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CROSS-REFERENCE TO RELATED APPLICATION(S)  
       [0001]     This application is a continuation-in-part of U.S. patent application Ser. No. 11/566,306 filed Dec. 4, 2006, which is a continuation-in-part of U.S. patent application Ser. No. 10/622,710 filed Jul. 17, 2003, the entire disclosure of each of which is hereby incorporated by reference herein for all purposes. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention concerns apparatus for drilling laser guided microbore tunnels and particularly a bore head for such apparatus.  
       BACKGROUND OF THE INVENTION  
       [0003]     In our application Ser. No. 11/566,306 being a c-i-p of Ser. No. 10/622,710, we describe microbore operations which create horizontal bores 2-6 m below ground for the introduction of pipes from 300-600 mm in diameter. These bring services such as sewerage, mains water, mains gas and the like to buildings where the runs are short but perhaps crowded such as suburban housing or industrial estates.  
         [0004]     The operation is preceded by the selection of an on-ground direction between two sites. A pit is excavated at each site and a laser is used to indicate the direction below ground level. Inclination of the beam then follows to ensure appropriate fall. Meanwhile a concrete base is cast on the pit floor or timbers are laid and the pit wall which is to receive the bore is faced with concrete and a circular aperture is formed in the wall using a plug.  
         [0005]     The drilling platform is lowered on to the base and a target on the shaft of the bore head and platform are aligned as a unit with the laser spot. The platform is secured in the pit using peripheral jacks and the ancillary services such as hydraulic power and mains water and vacuum operation are brought to the pit.  
         [0006]     The specification proposes various improvements to the equipment. In our co-pending Australian Application No. 2006907085 we describe ancillary equipment with which the platform and bore head of this invention are intended to be used.  
         [0007]     In our Australian Patent No. 2003262292 we describe a bore head in which a pair of rams disposed radially at 90° to each other. These are attached to the cylindrical wall of the bore head and are grouped at the leading end in order to provide the requisite steering movement, namely 15 mm either side of centre, while it would be preferable to place the target as close to the cutter as possible to give to the operator the truest possible picture of the drilling axis, the rams prevent this and the target therefore placed in front of the rams. While the operator had a good view of the laser spot on the target, the adjustment of the drilling axis would frequently result in oversteer.  
       SUMMARY OF THE INVENTION  
       [0008]     This invention concerns a boring head for laser guided drilling microbore tunnels using a liquid stream to remove soil, and an airstream to remove the soil and liquid mix, comprising a substantially cylindrical body with a leading end wall and a trailing end wall, an axial wall dividing the body into a component compartment and a flow compartment, the component compartment housing a steerable boring shaft which projects through the leading end wall to support a cutter a shaft bearing fixed to the axial wall near the trailing end, a liquid path through at least part of the shaft which exits beyond the leading end wall, a laser target mounted on the shaft close to the leading end wall and the cutter, and a camera mounted on the axial wall for shooting the target, the shaft being steered by rams mounted on the axial wall and acting at 90° to each other, up and down steering being provided by a first ram acting substantially parallel to the shaft and side to side steering being provided by a second ram acting transversely to the shaft, a passage through the flow compartment for liquid and air mix, a passage through the flow compartment for air.  
         [0009]     The bearing may be a thrust bearing and the bearing housing may be bolted to the base. This housing may have an inlet which connects to the incoming water supply to form the slurry and an outlet which feeds water to the shaft interior. The ram mounts may be frames of inverted U-shape fixed to the base. The valve components which supply fluid to the rams may be arranged alongside the shaft so as to be accessible for servicing. Similarly the camera may be mounted on a stand fixed to the base.  
         [0010]     When the components are grouped on a base, the attendant pipes and cables are easier to route and keep out of the way of the laser beam which must hit the target fixed to the shaft near the leading end thereof.  
         [0011]     The end walls of the head may be semi-circular having a circular central major passage for return air and slurry and two minor passages parallel thereto of a cross-section which in total exceeds the cross-section of the major passage.  
         [0012]     The central vacuum passage preferably ends in a coupling capable of connection to a pipe string which extends along the bore to the platform part and thence to the vacuum tank above the pit.  
         [0013]     The bore head may be prepared for use by attaching to the base a semi-cylindrical cover with semi-circular end walls. The cover is removable for cleaning and servicing.  
         [0014]     The bore head may be pushed by a carriage riding on a platform and may take drive from a motor mounted in the carriage in known manner.  
         [0015]     The platform may have a pair of polished rails and the carriage may have a pair of slides for engaging the rails. The slides may each have a groove therein of keyhole section adapted to partially encompass the rail and minimise the lost motion.  
         [0016]     The platform may have a pair of ram assemblies for advancing and retracting the carriage, each assembly comprising a pair of ganged rams, one extending in the bore direction and one in the reverse direction.  
         [0017]     The drive from the motor to the bore head may include a universal coupling. The coupling is preferably sited close to the carriage. A universal coupling inside the bore head allows the cutter shaft to waggle and respond to steering forces selected by the operator.  
         [0018]     The drive output from the motor may include a socket for receiving the ends of the rods which compose the string and the socket is spring loaded. This facilitates the coupling and uncoupling of the drill rods which is ongoing throughout the drilling operation.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]     One embodiment of the invention is now described by way of example with reference to the accompanying drawings, in which:  
         [0020]      FIG. 1  is a perspective of the platform and bore head with the cover removed for clarity.  
         [0021]      FIG. 2  is an end view of the platform including the reel looking towards the bore.  
         [0022]      FIG. 3  is an end view of the bore head showing the passages.  
         [0023]      FIG. 4  is a partial section of the drill rod.  
         [0024]      FIG. 5  is a plan view of variant of the bore head.  
         [0025]      FIG. 6  is a side view of the variant of the bore head of  FIG. 4 .  
         [0026]      FIG. 7  is a schematic showing the hydraulic and electrical pathways. 
     
    
     DETAILED DESCRIPTION  
     Platform  
       [0027]     Referring now to the drawings, especially  FIGS. 1 and 2 , the platform bearers  2  are mutually connected by zig zag ties  4 . The bearers are of C-shaped cross-section and are directionally positioned in the pit  6  by L-section thrusters  8 . The bearers each support a stainless steel rail  10  of keyhole section. Carriage  12  extends across the width of the platform with a floor  14  on which is mounted a hydraulic drive assembly  16 .  
         [0028]     The front end of the carriage has an upstanding pair of brackets  18 . A corresponding pair of brackets  20  extends from the rear of the platform. The cylinders of a pair of carriage rams  22  are connected side by side to the carriage. The connecting rods point in mutually opposite directions and react against brackets  18  and  20  thereby doubling the stroke of the rams. The platform rides on slides  24  ( FIG. 2 ) which embrace the rails and ensure accurate linear motion.  
         [0029]     The drive assembly comprises hydraulic motor  26  which delivers rotation to coupling  28  through drive guard  30 . The guard  30  has laser window  32  through which laser generator  34  directs a beam. Beneath coupling  28  is vacuum spigot  36  which projects towards the bore. Spigot  36  leads to vertical, rigid vacuum tube  38  to which a flexible vacuum tube (not shown) is attached. The flexible tube carries drilling slurry to ancillary apparatus described in co-pending Application No. 2006907085.  
         [0030]     The water from the slurry is obtained from an onsite piped supply. It is brought into the pit by a hose (not shown) which is coiled on reel  40  mounted above the drive assembly. As the drilling proceeds, the hose pays out and follows the boring head.  
         [0031]     The drive coupling  28  has a spring loaded hexagonal socket  60  which can be displaced by an operator when inserting an extra drill rod. The drill string works in the same way as described in Australian Patent No. 2003262292. A universal coupling  62  takes drive from the carriage to the bore head.  
         [0032]     The laser is directionally adjusted and then its inclination is adjusted to give appropriate fall. The platform is aimed by adjusting screw jack thrusters  8  until the laser beam strikes the centre of the target  64  in the bore head which is next described.  
         [0033]     Bore Head  
         [0034]     The bore head has a circular leading wall  66  and a trailing semi-circular wall  68 . A semi cylindrical body  70  made of sheet metal has a flat rectangular floor  72  upon which components are mounted. These are closed in by a semi cylindrical cover (not shown) which is secured to flanges  74  extending from walls  66  and  68 .  
         [0035]     Body  70  is hollow but central tube  76  is 5 inches across (100 mm) and conducts air and slurry rearwardly while air supply tubes  78 ,  80  allow air from the bore to pass through the walls  66 ,  68  which would otherwise be a barrier. End walls  66 ,  68  also contain shaft apertures for the cutter shaft  82  which extends through the bore head to the end of the drill string. The drill string in turn is driven by coupling  28 .  
         [0036]     A thrust bearing housing  90  is bolted to the floor  72 . The cutter shaft  82  reacts against the thrust bearing. Universal coupling  92  allows the shaft to waggle up to 30 mm. The leading end carries cutter  94 . The cutter shaft is hollow from the universal coupling forwards and the leading end of the cutter shaft is surrounded by sleeve  96  (see  FIG. 3 ) which is connected by inlet  98  to the external water supply pipe at the reel  40 . The shaft interior communicates with passages  100  in the cutter and water sparges from the cutter.  
         [0037]     Steering Rams  
         [0038]     A pair of inverted U-shaped mounts  102  are welded to the floor behind the leading end wall  68 . Each supports a ram  104 ,  106  which acts on a sleeve which is a slide fit on shaft  82 . Rams  104 ,  106  are disposed at 90° to each other and both are fed by mains pressure water via solenoid operated valves  108 ,  110 ,  112 ,  114  as described in Australian Patent No. 2003262292. Both ends of the ram are connected to either feed or drain. The drained water leaving the rams is dumped into the slurry exit tube  76 .  
         [0039]     The valves mounted on floor  72  are connected to the rams by flexible tubes  116 . A collar  118  on the shaft  82  supports target  64  marked with concentric rings. The target is viewed through a video camera  120  which supplies an image to a monitor located in the pit. The head is steered by draining water from one or both rams to bring the centre of the target to the static spot of laser light.  
         [0040]     The ram stroke is 15 mm and partial stroke movement suffices to correct deviation in drilling. If the soil is uniform and not unduly stony, steering corrections may not be required for several minutes.  
         [0041]     The space behind the cutter between the cutter and the leading wall  66  is purged of soil and water by the constant vacuum. When the bore has reached maximum distance which is about 120 m, the carriage is again reciprocated but upon each retraction the section of drill string and a length of vacuum tube is removed as a unit from the pit and the bore head emerges into the pit.  
         [0042]     The platform and head are lifted out of the pit, reversed and lowered into the pit so that drilling can proceed in the opposite direction. When the bore links the two selected sites, a pipe of suitable diameter is inserted and the gap between the pipe and the bore is filled with a hardenable construction mix in which the buoyant air-filled pipe floats.  
         [0043]     Referring now to  FIGS. 1 and 4 , during drilling the bore head progresses by the insertion of a drill rod assembly between the coupling  28  on the universal coupling  62  and the bore head.  
         [0044]     An assembly is shown in  FIG. 3  and consists of a steel tube  130  with the same diameter as the central tube  76 . The ends of the tube are constructed for coaxial overlap and the drilling thrust is transmitted by the annular wall  132  rendered gas light by rubber o-ring  134 . The assemblies once engaged are locked together by pins  136  inserted into interfitting flanges  138 ,  140 . Brackets  142  hold bearings which support a solid steel drive shaft  144  with a male hexagon socket  146  at one end and a female socket  148  at the opposite end. Pins  136  keep the string connected when the thruster reverses and pulls the bore head out of the bore. The carriage applies thrust through tube  130 . Drive shafts  144  bear no thrust.  
         [0045]      FIGS. 4 and 5  show a variant which utilises the base to greater advantage. The thrust bearing  90 , universal coupling  92 , shaft  82  and cutter are arranged as in  FIG. 1  and the shaft is free to waggle in an arc of about 30 mm. The steering rams are modified to allow the target  64  to be as close to the cutter as possible. The leading end of the shaft  82  passes through sleeve  96  which conducts water into the hollow centre of the shaft. The sleeve has a leading boss  150  and a trailing boss  152 , each of which contain a bearing  154  so that the sleeve remains static while the shaft  82  rotates. Each bearing is accommodated between a pair of seals  156  and the sleeve between the bosses acts as a water jacket  158  fed by port  98  from the water supply pipe.  
         [0046]     The shaft has a central water bore  100  which allows water to reach the cutter  94 . A radial port  160  connects the water passage to the jacket. The leading boss  150  has an upwardly projecting lug  162 .  
         [0047]     The mechanism from which the sleeve  96  depends is next described.  
         [0048]     A pair of trunnions  164  disposed at the leading end at 90° to the shaft axis support a yoke  166  made of flat steel bar. The central position has a cut out  168  which is spanned by a rod  170 . The rod is a slide fit in the bore  172  of the upwardly projecting lug  162 . An arm  174  extends at 90° from the yoke and first ram  106  actuates the yoke like a bell crank, causing the shaft to move up and down in a small steering arc. Even so it is necessary to fit the rod in the yoke with flexible inserts to allow slight rocking of the rod. This prevents binding and leads to smooth steering.  
         [0049]     The central part of the jacket  158  is surrounded by a metal collar  176 . Side to side steering is provided by the second ram  104  which reacts against post  178  and the collar  176  on the shaft. A spherical bearing (not shown) connects the ram to the post to permit up and down motion in the shaft of the order of 2-5 mm. The sideways steer motion is the same extent as the up and down motion.  
         [0050]     The shaft itself is made of a stainless steel alloy whose surface is chromed. The shaft projects through the waggle aperture  182  which is kept shut against the ingress of slurry by steel washer  184  urged against the end wall by spring  186 .  
         [0051]     Semi-circular hoops  188  extend over the hose for the reception of a semi-cylindrical steel cover plate. Removal of the cover is all that is necessary to render all the components accessible for inspection, cleaning and repair.  
         [0052]     The camera  120  has ample room and an unobstructed view of the target  64 . The lens is forwardly facing and the cross wires of the target are removably facing and neither become dirty despite the passage of water continually through the conduits to the rams and through the shaft to the cutter head, the movement of the base head through sandy soil and the flow of slurry through the flow passages. The 24v cables for the solenoid operated valves  108 - 114  and the camera cable  190  enter terminal box  192  and exit in an electrical socket  194 . Water enters the head at mains pressure through union  196 .  
         [0053]     The arrangement of the tubes and leads is seen in the schematic shown in  FIG. 7 . Union  196  on the trailing wall  68  of the bore head delivers mains water to the water jacket  158  and to each of the four valves  108 - 114  mounted on the base. Each valve has a water inlet  200 , a water outlet  202 , and a water drain  204 . The drain passes through the base and discharges into the slurry tube  76 .  
         [0054]     Both ends of the ram are subjected to mains pressure. The solenoid control in the valve connects the selected end to drain and the piston moves in the desired direction. Leads  206  conduct 24v dc to the solenoids from terminal box  192 . Socket  194  which receives the plug of a cable which is fed through the bore following behind the bore head. Camera  120  is connected to the same terminal box.  
         [0055]     We have found the advantages of the above embodiment to be:  
         [0056]     1. Placing the laser target as close as possible to the cutter cures oversteer, and permits stable direction for the bore head. It is possible in suitable ground to drill for five drill rod lengths without steering correction.  
         [0057]     2. Long drill runs are achievable without malfunction or damage to the bore head.  
         [0058]     3. Cleanliness in the components compartment means that the operator can always have a clear image of the target.  
         [0059]     4. The arrangement of the rams in the variant described allows the diameter of the bore to be reduced to mm.

Summary:
Boring apparatus for drilling laser guided microbore tunnels uses a liquid stream to remove soil as slurry and an airstream to conduct the slurry away from the bore head. The cylindrical head houses a drill shaft steered by a pair of remotely controlled rams according to the position of a laser spot on a target fixed close to the end of the drill shaft. Small arcuate steering movements shift the cutter up and down through a first ram alongside the shaft working through a linkage. Side to side steering is provided by a second ram acting directly on the shaft. The components are mounted on an axial base wall which gives repair access and camera view of the target. A drilling platform has rams for advancing the cylindrical head.