Technical Field

The present disclosure relates to cable bolts and in particular to dolly drive assemblies for tensioning cable bolts suitable for use in the mining and tunnelling industry to provide rock and wall support. The bolts and assemblies are suitable for use in hard rock applications as well as in softer strata, such as that often found in coal mines, and it is to be appreciated that the term "rock" as used in the specification is to be given a broad meaning to cover both these applications.

Background

Roof and wall support is vital in mining and tunnelling operations. Mine and tunnel walls and roofs consist of rock strata, which must be reinforced to prevent the possibility of collapse. Rock bolts, such as rigid shaft rock bolts and flexible cable bolts are widely used for consolidating the rock strata. i conventional strata support systems, a bore is drilled into the rock by a drill rod, which is then removed and a rock bolt is then installed in the drilled hole and secured in place typically using a resin or cement based grout. The rock bolt is tensioned which allows consolidation of the adjacent strata by placing that strata in compression.

To allow the rock bolt to be tensioned, the end of the bolt may be anchored

mechanically to the rock formation by engagement of an expansion assembly on the end of bolt with the rock formation. Alternatively, the bolt may be adhesively bonded to the rock formation with a resin bonding material inserted into the bore hole.

Alternatively, a combination of mechanical anchoring and resin bonding can be employed by using both an expansion assembly and resin bonding material. Summary of the Disclosure

Disclosed is a dolly for imparting rotary drive to an assembly having a shaft and a drive receiving portion which are rotatable with respect to one another, the dolly having a driven portion adapted to engage a drive, a drive imparting portion adapted to engage the drive receiving portion and a shaft drive portion adapted to engage the shaft, the dolly being operative to adopt a first mode in which the shaft drive portion rotates in response to rotation of the driven portion and a second mode in which the drive imparting portion rotates in response to rotation of the driven portion. In one form in the first mode the drive imparting portion and the shaft drive portion rotate concurrently with one another. In one form in the second mode the drive imparting portion rotates independently of the shaft drive portion.

In one form the dolly can be changed between the first mode and the second mode without disengaging the shaft drive portion from the shaft. In one form the dolly can change between the first mode and the second mode and returned to the first mode a plurality of times.

The dolly is operable in a plurality of modes. This is beneficial when the dolly is being utilised to spin and then place tension upon a rock bolt. B the rock bolt application, the dolly is installed and engages a shaft of the rock bolt and operates in a first mode, in which drive imparted to the dolly acts to spin the shaft. This is specifically useful in an application for anchoring the shaft in a bore either using resin or an anchoring device. The dolly is then moved to the second mode which in one form may be achieved without removing the dolly from engagement with the shaft to engage with the drive receiving portion. In the second mode the drive receiving portion of the rock bolt assembly is rotated by the drive imparted to the dolly while in one form allowing the shaft to remain fixed about the axis of rotation. This in one form allows for tensioning of the rock bolt. - 2 -

When resin bonding material is used, it penetrates the surrounding rock formation to adhesively unite the rock strata and to hold firmly the rock bolt within the bore hole. Resin is typically inserted into the bore hole in the form of a two component plastic cartridge having one component containing a curable resin composition and another component containing a curing agent (catalyst). The two component resin cartridge is inserted into the blind end of the bore hole and the rock bolt is inserted into the bore hole such that the end of the rock bolt ruptures the two component resin cartridge. Upon rotation of the rock bolt about its longitudinal axis, the compartments within the resin cartridge are shredded and the components are mixed. The resin mixture- fills the annular area between the bore hole wall and the shaft of the rock bolt. The mixed resin cures and binds the rock bolt to the surrounding rock.

Tension assemblies have been proposed to provide tension along rock bolts, for example, which in turn provides a compressive force on the substrate, such as a mine shaft roof substrate, about the bolt. In one such assembly, a nut placed onto a thread on the rock bolt is rotated, after setting of the resin, toward and to abut the substrate about the bore hole either directly or through a bearer plate disposed on the shaft between the substrate and the nut. Rotation of the nut is continued for a predetermined number of turns to provide tension along the cable.

Other arrangements of tension assemblies have been proposed which involve rotation of components to induce tension on the rock bolt in a similar was to that provided by the nut described above.

Accordingly it is desirable to impart rotary drive to a rock bolt for mixing resin or otherwise anchoring the rock bolt in the bore. It is also desirable to impart rotary drive to components associated with or engaged with the rock bolt for tensioning of the rock bolt with or without also rotating the rock bolt. The dolly can in one form also be changed to a third mode for servicing and then back to either of the first two modes. The act of moving between modes, therefore, does not reduce the availability of modes.

In one form the assembly comprises a rock bolt assembly having a shaft and a tensioning device and wherein the drive receiving portion is an element of the tensioning device.

In one form the drive imparting portion comprises a sheath, having an assembly engagement end, adapted to engage with the drive receiving portion, and a sheath drive portion. In one form the sheath drive portion is directly connected to or integrally formed with the driven portion of the dolly. In one form the drive receiving portion has a sheath engagement end. I one form the sheath engagement end and the assembly engagement end are profiled.

In one form the sheath engages the sheath drive portion by means of splines. In one form the sheath drive portion includes external splines and the sheath includes internal splines.

In one form the shaft drive portion is adapted to engage the shaft by means of a shaped cavity into which the shaft is inserted. In one form the shaft is a cable comprising individual twisted strands and the shaped cavity is "flower" shaped to engage the individual strands during rotation.

In one form the shaft drive portion is adapted to be moveable between a position in which the shaft drive portion engages the sheath such that the shaft drive portion and the sheath rotate concurrently and a position in which the shaft drive portion is disengaged from the sheath such that the shaft drive portion and the sheath can rotate with respect to one another. In one form engagement between the shaft drive portion and the sheath is achieved by splines. In one form the sheath includes internal splines and the shaft drive portion includes external splines.

In one form the splines are positioned on the sheath and the shaft drive portion such that longitudinal movement of the sheath with respect to the shaft drive portion is effective to move the sheath between a position in which the dolly adopts the first mode and a position in which the dolly adopts the second mode.

In one form the shaft drive portion and the sheath 'drive portion are engaged by means of a spindle which maintains axial alignment but allows the shaft drive portion and the sheath drive portion to rotate with respect to one another.

Γη a second aspect, disclosed is a dolly for imparting rotary drive to a rock bolt assembly having a shaft and a tensioning assembly having an actuator engaged with the shaft, the shaft and the actuator being rotatable with respect to one another, the dolly having a driven portion, adapted to engage a drive, an actuator drive portion adapted to engage the actuator and a shaft drive portion adapted to engage the shaft, the dolly being operative to adopt a first mode in which the shaft drive portion rotates in response to rotation of the driven portion and a second mode in which the actuator drive portion rotates in response to rotation of the driven portion. In one form in the first mode the actuator drive portion and the shaft drive portion rotate concurrently with one another. In one form in the second mode the actuator drive portion rotates independently of the shaft drive portion.

In one form the actuator drive portion comprises a sheath having an actuator engagement end. In one form the actuator engagement end is profiled.

In one form the sheath is located around the cable drive portion and the sheath is adapted to engage the cable drive portion by means of splines. In one form longitudinal movement of the sheath with respect to the cable drive portion is effective to change the dolly between the first mode and the second mode. In a third aspect, disclosed is a dolly for imparting drive to an assembly comprising a shaft and a drive receiving portion, the dolly comprising a sheath, adapted to engage the drive receiving portion; a shaft drive portion, adapted to engage the shaft; and, a drive portion, the drive portion operative to adopt a shaft drive mode in which the drive portion engages the shaft drive portion such that they rotate concurrently, and a sheath drive mode in which the drive portion engages the sheath such that the rotate concurrently.

In one form the shaft drive portion and the drive portion are disposed substantially within the sheath.

In one form, in the shaft drive mode, the shaft drive portion and the sheath are engaged such that the rotate concurrently. In one form, in the sheath drive mode, the sheath rotates independently of the shaft drive portion. ,

In one form longitudinal movement of the sheath with respect to the drive portion effects change of the dolly between the shaft drive mode and the sheath drive mode. In one form, in the first mode, the sheath and the cable drive portion are engaged by splines.

In another aspect, disclosed is a method of installing a rock bolt having a shaft and a drive receiving portion which are rotatable with respect to one another, the method comprising the steps of connecting a dolly to the rock bolt, the dolly being operative to adopt a first mode and a second mode; operating the dolly in the first mode to rotate the shaft of the rock bolt; operating the dolly in the second mode to rotate the drive receiving portion with respect to the shaft.

In one form the dolly is changed from the first mode to the second mode without disconnecting the dolly from the rock bolt. Brief Description of the Drawings

Embodiments will now be described, by way of example only, with reference to the accompanying drawings in which:

Fig. 1 is a perspective view of one embodiment of the tensioning device disposed on a cable bolt;

Fig. 2 is an exploded view of the tensioning device of Fig. 1;

Fig. 3 is a perspective view of the base member of a tensioning device of Fig. 1;

Fig. 4 is a cross-sectional view of the base member of Fig. 3;

Fig. 5 is a top view of the base member of Fig. 3;

Fig. 6 is a perspective view of the bearer member of a tensioning device of

Fig.l;

Fig. 7 is a cross-sectional view of the member of Fig. 6;

Fig. 8 is a top view of the member of Fig. 6;

Fig. 9 is a side elevation of the tensioning device of Fig. 1 connected to a bearing plate and cable bolt;

Fig. 10 is cross-sectional view of the device of the assembly of Fig. 9;

Figs. 11 A to C show a perspective view from above, a plan view and a cross- sectional elevation of an alternative bearer member;

Figs. 12A and B show a plan view and a cross-sectional side view of a bearing plate for use with the bearer member of Fig. 11; ¹

Figs. 13 A to C show a perspective view from below, a view from below and a side view of a bearing plate of a cable bolt tensioning assembly in accordance with a further embodiment;

Figs. 14 A, B and C show a perspective view from below, a view from below and a sectional view of a bearer member of a cable bolt tensioning assembly for use with the bearing plate of Fig. 13;

Figs. 15 A and B illustrate operation of the bearer member of Fig. 13 with the bearing plate of Fig. 14; Figs. 16A, B and C show a perspective view from below, a view from below and a side view of a bearing plate for a cable bolt tensioning assembly in accordance with a further embodiment;

Figs. 17A, B and C show a perspective view from below, a view from below, and a sectional view of a bearer member head for-a cable bolt tensioning assembly in accordance with a further embodiment for use with the bearing plate of Fig. 16;

Figs. 18A and B illustrate operation of the bearer member of Fig. 17 with the bearing plate of Fig.16;

Figs. 19A and B show a view from above and a side view of a bearer member head for a cable bolt tensioning assembly in accordance with yet a further embodiment;

Figs. 20A and B show a view from the side and a view from below of a bearing plate for use with the bearer member of Figs. 19A and B;

Figs. 21 A and B show a view from above and a side view of a bearer member head for a cable bolt tensioning assembly in accordance with yet a further embodiment;

Figs. 22A and B show a side view and a view from below of a bearing plate for use with the bearing member of Figs. 21A and 21B;

Fig 23 shows a cross-sectional elevation of a tensioning assembly according to yet a further form;

Fig. 24 is a perspective view from below of the actuator of a tensioning device of Fig.1;

Fig. 25 is a cross- sectional elevation of the actuator of Fig. 24;

Fig. 26 is a detailed view to an enlarged scale of the end engagement profile of the actuator of Fig. 24;

Fig. 27 is a perspective view of a cable bolt tensioning dolly according to one embodiment, in a first mode;

Fig. 28 is a cross-sectional view of the dolly of Fig. 27;

Fig. 29 is a perspective view of the dolly of Fig. 27 in a second mode;

Fig. 30 is a cross-sectional view of the dolly of Fig. 29;

Fig. 31 is a perspective view of the dolly of Fig. 27 in a third mode;

Fig. 32 is a cross-sectional view of the dolly of Fig. 31; and Figs. 33 to 42 are installation sequences (showing assembly side elevations and cross-sectional views) for installing the tensioning device of Fig. 1 using the dolly of Fig. 27 in rock strata.

Detailed Description of Embodiments

The following description relates with reference to Figs. 27 to 32 to a dolly drive coupling (otherwise known as a dolly) used to impart drive (typically from a mining drill rig) to a tensioning assembly. The description also relates to assemblies (best seen in Figs. 1 to 26) for tensioning cable bolts that have been installed in a bore in rock strata and anchored to the rock strata typically by a chemical and/or mechanical anchoring process and to installation procedures (shown in Figs. 33 to 42) utilising the described tensioning assemblies and/or the drive couplings.

Tensioning Assembly

Referring firstly to the Figs. 1 to 10, a first embodiment of a tensioning assembly 1 is shown. The tensioning assembly 1 is for use with a cable bolt 2 having a flexible shaft 3 typically formed from wire strands that are bundled together. In use, the cable bolt is installed in a bore 501 (see Fig. 33) formed in the rock strata 500 with a distal end (not shown) of the bolt 2 being disposed adjacent the blind end of the bore 501 and a proximal end portion 3b arranged to project from the bore 501. The tensioning assembly 1 is arranged to be fitted onto that proximal end portion 3b so that it is disposed at an exterior surface 502 of the rock strata.

The tensioning assembly comprises three primary components; a base member 5 which is fixed to the shaft 3, a bearer member 10 which is movable relative to the base member along the shaft and which is arranged to abut either directly or indirectly the rock strata 500, and an actuator 16 that is engageable with both the bearer member and the base member and operative to transmit a biasing force to move the bearer member away from the base member which in use provides tensioning to the cable as will be described in more detail below. In the illustrated form, the base member 5 comprises a first part that forms a barrel 7, a second part that forms a stem 8, and tension wedges 6 which are located within the barrel 7 which in use secure the base member 5 with respect to the shaft 3. The tension wedges 6 have an inner wedge face 6a for defining a cable receiving passage for receiving the cable 2 and an outer wedge face 6b, opposite the inner wedge face. The outer wedge face has a profile complementary to the interior of the barrel 7. The tension wedges 6 are forced into engagement with the cable under loading of the barrel in the direction of the cable proximal end 3b. Further the barrel 7 and wedges 6 have sufficient strength to prevent shear stress failure to ensure that the cable 2 is held in place by the tension wedges 6 within the barrel 7 under this loading.

The stem 8 of the base member 5 extends from the barrel 7 and along the cable 3. The stem 8 is cylindrical and merges with the barrel to form an annular shoulder 31 that in use faces towards the distal end of the cable bolt 2. An interior passage 32 is provided to allow the cable shaft 3 to be inserted through the stem and the stem has a non- circular exterior surface 33 that includes key surfaces 9 which as shown are formed as flats on the exterior 33 of the stem 8.

The bearer member 10 is mounted on, and moveable with respect to, the stem portion 8. As best seen in Figs. 6 to 8, the bearer member 10 comprises an externally threaded body 11 and a dome head 13 at one end of the body. The body 11 has an internal cavity 34, the walls 35 of which are complementary to the exterior 33 of the stem 8 and include internal keyed sections 12. The internal keyed sections 12 are located within the cavity such that when the bearer member 10 locates over the base member 5 (such that stem 8 extends into the cavity in bearer member 10), the external keyed sections 9 on the stem 8 engage with the internal keyed sections 12 on the bearer member 10 thereby inhibiting the rotation of the bearer member 10 with respect to the base member 12 about the longitudinal axis of the shaft 3. However, the bearer member 10 is movable along the stem 8 in the direction of the axis of the cable.

The bearer member 10 is arranged so that the dome head 13 engages directly or indirectly with the rock surface into which the cable bolt extends. The head 13 which incorporates an opening 39 to allow passage of the cable shaft 3 through the bearer member, may be shaped other than a dome (for example being flattened to form a plate like appearance) so that it is engageable directly with the rock surface. However, in the illustrated forms, the dome head 13 is arranged to engage a separate cable bolt bearer plate 30 (see Figs. 9 and 10) which in use is positioned between the rock surface and the bearer member 10.

The dome head 13 shown in Figs 1 to 10 is hemispherical and engages with an inner edge 36 of the plate 30 (as best shown in Fig. 10) formed on a boss 42 of the plate 30. This direct contact is arranged to provide sufficient frictional resistance so that in tensioning of the device 1 the engagement between the plate 30 and the head 13 inhibits rotation of the head relative to the plate 30. Further the use of a generally hemispherical head 30 allows the head to remain engaged (and thereby provide the rotational resistance) with the plate 30 when the bearer member 10 is tilted at an angle with respect to the bearing plate 30, allowing for the axis of the cable bolt to be tilted with respect to the bearing plate 30, which may occur in use. As will be explained in more detail below, the inhibiting of the rotation of the bearer member assists in preventing twisting of the cable during tensioning.

Figs. 11 to 22 disclose alternative embodiments of the tensioning device where, rather than relying on frictional resistance between the head and the plate 30, a positive engagement arrangement is provided where the head and plate have cooperating surfaces, to inhibit rotation of the head 13 relative to the plate 30.

In the arrangement of Figs. 11 and 12, the head 13a is profiled to include offset lateral buttress surfaces 91. The buttress surfaces 91 are angularly spaced apart about, and project radially from, the head 13a. The buttress surfaces are adapted to engage with corresponding surfaces 92 in the bearing plate 30a shown in Figs. 12A and 12B. In this way under clockwise rotation (looking from the lower end of the bearer 10) the surfaces 91, 92 are arranged to engage so as to provide positive engagement to inhibit rotation of the bearer member 10 with respect to the plate 30a. In the illustrated embodiment, the buttress surfaces 91 extend from the top of the "dome" of the head. This allows for the surfaces 91, 92 to remain engaged when the bearer member 10 is tilted at an angle with respect to the bearing plate 30a, again allowing for the axis of the cable bolt to be tilted with respect to the bearing plate 30a.

Figs. 13 through 15 illustrate an embodiment where the head 13b is provided with a key projection 100 which is arranged to interact with a corresponding slot 101 in the boss 42b of bearing plate 30b. In operation the key projection 100 fits within the slot 101 and relative rotation between the bearing plate 30b and bearer member 10 is prevented.

In the illustrated embodiment, the key projection 100 extends from the top of the dome of the head 13b to the lower end of the head. This allows for the key projection 100 to still engage with the slot 101 when the bearer member 10 is tilted at an angle with respect to the bearing plate 30b.

Figs. 15A and B illustrate how the bearer member head 13b interacts with the bearing plate 30b in operation, with the key 100 fitting into the slot 101.

Note, that in the drawings, only the dome head 13b of the bearer member 10 is shown, hi Fig. 14C the presence of the rest of the bearer member 10 is indicated by ghost lines 110.

Figs. 16 through 18 show an alternative embodiment, in which a slot 120 is provided in the domed head 13c of the bearer 10 and a complementary key projection 121 is mounted in the boss 42c of the bearing plate 30c. Operation of the embodiment of Figs. 16 through 18 is similar to the operation of the embodiment of Figs.13 through 15, except the key 121 is provided in the bearing plate 30c and the slot 120 is provided in the head 13c.

Figs 19 and 20 illustrate yet a further way in which the bearer member 10 may engage with the bearing plate. In this embodiment, the domed head 13d of the bearer member 10 is provided with a plurality of key surfaces 150. The key surfaces 150 have edges 151 that define boundaries between each key surface 150. Complementary receiving key surfaces 152 with edges 153 are provided in the receiving boss 42d of the bearing plate 30d.

In operation the key surfaces 150 of the head 13d engage with complementary key surfaces 152 of the boss 42d, preventing relative rotation between the bearer member 10 and the bearing plate 30d.

Figs. 21 and 22 show yet a further embodiment which utilises key surfaces 160 and edges 161 on the head 13c. These key surfaces 160 are similar in operation to the key surfaces of Figure 19, but there are less of them. Complementary key surfaces are provided on the boss 42e of the bearing plate 30e. They comprise complementary surfaces 163 and edges 164.

As well as the above embodiments, there may be other arrangements which facilitate engagement of the domed head of the bearer member 10 with the bearing plate so that the bearing member does not rotate, and the cable is not twisted. For example, the embodiments of Figs 13 through 18 show only one key in slot arrangement. There may be two key in slot arrangements on opposite sides of the domed surface/bearing plate boss, or more than two.

Arrangements causing interference between the head and bearing plate could even be used in cable bolt tensioning assemblies that vary from the embodiments described with reference to Figs 1 to 10. In fact, any cable bolt tensioning assembly which requires interaction between a head of a tensioning component and a bearing plate may utilise any of these arrangements.

A further embodiment of the tensioning device 1 h disclosed in Fig. 23 where the base member 5 does not include a stem portion but merely includes the barrel 7 and wedges 6 which clamp that member to the cable 3 as described above. To restrict rotational movement of the bearer member 10 relative to the cable, but still allow longitudinal movement (in a manner akin to that provided by keying of the bearer member 10 to stem 8 in the earlier embodiments), a "flower" insert 40 is provided in the cavity 35 which is contoured to receive the individual stands of the cable bolt shaft 3. In this way the bearer member 10 engages directly with the cable shaft rather than engages the base member 5 as in the earlier embodiment. The arrangement of Fig. 23 is not as preferred as the earlier arrangements, as the bearer member 10 is not able to move solely in the longitudinal direction of the shaft as it must follow the line of the individual strands which are helically wound along the length of the strand. Moreover, the bearer member is not isolated from the cable as occurs in the earlier arrangements by the presence of the stem 7 and as such there is some chance that the cable will twist under tensioning. Nonetheless the engagement of the bearer member with the cable does provide some resistance to inhibit twisting of the cable under tensioning.

In any of the forms described above, the actuator 16 is arranged to receive the body 11 of the bearer member 10 and extend partially over the base member 5. The actuator 16 is internally threaded so as to engage with the externally threaded body 11 of the bearer member 10 and includes a shoulder 17 which is adapted to engage with the shoulder 31 formed on the base member 5 at the junction between the barrel part 7 and the stem 8 (if present). In this way, the actuator engages both the base member (through abutment of the shoulders 17 and 31) and the bearer member 10 (through engagement of the cooperating threads on those members).

Rotation of the actuator in one direction (in the illustrated form being right hand or clockwise looking along the cable bolt from the proximal end 3b) allows for tensioning of the cable bolt. The actuator 16 is adapted to engage with a drive to impart this rotation with the actuator being shaped so as to engage a drive coupling (dolly) to transmit that rotational force. This may be by making an external surface of the actuator non-circular (such as a hexagonal or other polygonal profile) so that it can engage a dolly that incorporates a complementary shape and which locates over the actuator.

However, in the illustrated form, the actuator is provided with an end profile 20 on the actuator end 19 that engages in end to end relation with a specially shaped end drive on dolly 200 (see Figs. 27 to 32), which is described in more detail below. That end profile is best shown in Figs. 24 to 26.

The end profile 20 on the actuator 16 is shaped generally as a wave or toothed profile having alternating peaks 43 and troughs 44. The profile includes a base portion 45 that is of generally constant radius and opposing side walls 46 and 47. One wall 46 is sloped relative to the longitudinal axis of the actuator 16 and provides a lead in surface for the complementary teeth 231 of the dolly 200 to locate in the profile troughs 44, whereas the other wall 47 is disposed in the direction of the actuator axis and forms the abutment surface for the actuator profile that engages with the dolly drive to impart rotation.

Drive Dolly

Figs. 27 to 32 illustrate a drive dolly which is suitable for use with the tensioning device 1 described above. It is to be appreciated that the drive dolly may be advantageously used with the tensioning device 1, but is not limited to that use and may be adapted (with for example different drive ends) to be used in other applications where rotational drive is required to be imparted to a device.

The dolly driver 200 is arranged to couple a tensioning device such as device 1 (see Figs 1 - 10) to a drive apparatus (not shown) such as mining drill rig. The dolly is generally cylindrical and includes a first end 201 which incorporates a drive shaft 202 arranged to be fitted to the drive apparatus so that ¹ rotational drive can be imparted to shaft 202, and a second end 203 which is adapted to engage the actuator 16 of the cable tensioning device 1 at actuator end surface 19. The second end 203 includes a profiled end surface 204 which is complementary to the profiled actuator end 19 and has the characteristic (albeit mirror image of) wave or toothed profile incorporating the crests 231 and troughs 232 as described above.

The dolly 200 includes a central drive 205 which is connected to the drive shaft 202. The central drive 205 is formed from two drive portions, being a sheath drive portion 206 and a cable drive portion 207. An outer sheath 208 extends over the central drive 205 and is adapted to adopt different positions on ,the central drive 205 as will be described below.

The sheath drive portion 206 is coupled directly to the drive shaft 202 via a flange 209. The sheath drive portion includes a cylindrical member 210 which is fixed to the flange 209 typically by mechanical fasteners 211. The cylindrical member 210 incorporates a drive coupling in the form of splines 212 which engage internal splines 213 formed on an inner surface of the sheath 208. These splines 212, 213 are arranged to remain in register with each other regardless of the mode of the dolly as will be described below.

The cable drive portion 207 is connected to the sheath drive portion through a spindle 214 which holds the sheath cable drive portion 207 in axial alignment with the sheath drive portion and allows the cable drive portion to rotate about that axis relative to the sheath drive portion. A roller bearing 215 is disposed between the cable drive portion and sheath drive portion to allow the independent rotation of those elements.

The cable drive portion 207 also includes a generally cylindrical member 216 and incorporates splines 217 on an outer surface of that member 216. The splines 217 extend for a shorter distance along the outer surface of the cylindrival member 216 than the sheath drive splines extend along the sheath drive portion 206. The splines 217 of the cable drive portion 207 are operative to form a drive coupling with internal splines 218 formed on the inner surface of the sheath 208- These splines 217, 218 are arranged to move into and out of register depending on the position of the sheath 208 on the centre drive 205.

Types of releasable drive couplings other than the splines 212, 213, 217, and 218 discussed above may be used in the dolly driver as would be appreciated by persons skilled in the art.

The cable drive portion 207 incorporates a cable retention device 219 which in the illustrated form incorporates a profiled "flower" cavity 220 which in use is arranged to receive a proximal end 3b of the shaft of the cable bolt 2. This cavity 220 is arranged to allow insertion of the cable end into the cable drive portion 207, and once received, to inhibit relative rotation of the cable shaft end 3b relative to the cable drive portion 207. With this arrangement the dolly 200 is able to hold the end 3b of a cable bolt shaft 3 and to impart drive to that cable shaft via rotation of the cable drive portion 207.

The sheath 208 has an outer end 221 which in use forms the second end 203 of the dolly and incorporates the profiled end surface 204 which is arranged to engage with the profiled end 19 of the actuator 16 of the tensioning device 1. An inner end 222 of the sheath is disposed adjacent the flange 209 and is biased towards that flange by virtue of a compression spring 223 which acts between the sheath 208 and the central drive 205. The sheath 208 includes a generally U-shaped slot 224 which is formed in the sheath adjacent the inner end 222 and which is arranged to register with an index pin 225 which projects from the central drive 205.

The U-shaped slot 224 incorporates a seat 226 in the base of the U and the respective legs 227, 228 of the U slot are of different lengths. With this configuration engagement of the sheath with the index pin 225 within the slot 224 allows for the sheath to adopt three different positions relative to the central drive 205. Each of these positions allows the dolly 200 to adopt a different independent mode as is described below.

The first of the three independent modes is shown in Figs. 27 and 28. This mode is a general service mode for the dolly and is adopted by locating the indexing pin into the seat 226. In this position the sheath 208 is disposed in a forward position relative to the central drive 205 (i.e. in a position furthest away from the flange 209). In this position the splines 217 of the cable drive portion 207 are disengaged from the forward splines 218 of the sheath whilst the splines 213 of the sheath 208 are located at the extremity of the sheath drive portions splines 212. In this mode, the dolly is arranged to be serviced and in particular the components can be greased as part of a regular maintenance exercise.

The second of three independent modes is an operational mode, the cable drive mode, as best illustrated in Figs. 29 and 30. In this mode, the sheath 208 is in its most rearward position with its inner end 222 located in close proximity to the flange 209 and the index pin 225 is disposed in the end of the long leg

In the cable drive mode both sets of splines (212, 213 and 217, 218) are interengaged and the forward end 221 of the sheath is retracted thereby exposing the cable drive portion 207 and in particular the cable holding device 219. In this arrangement rotation imparted to the drive shaft 202 translates directly to the sheath drive portion 206 and then to the sheath 208 through the interengaging splines (212, 213) between the sheath drive portion and the sheath 208. Furthermore in view of the engagement of the forward sheath splines 218 with the splines 217 on the cable drive portion 207, this drive is imparted from the sheath 208 to the cable drive portion. With this arrangement rotation of the drive shaft 202 causes a corresponding rotation of the cable drive portion 207. This then allows the dolly to impart drive to the cable when the proximal end 3b of the cable is inserted within the holder 219 of the cable drive portion 207.

The second operational mode is illustrated in Figs. 31 and 32. This mode, referred to as the "tensioning mode" is adopted when the sheath 208 is in an intermediate position with respect to the central drive 205. The sheath is located in this position when the indexing pin 225 is disposed in the short leg 227 of the slot 222. In this position the forward end of the sheath 204 projects beyond the cable drive portion 207 so as to be in a position to engage the actuator 16 of the cable bolt tensioning device 1. Furthermore whilst the splines 212, 213 between the sheath drive portion 210 and the sheath 208 remain engaged, the splines (217, 218) which allow drive to be imparted from the sheath to the cable drive portion 207 are disengaged. As a result in this mode, drive imparted from the shaft 202 is imparted to the sheath 208 through the sheath drive portion 210 whilst the cable drive portion remains disengaged and therefore drive is not imparted to that portion 207. Moreover in the tensioning mode, the cable drive portion 207 is able to rotate independently of both the sheath 208 and the sheath drive portion 206.

The dolly 200 in these latter two modes (being the cable drive mode and the tensioning mode) is used in installing and tensioning a cable rock bolt as will be explained by the sequence diagrams illustrated in Figs. 33 to 42. Installation Procedure

In a first stage as disclosed in Figs. 33 and 34 a cable bolt 2 is inserted into a bore 501 formed in rock strata 500. Fitted to the cable bolt '2 is a bearing plate 30 and a cable bolt tensioning device 1 which is disposed adjacent a proximal end 3b of the cable bolt which projects beyond the bore 502. At this stage the cable bolt 2 is not point anchored in the bore 502 but resin cartridges and/or a mechanical anchor are installed in conjunction with the cable bolt adjacent the blind end (not shown) of the bore. To activate point anchoring (by shredding and mixing of the resin cartridges and/or activation of a mechanical anchor) the cable bolt 2 needs to be spun typically under right hand rotation.

To effect this rotation the dolly 200 is fitted onto the proximal end 3b of the cable bolt shaft 3 as shown in Figs. 33 and 34. The dolly 200 is disposed in the cable drive mode so as to allow the end of the cable bolt shaft to be fitted within the holder 220 disposed in the cable drive portion of the dolly 200. As best shown in Fig. 33 the sheath 207 is sufficiently retracted so that the drive end 204 of the sheath does not engage the actuator 6 of the tensioning device 1.

The dolly is fitted to a drive apparatus (not shown) such as a mining drill rig through the shaft 202. The drill rig imparts drive to the shaft 202 which in turn is transferred through to the cable drive portion 207 by virtue of the splines 217, 218 interengaging thereby allowing spinning of the cable bolt 3 to provide point anchoring of the cable bolt 2. Typically, thrust is also applied to the cable bolt along the axis of the bolt so as to push the cable bolt further into the bore 501 moving the plate 30 towards the surface 502 of the rock strata 500. This then places the cable bolt into a position as shown in Figs. 35 and 36 where the cable is point anchored by setting of the resin and/or by activation of the mechanical anchor.

The second stage commences after point anchoring. In this stage the dolly is moved into its tensioning mode by movement of the sheath forward relative to the central drive 205 into the position as illustrated in Figs. 37 and 38. In that position the sheath 208 moves forward so that the teeth of the sheath engage with the actuator whilst the end of the cable remains engaged with the cable drive portion 207. By having the dolly 200 adopt the tensioning mode the cable drive portion 207 becomes disengaged with the sheath 208 and is therefore not driven by the drive shaft 202 and moreover is able to rotate independently of that drive shaft and the sheath 208 This then allows rotation of the actuator by the dolly relative to the cable 3.

As best illustrated in Fig. 37, a feature of the engagement between the dolly and the actuator is that the diameter of the dolly is no greater than the diameter of the actuator. This has significant advantage in many mining applications as it allows the dolly to be located in more confined situations than would otherwise occur if a conventional dolly which mounted over the actuator (typically in the -form of a nut) was used. This can be particularly advantageous if a "timber jack" is used as a stabilizing and guiding mechanism for drilling and installing cables. The timber jack usually incorporates a confined opening through the centre section of the jack top head frame. Due to the reduced diameter of the dolly (as compared to more conventional dollies) it has been found in practice possible to tension the bolt using the dolly 200 without requiring removal of the timber jack. This improves both speed of operation and safety in the installation procedure.

Once the dolly 200 is installed in engagement both with the cable shaft and the actuator of the tensioning device, drive is imparted to the actuator whilst holding the cable shaft stationary (by virtue of engagement of the cable shaft with the cable drive portion). Rotation of the actuator causes that actuator 6 to unwind from the bearer member 11, this in turn causes the bearing member to move apart from the base member 5. Under an initial movement the bearer member movement forces the plate 30 into engagement with the rock surface 502. Engagement of the rock plate 30 hard against the rock surface 502 prevents further travel of the bearer member 6 towards the rock surface and also prevents any twisting of the bearer member by virtue of engagement of the bearer member head 13 with the plate 30.

Continued rotation of the actuator 6 under drive imparted from the dolly 200 forces the bearer head to continue to move away from the base member which causes increased loading to be induced on the base member 5 by the actuator which has the effect of pulling the cable 2 from the bore. This tensioning force applied to the base member is offset by a reaction force applied by engagement of the plate 30 against the rock surface and causes the cable to be placed in tension.

Once sufficient tension has been applied to the cable, the dolly 200 is removed thereby leaving the tensioned cable with the tensioning device still affixed in place as best illustrated in Figs. 41 and 42.

The tensioning device, dolly and installation as described in the above forms has the advantage that a rotatable actuator can apply an axial force to the cable (through the base member) without inducing twisting of the cable. In the particular form illustrated the moving component (the bearer member) is isolated from the cable and moreover the entire tensioning device is inhibited from twisting by virtue of engagement of the bearer head against the plate 30. In addition the tensioning device is of relatively compact form thereby allowing easy handling on site by use of the drive dolly installation and tensioning of the cable bolt can be achieved using a standard drill rig thereby obviating the need for specialist tensioning drives as has occurred in the prior art. In addition the drive dolly is of compact form allowing the dolly to be used in confined spaces often found in mining applications.

In the claims which follow and in the preceding summary, except where the context requires otherwise due to express language or necessary implication, the word

"comprising" is used in the sense of "including", that is the features specified may be associated with further features in various embodiments.

Variations and modifications may be made to the parts previously described without departing from the spirit or ambit of the above disclosure.