Separate screw thread helix fixed by means of claws

Abstract

A screw including a shank, at least one screw thread, which is arranged on the shank, winds around the shank and protrudes from the shank, and a separate helix element, which is arranged non-monolithically on the shank, wherein the separate helix element winds around the shank, protrudes from the shank, and constitutes at least a section of the at least one screw thread. The screw further includes at least one first claw, which projects from the shank, and which has both radial and axial overlap with the separate helix element, wherein the shank and the at least one first claw are monolithic with respect to one another.

Claims

1-12. (canceled)

13: A screw comprising: a shank having a tip end, a rear end located opposite the tip end, and a longitudinal axis extending through the rear end and through the tip end; at least one screw thread arranged on the shank to wind around the shank and protrude from the shank; a separate helix element arranged non-monolithically on the shank, the separate helix element winding around the shank, protruding from the shank, and constituting at least a section of the at least one screw thread; and at least one first claw projecting from the shank and having both radial and axial overlap with the separate helix element, the shank and the at least one first claw being monolithic with respect to one another.

14: The screw as recited in claim 13 wherein the first claw extends along at least 1/36 of a turn of the separate helix element.

15: The screw as recited in claim 1 further comprising at least one second claw projecting from the shank having both radial and axial overlap with the separate helix element, the shank and the at least one second claw being monolithic with respect to one another, and the at least one first claw and the at least one second claw, respectively, pointing in opposite axial directions.

16: The screw as recited in claim 15 wherein the second claw extends along at least 1/36 of a turn of the separate helix element.

17: The screw as recited in claim 15 wherein the at least one first claw and the at least one second claw delimit an undercut groove, the separate helix element being arranged in the undercut groove.

18: The screw as recited in claim 17 wherein the groove is a dovetail groove.

19: The screw as recited in claim 17 wherein the groove projects radially into the shank.

20: The screw as recited in claim 13 further comprising at least one toothing on the shank and engaged by the separate helix element.

21: The screw as recited in claim 13 wherein the shank consists of a first material and the separate helix element consists of a second material, wherein the first material and the second material are different materials.

22: The screw as recited in claim 21 wherein the both the first material and the second material are metal materials.

23: The screw as recited in claim 22 wherein the metal materials are steel materials.

23: The screw as recited in claim 21 wherein the second material is a steel material having a Vickers hardness between 550 HV10 and 800 HV10 and the first material is a steel material having a Vickers hardness between 250 HV10 and 800 HV10.

24: The screw as recited in claim 23 wherein the second material is a steel material having a Vickers hardness between between 650 HV10 and 750 HV10,

25: The screw as recited in claim 13 wherein the screw is a concrete screw.

26: The screw as recited in claim 13 wherein a ratio of the maximum outer thread diameter of the screw thread to the pitch of the screw thread is between 1 and 2 at least in some regions of the screw thread.

27: The screw as recited in claim 13 wherein a ratio of the maximum outer thread diameter of the screw thread to the pitch of the screw thread is between 1.2 and 1.6 at least in some regions of the screw thread.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The invention is explained in greater detail below with reference to preferred exemplary embodiments, which are depicted schematically in the accompanying drawings. Individual features of the exemplary embodiments presented below can be implemented either individually or in any combination within the scope of the present invention.

[0054] FIG. 1 is a side view of a screw.

[0055] FIG. 2 is a cross-sectional view A-A of the screw of FIG. 1, in which the cross-sectional plane is a longitudinal plane that includes the longitudinal axis of the screw.

[0056] FIGS. 3 and 4 show a detail of a middle region of the screw of FIG. 1, in FIG. 3 in a cross-sectional view A-A according to FIG. 1, in which the cross-sectional plane is a longitudinal plane that includes the longitudinal axis of the shank, and in FIG. 4 in a cross-sectional view B-B according to FIG. 3, in which the cross-sectional plane is a transverse plane that is perpendicular to the longitudinal axis of the shank.

[0057] FIG. 5 shows, again, a detail of a middle region of the screw of FIG. 1, in a cross-sectional view A-A according to FIG. 1, in which the cross-sectional plane is a longitudinal plane that includes the longitudinal axis of the shank, with the separate helix element omitted, and including size indications.

[0058] FIGS. 6 and 7 show, in a view analogous to that of FIG. 5, a modification of the embodiment of FIGS. 1 to 5, wherein the separate helix element is omitted in FIG. 6.

[0059] FIG. 8 shows, in a view analogous to that of FIG. 5, another modification of the embodiment of FIGS. 1 to 5.

[0060] FIG. 9 shows, in a view analogous to that of FIG. 5, another modification of the embodiment of FIGS. 1 to 5.

[0061] FIGS. 10 to 12 show possible modifications of the cross-section of the separate helix element.

[0062] FIGS. 13 and 14 show, in views analogous to those of FIGS. 3 and 4, respectively, another modification of the embodiment of FIGS. 1 to 5,

[0063] FIGS. 15 to 19 show another modification of the embodiment of FIGS. 1 to 5. FIG. 15 is an isometric view with the separate helix element left out. FIG. 16 is a view analogous to that of FIG. 3. FIG. 17 is another cross-sectional view, in which the cross-sectional plane is a longitudinal plane that includes the longitudinal axis of the shank, wherein this plane is slightly angularly offset to that of FIG. 16. FIG. 18 is a view analogous to that of FIG. 17, but with the separate helix element left out. FIG. 19 is a cross-sectional view B-B according to FIG. 18, in which the cross-sectional plane is a transverse plane that is perpendicular to the longitudinal axis of the shank, again with the separate helix element left out.

[0064] FIGS. 20 to 22 show another modification of the embodiment of FIGS. 1 to 5. FIG. 20 is an isometric view with the separate helix element left out. FIG. 21 is a view analogous to that of FIG. 3. FIG. 22 is a cross-sectional view B-B according to FIG. 21, in which the cross-sectional plane is a transverse plane that is perpendicular to the longitudinal axis of the shank.

DETAILED DESCRIPTION

[0065] FIGS. 1 to 5 illustrate an embodiment of an inventive screw. The screw comprises an elongate shank 10, which has a tip end 11. The tip end 11 is the leading end of the shank 10 and the shank 10 is intended to be inserted with the tip end 11 first into a borehole when the screw is installed. The shank 10 also has rear end 18, which is located on the shank 10 opposite the tip end 11. The screw furthermore has a screw drive 19 that is connected to the shank 10, monolithically in the present case by way of example, for applying torque to the shank 10. In the shown embodiment, the screw drive 19 is a hex head located at the rear end 18, but this is an example only. Any other type of screw drive 19 can be used, such as an external type, for example hex, line (ALH), square, or a socket head, for example Bristol, clutch, double hex, hex socket, hexalobular socket, line (ALR), polydrive, Robertson, spline, TP3, and others. The screw drive 19 could also be located within the shank 10 and/or remote from the rear end 18, in particular if the screw is headless and/or internally threaded.

[0066] The elongate shank 10 comprises a longitudinal axis 99, extending in the longitudinal direction of the shank 10 and through both the tip end 11 and through the rear end 18.

[0067] The screw furthermore comprises a separate helix element 37, which is located on the shank 10, and which winds around the shank 10 and/or the longitudinal axis 99. In particular, the separate helix element 37 is arranged coaxially with respect to the shank 10. The separate helix element 37 comprises a crest 39 and a root 34. In particular, the crest 39 is helical and radially adjoins the root 34, which is also helical. The root 34 is located on the radial inside of the separate helix element 37, i.e. it is located closer to the longitudinal axis 99 of the shank 10 than is the adjacent crest 39.

[0068] The separate helix element 37, in particular the crest 39 thereof, constitutes at least a helical section of a screw thread 30 of the screw. In shown embodiment, the separate helix element 37, in particular the crest 39 thereof, constitutes all of the screw thread 30 of the screw, but this is an example only, and the screw thread 30 might have additional helical sections. The screw thread 30 is located on the shank 10, winds around the shank 10 and/or the longitudinal axis 99, and projects radially, with respect to the longitudinal axis 99, from the shank 10. The screw thread 30 is an external screw thread.

[0069] The separate helix element 37 and the shank 10 are non-monolithic with respect to one another. Due to the latter, the screw thread 30 and the shank 10 are also non-monolithic with respect to one another, at least regionally.

[0070] The shank 10 consists of a first material. The separate helix element 37 consists of a second material. In the present embodiment, the first material and the second material are different materials. The second material can in particular be a metal material, preferably a steel material, most preferably a stainless steel. The first material can in particular be a metal material, preferably a steel material, most preferably a stainless steel. The shank 10 and/or the separate helix element 37 could also be provided with a respective coating, comprising one or more layers.

[0071] In the present embodiment, the separate helix element 37 and/or the screw thread 30 has a plurality of turns, namely approximately 8.5 turns. Preferably, at least two turns are provided. By way of example, the separate helix element 37 and/or the screw thread 30 spans, axially (i.e. in the direction parallel to the longitudinal axis 99), approximately 80% of the length l.sub.s of the shank 10. The screw thread 30 thus forms a main thread of the screw. The screw thread 30 can also span up to 100% of the length l.sub.s of the shank 10; preferably, it spans at least 20% of the length l.sub.s of the shank 10.

[0072] Whereas in the shown embodiment, no additional screw threads are shown, the screw might also have additional screw threads, formed monolithically or non-monolithically with respect to the shank 10.

[0073] The shank 10 is provided with a helical groove 40, which winds around the longitudinal axis 99 of the shank 10, and which projects, on the lateral surface of the shank 10, radially into the shank 10. The separate helix element 37, in particular the root 34 thereof, is arranged within the groove 40, whereas its crest 39 projects from the shank 10. The screw is provided with a first claw 51 and with a second claw 52, wherein both the first claw 51 and the second claw 52 secure the separate helix element 37 on the shank 10, in particular they secure the separate helix element 37, in particular its root 34, within the groove 40.

[0074] Both the first claw 51 and the second claw 52 project from the shank 10 and are monolithic with respect to the shank 10. Both the first claw 51 and the second claw 52 have both axial (with respect to the longitudinal axis 99) overlap and radial (with respect to the longitudinal axis 99) overlap with the adjacent separate helix element 37, in particular with the root 34 thereof. Both the first claw 51 and the second claw 52 clamp the separate helix element 37, in particular the root 34 thereof, against the shank 10. In particular, they clamp the separate helix element 37, in particular the root 34 thereof, in the radial and axial directions (with respect to the longitudinal axis 99). In the present embodiment, this clamping is tight. Accordingly, the first claw 51 and the second claw 52 clamp the separate helix element 37, in particular the root 34 thereof, tightly radially against the shank 10 as well as tightly in the axial direction. However, some play might be provided, for example due to manufacturing reasons or/and to provide additional functionality. Clamping of the separate helix element 37, in particular of its root 34, in the axial direction takes place in-between the first claw 51 and the second claw 52.

[0075] The first claw 51 projects forwardly, i.e. tipwardly, i.e. towards the tip end 11, whereas the second claw 52 projects rearwardly, i.e. towards the rear end 18, in particular headwardly. The first claw 51 clamps a rearwardly facing flank of the separate helix element 37, whereas the second claw 52 clamps a forwardly facing, i.e. tipwardly facing, flank of the separate helix element 37.

[0076] In the present embodiment, the first claw 51 and the second claw 52 extend all along the separate helix element 37, i.e. both the first claw 51 and the second claw 52 have the same number of turns as the separate helix element 37 has, wherein the first claw 51 and the second claw 52 subduct near the tip end 11. But this is an example only.

[0077] Both the first claw 51 and the second claw 52 face, and preferably adjoin, the separate helix element 37. Both the first claw 51 and the second claw 52 adjoin the groove 40, and the first claw 51 delimits the groove 40 rearwardly, and the second claw 52 delimits the groove forwardly (i.e. tipwardly), i.e. the first claw 51 forms a forwardly facing (i.e. tipwardly facing) flank of the groove 40, and the second claw 52 forms a rearwardly facing flank of the groove 40. The first claw 51 and the second claw 52 form an undercut structure at the groove 40, and the groove is thus an undercut groove 40. In the present embodiment, the undercut structure of the groove 40 extends all along the separate helix element 37, but this is an example only. The first claw 51, the second claw 52 and the undercut groove 40 are shown to be continuous, but could also be provided with discontinuities, e.g. voids. The undercut structure of the groove 40 secures the separate helix element 37, in particular the root 34 thereof, on the shank 10. The bottom of the groove 40 is formed by the shank 10, in particular by the lateral surface thereof. In the shown embodiment, the undercut groove 40 is a dovetail groove 40.

[0078] In particular, the flank angle of the groove 40 can be generally the same as thread flank angle of the root 34 of the separate helix element 37, for particularly efficient clamping.

[0079] The screw is a concrete screw, i.e. the screw thread 30 is able to tap, in particular cut, a corresponding mating thread in a concrete substrate. The screw thread 30 has an outer thread diameter d.sub.tr. At least near the tip end 11 of the non-installed screw, a ratio of the maximum outer thread diameter d.sub.tr of the screw thread 30 to the pitch p.sub.tr of the screw thread 30 is between 1 and 2, in particular between 1.2 and 1.6. In particular, the crest 39 of the separate helix element 37 is able to cut into a substrate and/or to form a positive interlock with the substrate.

[0080] The screw thread 30 might be strictly mathematically helical, but might also deviate from a helical form, which can e.g. provide additional functionality.

[0081] Preferably, the first claw 51 and the second claw 52 form the primary connection between the separate helix element 37 and the shank 10. An additional material connection (for example gluing, or material connections based on heat input, such as brazing or welding) could also be provided, but are preferably absent.

[0082] In the embodiment of FIGS. 1 to 5, the first claw 51 and the second claw 52 radially project over the adjacent lateral surface of the shank 10, i.e. they each form a raised shoulder that radially projects from the shank 10. However, the first claw 51 and the second claw 52 could also be flush with the adjacent lateral surface of the shank 10, as shown in FIGS. 6 and 7. The modification of FIGS. 6 and 7 might be combined with all the other presented embodiments.

[0083] In all presented embodiments, the geometry of the groove 40 and/or of the separate helix element 37 can be, preferably, chosen in following ranges (wherein d.sub.b is the nominal drill hole diameter and p.sub.tr is the pitch of the screw thread 30, and the remaining parameters specified in the figures, in particular FIGS. 5 to 7): [0084] d.sub.s/d.sub.b=0.7-0.99 (ratio shank diameter to nominal drill hole diameter). [0085] 2 h.sub.g/d.sub.s=0.1-0.4 (ratio 2× groove depth to shank diameter). [0086] d.sub.max/d.sub.b=0.9-1.2 (ratio maximum diameter of lateral clamping to nominal drill hole diameter). Note that if d.sub.max/d.sub.b>1.0 an additional threadlike interaction with the surrounding substrate is provided, in which the first claw 51 or/and the second claw 52 act against the surrounding substrate and preferably cut the surrounding substrate, which substrate is preferably concrete, as already mentioned. [0087] w.sub.c/p.sub.tr=0.2-0.7 (ratio width of the clamping to thread pitch). [0088] Depth of groove 40 (h.sub.g) can be constant along all of the groove 40. Alternatively, the groove 40 can subduct, in particular in its starting section located close to the tip end 11. This subduction of the groove 40 can be accompanied by a subduction of the screw thread 30 in its starting section located close to the tip end 11, i.e. by a taper of the outer thread diameter d.sub.tr towards the tip end 11. Accordingly, the starting section of the screw thread 30 would cut gradually in the surrounding substrate. [0089] h.sub.sg/h.sub.s=0.2-1.0 (ratio of radial embedment depth of the separate helix element 37 to total height of the separate helix element 37). Note that h.sub.sg/h.sub.s=1.0 means that the separate helix element 37 is completely sunk into the shank 10, which can be the case near the tip end 11. h.sub.sg/h.sub.s=0.2 means that 20% of the overall profile height of the height of the separate helix element 37 is located within the shank 10 and available for mechanical joining between the separate helix element 37 and the shank 10.

[0090] In the embodiment of FIGS. 1 to 5, and in the modification shown in FIGS. 6 and 7, the groove 40 is a dovetail groove 40. However, other groove cross-sections might be provided, such as a T-groove 40 (see FIG. 8) or a groove 40 having circular cross-section (see FIG. 9). The modifications of FIGS. 8 and 9, respectively, might be combined with all the other presented embodiments.

[0091] Preferably, the cross-section of the groove 40 corresponds to the cross-section of the root 34 of the separate helix element 37. In particular, both cross-sections are generally identical.

[0092] In the embodiment of FIGS. 1 to 5, and in the modification shown in FIGS. 6 and 7, the separate helix element 37 has generally triangular cross-section, namely that of an isosceles triangle, wherein the two sides of equal length are provided by the forwardly facing flank and the rearwardly facing flank of the separate helix element 37, respectively. However, other cross-sections might be provided for the separate helix element 37, such as a rearwardly tilting scalene triangle (see FIG. 10), a forwardly tilting scalene triangle (see FIG. 11), or a triangle with concavities in its flanks (see FIG. 12). The modifications of FIG. 10, FIG. 11 or FIG. 12, respectively, might be combined with all the other presented embodiments.

[0093] In the embodiment of FIGS. 1 to 5, axial loads and radial loads between the separate helix element 37 and the shank 10 can be transferred via positive connection, i.e. via interlocking elements (in particular via interlock of the separate helix element 37 as a first element and the first claw 51 and the second claw 52 as a second element). Circumferentially directed loads, on the other hand, for example torsional loads that arise during screw installation, can be transferred via friction between the separate helix element 37 as a first friction element and the first claw 51, the second claw 52 and/or the shank 10 as second friction elements. In order to further increase friction, it is possible to modify the cross-sections of the root 34 of the separate helix element 37 and of the corresponding groove 40. A possible modification is shown in FIGS. 13 and 14, where the root 34 has a hexagonal cross-section, in which the bottom of the root tapers towards the longitudinal axis 99, when seen in cross-section. Due to this taper, friction is increased when the separate helix element 37 is radially pushed towards the longitudinal axis 99, in analogy to a tapered interference fit/V-belt mechanism. The modifications of FIGS. 13 and 14 might be combined with all the other presented embodiments.

[0094] To further tighten transfer of circumferentially directed loads between the separate helix element 37 and the shank 10, for example torsional loads that arise during screw installation, it is possible to provide the screw with toothings 55 or 56, which are associated with the shank 10, and to have the separate helix element 37, in particular the root 34 thereof, engage these toothings.

[0095] In the embodiment of FIGS. 15 to 19, two toothings 55′ and 55″ are provided, which both have axially (with respect to the longitudinal axis 99 of the shank 10) projecting teeth. Toothing 55′ is provided in the first claw 51 and comprises forwardly, i.e. tipwardly projecting teeth, and toothing 55″ is provided in the second claw 52 and comprises rearwardly projecting teeth. Both toothings 55′ and 55″ mesh with the separate helix element 37, in particular with the root 34 thereof, thereby providing a two-sided lateral positive connection between the separate helix element 37 and the shank 10. Both toothings 55′ and 55″ project into the groove 40. In the shown embodiment, the toothings 55′ and 55″ extend generally all along the separate helix element 37, but they might also be shorter. For example, they may extend merely along the first 1-3 turns of the separate helix element 37 located closest to the tip end 11.

[0096] In the embodiment of FIGS. 20 to 22, a toothing 56 having radially outwardly (with respect to the longitudinal axis 99 of the shank 10) projecting teeth is provided on the shank 10, namely at the bottom of the groove 40. This toothing 56 projects into the groove 40 and meshes with the separate helix element 37, in particular with the root 34 thereof, thereby providing a radial positive connection between the separate helix element 37 and the shank 10. In the shown embodiment, the toothing 56 extends generally all along the separate helix element 37, but it might also be shorter. For example, it may extend merely along the first 1-3 turns of the separate helix element 37 which are located closest to the tip end 11.

[0097] The modifications of FIGS. 15 to 19 and 20 to 22, respectively, might be combined with all the other presented embodiments or they might be combined with each other.