Patent Publication Number: US-11028649-B2

Title: Raise boring head for rotary boring

Description:
RELATED APPLICATION DATA 
     This application is a § 371 National Stage Application of PCT International Application No. PCT/EP2016/060254 filed May 9, 2016 claiming priority to EP Application No. 15170073.9 filed Jun. 1, 2015. 
     FIELD OF INVENTION 
     The present invention relates to a raise boring head and in particular, although not exclusively, to a boring head having a mount face to mount a plurality of roller cutters with at least one guide block projecting from the mount face to facilitate the transport of cut material away from the mount face. 
     BACKGROUND ART 
     Raise boring operations may be performed in a mine or other underground works to provide access or to create ventilation shafts. The technique typically involves drilling a small diameter pilot hole from a first location to a second location. Once completed, the pilot bit is removed and a large diameter raise boring head is mounted at the drive shaft, with the shaft having a diameter corresponding to that of the pilot hole. The raise head is rotated and drawn upwardly along the pilot hole so as to enlarge the initial hole to the desired diameter. 
     Raise boring apparatus is accordingly subject to extreme operating forces and high-performance components are required to endure the harsh working environment and the physical and mechanical demands during cutting. The raise boring head includes replaceable roller cutters distributed over a mount face of the head that act to disintegrate the rock as they rotate independently. Accordingly, the distribution and configuration of the cutters at the boring head may be adapted in an attempt to maximise cutting performance whilst extending, as far as possible, their operational lifetime. Conventional raise bore apparatus is described in U.S. Pat. Nos. 4,228,863 and 4,386,670. 
     One problem with conventional boring heads is the accumulation of cut debris at the region around the roller cutters. Regrinding of accumulated debris impedes cutting efficiency and accelerates cutter wear. U.S. Pat. No. 4,179,000 describes a raise boring head having a generally conical main plate to mount the roller cutters in an attempt to prevent the build-up of cuttings and provide a self-cleaning head. However, via the conical mounting face, the roller cutters are configured to engage the rock at different respective axial height positions (relative to the drive shaft) and this is disadvantageous for a number of reasons. In particular, differential cutter wear necessitates interchange or premature replacement of the radially innermost cutters that are subject to greater stresses and compressive forces. Additionally, localised debris accumulation at the region of the saddles remains problematic and affects certain cutters of the array depending upon their position at the mount face. Accordingly, what is required is a raise boring head that addresses the above problems. 
     SUMMARY OF THE INVENTION 
     It is an objective of the present invention to provide a raise boring head for rotary boring that is optimised for cutting efficiency including in particular maximising the boring rate whilst extending, as far as possible, the service lifetime of the roller cutters. The objectives are achieved by providing a raise boring head that greatly facilitates the transport of cut material away from the active cutting face of the head to avoid debris accumulation at the region around, between or to the lateral sides of the roller cutters. Advantageously, the subject invention provides a raise boring head in which a face of a body that mounts the roller cutters comprises at least one or a plurality of guide blocks that project from the mount face. The guide blocks each comprise at least one guide surface being aligned transverse to the mount face of the body to facilitate the rearward transport of cut material during boring. Optionally, the body of the boring head may comprise one or a plurality of open channels extending axially through the body from the mount face to a rear face with a corresponding guide block positioned immediately adjacent the open end of the channel so as to direct or funnel cut material into the channel to fall under gravity downwardly away from the cutters. 
     According to a first aspect of the present invention there is provided a raise boring head for rotary boring in rock comprising: a body mountable at a drive shaft, the body having a mount face to extend radially outward from the shaft; a plurality of saddles provided at the mount face to rotatably mount respective roller cutters at the body; characterised by: at least one guide block attached to the body to project from the mount face at a position adjacent or spaced apart from the saddles, the guide block having at least one guide face aligned transverse to the mount face to facilitate the transport of cut material away from the mount face, wherein the guide block is separate to and formed non-integrally with the saddles. 
     Reference within this specification to the ‘mount face’ of the body encompasses a surface region of the body that is aligned generally perpendicular to the drive shaft and accordingly a central axis extending through the boring head and the drive shaft. The mount face may however be aligned transverse to the central axis so as to be inclined or declined relative to the drive shaft. Additionally, the mount face may be formed as a generally planar surface region having one or a plurality openings or holes that represent open ends of the debris flow channels that extend axially through the body from the mount face to a rear face. The mount face therefore may be formed as sections or regions of a grid or lattice structure that support the saddles and roller cutters. 
     Reference within this specification to the ‘body’ encompasses a raise boring head that may be extendable and formed as a modular, segmented reaming head. Alternatively, the boring head may be formed as an integral reaming head in which a single body is mounted directly to the drive shaft. Where the raise boring head is extendable, the drive shaft is mounted at the extension bodies indirectly. 
     Preferably, the roller cutters and saddles are mounted at the head such that the uppermost cutting region of the cutters are aligned at the same axial height (relative to the drive shaft) and separation distance from the mount face. Such an arrangement is advantageous to promote uniform wear of the cutters at the different radial positions on the mount face. 
     Optionally, the guide face is generally planar and inclined relative to the mount face. Optionally, the guide face may be curved relative to the mount face or comprise a curved region. The inclined or curved mount face acts to provide a surface over which the cuttings can pass (slide) under gravity as they are cut and ejected from the rock face by the rotating cutters. The inclination or curvature also acts to direct the cuttings to a particular discharge location such as over an inner or outer peripheral edge of the body or through an open channel extending axially through the body. 
     Preferably, the boring head further comprises at least one attachment bolt to secure the guide block to the mount face. Such an arrangement is advantageous to allow convenient and adjustable interchange and potential repositioning of the guide block(s) at the mount face to suit particular distributions of roller cutters at the body. For example, it may be desirable for a user to adjust the position of one or more guide blocks following a period of initial boring and the observation of any particular debris accumulation zones that may be dependent upon the rock type, the orientation of the boring and any other factors such as variations in the roller cutter configuration or stratum. Preferably each of the saddles are secured to the mount face via attachment bolts that are separate and independent to the attachment of the at least one guide block to the mount face via at least one respective attachment bolt. 
     Optionally, the guide blocks may be secured to the mount face by a weld material. Additionally, the guide blocks may be secured by any other permanent or reasonable attachment mechanisms including locking pins, tongue and groove arrangements, twist lock engagements, bayonet fixings etc. 
     Preferably, the guide block projects from the mount face by a distance that is less than a distance by which at least some of the saddles project from the mount face. Preferably, the guide block projects from the mount face by a distance that is less than a distance by which the closest neighbouring saddle to the guide block projects from the mount face. Optionally, at least some of the saddles may be recessing into the mount face. More preferably, the guide block projects from the mount face by a distance that is less than a distance by which each of the roller cutters project from the mount face. Such an arrangement is advantageous to avoid direct contact with the rock and accordingly the premature wear of the guide block. Preferably, the at least one guide block comprises a height that is less than half of the height of a saddle such that the roller cutters are mounted to stand proud of the guide blocks. Optionally, the at least one guide block projects from the mount face by a distance that is 10 to 50%, 15 to 45% or 25 to 40% of a distance by the saddles project from the mount face. Additionally, the at least one guide block may project from the mount face by a distance that is 10 to 50%, 15 to 45% or 25 to 40% of a distance by the roller cutters project from the mount face. 
     Preferably, the boring head comprises one or a plurality of open channels extending axially through the body from the mount face to a rear face. Preferably, the guide block or a plurality of guide block are positioned at the mount face adjacent an open end of the channel(s) to deflect cut material into the channel for transport from the mount face to the rear face. Optionally, a single guide block may be positioned laterally to one side of each open end of the channel or a plurality of guide blocks may be positioned adjacent the channel open end. Optionally, the guide block may be positioned at or towards a perimeter edge of the mount face representing the radially outermost region of a boring head. Optionally, the guide block may be positioned at a radially inner region of the mount face adjacent the drive shaft. Such configurations can accordingly be optimised to maximise the through transport of cuttings away from the mount face at zones where debris accumulation may be problematic due to a particular distribution of roller cutters at the body. It is preferable that the guide blocks are positioned at the mount face circumferentially or radially between the saddles where the saddles may be distributed at the same or different respective circumferential and radial spacing relative to one another. Optionally, the guide blocks may be positioned asymmetrically or symmetrically at the mount face with respect to the distribution of roller cutters (and saddles). 
     Optionally, where the boring head is modular, the body may comprise a main body (or hub) and at least one extension body removably mounted to a lateral side of the main body, the extension body having a corresponding mount face to provide a radial extension of the mount face of the main body. Optionally, the boring head may comprise the same or different extension bodies mountable at the lateral sides of the main body. Optionally, the boring head comprises a plurality of a first type of extension bodies and a plurality of a second type of extension bodies so as to radially extend the mount face and the operative cutting diameter of the boring head. Accordingly, the present raise boring head may be extendable and may be formed as a modular, segmented reaming head. Alternatively, the boring head may be formed as an integral reaming head in which a single body mounts a plurality of roller cutters and one or a plurality of guide blocks. 
     Optionally, where the boring head is segmented or extendable via one or more extension bodies, the boring head may comprise a guide block or a plurality of guide blocks positioned at the mount face of the main body and/or the extension body radially inside or radially outside the saddles. Such a configuration facilitates the deflection of cut material away from the mount face at all regions of the boring head including radially inner and radially outer sections. 
     As will be appreciated, the guide block according to the subject invention may comprise any geometry so as to provide a guide face that is aligned transverse to the mount face of the boring head. Optionally, the at least one guide block may be formed as a triangular prism having a single or dual guide face extending from the apex of the guide block. Optionally, the guide block is generally wedge shaped and is formed as a single piece component. Optionally, the guide block comprises one or a plurality of through bores to receive attachment bolts for mounting the guide block to the mount face. Where the guide block is formed as a triangular prism, a through bore may be formed through each of the two guide faces of the prism. Optionally, the guide face may be planar, curved, profiled or comprise channels or directing fins to facilitate the directing of material from the cutting face. Optionally, the guide blocks may be formed from a metal or metal alloy and may comprise a wear resistant, low friction coating on the guide face to facilitate debris transport. 
     According to a second aspect of the present invention there is provided boring apparatus comprising a raise boring head as claimed herein. 
     According to a third aspect of the present invention there is provided a method of raise boring comprising providing a self-cleaning raise boring head in which cut material is transported away from the mount face via a plurality of guide blocks formed non-integrally with the saddles and being attached to the mount face independently of the corresponding attachment of the saddles. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       A specific implementation of the present invention will now be described, by way of example only, and with reference to the accompanying drawings in which: 
         FIG. 1  is a schematic illustration of raise boring apparatus to create a borehole between a first and a second underground location using a boring head that mounts a plurality of roller cutters; 
         FIG. 2  is a perspective view of a main body of the boring head of  FIG. 1  mounting a plurality of saddles that in turn mount the roller cutters (removed for illustrative purposes) and a pair of guide blocks to facilitate the discharge of cut material away from the boring head during cutting according to a specific implementation of the present invention; 
         FIG. 3  is a magnified perspective view of the guide blocks and a mount face of the main body of  FIG. 2 ; 
         FIG. 4  is a further perspective view of the main body of  FIG. 3  with the saddles removed for illustrative purposes; 
         FIG. 5  is a perspective view of one of the guide blocks of  FIG. 4 ; 
         FIG. 6  is a side elevation view of one of the guide blocks, saddles and roller cutters attached to the mount face of the main body of  FIG. 4 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION 
     Referring to  FIG. 1 , raise boring apparatus comprises a raise boring head indicated generally by reference  105  mounted at one end of an elongate drive shaft  104  that is in turn rotatably driven by a drive rig  103 . Rig  103  according to the example illustration is mounted at a first underground location  101  being separated from a second underground location  102  by a layer of rock  100 . A pilot borehole  106  is formed within rock  100  as an initial pilot drilling operation using a pilot bit (not shown) attached to the end of drive shaft  104  (typically formed from end-to-end threaded rods). Following the creation of the pilot bore  106 , the pilot bit is replaced at the end of the shaft  104  by raise boring head  105  having an appreciably larger diameter than the initial pilot bit so as to create a larger diameter bore  109 . Both shaft  104  and boring head  105  are mounted centrally on longitudinal axis  111  such that the boring head  105  projects radially outward from axis  111  by a predetermined radius to achieve the desired diameter of bore  109 . Boring head  105  comprises a main body  110  that mounts a plurality of saddles  107  that in turn mount respective roller cutters  108 . As shaft  104  is rotated via rig  103 , main body  110  is configured to rotate with each cutter  108  also rotating independently to cut into the rock  100  as the shaft  104  is retracted axially towards rig  103  and the boring head  105  raised vertically into the rock  100  from the second location  102  to first location  101 . 
     Referring to  FIG. 2 , main body  110  is formed as an extendable or modular reaming head in which a central section provides a mounting for side extensions or wings (not shown). In particular, main body  110  comprises sidewalls  204  and respective attachment couplings  203 ,  210  positioned to secure the head extensions (not shown) against or opposed to sidewalls  204  so as to extend the diameter of the boring head  105  relative to axis  111 . Main body  110  comprises a planar mount face indicated generally by reference  200  that comprises a cylindrical through bore  201  (defined by a circular opening  208  within mount face  200 ) centred on axis  111  and extending axially through the main body  110  from the mount face  200  to a rear face  202  that mounts drive shaft  104  at boring head  105 . Mount face  200  also comprises a plurality of openings  211  distributed around central bore  201  that at least partially define channels  205  that also extend from mount face  200  to rear face  202 . Channels  205  are open at both faces  200 ,  202  to allow the downward discharge (under gravity) of cut material from the mount face  200  to the rear face  202  to then fall below boring head  105 . Accordingly, mount face  200  is divided into a plurality of spokes  209  extending radially from an outer perimeter edge  207  to the central bore  201 . 
     Each spoke  209  provides a mounting region for one or a plurality of saddles  107  that each mount respectively a roller cutter  108  (removed from  FIGS. 2 and 3  for illustrative purposes). Each saddle  107  projects upwardly from mount face  200  in a direction of axis  111  and drive shaft  104 . According to the specific implementation, a guide block  206  is also attached to mount face  200  at a radially inner region of two diametrically opposed spokes  209 . Guide blocks  206  are positioned radially inside respective saddles  107  so as to be positioned radially intermediate saddles  107  and central axis  111  (and drive shaft  104 ) during use. 
     Referring to  FIGS. 3 to 5 , each guide block  206  is formed as a single piece body in a form of a triangular prism having a base surface  400  mounted in contact with mount face  200  of main body  110 . A pair of substantially planar inclined guide faces  300   a ,  300   b  project upwardly from base surface  400  and together define an apex or ridge  500 . A pair of generally vertical side faces  501  extend perpendicular to the base surface  400  at each lateral side of the inclined guide faces  300   a ,  300   b . Accordingly, with guide block  206  secured in position at mount face  200 , guide faces  300   a ,  300   b  extend transverse to the generally horizontal planer mount face  200 . According to the specific implementation, the elongate apex  500  is aligned with the radially extending spoke  209  on which the guide block  206  is mounted and also a corresponding rotational axis (also extending in a radial direction from axis  111 ) about which the roller cutter  108  is configured to rotate when mounted at saddle  107  positioned radially outside and adjacent guide block  206  on the same spoke  209 . Accordingly, guide faces  300   a ,  300   b  are inclined upwardly from the lateral sides  303  of spoke  209  such that cut material is configured to slide downwardly over faces  300   a ,  300   b  to then fall into each channel  205  to each lateral side  303  of spoke  209 . 
     Each guide block  206  comprises a pair of through bores  301  that extend from each respective guide face  300   a ,  300   b  to base surface  400  so as to receive attachment bolts (not shown) to releasably attach each guide block  206  to main body  110  via mount face  200 . The bolts (not shown) are secured within threaded bores  401  extending axially into main body  110  from mount face  200 . Corresponding threaded bores  402  are also provided on each spoke  209  so as to releasably attach saddle  107  via separate corresponding bolts received through respective bores  302  formed through a base region of saddle  107 . 
     By configuring mount face  200  with a plurality of threaded bores  401 ,  402  at different locations, and via the appropriate attachment bolts (not shown) guide blocks  206  and saddles  107  are independently and interchangeably mounted at main body  110 . 
     Referring to  FIG. 6 , each guide block  206  projects upwardly from mount face  200  by a distance A corresponding to the vertical height of apex ridge  500  from mount face  200 . Each saddle  107  comprises a pair of upstanding arms  600  to receive roller cutter  108  therebetween for rotation about axis  603 . Each arm  600  comprises an uppermost end  601  that extends vertically above mount face  200  by a distance B. Roller cutter  108  comprises a plurality of cutting inserts  602  that represent the leading uppermost components of cutter  108  being configured to engage and cut the rock  100 . Cutting inserts  602  are separated by a maximum distance C from mount face  200  as the cutter  108  rotates about axis  603 . It is desirable that guide block  206  is mounted (in the axial height direction) below the uppermost cutting region of the cutters  108  and the uppermost end  601  of saddles  107  so as to avoid damage to the guide block  206  due to contact with the rock face  100  and a reduction in the cutting efficiency and boring rate of head  105 . Accordingly, apex  500  is positioned in the lower half of the height of saddle  107  and significantly below the upper cutting region of cutter  108 . In particular, distance A is approximately 30 to 40% of distance B and 25 to 37% of distance C. Additionally, according to the specific implementation, a length of guide blocks  206  is less than a corresponding length of each saddle  107  in a radial direction of spoke  209 . In particular and according to the specific implementation, a length of guide block  206  is slightly greater than half of the length of saddle  107 . According to the specific embodiment of  FIGS. 2 to 6 , guide blocks  206  are configured to prevent accumulation of debris at the radially inner region of the mount face  200  by directing the cut material into the channels  205  via guide faces  300   a ,  300   b.    
     According to further specific embodiments, guide blocks  206  may comprise generally curved guide faces  300   a ,  300   b  where the curvature may be concave or convex in the axial direction perpendicular to mount face  200 . Additionally, each guide block  206  may comprise a single guide face ( 300   a  or  300   b ) or may comprises a plurality of guide faces where the guide block is formed as a polyhedron. According to further embodiments, guide blocks  206  may be removably positioned towards the perimeter edge  207  so as to avoid the accumulation of debris material at the perimeter of the main body  110  and between the main body  110  and an extension body (not shown) attached at one or more of the sidewalls  204 . 
     The present reaming head may comprise a plurality of the same of different shaped guide blocks  206  and may comprise a symmetrical or asymmetrical distribution of guide blocks  206  at mount face  200 .