GB2453010A

GB2453010A - Plasterboard anchor

Info

Publication number: GB2453010A
Application number: GB0811381A
Authority: GB
Inventors: Robert Justin Beveridge
Original assignee: BE INVENTIVE Ltd
Current assignee: BE INVENTIVE Ltd
Priority date: 2007-06-21
Filing date: 2008-06-20
Publication date: 2009-03-25
Anticipated expiration: 2028-06-20
Also published as: GB0811381D0; GB0711996D0; GB2453010B

Abstract

A plasterboard anchor for fixing an object to a wall surface having an outer plasterboard layer 12 and an underlying structure 10 such as a brickwork substrate or a second plasterboard layer, the outer layer 12 being spaced from the underlying structure 10 by a cavity 16 comprises a threaded portion 52 for engaging with the outer layer 12 and means 54 for engaging or co-operating with the underlying structure 10. A threaded fastener engages the anchor to fix an object to the wall surface.

Description

FIXING APPARATUS AND METHOD 2453010 The present invention relates to a fixing apparatus and method and particularly, but not exclusively, to an apparatus and method for fixing an object to a wall or other surface. The invention finds advantageous application in the fixing of objects to so-called cavity walls, having an outer layer of plasterboard or the like, to which the object must be fixed, and a second or underlying layer spaced from the first layer by a cavity. Aspects of the invention relate to an apparatus, to a method, to a kit and to a structure.

There are various forms of cavity wall used in the building industry. One form of cavity wall is known as a dry-lined wall and generally comprises a support structure, such as a solid brick or blocked wall, which is overlaid by a dry sheeting material, such as plasterboard, also known as gypsum board or wall board. The plasterboard is often adhered to the exposed surface of the support structure by dabs of adhesive which, when cured, support the plasterboard in a spaced manner from the support structure so as to define a gap or "cavity" therebetween. In an alternative arrangement, the plasterboard layer is secured to batons fixed to the support structure such that the gap or cavity between the plasterboard and the support structure is substantially equal to the thickness of the batons.

Another form of cavity wall is known as a stud-wall or partition-wall. This type of wall generally comprises two layers of dry sheeting material, such as plasterboard, which are spaced apart by timbers or "studs" disposed at regular intervals between the layers. Stud-walls are relatively cheap and easy to erect and are therefore often used to form internal walls or partitions.

The securing of objects to such walls can be difficult, owing to the relatively fragile nature of the plasterboard. A number of existing devices adapted for securing objects to cavity walls are available. Known generally as wall plugs or wall anchors, these devices are arranged to secure a standard threaded fastener, such as a screw, either to the outer plasterboard layer or to the underlying support structure. An example of such a device is described in GB2241549, the contents of which are incorporated herein by reference.

Such devices are suitable for supporting only relatively light loads and tend to impose compressive, tensile and/or shear stresses on the outer plasterboard layer which can, in some cases, lead to damage or failure thereof. Furthermore, care must be taken during installation of these devices in order to prevent cosmetic damage to the plasterboard.

It is an aim of the invention to address one or more of these issues and to improve upon known technology. Embodiments of the invention may provide a fixing apparatus, suitable for use with a cavity wall, which addresses disadvantages of existing fixing devices. Other embodiments of the invention may provide a method of fixing an object to a wall which addresses disadvantages of known techniques.

Further aims and advantages of the invention will become apparent from the

following description, claims and drawings.

Aspects of the invention therefore provide an apparatus and a method as claimed in the appended claims.

According to another aspect of the present invention there is provided an apparatus for fixing an object to a wall surface having a first layer and a second layer spaced from the first layer, the apparatus comprising a body adapted to cooperate with a threaded fastener and an external thread for engaging with the first layer, wherein the apparatus comprises engagement means for engaging and/or cooperating with the second layer, in use.

In one embodiment, the invention comprises an improvement to a conventional plasterboard anchor such as that described in GB2241549 through the provision of an elongate projection extending from a driving tip of the anchor which is arranged to engage or cooperate with the second layer thereby to stabilise the anchor and improve its performance.

In one embodiment, the projection is adapted to be inserted in a recess formed in the second layer. In one embodiment, the projection is adapted to pierce a surface of the second layer. In one embodiment, the projection is adapted to abut or engage with a surface of the second layer.

Advantageously, by engaging and/or cooperating with the second layer, the apparatus provides significantly greater resistance to bending moment, thereby improving the stability and reliability of the fixing and increasing load capacity.

In one embodiment, the first layer comprises a plasterboard layer or surface and the second layer comprises a brick or blocked wall. In one embodiment, both the first and second layers comprise plasterboard layers or surfaces.

Within the scope of this application it is envisaged that the various aspects, embodiments, examples, features and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings may be taken individually or in any combination thereof.

The present 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 through a conventional dry-lined wall; Figure 2 is a cross-sectional view through a conventional stud-wall; Figure 3 illustrates a known device for fixing an object to walls of the type shown in Figures 1 and 2; Figure 4 illustrates the device of Figure 3 in use with a wall of the type shown in Figure 1; Figure 5 illustrates side, end and perspective views of an apparatus embodying one form of the invention; Figure 6 illustrates side, end and perspective views of an apparatus embodying another form of the invention; Figure 7 is a side view of an apparatus embodying yet another aspect of the invention; Figures 8 to 13 illustrate steps of a method for fixing an object to a wall of the type shown in Figure 1 using the apparatus of Figure 6; Figure 14 illustrates use of the apparatus of Figure 7 to fix an object to a wall of the type shown in Figure 2; Figure 15 illustrates an apparatus embodying a still further form of the invention; and Figure 16 illustrates use of the apparatus of Figure 15 to fix an object to a wall of the type shown in Figure 1.

In the drawings, as far as possible, like reference numerals indicate like parts. It will be understood that any references to direction or orientation are used only by way of example and in the context of the drawings and are not intended to be limiting in any way. Furthermore, the drawings are not necessarily shown to scale.

Referring firstly to Figure 1, this illustrates a section through a conventional dry-lined wall, as viewed from above. The wall comprises an underlying brickwork supporting structure or substrate 10 overlaid by a dry sheeting material 12 known as plasterboard. Plasterboard generally consists of a thick layer of gypsum plaster sandwiched between two paper or other cellulose-based retaining sheets. In use, the plasterboard sheets 12 are fixed to the surface of the brickwork substrate layer 10 by means of a specialised adhesive which is applied to the wall surface in a so-called "dot and dab" formation, wherein one or more adhesive beads 14 are applied to the wall surface at spaced intervals.

Each plasterboard sheet 12 is offered up to the wall 10 and pressed against the adhesive beads 14 which act to secure the sheet 12 to the brickwork substrate 10.

Due to the viscosity of the adhesive, the plasterboard sheet 12 is usually not pressed into direct contact with the brickwork 10 but, instead, leaves an air gap or cavity 16, often between 5 -30mm in depth, between the surface of the brickwork 10 and the opposing surface of the sheet 12. This type of arrangement is known as "dry-lining" and is completed by the application of a thin "skim" coat of plaster (not shown) to provide a smooth, aesthetically pleasing finish to the wall.

In another arrangement (not shown) the plasterboard sheets 12 are affixed to wooden laths or batons which are themselves secured to the brickwork substrate 10 in a vertical orientation. In this case, the width of the gap or cavity 16 between the plasterboard sheets 12 and the brickwork substrate layer 10 is substantially equal to the thickness of the batons.

Referring next to Figure 2, this illustrates a cross section through a conventional stud-wall, again as viewed from above. The stud-wall comprises two layers of plasterboard sheeting 12, 13 joined in spaced apart relationship by vertically oriented timbers 18 known as studs. The studs are spaced apart along the wall at a predetermined distance (usually approximately 0.5-0.6n1) and provide rigidity to the wall. In this case, the width of the cavity 16 defined between the front and rear layers of plasterboard 12, 13 is substantially equal to thickness of the studs 18. The cavity 16 may be provided with thermal or acoustic insulation (not shown), if desired, or may be left empty.

Figure 3 illustrates a known device for fixing objects to the types of cavity wall described with reference to Figures 1 and 2. This type of device is known as a plasterboard anchor and is described in, for example, GB2241 549.

The plasterboard anchor, denoted by reference numeral 20, comprises a generally cylindrical body 22 having a first end 24, hereafter termed the tip, and a second end 26, hereafter termed the driving head. The diameter of the body 22 is substantially constant from the driving head 26 to a mid point thereof, after which the body 22 tapers to a point at the tip 24.

The driving head 26 features a radially outwardly directed flange 28 and is adapted to receive the tip of a twist-drive device or tool such as a screwdriver. An internal bore 30 extends through a portion of the body 22, coaxially with the central axis of the device 20. The bore 30 is closed at its end proximal to the tip 24 of the body 22 but is open at the driving head 26 for receiving a conventional threaded fastener such as a screw. The internal surface of the bore 30 is provided with a thread (not shown) for cooperation with the external thread of the threaded fastener.

The external surface of the body 22 comprises a wide, large pitch, helical drilling thread 32, similar in shape to an Archimedean screw. The thread 32 extends from a point at or close to the driving head 26 to a point at or close to the tip 24. The thread 32 tapers towards the tip 24 such that the depth of the thread 32 reduces from the end adjacent to the driving head 26 to the end adjacent to the tip 24.

Figure 4 illustrates the device of Figure 3 securing an object to a dry-lined wall of the type shown in Figure 1. In use, a hole 36 of diameter approximately equal to the diameter of the body 22, is drilled in the plasterboard layer 12 using a conventional drilling tool. The tip 24 of the anchor 20 is then inserted in the hole until the end of the thread 32 proximal to the tip 24 engages with the plasterboard 12, a position hereafter termed the "pre-driving point".

Once at the pre-driving point, the anchor 20 is then twist-driven into the plasterboard 12 using a suitable tool, such as a screwdriver. As the anchor 20 is twisted about its longitudinal axis, the thread 32 cuts into the plasterboard 12 so as to form a cooperating thread therein. Thereafter, the anchor 20 is driven into threaded engagement with the plasterboard 12 until the flange 28 at the driving head 26 is in abutment with, or substantially flush with, the outer surface of the plasterboard 12.

Once the anchor 20 is fixed to the plasterboard 12 in the manner described above, a conventional threaded fastener 90 is inserted into the axial bore 30 formed in the anchor body 22 and twist-driven into engagement therewith so as to secure an object 92 to the wall, as shown in Figure 4. It will be understood from the foregoing that, in this arrangement, the weight of the object 92 fixed to the wall is carried entirely by the plasterboard layer 12.

A number of modifications and improvements to this form of device have been proposed. For example, as disclosed in EP0582374, the tip 24 of the anchor 20 may be provided with a short, pointed punch portion to enable the anchor 20 to be hammered or punched into the plasterboard 12 until the anchor reaches the pre-driving point. Thereafter, the anchor 20 is twist-driven into the plasterboard as described above. The addition of the punch portion eliminates the need for an initial drilling step in the installation of the anchor 20.

Devices of the type described above are widely used and provide a simple and inexpensive means for fixing relatively light objects to cavity walls. However, they are known to suffer from a number of disadvantages.

For example, since the weight of the fixed object 92 is carried entirely by the outer plasterboard layer 12, plasterboard anchors are generally capable of supporting only relatively light loads. Heavy loads may impose excess local stresses on the plasterboard which can lead to cracking or crumbling. By way of example, it is recommended that devices of the type of shown in Figure 3 are not used to fix loads greater than approximately 3kg.

In addition, the weight of the object 92 acting downwards, parallel to the surface of the wall (arrow A) causes a torque or moment to be applied to the anchor 20 about the point B, which tends to twist or rotate the anchor 20 within the plasterboard 12 in the direction of arrow C. Due to the friable nature of the plasterboard 12, such twisting can result in the fastener becoming loose, such that the reliability of the fixing is reduced.

Furthermore, conventional plasterboard anchors are prone to being over-driven into the plasterboard to the extent that further twisting of the anchor simply results in its spinning within the hole due to the friable nature of the plasterboard.

Finally, it is well known that plasterboard anchors of the type shown in Figure 3 are difficult to drive into the plasterboard at right angles to the wall surface. That is to say, unless extreme care is taken, conventional anchors have a tendency to "wobble" during insertion into the plasterboard 12 so that the axis of insertion is not always the optimum 900. This can cause the plasterboard 12 around the anchor to disintegrate which has an adverse effect on the reliability of the final fixing, as well as compromising the appearance thereof.

Referring now to Figure 4, an apparatus embodying one form of the invention is shown in perspective view generally at 40. In general, the apparatus 40 takes the form of an anchor or plasterboard fixing broadly similar to that shown in Figure 3, but with the addition of engagement means in the form of an elongate projection or "nose" extending from the tip thereof.

More specifically, the apparatus 40 comprises a generally cylindrical body portion 42 having a leading or tip end 44 and a driving head end 46. The body 42 is slightly tapered such that the diameter thereof reduces by a small amount from the driving head 46 to the tip 44.

The driving head 46 features a radially outwardly directed flange 48 and includes a central recess 49 adapted to receive the tip of a twist-drive device or tool such as a screwdriver or hexagonal key. An internal bore 50, open at the driving head 46, extends through the body 42, coaxially with the recess 49, and is arranged to receive a conventional threaded fastener such as a screw or a bolt. The internal surface of the bore 50 is provided with a thread (not shown) for cooperation with the external thread of the threaded fastener.

The external surface of the body portion 42 comprises a wide, large pitch, helical drilling thread 52, similar in shape to an Archimedean screw. The thread 52 extends from a point at or close to the driving head 46 to a point at or close to the tip 44. The thread 52 tapers towards the tip 44 such that the depth thereof reduces from the end adjacent to the driving head 46 to the end adjacent to the tip 44.

It will be appreciated that, to this extent, the apparatus 40 is broadly similar to that of the known anchor described with reference to Figure 3. However, the apparatus of the invention additionally comprises engagement means in the form of an elongate projection or "nose" 54, extending forwardly from the tip 44 of the body portion 42, substantially axially aligned with the central bore 50.

In the illustrated, non-limiting embodiment, the projection 54 is approximately twice as long as the body portion 42 and is generally cylindrical in shape, having a base 56 at one end, at which it is connected to the tip 44 of the body portion 42, and a generally rounded or blunt tip 58 at its free end. The projection 54 is slightly tapered from the base 56 towards the tip 58 such that the diameter thereof reduces by a small amount towards the free end. In the illustrated embodiment, the diameter of the base 56 is substantially equal to that of the tip 44 of the body portion 42.

The projection 54 features retention means in the form of a shallow, rounded thread 59 on its outer surface, the purpose of which is described below. The depth of the thread 59 remains substantially constant along the length of the projection 54 and is dimensioned such that the maximum outer diameter of the projection 54 is substantially equal to that of the tip 44 of the body portion.

Figure 6 illustrates an alternative form of apparatus embodying the invention. The apparatus of this embodiment is generally similar in form to that of Figure 5; however, the elongate projection or nose 54 is "cored out" so as to be generally cruciform in cross section, having a narrow cylindrical shank or hub along which extends four generally orthogonal arms. As in the embodiment of Figure 5, a shallow, rounded, helical thread 59 is wound around the projection 54, the purpose of which is described below.

Figure 7 illustrates a still further form of apparatus embodying the invention. In this embodiment, the tip 58 of the elongate projection or nose 54 is tapered to a sharp point 72. In all other respects, the apparatus of this embodiment is substantially identical to that of Figure 4.

Referring next to Figures 8 to 13, a method of installation and use of the apparatus of Figure 6 is shown. The method is shown in the context of fixing an object to a dry-lined wall, such as that shown in Figure 1, comprising an outer plasterboard layer 12 spaced from an underlying brickwork substrate 10 by a cavity 16.

As shown in Figure 8, the user firstly drills a hole 80 through the plasterboard 12 and into the underlying brickwork 10 to form a recess 82 therein. The hole 80 is drilled to a diameter substantially equal to, or slightly less than, the diameter of the body portion 42. Furthermore, the recess 82 is drilled into the brickwork substrate 10 to a depth approximately equal to, or slightly greater than, the length of the body portion 42 between the tip 44 and the driving head 46.

Next, as shown in Figure 9, the user inserts the apparatus 40 into the drilled hole 80 until it reaches the pre-driving point, that is to say the position at which the end of the drilling thread 52 abuts the outer surface of the plasterboard 12. At this point the projection 54 is aligned with, and partially inserted into, the recess 82 formed in the brickwork substrate 10 by the drilling step described above.

The user then twist-drives the apparatus 40 into the plasterboard 12, using a suitable tool engaged in the recess 49 in the driving head 46, as shown in Figure 10. As the apparatus 40 is rotated about its longitudinal axis, the drilling thread 52 engages with, and cuts into, the plasterboard layer 12, forming a cooperating female thread therein and drawing the apparatus 40 towards the brickwork substrate 10. As the apparatus is driven further into the plasterboard layer 12, the projection 54 extends further into the recess 82 in the brickwork 10. This engagement of the projection 54 in the recess 82 serves to guide the insertion of the apparatus 40, ensuring that it is driven in correct and true and is not twisted off axis.

In Figure 11, the apparatus 40 is shown fully inserted into the wall. At this point, the flange 48 at the driving head 46 of the body 42 is in abutment with the outer surface of the plasterboard 12 and the tip 44 of the body portion 42 protrudes into the cavity 16 between the plasterboard 12 and the brickwork substrate 10 (although it will be understood that this will depend on the length of the body portion 42 and the thickness of the plasterboard layer 12).

In addition, at its fully inserted position, the projection 54 extends substantially fully into the recess 82 in the brickwork substrate 12 and the apparatus 40 is well secured in the wall owing to the frictional engagement of the thread 52 with the plasterboard material 12.

Finally, as shown in Figure 12, an object 92 to be fixed to the wall, for example a bracket, is offered up with its fixing hole 94 aligned with the central bore 50 of the apparatus 40. A conventional threaded fastener, such as a bolt or screw 90 is then inserted into the central bore 50, through the fixing hole 94 in the object 92, and twist-driven into engagement therewith so as to secure the object 92 to the fixing 40.

When the threaded fastener 90 is tightened, the object 92 is effectively clamped between the head 96 of the threaded fastener 90 and the driving head 46 of the apparatus 40, as shown in Figure 13. This arrangement results in little or no damage to the plasterboard layer 12 and further tightening of the threaded fastener 90 simply results in a greater clamping force applied to the object 92.

The illustrated embodiment finds particularly beneficial, but not exclusive, use with dry-lined walls having an underlying brickwork substrate 10. However, as mentioned above, the apparatus may additionally be used with stud-walls, such as the type shown in Figure 2 comprising two plasterboard layers 12, 13 spaced by a cavity 16.

It will be understood by the skilled reader that it may be impractical, during the initial drilling step, to form the recess 82 in the rear plasterboard layer 13, owing to the relatively reduced thickness of the plasterboard layer 13 and the resulting accuracy that is required in order to avoid drilling fully therethrough.

In this application, therefore, a hole 80 is drilled in the front plasterboard layer 12 and the apparatus 40 is inserted to the pre-driving point. The apparatus 40 is then twist-driven into the plasterboard layer 12a, as described above. Here, the apparatus 40 is arranged so that, when the body portion 42 is fully inserted in the front plasterboard layer 13, the sharply pointed tip 72 of the projection 54 pierces the rear plasterboard layer 13 and engages therein to a depth of, for example, 2-10mm (depending on the thickness of the layer). The length of the projection 54 is selected having regard to the width of the cavity 16 and the thickness of the rear plasterboard layer 13 so that the tip 72 does not pass fully through the rear plasterboard layer 13.

In the embodiments described above, the engagement of the projection 54 with the rear layer of the wall, (i.e. the brickwork substrate 10 in a dry-lined wall or the second plasterboard layer 13 in a stud-wall) provides a considerable resistance to the torque or moment applied to the apparatus 40 by the weight of the object 92. This reduces or substantially eliminates twisting or rotation of the apparatus 40 within the plasterboard layer 12 (in the direction of arrow C shown in Figure 3) and results in a stronger, more reliable fixing which causes less damage to the plasterboard layer 12.

Furthermore, when used with dry-lined walls, such as that shown in Figure 1, the engagement of the projection 54 in the recess 82 in the brickwork substrate 10 creates a cantilever effect, permitting at least part of the load to be carried by the brickwork itself. This advantageously allows the apparatus to be used for supporting significantly greater loads than conventional plasterboard anchors, wherein the load is carried entirely by the outer plasterboard layer 12.

By way of example, the applicants have found empirically that the apparatus of the invention is able to support loads up to 50% greater than that of existing products with little or no damage to the plasterboard 12.

In addition, the projection 54 can assist installation of the apparatus: insertion of the projection 54 into the recess 82 as the apparatus 40 is being twist-driven into the wall may help to ensure that the apparatus is driven substantially perpendicularly relative to the wall surface, thereby improving the performance of the final fixing.

While the apparatus shown in Figures 4-7 and described above represent particularly advantageous embodiments of the invention, there are, nevertheless, a number of modifications or alternatives envisaged within the scope of the present invention.

For example, the central bore 50 of the body portion 42 may be open-ended or closed-ended. Where the central bore 50 is closed ended, it may extend only to the tip 44 of the body portion 42 or it may extend through a portion of, or substantially the full length of, the projection 54.

In one advantageous embodiment, shown in Figure 15, the bore extends substantially the full length of the projection 54 which is therefore substantially hollow.

Slots or grooves are formed longitudinally in the projection which permits the projection to expand when a threaded fastener is inserted therein, in the manner of a conventional wall plug.

In the event that the threaded fastener used is not sufficiently long to reach the projection, and additional cylindrical insert may be provided which, in use, is inserted into the bore 50 before the threaded fastener, and is then pushed towards the end of the projection by subsequent insertion of the threaded fastener.

Figure 16 shows the apparatus of Figure 15 in use in a conventional cavity wall.

Here, the threaded fastener 90 extends well into the projection 54 causing it to expand radially within the recess 82, thereby improving security of the fixing and resistance to axial withdrawal. In this case, the apparatus, or at least the projection 54, may be formed of a suitably flexible and/or resilient material.

The projection 54 may be formed integrally with the body portion 42, such that the apparatus is formed as a single piece (unitary). Alternatively, the projection 54 may be formed as a separate part which can be connected or attached to the tip 44 of the body portion 42 as desired. Such attachment may be by means of a screw thread, an interference attachment, an adhesive or by any other suitable means. This type of arrangement may provide greater flexibility but at an increased manufacturing cost.

The length of the projection 54 can be selected as desired. Where the apparatus 40 is used with a dry-lined or cavity wall of the type shown in Figure 1, the projection 54 should be of sufficient length to bridge the cavity 16 and insert in the recess 82 in the brickwork substrate 10 when the apparatus 40 is driven substantially fully into the wall. The projection 54 may be chosen to have a length sufficient to bridge the cavity 16 and at least partially enter the recess 82 when the apparatus is at the pre-driving point, as shown in Figure 9. For example, the length of the projection 54 may be between 30mm and 40mm although other lengths, greater or smaller, are equally possible, depending on the desired application.

Embodiments of the invention may be configured such that the length of the projecting nose can be adjusted to suit the desired application. For example, the nose may be formed of a plurality of discrete sections, joined together by w eakened regions. Where a projection 54 having a reduced length is required, for example where the cavity 16 is relatively narrow, the excess sections may be twisted or snapped off from the remaining sections at a weakened region to achieve the desired length.

Alternatively, the projection 54 may be attached to the tip of the body portion 42 by means of an elastic member such as a compression spring or a rubber section. In this embodiment, if the tip 58 of the projection 54 reaches the closed end of the recess 82 before the body portion 42 is fully inserted into the plasterboard 12, further insertion simply causes the elastic member to compress so as to reduce the effective length of the projection 54.

Here, it may be necessary to use, in the step shown in Figures 12 and 13, a threaded fastener 90 which is sufficiently long to extend through the elastic member and into the distal portion of the projection 54 when it is fully inserted. This may ensure that the structural rigidity of the apparatus 40 is not adversely affected by the

introduction of the flexible elastic member.

Alternatively still, the apparatus 40 may be sold as a kit comprising a body portion 42 and a plurality of projection members of various lengths which are connectable to the tip 44 of the body portion 42 as described above. In use, the user simply selects the desired length of the projection 54 and attaches the corresponding projection member to the body portion 42.

The main body of the projection 54 may taper towards the tip 58 thereof, such that its diameter at the base 56 is greater than that at the tip 58. This may aid insertion of the apparatus 40 into the drilled hole and the recess 82. Alternatively, the diameter of the projection 54 may be substantially constant along its length.

As shown in the illustrated embodiment, the projection 54 may optionally be provided with retaining means in the form of the helical thread 59. When the projection 54 is inserted into the recess 82, the thread 59 cooperates or engages with the wall of the recess 82 to further resist bending, torsional and/or axial forces applied to the apparatus 40. For example, such retaining means may increase resistance to axial withdrawal of the apparatus.

In addition, the helical thread may serve to remove any dust, swan or other particles left in the recess 82 following drilling. As the apparatus is twist-driven into the plasterboard 12, the projection 54 correspondingly rotates so that any such particles are drawn out in the manner of an Archimedean screw.

In another example, the projection 54 takes the form of two closely spaced, parallel fingers, in the manner of a conventional split pin. As the projection 54 is inserted into the recess 82 during installation of the apparatus 40, the fingers are pressed radially inwardly by the walls of the recess 82 such that an interference fit of the projection 54 within the recess 82 is achieved.

In addition, the apparatus 40 may be arranged such that the insertion of the threaded fastener 90 within the central bore 50 causes the fingers to spread radially outwardly, as in the embodiment of Figure 15, thereby enhancing the frictional engagement of the projection 54 within the recess 82 and further improving resistance to axial withdrawal.

The apparatus 40 may be formed from any suitable material such as metal or a plastics material. Where the projection 54 is formed as a separate part from the body portion 42, the two parts may be formed from the same or a different material.

In one embodiment, the projection 54 is coated with an adhesive, such as an impact adhesive, along its length and/or at the tip region 58, to further enhance engagement with the rear layer of the wall. For some applications, the use of an adhesive on the tip 58 of the projection 54 may eliminate the need for the projection to engage in a recess 82 or pierce the rear plasterboard layer 13 -when the tip 58 of the projection 54 contacts the surface of the rear layer 10, 13 during insertion of the apparatus 40, the adhesive alone may achieve a sufficient engagement therewith to provide some or all of the above-described advantages.

It will be appreciated that the present invention improves upon existing plasterboard anchors by providing means for cooperating and/or engaging with the rear-most layer of a cavity wall, for example the underlying brickwork substrate layer 10 of a dry-lined wall or the rear plasterboard layer 13 of a stud-wall, in addition to the front (outer) plasterboard layer 12, 13. This is in contrast with known plasterboard anchors which engage only with the outer plasterboard layer of the wall.

Engagement with the rear layer of the wall improves the load capacity of the fixing and reduces the adverse effects of twisting or bending of the apparatus within the plasterboard layer 12. As a result, damage to the plasterboard layer 12 is also reduced or substantially eliminated.

While only selected embodiments have been chosen to illustrate the present invention, it will be apparent to those skilled in the art that various changes and modifications can be made herein without departing from the scope of the invention as defined in the appended claims. For example, the size, shape, location or orientation of the various components can be changed as needed and/or desired.

Components that are shown directly connected or contacting each other can have intermediate structures disposed between them. The functions of one element can be performed by two, and vice versa. The structures and functions of one embodiment can be adopted in another embodiment. It is not necessary for all advantages to be present in a particular embodiment at the same time.

Each feature and/or method step recited in the appended claims or disclosed hereinabove may be taken independently or in combination with any other feature and/or method step. Multiple features and/or method steps may be combined and any and all such combinations are intended to be included within the scope of this application.

In the above description, and in the claims, the term "cavity wall" is used to refer collectively to walls of the types shown in Figures 1 and 2, and any other form of wall or structure having an first, outer layer spaced from a second, underlying layer by a gap or cavity.

Every feature and/or method step which is unique from the prior art, alone or in combination with other features and/or method steps, also should be considered a separate description of further inventions by the applicant, including the structural and/or functional concepts embodied by such feature(s). Thus, the foregoing descriptions of the embodiments according to the present invention are provided for illustration only, and not for the purpose of limiting the invention as defined by the appended claims and their equivalents.

This application claims priority from UK Patent Application No. GB0711996.9, filed 21st June 2007, the contents of which are expressly incorporated herein by reference.

Claims

CLAIMS: 1. An apparatus for fixing an object to a cavity wall having first and second layers spaced by a cavity, the apparatus comprising: means for threadedly engaging with the first layer; means for engaging or cooperating with the second layer; and means for engaging with a threaded fastener.
2. An apparatus as claimed in claim 1, comprising: a body having an external thread for engagement with the first layer and an axial bore for receiving a threaded fastener; and engagement means for engagement with the second layer.
3. An apparatus as claimed in claim 1 or claim 2, wherein the engagement means comprises a projection extending from the body.
4. An apparatus as claimed in claim 3, wherein the body has a first end comprising driving head and a second end from which the projection extends.
5. An apparatus as claimed in claim 4, wherein the driving head comprises at least one recess or projection arranged to cooperate and/or engage with a suitable tool or device for twist-driving and/or screwing the apparatus into the first layer.
6. An apparatus as claimed in claim 4 or claim 5, wherein the external thread extends from a position at or close to the driving head to a position at or close to the second end of the body.
7. An apparatus as claimed in any of claims 3 to 6, wherein the projection has a length that is between 1 and 3 times the length of the body.
8. An apparatus as claimed in any of claims 3 to 7, wherein the projection is tapered towards a free end or tip thereof.
9. An apparatus as claimed in any of claims 3 to 8, wherein the projection is solid along at least a portion of its length.
10. An apparatus as claimed in any of claims 3 to 9 wherein the projection is hollow along at least a portion of its length.
11. An apparatus as claimed in any of claims 3 to 10, wherein the projection comprises a plurality of fingers, ribs or arms extending along at least a portion of its length.
12. An apparatus as claimed in claim 11, wherein the plurality of fingers, ribs or arms are mutually joined at an axially central hub.
13. An apparatus as claimed in claim 11, wherein the plurality of fingers, ribs or arms are not joined.
14. An apparatus as claimed in any of claims 3 to 13, wherein the projection is arranged to insert within a recess in the second layer.
15. An apparatus as claimed in claim 14, wherein the projection is arranged to be radially inwardly compressed when inserted into the recess.
16. An apparatus as claimed in claim 14 or claim 15, wherein the projection has means for engaging with the walls of the recess.
17. An apparatus as claimed in claim 16, wherein the means for engaging with the walls of the recess comprises an external thread.
18. An apparatus as claimed in any of claims 14 to 17, wherein the projection is arranged to expand radially by engagement with the threaded fastener so as to engage with the walls of the recess.
19. An apparatus as claimed in any of claims 3 to 18, wherein the axial bore comprises an internal thread.
20. An apparatus as claimed in any of claims 3 to 19, wherein the bore is open at one or both ends thereof.
21. An apparatus as claimed in any of claims 3 to 20, wherein the bore extends substantially to the free end of the projection so as to receive at least a portion of the threaded fastener therein.
22. An apparatus as claimed in any of claims 3 to 21, wherein the body and the projection are formed as single piece.
23. An apparatus as claimed in any of claims 3 to 21, wherein the projection is formed separately and/or is separable from the body.
24. An apparatus as claimed in claim 23, wherein the projection is arranged to be attached to the body by at least one of an interference fit, a push fit, threaded engagement and an adhesive.
25. An apparatus as claimed in any of claims 3 to 24, wherein the body and/or the projection is formed from a plastics material and/or a metal.
26. An apparatus as claimed in any of claims 3 to 25, wherein the projection has a length of between 20mm and 80mm and preferably of between 3Omm-4Omm.
27. An apparatus as claimed in any of claims 3 to 26, wherein the projection is arranged to be adjustable in length.
28. An apparatus as claimed in any of claims 3 to 27, wherein a tip of the projection is arranged to pierce a surface of the second layer so as to engage therewith.
29. An apparatus as described in GB2241 549, the improvement comprising means for engaging with a second layer of a cavity wall.
30. A method of fixing an object to a surface comprising a first layer and a second layer spaced from the first layer by a cavity, the method comprising: twist driving an anchor into engagement with the first layer; engaging or cooperating the anchor with the second layer; and inserting a threaded fastener into the anchor.
31. An apparatus or a method as claimed in any preceding claim, wherein the first layer is a plasterboard layer or the like and wherein the second layer is a brick or blockwork wall or a second plasterboard layer or the like.
32. An apparatus constructed and arranged substantially as described herein with reference to accompanying figures 5-16.