WO2007001221A1

WO2007001221A1 - Van for use in a paper machine headbox, method and mold for producing such a vane

Info

Publication number: WO2007001221A1
Application number: PCT/SE2005/001034
Authority: WO
Inventors: Mats Eklund; Anders Lindgren
Original assignee: Chelton Applied Composites Ab
Priority date: 2005-06-28
Filing date: 2005-06-28
Publication date: 2007-01-04
Also published as: EP1910612A1

Abstract

A vane (1) for use in a paper machine headbox, comprises a sheet member (6) extending between an upstream edge (2) and a downstream edge (3). The upstream edge (2) has a portion of increased thickness adapted for being received in a receiving groove (11) of an anchoring element (10) or of a vane holder. The portion of increased thickness is formed by a portion of material (5a, 5b) which is molded or cast directly onto sheet member (2). The portion of material (5a, 5b) extends from the upstream edge (2) towards the downstream edge (3) by a length (b) that is less than or approximately equal to a depth (D) of the receiving groove (11). A method and a mold for producing the portion of increased thickness are also disclosed.

Description

VANE FOR USE IN A PAPER MACHINE HEADBQX, METHOD AND MOLD

FOR PRODUCING SUCH A VANE

Technical Field

The present invention relates to a vane for use in a paper machine headbox, a method for producing such a vane and a mold for producing such a vane

Background

Vanes for use in a paper machine headboxes are known from e.g. US 4,133,415, US 4,617,091, WO98/50625, US 6,521,095 Bl, US 6,491,793 B2, US 6,165,324 and US 2005/0092453 Al, the entire contents of which documents are hereby incorporated by reference. Reference is made to these documents for a more detailed explanation of the function of a paper machine headbox, and in particular of the vanes presented therein. Each vane comprises a thin, sheet member, which serves as a flow surface, across which pulp is allowed to flow from a set of feed pipes onto a paper forming surface. Typically, each vane is substantially plane having a width in a flow direction of about 400-800 mm and a length of about 2500-12000 mm. Each vane is mounted in a cantilevered manner with one of its long edges, herein referred to as the "upstream edge", being fixedly mounted in a wall of the paper machine, adjacent to the feed pipes. The other, opposing long edge, hereinafter referred to as the "downstream edge", is close to the forming surface.

The vanes may have a greater thickness at the upstream edge than at the downstream edge, i.e. taper in thickness. This tapering may occur either over the entire extension of the vane, from the upstream edge to the downstream edge, or the vane may have one portion of substantially constant thickness and another one tapering in thickness. Several devices for mounting the vane in the wall are known.

A first example is shown in US 4,133,715, wherein a vane holder is provided between the vane and the wall, with the purpose of providing a flexibility and reduced sensitivity to fatigue. The sheet of the vane is permanently secured in a laterally open groove of an anchor rod, which in turn is slidingly inserted into a laterally open cylindrical groove of the vane holder, which in its turn is received in a receiving groove in the wall of the paper machine. Apart from the fact that this arrangement requires the vane holder element arranged between the vane and the wall, mounting of the anchor rod on the vane is difficult, since it must be made certain that the edge of the vane is properly inserted and fixed into the groove of the anchor rod.

US 4,617,091 discloses a second example of a headbox vane, which is directly inserted into a groove of the paper machine wall. The thickness of the vane tapers from the upstream edge towards the downstream edge, and a bulbous ridge is formed at the upstream edge and pivotally received in a slot in the paper machine wall. The bulbous ridge necessarily needs to be formed in connection with the forming of the vane, and therefore it is not possible to adjust the width of the vane by cutting off the ridge and reinserting it into the slot. WO 98/50625 discloses a third example of a headbox vane, wherein the vane is mounted in the paper machine wall by means of a vane holder, and wherein the vane is held in place in the vane holder by means of pins, which interact with holes in the vane. Adjusting the width of the vane would require new holes to be made.

A similar headbox vane is disclosed in US 6,521,095 Bl, wherein screws are used instead of pins and holes for holding the vane in place in the vane holder.

In US 6,491,793 B2, the vane is held in place either by a coil spring construction, which runs through a series of holes in the edge of the vane, or by a snap-on anchoring rod having a laterally open groove with protrusions that engage a groove in the surface of the upstream vane edge portion. Adjusting the width of the vane would require new holes to be made, or a new groove to be made. / ^ US 6,165,3247 and US 2005/0092453 Al both involve a vane holder having a pin and hole construction for holding the vane in place relative to the vane holder.

Summary of the invention It is an objective to provide an improved or alternative vane for a paper machine headbox.

In particular, it is an objective to provide a vane, the width of which can be adjusted in a simple and cost effective manner. The object is wholly or partially achieved by a vane, a method and a tool as set forth in the respective independent claim.

According to a first aspect, there is provided a vane for use in a paper machine headbox, the vane comprising a sheet member extending between an upstream edge and a downstream edge, wherein the upstream edge has a portion of increased thickness adapted for being received in a receiving groove of an anchoring element or of a vane holder, wherein said portion of increased thickness is formed by a portion of material which is molded or cast directly onto the sheet member, and wherein said portion of material extends from said upstream edge towards the downstream edge by a length that is less than or approximately equal to a depth of the receiving groove.

By molding or casting the portion of material directly onto the sheet member, a perfect fit between the portion of material and the sheet member is obtainable. By selecting a suitable combination of materials for the portion of material and the sheet member, strong adhesion between them is obtainable.

Also, such a portion of material can easily be provided in connection with the adjustment of the width

(length between upstream edge and downstream edge) of the vane, by the vane being cut off and a new portion of material being molded or cast directly onto it.

The portion of material may be present only on one of the opposing surfaces of the sheet member.

Alternatively, the portion of material may be present on both opposing surfaces of the sheet member.

In yet another alternative, the portions of material may be present on both opposing surfaces and may be formed in one piece, thus enclosing the upstream edge of the sheet member.

In one embodiment, the portion of material may be adapted for providing a hinge joint when received in the receiving groove. This provides angular adjustability between the receiving groove in the wall of the paper machine and the vane. For example, the portion of material may have a curved profile. The sheet member may be a composite sheet comprising a polymer matrix and reinforcing fibers. Such composite sheets provide lightweight and high strength vanes.

The polymer matrix may be selected from a group consisting of a thermoplastic polymer and a thermosetting polymer.

The reinforcing fibers may be selected from a group consisting of aramid fibers, carbon fibers, natural fibers and glass fibers. Combinations of such fibers are also possible. Basically, any suitable reinforcing fibre may be used; the invention is not limited to the fibres disclosed herein.

The portion of material may be made from a material selected from a group consisting of thermoplastic poly- mer, an epoxy polymer, a polyurethane, a thermosetting polymer.

According to a second aspect, there is provided a method for providing a portion of increased thickness on a vane for use in a paper machine headbox, the portion of increased thickness being adapted for being received in a receiving groove of an anchoring element or of a vane holder, the vane comprising a sheet member extending between an upstream edge and a downstream edge. In the method, the portion of increased thickness is arranged along at least a part of the upstream edge. The method comprises forming said portion of increased thickness by molding or casting a portion of material directly onto said sheet member, such that said portion of material extends from said upstream edge towards the downstream edge by a length that is less than or approximately equal to a depth of the receiving groove.

Such a method is a simple and effective way of providing a portion of increased thickness on the vane, which does not necessarily require all facilities of a manufacturing workshop, but may be performed in the field, e.g. in connection with servicing or setting up of the paper machine. In the method, the upstream edge may placed in a mold, whereby a moldable material is introduced into said mold.

According to a third aspect, there is provided a mold for providing a portion of increased thickness along at least a portion of an edge of a vane for use in a paper machine headbox. The mold comprises a substantially flat surface adapted for interacting with a surface of the vane, a groove, formed in said substantially flat surface, and an injection opening, adapted to enable introduction of a moldable compound into said groove.

Such a mold provides an inexpensive tool for accurately providing a portion of increased thickness at the edge of the vane.

The mold may further comprise an abutment edge, adapted for interacting with the edge of the vane, wherein the groove extends along said guide edge. Such an abutment edge ensures accurate alignment between the mold and the vane .

The groove of the mold may extend in the plane of the substantially flat surface, away from said abutment edge by a length that is less than or approximately equal to a depth of the receiving groove.

Thus, the extension of the portion of material is limited to the edge portion of the vane.

Brief Description of the Drawings

The invention will now be described in more detail, with reference to the appended drawings. Fig. 1 is a schematic perspective view of a vane according to an embodiment described herein.

Figs 2a and 2b are schematic perspective views of a part of a vane received in a reception groove of a paper machine wall.

Figs 3a-3c schematically illustrate different embodiments of the vane.

Fig. 4 schematically illustrates an edge of a vane inserted into a mold.

Description of Embodiments

Fig. 1 illustrates a vane 1 according to an embodiment. The vane 1 comprises a sheet member 6 extending between an upstream edge 2 and a downstream edge 3. The upstream edge 2 and the downstream edge 3 are spaced apart from each other and substantially parallel. The width of the vane 1, i.e. the distance between the upstream edge 2 and the downstream edge 3 is denoted ^ΛW . The length of the vane, i.e. the length of the edges 2, 3 is denoted ^ΛL' . The sheet member 6 has a top surface 4a and a bottom surface 4b. In the embodiment illustrated in Fig. 1, there are portions of material 5a, 5b molded or cast directly onto the sheet member 6 at the upstream edge 2, the portions of material providing a portion of increased thickness.

The sheet member 6 may be made from a polymer material. Non-limiting examples are PC (polycarbonate), POM (polyoxymethylene) and PVC (polyvinylchloride) . In another embodiment, the sheet member may be made from a composite material, comprising e.g. a polymer matrix and reinforcing fibers. In further embodiments, the sheet member may be made from a metal, e.g. steel, titanium or aluminum. Fig. 2a illustrates a portion of a paper machine wall 10, having a receiving groove 11, and a portion of a vane 1, the upstream edge 2 of which is received in the receiving groove 11. Portions of material 5a, 5b provide a portion of increased thickness, enabling the upstream edge 2 of the vane 1 to be fixedly mounted in the receiving groove 11. The portions of material 5a, 5b are molded or cast directly onto respective surfaces 4a, 4b of the sheet member 6. The portion of material 5a, 5b has an extension b, which is less than or equal to the depth D of the receiving groove 11. In the case illustrated in Fig. 2a, the extension b is less than the depth D of the receiving groove 11. The portions of material illustrated in Fig. 2a form ridges of a semi-circular cross section along the upstream edge 2 of the sheet member.

Fig. 2b illustrates a portion of a paper machine wall 10, having a receiving groove 11, and a portion of a vane 1, the upstream edge 2 of which is received in the receiving groove 11. In the embodiment disclosed in Fig. 2b, the extension b of the portion of material 5a, 5b is slightly larger than the depth of the receiving groove 11. The portions of material illustrated in Fig. 2b also form ridges of a semi-elliptical cross section along the upstream edge 2 of the sheet member. Hence, it is clear that the extension b of the portion of material 5a, 5b may be either less than the depth D of the receiving groove 11, equal to the depth D of the receiving groove 11 or slightly larger than the depth D of the receiving groove 11. It is understood that the portion of increased thickness provided as described herein can be used either for direct attachment in a receiving groove of a paper machine wall, or together with a vane holder such as the one described in US 4,133,715.

Fig. 3a illustrates a first alternative embodiment, wherein the portions of material 5a, 5b have a different shape, in this case triangular cross sections, rather than semicircular cross sections. It is noted that the portions of material 5a, 5b may have any cross section that is compatible with the receiving groove 11 of the paper machine wall 10. Notably, semi-circular or convex shapes are suitable to provide adjustability, such that the angle of the vane relative to the wall 10 may be adjusted. The portions of material illustrated in Fig. 3a form ridges of a triangular cross section along the upstream edge 2 of the sheet member. Square, rectangular or dove-tail cross sections may be suitable for fixed installation, i.e. installation that does not allow for angular adjustment.

Fig. 3a illustrates a so-called turbulence vane, i.e. a vane wherein the thickness T of the sheet member 6 is substantially constant over at least a part of its extension between the upstream edge and the downstream edge. In turbulence vanes, the sheet member 6 may have a portion of tapering thickness at the downstream edge 3. Fig. 3b illustrates another alternative embodiment, wherein the sheet member is a so-called "wedge", i.e. a vane wherein the thickness T of the sheet member 6 tapers throughout substantially the entire extension between the upstream edge 2 and the downstream edge 3.

In the embodiments disclosed with reference to Figs 2, 3a and 3b, the portion of material is attached only to the main surfaces 4a, 4b of the sheet member 6, and not to the edge surface (indicated at the arrow 2 in Figs 2, 3a, 3b. Fig. 3c illustrates another alternative embodiment, wherein a portion of material 5 is molded or cast around the edge portion of the upstream edge 2.

In yet another embodiment, which is not shown, a portion of material is provided only on one surface of the sheet member 6.

Referring to Fig. 4, the description will now be directed to a mold for providing the portions of increased thickness at the upstream edge 2 of the vane 1. The mold 21, 22 may be formed of two cooperating members, where a first mold member 21 is adapted for providing the portion of material 5a (Fig. 2a) on the first surface 4a of the sheet member 6, and a second mold member 22 is adapted for providing the portion of material 5b on the second surface 4b of the sheet member 6.

The mold members 21, 22 may be provided in the form of sheets or strips, in which a groove 23, 24 of a cross section corresponding to the desired cross section of the portion of increased thickness, is provided. Typically, the groove 23, 24 extends along the entire sheet or strip, but it may also extend along part of the sheet or strip, whereby an intermittent portion of increased thickness would be formable. The mold 21, 22 members may have a length in the direction of the groove 23, 24 which is about the same as the length L of the vane. As an alternative, the mold members 21, 22 may be shorter. Shorter mold members may be used in a stepwise molding operation, whereby a part of the portion of increased thickness is formed in each step. Several such molding or casting steps are then repeated until the desired portion of increased thickness has been provided. As another alternative, several short mold members may be provided, whereby a number of short sheet members, the total length of which correspond to the length L of the vane 1 are arranged at the edge 2 and together form a mold.

The mold members may arranged to cooperate with each other to form the mold 21, 22. For example, the mold members 21, 22 may be provided with interacting alignment protrusions 25 and recesses or holes, whereby a protrusion on the first mold member 21 may be received in a recess or hole in the second mold member 22, thereby ensuring accurate mutual positioning of the mold members 21, 22 relative to each other. A plurality of such alignment protrusions 25 and recesses or holes may be arranged along a surface at which the mold members 21, 22 contact each other.

One, or both, of the mold members may be provided with an abutment surface 26, against which the edge 2 of the sheet member 6 may abut when inserted into the mold and during the molding or casting operation.

The alignment protrusions and the abutment surface may be dispensed with in favor of external arrangements for ensuring alignment of the portion of increased thickness with the edge 2 of the vane 1, and for ensuring mutual positioning of the mold members 21, 22.

The mold members may also be provided with holes for introducing the molding compound. These holes may be provided by the groove 23, 24 being open at the short sides of the molds 21, 22, thus enabling introduction of the molding compound through openings formed as is illustrated in Fig. 4.

In the alternative, through holes (not shown) may be provided from the groove 23, 24 to the outer side of the mold members 13, 24 to enable introduction of the molding compound. Such through holes may be arranged at the end portions of the grooves 23, 24.

In the case where a portion of increased thickness is to be formed only on one surface 4a, 4b of the sheet member 6, it may be sufficient to use only one mold member.

The mold members may be made of any material, preferably materials having good release properties vis- a-vis the molding compound. An example of such a material is POM (polyoxymethylene) . In the alternative, portions of the groove which are in contact with the molding compound may be coated with a material having good release properties or with a release agent. The description will now be directed to the method for providing the portion of increased thickness.

In a first step, a sheet member 6 of a desired width W is provided. The surface portions at the edge 2 of the sheet member 6 may be treated by e.g. grinding or polishing to provide a surface having good adhesion properties for the molding compound. The surface portions at the edge 2 may also be cleaned from e.g. grease, fingerprints and other contaminations. The edge 2 may also be provided with a primer. The edge 2 is then placed in a mold, e.g. as illustrated in Fig. 4, such that the edge abuts against an abutment surface 26 of the mold and such that interacting alignment protrusions and holes of the molds engage to provide mutual alignment of the mold members 21, 22.

The mold members 21, 22 are then clamped together, after which the molding compound is introduced into the mold. Thereafter, the molding compound is allowed to harden, e.g. by heating, subjecting it to radiation or simply by allowing it to sit for a sufficient time. In the case where a thermoplastic is used as molding com- pound, it may be sufficient to let it cool off, or it may be desirable to provide additional cooling means. After the molds are removed, the portion of increased thickness is completed.

The applicant has tested an embodiment wherein the vane is made from a sheet of glass fiber reinforced epoxy plastic. After a substantially straight vane edge had been provided, the surface at the edge portion 2 was sanded using a fine sand paper and cleaned using acetone. Mold members 21, 22 of POM having grooves 23, 24 of semi- circular cross section were then applied, after which a molding compound of epoxy plastic was injected into the grooves 23, 24. The vane was then allowed to harden in an oven, after which the molds were removed.

Claims

1. A vane (1) for use in a paper machine headbox, the vane (1) comprising a sheet member (6) extending between an upstream edge (2) and a downstream edge (3), wherein the upstream edge (2) has a portion of increased thickness adapted for being received in a receiving groove (11) of an anchoring element (10) or of a vane holder, wherein said portion of increased thickness is formed by a portion of material (5a, 5b) which is molded or cast directly onto said sheet member (2), and wherein said portion of material extends from said upstream edge (2) towards the downstream edge (3) by a length (b) that is less than or approximately equal to a depth (D) of the receiving groove (11).

2. The vane (1) as claimed in claim 1, wherein said portion of material is present only on one of the opposing surfaces (4a, 4b) of the sheet member (6).

3. The vane (1) as claimed in claim 1, wherein said portion of material (5a, 5b) is present on both opposing surfaces (4a, 4b) of the sheet member (6) .

4. The vane as claimed in claim 3, wherein portions of material (5a, 5b) , are present on both opposing surfaces (4a, 4b), and are formed in one piece.

5. The vane (1) as claimed in any one of the preceding claims, wherein said portion of material (5a, 5b) is adapted for providing a hinge joint when received in the receiving groove (11) .

6. The vane (1) as claimed in claim 5, wherein said portion of material (5a, 5b) has a curved profile.

7. The vane (1) as claimed in any one of the preceding claims, wherein the sheet member (6) is a composite sheet comprising a polymer matrix and reinforcing fibers .

8. The vane (1) as claimed in claim 7, wherein the polymer matrix is selected from a group consisting of a thermoplastic polymer and a thermosetting polymer.

9. The vane as claimed in claim 7 or 8, wherein the reinforcing fibers are selected from a group consisting of aramid fibers, carbon fibers, natural fibers and glass fibers .

10. The vane as claimed in any one of the preceding claims, wherein said portion of material (5a, 5b) is made from a material selected from a group consisting of thermoplastic polymer, an epoxy polymer, a polyurethane, a thermosetting polymer.

11. A method for providing a portion of increased thickness on a vane for use in a paper machine headbox, the portion of increased thickness being adapted for being received in a receiving groove (11) of an anchoring element (10) or of a vane holder, the vane (1) comprising a sheet member (6) extending between an upstream edge (2) and a downstream edge (3) , wherein the portion of increased thickness is arranged along at least a part of the upstream edge (2) , the method comprising: forming said portion of increased thickness by molding or casting a portion of material directly onto said sheet member (2), such that said portion of material (5a, 5b) extends from said upstream edge (2) towards the downstream edge (3) by a length (b) that is less than or approximately equal to a depth (D) of the receiving groove (11) .

12. The method as claimed in claim 11, wherein said upstream edge (2) is placed in a mold, and wherein a moldable material is introduced into said mold.

13. A mold (21, 22) for providing a portion of increased thickness along at least a portion of an edge (2) of a vane (1) for use in a paper machine headbox, the mold comprising: a substantially flat surface adapted for interacting with a surface (4a, 4b) of the vane (1), a groove (23, 24), formed in said substantially flat surface, and an injection opening, adapted to enable introduction of a moldable compound into said groove (23, 24) .

14. The mold as claimed in claim 13, further comprising a abutment edge (26) , adapted for interacting with the edge (2) of the vane (1) , wherein the groove (23, 24) extends along said guide edge (26).

15. The mold as claimed in claim 14, wherein the groove (23, 24) extends, in the plane of the substan- tially flat surface, away from said abutment edge (26) by a length (b) that is less than or approximately equal to a depth (D) of the receiving groove (11) .