Abstract:
A rock drilling system comprising a rock drill adapted to hold a drill steel to which a drill bit is connected, a drill feed rail for slidably supporting a drill feed that displaces the rock drill along the drill feed rail, a stinger-supported centralizer assembly for centralizing the drill steel, wherein the stinger-supported centralizer assembly has a centralizer base made of an elastomeric material, and a travelling cradle centralizer assembly slidable over the drill feed rail for centralizing the drill steel, wherein the travelling cradle centralizer assembly has a cradle made of an elastomeric material.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates generally to mining equipment and, in particular, to jumbo drilling (i.e. production drilling) and rock bolting, i.e. rock drilling for installing rock bolts as ground support in an underground mine. 
       BACKGROUND 
       [0002]    In a mine, ground support, e.g. rock bolts and screening, is used to prevent rock falls. Several different types of rock bolts may be used but all require that holes be drilled in the rock first. This is done with equipment known as rock drills or combined drilling-bolting systems. These are typically mobile units with a bolting head attached. To drill a hole in the rock to install ground support, the bolting head is placed against the rock face (which is called “stinging the face”) and then a hole is drilled into the rock. The unit is then indexed to install the rock bolt as ground support. 
         [0003]    Conventionally, rock drilling systems employ centralizer assemblies composed of many rigid metal components, which are prone to vibration and which increase the weight of the assembly. These include rigid metal stinger bases, centralizer bases and tops, steel centralizer bushings. The metal components transmit unwanted vibrations from the drill steel to the feed assembly, causing wear and loosening of components. 
         [0004]    In view of these shortcomings of the prior art, an improved rock drilling system remains highly desirable. 
       SUMMARY 
       [0005]    In broad terms, the novel rock drilling system includes one or more elastomeric centralizer bases that minimize vibration and weight. 
         [0006]    Accordingly, one inventive aspect of the present disclosure is a rock drilling system comprising a rock drill adapted to hold a drill steel to which a drill bit is connected, a drill feed rail for slidably supporting a drill feed that displaces the rock drill along the drill feed rail, a stinger-supported centralizer assembly for centralizing the drill steel, wherein the stinger-supported centralizer assembly has a centralizer base made of an elastomeric material, and a travelling cradle centralizer assembly slidable over the drill feed rail for centralizing the drill steel, wherein the travelling cradle centralizer assembly has a cradle made of an elastomeric material. 
         [0007]    Another inventive aspect of the present disclosure is a stinger-mounted centralizer assembly comprising a centralizer base made of an elastomeric material, the base having a lower portion that includes a bore dimensioned to receive a hydraulically extendable stinger rod to which a stinger pad is mounted, wherein the base also has an upper portion that includes a bushing support defining a round trough and a bushing fastened to the bushing support, wherein the bushing is dimensioned to receive a drill steel. 
         [0008]    Yet another inventive aspect of the present disclosure is a travelling cradle centralizer assembly comprising a cradle made of an elastomeric material, the cradle being slidable over a feed rail, a base mounted on the cradle, the base having an upper portion that includes a bushing support defining a round trough, and a bushing fastened to the bushing support, wherein the bushing is dimensioned to receive a drill steel. 
         [0009]    This summary is provided to highlight certain significant inventive aspects but is not intended to be an exhaustive or limiting definition of all inventive aspects of the disclosure. Other inventive aspects may be disclosed in the detailed description and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    Further features and advantages of the present invention will become apparent from the following detailed description, taken in combination with the appended drawings, in which: 
           [0011]      FIG. 1  is an exploded view of a stinger assembly in accordance with an embodiment of the present invention; 
           [0012]      FIG. 2  is a perspective view of an optional two-piece centralizer bushing; 
           [0013]      FIG. 3  is an exploded view of a stinger assembly in accordance with another embodiment of the present invention; 
           [0014]      FIG. 4  is a perspective view of an optional two-piece centralizer bushing; 
           [0015]      FIG. 5  is an exploded view of a travelling centralizer cradle assembly in accordance with an embodiment of the present invention; 
           [0016]      FIG. 6  is a perspective view of an optional two-piece centralizer bushing; 
           [0017]      FIG. 7  is an exploded view of a travelling centralizer cradle assembly in accordance with another embodiment of the present invention; 
           [0018]      FIG. 8  is a perspective view of an optional two-piece centralizer bushing; 
           [0019]      FIG. 9  is a schematic top view of a rock drilling system; and 
           [0020]      FIG. 10  is a side view of a drill rig that may incorporate one or more elastomeric centralizer bases. 
       
    
    
       [0021]    It will be noted that throughout the appended drawings, like features are identified by like reference numerals. It should furthermore be noted that the drawings are not necessarily to scale. 
       DETAILED DESCRIPTION 
       [0022]    In general, the embodiments of the present invention provide a novel rock drilling system and method. The system and method utilize elastomeric centralizer assemblies. Elastomeric assemblies reduce the amount of vibration that travels from the drill steel to the drill feed assembly, thereby reducing wear on the drill feed assembly. In one set of embodiments, an elastomeric centralizer assembly is mounted in a stationary position on the stinger to support a forward portion of the drill string. In another set of embodiments, an elastomeric travelling cradle centralizer assembly is designed to slide over a feed rail, i.e. a drill feed rail of a rock drilling system. In one particular implementation, the centralizer assemblies are made of urethane although these assemblies may be made of any other equivalent or suitable elastomeric material having similar mechanical properties. 
         [0023]    Replacing existing rigid metallic components of a centralizer assembly with an elastomeric material attenuates the vibrations that propagate from the drill steel to the feed assembly, thereby reducing wear on the feed components. This new elastomeric design also reduces the number of parts as well as the weight of the assembly. A lighter assembly requires less motive power and thus consumes less energy. 
         [0024]    In the embodiments depicted by way of example in  FIGS. 1-4 , a stinger-mounted centralizer assembly  10  has a centralizer base  12  made entirely of elastomeric material, e.g. urethane or equivalent. In the embodiment depicted by way of example in  FIG. 1 , the stinger-mounted elastomeric centralizer base is moulded or cast as one integral elastomeric part. This differs from a conventional, fully metal centralizer assembly. The latter would typically include two separate metal parts, namely a metal stinger base and a separate metal centralizer base bolted thereto. In this embodiment, however, the stinger base and the centralizer base are amalgamated together as a single elastomeric component, i.e. made of an elastomer as a single cast or moulded elastomeric part. A heat guard  13  (or heat shield) is optionally attached to the top of the elastomeric centralizer base  12 . The optional heat shield, made of a heat-insulating material, shields heat caused by friction between the drill steel and the centralizer bushing from conducting to the elastomeric centralizer base. 
         [0025]    A centralizer bushing  17  is attached via fasteners  16  to the optional heat guard  13  (or is attached directly to the base  12  if no heat guard is desired). The bushing  17  remains steel (or other suitable metal or metal alloy). In a variant, the heat guard and bushing may be a single component. 
         [0026]      FIG. 2  shows an alternate bushing composed of a bottom bushing half  14  and a top bushing half  15 . 
         [0027]    In the embodiment illustrated in  FIG. 1 , the stinger pad  11  is a separate elastomeric component that is attached to the forward end of the stinger and moves relative to the centralizer base. The stinger pad and centralizer base may be made of the same material or different materials. 
         [0028]    In the embodiment depicted by way of example in  FIG. 3 , the stinger-mounted elastomeric centralizer assembly  10  incorporates the stinger pad as an integral part of the centralizer base  18 . In other words, the pad is cast or moulded as part of the base  18 . The heat guard  13  and bushing  17  are mounted to the centralizer base in the same manner as described above with reference to the embodiment of  FIG. 1 . Accordingly, the elastomeric base  18  is an amalgamation of a stinger base, a centralizer base and a stinger pad which would, in a conventional design, be three separate metal components fastened together to form an assembly.  FIG. 4 , like  FIG. 2 , shows an alternate bushing composed of the bottom bushing half  14  and the top bushing half  15 . In  FIG. 3 , the stinger pad is integral (i.e. cast, moulded or formed as a single elastomeric component) so that the base moves with the stinger when the stinger and pad are extended. In contrast, the base  12  of  FIG. 1  does not move with the stinger pad when the stinger is extended. 
         [0029]    In the embodiments depicted by way of example in  FIGS. 5-8 , a travelling cradle centralizer assembly  20  has an elastomeric centralizer base that is made of an elastomeric material. The base may be an integrated base and cradle that are formed by casting or moulding a single elastomeric part or it may be composed of two separate parts (i.e. an elastomeric cradle and a separate base that may be either metal or elastomer). 
         [0030]    In the embodiment shown by way of example in  FIG. 5 , the assembly includes an elastomeric cradle  21  to which a base  22  (or bushing support member) is fastened by bolts or other fasteners  23 . The base  22  may be made of steel or an elastomeric material or a combination thereof. An optional heat guard  24  (heat shield) may be mounted as shown between the base  22  and the bushing  28 . The bushing  28  remains steel (or any other equivalent metal or metal alloy) and is fastened by fasteners  27 .  FIG. 6 , like  FIG. 2 , shows an alternate bushing composed of the bottom bushing half  25  and the top bushing half  26 . 
         [0031]    In the embodiment shown by way of example in  FIG. 7 , the assembly has a fully elastomeric centralizer base  29  that is formed by casting or moulding the base and cradle as a single part. For the sake of greater clarity, the base in  FIG. 7  is meant to include the integrated cradle. In other words, two parts (the travelling centralizer cradle and the centralizer base) that would conventionally be metal and bolted together are, in this embodiment, amalgamated together as a single integral elastomeric component. An optional heat guard  24  is fastened as shown. The centralizer bushing  28  remains steel (or any other equivalent metal or metal alloy) and is fastened by fasteners  27 .  FIG. 8 , like  FIG. 6 , shows an alternate bushing composed of the bottom bushing half  25  and the top bushing half  26 . 
         [0032]    The elastomeric centralizer assemblies, which may be made of urethane, may be manufactured using casting or moulding techniques that are known in the art. 
         [0033]    The elastomeric centralizer base and cradle depicted by way of example in the figures are composed of an amalgamation of parts that are made of one or more vibration-attenuating elastomeric materials. In addition to vibration attenuation, the elastomeric assembly reduces the number of parts required to perform the drill-centralizing function. The use of lightweight elastomeric materials also reduces the overall weight of the assembly. The elastomeric centralizer bases furthermore eliminate the need for a rigid metallic centralizer cap by directly fastening the steel centralizer bushing to the elastomeric centralizer base. This also reduces the number of components and the weight of the assembly. 
         [0034]      FIG. 9  depicts in schematic form a rock drilling system that includes a drill string  30 , a drill feed  32 , and a drill feed rail  34  over which the drill feed slides to advance toward, or to withdraw from, a rock face  40  of a rock formation that is to be drilled for the purposes of subsequently installing a rock bolt as ground support. As shown schematically in  FIG. 9 , the stinger pad  11  is mounted at a forward end of a hydraulically extendable stinger rod  19  which extends through a stinger channel in the stinger and centralizer base assembly  12 . The stinger extends to push the stinger pad against the rock face  40  to thereby stabilize the rock drilling system the during drilling operation. The drill string  30  is centralized by both the stinger-mounted centralizer assembly  10  and the travelling cradle centralizer  20 . The latter component is rail-mounted on the drill feed rail to slide over the drill feed rail. The drill feed may also slide to advance over the drill feed rail. Once the hole is drilled, the drill feed retracts the drill string. The rock drilling system may be part of a combined drilling and bolting system, also known as a drilling/bolting jumbo, rock bolter or drilling/bolting rig. In such as a system, a bolter feed is indexed into position (i.e. alignment with the hole that has been drilled) while the drill feed is indexed out of position. With the bolter aligned, the bolt can be driven into the hole using a hydraulically powered bolting feed. The hole may also be cemented in some embodiments. The bolt may also carry a washer-type plate in some embodiments. The drilling-bolting cycle is then repeated at various locations at the rock face where ground support is to be installed. 
         [0035]    It will be appreciated that the rock drilling system could utilize the elastomeric base in only the travelling cradle or only in the stinger-mounted centralizer although best vibration-attenuation results and weight savings will be obtained when both centralizer bases are elastomeric. The concept of elastomeric bases may be applied to centralizers on the bolting feed as well as the drilling feed although it most useful on the drilling feed because of the higher vibrations encountered in drilling. 
         [0036]    The inventive concept of an elastomeric centralizer assembly may be applied to other types of drilling equipment, drilling jumbos, or hydraulic rock drill systems. For example, a simple hydraulic percussive rock drill system disclosed in U.S. Pat. No. 3,995,700 (Mayer et al) may incorporate an elastomeric centralizer assembly in accordance with another embodiment. The rock drill system (or “drill rig”) of U.S. Pat. No. 3,995,700 is depicted in  FIG. 10  and generally designated by reference numeral  100 . The drill rig has a frame or undercarriage  102 . The centralizers  50 ,  52  (or “guides”), which centralize (guide) the drill steel  30 , may be may made of elastomeric material to minimize vibration and weight. The drill steel is driven forward by the drill feed  32  over a drill feed rail  34 . At the forward end of the drill steel is a drill bit  36 . The drill feed rail is supported by a movable boom  60  positioned by actuating various linear actuators  62 ,  64  and  66 . The drill is hydraulically powered by hydraulic supply hose  68 . First and second pumps  70 ,  72 , which are driven by an electric motor  74 , supply fluid pressure to the drill feed and actuators, respectively. The drill feed may be controlled and operated from a control station  76  having a pressure-adjusting control knob or any other lever, switch, toggle or input device. The concept of elastomeric centralizers may be applied to this type of drill rig, which is presented as another example of a rock drilling system that may benefit from vibration-reducing elastomeric centralizers. It will be appreciated that the concept of elastomeric centralizers may be applied to any other rock drilling system where the drill string is guided by one or more centralizers. The elastomeric centralizers may be used on a rock bolter or in other applications such as jumbo drilling (i.e. production drilling). 
         [0037]    It is to be understood that the singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a device” includes reference to one or more of such devices, i.e. that there is at least one device. The terms “comprising”, “having”, “including” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of examples or exemplary language (e.g., “such as”) is intended merely to better illustrate or describe embodiments of the invention and is not intended to limit the scope of the invention unless otherwise claimed. 
         [0038]    The present invention has been described in terms of specific embodiments, examples, implementations and configurations which are intended to be exemplary or illustrative only. Other variants, modifications, refinements and applications of this innovative technology will become readily apparent to those of ordinary skill in the art who have had the benefit of reading this disclosure. Such variants, modifications, refinements and applications fall within the ambit and scope of the present invention. Accordingly, the scope of the exclusive right sought by the Applicant for the present invention is intended to be limited solely by the appended claims and their legal equivalents.