Note: Descriptions are shown in the official language in which they were submitted.
2~78~
ROOF BOLT WITH PLASTIC SLEEVE AND MECHANICAL ANCHOR
BACKGROUND OF THE INVENTION
l. Field of the Invention
This invention relates to roof bolts and, more
particularly, to a roof bolt which is positioned in a bore
hole drilled in a rock formation in a mine roof and which
is held in place within the bore by both a mechanical
anchor and a quick-setting resin.
2. bescription of the Prior Art
It is a well-established practice in underground
mining work, such as coal mining, tunnel excavation or the
like, to reinforce or support the mine roof to prevent rock
falls or cave-ins. A common means presently used to
support mine roofs is an elongated bar which is inserted
into the rock formation above the mine roof in a bore hole
and which is securely fixed to the bo~e hole by an
anchoring means such as a mechanical anchor, a quick-
setting resin which surrounds the end of the bolt within
the hole, or both. The roof bolt, placed under the
tension, is used to hold a metal support plate in close
engagement with the roof.
The roof ~olt described in U.S. Patent No. 4,655,645
combines the features of a mechanical anchor and resin
bonding but also provides positive and complete mixing of
the resin components by an additional mixing mechanism.
This arrangement is relatively inexpensive and easy to
manufacture, forces the resin upwards along the bolt during
mixing, more violently mixes the resin for a shorter mix
time, and eliminates the use of a two-position coupling or
delay mechanism. While this arrangement functions well in
hard rock-like formations, it has been found to be less
effective in soft strata. Further, at times even this type
of mine roof bolt does not properly set in the roc~
formation because of slippaqe of the bolt. This problem
increases as a function of increased bore hole diameter
since the volume of the annulus between the roof bolt and
20~7~7
bore hole wall increases accordingly because, I believe, of
greasing the interface between the mechanical anchor and
bore hole wall.
A bail-type mechanical anchor, such as disclosed in
U.S. Patents Nos. 2,952,129; 4,483,645; 4,100,748; and
4,861,148 is typicially used in the soft type strata are
used. ~owever, when the bail-type anchor is used in
conjunction with a quick setting resin a phenomenon called
lockup often occurs. Specifically, lockup occurs when the
mine roof bolt is placed in a mine roof bore and rotated,
generally by a bolting machine, and at a certain point the
tension does not increase for a given increase of torque
applied to the bolt. Further, after the bolting machine is
removed the bolt tends to spring back or rotate in an
opposite direction. I believe this is caused by the resin
greasing the interface between the mechanical anchor and
the mine roof bore wall. This allows the leaves or
radially outwardly expandable sections of the shell to
slide down the bore hole with the threaded plug or wedge as
the bolt is rotated until the plug or wedge reach a non-
threaded portion of the roof bolt or a stopping mechanism
such as a jam nut. Thus, the result is a less than
satisfactory arrangement since the mine roof may not be
properly supported by the roof bolts because of the lockup
condition.
It is an object of the present invention to provide a
roof bolt arrangement that has a mechanical anchor, yet
does not exhibit lockup when used in conjunction with a
quick-setting resin.
It is a further object of the present invention to
provide a roof bolt arrangement requiring less resin than
is presently being used in resined mine roof anchor
assemblies.
It is still a further object of the present invention to
provide an improved roof bolt that can be used with or
without resin.
SUMMARY OF THE INVENTION
One embodiment of my invention is a mine roof anchor
2~3.~7
assembly including an elongated bolt having a first end and
a second end where the bolt is threaded for a portion of
its length at the second end. The threaded portion of the
bolt carries a mechanical anchor which includes an
expansion member having radially outwardly expandable
sections and a wedge member threadedly engaged with the
elongated bolt between the radially expandable sections.
The wedge forces the radially expandable sections outwardly
with respect to the longitudinal movement thereof as the
bolt is rotated. A section of the threaded portion extends
below the mechanical anchor toward the first end. The bolt
receives a frangible hollow sleeve which is positioned
about the threaded portion extending below the mechanical
anchor toward the first end. The frangible sleeve can be a
shell made of plastic, such as polyurethane, and have a
thickness of 0.075 inches.
The anchor bolt assembly can further include a
stopping element, such as a jam nut, attached to the bolt
below the mechanical anchor toward the first end. The
frangible sleeve is sandwiched between the stopping element
and the mechanical anchor. The stopping element can
include a plurality of axial passages whereby a resin can
pass from the second end of the bolt downwardly towards the
first end of the bolt.
When the anchor bolt assembly is used with a quick-
setting resin cartridge inserted in a mine roof opening,
the stopping element can also include a resin mixing
element, such as a coil, attached to the bolt and
positioned below the stopping element toward the first end.
The anchor assembly can also include an elongated bolt
having a head at one end and threaded for a portion of its
length at its other end. A bail-type mechanical anchor is
carried at the threaded end. The bail-type mechanical
anchor includes an expansion member and a wedge member.
The expansion member has diametrically opposed parts and a
connecting member having spaced legs and a base. Lower
ends of each of the legs are connected to a respective
upper portion of an opposed part. The base is joined to
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2 ~ 8 7
the upper ends of the legs. The wedge member is threadedly
engaged with the elongated bolt between the legs of the
connecting member and the opposed parts of the expansion
member. The wedge will force the opposed parts outwardly
with respect to longitudinal movement thereof as the bolt
is rotated.
Another embodiment of my invention includes an elongated
bolt having a head at one end and threaded for a portion of
its length at the other end, a mechanical expansion anchor
including a spreader on the threaded end with a section of
the threaded portion extending below the mechanical
expansion anchor, and a frangible hollow sleeve received by
the bolt and positioned about the threaded portion
extending below the mechanical expansion anchor toward the
head. This embodiment further includes a frangible support
element attached to the bolt and sandwiched between the
frangible sleeve and the mechanical expansion anchor, and a
stopping element attached below the mechanical anchor
toward the head, where the frangible sleeve is sandwiched
between the stopping element and the frangible support
element.
A further embodiment of my invention incudes an
elongated shaft having a first end and a shaft second end,
and a bail-type anchor on the threaded second end of the
shaft, with a section of the threads extending below the
bail-type mechanical anchor toward the first end. A
frangible hollow sleeve is received by the shaft and
positioned about the threaded section extending below the
bail-type anchor toward the first end. A stopping element
is attached to or is formed on the shaft below the bail-
type mechanical anchor toward the first end, with the
frangible sleeve sandwiched between the stopping element
and the mechanical anchor. A coupling is attached to the
shaft first end and a shaft having a head at one end is
attached to the coupling at its other end.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a side elevational view, partially in
section, showing a rock formation having a bore hole with a
2~3~7
first embodiment of a roof bolt assembly in accordance with
the present invention in place just prior to rupture of a
resin cartridge;
FIG. 2 is a side elevational view similar to FIG. 1
showing the roof bolt assembly as it is finally installed
in the bore hole:
FIG. 3 is a side elevational view, partially in section,
showing a rock formation having a bore hole with a second
embodiment of a roof bolt assembly in accordance with the
present invention in place just prior to rupture of a resin
cartridge;
FIG. 4 is a side elevational view similar to FIG. 3
showing the second embodiment of the roof bolt assembly as
it is finally installed in the bore hole:
FIG. 5 is a side elevational view, partially in section,
showing a rock formation having a bore hole with a third
embodiment of a roof bolt assembly in accordance with the
present invention in place iust prior to rupture of a resin
cartridge: and
~IG. 6 is a side elevational view similar to FIG. 5
showing the third embodiment of the roof bolt assembly as
it is finally installed in the bore hole.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIGS. 1 and 2, there is shown a first
embodiment of a roof bolt assembly, generally designated
10, in accordance with the present invention. The roof
bolt 10 is an elongated member often reaching lengths of
three to eight feet or longer. The roof bolt 10 is
positioned within a bore hole 12 which is drilled upwardly
through a generally horizontal mine roof surface 14 and
into the rock formation 16 above the mine entry.
A quick-setting resin cartridge 18 is positioned in
the blind or upward end of the bore hole 12. The resin
cartridge 18 is basically an enclosed, elongated tube which
includes two components, an active agent 20 and a reaction
agent 22 of a resin grouting mix, separated by a membrane
24. The active agent of a commonly available resin
cartridge includes a polyester resin as the major
~3a7!,7
component. The reaction agent is typically a catalyst or
curing or hardening agent. The two components 20, 22 of
the resin cartridge 18 remain in a semi-liquid or
thixotropic phase until mixed, whereupon the resin begins
to quickly solidify. Curing and solidification continue
unt.1 an extremely strong bond is formed by the resin
grout. While reference has been made to a ~resin~
cartridge, it is to be understood that any of the resin
systems, adhesive systems, cementitious systems, grouting
systems, and the like which are known and used in the art
can be used in the present invention, and are meant to be
encompassed by the term ~resin~. However, polyester or
other resin cartridges are preferred for use with the roof
bolt assembly 10.
The roof bolt assembly 10 includes an elongated bolt
shaft 26 with a head 28 on a first end and with threads 30
at a second end. The head 28 of a mine roof bolt can be
any shape, but is typically square. A two-faced friction
reducing washer 31, such as a hardened steel washer, is
positioned immediately above and rests upon the head 28.
A bail-type mechanical anchor 33 is carried on the
threaded end 30 of the bolt shaft 26. The bail-type
mechanical anchor 33 includes a two-part expansible
anchoring shell 34 and a wedged-shaped nut 36. The shell
34, which normally is generally circular in transverse
section and of a diameter only slightly less than that of
the bore hole 12, has two diametrically-opposed parts or
radially outwardly expansible sections 38. Each part 38 is
formed as a longitudinal segment of a cylinder and has
upwardly divergent tapering longitudinal plane edges 40.
The smaller upper ends of the two parts 38 of the
shell 34 are connected together by a band-like connecting
member 50 that is substantially U-shaped. The connecting
member 50 has two legs 52, which are normally generally
parallel to each other and extend longitudinally of the
shell 34, and a base 54, which extends transversely of the
shell 34 somewhat above the upper ends of the two shell
parts 38. The legs 52 of the connecting member 50 may be
2~3'~
secured to the shell parts 38 in any appropriate manner,
but preferably they should be pinned and crimped as is well
known in the art. The curved outer surfaces of the shell
parts 38 are preferably provided with a plurality of step-
like circumferential serrations 56 for embedding andgripping engagement with the side walls of the bore hole
12. Vertical serrations 57 are provided on the curved
outer surfaces of the shell parts 38 below the serrations
56. The wedge 36 is threaded on the threads 30 of the bolt
shaft 26 and is disposed between the two shell parts 38 and
has plane wedging surfaces 58 complementary to and in
mutually-wedging engagement with each pair of the opposed
side plane edges 40 of the shell parts 38. The exterior
surfaces of the wedge 36 between its wedging surfaces 58
are arcuate to correspond to the circular periphery of the
shell 34. At its larger end, the wedge 36 has longitudinal
channels or grooves 60 to accommodate the legs 52 of the
connecting member 50 passing thereby.
A plastic sleeve 61 in the shape of a hollow
cylindrical shell is received by the bolt and positioned
about a threaded portion of the threaded end extending
below the mechanical anchor toward the head 28. The outer
diameter of the sleeve 61 is slightly less than the outer
diameter of the curved outer surfaces of the shell parts 38
so that a top edge 62 of the sleeve 61 can abut against
bottom edges 63 of the shell parts 38. The diameter and
length of the sleeve are substantially greater than the
sleeve thickness, for example in a 10 to 1 ratio. A bottom
edge 64 of the sleeve 60 abuts against a top surface 66 of
a stopping element or jam nut 68 so that the sleeve 61 is
sandwiched between the mechanical anchor 33 and the jam nut
68.
The jam nut 68, which is well known in the art, is a
hexagonally shaped nut having a threaded bore and is
threadably received by the threads 30. A jam nut bottom
edge abuts against an interface formed between the threaded
portion and unthreaded portion of the bolt shaft 26.
The roof bolt 10 further includes a separate mechanism
- 7 -
7 X
connected thereto for mixing the two components 20, 22 of
the resin cartridge 18 after it has been ruptured.
Specifically, there is shown in FIGS. 1 and 2, one type of
mixing element, namely a helical coil 80 which is separate
from and surrounds the bolt shaft 26, and extends downward
in the annulus between the rock formation 16 and the bolt
shaft 26. An upper end 82 of the helical coil 80 is
connected to the bottom of the threads 30. In the
embodiment shown in FIG. 1, the upper end 82 of the helical
coil 80 forms a loop which surrounds and is loosely crimped
below the threads 30 below the jam nut 68. However, the
coil upper end 82 may also be welded to the jam nut 68. A
lower end 84 of the helical coil 80 may be affixed securely
to bolt shaft 26 or may hang freely in the annulus between
the rock formation 16 and the bolt shaft 26. It should be
noted that the jam nut 68 may be eliminated and the
stopping element for the sleeve 61 can be the upper end 82
of the coil 80.
The operation of roof bolt assembly 10 in accordance
with the present invention can be explained with reference
to the figures. Initially a resin cartridge 18 is placed
in the bore hole 12 above the roof bolt 10 and then the
roof bolt 10 is advanced upwardly into the bore hole 12.
FIG. 1 shows the arrangement just prior to the rupture of
the resin cartridge 18. The roof bolt 10 then continues to
advance into the bore hole 12 and ruptures the resin
cartridge 18. At the same time, the components 20, 22 of
the ruptured resin cartridge 18 are forced downward from
the upward displacement of the anchor assembly.
Th~ bolt head 28 and, hence, the entire bolt shaft 26,
is rotated continuously in one direction and is drawn
upward until the support plate 32 and the washer 31 are
compressed between the mine roof surface 14 and the bolt
head 28. Continued rotation draws the bail-type anchor 33
downward against the abutting sleeve 61 and forces the
opposed parts radially outward into an initial engagement
with the bore hole wall and causes an upper end of the bolt
shaft 26 to come into contact with the base 54 of the
~3 i 8
connecting member 50. The sleeve 61 prevents slippage
which would otherwise occur because of the initial
lubricating effect of the resin about the bore hole.
Thereafter, the wedge 36 is further drawn down, independent
of the expansion shell 34, and continues to force the shell
parts 38 outwardly into engagement with the bore hole wall
and cause the sleeve 61 to fail by crushing at a first
breaking point force. Further rotation causes the
connecting member 50 to subsequently break as shown in FIG.
2. Rotation of the roof bolt 10 is continued until the
proper tensioning force is reached. At times the wedge 36
will continue to travel down all the threaded portion so as
to the bolt 10 is rotated and stop against the jam nut top
surface 66.
While the roof bolt 10 is being rotated, the helical
coil 80 is simultaneously being rotated. The resin
components 20, 22 were previously forced downwardly to the
vicinity of the helical coil 80 when the bolt 10 was
advanced upwardly, and the action of rotating the helical
coil 80 violently mixes resin components 20, 22 together
and continually urges or forces the resin components 20, 22
upwardly. It is thus insured that the resin components are
thoroughly mixed together and completely fill the annulus
surrounding the upper portion of the roof bolt 10. The
final curing of the resin to its ultimate rigid condition
occurs after the rotation of the bolt 10 has stopped.
Ideally, a substantial portion of the helical coil 80 will
be embedded in the resin, but the exact proportion so
embedded will depend on the resin cartridge 18~ the
porosity of the surrounding rock formation 16 and the exact
diameter of the bore hole 12 and the bore shaft 26. The
configuration of the roof bolt 10 in place with the cured
resin 90 surrounding is shown in FIG. 2.
Actual mine roof anchor systems have been made and
installed in accordance with the above described
embodiment. Specifically, these anchor systems included
either 0.75~ or 1.00~ diameter bolts and polyurethane
plastic sleeves. The sleeves were approximately 1.25~ -
_ g _
2 Q ~ ~ ~ J
1.50~ in length, 1.125~ in outside diameter and a wallthickness of 0.075~. None of the mine roof anchor systems
tested experienced lock-up nor did any of the systems
become spinners where the opposed parts do not engage in
the roof bore wall.
Further, it is believed that the frangible sleeve can
be used in connection with any type of mechanical anchor
having radially outwardly expandable sections, such as for
example the expansion shell gripping fingers disclosed in
U.S. Patent No. 4,655,64S, where the frangible sleeve would
be sandwiched between the bottom of the expansion shell and
the upper end of the helical coil.
Referring now to FIGS. 3-4 there is shown a second
embodiment of a roof bolt assembly, generally designated
110, made in accordance with the present invention. The
roof bolt 110 is an elongated member similar to roof bolt
10. The roof bolt 110 is positioned within a bore hole 112
which is drilled through a mine roof surface 114 and into
the rock formation 116 above the mine entry.
A quick-setting resin cartridge 118 which is similar to
the resin cartridge 18, is positioned in the blind or
upward end of the bore hole 112. The resin cartridge 118
is basically an enclosed, elongated tube which includes two
components, an active agent 120 and a reaction agent 122 of
a resin grouting mix, separated by a membrane 124.
The roof bolt assembly 110 includes an elongated bolt
shaft 112 with a head 128 on one end and with threads 130
at the other end. A two-faced friction reducing washer
129, such as a hardened steel washer is positioned
immediately above and rests on the head 128. An expansion
anchor 131 comprising a tapered nut or spreader 132, having
therein an internally threaded axial bore, and an expansion
shell or gripping member 134, is carried on the threaded
end 130 of the bolt shaft 126. The gripping member 134 is
formed with a circular collar 136 at its base and with a
plurality of radially expandable gripping fingers 138
extending integrally therefrom. Each gripping finger 138
is provided on its external surface with some type of
-- 10 --
2~737
.
gripping or engagement mechanism, such as the plurality of
gripping teeth 140 as shown. The gripping fingers 138 are
preferably spaced apart from one another by a narrow
vertical slot 142. Further, the outer diameter of the
gripping member 134 is greater than the diameter of the
bore hole 112 so that the gripping member 134 can be held
in place when it is positioned into the bore hole 112.
The spreader 132 has a downwardly tapered configuration
with an enlarged upper end and a smaller lower end. A
portion of the inner surface of each gripping finger 138
abuts the tapered outer surface of the spreader 132. An
elongated key 143 on the outer surface of the spreader 132
and integral therewith is positioned within the vertical
slot 142 between an adjacent pair of gripping fingers 138
and helps to keep the gripping member 134 from rotating
along with the spreader 132 when the bolt shaft 126 is
rotated.
A first support 144, such as a hexagonal stamped support
nut, is threadably received on the threaded end 130 of the
bolt shaft 126 and is positioned directly beneath the
circular collar 136 of the gripping member 134 with the
gripping member 134 typically resting thereon. One stamped
support nut which works well in this application is a
Palnut~ support nut. The stamped support nut 144 is
preferably a stamped sheet metal nut and includes a first
surface 145 having a bore therethrough that threadably
receives the threaded bolt shaft 126 and upon when the
circular collar 136 of the gripping member 134 rests, and
six tabs 146 depending downwardly from the outer peripheral
edge of the first surface 145.
A plastic slee~e 161 similar to the sleeve 61 in the
shape of a hollow cylindrical shell is received by the bolt
and positioned about a threaded portion of the threaded end
e~tending below the mechanical anchor toward the head 128.
The outer diameter of the sleeve 161 is slightly less than
the outer diameter of the first support 144 so that a top
edge 162 of the sleeve 161 rests against the underside of
the first surface 145 of the first support 144 and the
~ 3~ 7
outer surface of the sleeve is surrounded by the tabs 146.
A bottom edge 164 of the sleeve 161 abuts against a top
surface 166 of a threaded stop 168.
The threaded stop 168 is a cylindrical ring having a
threaded bore which is threadably received by the threads
130. A bottom edge 170 of the stop 168 abuts against an
interface formed between the threaded portion and
unthreaded portion of the bolt shaft 126.
The roof bolt further includes a mixing element 180
attached to the stop 168 for mixing the two components 120,
122 of the resin cartridge 118 after it has been ruptured.
Specifically the mixing element 180 is an elongated element
which extends downwardly toward the head 128 and is
separate from the bolt shaft. A first end 182 of the
mixing element 180 attached to a bottom surface of the stop
168 and a second end 184 hangs freely. The first end 182
is wider than the second end 184 and the outer surface of
the mixing element 180 has a curved surface. Additionally,
the mixing element 180 has sufficient thickness to form a
step between the adjacent bolt shaft 126 outer surface and
the mixing element outer surface to promote mixing of the
resin cartridge components 120, 122.
The operation of the roof bolt assembly 11~ is similar
to that of the roof bolt assembly 10. Initially a resin
cartrid~e 118 is placed in the bore hole 112 above the roof
bolt 110 and the roof bolt 110 is advanced upwardly into
the bore hole 112. FIG. 3 shows the arrangement just prior
to the rupture of the resin cartridge 118. The roof bolt
110 then continues to advance into the bore hole 112 and
ruptures the resin cartridge 118. At the same time, the
components 120, 122 of the ruptured resin cartridge 118 are
forced downward from the upward displacement of the anchor
assembl~.
The bolt head 128, and, hence, the entire bolt shaft
126, is rotated continuously in one direction and is drawn
upward until a support plate 154 located immediately above
the washer 131 and head 128 and in contact with the washer
131 comes into contact with the mine roof surface 114.
- 12 -
.~3 ~
Continued rotation draws the expansion anchor 131 and the
stamped support nut 144 downward against the abutting
sleeve 161 and then cause the spreader 132 to move
downwardly along the threads 130. This downward movement
of the spreader 132 causes the gripping fingers 138 to
expand radially outward and force the gripping teeth 140
into a secure engagement with the rock formation 116
surrounding the bore hole 112 at which time the stamped
support nut 144 and the sleeve 161 fail as shown in FIG. 4.
The sleeve 161 prevents slippage which otherwise would
occur because of the initial lubricating effect of the
resin about the bore hole. .1~ I,cvo"
Actual mine roof anchor systems including _6~ and ~5~
diameter bolts have been made and installed having mixing
element lengths of approximately 6~ and having the plastic
sleeve dimensions previously discussed. None of the mine
roof anchor systems experienced lock-up nor did any of the
systems become spinners.
~eferring now to FIGS. 5 and 6 there is shown a third
embodiment of a roo~ bolt assembly in accordance with my
invention, generally designated 210. The roof bolt 210 is
a multi-sectioned elongated member often reaching lengths
of three to eight feet or longer. The roof bolt 210 is
positioned within a bore hole 212 which is drilled upwardly
through a generally horizontal mine roof surface 214 and
into the rock formation 216 above the mine entry.
A quick-setting resin cartridge 218 is positioned in the
blind or upward end of the bore hole 212. The resin
cartridge 218 is basically an enclosed, elongated tube
which includes two components, an active agent 220 and a
reaction agent 222 of a resin grouting mix, separated by a
membrane 224.
The roof bolt assembly 210 includes an elongated bolt
shaft 226 with a head 228 on a first end and with threads
230 at a second end. A two-faced friction reducing washer,
231, such as a hardened steel washer, is positioned
immediately above and rests upon the head 228. A
cylindrical shaped coupling 232 having a threaded bore 234
- 13 -
is threadably received by the threads 230 at a first end
236 of the coupling 232. A second end of 238 of the
coupling 232 receives a second shaft 240. Specifically,
the second bolt shaft includes a first threaded end 242,
threadably received by said second end 238 of said coupling
232, and a second threaded end 254.
A bail-type mechanical anchor 256 is carried on the
second threaded end 254 of the shaft 240. The bail-type
mechanical anchor 256 includes a two-part expansible
anchoring shell 258 and a wedged-shaped nut 260. The shell
258, which normally is generally circular in transverse
section and of a diameter only slightly less than that of
the bore hole 212, has two diametrically-opposed parts or
radially outwardly expansible sections 262. Each part 262
is formed as a longitudinal segment of a cylinder and has
upwardly divergent tapering longitudinal plane edges 264.
The smaller upper ends of the two parts 262 of the shell
258 are connected together by a band-like connecting member
274 that is substantially U-shaped. The connecting member
274 has two legs 276, which are normally generally parallel
to each other and extend longitudinally of the shell 258,
and a base 278, which extends transversely of the shell 258
somewhat above the upper ends of the two shell parts 262.
The legs 276 of the connecting member 274 may be secured to
the shell parts 262 in any appropriate manner, but
preferably they should be pinned and crimped as is well
known in the art. The curved outer surfaces of the shell
parts 262 preferably are provided with a plurality of
step-like circumferential serrations 280 for embedding and
gripping engagement with the side walls of the bore hole
212. Vertical serrations 281 are provided on the curved
outer surfaces of the shell parts 262 below the serrations
280. The wedge 260 is threaded on the threads 254 of the
second shaft 250 and is disposed between the two shell
parts 262 and has plane wedging surfaces 282 complementary
to and in mutually-wedging engagement with each pair of the
opposed side plane edges 264 of the shell parts 262. The
exterior surfaces of the wedge 260 between its wedging
- 14 -
r~
surfaces 282 are arcuate to correspond to the circular
periphery of the shell 258. At its larger end, the wedge
260 has longitudinal channels or grooves 284 to accommodate
the legs 276 of the connecting member 274 passing thereby.
A plastic sleeve 285 in the shape of a hollow
cylindrical shell, similar to sleeve 61, is received by the
shaft 240 positioned about a threaded portion of the
threaded end extending below the mechanical anchor toward
the head 228. The outer diameter of the sleeve 285 is
slightly less than the outer diameter of the curved outer
surfaces of the shell parts 262 so that a top edge 286 of
the sleeve 285 can abut against bottom edges 287 of the
shell parts 262. A bottom edge 28~ of the sleeve 285 abuts
against a top surface 290 of a cylindrical stopping element
lS 292 which has an outer diameter greater than that of the
sleeve 285 so that the sleeve 285 is sandwiched between the
bail-type anchor 256 and the stopping element 292.
The stopping element 292 is integral with the shaft 240
and can be formed by impact forging shaft 240. A plurality
of axial grooves or passages 294 are positioned about the
circumferential surface of the stopping element 292.
Grooves 294 permit resin to pass from an upper portion of
the bolt shaft 240 containing the bail-type anchor 256 to a
lower portion of the bolt assembly toward the coupling 252.
The stopping element 292 can be any shape and need not be
integral with the shaft 240, for example it coul~ be a
threaded nut having a plurality of axial grooves about its
outer surface to permit the resin to pass therethrough
carried on a threaded portion of the bolt 240 below the
sleeve 285.
The roof bolt further includes a threaded or knurled
segment 296 below the stopping element. Segment 296 mixes
the two components 220, 222 of the resin cartridge after it
has been ruptured. This segment 296 can be an extension of
the threads of the threaded first end 252 of the shaft 240.
Further, if the stopping element 292 is threaded onto the
k-~
shaft 240, the shaft 240 could then be completely threaded.
Further a mixing element such as previously discussed
herein could be used.
The operation of roof bolt assembly 210 in accordance
with the present invention can be explained with reference
to the FIGS. 5 and 6. Initially, a resin cartridge 218 is
placed in the bore hole 212 above the roof bolt 210 and
then the roof bolt 210 is advanced u~wardly into the bore
hole 212. FIG. 5 shows the arrangement just prior to
rupture of the resin cartridge 218. The roof bolt 210 then
continues to advance into the bore hole 212 and ruptures
the resin cartridge 218. At the same time, the components
220, 222 of the ruptured resin cartridge 218 are forced
downward from the upward displacement of the anchor
assembly. Much of the components 220, 222 pass through the
axial grooves 294 of the stopping element 292 into the
lower portion of the bolt assembly.
The bolt head 228 and shafts 226 and 240 are rotated
continuously in one direction and are drawn upward until a
support plate 298 and the washer 231 are compressed between
the mine roof surface 214 and the bolt head 228. Continued
rotation draws the bail-type anchor 256 downward a7ainst
the abutting sleeve 285 and forces the opposed parts
radially outward into an initial engagement with the bore
hole wall and causes an upper end of the bolt shaft 250 to
come into contact with the base 278 of the connecting
member 274. The sleeve 285 prevents slippage which would
otherwise occur because of the initial lubricating effect
of the resin about the bore hole. Thereafter, the wedge
260 is further drawn down, independent of the expansion
shell 258, so as to continue to force the shell parts 262
outwardly into engagement with the bore hole wall and cause
the sleeve 2~5 to fail by crushing. Further rotation
causes the connecting member 274 to subsequently break as
shown in FIG. 2. ~otation of the roof bolt 210 is
continued until the proper tensioning force is reached.
While the roof bolt 21~ is being rotated, the segment
2g2 is simultaneously being rotated. The resin components
16 -
i.'. ~ . ~s . 7 ,
220, 222 were previously forced downwardly to the vicinity
of the segment 292 through the stopping element grooves 294
when the bolt 210 was advanced upwardly, and the action of
rotating the segment 292 violently mixes resin components
5 220~ 222 together and, in the case of threads, continually
urges or forces the resin components 220 ~ 222 upwardly. It
is thus insured that the resin components are thoroughly
mixed together and completely fill the annulus surrounding
the upper portion of the roof bolt 210. The final curing
of the resin to its ultimate rigid condition occurs after
the rotation of the bolt 210 has stopped.
Actual mine roof anchor systems for a 1.375n diameter
hole have been made and installed including a 1.125"
diameter stopping element, a 1. 250n diameter coupling, a
15 frangible sleeve as previously discussed, and a ln diameter
segment below the stopping element. Not only were there no
spinners or lock-up experienced, but substantially less
resin was required to maintain the mine roof anchor system
in high tension.
20 The previously described anchor assemblies including the
frangible sleeves need not be used with a resin system.
Having described presently the preferred embodiments of
this invention, it is to be understood that it may be
otherwise embodied within the scope of the following
25 claims:
