GB2152832A - Filter press plate assembly - Google Patents

Abstract

A filter press plate and inflatable diaphragm assembly for a filter press has a plate (35) and a diaphragm consisting of two parts (37) one overlying each face of the plate. Each diaphragm part (37) has an enlarged bead surrounding its central aperture and the beads are clamped together by an annular clamp (38) having two parts (39) united by fasteners (40). The beads and adjacent sections of the diaphragm may be reinforced by inextensible annular members 41 with radial fingers 42. <IMAGE>

Description

SPECIFICATION Filter press This invention relates to a filter press.

The present invention is divided from application No. 8231844 to which the reader is referred.

A filter plate/diaphragm assembly for use in a filter press is known wherein the plate has a central feed aperture and is enclosed within a one-piece diaphragm having a perforate part overlying each face of the plate, the diaphragm thus having, when considered on an imaginary radial plane coinciding with the axis of the central aperture, a generally U shaped cross-section. The marrying of such a moulded diaphragm to its plate is a skilled operation and usually has to be carried out by the plate/ diaphragm manufacturer to avoid damage to the diaphragm. Further, if the diaphragm must be replaced, even though one of its halves may be perfectly functional.

It is an object of the present invention to provide an improved filter plate/diaphragm assembly.

The invention provides a filter plate/diaphragm assembly for a filter press, comprising a filter plate having a central aperture and a diaphragm constituted by a pair of diaphragm parts, one overlying each face of the plate, each diaphragm part having a central aperture and the peripheries of the central aperture in the diaphragm parts being clamped together by an annular clamp.

Preferably each inner edge of each diaphragm part has an annular bead of greater thickness than the body of the diaphragm part, the two beads being sandwiched by the clamp.

Each bead can enclose a restraining ring.

The restraining ring can have radially disposed reinforcement means attached, to or integral therewith and enclosed within the material of the body of the diaphragm part around the bead to discourage ballooning of the diaphragm part into the feed channel.

The invention will be described further, by way of example, with reference to the accompanying drawings, wherein: Fig. 1 is a longitudinal cross-sectional view showing a half of a pair of plates in a filter press, one of the plates being part of a filter plate/diaphragm assembly, not in accordance with the invention but shown for comparison purposes, the cross-section being taken on line I-I of Fig. 4; Fig. 1 a is a fragmentary view showing part of Figure 1 before clamping of the plates; Fig. 1 b shows a variation; Fig. 2 illustrates a preferred filter plate/diaphragm in assembly of the invention; Fig. 3 is a transverse cross-section view (line Ill-Ill in Fig. 4) through a plate of the assembly of the invention; Fig. 4 is a front elevation of a filter plate of the assembly of the invention;; Fig. 5 is an enlarged detail of the diaphragm; Fig. 6 is a further enlarged detail of the diaphragm; Fig. 7 is a view similar to Fig. 6 but showing a variation; Fig. 8 is a fragmentary front elevation of the assembly shown in Fig. 2; and Fig. 9 is a similar view showing a variation.

A filter plate/diaphragm assembly 10, not in accordance with the present invention, but included for comparison, is suitable for use in a filter press of the type described which has a plurality of assemblies 10, each having a filter plate 11, of uniform thickness, arranged in alternation with a plurality of plain recess plates 12 to form a horizontal stack, each filter plate 11 having a peripheral thicker portion 13, surrounding a smoothly curved and rounded hollow 14 defined by a thinner inner portion 15 surrounding a central through-aperture 16 and being substantially enclosed within a diaphragm 19.A filter cloth 17 encloses each assembly 10 and a filter cake can be built up by pumping a slurry via the central through passage to form a cake in each working chamber 18 defined by the hollows in adjacent plates, liquid passing through the filter cloths 17 and travelling along the working surfaces of the diaphragms 19 to drainage eyes 30 (Fig. 4) in, say, the corners of the plates 11 and 12 aligned to form an drainage passage extending longitudinally of the stack.

Each plate 11,12 is rounded at the central aperture and can have between the central aperture and the thicker outer portion a plurality of staybosses 20, 21 composed of a pair of protrusions 20a, 20b, 21a, 21b extending from the respective plate 11, 12 one on each side thereof and contacting protrusions staybosses of adjacent plates in the stack to steady the plates, and maintain them separate. The protrusions 21 a of staybosses 21 of plates 12 are greater in size than those of plates 11 so as to extend outside the peripheries of staybosses 20 for a purpose to be later described.

Each plate 11 has its diaphragm 19 in the form of a first part 19a covering one side thereof and united at the centre with a diaphragm part 19b on the other side to form an envelope about the plate 11 to the inside of which a fluid such as compressed air can be introduced through ports 22 in the plate 11 to "inflate" the envelope and compress a partlyformed filter cake in the chamber between the plate 11 and plate 12 to increase its solids content by expulsion of liquor.Each diaphragm 19 does not overlie the peripheral thicker portion 13 of the plate 11 of the protrusions 20a, 20b, of the staybosses 20, but has lips 23,24 at its various edge portions, which lips 23, 24 are accommodated in complementary recesses 25,26 in the inner periphery of the thicker edge portion and in the peripheries of the protrusions 20a, 20b this enabling the protrusions 20, 21 and the edge portions 13 of the plates 11 and thereof plates 13 to sandwich only the filter cloths 17 between them, thus reducing compressive stress on the diaphragms 19.

Nevertheless, the clamping together of the plates 11, 12 is effective to seal the diaphragms 19 to the plates 11 by urging the lips 23, 24 into engagement with the recesses 25, 26 these items being shaped to facilitate sealing.

The diaphragm 19 has a plurality of grooves 27 in its surface facing the cloth 17, which grooves 27 lead liquid passing through the filter cloth 17 to a drain channel 28 in one of two transverse ribs 2a in the diaphragm 19. Channels 28 can be restrained from closure by one or more solid inserts such as an open spiral or spaced tubular members (not shown). Ribs 29 are accommodated in complementary concavities in plate 11.

To encourage sealing between the diaphragm 19 and plate 11 at the lips 23,24 and recesses 25,26, the lips can be a force fit in the recesses as shown in Fig. la. Here lip 23 is shown being urged towards recess 23 by protrusion 21b during clamping. The lip 23 is wider than recess 26 and is thus compressed upon entry into the recess 26 to ensure a good seal.

As a variation the lips 23 and 24 can each have a metallic or similar hard insert such as 29 which presents an outer edge 30 which, on insertion into the recess bites into the wall thereof and resists withdrawal of the diaphragm 19.

The transverse ribs 29 can terminate in extension 31 accommodated in the plate 11 and to prevent pressurised air from travelling between the extensions 31 and the plate 11 the extensions can be reinforced by having a tubular insert therein lining a through passage and aligning with passages 32 in the plate 11 or being accommodated therein. In the latter case the passages 32 can have shoulders to prevent movement of the inserts away from the diaphragms.

As an alternative to drainage grooves 27 (Fig. 6) the diaphragm in 19 can have pips 33 which define drainage paths by supporting the cloth 17 clean of the diaphragm 19.

Fig. 2 shows a filter plateldiaphragm assembly conforming to the present invention, wherein a plate 35 similar to plate 11 has a diaphragm 36 which is in two complementary parts 37 one on each side of the plate 35.

At the centre of the plate 35, the edge portions of the central apertures in the diaphragms parts 37 are clamped together by an annular two part clamp 38 of outwardly facing C-section, the two halves 39 having rounded edges to reduce stress in the diaphragm parts 3, at this position and being united by setscrews, bolts or like fasteners 40. The edge portions of the diaphragms parts 37 at the centre may be reinforced by having flexible but inextensible members 41,42 moulded in during manufacture. These members can take the form of an annular mamber 41 from which extend radial spokes 42, of metal or textile material Fig. 8.

Alternatively, (Fig. 9) a metal plate 43 can be used having a central annulus 44 and radially outwardly extending fingers 45. The reinforcement tends to prevent ballooning of the diaphragm into the feed channel and bursting thereof when inflated.

The filter plate/diaphragm assembly of the invention has the advantage that if a diaphragm should become damaged it is only necessary to replace a small component and the whole plate does not have to be returned to the manufacturer for repair.

Claims (3)

1. A filter plate/diaphragm assembly for a filter press comprising a filter plate having a central aperture and a diaphragm constituted by a pair of diaphragm parts, one overlying each face of the plate, each diaphragm part having a central aperture and the peripheries of the central apertures in the diaphragm parts being clamped together by an annular clamp.

2. An assembly as claimed in claim 1, wherein each diaphragm has an annular bead of greater thickness than the body of the diaphragm part around its central aperture, the beads being clamped by the annular clamp.

3. An assembly as claimed in claim 1 or 2, wherein the restraining ring is flexible.

3. An assembly as claimed in claim 1 or 2, wherein each bead encloses a restraining ring.

4. An assembly as claimed in claim 3, wherein the restraining ring is flexible but inextensible.

5. An assembly as claimed in claim 3 or 4, wherein reinforceing members within the body of the diaphragm part extend outwardly from the restraining ring.

6. An assembly as claimed in claim 5, when appendant to claim 3, wherein the restraining ring and said reinforcement are integrally formed being constituted by a plate having a central annulus and outwardly extending fingers.

7. An assembly as claimed in any preceding claim wherein the clamp includes two parts urged towards each other by fasteners.

8. An assembly as claimed in clain 7, wherein the clamp is of outwardly open C-section.

9. A filter plate/diaghragm assembly, for a filter press, substantially as hereinbefore described with reference to and as illustrated in Figs. 2, 8 and 9 of the accompanying drawings.

Amendments to the claims have been filed, and have the following effect: (a) Claims 1,2,3,4 above have been deleted or textually amended.

*(b) New or textually amended claims have been filed as follows.

*(c) Claims 5,6,7,8,9, above have been renumbered as 4, 5,6,7, 8, and their appendancies corrected.

1. A filter plate/diaphragm assembly for a filter press comprising a filter plate having a central aperture and a diaphragm constituted by a pair of diaphragm parts, on overlying each face of the plate, each diaphragm part having a central aperture, an inextensible restraining ring being embedded in the material of the diaphragm surrounding the central aperture, and the peripheries of the central apertures in the diaphragm parts being clamped together by an annular clamp.

2. An assembly as claimed in claim 1, wherein in each diaphragm, the restraining ring is disposed within an annular bead of greater thickness than the body of the diaphragm part around its central aperture, the beads being clamped by the annular clamp.