GB2216051A - Rock bolt insertion tool - Google Patents

Abstract

A tool for rotating a rock bolt in a drilled hole in order to rupture and mix a resin cartridge at the far end of the hole has a recess 118 for holding a nut 160 on the bolt 154 and a locking mechanism for preventing relative axial movement between the nut and bolt. The locking mechanism comprises a locking member 136 which can take up one position where the nut on the end of the bolt is able to enter the tool, and a second position where the nut cannot move out of the tool in an axial direction. At the same time, a shoulder 152 prevents the end of the bolt from moving further through the nut. The tool can be fitted in the chuck of a rotary drill which then acts to rotate the bolt in the drilled hole in the rock and allows the bolt to be released once the necessary degree of mixing has taken place. <IMAGE>

Description

Title: Rock bolt insertion tool This invention relates to a tool for use in placing rock bolts, particularly in the roof and walls of a mine working.

Where rock bolts are anchored in the rock by means of a quick setting resi.n mixture, it is normal practice to insert one or more resin cartri.dge(s) having two separated components into the dri.lled rock bolt hole and then to i.ntroduce the bolt i.nto the hole and use the end of the bolt to break the resin cartridge and to mix together the two components. The mixing i.s done by rotating the bolt. Once the resin has set, a nut on the exposed end of the bolt is thightened to tensi.on the bolt to the desired extent.

It is desirable for the bolt and the nut together wi.th a washer on the bolt, to be assembled to one another before the bolt is inserted in the hole. However, if the nut is placed on the thread of the free end of the bolt, then i.t is difficult to hold the bolt i.n order to be able to rotate it to mix the resi.n components.

It is known to use specially designed stiff nuts, or to use some sort of plastic or resin plug in the nut to prevent the nut from initially turning on the threaded end of the bolt, but both these alternatives involve added complexity and expense, as well as bei.ng inconsistent in use.

According to the invention there i.s provi.ded a rock bolt insertion tool adapted to fit into the drill chuck of a rotary drill, the tool comprisi.ng a body with a cavity havi.ng an open end and a closed other end and adapted to receive a threaded end of a rock bolt with a nut engaged thereon, the cavity being provided wi.th means adapted to retain the nut against rotation relative to the cavi.ty, for example the walls of the cavity bei.ng shaped to engage the.

nut; and a moveable lock member at the open end of the cavity, the lock member being moveable between a first position where the rock bolt and nut can freely move axially i.nto and out of the cavity and a second lock position in which the nut i.s prevented from moving axially out of the cavi.ty.

This tool can therefore form an adaptor between the rock drill and the rock bolt. The tool is chucked in the drill and the end of the bolt with a nut on it is held in the cavity, usually with a washer journalled on the bolt and resting against the face of the tool. When the lock member is in its lock positi.on, the bolt i.s effecti.vely held against rotation i.n the tool and the bolt can therefore be spun into the hole to mix the resin components of the cartri.dge(s) in the hole by rotation of the drill.

In one form of the invention, the lock member is rotatably mounted on the body at the open end of the cavity and has an aperture through which a nut on the end of a rock bolt can pass, the lock member being arranged for rotati.on between a first position where the aperture registers with the cavity so that the nut can pass through the aperture into the cavity, and a second position where the aperture is out of regi.ster wi.th the cavity and prevents the nut from movi.ng axially out of the cavity.

In most cases, the rock bolt will have a hexagonal nut engaged thereon and both the aperture in the locking member and the cavi.ty itself preferably then have a hexagonal shape to hold the nut against rotation wi.th the axes of the hexagonal shapes being offset from the axis of rotati.on.

The body with the cavi.ty can comprise two relatively rotatable components, a first component which includes the means to retai.n the nut against rotation relative to the cavi.ty, and a second component which prevents or limits axial-movement of the rod i.nto the cavity, the second component having two axially spaced abutments for the rod, one of the abutments being i.n an operative posi.ti.on in one relati.ve rotational position of the first and second components, and the other of the abutments being i.n an operative position i.n another relative rotati.onal position.

Normally the second component will be adapted to fi.t into the dri.ll chuck of a rotary dri.ll, and the fi.rst and second components wi.ll be connected to one another by a spri.ng-loaded clutch. The clutch preferably is arranged so that the first and second components only rotate relative to one another when a predetermi.ned torque between the dri.ll chuck and the nut is exceeded.

The second component may include an access hole i.n the regi.on of the second abutment through which an implement can be introduced to release the bolt and the nut from the tool.

In an alternative form, the lock member may be a captive plate held in the tool body and moveable between a first position where the bolt end and nut can be placed in and removed from the cavi.ty, and the second lock position.

The plate can have a keyhole type slot so that either the part of the slot wi.th the large area registers with the axi.s of the cavity (the first posi ti.on) or the part wi.th the smaller area regi.sters with the axis (the lock position).

The plate can be pivotable or linearly moveable between these two posi.ti.ons and a spri.ng-loaded detent or other means can be provi.ded to hold the plate in either position.

The nut to be carried by the rock bolt wi.ll usually be of hexagonal cross-section, but other forms of nut can be used if desi.red. The cavity is provided with means for preventing the nut from rotating whilst in the cavity. This can be achieved i.n a number of ways, but is conveni.ently done by forming part or all of the axi.al depth of the cavity with walls which co-operate wi.th the nut to retain it against rotati.on. Thus, the cavity can be formed with flatted opposed walls between which the nut is a close fit.

However, it is prefered to form the cavity with the same general shape of cross-section as the nut, eg. with an hexagonal cross-section, into which the nut is a loose fi.t.

The closed end of the cavity is preferably provi.ded with a bearing surface whi.ch i.s adapted to assist free rotation of the rock bolt within the cavity and to receive axial loads transmitted through the end of the rock bolt. Such a beari.ng surface can be provi.ded by a smooth surface to the closed end of the cavity or a thrust washer or disc i.nsert rotatably carried at the closed end to the cavi.ty. A particularly preferred form of bearing i.s provided by a hardened steel or similar hard ball loosely fitted within the cavity. Preferably, the ball or other bearing surface i.s retai.ned within the cavi.ty adjacent the closed end thereof by a detent, eg, a grub screw or the like.

The invention wi.ll now be described, by way of example, wi.th reference to the accompanying drawi.ngs, in whi.ch: Figure 1 i.s a cross section through an i.nserti.on tool in accordance with the invention; Fi.gure 2 i.s an exploded vi.ew of the components of the tool of Figure 1, with some components omitted; Fi.gure 3 i.s a view of one of the components shown in Figure 2, taken i.n the di.recti.on of the arrow III; Figure 4 is a view of another of the components shown in Fi.gure 2, taken in the direction of the arrow IV;; Figure 5 i.s a cross section through a third of the components shown in Fi.gure 2, taken on the section li.ne V-V Fi.gure 6 is a vi.ew of a fourth of the components shown in Figure 2, taken in the di.recti.on of the arrow VI; Figure 7 i.s a view correspondi.ng to Figure 1 but showi.ng a rock bolt and nut in positi.on; The tool has a body 110 made up of two components; a fi.rst component 112 whi.ch has a stub shaft 114 whi.ch can be held i.n the chuck of a rotary drill, and a second component 116.

The second component has a hexagon shaped recess 118. The first component also has a central bore 120. The second component 116 can rotate relative to the first component about an axis which is coaxial with the axi.s of the stub shaft 114. However the bore 120 i.s offset relati.ve to this axis, as can be seen in Figure 1. Rotational movement between the first and second components i.s controlled by spring-loaded balls 122. The balls (there are two of them) sit in recesses 124 (see Figures 2 and 3). A plain lock nut 126 and a cammed lock nut 128 are threaded onto the external ci.rcumference of the component 116 at 130 (Fi.gure 2). A disc spring 132 then loads the lock nuts 126, 128 against the balls 122 and against a shoulder 134 of a thi.rd component 136.

Relative rotation can only take place between the components 112 and 116 when there is sufficient torque applied between the components to allow the spri.ng 132 to be compressed and to allow the cammed lock nut 128 to move axially against the spri.ng pressure and to ride over the balls 122.

The tool is completed by a lock member 136 whi.ch also has a hexagonal aperture 138 in its front face and whi.ch is connected to the first component 112 by means of two radial pi.ns 140. The pi.ns are threaded i.nto the wall of the component 112 and extend radi.ally inwardly into grooves 142 in the periphery of the lock-member. As can be seen in Figures 2 and 5, the grooves 142 do not extend around the full perimeter of the lock member, but the lock member can be rotated to the extent permi.tted by the engagement of the pins 140 i.n the grooves 142, as will be described below.It wi.ll be noted also from Figure 1 and from Figure 5 that the aperture 138 in the lock member 136 i.s offset from the axis of rotati.on of the lock member on the second component 116.

Further features of the tool will become apparent from the followi.ng descri.pti.on of the method of operation.

Initially, the tool will be set with the fi.rst and second components 112 and 116 rotated to a posi.ti.on where the balls 122 drop i.nto slots 144 i.n the cammed lock nut 128. The rotati.onal position of the cammed lock nut relative to the hexagon recess 118 i.n the second component will be set on assembly of the tool by first screwing the plain lock nut 126 onto the thread 130 to its li.mi.t;; then screwing the cammed lock nut 128 onto the same thread as far as i t wi.ll go against the plai.n lock nut and then backi.ng off the cammed lock nut to the correct rotati.onal posi.tion. The cammed and plai.n lock nuts are then locked to one another by two grub screws (not shown) whi.ch are screwed through drizzled and tapped holes 146 agai.nst the plai.n lock nut so as to lock the two together.

Next the locking member 136 i.s turned so that the aperture 138 registers with the aperture 118 in the second component 116. In this posi.ti.on, it will be seen that the side wall of the bore 120 in the component 112 overlaps the hexagonal apertures and i.s offset with respect to these hexagonal apertures. In Fi.gure 1 a hexagonal nut 148 is shown i.n place in the recess 118, and the threaded bore through thi.s nut is indicated i.n dotted lines at 150. It will be seen that the side wall 152 of the bore 120 obscures the threaded passage through the centre of the nut so that when a bolt is screwed into the nut, the bolt cannot be screwed ri.ght through the nut.

Havi.ng set the tool in thi.s manner, a rock bolt 154 with a threaded end 156, a washer 158 and a nut 160 are introduced into the recess 118. It is important that the nut 160 be screwed onto the bolt 154 only until the end of the bolt is flush with the surface of the nut. The locking member 136 i.s then rotated manually so that the aperture 138 i.s now out of register with the hexagon recess 118 and, as shown i.n Figure 7, this now acts to prevent the nut 160 moving axially out of the recess.

In practice the bolt 154 will be inserted i.n a dri.lled hole in a rock face, and at the remote end of the hole there will be a two-part resi.n cartridge. The threaded end 156 will be projecti.ng out of the rock face.

When the body 110 i.s rotated by a rotary drill, and the di.stant end of the rock bolt154 experi.ences some resi.stance to rotation, for example when it attempts to rotate within one or more resin cartridge(s) i.n the hole drilled in the rock, then the nut 160 wi.ll attempt to turn on the threads 156 of the bolt until the nut i.s jammed up against the locki.ng member 136 and the end of the bolt is jammed against the shoulder 152 of the component 112. At this point, the rod 154 can no longer rotate relative to the tool and the tool and the rod will turn as one.This causes the rock bolt to rupture the resi.n cartri.dge(s) in the rock bolt hole and to perform the necessary mixing of the components.

As the mixing continues the resin mi.xture will begin to harden and the torque required by the rotary dri.ll wi 11 increase. When the torque increases to a predetermined level, the balls 122 will ride out of the slots 144 in the cammed lock nut 128, onto the flat region 162, and rotation wi.11 continue for a further angle of about 140 until the balls come up against a stop 164. Once this relative rotation has ocurred, the bore 120 will be rotated to a positi.on where i.t does now regi.ster wi.th the hexagonal recess 118, and the threaded end 156 of the bolt 154 can enter the bore 120.

When this happens, the sudden decrease in torque required to drive the rotary dri.ll signals that the bolt i.s set i.n position, and the drill is then stopped. Locking member 136 i.s turned back to i.ts ori.gi.nal position and the tool i.s removed from the end of the bolt. The nut can then be tightened to clamp the washer 158 against the rock face usi.ng an appropri.ate nut runner or wrench to the requi.si.te torque as requi.red by the parti.cular appli.cati.on.

If the drill is not stopped qui.ckly enough, the end of the bolt 154 may come into contact wi.th the bottom of the bore 120 and i.f this happens and the bolt jams in the bore, then a tool can be introduced through an access hole 166 (Figure 2) to free the bolt.

The tool of the second embodi.ment, shown in Figures 8 to 10, has a body 10 with a stub shaft 12 whi.ch can be held in the chuck of a rotary dri.ll. The body has an axial cavity 14 having an open end 16 and a closed end 18. At the bottom of the closed end, a freely rotatable hardened steel ball 20 i.s located and prevented from falling out by means of a grub screw 22. The ball 20 reduces the risk that the end of the bolt 38 wi.ll become jammed i.n the body.

The body 10 also holds a transverse lock plate 24 which slides between two positions in a plane normal to the axi.s of the cavi.ty 14. As can be seen in Figure 10, the plate 24 has a keyhole shaped aperture 26 with a large diameter regi.on 28 and a small diameter regi.on 30. At the edge of the plate are two recesses 32 and 34 whi.ch co-operate wi.th a spring loaded detent 36 (Figure 8) to locate the plate 24 in one of two posi.ti.ons.

Operation of this tool will now be described. In Fi.gure 8, the threaded end of a rock bolt 38 i.s shown. The thread 40 on the bolt carri.es a hexagonal head nut 42, and the cavi.ty 14 is shaped so as to receive this nut and to prevent the nut rotating in the cavity. To reach the position shown in Fi.gure 8, the lock plate 24 must be moved to a posi.ti.on where the larger diameter region 28 i.s centred on the axis of the cavi.ty, and this larger diameter region will allow the nut 42 to pass i.nto the cavi.ty. Once the nut is inside the cavi.ty the lock plate i.s sli.d to its opposite posi.ti.on, as shown in Figure 8, and now the nut i.s held captive behind the lock plate.

When the body 10 is rotated by a rotary dri.ll, and the distant end of the rock bolt 38 experiences some resistance to rotati.on, for example when it attempts to rotate within one or more resin cartri.dge(s) in the bore dri.lled i.n the rock, the nut 42 wi.ll turn with the body 10 on the threads 40 until the nut bears up against the lock plate 24, and the free end of the bolt 38 bears against the ball 20. At this point the rod 38 can no longer rotate relative to the tool, and the tool and the rod will turn as one. This causes the the rock bolt to rupture the resin cartri.dge(s) in the rock bolt hole and to perform the necessary mixing of the components.

Once the necessary mixing has been done, the drill wi.ll be stopped and the resi.n wi.ll begi.n to set, typically taking less than 5 mi.nutes to harden. Once the resin has set, the rock bolt is tensi.oned by drawing the nut 42 hard up agai.nst a washer 50 carried by the bolt and bearing against the rock face around the mouth of the bore dri.lled i.nto the rock. To do this, the plate 24 is moved across to bring the larger diameter region 28 of its keyhole aperture i.nto regi.ster with the axi.s of the cavity and the bolt. This allows the nut to be driven along the threads of the bolt by rotation of the body 10 until the nut has drawn up ti.ght against washer 50.The nut 42 is ti.ghtened to the desi.red torque and the tool is then wi.thdrawn axially from the exposed end of the bolt.

The tool of the i.nventj.on thus enables a rock bolt carrying a premounted nut and washer thereon to be i.nserted i.nto a bore, rotated to rupture resin cartri.dges within that bore, and the nut on that bolt to be dghtened to the desired torque without the need for special nuts and wi.thout the need to remove the tool from the bolt during the whole operati.on. The tool can be appli.ed si.mply and effectively to securing standard bolts wi.thout the need for modification thereof. The tool can also be used to drive the dri.ll rod and bit so that the hole can be formed using the same tool, in which case the end of the dri.ll rod is compatible wi.th the profile of the cavity.

Claims (15)

Claims:

1. A rock bolt insertion tool adapted to fit into the dri.ll chuck of a rotary drill, the tool comprising a body with a cavi.ty having an open end and a closed other end and adapted to receive a threaded end of a rock bolt with a nut engaged thereon, the cavity bei.ng provi.ded with means adapted to retai.n the nut against rotation relative to the cavi.ty, and a movable lock member at the open end of the cavity, the lock member being movable between a first posi.ti.on where the rock bolt and nut can freely move axially into and out of the cavity and a second, lock position in which the nut is prevented from movi.ng axi.ally out of the cavity.

2. A tool as claimed in Clai.m 1, wherei.n the lock member is rotatably mounted on the body at the open end of the cavi.ty and has an aperture through which a nut on the end of a rock bolt can pass, the locki.ng member being arranged for rotation between a first position where the aperture registers with the cavity so that the nut can pass through the aperture i.nto the cavi.ty, and a second posi.ti.on where the aperture i.s out of register with the cavi.ty and prevents the nut from movi.ng axi.ally out of the cavi.ty.

3. A tool as claimed in Claim 1 or Claim 2, wherein the nut i.s hexagonal and both the aperture in the locking member and cavity itself have a hexagonal shape to hold the nut against rotation, the axes of the hexagonal shapes being offset from the axis of rotation about whi.ch the locki.ng member rotates on the body.

4. A tool as claimed in any precedi.ng claim, wherein the body wi.th the cavity comprises two relatively rotatable components, a first component which includes the means to retain the nut against rotation relati.ve to the cavi.ty, and a second component which limits axi.al movement of the rod into the cavi.ty, the second component having two axi.ally spaced abutments for the rod, one of the abutments being in an operative position in one relative rotational position of the first and second components, and the other of the abutments being i.n an operative position in another relative rotational positi.on.

5. A tool as claimed in Claim 4, wherein the second component is adapted to fit i.nto the drill chuck of a rotary drill, and the fi.rst and second components are connected to one another by a spring-loaded clutch.

6. A tool as claimed in Clai.m 5, wherei.n the clutch is arranged so that the first and second components only rotate relative to one another when a predetermined torque between the drill chuck and the nut is exceeded.

7. A tool as claimed in any one of Claims 4 to 6, wherei.n the second component includes an access hole in the regi.on of the second abutment through which an i.mplement can be introduced to release the bolt and the nut from the tool.

8. A tool as claimed i.n Claim 1, wherei.n the lock member i.s a capti.ve plate held in the body and movable between a first position where the bolt end and nut can be placed i.n and removed from the cavity, and the second, lock position.

9. A tool as claimed i.n Claim 8, wherein the plate has a keyhole type slot so that ei.ther the part of the slot with the large area regi.sters wi.th the access of the cavity (the first posi.ti.on) or the part with the smaller area registers with the access (the lock position).

10. A tool as claimed in ei.ther of Claims 8 or Claim 9, wherein the plate is pivotable between the first position and the lock position.

11. A tool as claimed in either of Clai.ms 8 or Claim 9, wherein the plate i.s linearly movable between the first position and the lock posi.ti.on.

12. A tool as claimed in any one of Clai.ms 8 to 11, wherei.n a spri.ng loaded detent is provi.ded to hold the plate in one or other of its two positions.

13. A tool as claimed in any preceding Claim, wherein the cavity has a form-locki.ng relationship with the nut whi.ch i.s to be retained in the cavi.ty against rotation.

14. A tool as claimed in any preceding Claim, wherein the closed end of the cavity i.s provided wi.th a bearing surface which assists free rotation of the rock bolt within the cavity and which receives axi.al loads transmi.tted through the end of the rock bolt.

15. A rock bolt i.nserti.on tool substanti.ally as herein described with reference to and as shown i.n any one embodiment i.llustrated in the accompanyi.ng drawi.ngs.