Oval Pan and Pan System for Rib and Roof Surface Control in Subterranean Excavation Applications

Abstract

A pan (10) and a pan system (100) for surface control of wall and/or roof material in a subterranean tunnel or room, the oval pan (10) having a convex central portion (20) held at an angle above a horizontal plane and an outermost edge angling downwards and meeting a planar pan edge portion (14) lying in the horizontal plane, both edges meeting at a transition point (16). The central portion includes a plurality of parallel concave rib members (18) arranged to span the shortest width of the pan. In use as a system (100), a bolt (40) drilled though a support plate (3) and the pan secures the pan system to the wall or roof. The force exerted onto the bolt transfers to the pan results in a dimpling of the central portion, allowing for a tighter application of the pan to the wall or roof.

Description

FIELD OF THE INVENTION

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.

BACKGROUND OF THE INVENTION

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.

DISCLOSURE OF INVENTION

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.

BRIEF DESCRIPTION OF THE DRAWINGS

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:

FIG. 1 is a top view of the pan according to the invention.

FIG. 2a is a cross-sectional side elevational view of the pan shown in FIG. 1 cut along lines A-A, showing the convex shape of the central portion and the concave profile of the rib members.

FIG. 2b is a cross-sectional side elevational view of the pan shown in FIG. 1, cut through the narrowest diameter of the pan parallel with the rib members, showing the convex shape of the central portion.

FIG. 2c is a cross-sectional side elevational view of a rib member shown in FIG. 2a at circle 2c.

FIG. 3 is a perspective view of a pan system according to the invention, showing the pan, a support plate, and a bolt in a typical installation on a rib or roof, and a perspective view of a prior art pan system as installed adjacent to the pan system according to the invention.

FIG. 4a is a top view of one side of the pan according to the invention.

FIG. 4b is a partial view of FIG. 4a taken at circle 4b, showing the outermost edge of the central portion and the peripheral portion.

FIGS. 4c-ce show embodiments of the pan according to the invention.

FIG. 5a 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.

FIG. 5b is a perspective view of the pan according to the invention, showing the generally convex shape of the unistalled pan.

FIG. 6 is a perspective view of two different sized pans according to the invention, showing optional through bores or apertures in addition to the through bore located in the center of the pan, and additionally highlighting the varying number and spacing of the rib members.

DRAWINGS LIST OF REFERENCE NUMERALS

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:

• 10 bearing plate or pan
• 12 through-bore
• 12a first aperture
• 12b second aperture
• 14 pan edge portion or peripheral portion
• 14a innermost edge of peripheral portion
• 14b second edge of peripheral portion
• 16 transition point
• 18 rib member
• 18a length of first rib member
• 18b length of second rib member
• 18c length of third rib member
• 18d length of fourth rib member
• 18e diameter of through-bore
• 18f width of rib member
• 18g angle or rise of rib member
• 18h height of rib member
• 18j width of pan edge
• 18k radius of pan edge
• 18l true radius of pan edge
• 18m width of rib crest
• 20 central portion
• 20a outermost edge of central portion
• 20b first diameter of central portion
• 20c second diameter of central portion
• 30 support plate
• 40 bolt
• 50 skin (roof and/or rib)
• 60 prior art pan system
• 100 pan system

DETAILED DESCRIPTION

Now referring to FIGS. 1-6, a bearing plate or pan 10 according to the invention is comprised an oval shaped, single piece of embossed or stamped metal, or alternatively, out of plastic, such as thermo-plastic. The pan 10 is comprised of a standard sized 1⅜ inch through-bore 12 cut into the center of a central portion 20 of the pan 10, the through-bore 12 sized and shaped to receive a bolt 40 (as shown in FIGS. 3 and 5). The central portion 20 includes a first diameter 20b and a second diameter 20c, the first diameter spanning the shortest width of the oval shaped central portion 20 and existing in a first horizontal plane. The first diameter 20b ranges from about 14 inches to about 18 inches. The second diameter 20c ranges from about 20 inches to 24 inches. The central portion 20 is defined by an outermost edge 20a curving downwards below the first horizontal plane in which the central portion 20 lies. Two additional apertures 12a 12b in spaced apart relation and on opposite sides of the through-bore 12 are formed in the central portion 20, and may be used to further secure the pan to a skin (rib and/or roof) 50 by each aperture receiving one bolt 40, as necessary when a typical installation using the central through-bore 12 is not possible, or as desired, in lieu of or in addition to installation using the central through-bore 12 (see FIG. 6).

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 FIG. 1, a pair of first rib member lengths 18a are about 8 inches long each, each one of four second rib member lengths 18b is about 12 inches long, and each one of four third rib member length 18c is about 14.5 inches long.

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 FIGS. 2a and 2b. The uninstalled pan 10 is thus largely convex in shape, as shown more clearly in FIG. 5b, with the peripheral portion 14 being flat, the entire pan 10 somewhat resembling a flattened bowler hat resting on its brim. The peripheral portion 14 is thus defined by the innermost edge 14a and a second edge 14b, the second edge 14b being the perimeter or outermost limit around the pan 10.

The pan 10 according to the invention, in a typical embodiment as shown in FIGS. 1-6, features a surface area of approximately 24×18 inches, when compared to the prior art pans results in a larger surface area of the pan 10 contacting the skin 50 when the pan is part of an installed pan system 100. The pan 10 has about 30% greater surface area than the 18×18 inch and 17×17 inch square prior art pans, allowing an operator of a coal mine greater flexibility in its roof and rib plan, and importantly, better safety due to the larger surface area controlled by the pan system 100, as shown more clearly in FIG. 3, where a prior art pan system 60 is comprised of a square prior art pan and support plate bolted to a rib, and the pan system 100 including the pan 10 according to the invention bolted to the same rib and adjacent to the prior art pan system 60. The single most critical characteristic of a skin control product such as the pan 10 is its ability to contact the surface of the mining tunnel skin with adequate stiffness characteristics which help eliminate progressive roof and rib failures. The oval shape of the pan 10 as well as the large, planar peripheral portion 14 allows for easier handling of the pan 10 during installation (no sharp edges or points), as well as superior strength derived from the oval and generally convex shape of the pan.

When the pan 10 is used in the pan system 100 and installed on the skin 50, as shown more clearly in FIGS. 3 and 5a, the convex central portion 20 is pushed towards the skin 50 by a support plate 30 and the bolt 40, causing the central portion 20 to dimple and become concave in shape, pushing the pan 10 tightly against the skin 50. When the pan system 100 is installed, pressure from the bolting machine transfers load energy to the transition point 16 causing a “riveting” process to occur. This energy “pops” the pan 10 tightly into place. Further, the planar peripheral portion 14 has a greater surface area for better load strength and allows the installed pan 10 to more tightly grip the skin throughout the life of the pan.

FIG. 2a 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 FIGS. 2a and 2c, each rib is about 0.125 inches deep 18h, with a diameter or width 18f of about 0.84 inches. Other embodiments of the pan 10 are provided with dimensions for the rib members ranging from depths 18h of 0.55 inches to 0.17 inches and diameters 18f from 0.75 inches to 0.84 inches. The width of the rib crest 18m is about 0.13 inches wide in a typical embodiment. The outermost edge 20a has a range of varying dimensions, the width 18j of the peripheral portion 14 ranging from about 0.9 inches to about 1 inch, and the radius 18k ranging from about 2 inches to 3 inches, with a true radius 181 of about 2.3 inches in a typical embodiment. The angle or rise of the rib member 18h, as shown in FIG. 2c, in a typical embodiment is about 22 degrees.

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. FIG. 1 shows 10 total rib members 18, however it should be noted that the number of rib members 18 per central portion 20 may vary, and at least two rib members 18 are needed per pan 10.

The pan 10 is typically made of galvanized steel, G-90 and/or G-60 galvanized hot dipped processed steel (see FIG. 6) to resist rust formation and deterioration of the pan. Plastic pans 10 are made of thermo-plastic or other suitable plastic materials. The metal pan 10 is typically stamped, guaranteeing the tolerances of the pan 10 are consistent during the manufacturing process. Plastic pans 10 are created using a thermo forming process using a tool.

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 FIG. 3, however any style support plate can be used in the pan system 100 and FIG. 3 should not be regarded as requiring solely the use of square support plates. Also, use and installation of the pan 10 or of the pan system 100 to the rib or to the roof is identical, and hence references to rib or roof, or rib and roof, or collectively to the skin are not meant to indicate different uses or installations of the pan 10 and/or the pan system 100. These are just a few possible modifications and alternative arrangements, and the appended claims are intended to cover such modifications and arrangements.

Claims

1. A pan suitable for use in a mine roof and rib support system having a pan, a support plate, and a bolt passing through a through-hole securing the pan and support plate to a mine surface, the pan comprising:

an oval convex central portion (20) defined by an outermost edge (20a) and having a first diameter (20b) and a second diameter (20c), the central portion (20) lying in a first horizontal plane;

a planar peripheral portion (14) further comprising an innermost edge (14a) and a second edge (14b), the planar peripheral portion (14) lying in a second horizontal plane;

a through-bore (12) centrally oriented in the central portion (20);

a plurality of rib members (18), at least one rib member (18) comprised of a concave cross section, the rib members (18) held in spaced apart relation and parallel to one another, oriented so as to span the first diameter (20b) of the central portion (20), and

a transition point (16) defined by an intersection of the outermost edge (20a) and the innermost edge (14a).

2. The pan (10) of claim 1, further comprising at least one aperture (12a 12b) in the central portion (20) in spaced apart relation to the through-bore (12).

3. The pan (10) of claim 1, wherein at least one rib member (18) has a radius of about ⅛ inch and a depth of about 3/16 inch.

4. A pan system (100) for surface control of a mine skin, the pan system comprising:

a pan (10) comprising a through-bore (12), a convex central portion (20), a plurality of concave rib members (18) arranged in parallel and in spaced apart relation formed on the central portion (20), and a planar peripheral portion (14), the convex central portion (20) adjoining the planar peripheral portion (14) at a transition point (16) lying in a horizontal plane below the plane of the convex central portion (20),

a bolt (40), and

a support plate (30),

whereby fastening the bolt through the through-bore and support plate causes the convex central portion to flex and become concave, drawing the pan and support plate against the mine skin.

5. The pan in claim 1, wherein the pan is made of thermo- plastic

6. The pan in claim 1, wherein the pan is made of galvanized steel.