WO2005078185A1

WO2005078185A1 - Dynamic counter blade support

Info

Publication number: WO2005078185A1
Application number: PCT/SE2005/000210
Authority: WO
Inventors: Per-Olof Bengtsson
Original assignee: Umv Machinery Ab
Priority date: 2004-02-18
Filing date: 2005-02-18
Publication date: 2005-08-25
Also published as: SE526974C2; SE0400386L; WO2005078185B1; SE0400386D0

Abstract

The invention refers to a foil arrangement (33) and a method for a double wire screen former. At least one foil (6) comprises a flexible counter blade (10) extending over the entire screen (3) width. The counter blade (10) is supported on a flexible device (12) mounted on a beam (13) extending in the lateral direction. The flexible device (12) is arranged to apply a flexible pressure on the counter blade (10) such that the counter blade (10) applies a flexible pressure on one of the screens (3). The foil arrangement comprises a dynamic anvil means (19) for dynamically applying a force on the counter blade (10) in the counter direction of the screen (3) movement.

Description

TITLE

DYNAMIC COUNTER BLADE SUPPORT

TECHNICAL FIELD The invention refers to a foil arrangement for a double wire screen former for manufacture of a fiber material web from a fiber material suspension. The foil arrangement comprises a number of foils, where at least one foil comprises a counter blade extending over the entire screen width, in the lateral direction in view of the machine direction. The counter blade is supported on a flexible device mounted on a beam extending in the lateral direction. The flexible device is arranged to apply a flexible pressure on the counter blade such that the counter blade applies a flexible pressure on one of the screens, essentially perpendicular to the extension of the screen. The counter blade comprises a vertical holding profile arranged to be vertically slidably fitted over the beam. The flexible device is fitted within the vertical holding profile between the beam and the vertical holding profile. The invention also refers to a method for ensuring flexible vertical motion of a counter blade.

BACKGROUND ART In the field of paper making machines it is known to use a dewatering unit for dehydrating a fibrous materials such as, for example, wood pulp, advancing between an endless top screen and an endless bottom screen. Each screen may be in the form of a wire screen arranged in a loop. Each wire screen runs around front and rear end rolls and is normally supported by a number of idling supporting rolls. The dewatering unit comprises rigid top foils (also called laths or lists) for applying a mechanical pressure on the top screen and flexible bottom foils for applying a flexible mechanical pressure on the bottom screen. The dewatering unit also comprises a suction unit for applying a negative pressure or vacuum on the top screen, preferably between the top foils, for suction of water from the top screen. Each bottom foil comprises a counter blade extending over the entire bottom screen width, in the lateral direction in view of the machine direction. The counter blade is supported on a flexible device, for example one or several springs, or one or several pneumatic cushions. The flexible device is mounted on a beam extending in the lateral direction which in turn is mounted to a support plate. The flexible device applies a flexible pressure on the counter blade such that the counter blade applies a flexible pressure on the bottom screen, essentially perpendicular to the bottom screen. The counter blade comprises a vertical holding profile arranged to be vertically slidably fitted over the beam. The vertical holding profile has a cross- sectional profile that can be explained as an open rectangular frame, i.e. a rectangular frame without one of its short sides. The flexible device is fitted within the vertical holding profile, between the beam and the vertical holding profile.

In order for the vertical holding profile to slide in the vertical direction, i.e. essentially perpendicular to the bottom screen, there are two pairs of support heads placed between the beam and the vertical holding profile at a vertical distance between the pairs. The heads are arranged to guide the vertical holding profile in its vertical motion about the beam.

One problem with the above described arrangement is that the bottom screen exerts friction forces on the counter blade in the machine direction, which causes rotational or tilting movement of the vertical holding profile such that the vertical holding profile may be jammed in a skew position with reference to the beam. In this jammed position the vertical holding profile cannot exercise free vertical movement, why the necessary flexible vertical movement of the counter blade is inhibited.

There is thus a need for an improved foil arrangement with an improved flexible vertical movement of the counter blade. DISCLOSURE OF INVENTION

The invention intends to remedy the above problems and to bring forward a foil arrangement with an improved flexible vertical movement of a counter blade. This is done by a foil arrangement a double wire screen former for the manufacture of a fiber material web from a fiber material suspension. The foil arrangement comprises a number of flexible foils, where at least one foil comprises a flexible counter blade extending over essentially the entire screen width, in the lateral direction in view of the machine direction. Even though the counter blade is stated to extend over essentially the entire width of the screen width, the counter blade may comprise a number of counter blade elements constituting the counter blade.

The counter blade is supported on a flexible device mounted on a beam extending in the lateral direction. The beam has an extension corresponding to the extension of the counter blade.

The flexible device is arranged to apply a flexible pressure on the counter blade such that the counter blade applies a flexible pressure on one of the screens, essentially perpendicular to the extension of the screen, i.e. in the vertical direction. In a preferred embodiment, the foil arrangement is placed in the paper making machine such that the flexible counter blade applies a flexible pressure on the bottom wire screen.

The counter blade comprises a vertical holding profile arranged to be vertically slidably fitted over the beam. The flexible device is fitted within the vertical holding profile between the beam and the vertical holding profile.

The invention is characterised in that the foil arrangement comprises a dynamic anvil means for dynamically applying a force on the counter blade in the counter direction of the screen movement, i.e. in the horizontal machine direction. One advantage of the invention is that the dynamic force applied on the counter blade in the horizontal direction releases the locking frictional forces between the vertical holding profile and the beam, such that the free flexible vertical movement of the counter blade is improved and ensured. This means that the vertical holding profile is not allowed to be jammed in a skew position, with reference to the beam, but the dynamic anvil means applies the dynamic force at a frequency high enough to ensure the free flexible movement of the counter blade. The frequency is adapted for each situation, for example, the speed of the wire screen and which type of flexible device used. The frequency may also be dynamic (i.e. altered), for example, dependent on information from a gauge. The frequency and the force applied may be controlled by a computer using a control sequence adapted for the prevailing conditions.

The anvil means preferably has a force point at a vertical position on the counter blade at apposition between the screen and the beam. The force point transmits any movement from the anvil means to the counter blade.

In one embodiment, the foil arrangement comprises a resilient means arranged between the anvil means and the counter blade for absorbing relative vertical movement between the anvil means and the counter blade. The resilient means is arranged in the force point for applying pressure on the counter blade. The advantage of using the resilient means lies in that micro movements in the vertical direction between the anvil means and the counter blade is absorbed.

In another embodiment, the resilient means may be replaced by a stiff member for transmitting the force from the force point.

The foil arrangement advantageously comprises a dynamic pressure device for dynamically applying pressure on the anvil means. The dynamic pressure device may be in the form of a mechanical device, or a hydraulic or pneumatic device.

In one embodiment, the anvil means advantageously comprises a lever arm articulately mounted on a shaft. The lever arm has a first end portion on one side of the shaft and a second end portion on the other side of the shaft. The first end portion is arranged to comprise the force point and the dynamic pressure device is arranged for applying dynamic pressure on the second end portion such that the lever arm rotates about the shaft and dynamically applies pressure on the counter blade via the force point.

The advantage of using a lever arm is that an optimum leverage, i.e. momentum, may be used when the lever arm transmits the dynamic pressure from the dynamic pressure device to the counter blade. Further advantages lies in that one dynamic pressure device may control a number of lever arms along the lateral extension of the counter blade. Each such lever arm comprises the means described above and is arranged to perform the function described, i.e. to apply a dynamic force on the counter blade.

The dynamic pressure device may, for example, constitute a flexible pneumatic or hydraulic cushion extending in the lateral direction over the essentially the entire width (lateral direction) of the bottom wire screen. A number of anvil means may then be arranged along the extension of the dynamic pressure device, each of which is affected by the dynamical change of the dynamical pressure device such that each of the anvil means apply a dynamic force on the counter blade.

In one embodiment of the invention, the foil arrangement comprises an adjustable pin for hindering the rotational movement of the lever arm in one direction. The adjustable pin is arranged at the second end portion on one side of the lever arm and where the dynamic pressure device is arranged on the opposite side of the lever arm. The adjustable pin is used for setting the optimal position of the vertical holding profile relative the beam such that the best possible flexible vertical movement is ensured. The optimal position is dependent on the position of the anvil means, i.e. in some embodiments the lever arm, against the counter blade. The foil arrangement advantageously comprises a stop arm in which the adjustable pin is adjustably mounted.

In one embodiment, the foil arrangement comprises a support plate onto which the beam and the dynamic pressure device and the stop arm are mounted.

The invention also refers to a method for ensuring a flexible vertical motion of the counter blade in a foil arrangement for a double wire screen former for the manufacture of a fiber material web from a fiber material suspension. The foil arrangement comprises a number of foils, where at least one foil comprises a flexible counter blade extending essentially over the entire screen width, in the lateral direction in view of the machine direction. The counter blade is supported on a flexible device mounted on a beam extending in the lateral direction. The flexible device applies a flexible pressure on the counter blade such that the counter blade applies a flexible pressure on one of the screens, essentially perpendicular to the extension of the screen. The counter blade comprises a vertical holding profile vertically slidably fitted over the beam. The flexible device is fitted within the vertical holding profile between the beam and the vertical holding profile. The method is characterised in the foil arrangement comprises a dynamic anvil means that applies a dynamical force on the counter blade in the counter direction of the screen movement.

The benefits of the method have been explained above in connection to the description of the apparatus.

BRIEF DESCRIPTION OF DRAWINGS The invention will below be described in view of a number of drawings, where;

Fig. 1 schematically shows a side view of a double wire screen former according to the invention;

Fig. 2 schematically shows a cross-sectional side view of the enhanced section A in fig. 1 of a foil arrangement according to the invention, and where;

Fig. 3 schematically shows a perspective view of the foil arrangement seen in the counter machine direction, i.e. in the x-direction.

MODES FOR CARRYING OUT THE INVENTION

In order to facilitate the description of the invention, figure 1 and 2 show three arrows indicating x-direction, y-direction and z-direction in an orthonorm system. The x-direction indicate the machine direction, the y-direction indicate the lateral direction and the Z-direction the vertical direction.

Fig. 1 schematically shows a side view of a dewatering unit 1 for a double wire screen former according to the invention. Figure 1 shows an endless top screen 2 and an endless bottom screen 3. Each screen is in the form of a wire screen arranged in a loop. Each wire screen runs around front and rear end rolls and is normally supported by a number of idling supporting rolls.

Each wire is both liquid and air permeable. The dewatering unit 1 comprises rigid top foils 5 (also called laths or lists) that applies a mechanical pressure on the top screen 2 and flexible bottom foils 6 for applying a flexible mechanical pressure on the bottom screen 3. The dewatering unit 1 also comprises a suction unit 7 for applying a negative pressure or vacuum on the top screen 2, preferably between the top foils 5, for suction of water from the top screen 2. In figure 1 there are a number of arrows pointing in the z- direction, i.e. from the top screen 2 to the suction unit 7. These arrows indicate the water transport direction due to the suction unit 7. Figure 1 shows that the bottom foils 6 are arranged both before the suction unit 7 and opposite the suction box. The bottom foils 6 may have a relative distance less to, equal to or greater than the relative distance between the top foils 5.

Figure 1 shows a fiber material web 8 from a fiber material suspension disposed between the top screen 2 and the bottom screen 3. The fiber web together with the top screen 2 and the bottom screen 3 is fed in the x- direction.

Figure 1 shows a transfer suction box 9 arranged against the bottom wire screen after the suction unit 7. The transfer suction box 9 applies a negative pressure on the bottom screen 3 such that the fiber material web 8 is attached to the bottom wire screen when the top screen 2 delaminates from the fiber material web 8.

Fig. 2 schematically shows a cross-sectional side view of the enhanced section A in fig. 1 of a foil arrangement according to the invention. Each bottom foil δcomprises a counter blade 10 extending over the entire bottom screen 3 width, i.e. in the lateral direction in view of the machine direction. The counter blade 10 comprises a gliding surface 11 arranged to be pressed against the bottom screen 3 and to allow the bottom screen 3 to glide over the surface with a preferably low friction factor between the gliding surface 11 and the bottom screen 3. The gliding surface 11 may be made from a ceramic, a plastic or another suitable material that does not wear the bottom screen 3 too much nor being worn too much itself.

The counter blade 10 is supported on a flexible device 12, for example one or several springs, or one or several pneumatic or hydraulic cushions. The flexible device 12 is mounted on a beam 13 extending in the lateral direction which in turn is mounted to a support plate 14. The flexible device 12 is fitted in a holder 15 extending in the lateral direction over the entire width of the bottom wire screen. The holder 15 has a shape that restricts the flexible device 12 to expand in any other direction than essentially in the vertical direction. The flexible device 12 applies a flexible pressure on the counter blade 10 such that the counter blade 10 applies a flexible pressure on the bottom screen 3, essentially perpendicular to the bottom screen 3. The counter blade 10 comprises a vertical holding profile 16 arranged to be vertically slidably fitted over the beam 13. The vertical holding profile 16 has a cross-sectional profile that can be explained as an open rectangle, i.e. a rectangle without one of its short sides. The flexible device 12 is fitted within the vertical holding profile 16, between the beam 13 and the vertical holding profile 16.

In order for the vertical holding profile 16 to slide in the vertical direction, i.e. essentially perpendicular to the bottom screen 3, there are two upper support heads 17 and two lower support heads 18 placed between the beam 13 and the vertical holding profile 16. The upper support heads 17 are placed at a vertical distance D2 from the lower support heads 18. The heads are arranged to guide the vertical holding profile 16 in its vertical motion about the beam 13.

In figure 2 the upper support heads 17 are part of the beam 13 structure and constitute a lip section placed on either side of the beam 13 and at the upper most part of the beam 13. The lip section extends in the lateral direction, whereas the beam 13 has a T-shaped cross-section. In figure 2 each lip has a rectangular cross-section, but may have a different cross-section, for example a half dome.

In figure 2, the two lower support heads 18 form part of the vertical holding profile 16 and are arranged as two heels on opposite side of the beam 13, extending along the vertical holding profile 16 in the lateral direction. In figure 2 each heel has a rectangular cross-section, but may have a different cross- section, for example a half dome.

Both the upper support heads 17 and the lower support heads 18 may be arranged with openings (not shown) in the vertical direction for allowing fluid to pass in the vertical direction. The openings may be formed by applying the upper support heads 17 intermittent on the beam 13 and by applying the lower support heads 18 intermittent on the beam 13. Furthermore, the openings may also be done by working the support heads with a suitable machine, for example drilling equipment or cutting or milling equipment.

Figure 2 shows that the foil arrangement comprises a dynamic anvil means 19 for dynamically applying horizontal (x-direction) force on the counter blade 0 in the counter direction of the screen movement. The anvil means 19 has a force point 20 at a vertical position on the counter blade 10 between the screen and the beam 13.

Here "dynamical force" means that a force may be applied or released intermittently, i.e. during a predetermined time period. The dynamical force may be obtained by use of computer using a control sequence.

Figure 2 shows that the foil arrangement comprises a resilient means 21 arranged between the anvil means 19 and the counter blade 10 for absorbing relative vertical movement between the anvil means 19 and the counter blade 10. The resilient means 21 is arranged in the force point 20 for transmitting a force on the counter blade 10 from the anvil means 19. Instead of the resilient means 21 , a stiff member may be used for transmitting the force from the anvil means 19.

Figure 2 shows that the foil arrangement comprises a dynamic pressure device 22 for dynamically applying the force on the anvil means 19. The dynamic pressure device 22 may be a mechanical device, or a hydraulic or pneumatic device, but may also be another suitable device that allows dynamical pressure changes.

Figure 2 shows the dynamic pressure device 22 in the form of a flexible pneumatic or hydraulic cushion extending in the lateral direction over the essentially the entire width of the bottom wire screen. The dynamic pressure device 22 is fitted in a holder 23 extending in the lateral direction over the entire width of the bottom wire screen. The holder 23 has a shape that restricts the dynamic pressure device 22 to expand in any other direction than essentially in the vertical direction. The dynamic pressure device 22 is on the opposite side of the holder 23 confined within a channel beam 24 turned up side down. The channel beam 24 is fitted over the holder 23 and the sides of the cannel beam 24 helps guiding the channel beam 24 in its vertical motion upon a volume expansion or volume contraction of the dynamic pressure device 22.

Figure 2 shows that the anvil means 19 further comprises a lever arm 25 articulately mounted on a shaft 26. The lever arm 25 has a first end portion 27 on one side of the shaft 26 and a second end portion 28 on the other side of the shaft 26. The first end portion 27 is arranged to comprise the force point 20 and the dynamic pressure device 22 is arranged for applying dynamic pressure on the second end portion 28 such that the lever arm 25 rotates about the shaft 26 and dynamically applies a force on the counter blade 10 via the force point 20.

Figure 2 shows that the foil arrangement comprises an adjustable pin 29 for hindering the rotational movement of the lever arm 25 in one direction. The adjustable pin 29 is advantageously a stop screw or a set screw. The adjustable pin 29 is arranged at the second end portion 28 on one side of the lever arm 25 and where the dynamic pressure device 22 is arranged on the opposite side of the lever arm. Figure 2 shows that the lever arm 25 is L-shaped, i.e. the arm is shaped with an essentially 90° angle between the first end portion 27 and the second end portion 28. The shaft 26 is positioned in the angled part of the lever arm 25 and is housed in a bearing 30 that will not be negatively affected by water or clay from the machine. The bearing 30 is preferably of a type that has a low friction when submitted to water. The bearing 30 may then be continuously or discontinuously cleaned by a water jet without any dysfunction. The cleaning may be controlled by a computer using a control sequence.

Figure 2 shows that the adjustable pin 29 is adjustable in the vertical direction and that the dynamic pressure device 22 is arranged in the foil arrangement such that it applies dynamical forces in the vertical direction. The dynamic forces acting on the second end part of the lever arm 25 causes the lever arm 25 to rotate about the shaft 26. Since the lever arm 25 is L- shaped, the vertical (z-direction) motion of the second end part causes a horizontal (x-direction) movement of the first end portion 27 of the lever arm 25. The horizontal motion of the first end portion 27 affects the resilient means 21 such that the resilient means 21 transmits the dynamic force from the dynamic pressure device 22 to the counter blade 10.

Figure 2 shows that the bottom screen 3, the fiber web and the top screen 2 moves in the y-direction and that the counter blade 0 is pressed against the bottom screen 3 in the z-direction. The relative motion between the bottom screen 3 and the gliding surface 11 affects the counter blade 10 by a frictional force working on the gliding surface 11 in the x-direction. The frictional force causes the counter blade 10 to move in the x-direction. Since the counter blade 10 is slidably supported on the beam 13 by the upper and the lower support heads 18, the motion of the counter blade 10 is a rotational movement about the upper support head. However, the rotational movement is hindered by the lower support head. In order for the counter blade 10 to be vertically adjusted, there is a play between the upper support heads 17 and the vertical holding profile 16 and a play between the lower support heads 18 and the beam 13. This play allows the rotational movement and causes the counter blade 10 to tilt somewhat. The tilting and the ongoing frictional force trying to rotate the counter blade 10, causes the counter blade 10 to jam in the tilted position.

The jamming is caused by internal frictional forces in the vertical guiding arrangement that comprises the vertical holding profile 16, the beam 13 and the upper support heads 17 and lower support heads 18. The internal frictional forces refer to the frictional forces between the vertical guiding means and the upper heads and the lower heads. The internal frictional forces lock the vertical holding profile 16 in a specific position. The jammed counter blade 10 cannot move in the vertical direction as intended why the flexible pressure from the counter blade 10 on the bottom screen 3 is not optimal. The situation is even worse in the case where the distance D1 between the gliding surface 11 and the upper support head is greater than the distance D2 between the upper support heads 17 and the lower support heads 18, since the greater distance D1 gives a leverage which causes an even greater rotation momentum which in turn gives a more severe jamming problem.

This problem is solved by the present invention by the dynamic force acting on the counter blade 10 in the horizontal (x-direction) counter direction of the bottom screen 3, i.e. in the counter direction of the rotational movement of the counter blade 10. Figure 2 shows the adjustable pin 29 set in position for the second end part of the lever arm 25. The adjustable pin 29 is set such that the vertical holding profile 16 is adjusted into the optimal position with regard to the play between the upper support heads 17 and the vertical holding profile 16, and with regard to the play between the lower support heads 18 and the beam 13. The dynamic pressure device 22 applies pressure against the second end portion 28 of the lever arm 25 such that the opposite side of the second part of the lever arm 25 is pressed against the adjustable pin 29. When the bottom screen 3 causes the rotational movement of the counter blade 10, the dynamic pressure device 22 releases its pressure and allows the lever arm 25 to rotate during a short time period, after which the dynamic pressure device 22 applies a force (or pressure) on the lever arm 25 such that the lever arm 25 rotates in an anti rotational movement with regard to the rotational movement caused by the bottom screen 3. In view of figure 2, this can be described as the bottom screen 3 causing the counter blade 10 to rotate in the anti clockwise direction and the dynamic pressure device 22 causing the counter blade 10 to rotate in the clockwise direction upon applying pressure.

The anti rotational movement of the counter blade 10 caused by the dynamic pressure device 22 unlock the jammed counter blade 10 and forces it back into its original optimal position with respect to the upper and lower heads. The dynamic pressure device 22 thus unlocks jammed positions when applying a force on the counter blade 10. The dynamic pressure device 22 may be controlled to apply or release pressure as often as needed, for example several times a minute, hence the expression dynamically applying pressure. This control may be done by a computer using a control sequence.

Figure 2 shows that the foil arrangement comprises a stop arm 31 in which the adjustable pin 29 is adjustably mounted, i.e. the pin is mounted such that it may be varied in the vertical direction.

Figure 2 shows that the foil arrangement comprises a support plate 14 onto which the beam 13 and the dynamic pressure device 22 and the stop arm 31 is mounted.

Figure 2 shows a reinforcing structure 32 in the form of a beam 13 with an essentially triangular cross-section. The reinforcing structure 32 is arranged between the lever arm 25s on the channel beam 24 13 in order to distribute the load from the dynamic pressure device 22 such that the channel beam 24 13 does not bulge due to the pressure from the dynamic pressure device 22. Fig. 3 schematically shows a perspective view of the foil arrangement seen in the counter machine direction, i.e. in the x-direction. In the embodiment shown in figure 3, there are three anvil means 19 working on the counter blade 10. The dynamic pressure device 22 extends essentially over the entire width of the bottom screen 3 and all three anvil means 19 are thus affected essentially simultaneous by the dynamic pressure device 22. For example, when the dynamic pressure means 10 exercises a pressure on the channel beam 24, the channel beam 24 transmits the pressure force to the second end portion 28 of the each lever arm 25 which in turn transforms the pressure force into a rotational movement about the shaft 26, such that each lever arm 25 rotates such that the first end portion 27 is brought into a movement in the counter direction of the bottom screen 3 movement, which movement causes a force to act on the counter blade 10 via each pressure point and each resilient means 21. The force acting on the counter blade 10 via each anvil means causes the vertical holding profile 16 to tilt in the counter direction of the bottom screen 3 movement, such that any locking frictional forces between the beam 13 and the vertical holding profile 16 is released and a flexible vertical movement of the counter blade is ensured. The flexible vertical movement is caused by the flexible device 12 acting on the counter blade in the vertical direction (z-direction).

Figure 3 also shows that the reinforcing structure 32 is mounted on the channel beam 24, between each anvil means 19. The reinforcing structure 32 is mounted on the channel beam 24 such that a space is left between each anvil means 19 and each part of the reinforcing structure 32. The space is there to allow free movement of each of the anvil means 19.

The invention is not limited to the above embodiments, but may be varied within the scope of the claims. For example, the dewatering unit 1 may comprise an open or solid forming roll that applies pressure on the top wire screen instead of the suction unit 7 with the top foils 5 as described in fig. 1. Furthermore, the invention may be used in a so called gap former, where the top wire screen is tensioned by use of a roll arrangement in order to apply a pressure on the fibrous web and the bottom wire screen. Also in the gap former, the suction unit 7 and corresponding top foils 5 described in fig 1 are lacking.

Furthermore, the lever arm 25 need not be L-shaped, but may have a different shape allowing the dynamic pressure device 22 to apply dynamic forces on the lever arm 25 such that the counter blade 10 dynamically may be affected by an impulse for releasing internal locking friction forces in the vertical guiding arrangement. Such shapes may be a bent shape, a straight shape or an arrangement comprising a number of lever arm 25s in different sizes and shapes that cooperates in transforming the dynamic pressure from the dynamic pressure device 22 into dynamic force acting horizontally on the counter blade 10.

Furthermore, the flexible device 12 and the dynamic pressure device 22 may each be a single pneumatic or hydraulic cushion or may comprise a number of cushions. The flexible device 12 and the dynamic pressure device 22 may each also be in the form of one or a number of mechanical devices, for example a jack.

Claims

1. A foil arrangement (33) for a double wire screen former for the manufacture of a fiber material web (8) from a fiber material suspension, comprising a number of foils (6), where at least one foil (6) comprises a flexible counter blade (10) extending over essentially the entire screen (3) width, in the lateral direction in view of the machine direction, wherein the counter blade (10) is supported on a flexible device (12) mounted on a beam (13) extending in the lateral direction, wherein the flexible device (12) is arranged to apply a flexible pressure on the counter blade (10) such that the counter blade (10) applies a flexible pressure on one of the screens (3), essentially perpendicular to the extension of the screen (3), the counter blade (10) comprises a vertical holding profile (16) arranged to be vertically slidably fitted over the beam (13), the flexible device (12) is fitted within the vertical holding profile (16) between the beam (13) and the vertical holding profile (16), characterized in that the foil arrangement comprises a dynamic anvil means (19) for dynamically applying a force on the counter blade (10) in the counter direction of the screen (3) movement.

2. A foil arrangement (33) according to claim 1, characterized in that the anvil means (19) has a force point (20) at a vertical position on the counter blade (10) between the screen and the beam (13).

3. A foil arrangement (33) according to claim 1 or 2, characterized in that the foil arrangement (33) comprises a resilient means (21) arranged between the anvil means (19) and the counter blade (10) for absorbing relative vertical movement between the anvil means (19) and the counter blade (10).

4. A foil arrangement according to claim 3, characterized in that the resilient means (21) is arranged in the force point (20) for applying pressure on the counter blade (10).

5. A foil arrangement (33) according to any one of the preceding claims, characterized in that the foil arrangement (33) comprises a dynamic pressure device (22) for dynamically applying pressure on the anvil means (19).

6. A foil arrangement (33) according to claim 9, characterized in that the dynamical pressure device (22) extends essentially along the entire lateral extension of the counter blade.

7. A foil arrangement (33) according to claim 5 or 6, characterized in that the anvil means (19) comprises a lever arm (25) articulately mounted on a shaft (26).

8. A foil arrangement (33) according to claim 7, characterized in that the lever arm (25) has a first end portion (27) on one side of the shaft (26) and a second end portion (28) on the other side of the shaft (26), where the first end portion (27) is arranged to comprise the force point (20) and where the dynamic pressure device (22) is arranged for applying dynamic pressure on the second end portion (28) such that the lever arm (25) rotates about the shaft (26) and dynamically applies pressure on the counter blade (10) via the force point (20).

9. A foil arrangement (33) according to claim 8, characterized in that the foil arrangement (33) comprises an adjustable pin (29) for hindering the rotational movement of the lever arm (25) in one direction, which adjustable pin 29 is arranged at the second end portion (28) on one side of the lever arm (25) and where the dynamic pressure device (22) is arranged on the opposite side of the lever arm (25).

10. A foil arrangement (33) according to claim 9, characterized in that the foil arrangement comprises a stop arm (31 ) in which the adjustable pin (29) is adjustably mounted.

11. A foil arrangement (33) according to claim 10, characterized in that the foil arrangement (33) comprises a support plate (14) onto which the beam (13) and the dynamic pressure device (22) and the stop arm (31 ) is mounted.

12. A foil arrangement (33) according to any one of the preceding claims, characterized in that the foil arrangement (33) comprises a number of anvil means (19) distributed along the lateral extension of the counter blade (10).

13. A method for ensuring a flexible vertical motion of a counter blade (10), where a foil arrangement (33) for a double wire screen former for the manufacture of a fiber material web (8) from a fiber material suspension, comprises a number of foils (6), where at least one foil (6) comprises a flexible counter blade (10) extending over the entire screen (3) width, in the lateral direction in view of the machine direction, wherein the counter blade (10) is supported on a flexible device (12) mounted on a beam (13) extending in the lateral direction, wherein the flexible device (12) applies a flexible pressure on the counter blade (10) such that the counter blade (10) applies a flexible pressure on one of the screens (3), essentially perpendicular to the extension of the screen (3), the counter blade (10) comprises a vertical holding profile (16) vertically slidably fitted over the beam (13), the flexible device (12) is fitted within the vertical holding profile (16) between the beam (13) and the vertical holding profile (16), characterized in that the foil arrangement comprises a dynamic anvil means (19) that applies a dynamical force on the counter blade (10) in the counter direction of the screen (3) movement.

14. A method according to claim 13, characterized in that the anvil means (19) applies force via a force point (20) at a vertical position on the counter blade 10 between the screen and the beam 13.

15. A method according to claim 13 or 14, characterized in that the foil arrangement (33) comprises a resilient means (21) arranged between the anvil means (19) and the counter blade (10) absorbing relative vertical movement between the anvil means (19) and the counter blade (10).

16. A method according to any one of claims 13-15, characterized in that the foil arrangement (33) comprises a dynamic pressure device (22) dynamically applying pressure on the anvil means (19).

17. A method according to claim 16, characterized in that the anvil means (19) comprises a lever arm (25) articulately mounted on a shaft (26), which lever arm (25) transmits the dynamical force from the dynamic pressure device (22) to the counter blade (10).

18. A method according to claim 17, characterized in that the lever arm (25) has a first end portion (27) on one side of the shaft (26) and a second end portion (28) on the other side of the shaft (26), where the first end portion (27) is arranged to comprise the force point (20) and where the dynamic pressure device (22) applies dynamic pressure on the second end portion (28) such that the lever arm (25) rotates about the shaft (26) and dynamically applies pressure on the counter blade (10) via the force point (20).

19. A method according to any one of claims 13-18, characterized in that the foil arrangement (33) comprises a number of anvil means (19) distributed along the lateral extension of the counter blade (10), applying pressure on a number of points along the counter blade

(10) extension.

20. A method according to claim 19, characterized in that the dynamical pressure device (22) extends essentially along the entire lateral extension of the counter blade, and applies dynamic pressure on each of the anvil means (19) essentially simultaneously.