AU2009201409A1 - Roofing screw (three piece) - Google Patents

Description

Regulation 3.2 -1 AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT APPLICANT: Loi & Tran Pty. Limited NUMBER: FILING DATE: Invention Title: ROOFING SCREW (THREE PIECE) The following statement is a full description of this invention, including the best method of performing it known to me: -2 ROOFING SCREW (THREE PIECE) Technical Area This invention relates to a screw and in particular to a roofing screw which is adapted to connect sheet material to battens, rafters or the like. Screws of this type may often be used in connecting roof or wall panels to a metalled framed building. Background to the Invention Historically, when this was to be done the fixer needed to first drill a hole through the sheet and batten (and in this specification we will use the word "batten" quite generallyto include studs, purlins, rafters and other members used in buildings); they would then use a self-tapping screw which had a nominal diameter appropriate for use with the hole which had been drilled and as this passed into the hole, the flights of the screw would effectively form threads in the sheet member and the batten and the screw would be drawn into position and ultimately be able to make a tight connection. Whilst from a result point-of-view Y:\SPEC\Loi & Tran Three Piece Cutting Screw Comp 050409.wpd AT/CM 5/4/09 -3 such means of fixing were quite satisfactory, they were uneconomic in that the fixer first had to drill the initial hole through the sheet and batten and then use a separate tool to drive the screw. Subsequently, endeavours were made to form screws with drill tips so that they could first drill the hole through the sheet and batten and then permit the thread which was formed above the Up to enter the hole and to effectively self-tap. These screws were generally not satisfactory as the material of the screw is inherently relatively soft asthe threads are rolled onto the screw, not cut onto the screw, and thus, the material has to be sufficiently malleable to enable the rolling of the thread and this, of course, means that the tip formed was not necessarily hard. A first proposal to overcome this difficulty was to form a tip of a harder steel, say, stainless steel, and weld it onto the end of a screw formed of a softer steel. Such arrangements, whilst an improvement on the previous form, were difficult to manufacture as the screw and tip are both relatively small in diameter, and the tip was relatively short in length, and it was difficult to ensure that the weld left a screw in which the body of the screw and the tip were coaxial. Y:\SPEC\Lol & Tran Three Piece Cuffing Screw Comp 050409.wpd AT/CM 514/109 -4 We later proposed, in our patent application PCT/AU2004/001794 entitled "Two Piece Cutting Screw" to manufacture a screw where the end of the screw body was broached and the tip was formed with a spigot of corresponding size and cross-section so that the two components could be fitted together effectively with a press-fit to provide a hardened tip and a softer screw body. Such screws were of a great benefit relative to those previously produced, but still had two disadvantages. It will be appreciated that the broach into the end of the screw and the spigot were very small in cross-section and as the screws are manufactured in the hundreds of thousands, the components may not be as precise as would be the case if they were made individually and, on occasions, when assembling the tips to the body, there was a degree of distortion before assembly started and as the tip was very much harder than the body, the internal walls of the broach could be distorted so the tip was not necessarily completely axial with the body. The other disadvantage was, because the two components were a press-fit, whilst there was no concern if the tip separated after the screw had been driven, and indeed, there are some applications where this can be even desirable, it is, of course, frustrating and time-consuming if any of the tips separated before the screws were used. The fixer would normally find that the screw was on his tool before he noticed the tip had been displaced, or he would have to endeavour to find tips for any of the screws which had lost them. Y:\SPEC\LoI & Tran Three Piece Cutting Screw Comp 050409.wpd AT/CM 5/4/09 -5 Further, the screws still relied on the thread formed on the shank of the screw to draw the screw into the batten. Outline of the Invention The object of the present invention is to minimise or overcome these previous difficulties. The invention includes a cutting screw, having a threaded shank or body with a head at one end by means of which it can be driven and made of a first material and a tip of a second material which is formed with a cutting point characterised in that between the drill tip and the shank there is a threaded portion which has a thread which corresponds to the thread on the shank. The first material may be of a relatively soft material such as mild steel which can be rolled to form the thread on the shank and the tip is made of a harder material such as a high carbon steel or a stainless steel to provide a good cutting action. In a preferred form of the invention, the cutting screw has three components, the body and the tip and an intermediate part which is of a hard material and which is threaded to initially form the thread in the purlin. In a preferred form of the invention, the body at its outer end has an axial Y:\SPEC\Loi & Tran Three Piece Cutting Screw Camp 050409.wpd ATIM 514109 -6 threaded bore and the tip has an outwardly-extending axial threaded spigot whereby the screw is assembled by the spigot being screwed into the bore so that the tip is positively located relative to the bore and is located axially thereto. Where a three piece arrangement is used, the threaded portion has a threaded spigot at the end directed towards the body and an axial bore at the end directed toward the tip with the bores and tips being threaded to cooperate with each other. From a manufacturing point of view this arrangement provides great flexibility and good economies in the cost of manufacturing. A single body can be used with threaded portions of different lengths to provide screws of different lengths for different applications and tips of different types, drill tip, screw tip or composite can be associated with the shank and intermediate portion to provide composite screws which can be made of optimum materials and various lengths for different applications. Description of an Embodiment of the Invention In order that the invention may be more readily understood, one particular form of screw will be described in relation to the accompanying drawings, in which: Fig 1 shows a side elevation of a screw of the invention; and Y:kSPEC\Loi & Tran Three Piece Cutting Screw Camp 050409.wpd AT/CM 5/4/09 -7 Fig 2 shows an exploded view of the components of the screw. The screw body 10 is manufactured by automatic processes from an initial coil of rod material and goes through various steps which include straightening the rod, rolling a thread 11 thereon, forming a head 12 thereon and ensuring that the free end is square to the body. These are standard operations in the manufacture of such screws but normally during the rolling operation a tip is formed on the screw.. In this particular embodiment, there is provided an axial bore 13 extending inwardly from the end of the body, which bore is threaded. The material of the screw may be a mild steel or the like as it needs to be able to have a thread rolled on relatively easily and without damaging the rolling dies. The tip 30 for the screw is formed separately and again can be formed from a coil of material and it may be preferred that this be a relatively hard material, such as a stainless or high carbon steel, and the tip is formed with a cutting point 31 at one end and this may be in the form of a drill point having a tapered end and formed to provide a cutting edge 32 and a cut-out portion 33 extending upwardly from this, partially to remove swarf and partly to retain that within the volume of the cut-out portion whilst the point is cutting through the sheet material. YASPEC\Loi & Tran Three Piece Cutting Screw Comp 050409.wpd AT/CM 8/4/09 -8 Alternatively, it could have a drill point, not illustrated but well known in the art, where the screw is to be used with wooden battens or a composite point, also not illustrated but also well known in the art, which can be used with both metal and wooden battens. At the end of the tip away from the cutting point, there is an outwardly-extending spigot 34 which is of a diameter smaller than the body of the cutting point and which has an external thread. There is an intermediate member 20 which can be of a hard material and have the same diameter as the tip and the body. This intermediate member 20 is threaded with a thread 21 which corresponds to the thread 11 on the body and at the end which will be directed to the body has a threaded spigot 22 which can cooperate with the counterbore 13 of the body and, at the other end a counterbore 23 which can cooperate with the spigot 35 on the tip 30. The screw is then assembled by screwing the intermediate portion into the body and the tip into the intermediate portion. The threads on the bore 13 and the spigot 22 are such that the thread 11 on the body 10 and the thread 21 on the intermediate portion 20 are aligned. It will be seen that in using such an arrangement, provided the bore(s) are axial Y:\SPEC\Loi & Tran Three Piece Cutting Screw Comp 050409.wpd ATJCM 8/4/09 -9 relative to the body and the spigot(s) axial relative to the tip, there can effectively be no misalignment between the components and, at the same time, it is most unlikely that in normal handling and transport there will be any separation between tips and bodies. It will be appreciated too that even if the components becomes slightly unscrewed, there will be at least two and normally at least three or four threads retaining the components. Even if the components becomes somewhat loose, this is of no importance as, as soon as the insertion operation commences, the tip would be restrained from rotating freely or rotation will be limited until the body has effected a rotation sufficient to tighten the components, at which time the tip will then be positively driven and pass through the sheet material which is to be connected to a batten. There can be some applications, for example, if the screw is being driven into a box-type batten or other member, where it could be desirable to remove the cutting tip. This would be particularly the case if the internal area is exposed and the cutting tip extended close to or beyond the outer surface of the batten. If this is required, once the screw is located, it is relatively simple to remove the cutting head simply by grasping it in a locking-jaw plier or the like and unscrewing it from the screw body. In this way, the sharp edges of the screw tip are removed from the end of the screw to provide a safer end. Y:\SPEC\LoI & Tran Three Piece Cutting Screw Comp 050409.wpd ATICM 5/4/09 -10 If the screw is to be connected to a wooden batten, the tip could be a screw point tip or a composite tip could be provided. There could be some application, where the screw is being driven into relatively soft material where the intermediate member could be omitted. As mentioned, the screw construction of the invention, from a manufacturing aspect is very satisfactory and provides economic production as the intermediate member can be of various lengths and different materials depending on the application and the materials and construction of the tips can also be varied for different applications so many different composite screws can be made when required without holding large inventories of completed screws. Whilst the components of the screws described herein are stated to be interconnected by screw threads, it would be possible to form the screws using other forms of interconnection of the components such as shaped bores and spigots so turning forces can be transmitted. Whilst there have been described herein particular forms of construction and materials of construction, it is to be understood that these can be varied, depending upon the application concerned. YASPEC\Loi & Tran Three Piece Cutting Screw Comp 050409.wpd AT/CM 8/4/09

Claims (8)

1. A cutting screw, having a threaded shank or body with a head at one end by means of which it can be driven and being made of a first material, a tip of a second material which is formed with a cutting point characterised in that between the drill tip and the shank there is a threaded portion which has a thread which corresponds to the thread on the shank.

2. A cutting screw as claimed in claim 1 wherein the first material is a relatively soft material such as mild steel which can be rolled to form the thread on the shank and the tip is made of a harder material such as a high carbon steel or a stainless steel to provide a good cutting action.

3. A cutting screw as claimed in claim 2 wherein the cutting screw has three components, the body and the tip and an intermediate part which is of a hard material and which is threaded to initially form the thread in the material into which the screw is being driven.

4. A cutting screw as claimed in claim 3 wherein the body at its outer end has an axial threaded bore, the intermediate part has an outwardly extending axial threaded spigot complementary to the bore on the body on one and at its other end an axial threaded bore and the tip has an outwardly-extending axial threaded spigot whereby the screw is Y:\SPEC\Loi & Tran Three Plece Cutting Screw Comp 050409.wpd AT/CM 514/09 -12 assembled by the spigots being screwed into the adjacent bores so that the tip is positively located relative to the bores and is located axially thereof.

5. A cutting screw as claimed in any preceding claim wherein a single body can be used with threaded portions of different lengths to provide screws of different lengths for different applications.

6. A cutting screw as claimed in any preceding claim which may have tips of different types, drill tip, screw tip or composite depending upoon the use to which the screw is to be put.

7. A cutting screw as claimed in any preceding claim wherein the intermediate portion may be made of different material depending upon the use for which the screw is to be used.

8. A cutting screw substantially as herein described with reference to the accompanying drawings. DATED this 7th day of April 2009 Loi & Tran Pty. Limited By its Patent Attorneys A TATLOCK & ASSOCIATES Y:\SPEC\LoI & Tran Three Piece Cutting Screw Comp 050409.wpd AT/CM 5/4/09