BACKGROUND TO THE INVENTION Scaffolding is commonly used in construction and other industries to provide a stable framework or platform upon which workers may stand. Scaffolding or similar frames may also be used to provide a tower or assembly for location of equipment or the like; for example, film or television cameras, lighting rigs, antennas, and the like.

Conventional scaffolding is simply a framework of individual lengths of tubing together with various connector pieces and the like assembled on site as needed. While this provides great flexibility in the structures which can be assembled, this is also labour- intensive, and can take some time to erect. Much time is lost erecting scaffolding, as well as transporting the individual scaffolding elements to the site. It is therefore desirable to provide a more rapid, easily-assembled scaffolding arrangement.

A number of alternative arrangements are known. For example, a mobile scaffold tower may be provided which consists of a number of modular scaffolding units, which may be stacked on top of one another to form a scaffolding tower. Such a device is described in GB7433I1 ; a more complex scaffolding tower erection device is described in GB2170180. However, construction of such a tower still requires a number of skilled workers, a significant amount of time, and transport of the scaffolding modules to the place of assembly. Problems may also arise from the use of excessive force to combine or to separate the components, or from the components being dropped from height.

One solution to some of these problems is the use of collapsible scaffolding which is provided as a single unit. The unit may be transported to the site as a single

component, and assembled rapidly on site without the need to join component parts.

GB2251019 describes such an unfolding scaffolding system; however, this system is only suitable for work at low levels. Hydraulic lifting platforms may instead be used, which provide a platform mounted above an extendable hydraulic'scissor'assembly to raise and lower the platform. One such device is described in GB2067513. Such platforms tend however to be expensive and heavy ; further, the user typically remains on the platform while being raised or lowered, an arrangement which creates a number of safety issues. In addition, such platforms typically only provide a single working surface on the platform, and so are not as flexible as scaffolding.

A further extensible scaffold frame is described in GB2022672, having fixed vertical rods along which slide horizontal crossbars. The crossbars are joined by a lazy tongs arrangement which is operated by a screw jack arrangement to raise or lower the crossbars. The lazy tongs are spring-biased to the extended position.

Other adjustable scaffold devices are described in W002/099225, having telescopic upright frame members ; GB1410274, being horizontally adjustable to conform to the curve of a ship's hull; GB2078288, being adjustable to sit on a staircase ; and GB939850, having an unfoldable bracing structure.

It is an object of embodiments of the present invention to obviate or alleviate these and other disadvantages of known scaffolding arrangements.

SUMMARY OF THE INVENTION According to a first aspect of the present invention, there is provided a collapsible scaffold assembly, the assembly comprising a plurality of connected frame members defining a frame element, the frame members being relatively movable to permit adjustment of the frame element, and an adjustable flexible tension member extending between at least two of said frame members, the tension member being operatively associated with the frame members such that adjustment of the tension member causes relative movement of said at least two of said frame members.

In use, therefore, the scaffold assembly of the present invention may be erected from a collapsed state by adjusting the tensioning of the tension member to cause movement of the frame members to alter the conformation of the frame element. It is adjustment of the tension member itself which results in movement of the frame members. Such an assembly is intended to be relatively straightforward and rapid to

erect, and to be erectable with fewer skilled workers than conventional scaffolding.

During erection of the scaffold assembly, the effective length of the tension member may be decreased, to increase tension in the member and to move the frame members into an erect configuration. Further, the use of a flexible tension member allows greater freedom in the arrangement of the member and in the tensioning or releasing of the member.

Preferably the assembly further comprises first and second pulley members operatively associated with the frame members and the flexible tension member. This arrangement allows for the action of the tension member to be multiplied over the pulleys, and allows a greater effective length of tension member without increasing the overall size of the assembly.

Preferably the pulley members and the tension member are arranged such that an increase in tension in the tension member acts to provide a force on the pulleys tending to drive the pulleys apart.

Preferably the first and second pulleys are mounted to first and second relatively movable rigid members, the rigid members being mounted to the frame members. The rigid members may be hollow, and the pulleys disposed within the rigid members.

Conveniently the rigid members extend along the main axis of collapse of the assembly; that is, if the assembly generally extends and collapses along a vertical axis in use, the rigid members extend along this axis. Alternatively, the rigid members may extend between opposite comers of a quadrilateral or other structure defined by the frame element.

Preferably the assembly further comprises locking means for restricting adjustment of the tension member. The locking means may be used to prevent excessive tension being exerted on the frame members by the tension member; such excessive tension may otherwise cause the frame element to deform beyond a desired state and to become unstable. The locking means prevents tension above a desired level being exerted on the frame members, such that the assembly may be erected with minimal skilled intervention.

Preferably the frame members are hinged to one another, to restrict relative movement of the frame members to a predetermined plane. This allows for more predictable movement of the frame members when the assembly is being erected or collapsed. Certain of the hinges may have their range of possible movement limited; for

example, to prevent the frame element from being collapsed in a particular direction.

Again, this serves to improve stability of the frame element and to increase the predictability of its movement.

Preferably the frame element has a generally quadrilateral structure. This arrangement allows the frame element in the erected configuration to include a pair of upright members and a pair of horizontal members. Each frame member itself may also be of a generally quadrilateral form ; thus, the whole frame element when erected may have a generally cuboidal structure.

The assembly may further comprise one or more locking members mounted to the frame element which are engageable to prevent or restrict movement of the frame members. The locking members may also serve as locking means for restricting adjustment of the tension member. The locking members are preferably movably mounted to the frame, to permit relative movement therebetween. The locking members may also or instead be movably mounted to one another. For example, paired locking members may be hinged to one another with the hinge being lockable to prevent relative movement of the members and so lock them together. The locking members may extend across the frame between frame members. Conveniently one or more pairs of locking members are provided, the paired members being engageable. Preferably the locking members are rigid members; conveniently rigid hollow members. These rigid hollow members may have pulleys disposed therein which are operatively associated with the flexible tension member.

In an alternative arrangement, the locking members are preferably mounted on the tension member to provide a sleeve thereon ; the tension member conveniently is freely received within the sleeve. This sleeve arrangement is preferred since it allows for the locking members to be maintained in alignment with one another. The sleeve may also serve to protect the tension member from damage or wear. Preferably also the locking members are mounted to the frame such that the tension member extends between the mounting locations. This further assists in maintaining the locking members in alignment with one another, and causes the locking members to move toward one another and to engage when the frame members are moved relative to one another by tensioning of the tension member.

Preferably a portion of one locking member of each pair may be received within a portion of the other locking member. Conveniently cooperating male and female

portions may be provided on the locking members to assist in guiding the members towards one another and in ensuring alignment of the locking members.

Where the locking means comprises paired engageable rigid members, the locking means may further comprise fastening means for releasably fastening pairs of members together. This allows for the locking members to be fastened in a particular position to prevent disengagement of the locking means and unwanted movement of the scaffold assembly. The fastening means may comprise a fastening pin or the like which may be inserted into each member of a pair.

Preferably the assembly comprises a plurality of frame elements, to provide a repeated structure. For example, each frame element may have a generally quadrilateral form, and the entire assembly may comprise two, three, or more quadrilateral frame elements to provide a stacked tower configuration. This arrangement provides for assemblies to be produced having a repeated structure of a desired maximum height.

The frame elements preferably share a common tension member ; thus, adjustment of the common tension member will be sufficient to erect or collapse each frame element.

Preferably the assembly comprises retaining means for restricting erection of a selected frame element. For example, the assembly may comprise a locking bar or the like which may be secured to upper and lower frame members of a frame element to prevent erection of that element. This allows for an assembly of several elements to be erected only to a restricted height ; for example, a locking bar may be secured to the lowermost element of an assembly of three frame elements. The upper two elements will therefore be erectable, to provide an assembly of lower height than if all three elements were to be used. It is preferred that the lowermost elements of an assembly are restricted, to provide greater stability to the erect assembly.

The assembly may further comprise one or more resilient members mounted to the frame members. The resilient member may comprise a spring or the like ; conveniently an elastomeric spring. In preferred embodiments of the invention, two types of resilient member are provided: a first type is arranged to be compressed by two or more frame members when the assembly is in the collapsed configuration, while a second type is arranged to be compressed by two or more frame members when the assembly is in the erect configuration. For example, with a quadrilateral frame, resilient members of the first type may be mounted to the lower horizontal frame member so as to contact the upper horizontal frame member when the assembly is collapsed, while the

second type of resilient member may be mounted in a corner between upright and horizontal frame members such that it is under compression when the assembly is in the erect configuration. The first type of resilient member provides a force tending to assist in the erection of the assembly, so reducing the initial tension needed on the tension member, while the second type aids in the initial collapse of the frame away from the erect configuration.

The assembly may comprise a single tension member, extending across all frame elements, or may comprise a plurality of tension members. In certain embodiments, two or more tension members may be provided, each of which extends across all frame elements ; this provides for redundancy and additional security to the assembly. Each such tension member may be provided in the same location (for example, within a single sleeve or the like), or may be provided in different locations on the assembly.

Preferably the assembly further comprises tensioning means for adjusting the tension in the tension member. Conveniently the tension member is a cable, rope, chain or the like, and the tensioning means comprises a winch or the like. The tensioning means may comprise a motor for actuating the tensioning means.

Preferably the assembly is transportable. For example, the assembly preferably further comprises ground-engaging wheels, rollers, tracks, or the like, for allowing movement of the assembly on the ground. The wheels or the like may be provided on a trailer within which the remainder of the assembly is mounted. The trailer may include means for securing the trailer to a vehicle. Thus, the assembly may be easily transported in the collapsed configuration by connecting the trailer to a vehicle. Alternatively, the assembly may be mounted on a vehicle. The assembly may further comprise braking means for preventing unwanted movement of the assembly. The assembly may comprise stabilising means for stabilising and providing support to a trailer or the like ; for example, the trailer may comprise one or more extendable legs for engaging with the ground.

Preferably the assembly further comprises additional scaffolding components.

For example, the assembly my comprise one or more of : ladders, platfonns, trapdoors, rails, barriers. These components are preferably integrated with the assembly in both the erect and collapsed configurations ; this allows the assembly to be provided in a

collapsed configuration with all components present, and then simply erected on site when needed.

According to a further aspect of the present invention, there is provided a collapsible frame element, the element comprising a plurality of connected frame members, the frame members being relatively movable to permit adjustment of the frame element, and an adjustable flexible tension member extending between at least two of said frame members, the tension member being operatively associated with the frame members such that adjustment of the tension member causes relative movement of said at least two of said frame members.

According to a further aspect of the present invention, there is provided a collapsible scaffold assembly, the assembly comprising a plurality of frame elements, each such element comprising a plurality of connected frame members, the frame members being relatively movable to permit adjustment of the frame element, and an adjustable flexible tension member extending between at least two of said frame members of each element, the tension member being operatively associated with the frame members such that adjustment of the tension member causes relative movement of said at least two of said frame members.

BRIEF DESCRIPTION OF THE DRAWINGS These and other aspects of the present invention will now be described, by way of example only and without limitation, with reference to the accompanying drawings, in which : Figure 1 shows a schematic illustration of a pantographic type construction, for background understanding of the present invention; Figure 2 shows a schematic illustration of two pantographic type elements ; Figure 3 shows two frame elements of a scaffolding assembly in accordance with an embodiment of the present invention ; Figure 4 shows a scaffolding assembly in accordance with a further embodiment of the present invention, in an erect configuration ; Figure 5 shows the assembly of Figure 4 in a partially collapsed configuration; Figure 6 shows the assembly of Figure 4 in a fully collapsed configuration ; and Figure 7 shows a schematic illustration of an alternative scaffold assembly in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS Referring first of all to Figure 1, this shows a schematic illustration of a pantographic type construction, useful for background understanding of the present invention. A pantographic construction is a jointed fiamework 10 including a number of rigid members 12 connected to form a parallelogram by hinged comer connections 14.

The shape that the framework adopts can be described by the distance X between any two points 16, 18 located on different rigid members 12; compare, for example, each of the positions shown in Figure la, lb, and lc, and the relative lengths of the distance X in each. Thus, the position of the framework can be controlled by regulating the distance X. If X is maintained at a constant length, the framework can no longer move, and a rigid structure results.

Figure 2 shows a schematic illustration of two pantographic type elements. The shape that the framework adopts can be described by the vertical distance Y between two points 116 and 118 located on different rigid members 12; compare, for example, each of the positions shown in Figure 2a, 2b, and 2c, and the relative lengths of the distance Y in each.

Referring now to Figure 3, this shows a scaffolding assembly 30 in accordance with an embodiment of the present invention. The assembly 30 comprises a pair of quadrilateral frame elements 32 including a number of rigid frame members 34 connected by pivoting hinges 36. Each rigid S'arne member 34 is itself a quadrilateral.

The frame members 34 may be steel, aluminium, or fibre reinforced plastic, among other materials.

A tension cable 38 is coimected to the frame members via a series of pulleys 39 and rigid tubular elements 41. The cable runs over the pulleys 39 which are themselves mounted to three tubular rigid elements 41 arranged adjacent one another. The two outermost rigid elements 41a, 41c are mounted to the lower horizontal frame member 34a and the upper horizontal frame member 34b respectively; the central member 41b is mounted to the outer rigid members via a tongue and groove sliding arrangement which allows relative vertical movement of the three members.

In order to erect the assembly 30, the cable 38 is tension via winch 43. This acts on the pulleys 39 to cause relative vertical movement of the rigid members 41a, b,

c, thereby increasing the distance between the upper and lower horizontal frame elements 34a, 34b, so bringing the frame element into a more rectangular configuration.

To collapse the assembly 30, tension in the cable 38 is lessened. The weight of the structure causes the rigid members to move together vertically, allowing the frame element to collapse.

In order to reduce the tension required in the cable when the assembly is in the nearly collapsed state, embodiments of the assembly may include compression springs 50 which are compressed between the lower horizontal frame member and upper horizontal frame member at low angles. This lowers the apparent weight of the upper horizontal frame member and reduces the tension needed to initially erect the scaffold.

Similarly, further compression springs may be provided which are compressed between the upper horizontal frame member and the upright frame member at high angles. These compression springs help prevent any free play in the erect position and aid in the initial collapse of the scaffolding by pushing the frame away from the stable upright position.

A further embodiment of the present invention is shown in Figure 4. This scaffold assembly 54 comprises a number of frame elements 32 as illustrated in Figure 3 stacked to form a scaffold tower. A single tension member 38 extends between all of the frame elements, with a vertical rigid member and associated pulleys for each element. Although in this embodiment, the pulleys are located on the outside of the rigid members, in certain embodiments of the invention the pulleys may be located within hollow rigid elements, with the tension member also located within the rigid elements.

In order to prevent movement of the frame members in the erect configuration a latching system in the form of lockable members 66, 68 is provided. One end of each member is rotationally connected to a respective one of the frame members 34. The latching system is hinged near the middle 69 with a lock permitting the hinge to be disabled, allowing the members to move relative to one another to allow assembly or collapse of the frame when not locked. An alternative arrangement of the latching system provides releasable catches at one or both of the connections to the frame members. Another alternative arrangement provides lockable members which engage with a telescopic connection, allowing relative movement thereof, with the telescopic connection being lockable to prevent relative movement.

The scaffold tower is located on a trailer body SG, which includes a pair of' wheels 58, a number of extendable supporting legs 60, and a towing attachment 62 for connecting the trailer to a vehicle.

The trailer body also carries a winch 64 attached to the tension cable 38. To erect or collapse the scaffold, the winch 64 is actuated in order to increase or decrease the tension in the tension member. Since a common tension member is used, and since all of the frame elements are connected, this will cause all of the elements to collapse or erect together. In embodiments of the invention, a lock such as a locking bar clamped to two horizontal frame members may be provided to prevent one or more of the frame elements from erecting in this way; this allows the scaffold to be only partially erected.

The scaffold assembly also includes a number of scaffold components ; these include working platforms, trap doors, and ladders formed by some of the upright frame members. These scaffold components are fixed to the frame elements, and so may be left in place when erecting or collapsing the scaffold. This allows for more rapid assembly and disassembly of the scaffold.

Figures 5 and 6 show stages in the collapse of the scaffold of Figure 4 to a fully collapsed configuration. In this configuration, the scaffold may be readily transported between sites, particularly when included with an integral trailer.

A further embodiment of the invention is shown in Figure 7. The assembly 130 comprises a quadrilateral frame element 132 including four rigid frame members 134 connected by pivoting hinges 136.

A tension cable 138 extends diagonally between the lower horizontal frame member 132 and the upper horizontal frame member ; the cable 138 is arranged to meet the frame members 132 at or in the same region as the pivoting hinges 136. The tension cable 138 is received within two sleeve portions 140, 142, each of which is pivotally connected to the lower and upper horizontal frame members respectively. The cable 138 is fixed within the upper sleeve portion 142, and freely movable within the lower sleeve portion 140. The sleeve portions 140, 142 include male 144 and female 146 portions which allow for the sleeves to be received and guided as they are brought together along the tension cable 138.

In order to erect the assembly 130, the cable 138 is tensioned. This brings together the two sleeve portions 140, 142, thereby reducing the distance between the corresponding points on the frame element 132. The frame element is brought into a

more rectangular configuration. The male and female portions of the sleeves ensure that as the sleeves are brought together, they are guided and received into one another. Once the sleeves are in contact, a flange 148 prevents further movement towards one another, so preventing further shortening of the cable 138 and further distortion of the frame element. In certain embodiments of the invention, a lock may be provided on the sleeves to secure them together and prevent unwanted release. In further embodiments of the invention, the male/female interlocking sleeve arrangement may be used purely as a locking means, in conjunction with the tension member as described above with respect to Figures 3 to 6. In still further embodiments the male/female connection may be extended such that they are in contact in all positions of the frame.

The joined sleeves may also act as a safety bar to help reduce accidents.

It will be seen that the present invention provides a scaffold assembly which is readily transportable, and may be erected or collapsed in a straightforward manner by relatively few skilled workers. Further, the inclusion of integral scaffold elements such as platforms and the like allows for less time to be spent on erecting scaffolding at each site.

It will further be understood that, although the present description is largely directed to use of the invention as scaffolding, the invention is not so limited. For example, frames of the present invention may be used to provide readily-erectable towers for mounting of equipment and the like.

It will also be appreciated that, although the invention has been described making use of a tension member, embodiments of the invention may use a compression member, for example, a hydraulic arm, a compression spring, or the like, in place of a tension member. The operation and construction of the device will be generally similar, although minor routine modifications will be necessary. For example, the sleeves may be provided with a locking portion to prevent the two sleeve portions from separating beyond a desired limit.