Abstract:
A cable bolt assembly incorporating a head that distributes loads and minimizes the risk of potential failure caused by cable bolt head protrusion through the load bearing plate due to plate deformation. A flush seat cable bolt head includes a tapered nose portion, a flush seating portion that acts to distribute loads and a head portion of any geometrical consideration, either external or internal that is used to drive the head.

Description:
CROSS-REFERENCE TO RELATED U.S. APPLICATIONS 
       [0001]    This application is a non-provisional of, and claims the benefit under 35 U.S.C. §119(e) of the earlier filing date of U.S. Provisional Application Ser. No. 61/471, 857, filed on Apr. 5, 2011, which is hereby incorporated by reference; and this application is also a continuation-in-part of, and claims the benefit under 35 U.S.C. §120 of the earlier filing date of U.S. patent application Ser. No. 13/221,138, filed on Aug. 30, 2011, pending, the contents of which are hereby incorporated by reference, which is a continuation of U.S. patent application Ser. No. 12/002,316, filed on Dec. 14, 2007, now U.S. Pat. No. 8,007,206, the contents of which are hereby incorporated by reference, which is a continuation-in-part of U.S. patent application Ser. No. 11/825,850, filed on Jul. 9, 2007, abandoned, the contents of which are hereby incorporated by reference, which itself claims the benefit under 35 U.S.C. §119(e) of the earlier filing date of U.S. Provisional Application Ser. No. 60/819,134 filed on Jul. 7, 2006, which is also hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The disclosure relates to roof support in underground mining operations, particularly to cable bolt assemblies incorporating a head that distributes loads and minimizes the risk of potential failure caused by cable bolt head protrusion through the load bearing plate due to plate deformation. 
       BACKGROUND OF THE INVENTION 
       [0003]    In the mining arts, roof cable bolts are often employed to strengthen and stabilize a mine roof. Typically, after a cable bolt is installed in a drilled hole, a plate and head protrude from the hole. The top of a protruding head is normally configured for being engaged with a tool that can rotate the cable into the hole and mix resin cartridges, thereby setting the cable fast in the drilled hole. 
         [0004]    A problem is commonly encountered in the context of coal seams that are sufficiently small as to result in low heights for mines or tunnels in the seam. Particularly, a problem of low clearances, e.g., for equipment and workers, becomes even worse. Since the head and wedges from a conventional cable bolt can protrude, e.g., 2 or 3 inches (or more) downwardly from the mine roof, a significant hazard is presented to people and equipment in the mine. 
         [0005]    Jennmar Corporation, based in Pittsburgh, Pa., has developed a system with the following characteristics:
       the use of a collared crater hole;   the use of a dust boot when drilling a collared crater hole using a special tool (see  FIG. 4   b ) to collect dust from the cratering action; and   the use of an inverted dome crater plate with a conventional head.       
 
         [0009]    However, this arrangement involves a level of complexity that adds time and cost to the installation process (as will be more fully appreciated herebelow), including the need for a dedicated process step to form the crater hole. 
         [0010]    A need has thus been recognized in connection with realizing bolt installation arrangements and processes that avert such complexity. 
       SUMMARY OF THE INVENTION 
       [0011]    In accordance with at least one embodiment of the present invention, in order to mitigate the problems described heretofore (among others), a roof cable bolt head can preferably be dimensioned such that most of its length fits inside a drilled hole in the mine roof. 
         [0012]    The present disclosure provides for a cable bolt head that distributes loads over a wide area. When fully assembled with a cable and retaining wedges or other devices, the cable head engages most of the area inside of the embossed area of a typical embossed load bearing plate. 
         [0013]    A roof cable bolt head according to embodiments of the invention includes a tapered nose area which passes through the center hole of a load bearing plate, and can protrude into the cavity created for the cable assembly. The head accepts most common underground roof bolting installation tools. 
         [0014]    The flush seating area not only helps to distribute the load onto the load bearing plate, it also acts as a deterrent to keep the cable bolt head from piercing the plate in the event of load bearing plate deformation caused by strata shift. 
         [0015]    The novel features which are considered characteristic of the present invention are set forth herebelow. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of the specific embodiments when read and understood in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    For the present invention to be clearly understood and readily practiced, the present invention will be described in conjunction with the following figures, wherein like reference characters designate the same or similar elements, which figures are incorporated into and constitute a part of the specification. 
           [0017]      FIG. 1   a  illustrates pieces of typical cable bolt ends as known in the mining arts. 
           [0018]      FIG. 1   b  illustrates assembled versions of typical cable bolt ends as known in the mining arts. 
           [0019]      FIGS. 2   a  and  2   b  respectively show two different assembled conventional cable bolts with plates. 
           [0020]      FIG. 3  illustrates a problem involving the protrusion of a conventional cable bolt from a roof. 
           [0021]      FIGS. 4   a  and  4   b  illustrate components from another conventional method. 
           [0022]      FIG. 5  illustrates, in perspective view, a low profile cable bolt head. 
           [0023]      FIG. 6  shows a cross-sectional view of a low profile cable bolt head. 
           [0024]      FIGS. 7   a - 7   d  show, respectively, a bottom view, a top view, a side view and a side cross-sectional view of a variant low profile cable bolt head. 
           [0025]      FIGS. 8A-8C  are perspective, side and cross-sectional side views of an additional embodiment of a cable bolt head. 
           [0026]      FIGS. 9A and 9B  are side and cross-sectional side views of a cable bolt head and embossed load bearing plate. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0027]    It is to be understood that the figures and descriptions of the present invention have been simplified to illustrate elements that are relevant for a clear understanding of the invention, while eliminating, for purposes of clarity, other elements that may be well known. The detailed description will be provided herebelow with reference to the attached drawings. 
         [0028]    Typical cable bolts  10 ,  20 , as known in the mining arts, are illustrated in  FIGS. 1   a/b . As shown in  FIG. 1   a , a cable  12  (i.e., a roof cable bolt as known in the mining arts) is normally integrable with 2 or 3 wedges  14 , which themselves fit into the interior diameter of a (e.g. hexagonal) head  16 .  FIG. 1   b  shows such components assembled, in two well known exterior design incarnations. 
         [0029]    Typically, after a cable bolt is installed in a drilled hole, the plate and head protrude from the hole.  FIGS. 2   a/b  (which respectively show two more or less equivalently functioning incarnations  30 ,  40 ) help illustrate this phenomenon. Typically, at least the top of each head  36 ,  46  is hexagonal so that the drill rig (normally fitted with a hexagonal wrench/spanner fitting) can rotate the cable  32 ,  42  into the hole and mix the resin cartridges, thereby setting the cable fast in the drilled hole. ( FIG. 2   b  shows a cable bolt with a cylindrical sheath—a small end portion of which is visible—disposed about the bolt.) 
         [0030]      FIG. 3  illustrates a commonly encountered problem as mentioned further above. Particularly, in the context of coal seams that are sufficiently small as to result in low heights for mines or tunnels in the seam, a problem of low clearances, e.g., for equipment and workers, becomes even worse. Particularly, since the head  50  and wedges  54  from a conventional cable bolt can protrude a distance h, e.g., 2 or 3 inches (or more) downwardly from the mine roof  56 , a significant hazard is presented to people and equipment in the mine. 
         [0031]    The features of the aforementioned Jennmar system can be appreciated from  FIGS. 4   a  and  4   b , which makes some strides in addressing the problem just outlined. Essentially, such a crater plate system just involves a specially designed counter-sinking drill bit  70  (as seen in  FIG. 4   b ) and an engineered high strength plate (as evident in  FIG. 4   a ). 
         [0032]      FIG. 4   a , as such, shows a conventional cable bolt end  60  and plate  69  while  FIG. 4   b  shows the aforementioned drill attachment  70  which forms a crater to be disposed at the initial opening of a roof hole, whereby the reverse crater plate will fit into this crater. After the crater has been formed by the tool in  FIG. 4   b , the rest of the hole is drilled (to a correct, desired length) using conventional drilling rods and bits. The result is that an installed bolt may likely protrude only about one inch from the plate. However, as mentioned previously, this arrangement involves a level of complexity that adds time and cost to the installation process, especially since the initial cratering operation represents yet another operation that needs to be undertaken. 
         [0033]      FIG. 5  shows, in perspective view, a low profile cable head design in accordance with an embodiment of the invention. Cable bolt head  500  preferably includes, as shown, a hexagonal profile portion  502  and a circular profile (or frustoconical) portion  504 . The view in  FIG. 5  is essentially “upside down”, in that the hexagonal portion  502  would most often protrude downwardly from a roof while circular/frustoconical portion  504  would extend into a roof hole. Hexagonal portion  502  includes six faces  508  as shown, which meet at edges  510 . 
         [0034]    An optional circular disc portion (or lip)  506  can be disposed at the transition between hexagonal portion  502  and circular/frustoconical portion  504 . (The term “circular”, as used with regard to component  504  and analogous components discussed herein, is intended to convey at least the concept of a circular cross-section of a portion when the portion is cut at an angle perpendicular to a central longitudinal axis of the portion in question.) Circular disc portion  506  essentially ensures that the head  500  can fit into a roof hole (or installation socket) of appropriate diameter without “over-deploying” into the hole in such a way that the head  500  would end up being disposed not sufficiently tightly or snugly against the roof. 
         [0035]    Also shown is an frustoconical throughhole  512  that preferably extends substantially all the way from an uppermost portion of head  500  to a lowermost portion, even through the transition between hexagonal portion  502  and circular/frustoconical portion  504 ; this will be better appreciated in  FIG. 6 . 
         [0036]    For its part,  FIG. 6  shows, in a cross-sectional view, a low profile cable bolt head  600  configured in accordance with an embodiment of the invention; it will be appreciated that  FIG. 6  has similar components to the head  600  shown in  FIG. 5 . The cross-section in  FIG. 6  is taken such that it cuts two opposing apices of a hexagonal profile (i.e., point-to-point across a maximum diameter of a hexagonal profile; in  FIG. 5  this would be between two opposing edges  510 ). In  FIG. 6 , there is no circular disc or lip portion analogous to component  506  of  FIG. 5 . 
         [0037]    Also indicated in  FIG. 6  are some dimensional variables a through f. Some non-restrictive and illustrative examples of such dimensions will be provided herebelow. It should further be understood that an appreciation of the relative dimensions involved, in the context of the mining arts, will certainly assist in highlighting the advantages associated with embodiments of the present invention. (As such, it should be noted that  FIG. 6  is not necessarily drawn to scale.) Components in  FIG. 6  that are analogous to those shown in  FIG. 5  have reference numerals advanced by 100 as compared to  FIG. 5 . 
         [0038]    As shown, a circular/frustoconical portion  604  transitions into hexagonal portion  602  such that the protrusion distance of head  600  beyond a roof plate  614  is small. (It should further be noted that as in  FIG. 5  the view in  FIG. 6  is essentially “upside down”; the hexagonal portion  602  would most often protrude downwardly from a roof while circular/frustoconical portion  604  would extend into a roof hole.) 
         [0039]    By way of example, height dimension e, representing a net protrusion of head  600  beyond plate  614 , could be about a mere 0.75 inch in accordance with at least one embodiment of the present invention, which represents a tremendous stride in providing additional vertical clearance for personnel in a mine. (Assuming that the thickness of plate  614  is about 0.25 inch or less, the total material protrusion from a mine roof will be less than or equal to about one inch.) At the same time, since all that is involved here essentially is a modification in the shape of the head, the installation process scarcely changes (in comparison with conventional arrangements other than the Jennmar crater plate system mentioned above), thus ensuring that the installation cost scarcely changes. 
         [0040]    The upper maximum diameter a (apex to apex) of hexagonal portion  602  could be about 1.75 inches. At the same time, an increase in this dimension to 2.00 inches could provide an even more adequate surface area for holding the plate  614  securely (though it will be appreciated that this may necessitate a larger cable bolt, e.g., 0.6 inch in diameter, and thus a larger installation socket). 
         [0041]    Other dimensions may be chosen and employed in a manner to provide degrees of strength and anchorage that may be desired. In a typical (albeit illustrative and non-restrictive) application, a maximum diameter b of frustoconical throughhole  612  could be about 1.13 inches and a minimum diameter c, about 0.72 inches. A minimum outer diameter d of circular/frustoconical portion  604 , on the other hand, could be about 1.10 inches. Finally, an overall height dimension f of head  600  could be about 1.75 inches. 
         [0042]    In a variant configuration, by way of an additional illustrative and non-restrictive example, essentially the same basic design as shown as in  FIG. 6  (i.e., a circular profile transitioning into a hexagonal profile) may be provided, yet with an even narrower inner profile. Accordingly, height dimension f could increase to about 1.90 inches while diametric dimensions c and d could be reduced to about 0.64 inch and about 1.00 inch, respectively. With such a configuration, a protrusion of about 0.75 inch of head  600  beyond plate  614  (dimension e) could still be attained, while, with an approximate 0.25 inch (or less) thickness of plate  614  the result again would be a net protrusion of 1 inch or less (of head  600  beyond plate  614 ). 
         [0043]    Optionally, a transitional corner  616  (between hexagonal portion, with or without a transitional disc portion,  602  and circular/frustoconical portion  604 ) and a terminal circular edge  618  (of circular/frustoconical portion  604 ) could be rounded (i.e., provided with radii), but this is not essential. 
         [0044]    It will be appreciated from the examples of  FIGS. 5 and 6  that a cable head, formed in accordance with at least one embodiment of the present invention, can be configured and dimensioned such that most of its length would fit inside the drilled hole in the mine roof (and would thus dig into the hole during the process of installing the cable bolt, via the drill rotation that mixes the resin). Again, the end result is that a low profile cable bolt would be provided to mines at literally no extra cost or effort to the end user, unlike the crater plate system mentioned heretofore (see  FIGS. 4   a/b ). 
         [0045]      FIGS. 7   a - 7   d  present a variant embodiment that lends itself to particularly easy installation by way of a standard socket wrench. As shown, the embodiment of  FIGS. 7   a - 7   b  present a cable bolt head with a generally rectilinear cross-sectional shape, or in this case a generally square cross-sectional shape. A basic tapered section is utilized similarly to that found in the “hexagonal” embodiments contemplated in accordance with  FIGS. 5 and 6 . Components in  FIG. 7  that are analogous to those shown in  FIGS. 5  and/or  6  have reference numerals advanced by 200 and 100, respectively as compared to  FIGS. 5 and 6 . 
         [0046]    Accordingly,  FIGS. 7   a - 7   d  show, respectively, a bottom view, a top view, a side view and a side cross-sectional view of a cable bolt head  700  in accordance with the aforementioned variant embodiment of the present invention. Reference will be made herebelow to all of  FIGS. 7   a - 7   d  collectively unless otherwise indicated. 
         [0047]    As shown, cable bolt head  700  preferably includes a rectilinear profile portion  702  and a circular profile (or frustoconical) portion  704 . Essentially, the rectilinear profile portion  702  would most often protrude downwardly from a roof while circular/frustoconical portion  704  would extend into a roof hole. 
         [0048]    Preferably, a circular disc portion (or lip)  706  is disposed at the transition between rectilinear portion  702  and circular/frustoconical portion  704 . As with the embodiment of  FIG. 5 , circular disc portion  706  essentially ensures that the head  700  can fit into a roof hole (or installation socket) of appropriate diameter without “over-deploying” into the hole in such a way that the head  700  would end up being disposed not sufficiently tightly or snugly against the roof. 
         [0049]    Also shown is frustoconical throughhole  712  that preferably extends substantially all the way from an uppermost portion of head  700  to a lowermost portion, even through the transition between rectilinear portion  702  and circular/frustoconical portion  704 . 
         [0050]    As with  FIG. 6 , there are shown some dimensional variables (here, a′ through g′ as well as Q′). Again, some non-restrictive and illustrative examples of such dimensions will be provided herebelow. Again, it should further be understood that an appreciation of the relative dimensions involved, in the context of the mining arts, will certainly assist in highlighting the advantages associated with embodiments of the present invention. 
         [0051]    By way of example, height dimension e′, representing a net protrusion of head  700  beyond a roof plate, could again be merely about 0.75 inch in accordance with at least one embodiment of the present invention. 
         [0052]    The width a′ (midpoint to midpoint) of rectilinear (here square) hexagonal portion  702  could be about 1.1 inches, while an outer diameter g′ of disc portion may be about 1.8 inches. 
         [0053]    Other dimensions may be chosen and employed in a manner to provide degrees of strength and anchorage that may be desired. In a typical (albeit illustrative and non-restrictive) application, a maximum inner diameter b′ of frustoconical throughhole  712  could be about 0.875 inches and a minimum inner diameter c′, about 0.70 inches. A minimum outer diameter d′ of circular/frustoconical portion  704 , on the other hand, could be about 1.10 inches, while a maximum outer diameter d″ thereof could be about 1.4 inches. A overall height dimension f′ of head  700  could be about 1.75 inches, while the pitch angle Q′ of hole  712  could be about 3 degrees. 
         [0054]    As is further shown, a transitional corner  716  (between disc portion  706  and circular/frustoconical portion  704 ) and a terminal circular edge  718  (of circular/frustoconical portion  704 ) could be rounded (i.e., provided with radii). The same holds true for edges  720  and  724 , as well as transitional corner  722 , as shown. 
         [0055]    Again, it will be appreciated that cable head  700  can be configured and dimensioned such that most of its length would fit inside a drilled hole in a mine roof, and would thus dig into the hole during the process of installing the cable bolt, via the drill rotation that mixes the resin. 
         [0056]    It will be appreciated from the foregoing that the variant embodiment broadly contemplated in accordance with  FIG. 7  lends itself to an improvement in the performance of a cable bolt head in its interaction with a bearing plate, in that the circular disc portion (shown as  706 ) acts as a flange or lip with a proportionately large bearing surface, while rounded corners and edges as just described can reduce a tearing tendency in the presence of non-axial loads. 
         [0057]    While the variant embodiment of  FIG. 7  presents a rectilinear/square profile portion for accommodating a tightening wrench, and while many conventional tightening wrenches can readily accommodate such a profile portion, it should be understood that a very wide variety of other cross-sectional profile shapes are conceivable for the same purpose. For instance, triangular, pentagonal, heptagonal or octagonal cross-sectional profiles shapes could be provided for the protruding profile portion of a roof bolt head, inasmuch as these could mate with a compatible recessed portion of a tightening wrench. 
         [0058]    An additional embodiment is shown in  FIGS. 8   a - 9   b . Referring to  FIGS. 8   a - 8   c , a flush seat cable bolt head  800  includes a tapered nose portion  802 , a flush seating portion  804  that acts to distribute loads and a head portion  806  of any geometrical consideration, either external or internal that is used to drive the head. For example, the external geometry of head portion  806  is shown as having a rectilinear shape similar to the embodiment shown in  FIGS. 7   a - 7   d , but could also have a hexangular shape similar to the embodiment shown in  FIGS. 5-6 . The internal through-hole portion  808  of this device is tapered to accept wedges (like wedges  14  of  FIG. 1   a ) or other devices necessary for cable securing. The cable bolt head embodiment shown in the figures is a single integral unitary piece. 
         [0059]    According to an embodiment, as shown in  FIGS. 8   a - 8   c , the tapered nose portion  802  is a first section of the cable bolt head  800  and is adapted for insertion into a roof hole. The tapered nose portion  802  is frustoconical and has a generally circular cross-section. The tapered nose portion  802  has a first end surface  810 . The flush seating portion  804  is a second section of the cable bolt head  800  for seating flush against the inside area of an embossed load bearing plate  812  having an embossed or concave portion  812   a  ( FIGS. 9   a - 9   b ) or other surface control fixture. The embossed or concave portion  812   a  of the embossed load bearing plate  812  is surrounded by an annular raised portion  812   b  of the embossed load bearing plate  812 . The flush seating portion  804  has a wide flat surface for load distribution. The head portion  806  is a third section of the cable bolt head  800  adapted for a tightening tool. The third section has a second end surface  814  of the cable bolt head  800 . The first tapered through-hole portion  808  extends through the tapered nose portion  802 , through the flush seating portion  804  and forming an opening in the head portion  806  for accommodating a cable bolt. 
         [0060]    The flush seating portion  804  has a diameter larger that the outer cross-sectional dimension of the tapered nose portion  802 . The flush seating portion  804  further has a curved load bearing roof plate contacting portion  816  disposed adjacent the tapered nose portion  802  upon initial insertion of the tapered nose portion  802  into a roof hole and engaging most of the contact surface area  818  inside of the load bearing plate embossed portion  812   a . The curved load bearing roof plate contacting portion  816  sets flush within the inside area of the load bearing embossed portion  812   a , an opposite (flat) surface is  820  approximately flush with the high point of the embossment. The shape of the roof plate contacting portion  816  helps securely seat the flush seating portion  804  inside the load bearing embossed portion  812   a  and provides for even load distribution. As shown in  FIG. 9   b , the curved shape of roof plate contacting portion  816  has a first portion  816   a  adjacent tapered nose portion  802 . First portion  816   a  is substantially transverse in cross-section to tapered nose portion  802 . The curved shape of roof plate contacting portion  816  has a second portion  816   b  extending at an angle to first portion  816   a  and having a third curved cross-sectional portion  816   c  therebetween. Second portion  816   b  has a substantially linear cross-sectional profile. The curved shape of roof plate contacting portion  816  has a fourth portion  816   d  disposed between second portion  816   b  and head portion  806 . Fourth portion  816   d  is substantially transverse to flat surface  820 . 
         [0061]    In general, a “cable bolt”, as set forth and described heretofore, can be understood as being interchangeable, in accordance with at least one embodiment of the present invention, with essentially any other type of roof bolt as employed in the mining arts, such as a bolt that is not necessarily formed from cable (e.g., a solid generally cylindrical bolt or a hollowed, generally cylindrical bolt). 
         [0062]    It should also be understood and appreciated that roof bolt assemblies as broadly contemplated herein will also preferably include wedges or other suitable arrangements to assist in securing a cable or other bolt within a throughhole of a roof bolt head so as to prevent a slipping of the cable or other bolt with respect to the roof bolt head. 
         [0063]    Without further analysis, the foregoing will so fully reveal the gist of the embodiments of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute characteristics of the generic or specific aspects of the embodiments of the present invention. 
         [0064]    If not otherwise stated herein, it may be assumed that all components and/or processes described heretofore may, if appropriate, be considered to be interchangeable with similar components and/or processes disclosed elsewhere in the specification, unless an express indication is made to the contrary. 
         [0065]    If not otherwise stated herein, any and all patents, patent publications, articles and other printed publications discussed or mentioned herein are hereby incorporated by reference as if set forth in their entirety herein. 
         [0066]    It should be appreciated that the apparatus and method of the present invention may be configured and conducted as appropriate for any context at hand. The embodiments described above are to be considered in all respects only as illustrative and not restrictive. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.