GB2365368A

GB2365368A - Filter assembly

Info

Publication number: GB2365368A
Application number: GB0018851A
Authority: GB
Inventors: Terence Butlin; Barrie Edward Green
Original assignee: Eco Filters Ltd
Current assignee: Eco Filters Ltd
Priority date: 2000-08-02
Filing date: 2000-08-02
Publication date: 2002-02-20
Anticipated expiration: 2020-08-02
Also published as: GB0018851D0; GB2365368B

Abstract

A filter assembly having a mounting platen 20, which corresponds in size to the mould 23 and 24, and a filter sheet 40 which covers one face of the platen 20 and is continuously attached to the platen 20. A marginal drainage formation 50 at the periphery of the platen 20 and filter sheet 40 allows the discharge of fluid in a parallel direction to the mounting platen 20. The marginal drainage formation may be a drainage band, 53, which has surface projections 57, for example ribs, that define fluid pathways with the platen 20. The band could be a knitted fabric and the filter sheet knitted or woven. The filter assembly is intended for use in a wet concrete press mould.

Description

<Desc/Clms Page number 1> FILTER ASSEMBLY The present invention relates to a filter assembly for a wet concrete press mould, in particular a filter assembly for the upper platen of the press mould.

A west concrete press mould normally comprises a mould cavity having closed bottom and sides. A metered amount of wet concrete mix is placed into the mould cavity and a movable platen is then moved toward the closed bottom to apply a high compressive pressure on to the wet concrete mix. Various actions within the concrete mix occur when pressure is applied, for example the concrete mix is compacted, it is shaped to the shape of the mould and excess water is squeezed out of the wet mixture.

The excess water is conducted away under the assistance of vacuum through the movable platen and through the closed bottom of the mould. It is known that the action of the platen causes the majority of the excess water to be expelled via the movable platen.

It is known to provide filters which cover the closed bottom and the movable platen in order to provide a release for removal of the moulded product from the mould and also to assist in preventing particulate material (such as cement particles and aggregate fines) from exiting the mould via the closed bottom or the platen.

Some filters, for example made of paper, are loosely retained in the mould so as to be removed with the moulded product. This is wasteful of filter material and also has the further disadvantage of requiring removal of the filter material from the moulded product.

Some filters are fixed to the platen or closed bottom of the mould so as to remain in the mould/on the platen after the moulding process and removal of the product.

In our UK patent 2277536 we have described a filter fabric which is suitable for this purpose.

However, although the filter fabric of UK patent 2277536 works well in use) it is a specially constructed fabric and so is relatively expensive when. compared to other types of filter fabric.

It is therefore desirable to provide a filter assembly which is capable of being fixed within a press mould, in particular to the movable platen, for repeated moulding operations whilst using non specialist filter materials.

A general aim of the present invention is to provide such a filter assembly. According to one aspect of the present invention there is provided a filter assembly for a wet mixture press mould, the filter assembly including a mounting plate having a peripheral edge corresponding to the shape and size of the mould, a filter sheet formed from a filter material, the filter sheet overlying one face of the plate and extending up to said peripheral edge to completely cover said one face, a marginal drainage formation extending continuously about said peripheral edge, the drainage formation underlying a marginal edge region of the filter sheet and being adapted to enable fluid to drain in a direction parallel to said one face from between said filter sheet and said one face of the mounting plate, the mounting plate and filter sheet being fixedly secured together continuously along and adjacent to said peripheral edge,

Preferably the marginal drainage formation is defined by a drainage band which is capable of transmitting fluid in its widthwise direction. Preferably the band is provided with surface projections which, in use, abut against the face of the mounting plate to define fluid pathways between the band and the plate.

Preferably the surface projections are in the form of ribs extending across the width of the band, the ribs being spaced from one another along the length of the band.

Preferably the band is formed from a knitted fabric. Preferably the filter material is a knitted or woven fabric.

Various aspects of the present invention are hereinafter described with reference to the accompanying drawings, in which:- Figure I is a schematic side view of a filter assembly according to an embodiment of the invention shown fitted to the movable platen of a press mould; Figure 2 is an enlarged part side view of the filter assembly shown in Figure 1; Figure 3 is a part sectional view taken along line III-111 in Figure 1; Figure 4 is a plan view of the filter assembly shown in Figure 1; Figure 5 is a schematic perspective view of a comer part of a slab moulded using the filter assembly of Figure 1; Figure 6 is a schematic side view of the top portions of two slabs of Figure 5 shown stacked for curing.

In Figure I there is shown a movable top platen 20 of a press mould 2 1. The platen 20 is movable in the direction of arrow M within a mould cavity 22 having sides 23 and a bottom 24.

The platen 20 has side edges 26 which are closely spaced from the sides 23 of the mould cavity. The lower surface 25 is thus of a shape and size which corresponds to the cross-sectional shape and size of the mould cavity.

The lower surface 25 is provided with fluid drainage channels 27 which extend outwardly across the surface 27 toward edges 26 from a central, axially extending fluid conduit 28. Fluid conduit 28 is connected to suction means (not shown) which assist in causing a flow of fluid into the conduit 28 from channels 27 for discharge to a remote location.

The platen 20 is formed from a rigid material capable of applying high compressive loads during the moulding process; a cast metal is a suitable material.

A filter assembly 30 according to an embodiment of the present invention is shown attached to the lower surface 25 of the platen 20.

The filter assembly 30 includes a mounting plate 31 having a peripheral shape and size corresponding to the shape and size of surface 25 of the platen 20.

The mounting plate 31 has an upper face 32 which is mounted in face to face contact with the surface 25 of platen 20.

A sheet 40 of filter material is mounted onto the mounting plate 31 so as to extend up to the peripheral edges 33 of the mounting plate and thereby cover the entire lower surface 36 of the mounting plate 3 1.

The sheet 40 is preferably secured to the mounting plate 31 adjacent to the periphery edges 33 only.

Preferably the mounting plate 31 is formed of a non-compressible material which may also be penetrated with a sewing needle to thereby enable the sheet 40 to be secured to the mounting plate by one or more lines of stitching 46 which extend continuously inboard around the periphery of the mounting plate 3 1.

In the illustrated embodiment, two lines of stitching 46 are shown; one 46a being located closely adjacent to edges 33 and one 46b being located further inboard.

The lines of stitching help to resist contraction of the sheet 40 away from the edges 3 3 of the mounting plate 3 1.

A suitable material for the mounting plate is a plastics material, such as for example polypropylene.

The mounting plate 31 includes a plurality of drainage apertures 39 spaced across its surface which enable fluid passing through the sheet 40 to drain through plate 31 and into channels 27.

Located around the periphery of the mounting plate 31 is a marginal drainage formation 50 which is interposed between the sheet 40 of filter material and the lower surface 25 of the platen 20.

The purposed of the drainage formation 50 is illustrated in Figure 2. The drainage formation 50 defines a fluid passageway 60 which enables fluid located inbetween the sheet 40 and mounting plate 31 to flow outwardly (in a direction parallel to the lower face 36 of the mounting plate) beyond the edges 33 of the mounting plate and into the slight gap between the mounting plate edges 33 and the sides 23 of the mould cavity. This enables fluid to then flow into the open ends of channels 27 for discharged through conduit 28.

It has been found that during the moulding process, the compressive forces applied by the platen 20 causes a large proportion of excess fluid to flow toward the peripheral edges 26 of the platen 20. Accordingly, the drainage forination 50 of the present invention provides a drainage passageway to the channels 27 which is of relatively large capacity and thereby enables a relatively large flow rate of excess fluid.

By providing the drainage formation of the present invention, it has been found that a wide variety of filter materials may be used for fori-ning sheet 40.

In fact, the filter material for forming sheet 40 may be any material which is capable of permitting fluid to pass therethrough during the moulding process whilst restricting passage therethrough of particulate material above a predetermined size.

Accordingly, woven or knitted fabrics of relatively simple structure may be used for forming sheet 40. Also non-woven fabrics may be used. Textile fabrics are preferred for forming sheet 40. However it will be appreciated

that other types of sheet material having the necessary fluid porosity/particle filtering characteristics may be used.

Preferably the drainage formation 50 is defined by a separate band 53 of suitable material which is secured inbetween the sheet 40 and mounting plate 3 1, preferably by the lines of stitching 46.

Preferably the band 53 has a substantially planar lower surface 54 which lies in face to face contact with the sheet 40 and has an upper surface 56 defined by projections 57 which lie in face to face contact with the lower face 36 of the mounting plate 31. The projections 57 in combination with face 36 thereby define fluid passageways 60 to enable excess fluid to flow to the edges 33 of the mounting plate 3 1.

Preferably the projections 57 are in the form of ribs which extend in the widthwise direction of the band 53; the ribs being spaced along the length of the band 53.

The band 53 may be formed of any suitable material which is sufficiently non-compressible during the moulding process to resist collapse and thereby maintain passageways 60 open.

The band 53 may therefore be formed from a suitable plastics material having the projections 57 formed on one face.

Alternatively, the band 57 may be a woven or knitted fabric wherein the ribs are formed by the woven or knitted structure, preferably a ribbed warp knit fabric.

Use of band 53 about the periphery of the mounting plate 31 causes a peripheral indentation 70 around the periphery of the mould product 71 as illustrated in Figure 5.

This is advantageous, particularly where the products are concrete paving slabs since it enables the slabs 71 to be stacked, as illustrated in Figure 6, for curing without damaging the peripheral side edges 73 of the slabs.

It is also envisaged that the band 53 may be integrally formed in the mounting plate 31 by providing suitable indentations spaced about the periphery of the plate 3 1.

The above described filter assembly is particularly suitable for use in a compression mould for the moulding of concrete products fon-ned by filling the mould cavity with a predetermined amount of a wet concrete mix. It will however be appreciated that the filter assembly may be used in compression moulds for the moulding of other types of wet mixed particulate materials.

Claims

CLAIMS 1 . A filter assembly for a wet mixture press mould, the filter assembly including a mounting plate having a peripheral edge corresponding to the shape and size of the mould, a filter sheet forined from a filter material, the filter sheet overlying one face of the plate and extending up to said peripheral edge to completely cover said one face, a marginal drainage formation extending continuously about said penipheral edge, the drainage formation underlying a marginal edge region of the filter sheet and being adaplied to enable fluid to drain in a direction parallel to said one face from between said filter sheet and said one face of the mounting plate, the mounting plate and filter sheet being fixedly secured together continuously along and adjacent to said peripheral edge.
2. An assembly according to Claim I wherein the marginal drainage formation is defined by a drainage band which is capable of transmitting fluid in its widthwise direction.
3. An assembly according to Claim 2 wherein the band is provided with surface projections which, in use, abut against the face of the mounting plate to define fluid pathways between the band and the plate.
4. An assembly according to Claim 3 wherein the surface projections are in the form of n*bs extending across the width of the band, the ribs being spaced from one another along the length of the band.
5. An assembly according to Claim 2, 3 or 4 wherein the band is formed from a knitted fabric.

<Desc/Clms Page number 10>
6. An assembly according to any preceding claim wherein the filter material is a knitted or woven fabric.
7. A filter assembly for a wet mixture press mould substantially as herein described with reference to and as illustrated in the accompanying drawinas. tn