Patent Publication Number: US-9404364-B2

Title: Rock bolting system, method of installing rock bolts, and flexible bolt centralizer

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional application and claims the benefit of priority from U.S. patent application Ser. No. 13/658,017, filed Oct. 23, 2012, which claims priority to CA Patent Application No. 2,792,592, filed on Oct. 22, 2012, the disclosures of which are hereby incorporated by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to mining equipment and, in particular, to rock bolting. 
     BACKGROUND 
     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 bolters. These are 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 ground support. 
     Conventionally, the bolter feeds have a fixed stinger. This is the part of the feed that stabilizes the feed assembly against the rock during the drilling process. With the conventional systems, the whole feed assembly must move to the rock face. In other words, in conventional rock bolter systems, the rock drill feed and the bolting feed are connected together and thus extend and retract. This is problematic in tight areas and in some cases makes indexing difficult. 
     A need therefore exists for an effective solution to this technical problem. 
     SUMMARY 
     In broad terms, the present invention provides a novel rock bolting system, a novel method of installing rock bolts, and a novel flexible bolt centralizer. 
     The system in accordance with the present invention has independently movable feeds to enable the system to operate in confined spaces. In other words, the system has independently extendable and retractable hydraulic stinger, drilling feed and bolting feed. This system therefore enables the operator to sting the face using the hydraulic stinger without having to move the entire assembly. This system facilitates stinging in tight places. The drill and bolter feeds can remain retracted to make indexing possible. With the optional addition of a gripping mechanism and a rotation element, this system may also function as a screen handler for the installing of screening over a rock face. 
     Accordingly, one aspect of the present invention is a rock bolting system comprising a hydraulic stinger for engaging a rock face to stabilize the rock bolting system, a drill feed for drilling a hole in the rock face, and a bolting feed for installing a rock bolt into the hole, wherein the hydraulic stinger, the drill feed and the bolting feed are each independently extendable and retractable. 
     Another aspect of the present invention is a method of installing ground support using a rock bolting system having a hydraulic stinger, a drill feed, and a bolting feed. The method entails independently extending the hydraulic stinger to engage a rock face while the drill feed and bolting feed remain retracted, and then, while the hydraulic stinger is extended, independently extending the drill feed. The method then involves drilling a hole in the rock with the hydraulic stinger engaging the rock face, indexing the system to rotate the bolting feed into alignment with the hole with the hydraulic stinger engaging the rock face, and installing a rock bolt into the hole using the bolting feed. 
     Yet another aspect of the present invention is a bolt centralizer for a bolting feed in a rock bolt system. The bolt centralizer comprises a flexible body capable of elastically flexing from an upright posture for centralizing a rock bolt to a folded posture that permits a bolting feed to advance. The centralizer comprises a passage for guiding the rock bolt into a hole drilled by the rock bolt system. The centralizer comprises a base for fastening the centralizer to a sliding carriage that is adapted to slide over the rails of the bolting feed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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: 
         FIG. 1  is a top view of a rock bolting system with the hydraulic stinger, drill feed and bolting feed all retracted; 
         FIG. 2  is a top view of the rock bolting system after rotation relative to the posture of  FIG. 1  showing the hydraulic stinger extended and the drill and bolting feeds retracted; 
         FIG. 3  is a top view of the rock bolting system of  FIG. 1  showing the hydraulic stinger and drill feed extended and the bolting feed retracted; 
         FIG. 4  is a top view of the rock bolting system after rotation relative to the posture of  FIG. 3  showing the hydraulic stinger and bolting feed extended and the drill feed retracted; 
         FIG. 5  is a side view of a hydraulic stinger in its extended posture; 
         FIG. 6  is a side view of the hydraulic stinger in its retracted posture; 
         FIG. 7  is cross-sectional view of the hydraulic stinger in its retracted posture; and 
         FIG. 8  is an exploded view of the hydraulic stinger; 
         FIG. 9  is side view of a variant of the (retracted) hydraulic stinger in which the support tube is the cylinder; 
         FIG. 10  is a side view of the variant of  FIG. 9  in its extended posture; 
         FIG. 11  is a front view of a bolt centralizer in accordance with an embodiment of the present invention; 
         FIG. 12  is a side view of the bolt centralizer of  FIG. 11  in its upright posture; 
         FIG. 13  is a side view of the bolt centralizer of  FIG. 11  in its flexed posture; 
         FIG. 14  is an isometric view of the bolt centralizer of  FIG. 11 ; 
         FIG. 15  is an isometric view of a screen-gripping attachment for mounting to an end of the hydraulic stinger for handling screens in accordance with another embodiment of the present invention; 
         FIG. 16  is a side view of the rock bolter with a flexible traveling centralizer and a flexible forward centralizer mounted to the bolting feed; 
         FIG. 17  is a rear view of the rock bolter of  FIG. 16 ; 
         FIG. 18  is an isometric view of the traveling centralizer mounted to the rock bolter; 
         FIG. 19  is an isometric view of the traveling centralizer with a bolt in the passage; 
         FIG. 20  is an isometric view of a rail-mounted bolting feed having a traveling centralizer mounted on rails and a stationary centralizer mounted at a forward end of the rails; 
         FIG. 21  is an isometric view of the traveling centralizer as it flexes; 
         FIG. 22  is an isometric view of the traveling centralizer as it is completely bent/folded; 
         FIG. 23  is an isometric view of the forward centralizer as it too flexes as the bolting feed advances; and 
         FIG. 24  is an isometric view of the forward centralizer as it is completely bent/folded. 
       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 
     By way of introduction, the present invention provides a novel rock bolting system, a novel method of installing rock bolts, and a novel flexible bolt centralizer. The present invention provides improvements in the field of ground support. 
     Rock Bolter 
     In general, a rock bolter is designed to drill a hole and then to install a rock bolt into the hole. For the purposes of the present specification, the term “rock bolt” is meant to encompass rebar, split sets, expandable bolts, anchors or any other bolt-like elements designed to be installed in a hole in a rock face to provide ground support. 
     With reference to  FIGS. 1-4 , the rock bolter (or rock bolting system), which is generally designated by reference numeral  10 , has a hydraulic stinger  20 , a drill feed  30  and a bolting feed  40 . Each is hydraulically actuated using a hydraulic actuator (hydraulic cylinder, piston and rod). In the embodiments of the present invention, each of the stinger, drill feed and bolting feed is independently movable (i.e. each is independently extendable and retractable). In operation, the rock bolter is brought close to a rock face. A rock face means either the roof or the walls of a mine. Once the rock bolter is properly positioned relative to the rock face, the rock bolter extends the stinger to sting the rock face. Stinging the rock face means engaging or contacting the rock face. Stinging is done to stabilize the rock bolter. Therefore, stinging requires that the stinger press against the rock face with sufficient force to stabilize the rock bolter. With the stinger engaged against the rock face, the rock bolter then extends the drill feed to drill a hole in the rock. The drill is withdrawn by retracting the drill feed while the stinger remains in contact with the rock face. The rock bolter is indexed to rotate the bolting feed into alignment with the hole. The bolting feed is then extended (with the stinger still engaging the rock face). The stinger ensures that the bolting feed remains aligned with the hole drilled by the drill feed. The bolting feed then installs the rock bolt into the hole drilled by the drill feed. The bolting feed is extended while the stinger is extended and the drill feed is retracted. After bolting, the bolting feed may be retracted. The stinger may then be retracted. The installation of the rock bolt is complete. The rock bolter may be moved to a new location to drill another hole and install another rock bolt. 
       FIG. 1  is a top view of a rock bolter or rock bolting system  10  with the hydraulic stinger  20 , drill feed  30  and bolting feed  40  all retracted. The stinger, drill feed and bolting feed are all retracted into the retracted posture shown in  FIG. 1  when the rock bolter is stored, transported or when manoeuvred in tight spaces. At the outset of a rock bolting operation, the rock bolter is in this posture. 
       FIG. 2  is a top view of the rock bolting system after rotation about a longitudinal axis.  FIG. 2  shows the hydraulic stinger  20  extended and the drill feed  30  and bolting feed  40  retracted.  FIG. 2  thus shows the posture of the rock bolter when the stinger is extended to sting the rock face. 
       FIG. 3  is a top view of the rock bolting system showing the hydraulic stinger and drill feed extended and the bolting feed retracted.  FIG. 3  thus shows the posture of the rock bolter when the drill feed is extended to drill the hole. Drilling is performed while the stinger is extended against the rock face to stabilize the rock bolter. Note that  FIG. 3  shows the same non-rotated posture of  FIG. 1 . 
       FIG. 4  is a top view of the rock bolting system in the same rotated posture as  FIG. 2 .  FIG. 4  shows the hydraulic stinger and bolting feed extended and the drill feed retracted.  FIG. 4  shows the rock bolter after the hole has been drilled and the drill feed has been retracted and after the bolting feed has been extended to install the rock bolt into the hole. 
     The hydraulic stinger  20  described above may be constructed in accordance with a first embodiment shown in  FIGS. 5-8  or in accordance with a second embodiment shown in  FIGS. 9-10 . 
       FIG. 5  is a side view of a first embodiment of the hydraulic stinger  20 , shown in its extended posture while  FIG. 6  shows the same embodiment of the hydraulic stinger in its retracted posture. The forward end of the stinger has a bumper pad  25 , as shown in the figures, for engaging/stinging the rock face. 
       FIG. 7  is a cross-sectional view of the hydraulic stinger in its retracted posture.  FIG. 7  is a cross-sectional view taken through section line  7 - 7  of  FIG. 6 . 
       FIG. 8  is an exploded view of the hydraulic stinger. In the embodiment of  FIGS. 5-8 , the stinger has a flanged support tube  21 , an inner tube  22 , a hydraulic cylinder (actuator)  23 , one or more bearing plates  24 , and the bumper pad  25 . 
     In the second embodiment shown in  FIGS. 9 and 10 , the hydraulic cylinder  23  functions as the support tube. Therefore, the support tube may be eliminated if a lighter design is preferred.  FIG. 9  is a side view of this second embodiment of the hydraulic stinger shown in a retracted posture whereas  FIG. 10  shows this stinger in its extended posture. 
     Method of Rock Bolting 
     The foregoing rock bolter (or rock bolting system) enables a novel method of rock bolting. This method comprises independently extending the hydraulic stinger to engage (or “sting”) a rock face while the drill feed and bolting feed remain retracted. While the hydraulic stinger is still extended, i.e. still stinging the face, the method then involves independently extending the drill feed. The hole is then drilled in the rock with the hydraulic stinger engaging (stinging) the rock face. Once drilling is complete, the drill is withdrawn. The system is indexed to rotate the bolting feed into alignment with the hole. This is done with the hydraulic stinger still engaging (stinging) the rock face. The method then entails installing a rock bolt into the hole using the bolting feed. 
     In one embodiment of this method, a flexible bolt centralizer is used to guide the bolt. The bolt centralizer is made of a flexible elastomeric material that is attached to a sliding carriage for traveling over the rails of the bolting feed. The bolt is advanced through the bolt centralizer until the advancing bolting feed of the rock bolt causes the bolt centralizer to fold flexibly into a substantially orthogonal posture (as shown in  FIG. 13 ) to permit the rock bolt to be advanced all the way to the rock face. 
     The method may further involve installing a replacement centralizer when the centralizer is damaged, loses its elasticity or becomes worn out. The detachable bolt centralizer may be detachably mounted (e.g. fastened) to the sliding carriage of the bolting feed via holes in a base of the bolt centralizer. 
     In a further embodiment, the method comprises mounting a screen-gripping attachment to the hydraulic stinger, gripping a screen with the screen-gripping attachment on the stinger, placing the screen against a rock face by extending the stinger and affixing the screen to the rock face. Gripping the screen may be done by hydraulically extending a plurality of finger extensions to grip the screen. This is described below in greater detail with reference to  FIG. 15 . 
     Flexible Bolt Centralizer 
     Optionally, the rock bolter may include a novel flexible bolt centralizer mounted on sliding carriage that travels on rails of the bolting feed  40 . 
       FIG. 11  is a front view of a flexible traveling bolt centralizer  100  in accordance with an embodiment of the present invention.  FIG. 12  is a side view of the traveling centralizer in its upright posture whereas  FIG. 13  is a side view of the traveling centralizer in its flexed or bent posture.  FIG. 14  is an isometric view of the traveling centralizer in its upright posture. 
     As depicted in  FIGS. 11-14 , the bolt centralizer has a flexible body  102  capable of elastically flexing from an upright posture ( FIG. 12 ) to a folded, flexed or bent posture ( FIG. 13 ) which may be, in some embodiments, substantially orthogonal to the upright posture. In the upright posture, the bolt centralizer centralizes or guides the rock bolt along a drilling and bolting axis into the drilled hole. In the flexed, bent or folded posture, the bolt centralizer permits the bolting feed of the rock bolter to pass by the centralizer. The flexure of the traveling bolt centralizer is designed to bend or flex in response to the force imposed on the centralizer by the bolting feed as it advances such that the flexible body folds about a folding axis that is perpendicular to the drilling and bolting axis. 
     The traveling centralizer  100  comprises a passage  104  for guiding the rock bolt into a hole drilled by the rock bolt system. This passage may be formed two finger-like members  106  or upwardly curving projections that may be spread apart to receive the bolt. The finger-like extensions are elastically biased to return to the generally closed posture shown in the figures. The passage may define a generally circular aperture to guide a rock bolt that has a generally circular shaft. In the illustrated embodiment, the finger-like members are (at rest) spaced apart by a gap G that is substantially smaller than a diameter D of the generally circular aperture. Above the gap G is a generally V-shaped mouth  108 . 
     The traveling centralizer  100  includes a base  110  for fastening the traveling centralizer to a sliding carriage (shown in  FIG. 18 ) that slides on the rails of the bolting feed (as shown in  FIGS. 20-24 ). As shown in  FIGS. 11-14 , the base may include two lobes  112  (i.e. feet, pads, or flange-like extensions) that contain holes  114  through which fasteners are inserted to fasten the centralizer to the rail-mounted carriage on the bolting feed. In variants, the number of holes, the shape of the lobes and/or the placement of the holes and lobes may be varied. 
     The centralizer may include a double concave body profile  116  to facilitate bending of the centralizer from an upright posture ( FIG. 12 ) to a flexed, bent or orthogonal posture ( FIG. 13 ). The double concave body profile includes a front concavity  118  and a rear concavity  120 . The front and rear concavities may be symmetrical when the body is upright and not flexed as shown in  FIG. 12 . Beneath the double concave profile is an archway  122  as shown in  FIG. 11 . 
     In one embodiment, the flexible body is elastomeric. In one specific embodiment, the flexible body is made of urethane although it will be appreciated that similar materials may be substituted. 
     To minimize wear and prolong service life, the traveling bolt centralizer  100  may include a metal liner  124  in the passage. The metal liner may be a steel or stainless sleeve (or other suitable metal, alloy, or composite). This sleeve may be detachably fastened to the centralizer so it can be inspected, replaced, cleaned, serviced or repaired. For example, the sleeve may be bolted, screwed or otherwise fastened to the centralizer using fasteners. 
     As shown in the embodiment depicted in  FIG. 14 , the traveling bolt centralizer  100  has a base having two spaced-apart holes that are substantially orthogonal to the passage. The holes are designed to receive fasteners for fastening the centralizer to the sliding carriage of  FIG. 18  which is designed to travel on the rails of the bolting feed. 
     Screen Handler 
     Optionally, the rock bolter may include a screen handler in the form of a screen-gripping (or screen-handling) attachment. 
       FIG. 15  is an isometric view of a screen-gripping attachment  200  for mounting to an end of the hydraulic stinger  20  of the rock bolter  10 . This screen-gripping attachment is an accessory that may optionally be mounted to a distal (working) end of the stinger to enable the stinger to grip (or handle) screens. As is known in the mining industry, wire mesh screening is installed in mines as another form of ground support, to prevent loose rocks from falling. As illustrated in  FIG. 15 , the screen-gripping attachment  200  includes gripping members which may be in the form of screen-gripping finger extension cylinders  210  and extension fingers  212 . These extension fingers  212  are hydraulically actuated by the cylinders  210  to extend and engage a wire mesh screen. A rotary actuator  220  is provided to rotate the screen. A free-wheeling rotation housing  230  supports the rotary actuator to permit the rotary actuator and the finger extensions to rotate relative to the stinger. The stinger itself may extend and retract. With the rotary actuator  220 , the stinger is able to both translate and rotate the screen gripped by the extensions fingers  212 . The bolting feed may be used to insert a bolt into the rock face to fasten the screen in place while the stinger is holding the screen against the rock face. 
     Operation of Rock Bolter with Flexible Centralizer 
       FIGS. 16 and 17  are side and rear views, respectively, of the rock bolter  10  having two bolt centralizers  100 ,  150 . In the embodiment depicted in these figures, the rock bolter  10  includes both a flexible traveling centralizer  100  and a flexible stationary centralizer  150  mounted to a forward end  41  of the rails  42  of the bolting feed  40 . 
       FIG. 16  shows the hydraulic stinger  20  and its forward bumper pad  25 . The rock bolter  10  includes a feed extension cylinder  28  and piston rod  29  for extending and retracting the hydraulic stinger. 
       FIG. 16  also shows that the rock bolter  10  includes a mounting frame  12  for mounting the rock bolter to a boom, platform, or other such structure. The rock bolter includes a carousel  14 , a turret  16 , and an indexing mechanism  18 . 
     The drill feed  30  includes a rock drill  32  and drill steel  33  that extends to the drill bit. The drill bit is advanced by the drill feed to drill the hole in the rock face. After indexing using the indexing mechanism, the bolting feed  40  then drives a bolt  45  into the hole that was drilled by the drill bit of the drill feed. The bolt  45  may include a bolt plate  46 . The bolt plate  46  of the rock bolt is the end plate (flange, washer or head) of the bolt that abuts the rock face when the rock bolt is inserted into the hole. 
     As depicted in  FIG. 17 , the indexing mechanism  18  indexes the bolting feed into alignment with the drilled hole by rotating the bolting feed about a center of rotation  35 . As depicted by way of example in  FIG. 17 , the center of rotation  35  is offset relative to the two parallel axes of the drill feed and the bolting feed, i.e. the center of rotation lies between and below the drill feed  30  and the bolting feed  40  as shown in  FIG. 17 . The indexing mechanism  18  includes an indexing cylinder  37  (i.e. a hydraulic actuator) that indexes the drill feed and bolting feed by rotating the drill feed and bolting feed about the center of rotation  35  such that the bolting feed is moved into alignment with the hole drilled by the drill feed. 
       FIG. 18  is an isometric view of the flexible traveling centralizer  100  and its sliding carriage  130  that is adapted to be mounted to the rails  42  of the bolting feed of the rock bolter  10 . The flexible traveling centralizer  100 , which may be made of urethane or any other suitable elastomeric material, rides on a sliding carriage that slides over the rails of the bolting feed. As depicted by way of example in  FIG. 18 , the sliding carriage may include a plurality of spaced-apart threaded bores that align with the holes in the base of the traveling centralizer, permitting threaded fasteners to be inserted through the holes of the centralizer and into the threaded bores in the carriage. The carriage may include a wheel that rolls along a surface of the bolting feed as the carriage is advanced and retracted. By supporting at least part of the weight of the carriage, the wheel helps to provide a smoother motion for the carriage as it slides over the rails. It will be noted that the wheel rotates in the space defined by the archway  122  introduced in  FIG. 11 . 
       FIG. 19  is an isometric view of the flexible traveling centralizer  100  with a bolt  45  in the passage of the flexible traveling centralizer. The flexible traveling centralizer acts in concert with the flexible stationary centralizer to provide a two-point support for the bolt  45  to guide the bolt  45  into the hole that has been drilled. As shown in  FIGS. 20-24 , the flexible traveling centralizer  100  bends or folds out of the way as the bolting feed  40  is advanced. Due to its elasticity, the traveling centralizer  100  returns to its original upright posture after the bolting feed  40  has been retracted. Due to its shape and material, the flexible traveling centralizer  100  is able to undergo a large number of bending-unbending cycles before it needs to be replaced. 
       FIGS. 20-24  depict the operation of these flexible centralizers  100 ,  150  as the bolting feed  40  is advanced on its rails  42 .  FIG. 20  shows a rail-mounted bolting feed  40  having a traveling centralizer  100  mounted on rails  42  and a stationary centralizer  150  mounted at a forward end  41  of the rails  42 . A bolt (not shown) extends from the bolt magazine  47  of the bolting feed  40 .  FIG. 21  shows how the traveling centralizer  100  flexes as the bolting feed  40  advances on its rails  42 .  FIG. 22  shows how the traveling centralizer  100  is then completely bent/folded/flexed as the bolting feed passes over top of the centralizer  100 .  FIG. 23  shows how the forward stationary centralizer  150  also flexes as the bolting feed  40  advances toward its maximum extension along the rails  42 . It is noteworthy that the stationary centralizer has a different body structure than the traveling centralizer. The stationary centralizer has two legs with a wide stance that spans the rails. However, the stationary centralizer has two finger-like extensions that define a V-shaped mouth and a passage for receiving the bolt, which may be similar to finger-like extensions, V-shaped mouth and passage of the traveling centralizer.  FIG. 24  shows the forward centralizer  150  completely bent/folded when the bolting feed reaches its maximum extension along the rails  42 . 
     The invention described above thus provides a number of improvements in the realm of rock bolting. The independently movable stinger, drill feed and bolting feed greatly facilitate the task of installing rock bolts in a rock face. The stinger may furthermore be used, with a screen-gripping attachment, to install protective screening. The flexible centralizer provides a novel design for both the traveling centralizer and the forward, stationary centralizer, eliminating the need for complex centralizer mechanisms. Each of these improvements facilitates, and renders more efficient, the installation of rock bolts in a mine. 
     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.