SHOE PRESS AND LOADING CYLINDER UNIT THEREFOR

Abstract: A shoe press for a paper or board machine, comprising a press shoe (1) and a counter roll (2), which between themselves form an extended nip (N) for a paper or cardboard web and a circulated flexible belt (3), a plurality of hydraulic loading cylinders (6) which are arranged between a horizontal beam (4) included in the frame system (5) of the shoe press and the press shoe (1) and adapted to press the press shoe against the counter roll, the pistons (8) of the loading cylinders being fixedly connected to the horizontal beam (4), the respective working chambers (10) of the loading cylinders being, for hydraulic fluid supply of the loading cylinders, connected by means of a vertical duct (11) formed in the piston (8) of the loading cylinder to a horizontal feeding duct (9) which extends in the cross-direction of the machine and which is common to all working chambers (10). The horizontal feeding duct (9) extends through the pistons (8) of the loading cylinders. In a loading cylinder unit, the horizontal feeding duct (9) is formed in a bar (14), which constitutes the ends of the pistons (8) of the loading cylinders or detachably connects said pistons.

Description: SHOE PRESS AND LOADING CYLINDER UNIT THEREFOR The present invention relates to a shoe press for a paper or board machine, comprising a press shoe and a counter roll, which between themselves form an extended nip for a paper or cardboard web and a circulated flex- ible belt, a plurality of hydraulic loading cylinders which are arranged between a horizontal beam included in the frame system of the shoe press and the press shoe and adapted to press the press shoe against the counter roll, the respective pistons of said loading cylinders being fixedly connected to the horizontal beam, the respective working chambers of the loading cylinders, being, for supplying the loading cylinders with hydraulic fluid, connected by means of a vertical duct formed in the piston of the loading cylinders, to a horizontal feeding duct extending in the shoe press in the machine direction and being common to all the working chambers. Such shoe presses are disclosed in, for instance, EP-345 501 B2; DE-195 15 832 Cl and DE-44 09 316 Cl. The working chamber in the loading cylinders in these prior-art shoe presses are pressurised by hydraulic fluid via ducts bored in the frame system of the shoe press. Boring the frame system, in most cases consisting of steel beams, in a shoe press for pressurising by hydraulic fluid is a complicated and expensive proce- dure and causes weakening of the beam, such that this is deflected more easily, which results in, inter alia, deformation of the duct. There is a need of simplifying and making the supply of hydraulic fluid to the working chamber in the loading cylinders less expensive, while obviating the other drawbacks mentioned above. This need is satisfied by the invention. More specifically, the shoe press described by way of introduction has the inventive features that the hori- zontal duct extends through the piston of the loading cylinders . Boring the pistons of the loading cylinders is essentially easier than boring the frame system of the shoe press, and moreover the frame of the shoe press need not be formed with weakening ducts for supplying the loading cylinders with hydraulic fluid. If the horizontal duct according to claim 2 is arranged in a separate bar, the additional advantage is obtained that the feeding duct can be manufactured in a particularly simple manner, for instance by extruding aluminium. Extrusion of aluminium allows the manufacture of bars in optional lengths for supplying an arbitrary number of loading cylinders. Such a bar also allows simple, easily accessible and easily releasable connection of the loading cylinders to the horizontal beam. The bar with the horizontal duct and the loading cylinders constitute a movable unit. According to claim 6, this idea is used to move the loading cylinders in the machine direction of the paper machine, thereby making it possible to vary the pressure profile on the paper/cardboard web in the nip, said variation in turn allowing optimum pressing of different paper/cardboard qualities. A particularly simple eccentric arrange- ment is stated in claim 7. The inventive idea is advantageously accomplishable also according to claim 4. A special advantage of this arrangement is that it allows freedom of choice for connecting the hydraulic fluid source to the horizontal duct, more precisely in one of the pipes connecting the bores, which connection can be easily carried out by means of conventional coupling elements. A special simple connection of the bores of the pistons and the pipes is achieved, according to claim 5, by easy insertion of the pipe ends, provided with seals in the bores. This results in a certain amount of flexibility in the connection and independence of heat expansion and deflection of horizontal beam of the frame. 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 in the cross-direction, Fig. 3 is a cross-sectional view of the second embodiment in the cross-direction, and Fig. 4 is a top plan view of an eccentric plate, section IV-IV in Fig. 2. It is understood that the press shoe is made in one piece, while the loading cylinders which are several in number, are distributed in the longitudinal direction of the press shoe (in the cross-direction) in one row or in several rows spaced from each other in the machine direction. The Figure shows 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 themselves 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 its side facing away from the press shoe, a plurality of loading cylinders 6 arranged in a row in the longitudinal direc- tion of the press shoe and having a cylinder part 7 and a piston 8, the latter being fixed to the beam 4 in a manner that will be described in more detail below. The press shoe 1 is in this case loosely arranged on the loading cylinder part 7, which can have, in a manner known per se, a hydrostatic compartment in its surface facing the press shoe for floatingly supporting the press shoe. In the piston 8 extends a horizontal duct 9 which is formed in the longitudinal direction of the shoe (cross-direction) and adapted to supply the working chamber 10 of the loading cylinders with hydraulic fluid, e.g. oil, via a vertical duct 11 in the piston 8, the duct 9 being common to the working chamber of all loading cylinders, while there is a vertical duct 11 for each working chamber, connecting the common duct 9 with the working chamber. An O-seal 12 seals between the piston 8 and the cylinder part 7. Reference is once more made to Fig. 1. The common duct 9 is formed in a separate horizontal bar 14, and the vertical ducts 11 consist of two vertical duct parts 11' and 11", the duct part 11' being bored through the wall of the bar to the duct 9 in the bar, and the duct part 11" is bored in the piston 8. In this manner, vertical ducts 11' can be bored in advance in the bar 14 and be sealed to be use later, if, for instance, further loading cylinders 6 are to be mounted, or be bored only on such occasions. Thus, the bar 14 forms part of all pistons 8, screws 15 providing for connection of the piston parts. Advantageously the bar is made of aluminium (alloy) which can be extruded to obtain the desired section of the bar 14 and the desired diameter of the common duct 9. When boring the vertical ducts 11', a space for an O-seal 11'" is formed in the end of these ducts 11'. The duct 9 is supplied with hydraulic fluid from a source (not shown) at one of its ends. A further possibility of commonly supplying a plurality of loading cylinders 6 is shown in Figs 2 and 3, where a shoe press with a plurality of loading cylinders 6 arranged in a row is indicated, two being shown. The common horizontal duct 9 is formed of bores 9' in the pistons 8 and of duct components 9", which extends between the loading cylinders 6 which mutually connect the bores 9'. The duct component 9'" is a T piece, whose leg, indicated by a dash-dot line, serves to connect the duct 9 to a hydraulic fluid source. The ends of the duct components 9" are simply inserted in the bores, which have widened ends 9a with an abutment 9b and an O-ring 9c for sealing. This embodiment allows in an advantageous manner connection of the hydraulic fluid source in the duct 9 between two optional neighbouring loading cylinders 6 and also allows in an advantageous manner absorption of forces caused by heat deformation. Besides, the same reference numerals as in Fig. 1 are used for equivalent shoe press components. The securing of the pistons 8 on the beam 4 is preferably carried out in such a manner that the loading cylinders 6 can, if desired, be moved relative to the press shoe 1 in the machine direction, for moving the centre lines Cl of the loading cylinder 6 relative to the centre line C2 of the shoe press. Such a desideratum can be of interest for reasons described above. The securing device consists, in the illustrated embodiments, of a suitable number of screws 16 and screw plates 18 on opposite sides, in the machine direction, of each piston 8, and of a groove 19 formed in the piston on each said piston side. The hole 18' of the plates 18 lets the screws 16 through which are screwed in the beam 4, and the plates 18 engage in the grooves 19 in the sides of the pistons 8, such that when tightening the screws at the screw heads 16', the latter clamp the plates 18 between themselves and the beam 4, thereby fixedly securing the piston 8 on the beam 4. The plates 18 are polygonal in the same way and, as shown, eccentric. The centre line Cl of the loading cylinders 6 can thus be moved relative to the centre line C2 of the shoe press, if desired, by loosening the screws 16 at their heads 16' and rotating the plates around the screws 16 for permitting the desired displacement of the loading cylinder 6 in the desired direction of movement (machine direction) . If the loading cylinder 6 in Fig. 1 is, for instance, to be moved in the direction of travel of the web W, the right plate 18 is rotated such that an edge thereof positioned further away from the centre axis of the screw 16 engages in the right groove 19, and the left plate 18 is rotated such that an edge thereof positioned correspondingly closer to the centre axis of the screw 16 engages in the left groove 19. Alternatively to eccentric plates, for instance, a single eccentrically flanged sectional rod or bar can be arranged on the respective sides of the loading cylinders engaging in the grooves 19 of the pistons 8 by means of a flange and screwed in the beam 4 by means of another flange, the desired movement of the loading cylinders being accomplishable by rotating, after loosening the screws, the rods about their longitudinal axis. By arranging the common duct 9 for feeding the work- ing chambers 10, it is achieved in an advantageous manner that the beam 4 is not weakened by a corresponding bore. The arrangement illustrated in Figs 1 and 2 for supplying one or more hydrostatic pockets 21 arranged in the side of the press shoe 1 facing the counter roll 2 with hydraulic fluid, serving to lubricate the press felt 3. The compartments 21 are supplied with hydraulic fluid by means of a pipe 22, whose hydraulic fluid conducting bore 22" (the hydraulic fluid source is not shown) is connected to each compartment by means of a duct 23 formed in the press shoe and a through hole 22" which can be formed in the wall of the pipe 22 and which can be formed as a throttle. The pipe 22 is attached to one side of the press shoe, in this case the upstream side, by means of pipe flanges 24 and screws 25. The pipe 22 can be common to all compartments 21 (Fig. 1) or can be separate for each compartment 21 (Fig. 2), the separate pipes 22 communicating with each other via pipe components 22a like the duct components 9", thereby making it possible to absorb heat-conditioned deformation forces applied to the pipe 22. Alternatively, the pipe 22 or the pipes 22 and the joint pipes 22a can feed hydrostatic compartments 26 between the press shoe and the opposing side of the loading cylinders 6 via ducts 27 (indicated by dashed lines) formed in the press shoe and holes formed in the pipe/ pipes, or another pipe or several other pipes with joint pipes can be arranged on the opposite longitudinal side edge of the press shoe for this purpose. The inventive shoe press is applicable also to calendering operations in a paper or board machine.

Claims: CLAIMS 1. A shoe press for a paper or board machine, com- prising a press shoe (1) and a counter roll (2), which between themselves form an extended nip (N) for a paper or cardboard web (W) and a circulated flexible belt (3) , a plurality of loading cylinders (6) arranged between a horizontal beam (4) included in the frame system (5) of the shoe press and the press shoe (1) and adapted to press the press shoe against the counter roll, the pistons (8) of the loading cylinders being fixedly connected to the horizontal beam (4), the respective working chambers (10) of the loading cylinders being, for supplying hydraulic fluid to the loading cylinders, connected by means of a vertical duct (11) formed in the piston (8) of the loading cylinder to a horizontal feeding duct (9) extending in the cross-direction of the machine, c h a r a c t e r i s e d in that the horizontal feeding duct (9) is common to all working chambers (10) and extends through the pistons (8) of the loading cylinders. 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 horizontal duct (9) is formed in a separate bar (14) which is detachably con- nected to said horizontal beam (4) and said pistons (8) and which forms the surface of said pistons facing the horizontal beam, and that the vertical duct (11) consists of two vertical parts, viz. a duct part (11") vertically formed in the bar (14) and a duct part (11') vertically formed in the piston (8), a seal (11'") being arranged in the position where these duct parts meet. 3. A shoe press as claimed in claim 2, c h a r a c t e r i s e d in that the bar (14) is made of aluminium and is extruded thereof. 4. A shoe press as claimed in claim 1, c h a r a c t e r i s e d in that the horizontal duct (9) consists of bores (9 1 ) in the pistons (8) and of pipes (9") extending between the pistons (8) and connecting said bores . 5. A shoe press as claimed in claim 4, c h a r a c t e r i s e d in that the pipes (9") connecting the bores (9') are detachably inserted in the bores and are sealed therein by means of 0 rings. 6. A shoe press as claimed in any one of claims 2 and 3, c h a r a c t e r i s e d in that eccentric means (18) are arranged on both sides of the bar (14) for mov- ing the loading cylinders (6) in the machine direction after releasing the connection between the bar (14) and the horizontal beam (4). 7. A shoe press as claimed in claim 6, c h a r a c t e r i s e d in that the eccentric means consist of polygonal eccentric plates (18) which engage in grooves (19) formed in the opposite sides of bar (14) and through which screws (16, 16') are passed for releasable fixing of the piston (8) to the horizontal beam (4). 8. A loading cylinder unit for a shoe press for a paper or board machine comprising a press shoe (1) and a counter roll (2), which between themselves form an extended nip (N) for a paper or cardboard web (W) and a circulated flexible belt (3), and a plurality of hydraulic loading cylinders for pressing the press shoe against the counter roll (3) , ducts being formed in the pistons of said loading cylinders and opening into the working chamber of the loading cylinders for supplying hydraulic fluid thereto, c h a r a c t e r i s e d in that the pistons of the loading cylinders at their end facing away from the working chamber are mutually releasably connected by means of a bar (14), or said ends being formed of a bar (14), in which a first duct (9) is formed, which extends in the longitudinal direction of the bar and from which ducts (11') extending through the wall of the bar are branched off and connect to a respective one of said piston ducts (11"). 9. A shoe press for a paper or board machine, comprising a press shoe (1) and a counter roll (2) which between themselves form an extended nip (N) for a paper or cardboard web and a circulated flexible belt (3) , a plurality of hydraulic loading cylinders (6) which are arranged between a horizontal beam (4) included in the frame system (5) in the shoe press and the press shoe (1) and are adapted to press the press shoe against the counter roll, the pistons (8) of the loading cylinders being fixedly connected to the horizontal beam (4), the respective working chambers (10) of said loading cylinders being, for hydraulic fluid supply, connected by means of a vertical duct (11) formed in the piston (8) of the loading cylinder to a horizontal feeding duct (9) extending in the cross-direction of the machine, c h a r a c t e r i s e d in that the horizontal feeding duct (9) extends through the pistons (8) or cylinder parts of the loading cylinders and is formed in a separate bar (14), which is detachably connected to said horizontal beam (4) and consists of extruded aluminium (alloy) .

Inventors: BROX ERIK, GUSTAVSSON LARS, BROX, ERIK, GUSTAVSSON, LARS
Applicants: VALMET KARLSTAD AB, VALMET-KARLSTAD AB
Application year: 1998
Main classification: D21F3
IPC codes: D21F3