Fastening element for use in mining and tunnel construction

Abstract

A fastening element for use in mining a tunnel construction, has a base body (12; 32; 42); and a plurality of weakenings (14, 15; 34, 35; 44, 45; 54) provided on an outer surface (13; 33; 43; 53) of the base body and a cross-section of which provides a break-off location and which are formed as a spiral extending along a longitudinal extent of the base body (12; 32; 42; 52).

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a fastening element for use in mining and tunnel construction and having a base body on the outer surface of which a plurality of weakenings, a cross-section of which forms a break-off location, is provided.

2. Description of the Prior Art

In mine and tunnel construction, the ceilings and side walls are secured with chemically or mechanically anchorable, bar-shaped fastening elements. Such fastening elements are also called as rock anchors. The base body of the fastening element is formed with a solid or hollow cross-section and have a round or polygonal outer circumference. E.g., in coal mine construction, the so-called longwalls are secured to further walls. During mining of coal with mining power tools such as, e.g., coal rollers or coal planes, the fastening elements, which secure the side walls, are destroyed or cut. The mined coal, together with pieces of fastening elements produced during mining, are transferred to the surface by conveyor belts. The pieces of the fastening elements, which remain in the coal, contaminate the coal and, therefore, must be separated. In addition, the pieces of fastening elements remaining in the coal, can interfere with transportation of the coal by conveyor apparatuses.

International Publication WO2008/051728 discloses a fastening element for use in mining and tunnel construction designed for securing side walls and having a base body made, preferably, of steel and provided on its outer side with a plurality of spaced from each other, radially extending weakenings the cross-section of which forms a break-off location of the fastening element. During mining of coal, the produced separate pieces of the fastening element, which have a certain length corresponding to the distance between the weakenings, are separated from the coal with magnets and by flotation.

The drawback of the known fastening element, especially of a chemically anchored fastening element, consists in that the base body upon being stricken by a mining tool, is not separated at break-off locations. As a result, partially bent pieces having sharp edges that can damage the conveyor belt, are formed.

Further, too long pieces of the fastening element can interfere with the transportation of the mined coal.

Accordingly, an object of the present invention is to provide a fastening element for use in mining and tunnel construction, in particular, for a coal mining industry, and which would not have the above-mentioned drawbacks.

Another object of the present invention is to provide a fastening element for use in mining and tunnel construction, in particular, for a coal mining industry and which can be easily separated in individual pieces independent on the type of anchoring of the fastening element.

SUMMARY OF THE INVENTION

These and other objects of the present invention, which will become apparent hereinafter are achieved by forming the weakenings as spirals extending in the longitudinal direction of the base body.

Because the weakenings of the cross-section of the base body continuously extend at least along a major part of the longitudinal extent of the base body, it is insured, independent on the type of anchoring of the fastening element, that the mining tool always strikes the base body at a location in which the base body cross-section is weakened. Therefore, the inventive fastening element is easily broken up. The weakening of the cross-section is effective essentially when a load is applied transverse to the longitudinal extent of the base body, so that the fastening element is preloaded in the direction of the longitudinal extent of the base body.

Advantageously, the fastening element is made of metal, in particular, steel, so that upon break-up, e.g., comminuting of the fastening element by the mining tool, the fastening element breaks into correspondingly small pieces. These broken-up, by the mining tool, pieces can be easily separated from the mined coal with a magnetic separator and by flotation. The broken-up pieces of the fastening element have, in accordance with the arrangement of the break-up locations, predetermined sizes which are so selected that they would not damage the conveyor belt during transportation of the mined coal.

Preferably, at least two weakenings have different direction of rotation so that these weakenings cross each other at least once along the longitudinal extent of the base body. Thus, upon the base body being struck by a mining tool, breaking of the fastening element in predetermined sections, e.g., pieces is advantageously insured.

According to an alternative embodiment, at least two weakenings have different gradients which likewise insures that the two weakenings cross each other at least once along the longitudinal extent of the base body. Thus, upon the base body being struck by the mining tool, breaking of the fastening element in predetermined sections or pieces is advantageously insured.

The crossing each other weakenings form a grid structure on the outer surface of the base body, whereby the fastening element is preloaded by a high preload force despite of the weakening of the cross-section.

Advantageously, the base body is formed tubular, whereby it is easily broken up by the mining tool, while simultaneously having a smaller weight in comparison with a base body with a solid cross-section.

Advantageously, at least one of the weakenings provided an outer side of the base body, is formed as a recess that can be easily formed.

Advantageously, the recess has a depth measured from the outer surface of the base body and corresponding to 0.01 to 0.3 times of an outer diameter of the base body. More advantageously, the recess depth correspond to 0.1 to 0.2 times of the outer diameter of the base body. Under outer diameter of the base body, in this connection, an outer core diameter of the base body, without any profile shapes and thread elevation, is understood. Such a recess insures an adequate weakening of the cross-section of the base body, which enables an easy break-up of the fastening element when it is struck by the mining tool, and simultaneously insures application of an adequate preload in direction of the longitudinal extent of the base body for preloading the fastening element.

Advantageously, the weakenings includes several weakenings extending in a same direction and circumferentially offset relative to each other. Thereby, an adequate weakening of the cross-section of the fastening element in the longitudinal direction of the base body is achieved. Advantageously, the extending in the same direction, weakenings simultaneously are uniformly distributed about the entire circumference of the base body at the same angular distance from each other.

Advantageously, the weakenings are formed by a partial thermal treatment of the base body and which can be easily integrated in the manufacturing process of the fastening element. Dependent on the type of the material of the base body, the thermal treatment can influence the strength of the fastening element, at least in some regions. Advantageously, the partial thermal treatment is effected by laser welding, e.g., using a CO₂-Laser.

According to an alternative embodiment of the present invention, the weakenings of the cross-section are formed by a partial deformation of the base body. Thereby, during formation of the weakenings, the treated material is displaced sidewise, becoming compressed in some regions. Advantageously, the weakenings are formed by a rolling process directly on the base body of the fastening element. The weakenings are formed, e.g., on the base body after the base body has been formed or during formation of the base body.

Advantageously, the weakenings are formed by squirting, and the produced depressions extend toward the middle point of the cross-section of the base body, whereby, e.g., with a round base body, on the inner cross-section of the base body, in some regions, projecting inwardly projections are formed. These projections can serve as distance holder or as guide sections for a component arranged additionally in the base body such as an inner tube for receiving an ejectable mass. The squirtings can be formed, e.g., by rollers or with non-passing-through dies.

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 side cross-sectional view of a fastening element according to the present invention in a set condition;

FIG. 2 a schematic view illustrating removal of pieces of the fastening elements from extracted coal;

FIG. 3 a side view of a second embodiment of the base body of the inventive fastening element;

FIG. 4 a cross-sectional view of the base body shown in FIG. 3 along line IV-IV in FIG. 3 at an increased, in comparison with FIG. 3, scale;

FIG. 5 a side view of a second embodiment of the base body of the inventive fastening element; and

FIG. 6 a partial cross-sectional view of a fourth embodiment of a fastening element according to the present invention.

Basically, in the drawings, the same elements are provided with same reference numerals.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A base body 12 of a fastening element 11 according to the present invention which is designed for use in mines and tunnel construction and which is shown in FIG. 1, is formed of steel. The base body, 12 is provided on its outer side 13 with several weakenings 14 and 15 the cross-section of which forms a break-off location. The weakening 14 and 15 are formed as spirals and continuously extend along the entire longitudinal extent of the base body 12. The weakening 14 has a flatter gradient than the weakening 15 so that the weakenings 14 and 15 cross each other many times along the longitudinal extent of the base body 12. Additionally, on the outer side 13 of the based body 12, there can be provided a shaped profile (not shown) for a better anchoring of a chemically anchorable fastening element 11.

Such a fastening element 11 is anchored in a preliminary formed borehole 7 with a hardenable mass 8 for securing, e.g., a side wall of coal stratum 6, and is pre-loaded, e.g., with a tension nut 9 (see FIG. 1). For mining the coal stratum 6, e.g., a schematically shown coal roller is used as a mining power tool 5 which, when striking the base body 12 of the fastening element 11, breaks up breaks up the fastening element 11. The mined coal, together with broken up pieces 16, 17 of the fastening element 11, are removed by a conveyor belt 21 (FIG. 2). Because the base body is formed of a magnetizable metal, with a magnetic separator 23, a high separation efficiency or separation ratio of the broken-up pieces 16, 17 from then mined coal 22 is insured. For a 100%-removal, finally, flotation is carried out in a vessel 24 and during which the pieces 17, which still remain after initial separation in the magnetic separator 23, are removed.

A fastening element 31, which is shown in FIGS. 3-4, has a tubular base body 32. On its outer side 33, the base body 32 is provided with several weakenings 34, 35 which are provided on the outer surface 33. The weakenings 34, 35 each has a shape of a spiral and extends continuously along the entire longitudinal extent of the base body 32. The weakenings 34, 35 have different rotational directions. The weakenings 34 and the weakening 35, are circumferentially offset relative to each other, with the angular region W between separate, extending in the same direction weakenings 34 and 35 is the same and amounts to 120° in the embodiment shown in the drawings.

The weakenings 34 and 35 are formed, respectively, as recesses provided on the outer surface 33 of the base body 32, and are formed by a partial thermal treatment of the base body 32 by laser treatment. The recesses have a depth T from the outer surface 33 of the base body 32, with the depth T corresponding to 0.1 of the outer diameter D of the base body 32. Advantageously, all of the recess-shaped weakenings 34 and 35 have the same thickness T which enables an easy manufacturing and easy breaking-up of the base body 32 and, thus, of the fastening element 31.

A fastening element 41, which is shown in FIG. 5, likewise has a tubular base body 42 on the outer side 43 of which weakenings 44, 45 are provided. The weakenings 44, 45 are formed, in cross-section, by a partial deformation of the base body 42 by a rolling process, e.g., a roll break-in process.

FIG. 6 shows a fastening element 51, having a section of a tubular base body 52 on the outer surface 53 of which one weakening 54 is provided and which is formed by squirting. The produced depressions 56 extend in the direction of the middle point of the cross-section of the base body 52. The depressions 56 form a spacing holder for an inner tube 61 located in the base body 52 and serving for receiving an ejectable mass 62 with which the fastening element 51 is provided.

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 art. It is therefore 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 fastening element for use in mining and tunnel construction, comprising a base body (12; 32; 42); and a plurality of weakenings (14, 15; 34, 35; 44, 45; 54) provided on an outer surface (13; 33; 43; 53) of the base body, each formed as a spiral extending along a longitudinal extent of the base body (12; 32; 42; 52), a cross-section of the weakenings defining a weakened cross-section of the base body, thereby providing a break-off location of the base body.

2. A fastening element according to claim 1, wherein at least two weakenings (14, 15; 34, 35; 44, 45) have different directions of rotation.

3. A fastening element according to claim 1, wherein at least two weakenings (14, 15) have different gradients.

4. A fastening element according to claim 1, wherein the base body (32; 42) is tubular.

5. A fastening element according to claim 1, wherein at least one of the plurality of weakenings (34, 35; 44, 45) is formed as a recess provided on the outer surface (33; 43) of the base body (32; 42).

6. A fastening element according to claim 5, wherein the recess has a depth (T) measured from the outer surface (33) of the base body (32) and corresponding to 0.05 to 0.3 times of an outer diameter (D) of the base body (32).

7. A fastening element according to claim 1, wherein the plurality of weakenings comprises weakenings extending in a same direction and circumferentially offset relative to each other.

8. A fastening element according to claim 1, wherein a cross-section of the weakenings (34, 35) is formed by a partial thermal treatment of the base body (32).

9. A fastening element according to claim 1, wherein a cross-section of the weakenings (44, 45) is formed by a partial deformation of the base body (42; 52).

10. A fastening element according to claim 9, wherein the weakenings (54) are formed by squirting, with produced depressions (56) extending in direction of a middle point of a cross-section of the base body (52).