Patent Publication Number: US-8523494-B2

Title: Expansion shell assembly

Description:
This application is a continuation of prior application U.S. Ser. No. 10/822,455, filed on Apr. 12, 2004, now U.S. Pat. No. 7,722,295, issued on May 25, 2010, which claims priority benefit of U.S. Pat. No. 6,742,966, issued on Jun. 1, 2004, which claims the priority benefit of U.S. Provisional Patent Application Ser. No. 60/261,495, filed on Jan. 12, 2001. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an improved expansion shell assembly for mine roof bolts and, more specifically, to an improved expansion shell assembly, and elements thereof, having novel features particularly adapted for the improved support and release of an expansion shell during installation of a mine roof bolt. 
     2. Description of the Art 
     It is well known in the art of mine roof control to tension bolts anchored in bore holes drilled into the mine roof in order to reinforce the unsupported rock formation above the roof. Conventionally, a hole is drilled into the rock formation. The end of the bolt in the rock formation is anchored either by engagement of an expansion shell assembly on the end of the bolt with the rock formation, by bonding the bolt with resin to the rock formation surrounding the bore hole, or by use of both an expansion shell assembly and resin together to retain the bolt within the hole. 
     Mechanical expansion shell assemblies for roof bolts have been used for many years in the anchorage of bolts in rock formations. An expansion shell assembly includes an expansion member such as a camming plug or tapered plug threaded onto one end of a mine roof bolt and positioned within the upper end portion of an expansion shell. The expansion shell is held in place by a support device such as a PALNUT positioned adjacent to the lower end portion of the expansion shell. 
     During rotation of the bolt, the frictional engagement of the expansion shell with the rock formation surrounding the bore hole prevents rotation thereof. Also, by virtue of the frictional engagement between the upper end of the support device with the lower end of the expansion shell, the support device will not rotate but, upon rotation of the bolt, the support device, the expansion shell and the tapered plug move downwardly along the bolt until the support device reaches the unthreaded portion of the bolt. 
     Continued rotation of the bolt causes the tapered plug to advance downwardly on the bolt and urges the expansion shell fingers to expand or deflect radially outwardly to grip the rock formation surrounding the bore hole. With the expansion shell engaged with the rock formation, continued rotation of the bolt causes the bolt to advance upwardly, thereby pushing or stripping the support device off the threaded portion of the bolt. Concurrently, rotation of the bolt urges a bearing plate positioned on the bolt at an end opposite the expansion shell assembly against the rock formation, putting the rock formation in compression and the bolt in tension. 
     Current practice provides roof bolt systems using resin in conjunction with a mechanical anchor. These types of systems require a resin cartridge to be inserted in the bore hole. The bolt is then inserted in the bore hole and thrust upwardly to rupture the resin cartridge. The bolt is rotated, mixing the resin and setting the mechanical anchor. Two of the advantages of resin-using systems are a tensioned resin anchor and quick installation provided by the mechanical anchor. 
     Examples of arrangements utilizing both an expansion shell assembly and resin to anchor a mine roof bolt in a rock formation are disclosed in U.S. Pat. Nos. 4,419,805; 4,413,930; 4,516,885 and 4,518,292, all expressly incorporated herein by reference. Other examples of both an expansion shell assembly and resin to anchor a mine roof bolt are disclosed in U.S. Pat. Nos. 3,188,815; 4,162,133; 4,655,645 and 4,664,561, all expressly incorporated herein by reference. 
     In general, any support device of an expansion shell assembly of the prior art performs three functions during installation of the roof bolt. First, the support device maintains the expansion shell in engagement with the camming plug during insertion in the bore hole. Second, with the support device positioned adjacent the lower end of the bolt threaded portion, the support device maintains the expansion shell in a fixed axial position on the bolt thereby allowing the tapered plug to advance downwardly on the bolt and urge the expansion fingers radially outwardly to grip the rock formation. Finally, with the expansion shell engaged with the rock formation, the support device strips off the threaded portion of the bolt thereby allowing the bolt to advance upwardly and be properly tensioned. 
     Some early combination resin/mechanical anchor systems used a PALNUT as the support device to maintain the expansion shell in engagement with the camming plug during insertion in the bore hole. However, because of the tight clearance between the expansion shell fingers and the bore hole wall, along with the high resistance to the flow of resin caused by the anchor, the PALNUT was prone to prematurely strip off the threaded portion of the bolt. When a premature failure occurred, the expansion shell was pushed downwardly and disengaged from the camming plug. The result was an expansion shell assembly unable to engage the rock formation, a condition known in the industry as a “spinner”. 
     Manufacturers now use a hex or round jamnut of a various thickness as the support device. Although the heavier jamnut solved the premature stripping problem, it created a different problem. It has been determined that the heavier jamnut may not strip off the threaded portion. As a result, rotation of the bolt causes the expansion shell to be compressed between the camming plug and the support device. The expansion shell may become severely distorted, ripped, torn or twisted. In addition, when the jamnut fails to release, significant tension occurs in the bolt threaded portion between the camming plug and the jamnut. This tension translates into torque being measured by the roof bolt installation machine. It is common practice to install a roof bolt to a predetermined desired torque. Since significant torque is being created at the expansion shell assembly, significantly reduced torque/tension is being applied to the roof bolt. Thus, the actual tension in the bolt may be significantly less than the desired tension in the bolt. 
     While expansion shell assemblies for anchoring mine roof bolts in bore holes are well known, there is need to improve the operability of the support device, particularly when used with resin. The support device must have the capability to support the expansion shell during insertion in the bore hole and engagement with the bore hole wall. At the same time, the support device must have the capability to release its axially supporting engagement with the expansion shell once the expansion shell is set in the rock formation to allow for proper tensioning of the bolt while reducing or eliminating torsion and/or compression between the camming plug and the support device. 
     SUMMARY OF THE INVENTION 
     In accordance with one aspect of the present invention, an expansion shell assembly for mine roof bolts comprises an expansion member threaded onto an associated mine roof bolt. A support device is annularly disposed around the associated roof bolt. An expansion shell is annularly disposed around the associated roof bolt between the expansion member and the support device. The expansion shell has a base ring for engaging the support device and fingers for engaging a peripheral edge of the tapered plug. The engagement between the base ring and the support device permits axial traverse movement of the support device relative to the expansion shell for tensioning the roof bolt. 
     In accordance with another aspect of the present invention, a bolt and anchor assembly for securing a mine roof bolt comprises an elongated bolt and an expansion shell having an aperture for receiving the elongated bolt. An expansion member is disposed on one end of the elongated bolt for expanding the expansion shell. A shell support has a shell engaging portion radially disposed between and in contact with the elongated bolt and the expansion shell for maintaining the axial position of the expansion shell relative to the elongated bolt while the expansion member forces the shell to engage a rock formation and for moving axially relative to the expansion shell while the elongated bolt is tensioned after engagement to the rock formation. 
     In accordance with another aspect of the present invention, an expansion shell assembly for mine roof bolts comprises an expansion member threaded onto an associated bolt. A support device is annularly disposed around the associated bolt. A shell is annularly disposed on the bolt between the expansion member and the support device. The expansion shell has a base ring with a tapered surface for mating engagement a corresponding tapered surface of the support device and fingers for engaging the expansion member. The mating engagement allows increasing friction forces to hold the support device in a non-rotating position at a predetermined bolt torque. 
     In accordance with yet another aspect of the present invention, a method for anchoring an elongated threaded member to a rock formation is provided. An elongated member having a threaded end portion that is to be anchored to a rock formation is provided. An expansion shell assembly is provided on the threaded end portion of the elongated member. The expansion shell assembly comprises an expansion shell, a plug for expanding the expansion shell, and a support member for supporting the expansion shell. A blind drilled hole is formed in the rock formation for the elongated member and the expansion shell assembly. The elongated member with the expansion shell assembly carried thereon is advanced into the blind drilled hole. The elongated member is rotated to effect a gripping of the rock formation by the expansion shell assembly within the blind drilled hole. The support member generally maintains engagement between the plug and the expansion shell. The elongated member is further rotated to tension the elongated member. The support member axially traverses within the expansion shell permitting the tensioning. 
     In accordance with still another aspect of the present invention, a method of installing a mine roof bolt assembly is provided. A mine roof bolt assembly is inserted into a hole of a rock formation. The mine roof bolt assembly comprises a mine roof bolt, an expansion member threadingly engaged to the mine roof bolt, an expansion shell, and a support. The expansion shell has fingers engaged with expansion member and a base portion engaged with the support. The hole is appropriately sized to frictionally prevent rotation of the expansion shell. The engagement of the fingers restricts rotation of the expansion member. The mine roof bolt assembly is anchored to the rock formation within the hole by rotating the mine roof bolt. Said rotation causes the support to force the expansion shell against the expansion member thereby forcing the fingers of the expansion shell to move radially outwardly and grip the rock formation. The mine roof bolt is tensioned by continuing to rotate the mine roof bolt. Said continued rotation causes the support to forcibly move within the base portion of the expansion shell. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention may take form in various components and arrangements of components, and in various steps and arrangements of steps. The drawings are only for purposes of illustrating the presently preferred embodiments and are not to be construed as limiting the invention. 
         FIG. 1   a  is an elevational view of an expansion shell assembly having a support device on a mine roof bolt in a precisely controlled diameter arrangement in accordance with a first preferred embodiment of the present invention; 
         FIG. 1   b  is a cross sectional view of the expansion shell assembly of  FIG. 1   a;    
         FIG. 2   a  is an elevational view of an expansion shell assembly on a mine roof bolt in a conventional shell arrangement in accordance with a second preferred embodiment of the present invention; 
         FIG. 2   b  is a cross section view of the expansion shell assembly of  FIG. 2   a;    
         FIG. 3   a  is an elevational view of an expansion shell assembly on a mine roof bolt in a notched shell arrangement in accordance with a third preferred embodiment of the present invention; 
         FIG. 3   b  is a cross sectional view of the expansion shell assembly of  FIG. 3   a;    
         FIG. 4   a  is an elevational view of an expansion shell assembly on a mine roof bolt in a split shell arrangement in accordance with a fourth preferred embodiment of the present invention; 
         FIG. 4   b  is a cross sectional view of the expansion shell assembly of  FIG. 4   a;    
         FIG. 4   c  is an enlarged partial view of a support device taper and radius of the expansion shell assembly of  FIG. 4   a;    
         FIG. 5   a  is an elevational view of the precisely controlled diameter arrangement of  FIG. 1  wherein a two-piece support device is substituted for the support device of  FIG. 1 ; 
         FIG. 5   b  is a cross sectional view of the precisely controlled diameter arrangement of  FIG. 5   a;    
         FIG. 6   a  is an elevational view of the precisely controlled diameter arrangement of  FIG. 1  wherein a two-piece support device having an antifriction washer is substituted for the support device of  FIG. 1 ; 
         FIG. 6   b  is a cross sectional view of the precisely controlled diameter arrangement of  FIG. 6   a;    
         FIG. 7   a  is an elevational view of an expansion shell assembly having an unthreaded support device on a mine roof bolt in a precisely controlled diameter arrangement in accordance with another preferred embodiment of the present invention; 
         FIG. 7   b  is a cross sectional view of the expansion shell assembly of  FIG. 7   a;    
         FIG. 8   a  is an elevational view of an expansion shell assembly on a mine roof bolt having a support device axially secured between rolled threads and a shoulder of the bolt in a precisely controlled diameter arrangement in accordance with another preferred embodiment of the present invention; 
         FIG. 8   b  is a cross sectional view of the expansion shell assembly of  FIG. 8   a;    
         FIG. 9   a  is an elevational view of an expansion shell assembly on a mine roof bolt having a support device formed integrally with the bolt in a precisely controlled diameter arrangement in accordance with a ninth preferred embodiment of the present invention; 
         FIG. 9   b  is a cross sectional view of the expansion shell assembly of  FIG. 9   a;    
         FIG. 10   a  is an elevational view of an expansion shell assembly having a tapered shell engaged to a tapered support device on a mine roof bolt in accordance with another preferred embodiment of the present invention; and 
         FIG. 10   b  is a cross sectional view of the expansion shell assembly of  FIG. 10   a.    
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In accordance with the present invention, there is provided an expansion shell assembly for anchoring a bolt in a bore hole that includes an expansion shell, an expansion member such as a tapered camming plug, and a novel support device. The expansion shell has a circular base portion or base ring and a plurality of longitudinally extending fingers generally equally spaced from one another. Each finger is formed integral at one end portion with the circular base portion and extends upwardly therefrom to form a free end portion for outward expansion of the finger. The fingers each have an inner surface for engaging the side wall of the camming plug and a ribbed outer surface for frictionally engaging the bore hole. The camming plug has a threaded axial bore for engaging the end of the bolt, an upper end portion, a lower end portion, and a surrounding side wall tapering inwardly from said upper end portion to said lower end portion. The inner surface of the fingers abuts the plug side wall. The novel support device in general consists of a ring-like structure with an axial bore that may or may not be threaded, a lower end portion, an upper end portion whose outer diameter is less than the lower end portion, and an outer surface of a predetermined transition configuration. 
     Unlike prior art where the support device such as a PALNUT or a jamnut had to be forced axially down the bolt by the expansion shell during tensioning of the bolt, this support device cooperates with the expansion shell base portion in one of two general ways. In one way, as illustrated in at least  FIGS. 1   a  through  9   b , the upper end portion of the support device cooperates with the expansion shell base portion to cause the expansion shell base portion to diametrically expand and/or fracture and, at a predetermined axial force, allow the support device to traverse axially therethrough during tensioning of the bolt. In another way, as illustrated in  FIGS. 10   a  and  10   b , the upper end portion of the support device cooperates with the expansion shell base portion to cause the support device to be held in a fixed, non-rotating position thereby allowing the bolt to advance upwardly at a predetermined torque. 
     There are several ways to practice the invention as discussed in detail below. However, it should be understood by one skilled in the art that the invention may be practiced otherwise than as specifically illustrated and described below. It should also be noted that the invention may be practiced with the following U.S. Pat. Nos. 4,413,930; 4,419,805; 4,516,885; 4,518,292; 4,664,561; 4,678,374; 4,679,966; 4,764,055; 4,904,123; 4,913,593; 4,969,778; 5,011,337; 5,244,314, all expressly incorporated herein by reference. 
     Referring now to the drawings wherein like reference characters represent like elements, with reference to  FIGS. 1   a  and  1   b , an expansion shell assembly is shown in a precisely controlled diameter arrangement. The expansion shell assembly connects to a mine roof bolt  12  on a threaded end  14  thereof and comprises an expansion shell  16 , a tapered camming plug  18 , and a support device  20  according to a first preferred embodiment of the present invention. 
     The expansion shell  16  has a circular base portion  22  and a plurality of longitudinally extending fingers  24  generally spaced apart from one another. The inner surface or inner diameter of the circular base portion  22  is a precisely controlled diameter relative to an outside diameter of the support device  20  creating a controlled interference fit such as a 0.030 inch diametral fit. That is, the inner diameter of the base portion  22  is 0.030 inches smaller than the outside diameter of the support device  20 . This is in contrast to conventional prior art expansion shells which are often formed by casting resulting in significantly higher tolerances. The controlled relationship between the controlled diameter and the outer diameter of the support device  20  facilitates fracture and/or expansion of the base portion  22  during installation as will be discussed in more detail below. Each of the fingers  24  is formed integral at one end with the circular base portion  22  and extends upwardly therefrom to form a free end portion for outward expansion of the finger  24 . The fingers  24  each have an inner surface for engaging one of a plurality of flat side walls  26  of the camming plug  18  and an outer ribbed surface  28  for frictionally engaging a bore hole (not shown) formed within a rock formation. 
     The tapered camming plug  18  has a threaded axial bore for engaging the threaded end portion  14  of the bolt  12 , an upper end  30 , a lower end  32 , and the surrounding flat side walls  26  tapering inwardly from the upper end  30  to the lower end  32 . Each of the plurality of side walls  26  abuts the inner surface of one of the fingers  24  of the expansion shell  16 . 
     The support device  20  has a threaded axial bore for threaded engagement with the bolt  12 , a lower end  36 , an upper end  38  whose outer diameter is less than the lower end  36 , and a surrounding side wall  40  that transitions outwardly from the upper end  38  to the lower end  36 . The outer transition surface  40  has an outwardly tapered portion  42  beginning at the upper end, a transition radius portion  44  (such as about 0.030 inches), and a straight portion  46  that is parallel to the axial bore ending at the lower end  36 . The straight portion  46  defines the outside diameter of the support device  20  which determines the size of the controlled diameter of the base portion  22 . In the precisely controlled diameter arrangement illustrated, the tapered portion  42  is approximately sixty degrees relative to a vertical axis of the bolt  12 . Of course, other taper angles can be used to achieve the same result and all such configurations are to be considered within the scope of the present invention. 
     For installation in the bore hole, the support device  20 , the expansion shell  16 , and the camming plug  18  are positioned on the threaded end portion  14  of the mine roof bolt  12  as illustrated. More specifically, the support device  20  is threaded onto the bolt  12  to a position located slightly above an unthreaded portion  48  as illustrated. Alternatively, the support device  20  can be threaded onto the bolt  12  until it reaches or is adjacent the unthreaded portion  48 . The expansion shell  16  and the camming plug  18  are then positioned on the bolt  12  such that the circular base portion  22  overlaps the tapered surface of the support device  20  as shown. As can readily be seen, the expansion shell  16  is sandwiched between the camming plug  18  and the support device  20 . The expansion shell assembly  10  and the bolt  12  are then inserted in the bore hole. In this instance, the expansion shell  16  and roof bolt  12  are utilized without resin bonding. However, it will be appreciated that the expansion shell assembly of the present invention can also be utilized with resin. 
     For resin bonding, a resin cartridge (not shown) is positioned within the bore hole above the expansion shell assembly. The expansion shell assembly, attached to the bolt  12  as described above, is thrust upwardly in the bore hole to rupture the resin cartridge. During insertion in the bore hole, the expansion shell fingers  24  are held in engagement with the camming plug  18  by the support device  20 . In particular, the outwardly tapered portion of the support device  20  cooperates with the circular base portion  22  of the expansion shell  16  thereby maintaining the shell fingers  24  in engagement with the camming plug  18 . 
     As the roof bolt  12  is rotated, the contents of the resin cartridge are mixed together. Also, by virtue of the frictional engagement of the expansion shell  16  with the rock formation surrounding the bore hole, the expansion shell  16 , the camming plug  18 , and the support device  20  move downwardly along the bolt  12  until the support device  20  reaches a thread runout or unthreaded portion  48  of the bolt  12 . Of course, if the support device  20  is initially positioned adjacent the unthreaded portion  48 , this step will not occur. 
     In either case, with the support device  20  located at the thread runout  48  and maintaining the expansion shell  16  at a fixed axial position on the bolt  12 , continued rotation of the bolt  12  allows the tapered plug  18  to advance downwardly on the bolt  12  thereby urging the expansion fingers  24  radially outwardly to engage the rock formation. More particularly, the outwardly tapered portion  42  of the support device  20  cooperates with the circular base portion  22  of the expansion shell  16  thereby maintaining the expansion shell  16  in a fixed axial position on the bolt  12 . 
     Finally, with the expansion shell  16  engaged with the rock formation, continued rotation of the bolt  12  increases the axial force between the expansion shell  16  and the support device  20 . By virtue of the outwardly tapered portion  42  of the support device  20 , the increasing axial force is accompanied by an increasing radial force which urges the circular base portion  22  of the expansion shell  16  to increase in diameter. Thus, because of the tapered portion  42  and/or the precisely controlled diameter of the base portion  22 , the circular base portion  22  of the expansion shell  16  diametrically expands at a predetermined axial force, such as approximately 4,300 lbs., and a corresponding bolt torque, such as a torque of less than approximately 100 ft. lbs., sufficient enough to allow the support device  20  to traverse axially within and through the base portion  22  of the expansion shell  16  thereby allowing the bolt  12  to advance upwardly and be properly tensioned. 
     More specifically, a reference point or datum  50  on the support device  20  converges with a reference point or datum  52  on the circular base portion  22  after or while the diametric expansion of base portion  22  occurs at the predetermined force and corresponding bolt torque. That is, a distance D between the datums  50  and  52  is reduced at the predetermined force and corresponding bolt torque. The relative movement between the support device  20  and the circular base portion  22  is unlike the prior art where the circular base portion and the support device move in tandem down the mine roof bolt when the support device strips off the threaded portion of the bolt. It should be appreciated that in the embodiment illustrated the support device  20  axially traverses through the circular base portion  22  but other variations are possible, such as having the support device axially traverse annularly around the circular base portion, and all such variations are to be considered within the scope of the present invention. Also, it will be appreciated that the circular base portion  22  may or may not fracture during this diametric expansion and traversing movement. 
     With reference to  FIGS. 2   a  and  2   b , a second preferred embodiment of the present invention is illustrated. In this embodiment, an expansion shell assembly in a conventional shell arrangement comprises the tapered camming plug  18 , a support device  60 , and a conventional expansion shell  62 . 
     The expansion shell  62  has a circular base portion  64  and a plurality of longitudinally extending fingers  66  generally spaced apart from one another. The circular base portion  64  of the expansion shell  62  is as typically manufactured, for example, an expansion shell commonly known as a D8 manufactured by Frazer &amp; Jones of Syracuse, N.Y. 
     Like the precisely controlled diameter arrangement, each finger  66  is formed integral at one end portion with the circular base portion  64  and extends upwardly therefrom to form a free end portion for outward expansion of the finger  66 . The fingers  66  each have an inner surface for engaging one of the plurality of flat side walls  26  of the camming plug  18  and an outer surface for frictionally engaging a bore hole (not shown) formed within a rock formation. 
     The support device  60  has, like the support device  20 , a threaded axial bore for threaded engagement with the bolt  12 , a lower end, an upper end whose outer diameter is less than the lower end, and a surrounding side wall  68  that transitions outwardly from the upper end to the lower end. The outer transition surface  68  has an outwardly and gradually tapered portion  70  beginning at the upper end, a transition radius portion  72  (such as about 0.030 inches), and a straight portion  74  that is parallel to the axial bore ending at the lower end. In this arrangement, the tapered portion  70  is angled at approximately ten degrees relative to a vertical axis of the bolt  12 . Of course, other taper angles can be used to accomplish the same result and all such configurations are to be considered within the scope of the present invention. 
     For installation in the bore hole, the support device  60 , the expansion shell  62 , and the camming plug  18  are positioned on the threaded end portion  14  of the mine roof bolt  12  as illustrated. More specifically, the support device  60  is threaded onto the bolt  12  to a position located slightly above the unthreaded portion  48  of the bolt  12  as illustrated. Like the precisely controlled diameter arrangement, the support device  60  alternatively can be threaded onto the bolt  12  until it reaches or is adjacent the unthreaded portion  48 . The expansion shell  62  and the camming plug  18  are positioned on the bolt  12  such that the circular base portion  64  slightly overlaps the support device  60 . Thus, the expansion shell  62  is sandwiched between the camming plug and the support device  60 . The remainder of the installation process occurs very similarly to the installation process described above in reference to the precisely controlled diameter arrangement with a few differences. 
     The main difference during installation is that when the circular base portion  64  of the expansion shell  62  diametrically expands, the expansion is likely to be sufficient enough to fracture the circular base portion  64 . That is, a predetermined axial force and corresponding bolt torque will cause the circular base portion  64  of the expansion shell  62  to diametrically expand sufficient enough to fracture. This is due, at least in part, to the transition surface  68  of the support device  60 . The expansion and subsequent fracture allows the support device  60  to traverse axially within and through the base portion of the expansion shell  62  at a predetermined axial force, such as approximately 4,300 lbs., thereby allowing the bolt  12  to advance upwardly and be properly tensioned. It may be, however, possible to diametrically expand the base portion  64  of the conventional shell  62  without fracturing it. In either case, the support device  60  is permitted to axially traverse relative to the expansion shell base portion  64  in the manner described in the controlled diameter arrangement. 
     With reference to  FIGS. 3   a  and  3   b , a third preferred embodiment of the present invention is illustrated. In this embodiment, an expansion shell assembly in a notched shell arrangement comprises the tapered camming plug  18 , a support device  80 , and a notched expansion shell  82 . 
     The expansion shell  82  has a circular base portion  84  and a plurality of longitudinally extending fingers  86  generally spaced apart from one another. The geometry of the circular base portion  84  of the expansion shell  82  is modified to reduce the strength of the base portion  84 . Specifically, the modification comprises adding at least one notch  88  in the base portion  84 . However, it is to be appreciated that a variety of configuration changes could be made in order to achieve the desired result of weakening the base portion  84 . For example, the base portion  84  may include, without limitation, one or more slots, holes, slits, deformations, channels, relieved areas or the like that may or may not extend completely through the circular base portion  84 . The fingers  86  are disposed in the same manner as the previously discussed preferred embodiments. 
     The support device  80 , like the support devices and  60 , has a threaded axial bore for threaded engagement with the bolt  12 , a lower end, an upper end whose outer diameter is less than the lower end, and a surrounding side wall  90  that transitions outwardly from the upper end to the lower end. The outer transition surface  90  has an outwardly tapered portion  92  beginning at the upper end, a transition radius portion  94  (such as about 0.030 inches), and a straight portion  96  that is parallel to the axial bore ending at the lower end. In this arrangement, the tapered portion  92  is angled at approximately twenty-five degrees relative to the vertical axis of the bolt  12 . Of course, other taper angles can be used to achieve the same result and all such configurations are to be considered within the scope of the present invention. 
     For installation, the support device  80 , the expansion shell  82 , and the camming plug  18  are positioned on the threaded end portion  14  of the mine roof bolt  12  as illustrated. More specifically, the support device  80  is threaded onto the bolt  12  to a position located slightly above the unthreaded portion  48  of the bolt  12  as illustrated. Like the previous arrangements, the support device  80  alternatively can be threaded onto the bolt  12  until it reaches or is adjacent the unthreaded portion  48 . The notched expansion shell  82  and the camming plug  18  are positioned on the bolt  12  such that the circular base portion  84  slightly overlaps the support device  80 . Thus, the expansion shell  82  is sandwiched between the camming plug  18  and the support device  80 . The remainder of the installation process occurs very similarly to the installation process described above in reference to the conventional shell arrangement. However, in this embodiment the diametric expansion and possible fracturing of the circular base portion  84  is facilitated by the notches  88  in the expansion shell  82  at a predetermined axial force, such as approximately 4,400 lbs. 
     With reference to  FIGS. 4   a ,  4   b  and  4   c , a fourth preferred embodiment of the present invention is illustrated. In this embodiment, an expansion shell assembly in a split shell arrangement comprises the tapered camming plug  18 , a support device  100 , and a circumferentially discontinuous expansion shell  102 . 
     The expansion shell  102  has a circular base portion  104  that is a non-continuous circular structure. More specifically, the base portion  104  defines a slot or split  106  and does not form a closed annular ring. Fingers  108  are still formed integrally with the circular base portion  104  and extend upwardly therefrom as described with reference to the prior arrangements. 
     The support device  100 , like the support devices  20 ,  60  and  80  has a threaded axial bore for threaded engagement with the bolt  12 , a lower end, an upper end whose diameter is less than the lower end, and a surrounding side wall  110  that transitions outwardly from the upper end to the lower end  2 . With specific reference to 
       FIG. 4   c , the outer transition surface  110  has an outwardly tapered portion  112  beginning at the upper end, a transition radius portion  114  (such as about 0.030 inches), and a straight portion  116  that is parallel to the axial bore ending at the lower end. In this arrangement, the tapered portion  112  is angled at approximately fifty-five degrees relative to the vertical axis of the bolt  12 . Of course, other taper angles can be used to achieve the same result and all such configurations are to be considered within the scope of the present invention. 
     For installation, the support device  100 , the expansion shell  102 , and the camming plug  18  are positioned on the threaded end portion  14  of the mine roof bolt  12  as illustrated. More specifically, the support device  100  is threaded onto the bolt  12  to a position located slightly above the unthreaded portion  48  of the bolt  12  as illustrated. Like the previous arrangements, the support device  100  alternatively can be threaded onto the bolt  12  until it reaches or is adjacent the unthreaded portion  48 . The expansion shell  102  and the camming plug  18  are positioned on the bolt  12  such that the circular base portion  104  slightly overlaps the support device  100 . Thus, the expansion shell  102  is sandwiched between the camming plug  18  and the support device  100 . The remainder of the installation process occurs very similarly to the installation process described above in reference to the precisely controlled diameter arrangement. However, in this embodiment the diametrical expansion of the circular base portion  104  at a predetermined axial force, such as approximately 5,000 lbs., is facilitated by the gap or slot  106  in the expansion shell  102 . 
     With reference to  FIGS. 5   a  and  5   b , an alternative two-piece support device may be used in place of any of the aforementioned support devices  20 ,  60 ,  80  or  100 . As shown, a two-piece support device  120  is substituted for the support device  20  in the precisely controlled diameter arrangement. The support device  120  comprises a lower threaded ring  122  and an unthreaded upper ring  124 . The lower ring  122  has a threaded axial bore  126 , a lower end, an upper end, and a surrounding side wall  128 . The side wall or outer surface  128  may be circular, hex, or otherwise shaped. 
     Although the upper ring  124  has an unthreaded axial bore  130  for sliding engagement over the threads of the bolt  12 , in most other respects the upper ring  124  is like the support device  20 ,  60 ,  80  or  100  that the two-piece support device is being substituted for, in this case the support device  20 . Thus, the upper ring  124  has a lower end, an upper end, and a surrounding side wall  132  that transitions outwardly form the upper end to the lower end. The outer transition surface  132  has an outwardly tapered portion  134  at the same angle as that of the tapered portion of the support being substituted for, in this case sixty degrees. The upper ring  124  also has a transition radius portion  136  and a straight portion  138  that is parallel to the axial bore  130 . 
     For installation, the lower ring  122 , the upper ring  124 , the expansion shell  16 , and the camming plug  18  are positioned on the threaded end portion  14  of the mine roof bolt  12  as illustrated. More specifically, the lower ring  122  is threaded onto the bolt  12  to a position located slightly above the unthreaded portion  48  as illustrated. Like all the other arrangements, the lower ring  122  can alternatively be positioned at or adjacent the unthreaded portion  48 . The upper ring  124  is then slid onto the bolt  12 . Next, the expansion shell  16  and the camming plug  18  are positioned on the bolt  12  such that the circular base portion  22  slightly overlaps the tapered surface  134  of the upper ring  124  as shown. The remainder of the installation occurs like the installation process described in reference to the precisely controlled diameter arrangement. However, rotation of the bolt  12  with the lower ring  122  located at thread runout  48  causes the lower ring  122  to rotate with the bolt  12 . Whereas, the upper ring  124  may not rotate, thus less torque is transferred to the expansion shell  16 . 
     As discussed above, it should be appreciated that a similar two-piece support device may be used with any of the other previously described arrangements. However, an exterior of the upper ring would be shaped like the support device  60 ,  80  or  100  being substituted. For example, if a two-piece support device is used in place of the support device  60  of  FIG. 2   a , the upper ring will be shaped like the support device  60  except that the axial bore will be unthreaded. Thus, if the two-piece support device is used in the conventional shell arrangement, a tapered portion of the upper ring will have an angle of approximately ten degrees. 
     It may also be desirable to add an antifriction washer between the rings of any two-piece support device. With reference to  FIGS. 6   a  and  6   b , an antifriction washer  140  is provided with the two-piece support device  120  between the lower ring  122  and the upper ring  124 . The antifriction washer  140  is one way to reduce the friction between the upper and lower rings  122 , 124 . Installation occurs in the same manner as described with reference to the two-piece support device discussed previously. Also, it should be appreciated that a two-piece support device having an antifriction washer may be used with any other previously described arrangements in the manner described above in reference to the two-piece support device without an antifriction washer. 
     Another way to reduce the friction between the upper and lower rings in any arrangement is to coat the upper ring or lower ring with an antifriction material such as Teflon. It should be appreciated that any other antifriction method could be used to achieve a similar effect. Further, any of the antifriction methods discussed herein could be used in any of the aforementioned arrangements. 
     With reference to  FIGS. 7   a  and  7   b , another preferred embodiment of the present invention is illustrated. In this embodiment, a mine roof bolt is provided without an unthreaded portion between its threaded end and shoulder. An unthreaded support device is slidably received on the bolt and rests against its shoulder. In many respects the support device of this embodiment is like the upper ring of the two-piece support device. Instead of providing a lower ring, the shoulder of the bolt is used to limit downward axial movement of the support device. 
     This embodiment may be used with any of the previously described arrangements. However, the outer surface configuration of the support device is dependent upon the shell and support device arrangement desired. In  FIGS. 7   a  and  7   b , a precisely controlled diameter arrangement is illustrated. Thus, an outer contour or outer transition surface  148  of a support device  150  is like the outer contour of the support device  20  of  FIGS. 1   a  and  1   b  and the precisely controlled diameter shell  16  of  FIGS. 1   a  and  1   b  is provided. Also, the taper angle of a tapered portion  152  of the support device  150  can be like the taper angle of the support device  20  such as sixty degrees. The support device  150  has an unthreaded bore  156 . 
     For installation, the support device  150  is slid onto a bolt  158  that does not have an unthreaded portion between a shoulder  160  and its threaded portion  162 . The support device  150  is positioned against the shoulder  160 . The precisely controlled diameter expansion shell  16  and the camming plug  18  are placed on the bolt  158  as described in reference to the precisely controlled diameter arrangement of  FIGS. 1   a  and  1   b . In fact, the remainder of the installation also occurs as described in reference to the precisely controlled diameter arrangement of  FIGS. 1   a  and  1   b.    
     Alternatively, an antifriction washer (not shown) such as the antifriction washer  140  can be used between the shoulder  160  of the bolt  158  and the support device  150 . 
     Although  FIGS. 7   a  and  7   b  illustrates the precisely controlled diameter arrangement, the support device  150  and/or shell  16  could be modified or substituted to create any of the other aforementioned arrangements. For example, the conventional shell arrangement could be utilized by using a conventional shell  62  and a support device having an outer contour like that of the support device  60  of  FIGS. 2   a  and  2   b . Likewise, the notched shell and split shell arrangements could also be utilized by similar modifications and/or substitutions to the shell and the support device. 
     With reference to  FIGS. 8   a  and  8   b , another preferred embodiment of the present invention is illustrated. In this embodiment, a bolt  166  includes an unthreaded portion  168  between a threaded end  170  and a shoulder  172  but the threads are rolled on after a support device  174  is slid onto the bolt  166  and positioned adjacent the shoulder  172 . Thus, the diameter of an axial bore  176  of the support device  174  is substantially similar to the diameter of the unthreaded portion  168  of the bolt  166 . 
     As described with reference to the support device  160  of  FIGS. 7   a  and  7   b , an outer surface configuration of the unthreaded support device of this embodiment varies and is dependent upon the shell and support device arrangement desired. In  FIGS. 8   a  and  8   b , a precisely controlled diameter arrangement is illustrated. Thus, an outer contour or outer transition surface  178  of the support device  174  is like the outer contour of the support device  20  of  FIGS. 1   a  and  1   b . Also, the taper angle can be like the taper angle of the support device  20  such as sixty degrees. 
     For manufacture, the support device  174  is slid onto the bolt  166  and positioned adjacent the shoulder  172  prior to the threads being rolled on the bolt  166 . The threads are then rolled on the bolt  166  thereby securing the axial position of the support device  174 . More specifically, the threads have an outer diameter greater than the diameter of the axial bore  176  of the support device  174  thereby preventing upward axial movement of the support device  174 . The shoulder  172  of the bolt  166  prevents downward axial movement. For installation, the expansion shell  16  and the camming plug  18  are placed on the bolt as described in reference to the precisely controlled diameter arrangement of  FIGS. 1   a  and  1   b . In fact, the remainder of the installation occurs as described with reference to the precisely controlled diameter arrangement of  FIGS. 1   a  and  1   b.    
     Alternatively, an antifriction washer (not shown) such as the antifriction washer  140  can be used between the shoulder  172  of the bolt  166  and the support device  174 . 
     Although  FIGS. 8   a  and  8   b  illustrates the precisely controlled diameter arrangement, the support device  174  and/or shell  18  could be modified or substituted to create any of the other aforementioned arrangements. For example, the conventional shell arrangement could be utilized by using a conventional shell  62  and a support device having an outer contour like that of the support device  60  of  FIGS. 2   a  and  2   b . Likewise, the notched shell and split shell arrangements could also be utilized by similar modifications and/or substitutions to the shell and the support device. 
     With reference to  FIGS. 9   a  and  9   b , another preferred embodiment of the present invention is illustrated. In this embodiment, a support device  184  is formed integrally with or as part of a bolt  186 . Again, the outer surface configuration of the support device varies and is dependent upon the shell and support device arrangement desired. In  FIGS. 9   a  and  9   b , a precisely controlled diameter arrangement is illustrated. Thus, the outer contour or outer transition surface  188  of the support device  184  is like the outer contour of the support device  20  of  FIGS. 1   a  and  1   b . Also, the taper angle can be like the taper angle of the support device  20  such as sixty degrees. 
     Installation occurs like the precisely controlled diameter arrangement of  FIGS. 1   a  and  1   b  except that the support device  184  is already on the bolt  186 . 
     Again,  FIGS. 9   a  and  9   b  only illustrate the precisely controlled diameter arrangement. Alternatively, the support device  184  and/or shell  18  could be modified or substituted to create any of the other aforementioned arrangements. For example, the conventional shell arrangement could be utilized by using a conventional shell  62  and a support device having an outer contour like that of the support device  60  of  FIGS. 2   a  and  2   b . Likewise, the notched shell arrangement and the split shell arrangement could also be utilized in the manner described in reference to the support device  184 . 
     With reference to  FIGS. 10   a  and  10   b , yet another embodiment of the present invention is illustrated. In this embodiment, an expansion shell assembly comprises the tapered camming plug  18 , a support device  190 , and an expansion shell  192 . 
     The expansion shell  192  has a circular base portion  194  that includes an inner surface  196  having an inward taper  198  from a lower end portion of the base portion  194  to engage a corresponding taper on the support device  190 . The expansion shell  192  also has a plurality of longitudinally extending fingers  199  generally spaced apart from one another. 
     Like the precisely controlled diameter shell  16  of  FIGS. 1   a  and  1   b , each finger  199  is formed integral at one end portion with the circular base portion  194  and extends upwardly therefrom to form a free end portion for outward expansion of the finger  199 . The fingers  199  each have an inner surface for engaging one of a plurality of flat side walls of the camming plug and an outer surface for frictionally engaging a bore hole (not shown) formed in a rock formation. 
     The support device  190  has a threaded axial bore for threaded engagement with the bolt  12 , a lower end, an upper end whose outer diameter is less than the lower end, and a surrounding side wall  200  that transitions outwardly from the upper end to the lower end. The outer transition surface  200  has corresponding taper or tapered portion  202  beginning at the upper end that corresponds to the inward taper of the shell  192 , a transition radius portion  204  (such as about 0.030 inches), and a straight portion  206  that is parallel to the axial bore ending at the lower end. 
     Installation occurs as described above with reference to the precisely controlled diameter shell arrangement of  FIGS. 1   a  and  1   b . However, upon continued rotation of the bolt  12  the axial force between the expansion shell  192  and the support device  190  increases. By virtue of this increasing axial force and corresponding increasing friction between the expansion shell  192  and support device  190 , the support device  190  is held in a fixed, non-rotating position. Thus at a predetermined bolt torque, the support device  190  is held in a fixed, non-rotating position thereby allowing the bolt  12  to advance upwardly and be properly tensioned. 
     The invention has been described with reference to the preferred embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.