AU653887B2

AU653887B2 - Split pavers

Info

Publication number: AU653887B2
Application number: AU32925/93A
Authority: AU
Inventors: John Charles Kitchener Peile
Original assignee: CLAYPAVE Pty Ltd
Current assignee: CLAYPAVE PTY Ltd
Priority date: 1992-03-05
Filing date: 1993-02-10
Publication date: 1994-10-13
Anticipated expiration: 2013-02-10
Also published as: AU3292593A

Description

653887

AUSTRALIA

Patents Act 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT o o r Name of Applicant(s): Actual Inventor(s): Address for Service: Invention Title: CLAYPAVE PTY. LTD.

JOHN CHARLES KITCHENER PEILE CULLEN CO., Patent Trade Mark Attorneys, 240 Queen Street, Brisbane, Qld. 4000, Australia.

SPLIT PAVERS Details of Associated Provisional Applications: No. PL 1200 5.3.92 The following statement is a full description of this invention, including the best method of performing it known to us: 2 THIS INVENTION relates to clay pavers for landscaping and flooring surfaces, and is particularly concerned with split paving tiles.

Split paving tiles, commonly referred to as split pavers, are a relatively new innovation which are produced with the same length and breadth dimensions as conventional pavers but which are approximately one half the thickness of conventional pavers. They are formed and sold in joined pairs which are separated from one another immediately before laying by cleaving them apart with a bolster or like implement.

.i S Their advantages over conventional pavers is that they are less expensive, lighter, cheaper to lay, and easier to cut.

However, professional tilers prefer to lay them in an adhesive bed atop a concrete base rather than lay them directly into a mortar bed, as is usual with high quality paving work. This means a considerable added expense since the back of the split paver has deep corrugations which require a large amount of adhesive, and adhesive is relatively expensive. Another disadvantage of split pavers, as also with conventional pavers, is the tendency for uneven rates of extrusion from the sides of the pavers to the middle thereof during their manufacture, with the result that a slight concavity or convexity of the side walls occurs during the subsequent burning process. This means that a perfect butt joint during laying, cannot be achieved.

It is therefore an object of the present invention to provide a split paving tile which has all the advantages of conventional split paving tiles hut which does not have either of the aforementioned disadvantages.

3 According to one aspect of the present invention, there is provided a process for the production of paving units which are separable along a horizontal mid-sectional plane into two paving tiles, which process comprises the steps of:preparing a clay tile paving mix; (ii) extruding the mix through a die having a rectangular opening and an associated insert which bisects the extrudate thickness into two substantially equal portions and forms a series of longitudinally extending pockets at the 1i:" interface between each portion; (iii) cutting the bisected extrudate into individual paving units; (iv) compressing the individual paving units; and firing the paving units in a kiln.

*The paving tiles which are cleaved from these paving units have true straight edges which make them particularly suitable for butt joining. Furthermore, the tiles can be easily separated from one another notwithstanding the compression step which would generally be considered to close up the region between the tiles to such an extent as to mitigate against separation. This factor is, indeed, quite unexpected but can be accounted for by the fact that clay has a memory and the original bisection formed during extrusion must therefore remain in place.

The third important characteristic of the paving tiles thus produced is that the corrugations formed on the reverse side thereof, are very shallow due to the compression step and the tiles can therefore be laid with a minimum amount of adhesive. The maximum depth of the corrugations is 4 generally in the order of about 2 millimetres with an average depth of approximately 1 millimetre.

The split paving tiles produced by the process of the invention thus overcomes all the disadvantages of conventional split paving tiles referred to above and provide the public with a product which is highly desirable yet no more costly.

Another aspect of the invention resides in the split paving tiles themselves. That is, according to this aspect, the invention provides a split paving tile whenever produced by the novel process defined above.

a. a According to a yet further aspect of the present invention, there is provided a paving unit comprising two paving tiles joined back-to-back by a common web, said paving unit being characterized in that when it is separated to form two paving tiles, each tile presents a corrugated back surface in which the corrugations are no more than about 2 millimetres in depth.

By the term "corrugation" as used here and throughout the specification, it is intended to mean a groove and ridge-type formation which is not necessarily regular in width or depth, or uniform in length.

The step (iv) of compressing in the process of the invention also provides the unique advantage of permitting embossed patterns to be set in the surface of the split pavers by the simple expedient of incorporating a patterned die in the press plates.

The die through which the clay tile paving mix is extruded can be a conventional paver die with the addition of a winged steel plate located within the die adjacent the entry thereof and arranged in an essentially flat horizontal disposition. The wing shaped steel plate will suitably incorporate a number of ridge sections for the purpose of forming the corrugations in the paver. Such ridge sections will extend transversely of the winged steel plate and each preferably incorporates a tapered rod extending outwardly therefrom in the direction of extrusion. There are most suitably two to four, preferably three ridge sections. To i enable smooth flow of the clay paver mix over the winged steel plate, the leading edge of the plate will preferably be tapered and the ridge sections will be rounded.

C

S" The bisected extrudate is preferably cut in two stages. In the first stage, it is cut into a longitudinal i1 billet by a vertically reciprocating cutter blade. In the second stage, the longitudinal billet is cut transversely by pushing the billet through a plurality of vertically arranged g. and tensioned wires. This second stage could also be effected by one or more vertically extending cutter blades.

The step of compressing the pliable extruded paving unit is just sufficient to almost close up the gaps formed in the paver during extrusion, while simultaneously producing true straight edges and flat, optionally embossed, surfaces.

To this end, a suitable press is one operating at tons/paver.

The steps of preparing the clay powder mix and firing in a kiln, may be carried out in a known conventional manner and will not therefore be described in detail here.

Suffice is to say, however, that a conventional clay mix is one comprising one or more clays in admixture with c shale and water. Such a mix is screened with a mesh having openings measuring 13 mm x 1.2 mm prior to use in the process.

The split pavers can be produced in a range of tile sizes and shapes with a total thickness varying between about and 55 mm. The preferred thickness is 40 mm such that each tile has a nominal thickness of only 20 mm. The most common size is 230 x 115 x 40 mm.

Preferred embodiments of the invention will now be described with reference to the accompanying drawings, in which:so 9 Figure 1 is a flow chart of the process according to S" the present invention; Figure 2 is an isometric view of an extrusion die used in the process of the present invention; 9 Figure 3 is an isometric view of a split paver according to the present invention; and Figure 4 is an isometric view of a tile formed from the split paver depicted in Figure 3.

Referring to Figure 1, a moist mix comprising 15% by weight Rochedale clay, 35% by weight Dinmore Terra Brown clay and 50% by weight Dinmore blue shale, are sieved through a screen having mesh openings of 13 mm x 1.2 mm, and loaded as a continual input into hopper 10. The mix is passed through a horizontal screw-mixer 11 in which water is blended into the mix to provide the correct consistency for subsequent processing. The blended mass is then passed through extruder 12 onto conveyor 13. The essential parts of the extruder 12 are illustrated in Figure 2. These include a rectangular 7 opening 14 which sets the length and thickness of the paver, and a section 15 which bisects the blended mass into an upper and a lower portion. The section 15 comprises a wing-shaped steel plate 16 arranged to lie in a horizontal plane, with three ridges 17 from which tapered rods 18 extend toward the rectangular opening 14. The tapered rods include fins near their extremities.

Referring back to Figure i, when the clay mass has been passed through the extruder 12, and separated by the winged-shaped steel plate 16 into upper and lower portions, and the tapered rods 18 have formed channels in the interface 5O S between the separated portions, it is cut into billets 19 by 0*e S• cutter 20. The billets are then transported on the conveyor 13 to a multiple wire cutter 21 where they are accurately cut to produce green paving units of the desired width. The green S paving units are then conveyed to a 200 ton press 22 where they are pressed in lots of 10 to form a product whose dimensions are within the fine tolerances called for in the objectives of the invention.

0O** 2Us.s.. From the press 22, the paving units are sent for stacking at station 2, firing in kiln 23 and then packaging for sale at 24.

The pavers thus produced are shown in Figure 3. It can be seen that they look like conventional pavers but, in fact, they have very straight edges. When split, they produce the tiles of Figure 4. These tiles have shallow ridges 25 and grooves 26 to enable them to be laid in adhesive without wastage of adhesive.

Whilst the above has been given by way of 8 illustrative example of the invention, many modifications and variations may be made thereto by persons skilled in the art without departing from the broad scope and ambit of the invention as herein set forth in the following claims.

es *oe* 6* o e

Claims

1. A process for the production of paving units which are separable along a horizontal mid-sectional plane into two paving tiles, which process comprises the steps of:-- preparing a clay tile paving mix; (ii) extruding the mix through a die having a rectangular opening and an associated insert which bisects the extrudate thickness into two substantially equal portions and forms a series of longitudinally extending pockets at the interface between each portion; (iii) cutting the bisected extrudate into individual paving units; 9 (iv) compressing the individual paving units; and firing the paving units in a kiln.

2. A process for the production of paving units as claimed in claim 1, wherein the step (iii) of cutting comprises two stages:- a first stage in which the extrudate is cut into a longitudinal billet, and a second stage in which the longitudinal billet is cut transversely to produce individual paving units.

3. A process for the production of paving units as claimed in claim 2, wherein the longitudinal billet in stage 2 is cut transversely by pushing the billet through a plurality of vertically arranged and tensioned wires.

4. A process for the production of paving units as i claimed in claim 1 or claim 2, wherein the stepA 44 .ii. of compressing comprises subjecting the individual paving units to a press operating at 20 tons per paving unit.

5. A process for the production of paving units as claimed in claim 1 or claim 2, wherein the clay paver mix comprises a mixture of one or more clays, shale and water which has been screened through a screen having openings of 13 mm x 1.2 mm.

6. A process for the production of paving units as claimed in claim 1 or claim 2, wherein the insert associated with the die comprises a wing shaped steel plate incorporating three ridge sections formed transversely thereof and from each of which extends a convergently tapered rod in the same ib:" direction as that which the extrudate passes.

7. A process for the production of paving units as claimed in claim 1, wherein simultaneous to compressing the individual paving units in step a pattern is embossed in the paving units.

8. A process for the production of paving units as claimed in claim 1, wherein the step (iii) of cutting produces paving units which can subsequently be split into paving tiles of 230 mm x 115 mm x 40 mm.

9. Paving units whenever manufactured by a process as claimed in any one of claims 1 8. Paving units substantially as herein described with reference to the accompanying drawings.

11. A process for the production of paving units substantially as herein described with reference to the accompanying drawings. DATED this 10th day of February 1993 CLAYPAVE PTY. LTD. By their Patent Attorneys CULLEN CO. 11 S"1. ABSTRACT Paving units which are separable into two paving tiles along a horizontal plane. They are manufactured by extruding a paving mix through a rectangular opening die 12 having an insert 15 which bisects the extrudate into two substantially equal portions and forms a series of pockets 26 at the interface of each portion. The extrudate is then cut into individual units compressed (22) and fired (23).