WO2021209678A1

WO2021209678A1 - A filter diaphragm, a plate frame, a plate frame assembly, a routing or milling tool set, and a horizontal filter press

Info

Publication number: WO2021209678A1
Application number: PCT/FI2020/050253
Authority: WO
Inventors: Mirva MUSTAKANGAS; Ismo JUVONEN; Janne KAIPAINEN; Teemu ELORANTA; Mika ILLI; Kari VÄNTTINEN
Original assignee: Metso Outotec Finland Oy
Priority date: 2020-04-17
Filing date: 2020-04-17
Publication date: 2021-10-21
Also published as: CZ36850U1; ES1296785U; BR212022020766U2; SK9757Y1; AU2020443145A1; FI13302Y1; PL131029U1; ES1296785Y; CN113521821B; SK500902022U1; DE212020000821U1; AT18011U1; CN216149102U; CN113521821A; AR121865A1

Abstract

The disclosure relates to a filter diaphragm (1), a plate frame (4) and a plate frame assembly. The disclosure is based on the idea of providing the both the diaphragm bead (3) and the frame groove (5) with an asymmetric cross-sectional profile, that resists torsion of the bead (3) within the groove (5) caused by a force exerted on the diaphragm (1) during inflation thereof and by the weight of the diaphragm itself, while providing sufficient sealing capabilities. This is achieved by providing, on the cross-sectional profile of the bead (3), a distal portion (3a) extending further from an asymmetry axis (A3) on a lateral outside (1b) thereof. Moreover, the cross-sectional shape of the frame's (4) groove (5) receiving the diaphragm's (1) bead (3) is shaped correspondingly. The disclosure further concern's and a routing or milling tool set for machining such a groove.

Description

A FILTER DIAPHRAGM, A PLATE FRAME, A PLATE FRAME ASSEMBLY, A ROUTING OR MILLING TOOL SET, AND A HORIZONTAL FILTER PRESS

FIELD OF THE DISCLOSURE

The present disclosure relates to horizontal plate and frame -type filter presses, such as tower presses, equipped with a filter diaphragm for squeezing filter cake formed in a filter chamber. More particularly, the present disclosure relates to filter diaphragms used in such filter presses. The present disclosure further concerns plate frames of such filter presses, to which diaphragm are attached to, and plate assemblies incorporating the plate frame and filter diaphragm. The present disclosure further concerns a routing or milling tool set for machining a groove into a plate frame for receiving a corresponding bead of filter diaphragm.

BACKGROUND OF THE DISCLOSURE

Diaphragms are used in filter presses to squeeze residual liquid content out of a filter cake formed in a filter chamber. Typically, the filter diaphragm is attached to a plate frame, which also supports a filter plate. During squeezing, a pressurized medium is introduced into a space between the filter plate and the filter diaphragm, thereby inflating the diaphragm into the filter chamber and squeezing the filter cake.

A conventional way of attaching a filter diaphragm to the plate frame has been to provide the diaphragm with a profiled bead and the plate frame with a correspondingly profiled groove, such that the bead can be elastically introduced into the groove, where it is form- fittingly retained.

In order to achieve a sufficiently secure attachment between the filter diaphragm and the plate frame, it is desirable to increase the difference between a neck portion and a bottom portion of the grove, and respectively between an intermediate portion and a distal portion of the bead. However, increasing such a difference in width makes it more difficult to insert the bead into the groove. It has also been discovered that increasing the width difference between the bottom portion and the neck portion of the groove both impairs the structural strength of the plate frame in the vicinity of the groove, and increases internal stresses exhibited thereat.

BRIEF DESCRIPTION OF THE DISCLOSURE

It is an object of the present disclosure to provide a more secure attachment between a profiled bead of a filter diaphragm and a profiled groove of a plate frame, without exposing the plate frame to increased internal stresses and maintaining the structural strength thereof. The object of the disclosure is achieved by a filter diaphragm, a plate frame, a plate frame assembly and a routing or milling tool set, which are characterized by what is stated in the independent claims. The preferred embodiments of the disclosure are disclosed in the dependent claims.

The disclosure is based on the idea of providing both the diaphragm bead and the frame groove with an asymmetric cross-sectional profile, that resists torsion of the bead within the groove caused by a force exerted on the diaphragm during inflation thereof and by the weight of the diaphragm itself while providing sufficient sealing capabilities. Typically, the weight of a filter diaphragm used in a filter range may range between 5 - 15 kg per square meter, whereas the size of such diaphragms ranges between 1 - 10 square meters. Moreover, the bead of the diaphragm together with the frame groove partially laterally seal the lateral inside (in which a filter chamber is formed) from the lateral outside. Typically, an overpressure (with respect to ambient pressure) ranging between 8-20 bar may be exerted in the filter chamber during operation. Consequently, strict requirements are posed on the diaphragm bead and the frame groove regarding their mutual sealing and retaining capabilities.

As a result, the installation of the bead into the groove is facilitated, as compared to a symmetric bead-and-groove -combination having similar retaining and sealing capabilities. Simultaneously, the form of the groove reduces less material thickness on a lateral inside of the plate frame, as compared to a symmetric bead-and-groove -combination having similar sealing retaining capabilities, contributing to the longevity of the frame itself.

Moreover, installation times of the diaphragm are reduced, and the longevity of the plate frame is increased, while secure attachment and sufficient sealing is ensured.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the disclosure will be described in greater detail by means of preferred embodiments with reference to the accompanying drawings, in which

Fig. 1 schematically illustrates a cross-sectional cut view of a filter diaphragm according to an embodiment of the present disclosure;

Fig. 1 a is a detailed view of Fig. 1 illustrating a bead of the diaphragm in more detail;

Fig. 2 schematically illustrates a partial cross-sectional cut view of a plate frame to an embodiment of the present disclosure;

Fig. 2a is a detailed view of Fig. 2 illustrating a groove of the plate frame in more detail, and Fig. 3 schematically illustrates a filter frame assembly incorporating the diaphragm of Fig. 1 and the plate frame of Fig. 2, as seen as partial cross-sectional cut view.

DETAILED DESCRIPTION OF THE DISCLOSURE

According to a first aspect of the present disclosure, a filter diaphragm 1 for a horizontal plate and frame -type filter, such as a tower press, is provided. The diaphragm comprises a sheet like body 2 having a flexible structure. That is, at least a portion of the diaphragm 1 is able to yield without permanent deformation, so as to squeeze a filter cake by being inflated with a pressurized medium.

The filter diaphragm 1 further comprises, at least on a plate frame -facing side 1d thereof, a bead 3 for attaching the diaphragm 1 to a plate frame 4 of the filter. The bead 3 runs along the periphery of the filter diaphragm 1 and delimits a central portion 1c of the diaphragm on a lateral inside 1 a of the bead. Correspondingly, a lateral outside 1 b is defined on a lateral side of the bead 3 opposite to the lateral inside 1a.

Most suitably, it is the central portion 1c that is able to yield into a filter chamber without permanent deformation, so as to squeeze a filter cake formed therein.

The bead 3 has a cross-sectional profile having a base portion 3b attaching the bead 3 to the remaining diaphragm 1 , a distal portion 3a and an intermediate 3c portion between the base portion 3b and the distal portion 3a. The laterally extending dimension W3a of the distal portion 3a exceeds that of the intermediate portion W3c. That is, in the cross- sectional profile of the bead 3, a narrowed waist is formed by the intermediate portion 3c, with respect to the distal portion 3a. This enables the bead 3 to be form-fittingly attached to an associated groove having a corresponding cross-sectional profile. Preferably, but not necessarily, the laterally extending dimension W3a of the distal portion 5a is defined as a maximum laterally extending dimension (i.e. width) thereof, whereas the laterally extending dimension W3c of the intermediate portion 3c is defined as a minimum laterally extending dimension (i.e. width) thereof.

The bead 3 has an asymmetric cross-sectional profile with respect to a vertical asymmetry axis A3 running through a lateral centre point of a minimum width section W3min of the intermediate portion 3c.

The vertical asymmetry axis A3 is perpendicular to a general plane of the diaphragm 1 , defined by a planarity of the central portion 1c, when laid on a flat surface.

The minimum width section W3min of the intermediate portion 3c is defined as a point of the cross-sectional profile of the bead 3 at which the intermediate portion 3c exhibits a smallest laterally extending dimension. That is, the minimum width section W3min is defined at the most narrow point of the intermediate portion 3c, i.e., at a point having the smallest dimension of the intermediate portion 3c along a horizontal direction, transverse to the running direction of the bead 3 and parallel with the general plane of the diaphragm 1.

Moreover, the distal portion 3a extends laterally further from the asymmetry axis A3 on the lateral outside 1 b than on the lateral inside 1 a.

The above described arrangement ensures that, when inserted into a corresponding groove 5, the bead 3 of the diaphragm 1 is able to better resist torsion caused by the weight of (or force exerted on) the central portion 1 c, thus pulling the bead out of the groove. More precisely, the weight of the central portion 1c strives to pivot the distal portion 3a towards the lateral outside 1 b and up away from a bottom 5a of an associated groove 5 about a pivot point formed on a lateral inside 4a of an aperture portion 5b of the groove 5. As the distal portion 3a extends laterally further away from the asymmetry axis A3, the mutually corresponding, form fitting shapes of the bead 3 and the groove 3 counteracts the torsion and pivoting of the bead 3, thereby improving secure attachment between the diaphragm 1 and the associated frame 4.

In an embodiment according to the first aspect of the present disclosure, the cross- sectional profile of the bead 3 is asymmetric at the intermediate portion 3c with respect to the vertical asymmetry axis A3.

Preferably, but not necessarily, an asymmetric concavity, with respect to the asymmetry axis A3, is provided on the intermediate portion 3c of the cross-sectional profile of the bead 3. That is, a curved indentation towards the asymmetry axis A3 is provided at the intermediate portion 3c. For example, a concavity may be provided on only on the lateral outside. If a concavity is provided on both the lateral inside 1 a and the lateral outside they may be positioned at different vertical positions on and/or have different curvatures (e.g., different radii of the curvatures)

More preferably, but not necessarily, a concavity having a curvature with a smaller radius is exhibited on the lateral outside than on the lateral inside, if any. This further improves the capability of the mutual forms of the bead and the groove to arrest the bead in place against the torsion and pivoting caused by the weight of the central portion 1c, as discussed above.

In an embodiment according to the first aspect of the present disclosure, the cross- sectional profile of the bead 3 is asymmetric at the distal portion 3a with respect any to vertical line running through the bead 3. Most suitably, the cross-sectional profile of the bead 3 is asymmetric at the distal portion 3a with respect to the asymmetry axis A3

In an embodiment according to the first aspect of the present disclosure, an asymmetric bulge 3d (i.e., a protuberance protruding from a surrounding curvature in the cross- sectional profile of the bead 3), with respect to the asymmetry axis A3, is provided on the distal portion 3a of the cross-sectional profile of the bead 3. Preferably but not necessarily, such a bulge is provided only on the lateral outside 1 b of the distal portion 3a.

This further improves the capability of the mutual forms of the bead and the groove to arrest the bead in place against the torsion and pivoting caused by the weight of the central portion 1c, as discussed above.

In an embodiment according to the first aspect of the present disclosure, a distal surface 3a’ of the distal portion is inclined with respect to the general plane of the diaphragm 1 , such that the distal surface 3a’ is inclined towards the intermediate portion 3c in a direction from the lateral inside 1 a towards the lateral outside 1 b. Again, this is considered to further improve the capability of the mutual forms of the bead 3 and the groove 5 to arrest the bead in place against the torsion and pivoting caused by the weight of the central portion 1c, as discussed above.

In an embodiment according to the first aspect of the present disclosure, a contour of the cross-sectional profile of the bead 3 is differentiable at each point thereof. That is, the curvature of the bead’s 3 cross-sectional profile is smooth with no sharp points.

This ensures that no excessively concentrated regions of internal stresses are formed on the correspondingly formed groove 5.

It should be noted that the first aspect of the present disclosure encompasses any combination of two or more embodiments, or variants thereof, as discussed above.

According to a second aspect of the present disclosure, a plate frame 4 for a horizontal plate and frame -type filter, such as a tower press, is provided. The purpose of the plate frame is to support a filter plate. The plate frame supporting the plate may be provided as a separate entity or as an assembly incorporating multiple separate entities. Furthermore, the plate frame 4 may be provided as an integral portion of a recessed plate -type plate.

The plate frame 4 defines a central opening 4c delimiting a lateral boundary of an associated filter chamber on a lateral inside 4a of the plate frame 4, when in use. Preferably, but not necessarily, the opening 4c extends through the plate frame 4. A lateral outside 4b is defined on a lateral side of the plate frame 4 opposite to the lateral inside 4a. The plate frame 4 comprises, on a plate -facing side 4d thereof, a continuous groove 5 for attaching a filter diaphragm 1. The groove 5 extends along the frame and surrounds the opening 4c.

The groove 5 has a cross-sectional profile having an aperture portion 5b, which opens to an outer surface of the frame, a bottom portion 5a and a neck portion 5c between the aperture portion 5b and the bottom portion 5a. The laterally extending dimension W5a of the bottom portion 5a exceeds that W5c of the neck portion 5c, thus enabling a form-fitting attachment of a correspondingly shaped bead 3 of filter diaphragm 1 . That is, in the cross- sectional profile of the groove 5, a narrowed waist is formed by the neck portion 5c, with respect to the bottom portion 5a. This enables an associated bead 3 having a corresponding cross-sectional profile to be form-fittingly attached to the groove 5. Preferably, but not necessarily, the laterally extending dimension W5a of the bottom portion 5a is defined as a maximum laterally extending dimension (i.e. width) thereof, whereas the laterally extending dimension W5c of the neck portion 5c is defined as a minimum laterally extending dimension (i.e. width) thereof.

The groove 5 has an asymmetric cross-sectional profile with respect to a vertical asymmetry axis A5 running through a lateral centre point of a minimum width section W5min of the neck portion 5c. The vertical asymmetry axis A5 is perpendicular to a general plane of the plate frame 4, which is defined by a planarity of a planar surface 4d’ on the plate -facing side 4d intended to oppose a filter plate, when in use. The minimum width section W5min of the neck portion 5c is defined as a point of the cross-sectional profile of the groove 5 at which the neck portion 5c exhibits a smallest laterally extending dimension. That is, the minimum width section W5min is defined at the most narrow point of the neck portion 5c, i.e., at a point having the smallest dimension of the neck portion 5c along a horizontal direction, transverse to the running direction of the groove 5 and parallel with the general plane of the frame 4.

Moreover, the bottom portion 5a extends laterally further from the asymmetry axis A5 on the lateral outside 4b than on the lateral inside 4a.

The above described arrangement ensures that, when inserted into the groove 5, a corresponding bead 3 the diaphragm is able to better resist torsion caused by the weight of the diaphragm 1 , as discussed above in connection with the first aspect of the disclosure. In an embodiment according to the second aspect of the present disclosure, the cross- sectional profile of the groove 5 is asymmetric at the neck portion 5c with respect to the asymmetry axis A5.

Preferably, but not necessarily, an asymmetric convexity, with respect to the asymmetry axis A5, is provided on the neck portion 5c of the cross-sectional profile of the bead 5. That is, a curved protrusion towards the asymmetry axis A5 is provided at the neck portion 5c. For example, a convexity may be provided on only on the lateral outside 4b. If a convexity is provided on both the lateral inside 4a and the lateral outside 4b, they may be positioned at different vertical positions on and/or have different curvatures (e.g., different radii of the curvatures)

More preferably, but not necessarily, a convexity having a curvature with a smaller radius is exhibited on the lateral outside 4b than on the lateral inside 4a, if any. This further improves the capability of the mutual forms of the bead 3 and the groove 5 to arrest the bead in place against the torsion and pivoting caused by the weight of the central portion 1c of the diaphragm, as discussed above in connection with the first aspect of the present disclosure.

In an embodiment according to the second aspect of the present disclosure, the cross- sectional profile of the groove 5 is asymmetric at the bottom portion 5a with respect to any vertical line running through the groove 5. Most suitably, the cross-sectional profile of the groove 3 is asymmetric at the bottom portion 5a with respect to the asymmetry axis A5.

In an embodiment according to the second aspect of the present disclosure, an asymmetric notch 5d (i.e., a dent depressed from a surrounding curvature in the cross- sectional profile of the groove 5), with respect to the asymmetry axis A5, is provided on the bottom portion 5a of the cross-sectional profile of the bead 5.

This further improves the capability of the mutual forms of the bead 3 and the groove 5 to arrest the bead 3 in place against the torsion and pivoting caused by the weight of the central portion 1c, as discussed above.

In an embodiment according to the second aspect of the present disclosure, a bottom surface 5a’ of the bottom portion 5a is inclined with respect to the general plane of the plate frame 4, such that the bottom surface 5a’ is inclined towards the neck portion 5c in a direction from the lateral inside 4a towards the lateral outside 4b. Again, this is considered to further improve the capability of the mutual forms of the bead 3 and the groove 5 to arrest the bead in place against the torsion and pivoting caused by the weight of the central portion 1c, as discussed above. In an embodiment according to the second aspect of the present disclosure, a contour of the cross-sectional profile of the groove 5 is differentiable at each point thereof. This ensures that no excessively concentrated regions of internal stresses are formed on the correspondingly formed groove.

It should be noted that the second aspect of the present disclosure encompasses any combination of two or more embodiments, or variants thereof, as discussed above.

According to a third aspect of the present disclosure, a plate frame assembly for a horizontal plate and frame -type filter, such as a tower press, is provided.

The plate frame assembly comprises the filter diaphragm 1 according to the first aspect of the present disclosure, and the plate frame 4 according to the first aspect of the present disclosure. The filter diaphragm 1 is attached to the plate frame 4 such that the bead 3 of the diaphragm 1 is received within the groove 5 of the plate frame 4. Moreover, the cross- sectional profile of the groove 5 corresponds to that of the bead 3 such that the bead 3 is at least partially compressed when received within the groove 5.

In an embodiment of the third aspect, the cross-sectional profiles of both bead 3 and the groove are asymmetric at the intermediate portion 3c and the neck portion 5c, respectively, as discussed abo in connection with the first and second aspects.

Preferably, but not necessarily, an asymmetric concavity, with respect to the asymmetry axis A3, is provided on the intermediate portion 3c of the cross-sectional profile of the bead 3, and an asymmetric convexity, with respect to the asymmetry axis A5 is provided on the neck portion 5c of the cross-sectional profile of the groove 5, as discussed above in connection with the first and second aspect of the present disclosure. Particularly, the asymmetric convexity of the groove 5 is received within the asymmetric concavity of the bead 3.

In an embodiment according to the third aspect of the present disclosure, the cross- sectional profile of the bead 3 is asymmetric at the distal portion 3a with respect to any vertical line running through the bead 3, and the cross-sectional profile of the groove 5 is asymmetric at the bottom portion 5a with respect to any vertical line running through the groove 5, as discussed above in connection with the first and second aspect of the present disclosure, respectively.

Preferably, but not necessarily, an asymmetric bulge 3d, with respect to the asymmetry axis A3, is provided on the distal portion 3a of the cross-sectional profile of the bead 3, and an asymmetric notch 5d, with respect to the asymmetry axis A5, is provided on the bottom portion 5a of the cross-sectional profile of the bead 5. Particularly, the asymmetric bulge 3d of the bead 3 is received in the asymmetric notch 5d of the groove 5. Most suitably, the bulge 3d and the notch 5d are provided on the lateral outside 1 b, 4b of the diaphragm and frame.

In an embodiment according to the third aspect of the present disclosure, an empty space residing between the bottom portion 5a of the groove 5 and the distal portion 3a of the bead 3, when the diaphragm is not compressed against the plate frame 4. This ensures, that there is sufficient space for the diaphragm to be compressed and expand within the groove during operation of the associated filter press. Preferably, but not necessarily, the space is arranged between the distal surface 3a’ and the bottom surface 5a’.

It should be noted that the third aspect of the present disclosure encompasses any combination of two or more embodiments, or variants thereof, as discussed above.

According to a fourth aspect of the present disclosure a routing or milling tool set for machining an asymmetric groove is provided.

The tool set comprises a first profile cutter having a first rotationally symmetrical contour for machining a first portion of the groove. The tool set further comprises a second profile cutter having a second rotationally symmetrical contour for machining a second portion of a groove.

At least a part of the first rotationally symmetrical contour corresponds to a first portion of a cross-sectional profile of the asymmetric groove, and at least a part of the second rotationally symmetrical contour corresponds to a second portion of the cross-sectional profile of the asymmetric groove 5.

Furthermore, cross-sectional profile of the asymmetric groove 5 correspond to the cross- sectional profile of the groove 5 of the filter plate frame 4 to the second aspect, as discussed above.

Particularly, the at least a part of the first rotationally symmetrical contour correspond to a laterally outer portion of cross-sectional profile of filter plate’s 4 groove 5. Correspondingly, the at least a part of the second rotationally symmetrical contour corresponds to a laterally inner portion of the cross-sectional profile of the filter plate’s 4 groove (5).

Most suitably, the laterally outer portion of the cross-sectional profile of filter plate’s 4 groove 5 and the laterally outer portion of the cross-sectional profile of the filter plate’s 4 groove 5 are divided along a vertical line extending through said groove 5.

According to a fifth aspect of the present disclosure a horizontal filter press, such as a tower press, is provided. The filter press comprises a plurality of plate frame assemblies according to the third aspect of the present disclosure. The plate frame assemblies are configured movable towards each other into a closed position in which a filter chamber is formed between adjacent plate frame assemblies, and away from each to an open position in which adjacent plate frame assemblies are spaced apart from each other.

The filter press further comprises a filter medium arranged between adjacent plate frame assemblies.

The filter press further comprises a translation arrangement for moving the plate frame assemblies towards each other so as to form a filter chamber between adjacent plate frame assemblies, and away from each other so as to open the filter chamber.

The filter press further comprises a feed arrangement for feeding slurry into the filter chamber.

The filter press further comprises a recovering arrangement for recovering filtrate from the filter chamber.

The filter press further comprises a discharge arrangement for discharging a filter cake formed within the filter chamber.

LIST OF REFERENCE NUMERALS 1 diaphragm

1a lateral inside side of bead

1 b lateral outside of bead

1c central portion of diaphragm

1d plate frame -facing side of diaphragm

1 e filter plate -facing side of diaphragm

2 body of diaphragm

3 bead

3a distal portion of bead

3a’ distal surface of bead

3b base portion of bead

3c intermediate portion of bead

3d asymmetric bulge W3a laterally extending dimension of distal portion

W3c laterally extending dimension of intermediate portion

A3 vertical asymmetry axis of bead

W3min minimum width section of the intermediate portion

4 plate frame

4a lateral inside of plate frame

4b lateral outside of plate frame

4c central opening of plate frame

4d plate -facing side of plate frame

4d’ planar surface on plate -facing side

5 continuous groove

5a bottom portion of groove

5a’ bottom surface of groove

5b aperture portion of groove

5c neck portion of groove

W5a laterally extending dimension of the bottom portion

W5c laterally extending dimension of the neck portion

A5 asymmetry axis of groove

W5min minimum width section of the neck portion

6 seal bead

Claims

1. A filter diaphragm (1) for a horizontal plate and frame -type filter, such as a tower press, comprising a sheet like body (2) having a flexible structure, wherein that the filter diaphragm (1) comprises, at least on a plate frame -facing side thereof (1d), a bead (3) for attaching the diaphragm (1) to a plate frame (4) of the filter, the bead (3) running along the periphery of the filter diaphragm (1) and delimiting a central portion (1c) of the diaphragm on an lateral inside (1a) of the bead, wherein a lateral outside (1 b) being defined on a lateral side of the bead (3) opposite to the lateral inside, wherein the bead (3) has a cross-sectional profile having base portion (3b) attaching the bead to the remaining diaphragm, a distal portion (3a) and an intermediate (3c) portion between the base portion (3b) and the distal portion (3a), such that the laterally extending dimension (W3a) of the distal portion (3a) exceeds that of the intermediate portion (W3c), characterized in that the bead (3) has an asymmetric cross-sectional profile with respect to a vertical asymmetry axis (A3) running through a lateral centre point of a minimum width section (W3min) of the intermediate portion (3c), wherein the vertical asymmetry axis (A3) is perpendicular to a general plane of the diaphragm (1), defined by a planarity of the central portion (1c), when laid on a flat surface, wherein the minimum width section (W3min) of the intermediate portion (3c) being defined as a point of the cross-sectional profile of the bead (3) at which the intermediate portion (3c) exhibits a smallest laterally extending dimension, and wherein the distal portion (3a) extends laterally further from the asymmetry axis (A3) on the lateral outside (1 b) than on the lateral inside (1a).

2. The filter diaphragm (1) according to Claim 1 , characterized in that the cross- sectional profile of the bead (3) is asymmetric at the intermediate portion (3c) with respect to the vertical asymmetry axis (A3).

3. The filter diaphragm according to Claim 2, characterized in that an asymmetric concavity, with respect to the asymmetry axis (A3), is provided on the intermediate portion (3c) of the cross-sectional profile of the bead (3).

4. The filter diaphragm (1) according to any of the preceding Claims 1-3, characterized in that the cross-sectional profile of the bead (3) is asymmetric at the distal portion (3a) with respect to any vertical line running through the bead (3)

5. The filter diaphragm (1 ) according to any of the preceding Claims 1 -4, characterized in that an asymmetric bulge (3d), with respect to the asymmetry axis (A3), is provided on the distal portion (3a) of the cross-sectional profile of the bead (3).

6. The filter diaphragm (1 ) according to any of the preceding Claims 1 -5, characterized in that a distal surface (3a’) of the distal portion is inclined with respect to the general plane of the diaphragm (1), such that the distal surface (3a’) is inclined towards the intermediate portion (3c) in a direction from the lateral inside (1a) towards the lateral outside (1b).

7. The filter diaphragm (1 ) according to any of the preceding Claims 1 -6, characterized in that a contour of the cross-sectional profile of the bead (3) is differentiable at each point thereof.

8. The filter diaphragm according to any of the preceding Claims 1-7, characterized by comprising, on a filter plate -facing side (1e) thereof, a continuous seal bead for sealing against a filter plate, wherein the seal bead delimits the central portion (1 c) on a lateral inside of the seal bead.

9. A plate frame (4) for a horizontal plate and frame -type filter, such as a tower press, defining a central opening (4c) delimiting a lateral boundary of an associated filter chamber on a lateral inside (4a) of the plate frame (4) wherein a lateral outside (4b) being defined on a lateral side of the plate frame (4) opposite to the lateral inside (4a) wherein the plate frame (4) comprises, on a plate -facing side (4d) thereof, a continuous groove (5) for attaching a filter diaphragm (1), the groove (5) extending along the frame and surrounding the opening wherein the groove (5) has a cross-sectional profile having an aperture portion (5b) opening to an outer surface of the frame, bottom portion (5a) and a neck portion (5c) between the aperture portion (5b) and the bottom portion (5a), such that the laterally extending dimension (W5a) of the bottom portion (5a) exceeds that (W5c) of the neck portion (5c) characterized in that the groove (5) has an asymmetric cross-sectional profile with respect to vertical asymmetry axis (A5) running through a lateral centre point of a minimum width section (W5min) of the neck portion (5c), wherein the vertical asymmetry axis (A5) is perpendicular to general plane of the plate frame (4), defined by a planarity of a planar surface (4d’) on the plate -facing side (4d) intended to oppose a filter plate, when in use, wherein the minimum width section (W5min) of the neck portion (5c) being defined as a point of the cross-sectional profile of the groove (3) at which the neck portion (5c) exhibits a smallest laterally extending dimension, and wherein the bottom portion (5a) extends laterally further from the asymmetry axis (5a) on the lateral outside (4b) than on the lateral inside (4a).

10. The plate frame (4) according to Claim 9, characterized in that the cross-sectional profile of the groove (5) is asymmetric at the neck portion (5c) with respect to the asymmetry axis (A5)

11. The plate frame (4) according to Claim 10, characterized in that an asymmetric convexity, with respect to the asymmetry axis (A5) is provided on the neck portion (5c) of the cross-sectional profile of the groove (5).

12. The plate frame (4) according to any of the preceding Claims 9-11 , characterized in that the cross-sectional profile of the groove (5) is asymmetric at the bottom portion (5a) with respect to any vertical line running through the groove (5).

13. The plate frame (4) according to Claim 12, characterized in that that an asymmetric notch (5d), with respect to the asymmetry axis (A5), is provided on the bottom portion (5a) of the cross-sectional profile of the bead (5).

14. The plate frame (4) according to any of the preceding Claims 9-13, characterized in that a bottom surface (5a’) of the bottom portion (5a) is inclined with respect to the general plane of the plate frame (4), such that the bottom surface (5a’) is inclined towards the neck portion (5c) in a direction from the lateral inside (4a) towards the lateral outside (4b).

15. The plate frame (4) according to any of the preceding Claims 9-14, characterized in that a contour of the cross-sectional profile of the groove (5) is differentiable at each point thereof.

16. A plate frame assembly for a horizontal plate and frame -type filter, such as a tower press, characterized by comprising

- the filter diaphragm (1) according to any of the preceding Claims 1-8, and

- the plate frame (4) according to any of the preceding Claims 9-15, wherein the filter diaphragm (1) is attached to the plate frame (4) such that the bead (3) of the diaphragm (1) is received within the groove (5) of the plate frame (4), and wherein the cross-sectional profile of the groove (5) corresponds to that of the bead (3) such that the bead (3) is at least partially compressed when received within the groove (5).

17. The plate frame assembly according to Claim 16, characterized by comprising the filter diaphragm (1) according to Claim 2 and the plate frame (4) according to Claim 10.

18. The plate frame assembly according to Claim 17, characterized by comprising

- the filter diaphragm (1) according to Claim 3, and

- the plate frame (4) according to Claim 11 , wherein the asymmetric convexity of the groove (5) is received within the asymmetric concavity of the bead (3).

19. The plate frame assembly according to any of the preceding Claims 16-18, characterized by comprising the filter diaphragm (1) according to Claim 4 and the plate frame (4) according to Claim 12.

20. The plate frame assembly according to Claim 19, characterized by comprising

- the filter diaphragm (1) according to Claim 5, and

- the plate frame (4) according to Claim 13, wherein the asymmetric bulge (3d) of the bead (3) is received in the asymmetric notch (5d) of the groove (5).

21. The plate frame assembly according to any of the preceding Claims 16-20, characterized by an empty space residing between the bottom portion (5a) of the groove (5) and the distal portion (3a) of the bead (3), when the diaphragm is not compressed against the plate frame (4).

22. A routing or milling tool set for machining groove having an asymmetric cross- sectional profile, comprising a first profile cutter having a first rotationally symmetrical contour for machining a first portion of the asymmetric cross-sectional profile a second profile cutter having a second rotationally symmetrical contour for machining a second portion of the asymmetric cross-sectional profile, characterized in that the cross-sectional profile of the asymmetric groove correspond to the cross-sectional profile of the groove (5) of the filter plate frame (4) according to any of the preceding Claims 8-14, such that the at least a part of the first rotationally symmetrical contour correspond to a laterally outer portion of cross-sectional profile of filter plate’s (4) groove (5), the at least a part of the second rotationally symmetrical contour corresponds to a laterally inner portion of the cross-sectional profile of the filter plate’s (4) groove (5), wherein the laterally outer portion of the cross-sectional profile of filter plate’s (4) groove (5) and the laterally outer portion of the cross-sectional profile of the filter plate’s (4) groove (5) being divided along a vertical line extending through said groove (5).

23. A horizontal filter press, such as a tower press, characterized in that the filter comprises: a plurality of plate frame assemblies according to any of the preceding Claims 16-21 , wherein the plate frame assemblies are configured movable towards each other into a closed position in which a filter chamber is formed between adjacent plate frame assemblies, and away from each to an open position in which adjacent plate frame assemblies are spaced apart from each other; a filter medium arranged between adjacent plate frame assemblies; a translation arrangement for moving the plate frame assemblies towards each other so as to form a filter chamber between adjacent plate frame assemblies, and away from each other so as to open the filter chamber; a feed arrangement for feeding slurry into the filter chamber; a recovering arrangement for recovering filtrate from the filter chamber, and a discharge arrangement for discharging a filter cake formed within the filter chamber;: