GB2313567A - Method and apparatus for casting reinforced concrete panels - Google Patents

Abstract

The present invention relates to a method for casting a reinforced concrete panel, characterised in that: a. the panel is cast in a vertical open topped mould unit; b. the concrete mix is subjected to external vibration in the mould unit to remove air entrained in the concrete mix and trapped in the mould unit; and c. the mould unit has an internal mould cavity which has a depth of less than 75 cms and a width of less than 75 mms. The invention also provides apparatus for use in the method of the invention which consists of side walls suspended vertically from a carrier frame and mould base members and end members cooperating with the wall members to form a mould unit, the units being demountable from the frame and readily dis-assembled for release of the moulded panel and cleaning and treatment of the moulding surfaces with mould-release agent.

Description

TITLE: METHOD AND APPARATUS The present invention relates to a method and apparatus, notably to a method of casting thin concrete building panels and to apparatus for use in the method.

BACKGROUND TO THE INVENTION: Buildings of many types have been built using pre-cast concrete panels for the wall construction. Such panels are made by casting the panel in a mould. Typically, the panel is comparatively thick, at least 150 mms thick, and contains re-inforcing rods, mesh or the like to give the panel the required thickness and structural strength. It has been proposed that such panels should be cast in a vertical mould and processes in which such thick panels have been cast on site using a number of moulds have been operated. However, during the casting of such a panel vertically, problems are encountered due to entrapped air in the mould and it is necessary to vibrate the concrete to release the trapped air. If this is not done adequately, surface blemishes and localised weak points will be formed in the resultant panel.

These problems are aggravated where the panel contains reinforcing metal mesh or grid since these impede the escape of air bubbles from the concrete mix.

Where the concrete panel is thin, ie. has a thickness less than about 75 mms, yet further problems arise. The mould required to cast such a panel vertically does not permit a vibration probe to be inserted into the concrete during casting, especially where re-inforcing wires, mesh or grid are present. If the re-inforcement is omitted to allow the insertion of a vibration probe into the mould, the resultant panel is structurally weak and must be cured before it can be removed from the mould, which can take several days. It has therefore been considered necessary to cast such reinforced thin panels in a horizontal mould and to apply external vibration to the mould to release the trapped air.

However, further problems arise in that external vibration causes segregation of the aggregate and cement powder particles in the concrete mix and can result in a stratified structure to the panel if excessive vibration is applied.

On the other hand, insufficient vibration can result in inadequate removal of the air bubbles. It is therefore necessary to control the vibration of the horizontal moulds carefully.

The horizontal casting technique for thin panels has now been developed to a high degree and readily lends itself to large scale continuous operation. This enables strict control of the vibration process and good quality control of the ingredients and the concrete mix to be achieved, thus aiding control of the rheological properties of the concrete mix and hence the release of air from the mix and its behaviour during vibration. However, such a factory operation requires large and complex apparatus and skilled labour to operate it and large capital investment. Because of this, manufacture of the panels has to be carried out at a centralised location and the fully cured panels then transported to the site where they are to be used.

Surprisingly, we have now found that such thin panels can be cast in a vertical mould using external vibration, despite the known air entrapment problems with casting a re-inforced thin panel, and that the expected problems of segregation are minimised if the vertical height of the panel is kept to below about 75 cms. The size of the panels is such that they and the moulds in which they are cast can be handled manually by two men, thus dispensing with the need for complex and expensive lifting gear, further assisting manual operation of the moulding system on site. Furthermore, due to the size of the panel, the stresses within the panel are reduced. The panel is supported by the mould itself during initial curing and is also supported by its internal reinforcement, so that the panels can be removed from the mould before they are fully cured and handled whilst still in the green or partially cured state. This allows a rapid turn round to be achieved and we have devised a moulding apparatus which allows panels to be produced on a 24 hour cycle in a battery of moulds. The apparatus and vertical casting method can be operated on site and with unskilled labour, enabling the panels to be cast close to the intended place of use and thus avoid the need to transport the panels from a central casting location. The casting apparatus can be constructed so that it is modular and readily transportable from one site to another giving the operator a simple and effective method for casting panels in situ and for transporting the apparatus to another site and expanding or contracting the capacity of the apparatus to suit the requirements for each individual site.

SUMMARY OF THE INVENTION: Accordingly, the present invention provides a method for casting a re-inforced concrete panel, characterised in that: a. the panel is cast in a vertical open topped mould; b. the concrete mix is subjected to external vibration in the mould to remove air entrained in the concrete mix and trapped in the mould; and c. the mould has an internal mould cavity which has a depth of less than 75 cms and a width of less than 75 mms.

Preferably, a plurality of the moulds is carried in side by side relationship upon a carrier frame which is subjected to vibration and a mould release agent is applied to the surfaces of the mould cavity to assist removal of air from the mould during casting of the concrete mix. Preferably, the method of the invention is operated on site to provide partially cured panels within a 24 hour cycle of operation.

It is also preferred to feed the concrete to the top of an array of the mould units and to cause the concrete to flow into the mould cavities under the influence of the external vibration. Surprisingly, we have found that the concrete flows more rapidly into the mould cavities, typically 21 cavities can be filed in a period of 5 to 10 minutes, than when the conventional method of pouring concrete into each individual mould cavity is used, which takes from 90 to 120 minutes where it is possible to insert a feed nozzle into the mould cavity.

The invention also provides a mould apparatus for use in the method of the invention, which apparatus comprises a plurality of generally rectangular mould units in side by side relationship to one another, each mould unit having a mould cavity with an internal lateral dimension, thickness, of less than 75 mms and an internal vertical dimension, depth, of less than 75 cms; and means for applying external vibration to the mould units.

Directional terms, such as inwardly or outwardly, are used herein with respect to the mould to denote directions from the exterior periphery of the mould cavity towards the centre of the cavity.

Preferably, the moulds are carried on a carrier frame which is provided with means for generating the vibration and each mould is demountable from the carrier frame and can be disassembled to release the cast panel. In a particularly preferred embodiment, the apparatus comprises: a. a generally horizontal rectangular support frame provided with vibration generating means; b. a series of substantially parallel moulds suspended from the frame, each mould comprising a substantially vertical side member defining the common side wall to two adjacent mould cavities, a mould base member connected to two mould end members forming the base and ends of the mould cavity between two adjacent side walls, the end members being provided with means whereby the end members can be lifted from the apparatus carrying with them the panel cast within the mould cavity; and c. means for urging the side walls into substantial sealing engagement with the mould end and base members thereby to form a series of substantially parallel individual mould cavities in side by side relationship to one another and separated by the mould side wall members.

For convenience the invention will be described in terms of this preferred embodiment.

The mould cavities are defined by the side walls, the end and base members. The mould end and base members may be formed as a unit, for example as a generally U shaped frame made from suitable metal box or bar members welded or otherwise secured together. However, it is preferred that the mould end and base members be formed as separate components which are demountable from one another.

Preferably, the end members carry downwardly directed pin members which engage in corresponding apertures or sockets at or adjacent the ends of the horizontal base members or vice versa. The pins and apertures inter-engage to locate the end members at or adjacent the ends of the base members and in a generally upright positions and prevent lateral movement of the end members with respect to the base member once in position.

It is preferred that the end members are provided with lateral feet which extend along at least part of the upper face of the base member. Preferably, the base members are indented to accommodate the feet and provide a flat basal surface to the mould cavity. Typically, the feet extend for from 5 to 20 cms and provide load-bearing surfaces upon which the weight of the cast panel is borne when the end members are lifted from the support frame as described below. To aid location of the cast panel on the feet and to minimise the risk of the panel twisting as the end members are lifted, the upper faces of the feet and/or the inwardly directed faces of the end members can be provided with inwardly directed projections or lugs. The lugs form corresponding recesses in the periphery of the cast panel and these may be used to assist inter-engagement of the panels during their later use. Typically, the lugs will extend inwardly from 1 to 5 cms and may extend for the full height of the mould end member so as to form a groove in the edge of the panel.

The end members are preferably provided with a hook or other means by which they can be lifted to remove the cast panel from the mould as described below. Typically, such means comprise a hook extending upwardly from the top end of the end member which can be engaged by a suitable lifting device. Preferably, the end members are substantially symmetrical, apart from the laterally extending foot, about their longitudinal axis and are made from a suitable metal or other box section so as to present a substantially flat inner face to the mould cavity.

The side walls of the mould cavities are provided by the side members which provide a common or party wall between adjacent mould cavities. The side members can take the form of simple plate members. However, this may require the use of excessively thick and heavy duty metal plate. It is therefore preferred to form the side members as hollow box section members having metal vertical wall faces welded or otherwise secured to a box section vertical frame. The wall faces extend for the full extent of the mould cavity and preferably extend beyond the end and base mould members described above so that the opposed faces of the mould end, base and side wall members form a closed bottom generally rectangular shaped mould cavity when they are brought into close contact with one another.

As stated above, the mould cavity has a thickness of less than 75 mms and a depth of less than 75 cms. The thickness of the mould end and base members determines the thickness of the mould cavity and the height of the mould end and side wall members determines the depth of the mould cavity. It is preferred to dimension these members so that the mould cavity corresponds to the largest size of panel to be made.

The moulds are supported on a support frame which also carries the means for vibrating the moulds. The support frame typically takes the form of an upper pair of rail members extending transversely of the longitudinal axis of the moulds. These upper rails are linked by suitable cross rails to form a fixed generally rectangular horizontal frame within which the moulds are suspended. Preferably, the side wall members of the moulds are suspended from the upper rails of the support frame by extensions of the top member of the box section support frame to the side walls. The moulds adopt a substantially vertical orientation with the mould base members substantially horizontal. The moulds are orientated parallel to the cross rails and one of the cross rails acts as a stop member against which the moulds can be urged to close up the components of the moulds upon one another to form the closed bottom mould cavities.

As indicated above, some means are provided to close up the mould components. This can take the form of screw or other jacks acting on the exposed face, for example the top box section of the wall support frame, of the last mould in the series of moulds in the frame to urge the series of moulds towards the end stop cross member. Preferably, the moulds are closed up by means of one or more hydraulic cylinders acting between a fixed stop on the upper rail against the exposed face of the last mould in the series of moulds. The stop can be provided by the other cross rail which is fixed at or adjacent the end of the upper rails. However, it is preferred to provide a separate stop member on the upper rails and for the second cross rail to be a moving cross rail upon which the cylinder acts and which spreads the closing up force substantially uniformly across the upper edge of the moulds. The closed up moulds are preferably locked in the closed up position by locking screws, latch mechanism or the like. If desired, some form of ratchet means can be provided to prevent retraction of the moving cross rail in the event of failure of the hydraulic pressure to the hydraulic cylinders.

The upper rails are supported, for example by one or more uprights at or adjacent each end of the rails, on a ground imbedded foundation so that the support frame adopts a substantially horizontal orientation with the moulds suspended substantially vertically thereform. Where the mould base member is formed as a unit with the mould end members, the closed moulds will each be supported as a coherent unit from the upper rails. However, where the mould base member is separate from the mould end members and connected thereto merely by the inter-engagement of the pins and sockets as described above, the base member could drop out of the mould before the mould is closed up to clamp it in position. It is therefore preferred to provide a second, lower pair of rails orientated transverse to the longitudinal axis of the moulds and located at the level of the base of the moulds to provide support for the base of the moulds. This lower second pair of rails is supported from the upper rails at suitable positions inset from each end of the moulds by suitable hangers or the like. The use of a second pair of rails to support the base of the moulds also permits the use of a light construction for the mould since the majority of the downward load of the concrete within the moulds will be carried by the second pair of rails.

The dimensions of the support frame can be of any suitable size having regard to the number of moulds it is intended the apparatus should contain and the size and weight of the panels to be cast. However, it will usually be preferred to size the support frame so as to accommodate from 15 to 30 moulds.

As stated above, the support frame for the moulds is provided with means for applying vibration externally to the moulds to aid escape of entrained air from the moulds during casting of the panels. This means can be mounted either on the upper pair of rails supporting the upper part of the moulds as described above, or on that part of the frame supporting the base of the moulds. For convenience, the invention will be described in terms of mounting the vibration means on either or both of the upper rails of the support frame. It is also preferred to incorporate some form of vibration damping between the support-frame and the ground foundation upon which it is mounted, for example rubber or other vibration absorbing pads between the upper rails and the ground foundation. The vibration can be generated by any suitable means, for example by means of rapid acting hydraulic cylinders or, more preferably, by means of electric motors driving an eccentric weight so as to apply a fixed or variable frequency continuous or pulsed vibration to the support frame. The use of an electric motor also allows the operator to select the frequency and duration of the application of the vibration to suit a given concrete mix and size of panel. By selecting the weight which is rotated, the operator can also select the amplitude of the vibration applied to the frame, thus giving a range of controls over the vibration to optimise air removal without causing significant segregation of the concrete mix in the moulds.

The vibration applied to the support frame will usually have a major up and down component. However, if desired the vibration can provide a significant side to side or forward and backward movement to the moulds, for example by mounting the vibration electric motors vertically as opposed to horizontally. The optimum type of vibration can be determined by simple trial and error by a skilled operator who can then set up the apparatus for subsequent use by nonskilled operators.

The apparatus is conveniently made from steel sheet, box section and I or U beams members to provide a simple and robust apparatus. By suitable selection of the length of the top and bottom pairs of rails of the support frame, the apparatus can be made to accommodate different numbers of moulds. By securing the pairs of rails on the cross rails by vibration resistant bolts or the like, the apparatus can readily be modified to accommodate different lengths of mould for different sized panels. However, it is preferred to form the support frame by welding the rails to form a permanent size and shape of support frame and to accommodate different lengths of mould by the use of elongated extensions to the top support box member of the mould side wall support frame. Similarly, it is preferred to locate the bottom rails in the support frame a specified fixed distance below the upper support rails so as to accommodate the deepest moulds envisaged. If it is desired to cast a panel which is not as deep, an insert box or spacer can be fitted into the mould cavity to reduce the depth of the mould cavity to the desired value.

The apparatus can thus be manufactured simply from readily available materials and yet can produce a wide range of sizes of panels. Furthermore, by removing or adding mould components to the series of moulds in the support frame, the production capacity of the apparatus can be increased or decreased at will. Since the side wall members can be formed with non-planar wall sheet members, the apparatus can be modified so that some or all of the moulds produce panels with surface patterns and the patterns from each mould cavity can be the same or different.

Furthermore, since the apparatus of the invention casts the panels vertically, it occupies a comparatively small plan area and can thus be accommodated in even a small site.

Thus, an operator can readily transport the apparatus, dissembled into its constituent parts from one site to another and can cast panels on site to suit the requirements of the site without the need for sophisticated and complex plant or the need to transport cast panels from a central casting factory. Since the apparatus can be designed to manufacture panels of a size the can readily be handled by two men, the component parts of the moulds can be readily assembled and used by two men. The apparatus thus is of especial application in the casting of panels for use in developing countries.

The apparatus is operated by assembling the appropriate mould end, base and side wall members upon the upper support rails of the support frame. The moulds are the closed up by application of the hydraulic jacks or other means, so as to form a series of closed base moulds with open tops. Since the moulds will usually be made from steel which promotes the formation of air bubbles on the surface of the cast panels, it will usually be necessary to apply a mould release oil or other material to the exposed faces of the interior of the mould cavity. Alternatively, the surfaces may have a PTFE, silicone or other mould release agent layer formed on them during manufacture. However, the use of a mould release oil is particularly preferred from a cost and simplicity point of view.

Once the moulds have been closed up and locked in the closed position, for example by passing a bolt transversely through the series of moulds, concrete is poured into the moulds from a conventional cement mixer or the like. Preferably, the concrete is poured to form a pool of concrete overlying the open tops to the moulds and the external vibration causes the concrete to flow into the mould cavities and displace air therefrom. If desired, some form of concrete retaining wall can be provided around the open tops to the moulds, for example by forming the moulds with a greater depth than required or by forming the support frame with a peripheral upstanding flange or rim to form a puddle of concrete over the mould tops. The vibration means is activated to cause entrapped air to escape up the side walls of the moulds and to cause the concrete to flow into and downwardly within the mould cavities. Care needs to be taken to avoid excessive vibration which can lead to segregation of the concrete mix. However, as indicated above, the optimum vibration form and duration for a given casting can be determined by a skilled operator and the frequency and amplitude of the vibration present. The optimum duration of the vibration can also be predetermined and set on a suitable timer so that the non-skilled operator can not adjust the vibration process once predetermined by the skilled operator.

Once the vibration has been completed, the casting is allowed to stand in the moulds in the apparatus for partial curing of the concrete mix to occur. It will typically take from 12 to 18 hours before the mix has developed sufficient mechanical strength to be handled. The moulds are then successively opened up and the green panel lifted out of the apparatus on the mould end members which provide vertical support to the end portions of the green panel. Since the panel is lifted in the vertical orientation, the internal re-inforcement and the support from the mould end members is sufficient to prevent the panel from disintegrating as would occur if the panel were lifted in the horizontal orientation in the same green state. It is thus possible to extract the panels from the apparatus at a much earlier stage than in a conventional horizontal casting process. The green panel can then be stacked in the generally upright orientation to complete curing whilst the apparatus is prepared for a subsequent casting cycle. We have found that it is possible to complete a casting cycle and the prepare the apparatus for the new casting cycle within a 24 hour period. This enables a high production rate to be achieved from a single apparatus.

Where the mould is made from separate components this is particularly valuable in assisting cleaning of the components and re-oiling them prior to re-assembly the moulds for the next casting cycle. Furthermore, since each component can be handled separately, it is possible to achieve levels of mould cleaning not hitherto possible with a fixed mould construction.

DESCRIPTION OF THE DRAWINGS: The invention will now be described by way of illustration only with respect to the preferred embodiment shown in the accompanying drawings in which Figure 1 is a plan view from above of the apparatus showing some of the moulds in the closed up position and others in the open position; Figure 2 is a vertical section across the apparatus of Figure 1 parallel to the mould side walls; Figure 3 is a vertical section through the apparatus of Figure 1 normal to the plane of the walls of the moulds; and Figure 4 is a part exploded view of the components of the mould side wall members.

DESCRIPTION OF THE PREFERRED EMBODIMENT: The apparatus comprises a rectangular support frame made from two parallel upper rails 1 and 2 linked by a fixed cross beam 3. The rails 1 and 2 are mounted via antivibration pads 4 and feet 5 to foundations 6 set into the ground at each end of the rails. The rails 1 and 2 are provided with vibration generators 7 fixed to the underside of each of the rails. There may be more that one generator as shown and each of the generators can be of a different type to provide variation in the types of vibration generated.

Suspended between the rails 1 and 2 are the mould units 10.

The units are suspended with their longitudinal axis substantially parallel to the fixed cross beam 3. A moving cross beam 8 is slidably located on the rails 1 and 2 and orientated generally parallel to beam 3, but on that side of the mould units 10 removed from beam 3.

Mounted parallel to but below rails 1 and 2 are two lower rails la and 2a supported by hanger beams 9 so that they support the bases of mould units 10 as shown in Figures 2 and 3. The mould units are suspended on rails 1 and 2 by the lateral extensions of the top box beam of the support frame of the side wall members shown in the exploded view of the construction of the wall member in Figure 4.

Mounted at the moving beam end of each of rails 1 and 2 is a hydraulic cylinder 20 which acts between an upstanding stop 21 fixed to the end of each of rails 1 and 2 and the moving cross beam 8. The cylinders 20 act on the moving cross beam 8 to move it towards the fixed cross beam 3 and thus close up the mould units 10 as described below. As shown in Figure 3, the underside of moving beam 8 can carry ratchet teeth which engage with similar teeth on the upper face of rails 1 and 2 to prevent retraction of the cross beam 8 if the hydraulic cylinders 20 for any reason fail once the process of closing up the moulds has commenced.

As shown in Figure 2, each mould unit comprises an end member 31, a base member 32 and a side wall member 33. The end member forms the upright end wall to the mould cavity and has a hook at its upper end by which it can be lifted.

The foot of end member 31 extends laterally into the mould cavity so as to form a foot 34 which underlies the edge of a panel cast in the mould cavity. Extending axially from the foot of end member 31 is a pin 35. End member 31 is conveniently made from steel box section of the width required for the thickness of the mould cavity.

The mould base member 32 is conveniently also a steel box section member of the length required for the side to side width of the mould cavity. The upper face of member 32 is indented to accommodate foot 34 on member 31 so as to present a flat base surface to the cavity. Member 32 also has a socket into which the pin 35 on the foot of member 31 engages to locate the foot of member 31 and prevent that member from moving laterally. As shown in Figure 2, member 32 rests upon the lower rails la and 2a, which are spaced apart by less than the length of member 32 and also serve to support much of the load of the filled mould units 10. If desired, the upper rails 1 and 2 can be separated by the width of the mould unit 10 so that the upper end of member 31 bears against the rails and is thus prevented from splaying. However, we have found that this is not usually necessary.

The side wall members 33 comprise two vertical wall plate members 40 supported on a frame 41 made from a box steel section. The frame can be located at the periphery of the plates 40 or there can be intermediate vertical or horizontal members 42 to provide additional stiffening to the wall plates. The upper box section member 43 of the frame extends laterally of the plate members 40 to provide the lateral extensions by which the member 33 is suspended from the rails 1 and 2. Each wall plate can be planar as shown or can carry a raised or recessed pattern so as to form a patterned or textured finish on the panel cast in the mould unit to which that wall plate 40 relates. As can be seen from Figures 1 and 3, each wall member 33 provides the common or party wall between two adjacent mould cavities 50.

To form the mould units 10, a first wall member 33 is placed in position against and substantially parallel to the fixed beam 3, a base member 32 is laid on rails la and 2a against the wall member 33 and the end members 31 are located on base member 32 with the pins 35 engaging in the sockets in member 32 and with feet 34 located in the indents in base member 32. A second wall member 33 is positioned against the exposed edges of members 31 and 32 to complete the first mould unit 10 with its cavity located between the opposed walls 40 of the two wall members 33. If it desired to form a smaller panel than the full size cavity would product, the width of the cavity can be reduced by inserting a blanking unit 60 into the cavity. Blanking unit 60 is of any suitable size and may be positioned in the middle of the cavity as shown in Figure 1, or may be placed at either or both ends of the cavity. Similarly, if a shallower panel is required, a bottom spacer 70 can be placed in the base of the cavity as shown in Figure 3.

As stated above, all components of the mould unit 10 are liberally oiled with a mould release oil which aids separation of the panel from the mould after casting and also assists escape of air from the mould.

Having assembled the desired number of mould units on the mesh moves relative to the internal wall of the mould.

Concrete is poured onto the top of the assembled array of mould units to cover the exposed open tops to the individual cavities and the external vibrators 7 actuated. The vibration causes the concrete to flow into and consolidate with the mould cavities. Concrete is continuously poured onto the exposed tops of the moulds until the individual cavities are full. Vibration is continued to release air from the concrete mix and to release air trapped in the mould. After a suitable time, which is usually preset by a skilled operator, the vibration is stopped and the cast panels allowed to cure within the mould units.

Once the panels have gained sufficient mechanical strength to be moved, the mould units are released from their closed up position, for example by undoing the locking screw passing through the mould base members 32 and the basal part of the internal support frame for side wall members 33.

Each mould unit is then successively opened up and the cast panel lifted out by lifting it on the feet 34 of end members 31. If desired, the upper face of foot 34 can carry an upstanding pin 36 and the inner face of member 31 can have a protruding lug 37, which form corresponding recesses in the foot and side of the panel as it is cast and serve to retain the panel on member 31 as it is lifted. The panels are still green and will normally be stacked to complete curing.

The opened up mould units are then dismantled into their component parts, the end member 31, the base member 32 and the side wall member 33. Each is then washed down and reoiled in readiness for the next casting cycle. We have found that it is possible to cast panels up to 50 mms thick and achieve adequate mechanical strength to remove the cast panel from the moulds after a cure time of 16 to 18 hours. It is therefore possible to achieve a casting cycle every twenty four hours and to produce up to thirty panels per apparatus in each casting cycle.

Claims (9)

CLAIMS:

1. A method for casting a re-inforced concrete panel, characterised in that: a. the panel is cast in a vertical open topped mould unit; b. the concrete mix is subjected to external vibration in the mould unit to remove air entrained in the concrete mix and trapped in the mould unit; and c. the mould unit has an internal mould cavity which has a depth of less than 75 cms and a width of less than 75 mms.

2. A method as claimed in claim 1, characterised in that a plurality of the mould units is carried in side by side relationship upon a carrier frame which is subjected to vibration.

3. A method as claimed in claim 1, characterised in that a mould release agent is applied to the surfaces of the mould cavity to assist removal of air from the mould unit during casting of the concrete mix.

4. A method as claimed in claim 1, characterised in that the concrete mix is fed to the top of an array of the mould units and the concrete is caused to flow into the mould cavities under the influence of the external vibration.

5. A method as claimed in claim 1, characterised in that the mould units comprise a series of components which are assembled on one another to form a mould unit; the concrete panel formed within the mould cavity is allowed to cure for a period of from 12 to 18 hours; the mould unit is disassembled to allow removal of the cast panel by lifting the panel from the mould unit; the components of the mould unit are cleaned and a mould separation agent is applied to the surfaces of the components mould prior to re-assembly of the mould unit for use in'a subsequent concrete cycle.

6. A method as claimed in claim 1, characterised in that the method is carried out on site at the location where the panels are to be used in the assembly of a building or other structure.

7. A method as claimed in claim 1, characterised in that the mould units have at least some mould cavities with different dimensions or shapes whereby different sizes of panels or panels with different surface patterns are formed concurrently.

8. A mould apparatus for use in the method of claim 1, which apparatus comprises a plurality of generally rectangular mould units in side by side relationship to one another, each mould unit having a mould cavity with an internal lateral dimension of less than 75 mms and an internal vertical dimension of less than 75 cms; and means for applying external vibration to the mould units 9. Apparatus as claimed in claim 8, characterised in that the mould units are suspended substantially vertically from a carrier frame which is provided with means for generating the vibration and each mould unit is demountable from the carrier frame and can be dis-assembled to release the cast panel.

10. Apparatus as claimed in claim 8, characterised in that the mould units are formed from a substantially vertical side member defining the common side wall to two adjacent mould cavities, a mould base member connected to two mould end members forming the base and ends of the mould cavity between two adjacent side walls, the end members being provided with means whereby the end members can be lifted from the apparatus carrying with them a concrete panel cast within the mould cavity, the said mould side, end and base members being demountable from one another to release a concrete panel cast within the mould cavity of the mould unit.

11. Apparatus for use in casting a plurality of re-inforced concrete panels having a thickness of less the 75 mms and a height of less than 75 cms, which apparatus comprises: a. a generally horizontal rectangular support frame for supporting a plurality of moulds units; b. a plurality of generally rectangular mould units, each mould unit having a mould cavity with an internal lateral dimension of less than 75 mms and an internal vertical dimension of less than 75 cms, each mould unit comprising a substantially vertical side member defining the common side wall to two adjacent mould cavities, a mould base member connected to two mould end members forming the base and ends of the mould cavity between two adjacent side walls, the end members being provided with means whereby the end members can be lifted from the apparatus carrying with them a concrete panel cast within the mould cavity, the said mould end, base and side wall members being demountable from one another to permit removal of a concrete panel cast within the mould cavity; c. means for urging the side walls into substantial sealing engagement with the mould end and base members thereby to form a series of substantially parallel individual mould cavities in side by side relationship to one another and separated by the mould side wall members; and d. means for applying external vibration to the mould units.

12. Apparatus as claimed in either of claims 8 or 11, characterised in that the mould end members are provided with laterally extending feet members which are to underlie the concrete panel cast in the mould cavity and to support the panel when it is removed from the apparatus.

13. Apparatus as claimed in claim in claim 9, characterised in that the mould units are suspended from a pair of upper rails in said carrier frame and the bases of said mould units are supported by a lower pair of rails generally parallel to but located below said upper rails.

14. A mould unit for use in the method of claim 1 or the apparatus of claim 8 characterised in that it comprises: a. a substantially vertical side wall member adapted to define the common side wall to the mould cavities in two adjacent mould units, b. a mould base member and two mould end members adapted to be connected together so as to form the base and ends of the mould cavity between two adjacent side wall members, the end members being provided with means whereby the end members can be lifted from the apparatus carrying with them a concrete panel cast within the mould cavity, the said mould side, end and base members being demountable from one another to release a concrete panel cast within the mould cavity of the mould unit.

Amendments to the claims have been filed as follows 1. A method for casting a plurality of concrete panels in which: a. a flowable concrete mix is fed to a plurality of substantially vertical open topped mould units each of which has an internal mould cavity which has a depth of less than 75 cms and a width of less than 75 mms, the mould units being demountably carried in side by side relationship upon a carrier frame and being formed from components which are demountable from one another and which include a substantially vertical side member defining a common side wall to the mould cavities of two adjacent mould units, a mould base member and two mould end members forming the base and ends of the mould cavity between two adjacent side walls, the end members being provided with means whereby the end members can be lifted from the apparatus carrying with them a concrete panel cast within the mould cavity, the said mould side, end and base members being demountable from one another whereby the mould unit can be dismantled to release a concrete panel cast within the mould cavity of the mould unit for lifting vertically; b. the mould units are subjected to external vibration to cause concrete mix fed to the open top of the mould units to flow into the said mould cavities and to remove air entrained in the concrete mix and trapped in the mould cavities; c. the concrete mix in the mould units is allowed to set to form coherent cast panels within the mould units; d. the mould units are successively dismantled to release successive cast panels from the mould units; and e. the mould end members together with the released cast panels are lifted away from the dismantled mould unit for storage and curing outside the mould unit.

2. A method as claimed in claim 1, characterised in that a mould release agent is applied to the surfaces of the components of the mould units to assist removal of air from the concrete mix in the mould cavity during casting of the concrete mix.

3. A method as claimed in claim 1, characterised in that the concrete mix within the mould cavities is allowed to cure for a period of from 12 to 18 hours; the mould units are successively dismantled to allow removal of the cast panel by lifting the mould end members and the panel from the dismantled mould unit; the cast panels are stored substantially vertically and the mould end members removed therefrom; and the components of the mould unit are cleaned and a mould separation agent is applied to the surfaces of the components prior to re-assembly of the mould unit for use in a subsequent casting cycle.

4. A method as claimed in claim 1, characterised in that the method is carried out on site at the location where the panels are to be used in the assembly of a building or other structure.

5. A method as claimed in claim 1, characterised in that the mould units have at least some mould cavities with different dimensions achieved by the insertion of one or more blanking members into the mould cavity.

6. A mould apparatus for use in the method of claim 1, which apparatus comprises: a. a generally horizontal rectangular carrier frame for supporting a plurality of moulds units; b. a plurality of substantially vertical open topped mould units, each of which has an internal mould cavity which has a depth of less than 75 cms and a width of less than 75 mms, the mould units being demountably carried in side by side relationship upon the carrier frame and being formed from components which are demountable from one another and which include a substantially vertical side member defining a common side wall to the mould cavities of two adjacent mould units, a mould base member and two mould end members forming the base and ends of the mould cavity between two adjacent side walls, the end members being provided with means whereby the end members can be lifted from the apparatus carrying with them a concrete panel cast within the mould cavity, the said mould side, end and base members being demountable from one another whereby the mould unit can be dismantled to release a concrete panel cast within the mould cavity of the mould unit for lifting with the mould end members from the dismantled mould unit c. means for urging the side walls into substantial sealing engagement with the mould end and base members thereby to form a series of substantially parallel individual mould cavities in side by side relationship to one another and separated by the mould side wall members; and d. means for applying external vibration to the mould units.

7. Apparatus as claimed in claim 6, characterised in that the mould end members are provided with transversely extending feet members which are to underlie the concrete panel cast in the mould cavity and to support the panel when the mould end members and the cast panel are lifted from the remainder of the dismantled mould unit.

8. Apparatus as claimed in claim in claim 6, characterised in that the mould units are suspended from a pair of upper rails in said carrier frame and the bases of said mould units are supported by a lower pair of rails generally parallel to but located below said upper rails.

9. A mould unit for use in the method of claim 1 or the apparatus of claim 6 characterised in that it comprises: a. a substantially vertical side wall member adapted to define the common side wall to the mould cavities in two adjacent mould units, b. a mould base member and two mould end members adapted to be connected together so as to form the base and ends of the mould cavity between two adjacent side wall members, the end members being provided with means whereby the end members can be lifted from the apparatus carrying with them a concrete panel cast within the mould cavity, the said mould side, end and base members being demountable from one another whereby the mould units can be dismantled to release a concrete panel cast within the mould cavity of the mould unit.