AU2009284007B2

AU2009284007B2 - Apparatus and method for fixing to a laminated material

Info

Publication number: AU2009284007B2
Application number: AU2009284007A
Authority: AU
Inventors: Richard Hall
Original assignee: HOLDFAST FIXINGS Ltd
Current assignee: HOLDFAST FIXINGS Ltd
Priority date: 2008-08-18
Filing date: 2009-08-18
Publication date: 2014-08-21
Anticipated expiration: 2029-08-18
Also published as: WO2010020768A1; GB2462866A; GB2462866B; GB2462818A; AU2009284007A1; GB0816953D0; GB0815064D0

Abstract

A fixing for a laminated material comprises an elongate shaft extending from a tip to a head, the shaft having an external screw thread comprising a first thread section proximate the tip and a second thread section proximate the head, the first thread section having a thread diameter or form that differs from a thread diameter or form of the second thread section thereby to adapt the first thread section to a different material. When used in a dry lined wall, this permits the first thread section to engage with the masonry in order to provide the necessary pull-out resistance. Meanwhile, the second thread section can engage with the plasterboard in order to hold the plasterboard in place (and therefore protect it) and also to use the resistance to shear forces that plasterboard is capable of providing. Thus, the first and second thread sections preferably have a combined length greater than about 20mm in length so that the first thread section can extend into the masonry. The first and second thread sections can have the same thread pitch so as to pass smoothly through the two layers without disturbing their relative position. Alternatively, such as for use in other laminate situations, the first thread section can have a thread pitch greater than that of the second thread section. This will tend to draw the outer layer more firmly toward the underlying layer. Such a fixing can be in the form of a screw or a plug.

Description

WO 2010/020768 PCT/GB2009/002007 -1 Apparatus and method for fixing to a laminated material FIELD OF THE INVENTION The present invention provides an apparatus and a method for fixing to a laminated material, such as a dry-lined wall. BACKGROUND ART The provision of secure fixings into laminated surfaces has presented problems for some time. This has however become more acute in recent decades with the development of the dry-lined wall (hereinafter "DLW") in which a layer of plasterboard or other gypsum-based board about 12.5 mm (1/2") is glued to a masonry surface by large pads of adhesive. This leaves a cavity of around 10 mm between the plasterboard and the underlying masonry surface. This gypsum surface is then covered with a layer of "skim" or plaster in order to provide a smooth outer surface that can be painted or otherwise decorated. A DLW has significant advantages during the constructional phase in that there is very much less water to expel from the plaster coat (as opposed to a plastered wall), allowing further constructional steps to take place days or weeks earlier than would otherwise be possible. Dry-lined walls do however present problems to the building owner after construction. It is common to add fittings to the building, such as shelves or INCORPORATED BY REFERENCE (RULE 20.6) 2 furniture units, and these must be attached to the wall using a suitable fitting. The dry-lining layer of such a wall offers little strength against pull-out or plucking forces, but it is difficult to make a secure connection to the underlying masonry wall without causing damage to the dry lining. A wide range of fixings for plasterboard walls are currently available, none of which are especially satisfactory for heavy loads. Very little is available for a dry-lined wall. Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field. It is an object of the invention to provide a fixing for a dry-lined wall which will overcome or ameliorate problems with such fixings at present, or at least one which will provide a useful choice. SUMMARY OF THE INVENTION The present invention therefore provides a fixing for a dry-lined wall (DLW) which has plasterboard fixed to masonry with a cavity of variable width therebetween, the fixing comprising an elongate shaft extending from a tip to a head and having a first region proximate the head and a second region proximate the tip, the fixing being sized so that the first region is, in use, adjacent the plasterboard of the DLW and the second region is, in use, adjacent the masonry of the DLW, the shaft comprising an internal bore for accepting and being gripped by a screw, in both of a first internal diameter between the first region and the second region and a second and lesser internal diameter in the second region, the first region having an external wall that is substantially non expanding on insertion of a screw and the second region having an external wall that expands on insertion of the screw and an external part of the first region being shaped to resist rotation of the fixing when inserted into the plasterboard of a dry-lined wall, the fixing further comprising a transverse slit extending from the tip towards the head and intersecting with the Continued on page 2a 2a bore only in the second region, thereby to permit expansion of the external wall of the second region on insertion of the screw into the second internal diameter. The wider bore section allows a screw to be engaged with the fixing and to traverse the first region before the applied torque has to be increased significantly to drive the screw into the second region. This means that the first and second regions can be sized to position them generally within the plasterboard layer and the underlying masonry, respectively. Thus, a firm grip is made to the masonry, without causing the fixing to rotate in its hole before the screw reaches the masonry. The bore can end short of the tip, either as a blind bore or by merging into a transverse slit extending from the tip towards the head. The slit preferably intersects with the bore only in the second region, and can have a width substantially equal to the internal diameter of the bore. Such an arrangement helps the second region to expand on insertion of the screw. Preferably, the bore has a substantially circular cross-section and is located centrally with respect to the shaft. Continued on page 3 WO 2010/020768 PCT/GB2009/002007 -3 The present invention therefore provides a fixing for a laminated material comprising an elongate shaft extending from a tip to a head, the shaft having an external engagement formations comprising a first set of formations proximate the tip and a second set of formations proximate the head, the first set of formations having an external diameter or form that differs from a external diameter or form of the second set of formations thereby to adapt the first set of formations to a different material. This permits the first thread section to engage with the masonry wall in order to provide the necessary pull-out resistance. Meanwhile, the second thread section can engage with the plasterboard layer in order to hold it in place (and therefore protect it) and also to use the resistance to shear forces that the plasterboard is capable of providing. Thus, the first and second thread sections preferably have a combined length greater than about 20mm in length so that the first thread section can extend into the masonry. The second set of formations can comprise a screw thread, as this tends to be especially suited to establishing and maintaining a grip in plasterboard material. The first set of formations can comprise a series of outwardly extending projections such as ribs, flanges or a second screw thread. The first and second thread sections can have the same thread pitch so as to pass smoothly through the two layers without disturbing their relative position. Alternatively, such as for use in other laminate situations, the first thread section can have a thread pitch greater than that of the second thread section. This will tend to draw the outer layer more firmly toward the underlying layer. Such a fixing can be (for example) in the form of a screw. Typically, this will have a head that is wider than the shaft. This can be adapted to be recessed when fitted, which will be particularly useful in securing a plasterboard sheet to a substrate, for example. Alternatively, the fixing can be in the form of a plug with suitable external threaded sections as defined above to secure the plug in place prior to screwing INCORPORATED BY REFERENCE (RULE 20.6) WO 2010/020768 PCT/GB2009/002007 -4 into the plug. This can include a head which comprises a flange extending outwardly of the shaft to prevent the plug from entering too far into the laminate structure. Such a flange is preferably circumferential. A special tool may be provided for screwing the fixing in to place. This is particularly useful if the fixing is made of plastic or Nylon, as conventional drive forms such as posidrive screws, or Allen key drives, may have difficulty in transmitting enough torque to the fixing. As the diameter of the fixing can not be conveniently extended, the depth of the engagement formation between the fixing and the tool can be extended. For the purpose of rotating and driving the tool, the tool may either have a handle, or a posidrive or Allen key form that can be driven by a screwdriver (either manual or electric). Further, the tool may have an external form that substantially matches the internal form of the entire fixing along its full depth. In this way, the tool provides support for the fixing as it is put into place. It will be appreciated that this is a benefit whether the fixing is screwed, or driven into place, as plastic fixings are vulnerable and relatively delicate during this operation. Thus the external form of the tool can comprise a round pin of a diameter to match the internal form of the fixing, and a triangular prism form to match the internal form of the head region of the fixing, and (optionally) a hexagonal or other non rotationally symmetric form which will extend outside the fixing for attachment to a source of torque. The fixing defined above can be of metal, plastic or Nylon. BRIEF DESCRIPTION OF THE DRAWINGS An embodiment of the present invention will now be described by way of example, with reference to the accompanying figures in which; Fig 1 shows a uniform material with pilot hole for fixing; Fig 2 shows a material covered with laminate of different material, with pilot hole; INCORPORATED BY REFERENCE (RULE 20.6) WO 2010/020768 PCT/GB2009/002007 -5 Fig 3 shows a fixing to thread forming single material; Fig 4 shows a fixing to laminated material; Fig 5 shows a uniform material with oversize pilot hole for fixing; Fig 6 shows a uniform material with fixing plug; Fig 7 shows a known fixing to non-thread forming single material; Fig 8 shows a known fixing to soft thread forming material such as plasterboard; Fig 9 shows an improved fixing to thread forming laminar materials; Fig 10 shows an improved fixing to attach threadable laminar material to different threadable material; Fig 11 shows an improved fixing to plasterboard laminar on wood; Fig 12 shows an improved fixing to attach plasterboard to wood with no screw head; Fig 13 shows a plasterboard laminate fixed to masonry wall, with small cavity between (a so-called Dry Lined wall, or DLW); Fig 14 shows a combination fixing suitable for use as a DLW fixing.; Fig 15 shows a combination fixing inserted into a DLW ; Fig 16 shows the completed fixing using a combination fixing in a DLW; DETAILED DESCRIPTION OF THE EMBODIMENTS Fig 1 shows a pilot hole 1 for a fixing, drilled into uniform material 2. Fig 2 shows a pilot hole 1 for a fixing, drilled into a material 3 covered with a lamina 2 of a different material. INCORPORATED BY REFERENCE (RULE 2061 WO 2010/020768 PCT/GB2009/002007 -6 In Fig 3, a conventional screw 5 is used to attach a bracket 4 to material 2. The screw can be chosen to suit the material. For example, if material 2 is a metal a self-tapping screw may be used. If material 2 is wood, a wood screw can be used. Many different types of screw have been designed, optimised for different materials. In Fig 4, a conventional screw 5 is used to attach bracket 4 to a laminate made of material 3 and material 2. The choice of screw 5 is a compromise between the requirements for material 3 and the requirements for material 2. When fixing to a non-threadable material such as brick or concrete, a known two part fixing is required as shown in Fig 7. In this case, an oversize pilot hole 7 (shown in figure 5) is drilled, and an expandable plug 8 (known as a "rawlplug") shown in fig. 6 is first inserted into hole 7. Bracket 4 can then be attached using screw 9 that screws into expandable plug 8. Figure 8 shows a known specialised plasterboard fixing 11 screwed into plasterboard material 10. Deeper serrations are provided on the fixing 11 to make a satisfactory grip in the plasterboard, in view of the greater friability of the board material. A bracket 4 may be attached by screwing a self-tapping screw 12 into fixing 11. Figure 9 shows a fixing screw 13 improved according to the current invention, so that thread form 14 is optimised for material 3, and thread form 15 is optimised for material 2. For example, for softwood laminated onto aluminium, thread form 14 is a self-tapping thread form, and thread form 15 is a woodscrew thread form. It should be noted that by optimising the fixing 13 for the two different materials, superior tensile and shear load performance is achieved for the fixing. In this example, most of the tensile load capability is derived from the thread form 14 in the aluminium, and most of the shear load capability is derived from the thread form 15 in the wood (as the wood is close to the bracket 4). It should be noted that to avoid creating any force that would pull the laminar 2 away from the material 3 the pitch of the two threadforms 14 INCORPORATED BY REFERENCE (RULE 2061 WO 2010/020768 PCT/GB2009/002007 -7 and 15 should be identical (even though the thread diameter and profile may be different). Figure 11 shows another embodiment of the current invention where fixing 20 is optimised for a wood and plasterboard lamina. Fixing 20 consists of wood screw threadform 21 and plasterboard threadform 22. Both threadforms have the same pitch, to avoid compression or extension of the plasterboard. Bracket 4 can be attached to the fixing 22 using self tapping screw 23. Figure 10 shows another embodiment of the current invention where fixing 16 is used to attach wood 2 to aluminium 3 without a protruding screwhead. In this case, threadform 17 is a metal self-tapping form and 18 is a wood screw threadform. In this case, the pitch of threadform 18 is marginally less than the pitch of threadform 17 so that when the fixing 16 is screwed into the materials (using posidrive form 19) the wood 2 is pulled tightly against aluminium 3. Figure 12 shows another embodiment of the current invention where fixing 24 is used to attach plasterboard 2 to wood 3. In this case, threadform 25 is a wood screw form, threadform 26 is optimised for plasterboard, and the pitch of threadform 26 is slightly less than the pitch of threadform 25 so that the plasterboard is pulled tightly to the wood without the need for an external screw head. Referring to figure 13, masonry 3 is covered in plasterboard material 2 which is fixed to the masonry using adhesive 27. A hole 7 is shown drilled ready for a fixing. Such a combination of materials is known as a "dry lined wall" (DLW), and is a relatively common alternative to conventional plastering of masonry. It should be noted that a cavity of variable width is usually found between the plasterboard and the masonry. When applying a fixing to such a combination of materials, the very different characteristics of the materials needs to be taken into account. Figure 14, 15 and 16 show a preferred embodiment of the invention to provide a superior DLW fixing. INCORPORATED BY REFERENCE (RULE 2061 8 Fig 14 shows a combination fixing, 32, where the fixing form is optimised along its length, for the two different materials that make up a DLW. In particular combination fixing 32 has an expandable section where it will be adjacent to the masonry 3 and a non-expandable section where it will be adjacent to the plasterboard 2. In addition, a compliant threaded section 33 adjacent to the masonry aids the insertion of the combination fixing and a threadform 34 is optimised for fixing to plasterboard. The pitch of both threadforms is the same, so that when the combination fixing is screwed into the hole, the plasterboard is not driven either to, or away from, the masonry, hence avoiding cracking and damage to the plasterboard. Figure 15 shows combination fixing, 32, located in the hole 7 that has been prepared in the DLW. To complete the fixing as shown in figure 16, screw 35 is driven through bracket 4 and into combination fixing 32. The screw 35 expands the combination fixing 32 in the region of the masonry only. This fixing achieves high tensile strength from the masonry section of the fixing, and high shear load capability from the plasterboard portion of the fixing (plasterboard is quite adequate for most applications in shear load, but is weak in "plucking" loads). Of course, the masonry section also provides high shear load capability, but it is particular important in the fixing that shear load capability is located close to the load, represented by the bracket 4 as a typical screw 35 while being very strong in tension, is relatively compliant when side loads are imparted if the screw is not well supported up to the head. The combination fixing 32 has a relatively complex internal form, as shown in figure 14. At the head end, in the region of threadform 34, the form is a deep triangular hole, extending for typically 10 mm. In the region of threadform 33, the internal form is a small diameter circular hole, so that when the screw 35 is inserted, this section will expand and grip the masonry. As already mentioned, this section is also slotted to facilitate this expansion. The hole between these two regions is larger diameter, such that the combination plug is gripped by the screw 35 but is not forced to expand.

WO 2010/020768 PCT/GB2009/002007 -9 The internal form of the fixing also assists in the fitting process. If the form has a uniform internal diameter, then the choice of this diameter is necessarily a compromise. Too wide, and the necessary radial compression within the masonry will not be achieved and the fixing will not be secure. Too narrow, and the torque necessary to insert a screw 35 will overcome the rotational resistance of the plasterboard layer 2 and allow the fixing to rotate with the screw thereby preventing the screw from progressing further into the fixing. The disclosed form, including a wider section nearer the head, allows for a lower insertion torque which the plasterboard 2 can withstand until the screw reaches a narrower section. By then, however, the screw has begun to expand the fixing within the masonry, thereby providing the necessary grip. Thus, by providing a suitably varying internal form, the compromise is avoided and a secure fixing can be provided which is capable of insertion into a dry-lined wall. Of course, other anti-rotation measures could be provided instead of the illustrated screw thread, such as longitudinal fins in the non-expandable section to grip in the plasterboard while the screw is being inserted, or external tabs or the like which could be gripped or secured during insertion of the screw and removed subsequently. With external tabs or the like in place, other parts of the external profile of the fixing could indeed be made wholly or partly smooth. The non-expandable section of the fixing should have strength in compression. It is almost inevitable that the screw 35 will be driven until it is in tension, holding the bracket 4 firmly against the wall. This tension needs to be counterbalanced by a compressive force elsewhere; if this is provided by the plasterboard 2 then it may be damaged or deflected inwardly. Thus, the compressive force is preferably carried by the fixing. This can be achieved in any one of a number of ways, such as by forming at least the non-expandable section of a complete cylindrical section - that is, one without any apertures, slots or the like. Transfer of the compressive forces to the fixing will also be aided by a outwardly extending flange at the head of the fixing. INCORPORATED BY REFERENCE (RULE 2061 10 The non-expandable section of the fixing should however be held in a snug relationship with the plasterboard, so that shear loads can be transferred easily. The combination fixing 32 may optionally be driven into place using a special tool that has an external form that matches the internal form of the combination fixing 32. Thus the external form is a round pin, of substantially identical diameter to match the internal form of the combination fixing, and a triangular prism form to match the internal form of the combination fixing 32 in the head region. The tool then has a hexagonal or other non rotationally symmetric form which will extend outside the fixing and can be used for fitting to an electric screwdriver. It will be appreciated that the tool not only provides rotational torque to the combination plug via the triangular form, but also longitudinal support, along the length of the combination fixing, with the round pin form. In particular, the very tip of the combination fixing 32 is supported by the tool. This crucially prevents the expanding section of the combination fixing 32 expanding through axial compression loads while the combination fixing 32 is driven into place. It will of course be understood that many variations may be made to the above-described embodiment without departing from the scope of the present invention. Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like, are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense, that is to say, in the sense of "including but not limited to".

Claims

1. A fixing for a dry-lined wall (DLW) which has plasterboard fixed to masonry with a cavity of variable width therebetween, the fixing comprising an elongate shaft extending from a tip to a head and having a first region proximate the head and a second region proximate the tip, the fixing being sized so that the first region is, in use, adjacent the plasterboard of the DLW and the second region is, in use, adjacent the masonry of the DLW, the shaft comprising an internal bore for accepting and being gripped by a screw in both of a first internal diameter between the first region and the second region and a second and lesser internal diameter in the second region; the first region having an external wall that is substantially non expanding on insertion of a screw and the second region having an external wall that expands on insertion of the screw; and an external part of the first region being shaped to resist rotation of the fixing when inserted into the plasterboard of a dry-lined wall, the fixing further comprising a transverse slit extending from the tip towards the head and intersecting with the bore only in the second region, thereby to permit expansion of the external wall of the second region on insertion of the screw into the second internal diameter.

2. A fixing according to claim 1 in combination with a screw inserted into the internal bore, the screw extending into the second region thereby to expand the external wall thereof, and projecting from the first region beyond the head thereby to support a load.

3. A fixing according to claim 1 or claim 2 in which the bore has a substantially circular cross-section.

4. A fixing according to any one of claims 1 to 3 in which the bore ends short of the tip. -12

5. A fixing according to claim 4 in which the bore is blind.

6. A fixing according to any one of claims 1 to 5 in which the slit has a width substantially equal to the internal diameter of the bore.

7. A fixing according to any one of claims 1 to 6 in which the bore is central with respect to the shaft.

8. A fixing according to any one of claims 1 to 7 in which the external part of the first region comprises a screw thread.

9. A fixing according to any one of claims 1 to 7 in which the external part of the first region comprises at least one longitudinal fin.

10. A fixing according to any one of claims 1 to 8 in which the external part of the first region comprises external tabs extending from the head of the fixing.

11. A fixing according to any one of claims 1 to 10 in which at least the first region comprises a wall around the internal bore in the form of a complete cylindrical section.

12. A fixing according to any one of claims 1 to 10 in which the portion of the bore at the head end comprises a hole in the form of a triangular prism.

13. A fixing according to claim 1 substantially as herein described with reference to and/or as illustrated in the accompanying figures.