SE541064C2

SE541064C2 - Screw for engagement with wood or similar composite material

Info

Publication number: SE541064C2
Application number: SE1651376A
Authority: SE
Inventors: Christofer Lindberg; Gustav Jansson; Jörgen Falck; Mathias Bergfjord
Original assignee: Essve Produkter Ab
Priority date: 2016-10-19
Filing date: 2016-10-19
Publication date: 2019-03-26
Also published as: WO2018074972A1; RU2019115116A; RU2744697C2; SE1651376A1; RU2019115116A3; EP3529505A4; EP3529505A1

Abstract

The present disclosure relates to a screw (10) for engagement with wood or similar composite material, such as a decking plane composite material (25), by rotating said screw in a rotational direction (W) around a rotational axis (AC) of said screw. Said screw extending in an axial direction (A) and comprising: a countersunk head portion (12) having a top side (19) for accommodating a driving tool to rotate said screw and an essentially frusto-conical shaped lower portion (18); a shank (14) extending from the head portion to a point tip (11) and having a threaded region (15); wherein said frusto-conical shaped lower portion (18) comprises a cutting recess section (20) having a trailing region (22) as seen in said direction of rotation (W); and wherein said trailing region (22) comprises a cutting edge (23) having a first axial end point (41) and a second axial end point (42) defining an imaginary line (Al), and wherein said imaginary line (Al) defines a positive cutting edge angle (a) relative to a plane (AP), said plane (AP) extending in a radial direction (R), from said rotational axis (AC) to said first axial end point (41), and in said axial direction (A).

Description

Screw for engagement with wood or similar composite material TECHNICAL FIELD This disclosure relates to a screw for engagement with wood or similar composite material, such as a decking plane composite material. The screw comprises a countersunk head portion having a top side for accommodating a driving tool to rotate the screw and an essentially frusto-conical shaped lower portion.

BACKGROUND ART Screws are generally required to be driven into a working piece directly or into a pilot hole in the working piece. One common type of screw configured for tapping its own hole as it is driven into the working piece is a self-tapping screw. Self-tapping screws are fasteners that are designed to drill their own hole as they are screwed into the working piece. In particular, self-tapping screws are suitable for softer working pieces such as wood or composite materials, e.g. a decking plane material. By using a driving tool, e.g. a screw driver, and a selftapping screw, precisely fitted threads are created.

These types of screws are available in several different shapes and sizes and are also available in numerous different head types. Within the field of wood screws and screws for decking plane materials, there is common to use a so-called countersunk head portion, which allows the head of the countersunk screw, when engaged with the working piece, to sit flush with or below the surface of the working piece. In addition, wood screws and decking plane screws are generally provided with a partially unthreaded shank below the head. The unthreaded portion of the shank is designed to slide through the top board (closest to the screw head) so that it can be pulled tight to the board to which it is being attached.

Although these types of screws are efficient in terms of providing a firm engagement with the working piece, one common problem is that the head portion may cause undesired deformation of the working piece or the surface of the working piece leading to splitting or denting of the material of the working piece. In order to partly alleviate these problems, some screw head portions are provided with ribs projecting outwardly from a lower part of the head portion or recesses having a cutting edge for cutting the fibres when the lower part of the head portion contacts the working piece upon rotation of the screw.

For example, US 5,683,217 A1 discloses a self-countersinking screw including an inverted-conical head portion having an underside with a plurality of generally triangular recesses. Each one of the recess of the plurality of the generally triangular recesses comprises a planar trailing wall forming a linear cutting edge at the merger of the trailing wall with surface of the of the underside.

However, it is not a simple task to design screws in order to provide a firm engagement with the working piece, while ensuring that the finish of the surface of the working piece remains relatively intact.

Thus, it would be desirable to further improve the function of a screw for wood and composite material such as decking plane materials.

Despite the activity in the field, exemplified by the above-cited disclosure, there remains a need for a screw which permits an improved engagement with the working piece, while minimizing the level of deformation of the material(s) making up the working piece such as a wooden working piece or a decking plane. In addition, it would be desirable to minimize the manufacturing costs in view of the mass -production of said screws.

SUMMARY OF THE INVENTION An object of the present disclosure is to provide an improved cutting action of a screw for engagement with wood or similar composite material, such as a decking plane composite material. This object is at least partly achieved by the features of claim 1.

The disclosure concerns a screw for engagement with wood or similar composite material, such as a decking plane composite material, by rotating said screw in a rotational direction around a rotational axis of the screw. The screw extends in an axial direction and comprises: - a countersunk head portion having a top side for accommodating a driving tool to rotate the screw and an essentially frusto-conical shaped lower portion; - a shank extending from the head portion to a point tip and having a threaded region; - wherein the frusto-conical shaped lower portion comprises a cutting recess section having a trailing region as seen in the direction of rotation; and - wherein the trailing region comprises a cutting edge having a first axial end point and a second axial end point defining an imaginary line. Moreover, the imaginary line defines a positive cutting edge angle a relative to a plane AP. The plane AP extends in a radial direction, at least from the rotational axis to the first axial end point, and in the axial direction A.

In this manner, there is provided a screw with an improved cutting action of fibres such as wood fibres or fibres of the decking material. In particular, there is provided a countersunkscrew having an improved cutting action of the head portion. A countersunk-screw is adapted for being countersunk into the material. In addition to an improved cutting action of the fibres, the screw is capable of removing the fibres from the material in an efficient and smooth manner, i.e. without risking a splitting of the wood material, composite material or the like as well as reducing the amount of fibres at engagement with and assembly of the screw to the working piece (e.g. a decking plane).

By the provision of having a cutting recess section disposed on the frusto-conical shaped lower portion of the head portion and adjacent the cutting edge, it becomes possible to accumulate the removed fibres within the recess, thus further decreasing the risk of splitting the material.

By the provision of having a recess with a positive cutting edge angle as defined above, the head portion is configured for cutting through the fibres and further pushing the fibres in a direction downwardly as opposed to an upward direction, which is typically the case with recesses having a negative cutting edge angle. In this manner, the improved cutting action of the screw due to the positive cutting edge angle contributes to reduce the amount of fibres when the screw head portion meets the working piece at the engagement and assembly of the screw to the working piece, thus increasing the chances of having an overall improved end result with a remained finish or surface of the wood material.

The positive cutting edge angle also contributes to direct the fibres of the material downwardly so that the fibres are pressed against the working piece and further consolidated between the working piece and the lowermost portion of the head portion of the screw. In this manner, it becomes possible to prevent that water from the outside, e.g. from rain, is accumulated and penetrated underneath the head portion of the screw.

The provision of having a head portion with an essentially frusto-conical shaped lower portion facilitates hiding of the screw in the wood material. By way of example, the screw may be inserted into the material with an insertion depth of about 4-7 mm, as defined between the top side of the screw and the surface of the decking plane.

The cutting recess section is capable of accommodating fibres developed by the countersinking of the screw. It is to be noted that the cutting recess section typically can be further defined by an inner volume, defined by the surfaces of the cutting recess section and a nominal surface of the frusto-conical shaped lower portion extending in line with a circumferential surface of the frusto-conical shaped lower portion.

Further advantages are achieved by implementing one or several of the features of the dependent claims.

Typically, the positive cutting edge angle a is in a range between 0 < ? < 90 degrees. In particular, the positive cutting edge angle a is in a range between 2 - 45 degrees. More particularly, the positive cutting edge angle a is in a range between 3 - 25 degrees. Even more particularly, the positive cutting edge angle a is in a range between 5 - 15 degrees.

According to some example embodiments, the cutting recess section is disposed on a circumferential surface of the frusto-conical shaped lower portion.

Typically, the cutting edge forms the intersection between the circumferential surface of the frusto-conical shaped lower portion and the trailing region of said cutting recess section.

The cutting recess section is typically defined as a closed recess disposed on the circumferential surface of the frusto-conical shaped lower portion. That is, the surface extension of the cutting recess section on the circumferential surface of the frusto-conical shaped lower portion is defined by a closed contour including the cutting edge. The closed contour can be provided in several different manners.

By way of example, an axial extension of the cutting recess section is defined by opposite axial end points. In other words, the cutting recess section is defined by the first axial end point and the second axial end point. Accordingly, the cutting recess section is distinguished from a groove or channel extending entirely from the top side surface of the head portion to the shank of the screw.

According to some example embodiments, the top side of the head portion is free from the cutting recess section.

Typically, although not strictly required, the top side of the head portion defines a circumferential circular continuous outer edge.

According to some example embodiments, the top side of the head portion comprises a driving tool-receiving recess configured for cooperating with the driving tool. By way of example, the driving tool is a torx-tool. However, other types of driving tools may also be conceivable in order to drive the screw into engagement with the material.

According to some example embodiments, the frusto-conical shaped lower portion comprises a plurality of cutting recess sections. Moreover, each one of the plurality of cutting recess sections having a corresponding trailing region, as seen in the rotational direction. Further, each one of the trailing regions comprises a corresponding cutting edge having corresponding first axial end point and second axial end point defining a corresponding imaginary line. The imaginary line defines a corresponding positive cutting edge angle relative to a corresponding plane, the corresponding plane extending in the radial direction, from the rotational axis to the corresponding first axial end point, and in the axial direction.

Typically, the plurality of the cutting recess sections is distributed in a number of 2 ? B ? 16 around the circumference of the frusto-conical shaped lower portion. However, the plurality of the cutting recess sections may even be distributed in a number greater than 16, e.g. 2 ? B ? 20, or even more than 20 cutting recess sections.

In one example embodiment, the plurality of the cutting recess sections is uniformly distributed in around the circumference of the frusto-conical shaped lower portion.

In one example embodiment, the length of the cutting edge is a function of the thread pitch of the thread region. In addition, or alternatively, the length of the cutting edge is a function of the thread lead of the thread region.

The cutting recess section is further defined by a leading region. The leading region resembles an essentially inverted D-shape. By having a cutting recess with an essentially inverted D-shape leading region, the shape of the recess further facilitates an efficient move of the fibres of the material in a direction downwardly so that the fibres are pressed against the working piece and consolidated between the working piece and the lowermost portion of the head portion of the screw. An inverted D-shape leading region, in combination with the trailing region according to the above, further enhances the capability of transporting the fibres of the material downwards into the working piece.

The screw according to any one of the example embodiments, as mentioned above, is typically configured as a self-tapping screw.

In general, a self-tapping screw refers to a screw that can tap its own hole as it is driven into the decking plane material, wood material and/or the composite material. The selftapping ability may typically be provided by the point tip that tapers to a gimlet point (in which no flute is needed). In some design variants, the screw may also be self-drilling, as is readily conceivable in the art.

It is to be noted that the cutting recess section typically defines an inner volume. The inner volume of the recess is typically, although not strictly necessary, defined by the surfaces of the cutting recesses and a nominal surface of the truncated-cone shaped lower portion.

In some example embodiments, the cutting edge is a straight cutting edge extending between the first axial end point and the second axial end point. In other example embodiments, the cutting edge is a curved cutting edge extending between the first axial end point and the second axial end point.

The term "thread" typically refers to a ridge or a groove that winds around the screw shank. Furthermore, a thread can be defined by its thread profile, i.e. the thread and/or thread region is defined by a thread profile. The term "thread profile" refers to the crosssectional shape, angle and pitch formed by the thread(s). In various implementations of the example embodiments of the screw, various thread profiles may be used for the thread(s) of the screw. The shape of the thread profile for a given thread and/or thread region is typically selected depending on the type of installation and type of use of the screw. In some examples, the thread is a helical ridge with a pitch. The pitch of a helix is the width of one complete helix turn as measured parallel to the axis of the helix. In addition, the pitch of the helix can be constant along the axial direction of the component. It is also conceivable that the screw may comprise a number of threads such as two congruent helices with the same axis, differing by a translation along the axis. Typically, the two congruent helices may have the same pitch.

Further features of, and advantages with, the example embodiments of the present disclosure will become apparent when studying the appended claims and the following description. The skilled person realize that different features of the example embodiments may be combined to create embodiments other than those described in the following, without departing from the scope of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS With reference to the appended drawings, below follows a more detailed description of embodiments of the disclosure cited as examples.

In the drawings: Fig. 1a is a side view of a screw according to an example embodiment of the present disclosure, which comprises a countersunk head portion having a top side for accommodating a driving tool to rotate the screw and an essentially frusto-conical shaped lower portion; Fig. 1b is another side view of a screw according to an example embodiment of the present disclosure, which comprises a countersunk head portion having a top side for accommodating a driving tool to rotate the screw and an essentially frusto-conical shaped lower portion; Figs, 1c-1e illustrate further details of the countersunk head portion of the screw according to the example embodiment in figs, 1a and 1b; Fig. 2 schematically illustrates a cross-sectional view B-B of the example embodiment of the screw in e.g. fig. 1a; Fig. 3 schematically illustrates a cross-sectional view A-A of the example embodiment of the screw in e.g. fig. 1a; Fig. 4 schematically illustrates a side view of another example embodiment of parts of a screw according to the disclosure; Fig. 5 is a cross-sectional view of the screw in fig. 4, corresponding to the crosssectional view A-A in fig. 3.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS Various aspects of the disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the disclosure are shown. The example embodiments of the disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiment set forth herein; rather, these embodiments are provided for thoroughness and completeness. Like reference character refer to like elements throughout the description.

For purposes of description herein the terms "top," "under," "upper," "lower," "bottom," "upwardly," "downwardly," "longitudinal," "inner," "outer," "radial," "axial," "circumferential,", and derivatives thereof relate to the example embodiment of the disclosure as oriented in e.g. figs, la and lb.

However, it is to be understood that the example embodiments may assume various alternative orientations, except where expressly specified to the contrary. It is also to be understood that the examples illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments. Hence, dimensions and other physical characteristics relating to the example embodiments disclosed herein are not to be considered as limiting, unless the appended claims expressly state otherwise.

The disclosure mainly refers to screws for engagement with wood or similar composite material. One type of composite material is a decking plane composite material. For sake of simplicity, the screw according to the example embodiments described in conjunction with the figs, 1a to 5 is a wood screw. However, such does not mean that the example embodiments of the disclosure will be limited to an installation of the screw into wood material. In contrary, the screw may be a so-called decking plane screw and the like. Thus, although not shown, it is also conceivable that the exemplary embodiments of the screw may be installed in a composite material such as a decking plane material. Further, it is to be noted that the general constructions of screws according to the above are well known in the art, and the wide variation of types of such screws and their various optional components will therefore not be further described herein.

Referring now to the drawings and fig. 1a in particular, there is depicted a screw 10 according to the example embodiments of the disclosure. In this example embodiment, the screw is a wood screw for engagement with a wood material. Moreover, in this example, the screw is configured as a self-tapping screw. Fig. 1a illustrates a side view of the screw according to example embodiments when the screw has partly penetrated into the wood material, while fig. lb illustrates the screw in a position when the screw has penetrated further into the wood material forming a working piece 25 so as to engage with the working piece. Typically, the working piece is a decking plane material. The decking plane material may either be a wood material or any suitable composite material. Further details of the screw according to the example embodiment in figs, 1a and 1b are described in conjunction with the figures 1c-1e and figs. 2-5.

The screw 10 in these examples is suitable for engagement with wood or similar composite material. One type of composite material is a decking plane composite material. In the figures, the wood material is indicated by reference numerals 25. The screw 10 engages with the wood material 25 by rotating the screw in a rotational direction W around a rotational axis AC of the screw. As shown in the figures, the screw extends in the axial direction A. In addition, the screw extends in a radial direction R. The screw also has a circumferential extension in the circumferential direction of the screw.

The screw comprises a countersunk head portion 12 having a top side 19 for accommodating a driving tool to rotate the screw and an essentially frusto-conical shaped lower portion 18. Thus, the top side is adapted for cooperating with the driving tool. In this example embodiment, the top side 19 of the head portion 12 comprises a driving toolreceiving recess 43 configured for cooperating with the driving tool, such as a torx-tool. One example of a driving tool-receiving recess 43 is shown in fig. 2, which is a cross-sectional view along B-B in fig. 1a. However, it is to be noted that the screw can be rotated by the driving tool in other possible ways in order to penetrate the screw into the working piece 25. In addition, the torx-tool is only one possible example of a number of various driving tool examples.

Turning again to fig. la, the rotational axis AC of the screw in this example corresponds essentially to a centre line extending across the screw in the axial direction A.

Moreover, as shown in the figures, e.g. figs, 1a and 1b, the essentially frusto-conical shaped lower portion of the head faces the shank.

In other words, a circumferential surface 18a of the frusto-conical shaped lower portion 18 forms the transition between the top side 19 of the head portion 12 and the shank 14. Accordingly, the transition from the top side 19 of the head to the shank 12 is formed by an oblique circumferential surface of the frusto-conical shaped lower portion 18. The inclination of the oblique circumferential surface can be defined by an angle ?. The angle ? is illustrated in respect to the example embodiment described in conjunction to fig. 4. However, this feature may likewise be incorporated in the example embodiment described in conjunction to e.g. figs, 1a-1e. By way of example, the angle ? is in the range of 160 - 40 degrees. In this example, as shown in e.g. figs, 1a to 1e, the angle ? is about 80 degrees. The angle ? may of course vary depending on type of screw and type of working piece material.

In addition, as shown in fig. 1a, the screw comprises a shank 14 extending from the head portion to a point tip 11. The shank has a threaded region 15. The thread region 15 extends at least partly on the shank. The extension of the thread region on the shank is determined on the basis of the type of screw, use and installation of the screw as well as material of the working piece. Typically, although not strictly required, the shank 14 further comprises an unthreaded shank portion arranged between the head portion and the thread region, as illustrated in fig. 1a.

With regards to the threaded region 15, it is to be noted that the thread region typically extends from a thread starting point at the tip 11 towards the head portion 12 of the screw. The thread region comprises the thread 15a. The thread 15a spirals along the screw 10 to permit the screw 10 to be screwed into the workpiece 25 through clockwise rotation, as seen from the head portion 12 towards the tip 11, around the rotational axis AC. The thread exhibits a thread lead. In addition, the thread exhibits a thread pitch. Possible variations and dimensions of the thread region, and the thread, are well-known in the art of screws, thus no further details are described herein. However, it is to be noted that the dimensions of the thread region, and the thread, are typically selected in view of the type of screw and type of working piece. It should also be understood that the thread region need not extend uninterrupted from the tip towards the head of the screw, but that the thread may be wholly or partly absent at one or several locations from a tread starting point at the tip to an end of the thread. In addition, the thread region may run entirely from the head portion to the tip of the screw.

Moreover, the frusto-conical shaped lower portion 18 comprises a cutting recess section 20 having a trailing region 22 as seen in the direction of rotation W. The cutting recess section 20 is capable of accommodating fibres developed by the countersinking of the screw. As such, the cutting recess section is configured for accommodating fibres or compressed materials from the workpiece when the head portion 12 of the screw 10 penetrates into the workpiece 25. In this example, the cutting recess section 20 is further defined by an inner volume 21. In other words, the inner volume is defined by the surfaces of the cutting recess section and a nominal surface 18b of the frusto-conical shaped lower portion extending in line with a circumferential surface 18a of the frusto-conical shaped lower portion 18, as will be further described below in conjunction with fig. 2.

As mentioned above, the cutting recess section 20 is disposed on a circumferential surface 18a of the frusto-conical shaped lower portion 18.

As illustrated in fig. 1a, the trailing region 22 comprises a cutting edge 23. The cutting edge 23 has a first axial end point 41 and a second axial end point 42. In this example, the cutting edge is an essentially straight edge extending between the first axial end point and the second axial end point. The cutting edge 23 and the axial end points are further illustrated in figs, 1c to 1e. In particular, fig. 1c illustrates a side view of the screw 10 corresponding to the side view of the screw 10 in fig. 1a, while fig. 1d illustrate another side view of the screw 10, in which the screw is rotated about 90 degrees in the rotational direction. In other words, the view of the screw 10 in fig. 1d is orthogonal to the view of the screw 10 in fig. 1c. Fig. 1e further illustrates a projection of the cutting edge 23 on a tangent plane TP, which coincides with the first axial end point 41. The tangent plane and fig. 1e will be further described below.

As shown in fig. 1c, the cutting edge having the first axial end point 41 and the second axial end point 42 can also be defined by an imaginary line Al. That is, the imaginary line Al extends between the first axial end point 41 and the second axial end point 42 of the cutting edge 23. The imaginary line Al is further illustrated in fig. 1e, which depicts a slightly curved cutting edge 23. In this figure, the cutting edge 23 is curved although extending between the first axial end point 41 and the second axial end point 42, while the imaginary line Al corresponds to a straight line defining the extension between the first axial end point 41 and the second axial end point 42 of the cutting edge. The curved cutting edge may form a convex curved edge or a concave curved edge with respect to the imaginary line Al, or an irregularly curved cutting edge. It should be readily appreciated, however, that the cutting edge 23 in some example embodiments, as shown in figs, 1a-1d, corresponds to the imaginary line Al. In other words, the cutting edge 23 is in this example embodiment a straight edge extending between the first and second axial end points 41 and 42.

Turning again to fig. 1c, there is depicted a trailing region 22 comprising a cutting edge 23 corresponding to a straight edge. In other words, the trailing region 22 here comprises a straight cutting edge 23 extending between the first axial end point 41 and the second axial end point 42.

Moreover, as mentioned above, the first axial end point 41 and the second axial end point 42 define the imaginary line Al. That is, the imaginary line extends between the first and second axial end points 41, 42 of the cutting edge. The imaginary line Al defines a positive cutting edge angle a relative to a plane AP. As may be gleaned from the figures 1c and 1d, the plane AP extends in the radial direction R, from the rotational axis AC to the first axial end point 41. In addition, the plane AP extends in the axial direction A.

Turning again to figs, 1c-1e, the positive cutting edge angle a is obtained by projecting the cutting edge 23 on the tangent plane TP coinciding with the first axial end point 41 (see e.g. fig. 1d). The tangent plane TP is further perpendicular to the plane AP and extends in the axial direction A and in a tangential direction T, as shown in fig. 1c in combination with fig. 1d. Hereby a projection of the imaginary line Al on the tangent plane TP defines the positive cutting edge angle a relative to the plane AP.

Accordingly, in some examples when the cutting edge 23 is a straight cutting edge extending between the axial end points 41, 42, the cutting edge 23 corresponds to the imaginary line Al, which defines the positive cutting edge angle a relative to the plane AP as mentioned above. However, in other examples, when the cutting edge 23 is a curved or slightly curved cutting edge, the imaginary line Al defines the positive cutting edge angle a relative to the plane AP, as mentioned above and as illustrated in fig. 1e. It should also be readily appreciated that the cutting edge 23 is radially inwardly inclined due to the shape of the frusto-conical shaped lower portion 18. In other words, as shown in e.g. fig. 1d, the cutting edge 23 is inwardly inclined from an upper first axial end point 41 and towards the centre line (axis of rotation) to the lower second axial end point 42, as seen in the radial direction R. The cutting edge 23 is configured for cutting the fibres when the frusto-conical shaped lower portion 18 makes contact with the surface of the working piece 25. In this example, the cutting edge 23 forms the intersection between the circumferential surface 18a of the frustoconical shaped lower portion 18 and the trailing region 22 of the cutting recess section 20.

By the provision of having a cutting edge 23 with a positive cutting edge angle, as defined in the example embodiments herein, the cutting edge 23 is configured to cut the fibres of the working piece material and direct the fibres downwardly so that the fibres are pressed against the working piece and further consolidated between the working piece and the lowermost portion of the head portion of the screw.

Accordingly, as will be readily understood from the description and figures of the various example embodiments, one example advantage of the example embodiments of the present disclosure is to provide an improved cutting action of the fibres, while enabling that the fibres are pushed in a direction downwardly as opposed to an upward direction (typically referring to opposite directions along the axial direction A in e.g. figure 1a), which is typically the case with recesses having a negative cutting edge angle. In this manner, the improved cutting action of the screw contributes to reduce the amount of fibres when the screw head portion meets the working piece at the engagement and assembly of the screw to the working piece, thus increasing the chances of having an overall improved end result with a remained finish or surface of the wood material.

Typically, the positive cutting edge angle a may be above zero degrees but less than ninety degrees. That is, the positive cutting edge angle a may be in a range between 0 < ? < 90 degrees. In this way, there is provided a cutting edge configured to provide an optimal cutting action, as described above. However, it should be readily appreciated that the size of the positive cutting edge angle a may be set to another angle depending on type of screw and/or type working piece. Thus, it should be conceivable that the value of the positive cutting edge angle a may be different for different screws and installations. In particular, the positive cutting edge angle a may be in a range between 2 -45 degrees. More particularly, the positive cutting edge angle a may be in a range between 3 - 25 degrees, even more particularly the positive cutting edge angle a may be in a range between 5 - 15 degrees. In some examples, the positive cutting edge angle a may be in a range between 4- 10 degrees. In this example, as shown in e.g. fig. 1a, the positive cutting edge angle a is about 6 degrees.

In addition, as mentioned above, the cutting edge 23 may be a straight edge as long as the imaginary line Al defines the positive cutting angle with respect to the plane AP. However, in some example embodiments, the cutting edge 23 may be a curved edge as long as the imaginary line Al between the axial end points defines the positive cutting angle with respect to the plane AP.

Turning again to e.g. fig. la, the cutting recess section 20 is typically a so called closed recess disposed on the circumferential surface 18a of the frusto-conical shaped lower portion 18. That is, the surface extension of the cutting recess section on the circumferential surface of the frusto-conical shaped lower portion is defined by closed contour including the cutting edge 23. In other words, the term closed contour may refer to an uninterrupted circumferential edge. The cutting recess section 23 is further defined by a leading region 28. The leading region here resembles an essentially inverted D-shape. As shown in the figures, e.g. fig. 1a and fig. 3, the inverted D-shape is defined by the leading edge 30. In these figures, it can also be appreciated that the leading edge 30 defines the contour of the cutting recess section 20 together with the cutting edge 23. In other words, the cutting recess section is typically formed by the leading region having the leading edge and the trailing region having the trailing edge (corresponding to the cutting edge).

Furthermore, in this example, the axial extension 31 of the cutting recess section 20 is defined by the opposite axial end points 41, 42. As shown in fig. la (and also fig. 4), the axial extension 31 of the cutting recess section 20 is defined by the upper first axial end point 41 and the lower second axial end point 42. To this end, the top side 19 of the head portion 12 is free from any cutting recess section. In this manner, the cutting recess section 20 defines a closed void as seen from top side 19 of the screw 10. A cutting recess section that does not extend into the top side of the head portion minimizes the risk of having fibres transported in the wrong direction, i.e. upwards (on the side above the top side as seen in the axial direction). Fibres that are pushed upwards often causes splits or cracks around the surface of the working piece (deck plane). In addition, fibres that are pushed upwards may often have a negative impact of the engagement of the screw with the working piece.

It should be readily appreciated that the axial extension of the inverted D-shaped leading edge 30 is here defined by the upper first axial end point 41 and the lower second axial end point 42.

In other words, as shown in the figures, e.g. fig. 3, the top side of the head portion defines a circumferential circular continuous outer edge 12a. Further details of the cutting recess section 20 are described below in conjunction with e.g. figs. 3 and 4.

Fig. 1b illustrates an example when the screw 10 is engaged with the working piece, such as a decking plane made in a wood material 25. By way of example, the screw may be inserted into the material with an insertion depth of about 7 mm, as defined between the top side 19 of the screw and the surface of the decking plane. In this context of the example embodiments, the provision of having a head portion with the essentially frusto-conical shaped lower portion facilitates hiding of the screw in the wood material. The effect of hiding the screw in the material is sometimes a desire when mounting decking planes.

Now turning to figs. 2 and 3, the screw according to the example embodiments in figs, la to le is illustrated further by two cross-sectional view across B-B and A-A. As shown in these figures, the screw 10 comprises a plurality of cutting recess sections 20. That is, the frusto-conical shaped lower portion 18 comprises a plurality of cutting recess sections 20. Each one of the plurality of cutting recess sections 20 comprises a corresponding trailing region 22, as seen in the rotation direction W. Further, each one of the trailing regions 22 comprises a corresponding cutting edge 23 having corresponding first axial end point 41 and second axial end point 42 defining a corresponding imaginary line Al. The imaginary line Al defines a corresponding positive cutting edge angle a relative to a corresponding plane AP. The corresponding plane AP extends in the radial direction R and in the axial direction A. In other words, the corresponding plane AP extends in the radial direction R, at least from the rotational axis AC to the corresponding first axial end point 41, and in the axial direction A (although not shown in figs. 2 and 3). It should be readily appreciated that each one of the corresponding recesses may include the features, examples and effects as mentioned in respect of the example of the screw and recesses described in figs, 1a-1e.

In addition, each one of the plurality of cutting recess sections 20 is here defined by a corresponding inner volume 21. In this example, the plurality of the cutting recess sections is uniformly distributed in a number of 6 around the circumference of the frusto-conical shaped lower portion 18.

Turning again to figs. 2 and 3, it is to be noted that each one of the cutting recess sections 20 extends essentially in the axial direction A. Further, each one of the cutting recess sections 20 is inclined inwardly towards the centre line (axis of rotation AC), as seen in the radial direction R. Analogously, each one of the cutting edges 23 extends essentially in the axial direction A. Further, each one of the cutting edges 23 is inclined inwardly towards the centre line (axis of rotation) as seen in the radial direction R.

As mentioned above, in the example embodiment shown in figs, 1a, 1b, and 2-3, each one of the cutting recess section 20 has a trailing region 22 defined by a trailing surface 22A and a leading region 28 defined by a leading surface 28A. In addition, each one of the cutting recess section has a bottom region 27 defined by a bottom surface 27A. Typically, the bottom region aligns the leading region with the trailing region. In other words, the bottom surface aligns the leading surface with the trailing surface. The above features are also possible to incorporate in the example described in relation to fig. 5 Furthermore, in this example embodiment, each one of the cutting recess sections 20 has an essentially triangular shaped cross section as seen in the circumferential direction and the radial direction. The essentially triangular shaped cross section is here defined by the leading surface, the bottom surface and the trailing surface. The trailing surface 22A (trailing region 22) essentially forms a right angle with respect to the circumferential surface 18a of the frusto-conical shaped lower portion 18. To this end, the cutting edge is configured to generate a cutting effect when being in contact with the working piece upon rotation of the screw as described above. However, it is to be noted that the angle between the trailing surface 22A and the circumferential surface 18a may vary depending on desired type of cutting effect. In some examples, the angle between the trailing surface 22A and the circumferential surface 18a may be an acute angle, or even a slightly obtuse angle as long as a desired cutting effect is obtained by the cutting edge.

In addition, as shown in e.g. fig. 2, the depth of the cutting recess section increases from the leading region 28 to the trailing region 22. That is, the depth of the cutting recess section increases from the leading surface 28A to the trailing surface 22A.

In addition, it should be readily appreciated that each one of the cutting recess sections is typically configured for containing fibres from the working piece.

It is to be noted that the maximum depth of the cutting recess section(s) may be defined as the depth in the radial direction R, and further defined as the distance from the nominal circumferential surface 18b to the bottom surface 27A of the cutting recess section.

In addition, the cutting recess section(s) of the screw may typically be regarded as depression(s) rather than a screw with projections areas, i.e. areas extruding from the nominal circumferential surface of the frusto-conical lower portion of the head portion of the screw.

Typically, although not strictly required, the leading surface 28A may have a somewhat curved contour, as illustrated in fig. 3. However, this design of the leading surface 28A is optional. Thus, in other example embodiments of the screw, the leading surface 28A may taper in an inclined manner towards the bottom surface 27A (bottom region 27).

It is to be noted that the dimensions of the cutting recess sections are typically selected depending on the size and installation of the screw according to the example embodiments. Thus, the extensions of the cutting recess section in the axial direction, the radial direction and in the circumferential direction are typically selected in view of the size of screw and the type of material of the intended working piece. However, the dimensions of the cutting recess sections are typically the same for each one of the cutting recess sections disposed on the screw. In addition, the distribution of the cutting recess sections around the circumferential surface 18a is typically uniform, i.e. the distances between adjacent cutting recess sections are constant around the circumferential surface 18a. However, other types of arrangement of the cutting recess sections may be conceivable in some example embodiments (although not shown).

In one example embodiment, as shown in figs. 4 and 5, a screw is provided essentially according to the example embodiments described in relation to figs, la-le and figs. 2-3, except that the frusto-conical shaped lower portion 18 of the head portion comprises one single cutting recess section 20. Thus, in brief, the screw comprises the countersunk head portion 12 having the top side 19 for accommodating a driving tool to rotate the screw and the essentially frusto-conical shaped lower portion 18. The top side is adapted for cooperating with the driving tool. Moreover, the top side 19 of the head portion 12 may comprise the driving tool-receiving recess 43 configured for cooperating with the driving tool, such as a torx-tool. Further, the screw comprises the shank extending from the head portion to the point tip. The shank has the threaded region 15. The thread region 15 extends at least partly on the shank. In addition, the frusto-conical shaped lower portion 18 comprises one cutting recess section 20 having the trailing region 22 as seen in the direction of rotation W. As mentioned above in relation to the example embodiment described in relation to figs. 1-3, the cutting recess section 20 is disposed on the circumferential surface 18a of the frusto-conical shaped lower portion 18. As illustrated in figs. 4 and 5, the trailing region 22 comprises the cutting edge 23 having the first axial end point 41 and the second axial end point 42 defining the imaginary line Al. The imaginary line Al defines the positive cutting edge angle a relative to the plane AP, as mentioned above. The screw as described in relation to figs. 4 and 5 may include similar functions and features as described with respect to the example embodiment in figs, la-lc and figs. 2 and 3. The example embodiment in figs. 4 and 5 may be mounted in a similar manner as the example embodiment in figs, la-lc and figs. 2 and 3.

It should be readily appreciated that the number of cutting recess sections may vary depending on type of screw and type of working piece material, and that the example described above in conjunctions with the figures are only two of several conceivable example. Thus, the number B of the cutting recess sections may e.g. be 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 or 16.

In all example embodiments of the screw, the axial length of the cutting edge is a function of the thread pitch of the thread region 15. In addition, or alternatively, the axial length of the cutting edge is a function of the thread lead of the thread region 15. In this manner, it becomes possible to provide a screw having a cutting edge with an effective length (i.e. the axial length of a cutting recess) corresponding to the entire outer periphery of a fibre being cut upon rotation and penetration of the screw into the working piece 25.

The disclosure also covers all conceivable combinations of the described aspects, variants, alternatives and example embodiments of the disclosure. Furthermore, the disclosure is not limited to the aforesaid aspects or examples, but is naturally applicable to other aspects and example embodiments within the scope of the following claims. Reference signs mentioned in the claims should not be seen as limiting the extent of the matter protected by the claims, and their sole function is to make claims easier to understand.

Claims

1. A screw (10) for engagement with wood or similar composite material, such as a decking plane composite material (25), by rotating said screw in a rotational direction (W) around a rotational axis (AC) of said screw, said screw extending in an axial direction (A) and comprising: a countersunk head portion (12) having a top side (19) for accommodating a driving tool to rotate said screw and an essentially frusto-conical shaped lower portion (18); a shank (14) extending from the head portion to a point tip (11) and having a threaded region (15); wherein said frusto-conical shaped lower portion (18) comprises a cutting recess section (20) having a trailing region (22) as seen in said direction of rotation (W); and wherein said trailing region (22) comprises a cutting edge (23) having a first axial end point (41) and a second axial end point (42) defining an imaginary line (Al), and wherein said imaginary line (Al) defines a positive cutting edge angle (a) relative to a plane (AP), said plane (AP) extending in a radial direction (R), at least from said rotational axis (AC) to said first axial end point (41), and in said axial direction (A) characterized in that the cutting recess section is further defined by a leading region (28), said leading region (28) resembling an essentially inverted D-shape (30).

2. Screw (10) according to claim 1, wherein said positive cutting edge angle (a) is obtained by projecting said cutting edge (23) on a tangent plane (TP) coinciding with said first axial end point (41), said tangent plane (TP) further being perpendicular to said plane (AP) and extending in the axial direction (A) and in a tangential direction (T), and whereby a projection of said imaginary line (Al) on said tangent plane (TP) defines the positive cutting edge angle (a) relative to said plane (AP).

3. Screw according to any one of the preceding claims, wherein the positive cutting edge angle (a) is in a range between 0 < ? < 90 degrees, in particular in a range between 2 45 degrees, in particular in a range between 3 - 25 degrees, more particularly in a range between 5 - 15 degrees.

4. Screw according to any one of the preceding claims, wherein said cutting recess section (20) is disposed on a circumferential surface (18a) of said frusto-conical shaped lower portion.

5. Screw according to claim 4, wherein said cutting edge (23) forms the intersection between said circumferential surface (18a) of said frusto-conical shaped lower portion and said trailing region of said cutting recess section.

6. Screw according to any one of the preceding claims, wherein an axial extension (31) of said cutting recess section is defined by said opposite axial end points (41, 42).

7. Screw according to any one of the preceding claims, wherein said top side of said head portion is free from said cutting recess section.

8. Screw according to any one of the preceding claims, wherein said top side of said head portion defines a circumferential circular continuous outer edge (12a).

9. Screw according to any one of the preceding claims, wherein the top side of said head portion comprises a driving tool-receiving recess (43) configured for cooperating with said driving tool, such a torx-tool.

10. Screw according to any one of the preceding claims, wherein said frusto-conical shaped lower portion comprises a plurality of cutting recess sections, each one of said plurality of cutting recess sections having a corresponding trailing region (22) as seen in said rotation direction (W); and wherein each one of said trailing regions comprises a corresponding cutting edge (23) having corresponding first axial end point (41) and second axial end point (42) defining a corresponding imaginary line (Al), and wherein said imaginary line (Al) defines a corresponding positive cutting edge angle (a) relative to a corresponding plane (AP), said corresponding plane (AP) extending in the radial direction (R), from said rotational axis (AC) to said corresponding first axial end point (41), and in said axial direction (A).

11. Screw according to claim 10, wherein the plurality of the cutting recess sections is distributed in a number of 2 ? B ? 16 around the circumference of said frusto-conical shaped lower portion.

12. Screw according to any one of the preceding claims, wherein the screw is configured as a self-tapping screw.