EP2882578B1

EP2882578B1 - Filter assembly and method for assembling said filter assembly

Info

Publication number: EP2882578B1
Application number: EP13762200.7A
Authority: EP
Inventors: Terence Butlin
Original assignee: Eco Filters Ltd
Current assignee: Eco Filters Ltd
Priority date: 2012-08-09
Filing date: 2013-08-05
Publication date: 2019-09-25
Anticipated expiration: 2033-08-05
Also published as: EP2882578A1; EP2882510B1; GB2504848A; WO2014023945A1; GB201311932D0; GB201313470D0; GB2504848B; EP2882510A1; GB2506011B; WO2014023946A1; GB2506011A

Description

The present invention relates to a filter assembly for use in a cementitious press mould such as a wet concrete, hermetic or semi-dry mix press mould, and to a method for assembling a filter assembly.
A known cementitious press mould comprises a mould cavity having a closed base and side walls. A metered amount of cementitious mix is placed into the mould cavity and a movable press head is then moved towards the closed base to apply a high compressive pressure on to the cementitious mix.
The press head comprises a die head having a head plate that comes into contact with the mixture contained in the mould. The head plate is of a shape and size that corresponds to the cross-sectional shape and size of the mould cavity.
The base of the press mould comprises a bottom former that has a shape and size that corresponds to the cross-sectional shape and size of the mould cavity.
Various actions within the cementitious mix occur when the compressive pressure is applied. For example, in a wet concrete press mould, a wet concrete mix is compacted, it is shaped to the shape of the mould, and excess water is squeezed out of the wet mixture.
A result of these actions is the formation of a moulded product, such as a paving slab or kerb, for example.
In a wet concrete press mould, excess water is conducted away from the die head under the assistance of a vacuum, created in the die head and through the bottom former of the mould cavity. It is known that the action of the press head causes the majority of the excess water to be expelled via the die head.
It has been found that during the moulding process, the compressive forces applied by the press head to the concrete mix cause a large proportion of the excess fluid to flow toward the edges of the die head, resulting in high pressure and frictional forces acting on the edges of the die head.
In a hermetic press mould, a cementitious mix designed specifically for the press mould is placed in the mould cavity. The cementitious mix usually consists of a face and back mix.
The face mix normally comprises expensive aggregates with a high cement content and is generally very wet when discharged into the mould. The back mix is a weak semi-dry cement mix, and is placed on top of the face mix within the cavity.
Due to the fact that a hermetic press mould comprises a sealed base, cement enriched water from the face mix is forced thorough the back mix when under pressure from the press head.
In a semi-dry press mould, a semi dry mix having a higher cement content, and slightly wetter consistency than the back mix of a hermetic press mould, is placed in the mould cavity. The water/cement ratio of the mix is such that on compaction from either pressure or vibration, the mix forms a solid mass to the required strength.
It is known to provide filters which cover the closed base and the moveable head plate 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 head plate.
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 head plate and/or to the lower former of the mould so as to remain in the mould / on the die head after the moulding process and removal of the product.
Such filters may be formed from any convenient material, or fabric, that allows liquid to pass through the filter whilst preventing particulate material from passing through.
A suitable filter fabric, which may be knitted or woven is described in our UK Patent No. GB 2 277 536B . However, other materials, such as plastics materials, may also be used.
In general, any permeable, woven, non-woven (such as needle felts), knitted or foam material may be used as a suitable filter fabric.
It is known to form perforations in both bottom former and the die head in order to assist the flow of excess fluid out of the mould.
In known cementitious press moulds, the filter fabric is mounted on a support layer which is generally formed from a plastics material to form a filter assembly.
The filter assembly must be attached to the carrier plate.
The support layer may be formed with perforations and these perforations may be aligned with the perforations in the carrier plate in order to allow proper drainage of the cementitious mix.
A problem with such known filter assemblies, is that it is generally necessary for a customer to attach the filter assembly to the carrier plate. This is achieved by means of an adhesive layer formed around the edge of the filter. In use, a customer removes a backing sheet from the adhesive layer and then positions the filter onto the carrier plate.
This can result in misalignment of the filter if the customer is not very careful when locating the filter assembly on the carrier plate.
If the filter assembly is misaligned, then the filter assembly will wear more quickly during use of the press mould, and drainage may be impaired. Further, it can be time consuming to have to attach the filter assembly to the carrier plate.
EP 0 629 477 A1 discloses a filter arrangement for a machine for manufacturing concrete slabs, wherein attachment means are provided to detachably secure the filter arrangement on the side of a pressure plate.
According to a first aspect of the present invention there is provided a filter assembly for a cementitious press mould with the features of claim 1.
By means of the invention it is not necessary to attach the filter sheet to a support plate. Instead, the filter sheet is attached to the filter frame, and the filter is engageable directly with the die plate. This means that, in use, the filter sheet is held in place directly over the first carrier portion in which perforations are formed, without needing to support the filter with a support plate.
The filter will form a face for contacting and applying compression to a mixture contained in the press mould.
The filter sheet and filter frame may be manufactured to appropriate dimensions to fit a particular carrier plate. The filter sheet may then be attached to the filter frame by any suitable means. These steps may be carried out at any suitable location, and not necessarily in the vicinity of the press mould to which the filter is to be fitted.
In some embodiments of the invention, the filter sheet may be attached to the filter frame by stitching the filter sheet to the filter frame.
In other embodiments, the filter sheet may be adhesively attached to the filter frame.
Other means of attaching the filter sheet to the filter frame may also be used. Ultrasonic techniques may be used in order to cause the fabric to melt onto the filter frame. Alternatively the edges of the filter sheet may be folded around the filter frame and then glued to an underneath surface of the filter frame, for example.
The filter frame may be made from any suitable material, such as a plastics material. In particular, the filter frame may be formed from polypropylene, fibreglass, carbon fibre, metal or wood, for example.
The filter frame may be formed from a single piece of material. Alternatively it may be formed from a plurality of frame sections each of which frame sections is engageable with one or more other frame sections to form the filter frame.
The filter is engageable with the die plate, such that when the filter is placed on the die plate, the filter and the carrier plate engage with one another to hold the filter in place on the carrier plate.
The die plate comprises a carrier engagement portion, and the filter comprises a corresponding filter engagement portion engageable with the carrier engagement portion. The die plate comprises a plurality of carrier engagement portions each comprising a protrusion, and the filter comprises a plurality of filter engagement portions each shaped to engage with a corresponding protrusion.
The carrier border comprises a plurality of raised corner portions, and the filter frame is shaped to fit within the raised corners of the carrier border.
The raised corner portions of the carrier border may be detachable in order that they may be replaced. This means that if the corner portions wear down they may be replaced by new corner portions without having to replace the carrier plate entirely. This can be advantageous, since the corners of the die plate tend to wear more quickly than the remainder of the die plate.
The carrier border may comprise a raised corner portion at each corner of the carrier border, although in some embodiments, there may be a raised corner portion at some, but not all corners of the carrier border.
In such embodiments, the corners of the filter frame that correspond to the raised corner portions of the carrier border are shaped to abut against the corresponding raised corner portion of the carrier border when the filter is positioned on the die plate.
In some embodiments the carrier border may be defined only by raised corner portions.
The filter frame may be formed from a single piece of material. Alternatively it may be formed from a plurality of frame sections each of which frame sections is engageable with one or more other frame sections to form the filter frame.
The filter is engageable with the die plate, such that when the filter is placed on the die plate, the filter and the carrier plate engage with one another to hold the filter in place on the carrier plate.
The carrier border comprises a plurality of raised corner portions, and the filter frame is shaped to fit within the raised corners of the carrier border.
The raised corner portions of the carrier border may be detachable in order that they may be replaced. This means that if the corner portions wear down they may be replaced by new corner portions without having to replace the carrier plate entirely. This can be advantageous, since the corners of the die plate tend to wear more quickly than the remainder of the die plate.
The carrier border may comprise a raised corner portion at each corner of the carrier border, although in some embodiments, there may be a raised corner portion at some, but not all corners of the carrier border.
In such embodiments, the corners of the filter frame that correspond to the raised corner portions of the carrier border are shaped to abut against the corresponding raised corner portion of the carrier border when the filter is positioned on the die plate.
In some embodiments the carrier border may be defined only by raised corner portions.
In use, the filter is positioned on the die plate such that the filter frame is located within the at least one channel.
In such embodiments of the invention, the carrier engagement portion comprises the raised first carrier portion or die insert, together with the one or more carrier engagement portions.
Other types of carrier protrusions are also possible, and so protrusions may be formed on the sides of the carrier border or die plate, for example. The filter will be correspondingly shaped so that the filter and the carrier engage with one another when the filter is placed on the carrier plate. The filter frame may, for example, comprise recesses formed on the frame to engage with protrusions on the carrier border.
In other embodiments, the carrier engagement portions may comprise recesses, and the corresponding filter engagement portions are shaped to engage with the recesses.
The die plate and filter may have any convenient shape, and may be, for example, substantially square or rectangular. Other shapes are also possible.
According to a second aspect of the invention there is provided a method for assembling a filter assembly, for a cementitious mould, with the features of claim 5.
The invention will now be further described by way of example only with reference to the accompanying drawings in which:

Figure 1 is a schematic representation of a press mould incorporating filter assemblies according to embodiments of the invention.
Figure 2 is an exploded perspective view of the press mould of Figure 1;
Figure 3 is an exploded schematic representation of part of a filter assembly according to an embodiment of the invention wherein the carrier plate is the head plate of the die head;
Figure 4 is a schematic representation of the underside of a filter according to an embodiment of the invention forming part of the filter assembly of Figure 3;
Figure 5 is a schematic representation of a filter frame not forming part of the invention and formed from a plurality of filter sections; and
Figure 6 is a partial schematic representation showing a joint between frame sections forming the filter frame of Figure 5.

Referring to Figures 1 and 2, a press mould 2 for making concrete slabs and incorporating filter assemblies in accordance with embodiments of the invention is shown. The mould 2 comprises a mould cavity having a bottom former 4 defining a closed base to the mould cavity, and a moveable press head 6. The press head 6 includes a die plate 8 having a die face. The press head 6 is connected to a ram (not shown) which enables the die face to be moveable toward the bottom former 4 for compressing cementitious material 12 therebetween for forming a concrete slab or kerb or other product.
A first filter 20 according to an embodiment of the invention is placed between the cementitious material 12 and the die plate 8. This first filter 20 is described in more detail below with reference to Figures 3 and 4.
In use, the first filter 20 overlays a surface of the die plate 8 in order to provide a release for removal of the moulded product from the mould and also to assist in preventing particulate material from exiting the mould via the die plate 8.
Turning now to Figures 3 and 4, the first filter 20 will be described in more detail.
The first filter 20 forms part of a filter assembly 22 which comprises a die plate 8, and first filter 20.
The die plate 8 comprises a first carrier portion 26 and a carrier border 28 surrounding the first carrier portion 26. The first carrier portion 26 is raised relative to the carrier border 28. The first carrier portion comprises a plurality of perforations 30 which allow liquid to pass through and out of the press mould. The border does not have any perforations, although in some embodiments it could.
The first filter 20 comprises a filter sheet 32 mounted on a filter frame 34. The filter sheet 32 may be formed from any suitable material such as a knitted or woven material that 25 allows liquid to pass through, but prevents passage of particulate material. The filter frame is made from any suitable material such as a plastics material.
The filter sheet 32 is attached to the filter frame 34 by any suitable means, and in this embodiment it is stitched to the frame 34, as shown in more detail in Figure 3.
The carrier border 28 comprises a plurality of carrier engagement portions each comprising a raised corner portion 36. The filter frame 34 comprises a plurality of corresponding engagement portions 38 (only three of which are shown) which each abut with a respective raised corner portion 36 when the filter is placed on the die plate 8.
The corresponding engagement portions (38) are in the form of shaped corner portions having an outer substantially flat surface 40 rather than an apex and an inner substantially flat surface 41. The surface 40 will abut with a corresponding corner portion 36.
Because the first carrier portion 26 is raised relative to the carrier border 28, a channel 37 is defined between each of the corner portions 36 and the first carrier portion 26. This means that when the filter 20 is in position, the filter frame fits between the raised corner portions 36 and the first carrier portion 26 within the channel 37 and hence is held in position.
In other words, the corner portions of the filter frame 34 defined by surfaces 40, 41 are located within the channels 37.
Although the filter frame shown in the embodiments illustrated in Figures 1 to 4 has been shown being formed from a single piece of material, it is also possible to form the filter frame from frame sections as shown in Figures 5 and 6.
A filter frame 88 not forming part of the invention comprises four frame sections 82 which connect together by any suitable means. In the embodiment shown in Figure 5, the frame 82 connect to one another by means of an engagement portion 84 formed at one end of a first frame section, which is engagable with a corresponding engagement recess 86 formed at one end of a second filter section.
Each frame section 82 comprises a first end at which is formed an engaging portion 84, and a second end at which is formed an engagement recess 86. Different arrangements may also be used.
The frame 88 could be formed from a different number of frame sections, and also the frame sections may be connected to one another by any convenient means.

Claims

A filter assembly (22) for a cementitious press mould the filter assembly comprising:
a die plate (8) comprising a first carrier portion (26) comprising a plurality of perforations (30), and a carrier border (28) surrounding the first carrier portion (26), the first carrier portion (26) being raised relative to the carrier border (28); and a filter (20) comprising a filter sheet (32) mounted on a filter frame (34),

characterised in that: the die plate (8) comprises a plurality of carrier engagement portions each comprising a raised corner portion (36) of the carrier border (28),

a channel (37) is defined between the first carrier portion (26) and each of the raised corner portions (36);

the filter frame (34) is shaped to fit between the raised corner portions (36) and the first carrier portion (26) within the channel (37);

the raised corner portions (36) are spaced apart from one another; and

the filter frame (34) comprises a plurality of corresponding engagement portions (38), each of which corresponding engagement portions is adapted to abut a respective raised corner portion (36) when the filter is placed on the die plate (8), wherein the corresponding engagement portions (38) are in the form of corner portions having an outer substantially flat surface (40) and an inner substantially flat surface (41).
A filter assembly (22) according to claim 1 wherein the filter sheet (32) is stitched to the filter frame (34).
A filter assembly (22) according to claim 1 or claim 2 wherein the filter sheet (32) is adhesively attached to the filter frame (34).
A filter assembly (22) according to claim 1 or claim 2 wherein the filter frame (34) is formed from a plastics material.
A method for assembling a filter assembly (22), for a cementitious mould, the filter assembly comprising:
a die plate (8) comprising a first carrier portion (26) comprising a plurality of perforations (30), and a carrier border (28) surrounding the first carrier portion (26); and

a filter (20) comprising a filter sheet (32) mounted on a filter frame (34),

the first carrier portion (26) being raised relative to the carrier border (28), characterized in that the filter frame (34) comprising a plurality of corresponding engagement portions (38),

the method comprising the steps of forming a plurality of carrier engagement portions on the die plate (8), each carrier engagement portion comprising a raised corner portion (36) of the carrier border, the raised corner portions being spaced apart from one another;

defining a channel (37) between the first carrier portion (26) and each of the raised corner portions (36); forming a filter frame (34) shaped to fit between the raised corner portions (36) and the first carrier portion (26) and within the channel (37); and

mounting the filter sheet (32) on the filter frame (34) such that each of the plurality of corresponding engagement portions (38) abuts with a respective raised corner portion (36) when the filter is placed on the die plate (8), wherein the corresponding engagement portions (38) are in the form of corner portions having an outer substantially flat surface (40) and an inner substantially flat surface (41).