Patent Application
20150139741
The present invention relates to a tool for installing a mine roof support and, more particularly, to a tool for installing a mine roof support including roof bolt and a domed support plate having a dome on one side and a flat surface on the other side.
In mine work, such as salt or coal mining, or in underground construction, such as tunnels or other excavations, it is necessary to support the roof of the excavation to prevent cave-ins. Among the most common means presently in use for effecting such support are roof bolts, which are inserted into bore holes and hold a metal support plate against the roof surface.
Prior art reveals two types of roof bolt installations. In the first, the support plate is installed dome-side facing the floor and the flat-side against the roof surface. The installation suffers from a serious drawback. The roof surface is generally not horizontal, but has undulations in its surface. The support plate is therefore not flush against the roof, and provides less than optimal support. When the plate is not horizontal, stresses on the support plate and bolt are uneven, resulting a weaker support system, and possible failure of the plate or bolt. Also, in some mines the strata shift horizontally. When the surface of the roof in the vicinity of the plate is uneven, there is a greater chance that horizontal shifting will cause bolt failure by preventing movement of the bolt.
In the second, as shown in U.S. Pat. Nos. 8,052,353 and 7,708,087, the disclosures of which are hereby incorporated by reference, a concave surface is drilled into the roof and the domed-side of the support plate is inserted into the concave recess. This installation method provides less than optimal support. The dome in the support plate provides structural integrity to the support plate. However, when the dome is facing the roof, there is a greater chance that the vertical pressure on the support plate will crush the dome.
A roof bolt installation tool and installation method is needed which overcomes these deficiencies of the prior art.
A roof bolt installation tool includes a central drill bit. A plate surrounds the central drill bit and has radial drill bits attached thereto such that when the central drill bit rotates, the plate rotates. The plate can include radial arms and the radial drill bits can be removably attached to the radial arms. In one embodiment, the radial drill bits are attached to the radial arms by C-clips.
A boot surrounds the plate and is rotationally isolated from the plate and central drill bit. The boot can be made from flexible material such as rubber. The boot can be rotationally isolated from the drill bit such that it does not rotate when the drill bit rotates. One method of rotational isolation is through the use of a bearing. In one embodiment, a base plate is beneath the plate and the boot attaches to the base plate by bolts, although other attachment methods are available.
A roof bolt and support plate can be installed by drilling a substantially vertical center hole into the mine roof. Simultaneously, a substantially horizontal recessed surface is cut in the mine roof. The roof bolt and support plate are installed into the mine roof such that the roof bolt is substantially vertical. The flat surface of the support plate contacts the mine roof and is substantially horizontal. The bolt head does not project beneath the mine roof in the vicinity of the recessed surface.
The foregoing and other objects, features, and advantages of the invention will be apparent from the following drawings and more particular description of the preferred embodiments of the invention.
Throughout the following description, specific details are set forth in order to provide a more thorough understanding of the invention. However, the invention may be practiced without these particulars. In other instances, well known elements have not been shown or described in detail to avoid unnecessarily obscuring the disclosure. Accordingly, the specification and drawings are to be regarded as illustrative rather than restrictive. It is to be further noted that the drawings are not to scale.
Radial bits 30 are attached to the radial arms 24. The radial drill bits 30 have cutting tips 38 which are in substantially the same plane as one another so that they cut a substantially planar surface. A base plate 40 is spaced apart from the plate 20. The base plate 40 and the plate 20 are rotationally isolated from one another by a bearing 36. A boot 50 is attached to the base plate 40 by bolts 52. Those of ordinary skill in the art will understand that other attachment methods are possible. The bolt heads 54 of bolts 52 are shown in
As will be apparent to those skilled in the art in light of the foregoing disclosure, many alterations and modifications are possible in the practice of this invention without departing from the spirit or scope thereof.
