GB2624194A

GB2624194A - A support mechanism

Info

Publication number: GB2624194A
Application number: GB2216704.3A
Authority: GB
Inventors: Kiss Paul
Original assignee: Abbey Pynford Holdings Ltd
Current assignee: Abbey Pynford Holdings Ltd
Priority date: 2022-11-09
Filing date: 2022-11-09
Publication date: 2024-05-15
Also published as: GB202216704D0

Abstract

The present invention relates to a support mechanism 2 for use in the formation of a concrete foundation raft or beam that is readily reusable. The disclosed support mechanism 2 comprises a base member 4 for engagement with the ground, a platform 14 to support formwork 16, in which a raft or beam is formed, and connecting means 10,12 for connecting the base member 4 and platform 14 such that they are relatively movable between a closed configuration and an open configuration. The support mechanism 2 is retained in the open configuration by a strut 20 which is itself retained by a breakable retaining member 24 extending through it. Later embodiments relate to a support system for use in the formation of a concrete foundation raft or beam and a method of forming a concrete foundation raft or low level beam.

Description

A Support Mechanism The present invention relates to a support mechanism and system for use in the formation of a concrete foundation raft or beam and a method of forming a concrete foundation raft or low level beam for a building or other superstructure.

When building on ground, which is liable to subsidence or heave, it is well known to erect the building or other superstructure on a raft or beam, itself supported by piles, with the underside of the raft or beam spaced above the ground by a void or compressible material. The void or compressible material, which prevents any heave from being significantly transmitted to the underside of the raft or beam, has, previously, taken a variety of forms.

Typically, a collapsible or crushable spacer, made for example of hardboard, cardboard, and/or polystyrene has been used. However, these techniques are generally expensive. Furthermore, collapsible spacers can collapse prematurely, typically in wet weather, and crushable spacers require additional space to avoid the transmission of heave to the raft through the crushed material. Another method of spacing the underside of the raft or beam above the ground is through the use of a reusable and collapsible support mechanism. However, such mechanisms may collapse prematurely, may not fully collapse, or be difficult to collapse, thus impeding construction of the raft or beam, or hindering the extraction of the support mechanism.

The present invention aims to provide a mechanism which overcomes the above problems, and which is easy and cheap to manufacture and simple in operation.

According to a first aspect of the present invention, there is provided a support mechanism for use in the formation of a concrete foundation raft or low level beam for a building or other superstructure, the support mechanism comprising: a base member for engagement, in use, with the ground; a platform for supporting formwork, on which the raft or beam is formed, in use; connecting means for connecting the base member and the platform such that they are relatively moveable between a closed configuration and an open configuration; and a strut provided between the base member and the platform for, in use, retaining the base member and the platform in the open configuration, wherein the strut is pivotally connected at one end to the base member or the platform, and the support mechanism further comprises a breakable retaining member extending through the strut and one of the base member or the platform so as to prevent movement of the strut in a likely direction of slip of the strut.

In use, when the support mechanism is in the open configuration, a surface of the platform of the support mechanism supports formwork for the construction of a raft or beam, and a surface of the base member of the support mechanism engages with a blinding which is provided over the surface of the ground. The strut extends between the base member and the platform and serves to retain the support mechanism in the open configuration. The breakable retaining member extends through the strut and either the base member and the platform, so as to prevent relative movement between the strut and said base member or platform. Accordingly, movement of the strut in a likely direction of slip is prevented and the breakable retaining member locks the strut in place. The support mechanism is therefore locked in the open configuration. In use, application of a pulling force to a free end of the strut in a direction perpendicular to the pivot axis generates a rotational movement of the strut about the pivot axis, which then acts on the breakable retaining member causing it to shear.

An advantage of the immediately above-described arrangement is that, by means of a simple support mechanism, a rigid structure is provided to support formwork, on which the necessary raft or beam can be formed, and which can be easily and reliably collapsed by breaking the breakable retaining member, when needed, thus ensuring that the support mechanism can be removed and reused.

Furthermore, no additional fluids, as required by other systems, need to be supplied to or removed from the location of the support mechanism. It is therefore easier to maintain a clean working environment.

With the arrangement of the present invention, the breakable retaining member extends through the strut and one of the base member and the platform. This arrangement provides a particular mechanical advantage to assist breaking of the retaining member when a pulling force is applied to the strut in a direction perpendicular to its pivot axis. A force is applied to the retaining member by the strut acting in the direction of pull, and an opposing force acts on the retaining member in an opposite direction by the static base member or platform through which the retaining member extends, the opposing forces acting to break the retaining member. Since the retaining member extends through the strut, the force applied on the retaining member by the strut is focussed on the point or points at which the retaining member extends through the strut (that is, the specific point(s) at which the strut engages with the retaining member when the strut is pulled).

Accordingly, the force of the strut can be focussed on a specific point or points of the retaining member, allowing the retaining member to be broken more readily. This may be coupled with, for example, a point or points of weakness in the retaining member, which are arranged to coincide with the positions at which the retaining member extends through the strut, as described in greater detail below.

The position at which the strut engages with the retaining member can thus be selected to optimise the mechanical advantage, depending on the particular arrangement of a given embodiment. For example, the retaining member may be held at its opposing ends by one of the base member or the platform, and the retaining member may be arranged to extend through the strut at a central portion of the retaining member (between its two ends) in order to maximise the force acting on the retaining member. Similarly, the position of the retaining member relative to the base member and platform can be optimally selected to provide the desired stability in use, and ease of breaking. For example, the retaining member may extend through either the base member or the platform, regardless of which one of the base member or platform the strut is pivotally connected to. For example, in one embodiment the strut may be pivotally connected to the platform, and the retaining member may be arranged to extend through the strut and the platform. Because the retaining member extends through the strut, it can prevent movement of the strut in a likely direction of slip of the strut, despite engaging with the strut at a location proximal to its pivotal connection. Other arrangements offering a particular mechanical advantage will be conceivable to the skilled person.

It is preferable that the breakable retaining member extends through the strut and said one of the base member and the platform in a direction parallel to a pivot axis of the strut.

In one embodiment, the retaining member of the above arrangement extends through the strut and the one of the base member and the platform to which the strut is pivotally connected. Accordingly, the retaining member is located proximal to the pivot point of the strut on either the base member or the platform to which the strut is pivotally connected. With this arrangement, it has been found that relatively little force is required to shear through the retaining member, compared to an arrangement in which the retaining member is located, in use, at an end of the strut distal to the pivot axis.

As discussed above, in use, a pulling force is applied to a free end of the strut i.e. an end of the strut that is distal to the pivot axis. As the pulling force is applied in a direction perpendicular to the pivot axis, a rotational movement of the strut about its pivot axis is generated, which then acts on the breakable retaining member at the point at which the retaining member extends through the strut (that is, the point at which the strut engages with the retaining member). The closer the retaining member is to the pivot point, the greater the force acting on the retaining member, for a given pulling force applied to the strut. Accordingly, by extending the retaining member through the strut and the one of the base member and the platform to which the strut is pivotally connected, the retaining member is located proximal to the pivot axis and the pulling force applied to the strut is magnified.

The strut of the present invention may comprise a locking portion extending in a plane perpendicular to the pivot axis of the strut, with the breakable retaining member extending through the locking portion of the strut so as to prevent movement of the strut in the likely direction of slip of the strut.

Preferably, the locking portion is located proximal to an end of the strut that is pivotally connected to the base member or the platform of the above-described arrangement. An advantage of locating the locking portion in this manner is that relatively little force is required to shear the breakable retaining member due to the proximity of the retaining member to the pivot axis of the strut, as outlined above. Preferably, the locking portion comprises an aperture for receiving the retaining member, in use, said aperture being located closer to the pivot axis of the strut than to a free end of the strut.

The locking portion of the support mechanism is preferably substantially planar. In this context, the locking portion being substantially planar is to be understood as meaning that a dimension of the locking portion extending in a plane perpendicular to the pivot axis of the strut is substantially larger than a dimension of the locking portion in a direction parallel to the pivot axis of the strut.

An advantage of this arrangement is that the locking portion defines a relatively small surface area that is in contact with the retaining member, resulting in a concentration of the shearing force onto a small area of the retaining member. This further reduces the force required to shear through the retaining member. The locking portion preferably has a dimension in a direction of the pivot axis of the strut that is less than a corresponding dimension of a main body of the strut. The dimension of the locking portion in the direction of the pivot axis of the strut is preferably 20mm or less, more preferably 10mm or less and most preferably 5mm or less.

The one of the base member and the platform through which the breakable retaining member extends preferably comprises a surface arranged to engage with the ground or to support a formwork, in use, and a wall portion extending substantially perpendicularly to the surface, wherein the retaining member extends through the wall portion and the locking portion of the strut so as to prevent movement of the strut in a likely direction of slip of the strut.

In a particularly preferred arrangement, the locking portion is planar, as described above, the locking portion is parallel to the wall portion, and the retaining member is arranged to extend through the locking portion and the wall portion in a direction of the pivot axis of the strut. This arrangement provides a particular mechanical advantage for breaking the retaining member when a pulling force is applied to the strut in a direction substantially perpendicular to its pivot axis.

Preferably, the one of the base member and the platform through which the breakable retaining member extends comprises two wall portions on opposing sides of the surface, each wall portion extending substantially perpendicularly to the surface, wherein the retaining member extends through both wall portions in a direction parallel to the pivot axis of the strut, and through the strut so as to prevent movement of the strut in a likely direction of slip of the strut.

Such an arrangement provides the advantage of securely holding the retaining member between the two wall portions and across the support mechanism in the direction of the pivot axis when the support mechanism is in the open configuration. The retaining member extends through the strut at a position between the two wall portions, such that a rotational force applied to the strut causes the strut to bear against the retaining member until the retaining member is eventually broken. This arrangement provides a mechanical advantage such that that breakable retaining member is more easily sheared.

Preferably, the locking portion of the strut is substantially equidistant between the two wall portions of the one of the base member and the platform through which the breakable retaining member extends.

An advantage of such an arrangement is that the breakable retaining member extending through holes in the locking portion and both wall portions in the open configuration, providing stable means to retain the support mechanism in the open configuration. When a pulling force is applied to the strut, the force exerted by the locking portion of the strut on the retaining member is located at a central portion of the retaining member, thus providing a further mechanical advantage allowing the retaining member to shear more easily.

In one embodiment, the strut is pivotally connected to the platform and comprises a cam portion extending in a plane perpendicular to the pivot axis of the strut, the cam portion being arranged to be received through an aperture in the platform.

An advantage of this arrangement is that, if the platform is adhered to the supported formwork, the cam portion, when protruding through the central aperture, can create a separation between the platform and supported formwork, in which the raft or beam is formed, resulting in a platform that can be more easily detached from the supported formwork as the support mechanism collapses. When the retaining member has been broken, the strut is free to pivot about its pivot axis. Accordingly, in the event that the support mechanism becomes jammed in the open configuration due to adhesion between the platform and an underside of the supported formwork, the cam portion can move pivotally with the strut to protrude through the aperture of the platform so as to force the platform away from the underside of the formwork and break any adhesion therebetween, thus permitting the support mechanism to collapse into the closed configuration.

To achieve this, the cam portion is preferably arranged to protrude through the central aperture in the platform when the base member and the platform are in the closed configuration. Most preferably, the cam portion does not protrude through the central aperture in the platform when the base member and the platform are in the open configuration. This arrangement provides an advantage in that it ensures that the supporting platform is fully engaged with and fully supports the supported formwork when in the open configuration.

Preferably the cam portion has an arcuate engaging edge arranged to extend through the aperture when the strut is pivoted relative to the platform to which the strut is pivotally connected.

If the platform becomes adhered to the supported formwork, the arcuate engaging edge of the cam portion engages with the supported formwork as the strut is pivoted about its pivot axis (after the retaining member has been broken). Due to the arcuate profile of the engaging edge of the cam portion, the transfer of load from the platform to the cam is gradual as opposed to if the edge were shaped otherwise in which case the load transfer could be sudden and jarring, potentially resulting in damage to the support mechanism and/or the supported formwork.

The cam portion preferably comprises the locking portion, the advantage of which is a reduction in design complexity and cost as the number of separate components is reduced. However, it will be appreciated that in alternative embodiments the cam portion and the locking portion of the strut may be provided separately.

Preferably, the breakable retaining member is a wooden dowel which has the advantage of being relatively cheap, easily accessible and readily breakable. Alternative breakable retaining members will be apparent to the skilled person. For example, the retaining member may be formed of a rigid material, such as wood or a rigid plastic, and may comprise one or more points of weakness to facilitate breaking of the retaining member. Said point or points of weakness may be arranged to coincide with a point at which the retaining member engages with one of the strut, base member or platform, such that the force exerted on the retaining member is located at a point of weakness to facilitate breaking.

The strut may also comprise an anchor portion arranged, in use, to be connected to a tension wire for pulling the strut in a direction perpendicular to the pivot axis, wherein the anchor portion is provided at or towards an end of the strut distal to the pivot axis of the strut. A benefit of this anchor portion is that it provides an anchor point onto which a tension wire may be securely attached in advance of use and thus provide a means for easy and reliable collapse of the support mechanism when required. A further benefit of the anchor portion is that it provides an anchor point allowing several support mechanisms to be linked together such that pulling on one tension wire on one support mechanism results in the simultaneous collapse of several other support mechanisms.

An advantage of the anchor portion being provided at a location on the strut distal to the pivot axis of the strut is that it provides a greater moment arm between the point at which the pulling force is applied to the strut and its pivot axis, thus requiring less force to shear the breakable retaining member.

The strut may further comprise a stop arranged to limit the fall of the platform as the support mechanism collapses to the closed configuration from the open configuration.

The extent to which the stop limits the fall of the platform is dependent on the length of the stop: a longer stop limits the fall of the platform to greater extent than a shorter stop. The provision of a stop limits the degree to which the platform engages with the base member when the support mechanism collapses into the closed configuration, thus preventing the support mechanism from becoming jammed in the closed configuration. The stop may be in the form of a bolt engaged with the strut.

Preferably, the connecting means of the support mechanism comprises a first leg and a second leg forming a parallelogram linkage with the base member and the platform.

Such an arrangement ensures that the platform and the base member of the support mechanism remain parallel to each other in both the open and closed configurations as well as at any point in between (partially closed configuration, for example).

In addition to the aperture arranged to receive the cam in the closed configuration, one or more additional apertures may be provided in the platform surface to reduce the overall surface area of the platform, which reduces the risk of the platform adhering to the supported formwork.

At least a portion of the platform may comprise a mesh material to reduce the overall contact area between the platform and the supported formwork, which reduces the risk of the platform adhering to the supported formwork.

In accordance with a second aspect of the present invention, there is provided a support system for use in the formation of a concrete foundation raft or low level beam for a building or other superstructure, the support system comprising a plurality of support mechanisms in accordance with the first aspect, the support mechanisms being connected in series by means of one or more tension lines. This arrangement permits the support mechanisms to be collapsed and removed from underneath the newly formed concrete raft or beam in tandem. The interconnecting nature of the support mechanisms allows one or more of the support mechanisms to be placed at a significant distance from an edge section of the concrete raft being formed, whilst still permitting easy removal of each support mechanism. Accordingly, the support system can be used to support a concrete rafts of any size without limitation on the distance from the edge section of the raft at which the support mechanism can be placed.

In one embodiment, the support system comprises at least three support mechanisms, wherein first and second support mechanisms are connected by a first tension line, second and third support mechanisms are connected by a second tension line, and wherein the second tension line has a length greater than the first tension line. This arrangement facilitates release of the third support mechanism, which may be situated further away from the user when the support mechanisms are removed from underneath a newly formed concrete raft or beam. The greater length of the second tension line permits a jolting action to be applied to the third support mechanism in the event that it cannot be initially released.

The or each tension line is preferably connected to the strut of a respective supporting mechanism, such that pulling on the tension line can effect breakage of the retaining member of said support mechanism and subsequent collapse of the support mechanism into the closed configuration for removal.

The or each tension line is preferably flexible. The material and/or construction of the tension line is not particularly limited and may be any appropriate flexible member, such as a rope, cord, cable or wire.

The present invention also envisages a method of forming a concrete foundation raft or low level beam for a building or other superstructure, the method comprising the steps of: erecting formwork, which is spaced above the ground by means of one or more support mechanisms in accordance with the first aspect of the present invention, pouring concrete in the formwork to form the raft or beam; and when the concrete is set, collapsing the support mechanism to its closed configuration to provide a void between the underside of the formwork and the ground Preferably, the or each support mechanism is recovered after use so that it can be reused Non-limiting embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a schematic side view of a support mechanism in accordance with an embodiment of the present invention, the support mechanism being in an open configuration; Figure 2 is a schematic front view of the support mechanism of Figure 1 in the open configuration; Figure 3 is a schematic side view of the support mechanism of Figure 1 in a partially closed configuration; Figure 4 is a schematic side view of the support mechanism of Figure 1 in a closed configuration; Figure 5 is a schematic top view of the support mechanism of Figure 1; Figure 6 is a schematic side view of the support mechanism of Figure 1, wherein the support mechanism is jammed in an open configuration' Figures 7a and 7b are schematic cross-sectional views of the support mechanism of Figure 1, taken along line VII-VII as shown in Figure 4 in the open and closed configuration respectfully; Figure 8 is a schematic side view of an alternative embodiment of a support mechanism in accordance with the present invention, the support mechanism in the open 30 configuration; Figure 9 is a schematic top view of a further embodiment of a support mechanism in accordance with the present invention; Figure 10 is a schematic top view of a further embodiment of a support mechanism in accordance with the present invention; and Figure 11 is a schematic side view of a support system in accordance with a further aspect of the present invention.

With reference to Figures 1 and 2, there is shown a support mechanism 2 in accordance with an embodiment of the present invention. The support mechanism 2 is shown in an open configuration and includes a base member 4, resting on top of a blinding 6, which is provided over the surface of the ground 8. A first leg 10 and second leg 12 interconnect the base member 4 with a platform 14, which, in use, supports formwork 16 on which a raft or beam 18 can be formed. The legs 10, 12 are pivotally connected at respective ends to the base member 4 and the platform 14, such that the base member 4 and the platform 14 are relatively movable between the open configuration, as shown in Figures 1 and 2, in which they are spaced apart, and a closed configuration in which the spacing therebetween is reduced, described in further detail below.

A strut 20, pivotally connected to the platform 14, retains the support mechanism 2 in the open configuration and comprises a locking portion 22 located proximal to a proximal end 20a of the strut 20 that is pivotally connected to the platform 14. A distal end 20b of the strut 20 bears against the base member 4 to retain the support mechanism 2 in the open configuration.

The strut 20 is at least partially retained in place by friction between the distal end 20b of the strut 20 and the base member 2. In use, in the open configuration, the strut 20 is further fixed in place by means of a breakable retaining member 24, which is provided in the construction through holes 26 formed in two wall portions 40 of the platform 14 and a hole 28 formed in the locking portion 22 of the strut 20. The breakable retaining member 24 thus extends through the platform 14 and the strut 20 and acts as a pin to lock the strut 20 in place relative to the base member 4 and platform 14 and prevent any slip of the strut 20 to maintain the support mechanism 2, when in the open configuration. The breakable retaining member 24 is preferably formed from a thin piece of wood such as a wooden dowel.

An anchor 30 in the form of a closed hook is located proximal to the free end 20b of the strut 20 and arranged such that a tension wire 32 can be looped through it. This arrangement is such that, when in use in the open configuration, the wire can be used to apply a pulling force on the strut 20 connected to the hook, generating a rotational force of the strut 20 about its pivot axis A. The rotational force causes the locking portion 22 of the strut 20 to press against and ultimately shear through the breakable retaining member 24, thus allowing the strut 20 to pivot about its pivot axis A, in turn permitting the support mechanism 2 to collapse.

The tension wire 32, in the illustrated example, is formed from a steel wire, but could be made of any suitable material. In other embodiments, a hooked tool may be inserted between the supported formwork 16 and blinding 6 to hook onto the anchor 30 or any other appropriate part of the strut 20, in order to pull on the strut 20 in a direction perpendicular to the pivot axis A of the strut 20.

Figure 1 also shows a stop bolt 36 which may be provided on the strut 20 arranged to limit the fall of the platform 14 in the closed configuration.

Figure 2 is a front view of the support mechanism 2 in the open configuration. The platform 14 comprises a first supporting surface 38 arranged to support and engage with formwork 16, in use. The platform 14 further comprises two wall portions 40 substantially perpendicular to the first supporting surface 38 and located on opposing lateral edges of the first supporting surface 38. The breakable retaining member 24 extends through and between the two opposing wall portions 40 of the platform 14 and through the locking portion 22 of the strut 20.

The base member 4 comprises a second supporting surface 42 arranged to engage with blinding 6, in use. The base member 4 further comprises two upstanding wall portions 44 substantially perpendicular to the second supporting surface 42 and located on opposing lateral edges of the second supporting surface 42.

The locking portion 22 is substantially equidistant between the two opposing wall portions 40 of the platform 14. That is, a centre point of the locking portion 22 in the direction of the pivot axis A is substantially equidistant between the two opposing wall portions 40 of the platform 14. Accordingly, when a pulling force is applied to the strut 20, said pulling force is transmitted to the retaining member 24 in a central portion thereof. At the same time, an opposing force is applied on the retaining member 24 at the ends of the retaining member 24 that extend through the wall portions 44 of the platform 14. This arrangement provides an enhanced mechanical advantage to facilitate breaking of the retaining member 24.

Referring again to Figure 1, when a pulling force is applied to the strut 20 in a direction perpendicular to the pivot axis A of the strut by the tension wire 32 (as indicated by arrow 33 in Figure 1), or by any other means, the pulling force is transmitted to the retaining member 24 via the locking portion 22 (through which the retaining member 24 extends). The platform 14 applies an opposing force on the retaining member 24 via edges of the through holes 26 that engage with the retaining member 24. When sufficient force is applied, the retaining member 24 breaks at the point at which the locking portion 22 engages with the retaining member 24, thus releasing the strut 20 to pivot about its pivot axis A. The retaining member 24 is sheared effectively via a cutting action between the locking portion 22 and the platform 14.

In this regard, the strut 20 operates as a mechanical lever, wherein the retaining member 24 (load) is located between the point at which the pulling force (effort) is applied to the strut 20 and the pivot axis A (fulcrum). The force acting on the retaining member 24 (load) is dependent on the magnitude of the pulling force applied at the free end 20b of the strut (effort) and the ratio of the effort arm (distance between the applied pulling force and the pivot axis A acting as the fulcrum) to the load arm (distance between the retaining member 24 and the pivot axis A acting as the fulcrum). Thus, by locating the locking portion 22 proximal to the pivot axis A of the strut 20, the ratio of the effort arm to the load arm is increased, and the puling force applied at the free end 20b of the strut 20 is magnified at the point at which the locking portion 22 engages with the retaining member 24. Accordingly, the pulling force required to shear through the retaining member 24 is reduced.

Referring now to Figure 3, once the retaining member 24 has been broken, further pulling on the tension wire 32 in the direction indicated by arrow 33 further rotates the strut 20 around its pivot axis A. Platform 14 is pulled in the direction of arrow 33, and legs 10, 12 connecting the base member 4 and the platform 14 pivot, moving the platform 14 and the base member 4 closer together. This creates a separation between the platform 14 and the underside of the formwork 16, permitting the entire support mechanism 2 to be removed from underneath the newly formed raft or beam 18 (or other structure). Figure 4 shows the support mechanism 2 in a fully collapsed (closed) configuration. As the strut 20 pivots towards the platform 14, the locking portion 22, which previously held the breakable retaining member 24, protrudes through a central aperture in the first supporting surface of the platform 14, as will be described in greater detail below.

It is possible that the support mechanism 2 may become jammed in the open configuration even after the retaining member 24 has been broken, for example due to ingress of concrete through the formwork 16 onto the platform 14. In order to overcome this problem, the support mechanism 2 comprises a cam portion 23 arranged to be received through a central aperture 34 in the first supporting surface 38 of the platform 14, as shown most clearly in Figures 5 and 6.

Figure 5 shows a top view of the support mechanism 2, wherein the central aperture 34 arranged to receive the cam portion 23 is located in the platform 14. Figure 6 is a side view of the support mechanism in a jammed state, wherein the platform 14 remains engaged with the underside of the formwork 16, despite the retaining member 24 having been broken.

In the illustrated embodiment, the cam portion 23 comprises the locking portion 22. That is, the locking portion 22 and the cam portion 23 are a common component of the strut 20. In other embodiments, the locking portion 22 and the cam portion 23 may be separate components, as described in greater detail below.

With reference to Figure 6, in particular, in the event of jamming, a continued pulling force acting on the tension wire 32 causes the strut 20 to rotate further about its pivot axis A. The cam portion 23, which is located proximal to the pivot axis A, protrudes through the central aperture 34 in the platform 14 and bears against the supported formwork 16, forcing the platform 14 away from the formwork 16. In this way, the platform 14 can be released from the underside of the formwork 16, allowing the support mechanism 2 to collapse.

Figures 7a and 7b show enlarged cross sections of the support mechanism 2 in the open and closed configurations, respectively, taken along the line VII-VII of Figure 5. As shown in Figure 7a, the cam portion 23 does not protrude through the central aperture 34 whilst the support mechanism 2 is in the open configuration. Accordingly, the cam portion 23 does not interfere with the engagement of the first supporting surface 38 of the platform 14 with the formwork 16 when the support mechanism 2 is in use. As shown in Figure 7b, in the closed configuration, the cam or locking portion 22 protrudes through the central aperture 34 A hole 28 is provided in the cam portion 23 for receiving the breakable retaining member 24, such that the cam portion 23 also acts as the locking portion 22 as described above.

Figure 8 shows an alternative embodiment of a support mechanism 2 in accordance with the present invention, wherein the breakable retaining member 24 extends through holes 46 formed in two upstanding side wall portions 44 of the base member 4 and holes 48 formed in side portions of the strut 20, distal from the end of the strut 20 pivotally connected to the platform 14. The side portions of the strut 20 therefore act as the locking portion 22, through which the retaining member 24 extends to retain the strut 20 and thus lock the support mechanism 2 in the open configuration. Accordingly, in this embodiment, the locking portion 22 and the cam portion 23 are separate components of the strut 20.

Figure 9 shows a top view of a further embodiment of a support mechanism 2 in accordance with the present invention, wherein the platform 14 comprises a plurality of additional apertures 50, in addition to the central aperture 34 arranged for receiving the cam portion 23. These additional apertures 50 may be provided in the platform 14 surface to reduce the overall surface area of the platform 14 in contact with the supported formwork 16, resulting in a reduced chance of adhesion of the platform 14 surface to the supported formwork 16.

Figure 10 shows a top view of a further embodiment of a support mechanism 2 in accordance with the present invention, wherein sections of the platform 14 surface comprise a mesh 52 material to reduce the overall surface area of the platform 14 in contact with the supported formwork 16, resulting in a reduced chance of adhesion of the platform 14 surface to the supported forrnwork 16.

Referring now to Figure 11, there is shown a support system in accordance with a further aspect of the present invention. The support system comprises a plurality of support mechanisms 2, 2', 2" in accordance with the first aspect of the present invention.

A first support mechanism 2 is connected to a second support mechanism 2' by means of a first tension line 54a and the second support mechanism 2' is connected to a third support mechanism 2" by means of a second tension line 54b, such that the first, second and third support mechanisms 2, 2', 2" are connected in series. This allows the support mechanisms to be removed from under the concrete raft or beam after use in tandem.

For example, the first support mechanism 2 can be collapsed and removed by pulling tension line 32 to cause breakage of the retaining member 24 and release of the strut 20 as described above. As the first support mechanism 2 is withdrawn from under the concrete raft or beam, the first tension line 54a is brought into tension and applies a pulling force to the strut 20' of the second support mechanism 2', to which the first tension line 54a is connected via anchor portion 30. The second support mechanism 2' is thereby collapsed. In turn, a pulling force is applied to the third support mechanism 2" via the second tension line 54b to collapse the third support mechanism 2".

In the illustrated embodiment, the second tension line 54b has a length greater than the first tension line 54a. In use, the tension lines 54a, 54b are in a relaxed state to permit the support mechanisms 2, 2', 2" to be positioned as desired. After use, the tension lines 54a, 54b are brought into tension as described above to permit removal of the support mechanisms 2, 2', 2" from underneath the newly formed concrete raft or beam.

Since the third support mechanism 20" will be located further away from the user pulling the support mechanisms 2, 2', 2" in tandem, additional force may be required to break the retaining member 24" of the third support mechanism 20" for its collapse. Accordingly, the longer tension line 54b permits the user to apply an additional jolting force to the third support mechanism 2" in the event that it cannot initially be collapsed and released. The second tension line 54b may be made of sufficient length to extend beyond the edge of the newly formed concrete raft or beam, such that the user can pull directly on the second tension line 54b to jolt the third support mechanism 20" and effect breakage of the retaining member 24".

The invention has been described above with reference to specific embodiments, given by way of example only. It will be appreciated that different arrangements of the system are possible, which fall within the scope of the appended claims.

Claims

Claims 1. A support mechanism for use in the formation of a concrete foundation raft or low level beam for a building or other superstructure, the support mechanism comprising: a base member for engagement with the ground, in use; a platform for supporting formwork on which the raft or beam is formed, in use; connecting means for connecting the base member and the platform such that they are relatively movable between a closed configuration and an open configuration; and a strut provided between the base member and the platform for, in use, retaining the base member and the platform in the open configuration; wherein the strut is pivotally connected at one end to the base member or the platform, and the support mechanism further comprises a breakable retaining member extending through the strut and one of the base member or the platform so as to prevent movement of the strut in a likely direction of slip of the strut.
2. A support mechanism according to claim 1, wherein the retaining member extends through the strut and the one of the base member and the platform to which the strut is pivotally connected.
3. A support mechanism according to claim 1 or 2, wherein the strut comprises a locking portion extending in a plane perpendicular to the pivot axis of the strut, and wherein the breakable retaining member extends through the locking portion of the strut so as to prevent movement of the strut in the likely direction of slip of the strut.
4. A support mechanism according to claim 3, wherein the locking portion is located at, or proximal to, an end of the strut that is pivotally connected to the base member or the platform.
5. A support mechanism according to claim 4, wherein the locking portion is substantially planar.
6. A support mechanism according to claim 5, wherein the one of the base member and the platform through which the breakable retaining member extends comprises a surface arranged to engage with the ground or to support the formwork, in use, and a wall portion extending substantially perpendicularly to the surface, wherein the retaining member extends through said wall portion of the base member or platform and the locking portion of the strut so as to prevent movement of the strut in a likely direction of slip of the strut.
7. A support mechanism according to claim 6, wherein said one of the base member and the platform through which the retaining member extends comprises two wall portions on opposing sides of the surface, each wall portion extending substantially perpendicularly to the surface, wherein the retaining member extends through both wall portions and the strut so as to prevent movement of the strut in a likely direction of slip of the strut.
8. A support mechanism according to claim 7, wherein the locking portion is substantially equidistant between said two wall portions.
9. A support mechanism according to any preceding claim, wherein the strut is pivotally connected to the platform, and wherein the strut comprises a cam portion extending in a plane perpendicular to the pivot axis of the strut, the cam portion being arranged to be received through an aperture in the platform.
10. A support mechanism according to claim 9, wherein the cam portion is arranged to protrude through the aperture in the platform when the base member and the platform are in the closed configuration.
11. A support mechanism according to claim 9 or 10, wherein the cam portion does not protrude through the aperture in the platform when the base member and the platform are in the open configuration.
12. A support mechanism according to any one of claims 9 to 11, wherein the cam portion has an arcuate engaging edge arranged to extend through the aperture when the strut is pivoted relative to the platform to which the strut is pivotally connected.
13. A support mechanism according to any one of claims 9 to 12, when dependent on any one of claims 3 to 8, wherein the cam portion comprises the locking portion.
14. A support mechanism according to any preceding claim, wherein the breakable retaining member is a wooden dowel.
15. A support mechanism according to any preceding claim, wherein the breakable retaining member is formed of a rigid material and comprises one or more points of weakness.
16. A support mechanism according to claim 15, wherein one or more points of weakness of the retaining member are arranged, in use, to coincide with a point at which the retaining member engages with one of the strut and/or the base member or platform.
17. A support mechanism according to any preceding claim, wherein the strut comprises an anchor portion arranged, in use, to be connected to a tension wire for pulling the strut in a direction perpendicular to the pivot axis, wherein the anchor portion is provided at or towards an end of the strut distal to the pivot axis of the strut.
18. A support mechanism according to any preceding claim, wherein the connecting means comprises a first leg and a second leg forming a parallelogram linkage with the base member and the platform.
19. A support system for use in the formation of a concrete foundation raft or low level beam for a building or other superstructure, the support system comprising a plurality of support mechanisms as claimed in any one of claims 1 to 18 connected in series by means of one or more tension lines.
20. A support system according to claim 19, comprising at least three support mechanisms, wherein first and second support mechanisms are connected by a first tension line, second and third support mechanisms are connected by a second tension line, and wherein the second tension line has a length greater than the first tension line.
21. A method of forming a concrete foundation raft or low level beam for a building or other superstructure, the method comprising the steps of: erecting formwork, which is spaced above the ground by means of a support mechanism according to any one of the preceding claims; pouring concrete in the formwork to form the raft or beam; and when the concrete is set, collapsing the support mechanism to its closed configuration to provide a void between the underside of the raft or beam and the ground.
22. A method according to claim 21, further comprising the step of recovering the support mechanism after use so that it can be reused.