Patent Application
20090245944
The present disclosure relates generally to roof support devices used in underground mining operations, and more particularly, to low-profile roof support devices.
In mining operations, bolts are often used to support the roof of the mine. Typically, a bore is drilled into the rock formation that forms the mine roof, and then a mine roof bolt is placed in the bore and secured by a fast-curing resin material or other suitable substance. The roof bolt, which can be formed of wire strands woven or wound together to form a cable, engages a widened bearing plate that bears against a portion of the roof, thus holding a portion of the roof in place.
One approach for installing such bolts is to drill an over-sized bore into the rock and then insert one or more resin cartridges into the bore. The elongated cable portion of the mine roof bolt is then forced into the bore, and rotated. This process ruptures the resin cartridges and mixes the two resin components together within the space between the cable portion of the bolt structure and the over-sized bore.
Such systems typically include a wedge barrel. The wedge barrel provides a bearing surface so that the tensile load carried by the elongated cable bolt can be suitably transferred to the bearing plate. The wedge barrel is commonly joined to the cable bolt by a plurality of wedges which are wedged between the cable itself and an inside tapered surface of the wedge barrel prior to installation of the roof bolt. Using a suitable tool, the wedge barrel is spun to rotate the cable within the bore as mentioned above. So configured, the bearing plate and wedge barrel can intrude upon the workspace within the mine because they extend below the mine roof.
The present disclosure provides a low-profile mine roof support device comprising a plate and a barrel. The plate comprises a bore and a seating surface disposed adjacent to the bore and is adapted to be abutted against a mine roof. The barrel comprises a first end and a second end. The barrel defines a nose portion disposed at the first end and a shoulder portion disposed at the second end. The nose portion defines a tapered bore adapted to receive a cable and at least one wedge for securing the cable in the barrel and the plate against the mine roof. The shoulder portion can comprise either a recess for receiving an internal drive mechanism or a nut for accommodating an external drive mechanism, and additionally defines a convex external surface. The convex external surface of the shoulder portion has an average diameter that is greater than an average diameter of the nose portion such that it removably engages the seating surface of the plate. So disposed, the nose portion passes through the plate and a majority of the barrel extends beyond the plate away from the shoulder portion and into a drilled hole in the mine roof, thereby minimizing the extent to which the barrel extends into the workspace of the mine.
The examples described herein are not intended to be exhaustive or to limit the scope of the invention to the precise form or forms disclosed. Rather, the following embodiments have been chosen to provide examples to those having ordinary skill in the art.
Referring now to
As illustrated in
Further still, as depicted in
Similar to the external surface 16a of the nose portion 16, the external surface 18a of the shoulder portion 18 converges from a beginning end 19 disposed at the second end 14b of the barrel 14 to a terminal end 25 disposed at the interface 21 between the nose portion 16 and the shoulder portion 18. So configured, the convex external surface 18a of the shoulder portion 18 has maximum diameter D2max, a minimum diameter D2min, and an average diameter D2. The minimum diameter D2min occurs generally adjacent to the interface 21 with the nose portion 16 of the barrel 14. The maximum diameter D2max occurs at the beginning end 19, which constitutes the second end 14b of the barrel 14. The average diameter D2 of the convex external surface 18a of the shoulder portion 18 is larger than the average diameter D1 of the convex external surface 16a of the nose portion 16.
Referring back to
In the disclosed embodiment, the first plane P1 is parallel to the second plane P2 such that the first and second surfaces 24, 26 are parallel to each other at least in the region immediately surrounding the through-bore 28. The through-bore 28 comprises a generally cylindrical bore extending between the first and second surfaces 24, 26 of the roof plate 12. Accordingly, the roof plate 12 defines a circular seating surface 30 at the interface between the second surface 26 and the through-bore 28. The through-bore 28 and seating surface 30 each have a diameter D3 sized and configured to receive the nose portion 16 of the barrel 14. Therefore, the diameter D3 of the through-bore 28 and seating surface 30 is larger than the maximum diameter D1max of the external surface 16a of the nose portion 16.
Moreover, the diameter D3 of the through-bore 28 and seating surface 30 is larger than the minimum diameter D2min of the external surface 18a of the shoulder portion, as well as smaller than the maximum diameter D2max of the external surface 18a of the shoulder portion 18. So configured, the shoulder portion 18 seats against the seating surface 30, and more particularly, the external surface 18a of the shoulder portion 18 seats against the seating surface 30. Because the external surface 18a of the disclosed embodiment of the shoulder portion 18 is convex, the barrel 14 can pivot relative to the plate 12.
Finally, as mentioned above, the barrel 14 of the presently disclosed embodiment of the roof support device 10 further includes the bore 36 for receiving a cable and accommodating the wedges 37. Moreover, the barrel 14 includes a recess 38 for receiving a nut (not shown) or wrench (not shown) of an internal drive mechanism, for example, which can be used to secure the mine roof support device 10 to a mine roof.
The bore 36 comprises a tapered bore that diverges from the first end 14a of the barrel 14 toward the second end 14b of the barrel 14. More specifically, with reference to
As illustrated in
While the recess 38 has been described as including a square cross-section, other configurations are intended to be within the scope of the invention. Further, while the barrel 14 has been described as including the recess 38 for receiving a nut or wrench, for example, thereby defining an “internal drive” barrel 14, an alternative embodiment of the barrel 14 can comprise an “external drive.” For example, one alternative embodiment of the barrel 14 can include the shoulder portion 18 of the barrel 14 being shaped to accept an external drive mechanism. For example,
Referring back to
Nevertheless, the cable (not shown) that suspends from the mine roof is received within the tapered bore 36 of the barrel 14 and secured thereto with the wedges 37 in a known manner. The thrust from the bolter seats the barrel 14 against the roof plate 12. As described above, the external surface 18a of the shoulder portion 18 of the barrel 14 seats against the seating surface 30 of the roof plate 12. More specifically, because the seating surface 30 of the presently disclosed embodiment is defined by the interface between the second surface 26 of the roof plate 12 and the through-bore 28, the seating surface comprises a circular edge of the roof plate 12. So configured, the convex external surface 18a of the shoulder portion 18 of the barrel 14 is in line contact with the seating surface 30. During installation, the curvature of the external surface 18a can advantageously assist in aligning the barrel 14 relative to the roof plate 12 even when the mine roof, for example, is not very flat. Moreover, the line contact between the shoulder portion 18 of the barrel 14 and the seating surface 30 of the roof plate 12 minimizes friction therebetween, which can also assist in aligning the barrel 14 relative to the roof plate 12 during installation by enabling the barrel 14 to easily pivot relative to the roof plate 12 if required. Furthermore, the generally tapered external surface 16a of the nose portion 16 can assist in the installation of the roof support device 10 by facilitating alignment of the barrel 14 with the bore 28 in the plate 12.
Still referring to
More specifically, the nose portion 16 intersects the first surface 24 of the roof plate 12, thereby also intersecting the first plane P1. No portion of either the nose portion 16, the tapered bore 36, or the wedges 37 extends beyond the second surface 26 of the plate 12 toward the shoulder portion 18 of the barrel 14. In fact, as depicted in
Additionally, as depicted in
Referring back to
Moreover, preferably, the radius R1 of the profile of the external surface 18a of the shoulder portion 18 is approximately 1.0″ (25.4 mm), the radius R2 of the external surface 16a of the nose portion 16 is approximately 3.5″ (88.9 mm), a radius of the concave interface 21 between the shoulder portion 18 and the nose portion 16 can be approximately 0.25″ (6.4 mm), and a radius of the convex bull-nosed surface 23 disposed at the first end 14a of the barrel 14 can be approximately 0.19″ (4.8 mm). The minimum diameter D1min of the external surface 16a of the nose portion 16 can be approximately 1.03″ (26.3 mm), the maximum diameter D1max of the external surface 16a of the nose portion 16 can be approximately 1.72″ (43.7 mm), and the average diameter D1 of the external surface 16a of the nose portion 16 can be approximately 1.38″ (35 mm). The minimum diameter D2min of the external surface 18a of the shoulder portion 18 can be approximately 1.62″ (41.2 mm), the maximum diameter D2max of the external surface 18a of the shoulder portion 18 can be approximately 2.12″ (53.9 mm), and the average diameter D2 of the external surface 18a of the shoulder portion 18 can be approximately 1.87″ (47.5 mm).
One advantage provided by the disclosed embodiment of the mine roof support device 10 is that it extends a shorter distance below the mine roof and into the mine than a conventional mine roof support device. Conventional mine roof support devices can extend in the range of approximately 2.2″ (5.5 cm) to approximately 2.6″ (6.6 cm) below the mine roof. To the contrary, because the disclosed embodiment of the barrel 14 includes a nose portion 16 that extends substantially through the plate and into the mine roof, and which completely contains the tapered bore 25, the shoulder portion 18 only requires a minimal longitudinal dimension L2 such that the shoulder portion 18 only extends approximately 0.64″ (16.2 mm) below the second surface 26 of the roof plate 12. In the embodiment depicted in
Therefore, in light of the foregoing, a mine roof support device 10 constructed in accordance with the disclosed embodiment provides for a low-profile mine roof support 10 that can be installed adjacent an underground mine roof with minimal intrusion into the workspace of the mine.
In addition, the presently disclosed barrels 14 reduce the extent to which the barrel 14 extends into the workspace of the mine without substantially sacrificing the working length of the tapered bore 36. For example, conventional barrels can have a total barrel length of approximately 2.7″ (6.92 cm), while the disclosed embodiment of the barrel 14 includes an overall length L of approximately 2.39″ (60.6 mm). Thus, the barrel 14 is sufficiently dimensioned to define an internal bore 36 that is sufficiently dimensioned to receive conventional wedges 37 and generate sufficient force to secure a tensioning cable therein while minimizing mine intrusion. In the disclosed embodiment, the tapered bore 36 includes a longitudinal dimension that is approximately equal to the longitudinal dimension L1 of the nose portion 16, which is approximately 1.71″ (43.4 mm). Additionally, in a preferred embodiment, the first end 36a of the tapered bore 36 includes a diameter of approximately 0.71″ (17.9 mm), and the second end 36b includes a diameter of approximately 1.125″ (28.6 mm).
Moreover, as described, the line contact between the convex external surface 18a of the shoulder portion 18 of the barrel 14 and the seating surface 30 of the plate 12 provides for reduced friction to enable the barrel 14 to easily align itself during installation. However, alternative embodiments of the seating surface 30 can include geometries other than the circular edge between the through-bore 28 and the second surface 26 of the plate 12. For example, the seating surface 30 can include a frustoconical surface, which would provide a surface contact between the barrel 14 and the roof plate 12. Another alternative seating surface 30 could include a rounded surface, i.e., a bull-nosed surface, which would also provide a line contact. Therefore, the seating surface 30 is not limited to that which is described herein.
While the roof plate 12 has been disclosed herein as comprising first and second surfaces 24, 26 disposed in parallel planes P1, P2, respectively, in the region surrounding the through-bore 28, an alternative embodiment of the roof plate 12 can include first and second surfaces 24, 26 completely disposed within the respective first and second planes P1, P2.
Moreover, in a further alternative embodiment, the roof plate 12 can include a curved roof plate such as that depicted in
Generally, the arrangement of the barrel 14 and the roof plate 12 depicted in
While the roof plate 12 depicted in
Finally, while the nose and shoulder portions 16, 18 of the barrel 14 have been described herein as including convex external surfaces 16a, 18a, alternative embodiments can be otherwise designed. For example, in one embodiment, either or both of the nose and shoulder portions 16, 18 can be generally frustoconical external surfaces 16a, 18a. In another alternative embodiment, the nose portion 16 can have a generally frustoconical external surface 16a and the shoulder portion 18 can have any other shape external surface 18a. Therefore, the invention is not limited to the specific embodiments disclosed herein.
Accordingly, it will be appreciated that the details of the various embodiments discussed herein are not intended to be mutually exclusive. Thus, various aspects and details of the disclosed examples can be interchanged.
Numerous additional modifications and alternative embodiments of the invention will be apparent to those skilled in the art in view of the foregoing description. This description is to be construed as illustrative only, and is for the purpose of teaching those skilled in the art the best mode of carrying out the invention. The details of the structure and method may be varied substantially without departing from the spirit of the invention, and the exclusive use of all modifications which come within the scope of the appended claims is reserved.
