US20080286054A1

US20080286054A1 - Self-drilling rock anchor

Info

Publication number: US20080286054A1
Application number: US12/152,588
Authority: US
Inventors: Michael Bayerl; Wolfgang Ludwig; Kay Heemann
Original assignee: Hilti AG
Current assignee: Hilti AG
Priority date: 2007-05-16
Filing date: 2008-05-14
Publication date: 2008-11-20
Also published as: EP1992782A2; AU2008201909A1; AU2008201909A8; EP1992782A3; AU2008201909B2; CN101307694A; NZ567821A; ZA200801675B; AU2008201909B8; DE102007000277A1

Abstract

A self-drilling rock anchor includes a drilling head (16; 46) provided at one end (13) of the receiving body (12), an inner tube (21) for receiving a pressurable-out hardenable mass (26) and provided in the receiving body (12) and having an outlet opening (22) spaced from the drilling head (16; 46), and a mixing member (31; 61) displaceably supported in the inner tube (21), with the drilling head (16; 46) having a receptacle (18; 48) adjacent to the mixing member (31; 61) for receiving a free end (32; 62) of the mixing member (21; 61) and a through-opening (17) for the hardenable mass (26), and the receptacle (18; 48) of the drilling head (16; 46) having a centering section (20; 50) that cooperates with a counter-centering section (33; 63) provided at the free end (32; 62) of the mixing member (31; 61) adjacent to the drilling head (16; 46).

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a self-drilling rock anchor including a hollow cylindrical receiving body, a drilling head provided at one end of the receiving body, an inner tube for receiving a pressurable-out hardenable mass and provided in the receiving body and having an outlet opening spaced from the drilling head, a mixing member displaceably supported in the inlet tube, with the drilling head having a receptacle adjacent to the mixing member for receiving a free end of the mixing member and a through-opening for the hardenable mass.
2. Description of the Prior Art
Rock anchors are attachment elements which are used for stabilization of walls of hollow spaces such as tunnels, galleries, and the like and, in particular, for connecting rock regions adjacent to a wall with each other. In many cases, the regions which are located immediately adjacent to the wall and mechanical characteristics of which, in particular the load-carrying capacity, are reduced as a result of formation of hollow spaces, are connected to more remote, undamaged regions. The wall, in this regard, means the ceiling and side walls of a hollow space and also its bottom.
German Publication DE 103 01 968 A1 discloses a self-drilling rock anchor provided at the working tool side with a pressable-out mortar mass. The rock anchor is drilled in a constructional component. In the intermediate space between the inner tube and the receiving member and in the free space between the outlet opening of the inner space and the drilling head, at a dry drilling process, particles, which are commutated by the drilling head, so-called drillings, are aspirated. Alternatively, at a wet drilling process, rinsing water is fed to the drilling head through the intermediate space and the free space. In order to provide a sufficient intermediate space, spacers are provided on the inner tube. The spacers are separate elements or are formed during manufacturing of the inner tube. Upon reaching a desired setting depth, the mortar mass, which is located in the inner tube, e.g., is packed in a film bag, is squeezed out under pressure, with a mixing element which is located in front of the pressable-out mass, being displaceable in a receptacle of the drilling head. The squeezable-out mortar mass, e.g., a multicomponent mortar mass, upon further application of pressure, is mixed in the mixing element and is squeezed through the through-opening of the drilling head into the space that surrounds the rock anchor.
Because of the initially displaced mixing element, no hardenable mass penetrates in the intermediate space between the receiving member and the inner tube. In this way, the need in an expensive hardenable mass is limited to the amount necessary to fill the space between the outer body and the bore wall. After hardening of the mortar mass, the rock anchor is chemically anchored in the constructional component.
Dependent on the type of the constructional component, a plurality of rock anchors must be used for stabilization of walls of hollow spaces. Therefore, there is further a need, with such, rock anchors, to reduce their manufacturing costs.
Accordingly, an object of the present invention is to provide a rock anchor that can be economically produced in comparison with the known rock anchors.
Another object of the present invention is to provide a rock anchor that would insure pressing out of the pressable-out of the pressable-out mass into the space that surrounds the receiving member, almost without any loss of the hardenable mass.

SUMMARY OF THE INVENTION

These and other objects of the present invention, which will become apparent hereinafter, are achieved by providing a rock anchor of the type discussed above in which the receptacle of the drilling head has a centering section that cooperates with a counter-centering section provided at the free end of the mixing member adjacent to the drilling head. In this way, the free end of the mixing member, which is located adjacent to the drilling head, as a result of the press-out process, upon being displaced, is automatically received in the drilling head receptacle. This takes place without use of a separate spacer or an additional guide member arranged in the receiving tube such as, e.g., a ramp. When the free end of the mixing member impacts an edge of the drilling head adjacent thereto, the mixing member, as a result of the shape of the free end thereof, upon continuation of the press-out process, is deflected in the receptacle of the drilling head. As soon as the free end of the mixing member occupies a proper position in the centering section of the receptacle of the drilling head, the mixed hardenable mass can flow through the through-opening in the drilling head and fill the space that surrounds the receiving body.
Advantageously, the mixing member is formed of a plastic material and has, in particular, in the region of the counter-centering section of the free end of the mixing member, elastic deformation characteristics. Advantageously, the free end of the mixing member is provided, in the region of the counter-centering section, with slots extending parallel to the longitudinal axis of the inner tube. The slots advantageously insure elastic deformation characteristics of the counter-centering section upon joint displacement with the centering section of the receptacle of the drilling head.
During a drilling process, the inner tube, together with the pressable-out mass, can wobble, so that an adequate intermediate space between the inner tube and the receiving body for aspirating drillings or drilling dust or for feeding of rinsing water to the drilling head is insured.
The manufacturing costs of the inventive rock anchor in comparison with the known rock anchor are reduced, which is an important advantage of such a mass-produced element. Despite this, a perfect use of the self-drilling rock anchor is insured.
Advantageously, the centering section of the receptacle of the drilling head has a funnel shape and tapers toward the free end of the drilling head. This shape of the centering section facilitates joint displacement with the free conical end of the mixing member tapering in a direction of the drilling head.
Advantageously, a wall section of the centering section that surrounds the receptacle of the drilling head is formed concave. Thereby, during the displacement of the mixing member, an advantageous deflection of the free end of the mixing member in the receptacle of the drilling head is insured. In this connection, the term “concave” relates to the shape of the corresponding wall section. According to an advantageous embodiment, the wall section that surrounds the receiving space of the drilling head receptacle, forms a partially spherical receptacle.
Advantageously, a wall section of the counter-centering section that surrounds the end region of the free end of the mixing member is formed convex. Thereby, upon displacement of the mixing member, an advantageous deflection of the free end of the mixing member in the drilling head receptacle is insured. In this connection, the term “convex” relates to the shape of the corresponding wall section. According to an advantageous embodiment the wall section that surrounds the end region of the free end of the mixing member, forms a crowned or spherical shape of the free end of the mixing member.
Advantageously, the centering section of the receptacle of the drilling head has a diameter larger than a diameter of the counter-centering section of the free end of the mixing member. This insures that the free end of the mixing member can be received in the receptacle of the drilling head.
Advantageously, the counter-centering section is formed of several centering elements formed at the free end of the mixing member. The plurality of centering elements provide for deflection of the free end of the mixing member in the receptacle of the drilling head. It is particularly advantageous when the centering elements are arranged rotationally symmetrically with respect to a longitudinal axis of the inner tube, e.g., along a double-or-multiple rotational axis. Thereby, the free end of the mixing element can be deflected in the drilling head receptacle in each position of the inner tube.
Preferably, a stop for the mixing member is provided in the receptacle of the drilling head, which limits the displacement of the mixing member. The stop is formed, e.g., as a circumferential rim provided in the receptacle of the drilling head in the direction of the free end of the drilling head adjacent to the centering section. The stop would limit the displacement of the mixing member during the press-out process. This insures that the end region of the free end of the mixing member is not deformed, during its displacement, to an extent that the discharge of the mixed, pressed-out mass is restricted.
The novel features of the present invention, which are considered as characteristic for the invention, are set forth in the appended claims. The invention itself, however, both as to its construction and its mode of operation, together with additional advantages and objects thereof, will be best understood from the following detailed description of preferred embodiments, when read with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings show:

FIG. 1 A longitudinal cross-sectional view of a first embodiment of a rock anchor according to the present invention;

FIG. 2 a longitudinal cross-sectional view of a front portion of a second embodiment of the rock anchor according to the present invention; and

FIG. 3 a view at the free end of the mixing member of the rock anchor shown in FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A self-drilling rock anchor 11, which is shown in FIG. 1, has a hollow cylindrical receiving body 12, a drilling head 16 provided at a first, facing in the setting direction S, end 13 of the receiving body 12, and rotation application means 15, e.g., in form of a polygon connectable with a rotary drilling tool, and which is provided at an opposite, second end 14 of the receiving body 12. The drilling head 16 has a through-opening 17 and a receptacle 18 with a funnel-shaped centering section 20 tapering toward the free end of the drilling head 16.
In the receiving body 12, and inner tube 21 is arranged in which a pressable-out and hardenable mass 26, which is packed in a foil bag, is arranged. The inner tube 21 has an outlet opening 22 spaced from the drilling head 16. In the inner tube 21, between the hardenable mass 26 and the drilling head 16, there is provided a displaceably supported mixing member 31 in an end region of which at the free end 32 of the mixing member 31, there is provided a counter-centering section 33 that cooperates with the centering section 20 of the receptacle 18 of the drilling head 16.
A wall section of the centering section 20 of the receptacle 18 of the drilling head 16, which is adjacent to the mixing member 31, is formed concave. In the receptacle 18 of the drilling head 16, there is provided a stop 19 for the mixing member 31. A wall section of the counter-centering section 33, which surrounds the free end 32 of the mixing member 31, is formed convex. The diameter D1 of the central section 20 of the receptacle 18 of the drilling head 16 is larger than the diameter d1 of the counter-centering section 33 of the end region of the free end 32 of the mixing member 31.
Upon reaching a desired bore depth, the pressable-out mass 26 is ejected under pressure. At that, firstly the mixing member 31 is displaced in the direction of the drilling head 16 until the free end 32 of the mixing member 31 lies in the receptacle 18 of the drilling head 16.
Upon application of pressure further to the pressable-out mass 26, it is ejected through the opening 17 in the drilling head 16 and out of the rock anchor 11.
A self-drilling rock anchor 41, which is shown partially in FIGS. 2-3, is formed identically to the rock anchor 11 up to the shape of the centering section 50 of the receptacle 48 of the drilling head 46 and the counter-centering section 63 of the free end 62 of the mixing member 61, and identical parts are designated with the same reference numerals.
The wall sections that surround the centering section 50 are formed concave and have a diameter D2. At the free end 62 of the mixing member 61, there are provided several centering elements 64 which are arranged rotationally symmetrically with respect to a longitudinal axis 23 of the inner tube 21. The free ends of the centering elements 64 are adjacent to each other. The wall sections which surround the counter-entering section 63 and which correspond to the radially outer surfaces of the centering elements 64, form a convex or crowned shape of the end region of the free end 62 of the mixing member 61. The diameter d2 of the counter-centering section 63 is smaller than the diameter D2 of the centering section 50.
Though the present invention was shown and described with references to the preferred embodiments, such are merely illustrative of the present invention and are not to be construed as a limitation thereof and various modifications of the present invention will be apparent to those skilled in the not intended that the present invention be limited to the disclosed embodiments or details thereof, and the present invention includes all variations and/or alternative embodiments within the spirit and scope of the present invention as defined by the appended claims.

Claims

1. A self-drilling rock anchor (11; 41), comprising:

a hollow cylindrical receiving body (12);

a drilling head (16; 46) provided at one end (13) of the receiving body (12);

an inner tube (21) for receiving a pressurable-out hardenable mass (26) and provided in the receiving body (12) and having an outlet opening (22) spaced from the drilling head (16; 46);

a mixing member (31; 61) displaceably supported in the inner tube (21), the drilling head (16; 46) having a receptacle (18; 48) adjacent to the mixing member (31; 61) for receiving a free end (32; 62) of the mixing member (21; 61) and a through-opening (17) for the hardenable mass (26), and the receptacle (18; 48) of the drilling head (16; 46) having a centering section (20; 50) that cooperates with a counter-centering section (33; 63) provided at the free end (32; 62) of the mixing member (31; 61) adjacent to the drilling head (16; 46).

2. A rock anchor according to claim 1, wherein the centering section (20) of the receptacle (18) of the drilling head (16) has a funnel shape and tapers toward the free end of the drilling head (16).

3. A rock anchor according to claim 1, wherein a wall section of the centering section (50) that surrounds the receptacle (48) of the drilling head (46) is formed concave.

4. A rock anchor according to claim 1, wherein a wall section of the counter-centering section (63) that surrounds the end region of the free end of the mixing member (61) is formed convex.

5. A rock anchor according to claim 1, wherein the centering section (20; 50) of the receptacle (18; 48) of the drilling head (16; 46) has a diameter (D1; D2) larger than a diameter (d1, d2) of the counter-centering section (33; 63) of the free end (32; 62) of the mixing member (31; 61).

6. A rock anchor according to claim 1, wherein the counter-centering section (63) is formed of several centering elements (64) formed at the free end (62) of the mixing member (61).

7. A rock anchor according to claim 6, wherein the centering elements (64) are arranged rotationally symmetrically with respect to a longitudinal axis (23) of the inner tube (21).

8. A rock anchor according to claim 1, further comprising a stop (19; 49) for the mixing member (31; 61) provide din the receptacle (18; 48) of the drilling head (16; 46).