1. Field of the Invention
This invention relates to a truss shoe with a wedge retaining sleeve, and more particularly, to a truss shoe having a wedge retaining sleeve, or locking tube to detachably secure a cable retention assembly in the passageway of a cable receiving section of the truss shoe.
2. Discussion of the Presently Available Technology
Truss-type mine roof supports are well known in the art of supporting the roof of an underground passageway, such as a mine passage. A basic truss system includes one or more rods extending horizontally the width of the mine passage adjacent the roof and connected at their ends to anchor bolts, which extend at an angle adjacent the ribs of the passage into the rock strata over a solid pillar. The rods are tensioned and vertical components of compressive forces are transmitted into the solid material over the pillars, as opposed to the unsupported rock material immediately above the passage.
With this arrangement, a truss system shifts the weight of the rock strata from over the mined-out passage back onto the pillars. Conventionally, holes are drilled into the mine roof at a 45° angle from the horizontal adjacent to the mine rib so that the holes extend into the supported rock structure over a pillar.
Once the holes are drilled at an angle into the strata over the pillars at the rib line, anchor bolts are inserted into the drilled holes and are secured in place using mechanical expansion shell assemblies and/or a resin made from a mixture of a resin component and an epoxy component. Before the bolts are inserted in the drilled holes, truss shoes or bearing blocks are positioned on the bolt at the emergent end of the bolt from the hole. As the bolts are securely anchored in the drilled holes, the bearing surfaces of the truss shoes or bearing blocks are compressed into engagement with the mine roof.
For an uneven mine roof or a roof having severely potted areas, the truss shoe preferably has sufficient bearing surface to contact the mine roof so that the truss shoe is correctly positioned for engagement with the horizontal truss members. Once the truss shoes are securely positioned at the mine roof adjacent the ribs, the horizontal truss members are assembled and connected to the truss shoes. The truss members are tightened to a preselected load to exert tension on the truss members so that the weight of the rock strata over the mined out area beneath the roof is shifted along the horizontal truss members upwardly into the solid rock strata over the pillars at the rib line.
The truss hardware is connected under tension to the truss shoes that are held tightly against the mine roof by the anchored angle bolts. A wide variety of truss hardware is commercially available to form a truss system between the anchored angle bolts. For example and not limiting to the discussion, U.S. Pat. No. 7,261,494 (hereinafter also referred to as “USPN '494”) to the Jennmar Corporation discloses a cable truss system including a pair of truss shoes, a pair of inclined bolts, and a truss assembly. Each truss shoe attaches to a roof through an inclined bolt and includes a surface for contacting the roof and a truss supporting member. The truss assembly extends between the truss supporting members of the pair of truss shoes for applying an uplifting force to the roof to support the roof above the passage. The truss assembly includes a pair of cables engaged to the truss shoes attached to the roof.
Several non-limiting embodiments of truss shoes are disclosed in USPN '404. Of particular interest in this discussion is the truss shoes shown in FIGS. 15-18 of USPN '404. In general, the truss shoe includes a bolt receiving end portion to receive the bolt that attaches the truss shoe to the roof and an opposite cable receiving and retaining end portion to receive an end of a cable and to secure the cable to the truss shoe. The cable receiving and retaining end portion includes a tapered passageway for receiving a wedge or cone-shaped retention assembly. The retention assembly has three pieces held together by a flexible band and has an expander to bias the pieces away from one another to pass a cable into an end of the retention assembly.
The retention assembly having the expander is placed in the passageway of the assembly and secured in the passageway by a washer. More particularly, the bottom portion of the washer is placed in a groove formed in the shoe, and the upper portion of the washer is secured in position by a tab bent over the top of the washer. In the event the expander moves out of the retention assembly during the handling and shipping of the truss shoe, or it is necessary or desired to remove the retention assembly from the passageway of the truss shoe, the washer is removed by lifting the tab and lifting the washer from the groove in the truss shoe. After a retention assembly is placed in the passageway, the washer is secured over the passageway as previously discussed.
Although the truss shoes of USPN '494 discussed above are acceptable, there are limitations. More particularly, bending the tab toward or away from the top of the washer causes fatigue of the tab, and the tab brakes from the truss shoe. When the tab breaks from the truss shoe, the washer is usually secured in position by welding the top of the washer to the truss shoe. As is appreciated by those skilled in the art, breaking the weld to release the washer from, and welding the washer to, the truss shoe is time consuming.
As can be appreciated by those skilled in the art, it would be advantageous to provide an arrangement for securing the cable retention assembly in, and for removing the cable retention assembly from, the passageway of the cable receiving section of a truss shoe that does not have the limitations of the presently available arrangements, e.g. the washer and tab or weld arrangement discussed above.