WO1998017861A1

WO1998017861A1 - A clamping ring for an enclosed shoe press

Info

Publication number: WO1998017861A1
Application number: PCT/SE1997/001762
Authority: WO
Inventors: Kenth R. TÖRNQVIST; Bo I. Dahlbom; Lars O. T. Gustavsson; U. Mikael Nyman; L. Stefan Karlsson
Original assignee: Valmet-Karlstad Ab
Priority date: 1996-10-22
Filing date: 1997-10-21
Publication date: 1998-04-30
Also published as: SE9603884L; SE508591C2; SE9603884D0; DE29723967U1; AT4761U1

Abstract

An elastic clamping ring (24) for an enclosed shoe press roll (2) intended to clamp the jacket (3) of the shoe press roll (2) to end walls (4, 5) of the shoe press roll. A rigid clamping ring (25) is arranged on the inner side of each end wall (4, 5) to form a groove (26) which opens outwardly in the radial direction and in which the elastic clamping ring (24) is received. A stop member (27) is arranged radially outside the elastic clamping ring (24). By means of a plurality of clamping bolts (31) that are circumferentially evenly distributed, the rigid clamping ring (25) is pulled in the direction of the peripheral end wall part (6, 7) in order to squeeze the elastic clamping ring (24) such that it expands outwardly in the radial direction and clamps the edge of the jacket (3) between itself and the stop member (27). The clamping ring (24) has a hexagonal cross section. The invention also relates to a shoe press roll (2) that uses an elastic clamping ring (24) with a hexagonal cross section for clamping of the jacket of the shoe press roll (2) to the end walls (4, 5) of the shoe press roll.

Description

A CLAMPING RING FOR AN ENCLOSED SHOE PRESS

FIELD OF THE INVENTION

The present invention relates to an elastic clamping ring for a shoe press roll, the shoe press roll being provided with a concave pressure shoe and a flexible jacket and intended to cooperate with a counter roll to form a press with an extended nip for paper or board machines. The elastic clamping ring is intended to fasten the flexible jacket to end walls of the shoe press roll. The edge of the jacket, which is located radially outside the elastic clamping ring and radially inside an outer stop member, is clamped to an end wall of the shoe press roll when the elastic clamping ring is compressed between a rigid clamping ring and a part of the end wall whereby the clamping ring expands radially and clamps the jacket against the outer stop member. The invention also relates to a shoe press roll that makes use of such a clamping ring for fastening the edges of the flexible jacket to the end walls.

BACKGROUND OF THE INVENTION For the production of paper and board, the use of shoe presses has become increasingly widespread. In such a press, a press nip is formed between a rotating roll and a concave shoe whereby a flexible endless band or belt runs around the concave shoe. The first shoe presses were of the so called open type where the flexible endless belt was not closed at it's edges. This caused problems since a lubricant must be supplied between the shoe and the flexible belt. For this reason, an open shoe press entails the problem of lubricant leakage that results in a high consumption of lubricant as well as a risk that the paper web comes into direct contact with the lubricant which is usually oil. Modern shoe presses are therefore usually made as enclosed shoe presses. In an enclosed shoe press, a press roll is used that comprises a concave pressure shoe and two end walls. The endless flexible band consists of a tubular jacket impervious to liquid that runs over the concave shoe and which is fixed at it's edges to peripheral parts of the end walls. The tubular jacket is thereby closed at it's ends such that the problems associated with leakage of the lubricant are eliminated. The fixing to the end walls of the edges of the jacket is thus an essential feature of the enclosed shoe press and a number of different solutions for the fixing of the edges of the jacket have been proposed, see for example US Patent No. 4,975,152 to Filzen et al, US Patent No. 5, 011,578 to Lange et al and US Patent No. 5,098,523 to Ilmarinen et al.

In Finnish Patent No. 90120 (Tampella Papertech OY), an enclosed shoe press roll is disclosed where the jacket is clamped by an elastic clamping ring against a stop ring whereby the elastic clamping nng is compressed between an inner or an outer clamping ring of metal and a peripheral end wall member and expands radially outwards to form a mechanical joint that locks the flexible jacket of the shoe press roll to the end wall of the shoe press roll In Finnish Patent No 90120, two different types of elastic nng are proposed According to a first embodiment, an elastic clamping nng with a substantially rectangular cross section is proposed According to a second embodiment, an elastic clamping nng with a substantially V-shaped cross section is proposed

Tests have showed that the proposed rectangular cross section is capable of fulfilling it's function However, it has been found that repeated loadings, or loading dunng long penods of time, causes a permanent deformation of the rectangular clamping nng such that the cross section of the nng passes from a rectangular shape to a shape that can be described as mushroom-shaped or "chefs- cap shaped" As a result of this phenomenon, problems can arise when the jacket is to be replaced since the elastic clamping nng does not return to it's original shape but remains in a position where it still clamps the jacket Moreover, the rectangular cross section disclosed in Finnish Patent No 90120 is, as showed in the drawings, shaped in such a way that it has greater height than width This entails the disadvantage that the elastic clamping ring must be subjected to a relatively high loading in the axial direction of the shoe press roll in order for the ring to be sufficiently deformed to clamp the flexible jacket of the press roll

The proposed V-shaped cross section can be described in terms of two inclined legs separated by a groove in the ring whereby the groove in the nng faces inwardly Such a cross section of the elastic clamping ring entails two disadvantages Firstly, the groove in the ring makes the deformation of the ring dunng loading more difficult to predict and control Moreover, the bottom of the groove is a risk from the point of view of strength and this profile is therefore not so suitable in connection with the relatively high loadmgs the nng will be subject to when it is used

DISCLOSURE OF THE INVENTION

The purpose of the present invention is to accomplish an elastic clamping nng for clamping the flexible jacket in a shoe press roll to the end walls of the shoe press roll that can be subjected to repeated loadings and be loaded during long periods of time without risk for such permanent deformation that would make the loosening of the mechanical joint difficult or impossible, for example during change of the flexible jacket The clamping ring should also be suited for being subjected to high loadings and be able to be deformed radially outwards without being subjected to unnecessarily high loadings m the axial direction of the press roll An other objective of the invention is to accomplish a shoe press roll that makes use of such a clamping nng

The objective of the invention is met by an elastic clamping nng that is shaped as a solid body (1 e without groove or cavity) and that has a cross section which is substantially square but that deviates from a square cross section in that two of the edges of the square cross section have been provided with bevels The clamping ring thereby obtains the shape of a ring having a first and a second planar side surface that are parallel with each other and peφendicular to the axis of the shoe press roll when the clamping nng is mounted on the end wall of the shoe press, a third side surface that is smooth and circular cyhndncal and that connects the first and the second side surfaces with each other and is peφendicular to the first and the second side surface, a fourth side surface which is smooth and circular cylindrical and peφendicular to the first and second side surface and concentric with the third side surface, a fifth side surface connecting the first side surface with the fourth side surface and a sixth side surface connecting the second side surface with the fourth side surface The third side surface is constituted by one single continuous surface which in it's entirety is peφendicular to the first and to the second side surface The fifth side surface and the sixth can be arched in a plane peφendicular to the plane of the first and the second side surface According to an other embodiment of the invention, the fifth side surface and the sixth side surface can have a frusto- conical shape In the embodiment where the fifth and sixth side surfaces have a frusto-conical shape, the elastic clamping nng will have the cross section of a hexagon with sides of different length In cross section, the elastic clamping rmg will thus have the following shape when the fifth and sixth side surfaces have a frusto-conical shape A first straight side conesponding to the first planar side surface, a second straight side corresponding to the second planar side surface, the second straight side bemg parallel to the first straight side, a third straight side conesponding to the third side surface, the third side bemg peφendicular to the first and the second straight side, a fourth straight side corresponding to the fourth side surface, the fourth side bemg parallel with the third straight side and peφendicular to the first and the second straight sides, a fifth straight side corresponding to the fifth side surface, the fifth straight side connecting the first straight side with the fourth straight side and forming an angle with both the first straight side and the fourth straight side, a sixth straight side corresponding to the sixth side surface, the sixth straight side connecting the second straight side with the fourth straight side and the sixth straight side forming an angle with the second straight side and the fourth straight side When the elastic clamping ring is used, the clamping ring is placed at a peripheral end wall member of a shoe press roll for clamping of the flexible jacket of the shoe press roll. The shoe press roll, which is intended to cooperate with a counter roll to form a press with an extended nip, comprises two end walls, a tubular flexible jacket which is impermeable to liquids and which is locked at it's edges by the elastic clamping ring to peripheral end wall members and stationary carrying elements for the supporting the end walls, the end walls comprising bearing members arranged to permit rotation of the jacket and a section of each end wall located radially outside of the bearing member in relationship to the stationary carrying elements whereby the press roll comprises a pressure shoe intended to form together with the counter roll a press zone with an extended nip through which the jacket is moved in sliding contact with the pressure shoe. A rigid clamping ring is screwed on the inside of the end wall member by means of a plurality of clamping bolts in order to press the elastic clamping ring, which is can be expanded radially outwards, between the rigid clamping ring and the inside of the end wall member such that the edge of the jacket is clamped against a stop member arranged radially outside the elastic clamping ring. The elastic clamping ring has, as has been mentioned above, a first and a second side surface, the first and second side surfaces both being planar and parallel with each other, a third side surface facing away from the jacket and connecting the first and second side surfaces with each other, a fourth side surface which is circular cylindrical and faces the jacket, the fourth side surface being peφendicular to the first side surface and the second side surface, a fifth side surface connecting the first side surface to the fourth side surface and a sixth side surface connecting the second side surface with the fourth side surface. Moreover, the clamping ring forms a solid body and has thus no groove or internal cavity profile.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 schematically shows parts of a wet press having a press roll comprising end walls.

Figure 2 shows a lateral view of one of the end walls according to Figure 1.

Figure 3 is a cross sectional view along the line A-A in Figure 2.

Figure 4 shows a cross sectional view along the line C-C in Figure 2 Figure 5 shows a part of the end wall of Figure 3 before an elastic clamping ring of rectangular cross section has been made to expand radially.

Figure 6 shows a part of the end wall corresponding to Figure 5 after clamping bolts at the end wall have been screwed in with a subsequent expansion of the elastic clamping ring and clamping of the jacket.

Figure 7 is an enlarged representation of the cross sectional shape of an elastic clamping ring of rectangular cross section after expansion of the clamping ring to clamping of the jacket.

Figure 8 A shows the cross sectional shape of the clamping ring according to the present invention when the clamping ring is in an unloaded condition.

Figure 8B shows a segment of the clamping ring according to the present invention.

Figure 8C shows the same segment as Figure 8B in a different perspective.

Figure 9 shows a part of the end wall conesponding to Figure 5 before an elastic clamping ring according to the present invention has been made to expand radially.

Figure 10 shows a part of the end wall conesponding to Figure 8 after the elastic clamping ring according to the present invention has been made to expand radially outwards.

Figure 11 shows the cross sectional form of a previously known clamping ring having a V-shape.

DETAILED DESCRIPTION OF THE INVENTION

With reference to Figure 1, this figure schematically shows parts of a wet press arranged in the wet section of a paper machine or a board machine in order to press water out of and to consolidate a formed wet fibrous web 65.

The wet press comprises a rotatable counter roll 1 and a shoe press roll 2 having a tubular liquid impervious jacket 3 of a flexible material, such as plastics or rubber, and two opposed circular end walls 4, 5 having peripheral members 6, 7, at which the edges 8, 9 of the jacket is connected in air and liquid tight manner by means of an endless elastic clamping ring 24 made of a suitable rubber material or rubber-like material. The shoe press roll is mounted in two frame parts 10, 11 by means of carrying elements in the shape of two stationary neck journals 12, 13 with a circular cross section that extend through central openings in the end walls 4, 5 in air and liquid tight manner. The end walls 4, 5, the jacket 3 and the neck journals 12, 13 thereby enclose a liquid tight chamber 14 that can be sufficiently pressurized, for example 0,5 bar oveφressure, such that the end walls 4, 5 are moved away from each other to keep the jacket 3 sufficiently stretched. Consequently, the end walls 4, 5 are axially displaceable relative to the neck journals 12, 13. Alternatively, spring elements can be arranged in the press roll pressing against the end walls or against one of them in order to stretch the jacket in an axial direction. It is also possible to use pneumatic or hydraulic cylinders for this puφose as well as any suitable combination of the anangements mentioned.

The shoe press roll 2 further comprises a pressure shoe 15, arranged facing the counter roll 1 and forming together with the counter roll a press zone with an extended nip within a predetermined sector of the counter roll 1, where the jacket 3 is thus pressed down against the pressure shoe 15 and runs around a part of the circumference of the counter roll 1. The pressure shoe 15 is carried by an inner support member 16 that is fixedly mounted at the inner parts of the neck journals 12, 13.

The fibrous web, which shall be dewatered, is enclosed between two felts, 66, 67, each of which is arranged to run in it's own loop over a plurality of rolls (not showed) and through said press zone. In operation, the continuous wet fiber web runs through the press zone together with the felts 66, 67 that absorb liquid pressed from the fibrous web.

The showed pressure shoe 15 consists of a slide part 17 and a frame part 18 and the slide part 17 has a sliding surface along which the jacket 3 moves in sliding contact. The pressure shoe 15 that faces the counter roll 1, extends across the jacket 3 parallel to the rotational axis 19 of the counter roll and it has a length that corresponds to or is somewhat less than the length of the counter roll 1, which in turn is somewhat shorter than the shoe press roll 2, such that between the end walls 4, 5 and the counter roll 1, sections 20, 21 of the jacket 3 are formed within the area of the press zone which sections 20, 21 are inclined and retracted in relation to the counter roll 1. In the disclosed embodiment, the pressure shoe 15 is connected to the frame 15 through a jack unit 22 having a plurality of jacks 23 by means of which the pressure of the pressure shoe against the jacket 3 and the fiber web can be regulated. Moreover, there are channel systems (not showed) arranged in the pressure shoe 15 for the supply of lubricant to the sliding surface of the slide part 17 such that a friction-reducing film is formed and maintained between the jacket 3 and the pressure shoe 15. The pressure shoe 15 may be provided with hydrostatic pockets (not showed) that are filled with fluid under pressure acting against the inside of the jacket to compress the fiber web in a controlled manner.

The end walls 4, 5 have circular bearing members 35 for rotation of the jacket and the section 68 of each end wall, located radially outside the bearing member 35, around a rotational axis 36, of which section 68 the peripheral end wall part 6 and 7 respectively thus form a part together with a center part at which the peripheral end wall part is screwed by means of bolts (see Figure 3). The end wall section 68 is rigid and consists of a suitable metallic material. In the embodiment according to Figure 1, the bearing members 35 consist of anti -friction bearings such as ball bearings or roller bearings. Alternatively, slide bearings with plane or spherical sliding surfaces may be used. Furthermore, each end wall 4, 5 comprises cylindrical slide bearings 37 arranged such that the end wall can be axially displaced in relation to the neck journals 12, 13. Alternatively, only one end wall is provided with such a slide bearing 37. In addition, the end walls 4, 5 comprise elements 38 that encircle the rotational axis 36 of the jacket and are concentric with the rotational axis, the concentric elements 38 being ananged so that the peripheral end wall parts 4, 5 may be freely displaced in the axial direction towards each other and against the pressure shoe 15 or the nip area under influence of the axial tensions that arise in the jacket 3 during it's passage through the press zone. The peripheral end wall parts 6, 7 can be pulled inwards and be given an inclination in the nip area with a small angle of about 0,5°. The said local axial tensions will thereby be considerably reduced. The tension-reducing elements 38 may consist of spherical bearings as showed or built-in elastic rings or end wall parts.

Since the jacket together with it's edges is fixed to the end walls, more precisely at the peripheral end wall parts 6, 7 and since the concentric elements 38 are arranged to permit free axial displacement inwards of the peripheral end wall parts 6, 7 within the press zone through the effect of said axial tensions in the jacket 3 the end walls 4, 5 will be inclined in a self-adjusting way during operation.

An endless rigid clamping ring 25 is ananged on the inner side of each end wall 4, 5 to form between itself and the peripheral end wall part 6, 7 a groove 26 which is open outwards in the radial direction. The elastic clamping ring 24 is received in the groove 26. A stop member 27 is arranged radially outside the elastic clamping ring 24 in order to form a concentric slot 30 between itself and opposing cylindric surfaces of the rigid clamping ring 25 and the peripheral end wall part 6, 7. The concentric slot 30 is open inwards to receive the edge 8, 9 of the jacket, initially with a small play. By means of a plurality of axial clamping bolts 31 with an even circumferential distribution, the rigid clamping ring 25 is pulled in the direction of the peripheral end wall part 6, 7 to squeeze the elastic clamping ring 24 in such a way that it expands radially outwards and clamps the edge 8, 9 of the jacket 3 between the elastic clamping ring and said stop member 27 as can be seen in Figures 6 and 10. In the disclosed embodiment, the stop member 27 is formed by one leg of a segmented L- shaped ring 32. At it's second leg 33, the ring 32 is screwed by means of bolts 61 to the peripheral end wall part 6, 7 (see Figure 4). The leg 33 has an axial lip 62 resting in a corresponding axial groove in the peripheral end wall part 6, 7 in order to absorb the torque load that occurs when the jacket 3 is pressed against the outer leg 27.

With reference to Figures 6 and 7, it can be seen what happens to a clamping ring of rectangular cross section when it is made to expand radially outwards. When the clamping ring is subjected to pressure in the axial direction of the shoe press roll and is made to expand radially, the clamping ring obtains a mushroom-shaped or "chefs cap-shaped" cross section with protruding bulges 69, 70. When the clamping ring is relieved, the bulges 69, 70 disappear and the clamping ring resumes it's rectangular cross section. However, the inventors have found that when the clamping ring is subjected to repeated loadings or when it is loaded during a long period of time, the clamping ring can be permanently deformed in such a way that the bulges 69, 70 become permanent. When the mechanical joint is to be loosened, which is necessary when the flexible jacket is to be replaced, it will be found that the clamping ring remains in a position where it still locks the flexible jacket 3.

With reference to Figures 8A, 8B and 8C, the cross section of a clamping ring according to the present invention is showed. This clamping ring has the shape of a hexagon where the sides of the hexagon have different lengths. In cross section, the clamping ring has a first straight side 71, a second straight side 72 which is parallel with the first straight side 71, a third straight side 73 that connects the first straight side with the second straight side 72. The third straight side 73 is peφendicular to the first straight side 71 and the second straight side 72. A fourth straight side 74 is parallel with the third straight side 73 and peφendicular to the first straight side 71 and the second straight side 72. A fifth straight side 75 connects the first straight side 71 with the fourth straight side 74 and a sixth straight side 76 connects the second straight side 72 with the fourth straight side 74. The straight sides 71-76 thus form a hexagon with sides of different length. However, the first straight side 71 has the same length as the second straight side 72. The fourth straight side 74, that forms an outer side, will be facing the flexible jacket 3 when the clamping ring is used while the third straight side 73, that forms an inner side, will be facing the bottom of the groove 26 when the clamping ring is used.

It will now be understood that the clamping ring will have a first planar side surface conesponding to the first straight side 71 of the cross sectional shape of the clamping ring and a second planar side surface corresponding to the second straight side 72. Furthermore, the elastic clamping ring has a third side surface corresponding to the third straight side 73 of the cross sectional shape of the clamping ring, the third side surface forming one single continuous surface that in it's entirety is peφendicular to the first side surface and the second side surface. The third side surface is circular cylindrical and connects the first planar side surface with the second planar side surface. The third side surface is peφendicular to the first side surface and the second side surface. A fourth side surface conesponding to the straight side 74 of the cross section of the clamping ring is peφendicular to the first side surface and to the second side surface. Moreover, the fourth side surface is concentric with the third side surface. A fifth side surface conesponding to the fifth straight side 75 connects the first side surface with the fourth side surface. The fifth side surface has a frusto-conical shape. A sixth side surface conesponding to the sixth straight side 76 connects the second side surface with the fourth side surface. The sixth side surface also is frusto-conical. With reference to Figures 8A, 8B and 8C, a part of the elastic clamping ring 24 is showed where the side surfaces of the ring have been drawn. Each side surface has thereby been given the same reference numeral as the conesponding side of the cross sectional shape of the ring. The first straight side 71 in Figure 8 A thus corresponds to a plane side surface 71 in Fig. 8B, the second straight side 72 according to Fig. 8A to a plane side surface 72 in Fig. 8C, the third straight side 73 according to Fig. 8A to a circular cylindrical surface 73 in Figs. 8B and 8C, the fourth straight side 74 according to Fig. 8A to a circular cylindrical surface 74 according to Figs. 8B, 8C and the fifth and sixth straight side surface respectively to surfaces 75, 76 having a frusto-conical shape as showed in Figs. 8B and 8C. However, the sides 75, 76 can also be curved in a plane peφendicular to the plane of the first plane side surface.

With reference to Figure 10, it is showed what happens when the elastic clamping ring according to the present invention is made to expand radially. Indeed, the ring expands radially but no such bulges 69, 70 are formed as occur when a ring of rectangular shape is used. To the extent that the clamping ring eventually obtains permanent shape changes, for example as a result of being loaded during a long period of time, no problems of unwanted locking of the flexible jacket occur.

With reference to Figure 11, we finally show the cross sectional shape of a previously known elastic clamping ring having a V-shape. Since this cross sectional shape comprises a deep groove 77, the radial expansion of the clamping ring is difficult to control. Moreover, such a cross sectional shape entails undesired problems of strength of material that are eliminated by an elastic clamping ring according to the present invention.

The elastic clamping ring according to the present invention has a cross sectional shape which is formed starting from a square or substantially square cross section. However, the cross sectional shape of the clamping ring according to the present invention deviates from the square cross section in that two of the sides of the clamping ring have bevels as has been described above with reference to the enclosed drawings. However, the clamping ring according to the present invention has a cross section that is similar to a square cross section in that the shortest distance from the third side surface to the fourth side surface is equal to the shortest distance between the first side surface and the second side surface. Hence, the clamping ring does not need to be loaded so much in the axial direction of the shoe press roll in order to achieve sufficient radial expansion of the clamping ring. If the clamping ring had instead been of such a shape that the shortest distance between the third side surface and the fourth side surface was greater than the shortest distance between the first side surface and the second side surface, a higher loading would be required.

With an elastic clamping ring according to the present invention, the risk for undesired locking of the clamping ring is eliminated and the ring obtains good properties of strength and deformation.

Claims

1. A press roll (2) intended to cooperate with a counter roll (1) to form a press with an extended nip for paper or board machines, the press roll comprising two end walls (4, 5), a tubular flexible jacket (3) which is liquid impermeable and which with it's edges (8, 9) is connected to peripheral parts (6, 7) of the end walls (4, 5) by means of an elastic clamping ring (24) and stationary carrying elements (12, 13) for carrying the end walls (4, 5), the end walls (4, 5) comprising bearing elements (35) ananged to permit rotation of the jacket (3) and a section (68) of each end wall (4, 5) that in relation to the stationary carrying elements (12, 13) is located radially outside the bearing element (35) where the press roll (2) furthermore comprises a pressure shoe (15) which is intended to form together with the counter roll (1) a press zone with an extended nip through which the jacket (3) is moved in sliding contact with the pressure shoe (15) and where a rigid clamping ring (25) is screwed to the inner side of the end wall part (6, 7) by means of a plurality of clamping bolts (31) to squeeze the radially outwardly expandable clamping ring (24) between itself and the end wall part such that the edge part (8, 9) is clamped against a stop member (27) ananged radially outside the elastic clamping ring, c h a r a c t e r i z e d in that the elastic clamping ring has a first (71) and a second (72) side surface, the first and the second side surface (71, 72) both being planar and parallel with each other, a third side surface (73) connecting the first and the second side surface (71, 72) with each other, the third side surface facing away from the jacket, a fourth side surface (74) which is circular cylindrical and faces the jacket (3), the fourth side surface (74) moreover being peφendicular to the first and the second side surface (71, 72), a fifth side surface (75) connecting the first side surface (71) with the fourth side surface (74) and a sixth side surface (76) connecting the second side surface (72) with the fourth side surface (74) and in that the clamping ring constitutes a solid body.

2. An elastic clamping ring (24) intended for a press roll (2) comprising a pressure shoe and a flexible jacket (3) to clamp the flexible jacket to an end wall (4, 5) of the press roll c h a r a c t e r i z e d in that the elastic clamping ring has a first and a second side surface (71, 72), the first and second side surfaces (71, 72) both being planar and parallel with each other, a third side surface (73) connecting the first side surface and the second side surface (71, 72) with each other, a fourth side surface (74) which is circular cylindrical and peφendicular to the first and the second side surface and located radially outside the third side surface (73) such that the third side surface (73) forms an inner side surface and the fourth side surface (74) forms an outer side surface, a fifth side surface (75) connecting the first side surface (71) with the fourth side surface (74) and a sixth side surface (76) connecting the second side surface (72) with the fourth side surface (74).

3. An elastic clamping ring (24) according to claim 2characterized in that the third side surface (73) is circular cylindrical and concentric with the fourth side surface (74).

4. An elastic clamping ring according to claim 2characterized in that the fifth and sixth side surface (75, 76) both have a frusto-conical shape.

5. An elastic clamping ring (24) according to claim 2characterized in that the fifth and the sixth side surface both are curved in a plane peφendicular to the plane of the first side surface (71).

6. An elastic clamping ring (24) intended for a press roll comprising a pressure shoe and a flexible jacket to clamp the flexible jacket to an end wall of the press roll characterized in that the clamping ring (24) has the cross sectional shape of a hexagon.

7. An elastic clamping ring (24) according to claim όcharacterized in that the clamping ring (24) has the cross sectional shape of a hexagon with sides (71, 72, 73, 74, 75, 76) of different length.

8. An elastic clamping ring (24) for a press roll (2) comprising a pressure shoe and a flexible jacket (3), the elastic clamping ring being intended to clamp the flexible jacket to an end wall (4, 5) of the press roll characterized in that the elastic clamping ring has a first and a second side surface (71, 72) both the first and the second side surface being planar, a third side surface (73) connecting the first and the second side surface (71, 72) with each other, a fourth side surface (74) which is circular cylindrical a fifth side surface 75 connecting the first side surface (71) with the fourth side surface (74) and a sixth side surface (76) connecting the second side surface (72) with the fourth side surface (74).

9. An elastic clamping ring according to claim 8characterized in that the third side surface (73) is circular cylindrical and concentric with the fourth side surface (74).

10. An elastic clamping ring according to claim 9 c h a r a c t e r i z e d in that the first and the second side surface (71, 72) are parallel with each other and peφendicular to the third and the fourth side surface (73, 74)

11. A press roll (2) intended to cooperate with a counter roll (1) to form a press with an extended nip for paper or board machines, the press roll comprising two end walls (4, 5), a tubular flexible jacket (3) impermeable to liquid, the edges (8, 9) of which is connected by means of an elastic clamping ring (24) to peripheral parts (6, 7) of the end walls and stationary carrying elements (12, 13) for carrying the end walls, the end walls (4, 5) comprising bearing members (35) ananged to permit rotation of the jacket (3) and a section (68) of each end wall (4, 5) located radially outside the bearing member (35) in relation to the stationary carrying elements (12, 13) and where the press roll (2) further comprises a pressure shoe (15) intended to form together with the counter roll (1) a press zone with an extended nip through which the jacket (3) is moved in sliding contact with the pressure shoe (15) and where a rigid clamping ring (25) is screwed to the inner side of the end wall part (6, 7) by means of a plurality of clamping bolts (31) in order to squeeze the radially outwardly expandable elastic ring (24) between itself and the inner side of the end wall part such that the edge part (8, 9) of the jacket is clamped against a stop member located radially outside the elastic clamping ring (24) c h a r a c t e r i z e d in that the elastic clamping ring has a shape according to any of the claims 2-10.