AU2008201909A8

AU2008201909A8 - Self-boring rock anchor

Info

Publication number: AU2008201909A8
Application number: AU2008201909A
Authority: AU
Inventors: Michael Bayerl; Kay Heemann; Wolfgang Ludwig
Original assignee: Hilti AG
Current assignee: DSI Underground Australia Pty Ltd
Priority date: 2007-05-16
Filing date: 2008-04-30
Publication date: 2011-09-01
Anticipated expiration: 2028-04-30
Also published as: EP1992782A2; AU2008201909A1; EP1992782A3; AU2008201909B2; CN101307694A; US20080286054A1; NZ567821A; ZA200801675B; AU2008201909B8; DE102007000277A1

Abstract

A self-boring rock anchor (11) has a hollow-cylindrical mounting body (12), that at one end (13) has a boring head (16), and an internal tube (21) provided in the mounting 5 body (12), the internal tube having an outlet opening (22) at a distance from the boring head (16) and accommodating a hardenable compound (26) that can be squeezed out. Between the hardenable compound (26) and the boring head (16) a mixing element (31) is provided in a displaceable manner in the internal tube (21). The boring head (16) has a holding fixture (18) facing the mixing element (31) for a free end (32) of the mixing to element (31) as well as a passing-through opening (17) for the hardenable compound (26). The holding fixture (18) of the boring head (16) has a centring section (20) and the mixing element (31) at its free end (32) which is facing the boring head (16) has a counter-centring section (33) that can be joined with the centring section (20) of the holding fixture (18) of the boring head (16). (Fig. 1)

Description

AUSTRALIA PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT ORIGINAL Name of Applicant: Hilti AG Actual Inventors: Michael Bayerl and Wolfgang Ludwig and Kay Heemann Address for Service is: SHELSTON IP 60 Margaret Street Telephone No: (02) 9777 1111 SYDNEY NSW 2000 Facsimile No. (02) 9241 4666 CCN: 3710000352 Attorney Code: SW Invention Title: SELF-BORING ROCK ANCHOR The following statement is a full description of this invention, including the best method of performing it known to me/us: File: 57334AUP00 2 Self-boring rock anchor The invention relates to rock anchors and, more particularly to a self-boring rock anchor. 5 Any discussion of the prior art throughout the specification should in no way be considered as an admission that such prior art is widely known or forms part of common general knowledge in the field. Rock anchors are fastening elements and serve the purpose of stabilisation of the walls of 10 hollow spaces like tunnels, galleries and the like, in such a manner that for the construction of a wall, adjacent rock regions are fastened to one another. In many cases regions, which by virtue of the construction of the hollow space, end up with impaired mechanical properties especially load-bearing capacity in the immediate vicinity of the wall, are fastened to undamaged rock regions. In this connection, the term 'wall' of a hollow space 15 is understood to include the floor of a region, in addition to the roof section and the lateral walls. DE 103 01 968 Al describes a self-boring rock anchor that is fitted with an extrudable mortar compound at the factory. The rock anchor is bored into the substratum. When a 20 dry boring method is used rock, so called drillings and quarry dust, comminuted by the boring head, can be sucked in by the boring head into the intermediate space between the internal tube and the mounting body as well as in the free space between the outlet opening of the internal tube and the boring head. When a wet boring method is used, flushing water can be conveyed to the boring head. To ensure a sufficiently large intermediate 25 space, spacers are provided on the internal tube. The spacers are separate elements or are formed on the internal tube during its manufacture. After reaching the desired jigging depth the mortar compound, provided in the internal tube, for example packed in a foil bag, is squeezed out using pressure, while the mixing element, situated in the direction of jigging in front of the mortar compound to be squeezed out, is displaced into a holding 30 fixture of the boring head. The mortar compound to be pressed out, e.g. a multi component mortar compound, is mixed in the mixing element during a further application of pressure and introduced through the passing-through opening in the boring head into the 3 space surrounding the rock anchor. As a result of the forward moved mixing element during the squeezing-out process no hardenable compound penetrates into the intermediate space between the body of the holding fixture and the internal tube. Thus the necessity of a more expensive hardenable compound is limited to the space to be filled between the 5 external body and the wall of the bored hole. After the hardening of the compound the rock anchor is chemically anchored in the substratum. Depending on the type of the substratum to be secured, for the stabilisation of the walls of hollow spaces a plurality of rock anchors have to be set, so that there is the further 10 requirement to reduce the manufacturing costs for rock anchors of this type. It is an object of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative. 15 According to the invention, there is provided a self-boring rock anchor with a hollow cylindrical mounting body, that at one end has a boring head, and with an internal tube provided in the mounting body, the internal tube having an outlet opening at a distance from the boring head and accommodating a hardenable compound that can be squeezed out, while between the hardenable compound and the boring head a mixing element is 20 provided in a displaceable manner in the internal tube and the boring head has a holding fixture facing the mixing element for a free end of the mixing element as well as a passing through opening for the hardenable compound wherein the holding fixture of the boring head has a centring section and the mixing element at its free end which is facing the boring head has a counter-centring section that can be joined with the centring section of 25 the holding fixture of the boring head. The free end of the mixing element, facing the boring head, due to the squeezing-out process during advancement, independently and automatically locates the holding fixture in the boring head. This locating takes place without a separate spacer element or an 30 additional guiding element in the holding fixture tube, like a slope, for example. When the free end of the mixing element butts against an edge of the boring head that faces the mixing element, by virtue of the construction of the free end of the mixing element the 4 mixing element will deflect in the holding fixture in the boring head during further squeezing-out process. As soon as the free end of the mixing element abuts against the centring section of the holding fixture in the boring head, the mixed hardenable compound can fill the space surrounding the holding fixture through the passing-through opening of 5 the boring head. The mixing element is preferably made from a plastic material and is elastically deformable especially in the region of the counter-centring section of the free end of the mixing element. The free end of the mixing element in the region of the counter-centring 10 section preferably has slots that are substantially parallel with the longitudinal axis of the internal tube, said slots also enable an advantageous elastic deformation of the counter centring section during the joining with the centring section of the holding fixture of the boring head. 15 During the boring process the internal tube can wobble with the compound to be expressed in the mounting body, so that sufficient intermediate space is ensured between the internal tube and the mounting body to evacuate drillings and quarry dust or to introduce flushing water to the boring head. 20 When compared with known rock anchors, the manufacturing costs of at least preferred embodiments of the present rock anchor can be reduced, representing a basic advantage in the case of a mass-produced product of this kind. Nevertheless a satisfactory application of the self-boring rock anchors is ensured. 25 The centring section of the holding fixture of the boring head preferably has a funnel shaped construction and tapers towards the free end of the boring head. As a result of this construction the joining of a mixing element with a conical free end, tapering in the direction of the boring head, is simplified. 30 A wall section of the centring section, surrounding the holding fixture of the boring head, preferably has a concave construction, due to which during displacement of the mixing element an advantageous deflection of the free end of the mixing element in the holding 5 fixture of the boring head is enabled. In this connection the term concave refers to the construction of the corresponding wall section. In a further preferred form the wall sections, forming the holding fixture of the boring head, form a partially spherical receptacle. 5 The wall section of the counter-centring section surrounding the end region of the free end of the mixing element preferably has a convex construction, such that during the displacement of the mixing element an advantageous deflection of the free end of the mixing element in the holding fixture of the boring head is provided. In this connection 1o the term convex refers to the construction of the corresponding wall section. In a preferred form the wall sections surrounding the end region of the free end of the mixing element have a ball-shaped or spherical configuration of the free end of the mixing element. The diameter of the centring section of the holding fixture of the boring head is preferably 15 greater than the diameter of the counter-centring section of the free end of the mixing element, by virtue of which the free end of the mixing element can be accommodated in the holding fixture of the boring head. The counter-centring section is preferably formed on the free end of the mixing element 20 from a plurality of centring elements, ensuring a deflection of the free end of the mixing element in the holding fixture of the boring head. In a particularly preferred manner the centring elements are symmetrical relative the longitudinal axis of the internal body, for example according to twin or multiple axis of rotation, by virtue of which the free end of the mixing element will be deflected in the holding fixture of the boring head in every 25 position of the internal tube. Preferably a stop is provided in the holding fixture of the boring head for the mixing element, said stop limiting the advancement of the mixing element. The stop can be formed, for example, as a continuous edge, that advantageously is provided in the holding 30 fixture of the boring head in the direction of the free end of the boring head adjacent to the centring section. By virtue of this stop in the boring head the advancement of the mixing element is limited during the squeezing-out process, so that the end region of the free end 6 of the mixing element during advancement will not deform so that to reduce the flow of the mixed compound, to be squeezed out. A preferred embodiment of the invention will now be described, by way of example only, 5 with reference to the accompanying drawings in which: Fig. I shows a first embodiment of a rock anchor according to the invention, longitudinally sectioned; 10 Fig. 2 shows a detailed view of the front end of a second embodiment of a rock anchor according to the invention; and Fig. 3 shows a view on the free end of the mixing element shown in Fig.2. 15 The same parts are essentially designated with the same reference numerals in the figures. The self-boring rock anchor 11, illustrated in Fig. 1, has a hollow-cylindrical mounting body 12, that on a first end 13, situated in the direction of jigging S, has a boring head 16 and on the opposite situated end 14 has means 15 to transfer the rotation, for example in 20 the form of a polygon that can be coupled with the boring machine. The boring head 16 has a passing-through opening 17 as well as a holding fixture 18 with a centring section 20 that has a funnel shape and tapers towards the free end of the boring head 16. In the mounting body 12 an internal tube 21 is provided, in which a hardenable compound 25 26, that is packed in a foil bag and can be squeezed out, is provided. The internal tube 21 has an outlet opening 22 at a distance from the boring head. Between the hardenable compound 26 and the boring head 16 a mixing element 31 is provided in a displaceable manner in the internal tube 21, said mixing element 31 having at one end region at its free end 32 a counter-centring section 33 that can be joined with the centring section 20 of the 30 holding fixture 18 of the boring head 16.

7 The wall section of the centring section 20 of the holding fixture 18 of the boring head 16, facing the mixing element 31, has a concave construction. Furthermore, a stop 19 for the mixing element 31 is provided in the holding fixture 18 of the boring head 16. The wall section, surrounding the end region of the free end 32 of the mixing element 31 has a 5 convex construction. The diameter Dl of the centring section 20 of the holding fixture 18 of the boring head 16 is greater than the diameter dI of the counter-centring section 33 of the end section of the free 32 end of the mixing element 31. After reaching the desired boring depth the squeezable compound 26 is pressed out using 10 pressure, whereby first the mixing element 31 is displaced in the direction of the boring head 16 until the free end 32 of the mixing element 31 comes to a stop in the holding fixture 18 of the boring head 16. Following further application of pressure the compound 26 to be squeezed out leaves the rock anchor 11 through the passing-through opening 17 in the boring head 16. 15 The self-drilling rock anchor 41, partially illustrated in Figs. 2 and 3, has the same construction as rock anchor 1 1 with the exception of the construction of the centring section 50 of the holding fixture 48 of the boring head 46 and of the counter-centring section 63 of the free end 62 of the mixing element 61, for which reason identical parts are 20 referenced using the same reference numerals. The wall sections surrounding the centring section 50 have a concave construction and have a diameter D2. At the free end 62 of the mixing element 61 a plurality of centring elements 64 are provided, which are symmetrical relative the longitudinal axis 23 of the 25 internal tube 21. The free ends of the centring element 64 are facing one another, while the wall sections surrounding the counter-centring section 63, corresponding to the radial external surfaces of the centring element 64, form a convex or spherical construction of the end region of the free end 62 of the mixing element 61. The diameter d2 of the counter centring section 63 is smaller than the diameter D2 of the centring section 50. 30 Accordingly, it is an advantage of at least a preferred embodiment of the invention to provide a self-boring rock anchor which can be produced economically. It is a further 8 advantage of at least a preferred embodiment of the invention to provide a self-boring rock anchor which reduces the loss of the hardenable compound during squeezing out of the compound into the space surrounding the body of the holding fixture. 5 Although the invention has been described with reference to specific examples it will be appreciated by those skilled in the art that the invention may be embodied in many other forms.

Claims

1. A self-boring rock anchor with a hollow-cylindrical mounting body, that at one end has a boring head, and with an internal tube provided in the mounting body, the internal 5 tube having an outlet opening at a distance from the boring head and accommodating a hardenable compound that can be squeezed out, while between the hardenable compound and the boring head a mixing element is provided in a displaceable manner in the internal tube and the boring head has a holding fixture facing the mixing element for a free end of the mixing element as well as a passing-through opening for the hardenable compound 10 wherein the holding fixture of the boring head has a centring section and the mixing element at its free end which is facing the boring head has a counter-centring section that can be joined with the centring section of the holding fixture of the boring head.

2. A rock anchor according to claim I wherein the centring section of the holding 15 fixture of the boring head has a funnel-shaped construction and tapers towards the free end of the boring head.

3. A rock anchor according to claim I or claim 2 wherein a wall section of the centring section, surrounding the holding fixture of the boring head, has a concave construction. 20

4. A rock anchor according to any one of claims I to 3 wherein a wall section of the counter-centring section surrounding the end region of the free end of the mixing element has a convex construction. 25

5. A rock anchor according to any one of claims 1 to 4 wherein the diameter of the centring section of the holding fixture of the boring head is greater than the diameter of the counter-centring section of the free end of the mixing element.

6. A rock anchor according to any one of claims 1 to 5 wherein the counter-centring 30 section is formed on the free end of the mixing element from a plurality of centring elements. 10

7. A rock anchor according to claim 6 wherein the centring elements are symmetrical relative to the longitudinal axis of the internal body tube.

8. A rock anchor according to any one of claims I to 7 wherein a stop is provided in the 5 holding fixture of the boring head for the mixing element.

9. A self-boring rock anchor substantially as herein described with reference to any one of the embodiments of the invention illustrated in the accompanying drawings and/or examples.