AU2014100200A4 - A Screw - Google Patents

Abstract

The present invention provides a screw (20) comprising a shank (24) having a head (22) at one end and a cutting tip (26) at the other end. A thread (25) is formed on the shank (24) extending at least partially between the head (22) and the cutting tip (26). At least one fin (23) is formed on the shank (24) between the head (22) and the thread (25). The at least one fin (23) comprises a body that extends radially from the shank (24) in a direction substantially perpendicular to a longitudinally extending axis of the shank (24). F-

Description

A SCREW FIELD OF INVENTION The present invention relates generally to a screw, and in particular, to a self drilling screw for use with wood or composite material. 5 BACKGROUND OF THE INVENTION For many building applications, wood is a commonly used product due to its natural properties, including durability and its ability to be treated for moisture, insect and fire resistance. More recently, composite materials, which combine wood with a synthetic material, have also been proposed to provide a product 10 having improved durability and wear, while also providing an environmentally acceptable alternative building product. Due to the aesthetic properties of wood and/or composite materials, such materials often used in building applications where they remain exposed, such as floor material or roof or wall cladding material. The material is often secured in 15 position by way of one or more anchorage members, such as screws, which are able to penetrate the material to secure it to a joist or bearing located underneath. Conventionally, the process of securing the material in position by way of a screw or similar fastening device has required pilot holes to initially be drilled into the material for receiving the screws. This has traditionally been performed 20 to ensure that the screw is orientated correctly and to avoid cracking or splitting of the material during the fixation step. Whilst this procedure has proven effective in securing material to an underlying structure, the procedure adds significantly to the time to the process as well as an increased demand on labour required to secure the material. More recently, screws have been developed 25 having a tip configured to be self drilling, thereby obviating the need to drill pilot holes in to the material and significantly reducing labour and times involved with laying flooring, cladding and the like. However, a problem with using material such as wood and/or composite materials is that when a screw is drilled into the material, a mound or bump is 30 typically formed in the surface of the material around the screw. This has typically been referred to as "mushrooming" and is caused by the action of the cutting tip of the screw displacing the material in an upward direction as the screw is driven into the material. This displacement of material thereby creates 1 the unsightly bump or mound in the surface of the material. In applications where a tidy or flush finish is required in the surface of the material, the provision of mounds or bumps around the screw created by the phenomenon of "mushrooming" is highly undesirable and can have a significant negative effect 5 on aesthetic appearance of the finished product. Whilst methods have been proposed to reduce the effect of mushrooming by hammering down the mounds or bumps or sanding away the surface of the material following the fastening step, such methods do not address the occurrence of the phenomenon of "mushrooming" but rather address the result and are labour intensive and tend to 10 still leave behind marks and undesirable impressions in the surface of the material. Thus, there is a need to provide a screw that is capable of eliminating or substantially reducing the likelihood of "mushrooming" occurring during the step of fixing the material in position. 15 The above references to and descriptions of prior proposals or products are not intended to be, and are not to be construed as, statements or admissions of common general knowledge in the art. In particular, the above prior art discussion does not relate to what is commonly or well known by the person skilled in the art, but assists in the understanding of the inventive step of the 20 present invention of which the identification of pertinent prior art proposals is but one part. STATEMENT OF INVENTION The invention according to one or more aspects is as defined in the independent claims. Some optional and/or preferred features of the invention are defined in 25 the dependent claims. Accordingly, in one aspect of the invention there is provided a screw comprising: a shank having a head at one end and a cutting tip at the other end; a thread formed on the shank extending at least partially between the head and the cutting tip; and 30 at least one fin formed on the shank between the head and the thread, the at least one fin comprising a body that extends radially from the shank in a direction substantially perpendicular to a longitudinally extending axis of the shank. 2 The at least one fin may extend radially from the shank a distance greater that the distance the thread extends from the shank. The radial distance that the at least one fin extends from the shank may be less than the radial distance that the head extends from the shank. 5 A plurality of fins may be formed on the shank, each fin may extend parallel to each other fin. At least a surface of the at least one fin may be configured to perform a cutting or abrading action. BRIEF DESCRIPTION OF THE DRAWINGS 10 The invention may be better understood from the following non-limiting description of preferred embodiments, in which: Fig. 1 is a side view of a prior art arrangement of a self-drilling or self tapping screw; Fig. 2 is an enlarged view of the prior art screw of Fig. 1 driven into a 15 material depicting the phenomena of "mushrooming" about the head of the screw; Fig. 3 is a side view of a screw in accordance with the present invention; and Fig. 4 is an enlarged view of the screw of Fig. 3 driven into a material; 20 DETAILED DESCRIPTION OF THE DRAWINGS Preferred features of the present invention will now be described with particular reference to the accompanying drawings. However, it is to be understood that the features illustrated in and described with reference to the drawings are not to be construed as limiting on the scope of the invention. 25 The present invention will be described below in relation to its application for securing a wood product, such as a timber, to an underlying support, such as a joist. However, it is to be appreciated that the type of material to be used with the present invention and the application may vary and still fall within the spirit of the present invention. 3o Referring to Figs. 1 and 2, there is depicted a screw 10 in accordance with a prior 3 art arrangement for securing a timber plank 5 or the like to an underlying support beam (not shown). The screw 10 generally comprises a head portion 12 which is configured to engage with a driving mechanism, such as a drill or screw driver, so as to impart a rotational force to the screw 10 to cause the screw to be driven 5 into the plank 5. Whilst not shown, the upper surface of the head 12 may be configured to engage with the driving mechanism by a conventional manner, including a groove or indentation to facilitate engagement with a conventional screw driver or the like. A shank 14 extends from an underside of the head 12, with the shank 14 having a 10 lesser diameter than the head 12. A thread 15 extends in a spiral manner along the surface of the shank 14 towards the tip 16. The tip 16 comprises a drilling surface 17 formed therein which tapers towards an end point 18. The drilling surface 17 of the tip 16 typically comprises at least one cutting edge 19. Typically two opposing cutting edges 19 are provided on the tip 16 and extend at 15 an angle to the axis of the screw 10. A flute 19a is associated with each cutting edge 19 to provide a path for the removal of material being cut by the cutting edges 19. In this arrangement, when the screw 10 is placed on the surface 6 of the timber plank 5 and rotated under action of the driving mechanism, the cutting edges 19 at the tip 16 function to drill a pilot hole for itself to enable the screw to 20 penetrate into the timber plank 5. As is shown in Fig. 2, when the screw 10 is driven into the plank 5, a phenomenon known as "mushrooming" typically occurs at the surface 5 of the plank 6. This occurs due to the action of the cutting edges 19 at the tip 16 acting to displace the removed material of the plank 5 as it penetrates into the material. 25 The material being removed is drawn into an upward direction due to the angular orientation of the cutting edges 19 and the provision of the flutes 19a. As the screw 10 is further driven into the plank 5 the material being removed is further transported upwards by the thread 15 where a bulge 8 is created in the surface 5 around the head 12 of the screw 10, as depicted. This effect of "mushrooming" is 30 undesirable and has a significant adverse effect in the finished appearance of the material. To address this phenomenon, a screw 20 in accordance with an embodiment of the present invention is provided, as depicted in Figs 3 and 4. The screw 20 generally resembles a conventional screw, such as that shown as screw 10 in Fig 35 1. The screw 20 comprises a head portion 22 which is configured to engage with a 4 driving mechanism, such as a drill or screw driver, so as to impart a rotational force to the screw 20 to cause the screw to be driven into the plank 5. Whilst not shown, the upper surface of the head 22 may be configured to engage with the driving mechanism by a conventional manner., for example via a cross-head or 5 "Phillips-head" arrangement. A shank 24 extends from an underside of the head 22, with the shank 24 having a lesser diameter than the head 22. A thread 25 extends in a spiral manner along the surface of the shank 24 towards the tip 26. Located on the shank 24 between the head 22 and the commencement of the thread 25 are provided a plurality of 10 fin members 23, as shown. The fin members 23 extend radially from the shank 24. In the embodiment depicted in Figs. 3 and 4, three fin members 23 are provided, although it will be appreciated that the number of fin members 23 may vary and still fall within the spirit of the present invention. Each of the fin members 23 are formed integrally with the shank 24 and extend 15 substantially perpendicular to the axis of the shank 24. The fin members 23 are each formed such that they extend are parallel to each other and project a distance 'X' beyond the surface of the shank 24. In the embodiment as shown, each fin member 23 projects the same distance 'X'; however, it will be appreciated that the fin members may project for different distances 'X' and still fall within the 20 spirit of the present invention. The distance 'X' of projection of the fin members 23 is greater than the distance of projection 'Y' of the thread 25 beyond the surface of the shank 24. However, the distance 'X' is less than the distance 'Z' in which the head 22 projects beyond the surface of the shank 24, such that the head 22 of the screw 20 remains the widest part of the screw 20 thereby enabling the 25 screw to be recessed into the plank 5 in an aesthetically pleasing manner as depicted in Fig. 4. In a preferred embodiment of the present invention, the screw 20 is a self drilling or self-tapping screw. As such, the tip 26 comprises a drilling surface 27 formed therein which tapers towards an end point 28, when viewed in side profile. The 3o drilling surface 27 of the tip 26 typically comprises at least one cutting edge 29. Typically, two opposing cutting edges 29 are provided on the tip 26 and extend at an angle to the axis of the screw 20. A flute 29a is associated with each cutting edge 29 to provide a path for the removal of material being cut by the cutting edges 29. In this arrangement, when the screw 20 is placed on the surface 6 of 35 the timber plank 5 and rotated under action of the driving mechanism, the cutting edges 29 at the tip 26 function to drill a pilot hole for itself to enable the screw to penetrate into the timber plank 5. It will be appreciated that other configurations 5 for forming the cutting tip are also envisaged. As is shown in Fig. 4, the screw 20 in accordance with the present invention, functions to compress the material removed and transported upwards by the screw to avoid the occurrence of mushrooming occurring at the surface 6 of the 5 plank 5. In this regard, as the removed material is transported towards the surface 6 of the plank 5 by way of the thread 25 of the screw 20, the material comes into contact with the fin members 23 which act to compress the material into the hole created by the screw 20. This then prevents the material from rising further, thus reducing the likelihood of a bulge or mound being created at the 1o surface 6 of the plank. Further to this, the surface and edges of at least the lowermost fin member 23 may be roughened or processed with an abrasive coating such that they act to remove material upon rotation to accommodate the increased width of the fin members 23 with respect to the thread 25, as the screw 20 advances into the plank 5. It will be appreciated that the additional width of 15 the hole created by the fin members 23 will also provide additional space in which to accommodate the removed material, to further reduce the likelihood of "mushrooming" occurring at the surface 6 of the plank 5. In the embodiment as shown, the head 22 of the screw 20 is able to be recessed below the surface 6 without generating a bulge or mound about the screw head. 20 In this arrangement, there is no requirement to further process the surface 6 to remove the effect of "mushrooming" thereby greatly reducing the time and labour required to finish the surface 6. It will be appreciated that a screw in accordance with the present invention functions to compress and accommodate the rising material being removed by the 25 cutting tip in the action of drilling the screw into position. As such, the screw provides a means for reducing the likelihood of a bulge or mound occurring around the head of the screw, thereby obviating the need to apply removal or reductions processes after the act of securing is performed. Throughout the specification and claims the word "comprise" and its derivatives 3o are intended to have an inclusive rather than exclusive meaning unless the contrary is expressly stated or the context requires otherwise. That is, the word "comprise" and its derivatives will be taken to indicate the inclusion of not only the listed components, steps or features that it directly references, but also other components, steps or features not specifically listed, unless the contrary is 35 expressly stated or the context requires otherwise. 6 Orientational terms used in the specification and claims such as vertical, horizontal, top, bottom, upper and lower are to be interpreted as relational and are based on the premise that the component, item, article, apparatus, device or instrument will usually be considered in a particular orientation, typically with the 5 screw uppermost. It will be appreciated by those skilled in the art that many modifications and variations may be made to the methods of the invention described herein without departing from the spirit and scope of the invention. 7

Claims (5)

1. A screw comprising: a shank having a head at one end and a cutting tip at the other end; a thread formed on the shank extending at least partially between the head 5 and the cutting tip; and at least one fin formed on the shank between the head and the thread, the at least one fin comprising a body that extends radially from the shank in a direction substantially perpendicular to a longitudinally extending axis of the shank. 10

2. A screw according to claim 1, wherein the at least one fin extends radially from the shank a distance greater that a radial distance that the thread extends from the shank.

3. A screw according to claim 2, wherein the radial distance that the at least one fin extends from the shank is less than a radial distance that the head 15 extends from the shank.

4. A screw according to any one of the preceding claims, wherein a plurality of fins are formed on the shank, each fin extending parallel to each other fin.

5. A screw according to any one of the preceding claims, wherein at least a 20 surface of the at least one fin is configured to perform a cutting or abrading action. 8