CA2439397A1 - Mine roof bolt assembly - Google Patents
Mine roof bolt assembly Download PDFInfo
- Publication number
- CA2439397A1 CA2439397A1 CA 2439397 CA2439397A CA2439397A1 CA 2439397 A1 CA2439397 A1 CA 2439397A1 CA 2439397 CA2439397 CA 2439397 CA 2439397 A CA2439397 A CA 2439397A CA 2439397 A1 CA2439397 A1 CA 2439397A1
- Authority
- CA
- Canada
- Prior art keywords
- bore
- pins
- threaded
- fastener
- nut
- 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.)
- Abandoned
Links
- 239000011347 resin Substances 0.000 claims description 30
- 229920005989 resin Polymers 0.000 claims description 30
- 238000010008 shearing Methods 0.000 claims description 10
- 238000003780 insertion Methods 0.000 claims description 9
- 230000037431 insertion Effects 0.000 claims description 9
- 230000000295 complement effect Effects 0.000 claims description 8
- 229910000831 Steel Inorganic materials 0.000 claims description 7
- 239000010959 steel Substances 0.000 claims description 7
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 4
- 229910052742 iron Inorganic materials 0.000 claims description 2
- 239000002184 metal Substances 0.000 claims 3
- 229910052751 metal Inorganic materials 0.000 claims 3
- 239000000956 alloy Substances 0.000 claims 1
- 229910045601 alloy Inorganic materials 0.000 claims 1
- 150000002739 metals Chemical class 0.000 claims 1
- 239000012634 fragment Substances 0.000 abstract description 17
- 238000004513 sizing Methods 0.000 abstract description 2
- 239000011435 rock Substances 0.000 description 24
- 230000003014 reinforcing effect Effects 0.000 description 14
- 238000010276 construction Methods 0.000 description 9
- 238000004873 anchoring Methods 0.000 description 4
- 238000009434 installation Methods 0.000 description 3
- 230000002411 adverse Effects 0.000 description 2
- 230000004323 axial length Effects 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 229910000851 Alloy steel Inorganic materials 0.000 description 1
- 229910001208 Crucible steel Inorganic materials 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 239000011440 grout Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000007790 scraping Methods 0.000 description 1
- 238000009987 spinning Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
Classifications
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D21/00—Anchoring-bolts for roof, floor in galleries or longwall working, or shaft-lining protection
- E21D21/008—Anchoring or tensioning means
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
- E21D20/00—Setting anchoring-bolts
- E21D20/02—Setting anchoring-bolts with provisions for grouting
- E21D20/025—Grouting with organic components, e.g. resin
Landscapes
- Engineering & Computer Science (AREA)
- Mining & Mineral Resources (AREA)
- Structural Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Geology (AREA)
- Joining Of Building Structures In Genera (AREA)
Abstract
A mine roof bolt assembly for use in a bolt hole includes a rebar having an externally threaded end and a nut or other suitable fastener which is configured to threadedly engage the threaded end of the rebar. Bores formed through the nut and rebar are configured for alignment when the nut is positioned on the rebar in a first or initial position. A pair of shear pins are inserted so as to locate partially within segments of the bore formed in the nut, as well as within the bore formed through the rebar. The pins have a sizing selected so as to maintain a spacing between the innermost pin ends which are proximate to each other. The spacing in between the inner ends of the pins is selected so that when the fastener is rotated relative to the rebar under a predetermined minimum torque, the pins fracture or shear at the junction between the nut and the rebar. The pin fragments within the rebar thus may move inwardly into the spacing towards each other so as not to interfere or otherwise wedge between the bolt and nut threads, as the nut is threaded onto the bolt.
Description
MINE ROOF BOLT ASSEMBLY
SCOPE OF THE INVENTION
The present invention relates to a mine roof bolt assembly, and more particularly a bolt assembly which includes a reinforcing anchor rod or rebar having a threaded end which is engaged by a nut, and wherein the nut is secured in an initial position against movement relative to the rod by a pair of shear pins, and which upon the application of a predetermined minimum torque force, fracture or shear to permit the nut to run freely onto the rod.
BACKGROUND OF THE INVENTION
In mine roof and wall support systems (hereinafter collectively referred to as "mine roof support systems"), a threaded rod-like reinforcing bolt or rebar is embedded into a bolt hole drilled in the rock face. A nut or threaded fastener is thereafter coupled to the rod and tightened against the rock face to consolidate forces therein and prevent or control ground movement.
Typically, the rebar reinforcing rod comprises a four to eight foot length of steel which is threaded along its outermost proximal end. The rebar is inserted into a bore hole drilled into the rock so that the threaded end projects outwardly beyond the rock face, permitting the threaded coupling of the nut thereto.
United States Patent No. 5,873,689 to Mensour et al, which issued 23 February 1999, discloses a prior method and system of securing an anchor rebar in a bolt hole by the use of one or more resin cartridges. The resin cartridges are inserted into the bolt hole in advance of the rebar. Following their insertion, the rebar is slid into the bolt hole and driven through the resin cartridges, causing their rupture and the mixing of the resin to fixedly retain the rebar once the resin has set.
SCOPE OF THE INVENTION
The present invention relates to a mine roof bolt assembly, and more particularly a bolt assembly which includes a reinforcing anchor rod or rebar having a threaded end which is engaged by a nut, and wherein the nut is secured in an initial position against movement relative to the rod by a pair of shear pins, and which upon the application of a predetermined minimum torque force, fracture or shear to permit the nut to run freely onto the rod.
BACKGROUND OF THE INVENTION
In mine roof and wall support systems (hereinafter collectively referred to as "mine roof support systems"), a threaded rod-like reinforcing bolt or rebar is embedded into a bolt hole drilled in the rock face. A nut or threaded fastener is thereafter coupled to the rod and tightened against the rock face to consolidate forces therein and prevent or control ground movement.
Typically, the rebar reinforcing rod comprises a four to eight foot length of steel which is threaded along its outermost proximal end. The rebar is inserted into a bore hole drilled into the rock so that the threaded end projects outwardly beyond the rock face, permitting the threaded coupling of the nut thereto.
United States Patent No. 5,873,689 to Mensour et al, which issued 23 February 1999, discloses a prior method and system of securing an anchor rebar in a bolt hole by the use of one or more resin cartridges. The resin cartridges are inserted into the bolt hole in advance of the rebar. Following their insertion, the rebar is slid into the bolt hole and driven through the resin cartridges, causing their rupture and the mixing of the resin to fixedly retain the rebar once the resin has set.
To enhance mixing of the resin, it is known to rotate the rebar about its longitudinal axis.
United States Patent No. 5,873,689 discloses a dome-nut type fastener which is characterized by a covered nut end. The nut is positioned over the threaded end of the rebar and rotated about its axial length with a power winch or socket drive. The nuts are formed such that the engagement of the covered end of the nut under initial torque forces results in the rebar rotating together with the turning of the nut. As the resin sets, resistance to the rotation of the rebar increases until the rotational force applied to the nut exceeds a critical minimum torque force.
Upon reaching the predetermined torque force, the cover portion or domed end distorts or splits by contact forces between the rebar and nut as the nut is moved along the rebar thread. The deformation allows the nut to thereafter be tightened along the rod and against the rock face.
Although the dome nut of United States Patent No. 5,873,689 achieves satisfactory deformation with low torque applications where, for example, the covered end is adapted to deform or detach at less than about 50 Ft. Lbs. or less, conventional dome nuts have proven inconsistent in providing a precise torque deformation range where higher torque applications are desired. In addition, where dome nuts are made by casting, thickness cannot precisely be controlled, resulting in imprecise control in the breakage strength of the dome. In case the dome portion is not strong enough, earlier breakage occurs, which results in under-mixing of resin. On the other hand, if the dome portion is too strong to break, the nut cannot be rotated further and therefore the bar cannot be tensioned.
Both cases are termed as failure of installation.
Various other manufacturers have proposed different torque nuts which incorporate a nut secured to the rod by means of a shear pin which fractures under higher predetermined minimum torques. United States Patent No. 4,173,918 to Piersall discloses an earlier expansion bolt construction in which a single shear pin is inserted through a bore hole formed transversely through a nut and mine roof anchor rod. The pin is used to permit rotation of the rebar about its axial length to permit the positioning of a threaded wedge anchor, and which following its placement, the predetermined minimum torque is applied to the nut, causing the pin to shear, and allowing the nut to be tightened along the rebar. The applicant has appreciated, however, that upon initial deformation of the pin of Piersall, the pin may initially be bent into an S-shape, rather than shearing cleanly. As a result, the S-shape bending of the shear pin tends to result in the pin fragments partially wedging between the internal threads of the nut and the external threads of the bolt. This in turn may result in distortion or deformation of the rebar threads, or even the wedging of the nut on the rebar in an untightened position. The wedging of the pin fragments between the bolt and nut thread could disadvantageously result in the over torqueing of the rod in the set resin, resulting in the detachment of the rod from the resin and its spinning in the bolt hole, or the twist failure of the rod.
SUMMARY OF THE INVENTION
To at least partially overcome the disadvantages of prior art dome nuts used in the mixing of resins, the applicant has considered providing a mine roof bolt assembly which includes a threaded fastener or nut which is secured to the bolt or rebar by means of pins which are adapted to shear following the application of a predetermined minimum torque.
The applicant has further appreciated that where the pin fragments wedge between the nut and bolt, the fragments may adversely score, deform or otherwise distort the bolt threads, making it difficult to subsequently secure thereto mesh screens, push-on plates, seal nuts or other safety screens used in the mine roof bolt assembly.
Accordingly, one object of the invention is to provide a threaded fastener for use in a mine roof/wall reinforcing system which is inexpensive and is easy to manufacture.
Another object of the invention is to provide a mine roof bolt assembly which is suitable for use with resin anchoring techniques, and which may be used in a variety of torque applications including, without restriction, high torque applications of more than 100 Ft. Lbs., and more preferably more than about 125 Ft. Lbs. and in which a threaded fastener is adapted for reliable deformation with minimum tolerances upon the application of a predetermined minimum torque.
Another object of the invention is to provide a pin nut construction for use in a mine roof or wall or other anchor support system which is constructed to minimize the likelihood of the wedging of pin fragments between the nut and anchor rod as the pins shear.
Another object of the invention is to provide a threaded fastener for use with a reinforcing rod in a mine roof support system which, in assembly, minimizes any deformation, scoring, scraping or otherwise adversely altering the threads of a reinforcing rod.
A further object of the invention is to provide a mine roof support system for use in hard rock applications which incorporates a threaded fastener which is secured in an initial position to a roof bolt or rebar by one and more preferably a pair of shear pins, and which upon exceeding a precise predetermined minimum torque, shear to allow the nut to be threaded onto the bolt against the rock face.
Accordingly, to at least partially overcome the disadvantages of prior art dome nuts, the applicant has proposed a roof bolt assembly for use in a bolt hole which includes an elongated anchor rod or rebar which is characterized by an externally threaded end, and a nut or other suitable fastener which is configured to threadedly engage the threaded end of the rebar. A bore is formed through the sides of each of the anchor rod and the nut. The bores formed through the nut and rebar are configured for general alignment when the nut is positioned on the rebar in a first or initial position, as for example, so that the nut may be optimally driven by a power socket or wrench so as to rotate the rod in the bolt hole. The bore formed through the nut most preferably extends into the internally threaded nut aperture and is characterized by a pair of bore segments which extend inwardly from the side surfaces of the nut. The bore segments, although not essential, are most preferably aligned with each other. A pair of retaining shear pins are insertable in a retaining position so as to locate partially within one respective bore segment, as well as within the bore formed through the rebar. The pins have a sizing selected so that when inserted in the retaining position, a minimum spacing is maintained within the rebar bore between the innermost ends of the pins which are proximate to each other. Most preferably, the space in between the inner ends of the pins is selected at least as large as twice the depth of the threads on the rebar and/or the nut, and more preferably at least greater than twice the thread Lager gap. Smaller gaps may be used, albeit with an increased risk of the fractured pin causing the nut and rebar to seize. The pins have a thickness and/or hardness selected so that when the fastener is rotated relative to the rebar under a predetermined minimum torque, the pins fracture and shear at the junction between the nut and the rebar. Most preferably, the predetermined minimum torque is selected at at least 100 Ft. Lbs., and more preferably about 125 to 150 Ft.
Lbs., however higher or lower torques may also be used. Upon fracture of the pins, the pin fragments located within the rebar bore thus may move radially inwardly towards each other so as not to interfere or otherwise wedge between the bolt and nut threads, as the nut is threaded onto the bolt.
Accordingly, in one aspect the present invention resides in a mine roof bolt assembly for use in a predrilled bolt hole comprising, an anchor member being elongated along an axis and extending from a distal end sized for insertion into said bolt hole to an externally threaded proximal end, a first bore extending through said anchor member remote from said distal end, the first bore extending in a direction generally transverse to said axis, a threaded fastener including, a body having first and second end portions, a generally cylindrical opening extending axially through said body from said first end portion to said second end portion, internal threads being provided along at least part of said opening, the internal threads sized for threaded engagement with the externally threaded proximal end of the anchor member whereby the relative rotational movement of the threaded fastener and the anchor member moves the threaded fastener axially along the anchor member, a second bore extending through said fastener from a first side of said body to a second generally opposing side, said second bore being oriented transverse to said axis and being adapted for substantial alignment with said first bore when said threaded fastener is coupled in a first position to said anchor member, the second bore including a first bore segment extending inwardly from said first side to said cylindrical opening, and a second bore segment extending inwardly from the second side to the cylindrical opening, a pair of retaining pins for limiting rotational movement of the threaded fastener from a first position relative to the anchor member up to a predetermined rotational torque, whereby when said threaded fastener in said first position, a first one of said pins being located at least partially within said first bore segment and said first bore, and the second other pin being located at least partially within said second bore segment and said first bore, and wherein adjacent innermost ends of the pins being spaced apart from each other within the first bore by a predetermined spacing.
In another aspect, the present invention resides in a roof or well bolt assembly comprising, an anchor rod being elongated along an axis and extending from a distal end to an externally threaded proximal end, a first bore extending through an axial centre of said threaded proximal end, a threaded fastener including, a body extending axially from a first end portion to a second end portion and further including at least one pair of generally planar opposing side surfaces, an internally threaded opening extending axially through said body, the internal threads of said opening being sized for complementary threaded engagement with the externally threaded proximal end of the anchor rod whereby the relative rotational movement of the threaded fastener and the anchor rod moves the threaded fastener axially along the proximal end, a second bore extending through said fastener from a first one of said planar side surfaces to the second other opposing side surface and said second bore being movable into substantial alignment with said first bore when said threaded fastener is coupled in a first position to said proximal end, including a first bore segment extending inwardly towards the axis from said first planar side to said opening, and a second bore segment extending inwardly towards the axis from the second other planar side to the opening, a pair of retaining pins for limiting relative rotational movement of the threaded fastener and the anchor rod from a first position up to a predetermined rotational torque, whereby when said threaded fastener is in said first position, a first one of said pins locates at least partially within said first bore segment and said first bore, and the second other of the pins locates at least partially within said second bore segment and said first bore, with adjacent innermost ends of the pins being spaced apart from each other in the first bore by a predetermined spacing.
In a further aspect, the present invention resides in a mine roof bolt assembly for use in a mine roof support system, the assembly comprising, a generally cylindrical anchor rod, the rod being elongated along an axis from a distal end to an externally threaded proximal end, a first bore extending through said anchor rod remote from said distal end, a threaded fastener sized for threaded engagement with the proximal end of the bolt and including, a body extending from a first end portion to a second end portion as further including at least two opposing pairs of generally planar axially extending side surfaces, a generally cylindrical opening extending axially through said body from said first end portion to said second end portion, an internal helical thread provided along at least part of said opening, the internal thread having a thread depth selected for complementary threaded engagement with the externally threaded proximal end of the anchor rod whereby the relative rotational movement of the threaded fastener and the anchor rod moves the threaded fastener axially along the rod, a second bore extending through said fastener from a first one of a first of said pair of planar sides to the second other opposing one of said first pair of sides, said second bore being oriented for substantial alignment with said first bore when said threaded fastener is coupled in a first position to said anchor rod, the second bore including a first bore segment extending inwardly from said first side open to said cylindrical opening, and a second bore segment extending inwardly from the second side open to the cylindrical opening a pair of shear pins for limiting rotational movement of the threaded fastener from a first position relative to the anchor member up to a predetermined rotational torque, each of the retaining pins including an inner end portion and an outer end portion with said fastener in the first position, a first one of said pins being located with its outer end portion disposed within said first bore segment and its inner end portion disposed within said first bore, and said second pin being located with its outer end portion within said second bore segment and its inner end portion disposed within said first bore, and whereby the adjacent inner end portions of the pins being spaced apart from each other within the first bore by a spacing selected as large as at least twice the thread depth of the internal fastener thread, and whereupon the application of the predetermined torque on one of the rod and the fastener results in the shearing of each of the pins between the respective inner and outer end portions to permit the fastener to move axially along the threaded end portions.
BRIEF DESCRIPTION OF THE DRAWINGS
Reference may now be had to the following detailed description taken together with the accompanying drawings in which:
Fig. 1 shows a conventional dome-nut type fastener fully installed as part of a mine roof support system;
Fig. 2 shows a cross-sectional view of a mine roof bolt assembly in accordance with a preferred embodiment of the invention, with the anchor rod and fastening pin nut provided in an initial position and coupled against movement relative to each other for mixing anchoring resin;
Figs. 3 to 5 show a series of schematic views of a rock structure, illustrating the initial placement of the mine roof bolt assembly to the position shown in Figure 2;
Fig. 6 shows a cross-sectional view of the mine roof bolt assembly shown in Figure 2 with the pin nut tensioned against the rock face following the application of a predetermined minimum torque to the nut;
Fig. 7 illustrates a cross-sectional view of the mine roof bolt assembly shown in Figure 6 illustrating the placement of a mesh screen and subsequent anchor nut on the anchor rod, following tightening of the fastening nut;
Fig. 8 shows an exploded end view of the anchor rod, pin nut and shear pins, used in the mine roof bolt assembly of Figure 2, illustrating the placement of the shear pins in bores formed through the nut and rod in the securing of the pin nut in the initial position;
Fig. 9 illustrates a cross-sectional view of the pin nut and rod shown in Figure 2 taken along line 9-9;
Fig. 10 shows an exploded perspective view of the rod, pin nut and anchor pins shown in Figure 8;
Fig. 11 illustrates an exploded cross-sectional view of a anchor rod, pin nut and retaining shear pins for use in the mine roof bolt assembly in accordance with a further embodiment of the invention;
Fig. 12 illustrates an exploded cross-sectional view of an anchor rod, pin nut and shear pins for use in the mine roof bolt assembly in accordance with a still further embodiment of the invention; and Fig. 13 shows a perspective view of a threaded pin nut for use with the anchor rod in accordance with a further embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Figure 1 shows a conventional rock support assembly 10 used to reinforce a rock complex 8 and which, for example, would include a mine roof. The assembly 10 includes a cast steel dome nut 12 and a steel rock bolt or reinforcing rod 14 or rebar. The reinforcing rod 14 has an externally threaded proximal end portion 16 and a distal portion 18 which is sized for placement within an elongated bolt hole 20. In the fully assembled configuration, the distal end portion 18 is inserted into the bolt hole 20 which is preferably preformed in the rock complex 8 and is secured therein by a mixed resin 22. The dome nut 12 is tightened over the threaded portion of the proximal end portion 16 of the rod 14 which projects outwardly from the bore hole to secure a reinforcing plate under tension against the rock face 25.
In installation, the bore hole 20 is drilled to a desired diameter and depth having regard to the length and diameter of the rod 14, and typically extends between about 4 and 8 feet from the rock face 25 into the rock complex 8. A number of two-part resin cartridges 24a,24b (shown in Figure 3) are slid axially into the bolt hole 20 ahead of the distal end portion 18 of the anchor rod 14. The distal end portion 18 of the rod 14 when inserted into the bolt hole 20, piercing and shredding the cartridges 24a,24b and mixing the resin 22. The steel reinforcing plate 26 is thereafter positioned over the rod 14, and the dome nut 12 threaded onto the proximal tip 28.
The dome nut 12 is rotated, turning the rod 14 while the resin 22 remains unset. Once the resin 22 sets, it encases and fixedly retains the end portion 18 of the rod 14 in the bolt hole 20. The dome nut 12 is then driven in rotation on the threaded end portion 16 of the rod 14 by a socket driver power wrench (not shown) with a minimum required torque. The treaded engagement of the proximal end portion 16 with the nut 12 causes the rock complex 8 to compress, and the threaded end portion 16 to deform the closed end of the nut 12.
Figures 2 to 10 show best a mine roof bolt assembly 30 for use in a predrilled bolt hole 20 as part of a mine roof support system in accordance with a first embodiment of the invention.
The assembly 30 incorporates a steel rock bolt or rod 14 which, as with prior art systems, is elongated along an axis A,-A1 (Figure 2) and which includes a distal end portion 18 sized for fitted insertion within the bolt hole 20, and an externally threaded proximal end portion 16. As will be described, the bolt 14 operates in conjunction with a pin nut 36 and a pair of shear pins 60a,60b to achieve mixing of onset anchoring resin 22 (Figure 5) within the bolt hole 20, and the subsequent compression of a rock complex 8.
The threaded proximal end portion 16 of the rod 14 preferably extends approximately two to six inches from the proximal endmost rod tip 28 (Figure 4). As shown best in Figures 2, 8 and 9, the rod 14 has a typical length of between about 4 and 8 feet, depending on the depth of the bolt hole 20. A through bore 34 is formed through the threaded proximal end portion 16 of the rod 14 adjacent to the proximal end tip The proximal end portion 16 is characterized by a helically extending thread 32 which has a thread depth d. The bore 34 is formed through the axial centre of the rod 14 extending in an orientation generally normal thereto.
Figures 2, 6, 8, 9 and 10 further show the pin nut 36 as comprising a high alloy steel body 3 8 having a generally flattened square configuration, and which extends from an inner end face surface 40 to an outer end face surface 42. 'The body 38 includes two opposing pairs of parallel side surfaces 44a,44b and 46a,46b. A through aperture 48 (Figure 10) extends through the axial centre of the body 38 from the inner end surface 40 to the outer end surface 42. As shown best in Figure 10, the aperture 48 is characterized by an internal thread 50. The internal threads 50 extend helically and have a thread depth d substantially equal to that of the external rod thread 32, and which is oriented for complementary threaded engagement with the external threads 32 provided on the proximal end portion 16 of the rod 14.
Figures 8 to 10 further show the body 38 as including a through bore 52 extending therethrough along the bore axis AB-AB (Figure 10) from side surface 44a to side surface 44b.
The through bore 52 has essentially the same cross-sectional diameter as through bore 34 and extends as a cylindrical bore through the axis A~-A~ in an orientation generally normal thereto.
The through bore 52 includes a first bore segment 54a which extends from the central portion of the sidewall 44a towards the axis A~-A~ to an opening into the through aperture 48, and a second coaxially aligned bore segment 54b which extends in an essential mirror arrangement from the side surface 44b towards the axis A1-A~ to and opening into an opposing side of the through aperture 48.
The through bores 34,52 are formed respectively through rod 14 and nut 36 so as to permit the coaxial alignment of the bores 34,52 in the position shown in Figure 8 when the nut 36 is threaded on to the distal endmost portion 16 of the rod 14 in a first initial position, as for example is shown in Figure 2. It is to be appreciated that the initial position at which the through bores 34,52 align is preferably selected to enable the nut 36 to be engaged and driven in rotation about the bolt axis A1-A~ by a power socket or wrench.
Figures 2 and 8 to 10 show best the assembly 30 as further including a pair of shear pins 60a,60b. In a simplified construction, the shear pins 60a,60b are formed as steel roll pins. The pins 60a,60b have a generally cylindrical shape and complementary cross-sectional size to permit their insertion in the through bores 52,34. The pins 66a,66b are manufactured having a hardness selected to fracture or shear cross-sectionally across their length upon the application of a predetermined minimum torque, and most preferably a torque of at least about 100 Ft. Lbs., and preferably about 125 to 50 Ft. Lbs.
The pins 60a,60b have a length selected to permit each pin 60a,60b to be inserted from each respective side 40a,40b of the nut 36 through a bore segment 54a,54b and so as to locate in a locking or retaining position partially within the through bore 34, as for example is shown in Figure 9. When so positioned, the pins 60a,60b each respectively locate partially within the bore segments 54a,54b and through bore 34, thereby preventing the movement of the nut 36 relative to the rod 14 and along the threaded portion 16 under torque conditions which do not exceed the predetermined minimum threshold torque at which the pins 60a,60b shear. The pins 60a,60b have a length selected so that when positioned in the retaining position shown in Figure 9, the innermost ends 62a,62b of the pins 60a,60b, respectively, which are spaced closest to each other and the axis A1-Ai are separated from each other by a spacing distance D
(Figure 9). Most preferably, the distance D separating the pins 60a,60b is selected at least as large as twice the thread depth d of the internal nut threads 50 provided along the through aperture 48 and/or the external threads 32 of the proximal end portion 16 of the rod 14. The applicant has appreciated that the provision of a spacing D between the innermost ends 62a,62b of the shear pins 60a,60b permits the fractured inner end fragments 64a,64b (Figure 3) of each pin 60a,60b to move inwardly towards each other and the axis A,-A~ following the shearing of the pins 60a,60b upon the application of the predetermined minimum torque to the nut 30. The inner movement of the fractured ends 64a,64b of the pins 60a,60b ensures that the pin fragments 64a,64b do not lodge between the threads 50 and exterior rod threads 72 where they may otherwise score the threads or deform the threads 50,32 or otherwise interfere with the threaded movement of the nut 36 along the proximal end 16 of the rod 14.
Figures 3 to 7 illustrate the installation of the mine roof rock support assembly 10 using the nut 36 and shear pins 60a,60b in accordance with a first preferred embodiment of the invention. As shown best in Figure 3, a bolt hole 20 is initially drilled to a depth of about 8 feet in the rock complex 8 which is to be reinforced. The reinforcing rod 14 is chosen from a suitable iron or steel having an axially elongated length which most preferably is two to six inches longer than the bolt hole 20.
In a preferred construction, the nut 36 is pre-coupled to the rod 14 prior to its insertion into the bore hole 20. The nut 36 is initially threaded onto the externally threaded portion 16 of the rod and moved to the initial position with the through bores 52 and 34 aligned. As shown in Figure 10, once so positioned, the pins 60a,60b are inserted laterally into the respective bore segments 54a,54b so that their outermost ends 66a,66b (Figure 9) lie flush with the nut side surfaces 44a,44b respectively, and the innermost ends 62a,62b locate within the through bore 34 with the spacing D as shown in Figure 9. Optionally, with the nut 36 so prepositioned, the reinforcing plate 26 may be slid over the distal end 18 of the rod 14 for positioning against the rock face 25. It is to be appreciated that when the nut 36 is moved to the initial position shown in Figure 2 and the pins 60a,60b are inserted into the respective bore segments 54a,54b and partially into the through bore 34 in the manner shown in Figure 9, the pins 60 act to couple the nut 36 to the end of the rod 14. Rotational forces applied to the nut 36 which do not exceed the predetermined minimum torque thus act to rotate the rod 14 about its axis A~-A1.
As with conventional systems, a number of two-part resin cartridges 24a,24b (Figure 3) are then slid into the bore hole 20, the number of which most preferably, are selected to fully grout the hole 20. Following the positioning of the resin cartridges 24a,24b, the distal end portion 18 of the rod 14 is inserted into the bore hole 20 and is forced axially therein to crush and rupture the cartridges 24a,24b, thereby releasing the resin 22. With the rod 14 fully inserted into the bolt hole 20 as for example is shown in Figures 2 and 5, the threaded end portion 16 projects from the rock complex 8 a preferred distance of between about 1.5 to 6 inches.
The fully inserted rod 14 is thereafter rotated about its axis A~-A1 by applying rotational forces to the nut 36 by means of a socket drive. The initial rotational forces on the nut 36 and the engagement of the shear pins 60a,60b in each of the through bores 52 and 34 prevent relative movement of the nut 36 along the proximal end 16 of the rod 14, rotating the rod 14 together with the nut 36 to mix the liquefied resin 22 in the bore hole 20.
Following mixing of the resin 22, rotation of the pin nut 36 is stopped and the resin 22 is permitted to set, securing the rod 14 against further rotational movement in the bolt hole 20.
Once the resin 22 has hardened, the socket drive is again activated to rotate the pin nut 36 at the predetermined minimum torque of preferably greater than about 100 Ft. Lbs. The application of the predetermined torque force on the nut 36 thus results in the pins 60a,60b shearing at the junction between each of the respective bore segments 54a,54b and the through bore 34. As a result, the portion of the pin 60a,60b which originally located in the through bore 34 remain as respective fragments 64a,64b, as for example is shown in Figures 6 and 7. The portion of the pins 60a,60b locating originally in the bore segments 54a,54b similarly remains therein as pin fragments 68a and 68b, respectively. Because the pin fragments 64a,64b move inwardly in the through bore 34 towards the axis A1-A1, the pin fragments 64a,64b do not otherwise interfere with the threaded movement of the nut 36 along the proximal end portion 16.
The nut 36 thus may thereafter be tightened against the reinforcing plate 26 and/or directly against the rock face as for example is shown in Figure 6.
Following securement of the nut 36 against the plate 26, a safety screen 72 may be positioned over the remaining projecting portion of the proximal end portion 16, and a second threaded fastener or nut 74 (or other suitable hardware) of a conventional design thereafter used to retain the safety screen 72 in place.
Although the preferred embodiment describes the prepositioning of the nut 36 prior to the insertion of the rod 14 in the bore hole 20, it is to be appreciated that the invention is not so limited. If desired, the nut 36 and pins 60a,60b could be aligned through bores 34,52 following initial placement of the rod 14 for mixing the resin 22.
Figure 11 shows an alternate possible fastener arrangement wherein like reference numerals are used to identify like components. In Figure 1 l, the through bore 34 is provided as a cylindrical bore having a reduced diameter relative to the through bore 52.
Each of the pins 60a,60b are provided with a reduced diameter end portion which is adapted to shear as inner fragments 64a,64b, and an enlarged diameter outer end portion which are adapted to shear as outer fragments 68a,68b, respectively. The inner and outer portions of the pins 60a,60b are each sized for complementary insertion within the respective through bores 34 and 52. The provision of pins 60a,60b and through bores 34,52 with portions having differing cross-sectional diameters, advantageously act as locating elements which prevent the pins 60a,60b from being inserted too far into the through bore 34, and maintain the optimum desired spacing between the inner ends 62a,62b of the pins when so inserted. In addition, the reduced diameter fragment 64a,64b portions may be formed with a desired cross-sectional thickness which is directly proportional to the amount of predetermined minimum torque requirement for shearing of the pins. The construction of Figure 11 thus is suitable for lower torque applications where, for example, the pins 60a,60b are to shear upon the application of a comparatively lower predetermined minimum torque of between about 40 and 50 Ft. Lbs.
Figure 12 illustrates an alternate possible pin 60 construction, wherein like reference numerals are used to identify like components. Each of the pins 60a,60b are provided at their outer ends 66a,66b with an enlarged diameter flattened head flange 80. The head flange 80 extends transverse to the direction of elongation of each of the pins 60 and most preferably is provided with a generally flat construction so as not to significantly project outwardly beyond the sides 44a,44b of the nut 36 where they may otherwise interfere with the placement of a socket during rotation of the nut 36 and rod 14. As with the differing diameters of the pin sections shown in Figure 11, the pin head flange 80 advantageously acts as a locating element to assist in positioning the pins 60a,60b in the through bores 52,34 with the desired spacing D
(Figure 9) maintained between the inner ends 62a,62b.
In Figure 12, each of the pins 60a,60b is further provided with a reduced diameter neck 86. The neck 86 provides a point of weakness, to facilitate shearing of the pins 60 upon the application of the predetermined minimum torque. Most preferably, the reduced diameter neck 86 is provided along the longitudinal length of the pin so as to locate at the internal thread 50/external thread 32 junction when the pins 60a,60b are fully inserted within their respective bore segments 54a,54b, with their head flange 80 engaging the nut sides 44a,44b. The reduced diameter neck portion 86, although not essential, most preferably includes a sloping edge surface 90. The sloping edge surface 90 advantageously acts as a Gaming surface upon the shearing of the pin 60, facilitating movement of the pin fragment 64a,64b (Figure 5) radially inwardly into the rod 14, and towards the axis A~-A~ upon shearing of the pins 60.
While Figures 9 to 12 illustrate the pin nut 36 as having four planar side surfaces 44a,44b,46a,46b, the invention is not so limited. If desired, other fastener shapes may also be adopted and will now become apparent. By way of non-limiting example, Figure 13 illustrates a further possible pin nut 36 construction in which the nut 36 is formed with a generally hexagonal profile having three pairs of parallel side surfaces 44a,44b,46a,46b and 124a,124b, each symmetrically spaced around the centre axis A,-A1.
Although the preferred embodiment illustrates the mine roof bolt assembly as including a pair of shear pins 60a,60b, the invention is not so limited. In a less preferred embodiment, the applicant has appreciated that a single shear pin 60 could be used to couple the nut to the rod under torque forces less than the predetermined minimum torque. In testing, however, the applicant has found that the provision of two opposedly positioned and spaced pins 60a,60b provides more accurate and reliable pin shear rates. In particular, it has been found that where a single pin is used, there may exist up to a 10% deviation in required torque forces needed to produce pin shear. This deviation, however, is lowered to less than about 3%
where two shear pins 60a,60b are provided, as for example, is shown in Figure 9.
Although the preferred embodiment describes the use of the roof bolt assembly as being used in mine roof support systems, it is to be appreciated that the assembly is equally suited for other reinforcing uses. These would include, without restriction, construction and engineering applications.
While the detailed description describes the anchor rod and pin nut as being used in the mixing of anchoring resins, it is to be understood that the present invention is equally suited for use with wedge-anchor and other such mechanically affixed rods.
Although Figure 5 illustrates the through bore 52 and through bore 34 as each comprising a cylindrical bore having the same cross-sectional diameter, the invention is not so limited. If desired, each of the through bores 34,52 could be provided with a square or other geometric cross-sectional profile, with a corresponding modification to the shear pins 60.
Although the detailed description of the invention describes and illustrates various preferred embodiments, the invention is not so limited. Many modifications and variations will now occur to persons skilled in the art. For a definition of the invention, reference may be had to the appended claims.
United States Patent No. 5,873,689 discloses a dome-nut type fastener which is characterized by a covered nut end. The nut is positioned over the threaded end of the rebar and rotated about its axial length with a power winch or socket drive. The nuts are formed such that the engagement of the covered end of the nut under initial torque forces results in the rebar rotating together with the turning of the nut. As the resin sets, resistance to the rotation of the rebar increases until the rotational force applied to the nut exceeds a critical minimum torque force.
Upon reaching the predetermined torque force, the cover portion or domed end distorts or splits by contact forces between the rebar and nut as the nut is moved along the rebar thread. The deformation allows the nut to thereafter be tightened along the rod and against the rock face.
Although the dome nut of United States Patent No. 5,873,689 achieves satisfactory deformation with low torque applications where, for example, the covered end is adapted to deform or detach at less than about 50 Ft. Lbs. or less, conventional dome nuts have proven inconsistent in providing a precise torque deformation range where higher torque applications are desired. In addition, where dome nuts are made by casting, thickness cannot precisely be controlled, resulting in imprecise control in the breakage strength of the dome. In case the dome portion is not strong enough, earlier breakage occurs, which results in under-mixing of resin. On the other hand, if the dome portion is too strong to break, the nut cannot be rotated further and therefore the bar cannot be tensioned.
Both cases are termed as failure of installation.
Various other manufacturers have proposed different torque nuts which incorporate a nut secured to the rod by means of a shear pin which fractures under higher predetermined minimum torques. United States Patent No. 4,173,918 to Piersall discloses an earlier expansion bolt construction in which a single shear pin is inserted through a bore hole formed transversely through a nut and mine roof anchor rod. The pin is used to permit rotation of the rebar about its axial length to permit the positioning of a threaded wedge anchor, and which following its placement, the predetermined minimum torque is applied to the nut, causing the pin to shear, and allowing the nut to be tightened along the rebar. The applicant has appreciated, however, that upon initial deformation of the pin of Piersall, the pin may initially be bent into an S-shape, rather than shearing cleanly. As a result, the S-shape bending of the shear pin tends to result in the pin fragments partially wedging between the internal threads of the nut and the external threads of the bolt. This in turn may result in distortion or deformation of the rebar threads, or even the wedging of the nut on the rebar in an untightened position. The wedging of the pin fragments between the bolt and nut thread could disadvantageously result in the over torqueing of the rod in the set resin, resulting in the detachment of the rod from the resin and its spinning in the bolt hole, or the twist failure of the rod.
SUMMARY OF THE INVENTION
To at least partially overcome the disadvantages of prior art dome nuts used in the mixing of resins, the applicant has considered providing a mine roof bolt assembly which includes a threaded fastener or nut which is secured to the bolt or rebar by means of pins which are adapted to shear following the application of a predetermined minimum torque.
The applicant has further appreciated that where the pin fragments wedge between the nut and bolt, the fragments may adversely score, deform or otherwise distort the bolt threads, making it difficult to subsequently secure thereto mesh screens, push-on plates, seal nuts or other safety screens used in the mine roof bolt assembly.
Accordingly, one object of the invention is to provide a threaded fastener for use in a mine roof/wall reinforcing system which is inexpensive and is easy to manufacture.
Another object of the invention is to provide a mine roof bolt assembly which is suitable for use with resin anchoring techniques, and which may be used in a variety of torque applications including, without restriction, high torque applications of more than 100 Ft. Lbs., and more preferably more than about 125 Ft. Lbs. and in which a threaded fastener is adapted for reliable deformation with minimum tolerances upon the application of a predetermined minimum torque.
Another object of the invention is to provide a pin nut construction for use in a mine roof or wall or other anchor support system which is constructed to minimize the likelihood of the wedging of pin fragments between the nut and anchor rod as the pins shear.
Another object of the invention is to provide a threaded fastener for use with a reinforcing rod in a mine roof support system which, in assembly, minimizes any deformation, scoring, scraping or otherwise adversely altering the threads of a reinforcing rod.
A further object of the invention is to provide a mine roof support system for use in hard rock applications which incorporates a threaded fastener which is secured in an initial position to a roof bolt or rebar by one and more preferably a pair of shear pins, and which upon exceeding a precise predetermined minimum torque, shear to allow the nut to be threaded onto the bolt against the rock face.
Accordingly, to at least partially overcome the disadvantages of prior art dome nuts, the applicant has proposed a roof bolt assembly for use in a bolt hole which includes an elongated anchor rod or rebar which is characterized by an externally threaded end, and a nut or other suitable fastener which is configured to threadedly engage the threaded end of the rebar. A bore is formed through the sides of each of the anchor rod and the nut. The bores formed through the nut and rebar are configured for general alignment when the nut is positioned on the rebar in a first or initial position, as for example, so that the nut may be optimally driven by a power socket or wrench so as to rotate the rod in the bolt hole. The bore formed through the nut most preferably extends into the internally threaded nut aperture and is characterized by a pair of bore segments which extend inwardly from the side surfaces of the nut. The bore segments, although not essential, are most preferably aligned with each other. A pair of retaining shear pins are insertable in a retaining position so as to locate partially within one respective bore segment, as well as within the bore formed through the rebar. The pins have a sizing selected so that when inserted in the retaining position, a minimum spacing is maintained within the rebar bore between the innermost ends of the pins which are proximate to each other. Most preferably, the space in between the inner ends of the pins is selected at least as large as twice the depth of the threads on the rebar and/or the nut, and more preferably at least greater than twice the thread Lager gap. Smaller gaps may be used, albeit with an increased risk of the fractured pin causing the nut and rebar to seize. The pins have a thickness and/or hardness selected so that when the fastener is rotated relative to the rebar under a predetermined minimum torque, the pins fracture and shear at the junction between the nut and the rebar. Most preferably, the predetermined minimum torque is selected at at least 100 Ft. Lbs., and more preferably about 125 to 150 Ft.
Lbs., however higher or lower torques may also be used. Upon fracture of the pins, the pin fragments located within the rebar bore thus may move radially inwardly towards each other so as not to interfere or otherwise wedge between the bolt and nut threads, as the nut is threaded onto the bolt.
Accordingly, in one aspect the present invention resides in a mine roof bolt assembly for use in a predrilled bolt hole comprising, an anchor member being elongated along an axis and extending from a distal end sized for insertion into said bolt hole to an externally threaded proximal end, a first bore extending through said anchor member remote from said distal end, the first bore extending in a direction generally transverse to said axis, a threaded fastener including, a body having first and second end portions, a generally cylindrical opening extending axially through said body from said first end portion to said second end portion, internal threads being provided along at least part of said opening, the internal threads sized for threaded engagement with the externally threaded proximal end of the anchor member whereby the relative rotational movement of the threaded fastener and the anchor member moves the threaded fastener axially along the anchor member, a second bore extending through said fastener from a first side of said body to a second generally opposing side, said second bore being oriented transverse to said axis and being adapted for substantial alignment with said first bore when said threaded fastener is coupled in a first position to said anchor member, the second bore including a first bore segment extending inwardly from said first side to said cylindrical opening, and a second bore segment extending inwardly from the second side to the cylindrical opening, a pair of retaining pins for limiting rotational movement of the threaded fastener from a first position relative to the anchor member up to a predetermined rotational torque, whereby when said threaded fastener in said first position, a first one of said pins being located at least partially within said first bore segment and said first bore, and the second other pin being located at least partially within said second bore segment and said first bore, and wherein adjacent innermost ends of the pins being spaced apart from each other within the first bore by a predetermined spacing.
In another aspect, the present invention resides in a roof or well bolt assembly comprising, an anchor rod being elongated along an axis and extending from a distal end to an externally threaded proximal end, a first bore extending through an axial centre of said threaded proximal end, a threaded fastener including, a body extending axially from a first end portion to a second end portion and further including at least one pair of generally planar opposing side surfaces, an internally threaded opening extending axially through said body, the internal threads of said opening being sized for complementary threaded engagement with the externally threaded proximal end of the anchor rod whereby the relative rotational movement of the threaded fastener and the anchor rod moves the threaded fastener axially along the proximal end, a second bore extending through said fastener from a first one of said planar side surfaces to the second other opposing side surface and said second bore being movable into substantial alignment with said first bore when said threaded fastener is coupled in a first position to said proximal end, including a first bore segment extending inwardly towards the axis from said first planar side to said opening, and a second bore segment extending inwardly towards the axis from the second other planar side to the opening, a pair of retaining pins for limiting relative rotational movement of the threaded fastener and the anchor rod from a first position up to a predetermined rotational torque, whereby when said threaded fastener is in said first position, a first one of said pins locates at least partially within said first bore segment and said first bore, and the second other of the pins locates at least partially within said second bore segment and said first bore, with adjacent innermost ends of the pins being spaced apart from each other in the first bore by a predetermined spacing.
In a further aspect, the present invention resides in a mine roof bolt assembly for use in a mine roof support system, the assembly comprising, a generally cylindrical anchor rod, the rod being elongated along an axis from a distal end to an externally threaded proximal end, a first bore extending through said anchor rod remote from said distal end, a threaded fastener sized for threaded engagement with the proximal end of the bolt and including, a body extending from a first end portion to a second end portion as further including at least two opposing pairs of generally planar axially extending side surfaces, a generally cylindrical opening extending axially through said body from said first end portion to said second end portion, an internal helical thread provided along at least part of said opening, the internal thread having a thread depth selected for complementary threaded engagement with the externally threaded proximal end of the anchor rod whereby the relative rotational movement of the threaded fastener and the anchor rod moves the threaded fastener axially along the rod, a second bore extending through said fastener from a first one of a first of said pair of planar sides to the second other opposing one of said first pair of sides, said second bore being oriented for substantial alignment with said first bore when said threaded fastener is coupled in a first position to said anchor rod, the second bore including a first bore segment extending inwardly from said first side open to said cylindrical opening, and a second bore segment extending inwardly from the second side open to the cylindrical opening a pair of shear pins for limiting rotational movement of the threaded fastener from a first position relative to the anchor member up to a predetermined rotational torque, each of the retaining pins including an inner end portion and an outer end portion with said fastener in the first position, a first one of said pins being located with its outer end portion disposed within said first bore segment and its inner end portion disposed within said first bore, and said second pin being located with its outer end portion within said second bore segment and its inner end portion disposed within said first bore, and whereby the adjacent inner end portions of the pins being spaced apart from each other within the first bore by a spacing selected as large as at least twice the thread depth of the internal fastener thread, and whereupon the application of the predetermined torque on one of the rod and the fastener results in the shearing of each of the pins between the respective inner and outer end portions to permit the fastener to move axially along the threaded end portions.
BRIEF DESCRIPTION OF THE DRAWINGS
Reference may now be had to the following detailed description taken together with the accompanying drawings in which:
Fig. 1 shows a conventional dome-nut type fastener fully installed as part of a mine roof support system;
Fig. 2 shows a cross-sectional view of a mine roof bolt assembly in accordance with a preferred embodiment of the invention, with the anchor rod and fastening pin nut provided in an initial position and coupled against movement relative to each other for mixing anchoring resin;
Figs. 3 to 5 show a series of schematic views of a rock structure, illustrating the initial placement of the mine roof bolt assembly to the position shown in Figure 2;
Fig. 6 shows a cross-sectional view of the mine roof bolt assembly shown in Figure 2 with the pin nut tensioned against the rock face following the application of a predetermined minimum torque to the nut;
Fig. 7 illustrates a cross-sectional view of the mine roof bolt assembly shown in Figure 6 illustrating the placement of a mesh screen and subsequent anchor nut on the anchor rod, following tightening of the fastening nut;
Fig. 8 shows an exploded end view of the anchor rod, pin nut and shear pins, used in the mine roof bolt assembly of Figure 2, illustrating the placement of the shear pins in bores formed through the nut and rod in the securing of the pin nut in the initial position;
Fig. 9 illustrates a cross-sectional view of the pin nut and rod shown in Figure 2 taken along line 9-9;
Fig. 10 shows an exploded perspective view of the rod, pin nut and anchor pins shown in Figure 8;
Fig. 11 illustrates an exploded cross-sectional view of a anchor rod, pin nut and retaining shear pins for use in the mine roof bolt assembly in accordance with a further embodiment of the invention;
Fig. 12 illustrates an exploded cross-sectional view of an anchor rod, pin nut and shear pins for use in the mine roof bolt assembly in accordance with a still further embodiment of the invention; and Fig. 13 shows a perspective view of a threaded pin nut for use with the anchor rod in accordance with a further embodiment of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Figure 1 shows a conventional rock support assembly 10 used to reinforce a rock complex 8 and which, for example, would include a mine roof. The assembly 10 includes a cast steel dome nut 12 and a steel rock bolt or reinforcing rod 14 or rebar. The reinforcing rod 14 has an externally threaded proximal end portion 16 and a distal portion 18 which is sized for placement within an elongated bolt hole 20. In the fully assembled configuration, the distal end portion 18 is inserted into the bolt hole 20 which is preferably preformed in the rock complex 8 and is secured therein by a mixed resin 22. The dome nut 12 is tightened over the threaded portion of the proximal end portion 16 of the rod 14 which projects outwardly from the bore hole to secure a reinforcing plate under tension against the rock face 25.
In installation, the bore hole 20 is drilled to a desired diameter and depth having regard to the length and diameter of the rod 14, and typically extends between about 4 and 8 feet from the rock face 25 into the rock complex 8. A number of two-part resin cartridges 24a,24b (shown in Figure 3) are slid axially into the bolt hole 20 ahead of the distal end portion 18 of the anchor rod 14. The distal end portion 18 of the rod 14 when inserted into the bolt hole 20, piercing and shredding the cartridges 24a,24b and mixing the resin 22. The steel reinforcing plate 26 is thereafter positioned over the rod 14, and the dome nut 12 threaded onto the proximal tip 28.
The dome nut 12 is rotated, turning the rod 14 while the resin 22 remains unset. Once the resin 22 sets, it encases and fixedly retains the end portion 18 of the rod 14 in the bolt hole 20. The dome nut 12 is then driven in rotation on the threaded end portion 16 of the rod 14 by a socket driver power wrench (not shown) with a minimum required torque. The treaded engagement of the proximal end portion 16 with the nut 12 causes the rock complex 8 to compress, and the threaded end portion 16 to deform the closed end of the nut 12.
Figures 2 to 10 show best a mine roof bolt assembly 30 for use in a predrilled bolt hole 20 as part of a mine roof support system in accordance with a first embodiment of the invention.
The assembly 30 incorporates a steel rock bolt or rod 14 which, as with prior art systems, is elongated along an axis A,-A1 (Figure 2) and which includes a distal end portion 18 sized for fitted insertion within the bolt hole 20, and an externally threaded proximal end portion 16. As will be described, the bolt 14 operates in conjunction with a pin nut 36 and a pair of shear pins 60a,60b to achieve mixing of onset anchoring resin 22 (Figure 5) within the bolt hole 20, and the subsequent compression of a rock complex 8.
The threaded proximal end portion 16 of the rod 14 preferably extends approximately two to six inches from the proximal endmost rod tip 28 (Figure 4). As shown best in Figures 2, 8 and 9, the rod 14 has a typical length of between about 4 and 8 feet, depending on the depth of the bolt hole 20. A through bore 34 is formed through the threaded proximal end portion 16 of the rod 14 adjacent to the proximal end tip The proximal end portion 16 is characterized by a helically extending thread 32 which has a thread depth d. The bore 34 is formed through the axial centre of the rod 14 extending in an orientation generally normal thereto.
Figures 2, 6, 8, 9 and 10 further show the pin nut 36 as comprising a high alloy steel body 3 8 having a generally flattened square configuration, and which extends from an inner end face surface 40 to an outer end face surface 42. 'The body 38 includes two opposing pairs of parallel side surfaces 44a,44b and 46a,46b. A through aperture 48 (Figure 10) extends through the axial centre of the body 38 from the inner end surface 40 to the outer end surface 42. As shown best in Figure 10, the aperture 48 is characterized by an internal thread 50. The internal threads 50 extend helically and have a thread depth d substantially equal to that of the external rod thread 32, and which is oriented for complementary threaded engagement with the external threads 32 provided on the proximal end portion 16 of the rod 14.
Figures 8 to 10 further show the body 38 as including a through bore 52 extending therethrough along the bore axis AB-AB (Figure 10) from side surface 44a to side surface 44b.
The through bore 52 has essentially the same cross-sectional diameter as through bore 34 and extends as a cylindrical bore through the axis A~-A~ in an orientation generally normal thereto.
The through bore 52 includes a first bore segment 54a which extends from the central portion of the sidewall 44a towards the axis A~-A~ to an opening into the through aperture 48, and a second coaxially aligned bore segment 54b which extends in an essential mirror arrangement from the side surface 44b towards the axis A1-A~ to and opening into an opposing side of the through aperture 48.
The through bores 34,52 are formed respectively through rod 14 and nut 36 so as to permit the coaxial alignment of the bores 34,52 in the position shown in Figure 8 when the nut 36 is threaded on to the distal endmost portion 16 of the rod 14 in a first initial position, as for example is shown in Figure 2. It is to be appreciated that the initial position at which the through bores 34,52 align is preferably selected to enable the nut 36 to be engaged and driven in rotation about the bolt axis A1-A~ by a power socket or wrench.
Figures 2 and 8 to 10 show best the assembly 30 as further including a pair of shear pins 60a,60b. In a simplified construction, the shear pins 60a,60b are formed as steel roll pins. The pins 60a,60b have a generally cylindrical shape and complementary cross-sectional size to permit their insertion in the through bores 52,34. The pins 66a,66b are manufactured having a hardness selected to fracture or shear cross-sectionally across their length upon the application of a predetermined minimum torque, and most preferably a torque of at least about 100 Ft. Lbs., and preferably about 125 to 50 Ft. Lbs.
The pins 60a,60b have a length selected to permit each pin 60a,60b to be inserted from each respective side 40a,40b of the nut 36 through a bore segment 54a,54b and so as to locate in a locking or retaining position partially within the through bore 34, as for example is shown in Figure 9. When so positioned, the pins 60a,60b each respectively locate partially within the bore segments 54a,54b and through bore 34, thereby preventing the movement of the nut 36 relative to the rod 14 and along the threaded portion 16 under torque conditions which do not exceed the predetermined minimum threshold torque at which the pins 60a,60b shear. The pins 60a,60b have a length selected so that when positioned in the retaining position shown in Figure 9, the innermost ends 62a,62b of the pins 60a,60b, respectively, which are spaced closest to each other and the axis A1-Ai are separated from each other by a spacing distance D
(Figure 9). Most preferably, the distance D separating the pins 60a,60b is selected at least as large as twice the thread depth d of the internal nut threads 50 provided along the through aperture 48 and/or the external threads 32 of the proximal end portion 16 of the rod 14. The applicant has appreciated that the provision of a spacing D between the innermost ends 62a,62b of the shear pins 60a,60b permits the fractured inner end fragments 64a,64b (Figure 3) of each pin 60a,60b to move inwardly towards each other and the axis A,-A~ following the shearing of the pins 60a,60b upon the application of the predetermined minimum torque to the nut 30. The inner movement of the fractured ends 64a,64b of the pins 60a,60b ensures that the pin fragments 64a,64b do not lodge between the threads 50 and exterior rod threads 72 where they may otherwise score the threads or deform the threads 50,32 or otherwise interfere with the threaded movement of the nut 36 along the proximal end 16 of the rod 14.
Figures 3 to 7 illustrate the installation of the mine roof rock support assembly 10 using the nut 36 and shear pins 60a,60b in accordance with a first preferred embodiment of the invention. As shown best in Figure 3, a bolt hole 20 is initially drilled to a depth of about 8 feet in the rock complex 8 which is to be reinforced. The reinforcing rod 14 is chosen from a suitable iron or steel having an axially elongated length which most preferably is two to six inches longer than the bolt hole 20.
In a preferred construction, the nut 36 is pre-coupled to the rod 14 prior to its insertion into the bore hole 20. The nut 36 is initially threaded onto the externally threaded portion 16 of the rod and moved to the initial position with the through bores 52 and 34 aligned. As shown in Figure 10, once so positioned, the pins 60a,60b are inserted laterally into the respective bore segments 54a,54b so that their outermost ends 66a,66b (Figure 9) lie flush with the nut side surfaces 44a,44b respectively, and the innermost ends 62a,62b locate within the through bore 34 with the spacing D as shown in Figure 9. Optionally, with the nut 36 so prepositioned, the reinforcing plate 26 may be slid over the distal end 18 of the rod 14 for positioning against the rock face 25. It is to be appreciated that when the nut 36 is moved to the initial position shown in Figure 2 and the pins 60a,60b are inserted into the respective bore segments 54a,54b and partially into the through bore 34 in the manner shown in Figure 9, the pins 60 act to couple the nut 36 to the end of the rod 14. Rotational forces applied to the nut 36 which do not exceed the predetermined minimum torque thus act to rotate the rod 14 about its axis A~-A1.
As with conventional systems, a number of two-part resin cartridges 24a,24b (Figure 3) are then slid into the bore hole 20, the number of which most preferably, are selected to fully grout the hole 20. Following the positioning of the resin cartridges 24a,24b, the distal end portion 18 of the rod 14 is inserted into the bore hole 20 and is forced axially therein to crush and rupture the cartridges 24a,24b, thereby releasing the resin 22. With the rod 14 fully inserted into the bolt hole 20 as for example is shown in Figures 2 and 5, the threaded end portion 16 projects from the rock complex 8 a preferred distance of between about 1.5 to 6 inches.
The fully inserted rod 14 is thereafter rotated about its axis A~-A1 by applying rotational forces to the nut 36 by means of a socket drive. The initial rotational forces on the nut 36 and the engagement of the shear pins 60a,60b in each of the through bores 52 and 34 prevent relative movement of the nut 36 along the proximal end 16 of the rod 14, rotating the rod 14 together with the nut 36 to mix the liquefied resin 22 in the bore hole 20.
Following mixing of the resin 22, rotation of the pin nut 36 is stopped and the resin 22 is permitted to set, securing the rod 14 against further rotational movement in the bolt hole 20.
Once the resin 22 has hardened, the socket drive is again activated to rotate the pin nut 36 at the predetermined minimum torque of preferably greater than about 100 Ft. Lbs. The application of the predetermined torque force on the nut 36 thus results in the pins 60a,60b shearing at the junction between each of the respective bore segments 54a,54b and the through bore 34. As a result, the portion of the pin 60a,60b which originally located in the through bore 34 remain as respective fragments 64a,64b, as for example is shown in Figures 6 and 7. The portion of the pins 60a,60b locating originally in the bore segments 54a,54b similarly remains therein as pin fragments 68a and 68b, respectively. Because the pin fragments 64a,64b move inwardly in the through bore 34 towards the axis A1-A1, the pin fragments 64a,64b do not otherwise interfere with the threaded movement of the nut 36 along the proximal end portion 16.
The nut 36 thus may thereafter be tightened against the reinforcing plate 26 and/or directly against the rock face as for example is shown in Figure 6.
Following securement of the nut 36 against the plate 26, a safety screen 72 may be positioned over the remaining projecting portion of the proximal end portion 16, and a second threaded fastener or nut 74 (or other suitable hardware) of a conventional design thereafter used to retain the safety screen 72 in place.
Although the preferred embodiment describes the prepositioning of the nut 36 prior to the insertion of the rod 14 in the bore hole 20, it is to be appreciated that the invention is not so limited. If desired, the nut 36 and pins 60a,60b could be aligned through bores 34,52 following initial placement of the rod 14 for mixing the resin 22.
Figure 11 shows an alternate possible fastener arrangement wherein like reference numerals are used to identify like components. In Figure 1 l, the through bore 34 is provided as a cylindrical bore having a reduced diameter relative to the through bore 52.
Each of the pins 60a,60b are provided with a reduced diameter end portion which is adapted to shear as inner fragments 64a,64b, and an enlarged diameter outer end portion which are adapted to shear as outer fragments 68a,68b, respectively. The inner and outer portions of the pins 60a,60b are each sized for complementary insertion within the respective through bores 34 and 52. The provision of pins 60a,60b and through bores 34,52 with portions having differing cross-sectional diameters, advantageously act as locating elements which prevent the pins 60a,60b from being inserted too far into the through bore 34, and maintain the optimum desired spacing between the inner ends 62a,62b of the pins when so inserted. In addition, the reduced diameter fragment 64a,64b portions may be formed with a desired cross-sectional thickness which is directly proportional to the amount of predetermined minimum torque requirement for shearing of the pins. The construction of Figure 11 thus is suitable for lower torque applications where, for example, the pins 60a,60b are to shear upon the application of a comparatively lower predetermined minimum torque of between about 40 and 50 Ft. Lbs.
Figure 12 illustrates an alternate possible pin 60 construction, wherein like reference numerals are used to identify like components. Each of the pins 60a,60b are provided at their outer ends 66a,66b with an enlarged diameter flattened head flange 80. The head flange 80 extends transverse to the direction of elongation of each of the pins 60 and most preferably is provided with a generally flat construction so as not to significantly project outwardly beyond the sides 44a,44b of the nut 36 where they may otherwise interfere with the placement of a socket during rotation of the nut 36 and rod 14. As with the differing diameters of the pin sections shown in Figure 11, the pin head flange 80 advantageously acts as a locating element to assist in positioning the pins 60a,60b in the through bores 52,34 with the desired spacing D
(Figure 9) maintained between the inner ends 62a,62b.
In Figure 12, each of the pins 60a,60b is further provided with a reduced diameter neck 86. The neck 86 provides a point of weakness, to facilitate shearing of the pins 60 upon the application of the predetermined minimum torque. Most preferably, the reduced diameter neck 86 is provided along the longitudinal length of the pin so as to locate at the internal thread 50/external thread 32 junction when the pins 60a,60b are fully inserted within their respective bore segments 54a,54b, with their head flange 80 engaging the nut sides 44a,44b. The reduced diameter neck portion 86, although not essential, most preferably includes a sloping edge surface 90. The sloping edge surface 90 advantageously acts as a Gaming surface upon the shearing of the pin 60, facilitating movement of the pin fragment 64a,64b (Figure 5) radially inwardly into the rod 14, and towards the axis A~-A~ upon shearing of the pins 60.
While Figures 9 to 12 illustrate the pin nut 36 as having four planar side surfaces 44a,44b,46a,46b, the invention is not so limited. If desired, other fastener shapes may also be adopted and will now become apparent. By way of non-limiting example, Figure 13 illustrates a further possible pin nut 36 construction in which the nut 36 is formed with a generally hexagonal profile having three pairs of parallel side surfaces 44a,44b,46a,46b and 124a,124b, each symmetrically spaced around the centre axis A,-A1.
Although the preferred embodiment illustrates the mine roof bolt assembly as including a pair of shear pins 60a,60b, the invention is not so limited. In a less preferred embodiment, the applicant has appreciated that a single shear pin 60 could be used to couple the nut to the rod under torque forces less than the predetermined minimum torque. In testing, however, the applicant has found that the provision of two opposedly positioned and spaced pins 60a,60b provides more accurate and reliable pin shear rates. In particular, it has been found that where a single pin is used, there may exist up to a 10% deviation in required torque forces needed to produce pin shear. This deviation, however, is lowered to less than about 3%
where two shear pins 60a,60b are provided, as for example, is shown in Figure 9.
Although the preferred embodiment describes the use of the roof bolt assembly as being used in mine roof support systems, it is to be appreciated that the assembly is equally suited for other reinforcing uses. These would include, without restriction, construction and engineering applications.
While the detailed description describes the anchor rod and pin nut as being used in the mixing of anchoring resins, it is to be understood that the present invention is equally suited for use with wedge-anchor and other such mechanically affixed rods.
Although Figure 5 illustrates the through bore 52 and through bore 34 as each comprising a cylindrical bore having the same cross-sectional diameter, the invention is not so limited. If desired, each of the through bores 34,52 could be provided with a square or other geometric cross-sectional profile, with a corresponding modification to the shear pins 60.
Although the detailed description of the invention describes and illustrates various preferred embodiments, the invention is not so limited. Many modifications and variations will now occur to persons skilled in the art. For a definition of the invention, reference may be had to the appended claims.
Claims (20)
1. A mine roof bolt assembly for use in a predrilled bolt hole comprising, an anchor member being elongated along an axis and extending from a distal end sized for insertion into said bolt hole to an externally threaded proximal end, a first bore extending through said anchor member remote from said distal end, the first bore extending in a direction generally transverse to said axis, a threaded fastener including, a body having first and second end portions, a generally cylindrical opening extending axially through said body from said first end portion to said second end portion, internal threads being provided along at least part of said opening, the internal threads sized for threaded engagement with the externally threaded proximal end of the anchor member whereby the relative rotational movement of the threaded fastener and the anchor member moves the threaded fastener axially along the anchor member, a second bore extending through said fastener from a first side of said body to a second generally opposing side, said second bore being oriented transverse to said axis and being adapted for substantial alignment with said first bore when said threaded fastener is coupled in a first position to said anchor member, the second bore including a first bore segment extending inwardly from said first side to said cylindrical opening, and a second bore segment extending inwardly from the second side to the cylindrical opening, a pair of retaining pins for limiting rotational movement of the threaded fastener from a first position relative to the anchor member up to a predetermined rotational torque, whereby when said threaded fastener in said first position, a first one of said pins being located at least partially within said first bore segment and said first bore, and the second other pin being located at least partially within said second bore segment and said first bore, and wherein adjacent innermost ends of the pins being spaced apart from each other within the first bore by a predetermined spacing.
2. The mine roof bolt assembly as claimed in claim 1 wherein said anchor member comprises a generally cylindrical metal rod, said first bore extending radially inwardly through an axial centre of said rod.
3. The mine roof bolt assembly as claimed in claim 2 wherein each of said retaining pins comprise a metal roll pin.
4. The mine roof bolt assembly as claimed in claim 1 further comprising at least one settable resin cartridge sized for insertion in said bolt hole, whereby said predetermined torque comprises a torque selected less than a torque required to rotate said anchor member in said bolt hole following the setting of said resin.
5. The mine roof bolt assembly as claimed in claim 3 wherein said first and second bores comprise generally cylindrical bores having substantially the same cross-sectional diameter.
6. The mine roof bolt assembly as claimed in claim 5 wherein said first bore extends through said threaded proximal end.
7. The mine roof bolt assembly as claimed in claim 1 wherein said externally threaded portion is characterized by helically extending threads having a selected thread depth, and said predetermined spacing is at least twice as large as said selected thread depth.
8. The mine roof bolt assembly as claimed in claim 6 wherein each of said pins includes an inner portion and an outer portion, and wherein with said fastener in said first position, the first pin outer portion locating in said first bore segment and the first pin inner portion disposed within the first bore, the second pin outer portion locating in said second bore segment with the second pin inner portion disposed in the first bore, said internal threads having a thread depth selected for complementary threaded engagement with said externally threaded portion, and said predetermined spacing being at least about twice as large as said thread depth, whereby the application of said predetermined rotational torque on the fastening member results in the shearing of the inner portions of each of the pins from the respective outer portions to permit the fastener to move axially along the anchor rod.
9. The mine roof bolt assembly as claimed in claim 1, wherein the anchor member comprises a generally cylindrical rod and said fastener comprises a pin nut, each of the rod and the nut being formed from metals selected from the group consisting of steel, iron and alloys thereof.
10. A roof or well bolt assembly comprising, an anchor rod being elongated along an axis and extending from a distal end to an externally threaded proximal end, a first bore extending through an axial centre of said threaded proximal end, a threaded fastener including, a body extending axially from a first end portion to a second end portion and further including at least one pair of generally planar opposing side surfaces, an internally threaded opening extending axially through said body, the internal threads of said opening being sized for complementary threaded engagement with the externally threaded proximal end of the anchor rod whereby the relative rotational movement of the threaded fastener and the anchor rod moves the threaded fastener axially along the proximal end, a second bore extending through said fastener from a first one of said planar side surfaces to the second other opposing side surface and said second bore being movable into substantial alignment with said first bore when said threaded fastener is coupled in a first position to said proximal end, including a first bore segment extending inwardly towards the axis from said first planar side to said opening, and a second bore segment extending inwardly towards the axis from the second other planar side to the opening, a pair of retaining pins for limiting relative rotational movement of the threaded fastener and the anchor rod from a first position up to a predetermined rotational torque, whereby when said threaded fastener is in said first position, a first one of said pins locates at least partially within said first bore segment and said first bore, and the second other of the pins locates at least partially within said second bore segment and said first bore, with adjacent innermost ends of the pins being spaced apart from each other in the first bore by a predetermined spacing.
11. The bolt assembly as claimed in claim 10 wherein said first bore extends in a direction generally transverse to said axis.
12. The bolt assembly as claimed in claim 11 wherein each of the first and second bores are generally cylindrical and have substantially equal cross-sectional diameters, and said pins each comprise a generally cylindrical roll pin.
13. The bolt assembly as claimed in claim 12 wherein the first pin has a length selected marginally greater than a length of said first bore segment, and the second pin has a length selected marginally greater than a length of said second bore segment.
14. The bolt assembly as claimed in claim 10 wherein each of said pins comprises shear pins having a first diameter portion and a smaller second diameter portion.
15. The bolt assembly as claimed in claim 10 wherein said externally threaded proximal end comprises helically extending threads, and said predetermined spacing is selected at least twice the radial thread depth of said threads.
16. A mine roof bolt assembly for use in a mine roof support system, the assembly comprising, a generally cylindrical anchor rod, the rod being elongated along an axis from a distal end to an externally threaded proximal end, a first bore extending through said anchor rod remote from said distal end, a threaded fastener sized for threaded engagement with the proximal end of the bolt and including, a body extending from a first end portion to a second end portion as further including at least two opposing pairs of generally planar axially extending side surfaces, a generally cylindrical opening extending axially through said body from said first end portion to said second end portion, an internal helical thread provided along at least part of said opening, the internal thread having a thread depth selected for complementary threaded engagement with the externally threaded proximal end of the anchor rod whereby the relative rotational movement of the threaded fastener and the anchor rod moves the threaded fastener axially along the rod, a second bore extending through said fastener from a first one of a first of said pair of planar sides to the second other opposing one of said first pair of sides, said second bore being oriented for substantial alignment with said first bore when said threaded fastener is coupled in a first position to said anchor rod, the second bore including a first bore segment extending inwardly from said first side open to said cylindrical opening, and a second bore segment extending inwardly from the second side open to the cylindrical opening a pair of shear pins for limiting rotational movement of the threaded fastener from a first position relative to the anchor member up to a predetermined rotational torque, each of the retaining pins including an inner end portion and an outer end portion with said fastener in the first position, a first one of said pins being located with its outer end portion disposed within said first bore segment and its inner end portion disposed within said first bore, and said second pin being located with its outer end portion within said second bore segment and its inner end portion disposed within said first bore, and whereby the adjacent inner end portions of the pins being spaced apart from each other within the first bore by a spacing selected as large as at least twice the thread depth of the internal fastener thread, and whereupon the application of the predetermined torque on one of the rod and the fastener results in the shearing of each of the pins between the respective inner and outer end portions to permit the fastener to move axially along the threaded end portions.
17. The mine roof bolt assembly as claimed in claim 16 wherein said first bore extends through an axial center of the rod in an orientation substantially normal to the axis, and each of the shear pins further comprising a locating member to assist in positioning the pins within the first and second bores with the adjacent inner end portions a desired spacing from each other.
18. The mine roof bolt assembly as claimed in claim 17 wherein the first bore extends through the threaded proximal end.
19. The mine roof bolt assembly as claimed in claim 17 wherein each of the first and second bores are generally cylindrical and have substantially equal cross-sectional diameters, and said pins each comprise a generally cylindrical roll pin.
20. The mine roof bolt claimed in claim 17 wherein the inner end portion of each of said pins has a first cross-sectional diameter, and the outer end portion of each of said pins has a second cross-sectional diameter different from said first.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2439397 CA2439397A1 (en) | 2003-08-11 | 2003-08-11 | Mine roof bolt assembly |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2439397 CA2439397A1 (en) | 2003-08-11 | 2003-08-11 | Mine roof bolt assembly |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2439397A1 true CA2439397A1 (en) | 2005-02-11 |
Family
ID=34120738
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2439397 Abandoned CA2439397A1 (en) | 2003-08-11 | 2003-08-11 | Mine roof bolt assembly |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2439397A1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7632045B2 (en) | 2006-04-18 | 2009-12-15 | Mansour Mining Inc. | Detachable anchor bolt mixing head for use in mine roof support systems and method of using same |
| US20150233244A1 (en) * | 2014-02-18 | 2015-08-20 | Mine Support Products (Pty) Ltd | Rock bolt |
-
2003
- 2003-08-11 CA CA 2439397 patent/CA2439397A1/en not_active Abandoned
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7632045B2 (en) | 2006-04-18 | 2009-12-15 | Mansour Mining Inc. | Detachable anchor bolt mixing head for use in mine roof support systems and method of using same |
| US20150233244A1 (en) * | 2014-02-18 | 2015-08-20 | Mine Support Products (Pty) Ltd | Rock bolt |
| EP2913477A3 (en) * | 2014-02-18 | 2016-07-13 | Mine Support Products (pty) Ltd | Rock bolt |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US7632045B2 (en) | Detachable anchor bolt mixing head for use in mine roof support systems and method of using same | |
| US7093402B2 (en) | Coupling device | |
| US8899883B2 (en) | Anchor tendon with selectively deformable portions | |
| US6270290B1 (en) | Tensionable cable bolt | |
| AU580140B2 (en) | Deformed bar for adhesion and applying tension | |
| EP2034197A1 (en) | Fixation device | |
| US20140105690A1 (en) | Tension Cable Bolt | |
| AU725299B2 (en) | Low torque threaded fastener and mine roof support system using such a fastener | |
| CA2089609C (en) | Rockbolt | |
| CA2072852C (en) | Threaded fastener, method of fabrication thereof and method of supporting a mine roof using such a fastener | |
| AU1546602A (en) | Cable bolt with mixing delay device | |
| CA2452271C (en) | An improved apparatus for ground support | |
| US20040168397A1 (en) | Shear connector | |
| CA2506342A1 (en) | Yieldable cone bolt for use in small diameter bolt holes and method of installing the same | |
| CA2439397A1 (en) | Mine roof bolt assembly | |
| CA2194818C (en) | Cable bolt head | |
| CA2504058A1 (en) | Mine roof support system having torque indicating washer | |
| EP4055253A1 (en) | Visual indicator for correct torsion of a rock bolt | |
| CA2444192A1 (en) | Mine roof bolt assembly and fastener for use therein | |
| WO2005106201A1 (en) | Locking member, a nut break-out device and a nut break-out system containing same | |
| AU2004202913B2 (en) | Rock Bolt Assembly | |
| EP0154466A1 (en) | Bolt anchor | |
| WO2004063531A1 (en) | Rock bolt re-tensioning | |
| GB2388124A (en) | Reinforcing bar coupling | |
| CA1284734C (en) | Torque limited threaded locking fastener and a method for setting it to form an assembly |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Dead |