EXTENSION DRILLING SYSTEM

Abstract: An extension drilling system for use with a semi-automatic drilling rig. The drilling system includes a plurality of extension rods (22) constituting a drill rod string and having co-operating male and female threaded couplings (23) therebetween, and being right-hand rope threaded couplings. A chuck (21) of a drilling rig drives either directly, or via an adaptor, the outside of the female threaded end (24) of an associated extension rod, whereby to result in only one threaded coupling between the chuck and a pair of grippers (27) and to ensure that when the grippers are moved to a clamping position, and the chuck is rotated in reverse, only the desired coupling is uncoupled. The drill rods can have axial passages (28) therethrough in communication with each other and through which flushing fluid is delivered to an associated drill bit and a non-return valve (28a, 29) is incorporated in the passage through at least one of the drill rods to shorten the delay time in delivering flushing fluid to the drill bit before re-commencement of drilling after a drill rod is added to the drill rod string.

Description: EXTENSION DRILLING SYSTEM Technical Field This invention relates to an extension drilling system, and more particularly, but not exclusively, to extension drilling systems for use on a semiautomatic drilling rig and used to drill holes (bores) in subterranium mining operations such as coal mining where the structure of the roof of a tunnel is to be rendered more secure by the insertion of rock bolts into holes drilled into the roof structure. Background Art In the past, extension drilling in coal mines was carried using square threaded rods, such as XRT-Rods with a 4TPI Acme thread. We have experimented with the use of right-hand rope threaded drill rods because of their easier uncoupling and with a male thread less prone to damage. Although various extension drilling systems had been developed based on the experimental work, we have found that they did not work with semi-automatic drilling rigs. The primary problem with conventional drill rods for extension drilling systems, when used with semi-automatic drill rigs is that, when the drill string (a series of drill rods coupled together) are to be uncoupled there are two threaded couplings between the grippers and the chuck. As the grippers are operated, and the chuck spun slowly in reverse, the threaded joint between the drive adaptor and the bottom extension rod can become uncoupled which is undesirable as distinct from the desired uncoupling between the bottom and second bottom extension rods. A secondary problem is that the use of a drive adaptor takes up valuable boom height on the rig thus reducing the length of the extension rods that can be used. It is therefore an object of the present invention to overcome, or at least minimise, the above problems with known extension drilling systems when associated with semi-automatic drilling rigs. Disclosure of the Invention The invention therefore envisages an extension drilling system for use with a semi-automatic drilling rig, said drilling system including a plurality of extension rods constituting a drill rod string and each having co-operating male and female threaded couplings therebetween, said couplings being right-hand rope threaded couplings and wherein, in use, a chuck of a drilling rig drives either directly, or via an adaptor, the outside of the female threaded end of an associated extension rod, whereby to result in only one threaded coupling between the chuck and a set of grippers and to ensure that when the grippers are moved to a clamping position, and the chuck is rotated in reverse, only the desired coupling is uncoupled. Preferably the drill rods have axial passages therethrough in communication with each other and through which flushing fluid is delivered to an associated drill bit. Preferably a non-return valve is incorporated in at least one of the drill rods to shorten the delay time in delivering flushing fluid to the drill bit before re-commencement of drilling after a drill rod is added to the drill rod string. Preferably the drill rods are of hexagonal cross-section or any other suitable cross-section and may be forged or welded rods which are selectively or fully heat treated. The invention also envisages an extension drill rod for use in the extension drilling system defined above. Brief Description of the Drawings Two preferred embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a longitudinal side elevational view of an extension drilling system in accordance with a first preferred embodiment of the invention, Figure 2 is a longitudinal side elevational view of an extension rod as used in the system of Figure 1 , Figure 3 is a longitudinal side elevational view, partly sectioned, of an alternative direct drive chuck for use in the extension drilling system of Figures 4 to 5, Figure 4 is a longitudinal side elevational view, partly sectioned, of an extension drilling system in accordance with the first preferred embodiment of the invention, Figure 4A is a cross-sectional view taken along line A-A of Figure 4, Figure 4B is a cross-sectional view taken along line B-B of Figure 4, Figure 5 is a longitudinal side elevational view of an extension drill rod as used in the system of Figure 4, Figure 6 shows side elevational views and an end view of a drill bit for use in the system of Figures 1 , 2 and 3, and Figure 7 shows side elevational views and an end view of a drill bit for use in the system of Figures 4 and 5. Deatiled Description of Preferred Embodiments With reference to Figures 1 and 2 of the drawings, the extension drilling system of this first preferred embodiment of the invention, and generally indicated as 20, utilises a drive chuck 21 mounted on a Mining/Roof bolter (not shown) having a pair of clamping grippers 27. The drive chuck maybe a TL2 drive chuck as manufactured by McSweeney's, Inc. of the USA, and the drive chuck directly rotatably drives a string of extension rods 22, (see also Figure 2 of the drawings), coupled together by one or more couplings 23 comprising cooperating right-hand rope threaded female sockets 24 in one end of the respective rods, and right-hand rope threaded male members 25 carried by the other end of the respective rods. The ends of the drill rods when coupled together abut each other via shoulders 22a surrounding the male member 25 and bearing on end faces 22b surrounding the entrance to the sockets 24. The male member 25 on the outer end of the outermost rod is coupled to a drill bit, (not shown in Figures 1 and 2), but which may be the drill bit 16 shown in Figure 6 of the drawings. Axial passages 28 are provided through the respective drill rods, and in communication with each, and through which flushing fluid can be delivered through to the associated drill bit. In this preferred embodiment the passages 28 through each of the drill rods are stepped at 28a to provide a transition between larger and smaller diameter portions of the passage whereby to provide valve seats forming part of the ball valve mechanisms, with the remainder of the mechanisms being made up of stainless steel or glass balls 29 which selectively seat on, or unseat from, the valve seat 28a, as required to shorten the delay time in delivering flushing fluid to the drill bit before the recommencement of drilling after a drill rod has been added to the drill string. Figure 3 of the drawings shows a modified (alternative) direct drive chuck for use in the extension drilling systems of Figures 4 to 5, and is in fact the drive chuck preferred, and which is a modular assembly 21a comprising a male drive member 21b having a drive shaft 21c and coupled to a female drive member 21 d with a socket 21 e. The drive members are coupled by bolts 21f through holes 21g in the male drive member 21b and into threaded blind holes 21 h in the female drive member 21 d with interposed spring washers 21 i. The male and female members may also be "dogged" together, that is, interlocked. The socket 21 e receives a sealing member 21 j which may be formed from polyurethane, moulded around a stainless steel washer body, and which seats on a step 21k in the end of the male drive member 21b. The modular drive chuck of this embodiment, in being formed in two separable parts, allows the drive members 21b and 21 d to be interchangeable for different drive configurations, and also allows for the sealing member 21j to be replaced when worn. With reference to Figure 4 of the drawings, the extension drilling system of the second preferred embodiment of the invention, and generally indicated as 10, utilises a drive chuck 11 mounted on a Mining/Roof bolter (not shown). The drive chuck may be a TL2 drive chuck as manufactured by McSweeney's Inc. of the USA. In accordance with this preferred embodiment of the invention, and also with reference to Figure 5 of the drawings, the drive chuck 11 rotatably drives a string of extension drill rods 12, and, in this preferred embodiment via a chuck adaptor 19, with the drill rods being coupled together by one or more couplings 13 comprised of co-operating right-hand rope threaded female sockets 14 in one end of the respective rods and right-hand rope threaded male members 15 carried by the other end of the respective rods. The ends of the drill rods, when coupled, abut each other via shoulders 12a surrounding the male members 15 and bearing on end faces 12b surrounding the entrances to the sockets 14. The male member 15 on the outer end of the outermost rod is coupled to a drill bit (not shown in Figures 4 and 5) which may be the drill bit 16 shown in Figure 7 of the drawings. A pair of clamping grippers 17 carried by the Mining/Roofing bolter serves to grip the drill string during coupling and uncoupling of the drill rod. Axial passages 18 are also provided through the respective drill rods and in communication with each other and through which flushing fluid can be delivered to the associated drill bit. With reference to Figures 4 and 5 of the drawings, the internal detail of the chuck adaptor 19 is according to that shown in Figure 4A of the drawings and is shaped as a hexagon 19a offset by 20° of rotation. A chuck adaptor cover 19b as shown in Figure 4B is bolted to the remainder of the chuck adaptor by bolts 19c. The cover provides a hole 19d for the drill rod to fit into and which has a normal hexagonal shape. The end of the drill rod which fits into the chuck adaptor 19, and incorporating the female socket 14 which is not drivingly engaged by the chuck adaptor, has an hexagonal exterior 12c and above that a round section 12d. When the drill rod end is fitted into the chuck adaptor, the hexagon 12c on the end of the rod is aligned with the hexagonal hole 19d through the chuck adaptor cover 19b. The rod is then slid down into the chuck adaptor to its full extent, and as positive rotation is commenced the chuck adaptor rotates 20° in relation to the rod and the drive flats of the hexagonal 19a in the chuck adaptor engage against the hexagonal shaped end 12c on the rod to thus rotatably drive the rod. The round section 12d on the rod is provided so that, as the rod is rotated through 20°, the hexagon through the chuck adaptor cover 19b does not bind on the rod. As long as positive rotation is maintained in the chuck adaptor the rod cannot be removed as the two hexagons are misaligned by 20° and the rod needs to be rotated through 20° so that the corners of the hexagon 12c will clear the hexagonal hole 19d through the chuck adaptor cover 19b in order for the rod to be removed. The drive chuck as described above in providing a twist locking action between the chuck and the rod improves the safety of the drilling system because of the locking of the rod in the drive chuck whilst maintaining positive rotation. In the case of both embodiments of the invention, the drill rods are of hexagonal cross-section, as previously described with reference to the embodiment of Figures 4 to 5, or of round cross-section or of any other suitable cross-sectional shape whereby they can be driven by the chuck adaptor 19 in the case of the embodiment of Figures 4 to 5 or directly by the drive chuck 21 or 21a in the embodiment of Figures 1 , 2 and 3. The drill rods may be forged or welded rods which are selectively or fully heat treated.

Claims: CLAIMS: 1 An extension drilling system for use with a semi-automatic drilling rig, said drilling system including a plurality of extension rods (12;22) constituting a drill rod string and each having co-operating male and female threaded couplings (13;23) therebetween, c h a r a c t e r i s e d i n that the couplings are right-hand rope threaded couplings and wherein, in use, a drive chuck (11 ;21) of a drilling rig directly drives the outside of the female threaded end (14;24) of an associated extension rod (12;22), whereby to result in only one threaded coupling between the chuck and a set of grippers (17;27) and to ensure that when the grippers are moved to a clamping position, and the chuck is rotated in reverse, only the desired coupling is uncoupled. 2. An extension drilling system as claimed in claim 1 , wherein the drill rods (12;22) have axial passages (18;28) therethrough in communication with each other and through which flushing fluid is delivered to an associated drill bit (16). 3. An extension drilling system as claimed in claim 2, wherein the axial passage (28) through at least one of the drill rods (22) incorporates a nonreturn valve (28a,29) to shorten the delay time in delivering flushing fluid to the drill bit (16) before re-commencement of drilling after a drill rod is added to the drill rod string. 4. An extension drilling system as claimed in any one of the preceding claims, wherein the drill rods (12;22) are of hexagonal or round cross-section or of any other suitable cross-section whereby they can be driven by the drive chuck (11 ;21 ) either directly or via an adaptor (19;21 a) having a socket (19d;21e) therein of similar cross-section. 5. An extension drilling system as claimed in claim 4, wherein the co- operation between the drive chuck or the adaptor and the associated drill rod directly associated therewith is such that limited relative rotational movement therebetween misaligns the respective cross-sections to prevent separation of the rod whilst maintaining driving engagement. 6. An extension drill rod for use in the extension drilling system defined in claim 1, said drill rod having male (15;25) and female (14;24) threads at opposed ends thereof, c h a r a c t e r i s e d i n that the threads are right-hand rope threads and that the outside of the female threaded end (14;24) of the rod is of hexagonal or round cross-section or of any other suitable cross-section whereby it can be rotationally driven. 7. An extension drill rod as claimed in claim 6, wherein the drill rod (12;22) has an axial passage (18;28) therethrough and through which flushing fluid can be delivered to an associated drill bit. 8. An extension drill rod as claimed in claim 7, wherein the axial passage (28) through the drill rod (22) incorporates a non-return valve (28a, 29).

Inventors: MCLEAN MICHAEL, WEAVER STEVEN, MCLEAN, MICHAEL, WEAVER, STEVEN
Applicants: SANDVIK AB
Application year: 1998
Main classification: E21B19
IPC codes: E21B17, E21B19, E21B21