The invention relates to a roll arrangement having a device for regulating the roll nip, comprising a roll pair which consists of an upper roll and a lower roll, between which a roll nip is formed, wherein each roll is provided with two roll journals which lie axially diametrically opposite one another, at least two bearing blocks for each roll journal, wherein one or more bearings are received in a bearing block, and a bearing block which lies in each case on the outside on the roll journal, in a clamping latch which has a first lever arm and a second lever arm, wherein the second lever arm of the respective clamping latch of the upper roll and the second lever arm of the respective clamping latch of the lower roll are connected to one another via a first actuating element, mutually corresponding bearing jewels and clamping latches of the upper roll and the lower roll lie opposite one another, and a controller which acts on the first and the second actuating element. Further, the invention relates to a method for regulating the roll nip in that roll arrangement. An arrangement of that type and a method of that type are known from CN 101 254 509 A.
It is a long-standing need to provide a roll arrangement having a device for regulating the roll nip, wherein a homogenous thickness of a material web passing the roll nip is guaranteed. This means essentially that the roll nip must be kept constant independent of the existing linear load.
A roll arrangement having one or more pressing devices for keeping the roll nip constant is known from DE 16 02 099 A1. The roll arrangement comprises chocks for respective supporting rolls which the work rolls are abutting which in turn are supported in respective chocks. The chocks for the supporting rolls are compensated by small pressure cylinders providing for the control pressure during the roll process. The roll pressure occurring in the roll arrangement during the roll process is generally substantially higher than the control pressure. By introducing the rolling workpieces into the roll nip, a sudden pressure or a load rise between the rolls results which has as a consequence that the rolling workpiece is thicker when exiting the roll nip than expected with respect to the previous adjustment. In order to compensate for that, the roll nip is adjusted to the desired rolling workpiece thickness by means of a wedge. The wedge absorbs the load, so that the load within the roll nip is constantly zero. It has proven that only a comparatively narrow control range can be controlled by this type of regulation and that moreover now as before undesired impact on the thickness of the rolling workpiece is the result which adversely affects thickness deviations, since only a comparatively slowly reacting regulation is taking place.
For an improvement, DE 22 64 333 C3 proposes to further provide back bending bearings at roll journals with displacement sensors detecting the distance thereof and to provide regulating means acting on the back bending cylinders with a feedback control system to keep superimposed distances constant which are defined by set points and/or supporting forces.
Further, DE 199 24 860 A1 describes a roll arrangement in which the distance between a hydrostatic thrust bearing and a roll can always be maintained, even in a transition state before and after start of rolling, in order to prevent damages of these components caused by a contact between them. Hydrostatic thrust bearings for contact-free support of cylinder section of idle rolls by means of fluid pressure are substantially provided along the horizontal direction, wherein these idle rolls support the work rolls substantially along the horizontal direction. Rolls for keeping the gap constant are provided which prevent that the gaps between the hydrostatic thrust bearing and the idle rolls will become smaller than a predetermined value.
It is known from DE 103 05 511 C3 to arrange inner bearing blocks in bearing jewels on roll journals.
The difficulties arise when the material web falls below a critical value with respect to the calendar size, i.e. when particularly thin materials having a thickness of less than 1 mm having high density and high stiffness must be processed. There is a risk in conventional roll arrangement that, when the calendar passes a thin region or a disruption, the pre-tensioned mechanical elements, such as bearings, bearing seats, rolls, roll journals, fall on each other caused by their spring pre-tensions, and thus local overstress of roll surfaces or the material web will result.
Particular problems are posed in a situation that the material web comprises different thicknesses while passing the roll nip. This can be the case when material webs are intermittently coated, laminated or consist of several layers. One example is coated aluminum or copper films for producing lithium ion batteries. An exact densification must be assured across the entire working width by the micrometer. If this is successful, the contact between the particles within the electrode materials is improved on the one hand, and electron transport is optimized, on the other hand, also the volume power density of the batteries is increased.
The problem of producing electrode materials which are densified by means of rolls is addressed, for example, in JP 2000/133 251 A. A roll pair, where the center distance of the rolls is variable, is exposed to hydraulic cylinders which apply a previously defined pressure in one direction to decrease the distance between rolls. Compensation cylinders for roll bending are provided, and the roll pairs are each shaped that they have, in a center region, a slightly larger diameter than at both ends.
The velocity problem when calendaring material webs of varying thickness is addressed in JP 2000/079 407 A. An upper roll and a lower roll are freely rotatable supported in bearing blocks which are exposed to hydraulic cylinders. These hydraulic cylinders urge the upper roll downwards, the lower roll upwards. Counter bending forces are exerted to independent auxiliary bearings at the respective rolls.
It is the object of the present invention to provide for a compact roll arrangement having a device for regulating the roll nip as well as a corresponding method, so that in particular intermittently coated films may be calendared precisely.
This object is achieved by a roll arrangement of claim 1 and a method of claim 4. Preferred embodiments are subject-matter of respective subclaims referring thereto.
According to the invention, in a roll arrangement of the type mentioned in the introductory, it is provided that the bearing block which lies in each case on the inside on the roll journal is arranged in a bearing jewel and the first lever arm of the clamping latch of the upper roll and the first lever arm of the clamping latch of the lower roll are connected rigidly to one another, and bearing jewels which lie opposite to one another, of the upper roll and the lower roll are connected to one another via the second actuating element. A controller is provided acting on the first actuating elements and the second actuating elements, so that the first actuating elements are moved to adjust the roll nip according to a predetermined thrust and a predetermined linear load, and the second actuating elements are moved to maintain the bearing jewels in a relative rest position which is defined by specified densification of a material web passing the roll nip.
Thus, the roll nip is initially adjusted according to the required thrust and the required linear load. This is achieved in that the clamping latches are respectively adjusted by means of an actuating element. Simultaneously, however, the bearing jewels rest with the bearings on the journals on the first actuating elements which, for example, dependent on the information from a position sensor keep the bearing jewels in a rest position relatively to another. The distance of the bearing jewels is adjusted until the required densification of the material web is achieved.
By applying the loads to the individual introduction points, the bearing shells of rolling elements are pushed free of play and are internally pre-tensioned across the entire hole bearing. In addition, the roles deform spring elastically. This depends on the construction mainly in the transitions from the journals to the barrel and in the barrel itself in a negligible amount, since these are adequately selected according to their diameter.
According to an advantageous embodiment, the first actuating element and/or the second actuating element are embodied as a hydraulically operating actuating element, a pneumatically operating element, or as a mechanically operating element which is electrically driven. The required load may, for example, be introduced via a hydraulic or pneumatic cylinder or via a spindle mechanism. The construction is embodied so that the clamping latches introduce the load into the journal according to the principal of the lever. The clamping latches, the bearing jewels and the roll journals, respectively, are associated with a position sensor system which, by means of a program and corresponding drives, such as hydraulic cylinders or electric linear gearings, recognizes the position of the roll journals and keeps it constant.
When the power rise in the roll nip is changed by different material thicknesses within the material web, in particular caused by an intermittently formed coating, the first actuating elements of the bearing jewels are moved upwards. This is achieved in that the role bending caused by the previously increased line load is now maintained by the introduced equivalent load. Regulation is performed so that a vibrational response will not occur since the roll pair remains in a deformed state. Rolls bend caused by process forces in the roll nip. Edge forces applied to the bearing produced thereby significantly reduce the lifetime thereof.
Consequently, it is advantageous that a bearing block comprises a pivoted bearing housing in which the bearings accommodated therein are arranged pivotally about a common axis. Accordingly, the bearing is freed corresponding to the load direction in the decrease of freedom by spherical receptacles so that no excessive load occurs. The total bearing depends on the tilting motion caused by roll bending, production of undesired edge forces acting on the bearing blocks is avoided.
Moreover, it is provided that the bearing bias is always maintained in the same direction, so that hopping of the bearing elasticity is avoided.