GB1575000A

GB1575000A - Method and apparatus for pressing concrete bodies

Info

Publication number: GB1575000A
Application number: GB3072576A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1977-02-07
Filing date: 1977-02-07
Publication date: 1980-09-17

Description

(54) AN IMPROVED METHOD AND APPARATUS FOR PRESSING CONCRETE BODIES (71)1 I, PEThR GEOFFREY LAWTON of West Hadlow, Albert Promenade, Halifax in the County of York, a British subject, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to apparatus for pressing concrete bodies and more particularly, but not exclusively, to apparatus for pressing concrete paving stones.

It is usual to produce concrete paving stones by inserting a wet concrete mix into a mould and compressing the concrete mix in the mould to compact the mix. The concrete mix in the mould is normally compressed by the introduction of a ram member into the upper portion of the mould and the concrete mix is compressed between the internal surfaces of the mould and the ram member. During this compression, the concrete mix is compacted and formed into a paving stone whose shape corresponds . to the shape of the mould and in addition at least part of the water content of the wet concrete mix in extracted therefrom.

In order to assist the release of the water content from the concrete mix during compression, it is usual to place a sheet of filter material between the base of the mould and the concrete mix and between the ram member and the concrete mix. When the concrete mix has been compressed and the paving stone is removed from the mould, the sheet of filter material is peeled from the paving stone. It is. usual for the filter material to consist of a paper sheet and it has been found that the sheets of paper have to be discarded after they have been used to produce one paving stone.

The object of this invention is to provide an apparatus for pressing concrete bodies having an improved filter material.

According to this invention, apparatus for pressing concrete bodies comprises a ram member and a mould into which the ram member is insertable to compress a wet concrete mix inserted in the mould to form the concrete body, and a layer of filter material disposed so that it is between the wet concrete mix, when the mix is in the mould, and the ram member and secured to the ram member, and/or disposed so that it is between the wet concrete mix when the mix is in the mould, and secured to the mould; wherein the filter material has been subjected to a process to produce a smooth non-fibrous but porous surface on the layer of filter material.

In the preferred form, the porous surface produced on the filter material has a porosity such that it permits the passage of water therethrough, whilst retaining the cement content of the mix on the surface, so that the filter material does not become blinded, and hence can be used repeatedly.

Preferably, the or each layer of filter material is formed of thermo-plastic fibres, and the fibres may be formed of polypropylene.

The surface of the or each layer of the filter material which is arranged to contact the wet concrete mix has been preferably, subjected to a hot calendering process to produce the smooth non-fibrous but porous surface on the layer of filter material. Preferably, the hot calendering process comprised passing the layer of filter material over a heated roller. Preferably, also, the filter material after calendering was subjected to a process to burst the material after calendering, thereby releasing any fibres in the core of the material which had adhered together as a result of the calendering process, and the process, preferably, consisted of a water proofing and heating process. The side edges of the or each layer of filter material have been, preferably, heat sealed to reduce the fibrous nature thereof.

Preferably, the filter material is secured to the ram member and/or to the mould by one or more screw-threaded members extending therethrough which members are screwed into screw-threaded bores formed in the ram member and! or in the mould.

Alternatively, the filter material may be secured to the ram member and/or to the mould by adhesive. The adhesive may be applied in the form of a self-sustaining web and in a manner which ensures that substantially all the perforations in the ram member and/or the mould are unobscured by the adhesive. Ih one way of doing this, a polyamide web of material is disposed between the ram and! our the mould and the filter material to form the adhesive.

Preferably, the filter material is secured to a perforated metal plate which is mounted on the mould or on the ram member. Preferably, also, the filter material is secured to the metal plate by one or more screw-threaded members extending therethrough and engaging in the metal plate.

Alternatively, the filter material may be secured to the metal plate by adhesive such adhesive may be applied in the form of a self-sustaining web and in a manner which ensures that substantially all the perforations in the metal plate are unobscured by the adhesive. Preferably, a polyamide web of material is disposed between the metal plate and the filter material to form the adhesive.

Alternatively, the layer of filter material may be secured to a layer of porous metal foam which is mounted on the mould or on the ram member.

A preferred embodiment of this invention will now be described, by way of example only, with reference to the accompanying drawing which is a diagrammatic sectional side elevation of an apparatus for forming concrete bodies.

Referring now to the drawings, an apparatus for forming a concrete body such as, for example, a concrete paving stone comprises a mould indicated generally at 10 having side walls 12 which define a substantially rectangular cavity having an open top surface and an open bottom surface.

The bottom surface of the mould 10 is closed by a lower press plate 14 which is adapted to be moved upwardly through the mould cavity by an injection mechanism (not shown). The lower press plate 14 is also provided with a series of drain holes and connecting channels 16 to allow liquid to drain therethrough from the mould cavity.

A ram mechanism indicated generally at 18 which includes a diehead is mounted above the mould 10 and is adapted to be moved downwardly towards the mould 10, and a compression plate 20 is mounted on the diehead of the ram mechanism 18. The compression plate 20 is arranged to be a close fit in the mould cavity and when the ram mechanism 18 moves downwardly towards the mould 10, the plate 20 slides into the open top of the mould cavity. The compression plate 20 is provided with a series of drain holes and connecting channels 21 through which liquid can be drawn from the mould cavity.

A perforated metal plate 22 is mounted on the lower surface of the compression plate 20 and is connected thereto by countersunk setscrews 24. The perforated metal plate 22 is arranged to conform closely in shape to the shape of the mould cavity and the edges thereof are ground to give a sharp edge to the concerte body.

A similar perforated metal plate 26 is mounted on the upper surface of the lower press plate 14 and is connected thereto by countersunk setscrews 28. Two layers of filter material 30 and 32 are provided which both closely conform to the shape of the mould cavity and each layer of filter material 30, 32 is formed of thermo-plastic fibres such as polypropylene fibres.

The upper and lower surfaces of the layers of filter material 30 and 32 are subjected to a hot calendering process to produce a surface of a smooth non-fibrous nature which is porous to water. The hot calendering process consists of, for example, passing the layer of filter material over a heated roller (not shown). The layers of filter material are then cut to size by means of a hot knife (not shown) and during this cutting operation the side edges of each layer of filter material 30 and 32 are heat sealed to reduce the fibrous nature thereof and assist in producing a sharp edge on the concrete body.

Each layer of filter material 30 and 32 is then subjected to a waterproofing and heating process. The waterproofing process increases the surface tension on the fibres and reduces any tendency for particles to adhere to the fibres in the core of the material. The heating process, which is carried out after calendering, bursts the material thereby releasing any fibres in the core - of the filter material which have adhered together as a result of the calendering process. This bursting of the filter material reduces the tendency of the material to become prematurely clogged or blinded during the production of the concrete bodies, thereby extending the useful life of the filter material.

The layers of filter material 30 and 32 are secured to the associated metal plates 22 and 26 by means of screws (not shown) which extend therethrough and are screwed into the associated plates 22 and 26. Alter naively; the layers of filter material 30 and 32 can be secured to the associated metal plates 22 and 26 by bonding them thereto with an adhesive.

One particularly effective way of bonding each layer of filter material to its associated plate is to heat the plate to a temperature of approximately 250 Fahrenheit to 400" Fahrenheit and then apply the layer of filter material with a polyamide spun web interposed therebetween. The polyamide spun web melts when it is brought into contact with the hot plate, and when the plate cools, the molten web material sets and bonds the layer of filter material to the plate. The use of an open polyamide spun web as a bonding material avoid the blockage of the holes in the perforated metal plates, as any portion of the web which extends across one of the holes in the plate is attracted, as the web melts, to the hot metal surrounding the boles, leaving the holes in the plate substantially unobstructed.

When this method of securing the layers of filter material to the associated metal plates is used, it is advantageous to trim the edges of the filter material to the exact size of the plate with an electrically heated hot knife, thereby leaving a hard plastics film around the edges of the filter material to seal the edges thereof so that a sharp edge is produced on the concrete block.

In operation, the lower press plate is disposed at the bottom of the mould cavity, as shown in the drawing, with the layer of filter material 32 and the perforated metal plate 26 secured thereto. A quantity of wet concrete mix 34 is placed into the mould 10 to fill the mould cavity to the required depth, which depth is dependent upon the desired thickness of the paving stone which is to be produced.

The layer of filter material 30 and the perforated metal plate 22 associated therewith are secured to the lower surface of the compression plate 20 and the ram mechanism 18 is then operated to move the plate 20 downwardly towards the mould 10 to the position shown in the drawing. The concrete mix 34 and the layers of filter material 30 and 32 are compressed between the plates 14 and 20 and the compaction of the concrete mix 34 causes at least part of the water content therein to be expelled therefrom. The water passes through the porous surfaces of the layers of filter material 30 and 32 which allow the passage of water but retain the cement content in the concrete mix 34.The water then flows through the perforations in the metal plates 22 and 26 and thence out of the mould cavity vim the series of holes and channels 16 and 21 formed respectively in the lower press plate 14 and the compression plate 20. The concrete mix 34 takes up the shape of the concrete paving stone defined by the mould cavity and the heat sealing of the side edges of the layers of filter material 30 and 32 assist in producing a paving stone having sharply defined edges.

After compression of the concrete mix 34, the compression plate 20 is withdrawn from the mould 10 by actuation of the ram mechanism 18 and the concrete paving stone is ejected from the mould cavity by actuating the ejection mechanism (not shown) which moves the lower press plate 14 upwardly through the mould 10.

The concrete paving stone thus formed is removed from the layer of filter material 32, which is attached to the lower press plate 14, and the paving stone is then allowed to cure. The layers of filter material 30 and 32 are retained on the compression plate 20 and the lower press plate 14 respectively and the apparatus can then be used to repeat the above operation and produce further concrete paving stones.

The release of the paving stone from the layers of filter material 30 and 32 can be assisted by the impregnation thereof with a release agent such as, for example, silicone.

The production of the layers of filter material from thermo-plastics fibres such as polypropylene fibres allows the filter material to be re-used to produce a number of paving stones without the necessity of changing the filter material for each paving stone produced and this facilitates the rapid production of paving stones by this process, particularly where the above operations are carried out automatically.

In a modification, the perforated metal plates 22 and 26 are replaced by respective layers of porous metal foam, such as a metal foam formed of nickel and chromium.

In another modification, each layer of filter material 30 and 32 tqgether with the associated perforated metal plates 22 and 26 are each replaced with a filter comprising an open porous layer of metal foam having a high porosity, which provides a reservoir for the water passing thereto from the wet concrete mix. This reservoir allows time for the water to drain from the mould cavity through the compression plate 20 and/or the lower press plate 14, which both have a limited porosity. The filter also includes a further layer of metal foam which although it is also porous, it has a porosity which is less than the porosity of the open porous layer of metal foam, and an additional layer of filter material such as the material formed of thermo-plastic fibres is disposed thereon to complete the filter.The layers of the filter are con nected together and the filter itself is secured to the compression plate 20 or the lower press plate 14 so as to be retained thereon. The depth of the layer of the open porous metal foam, and thus the volume of the reservoir formed thereby, is selected according to the water content of the wet concrete mix which is being used in the formation of the concrete body.

WHAT I CLAIM IS:- 1 Apparatus for pressing concrete bodies comprising a ram member and a mould into which the ram member is insertable to compress a wet concrete mix inserted in the mould and form the concrete body, and a layer of filter material disposed so that it is between the wet concrete mix, when the mix is in the mould, and the ram member and secured to the ram member, and/or disposed so that it is between the wet concrete mix, when the mix is in the mould, and secured to the mould; wherein the filter material has been subjected to a process to produce a smooth non-fibrous but porous surface on the layer of filter material.

2. Apparatus according to Claim 1, wherein the porous surface produced on the filter material has a porosity such that it permits the passage of water therethrough whilst retaining the cement content of the mix on the surface, so that the filter material does not become blinded, and hence can be used repeatedly.

3. Apparatus according to Claim 1 or Claim 2, wherein the surface of the filter material is calendered and glazed.

4. Apparatus according to any one of Claims 1 to 3, wherein the or each layer of filter material is formed of thermo-plastic fibres.

5. Apparatus according to Claim 4, wherein the thermo-plastic fibres are formed of polypropylene.

6. Apparatus according to any one of the preceding claims, wherein the surface of the or each layer of the filter material which is arranged to contact the wet concrete mix has been subjected to a hot calendering process to produce the smooth non-fibrous but porous surface on the layer of filter material.

7. Apparatus according to Claim 6, wherein the hot calendering process comprised passing the layer of filter material over a heated roller.

8. Apparatus according to any one of the preceding claims, wherein the filter material after calendering was subjected to a process to burst the material thereby releasing any fibres in the core of the material which had adhered together as a result of the calendering process.

9. Apparatus according to Claim 8, wherein the process consisted of a water proofing and heating process.

10. Apparatus according to any one of the preceding claims, wherein the side edges of the or each layer of filter material have been heat sealed to reduce the fibrous nature thereof.

11. Apparatus according to any one of the preceding claims, wherein the filter material is secured to the ram member and/or to the mould by one or more screwthreaded members extending therethrough which members are screwed into screwthreaded bores formed in the ram member and/or in the mould.

12. Apparatus according to any one of Claims 1 to 10, wherein the filter material is secured to the ram member and/or to the mould by adhesive.

13. Apparatus according to Claim 12, wherein the adhesive is applied in the form of a self-sustaining web and in a manner which ensures that substantially all the perforations in the ram member and/or the mould are unobscured by the adhesive.

14. Apparatus according to Claim 13, wherein a polyamide web of material is disposed between the ram and/or the mould and the filter material to form the adhesive.

15. Apparatus according to any one of the preceding claims, wherein the filter material is secured to a perforated metal plate which is mounted on the mould or on the ram member.

16. Apparatus according to Claim 15, wherein the filter material is secured to the metal plate by one or more screw-threaded members extending therethrough and engaging in the metal plate.

17. Apparatus according to Claim 15, wherein the filter material is secured to the metal plate by adhesive.

18. Apparatus according to Claim 17, wherein the adhesive is applied in the form of a self-sustaining web and in a manner which ensures that substantially all the perforations in the metal plate are unobscured by the adhesive.

19. Apparatus according to Claim 18, wherein a polyamide web of material is disposed between the metal plate and the filter material to form the adhesive.

20. Apparatus according to any one of Claims 1 to 19, wherein the layer of filter material is secured to a layer of porous metal foam which is mounted on the mould or on the ram member.

21. Apparatus for producing concrete bodies constructed, arranged and adapted to operate substantially as hereinbefore described with reference to the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. nected together and the filter itself is secured to the compression plate 20 or the lower press plate 14 so as to be retained thereon. The depth of the layer of the open porous metal foam, and thus the volume of the reservoir formed thereby, is selected according to the water content of the wet concrete mix which is being used in the formation of the concrete body. WHAT I CLAIM IS:-

1 Apparatus for pressing concrete bodies comprising a ram member and a mould into which the ram member is insertable to compress a wet concrete mix inserted in the mould and form the concrete body, and a layer of filter material disposed so that it is between the wet concrete mix, when the mix is in the mould, and the ram member and secured to the ram member, and/or disposed so that it is between the wet concrete mix, when the mix is in the mould, and secured to the mould; wherein the filter material has been subjected to a process to produce a smooth non-fibrous but porous surface on the layer of filter material.