus in accordance with a second embodiment of the invention;

Figures 3, 4 and 5 are diagramamatic side elevation, plan and end elevation, respectively, of a preferred form of roller leveller; and

Figure 6 is a diagram showing the operation of the leveller of Figures 3 to 5.

Referring to Figure 1, a pair of steering pinch rolls 1 are shown downstream of the last stand of a hot strip mill. A roller leveller 3 is positioned between the pinch rolls 1 and a pair of turn-down pinch rolls 5. A coiler is located downstream of the turn¬ down pinch rolls. Rolls 9 are the lower rolls of the roller 3 leveller and rolls 11 the upper rolls. Rolls 13 are the normal run-out table conveyor rolls. The upper rolls of the leveller 3 are mounted on a pivoting frame 15 which is pivoted around a pin 17.

In use, the steering pinch rolls 1 and leveller 3 are initially open in a retracted position so that the head end of the strip 8 leaving the hot mill can pass freely into the turn-down pinch rolls 5 and to the coiler 7. Side guides are positioned according to strip width to help guide the strip into the pinch rolls and coiler. (These side guides are not shown in the attached sketches for sake of clarity). As soon as coiling starts and tension is established in the strip, the steering pinch rolls are brought into their closed working position when they

begin to steer the strip and hold it on to the mill centre-line and simultaneously the strip side guides are retracted away from the strip. Simultaneously, or shortly afterwards, the upper rolls of the leveller are also brought into engagement with the strip at positions between the rollers of the lower set. After this has happened, the remainder of the strip continues to pass through the steering rolls and leveller until it is coiled. Before the head end of the next strip comes along, the steering rolls and leveller are again moved to their retracted position.

In the Figure 2 arrangement, the roller leveller 19, comprising upper rolls 20 and lower rolls 21, is positioned downstream of the turn-down pinch rolls 5 and upstream of the coiler 7. The pinch rolls 5 may also be made to steer the strip 8.

Once coiling starts, the strip 8 is subjected to a high tension which helps the flattening process which takes place at the leveller. When the tail end of the strip leaves the mill, strip tension in the Figure 1 arrangement falls to a fairly low value and the flattening process is not so effective. However, strip tension can be maintained in the Figure 2 arrangement between the pinch rolls 5 and the coiler 7 because the drive to pinch rolls 5 and the drive to coiler 7 can maintain this tension. The levelling process which takes place at rolls 20 and 21 is, therefore, effective more or less throughout the whole

length of the strip. Rolls 20 and 21 would normally be held in a retracted position until the head end of the strip has started coiling and then rolls 20 and 21 would be brought into engagement with the strip.

The roller leveller may also be used to steer the strip, in which case the pinch rolls 1 shown in Figures 1 and 2 are not required.

Referring to Figures 3 to 5, the upper rolls 30 are mounted in a support 32 which, in turn, is mounted on pivoting arms 34. These arms are pivoted at 35 to a frame 36 which comprises side plates 37 and base 38. The lower rolls 40 are also mounted on the base 38. The frame 36 is mounted on a sub-base 41 with a pivot pin 42 between them. A clevis 43 is attached to the frame 36 and a piston-cylinder device 44 is connected to the clevis.

In use, the upper rolls of the leveller are retracted and strip side guides are put into position. As soon as the head end of the strip has passed by, and coiling has commenced, the upper rolls of the leveller are brought into engagement with the strip at positions between the lower rolls for flattening and also to steer the strip.

Figure 6 shows the position of the lower rolls when the entire leveller unit has been pivoted to a small angle 0 in relation to the centre-line of the mill. In this position, the leveller rolls will cause the strip to begin to move sideways and this is the

steering action caused by pivoting the leveller. Sensors 50 (Figure 1) are used to detect the position of the strip in relation to the centre-line of the mill and, if the strip moves off-centre, the sensors send an error signal to a control unit which controls the piston-cylinder device 44. This device causes the leveller to be pivoted about the pivot 42 so that the rolls steer the strip back on to its correct position with respect to the centre-line of the mill.