Plug screw

Description

[0001] The present invention relates to a self-tapping screw, in particular a dowel screw according to the preamble of claims 1 and 2. Documents EP 1 591 675 A and EP 0 824 198 A disclose previously known screws.

[0002] Self-tapping screws are versatile and particularly well-suited for driving screws into wood or plastic. For use in stone or similar materials, they are used in conjunction with plastic anchors, where the anchor is inserted into a pre-drilled hole and then the screw is driven in.

[0003] The problem with these well-known self-tapping screws is that the anchor is damaged during insertion to such an extent that its holding function in the respective component is impaired. The weakening of the anchor is primarily caused by the screw digging into the anchor wall, thus weakening it. With anchors suitable for both solid and hollow walls, the tip of these screws can damage the end nut.

[0004] The present invention is based on the objective of creating a self-tapping screw that reduces the risk of digging into the dowel wall, especially when screwing in at an angle, and also minimizes damage to the end dowel nut of hollow wall anchors.

[0005] According to the invention, this is achieved by rounding off the flank tip of the thread running on the screw shaft, wherein the radius of the rounding of the rounded flank tip is 1% to 10% of the nominal diameter of the screw.

[0006] The rounded flank tip of the thread prevents the thread from cutting into the dowel wall in such a way as to cause partial or complete destruction of the dowel wall.

[0007] Advantageously, the radius of the rounding of the rounded thread tip is 2% of the nominal diameter of the screw.

[0008] Furthermore, a first embodiment according to the invention comprises the features that the thread flanks of the thread are each formed from two flank sections that form an obtuse angle with each other, wherein the flank section beginning at the thread shank has a radial height H1 perpendicular to the longitudinal axis of the screw shank, and the flank section adjoining it has a radial height H2 perpendicular to the longitudinal axis of the screw shank and terminates in the rounded flank tip, wherein the sum of H1 and H2 constitutes the thread height H of the thread. This embodiment according to the invention achieves an increased expansion effect when screwing into the respective anchor. Advantageously, the radial height H1 is greater than or equal to 30% and less than or equal to 70% of the total height H of the thread, and the radial height H2 is greater than or equal to 30% and less than or equal to 70% of the total height H of the thread. Optimally, H1 = H2.

[0009] Furthermore, it is advantageous if the opposing flank sections with radial height H1 form an acute angle of 20° to 40°, preferably 30°, when viewed in longitudinal section. It is also advantageous according to the invention if the opposing flank sections with radial height H2 form an acute angle of 50° to 70°, preferably 50°, with each other. The aforementioned dimensioning of the respective angles formed by the flank sections optimizes the expansion effect of the screw according to the invention in the anchor; it also allows the flanks of the thread to easily penetrate the anchor nut.

[0010] According to the invention, it is further advantageous if the screw tip at the end of the screw shank is rounded at its free end. Advantageously, the radius of the rounding is 10% of the nominal diameter of the screw according to the invention, whereby a range of 5% to 20% of the nominal diameter of the screw can advantageously be selected.

[0011] A second embodiment of the invention comprises the feature that the screw tip, viewed in longitudinal section, has concave side surfaces. A screw tip designed with such a concave outline improves the centering of the screw according to the invention when screwed into the so-called dowel nut of the hollow wall anchor and enables easy and secure screwing in.

[0012] Furthermore, in longitudinal section, the lateral faces of the screw tip enclose an acute angle W at their intersection point, with a magnitude ranging from 20° to 40°. Additionally, in a first section of the screw tip adjoining the screw shank, an angle W1 with a magnitude ranging from 20° to 40°, particularly 30°, is enclosed by its lateral faces, and in a second section adjoining this, an angle W2 with a magnitude ranging from 10° to 20°, particularly 15°, is enclosed by its lateral faces. Angle W1 is smaller than angle W1 and larger than angle W2.

[0013] According to the invention, it is further advantageous if the screw thread has a larger pitch in the area of ​​the screw tip and in an adjacent shank area than in the rest of the shank area. This results in faster knotting and better expansion of the anchor.

[0014] Furthermore, it may be advantageous to design the screw according to the invention as a partially threaded screw.

[0015] Further advantageous embodiments are included in the dependent claims. The invention is explained in more detail with reference to the exemplary embodiment shown in the accompanying drawings. These show: Fig. 1 a perspective view of a screw according to the invention, Fig. 2 a longitudinal section along the section line II-II in Fig. 1 , Fig. 3 a detail at B in Fig. 2 , Fig. 4 a detail at C in Fig. 2 and Fig. 5 a perspective view of a partially threaded screw according to the invention.

[0016] In the various figures of the drawing, identical parts are always labelled with the same reference symbols.

[0017] The following description claims that the invention is not limited to the exemplary embodiments and not to all or several features of the described embodiments.

[0018] In Fig. 1 and 2Figure 1 shows a screw according to the invention, in particular made of metal or reinforced plastic, especially a dowel screw. Such a screw has a screw shank 1 with a total length I. At one end of the screw shank 1, a screw head 2 with a force-applying surface 3 is formed, and at an end of the screw shank 1 opposite the screw head 2, a screw tip 4 is present, tapering towards its free end. Furthermore, the screw according to the invention has a screw thread 6 extending at least over a partial section of the screw shank 1, which extends to the free end of the screw tip 4. This screw thread is designed as a self-tapping screw thread. In the illustrated embodiment, the screw thread 6 extends from the screw head 2 to the screw tip 4 and terminates at the free end of the screw tip 4.In the illustrated embodiment, a single-start screw thread 6 with a helical thread 6a is formed. However, it is also within the scope of the invention if a multi-start screw thread is present on the screw shank 1 and / or on the screw tip 4.

[0019] The thread 6a of the screw thread 6, viewed longitudinally, has a triangular cross-section with two thread flanks 8, 9 intersecting at a flank tip 7, see Fig. 4 , wherein the flank tip 7 is rounded. The nominal diameter of the screw corresponds to the outside diameter of the screw thread 6 located on the screw shank 1, specifically in the region of the largest outside diameter of the screw thread 6.

[0020] In the illustrated embodiment, the screw thread 6 has a consistently uniform thread outer diameter in the area of ​​the threaded shank. In the area of ​​the screw tip 4, the thread outer diameter decreases towards the free end of the screw tip 4 in the illustrated embodiment.

[0021] The radius of the rounding of the rounded flank tip 7 is 1% to 10%, in particular 2% of the nominal diameter of the screw.

[0022] For example, in Fig. 3As shown, according to a first variant of the invention, the screw thread 6 is designed such that the thread flanks 8, 9 of the thread 6a are formed from two flank sections 11, 12 which form an obtuse angle with each other, wherein the flank section 11 beginning at the screw shank 1 has a radial height H1 perpendicular to a longitudinal axis XX of the screw shank 1, and the flank section 12 adjoining it has a radial height H2 perpendicular to the longitudinal axis XX and ends in the rounded flank tip 7, wherein the sum of the radial heights H1 and H2 forms the thread height H.

[0023] Advantageously, the radial height H1 of the flank section 11 is greater than or equal to 30% and less than or equal to 70% of the thread height H of the thread pitch 6a, and the radial height H2 of the flank section 12 is greater than or equal to 30% and less than or equal to 70% of the total height H of the thread pitch 6a. It is particularly advantageous if the radial height H1 is equal to the radial height H2.

[0024] Furthermore, it is advantageous, as this is shown in Fig. 4 This is particularly evident when the screw tip 4 is rounded at its free end with a radius 4a. The radius of the radius 4a of the rounded screw tip 4 is particularly 5% to 20%, preferably 10%, of the nominal diameter of the screw. The radius prevents the tip from digging into the material of the anchor when screwed in off-center. Instead, the screw tip is guided into the hole of the anchor nut, particularly by a slight deformation of the anchor.

[0025] Furthermore, in a second variant, the screw tip 4 has concave side surfaces 13 when viewed in longitudinal section, so that the screw tip 4 has a concave outer contour. This reduces the resistance when screwing the screw into the dowel nut.

[0026] Viewed in longitudinal section, the side surfaces 13 of the screw tip 4 enclose an acute angle W at their intersection, with a magnitude ranging from 20° to 40°. The screw tip 4 is formed into two sections 14, 15, which lie one behind the other in the longitudinal direction. Section 15, terminating at the free end of the screw tip 4, has side surfaces that together enclose an acute angle W2 with a magnitude ranging from 10° to 20°, in particular 15°. The adjoining section 14, extending towards the screw head, has side surfaces that enclose an acute angle W1 with a magnitude ranging from 20° to 40°, in particular 30°. Angle W is smaller than angle W1 and larger than angle W2. The angle dimension achieves the same effect as a concavity.

[0027] According to the invention, it is advantageous if the screw thread 6 has a thread pitch that is 35% to 70%, in particular 60% to 70%, of the nominal diameter of the screw. By forming a coarser thread and a pitch greater than 50% of the nominal diameter, in particular 60% to 70%, a noticeable increase in the tightening torque is achieved, so that the end point of the tightening movement is clearly defined.

[0028] It can also be advantageous if the pitch of the screw thread 6 in the area of ​​the screw tip 4 and in a shaft area extending from the screw tip 4 towards the screw head 2, which preferably comprises 1 / 4 to 1 / 2 of the screw-in length of the shaft section in a dowel, is greater than in the remaining shaft area of ​​the screw shaft 1. This ensures that the dowel nut knots quickly.

[0029] A screw according to the invention is expediently dimensioned such that the nominal diameter has 60% to 90% of a bore diameter of a bore present in a component, in particular the outside diameter of the thread is 70% to 80% of the bore diameter.

[0030] In particular, a screw according to the invention is dimensioned such that its outer diameter is 1 mm to 2.5 mm smaller than the nominal diameter of a dowel with which the screw according to the invention is used. The nominal diameter of the dowel corresponds to the bore diameter of a hole into which the dowel is inserted. This optimizes the function of the dowel.

[0031] The screw head 2 of a screw according to the invention can be designed as a countersunk head, but other head shapes are also possible.

[0032] In a design of the screw according to the invention as a partially threaded screw, the ratio l1 / l2 between the length l1 of the unthreaded section 1a of the screw shank 1 ending at the screw head 2 and the length l2 of the section 1b having the screw thread 6 up to the beginning of the screw tip 4 is preferably 20 / 80, 50 / 50 or 40 / 60, based on the total length l of the screw shank 1. Such a partially threaded screw is in Fig. 5 shown, whereby this partially threaded screw, in terms of its design, is otherwise as described in the Figs. 1 to 4 The partial thread, when used in a blind hole, pulls the dowel nut closer, thereby improving the holding forces.

[0033] The invention is not limited to the embodiments shown and described. Reference sign

[0034] 1 Screw shank 1a Unthreaded section 1b Threaded section 2 Screw head 3 Force application 4 Screw tip 4a Rounding 6 Screw thread 6a Thread pitch 7 Flank tip 8, 9 Thread flanks 11, 12 Flank sections 13 Side faces 14 First section 15 Second section lTotal length of the screw shank l1 Length of the unthreaded section l2 Length of the threaded section

Claims

1. Screw, in particular dowel screw, having a screw shaft (1) with a screw head (2), arranged at a shaft end, with a force application point (3) and a screw tip (4) opposite the screw head (2) and formed at the end of the screw shaft (1), which screw tip (4) tapers towards its free end, as well as with a screw thread (6) extending at least over a section of the screw shaft (1) and over the screw tip (4), the thread pitch (6a) of said screw thread having a triangular cross section viewed in longitudinal section, with two thread flanks (8, 9) intersecting in a flank tip (7), characterized in that the flank tip (7) is rounded, wherein a radius of the curve of the rounded flank tip (7) is selected in the size of 1 % to 10 % of the nominal diameter of the screw and wherein the thread flanks (8, 9) are each formed of two flank sections (11, 12), which together form an obtuse angle, a) wherein the flank section (11) beginning at the screw shaft (1) has a radial height (H1) perpendicular to the longitudinal axis (X-X) of the screw shaft (1), and b) the adjoining flank section (12) has a radial height (H2) perpendicular to the longitudinal axis (X-X) of the screw shaft (1), and ends in the rounded flank tip (7), wherein the sum of the radial heights (H1, H2) corresponds to the thread height (H).

2. Screw, in particular dowel screw, having a screw shaft (1) with a screw head (2), arranged at a shaft end, with a force application point (3) and a screw tip (4) opposite the screw head (2) and formed at the end of the screw shaft (1), which screw tip tapers towards its free end, as well as with a screw thread (6) extending at least over a section of the screw shaft (1) and over the screw tip (4), the thread pitch (6a) of said screw thread (6) having a triangular cross section viewed in longitudinal section, with two thread flanks (8, 9) intersecting in a flank tip (7), characterized in that the flank tip (7) is rounded, wherein a radius of the curve of the rounded flank tip (7) is selected in the size of 1 % to 10 % of the nominal diameter of the screw and the screw tip (4) at its free end a) has concave side surfaces (13) viewed in longitudinal section, such that the screw tip (4) has a concave outline or b) viewed in longitudinal section in a first section (14) adjoining the screw shaft (1) its side surfaces (13) form at their point of intersection an acute angle (W1) having a size in a range from 20° to 40°, in particular having a size of 30°, and in a second adjoining section (15) extending as far as the free end of the screw tip (4) its side surfaces (13) form an acute angle (W2) having a size in a range of 10° to 20°, preferably having a size of 15°, wherein the angle (W) is smaller than the angle (W1) and the angle (W) is larger than the angle (W2).

3. Screw according to Claim 1 or 2, characterized in that the radius of the curve of the rounded flank tip (7) is 2 % of the nominal diameter of the screw.

4. Screw according to Claim 2, characterized in that the thread flanks (8, 9) are each formed of two flank sections (11, 12), which together form an obtuse angle, wherein the flank section (11) beginning at the screw shaft (1) has a radial height (H1) perpendicular to the longitudinal axis (X-X) of the screw shaft (1), and the adjoining flank section (12) has a radial height (H2) perpendicular to the longitudinal axis (X-X) of the screw shaft (1), and ends in the rounded flank tip (7), wherein the sum of the radial heights (H1, H2) corresponds to the thread height (H).

5. Screw according to Claim 1 or 4, characterized in that the radial height (H1) is greater than / equal to 30 % and smaller than / equal to 70 % of the overall height (H), and the radial height (H2) is greater than / equal to 30 % and smaller than / equal to 70 % of the radial overall height (H).

6. Screw according to Claim 5, characterized in that the radial height (H1) is equal to the radial height (H2).

7. Screw according to one of Claims 1 to 6, characterized in that the screw tip (4) is rounded at its free end, wherein the radius of the curve (4a) of the rounded screw tip (4) is 5 % to 20 %, in particular 10 % of the nominal diameter of the screw.

8. Screw according to one of Claims 1 to 7, characterized in that the screw tip (4) forms an acute angle (W) having a size in a range of 20° to 40° at its free end at the point of intersection in its side surfaces (13).

9. Screw according to Claim 1, characterized in that the screw tip (4) has concave side surfaces (13) at its free end viewed in longitudinal section, such that the screw tip (4) has a concave outline.

10. Screw according to Claim 1, characterized in that viewed in longitudinal section in a first section (14) adjoining the screw shaft (1) its side surfaces (13) form at their point of intersection an acute angle (W1) having a size in a range from 20° to 40°, in particular having a size of 30°, and in a second adjoining section (15) extending as far as the free end of the screw tip (4) its side surfaces (13) form an acute angle (W2) having a size in a range of 10° to 20°, preferably having a size of 15°, wherein in particular the angle (W) is smaller than the angle (W1) and the angle (W) is larger than the angle (W2).

11. Screw according to one of Claims 1 to 10, characterized in that the screw thread (6) has a pitch that is 35 % to 70 %, in particular 60 % to 70 % of the nominal diameter of the screw thread (6).

12. Screw according to one of Claims 1 to 11, characterized in that the pitch of the screw thread (6) in the section of the screw tip (4) and in a shaft section adjoining the screw tip (4), which shaft section is in particular 1 / 4 to 1 / 2 of the reach of the screw shaft (1) in a dowel, is greater than in the rest of the shaft section of the screw shaft (1).

13. Screw according to one of Claims 1 to 12, characterized in that the flank sections (8,9) form an acute angle of 20° to 40°, preferably 30° in the region of their surface sections (11) with the radial height (H1).

14. Screw according to one of Claims 1 to 13, characterized in that the flank sections (8,9) form an acute angle of 50° to 70°, preferably 50° with their surface sections (12) with the radial height (H2).

15. Screw according to one of Claims 1 to 14, characterized in that the diameter of the screw thread (6) decreases over the length of the screw tip (4) to the free end thereof.

16. Screw according to one of Claims 1 to 15, characterized in that the screw thread (6) is only formed over a partial length (l2), beginning at the screw tip (4), of the screw shaft (1) and has an adjoining thread-free shaft section (1a).

17. Screw according to Claim 16, characterized in that the ratio (l1 / l2) of the length (l1) of the thread-free shaft section (1a) to the length (l2) of the shaft section (1b) having the screw thread (6) in relation to the overall length (1) of the threaded shaft (1) is l1 / l2 = 20 / 80 or 50 / 50 or 40 / 60.

18. Screw according to one of Claims 1 to 17, characterized in that it is made of metal or reinforced plastic.

19. Combination of a screw according to one of Claims 1 to 18 and a dowel, characterized in that the external diameter of the screw thread (6) in the region of the screw shaft (1) is constant and is 1 mm to 2.5 mm smaller than a nominal diameter of the dowel to be used with the screw.