Installation for levelling a metal strip

An installation for levelling a metal strip (3) by advancing it along an undulating path in a levelling stand (10) associated with a plurality of rolls (2, 15, 16, 18) with narrowed ends which may be displaced axially in opposite directions. Narrowed sections (25) are provided at opposite ends of two active levelling rolls (23) (24), and the levelling unit (4) (5) formed by each active roll and associated carrying rollers is mounted on two horizontal beams sliding vertically and associated with jacks (39) (64) for adjusting the axial and vertical position of each levelling unit (4) (5).

FIELD OF THE INVENTION 
The invention relates to a process and an installation for levelling a 
metal strip which may be used especially for obtaining flat products 
without edge defects, in particular those which are caused by the fact 
that the properties, particularly mechanical or metallurgical properties, 
over a certain width at the edge of the strip are markedly different from 
those of the central section of the strip. 
BACKGROUND OF THE INVENTION 
In installations for producing metal products in a strip form, such as thin 
rolled sheet metal, the product is subjected, after rolling, galvanizing, 
tinning or another process, to a certain number of finishing operations, 
to eliminate certain defects. In particular, the strip is passed through a 
leveller stand which is intended to eliminate twisting caused by the fact 
that the metal fibers are not of a regular length over the width of the 
sheet metal. To this end, the sheet metal is advanced on rollers defining 
an undulating path and subjected to tension, so as to produce elongations 
by means of traction deflection. 
A leveller therefore generally consists of a levelling stand disposed 
between two tension blocks, one located at the entrance and one at the 
exit, within which stand are mounted a plurality of levelling rolls, the 
axes of which are disposed in a staggered arrangement with respect to one 
another on different levels, so as to define an undulating path. 
The levelling stand may also be combined with another device which is 
located upstream thereof and which has a different function such as, for 
example, a rolling stand called a "skin-pass" which effects a slight 
elongation. 
By way of example, a conventional type of leveller is represented 
diagrammatically in FIG. 1. The leveller conventionally comprises two 
tension blocks at the entrance 11 and at the exit 12 between which a 
levelling stand 10 is disposed. 
Each tension block 11 or 12 comprises a certain number of rollers 13 and 17 
which are intended to keep under tension the strip 3 that is being 
advanced and to confer on it an elongation by appropriate means. The 
levelling stand 10, disposed between the tension blocks, generally 
consists of two or four active levelling rolls 2 on which the strip 3, 
advancing in directions perpendicular to the axes of the rolls, is 
subjected to traction-deflection distortions in the elastoplastic range. 
To this end, the active rolls preferably have a very small diameter 
relative to their length, and for this reason each of the active rolls 2 
is generally placed either on two rollers 21, called intermediate rolls, 
which rest on three rows of back-up rolls, or directly on two rows of 
back-up rolls 22, all combinations being possible according to the 
specifications of the machine. Special stops are provided at the ends of 
the rolls to enable them to operate satisfactorily. The assembly 
consisting of an active roll and its carrying rollers is termed "levelling 
unit". 
The levelling unit or units may be followed by devices which are intended 
to correct a transverse crossbow of the strip or a longitudinal camber; 
the active rolls of these devices are called: anti-crossbow roll 15 and 
anti-camber roll 16. These two latter functions are sometimes combined. 
Deflector rollers 18, whose number depends on the arrangement of the 
machine, may be located at different places in order to cause the strip 3 
to follow a particular path when passing through the machine, or to 
perform other functions. 
The tangential speed of the rollers 17 of the exit block 12 is greater than 
that of the rollers 13 of the entrance block 11, so as to subject the 
strip to an adjustable elongation. Moreover, the positions of the 
levelling rolls 2, anti-crossbow rolls 15 and anti-camber rolls 16 are 
adjustable in height relative to the middle plane of advance of the strip, 
which thus follows a zig-zag path, which may be adjusted. The strip which 
is subjected to elongation and traction as it passes over each 
small-diameter active roll, and the adjustment in height of the active 
rolls, makes it possible to modify the distortion stress applied to the 
strip. The latter is thus distorted in the plastic range over each active 
roll, with a wrap angle, by undergoing an elongation, which confers on it 
the shape of a developable surface, each of the active rolls 14, 15 and 16 
performing its own role. 
In such installations, all the longitudinal fibers are brought to the same 
length in the plastic range and, for current materials, all defects in 
surface evenness, such as "long edges", "long centers", "pockets", etc., 
may be corrected. 
In some cases, in order to improve the effect of correcting the surface 
evenness, it has already been proposed to provide the ends of certain 
rolls over which the strip advances with narrowed sections whose diameter 
progressively decreases relative to that of the central section of the 
roll so that the path traveled is longer in the central area than at the 
edges. 
By thus causing paths to be traveled which have different lengths in the 
central area and at the edges of the strip which is subjected 
simultaneously to distortion in the elastoplastic range, elongations over 
the central area of the strip are increased during the levelling operation 
in a manner such that, after leaving the leveller, the fibers all have 
substantially the same length. 
The narrowed sections may be provided at both ends of one and the same roll 
whose central section, forming the working bed and normally having a 
constant diameter, covers the central area of the strip over a constant 
width, the areas of the two edges passing over the two narrowed ends. 
The result of this is that a roll of a specific profile may be suitable 
only for levelling strips whose width varies only to a small degree. Each 
roll is therefore given a width range and, when a strip of greater or 
smaller width than the set limits is to be processed, the roll must be 
replaced with another roll whose narrowed sections are separated from one 
another by the desired distance. 
It is thus necessary to have different levelling rolls with central roll 
sections of different lengths that each corresponding to a width range, 
which rolls are exchanged according to requirements. This has drawbacks 
due, in particular, to the time required for the exchange. 
In order to remedy this drawback, the use of rolls provided with a narrowed 
section at only one end has already been proposed, two successive rolls 
being equipped with narrowed sections located at opposite ends in a manner 
such that one edge of the strip passes over the narrowed section of one of 
the rolls, the other edge passing over the narrowed section of the other 
roll. By displacing the two rolls parallel to their axis and in opposite 
directions, on either side of the median longitudinal plane of the strip, 
it is possible to adjust the distance between the two narrowed sections 
according to the width of the strip. 
However, such an arrangement, which is attractive in principle, creates 
problems in practice. In fact, even if such an arrangement enables the 
positioning of the narrowed sections to be adjusted according to the width 
of the strip, it is necessary to retain the possibility of easily 
replacing the working rolls, for example in the event of wear. Thus, 
intervention on the machine leads to a stoppage or, in any case, a curbing 
of production, and it must therefore be possible to perform this as 
rapidly as possible given the productivity of current installations which 
permit strip advance speeds of the order of 800 m/min to be attained. 
Moreover, it is necessary to retain the possibility of adjusting the 
relative heights of the working rolls. 
For this reason, it is generally preferred to separate the functions and to 
provide narrowed ends not on the active levelling rolls but on other 
rolls, for example the deflecting rollers which are changed less often and 
whose axial positions are more easily adjusted. 
However, passage over the narrowed sections is more effective when the 
latter are provided on small diameter rolls such as the active roll, over 
which the strip is subjected to distortion in the plastic range. 
However, difficulties in production and installation are then encountered, 
the more so since there is generally a restricted space available and 
since it is often necessary to improve existing installations. 
SUMMARY OF THE INVENTION 
The object of the invention is to propose special arrangements which make 
if possible to provide narrowed sections on the active levelling rolls 
while retaining possibilities for adjusting the latter both in height and 
in the axial direction without substantially increasing the overall size 
of the levelling stand. 
According to the invention, the narrowed sections are therefore provided at 
opposite ends, respectively, of two asymmetrical active levelling rolls, 
each resting on carrying rollers, and the levelling units thereby formed 
by each active roll and the carrying rollers associated with the latter 
are each mounted, respectively, on an upper beam and a lower beam which 
are mounted so as to slide vertically on uprights of the housing of the 
levelling stand and are each associated (a) with height-adjusting means 
for adjusting the level of the corresponding active roll, and (b) with 
means for controlling the sliding of the whole levelling unit parallel to 
the axes of the rolls for adjusting the axial position of the narrowed 
section one each active roll relative to the axis of the strip. 
In a first embodiment of the invention, each asymmetrical roll is mounted 
with its supporting unit in a frame forming a case mounted so as to be 
axially movable on the corresponding supporting beam, and the means for 
adjusting the axial position of each roll consist of jacks resting on the 
case and on the corresponding beam, respectively. 
However, in a preferred embodiment of the invention, the two active 
asymmetrical rolls, which are each associated with a levelling unit, are 
fixed on an upper beam and on a lower beam, respectively, which are 
mounted so as to slide vertically on the uprights of the housing of the 
stand and are each borne by means of rollers on rails extending 
horizontally between the two uprights of the stand in a direction 
transverse to the axis of the strip, so as to allow the vertical 
displacement of the beam, the adjustment of the axial position of each 
asymmetrical roll being effected by transverse displacement of the 
corresponding beam on these supporting rails. 
In a particularly advantageously manner, the supporting rollers of the 
upper beam are mounted in a pair at each end of the beam on arms 
articulated about horizontal axes enabling the beam with the levelling 
unit to be towed into a working position, through the action of jacks, and 
the lifting of the beam into a raised position for disassembly. 
Moreover, each supporting beam of a levelling unit with asymmetrical rolls 
is associated with an axial adjustment device comprising a centering plate 
mounted so that it can slide perpendicularly to the beam on a carriage 
mounted so as to slide on slides extending between the two uprights of the 
housing parallel to the beam, it being possible for the end of the plate 
to engage in a guide groove provided on the beam in a vertical direction. 
By virtue of these arrangements and other features described in detai 
below, the different elements necessary for adjusting the active rolls in 
height and for the axial adjustment of the active rolls form a 
particularly compact assembly which may be housed in a restricted space, 
this feature being particularly advantageous in the case of small size 
machines and/or for adapting existing lines. 
Moreover, it is necessary to process on levelling machines metal strips 
which not only have defects of surface evenness but also different 
properties on the edges relative to the central section of the strip (for 
example, substantially different limits of elasticiity). This is the case, 
in particular, with steels known as "full hard". 
With such products having a behavior different from current products, the 
result may be that the final product has a slight residual edge defect 
caused by these differences in properties, although all the longitudinal 
fibers have been given the same length in the leveller. 
Such defects may also be corrected by virtue of the arrangements according 
to the invention which make it possible to effect an axial adjustment of 
quite a substantial extent and, moreover, to provide narrowed sections 
over a relatively great length at the end of each active roll, in a manner 
such that each narrowed section covers a lateral area of the strip of a 
width which is determined according to the defects to be corrected. 
It is thus possible to remedy the defects in homogeneity of the strip over 
its width, and particularly those which may be caused by the existence of 
markedly different properties at the edges of the strip relative to the 
central section. The invention also makes it possible to correct a defect 
caused by such a difference in properties, if necessary on only one edge. 
However, the invention may also be useful in the event that the strip, 
before levelling, has long edges such that it is not possible to correct 
them totally. In the text which follows, the term "defect" will therefore 
be used both for excessive long edges of the strip before levelling and 
for defects caused by different mechanical properties at the edges over a 
certain width relative to all the central section of the strip, it being 
understood that it is the correction of the effects of this latter type of 
defect which is particularly sought after.

DESCRIPTION OF PREFERRED EMBODIMENTS 
A conventional levelling installation has already been described above with 
reference to FIGS. 1 and 2; 
FIG. 3 shows diagrammatically in perspective the passage of the strip 3 
over two rolls 23, 24 held centered on their axes by means of end pieces 
27 and defining an undulating path. 
Two different active rolls, 23 and 24 respectively, of the stand are 
equipped with an asymmetrical profile, each roll being equipped with a 
narrowed section 25, 25' at only one of its ends and having a diameter 
which is substantially constant over the normal section 26 covering the 
greater part of its length, up to the other end. The narrowed sections 25, 
25' are located respectively at two opposite ends of the two rolls 23 and 
24, on either side of the longitudinal axis 30 of the strip, and the two 
rolls 23 and 24 may be displaced in opposite directions parallel to their 
axis according to the arrows (f) so as to adjust their axial positions so 
that each narrowed section 25, 25', respectively, is located perpendicular 
to one of the two edges 31, 31', respectively, of the strip 3. As shown in 
detail in FIG. 4, each narrowed section 25, 25' having a length a, it is 
possible axially to adjust the positions of the two rolls so that the 
diameter D of the roll progressively decreases from a line located at a 
distance L from the edge 31 of the strip 3. This latter therefore 
comprises two lateral areas 32, 32' of width L and L' passing over the 
narrowed sections 25 of the rolls 23 and 24 and framing a central area 33 
passing over the roll sections 26 of the two rolls, and it is possible, by 
acting individually on each of the rolls, to adjust the widths L, and L' 
respectively, of the two lateral areas 32, 32'. 
In FIG. 3, the narrowed sections 25 have a conical shape linked to the roll 
section 26 by a rounded section, but it would also be possible to provide 
a different profile, for example a parabolic or similar profile. 
FIG. 5 is a diagrammatic representation, by way of example, of a first 
embodiment of the invention. 
Each levelling roll 23, 24 may be located, with the corresponding 
supporting unit, in a frame 35 forming a case mounted so as to slide 
axially on a supporting beam 36 on which rests a means for controlling the 
axial displacement of the case, such as a jack 37. 
At least one of the two beams, the upper beam 36 and the lower beam 36' 
respectively, may be mounted so as to slide vertically in a housing 38 
under the action of jacks 39, making it possible to adjust the level in 
height of the roller and to separate the cases on either side of the plane 
of the strip 3, in a position for disassembly and reassembly. 
Thus the invention makes it possible not only to make precise adjustments 
to the width of the strip without exchanging the levelling rolls, but also 
to adjust the position of each edge of the strip over the narrowed section 
of the corresponding roll and, consequently, to cause a variation in 
length of the paths traveled over the lateral areas of the strip relative 
to the central section, by adjusting the relative positions of the 
narrowed sections 25 relative to the longitudinal axis of advance 30. 
It should be noted that the axial displacements of the two levelling rolls 
23, 24 do not have to be equal and it is therefore possible, if necessary, 
to vary the widths L and L' of the lateral areas whose path lengths are 
modified. 
Moreover, it is also posssible to act on the profile of the rolls, for 
example by modifying the ratio of the respective lengths of the narrowed 
section 25 relative to the cylindrical section 26 or even by giving the 
rollers a bulged shape over their entire length. 
It will therefore be seen that it is possible to make adjustments in a 
manner that is very adaptable to requirements, in particular for 
correcting defects due to the differences in properties in the different 
areas of the metal strip 3. 
In FIGS. 6, 7 and 8, a preferred embodiment of the installation according 
to the invention has been represented in greater detail by way of example. 
The asymmetrical rolls 23 and 24 form part of two levelling units 4 and 5 
which are fixed on an upper beam 41 and a lower beam 51, respectively, and 
which are mounted so as to slide transversely to the axis of advance in a 
housing 6 comprising, as may be seen in FIG. 6, two uprights 61 within 
which windows 62 are provided for the passage of the beams 41 and 51. 
In working position, the two beams 41 and 51 may also slide vertically 
along the guide surfaces 63 provided on the uprights 61 of the housing 6. 
Jacks 64 and 65 control the vertical displacements of the upper beam 41 
and of the lower beam 51, respectively. In the example represented, the 
jacks 64 and 65 are of the hydraulic and electro-mechanical type, but they 
could be of any other type. 
The upper beam 41 is borne by rollers 42 which run on rails 66 extending 
horizontally in the upper part of the frame 6. 
The connection between the beam 41 and the supporting rails 66 is achieved 
so as to permit the vertical sliding of the beam 41 in a working position 
under the action of jacks 64 and its return to the level of the rails 66 
in a disassembly position. 
For example, the rollers 42 may be mounted on sliding frames or on 
articulated arms of a length which is sufficient to permit the lowering of 
the levelling roll 24 in the working position represented in dotted lines 
in FIG. 6. 
Such a mobile assembly of the rollers relative to the beams is not 
indispensable for the beam 51, which may be simply raised by mechanical 
jacks 65, whose principal role is the correct positioning of the beam, the 
weight of all the equipment ensuring the return to a low position of the 
beam 51 which comes to rest on the horizontal rails 67 by means of rollers 
permitting the axial displacement of the beam 51. 
The lower beam may at time also be operated by a hydraulic jack which is 
added to the mechanical jacks 65 in order to permit rapid opening of the 
stand from below. 
It is therefore possible, when the units 4 and 5 are in a divergent 
position, to exchange, as usual, a unit by causing each beam 41, 51 to 
roll horizontally on the rails 66, 67, passing through the windows 62 of 
the uprights 61 of the frame 6. 
The horizontal displacement of each beam 41, 51 to bring it into a working 
position may be achieved by a mechanism of the jack, automotive carriage, 
winch, chain or other type (not shown). 
On the other hand, adjustment of the axial position of each levelling unit 
relative to the plane of symmetry P is preferably achieved by centering 
devices 7 mounted beside each beam 41,51 between the two uprights 61 of 
the frame 6. 
As may be seen in FIG. 8, each centering device 7 is borne by a carriage 8 
which slides along slides 81 extending between the two uprights 61 of the 
housing 6 parallel to the axes of the levelling rolls. A mechanical or 
hydraulic jack 82 resting on one of the uprights 61 makes it possible to 
adjust the position of the centering device 7 along the corresponding beam 
41. 
As may be seen in FIG. 6, a similar device 7' is associated with the lower 
beam 51. 
The centering device 7 (7') comprises a centering plate 71 (71') which is 
mounted so as to slide on the carriage 8 perpendicularly to the slides 81 
and to the axes of the rolls, and whose end 74 may engage in a groove 47 
provided on the beam 41 in a vertical direction. The transverse sliding 
movement of the plate 71 relative to the beam 41 is controlled by a 
retraction jack 72, the body and the rod of which are articulated, 
respectively, on the carriage 8 and on a fastening lug 73 solid with the 
centering plate 71. 
When positioning each beam 41 (51), the corresponding centering plate 71 
(71') is retracted by the jack 72 so as not to interfere with the passage 
of the beam (41) (51). 
The plate 71 is placed in position opposite the corresponding groove 47 by 
means of the jack 82, and by means of the jack 72 the plate is engaged in 
the groove. 
The jack 82 then makes it possible, by means of the plate 71, to adjust 
precisely the axial position of the beam 41 to position exactly the 
narrowed section of the levelling roll relative to the edge of the sheet 
metal. The carriage 8 is then held in this position by the jack 82, and 
the end 74 of the plate 71 forms a guide for the vertical displacement of 
the beam 41 under the action of jacks 64. 
The adjustment of the lower beam 51 is effected in the same manner by the 
centering device 7'. 
The arrangements shown in the drawings normally make it possible to effect 
the horizontal adjustment of two levelling units only when the stand is in 
"open" position, the two upper and lower beams being in a high position 
and in a low position, respectively, so that no load is applied on the 
rods of the jacks. 
However, axial adjustment could also be effected in working position by 
equipping the clamping jacks with retention devices and/or permitting the 
sliding of the beams. 
It is also possible automatically to control the position of the special 
rolls as a function of the width of the strip or of that of the lateral 
defects. The displacement of the rolls as a function of the width of the 
strip is in principle symmetrical, but the system could also be equipped 
so as to produce different axial displacements of the rolls. 
The order in which the two asymmetrical rolls are placed will be selected 
as a function of construction requirements and different desired strip 
paths. One may therefore also choose to apply this correction principle 
to, for example, two rolls located not on either side of the strip but on 
the same side relative to a surface of the strip. They also need not be 
directly adjacent. 
Moreover, adjustment of position may be performed whether or not the strip 
is engaged in the machine, and whether or not it is moving.