Patent Application
20140178133
The present invention pertains to the field of subterranean excavation. More particularly, the present invention pertains to devices used to stabilize material forming the walls, roof, and pillars of a tunnel, room, or other subterranean excavation to prevent collapse of the material into the excavated space.
Coal mining in the United States is a major industry, reaching an all-time high in the production in 2008 at 1.17 billion short tons being mined in 25 states. Coal accounts for approximately half of all electricity produced in the United States, and provides 40% of the world's electricity needs.
Mining has always been a very dangerous activity, although in recent years improvements in technology have decreased the number of fatalities and accidents. Still, many fatalities and accidents occur due to a collapse of a tunnel roof or the collapse of a tunnel rib. A rib is defined as the side wall of a tunnel. Tunnels are developed in an engineered layout so that sufficiently sized pillars are left in place to support the overall mining system. Roofs have been supported by various means, and to various degrees, for the history of mining. In 2007, areas of the Crandall Canyon Mine in Utah collapsed due to pillar failures. A second collapse ultimately trapped and killed six miners, and a third collapse killed three would-be rescuers. Given the prevalence of mining worldwide, coupled with the desire to reduce mining deaths, further improvements to safety will remain a primary and overarching concern.
Surface control of the tunnel roof and ribs is an important concern of the mining business during the development of the tunnels and while men and material are transported through these tunnels. Once the mined material is exposed, the surfaces comprising the roof and ribs are commonly referred to as “the skin”. Ideally, the skin of the roof is supported by a primary support system, usually consisting of resin bolts installed on an approved pattern. Secondary systems are also applied when conditions are less than favorable. This secondary supporting system is responsible for controlling local skin failures, defined as mined material and loose rock that slip away from the surface of the rib or roof. This mined material and loose rock that fall from the roof and ribs are responsible for many accidents and deaths.
Most surface control problems (rib skin failures) of the ribs result from the separation of mined material due to anomalies in the mined material, such as fracture planes, allowing the mined material to fall to the mine floor, possibly injuring anyone near.
To minimize these skin failures and the associated accidents and issues, several product styles have evolved: Pans (“Mine Safe Draw Rock Shields”), Mesh/Geogrid, Mats, Boards, and Channel. Each product style is designed to help create and aid in the secondary support system. The variety of styles reflect the different and unique properties of the rib and roof to which they are applied, and thus the products styles are neither necessarily interchangeable, nor is selection of a particular product style purely a matter of preference. The different product styles thus reflect differences in equipment, time, and skill required to install the products, the characteristics of the material forming the rib and roof, as well as the cost of the actual product itself.
Pan systems involve the use of a pan and a plate machine bolted into the skin. The pan system stiffens the skin, and thus helps prevent skin failures. The term pan, as commonly used in the industry, is a bearing plate bolted directly against the skin to stabilize the skin, and is usually used in conjunction with a support plate, which is a smaller plate sandwiched between the pan and the bolt, effectively further stabilizing the through hole of the pan. Pan products are advantageous due to their fast installation, the limited expertise and specialized equipment need for such installation, their relatively small size for ease of handling by installers, and versatility in terms of placement location, resulting in a competitively priced product compared to other systems. A typical pan, such as that detailed in U.S. Pat. No. 7,284,993 B2, features a through hole for receiving a bolt, and a square, planar central surface immediately surrounding the through-hole, with one or more continuous channels circumscribing the through-hole. Another typical pan is the so-called spider plate made by Minova http://www.minovausa.com/pdfs/Products/SpiderPlate.pdf, featuring a plurality of “legs” or channels extending from the center of the pan to the perimeter or outer boundary of the pan. The '933 (Jenmar) pan, as well as other pans, are not fail-proof, and their small design size requires a greater number of pans be used in any given area to create surface control. Given the high cost of skin failures, further improvements in safety products is highly desirable.
What is needed is a pan that overcomes deficiencies in the prior art pan category of skin controlling products, specifically a pan that allows a mine operator or others performing subterranean excavation, the flexibility of placement, simple installation, and increased skin stabilization per installed pan.
Accordingly, the invention provides for an oval bearing plate or pan having a largely convex central portion existing in a first horizontal plane, and a planar peripheral portion or edge portion existing in a second horizontal plane below the first horizontal plane, the convex central portion joined to the peripheral portion by an outermost edge of the central portion angling downwards from the central portion to meet the innermost edge of the peripheral portion. The central portion further includes a plurality of parallel rib members held in spaced apart relationship, the rib members configured as a series of concave channels oriented so as to span the narrowest width of the oval pan. The invention further provides for an oval pan comprised of either galvanized metal or plastic. The invention still further provides for a pan system in which the installed pan becomes largely concave in shape.
The features and advantages of the invention will become apparent from a consideration of the subsequent detailed description presented in connection with accompanying drawings, in which:
a is a cross-sectional side elevational view of the pan shown in
b is a cross-sectional side elevational view of the pan shown in
c is a cross-sectional side elevational view of a rib member shown in
a is a top view of one side of the pan according to the invention.
b is a partial view of
c-ce show embodiments of the pan according to the invention.
a is a cross-sectional, side elevational view of the pan according to the invention, in a typical installation on a rib or roof, showing the concave shape of the installed pan.
b is a perspective view of the pan according to the invention, showing the generally convex shape of the unistalled pan.
The features and advantages of the invention will become apparent from a consideration of the subsequent detailed description presented in connection with accompanying drawings, in which:
Now referring to
A plurality of parallel rib members 18, in spaced apart relation, are embossed or stamped onto the central portion 20, each rib member 18 further comprising a concave channel spanning the first diameter 20b of the central portion 20. The central portion 20 is largely convex in shape, with the area upon which the rib members 18 are embossed lying in the first horizontal plane, parallel to the first diameter 20b and to one another. The rib members 18 have at least two and in some embodiments, three different lengths. In a typical embodiment, shown in
The central portion's outermost edge 20a meets an innermost edge 14a of a pan edge portion or peripheral portion 14 at a transition point 16, the peripheral portion 14 and the transition point 16 lying in a second horizontal plane, as shown more clearly in
The pan 10 according to the invention, in a typical embodiment as shown in
When the pan 10 is used in the pan system 100 and installed on the skin 50, as shown more clearly in
a shows a side elevational cross section of the pan 10 according to the invention. The rib members 18 are arranged in parallel, spaced apart relation, each rib member 18 having a concave cross section so as to form a channel in the central portion 20. Each rib member has a greater depth than the average rib member of the prior art. In a typical embodiment according to the invention, shown in
The arrangement and number of rib members 18 per pan 10 provide approximately five times the strength of the prior art pans. The rib members 18 provide strength, and as load-weight is exerted onto the pan 10, the energy expands onto the convex central portion 20, the rib members 18 pushing the load energy to the outer edges of the pan, thus aiding in surface tension control.
The pan 10 is typically made of galvanized steel, G-90 and/or G-60 galvanized hot dipped processed steel (see
It should be noted that the present invention is not only useful for roof and wall stabilization in mining, but can also be used for any tunneling or other subterranean excavation, such as for placement of utilities beneath the surface.
Finally, it is to be understood that the above-described arrangements are only illustrative of the application of the principles of the present invention. Numerous modifications and alternative arrangements may be devised by those skilled in the art without departing from the scope of the present invention. For instance, in some embodiments (not shown), two or more pans 10 may be stacked and used together to form a pan system, with or without the use of the support plate 30, and plastic pans 10 may be used in combination with metal pans 10, either side by side in a pan system 100 or stacked together. The dimensions and shape of the pan 10 may also be modified to have a rectangular peripheral portion but retaining an oval shaped pan central portion, and the dimensions may be larger or smaller than 24×18 inches, as desired. A square support plate 30 is shown in
| Number | Date | Country | |
|---|---|---|---|
| 61709609 | Oct 2012 | US |
