Abstract:
The invention provides a down-the-hole drill assembly ( 21 ) comprising an assembly of a bit ( 9 ) and co-operating chuck ( 19 ) including a bit ( 9 ) mounting with an external sleeve ( 4 ) surrounding the bit ( 9 ) mounting, the sleeve ( 4 ) during operation of the drill being clamped between the chuck ( 19 ) and the bit head ( 9 ). The sleeve ( 4 ) provides a shield against ingress of debris into the bit and chuck assembly, and provides control of exhaust from the assembly. The sleeve ( 4 ) further provides control of a pin ( 107 ) releasably engaging the bit ( 9 ) to the chuck ( 19 ).

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to down-the-hole hammer drill assembly well known in the rock drilling industry particularly in the drilling into the earth from the surface. 
       BACKGROUND TO THE INVENTION 
       [0002]    These hammer drills are high energy consuming items of equipment and they are also subject to heavy wear. There is thus a combining need for equipment having reduced wear and reduced down time which need is accentuated by the depths to which holes are drilled at the present time. 
       OBJECT OF THE INVENTION 
       [0003]    It is the object of the invention to provide improved equipment of the kind referred to with particular reference to the protection of the drill head components against damage from the operating environment while also ensuring a simplicity of assembly and dissassembly. 
       SUMMARY OF THE INVENTION 
       [0004]    According to this invention there is provided a down-the-hole drill assembly comprising an assembly of a bit and co-operating chuck including a bit mounting with an external sleeve surrounding the bit mounting, the sleeve during operation of the drill being clamped between the chuck and the bit head. 
         [0005]    Further features of this invention provide for the sleeve to provide a shield against the ingress of debris into the bit and chuck assembly during use and to provide a control for the exhaust of operating fluid from the lower chamber. 
         [0006]    The invention further provides for the control of the operating fluid exhaust from the assembly to flow through the wall of the chuck and provide reverse circulation through pick up holes in and through the bit. 
         [0007]    Further features of this invention provide for the assembly to include splines in the chuck engaging with splines on the bit and both sets of splines engaging with splines in the sleeve. 
         [0008]    The invention also provides for the splines in the sleeve to be equal in length to the sum of the lengths of splines in the chuck and those on the bit and for the lengths of the splines in the chuck and on the bit to be equal or unequal depending on the particular application of the drill assembly. 
         [0009]    The invention further provides for the sleeve to provide control of a pin releasably engaging the bit to the chuck. 
         [0010]    Further features of the invention provide for the assembly to comprise a stepped drill bit engageable with its narrow end within a drill chuck and having a transverse retaining pin engaged through the chuck and a slot in the bit with a sleeve slidably mounted on the chuck to be operatively held on the chuck against the step on the bit. 
         [0011]    Yet further features of the invention provide for the chuck to be stepped to enable the sleeve to slide on a reduced diameter end of the chuck to be clamped between the chuck or the end of the wear sleeve and the bit head. 
         [0012]    According to further features of this invention there is provided a down-the-hole drill bit assembly comprising a drill bit having a shank engageable in the end of a chuck adapted to be retained in the end of the drill casing, the shank and chuck provided with alignable longitudinally extending transverse slots and means to releasably retain a pin on which the shank can be reciprocated. 
         [0013]    Further features of the invention provide for the pin to be flat and have a shaped head on each end, for the chuck and drill shank to have a series of mating splines and for a head on the bit to seat on the end of the drill chuck which is securable in the end of a drill string wear sleeve. 
         [0014]    The invention also provides for the heads of the pin to be offset on the ends of the pin. 
         [0015]    These and still further features of the invention will become more apparent from the following description of some embodiments of the invention where reference is made to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    Preferred embodiments of this invention are described with reference to the accompanying drawings, in which: 
           [0017]      FIG. 1  shows a longitudinal cross-section through a hammer drill assembly; 
           [0018]      FIG. 2  shows a hammer assembly with a sleeve used as a coupling. Both engaged and disengaged conditions of the assembly are shown; 
           [0019]      FIG. 4  shows the coupling in use with venting exhaust passages for a hammer drill; 
           [0020]      FIG. 4A  a modification to  FIG. 4  showing a foot valve tube; 
           [0021]      FIG. 5  shows an alternative construction of a drill assembly; 
           [0022]      FIG. 6  shows the assembly modified to provide for reverse air circulation through the bit for sample collection; 
           [0023]      FIGS. 7 &amp; 8  show the invention applied to an alternative bit and chuck assembly; and 
           [0024]      FIGS. 9 &amp; 10  show a modification of the embodiments in  FIGS. 7 &amp; 8 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    The use of making screwthreads on contiguous components in down-the-hole drill assemblies has been described in my co-pending PCT Application No. PCT/IB2010/053549 filed on Aug. 05, 2010. That disclosure is included in this specification by reference and should be read together with this specification particularly for an understanding of the use of the expression “stopping threads”. This means making screwthreads which may be screwed through each other so that the components are prevented from relative longitudinal co-axial movement in one direction while being free for such movement in the opposite direction. This movement is used, to permit direct striking of the piston on the bit and providing a simple method of releasing the bit from the chuck. 
         [0026]    A first embodiment of the invention is described with reference to  FIG. 1  which illustrates the operation of one form of hammer drill utilizing the present invention. 
         [0027]    This is disclosed in the specification and priority document for patent application 2010/07703. 
         [0028]    One feature required to make a hammer more efficient and increase the performance is by increasing the frequency of the piston blows whilst maintaining the same stroke. A larger surface area at the bottom of the piston for the compressed air to act on will propel the piston in the upward stroke away from the bit faster thereby increasing the blows per minute. The outside diameter of the hammer is restricted according to the confined diameter of the hole that is being drilled and to maintain a reasonable wall thickness on the wear sleeve it is not possible to simply increase the piston diameter to achieve this end. The wall of the wear sleeve becomes too thin if the hole size is maintained. 
         [0029]    When using a stepped piston with continuous pressure on the stepped shoulder as in my SA Patent 2009/04814 included herein by reference, cutouts ( 47 ) on the piston shown in  FIG. 2  and, the cut out ( 57 ) shown in the bore of the cylindrical extension of the back head in  FIG. 3 , are replaced in the present invention with porting through the piston wall and no cut out in the cylindrical bore of the back head. The specification of this patent is also included in this specification by reference only as background to the present invention. 
         [0030]    As shown in  FIG. 1 , (which is extracted from the specification of South African patent application 2010/07703 referred to above, a priority document of this application), compressed air enters and opens the check valve ( 1 ) downwardly. This air then passes through ports A, into cutout B between the cylindrical portion of the back head ( 2 ) and the bore ( 3 ) of the wear sleeve ( 4 ) through ports C into space D around the piston stepped head ( 5 ) thus applying pressure on the shoulder surface area ( 6 ), passes the major piston diameter ( 7 ) at cutout E into lower chamber F where it acts on the bottom surface area of the piston ( 8 ). This causes the piston to lift away from the bit ( 9 ) and the piston stem ( 10 ) disengages from the piston stem bush ( 11 ) for lower chamber F to exhaust through the axial bore G in the bit ( 9 ). The piston ( 8 ) continues traveling upward and ports I, through the wall of the piston ( 8 ), communicate with ports H in the cylindrical lower part ( 12 ) of the back head ( 2 ). 
         [0031]    Compressed air then flows through ports I into upper chamber J above the piston ( 8 ). At this stage the major diameter ( 7 ) of the piston is a well up the bore ( 3 ) of the wear sleeve ( 4 ) and the lower chamber is sealed off. 
         [0032]    The pressure, that is now on the shoulder surface area, combined with the pressure on the surface area of the piston exposed to the upper chamber J, the axial exhaust passage K through the piston ( 8 ) is sealed off by the control rod ( 14 ). This will propel the piston ( 8 ) towards the bit ( 9 ) to strike the bit. The control rod ( 14 ) has now disengaged from piston passage K and upper chamber J exhausts through K and then G through the bit ( 9 ). E has opened again and compressed air is reintroduced into chamber F to repeat the cycle. 
         [0033]    The back head as described is in one piece with the cylinder (the cylindrical extension of the back head) but could be in two pieces. 
         [0034]    When the hammer is lifted off the bottom of the hole the bit ( 9 ) drops forward for a limited travel. With the piston following the bit and port H is exposed to chamber J allowing the compressed air to flow freely down K and G to the atmosphere. Lower chamber F is shut off by the piston major diameter ( 7 ) sealing off against the land L in the bore of the wear sleeve ( 4 ) thus rendering the hammer inoperative and in flushing mode. 
         [0035]    Of particular importance to the present invention is the sleeve ( 15 ) mounted on the shoulder ( 16 ) of the bit ( 9 ). In the operative position shown the sleeve ( 15 ) has splines ( 17 ) which move through splines ( 18 ) on the outside of the chuck ( 19 ) which forms an extension to the piston sleeve bush ( 11 ). 
         [0036]    This sleeve ( 15 ) is held during operation of the drill between the stepped end of the chuck ( 19 ) and the shoulder ( 16 ) of the bit ( 9 ) and where it shields components within it from debris generated by the drilling operation. 
         [0037]    This feature of the invention will become clear from the description of the further embodiments described below. 
         [0038]    Referring now to  FIG. 2  the operatively lower end of a down-the-hole drill assembly ( 21 ) is shown in the operative position ( 22 ) on the right hand side of the drawings and in flushing mode ( 23 ) on the left hand side. 
         [0039]    The components illustrated are the chuck ( 24 ) and bit ( 25 ) carrying splines ( 26 ) and ( 27 ). The splines ( 26 ) on the chuck ( 24 ) are longer than those ( 27 ) on the bit ( 25 ). 
         [0040]    Stopping threads ( 28 ) and ( 29 ) are provided on the outer end of the bit ( 25 ) shank and on the inside of the operatively lower end of the chuck ( 24 ). Those threads ( 28 ) and ( 29 ) are shown disengaged so that the bit shank may slide in the chuck ( 24 ) but prevent the shank from being withdrawn from the chuck. This release can be achieved by engaging the threads and unscrewing the bit shank out of the chuck ( 24 ). 
         [0041]    A locking sleeve ( 30 ) is located around the external splines ( 26 ) and ( 27 ). The locking sleeve ( 30 ) has internal splines ( 31 ) which mate with the splines ( 26 ) and ( 27 ) to slide relative thereto and the length of the sleeve ( 30 ) is substantially the same as the combined length of the splines ( 26 ) and ( 27 ). 
         [0042]    Thus, in the flushing mode of the drill the locking sleeve ( 30 ) slides with the bit ( 25 ) down into the bit position shown in the left hand side of  FIG. 2 . In this position the free ends ( 32 ) of the splines ( 26 ) are still in contact with the splines ( 31 ) in the sleeve ( 30 ) and the bit ( 25 ) can be driven to rotate by a conventional rotary motion mechanism for the drill. 
         [0043]    To enable the bit ( 25 ) to be unscrewed from the chuck ( 24 ) the sleeve ( 30 ) is moved upwardly on the splines ( 26 ) into the position shown on the right hand side of  FIG. 2 . Because of the difference in the length of the splines ( 26 ) and ( 27 ) the splines ( 31 ) in the sleeve ( 30 ) will no longer engage the splines ( 27 ) and the bit ( 25 ) can be unscrewed. 
         [0044]    With the bit ( 25 ) removed the sleeve ( 30 ) can also be removed from the chuck ( 24 ). 
         [0045]    This engagement enables the sleeve to be assembled onto the chuck ( 24 ) and the bit to be screwed into the chuck ( 24 ) releasing the thread engagement and the drill will be in the flushing mode and ready to be operational. 
         [0046]    This condition of the assembly with the bit hanging but not removed from the chuck is a useful condition. It enables the drill operator to use the bit in a grinding manner, for example, in drilling operations through collapsed sections in a borehole. The assembly thus enables hammer operations to be conducted when both bit and chuck splines are fully engaged by the sleeve and grinding to be effected when the bit and sleeve are hanging with the assembly in flushing mode described above and the ends of the bit and chuck threads in contact. 
         [0047]    Referring back to  FIG. 2 , when it is necessary to remove the bit the drill is raised with the components in the flushing condition. Once on surface the sleeve can be manually lifted into the position shown on the right hand side of  FIG. 2  and the bit screwed out of the stopping threads as described. 
         [0048]    The arrangement of the splines on the bit and chuck and within the sleeve can conveniently be about twelve splines on each component with a minimum of two opposite each other for even load distribution. 
         [0049]    A further modification to the hammer assembly utilizes the sleeve for alternative or additional purposes. 
         [0050]    Shown in the right hand side of  FIG. 3  the hammer assembly piston ( 40 ), locking sleeve ( 41 ) and bit ( 42 ) are pushed up into the drilling position. In this position the locking sleeve ( 41 ) is sealing venting holes ( 43 ) and the lower chamber ( 44 ) can receive compressed air to drive the piston ( 40 ) upwards away from the bit ( 42 ). When the bit ( 42 ) drops forward, shown in the left hand side of  FIG. 3 , the piston ( 40 ) follows and the indicated sealing surfaces ( 45 ) and ( 46 ) on the piston ( 40 ) and in bore ( 47 ) of the wear sleeve ( 48 ) will seal and prevent compressed air from entering lower chamber ( 44 ). At this time the locking sleeve ( 41 ) will uncover the venting holes ( 43 ) in order for the air cushion which has built up beneath the piston ( 40 ) to escape via the open venting holes ( 43 ). As the piston ( 40 ) drops further the slot ( 49 ) in the piston ( 40 ) is uncovered and locates opposite cutout ( 50 ) in the sleeve. This will allow compressed air to flow down the splines to clear them of rock cuttings and abrasive dust. 
         [0051]    Those skilled in the art can create the sealing of the venting holes between any two of the parts moving relevant to each other. For example, between stationary wear sleeve and chuck or a moving locking sleeve and bit. 
         [0052]      FIG. 4  shows an alternative way of sealing off as well as unsealing the venting ports ( 65 ) by the threaded bit anvil end ( 66 ). When the bit is in drilling mode the anvil head is opposite the undercut ( 67 ) and seals the opening ( 68 ) of the venting holes ( 69 ). As the bit drops forward, the undercut ( 67 ) is exposed and venting of the lower chamber ( 63 ) can take place through the bore ( 69 ) of the bit. There is a second undercut ( 70 ) which is connected to the bottom of the splined chuck end ( 71 ) by ports ( 72 ) which would receive air from the uncovered venting ports ( 65 ) and provide air pressure to the bore of the locking sleeve ( 73 ) from where it can exhaust through the splines ( 74 ) to clear them from debris as well as lubricate the splines. 
         [0053]    Referring to  FIG. 4A  this shows a modification to that shown in the right hand side of  FIG. 4 . It illustrates the inclusion of a foot valve tube ( 64 B) which engages with the bore ( 61 ) of the piston ( 62 ) for sealing of the lower chamber ( 63 ) instead of the alternative of the piston stem sealing within the piston stem bush. The clearance gap ( 64 A) demonstrates that there is no sealing between a piston stem bush and the piston stem as shown in  FIG. 4 . The same bit (fitted with a foot valve tube) and chuck could be used on the same hammer as for one without the foot valve. 
         [0054]    The locking sleeve ( 73 ) acts in similar manner to that described with reference to  FIG. 3  to provide rotation of the bit, sealing and enmeshing of venting passages of the lower chamber and clearing of the connecting splines. 
         [0055]      FIG. 5  shows a different bit ( 80 ) and chuck ( 81 ) arrangement and shows how the bit splines ( 82 ) and chuck splines ( 83 ) engage directly into each other. The drilling position is on the right hand side with the bit dropped forward on the left hand side and with a replaceable cover sleeve ( 84 ) around the splines to protect them from outside abrasive wear. Once the bit ( 80 ) has been screwed through the stopping thread ( 85 ) in the chuck ( 81 ), the splines ( 83 ) will be in position to enter into engagement with each other. When the bit ( 80 ) is pushed up into the splines ( 83 ), the cover sleeve ( 84 ) will be clamped between the bit ( 80 ) and chuck ( 81 ) and at the same time seal the venting holes (not shown). 
         [0056]    When the bit ( 80 ) drops forward the venting holes (not shown) will be unsealed for the same purpose as described above. 
         [0057]    Referring now to  FIG. 6  the sleeve ( 90 ) is shown used as a shroud around the bit shank to direct the exhaust air between the sleeve ( 90 ) and bit shank ( 91 ) to the bottom of the borehole and thus force the rock sample cuttings up the centre of the bit. 
         [0058]    Exhaust ports ( 92 ) are provided between the air passage ( 93 ) through the chuck ( 94 ) into the splined area ( 95 ) between the chuck ( 94 ) and a cutout ( 96 ) to the bit face ( 97 ). 
         [0059]    In use when the piston stem (not shown) pulls out of the piston stem bush and the sample tube is in centre bore A, the exhaust air will flow through the exhaust ports ( 92 ) past the splined area of the chuck and bit and down exhaust cutout ( 96 ) in the bit to the bit face ( 97 ) where it picks up the drilled cuttings and conveys them to the bore A in the bit and then through the sample tube and up the centre pipe of the dual tube drill string to the surface where the cuttings are then collected for inspection. The sleeve ( 90 ) will direct the exhaust air to finally reach the bit face. 
         [0060]    The assembly using the sleeve also affords protection of the sliding surfaces of the bit and chuck during drilling operations. 
         [0061]    Referring to  FIGS. 7 and 8  there is illustrated a conventional drill bit ( 101 ) which is slidable in a chuck ( 102 ) which has a stepped shoulder ( 103 ) to locate the free end of a sleeve ( 109 ) during drilling operations. The chuck has internal longitudinally extending splines ( 104 ) slideably engaged with complementary splines ( 105 ) on the shank ( 106 ) of the drill bit ( 101 ). 
         [0062]    The free end of the chuck ( 102 ) is screw threaded for engagement in the end of the drill wear sleeve (not shown). 
         [0063]    The chuck ( 102 ) also locates a diametrically extending pin ( 107 ) which engages in a longitudinally extending slot ( 108 ) through the drill shank ( 106 ). 
         [0064]    The drawings show in  FIG. 7  the pin ( 107 ) in the upper end of the slot where the drill assembly is in the flushing mode. 
         [0065]    A sleeve ( 109 ) slides on the outer reduced diameter surface of the chuck ( 102 ).  FIG. 7  shows the assembly in flushing mode with the bit dropped forwardly to extend out of the chuck ( 102 ) and the sleeve extending forwardly to rest on the shoulder ( 110 ) on the drill shank ( 106 ). 
         [0066]    In this condition the pin ( 107 ) can be moved through the slot ( 108 ) and out of the assembly to release the bit from the chuck. 
         [0067]      FIG. 8  shows the assembly in the drilling mode in which the pin ( 107 ) engages the opposite end of the slot ( 108 ) to that described above and the sleeve ( 109 ) is trapped between the shoulders ( 110 ) on the bit and ( 103 ) on the chuck. The pin ( 107 ) is trapped within the sleeve ( 109 ) which also acts to prevent the ingress of debris between the splines on the bit shank ( 106 ) and in the chuck ( 102 ). 
         [0068]    The drill assembly is simple and prevents binding of the bit in the chuck during use. 
         [0069]      FIGS. 9 and 10  illustrate yet a further embodiment utilizing a sleeve in the bit assembly. This assembly ( 120 ) has a chuck ( 121 ) which can be engaged in the end of a drill string wear sleeve (not shown). A longitudinally extending series of engaging splines ( 122 ) are formed on the bit shank ( 123 ) and in the chuck ( 121 ) to provide the connection to provide a rotary drive for the drill bit ( 124 ). 
         [0070]    Transverse longitudinally extending slots ( 125 ) are provided through the chuck ( 121 ) at ( 126 ) and through the shank ( 123 ) at ( 127 ) to extend diametrically through the assembly. 
         [0071]    A flat pin ( 128 ) with a head ( 129 ) at each end fits through the slot at ( 125 ) so that the heads ( 129 ) are located in the wall of the chuck ( 121 ) and the body of the pin ( 128 ) is slidable in the bit shank ( 123 ) between the ends of the slot ( 125 ). 
         [0072]    It will be appreciated that the pin ( 128 ) can be removed from the assembly only when the holes through the shank ( 123 ) and chuck ( 121 ) are aligned. This configuration must be obtained with the assembly removed from the drill hole. 
         [0073]    The slot ( 125 ) and pin ( 128 ) are dimensioned to permit movement of the bit ( 124 ) in the chuck ( 121 ) between drilling and flushing positions. 
         [0074]    Further the body of the pin ( 128 ) may be offset between the heads ( 129 ) towards the operatively forward end of the bit head. This facilitates obtaining a sufficient length of movement between drilling and flushing positions of the bit ( 124 ) in the chuck ( 121 ). 
         [0075]    In use the bit ( 124 ) is inserted into the chuck ( 121 ) and located so that one head ( 129 ) of the pin ( 128 ) can be threaded through the wall of the chuck ( 121 ) and the bit shank ( 123 ) into the wall of the chuck ( 121 ) diametrically opposite the point of insertion. The heads ( 129 ) of the pin ( 128 ) will be captured in the wall of the chuck ( 121 ). Operation of the drill in the drill hole will prevent any longitudinal movement of the pin ( 128 ) and rotation of the chuck ( 121 ) will together with the engaging splines on the bit shank ( 123 ) and chuck ( 121 ) provide the necessary drive for rotation of the bit head. 
         [0076]    Impacts on the bit head do not cause binding of the bit ( 124 ) in the chuck ( 121 ) because of the free movement available for the bit ( 124 ) in the chuck ( 121 ) on the pin. All the impact power transfers directly onto the bit ( 124 ) to provide maximum drilling effect. 
         [0077]    The assembly is also effective and avoids the well know difficulties in replacing the bit in an operating drill assembly ( 120 ) while ensuring firm retension during drilling operations. 
         [0078]    A sleeve ( 130 ) is clamped between the shoulder ( 131 ) on the bit head ( 124 ) against a cut away section ( 132 ) of the head ( 129 ) of pin ( 128 ) and within a recess ( 133 ) formed in the bottom end of the chuck ( 121 ). 
         [0079]    When the bit drops into flushing mode the sleeve ( 130 ) is released from engagement with the pin head ( 129 ) and can be manipulated through the chuck ( 121 ) to release the bit ( 124 ). 
         [0080]    The sleeve ( 130 ) also acts to prevent the ingress of debris through the chuck ( 121 ) into the bit assembly.