Method for Rating a Screw which is Purportedly Embedded in Grout

Abstract

A method for rating a screw which is disposed in a hole in a concrete or masonry substrate includes applying a screw torque to the screw, measuring motion data of the screw in response to the applied screw torque, and rating the screw as either satisfactory or unsatisfactory on a basis of the measured motion data.

Claims

1.-11. (canceled)

12. A method for rating a screw which is disposed in a hole in a concrete or masonry substrate, comprising the steps of: applying a screw torque to the screw; measuring motion data of the screw in response to the applied screw torque; and rating the screw as either satisfactory or unsatisfactory on a basis of the measured motion data.

13. The method according to claim 12, wherein the screw torque is applied to the screw in an unscrewing direction of the screw.

14. The method according to claim 12 further comprising ramping up the screw torque applied to the screw to a predetermined maximum measurement value only, wherein the screw is rated as unsatisfactory when the screw becomes loose in response to the screw torque before the screw torque reaches the predetermined maximum measurement value and wherein the screw is rated as satisfactory when the screw does not become loose in response to the screw torque before the screw torque reaches the predetermined maximum measurement value.

15. The method according to claim 14, wherein the predetermined maximum measurement value is between a first loosening torque of the screw when embedded in grout and a second loosening torque of the screw when not embedded in grout.

16. The method according to claim 14, wherein the ramping up the screw torque is aborted when the screw becomes loose in response to the applied screw torque before the screw torque reaches the predetermined maximum measurement value.

17. The method according to claim 12, wherein the screw torque is applied to the screw using a torque wrench.

18. The method according to claim 14, wherein the screw torque is applied to the screw using a torque wrench and wherein the torque wrench is set to the predetermined maximum measurement value.

19. The method according to claim 12, wherein the screw torque is applied to the screw using a powered impact wrench.

20. The method according to claim 12, wherein the screw has a head.

21. The method according to claim 12, wherein a ratio of a diameter of a thread of the screw to a pitch of the thread of the screw is between 1 and 2.

22. The method according to claim 12, wherein satisfactory indicates that the screw is embedded in grout and wherein unsatisfactory indicates that the screw is at least partially not embedded in grout.

23. A method for installing a screw in a hole in a concrete or masonry substrate, comprising the steps of: placing grout in the hole; subsequently to the placing, screwing the screw into the hole; and subsequently to the screwing, rating the screw according to the method of claim 12.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIGS. 1 to 5 illustrate consecutive steps of an example of a method for installing a screw in a hole in a mineral substrate, including a first example of a method for rating the screw, the setup for this rating method being shown in FIG. 5;

[0037] FIGS. 6 and 7 show exemplary parameters obtained in a method for rating a screw; and

[0038] FIG. 8 illustrates the setup for an alternative embodiment of a method for rating a screw.

DETAILED DESCRIPTION OF THE DRAWINGS

[0039] FIGS. 1 to 5 show, in side view, consecutive steps of an example of a method for installing a screw in a hole in a mineral substrate, including a first method for rating the screw.

[0040] First, and as shown in FIG. 1, a hole 90 is provided in a substrate 6. The substrate 6 is preferably a concrete substrate, and the hole 90 can be a blind hole, that can for example be provided by drilling.

[0041] Subsequently, and as shown in FIG. 2, a quantity of hardenable grout 20 is placed in the hole 90. This can for example be done by injecting the grout into the hole 90 using a dispenser or by placing a cartridge containing the hardenable grout 20 in the hole 90. If a cartridge is used, the hardenable grout 20 can be a two component hardenable grout. In particular, the hardenable grout 20 can be a mortar.

[0042] An attachment part 4 is arranged at the surface of the substrate 6 surrounding the hole 90, so that an opening in the attachment part 4 is aligned with the hole 90. This can be done after placing, during placing or, as shown by way of example here, before placing the hardenable grout 20 in the hole 90.

[0043] As shown in FIG. 3, a screw 10 is then provided, which has a shaft 12 defining a longitudinal axis 99 and a thread 13 arranged on the shaft 12 and helically surrounding the shaft 12 and the longitudinal axis 99. The screw 10 is a tapping screw, which means that the screw 10, in particular its thread 13, is able to cut the substrate 6 and to form a mating thread 63 in the substrate 6. The screw 10 has a drive for imparting screw torque on the screw 10. In the present case, the drive is a head 11, in particular a hex-head.

[0044] The screw 10 is screwed into the hole 90, around the longitudinal axis 99, and in this connection, the thread 13 of the screw 10 forms a mating thread 63 in the substrate 6 in the wall of the hole 90.

[0045] As the screw 10 is lowered into the hole 90, it displaces hardenable grout 20, causing hardenable grout 20 to flow alongside the shaft 12 of the screw 10 towards the mouth of the hole 90. The hardenable grout 20 forms a liner 22 there, covering the wall of the hole 90. The screw 10 is screwed into the hole 90 until the head 11 of the screw 10, directly or via for example a washer, abuts on the attachment part 4, resulting in the configuration shown in FIG. 4.

[0046] The hardenable grout 20 of the liner 22 hardens and the liner 22 made up of the hardened grout 20 can improve performance of the screw 10. It is therefore of interest if the liner 22 is present as intended. However, since the head 11 of the screw 10 covers the hole 90 in the substrate 6, presence of the liner 22 cannot be easily determined visually. A dedicated method for rating the screw 10 either “satisfactory” or “unsatisfactory” is therefore employed.

[0047] In this method, which is indicated in FIG. 5, screw torque τ is applied on screw 10, in particular on the head 11 of the screw 10, the screw torque τ being directed around the longitudinal axis 99 and, preferably, in the unscrewing direction of the screw 10. In the embodiment shown in FIG. 5, screw torque τ is applied using a torque wrench 7.

[0048] The torque τ applied on screw 10 is ramped up, i.e., increased, but only to a predetermined maximum measurement value τ.sub.max, not any higher. Limiting the applied screw torque τ to the maximum measurement value τ.sub.max can be achieved by setting the maximum measurement value τ.sub.max on the torque wrench 7. The maximum measurement value τ.sub.max is chosen between a loosening torque τ.sub.grout+ of the screw 10 embedded in a grout liner 22 and a loosening torque τ.sub.grout− of the screw 10 not embedded in a grout liner 22.

[0049] Motion data of the screw 10 in response to the screw torque τ applied to the screw 10—for example the angular position α of the screw or the mere presence or absence of rotational movement—is measured using a sensor 9, which sensor 9 can be, in a particularly easy-to-perform embodiment, also the naked eye that watches movement of the screw 10 or the body of an installer that senses movement of the screw 10.

[0050] Based on the motion data of the screw 10, the screw 10 is either rated “satisfactory”, namely when the screw 10 does not become loose despite the screw torque τ being increased to the maximum measurement value τ.sub.max, or it is rated “unsatisfactory”, namely when screw 10 becomes loose and starts screwing, in particular unscrewing, before the screw torque τ reaches the maximum measurement value τ.sub.max.

[0051] FIG. 6 shows a first set of exemplary parameters obtained in the rating method. The top chart of FIG. 6 shows the screw torque τ that is applied on the screw 10 versus time t, and the bottom chart shows the angular position α of the screw 10 with respect to the substrate 6 versus time t.

[0052] The top chart of FIG. 6 shows that the maximum measurement value τ.sub.max is chosen to be within the band between the loosening torque τ.sub.grout+ of the screw 10 embedded in hardened grout 20 and the loosening torque τ.sub.grout− of the screw 10 not embedded in hardened grout 20.

[0053] As shown in the top chart of FIG. 6, screw torque τ applied on the screw 10 is increased with time, towards the maximum measurement value τ.sub.max. By way of example, screw torque τ is increased in a non-linear manner here. FIG. 6 illustrates an example in which the grout embedment of the screw 10 is absent. Therefore, once the screw torque τ applied on the screw 10 reaches the loosening torque τ.sub.grout− of the screw 10 not embedded in grout 20, which happens at t=t.sub.rot here, the screw 10 becomes loose and starts rotating, and the angular position α of the screw 10 around its longitudinal axis 99 changes, as shown in the bottom chart of FIG. 6. This rotation is sensed by sensor 9. After the screw has become loose, increasing the screw torque τ applied on the screw 10 towards the maximum measurement value τ.sub.max is aborted, for example by not turning the torque wrench 7 further, and the screw 10 is ranked “unsatisfactory”.

[0054] FIG. 7 shows a second set of exemplary parameters obtained in the rating method, the charts being analogous to those of FIG. 6. In case of FIG. 7, however, the screw 10 is embedded in grout 20 as intended. Therefore, screw torque τ applied on the screw 10 is ramped up all the way up to the maximum measurement value τ.sub.max, but the screw 10 does not become loose, i.e., the angular position α of the screw 10 does not significantly change (only negligible changes due to elastic effects take place). Based on this finding, the screw 10 is ranked “satisfactory”.

[0055] FIG. 8 shows an alternative embodiment of a method for rating the screw 10 either “satisfactory” or “unsatisfactory”. In contrast to the embodiment of FIG. 5, where a torque wrench 7 is used for applying torque τ on the screw 10, the embodiment of FIG. 8 uses a powered, particularly electrically powered, preferably cordless impact wrench 8 for this purpose. According to the embodiment of FIG. 8, torque τ applied on the screw 10 is a series of pulses, and limiting the applied screw torque τ to the maximum measurement value τ.sub.max can be achieved by appropriate design of the impact wrench 8. Beyond that, the description of the method illustrated in FIG. 5 applies mutatis mutandis. In particular, the method shown in FIG. 8 can be used in connection with the steps shown in FIGS. 1 to 4, and in replacement of the method shown in FIG. 5.