Soft nip calender employing a continuous elastic belt

#Not applicable.

#The present invention relates to improved calenders for calendering a web.

#During the 1990's a new calendering technique was introduced: the extended soft nip or the LN-calender (i.e., Long Nip) where the advantages of soft calendering were further developed. Compared to conventional soft nips, the local stress concentrations in the calender nip are substantially reduced with the extended soft nip. The required smoothing of the paper surface can therefore be obtained with minor or no increase of the local variations of the surface properties.

#FIG. 1A is a side elevational view of a prior art long nip calender of the shoe-belt type.

#FIG. 1B is a side elevational view of a prior art long nip calender of the lubricated roll belt type.

#FIG. 1C is a detail view of the lubricating system for the prior art calender of FIG. 1A.

#Referring more particularly to FIGS. 1A-4 wherein like numbers refer to similar parts, a new concept for LN-calender 24 is proposed in which the same order of compressive stress can be applied as with the “traditional roll-belt configuration.” At the same time it takes care of the difficulties with the traditional roll-belt configuration.

#Specifically, the LN-calender 24 provides a calender for calendering a web 26, such as a paper web, coated paper web, or paper board web. The LN-calender 24 has a rotating and heatable first calendering roll 28. The surface 30 of the first roll shell 32 which comes into contact with the web 26 has a hard and smooth calendering surface 30. A rotary soft surface counter roll system 34 cooperates with the heatable calendering roll 28 for defining therebetween a calendering nip 36 for the passage therethrough of the web 26. The soft surface counter roll system 34 comprises a smooth polymer mantle belt 38 on the surface of a rotary second calender shell 40 of the second calender roll 41. The inner diameter 42 of the mantle belt 38 is 5-50 mm larger than the outer diameter 44 of the second roll shell 40.

#In one embodiment of the invention, the polymer mantle belt 38 is joined to and positioned with respect to the gable 46 of the roll 41 by means of a clamping ring 48, which is preferably attached to the roller gable 46 by bearings 50.