WO2000068497A1

WO2000068497A1 - Shoe press

Info

Publication number: WO2000068497A1
Application number: PCT/IB2000/000574
Authority: WO
Inventors: Juha Kivimaa; Timo Pirinen; Jorma Snellman
Original assignee: Metso Paper Oy; Valmet Oy
Current assignee: Valmet Technologies Oy
Priority date: 1999-05-06
Filing date: 2000-05-04
Publication date: 2000-11-16
Anticipated expiration: 2001-11-06
Also published as: EP1198639A1; EP1198639B1; DE60014908T2; DE60014908D1; ATE279575T1

Abstract

A shoe press for a paper or board machine, comprising a press shoe (1) and a counter roll (2), which between them form an extended nip (N) for a paper or cardboard web and circulated flexible belt (3), at least one loading cylinder (6) which is arranged between a horizontal beam (4) included in the frame system (4, 5) of the shoe press, and the press shoe (1) and adapted to press the press shoe towards the counter roll (2). The cylinder (7) or piston (8) of the loading cylinder is turnably mounted about an axis (C) in relation to which the axis (C1) which forms an axis of symmetry for the working chamber (8') of the loading cylinder is eccentric, and that the shoe press has operating means (18, 18'; 42, 42', A) for turning the cylinder or piston of the loading cylinder for controlling the pressure profile of the shoe press, said operating means comprising an actuating member (A) extending outside the belt (3).

Description

SHOE PRESS

The present invention relates to a shoe press for a paper or board machine according to the preamble to claim 1.

A shoe press with a device for displacing a press shoe relative to the centre line of the shoe press, containing the centre line of the counter roll, is known from Fig. 6 in DE-A1-331 74 57 where the device comprises a pressure-fluid-actuatable tube and a spring. Various other devices for displacing the centre of gravity of the supporting force acting on the press shoe relative to the press shoe are disclosed in US-A-4 , 713 , 147, in which a press shoe support between the press shoe and the frame system of the shoe press is displaceable in the cross direction relative to the press shoe. In one variant, the press shoe support is a pressure-fluid-actuatable loading cylinder for pressing the press shoe towards the counter roll.

The above-mentioned possibilities of displacement serve to allow variation of the press force or pressure profile on the paper or cardboard web in the nip between the press shoe and the counter roll, said variation in turn aiming at being able to optimally press different paper/cardboard qualities. For example, when pressing thin paper qualities that are exposed to rewetting at the outlet end of the extended nip, a press force pattern is required, which has its maximum close to said outlet end and, when pressing cardboard qualities that are exposed to the risk of breaking if the press force pattern is too pronounced, a relatively uniform press force pattern is required, which has its press force maximum close to the centre of the extended nip.

The invention is based on said variant according to US-A-4 , 713 , 147 and its object is to simplify and make the device for displacing the centre line of the loading cylinder relative to the centre line of the press less expensive, and in particular to be able to easily displace the centre line of a plurality of loading cylinders simultaneously. The object is achieved by a shoe press of the type described by way of introduction and having the features defined in claim 1. Advantageous embodiments have the features stated in the dependent claims.

The invention will now be described in more detail with reference to the accompanying drawings, in which

Fig. 1 is a cross-sectional view of a non-limiting embodiment of the invention in the machine direction,

Fig. 2 is a cross-sectional view of another embodiment of the invention in the machine direction, parts of the shoe press according to Fig. 1 being removed for better clarity, and

Figs 3a, 3b and 3c are schematic top plan views of the second embodiment in a basic position corresponding with the position in Fig. 3 and two other operating posi- tions in the cross direction.

Fig. 1 illustrates a shoe press for the press section of a paper or board machine, said machine comprising the conventional shoe press components press shoe 1, counter roll 2 having the direction of rotation R, which between them form an extended nip N, in which a paper or cardboard web , which is to be dewatered, runs together with a circulated flexible press belt 3 and one or two press felts F, of which one is shown. A horizontal beam 4 associated with the frame system 5 of the shoe press has, between its side facing the press shoe and the opposite side of the press shoe, a number of loading cylinders 6 which are arranged in a row or in several rows in the longitudinal direction of the shoe press and have a cylinder and a piston. The cylinder consists of two parts 1 , 1 ' and a uniform piston 8 through which a duct 8' extends and mutually connects two working chambers 8", 8 '" of the loading cylinder, which can be considered as a single working chamber if the duct 8' is very wide. The cylinder part 7 is fixed to the upper side of the horizontal beam 4 by means of two sectional rails 9, 9¹ arranged in the longitudinal direction of the press shoe 1 in diametrically opposed positions of the cylinder part 7, and screws 10 extending through the rails 9, 9' and being screwed into the beam 4, as illustrated. Analogously the cylinder part 7' is fixed to the underside of the press shoe 1 by means of two sectional rails 11, 11' and screws 12 which are screwed into the press shoe 1, in this case, however, via an adapter 13. The sectional bars 9, 9'; 11, 11' engage with the cylinder parts 7, 7' in such manner that the latter can be made to turn about a common centre axis C, secured against displacement in the machine direction, i.e. the position of the axis C being fixed within predetermined tolerance limits so that said turning of the cylinder parts 7, 7' is allowed without jamming. In the embodiment, flanges 14, 14' are arranged for this purpose on the cylinder parts 7, 7' and guiding grooves 15a-15d are formed in the sectional rails 9, 9' ; 11, 11' .

The piston 8 is laterally sealed against the cylindrical inner surface of each cylinder part 7, 7' by means of a sealing ring 16, 16 ' . The cylinder parts 7, 7' are eccentrically formed in such manner that they have one and the same outer radius counted from their common centre axis C, in relation to which the common centre axis Cl of the internal cylinder surfaces of the cylinder parts 7, 7' and, thus, of the outer surface of the piston 8 is displaced in parallel.

In this embodiment, the axis C extends in the centre line of the shoe press, in the so-called press plane of the shoe press, in which also the centre axis of the counter roll 2 extends. With a press shoe which is symmetrical relative to the press plane (axis C) , the press force has its maximum in the press plane if C=C1, seen in the machine direction. With a view to obtaining the regulation, mentioned by way of introduction, of the press force pattern or the pressure profile on the paper or cardboard web in the extended nip N between the press shoe 1 and the counter roll 2, the distance in the machine direction between the axes C and Cl is according to the invention regulated by turning the cylinder parts 7, 7' about their common centre axis C.

For the purpose of turning, the cylinders 7, 7' are in this embodiment each formed with a circumferential toothing 17, 17' with vertical teeth which can be formed of gear rims fixed to the cylinder parts 7, 7', and the toothings 17, 17' engage, along the cylinder generatrix, with a toothing on a gear rack 18, 18' each, which can be made to move in a translatory manner in its longitudinal direction, which corresponds with the longitudinal direction of the press shoe, i.e. the cross direction, during turning of the cylinder parts 7, 7'. The sectional rails 9, 9'; 11, 11' have for this purpose guiding grooves 19, 19' for the gear racks 18, 18', said guiding grooves holding the gear racks in such manner that they can only move in their longitudinal direction when being operated.

The gear racks 18, 18' are operable, for said turning of the cylinder part, from a position outside the shoe press, so that the press force or pressure profile of the shoe press (determined by the distance in the machine direction C-Cl) can be changed or controlled when necessary, without the belt 3 of the shoe press having to be dismounted. Of course, the gear racks 18, 18' are to be operated in unison. The gear racks 18, 18' can therefore be mutually fixedly interconnected outside the one end wall or both end walls of the shoe press, where the operating means for displacement of the gear racks are arranged. A person skilled in the art can easily find constructions of the operating means in his normal source of knowledge, for instance a crank mechanism or a hydraulic jack, which is allowed to press or pull the ends of the gear racks 18, 18' positioned outside said end wall/end walls, thereby effecting turning of the cylinder parts 7, 7' in unison in one or the other turning direction as the rela- tive displacement C-Cl is to involve becoming mutually closer or more remote. The two gear racks 18, 18' can also be combined to a single, broader gear rack.

An arbitrary suitable operating means adjacent to the two end walls G of the shoe press is designated A in Fig. 3.

It goes without saying that the loading cylinders 9 are supplied with pressure fluid for pressing the press shoe towards the counter cylinder 2 for treating the paper/cardboard web W in the extended nip of the shoe press. To this end, there is a pressure fluid duct 20, extending from a source (not shown) via duct branches 20' and apertures 21 formed in the end wall of the cylinder part 7' to the working chambers 8", 8'" of the loading cylinders 6. The duct 20 and the branches 20' are here formed in the adapter 13 (which serves merely to facilitate the making of the duct 20 and the branches 20'; it should be possible to form these directly in the shown press shoe 1) , and a sealing ring 22 is arranged to seal between the adapter and the opposing surface of the cylinder 7 ' .

The Figures also illustrate components which are not necessary for the understanding of the invention: a lubrication bore relief 30 which is formed in the surface of the press shoe 1 facing the counter cylinder 2 and to which lubricating fluid is supplied from a source (not shown) , via a pipe 31 which is fixed to the inlet side of the press shoe and has holes 32 in its wall, and a duct 33 formed in the press shoe 1, the pipe 31 being able to supply a plurality of lubrication bore reliefs 30 spaced apart in the longitudinal direction of the press shoe 1, via a corresponding number of ducts 33 and holes 32. The pipe 31 and a rounded portion 34 on the outlet side of the press shoe 1 as well as opposite supports 35, 36 form guide means for the press shoe. An abutment for the stroke of the piston 8 is designated 37.

The two-piece cylinder 7, 7' is advantageous by allowing the piston 8 to be floatingly supported and freely movable in all directions in the cylinder parts 7, 7'. However, the invention is, of course, also applicable to a loading cylinder which is formed in one piece, corresponding to the cylinder part 7', like the piston, and which rests against the beam 4, the working chamber of the loading cylinder 6 being supplied with pressure fluid through a duct in the beam 4 and a duct in the piston. The invention is also applicable to a loading cylinder with a two-piece piston and a cylinder, the two pis- tons defining between them the common working chamber of the loading cylinder, said working chamber being supplied with pressure fluid through a duct in the beam or the press shoe and a duct in each piston part. On the whole, the invention is applicable in cases where there is a detachable or movable connection between the loading cylinder and the press shoe.

A second embodiment of the invention is shown in Fig. 2, in which merely the inventive principle is illustrated in more detail. The same reference numerals in Figs 1 and 2 designate equivalent components. In this second embodiment, the cylinder parts 7, 7' of the cylinder, which is here also made in two pieces, have the same inner and outer diameter and an eccentricity C-Cl is obtained by mounting the cylinder parts 7, 7' to be turn- ed about an axis C in the centre line of the shoe press in the press plane which is parallel with, but spaced from the common centre axis Cl of the cylinder parts 7, 7'. The mounting is effected by means of pivot pins 40, 40' which extend through the end wall of the cylinder parts 7, 7' and are attached by screwing to the press shoe 1 and the beam 4, respectively. The pin 40 which is attached to the press shoe 1 also acts as an inlet open- ing, corresponding to the hole 32 in Fig. 1, for pressure fluid to the working chamber 8' of the loading cylinder.

For turning of the cylinder parts 7, 7', turning arms 41, 41' are fixed to the cylinder parts 7, 7' and are at their free end articulated each to an operating rod 42, 42'. The articulated joint is shown at 43. It will now be appreciated that when pressing or pulling the operating rods 42, 42', the cylinder parts 7, 7' are turned about the axis C, whereby the common centre axis Cl of the cylinder parts is displaced relative to the axis C and the press force pattern or pressure profile in the extended nip N changes .

Figs 3a-3c are schematic top plan views of loading cylinders 7, 7' and illustrate schematically the turning in unison of three loading cylinders 6 (7, 7') from a basic state (C=C1 in the machine direction) in Fig. 3a, corresponding with Fig. 2, to two other operating states. Fig. 3b illustrates pushing of the operating rods 42 (42') for turning of the loading cylinders 6 (7, 7') in counterclockwise direction from the basic state, and

Fig. 3c shows pulling of the operating rods 42, 42' for turning of the loading cylinders 6 (7, 7') in clockwise direction from the state in Fig. 3a or 3b.

The dashed line Ca represents the press plane con- taining the axis of rotation C of the loading cylinders and the dashed line Cb represents the eccentricity. The dashed lines Cc and Cd represent planes containing Cl, where the maximum press force is obtained at a distance from the press plane on, for instance, the outlet side of the shoe press or on the inlet side thereof. If desired, the possibility of varying the press force can be limited to one side only of the press plane.

It will be appreciated that the load pressure from the loading cylinders on the press shoe is to be neutra- lised or reduced while the turning operation as described above proceeds . The inventive principle is also applicable to shoe presses in an inverted position compared with Figs 1 and 2, i.e. shoe presses where the counter roll 2 is positioned at the bottom and the press shoe 1 and the loading cylinders 6 at the top.

The term shoe press should in this description be understood to comprise also a shoe press for calendering.

It goes without saying that the invention is also applicable to a shoe press with a single loading cylin- der.

Claims

1. A shoe press for a paper or board machine, com- prising a press shoe (1) and a counter roll (2) , which between them form an extended nip (N) for a paper or cardboard web and a circulated flexible belt (3) , at least one loading cylinder (6) which is arranged between a horizontal beam (4) included in the frame system (4, 5) of the shoe press, and the press shoe (1) and adapted to press the press shoe (1) in the direction of the counter roll (2) , c h a r a c t e r i s e d in that the cylinder

(7) or piston (8) of the loading cylinder is turnably mounted about an axis (C) , in relation to which the axis (Cl) which forms an axis of symmetry for the working chamber (8') of the loading cylinder is eccentric, and that the shoe press has operating means (18, 18'; 42, 42 ' , A) for turning the cylinder or piston of the loading cylinder for controlling the pressure profile of the shoe press, said operating means comprising an actuating member (A) extending outside the belt (3) .

2. A shoe press as claimed in claim 1, c h a r a c t e r i s e d in that the cylinder (7, 7') of the loading cylinder (6) has a casing wall of non-uniform thickness.

3. A shoe press as claimed in claim 1, c a r a c t e r i s e d in that the cylinder (7, 7') of the loading cylinder (6) has a uniform wall thickness and eccentrically mounted for turning relative to the axis of symmetry (Cl) of the working chamber (8) .

4. A shoe press as claimed in any one of claims 1-3, c h a r a c t e r i s e d in that the cylinder (7, 7') of the loading cylinder (6) has an external toothing (17,

17 ' ) which extends along the circumference and with which a gear rack (18, 18') engages, which is connected to the operating means (A) .

5. A shoe press as claimed in any one of claims 1-4, c h a r a c t e r i s e d in that the cylinder (7, 7') of the loading cylinder (6) is connected to an arm (41, 41') which in turn is connected to the actuating member (A) .

6. A shoe press as claimed in claim 5, in which a plurality of loading cylinders (6) are arranged, c h a r a c t e r i s e d in that the arms (41, 41') are articulated to a rod (42, 42') which in turn is connected to the actuating member (A) .