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This application is a continuation of U.S. Ser. No. 13/291,811, filed Nov. 8, 2011. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     The invention relates to drill steel members for a roof drilling system used in mines. 
     BACKGROUND OF THE INVENTION 
     In the mining industry, it is known to support the roof of a mine by drilling vertical holes in the overhead rock strata, and then installing roof bolts into the newly drilled holes. The roof bolts are generally installed into the drilled holes with an adhesive to further secure the bolts within the drilled holes. The bolts secure a metal plate that is positioned to support the rock strata to prevent collapse of the mine roof. 
     To drill holes in the rock strata, a roof drilling machine is utilized. The drilling machines include a drill driving device and drill steel members. A carbide bit is attached to one end of the final drill steel member, to drill the holes in the mine roof. These drill steel members are generally coupled on the other end to the drill driving device by a chuck located on the drilling machine. This driving device rotates the drill steel member, and thus the drill bit, to remove material and debris from the drilled hole. Many drilling machines incorporate a vacuum suction collection system wherein the drill steel member is a hollow steel tube having a central passage, and the drill bit includes a passageway open to the central passage. The vacuum system collects the debris as it is passed through the bit passageway and the central passage during drilling of the rock strata. 
     In elevated height mines, the drill steel members are provided with a sufficient length for drilling the desired seam, without the need to replace or extend the drill steel member. In low height mines the hole is initially drilled with a shorter drill steel member, often known as a starter, and then the starter is replaced with additional sections of drill steel, such as drivers, extensions and finishers, to drill the remaining depth of the hole. The additional sections are joined together by component parts that include, for example, a drill bit seat, male and female connectors, and a drive end component. The components are attached or configured to connect to the ends of the drill steel members or sections. 
     According to one system, a drill steel section is cut to the desired drilling length for a particular member and then the ends of the section are beveled and then component parts are welded onto the corresponding ends of the drill steel section. 
     Many drawbacks for this manufacturing method exist. Welding components and drill sections can induce stress fractures and misalignments. 
     Other methods have been developed. U.S. Pat. No. 3,554,306 discloses a vacuum drill rod system utilizing tubular members. The tubular members have hexagonal inner and outer cross sectional perimeters which interact with comparable outer and inner cross sectional perimeters of cooperating elements when the rod system is connected to achieve concurrent rotation of the elements of the system. However, this system suffers the drawback that the drill steel rods have hexagonal cross sections that are rotated within the drilled hole. Such rods have been known to cause excessive sound levels within the mine due to the rattling or impact of the hexagonal surface of the drill steel against the round drilled hole. 
     U.S. Pat. No. 6,189,632 discloses a drilling system utilizing round, hollow drill steel members interconnectable by short components. The short components include a male component machined onto an end of the drill steel member and a corresponding female coupling. The male component comprises an extension with a cross-section defining an external hexagonal perimeter, and the corresponding female coupling element has a cross-section defining an internal hexagonal perimeter, the female component press fit onto the male component. One drawback of this described system is that the drill steel member must be precisely machined to length and must have the aforementioned machined end. 
     U.S. Pat. No. 6,598,688 discloses a drilling system incorporating a drill member having a central through bore and opposite open ends. The drill member has a cross section that defines a circular outside perimeter and a polygonal inside perimeter. The polygonal inside perimeter allows for convenient coupling of the drill member to drill bits at one end and to a motorized drill driving device at an opposite end. The polygonal inside perimeter allows for coupling of the drill members to other drill members using couplings. In order to couple the drill member to a motorized drill driving device, a base assembly is used. The base assembly includes a stub member and a base member. The base member includes a bottom fixture having a cross section defining a polygonal outside perimeter for being received into a correspondingly shaped socket or chuck of the motorized drill driving device. The base member includes a socket having a polygonal inside perimeter. The base member also includes a collar for receiving axial force from the drill driving device. The stub member includes a bottom fixture having a cross section defining a polygonal outside perimeter that is received into the socket formed in the base member. The stub member further includes a flange that is supported on an internal shoulder within the socket of the base member. In this way, the axial force exerted on the base member by the drill driving device is transferred to the flange of the stub member. The stub member further includes a stub shaft extending upwardly from the flange and having a cross section defining an outside polygonal perimeter, sized and shaped to snugly fit within the open end of the drill member. The socket of the base member is sized such that the drill member fits over the stub shaft and is partially recessed into the socket to press against a top side of the flange of the stub member. In this way, the axial thrust from the base member to the flange is transferred to the end face of the drill member. 
     The present inventor has recognized the desirability of providing a drilling system for drilling holes for mine roof bolts which does not require undue machining of the drill steel, which does not require the drill steel to be cut to predetermined lengths and which does not produce excessive noise. The present inventor has recognized the desirability of providing a drilling system that does not require special adaptors or parts to couple the drill members or “drill steel” to the chuck of the drill driving device. 
     SUMMARY OF THE INVENTION 
     The invention provides an improved drill member, or “drill steel,” for use in a drilling system for installing roof bolts in a mine. The invention provides an improved drilling system incorporating the drill member. The drill member comprises an elongated tube having a central through bore and opposite open ends. The tube has a cross section that defines a circular outside perimeter along most of its length and a polygonal inside perimeter throughout its length. At least one end portion of the drill member tube has a polygonal outside perimeter. The end portion can be inserted into a corresponding socket of the drill chuck having a polygonal inside perimeter. The need for a stub member and base member as described in U.S. Pat. No. 6,598,688 is obviated. The polygonal inside perimeter of the drill member tube allows for convenient coupling of the drill member to drill bits at one end and to a motorized drill driving device at an opposite end. The polygonal inside perimeter allows for coupling of the drill members to other drill members using couplings. 
     The drill members can be cut to any length and the cut open end can accommodate components or interposed couplings without the need for machining a specialized coupling element or configuration onto the member. Additionally, the round outside perimeter allows the drill steel to be more quietly rotated within the drilled hole. 
     Numerous other advantages and features of the present invention will be become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagrammatic view of a prior art drill system, in use in a mine; 
         FIG. 2A  is an enlarged plan view of the prior art drill components of the drill system of  FIG. 1 ; 
         FIG. 2B  is an exploded view of the prior art drill components of  FIG. 2A ; 
         FIG. 3A  is an enlarged plan view of the prior art drill member of the drill components shown in  FIGS. 2A-2B ; 
         FIG. 3B  is a side view of the prior art drill member of  FIG. 3A ; 
         FIG. 4A  is a side view of a first embodiment drill member according to the invention; 
         FIG. 4B  is a right side end view of the first embodiment drill member shown in  FIG. 4A ; 
         FIG. 5A  is a side view of a second embodiment drill member according to the invention; 
         FIG. 5B  is a right side end view of the second embodiment drill member shown in  FIG. 5A ; 
         FIG. 6  is a sectional view of a drill member of  FIG. 4A or 5A  in a chuck of a drilling head; 
         FIG. 6A  is a sectional view taken along line  6 A- 6 A of  FIG. 6 ; and 
         FIG. 7  is an enlarged plan view of the assembled, extended drill components of the drill system of  FIGS. 4A-5B . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     While this invention is susceptible of embodiment in many different forms, there are shown in the drawings, and will be described herein in detail, specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated. 
     This application is a continuation of U.S. Ser. No. 13/291,811, filed Nov. 8, 2011 and incorporates that application in its entirety. 
       FIG. 1  illustrates a prior art roof drilling machine  20  as described in U.S. Pat. No. 6,598,688. The machine  20  is designed to operate within low seams  21 , such as seams of coal. The drilling machine includes a chassis  22  that is supported on wheels  24  from the mine floor  25 . Articulated boom components  28  support a drill head  34  that is a motorized drill driving device. 
     A base assembly  42  is fit onto, and into, the drill head  34 . The base assembly  42  is used to couple a lowest drill member  46   d  to the drill head  34 . A drill bit  56  is fixed to an end of the highest drill member  46   a  via a bit seat  59 . Drill members  46   a ,  46   b ,  46   c  extend from the lowest drill member  46   d  into the drilled hole  47  into the roof  48 . 
     The hole  47  is initially started by the drill member  46   a  extending from the base  42 , and the drill members  46   b ,  46   c ,  46   d  are progressively added, as needed, as the bit  56  progresses into the rock. The drill members  46   a ,  46   b ,  46   c ,  46   d  are connected by interposed connectors or couplings  49 , shown in detail in  FIGS. 5E and 5F . 
     Once the hole  47  is drilled, an anchor  64  mounted on a shank  68 , is inserted into the hole  47  and a threaded end  69  of the shank receives a nut  72 . The nut  72  is tightened to secure a roof plate  76  against the roof  48 . 
       FIGS. 2A-2B  illustrate, as an example, the drill members  46   a ,  46   b , coupled together and coupled to the base  42 , and the bit  56  via a bit seat  59 . The drill members  46   a ,  46   b  (and also  46   c ,  46   d , not in use yet in the configuration shown in  FIGS. 2A-2B ) each comprise an elongated tube having a round outside perimeter  112   c  and a hexagonal inside perimeter  112   d  defining a central through bore  112  and opposite open ends  112   a ,  112   b  (shown in  FIGS. 3A, 3B ). 
     The bit seat  59  includes a bit shank  59   a  and a base shank  59   b  each having polygonal, preferably hexagonal, outside perimeters. The drill bit  56  includes a socket  57  having a polygonal, preferably hexagonal, inside perimeter  57   a . The bit shank  59   a  and a button clip  59   c  fit within the socket  57  and are used together to tightly engage the bit seat  59  to the bit  56  as explained in U.S. Pat. No. 6,189,632, herein incorporated by reference. The outside perimeter  59   b  of the bit seat shank  59   b  is shaped to snugly fit within the open end  112   a  of the drill member  46   a . The seat  59  also includes a rounded flange  59   d  that matches the outside diameter of the drill member  46   a.    
       FIGS. 3A, 3B  illustrate that the members  46   a ,  46   b ,  46   c ,  46   d  each has a cross section that defines the circular outside perimeter  112   c , and the polygonal inside perimeter  112   d , defining the through-bore  112 . 
     Returning to  FIGS. 2A-2B , the base assembly  42  includes a stub member  120 , and a base member  126 . The base member  126  includes a bottom fixture  131  having a cross section defining a polygonal outside perimeter  131   a . The polygonal outside perimeter  131   a  is provided by a square lug portion  170  shown in  FIGS. 6A and 60  and described below. The outside perimeter  131   a  is sized to be received into a correspondingly shaped socket (not shown) of the motorized drill driving device  34  to couple the fixture  131  and the drill driving device  34  for mutual rotation. The base member  126  includes a collar  134  for receiving axial (upward) force from the drill driving device  34 . 
       FIGS. 4A-5B  illustrate drill members  146 ,  246  according to the present invention. 
     A first embodiment drill member of  FIGS. 4A-4B  includes a tube  148  having a cylinder portion  150  having a circular perimeter  152  throughout most of its length. The tube has an overall length “A.” The length “A” can be any practical length but preferably is 24 inches, 36 inches or 48 inches. The perimeter has a preferred diameter D 1  of about 0.95 inches or 1.25 inches. 
     The tube  148  also includes an end portion  156  having a polygonal outside perimeter  160 . Preferably the polygonal outside perimeter  160  is hexagonal and has a flat-to-flat dimension F 1  of about 0.87 inches or 1.12 inches. Preferably, the end portion has a length B of less than one foot and preferably about 6 inches and is machined into the circular perimeter that otherwise defines the cylindrical portion  150 . The tube  148  has an inside through-opening  168  having a polygonal inside perimeter  170 . Preferably, the polygonal inside perimeter  170  is hexagonal and has a flat-to-flat dimension F 2  of about 0.63 inches or 0.82 inches. Preferably, the polygonal inside perimeter  170  has a point to point dimension F 3  of about 0.71 inches or 0.92 inches. 
     A second embodiment drill member of  FIGS. 5A-5B  includes a tube  248  having a cylinder portion  250  having a circular perimeter  252  throughout most of its length. The tube has an overall length “G.” The length “G” can be any practical length but preferably is 144 inches. The perimeter has a preferred diameter J 1  of about 0.95 inches or 1.2 inches. The tube  248  also includes end portions  256 ,  257  each having a polygonal outside perimeter  260 . Preferably the polygonal outside perimeter  260  is hexagonal and has a flat-to-flat dimension K 1  of about 0.87 inches or 1.12 inches. 
     Preferably, the end portion has a length H of less than one foot and preferably about 6 inches and is machined into the circular perimeter that otherwise defines the cylindrical portion  250 . The tube  248  has an inside through-opening  268  having a polygonal inside perimeter  270 . Preferably, the polygonal inside perimeter  270  is hexagonal and has a flat-to-flat dimension K 2  of about 0.63 inches or 0.82 inches. Preferably, the polygonal inside perimeter  270  has a point to point dimension K 3  of about 0.70 inches or 0.92 inches. The drill member  246  is especially suitable as drill member stock that can be cut to desired lengths in the mine. Each part of a cut drill member  246  would thus include an end portion  256 ,  257 . 
     The drill members  146 ,  246  are preferably composed of 4130 30CrMo. 
       FIG. 6  illustrates how either drill member  146 ,  246  is coupled directly to a chuck  300  of a drilling head  34 . The chuck  300  includes a generally cylindrical body  302  of steel or iron and has a countersunk axial bore  306 . The bore  306  includes three regions of differently sized and shaped sockets that are adaptable to receive different types of drilling elements. A top region  308  has a large square cross-section  308   a . A next region  310  has a large hexagonal cross-section  310   a . A lower region  312  has a smaller hexagonal cross-section  312   a . The hexagonal cross-section  312   a  of the lower region  312  is sized and shaped to snugly surround the outside polygonal perimeter of the end portion  156 , or the end portion  256 ,  257 , of either drill members  146 ,  246 . A bottom shoulder  320  defines a bottom opening  322  and supports an end face  330  of either member  146 ,  246  in order to urge the drill member  146  or  246  axially during drilling. 
     The chuck  300  includes keys  336 ,  338  insertable into key ways (not shown) of the drilling head  34  to lock the chuck  300  for rotation to the drilling head  34  for motorized turning during drilling operation. 
     As illustrated in  FIG. 7 , a drill member  146  can be used to initially engage into the chuck  300  (shown schematically in phantom) of the drilling head at a base end  146   a  and receives a drill bit  56  and coupling  59  on the distal end  146   b . As the drilled hole extends into the rock, an additional drill member  146 ′ can be coupled between the base end  146   a  of the drill member  146  and the chuck  300  of the drilling head  34 . The member  146 ′ can be configured as a preconfigured piece such as a drill member  146  or can be a cut off section from a drill member  246 , sized to suit. Multiple added drill members  146 ′ can be added via couplings  49  as the drill assembly extends deeper into the rock. The drill member  246  includes end portions  256 ,  257  that are each configured to engage into the chuck of the drilling head. Thus, a drill member  246  can be cut to provide two lengths of drill member, equal lengths or not equal lengths that can be used to sequentially couple to the chuck of the drilling head. In effect, a first cut-off portion of a drill member  246  can be drilled into the rock and then the second cut-off portion of the drill member  246  can be coupled to the chuck and to the training end of the first cut-off portion to continue drilling. 
     The coupling elements  49 ,  59  and the drill  56  are configured and coupled to the drill members  146 ,  146 ′ using the inside polygonal perimeters of the drill members as described in the embodiment of  FIGS. 2A and 2B . 
     The drill members  146 ,  246  can be cut to any length, and the resultant cut open end can accommodate components without the need for machining a specialized coupling element or configuration. Additionally, the round outside perimeter of the tubes  148 ,  248  allows the drill member to be more quietly rotated within the drilled hole  47 . 
     The inventive method is further characterized in that suction can be applied to the chuck  300  through the opening  322  of the chuck  300  to collect debris produced by the action of the drill bit  56 , through the interior polygonal through opening of the drill members and couplings. 
     From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred. It is, of course, intended to cover by the appended claims all such modifications as fall within the scope of the claims.

Summary:
A drilling system for drilling vertical holes in a mine roof includes a chuck configured to be driven in rotation by a motorized drill head. The chuck is cylindrical has a bore having a first polygonal inside perimeter. A drill member has an elongated hollow body with a cross section defining a circular outside perimeter over most of its length and a constant, second polygonal inside perimeter along substantially the entire length of the drill member. The drill member has at least one end region having a first polygonal outside perimeter that is sized to fit into the first polygonal inside perimeter to rotationally engage the drill member with the chuck. Drill bits having a bit fixture having a cross section with a second polygonal outside perimeter are sized and configured to fit snugly inside the second polygonal inside perimeter to be mounted to the drill member opposite the chuck.