GB2592971A

GB2592971A - Shutter member

Info

Publication number: GB2592971A
Application number: GB2003612.5A
Authority: GB
Inventors: Kiss Paul
Original assignee: Abbey Pynford Holdings Ltd
Current assignee: Abbey Pynford Holdings Ltd
Priority date: 2020-03-12
Filing date: 2020-03-12
Publication date: 2021-09-15
Anticipated expiration: 2040-03-12
Also published as: GB2592971B; GB202003612D0

Abstract

The shutter member for concrete or other settable material comprises a substantially planar wall portion extending substantially perpendicularly, in use, to a substantially planar base portion comprising at least one tab 21. The tab, substantially in the plane of the base portion, is arranged in use to extend outwardly from an edge 23 of the base portion and to be secured to an underlying surface. The tab may be formed integrally with the base portion and may be foldable between first and second positions wherein it respectively does not and does extend outwardly from an edge thereof. The tab may be cut out from the base portion and may be foldable at a predefined line of weakness (e.g. perforations, thinning) and/or comprise a narrowed waist portion. Indentations or deformations 26 may be provided adjacent to edges defining the tab, e.g. extending parallel to the edges. The shutter member may be a single component stamped or cut from sheet metal. Portions 8,9 of tie members may be cut from the base and wall portions.

Description

Shutter member The present invention relates to a shuttering system for concrete or other settable material and particularly, but not exclusively, to a shuttering system for use in forming a concrete raft of a building.

In the construction of domestic and commercial buildings, concrete rafts are commonly used as alternatives to traditional foundations such as strip footings or piles and ground beams. Such rafts comprise a concrete slab reinforced by steel bars, which may be supported directly on appropriately treated ground (possibly by compaction where soil type permits this) or supported by piles.

Whether the concrete raft is to be supported directly by the ground or from piles, it is first necessary to provide appropriate formwork to receive the poured concrete and define the shape of the raft. The formwork will include a substrate to support the poured concrete of the raft until it has set. If the raft is to be formed on appropriately treated ground, then the substrate will often be a levelled rough concrete working surface. Alternatively, where the raft is to be supported from piles, the substrate will normally be a temporary substrate built around the piles, such as a plywood deck supported by temporary deck support units. When the concrete has set to form the raft, the deck support units and deck are subsequently removed, to leave the raft supported by piles and to provide a void under the deck. Such a void may be particularly advantageous where ground heave may otherwise be a problem or ventilation is required for degassing, for example when building on a previous brown field site, avoiding the need to remove possibly contaminated soil.

An advantage of using a concrete raft for the base of a building is that the walls of the building may be supported by the concrete raft, avoiding the need for traditional footings and excavations. However, this in turn means there is no sub-structure brick work or block work to retain the poured concrete when the raft is being formed. Therefore, in addition to providing formwork in the form of a substrate on which to form the raft, it is also necessary to provide formwork to shutter the concrete to define the edge of the raft.

Traditionally, wooden shuttering is used to define the edge of a raft. However, wooden shuttering is relatively time consuming and expensive to erect. Furthermore, it is necessary to "strike" the shuttering to clear the shuttering from the site once the raft has set. In addition, it is also difficult with wooden shuttering to form features on or in the raft. For example, it is sometimes desirable to provide a notch (step down) along the edge of the raft to decrease the thickness of the raft at the edges.

As an alternative to wooden shuttering, metal shuttering systems have been developed, which provide a relatively inexpensive and facile means for defining the edges of a concrete raft and any additional features provided on or in the raft. For example, UK Patent Applications, Publication Nos. GB 2522886, GB 2522887 disclose a range of shuttering systems comprising metal shutter members arranged to be interconnected to define the edges of a raft to be poured, which raft may be formed from concrete or other settable material.

Such shutter members generally comprise base portions arranged to be placed on a substrate in a substantially horizontal orientation, and one or more wall portions extending perpendicularly from the base portion, in a substantially vertical orientation. The one or more wall portions provide barriers to retain concrete or other settable material, thus defining the edges of the raft being formed. The shutter members may comprise apertures to allow reinforcing bars to pass through from one part of the raft defined by a first wall portion, to a another part of the raft defined by a second wall portion. Such apertures may also allow the passage of concrete or other settable material through the wall portions and/or base portion.

The configuration of the shutter members depends upon the particular application.

A range of shutter members having different configurations for different applications are disclosed in GB 2522886. The shutter members are therefore preformed into the desired shape and configuration, and are subsequently transported to the construction site, where they are assembled to form the shuttering system. However, since the shutter members are preformed into the desired shape at the point of manufacture, space is required storage and transportation of the shutter members prior to use.

Such shutter members are generally sacrificial, meaning that the shutter members are retained within the concrete structure once the concrete has set. Even if the shutter members are removed, at least partially, by striking, the shutter members are generally not reusable and thus the material used to form the shutter members cannot be recovered.

It is an object of the present invention to provide an improved shutter member for shuttering systems used in the formation of concrete foundations.

According to the present invention there is provided a shutter member for a shuttering system for concrete or other settable material, the shutter member comprising a substantially planar wall portion and a substantially planar base portion, the wall portion being arranged, in use, to extend substantially perpendicularly to the base portion, wherein the base portion comprises at least one tab arranged, in use, to extend outwardly from an edge of the base portion, wherein the at least one tab lies substantially in the plane of the base portion, the tab being further arranged to be secured to a surface underlying the base portion in use.

The shutter member of the present invention provides tabs on the base portion which extend beyond an edge of the base portion. Accordingly, the shutter member can be secured to an underlying surface, such as a concrete substrate, at a point beyond said edge of the base portion. This allows the base portion to provide a more stable base for the shutter member by effectively extending the area of the base portion, without the need to increase the area of the entire base portion. Accordingly, the overall dimensions of the base portion can be reduced, thus reducing the amount of material, for example steel, needed to manufacture the shutter members and reducing the cost of manufacture, whilst maintaining a stable structure.

Preferably the at least one tab is formed integrally with the base portion, such that the tab need not be formed separately and subsequently attached to the base portion.

In a preferred embodiment, the tab is foldable relative to the base portion and is arranged to fold from first position in which the tab does not extend outwardly from an edge of the base portion, to a second position in which the tab extends outwardly from an edge of the base portion, wherein the tab lies substantially in the plane of the base portion in both the first and second positions. This arrangement obviates the need for tabs which constantly extend outwardly from an edge of the shutter member, reducing the area occupied by the shutter member in the flat configuration and thus improving the ease of storage. For example, adjacent stacks of flat shutter members may be placed closer together due to the lack of components extending outwardly from the edges of the base portion.

The at least one tab is preferably formed wholly within the base portion and is cut out from the base portion. Accordingly, the tab is a section of the base portion, which is cut out of the base portion and remains joined to the base portion in a manner which enables the tab to fold over an edge of the base portion so as to extend outwardly from said edge. This allows the tab to be provided integrally with the shutter member, whilst minimising the wastage of sheet material when manufacturing the shutter member, since the tabs do not extend outwardly from the edge of the base portion until folded.

The tab may be joined to the base portion at a predefined line of weakness, the tab being foldable about the predefined line of weakness Within the context of the present specification, including the appended claims, the term predefined line of weakness refers to a linear section of the material of the shutter member, which has been intentionally weakened to facilitate folding and bending of the material about the line of weakness, such that the material folds or bends along said line of weakness in preference to another position or location within the material. It will be appreciated that the predefined line of weakness may be provided by any appropriate means. In one embodiment of the present invention, the predefined line of weakness comprises one or more perforations formed in the material of the shutter member. In other embodiments, the predefined line of weakness comprises a linear section of the base portion in which the base portion is thinned. Other means are known and may be used, such as laser treatment to change and weaken the structure of the metal to define a line of weakness.

The tab is preferably defined by three edges cut out from the base portion and the predefined line of weakness. Accordingly, the tab has a substantially square or rectangular shape.

It will be appreciated that the tab may be foldable relative to the base portion without the presence of a predefined line of weakness. For example, where the sheet material from which the shutter member is formed is sufficiently malleable and/or the tab is sufficiently narrow, it will be possible to fold the tab relative to the base portion so as to extend outwardly from the edge of the base portion.

In some embodiments, the tab may comprise a head portion and a waist portion, the tab being joined to the base portion at the waist portion, wherein the waist portion of the tab is narrower than the head portion. Accordingly, at the position at which the tab is joined to the base portion (and thus at the position at which the tab folds relative to the base portion) the tab is relatively narrow, thus facilitating folding of the tab relative to the base portion. This allows the width of the head portion of the tab to be large relative to the waist portion, this providing a stable base for securing the shutter member to an underlying surface, whilst also permitting the tab to fold easily.

The "waisted" configuration of the tab may be provided as an alternative to a predefined line of weakness, or in addition to a predefined line of weakness.

The shutter member may further comprise one or more indentations or deformations formed within the material from which the shutter member is formed, said one or more indentations or deformations being provided in a region adjacent one of the edges cut from the base portion to define the tab. The indentations or deformations act to strengthen and enhance the rigidity of the shutter member in the portion in which they are formed. Accordingly, positioning of the indentations or deformations in a region adjacent a cut in the material acts to strengthen the material in the region in which it has been cut.

The one or more indentations or deformations may be elongate, each being arranged to extend parallel to a respective edge of the base portion from which the tab has been cut.

The shutter member is preferably stamped or cut from sheet metal as a single component. Accordingly, all the components necessary for the formation of a shuttering system are provided as a unitary shutter member.

The base portion of the shutter member preferably has a square or rectangular shape and has a width defined as the distance between an edge of the base portion which adjoins the wall portion and an opposing edge of the base portion. In some embodiments, the width of the base portion is less than half the height of the wall portion, the height of the wall portion being the distance from an edge of the wall portion adjoining the base portion to an uppermost edge of the wall portion.

In use, the tab extends outwardly from an edge of the base portion, such that the distance from an edge of the base portion adjoining the wall portion to a distal edge of the tab is greater than the width of the base portion. In some embodiments, the distance from an edge of the base portion adjoining the wall portion to a distal edge of the tab is approximately half the height of the wall portion.

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 cross-sectional view of a prior art shutter member, shown mounted to a substrate and with concrete retained by the shutter member; Figure 2 is a side view of the shutter member of Figure 1 shown in a folded configuration; Figure 3 is a perspective view of the shutter member of Figure 1, shown in a folded configuration; Figure 4 is a plan view of the shutter member of Figure 1, shown in a flat configuration; Figure 5 is a perspective view of a shutter member according to the present invention, shown in a folded configuration; Figure 6 is a perspective view of the shutter member of Figure 5, shown in a folded configuration with tabs extended; Figure 7 is a plan view of the shutter member of Figure 5, shown in a folded configuration with tabs extended; Figure 8 is a side view of the shutter member of Figure 5, shown in a folded configuration; Figure 9 is a cross-sectional view of the shutter member of Figure 5, shown mounted to a substrate and with concrete retained by the shutter member; and Figure 10 is a plan view of the shutter member of Figure 5, shown in a flat configuration.

Referring to Figures 1 to 4, there is shown a shutter member known in the prior art.

As shown in Figure 1, the shutter member, indicated generally as 1, is used to define a single vertical edge of a concrete raft 2. The shutter member comprises a substantially planar base portion 3 secured to an appropriately levelled concrete working surface 4 by fasteners 5. The concrete working surface 4 forms a substrate on which the concrete raft 2 is formed, with reinforcing bars 6 assembled over the working surface.

The shutter member further comprises a substantially planar wall portion 7 arranged, in use, to extend substantially perpendicularly to the base portion 3, in an approximately vertical orientation. When the concrete of the raft 2 is poured, the wall portion 7 of the shutter member 1 retains the poured concrete in place until it sets to form the concrete raft 2.

The shutter member 1 comprises a plurality of base ties 8 arranged to extend from the base portion 3 and a plurality of wall ties 9 arranged to extend from the wall portion 4. Each base tie 8 engages with a corresponding wall tie 8 so as to secure the base tie 8 and the wall tie 9 together. When concrete is poured, the force exerted by the concrete on the wall portion 7 and the base portion 3 bring the wall tie 9 and the base tie 8 into tension, thus holding the wall portion 7 of the shutter member 1 in a substantially vertical orientation.

With particular reference to Figures 2 and 3, a distal end portion 10 of each wall fie 9 is arranged to insert through a slot 11 formed in a distal end portion of a corresponding base tie 8. Each distal end portion 10 is foldable relative to the respective wall tie 9. Once inserted through a corresponding slot 11, each distal end portion 10 is folded so as to engage the wall tie 9 with the base tie 8.

Each base tie 8 and wall tie 9 is cut out from the respective base portion 3 or wall portion 7 in which it is formed, and remains joined thereto at a proximal end 12, 13. The base ties 8 and wall ties 9 are each foldable about a predefined line of weakness provided at their proximal ends 12, 13. Accordingly, the ties 8, 9 can each be folded outwardly from the base or wall portion 3, 7 so as to protrude out of the plane of said base or wall portion 3, 7. This enables the corresponding pairs of base ties 8 and wall ties 9 so be brought into engagement as described above.

The base portion 3 is delimited from the wall portion 7 by a predefined line of weakness 14 defining respective adjoining edges of the base portion 3 and the wall portion 7. The wall portion 7 is foldable relative to the base portion 3 about the predefined line of weakness 14.

The wall portion 7 comprises a foldable edge portion 15 defined by two parallel predefined lines of weakness 16, 17, extending along the length of the wall portion 7. The foldable edge portion 15 defines an uppermost edge 18 of the wall portion 7 when in the folded configuration, as shown in Figures 2 and 3. When in the folded configuration, the edge portion 15 has a profile which is n-shaped in cross-section, by being folded about both parallel lines of weakness 16, 17. Accordingly, in use, the wall portion 7 has an uppermost edge 18 which sits substantially parallel and flush to the top surface of the concrete contained by the wall portion 3, and a further portion 19 extending downward into the settable material, as shown in Figure 1. With this arrangement, the portion 19 extending down into the settable material prevents the wall portion 7 from peeling away from the concrete once set. Furthermore, the n-shaped profile of the upper edge of the wall portion 7 provides additional rigidity to the shutter member 1.

The shutter member 1 can be formed as a single component by stamping or cutting from a planar sheet of appropriate material, preferably a metal and most preferably stainless steel. Figure 4 shows the shutter member 1 in a flat configuration, wherein appropriate cuts and predefined lines of weakness described above are formed in the sheet material, to enable the shutter member to be folded from the flat configuration into the folded configuration shown in Figures 1 to 3.

As can be seen from Figure 4, each base tie 8 is integral with the base portion 3 and is formed wholly within the base portion 3. Each base tie 8 is defined by three edges 8a, 8b, 8c cut out from the base portion, and the predefined line of weakness 12 at which the distal end of the base tie 8 remains joined to the base portion 3. In the same way, each wall tie 9 is integral with the wall portion 7 and is formed wholly within the wall portion 7. Each wall fie 9 is defined by three edges 9a, 9b, 9c cut out from the wall portion, and the predefined line of weakness 13 at which the distal end of the wall tie 9 remains joined to the wall portion 7.

When in the flat configuration, a plurality of the shutter members 1 may be stacked such that a detail on one shutter member is aligned with and/or accommodated within an equivalent detail of an adjacent shutter member in the stack. For example, any ties formed integrally with a first shutter member are preferably arranged to be aligned with corresponding ties of a second shutter member stacked above or beneath the first shutter member.

Referring now to Figures 5 to 10, there is shown an embodiment of a shutter member 20 in accordance with the present invention. A number of the features of the shutter member 20 are identical to those previously described for the shutter member 1 of Figures 1 to 4 and are referenced with like numerals.

With reference to Figure 5, the shutter member 20 comprises a plurality of tabs 21 formed in the base portion 3. Each tab 21 is cut out from the base portion 3 and remains joined thereto at a predefined line of weakness 22 provided at the proximal end of the tab 21. Accordingly, each tab 21 is defined by three cuts 21a, 21b, 21c in the shutter member 20 and a predefined line of weakness 11. In the configuration shown in Figure 5, the tabs 21 lie substantially in the plane of the base portion 3 Each tab 21 is foldable about a respective predefined line of weakness 22 provided at its proximal end 22. Accordingly, the tabs 21 can each be folded outwardly from the base portion 3 so as to protrude out of the plane of the base portion 3.

It will be appreciated that alternative embodiments may not comprise a predefined line of weakness, provided that the tab is foldable relative to the base portion. Alternative or additional means for facilitating folding to the tab relative to the base portion may be provided. For example, the tab may be joined to the base portion at a waist portion of the tab which is narrower than a head portion of the tab. Due to the narrow width of the waist portion, the tab can be folded more easily.

Referring to the embodiment of Figures 6 and 7, the tabs 21 can be folded about the respective predefined line of weakness 22 to an angle of approximately 180 degrees, so as to overlap a longitudinal edge 23 of the base portion 3 and to extend outwardly from said longitudinal edge 23. When fully folded, each tab 21 lies substantially in the plane of the base portion 3.

It will be appreciated that when the tabs 21 are folded at approximately 180 degrees the tabs do not lie wholly within the plane of the base portion 3, at least in the region in which the tabs 21 overlap the base portion 3. In the context of the present specification, including the appended claims, the phrase "substantially in the plane of the base portion" therefore includes the arrangement of Figures 6 and 7, wherein the tab or tabs are folded so as to extend outwardly from the edge of the base portion, such that the outwardly-extending part of the tab or tabs lie substantially flat against an underlying surface, as shown in Figure 9 and discussed in more detail below.

When the tabs 21 are folded outwardly, corresponding apertures 24 are formed in the base portion 3 of the shutter member 20. These apertures 24 allow concrete poured into the shutter member 20 to adhere to a substrate upon which the shutter member 20 is placed. Each tab 21 further comprises an aperture 25 through which a fixing screw may be placed to secure the base portion 3 to an underlying substrate, as described below.

Referring to Figure 6, a plurality of 'blisters' 26 is provided in the wall portion 7.

Each 'blister' 26 comprises an elongate indentation formed within the wall portion 7. The elongate blisters 26 may extend in a transverse direction, a longitudinal direction or some intermediate direction of the shutter member 20. A combination of transversely-extending and longitudinally-extending elongate blisters 26 may be provided. The blisters 26 act to strengthen the wall portion 7 in which they are formed, thus enhancing the rigidity of the shutter member 20 as a whole. Blisters of other shapes may alternatively or additionally be provided.

In the illustrated embodiment, blisters 26 are provided in the form of elongate indentations, which are provided in a region adjacent one of the edges cut from the wall portion 7 to define each wall tie 9. Accordingly, the shutter member 20 is strengthened in the regions in which the cuts are formed. Blisters may similarly be provided in the regions adjacent cuts in the base or wall portion 3, 7 defining edges of the base ties 8 or tabs 21 Figure 8 is a side-view of the shutter member 20 with base ties 8 engaged with corresponding wall ties 9 to bring the wall portion 7 into a vertical alignment, with respect to the base portion 3. Tabs 21 (not visible) are not folded outwardly and thus lie wholly within the base portion 3 (i.e. they do not extend outwardly from any edge of the base portion 3) and remain substantially within the plane of the base portion 3.

Figure 9 shows the shutter member 20 in use. The tabs 21 are folded outwardly at approximately 180 degrees so as to extend outwardly from the longitudinal edge 23 of the base portion 3, wherein the outwardly-extending part of the tab 21 lies substantially flat against the underlying substrate 4, substantially in the plane of the base portion 3. Fixing screws 5a, 5b extend through the base member 3 and into the underlying substrate 4 so as to secure the base portion 3 to the substrate 4. In particular, fixing screws 5b extend through the apertures 25 formed in the tabs 21 at a point beyond the longitudinal edge 23 of the base portion 3. It will be appreciated that in alternative embodiments of the present invention, alternative means may be used to secure the tabs 21 of the base portion 3 to an underlying substrate. For example, fixing screws may be drilled directly through the tabs 21.

In order for a shutter member of the kind described above to have sufficient stability when assembled with the wall portion 7 extending substantially perpendicularly to the base portion 3, and with the base portion 3 secured to the substrate 4, it is desirable that the base portion 3 is secured to the substrate 4 at a distance away from the upwardly extending wall portion 7 which is approximately half of the height H of the wall portion 7. In the prior art shutter member 1 shown in Figure 3, this is achieved by making the width W of the base portion 3 (that is, the distance between the edge of the base portion 3 adjoining the wall portion 7 at the predefined line of weakness 14 to the opposing longitudinal edge 23 of the base portion 3) approximately half the height H of the wall portion. Accordingly, when the shutter member 1 is secured to the substrate 4, a fixing screw 5 is provided towards the longitudinal edge 23 of the base portion 3, so as to secure the base portion 3 at the desired location and so as to provide the desired stability.

With the arrangement of the shutter member 20 according the present invention as shown in Figures 5 to 10, the base member 3 may be secured to the underlying substrate 4 at a point beyond the longitudinal edge 23 of the base portion 3 by means of the tabs 21. With reference to Figure 6, it can be seen that the tabs 21 are secured to the substrate 4 at a distance approximately equal to half the height H of the wall portion 7, whilst the width W of the base portion 3 (that is, the distance between the edge of the base portion 3 adjoining the wall portion 7 at the predefined line of weakness 14 to the opposing longitudinal edge 23 of the base portion 3) is significantly less than half the height H of the wall portion 7. Accordingly, by the provision of the tabs 21 extending outwardly from the longitudinal edge 23 of the base portion 3, the base portion 3 of the shutter member 20 can be made relatively narrow (relative to the base portion 3 of the prior art shutter member 1 of Figures 1 to 4), whilst still enabling the base portion 3 to be secured to the underlying substrate 4 at a distance away from the upwardly extending wall portion 7 which provides the required stability to the shutter member 20. This has the advantage that the amount of material, for example steel, used to manufacture the shutter member 20 is reduced, thus reducing the cost of manufacture, without compromising the stability of the shutter member 20 when in use.

As shown in Figure 10, the shutter member 20 can be formed as a single component by stamping or cutting from a planar sheet of appropriate material, preferably a metal and most preferably stainless steel. Figure 10 shows the shutter member 1 in a flat configuration, wherein appropriate cuts and predefined lines of weakness described above are formed in the sheet material, to enable the shutter member 20 to be folded from the flat configuration into the folded configuration shown in Figures 5 to 9. A plurality of identical shutter members 20 may be stacked in a flat configuration such that a detail on one shutter member is aligned with and/or accommodated within an equivalent detail of an adjacent shutter member in the stack. For example, any base ties 8, wall ties 9 or tabs 21 formed integrally with a first shutter member 20 are arranged to be aligned with corresponding base ties 8, wall ties 9 or tabs 21 of a second shutter member stacked above or beneath the first shutter member. Similarly, any strengthening blisters 26 formed within the first shutter member are preferably arranged to be aligned with corresponding blisters 26 of the second identical shutter member. Where the blisters comprise indentations formed in the shutter member 20, the protruding portion of each blister 26 formed on an upper side of the first shutter member is at least partially accommodated within a recessed portion of a corresponding blister 26 formed on a lower side of the second shutter member stacked atop the first shutter member.

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 shutter member for a shuttering system for concrete or other settable material, the shutter member comprising a substantially planar wall portion and a substantially planar base portion, the wall portion being arranged, in use, to extend substantially perpendicularly to the base portion, wherein the base portion comprises at least one tab arranged, in use, to extend outwardly from an edge of the base portion, wherein the at least one tab lies substantially in the plane of the base portion, the tab being further arranged to be secured to a surface underlying the base portion in use.
2. A shutter member according to claim 1, wherein the tab is formed integrally with the base portion.
3. A shutter member according to claim 2, wherein the tab is foldable relative to the base portion and is arranged to fold from first a position in which the tab does not extend outwardly from an edge of the base portion, to a second position in which the tab extends outwardly from an edge of the base portion, wherein the tab lies substantially in the plane of the base portion in both the first and second positions.
4. A shutter member according to claim 3, wherein the tab is formed wholly within the base portion and is cut out from the base portion.
5. A shutter member according to claim 4, wherein the tab is joined to the base portion at a predefined line of weakness, the tab being foldable about the predefined line of 25 weakness.
6. A shutter member according to claim 5, wherein the predefined line of weakness comprises one or more perforations formed in the base portion.
7. A shutter member according to claim 5, wherein the predefined line of weakness comprises a linear section of the base portion in which the base portion is thinned.
8. A shutter member according to any one of claims 4 to 7, wherein the tab has a head portion and a waist portion, the tab being joined to the base portion at the waist portion of the tab, wherein the waist portion of the tab is narrower than the head portion.
9. A shutter member according to any one of claims 4 to 8, wherein the tab is defined by three edges cut out from the base portion and the predefined line of weakness.
10. A shutter member according to claim 9, further comprising one or more indentations or deformations formed within the material from which the shutter member is formed, said one or more indentations or deformations being provided in a region adjacent one of the edges cut from the base portion to define the tab.
11. A shutter member according to claim 10, wherein said one or more indentations or deformations are elongate, each being arranged to extend parallel to a respective edge of the base portion from which the tab has been cut.
12. A shutter member according to any preceding claim, wherein the shutter member is stamped or cut from sheet metal as a single component.
13. A shutter member according to any preceding claim, wherein, in use, the distance from an edge of the base portion adjoining the wall portion to an opposing edge of the base portion is less than half the height of the wall portion from an edge of the wall portion adjoining the base portion to an uppermost edge of the wall portion.
14. A shutter member according to claim 13, wherein, in use, the distance from an edge of the base portion adjoining the wall portion to a distal edge of the tab is approximately half the height of the wall portion from an edge of the wall portion adjoining the base portion to an uppermost edge of the wall portion.
15. A shutter member according to any preceding claim, wherein the wall portion comprises a plurality of first portions of fie members cut from it and the base portion comprises a plurality of second portions of tie members cut from it, wherein the first and second portions of the ties members are arranged to engage with each other to tie the wall portion to the base portion.