CA1249446A - Method and apparatus for combining resin bonding and mechanical anchoring of a bolt in a rock formation - Google Patents
Method and apparatus for combining resin bonding and mechanical anchoring of a bolt in a rock formationInfo
- Publication number
- CA1249446A CA1249446A CA000567576A CA567576A CA1249446A CA 1249446 A CA1249446 A CA 1249446A CA 000567576 A CA000567576 A CA 000567576A CA 567576 A CA567576 A CA 567576A CA 1249446 A CA1249446 A CA 1249446A
- Authority
- CA
- Canada
- Prior art keywords
- bolt
- shell
- plug
- bore hole
- resin
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Abstract
ABSTRACT OF THE DISCLOSURE
A mechanical anchor including an expansion shell and a camming plug positioned in the shell is threaded onto the end of a mine roof bolt.
A roof support plate is carried on the opposite end of the bolt. The mechanical anchor is inserted in a bore hole drilled in a rock formation with one or more resin cartridges advanced by upward movement of the bolt to the end of the bore hole. The cartridge is ruptured by upward thrust and rotation of the bolt to release the resin components for mixing. A
stop device extending through the plug abuts a tapered end of the bolt to prevent axial movement of the plug on the bolt when the bolt is rotated in a preselected direction to mix the resin components before the shell is expanded. Rotation of the bolt continues without expansion of the shell for a period of time to permit formation of a curable resin mixture. As the resin mixture begins to harden rotation of the shell and plug is resisted until the stop device is displaced by the bolt tapered end permitting relative rotation between plug and the bolt. The plug nonro-tatably moves down the bolt upon continued rotation of the bolt in the same preselected direction to expand the shell into engagement with the wall of the bore hole before the resin mixture cures. The cured resin bonds the bolt and expanded shell to the rock formation to resist slippage of the expanded shell and maintain the bolt in tension.
A mechanical anchor including an expansion shell and a camming plug positioned in the shell is threaded onto the end of a mine roof bolt.
A roof support plate is carried on the opposite end of the bolt. The mechanical anchor is inserted in a bore hole drilled in a rock formation with one or more resin cartridges advanced by upward movement of the bolt to the end of the bore hole. The cartridge is ruptured by upward thrust and rotation of the bolt to release the resin components for mixing. A
stop device extending through the plug abuts a tapered end of the bolt to prevent axial movement of the plug on the bolt when the bolt is rotated in a preselected direction to mix the resin components before the shell is expanded. Rotation of the bolt continues without expansion of the shell for a period of time to permit formation of a curable resin mixture. As the resin mixture begins to harden rotation of the shell and plug is resisted until the stop device is displaced by the bolt tapered end permitting relative rotation between plug and the bolt. The plug nonro-tatably moves down the bolt upon continued rotation of the bolt in the same preselected direction to expand the shell into engagement with the wall of the bore hole before the resin mixture cures. The cured resin bonds the bolt and expanded shell to the rock formation to resist slippage of the expanded shell and maintain the bolt in tension.
Description
~9~3~
TITLE
METHOD AND APPARATUS FOR CCMBINING RESIN
BONDING AND MECHANIC~L ANCHORING OF A
BOLT IN ~ RCCK FORMATION
BACKGROUND OF THE INVENTION
1. Field of the Invention .
This invention relates to a method and apparatus for combining resin bonding and mechanical anchoring of a bolt in a rock formation and more par-ticularly to an expansion shell assembly adapted for use with bonding material where mixing of the bonding material components and expansion of the shell take place upon continuous rotation of the bolt in one rotational direction.
TITLE
METHOD AND APPARATUS FOR CCMBINING RESIN
BONDING AND MECHANIC~L ANCHORING OF A
BOLT IN ~ RCCK FORMATION
BACKGROUND OF THE INVENTION
1. Field of the Invention .
This invention relates to a method and apparatus for combining resin bonding and mechanical anchoring of a bolt in a rock formation and more par-ticularly to an expansion shell assembly adapted for use with bonding material where mixing of the bonding material components and expansion of the shell take place upon continuous rotation of the bolt in one rotational direction.
2. Description of the Prior Art It is well known in the art of mine roof support to tension bolts anchored in bore holes drilled in the mine roof to reinforce the unsupported rock formation above the roof. Conventionally a hole is drilled through the roof into the rock formation. The end of the bolt in the rock formation is anchored by either engagement of an expansion shell on the end of the bolt with the rock formation or adhesively bonding the bolt by a thermosetting resin to the rock formation surrounding the bore hole. The resin also penetrates onto the surrounding rock formation to adhesively unite the rock strata and to firmly hold the bolt in position in the bore hole. The resin mixture fills the annulus between the bore hole wall and the rod along a substantial length of the rod.
With a conventional expansion shell it is also known to chamfer the end of the bolt so that the threads on the end of the bolt that receive the expansion shell terminate at a point spread from the extreme end of the bolt. This arrangement prevents damage to the threads to ~ermit recovery and reuse of the bolt.
United States Patents 3,324,662 and 3,394,527 disclose adhe-sively bonding a rod positioned in hole drilled in a rock formation by a thenmosetting polyester resin composition having thixotropic proper-ties.
B~
Y~
It is well known that a holt which is adhesively bonded in a bore hole can not be tensioned; on the other hand, a bolt mechanically anchored in a mine roof is capable of being tensioned but the contact of the roof bolt with the rock formation is confined to enga~ement of the ex-panded shell with the bore hole wall. Also, it is well known that dete-rioration of the rock formation surrounding the expanded shell reduces the contact area between the shell and the rock formation. Consequently the expanded shell slips and the tension on the bolt decreases, thereby reducing the roof support. Slippage of a tensioned mechanical roof bolt occurs most commonly in rock formations, such as shale, sa~lstone, mudstone, and the like.
In an attempt to resolve the disadvantages of anchoring by resin bonding or anchoring by expansion shells various ty~oes of mine roof support systems have been developed that combine mechanical anchoring and resin anchoring. The two systems have been combined by threading a bolt into a seperate member such as a nut or coupling which is attached to a "rebar" anchored in the bore hole by a resin. ~ bolt with a plate held against the surface of the mine roof surrounding the bore hole is threaded into the seperate member. Tightening the bolt places the bolt under tension.
United States Patent 3,702,060 discloses an expansion shell assembly that includes a resin container which is fixed to the end of an expander positioned within an expansion shell. The container is ruptured after the shell begins to expand. Rotation of the bolt mixes the resin components, and the resin mixture surrounds the shell to e~bed the shell in the cured resin to bond the shell to the rock strata. When the resin is fully cured, a nut on the end of the holt opposite a roof plate on the bolt is rotated to bring the roof plate to its fully seated position against the mine roof to fully tension the bolt.
~2~
Combining bolt tensioning and resin bonding of a mine roof bolt in the bore hole is disclosed in United States Patents 3,877,235 and 4,051,683. me devices disclosed in these patents utilize an intern-ally threaded member such as a nut or coupling which is connected at one to a "rebar" anchored within -the bore hole by the mixed and cured resin.
A bolt is then connected to the other end of the nut or coupling and includes a bearing or roof plate advanced into abutting relation with the mine roof. ~ stop means provided in the coupling limits axial advancement of the bolt into the coupling to prevent relative rotation of the coupling and the bolt as the assembly is rotated to break the resin cartridge and mix the resin components. When the resin cures -the "rebar" above the coupling is adhesively bonded to the rock formation. Thereafter rotation of the bolt in the coupling fractures the stop means to permit the bolt to move upwardly in the bore hole so that sufficient torque is applied to the bolt to tension the bolt.
Similar devices which utilize a rod anchored within the drill hole by resin bonding and connected to a bolt by a coupling with a stop device to restrain relative rotation between the members of the assembly until the resin hardens so that the bolt can be tensioned are disclosed in United States Patents 4,122,681 and 4,192,631. These devices rely upon the bonding of the elongated rod to the rock formation by the resin mixture. They do not utilize a mechanical anchor.
United States Patents 4,160,614 and 4,162,133 disclose a mech-anical anchor in combination with resin bonding of the bolt and the rock formation. Rotation of the bolt with the mechanical anchor attached to the end thereof in a first direction effects mixing of the resin components of a ruptured cartridge. An anti~rotation device prevents relative rotation between the camming plug and the bolt so that the plu~
is not threaded off the end of the bolt during mixing of the resin compo-nents. With this arrangement the resin components are thoroughly mixed ~Z~ 46 before the shell is expanded. After a period of time sufficient for mixing the resin and before the resin hardens direction of rotation of the bolt is reversed to disengage the anti-rotation device. The camming plug is then free to advance downwardly on the bolt and expand the shell into gripping engagement with the wall of the bore hole.
The point anchor resin roof bolt support system utilizes the concept of anchoring a reinforcing rod in a mine roof by resin bonding and tensioning the bolt. The rod is anchored at its upper end in the bore hole by resin. A nut is positioned on the threaded end of the rod that emerges from the bolt hole and abuts a roof plate positioned in contact with the mine roof. The end of the rod at the nut is rotated to effect mixing of the resin. Rotation is terminated for a period of 30 to 60 seconds while the resin mixture cures. After the resin is set, then the bolt is rotated at a preselected torque to tension the bolt.
While it has been suggested by the prior art systems to anchor a roof bolt in a bore hole by combination resin bonding and bolt tension-ing where mechanical anchors have been used it has not been possible to mix the resin and set the anchor by continuous rotation of the bolt in one directon. With the known systems the bolt must be rotated in a first direction to mix the resin while preventing expansion of the shell. When the mixed resin has begun to cure, then the directon of rotation of the bolt is reversed to expand the shell and set the anchor~
Consequently careful attention must be given to rotating the bolt in the proper direction to mix th~ resin before the shell is set and not expand the shell before the resin i5 mixed. Furthermore when the bolt is rotated in the direction to effect mixing of the resin, necessary means must be provided to prevent threading the expander plug off the end of the bolt.
~Z'~'3 1~6 Therefore there is need in the system of conbining resin bonding and mechanical anchoring of a bolt in a rock formation to provide a roof bolt anchor assembly that permits continuous rotation of a roof bolt in a single rotational direction to carry out both the operations of mixing the resin and expanding the shell.
StlMMARY OF THE INVENTION
In accordance with the present invention there is provided a roof bolt assembly for securing a bolt in a bore hole having a bond-ing material therein that includes a bonding material adapted to the positioned in an unmixed condition in a bore hole. A roof bolt with a threaded end portion has a camming plug with an internally threaded bore and an outer surface threadedly engaged to the bolt threaded end portion. The camming plug is positioned to move axially on the bolt upon rotation of the bolt in a preselected direction. An expandable shell with a plurality of longitudinally extending fingers that have an inner surface and an outer surface is positioned with a portion of the inner surface of the fingers abutting a portion of the camming plug outer surface and a portion of the inner finger outer surface adapted to engage the wall of the bore holeO The expandable shell fingers are arranged to expand outwardly to enga~e the outer surface of the fingers to the wall of the bore hole by longitudinally movement of the camming plug relative to the bolt threaded end portion and the expandable shell. Means are provided for mixing at least a portion o the bonding material in the bore hole upon rotation of the bolt in a preselected direction in the bore hole while maintaining the expanxion fingers in an unexpanded condition. Means are also provided for moving the camming plug axially on the bolt threaded end portion and relative to the expandable shell fingers upon rotation of the bolt in the sa~e preselected direction to expand the fingers and anchor the bolt in the bore hole.
:~2~94'~6 Further in accordance with the present invention there is provided a method of anchoring a bolt in a bore hole including the steps of positioning a camming plug having an internally threaded bore and an outer surface into the upper portion of an expansion shell with a portion of the camming plug outer surface in abutting relation with a portion of the inner surface of a plurality of fingers extending upwardly from a lower ring portion of the expansion shell. The expansion shell is positioned on the threaded end portion of the bolt and threadedly engages the camming plug to the end of the threaded portion of the bolt so that the camming plug is movable longitudinally on the bolt threaded portion.
bonding material is inserted into a bore hole. The bolt with the camming plug threadedly engaged thereto is thereafter inserted into the bore hole. The bolt is rotated in a preselected direction while the camming plug is maintained in fixed relation with the expansion shell to thereby mix at least a portion of the bonding material. Thereafter the bolt is rotated in the same preselected direction to move the camming plug on the bolt to expand the fingers of the expansion shell and apply a tension to the bolt in the bore hole.
Prior to insertion of the expansion shell assembly and the bolt in the bore hole a suitable bonding material, such as an adhesive resin material, packaged in a breakable cartridge, is inserted in the bore hole. The cartridge is advanced to the blind end of the bore hole by upward extension of the bolt with the expandable shell assembly attach-ed to the bolt. Further upward advancement of the bolt fractures the cartridge, and thereafter the bolt together with the expansion shell assembly are rotated in a preselected direction to begin mixing the components of the adhesive material that were seperated within the cart-ridge. Rotation of the bolt agitates the components to interact and form a curable adhesive mixture~
:
The stop means in one embodiment includes a shearable pin extending through a bore of the camming plug. End portions of the pin are retained in aligned bores of the camming plug. The pin passes trans-versely through the bore of the plug that receives the threaded upper end of the bolt. Preferably, the upper end of the bolt terminates in a reduced diameter end portion formed by tapering the end of the bolt.
The bolt tapers to a preselected diameter determined by the diameter of the bolt and the type of shearable pin used. For example, a bolt having a diameter of 5/8 inch is tapered at an angle oE about 45 degrees at the end of the bolt, and the longitudinal length of the taper is about 1/4 inch. The tapered end of the bolt abuts the pin to prevent initial downward axial movement of the plug on the bolt during rotation of the bolt to effect mixing of the adhesive components.
With the camming plug being restrained from downward movement on the bolt there is no relative rotation between the camming plug and the bolt. Thus the bolt, camming plug, and shell rotate as a single unit to effect mixing of the adhesive components in the bore hole.
The curable mixture flows downwardly into contact with the shell and camming plug and fills the voids between the shell and the wall of the bore hole. The presence of the shear pin prevents downward movement of the camming plug on the bolt for the period of time required to complete mixing of the resin components. For a quick setting-type of adhesive material expansion of the shell is delayed for about 20 to 30 seconds to permit complete mixing of the adhesive c~mponents before the shell is expanded.
As the adhesive mixture begins to harden around the shell and the camming plug, the mixture exerts a force upon the shell and camming plug resisting rotation of the shell and plug. When -the torque applied to the bolt exceeds a predetermined torque the anti-rotation forces exerted by the curing adhesive material exceed the material stren-gth of the pin and the pin fractures or is dislodged from the camming plug at the point of contact of the camming plug with the tapered end of the bolt. The tapered configuration at the end of the bolt and abutting the pin assures dislodgement of the pin from the camming plug when the torque applied to the bolt exceeds a predetermined torque. The plug is then free to advance downwardly on the bolt upon continued rotation of the bolt in the same direction for mixing to expand the fingers of the shell Out~ardly to grip the bore hole wall.
Expansion of the shell occurs after a preselected time ~eriod of continued rotation of the bolt in one rotational direction. Thus the bolt is rotated in a single direction to effect both mixin~ of the adhesive material and expansion of the bolt. This arrangement eliminates the need for reversing the direction of rotation of the bolt to expand the shell after the adhesive material is mixed.
For an adhesive material of the quick setting resin-type, the mixed resin begins to harden within 20 seconds after rupture of the cartridge. The stop means in the e~bodiment of a shearable pin is constructed of a preselected material and has a preselected cross sec-tional area to control the material strength of the pin. Thus the pin is operable to fracture when the mixing stage is complete and before the resin mixture hardens. m is assures that the shell will expand before the resin cures and after the resin is completely mixed. For a selected resin system the pin is designed to fracture or shear in the bore of the camming plug when the tcrque applied to the bolt exceeds a predetermined torque. Preferably, the predetermined torque re~uired to shear the pin is not reached until after, for example, the bolt is rotated for 20 to 30 seconds, i.e., the period of time required for mixing the resin ccmpon-ents.
The stop means in one embodiment includes a pin fabricated of aluminum and having a preselected diameter. In another eimbodiment the stop means includes a steel pin having a length and diameter diff-ering from that of -the aluminum pin because of the difEerence in material strength of aluminum and steel. Further the location of the pin rela-tive to the plug is selective~ i.e. it can be retained in a selected axial position in the plug and abutting the tapered end of the bolt or it can be retained in the bolt only and abutting the bottom of the plug. In each case by selecting the material composition and size of the pin, as well as, the position of the pin, the fracturing or shearing of the pin is controllable to meet the specifications oE the resin system utilized.
Thus a stop means is provided to permit mixing of the resin system for the period of time required for the selected resin system used before the shell is expanded upon continuous rotation of the bolt in one direction.
Further in accordance with the present invention there is provided a method of anchoring a bolt in a bore hole that includes the steps of threadedly engaging a camming plug to the end of the bolt for axial movement thereon. An expandable shell having a plurality of longitudinally extending fingers is positioned in surrounding relation with the camming plug on the bolt. Axial movement of the camming plug on the bolt is prevented by a stop means associated with the bolt upon rotation of the bolt in a preselected rotational direction~ The stop means is displaced by the bolt as the bolt continues to rotate in said preselected rotational direction when a torque in excess of a predeter-mined torque is applied to the bolt. Thereafter the camming plug is moved on the bolt upon displacement of the stop means to expand the fingers to anchor the bolt in the bore hole.
Accordingly, the principal object of the present invention is to provide a method and apparatus for conbining resin bonding and mechanical anchoring of a mine roof bolt in a rock formation by an expansion shell ass~nbly provided with stop means that restrains expansion of the shell as the bolt is rotated in a preselected direction until a torque in excess of a predetermined torque is applied to the bolt to displace the stops means and permit expansion of the shell.
Another object of the present invention is to provide a mech-anical anchor for a mine roof bolt that is also adhesively bonde~ within a bore hole where the bolt is continuously rotated in a preselected direction to permit the sequential operations of mixing the resin material and thereafter expanding the shell after the resin is mixed but beore it is cured to engage the wall oE the bore hole.
~ further object of the present invention is to provide a stop device associated with an expandable shell assembly that is operable to restrain the expansion of the shell for a period of time re~uired to permit mixing of resin components in a bore hole where expansion of the shell is delayed until a preselected torque is applied to the bolt and after the resin is mixed but before the resin is cured.
An additional object of the present invention is to provide a roof bolt with a selectively dimensioned tapered end portion operable to facilitate shearing of a stop device associated with an expandable shell assembly aEter an initial period of rotation of the shell to mix a resin system surrounding the shell where expansion of the shell is delayed until after the resin components are mixed.
These and other objects of the present invention will be more c~mpletely disclosed and described in the following specification, the accompanying drawings, and the appended claims.
BRIEF DESCRIPTION OF THE DE~AWINGS
Figure 1 is a fragmentary enlarged view in side elevation of an expansion shell assembly positioned on the threaded end of an elongated bolt, illustrating a stop device carried by a camming plug and enyaging an upper end of the bolt for restraining movement of the pluy on the bolt.
- 10 - `
Figure 2 is a top plan view of the expansion shell assembly shown in Figure 1, illustrating the stop device in the form of a shearable pin extending through the bolt and having end portions retained in the camming plug.
Figure 3 is an enlarged fragmentary view in side elevation of the configuration of the threaded upper end of the bolt, illustrat-ing a tapered end of the bolt to facilitate shearing of the pin stop device.
Figure 4 is a fragmentary exploded view of the expansion shell assembly of the present invention, illustrating the shearable pin which is retained in a bore of the camming plug and arranged to abut the tapered end of the bolt.
Figure S is a fragmentary sectional view in side elevation of the camming plug positioned on the bolt with the shell removed, illustrating the shearable pin extending through the camming plug and abutting the tapered end of the bolt.
Figure 6 is a view similar to Figure 5, illustrating the pin in a lower position in the camming plug and provided with parallel grooves on the opposite ends of the pin to control shearing of the pin.
Figure 7 is a view similar to Figure 1, illustrating the stop device used with a bail-type expansion shell assembly.
Figure 8 is a view similar to Figures 5 and 6 illustrating the shearable pin extending through the bolt only and posit~oned in abutting relation with the lower end of the camming plug.
Figure 9 is a side elevation partially in section of the first step in the method of installing the roof bolt in the bore hole, illustrating a resin cartridge in position at the end of the bore hole for rupture by the expansion shell assembl~ of the present invention~
94'~6 Figure 10 is a view similar to Figure 9, illustrating mixing of the components of the ruptured cartridge by rotation of the bolt with the stop de.vice restraining downward movelment of the plug during mixingO
Figure 11 is a view similar to Figures 9 and 10, illustrat-ing a further step of continuing rotation of the bolt in the sr~me direct-ion to fracture the stop device after the mixing step to permit the plug to advance downwardly on the bolt and expand the shell.
Figure 12 is a view further illustrating the method of the present inventlon where the plug is advanced downward on the bolt to fully expand the shell fingers into engagement with the wall bore hole with the cured and hardened resin surrounding and embedding the expanded shell.
DESCRIPTION OF rrHE P~EFERRED EMBODIMENTS
Referring to the drawings and particularly to Fig~res 1 and 4 there is illustrated an expansion shell assembly generally designated by the numeral 10 for securing a bolt 12 in a bore hole 14 drilled in a rock formation 16 (illustrated in Figures 9-12) to support the rock formation 16 that overlies an underground excavation, a mine passage-way, or the like. The bolt 12 has a threaded upper end portion 18 which is positioned in the upper blind end o~ the bore hole 14. The bore hole 14 is drilled to a preselected depth into the rock formation 16 as deter-mined by the load bearing properties to be provided by the expansion shell assembly 10 and the bolt 12.
The bolt 12 has an enlarged opposite end portion 20 as seen in Figures 9-12 which extends from the open end of the bore hole 14.
A roof or bearing plate 22 is retained by the bolt enlarged end portion 2~ on the end of the bolt 12. Further in accordance with the present invention a breakable cartridge 24 containing a conventional two ~omponent bonding material, such as disclosed in United States Patents 3,324,662 and ~2'~
With a conventional expansion shell it is also known to chamfer the end of the bolt so that the threads on the end of the bolt that receive the expansion shell terminate at a point spread from the extreme end of the bolt. This arrangement prevents damage to the threads to ~ermit recovery and reuse of the bolt.
United States Patents 3,324,662 and 3,394,527 disclose adhe-sively bonding a rod positioned in hole drilled in a rock formation by a thenmosetting polyester resin composition having thixotropic proper-ties.
B~
Y~
It is well known that a holt which is adhesively bonded in a bore hole can not be tensioned; on the other hand, a bolt mechanically anchored in a mine roof is capable of being tensioned but the contact of the roof bolt with the rock formation is confined to enga~ement of the ex-panded shell with the bore hole wall. Also, it is well known that dete-rioration of the rock formation surrounding the expanded shell reduces the contact area between the shell and the rock formation. Consequently the expanded shell slips and the tension on the bolt decreases, thereby reducing the roof support. Slippage of a tensioned mechanical roof bolt occurs most commonly in rock formations, such as shale, sa~lstone, mudstone, and the like.
In an attempt to resolve the disadvantages of anchoring by resin bonding or anchoring by expansion shells various ty~oes of mine roof support systems have been developed that combine mechanical anchoring and resin anchoring. The two systems have been combined by threading a bolt into a seperate member such as a nut or coupling which is attached to a "rebar" anchored in the bore hole by a resin. ~ bolt with a plate held against the surface of the mine roof surrounding the bore hole is threaded into the seperate member. Tightening the bolt places the bolt under tension.
United States Patent 3,702,060 discloses an expansion shell assembly that includes a resin container which is fixed to the end of an expander positioned within an expansion shell. The container is ruptured after the shell begins to expand. Rotation of the bolt mixes the resin components, and the resin mixture surrounds the shell to e~bed the shell in the cured resin to bond the shell to the rock strata. When the resin is fully cured, a nut on the end of the holt opposite a roof plate on the bolt is rotated to bring the roof plate to its fully seated position against the mine roof to fully tension the bolt.
~2~
Combining bolt tensioning and resin bonding of a mine roof bolt in the bore hole is disclosed in United States Patents 3,877,235 and 4,051,683. me devices disclosed in these patents utilize an intern-ally threaded member such as a nut or coupling which is connected at one to a "rebar" anchored within -the bore hole by the mixed and cured resin.
A bolt is then connected to the other end of the nut or coupling and includes a bearing or roof plate advanced into abutting relation with the mine roof. ~ stop means provided in the coupling limits axial advancement of the bolt into the coupling to prevent relative rotation of the coupling and the bolt as the assembly is rotated to break the resin cartridge and mix the resin components. When the resin cures -the "rebar" above the coupling is adhesively bonded to the rock formation. Thereafter rotation of the bolt in the coupling fractures the stop means to permit the bolt to move upwardly in the bore hole so that sufficient torque is applied to the bolt to tension the bolt.
Similar devices which utilize a rod anchored within the drill hole by resin bonding and connected to a bolt by a coupling with a stop device to restrain relative rotation between the members of the assembly until the resin hardens so that the bolt can be tensioned are disclosed in United States Patents 4,122,681 and 4,192,631. These devices rely upon the bonding of the elongated rod to the rock formation by the resin mixture. They do not utilize a mechanical anchor.
United States Patents 4,160,614 and 4,162,133 disclose a mech-anical anchor in combination with resin bonding of the bolt and the rock formation. Rotation of the bolt with the mechanical anchor attached to the end thereof in a first direction effects mixing of the resin components of a ruptured cartridge. An anti~rotation device prevents relative rotation between the camming plug and the bolt so that the plu~
is not threaded off the end of the bolt during mixing of the resin compo-nents. With this arrangement the resin components are thoroughly mixed ~Z~ 46 before the shell is expanded. After a period of time sufficient for mixing the resin and before the resin hardens direction of rotation of the bolt is reversed to disengage the anti-rotation device. The camming plug is then free to advance downwardly on the bolt and expand the shell into gripping engagement with the wall of the bore hole.
The point anchor resin roof bolt support system utilizes the concept of anchoring a reinforcing rod in a mine roof by resin bonding and tensioning the bolt. The rod is anchored at its upper end in the bore hole by resin. A nut is positioned on the threaded end of the rod that emerges from the bolt hole and abuts a roof plate positioned in contact with the mine roof. The end of the rod at the nut is rotated to effect mixing of the resin. Rotation is terminated for a period of 30 to 60 seconds while the resin mixture cures. After the resin is set, then the bolt is rotated at a preselected torque to tension the bolt.
While it has been suggested by the prior art systems to anchor a roof bolt in a bore hole by combination resin bonding and bolt tension-ing where mechanical anchors have been used it has not been possible to mix the resin and set the anchor by continuous rotation of the bolt in one directon. With the known systems the bolt must be rotated in a first direction to mix the resin while preventing expansion of the shell. When the mixed resin has begun to cure, then the directon of rotation of the bolt is reversed to expand the shell and set the anchor~
Consequently careful attention must be given to rotating the bolt in the proper direction to mix th~ resin before the shell is set and not expand the shell before the resin i5 mixed. Furthermore when the bolt is rotated in the direction to effect mixing of the resin, necessary means must be provided to prevent threading the expander plug off the end of the bolt.
~Z'~'3 1~6 Therefore there is need in the system of conbining resin bonding and mechanical anchoring of a bolt in a rock formation to provide a roof bolt anchor assembly that permits continuous rotation of a roof bolt in a single rotational direction to carry out both the operations of mixing the resin and expanding the shell.
StlMMARY OF THE INVENTION
In accordance with the present invention there is provided a roof bolt assembly for securing a bolt in a bore hole having a bond-ing material therein that includes a bonding material adapted to the positioned in an unmixed condition in a bore hole. A roof bolt with a threaded end portion has a camming plug with an internally threaded bore and an outer surface threadedly engaged to the bolt threaded end portion. The camming plug is positioned to move axially on the bolt upon rotation of the bolt in a preselected direction. An expandable shell with a plurality of longitudinally extending fingers that have an inner surface and an outer surface is positioned with a portion of the inner surface of the fingers abutting a portion of the camming plug outer surface and a portion of the inner finger outer surface adapted to engage the wall of the bore holeO The expandable shell fingers are arranged to expand outwardly to enga~e the outer surface of the fingers to the wall of the bore hole by longitudinally movement of the camming plug relative to the bolt threaded end portion and the expandable shell. Means are provided for mixing at least a portion o the bonding material in the bore hole upon rotation of the bolt in a preselected direction in the bore hole while maintaining the expanxion fingers in an unexpanded condition. Means are also provided for moving the camming plug axially on the bolt threaded end portion and relative to the expandable shell fingers upon rotation of the bolt in the sa~e preselected direction to expand the fingers and anchor the bolt in the bore hole.
:~2~94'~6 Further in accordance with the present invention there is provided a method of anchoring a bolt in a bore hole including the steps of positioning a camming plug having an internally threaded bore and an outer surface into the upper portion of an expansion shell with a portion of the camming plug outer surface in abutting relation with a portion of the inner surface of a plurality of fingers extending upwardly from a lower ring portion of the expansion shell. The expansion shell is positioned on the threaded end portion of the bolt and threadedly engages the camming plug to the end of the threaded portion of the bolt so that the camming plug is movable longitudinally on the bolt threaded portion.
bonding material is inserted into a bore hole. The bolt with the camming plug threadedly engaged thereto is thereafter inserted into the bore hole. The bolt is rotated in a preselected direction while the camming plug is maintained in fixed relation with the expansion shell to thereby mix at least a portion of the bonding material. Thereafter the bolt is rotated in the same preselected direction to move the camming plug on the bolt to expand the fingers of the expansion shell and apply a tension to the bolt in the bore hole.
Prior to insertion of the expansion shell assembly and the bolt in the bore hole a suitable bonding material, such as an adhesive resin material, packaged in a breakable cartridge, is inserted in the bore hole. The cartridge is advanced to the blind end of the bore hole by upward extension of the bolt with the expandable shell assembly attach-ed to the bolt. Further upward advancement of the bolt fractures the cartridge, and thereafter the bolt together with the expansion shell assembly are rotated in a preselected direction to begin mixing the components of the adhesive material that were seperated within the cart-ridge. Rotation of the bolt agitates the components to interact and form a curable adhesive mixture~
:
The stop means in one embodiment includes a shearable pin extending through a bore of the camming plug. End portions of the pin are retained in aligned bores of the camming plug. The pin passes trans-versely through the bore of the plug that receives the threaded upper end of the bolt. Preferably, the upper end of the bolt terminates in a reduced diameter end portion formed by tapering the end of the bolt.
The bolt tapers to a preselected diameter determined by the diameter of the bolt and the type of shearable pin used. For example, a bolt having a diameter of 5/8 inch is tapered at an angle oE about 45 degrees at the end of the bolt, and the longitudinal length of the taper is about 1/4 inch. The tapered end of the bolt abuts the pin to prevent initial downward axial movement of the plug on the bolt during rotation of the bolt to effect mixing of the adhesive components.
With the camming plug being restrained from downward movement on the bolt there is no relative rotation between the camming plug and the bolt. Thus the bolt, camming plug, and shell rotate as a single unit to effect mixing of the adhesive components in the bore hole.
The curable mixture flows downwardly into contact with the shell and camming plug and fills the voids between the shell and the wall of the bore hole. The presence of the shear pin prevents downward movement of the camming plug on the bolt for the period of time required to complete mixing of the resin components. For a quick setting-type of adhesive material expansion of the shell is delayed for about 20 to 30 seconds to permit complete mixing of the adhesive c~mponents before the shell is expanded.
As the adhesive mixture begins to harden around the shell and the camming plug, the mixture exerts a force upon the shell and camming plug resisting rotation of the shell and plug. When -the torque applied to the bolt exceeds a predetermined torque the anti-rotation forces exerted by the curing adhesive material exceed the material stren-gth of the pin and the pin fractures or is dislodged from the camming plug at the point of contact of the camming plug with the tapered end of the bolt. The tapered configuration at the end of the bolt and abutting the pin assures dislodgement of the pin from the camming plug when the torque applied to the bolt exceeds a predetermined torque. The plug is then free to advance downwardly on the bolt upon continued rotation of the bolt in the same direction for mixing to expand the fingers of the shell Out~ardly to grip the bore hole wall.
Expansion of the shell occurs after a preselected time ~eriod of continued rotation of the bolt in one rotational direction. Thus the bolt is rotated in a single direction to effect both mixin~ of the adhesive material and expansion of the bolt. This arrangement eliminates the need for reversing the direction of rotation of the bolt to expand the shell after the adhesive material is mixed.
For an adhesive material of the quick setting resin-type, the mixed resin begins to harden within 20 seconds after rupture of the cartridge. The stop means in the e~bodiment of a shearable pin is constructed of a preselected material and has a preselected cross sec-tional area to control the material strength of the pin. Thus the pin is operable to fracture when the mixing stage is complete and before the resin mixture hardens. m is assures that the shell will expand before the resin cures and after the resin is completely mixed. For a selected resin system the pin is designed to fracture or shear in the bore of the camming plug when the tcrque applied to the bolt exceeds a predetermined torque. Preferably, the predetermined torque re~uired to shear the pin is not reached until after, for example, the bolt is rotated for 20 to 30 seconds, i.e., the period of time required for mixing the resin ccmpon-ents.
The stop means in one embodiment includes a pin fabricated of aluminum and having a preselected diameter. In another eimbodiment the stop means includes a steel pin having a length and diameter diff-ering from that of -the aluminum pin because of the difEerence in material strength of aluminum and steel. Further the location of the pin rela-tive to the plug is selective~ i.e. it can be retained in a selected axial position in the plug and abutting the tapered end of the bolt or it can be retained in the bolt only and abutting the bottom of the plug. In each case by selecting the material composition and size of the pin, as well as, the position of the pin, the fracturing or shearing of the pin is controllable to meet the specifications oE the resin system utilized.
Thus a stop means is provided to permit mixing of the resin system for the period of time required for the selected resin system used before the shell is expanded upon continuous rotation of the bolt in one direction.
Further in accordance with the present invention there is provided a method of anchoring a bolt in a bore hole that includes the steps of threadedly engaging a camming plug to the end of the bolt for axial movement thereon. An expandable shell having a plurality of longitudinally extending fingers is positioned in surrounding relation with the camming plug on the bolt. Axial movement of the camming plug on the bolt is prevented by a stop means associated with the bolt upon rotation of the bolt in a preselected rotational direction~ The stop means is displaced by the bolt as the bolt continues to rotate in said preselected rotational direction when a torque in excess of a predeter-mined torque is applied to the bolt. Thereafter the camming plug is moved on the bolt upon displacement of the stop means to expand the fingers to anchor the bolt in the bore hole.
Accordingly, the principal object of the present invention is to provide a method and apparatus for conbining resin bonding and mechanical anchoring of a mine roof bolt in a rock formation by an expansion shell ass~nbly provided with stop means that restrains expansion of the shell as the bolt is rotated in a preselected direction until a torque in excess of a predetermined torque is applied to the bolt to displace the stops means and permit expansion of the shell.
Another object of the present invention is to provide a mech-anical anchor for a mine roof bolt that is also adhesively bonde~ within a bore hole where the bolt is continuously rotated in a preselected direction to permit the sequential operations of mixing the resin material and thereafter expanding the shell after the resin is mixed but beore it is cured to engage the wall oE the bore hole.
~ further object of the present invention is to provide a stop device associated with an expandable shell assembly that is operable to restrain the expansion of the shell for a period of time re~uired to permit mixing of resin components in a bore hole where expansion of the shell is delayed until a preselected torque is applied to the bolt and after the resin is mixed but before the resin is cured.
An additional object of the present invention is to provide a roof bolt with a selectively dimensioned tapered end portion operable to facilitate shearing of a stop device associated with an expandable shell assembly aEter an initial period of rotation of the shell to mix a resin system surrounding the shell where expansion of the shell is delayed until after the resin components are mixed.
These and other objects of the present invention will be more c~mpletely disclosed and described in the following specification, the accompanying drawings, and the appended claims.
BRIEF DESCRIPTION OF THE DE~AWINGS
Figure 1 is a fragmentary enlarged view in side elevation of an expansion shell assembly positioned on the threaded end of an elongated bolt, illustrating a stop device carried by a camming plug and enyaging an upper end of the bolt for restraining movement of the pluy on the bolt.
- 10 - `
Figure 2 is a top plan view of the expansion shell assembly shown in Figure 1, illustrating the stop device in the form of a shearable pin extending through the bolt and having end portions retained in the camming plug.
Figure 3 is an enlarged fragmentary view in side elevation of the configuration of the threaded upper end of the bolt, illustrat-ing a tapered end of the bolt to facilitate shearing of the pin stop device.
Figure 4 is a fragmentary exploded view of the expansion shell assembly of the present invention, illustrating the shearable pin which is retained in a bore of the camming plug and arranged to abut the tapered end of the bolt.
Figure S is a fragmentary sectional view in side elevation of the camming plug positioned on the bolt with the shell removed, illustrating the shearable pin extending through the camming plug and abutting the tapered end of the bolt.
Figure 6 is a view similar to Figure 5, illustrating the pin in a lower position in the camming plug and provided with parallel grooves on the opposite ends of the pin to control shearing of the pin.
Figure 7 is a view similar to Figure 1, illustrating the stop device used with a bail-type expansion shell assembly.
Figure 8 is a view similar to Figures 5 and 6 illustrating the shearable pin extending through the bolt only and posit~oned in abutting relation with the lower end of the camming plug.
Figure 9 is a side elevation partially in section of the first step in the method of installing the roof bolt in the bore hole, illustrating a resin cartridge in position at the end of the bore hole for rupture by the expansion shell assembl~ of the present invention~
94'~6 Figure 10 is a view similar to Figure 9, illustrating mixing of the components of the ruptured cartridge by rotation of the bolt with the stop de.vice restraining downward movelment of the plug during mixingO
Figure 11 is a view similar to Figures 9 and 10, illustrat-ing a further step of continuing rotation of the bolt in the sr~me direct-ion to fracture the stop device after the mixing step to permit the plug to advance downwardly on the bolt and expand the shell.
Figure 12 is a view further illustrating the method of the present inventlon where the plug is advanced downward on the bolt to fully expand the shell fingers into engagement with the wall bore hole with the cured and hardened resin surrounding and embedding the expanded shell.
DESCRIPTION OF rrHE P~EFERRED EMBODIMENTS
Referring to the drawings and particularly to Fig~res 1 and 4 there is illustrated an expansion shell assembly generally designated by the numeral 10 for securing a bolt 12 in a bore hole 14 drilled in a rock formation 16 (illustrated in Figures 9-12) to support the rock formation 16 that overlies an underground excavation, a mine passage-way, or the like. The bolt 12 has a threaded upper end portion 18 which is positioned in the upper blind end o~ the bore hole 14. The bore hole 14 is drilled to a preselected depth into the rock formation 16 as deter-mined by the load bearing properties to be provided by the expansion shell assembly 10 and the bolt 12.
The bolt 12 has an enlarged opposite end portion 20 as seen in Figures 9-12 which extends from the open end of the bore hole 14.
A roof or bearing plate 22 is retained by the bolt enlarged end portion 2~ on the end of the bolt 12. Further in accordance with the present invention a breakable cartridge 24 containing a conventional two ~omponent bonding material, such as disclosed in United States Patents 3,324,662 and ~2'~
3,394,527 is initially inser-ted in the bore hole 14 and advanced to the blind end of the bore hole 14, as shown in Figure 9, by upward advancement of the bolt 12 in the bore hole 14. Gnce the cartridge 24 is ruptured and the components thereof are mixed by rotation of the bolt 12 in a presel-ected direction, a stop device generally designated by the numeral 26 restrains expansion of the shell assembly 10 until the roof plate 22 is in abutting relation with the surface of the rock formation 16 and the adhesive components are mixed.
The bolt is continuously rotated in the same preselected direction for a period of time sufficient to complete mixing of the components of the bonding material. The stop device 26 prevents expan-sion of the shell assembly 10 during the mixing stage. The bolt contin-ues to rotate in the same initial directon. When the torgue applied to the bolt exceeds a predetermined torque, as determined by the time for mixing the bonding material, the stop device 26 fractures. The expansion shell assembly 10 is then free to expand into gripping engage-ment with the wall of the bore hole 14. The continuous rotation of the bolt in the same initial direction completes the setting of the assembly 10. Thus the bolt is both mechanically anchored and adhesively bonded in the bore hole to prevent slippage of the expanded assembly 10 so that the bolt 12 remains tensioned to support the rock formation.
Now referring in greater detail to the structure of the expan-sion shell asse~bly 10 there is provided a shell member 28 conventional in design and including a solid ring end portion 30. The shell member 28 is expandable and has a plurality of longitudinally extendin~ fingers 32 that extend axially from the ring end portion 30. Each of the fingers 32 has a lower end portion 34 connected to the ring end portion 30 and an upper end portion 36. Longitudinally slots 38 (only one of which is shown in Figure 1) divide the fingers 32 fr~m one another. Each of the slots 38 has a closed end portion 40 adjacen-t the ring end portion 30 and an open end portion 42 adjacent the upper en~ portion 36 of the respective finger 32.
~Z~f39.'~
Each finger 32 inc].udes an outer gripping surface 44 and an inner smooth sur-face 46. The outer surface 44 includes a gripp-ing portion 48 that extends from the finger upper end portion 36 to a position spaced from the finger lower end portion 34. The gripp-ing portion 48 of each finger 32 includes a series of spaced parallel, tapered horizontal grooves 50. The grooves 50 from a series of downwardly extending serrations that are operable upon expansion of the shell member 28 to engage the wall of the bore hole 14 as the fingers 32 bend out-wardly.
The gripping portion 38 of each finger 32 is urged into contact with the wall of the bore hole 14, as seen in Figures 10 and 11, by a camming plug or wedge generally designated by the numeral 52. The camming plug 52 includes a threaded axial bore 54 threadedly engaged to the bolt threaded end portion 18. The camming plug 52 has a tapered configuration with an enlarged upper end portion 56 and a reduced lower end portion 58.
A portion of the inner surface 46 of each finger 32 abuts a tapered planar surface 68 of the camming plug 52.
As illustrated in Figure 1, the camming plug 52 and the shell member 28 are maintained in assembled relation on the bolt threaded end portion 18 prior to anchoring the assembly in the bore hole 14 drilled in the mine roof. Also as well known in the art and illustrated in Figure 7, the camming plug 52 and the shell me.~ber 28 are connected by a yieldable strap or bail 60. The bail 60 is conventional and extends across the top of the ca~ming plug 52. The bail 60 includes leg portions 62 that extend downwardly on opposite sides of the shell me~ber 28. The leg portion 62 are positioned in a pair of opposed slots 64. The leg portions 62 termin ate in in-turned end portions 66 that extend into the slots 64 and into engagement with the inner surface 46 of the shell member 28. With this arrangement the bail 60 is engaged to the shell me.~ber 28 to maintain the camming plug 52 assembled within the shell me~ber 28.
3~
As illustrated in Figure 4, the camming plug 52 includes a plurality of tapered planar surfaces 68 divided from one another by longitudinally extencling grooves 70. ~s described above, the inner surface 46 of each finger 32 abuts a respective tapered planar surface 68. In one embodiment of the present invention as seen in Figure 5 the stop device 26 is positioned in a bore 72 that extends through the camming plug 52 transversely to the threaded bore 54 of the camming plug 52. ~s seen in Figure 5, the transverse bore 72 includes opposite end portions 74 that extend through the plug 52 and emerge through a pair of oppositely aligned grooves 70 of the plug 52.
Further as illustrated in Figures 1 - 5, the stop device 26 includes a shearable pin 76 fabricated of a preselected yieldable material and having a preselected size and in the case of a circular pin, a preselected diameter. The pin 76 is retained in the transverse bore 72 and includes respective end portions 78 and 80. The pin end portions 78 and 80 are retained in the bore end portions 74 of the plug 52 as illustrated in the e~bodiment of the stop device 26 in Figures 1 - 7.
The intermediate body portion of the pin 76 extends transversely through the plug longitudinal bore 54.
The shearable pin 76 is selectively positioned to extend through the plug threaded bore 54 at a location to o~struct or pre~ent axial movement of the bolt threaded end portion 18 beyond a preselected depth into the camming plug bore 54. Thus upon initial assembly of the expansion shell asse~bly 10, the bolt threaded end portion 18 is advanced into the camming plug 52 until the bolt end portion 18 abuts the shearable pin 76 and can advance no further into the camming plug threaded bore 54.
The location of the transverse bore 72 through the camming plug 52 for positioning the shearable pin 76 is selective along the longitudinal length of the camming plug 52. To this end, as illustrated in Figure 5, the shearable pin 76 is positioned in the camming plug transverse bore 72 at a location adjacent the plug upper end portion 56. In the embodiment of the present invention illustrated in Figure 6, the shearable pin 76 is positioned in a plug transverse bore 82 located adjacent the plug lower end portion 58.
With the embodiment illustrated in Figure 5 the length of the bolt threaded end portion 18 that extends into the camming plug bore 54 is less than that length when the shearable pin 76 is retained in the camming plug 52 adjacent the plug upper end portion 56. In the position of the shearable pin 76 in the camming plug 52, as illustrated in Figure 6, the camming plug 52 is threaded on the bolt 12 to engage only several of the threads on the bolt end portion 18. The intermediate body portion of the shearable pin 76 prevents the bolt 12 from passing any further into the cam~ing plug threaded bore 54.
The material from which the shearable pin 76 is fabricated is selective, as for example in one embodiment the pin 76 can be fabricated of 1/4 inch diameter steel; while, in another e~bodiment it can be fabric-ated of 5/16 diameter aluminum. The type of material comprising the pin 76, as well as, the dimensions and cross sectional area of the pin 76 are selective to control the shearing or fracturing of the pin depend-ing upon. the type of bonding material .utilized and the period of time required for mixing of the material components. Further to ensure shear-ing or fracturing of the stop device 26 before the curable mixture hardens a stop device, such as a steel pin 77 illustrated in Figure 6~ i5 pro-vided with deformations, such as longitudinally extending, parallel Spaced grooves or recesses 84 positioned on the opposite end portions 78 and 80 of the pin 77.
The material composition and structural design of the stop device 26, such as the pins 76 and 77 illustrated in Figures 5 and 6, are selected in accordance with the curing time of the particular type o bonding material utilized. For example with a cc~[mercially available quick settlng type of resin system which begins to harden within 20 to 30 seconds or less following the rupture of the cartridge 24 and mixing of the components, the size and material canposition of the stop device 26 are selected to permit fracture after 20 seconds or less of rotation of the bolt 12. Thus when the resin mixture begins to harden a force is applied to the assembly 10 tending to resist rotation of the shell member 2~ and plug 52. The anti-rotational forces increase to a magnitude where the stop device 26 fractures.
Fracture of the stop device 26 occurs when the torque applied to the bolt 12 exceeds a pre etermined torque. ~en the stop device 26 is no longer capable of resisting the anti-rotational forces of the adhesive material applied to the rotating shell assembly 10, the stop device 26 fractures or shears. Relative rotation between the car[lming plug 52 and the bolt 12 is no longer prevented. The camming plug 52 is then free to move downwardly on the bolt 12 as the bolt 12 continues to rotate in the same preselected rotational direction.
The ability to control the shearing of the pin 76 provides a versatile expansion shell assembly 10 operable for use in ccmbination with adhesive materials of varying curing characteristics, such as a quick setting-type resin curable within 20 seconds or less of mixing or the type of adhesive material requiring 2 to 3 minutes o mixing before hardening begins. By selecting the material composition and cross sectional area of the stop device 26 in the form of a shear pin, as well as, the location of the shear pin relative to the car~ning plug 52, expansion of the shell m~mber 28 is prevented until after lapse of the time required to efect the necessary mixing of the adhesive components.
Once the curable mixture is formed and be~ins to harden, the mixture exerts anti-rotational forces upon the camming plug 52 rotating with the bolt 18. When the shear pin is no longer capable of resisting thPse forces, the pin fractures or is dislodged from the camming plug 52 freeing the bolt 18 to rotate relative to the camming plug 52. This action co~mences downward movement of the plug 52 and expansion of the shell 28. Significantly, the entire operation is carried out by contin-uous rotation of the bolt 18 in the same or a single rotational direction.
Preferably the shear pin fractures before the adhesive mixture completely Solidifies or hardens so that the expandable fingers 32 are movable outwardly into gripping engagement with the wall of the bore hole 14.
Now referring to Figure 3 there is illustrated in greater detail the configuration of the threaded upper end 18 of the bolt 12.
The bolt threaded upper end 18 terminates in a tapered end portion generally designated by the numeral 71. The tapered end portion 71 is tapered for the maximum diameter of the bolt 12 to a reduced diameter at the extreme end 73 of the bolt 12. The bolt tapered end portion 71 has a preselected dimension, that is, an angle A and a longitudinal length B. The magnitude of angle A and length B is selected as deter-mined, for example, by the diameter of the bolt 12, the size and material of the shear or stop device 26, the type of bonding material used, and the nature of the rock formation in which the bolt 12 is anchored.
Thus with the aboYe arrangement, a cone frustum is formed at the threaded upper end 18 of the bolt 12.
For example in one embodiment of the present invention, a bolt 12 having a diameter of 5/8 inch is used in combination with a 1/4 inch diameter steel pin stop device 76. The tapered end portion 71 has an angle A of 45 and a length B of 1/4 inch~ Thus the bolt 12 tapers frcm a 5/8 inch diameter to 1/8 inch diameter at the extreme end 73 of the bolt 12A The extreme end 73 of the bolt 12 is flat and bears against the pin 76A
The tapered end 71 of the bolt 12 applies a concentrated force upon a portion of the pin 76 as opposed to applying a force upon the full length of the portion of the pin 76 that is positioned in the plug bore 54. By tapering the bolt end portion 71 in accordance with the above example, a 1/8 inch section of the bolt extreme end 73 abuts the pin 76 rather than the full 5/3 inch diameter of the bolt 12~ This ensures breaking the pin 76 or dislodging the pin 76 fran a position in the plug bore 54 obstructing downward movement of the plug 52 when a preselected torque is applied to the bolt 12 after mixing of the bonding components is complete~
As stated the dimensions A and B of the bolt tapered end portion 71 are selected to meet the specific circumstances and conditions for the type of expansion shell assembly 10 and bolt 12 used with a part-icular bonding material. For example, the tapered end portion 71 can be provided with an angle A that varies in the range between about 15 to 65 and a length B that varies in a range corresponding to the angle ~a2~
A. However, regardless of the selected dimensions of the taper angle A and length B, the presence of the tapered end portion 71 on the bolt 12 facilitates re~oval of the pin 76 from a position in the plug bore 54 obstructing downward mov~ment of the plug 52 on the bolt 12 by concent-rating the upward thrust exerted by the bolt 12 on a portion of the pin 76.
A further embodiment of the shear device 26 is illustrated in Figure 8. In this embodiment a shear pin 79 is retained solely in a bore 86 extend;ng transversely through the threaded end portion 18 of the bolt 12 adjacent the tapered end portion 71 thereof. The shear pin 79 includes an intermediate portion 81 retained in the transverse bore 86 and a pair of opposite end portion 83 and 85. The pin end portions 83 and 85 extend outwardly from the bore 8~ and in the assembly 10 are positioned oppositely of a pair of slots 38 between adjacent shell fingers 32. The camming plug 52 is advanced downwardly on the bolt until the lower end portion 58 of the plug 52 abuts the pin end portions 83 and 85. The pin end portions 83 and 85 abutting the camming plug 52 prevent ~urther downward movement of the camming plug 52 on the bolt 1~.
As with the above described embodiments of the stop device 26 the shearable pin 79 resists relative rotation between the bolt 12 and the ca~ming plug 52 until a torque in excess of a predetermined torque is applied to the end of the bolt. ~t this torque the resistance offered by the curable bonding mix-ture to rotation of the plug 52 results in fracturing of the pin 79. The pin 79 is designed so that it does not fracture until the mixi~g of the bonding materials is complete and the mixture begins to harden. The pin end portions 83 and 85 break off from the intermediate portion 81 and are free to move through the shell slots 38.
When the torque for break~ng the pin 79 is reached1 the mixing is complete. The pin 79 breaks permitting downward movement of the ~2~3~
camming plug 52 to expand the shell member 280 Expansion of the shell me~ber 28 is delayed until the bonding material is mixed but not after the mixture rigidifies in the bore hole 14.
It should also be unders-tood that the stop device 26 includes any suitable .device that restrains axial movement of the plug 52 on the bolt 12 beyond a preselected point on the threaded end portions 18 of the bolt 12, as for example, an obstruction member suitably retained in the plug threaded bore 54. The obstruction member is operable to restrain relative rotation between the bolt 18 and the plug 52 until a preselected torque is applied to the bolt 18. BeEore the preselected torque is applied, the bonding material is mixed. When a torque in excess of the preselected torque is applied, the obstruction member is either broken or displaced in the plug bore 54 to the extent permitting relative rotation between the bolt 18 and the plug 52 permitting downward move~ent of the plug 52 on the bolt. This results in expansion of the shell member 28 and anchoring of the assembly 10 in the bore hole 14.
The stop device 26 in another embodiment can include an ob-struction which is not required to break or shear before expansion of the shell member 28 begins. This type of stop device 26 can include a flexible member, such as wire or the like, having end portions secured to the cc~mming plug 52 and extending through the plug bore 54 obstructing the path of the rotating bolt 18. The wire abutting the extr~me end 73 of the bolt tapered end portion 71 prevents downward move~ent of the plu~ 52 on the bolt 18. Movement of the plug 52 is restrained until the anti-rotational forces of the bonding mixture applied to the plug 52 results in yielding or bending of the wire permitting downward movement of the plug 52 on the bolt 12 upon continued rotation of the bolt 12.
The application of the torque which results in bending of the wire correspon~s to the formation of a curable bonding mixture and the in-itiation of expansion of the shell menber 28.
Now referring to Figures 9 - 12, there is illustrated the method of anchoring the apparatus lO and the bolt 12 in the bore hole 14 of the rock formation 16. Initially, as illustrated in Figure 9, the resin cartridge 24 is inserted in the hole 14 drilled in the mine roof or rock formation 16 by upward advancement by the bolt 12 with the apparatus lO attached to the threaded end portion 18 of the bolt 12. The cartridge 24 is pushed to substantially the blind end of the bore hole 14. With the cartridge 24 inserted in the upper part of the bore hole 14, as illu-strated in Figure 9, the bolt 12 is thrust upwardly to rupture the cartridge 2~
Thereafter, the entire asse~bly lO is rotated in a preselected direction as indicated by the arrow in Figure 9 by applying a torque to the bolt enlarged end portion 20. The stop device 26 in the form of the shear pin 76 illustrated in Figures 9 - 12, fabricated of a preselect-ed material and of a preselected size prevents relative rotation between the camming plug 52 and the bolt 12 during the initial rotation of the bolt 12 to rupture the cartridge and mix the resin components. In this manner the ca~ming plug 52 is restrained from moving downwardly on the bolt 12 by the bolt tapered end portion 71 abutting the shear pin 76 during the initial rotation of the bolt 12.
Rotation of the bolt 12 efects mixing of the resin conponents which are released from the cartridge 24 when the cartridge 24 is rup-tured. Preferably the resin components include a thermoplastic resin and a catal~st. As the bolt 12 is rotated the resin and the catalys-t are mixed to form a curable resin mixture 88. The resin mixture 88 by virtue of its t~ixotropic characteristics is retained within the bore hole 14.
To effectively retain the volume of the mixture 88 in surrounding relation with the assembly 10 a suitable device, such as a washer 90, is retained on the bolt 12 adjacent the bolt threaded end portion 18. The washer 90 has a diameter sufficient to permit the washer to move freely in the bore hole 14 with the bolt 12 into position. In one embodiment, the washer 90 is fabricated of metal and may be either welded or press fit on the bolt 12 spaced a preselected distance below the bolt threaded portion 18. In another embodiment the washer 90 is fabricated of an elastcmeric material. The elastomeric washer 90 is retained in gripping engagement on the bolt 12 below the threaded end portion 18.
The resin mixture 88 polymerizes at room temperature, i.e.
a temperature in the range between about 40 to ~0 F~ The bolt 12 is rotated continuously in the direction indicated by the arrow in Figure 10 to effect mixing of the resin. The shear pin 76 abutting the extreme end 73 of the bolt tapered rotation between the camming plug 52 and the bolt 12. This prevents the camming plug 52 from moving downwardly on the bolt 12 until the mixing of the resin components is complete.
The period of time for mixing quick setting-type resin is generally between about 20 to 30 seconds. During the mixing stage as seen in Figure 10 the bolt 12 is held in position within the bolt hole 14 with the roof plate 22 abutting the rock formation 16 around the open end of the bolt hole 14.
The shear pin 76 by restraining downward movement of the camming plug 52 on the bolt 12 ensures complete mixing of the resin components before the shell 28 is expanded~ However, due to the shear character-istics of the pin 76 designed for the resin system utilized, the shell 28 expands before the resin mixture 88 completely hardens around the shell member 28. From the time the cartridge 24 is ruptured, the bolt 12 is continuously rotated in one direction only, i.e~ either clockwise or counterclockwise, to mix the resin components, as well as, expand the shell member 28. As the bolt 12 rotates the curable resin mixture 88 flows into the fissures and faults of ths rock formation 16 surrounding the bore hole 1~. In this well known manner, the rock strata are adhes-ively united to further reinforce the rock formation.
6~
After the mixing stage, resin mixture 88 begins to cure or harden in the bore hole 14. As the resin mixture 88 begins to harden it exerts forces on the rotating shell member 28 and the camming plug 52 resisting their rotation. At a predetermined torque applied to the bolt 121 which is reached after an elapse of time to complete the mixing, the material strength of the shear pin 76 is exceeded by the anti-rotat-ional forces exerted by the resin mixture 88 and the pin 76 fractures or shears. Consequently, the intermediate portion of the pin 76 in the plug bore 5~ abutting the bolt tapered end portion 71 is bent and broken off from the pin end portions 78 and 80 which are retained in the plug, as seen in Figure 11. This permits the pin 76 to be displaced in the camming Plug bore 54 so that the plug 52 is free to move downwardly on the bolt threaded end portion 18.
Referring to Figure 11, downward move~ent of the camming plug 52 on the bolt 12, upon rotation of the bolt 12 in the same direction for forming the resin mixture 88, expands the shell member 28. The fingers 32 are bent outwardly about the shell ring end portion 30 to move the outer gripping surfaces 34 into gripping engage~ent with the ~all of the bore hole 14. The rotation of the bolt 12 is continuous in the direction indicated by the arrows in Figures 10 and 11 through the resin mixing and shell expanding stages. Rotation of the bolt 12 continues until a preselected torque is applied to the bolt 12. ~hen the preselect-ed torque is applied, the shell member 28 is fully expanded and the gripping portions 48 of the fingers 32 are e~bedded in the rock formation to securely anchor the bolt 12 ;n the bore hole 1'1.
When the shell member 28 is expanded the resin mix-ture 88 is cured. By anchoring the bolt 12 in the bore hole 14 by the expansion shell member 2~, the bolt 12 ls tensioned. The addition of the cured resin in surrounding relation with the bolt 12 and the expanded shell member 28 prevents slippage of the shell member 28 in the bore hole 14. Tension on the bolt is thus maintained and is not reduced by slippage of the expanded shell member 28 in the bore hole.
By the provision of the stop device 26, the expansion shell assembly 10 is operable as a mixing tool to admix the components of the resin cartridge 24 to form the curable mixture 88 before the shell member 28 is expanded. The stop device 26 prevents downward movement of the camming plug 52 on the bolt 12 during the period in which the resin components are mixed~ Also by the provision of the stop device 26, the bolt 12 is continuously rotated in the same preselected direction to effect both mixing of the resin components and expansion of the shell member 28. Thus it is not necessary with the present invention to rotate the bolt 12 in a first direction to effect mixing of the resin components and then followed by reversal of the direction of rotation of the bolt 12 to effect expansion of the shell member 28.
The provision of the stop device 26 associated with the camming plug 52 substantially improves the efficiency and ease of installation of a roof bolt that is both mechanically anchored and resin bonded within a bolt bore hole. It should also be understood even though the direction of rotation for both mixing the resin components and expanding the shell member 28 is illustrated in a counterclockwise direction in Figures 11 and 12, the direction of rotation can be clockwise as well depending upon whether the bolt end portion 18 is left-hand threaded or right-hand threaded.
According to the provisions of the patent statutes, I have explained the principle, preferred construction and mode of operation of my invention and have illustrated and described what I now consider to represent its best embodiments. ~lowever, it shc~ld be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.
This application is a division of 541,932 filed July 13, 1987, a division of 390,107, filed November 16, 1981.
The bolt is continuously rotated in the same preselected direction for a period of time sufficient to complete mixing of the components of the bonding material. The stop device 26 prevents expan-sion of the shell assembly 10 during the mixing stage. The bolt contin-ues to rotate in the same initial directon. When the torgue applied to the bolt exceeds a predetermined torque, as determined by the time for mixing the bonding material, the stop device 26 fractures. The expansion shell assembly 10 is then free to expand into gripping engage-ment with the wall of the bore hole 14. The continuous rotation of the bolt in the same initial direction completes the setting of the assembly 10. Thus the bolt is both mechanically anchored and adhesively bonded in the bore hole to prevent slippage of the expanded assembly 10 so that the bolt 12 remains tensioned to support the rock formation.
Now referring in greater detail to the structure of the expan-sion shell asse~bly 10 there is provided a shell member 28 conventional in design and including a solid ring end portion 30. The shell member 28 is expandable and has a plurality of longitudinally extendin~ fingers 32 that extend axially from the ring end portion 30. Each of the fingers 32 has a lower end portion 34 connected to the ring end portion 30 and an upper end portion 36. Longitudinally slots 38 (only one of which is shown in Figure 1) divide the fingers 32 fr~m one another. Each of the slots 38 has a closed end portion 40 adjacen-t the ring end portion 30 and an open end portion 42 adjacent the upper en~ portion 36 of the respective finger 32.
~Z~f39.'~
Each finger 32 inc].udes an outer gripping surface 44 and an inner smooth sur-face 46. The outer surface 44 includes a gripp-ing portion 48 that extends from the finger upper end portion 36 to a position spaced from the finger lower end portion 34. The gripp-ing portion 48 of each finger 32 includes a series of spaced parallel, tapered horizontal grooves 50. The grooves 50 from a series of downwardly extending serrations that are operable upon expansion of the shell member 28 to engage the wall of the bore hole 14 as the fingers 32 bend out-wardly.
The gripping portion 38 of each finger 32 is urged into contact with the wall of the bore hole 14, as seen in Figures 10 and 11, by a camming plug or wedge generally designated by the numeral 52. The camming plug 52 includes a threaded axial bore 54 threadedly engaged to the bolt threaded end portion 18. The camming plug 52 has a tapered configuration with an enlarged upper end portion 56 and a reduced lower end portion 58.
A portion of the inner surface 46 of each finger 32 abuts a tapered planar surface 68 of the camming plug 52.
As illustrated in Figure 1, the camming plug 52 and the shell member 28 are maintained in assembled relation on the bolt threaded end portion 18 prior to anchoring the assembly in the bore hole 14 drilled in the mine roof. Also as well known in the art and illustrated in Figure 7, the camming plug 52 and the shell me.~ber 28 are connected by a yieldable strap or bail 60. The bail 60 is conventional and extends across the top of the ca~ming plug 52. The bail 60 includes leg portions 62 that extend downwardly on opposite sides of the shell me~ber 28. The leg portion 62 are positioned in a pair of opposed slots 64. The leg portions 62 termin ate in in-turned end portions 66 that extend into the slots 64 and into engagement with the inner surface 46 of the shell member 28. With this arrangement the bail 60 is engaged to the shell me.~ber 28 to maintain the camming plug 52 assembled within the shell me~ber 28.
3~
As illustrated in Figure 4, the camming plug 52 includes a plurality of tapered planar surfaces 68 divided from one another by longitudinally extencling grooves 70. ~s described above, the inner surface 46 of each finger 32 abuts a respective tapered planar surface 68. In one embodiment of the present invention as seen in Figure 5 the stop device 26 is positioned in a bore 72 that extends through the camming plug 52 transversely to the threaded bore 54 of the camming plug 52. ~s seen in Figure 5, the transverse bore 72 includes opposite end portions 74 that extend through the plug 52 and emerge through a pair of oppositely aligned grooves 70 of the plug 52.
Further as illustrated in Figures 1 - 5, the stop device 26 includes a shearable pin 76 fabricated of a preselected yieldable material and having a preselected size and in the case of a circular pin, a preselected diameter. The pin 76 is retained in the transverse bore 72 and includes respective end portions 78 and 80. The pin end portions 78 and 80 are retained in the bore end portions 74 of the plug 52 as illustrated in the e~bodiment of the stop device 26 in Figures 1 - 7.
The intermediate body portion of the pin 76 extends transversely through the plug longitudinal bore 54.
The shearable pin 76 is selectively positioned to extend through the plug threaded bore 54 at a location to o~struct or pre~ent axial movement of the bolt threaded end portion 18 beyond a preselected depth into the camming plug bore 54. Thus upon initial assembly of the expansion shell asse~bly 10, the bolt threaded end portion 18 is advanced into the camming plug 52 until the bolt end portion 18 abuts the shearable pin 76 and can advance no further into the camming plug threaded bore 54.
The location of the transverse bore 72 through the camming plug 52 for positioning the shearable pin 76 is selective along the longitudinal length of the camming plug 52. To this end, as illustrated in Figure 5, the shearable pin 76 is positioned in the camming plug transverse bore 72 at a location adjacent the plug upper end portion 56. In the embodiment of the present invention illustrated in Figure 6, the shearable pin 76 is positioned in a plug transverse bore 82 located adjacent the plug lower end portion 58.
With the embodiment illustrated in Figure 5 the length of the bolt threaded end portion 18 that extends into the camming plug bore 54 is less than that length when the shearable pin 76 is retained in the camming plug 52 adjacent the plug upper end portion 56. In the position of the shearable pin 76 in the camming plug 52, as illustrated in Figure 6, the camming plug 52 is threaded on the bolt 12 to engage only several of the threads on the bolt end portion 18. The intermediate body portion of the shearable pin 76 prevents the bolt 12 from passing any further into the cam~ing plug threaded bore 54.
The material from which the shearable pin 76 is fabricated is selective, as for example in one embodiment the pin 76 can be fabricated of 1/4 inch diameter steel; while, in another e~bodiment it can be fabric-ated of 5/16 diameter aluminum. The type of material comprising the pin 76, as well as, the dimensions and cross sectional area of the pin 76 are selective to control the shearing or fracturing of the pin depend-ing upon. the type of bonding material .utilized and the period of time required for mixing of the material components. Further to ensure shear-ing or fracturing of the stop device 26 before the curable mixture hardens a stop device, such as a steel pin 77 illustrated in Figure 6~ i5 pro-vided with deformations, such as longitudinally extending, parallel Spaced grooves or recesses 84 positioned on the opposite end portions 78 and 80 of the pin 77.
The material composition and structural design of the stop device 26, such as the pins 76 and 77 illustrated in Figures 5 and 6, are selected in accordance with the curing time of the particular type o bonding material utilized. For example with a cc~[mercially available quick settlng type of resin system which begins to harden within 20 to 30 seconds or less following the rupture of the cartridge 24 and mixing of the components, the size and material canposition of the stop device 26 are selected to permit fracture after 20 seconds or less of rotation of the bolt 12. Thus when the resin mixture begins to harden a force is applied to the assembly 10 tending to resist rotation of the shell member 2~ and plug 52. The anti-rotational forces increase to a magnitude where the stop device 26 fractures.
Fracture of the stop device 26 occurs when the torque applied to the bolt 12 exceeds a pre etermined torque. ~en the stop device 26 is no longer capable of resisting the anti-rotational forces of the adhesive material applied to the rotating shell assembly 10, the stop device 26 fractures or shears. Relative rotation between the car[lming plug 52 and the bolt 12 is no longer prevented. The camming plug 52 is then free to move downwardly on the bolt 12 as the bolt 12 continues to rotate in the same preselected rotational direction.
The ability to control the shearing of the pin 76 provides a versatile expansion shell assembly 10 operable for use in ccmbination with adhesive materials of varying curing characteristics, such as a quick setting-type resin curable within 20 seconds or less of mixing or the type of adhesive material requiring 2 to 3 minutes o mixing before hardening begins. By selecting the material composition and cross sectional area of the stop device 26 in the form of a shear pin, as well as, the location of the shear pin relative to the car~ning plug 52, expansion of the shell m~mber 28 is prevented until after lapse of the time required to efect the necessary mixing of the adhesive components.
Once the curable mixture is formed and be~ins to harden, the mixture exerts anti-rotational forces upon the camming plug 52 rotating with the bolt 18. When the shear pin is no longer capable of resisting thPse forces, the pin fractures or is dislodged from the camming plug 52 freeing the bolt 18 to rotate relative to the camming plug 52. This action co~mences downward movement of the plug 52 and expansion of the shell 28. Significantly, the entire operation is carried out by contin-uous rotation of the bolt 18 in the same or a single rotational direction.
Preferably the shear pin fractures before the adhesive mixture completely Solidifies or hardens so that the expandable fingers 32 are movable outwardly into gripping engagement with the wall of the bore hole 14.
Now referring to Figure 3 there is illustrated in greater detail the configuration of the threaded upper end 18 of the bolt 12.
The bolt threaded upper end 18 terminates in a tapered end portion generally designated by the numeral 71. The tapered end portion 71 is tapered for the maximum diameter of the bolt 12 to a reduced diameter at the extreme end 73 of the bolt 12. The bolt tapered end portion 71 has a preselected dimension, that is, an angle A and a longitudinal length B. The magnitude of angle A and length B is selected as deter-mined, for example, by the diameter of the bolt 12, the size and material of the shear or stop device 26, the type of bonding material used, and the nature of the rock formation in which the bolt 12 is anchored.
Thus with the aboYe arrangement, a cone frustum is formed at the threaded upper end 18 of the bolt 12.
For example in one embodiment of the present invention, a bolt 12 having a diameter of 5/8 inch is used in combination with a 1/4 inch diameter steel pin stop device 76. The tapered end portion 71 has an angle A of 45 and a length B of 1/4 inch~ Thus the bolt 12 tapers frcm a 5/8 inch diameter to 1/8 inch diameter at the extreme end 73 of the bolt 12A The extreme end 73 of the bolt 12 is flat and bears against the pin 76A
The tapered end 71 of the bolt 12 applies a concentrated force upon a portion of the pin 76 as opposed to applying a force upon the full length of the portion of the pin 76 that is positioned in the plug bore 54. By tapering the bolt end portion 71 in accordance with the above example, a 1/8 inch section of the bolt extreme end 73 abuts the pin 76 rather than the full 5/3 inch diameter of the bolt 12~ This ensures breaking the pin 76 or dislodging the pin 76 fran a position in the plug bore 54 obstructing downward movement of the plug 52 when a preselected torque is applied to the bolt 12 after mixing of the bonding components is complete~
As stated the dimensions A and B of the bolt tapered end portion 71 are selected to meet the specific circumstances and conditions for the type of expansion shell assembly 10 and bolt 12 used with a part-icular bonding material. For example, the tapered end portion 71 can be provided with an angle A that varies in the range between about 15 to 65 and a length B that varies in a range corresponding to the angle ~a2~
A. However, regardless of the selected dimensions of the taper angle A and length B, the presence of the tapered end portion 71 on the bolt 12 facilitates re~oval of the pin 76 from a position in the plug bore 54 obstructing downward mov~ment of the plug 52 on the bolt 12 by concent-rating the upward thrust exerted by the bolt 12 on a portion of the pin 76.
A further embodiment of the shear device 26 is illustrated in Figure 8. In this embodiment a shear pin 79 is retained solely in a bore 86 extend;ng transversely through the threaded end portion 18 of the bolt 12 adjacent the tapered end portion 71 thereof. The shear pin 79 includes an intermediate portion 81 retained in the transverse bore 86 and a pair of opposite end portion 83 and 85. The pin end portions 83 and 85 extend outwardly from the bore 8~ and in the assembly 10 are positioned oppositely of a pair of slots 38 between adjacent shell fingers 32. The camming plug 52 is advanced downwardly on the bolt until the lower end portion 58 of the plug 52 abuts the pin end portions 83 and 85. The pin end portions 83 and 85 abutting the camming plug 52 prevent ~urther downward movement of the camming plug 52 on the bolt 1~.
As with the above described embodiments of the stop device 26 the shearable pin 79 resists relative rotation between the bolt 12 and the ca~ming plug 52 until a torque in excess of a predetermined torque is applied to the end of the bolt. ~t this torque the resistance offered by the curable bonding mix-ture to rotation of the plug 52 results in fracturing of the pin 79. The pin 79 is designed so that it does not fracture until the mixi~g of the bonding materials is complete and the mixture begins to harden. The pin end portions 83 and 85 break off from the intermediate portion 81 and are free to move through the shell slots 38.
When the torque for break~ng the pin 79 is reached1 the mixing is complete. The pin 79 breaks permitting downward movement of the ~2~3~
camming plug 52 to expand the shell member 280 Expansion of the shell me~ber 28 is delayed until the bonding material is mixed but not after the mixture rigidifies in the bore hole 14.
It should also be unders-tood that the stop device 26 includes any suitable .device that restrains axial movement of the plug 52 on the bolt 12 beyond a preselected point on the threaded end portions 18 of the bolt 12, as for example, an obstruction member suitably retained in the plug threaded bore 54. The obstruction member is operable to restrain relative rotation between the bolt 18 and the plug 52 until a preselected torque is applied to the bolt 18. BeEore the preselected torque is applied, the bonding material is mixed. When a torque in excess of the preselected torque is applied, the obstruction member is either broken or displaced in the plug bore 54 to the extent permitting relative rotation between the bolt 18 and the plug 52 permitting downward move~ent of the plug 52 on the bolt. This results in expansion of the shell member 28 and anchoring of the assembly 10 in the bore hole 14.
The stop device 26 in another embodiment can include an ob-struction which is not required to break or shear before expansion of the shell member 28 begins. This type of stop device 26 can include a flexible member, such as wire or the like, having end portions secured to the cc~mming plug 52 and extending through the plug bore 54 obstructing the path of the rotating bolt 18. The wire abutting the extr~me end 73 of the bolt tapered end portion 71 prevents downward move~ent of the plu~ 52 on the bolt 18. Movement of the plug 52 is restrained until the anti-rotational forces of the bonding mixture applied to the plug 52 results in yielding or bending of the wire permitting downward movement of the plug 52 on the bolt 12 upon continued rotation of the bolt 12.
The application of the torque which results in bending of the wire correspon~s to the formation of a curable bonding mixture and the in-itiation of expansion of the shell menber 28.
Now referring to Figures 9 - 12, there is illustrated the method of anchoring the apparatus lO and the bolt 12 in the bore hole 14 of the rock formation 16. Initially, as illustrated in Figure 9, the resin cartridge 24 is inserted in the hole 14 drilled in the mine roof or rock formation 16 by upward advancement by the bolt 12 with the apparatus lO attached to the threaded end portion 18 of the bolt 12. The cartridge 24 is pushed to substantially the blind end of the bore hole 14. With the cartridge 24 inserted in the upper part of the bore hole 14, as illu-strated in Figure 9, the bolt 12 is thrust upwardly to rupture the cartridge 2~
Thereafter, the entire asse~bly lO is rotated in a preselected direction as indicated by the arrow in Figure 9 by applying a torque to the bolt enlarged end portion 20. The stop device 26 in the form of the shear pin 76 illustrated in Figures 9 - 12, fabricated of a preselect-ed material and of a preselected size prevents relative rotation between the camming plug 52 and the bolt 12 during the initial rotation of the bolt 12 to rupture the cartridge and mix the resin components. In this manner the ca~ming plug 52 is restrained from moving downwardly on the bolt 12 by the bolt tapered end portion 71 abutting the shear pin 76 during the initial rotation of the bolt 12.
Rotation of the bolt 12 efects mixing of the resin conponents which are released from the cartridge 24 when the cartridge 24 is rup-tured. Preferably the resin components include a thermoplastic resin and a catal~st. As the bolt 12 is rotated the resin and the catalys-t are mixed to form a curable resin mixture 88. The resin mixture 88 by virtue of its t~ixotropic characteristics is retained within the bore hole 14.
To effectively retain the volume of the mixture 88 in surrounding relation with the assembly 10 a suitable device, such as a washer 90, is retained on the bolt 12 adjacent the bolt threaded end portion 18. The washer 90 has a diameter sufficient to permit the washer to move freely in the bore hole 14 with the bolt 12 into position. In one embodiment, the washer 90 is fabricated of metal and may be either welded or press fit on the bolt 12 spaced a preselected distance below the bolt threaded portion 18. In another embodiment the washer 90 is fabricated of an elastcmeric material. The elastomeric washer 90 is retained in gripping engagement on the bolt 12 below the threaded end portion 18.
The resin mixture 88 polymerizes at room temperature, i.e.
a temperature in the range between about 40 to ~0 F~ The bolt 12 is rotated continuously in the direction indicated by the arrow in Figure 10 to effect mixing of the resin. The shear pin 76 abutting the extreme end 73 of the bolt tapered rotation between the camming plug 52 and the bolt 12. This prevents the camming plug 52 from moving downwardly on the bolt 12 until the mixing of the resin components is complete.
The period of time for mixing quick setting-type resin is generally between about 20 to 30 seconds. During the mixing stage as seen in Figure 10 the bolt 12 is held in position within the bolt hole 14 with the roof plate 22 abutting the rock formation 16 around the open end of the bolt hole 14.
The shear pin 76 by restraining downward movement of the camming plug 52 on the bolt 12 ensures complete mixing of the resin components before the shell 28 is expanded~ However, due to the shear character-istics of the pin 76 designed for the resin system utilized, the shell 28 expands before the resin mixture 88 completely hardens around the shell member 28. From the time the cartridge 24 is ruptured, the bolt 12 is continuously rotated in one direction only, i.e~ either clockwise or counterclockwise, to mix the resin components, as well as, expand the shell member 28. As the bolt 12 rotates the curable resin mixture 88 flows into the fissures and faults of ths rock formation 16 surrounding the bore hole 1~. In this well known manner, the rock strata are adhes-ively united to further reinforce the rock formation.
6~
After the mixing stage, resin mixture 88 begins to cure or harden in the bore hole 14. As the resin mixture 88 begins to harden it exerts forces on the rotating shell member 28 and the camming plug 52 resisting their rotation. At a predetermined torque applied to the bolt 121 which is reached after an elapse of time to complete the mixing, the material strength of the shear pin 76 is exceeded by the anti-rotat-ional forces exerted by the resin mixture 88 and the pin 76 fractures or shears. Consequently, the intermediate portion of the pin 76 in the plug bore 5~ abutting the bolt tapered end portion 71 is bent and broken off from the pin end portions 78 and 80 which are retained in the plug, as seen in Figure 11. This permits the pin 76 to be displaced in the camming Plug bore 54 so that the plug 52 is free to move downwardly on the bolt threaded end portion 18.
Referring to Figure 11, downward move~ent of the camming plug 52 on the bolt 12, upon rotation of the bolt 12 in the same direction for forming the resin mixture 88, expands the shell member 28. The fingers 32 are bent outwardly about the shell ring end portion 30 to move the outer gripping surfaces 34 into gripping engage~ent with the ~all of the bore hole 14. The rotation of the bolt 12 is continuous in the direction indicated by the arrows in Figures 10 and 11 through the resin mixing and shell expanding stages. Rotation of the bolt 12 continues until a preselected torque is applied to the bolt 12. ~hen the preselect-ed torque is applied, the shell member 28 is fully expanded and the gripping portions 48 of the fingers 32 are e~bedded in the rock formation to securely anchor the bolt 12 ;n the bore hole 1'1.
When the shell member 28 is expanded the resin mix-ture 88 is cured. By anchoring the bolt 12 in the bore hole 14 by the expansion shell member 2~, the bolt 12 ls tensioned. The addition of the cured resin in surrounding relation with the bolt 12 and the expanded shell member 28 prevents slippage of the shell member 28 in the bore hole 14. Tension on the bolt is thus maintained and is not reduced by slippage of the expanded shell member 28 in the bore hole.
By the provision of the stop device 26, the expansion shell assembly 10 is operable as a mixing tool to admix the components of the resin cartridge 24 to form the curable mixture 88 before the shell member 28 is expanded. The stop device 26 prevents downward movement of the camming plug 52 on the bolt 12 during the period in which the resin components are mixed~ Also by the provision of the stop device 26, the bolt 12 is continuously rotated in the same preselected direction to effect both mixing of the resin components and expansion of the shell member 28. Thus it is not necessary with the present invention to rotate the bolt 12 in a first direction to effect mixing of the resin components and then followed by reversal of the direction of rotation of the bolt 12 to effect expansion of the shell member 28.
The provision of the stop device 26 associated with the camming plug 52 substantially improves the efficiency and ease of installation of a roof bolt that is both mechanically anchored and resin bonded within a bolt bore hole. It should also be understood even though the direction of rotation for both mixing the resin components and expanding the shell member 28 is illustrated in a counterclockwise direction in Figures 11 and 12, the direction of rotation can be clockwise as well depending upon whether the bolt end portion 18 is left-hand threaded or right-hand threaded.
According to the provisions of the patent statutes, I have explained the principle, preferred construction and mode of operation of my invention and have illustrated and described what I now consider to represent its best embodiments. ~lowever, it shc~ld be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.
This application is a division of 541,932 filed July 13, 1987, a division of 390,107, filed November 16, 1981.
Claims (4)
1. A method of anchoring a bolt in a bore hole comprising the steps of, threadedly engaging a camming plug to the end of the bolt for axial movement thereon, positioning an expandable shell having a plurality of longitudinally extending fingers in surrounding relation with the camming plug on the bolt, preventing axial movement of the camming plug on the bolt by a stop means associated with the bolt upon rotation of the bolt in a preselected rotational direction, displacing the stop means by the bolt as the bolt continues to rotate in said preselected rotational direction when a torque in excess of a predetermined torque is applied to the bolt, and moving the camming plug on the bolt upon displacement of the stop means to bend the fingers outwardly to anchor the bolt in the bore hole.
2. A method of anchoring a bolt in a bore hole as set forth in claim 10 which includes, positioning a bonding material in an unmixed condition in the bore hole ahead of the expandable shell, abutting the stop means on the camming plug with the bolt to prevent rotation of the bolt relative to the camming plug, rotating the bolt in said preselected direction to effect mixing of the bonding material in the bore hole, fracturing the stop means when the mixed bonding material exerts a force resisting rotation of the camming plug with the bolt, displacing the stop means from abutting relation with the bolt, and moving the camming plug downwardly on the bolt to bend the fingers outwardly in the bore hole to anchor the bolt.
3. A method of anchoring a bolt in a bore hole as set forth in claim 10 which includes, obstructing downward movement of the camming plug on the bolt until the torque in excess of the predetermined torque is applied to the bolt, and displacing the stop means relative to the camming plug to permit rotation of the bolt relative to the camming plug and outward bending of the shell fingers in the bore hole.
4. A method of anchoring a bolt in a bore hole as set forth in claim 10 which includes, extending the stop means through the camming plug and abutting the bolt to prevent advancement of the camming plug on the bolt upon initial rotation of the bolt in the preselected direct-ion, and shearing the stop means by application of a preselected torque to the bolt to permit downward movement of the camming plug on the bolt to bend the fingers of the shell outwardly in the bore hole.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000567576A CA1249446A (en) | 1980-11-21 | 1988-05-24 | Method and apparatus for combining resin bonding and mechanical anchoring of a bolt in a rock formation |
Applications Claiming Priority (6)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/209,134 US4419805A (en) | 1980-11-21 | 1980-11-21 | Method for combining resin bonding and mechanical anchoring of a bolt in a rock formation |
| US209,134 | 1980-11-21 | ||
| US06/238,760 US4413930A (en) | 1980-11-21 | 1981-02-27 | Method and apparatus for combining resin bonding and mechanical anchoring of a bolt in a rock formation |
| US238,760 | 1981-02-27 | ||
| CA000541932A CA1240162A (en) | 1980-11-21 | 1987-07-13 | Method and apparatus for combining resin bonding and mechanical anchoring of a bolt in a rock formation |
| CA000567576A CA1249446A (en) | 1980-11-21 | 1988-05-24 | Method and apparatus for combining resin bonding and mechanical anchoring of a bolt in a rock formation |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000541932A Division CA1240162A (en) | 1980-11-21 | 1987-07-13 | Method and apparatus for combining resin bonding and mechanical anchoring of a bolt in a rock formation |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1249446A true CA1249446A (en) | 1989-01-31 |
Family
ID=27167743
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000567576A Expired CA1249446A (en) | 1980-11-21 | 1988-05-24 | Method and apparatus for combining resin bonding and mechanical anchoring of a bolt in a rock formation |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1249446A (en) |
-
1988
- 1988-05-24 CA CA000567576A patent/CA1249446A/en not_active Expired
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