AU2011101643A4 - Screw fastener - Google Patents

Abstract

C RPonb\DCC\PLW\4(X)%1 5_1 DOC. 14/12/21,11 -5 A self-drilling screw comprising a shank with a drilling portion at one end and a head at the opposite end, the head having a hexagonal drive part for engagement within a 5 hexagonal drive socket and an integral washer, wherein the shank is of 12g or 14g size or metric equivalent, and the height of the head between the underside of the washer and outer end surface of the hexagonal drive part is a maximum of about 5.15mm. o 00 -0

Description

Regulation 3.2 AUSTRALIA Patents Act 1990 INNOVATION PATENT SPECIFICATION (ORIGINAL) Name of Applicant: Illinois Tool Works Inc. of 3600 West Lake Avenue, Glenview, Illinois 60026, United States of America Actual Inventors: John Mallet David Collinson Derek Andrews Address for Service: DAVIES COLLISON CAVE, Patent Attorneys, I Nicholson Street, Melbourne 3000, Victoria, Australia Innovation Patent specification for the invention entitled: "Screw fastener" The following statement is a full description of this invention, including the best method of performing it known to us: C:NRPonbj\DCCPLW\4'0X0%I S_1 DOC-14/12/2011 SCREW FASTENER The present invention relates to screw fasteners and more particularly to self-drilling screws for use in fixing metal roof sheets. 5 Conventionally, metal roof sheets are fixed to underlying structure such as steel or timber purlins either by the use of screws which pierce the sheet at the crest or valley of the profile of the sheet, or by clipping the sheet to metal clips which are fastened to the underlying structure. Whichever method of fixing is used, the securement to the 10 underlying structure is effected by means of self-drilling screws. Conventionally, self drilling screws for this purpose have a hexagonal head with integral washer and to ensure adequate strength it is conventional to use either a 12 gauge screw (corresponding to a thread tip diameter of approximately 5.5mm) or a 14 gauge screw (corresponding to a thread tip diameter of approximately 6.3mm). Standard 12g and 14g screws tend to have 15 substantially standard head sizes in terms of head height (the distance between the underside of the washer and the outer end of the hexagonal drive part), washer diameter, and the "across flats" dimension of the hexagonal drive part and which corresponds to a standard size of hexagonal drive socket. In particular, a standard 12g screw has a head height of 6.6mm maximum, a washer diameter of 14.7mm maximum, and an across flats 20 dimension of the hexagonal drive part of 5/16 inch (8.0mm); a standard 14g screw has a head height of 6.7mm maximum, a washer diameter of 14.7mm maximum, and an across flats dimension of the hexagonal drive part of 3/8 inch (9.5mm). These head height dimensions have been designed to ensure that the screw can easily be driven without "break out" from the drive socket. In practice, the variation from the maximum 25 dimensions given is very small, typically no more than about -0.4mm. With a standard head height at 6.6mm or thereabouts, when the roof sheet is fixed using the clipping method discussed above, the roof sheet lies above the screws which are used to fasten the clips to the purlins or other underlying structure and in some cases the 30 underside of the roof profile can engage the top surface of the screw head thereby restricting movement to the sheet which occurs during the temperature change from night C:\NRPortbl\DCC\PLW\X4%15 1.DOC-14/112/2WI -2 to day. This restriction in the movement of the sheet can sometimes cause a failure of the screw either by the screw shearing at its shank or the screw pulling out of the underlying structure. 5 The present invention provides a screw with a 12g or 14g (or metric equivalent) shank for appropriate strength but with a smaller head size to avoid engagement between the roof' sheet and underlying screw head. According to the present invention there is provided a self-drilling screw comprising a 10 shank with a drilling portion at one end and a head at the opposite end, the head having a hexagonal drive part for engagement within a hexagonal drive socket and an integral washer, wherein the shank is of 12g or 14g size or metric equivalent, and the height of the head between the underside of the washer and outer end surface of the hexagonal drive part is a maximum of about 5.15mm. 15 In a preferred embodiment the thickness of the integral washer is between approximately 1.15 and 1.40mm. This enables the required overall reduction in head height without the need to reduce the height of the hexagonal drive part which can remain of dimensions equivalent to those in standard screws of corresponding gauge whereby the driving 20 capacity of the screw is not impaired. An embodiment of the invention will now be described by way of example only with reference to the accompanying drawings in which: Figure I is a side view of a self-drilling screw in accordance with a preferred 25 embodiment of the invention; Figure 2 is a fragmentary perspective view showing screws in accordance with the invention applied in a concealed fixing situation to secure a clip to underlying structure, with roof sheets being applied to the clip above the screws; and Figure 3 is a side view corresponding to Figure 2. 30 The screw in accordance with a preferred embodiment of the invention is a substantially C:\NRPorb\DCC\PLVA40% IS .DOC- W 12/2011 -3 conventional self-drilling screw having a 12g or 14g shank size save for the dimensions of its head. As shown, the shank has a drilling portion 2 with a drilling tip 4 and diametrically opposed flutes 6 extending from the drilling tip to the threaded portion of the shank. It is however to be understood that the drilling portion could be different from that 5 shown. For example it could be in the form described in patent no. 719725 in the name of ITW AFC Pty Ltd. It could even be in the form of a type 17 screw or other screw suitable for the purpose. The screw head consists of hexagonal drive part 8 and integral washer 10. The washer diameter is reduced in relation to that in standard screws and is between approximately 10.8mm and 11.5mm which permits the thickness of the washer 10 to be 10 reduced in relation to that in standard screws thereby reducing the overall head height H- to a maximum of about 5.15mm. The thickness of the washer is between approximately 1.15 and 1.40mm, in comparison to a thickness of between approximately 2.0 and 2.3mm in standard screws. The reduction in head height H is achieved without reducing the height W of the hexagonal drive part which still has an across flats dimension of 5/16 inch 15 (8.0mm) for a 12g shank or 3/8 inch (9.5mm) for a 14g shank whereby the driving capability of the screw is not impaired in the sense that the screw head should not break out of the drive socket. The reduced head height when the screw is used to fix a clip to the underlying structure 20 ensures that the upper edge of the head lies sufficiently beneath the under surface of the roof sheet to ensure that the roof sheet does not engage the screw during thermally induced movement of the roof sheet. Figures 2 and 3 show a support clip 20 fastened to underlying structure by screws in accordance with a preferred embodiment and roof sheets 22 applied to the clip 20 by pushing a crest portion of the sheet over the clip. Figure 3 shows the 25 clearance which exists between the head of the screw and underside of the sheet as a result of the reduced head height. The embodiment has been described by way of example only and modifications are possible within the scope of the invention.

Claims (5)

1. A self-drilling screw comprising a shank with a drilling portion at one end and a head at the opposite end, the head having a hexagonal drive part for engagement within a 5 hexagonal drive socket and an integral washer, wherein the shank is of 12g or 14g size or metric equivalent, and the height of the head between the underside of the washer and outer end surface of the hexagonal drive part is a maximum of about 5.15mm.

2. A screw according to claim 1, wherein the washer diameter is between 10 approximately 10.8 and 11.5mm.

3. A screw according to claim I or claim 2, wherein the thickness of the washer is between approximately 1.15 and 1.40mm. 15

4. A screw according to any one of claims I to 3, wherein the dimension of the hexagonal drive part across the flats is 5/16 inch (or metric equivalent) for a 12g shank, and 3/8 inch (or metric equivalent) for a 14g shank.

5. A screw according to any one of claims I to 4 when used to fix to underlying 20 structure a clip to which roof sheet is attached, wherein the roof sheet lies above the screw head and the underneath surface of the roof sheet is spaced from the upper end surface of the screw head to provide continual clearance therebetween despite movement of the sheet arising from temperature variation.