Screw with Milling-Ribs for Countersinking the Screw and Use of the Screw

Abstract

In order to prevent wood fringes at the edge of a hole from a countersunk screw (1), the screw-head (2) is provided with a tapering underside and inclined milling-ribs with cavities between the milling-ribs on the tapering underside.

Claims

1. A screw (1) comprising a screw-head (2) at a first end (1a) of the screw (1) and a shank (3) extending from the screw-head (2) towards an opposite, second end (1b) of the screw (1) where a thread (5) is provided on the shank (3) for screwing the screw (1) into a material by a fastening-tool; wherein the screw (1) has a longitudinal central axis (6) extending between the first end (1a) and the second end (1b); wherein the screw-head (2) has an upper side (2a) and an underside (2b), wherein the upper side (2a) comprises a tool-receiver (4) for engagement with the fastening-tool; wherein the underside (2b) of the screw-head (2) comprises a tapered surface (7) with a taper-direction (19) towards the shank (3), the taper-direction (19) being in a plane that contains the central axis (6); the tapered surface (7) being provided with a plurality of milling-ribs (8), each milling-rib (8) comprising a front-side (15) that is oriented towards a milling direction and delimited by a milling-edge (17) for milling material during countersinking of the screw-head (2), and each milling-rib (8) comprising a back-side opposite to the front-side; wherein the front-side (15) is inclined relatively to the taper-direction (19), wherein the inclination of the front-side (15) and the milling-edge (17) are oriented for inward-pressing of milled material towards the shank (3) during countersinking of the screw-head (2) in the material; wherein smoothly bending cavities (14) are provided between the milling-ribs (8), the cavities (14) extending into the underside (2b) of the screw-head (2), wherein each of the cavities (14) is smoothly concavely curved from one milling-rib (8) to a neighbouring milling-rib (8).

2. A screw according to claim 1, wherein the front-side (15) of the milling rib (8) is straight planar.

3. A screw according to claim 1, wherein each of the cavities (14) is smoothly concavely curved from the front-side (15) of one milling-rib (8) to a neighboring milling-rib (8).

4. A screw according claim 1, wherein the underside (2b) of the screw-head comprises a flat edge-region (11) along a rim (12) of the screw-head (2) and is delimited by a cutting edge (13) at the rim (12) for cutting in material during countersinking of the screw-head (2) into the material; the flat edge-region (11) extending from the cutting edge (13) to the cavities (14) and the milling-ribs (8).

5. A screw according to claim 4, wherein the flat edge-region (11) has a surface parallel to a plane perpendicular to the central axis (6)

6. A screw according to claim 4, wherein the width of the flat edge-region when measured from the rim of the head to the end of the ribs near the rim is between 1% and 25% of the diameter of the screw-head (2).

7. A screw according to claim 4, wherein the cavity (14) at its connection to the flat edge-region (11) forms a smooth concavely curving connection line (C3) with the flat edge-region (11).

8. A screw according to claim 1, wherein the milling-edges (17) are following a frusto-conical surface for milling a frusto-conical hole in the material when countersinking the screw (1).

9. A screw according to claim 1, wherein the milling-rib (8) has a constant width from the shank (3) towards a rim (12) of the screw-head (2).

10. Use of a screw according to claim 1 for screwing into wood or fibrous composite material or into polymer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The invention will be described in more detail with reference to the drawings, in which:

[0036] FIG. 1 is an overview image of the screw;

[0037] FIG. 2a is a side view of the screw head,

[0038] FIG. 2b a view onto the underside of the screw head in a direction parallel with the screw axis,

[0039] FIG. 2c is a different side view,

[0040] FIG. 2d-2f are different perspective views of the underside of the screw head;

[0041] FIGS. 3a and 3b are two perspective views of comparative screw according to prior art CN103047345A, and FIGS. 3c and 3d are illustrating inventive features in comparison;

[0042] FIG. 4 illustrates an example of a tool receive in the screw head.

DETAILED DESCRIPTION OF THE INVENTION

[0043] FIG. 1 illustrates a screw that is explained in more detail in the following. The screw 1 comprises a screw-head 2 at a first end 1a of the screw 1 and a shank 3 extending from the screw-head 2 towards an opposite, second end 1b of the screw 1. A thread 5 is provided on the shank 3 for screwing the screw 1 into a material by a fastening-tool.

[0044] For the fastening tool, the screw-head 2 comprises a tool-receiver 4, for example a Hexalobular (Torx®) socket as illustrated in FIG. 4, for engagement with a corresponding fastening-tool for screwing of the screw 1.

[0045] Optionally, the screw 1 comprises a cutting-notch 9 in the thread 5 in order for the screw 1 to cut its way easier into the material. The cutting-notch 9 extends along the shaft 3 and is exemplified as extending over seven windings of the thread and with sharp edges. The cutting-notch 9 could extend over fewer or more windings.

[0046] Optionally, the screw 1 comprises a knurled shoulder 10 to reduce drag when the screw 1 is driven into the material, for example wood. The knurled shoulder 10 has an outer diameter larger than the diameter of the shank 3 near the screw-head 2 in order to create a hole wider than the shank 3. Typically, the knurled shoulder 10 is provided in immediate extension of the thread 5.

[0047] FIG. 2 illustrates the screw head 2 in various perspectives. FIG. 2a is a side view of the screw head 2, FIG. 2b a view onto the underside 2b of the screw head 2 in a direction parallel with the screw axis 6, FIG. 2c is a different side view, FIG. 2d-2f are different perspective views of the underside of the screw head.

[0048] A plurality of milling-ribs 8 are provided on the tapered surface 7 on the underside 2b of the screw head 2. The milling-ribs 8 are inclined relatively to a plane parallel with the screw axis 6 for inward-pressing of the material towards the shank 3 during countersinking of the screw-head 2.

[0049] A typical number of milling-ribs are 3-8, for example the exemplified 6 milling-ribs 8. For example, the milling-ribs 8 are arranged with identical mutual angular distance. In the present case with 6 milling-ribs, the angular distance is 60°.

[0050] The underside 2b of the screw-head 2 is provided with a tapered surface 7 that is tapering inwards towards the shank 3, wherein the taper-direction 19 is within a plane that contains the central axis 6. Typically, the full angle spanned by the tapered surface is in the range of 40°-120°, for example 60° when projected onto the plane of the drawing, when the plane also contains the central axis 6.

[0051] FIG. 3c and FIG. 3d illustrate some features of the screw head 2 and the milling-ribs 8 in comparison with a comparative screw head 2′, which is from the prior art document CN103047245A and which is shown in FIG. 3a and FIG. 3b.

[0052] In comparison, the following observations are made when comparing the prior art drawings FIGS. 3a and 3b with the drawings in relation to the invention in FIGS. 3c and 3d and FIG. 2, especially FIG. 2f.

[0053] Whereas the milling-ribs C9 of the comparative screw extend to the rim of the screw head, the milling-ribs 8 in FIG. 3c do not. As also seen in detail in FIG. 3c, the milling ribs 8 end within a circle 20 that has a smaller diameter than the screw head 2 at its rim 12. This leaves a flat edge-region 11 between the rim 12 on the underside of the screw-head 2 and the circle 20, which is the side opposite the upper side with the tool-receiver 4. The flat edge-region 11 at the rim 12 comprises a cutting-edge 13 that cuts-off the wood fibers when the screw-head 2 is countersunk, for the example into wood.

[0054] The cutting-edge 13 creates a neatly cut edge of the countersunk hole for the screw-head 2. The flat edge region 11 extends as a circle all around the milling ribs 8 along the rim 12 of the screw head 2. In comparison, the comparative screw does not have a flat edge region that extends around as a circle, only sections C11 are provided which are located between the millig ribs C9. These sections do not have the same effect as the circular flat edge region with the circular cutting edge 13.

[0055] Whereas the milling edges C2 of the milling-ribs C9 of the comparative screw of FIGS. 3a and 3b are bending along a concave curve, the front-side 15 of the milling-rib 8 is straight planar so that the milling-edges 17 in FIGS. 3c and 3d are following a curve in a straight plane. The back-edge 17′ of the milling-rib 8 is within a plane parallel with the plane of the planar front-side 15, as illustrated by the two parallel lines C7 and C8 in FIG. 3. Accordingly, the milling edges (8) have constant width.

[0056] Whereas the cavities between the milling-ribs in the comparative screw of FIGS. 3a and 3b are following a conical surface and therefore are convex, see also indicated lines C5 and C6, the cavities 14 in FIGS. 3c and 3d are concave. They are smoothly curving inwards from one milling edge to the neighboring milling edge. Furthermore, at the rim of the screw head in a plane perpendicular to the axis 6, the cavities are following a concave curve, illustrated by the curve C3 in FIG. 3c. Due to the concave cavities 14 on the underside of the head 2 as illustrated in FIG. 2f and FIG. 3c, the area under the head 1 is larger than in the comparative screw, which increases the grip in the material, for example wooden material, composite, or polymer, when countersunk.

[0057] In a plane perpendicular to the central axis 6, the cavities 14 follow a concave curve C3 near to the rim 12 and a convex curve C4 at the shank 3, as illustrated in FIG. 3c. However, the cavities 14 themselves are concave between the curves C3 and C4, thus bending inwards into the screw-head 2.

REFERENCE NUMBERS

[0058] 1 screw [0059] 1a first end of the screw [0060] 1b second end of the screw 1 [0061] 2 screw head [0062] 2a upper side of screw head 2 [0063] 2b underside of screw head 2 [0064] 3 shank [0065] 4 tool receiver in screw head [0066] 5 thread on the shank 3 [0067] 6 central axis [0068] 7 tapered surface [0069] 8 milling-ribs [0070] 9 cutting-notch (optional) [0071] 10 knurled shoulder (optional) [0072] 11 flat edge-region along the rim 12 [0073] 12 rim of the screw head [0074] 13 cutting-edge at rim 12 [0075] 14 cavity between milling-ribs 8 [0076] 15 front-side of milling-rib [0077] 17 milling edge [0078] 19 taper direction towards shank 3 [0079] 20 circle within which milling ribs 8 are provided