This invention relates to a means and method of construction of building panels, and has particular but not exclusive application to load bearing wall panels used for both internal and external walling systems.

In my earlier filed application 60234/90 dated 7th August 1990 there is described a method of moulding an hollow building panel unit comprising a pair of opposed spaced apart rectangular facing panels, preferably of glass fibre reinforced plaster, and a plurality of parallel, spaced apart elongate web members, also formed preferably of glass fibre reinforced plaster, interconnecting and jointing together said panels in parallel relation and extending transversely thereof, the web members forming internal cores or cavities which extend between opposite sides of the moulded panel. Whilst the moulding technique described in the aforesaid patent specification has been found generally satisfactory and viable for small production runs, it is not satisfactory for high volume production on account of it being too labour intensive.

Accordingly, it is the main object of the present invention to provide an improved moulding process for the production of a building panel unit of the type described and claimed in my earlier filed patent application 60234/90, which is less labour intensive and in turn more commercially viable for high volume production runs.

According to one form of this invention, a method of moulding an integral hollow building panel having first and second opposed outer panel walls interconnected by a plurality of spaced apart transversely extending webs which together with the panel walls form internal cavities extending between opposite sides of the moulded panel, essentially comprises the steps of (not necessarily in order)

(i) adding a first layer of a wet pourable mix, preferably of plaster and water, into an elongate tray-like mould for forming said first panel wall,

(ii) introducing a layer of reinforcement material, e.g. glass rovings, into the mould;

(iii) inserting a plurality of closely spaced parallel removable plug members to extend transversely of the mould between the opposite longitudinal sides thereof and being supported with their underside surfaces spaced from the base wall of the mould, the spaces between adjacent plug members defining internal mould cavities for the formation of the webs of the panel;

(iv) adding a further quantity of said wet pourable mix, into the mould sufficient to fill said spaces between the plug members and to form a second layer on top of the plug members for forming said second panel wall, with the external surfaces of the plug members forming internal mould surfaces;

(v) adding further reinforcement material, e.g. glass rovings, to said second layer of plaster and into the spaces between the plug members;

(vi) allowing the wet pourable mix in the mould to set;

(vii) withdrawing by mechanical means, the internal plug members horizontally sideways from the mould; and

(viii) removing the thus formed hollow building panel unit comprising first and second opposed panel walls united by transverse webs, from the mould.

In a preferred arrangement, the mould is movably carried on a travelling carriage or table which is guided along tracks and is designed to travel under a stationary liquid plaster supply bin from which liquid plaster discharges into the moving mould, and also under a stationary multi-head glass cutter unit which applies the fibre reinforcement material. It would, of course be possible to utilise a stationary mould and have the plaster supply bin and glass cutter unit supported overhead for travel along the length of the mould.

According to a preferred embodiment of the invention, the method is carried out by initially applying a first layer of reinforcement material onto the horizontal base wall of the mould as it passes beneath the reinforcement material feeder unit, the plug members then being inserted horizontally into the mould (which is at rest) from one side thereof so as to lie transversely of the mould, following which the first quantity of wet mix is added to the mould as it travels under a liquid plaster supply bin.

Preferably the first layer of reinforcement material is held down by transversely extending vertical plates whilst the plug members are inserted into position (the plates being spaced lengthwise along the mould by a distance slightly greater than the width of the plug) . The plates are carried by a mounting frame which itself is movably mounted above the path of the travelling carriage and which can be raised and lowered relative thereto. The plates act as retention blades which effectively pin down the layer of reinforcement material so that it is not dislodged or disturbed when the plugs are slidably inserted across the mould.

Preferably, the mould is vibrated during the moulding process by vibration devices attached to the underside of the mould support table, to ensure that the reinforcement material is properly worked into the liquid plaster mix.

Preferably the travelling table passes beneath a grease spray unit for suitably greasing the mould surfaces prior to liquid plaster being poured into the mould. The plug members should also be greased with a suitable release agent prior to their insertion into the mould.

Preferably the mould comprises upstanding parallel side walls extending along opposite longitudinal margins thereof, one of said side walls being provided with a plurality of apertures or openings spaced along the length thereof and through which the plug members are inserted (and subsequently withdrawn after the liquid plaster has set) . Preferably, each of the plugs has a locating projection extending centrally from its leading end face and which locates in an aperture in the other of said side walls when the plug is fully inserted, whereby the plug is stably supported at its opposite ends above the base wall of the mould during the moulding process.

Preferably a gripping bar or rail to which the trailing ends of the plug members are releasably coupled, is used to simultaneously insert the plug members horizontally sideways into the mould and also to withdraw the plug members from the mould. Preferably, the gripping bar is operatively coupled to an hydraulic ram which operates to effect initial part- extraction of the plugs, in order to break the bonding between the set plaster material and the surfaces of the plug members. After such bonding has been severed, the plugs can be extracted fully from the mould by a mechanical conveyor system coupled to the gripping bar.

The plugs need not be one-piece members and may, for example, comprise two co-axial mating halves which connect together at their inner ends when inserted into the mould. In this case, the plug halves would be inserted from opposite sides of the mould, with each plug half passing through a respective aperture formed in a side wall of the mould. The extraction of the plug halves would be to opposite sides of the mould.

By using two shorter plug halves, the bonding between the plugs and the set plaster can be more readily broken than that for a relatively long unitary plug member.

When the mouldable material is sufficiently hardened, the mould is transferred from the carriage to a tilt transfer table mounted to one side of the carriage and which can be rotated by drive means, from a horizontal loading position to an approximately vertical ejection position whereat the panel can be removed from the mould for storage.

The method of this invention may be performed by driving, eg by a cable and winch mechanism, the travelling table or carriage back and forth along a straight track so that it passes beneath an overhead liquid plaster feeder bin or hopper and an overhead reinforcement material feeder unit mounted intermediate the ends of the track, with the plug insertion and extraction mechanism and tilt table mounted adjacent one end of the track on opposite sides thereof. The overhead reinforcement material retention device would normally be mounted at said one end of the track directly there above.

It will of course be appreciated that the method may be carried out using a continuous production line with the various work stations positioned at spaced intervals along the length of the track. A continuous conveyor assembly may be employed to transfer a mould from one station to the next.

In order to further explain the present invention, an embodiment thereof is described hereunder in some further detail with reference to and as illustrated schematically in the accompanying drawings wherein:

Fig 1 is a schematic representation of a panel moulding production line according to a preferred embodiment of the invention;

Fig 2 is a schematic side elevational view of the production line shown in Fig 1;

Fig 3 is a fragmentary side elevational view showing the reinforcement material retention unit in a partly lowered position above the mould containing a layer of glass fibres, with the plugs being inserted on top of the fibres;

Fig 4 is an end elevational view of the assembly shown in Fig 3;

Fig 5 is a fragmentary schematic end elevational view showing the manner in which the mould is transferred from the travelling carriage onto the tilt transfer table;

Fig 6 is an end elevational view of the tilt transfer table shown in its titled position ready for removal of the moulded panel from the mould which is releasably fastened to the transfer table;

Figs 7(a) & (b) are schematic views showing the manner of operation of the plug insertion and extraction device with the plug fully extracted, and the plug fully inserted respectively, whilst

Fig 8 is an elevational view of a building panel produced in accordance with the invention.

Referring to Fig 8 of the drawings, a building panel 10 is formed from glass fibre reinforced plaster (gypsum) and comprises a pair of spaced apart opposed rectangular outer walls 11, 12 united together by a plurality of spaced apart elongate web members 13 extending transversely thereof, the inner surfaces of the walls and the opposed vertical faces of the webs together defining a plurality of rectangular shaped cores or cavities 14 extending between the panel walls 11, 12

across the width thereof. In this embodiment, the web members 13 are parallel to one another and of rectangular cross sectional shape, although other cross-sectional shapes can be used.

In the batch-type table moulding process shown in Figs 1 and 2, a tray-like mould 15 in which the panel 10 is formed, is supported on a travelling carriage 16 which is arranged to travel along rails 17 and initially passes under a spray unit (not shown) which sprays a suitable mould releasing agent over the surfaces of the mould 15 to ensure that the moulded panel, after setting, can be easily removed therefrom. From the grease spray unit, the carriage 16 passes under a reinforcement material receiving station comprising a multi-head glass cutter/oscillator feeder 18 (which is known in the art) which feeds glass rovings into the moving mould 15 so as to form an approximately even layer 19 covering the base wall of the mould 15.

After the first layer 19 of reinforcement material has been added, the carriage 16 is moved to a plug loading station whereat, with the carriage 16 stationary, a plurality of removable hollow plugs 20 are inserted horizontally sideways by a plug insertion and extraction unit 21 through apertures in one of the side walls of the mould so as to extend across the width thereof with their underside surfaces contiguous with the first layer 19 of glass fibres. The plugs 20 are positioned and supported in parallel relationship and spaced apart by a short distance (e.g. 20mm) so as to form a series of vertical cavities which form the web members 13 in the finished panel 10. The metal plugs 20 are approximately oval shaped in cross-section having opposed parallel upper and lower planar walls joined by curved end walls. With the plugs thus inserted, their upper surfaces are approximately coplanar and act as internal mould surfaces.

In this embodiment, a vertically movable glass-fibre retention device 22 comprising a series of lengthwise spaced apart elongate blades 23 are used to hold-down the glass layer 19 whilst the plugs 20 are slidably inserted into the mould cavity, with each of the plugs 20, locating between a pair of adjacent blades 23 (refer Fig 3). Once the plugs 20 are fully inserted, the blades 23 are simultaneously raised to a retracted position above the carriage 16.

The mobile table 16 then once again travels under the grease spray unit in order to suitably spray the surfaces of the plugs 20, and thereafter passes under a liquid plaster supply bucket 25 into which plaster is fed from an overhead silo or hopper 26, the plaster being mixed with water in the bucket 25. Liquid plaster is discharged into the mould 15 to a depth which approximates to the thickness of wall 12 of the finished panel. Vibrators 27 attached to carriage 16 are activated to vibrate the wet mix in the mould.

The mould 15 then completes a further pass (or passes) under the glass fibre feeder unit 18 and further glass rovings are laid on top of the plugs 20 across the width of the mould. With the carriage 16 at rest, the glass rovings are manually worked into the spaces between adjacent plugs 20 by a manual beater bar or blade 29. Thereafter, the mould travels along the track and further liquid plaster from the bucket 25 is poured into the mould 15 so as to embed the plugs 20 and fill the spaces therebetween until the mould is filled. The liquid plaster is then screeded evenly across the open top of the mould 15. Finally a further layer of chopped glass rovings is applied to the upper surface of the wet mix and suitably rolled into the mix by means of a manual roller 30 (a procedure which is well-known in the art).

After setting of the wet mix, the plug extraction device 21 is used to remove the internal plugs 20 from the mould 15, the extraction device 21 being actuated so that its gripper

bar or rail 31 along with the plugs 20, is initially retracted a short distance horizontally sideways away from the mould 15, such movement being sufficient to break the bonding between the set plaster material and the surfaces of the plugs 20. After such initial separation, the gripper bar or rail 31 is retracted a relatively long distance so that the plugs 20 are fully withdrawn from the mould 15, the plugs 20 passing through correspondingly shaped openings 32 formed in one of the longitudinal marginal walls 33 of the mould 15, (refer Fig 7(a)). With the plugs thus withdrawn, the mould 15 is transferred from the carriage 16 to a tilt transfer table 35 rotatably mounted on a support frame 36 which is located opposite to the extraction device 21 on the other side of the tracks 17 (refer Fig 5). The tilt table 35 is then tilted through approximately 90° (refer Fig 6), the panel ejected from the mould 15 and transferred to a mobile rig (not shown) which transfers the panel to a drying rack (not shown) .

The carriage 11 can then return to its original position ready to repeat the same procedure.

Referring again to Fig 5, the transfer of the mould 15 to the tilt table 35 is assisted by a series of freely rotatable, elongate support rollers 38, 39 mounted on top of the carriage 16 and tilt table 35 respectively. The mould is drivingly rolled across the rollers 38 by means of a series of link chains 40 attached to the underside of the base of the mould 15, each chain 40 cooperating with a drive sprocket 41 drivingly coupled to a motor (not shown) .

Referring to Fig 6, the tilt table 35 has an offset pivot shaft 42 which is journalled for rotation in frame 36, the rotation of the table 35 being effected by means of two or more separate cables 43 (one only being shown) each of which passes around a respective part-circular segment 44 secured

to the underside of the table 35 and around a 2-way winch drum 45 which in turn is drivingly coupled to a motor 47. The table 35 is provided with a counter weight (not shown) in order to counterbalance its upward tilting movement.

Once the tilt table 35 is in its almost vertical tilted position, three of the side walls 48 of the mould 15 are hinged outwardly to facilitate the removal of the moulded panel from the mould 15 and its transfer onto the mobile rig.

Referring to Figs 3 & 4 of the drawings, the metal plate-like blades 23 of the glass retention device 22 which temporarily restrains the glass fibres laid in the mould 15 whilst the plugs are being inserted, are supported by an overhead frame

50 which in turn is mounted to an overhead support structure

51 by means of pneumatic rams 52 which operate to raise and lower the frame 50 along with the blades 23. In this embodiment, each of the blades 23 is spring-loaded by means of a coil spring 54 which extends between the blade carrier 55 and the mounting frame 50, this being effective to produce a cushioning effect when the blades 23 are lowered into the mould 15 and engage the base wall thereof.

Referring again to Figs 7(a) & (b), the plug insertion and extraction device 21 has its gripper bar 31 secured, eg by welding, to one or more links of a series of lengthwise extending, heavy duty roller chains 58 spaced across the width of the device 21 and each of which is driven by a motor 59 via a drive belt 60. A support roller 62 which is mounted at one end of a pneumatic ram (not shown) for vertical up and down movement, is used to support the leading end of each plug 20 as the plugs are inserted, the roller 62 being lowerable to allow the gripper bar 31 to make its full traverse to a position adjacent the side 33 of the mould 15.

The gripper bar 31 is provided with a jaw which defines an internal T-shaped slotted opening 64 extending along the

length thereof for releasably engaging the ends 65 of the plugs 20. The ends 65 of the plugs slidingly locate within the opening 64 as the mould, with the plugs inserted, undergoes its pass of the stationary bar 31.

The plug ends 65 disengage from the jaw of the bar 31 when the mould moves along the tracks in a direction away from the bar 31.

When the plugs 20 are to be extracted, an hydraulic ram (not shown) is used to effect initial retraction of the gripper bar 31 along with the plugs 20, away from the mould 15, the gripper bar 31 and the plugs 20 thereafter being fully retracted by means of the roller chain assembly 58. It will be appreciated that significant forces are required initially to break the bonding between the set plaster and the internal plugs 20 and this is achieved in this embodiment through the use of a horizontally mounted power ram (not shown) to which the gripper bar 31 is mechanically connected.

As shown in Fig 7(a), each of the plugs 20 has a central boss or projection 67 on its leading end face which is arranged to locate in a hole 68 formed in side wall 48 of the mould 15 when the plug is fully inserted. In some cases, it may be desirable to use bolts which are inserted through the holes 68 (from outside the mould) and which threadably engage in tapped bores formed in the projections 67. This ensures that the plugs 20 are firmly retained in position during the moulding procedure.

A brief consideration of the above described embodiment will indicate that the invention provides a vastly improved method of production of a building panel in a very low cost effective manner, with the panel being formed with a finished surface ready for painting, wallpapering or the like.