AU2016100659A4 - A self drilling screw - Google Patents

Abstract

A self drilling roofing screw is provided to secure sheet roofing material to a supporting structure such as overlapped purlins. The self drilling screw includes: a shank defining a longitudinal axis; first and second longitudinal ends; a drill tip portion at the first end; a 5 fastener head at the second end, and a threaded length extending from the drill tip portion towards the fastener head. The drill tip portion has a longitudinal length of at least 9.9mm, and the threaded length has at least one thread and has less than 16 threads per inch. 0i

Description

A Self Drilling Screw

Field of the invention

The present disclosure relates to self drilling screws to secure sheet material to a supporting structure, and more particularly (but not exclusively) to secure roofing sheets to secure sheet material to metal purlins and/or battens.

Background of the invention

When roof sheets (such as metal and polycarbonate roof sheets) are being screwed to a supporting structure (such as timber, metal battens and metal purlins), the self drilling screw passes through the sheet material to engage the supporting structure below.

Self drilling screws with a coarse thread are typically used to fasten thinner materials, whereas screws with a fine thread are typically used to fasten thicker materials.

In self drilling screw manufacture, a screw with a fine thread will normally have 16 threads per inch or greater, depending on the diameter; whereas a screw with a coarse thread will normally have less than 16 threads per inch, down to about 8 threads per inch.

Self drilling screws having a coarse thread are usually used to drill through thinner steel thicknesses. These screws normally have a drill point length that ranges from 4.8mm to 9.5mm. On the other hand, fine thread screws are designed to drill through thicker steel thicknesses and therefore will typically have a drill point length that ranges from 5.5mm up to 17mm.

Overlapped purlins will generally have an air gap between them. This can vary from site to site. This may create a difficulty for self drilling screws, as the drill point may be drilling through the lower piece of purlin whilst the threaded portion of the screw will threadingly engage the upper piece of purlin which has been separated by the air gap. The disadvantage is that when both drilling and threading occurs at the same time, there is a differential between the torque exerted on the screw at the point as compared to the torque exerted on the thread as it passes through the upper piece of purlin. The drill point of the screw shank may break under these circumstances.

Threaded fasteners as described above are described in Australian Patent Specifications 2003100147, 200010193 and 2002214828.

Reference to any prior art in the specification is not an acknowledgment or suggestion that this prior art forms part of the common general knowledge in any jurisdiction or that this prior art could reasonably be expected to be understood, regarded as relevant, and/or combined with other pieces of prior art by a skilled person in the art.

Summary of the invention

There is disclosed herein a threaded fastener to secure to sheet material to a supporting structure, the fastener including: a shank opposite first and second longitudinal ends, and a longitudinal axis; a drill tip at the first end; a head at the second end; a threaded length extending from the tip towards the head; and wherein the drill tip has a longitudinal length of at least 9.9mm, and the threaded length has at least one thread and has less than 16 threads per inch.

The drill tip length may be 10 to 12mm, or 10 to 11 mm.

The threaded length may have about 14 threads per inch.

The threaded length may alternatively have about 10 threads per inch.

The threaded fastener may be a self drilling screw.

As used herein, except where the context requires otherwise, the term "comprise" and variations of the term, such as "comprising", "comprises" and "comprised", are not intended to exclude further additives, components, integers or steps.

Further aspects of the present invention and further embodiments of the aspects described in the preceding paragraphs will become apparent from the following description, given by way of example and with reference to the accompanying drawings.

Brief description of the drawings

Preferred forms of the present disclosure will now be described by way of example with reference to the accompanying drawings wherein:

Figure 1 is a side elevation of a self drilling roofing screw;

Figure 2 is end elevation of the screw of Figure 1;

Figure 3 is a sectioned side elevation of the head of the screw of Figure 1; and

Figure 4 shows a cutaway side view of the self-drilling roofing screw of Figure 1 fastening a roofing sheet to two air-gapped purlins.

Detailed description of the embodiments

In the accompanying drawings there is depicted a threaded fastener or roofing screw 10 that is intended to attach sheet material to metal battens and metal purlins. The threaded fastener 10 includes a shank 11 having a longitudinal axis 12. The shank 11 has, at a first end, a head 13, and at a second end, a drill tip portion 14.

The head 13 includes a hexagonal nut 15 and a washer portion 16, with the washer portion 16 usually engaging a resilient washer formed of plastics or rubber material.

The shank 11 includes a first threaded length portion 17 that is provided with a thread 18, and may include a second threaded length portion 19 provided with a thread 20.

The threaded length portion 17 includes a start length portion 24 at which the outer diameter of a thread 18 gradually diminishes or tapers towards the drill tip portion 14.

The drill tip portion 14 has a longitudinal length portion 25 that is greater than 9.9mm. The length may be 10 to 12mm or 10 to 11 mm.

The threaded length portion 17 has less than 16 threads per inch. Accordingly it will have a threaded pitch less than .0625 inches (1.5875mm). Preferably, the length portion 17 has about 14 threads per inch (tpi), and a pitch of about 1.81mm. In another preferred form, the length has about 10tpi. Typically, the minimum threads per inch is 10 tpi, and the threads per inch range may be from 10 tpi to 14 tpi more.

Threaded length 19 may have a pitch the same as the threaded length 17.

Referring to Figure 4, in the above described embodiment the drill tip portion 14 has a length 25 of 10-11mm. This drill tip length portion 25 is sufficiently long to drill through upper and lower overlapped purlins 30 and 32, each having a typical thickness of between 1.2mm and 4mm, most typically 1.5mm to 2.4mm. The purlins are separated by air gap 34, so that the end of the drill tip 14 has already emerged through the bottom purlin 32 while the shaft of the drill tip is still travelling through the upper purlin 30, as can be seen at 36. It will be appreciated that the shaft portion is sufficiently long to ensure that even when the air gap increases to up to 6mm the threaded portion does not engage the upper purlin while the lower purlin is still being drilled, thereby ensuring that the differential torque problem does not arise.

Accordingly, a threaded fastener such as that in the above described embodiment with a sufficiently large drill tip length 25 will only experience one torsional force rather than two, when fastening roofing sheets 40 to air-gapped purlins 30 and 32. In the particular embodiment, the roofing screw 10 is shown with an intermediate knurled portion 42 which assists in reaming a sufficiently large aperture in the roof sheet to accept the bigger diameter thread 20.

It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention.

Claims (5)

1. A self drilling screw to secure sheet material to a supporting structure, the self drilling screw including: a shank defining a longitudinal axis; first and second longitudinal ends; a drill tip portion at the first end; a fastener head at the second end; a threaded length extending from the drill tip portion towards the fastener head; wherein the drill tip portion has a longitudinal length of at least 9.9mm, and the threaded length has at least one thread and has less than 16 threads per inch.

2. A self drilling screw to secure sheet material to a supporting structure, the self drilling screw comprising: a shank defining a longitudinal axis; first and second longitudinal ends; a drill tip portion at the first end; a fastener head at the second end; a threaded length extending from the drill tip portion towards the fastener head; wherein the fastener head comprises a hexagonal nut portion and a washer portion for receiving a roofing washer; and the threaded length includes a first threaded portion and a second threaded portion spaced from the first threaded portion by a spacer portion, the first threaded portion extending from the drill tip portion to the spacer portion and the second threaded portion extending from the washer portion to the spacer portion.

3. A self drilling screw according to claim 2, wherein the self drilling screw further comprises: a knurled portion occupying the spacer portion between the first threaded portion and the second threaded portion; and the second threaded portion has a larger diameter than the first threaded portion, wherein the knurled portion is configured to ream a larger diameter aperture for accommodating the second threaded portion.

4. A self drilling screw according to any one of claims 1 to 3 wherein the drill tip portion length is 10 to 12mm.

5. A self drilling screw according to any one of claims 1 to 4 wherein the threaded length portion has from about 10 to about 14 threads per inch.