Screw with separate thread helix and integral thread start

Abstract

A screw including a shank having a tip end and a rear end, which is located opposite the tip end, and at least one screw thread, which is arranged on the shank, which winds around the shank and which protrudes from the shank, wherein the screw thread includes a separate screw thread section, which is constituted by a separate helix element that is non-monolithically arranged on the shank. The at least one screw thread includes a thread start, which extends further towards the tip end than does the separate screw thread section, and which forms a generally helical continuation of the separate screw thread section, wherein the thread start and the shank are monolithic.

Claims

1-9. (canceled)

10. A screw comprising: a shank having a tip end and a rear end located opposite the tip end; and at least one screw thread arranged on the shank to wind around the shank and protrude from the shank, the screw thread including a separate screw thread section constituted by a separate helix element non-monolithically arranged on the shank, the at least one screw thread also including a thread start extending further towards the tip end than the separate screw thread section, the thread start and the shank being monolithic.

11. The screw as recited in claim 10 wherein the thread start consists of a first material and the separate helix element consists of a second material, the first material and the second material being different materials.

12. The screw as recited in claim 11 wherein both the first material and the second material are metal materials, in particular steel materials.

13. The screw as recited in claim 12 wherein the metal materials are steel materials.

14. The screw as recited in claim 11 wherein the second material is a steel material having a Vickers hardness between 550 HV10 and 800 HV10.

15. The screw as recited in claim 14 wherein the second material has a Vickers hardness between 550 HV10 and 800 HV10.

16. The screw as recited in claim 11 wherein the first material is a steel material having a Vickers hardness between 400 HV10 and 800 HV10.

17. The screw as recited in claim 10 wherein a maximum outline of the thread start is at least equal size than a maximum outline of the separate screw thread section.

18. The screw as recited in claim 10 wherein a maximum outline of the thread start is larger than a maximum outline of the separate screw thread section.

19. The screw as recited in claim 10 wherein the thread start has a maximum outer thread diameter at least equal to a maximum outer thread diameter of the separate screw thread section.

20. The screw as recited in claim 10 wherein the thread start includes a helix element overlapping portion overlapping the separate helix element.

21. The screw as recited in claim 10 wherein the screw is a concrete screw.

22. The screw as recited in claim 10 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.

23. The screw as recited in claim 10 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.

24. The screw as recited in claim 10 wherein the thread start forms a helical continuation of the separate screw thread section.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0047] 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.

[0048] FIG. 1 is a side view of a concrete screw.

[0049] 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 shank.

[0050] FIG. 3 is a front view of the screw of FIG. 1.

[0051] FIG. 4 shows, in a single drawing, the outlines of both the thread start and of the separate helix element of the screw of FIG. 1, in a cross-sectional view in which the cross-sectional plane is a longitudinal plane that includes the longitudinal axis of the shank.

DETAILED DESCRIPTION

[0052] FIGS. 1 to 4 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 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.

[0053] 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.

[0054] The screw furthermore comprises a screw thread 30, which is located on the shank 10, which winds around the shank 10 and/or the longitudinal axis 99, and which projects radially, with respect to the longitudinal axis 99, from the shank 10. The screw thread 30 is an external screw thread.

[0055] The screw thread 30 comprises at least two distinct helical sections, namely a separate screw thread section 38 and a thread start 31, which is located in front of the separate screw thread section 38. The separate screw thread section 38, in particular the tipward end thereof, and the thread start 31, in particular the rearward end thereof, are helically aligned with each other to constitute at least parts of the screw thread 30. In the present embodiment, they constitute the entirety of the screw thread 30, but this is an example only. The thread start 31 is located axially in front of separate screw thread section 38, i.e. the thread start 31 extends further towards the tip end 11 than does the separate screw thread section 38. The separate screw thread section 38 reaches further towards the rear end 18 of the shank 10 than does the thread start 31. The separate screw thread section 38 is thus located rearwardly of the thread start 31. The thread start 31 and the separate screw thread section 38 are located adjacent to one another. In the shown embodiment, they are in contact with one another, but there might also be some gap between the thread start 31 and the separate screw thread section 38, e.g. due to manufacturing tolerances. Both the thread start 31 and the separate screw thread section 38 wind around the shank 10 and/or around the longitudinal axis 99.

[0056] In the shown embodiment, the thread start 31 has approximately one turn. However, a thread start 31 which is shorter and has less than one turn, or a thread start 31 which is longer, having more than one turn, can also be envisaged, but advantageously, the thread start 31 has less than two turns. The separate screw thread section 38 has a plurality of turns, namely approximately nine turns in the shown embodiment. Preferably, it has at least two turns.

[0057] The separate screw thread section 38 is constituted by a separate helix element 37, in particular by a helical crest of the separate helix element 37. The separate helix element 37, which is a part of the screw, 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. Whereas the thread start 31 and the shank 10 are monolithic with respect to one another, the separate helix element 37 and the shank 10 are non-monolithic with respect to one another. Due to the latter, the separate screw thread section 38 and the shank 10 are non-monolithic with respect to one another.

[0058] The shank 10, and therefore also the monolithic thread start 31, consist of a first material. The separate helix element 37, and therefore also the separate screw thread section 38, consist 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, the monolithic thread start 31, the separate screw thread section 38 and/or the separate helix element 37 could also be provided with a respective coating, comprising one or more layers.

[0059] In the present embodiment, the screw thread 30 spans, longitudinally (i.e. in the direction parallel to the longitudinal axis 99), approximately 80% of the length I.sub.s of the shank 10. The screw thread 30 thus forms a main thread of the screw. The thread start 31 spans approximately 10% of the length I.sub.s of the shank 10 and the separate screw thread section 38 spans approximately 70% of the length I.sub.s of the shank 10. The ratio of the length of the thread start 31 to the length of the separate screw thread section 38 is about 14% in this embodiment. 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.

[0060] The separate helix element 37 and therefore the separate screw thread section 38 is fixed to the shank 10. In the shown embodiment, this fixation is tight, but it might also allow some displacement, in particular axial displacement, of the separate screw thread section 38 with respect to the shank 10. In the shown embodiment, fixation of the separate helix element 37 on the shank 10 is provided at a helical root 34 of the separate helix element 37, which root 34 is arranged within a helical groove 40 provided within the shank 10. In particular, the groove 40 has an undercut structure and the root 34 a corresponding structure that corresponds to the undercut structure. In the present embodiment, the undercut structure of the groove 40 is a female dovetail, and the corresponding structure of the root 34 is a male dovetail. However, other undercut structures such as T-structures could also be envisaged. Other types of connections, such as frictional connections or material connections (for example gluing, soldering or welding) could also be provided in addition or as an alternative, in order to provide fixation of the separate helix element 37 on the shank 10.

[0061] The screw is a concrete screw, i.e. the screw thread 30, in particular the thread start 31, 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.

[0062] The screw thread 30 might be strictly mathematically helical, but might also deviate from a helical form, which can e.g. provide additional functionality.

[0063] As can be seen in FIG. 3, the thread start 31 comprises a helix element overlapping portion 35. This helix element overlapping portion 35 covers, in particularly radially and/or axially, the separate helix element 37, in particular the separate screw thread section 38 thereof. In particular, the helix element overlapping portion 35 forms a holding-down claw for securing the tipward end of the separate helix element 37 on the shank 10, which holds the separate helix element 37 between the helix element overlapping portion 35 and the shank 10 in the radial direction. In addition, the helix element overlapping portion 35 can provide a bifurcation, in which the separate helix element 37 is embedded in the axial direction so as to laterally support the separate helix element 37.

[0064] As can also be seen in FIG. 3, the outer diameter of the thread start 31 continuously increases, starting from the diameter of the shank 10, towards the level of the outer diameter of the separate screw thread section 38.

[0065] As can be gathered from FIG. 4, the maximum outline, i.e. the maximum longitudinal thread cross-section, of the thread start 31 is slightly larger than that of the separate screw thread section 38. In particular the thread start 31 has a maximum outer thread diameter d.sub.tr, 31 which slightly larger than a maximum outer thread diameter d.sub.tr, 38 of the separate screw thread section 38. As a consequence, substrate tapping action, in particular concrete substrate tapping action, will concentrate on the integral thread start 31. The thread start 31 thus forms the tapping section of the screw, whereas the separate screw thread section 38 forms the load bearing section of the screw.