Background of the invention Portable structures can be used for a number of purposes including the erection of poles, posts, signs or banners and in conjunction with longitudinally extending frame members such as stairs, scaffolding and portable buildings.

Scaffolding provides a temporary platform and can be used for many purposes including the following: in the construction of buildings; as a base for supporting labourers working on an external building face; in the internal renovations of buildings ; While portable buildings can be used as sheltered hospitality and entertaining areas; * temporary extensions to existing buildings or structures; temporary accommodation or storage facilities; site offices or remote field stations; sheltered Information and trade display areas.

Typically, the framework of a portable structure is erected on steel plates fixed to the ground by anchoring stakes, or in the case where the structure is erected over concrete or asphalt surfaces, it may be secured to the surface with loxens.

However known designs of such portable structures have a number of disadvantages. In the case of more complex structures with longitudinally extending frame members the beams are connected together by aligning adjacent holes in the end of the beams and

passing bolts or pins and hence the beams are held in position by tightening a nut to the bolts or some form of locking clip to the pins. The final sub structure is rigid and needs to be erected perpendicular to level surface. Since the framework is often fixed to the steel plates which engage the ground, the steel plates need to be placed on ground that is substantially level.

However, portable structures may need to be erected in less than ideal circumstances and on ground that is far from level. The ground can be sloping or consist of mounds, potholes, gutters and other depressions.

The problem is magnified in emergency situations where the level ground may be unavailable because it is subject to the effects of flood or fire.

Typically portable structures may need to erected in situ, often by labourers who lack the requisite skills of an engineer and are unable to adjust for construction on uneven or graded ground. Construction may not only prove difficult to coordinate but may ultimately prove dangerous as segments need to be manually propped up as the structure begins to take shape.

Further, even if it is possible to erect the temporary structure on a sloping surface, the redistribution of stress acting on the connecting bolts as a result of the prevailing gradient may place extreme stress on these components. The connecting bolts may not be able to tolerate such stress and as a result the portable structure may become unstable and more likely to fall.

A common solution to this problem is to place wooden blocks or bricks under one or more steel plates of the portable structure. However, particularly in emergency situations, suitable blocks or bricks may not be available.

Furthermore even if suitable blocks can be found, an unstable erection may eventuate.

The blocks or bricks may, over a period of time slide in relation to the temporary structure or even may buckle under the sheer weight of supporting the portable structure.

Another obvious solution is to level the ground by means of a bulldozer or similar earth moving device. However, this is time consuming and costly and to some extent defeats the benefit of a portable structure. Furthermore, a suitable earth moving device may not

be available at the time of erection or it may not have the required access to the erection site. This alternative would be particularly impractical in times of emergency.

Object of the invention It is an object of the present invention to ameliorate the limitations of current temporary structures by providing a simple to operate system for erecting a portable structure on uneven ground.

Summary of the invention According to one form of the invention a connecting system for releasably connecting a first structural member and a second structural member together is provided comprising: (a) a first connector of adjustable length having (i) an end locatable in or on an end of the first structural member and (ii) another end defining a head section: and (b) a second connector having (i) an end locatable in or on an end of the second structural member; and (ii) another end defining a cavity to releasably retain the head section; wherein the head section is insertable in the cavity at a first orientation between the first structural member and the second structural member and retained therein upon movement of the first structural member and second structural member from that first orientation.

The second connector is preferably rotatable relative to the structural member to which it is attached to permit the first and second structural members on connection to be rotated relative to one another.

The first connector may be integral with the first structural member. The second connector may be integral with the second structural member.

Typically the first connector has a stem intermediate its ends. The stem may be receivable in a channel formed in the second connector to assist in positioning or otherwise locating the head section in the cavity of the second connector. Typically in

this form of the invention a plane of the first structural member is substantially parallel with a plane of the second structural member at the first orientation. Where a structural member comprises a beam, the plane is typically an axial plane of the beam. Where a structural member comprises a substantially planar support plate, the plane is typically the plane of the plate surface.

In one preferred form of the invention, the beam is movable from a first position where an axial plane of the beam is substantially parallel to the plane of the support plate and the stem is aligned in the channel, to a second position where the respective planes are substantially non-parallel.

In one preferred form of the invention the first connector is pivotable relative to the second connector to allow the angle between the first and second structural members to be varied.

The head section of the first connector is preferably retained by the cavity in positions other than when the axis of the first structural member is disposed at substantially 90° to the axis of the second structural member.

The head section is in this embodiment preferably retained by reason of its relative dimensions in the cavity by a wall having an inwardly projecting lip extending at least partly about the periphery of the cavity. This arrangement is such that the inner dimension of the periphery of the cavity is less than the external dimension of the head section in positions other than when the axis of the first structural member (such as the longitudinal axis of a beam) is disposed at substantially 90° to an axis of the second structural member (such as the axis of rotation of a support plate). Accordingly when the first and second structural members are on connection moved relative to one another they are maintained in a connected state by reason of the retention of the head section by the cavity.

A first connector according to the invention may be permanently retained in the cavity of the second connector.

In another preferred form of the invention, at least one projection is provided on one of the connectors, the projection being locatable in a recess in the other of the connectors to prevent the head section of the first connector from rotating axially when the head

section is inserted in and retained in the cavity of the second connector upon movement of the first structural member relative to the second structural member. In one particularly preferred aspect of this form of the invention, a pair of projections are provided on one of the connectors for location in a corresponding pair of recesses in the other of the connectors to prevent the head section of the first connector from rotating axially when the head section is inserted in and retained in the cavity of the second connector upon movement of the first structural member relative to the second structural member. Typically a, or each, projection is provided on the first connector and a, or each, recess is provided in the second connector.

The first connector may comprise a body portion and a pair of wings, at least part of the body portion and said wings being receivable in complementary parts of the first structural member for attachment of the first connector to the first structural member.

Adjustment of length may be achieved according to the invention by means of a threaded section carried by the first connector to permit axial rotation of the beam relative to the first connector.

The threaded section may be receivable in the body portion and be rotatable relative to the body portion when the body portion is received in a complementary part of a structural member according to the invention.

Typically one of the structural members comprises a beam and the other of the structural members comprises a support plate, although it will be appreciated that both structural members may comprise beams.

In a preferred form of connecting system according to the invention, the male member and female member have irregular complementary cross-sectional shapes.

In a further preferred form of the connecting system the irregular shape of the male member's head section is semi spherical.

In a further preferred form of the connecting system the irregular cross-sectional shape of the female member is concave.

In another preferred form of the invention, a projection from the male member locates in a recess in the female member to coordinate rotation between the male member and the female member.

According to another form of the invention, a two-part connecting system for releasably connecting a first structural member to a second structural member is provided, comprising a first connector attachable to one of the structural members and a second connector attachable to the other of the structural members, the first connector having a head section adapted to seat in a cavity of the second connector and be retained therein on movement of the first structural member relative to the second structural member, so as to vary the angle between the structural members by said relative movement, and adjustment means being provided by one of the connectors so as to vary the distance between the structural members as desired.

In this embodiment the first connector may be integral with one of the structural members. The second connector may be integral with one of the structural members.

According to another form of the invention a two-part connecting system for releasably connecting a beam to a substantially planar support plate is provided, comprising a first connector attachable to the beam and a second connector attachable to the support plate, the beam and support plate being pivotable relative to one another by said connection, the first connector having a head section and at least one projection, the second connector having a cavity for receiving the head section and at least one complementary recess for receiving the or each projection, the recess and projection arrangement being adapted to limit the degree of axial rotation of the head section when the head section is received in the cavity, the head section adapted to seat in a cavity of the second connector and be retained therein on movement of the beam relative to the support plate so as to vary the angle between the structural members by said relative movement.

According to another form of the invention a structure is provided comprising a plurality of structural members having at least one pair of structural members connected in accordance with a connecting system as described herein.

The structure may be a temporary or demountable structure.

Description of the drawings The invention will now be further explained and illustrated by reference to the accompanying drawings in which:

Figure 1 is an example of a framework erected on a steel plate in accordance with the prior art.

Figure 2 is a side view of a male member according to one embodiment of the present invention.

Figure 3 is an end view of the male member depicted in Figure 2.

Figure 4 is a perspective view of a connecting system according to one embodiment of the invention in a position ready for connection.

Figure 5 is a partially cut-away side elevation of the connecting system of Figure 4.

Figure 6 is a partially cut-away side elevation of the connecting system in a raised position.

Figure 7 is a perspective view of the current invention as it is erected on depressed ground.

Referring to Figure 1, a conventional beam 1 is depicted according to the prior art. The beam 1 is welded on to a steel plate 2 which can be fixed to the ground by anchoring stakes.

In a preferred example of the invention as depicted in Figures 2 and 3, the male member 4 has a body portion 5 which is cylindrically shaped and extending from it are wings 6 and 7. The wings form the attachment between the male member 4 and the beam 3.

Also extending from the cylindrical body portion 5 is a threaded neck section 8 having a head section 9. The length of the threaded neck section 8 can be easily adjustable in relation to the cylindrical body portion 5 by rotating it either clockwise or anti clockwise. The head section 9 is of a generally semi-spherical portioned shape and has two corresponding projections 10 and 11 which are designed to be located in recesses to fix the male member 4 against rotation when the male member is in the locked position.

The current invention is adapted to be used with, or in conjunction with, the beam 3 of a temporary structure as described above. The male member 4 is designed to be located in an end of a beam 3 as shown in Figures 4 to 6. Typically it may be fixed into such a beam by punching extensions from the beam.

As can be seen from Figures 4 to 6, the female member 12 has a body 13 of generally cylindrical shape and is mounted on a protruding circular base (not shown). As shown in those Figures, the base allows the female member 12 to be located within a support plate 14 by welding a corresponding cap 15 over the base (not shown). The cap 15 allows the female member 12 to rotate axially within the cap 15 and simultaneously attaches the female member 12 to the support plate 14.

The body 12 has a generally concave inner surface 16 (as shown more particularly in Figure 6) and corresponding recesses 17 and 18 are provided to be engaged by the projections 10 and 11 of the male member 4, while a channel 19 is provided to specifically cater for the threaded neck section 8 of the male member 4. It can be seen from Figure 4 that by virtue of the concavity of the inner surface 16 of body 12 an inwardly projecting lip 13a extends at least partly about the periphery of the wall. In practical terms this means that the head section is retained by the cavity in positions other than when the longitudinal axis of the beam is disposed at substantially 90° to the axis of the support plate.

The sequence of connecting the male member 4 as installed in a beam 3 to the female member 12 as located in a support plate 14 is depicted in Figures 4,5 and 6. In Figure 5 the male member 4 as installed in the beam 3 is lowered substantially parallel to the support plate 14 so that threaded neck section 8 and projections 10 and 11 are aligned with the channel 19, and recesses 17 and 18 as shown in that Figure. The beam 3 can then be raised perpendicular to the support plate 14 to a locked position as clearly shown in Figure 6. In this position the threaded neck region section 8 is no longer aligned within the channel 19 and the head region 8 is pivotally retained within the concave interior 16 of the female member 12. In this final stage of connection the invention works as a ball within a socket. As a result the beam 3 is anchored to the support plate 14 but at the same time can be pivotably moved in relation to the support plate.

This arrangement can then be used to erect a temporary structure on uneven ground.

As shown in Figure 7 the invention can be used when the beam 3 is required to be placed on sloping ground. The support plate 14 can engage the ground according to the prevailing gradient and the support beam 3 can be raised pivotally in relation to the

support plate 14 so that it can be held at a angle substantially perpendicular to the horizontal plane of the uneven ground.

The beam can then be rotated relative to the plate to lengthen or extend the threaded neck section 8 of the male member 4. This will in turn"lengthen"the beam 3 so that the temporary structure can be erected as if all beams were placed on substantially level ground.

In instances where the temporary structure is more complex in nature and comprises a series of parallel frames which are inter connected by longitudinally extending frame members (scaffolding or portable buildings) a support plate 14 can be placed on a raised area and to compensate for the raised beam a corresponding beam can be suitably "lengthened"to ensure that the longitudinally extending frame members run parallel to the horizontal plane of uneven ground.

Hence by using the invention on all the support plates a more complex temporary structure can be erected as if all beams where placed on substantially level ground.

It will appreciated that by using the above sequence a temporary structure can be erected on ground that is uneven by adjusting the length of the beams by the above sequence. It will also be appreciated that by using the components of the invention it is possible to provide a quick and easy means of erecting a temporary structure without the need for tools, machinery or the requisite skill required to level the ground on which it is erected.

Temporary structures incorporating the invention may be quickly erected on uneven ground making them ideal for crisis situations.

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