Background of the invention Whilst the following discussion illustrates the press as used for manufacture of pre- fabricated building components in particular Posi Joists, it is to be understood that the press may be used in other engineering applications.

Traditionally, trusses that are destined for the building industry may be constructed on-site or prefabricated. Pre-fabricated trusses of standard designs are very popular as they can be mass-produced by passing the assembled components between a press which fixes the components together at appropriate locations.

Another existing method of making a truss is to (a) locate two timber cords (top and bottom) into a jig and spaced at the appropriate distance apart (b) place the metal web components (posi struts or multi struts) between the cords and (c) using a platen, imbed the nail plates (that are inbuilt in the struts) into the timber. The equipment required to do this is a layout table (lower platen) with a travelling press (upper platen) that moves across the table, stops, presses, accelerates to the next point, stops. re presses. This cycle is repeated until all components are pressed. This truss is referred to in the industry as a steel web truss. One form of this truss is sold under the name of Posi Joist. These trusses have several avantages over solid joists including: <BR> <BR> <BR> <BR> allowing plumbing and electrical conduits and other services to be run between the struts or webs; <BR> <BR> <BR> providing additional width and a larger span for fixing flooring :<BR> <BR> <BR> <BR> <BR> <BR> eliminating or reducing the need ior internal load bearing walls or stumps : and<BR> <BR> <BR> <BR> <BR> <BR> <BR> the elimination of shrinkage problems associated w ith solid wood.

The problem associated with the current technology is that the continual stop start operation results in a relative high pressing time (approximately 50 seconds per 8 meter truss).

One other known fabrication technique uses a roller press that completes this task for wood joists. The upper platen is a roll that rolls over the truss assembly and applies the necessary pressure to force the nail plates into the components. However. a simple roller press is unsuitable for posi joists. The reason for this is that the steel components of the posi struts will deflect under the process of rolling and cause permanent deflection. Whilst this would not be a problem in tension members. it is a problem for compression members which rely upon their web structure to withstand inward compression forces. Therefore a simple rolling process is unsuitable.

Object of the invention It is an objective of the present invention to provide a press which ameliorates one or more of the above problems.

Summary of the invention Accordingly there is provided a press for fabrication of building components comprising: (a) an upper platen and a lower platen defining a gap therebetween; (b) at least one graded track system locatable on one of the platens comprising: (i) at least two spaced rollers; and (ii) a continuous belt engaging and movable with the rollers; wherein the rollers are arranged so that the continuous belt is inclined at an angle to the other of the platens so that the gap narrows as the building components move between the platens; and (c) a drive to actuate the continuous belt.

The rollers can be of the same or different diameters. The disposition of the rollers to create an inclined surface will depend on the diameter of the rollers.

Preferably, the upper platen and lower platen are movable relative to one another. More preferably, both the upper platen and lower platen are movable.

Preferably, there are two spaced graded track systems which are parallel to each other. In this arrangement. the press only contacts the nail plates and timber cords, thus minimizing deformation of the truss web.

Preferably, the graded track system further comprises an adjuster to alter the vertical disposition of the rolls relative to one another. In this way. the inclined continuous belt may be adjusted so it may adopt an opposite inclination or a pair of oppositely inclined surfaces.

In another preferred embodiment of the invention, the graded track system is pivotably mounted so that the inclination of the continuous belt may be adjusted or reversed.

Typically, hydraulic cylinders are used to adjust the inclination.

In another preferred form of the invention, the graded track system has three rollers, the central roller of which extends below the other two rolls. In this arrangement the continuous belt has a pair of oppositely inclined surfaces.

The continuous belt can be fabricated from various materials including rubber or metal strips. Another option is to use conveyor chains. If conveyor chains are used then the rollers can be gears which engage the conveyor chain to turn it.

Preferably, the graded track system further comprises one or more supports between the rollers. The supports inhibit the tendency of the continuous belt to move away from the building component and therefore causes the building component to be subjected to a more consistent and continuous pressure. The supports may be a series of support rollers or a support rod.

If the continuous belt is fabricated from conveyor chains and the graded track system has a support between the rollers, it is preferable for there to be friction reducing modifications.

For example. the protrusions on the conveyor chain could be reduced so that they do not rub against the supports. Alternatively, the supports could further comprise a continuous belt.

At least one of the inclined surfaces is, in use, inclined towards the truss to be fabricated.

The incline is typically just sufficient to allow the nail plate on the fabricated truss, to engage the lower and upper platen from zero to full pressure on the inclined surface. As the press proceeds, a continuous gradient of increasing pressure is imparted to the truss until the nail plate is fully fixed. This technique results in less deformation to the truss web.

Typically, the driver is either electric or hydraulic in nature.

In another aspect the invention provides a method for fabricating a building component comprising: (a) positioning nail plates of webbing in contact with joists to form a loose assembly; and (b) feeding the loose assembly through a gap formed between a pair of platens to press the nail plates into nailing securement with the joists wherein at least one of the platens comprises at least two spaced rollers and a continuous belt engaging and movable with the rollers and the rollers are arranged so that the continuous belt is inclined at an angle to the other of the platens so that the gap narrows as the building components move between the platens.

Description of the drawings The invention will now be further explained and illustrated by reference to the accompanying drawings in which: Figure 1 is a perspective view of a Posi Joist building component; Figure 2 is a simplified front view of a first form of a press according to the invention; Figure 3 is a side view of the press of Figure 2 along pathway A illustrating a first form of a graded track system; Figure 4 is a side view of a press illustrating a second form of the invention; Figure 5 is a side view of a press illustrating a third form of the invention; Figure 6 is a side view of a press illustrating a fourth form of the invention; Figure 7 is a side view of a second form of a graded track system; Figure 8 is a side view of a third form of a graded track system; Figure 9 is a side view of a fourth form of a graded track system; Figure 10 is a side view of a fifth form of a graded track system; Figure 11 is a partial side view of the graded track system of Figure 9;

Figure 12 is a perspective view of the continuous belt of the graded track system of Figure<BR> <BR> <BR> <BR> <BR> <BR> 9 : Figure 13 is a top view of the graded track system of Figure 2; and Figure 14 is a top view of a sixth form of the graded track system.

In the drawings like elements are designated by the same numbers.

Figure 1 is a perspective view of the Posi Joist building component 1. Nail plates 2 are located on the external edges of the webbing 3. These nail plates 2 are embedded in to the external edges 4 and 5 of the parallel timber joists 6 and 7 to firmly secure the joists in relation to each other to form the building component 1.

As shown in Figure 2, a press 8 has an upper platen 9 and a lower platen 10. Both platens 9 and 10 are movable towards one another by an electric motor (not shown).

As more particularly illustrated in Figure 3, the upper platen (not shown) has two downwardly extending arms 12. Spanning across the two arms 12 is a graded track system 13. The graded track system 13 has a front roller 14 and a rear roller 15 which are both enveloped by a continuous belt 16. The lower surface of the front roller 14 is vertically displaced upwardly from the lower surface of the rear roller 15 so as to create an inclined surface on the belt 16.

As seen in Figure 3. the continuous belt 16 about the front roller 14 initially engages the upper surface of component 1. The front roller 14 is displaced upwardly at a level just above the nail plate 2 located upon the upper surface of component 1. The continuous belt 16 applies an increasing gradual pressure to the nail plate 2 and associated portions of the upper surface of the component 1. The process continues until the influence of the continuous belt 16 about the rear roller 15 ceases as the component 1 moves to the right.

It will be appreciated that with this arrangement, the graded track system 13 has been caused to pass in an incremental way over the building component 1. The fixing pressure is transferred through the continuous belt 16 to apply sustained and gradually increasing pressure upon the building component 1. Consequently, the webbing 3 of the building component 1 is safeguarded against deflection. The completion of this process allows the webbino 3 to be fully fixed to the parallel wooden joists 6 and 7.

The assembled building component I can then be removed. a partially assembled building component 1 placed in the press 8, and the process repeated until the required number of building components are fabricated.

In Figure 4, the press 17 has a graded track system 18 pivotally locatable upon the upper platen (not shown). The pivotal attachment 20 allows the track system 18 to pivot in relation to the press 17 by actuating hydraulic cylinders (not shown). The activation of the hydraulic cylinders allows the gradient of the track system 18 to be varied and even reversed. Consequently, press 17 is adapted to accommodate building components 1 of different thickness and have building components 1 fed to it from either the left or right hand sides of the press 17. <BR> <BR> <BR> <BR> <BR> <P>In Figure 5, the press 22 has a graded track system 23 pivotally locatable upon each arm 24 of the upper platen (not shown). The pivotal attachment (not shown) allows each track system 23 to be pivoted in relation to the press 22 by actuating hydraulic cylinders (not shown). The activation of the hydraulic cylinders allows the gradient of each of the track systems 23 to be varied and even reversed. Consequently, press 22 is also adapted to have building components 1 fed to it from either the left or right hand sides of the press 22 and to accommodate building components 1 of different thickness.

In Figure 6, the track system 26 comprises a front roller 27 and rear roller 29 of similar diameter. and a central roller 28 of larger diameter. The lower surface of central roller 28 is vertically displaced to the lower surfaces of rollers 27 and 28. The continuous belt 30 envelopes each of these rollers and is typically fabricated from metal strips (not shown) which are linked together. In this arrangement the belt 30 will have two oppositely inclined surfaces 32 and 33 which adapts it to use in a press which may be fed with components 1 from either side of the press.

Figure 7 illustrates a graded track system 40 further comprising a support 41 between the rollers. The support 41 consists of a support rod. Figure 8 illustrates a graded track system 42 further comprising a support 43 which consists of support rollers. The supports 41 and 43 prevent the continuous belt 30 from moving away from the building component 1 and cause the graded track systems 40 and 42 respectively to provide a constant and consistent pressure.

Figure 9 illustrates a graded track system 44 with a continuous belt 45 fabricated from conveyor chains. Figure 10 illustrates a graded track system 46 with a continuous belt 47 fabricated from a plurality of slats 60 arranged perpendicular to the direction of travel on the continuous belt 47. The slats 60 are mounted on continuous chains or mesh 61 forming a part of the continuous belt 47.

Figure 11 is a detailed view of the graded track system 44 as building component 1 enters the press. Figure 12 is a detailed view of the conveyor chain making up the continuous belt 45. Due to the fact that continuous belt 45 consists of chain links 58 connected together such that gaps 57 are formed between the chain links 58, the roller 55 can have teeth 56 to engage the continuous belt 45 to turn the continuous belt 45.

Figure 13 illustrates that the graded track system 13 in Figure 3 fully spans component 1 in operation and contacts all of web 3. Figure 14 illustrates a press 50 with two graded track systems 51. Graded track systems 51 are of a size to apply sufficient pressure to nail plates 2 and embed them in joists 6 and 7. However, graded track systems 51 do not span across component 1 and therefore the deformation of the web 3 by the press 50 is minimized.

The word'comprising'and forms of the word'comprising'as used in this description and in the claims does not limit the invention claimed to exclude any variations or additions.

Modifications and improvements to the invention will be readily apparent to those skilled in the art. Such modifications and improvements are intended to be within the scope of this invention.