AU657599B2 - Production of moulded building products - Google Patents

Description

P/00/011 Regulation 3.2 657599

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT 9* Name of Applicant: Actual Inventor: Address for Service: Sr* ANTHONY LEON STEPHENS Anthony Leon Stephens TREVOR DREDGE ASSOCIATES Patent Trade Mark Attorneys 13th Floor, 379 Queen Street BRISBANE, QLD, 4000 (GPO Box 1339, BRISBANE, 4001) "Production of Moulded Building Products" Australian Patent Application No.

PL0698 filed 4 February, 1992 Invention Title: Details of Associated Provisional Application No: The following statement is a full description of this invention, including the best method of performing it known to me: I 2 THIS INVENTION relates to the production of moulded building products and in particular but not limited to moulded sandstone building products.

Conventional masonry building blocks are made from, amongst other ingredients, ash and cement powder and have a grey appearance. The blocks can be moulded with cavities to provide service ducts in completed walls. On the other hand, natural stone blocks have to be hewn or sawn from naturally occurring deposits and as a consequence, are much more expensive than their moulded counterparts. It has been proposed to colour masonry blocks, and to this end, coloured masonry blocks have been produced in an effort to imitate or provide a "natural look" but the blocks produced to date lack the detail and fidelity of the natural product. In addition, natural blocks are usually sawn or split or chipped giving traditional surface effects including "rock face" and "pick" and these cannot be achieved using conventional moulding techniques.

0.0 It would be desirable to provide a moulded block which provides a nearer approximation to the actual rock than can be provided using current techniques. Furthermore, it would be desirable to provide a method and apparatus for producing moulded blocks having the "traditional" look.

In one aspect therefore, the present invention resides in a selection of stone for grinding or milling and subsequent moulding, the selected stone having a high percentage of naturally occurring cementitious material so that when milled and moulded to form a block, a minimal amount of cementitious additive is required so as to minimise discolouration from the original stone colour.

For example, in the case of sandstone, heavily weathered sandstone or sandstone which has formed by compaction alone having low proportions of naturally occurring cementitious material would need large amounts of cement powder for effective moulding otherwise the block would not cure and be unsuitable for building.

Unfortunately, the addition of large amounts of cement powder brings about discolouration of the moulded product and therefore, the natural look is lost.

On the other hand, the applicant has found that sandstone having a high felspathic cement content is *o particularly suitable for processing using the teachings of the present invention. The naturally occurring stone can be milled and moulded with relatively minute additions of S cement powder so that discolouration is minimised, this results in a more natural look than was otherwise possible.

In another aspect, the invention resides in a method for producing a moulded building product from finely divided particulate material including the steps of:selecting stone material having a colouration and texture desirable in the finished product, the stone material having a high content of naturally occurring cementitious material; milling or grinding the stone into a finely divided form suitable for moulding; forming a Moist mixture of the finely divided material and supplementing, where necessary, the naturally occurring cementitious material with a small quantity of cement powder or its functional equivalent; and moulding the product from the mixture while wet and allowing the product to cure.

The selected stone is typically processed using a block mould for moulding blocks having a raised or projecting internal mould surface providing a raised surface in a completed block, the mould surface comprising retractable raised surface defining walls so that the walls .o t can be retracted in order to release a moulded block from *5*o the mould.

The mould is preferably arranged to produce a plurality of blocks with back-to-back raised surface defining walls being employed. Typically, the mould is arranged so that four blocks are produced at one time. The raised surface defining walls can be horizontal or vertical 5 walls but are typically vertical or are retractable side walls of the mould. Extension and retraction of the side walls is preferably accomplished using a timed hydraulic drive assembly operation of which is timed in relation to other operations in a moulding sequence.

The mould preferably includes vibration means enabling vibration of material in the mould adjacent the raised surface defining walls. The raised surface defining walls or portions thereof are typically moveable or can be subjected to vibration to assist compaction adjacent the raised surface defining walls of the mould.

In order that the present invention can be more readily understood and be put into practical effect, reference will now be made to the accompanying drawings and wherein:- Figure 1 is a schematic view illustrating a preferred mould according to the present invention and shown prior to the commencement of a moulding sequence; Figure 2 is a view similar to that of Figure 1 showing mould material in the mould; Figure 3 is a pictorial view illustrating a traditional rock face type block made using the mould of Figures 1 and 2; and Figure 4 is a pictorial view illustrating a typical t raised surface defining wall suitable for a mould of the type illustrated in Figures 1 and 2.

Referring to the drawings and initially to Figures 1 and 2, the Figures illustrate a mould 10 for producing blocks having a raised or projecting surface (see Figure *t the mould includes in this case four retractable raised surface defining walls 11 which are shown retracted to a ***release position in Figure 1 and extended to a moulding portion in Figure 2. The walls 11 are moved between their extended and retracted positions using hydraulic cylinder assemblies 12 and 13 and accompanying linkages 14 and respectively. Each wall 11 has a recessed mould surface 16 (Shown in phantom in Figures 1 and 2) but shown in cut-away in Figure 2 at 16 and as will be appreciated on retraction of the walls 11 using the rams 12 and 13, the moulded blocks 17 can be pushed from the mould without interference. The mould 10 includes four block mould sections 18, each of which includes cavity defining columns 19 so that cavities are formed in the completed blocks.

Columns 19 protrude into the cavities and co-act in adjacency with a suitable tramping or compacting means which assists in downward or vertical compaction of the material in the mould. In order to improve compaction of material entering the recess 16, each wall 11 is equipped with a vibrator 20 and to this end, the surfaces 16 are typically of metal diaphragm type or otherwise moveable so that small vibrations can be used to assist in providing i fairly compacted surface effect in the final block.

f Referring to Figure 3, a typical block 21 is illustrated and in this case, the block has been moulded 9from milled helidon sandstone from quarries at Helidon in Queensland where sandstone composed of quartz grain material, with a high felspathic cement content can be s 9o 000 .obtained in solid rock form. The sandstone is milled to a finely divided form, water and 2% cement powder by weight was added to form a mixture for moulding. The sandstone was compacted into the mould using the process illustrated in Figures 1 and 2 and a cavity block having a framed rock face appearance on one side thereof, as depicted in Figure 3, resulted from this process.

Figure 4 illustrates a wall 11 viewed from the rear showing in more detail vibrator 20 and the relatively thin diaphragm type metal wall 15. In the illustrated embodiment, the vibrator is electrically driven but other forms of vibrators can be used, it will be appreciated that although one form of vibration has been illustrated, many other techniques can be employed to bring about improved compaction of the material forming the raised surface of the block illustrated in Figure 3, and to this end, this can also be achieved empirically by trial and error adjustment of the water content of the mould material prior to moulding.

It will be appreciated from the foregoing that the teachings of the present invention can be applied to any rock material which satisfies the criteria of having sufficient naturally occurring cementitious material so that moulding can take place to form a suitable building product without the addition of additives that would bring .about other than commercially acceptable discolouration of the final product. Likewise, the mould illustrated is only exemplary from and many other moulding techniques can be employed, indeed straight faced blocks can be formed using conventional moulding techniques. Blocks formed according 0 to the present invention need not have the traditional raised surface effect. It will therefore be appreciated that although the above has been given by way of the illustrative example of the present invention, many variations and modifications thereto will be apparent to those skilled in the art without departing from the broad ambit and scope of the invention as set forth in the appended claims.

Claims (8)

1. A selection of stone for grinding or milling and subsequent moulding, the selected stone having a high percentage of naturally occurring cementitious material so that when milled and moulded to form a block, a minimal amount of cementitious additive is required so as to minimise discolouration from the original stone colour.

2. A selection of stone according to claim 1 wherein the stone is sandstone having a high felspathic cement content.

3. A selection according to claim 2 wherein the sandstone is of the helidon sandstone type obtainable from quarries at Helidon in Queensland and is generally composed of quartz grain material, with a high felspathic cement Scontent.

4. A method for producing a moulded building product from finely divided particulate material including the steps o 9* of:- selecting stone material having a colouration and texture desirable in the finished product, the stone material having a high content of naturally occurring cementitious material; milling or grinding the stone into a finely divided form suitable for moulding; forming a moist mixture of the finely divided material and supplementing, where necessary, the naturally occurring cementitious material with a small quantity of cement powder or its functional equivalent; and moulding the product from the mixture while wet and allowing the product to cure.

The method of claim 4 wherein the product is moulded in a block mould having a raised or projecting internal mould surface providing a raised surface in a completed block, the mould surface comprising retractable raised surface defining walls so that the walls can be retracted in order to release a moulded block from the mould.

6. The method according to claim 5 wherein the walls are side walls of the mould and extension and retraction of the side walls is accomplished using a timed hydraulic drive assembly operation of which is timed in relation to S" operations in a moulding sequence.

7. The method according to any one of the preceding 9 0: method claims wherein the stone is sandstone and the sandstone is milled to a finely divided form, water and about 2% cement powder by weight is added to form the mixture for moulding.

8. The method according to any one of the preceding claims wherein the stone is sandstone of the helidon type obtainable from quarries in Queensland. A method for producing a moulded building product substantially as described herein. A block produced using the method according to any one of claims 5 to 9 using st•ne material selected according to any one of claims 1 to 4. DATED this fourth day of February, 1993. ANTHONY LEON STEPHENS By his Patent Attorneys T' s TREVOR DREDGE ASSOCIATES ABSTRACT A selection of stone for grinding or milling and subsequent moulding, the selected stone having a high percentage of naturally occurring cementitious material so that when milled and moulded to form a block, a minimal amount of cementitious additive is required so as to minimise discolouration from the original stone colour. *.1 o 9I9 99 o9 9 9 9