Rolling mill for sheet material

A rolling mill for the treatment of sheet material comprises two work rolls (1, 2) which define a nip between which a web of material (3) is passed for rolling. The work rolls (1,2) are offset in a horizontal direction relatively to back-up rolls (4,5), so that the plane containing the axes (A,A) extends parallel to but offset relative to the plane containing the axes (B,B) of the back-up rolls (4,5). Supporting devices (9) are associated with the work rolls (1,2) and support the work rolls in the direction opposite to that in which they are offset from the back up rolls. The supporting devices (9) comprise hydrostatic supporting elements (19,20,21) which are arranged parallel to the longitudinal axis (A) of the work rolls (1,2) and comprise hydrostatic pressure pockets (29) which face towards the surfaces being supported in each case and can be individually controllable. The work rolls (1,2) with the supporting devices (9) associated therewith can be arranged in the rolling mill stand for horizontal displacement generally parallel to the web of material (3).

BACKGROUND TO THE INVENTION 
The invention relates to rolling mills for sheet material normally in the 
form of a continuous band or web, in which two work rolls define a nip 
between which the material to be processed is guided. Such mills also 
usually include one or more back-up rolls associated with each work roll. 
In mills of the type to which the present invention relates, the plane 
containing the axes of the work rolls is offset relative to the plane 
containing the axes of the back-up rolls, and the work rolls are supported 
against the direction of offset from the back up rolls. 
Rolling mills of this kind, which are described for example in U.S. Pat. 
No. 4,059,976, have considerable advantages over the usual four-high 
arrangement wherein the axes of the work rolls and of the back-up rolls 
are situated in one vertical plane, particularly when thin metal sheeting 
is being rolled, such as thin aluminium foils. Where the foil thickness is 
for example 0.1 mm, owing to the elasticity of the system it is 
impossible, when deflection of the rolls occurs, to apply working pressure 
of a specific quality uniformly over the entirety of the roll gap. 
Supporting devices can counteract the elastic deflection phenomena of the 
roll system. In one known construction; e.g., in rolling mills produced 
under the name MKW (multipurpose cold rolling mill) by the German firm of 
Schloemann Siemag AG., a system of bearing rolls is provided which accepts 
the load of the work roll in the horizontal direction and with which the 
deflections of the work roll in the horizontal direction can also be 
corrected. In certain cases this can be done by preloading or by convexing 
the rolls. 
Rolling mills of this kind are operable in both possible rolling 
directions, in each case by reversal of the direction of rotation of the 
rolls. But the circumstances and the components of force vary in the 
respective individual rolling or rotation directions, so that the rolling 
mill has to be suitably adaptable or adjustable to the particular rolling 
programme to be carried out; i.e., both when changing the rolling 
direction and also when making corrections during a pass. With present-day 
rolling mills, problems arise more particularly in connection with such 
supporting devices and their adjustability. Mechanical friction occurs 
between the component parts, and such friction phenomena vary with the 
forces applied. Further, marking can develop, of which traces may be 
reproduced as far as on to the often highly polished rolling surfaces of 
the work rolls. Thus work rolls supported by such mechanisms are subject 
to additional wear. 
SUMMARY OF THE INVENTION 
The present invention is a development of rolling mills of the type just 
described, and seeks to facilitate not only the construction of the mill, 
but also adjustment of the mill once it is installed. Means are provided 
by which mechanical friction between the parts which are to be under load 
can be minimized or eliminated, and the working life of such parts thereby 
extended. Provision is also made for cooling systems of various forms, 
also to minimized wear and damage through overheating. 
According to the invention, a rolling mill comprises a roll stand with two 
work rolls defining a nip therebetween for passage of sheet material to be 
rolled, and displaceable in a direction generally parallel to the path of 
such sheet material through the nip; a back up roll associated with each 
work roll, all the rolls being rotatable on parallel axes, but the plane 
containing the back up roll axes being offset from that containing the 
work roll axes; and support devices for supporting the work rolls against 
movement away from the plane of the back up roll axes and against the 
surfaces thereof to apply pressure on a sheet material in said nip, which 
devices comprise hydrostatic elements arranged parallel to the respective 
work roll axis. The supporting devices can be controlled, for example 
individually or in groups, to enable non uniform deflections of the work 
rolls to be accommodated and counteracted. 
At least one, normally each, of the back up rolls is preferably a 
deflection compensation roll comprising a roll shell rotatably mounted on 
a support by means of support members adjustable to maintain the line of 
action of the support members in the plane containing the axes of the 
respective work and back up rolls. Deflection compensation, or adjustment 
rolls can also be used in the support devices. In an alternative 
arrangement, the support devices act on the external surface of a 
supported roll. The devices may act directly on the work rolls, or through 
one or more intermediate rolls. The hydrostatic elements define pockets 
acting on a supported surface and are arranged parallel to the 
longitudinal axis of the respective work roll. They are controllable, and 
the work rolls are normally displaceable in the direction of rolling to 
enable not only the effective use of the support devices but also to 
accommodate different rolling processes. 
Because of the measures proposed by the present invention, construction of 
the rolling mill is simplified, since it is possible to let the 
hydrostatic supporting elements act directly or indirectly on the surface 
which is to be supported or is subject to load. With a film of fluid 
present, no damaging friction comes to occur between the supported surface 
and the supporting elements. The force to be applied against the surface 
can be hydraulically regulated precisely and simply as regards magnitude 
and location. It is possible not only simply to support the work roll 
linearly but also to load the work roll differently by individual 
elements, in order; e.g., to bring about a greater working pressure in the 
middle of the roll gap than at the side regions of the gap. This is 
possible even if for space reasons; e.g., in the case of very thin work 
rolls, one or more intermediate rolls have to be arranged between the work 
roll and the supporting elements. By eliminating damaging friction 
phenomena the working life of the rolling mill is prolonged, and this is 
likewise promoted by the fact that by means of the film of fluid the 
surfaces may be cooled when necessary. 
In one preferred embodiment, the elements of the support devices each 
comprise an head portion which defines said pockets and a body with 
respect to which the head portion is slidingly mounted; and a drawing 
device for moving the head portion away from said supported roll to permit 
greater flow of hydraulic fluid through the element. This enhances cooling 
and is particularly effective when the support devices act on the external 
surface of a roll. Another means by which the hydraulic fluid may be used 
for additional cooling is by making provision for controlled leakage of 
fluid from the element onto the working parts or onto the sheet material 
being rolled. 
Embodiments of the invention will now be described by way of example and 
with reference to the accompanying schematic drawings. It will be 
appreciated that various of the features illustrated in one embodiment can 
be used to advantage also in others.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The rolling mills shown diagrammatically in FIGS. 1 to 6 each comprise two 
work rolls 1 and 2, between which a web of material 3 is conducted from an 
entry side (the left as shown) of the rolling mill for rolling. The work 
rolls 1 and 2 are driven, respectively in the directions shown by the 
arrows in the drawings. Their axes are designated as A in the drawings. 
Accordingly, the web of material 3 moves between the work rolls 1 and 2 
and is drawn away, treated, at the exit side of the rolling mill (the 
right as shown) with the use of a force Z. To load each work roll 1 and 2 
respectively with a working pressure in the direction towards the web of 
material 3 back up rolls 4 and 5 respectively are associated one with each 
work roll. In the constructional example according to FIG. 1 the back up 
rolls 4 and 5 are driven solid rolls, so that the work rolls 1 and 2 are 
entrained and thus driven by friction without slip by the back up rolls. 
By reversing the driving direction the rolling mill can also operate in 
the reverse direction. To load the work rolls, the axles of the back up 
rolls are loaded in the direction towards the material web. 
In the other embodiments shown in FIGS. 2 to 6 the back up rolls 4 and 5 
are constructed as deflection adjustment or compensation rolls (known per 
se), with a stationary support member 6 which is secured in the stand (not 
shown) of the rolling mill and about which there is arranged a rotatably 
roll shell 7 which bears by means of supporting elements 8 on the support 
member 6. The supporting elements 8 are incorporated like pistons in the 
support member, arranged in a row parallel to the axis of the support 
member 6, and hydraulically operated, so that the working pressure to be 
applied acts from the support member 6 via the supporting elements 8 and 
the roll shell 7 on the work roll 1 or 2. When using deflection adjustment 
rolls as back up rolls it is more practical for the work rolls 1 and 2 to 
be driven direct through their axles. 
The work rolls 1 and 2 and the back up rolls 4 and 5 are so positioned that 
the plane A--A containing the axes A,A of the work rolls 1 and 2 is offset 
in a horizontal direction, towards the left as shown, relative to the 
plane B--B containing the axes B,B of the back up rolls 4 and 5. 
With this arrangement and force transmission system, the work rolls tend to 
yield under working load, resulting for example in deflection of the rolls 
in a horizontal direction. To counteract this tendency, the work rolls are 
supported laterally with supporting devices 9. The supporting devices 9 
are so associated with the work rolls 1 and 2 that they support the work 
rolls in the direction oppositely to the direction of offset. Thus in the 
illustrated constructional examples they are arranged on the left of the 
work rolls, since here the work rolls are offset towards the left relative 
to the back-up rolls. 
The supporting devices 9 comprise hydrostatic supporting elements 19 or 20 
or 21 respectively, which are arranged in the supporting device parallel 
to the longitudinal axis of the respective work roll 1 or 2 which is being 
supported, and have hydrostatic pressure pockets or channels 29 which are 
open towards the surface being supported and are directed towards said 
surface. The surface to be supported is for example in the case of the 
embodiments of FIGS. 2, 4, 5 and 6 the cylindrical surface of the work 
roll 1 or 2. 
In the embodiment of FIG. 3 the surface to be supported is the inner 
surface of the roll shell 16 of a deflection adjustment roll 13 used here 
in the supporting device. The supporting element in this case is 
designated 15. If necessary a plurality of parallel-arranged intermediate 
rolls 45 may or have to be arranged in between a work roll, particularly 
if it is of a small diameter, and the supporting device or elements. Then 
a surface to be supported is the cylindrical surface of an intermediate 
roll 45 (see FIG. 1) which abuts on the supporting elements. For the sake 
of simplicity such intermediate rolls which may be provided are shown only 
in FIG. 1. 
The work rolls 1 and 2 with the associated supporting devices 9 are 
arranged in the stand (not shown) of the rolling mill to be displaceable 
horizontally and generally parallel to the web of material 3. This serves 
inter alia for adapting the rolling mill for different processing tasks 
and for different material webs. Thus it is possible in accordance with 
the needs of the particular processing task to shift the aforesaid plane 
A--A; i.e., the work rolls 1 and 2 relatively to the aforesaid plane B--B; 
i.e., relatively to the back-up rolls 4 and 5 and thus to provide 
appropriate or desired force conditions. To shift the work rolls 1 and 2, 
shifting units 10 (see FIG. 1) are provided which bear on the one hand on 
the stand of the rolling mill and on the other hand engage on shafts of 
the displaceably mounted work rolls 1 and 2, in order to enable 
displacement of the work rolls with the associated supporting devices 9 
generally parallel to the path of the material web 3. They may be 
servomotors 11 as in this embodiment, connected by means of their 
actuating rods 12 to the shafts of the work rolls 1 and 2. 
For the fully effective provision or utilisation of the desired force 
conditions it is also important that the support members 6 of the back up 
rolls 4 and 5, when constructed as deflection adjustment rolls with 
supporting elements 8, are adjustably mounted in the stand. The support 
member 6 of the back up roll 4 or 5 as the case may be, in which 
supporting elements 8 are arranged in a row extending parallel to the axis 
of said support member, can be rotated in its bearing arrangement and can 
thus turn to a position in which the axis B of the support member 6, the 
longitudinal axes of the supporting elements 8 and the axis A of the work 
roll 1 or 2 which is associated with the back up roll 4 or 5 respectively 
and is offset oppositely to the direction of travel of the material web 3, 
are situated in a common plane A-B. 
This advantageous position, in which the pressure application force is 
transmitted from the support member 6 via the supporting elements 8 to the 
roll cylinder or shell 7 to the work roll 1 or 2 respectively most 
effectively, is shown particularly clearly in FIGS. 2 and 3. 
According to FIG. 3, deflection adjustment rolls 13 are provided as 
supporting devices 9 laterally of the work rolls 1 and 2. They comprise 
stationary support members 14 in which supporting elements 15 are embedded 
in piston-like manner, and a roll shell 16 is arranged to be capable of 
rotating about the support member. A fluid under pressure is fed through 
conduits 17 to the supporting elements 15. A pressure fluid is fed through 
conduits 18 to the supporting elements 8 of the back up rolls 4 and 5 
respectively. 
In the embodiments shown in the other FIGS. 1, 2 and 4 to 6, hydraulic 
supporting elements 19 (FIGS. 1, 2 and 6), 20 (FIG. 4), and 21 (FIG. 5) 
are provided in the supporting devices 9. 
Supporting devices 9 with such supporting elements 19 or 20 or 21 
respectively are used when in the case of a particular processing 
operation the work rolls 1 and 2 have to be cooled to an increased extent, 
possibly through the agency of intermediate rolls which may also be 
provided. The supporting elements are secured on a support beam 22 
supported on the stand of the rolling mill and arranged in a row parallel 
to the axis of the associated work roll 1 or 2, and thus support the work 
roll laterally. A fluid under pressure flows through the head parts 23 and 
24 respectively of the supporting elements out on to the supported work 
roll, with a cooling effect. The head parts 23 and 24 are embedded in the 
manner of pistons in bodies 25 of the supporting elements. Provided in the 
body 25, below the head part, is a pressure chamber 27 into which a 
pressure fluid is introduced through a conduit 28. The head part is 
pressed towards the work roll to support the roll with the force which is 
produced in the pressure chamber 27. The head part comprises at least one 
pressure pocket 29 which is open towards the work roll and in which an 
hydraulic pressure cushion is built up, and from which the pressure fluid 
flows out continually on to the work roll. The pressure fluid flows in 
conventional manner from the pressure chamber 27 through ducts 30 into the 
pressure pockets 29 and out of these on to the work roll, cooling it. 
To increase the throughflow of pressure fluid through the head part; i.e., 
to increase the cooling effect, it is proposed as shown in FIG. 4 and 7 to 
arrange a conduit 31 for the pressure fluid to debouch into the pressure 
pocket 29, so that the throughflow can be regulated, by controlling the 
passage of fluid through conduit 31, in accordance with cooling 
requirements. 
Again for the purpose of increasing the throughflow of pressure fluid 
towards the work roll, a drawing device can be provided, as shown in FIG. 
5 and 8 which acts oppositely to the direction of the pressure application 
force shifting the head part 23 in the pressure chamber 27. Below the 
pressure chamber 27 there is also provided a cylinder-like pressure 
chamber 34 in which a piston 26 is arranged. This piston 26 is connected 
to the head part 23 by means of a draw rod 33. A fluid under pressure is 
introduced into the pressure chamber 34 through a conduit 32. The force 
produced in this pressure chamber 34 acts on the piston 26 and via the rod 
33 on the head part 23 oppositely to the pressure application force which 
acts on the head part 23 in the pressure chamber 27 with a displacing 
effect. As a result a greater distance is produced between the head part 
23 and the work roll 1 or 2, and also a greater pressure in the pressure 
chamber 27, so that more pressure fluid flows out through the ducts 30 and 
through the pressure channel 29 on to the work roll. 
When there is an additional need for cooling for the work rolls land 2 a 
cooling device is provided as shown in FIG. 6 at the outlet side of the 
rolling mill relatively to the direction in which the web of material 
moves; i.e., on the right as shown. The device comprises a first limiting 
roll 35 arranged to abut on the work roll 1 or 2 with a spacing from the 
shell 7 of the back up roll 4 or 5, and a second limiting roll 36 which 
abuts on the first limiting roll 35 and on the shell 7 of the back up roll 
4 or 5. Thus the limiting rolls 35 and 36, the work rolls 1 and 2 
respectively and the shells 7 of the back up rolls 4 and 5 respectively in 
each case form the boundaries of a cooling chamber 37 which is filled with 
cooling medium. Each cooling chamber 37 is provided at each end with a 
sealing apron (not shown). Advantageously the first limiting roll 35 has a 
flexible roll shaft which is surrounded by an elastic jacket; e.g., a 
rubber jacket, and the second limiting roll 36 is constructed as a 
deflection adjustment roll, with an elastic roll shell 39 which is 
arranged to be rotatable about a stationary support member 38 and bears on 
the support member 38 by means of supporting elements 40. In this way the 
cooling chamber 37 can be reliably sealed by means of the limiting rolls. 
The limiting rolls 35 and 36, and also the shells 7 of the back up rolls 4 
and 5, are driven by friction through the driven work rolls 1 and 2 and 
through the back up rolls, respectively. 
Advantageously the supporting elements 19, 20, 21 used in the supporting 
devices 9, and 15 in the deflection adjustment roll 13 in FIG. 3 are 
regulatable individually or in groups, to allow of producing varying 
magnitudes of working pressure in the rolling gap between the work rolls 1 
and 2. More particularly for the flattening of very thin foils which have 
to be produced it is sometimes necessary to use a higher working pressure 
in the middle of the rolling gap than at the sides of the gap. Previously 
this has been achieved by for example, giving the rolls concerned a 
convexity which has been predetermined from experience. A desirable 
rolling gap profile for rolling purposes can now be adjusted 
hydraulically. Owing to the film of fluid provided between the supporting 
elements and the surfaces being supported the; e.g., polished surfaces are 
not worn or damaged by metal contact. 
The rolling mill according to the invention allows a web of material to be 
processed in an alternating manner. In that case the material web is 
rolled in one direction through the rolling mill and then rolled back 
again in the opposite direction. Since different force conditions obtain 
in each of the two directions, or different working pressures have to be 
used, the good regulating ability of the hydraulically operated supporting 
elements is a significant advantage. 
FIG. 7 shows one of the supporting elements 9 of FIG. 4 on a larger scale, 
using the same reference numerals. 
FIG. 8 shows similarly and again on a larger scale one of the supporting 
elements 19 which is shown in FIG. 5.