Hydraulic and earth engineering – Earth treatment or control – Rock or earth bolt or anchor
Reexamination Certificate
1999-08-27
2001-08-07
Pezzuto, Robert E. (Department: 3673)
Hydraulic and earth engineering
Earth treatment or control
Rock or earth bolt or anchor
C405S259100, C405S302200, C411S008000, C411S082000
Reexamination Certificate
active
06270290
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to tensionable cable mine roof bolts, in particular, a tensionable cable mine roof bolt which is adapted to be resin grouted and mechanically anchored in a mine roof bore hole.
2. Prior Art
Cable mine roof bolts are gaining popularity in the mining industry for their ease of handling and installation. Cable bolts are substantially easier to fit into a bore hole than the elongated rods of conventional rod bolt systems. Regardless of the height limitations in a mine, cable bolts may be adapted to bore holes of any length due to their flexibility. The strength capacity of cables exceeds that of conventional rod bolts and, therefore, cable is the preferred reinforcement for certain roof conditions.
Conventional cable mine roof bolts are installed by placing a resin cartridge including catalyst and adhesive material into the blind end of a bore hole, inserting the cable bolt into the bore hole so that the upper end of the cable bolt rips open the resin cartridge and the resin flows in the annulus between the bore hole and the cable bolt, rotating the cable bolt to mix the resin catalyst and adhesive and allowing the resin to set about the cable bolt. Typically, the resin is set after two to three minutes. Cable bolts have heretofore been primarily used as secondary roof support structures with tensionable rock bolts serving as the primary anchorage mechanism.
Tensionable cable bolts are the subject of U.S. Pat. No. 5,378,087 to Locotos and U.S. Pat. No. 5,525,013 to Seegmiller et al. Each of the bolts described therein are resin grouted at the blind end of a bore hole and following setting of the resin, they are tensioned by rotation of a nut on an externally threaded sleeve surrounding the free end of the cable. U.S. Pat. No. 5,531,545 to Seegmiller et al. and U.S. Pat. No. 5,556,233 to Kovago both disclose tensionable bolts with a mechanical anchor mounted on the upper end of the cable bolt and tensioning mechanisms disposed on their free ends for post-installation tensioning. These prior art cable bolts are tensionable and require two installation steps; namely, a first step to anchor the upper end of the cable bolt in the bore hole and a second step to tension the bolt.
U.S. Pat. No. 5,375,946 to Locotos discloses a cable bolt having a shaft connected at its upper end, the shaft bearing an expansion anchor. The expansion anchor is not directly connected to the cable, but instead, the shaft is coupled to the cable and the expansion anchor is threaded onto the shaft. This bolt necessitates the use of a sold shaft, similar to conventional bolts having mechanical anchors, for attachment of the expansion anchor. Coupling of the solid shaft to the cable remains problematic. Another drawback to the bolt is that it is difficult to determine the amount of tension exerted upon the bolt during installation.
It is an object of the present invention to provide a tensionable cable bolt having a plurality of locations of anchorage within a bore hole and which is tensionable to a predetermined load.
SUMMARY OF THE INVENTION
This object is met by the tensionable cable mine roof bolt of the present invention. In one embodiment, the cable bolt includes an elongated member having an upper portion adapted to be resin grouted within a bore hole in rock and a lower portion adapted to be mechanically anchored to the rock. The upper portion includes a length of multi-strand cable, whereby when the elongated member is rotated the lower portion anchors to the rock thereby tensioning the bolt and the upper portion simultaneously mixes resin within the bore hole. A drivehead is attached, such as by press fitting, to a lower end of the elongated member. When resin is inserted into the bore hole and the drivehead is rotated, the upper portion rotates and mixes the resin and the lower portion anchors to the rock.
The cable includes a first end, a second end and a mixing portion disposed between the first and second ends. The mixing portion may include a plurality of birdcaged portions of the cable or similar mixing devices. The birdcaged portions may include a nut positioned on the central strand of the cable.
The bolt lower portion may include an externally threaded shaft, preferably with twelve threads per inch, attached to the cable and a mechanical anchor threaded onto the threaded shaft. Preferably, the shaft is hollow and is in the form of a sleeve through which the cable extends. The sleeve may be swaged to the cable. Alternatively, the bolt may include a coupler body coupling the cable to the threaded sleeve.
The threaded sleeve bearing the mechanical anchor may be positioned on the cable between the bolt head and the mixing portion, for example, proximal to the mixing portion. The bolt may further include a stiffener tube surrounding a portion of the cable between the threaded sleeve and the bolt head.
A barrel and wedge assembly is attached to the cable between the drivehead and the shaft. The drivehead can be adapted to break away from the cable when the bolt is tensioned to a predetermined load or remain intact for post installation torque checks.
The cable includes a plurality of strands wrapped around each other. The mixing portion includes a region of the cable wherein the strands are spaced apart from each other. Preferably, the mixing portion includes a plurality of regions in which the strands are spaced apart from each other. The cable further includes a central strand and a plurality of surrounding strands and the bolt further includes a nut, the nut being received on the central strand in one of the mixing regions at a position about three feet from the cable second end. A fixing sleeve is mounted on the cable second end whereby the ends of each strand are fixed relative to each other within the fixing sleeve.
The present invention further includes a tensionable cable mine roof bolt for insertion into a bore hole in rock and adapted to be resin grouted. The cable bolt includes a bearing plate, a barrel and wedge assembly supporting the bearing plate and a multi-strand cable having a first end which is attached to the barrel and wedge assembly. The cable includes a resin mixing portion positioned on the cable distal from the first end. A drivehead is releasably mounted on the first end of the cable opposite the barrel and wedge assembly from the bearing plate. An externally threaded shaft is mounted on the cable between the bearing plate and the resin mixing assembly, and a mechanical anchor is threaded onto the shaft. The shaft may be swaged to the cable. When the bolt is rotated within the bore hole to mix the resin, the mechanical anchor engages the rock to permit tensioning of the bolt. The drivehead may be press fitted onto the cable and may be adapted to break away from the cable when the bolt is tensioned to a predetermined load or remain in place for post installation torque checks.
The mixing portion includes a plurality of regions wherein the strands of the cable are spaced apart from each other. The cable includes a central strand and a nut is received on the central strand in one of the mixing regions. Prior to installation of the bolt in the bore hole, an outside diameter of one of the mixing regions is larger than an inside diameter of the bore hole.
The present invention also includes a method of installing a cable mine roof bolt in a bore hole formed in the rock of the mine roof having the steps of placing a resin cartridge into the bore hole; inserting the cable mine roof bolt into the bore hole, the bolt having a drivehead mounted on the bolt at a first end thereof, the cable including a resin mixing portion distal from the first end, the bolt further including a mechanical anchor mounted on the bolt at a position between the drivehead and the resin mixing portion; and rotating the drivehead to simultaneously rotate the resin mixing portion and to engage the mechanical anchor with the rock thereby tensioning the bolt. The inventive method may further includes tensioning the bolt to a pred
Stankus John C.
Taylor Kendal L.
Jennmar Corporation
Pechhold Alexandra K.
Pezzuto Robert E.
Webb Ziesenheim & Logsdon Orkin & Hanson, P.C.
LandOfFree
Tensionable cable bolt does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Tensionable cable bolt, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Tensionable cable bolt will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2436628