Method for rebuilding a calender

#The present invention relates to a calender having a supporting frame and a set of rolls attached to vertical portions of the supporting frame so as to form a stack of rolls in which adjacent rolls are arranged one above the other forming calendering nips therebetween, the stack including a top roll, a bottom roll and a plurality of intermediate rolls arranged between the top roll and the bottom roll. The invention also relates to a method of rebuilding a calender where the structure of an existing calender is employed in the constructing a modernized calender.

#The set of rolls in a calender conventionally comprises a plurality of rolls which are arranged one above the other as a stack of rolls. The rolls are placed one above another and adjacent rolls in the stack are in nip contact with one another, the nips defined between adjacent rolls being structured and arranged for calendering a paper or board web or equivalent run between the nips of the rolls. The rolls are journaled on bearing housings for permitting the rotation of rolls, which in turn are normally attached to slides fitted on vertical guides provided in the frame of the calender. The slides are suspended through spindle nuts on vertical lifting spindles provided in the frame of the calender. Thus, the rolls of the set of rolls are not rigidly fixed at their bearing housings to the frame of the calender, but, instead, the rolls can move in a vertical direction.

#The mass of the bearing housings of the rolls and the auxiliary devices attached thereto, such as, fly rolls, are quite large, and as such, cause in conventional calenders the considerable drawback of distortions in the distribution of the linear loads of the nips. For this reason, calenders have started to incorporate relief devices which are supported on the slides of the rolls, on one hand, and on spindle nuts provided on the lifting spindles, on the other hand. In this manner, distortions caused by the weight of the bearing housings of the rolls and the auxiliary devices attached thereto in the linear load profiles between the rolls can be relieved by means of relief devices. One such arrangement is disclosed in U.S. Pat. No. 4,901,637, the entire disclosure of which is incorporated herein by reference.

#Additional objects of the invention will be apparent from the following description of the preferred embodiment thereof taken in conjunction with the accompanying non-limiting drawings, in which:

#FIG. 1 is a side view of a portion of the calender roll stack in a modernized calender,

#FIG. 2 is a front view of the same,

#FIG. 1 shows the lower part of a calender stack showing the bottom roll 1 and two lowermost intermediate rolls 2. The intermediate rolls 2 are attached at their both ends revolvingly to arms 3, that is, each intermediate roll 2 is supported by a pair of arms 3, to which the respective bearing housings 4 of the rolls are fixed. The arms 3 are pivoted at 5 to an auxiliary frame 6, which extends vertically in the direction of the vertical portion 7 of the old frame. The auxiliary frames 6 wrap around the respective vertical frame portions 7 that exist in the old calender at both edges of the vertical calender stack. The attachment to the old frame will be described hereinafter in more detail.

#Further, at each end of an intermediate roll 2, there is an actuator 8 disposed between a forwardly protruding bracket 9 of the auxiliary frame 6 and the arm 3 to provide movements of the roll 2 and to provide relief force, when necessary during the calendering, and they are used to control the load in the calendering nips. The actuators 8, which are preferably hydraulic cylinders, can act on the same principle as disclosed in the aforementioned U.S. Pat. Nos. 5,438,920 and 5,806,415 and international application WO 98/50628.

#FIG. 1 also shows a shelf 3a in each arm 3 forming a support surface under the bearing housing to make the roll change easier and safer. These support surfaces can act as a temporary support for a roll when it is fastened to the arms by its bearing housing.