Screw, its use and a method for fastening workpieces and decking a terrace

Abstract

In order to secure the wood-plastic composite panel (18) to the underlying wooden support structure, the screw (1) is provided with a drill tip (3) with an eccentric tip (7).

Description

Technical Field

[0001] This invention relates to screws, their use, and methods for securing plastic or wood-plastic composite workpieces (especially panels) to supports (especially wooden support structures). The invention also relates to methods for paving platforms or balconies with panels. In particular, the invention relates to screws, their use, and methods according to the independent claims. Prior Technology

[0002] For insulating panels (where the insulating material is located between two metal sheets), it is customary to provide screws with drill tips so that the screws can drill through the metal layers before they grip into the underlying roof or wall structure (typically a wooden structure).

[0003] An example of a screw used for this type of insulating panel is disclosed in U.S. Patent No. 4,568,229. The screw comprises a predominantly conical drill tip centered around the screw's central axis. The drill tip includes two sets of cutting edges. The foremost primary set of cutting edges meets at its foremost tip, which is slightly off-center from the central axis. The disclosure states that the screw penetrates the metal sheet quickly because of this slight off-center foremost tip. During the helical process, the off-center tip enters the metal first, after which the remaining conical drill tip is paved through the metal by the first primary cutting edge and subsequently widened by the secondary cutting edges to penetrate the metal sheet.

[0004] German Patent Publication No. 2913482 discloses different screws for metal sheets, wherein the foremost tip portion is slightly off-center to prevent the screw from moving away from the desired hole.

[0005] U.S. Patent No. 7,214,019 discloses a self-tapping screw with an eccentric tip. When the screw has helically penetrated a panel made of a brittle material and reached the underlying metal layer, the eccentric tip causes the screw to wobble before drilling into the metal layer on the opposite side of the brittle material. This wobble creates a wide hole in the brittle material panel, allowing the panel to move around the screw without breaking when the temperature changes.

[0006] Screws designed for drilling through metal sheets for various purposes have not been proposed for screwing into wood, as the centered drill tip has proven highly efficient for wood. Screws with centered tips are also typically used in polymer panels and even tough materials, as described below.

[0007] Durable polymer panels are commonly used in outdoor construction. In particular, panels made of wood-plastic composite (WPC) are popular for outdoor flooring due to the material's toughness, weather resistance, and longevity. Typically, panels made of this material are screwed to a support structure made of wooden planks. The screws must be constructed to maintain good grip within the wooden support. Providing long-term screw stability can be achieved by drilling a hole through the panel and then inserting the screw through the hole and into the underlying wood. However, this requires two processing steps, which is undesirable for rapid construction. To reduce time and effort when laying panels, screws with drill tips are desirable, allowing them to drill through the panel and then screw into the underlying wooden support structure. However, drilling screws through tough WPC material is often difficult because the screws become very hot. Additionally, pressing the material to the side while screwing can cause it to rise around the drilled hole. Therefore, drilling through WPC panels has become challenging, and many screws fail to meet this requirement satisfactorily.

[0008] To overcome some of the challenges posed by WPC panels, prior art has revealed screws that differ from more conventional types of screws. Some such examples are disclosed in U.S. Patents 8,926,249 and 9,103,364, in which the screw has a triangular cross-section. While meeting the requirements, the manufacture of such screws is both complex and expensive.

[0009] Given the large number of screws used to secure WPC flooring, there is a need for high-performance drill screws that can be provided at a lower cost. Accordingly, there is a general demand for more cost-effective screws that can drill through the WPC panels and secure them to the underlying wooden support structure in a satisfactory manner, especially without the screw head rising around the screw hole when it is embedded in the material. Summary of the Invention

[0010] Therefore, the object of the present invention is to provide technical improvements. In particular, the object is to provide improved screws and methods for securing wood-plastic composite (WPC) panels to a support structure made of wood. A further object is to provide an improved method for paving platforms or balconies by securing plastic panels or plastic composite panels. A further object is to provide screws that are simple to manufacture and involve low manufacturing costs. These objects are achieved by the screws and methods described in the following description and claims. In particular, for drilling through wood-plastic composites and for drilling through paving panels made of plastic with or without reinforcing materials in the plastic matrix, the screw is provided with a drill tip with an eccentric tip. Further advantages will become apparent in the following description.

[0011] Primarily, the screws proposed here are designed to drill into and spiral into workpieces made of wood-plastic composite (WPC), which places substantial demands on the drilling capability of the drill tip at the screw's tip. The WPC panels contain wood fibers as a reinforcing material within the plastic matrix.

[0012] This requires, on the one hand, that the tip of the screw penetrating the polymer matrix (despite its substantial thickness) has good penetration ability, followed by good gripping and spiral entry ability on the underlying wood structure, and appropriate embedding ability in the fiber composite.

[0013] As will be shown below, screws are particularly useful for paving platforms or balconies with plastic panels (especially plastic composite panels) on a supporting structure (typically a wooden supporting structure).

[0014] However, while screws are particularly useful for outdoor WPC flooring, they are general-purpose and can also be used for vertically oriented or angled WPC panels. An example is building exterior cladding.

[0015] Similar to other prior art screws, this screw has a central longitudinal axis and includes a shank (e.g., a cylindrical shank), with a screw head at a first end, a drill tip at an opposite second end, and a first thread around the shank, wherein the first thread is adjacent to the drill tip and is configured to helically enter and penetrate the workpiece and underlying potential support structure after being pre-drilled by the drill tip. The drill tip is a foremost tip used for initiating contact with the workpiece during the initial period of drilling and helicaling into the workpiece.

[0016] However, compared to the prior art screws used in WPC panels, this tip is offset from the central axis. As discussed above, eccentric drill tips have not yet been used to screw through WPC panels to secure such panels (especially outdoor panels for paved platforms) to an underlying support structure made of wood. However, screws with eccentric tips have proven particularly advantageous in experiments for drilling into WPC panels.

[0017] In practice, a support structure made of wood is provided, against which the panel is placed. A screw, longer than the thickness of the panel, is driven into the underlying wood structure with a portion of its first thread, securing the panel to the support structure. Simultaneously, the screw head pulls the panel toward the support structure. Alternatively, the screw is advanced until its head is fully embedded in the panel.

[0018] In a practical embodiment, the drill tip includes a cutting edge extending from the tip to the shaft and a facet extending inward from the cutting edge toward the interior of the drill tip. The angle of the facet may vary, but lateral or near-lateral extension from the cutting edge has been found useful. Thus, alternatively, the facet may extend inward from the cutting edge toward the center of the screw.

[0019] For example, the cut surface is flat. In a useful embodiment, the flat cut surface is parallel to the central axis. Alternatively, the cut surface extends laterally from the cutting edge and radially inward toward the central axis, so as to follow a plane parallel to and containing the central axis.

[0020] In some embodiments, the cutting edge extends to the central axis; however, in other embodiments, it extends toward the central axis but does not reach it. In a further embodiment, it intersects the central axis and extends to the opposite side of the central axis.

[0021] While flat cut surfaces have been found to be useful, deviations from flat surfaces, such as slight curvature, may also be used.

[0022] The cut surface will form the first side of the longitudinal groove in the drill tip, and will be constructed during the drilling and spiraling process of the workpiece in the screw in the workpiece.

[0023] The curved outer surface tapers from the shaft to the tip, typically smoothly. For example, the outer surface is formed as part of an inclined cone. Alternatively, the curved outer surface tapers from the shaft to the foremost tip along a concave or convex curve.

[0024] Advantageously, the convex tapering surface extends from the cutting edge around the central axis at an angle of not less than 225 degrees and not more than 330 degrees, for example, not less than 240 degrees and / or not more than 315 degrees. Angles within this range have been found useful in experiments.

[0025] The second face will extend from the curved outer surface to the cut surface and form the second side of the slot. Accordingly, the drill tip is formed by a longitudinal slot and a convex, tapering, and smoothly curved surface (for example, a circular, inclined conical surface), wherein the curve bends from the cutting edge around the central axis to the second face of the longitudinal slot. The term longitudinal slot is used here because the slot extends longitudinally to the tip of the screw.

[0026] Alternatively, the transition between the second surface and the convex, tapering curved surface (e.g., a circular, inclined conical surface) is smooth. Alternatively, an edge is provided as the transition between the second surface and the tapering curved surface.

[0027] The result is that the screws drill into the WPC panels with great efficiency. In particular, compared to previous techniques, the drill tip is simple and requires only a single tip and a single facet. Experiments have even shown that a single tip is advantageous over screws with two identical tips at the front, because the symmetry of the drill tip increases the risk of the plastic getting stuck and melting due to friction, which deprives it of drilling efficiency.

[0028] In an embodiment particularly useful for WPC panels, the screw includes a second thread between a first thread and a screw head, the second thread having a helical direction opposite to that of the first thread. The first thread is for causing the screw to heel into and penetrate the workpiece (e.g., the panel), while the second thread is constructed to pull material (including reinforcing fibers) deeper into the workpiece from a drilled hole during the screw's heeling penetration. Advantageously, the second thread has an outer diameter larger than that of the first thread.

[0029] In cases where the head should be submerged, the material pressed into the workpiece must accumulate in the hole; otherwise, it will be pressed to the side and create unwanted bulges around the screw head. To provide this space for material accumulation in the hole, the shank may optionally be included in an unthreaded region between the head and the second thread, the diameter of which is smaller than the outer diameter of the second thread. Typically, the length of this region is not less than the pitch of the second thread and / or the height of the head. Since the hole milled by the second thread is larger than the shank under the head, the material pressed into the hole by the head due to submersion accumulates in this space.

[0030] Alternatively, the head may have a sharp periphery on its underside to allow it to cut a path into the material and thus smoothly enter the workpiece. The cutting edge may also cut wood fibers around the head, thus avoiding the formation of a flange around the head in the recessed hole.

[0031] In order to secure the wood-plastic composite panel to the supporting wood structure, the screw must be longer than the thickness of the panel so that it can be drilled through the entire panel and partially threaded into the underlying wood structure, thus securing the panel to the supporting structure with the first thread.

[0032] For paneling used as paving on decks and balconies, typical dimensions are applicable. Thickness typically ranges from 5 to 50 millimeters. In the United States, a preferred thickness is 1 inch = 25.4 millimeters. Width typically ranges from 100 to 305 millimeters. In the United States, a preferred width is 6 inches = 152 millimeters. Typical standard lengths for paneling used in paving in the United States are 12 feet, 16 feet, and 20 feet (3.7 meters, 4.9 meters, and 6.1 meters).

[0033] For reinforced panels, the plastic weight concentration is typically in the range of 25-60%, but often in the range of 40-50%. Typically, additives such as colorants and lubricants constitute 5-10% by weight. Accordingly, the typical weight concentration of reinforcing fiber fillers (especially wood fibers) is in the range of 40-65%. Simple Explanation of the Diagram

[0034] This invention will be explained in more detail with reference to the drawings, wherein [Figure 1] Demonstration of an embodiment of screws used for WPC panels; [Figure 2] More detailed view of the drill tip; [Figure 3] shows different perspective views of the drill tip (Figures 3A and 3B), as well as angle indications for different side views (Figures 3C and 3D); [Figure 4] shows an alternative optional embodiment; [Figure 5] shows an alternative optional embodiment; [Figure 6] shows an alternative optional embodiment; [Figure 7] shows an enlarged view of the screw head; [Figure 8] is a photograph of a screw embedded in a workpiece; [Figure 9] is a photograph of the tip of the screw used in Figure 8; [Figure 10] Shows the drill tip of the prior art before drilling into the WPC panel (Figure 10A) and after drilling into the WPC panel (Figure 10B); [Figure 11] shows another prior art drill tip before drilling into the WPC panel (Figure 11A) and after drilling into the WPC panel (Figure 11B), and its illustration (Figure 11C). Implementation

[0035] []

[0036] Figure 1 illustrates screw 1, which is particularly useful for drilling through WPC panels and securing the panel to the wooden support structure.

[0037] Screw 1 includes a shaft 4, a screw head 2 at a first end of the shaft 4, and a drill tip 3 at the opposite second end. A first thread 5 is provided around the shaft 4 adjacent to the drill tip 3 and is constructed to helve into the wood. Screw 1 also includes a second thread 6, the direction of which is opposite to that of the first thread 5. As screw 1 heels into and penetrates the panel to the underlying wooden support structure, the second thread 6 pulls the panel material deeper into the hole, thus ensuring a clean entry point for the drilled hole free of debris from the helical and drilling motion.

[0038] The drill tip 3 is shown in further detail in the side view of enlarged section A in Figure 1, and in the perspective view of similar enlarged section B in Figures 2, 3A, and 3B. The drill tip 3 comprises a tip 7 at its foremost point. The tip 7 is offset by a distance d from the central axis 8 of the screw 1. The offset d is measured from the central axis 8 to the foremost point of the tip 7, which is typically slightly rounded for manufacturing and mechanical stability reasons. The ratio between the distance d and the radius R of the shaft 4 is typically in the range of 0.1 to 0.7. However, the possible range of d / R can be as large as 0.1 to 0.95 or even as large as 0.1 to 1.0 in principle, because the eccentric tip 7 can be flush with the dry edge of the shaft 4.

[0039] The cutting edge 10 extends from the shaft 4 to the eccentric tip 7. The length of the drill tip 3 is measured from the foremost point of the tip 7 to the transition 4A between the shaft 4 and the drill tip 3. Typically, the length L of the drill tip 3 is in the range of 2 to 5 times the radius R of the shaft 4.

[0040] The cut surface 11 extends longitudinally along the cutting edge 10 and laterally from the cutting edge 10 toward the central axis 8. In the direction toward the central axis 8, the cut surface 11 is defined by the edge 13A of the second surface 13, which exemplifies an upwardly convex curved transition surface.

[0041] In the lower left of Figure 1, the eccentric tip 7 is seen from the front view of the drill tip 3. Because the tip 7 is eccentric relative to the central line 8, the drill tip 3 is not a regular cone shape. Instead, the drill tip 3 is confined by a tapered, upward-convex surface 9, which is the W=270 degree portion of an inclined cone extending from the cutting edge 10 around the central axis 8 to the second edge 12 of the drill tip 3. A second face 13 extends from the second edge 12 to the cut surface 11, forming a convex transition surface. The second face and the cut surface 11 form a slot 14 in the drill tip 3. Thus, the drill tip, as demonstrated, is formed by the tapered, upward-convex surface 9 and the slot 14. Alternatively, the transition between the second face 13 and the curved surface 9 could be smooth, with the second edge 12 as an alternative.

[0042] The tapering convex surface 9 extending around the central axis 8 to an angle W=270° implies that the groove 14 between the cutting edge 10 and the second edge 12 extends to 360°-W=90°.

[0043] In the illustrated embodiment, the drill tip 3 is formed by an upwardly convex surface 9, a cross-section 10, and a second surface 13 in the form of an upwardly convex transition surface. This construction is thus simpler than prior art, particularly compared to the screw in U.S. Patent No. 4,458,229, which has a variety of cross-sections and requires a wide range of tools for shaping.

[0044] The angular span W of the inclined conical surface 9 is not necessarily 270 degrees but may vary to a slightly larger or smaller angle, for example, in the range of 225 to 315 degrees, such as 240 to 315 degrees. However, if the angle becomes too large, there is a risk of material accumulation in the slot 14 between the edges 10 and 12; if the angle becomes too small, sufficient stability of the drilling is compromised.

[0045] Figure 3C shows a front view of the cross-section and indicates the angle V1 between the cutting edge 10 and the central axis 8. The angle V1 between the cutting edge 10 and the central axis 8 is determined by the radius R of the shaft, the length L of the drill tip 3, and the offset d of the tip 7.

[0046] As illustrated in Figure 3D (tangent diagram of the second edge 12), the angle V4 between the second edge 12 and the central axis 8 is greater than V1. Because the tapered curved surface 9 is an inclined cone rather than a regular cone, when moving in a circular motion from the cutting edge 10 to the second edge 12 about the central axis 8 and along the curved surface 9, the angle between this surface and the rod 4 (or equal to the central axis 8) continuously increases from V1 to V4 and passes through V2 and V3, as indicated. In the illustrated example, angles W = 270°, V1 = 10°, and V4 = 20°.

[0047] These angles vary along with the cone angle V5, depending on the construction and dimensions of the drill tip 3. Some examples are shown below.

[0048] As screw 1 rotates around central axis 8 during its helical movement, tip 7 moves in a circular motion around central axis 8. Initially, when tip 7 is placed on the surface of the panel, the rotation of tip 7 at a single point causes screw 1 and the helical tool to twist, as tip 7 typically stays at a single point and drills a path through the panel surface. This twisting of the screw gradually decreases as drill tip 3 opens a path through the surface and into the panel. Once the shaft 4 enters the panel material and the first thread 5 grips the panel, the twisting of screw 1 stops, and the threaded shaft 4 guides screw 1 axially through the material. As screw 1 moves further forward linearly, tip 7 moves in a circular motion around central axis 8 during the advance of screw 1 and helically penetrates the material. The combination of helical tip 7 and cutting edge 10 results in machining through the material, a combination of drilling and milling, resulting in remarkable efficiency.

[0049] Preliminary studies conducted with reference to certain prior art screws available on the market best illustrate the advantages of the eccentric tip of drill tip 3. Figure 10A is a photograph of a prior art screw with a centered drill tip at the end. This drill tip attempts to screw into a WPC panel but fails. The screw heats up, and the polymer melts around the tip, as shown in photograph 10B, and the polymer becomes adhered to the drill tip to the extent that further drilling is prevented. A similar failure was observed in the screw of the type shown in Figure 11A, as shown in photograph 11B, illustrated in Figure 11C.

[0050] Compared to screws of this prior art, as described above, screws with eccentric tips drill into the WPC panels used in the penetration test more efficiently.

[0051] Figure 4 illustrates different embodiments in which the cutting edge 10 is parallel to the central axis 8, and the tip 7 has a distance d from the central axis that is close to the radius R of the stem 4, for example, 0.95·R. For the tip 7 to be flush with the stem 4, the tip 7 must have an asymmetrical and sharp edge. However, in practice, the tip 7 is advantageously slightly rounded for strength reasons and also for ease of manufacturing. In this case, the second edge 12 is not parallel to the central axis 8, as this would result in an extremely wide cut 11, which is typically undesirable. In the illustrative embodiment, W = 240°.

[0052] Figure 5 illustrates an alternative selective embodiment in which angle V1 is greater than that shown in Figure 3C and the drill tip is on the opposite side of the central axis R. For example, in this illustration, V1 = 20°, V2 = 11°, and W = 295°.

[0053] Figures 6a and 6b illustrate a further alternative selective embodiment in which angle V1 is greater than that shown in Figure 3C and the drill tip is on the opposite side of the central axis R. The cutting edge 11 extends obliquely to a line parallel to the shaft 4. For example, in this illustration, V1 = 30°, V2 = 0°, and W = 315°.

[0054] Figure 7 illustrates the head 2 of screw 1, which includes a recess 16 for receiving a tool (typically a tool marketed under the brand name Torx®). The underside of head 2 includes a sharp edge 17 at the end of a conical surface 15. The sharp edge 17 on the underside of head 2, adjacent to the periphery of head 2, facilitates the embedment of screw head 2. Due to the reverse thread 6, as the screw is driven through the insert, the hole in the insert just below head 2 becomes wider than the shaft 4, so that the insert material cut into the hole by edge 17 and then pressed into the hole by the head during embedment accumulates in the volume around the shaft 4 just below head 2.

[0055] An example of a screw head 2 embedded in a WPC panel 18 according to the present invention is shown in a photograph of FIG8. It is observed that the hole edge 19 of the hole 20 is cleanly cut, so that no debris or flange extends from the hole 20. FIG9 is a photograph of the tip of the screw used in FIG8.

[0056] For example, the screws have the following dimensions in millimeters: Screw length: 70 mm Length of the first thread: 50 mm Length of the second thread: 15 mm The diameter of the rod in the first thread is 3 mm. Outer diameter of the first thread: 5 mm The outer diameter of the second thread is 5.3 mm. The diameter of the rod between the second thread and the head is 4 mm. The pitch of the second thread is 2.5 mm. Head diameter: 7 mm Drill tip length: 5 mm Distance between tip and central axis: 0.4 (27% of shaft radius R) Head angle w: 6 degrees Angle between the central axis and the cutting edge: 11 degrees

[0057] However, the size can vary depending on the requirements, for example, within the following range: Screw length: 20~150 mm Length of the first thread: 10~90 mm Length of the second thread: 3~40 mm The diameter of the rod in the first thread is 2-6 mm. The outer diameter of the first thread: 3~8 mm The outer diameter of the second thread: 3.5~10 mm The diameter of the rod between the second thread and the head: 2~8 mm The pitch of the first thread: 0.8~6 mm The pitch of the second thread: 1~6 mm Head diameter: 4~15 mm Drill tip length: 3~10 mm Head angle w: 0~25 degrees Angle between the central axis and the cutting edge: 0~60 degrees The eccentricity between the tip and the central axis is 10 to 100% of the rod radius, but typically 10 to 95% of R due to rounding the tip.

[0058] 1: Screw 2: Screw head 3: Drill tip 4: Pole trunk 4A: Transition between the shaft and the drill tip 4B: The unthreaded area of ​​the shaft under the screw head 5: First thread 6: Second thread 7: The tip of the drill bit 8: Central Axis 9: A convex surface, such as part of a tilted cone. 10: Cutting edge 11: Cross-section 12: Second Edge 13: The second surface, for example, is a convex transition surface. 13A: Edge between the cut surface and the second surface 14: Groove between the cutting edge and the second edge 15: Conical surface on the underside of the screw head 16: Recess in the screw head for use with tools 17: Sharp edge around the bottom side of the screw head 18: WPC Panel 19: Hole edges in WPC panels 20: Holes in WPC panels d: offset, distance L: Length R: radius V1~V5: Angle w: Head angle W: Angle span []

Claims

1. A screw (1) for drilling into and helically penetrating a workpiece (18) of plastic or wood-plastic composite, wherein the screw (1) has a longitudinal central axis (8), and wherein the screw (1) comprises a shaft (4) having a screw head (2) at a first end, a drill tip (3) at an opposite second end, and a first thread (5) around the shaft (4), wherein the first thread (5) is adjacent to the drill tip (3) and is configured to helically enter and penetrate the workpiece (18) after being pre-drilled with the drill tip (3), wherein the drill tip (3) includes a foremost tip (7) for initiating contact with the workpiece (18) during the initial period of drilling into and helically penetrating the workpiece (18), wherein the tip (7) is eccentrically displaced from the central axis (8), wherein the drill tip (3) comprises: A cutting edge (10) extends from the tip (7) to the shaft (4); and a cutting surface (11) extends inward from the cutting edge (10) toward the interior of the drill tip (3) and forms a first side of the slot (14) in the drill tip (3), the cutting surface (11) being constructed to process the workpiece (18) during the drilling and spiraling of the screw (1) in the workpiece (18); an upwardly curved outer surface (9) tapering from the shaft (4) along the drill tip (3) to the tip (7) and extending from the cutting edge (10) around the central axis (8) at an angle of not less than 225 degrees and not more than 330 degrees; and a second surface (13) extending inward from the upwardly curved outer surface (9) to the cutting surface (11) and forming a second side of the slot (14); The feature is that the cut surface (11) is flat and parallel to the central axis, and extends radially inward from the cutting edge (10) toward the central axis (8) to the central axis (8), so as to follow a plane containing the central axis (8).

2. The screw according to claim 1, wherein the drill tip (3) comprises only a single tip (7) and a single facet (11).

3. The screw according to claim 1 or 2, wherein the convex curved outer surface (9) that tapers from the shaft (4) to the tip (7) is formed as part of an inclined cone ending at the tip.

4. The screw according to claim 1 or 2, wherein the cutting edge (10) extends to the central axis (8) but does not intersect the central axis (8) and does not extend to the opposite side of the central axis (8).

5. The screw according to request item 1 or 2, wherein the second face (13) is convex on the surface.

6. The screw according to claim 1 or 2, wherein the shaft (4) is a cylinder with a circular cross section, and wherein the first thread (5) is circular when projected onto a plane perpendicular to the central axis (8).

7. The screw according to claim 1 or 2, wherein the tapered, convex, curved outer surface (9) extends to an angle W ranging from 240 to 315 degrees, and the slot (14) extends to an angle W of 360 degrees.

8. The screw according to claim 1 or 2, wherein the screw (1) includes a second thread (6) between the first thread (5) and the screw head (2), the second thread (6) having a helical direction opposite to that of the first thread (5), and being configured to draw material from the drilled hole deeper into the workpiece (18) during the period when the screw (1) helically penetrates the workpiece (18).

9. The screw according to claim 8, wherein the second thread (6) has an outer diameter greater than the outer diameter of the first thread (5).

10. The screw according to claim 8, wherein the shaft (4) includes a threadless region (4B) between the screw head (2) and the second thread (6), the region (4B) having a diameter smaller than the outer diameter of the second thread (6) and a length not less than at least one of the pitch of the second thread (6) and the height of the screw head (2).

11. The screw according to claim 1, wherein the convex curved outer surface (9) tapering from the shaft (4) to the tip (7) is formed as part of an inclined cone, wherein the tapering convex curved outer surface (9) extends to an angle W ranging from 240 to 315 degrees, and the slot (14) extends to an angle of 360-W; wherein the drill tip (3) comprises only a single tip (7) and a single facet (11), wherein the second facet (13) is smoothly convex, wherein the shaft (4) is a cylinder having a circular cross section; wherein the screw (1) includes a second thread (6) between the first thread (5) and the screw head (2), the second thread (6) having a helical direction opposite to that of the first thread (5), and being configured to draw material deeper into the workpiece (18) from the bore during the screw (1) helically penetrating the workpiece (18), wherein the second thread (6) has an outer diameter greater than that of the first thread (5).

12. The use of a screw according to any one of claims 1 to 11 is for securing workpieces in the form of panels made of plastic or wood-plastic composites to a wooden support structure, particularly for providing outdoor paving on platforms or balconies.

13. A method for securing a workpiece (18) made of a wood-plastic composite to an underlying wooden support, the method comprising: providing a support structure made of wood, placing the workpiece (18) against the support structure, and providing a screw (1) according to any one of claims 1 to 11, the length of which is greater than the thickness of the workpiece (18); wherein the method comprises: drilling the screw (1) through the workpiece (18) and screwing the screw (1) such that a portion of the first thread (5) enters the underlying wooden structure, and securing the workpiece (18) to the underlying support structure with the first thread (5), and continuing to rotate the screw (1) to advance it until the screw head (2) is embedded in the workpiece (18).

14. The method according to claim 13, wherein the screw (1) includes a second thread (6) between the first thread (5) and the screw head (2), the second thread (6) having a helical direction opposite to that of the first thread (5), and wherein the method includes: during the period when the screw (1) advances through the workpiece (18), drawing material from the borehole deeper into the workpiece (18) via the second thread.

15. A method for paving a platform or balcony with a workpiece (18), the workpiece (18) being a plastic composite panel containing reinforcing material in a plastic matrix or a plastic panel without reinforcing material; the method comprising: providing an underlying support structure made of wood, placing the workpiece (18) on top of the support structure, and providing a screw (1) according to any one of claims 1 to 11, the length of which is greater than the thickness of the workpiece (18); wherein the method comprises: drilling the screw (1) through the workpiece (18) and screwing the screw (1) such that a portion of the first thread (5) enters the underlying wood structure, and securing the workpiece (18) to the underlying support structure with the first thread (5), and continuing to rotate the screw (1) to advance until the screw head (2) is embedded in the workpiece (18).

16. The method of claim 15, wherein the screw (1) includes a second thread (6) between the first thread (5) and the screw head (2), the second thread (6) having a helical direction opposite to that of the first thread (5), and wherein the method comprises: during the period when the screw (1) advances through the workpiece (18), drawing material from the borehole deeper into the workpiece (18) via the second thread.

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