HAMMER-IN CONCRETE SCREW

Abstract

A screw including a shank, wherein a thread helix receiving groove that winds around the shank is provided in the shank, and wherein the shank has a screw tip, and further including a thread helix having a base and a crest, wherein the thread helix and the shank are separate parts, wherein the base of the thread helix is arranged in the thread helix receiving groove, and wherein the crest of the thread helix projects radially from the shank. The crest of the thread helix of the unconstricted screw is displaceable towards the shank by linearly driving the shank, together with the thread helix, into an undersized borehole in a concrete or masonry substrate. A method for installing such a screw is also provided.

Claims

1-9. (canceled)

10. A screw comprising: a shank, a thread helix receiving groove provided in the shank winding around the shank, the shank having a screw tip, and a thread helix having a base and a crest, the thread helix and the shank being separate parts, the base of the thread helix being arranged in the thread helix receiving groove, and the crest of the thread helix projecting radially from the shank, the crest of the thread helix of the screw in an unconstricted state being displaceable towards the shank by linearly driving the shank, together with the thread helix, into an undersized borehole in a concrete or masonry substrate.

11. The screw as recited in claim 10 wherein the thread helix receiving groove includes a thread helix accommodation cavity for receiving at least a portion of the thread helix when displaced towards the shank.

12. The screw as recited in claim 10 wherein the crest of the thread helix of the unconstricted screw is displaceable towards the shank by swivelling at least the crest of the thread helix away from the screw tip by linearly driving the shank, together with the thread helix, into the undersized borehole in the concrete or masonry substrate.

13. The screw as recited in claim 12 wherein the crest of the thread helix of the unconstricted screw is displaceable towards the shank by jointly swivelling the crest of the thread helix and the base of the thread helix away from the screw tip by linearly driving the shank, together with the thread helix, into the undersized borehole in the concrete or masonry substrate.

14. The screw as recited in claim 11 wherein the thread helix accommodation cavity axially adjoins the thread helix.

15. The screw as recited in claim 10 wherein the crest of the thread helix of the unconstricted screw is elastically displaceable towards the shank by linearly driving the shank, together with the thread helix, into the undersized borehole in the concrete or masonry substrate.

16. The screw as recited in claim 10 further comprising a drive for transmitting torque to the shank, the drive being arranged on the shank remote from the screw tip.

17. A method for installing the screw as recited in claim 10, the method comprising: hammering in the shank into the undersized borehole in the concrete or masonry substrate, thereby displacing at least the crest of the thread helix towards the shank.

18. The method as recited in claim 17 wherein following the hammering-in step, the crest of the thread helix is biased radially outwards against a wall of the borehole.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG. 1 is a perspective representation of a screw.

[0023] FIG. 2 is a perspective representation of the screw of FIG. 1 with the thread helix omitted.

[0024] FIG. 3 is an enlarged longitudinal cross-section of the region of the of the screw of FIG. 1 marked with a rectangle in FIG. 1, showing two different positions of the thread helix for illustrating a method for installing the screw.

DETAILED DESCRIPTION

[0025] The figures show an embodiment of an inventive screw 1. The screw 1 comprises a shank 10 having a screw tip 11 at its front end. The screw 1 further comprises a drive 19, which is connected to the shank 10 at the rear end of the shank 10 to transmit torque to the shank 10. The shown drive 19 is, by way of example, a hex drive. However, other drives, can alternatively be used instead.

[0026] The screw 1 furthermore comprises a helical thread helix 20, having base 22 and a crest 21, wherein the thread helix 20 tapers from the base 22 towards the crest 21. The shank 10 is provided with a helical thread helix receiving groove 12, winding around the shank 10 and around the longitudinal axis 99 of the shank 10. The thread helix 20 is located in this thread helix receiving groove 12. In particular, the base 22 of the thread helix 20 is received in the thread helix receiving groove 12, whereas the crest 21 projects radially from the shank 10.

[0027] FIG. 3 depicts the thread helix 20, using different line types, in two distinct positions: the dashed-line thread helix 20 illustrates a position that is present when the screw 1, in particular its thread helix 20, are unconstricted, whereas the solid-line thread helix 20 illustrates a position that is present during linear driving-in of the shank 10 into an undersized borehole 98 in a concrete or masonry substrate 5, in particular in a hammering-in step. In FIG. 3, the arrow marked with reference numeral 11 points to the screw tip 11, i.e. it points in the installation direction, which is the linear driving-in direction.

[0028] As can be taken from FIG. 3, the thread helix 20 can swivel backwards, i.e. away from the screw tip 11, as the wall of the undersized borehole 98 acts against the thread helix 20 when driving-in the shank 10 and the thread helix 20 into the undersized borehole 98. The thread helix receiving groove 12 comprises a thread helix accommodation cavity 25 that can receive the thread helix 20 as it swivels backwards. As the thread helix 20 swivels backwards, the crest 21 of the thread helix 20 approaches the shank 10 and the longitudinal axis 99 thereof. Accordingly, when the shank 10 is driven into a borehole 98, the thread helix 20 can tilt form the dashed-line position into the solid-line position of FIG. 3, leading to a reduction of the outer diameter of the thread helix 20, which allows to drive the shank 10 into a borehole 98 that is, on purpose, undersized with respect to the thread helix 20 in its original, i.e. dashed-line position. Accordingly, the crest 21 of the thread helix 20 of the previously unconstricted screw 1 is displaceable towards the shank 10 through linearly-only driving the shank 10 into the undersized borehole 98 in the concrete or masonry substrate 5.

[0029] Once the driving-in is completed, the thread helix can swivel back towards its original, i.e. dashed-line position, e.g. by elastic restoration forces, by applying a pull-out force to the screw 1 (i.e. a force that is directed opposite to the driving-in direction) or/and by rotation of the shank 10 in the borehole 98. The thread helix 20 is thus activated and locks the screw 1 in the borehole 98. Should the borehole 98 widen, for example by crack opening, the thread helix 20 can further expand radially, reliably locking the screw 1 also in seismic conditions.