AU757669B2 - Threaded fastening system - Google Patents

Description

WO 00/20767 PCT/AU99/00859 1 THREADED FASTENING SYSTEM Background and Summary of the Invention This invention concerns the use of threaded screw fasteners and has particular relevance to screws for affixing to an underlying structure architectural sheet profiles made from materials which have a high coefficient of thermal expansion. It is especially useful with roofing profiles made from non-metallic roofing profiles such as those made from polycarbonate, PVC or fibreglass reinforced polyester resin.

Transparent and translucent roofing materials made from non-metallic materials are becoming increasingly popular. These are used alone or in conjunction with roll formed steel sheeting to allow light transmission through the roof. When compared with glass, such plastics are lighter in weight, more resistant to impact damage, easier to install and considerably cheaper. Polycarbonate sheeting in particular is becoming increasingly popular because of its perceived superior performance.

However a major difficulty with non-metallic sheeting is its relatively high coefficient of thermal expansion. A 3 metre long sheet of polycarbonate for example will expand by approximately 2.1 mm for each 10°C temperature increase. A 5 metre long sheet restrained at one end by being butted up against a brick wall can have its free end move by over 10mm in the course of a day with a 30 0 C temperature rise. PVC sheeting is now used less often than polycarbonate and, although PVC has the advantage of a lower cost, PVC also has a high coefficient of thermal expansion.

Conventional sheet fastening practices for a wide range of other building materials involve drilling a hole just sufficiently large enough for the screw being used, but this practice does not take account of the properties of materials with a large coefficient of thermal expansion and buckling and other distortion of sheets often occurs as a consequence of incorrect fastening practice.

WO 00/20767 PCT/AU99/00859 2 Current industry practice is to ream a 10mm hole in a non-metallic roofing profile to install a 4.5mm diameter screw. This requires two tools, two operations and a reasonable amount of time, effort and skill. It is a significant time consuming procedure. Also it commonly occurs in practice that the screw is positioned at one side of the hole, instead of in the centre, and this can result in there being no clearance for expansion in a relevant direction.

Another difficulty in the installation of sheet roofmng profiles is screw over-run or over-drive. This is the over-tightening of fixing screws such that there is a squashing of the raised profile through which the screw is passed. It is quite common for even professional installers to overdrive a fastening screw, squashing the relevant ridge in the profile, and requiring them to reverse the screw rotation in a secondary operation to bring it to the correct position. Not only does this procedure take more time than necessary, but it may also damage the sheets.

An object of the present invention is to alleviate the disadvantages of the prior art.

The more preferred embodiments provide self-drilling fasteners which create a sufficiently large hole in sheeting to provide for thermal expansion without the need for the additional reaming operation, allow for single tool operation for installation, overcome the difficulties of centring and overcome the difficulties of over-driving.

Accordingly, in one aspect the invention provides a screw fastener for attaching a profiled sheeting panel to a support, said fastener having: an elongate cylindrical shank; (ii) an enlarged head at one end of the shank adapted for engagement with a driving tool; (iii) a piercing tip on the other end of the shank; (iv) a threaded portion on the shank, adjacent the drilling tip, adapted to screw into the support; and a cutting means attached to the shank and spaced from the head and adapted to make a circular incision through the panel during the screwing operation.

WO 00/20767 PCT/AU99/00859 3 Preferably the cutting means is cup shaped. Preferably said shank passes axially through the cup shaped cutting means. Preferably the cutting means comprises a circular cup with cutting teeth spaced around its perimeter. Preferably the cutting means is captive upon said shank and the shank passes axially through the centre of the cup.

The cutting means may engage with the shank by means of a keyed bore on the cutting means engaging with a matingly keyed portion on the shank. The cutting means may have a smooth bore which frictionally engages with a tapered serrated collar on the shank. The cutting means may have a bore which frictionally engages with tapered ramps upstanding from the shank.

Preferably an elastomeric sealing means is fitted on the fastener between the cutting means and the head. Preferably the sealing means comprises a domed topside, a central bore and a dished underside, said underside having two concentric sealing rims each of larger diameter than said circular incision.

In another aspect the invention provides a method of fixing a profiled architectural sheet to a support member whereby a threaded fastener passes through the sheet and into the support member, said fastener having a head at one end and a tip on its threaded portion at the other end and a cutter portion distant from the tip, said method comprising: with the tip of the fastener, piercing the sheet with a hole having a diameter about that of the threaded portion of the fastener, (ii) extending the fastener into the hole to engage the support member and driving the thread partly into Vhe support member; (iii) as the thread continues to screw into the supporting member, engaging the cutter portion with the sheet to inscribe a circle into and through the sheet; and (iv) continuing to screw the fastener into the supporting member.

WO 00/20767 PCT/AU99/00859 4 Preferably the fastener is screwed into the supporting member until the cutter bears against the support member. Preferably a resilient washer is provided on the fastener between the cutter and the head, and the washer forms a waterproof seal between the head and the sheet when the cutter portion bears against the supporting member.

Preferably the fastener cuts out a washer shape from the sheet and that washer shaped cutout is retained on the fastener.

The fasteners of the present invention are thus able to cut a hole through the sheeting with a substantial clearance for the fastener. The panels are therefore able to expand and contract considerably relative to the supporting frame without contacting the fastening screws. The preferred fasteners also stop at the correct depth and avoid being over-driven.

Brief Description of the Drawings Examples of the invention will now be described with reference to the attached drawings where: Figure 1 is a generally side-on view of a fastener according to a first embodiment of the present invention; Figure 2 is another view of the fastener shown in Figure 1; Figure 3 is a side view of one component of a second embodiment which is a similar fastener to that shown in Figures 1 and 2; Figure 4 is a plan view of another component of the second embodiment; Figure 5 is a cross section along line A-A shown in Figure 4; Figure 6 is a side view of the component shown in Figure 4; Figure 7 is a view similar to Figure 1 but showing a fastener according to a third embodiment of the invention which is more preferred; Figure 8 is a view similar to Figure 2 but showing the fastener of Figure 7; Figure 9 is a cross section view through the centre of a component of the fastener shown in Figure 8; WO 00/20767 PCT/AU99/0059 Figure 10 is a view similar to Figure 7 but showing a fastener according to a fourth and most preferred embodiment of the invention; Figure 11 is a view similar to Figure 8 but showing the fastener of Figure Figure 12 is a perspective view of one coinponent of the fastener shown in Figure Figure 13 is a side view of the component shown in Figure 12; Figure 14 is a side view of the fastener shown in Figure 10 part way through its installation with a roofing profile; and Figure 15 is a view like that of Figure 14 but with the fastener fully installed.

Detailed Description of the Invention Referring to Figure 1, the screw fastener 2 is an assembly of three main components, namely a body 4, a weather seal 30 and a cutter 40. The body 4 has an elongated cylindrical shank 6 with an enlarged head 8 at one end. The head has a hexagonal top for engagement with a driving tool, and a collar 12. At the other end of the shank 6 is a thread 14 with a drilling tip 16 formed by a slot 18 cut into the thread.

A weather seal 30 is fitted to the shank 6 beneath the collar 12. The weather seal is a type of washer moulded from a suitable rubber, other elastomer or other resilient material. The seal 30 has a domed top 32 and a tapered boss 34 within a concave underside 36. It should be noted however that it is preferred that the boss 34 is omitted so that it cannot fill the hole in the sheet and limit lateral movement of the sheet relative to the fastener.

A cutter 40 is fitted to the shank 6 by way of its keyed bore 46 engaging with four upstanding keys 48 on the shank which prevent rotation of the cutter 40 relative to the shank 6. The cutter is generally square in shape, with four turned down teeth 50 at its perimeter. The cutter 53 has a generally planar square shaped body portion 55 from which four peripheral teeth 50 extend towards the drilling tip end of the fastener. In operation the cutter acts in the general manner of a hole saw, cutting the periphery of the required hole.

WO 00/20767 PCT/AU99/00859 6 With reference to Figures 3 to 6, the second embodiment fastener 51 has a screw body 52 and cutter 53 which are similar to the corresponding components in Figures 1 and 2. The major difference is that instead of the keys 48 and keyed bore 46 of the first embodiment, the second embodiment has a smooth bore 54 in the cutter 53 which press fits onto a serrated collar 56 on the shank of body 52. The collar 56 is tapered at 150 to provide a suitable lock with the bore 54 and the serrations on the collar are aligned with a right-handed twist in order to provide an even better lock into the bore 54. The fastener's weather seal is like the seal 30 in Figure 1 but has been omitted from Figure 3 for ease of illustration.

The installation of the fasteners 2 and 51 proceed in a substantially identical manner.

The hexagonal top 10 is engaged with a driving tool and rotated with the tip 16 in contact with the sheeting being fastened as cladding material. The tip 16 and then the slot 18 cut their way through the sheeting, creating a hole about equal to the minor diameter of thread, and move on to contact the support frame which would usually be timber or metal. The tip 16 commences drilling into the support and this locates the tip to prevent it sliding around on the surface.

As the tip penetrates further into the support, and the screw thread bites into the support so pulling the fastener further into the support, the teeth 50 engage the top of the cladding. Up to this point the keyed cutter 40 of fastener 2 would have been fully engaged with the keys 48 and the cutter 40 would be spinning locked with the shank of the screw. But the taper locked cutter 53 of the fastener 51 is supplied loosely spinning on the shank and only locks onto the collar 56 when pressed on to it. So, as the teeth 50 engage the top of the cladding and thus press the cutter back against the serrated collar 56, the cutter starts rotating. In each case the teeth then cut, in the manner of a hole saw, a circular groove in the cladding. The groove is spaced away from the hole created by the drilling tip 16. The teeth cut the enlarged hole by cutting along the line of a circle which circumscribes cladding material which is not being cut. When the teeth 50 cut fully through the cladding, a washer-like piece of cladding material is left on the screw and this rises to nest between the teeth of the cutter, WO 00/20767 PCT/AU99/00859 7 taking no further active part in the operation. The teeth are drawn onto and into the cladding by the thread 14 feeding into the support frame. The cladding is cut through within one or two rotations of the fastener.

The cutter mechanically works the sheet material in the peripheral groove which the teeth excavate, and creates the required large clearance hole without mechanically working most of the material removed from the hole. This is substantially more efficient than conventional drilling of a hole where all the material removed is mechanically worked.

The screw then continues to penetrate the support until the cutter 40 or 53 bears against the support surface, which causes a large and rapid increase in the torque required to rotate it further, and thus indicates to the operator rotation should stop, so stopping further penetration and thus preventing over-drive of the fastener.

At that stage of installation the weather seal 30 has come into the appropriate degree of contact and pressure against the sheeting. The location of the cutter on the shank of the screw is preferably predetermined relative to the underside of the collar 12 for the particular profile of cladding being fixed, and this location takes account of the dimensions of the weather seal. The method of installation ensures that the fastener is installed exactly central to the clearance hole in the sheeting.

The embodiment of fastener shown in Figures 7 and 8 is a screw 59 which is also very similar to that shown in Figures 1 and 2. The two significant differences are the means by which the cutter 60 is prevented from rotating and the shaping of the underside of the weather seal 66.

The cutter 60 of Figures 7 and 8, like the cutter 53 of Figure 4, has a smooth bore and locks onto the shank 62 by way of interference with a series of ribs or protrusions on the shank. In Figures 7 and 8 these ribs take the form of six gently sloping ramps 64 upstanding from the shank 62. The outermost surfaces of the ramps form a taper of about 50 onto which the bore of the cutter is, or becomes, jammed. This taper is WO 00/20767 PCT/AU99/00859 8 significantly shallower in slope than the bevelled section on the collar 56 in Figure 3.

The ramps 64 are evenly spaced around the shank and spiral in a right handed helix to better grip the bore of cutter 60 and prevent it spinning. In this respect the ramps 64 can be considered as forming a very coarse multi-start thread which gradually increases its diameter.

However whereas the cutters 40 and 53 described earlier feed onto the main screw threads 14 and 63 respectively, the cutter 60 is captive upon the unthreaded portion of the screw shank between the main screw thread 63 and the ramps 64. This may be achieved by assembling the cutter 60 onto the shank 62 before the thread 63 is rolled onto the screw body.

The fastener is preferably supplied to the end user as a pre-assembled combination of the screw body 61, rubber weather seal 66 and cutter 60. However the cutter need not be supplied fully engaged with, or jammed onto, the ramps 64; it may conveniently be left partly along the screw thread. Whatever its initial position, the cutter will automatically be pushed up onto the ramps 64 when the thread feeds into the support frame.

Whereas the rubber weather seal 30 shown in Figure 2 has a tapered boss 34, the weather seal 66 seen in Figure 8 has no such boss but instead carries an additional sealing rim. This is most clearly shown in Figure 9 which is a cross section view through the seal 66. The seal has a domed top 67 with a central bore 70 surrounded by an outer rim 68 and an inner rim 69. In use the screw is tightened sufficiently that both inner and outer rims make contact fully around their perimeter with the sheeting being fastened. The resilience of the seal's rubber material means the rims 68 and 69 can adapt to and seal against a wide variety of sheeting profiles. The diameter of the inner rim 69 is greater than the diameter of the hole cut by the cutter in the sheeting.

Thus, when the screw body 61 is central in the hole through the sheeting, there are two barriers which outside water must pass by in order to leak through the hole in the sheeting. However if, due to thermal expansion, the screw is not central to the hole, then the hole may extend beyond the inner rim 69 and only one barrier would be WO 00/20767 PCT/AU99/0059 9 effective at that time. It is of course essential that the hole be fully covered by the outer rim 68 at all times for effective weatherproofming.

Referring to Figures 10 to 13, the embodiment illustrated therein is the most preferred. The body 72 of the fastener 71 and the weather seal 74 are almost the same as the equivalent components shown in Figures 7 and 8. The only significant difference is that the spiral ramps 76 on fastener body 72 are somewhat shorter and more steeply inclined at 71/20 compared with the 50 inclination of ramps 64 in Figure 8. The peripheral surface of the ramps is preferably inclined at between 6.5' and 8.5 However the cutter 78 mounted on fastener 71 is substantially different to cutter 60 on fastener 59. Cutter 78 has a circular shaped planar main body 80 from which four equally spaced cutting teeth 82 extend axially of the fastener. It is press formed from sheet metal such as 1mm thick sheet steel. The cutter's central bore 84 is a slack clearance fit on the unthreaded portion of the screw body 72, but is small enough such that it cannot easily be removed over the main thread of the fastener.

The circular cutter 78 is preferred because it more reliably accommodates a cut off disc of curved sheeting material within the cutter without jamming when overlapping sheets mean more than a single sheet is being drilled at the same time.

The cutter 78 is shown in the Figures as having a flat upper face 86. A modification whereby this upper face is domed has been found to provide a significant improvement in the stiffness of the cutter so that it undergoes less distortion when it engages abruptly with the support timber or steel into which the fastener is being screwed.

Referring to Figures 10, 14 and 15, the installation of fastener 71 follows the same general procedure described above in relation to the fasteners of Figures 2 and 3. The hexagonal head 73 is engaged with a driving tool and rotated with the tip 75 in contact with the profiled sheeting 88 being fastened. The tip 75 and then the slot 77 cut their way through the sheeting, creating a hole about equal to the minor diameter WO 00/20767 PCT/AU99/00859 of thread on the body 72, and move on to contact a support 90 which is metal in this illustration. The tip 75 commences drilling into the support 90 and this locates the tip to prevent it sliding around on the surface.

As the tip penetrates further into the support, the slot 77 engages and then the screw thread bites into the support so pulling the fastener further into the support, the teeth 82 engage the top of the sheeting 88. Up to this point the fastener body 72 has been freely spinning inside the bore of cutter 78. But as the teeth 82 engage the top of the sheeting and thus press the cutter back into engagement with the ramps 76, the cutter starts rotating. The teeth then cut, in the manner of a hole saw, a circular groove into and finally through the sheeting. The teeth are drawn onto and into the cladding by the thread being engaged with and drawn into the support 90. The sheeting is cut through within one or two rotations of the fastener. A washer-like piece of sheeting material is left on the screw and this rises to nest between the teeth of the cutter, taking no further active part in the operation. This is the stage of the installation shown in Figure 14.

The screw 71 then continues to penetrate into the support 90 until the tips of the teeth 82 hit the support surface. This causes a large and rapid increase in the torque required to rotate it further, and thus indicates to the operator rotation should stop. In the case of a steel support 90, the stopping is particularly abrupt and a torque limiting power tool is recommended. This is the stage of the installation shown in Figure The weather seal 74 has come into the appropriate degree of contact and pressure against the sheeting.

The present invention utilises a cutter which cuts only the circumference of a circle and leaves a disc of sheeting material on the shank of the fastener. Such a method of making the relatively large hole is advantageous because it involves cutting the minimum amount of sheeting material. This is advantageous when the cutter is being fed through the sheeting at such a high rate in accordance with the pitch of the thread.

WO 00/20767 PCT/AU99/00859 11 It is to be understood that various alterations, modifications and/or additions may be introduced into the constructions and arrangements of parts previously described without departing from the spirit or ambit of the invention. By way of example only, the preferred embodiments described above utilize a slotted tip to pierce the sheet and enter the support frame. Other types of drilling tips such as fluted tips may also be suitable, as could be tips for flow drilling. Tips suited to percussive penetration may also be used, in which case the screw tip would, by impact, penetrate the sheet and partly into the support frame and thereafter be rotated in order for the thread to feed into the support frame and the cutter to circumscribe its groove through the sheet at the circumference of the hole.

As a further example of a modification which may be used, the toothed hole-saw type of configuration of the cutter may be replaced by a sharp edged slicing arrangement which may have a continuous or discontinuous edge. Alternatively, the cutter may carry an abrasive edge or an edge that cuts by melting the sheet material. However the toothed type of cutter is preferred because of its ability to displace a large amount material with a minimum rotation of the fastener, this being important because the fastener thread is feeding at a fixed rate defined by the pitch of the thread at the time the circle is being cut.

It is estimated that when compared with using prior art fasteners, use of the present invention can result in a saving of more than 50% of the time required for fastening non-metallic roofing.

The fasteners of the embodiments described above with reference to the Figures, all have a hexagonal head. Other types of driven heads are also applicable to the invention and these include slotted heads, Philips heads, hexagonal socket heads and 6-lobed heads.

Throughout this specification, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood WO 00/20767 PCT/AU99/00859 to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

Claims (15)

1. A screw fastener for attaching a profiled sheeting panel to a support, said fastener comprising: an elongate cylindrical shank; (ii) an enlarged head at one end of the shank adapted for engagement with a driving tool; (iii) a piercing tip on the other end of the shank; (iv) a threaded portion on the shank, adjacent the piercing tip, adapted to screw into the support; and a cutting means attached to the shank and spaced firom the head and adapted to make a linear circular incision through the panel and spaced from the shank during the screwing operation.

2. A fastener according to claim 1 wherein the cutting means is cup shaped.

3. A fastener according to claim 2 wherein said shank passes axially through the cup shaped cutting means.

4. A fastener according to any one of claims 1 to 3 wherein the cutting means comprises a circular cup with cutting teeth spaced around its perimeter.

A fastener according to any one claims 2 to 4 wherein the cutting means is captive upon said shank and the shank passes axially through the centre of the cup.

6. A fastener according to any one of claims 1 to 6 wherein the cutting means engages with the shank by means of a keyed bore on the cutting means engaging with a matingly keyed portion on the shank.

7. A fastener according to any one of claims 1 to 6 wherein the cutting means has a smooth bore which frictionally engages with a tapered serrated collar on the shank. AMENDED SHEET IPEAIAU PCT/AU99/00S59 Received 15 January 2001 14

8. A fastener according to any one of claims 1 to 6 wherein the cutting means has a bore which frictionally engages with tapered ramps upstanding from the shank.

9. A fastener according to any one of the previous claims wherein an elastomeric sealing means is fitted on the fastener between the cutting means and the head.

A fastener according to claim 9 wherein the sealing means comprises a domed topside, a central bore and a dished underside, said underside having two concentric sealing rims each of larger diameter than said circular incision.

11. A method of fixing a profiled architectural sheet to a support member whereby a threaded fastener passes through the sheet and into the support member, said fastener having a head at one end and a tip on its threaded portion at the other end and a cutter portion distant from the tip, said method comprising: with the tip of the fastener, piercing the sheet with a hole having a diameter about that of the threaded portion of the fastener, (ii) extending the fastener into the hole to engage the support member and driving the thread partly into the support member; (iii) as the thread continues to screw into the support member, engaging the cutter portion with the sheet to incise the line of a circle, spaced from said hole, into and through the sheet; and (iv) continuing to screw the fastener into the support member.

12 A method according to claim 1 1 wherein the fastener is screwed into the support member until the cutter portion bears against the support member.

13. A method according to claim 11 or 12 wherein the fastener cuts out a washer shape from the sheet and that washer shaped cutout is retained on the fastener.

14. A method according to any one of claims 1 1 to 13 wherein a resilient washer is provided on the fastener between the cutter portion and the head, and the washer 4AMENDED SHEET IPI-JAU PCT/AU99/008 5 9 Received

15 January 2001 forms a waterproof sealing means between the head and the sheet when the cutter portion bears against the support member. AMENDED SHEET IPEA/AU