NZ531905A - Fastening system and components therefor - Google Patents

Abstract

A fastener assembly for fastening the foot of a top hat section batten 46 to a structural member 44 and a method of fastening the assembly are disclosed. The assembly includes a self drilling screw 42 and an oblong shaped washer 60 captively held on the shank of the screw. The washer is elongated and substantially flat with a stiffening portion extending across the width of the washer on each side of the washer's hole.

Description

53 1 9 0 5 1 Number: Dated: 23 March 2004 COMPLETE SPECIFICATION FASTENING SYSTEM AND COMPONENTS THEREFOR We, AJAX COOKE PTY LTD, an Australian company of 76-88 Mills Road, Braeside, Victoria 3195, Australia do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement. 40 2 Fastening System and Components Therefor Field of the Invention This invention concerns the fastening of cold rolled steel battens to other framing components when erecting buildings. It is particularly adapted, but not limited, to the fastening of top hat section battens when constructing roof structures of buildings. The invention also concerns the manufacture and use of assemblies of washers and threaded fasteners adapted particularly to the fastening of top hat section battens.

Background to the Invention When buildings are subjected to strong wind conditions such as those present in cyclones or hurricanes, many sheet metal roofs are torn, as a whole or in large 15 sections, from the rafters and lifted away onto neighbouring land or other buildings. Studies of such damage have shown that a common failure mode is at the fastening between steel battens and the underlying rafters. Rafters may be beams or trusses.

Top-hat section battens are cold rolled from steel strip and are named after their cross-20 sectional shape which resembles a top hat. While they are particularly popular for attachment to underlying steel structural members, they are also often used for attachment to timber underlying structural members. There is a trend for top-hat sections to be manufactured from increasingly thinner gauge higher strength steel and this makes them more prone to some types of failure.

In cases where top-hat sections have been used for battens in a roof which has lifted under high wind conditions, it has been found that commonly the battens are still fastened to the sheet metal roofing but that the screw fasteners by which the battens were attached to the rafters are still in the rafters, the head of the fasteners having torn 30 through the bottom flanges on the feet of the top-hat section battens. 3 Various means have been tried to increase the strength of the bottom flanges subject to the failure mode described above, but the problem is compounded by the fact that the removal of metal when drilling the fastening holes through the flanges creates a weaker section, and therefore a higher stress region, at the point where the maximum 5 bending moment is exerted on the flange due to the uplift induced by wind acting on the roof. To satisfactorily strengthen that part of the top-hat section would require a significant increase in the weight of the section, much of that increase going to places where the increased strength is not required.

A localised strengthening could be provided by using a conventional washer under the head of the fastener, but the foot flanges of top-hat sections are too narrow to use a normal washer in order to gain the desired strength. Also, any normal washer may easily make the situation worse by providing a shaip-edged section discontinuity causing increased stress concentration and hence premature failure which may 15 particularly occur due to fatigue from cyclic loadings.

An aim of the present invention is to provide a special washer, a fastening system incorporating the washer, and also a fastening method which can satisfactorily strengthen the fastening between a batten and an underlying structural member such 20 as a rafter.

However the invention is not limited to use in such particular applications and may be also used in fastening battens to wall studs, fastening billboard frames or fastening fence rails for example.

The underlying structural member may be a thin walled or thick walled steel section or may be any other suitable material such as timber. It may be a beam or form part of a truss. 4 Summary of the Invention In one aspect the invention provides a method of fastening a foot of a top-hat section batten formed from sheet metal to an underlying structural member in a structure; said foot having: - a flange portion extending from a web of the top-hat section, and - a lip turned outwardly from the flange portion, whereby the web, flange portion and lip together form an open channel having outwardly sloping sides; the channel having a first straight inside corner where the web and the flange portion 10 blend, and a second straight inside corner where the lip and the flange portion blend; said method comprising: - screwing through the flange portion into said structural member a threaded fastener having a head at one end and a point at the other end, - providing a washer between the fastener head and the flange portion, said 15 washer comprising a main body portion having an upper face which faces the head of the screw, a lower face which faces the foot, and a hole through which the fastener passes, - tightening the fastener until edges of the main body portion nest into or close to said first and second straight inside corners, and said lower face covers an area of the flange portion greater than that area which would be covered by a circular washer spanning fully between said straight inside corners, and - further tightening the fastener to clamp said flange portion of the foot between the washer and the structural member.

Preferably the washer has a shape elongated in the direction of the length of the channel, the main body portion has a pair of long sides and a pair of short sides, and the long sides nest into or close to respective said straight inside corners.

The main body portion preferably has a stiffening portion raised from the upper face and extending across the width of the main body portion on opposite sides of the hole.

The threaded fastener is preferably a self-drilling screw which drills a hole through the flange portion and through portion of the structural member.

In another aspect the invention provides a fastener assembly for fastening the foot of a 5 top hat section batten to an underlying structural member, the fastener assembly comprising: - a self drilling screw having a head at one end, a drilling tip at the other end, a shank, a threaded portion, and - a washer captively held on the shank, the washer comprising: - an elongated main body portion having a pair of long sides, a pair of short sides, an upper face which faces the head of the screw, a lower face which faces the drilling tip, and a hole through which said shank passes, and - a stiffening portion raised from the upper face and extending across the width of the main body portion on each of opposite sides of the hole.

Preferably most of the main body portion is substantially flat. The main body portion is preferably oblong shaped. The washer is preferably oblong shaped.

The stiffening portions preferably comprise an upturned lip formed along each of said 20 short sides and extending from said main body portion.

Alternatively the stiffening portions may comprise a ridge formed across the washer between the hole and each short side of the main body, the ridge being raised on that side of the washer which contacts the head of the screw.

The stiffening portions may each comprise a ridge formed by material displaced from the plane of the main body of the washer. Such ridges are preferably located midway between the short sides and the hole. A plurality of ridges may extend across the width of the main portion on each of opposite sides of the hole. 6 Where the washer has an upturned lip formed along each short side of the main body, said upturn preferably has an outside curvature which forms a rounded edge.

The upturn along said each short side may form an end flange angled in the range 30°-5 90°, preferably greater than 60°, to the main body portion. In a preferred embodiment the end flange is angled in the range 85°-90° to the main body portion.

The washer may have an upturned lip formed along each long side of the main body portion. The upturn along said each long side may form a side flange angled in the 10 range 30°-90° to the main body portion. In a preferred embodiment the upturn forms a side flange angled in the range 85°-90° to the main body portion.

Said side flanges and end flanges may together form an upturned edge or rim around the full perimeter of the main body portion and the washer may have the general form 15 of a deep rectangular tray.

The hole through the washer is preferably central to the main body.

In another aspect the invention provides a washer for use with a threaded fastener, the 20 washer comprising: - a substantially flat elongated main body portion having a generally central hole extending therethrough from an upper face of the main body portion to a lower face of the main body portion, - a wing portion extending from each long side of the main body portion to form 25 a side flange angled upwardly from the main body portion at between 30° and 75° to the main body portion, each said wing portion having a central portion nearest said hole and end portions either side of said central portion, the central portion extending further from the main body portion than does each end portion, and - a rounded or bevelled edge, facing downwardly from the main body portion, along each short side of the main body portion. 7 An upturned lip may be formed along each said short side of the main body portion, said upturn having an outside curvature which forms said rounded or bevelled edge along each said respective short side.

Preferably the main body portion is rectangular and each said wing is joined to the main body portion at a respective fold or bend which is straight. Preferably each said lip is joined to the main body portion at a respective fold or bend which is straight.

In some embodiments the wing portions may be angled at less than 60° to the main 10 body portion of the washer, and may be angled at less than 50°. They are preferably angled at more than 30° to the main body portion of the washer, and in some embodiments are more preferably angled at about 45°. In other embodiments the wing portions are angled at about 90° to the main body.

In another aspect the invention provides a method of fastening a foot of a top-hat section batten to an underlying structural member in a structure, said foot having: - a flange portion extending from a web of the top-hat section, - a lip turned outwardly from the flange portion, and - the web, flange portion and lip together forming an open channel having 20 outwardly sloping sides, said method comprising: - screwing through the flange portion into said structural member a threaded fastener having a head at one end and a point at the other end, - providing a washer between the fastener head and the foot, said washer 25 having: - a main body portion having a hole through which the fastener passes, and - extending from said main body portion a pair of outwardly sloping sides which together with the main body portion form an open- channel-shaped cross-section, 8 - tightening the fastener until the sides of the washer contact the web and lip of the top-hat section, - further tightening the fastener to cause deformation of the sides of the washer and/or the web and the lip, - further tightening the fastener to bring the main body portion of the washer into firm contact with the flange portion of the foot, and - further tightening the fastener to clamp said flange portion between the washer and the structural member. ; / Preferably most of the main body portion of the washer is at least substantially flat.

Preferably the clamping force is sufficient to prevent significant sliding movement of the flange portion of the foot relative to the washer and the structural member. The washer and flange portion would thus tend to behave basically as a single integrally 15 formed component.

The structural member may be a beam, a truss, a rafter in the roof structure of a building, or a joist in a wall of a building, or a rail in a fence. The top-hat section batten is preferably a length formed from cold rolled sheet steel.

Brief Description of the Drawings In order that the invention may be more fully understood there will now be described, by way of example only, some embodiments and other aspects of the invention with 25 reference to the accompanying drawings where: Figure 1 is a cross-section view of a typical top-hat section batten as used in preferred forms of the present invention, Figure 2 is a plan view of a washer according to one embodiment of the present invention, Figure 3 is a cross section view along A-A shown in Figure 2, Figure 4 is a cross section view along B-B shown in Figure 2, 9 Figure 5 is a cross section through some components early in a fastening operation according to a further embodiment of the invention and incorporating a batten of the type shown in Figure 1 and a washer of the type shown in Figures 2 to 4, Figure 6 is a cross section through some of the components shown in Figure 5 with the screw fastener (not shown) partly tightened, Figure 7 is a cross section through the components shown in Figure 6 with the screw fastener fully tightened, Figure 8 is a plan view of a washer according to another embodiment of the present invention, Figure 9 is a cross section view along C-C shown in Figure 8, Figure 10 is a cross section view along D-D shown in Figure 8, Figure 11 is a longitudinal cross section similar to Figure 9 but for a washer according to another embodiment of the invention, Figure 12 is a longitudinal cross section similar to Figure 9 but for a washer according to a further embodiment of the invention, Figure 13 is a general perspective view of a washer according to a further embodiment of the present invention, Figure 14 is a plan view of the washer in Figure 13, Figure 15 is a cross section view along E-E shown in Figure 14, Figure 16 is a cross section view along F-F shown in Figure 14, Figure 17 is a cross section through some components early in a fastening operation according to a further embodiment of the invention and incorporating a washer of the type shown in Figures 13 to 16, Figure 18 is a cross section through some of the components shown in Figure 17 with the screw fastener (not shown) partly tightened, and Figure 19 is a cross section through the components shown in Figure 18 with the screw fastener fully tightened.

Description of Particular Embodiments and Features of the Invention Referring to Figure 1, a typical top-hat batten 40 is roll formed from cold rolled steel strip. The steel used typically has a thickness in the range 0.48 to 1.6mm with the thicker strip being used for larger sections.

The batten 40 has a wide top flange 46, two narrower foot flanges 52 parallel to the top flange (sometimes called bottom flanges) on two respective feet 48, and two webs 50 which join the top flange 46 to respective foot flanges 52. Each foot 48 has a lip 54 bent upwards from the outer edge 53 of its respective foot flange 52. Each web 50, foot flange 52 and lip 54 together form an open channel 56 having outwardly sloping sides. Where the web 50 and the foot flange 52 blend, a first inside corner 57 runs straight along the inside of the channel 56. Similarly, where the lip 54 and the foot flange 52 blend, a second inside corner 58 runs straight along the inside of the channel.

Some steel top-hat sections are manufactured with one or more lengthwise corrugations in each of the bottom flanges. These can provide increased performance of the sections due to local work hardening of the steel at the corrugations and due to an increase in the effective thickness of the flange.

Top-hat sections are well known and commonly used as battens in roof structures of buildings where the bottom flanges 52 are fastened to underlying rafters in roof structures and the wide top flange 46 provides an efficient surface for fastening roofing sheets. Top-hat sections are also used as battens for attachment of sheet materials to wall structures.

Referring to Figures 2 to 4, the washer 60 shown is formed from sheet steel having a thickness in the range 0.75 to 1.5mm. It has a flat, oblong shaped main body portion 62 with its longer pair of sides 64 being approximately 2.6 times the length of the shorter pair of sides 66. A hole 18 is formed through the washer, extending from the upper face 76 of the washer to the lower face 78, in the centre 63 of the main body 11 portion 62. The separation between the longer sides 64 sets the width 65 of the main body portion 62 and the separation between the shorter sides 66 sets the length 67 of the main body portion.

From each of the long sides 64 of the washer main body 62 an upturned edge 70 extends at approximately right angles from the washer main body 62 such that the upturned edges together form a pair of walls 70. A fold line or bend 74 extends along where each wall 70 and the main body portion 62 meet and thejine of this bend is straight. The bend 74 is preferably not formed as a sharp crease but is instead a 10 curved bend as best seen in Figure 4. The walls 70 have a generally uniform height along their length.

From each of the short sides 66 of the washer main body 62 a lip or wall 82 is turned out of the plane of the main body portion 62 at about right angles to the same side of 15 the washer as the walls 70 are directed. Each lip/wall 82 extends outwards from the main body portion 62 about the same distance as do the walls 70. A bend 84 is formed along the junction between the walls 82 and the main body portion 62 and the line of this bend runs straight across the width 65 of the main body portion at right angles to the line of the bend 74. The radius of curvature of the bend 84 is about the 20 same as that for the bend 74 and is preferably in the range of 2 to 5 times the thickness of the metal forming the main body portion, more preferably in the range of 3 to 4 times the thickness.

Preferably the walls 70 and 82 are all of substantially the same height and form a rim 25 around the full perimeter of the main body portion 62, the washer having the appearance of a deep rectangular tray with rounded edges where the surfaces blend.

The washer 60 may be pressed from a sheet steel parent material with the central hole and walls being formed in the same single pressing operation which separates the 30 washers from the parent steel sheet. However the washer may alternatively be formed in a multi-stage process. 12 It will be appreciated that the walls 70 and 82 are conveniently not exactly at right angles to the main body portion in order to allow the washers to separate from their tooling during manufacture. The angle is therefore preferably in the range 85° to 90°.

Referring now to Figures 5 to 7, a top-hat section batten 40 is shown being fastened by means of a threaded fastener 42 to an underlying steel rafter 44 which forms a structural member in a building roof structure. For clarity of illustration, only parts of the batten 40 and rafter 44 are shown in the Figures, and in Figures 6 and 7 the 10 threaded fastener is also omitted from the drawing.

The threaded fastener used may be of any suitable type although in the Figures a relatively short self-drilling screw 42 is illustrated. The point 41 of the screw 42 carries a drilling tip 45. The type of drilling tip may be chosen to suit the particular 15 application. The screw 42 shown has a flanged hexagonal head 43 but this is by way of example only and any suitable drive configuration may be utilised. The screw 42 forms a thread in the steel rafter 44 and uses that thread to tighten in due course. If the underlying structural member (rafter) was timber then a self drilling woodscrew would be appropriate.

The installation process takes the following steps: 1. The screw 42 is fitted with a washer 60, the bottom of the head 43 of the screw adjacent to the upper face 76 inside the dished form of the washer, with the walls 70 and lips 82 on either side of the head 43. The washer 60 may be supplied already fitted to the screw or may be provided separately. 2. At the stage shown in Figure 5, the screw 42 has drilled through the flange 52 and the underlying rafter 44 but has not yet begun to be tightened. 3. As seen in Figure 6, the screw (not shown) has started to be tightened and the washer 60 moves towards the flange 52. 4. As the screw is tightened further, the lower face 78 of the washer 60 eventually makes contact (as shown in Figure 7) with the flange 52 of the 13 foot of the top-hat section. The outer surface 75 of the bend 74 nests into the inside corners 57 and 58 on the foot of the top hat section.

. As the screw 42 is further tightened, the flange 52 is clamped and compressed between the main body portion 62 of the washer and the rafter 5 44. The tightening, and clamping preferably proceeds until a little before the threaded connection between the rafter and screw would fail.

When a load is applied to the structure so fastened, the washer and batten move together basically as a single component because there is basically no slippage 10 between their faces.

The screw 42 and washer 60 may be supplied to a user together as a fastener assembly where the washer is captively held on the shank of the screw. This provides a greater assurance that the correct size and type of screws are used with the washers. A 15 washer may be captively retained on a screw by rolling the screw thread after fitting the washer to the shank of the screw.

The gentle curvature of the bend 84 in the washer substantially reduces the stress concentrations in the flange 52 in that region when a fastening between a batten and 20 an underlying rafter is approaching failure due to high wind loads.

Referring to Figures 8 to 10, the washer 90 of this embodiment is formed from sheet steel having a thickness in the range 1.5 to 2.5mm. It has a flat, oblong shaped main body portion 92 with a pair of longer sides 94, a pair of shorter sides 96, an upper face 25 91, a lower face 93 and a hole 18 formed through the washer. The separation between the longer sides 94 sets the width 95 of the main body portion 62 and the separation between the shorter sides 96 sets the length 97 of the main body portion.

The long sides 94 have no upturned or gently rounded edge. However from each of 30 the short sides 96 of the washer main body 92, a lip 98 is turned out of the plane of the main body portion 92 at about 30° towards the upper face 91 side of the washer. 14 The lips 98 are thus raised from the upper face 91 and provide a stiffening for the washer in the widthways direction, although not as much stiffening as would be provided by the lips 82 on the embodiment shown in Figure 3.

A bend 99 is formed along the junction between the lips 98 and the main body portion 92 and the line of this bend runs straight across the width 95 of the main body portion at right angles to the long sides 94. The radius of curvature of the bend 99 is greater than that for the bend 84 in Figure 3 and is preferably in the range of 5 to 10 times the thickness of the metal forming the washer. Having a gentle bend instead of a sharp 10 edge at this area substantially reduces the stress concentrations in the area when a fastening between a batten and an underlying is approaching failure due to high wind loads.

The washer 90 shown in Figure 9 is simpler to manufacture than the washer 60 shown 15 in Figure 3 because there is less working of the edges to form stiffening walls. However the washer in Figure 9 requires thicker steel for its manufacture in order to achieve equivalent stiffness.

A variation (not shown in the Figures) of the washer in Figures 8 to 10 has the main 20 body portion gently curved so it is humped in the direction of the longer sides 94. The washer is thus arched towards the upper face 91 so the upper face has a convex shape over most of its length. Accordingly when that washer is used to fasten a top-hat batten 40 as described above, the shorter sides 96, with their lips 98, contact the flange 52 first and the centre portion of the lower face 93 is brought into contact with 25 the flange 52 only upon tightening the fastener.

The washer 110 shown in Figure 11 is an embodiment made from steel having a thickness in the range 3.0 to 4.5mm. This is thicker than that used for the washer shown in Figure 9. Instead of having lips forming upturned edges from the shorter 30 sides of the main body portion, the washer 110 has rounded edges 118 where the shorter sides 116 blend into the lower face 113. This embodiment therefore does not have a stiffening portion raised from the upper face 111. But thicker steel is required for washer 110 in order to achieve the desired stiffness.

The rounded edge 118 provides a means by which stress concentrations are reduced in 5 the foot flange 52 of a batten in a similar manner as was described above in relation to the bend 99 in the embodiment in Figure 9. The rounded edge 118 could be replaced by a bevelled edge but this would not be as effective in reducing stress concentrations.

Referring now to Figure 12, the washer 130 shown is made from a similar thickness 10 steel to that used for washer 90 shown in Figure 9. The washer 130 has no walls along the longer sides of the main body portion 132. Instead of the necessary stiffening being provided by lips extended from the shorter sides 136 of the main body portion of the washer, the washer 130 has a pair of ridges 140 pressed from its main body portion 132. Each ridge 140 is positioned midway between the hole 18 15 and the respective shorter side 136. The ridges 140 run fully across the width of the main body portion 132, are raised from the upper face 131 and provide a stiffening against bending of the washer widthwise to the washer. The ridges 140 are formed by a pressing operation in which a strip of metal is displaced upwards from the plane of the main body of the washer so that the ridges 140 are raised from the upper face 131.

The ridges 140 could alternatively be positioned closer to either the hole 18 or to the shorter sides 136, but this is not preferred. More than one ridge may be provided on either side of the hole in order to increase lateral stiffness of the washer.

The sides 136 have rounded edges 138 where the sides 136 blend into the lower face 133 in order to reduce stress concentrations in an underlying batten flange in use.

The washers made from thinner steel preferably have both longitudinal and lateral stiffening portions formed into them. Those made from somewhat thicker metal may 30 have lateral stiffening formations but not longitudinal stiffening formations. Washers 16 made from even thicker steel may perform satisfactorily with no additional stiffening formations formed into them.

Using the washers according to the above description produces an increase in lateral 5 stiffiiess of the foot of a fastened batten. That increase is about a factor of 2 to 5, preferably about 3.

Referring to Figures 13 to 16, the washer 210 shown is of elongate form. The washer 210 has a flat main body portion 212 which is rectangular in shape, the longer pair of 10 sides 214 being approximately 2.6 times the length of the shorter pair of sides 216. A hole 218 is formed through the washer in the centre 213 of the main body portion 212.

From each of the long sides 214 of the washer main body 212 an upturned edge 15 extends outwardly from the washer main body at an angle of about 45° such that the edges together form a pair of wings 220. The particular angle may be chosen to best suit the particular application. A fold line or bend line 224 extends along where each wing 220 and the main body 212 meet and this bend line is straight. The bend line 224 is preferably not formed as a sharp crease but is instead a curved bend as best 20 seen in Figure 16.

The wings 220 have a curved outer edge 222 and the shape of that curve is such that the length of the wing from the bend line 224 to the edge 222 is greatest at the central portion 226 of the wing. In other words the central portion 226 of the wing, which is 25 that portion nearest the hole 218, extends further away from the bend line 224 than do the end portions 228 of the wing.

From each of the short sides 216 of the washer main body 212 a lip 232 is turned out of the plane of the main body portion 212 to the same side of the washer as the wings 30 220 are directed. The lip is turned out less than the wings are, both in terms of angular displacement and as the width of the lip. A bend line 234 is formed along the 17 junction between the lips 232 and the main body portion 212 and this bend line runs straight across the washer at right angles to the bend line 224. The radius of curvature of the bend along line 234 is greater than that for bend along line 224 and the angular extent of bending is less than that for bend line 224.

The bend along line 234 forms an outer radius and curvature which faces away from the wings 220. The lip angles upwards at an angle of 5° to 30°. As a less desirable alternative, the upturned lip 232 could be replaced by a bevelled or curved edge (radius of curvature 5 to 15 mm) along that edge of the washer.

The washer 210 shown may be pressed from a sheet steel parent material.

Referring now to Figures 17 to 19, a top-hat section batten 40 is shown being fastened by means of a threaded fastener 42 to an underlying steel rafter 44 in a building roof 15 structure. The batten 40, fastener 42 and rafter 44 are the same as those described with reference to Figures 5 to 7.

The installation process takes the following steps: 1. The screw is fitted with a washer 210 of the form described earlier in this specification with reference to Figures 13 to 16. The head 43 of the screw is adjacent the upper face 236 of the washer inside the dished form of the washer, the wings 220 rising on either side of the head 43. The washer may be supplied already fitted to the screw or may be provided separately. 2. At the stage shown in Figure 17, the screw 42 has drilled through the flange 52 and the underlying steel rafter 44 but has not yet begun to be tightened. 3. As the screw is tightened the outer edges 222 of the two wings 220 make contact with the respective web 50 and lip 54 (as seen in Figure 18) and force the web and lip to elastically deform outwards from the washer while the wings 220 elastically deform inwards of the washer. 4. As the screw is tightened further the lower face 237 of the washer 210 eventually makes contact (as shown in Figure 19) with the flange 52 of the 18 foot of the top-hat section. The longer sides 214 of the main body portion of the washer nest into the inside corners 57 and 58 of the foot of the batten.

. As the screw is further tightened, the flange 52 is clamped and compressed 5 between the main body portion 212 of the washer and the rafter 44. The tightening and clamping preferably proceeds until a little before the threaded connection between the rafter and screw would fail.

The intimate physical contact between the clamped together surfaces of the washer 10 and the top-hat section greatly strengthens the batten at and around the region where the hole is drilled through it. This greatly reduces the tendency of the foot of the top-hat to kink and crack at that region during upward lifting due to wind loads.

The upward curve joining the lips 232 to the main body 212 provides a more gentle 15 curving radius for the metal in the flange 52 during uplift than would be provided by a washer having plain sharp flat edges.

The degree of tightening in step 5 of the above description with reference to Figure 19 is such that it is considered that tightening to between 50% and 80% of the full 20 clamping load is appropriate, where the full clamping load is that which would be achieved at the point where the threaded connection would begin to fail. Preferably the tightening proceeds until 60-70% of full clamping load. A clamping load of 30% of full clamping load is considered only a snug fit and is not preferred. This same degree of tightening is applicable to step 5 described earlier with reference to Figure 25 7.

It is important that the washers at least substantially cover the full width of the flange on the inside of the foot of the top hat section.

Where the word "elongate" and "elongated" are used in this specification when describing the shape of a washer, the meaning is intended to confer that the washer's length is significantly greater than its width, not that the elongation is extended to the 19 point where the washer has a long ribbon-like form. The washers used in the present invention preferably have the length of the longer side of their main body portion greater than 1.5 times the length of their shorter side. Preferably they are in the range of 2 to 4 times the length of the shorter side.

Preferably the length of the washer is close to the width of the rafter or other structural member underlying the foot. This maximizes the clamping of the foot flange. It will be understood however that in the extreme, some embodiments of this invention may incorporate washers which do not have an elongate main body portion.

Whilst the above description includes the preferred embodiments of the invention, it is to be understood that many variations, alterations, modifications and/or additions may be introduced into the constructions and arrangements of parts previously described without departing from the essential features or the spirit or ambit of the 15 invention.

For example, although both washers illustrated in the Figures have raised lips, wings or the like along their long edges, in other embodiments the washer may be flat at the long edges and carry a lip or flange at only the short edges. Also, washers may be 20 utilized which have raised lips or walls for stiffening along their longitudinal walls but not laterally to the foot flange.

In some geographic regions the term purlin is used instead of, or interchangeably with, batten. However the term purlin is usually reserved for a beam running along a 25 length of a roof and supporting common rafters above, whereas a batten is something fastened to the top of the rafters. Nevertheless the term batten when used in this specification is intended to encompass structural components called purlins when used in the manner described in this specification.

It will be also understood that where the word "comprise", and variations such as "comprises" and "comprising", are used in this specification, unless the context requires otherwise such use is intended to imply the inclusion of a stated feature or features but is not to be taken as excluding the presence of other feature or features.

Claims (19)

Claims

1. A method of fastening a foot of a top-hat section batten formed from sheet metal to an underlying structural member in a structure; said foot having: - a flange portion extending from a web of the top-hat section, and - a lip turned outwardly from the flange portion, whereby the web, flange portion and lip together form an open channel having outwardly sloping sides; the channel having a first straight inside corner where the web and the flange portion blend, and a second straight inside corner where the lip and the flange portion blend; said method comprising: - screwing through the flange portion into said structural member a threaded fastener having a head at one end and a point at the other end, - providing a washer between the fastener head and the flange portion, said washer comprising a main body portion having an upper face which faces the head of the screw, a lower face which faces the foot, and a hole through which the fastener passes, - tightening the fastener until edges of the main body portion nest into or close to said first and second straight inside corners, and said lower face covers an area of the flange portion greater than that area which would.be covered by a circular washer spanning fully between said straight inside corners, and - further tightening the fastener to clamp said flange portion of the foot between the washer and the structural member.

2. A method according to claim 1 wherein the washer has a shape elongated in the direction of the length of the channel, the main body portion has a pair of long sides and a pair of short sides, and the long sides nest into or close to respective said straight inside corners. 'pOAiz 02m*It <006 21

3. A method according to claim 2 wherein the main body portion has a stiffening portion raised from the upper face and extending across the width of the main body portion on opposite sides of the hole. 5

4. A method according to any one of claims 1 to 3 wherein the threaded fastener is a self-drilling screw which drills a hole through the flange portion and through portion of the structural member.

5. A fastener assembly for fastening the foot of a top hat section batten to an underlying structural member, the fastener assembly comprising: - a self drilling screw having a head at one end, a drilling tip at the other end, a shank, a threaded portion, and - an oblong shaped washer captively held on the shank, the washer comprising: - an elongated, substantially flat, oblong shaped main body portion having a pair of long sides, a pair of short sides, an upper face which faces the head of the screw, a lower face which faces the drilling tip, and a hole through which said shank passes, and - a stiffening portion raised from the upper face and extending across the width of the main body portion on each of opposite sides of the hole.

6. A fastener assembly according to claim 5 wherein the stiffening portions comprise an upturned lip formed along each of said short sides and extending from said main body portion. 25

7. A fastener assembly according to any one of claims 5 or 6 wherein the stiffening portions comprise a ridge formed across the washer between the hole and each short side of the main body, the ridge being raised on that side of the washer which contacts the head of the screw. 22

8. A fastener assembly according to claim 7 wherein the stiffening portions each comprise a ridge formed by material displaced from the plane of the main body of the washer. 5

9. A fastener assembly according to claim 7 or 8 wherein the ridges are located midway between the short sides and the hole.

10. A fastener assembly according to any one of claims 5 or 6 wherein a plurality of ridges extend across the width of the main portion on each of opposite sides of the 10 hole.

11. A fastener assembly according to claim 6 wherein said upturns each have an outside curvature which forms a rounded edge. 15

12. A fastener assembly according to any one of claims 6 and 11 wherein the upturn along said each short side forms an end flange angled in the range 30°-90° to the main body portion.

13. A fastener assembly according to claim 12 wherein the upturn along each 20 short side forms an end flange angled at greater than 60° to the main body portion.

14. A fastener assembly according to claim 13 wherein the end flange is angled in the range 85°-90° to the main body portion. 25

15. A fastener assembly according to any one of claims 5 to 14 wherein the washer has an upturned lip formed along each long side of the main body portion.

16. A fastener assembly according to claim 15 wherein the upturn along said each long side forms a side flange angled in the range 30°-90° to the main body portion. 30

17. A fastener assembly according to claim 16 wherein the upturn forms a side flange angled in the range 85°-90° to the main body portion. 23

18. A fastener assembly according to any one of claims 12 to 14 wherein the washer has an upturned lip formed along each long side of the main body portion to form side flanges to the main body portion, and said side flanges and end flanges together form an upturned edge or rim around the full perimeter of the main body portion so that the washer has the general form of a deep rectangular tray.

19. A fastener assembly according to any one of claims 5 to 18 wherein the hole through the washer is central to the main body. END OF CLAIMS IPonz