AU2011200852A1 - Improved Rock Drill - Google Patents

Abstract

A rock drill (2) comprising an impulse generating mechanism (60), for generating shockwaves in a drill rod (10) associated with the drill (2), a damping 5 mechanism (50), a rotation generating mechanism (40), for generating rotation in said associated drill rod, a cover plate (30) and a front head (20) characterised in a restraint arrangement having a drill operation configuration and a drill field servicing configuration, the restraint arrangement being configured, when in a drill operation configuration to restrain in relative disposition said impulse generating mechanism, 10 damping mechanism, rotation generating mechanism, cover plate and front head; and when in a drill field servicing configuration to restrain in said relative disposition said impulse generating mechanism (60), damping mechanism (50) and rotation generating mechanism (40) whereby the front head (20) may be moved from said relative disposition and the associated drill rod (10) removed from the drill during field 15 servicing whilst said impulse generating mechanism (60), damping mechanism (50) and rotation generating mechanism (40) remain restrained in said relative disposition. 'I t C) C) 04 0') 0 Poo C) lqT C) co C) 04 C) T T Pt 17 1-1 e% T Cl 17 17 Cl Pt Pt 17 T T Pt 17

Description

WADESON AUSTRALIA Patents Ad 1990 COMPLETE SPECIFICATION Rockdrill Services Australia Pty Ltd Invention title IMPROVED ROCK DRILL The IIowintg stnlement Is a full description of the Invention, Induding the best method or performing known to us: 1 IMPROVED ROCK DRILL FIELD OF THE INVENTION The present invention relates to industrial ore mining drill tools and specifically to rock drills that provide percussive and rotary energy to a drill string. 5 BACKGROUND Rock drills drive a drill rod (also known as a drill shank) that transmits (via a drill string) rotary and percussive energy to a drill bit which has a working or rock facing end. The drilling tool also supplies flushing medium (commonly air or water) via the drill rod and drill string. 10 Typically the rock drill generates high speed rotary motion of the drill rod via a gearing arrangement which is itself driven by an offset drive shaft. Typically the drill rod rotates at speeds of up to around 220 rpm. This rotation is transmitted via the drill string to the drill bit at the rock face to enable holes to be drilled in the rock. Rock drills also generate percussive force on the drill rod, by generating a 15 shock wave that is transmitted via the drill string to the drill bit and rock face. This percussive force or shock wave is generated by impact force from an impact piston aligned on the same axis as the drill rod. The impact piston is hydraulically driven back and forth so that an end impacts an end of the drill rod. Force on the order of 2.8 tonnes at 60 Hz is typical. 20 Such rock drills are frequently required to drive a drill string of around 3 to 6 metres weighing around 35 kilograms. Depending on the nature of the rock, they may drill through up to around 60 metres of rock per hour. Another function performed by rock drills is to provide flushing medium (commonly air or water) to the rock face. Medium fed to the drilling tool flows through 25 the hollow centre of the drill rod or drill shank, and passes along the drill string to the rock face. A typical flow rate is 100 litres per minute at 20 Bar.

2 Rock drills suffer from numerous problems in actual operation. The operating conditions are difficult and dirty, the loads and forces involved are significantly high, and a number of failure modes are common. The housings of numerous components and sub-assemblies of a rock drill are 5 held together via long preloaded tie bars (which may be bolts or rods) extending between the forward and rearward ends of the drill. This provides structural strength during operation and additionally seals the component bodies and housings against each other to prevent ingress of dirt and contaminants into the drill. A forward end of a tie bar is releasably secured to the front head and a 10 rearward end is releasably secured to the impact body at the rear. Other components, housings and sub-assemblies are located between the front head and impact body. The tie bar could be threaded at each end and be tightened using a nut on each end, or could have a bolt head at one end and a thread/nut for tightening at the 15 other. Tightening the nut places the tie bar into tension and compresses the drill components and sub-assemblies together. Another way of releasably securing the tie bar to the front head or impact body is to provide the tie bar with a threaded end which is engageable with a thread on the front head or impact body housing. Where a nut is used at each end of the tie bar, the tie bar may have a protruding stop or cam 20 like arrangement located part way along its length to prevent rotation of the tie bar while the nuts are being tightened. As the nuts are tightened, rotation of the tie bar is halted once the stop or cam engages against a matching surface on a cover plate located between the front head and the gear box housing. Tie bars can be broken or weakened in a number of ways. If the drilling 25 machine is operated but there is no back pressure through the drill rod, i.e. the drill bit is not engaging with a rock surface, or is engaging with a soft surface that does not provide appropriate resistance, the tie bars can be broken due to stress as the drill rod chuck may not be pushed back against the damping piston. Another failure mode 3 is where tie bars have been over tightened (i.e. placed under too much tension), or where there are several tie bars, have been unevenly tightened. A further failure mode on tie bars having stops or cams is fracture of the tie bar at or adjacent to the cam, which relates to the torsional stress caused by tightening with a cam in this way. 5 Typically, in the factory a tie bar will be loaded (tensioned) to around 300Nm, as this ensures that the various bodies and housings of the drill are held compressed against each other without any gaps or misalignment between them developing and without overstressing the tie bar. However, in order to change the drill rod in the field, the dome nuts on the front end of the long tie bars are removed (and thus the tie bar 10 is loosened and no longer loaded at the front end) to enable removal of the front head. The dome nuts are then replaced by workers in the field, who tighten them to load each tie bar by a random amount. Generally, the random amount will be too high as the operators want to ensure that the bodies and housings are held together tightly enough. For example the tie bars could be tightened back up to a tension of 15 450Nm, or several tie bars on the same drill could be tightened to random different amounts. The overstressing, combined with possibly uneven tension on each side of the drill, torsional stresses and with high impact load generated by the drill, causes failure. If a tie rod breaks the impact piston can also break due to imbalance or 20 misalignment of the impact piston which typically may have a clearance of 0.02mm with its cylinder. If the impact piston runs while misaligned it will break. This causes a high level of damage to the drill caused by the impact piston itself and shrapnel generated by the impact piston. This requires replacement of many parts and causes downtime while the drill is out of service. There are also safety concerns with the 25 shrapnel. Another issue with tie bars is that when a tie bar is loosened to change the drill rod, the various components of the drill are no longer sealed by being compressed together. Thus dirt and other contaminants may ingress into the various hydraulic 4 systems, mechanical systems or flushing system. This is a problem given the dirty operational environment. It is also very important that the flushing medium does not enter the other systems. Seals are provided to prevent the medium from leaking rearward out of the 5 front head towards the rear of the drill. A typical arrangement is to provide one forward seal preventing the flushing medium from entering the forward area of the front head, a first rearward seal preventing medium from entering the rear area of the front head, a telltale hole though which a small amount of medium will leak if the first rearward seal fails, and a second rearward seal preventing medium from entering the 10 rear area of the front head or other rearward component of the drill after the first seal has failed. Unfortunately, in the field the leak from the telltale hole (which is typically located on the underside of the drill and difficult to see in normal operation) is often missed or ignored, and failure of the second rearward seal quickly results, with the adverse consequences of medium entering the rear end of the drill and subsequent 15 major damage. It would be desirable to alleviate one or more of the above issues with rock drills. Use of the terms 'forward', 'rearward' or other relative terms is made for ease of understanding of the relative disposition of components and is not to be taken as 20 limiting the drill or components to operation in a particular orientation. Any reference to prior art in this specification is not, and should not be taken as, an acknowledgement or admission that the prior art forms part of the common general knowledge of a person skilled in the relevant art or could reasonably be expected to be ascertained, understood or regarded as relevant by a person skilled in 25 the relevant art.

5 SUMMARY OF THE INVENTION A first aspect of the invention provides a rock drill comprising a plurality of bodies and housings, including a front head, characterised in a restraint arrangement having a drill operation configuration and a drill field servicing configuration, the 5 restraint arrangement being configured: a) when in a drill operation configuration to restrain in relative disposition said plurality of bodies and housings; and b) when in a drill field servicing configuration to restrain in said relative disposition said plurality of bodies and housings other than the front 10 head; whereby the front head may be removed from the drill during field servicing whilst the remaining plurality of bodies and housings other than the front head remain restrained in said relative disposition. A second aspect of the invention provides a rock drill comprising a plurality of 15 bodies and housings including: - an impulse generating mechanism body; - a damping mechanism body; - a rotation generating mechanism housing; - a cover plate; and 20 - a front head; characterised in a restraint arrangement having a drill operation configuration and a drill field servicing configuration, the restraint arrangement being configured: a) when in a drill operation configuration to restrain in relative disposition said impulse generating mechanism body, damping mechanism body, 25 rotation generating mechanism housing, cover plate and front head; and 6 b) when in a drill field servicing configuration to restrain in said relative disposition said impulse generating mechanism body, damping mechanism body, and rotation generating mechanism housing; whereby the front head may be moved from said relative disposition and the 5 associated drill rod removed from the drill during field servicing whilst said impulse generating mechanism body, damping mechanism body, and rotation generating mechanism housing remain restrained in said relative disposition. Preferably the drill is further characterised in the restraint arrangement being configured, when in a drill field servicing configuration, to restrain in said relative 10 disposition said impulse generating mechanism body, damping mechanism body, rotation generating mechanism housing and cover plate; whereby the front head may be moved from said relative disposition and the associated drill rod removed from the drill during field servicing whilst said impulse generating mechanism body, damping mechanism body, rotation generating mechanism housing and cover plate remain 15 restrained in said relative disposition. Preferably said relative disposition is in compression. Advantageously, the restraint arrangement enables field servicing to change a drill rod (through moving or removing the front head) without the need to unseal the back end of the drill. This prevents ingress of dirt or contaminants into the back end 20 areas of the drill. In a preferred embodiment of the invention, the restraint arrangement includes a first rear tie bar securable to the impulse generating mechanism body and to the rotation generating mechanism housing. Preferably, the first rear tie bar is a tie rod, respective ends of which are releasably securable to the impulse generating 25 mechanism body and to the rotation generating mechanism housing. Preferably the restraint arrangement includes a plurality of first rear tie bars securable to the impulse generating mechanism body and to the rotation generating mechanism housing. One preferred embodiment has two first rear tie rods, respective ends of which are 7 releasably securable to the impulse generating mechanism body and to the rotation generating mechanism housing. In a further embodiment, an end of a first tie bar could be permanently secured to the impulse generating mechanism body or to the rotation generating mechanism housing. 5 In a preferred embodiment of the invention, the restraint arrangement includes a second or cover plate rear tie bar securable to the impulse generating mechanism body and to the cover plate. It is noted that the second or "cover plate" rear tie bar could be used independently or in conjunction with a first rear tie bar. Preferably said cover plate rear tie bar is a tie bolt, respective ends of which are releasably securable 10 to the impulse generating mechanism body and to the cover plate. Preferably the restraint arrangement includes a plurality of cover plate rear tie bars securable to the impulse generating mechanism body and to the cover plate. One preferred embodiment has two cover plate rear tie bolts, respective ends of which are releasably securable to the impulse generating mechanism body and to the cover 15 plate. Advantageously, the rear tie bars are tightened (tensioned) to factory settings in the factory or a service workshop and do not need to be loosened in the field when it is necessary to change the drill rod. Thus, problems associated with over-tightening (over-tensioning) or uneven tightening in the field are avoided. This reduces the 20 incidence of failure. Additionally, the first rear tie bars only extend between the rear end of the drill (the impact body or impulse generating mechanism) and the mid-area of the drill (the housing of the gear box or rotation generating mechanism). Thus they are less likely to fail than a similar tie bar of greater length. The second or cover plate rear tie bars restrain the cover plate which preloads the gearbox bearings and again 25 factory settings can be retained during field servicing to change a drill rod. Furthermore, use of stops or cams on the tie bars is not necessary as the tie bars can be releasably securable via a thread directly to the impact body, impulse generating mechanism or cover plate, or if both ends are secured with nuts, a nut on one end can be held with a second spanner, while a first spanner is used to tighten the nut on 8 another end, as this will be easier in a factory or service workshop than in the field (where a second spanner of the right size may not be available). Inappropriate torsional stresses are also reduced. In another preferred embodiment of the invention, the restraint arrangement 5 includes a front tie bar securable to the rotation generating mechanism and to the front head. The front tie bar may be a tie stud such as a relatively short front head stud secured to the front head with a dome nut. Alternatively, the front head stud could be a tie bolt, respective ends of which are releasably securable to the rotation generating mechanism housing and to the front head. 10 Preferably the restraint arrangement includes a plurality of front tie bars securable to the rotation generating mechanism housing and to the front head. One preferred embodiment has four front head studs, respective ends of which are releasably securable to the rotation generating mechanism housing and to the front head. In a further embodiment, an end of a tie bar could be permanently secured to 15 the rotation generating mechanism housing or the front head. Advantageously, the front tie bars can be released, for example by loosening dome nuts from the front head studs, and the front head removed to allow changing of a drill rod in the field without the need to unseal the back end of the drill. Furthermore, the front tie bars (front head studs) are relatively short and less 20 likely to be stressed through incorrect tightening in the field when it is necessary to change the drill rod than long tie bars extending the major length of the drill would be. Again, use of stops or cams is not necessary and inappropriate torsional stresses are also reduced. Additionally, a failure of the front tie bars, while undesirable, is less likely to result in failure of the impact piston than failure of long tie bars extending 25 from the front to the rear of the drill.

9 A third aspect of the invention provides a method of changing an old drill rod for a new drill rod, the old drill rod associated with a rock drill according to any one of previously described embodiments, characterised in the steps of: a) configuring the restraint arrangement to a drill field servicing 5 configuration whereby said impulse generating mechanism body, damping mechanism body and rotation generating mechanism housing are restrained in said relative disposition; b) removing said front head from said relative disposition; c) removing the old drill rod from the drill and replacing it with the new drill 10 rod; d) moving said front head back to said relative disposition; e) configuring the restraint arrangement to a drill operation configuration wherein said impulse generating mechanism body, damping mechanism body, rotation generating mechanism housing, cover plate and front 15 head are restrained in said relative disposition. Preferably the step of configuring the restraint arrangement to a drill field servicing configuration is further characterised in that said impulse generating mechanism body, damping mechanism body, rotation generating mechanism housing and cover plate are restrained in said relative disposition. 20 A fourth aspect of the invention provides a rock drill comprising a first flushing seal housing having a first forward seal and a first rearward seal, and having a second rearward seal, characterised in an overflow relief arrangement configured to allow overflow to atmosphere of fluid from between the first and second seals. Advantageously, the overflow relief arrangement prevents substantial build up 25 of flushing medium or pressure inside the front head, making a failure of the second rearward seal unlikely and thus reducing the incidence of consequential damage to the rear end of the drill.

10 Preferably, the overflow relief arrangement has a predetermined flow capacity substantially equivalent to a maximum predetermined flushing fluid supply flow capacity. Preferably the second rearward seal is positioned on a second flushing seal carrier disposed rearwardly of the first flushing seal housing. 5 BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment of the invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is a perspective view of a rock drill according to an embodiment of the invention; 10 Figure 2 is a front elevation of the embodiment of Figure 1; Figure 3 is a cross-sectional view of the embodiment of Figure 2, taken along the line A-A on Figure 2; Figure 4 is a cross-sectional view of the embodiment of Figure 2, taken along the line B-B on Figure 2; 15 Figure 5 is a cross-sectional view of the embodiment of Figure 2, taken along the line C-C on Figure 2; Figure 6 is an enlarged view of a portion of Figure 5; and Figure 7 is an exploded view of the embodiment of Figure 1. DESCRIPTION OF A PREFERRED EMBODIMENT 20 Figures 1 and 2 show a rock drill 2 in drill operation configuration, the drill 2 having a front head 20, cover plate 30, housing of a rotation generation mechanism or gear box 40, damping mechanism or damping body 50 and impulse generating mechanism or impact body 60. These bodies and housings are compressively restrained in relative disposition to each other by a restraint arrangement 80, 90, 96. 25 They are supported on cradle assembly 70.

11 A drill rod or shank adaptor 10 associated with the rock drill is also shown in the operational position. In use, drill rod 10 is connected to a drill string (not shown) for transmission of rotary motion and percussive force to a drill bit (not shown) working at a rock face. 5 Referring to Figures 2, 3 and 4, the restraint arrangement includes four rear tie bars, being two upper rear tie rods 90 and two lower rear tie bars (which may be tie rods, or be strapping bolts as shown) 96, and four front tie bars (or front head studs) 80. The four rear tie bars 90, 96 and the four front tie studs 80 each have a longitudinal axis that extends parallel to the centreline or drill axis 4, which is defined 10 as the longitudinal axis of the drill rod 10 (and of the impact piston 66 shown in Figure 5). As shown in Figure 2, the configuration of the four rear tie bars 90, 96 and the four front tie studs 80 is left-to-right symmetrical or mirrored about each side of the plane C-C. Thus stresses on the left and right hand sides of the drill are also mirrored. Furthermore, the axes of the four front head studs 80 having nuts 82 are each spaced 15 the same radial distance from the drill axis 4. As shown in Figure 3, the left hand upper rear tie rod and left hand upper front head stud have the same axis, and the right hand upper rear tie bar and right hand upper front head stud have the same axis. Arranging the four front head studs such that their axes are spaced apart in a rectangular or square configuration provides additional structural strength to the drill, 20 as the second moment of area of the drill is improved (when compared to a drill having three tie bars of equivalent cross sectional area) and thus has improved bending resistance. In a drill operation configuration, the various tie rods and studs of the restraint arrangement are secured to bodies and housings of the drill such that the tie rods and 25 studs are under tension and the bodies and housings are held under compression in relative disposition to each other. In a drill field servicing configuration, the front tie studs are released or removed, but the rear tie rods and bolts remain secured such that they are under tension and the rear end bodies and housings of the drill are held under compression in relative disposition to each other.

12 As shown in Figure 3, the housing of the gearbox 40 has two rearwardly facing threaded holes 44 within which the upper rear tie rods 90 are releaseably securable at their respective threaded forward ends. The upper rear tie rods 90 pass through respective damping body tie rod holes 52 but do not engage with the damping body 5 50. The upper rear tie rods 90 also pass through respective impact body tie rod holes 64 and are releasably securable at their respective threaded rearward ends to the impact body 60 by respective nuts 92. In alternative embodiments, the upper rear tie rods could be replaced with tie bolts, or even have one end permanently secured to the housing of the gear box or 10 impact body. As shown in Figure 4, the impact body 60 has two forward facing threaded holes 62 within which the lower strapping bolts 96 are releaseably securable at their respective threaded rearward ends. The lower strapping bolts 96 pass through respective damping body tie rod holes 52 but do not engage with the damping body 15 50. The lower strapping bolts 96 also pass through respective gear box bottom tie rod holes 45 but do not engage with the housing of the gear box 40. The lower strapping bolts 96 also pass through respective cover plate bolt holes 34 and are releasably securable at their respective forward ends to the cover plate 30 by bolt heads 94. The cover plate 30 preloads the tapered bearings 47, 49 inside the 20 gearbox. This it is advantageous that it may be restrained in position with the gearbox even when the front head is removed, as factory preload settings are thus unlikely to be affected by servicing operations in the field. In alternative embodiments, the lower rear tie bolts could be replaced with tie rods or studs, or even have one end permanently secured to the cover plate or impact 25 body. Returning to Figures 2 and 3, the housing of the gearbox 40 has four forwardly facing threaded holes 42 within which the front head studs 80 are releaseably securable at their respective threaded rearward ends. The front head studs 80 pass 13 through respective cover plate stud holes 32. The front head studs 80 also pass through respective front head stud holes 22 and are releasably securable at their respective threaded forward ends to the front head 20 by respective nuts 82. Each front head stud 80 has a stepped shoulder that is engageable with the respective 5 cover plate hole 32. The restraint arrangement thus may restrain in compression the front head 20, cover plate 30, housing of the gear box 40, damping body 50 and impact body 60, or where the front head studs 80 are released by loosening the nuts 82, the rear tie bars (tie rods 90, strapping bolts 96) restrain in compression the lower end of the cover 10 plate 30 together with the housing of the gear box 40, damping body 50 and impact body 60, while the front head 20 may be removed. In the field, in order to replace an associated drill rod 10 retained on the drill 2, the restraint arrangement is configured to a drill field servicing configuration in which the rearward end of the drill is restrained in relative disposition - the coverplate, 15 gearbox, damping mechanism and impact body are held in compression by lower strapping bolts 96 and upper rear tie rods 90, while the front head 20 is removed from the relative disposition by loosening and removing the nuts 82 from front head studs 80. At this stage the cover plate 30 is retained against gear box 40 by the lower strapping bolts 96, making the front head removal process easy. If necessary in a 20 workshop servicing situation, the cover plate 30 may be removed by removing the front head stud nuts 82 and the lower strapping bolts 96 and yet the gearbox housing, damping mechanism and impact body are still usefully held together by the upper rear tie rods 90. Returning to the field servicing situation, the associated old drill rod 10 may 25 then be changed over for a new drill rod. The front end of the drill is then re assembled and the restraint arrangement is then configured to a drill operation configuration in which the whole drill is restrained in relative disposition by replacing the front head 20 and replacing and tightening nuts 82 on front head studs 80.

14 In the drill operation configuration the gearbox, damping mechanism and impact body are held in compression by upper rear tie rods 90, the cover plate, gearbox, damping mechanism and impact body are held in compression by lower strapping bolts 96, while the front head, cover plate and gearbox are held in 5 compression by front head studs 80. Thus in normal use and normal field servicing, the upper rear tie rods 90 and lower rear strapping bolts 96 are left in position with the original factory tensioning as it is not necessary to release them to remove the front head 20. Field servicing related problems are more likely to be isolated to the front end of the drill, less likely 10 to involve damage of the impact piston and thus are less likely to be serious in nature. Figure 6 shows a detail view of the front end of the drill 2, with an associated drill rod 10 mounted in operating position. A seal housing 150 defines together with drill rod 10 an inner cavity, being flushing medium cavity 152 into which flushing medium may be fed via fluid supply inlet 156, at a typical rate of 100 litres per minute 15 at 20 Bar. In operation, the medium passes from the flushing medium cavity 152 through drill rod inlet 14 to the hollow centre of the drill rod, flushing medium path 12. The medium is then supplied via flushing medium path 12 to the drill string and thus to the rock working face. The seal housing 150 has seals to prevent egress of fluid from flushing fluid 20 cavity 152 along the outside of the drill rod 10 into other parts of the drill 2. Forward and rearward wear strips 162, 172 are provided either end of the cavity 152. A first forward seal, cup seal 160 is provided in front of the wear strip 162 and a first rearward seal, cup seal 170 is provided behind the other wear strip 172. A second rearward flushing seal carrier 190 is disposed rearwardly of the seal housing 150. The 25 second seal carrier 190 has a second rearward seal, cup seal 180. If seal 170 fails, seal 180 prevents fluid from entering the rear end of the drill.

15 Advantageously, an overflow relief arrangement is also provided through providing the second rearward seal 180 on a carrier 190 separate from the first seal housing 150, and an overflow relief path to atmosphere. The seal housing 150 defines together with front head 20 an outer cavity 154. 5 which is open to the atmosphere at its lower end. Any fluid entering the outer cavity may overflow to atmosphere, as shown by the example large arrow in Figure 6. If the first rearward seal 170 fails, fluid under pressure will flow from inner flushing fluid cavity 152 along the surface of drill rod 10 and past the failed seal 170. The fluid will then flow via an overflow relief path, through a gap between seal housing 150 and 10 second seal carrier 190, and through outer cavity 154 as it overflows to atmosphere via the lower end of cavity 154. Although some fluid may continue to be delivered to the drill rod 10, fluid that passes the failed seal 170 will follow the path of least resistance to atmosphere. Thus the second rearward seal 180 is unlikely to be exposed to high pressures and thus is less likely to fail. In a similar manner, if the 15 forward seal 160 fails, fluid will flow via an overflow relief path, through a gap between seal housing 150 and front head bushing 28, and through outer cavity 154 as it overflows to atmosphere via the lower end of cavity 154. A second forward seal, cup seal 164, is located at the front head bushing 28, so that ingress of rock debris and dirt is prevented. This reduces abrasive wear of the front head bushing. 20 For a given drill and expected operating use, the overflow relief path and opening to atmosphere has a predetermined size providing a predetermined overflow relief flow capacity that is matched to a maximum predetermined or expected flushing fluid supply flow capacity. In the embodiment shown, the size is 235 square mm to allow flow of around 100 litres per minute at 20 Bar. Provision of an overflow relief 25 path having sufficient flow capacity means that the second rearward seal 180 is not subject to high pressure build up and rapid failure. Furthermore, an overflow of up to around 100 litres per minute from the front end of the drill cannot be overlooked or ignored, firstly as it will become difficult to 16 operate the drill and secondly because the drill will not be delivering sufficient fluid to the rock face. Maintenance will thus be performed, and will occur prior to any rupture of the second rearward seal, protecting the rear end of the drill from expensive and time consuming damage. 5 Figure 7 shows an exploded view of the various parts comprising the drill 2. While the above description refers to one embodiment of a rock drill, it will be appreciated that other embodiments can be adopted by way of different combinations of features. Such embodiments fall within the spirit and scope of this invention. The term "comprises" and its grammatical variants have a meaning that is 10 determined by the context in which they appear. Accordingly, the term should not be interpreted restrictively unless the context dictates so.

Claims (23)

1. A rock drill comprising a plurality of bodies and housings, including a front head, characterised in a restraint arrangement having a drill operation configuration and a drill field servicing configuration, the restraint arrangement being configured: 5 a) when in a drill operation configuration to restrain in relative disposition said plurality of bodies and housings; and b) when in a drill field servicing configuration to restrain in said relative disposition said plurality of bodies and housings other than the front head; 10 whereby the front head may be removed from the drill during field servicing whilst the remaining plurality of bodies and housings other than the front head remain restrained in said relative disposition.

2. A rock drill comprising a plurality of bodies and housings including: - an impulse generating mechanism body; 15 - a damping mechanism body; - a rotation generating mechanism housing; - a cover plate; and - a front head; characterised in a restraint arrangement having a drill operation configuration and 20 a drill field servicing configuration, the restraint arrangement being configured: a) when in a drill operation configuration to restrain in relative disposition said impulse generating mechanism body, damping mechanism body, rotation generating mechanism housing, cover plate and front head; and b) when in a drill field servicing configuration to restrain in said relative 25 disposition said impulse generating mechanism body, damping mechanism body, and rotation generating mechanism housing; whereby the front head may be moved from said relative disposition and the associated drill rod removed from the drill during field servicing whilst said impulse 18 generating mechanism body, damping mechanism body, and rotation generating mechanism housing remain restrained in said relative disposition.

3. A rock drill according to claim 2 further characterised in the restraint arrangement being configured, when in a drill field servicing configuration, to 5 restrain in said relative disposition said impulse generating mechanism body, damping mechanism body, rotation generating mechanism housing and cover plate; whereby the front head may be moved from said relative disposition and the associated drill rod removed from the drill during field servicing whilst said impulse 10 generating mechanism body, damping mechanism body, rotation generating mechanism housing and cover plate remain restrained in said relative disposition.

4. A rock drill according to claim 2 or 3 further characterised in that the restraint arrangement includes a first rear tie bar securable to the impulse generating mechanism body and to the rotation generating mechanism housing. 15

5. A rock drill according to claim 4 further characterised in that the first rear tie bar is a tie rod, respective ends of which are releasably securable to the impulse generating mechanism body and to the rotation generating mechanism housing.

6. A rock drill according to claim 4 or 5 further characterised in a plurality of first rear tie bars securable to the impulse generating mechanism body and to the rotation 20 generating mechanism housing.

7. A rock drill according to claim 6 further characterised in having two first rear tie rods, respective ends of which are releasably securable to the impulse generating mechanism body and to the rotation generating mechanism housing. 19

8. A rock drill according to any one of claims 2 to 7 further characterised in that the restraint arrangement includes a cover plate rear tie bar securable to the impulse generating mechanism body and to the cover plate.

9. A rock drill according to claim 8 further characterised in that the said cover plate 5 rear tie bar is a tie bolt, respective ends of which are releasably securable to the impulse generating mechanism body and to the cover plate.

10.A rock drill according to claim 8 or 9 further characterised in a plurality of cover plate rear tie bars securable to the impulse generating mechanism body and to the cover plate. 10

11. A rock drill according to claim 10 further characterised in having two cover plate rear tie bolts, respective ends of which are releasably securable to the impulse generating mechanism body and to the cover plate.

12.A rock drill according to any one of claims 2 to 11 further characterised in that the restraint arrangement includes a front tie bar securable to the rotation generating 15 mechanism housing and to the front head.

13.A rock drill according to claim 12 further characterised in that the front tie bar is a tie stud, respective ends of which are releasably securable to the rotation generating mechanism housing and to the front head.

14.A rock drill according to claim 12 or 13 further characterised in a plurality of front 20 tie bars securable to the rotation generating mechanism housing and to the front head.

15.A rock drill according to claim 14 further characterised in having four front tie studs, respective ends of which are releasably securable to the rotation generating mechanism housing and to the front head. 20

16.A rock drill according to any one of the preceding claims further characterised in that said relative disposition is in compression.

17.A method of changing an old drill rod, the old drill rod associated with a rock drill according to any one of the claims 2 to 16 characterised in the steps of: 5 a) configuring the restraint arrangement to a drill field servicing configuration whereby said impulse generating mechanism body, damping mechanism body, and rotation generating mechanism housing are restrained in said relative disposition; b) removing said front head from said relative disposition; 10 c) removing an old drill rod from the drill and replacing it with a new drill rod associated with the drill; d) moving said front head back to said relative disposition; e) configuring the restraint arrangement to a drill operation configuration wherein said impulse generating mechanism body, damping mechanism 15 body, rotation generating mechanism housing, cover plate and front head are restrained in said relative disposition

18.A method of changing an old drill rod according to claim 17 wherein the step of configuring the restraint arrangement to a drill field servicing configuration is further characterised in that said impulse generating mechanism body, damping 20 mechanism body, rotation generating mechanism housing and cover plate are restrained in said relative disposition;

19.:A rock drill comprising a first flushing seal housing having a first forward seal and a first rearward seal, and having a second rearward seal, characterised in an overflow relief arrangement configured to allow overflow to atmosphere of fluid 25 from between the first and second seals. 21

20.A rock drill according to claim 19 further characterised in that the overflow relief arrangement has a predetermined flow capacity substantially equivalent to a maximum predetermined flushing fluid supply flow capacity.

21.A rock drill according to any one of claims 19 to 20 further characterised in that the 5 second rearward seal is positioned on a second flushing seal carrier disposed rearwardly of the first flushing seal housing.

22.A rock drill substantially as hereinbefore described, with reference to the embodiment shown in the accompanying Figures 1 to 7.

23.A method of servicing a rock drill substantially as hereinbefore described, with 10 reference to the embodiment shown in the accompanying Figures 1 to 7. ROCKDRILL SERVICES AUSTRALIA PTY LTD WADESON 15 Patent & Trade Marks Attorneys P1016AUAU