GB2088231A - Improvements in filter cloths for filter presses - Google Patents

Abstract

In order to overcome the problems of fitting filter cloths 1, 2 on opposite sides of a filter press 3 the cloths are secured to respective annular members 8, 9 which are constructed to connect releasably together in the manner of a snap fastening. The members then define a passage through plate 3 for material to be filtered. Cloths 1, 2 may be separate cloths or two halves of a single cloth folded over the upper edge of the plate.

Description

SPECIFICATION Improvements in filter cloths for filter presses The present invention relates to improvements in filter cloths for filter presses and in particular to presses of the recessed plate type, such as are used in ceramic, chemical and effluent processes for separation of solids from liquids.

It is known to provide on filter presses and some other filter types filter plates having a slurry feed hole in the filtering area. Both sides of such a filter plate are covered with a layer of filter material and each layer is provided with a feed hole. It is necessary to prevent the slurry from escaping between the filter layers and the filter plate in the region of the feed hole.

In one known arrangement a connecting device consisting essentially of a short cylinder having a flange at one end and threaded at the other is passed through the feed hole of one layer, through the hole in the filter plate and through the hole in the other layer. An annular ring is placed over the projecting cylindrical portion and a nut is screwed onto the threaded portion so pressing the layers of filter material between the flanges and the filter plate to provide a seal. This type of fixing is difficult and time consuming to assemble and often difficult to dismantle when the filter cloth has reached the end of its useful life.

In another known arrangement the two layers of filter material are interconnected at the feed hole by a cylindrical portion made from the filter cloth material which portion is stitched at one end to one layer and at the other end to the other layer to form a so called "barrel neck" filter cloth. The stitching operation is particularly time consuming and installing the filter cloth necessitates passing one layer of the cloth through the feed hole in the filter plate. Furthermore if the filter cloth becomes hardened during use it is often impossible to remove the cloth without cutting, thus removal for washing is prevented and the useful life of the filter cloth is reduced. Also if one side of the cloth becomes damaged the complete filter cloth must be disregarded.

In order to overcome the problem of stitching a known filter cloth (described in GB Patent Specification No. 1459099) of the "barrel neck" type utilises a hollow plastics cylinder which is secured to the two layers of the filter cloth by heat bonding. However, the problems of fitting and removing the cloth still remain.

In another known arrangement described in German Published Patent Specification No.

2110860 a pair of filter cloths which cover the respective sides of a filter plate are each provided with a connecting device which is semi-circular in cross-section and which is made from an elastic deformable material. The device is secured to the filter cloth and when installed in the press the semi-circular portions of each device lay tightly over one another.

In practice connections of this type have been found to be difficult to install because the semicircular section must be deformed substantially. In addition some support is required for the connection to ensure adequate sealing between the two components.

It is an object of the present invention to provide a filter cloth which overcomes the aforementioned problems.

According to the present invention there is provided a filter cloth for a filter press, including two layers of material each having a feed opening therein, and a feed passage between the feed openings defined by at least first and second members of a snap fastener which are connectible releasably, the first member being secured to one layer of material and the second member being secured to the other layer of material.

Preferably the first member of the snap fastener is sleeve-like, preferably cylindrical, having at one end a flange for securing to the filter cloth material and at the other end a continuous recess, preferably annular. The second member is similarly sleeve-like with a flange for securing to the filter cloth material and at the free end of the sleeve remote from the flange, a continuous projection which is adapted to be a snap fit in the recess of the first member.

Preferably the snap fastener is a plastics material and the respective flanges of the fastener are secured to the filter cloth material by means of staples or any other similar device such as rivets.

The filter cloth material being sandwiched between an annular support plate and the flange.

This method of attaching the snap fastener to the filter cloth provides an effective seal preventing the escape of particulate material from the feed side of the filter.

In an alternative embodiment both the first and second members of the snap fastener carry either a recess or a projection and a sleeve-like intermediate member is provided to interconnect the first and second members. The ends of the intermediate member being provided with a recess or a projection as the case may be. Such an arrangement has the advantage that only one type of filter cloth and fitting is necessary and yet different thicknesses of filter plate can be catered for by utilising intermediate members of differing lengths.

The present invention will now be described further, by way of example only, with reference to the accompanying drawing which illustrates a section through a filter press having a filter cloth in accordance with the invention.

A filter cloth for a filter press has two layers of material 1, 2 which are disposed, in use, on opposite sides of a filter plate 3. Each layer has a feed opening 4, 5 which, when assembled in the filter press, lie adjacent a feed hole 6 in the filter plate 3. The filter cloth is provided with a snap fastener, generally indicated as 7, which comprises a first member 8 and a second member 9 which are connectible, releasably.

The first member 8 has a hollow cylindrical portion 10 having at one end a flange 11 and at the other end a continuous annular projection 12 which has a rounded end 13, a portion of which extends radially inwardly. The flange 11 is secured to the layer of filter cloth material 1 by means of a plurality of staples 1 5 and an annular plate 14 having a central opening which is larger than the external dimension of the cylindrical portion 10 is provided on the opposite side of the material layer to the flange 11 to act as a support ring. The layer of filter material is thus sandwiched between the flange 1 1 and the annular plate 14 in a sealing manner which prevents the escape of the particulate material.

The second member 9 likewise has a hollow cylindrical portion 10' which carries at one end a flange 11' and at the other end has a continuous annular recess 16. The recess 16 is adapted to receive the projection of the first member 8 and has a lip 17 which acts as a stop to prevent accidental withdrawal of the two parts once assembled.

The flange 11' of the second member 9 is secured to the second layer of filter material 2 in the same manner as the first member, namely by means of a plurality of staples 1 5'. An annular plate 14' is likewise provided and the layer 2 is thus sandwiched between the flange 11' and the plate 14'.

The parts of the snap fastener, namely the first member 8 and the second member 9, together with the annular plates 14, 14' are made of a plastics material, for example polypropylene but any other mouldabie plastic with the appropriate physical characteristics would be suitable. The staples are metal, preferably an alloy of nickel and copper e.g. monel.

The plastics material is sufficiently soft to permit it to be stapled and yet is rigid so that it is not essential to support the fastening. The plastic has the required flexibility to permit the two parts of the fastener to be snapped together and unfastened when required.

With the present invention the filter cloth for a recessed plate type press may comprise a single cloth having two openings therein to which are attached to the respective halves of the snap fastener. In use the filter cloth is draped over the filter plate to overlie each side of the plate so that the apertures in the respective layers are aligned with the feed hole in the plate. The two halves of the snap fastener are then pressed together to interconnect them. Thus the required connection is made in a simple and quick manner.

Alternatively each layer of the filter cloth may be individual each having an aperture therein around which is secured the appropriate half of the snap fastener. In use, the halves of the fastener are aligned with the feed hole in the filter plate and the parts are snapped together.

In an alternative embodiment (not illustrated) the first and second members secured to the respective layers of the filter cloth carry at the free end identical projections, and sleeve-like intermediate member is provided with recesses at each end which are adapted to receive the said projections. Thus different thicknesses of filter plate may be accommodated by utilising different lengths of intermediate member, and the arrangement has the advantage that each layer of the filter cloth is identical and matched pairs are not required. Naturally the first and second members may carry the recesses and the intermediate member the projections. The projections and recesses correspond in shape to those described with respect to the illustrated embodiment.

Claims (14)

1. A filter cloth for a filter press, including two layers of material each having a feed opening therein, and a feed passage between the feed/openings defined by at least first and second members of a snap fastener which are connectible releasably, the first member being secured to one layer of material and the second member being secured to the other layer of material.

2. A filter cloth as claimed in claim 1, in which the first and second members are connectible releasably by means of an intermediate sleeve-like member.

3. A filter cloth as claimed in claim 1 or 2, in which the intermediate member carries at each axial end face a continuous axial recess or projection which cooperates with a correspondingly shaped projection or recess carried by the first and second members.

4. A filter cloth as claimed in claim 1, in which the first member carries at a free end remote from the layer of filter cloth material to which is is secured a continuous recess which is adapted to receive, as a snap fit, a continuous projection carried by the second member at its free end remote from the layer of filter cloth material to which it is secured.

5. A filter cloth as claimed in claim 4, in which the continuous recess and continuous projection are annular and are formed on the axial end faces of the respective first and second members.

6. A filter cloth as claimed in any of claims 1 to 5, in which the first and second members are in the form of sleeves each having a flange for securing to a respective layer of the filter cloth.

7. A filter cloth as claimed in any of claims 2 or 3, in which the first and second members are identical.

8. A filter cloth as claimed in any preceding claim, in which the snap fastener is a plastics material and the respective members are secured to the associated filter cloth layer by mechanical attachment means.

9. A filter cloth as claimed in claim 8, in which the mechanical attachment means are staples or rivets.

10. A filter cloth as claimed in any of claims 4 to 9, in which the filter cloth layer is sandwiched between the flange and an annular support plate.

1 A filter cloth as claimed in claim 10, when appendent to claim 9, in which the staples or rivets pass through the flange, the filter cloth and the annular support plate.

12. A filter cloth as claimed in any preceding claim in which the layers are formed by one piece of filter cloth material having two feed openings therein.

13. A filter cloth as claimed in any of claims 1 to 11, in which the layers are formed by individual filter cloths.

14. A filter cloth constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawling.