WO1998026153A1

WO1998026153A1 - Apparatus for connecting and disconnecting drill rods

Info

Publication number: WO1998026153A1
Application number: PCT/AU1997/000845
Authority: WO
Inventors: Eberhard Moll
Original assignee: Universal Drilling Systems (Aust) Pty. Ltd.
Priority date: 1996-12-11
Filing date: 1997-12-11
Publication date: 1998-06-18
Also published as: ZA9711147B; AUPO418296A0

Abstract

An apparatus for connecting and disconnecting threaded drill rods comprises gripping means comprising a plurality of cams (a) for gripping a drill rod in a connecting position in which drive can be imparted to the drill rod through the cams to rotate the drill rod in a first direction for threadingly engaging the drill rod with an adjacent drill rod, and (b) for gripping the drill rod in a disconnecting position in which drive can be imparted to the drill rod through the cams to rotate the drill rod in a second direction for threadingly disengaging the drill rod from an adjacent drill rod; and drive means comprising a power source arranged to rotate a first sprocket coupled by a chain to a second sprocket for moving the gripping means between the connecting position and the disconnecting position and for imparting drive to a gripped drill rod in either the first direction or the second direction.

Description

APPARATUS FOR CONNECTING AND DISCONNECTING DRILL RODS

FIELD OF THE INVENTION

The present invention relates to an apparatus for connecting and disconnecting drill rods. BACKGROUND TO THE INVENTION

Drill rods are lengths of hollow pipe which have a male thread at one end and a female thread at the other end. Drill rods range in size up to about ten metres long and a plurality of drill rods are assembled in forming a drill string by engaging the male thread of an upper drill rod with the female thread of an adjacent lower drill rod or vice versa. The lower end of a drill string culminates in a cutting head which drills through the ground when rotated. In operation, the upper end of the drill string is rotated by a drive mechanism mounted on a drilling rig from which the drill string downwardly projects. A drill string may project vertically from a drill rig or at a desired angle to vertical. Drill strings are commonly many hundreds of metres long and can be thousands of metres long. Rotation of the cutting head by action of the drive mechanism therefore necessitates that drill rods are rigidly connected together.

The making (connecting) of drill rod joints is typically performed manually by an operator locating the appropriately threaded end of a drill rod to be added to the drill string into the mating thread of the uppermost drill rod in the drill string so far assembled. The drill rod to be added to the drill string is then rotated into threaded engagement with the adjacent drill rod below it using a pair of stillsons. The drill string which has been lengthened by connection of the drill rod is then rotated by the drive mechanism until it moves a further distance into the ground, with a further drill rod then connected and so on. The operator must exert considerable force on the stillsons to connect the drill rods sufficiently firmly. The breaking (disconnecting) of drill rods from a drill string (tripping the string) is essentially the reverse of the making procedure. The making and breaking of drill strings are inherently dangerous operations with injuries to operators an ever present possibility. For example, when making a drill string an operator's finger can be severed if it is caught between adjacent drill rods and severe injury can result if the drill string drive mechanism is accidentally actuated whilst a pair of stillsons are attached to a drill rod. It is therefore desirable to provide an apparatus which improves operator safety. SUMMARY OF THE INVENTION

The present invention provides an apparatus for connecting and disconnecting threaded drill rods, the apparatus comprising gripping means comprising a plurality of cams (a) for gripping a drill rod in a connecting position in which drive can be imparted to the drill rod through the cams to rotate the drill rod in a first direction for threadingly engaging the drill rod with an adjacent drill rod, and (b) for gripping the drill rod in a disconnecting position in which drive can be imparted to the drill rod through the cams to rotate the drill rod in a second direction for threadingly disengaging the drill rod from an adjacent drill rod; and drive means comprising a power source arranged to rotate a first sprocket coupled by a chain to a second sprocket for moving the gripping means between the connecting position and the disconnecting position and for imparting drive to a gripped drill rod in either the first direction or the second direction.

An amount of torque must be applied to break a drill rod from a drill string. In so-called RC drilling up to 20000Nm of torque may be required. The present invention is preferably concerned with drilling apparatus which require lower levels of torque such as so-called wireline core drilling, diamond drilling and slim hole oil drilling where a maximum of 5000Nm is required. Preferably, a first gear is fixed to each cam and the second sprocket is arranged to rotate a second gear arranged to rotate the first gears. Preferably, the second gear is a ring gear secured to the second sprocket .

Preferably, the apparatus is arranged such that in movement between the connecting position and the disconnecting position the gripping means adopts a neutral position in which the gripping means is spaced apart from the drill rod thereby enabling the drill rod to be rotated independently of the apparatus .

The gripping means preferably has three cams and, preferably, each cam includes a wear portion which bears against a drill rod in gripping the drill rod and which can be periodically replaced as it wears away. Preferably, each cam includes a plurality of wear portions located at different positions to enable drill rods of different diameters to be gripped.

Preferably, the apparatus is arranged to move with a drill rod gripped by the gripping means when the drill rod is rotated in either the first direction or the second direction by the drive means. For example, if the apparatus is being used to threadingly engage a drill rod with a vertically positioned drill rod below it, the apparatus preferably moves vertically downwardly with the gripped drill rod as it threadingly engages with the stationary drill rod below it.

Preferably, the power source is a hydraulic motor. BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment of the present invention is described below, by way of example only, with respect to the accompanying drawing in which:

Figure 1 is an inverted plan view of an apparatus according to the present invention in a neutral position; Figure 2 is a cross -sectional view of the apparatus of Figure 1 through line A-A of Figure 1;

Figure 3 is an inverted plan view of the apparatus of Figure 1 in a connecting position; Figure 4 is an inverted plan view of the apparatus of Figure 1 in a disconnecting position;

Figure 5 is a front elevation of the apparatus of Figure 1 mounted to a drill mast; Figure 6 is an inverted plan of Figure 5; and Figure 7 is a side elevation of Figure 5. BEST MODE FOR CARRYING OUT THE INVENTION

Referring firstly to Figures 1 and 2, the apparatus 8 broadly comprises a power source in the form of a hydraulic motor 10 which is attached to a housing 12 which houses a driving portion 14 and a driven portion 16.

The driving portion 14 comprises a sprocket 18 and keyway 19, a captive washer 20 and a capscrew 21. A clamping plate 22 is located between the driving portion 14 and the housing 12. Bolts (not shown) which pass through the hydraulic motor 10, the housing 12 and the clamping plate 22 are tightened to clamp the hydraulic motor 10 and the driving portion 14 to the housing 12 and prevent relative movement between the hydraulic motor 10 and the driving portion 14. A shaft 23 from the hydraulic motor 10 passes through the housing 12 and the sprocket 18 with the sprocket 18 keyed onto the shaft to stop relative movement therebetween. The driven portion 16 comprises a sprocket 24; a slewing ring 26; top and bottom plates 28 and 30 respectively; ring gear 32; gripping means comprising three cams 34 each having silver soldered thereto wear portions in the form of three sets of tungsten inserts 36a and 36b, 38a and 38b and 40a and 40b respectively; internally mounted spur gears 41 for the cams 34; locating pins 42 for the cams 34; triangular prismatic supports 44; phosphorus bronze wear rings 46; a preloading device 48; pressed phosphorus bronze bushes 50; a rectangular neck bush which prevents mud from entering the top thrust surface; and phosphorus bronze thrust washers 52. The driving portion 14 and the driven portion 16 are connected by a chain 53 which can be tensioned by movement of the driving portion 14 relative to the driven portion 16.

The sprocket 24, ring gear 32, cams 34, triangular supports 44 and locating pins 42 are all located rigidly with respect to each other and are enclosed within a cage formed by top and bottom plates 28 and 30 respectively which are welded to the supports 44. As the sprocket 24 is driven by the sprocket 18 under action of the hydraulic motor 10, the sprocket 24 rotates on the slewing ring 26 which is fixed to the housing 12 via capscrews 54. The sprocket 24 is attached to the slewing ring 26 by welds 55. A spigot machined into the sprocket 24 fits into a mating recess machined into the ring gear 32. The sprocket 24 and ring gear 32 are fixed relative to each other via socket head capscrews 56. The spur gears 41 are similarly fixed to the cams 34 with socket head capscrews 58. The locating pins 42 sit on the bottom of reamed holes in the bottom plate 30 and are fixed relative to the bottom plate 30 via capscrews 60.

The bottom plate 30 is supported via bracket 62 which lies inside the slewing ring 26 and is mounted to the housing 12 via capscrews 63. The bottom plate 30 rubs against a bronze ring 46 which is mounted to the bracket 62 via countersunk screws 66. The bronze ring 46 is also attached to the top of the top plate 28 via countersunk screws 68 to reduce wear in the top plate 30 and the housing 12. Apertures 70 and 72 are located in top and bottom plates 28 and 30 respectively with corresponding apertures 74 and 76 located in corresponding portions of the housing 12 to allow a drill rod (not shown) to be positioned between the cams 34 such that the longitudinal axis of the drill rod is aligned with the longitudinal axes of the cams 34. The three pairs of tungsten inserts 36a and 36b, 38a and 38b, and 40a and 40b are positioned on their respective cams 34 to grip drill rods of three different diameters. Tungsten inserts 36a and 36b are arranged to grip a drill rod 78 illustrated in Figure 1. Further description will be in relation to tungsten inserts 36a and 36b and drill rod 78 but it is to be understood that tungsten inserts 38a and 38b are arranged to grip a drill rod 80 of smaller diameter than drill rod 78 with tungsten inserts 40a and 40b arranged to grip a drill rod 82 of still smaller diameter. The drill rods 78, 80 and 82 are illustrated in Figures 1, 3 and 4 merely for ease of description and do not form part of the inventive apparatus 8.

As the driving portion 14 drives the driven portion 16 the driven portion 16 rotates. The driven portion 16 can be rotated either in a clockwise or a counterclockwise manner. This rotational movement can be used to either threadingly engage adjacent drill rods or threadingly disengage adjacent drill rods.

Actuation of the hydraulic motor 10 drives the sprocket 18 which rotates the sprocket 24. This rotation can be in either direction. Rotation of the sprocket 24 results in rotation of the ring gear 32. The ring gear 32 drives against the internal spur gears 41. Rotation of the ring gear thus results in either the rotation of the entire cage or the rotation of the internal spur gears 41 around the pins 42. The pre-load device 48 is adjusted such that before the cams 34 come into contact with the drill rod 78, less force is required to rotate the cams 34 about the pins 42 than that required to rotate the entire cage. Rotation of the entire cage results in rubbing of the top and bottom plates 28 and 30 respectively against the bronze rings 46 which in turn rub against the housing 12 and bottom supports 62 respectively. As the cams 34 rotate either tungsten inserts 36a or 36b are brought into contact with drill rod 78 depending on the direction of rotation. Once the tungsten inserts 36a or 36b grip the drill rod 78 the force required to rotate the cams 34 about the pins 42 becomes greater than the force required to rotate the entire cage. The cams 34 therefore cease to rotate about the pins 42 and the pins 42 begin to rotate around the drill rod 78. As a result the drill rod is either threaded (connected) onto an adjacent drill rod or unthreaded (disconnected) from a drill rod to which it has been previously connected, depending upon which direction the driven portion 16 is rotated by the driving portion 14. Referring now to Figure 3, the hydraulic motor 10 has been driven in a direction such that the sprocket 18 has been rotated in a clockwise direction as viewed in Figure 3 with the ring gear 32 similarly having been rotated clockwise. Consequently, the cams 34 have been rotated clockwise about the pins 42 until the tungsten inserts 36a grip the drill rod 78. At this point the force to rotate the cams 34 about the pins 42 becomes greater than that required to rotate all three pins 42 about the drill rod 78. As a result, continued application of drive to the driven portion 16 causes the pins 42 to rotate in a clockwise direction about the drill rod 78 while it is being gripped by tungsten inserts 36a to rotate the drill rod 78 into threaded engagement with an adjacent drill rod. Manufacturers of drill rods typically specify an optimum torque for making drill rods. The torque delivered to a drill rod by the apparatus 8 can be calculated as a function of the hydraulic pressure delivered to the hydraulic motor 10 and the length of the lever arm extending between the centre of the locating pins 42 and the outside diameter of the drill rod. Accordingly, torque can be tailored by appropriate adjustment of the hydraulic pressure delivered to the hydraulic motor 10.

Referring now to Figure 4, the hydraulic motor 10 has been driven in a direction opposite to that referred to in relation to Figure 3 which has rotated the sprocket 18 in a counter-clockwise direction as viewed in Figure 4. This has resulted in the ring gear 32 rotating in a counter-clockwise direction which has in turn resulted in cams 34 rotating in a counter-clockwise direction about pins 42 until tungsten inserts 36b grip the drill rod 78. At this point the force to rotate the cams 34 about the pins 42 becomes greater than that required to rotate all three pins 42 about the drill rod 78. This results in the drill rod 78 being rotated in a counter-clockwise direction to threadingly disengage it from an adjacent drill rod to which it had previously been threadingly engaged. As in the case of making drill rods, the torque delivered to a drill rod in breaking it from an adjacent drill rod can be tailored by appropriate adjustment of the hydraulic pressure delivered to the hydraulic motor 10. Referring to Figures 5, 6 and 7 the apparatus 8 is attached to a drill mast 84 via a swing arm assembly 86. Each swing arm assembly 86 enables the necessary reaction to be provided by the drill mast 84 to counter reverse torque effects which act on the apparatus 8 as a result of the torque which is applied to drill rod 78 by the apparatus 8. The swing arm assembly 86 prevents the apparatus 8 from rotating about drill rod 78 and allows the apparatus 8 to move with the drill rod 78 in a direction aligned with the longitudinal axis of the mast 84 during both threading and unthreading. The swing arm assembly 86 is attached to the mast 84 such that the swing arm assembly 86 can float between predetermined limits in a direction which is aligned with the longitudinal axis of the mast irrespective of the angle of inclination of the mast.

The swing arm assembly 86 generally comprises a mounting bracket 88, mounting shaft 90, linear bearings 92, spring support 94, adjustment nut 96, spring 98, vertical support 100, fixed extension 102, pivot 104, support arm 106 and guide members 108 and 110. The mounting bracket 88 attaches directly to the mast 84 and supports brackets 112 which extend from upper and lower portions of the mounting bracket 88 to receive the mounting shaft 90.

The mounting shaft 90 receives upper and lower linear bearings 92, spring support 94 and adjustment nut 96. The spring support 94 and adjustment nut 96 are fixed and releasably fixed respectively longitudinally relative to the mounting shaft 90. The position of the adjustment nut 96 can be adjusted along the mounting shaft 90 and provides a support which receives a lower end of the spring 98.

The vertical support 100 is attached to the upper and lower linear bearings 92 which provide the vertical support 100 with movement in a direction aligned with the longitudinal axis of the mounting shaft 90. The vertical support 100 is pivotally attached to the apparatus 8 via the fixed extension 102, pivot 104 and support arm 106. Such a pivotal attachment enables the apparatus 8 to be pivoted out of alignment with drill rod 78 when not in use. Location of the apparatus 8 when in use is achieved via guide members 108 and 110. The guide member 108 comprises a roller bearing 112 which is appropriately positioned relative to the support arm 106 such that it can move in a direction aligned with the longitudinal axis of a tube 114 along a side 116 of the tube 114. The guide 110 similarly comprises a roller bearing 118 which similarly moves with respect to a tube 120. The guide 110 further comprises a clip 122 which can be rotated into and out of engagement with a side 124 of the tube 120. By rotating the clip 122 into an engaged position the location of the apparatus 8 can be fixed relative to drill rod 78.

The mast 84 tilts in substantially only one plane, that plane being substantially perpendicular to the longitudinal axes of the cylindrical roller bearings 112 and 118. Furthermore, the mast 84 tilts in only one direction from the vertical position shown in Figures 5- 7. The direction in which the mast 84 tilts is such that the cylindrical roller bearings 112 and 118 support part of the weight of the apparatus 8 as the apparatus 8 attempts to pivot about the pivot 104.

The amount of travel that the swing arm assembly 86 must provide in a direction aligned with the longitudinal axis of the mast is dependent on the length of thread of drill rod 78. The adjustment nut 96 is fixed on the mounting shaft 90 such that upon both threading and unthreading operations the vertical support 100 is able to move in a direction aligned with the direction of movement of the apparatus 8 for the full extent of that movement. That is to say that the spring 98 is compressed when drill rod 78 is fully threaded and extended when drill rod 78 is fully unthreaded. By appropriately adjusting the position of the nut 96 the apparatus 8 is positioned by the spring 98 in an intermediate position between the aforementioned fully threaded and fully unthreaded positions.

Claims

1. An apparatus for connecting and disconnecting threaded drill rods, the apparatus comprising gripping means comprising a plurality of cams (a) for gripping a drill rod in a connecting position in which drive can be imparted to the drill rod through the cams to rotate the drill rod in a first direction for threadingly engaging the drill rod with an adjacent drill rod, and

(b) for gripping the drill rod in a disconnecting position in which drive can be imparted to the drill rod through the cams to rotate the drill rod in a second direction for threadingly disengaging the drill rod from an adjacent drill rod; and drive means comprising a power source arranged to rotate a first sprocket coupled by a chain to a second sprocket for moving the gripping means between the connecting position and the disconnecting position and for imparting drive to a gripped drill rod in either the first direction or the second direction.

2. An apparatus as claimed in claim 1 wherein the drive means is arranged to impart torque up to 5000Nm to a gripped drill rod.

3. An apparatus as claimed in claim 1 or claim 2 wherein the gripping means has three cams.

4. An apparatus as claimed in any one of the preceding claims wherein a first gear is fixed to each cam and the second sprocket is arranged to rotate a second gear arranged to rotate the first gears.

5. An apparatus as claimed in claim 4 wherein the second gear is a ring gear secured to the second sprocket.

6. An apparatus as claimed in any one of the preceding claims wherein, in movement between the connecting position and the disconnecting position, the gripping means adopts a neutral position in which the gripping means is spaced apart from the drill rod.

7. An apparatus as claimed in any one of the preceding claims wherein each cam includes a wear portion which bears against a drill rod in gripping the drill rod and which can be periodically replaced as it wears away.

8. An apparatus as claimed in claim 7 wherein each cam includes a plurality of wear portions located at different positions whereby drill rods of different diameters can be gripped.

9. An apparatus as claimed in any one of the preceding claims wherein the power source is a hydraulic motor.

10. An apparatus as claimed in any one of the preceding claims wherein the apparatus further comprises mounting means for mounting the apparatus to a drill mast whereby the apparatus moves aligned with the longitudinal axis of the mast during threading and unthreading of a drill rod irrespective of the angle of inclination of the mast.