Calender roller mounting arrangement

An apparatus for the clearance-free mounting of at least one of the rollers in the support column of a calender. The mounting is for producing plastics material films achieved by means of a roller bearing which is divided into three, a central section or ring and two laterally outer sections or rings in a direction transverse to the major axis of the roller journalled to rotate therein. Each bearing ring or section comprises an inner ring portion, at least one row of cylinder rollers, an outer ring portion and a bearing body portion. Pressure applicator means are provided for displacing the central section relative to the two laterally outer sections or rings in a direction towards and away from the roller journalled therein so as to eliminate play within the bearing. To eliminate the play between the bearing body and the calender support column, an additional pressure applicator means is provided which is incorporated in the calender support column.

FIELD OF THE INVENTION 
The present invention relates to a calender roller mounting arrangement 
and, more particularly, to an apparatus for the clearance-free mounting of 
at least one of the rollers in a multiple-roller calender used, for 
example, in the production of plastics material films. 
BACKGROUND OF THE INVENTION AND PRIOR ART DISCUSSION 
Multiple-roller calenders are known and are used for the production of 
plastics material films. It is very important for the penultimate roller 
traversed by the plastics material to be mounted in the calender support 
column in a clearance-free manner. More especially, it must be ensured 
that counter-bending devices normally used in such calenders, and also the 
separating forces produced by the material being calendered, have as 
little effect as possible on the bending of the penultimate roller. For 
accurate calendering, the penultimate roller must be retained accurately 
in its desired position in the calender support columns. 
A calender of this general type is disclosed in U.S. Pat. No. 3,347,157. 
Such calender includes a roller bearing arrangement comprising a friction 
bearing formed from two half shells, one portion of which can be acted 
upon by hydraulically-actuated means in order to make the bearing itself 
clearance-free. 
The above-described arrangement is not entirely satisfactory because there 
are numerous disadvantages associated therewith. The greatest disadvantage 
resides in the fact that it is impossible to achieve uniform absorption of 
forces in the split bearing ring. 
If relatively strong forces are applied to the half-shells in order to 
compensate for play in the bearing, a considerable braking effect is 
exerted upon the roller journals and hence upon the inner bearing ring. 
Consequently, these bearing components become subject to considerable wear 
phenomena. As the wear sustained by the curved bearing component 
increases, it loses its original shape, with the result that the forces 
are non-uniformly transmitted. This, in turn, leads to the wear phenomena 
being further increased. 
In addition, the provision of the hydraulically-actuated cylinders is 
disadvantageous in itself. Such hydraulically-actuated cylinders occupy a 
relatively large volume and hinder the operator of the calendering device. 
In order to overcome this problem, suitable covers therefor must be 
provided which occupy additional space and are expensive. 
OBJECTS OF THE INVENTION 
The present invention seeks to provide a calender roller mounting apparatus 
by means of which the bearing play of at least one of the rollers in a 
multiple roller calender is substantially eliminated. In other words, the 
invention seeks to provide an apparatus which will retain the penultimate 
roller in an absolutely axis-parallel position and ensures that the forces 
applied by supplementary means provided to compensate for the bending of 
the rollers adjacent thereto are always restricted solely to such rollers 
and do not affect the penultimate roller. 
SUMMARY OF THE INVENTION 
According to the present invention, there is provided a calender roller 
mounting arrangement for the clearance-free mounting of at least one of 
the rollers of a multiple roller calender utilised for the production of 
plastics material films, the rollers being mounted in a support column, 
the arrangement including a roller bearing, the bearing comprising an 
inner ring portion, a plurality of rows of cylinder rollers, an outer ring 
portion and a bearing body, the roller bearing in which the horizontally 
disposed calender roller is journalled to rotate being divided, in a 
direction transverse to the major axis of the roller, into a central 
section and two laterally outer sections disposed one on each side of the 
central section, the central section being displaceable relative to the 
outer sections in a direction towards and away from the calender roller by 
pressure applicator means, the pressure applicator means being disposed 
within the bearing body and further pressure applicator means being 
provided for absorbing the play between the bearing body and the calender 
support column, which further pressure applicator means are disposed in 
the calender support column. 
The provision of a roller bearing having a plurality of rows of cylinder 
rollers and which is divided into a central section and two lateral 
sections in a direction which is transverse to the major axis of the 
calender journalled to rotate therein shows advantages compared with a 
friction bearing which is divided in a direction parallel to the major 
axis of the calender roller. This is because the bearing arrangement of 
the present invention uniformly absorbs the forces which must be applied 
to achieve a clearance-free mounting. 
The central cylinder roller section or ring ensures that the forces are 
distributed over the bearing journal in a very uniform and wear-free 
manner. If pressure is applied to the central section or ring in, for 
example, an upward direction, the two outer or lateral rings or sections 
of the bearing are subjected to a force component in a downward direction. 
Accordingly, the roller journal rotates in the bearing in a play-free 
manner and the penultimate roller of the calender is thus retained exactly 
in its desired position. The play within the bearing is thus eliminated. 
It must be emphasized that, even with variable pressures being applied to 
the central ring or section a uniform zero tolerance is always maintained 
within the bearing rings or sections. This is not so in the case of the 
arrangement described in the aforementioned U.S. Patent Specification. 
This is because, in such known arrangement, a reduction in the pressure 
applied to the half-shell leads to a smaller bearing tolerance, that is to 
say, a smaller bearing play, being set. Variable tolerances are 
consequently achieved in dependence upon the pressure applied, with the 
result that the roller journal may also be free to adopt variable 
positions within the bearing. 
To illustrate the importance of even minimum tolerances of the bearings and 
of the entire calender, it is pointed out that plastics material calenders 
produce, for example, polyvinyl chloride films which have a thickness of 
40.mu.. The thickness tolerances of the calendered films is .+-.2.5.mu. 
which must be maintained over a web width which may be as great as 2,600 
mm. 
To provide a free working area in the vicinity of the bearing bodies, the 
pressure applicator means or tensioning members for the central cylinder 
roller ring or section are disposed in the bearing housing. 
To eliminate the play between the bearing body and the calender support 
column whilst simultaneously providing a simple and neat arrangement, the 
further pressure applicators or pretensioning members which engage with 
the bearing body are incorporated in the calender support column. 
In a preferred embodiment of the invention, four rows of cylinder rollers 
are provided.

DESCRIPTION OF PREFERRED EMBODIMENT 
In FIG. 1 there is shown a calender which comprises four rollers 11, 12, 13 
and 14 schematically illustrated in cross-section. The material to be 
calendered, such as polyvinyl chloride, is inserted into the gap between 
the two upper rollers 11 and 12. Subsequently, the material passes through 
the roller gaps between the roller pairs 12 and 13 and 13 and 14, thereby 
forming a so-called rolling sheet on each occasion. The material is 
removed from the lowermost roller 14 in the form of a film 15. 
The roller 13, that is to say, the penultimate roller of the calender, must 
be retained in a true axis-parallel position, so that supplementary means 
(not shown) which compensate for the bending of the calender 
roller--caused by the rolling sheets of material and by the inherent 
weight of the roller--can be effectively used. It must be ensured that 
these supplementary means which compensate for the bending of the two 
rollers 12 and 14 on either side of the penultimate roller act solely on 
such rollers 12 and 14 and do not affect the penultimate roller 13. 
To achieve this, the present invention provides a roller mounting apparatus 
including a bearing arrangement for the penultimate roller. Such bearing 
arrangement will now be described with reference to FIGS. 3-5. Cylinder 
roller bearings are disposed at each end of the roller 13. The roller 13 
includes journalled end regions 13a which rotate within a radially inner 
ring 1 of the bearing. The ring 1, which may be continuous or divided, 
accommodates rollers 2, shown specifically in FIG. 3 as rows 2a, 2b, 2c 
and 2d of cylinder rollers. 
The rows of cylinder rollers are located between the inner ring 1 and a 
divided radially outer ring. The outer ring of rollers 3, shown more 
specifically in FIG. 3 as ring portions 3a, 3b and 3c portion 3a covers 
the roller row 2a, portion 3c covers the roller row 2d and portion 3b 
covers roller ring 2b and 2c. The divided outer ring of the bearing is 
covered by a correspondingly divided bearing body. The central portion 4 
of the bearing body covers outer ring portion 3b and the lateral portions 
4a and 4b cover the outer ring portions 3a and 3b respectively. 
The central bearing body portion 4 is provided with laterally extending 
arms 8 and 9 which engage with the piston rods of double-acting hydraulic 
piston and cylinder arrangements 17 and 16 respectively. These piston and 
cylinder arrangements may, as shown in FIG. 4, be disposed in the lateral 
bearing body portions 4a and 4b respectively. 
Actuation of the double-acting hydraulic piston and cylinder arrangements 
16 and 17 cause the main bearing body 4 to be moved either radially 
outwardly so as to relieve the rows of cylinder rollers 2b and 2c or 
radially inwardly so as to press them towards the rows of rollers. By 
pressing the central bearing body portion 4 towards the rows of cylinder 
rollers 2b and 2c, the bearing play between the inner ring 1, the rows of 
cylinder rollers 2a, 2b, 2c and 2d, the central bearing body portion 4 and 
the lateral secondary bearing body portions 4a and 4b is eliminated. 
To eliminate the play between the bearing body portions 4, 4a, and 4b and a 
calender support column 5 in which the rollers 11, 12, 13 and 14 are 
mounted, pressure application devices such as hydraulic piston and 
cylinder arrangements 7 or pre-tensioned springs are provided which act on 
the central bearing body portion 4. In FIG. 3, the piston and cylinder 
arrangement 7 is located in recess 6 formed in the support column 5. The 
roller 13 thus has no mechanical free play and is, therefore, retained 
exactly in its desired position. 
By disposing the hydraulic piston and cylinder arrangements 16 and 17 used 
for eliminating the play within the bearing in the lateral bearing body 
portions 4a and 4b, and by disposing the hydraulic piston and cylinder 
arrangements 7 in the calender support column 5, a neat space-saving 
arrangement is achieved. This is particularly apparent when such 
arrangement is compared with that disclosed in U.S. Pat. No. 3,347,157.