TENSIONABLE BOLT WITH HANGER CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 60/809,212 filed May 30, 2006, which is hereby incorporated by reference in its entirety.

BACKGROTOfP OF THE INVENTION Field of the Invention

[0002] The present invention relates to a mine roof bolt anchored in a bore hole by mechanical anchoring and resin bonding. Prior Art

[0003] Typically, the roofs of mines are supported by inserting 4 to 6 feet long steel bolts into bore holes drilled into the roof. The bolts are then tightened to apply tension to the rock above, making the roof material more stable and supported. These bolts may be anchored into the rock by either a mechanical anchor with an expansion assembly at the end of the bolt or may be adhesively bonded to the rock with a resinous material. Both methods of anchoring may also be used on the same bolt.

[0004] Mechanically anchored roof bolts typically have an expansion assembly threaded onto one end of the bolt and a drive head for rotating the bolt. Between the drive head and the mine roof, a mine roof plate is positioned to brace the bolt. The expansion assembly usually includes a multi-prong shell supported by a threaded ring with a plug threaded onto the end of the bolt. When the bolt is inserted into the bore hole and rotated, the plug threads downwardly and causes the multi-prong shell to expand outward. The bolt rotates until the shell is tightly engaged with the rock surrounding the bore hole.

[0005] Bolts anchored with resin bonding material typically work by inserting a two component cartridge (one part curable resin and one part curing agent) into the blind end of the bore hole. The mine bolt is then inserted into the bore hole, rupturing the cartridge. The bolt is rotated about its longitudinal axis, shredding the cartridge and mixing the two components together. Rotation of the mine roof bolt continues until the resin fully cures, thereby bonding the bolt to the surrounding rock. Resin anchoring and mechanical anchoring may also be used in combination.

[0006] By either method of anchoring the mine roof bolt, there is a need to be able to rotate the bolt using a drive head. However, having a drive head permanently fixed to the end of the bolt limits the functionality of the driving end of the mine roof bolt. One solution has been to thread a nut onto the mine roof bolt at the driving end and include a stop (such as an

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interruption) in the threads below the nut to prevent the nut from coming off the bolt. In this manner, the nut can be threaded downwardly until it abuts the stop. Further rotational forces on the nut cause the bolt to rotate in one direction to mix the resin. After mixing is complete, rotation of the nut in the opposite direction tightens the nut against the bearing plate to compress the rock.

[0007] Such prior bolts not only require rotation in different directions when anchoring the bolt with a resin versus a mechanical expansion assembly, but also limit the functionality of the driving end of the bolt. The portion of the bolt below the stop is unusable for any other purpose, such as attaching accessories or holding cables. A need remains for improved functionality of the driving end of the bolt.

SUMMARY OF THE INVENTION

[0008] This need is met by the mine roof bolt of the present invention, which includes an elongated rod having a drive end and anchored end, the drive end bearing threads, a stop in the threads and a nut threaded onto the threads, wherein the stop is positioned to prevent threading of the nut in a direction of the anchored end beyond the stop. [0009] The present invention also includes a method of supporting a mine roof bolt having steps of inserting a mine roof bolt into a bore hole of a mine roof, the mine roof bolt comprising an elongated rod having a drive end and an anchored end, the drive end bearing threads and a stop on the threads; threading a nut onto the threads until the nut abuts the stop; and continuing to rotate the nut such that the mine roof bolt rotates within the bore hole and is anchored therein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Fig. 1 is a side-elevational view of the mine roof bolt of the present invention prior to anchoring with a drive nut;

[0011] Fig. 2 is a side-elevational view of Fig. 1, showing the mine roof bolt fully installed;

[0012] Fig. 3 is a side-elevational view of the mine roof bolt of Fig. 2 with a hanger threaded thereon; and

[0013] Fig. 4 is a side-elevational view of the mine roof bolt of Fig. 2 with the drive nut removed and a hanger threaded thereon.

DETAILED DESCRIPTION QF THE INVENTION

[0014] A complete understanding of the present invention will be obtained from the following description taken in connection with the accompanying drawing figures, wherein like reference characters identify the parts throughout.

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[0015] For the purposes of the following description, the terms "above," "below," "top," "bottom," "vertical," "horizontal," and derivatives thereof refer to the invention as oriented in the drawing figures. However, it is to be understood that the invention may assume alternative variations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings and described in the following specification are exemplary embodiments of the invention. Specific dimensions and other physical characteristics related to the embodiments disclosed herein are not considered to be limiting.

[0016] Referring to Figs. 1 and 2, a mine roof bolt 10 is shown placed into a bore hole 12 drilled into a rock formation 14 to support the rock formation 14 above an underground excavation site such as a mine passageway. The bore hole 12 is drilled to a pre-selected depth into the rock formation 14 as determined by the load bearing requirements. [0017] The bolt 10 includes an elongated rod 16 with an anchored end or blind end 18 to be positioned in the blind end of the bore hole 12 and a threaded drive end 20 that extends into the mine passageway from the open end of the bore hole 12. A roof or bearing plate 22 is placed flush with the opening of the bore hole 12 at the drive end 20. Other components (not shown) may be included adjacent the mine roof such as a mat or a mesh. A nut 24 is threaded onto drive end 20. Drive end 20 includes a stop 26 for preventing nut 24 from threading toward blind end 18 beyond a predetermined position. The stop 26 is shown in Figs. 1 and 2 as being an interruption in the threads of the drive end 20. Stop 26 may be produced by machine pressing or otherwise deforming threaded end 20 such that a threaded device cannot move past the stop 26. The manner of producing the stop 26 and the configuration thereof is not limited, provided that stop 26 prevents movement of nut 24 across the stop 26. In one embodiment, the stop 26 shown in Figs. 1 and 2 is produced by pinching opposing portions of the rod 16 at two radial locations, thereby disturbing the threads. This is not meant to be limiting as other structures for step 26 are contemplated, such as an additional component fixed to drive end 20.

[0018] An expansion assembly 28 is provided at the blind end 18 of the bolt 10. In one non-limiting embodiment, expansion assembly 28 includes a threaded tapered plug 30 and a multi-prong shell 32 supported by ring 34. The tapered plug 30 is threaded on the rod 16 into the inside of the expansion shell 32. Rotation of bolt 10 is accomplished by threading nut 24 upwardly on drive end 20 until nut 24 abuts stop 26. Continued rotation of nut 24 causes the entire bolt 10 to rotate. Upon rotation of the bolt 10 as shown in Fig. 2 (arrow A), plug 30 threads downwardly on rod 16 and forces shell 32 to expand and engage with a surface of the

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rock formation 14. Other expansion shell assemblies that may be used in the present invention include bail type shells in which a pair of expansion leaves is supported by a bail that extends over the end of the mine roof bolt and prevents expansion of the leaves from moving axially relative to the bolt until desired. Mine roof bolt 10 may be anchored mechanically, with or without adhesive anchoring. To adhesively anchor bolt 10, a dual component cartridge 36 of resin and curing agent is inserted at the blind end 18 of the bore hole 12. The bolt 10 is pushed upward until the blind end 18 ruptures the cartridge 36 releasing the curable resin and curing agent. Rotating the bolt 10 about its longitudinal axis mixes the components of the cartridge 36 to produce a resin composition 38 that flows downwardly around the bolt 10. The expansion assembly 28 may include a stop mechanism (not shown) such as disclosed in United States Patent No. 4,419,805 to Calandra, Jr., incorporated herein by reference. Such a stop device temporarily prevents expansion of the expansion shell during the stage of mixing resin with the bolt. As the resin cures, the expansion assembly 28 is prevented from rotating. Further rotation of the bolt 10 fractures the stop device, and the plug is again threaded downwardly on the rod 16 such that the expansion shell expands into gripping engagement with the rock 14 surrounding the bore hole 12.

[0019] The drive end 20 of the rod 16 is sized and configured such that after anchoring bolt 10 in bore hole 12, a free threaded portion 40 extends beyond nut 24 and into the mine passageway. An internally threaded accessory or device such as a hanger 42 may be threaded onto the free threaded portion 40 of the rod 16. Fig. 3 shows a hanger 42 having a nut portion 44 and a J-shaped portion 46 extending therefrom, but this is not meant to be limiting as other internally threaded components may likewise be threaded onto free threaded portion 40 as desired. As shown in Fig. 4, after anchoring of bolt 10, nut 24 may be removed from the bolt 10 and hanger 42 may be threaded onto free threaded portion 40.

[0020] While the present invention has been described with reference to a particular embodiment of a mine roof bolt and a method associated therewith, those skilled in the art may make modifications and alterations to the present invention without departing from the spirit and scope of the invention. Accordingly, the foregoing detailed description is intended to be illustrative rather than restrictive. The invention is defined by the appended claim 6, and all changes to the invention that fall within the meaning and range of equivalency of the claims are embraced within their scope.

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