US-12624721-B2 - 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.

Inventors

• Roland Schneider
• Florian ZIELBAUER
• Christian Gebauer
• Guenter DOMANI

Assignees

• HILTI AKTIENGESELLSCHAFT

Dates

Publication Date

20260512

Application Date

20210518

Priority Date

20200528

Claims (19)

1. 1 . 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 element formed in a shape of a helix 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, wherein the thread start forms a helical continuation of the separate screw thread section.
2. 2 . The screw as recited in claim 1 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.
3. 3 . The screw as recited in claim 2 wherein both the first material and the second material are metal materials.
4. 4 . The screw as recited in claim 3 wherein the metal materials are steel materials.
5. 5 . The screw as recited in claim 2 wherein the second material is a steel material having a Vickers hardness between 550 HV10 and 800 HV10.
6. 6 . The screw as recited in claim 5 wherein the second material has a Vickers hardness between 650 HV10 and 750 HV10.
7. 7 . The screw as recited in claim 2 wherein the first material is a steel material having a Vickers hardness between 400 HV10 and 800 HV10.
8. 8 . The screw as recited in claim 1 wherein a maximum outline of the thread start is at least equal size to a maximum outline of the separate screw thread section.
9. 9 . The screw as recited in claim 1 wherein a maximum outline of the thread start is larger than a maximum outline of the separate screw thread section.
10. 10 . The screw as recited in claim 1 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.
11. 11 . The screw as recited in claim 1 wherein the thread start includes a helix element overlapping portion overlapping the separate helix element.
12. 12 . The screw as recited in claim 1 wherein the screw is a concrete screw.
13. 13 . The screw as recited in claim 1 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.
14. 14 . The screw as recited in claim 1 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.
15. 15 . The screw as recited in claim 1 wherein the separate screw thread section and the thread start are helically aligned with each other to constitute at least parts of the screw thread, and located adjacent to one another.
16. 16 . The screw as recited in claim 1 wherein the separate screw thread section reaches further towards the rear end of the shank than the thread start.
17. 17 . The screw as recited in claim 1 wherein the separate screw thread section has more turns than the thread start.
18. 18 . The screw as recited in claim 1 wherein the screw thread spans, parallel to a longitudinal axis, 80% of a length of the shank.
19. 19 . The screw as recited in claim 18 wherein the thread start spans, parallel to the longitudinal axis, 10% of the length of the shank, and the separate screw thread section spans parallel to the longitudinal axis, 70% of the length of the shank.

Description

The invention relates to a screw. A screw of this type comprises 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 comprises a separate screw thread section, which is constituted by a separate helix element that is non-monolithically arranged on the shank. BACKGROUND US20100247267 A1 discloses concrete screws, i.e. screws that can be tappingly screwed into a borehole in a concrete substrate. The screws of US20100247267 A1 are monolithic throughout. US20180283435 A1 discloses a concrete screw that has a separate helix element which is separate from the shank. The separate helix element is located in a receiving groove, which is provided within the shank. The receiving groove has an inclined rearwardly facing wedge flank. The receiving groove also has an inclined forwardly facing flank, but in contrast to the rearwardly-facing flank, the forwardly facing flank is relatively steep. US20110142569 A1 discloses a concrete screw, wherein most of the screw thread is monolithic with respect to the shank, except for the region closest to the tip end, which is a separate part. The material of this separate part is chosen for tapping concrete. EP3620673 A1 and EP3620672 A1 disclose further concrete screws with separate thread parts, which are intended to tap into concrete, wherein a rear section of the respective screw thread can again be monolithic with respect to the shank. Another screw with a separate helix element is described in European patent application number 20158000.8, published as EP3869051. This application proposes to use stainless steels of specific hardness values for the separate helix element and for the shank. European patent application number 19172762.7, published as EP3966460 A1, also relates to a concrete screw having a separate helix element. In this case, it is proposed to provide the separate helix element with slots, which are intended to facilitate radial expansion. US20100290858 A1 (EP2185829 B1) discloses screws comprising a shank-like element and a separate helix element attached thereto. According to US20100290858 A1, the separate helix element or the shank-like element, respectively, can be provided with recesses arranged at regular distances, wherein the respective other element (i.e. the shank-like element or the separate helix element, respectively), are provided with matching projections, which can engage with the recesses. Moreover, the separate helix element can be welded or bonded on the periphery of the shaft. US20200063231 A1 describes a martensitically hardenable steel and its use in concrete screws. DE8713708 U1 describes a screw connection consisting of two elements comprising a helical thread groove each; these elements are joined by a separate helical element providing positive locking. DE102015214257 A1 describes a shaft-hub connection, in which the shaft has an external toothing and a coaxially arranged hub has a corresponding internal toothing. SUMMARY OF THE INVENTION It is an object of the invention to provide a screw that has particularly good performance, resistance and/or installation properties. In an inventive screw, the at least one screw thread comprises a thread start, which extends further towards the tip end than does the separate screw thread section, and which, in particular, forms a generally helical continuation of the separate screw thread section, wherein the thread start and the shank are monolithic. In connection with the invention, it was found that when a concrete tapping screw is provided with a separate helix element, the tapping forces which arise during installation of the screw tend unwind the separate helix element from the shank. As a consequence, a particularly strong connection between the separate helix element and the shank is required, which can make manufacturing complex and/or expensive. In view of this, the present invention provides the shank with a thread start, which leads the separate helix element during installation of the screw, and provides this thread start monolithically with respect to the shank. This thread start can shield the trailing separate helix element at least partly from the arising concrete and therefore from tapping forces, and can therefore efficiently counteract the above-mentioned unwinding tendency. Since the thread start is monolithic with respect to the shank, its tendency to separate from the shank is usually significantly smaller as compared to separate helix elements. Thus, a particularly robust-performing screw can be manufactured at particularly low effort and cost. In addition, the integral thread start can contribute to the fixation of the separate helix element on the shank, which can further facilitate manufacturing. The shank is an elongate member and can, and in particular, be generally cylindrical, more preferabl