AT506853A2 - CALENDER - Google Patents

Description

FIELD OF THE INVENTION

The invention relates to a method according to the preamble of claim 1.

The invention also relates to a calender according to the preamble of claim 2.

STATE OF THE ART

Calendering is generally performed to improve the properties, such as smoothness and gloss, of a web-like material, such as a paper or paperboard web. In calendering, the web becomes nip or nip, i. H. a calendering nip formed between rollers pressed against each other, wherein in the nip the web is deformed due to the action of temperature, humidity and nip pressure. In a calender, nips are formed between a smooth-surfaced press roll, such as a metal roll, and a flexible top-coated roll, such as a polymer roll.

The roll with a flexible surface conforms to the shapes of the web surface and uniformly presses the opposite side of the web against the smooth-surfaced press roll. Hereinafter, calender rolls refers to calendering nip forming rolls, an upper roll refers to the uppermost roll of a roll stack, a lower roll refers to the lowermost roll of a roll stack, and an intermediate roll refers to an o-roll multiple rolls between the upper roll and the lower roller. An upper nip refers to the uppermost calendering nip, which is located between the upper roll and the uppermost roll. ···················································································································································································································································· on the lowermost calendering nip of the roll stack formed between the lower roll and the Ka-leveling roll above the lower roll and intermediate nips refer to the calendering nips formed by the intermediate rolls between the upper nip and the lower nip of the calender.

Finnish Patent 96334 describes a method for calendering paper or similar sheet material in a calender. In the method, the sheet material to be calendered is passed through nips formed by a deflection-compensated upper roll and a deflection-compensated lower roll and by two or more intermediate rolls disposed between the upper and lower rolls. The rolls are arranged as a substantially vertical roll stack. Such rolls, in which the shape of the natural bending line created by their own weight is substantially the same, are used as intermediate rolls.

The nip load generated by the masses of the intermediate rolls and auxiliary devices associated therewith is substantially completely relieved in the process and an adjustable load is provided by means of the deflection-compensated upper or lower roll and / or by means of an external load applied to the upper or lower roll applied to the calendering nips.

Typically, compression in a multi-roll calender is created by securing the top or bottom roll of the roll stack in place and pressing the roll stack against the roll mounted in place. Alternatively, it is possible to press both the upper and lower rollers together, either so that none of the intermediate rollers. ··· · · · · · ······· or at least one of the intermediate rolls is firmly locked in place. It is possible to compensate for the bends of the rolls by means of deflection compensating devices disposed in the upper and lower rolls, so that the nips require a linear shape.

The relief of moving intermediate rolls is performed in arrangements known from the prior art by means of so-called UNIX data processing or calculation. UNIX data processing is based on a mechanism in which the roller and associated parts, such as bearing shells, support arms and unloading cylinders, are modeled into a system of moving masses. These are very complicated calculations that require their own HP workstation and a person highly specialized in calculating intermediate rolls.

SUMMARY OF THE INVENTION

In the arrangement according to the invention, the UNIX data processing is replaced by automatic weighing. Automatic weighing is achieved by providing the unloading cylinders of each intermediate roll with a pQ valve and a linear sensor on both the drive and operator side. Each intermediate roll is slowly raised from the uppermost intermediate roll to the Q command of the valve and by monitoring the reading of the linear sensor to the normal operating position. Near the operating position, pressure values are read during the upward and downward movement and the average of the measured values is used as the relief pressure, to which possible over- and underloads are added. -4- -4- ·····································································

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The principal characterizing features of the method according to the invention are indicated in the characterizing part of claim 1.

The principal characterizing features of the calender according to the invention are indicated in the characterizing part of claim 2.

In automatic weighing changes of the masses of the intermediate rolls are considered, which can occur after commissioning and which z. B. caused by the fact that the customer shut down a doctor blade connected to an intermediate roller after many years.

In automatic weighing, it is possible to consider the creeping of the relief pressure sensors. Furthermore, the mass difference of the driving and operating side can be compensated automatically, which required manual adjustment in arrangements according to the prior art.

Automatic weighing takes into account frictions associated with the intermediate roll support systems and automatic weighing can be used as an aid to troubleshooting.

Automatic weighing also takes into account the change in the center of the masses caused by an offset device. Nowadays, this is not considered in arrangements known from the prior art. -5- ···· # ··· · · ··············································································· · · ···································

The arrangement according to the invention can be used in all Mehrwalzenkalandern, which include at least one intermediate roll. The multi-roll calender may consist of a set of rolls or many sets of rolls in which the rolls form a roll stack. The roll stack may be vertical or it may form an angle with the vertical plane.

BRIEF DESCRIPTION OF THE FIGURES

Fig. 1 shows a Mehrwalzenkalander formed from two sets of rollers, in which the arrangement according to the invention can be used.

Fig. 2 shows the second set of rolls of the multi-roll calender shown in Fig. 1 and holding systems connected to the rolls.

Fig. 3 shows a portion of a mounting arrangement of an intermediate roll.

DESCRIPTION OF ADVANTAGEOUS EMBODIMENTS

Fig. 1 shows a multi-roll calender in which the arrangement according to the invention can be used. The multi-roll calender has two sets of rolls 20A, 20B, wherein a fiber web W is calendered in the nips between the calender rolls of the set of rolls. The rollers of a first set of rollers 20A are designated by the reference numerals 21A-25A when viewed from above and the rollers of a second set of rollers 20B by the reference numerals 21B-25B. Top and bottom rollers 21A, 25A; 21B, 25B of both sets of rollers 20A, 20B are provided with a polymer surface bending -6 -6 · · · · «·« · · · · · · # ··· · · · · · I ·· ·· ··· ·

········ · · · · · · · Compensated Sym rollers. Uppermost and lowermost intermediate rolls 22A, 24A; 22B, 24B of both sets of rolls 20A, 20B are again steel rolls, either heatable and / or coolable rolls, and middle rolls 23A, 23B are rolls provided with a polymer surface.

FIG. 2 shows the second set of rolls 20B of the multi-roll calender shown in FIG. 1 and holding systems associated with the rolls. The lower roller 25B of the roller set 2OB is held on its bearing shells on both the driving and operating sides with a cylinder device 50, and the upper roller 21B is fixedly mounted on the calender frame. The intermediate rolls 22B-24B are held on the calender frame by means of pivot arms 32B, 33B, 34B and the pivot arms are moved about pivot points by means of relief cylinder means 42B, 43B, 44B.

Each relief cylinder device 42B, 43B, 44B is provided with a pQ valve A and a linear sensor B, which are connected to a control unit 100. The intermediate rolls are slowly raised from the uppermost intermediate roll 22B to the Q command of the pQ valve A and by monitoring the measurement value of the linear sensor B to the normal operating position. Near the operating position, pressure values are read during the upward and downward movement and the average of the measured values is used as the relief pressure to which possible over- and under-discharges are added.

As the upper 21B and the lower roll 25B of the set of rolls 2OB, rolls having a movable shell may be used, whereby the intermediate rolls 22B-24B may be floating between the upper 21B and the lower roll 25B ····· ···· · • · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · . The nips of the set of rolls 20B are closed by lifting the lower roll 25B upwardly by the cylinder means 50, after which the nips are loaded by the shells of the upper 21B and lower roll 25B.

Fig. 3 shows a section of a fastening arrangement of an intermediate roll. A shaft 22C of the intermediate roller 22B is located in a bearing shell 22D held by a pivot arm 32B. The swing arm 32B is attached to the frame R by a bolt 32C at the pivot point. The relief cylinder is attached to the pivot arm 32B at a point 32D. The movement of the relief cylinder is perpendicular to the plane of the figure. The bearing of the pivot arm 32B in the bolt 32B mounted on the frame R is usually performed by bronze bearings in which it is difficult to provide effective lubrication under all conditions. The movements of the set of rollers are small and the movement cycles are periodic. Due to the lubrication problem, the frictional forces increase and this in turn makes controlling the nip forces difficult. A separate lubrication system also adds cost and a service requirement. The bronze bushes of the intermediate rolls and the slideways of the lower roll may be replaced by self-lubricating bronze material, which usually includes graphite. Also bearing bushes made of composite material can serve as bearing elements. With such an arrangement, constant friction conditions are achieved and, because it is maintenance-free, no separate lubrication systems are required.

In the embodiments shown in the figures, the roll stacks 20A, 20B are substantially vertical, but the roll stacks 20A, 20B may be viewed from the aspect of the invention. -8- ········ • · · · · · · · · · · ♦ • I · · · · · · ··········

··· · ♦ ·· Of course, also make an angle with the vertical plane. A line drawn over the centers of the rolls may form a straight or a dashed line.

Only a few advantageous embodiments of the invention have been described above and it will be apparent to those skilled in the art that various changes can be made therein as they come within the scope of the appended claims.

claims:

Claims (2)

GIBLER & POTH Patentanwälte OEG Dorotheergasse 7 - A-1010 Vienna - patent@aon.at Tel: +43 (1) 512 10 98 - Fax: +43 (1) 513 47 76 Claims 1. A method for relieving intermediate rolls of a calender, characterized in that the method comprises the following steps: - each intermediate roll (22B-24B), starting from an uppermost intermediate roll (22B) with the Q command of a pQ-valve (A) connected to a relief cylinder (42B-44B) Intermediate roll is connected, and raised to the normal operating position of the intermediate roll (22B-24B) by monitoring the reading of a linear sensor (B), - the pressures of the pQ valve are adjusted during the upward and downward movement of the intermediate roll (22B-24B) and the average of the measured values is used as the relief pressure of the respective intermediate roll (22B-24B), to which possible over- and under-reliefs are added. 2. calender having at least one roll stack (20 B) on which has a lower (25 B) and an upper roller (21 B) and at least one intermediate roller (22 B-24 B) whose bearing shells on the drive and operating side of a swing arm (32B-34B), said swing arm (32B-34B) being further supported on a relief cylinder (42B-44B), -10- -10- • ············ ·································································. Characterized in that each relief cylinder (42B-44B) is provided with a pQ valve (A) and a linear sensor (B). The patent attorney: t@aon.at 513 47 76