WO2008071996A1

WO2008071996A1 - A filter assembly for use in a press mould

Info

Publication number: WO2008071996A1
Application number: PCT/GB2007/004825
Authority: WO
Inventors: Eric Cashmore; Kenneth Shepard
Original assignee: Eco Filters Ltd
Current assignee: Eco Filters Ltd
Priority date: 2006-12-15
Filing date: 2007-12-14
Publication date: 2008-06-19
Anticipated expiration: 2009-06-15
Also published as: GB2458843A; GB0625072D0; GB0912289D0

Abstract

A filter assembly (44) for a cementitkms press mould, the filter assembly (44) having a first face (45) intended to contact and apply compression to a mixture contained in a press mould, the filter assembly (44) including a carrier plate (48) which carries a wear component (50) and to which a filter sheet (52) is attached, the wear component (52) and the filter sheet collectively defining said first face (45), wherein the wear component (50) comprises a channel (78) adapted to receive the carrier plate therein, whereby a portion of the carrier plate (48) is partially enclosed in the channel (78).

Description

A FILTER ASSEMBLY FOR USE IN A PRESS MOULD

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 in particular to a filter assembly, for a movable press head of a press mould.

A known cementitious press mould comprises a mould cavity having closed lower 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 lower wall, to apply a high compressive pressure on to the cementitious mix.

The press head comprises a die head having a die head face that comes into contact with the mixture contained in the mould. The die head is of 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.

The corner edges of the moulded product are usually the most brittle section of the product, especially when the products comprise paving slabs. It is known therefore to build up the corners of the die head to form corresponding depressed corners in the moulded product. The corners of the stacked mould products consequently are less likely to come into contact with one another, and therefore less likely damage the comers of other moulded products, when the products are stacked.

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 lower surface 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.

These high pressure and frictional forces result in the corners of the die head wearing out at a faster rate than other parts of the die head. The effect of the wear of the corners is that the corresponding depressed corners in the moulded products become increasingly shallow, thus increasing the likelihood that the corners of the moulded products will be damaged through contact with the corners of other products when stacked.

In order to maintain a consistent standard of mould products, it is known to replace the die head once the wear of the built up corners has reached an unacceptable level. This is time consuming and expensive, as the press mould cannot be used while the die head is being replaced. In addition, the die head itself is expensive.

Replacement of the whole die head is also wasteful since most of the die head is still in a usable state.

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 lower wall, 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.

According to a first aspect of the present invention, there is provided a filter

^• assembly for a cementitious press mould, the filter assembly having a first face intended to contact and apply compression to a mixture contained in a press mould, the filter assembly including a carrier plate which carries a wear component and to which a filter sheet is attached, the wear component and the filter sheet collectively defining said first face, wherein the wear component comprises a channel adapted to receive the carrier plate therein, whereby a portion of the carrier plate is partially enclosed in the channel.

Advantageously, the carrier plate is either a head plate or a former plate of a press mould assembly.

In an embodiment of the invention where the carrier plate is a head plate, the first face of the filter assembly defines a contact face, which contact face is a die head face of the die head of the press mould, and the wear component is positioned where the high pressure and frictional forces acting on the die head face during the moulding process result in excessive wear of the die head and/or filter.

In an embodiment of the invention where the carrier plate is a former plate, the first face of the filter assembly defines a contact face, which contact face is a former plate face, and the wear component is positioned where the high pressure and frictional forces acting on the former plate face during the moulding process result in excessive wear of the former plate and/or filter. Preferably the wear component is detachably mounted on the carrier plate to enable removal and replacement of a worn wear component with the filter sheet remaining in situ. This means that a wear component can be replaced when worn obviating the need to replace the die head, former plate, and/or filter assembly.

Since the high pressure and frictional forces are likely to act at the corners of the contact face, the wear component is preferably positioned at, or close to a corner of the filter assembly.

The channel may be open or closed at one end.

The wear component preferably comprises a first section, a second section spaced apart from the first section, and a third section connecting the first section to the second section, the channel being formed between the first, second and third sections.

The wear component is shaped such that, in use, an inner surface of each of the first, second and third sections of the wear component engages with an outer surface of the carrier plate to ensure secure engagement of the wear component with the carrier plate.

Preferably the carrier plate comprises a recess adapted to receive the second section of the wear component. In use, the second section of the wear component is seated in the recess formed in the carrier plate. Thus in use lateral movement of the wear component relative to the carrier plate is restricted and detachment of the wear component from the filter assembly is prevented.

The second section of the wear component may comprise a fastener for further securing the wear component to the carrier plate. The fastener may be any suitable fastener, preferably a detent.

The carrier plate may comprise a socket adapted to receive the fastener therein, in order to prevent unintentional detachment of the wear component from the carrier plate when in use. The weax component is preferably resiliently deformable such that it is capable of being snap fitted onto the carrier plate in order to ensure secure engagement between the wear component and the carrier plate.

As a press head applies a pressing force against a cementitious mix within the press mould, a resultant force is applied against the carrier plate. Over time, this resultant force generally results in deformation of the carrier plate causing it to spread outwards, resulting in a reduction in the thickness of the carrier plate.

An added advantage of the resiliency of the wear component is that the wear component is able to accommodate a decrease in the thickness of the carrier plate, as a result, the wear component is less likely to become disengaged from the carrier plate if the thickness of the head plate decreases.

Preferably the wear component is formed of a non-compressible material. Conveniently the non-compressible material is a plastic polymer.

Preferably the wear component comprises a cover plate portion adapted to overlie a marginal edge of the filter sheet in order to prevent cementitious particles from settling between the filter sheet and the wear component.

The cover plate portion may form part of the first section or form part of a cover plate attached to the first section of the wear component.

Preferably the filter sheet is formed from a filter material. Advantageously the filter sheet material is a knitted or woven fabric, which fabric may be mounted on a plastics sheet.

Preferably the carrier plate carries a plurality of wear components and each wear component is positioned at a location where the high pressure and factional forces are likely to occur. According to a second aspect of the present invention there is provided a wear component for a filter assembly according to the first aspect of the invention.

According to a third aspect of the present invention there is provided a movable die head assembly for a cementitious press mould comprising a filter assembly according to the first aspect of the present invention.

The cementitious press mould may comprises one of: a wet concrete press mould; a hermetic press mould; or semi-dry mix press mould.

There now follows a description of a preferred embodiment of the present invention, by way of non-limiting example, with reference being made to the accompanying drawings, in which:

Figure 1 is a side view of a wet concrete press mould including a loosely retained filter assembly, according to the prior art;

Figure 2 is a cut-away view of a general arrangement of a known press assembly within a press mould;

Figure 3 is a side view of a wet concrete press mould including a filter assembly according to an embodiment of the invention fixed to a movable die head;

Figure 4 is a plan view of a contact face forming part of the filter assembly of Figure 3;

Figure 5 is an exploded schematic view of the die head of Figure 3;

Figure 6 is a schematic view of a carrier plate for the filter assembly shown in Figure 3;

Figure 7 is an enlarged view of a corner of the carrier plate shown in Figure 6; Figure 8 is a perspective view of the wear component forming part of the filter assembly of Figure 3;

Figure 9 is a side view of the wear component of Figure 8; and

Figure 10 is a schematic view of the wear component of Figure 8 secured to a carrier plate.

Referring initially to Figure 1, a sectional view of a known press mould 2 for making concrete slabs according to the art is shown. The mould 2 comprises a mould cavity having a former plate 8 on a closed lower wall, and sidewalls 10.

The mould 2 further comprises a movable press head 6. The press head 6 includes a die head 14 having a die head face 16. The press head 6 is connected to a ram

(not shown), which enables the die head face 16 to be movable towards the former plate 8 for compressing cementitious material 18 therebetween for forming a concrete slab or kerb or other product.

A first filter is placed between the cementitious material 18 and the former plate 8. A second filter is placed between the die head 14 and the cementitious material 18, said filter being loosely retained in the cavity.

In use, the first and second filters overlay a surface of the former plate 8 and the die head 14 respectively in order to provide a release for removal of the moulded product 4 from the mould and also to assist in preventing particulate material from exiting the mould via the former plate 8 or the die head 14.

The filter typically comprises a filter sheet 20 and a mounting plate 22, and is arranged such that a face of filter sheet is in contact with the cementitious material. The mounting plate 22 being in contact with a corresponding face of the lower wall 8 or die head 14.

Built up corners 24 are added to the die head so as to form corresponding depressed corners in the moulded product. The built up corners 24 are wedge shaped and have a height d, corresponding to the required depressed depth of the corners of moulded product.

Figure 2 shows a general arrangement of a press assembly within a mould. Corresponding reference numerals to those of Figure 1 are used to indicate corresponding features for clarity. A filter is fixed to a die head 14 of the press assembly rather than loosely retained in the cavity, as shown in Figure 1.

The die head 14 in this arrangement comprises a die block 28, a head plate 26 and means 30 for connecting the head plate to the die block to form the die head 14.

A contact face of the die head is defined by a surface of the filter overlying the die head, which comes into contact with the wet concrete mix.

In the conventional arrangements shown in Figures 1 and 2, the filter becomes worn at the locations where high pressure and frictional forces occur.

Referring to Figure 3, a filter assembly according to an embodiment of the invention forming part of a cementitious press mould 39 is designated generally by the reference numeral 44.

The filter assembly 44 forms part of a press head 40 comprising a die head 42 and a contact face 45 which comes into contact with a cementitious mixture 66 within a press mould.

The filter assembly 44 comprises a filter sheet 52, a plurality of wear components 50 and a carrier plate 43.

In this embodiment the carrier plate 43 comprises a head plate 48.

The wear components 50 and the filter sheet 52, collectively define a first face of the filter assembly 44 as shown in Figure 4, which first face corresponds to the respective contact face 45. The wear components 50 are positioned within the contact face 45 at locations where high pressure and frictional forces are likely to occur.

The wear components 50 thus enable the filter sheet 52 to be used many more times than was previously possible while maintaining an acceptable quality of moulded product.

An exploded view of the press head 40 is shown in Figure 5. The die head 42 comprises a front face 58 and an opposite face 60. The head plate 48 of the filter assembly 44 comprises a front face 62 and an opposite face 64. The die head 42 and the head plate 48 are connectable such that the front face 58 of the die head 42 and the opposite face 64 of the head plate 48 face one another.

In the embodiment shown, the die head 42 and the head plate 48 are connectable by means of a pair of elongate bars 46, preferably having a T-shaped profile, attached to the opposite surface 64 of the head plate 48. Each elongate bar 46 is received in a corresponding T-shaped slot 56 in the die head 42.

The filter sheet 52 is secured to the front face 62 of the head plate 48, preferably along its periphery only by means of an adhesive or by staples 54 as shown in Figure 5.

In an alternative embodiment, the filter sheet is mounted, preferably along its periphery, on a plastics sheet which is secured to the front face 62 of the head plate 48 by means of an adhesive.

The filter sheet 52 is preferably formed from a filter material. The filter material 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.

The filter sheet 52 is sized and shaped to overlay the exposed front face 62 of the head plate 48, such that a side surface of the wear components 50 abuts a corresponding side face of the filter sheet 52. In use, a front surface 76 of the wear components and a front surface of the filter sheet 52 define the contact face 45 which makes contact with the cementitious material 66 within the press mould.

Each area of the contact face defined by a wear component 50 may be any suitable geometric shape for example triangular, circular, diamond, rectangular etc. The wear components 50 are carried by the head plate 48 at positions corresponding to locations where high pressure and frictional forces are likely to occur. In the embodiment shown, the wear components 50 are located at the corners of the filter assembly 44 and each defines an area of the contact face 45 that is substantially triangular in shape as shown in Figure 4.

Referring to Figures 6 and 7, the head plate 48 may comprise a plurality of perforations or apertures 68 spaced across its surface which are preferably arranged in an array of columns 70 and rows 72. The perforations 68 act to provide a flow path for water which is extracted from the cementitious material 66 during the pressing operation of a wet concrete press mould.

The corners 74 of the head plate are chamfered at the locations where the wear components 50 are positioned in the filter assembly.

The wear components 50 are resiliently deformable such that they may be easily fitted to the head plate 48.

The wear components 50 may be formed of any suitably material which is sufficiently non-compressible during the moulding process, for example plastic polymer, aluminium, steel etc. Preferably the wear components 50 are formed from a non-compressible plastic polymer.

The wear components 50 are releasably secured to the head plate 48, and the filter sheet 52 and are arranged such that they can be replaced while leaving the filter sheet 52 in position.

This means that the whole head plate 48 does not need to be replaced when a wear component 50 becomes worn and needs to be replaced. Because the wear components 50 are resiliency deformable, a filter sheet 52 may be readily inserted into the wear components 50 during use of the head plate. This allows the filter sheet 52 is to be fitted to the die head after the wear components 50 are in place.

Referring to Figures 8 and 9 the wear component according to the invention will be described in more detail. Each wear component 50 comprises a channel 78 adapted to receive the head plate 48 therein, whereby a portion of the head plate 48 is partially enclosed in the channel 78.

Each wear component 50 comprises a first section 82, a second section 84 spaced apart from the first section, and a third section 80 connecting the first section 82 to the second section 84, the channel 78 being formed between the first, second and third sections.

The channel 78 is shaped such that when the wear component 50 is secured with the head plate 48, an inner surface of each of the first, second and third sections of the wear component 50 engages with an outer surface of the head plate 48.

hi the embodiment shown, the head plate 48 comprises a recess 86 on its opposite face 64 at each corner 74 for receiving the second section 84 of a corresponding wear component, in order to restrict sideways movement of the wear components 50 relative to the head plate 48.

The second section 84 of the wear components 50 may include a fastener 88 for releasably securing the wear component to the head plate 48.

The fastener 88 may be a detent and the head plate 48 may further comprise a socket 90 for receiving the detent 88 therein.

The wear components 50 may further comprise a cover plate portion 92 on the first section which, when the filter assembly 44 is assembled, overlays a marginal edge of the filter sheet 52 adjacent the side face of the filter sheet 52 as shown in Figure 10.

The cover plate portion 92 may be integrally formed with the first section 82 of the wear component 50. Alternatively a cover plate may be securely fixed onto the first section of the wear component 50 to form a cover plate portion 92.

The addition of the cover plate portion 92 helps prevent cementitious particles from settling between the side surface of the wear components 50 and the side face filter sheet 52.

The settling of cementitious particles between the wear components 50 and the filter sheet 52 accelerates the wear of the filter sheet 52 and also diminishes the quality of the moulded product.

The cover plate portion 92 also allows the filter assembly 44 to be assembled without gaps between the wear components 50 and the filter sheet 52 being exposed to the mix.

In order to secure the wear component 50 to the head plate 48, the wear component is first positioned at the corner 74 of the head plate 74. The second section 84 of the wear component is then aligned with the recess 86 of the head plate 48 and pushed towards the head plate 48 such that a portion of the head plate 48 is received within the channel 78. The wear component 50 snap fits onto the head plate 48 with the second section 84 of the wear component seated in the recess 86 and the detent 88 positioned in the socket 90.

In order to detach the wear component 50 from the head plate 48, a user uses a tool such as a screwdriver to lift the detent 88 out of the socket. The second section 84 of the wear component 50 is then able to be pulled out of the recess 86 and the wear component disengaged from the head plate.

The cementitious press mould 39 has been described hereinabove as having one filter assembly 44 in accordance with an embodiment of the invention. However, the cementitious mould may comprise a second filter assembly 47 on a closed lower wall 55 of the press mould 39 as shown in Figure 3. It is to be understood that this filter assembly may also comprise wear components in accordance with the invention.

Claims

1. A filter assembly for a cementitious press mould, the filter assembly having a first face intended to contact and apply compression to a mixture contained in a press mould, the filter assembly including a carrier plate which carries a wear component and to which a filter sheet is attached, the wear component and the filter sheet collectively defining said first face, wherein the wear component comprises a channel adapted to receive the carrier plate therein, whereby a portion of the carrier plate is partially enclosed in the channel.

2. A filter assembly according to Claim 1, wherein the wear component is detachably mounted on the carrier plate.

3. A filter assembly according to any one of the preceding claims wherein the wear component is positioned at, or close to a corner of the filter assembly.

4. A filter assembly according to any one of the preceding claims wherein the wear component comprises a first section, a second section spaced apart from the first section, and a third section connecting the first side to the second side, the channel being formed between the first, second and third sections.

5. A filter assembly according to Claim 4 wherein the carrier plate comprises a recess formed on an outer surface thereof adapted to receive the second section of the wear component.

6. A filter assembly according to Claim 4 or Claim 5 wherein the second section of the wear component comprises a fastener.

7. A filter assembly according to Claim 6 wherein the fastener is a detent.

8. A filter assembly according to Claim 6 or 7 wherein the carrier plate comprises a socket adapted to receive the fastener of the wear component.

9. A filter assembly according to any one of the preceding claims wherein the wear component is resiliently deformable.

10. A filter assembly according to any one of the preceding claims wherein the wear component is formed of a non-compressible material.

11. A filter assembly according to Claim 10 wherein the non-compressible material is a plastic polymer.

12. A filter assembly according to any one of the preceding claims wherein the wear component comprises a cover plate portion adapted to overlie a marginal edge of the filter sheet.

13. A filter assembly according to any one of the preceding claims wherein the filter sheet is formed from a filter material.

14. A filter assembly according to Claim 13, wherein the filter sheet material is a knitted or woven fabric.

15. A filter assembly according to any one of the preceding claims wherein the carrier plate carries a plurality of wear components.

16. A filter assembly according to any one of the preceding claims wherein the carrier plate is a head plate.

17. A filter assembly according to any one of the preceding claims wherein the carrier plate is a former plate.

18. A wear component for a filter assembly as claimed in any one of Claims 1 to 17.

19. A movable die head assembly for a cementitious press mould comprising a filter assembly as claimed in any one of Claims 1 to 16.

20. A moveable die head according to Claim 17 wherein the cementitious press mould comprises one of: a wet concrete press mould; a hermetic press mould; or semi-dry mix press mould.

21. A filter assembly for a die head for a cementitious press mould as generally hereinbefore described with reference to and/or illustrated in Figures 3 to 10 of the accompanying drawings.

22. A wear component for a filter assembly as generally hereinbefore described with reference to and/or illustrated in Figures 3 to 10 of the accompanying drawings.