WO2003021035A1

WO2003021035A1 - Shoe press and support beam therefor

Info

Publication number: WO2003021035A1
Application number: PCT/SE2002/001574
Authority: WO
Inventors: Lars Gustavsson; Jorma Snellman
Original assignee: Metso Paper Karlstad Ab
Priority date: 2001-09-06
Filing date: 2002-09-04
Publication date: 2003-03-13
Also published as: SE0102952L; SE519994C2; SE0102952D0

Abstract

A support beam for use in a shoe press is asymmetrical in reference to its centre of gravity. In a shoe press with such a support beam (4), the beam's centre of gravity is on a press cylinder centre line (C), spaced from the press plane (C1).

Description

SHOE PRESS AND SUPPORT BEAM THEREFOR

The present invention relates to a shoe press and a support beam for the. shoe press. In a shoe press or in an extended nip press, it is often desirable to have an asymmetrical pressure profile in the running direction of a paper or board web (the machine direction), more specifically so that the pressure on the paper or board web is higher on the exit side of the press nip - formed between a press shoe and a counter roll - than on the entry side (so called tilt). An example hereof is shown in US-A 4,713,147, Fig. 2. This publication discloses also methods and devices for moving the maximum pressure to a desired place in the press nip, so as to enable an optimal pressing of various paper grades. This is done by means of hydraulic loading devices acting on the press shoe of the extended nip press roll, supported by a horizontal support beam or a structural element, which is connected to the shoe press framework. The loading element is movable in the machine direction relative to the press shoe or a plurality of loading elements spaced from one another in the machine direction are operated with different hydraulic pressures.

It is to be understood that in the shoe press, the paper or board web is sandwiched between a press jacket, that runs direct over the press shoe, and the counter roll, in direct contact with one or two press fabrics.

In the shoe press according to US-A 4,931,142, the structural element, the loading device (press chamber) and the counter roll are symmetrically arranged in relation to a vertical press plane, which symmetrical arrangement is indicated as an essential feature, so that the press forces are directed to the press plane in the structural element. Inclined force directions or force directions that are displaced relative each other, as proposed in DE-A 3030 233, are condemned in US-A 4,931,142 as being undesirable due to generation of disturbing transverse forces or bending moments. In US-A 4,931,142, the sliding surface of the press shoe, that is contacting the press jacket, is displaced relative to the press plane, so that the pressure in the press nip is asymmetrical in the machine direction.

The object of the invention is to avoid the influence of the disturbing transverse forces and bending moments on the support beam or the structural element of a conventional shoe press, also in case the shoe press is given the possibility of varying the pressure in the nip in the machine direction.

This object is achieved with a shoe press and the structural element or the support beam according to the independent claims, while preferred embodiments are given the features of the dependent claims.

Thus, the inventive idea, in contrary to the known technique, is to make the structural element or the support beam of a shoe press asymmetrical in such manner that the support beam's centre of gravity is outside of the press plane of the shoe press in the symmetry line of the loading device. The invention will now be described in more detail with reference to the appended drawings.

FIG. 1 shows a cross sectional view of a shoe press with a support beam or a structural element of the conventional symmetrical design.

FIG. 2 shows a cross sectional view of a shoe press with a support beam or a structural element according to the invention.

FIG. 3 shows a cross sectional enlarged view of the press shoe with a press roll in the FIG. 2, wherein the press shoe's sliding surface is displaceable in the machine direction for varying of the pressure in the nip.

FIG. 4 shows an eccentric block with a screw seen from the under side in FIG. 3, in the direction IV-IV.

It is to be understood that the press shoe is a one-piece device, while preferably there is a plurality of loading cylinders, which in the longitudinal direction of the press shoe are allocated in one row or in a few rows that are spaced from each other in the cross direction of the press shoe. In FIGS. 1 - 3 a shoe press for a paper- or a paperboard machine press section is shown. The machine comprises the conventional shoe press components press shoe 1, and counter roll 2 with the rotation direction R, which together form an extended nip N, through which the paper or paperboard web W, which is to be dewatered, runs together with a rotating flexible press jacket 3 and one or two press fabrics F, one of which is shown. A horizontal I beam 4, which belongs to the shoe press framework system (not shown, but a neck of the support beam for a pedestal bearing has reference numeral 5) has a plurality of press cylinders 6, each having a cylinder 7 and a piston 8, which press cylinders 6 are placed in a row in the longitudinal direction of the shoe between a beam side that faces the press shoe and an opposed side of the press shoe. The cylinder 7 is a two-part cylinder, one cylinder part 7' being attached to the press shoe 1 and the other cylinder part 7 "being attached to the beam 4. The attachment is made by means of screws 9 and 9', respectively. Sealing rings 10, 10' that are placed on the outer side of the piston 8, which is common to the two cylinder parts 7', 7", seal two working chambers 11, 11' against a leakage of the pressurised fluid that is fed into the chambers 11, 11' via a duct 12 in a cylinder base 7a and an orifice 12' in the cylinder part 7". The base 7a and the duct 12 are common to all of the press cylinders 6, and there is a branch from the duct 12 to each orifice 12', which branch extends perpendicularly to the sectional view of FIG. 3. As known per se, the press shoe may have hydrostatic pockets 15 in its surface facing the counter roll for known lubrication purposes. These pockets, if provided, can be supplied with pressurised fluid by a detachably attached pipe 16 mounted along one long side of the press shoe, which pipe 16 communicates with the pockets via openings 17 in the pipe walls and drillings 18 made in the press shoe. The design of the press cylmders 6 described hitherto has large similarities to the press cylinder described in WO 00/68497, to which is referred for more detailed information. The above described embodiment of the press cylinder - with two cylinder parts - is advantageous as it will permit free movement of the press shoe both in the machine direction and the cross machine direction, i.e. the risk of seizing between the press shoe and the piston of the press cylinder is reduced.

In prior art designs, see FIG. 1, the centre line C of the press cylinders 6 is spaced from the shoe press centre line Cl, which is in the press plane and contains the centre of gravity T.P. of the support beam. This causes stresses in the beam and may cause deformations therein. In contrast thereto and according to the invention, see FIG. 2, the press cylmders 6 are arranged so that their centre line C contains the support beam centre of gravity T.P. However, the centre line C of the press cylinders still is spaced from the press plane, so that an asymmetrical pressure prevails in the extended press nip N. This displacement of the centre of gravity of the support beam is achieved by means of an asymmetrical I beam 4, where, as shown in FIG. 2, the flanges on the right side of the I beam are made thicker then on the left side of the I beam web, in the symmetry axis of which the T.P. is situated.

To permit a variation in the machine direction of the press force against the web to be dewatered, the mounting of press shoe 1 on cylinder part 7 is carried out via eccentric blocks 19, which engage the cylinder part 1 here via a flange 7'" provided on cylinder part 7'. The blocks are equilateral polygons. Consequently, the press shoe 1 can be moved in the machine direction on the press cylinders 6 by loosening the screws 9 and thereafter turning blocks 19 on the screws 9. If the press shoe 1, for instance, is to be moved in the running direction of the paper web, the right block 19 (FIGS. 3 and 4) is rotated about its screw 9 so that the block's 19 distal side edge, in relation to the screw axis, engages the flange, and the left block 19 is rotated about its screw so that the block's proximate side edge, in relation to the screw axis, engages the flange.

Claims

1. Support beam for use in a shoe press, characterised in that it is asymmetrical in reference to its centre of gravity.

2. Support beam according to claim 1, characterised in that the beam is an

I beam.

3. Shoe press for a paper or board machine, the shoe press comprising a press shoe (1) and at least one press cylinder (6), which is located between the press shoe and a horizontal support beam (4) included in a frame system for the shoe press, said press cylinder having working chambers (11, 11 % which can be loaded with hydraulic fluid, for pressing the shoe against a counter roll (2) to form an extended nip (N) for pressing a paper or board web, characterised in that the said beam (4) is asymmetrical so that its centre of gravity is on a press cylinder centre line (C), spaced from the pressure plane (Cl) of the press.

4. Shoe press according to claim 3, characterised in that the press shoe (1) is arranged to be movable in the machine direction on the press cylinder (6).

5. Shoe press according to any one of claims 3 and 4, characterised in that the beam is an I beam.